JP7522430B2 - Flame Retardant Fabric - Google Patents

Description

The present invention relates to flame-retardant textiles.

Many flame-retardant fabrics have been proposed and are widely used in industrial materials, clothing, and other applications (e.g., Patent Document 1).

JP 2016-113725 A

If a flame-retardant fabric has too high water absorption, it may become heavy due to absorption of moisture such as sweat or rain, and workability may decrease. Therefore, there is a demand for flame-retardant fabrics that have appropriate water absorption and moisture absorption properties that are not too high, and have excellent quick-drying properties. For example, in Patent Document 1, a water-repellent treatment is applied to the surface of the fabric to impart appropriate water absorption, moisture absorption, and quick-drying functions, but the abrasion strength of the water-repellent fabric may be insufficient, and there is still room for further improvement.

The present invention aims to solve the problems of the prior art as described above, and to obtain a flame-retardant fabric that has excellent flame retardancy and quick-drying properties, moderate water absorption and moisture absorption properties, and excellent abrasion resistance even when treated with a water-repellent finish.

The inventors discovered that by forming a fabric with a specific weaving structure, including spun yarn containing flame-retardant synthetic fibers and cellulosic fibers, it is possible to obtain a fabric that is excellent in flame retardancy and quick-drying properties, has moderate water absorption and moisture absorption properties, and has excellent abrasion resistance even when treated with a water-repellent finish, and thus completed the present invention.

That is, the present invention includes the following (1) to ( 8 ).
(1) A woven fabric including a spun yarn containing a flame-retardant synthetic fiber and a cellulosic fiber,
The spun yarn has a count of 10 to 45,
The blending rate of spun yarn in the woven fabric is 80% by mass or more, and the blending rate of flame-retardant synthetic fiber is 50 to 90% by mass,
The woven fabric has a cross section of two or more parallel warp yarns and two or more parallel weft yarns, the cross section being 2.54 cm x 2.54 cm or more in size;
The flame-retardant fabric has a butcher structure or a ripstop structure, is water-repellent by laminating a silicone-based water-repellent layer or a fluorine-based water-repellent layer on the surface , and has a flat abrasion strength of 200 times or more as measured in accordance with JIS L1096 A-1 method (load 4.45 N, using P800-Cw as abrasive paper) .
(2) The flame-retardant fabric according to (1), having a limiting oxygen index (LOI) value of 25 or more as measured according to JIS L 1091 E method.
(3) A flame-retardant fabric according to (1) or (2), having a water retention rate of 50% or less as measured by the following measurement method.
The mass (W ₀ ) of a 25 cm x 25 cm test piece is measured. The sample is then immersed in distilled water for 10 minutes, one of the four corners of the sample is lifted and left to stand in that position for 10 minutes, after which the mass (W ₁ ) is measured. The water retention is calculated using the following formula.
Water retention rate (%) = [(W ₁ - W ₀ )/W ₀ ] x 100
(4) The flame-retardant fabric according to any one of (1) to (3), having a diffusion drying speed of 40 minutes or less as measured by the following measurement method.
The mass (W) of a 10 cm x 10 cm test piece is measured. Next, 0.6 ml of water is dropped onto the back side of the test piece, and the mass (W0) is measured. Then, the mass (Wt) of the test piece after the water has been dropped is measured under standard conditions (temperature 20°C, humidity 65%). Then, while the test piece is still on the balance, the time until the mass (Wt) becomes 10% or less as calculated by the following formula is measured, and this time is taken as the diffusion drying speed.
Residual moisture percentage (%) = {(Wt-W)/(W0-W)}×100
(5) The flame-retardant fabric according to any one of (1) to (4), which has a flammability classification of 3 or more in a flammability test classified according to JIS L 1091 A-1.
(6) The flame-retardant fabric according to any one of (1) to (5), having a heat consumption of 15 W/( ^m2 ·°C) or less, as measured in an environment of 20°C and 65 % humidity using a Thermo Labo II type testing machine (manufactured by Kato Tech Co., Ltd.).
(7) The flame-retardant fabric according to any one of (1) to ( 6 ), wherein the flame-retardant synthetic fiber is a flame-retardant vinylon fiber.
(8) The flame-retardant fabric according to any one of (1) to ( 7 ), wherein the mass ratio of the flame-retardant synthetic fiber to the cellulosic fiber is (flame-retardant synthetic fiber):(cellulosic fiber)=90:10 to 60:40.

