Near-infrared absorbing fiber and textile product

Abstract

The present invention addresses the problem of providing a near-infrared absorbing fiber which contains composite tungsten oxide particles that are capable of forming an aqueous dispersion using water as a dispersion medium by adding water thereto.　A near-infrared absorbing fiber (10) according to the present invention contains a nonionic polymer dispersant, composite tungsten oxide particles (12), and a polyamide resin. The composite tungsten oxide particles (12) contain a composite tungsten oxide that has a hexagonal crystal structure and that is represented by general formula MxWOy (wherein element M contains one or more elements selected from Cs and Rb, and x and y satisfy 0.1 ≤ x ≤ 1.0 and 2.0 ≤ y < 4.0).

Description

Near-infrared absorbing fiber, fiber product

[0001] The present invention relates to a near-infrared absorbing fiber and a fiber product.

[0002] Conventionally, resin films and the like that can control the transmission and reflection characteristics of near-infrared rays and visible light have been studied in the agricultural and architectural fields.

[0003] For example, in Patent Document 1, a heat-insulating sheet for covering the ground is proposed, in which a strip-shaped film having infrared reflectivity and a strip-shaped film having infrared absorbency are woven as warp or weft threads to form a woven fabric.

[0004] Further, in Patent Document 2, a film for cultivating crops is proposed, in which a pigment such as carbon black or blue is dispersed in a binder and printed on the surface of a film whitened so that the total transmittance of light is 30% or more and the diffuse reflectance is 40% or more. ​​​​​​​​​​​​​Masterbatches containing composite tungsten oxide particles are manufactured, for example, by dispersing the composite tungsten oxide particles into a dispersion and then kneading it with a resin or the like. Conventionally, when preparing dispersions of composite tungsten oxide particles, organic solvents were mainly used as the dispersion medium. From the viewpoint of reducing environmental impact, there has been a demand for dispersions that do not use organic solvents as the dispersion medium. There has also been a demand for composite tungsten oxide particles that can be dispersed into an aqueous dispersion by adding water, and for near-infrared absorbing fibers using such composite tungsten oxide particles.

[0010] Therefore, one aspect of the present invention aims to provide a near-infrared absorbing fiber containing composite tungsten oxide particles that can be converted into an aqueous dispersion using water as a dispersion medium by adding water.

[0011] A near-infrared absorbing fiber according to one aspect of the present invention comprises a nonionic polymer dispersant, composite tungsten oxide particles, and a polyamide resin, wherein the composite tungsten oxide particles have a hexagonal crystal structure and are of general formula M ｘ WO ｙ (However, the element M includes one or more elements selected from Cs and Rb, and x and y satisfy 0.1 ≤ x ≤ 1.0 and 2.0 ≤ y < 4.0) and contains a composite tungsten oxide.

[0012] According to one aspect of the present invention, a near-infrared absorbing fiber containing composite tungsten oxide particles can be made into an aqueous dispersion using water as a dispersion medium by adding water.

[0013] Figure 1 is an explanatory diagram of a near-infrared absorbing fiber according to one aspect of the present disclosure.

[0014] The embodiments for carrying out the present invention will be described below with reference to the drawings, but the present invention is not limited to the embodiments described below, and various modifications and substitutions can be made to the embodiments described below without departing from the scope of the present invention. [Near-infrared absorbing fiber] A near-infrared absorbing fiber according to one embodiment of the present disclosure (hereinafter referred to as "this embodiment") comprises a nonionic polymer dispersant, composite tungsten oxide particles, and a polyamide resin.

[0015] Figure 1 shows a schematic diagram of the near-infrared absorbing fiber of this embodiment. Figure 1 schematically shows a cross-sectional view of the near-infrared absorbing fiber 10 in a plane passing through the central axis CA of the fiber 11. As shown in Figure 1, the near-infrared absorbing fiber 10 of this embodiment may include the fiber 11 and composite tungsten oxide particles 12.

[0016] The arrangement of the composite tungsten oxide particles 12 is not particularly limited, but the composite tungsten oxide particles 12 can be placed in one or more locations selected from, for example, the surface 11A and the interior 11B of the fiber 11. Figure 1 is a schematic diagram showing an example in which the composite tungsten oxide particles 12 are placed on both the surface 11A and the interior 11B of the fiber 11, but the invention is not limited to this configuration. The composite tungsten oxide particles 12 may be placed on only one of the surface 11A and the interior 11B of the fiber 11. Furthermore, although the composite tungsten oxide particles 12 are depicted as spherical particles in Figure 1, the shape of the composite tungsten oxide particles 12 is not limited to this configuration and can have any shape.

[0017] The components contained in near-infrared absorbing fibers are described below. (1) Composite tungsten oxide particles (1-1) Composition The composite tungsten oxide particles have the general formula M ｘ WO ｙ It can contain a composite tungsten oxide that can be represented by [formula]. The composite tungsten oxide particles may also be particles of the composite tungsten oxide.

[0018] However, the M element in the above general formula may contain one or more elements selected from Li (lithium), Na (sodium), K (potassium), Rb (rubidium), Cs (cesium), Fr (francium), Be (beryllium), Mg (magnesium), Ca (calcium), Sr (strontium), Ba (barium), and Ra (radium). This is because when the M element contains one or more selected from Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, and Ra, the composite tungsten oxide particles are likely to have a hexagonal crystal structure, particularly enhancing the light transmittance in the visible light region and also enhancing the near-infrared shielding function. Among them, considering the ease of handling of raw materials, etc., it is more preferable that the M element contains one or more selected from, for example, Cs, Rb, K, and Ba, and it is more preferable that the M element contains one or more elements selected from Cs and Rb. In the above general formula, W represents tungsten, O represents oxygen, x may be 0.1 ≦ x ≦ 1.0, or may be 0.25 ≦ x ≦ 0.39. y may satisfy 2.0 ≦ y < 4.0.

[0019] Typical examples of the material of the composite tungsten oxide particles include Cs ０．３３ WO ３ , Rb ０．３３ WO ３ , K ０．３３ WO ３ , Ba ０．３３ WO ３ and the like. However, as long as x and y are within the above ranges, useful near-infrared shielding characteristics can be obtained.

[0020] The composite tungsten oxide can have one or more tungsten bronze-type crystal structures selected from, for example, tetragonal, cubic, and hexagonal. And it is preferable that the composite tungsten oxide contained in the composite tungsten oxide particles included in the near-infrared absorbing fiber of the present embodiment has a hexagonal crystal structure.

[0021] When the composite tungsten oxide has a hexagonal crystal structure, the transmittance of the particles containing the composite tungsten oxide in the visible light region is improved, and the absorption of light in the near-infrared region is improved.

[0022] Composite tungsten oxides also function as near-infrared shielding materials when they adopt a tetragonal or cubic tungsten bronze-type crystal structure. However, the absorption position of light in the near-infrared region tends to change depending on the crystal structure of the composite tungsten oxide. This absorption position of light in the near-infrared region tends to shift to longer wavelengths when the crystal structure is tetragonal compared to cubic, and further to longer wavelengths when the crystal structure is hexagonal. In addition, in conjunction with this variation in absorption position, the absorption of light in the visible region is least in the hexagonal crystal, followed by the tetragonal crystal, and among these, the absorption of light in the visible region is greatest in the cubic crystal. Therefore, for applications that transmit more visible light and shield more near-infrared light, it is preferable to use a composite tungsten oxide having a hexagonal tungsten bronze-type crystal structure. For this reason, the composite tungsten oxide particles contained in the near-infrared absorbing fiber of this embodiment can have, for example, a hexagonal crystal structure. (1-2) Average particle diameter and crystallite diameter of composite tungsten oxide particles (Average particle diameter) The average particle diameter of the composite tungsten oxide particles used in the near-infrared absorbing fiber of this embodiment is not particularly limited and can be selected according to the purpose of use, etc.

[0023] The composite tungsten oxide particles preferably have an average particle diameter of 800 nm or less. This is because, by having an average particle diameter of 800 nm or less, localized surface plasmon resonance occurs, preventing complete blocking of light in the visible light region due to scattering, thus improving visibility in the visible light region. Furthermore, the composite tungsten oxide particles efficiently absorb near-infrared light irradiated onto the near-infrared absorbing fiber, making it easier to convert it into thermal energy.

[0024] The average particle size of the composite tungsten oxide particles is more preferably 200 nm or less. If the average particle size of the composite tungsten oxide particles is 200 nm or less, the localized surface plasmon resonance becomes stronger, allowing for more powerful absorption of irradiated infrared radiation. The average particle size of the composite tungsten oxide particles is even more preferably 100 nm or less. By setting the average particle size of the composite tungsten oxide particles to 100 nm or less, the characteristics of nanoparticles are emphasized.

[0025] The lower limit of the average particle diameter of composite tungsten oxide particles is not particularly limited, but for ease of industrial manufacturing, the average particle diameter may be, for example, 1 nm or more.

[0026] In other words, the average particle size of the composite tungsten oxide particles may be 1 nm to 800 nm, 1 nm to 200 nm, or 1 nm to 100 nm.

