Flame-retardant fiber composite

Abstract

The present invention relates to a flame-retardant fiber composite comprising, as main components, (A) a flame-retardant acrylic fiber and (B) a polyvinyl alcohol-based fiber, wherein the composite ratio (mass ratio, flame-retardant acrylic fiber (A) / polyvinyl alcohol-based fiber (B)) between the flame-retardant acrylic fiber (A) and the polyvinyl alcohol-based fiber (B) is 90 / 10 to 30 / 70; the flame-retardant acrylic fiber (A) has a copolymer structure of acrylonitrile and a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer and contains an antimony compound; and the polyvinyl alcohol-based fiber (B) contains an organic sulfur compound.

Description

Flame-retardant fiber composite

[0001] The present invention relates to a flame-retardant fiber composite comprising a flame-retardant acrylic fiber and a polyvinyl alcohol fiber, and a textile product comprising the flame-retardant fiber composite.

[0002] Conventionally known flame-retardant fibers include acrylic fibers copolymerized with flame-retardant monomers, acrylic fibers kneaded with or reacted with flame-retardant chemicals, regenerated cellulose fibers, polyester fibers, aramid fibers, whose polymers are flame-retardant themselves, and cotton or wool that has been post-treated with flame-retardant chemicals.

[0003] When flame-retardant fibers are used in clothing such as safety workwear and textile products for bedding, in addition to flame retardancy, they are required to have mechanical properties such as strength, texture, moisture absorption, and washability. Because it is difficult for a flame-retardant fiber alone to meet these high performance requirements, numerous studies have been conducted to obtain flame-retardant fiber composites by combining a flame-retardant fiber with a flammable fiber (non-flame-retardant fiber) that has characteristics different from those of the flame-retardant fiber. For example, Patent Document 1 describes a flame-retardant fiber composite in which cotton is blended with modacrylic fiber in which a halogen-containing polymer contains an Sb compound as a flame retardant. Patent Document 2 also describes a composite flame-retardant fiber in which a halogen-containing acrylic fiber is blended with cotton and a polyvinyl alcohol-based fiber.

[0004] JP-A-7-252735 JP-A-4-209823

[0005] Conventional flame-retardant fiber composites such as those described in the above patent documents have sometimes had the problem that the flame retardancy of the composite is lower than that of the flame-retardant fiber before being compounded. Therefore, an object of the present invention is to provide a flame-retardant fiber composite that has high flame retardancy equal to or higher than that of the flame-retardant fiber before being compounded and has excellent strength, and a textile product containing the flame-retardant fiber composite.

[0006] The present inventors conducted extensive research to solve the above-mentioned problems and found that a flame-retardant fiber composite containing a flame-retardant acrylic fiber (A) having a copolymer structure of acrylonitrile with a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer and containing an antimony compound and a polyvinyl alcohol fiber (B) containing an organic sulfur compound in a predetermined ratio has flame retardancy equal to or greater than that of the flame-retardant fiber before being composited, thereby completing the present invention. Although the exact mechanism by which flame retardancy is maintained or improved is unknown, it is presumed that the presence of the organic sulfur compound in the polyvinyl alcohol fiber promotes the dehydroxylation of polyvinyl alcohol by halogen, which in turn facilitates carbonization of the polyvinyl alcohol, thereby suppressing combustion.

[0007] That is, the present invention encompasses the following preferred embodiments. [1] A flame-retardant fiber composite comprising flame-retardant acrylic fibers (A) and polyvinyl alcohol-based fibers (B) as main components, wherein the composite ratio of the flame-retardant acrylic fibers (A) to the polyvinyl alcohol-based fibers (B) (mass ratio, flame-retardant acrylic fibers (A) / polyvinyl alcohol-based fibers (B)) is 90 / 10 to 30 / 70, the flame-retardant acrylic fibers (A) have a copolymer structure of acrylonitrile and a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer and contain an antimony compound, and the polyvinyl alcohol-based fibers (B) contain an organic sulfur compound. [2] The flame-retardant fiber composite according to claim 1, wherein the total mass of the flame-retardant acrylic fibers (A) and the polyvinyl alcohol-based fibers (B) is 80 mass% or more of the total mass of the flame-retardant fiber composite. [3] The flame-retardant fiber composite according to [1] or [2], wherein the polyvinyl alcohol-based fiber (B) contains an organic sulfur compound in an amount of 0.001 to 0.5% by mass, expressed as sulfur content relative to the total mass of the polyvinyl alcohol-based fiber (B). [4] The flame-retardant fiber composite according to any one of [1] to [3], wherein the flame-retardant acrylic fiber (A) accounts for 24 to 90% by mass, relative to the total mass of the flame-retardant fiber composite. [5] The flame-retardant fiber composite according to any one of [1] to [4], wherein the polyvinyl alcohol-based fiber (B) accounts for 8 to 70% by mass, relative to the total mass of the flame-retardant fiber composite. [6] The flame-retardant fiber composite according to any one of [1] to [5], wherein the polyvinyl alcohol-based fiber (B) has a limiting oxygen index of less than 25 according to the method described in JIS K-7201. [7] The flame-retardant fiber composite according to any one of [1] to [6], wherein the polyvinyl alcohol-based fiber (B) has a strength of 2 cN / dtex or more. [8] The flame-retardant fiber composite according to any one of [1] to [7], wherein the flame-retardant acrylic fiber (A) comprises an acrylic copolymer containing, relative to all monomer units constituting the copolymer, 30 to 70 mass% of structural units derived from acrylonitrile, 70 to 30 mass% of structural units derived from a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer, and 0 to 10 mass% of structural units derived from a vinyl monomer copolymerizable therewith.[9] The flame-retardant fiber composite according to any one of [1] to [8], wherein the amount of the other fiber (C) different from the flame-retardant acrylic fiber (A) and the polyvinyl alcohol-based fiber (B) is 15 mass% or less based on the total mass of the flame-retardant fiber composite.

[10] The flame-retardant fiber composite according to any one of [1] to [9], wherein the limiting oxygen index of the flame-retardant fiber composite is higher than the limiting oxygen index of the flame-retardant acrylic fiber (A) alone.

[11] A textile product comprising the flame-retardant fiber composite according to any one of [1] to

[10] .

[0008] According to the present invention, it is possible to provide a flame-retardant fiber composite having high flame retardancy equal to or greater than that of the flame-retardant fiber before being compounded and excellent strength, and a textile product containing the flame-retardant fiber composite.

[0009] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

[0010] [Flame-Retardant Fiber Composite] The flame-retardant fiber composite of the present invention is a flame-retardant fiber composite comprising a flame-retardant acrylic fiber (A) and a polyvinyl alcohol-based fiber (B) as main components, wherein the flame-retardant acrylic fiber (A) and the polyvinyl alcohol-based fiber (B) are combined in a ratio (mass ratio, flame-retardant acrylic fiber (A) / polyvinyl alcohol-based fiber (B)) of 90 / 10 to 30 / 70, the flame-retardant acrylic fiber (A) has a copolymer structure of acrylonitrile and a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer, and contains an antimony compound, and the polyvinyl alcohol-based fiber (B) contains an organic sulfur compound. The flame-retardant fiber composite of the present invention, which contains such a flame-retardant acrylic fiber and a polyvinyl alcohol-based fiber containing an organic sulfur compound in a specific ratio, exhibits high flame retardancy equal to or greater than that of the flame-retardant acrylic fiber before combination.

