Textile structures and methods for dyeing them

Abstract

This invention provides a fiber structure and a dyeing method thereof that increase the amount of dye absorbed by graft polymerization of monomers whose ionic and nonionic states can be controlled by pH, thereby enabling efficient reaction of reactive dyes during the dye fixing stage and reducing uneven dyeing. [Solution] The fiber structure includes modified cellulose fibers, in which compounds containing pH-responsive groups and ethylenically unsaturated double bond groups are grafted onto the modified cellulose fibers, and the fiber structure is dyed with a reactive dye. The dyeing method involves grafting compounds containing pH-responsive groups and ethylenically unsaturated double bond groups onto cellulose fibers to create modified cellulose fibers, and then dyeing them with a reactive dye. The solution is kept acidic or neutral to allow the reactive dye to be absorbed by the fibers, and then the dyeing solution is kept basic to fix the dye.

Description

[Technical Field]

[0001] This invention relates to a fibrous structure containing cellulose fibers and a method for dyeing the same. [Background technology]

[0002] Efficient methods for using dyes in textile dyeing have been studied for many years. Various methods have been employed to reduce the amount of dye used on the fibers, increase the fixation rate of the dye, and prevent dye fading. Traditionally, direct dyes and anionic dyes such as reactive dyes have been used to dye cellulose fibers such as cotton. In response to this, cationization of cellulose fibers has been proposed with the aim of improving the dyeability of cellulose fibers (specifically, shortening dyeing time and reducing dye loss). For example, Patent Document 1 describes a method and system for cationizing and dyeing natural fiber-containing textiles, and proposes a method of steam treatment of a textile padded with a base and a cationizing agent (bisetherhaled dihydroxylylated ammonium compound) at a predetermined temperature range (over 100°C to under 110°C) and for a predetermined time (1 to 10 minutes). Patent Document 2 proposes a method for treating cellulose fibers, which includes the step of contacting the cellulose fibers with a solution containing a wetting agent, an alkaline composition, and an ammonium salt. Patent Document 3 proposes a method for producing cellulose fibers with modified dyeability, which involves polymerizing monomers containing quaternary amines and having unsaturated double bonds within the cellulose fibers. This method allows the cation moieties (e.g., quaternary ammonium structures) introduced into the cellulose fibers to ionically bond with the anionic dyes, thereby firmly dyeing the cellulose fibers. This shortens the dyeing time, reduces dye loss, and lowers the environmental burden. Patent Document 4 describes a method for producing post-dyed melange yarn made from cellulose fibers, which involves cationizing cellulose fibers in the form of cotton, sliver, or yarn, spinning the processed cellulose fibers and unprocessed cellulose fibers separately, then twisting them together, and finally dyeing them. This method utilizes the difference in dyeability caused by the cationization treatment to produce melange yarn. It has been known for some time that there is a difference in dyeability between cationized cellulose fibers and unprocessed fibers, resulting in uneven yarn. Patent Document 5 proposes a uniform dyeing agent to improve uniformity when dyeing cationized cellulose fibers. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2023-512662 [Patent Document 2] Special Publication No. 2016-511331 [Patent Document 3] Japanese Patent Application Publication No. 55-12826 [Patent Document 4] Japanese Patent Application Publication No. 9-87969 [Patent Document 5] Japanese Patent Publication No. 2021-46634 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, the aforementioned conventional technology had a problem in that when a quaternary ammonium salt was introduced into the fibers and mixed into the fiber structure, uneven dyeing tended to occur between the fibers in which the salt was introduced and those that were not.

[0005] To solve the above problems, the present invention provides a fiber structure and a dyeing method thereof in which monomers whose ionic and nonionic states can be controlled by pH are graft polymerized onto fibers, thereby increasing the amount of dye absorbed into the fibers, increasing the dye concentration near the dyeing surface during the dye fixing stage, thereby enabling efficient reaction of the reactive dye, and reducing uneven dyeing. [Means for solving the problem]

[0006] One embodiment of the present invention relates to a fiber structure comprising modified cellulosic fibers, wherein the modified cellulosic fibers are grafted with compounds containing pH-responsive groups and ethylenically unsaturated double bond groups.