[0027] Here, the average particle diameter is the average value of the diameter of individual, non-aggregated composite tungsten oxide particles, and is the average value of the particle diameter of composite tungsten oxide particles contained in a composite tungsten oxide particle dispersion obtained by dispersing composite tungsten oxide particles in a solid medium such as a resin.

[0028] The average particle diameter does not include the diameter of aggregates of composite tungsten oxide particles and is therefore different from the dispersed particle diameter.

[0029] The average particle size is measured and calculated from electron microscope images of the composite tungsten oxide particles.

[0030] To measure the average particle size of composite tungsten oxide particles contained in a composite tungsten oxide particle dispersion, a thin section of the dispersion obtained by cross-sectional processing can be used. Then, 100 composite tungsten oxide particles can be selected from the transmission electron microscope image of the thin section, and the particle size of the selected particles can be measured using an image processing device, and the average value can be calculated. If 100 composite tungsten oxide particles cannot be observed in a single observation field, composite tungsten oxide particles can be selected and observed in multiple observation fields that do not overlap, totaling 100 particles.

[0031] The average value is the arithmetic mean, which is the sum of the particle diameters of 100 composite tungsten oxide particles divided by the number of particles, 100. Furthermore, the particle diameter of each composite tungsten oxide particle represents its diameter in terms of a circle. In other words, the particle diameter of each composite tungsten oxide particle measured using a thinned sample can be considered the diameter of a circle with the same area (cross-sectional area) as the area of ​​each composite tungsten oxide particle.

[0032] For cross-sectional processing to obtain thin sections for evaluation, a microtome, cross-section polisher, focused ion beam (FIB) apparatus, etc., can be used. The average particle size of the composite tungsten oxide particles contained in the composite tungsten oxide particle dispersion is the average value of the particle sizes of the composite tungsten oxide particles dispersed in the solid medium that serves as the matrix.

[0033] (Cryslite size) The crystallite size of the composite tungsten oxide particles is not particularly limited, but from the viewpoint of exhibiting particularly excellent near-infrared absorption characteristics, the crystallite size of the composite tungsten oxide particles is preferably, for example, 10 nm to 100 nm, more preferably 10 nm to 80 nm, even more preferably 10 nm to 60 nm, and most preferably 10 nm to 40 nm. By setting the crystallite size of the composite tungsten oxide particles to 10 nm to 100 nm, particularly excellent near-infrared absorption characteristics can be exhibited.

[0034] A composite tungsten oxide particle dispersion can be obtained by adding composite tungsten oxide particles to a dispersion medium and subjecting them to crushing, grinding, or dispersion treatment. The crystallite size of the composite tungsten oxide particles contained in the composite tungsten oxide particle dispersion can be maintained even after volatile components, etc., are removed from the composite tungsten oxide particle dispersion. For example, even in composite tungsten oxide particles obtained by removing the liquid medium, etc., from the composite tungsten oxide particle dispersion, the crystallite size of the composite tungsten oxide particles contained in the composite tungsten oxide particle dispersion can be maintained. Furthermore, even in composite tungsten oxide particles contained in a composite tungsten oxide particle dispersion obtained using the composite tungsten oxide particle dispersion, the crystallite size of the composite tungsten oxide particles contained in the composite tungsten oxide particle dispersion can be maintained. (1-3) Regarding the content of composite tungsten oxide particles, the content of composite tungsten oxide particles in the near-infrared absorbing fiber of this embodiment is not particularly limited and can be selected according to the properties required for the near-infrared absorbing fiber. Because composite tungsten oxide particles have a very high near-infrared absorption capacity per unit weight, they can exert their effects with only about one-quarter to one-tenth the amount used compared to ITO (tin-doped indium oxide) or ATO (antimond-doped tin oxide).

[0035] In the near-infrared absorbing fiber of this embodiment, the content of composite tungsten oxide particles may be 0.001% by mass or more and 80% by mass or less. Furthermore, considering the weight of the fiber after the addition of composite tungsten oxide particles and the cost of raw materials, in the near-infrared absorbing fiber of this embodiment, for example, the content of composite tungsten oxide particles may be 0.005% by mass or more and 50% by mass or less, 0.005% by mass or more and 30% by mass or less, or even 0.005% by mass or more and 20% by mass or less, 0.005% by mass or more and 10% by mass or less, or 0.005% by mass or more and 5% by mass or less.

[0036] By containing composite tungsten oxide particles in a proportion of 0.001% by mass or more, near-infrared absorbing fibers can achieve a sufficient near-infrared absorption effect even when the fabric containing the composite tungsten oxide particles is thin. Furthermore, by containing composite tungsten oxide particles in a proportion of 80% by mass or less, a decrease in spinnability due to clogging of the filter or breakage of the yarn can be more reliably avoided when spinning the near-infrared absorbing fibers. In addition, by limiting the composite tungsten oxide particle content to 80% by mass or less, damage to the physical properties of the fibers can be more reliably avoided.

[0037] By increasing the content of composite tungsten oxide particles in near-infrared absorbing fibers to 0.001% by mass or more, the heat generation effect when absorbing near-infrared rays can be particularly enhanced. Furthermore, by reducing the content of composite tungsten oxide particles in near-infrared absorbing fibers to 80% by mass or less, the strength of the near-infrared absorbing fibers can be increased. By increasing the strength of the near-infrared absorbing fibers, it is possible to particularly prevent the fabric from tearing due to pulling or needle pressure during sewing, and to prevent seams from unraveling. In addition, it is possible to prevent tearing due to friction when the fabric is made, increase the firmness and resilience of the fabric, and prevent deformation and wrinkles.

[0038] Near-infrared absorbing fibers and general-purpose fibers (fibers that do not contain composite tungsten oxide particles) may be used in combination, and the two may be integrated into a single yarn during the twisting process. This makes it possible to have the properties of near-infrared absorbing fibers while also providing the durability and flexibility of general-purpose fibers. It also reduces costs. (1-4) Method for manufacturing composite tungsten oxide particles The method for manufacturing the composite tungsten oxide particles contained in the near-infrared absorbing fibers of this embodiment is not particularly limited. Composite tungsten oxide particles can be manufactured using, for example, a thermal plasma method or a solid-phase reaction method. The properties of the composite tungsten oxide particles, such as the crystallite size, can be easily controlled by the conditions when manufacturing the composite tungsten oxide particles. The method for manufacturing the composite tungsten oxide particles used in the near-infrared absorbing fibers of this embodiment can be any method that can produce composite tungsten oxide particles that satisfy the general formula and crystal structure described above.

[0039] A method for producing composite tungsten oxide particles may include, for example, a heat treatment step in which the starting material is heat-treated in an inert gas atmosphere or a reducing gas atmosphere.

[0040] A method for producing composite tungsten oxide particles may also include an oxidation treatment step after a heat treatment step, in which an oxidation treatment is performed.

[0041] The following describes each process. (Heat treatment process) The starting materials used in the heat treatment process may include tungsten-containing raw materials that serve as a source of tungsten.

[0042] The tungsten raw material may include one or more selected from, for example, tungstic acid, tungsten trioxide powder, tungsten dioxide powder, tungsten oxide hydrate, tungsten hexachloride powder, ammonium tungstate powder, tungsten oxide hydrate powder, tungsten compound powder, and metallic tungsten powder.

[0043] As hydrated tungsten oxide, for example, hydrated tungsten oxide powder obtained by dissolving tungsten hexachloride in alcohol and then drying it, or hydrated tungsten oxide powder obtained by dissolving tungsten hexachloride in alcohol, adding water to precipitate it, and then drying it can be used.

[0044] The tungsten compound powder may be a powder obtained by drying an aqueous solution of ammonium tungstate.

[0045] The tungsten raw material may include a solution containing one or more materials selected from the above materials.

[0046] When manufacturing composite tungsten oxide particles, if the starting material is a solution, the elements contained in the starting material can be easily and uniformly mixed. For this reason, it is more preferable to use a solution such as an aqueous solution of ammonium tungstate or a tungsten hexachloride solution as the tungsten raw material.

[0047] The starting material may also include element M raw materials containing element M, which serve as a source of element M.

[0048] The element M raw material may include one or more selected elements, such as element M in its elemental form or compounds containing element M.

[0049] The starting material may be a mixture of tungsten raw material and element M raw material.

[0050] In order to produce starting materials in which each component is uniformly mixed at the molecular level, it is preferable to mix each raw material in the form of a solution. Therefore, it is preferable that the element M raw material containing element M is soluble in a solvent such as water or an organic solvent. For example, the element M raw material may be one or more selected from tungstates, chlorides, nitrates, sulfates, oxalates, oxides, carbonates, hydroxides, etc., that contain element M, but is not limited to these, and any material that can be dissolved in solution can be suitably used.

[0051] In the heat treatment process, a temperature of 650°C or higher is preferred for the heat treatment in an inert gas atmosphere. Starting materials heat-treated at 650°C or higher have sufficient near-infrared absorption capacity and are efficient as near-infrared absorbing particles. The upper limit of the heat treatment temperature in an inert gas atmosphere is not particularly limited, but it can be, for example, 1200°C or lower.

[0052] In other words, the heat treatment conditions in an inert gas atmosphere may be between 650°C and 1200°C.