[0011] The flame-retardant acrylic fiber (A) (hereinafter also referred to simply as "fiber (A)") and polyvinyl alcohol fiber (B) (hereinafter also referred to simply as "fiber (B)") in the flame-retardant fiber composite have a composite ratio (fiber (A) / fiber (B)) of 90 / 10 to 30 / 70 by mass. When the composite ratio of the two fibers is within the above range, the flame retardancy of the resulting fiber composite can be improved. Furthermore, the strength of the resulting fiber composite can be improved. This allows for the production of highly durable fabrics and thin or lightweight fabrics that have high flame retardancy. To further enhance the above effects, the composite ratio is preferably 80 / 20 to 40 / 60, more preferably 75 / 25 to 45 / 55, and even more preferably 70 / 30 to 50 / 50.

[0012] Fiber (A) and fiber (B) are the main components of the flame-retardant fiber composite of the present invention. Here, in this specification, the term "main component" of the flame-retardant fiber composite means that the total amount of fiber (A) and fiber (B) is greater than 50 mass% relative to the total mass of the flame-retardant fiber composite. By constructing a fiber composite using fiber (A) and fiber (B) as the main components, a fiber composite having both high flame retardancy and high strength can be formed. The total mass of fiber (A) and fiber (B) contained in the flame-retardant fiber composite of the present invention is preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 80 mass% or more, and particularly preferably 85 mass% or more, relative to the total mass of the flame-retardant fiber composite. When the total amount of fiber (A) and fiber (B) in the flame-retardant fiber composite is within the above range, a flame-retardant fiber composite with even better flame retardancy and strength can be obtained. The total amount of fiber (A) and fiber (B) may be 100 mass% relative to the total mass of the flame-retardant fiber composite. In one embodiment of the present invention, the total mass of fiber (A) and fiber (B) in the flame-retardant fiber composite is preferably 60 to 100 mass%, more preferably 70 to 100 mass%, even more preferably 80 to 100 mass%, and particularly preferably 85 to 100 mass%, relative to the total mass of the flame-retardant fiber composite.

[0013] From the viewpoint of enhancing the flame retardancy of the flame-retardant fiber composite, the content of fiber (A) relative to the total mass of the flame-retardant fiber composite is preferably 24 to 90 mass%, more preferably 30 to 85 mass%, even more preferably 32 to 80 mass%, even more preferably 36 to 75 mass%, and particularly preferably 40 to 70 mass%. When the content of fiber (A) is within this range, a composite fiber with excellent flame retardancy and strength can be obtained. In one embodiment of the present invention, the amount of fiber (A) is preferably selected so that, together with the amount of fiber (B), it is within the range of the total amount of fiber (A) and fiber (B) in the flame-retardant fiber composite described above.

[0014] The content of fiber (B) relative to the total mass of the flame-retardant fiber composite is preferably 8 to 70 mass%, more preferably 12 to 65 mass%, even more preferably 16 to 60 mass%, even more preferably 20 to 55 mass%, and particularly preferably 24 to 50 mass%. When the content of fiber (B) is within this range, a composite fiber with excellent flame retardancy and strength can be obtained. In one embodiment of the present invention, the amount of fiber (B) is preferably selected so that, together with the amount of fiber (A), it is within the range of the total amount of fiber (A) and fiber (B) in the flame-retardant fiber composite described above.

[0015] The content (proportion) of fiber (A) and / or fiber (B) relative to the total mass of the flame-retardant fiber composite may be calculated from the mixing ratio of each raw material when producing the flame-retardant fiber composite. Alternatively, for example, the content (proportion) of the flame-retardant fiber composite may be calculated by analyzing and measuring the flame-retardant fiber composite according to the method described in JIS L1030-2, Test Method for Fiber Product Blend Ratio—Part 2: Fiber Blend Ratio. For example, when the flame-retardant fiber composite consists of only two types of fiber (A) and fiber (B), the blend ratio can be determined by dissolving fiber (A) in warm dimethylformamide or dissolving fiber (B) in 70% sulfuric acid.

[0016] <Flame-retardant acrylic fiber (A)> The flame-retardant fiber composite of the present invention contains a flame-retardant acrylic fiber (A). The fiber (A) has a copolymer structure of acrylonitrile and a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer, and also contains an antimony compound. Hereinafter, a copolymer having a copolymer structure of acrylonitrile and a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer will also be referred to as an "acrylic copolymer."

[0017] The halogen-containing vinyl monomer and / or halogen-containing vinylidene monomer constituting the fiber (A) is not particularly limited as long as it is a vinyl monomer containing a halogen atom, and known monomers can be used. Preferred are vinyl monomers containing a chlorine atom or a bromine atom. Specific examples include vinyl chloride, vinylidene chloride, vinyl bromide, and vinylidene bromide. From the viewpoints of availability and flame retardancy, vinyl chloride and vinylidene chloride are preferred. These monomers may be used alone or in combination of two or more.

[0018] The acrylic copolymer may be composed of acrylonitrile, a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer, and a vinyl monomer copolymerizable therewith (hereinafter also referred to as a "copolymerizable vinyl monomer"). Examples of such copolymerizable vinyl monomers include acrylic acid; acrylic acid esters such as ethyl acrylate and propyl acrylate; methacrylic acid; methacrylic acid esters such as methyl methacrylate and ethyl methacrylate; acrylamide; vinyl acetate; vinyl sulfonic acid; vinyl sulfonates such as sodium vinyl sulfonate; styrene sulfonic acid; styrene sulfonates such as sodium styrene sulfonate. These may be used alone or in combination of two or more.

[0019] In the acrylic copolymer constituting the fiber (A) having a copolymer structure of acrylonitrile and a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer, the content of structural units derived from acrylonitrile is preferably 30 to 70 mass% and more preferably 40 to 60 mass% relative to the total monomer units (100 mass%) constituting the acrylic copolymer. Furthermore, in the acrylic copolymer, the content of structural units derived from halogen-containing vinyl monomers and / or halogen-containing vinylidene monomers is preferably 30 to 70 mass% and more preferably 40 to 60 mass% relative to the total monomer units (100 mass%) constituting the acrylic copolymer. Furthermore, in the acrylic copolymer, the content of structural units derived from copolymerizable vinyl monomers is preferably 0 to 10 mass% and more preferably 1 to 5 mass% relative to the total monomer units (100 mass%) constituting the acrylic copolymer. In addition, when the acrylic copolymer is composed of acrylonitrile, a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer, and an arbitrary copolymerizable vinyl monomer, the total of the structural units derived from these monomers in the acrylic copolymer is 100 mass%.

[0020] In an acrylic copolymer, when the proportion of structural units derived from acrylonitrile is equal to or greater than the lower limit and the proportion of structural units derived from halogen-containing vinyl monomers and / or halogen-containing vinylidene monomers is equal to or less than the upper limit, sufficient heat resistance is easily obtained. Furthermore, when the proportion of structural units derived from acrylonitrile is equal to or less than the upper limit and the proportion of structural units derived from halogen-containing vinyl monomers and / or halogen-containing vinylidene monomers is equal to or greater than the lower limit, sufficient flame retardancy is easily ensured. Furthermore, when the proportion of copolymerizable vinyl monomers in an acrylic copolymer is equal to or less than the upper limit, the two properties characteristic of halogen-containing flame-retardant fibers, flame retardancy and texture, are easily achieved.

[0021] The acrylic copolymer can be prepared by polymerizing a monomer mixture containing acrylonitrile, a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer, and, if necessary, a vinyl monomer copolymerizable therewith. The method for obtaining such an acrylic copolymer is not particularly limited, and any of ordinary vinyl polymerization methods, such as slurry polymerization, emulsion polymerization, and solution polymerization, may be used.

