Water-repellent hygroscopic fibers

Abstract

[Problem] There are reports of attempts at adhering a water-repellent agent to the surface of hygroscopic fibers in order to reduce a sensation of dampness and a decrease in hygroscopic ability which are caused by water absorption and which are problems for hygroscopic fibers. However, there is the problem that the water-repellent agent adhered to the fibers comes off during a washing step which is performed after adhering the water-repellent agent to the fibers. [Solution] Water-repellent hygroscopic fibers obtained by adhering a water-repellent agent to hygroscopic fibers which comprise a polymer that contains a carboxyl group, said water-repellent hygroscopic fibers being characterized in that the energy of adhesion of water to the water-repellent agent is not more than 10 mJ / m2.

Description

Water-repellent and moisture-wicking fiber

[0001] The present invention relates to a water-repellent and moisture-absorbing fiber.

[0002] In recent years, growing awareness of comfort has led to a demand for the development of materials with moisture-absorbing properties, and development is also being actively conducted in the field of textiles. For example, Patent Document 1 reports a highly moisture-absorbing and moisture-releasing fiber in which acrylic fibers are crosslinked with hydrazine and some of the remaining nitrile groups are converted to salt-type carboxyl groups or amide groups. While such fibers have excellent moisture absorption and moisture-absorbing heat generation properties, such fibers often also have excellent water absorption properties. When such fibers are used in textile structures such as clothing and bedding, they may cause a wet feeling due to water absorption and a decrease in moisture absorption performance, which may significantly impair comfort.

[0003] In contrast, the hydrophobic highly cross-linked polyacrylate fiber described in Patent Document 2 has a hydrophobizing agent bonded to the highly cross-linked polyacrylate fiber, and by adsorbing moisture in the gas phase (hygroscopicity) while repelling moisture in the liquid phase (water repellency), the deterioration of moisture absorption performance due to water absorption is suppressed.

[0004] JP-A-5-132858 Patent No. 5721746

[0005] When producing a water-repellent and moisture-absorbent fiber by attaching a water-repellent agent to a moisture-absorbent fiber, a process of removing the water-repellent agent that has not adhered to the fiber by washing with water is usually carried out after the water-repellent treatment to prevent the water-repellent agent that has not adhered to the fiber from adhering to the production equipment and contaminating the equipment. However, there is a problem in that the water-repellent agent that has adhered to the fiber is removed by this washing. The present invention has been devised to solve the above-mentioned problems, and its object is to provide a water-repellent and moisture-absorbent fiber that maintains sufficient moisture absorption performance while suppressing the removal of the water-repellent agent by washing with water after the water-repellent treatment.

[0006] The present inventors have conducted extensive research into methods for resolving the above-mentioned problems, and as a result have discovered that by using a water repellent agent that has a water adhesion energy within a specific range for the water repellent agent to be attached to the hygroscopic fiber, the removal of the water repellent agent due to washing with water after the water repellent treatment can be suppressed, and have arrived at the present invention.

[0007] That is, the present invention has the following features (1) to (8): (1) A water-repellent and hygroscopic fiber comprising a hygroscopic fiber made of a polymer containing a carboxyl group and a water repellent agent attached thereto, wherein the water adhesion energy of the water repellent agent is 10 mJ / m ２ A water-repellent, hygroscopic fiber characterized by the following: (2) The water-repellent, hygroscopic fiber according to (1), characterized in that the water-repellent agent exhibits a zeta potential of 20 mV or more when the water-repellent agent is dispersed in water at a solids concentration of 0.1 wt % and a pH of 10. (3) The water-repellent, hygroscopic fiber according to (1) or (2), characterized in that the water-repellent agent does not contain fluorine atoms. (4) The water-repellent, hygroscopic fiber according to any one of (1) to (3), characterized in that the amount of the water-repellent agent attached is 0.05 to 5 wt % based on the hygroscopic fiber made of a polymer containing carboxyl groups. (5) The water-repellent, hygroscopic fiber according to any one of (1) to (4), characterized in that the hygroscopic fiber made of a polymer containing carboxyl groups contains 2 to 9 mmol / g of carboxyl groups. (6) The water-repellent, hygroscopic fiber according to any one of (1) to (5), characterized in that the hygroscopic fiber made of a polymer containing carboxyl groups is an acrylate fiber. (7) The water-repellent and moisture-absorbent fiber according to any one of (1) to (6), characterized in that the saturated moisture absorption rate in an atmosphere of 20°C and a relative humidity of 65% is 10 to 50%. (8) A fiber structure containing the water-repellent and moisture-absorbent fiber according to any one of (1) to (7).