According to the present invention, by forming a fabric with a specific weaving structure including spun yarn containing flame-retardant synthetic fibers and cellulosic fibers, it is possible to provide a flame-retardant fabric that has excellent flame retardancy and quick-drying properties, as well as moderate water absorption and moisture absorption properties and excellent abrasion resistance even when treated with a water-repellent finish.

FIG. 2 is a schematic diagram showing the weave (butcher weave) of the flame-retardant fabric obtained in Example 1. FIG. 2 is a schematic diagram showing the weave structure (lip structure) of the flame-retardant fabric obtained in Example 2. FIG. 2 is a schematic diagram showing the weave (twill weave) of the flame-retardant fabric obtained in Comparative Example 3.

The present invention will be described in detail below.
The flame-retardant fabric of the present invention includes a spun yarn containing a flame-retardant synthetic fiber and a cellulosic fiber. By including such a spun yarn, the fabric has excellent flame retardancy and appropriate water absorption and moisture absorption properties.

Flame-retardant synthetic fibers are not particularly limited, and examples thereof include flame-retardant vinylon fibers, flame-retardant rayon, flame-retardant acrylic fibers, flame-retardant polyester fibers, meta-aramid fibers, para-aramid fibers, polyparaphenylenebenzoxazole fibers, polybenzimidazole fibers, polyimide fibers, polyetherimide fibers, polyamideimide fibers, carbon fibers, polyphenylene sulfide fibers, polyvinyl chloride fibers, modacrylic fibers, melamine fibers, and fluorine fibers. Among these, flame-retardant vinylon fibers (sometimes referred to as flame-retardant vinylon fibers in the present invention) are preferred because of their excellent flame retardancy and abrasion resistance, as well as their excellent water absorption and moisture absorption properties, and because of the safety of combustion gases and cost.

Flame-retardant synthetic fibers preferably have an LOI (limiting oxygen index) value, which is an indicator of flame retardancy and is measured according to JIS L1091 E method, of 25 or more, and more preferably 26 or more.

The single yarn fineness of the flame-retardant synthetic fiber is not particularly limited, but from the viewpoints of spinnability and strength, it is preferably 0.5 to 3 dtex. If it is less than 0.5 dtex, the strength may be poor, and if it exceeds 3 dtex, the number of cotton threads that can be used for spinning may decrease, which may cause problems with spinnability. In addition, the fiber length of the flame-retardant synthetic fiber is not particularly limited, but from the viewpoint of spinnability, it is preferably 20 to 100 mm. If it is less than 20 mm, the length of the entangled yarn may not be sufficient, resulting in insufficient spinnability. On the other hand, if it exceeds 100 mm, it may become difficult to apply drawing, etc., and the spinnability may instead be insufficient.

The cellulose-based fiber is not particularly limited, and examples thereof include natural cellulose fibers such as cotton and hemp, and regenerated cellulose fibers such as viscose rayon and solvent-spun cellulose fibers. Among these, when flame-retardant vinylon fiber is used as the flame-retardant synthetic fiber, cotton is preferred because of its compatibility with flame retardancy.

Examples of cotton include American cotton, Australian cotton, Brazilian cotton, Indian cotton, Egyptian cotton, Chinese cotton, Greek cotton, etc. Two or more types of such cotton may be mixed and used.

