Inorganic fiber nonwoven fabric and method of producing the same

Abstract

To provide an inorganic fiber nonwoven fabric that has fabric-making characteristics of producing an inorganic fiber nonwoven fabric in a trouble-free manner, has excellent strength retention, can prevent the inorganic fiber from falling off, and has excellent heat resistance.SOLUTION: The problem can be solved by an inorganic fiber nonwoven fabric including an inorganic fiber, an inorganic binder, and a water-soluble organic polymer, with the content of the inorganic fiber in the inorganic fiber nonwoven fabric being not less than 70 mass% and not more than 99 mass% relative to the inorganic fiber nonwoven fabric, the content of the inorganic binder in the inorganic fiber nonwoven fabric being not less than 0.5 mass% and less than 29.5 mass% relative to the inorganic fiber nonwoven fabric, and the content of the water-soluble organic polymer in the inorganic fiber nonwoven fabric being not less than 0.5 mass% and less than 10 mass% relative to the inorganic fiber nonwoven fabric.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a heat-resistant inorganic fiber nonwoven fabric suitable for use as a building material or industrial member, and a method for producing the same. [Background technology]

[0002] Inorganic fibers, particularly glass fibers, are inexpensive and have excellent heat resistance and flame retardancy, and therefore have been widely used in building materials, automobile parts, insulators, industrial parts, etc. In building materials, inorganic fibers are used for applications requiring flame retardancy, heat resistance, and non-combustibility, such as wallpaper materials, cushioned flooring, and ceiling materials. In automobile parts, inorganic fibers are used for applications requiring flame retardancy, heat resistance, and non-combustibility, such as battery covers, brake pads, front bumpers, ceiling materials, and interior materials. In addition, several applications of nonwoven fabrics using inorganic fibers such as glass fibers have been proposed.

[0003] For example, inorganic fiber paper containing inorganic fibers and obtained by the following wet papermaking process is known (see, for example, Patent Document 1). The inorganic fiber paper is a sheet-form substrate obtained by wet papermaking using biosoluble ceramic fibers, glass fibers having a blend ratio of 0% by weight or more and 70% by weight or less in the fiber content, organic fibers having an average fiber diameter of 17 μm or more and 25 μm or less, at least one cationic inorganic binder selected from aluminum sulfate, polyaluminum chloride, cationic colloidal silica, and alumina sol, and sepiolite having a blend ratio of 20% by weight or more and 60% by weight or less in the fiber content. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-007698 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, inorganic fiber nonwoven fabrics containing a large amount of inorganic fibers such as glass fibers have problems such as a decrease in strength of the inorganic fiber nonwoven fabric and the fall-off of inorganic fibers. The fallen inorganic fibers may fly off and have a negative effect on the human body. For example, when an organic polymer or pulp is added to the inorganic fiber nonwoven fabric in order to maintain the strength of the inorganic fiber nonwoven fabric and suppress the fall-off of the inorganic fibers, the heat resistance tends to decrease. Therefore, it is very difficult for the inorganic fiber nonwoven fabric to simultaneously maintain the strength, suppress the fall-off of the inorganic fibers, and have good heat resistance.

[0006] The inorganic fiber paper described in Patent Document 1 uses biosoluble ceramic fibers that have little effect on the human body, and is impregnated with an impregnation liquid in which particles of a catalyst or adsorbent, or an inorganic binder, are dispersed, and then fired. This method improves the impregnation property before firing.

[0007] An object of the present invention is to provide an inorganic fiber nonwoven fabric having a high inorganic fiber content of 70 mass% or more relative to the nonwoven fabric, yet having no problems in papermaking to obtain the inorganic fiber nonwoven fabric, and which combines strength maintenance, suppression of inorganic fiber shedding, and good heat resistance, and a method for producing the same. [Means for solving the problem]

[0008] As a result of intensive research into solving the above problems, the present inventors have found the following embodiments of the invention. The embodiments of the invention include an inorganic fiber nonwoven fabric and a method for producing an inorganic fiber nonwoven fabric having the following aspects.

[0009] [1] An inorganic fiber nonwoven fabric comprising inorganic fibers, an inorganic binder, and a water-soluble organic polymer, The content of the inorganic fibers in the inorganic fiber nonwoven fabric is 70% by mass or more and 99% by mass or less with respect to the inorganic fiber nonwoven fabric, The content of the inorganic binder in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 29.5% by mass with respect to the inorganic fiber nonwoven fabric; and The content of the water-soluble organic polymer in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 10% by mass with respect to the inorganic fiber nonwoven fabric. Inorganic fiber nonwoven fabric. [2] The inorganic fiber nonwoven fabric according to the above [1], wherein the inorganic binder is bound to the inorganic fibers and the water-soluble organic polymer is in a crosslinked state with the inorganic binder. [3] The inorganic fiber nonwoven fabric according to [1] or [2] above, wherein the inorganic fibers are glass fibers. [4] The inorganic fiber nonwoven fabric according to any one of the above [1] to [3], wherein the inorganic binder is one or more selected from the group consisting of aluminum sulfate, polyaluminum chloride, sepiolite, colloidal silica, water glass, alumina sol, lithium silicate, and bentonite. [5] The inorganic fiber nonwoven fabric according to any one of the above [1] to [4], wherein the water-soluble organic polymer comprises one or more selected from the group consisting of poly(meth)acrylic acid, copolymers of (meth)acrylic acid and various monomers, poly(meth)acrylates, copolymers of (meth)acrylates and various monomers, poly(meth)acrylamide, and copolymers of (meth)acrylamide and various monomers. [6] The inorganic fiber nonwoven fabric according to any one of the above [1] to [5], wherein the inorganic fiber nonwoven fabric further contains fibrillated fibers, and the content of the fibrils or fibers in the inorganic fiber nonwoven fabric is 0.1% by mass or more and 6% by mass or less relative to the inorganic fiber nonwoven fabric. [7] The inorganic fiber nonwoven fabric according to any one of [1] to [6], wherein the inorganic fiber nonwoven fabric further contains a thermally adhesive binder fiber, and the content of the thermally adhesive binder in the inorganic fiber nonwoven fabric is 0.1 mass% or more and 6 mass% or less relative to the inorganic fiber nonwoven fabric. [8] A method for producing an inorganic fiber nonwoven fabric containing inorganic fibers, comprising the steps of: A step of preparing a raw material slurry containing inorganic fibers, an inorganic binder, a water-soluble organic polymer, and a liquid medium; and A step of wet-forming the raw material slurry to obtain a sheet Including, The content of the inorganic fibers in the raw material slurry is 70% by mass or more and 99% by mass or less based on all components of the raw material slurry excluding the medium liquid, The content of the inorganic binder in the raw slurry is 0.5% by mass or more and less than 29.5% by mass based on all components of the raw slurry excluding the medium liquid; and The content of the water-soluble organic polymer in the raw slurry is 0.5% by mass or more and less than 10% by mass based on all components of the raw slurry excluding the medium liquid. A method for manufacturing inorganic fiber nonwoven fabric. [9] The method for producing an inorganic fiber nonwoven fabric according to the above [8], wherein the inorganic fibers are glass fibers.

