Flame-retardant non-woven fabric and vehicle interior material

Abstract

One or more aspects of the present invention relate to a flame-retardant nonwoven fabric including modacrylic fibers A and regenerated cellulose fibers B. The modacrylic fibers A contain a magnesium compound. The regenerated cellulose fibers B contain silica. The flame-retardant nonwoven fabric contains the modacrylic fibers A in an amount of 15 to 45 mass% and the regenerated cellulose fibers B in an amount of 55 to 85 mass%. The flame-retardant nonwoven fabric contains the magnesium compound derived from the modacrylic fibers A in an amount of 0.75 mass% or more. The flame-retardant nonwoven fabric has a basis weight of 80 g / m2 or more. The flame-retardant nonwoven fabric satisfies a V-0 standard for a UL94 vertical flammability test.

Description

Technical Field

[0001] The present invention relates to a flame-retardant nonwoven fabric that includes modacrylic fibers and regenerated cellulose fibers, and a vehicle interior material.Background Art

[0002] Nonwoven fabric for use in interior materials such as seat materials of transportation means (e.g., aircraft, automobiles, railroad vehicles, and vessels) and facing materials therefor is flame-retardant nonwoven fabric from the viewpoint of safety. For example, Patent Document 1 proposes, as nonwoven fabric for use in interior materials such as seat facing materials, flame-retardant nonwoven fabric with a three-layer structure in which modacrylic fibers containing a halogen and antimony are used in a back layer and an intermediate layer.Prior Art DocumentsPatent Document

[0003] Patent Document 1: JP 2009-299199ADisclosure of InventionProblem to be Solved by the Invention

[0004] However, although antimony-containing modacrylic fibers are used in Patent Document 1, there has been concern that elution or discharge of an antimony compound affects the environment and human bodies in recent years, and an improvement has been required. Also, interior materials such as seat materials of transportation means often come into contact with human bodies and are required to have excellent texture.

[0005] In order to solve the aforementioned conventional problems, the present invention provides flame-retardant nonwoven fabric having favorable texture and high flame retardancy in a vertical flammability test, and a vehicle interior material containing the flame-retardant nonwoven fabric.Means for Solving Problem

[0006] One or more aspects of the present invention relate to a flame-retardant nonwoven fabric including: modacrylic fibers A; and regenerated cellulose fibers B, wherein the modacrylic fibers A contain a magnesium compound, the regenerated cellulose fibers B contain silica, the flame-retardant nonwoven fabric contains the modacrylic fibers A in an amount of 15 to 45 mass% and the regenerated cellulose fibers B in an amount of 55 to 85 mass%, the flame-retardant nonwoven fabric contains the magnesium compound derived from the modacrylic fibers A in an amount of 0.75 mass% or more, the flame-retardant nonwoven fabric has a basis weight of 80 g / m 2< or more, and the flame-retardant nonwoven fabric satisfies a V-0 standard for a UL94 vertical flammability test.

[0007] One or more aspects of the present invention relate to a vehicle interior material that includes the flame-retardant nonwoven fabric.Effects of the Invention

[0008] With the present invention, it is possible to provide a flame-retardant nonwoven fabric having favorable texture and high flame retardancy in a vertical flammability test, and a vehicle interior material containing the flame-retardant nonwoven fabric.Description of the Invention

[0009] The inventors of the present invention conducted numerous studies in order to improve the flame retardancy and the texture of a nonwoven fabric for use in a vehicle interior material. As a result, it was found that the texture of the nonwoven fabric is improved by using modacrylic fibers A containing a magnesium compound and regenerated cellulose fibers B containing silica together, and high flame retardancy that satisfies the highest level V-0 standard for the UL94 vertical flammability test is achieved by setting the blend ratio of the modacrylic fibers A and the regenerated cellulose fibers B in the nonwoven fabric to a predetermined ratio and setting the content of the magnesium compound derived from the modacrylic fibers A in the nonwoven fabric to a predetermined content. This effect was unique and could not be achieved when modacrylic fibers containing a magnesium compound and other flame-retardant fibers such as regenerated cellulose fibers and polyester fibers containing a phosphorus-based flame retardant were used together. The reason for this is a matter of speculation and does not limit the present invention, but it is assumed that shrinkage resistance of the nonwoven fabric is improved due to the synergistic effect of the magnesium compound derived from the modacrylic fibers A and the silica derived from the regenerated cellulose fibers B, and thus high flame retardancy is exhibited.

[0010] In particular, the flame-retardant nonwoven fabric above has excellent sound insulating properties or sound absorbing properties and can be favorably used as a flame-retardant sound insulating material or flame-retardant sound absorbing material.

[0011] In one or more embodiments of the present invention, the flame-retardant nonwoven fabric and the modacrylic fibers A contain substantially no antimony compound, thus making it possible to reduce concern regarding the impact of elution or discharge of an antimony compound on the environment and human bodies as well as reduce the cost. In this specification, the wording "containing substantially no antimony compound" means that an antimony compound serving as a flame retardant is not added to fibers or nonwoven fabric on purpose. For example, containing an antimony compound as an impurity (e.g., in an amount of 0.001 mass% or less) is considered as "containing substantially no antimony compound".

[0012] In this specification, when a numerical range is shown using "to", the numerical range includes the values at both ends (i.e., the upper limit and the lower limit). For example, a numerical range "A to B" is a range that includes A and B, which are the values at the two ends of the range, and is the same range as "A or more and B or less". Also, any number and any included range falling within the range is specifically disclosed. Also, when a plurality of numerical ranges are described in this specification, numerical ranges obtained by using the upper limits and the lower limits of the different numerical ranges in combination as appropriate are included. Also, when a plurality of upper limits and lower limits of numerical ranges are separately described, numerical ranges obtained by using the upper limits and the lower limits in combination as appropriate are included.

[0013] The flame-retardant nonwoven fabric according to one or more embodiments of the present invention contains modacrylic fibers A and regenerated cellulose fibers B.Modacrylic Fiber A

[0014] The modacrylic fibers A contain a modacrylic polymer and a magnesium compound and contain substantially no antimony compound. Specifically, the modacrylic fibers A contain the magnesium compound inside the fibers. The content of the magnesium compound in the modacrylic fibers A is not particularly limited as long as the content of the magnesium compound in the flame-retardant nonwoven fabric is within the range described below. For example, the content of the magnesium compound is preferably 2 to 25 parts by mass, more preferably 3 to 20 parts by mass, even more preferably 4 to 15 parts by mass, even more preferably 4 to 10 parts by mass, and even more preferably 4 to 8 parts by mass, with respect to 100 parts by mass of the modacrylic polymer. When the content of the magnesium compound is 2 parts by mass or more, the flame retardancy of the flame-retardant nonwoven fabric containing the modacrylic fibers A is improved. When the content of the magnesium compound is 25 parts by mass or less, generation of static electricity on the modacrylic fibers A is suppressed during passing through the card, the processability is improved, and particularly the mass productivity is improved.