[0008] The water-repellent and moisture-absorbent fiber of the present invention has both water repellency (repelling water in a liquid phase) and moisture absorption (absorbing water in a gas phase), and furthermore, is inhibited from being washed away with water after the water-repellent treatment. Furthermore, by incorporating the fiber into a textile structure such as clothing or a futon, the above-mentioned water repellency and moisture absorption properties can be imparted to the textile structure.

[0009] The present invention will be described in detail below. The water-repellent and moisture-absorbent fiber of the present invention is obtained by adhering a water repellent agent to a moisture-absorbent fiber (hereinafter simply referred to as "moisture-absorbent fiber") made of a polymer containing a carboxyl group.

[0010] The water repellent agent in the present invention has a water adhesion energy of 10 mJ / m to prevent the water repellent agent from falling off from the water-repellent and hygroscopic fiber during washing after the treatment of adhering the water repellent agent to the hygroscopic fiber (hereinafter simply referred to as "water repellent treatment"). ２ less than 8 mJ / m ２ The water adhesion energy is an index showing the difficulty of water droplets separating from the surface of a solid; the higher this value, the more difficult it is to separate water from the solid surface. The water adhesion energy of a water repellent in the present invention refers to the water adhesion energy on the surface of a layer made of the water repellent, and is calculated from the following formula 1 based on the results obtained from the water adhesion energy measurement method described in the Examples below: (Formula 1) Water adhesion energy E = mg (sin α) / 2πr m: mass of water droplet g: gravitational acceleration α: sliding angle r: radius of contact surface between solid surface and water droplet In the fibers after the water repellent treatment described above, the water repellent is considered to be insufficiently fixed because it has not yet undergone a drying process. Therefore, the greater the water adhesion energy of the water repellent, i.e., the higher the affinity between the water repellent and water, the more likely it is that insufficiently fixed water repellent will fall off from the fibers into the wash water when washed with water after the water repellent treatment. For this reason, a water repellent whose water adhesion energy is within the above-mentioned range is used in the present invention. In the present invention, the lower the adhesion energy of water, the more preferable it is, and therefore there is no particular restriction on the lower limit.

[0011] From the viewpoint of ease of attachment to the moisture-absorbing fiber, the water-repellent agent preferably exhibits a zeta potential of 20 mV or more, and more preferably 30 mV or more, when the water-repellent agent is dispersed in water at a solids concentration of 0.1 wt % and a pH of 10. When the zeta potential is 20 mV or more, the water-repellent agent is adsorbed to the carboxyl groups of the moisture-absorbing fiber, and is easily attached to the fiber.

[0012] The lower limit of the amount of the water repellent agent attached to the hygroscopic fiber is preferably 0.05 wt %, more preferably 0.1 wt %. If the amount is less than 0.05 wt %, sufficient water repellency may not be obtained. The upper limit is preferably 5 wt %, more preferably 3 wt %, and even more preferably 2 wt %. If the amount is more than 5 wt %, production costs will increase and there is a risk of contamination of the production equipment.