The single yarn fineness of the cellulose fiber is not particularly limited, but from the viewpoint of spinnability and strength, it is preferably 0.5 to 3.0 dtex. If it is less than 0.5 dtex, the strength may be poor, and if it exceeds 3.0 dtex, the number of cotton threads that can be used for spinning may decrease, resulting in poor spinnability. The fiber length of the cellulose fiber is not particularly limited, but from the viewpoint of spinnability, it is preferably 20 to 100 mm. If it is less than 20 mm, the length of the entangled yarn may be insufficient, resulting in insufficient spinnability, and if it exceeds 100 mm, it may become difficult to apply drawing, etc., resulting in insufficient spinnability.

The count of the spun yarn containing flame-retardant synthetic fibers and cellulosic fibers is 10 to 45, preferably 15 to 45, and more preferably 20 to 40. If the count is less than 10, the yarn will be too thick when woven into a fabric, losing its texture and resulting in poor quality. If the count is more than 45, the yarn will be too thin when woven into a fabric, resulting in poor abrasion resistance and a low flammability classification.

In spun yarns containing flame-retardant synthetic fibers and cellulosic fibers, the mass ratio of the flame-retardant synthetic fibers to the cellulosic fibers is preferably (flame-retardant synthetic fibers):(cellulosic fibers) = 90:10 to 60:40, and more preferably 80:20 to 65:35. By keeping it in the above range, it is possible to achieve an excellent balance between flame retardancy and comfort such as water absorption and moisture absorption, and to further improve strength.

The spun yarn may be a two-ply yarn or a single yarn.

In the flame-retardant fabric of the present invention, the blending ratio of the above-mentioned spun yarn is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.

The blending ratio of flame-retardant synthetic fibers in the flame-retardant fabric of the present invention is preferably 50 to 90% by mass, and more preferably 60 to 85% by mass. If it is less than 50% by mass, the flame retardancy or strength may decrease. On the other hand, if it exceeds 90% by mass, the water absorption, moisture absorption, and texture may decrease.

The blending ratio of cellulosic fibers in the flame-retardant fabric of the present invention is preferably 10 to 50% by mass, and more preferably 15 to 40% by mass. If it is less than 10% by mass, the water absorption and moisture absorption properties may decrease, resulting in a decrease in comfort, while if it exceeds 50% by mass, the flame retardancy may be insufficient.

The flame-retardant fabric of the present invention may contain yarns other than the above-mentioned spun yarns, as long as the effect of the present invention is not impaired. Examples of such yarns include multifilaments made of synthetic fibers such as polyester fibers, polyamide fibers, polyolefin fibers, and polyurethane fibers, and spun yarns made of natural fibers other than cellulosic fibers. The mixing ratio of yarns other than the above-mentioned spun yarns is, for example, preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 0% by mass.

The thickness of the flame-retardant fabric of the present invention is preferably 0.3 to 1.0 mm, and more preferably 0.4 to 0.8 mm. If the thickness is less than 0.3 mm, the flame retardancy may decrease or holes may be easily generated during combustion. On the other hand, if the thickness exceeds 1.0 mm, the texture may be impaired and the quality may be inferior.

In the flame-retardant fabric of the present invention, there is at least one intersection between two or more parallel warp threads and two or more parallel weft threads, preferably at least four intersections per 2.54 cm x 2.54 cm, more preferably at least 10 intersections per 2.54 cm x 2.54 cm, and even more preferably at least 50 intersections per 2.54 cm x 2.54 cm. The presence of such intersections makes the fabric less susceptible to breakage during wear, and improves wear resistance even when the fabric is water-repellent. The intersections are indicated by reference numeral 1 in Figs. 1 and 2.

The surface of the flame-retardant woven fabric of the present invention must be water-repellent. By applying the water-repellent treatment, the water retention rate and diffusion drying speed described below can be set within a preferred range, and the fabric does not absorb too much water and has excellent quick-drying properties. When the fabric is water-repellent, the abrasion resistance of the fabric surface tends to decrease, but the present invention uses the weave structure described above, so the abrasion resistance can be improved. The method of applying the water-repellent treatment is not particularly limited, but examples include a method in which a water-repellent agent is applied to the surface of the flame-retardant woven fabric by a known method.