[0015] Examples of the magnesium compound include magnesium oxide, magnesium peroxide, magnesium hydroxide, magnesium fluoride, magnesium chloride, magnesium bromide, magnesium iodide, magnesium hydride, magnesium diboride, magnesium nitride, magnesium sulfide, magnesium carbonate, calcium magnesium carbonate, magnesium nitrate, magnesium sulfate, magnesium sulfite, magnesium perchlorate, trimagnesium phosphate, magnesium permanganate, magnesium phosphate, and the like. Out of these compounds, one or more selected from the group consisting of magnesium oxide and magnesium hydroxide are favorably used from the viewpoint of ease of handling, and magnesium hydroxide is favorably used from the viewpoint of further improving the processability.

[0016] The magnesium hydroxide is not particularly limited, but examples thereof include powder obtained by pulverizing natural brucite, powder obtained by neutralizing an aqueous solution of a magnesium salt with an alkali, powder obtained by treating magnesium hydroxide particles with a phosphate, a borate, or the like, magnesium hydroxide obtained using a method of hydrating magnesium oxide to gradually generate magnesium hydroxide, and the like. Also, the magnesium hydroxide may have a coating layer that is formed through adsorption of an adsorbable substance around magnesium hydroxide particles, or that is formed through surface treatment with a surface treatment agent. In particular, magnesium hydroxide having a coating layer formed through surface treatment with a silane coupling agent is preferable from the viewpoint of suppressing static electricity. The reason why suppression of static electricity is improved through surface treatment with a silane coupling agent is a matter of speculation, but is considered to be as follows. It is conceivable that conducting silane coupling treatment on the surface of a magnesium hydroxide particle improves the compatibility of modacrylic fibers with the magnesium hydroxide subjected to the silane coupling treatment, which results in suppression of static electricity. Furthermore, when a process of applying an oil solution to the fiber surface is conducted for the purpose of improving the processability, an effect of the oil solution sufficiently reaches the surface of the magnesium hydroxide particle as well, and thus the processability is significantly improved. The type of silane coupling agent is preferably a silane coupling agent capable of improving the compatibility with a modacrylic polymer, and may be a cross-linked silane coupling agent or a non-cross-linked silane coupling agent, but is not particularly limited. As the magnesium hydroxide subjected to the surface treatment with a silane coupling agent, for example, commercially available products such as KISMA (registered trademark) 5P and KISMA (registered trademark) 5L manufactured by Kyowa Chemical Industry Co., Ltd. may be used, but there is no particular limitation thereto.

[0017] The average particle diameter of the magnesium compound represented as a median diameter (D50) is preferably 0.3 to 3.0 µm and more preferably 1.0 to 2.5 µm. When the average particle diameter is 0.3 µm or more, the surface area of the magnesium compound particle does not excessively increase, and electrostatic generation is suppressed during a fiber processing step, which facilitates the processing. When the average particle diameter is 3.0 µm or less, blockage of a spinneret is avoided during a spinning process, resulting in favorable spinnability. In this specification, the average particle diameter of the magnesium compound, for example, in the form of a powder can be measured using a laser diffraction / scattering method, and the average particle diameter of the magnesium compound in a dispersion (dispersion liquid) obtained by dispersing the magnesium compound in water or an organic solvent can be measured using a laser diffraction / scattering method or a dynamic light scattering method. The average particle diameter of the magnesium compound inside a fiber can also be examined by, for example, measuring the particle diameters of a hundred particles of the magnesium compound inside a fiber using a microscope and determining the arithmetic average diameter.

[0018] The modacrylic polymer preferably contains structural units derived from acrylonitrile in an amount of 30 to 85 mass%, structural units derived from a halogen-containing monomer in an amount of 15 to 70 mass%, and structural units derived from another copolymerizable vinyl monomer in an amount of 0 to 5 mass%, more preferably structural units derived from acrylonitrile in an amount of 35 to 80 mass%, structural units derived from a halogen-containing monomer in an amount of 20 to 65 mass%, and structural units derived from another copolymerizable vinyl monomer in an amount of 0 to 5 mass%, and even more preferably structural units derived from acrylonitrile in an amount of 40 to 70 mass%, structural units derived from a halogen-containing monomer in an amount of 30 to 60 mass%, and structural units derived from another copolymerizable vinyl monomer in an amount of 0 to 5 mass%.

[0019] The halogen-containing monomer is preferably one or more selected from the group consisting of halogen-containing vinyl monomers and halogen-containing vinylidene monomers. Examples of the halogen-containing vinyl monomers include vinyl chloride, vinyl bromide, and the like, and examples of the halogen-containing vinylidene monomers include vinylidene chloride, vinylidene bromide, and the like. From the viewpoint of improving the flame retardancy and suppressing coloring of the modacrylic polymer, it is preferable that the halogen-containing monomer includes vinyl chloride. One of these halogen-containing monomers may be used alone, or two or more of them may be used in combination.

[0020] The other copolymerizable vinyl monomer is not particularly limited, but examples thereof include unsaturated carboxylic acids such as acrylic acid and methacrylic acid, salts of the unsaturated carboxylic acids, methacrylic acid esters such as methyl methacrylate, esters of unsaturated carboxylic acids such as glycidyl methacrylate, vinyl esters such as vinyl acetate and vinyl butyrate, a sulfonic acid group-containing monomer, and the like. From the viewpoint of dyeability, the sulfonic acid group-containing vinyl monomer can be favorably used. Examples of the sulfonic acid group-containing monomer include allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, isoprenesulfonic acid, and 2-acrylamido-2-methylpropanesulfonic acid, and metallic salts (e.g., sodium salts) thereof and amine salts thereof, and the like. The sulfonic acid group-containing monomer may be used alone, or two or more of them may be used in combination. The sulfonic acid group-containing vinyl monomer is used as needed, but when the content of structural units derived from the sulfonic acid group-containing vinyl monomer in the modacrylic polymer is 3 mass% or less, the production stability during the spinning process is further improved.