[0013] The water repellent employed in the present invention is not particularly limited as long as the adhesion energy of water is within the aforementioned range, and known water repellents such as silicone-based water repellents, fluorine-based water repellents, and paraffin-based water repellents can be employed. Among these, cationic water repellents such as amino-modified silicone-based water repellents, amino-modified fluorine-based water repellents, and cationic paraffin-based water repellents are preferably employed because they can form ionic bonds with carboxyl groups in the moisture-absorbing fiber, thereby strengthening adhesion. Furthermore, from the viewpoint of environmental impact, it is preferable that the water repellent does not contain fluorine atoms.

[0014] Next, the moisture-absorbing fiber made of a polymer containing a carboxyl group, which is used in the present invention, will be described.

[0015] The moisture-absorbing fiber of the present invention contains a polymer containing carboxyl groups, and these carboxyl groups are what give the moisture-absorbing fiber its moisture-absorbing properties. The lower limit of the amount of carboxyl groups contained in the moisture-absorbing fiber is preferably 2 mmol / g, more preferably 3 mmol / g. If the amount of carboxyl groups is less than 2 mmol / g, sufficient moisture absorption and moisture-absorbing heat generation may not be achieved. The upper limit is preferably 9 mmol / g, more preferably 7.5 mmol / g. If the amount of carboxyl groups exceeds 9 mmol / g, the fiber's physical properties may deteriorate, making it difficult to handle.

[0016] The counter ion of the carboxyl group can be one or more selected depending on the required properties from cations of alkali metals such as sodium, potassium, and lithium, cations of alkaline earth metals such as magnesium and calcium, ammonium ions, hydrogen ions, etc. When a carboxyl group having a counter ion other than a hydrogen ion (hereinafter referred to as a salt-type carboxyl group) is present, the saturated moisture absorption amount and moisture absorption rate become larger, thereby improving comfort when used as padding.

[0017] Next, a method for producing the moisture-absorbing fiber will be described.

[0018] The method for obtaining the moisture-absorbing fiber is not particularly limited, and any known method may be used, such as a method of polymerizing a monomer containing a carboxyl group to form a polymer and spinning the polymer to obtain the moisture-absorbing fiber, or a method of polymerizing a monomer having a functional group that can be converted to a carboxyl group to form a polymer, spinning the polymer to form a fiber, and then chemically modifying the polymer to express the carboxyl group, or a commercially available product may be used. Furthermore, if the moisture-absorbing fiber is an acrylate-based fiber, it is preferable because it has excellent moisture-absorbing performance.

[0019] Such acrylate fibers may be produced by known methods, such as the method for producing acrylate fibers by crosslinking and hydrolyzing acrylic fibers described in JP 2000-314082 A, or may be commercially available products, such as Ex (registered trademark), Dismel (registered trademark), Moisfine (registered trademark), and Moiscare (registered trademark), which are acrylate fibers manufactured by Toyobo Co., Ltd., and Sunburner (registered trademark), which is an acrylate fiber manufactured by Teijin Frontier Co., Ltd.

[0020] The water-repellent and moisture-absorbent fiber of the present invention can be obtained by attaching a water repellent to the moisture-absorbent fiber. There are no particular limitations on the method for attaching the water repellent to the moisture-absorbent fiber. Known methods can be used, such as preparing a liquid containing the water repellent and spraying the prepared liquid onto the moisture-absorbent fiber or a fiber structure containing the fiber (spray method), or immersing the moisture-absorbent fiber or a fiber structure containing the fiber in the prepared liquid (immersion method). When the immersion method is used, the concentration of the water repellent in the prepared liquid is preferably 0.1 to 5.0 wt % solids concentration, the temperature of the prepared liquid is preferably 10 to 70°C, and the immersion time is preferably 30 to 120 minutes. The water repellent may also be used in an emulsion state, dispersed in a solvent such as water. Examples of such water repellents include "NEOSEED (registered trademark) NR-7080," a cationic paraffin-based water repellent emulsion manufactured by Nicca Chemical Co., Ltd., and "NK GUARD (registered trademark) S-0671," a cationic fluorine-based water repellent emulsion.

