WO2018173702A1

WO2018173702A1 - Hygroscopic granulated wool and batting containing same granulated wool

Info

Publication number: WO2018173702A1
Application number: PCT/JP2018/008103
Authority: WO
Inventors: 西崎直哉; 藤本克也
Original assignee: 日本エクスラン工業株式会社
Priority date: 2017-03-23
Filing date: 2018-03-02
Publication date: 2018-09-27
Also published as: CN110446808A; TW201835408A; JP6399378B1; KR102378343B1; KR20190126063A; JPWO2018173702A1; CN110446808B; TWI771378B

Abstract

Hygroscopic fibers have low loft or resilience, which makes development thereof into a batting problematic. Although several techniques are known for enhancing loft, only initial loft is secured, and there is a significant tendency for loft to decrease due to moisture, repeated use, passage of time, and other factors. The present invention was developed in view of the current state of the prior art, and the purpose thereof is to provide a hygroscopic granulated wool and a batting containing the granulated wool, whereby hygroscopic properties and continuous loft are obtained at the same time. The present invention is a granulated wool containing a surface layer part comprising a polymer having a cross-linked structure and a carboxyl group, and a center part comprising an acrylonitrile-based polymer, the hygroscopic granulated wool being characterized in that the volumetric expansion rate indicating the degree of expansion of the volume thereof after a fixed load is removed with respect to the volume thereof under the load is 15% or greater, and the moisture absorption coefficient thereof in an environment at 20°C and a relative humidity of 65% is 4% or greater.

Description

Hygroscopic granular cotton and batting containing the granular cotton

The present invention relates to a hygroscopic granular cotton having both hygroscopicity and sustained bulkiness, and a batting containing the granular cotton.

Conventionally, it has been proposed to use moisture-absorbing / releasing fibers for clothing and bedding (Patent Document 1). The batting using moisture-absorbing / releasing fibers is expected to have functions such as humidity control by moisture-absorbing / releasing properties and heat retention using heat generated by moisture absorption. However, moisture-absorbing / releasing fibers have low bulkiness and resilience, and are a major issue in developing into batting.

In response to this problem, Patent Document 2 discloses a technique for improving bulkiness by modifying a moisture absorbing / releasing fiber. Moreover, in patent document 3, the technique which improves bulkiness by raising the crimp of a moisture absorption / release fiber is disclosed. Furthermore, Patent Document 4 discloses a technique for improving the bulkiness by making hygroscopic fibers granular with other synthetic fibers and collecting a large number of these.

Japanese Patent Laid-Open No. 10-313995 International Publication No. 2013/002367 Pamphlet International Publication No. 2015/041275 Pamphlet JP 2003-286638 A

However, in the techniques of Patent Documents 2 to 4, although the initial bulkiness can be secured, the bulkiness tends to decrease due to moisture absorption, repeated use, and aging. The present invention was created in view of the current state of the prior art, and its object is to provide a hygroscopic granular cotton having both hygroscopicity and sustained bulkiness, and a filling containing the granular cotton. It is in.

As a result of diligent investigations to achieve the above-mentioned object, the present inventors have reduced the number of fluff protruding from the surface of the granular cotton, and when the granular cotton is pressed against each other by moisture absorption, pressure, deformation, etc. It has been found that the entanglement between the granular cottons can be suppressed and the bulk can be easily recovered.

That is, the present invention is achieved by the following means.
(1) A granular cotton containing hygroscopic fibers composed of a surface layer portion made of a polymer having a crosslinked structure and a carboxyl group and a central portion made of an acrylonitrile-based polymer, and having a volume expansion coefficient by the following measuring method. A hygroscopic granular cotton having a moisture absorption rate of 4% or more in an environment of 15% or more and 20 ° C. and a relative humidity of 65%.
<Measurement method>
A sample that has been conditioned for at least 24 hours in a constant temperature and humidity machine at 20 ° C. and a relative humidity of 65% RH is put into a 1000 ml scale position of a 1000 ml graduated cylinder (inner diameter 63 mm). Next, a circular mount (0.8 g) slightly smaller than the inner diameter is placed on the sample, and a 50 g weight is slowly placed thereon. Wait until the weight sinks, and read the position of the circular mount from the scale of the graduated cylinder (H1). Next, the weight is removed, and the position of the circular mount after one minute has elapsed is read from the scale of the graduated cylinder (H2). From the above, the volume expansion coefficient is calculated by the following equation.
Volume expansion coefficient [%] = (H2−H1) / H1 × 100
(2) The hygroscopic granular cotton according to (1), wherein the content of the hygroscopic fiber is 10 to 70% by mass.
(3) The Young's modulus of the hygroscopic fiber is 7 to 20 cN / dtex, and the numerical value A represented by the following formula is 0.050 or more and less than 0.080, (1) or (2 The hygroscopic granular cotton described in 1.).
[Formula] A = Carboxyl group amount [mmol / g] / Ratio of surface layer cross section in fiber cross section [%]
(5) A batting comprising the hygroscopic granular cotton according to any one of (1) to (3).