[10] The method for producing an inorganic fiber nonwoven fabric according to [8] or [9] above, wherein the inorganic binder is one or more selected from the group consisting of aluminum sulfate, polyaluminum chloride, sepiolite, colloidal silica, water glass, alumina sol, lithium silicate, and bentonite.

[11] The method for producing an inorganic fiber nonwoven fabric according to any one of the above [8] to

[10] , wherein the water-soluble organic polymer comprises one or more selected from the group consisting of poly(meth)acrylic acid, copolymers of (meth)acrylic acid and various monomers, poly(meth)acrylates, copolymers of (meth)acrylates and various monomers, poly(meth)acrylamide, and copolymers of (meth)acrylamide and various monomers.

[12] The method for producing an inorganic fiber nonwoven fabric according to any one of the above [8] to

[11] , wherein the raw material slurry further contains fibrillated fibers, and the content of the fibrillated fibers in the raw material slurry is 0.1 mass % or more and 6 mass % or less based on all components of the raw material slurry excluding the liquid medium.

[13] The method for producing an inorganic fiber nonwoven fabric according to any one of the above [8] to

[12] , wherein the raw material slurry further contains a heat-fusible binder fiber, and the content of the heat-fusible binder in the raw material slurry is 0.1 mass % or more and 6 mass % or less based on all components of the raw material slurry excluding the liquid medium.

[14] An inorganic fiber nonwoven fabric produced by the method for producing an inorganic fiber nonwoven fabric according to any one of the above items [8] to

[13] . Effect of the Invention

[0010] According to an embodiment of the present invention, there are provided an inorganic fiber nonwoven fabric and a manufacturing method thereof, which have a high inorganic fiber content of 70 mass% or more relative to the inorganic fiber nonwoven fabric, yet have no problems in papermaking to obtain the inorganic fiber nonwoven fabric, and can maintain strength, inhibit inorganic fiber shedding, and have good heat resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In this specification, the "content" is a value (% by mass) calculated from the amount of dry solids (mass of dry solids) for each target area of ​​each target object.

[0012] The inorganic fiber nonwoven fabric according to one embodiment of the present invention includes inorganic fibers, an inorganic binder, and a water-soluble organic polymer. The content of the inorganic fibers in the inorganic fiber nonwoven fabric is 70% by mass or more and 99% by mass or less with respect to the inorganic fiber nonwoven fabric, The content of the inorganic binder in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 29.5% by mass with respect to the inorganic fiber nonwoven fabric; and The content of the water-soluble organic polymer in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 10% by mass with respect to the inorganic fiber nonwoven fabric. In the inorganic fiber nonwoven fabric of the present embodiment, specific amounts of an inorganic binder and a water-soluble organic polymer are contained, so that the inorganic binder is bound to the inorganic fibers, and the water-soluble organic polymer crosslinks the inorganic binder. As a result, the inorganic fiber nonwoven fabric of the present embodiment can maintain a high content of inorganic fibers in the inorganic fiber nonwoven fabric, so that good heat resistance can be obtained, and strength can be maintained and the fall-off of inorganic fibers can be suppressed.

[0013] In the inorganic fiber nonwoven fabric of this embodiment, the inorganic binder is bound to the inorganic fibers, and the water-soluble organic polymer crosslinks the inorganic binder. This state can be confirmed by microscopic observation using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or the like. In addition, when the elements contained in the inorganic fibers and the elements contained in the inorganic binder are different, the state can be confirmed by elemental analysis using EDS (energy dispersive X-ray spectroscopy).

[0014] In this embodiment, the inorganic fiber may be one that is conventionally known in the field of nonwoven fabrics. Examples of the inorganic fiber include ceramic fibers such as silica fiber, alumina fiber, alumina silicate fiber, zirconia fiber, carbon fiber, soluble fiber, refractory ceramic fiber, aerogel composite fiber, magnesium silicate fiber, alkaline earth silicate fiber, potassium titanate fiber, and potassium titanate whisker fiber; glass fibers such as glass fiber, chopped strands, and glass wool; and mineral fibers such as rock wool, basalt fiber, and wollastonite fiber. In some embodiments, the inorganic fiber is one or more types selected from the group consisting of these. In some embodiments, the inorganic fibers include glass-based fibers such as glass fibers, chopped strands, and glass wool. In at least one embodiment, the inorganic fibers include glass fibers. In at least one embodiment, the inorganic fibers are glass fibers. The reason for this is that they are more excellent for forming inorganic fiber nonwoven fabrics.

[0015] The cross-sectional shape of the inorganic fibers may be any of a circular shape, an elliptical shape, a flat shape, etc. When the cross-sectional shape of the inorganic fibers is flat, the dimensions of the average major axis and the average minor axis of the flat shape are not particularly limited. In some embodiments, the cross-sectional shape of the inorganic fibers is flat, and the ratio of the average major axis to the average minor axis of the flat shape (ratio = "average major axis" ÷ "average minor axis") is from 3 to 5. The reason for this is that the inorganic fiber nonwoven fabric can be well-balanced in terms of strength maintenance and texture. In some embodiments, the cross-sectional shape of the inorganic fiber is flat, and the equivalent fiber diameter of the flat shape is 5 μm or more and 17 μm or less. This is because it is advantageous in producing inorganic fibers. In this specification, the equivalent fiber diameter means the diameter of the cross section of an inorganic fiber having a circular cross-sectional shape and having the same cross-sectional area as the cross-sectional area of ​​an inorganic fiber having a flat cross-sectional shape.

[0016] In some embodiments, the inorganic fibers have an average fiber length in the range of 1 mm or more and 15 mm or less, because this allows the inorganic fiber nonwoven fabric to maintain its strength and texture well at the same time.

[0017] In this embodiment, the content of the inorganic fibers in the inorganic fiber nonwoven fabric is 70% by mass or more and 99% by mass or less with respect to the inorganic fiber nonwoven fabric. This allows the inorganic fiber nonwoven fabric of this embodiment to have good heat resistance. If the content of the inorganic fibers in the inorganic fiber nonwoven fabric is less than 70% by mass, the inorganic fiber nonwoven fabric cannot have good heat resistance. On the other hand, if the content of the inorganic fibers in the inorganic fiber nonwoven fabric is more than 99% by mass, the inorganic binder and / or water-soluble organic polymer is insufficient, and the inorganic fiber nonwoven fabric is deteriorated in terms of strength maintenance and prevention of inorganic fiber shedding, as well as papermaking properties. When the deterioration in terms of strength maintenance is significant, the inorganic fiber nonwoven fabric cannot be manufactured. In some embodiments, from the viewpoint of obtaining better heat resistance of the inorganic fiber nonwoven fabric, the content of the inorganic fibers in the inorganic fiber nonwoven fabric is 72% by mass or more and 99% by mass or less with respect to the inorganic fiber nonwoven fabric.