Examples of water repellents include silicone-based water repellents and fluorine-based water repellents. Among them, from the viewpoint of water repellency, fluorine-based water repellents are preferred. Examples of fluorine-based water repellents include fluorine-based water repellents having a fluoroalkyl acrylate group with 6 or less carbon atoms. Among them, fluorine-based water repellents mainly composed of C4-6 organic fluorine compounds (C4-C6) in which fluorine atoms are bonded to 4-6 carbon atoms are preferred, and perfluorohexanoic acid (C6)-based water repellents are more preferred. Furthermore, from the viewpoint of environmental considerations, it is preferred that the fluorine-based water repellent does not substantially contain PFOA (perfluorooctanoic acid). Examples of fluorine-based water repellents that do not substantially contain PFOA (perfluorooctanoic acid) include Asahi Guard E Series (manufactured by Asahi Glass Co., Ltd.), NK Guard S Series (manufactured by Nicca Chemical Co., Ltd.), and Unidyne Multi Series (manufactured by Daikin Industries, Ltd.).

One method for applying the water repellent to the surface of a woven fabric is, for example, to impregnate the fabric with an aqueous solution containing the water repellent and then to subject the fabric to a heat treatment. In addition, it is preferable for the aqueous solution containing the water repellent to contain a crosslinking agent in order to further improve the quick-drying washing durability. In addition, the aqueous solution containing the water repellent can also contain various additives such as surfactants, fabric softeners, and antibacterial agents. For example, the usual pad-dry method can be used to impregnate the fabric with the aqueous solution containing the water repellent.

The amount of water repellent applied to the flame-retardant fabric is preferably, for example, 50 to 150% by mass relative to 100% by mass of spun yarn. If it is less than 50% by mass, water repellency may be difficult to achieve, and if it exceeds 150% by mass, stains such as resins may easily adhere to the fabric.

The flame-retardant woven fabric of the present invention has excellent flame retardancy, and the LOI value (limiting oxygen index) measured according to JIS L 1091 E method is preferably 25 or more, more preferably 26 or more, and even more preferably 27 or more. In order to set the LOI value in the above range, for example, the LOI value of the flame-retardant synthetic fiber used and its mixing ratio can be set to a preferred range.

The flame-retardant fabric of the present invention has moderate water absorption and moisture absorption that are not too high, and the water retention is preferably 50% or less, and more preferably 45% or less. If the water retention is within the above range, it is less likely to become heavy when wet and movement during work is less likely to be hindered. In the present invention, the water retention can be set to the above range by applying a water-repellent finish to the surface of the fabric. In order to set the water retention in a more preferable range, for example, the blend ratio of cellulosic fibers can be set to a specific range. The method for measuring the water retention will be described in detail in the Examples.

The flame-retardant woven fabric of the present invention has excellent drying properties, and the diffusion drying rate is preferably 40 minutes or less, more preferably 35 minutes or less, and even more preferably 30 minutes or less. If the diffusion drying rate is within the above range, the fabric dries easily after getting wet, and the time during which movement is hindered during work or the time during which the fabric feels uncomfortable when in contact with the skin is shortened. In the present invention, the diffusion drying rate can be set within the above range by applying a water-repellent finish to the surface of the woven fabric. The method for measuring the diffusion drying rate will be described in detail in the Examples.

The flame-retardant fabric of the present invention preferably has a flammability classification of 3 or more in a flammability test classified according to JIS L 1091 A-1. In order to set the flammability classification within the above range, for example, the blending ratio of flame-retardant vinylon fiber or the count of the spun yarn can be set to a specific range.