The hygroscopic granular cotton of the present invention has both hygroscopicity and sustained bulkiness. More specifically, since it has better moisture absorption and release performance than general polyester as a batting, it is difficult to stuffy, and it is difficult to pass even if it is continuously used, and it can maintain bulkiness. The hygroscopic granular cotton of the present invention having such performance is useful as a batting, and particularly for applications that come into contact with or close to the human body, such as batting for duvets, batting such as cushions and chairs, or ski wear, winter clothes, coats, It can be suitably used for clothing items such as jumpers, gloves and semi-wraps.

The present invention is described in detail below. The hygroscopic granular cotton of the present invention has a volume expansion coefficient of 15% or more, more preferably 20% or more, still more preferably 25% or more by the method described later. Such a granular cotton having a volume expansion rate of less than 15% is too hard and has a rough texture, or the bulkiness is greatly reduced during repeated use. Problems such as a significant decrease in heat retention or a collapse of the shape occur. On the other hand, although there is no restriction | limiting in particular as an upper limit of a volume expansion coefficient, It seems that it is difficult to produce hygroscopic granular cotton which exceeds 100% in this invention.

The hygroscopic granular cotton of the present invention has a 20 ° C. × 65% RH hygroscopicity of 4% or more, more preferably 5% or more, and further preferably 6% or more. When the moisture absorption rate is less than 4%, the moisture absorption performance is insufficient, and when used in an application that comes into contact with or close to the human body, the water vapor emitted from the human body cannot be sufficiently absorbed, resulting in a strong stuffiness. If it becomes severe, water vapor may condense, causing stickiness and cold sweat.

Furthermore, the hygroscopic granular cotton of the present invention contains hygroscopic fibers composed of a surface layer portion made of a polymer having a crosslinked structure and a carboxyl group and a central portion made of an acrylonitrile-based polymer. In such a hygroscopic fiber, moisture absorption / release performance is exhibited in the surface layer portion, and a certain level of fiber hardness (hardness) is maintained in the central portion. When the central part is made of a polymer having a crosslinked structure and a carboxyl group as in the case of the surface layer part, the fiber is very easy to pass and it is difficult to maintain bulkiness.

The proportion of the hygroscopic fibers contained in the hygroscopic granular cotton is preferably 10 to 70% by mass, more preferably 15 to 40% by mass, and further preferably 20 to 35% by mass. If it is less than 10% by mass, the moisture absorption / release performance of the hygroscopic granular cotton may be insufficient. If it exceeds 70% by mass, the bulkiness and sustainability of the hygroscopic granular cotton may be insufficient. Examples of fibers used in addition to the hygroscopic fibers include polyester fibers, polypropylene fibers, polyethylene fibers, polyamide fibers, acrylic fibers, cellulosic fibers, cotton, wool, and silk. Among these, polyester fibers are preferably used because they are effective in improving bulkiness and sustainability.

The fineness of the hygroscopic fiber employed in the present invention is preferably 1 to 6 dtex, more preferably 1.7 to 5 dtex, and further preferably 2 to 4 dtex. If it is less than 1 dtex, the bulkiness and sustainability of the hygroscopic granular cotton may be insufficient. If it exceeds 6 dtex, it may be difficult to form granular cotton.

The fiber length of the hygroscopic fiber employed in the present invention is preferably 20 to 80 mm, more preferably 20 to 40 mm, from the viewpoint of easy formation of granular cotton and the reduction of fluff protruding from the surface of the granular cotton. . When other fibers are used in combination, the fiber length of the other fibers is preferably the same as that of the hygroscopic fiber employed in the present invention.

