JP7770974B2 - Method for producing metal carboxylate-grafted cellulose fiber and method for producing moisture-absorbing and heat-generating fiber structure - Google Patents

Description

The present invention relates to a method for producing metal carboxylate-grafted cellulose-based fibers and a method for producing moisture-absorbing and heat-generating fiber structures.

Hygroscopic heat generation is the property of dry fabrics that generate heat when they absorb moisture (water). For example, if you bring a futon that has been exposed to the sun during the day into a room, even if it has cooled to the same temperature as the room after a few hours, it will still feel warm when you put your skin against it.

The present applicant has proposed a method for imparting moisture-absorbing and heat-generating properties to cellulosic fibers by grafting a compound containing an ethylenically unsaturated double bond onto the cellulosic fibers and introducing a carboxyl group (-COOH) or its sodium salt derived from the compound into the cellulosic fibers (Patent Document 1).

Japanese Patent Application Laid-Open No. 2021-127545

However, the sodium salt of the carboxyl group introduced into cellulosic fibers has a high affinity for water, causing the fiber to become sticky when wet.

In order to solve the above problems, the present invention provides a method for producing metal carboxylate-grafted cellulosic fibers, in which the carboxyl groups introduced into sliver-like cellulosic fibers are prevented from converting into alkali metal salts such as Na salts, which have a high affinity for water.
The present invention also provides a method for producing a moisture-absorbing and heat-generating fiber structure using the metal carboxylate-grafted cellulosic fiber of the present invention.

The present invention, in one aspect, comprises:
a grafting step of grafting a carboxyl group-containing compound having an ethylenically unsaturated double bond onto a sliver-like cellulosic fiber to introduce a carboxyl group;
and a blocking step of contacting the grafted cellulosic fiber with a treatment liquid containing at least one metal ion selected from Ca, Mg, and Zn to convert the carboxyl groups into metal salts thereof.

In another aspect, the present invention comprises:
a step of preparing a metal carboxylate-grafted cellulose fiber by the method of producing a metal carboxylate-grafted cellulose fiber of the present invention;
preparing a fiber structure comprising the metal carboxylate-grafted cellulosic fiber;
a moisture-absorbing and heat-generating processing step of subjecting the fiber structure to a moisture-absorbing and heat-generating processing;
The present invention relates to a method for producing a moisture-absorbing and heat-generating fiber structure comprising the above-mentioned compound.

In the method for producing a metal carboxylate-grafted cellulosic fiber of the present invention, a carboxyl group-containing compound having an ethylenically unsaturated double bond is grafted onto a sliver-like cellulosic fiber to introduce a carboxyl group, and then the fiber is brought into contact with a treatment liquid containing at least one metal ion selected from Ca, Mg, and Zn, thereby converting the carboxyl group into its metal salt.
Therefore, during the manufacturing process of the moisture-absorbing and heat-generating fiber structure containing the metal carboxylate-grafted cellulose fiber of the present invention, the carboxyl groups can be prevented from converting into alkali metal salts such as Na salts, which have a high affinity for water, thereby reducing the problem of stickiness due to contact with moisture.

Furthermore, the method for producing a moisture-absorbing and heat-generating fiber structure of the present invention includes the carboxylate metal salt-grafted cellulosic fiber of the present invention, which reduces the stickiness problem and improves processability.

FIG. 1 is a flow diagram showing the flow of steps in a method for producing a metal carboxylate-grafted cellulosic fiber according to one embodiment of the present invention. FIG. 2 is a flow diagram showing the process flow of a method for producing a moisture-absorbing and heat-generating fiber structure (fabric) according to one embodiment of the present invention. FIG. 3 is a flow chart showing the process flow of a method for producing a moisture-absorbing and heat-generating fiber structure (spun yarn) according to another embodiment of the present invention.

[Production of metal carboxylate-grafted cellulosic fibers]
In one embodiment of the method for producing a metal carboxylate-grafted cellulosic fiber of the present invention, as shown in Figure 1, a sliver of cellulosic fiber is prepared, and a carboxyl group-containing compound containing an ethylenically unsaturated double bond is grafted onto the cellulosic fiber to introduce carboxyl groups derived from the carboxyl group-containing compound (grafting step). Next, the cellulosic fiber to which the carboxyl group-containing compound has been grafted and into which carboxyl groups have been introduced is contacted with a treatment solution containing at least one metal ion selected from Ca, Mg, and Zn to convert some or all of the introduced carboxyl groups into their metal salts (blocking step).