[0021] The modacrylic polymer preferably contains structural units derived from acrylonitrile in an amount of 30 to 85 mass%, structural units derived from a halogen-containing monomer in an amount of 15 to 70 mass%, and structural units derived from a sulfonic acid group-containing vinyl monomer in an amount of 0 to 3 mass%, and more preferably structural units derived from acrylonitrile in an amount of 35 to 80 mass%, structural units derived from a halogen-containing monomer in an amount of 19.5 to 64.5 mass%, and structural units derived from a sulfonic acid group-containing vinyl monomer in an amount of 0.5 to 3 mass%.

[0022] The modacrylic polymer can be obtained through known polymerization methods such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization. In particular, suspension polymerization, emulsion polymerization, or solution polymerization is preferable from an industrial point of view.

[0023] The modacrylic fibers A may contain the modacrylic polymer in an amount of 80 to 98 mass% and magnesium in an amount of 2 to 20 mass%, or may contain the modacrylic polymer in an amount of 83 to 97 mass% and magnesium in an amount of 3 to 17 mass%, or may contain the modacrylic polymer in an amount of 85 to 96 mass% and magnesium in an amount of 4 to 15 mass%, or may contain the modacrylic polymer in an amount of 87 to 96 mass% and magnesium in an amount of 4 to 13 mass%. Also, the modacrylic fibers A may contain other additives such as an antistatic agent, a coloration inhibitor, a light resistance improver, a whiteness improver, a devitrification inhibitor, and a coloring agent, as needed, as long as the effects of the present invention are not inhibited. The other additives may be contained in an amount of 5 parts by mass or less, 3 parts by mass or less, or 1 part by mass or less, with respect to 100 parts by mass of the modacrylic polymer.

[0024] The cross-sectional shape of the modacrylic fibers A is not particularly limited, and may be, for example, a circular shape or any other shape (non-circular shape) such as a dog bone shape.

[0025] The modacrylic fibers A can be produced by a wet spinning in the same manner as in the case of typical modacrylic fibers, except that a spinning solution containing the modacrylic polymer, a magnesium compound, and optionally other additives is used, but there is no particular limitation thereto. When the wet spinning method is used, the modacrylic fibers A can be obtained, for example, in the following manner: a polymer solution is prepared by dissolving the modacrylic polymer in a solvent, a spinning solution is prepared by adding the magnesium compound (and optionally other additives) to the polymer solution and mixing the resulting solution, the obtained spinning solution is extruded into a coagulation bath through a nozzle and is thus coagulated, and then the coagulated filament is washed with water, dried, drawn, treated with heat, and cut to produce the modacrylic fibers A. The solvent is not particularly limited, and examples thereof include organic solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, acetone, and dimethylsulfoxide, and inorganic solvents such as an aqueous solution of a rhodan salt and an aqueous solution of nitric acid. The nozzle hole shape may be a circular shape.

[0026] The single fiber fineness of the modacrylic fibers A is not particularly limited, but is preferably 0.5 to 20 dtex, more preferably 0.6 to 15 dtex, even more preferably 0.7 to 10 dtex, even more preferably 0.8 to 8 dtex, even more preferably 0.9 to 5 dtex, and particularly preferably 1 to 3 dtex, from the viewpoint of the strength and the sound absorption coefficient. The fiber length of the modacrylic fibers A is not particularly limited, but is preferably 38 to 127 mm and more preferably 38 to 76 mm from the viewpoint of the strength. One type of the modacrylic fibers A may be used alone, or two or more types of them may be used in combination.

[0027] The regenerated cellulose fibers B are not particularly limited as long as regenerated cellulose fibers containing silica are used. Examples of the regenerated cellulose fibers include rayon fibers, cupra, lyocell, and the like. Silica-containing rayon fibers can be favorably used as the regenerated cellulose fibers B from the viewpoint of ease of staining, the flame retardancy, and the cost, and the viewpoint of the availability. It is preferable that the regenerated cellulose fibers containing silica contains the silica inside the fibers from the viewpoint of washing durability. As the silica-containing rayon fibers containing the silica inside the fibers, commercially available products such as "Silica Rayon" manufactured by China Hailong Textile Co., Ltd. and "FR CORONA (registered trademark)" manufactured by Daiwabo Rayon Co., Ltd. may also be used. One type of the regenerated cellulose fibers B may be used alone, or two or more types of them may be used in combination.

[0028] The regenerated cellulose fibers B preferably contain silica in an amount of 10 mass% or more, more preferably 13 mass% or more, and even more preferably 15 mass% or more, from the viewpoint of the flame retardancy. The regenerated cellulose fibers B preferably contain silica in an amount of 30 mass% or less, more preferably 25 mass% or less, and even more preferably 20 mass% or less, from the viewpoint of the strength of the fibers and the strength of the nonwoven fabric. Specifically, the regenerated cellulose fibers B may contain silica in an amount of 10 to 30 mass%, 13 to 25 mass%, or 15 to 20 mass%.

[0029] The single fiber fineness of the regenerated cellulose fibers B is not particularly limited, but is preferably 0.5 to 20 dtex, more preferably 0.6 to 15 dtex, even more preferably 0.7 to 10 dtex, even more preferably 0.8 to 8 dtex, even more preferably 0.9 to 5 dtex, and particularly preferably 1 to 3 dtex, from the viewpoint of the strength and the sound absorption coefficient. The fiber length of the regenerated cellulose fibers B is not particularly limited, but is preferably 38 to 127 mm and more preferably 38 to 76 mm from the viewpoint of the strength.

[0030] The flame-retardant nonwoven fabric contains the modacrylic fibers A in an amount of 15 to 45 mass%, and the regenerated cellulose fibers B in an amount of 55 to 85 mass%. When the content of the modacrylic fibers A is less than 15 mass% or the content of the regenerated cellulose fibers B is less than 55 mass%, the V-0 standard for the UL94 vertical flammability test cannot be satisfied. The flame-retardant nonwoven fabric preferably contains the modacrylic fibers A in an amount of 18 to 42 mass% and the regenerated cellulose fibers B in an amount of 58 to 82 mass%, and more preferably contains the modacrylic fibers A in an amount of 20 to 40 mass% and the regenerated cellulose fibers B in an amount of 60 to 80 mass%.