The flame-retardant woven fabric of the present invention has excellent abrasion strength, and the flat abrasion strength measured according to JIS L1096 A-1 method (load 4.45N, using P800-Cw as abrasive paper) is preferably 200 times or more, more preferably 210 times or more, and even more preferably 220 times or more. By adopting a structure for the woven fabric in which a warp yarn made of two or more parallel threads and a weft yarn made of two or more parallel threads intersect at one location/2.54 cm x 2.54 cm or more as described above and setting the yarn count of the spun yarn to a specific range, the flat abrasion strength can be set to the above range. The method for measuring the flat abrasion strength will be described in detail in the Examples.

The flame-retardant fabric of the present invention preferably has a heat consumption of 15 W/( ^m2 ·°C) or less, more preferably 13 W/( ^m2 ·°C) or less, and even more preferably 11 W/( ^m2 ·°C) or less. The heat consumption in the above range is an indicator that the flame-retardant fabric is less likely to lose body heat when it comes into contact with the skin in a wet state. The heat consumption can be set to the above range by applying a water-repellent finish to the surface of the fabric. The method for measuring the heat consumption will be described in detail in the Examples.

The flame-retardant fabric of the present invention has excellent flame retardancy, moderate water absorption and moisture absorption, and excellent quick-drying and abrasion resistance, and can be used for various applications such as industrial materials and general clothing. Examples of applications include protective clothing, flame-retardant protective clothing, work clothes, gloves, aprons, uniforms, outdoor goods, and interior goods. Among these, it is particularly suitable for applications in the rain or applications where it is expected to get wet.

The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.
The methods for measuring or evaluating each physical property are as follows.

<Number of intersections between two or more parallel warp threads and two or more parallel weft threads>
A surface photograph of the 2.54 cm x 2.54 cm test piece was taken using a digital microscope VHX-900 manufactured by Keyence Corporation, and the number of particles was counted.

<LOI value (Limit Oxygen Index)>
The measurement was performed in accordance with JIS L1091, Method E.
<Water retention rate>
The mass (W ₀ ) of a 25 cm x 25 cm test piece was measured, and then the test piece was immersed in distilled water for 10 minutes. After immersion, one of the four corners of the test piece was lifted and left to stand in that state for 10 minutes, and then the mass (W ₁ ) was measured. The water retention was calculated using the following formula.
Water retention rate (%) = [(W ₁ - W ₀ )/W ₀ ] x 100

<Diffusion drying speed>
The mass (W) of a 10 cm x 10 cm test piece was measured. Next, 0.6 ml of water was dropped onto the back side of the test piece, and the mass (W0) was measured. The mass (Wt) of the test piece after the water was dropped was measured under standard conditions (temperature 20°C, humidity 65%). Then, while the test piece was still on the balance, the time until the mass (Wt) reached a residual moisture content (%) of 10% or less, calculated by the following formula, was measured, and this time was taken as the diffusion drying speed.
Residual moisture percentage (%) = {(Wt-W)/(W0-W)}×100

<Flammability classification>
The evaluation was carried out according to the classification of the A-1 method of JIS L1091.

<Flat abrasion strength>
The measurement was performed according to JIS L0196 A-1 method (plane method), except that the load was 4.45 N and the abrasive paper used was "P800-CW" manufactured by Nippon Abrasive Paper Co., Ltd.

<Heat consumption>
The measurement was performed using a Thermo Labo II type tester (manufactured by Kato Tech Co., Ltd.) The measurement environment was a temperature of 20° C. and a humidity of 65%.

Example 1
A sliver of flame-retardant vinylon fiber (manufactured by Unitika Trading Co., Ltd., product name Mulon FR) (single yarn fineness: 1.5 dtex, fiber length: 38 mm) with an LOI value of 35 and a sliver of cotton fiber (single yarn fineness: 1.42 dtex, fiber length: 32 mm) were prepared.