<Grafting step>
In one embodiment of the method for producing a metal carboxylate-grafted cellulosic fiber of the present invention, for example, a carboxyl group-containing compound containing an ethylenically unsaturated double bond (hereinafter, sometimes abbreviated as "carboxyl group-containing compound") is grafted onto a cellulosic fiber such as cotton in the form of a sliver (fiber bundle), thereby introducing a carboxyl group derived from the carboxyl group-containing compound.

Examples of carboxyl group-containing compounds include compounds containing one ethylenically unsaturated double bond and one or two carboxyl groups. Specifically, the carboxyl group-containing compound is preferably at least one carboxylic acid selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid. Grafting these compounds onto the surface of cellulosic fibers such as cotton can impart washable moisture-absorbing and heat-generating properties during the manufacturing process of moisture-absorbing and heat-generating fiber structures.

Grafting of carboxyl group-containing compounds onto cellulosic fibers can be carried out using conventional methods. Graft bonds are formed through a variety of reactions, such as irradiating sliver-state cellulosic fibers with an electron beam to generate radicals on the surface of the cellulosic fibers, and then contacting the generated radicals with a carboxyl group-containing compound to graft carboxylic acid groups as graft chains onto the surface of the cellulosic fibers as compound groups derived from the carboxyl group-containing compound. This introduces carboxyl groups into the cellulosic fibers.

The amount of the carboxyl group-containing compound added is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass, relative to the cellulosic fiber. The mass proportion of carboxylic acid groups, which are graft chains, in the cellulosic fiber into which carboxyl groups have been introduced is preferably 1 to 30% by mass, and more preferably 5 to 30% by mass. If the amount added is within this range, even when blended with untreated fibers such as ungrafted untreated cotton, excellent moisture-absorbing and heat-generating functionality can be exhibited after the moisture-absorbing and heat-generating processing step in the manufacturing method for moisture-absorbing and heat-generating fiber structures described below.

Next, an example of a graft-bonding process will be described using cotton (natural cellulose fiber) as the cellulosic fiber. In the case of a continuous process, cotton sliver for spinning is irradiated with an electron beam in a nitrogen atmosphere to generate radicals on the surface of the cotton fiber, and immediately thereafter, the cotton fiber is continuously contacted with a carboxyl group-containing compound containing an ethylenically unsaturated double bond. The reason for contacting the carboxyl group-containing compound with the surface of the cotton fiber immediately after electron beam irradiation is to prevent the radicals generated by electron beam irradiation from decaying. Because radicals are deactivated over time, it is preferable to contact the carboxyl group-containing compound with the surface of the cotton fiber immediately after electron beam irradiation.

Furthermore, it is preferable to continuously bring the carboxyl group-containing compound into contact with the surface of the cotton fibers after electron beam irradiation, as this allows the carboxyl group-containing compound to efficiently come into contact with the radicals generated on the surface of the cotton fibers. Furthermore, continuously bringing the carboxyl group-containing compound into contact with the surface of the cotton fibers is advantageous for graft bonding to a long spinning sliver. Furthermore, irradiating with electron beams under a nitrogen atmosphere is preferable, as this makes it difficult for the generated radicals to be deactivated. Regarding the electron beam irradiation method, a so-called simultaneous irradiation method is also possible, in which the carboxyl group-containing compound is brought into contact with the surface of the cotton fibers and irradiated at the same time.

In the case of continuous processing, the cellulosic fibers irradiated with the electron beam are preferably in the form of a continuous sheet such as a sliver or wrap, but in the case of batch processing, they are not limited to such a continuous form.

The carboxyl group-containing compound can be brought into contact with the surface of cellulosic fibers such as cotton by any method, such as immersion or spraying. For example, a preferred method is to prepare an aqueous solution of the carboxyl group-containing compound and immerse the sliver in the aqueous solution, or to spray the aqueous solution onto the sliver.

As described above, after grafting the carboxyl group-containing compound onto the sliver-like cellulosic fiber in the grafting process, the fiber is preferably washed with water and then dried to obtain cellulosic fiber with introduced carboxyl groups.

<Blocking process>
The grafted cellulose-based fibers having the carboxyl groups introduced therein are contacted with a treatment solution containing at least one metal ion selected from Ca, Mg, and Zn. Preferably, the treatment solution contains at least one metal ion selected from Ca and Zn. This treatment converts the carboxyl groups introduced into the cellulose-based fibers into their metal salts. The metal of the metal salt is at least one selected from Ca, Mg, and Zn, preferably at least one selected from Ca and Zn. This prevents the carboxyl groups from becoming alkali metal salts such as Na salts.