[0031] The flame-retardant nonwoven fabric contains the magnesium compound derived from the modacrylic fibers A in an amount of 0.75 mass% or more. When the content of the magnesium compound is less than 0.75 mass%, the flame retardancy is poor, and the V-0 standard for the UL94 vertical flammability test cannot be satisfied. The flame-retardant nonwoven fabric preferably contains the magnesium compound derived from the modacrylic fibers A in an amount of 0.80 mass% or more, more preferably 0.85 mass% or more, even more preferably 0.90 mass% or more, and particularly preferably 0.95 mass% or more. The upper limit of the content of the magnesium compound in the flame-retardant nonwoven fabric is not particularly limited, but is preferably 6.0 mass% or less, more preferably 5.0 mass% or less, even more preferably 4.5 mass% or less, even more preferably 4.0 mass% or less, and even more preferably 3.5 mass% or less, from the viewpoint of, for example, suppressing the generation of static electricity during passing through the card and improving the productivity, particularly the mass productivity. More specifically, the flame-retardant nonwoven fabric may contain the magnesium compound derived from the modacrylic fibers A in an amount of 0.75 to 6.0 mass%, 0.80 to 5.0 mass%, 0.85 to 4.5 mass%, 0.90 to 4.0 mass%, or 0.95 to 3.5 mass%.

[0032] The content of the magnesium compound in the modacrylic fibers or flame-retardant nonwoven fabric can be determined by conducting fluorescence X-ray analysis on the modacrylic fibers or flame-retardant nonwoven fabric. The mass of the regenerated cellulose fibers B contained in the flame-retardant nonwoven fabric can be determined by, for example, immersing the nonwoven fabric in an organic solvent such as dimethylsulfoxide (DMSO), N,N-dimethylformamide (DMF), or N,N-dimethylacetamide (DMAc), heating the nonwoven fabric to dissolve the modacrylic fibers B, and extracting the remaining regenerated cellulose fibers B.

[0033] The flame-retardant nonwoven fabric preferably contains silica derived from the regenerated cellulose fibers B in an amount of 7.5 to 20 mass%, and more preferably 8.0 to 15 mass%, from the viewpoint of, for example, achieving favorable strength while further improving the flame retardancy, but there is no particular limitation thereto. The content of the silica in the regenerated cellulose fibers B or flame-retardant nonwoven fabric can be measured through SEM-EDS analysis.

[0034] The flame-retardant nonwoven fabric may contain other fibers as long as the object and the effects of the present invention are not inhibited. Examples of the other fibers include natural fibers, chemical fibers other than the modacrylic fibers A and the regenerated cellulose fibers B, and the like. Examples of the natural fibers include natural animal fibers such as wool fibers, cashmere fibers, and silk fibers, and the like. Examples of the chemical fibers include polyester fibers (e.g., polyethylene terephthalate fibers, polyethylene naphthalate fibers, and the like), aramid fibers, acrylic fibers, polyvinyl chloride fibers, polyvinylidene chloride fibers, polyethylene fibers, polyurethane fibers, polyimide fibers, and the like. The flame-retardant nonwoven fabric may contain the other fibers in an amount of 10 mass% or less, 8 mass% or less, or 1 mass% or less.

[0035] The single fiber fineness of the other fibers is not particularly limited, but is preferably 0.5 to 20 dtex, more preferably 0.6 to 15 dtex, even more preferably 0.7 to 10 dtex, even more preferably 0.8 to 8 dtex, even more preferably 0.9 to 5 dtex, and particularly preferably 1 to 3 dtex, from the viewpoint of the strength and the sound absorption coefficient. The fiber length of the other fibers is not particularly limited, but is preferably 38 to 127 mm and more preferably 38 to 76 mm from the viewpoint of the strength.

[0036] The flame-retardant nonwoven fabric has a basis weight of 80 g / m 2< or more. When the basis weight is less than 80 g / m 2< , the flame retardancy is poor, and the V-0 standard for the UL94 vertical flammability test cannot be satisfied. The basis weight of the flame-retardant nonwoven fabric is preferably 85 g / m 2< or more from the viewpoint of further improving the flame retardancy. The basis weight of the flame-retardant nonwoven fabric is preferably 350 g / m 2< or less, more preferably 300 g / m 2< or less, even more preferably 250 g / m 2< or less, and particularly preferably 230 g / m 2< or less, from the viewpoint of the texture and the cost. More specifically, the basis weight of the flame-retardant nonwoven fabric may be 80 to 350 g / m 2< , 80 to 300 g / m 2< , 85 to 250 g / m 2< , or 85 to 230 g / m 2< .

[0037] The thickness of the flame-retardant nonwoven fabric is not particularly limited, but is preferably 0.5 to 6 mm and more preferably 1 to 5 mm, for example, when the flame-retardant nonwoven fabric is used as a sheet for a vehicle interior material such as a sound insulating material or a ceiling material.

[0038] The bulk density of the flame-retardant nonwoven fabric is not particularly limited, but is preferably 0.01 to 0.10 g / cm 3< , more preferably 0.015 to 0.08 g / cm 3< , even more preferably 0.018 to 0.07 g / cm 3< , and even more preferably 0.02 to 0.06 g / cm 3< , from the viewpoint of, for example, the lightweight properties, the sound absorbing properties, and the like.

[0039] Examples of the flame-retardant nonwoven fabric include carded nonwoven fabric, airlaid nonwoven fabric, thermal bonded nonwoven fabric, chemical bonded nonwoven fabric, needle-punched nonwoven fabric, hydroentangled nonwoven fabric, stitch bonded nonwoven fabric, and the like, but there is no particular limitation thereto. One or more selected from the group consisting of thermal bonded nonwoven fabric and needle-punched nonwoven fabric are preferable from the viewpoint of the cost, and needle-punched nonwoven fabric is more preferable from the viewpoint of further improving the flame retardancy. The flame-retardant nonwoven fabric may have any of a structure that is uniform in the thickness direction, the width direction, and the length direction, a clear laminate structure, and an unclear laminate structure. Note that when the flame-retardant nonwoven fabric has a laminate structure, it is desirable that all the layers contain the modacrylic fibers A and the regenerated cellulose fibers B. A nonwoven fabric having a single layer structure is preferable from the viewpoint of the air-permeability and the flexibility.

[0040] The flame-retardant nonwoven fabric has excellent flame retardancy and satisfies the V-0 standard for the UL94 vertical flammability test. It is preferable that in the UL94 vertical flammability test, the combustion times of each test piece after both the first and second contact with flame are 5 seconds or less, the sum of the results from the flammability test on the five test pieces after ten repetitions of contact with flame is 25 seconds or less, and the sum of the combustion time and the glowing time after the second contact with flame is 30 seconds or less. Moreover, it is more preferable that in the UL94 vertical flammability test, the combustion times of each test piece after both the first and second contact with flame are 0 seconds, the sum of the results from the flammability test on the five test pieces after ten repetitions of contact with flame is 0 seconds, and the sum of the combustion time and the glowing time after the second contact with flame is 0 seconds.