Both slivers were drawn and spun to produce a roving consisting of the flame-retardant vinylon fiber and the cotton fiber. This roving was then introduced into a ring spinning machine and spun to produce a spun yarn with a twist factor of 3.8 and a count of 30 (British cotton count). The blend ratio of the flame-retardant vinylon fiber in the resulting spun yarn was 70% by mass, and the blend ratio of the cotton fiber was 30% by mass.

Next, two of these spun yarns were twisted together to obtain a two-ply yarn of 15 count. Using the obtained two-ply yarn, a fabric of 75 warp threads/2.54 cm and 56 weft threads/2.54 cm was woven using an air jet loom (manufactured by Ishikawa Seisakusho Co., Ltd.). The weave structure was a butcher structure in which the warp threads and weft threads were woven randomly in pairs, as shown in Figure 1. In this structure, there were 96 points/2.54 cm x 2.54 cm where two or more warp threads pulled together intersected with two or more weft threads pulled together.

The obtained fabric was subjected to the usual desizing, scouring, bleaching, and mercerization, and then dyed with a threne dye by a continuous dyeing method to obtain a khaki fabric. The dyed fabric was immersed in an aqueous solution of the following formulation 1. The immersed fabric was then taken out, squeezed with a mangle, and heat-treated at 130°C for 2 minutes to obtain the flame-retardant fabric of Example 1.
<Formulation 1>
Asahiguard LSE-009 (manufactured by Meisei Chemical Industry Co., Ltd., fluorine-based water repellent): 140 g/l
NK Assist V (manufactured by Nicca Chemical Industry Co., Ltd., isocyanate-based crosslinking agent): 30 g / l
Riken Resin MM-35 (Miki Riken Kogyo Co., Ltd., melamine resin): 3.5 g / l
Riken Resin MS-150 (manufactured by Miki Riken Kogyo Co., Ltd., glyoxal-based resin): 50 g/l
Hi-Softer K15 (manufactured by Meisei Chemical Industry Co., Ltd., silicone-based fabric softener): 30 g/l
Minex SO (Meisei Chemical Industry Co., Ltd., penetrating agent): 2 g/l

Example 2
A flame-retardant woven fabric of Example 2 was obtained in the same manner as in Example 1, except that the weave structure was changed to the rip structure shown in Figure 2. In this structure, there were four locations/2.54 cm x 2.54 cm where a warp yarn consisting of two or more parallel threads crossed a weft yarn consisting of two or more parallel threads.

(Comparative Example 1)
A flame-retardant fabric of Comparative Example 1 was obtained in the same manner as in Example 1, except that the spun yarn used was changed to a spun yarn obtained using 100 mass% cotton fiber (single yarn fineness: 1.42 dtex, fiber length: 32 mm).

(Comparative Example 2)
A flame-retardant woven fabric of Comparative Example 2 was obtained in the same manner as in Example 1, except that the spun yarn used was changed to a single yarn of 50 count.

(Comparative Example 3)
A flame-retardant fabric of Comparative Example 3 was obtained in the same manner as in Example 1, except that the weave was a 2/1 twill weave as shown in Figure 3. In this weave, there was no portion where a warp yarn made up of two or more parallel threads crossed a weft yarn made up of two or more parallel threads.

(Comparative Example 4)
A flame-retardant woven fabric of Comparative Example 4 was obtained in the same manner as in Example 1, except that the finishing formulation was changed from Formulation 1 to Formulation 2 below, which did not contain a water repellent agent.
<Formulation 2>
Riken Resin MM-35 (Miki Riken Kogyo Co., Ltd., melamine resin): 3.5 g / l
Riken Resin MS-150 (manufactured by Miki Riken Kogyo Co., Ltd., glyoxal-based resin): 50 g/l
Hi-Softer K15 (manufactured by Meisei Chemical Industry Co., Ltd., silicone-based fabric softener): 30 g/l

The evaluation results for the examples and comparative examples are shown in Table 1.