Calcium carboxylates, magnesium carboxylates, and zinc carboxylates, obtained by replacing the hydrogen atoms of one or more carboxyl groups contained in the carboxylic acid groups (graft chains) on cellulosic fibers with at least one metal selected from calcium, magnesium, and zinc, are more stable than sodium carboxylates, do not become sticky when in contact with moisture, and are less likely to undergo chemical changes during the various treatments and processes, such as scouring, bleaching, and dyeing, that are carried out in the manufacturing process of moisture-absorbing and heat-generating fiber structures.

The treatment solution is preferably an aqueous solution obtained by dissolving a compound of at least one metal selected from Ca, Mg, and Zn in water. The concentration of the metal compound in the aqueous solution is preferably 0.01 to 50 g/L, more preferably 0.1 to 20 g/L, even more preferably 0.5 to 20 g/L, and even more preferably 5 to 20 g/L. Examples of the metal compound that serves as a source of at least one metal ion selected from Ca, Mg, and Zn include metal compounds such as calcium chloride, calcium acetate, magnesium chloride, magnesium acetate, zinc chloride, and zinc acetate, and more preferably calcium chloride, calcium acetate, and zinc acetate. Therefore, the treatment solution is preferably an aqueous calcium chloride solution, calcium acetate solution, magnesium chloride solution, magnesium acetate solution, zinc chloride solution, zinc acetate solution, or a combination thereof. More preferably, it is an aqueous calcium chloride solution, calcium acetate solution, zinc acetate solution, or a combination thereof. Even more preferably, it is an aqueous calcium chloride solution, calcium acetate solution, or a combination thereof.

From the perspective of preventing stickiness, the treatment solution containing at least one metal ion selected from Ca, Mg, and Zn preferably contains substantially no alkali metal ions, and preferably no alkali metals. If alkali metal ions such as Na are contained and these form alkali metal salts such as sodium carboxylates, stickiness tends to occur when the solution comes into contact with moisture during the manufacturing process of moisture-absorbing, heat-generating fiber structures such as yarns and fabrics. Therefore, it is not preferable to use water containing a relatively large amount of alkali metal ions such as Na as the water used to prepare the treatment solution or treatment solution (aqueous solution).

The phrase "substantially free of alkali metals" here means that, from the standpoint of productivity and the like, it is acceptable for the treatment solution to inevitably contain small amounts of alkali metal ions such as Na. The concentration of the unavoidably contained alkali metal ions is preferably 200 mg/L or less, more preferably 100 mg/L or less, even more preferably 40 mg/L or less, and even more preferably 10 mg/L or less. There is no particular lower limit for the concentration of the unavoidably contained alkali metal ions, but it is usually 1 mg/L or more.

As described above, in the blocking step, the grafted cellulosic fibers are brought into contact with the treatment solution to convert the carboxyl groups introduced into the cellulosic fibers into their metal salts. The fibers are then preferably washed with water and then dried to obtain metal carboxylate-grafted cellulosic fibers.

[Production of moisture-absorbing and heat-generating fiber structure]
The method for producing a moisture-absorbing and heat-generating fiber structure of the present invention includes a step of producing a fiber structure containing a metal carboxylate-grafted cellulose fiber (hereinafter also referred to as a "treated fiber") produced by the method for producing a metal carboxylate-grafted cellulose fiber of the present invention. The fiber structure is specifically a yarn or a fabric such as a knitted or woven fabric. The following description will be given taking the case where the fiber structure is a fabric as an example.

(Manufacturing of moisture-absorbing and heat-generating fabrics)
In one embodiment, the method for producing a moisture-absorbing, heat-generating fiber structure of the present invention is a method for producing a moisture-absorbing, heat-generating fabric. As shown in Figure 2, the method for producing a moisture-absorbing, heat-generating fiber structure of the present invention includes the steps of producing a sliver of treated fiber by the method for producing a metal carboxylate-grafted cellulosic fiber of the present invention, a spinning step of converting the sliver containing the treated fiber into a treated-fiber-containing spun yarn, a step of producing a fabric using at least the treated-fiber-containing spun yarn, and a moisture-absorbing, heat-generating processing step of subjecting the fabric to a moisture-absorbing, heat-generating processing.

In one embodiment, the method for producing a moisture-absorbing and heat-generating fiber structure of the present invention may include a step of preparing a yarn of untreated fiber, and fabric may be produced using both the spun yarn containing treated fiber and the yarn of untreated fiber.

In one embodiment of the method for producing a moisture-absorbing and heat-generating fiber structure of the present invention, the fiber structure (fabric) is subjected to one treatment selected from scouring, bleaching, and dyeing. If any of these treatments is performed, it is preferable that each be performed before the moisture-absorbing and heat-generating processing step.