[0018] In this embodiment, the inorganic binder may be one that is conventionally known in the field of nonwoven fabrics that can be bound to inorganic fibers. The inorganic binder may be, for example, a hydraulic inorganic compound containing one or more inorganic atoms selected from the group consisting of Si, Al, Ti, Zr, Ca, Fe, V, Sn, Li, Be, B, and P, and cements. More specific examples of the inorganic binder include aluminum sulfate, polyaluminum chloride, sepiolite, colloidal silica, water glass, alumina sol, lithium silicate, and bentonite. In some embodiments, the inorganic binder is one or more selected from the group consisting of aluminum sulfate, polyaluminum chloride, sepiolite, colloidal silica, water glass, alumina sol, lithium silicate, and bentonite. In some embodiments, the inorganic binder includes at least one selected from the group consisting of colloidal silica and alumina sol. In some embodiments, the inorganic binder is at least one selected from the group consisting of colloidal silica and alumina sol. This is because colloidal silica and alumina sol are easily available as chemical products and have excellent effects as an inorganic binder. In at least one embodiment, the inorganic binder is a combination of at least one selected from the group consisting of colloidal silica and alumina sol, and sepiolite, because this can improve the strength maintenance of the inorganic fiber nonwoven fabric. In addition, in the case of an aqueous dispersion of a particulate inorganic binder such as colloidal silica or alumina sol, when the inorganic fiber nonwoven fabric is finally dried, at least a part of the dispersion medium has evaporated and the inorganic binder is bound to the inorganic fibers.

[0019] In this embodiment, the content of the inorganic binder in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 29.5% by mass relative to the inorganic fiber nonwoven fabric. If the content of the inorganic binder in the inorganic fiber nonwoven fabric is less than 0.5% by mass, the inorganic binder is insufficient, and therefore the strength of the inorganic fiber nonwoven fabric cannot be maintained, the inorganic fibers cannot be prevented from falling off, and good papermaking properties cannot be obtained. On the other hand, if the content of the inorganic binder in the inorganic fiber nonwoven fabric is 29.5% by mass or more, the flowability of the raw material slurry for producing the inorganic fiber nonwoven fabric described below tends to decrease, and the texture of the inorganic fiber nonwoven fabric deteriorates, resulting in uneven heat resistance. In one embodiment, the content of the inorganic binder in the inorganic fiber nonwoven fabric can be, for example, 0.5% by mass or more and less than 28% by mass, for example, 0.5% by mass or more and less than 22% by mass, for example, 0.5% by mass or more and less than 15.5% by mass relative to the inorganic fiber nonwoven fabric.

[0020] In this embodiment, the water-soluble organic polymer may be a conventionally known one, for example, an organic polymer having a polar group such as a hydroxyl group, a carbonyl group, a carboxyl group, a sulfonic acid group, an ether group, an amino group, an amide group, a carboxyl group, or a urethane group. The water-soluble organic polymer is roughly classified into, for example, a natural water-soluble organic polymer, a semi-synthetic water-soluble organic polymer, and a synthetic water-soluble organic polymer. In some embodiments, the water-soluble organic polymer is an organic polymer having a molecular weight of 10,000 or more, and which is not separated or precipitated even when an aqueous solution of the finally prepared organic polymer having a concentration of 0.1% by mass in water is left at 20° C. for 12 hours.

[0021] Examples of natural water-soluble organic polymers include starches such as potato starch, sweet potato starch, wheat starch, rice starch, tapioca starch, corn starch, and dextrin; resin polysaccharides such as gum arabic, tragacanth gum, karaya gum, and albino aoi; seed polysaccharides such as guar gum, tara gum, locust bean gum, and tamarind seed polysaccharide; seaweed polysaccharides such as sodium alginate, carrageenan, agar, and funori; microbial fermentation polysaccharides such as xanthan gum, pullulan, curdlan, dextran, and levan; proteins such as casein, gelatin, albumin, glue, and collagen; pectin, chitin, and chitosan.

[0022] Examples of the semi-synthetic water-soluble organic polymer include celluloses such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, and sodium cellulose sulfate; modified starches such as soluble starch, oxidized starch, carboxymethyl starch, hydroxyethyl starch, hydroxypropyl starch, dialdehyde starch, phosphated starch, and acetylated starch; and propylene glycol alginate.

[0023] Examples of synthetic water-soluble organic polymers include poly(meth)acrylic acid, copolymers of (meth)acrylic acid and various monomers, poly(meth)acrylates, copolymers of (meth)acrylates and various monomers, poly(meth)acrylamide, copolymers of (meth)acrylamide and various monomers, polyvinylpyrrolidone, polyvinyl alkyl ether, copolymers of maleic anhydride and various monomers, copolymers of maleic acid and various monomers, copolymers of maleic acid and various monomers, copolymers of maleate and various monomers, polyvinyl alcohols such as polyvinyl alcohol and various modified polyvinyl alcohols, water-soluble polyvinyl organic polymers such as polyvinylpyrrolidone and polyvinyl alkyl ethers, water-soluble vinylidene organic polymers, water-soluble polyester organic polymers, water-soluble polyamine organic polymers, water-soluble polyamide organic polymers, water-soluble polyether organic polymers, water-soluble polyglycol organic polymers, and water-soluble polyalkylene oxide organic polymers. The various monomers in the copolymer may be any as long as the resulting copolymer is water-soluble. Examples of the various monomers include (meth)acrylic acid monomers, maleic acid monomers, sulfonic acid monomers, alkyl monomers, and styrene monomers.

[0024] In some embodiments, the water-soluble organic polymer is one or more selected from the group consisting of the above specific examples of natural water-soluble organic polymers, semi-synthetic water-soluble organic polymers, and synthetic water-soluble organic polymers. In some embodiments, the water-soluble organic polymer comprises one or more selected from the group consisting of poly(meth)acrylic acid, copolymers of (meth)acrylic acid and various monomers, poly(meth)acrylates, copolymers of (meth)acrylates and various monomers, poly(meth)acrylamide, and copolymers of (meth)acrylamide and various monomers. In some embodiments, the water-soluble organic polymer is one or more selected from the group consisting of poly(meth)acrylic acid, copolymers of (meth)acrylic acid and various monomers, poly(meth)acrylates, copolymers of (meth)acrylates and various monomers, poly(meth)acrylamide, and copolymers of (meth)acrylamide and various monomers. The reason for this is that the strength of the inorganic fiber nonwoven fabric is maintained and the shedding of inorganic fibers is suppressed. In at least one embodiment, the water-soluble organic polymer is a combination of one or more selected from the group consisting of poly(meth)acrylic acid, copolymers of (meth)acrylic acid and various monomers, poly(meth)acrylates, copolymers of (meth)acrylates and various monomers, poly(meth)acrylamide, and copolymers of (meth)acrylamide and various monomers, and one or more selected from the group consisting of polyvinyl alcohols, because this improves the strength maintenance of the inorganic fiber nonwoven fabric and improves the prevention of the shedding of inorganic fibers from the inorganic fiber nonwoven fabric.