[0053] Examples of inert gases include Ar and N ２ Inert gases such as the above can be used.

[0054] In the heat treatment process, when heat treatment is performed in a reducing gas atmosphere, it is preferable to first heat-treat the starting material in a reducing gas atmosphere at a temperature of 300°C to 1000°C, and then heat-treat it in an inert gas atmosphere at a temperature of 650°C to 1200°C.

[0055] The reducing gas used in the reducing gas atmosphere is not particularly limited, but H ２ This is preferable. And, as a reducing gas, H ２ When using this, the composition of the reducing gas atmosphere is, for example, Ar, N ２ H ２It is preferable to mix them in a volume ratio of 0.1% or more, and more preferably 0.2% or more. ２ If the volume ratio is 0.1% or more, the reduction can be carried out efficiently.

[0056] H in a reducing gas atmosphere ２ The upper limit of the concentration is not particularly limited, but for example, it can be 100% or less by volume. (Oxidation treatment process) In the oxidation treatment process, the composite tungsten oxide particles obtained in the heat treatment process can be oxidized in a mild environment.

[0057] The oxygen source gas used in the oxidation treatment process is not particularly limited, but one or more selected from oxygen, air, and water vapor is preferred. The concentration of the oxygen source can be appropriately selected according to the heat treatment temperature and the amount of material to be heat treated, and is not particularly limited. The heat treatment temperature can also be appropriately selected according to the amount of material to be heat treated, and is not particularly limited, but for example, 400°C to 850°C is preferred. (Other steps) The method for producing composite tungsten oxide particles may also include a surface treatment step in which the surface is treated with at least one selected from silane compounds, titanium compounds, aluminum compounds, and zirconia compounds. By coating the surface of the composite tungsten oxide particles with a compound containing one or more selected from Si, Ti, Al, and Zr, the weather resistance can be improved. (2) Nonionic polymer dispersants Dispersants that are water-soluble and can surface coat composite tungsten oxide particles include nonionic dispersants, anionic dispersants, and cationic dispersants. Here, it is necessary to consider the compatibility of the resin and dispersant when forming the masterbatch. Of these, nonionic dispersants can maintain the dispersion state of particles during masterbatching with polyamide resin. For example, when anionic or cationic dispersants are used, composite tungsten oxide particles are difficult to disperse.

[0058] A nonionic polymer dispersant can disperse composite tungsten oxide particles in water, which is the solvent, to form an aqueous dispersion. The nonionic polymer dispersant may also be a water-soluble polymer dispersant. Therefore, by containing a nonionic polymer dispersant in the near-infrared absorbing fiber of this embodiment, it becomes possible to use water instead of an organic solvent as the dispersion medium in the manufacturing process. As a result, it becomes possible to produce a near-infrared absorbing fiber with reduced residual organic solvents.

[0059] As a nonionic polymer dispersant, a polymer dispersant containing one or more groups selected from carbonyl groups, vinyl groups, pyrrolidone groups, amide groups, and hydroxyl groups may be used. This is because the inclusion of one or more groups selected from carbonyl groups, vinyl groups, pyrrolidone groups, amide groups, and hydroxyl groups in the nonionic polymer dispersant allows for the formation of bonds such as hydrogen bonds on the surface of the composite tungsten oxide particles, making it easier for the dispersant to disperse on the surface of the composite tungsten oxide particles.

[0060] Examples of nonionic polymer dispersants include one or more selected from polyvinylpyrrolidone, polyvinyl alcohol, and the like.

[0061] Polyvinylpyrrolidone can be represented by the following chemical formula (1).

[0062] Polyvinyl alcohol can be represented by the following chemical formula (2).

[0063] The average molecular weight of the nonionic polymer dispersant is not particularly limited, but may be, for example, 1,000 to 400,000, or 5,000 to 200,000.

[0064] In this specification, average molecular weight refers to the weight-average molecular weight measured by the GPC (Gel Permeation Chromatography) method and calculated using a calibration curve based on standard polystyrene.

[0065] The amount of nonionic polymer dispersant added can be selected depending on the type of other polymer dispersants and composite tungsten oxide particles, as well as the specific surface area of ​​the composite tungsten oxide particles, and is not particularly limited.

[0066] For example, the amount of nonionic polymer dispersant added may be 0.1 parts by mass or more and 150 parts by mass or less per 100 parts by mass of composite tungsten oxide particles. That is, the near-infrared absorbing fiber of this embodiment may contain a nonionic polymer dispersant in a proportion of 0.1% by mass or more and 150% by mass or less when the composite tungsten oxide particle content is 100 parts by mass. In the aqueous dispersion of this embodiment, by adding 0.1 parts by mass or more and 150 parts by mass or less of nonionic polymer dispersant per 100 parts by mass of composite tungsten oxide particles, a particularly good dispersion state can be achieved for the composite tungsten oxide particles. The amount of nonionic polymer dispersant added may be 0.1 parts by mass or more and 100 parts by mass or less per 100 parts by mass of composite tungsten oxide particles. From the viewpoint of improving the dispersibility of composite tungsten oxide particles, the amount of nonionic polymer dispersant added may be 20 parts by mass or more per 100 parts by mass of composite tungsten oxide particles. Therefore, the amount of nonionic polymer dispersant added may be 20 parts by mass or more and 150 parts by mass or 20 parts by mass or more and 100 parts by mass per 100 parts by mass of composite tungsten oxide particles.

[0067] In the near-infrared absorbing fiber of this embodiment, the nonionic polymer dispersant may also be present in the fiber, and depending on the amount of nonionic polymer dispersant added, it may affect the affinity of the fiber to water. By setting the amount of nonionic polymer dispersant to 150 parts by mass or less per 100 parts by mass of composite tungsten oxide particles, for example, the effect on the affinity of the fiber to water can be reduced. Therefore, by setting the amount of nonionic polymer dispersant to 150 parts by mass or less per 100 parts by mass of composite tungsten oxide particles, the fiber can exhibit the desired water-repellent effect when a water-repellent treatment is applied to the fiber.

[0068] The nonionic polymer dispersant contained in the near-infrared absorbing fiber of this embodiment is preferably 20% by mass or less, and more preferably 10% by mass or less. By limiting the amount of nonionic polymer dispersant contained in the near-infrared absorbing fiber to 20% by mass or less, the influence of the nonionic polymer dispersant on the function imparted to the near-infrared absorbing fiber is reduced, making it easier for the near-infrared absorbing fiber to exhibit the desired function.

[0069] The nonionic polymer dispersant contained in the near-infrared absorbing fiber of this embodiment can be more than 0% by mass. Therefore, the near-infrared absorbing fiber of this embodiment may contain more than 0% by mass and 20% by mass or more than 0% by mass and 10% by mass or less of the nonionic polymer dispersant.

[0070] The composite tungsten oxide particles used in the near-infrared absorbing fibers of this embodiment may have a nonionic polymer dispersant disposed on their surface. The surface of the composite tungsten oxide particles used in the near-infrared absorbing fibers of this embodiment may be modified with a nonionic polymer dispersant. By modifying the surface of the composite tungsten oxide particles with a nonionic polymer dispersant, dispersibility can be improved even when a dispersion is prepared using water as the dispersion medium. Therefore, it becomes possible to use them in the manufacture of masterbatches containing composite tungsten oxide particles and near-infrared absorbing fibers.

[0071] (3) Polyamide resin The near-infrared absorbing fiber of this embodiment may contain polyamide resin.

[0072] As the polyamide resin, one or more types selected from, for example, nylon, nylon 6, nylon 66, nylon 610, nylon 11, nylon 12, nylon 612, aromatic nylon, aramid, etc. may be used.

[0073] The near-infrared absorbing fiber of this embodiment may contain polyamide resin, for example, in the form of fibers. That is, the near-infrared absorbing fiber of this embodiment may contain polyamide fibers. Even if the near-infrared absorbing fiber of this embodiment contains polyamide fibers, if it is to impart the functions of other fibers, the near-infrared absorbing fiber of this embodiment may also contain fibers other than polyamide fibers.

[0074] The cross-sectional shape of the polyamide fiber is not particularly limited, but examples include one or more types selected from circular, triangular, hollow, flattened, Y-shaped, star-shaped, core-sheath shape, etc.

[0075] The inclusion and arrangement of composite tungsten oxide particles in the polyamide fiber are not particularly limited. For example, if the cross-sectional shape of the fiber is core-sheath type, the composite tungsten oxide particles may be included in the core or the sheath of the fiber. Also, the shape of the polyamide fiber is not particularly limited and may be a filament (long fiber) or a staple (short fiber). (4) Other optional components The near-infrared absorbing fiber of this embodiment may consist only of a nonionic polymer dispersant, a polyamide resin, and composite tungsten oxide particles, but may also contain any other optional components. The near-infrared absorbing fiber of this embodiment may also contain, for example, far-infrared emitting substances or additives as described below, depending on the purpose. (4-1) Additives The near-infrared absorbing fiber according to this embodiment may contain antioxidants, flame retardants, deodorants, insecticides, antibacterial agents, etc., as additives, depending on the purpose, as long as it does not impair the performance of the fiber.