In one embodiment, the method for producing a moisture-absorbing and heat-generating fiber structure of the present invention includes a step of blending the treated fiber with other untreated fibers and spinning the blend to produce a spun yarn (blended yarn) containing the treated fiber. Blending of treated and untreated fibers is preferably carried out in a drawing process, which typically includes a doubling step. However, blending can also be carried out in a carding process, roving process, or spinning process. For example, blending can be carried out by aligning multiple webs, slivers, fleeces, or roving yarns and stretching them to a predetermined ratio in the roving and spinning processes. In the roving and spinning processes, blending can be achieved by migration of the constituent fibers during twisting. The treated fiber (spinning sliver) can also be blended with other untreated fibers (slivers) in the blending process to achieve the desired blend ratio.

In one embodiment of the method for producing a moisture-absorbing and heat-generating fiber structure of the present invention, the treated fiber, for example, treated cotton, is blended with the untreated fiber, for example, untreated cotton, and then the blended spun yarn is produced in accordance with conventional methods.

In one embodiment of the method for producing a moisture-absorbing and heat-generating fiber structure of the present invention, after fabric is produced according to conventional methods, the fabric is subjected to a moisture-absorbing and heat-generating processing step, preferably at the final stage of the moisture-absorbing and heat-generating fabric manufacturing process. The moisture-absorbing and heat-generating processing step imparts moisture-absorbing and heat-generating properties to the treated fiber. Here, the "final stage" refers to a stage after any of the following treatments if a treatment selected from scouring, bleaching, and dyeing is performed; or, if a finishing process is performed with an aqueous solution containing a water-absorbing softener, refers to a stage before the finishing process.

In the moisture-absorbing, heat-generating processing step, the fabric is preferably treated with an acid at a pH of 5 or less, and then rinsed with water. It is then treated with an alkali at a pH of 7.5 or more, rinsed with water, and dried. This allows the fabric to stably exhibit its moisture-absorbing, heat-generating function.

The acid treatment is preferably a treatment in which the fiber structure (fabric) is immersed in an aqueous solution obtained by adding citric acid, malic acid, or the like to water. Citric acid is added so that the concentration of the aqueous solution is approximately 1 to 10 g/L, preferably approximately 2 to 8 g/L. If the pH of the aqueous solution exceeds 5, it is preferable to add citric acid until the pH becomes 5 or less. The acid treatment conditions are preferably an aqueous solution temperature of 30 to 50°C and an immersion time of 10 to 30 minutes. After the acid treatment, the fiber is preferably washed with water at room temperature (25°C) for approximately 5 minutes. Ca, Mg, Zn, and the like can be removed by the acid treatment.

The alkali treatment involves immersing a fiber structure (fabric) in an aqueous solution prepared by adding a chelating agent (sequestering agent) and sodium bicarbonate (sodium bicarbonate, NaHCO ₃ ) to water. The chelating agent (sequestering agent) is preferably added to the aqueous solution at a concentration of approximately 1.0 g/L, particularly approximately 0.3 to 1.5 g/L, and sodium bicarbonate (sodium bicarbonate) is preferably added at a concentration of approximately 4 g/L. Soda ash (Na ₂ CO ₃ ) can also be used instead of sodium bicarbonate (sodium bicarbonate, NaHCO ₃ ). If the pH of the aqueous solution is less than 7.5, it is preferable to add sodium bicarbonate until the pH reaches 7.5 or higher. The alkali treatment is preferably performed under conditions where the aqueous solution temperature is 30 to 50°C and the immersion time is 10 to 30 minutes. After the alkali treatment, the fiber structure is preferably washed twice with water at room temperature (25°C), for approximately 5 minutes each time.

Examples of chelating agents (sequestering agents) that can be used include ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), tetrasodium L-glutamate diacetate, glycol ether diaminetetraacetic acid, ethylenediamine, bipyridine, phenanthroline, porphyrin, and crown ether.

By performing the acid treatment followed by the alkali treatment in this manner, it is possible to remove Ca, Mg, and Zn from the carboxyl groups that were converted into metal salts with at least one metal selected from Ca, Mg, and Zn in the blocking process. This allows the carboxyl group (-COOH) or its sodium salt (-COONa) to be present in the graft chains, thereby maintaining moisture-absorbing heat generation properties.

In the manufacturing method of the moisture-absorbing heat-generating fiber structure of the present invention, if at least one of the following treatments is performed: scouring, bleaching, and dyeing, it is preferable to perform these treatments before the acid treatment. Among the treatments and processes performed during the manufacturing process of the moisture-absorbing heat-generating fiber structure, at least one of scouring, bleaching, and dyeing, in particular, can cause chemical changes in carboxyl groups. Therefore, in the past, there was a risk that the moisture-absorbing heat-generating properties imparted to cellulosic fibers would be deteriorated by these subsequent treatments. By completing these treatments before the moisture-absorbing heat-generating processing step, the risk of deterioration of the carboxyl group (-COOH) or its sodium salt (-COONa) introduced during the moisture-absorbing heat-generating processing step is eliminated, and a moisture-absorbing heat-generating fiber structure with excellent moisture-absorbing heat-generating properties can be provided.