[0007] Another embodiment of the present invention relates to a dyeing method using the aforementioned fibrous structure, wherein a modified cellulose fiber is formed by grafting a compound containing a pH-responsive group and an ethylenically unsaturated double bond group onto a cellulose fiber, and the fibrous structure containing the modified cellulose fiber is dyed with a reactive dye, wherein the dyeing solution is kept acidic or neutral to allow the reactive dye to be absorbed by the fibrous structure containing the modified cellulose fiber, and then the dyeing solution is kept basic to fix the dye. [Effects of the Invention]

[0008] In the fiber structure of the present invention, the modified cellulose fibers are grafted with a compound containing a pH-responsive group and an ethylenically unsaturated double bond group. This allows for the control of the ionic and nonionic states of the compound depending on the pH of the solution, enabling efficient reaction with reactive dyes, reducing uneven dyeing, and providing a uniformly dyed fiber structure.

[0009] Furthermore, the dyeing method of the present invention, when dyeing a fiber structure containing the modified cellulose fibers with a reactive dye, involves first maintaining the dyeing solution at an acidic or neutral pH to allow the reactive dye to be absorbed by the modified cellulose fibers, and then maintaining the dyeing solution at a basic pH to react the dye and dye the material. This allows for efficient reaction of the reactive dye and reduces uneven dyeing. Specifically, in the dye adsorption step (primary absorption step), the dyeing solution is made acidic or neutral to allow the dye to be absorbed by the fiber structure, and then in the dye fixing step, the dyeing solution is made basic. This allows the dye to covalently bond with the dyeing surface, and at the same time, the ionic bond with the ionized tertiary amine is broken, enabling efficient reaction of the reactive dye. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is an explanatory diagram showing a typical dyeing process using a reactive dye according to one embodiment of the present invention. [Figure 2] Figure 2 is a graph showing the absorption curve and fixation curve of a reactive dye according to one embodiment of the present invention. [Figure 3] Figure 3 is an explanatory diagram showing the conditions for the dyeing process of a reactive dye according to one embodiment of the present invention. [Modes for carrying out the invention]

[0011] The present invention includes modified cellulose fibers that can be dyed with reactive dyes. Reactive dyes are anionic, water-soluble dyes that have a reactive group in the dye molecule that can chemically bond with functional groups in the fiber, such as hydroxyl groups (-OH) in the case of cellulose fibers, and that chemically react with the functional groups in the fiber during the dyeing process to form covalent bonds. The basic structure of a reactive dye is represented as D (pigment matrix)-X (linking group)-R (reactive group). D (pigment matrix) is an anionic group (e.g., sulfonic acid group (-SO3)). - It contains ). Reactive dyes include, for example, sulfatoethylsulfone (vinylsulfone), S-triazine, and pyrimidine compounds. Reactive dyes are applied to cellulose fibers such as cotton, rayon, and linen, as well as wool and nylon fibers.

[0012] The modified cellulose fiber of the present invention has a graft bond of a compound containing a pH-responsive group and an ethylenically unsaturated double bond group (hereinafter also referred to as "graft monomer"). As an example, the pH-responsive group is preferably a tertiary amino group. The tertiary amino group is cationized in an acidic or neutral solution and neutralized to a tertiary amino group in a basic solution. Here, neutralization refers to the non-ionized state of the molecule. The acid dissociation constant pKa of the graft monomer is preferably 7 to 10. If the pKa is small, the effect of attracting a dye having an anionic group by neutralization even in a neutral solution is reduced. If the pKa of the graft monomer is large, it exists as a cation even in a basic solution, and the ionic bond with the dye cannot be cleaved well, which may cause uneven dyeing.

[0013] As the ethylenically unsaturated double bond group, for example, a methacryl group, an acryl group, an itacon group, a malein group, a fumar group or a vinyl group is preferable. Particularly preferred are a methacryl group, an acryl group or a vinyl group. The ethylenically unsaturated double bond of these compounds is cleaved and graft-bonded to the surface of the cellulose fiber.

[0014] The graft monomer is preferably a tertiary amine shown in the following (Chemical Formula 1). However, R 1 is a methyl group or a hydrogen atom, R 2 is a hydrocarbon chain having 1 to 4 carbon atoms, R 3 and R 4 are hydrocarbon groups having 1 to 4 carbon atoms or R 3 and R 4 is an organic group in which a carbon chain having 4 or 5 carbon atoms connects them to form a heterocyclic ring. The neutral form is a tertiary amine as shown in the following (Chemical Formula 2), and the cationized form is a quaternary ammonium salt as shown in the following (Chemical Formula 2).