Next, the Young's modulus of the hygroscopic fiber employed in the present invention is preferably 7 to 20 cN / dtex, more preferably 7.5 to 18 cN / dtex, and still more preferably 8 to 15 cN / dtex. When the Young's modulus is within the range of 7 to 20 cN / dtex, it is easy to form granular cotton, and the shape is not an irregular shape such as a rice grain shape or a tadpole shape, but can be obtained in a shape close to a sphere. It becomes easy. Furthermore, the fluff which protrudes from the surface of granular cotton can be decreased, and even when compressed, etc., each other is less likely to be entangled, and it is easy to show a good bulk recovery.

The crimp rate of the hygroscopic fiber employed in the present invention is preferably 3 to 12%, more preferably 4 to 9%, and the number of crimps is preferably 4 to 12 peaks / 25 mm, more Preferably, it is 5 to 10 mountain / 25 mm. If the crimp ratio and the number of crimps are in the range, the entanglement between the fibers becomes an appropriate level during granulation, the hygroscopic fibers are efficiently taken into the granular cotton, and the fluff protruding from the surface of the granular cotton is reduced. However, it is also easy to obtain a shape that is almost a sphere, rather than an irregular shape such as rice grain or tadpole.

In the hygroscopic fiber employed in the present invention, the numerical value A represented by the following formula is preferably 0.050 or more and less than 0.080, more preferably 0.055 or more and less than 0.070.
[Formula] A = Carboxyl group amount [mmol / g] / Ratio of surface layer cross section in fiber cross section [%]

Here, the numerical value A is a numerical value correlated with the concentration of the carboxyl group in the fiber surface layer portion. The larger this value, the higher the concentration of carboxyl groups, which are polar functional groups, on the fiber surface, so static electricity during the formation of granular cotton can be suppressed, and in a rugged shape like a tadpole. It becomes easy to obtain almost in the shape of a sphere. In order to obtain such an effect, the numerical value A is preferably 0.050 or more, and more preferably 0.055 or more. However, when the numerical value A is 0.08 or more, the fiber surface layer portion becomes sticky due to moisture absorption, and the fibers tend to stick to each other. Or the ratio of the other fibers that are used together from the granular cotton may jump out due to the influence.

In addition, as a counter ion of a carboxyl group in a polymer having a crosslinked structure and a carboxyl group, a cation of an alkali metal such as lithium, sodium or potassium, a cation of an alkaline earth metal such as magnesium or calcium, manganese, copper, One or more kinds can be selected according to the required properties from cations of other metals such as zinc and silver, ammonium ions and hydrogen ions. For example, in the case of sodium and potassium, although the bulkiness is difficult to increase, the moisture absorption rate and the amount of moisture absorption increase, and when a polyvalent metal ion such as magnesium, calcium, or zinc is adopted, the moisture absorption rate is Although it becomes slow, it tends to increase the bulkiness.

The hygroscopic granular cotton of the present invention preferably has an average diameter of 3 to 9 mm, more preferably 4 to 6 mm. Granulation with an average diameter of less than 3 mm is difficult. On the other hand, if the average diameter exceeds 9 mm, problems may occur during product processing such as blowing.

The specific volume of the hygroscopic granular cotton of the present invention is preferably 100 cm ³ / g or more, more preferably 150 cm ³ / g or more, and further preferably 200 cm ³ / g or more from the viewpoint of obtaining sufficient bulkiness. Although there is no restriction | limiting in particular as an upper limit of a specific volume, It seems that it is difficult to produce a hygroscopic granular cotton which exceeds 500 cm < ³ > / g in this invention.

Next, as a method for producing the hygroscopic fiber employed in the present invention, a method of subjecting the surface layer portion of the acrylonitrile fiber to a crosslinking introduction treatment and a hydrolysis treatment can be employed. The acrylonitrile fiber used as a raw material can be produced from an acrylonitrile polymer by a known method. The acrylonitrile polymer preferably has an acrylonitrile content of 50% by mass or more, more preferably 80% by mass or more, and still more preferably 85% by mass or more. As will be described later, since the crosslinked structure is formed by the reaction of the nitrile group of the acrylonitrile polymer and the crosslinking agent, when the acrylonitrile content in the acrylonitrile polymer is small, the amount that the crosslinked structure can be introduced decreases. The fiber strength may be insufficient in processing and practical use.