The moisture-absorbing, heat-generating fiber structure (fabric) contains cellulosic fibers that have been treated to absorb and generate heat, as well as other fibers. When the fiber structure (fabric) is taken as 100% by mass, the content of the moisture-absorbing, heat-generating fiber is preferably 5 to 40% by mass. This allows the fiber structure (fabric) to achieve sufficient moisture-absorbing and heat-generating functionality, while reducing the proportion of cellulosic fibers that are damaged during the electron beam grafting process, resulting in a fabric that maintains overall strength.

The other fibers are preferably at least one type of fiber selected from cellulosic fibers that have not been subjected to moisture-absorbing and heat-generating processing, polyester fibers, nylon fibers, acrylic fibers, and polyurethane elastic fibers. When elastic yarn made of polyurethane elastic fibers is used in the production of fabric, the resulting fabric is suitable for innerwear such as shirts and pants.

As mentioned above, it is preferable to carry out the scouring, bleaching, and dyeing processes before the moisture-absorbing and heat-generating processing step. The scouring, bleaching, and dyeing processes can each be carried out by conventional methods. Cellulosic fibers become white through scouring and bleaching. In particular, cotton, if not scouring and bleaching, will have reduced water absorption, a dull color, and its product value will decrease regardless of whether it is dyed or not. The scouring and bleaching processes can be carried out, for example, by immersing the fiber structure (fabric) in an aqueous solution obtained by adding hydrogen peroxide (H ₂ O ₂ ) and sodium hydroxide (NaOH) to water.

Dyeing is preferably carried out as needed after scouring and bleaching. If the textile structure (fabric) is white, it may not be dyed or may be treated with a fluorescent whitening agent. If the textile structure (fabric) is colored, the type of dye should be selected depending on the type of untreated fiber. If the textile structure (fabric) is made of the treated fiber (metal carboxylate-grafted cellulose fiber) and untreated cellulose fiber, it is preferable to dye it with a reactive dye. If the textile structure (fabric) is made of the treated fiber (metal carboxylate-grafted cellulose fiber) and polyurethane fiber, it is preferable to dye it with at least one dye selected from reactive dyes and disperse dyes (they can be used in combination). After dyeing, the textile is neutralized, soaped, and washed in the usual manner.

In one embodiment of the method for producing a moisture-absorbing heat-generating fiber structure of the present invention, it is preferable to perform a finishing process using an aqueous solution containing a water-absorbent softener after the moisture-absorbing heat-generating processing step. The use of a water-absorbent softener can impart softness without reducing the moisture-absorbing heat-generating properties. The use of a water-repellent softener is not preferable because it reduces water absorption and moisture-absorbing heat-generating properties.

In a moisture-absorbing, heat-generating fiber structure (fabric) containing cellulose-based fibers that have been subjected to moisture-absorbing, heat-generating processing and other fibers, the moisture-absorbing, heat-generating processed cellulosic fibers preferably account for 5 to 40% by mass when the total mass of the moisture-absorbing, heat-generating fiber structure (fabric) is taken as 100% by mass. This range allows the fiber structure (fabric) to exhibit high moisture-absorbing, heat-generating properties. For the same reason, the mass proportion of the treated fibers in the fiber structure (fabric) subjected to the moisture-absorbing, heat-generating processing step is preferably 5 to 40% by mass when the total mass of the fabric is taken as 100% by mass.

When the fiber structure (fabric) is a knitted fabric suitable for use as an inner layer, for example, three yarns are used as supply yarns, one of which is a blended spun yarn containing 30% by mass of the treated fiber (metal carboxylate-grafted cellulose fiber) and 70% by mass of ordinary untreated cellulose fiber, and the remaining two are untreated cellulose spun yarns. If the total mass of the fiber structure (fabric) is taken as 100% by mass, a fiber structure (fabric) containing 10% by mass of the treated fiber is obtained. By subjecting this fiber structure (fabric) to the moisture-absorbing and heat-generating treatment described above, a moisture-absorbing and heat-generating fiber structure (fabric) containing 10% by mass of moisture-absorbing and heat-generating cellulose fiber is obtained. It is preferable that the supply yarns used to produce knitted fabrics suitable for use as inner layers further include an elastic yarn made of an elastic fiber such as polyurethane fiber.