[0076] Furthermore, the near-infrared absorbing fiber of this embodiment can be manufactured, for example, using a masterbatch composition or masterbatch, as described later. For this reason, the near-infrared fiber of this embodiment may contain one or more additives selected from the masterbatch composition, dyes, pigments, stabilizers, release agents, coupling agents, ultraviolet absorbers, surfactants, antistatic agents, dispersants having carboxyl groups, etc. (4-2) Far-infrared emitting material A far-infrared emitting material is a material that has the ability to emit far-infrared rays and is preferably in particulate form. That is, far-infrared emitting material particles can be suitably used as the far-infrared emitting material.

[0077] Far-infrared emitting material can be placed at one or more selected locations on the surface and within the fiber.

[0078] Examples of far-infrared emitting materials include ZrO ２ SiO ２ , TiO ２ Al２ O ３ MnO ２ , MgO, Fe ２ O ３ Metal oxides such as CuO, carbides such as ZrC, SiC, and TiC, ZrN, Si ３ N ４ One or more types selected from nitrides such as AlN are examples.

[0079] Examples of composite tungsten oxide particles include particles containing cesium tungsten oxide. Cesium tungsten oxide has the property of absorbing solar energy with wavelengths between 300 nm and 3000 nm, and in particular selectively absorbs infrared energy in the region around 900 nm to 2500 nm, converting it into heat or re-radiating it.

[0080] On the other hand, particles of far-infrared emitting materials have the ability to receive energy absorbed by cesium tungsten oxide, an infrared absorbing material, and convert that energy into thermal energy in the mid- and far-infrared wavelength range, which is then emitted. For example, ZrO ２ The particles convert this energy into thermal energy with wavelengths between 2000 nm and 20000 nm, and radiate it. Therefore, when far-infrared radiating material with the ability to emit far-infrared rays and composite tungsten oxide particles coexist inside and on the surface of the fiber, the solar energy absorbed by the composite tungsten oxide particles is efficiently consumed inside and on the surface of the fiber. As a result, effective heat retention is achieved.

[0081] The content of far-infrared emitting material in near-infrared absorbing fibers is not particularly limited and can be selected according to the performance required of the near-infrared absorbing fiber.

[0082] The near-infrared absorbing fiber of this embodiment may contain a far-infrared emitting material in a proportion of, for example, 0.001% by mass or more and 80% by mass or less.

[0083] This is because, by setting the content of far-infrared emitting material to 0.001% by mass or more, a sufficient thermal energy radiation effect can be obtained even with a thin fabric containing near-infrared absorbing fibers. Furthermore, by setting the content of far-infrared emitting material to 80% by mass or less, a decrease in spinnability due to clogging of the filter or breakage of the yarn during spinning can be more reliably avoided.

[0084] As described above, the near-infrared absorbing fiber according to this embodiment contains composite tungsten oxide particles as a near-infrared absorbing component. The near-infrared absorbing fiber according to this embodiment efficiently absorbs near-infrared rays from sunlight and other sources and converts them into heat, even with a small amount of composite tungsten oxide particles, making it possible to provide a fiber with excellent heat retention even with a low content of composite tungsten oxide particles. Furthermore, because the near-infrared absorbing fiber according to this embodiment can reduce the content of composite tungsten oxide particles, it does not impair the design of the textile product and avoids impairing the basic physical properties of the fiber, such as strength and elongation. As a result, the near-infrared absorbing fiber according to this embodiment can be used in various applications such as cold-weather clothing, sportswear, stockings, curtains and other industrial textile products that require heat retention. Moreover, when the near-infrared absorbing fiber according to this embodiment is used in clothing, the amount of infrared rays contained in natural light that reach the human skin can be reduced, thereby reducing damage to the skin. If the textile product containing the near-infrared absorbing fibers of this embodiment is used as a curtain and placed in the windows of a building, the curtain will absorb near-infrared rays contained in sunlight, becoming a curtain with a near-infrared shielding function. As a result, near-infrared rays from sunlight entering the window will be blocked, and the rise in room temperature during the summer can also be suppressed.

[0085] The near-infrared shielding and absorbing fibers of this embodiment can use aqueous dispersions or dispersed powders as raw materials, as will be described later in the method for manufacturing near-infrared absorbing fibers, and therefore the content of organic solvents can be reduced. The near-infrared absorbing fibers of this embodiment can have a residual organic solvent content of, for example, 5% by mass or less, 0.1% by mass or less, or even 0% by mass.

[0086] The residual organic solvents referred to here are the organic solvent content percentages resulting from the liquid medium of the composite tungsten oxide particle dispersion prepared in the process of manufacturing near-infrared absorbing fibers and masterbatches. [Method for Manufacturing Near-Infrared Absorbing Fibers] (1) Method for Manufacturing Near-Infrared Absorbing Fibers The method for manufacturing near-infrared absorbing fibers according to this embodiment will be described below. Since the method for manufacturing near-infrared absorbing fibers according to this embodiment can produce near-infrared absorbing fibers according to one aspect of the present disclosure, the matters already described will be omitted from the explanation.

[0087] The method for producing near-infrared absorbing fibers according to this embodiment may include a near-infrared absorbing fiber manufacturing step for producing near-infrared absorbing fibers containing polyamide resin and composite tungsten oxide particles.

[0088] Since the composite tungsten oxide particles and polyamide resin have already been explained, we will omit their explanation here.

[0089] In the near-infrared absorbing fiber manufacturing process, specifically, for example, composite tungsten oxide particles can be placed on the surface of the fiber and at one or more selected locations within the fiber.

[0090] The method for arranging the composite tungsten oxide particles at one or more selected locations on the surface and inside of the fiber is not particularly limited. For example, any of the following methods (a) to (d) can be used: (a) A method of directly mixing the composite tungsten oxide particles into the raw material polymer of the synthetic fiber and spinning the fibers. (b) A method of preparing a masterbatch containing a high concentration of composite tungsten oxide particles in a portion of the raw material polymer in advance, and then diluting the masterbatch to a predetermined concentration before spinning. (c) A method of preparing a dispersion solution in which the composite tungsten oxide particles are dispersed in a raw material monomer or oligomer solution, and then synthesizing the target raw material polymer using the dispersion solution, while simultaneously dispersing the composite tungsten oxide particles in the raw material polymer, and then spinning the fibers. (d) A method of attaching the composite tungsten oxide particles to the surface of a fiber obtained by spinning in advance using a binder or the like.

[0091] The methods for manufacturing near-infrared absorbing fibers can be described as (a) to (d) above. Methods (a) and (b) will be further explained with specific examples.

[0092] Let's take the example of using nylon fiber, a type of polyamide fiber, as the fiber.

[0093] First, nylon resin pellets, which are thermoplastic resins, and a dispersed powder of composite tungsten oxide particles are uniformly mixed in a blender. The mixture is melt-kneaded in a twin-screw extruder to obtain a masterbatch containing the composite tungsten oxide particles. The obtained masterbatch is melt-mixed at or near the melting temperature of the thermoplastic resin, and near-infrared absorbing fibers can be produced by spinning, for example, by various known methods.

[0094] The method for producing a masterbatch is not particularly limited. For example, a dispersion of composite tungsten oxide particles, powder or pellets of a thermoplastic resin such as nylon, and other additives as needed can be melt-mixed using a kneader while removing the dispersion medium. By melt-mixing, a masterbatch can be prepared in which composite tungsten oxide particles are dispersed in a thermoplastic resin such as nylon. Alternatively, a masterbatch may be produced by melt-kneading a composite tungsten oxide dispersion powder and powder or pellets of a thermoplastic resin such as nylon using a twin-screw extruder. Masterbatch compositions, masterbatches, and methods for producing them will be described later.

[0095] The mixing machine is not particularly limited, but for example, one or more types selected from mixing machines such as ribo blenders, tumblers, Nauter mixers, Henschel mixers, super mixers, and planetary mixers, as well as Banbury mixers, kneaders, rolls, kneader-ruders, single-screw extruders, twin-screw extruders, etc., can be used.

[0096] The method for preparing a masterbatch in which composite tungsten oxide particles are dispersed in a nylon resin is not limited to the above-described form.

[0097] For example, after preparing a dispersion of composite tungsten oxide particles, the dispersion medium is first removed from the dispersion by a known method. Then, the powder obtained by removing the dispersion medium is uniformly melt-mixed with granular or pelletized nylon resin, which is a thermoplastic resin, and other additives as needed, to produce a mixture in which composite tungsten oxide particles are dispersed in nylon resin.

[0098] In addition, to produce a mixture in which composite tungsten oxide particles are dispersed in a thermoplastic resin such as nylon resin, a method may be used in which the composite tungsten oxide particles are directly added to the thermoplastic resin such as nylon resin and melt-mixed.

[0099] A masterbatch containing the composite tungsten oxide particles can be obtained by kneading a mixture of the obtained composite tungsten oxide particles and a thermoplastic nylon resin using a vented single-screw or twin-screw extruder and processing it into pellets.

[0100] A masterbatch containing composite tungsten oxide particles and a desired amount of a masterbatch made of nylon without composite tungsten oxide particles can be melt-mixed at or near the melting temperature of the resin and spun according to a known method.