[0021] In the water-repellent and moisture-absorbent fiber of the present invention, the water adhesion energy of the water repellent agent is within the above-mentioned range, so that the water repellent agent can be prevented from falling off during washing after the water repellent treatment. Here, the washing time is preferably 5 to 120 minutes, and the washing temperature is preferably 10 to 70°C.

[0022] The saturated moisture absorption rate of the water-repellent and moisture-absorbing fiber of the present invention under conditions of 20°C x 65% RH is preferably 10% as a lower limit, and more preferably 25%. If the saturated moisture absorption rate is below 10%, moisture cannot be sufficiently absorbed, and it may be difficult to provide comfort to clothing, bedding, etc. containing the fiber. The upper limit is preferably 50%, and more preferably 40%. If the saturated moisture absorption rate exceeds 50%, physical properties and shape retention of the fiber may be reduced. Note that "20°C x 65% RH" refers to an atmosphere where the temperature is 20°C and the relative humidity is 65%.

[0023] The fiber structure of the present invention may use the water-repellent and moisture-absorbent fiber described above alone or in combination with other fibers. Examples of other fibers include natural fibers such as wool, animal hair, silk, and cotton, and chemical fibers such as polyester fibers, polypropylene fibers, polyethylene fibers, polyamide fibers, acrylic fibers, and regenerated cellulose fibers. The type of fiber structure is not particularly limited, and examples include carded cotton, various nonwoven fabrics, granular cotton, blown cotton, spun yarn, knitted fabrics, woven fabrics, and pile fabrics.

[0024] When other fibers are used in the fiber structure of the present invention, the blend ratio of the water-repellent and moisture-absorbent fiber of the present invention may be set so as to obtain the desired properties depending on the intended use of the fiber structure. For example, when used as batting for a futon or clothing, the blend ratio of the water-repellent and moisture-absorbent fiber of the present invention relative to the total weight of the batting is preferably 10% by weight as a lower limit, more preferably 20% by weight. The upper limit is preferably 90% by weight, more preferably 80% by weight.

[0025] Examples are given below to facilitate understanding of the present invention, but these are merely illustrative and the gist of the present invention is not limited to these.

[0026] <Method for measuring saturated moisture absorption rate> Approximately 5.0 g of sample is dried in a hot air dryer at 105°C for 16 hours and the weight (a) is measured. Next, the sample is placed in a thermo-hygrostat set at 20°C and 65% RH for 24 hours to absorb moisture, and then the weight (b) of the sample is measured. From the above measurement results, the saturated moisture absorption rate [%] is calculated using the following formula: Saturated moisture absorption rate [%] = {(b - a) / a} x 100

[0027] <Method for Measuring Carboxyl Group Amount> Approximately 1 g of sample was immersed in 50 mL of 1 mol / L aqueous hydrochloric acid for 30 minutes. The sample was then immersed in water at a bath ratio of 1:500. After 15 minutes, the bath pH was confirmed to be 4 or higher, and the sample was thoroughly dried (if the bath pH was less than 4, the sample was washed again with water). Approximately 0.2 g of the dried sample was then weighed (W [g]), 100 mL of water was added, and 15 mL of 0.1 mol / L aqueous sodium hydroxide, 0.4 g of sodium chloride, and phenolphthalein were added and stirred. After 15 minutes, the sample and filtrate were separated by filtration. The filtrate was then titrated with 0.1 mol / L aqueous hydrochloric acid until the color of the phenolphthalein disappeared, and the amount of aqueous hydrochloric acid consumed (V [mL]) was determined. The amount of carboxyl groups was calculated using the following formula: Amount of Carboxyl Groups [mmol / g] = (0.1 x 15 - 0.1 x V) / W