[0022] The fiber (A) contains an antimony compound. The antimony compound is a flame retardant that serves to impart flame retardancy to the acrylic fiber. Preferred examples of the antimony compound include inorganic antimony compounds such as antimony trioxide, antimony pentoxide, antimonic acid, and antimony oxychloride. These compounds may be used alone or in combination of two or more.

[0023] The content of the antimony compound in the fiber (A) is preferably 10 to 30% by mass, more preferably 12 to 25% by mass, and even more preferably 15 to 25% by mass, relative to the acrylic copolymer (100% by mass) contained in the fiber (A). When the content of the antimony compound is within the above range, the flame retardancy of the fiber (A) can be sufficiently enhanced without reducing the strength or elongation of the fiber (A). Another advantage is that problems such as nozzle clogging during production are less likely to occur. After softening and water- and oil-repellent treatments, the content of the antimony compound is preferably 12% by mass or more, more preferably 15% by mass or more, relative to the acrylic copolymer, in order to obtain a highly flame-retardant acrylic fiber. The content of the antimony compound in the fiber (A) can be measured, for example, by the method described in the Examples below.

[0024] The halogen content (particularly the amount of chlorine and bromine) in the fiber (A) is preferably 15 to 65 mass%, more preferably 20 to 55 mass%, based on the acrylic copolymer (100 mass%). The halogen content refers to the content of halogen elements measured by fluorescent X-ray quantitative analysis.

[0025] Examples of methods for obtaining fiber (A) by incorporating an antimony compound, which is a flame retardant, into an acrylic copolymer include a method of dissolving the acrylic copolymer constituting fiber (A) in a solvent capable of dissolving the copolymer, and then mixing and dispersing an antimony compound in the obtained solution to produce fiber, and a method of incorporating the antimony compound by post-processing, such as immersing fiber obtained from the acrylic copolymer in an aqueous binder solution containing an antimony compound, and then squeezing, drying, and heat treating the fiber. The method for obtaining fiber (A) containing an antimony compound is not limited to these, and other methods known in the field may also be used.

[0026] As the fiber (A), commercially available products may be used, such as "Protex" (registered trademark) M type and C type manufactured by Kaneka Corporation.

[0027] In the present invention, the limiting oxygen index (LOI) of fiber (A) alone, as measured according to JIS K-7201, is preferably 30 or more, more preferably 32 or more, and even more preferably 34 or more. When the LOI of fiber (A) is equal to or greater than the lower limit, a flame-retardant fiber composite having superior flame retardancy can be obtained in combination with fiber (B), which will be described later. The upper limit of fiber (A) is not particularly limited, but is usually 40 or less. The limiting oxygen index (LOI) of fiber (A) alone is measured according to JIS K-7201. Specifically, the fiber (A) is formed into a web shape, and vertical cylindrical test pieces are prepared by the method described in the Examples, which will be described later, and the LOI can be measured according to JIS K-7201.

[0028] <Polyvinyl alcohol-based fiber (B)> The flame-retardant fiber composite of the present invention contains a polyvinyl alcohol-based fiber (B). The fiber (B) contains an organic sulfur compound.

[0029] By including an organic sulfur compound in fiber (B), a fiber composite can be obtained with high flame retardancy exceeding that of the flame-retardant acrylic fiber (A) alone before compounding. Although the mechanism by which flame retardancy is improved is not entirely clear, it is presumed that the presence of a predetermined amount of organic sulfur compound in fiber (B) promotes the dehydration reaction of polyvinyl alcohol when fiber (B) is heated in an inert gas derived from halogens such as chlorine contained in fiber (A), thereby facilitating carbonization of polyvinyl alcohol and suppressing combustion of the fiber composite. To achieve the above-mentioned flame retardancy improvement effect, it is important that polyvinyl alcohol and the organic sulfur compound are present in close proximity, and the organic sulfur compound must be present in fiber (B). In other words, even if an organic sulfur compound is present in fiber (A) or a fiber (C) other than fiber (A) and fiber (B), the flame retardancy improvement effect cannot be expected.

[0030] The sulfur compound contained in the fiber (B) is an organic sulfur compound. The organic sulfur compound is an organic compound containing a sulfur atom in the molecule. The sulfur contained in the fiber (B) is derived from the organic sulfur compound, thereby achieving the flame retardancy improvement effect of the present invention. The reason for this effect is not entirely clear, but it is presumed to be due to the stability of the sulfur compound at combustion temperatures. Such an effect cannot be expected even if an inorganic sulfur compound is present in the fiber (B).

[0031] Examples of organic sulfur compounds that can be contained in the fiber (B) include thiol compounds, sulfide compounds, sulfoxide compounds, sulfone compounds, thioketone compounds, sulfonic acids, and sulfinic acids. Among these, the organic sulfur compounds are preferably compounds selected from the group consisting of sulfide compounds and sulfoxide compounds, and sulfoxide compounds are more preferred. These organic sulfur compounds can be incorporated into the fiber (B) during the manufacturing process of the fiber (B), making it easy to control the amount of sulfur in the fiber (B). The organic sulfur compounds contained in the fiber (B) may be one type or two or more types.

[0032] Examples of sulfoxide compounds include dialkyl sulfoxides, alkylaryl sulfoxides, diaryl sulfoxides, etc. Specific examples include dimethyl sulfoxide (DMSO), diethyl sulfoxide, dipropyl sulfoxide, dibutyl sulfoxide, tetramethylene sulfoxide, diphenyl sulfoxide, methylphenyl sulfoxide, phenylvinyl sulfoxide, dibenzyl sulfoxide, etc. Among these, dimethyl sulfoxide is preferred.

[0033] The content of the organic sulfur compound in fiber (B) is preferably 0.001 to 0.5 mass% in terms of the amount of sulfur relative to the total mass of fiber (B). When the content of the organic sulfur compound in fiber (B) is equal to or greater than the lower limit, a fiber composite with superior flame retardancy can be obtained. Furthermore, when the content of the organic sulfur compound is equal to or less than the upper limit, the strength improvement effect of adding fiber (B) can be sufficiently obtained. Furthermore, it is advantageous in terms of suppressing discoloration and odor of fiber (B) and preventing the generation of gases such as sulfur dioxide during combustion. From the viewpoint of further enhancing the above-mentioned effects, the content of the organic sulfur compound in fiber (B) is more preferably 0.005 to 0.4 mass%, and may be, for example, 0.01 to 0.3 mass%, in terms of the amount of sulfur relative to the total mass of fiber (B).

[0034] The content of organic sulfur compounds in the fiber (B) can be measured and calculated, for example, by gas chromatography-mass spectrometry. Specifically, the content can be measured, for example, according to the method described in the Examples below. The extract used for the measurement is appropriately selected depending on the compound to be measured.

[0035] In the present invention, the fiber (B) contains an organic sulfur compound, but may also contain an inorganic sulfur compound in addition to the organic sulfur compound, as long as the effects of the present invention are not affected. The total amount of sulfur contained in the fiber (B) (the total amount of organic sulfur compounds and inorganic sulfur compounds) is preferably 0.001 to 0.5 mass%, more preferably 0.005 to 0.4 mass%, and may be, for example, 0.01 to 0.3 mass%, relative to the total mass of the fiber (B). The total amount of sulfur in the fiber (B) can be measured and calculated, for example, by quantitative analysis using ICP atomic emission spectrometry. In more detail, it can be measured, for example, according to the method described in the Examples below.