[0101] When attaching and mixing composite tungsten oxide particles to fibers or polymers that serve as their raw materials, the dispersion of composite tungsten oxide particles can be directly mixed with the fibers or polymers. Furthermore, if necessary, the pH of the composite tungsten oxide particle dispersion may be adjusted by adding acids or alkalis, or various surfactants and coupling agents may be added to further improve the dispersion stability of the composite tungsten oxide particles.

[0102] The near-infrared absorbing capacity per unit weight of the composite tungsten oxide particles in the near-infrared absorbing fiber of this embodiment is very high, so it can exert its effect with about one-quarter to one-tenth the amount used compared to ITO or ATO. Specifically, the content of composite tungsten oxide particles contained on the surface or inside the fiber may be, for example, 0.001% by mass or more and 80% by mass or less. Furthermore, considering the mass of the fiber and raw material costs after the addition of composite tungsten oxide particles, the content of composite tungsten oxide particles in the near-infrared absorbing fiber of this embodiment may be 0.005% by mass or more and 50% by mass or less, 0.005% by mass or more and 30% by mass or less, or even 0.005% by mass or more and 20% by mass or less, 0.005% by mass or more and 10% by mass or less, or 0.005% by mass or more and 5% by mass or less.

[0103] If the content of composite tungsten oxide particles in the near-infrared absorbing fiber of this embodiment is 0.001% by mass or more, a sufficient near-infrared absorption effect can be obtained even with a thin fabric. Furthermore, if the content of composite tungsten oxide particles in the near-infrared absorbing fiber of this embodiment is 80% by mass or less, a decrease in spinnability due to clogging of the filter or breakage of the yarn can be avoided during the spinning process.

[0104] Furthermore, from the viewpoint of maintaining the physical properties of the fibers, it is preferable to have a low content of composite tungsten oxide particles. From this viewpoint, the content of composite tungsten oxide particles may be 50% by mass or less, 30% by mass or less, 20% by mass or less, 10% by mass or less, or 5% by mass or less. (2) Masterbatch composition and masterbatch A masterbatch composition and masterbatch that can be used in the production of near-infrared absorbing fibers may include a nonionic polymer dispersant, a polyamide resin which is a solid medium, and composite tungsten oxide particles.

[0105] The masterbatch composition of this embodiment may be a mixture of a nonionic polymer dispersant, a solid medium, and composite tungsten oxide particles. In the masterbatch composition of this embodiment, the nonionic polymer dispersant may be arranged on the particle surface of the composite tungsten oxide particles and may modify the particle surface of the composite tungsten oxide particles.

[0106] Masterbatches can be used as raw materials for near-infrared absorbing fibers and various molded articles. A masterbatch can be made by melt-kneading a masterbatch composition and processing it, for example, into pellets. In other words, a masterbatch is a molded article of a masterbatch composition. Therefore, a masterbatch can contain the same components as the masterbatch composition. In a masterbatch, the polyamide resin can be arranged to cover, for example, composite tungsten oxide particles, or to enclose them. Alternatively, composite tungsten oxide particles may be dispersed in the polyamide resin in the masterbatch.

[0107] The masterbatch may include, for example, composite tungsten oxide particles and a polyamide resin, where the composite tungsten oxide particles can be arranged in the polyamide resin. Preferably, the composite tungsten oxide particles are dispersed in the polyamide resin.

[0108] The composite tungsten oxide particles may have a coating on their surface, for example. The masterbatch may also further contain a nonionic polymer dispersant. The nonionic polymer dispersant may be arranged on the surface of the composite tungsten oxide particles, or it may modify the surface of the composite tungsten oxide particles. The masterbatch may also contain other additives as needed. (2-1) Regarding the masterbatch composition and its components: Details of the masterbatch composition, the nonionic polymer dispersant contained in the masterbatch, the composite tungsten oxide particles, and other optional components, as well as their preferred properties, have already been described and will be omitted here. The composite tungsten oxide particles have a hexagonal crystal structure and are generally formulated as M ｘ WO ｙIt can be expressed as follows. Other optional components include dispersants having carboxyl groups and far-infrared emitting materials. Here, the masterbatch composition and the polyamide resin contained in the masterbatch will be described. (Polyamide resin) In the masterbatch composition and masterbatch of this embodiment, the polyamide resin contained is not particularly limited, but can be one or more selected from, for example, nylon, nylon 6, nylon 66, nylon 610, nylon 11, nylon 12, nylon 612, aromatic nylon, aramid, etc. (Dispersant having carboxyl groups) As described above, the masterbatch composition and masterbatch may further contain a dispersant having carboxyl groups. For this reason, the near-infrared absorbing fiber of this embodiment may also further contain a dispersant having carboxyl groups. By including a dispersant having carboxyl groups in the masterbatch composition, masterbatch, and the near-infrared absorbing fiber of this embodiment, the dispersibility of composite tungsten oxide particles in the polyamide resin can be further improved. The amount of dispersant having carboxyl groups can be selected according to the type of composite tungsten oxide particles and the specific surface area of ​​the composite tungsten oxide particles, and is not particularly limited.

[0109] For dispersants containing carboxyl groups, the heat resistance temperature is preferably 280°C or higher, and the dropping point is preferably 75°C or higher, compared to the melting and kneading temperature of the polyamide resin.

[0110] For example, the content of the dispersant having a carboxyl group may be 0.1 parts by mass or more and 100 parts by mass or less per 100 parts by mass of composite tungsten oxide particles. By including the dispersant having a carboxyl group within the above content range, the composite tungsten oxide particles can be dispersed in a particularly good state. The content of the dispersant having a carboxyl group may be within the same range for near-infrared absorbing fibers as well.

[0111] Examples of dispersants containing carboxyl groups include Kyoeisha Chemical Co., Ltd.'s Floren G-700AMP, Floren GW-1500, Floren GW-1640, Sanyo Chemical Industries' Nopcol 5200, Nopcol 6100, SN Dispersant 5027, and BYK-MAX P 4102. (Other additives) The masterbatch composition and masterbatch may also contain other general additives.

[0112] For example, to adjust the color tone as needed, the masterbatch composition and masterbatch may contain dyes or pigments.

[0113] As dyes and pigments, materials commonly used for coloring thermoplastic resins can be used, such as one or more selected from azo dyes, cyanine dyes, quinoline dyes, perylene dyes, carbon black, etc.

[0114] Furthermore, the masterbatch composition and masterbatch of this embodiment may also contain one or more stabilizers such as hindered phenols and phosphorus-based agents, release agents, ultraviolet absorbers such as hydroxybenzophenones, salicylic acids, HALS, triazoles, and triazines, coupling agents, surfactants, antistatic agents, etc.

[0115] The masterbatch composition and masterbatch of this embodiment contain additives such as dyes, pigments, stabilizers, and release agents, but the amount of these additives is not particularly limited. For example, each additive can be added and included in an amount that is effective in exhibiting a predetermined function. (2-2) Method for producing a masterbatch composition The method for producing a masterbatch composition may include a dispersion preparation step, a surface modification step, a dispersion powder preparation step, and a masterbatch composition preparation step. Each step will be described below.

[0116] (Dispersion Preparation Process) In the dispersion preparation process, the composite tungsten oxide particles and water are mixed, and the composite tungsten oxide particles are crushed and dispersed to prepare the dispersion. In addition, the composite tungsten oxide particles can also be crushed in the dispersion preparation process.

[0117] The composite tungsten oxide particles used in the dispersion preparation process have already been described, so the explanation will be omitted here. The composite tungsten oxide contained in the composite tungsten oxide particles has a hexagonal crystal structure and its general formula is M ｘ WO ｙ It can be expressed as follows.

[0118] The specific method for grinding and dispersing the composite tungsten oxide particles in the dispersion preparation step is not particularly limited, but one or more methods selected from, for example, a bead mill, ball mill, sand mill, or ultrasonic dispersion can be used. The dispersion preparation step can also be carried out in multiple stages, and the composite tungsten oxide particles may be ground and dispersed by multiple steps.

[0119] In the dispersion preparation step, for example, the conditions for grinding and dispersion treatment can be selected so that the average particle size of the composite tungsten oxide particles contained in the dispersion powder obtained after the dispersion powder preparation step or the masterbatch composition preparation step is within a predetermined range. For example, as already explained, the average particle size of the composite tungsten oxide particles is preferably 800 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less. The average particle size of the composite tungsten oxide particles may be, for example, 1 nm or more. (Surface modification step) In the surface modification step, a nonionic polymer dispersant can be added to the dispersion obtained in the dispersion preparation step to modify the surface of the composite tungsten oxide particles.

[0120] The amount of nonionic polymer dispersant added is not particularly limited, but it can be added in an amount of 0.1 parts by mass or more and 150 parts by mass or less per 100 parts by mass of composite tungsten oxide particles. The nonionic polymer dispersant may be added in an amount of 0.1 parts by mass or more and 100 parts by mass or less per 100 parts by mass of composite tungsten oxide particles. The amount of nonionic polymer dispersant added may be 20 parts by mass or more per 100 parts by mass of composite tungsten oxide particles. Therefore, the amount of nonionic polymer dispersant added may be 20 parts by mass or more and 150 parts by mass or 20 parts by mass or more and 100 parts by mass or less per 100 parts by mass of composite tungsten oxide particles.