Chemical Formula

Chemical Formula

[0015] Preferred monomers include, specifically, 2-diethylaminoethyl (meth)acrylate, 2-dimethylaminoethyl (meth)acrylate, 2-dipropylaminoethyl (meth)acrylate, 2-dibutylaminoethyl (meth)acrylate, 2-pyrrolidinoethyl (meth)acrylate, 2-piperidinoethyl (meth)acrylate, diethylaminomethyl (meth)acrylate, dimethylaminomethyl (meth)acrylate, dipropylaminomethyl (meth)acrylate, dibutylaminomethyl (meth)acrylate, pyrrolidinomethyl (meth)acrylate, or piperidinomethyl (meth)acrylate. In this specification, the notation 2-diethylaminoethyl (meth)acrylate encompasses both 2-diethylaminoethyl acrylate and 2-diethylaminoethyl methacrylate. The polymer of the graft monomer, poly(2-diethylamino)ethyl methacrylate, has an acid dissociation constant (pKa) of approximately 8.3, and the transfer of protons switches at this pKa. In other words, the polymer accepts protons and becomes cationized in the dye adsorption process (primary exhaustion process) under acidic or neutral conditions, and releases protons and becomes neutral in the dye fixation process under basic conditions. The ionic bond with the dye disappears, and the dye is thought to freely adhere to the dyeing surface by covalent bonds.

[0016] In the case of 2-diethylaminoethyl acrylate, the neutral form is a tertiary amine as shown in (Chemical Formula 3) below, and the cationized form is a quaternary ammonium salt as shown in (Chemical Formula 4) below. [ka] [ka]

[0017] The dyeing process begins by maintaining the dye solution at an acidic or neutral pH to cationize the pH-responsive groups, allowing the fibrous structure containing the modified cellulose fibers to absorb the reactive dye. Here, the presence of cations in the cellulose fiber structure attracts the reactive dye with anionic groups to the cations, increasing the amount of dye absorbed compared to unmodified cellulose fibers, and raising the dye concentration near the dyeing surface. Next, by making the dyeing solution basic and neutralizing the pH-responsive groups, the reactive dye attracted to the cations becomes free near the dyeing surface, and at the same time, the reaction between the hydroxyl groups (-OH) of the fibers and the reactive dye begins, fixing the dye to the fibers and dyeing them. As a result, a fiber structure is dyed more efficiently compared to unmodified cellulose fibers.

[0018] Both the quaternary ammonium salts of the conventional technology and the tertiary amines used as graft monomers in the present invention attract dyes to the vicinity of the fibers, allowing for more efficient dye binding to the fibers. However, when using quaternary ammonium salts as graft monomers, uneven dyeing occurs due to the large difference in dye adsorption capacity between the modified and unmodified portions. Therefore, using the graft monomers of the present invention reduces uneven dyeing by moving the dye, which is concentrated on the cations, to the dyeing area, resulting in a more uniformly dyed fiber structure.

[0019] It is preferable that 0.5 to 30 parts by mass of the compound containing the pH-responsive group and the ethylenically unsaturated double bond group be grafted onto 100 parts by mass of cellulose fiber, more preferably 0.5 to 20 parts by mass, and even more preferably 0.5 to 15 parts by mass.

[0020] Cellulose fibers include natural fibers such as cotton and linen, and regenerated fibers such as rayon. Of these, cotton is preferred because of its versatility as clothing.

[0021] The fibrous structure may include modified cellulose fibers and other fibers. Other fibers include unmodified cellulose fibers, wool, silk, polyester fibers, nylon fibers, acrylic fibers, etc. The fiber form may be short fibers or filament fibers. It is preferable to mix the modified cellulose fibers and other fibers by blending, blending, weaving, or knitting. Any method can be used for blending, such as blended cotton blending, carded blending, drawn strip blending, or sliver blending. Fiber structures include cotton, fiber bundles, yarn, woven fabrics, knitted fabrics, or nonwoven fabrics.

[0022] When a fibrous structure is composed of modified cellulose fibers and unmodified cellulose fibers, it is preferable to use 5 to 50% by mass of modified cellulose fibers and 50 to 95% by mass of unmodified cellulose fibers. With the above ratio, both improved dyeing efficiency and reduced dyeing unevenness can be achieved.