[0025] In this embodiment, the content of the water-soluble organic polymer in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 10% by mass with respect to the inorganic fiber nonwoven fabric. If the content of the water-soluble organic polymer in the inorganic fiber nonwoven fabric is less than 0.5% by mass, the strength of the inorganic fiber nonwoven fabric cannot be maintained. On the other hand, if the content of the water-soluble organic polymer in the inorganic fiber nonwoven fabric is 10% by mass or more, the heat resistance of the inorganic fiber nonwoven fabric tends to deteriorate. In addition, if the content of the water-soluble organic polymer in the inorganic fiber nonwoven fabric is 10% by mass or more, the fluidity of the raw material slurry for producing the inorganic fiber nonwoven fabric tends to decrease. Due to the influence of the decrease in the fluidity of the raw material slurry, in the papermaking of the raw material slurry, paper breaks (breakage of the sheet), scorching to the Yankee dryer, and clogging of the papermaking wire occur, and the papermaking properties deteriorate.

[0026] In some embodiments, the inorganic fiber nonwoven fabric further contains fibrillated fibers. In at least one embodiment, the inorganic fiber nonwoven fabric contains fibrillated fibers, and the content of the fibrillated fibers in the inorganic fiber nonwoven fabric is 0.1% by mass or more and 6% by mass or less relative to the inorganic fiber nonwoven fabric. This is because the strength of the inorganic fiber nonwoven fabric is maintained and the fall-off of inorganic fibers is suppressed better. However, since the fibrillated fibers can deteriorate the heat resistance of the inorganic fiber nonwoven fabric, an upper limit is determined for the content of the fibrillated fibers.

[0027] In at least one embodiment, the inorganic fiber nonwoven fabric comprises inorganic fibers, an inorganic binder, a water-soluble organic polymer, and fibrillated fibers, and the content of the inorganic fibers in the inorganic fiber nonwoven fabric is 70% by mass or more and 98.9% by mass or less, relative to the inorganic fiber nonwoven fabric, the content of the inorganic binder in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 29.5% by mass, and the content of the water-soluble organic polymer in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 10% by mass, relative to the inorganic fiber nonwoven fabric, and the content of the fibrillated fibers in the inorganic fiber nonwoven fabric is 0.1% by mass or more and 6% by mass or less, relative to the inorganic fiber nonwoven fabric.

[0028] In this specification, the fibrillated fibers are fibers obtained by physically grinding fibers such as cellulose using various beating machines or homogenizing devices such as a beater, a conical refiner, a single disc refiner, a double disc refiner, a stone mill grinder, a homogenizer, a high-pressure homogenizer, and a sand mill, and the surfaces of the fibers before the grinding and the fibers themselves are very finely cracked and branched, and at least some of the branch ends have a fiber diameter of 1 μm or less. Examples of the fibrillated fibers include fibers obtained by fibrillating resins such as cellulose, solvent-spun cellulose, acrylic, wholly aromatic polyamide, wholly aromatic polyester, polyimide, polyamideimide, polyetheretherketone, polyethersulfone, polyphenylene sulfide, polybenzimidazole, poly-p-phenylenebenzobisthiazole, poly-p-phenylenebenzobisoxazole, and polytetrafluoroethylene. Examples of the wholly aromatic polyamides include para-aromatic polyamides such as poly(p-phenyleneisophthalamide) and poly(p-phenyleneterephthalamide), and meta-aromatic polyamides such as poly(m-phenyleneisophthalamide) and poly(m-phenyleneterephthalamide).

[0029] In some embodiments, the fibrillated fibers are fibrillated cellulose fibers obtained by fibrillating cellulose fibers. This is because the inorganic fiber nonwoven fabric is more effectively prevented from falling off. Examples of the cellulose fibers include natural cellulose fibers and regenerated cellulose fibers. Examples of the natural cellulose fibers include wood pulp such as coniferous pulp and broadleaf pulp, and woody or herbaceous pulp such as straw pulp, bamboo pulp, linter pulp, and kenaf pulp. Examples of the regenerated cellulose fibers include rayon, cupra, and lyocell. Examples of the cellulose fibers include pulp obtained from waste paper and paper breakage generated in paper mills.

[0030] In some embodiments, the fibrillated fiber is a fiber obtained by fibrillating one or more types selected from the group consisting of softwood pulp, linter pulp, and lyocell. In at least one embodiment, the fibrillated fiber is a fiber obtained by fibrillating lyocell. The reason for this is that the inorganic fiber nonwoven fabric is more effectively prevented from falling off.

[0031] Examples of the apparatus for fibrillating fibers include beaters, conical refiners, single-disk refiners, double-disk refiners, PFI mills, stone-type grinders, homogenizers, and sand mills. Examples of the apparatus for fibrillating fibers include ball mills, dyno mills, mixers, grinders, rotary blade homogenizers that apply shearing force with high-speed rotary blades, double-cylinder high-speed homogenizers that generate shearing force between a cylindrical inner blade rotating at high speed and a fixed outer blade, ultrasonic crushers that pulverize fibers by ultrasonic impact, and high-pressure homogenizers that apply a pressure difference of at least 20 MPa to a fiber suspension, pass it through a small-diameter orifice at high speed, and collide with it to rapidly decelerate it, thereby applying shearing force and cutting force to the fibers. One or more of the apparatuses for fibrillation selected from the group consisting of these can be used. The processing conditions of the device can be appropriately set, for example, the fiber concentration, temperature, pressure, rotation speed, shape of the refiner blades, gap between the refiner plates, number of processing times, etc.

[0032] The degree of fibrillation can be estimated by measuring the modified freeness of the fibrillated fiber. The smaller the value of the modified freeness, the more fibrillated the fiber. The modified freeness is a value determined in accordance with JIS P8121-2:2012 "Pulp - Freeness test method - Part 2: Canadian standard freeness method" except that an 80-mesh wire screen with a wire diameter of 0.14 mm and an opening of 0.18 mm is used as the sieve plate and the concentration of the sample is 0.1% by mass. In some embodiments, the modified freeness of the fibrillated fibers is 0 ml or more and 300 ml or less, because this improves the maintenance of the strength of the inorganic fiber nonwoven fabric and the prevention of the inorganic fibers from falling off.

[0033] In some embodiments, the fibrillated fibers have a length-weighted average fiber length of 0.02 mm or more and 1.50 mm or less, because this improves the prevention of the inorganic fibers from falling off from the inorganic fiber nonwoven fabric.

[0034] In some embodiments, the fibrillated fibers have an average fiber width of 0.5 μm or more and 40.0 μm or less, because this improves the maintenance of strength of the inorganic fiber nonwoven fabric and the prevention of shedding of the inorganic fibers.