[0041] The flame-retardant nonwoven fabric has excellent sound absorbing properties, and the normal incidence sound absorption coefficient measured in conformity with JIS A 1405-2:2007 is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, even more preferably 85% or more, and even more preferably 90% or more, within a thickness range of 20 to 30 mm and a frequency range of 2500 to 6500 Hz. When the sound absorption coefficient within a frequency range of 2500 to 6500 Hz is 70% or more, noise within a frequency range of 2500 to 6500 Hz can be reduced. Moreover, when the sound absorption coefficient is 80% or more, substantially no noise within a frequency range of 2500 to 6500 Hz is felt. Also, the flame-retardant nonwoven fabric has excellent sound absorbing properties, and the normal incidence sound absorption coefficient measured in conformity with JIS A 1405-2:2007 is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, even more preferably 85% or more, and even more preferably 90% or more, within a thickness range of 20 to 30 mm and at each of frequencies of 2500 Hz, 3500 Hz, 4500 Hz, 5500 Hz, and 6500 Hz.

[0042] In one or more embodiments of the present invention, the flame-retardant nonwoven fabric can be used in facing materials of interior materials such as seat materials, ceiling materials, and floor materials and door accent materials of transportation means (e.g., aircraft, automobiles, railroad vehicles, and vessels), and can be favorably used particularly as facing materials of vehicle interior materials for automobiles, railroad vehicles, and the like. In particular, the flame-retardant nonwoven fabric has excellent flame retardancy and sound absorbing properties and can thus be favorably used as a flame-retardant sound insulating material or flame-retardant sound absorbing material for a vehicle such as an automobile or a railroad vehicle. More specifically, for example, a product obtained by placing, as a facing material, the flame-retardant nonwoven fabric on the surface of a foam made of urethane or the like may be used as a flame-retardant sound insulating material for a vehicle or a flame-retardant sound absorbing material for a vehicle.Examples

[0043] Hereinafter, the present invention will be more specifically described by way of examples. Note that the present invention is not limited to the following examples.

[0044] The measurement methods and the evaluation methods used in examples and comparative examples are as follows.Content of Silica

[0045] 5 g of silica-containing fibers (raw cotton) was analyzed under the following conditions using SEM-EDS analysis (desktop scanning electron microscope and energy dispersive X-ray analyzer JCM-6000PLUS, manufactured by JEOL Ltd.), and thus the silica content was determined based on the approximate element mass.Measurement conditions

[0046] Acceleration voltage: 15.0 kV PHA mode: T3 Energy range: 0 to 20 keV Average Particle Diameter

[0047] The average particle diameter (D50) of a compound was measured using a laser diffraction / scattering method.Static Electricity during Passing through Card

[0048] In the production of the nonwoven fabric, the amount of static electricity generated on fibers during passing through the card was measured using a static electricity measuring instrument (manufactured by SIMCO JAPAN; model number "FMX-003").Basis Weight

[0049] A 10-cm square cut piece of the nonwoven fabric was used as a sample. The mass of the sample was measured using a weight meter (Personal electronic even balance EX-120G, manufactured by A&D Company, Limited), and the basis weight (g / m 2< ) was calculated based on the mass and the area of the sample.Thickness

[0050] The thickness of the nonwoven fabric was measured using a vernier caliper (M-type standard vernier caliper, manufactured by Mitsutoyo Corporation).Bulk Density

[0051] The bulk density (g / cm 3< ) was calculated based on the basis weight and the thickness of the nonwoven fabric.Flame Retardancy

[0052] The UL94 vertical flammability test was conducted, and the flame retardancy was evaluated based on the standards shown in Table 1 below. Five test pieces were prepared for each nonwoven fabric.Sound Absorption Coefficient

[0053] The normal incidence sound absorption coefficient was measured in conformity with JIS A 1405-2:2007 "Acoustics-Determination of sound absorption coefficient and impedance in impedance tubes-Part 2: Transfer-function method". Four circular test pieces with a diameter of 29 mm were collected from the nonwoven fabric, and these test pieces were stacked in the thickness direction and were used as a measurement sample. A normal incidence sound absorption coefficient measuring instrument (Model: DS-2000 series) manufactured by Ono Sokki Co., Ltd. was used as a test apparatus, and the measurement sample was set in a holder for a sample thickness of 20 mm, and then the measurement was started. It was possible to measure sound absorption coefficients for every 10 Hz. Out of the obtained sound absorption coefficients, the values at frequencies of 2500 Hz, 3500 Hz, 4500 Hz, 5500 Hz, and 6500 Hz and the minimum value and the maximum value within a range of 2500 to 6500 Hz were employed. Table 1StandardV-2V-1V-0Combustion times of each test piece after both first and second contact with flame30 seconds or less30 seconds or less10 seconds or lessSum of results from flammability test on five test pieces after ten repetitions of contact with flame250 seconds or less250 seconds or less50 seconds or lessWhether or not test piece burned to holding positionNoNoNoWhether or not absorbent cotton burned due to fallen dripYesNoNoSum of combustion time and glowing time after second contact with flame60 seconds or less60 seconds or less30 seconds or less Production Example 1

[0054] A modacrylic copolymer containing structural units derived from acrylonitrile in an amount of 49.5 mass%, structural units derived from vinyl chloride in an amount of 49.5 mass%, and structural units derived from sodium p-styrenesulfonate in an amount of 1.0 mass% was dissolved in acetone such that the polymer concentration was 30 mass%. A spinning solution was obtained by adding a magnesium hydroxide dispersion liquid (concentration: 30 mass%) to the obtained modacrylic polymer solution such that the content of magnesium hydroxide was 5 parts by mass with respect to 100 parts by mass of the modacrylic polymer. The magnesium hydroxide dispersion liquid was produced by adding magnesium hydroxide (manufactured by Kyowa Chemical Industry Co., Ltd.; trade name: "KISMA (registered trademark) 5P") to acetone and uniformly dispersing it. In the dispersion liquid of the magnesium hydroxide, the average particle diameter of the magnesium hydroxide was 2.0 µm. The obtained spinning solution was extruded into an aqueous solution of acetone (concentration: 50 mass%) through a nozzle (hole shape: circular shape) and was coagulated, followed by washing by water and drying at 120°C. The dried products were drawn until the lengths were tripled, followed by heat treatment at 145°C for 5 minutes. Then, the resulting products were cut to obtain modacrylic fibers. The obtained modacrylic fibers had a single fiber fineness of 2.2 dtex and a cut length of 51 mm.Production Example 2