[0028] <Method for Measuring Water Adhesion Energy> 5.0 g of water, 100 μL of water repellent, and 5 mL of ethanol were added to a beaker and stirred. An appropriate amount of this solution was then dropped onto 3M (registered trademark) OHP film PP2300 manufactured by 3M Japan Ltd. The solution was then spread using a bar coater and dried at 80°C for 10 minutes. The film was then washed with running water for 3 minutes and dried again at 80°C for 10 minutes to prepare a measurement film. A 40 μL water droplet was dropped onto the measurement film, and the radius of the contact surface between the water droplet and the film was measured. The film was then tilted, and the angle at which the water slid down (sliding angle) was measured. The same measurement was also performed at another location on the same measurement film, and the average of the resulting sliding angles was taken as the measured value (α degrees). The water adhesion energy E was then calculated according to the following equation 1. (Equation 1) Adhesion energy of water E = mg (sin α) / 2πr m: Mass of water droplet (unit: g) g: Gravitational acceleration (unit: m / s ２ ) α: sliding angle (unit: degree) r: radius of contact surface of water droplet on solid surface (unit: m)

[0029] <Method for Measuring Water Retention Difference (Ease of Falling Off)> The water-repellent treated hygroscopic fiber was washed with circulating water for 1 hour and then dried at 105°C for 3 hours. After drying, the sample was opened using a carding machine, and approximately 0.3 g was weighed out and precisely weighed (W1 [g]). The precisely weighed sample was submerged in water in a beaker for 10 seconds, then pulled out and allowed to rest for 10 seconds. The weight of the sample was then measured (W2 [g]), and the water retention (with water washing) was calculated using the following formula: Water retention [g / g] = {(W2 - W1) / W1} - 1 Next, the same measurement method as above was used except that circulating water washing was not performed, and the water retention (without water washing) was calculated using the above formula. Here, if the water repellent agent is removed by water washing, the hydrophilicity of the fiber increases, and the water retention tends to increase. Therefore, the greater the difference between the water retention rate (with water washing) and the water retention rate (without water washing) (hereinafter simply referred to as the water retention rate difference), the more water repellent agent is removed by washing. Such a water retention rate difference is preferably 0.6 or less, and more preferably 0.4 or less. When the water retention rate difference is 0.6 or less, it can be said that a decrease in water repellency due to washing, i.e., removal of the water repellent agent, is suppressed.

[0030] <Method for measuring zeta potential> The water repellent agent was dispersed in water to a solids concentration of 0.1% by weight, and a 0.1N aqueous solution of sodium hydroxide was added to adjust the pH to 10. The zeta potential of this aqueous dispersion was measured using an "ELSZ-2000ZS" zeta potential / particle size / molecular weight measurement system manufactured by Otsuka Electronics Co., Ltd.

[0031] <Method for measuring the amount of water repellent agent attached> After drying a water-repellent and hygroscopic fiber sample at 105°C for 3 hours, approximately 5 g of the fiber sample was weighed out and precisely weighed (W3 [g]). Next, the fiber sample was subjected to reflux extraction in ethanol for 3 hours using a Soxhlet extractor. Thereafter, the extract was evaporated and dried at 90°C for 1 hour, and the weight of the resulting solid matter was measured (W4 [g]). The amount of water repellent agent attached to the fiber sample was calculated using the following formula: Amount of water repellent agent attached (wt%) = W4 / W3 x 100