[0035] In this specification, the length-weighted average fiber length of the fibrillated fibers is a value measured using a Fiber Quality Analyzer (FQA-360) manufactured by OpTest Equipment Inc. based on JIS P8226-2:2011 "Pulp - Fiber length measurement method by optical automatic analysis method, Part 2: Non-polarized method". As used herein, the average fiber width of fibrillated fibers is the fiber width measured in projected fiber length (Proj) mode using Kajaani FiberLab V3.5 from Metso Automation.

[0036] In some embodiments, the inorganic fiber nonwoven fabric further contains a heat-fusible binder fiber. In at least one embodiment, the inorganic fiber nonwoven fabric further contains a heat-fusible binder, and the content of the heat-fusible binder in the inorganic fiber nonwoven fabric is 0.1% by mass or more and 6% by mass or less relative to the inorganic fiber nonwoven fabric. This is because the inorganic fibers in the inorganic fiber nonwoven fabric are more effectively prevented from falling off. However, the heat-fusible binder can deteriorate the heat resistance of the inorganic fiber nonwoven fabric, so an upper limit is set for the content of the heat-fusible binder.

[0037] In at least one embodiment, the inorganic fiber nonwoven fabric comprises inorganic fibers, an inorganic binder, a water-soluble organic polymer, fibrillated fibers, and a heat-fusible binder, and the content of the inorganic fibers in the inorganic fiber nonwoven fabric is 70% by mass or more and 98.8% by mass or less, the content of the inorganic binder in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 29.5% by mass, the content of the water-soluble organic polymer in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 10% by mass, the content of the fibrillated fibers in the inorganic fiber nonwoven fabric is 0.1% by mass or more and 6% by mass or less, and the content of the heat-fusible binder in the inorganic fiber nonwoven fabric is 0.1% by mass or more and 6% by mass or less, based on the inorganic fiber nonwoven fabric.

[0038] In this specification, the heat-fusible binder fiber is a binder fiber that softens when heated to exhibit an adhesive function. Examples of the heat-fusible binder fiber include composite fibers such as core-shell fibers, side-by-side fibers, and radially split fibers, undrawn fibers, and low-melting synthetic resin monofilaments. The heat-fusible binder fiber has a low glass transition temperature or melting temperature (melting point) in its entirety or in part, and exhibits an adhesive function in the drying process of a papermaking machine.

[0039] In some embodiments, the heat-fusible binder fiber is the above-mentioned composite fiber. This is because the composite fiber is difficult to form a film, and therefore the inorganic fiber nonwoven fabric, which has an advantageous heat resistance, can maintain the strength of the inorganic fiber nonwoven fabric while leaving interfiber voids. Examples of the composite fiber include a combination of polypropylene (core) and polyethylene (sheath), a combination of polypropylene (core) and ethylene vinyl alcohol (sheath), a combination of a high melting point polyester (core) and a low melting point polyester (sheath), and a combination of a high melting point polyester (core) and polyethylene (sheath).

[0040] The undrawn fibers include, for example, undrawn fibers of polyester and the like. The low melting point synthetic resin short fibers may be, for example, monofilaments made only of a low melting point resin such as polyethylene or polypropylene.

[0041] The thickness of the inorganic fiber nonwoven fabric can be set arbitrarily depending on the application of the inorganic fiber nonwoven fabric. In some embodiments, the thickness of the inorganic fiber nonwoven fabric is 0.1 mm or more and 0.8 mm or less. This is because the strength of the inorganic fiber nonwoven fabric is better maintained. This is also because the operational stability during the production of the inorganic fiber nonwoven fabric is better. Furthermore, this is because the inorganic fiber nonwoven fabric is more advantageous in terms of production cost. The thickness can be set to a predetermined value by adjusting the papermaking conditions.

[0042] The density of the inorganic fiber nonwoven fabric can be set arbitrarily depending on the application of the inorganic fiber nonwoven fabric. In some embodiments, the density of the inorganic fiber nonwoven fabric is 0.10 g / cm 3 More than 0.50g / cm 3 The reason is as follows. The reason is that the strength of the inorganic fiber nonwoven fabric is maintained better. Also, the reason is that the operational stability during the production of the inorganic fiber nonwoven fabric is improved. The density can be set to a predetermined value by adjusting the papermaking conditions.

[0043] The inorganic fiber nonwoven fabric of this embodiment can be obtained by a method conventionally known in the field of nonwoven fabrics. For example, a wet papermaking method can be used in which a raw material slurry containing each fiber is made using a papermaking machine having a papermaking screen such as a cylinder, fourdrinier, short wire, or inclined wire. In addition to the above-mentioned materials, additives such as a dispersant, a paper strength agent, a thickener, an inorganic filler, an organic filler, and an antifoaming agent can be appropriately added to the raw material slurry as necessary.

[0044] One embodiment of the present invention is a method for producing an inorganic fiber nonwoven fabric containing inorganic fibers, comprising: A step of preparing a raw material slurry containing inorganic fibers, an inorganic binder, a water-soluble organic polymer, and a liquid medium; and A step of wet-forming the raw material slurry to obtain a sheet Including, The content of the inorganic fibers in the raw material slurry is 70% by mass or more and 99% by mass or less based on all components of the raw material slurry excluding the medium liquid, The content of the inorganic binder in the raw slurry is 0.5% by mass or more and less than 29.5% by mass based on all components of the raw slurry excluding the medium liquid; and The content of the water-soluble organic polymer in the raw slurry is 0.5% by mass or more and less than 10% by mass based on all components of the raw slurry excluding the medium liquid. A method for producing inorganic fiber nonwoven fabric. According to the manufacturing method of the inorganic fiber nonwoven fabric of this embodiment, the raw material slurry contains a specific amount of inorganic binder and water-soluble organic polymer, and in the sheet and inorganic fiber nonwoven fabric obtained by wet-processing the raw material slurry, the inorganic binder is bound to the inorganic fiber, and the water-soluble organic polymer is crosslinked to the inorganic binder. As a result, the inorganic fiber nonwoven fabric obtained by the manufacturing method of this embodiment can maintain a high content of inorganic fibers in the inorganic fiber nonwoven fabric, so that it can obtain good heat resistance, and can achieve strength maintenance and prevention of inorganic fiber shedding. In addition, according to the manufacturing method of the inorganic fiber nonwoven fabric of this embodiment, the raw material slurry contains a specific amount of inorganic binder and water-soluble organic polymer, so that it can have papermaking properties that are free from problems in papermaking to obtain the inorganic fiber nonwoven fabric.

[0045] The inorganic fibers, inorganic binder, and water-soluble organic polymer used in the manufacturing method of this embodiment are the same as those contained in the inorganic fiber nonwoven fabric of the above embodiment, and therefore the descriptions thereof in the above embodiment also apply to this embodiment.

[0046] In one embodiment, the liquid medium can be water, an alcohol such as ethanol, or a combination thereof, preferably water.

[0047] In one embodiment, the raw material slurry further contains fibrillated fibers, and the content of the fibrillated fibers in the raw material slurry is 0.1% by mass or more and 6% by mass or less based on all components of the raw material slurry excluding the liquid medium. Regarding the fibrillated fibers, the explanations in the above embodiment are also applied to this embodiment.