[0023] The method for producing the fibrous structure of the present invention includes the following steps. (1) Grafting process Cellulose fibers are modified by grafting graft monomers onto them. Methods for grafting include, for example, irradiation with an electron beam or cleaving the ethylenically unsaturated double bond group using a catalyst. In the electron beam irradiation method, the cellulose fibers (cotton, fiber bundles (sliver), spun yarn, woven fabric, knitted fabric, or nonwoven fabric) are irradiated with an electron beam under a nitrogen gas atmosphere using an electron beam irradiation device. Electron beam irradiation can be performed either before or after (or simultaneously with) the application of the graft monomer, but irradiation under a nitrogen atmosphere is preferable because the generated radicals are less likely to be deactivated. Before, after, or simultaneously with the radical generation step, the material is brought into contact with a solution containing the graft monomer. Methods for contact include immersion, pad application, spraying, and printing, all of which can be used. Graft bonds are formed through a variety of reactions, including a reaction that generates radicals on the surface of cellulose fibers by means of electron beam irradiation, a reaction that grafts onto the surface of cellulose fibers by contacting the generated radicals with graft monomers, and a reaction in which further monomers are bonded by the radicals generated on the monomers. When a catalyst is used, radical-generating catalysts such as platinum, palladium, cerium ammonium nitrate, benzoyl peroxide, and azobisisobutyronitrile are used to cleave the ethylenically unsaturated double bond group. Afterward, rinse and wring out the water according to the usual method, and then dry. (2) Blending process This process can be appropriately adopted or omitted depending on the form of the fiber structure attached to the grafting process. The fiber structure containing modified cellulose fibers can be transformed into another form of fiber structure. For example, a fiber structure in the form of yarn can be made by blending or fusing modified cellulose fibers, or a fiber structure in the form of yarn, using yarn containing modified cellulose fibers. For example, a fiber structure in the form of fabric such as woven or knitted fabric can be made using yarn containing modified cellulose fibers. (3) Dyeing process When dyeing a fiber structure containing modified cellulose fibers with a reactive dye, the dyeing solution is kept acidic or neutral to allow the reactive dye to be absorbed by the fiber structure containing the modified cellulose fibers. Then, the dyeing solution is kept basic to allow the fiber structure containing the modified cellulose fibers to react with the reactive dye, fixing the dye to the dye-fixing sites (hydroxyl groups: -OH) in the cellulose fibers and dyeing the structure. Afterward, rinse and wring out the water according to the usual method, and then dry.

[0024] The following explanation will be given using the drawings. Figure 1 is an explanatory diagram showing a general dyeing process of a reactive dye according to one embodiment of the present invention. In the absorption process (primary exhaustion process, dye adsorption process), as an example, sodium sulfate (Na2SO4) is added to maintain an acidic or neutral state, allowing the dye to be absorbed into the fibers. Subsequently, in the fixing process (dye fixing process), as an example, soda ash is added to maintain a basic state, allowing the reactive dye to react with the fiber structure containing modified cellulose fibers, and the dye is fixed to the dyeing sheets (hydroxyl groups: -OH) in the cellulose fibers, resulting in dyeing. After that, a soaping agent is added to remove unreacted dye from the fibers, and after washing and dewatering, the fibers are dried.

[0025] Figure 2 is a graph showing the absorption curve and fixation curve of a reactive dye according to one embodiment of the present invention, and Figure 3 is an explanatory diagram showing the conditions of the dyeing process of the reactive dye according to one embodiment of the present invention. The dye is added to water at 40°C and stirred, the fabric is immersed in the bath at a bath ratio of 1:20 and held for 10 minutes, sodium sulfate (Na2SO4) is added to maintain an acidic or neutral state and held for 10 minutes, soda ash (sodium carbonate: Na2CO3) is added to maintain an alkaline state, the temperature is raised to 60°C and held at 60°C for 40 minutes. The absorption curve of the dye is shown by the dashed line in Figure 2, and the fixation curve is shown by the solid line. As shown by the solid fixation curve, when the state is maintained in an alkaline state, the reaction between the dye and the dyeing agent begins, and the fixation of the dye proceeds rapidly. After that, a soaping agent is added to remove the fibers and unreacted dye, and after rinsing and dewatering, the fabric is dried. Another example of the conditions for the dyeing process with reactive dyes is to put water, dye, and Glauber's salt into the dyeing pot of the dyeing machine at room temperature, and if using a leveling agent, add 1 cc / L at this time. Then add the fabric and gradually raise the temperature to 60°C over about 10 minutes, and stir for 20 minutes. After that, add the alkaline agent and dye at the same temperature for 40 minutes while stirring well. [Examples]