The fabric is preferably a knitted or woven fabric. Knitted and woven fabrics are suitable for use as innerwear. Knitted fabrics are particularly suitable for use as innerwear due to their stretchability and flexibility. It is preferable that one or two out of every three yarns constituting the fabric be the blended spun yarn, and the remaining yarn be a cotton spun yarn that has not been treated for moisture absorption and heat generation. Knitted fabrics include circular knitting, weft knitting, warp knitting (including tricot knitting and raschel knitting), and pile knitting, and may be plain knitting, jersey knitting, rib knitting, smooth knitting (double knitting), rib knitting, purl knitting, Denbigh knitting, cord knitting, atlas knitting, chain knitting, insertion knitting, or combinations thereof. Various interlacing methods are used to produce knitted fabrics. Interlacing knitted fabrics may be warp knitting or weft knitting, and examples include tricot, raschel knitting, and circular knitting. Furthermore, the knitting structure may be any of half knitting, reverse half knitting, double atlas knitting, double Denbigh knitting, and combinations thereof. Examples of woven fabrics include plain weave, twill weave, satin weave, varied plain weave, varied twill weave, varied satin weave, patterned weave, single-ply weave, double weave, multi-ply weave, warp pile weave, weft pile weave, leno weave, and combinations of these. Of these, weft knitted fabrics, including circular knitting, or warp knitted fabrics are preferred.

The mass per unit area of the fabric is preferably 80 to 300 g/m ² , more preferably 90 to 250 g/m ² , and even more preferably 100 to 200 g/m ^2. If the mass per unit area of the fabric is within the above range, it is suitable for use as innerwear.

(Production of moisture-absorbing heat-generating cellulose-based spun yarn)
In one embodiment, the method for producing a moisture-absorbing, heat-generating fiber structure of the present invention is a method for producing a moisture-absorbing, heat-generating cellulosic spun yarn. As shown in Figure 3, the method for producing a moisture-absorbing, heat-generating fiber structure of the present invention includes a step of producing treated fiber by the method for producing a metal carboxylate-grafted cellulosic fiber of the present invention, a spinning step of converting a sliver containing the treated fiber into a treated-fiber-containing spun yarn, and a moisture-absorbing, heat-generating processing step of subjecting the treated-fiber-containing spun yarn to a moisture-absorbing, heat-generating processing.

In one embodiment of the method for producing a moisture-absorbing and heat-generating fiber structure of the present invention, the treated fiber-containing spun yarn may be a spun yarn containing 100% by mass of the treated fiber (metal carboxylate-grafted cellulose fiber), or may be a blended spun yarn of the treated fiber (metal carboxylate-grafted cellulose fiber) and untreated fiber. Preferred untreated fibers are the same as those described above (Production of moisture-absorbing and heat-generating fabric).

In one embodiment of the method for producing a moisture-absorbing heat-generating fiber structure of the present invention, the fiber structure (spun yarn) is subjected to one treatment selected from scouring, bleaching, and dyeing. When these treatments are performed, they are preferably performed before the moisture-absorbing heat-generating processing step. Each of these treatments can be performed using conventional methods. By completing these treatments before the moisture-absorbing heat-generating processing step, a moisture-absorbing heat-generating fiber structure (dyed yarn) with good moisture-absorbing heat-generating properties can be provided.

The moisture-absorbing and heat-generating processing step in the method for producing moisture-absorbing and heat-generating cellulose-based spun yarn of the present invention is the same as the method described above (production of moisture-absorbing and heat-generating fabric), except that the moisture-absorbing and heat-generating processing is performed on yarn.

The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples.
<Hygroscopic heat generation>
(1) A sample of fabric (knitted fabric) is taken to a size of 20 cm x 20 cm, dried in a dryer for 4 hours, and left overnight in a desiccator containing silica gel.
(2) After drying, the sample fabric is folded in half, a thermocouple temperature sensor is attached to the center, and the fabric is folded in half again to form a test specimen.
(3) After treating the test specimen in a thermo-hygrostat at 20°C and 40% RH for 2 hours, the thermo-hygrostat settings are changed to 20°C and 90% RH, and the temperature change is measured every minute for 15 minutes.
(4) A knitted fabric made of 50-count cotton yarn using untreated cotton sliver (Comparative Example 1 below) was used as the reference fabric, and the difference between the maximum temperature of the reference fabric and the maximum temperature of the fabric of Example 1 during the 15-minute measurement was calculated as the maximum temperature difference (°C).