[0036] To fully achieve the flame retardancy improvement effect, the content of the organic sulfur compound relative to the total amount of sulfur contained in the fiber (B) is preferably 15% by mass or more, more preferably 20% by mass or more. Furthermore, from the viewpoint of improving the flame retardancy and strength of the fiber composite in a balanced manner, in one embodiment of the present invention, the content of the organic sulfur compound relative to the total amount of sulfur contained in the fiber (B) is preferably 85% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and may even be 100% by mass. The content of the inorganic sulfur compound in the fiber (B) can be measured and calculated, for example, by ion chromatography analysis. More specifically, it can be measured, for example, according to the method described in the Examples below. The extract used for the measurement is appropriately selected depending on the compound to be measured.

[0037] The content of the organic sulfur compound in the fiber (B) can be controlled, for example, by the type, amount, combination, and washing method and conditions of the solvent used in the process of producing the fiber (B), or by intentionally adding or applying the organic sulfur compound.

[0038] In the present invention, the polyvinyl alcohol-based resin (hereinafter also referred to as "PVA-based resin") constituting the fiber (B) is not particularly limited as long as it contains vinyl alcohol units as the main component (for example, 50 mol % or more of all monomer units constituting the PVA-based resin). The vinyl alcohol units of the PVA-based resin can usually be derived from vinyl ester units. Therefore, depending on the conditions for converting the vinyl alcohol units, vinyl ester units may remain in the PVA-based resin. Therefore, the PVA resin may contain vinyl ester units.

[0039] Examples of vinyl esters of the vinyl ester unit include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, and vinyl benzoate. Of these, vinyl acetate is preferred from an industrial viewpoint.

[0040] Furthermore, the PVA-based resin may contain other structural units (modifying units) than the vinyl alcohol unit and the vinyl ester unit, if desired, as long as the effects of the present invention are not impaired. Examples of such modifying units include olefins (e.g., ethylene, propylene, butylene, etc.), acrylic acids (e.g., acrylic acid and its salts, acrylic acid esters such as methyl acrylate, etc.), methacrylic acids (e.g., methacrylic acid and its salts, methacrylic acid esters such as methyl methacrylate, etc.), acrylamides (e.g., acrylamide, N-methylacrylamide, etc.), methacrylamides (e.g., methacrylamide, N-methylolmethacrylamide, etc.), N-vinyllactams (e.g., N-vinylpyrrolidone, etc.), N-vinylamides (e.g., N-vinylformamide, N-vinylacetamide, etc.), vinyl ethers (e.g., allyl ethers having a polyalkylene oxide in the side chain, methyl vinyl ether, etc.), nitriles (e.g., acrylonitrile, etc.), halogenated vinyl compounds (e.g., vinyl chloride, etc.), unsaturated dicarboxylic acids (e.g., itaconic acid, maleic acid, salts thereof, anhydrides thereof, and esters thereof), and sulfonic acid-containing vinyl compounds. These modifying units can be used alone or in combination. The method for introducing such a modifying unit may be a copolymerization method or a post-reaction method.

[0041] The molar ratio of the modifying unit to the vinyl alcohol unit and vinyl ester unit [(vinyl alcohol unit and vinyl ester unit) / (modifying unit)] may be appropriately determined depending on the desired physical properties and characteristics of the polyvinyl alcohol fiber (B), and may be, for example, 85 / 15 to 100 / 0, preferably 88 / 12 to 100 / 0, and more preferably 90 / 10 to 100 / 0.

[0042] The resin may contain additives such as flame retardants, antifreeze agents, pH adjusters, opacifying agents, colorants, oils, and special functional agents depending on the purpose, as long as the effects of the present invention are not impaired. These additives may be contained alone or in combination.

[0043] The viscosity-average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose and is not particularly limited. Considering the mechanical properties and productivity of the resulting fiber, the viscosity-average degree of polymerization calculated from the viscosity of an aqueous solution at 30°C is preferably 500 to 20,000, more preferably 800 to 15,000, and particularly preferably 1,000 to 10,000. From the viewpoint of resin production costs or fiberization costs, the viscosity-average degree of polymerization may be preferably 1,200 to 2,500, more preferably 1,300 to 2,400.

[0044] The saponification degree of the PVA-based resin is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of the mechanical properties of the resulting fiber, processability, production costs, etc., the saponification degree may be, for example, 88 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, and may even be 100 mol%.

[0045] The degree of saponification and viscosity-average degree of polymerization of the PVA-based resin can be measured based on the method described in JIS K 6726 "Testing methods for polyvinyl alcohol."

[0046] The PVA-based resin may be one PVA-based resin, or two or more PVA-based resins that differ in one or more of the following: type of modifying unit, molar ratio of modifying unit to vinyl alcohol unit, viscosity-average degree of polymerization, and degree of saponification.

[0047] (Method for producing polyvinyl alcohol-based fibers) In the present invention, the method for producing fiber (B) is not particularly limited as long as it can incorporate an organic sulfur compound into the fiber, and any commonly used method for producing PVA-based fibers can be used. Examples include aqueous dry spinning and aqueous wet spinning, which use water or an aqueous solution as the solvent, and solvent-based wet spinning, which uses an organic solvent as the solvent. Among these, solvent-based wet spinning is preferred. From the standpoints of productivity and quality, aqueous or solvent-based wet spinning is preferably used. Aqueous wet spinning, which does not use an organic solvent, is advantageous in terms of the environment and health.

[0048] In the present invention, for example, when solvent-based wet spinning is employed, fiber (B) can be produced by the following procedure. First, a spinning dope containing a PVA-based resin constituting the PVA-based fiber, a solvent, and optional additives is prepared. As the solvent for the spinning dope, various polar solvents capable of dissolving the PVA-based resin can be used. For example, organic solvents [sulfoxides such as dimethyl sulfoxide (hereinafter referred to as "DMSO"); nitrogen-containing polar solvents such as dimethylacetamide, dimethylformamide, and N-methylpyrrolidone; polyhydric alcohols such as glycerin and ethylene glycol], or mixtures of these with swelling metal salts such as rhodanides, lithium chloride, calcium chloride, and zinc chloride, can be used. These solvents can be used alone or in combination. Of these, DMSO is preferred from the standpoint of cost and processability, such as recoverability.

[0049] The concentration of the PVA-based resin in the spinning dope varies depending on the composition of the spinning dope, the viscosity-average degree of polymerization of the PVA-based resin, and the type of solvent. For example, if the viscosity-average degree of polymerization of the PVA-based resin is 1,500 to 2,500, the concentration is preferably about 10 to 25% by mass (more preferably about 12 to 20% by mass) from the viewpoint of spinnability.

[0050] In producing the fiber (B), the spinning dope may contain additives such as surfactants, decomposition inhibitors, antifreezing agents, pH adjusters, masking agents, colorants, oils, crosslinking agents, etc., depending on the purpose, as long as the effects of the present invention are not impaired. Furthermore, from the viewpoint of enhancing the flame retardancy of the fiber (B) itself, additives such as chlorine-containing polymers, tin compounds, silicon compounds, antimony compounds, etc. may be contained.

[0051] When adding an additive, the additive may be added to the solvent of the spinning dope before dissolving the PVA-based resin. Alternatively, a solution or dispersion of the additive dissolved or dispersed in a solvent, or the additive may be added to the spinning dope in which the PVA-based resin has been dissolved, and mixed. Furthermore, the additive may be added to the PVA-based fiber once the drying process has been completed by immersion or spraying.

[0052] When a crosslinking agent is used as an additive, the crosslinking agent may be added to the spinning dope, the fibers may be spun into a coagulation bath containing a reaction catalyst, and the crosslinking treatment may be carried out in the process up to drying. Alternatively, the reaction catalyst may be applied in a subsequent process after the coagulation bath (e.g., a drawing bath), and the crosslinking treatment may be carried out in the process up to drying. Furthermore, even if the fibers have been dried, if necessary, a liquid containing a crosslinking agent may be added to the fibers by a method such as immersion or spraying to carry out a crosslinking treatment.