[0026] The following will be explained using examples. However, the present invention is not limited to the following examples. (Example 1) <Grafting onto fabric> A plain weave fabric made using 40-count (cotton count) single yarns for both warp and weft has a mass per unit area (basis weight) of 122.5 g / m². 2 It uses 100% bleached cotton fabric. A fabric sample of 250 mm in length and 150 mm in width (about 4.5 g) was taken from the base fabric. On one surface of this fabric, an electron beam irradiation device of the electro-curtain type (EC250 / 30 / 90L manufactured by Iwasaki Electric Co., Ltd.) was used to irradiate the fabric with an electron beam under a nitrogen gas atmosphere at an acceleration voltage of 200 kV and an irradiation dose of 40 kGy. Then, it was placed in a container and immersed in a solution containing (2-diethylamino)ethyl methacrylate (graft monomer) shown in (Chemical Formula 1) at a bath ratio of 1:20 for 20 minutes for graft reaction. After that, the fabric was taken out of the container, washed with water, and air-dried. The grafting rate was calculated as 100×[(A - B) / B (%)] from the mass (A) of the processed sample and the mass (B) of the sample before processing, and it was 15.2%. <Dyeing process for the fabric> (1) Dyeing solution The dyeing solution was composed of water and 1.0% o.w.f of a reactive dye (C.I Reactive Red 195, Sumifix Supra Brilliant Red 3BF liquid 40%), and sodium sulfate (Na2SO4) was made into a 1.4 mass% aqueous solution. (2) Dyeing conditions The fabric was immersed in the above dyeing solution in a dyeing machine, heated to 60°C, and the dye was adsorbed onto the fabric at 60°C for 20 minutes (dye adsorption step). Then, an alkali agent (Esporon A-171 (Lion Specialty Chemicals Co., Ltd.)) was added, and the reaction was carried out at 60°C for 40 minutes (dye fixation step). After that, the dyeing solution was drained from the dyeing machine, and the fabric was rinsed three times with warm water. Then, it was dried to obtain the dyed fabric. The exhaustion rate of the dye was determined by calculating the weight of the dye that did not adhere to the fabric by collecting the dyeing solution and rinsing solution after dyeing. The exhaustion rate of the dye was calculated from the mass (C) of the dye used, the concentration (D) of the combined dyeing solution and rinsing solution after dyeing, and the volume (V D ) as 100×[(C - D×V D ) / C (%)] (3) Dyeing results The obtained dyed fabric had no dyeing unevenness and was uniformly dyed. Also, the color depth (K / S) was 7.40 and the exhaustion rate of the dye was 67%. When the exhaustion rate of the dye is high, there is no waste of the dye, less dye is used, the waste liquid treatment is easier, and the overall dyeing cost is reduced.

[0027] (Comparative Example 1) The dyeing treatment was carried out in the same manner as in Example 1, except that electron beam irradiation and graft polymerization were not performed. The resulting dyed fabric had a color intensity (K / S) of 4.16 and a dye exhaustion rate of 51%. There was no uneven dyeing, but both the dye exhaustion rate and K / S were lower compared to Example 1.

[0028] (Example 2) <Grafting of cotton> The cotton fibers were grafted in the same manner as in Example 1. The grafting rate of the resulting grafted cotton was 16%. Grafted cotton (10 wt%) and untreated cotton (90 wt%) are blended in a cotton-blending process, spun using a quick-spin system to produce a 26 count yarn, and this single yarn has a weight of 148 g / m. 2 I created the knitted fabric. This knitted fabric was dyed in the same manner as in Example 1. The resulting dyed fabric had a color intensity (K / S) of 3.09, and the dyed fabric was uniformly dyed without any unevenness in color.

[0029] (Example 3) The procedure was carried out in the same manner as in Example 2, except that 20 wt% grafted cotton and 80 wt% untreated cotton were used. The resulting dyed fabric had a color intensity (K / S) of 3.31, and the dyed fabric was uniformly dyed without any unevenness in color.