[0121] In the surface modification step, a nonionic polymer dispersant may be added to the dispersion, and the dispersion may be stirred as needed.

[0122] By performing a surface modification process, an aqueous dispersion, which is a composite tungsten oxide particle dispersion using water as the liquid medium, can be prepared.

[0123] The dispersion preparation process and the surface modification process can be carried out simultaneously. That is, a water dispersion may be prepared by mixing composite tungsten oxide particles, water, and a nonionic polymer dispersant, and then grinding and dispersing the composite tungsten oxide particles. (Dispersion powder preparation process) In the dispersion powder preparation process, the dispersion powder can be prepared by evaporating water from the dispersion after the surface modification process.

[0124] The specific method for evaporating water from the dispersion in the dispersion powder preparation process is not particularly limited. For example, one or more methods selected from natural drying in the atmosphere, heat drying using a dryer, vacuum drying in a vacuum atmosphere, spray drying, etc., can be used. In addition, multiple methods for evaporating water from the dispersion in the dispersion powder preparation process can be combined and carried out in multiple stages as needed.

[0125] The dispersed powder in this embodiment may contain residual moisture from the aqueous dispersion. However, it is preferable that the moisture content of the dispersed powder be low. Specifically, it may be 8% by mass or less, 6% by mass or less, or 5% by mass or less. By reducing the moisture content of the dispersed powder to 8% by mass or less, the moisture can be further reduced by heating during melting and kneading in the masterbatch formation process, thereby keeping the moisture content of the masterbatch low.

[0126] While it is preferable for the dispersion powder of this embodiment to have a low moisture content, it is difficult to completely eliminate moisture from the dispersion powder considering cost and productivity. For this reason, the dispersion powder of this embodiment may contain moisture, and the moisture content of the dispersion powder of this embodiment may be, for example, 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more.

[0127] The moisture content of the dispersed powder in this embodiment may be 0.1% by mass or more and 8% by mass or less, 0.5% by mass or more and 6% by mass or less, or 1% by mass or more and 5% by mass or less. In this specification, the moisture content of the dispersed powder can be calculated by heating the dispersed powder sample at 125°C for 10 minutes and considering the decrease in mass after heating compared to before heating as being due to the moisture contained in the dispersed powder. For example, when heating at 125°C for 10 minutes, if the mass of the dispersed powder sample before heating is W1 and the mass of the dispersed powder sample after heating is W2, the moisture content can be calculated as follows: Moisture content = (W1 - W2) ÷ W1 × 100. (Masterbatch composition preparation step) In the masterbatch composition preparation step, the dispersed powder and the polyamide resin are mixed to prepare the masterbatch composition.

[0128] Suitable mixers for mixing include one or more types selected from ribbon blenders, tumblers, Nauter mixers, Henschel mixers, Super mixers, planetary mixers, and the like.

[0129] If an aqueous dispersion has been prepared in advance, the masterbatch manufacturing method can also be started from the dispersion powder preparation step. Alternatively, if a dispersion powder has been prepared in advance, the masterbatch manufacturing method can also be started from the masterbatch composition preparation step. Any components that can be contained in the masterbatch composition, such as dispersants having carboxyl groups and other additives, can be added at any time, for example, in the dispersion preparation step, surface modification step, or masterbatch composition preparation step. (2-3) Method for manufacturing a masterbatch A masterbatch can be prepared by melting and kneading the masterbatch composition using a melt kneader and processing it into pellets.

[0130] The temperature during melt mixing can be maintained at a temperature that prevents the polyamide resin, which is the solid medium used, from decomposing.

[0131] Suitable kneaders for melt-kneading include single-screw extruders and twin-screw extruders.

[0132] Masterbatch pellets can be obtained by cutting the most common molten extruded strands. Therefore, their shapes can be cylindrical or prismatic. Alternatively, a so-called hot-cut method, where the molten extruded material is cut directly, is also possible. In this case, the masterbatch is generally nearly spherical.

[0133] The masterbatch can take any form or shape. However, it is preferable that the masterbatch has the same or similar size and shape as the thermoplastic resin used to dilute the masterbatch when manufacturing near-infrared absorbing fibers.

[0134] As described above, masterbatch compositions and masterbatches can be made from aqueous dispersions or dispersed powders. Therefore, the content of organic solvents in masterbatch compositions and masterbatches can be reduced. For example, the percentage of residual organic solvents can be reduced to, for instance, 5% by mass or less, 0.1% by mass or less, or even 0% by mass. In other words, it can be reduced to below the detection limit.

[0135] In the masterbatch manufacturing process, the mixture is melted and kneaded, so some of the residual moisture in the dispersed raw material evaporates, and the remainder remains in the masterbatch. The moisture content of the masterbatch is preferably low, and may be 0.8% by mass or less, or 0.6% by mass or less.

[0136] While a low moisture content in the masterbatch is preferable, it may be 0.0001% by mass or more from the viewpoint of cost and productivity. Therefore, the moisture content of the masterbatch may be 0.0001% by mass or more and 0.8% by mass or less, or 0.0001% by mass or more and 0.6% by mass or less.

[0137] When spinning using the masterbatch of this embodiment, the moisture content can be further reduced by keeping the masterbatch dry.

[0138] The moisture content of the masterbatch may be evaluated by the Karl Fischer method with a heating temperature of 160°C. [Textile Products] The textile products of this embodiment are made by processing near-infrared absorbing fibers according to one aspect of the present disclosure, and may include near-infrared absorbing fibers according to one aspect of the present disclosure. The textile products of this embodiment may be composed of the near-infrared absorbing fibers described above, and may also include the near-infrared absorbing fibers of this embodiment and other fibers.

[0139] The amount of composite tungsten oxide particles contained in textile products is 0.02 g / m² per unit area of ​​the textile product. ２ The above is preferable, and 0.03 g / m ２ The above is even more preferable, 0.04 g / m ２ The above is more preferable. The content of composite tungsten oxide particles per unit area of ​​the textile product is 0.02 g / m². ２ By doing so, a sufficient heat-generating effect can be expected when textile products absorb near-infrared rays.

[0140] The amount of composite tungsten oxide particles contained in textile products is 1.0 g / m² per unit area of ​​the textile product. ２ The following may also be true: 0.6 g / m ２ The following is also acceptable: The content of composite tungsten oxide particles per unit area of ​​the textile product is 1.0 g / m². ２ By doing the following, color changes caused by composite tungsten oxides can be reduced. This prevents the development of vivid colors such as yellow and orange in textile products, thereby enhancing their design appeal.

[0141] Therefore, the amount of composite tungsten oxide particles contained in textile products is 0.02 g / m² per unit area of ​​the textile product. ２ 1.0g / m or more ２ It may also be less than 0.03 g / m ２ 1.0g / m or more ２ It may also be less than 0.04 g / m ２ 1.0g / m or more ２ It may also be less than 0.04 g / m ２ 0.6g / m or more ２ The following is also acceptable.

[0142] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. [1] Evaluation method (composition analysis) The composition of the composite tungsten oxide particles was evaluated by the following chemical analysis.

[0143] The mass ratios of Cs and Rb were calculated as the average of three measurements taken for each sample using a polarized Zeeman atomic absorption spectrophotometer (AAS, model: ZA3300, manufactured by Hitachi High-Tech Corporation).

[0144] The mass percentage of W was calculated as the average value obtained by analyzing each sample three times using inductively coupled plasma optical emission spectroscopy (ICP-OES, model: ICPE-9800, manufactured by Shimadzu Corporation).

[0145] The mass percentage of oxygen was determined by using an oxygen, nitrogen, and hydrogen analyzer (ON-836, LECO Japan Corp.) with an infrared detector (IRS) for oxygen detection, and the average value was obtained by analyzing each sample three times. (Crystal structure, crystallite size, average particle size) For the measurement of the crystal structure of the composite tungsten oxide particles obtained in the following examples and comparative examples, composite tungsten oxide particles after the heat treatment process were used.

[0146] For measuring the crystallite size, composite tungsten oxide particles obtained by removing the liquid medium from a dispersion of composite tungsten oxide particles were used.

[0147] To measure the crystal structure and crystallite size of the composite tungsten oxide particles, the X-ray diffraction pattern of the composite tungsten oxide particles was measured. The X-ray diffraction pattern was measured using powder X-ray diffraction (θ-2θ method) with a powder X-ray diffractometer (X'Pert-PRO / MPD manufactured by PANallytical, Spectris Corporation). From the obtained X-ray diffraction pattern, the crystal structure of the composite tungsten oxide contained in the composite tungsten oxide particles was identified, and the crystallite size was further calculated using the Rietveld method.

[0148] The average particle size of the composite tungsten oxide particles was measured and calculated using the methods and conditions already described, so the explanation is omitted. [2] Examples and comparative examples [Example 1] (1) Production of composite tungsten oxide particles (heat treatment process) After preparing the starting material according to the following procedure, the starting material was subjected to a heat treatment process to produce composite tungsten oxide particles.