[0053] The obtained spinning dope is then discharged from a nozzle into a coagulation bath capable of solidifying the PVA-based resin. In the case of wet spinning using an organic solvent, the coagulation bath may be an organic solvent capable of solidifying the PVA-based resin, such as alcohols (e.g., methanol, ethanol, propanol, and butanol) or ketones (e.g., acetone, methyl ethyl ketone, and methyl isobutyl ketone).

[0054] Following the coagulation bath, the solidified raw yarn may be passed through an extraction bath to extract and remove the solvent from the spinning solution. For example, organic solvents such as DMSO can be removed from the raw yarn by washing the fibers in an extraction bath containing an alcohol such as methanol. In this case, by appropriately adjusting the washing time and washing temperature, a certain amount of organic sulfur compound (e.g., DMSO) contained as the organic solvent can be contained in the fiber (B).

[0055] The conditions such as the washing temperature and washing time can be appropriately determined depending on the type and concentration of the washing solution used, the desired organic sulfur compound content in the fiber (B), the single yarn fineness, the tow fineness, etc. For example, when DMSO is used as the organic solvent, in one embodiment of the present invention, the washing temperature is preferably 5 to 40°C, more preferably 10 to 35°C. The washing time is preferably 1 to 120 minutes, more preferably 3 to 120 minutes, even more preferably 3 to 60 minutes, and may be, for example, 3 to 15 minutes, 3 to 10 minutes, or 5 to 10 minutes.

[0056] Alternatively, after removing the organic solvent from the raw yarn, a desired organic sulfur compound (e.g., DMSO) can be added to a cleaning solution or the like, thereby allowing a certain amount of the organic sulfur compound (e.g., DMSO) to be contained in the fiber (B).

[0057] Furthermore, if necessary, a treatment such as wet drawing (usually 1.5 to 8 times) may be carried out by a known or conventional method. Thereafter, the raw yarn or drawn yarn is usually subjected to a drying step. Furthermore, the dried raw yarn or drawn yarn may be subjected to a heat treatment such as dry hot drawing (usually at a temperature of 100°C or higher, preferably 150 to 240°C, 1.5 to 15 times). Furthermore, the PVA-based fiber obtained in this manner may be subjected to an acetalization treatment with a monoaldehyde such as formaldehyde, a dialdehyde such as glutaraldehyde or nonanedial, or a derivative thereof, such as an acetalized product, to impart water resistance.

[0058] In the present invention, when aqueous wet spinning is employed, the fiber (B) can be produced by, for example, preparing a spinning dope containing a PVA-based resin constituting a PVA-based fiber, water, and optional additives, wet-spinning the dope to obtain a filament, and then immersing the filament in a DMSO / ethanol mixed solution, or by other steps to provide sulfur in the process.

[0059] The concentration of the PVA-based resin in the spinning solution and the additives that can be used are in the same range and include the same additives as those in the solvent-based wet spinning. The solution used in the coagulation bath can be, for example, an aqueous solution containing sodium hydroxide and sodium sulfate.

[0060] The coagulation bath may be followed by neutralization, washing, etc. The conditions for these steps, the compounds and solutions to be used, etc. can be appropriately selected depending on the composition of the spinning dope, the types of compounds used in the spinning, coagulation, neutralization, etc.

[0061] The resulting fibers are then immersed in a solution containing a desired organic sulfur compound (e.g., DMSO), thereby allowing a certain amount of the organic sulfur compound (e.g., DMSO) to be incorporated into the fibers (B). For example, a DMSO / ethanol mixed solution can be used as the immersion solution. The mixing ratio of DMSO to ethanol (DMSO / ethanol) may be, for example, 0.1 / 99.9 to 10 / 90 by volume. The temperature of the solution used for immersion is, for example, 5 to 30°C, preferably 10 to 25°C. The immersion time can be determined appropriately depending on the concentration and temperature of the organic sulfur compound in the solution, but is, for example, 1 to 10 minutes, preferably 1 to 5 minutes, and more preferably 1 to 3 minutes.

[0062] In the production of fiber (B) by aqueous wet spinning, if necessary, treatment such as wet drawing (usually 1.5 to 8 times) may be carried out by a known or conventional method. Furthermore, the raw yarn or drawn yarn is usually subjected to a drying step. Furthermore, the dried raw yarn or drawn yarn may be subjected to heat treatment such as dry hot drawing (usually at a temperature of 100°C or higher, preferably 150 to 240°C, at 1.5 to 15 times). Furthermore, the PVA-based fiber obtained in this manner may be subjected to an acetalization treatment with a monoaldehyde such as formaldehyde, a dialdehyde such as glutaraldehyde or nonanedial, or a derivative thereof, such as an acetalized product, to impart water resistance.

[0063] The fineness of a single yarn of the fiber (B) is preferably 1 to 20 dtex, more preferably 1.4 to 15 dtex. When the fineness of a single yarn of the PVA-based fiber (B) is within the above range, it is easy to obtain high flexibility, a good wearing comfort, and stable fiber productivity. The fineness of the fiber (B) can be measured, for example, by the method described in JIS L1015 "Testing Methods for Staple Chemical Fibers."

[0064] The fiber strength (tensile strength) of a single yarn of fiber (B) is preferably 2 cN / dtex to 15 cN / dtex, more preferably 3 cN / dtex to 14 cN / dtex, and even more preferably 6 cN / dtex to 13 cN / dtex. Having a fiber strength within this range allows a textile product produced using a flame-retardant fiber composite containing fiber (B) to have both durability and a good feel, and also prevents problems such as yarn breakage during processing to produce textile products, such as spinning and weaving, improving processability. The fiber strength of the PVA-based fiber can be adjusted by the viscosity-average degree of polymerization of the PVA-based polymer, the fineness, average diameter or cross-sectional shape of fiber (B), or the drawing conditions (wet draw ratio, dry heat draw ratio, dry heat drawing temperature). The fiber strength of fiber (B) can be measured in accordance with JIS L 1015, the test method for chemical fiber staples. Specifically, it can be measured by the method described in the Examples below.

[0065] The limiting oxygen index (LOI) of the fiber (B) alone (in web form), measured according to the method described in JIS K-7201, may be preferably less than 25, more preferably less than 23, and even more preferably less than 22. When the LOI of the fiber (B) alone is within the above range, the effect of improving the flame retardancy of the fiber (A) alone tends to be further enhanced. The lower limit of the LOI of the fiber (B) alone is not particularly limited, but is usually 18 or more. Specifically, the limiting oxygen index (LOI) of the fiber (B) can be measured according to the method described in the Examples below, by preparing a vertical cylindrical test piece and measuring it according to the method described in JIS K-7201.

[0066] The flame-retardant fiber composite of the present invention may contain other fibers (hereinafter also referred to as "other fibers (C)") different from the flame-retardant acrylic fiber (A) and the polyvinyl alcohol fiber (B) as long as the effects of the present invention are not impaired. The other fibers (C) may be natural fibers or synthetic fibers. Examples of the other fibers (C) include flammable fibers such as cellulose-based fibers and acrylic fibers, and flammable fibers such as wool, nylon fibers, and polyester fibers.

[0067] When the flame-retardant fiber composite of the present invention contains other fibers (C), the amount thereof is preferably 15 mass% or less, more preferably 10 mass% or less, even more preferably 5 mass% or less, and particularly preferably 1 mass% or less, relative to the total mass of the flame-retardant fiber composite. In one embodiment of the present invention, the flame-retardant fiber composite of the present invention does not contain other fibers (C) (i.e., the content of other fibers (C) is 0 mass%).