A crosslinked structure is introduced into the surface layer of the acrylonitrile fiber as described above. For the introduction of the crosslinked structure, a conventionally known crosslinking agent may be used, but it is preferable to use a nitrogen-containing compound from the viewpoint of the introduction efficiency of the crosslinked structure. As the nitrogen-containing compound, it is preferable to use an amino compound or a hydrazine compound having two or more primary amino groups. Examples of amino compounds having two or more primary amino groups include diamine compounds such as ethylenediamine and hexamethylenediamine, diethylenetriamine, 3,3′-iminobis (propylamine), N-methyl-3,3′-iminobis ( Triamine compounds such as propylamine), triethylenetetramine, N, N′-bis (3-aminopropyl) -1,3-propylenediamine, N, N′-bis (3-aminopropyl) -1,4- Examples include tetramine compounds such as butylenediamine, polyvinylamine, polyallylamine, and the like, and polyamine compounds having two or more primary amino groups. Examples of the hydrazine compound include hydrazine hydrate, hydrazine sulfate, hydrazine hydrochloride, hydrazine hydrobromide, hydrazine carbonate, and the like. The upper limit of the number of nitrogen atoms in one molecule is not particularly limited, but is preferably 12 or less, more preferably 6 or less, and particularly preferably 4 or less. When the number of nitrogen atoms in one molecule exceeds the above upper limit, the cross-linking agent molecule becomes large and it may be difficult to introduce a cross-linked structure into the fiber. The conditions for introducing the cross-linked structure are not particularly limited, and can be appropriately selected in consideration of the reactivity between the cross-linking agent employed and the acrylonitrile fiber, the amount of the cross-linked structure, and the like. For example, when a hydrazine compound is used as the crosslinking agent, the acrylonitrile fiber described above is immersed in an aqueous solution to which the hydrazine compound is added so that the hydrazine concentration is 0.1 to 10% by mass. And a method of treating at 2 ° C. for 2 to 10 hours.

After the cross-linked structure is introduced, hydrolysis treatment with an alkaline metal compound is performed, and nitrile groups present in the surface layer portion of the fiber are hydrolyzed to form carboxyl groups. Specific treatment conditions may be set as appropriate in consideration of the above-mentioned carboxyl group concentration and the like, and various conditions such as the concentration of the treating agent, reaction temperature, reaction time, etc. may be set as appropriate, preferably 0.5 to 10% by mass, More preferably, a means for treating in a 1 to 5% by mass aqueous treatment chemical solution at a temperature of 80 to 150 ° C. for 2 to 10 hours is preferred from the industrial and fiber properties viewpoints. In the present invention, it is preferable that the above-described cross-linking introduction treatment and hydrolysis treatment are collectively performed simultaneously using an aqueous solution in which the respective treatment chemicals are mixed, rather than sequentially performing as described above. Furthermore, in the present invention, it is preferable that this simultaneous treatment is performed under mild conditions using a lower concentration of alkaline metal compound than before, and the subsequent acid treatment is performed under severer conditions at a higher temperature than before. By doing in this way, the hygroscopic fiber of this invention can take the structure where many carboxyl groups existed in the narrow surface layer part conventionally, and the comparatively hard acrylonitrile-type polymer was preserve | saved in the center part.

The formed carboxyl group includes a salt-type carboxyl group whose counter ion is a cation other than a hydrogen ion, and an H-type carboxyl group whose counter ion is a hydrogen ion. In order to obtain a high moisture absorption rate, it is desirable that 50% or more of the carboxyl groups are salt-type carboxyl groups. Methods for adjusting the ratio of salt-type carboxyl groups to H-type carboxyl groups within the above range include ion exchange treatment with metal salts such as nitrates, sulfates and hydrochlorides, and acid treatments with nitric acid, sulfuric acid, hydrochloric acid, formic acid, etc. Alternatively, a method of performing pH adjustment treatment with an alkaline metal compound or the like can be mentioned.