Example 1
<Sliver processing>
Cotton sliver (mass per unit length, unit grain: 25.0 g/6 yd (4.6 g/m)) was irradiated with an electron beam at a dose of 40 kGy and an acceleration voltage of 200 kV under a nitrogen atmosphere using an electrocurtain-type electron beam irradiation device EC250/30/90L (manufactured by Iwasaki Electric Co., Ltd.). The irradiated sliver was immediately immersed in a 16% by weight aqueous solution of acrylic acid (manufactured by Nacalai Tesque Inc.) containing 0.5% by weight of a penetrant and squeezed with a mangle to achieve a pickup rate of approximately 100% by weight of the sliver. The amount of acrylic acid added was such that the mass ratio of acrylic acid groups (graft chains) in the carboxyl-introduced cotton sliver was 8% by weight. The sliver was then washed with water to remove unreacted acrylic acid, and then impregnated with a calcium chloride aqueous solution ( ₁₀ g/L of CaCl2). This converted the carboxyl groups of the grafted acrylic acid into calcium salts. The cotton was then washed again with water, dried at 80°C, and coiled and stored in a container to obtain cotton grafted with calcium acrylate. The sliver obtained in this way is called "treated cotton."

<Production of spun yarn>
(1) Blended Yarn Containing Treated Cotton The treated cotton and untreated cotton were blended in a blending process to spin a yarn having a cotton count of 50. The proportion of treated cotton in the blended yarn was 30% by mass.
(2) Untreated Cotton Spun Yarn Untreated cotton was used to spun yarn having a yarn count of 50.

<Knitted fabric manufacturing>
The treated cotton blended yarn, untreated cotton spun yarn, and elastic yarn were prepared. The blended yarn containing the treated cotton was fed in a ratio of two untreated cotton spun yarns to one treated cotton blended yarn, and the elastic yarn was inserted so that it accounted for 7% by mass of the fabric. A commercially available polyurethane elastic yarn, 22 decitex, was used as the elastic yarn. The elastic yarn was inserted as a plated yarn to each yarn under tension so that it was stretched 2.5 times its original length. A plain knit fabric was knitted using a circular knitting machine. The knit fabric was then heat-treated at 200°C for 90 seconds.

<Scouring, bleaching, dyeing>
The resulting knitted fabric was subjected to a conventional scouring treatment, a bleaching treatment, and a dyeing treatment using a reactive dye.

<Hygroscopic heat-generating processing step (calcium release step)>
After the dyeing treatment, the following (1) acid treatment and (2) alkali treatment were carried out as moisture absorbing and heat generating processing steps.
(1) Acid Treatment An aqueous solution of 2 g/L citric acid (pH 5 or less) was prepared. The knitted fabric was immersed in this aqueous solution at a bath ratio of 1:15 and subjected to an acid treatment at 40°C for 20 minutes. Thereafter, the fabric was washed with water at room temperature (25°C) for 5 minutes.
(2) Alkali Treatment Next, an aqueous solution containing 4 g/L of sodium bicarbonate ( _NaHCO3 ) and 1 g/L of a chelating agent (diethylenetriaminepentaacetic acid (DTPA)) was prepared to have a pH of 7.5 or higher. The knitted fabric was immersed in this aqueous solution at a bath ratio of 1:15 and subjected to an alkali treatment at 40°C for 20 minutes. This was followed by two 5-minute water washes at room temperature (25°C).
Thereafter, the washed knitted fabric was dried to obtain the moisture-absorbing and heat-generating fabric of Example 1.

In the moisture-absorbing and heat-generating fabric of Example 1, when the total mass of the moisture-absorbing and heat-generating fabric was taken as 100 mass%, the content of the moisture-absorbing and heat-generating processed cotton was 9 mass%, and the content of the entire untreated cotton was 84 mass%. The mass of the fabric was 170 g/ ^m2 .
The blended yarn containing the treated cotton used in the production of the moisture-absorbing and heat-generating fabric of Example 1 has been subjected to the moisture-absorbing and heat-generating processing step (calcium release step) to become a moisture-absorbing and heat-generating cellulose-based spun yarn. If the moisture-absorbing and heat-generating cellulose-based spun yarn is taken as 100% by mass, the content of moisture-absorbing and heat-generating processed cellulose fiber contained therein is 30% by mass.

(Comparative Example 1)
A fabric of Comparative Example 1 was obtained in the same manner as in Example 1, except that untreated cotton spun yarn was used instead of the blended yarn containing treated cotton.

The maximum temperature of the resulting moisture-absorbing and heat-generating fabric of Example 1 and the fabric of Comparative Example 1 (reference fabric) was measured according to the above <Moisture-absorbing and heat-generating properties>, and the moisture-absorbing and heat-generating properties of the moisture-absorbing and heat-generating fabric of Example 1 were evaluated. The maximum temperature difference (°C) was 0.6°C.