[0149] 39.9g of water and Cs ２ CO ３ Dissolve 17.7g and add H ２ WO ４ It was added to 82.3 g and dried in a vacuum dryer while stirring. The resulting dried powder a was then N ２ 5 volume% H with gas as carrier ２ After firing at a temperature of 550°C for 1 hour under a gas atmosphere, N ２ Particle a was obtained by firing at 800°C for 1 hour under a gas atmosphere.

[0150] Particle a has a composition of Cs, according to chemical analysis. ０．３３ WO ２．４５ The measured powder X-ray diffraction pattern was hexagonal Cs ０．３ WO ３The X-ray diffraction pattern matched that of the hexagonal crystal structure. (2) Production of the masterbatch composition (Dispersion preparation step) Next, particles a were weighed in a ratio of 15% by mass and water in a ratio of 85% by mass. The weighed material was pulverized and dispersed for 14 hours in a paint shaker containing 0.3 mmφ ZrO2 beads to prepare a composite tungsten oxide particle dispersion (Solution A). The crystallite size of the composite tungsten oxide particles in Solution A was measured to be 32.2 nm. The average particle size was 34.8 nm. (Surface modification step) Next, polyvinylpyrrolidone (average molecular weight 45,000), a nonionic polymer dispersant, was added to Solution A in a ratio of 12% by mass relative to particles a, and the mixture was held for 10 hours while stirring. Through this operation, an aqueous dispersion containing composite tungsten oxide particles surface-treated with a nonionic polymer dispersant was obtained (hereinafter also referred to as "Solution A1"). (Dispersion powder preparation process) Subsequently, water was removed from liquid A1 using a large vacuum grinder to obtain a composite tungsten oxide particle dispersion powder (dispersion powder A). The moisture content of dispersion powder A after drying at 125°C for 10 minutes using a heating and drying type moisture meter MX-50 (manufactured by A&D Co., Ltd.) was 4.7% by mass.

[0151] Dispersion powder A, which was prepared in this embodiment, and the dispersion powders prepared and used in the following other embodiments, have been confirmed to disperse in water and become aqueous dispersions again when water is added. (Masterbatch composition preparation process) The obtained dispersion powder A and nylon 6 resin pellets were uniformly mixed using a blender to prepare a masterbatch composition. (3) Production of the masterbatch The masterbatch composition, which is the mixture obtained in the masterbatch composition preparation process, was melt-kneaded at 270°C using a twin-screw extruder, and the extruded strands were cut into pellets with a pelletizer. The obtained masterbatch had a composite tungsten oxide particle concentration of 3.0% by mass (hereinafter also referred to as "masterbatch A"). At this time, the moisture content measured by the Karl Fischer method (heating temperature 160°C) was 0.38% by mass.

[0152] The content of each component in the masterbatch is as shown in the Masterbatch column of Table 1. (4) Production of near-infrared absorbing fibers and textile products (Near-infrared absorbing fiber production process) The obtained masterbatch A was melt-spun and then drawn to produce nylon multifilament yarn A, which is a near-infrared absorbing fiber.

[0153] The obtained nylon multifilament yarn A was cut to produce nylon staples, which were then used to manufacture spun yarn a. Since spun yarn a was manufactured using masterbatch A, the content of composite tungsten oxide particles is 3.0% by mass.

[0154] Then, by knitting this spun yarn a, a knitted product sample according to Example 1, which has heat retention properties, was obtained. The solar reflectance of the prepared knitted product sample was adjusted to 8%. The adjustment of the solar reflectance of the knitted product sample to 8% was performed in all of the examples and comparative examples described later.

[0155] The spectral characteristics of the fabricated knit product samples were measured using a Hitachi U-4100 spectrophotometer to determine the transmittance and reflectance of light in the wavelength range of 200 nm to 2100 nm. The solar absorptance was calculated according to JIS A 5759:2016. The solar absorptance was calculated using the following formula (1).

[0156] The calculated solar absorptance was 51.8%. The measurement results for the knitted product sample are shown in the "Knitted Product Sample" column of Table 1. Table 1 also includes the measurement results for Examples 2 to 9, which will be described later. In Table 1, the content of composite tungsten oxide particles per unit area in the knitted product sample is shown in the "Composite Tungsten Oxide Particles" column under the "Knitted Product Sample" column.

[0157] Next, the temperature rise effect on the reverse side of the fabric of the prepared knitted product sample was measured as follows.

[0158] Under conditions of 20°C and 60% RH, a solar approximation spectrum lamp (Solar Simulator XL-03E50 modified, manufactured by Seric Co., Ltd.) was irradiated from a distance of 30 cm from the fabric of the knitted product sample. The temperature of the back surface of the fabric was measured using a radiation thermometer (HT-11, manufactured by Minolta, Inc.) before irradiation and 10 minutes after the start of irradiation. The measurement results are shown in the "Knitted Product Sample Temperature" column of Table 1. The value shown in the "Before Irradiation" column is the temperature of the back surface of the fabric before irradiation, and the value shown in the "10 Minutes After Irradiation" column is the temperature of the back surface of the fabric 10 minutes after the start of irradiation. Table 1 also includes the measurement results for Examples 2 to 9, which will be described later. [Example 2] When preparing the starting material to be subjected to the heat treatment process in order to prepare composite tungsten oxide particles, Rb was used as the element M raw material. ２ CO ３ H as a tungsten raw material ２ WO ４ We used Rb. ２ CO ３ and H ２ WO ４ The two materials were weighed and mixed so that the molar ratio Rb / W = 0.33, and used as the starting material.

[0159] Except for using the above-mentioned starting materials, near-infrared absorbing fibers and knit product samples were manufactured and evaluated under the same conditions and procedures as in Example 1. The crystallite size measured for the composite tungsten oxide particles in the dispersion preparation step was 32.4 nm, and the average particle size was 35.1 nm. In Example 2, the moisture content of the dispersed powder measured by drying at 125°C for 10 minutes using a heat-drying type moisture meter MX-50 was 4.9% by mass. The moisture content of the masterbatch manufactured using the dispersed powder, measured by the Karl Fischer method (heating temperature 160°C), was 0.38% by mass.

[0160] The evaluation results are shown in Table 1. [Example 3] In the surface modification step, polyvinylpyrrolidone was added at a concentration of 70% by mass relative to particle a. In the masterbatch composition preparation step, dispersion powder C, which is the dispersion powder obtained in the dispersion powder preparation step of this example, and nylon 6 resin pellets were added so that the composite tungsten oxide particle concentration was 1.0% by mass, and the mixture was uniformly mixed in a blender. The mixture obtained in the masterbatch composition preparation step was melt-kneaded in a twin-screw extruder, and the extruded strands were cut in a pelletizer to obtain a masterbatch. In all other respects, nylon multifilament yarn and knit product samples according to Example 3 were obtained and evaluated under the same conditions and procedures as in Example 1. In Example 3, the moisture content of dispersion powder C measured by drying at 125°C for 10 minutes using a heated drying type moisture meter MX-50 was 4.8% by mass. The moisture content of the masterbatch produced using dispersion powder C measured by the Karl Fischer method (heating temperature 160°C) was 0.37% by mass.

[0161] The evaluation results are shown in Table 1. [Example 4] Except for using nylon 66 resin pellets instead of nylon 6 resin pellets in the masterbatch composition preparation process, nylon multifilament yarn and knit product samples according to Example 4 were obtained and evaluated under the same conditions and procedures as in Example 3. In Example 4, the moisture content of the dispersed powder measured by drying at 125°C for 10 minutes using a heat-drying type moisture meter MX-50 was 4.8% by mass. The moisture content of the masterbatch produced using the dispersed powder, measured by the Karl Fischer method (heating temperature 160°C), was 0.37% by mass.

[0162] The evaluation results are shown in Table 1. [Example 5] The dried powder a obtained in Example 1 was N ２ 5 volume% H with gas as carrier ２ It was fired at a temperature of 570°C for 1 hour under a gas atmosphere. Then, N ２ The material was calcined at 800°C for 1 hour in a 1 volume% air atmosphere using gas as a carrier, and then further treated with N ２ Particle e was obtained by calcining at 820°C for 0.5 hours under a gas atmosphere. Chemical analysis revealed that particle e has a composition of Cs ０．２７ WO ２．８６The measured powder X-ray diffraction pattern was hexagonal Cs ０．３ WO ３ The X-ray diffraction pattern matches that of the sample, confirming that it has a hexagonal crystal structure.

[0163] Except for using particle e, nylon multifilament yarn and knitted product samples according to Example 5 were obtained and evaluated using the same procedure and conditions as in Example 4. The crystallite size of the composite tungsten oxide particles was 32.2 nm. The average particle size was 34.7 nm. In Example 5, the moisture content of the dispersed powder measured by drying at 125°C for 10 minutes using a heat-drying type moisture meter MX-50 was 4.6% by mass. The moisture content of the masterbatch produced using the dispersed powder, measured by the Karl Fischer method (heating temperature 160°C), was 0.36% by mass.