(Discussion)
The flame-retardant woven fabrics of the present invention obtained in Examples 1 and 2 were excellent in flame retardancy and quick-drying property, and also had appropriate water absorption and moisture absorption properties, and further had excellent abrasion strength.

The fabric obtained in Comparative Example 1 was inferior in flame retardancy since no flame-retardant vinylon fiber was used.
The fabric obtained in Comparative Example 2 was inferior in abrasion resistance because a fine single yarn count of 50 was used as the spun yarn. Furthermore, the flammability classification was low.
The fabric obtained in Comparative Example 3 was constructed with a twill weave, and had poor abrasion resistance because there were no parts where two or more warp threads aligned in parallel crossed with two or more weft threads aligned in parallel.
The fabric obtained in Comparative Example 4 was not treated with a water-repellent finish, and therefore had excessively high water absorption and moisture absorption properties, was poor in quick-drying properties, consumed a high amount of heat, and was prone to absorbing body heat when it came into contact with the skin in a wet state.

1. The part where two or more parallel warp threads cross over two or more parallel weft threads.

Claims (8)

A woven fabric comprising a spun yarn containing a flame-retardant synthetic fiber and a cellulosic fiber,
The spun yarn has a count of 10 to 45,
The blending rate of spun yarn in the woven fabric is 80% by mass or more, and the blending rate of flame-retardant synthetic fiber is 50 to 90% by mass,
The woven fabric has a cross section of two or more parallel warp yarns and two or more parallel weft yarns, the cross section being 2.54 cm x 2.54 cm or more in size;
The flame-retardant fabric has a butcher structure or a ripstop structure, is water-repellent by laminating a silicone-based water-repellent layer or a fluorine-based water-repellent layer on the surface , and has a flat abrasion strength of 200 times or more as measured in accordance with JIS L1096 A-1 method (load 4.45 N, using P800-Cw as abrasive paper) . The flame-retardant fabric according to claim 1, which has a limiting oxygen index (LOI) value of 25 or more as measured according to JIS L 1091 E method. 3. The flame-retardant fabric according to claim 1, which has a water retention rate of 50% or less as measured by the following measurement method.
The mass (W ₀ ) of a 25 cm x 25 cm test piece is measured. The sample is then immersed in distilled water for 10 minutes, one of the four corners of the sample is lifted and left to stand in that position for 10 minutes, after which the mass (W ₁ ) is measured. The water retention is calculated using the following formula.
Water retention rate (%) = [(W ₁ - W ₀ )/W ₀ ] x 100 The flame-retardant fabric according to any one of claims 1 to 3, having a diffusion drying speed of 40 minutes or less as measured by the following measurement method.
The mass (W) of a 10 cm x 10 cm test piece is measured. Next, 0.6 ml of water is dropped onto the back side of the test piece, and the mass (W0) is measured. Then, the mass (Wt) of the test piece after the water has been dropped is measured under standard conditions (temperature 20°C, humidity 65%). Then, while the test piece is still on the balance, the time until the mass (Wt) becomes 10% or less as calculated by the following formula is measured, and this time is taken as the diffusion drying speed.
Residual moisture percentage (%) = {(Wt-W)/(W0-W)}×100 The flame-retardant fabric according to any one of claims 1 to 4, which has a flammability classification of 3 or higher in a flammability test classified according to JIS L 1091 A-1 method. The flame-retardant fabric according to any one of claims 1 to 5 , wherein the heat consumption measured in an environment of a temperature of 20°C and a humidity of 65% using a Thermo Labo II type testing machine (manufactured by Kato Tech Co., Ltd.) is 15 W/( ^m2 ·°C) or less. The flame-retardant fabric according to any one of claims 1 to 6 , wherein the flame-retardant synthetic fiber is a flame-retardant vinylon fiber. The flame-retardant fabric according to any one of claims 1 to 7 , wherein a mass ratio of the flame-retardant synthetic fibers to the cellulosic fibers is (flame-retardant synthetic fibers):(cellulosic fibers)=90:10 to 60:40.