As the method for producing the hygroscopic granular cotton of the present invention described above, conventionally known methods and conditions can be employed. For example, the following methods can be mentioned. First, the hygroscopic fibers obtained as described above and fibers that are used in combination as needed are sufficiently opened using a card having a plurality of rollers with garnet wires provided on the surface. Subsequently, fibers that have been sufficiently opened are blown into a room provided with a rotating body having a plurality of fins in a cylindrical space where air turbulence is likely to occur, and can be taken out after turbulent stirring for a predetermined time. It is possible to form hygroscopic granular cotton by spheroidizing with a device such as the above, or by allowing fibers that have been sufficiently opened to stay in a large room while causing vortex of air to spheroidize and spheroidize it can.

In addition to these, Japanese Patent Application Laid-Open No. 2007-169646, Japanese Patent Application Laid-Open No. 10-259559, Japanese Patent Application Laid-Open No. 61-125377, Japanese Patent Publication No. 57-48 using a mechanical share, Japanese Patent Application Laid-Open No. Sho 62-33856. And the method disclosed in Japanese Patent Publication No. 62-27833 can be employed.

In addition to using the above-described hygroscopic granular cotton of the present invention alone, the batting of the present invention may be a combination of other fiber cotton. Here, examples of other fiber cotton include feathers, wool, animal hair, silk, cotton, polyester fiber, polypropylene fiber, polyethylene fiber, polyamide fiber, acrylic fiber, cellulosic fiber, etc. be able to. Such batting of the present invention is used in contact with or close to the human body, for example, batting for duvets, padding for cushions and chairs, or batting for clothing items such as ski wear, winter clothes, coats, jumpers, gloves and semi-wraps. It can be particularly suitably used.

Examples are shown below for facilitating the understanding of the present invention. However, these are merely examples, and the gist of the present invention is not limited thereto. In the examples, parts and percentages are shown on a mass basis unless otherwise specified. Moreover, the evaluation method of the characteristic in an Example is as follows.

<Fineness, fiber length, Young's modulus (initial tensile resistance), crimp rate, number of crimps>
Measured according to “8.4 Fiber Length”, “8.5 Fineness”, “8.11 Initial Tensile Resistance”, and “8.12 Crimp” of JIS L 1015: 2010.

<Calculation of numerical value A>
1. Ratio of surface area cross-sectional area in fiber cross section Sample fiber is a bath ratio of 1:80 in a dyeing bath containing 2.5% cationic dye (Nicilon Black G 200) and 2% acetic acid based on the fiber mass. After being soaked and boiled for 30 minutes, it is washed with water, dehydrated and dried. The obtained dyed fiber is sliced thinly perpendicular to the fiber axis, and the fiber cross section is observed with an optical microscope. At this time, the central portion made of the acrylonitrile-based polymer is dyed black, and the surface layer portion having many carboxyl groups becomes green because the dye is not sufficiently fixed. In the fiber cross section, the fiber diameter (L1) and the diameter of the central part (L2) dyed black with the part starting to change color from green to black as a boundary are measured. Calculate the percentage of the cross-sectional area. The average value of 10 samples is taken.
Ratio of cross-sectional area of surface layer portion in fiber cross section [%] = [{(L1 / 2) ² π− (L2 / 2) ² π} / (L1 / 2) ² π] × 100

2. About 1 g of the carboxyl group-weight fiber sample is immersed in 50 ml of a 1 mol / l hydrochloric acid aqueous solution for 30 minutes. The fiber sample is then immersed in water at a bath ratio of 1: 500. When it is confirmed that the bath pH is 4 or more after 15 minutes, the bath is dried (if the bath pH is less than 4, it is washed again with water). Next, about 0.2 g of a sufficiently dried fiber sample is precisely weighed (W1 [g]), 100 ml of water is added, and 15 ml of a 0.1 mol / l sodium hydroxide aqueous solution and 0.4 g of sodium chloride are added. And add phenolphthalein and stir. After 15 minutes, the sample fibers and filtrate are separated by filtration, and the sample fibers are subsequently washed with water until there is no coloration of phenolphthalein. The combined washing water and filtrate at this time are titrated with 0.1 mol / l hydrochloric acid aqueous solution until the phenolphthalein is no longer colored, and the aqueous hydrochloric acid consumption (V1 [ml]) is determined. From the obtained measured value, the total carboxyl group amount is calculated by the following formula.
Amount of carboxyl group [mmol / g] = (0.1 × 15−0.1 × V1) / W1