[0055] Modacrylic fibers were obtained in the same manner as in Production Example 1, except that a spinning solution obtained by adding the magnesium hydroxide dispersion liquid (concentration: 30 mass%) to the modacrylic polymer solution such that the content of magnesium hydroxide was 10 parts by mass with respect to 100 parts by mass of the modacrylic polymer was used. The obtained modacrylic fibers had a single fiber fineness of 1.7 dtex and a cut length of 51 mm.Production Example 3

[0056] Modacrylic fibers were obtained in the same manner as in Production Example 1, except that a spinning solution obtained by adding the magnesium hydroxide dispersion liquid (concentration: 30 mass%) to the modacrylic polymer solution such that the content of magnesium hydroxide was 20 parts by mass with respect to 100 parts by mass of the modacrylic polymer was used. The obtained modacrylic fibers had a single fiber fineness of 1.7 dtex and a cut length of 51 mm.Production Example 4

[0057] Modacrylic fibers were obtained in the same manner as in Production Example 1, except that a dispersion liquid of magnesium oxide (manufactured by Kyowa Chemical Industry Co., Ltd.; trade name: "500-04R") (average particle diameter of magnesium oxide: 2.0 µm) was used instead of the magnesium hydroxide dispersion liquid. The obtained modacrylic fibers had a single fiber fineness of 1.7 dtex and a cut length of 51 mm.Production Example 5

[0058] Modacrylic fibers were obtained in the same manner as in Production Example 1, except that a spinning solution obtained by adding the magnesium hydroxide dispersion liquid (concentration: 30 mass%) to the modacrylic polymer solution such that the content of magnesium hydroxide was 3 parts by mass with respect to 100 parts by mass of the modacrylic polymer was used. The obtained modacrylic fibers had a single fiber fineness of 1.7 dtex and a cut length of 51 mm.Production Example 6

[0059] Modacrylic fibers were obtained in the same manner as in Production Example 1, except that a dispersion liquid of magnesium hydroxide with an average particle diameter of 0.5 µm was used. The obtained modacrylic fibers had a single fiber fineness of 1.7 dtex and a cut length of 51 mm.Production Example 7

[0060] Modacrylic fibers were obtained in the same manner as in Production Example 1, except that a spinning solution obtained by adding, instead of the magnesium hydroxide dispersion liquid, an antimony trioxide dispersion liquid containing antimony trioxide with an average particle diameter of 2.0 µm to the modacrylic polymer solution such that the content of antimony trioxide was 26 parts by mass with respect to 100 parts by mass of the modacrylic polymer was used. The obtained modacrylic fibers had a single fiber fineness of 2.2 dtex and a cut length of 38 mm.Production Example 8

[0061] Modacrylic fibers were obtained in the same manner as in Production Example 7, except that a modacrylic polymer containing structural units derived from acrylonitrile in an amount of 51.1 mass%, structural units derived from vinylidene chloride in an amount of 47.9 mass%, and structural units derived from sodium p-styrenesulfonate in an amount of 1.1 mass% was used as the modacrylic polymer, and an antimony trioxide dispersion liquid containing antimony trioxide with an average particle diameter of 1.0 µm was used. The obtained modacrylic fibers had a single fiber fineness of 2.2 dtex and a cut length of 38 mm.

[0062] The following fibers were also used in examples and comparative examples. Silica-containing rayon fibers: "FR CORONA (registered trademark)" manufactured by Daiwabo Rayon Co., Ltd.; single fiber fineness: 1.7 dtex; fiber length: 51 mm; silica content: 17.2 mass% Flame-retardant rayon fibers: "Lenzing FR" manufactured by Lenzing, containing a phosphorus-based flame retardant in an amount of 0.5 to 0.8 mass%; single fiber fineness: 2.2 dtex; fiber length: 51 mm Polyester fibers: "TETORON" manufactured by Toray Industries, Inc.; single fiber fineness: 1.6 dtex; fiber length: 51 mm Flame-retardant polyester fibers: "ESLON" manufactured by Toray Chemicals Co., Ltd.; single fiber fineness: 1.4 dtex; fiber length: 51 mm Examples 1 to 10 and Comparative Examples 1 to 5, 9, and 10

[0063] Modacrylic fibers and silica-containing rayon fibers shown in Table 2 below were mixed in the blend amount shown in Table 2 below and were opened using a card. Then, nonwoven fabric having a basis weight shown in Table 2 below was produced using a needle-punching method.Comparative Example 6

[0064] Modacrylic fibers and flame-retardant rayon fibers shown in Table 2 below were mixed in the blend amount shown in Table 2 below and were opened using a card. Then, nonwoven fabric having a basis weight shown in Table 2 below was produced using a needle-punching method.Comparative Example 7

[0065] Modacrylic fibers and polyester fibers shown in Table 2 below were mixed in the blend amount shown in Table 2 below and were opened using a card. Then, nonwoven fabric having a basis weight shown in Table 2 below was produced using a needle-punching method.Comparative Example 8

[0066] Modacrylic fibers and flame-retardant polyester fibers shown in Table 2 below were mixed in the blend amount shown in Table 2 below and were opened using a card. Then, nonwoven fabric having a basis weight shown in Table 2 below was produced using a needle-punching method.