By performing moisture-absorbing and heat-generating processing after the dyeing process, the moisture-absorbing and heat-generating properties were stabilized, and the maximum temperature difference (°C), an evaluation index of moisture-absorbing and heat-generating properties, was 0.6°C, resulting in a cellulosic fiber fabric with good moisture-absorbing and heat-generating properties.

By converting the carboxyl groups of the acrylic acid grafted onto the surface of the cellulose fibers in the sliver state into calcium salts, the carboxyl groups are prevented from becoming alkali metal salts such as sodium salts. This means that the moisture-absorbing and heat-generating fabric does not become sticky even when it comes into contact with moisture during the manufacturing process, and it is easy to process.

An inner shirt was sewn using the moisture-absorbing and heat-generating fabric of Example 1, and a wear test was conducted, confirming that the shirt was warm, comfortable to wear, and gentle on the skin.

The moisture-absorbing, heat-generating fabrics and moisture-absorbing, heat-generating spun cellulose yarns containing the metal carboxylate-grafted cellulose fibers produced by the method of the present invention for producing metal carboxylate-grafted cellulose fibers are suitable for use in innerwear such as shirts, pants, and socks. They are also suitable for use in T-shirts and other items.

Claims (11)

a grafting step of grafting a carboxyl group-containing compound having an ethylenically unsaturated double bond onto a sliver-like cellulosic fiber to introduce a carboxyl group;
a blocking step of contacting the grafted cellulosic fiber with a treatment liquid containing at least one metal ion selected from Ca, Mg, and Zn to convert the carboxyl groups into metal salts thereof. The method for producing metal carboxylate-grafted cellulosic fibers according to claim 1, wherein the treatment liquid is substantially free of alkali metal ions. The method for producing metal carboxylate-grafted cellulose-based fibers according to claim 1 or 2, wherein the treatment liquid is an aqueous calcium chloride solution, an aqueous calcium acetate solution, an aqueous magnesium chloride solution, an aqueous magnesium acetate solution, an aqueous zinc chloride solution, an aqueous zinc acetate solution, or a combination thereof. A process for preparing a metal carboxylate-grafted cellulose fiber by the method for producing a metal carboxylate-grafted cellulose fiber according to any one of claims 1 to 3;
preparing a fiber structure comprising the metal carboxylate-grafted cellulosic fiber;
a moisture-absorbing and heat-generating processing step of subjecting the fiber structure to a moisture-absorbing and heat-generating processing;
A method for producing a moisture-absorbing and heat-generating fiber structure, comprising: Before the moisture absorption and heat generation processing step,
The method for producing a moisture-absorbing and heat-generating fiber structure according to claim 4, wherein the fiber structure is subjected to a refining and bleaching treatment, and optionally a dyeing treatment. The method for producing a moisture-absorbing, heat-generating fiber structure according to claim 4 or 5, wherein the moisture-absorbing, heat-generating processing step involves subjecting the fiber structure to an acid treatment at a pH of 5 or less, followed by rinsing with water, then an alkali treatment at a pH of 7.5 or more, followed by rinsing with water, and then drying. The method for producing a moisture-absorbing and heat-generating fiber structure according to claim 6, wherein the acid treatment is a treatment in which the fiber structure is immersed in an aqueous solution containing citric acid, and the alkali treatment is a treatment in which the fiber structure is immersed in an aqueous solution containing a chelating agent and sodium bicarbonate (baking soda). The method for producing a moisture-absorbing and heat-generating fiber structure according to claim 7, wherein the temperature of the aqueous solution is 30 to 50°C and the immersion time is 10 to 30 minutes in both the acid treatment and the alkali treatment. The method for producing a moisture-absorbing, heat-generating fiber structure according to any one of claims 4 to 8, wherein the moisture-absorbing, heat-generating fiber structure comprises graft-treated cellulose fibers that have been subjected to moisture-absorbing, heat-generating processing and other fibers, and the content of the moisture-absorbing, heat-generating cellulose fibers is 5 to 40 mass% when the total mass of the moisture-absorbing, heat-generating fiber structure is taken as 100 mass%. The method for producing a moisture-absorbing and heat-generating fiber structure according to claim 9, wherein the other fibers are at least one type of fiber selected from cellulosic fibers, polyester fibers, nylon fibers, acrylic fibers, and polyurethane elastic fibers that have not been subjected to moisture-absorbing and heat-generating processing. The method for producing a moisture-absorbing and heat-generating fiber structure according to any one of claims 4 to 10, wherein the fiber structure is a yarn, knitted fabric, or woven fabric.