[0048] In one embodiment, the raw material slurry further contains a heat-fusible binder fiber, and the content of the heat-fusible binder in the raw material slurry is 0.1% by mass or more and 6% by mass or less based on all components of the raw material slurry excluding the liquid medium. The heat-fusible binder fiber described in the above embodiment also applies to this embodiment.

[0049] The raw material slurry can be prepared by adding inorganic fibers, inorganic binders, water-soluble organic polymers, and, if necessary, fibrillated fibers, heat-fusible binder fibers, and other additives to a liquid medium and mixing them. For example, a known pulper can be used for mixing. In some embodiments, the solid content concentration of the raw material slurry is 0.001% by mass or more and 0.5% by mass or less. In at least one embodiment, the raw material slurry is further diluted to a predetermined solid content concentration to form a papermaking slurry, which is then paper-made. The other additives may be dispersants, paper strength agents, thickeners, inorganic fillers, organic fillers, and defoamers. The types and amounts of each additive are the same as in the conventional methods.

[0050] In this embodiment, the raw material slurry is wet-formed into a sheet. The wet-formed sheet can be produced by a wet papermaking method using a known papermaking machine having a wire such as a cylinder, a fourdrinier, a short wire, or an inclined wire.

[0051] The wet sheet web obtained by wet papermaking is nip-pressed with a press roll or the like, and then dried using a Yankee dryer to form a nonwoven fabric. In the drying step, a heating device such as a hot air dryer, a heating roll, or an infrared heater can be used in combination with the Yankee dryer as an auxiliary. In one aspect, the method for producing an inorganic fiber nonwoven fabric of the above embodiment further includes a step of nip-pressing the sheet and a step of drying the sheet.

[0052] In some aspects, the inorganic fiber nonwoven fabric of the above embodiment has an inorganic particle layer containing inorganic particles and an organic binder on at least one side of the inorganic fiber nonwoven fabric. The reason for this is that the inorganic fiber nonwoven fabric has an inorganic particle layer, which further improves the prevention of inorganic fibers from falling off and the heat resistance of the inorganic fiber nonwoven fabric.

[0053] The inorganic particles of the inorganic particle layer may be any particles known in the art of coating. Examples of inorganic particles include aluminum hydroxide, aluminum hydroxide oxide, magnesium hydroxide, calcium hydroxide, dihydrated gypsum, tricalcium aluminate, clay, kaolin, calcined kaolin, carbonates such as calcium carbonate, magnesium carbonate, and barium carbonate, talc, and titanium dioxide. In some embodiments, the inorganic particles are one or more selected from the group consisting of the above. In at least one embodiment, the inorganic particles are one or more selected from the group consisting of aluminum hydroxide oxide, clay, kaolin, calcined kaolin, and carbonates. This is because the inorganic fiber nonwoven fabric is more improved in terms of the prevention of shedding of inorganic fibers and heat resistance.

[0054] The organic binder of the inorganic particle layer may be any of those conventionally known in the field of coating. Examples of the organic binder include the resins exemplified in the water-soluble organic polymer, fibrillated fiber, and heat-fusible binder fiber, as well as styrene-butadiene, styrene-acrylonitrile, ethylene-acrylonitrile, vinyl chloride-vinyl acetate, and ethylene-vinyl acetate copolymer resins, urethane resins, alkyd resins, and polyester resins, as well as thermosetting synthetic resins such as melamine resins and urea resins, and natural rubbers.

[0055] In some embodiments, the coating amount of the inorganic particle layer is 5 g / m 2 per side of the inorganic fiber nonwoven fabric. 2 More than 40g / m 2 The reason is that the inorganic fibers of the inorganic fiber nonwoven fabric are prevented from falling off and the heat resistance is improved without decreasing the flexibility of the inorganic fiber nonwoven fabric due to the inorganic particle layer.

[0056] The method of providing an inorganic particle layer on an inorganic fiber nonwoven fabric can include a method of applying a coating solution for an inorganic particle layer to the inorganic fiber nonwoven fabric. For example, the coating can be performed using a coating device conventionally known in the coating field. Examples of the coating device include a two-roll size press, a gate roll coater, a gravure coater, a die coater, a lip coater, a blade coater, a curtain coater, an air knife coater, a rod coater, a kiss coater, and a dip coater. In one aspect, the method of producing an inorganic fiber nonwoven fabric of the above embodiment further includes a step of providing an inorganic particle layer on the inorganic fiber nonwoven fabric.

[0057] The coating liquid for the inorganic particle layer is a composition in which inorganic particles, an organic binder, and other additives used as necessary are uniformly dissolved and / or dispersed in a medium. Examples of the medium include organic solvents such as aromatic hydrocarbons such as toluene, ethers such as tetrahydrofuran, ketones such as methyl ethyl ketone, alcohols such as isopropyl alcohol, N-methyl-2-pyrrolidone (NMP), dimethylacetamide, dimethylformamide, and dimethylsulfoxide, and aqueous solvents such as ion-exchanged water, distilled water, and pure water. In some embodiments, the medium is one or more selected from the group consisting of the organic and aqueous media. In at least one embodiment, the medium for preparing the coating liquid for the inorganic particle layer is water, from the viewpoint of the safety of the medium.

[0058] Other additives that may be used as necessary in the coating liquid for the inorganic particle layer are conventionally known, and examples of such additives include dispersants, thickeners, water retention agents, wetting agents, preservatives, and antifoaming agents.

[0059] The inorganic fiber nonwoven fabric of the above embodiment can be used for building materials, automotive parts, insulators, industrial parts, etc. The inorganic fiber nonwoven fabric of the above embodiment has excellent strength and heat resistance, and is therefore particularly suitable for applications requiring flame retardancy, heat resistance, and non-combustibility. Examples of building materials include wallpaper materials, cushion flooring, ceiling materials, etc. Examples of automotive parts include battery covers, brake pads, front bumpers, ceiling materials, and interior materials. In addition, the nonwoven fabric can be used as a fire prevention sheet for electric vehicle (EV) batteries, a base material for non-combustible certified building materials, a process sheet for thermal processing of non-ferrous metals and glass, a protective sheet against sparks (welding, laser processing), an insulating material for electrical equipment, etc. EXAMPLES

[0060] The present invention will be described below with reference to examples. However, the present invention is not limited to these examples. In the examples, the units "mass% (mass percentage)" and "parts by mass" refer to the values ​​of dry solids and / or substantial components unless otherwise specified.