[0032] Example 1: An acrylonitrile-based polymer containing 88% by weight of acrylonitrile and 12% by weight of vinyl acetate was dissolved in a 48% by weight aqueous solution of sodium rhodanate to prepare a spinning dope. Spinning, water washing, drawing, crimping, heat treatment, and cutting were performed according to the standard wet acrylic fiber manufacturing method to obtain an acrylic fiber with a single fiber fineness of 1.7 dtex and a fiber length of 76 mm. The acrylic fiber was simultaneously subjected to a crosslinking structure introduction treatment and hydrolysis treatment at 115°C for 2 hours in an aqueous solution containing 1.0% by weight of hydrazine hydrate and 0.55% by weight of sodium hydroxide, followed by treatment with an 8% by weight aqueous nitric acid solution at 120°C for 3 hours and water washing. The obtained fiber was immersed in water, adjusted to pH 9 by adding sodium hydroxide, washed with water, and dried to obtain a hygroscopic crosslinked acrylate fiber with a sodium salt-type carboxyl group (carboxyl group amount: 3.3 mmol / g). Next, the moisture-absorbing crosslinked acrylate fiber was treated by immersing it in an aqueous solution of a cationic paraffin-based water repellent emulsion "NEOSEED (registered trademark) NR-7080" (zeta potential: 34.7 mV) manufactured by NICCA Chemical Co., Ltd., which had a solids concentration of 0.1% by weight, at a bath ratio of 1:11 at 50°C for 30 minutes, followed by dehydration and drying to obtain the water-repellent and moisture-absorbing fiber of Example 1 (saturated moisture absorption rate at 20°C x 65 RH: 38.2%, water repellent adhesion amount: 0.18% by weight).

[0033] Example 2 A water-repellent and moisture-absorbing fiber of Example 2 was obtained in the same manner as in Example 1, except that the water repellent was changed to a cationic fluorine-based water repellent emulsion "NK Guard (registered trademark) S-0671" (zeta potential: 36.3 mV) manufactured by Nicca Chemical Co., Ltd. (saturated moisture absorption rate at 20°C x 65 RH: 36.9%, amount of water repellent applied: 0.20 wt%).

[0034] Comparative Example 1 A water-repellent and moisture-absorbing fiber of Comparative Example 1 was obtained in the same manner as in Example 1, except that the water repellent was changed to a fluorine-based water repellent emulsion "NK Guard (registered trademark) S-09" (zeta potential: 38.3 mV) manufactured by Nicca Chemical Co., Ltd. (saturated moisture absorption rate at 20°C x 65 RH: 37.2%, amount of water repellent applied: 0.21 wt%).

[0035] The water repellents used in the above examples and comparative examples and the resulting water-repellent and moisture-absorbent fibers were subjected to various measurements. The measurement results are shown in Table 1.

[0036]

Claims

1. A water-repellent and hygroscopic fiber comprising a hygroscopic fiber made of a polymer containing a carboxyl group and a water repellent attached thereto, the water adhesion energy of the water repellent being 10 mJ / m ２ A water-repellent and moisture-absorbent fiber characterized by the following:

2. The water-repellent and moisture-absorbent fiber according to claim 1, characterized in that the water-repellent exhibits a zeta potential of 20 mV or more when the water-repellent is dispersed in water having a solids concentration of 0.1% by weight and a pH of 10.

3. The water-repellent and moisture-absorbent fiber according to claim 1, wherein the water-repellent agent does not contain fluorine atoms.

4. The water-repellent and moisture-absorbent fiber according to claim 1, characterized in that the amount of the water-repellent agent attached is 0.05 to 5% by weight based on the weight of the moisture-absorbent fiber made of a polymer containing a carboxyl group.

5. The water-repellent and moisture-absorbent fiber according to claim 1, characterized in that the moisture-absorbent fiber made of a polymer containing carboxyl groups contains 2 to 9 mmol / g of carboxyl groups.

6. The water-repellent and moisture-absorbent fiber according to claim 1, characterized in that the moisture-absorbent fiber made of a polymer containing a carboxyl group is an acrylate fiber.

7. The water-repellent and moisture-absorbent fiber according to claim 1, characterized in that the saturated moisture absorption rate in an atmosphere at 20°C and a relative humidity of 65% is 10 to 50%.

8. A fiber structure comprising the water-repellent and moisture-absorbent fiber according to any one of claims 1 to 7.

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