[0068] The flame-retardant fiber composite of the present invention can be produced by blending, twisting, interweaving, or the like, the fiber (A) and the fiber (B) in the specific blending ratio described above.

[0069] For example, when producing a blended spun yarn from fiber (A) and fiber (B), they are blended in a known cotton spinning process, worsted spinning process, woolen spinning process, or silk spinning process, and then spun to form a spun yarn. The blending method may involve blending the raw cotton before the carding process, or blending the sliver after passing each fiber through a separate carding machine. Alternatively, the fibers may be roved separately and then blended together. In the case of cotton spinning or worsted spinning, blending the sliver is preferred, while in the case of woolen spinning, blending the raw cotton is preferred. The spun yarn of the present invention can be used for various purposes, either as a single yarn or twisted into a woven or knitted yarn.

[0070] From the viewpoint of high flame retardancy, the flame-retardant fiber composite of the present invention preferably has a limiting oxygen index (LOI) of 30 or more, more preferably 32 or more, and even more preferably 34 or more, as measured according to the method described in JIS K-7201. The upper limit of the LOI of the flame-retardant fiber composite of the present invention is not particularly limited, but is usually 45 or less. The limiting oxygen index (LOI) of the flame-retardant fiber composite is measured by the method described in the examples below. Specifically, a vertical cylindrical test piece is prepared and the LOI can be measured according to the method described in JIS K-7201.

[0071] In the present invention, the LOI of the flame-retardant fiber composite is preferably higher than the LOI of the flame-retardant fiber (A) alone. For example, the difference between the LOI of the flame-retardant fiber composite and the LOI of the fiber (A) alone (LOI of the flame-retardant fiber composite - LOI of the fiber (A) alone) is preferably 0.2 to 10, more preferably 0.5 to 8, and even more preferably 0.8 to 6, and may be, for example, 1.0 to 5.5 or 1.0 to 5. When the difference between the LOI of the flame-retardant fiber composite and the LOI of the fiber (A) alone is within the above range, a flame-retardant fiber composite having high strength while having higher flame retardancy than the fiber (A) alone can be obtained. In the present application, when comparing the flame-retardant fiber composite and the fiber (A), values ​​measured by the method described in JIS L-1091 as well as JIS K-7201 may be compared. When values ​​measured by the same method are compared, it is preferable that the limiting oxygen index of the flame-retardant fiber composite is higher than the limiting oxygen index of the flame-retardant acrylic fiber (A) alone.

[0072] From the viewpoint of having high strength, the flame-retardant fiber composite of the present invention has a tensile strength of preferably 1.8 to 15 cN / dtex, more preferably 2 to 14 cN / dtex, and even more preferably 2.2 to 13 cN / dtex, and may be, for example, 2.5 to 12 cN / dtex. The strength (tensile strength) of the flame-retardant fiber composite can be measured, for example, by the method described in the examples below.

[0073] [Textile Products] The flame-retardant fiber composite can be used to form textile products such as spun yarn, strings, ropes, and fabrics (nonwoven fabrics, woven and knitted fabrics).

[0074] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these examples in any way.

[0075] 1. Flame-retardant acrylic fiber <Flame-retardant acrylic fiber 1> As flame-retardant acrylic fiber 1, a staple fiber (single yarn fineness: 2.2 dtex, fiber length: 38 mm) was used, which was made by adding 23% by mass of antimony trioxide based on the mass of an acrylonitrile-based copolymer containing 50% by mass of structural units derived from acrylonitrile, 49% by mass of structural units derived from a halogen-containing vinyl monomer (vinylidene chloride), and 1% by mass of structural units derived from a sodium styrene sulfonate monomer.

[0076] <Flame-retardant acrylic fiber 2> Flame-retardant acrylic fiber 2 was prepared by immersing flame-retardant acrylic fiber 1 in a DMSO / ethanol mixed solution (mixing volume ratio 1 / 99) for 3 minutes and then drying at 80°C for 10 minutes.

[0077] 2. Preparation of Polyvinyl Alcohol-Based Fibers (PVA-Based Fibers) (Production Example 1) <Preparation of PVA-Based Fiber 1> PVA with a viscosity-average degree of polymerization of 1,700 and a degree of saponification of 99.9 mol% was dissolved in DMSO to a PVA concentration of 20% by mass to obtain a spinning dope. The spinning dope was then wet-spun through a nozzle with a 0.1 mm hole diameter and 1,000 holes in a solidification bath containing a 70 / 30 mass ratio methanol / DMSO mixture at 5°C to obtain a yarn. The resulting yarn was wet-stretched 3x in methanol at 20°C and countercurrently contacted with methanol for 8 minutes to extract and remove the DMSO. It was then dried with hot air at 100°C and hot-stretched 5x in a hot air oven at 230°C to obtain a PVA fiber with a fineness of 1.7 dtex. The yarn was then crimped and cut to 38 mm to obtain the raw fiber of PVA fiber 1.

[0078] (Production Example 2) <Preparation of PVA-Based Fiber 2> PVA with a viscosity-average degree of polymerization of 1700 and a degree of saponification of 99.9 mol% was added to water to a PVA concentration of 16.5% by mass. To this, boric acid was further added in an amount of 3.0% by mass / PVA to dissolve the PVA, yielding a spinning dope. The spinning dope was then wet-spun through a nozzle with a 0.1 mm hole diameter and 1000 holes in a solidification bath consisting of an aqueous solution containing 15 g / L of sodium hydroxide and 350 g / L of mirabilite at 40°C to obtain a yarn. The obtained yarn was neutralized with an aqueous solution containing sulfuric acid, subjected to 3x wet stretching, and then countercurrently contacted with water for 3 minutes to remove sulfuric acid and mirabilite. The yarn was then dried with hot air at 100°C and hot-drawn 4x in a hot air oven at 230°C to obtain a PVA fiber with a fineness of 1.7 dtex. Subsequently, the fiber was subjected to a crimping treatment and cut to a length of 38 mm to obtain raw fiber of PVA fiber 2.

[0079] (Production Example 3) <Preparation of PVA-Based Fiber 3> PVA with a viscosity-average degree of polymerization of 1,700 and a degree of saponification of 98.2 mol% was mixed with a PVC (polyvinyl chloride) emulsion with an average degree of polymerization of 1,000 (40% / total polymer amount), tin oxide with an average particle size of 0.8 μm, and antimony pentoxide sol with an average particle size of 0.03 μm (each 3% / total polymer amount). Water was added to the mixture to achieve a total solids concentration of 16% by mass. Boric acid was then added in an amount of 3.0% by mass / PVA, and the components were dissolved to obtain a spinning dope. The spinning dope was then wet-spun through a nozzle with a 0.1 mm hole diameter and 1,000 holes in a solidification bath containing 15 g / L of sodium hydroxide and 350 g / L of sodium sulfate at 40°C to obtain a yarn. The resulting yarn was neutralized with an aqueous solution containing 100 g / L of sulfuric acid, wet-stretched 2.7 times, and then countercurrently contacted with water for 3 minutes to remove sulfuric acid and sodium sulfate. It was then dried with hot air at 100°C and dry-stretched 3.5 times in a hot air oven at 230°C to obtain PVA fiber with a fineness of 1.7 dtex. It was subsequently crimped and cut to 38 mm to obtain raw cotton. The raw cotton was immersed in a DMSO / ethanol mixed solution (volume ratio 0.1 / 99.9, 25°C) for 3 minutes and then dried at 80°C for 10 minutes to obtain raw cotton of PVA fiber 3.