[0061] <Inorganic fiber nonwoven fabric> A raw material slurry containing inorganic fibers, an inorganic binder, and a water-soluble organic polymer, as well as optional materials such as fibrillated fibers and heat-fusible binder fibers, and water as a liquid medium was prepared using a vertical pulper. The raw material slurry was paper-formed by a wet paper-forming method using an inclined wire system to obtain a wet sheet. The wet sheet was subjected to a nip press treatment using a press roll, and the sheet was dried using a Yankee dryer with a surface temperature of 130°C to obtain an inorganic fiber nonwoven fabric. The basis weight (g / m2) of the inorganic fiber nonwoven fabric was 2 The papermaking conditions were adjusted so that the fiber density was a predetermined value. The contents (mass%) of each material, inorganic fiber, inorganic binder, water-soluble organic polymer, fibrillated fiber, and heat-fusible binder fiber, are shown in Tables 1 and 2. The basis weight of the inorganic fiber nonwoven fabric was approximately 100 g / m 2 It was decided.

[0062] [Table 1] [Table 2] The following fibers were used for each of the fibers listed in Tables 1 and 2.

[0063] Inorganic fiber 1: Glass fiber with a flat cross section. Manufactured by Nitto Boseki Co., Ltd. Average major axis: 28 μm, average minor axis: 7 μm, Average fiber length: 13mm. Inorganic fiber 2: Glass fiber with circular cross section. Manufactured by Nitto Boseki Co., Ltd. Average fiber diameter: 10.5 μm, average fiber length: 6 mm. Inorganic binder 1: Colloidal silica. Manufactured by Nissan Chemical. Average particle size: 12 nm. The amounts in the table are the dry solid content. Inorganic binder 2: alumina sol. Manufactured by Nissan Chemical Co., Ltd. The amounts in the table are the dry solid content. Inorganic binder 3: Sepiolite. Water-soluble organic polymer 1: Sodium polyacrylate. Manufactured by Mitsubishi Chemical Corporation. Water-soluble organic polymer 2: polyacrylamide. Manufactured by Meisei Chemical Industry Co., Ltd. Water-soluble organic polymer 3: Silanol-modified PVA fiber. Manufactured by Kuraray, Product name: SPG056-11, Fineness: 0.6 decitex, average fiber length: 3 mm. Fibrillated fibre: Lyocell fibre. Heat-bondable binder fiber: Sheath-core binder fiber. Teijin, product name: TJ04CN, Fineness: 1.1 decitex, average fiber length: 5 mm.

[0064] <Fibrillated fiber> The fibrillated fiber was made of cellulose with an average fiber length of 0.8 mm, an average fiber width of 8 μm, and a modified freeness of 90, which was prepared by processing Lyocell fiber (fineness 1.7 dtex, average fiber length 3 mm) using a double disc refiner to adjust the amount of branches produced from the trunk.

[0065] The inorganic fiber nonwoven fabrics of each Example and Comparative Example were evaluated as follows. The evaluation results are shown in Tables 1 and 2.

[0066] <Maintaining strength> The strength maintenance of the inorganic fiber nonwoven fabric was evaluated by measuring the tensile strength. The test pieces for evaluation were inorganic fiber nonwoven fabric cut into a size of 50 mm in the width direction × 250 mm in the machine direction. A tensile test was performed on each of the five test pieces at a tensile speed of 100 mm / min using a tabletop universal testing machine (manufactured by A&D Co., Ltd., STB-1225S) in accordance with JIS P8113:2006 "Paper and paperboard - Test method for tensile properties - Part 2: Constant speed extension method", and the state of the test pieces 5 seconds after the start of tension was observed. The evaluation was performed based on the observation results and on the following criteria. The worst evaluation of the five pieces was adopted as the result. In the present invention, an inorganic fiber nonwoven fabric is considered to have strength maintenance if it is rated A, B, or C. A: No signs of fracture or cracking were observed. B: Inferior to A above. Although it did not break, signs of cracking were observed. C: Inferior to B above. Although not completely broken, the beginnings of cracking were observed. D: Complete rupture.

[0067] <Prevention of inorganic fiber shedding> The inorganic fiber nonwoven fabric was evaluated for its ability to suppress shedding of inorganic fibers by rubbing the surface of the inorganic fiber nonwoven fabric with a cloth. The test piece for evaluation was an inorganic fiber nonwoven fabric cut to a size of 50 mm in the width direction × 200 mm in the flow direction. The test piece was rubbed five times with a black cloth on the side of the inorganic fiber nonwoven fabric that was not in contact with the Yankee dryer, and the shedding of inorganic fibers was visually observed. The evaluation was performed based on the observation results and on the following criteria. In the present invention, an inorganic fiber nonwoven fabric is considered to have the ability to suppress shedding of inorganic fibers if it is rated A, B, or C. A: The number of inorganic fibers that have fallen off is within the range of 5 or less. The dropout prevention is good. B: The number of inorganic fibers that have fallen off is in the range of 6 to 13. The prevention of shedding is generally good. C: The number of inorganic fibers that have fallen off is in the range of 14 to 20, The dropout suppression is within an acceptable range. D: The number of inorganic fibers that have fallen off is in the range of more than 20, The shedding control is insufficient.

[0068] <Formability> The papermaking properties of the inorganic fiber nonwoven fabric were evaluated by observing the occurrence of paper breaks (breakage of the sheet), burning on the Yankee dryer, and clogging of the papermaking wire during papermaking of the inorganic fiber nonwoven fabric. The evaluation was performed based on the observation results and on the following criteria. In the present invention, an inorganic fiber nonwoven fabric is considered to have papermaking properties if it is rated A or B. A: No breaks in the paper, no burning on the dryer, and no clogging of the papermaking wires. B: Slight paper breaks, burning on the dryer, and clogging of the papermaking wire are observed. However, it can be controlled by the papermaking conditions. C: Paper breaks, burning on the dryer, and clogging of the papermaking wire were observed. Moreover, it cannot be controlled by papermaking conditions.

[0069] The heat resistance of the inorganic fiber nonwoven fabric was evaluated from the viewpoints of fire resistance and noncombustibility.

[0070] <Heat resistance (fire resistance)> The fire resistance of the inorganic fiber nonwoven fabric was evaluated by actually applying a flame to the inorganic fiber nonwoven fabric. The test pieces for evaluation were inorganic fiber nonwoven fabric cut into a size of 100 mm in the width direction × 100 mm in the flow direction. For each of the three test pieces, a flame (1000°C) from a burner (product name: Lab Burner APTL, manufactured by Phoenixdent Co., Ltd.) was applied to the center of the test piece for 5 minutes on the side of the inorganic fiber nonwoven fabric that was not in contact with the Yankee dryer, and the part of the inorganic fiber nonwoven fabric that was exposed to the flame was observed. The evaluation was performed based on the observation results and on the following criteria. The worst evaluation of the three sheets was adopted as the result. In the present invention, if the inorganic fiber nonwoven fabric is rated A, B, or C, it is considered to have heat resistance (fire resistance). A: No dents, cracks or holes were found in the area exposed to the flame. B: There is a slight dent in the area where the flame hit, but No cracks or holes are permitted. C: Although there is a dent in the part where the flame was applied, Generally no cracks or holes are observed. D: There are obvious dents, cracks and / or holes in the area where the flame was applied.