[0030] (Comparative Example 2) Comparative Example 2 was conducted in the same manner as Example 2, except that it was a knitted fabric made only from untreated cotton and did not contain grafted cotton. The resulting dyed fabric had a color intensity (K / S) of 2.76, which was lower than that of Examples 2 and 3, indicating a lighter color.

[0031] The results above can be summarized as follows: (1) When a tertiary amine is used, the ionic and nonionic states of the tertiary amine can be switched by the pH of the dyeing solution. At the start of the dyeing process (dye adsorption process), by keeping the pH near neutral, the tertiary amine becomes cationized, and the dye having anionic groups is absorbed near the dyeing seats on the fibers. (2) When quaternary ammonium is used, there is a large difference in the adsorption of dye between the modified and unmodified parts, resulting in uneven coloring. However, in the case of tertiary amine, the cations are deionized during the basic dye fixing process, so the ionic bonds are broken and the dye molecules can move from the adsorbed site, and the dye reacts with the dyeing sheet regardless of whether it is modified or unmodified cellulose. (3) The fiber structure of the present invention can absorb more dye in the dye adsorption process compared to an unmodified fiber structure, and the dye concentration near the dyeing area is higher, which improves dyeing efficiency and allows for darker coloring with the same amount of dye than in the unprocessed case. (4) The ionic bonds are broken, and the dyed sheets of both modified and unmodified cellulose react, resulting in no uneven coloring. [Industrial applicability]

[0032] The present invention provides a cellulose fiber-containing fibrous structure and a dyeing method thereof, which can be applied to cotton, fiber bundles, yarn, woven fabrics, knitted fabrics, or nonwoven fabrics, and is useful for a variety of fibrous structures such as clothing like shirts and pants, bedding like pajamas, sheets, futon covers, and futon covers, interior items like curtains and carpets, and towels.

Claims

1. A fibrous structure containing modified cellulose fibers, The modified cellulosic fiber is a fibrous structure in which compounds containing pH-responsive groups and ethylenically unsaturated double bond groups are grafted.

2. The fiber structure according to claim 1, wherein the pH-responsive group is a tertiary amino group.

3. The fiber structure according to claim 1, wherein the ethylenically unsaturated double bond group is a methacrylic group, an acrylic group, or a vinyl group.

4. The fibrous structure according to claim 1, wherein the compound containing the pH-responsive group and the ethylenically unsaturated double bond group is a tertiary amine shown in (Chemical Formula 1) below in its neutral form, and a quaternary ammonium salt shown in (Chemical Formula 2) below in its cationized form. However, R 1 R is a methyl group or a hydrogen atom. 2 R is a hydrocarbon chain having 1 to 4 carbon atoms. 3 and R 4 is a hydrocarbon group having 1 to 4 carbon atoms or R 3 and R 4 It is an organic group in which carbon atoms are linked by a carbon chain having 4 or 5 carbon atoms, forming a heterocycle. 【Chemistry 1】 【Chemistry 2】

5. The fibrous structure according to claim 1, wherein the compound comprising the pH-responsive group and the ethylenically unsaturated double bond group is cationized in an acidic or neutral solution and neutralized in an alkaline solution.

6. The fiber structure according to claim 1, wherein 0.5 to 30 parts by mass of the compound containing the pH-responsive group and the ethylenically unsaturated double bond group are grafted onto 100 parts by mass of the cellulose fiber.

7. The fiber structure according to claim 1, further comprising fibers other than modified cellulose fibers.

8. The fiber structure according to claim 1, wherein the fiber structure is a blend of modified cellulose fibers and unmodified cellulose fibers, with modified cellulose fibers making up 5 to 50% by mass and unmodified cellulose fibers making up 50 to 95% by mass.

9. The fiber structure according to claim 1, wherein the fiber structure is at least one selected from the group consisting of cotton, fiber bundles, yarn, woven fabric, knitted fabric and nonwoven fabric.

10. A dyeing method using a fibrous structure according to any one of claims 1 to 9, A modified cellulose fiber is formed by grafting a compound containing a pH-responsive group and an ethylenically unsaturated double bond group onto a cellulose fiber. A dyeing method for dyeing a fibrous structure containing the modified cellulose fibers with a reactive dye, wherein the dyeing solution is kept acidic or neutral to allow the reactive dye to be absorbed by the fibrous structure containing the modified cellulose fibers, and then the dyeing solution is kept basic to fix the dye.

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