[0080] (Production Example 4) <Preparation of PVA-Based Fiber 4> PVA with a viscosity-average degree of polymerization of 1700 and a degree of saponification of 99.9 mol% was dissolved in DMSO to a PVA concentration of 20% by mass to obtain a spinning dope. The spinning dope was then wet-spun through a nozzle with a 0.1 mm hole diameter and 1000 holes in a solidification bath containing a 70 / 30 methanol / DMSO mixture at 5°C to obtain a filament. The resulting filament was wet-stretched 3x in methanol at 20°C and countercurrently contacted with the methanol for 20 minutes to extract and remove the DMSO. The filament was then dried with hot air at 100°C and hot-stretched 5x in a hot air oven at 230°C to obtain a PVA fiber with a fineness of 1.7 dtex. The filament was subsequently crimped and cut to a length of 38 mm to obtain the raw fiber of PVA fiber 4.

[0081] (Production Example 5) <Preparation of PVA-Based Fiber 5> PVA with a viscosity-average degree of polymerization of 1700 and a degree of saponification of 99.9 mol% was dissolved in DMSO to a PVA concentration of 20% by mass to obtain a spinning dope. The spinning dope was then wet-spun through a nozzle with a 0.1 mm hole diameter and 1000 holes in a solidification bath containing a 70 / 30 methanol / DMSO mixture at 5°C to obtain a yarn. The resulting yarn was wet-stretched 3x in methanol at 20°C and countercurrently contacted with methanol for 13 minutes to extract and remove the DMSO. The yarn was then dried with hot air at 100°C and hot-stretched 5x in a hot air oven at 230°C to obtain a PVA fiber with a fineness of 1.7 dtex. The yarn was then crimped and cut to a length of 38 mm to obtain the raw fiber of PVA fiber 5.

[0082] (Production Example 6) <Preparation of PVA-Based Fiber 6> PVA with a viscosity-average degree of polymerization of 1700 and a degree of saponification of 99.9 mol% was dissolved in DMSO to a PVA concentration of 20% by mass to obtain a spinning dope. The spinning dope was then wet-spun through a nozzle with a 0.1 mm hole diameter and 1000 holes in a solidification bath containing a 70 / 30 methanol / DMSO mixture at 5°C to obtain a filament. The resulting filament was wet-stretched 3x in methanol at 20°C and countercurrently contacted with the methanol for 3 minutes to extract and remove the DMSO. The filament was then dried with hot air at 100°C and hot-stretched 5x in a hot air oven at 230°C to obtain a PVA fiber with a fineness of 1.7 dtex. The filament was subsequently crimped and cut to a length of 38 mm to obtain the raw fiber of PVA fiber 6.

[0083] (Production Example 7) <Preparation of PVA-Based Fiber 7> PVA with a viscosity-average degree of polymerization of 1700 and a degree of saponification of 99.9 mol% was dissolved in DMSO to a PVA concentration of 20% by mass to obtain a spinning dope. The spinning dope was then wet-spun through a nozzle with a 0.1 mm hole diameter and 1000 holes in a solidification bath containing a 70 / 30 methanol / DMSO mixture at 5°C to obtain a filament. The resulting filament was wet-stretched 3x in methanol at 20°C and countercurrently contacted with methanol for 1 minute to extract and remove the DMSO. The filament was then dried with hot air at 100°C and hot-stretched 5x in a hot air oven at 230°C to obtain a PVA fiber with a fineness of 1.7 dtex. The filament was subsequently crimped and cut to a length of 38 mm to obtain the raw fiber of PVA fiber 7.

[0084] 3. Physical properties of each fiber

[0085] (1) Fiber Strength (Before Spinning) The fiber strength (tensile strength) of each fiber was measured by the following method. In accordance with JIS L 1015, a test method for synthetic fiber staples, the fiber that had been previously conditioned was measured using a tensile tester under the following conditions: a gripping distance of 20 mm, an initial load of 4.41 mN × indicated tex (for PVA-based fibers) or 8.82 mN × indicated tex (for flame-retardant acrylic-based fibers), and a pulling speed of 20 mm / min. The average value of n = 30 was used as the fiber strength. The measurement results are shown in Table 1.

[0086] (2) Measurement of the content of halogens (Cl, Br) contained in flame-retardant acrylic fiber The halogens (Cl, Br) contained in the flame-retardant acrylic fiber were measured by subjecting the fiber sample to measurement to quantitative X-ray fluorescence analysis. The results are shown in Table 1. The content is essentially a value relative to 100% by mass of the acrylic copolymer constituting the flame-retardant acrylic fiber.

[0087] (3) Measurement of antimony (Sb) content in flame-retardant acrylic fiber The antimony (Sb) content in flame-retardant acrylic fiber was measured as follows. As a pretreatment, nitric acid and sulfuric acid were added to the fiber sample to be measured, and microwave decomposition was performed. Next, after measuring, the sample was filtered through a PTFE filter and quantitatively analyzed by ICP emission spectrometry. The results are shown in Table 1. Note that the content is essentially a value relative to 100% by mass of the acrylic copolymer constituting the flame-retardant acrylic fiber.

[0088] (4) Measurement of sulfur content in each fiber (i) Measurement of total sulfur content: As a pretreatment, nitric acid and sulfuric acid were added to each fiber sample to be measured, and microwave decomposition was performed. Next, the sample was filled up and filtered with a PTFE filter, and quantitative analysis was performed by ICP emission spectrometry. The results are shown in Table 1. The content is a value relative to the total mass of the PVA-based fiber.

[0089] (ii) Amount of sulfur derived from DMSO: As a pretreatment, DMSO was extracted from each fiber sample to be measured using a Soxhlet extractor with methanol. The resulting extract was then used as a test liquid and quantitatively analyzed by gas chromatography-mass spectrometry. The results are shown in Table 1. The content is a value relative to the total mass of the PVA-based fiber.

[0090] (iii) Amount of sulfur derived from sodium sulfate: Each fiber sample to be measured was subjected to hot water extraction as a pretreatment to extract ionic components. The obtained extract was then used as a test liquid to quantify sulfate ions by ion chromatography. The results are shown in Table 1. The content is a value relative to the total mass of the PVA-based fiber.

[0091] 4. Preparation of Fiber Composites (1) Example 1 Flame-retardant acrylic fiber 1 and PVA fiber 1 were blended in the proportions shown in Table 2, pre-opened, and then passed through a carding machine to prepare a mixed web, which was a flame-retardant fiber composite.

[0092] (2) Example 2 A mixed web, which is a flame-retardant fiber composite, was produced in the same manner as in Example 1, except that the blending ratio of the flame-retardant acrylic fiber 1 and the PVA fiber 1 was changed to the ratio shown in Table 2.

[0093] (3) Example 3 A mixed web, which was a flame-retardant fiber composite, was produced in the same manner as in Example 1, except that PVA-based fiber 1 was replaced with PVA-based fiber 3.

[0094] (4) Example 4 A mixed web, which was a flame-retardant fiber composite, was prepared in the same manner as in Example 2, except that PVA-based fiber 1 was replaced with PVA-based fiber 3.

[0095] (5) Example 5 A mixed web, which was a flame-retardant fiber composite, was prepared in the same manner as in Example 1, except that PVA-based fiber 1 was replaced with PVA-based fiber 5.

[0096] (6) Example 6 A mixed web, which was a flame-retardant fiber composite, was produced in the same manner as in Example 1, except that PVA-based fiber 1 was replaced with PVA-based fiber 6.

[0097] (7) Example 7 A mixed web, which was a flame-retardant fiber composite, was produced in the same manner as in Example 1, except that PVA-based fiber 1 was replaced with PVA-based fiber 7.