3. Numerical value A
It calculates by the following formula using the numerical value calculated | required above.
Numerical value A = carboxyl group amount [mmol / g] / ratio of surface layer cross-sectional area in fiber cross section [%]

<Ratio of salt-type carboxyl group to H-type carboxyl group>
In the above method for measuring the amount of carboxyl groups, the amount of H-type carboxyl groups is calculated in the same manner except that the first immersion in 1 mol / l hydrochloric acid aqueous solution and the subsequent immersion in water (water washing) are not performed. By subtracting the amount of H-type carboxyl groups from the total amount of carboxyl groups, the amount of salt-type carboxyl groups is calculated, and the ratio of salt-type carboxyl groups to H-type carboxyl groups is determined.

<Specific volume>
The sample is placed in a constant temperature and humidity machine at 20 ° C. and a relative humidity of 65% RH for 24 hours or more, and is allowed to stand until the amount of moisture absorption becomes balanced. Next, put the conditioned sample into a 1000 ml graduated cylinder (inner diameter 63 mm) little by little, level it with a stick, taking care not to squeeze it, and put the sample to the 1000 ml scale position. Next, the input sample is taken out, and the mass (W2 [g]) after drying at 105 ° C. for 5 hours is measured. From the above, the specific volume is calculated by the following equation.
Specific volume [cm ³ / g] = 1000 / W 2

<Volume expansion coefficient>
In the same manner as in the above specific volume measurement method, the sample is put into the 1000 ml scale position of a 1000 ml graduated cylinder (inner diameter 63 mm). Next, a circular mount (0.8 g) slightly smaller than the inner diameter is placed on the sample, and a 50 g weight is slowly placed thereon. Wait until the weight sinks, and read the position of the circular mount from the scale of the graduated cylinder (H1). Next, the weight is removed, and the position of the circular mount after one minute has elapsed is read from the scale of the graduated cylinder (H2). From the above, the volume expansion coefficient is calculated by the following equation.
Volume expansion coefficient [%] = (H2−H1) / H1 × 100

<20 ° C x 65% RH moisture absorption rate>
About 2.5 g of a sample is dried with a hot air dryer at 105 ° C. for 16 hours, and the mass is measured (W3 [g]). Next, the sample is placed in a thermo-hygrostat adjusted to a temperature of 20 ° C. and a relative humidity of 65% for 24 hours. The mass of the sample thus absorbed is measured (W4 [g]). From these measurement results, a 20 ° C. × 65% RH moisture absorption rate is calculated by the following equation.
20 ° C. × 65% RH moisture absorption [%] = (W4−W3) / W3 × 100

<Average diameter of granular cotton>
Select 100 samples at random, measure the diameter with calipers, and determine the average value. Here, when the granular cotton is not spherical, the average value of the major axis and the minor axis is taken as the diameter of each sample.

<The shape of granular cotton>
The shape and fluff state were confirmed by visual observation.

[Production Example 1]
An acrylonitrile polymer (90% by mass of acrylonitrile and 10% by mass of acrylic acid methyl ester (intrinsic viscosity [η] = 1.5) in dimethylformamide at 30 ° C.) was dissolved in a 48% by mass aqueous rhodium soda solution, Prepared. The spinning solution was spun, washed, drawn, crimped, and heat-treated according to a conventional method to obtain an acrylic fiber having a single fiber fineness of 1.7 dtex.

The obtained acrylic fiber was subjected to crosslinking introduction treatment and hydrolysis treatment simultaneously in an aqueous solution containing 0.5% by mass of hydrazine hydrate and 2.0% by mass of sodium hydroxide for 8 hours. The mixture was treated with a 100% aqueous nitric acid solution at 100 ° C. for 3 hours and washed with water. The obtained fiber was immersed in water, adjusted to pH 9 by adding sodium hydroxide, washed with water and dried to obtain hygroscopic fiber A. The details and evaluation results of the obtained hygroscopic fibers are shown in Table 1. In the infrared absorption measurement of such a fiber, absorption is in the vicinity of 2250 cm ⁻¹ derived from the nitrile group, and the hydrolysis of the nitrile group proceeds in the fiber surface layer portion, but the nitrile group is present in the fiber center portion. It was confirmed that it remained.