[0164] The evaluation results are shown in Table 1. [Example 6] A hybrid plasma reactor was used, which superimposed DC plasma and high-frequency plasma. The reaction system was evacuated to approximately 0.1 Pa (approximately 0.001 torr) using a vacuum pump, and then completely replaced with argon gas to create a flow system at 1 atmosphere. Subsequently, 8 L / min of argon gas was flowed from the plasma generation gas supply port to generate DC plasma. The DC power input at this time was 6 kW. Furthermore, 40 L / min of argon gas and 3 L / min of hydrogen gas were flowed spirally from the sheath gas supply port along the inner wall of the water-cooled quartz tube as gases for generating high-frequency plasma and protecting the quartz tube, and high-frequency plasma was generated. The high-frequency power input at this time was 45 kW. After generating the hybrid plasma in this way, a mixed gas of 3 L / min of argon gas and 0.15 L / min of oxygen gas was used as a carrier gas, and the dried powder a obtained in Example 1 was supplied into the plasma at a rate of 2 g / min from the raw material powder supply device. As a result, the raw material instantly evaporated, condensed in the plasma tail flame, and was pulverized to obtain particle f. Chemical analysis of particle f revealed that its composition is Cs ０．３１ WO ３．２１ The measured powder X-ray diffraction pattern was hexagonal Cs ０．３ WO ３ The X-ray diffraction pattern matches that of the sample, confirming that it has a hexagonal crystal structure.

[0165] Except for using particle f, nylon multifilament yarn and knitted product samples according to Example 6 were obtained and evaluated using the same procedure and conditions as in Example 4. The crystallite size measured for the composite tungsten oxide particles in the dispersion preparation step was 24.6 nm. The average particle size was 27.0 nm. In Example 6, the moisture content of the dispersed powder measured by drying at 125°C for 10 minutes using a heat-drying type moisture meter MX-50 was 4.4% by mass. The moisture content of the masterbatch produced using the dispersed powder, measured by the Karl Fischer method (heating temperature 160°C), was 0.36% by mass.

[0166] The evaluation results are shown in Table 1. [Example 7] In the masterbatch composition preparation process, dispersion powder C, nylon 66 powder, and a dispersant having carboxyl groups were uniformly mixed using a blender. At this time, both components were added so that the content ratio of the composite tungsten oxide particles was 1.0% by mass relative to the total amount of nylon 66 powder and composite tungsten oxide particles. In addition, a dispersant having carboxyl groups (dropping point > 75°C, heat resistance temperature 300°C, density 1 g / cm³) was added. ３ The compound was added in such a manner that it amounted to 30.0% by mass relative to the composite tungsten oxide particles. Except for the points mentioned above, nylon multifilament yarn and knit product samples according to Example 7 were obtained and evaluated using the same procedure and conditions as in Example 4. Note that the percentage of carboxyl group-containing dispersants contained in the masterbatch is omitted from Table 1. The moisture content of the masterbatch produced in Example 7, measured by the Karl Fischer method (heating temperature 160°C), was 0.37% by mass.

[0167] The evaluation results are shown in Table 1. [Example 8] Except for adding dispersed powder C and nylon 6 resin pellets in the masterbatch composition preparation step so that the composite tungsten oxide particle concentration was 0.1% by mass, nylon multifilament yarn and knit product samples according to Example 8 were obtained and evaluated under the same conditions and procedures as in Example 3. The moisture content of the masterbatch produced in Example 8, measured by the Karl Fischer method (heating temperature 160°C), was 0.35% by mass.

[0168] The evaluation results are shown in Table 1. [Example 9] Nylon 6 powder was used instead of nylon 66 powder. Except for the above, nylon multifilament yarn and knit product samples according to Example 9 were obtained and evaluated under the same conditions and procedures as Example 7. The moisture content of the masterbatch, measured by the Karl Fischer method (heating temperature 160°C), was 0.36 wt%.

[0169] The evaluation results are shown in Table 1. [Comparative Example 1] Except for the fact that polyvinylpyrrolidone was not added in the dispersion preparation step and the surface modification step, and the masterbatch was formulated as shown in Table 1, the near-infrared absorbing fiber and knit product samples were attempted to be manufactured under the same conditions and procedures as in Example 1.

[0170] However, the masterbatch obtained in Comparative Example 1 showed significant color unevenness in its visual appearance, and the dispersibility of the composite tungsten oxide particles was poor, making spinning impossible. [Comparative Example 2] In the surface modification step, cetyltrimethylammonium chloride was added to the composite tungsten oxide particle dispersion (Solution A) prepared in Example 1 at a ratio of 10% by mass relative to the composite tungsten oxide particles, and the mixture was held for 6 hours while stirring. Through the above operation, an aqueous dispersion containing composite tungsten oxide particles surface-modified with cetyltrimethylammonium chloride, an ammonium salt that acts as a cationic dispersant, was obtained (Solution K1).

[0171] Using a large vacuum grinder, water was removed from liquid K1 to obtain a composite tungsten oxide particle dispersion powder (hereinafter also referred to as "dispersion powder K").

[0172] A masterbatch was prepared under the same conditions and procedure as in Example 1, except that dispersed powder K was used.

[0173] Visual inspection of the masterbatch obtained in Comparative Example 2 revealed significant color unevenness, and it was determined that the dispersibility of the composite tungsten oxide particles was poor, so the near-infrared absorbing fibers were not produced. [Reference Example] In the surface modification step, polyvinylpyrrolidone was added at a concentration of 11% by mass relative to particle a. Except for the above, the dispersion according to the reference example was prepared under the same conditions and procedures as in Example 1.

[0174] However, during the masterbatch manufacturing process, some of the composite tungsten oxide particles aggregated. While this did not pose a problem in product manufacturing, it resulted in slight color unevenness, and therefore, near-infrared absorbing fibers were not produced. It has been confirmed that the above aggregation can be reduced by adjusting the amount of composite tungsten oxide particles added and the melting and kneading conditions during masterbatch manufacturing.

[0175] As shown in Table 1 above, the near-infrared absorbing fibers of Examples 1 to 9 had a solar absorptance of 20% or more, and in particular, the near-infrared absorbing fibers of Examples 1 to 7 and Example 9 were confirmed to have a solar absorptance of 48% or more.

[0176] Furthermore, when a test was conducted to assess the effect of raising the temperature on the back surface of the fabric, the fabric temperature of Examples 1 to 9 increased by 23°C or more, confirming excellent heat generation properties. [Note] The embodiments of this disclosure are, for example, as follows.

[0177] (1) A nonionic polymer dispersant, composite tungsten oxide particles, and a polyamide resin, wherein the composite tungsten oxide particles have a hexagonal crystal structure and are of general formula M ｘ WO ｙ A near-infrared absorbing fiber containing a composite tungsten oxide represented by (wherein element M includes one or more elements selected from Cs and Rb, and x and y satisfy 0.1 ≤ x ≤ 1.0 and 2.0 ≤ y < 4.0).

[0178] (2) The near-infrared absorbing fiber according to (1), wherein the content of the composite tungsten oxide particles is 0.001% by mass or less and 80% by mass or less.

[0179] (3) The near-infrared absorbing fiber according to (1) or (2), further comprising a dispersant having a carboxyl group.

[0180] (4) A near-infrared absorbing fiber according to any one of (1) to (3), wherein the amount of residual organic solvent is 5% by mass or less.

[0181] (5) A textile product containing a near-infrared absorbing fiber as described in any of (1) to (4).

[0182] (6) The content of the composite tungsten oxide particles is 0.02 g / m² per unit area of ​​the textile product. ２ The above is the textile product described in (5).

[0183] This application claims priority based on Japanese Patent Application No. 2024-181314, filed with the Japan Patent Office on 16 October 2024, and Japanese Patent Application No. 2025-060804, filed with the Japan Patent Office on 1 April 2025, and the entire contents of Japanese Patent Application No. 2024-181314 and Japanese Patent Application No. 2025-060804 are incorporated herein by reference.

[0184] 11 Fiber 11A Surface 11B Interior 12 Composite tungsten oxide particles CA Central axis

Claims

1. A nonionic polymer dispersant, composite tungsten oxide particles, and a polyamide resin, wherein the composite tungsten oxide particles have a hexagonal crystal structure and are of general formula M ｘ WO ｙ A near-infrared absorbing fiber containing a composite tungsten oxide represented by (wherein element M includes one or more elements selected from Cs and Rb, and x and y satisfy 0.1 ≤ x ≤ 1.0 and 2.0 ≤ y < 4.0).

2. The near-infrared absorbing fiber according to claim 1, wherein the content of the composite tungsten oxide particles is 0.001% by mass or less (80% by mass or less).

3. The near-infrared absorbing fiber according to claim 1 or claim 2, further comprising a dispersant having a carboxyl group.

4. The near-infrared absorbing fiber according to any one of claims 1 to 3, wherein the amount of residual organic solvent is 5% by mass or less.

5. A textile product comprising a near-infrared absorbing fiber according to any one of claims 1 to 4.

6. The content of the composite tungsten oxide particles is 0.02 g / m² per unit area of ​​the textile product. ２ The textile product according to claim 5.

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