[0098] (8) Example 8 A mixed web, which was a flame-retardant fiber composite, was produced in the same manner as in Example 1, except that PVA-based fiber 1 was replaced with PVA-based fiber 4.

[0099] (9) Comparative Example 1 A web made of flame-retardant acrylic fiber 1 was produced using only flame-retardant acrylic fiber 1 without using any PVA fiber, and after pre-opening, the fiber was passed through a carding machine.

[0100] (10) Comparative Example 2 A mixed web, which is a flame-retardant fiber composite, was produced in the same manner as in Example 1, except that the blending ratio of flame-retardant acrylic fiber 1 and PVA fiber 1 was changed to the ratio shown in Table 2.

[0101] (11) Comparative Example 3 A web made of PVA-based fiber 1 was produced in the same manner as in Comparative Example 1, except that no flame-retardant acrylic fiber was used and only PVA-based fiber 1 was used.

[0102] (12) Comparative Example 4 A mixed web, which was a flame-retardant fiber composite, was produced in the same manner as in Example 1, except that the PVA-based fiber 1 was replaced with the PVA-based fiber 2.

[0103] (13) Comparative Example 5 A mixed web, which was a flame-retardant fiber composite, was produced in the same manner as in Example 2, except that the PVA-based fiber 1 was replaced with the PVA-based fiber 2.

[0104] (14) Comparative Example 6 A web made of PVA-based fiber 2 was produced in the same manner as in Comparative Example 3, except that PVA-based fiber 1 was replaced with PVA-based fiber 2.

[0105] (15) Comparative Example 7 A mixed web, which was a flame-retardant fiber composite, was produced in the same manner as in Example 2, except that the flame-retardant acrylic fiber 1 was replaced with the flame-retardant acrylic fiber 2 and the PVA-based fiber 1 was replaced with the PVA-based fiber 2.

[0106] (16) Comparative Example 8 A web made of flame-retardant acrylic fiber 2 was produced in the same manner as in Comparative Example 1, except that flame-retardant acrylic fiber 1 was replaced with flame-retardant acrylic fiber 2.

[0107] (17) Comparative Example 9 A web made of PVA-based fiber 3 was prepared in the same manner as in Comparative Example 3, except that PVA-based fiber 1 was replaced with PVA-based fiber 3.

[0108] (18) Comparative Example 10 A web made of PVA-based fiber 4 was prepared in the same manner as in Comparative Example 3, except that PVA-based fiber 1 was replaced with PVA-based fiber 4.

[0109] 5. Evaluation of Mixed Webs / Webs (1) Limiting Oxygen Index (LOI) Value Vertical cylindrical test specimens were prepared from the mixed webs or webs prepared in the above Examples and Comparative Examples. Specifically, a web approximately 100 mm wide was wound around a wire 0.9 mm in diameter in a roll shape to form a cylindrical shape 100 mm long and 10 mm in diameter, and glass fiber was wound around it in a spiral shape at a 45-degree angle with 10 mm intervals to fix the web, and then the wire was removed. The test specimens were then dried at 105°C for 1 hour, and the limiting oxygen index (LOI value) was measured using the apparatus, ignition method, and evaluation criteria in accordance with JIS K-7201. The measurement results are shown in Table 2.

[0110] (2) Fiber Strength of Spun Yarn Each fiber was blended, carded, and drawn in the proportions shown in Table 2 to form a sliver, which was then spun using a ring spinning frame with an S twist and a first twist coefficient of 2.8 to produce a single yarn with a count of 20s. Two of these single yarns were then paralleled and Z twisted at 65% of the first twist to obtain a two-ply yarn with a count of 20 / 2s. The resulting spun yarn was measured using a tensile tester in accordance with JIS L1095, a general spun yarn testing method, under conditions of a grip distance of 25 cm, an initial load of 0.147 N, and a pulling speed of 25 cm / min. The average value of n = 30 was used as the fiber strength. The results are shown in Table 2.

[0111]

[0112]

[0113] In the flame-retardant fiber composites of Examples 1 to 8, the PVA-based fiber contained an organic sulfur compound, and the LOI value and fiber strength of the spun yarn were higher than those of Comparative Example 1 or 8, which consisted of flame-retardant acrylic fiber alone (100% by mass). On the other hand, the fiber composites of Comparative Examples 4, 5, and 7, in which the PVA-based fiber did not contain an organic sulfur compound, and the fiber composites of Comparative Examples 2, 3, 6, 9, and 10, in which the flame-retardant acrylic fiber (A) and PVA-based fiber (B) were mixed at ratios outside the specified range, had lower LOI values ​​than those of the flame-retardant acrylic fiber alone (100% by mass).

[0114] The flame-retardant fiber composite of the present invention can be suitably used for, for example, various vehicle seats, interior products, work clothes, tent materials, and the like, which require flame retardancy.

Claims

1. A flame-retardant fiber composite comprising flame-retardant acrylic fiber (A) and polyvinyl alcohol fiber (B) as main components, wherein the composite ratio of the flame-retardant acrylic fiber (A) to the polyvinyl alcohol fiber (B) (mass ratio, flame-retardant acrylic fiber (A) / polyvinyl alcohol fiber (B)) is 90 / 10 to 30 / 70, the flame-retardant acrylic fiber (A) has a copolymer structure of acrylonitrile and a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer, and contains an antimony compound, and the polyvinyl alcohol fiber (B) contains an organic sulfur compound.

2. The flame-retardant fiber composite according to claim 1, wherein the total mass of the flame-retardant acrylic fiber (A) and the polyvinyl alcohol fiber (B) is 80 mass% or more of the total mass of the flame-retardant fiber composite.

3. The flame-retardant fiber composite according to claim 1, wherein the polyvinyl alcohol-based fiber (B) contains an organic sulfur compound in an amount of 0.001 to 0.5 mass % as sulfur relative to the total mass of the polyvinyl alcohol-based fiber (B).

4. The flame-retardant fiber composite according to claim 1, containing 24 to 90 mass% of the flame-retardant acrylic fiber (A) based on the total mass of the flame-retardant fiber composite.

5. The flame-retardant fiber composite according to claim 1, containing 8 to 70 mass% of polyvinyl alcohol-based fiber (B) based on the total mass of the flame-retardant fiber composite.

6. The flame-retardant fiber composite according to claim 1, wherein the polyvinyl alcohol fiber (B) has a limiting oxygen index of less than 25 as measured according to the method described in JIS K-7201.

7. The flame-retardant fiber composite according to claim 1, wherein the strength of the polyvinyl alcohol fiber (B) is 2 cN / dtex or more.

8. The flame-retardant fiber composite according to claim 1, wherein the flame-retardant acrylic fiber (A) comprises an acrylic copolymer containing, relative to all monomer units constituting the copolymer, 30 to 70 mass% of structural units derived from acrylonitrile, 70 to 30 mass% of structural units derived from a halogen-containing vinyl monomer and / or a halogen-containing vinylidene monomer, and 0 to 10 mass% of structural units derived from a vinyl monomer copolymerizable therewith.

9. A flame-retardant fiber composite as described in claim 1, in which the amount of other fiber (C) different from the flame-retardant acrylic fiber (A) and the polyvinyl alcohol fiber (B) is 15 mass% or less based on the total mass of the flame-retardant fiber composite.

10. The flame-retardant fiber composite according to claim 1, wherein the limiting oxygen index of the flame-retardant fiber composite is higher than the limiting oxygen index of the flame-retardant acrylic fiber (A) alone.

11. A textile product comprising the flame-retardant fiber composite of claim 1.

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