[0067] In Examples 1 to 10 and Comparative Examples 1 to 10, the amount of static electricity during passing through the card was measured as described above, and the results are shown in Table 2 below. The flame retardancies and the sound absorption coefficients of the nonwoven fabric obtained in Examples 1 to 10 and Comparative Examples 1 to 10 were measured as follows, and the results are shown in Tables 3 and 4 below. Table 2Modacrylic fiberFiber composition of nonwoven fabric (mass%)Content in nonwoven fabric (mass%)Nonwoven fabricAmount of static electricity during passing through card (kV)Prod. Ex.Flame retardantModacrylic fiberSilica-containing rayon fiberFlame-retardant rayon fiberPolyester fiberFlame-retardant polyester fiberMagnesium hydroxideAntimony trioxideSilicaBasis weight (g / m 2< )Thickness (mm)Bulk density (g / cm 3< )Compound nameContent (parts by mass)Ex. 11Magnesium hydroxide530700001.43012.01204.40.027Ex. 21Magnesium hydroxide530700001.43012.01684.30.039Ex. 31Magnesium hydroxide530700001.43012.022250.044Ex. 41Magnesium hydroxide520800000.95013.81064.70.0230.00 to 0.03Ex. 52Magnesium hydroxide1040600003.64010.31013.80.0270.10 to 0.23Ex. 63Magnesium hydroxide2040600006.67010.31063.60.0290.85 to 1.0Ex. 74Magnesium oxide530700001.43012.010450.0210.00 to 0.03Ex. 86Magnesium hydroxide520800000.95013.82094.20.0500.00 to 0.03Ex. 96Magnesium hydroxide540600001.90010.3883.80.0230.00 to 0.03Ex. 106Magnesium hydroxide540600001.90010.323350.0470.00 to 0.03Comp. Ex. 11Magnesium hydroxide530700001.43012.07840.020Comp. Ex. 21Magnesium hydroxide550500002.3808.612540.0310.00 to 0.03Comp. Ex. 35Magnesium hydroxide320800000.58013.81203.70.0320.00 to 0.03Comp. Ex. 42Magnesium hydroxide1010900000.91015.51124.90.0230.08 to 0.15Comp. Ex. 51Magnesium hydroxide515850000.71014.61204.60.0260.01 to 0.09Comp. Ex. 61Magnesium hydroxide530070001.4300.01084.50.024Comp. Ex. 71Magnesium hydroxide530007001.4300.01255.20.0240.00Comp. Ex. 81Magnesium hydroxide530000701.4300.01085.10.0210.00Comp. Ex. 97Antimony trioxide26307000006.1912.01293.90.033Comp. Ex. 108Antimony trioxide26307000006.1912.02041.480.1380 Table 3 UL94 vertical flammability testCombustion times of each test piece after both first and second contact with flame (s)Sum of combustion time and glowing time after second contact with flame (s)Sum of results from flammability test on five test pieces after ten repetitions of contact with flame (s)Whether or not test piece burned to holding positionWhether or not absorbent cotton burned due to fallen dripV-2V-1V-0Ex. 1000NoNoPassPassPassEx. 2000NoNoPassPassPassEx. 3000NoNoPassPassPassEx. 4000NoNoPassPassPassEx. 5000NoNoPassPassPassEx. 6000NoNoPassPassPassEx. 7000NoNoPassPassPassEx. 8000NoNoPassPassPassEx. 9000NoNoPassPassPassEx. 10000NoNoPassPassPassComp. Ex. 1000YesNoFailFailFailComp. Ex. 2000YesNoFailFailFailComp. Ex. 3000YesYesFailFailFailComp. Ex. 4000YesNoFailFailFailComp. Ex. 5000YesNoFailFailFailComp. Ex. 6000YesNoFailFailFailComp. Ex. 712--YesYesFailFailFailComp. Ex. 813--YesYesFailFailFailComp. Ex. 9000NoNoPassPassPassComp. Ex. 10000NoNoPassPassPass Table 4 Frequency (Hz)25003500450055006500Range of 2500 to 6500Minimum valueMaximum valueEx. 189849491878494Ex. 289879692878796Ex. 390889692878796Ex. 490859489808094Ex. 593939991909099Ex. 694929992959299Ex. 791879692878796Ex. 89696100929892100Sound absorption coefficient (%)Ex. 991889792898897Ex. 1094949993959399Comp. Ex. 186839291848392Comp. Ex. 292889788928892Comp. Ex. 395929990979299Comp. Ex. 492879688898796Comp. Ex. 592909892949094Comp. Ex. 693909892979098Comp. Ex. 788839387738393Comp. Ex. 891889691898896Comp. Ex. 989839492898394Comp. Ex. 1095939989968999

[0068] As can be seen from the data shown in Tables 2 and 3 above, the nonwoven fabric of the examples has high flame retardancy that satisfies the highest level V-0 standard for the UL94 vertical flammability test. As can be seen from the data shown in Table 4 above, the nonwoven fabric of the examples had a sound absorption coefficient of 80% or more within a thickness range of 20 to 30 mm and a frequency range of 2500 to 6500 Hz, and can thus be favorably used as a flame-retardant sound insulating material or flame-retardant sound absorbing material for a vehicle such as an automobile or a railroad vehicle.

[0069] Meanwhile, the nonwoven fabric of Comparative Example 1 having a basis weight of 80 g / m 2< , the nonwoven fabric of Comparative Example 2 containing the silica-containing rayon fibers in an amount of less than 55 mass%, the nonwoven fabric of Comparative Examples 3 and 5 containing the magnesium compound in an amount of less than 0.75 mass% in the nonwoven fabric, and the nonwoven fabric of Comparative Example 4 containing the magnesium-containing modacrylic fibers in an amount of less than 15 mass% did not satisfy even the V-2 standard for the UL94 vertical flammability test and had poor flame retardancy. Also, the nonwoven fabric of Comparative Example 6 containing, as the regenerated cellulose fibers, the flame-retardant rayon fibers with a phosphorus-based flame retardant did not satisfy even the V-2 standard for the UL94 vertical flammability test and had poor flame retardancy. Both Comparative Example 7 in which the magnesium compound-containing modacrylic fibers were used together with the polyester fibers and Comparative Example 8 in which the magnesium compound-containing modacrylic fibers were used together with the flame-retardant polyester fibers did not satisfy even the V-2 standard for the UL94 vertical flammability test and had poor flame retardancy. The nonwoven fabric of Comparative Examples 9 and 10 containing the modacrylic fibers with antimony trioxide as the modacrylic fibers satisfied the V-0 standard for the UL94 vertical flammability test and had excellent flame retardancy, but there was concern that elution or discharge of antimony trioxide affects the environment and human bodies.

[0070] It is found from the results above that unlike the case where magnesium compound-containing modacrylic fibers are used together with other flame-retardant fibers, unique effects are exhibited by using the magnesium compound-containing modacrylic fibers and the silica-containing regenerated cellulose fibers together at a predetermined ratio and setting the content of magnesium in the nonwoven fabric to a predetermined content, and the flame retardancy of the nonwoven fabric is improved.

[0071] The fabric of the examples in which the magnesium compound-containing modacrylic fibers were used together with the silica-containing rayon fibers had favorable texture compared with the nonwoven fabric of Comparative Examples 7 and 8 in which the magnesium compound-containing modacrylic fibers were used together with the polyester fibers and the flame-retardant polyester fibers.

[0072] As can be seen from the comparison of Examples 4 to 6 with Example 7, when the content of the magnesium compound derived from the modacrylic fibers in the nonwoven fabric exceeds 6.5 mass%, a large amount of static electricity is generated on the fibers during passing through the card, resulting in poor mass productivity.