[0071] <Heat resistance (nonflammable)> The evaluation of the non-flammability of the inorganic fiber non-woven fabric was performed by a method of heating with heating electricity. The test piece for evaluation was an inorganic fiber non-woven fabric cut into a size of 100 mm in the width direction × 100 mm in the flow direction. Two test pieces were inserted into an electric heating furnace capable of maintaining a temperature of 750°C ± 5°C, with the side of the inorganic fiber non-woven fabric not in contact with the Yankee dryer facing downward, and the state was observed. The evaluation was performed based on the observation results and on the following criteria. The worst evaluation of the two pieces was adopted as the result. In the present invention, an inorganic fiber non-woven fabric is considered to have heat resistance (non-flammability) if it is rated A, B, or C. A: It does not ignite after insertion. B: After insertion, there is a slight spark for a moment. C: After insertion, it is inferior to B above and ignites for a moment. D: After insertion, it is inferior to C above and ignites.

[0072] From the results in Tables 1 and 2, it is understood that Examples 1 to 18, which correspond to inorganic fiber nonwoven fabrics satisfying the constitution of the present invention, have papermaking properties without problems in papermaking to obtain inorganic fiber nonwoven fabrics, and have strength maintenance, inhibition of inorganic fiber shedding, and good heat resistance. On the other hand, it is understood that Comparative Examples 1 to 6, which are nonwoven fabrics not satisfying the constitution of the present invention, do not satisfy at least any of strength maintenance, inhibition of inorganic fiber shedding, heat resistance, and papermaking properties.

[0073] Mainly from a comparison between Examples 8 to 11, it can be seen that when the inorganic fiber nonwoven fabric further contains fibrillated fibers and the content of the fibrils in the inorganic fiber nonwoven fabric is 0.1% by mass or more and 6% by mass or less relative to the inorganic fiber nonwoven fabric, the strength of the inorganic fiber nonwoven fabric is maintained, the inorganic fibers are prevented from falling off, and the heat resistance of the inorganic fiber nonwoven fabric is somewhat improved in a well-balanced manner.

[0074] Mainly from a comparison between Example 8 and Examples 12 to 14, it is clear that when the inorganic fiber nonwoven fabric further contains heat-fusible binder fibers and the content of the heat-fusible binder fibers in the inorganic fiber nonwoven fabric is 0.1% by mass or more and 6% by mass or less relative to the inorganic fiber nonwoven fabric, the strength maintenance of the inorganic fiber nonwoven fabric is improved.

Claims

1. An inorganic fiber nonwoven fabric comprising inorganic fibers, an inorganic binder, and a water-soluble organic polymer, The content of the inorganic fibers in the inorganic fiber nonwoven fabric is 70% by mass or more and 99% by mass or less with respect to the inorganic fiber nonwoven fabric, The content of the inorganic binder in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 29.5% by mass with respect to the inorganic fiber nonwoven fabric; and The content of the water-soluble organic polymer in the inorganic fiber nonwoven fabric is 0.5% by mass or more and less than 10% by mass with respect to the inorganic fiber nonwoven fabric. Inorganic fiber nonwoven fabric.

2. 2. The inorganic fiber nonwoven fabric according to claim 1, wherein the inorganic binder is bound to the inorganic fibers, and the water-soluble organic polymer is crosslinked to the inorganic binder.

3. The inorganic fiber nonwoven fabric according to claim 1 or 2, wherein the inorganic fibers are glass fibers.

4. The inorganic fiber nonwoven fabric according to any one of claims 1 to 3, wherein the inorganic binder is one or more selected from the group consisting of aluminum sulfate, polyaluminum chloride, sepiolite, colloidal silica, water glass, alumina sol, lithium silicate, and bentonite.

5. The inorganic fiber nonwoven fabric according to any one of claims 1 to 4, wherein the water-soluble organic polymer comprises one or more selected from the group consisting of poly(meth)acrylic acid, copolymers of (meth)acrylic acid and various monomers, poly(meth)acrylates, copolymers of (meth)acrylates and various monomers, poly(meth)acrylamide, and copolymers of (meth)acrylamide and various monomers.

6. The inorganic fiber nonwoven fabric according to any one of claims 1 to 5, further comprising fibrillated fibers, the content of the fibrillated fibers in the inorganic fiber nonwoven fabric being 0.1% by mass or more and 6% by mass or less relative to the inorganic fiber nonwoven fabric.

7. The inorganic fiber nonwoven fabric according to any one of claims 1 to 6, further comprising a thermally adhesive binder fiber, and the content of the thermally adhesive binder in the inorganic fiber nonwoven fabric is 0.1 mass% or more and 6 mass% or less with respect to the inorganic fiber nonwoven fabric.

8. A method for producing an inorganic fiber nonwoven fabric containing inorganic fibers, comprising: A step of preparing a raw material slurry containing inorganic fibers, an inorganic binder, a water-soluble organic polymer, and a liquid medium; and A step of wet-forming the raw material slurry to obtain a sheet Including, The content of the inorganic fibers in the raw material slurry is 70% by mass or more and 99% by mass or less based on all components of the raw material slurry excluding the medium liquid, The content of the inorganic binder in the raw slurry is 0.5% by mass or more and less than 29.5% by mass based on all components of the raw slurry excluding the medium liquid; and The content of the water-soluble organic polymer in the raw slurry is 0.5% by mass or more and less than 10% by mass based on all components of the raw slurry excluding the medium liquid. A method for manufacturing inorganic fiber nonwoven fabric.

9. The method for producing an inorganic fiber nonwoven fabric according to claim 8, wherein the inorganic fibers are glass fibers.

10. The method for producing an inorganic fiber nonwoven fabric according to claim 8 or 9, wherein the inorganic binder is one or more selected from the group consisting of aluminum sulfate, polyaluminum chloride, sepiolite, colloidal silica, water glass, alumina sol, lithium silicate, and bentonite.

11. The method for producing an inorganic fiber nonwoven fabric according to any one of claims 7 to 10, wherein the water-soluble organic polymer comprises one or more selected from the group consisting of poly(meth)acrylic acid, copolymers of (meth)acrylic acid and various monomers, poly(meth)acrylates, copolymers of (meth)acrylates and various monomers, poly(meth)acrylamide, and copolymers of (meth)acrylamide and various monomers.

12. The method for producing an inorganic fiber nonwoven fabric according to any one of claims 7 to 11, wherein the raw material slurry further contains fibrillated fibers, and the content of the fibrillated fibers in the raw material slurry is 0.1 mass% or more and 6 mass% or less based on all components of the raw material slurry excluding the liquid medium.

13. The method for producing an inorganic fiber nonwoven fabric according to any one of claims 7 to 12, wherein the raw material slurry further contains a heat-fusible binder fiber, and the content of the heat-fusible binder in the raw material slurry is 0.1 mass% or more and 6 mass% or less based on all components of the raw material slurry excluding the liquid medium.

14. An inorganic fiber nonwoven fabric produced by the method for producing an inorganic fiber nonwoven fabric according to any one of claims 7 to 13.

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