[Production Example 2]
A hygroscopic fiber B was obtained in the same manner as in Production Example 1 except that the concentration of sodium hydroxide was 1.5% by mass. The details and evaluation results of the obtained hygroscopic fibers are shown in Table 1.

[Production Example 3]
A hygroscopic fiber C was obtained in the same manner as in Production Example 1 except that the concentration of sodium hydroxide was 2.5% by mass. The details and evaluation results of the obtained hygroscopic fibers are shown in Table 1.

[Production Example 4]
In the same manner as in Production Example 1, except that the single fiber fineness of the acrylic fiber is 0.9 dtex and the treatment in the aqueous solution containing hydrazine hydrate and sodium hydroxide is 95 ° C. × 2 hours, the hygroscopic fiber D was obtained. The details and evaluation results of the obtained hygroscopic fibers are shown in Table 1.

[Production Example 5]
A hygroscopic fiber E was obtained in the same manner as in Production Example 1 except that the concentration of sodium hydroxide was 3.5% by mass. The details and evaluation results of the obtained hygroscopic fibers are shown in Table 1.

[Production Example 6]
A hygroscopic fiber F was obtained in the same manner as in Production Example 1 except that sodium hydroxide was added to adjust the pH to 9. The details and evaluation results of the obtained hygroscopic fibers are shown in Table 1.

[Examples 1 to 5, Comparative Examples 1 to 3]
Each hygroscopic fiber and polyester fiber (fineness 3.3 dtex, fiber length 38 mm, crimp number 5.0 mountain / 25 mm, crimp degree 10.0%) are mixed at the ratio shown in Table 2, and the garnet wire is on the surface. A card with a plurality of rollers provided in a room with a rotating body that is fully opened and that rotates with a plurality of fins in a cylindrical space where air turbulence is likely to occur. Then, hygroscopic granular cotton was obtained with an apparatus in which fibers were blown in and allowed to be taken out after turbulent stirring for a predetermined time. Table 2 shows the characteristics of the obtained granular cotton.

Examples 1 to 5 all had good hygroscopicity and bulky restoring properties. On the other hand, in Comparative Example 1, the amount of hygroscopic fibers was small and a sufficient moisture absorption rate was not obtained. In the comparative example 2, since the numerical value A of the hygroscopic fiber used was large, it became a rice grain shape with many protruding fibers, and the volume expansion rate was inferior. In Comparative Example 3, the Young's modulus of the hygroscopic fiber used was low and the volume expansion coefficient was inferior.

Claims

A granular cotton containing hygroscopic fibers composed of a surface layer portion made of a polymer having a crosslinked structure and a carboxyl group and a central portion made of an acrylonitrile-based polymer, and having a volume expansion coefficient of 15% or more by the following measurement method And a hygroscopic granular cotton having a moisture absorption rate of 4% or more in an environment of 20 ° C. and a relative humidity of 65%.
<Measurement method>
A sample that has been conditioned for at least 24 hours in a constant temperature and humidity machine at 20 ° C. and a relative humidity of 65% RH is put into a 1000 ml scale position of a 1000 ml graduated cylinder (inner diameter 63 mm). Next, a circular mount (0.8 g) slightly smaller than the inner diameter is placed on the sample, and a 50 g weight is slowly placed thereon. Wait until the weight sinks, and read the position of the circular mount from the scale of the graduated cylinder (H1). Next, the weight is removed, and the position of the circular mount after one minute has elapsed is read from the scale of the graduated cylinder (H2). From the above, the volume expansion coefficient is calculated by the following equation.
Volume expansion coefficient [%] = (H2−H1) / H1 × 100
2. The hygroscopic granular cotton according to claim 1, wherein the content of the hygroscopic fiber is 10 to 70% by mass.
The moisture absorption according to claim 1 or 2, wherein the hygroscopic fiber has a Young's modulus of 7 to 20 cN / dtex, and a numerical value A represented by the following formula is 0.050 or more and less than 0.080. Natural cotton.
[Formula] A = Carboxyl group amount [mmol / g] / Ratio of surface layer area in fiber cross section [%]
A batting comprising the hygroscopic granular cotton according to any one of claims 1 to 3.