[0073] The present invention preferably encompasses the following embodiments, but is not particularly limited thereto. [1] Aflame-retardant nonwoven fabric including: modacrylic fibers A; and regenerated cellulose fibers B, wherein the modacrylic fibers A contain a magnesium compound, the regenerated cellulose fibers B contain silica, the flame-retardant nonwoven fabric contains the modacrylic fibers A in an amount of 15 to 45 mass% and the regenerated cellulose fibers B in an amount of 55 to 85 mass%, the flame-retardant nonwoven fabric contains the magnesium compound derived from the modacrylic fibers A in an amount of 0.75 mass% or more, the flame-retardant nonwoven fabric has a basis weight of 80 g / m 2< or more, and the flame-retardant nonwoven fabric satisfies a V-0 standard for a UL94 vertical flammability test. [2] The flame-retardant nonwoven fabric according to [1], wherein the regenerated cellulose fibers B include silica-containing rayon fibers. [3] The flame-retardant nonwoven fabric according to [1] or [2], wherein the flame-retardant nonwoven fabric contains substantially no antimony compound. [4] The flame-retardant nonwoven fabric according to any one of [1] to [3], wherein the flame-retardant nonwoven fabric contains the magnesium compound derived from the modacrylic fibers A in an amount of 5 mass% or less. [5] The flame-retardant fabric according to any one of [1] to [4], wherein the magnesium compound includes one or more selected from the group consisting of magnesium hydroxide and magnesium oxide. [6] The flame-retardant nonwoven fabric according to any one of [1] to [5], wherein the flame-retardant nonwoven fabric contains the silica derived from the regenerated cellulose fibers B in an amount of 7.5 to 20 mass%. [7] The flame-retardant nonwoven fabric according to any one of [1] to [6], wherein a modacrylic polymer included in the modacrylic fibers A contains structural units derived from acrylonitrile in an amount of 30 to 85 mass%, structural units derived from one or more halogen-containing monomer selected from the group consisting of halogen-containing vinyl monomers and halogen-containing vinylidene monomers in an amount of 15 to 70 mass%, and structural units derived from a sulfonic acid group-containing vinyl monomer in an amount of 0 to 3 mass%. [8] The flame-retardant nonwoven fabric according to [7], wherein the modacrylic fibers A contain the magnesium compound in an amount of 3 to 25 parts by mass with respect to 100 parts by mass of the modacrylic polymer. [9] The flame-retardant nonwoven fabric according to any one of [1] to [8], wherein the regenerated cellulose fibers B contain the silica in an amount of 10 to 30 mass%.

[10] The flame-retardant nonwoven fabric according to any one of [1] to [9], wherein the modacrylic fibers A has a single fiber fineness of 0.5 to 5 dtex.

[11] The flame-retardant nonwoven fabric according to any one of [1] to

[10] , wherein the flame-retardant nonwoven fabric has a normal incidence sound absorption coefficient of 80% or more within a thickness range of 20 to 30 mm and a frequency range of 2500 to 6500 Hz, the normal incidence sound absorption coefficient being measured in conformity with JIS A 1405-2:2007.

[12] A vehicle interior material including the flame-retardant nonwoven fabric according to any one of [1] to

[11] .

[13] The vehicle interior material according to

[12] , which is a flame-retardant sound insulating material.

Claims

1. A flame-retardant nonwoven fabric comprising: modacrylic fibers A; and regenerated cellulose fibers B, wherein the modacrylic fibers A comprise a magnesium compound, the regenerated cellulose fibers B comprise silica, the flame-retardant nonwoven fabric comprises the modacrylic fibers A in an amount of 15 to 45 mass% and the regenerated cellulose fibers B in an amount of 55 to 85 mass%, the flame-retardant nonwoven fabric contains the magnesium compound derived from the modacrylic fibers A in an amount of 0.75 mass% or more, the flame-retardant nonwoven fabric has a basis weight of 80 g / m2 or more, and the flame-retardant nonwoven fabric satisfies a V-0 standard for a UL94 vertical flammability test.

2. The flame-retardant nonwoven fabric according to claim 1, wherein the regenerated cellulose fibers B comprises silica-containing rayon fibers.

3. The flame-retardant nonwoven fabric according to claim 1, wherein the flame-retardant nonwoven fabric contains substantially no antimony compound.

4. The flame-retardant nonwoven fabric according to claim 1, wherein the flame-retardant nonwoven fabric comprises the magnesium compound derived from the modacrylic fibers A in an amount of 5 mass% or less.

5. The flame-retardant fabric according to claim 1, wherein the magnesium compound comprises one or more selected from the group consisting of magnesium hydroxide and magnesium oxide.

6. The flame-retardant nonwoven fabric according to claim 1, wherein the flame-retardant nonwoven fabric comprise the silica derived from the regenerated cellulose fibers B in an amount of 7.5 to 20 mass%.

7. The flame-retardant nonwoven fabric according to claim 1, wherein a modacrylic polymer included in the modacrylic fibers A comprises structural units derived from acrylonitrile in an amount of 30 to 85 mass%, structural units derived from one or more halogen-containing monomer selected from the group consisting of halogen-containing vinyl monomers and halogen-containing vinylidene monomers in an amount of 15 to 70 mass%, and structural units derived from a sulfonic acid group-containing vinyl monomer in an amount of 0 to 3 mass%.

8. The flame-retardant nonwoven fabric according to claim 7, wherein the modacrylic fibers A comprise the magnesium compound in an amount of 3 to 25 parts by mass with respect to 100 parts by mass of the modacrylic polymer.

9. The flame-retardant nonwoven fabric according to claim 1, wherein the regenerated cellulose fibers B comprises the silica in an amount of 10 to 30 mass%.

10. The flame-retardant nonwoven fabric according to claim 1, wherein the modacrylic fibers A have a single fiber fineness of 0.5 to 5 dtex.

11. The flame-retardant nonwoven fabric according to claim 1, wherein the flame-retardant nonwoven fabric has a normal incidence sound absorption coefficient of 80% or more within a thickness range of 20 to 30 mm and a frequency range of 2500 to 6500 Hz, the normal incidence sound absorption coefficient being measured in conformity with JIS A 1405-2:2007.

12. A vehicle interior material comprising the flame-retardant nonwoven fabric according to any one of claims 1 to 11.

13. The vehicle interior material according to claim 12, which is a flame-retardant sound insulating material.

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