Fire-resistant sheet for wallpaper backing

Abstract

To provide a fire-resistant sheet for wall paper lining which is excellent in coating property of an inorganic particle layer, has good flatness of a polyvinyl chloride resin coating surface in the fire-resistant sheet for wall paper lining, causes no strike-through of the polyvinyl chloride resin, has flexibility, fire resistance and incombustibility, and is excellent in folding strength.SOLUTION: A fire-resistant sheet for wall paper lining contains a base material and an inorganic particle layer, wherein the base material contains a glass fiber, a moist heat adhesive binder fiber and a fibrillated fiber, the glass fiber contains at least a glass fiber having a flat cross section, the percentage content of the fibrillated fiber is 6 mass% or more and 12 mass% or less with respect to the total amount of the constituents of the base material, and the inorganic particle layer contains inorganic particles and an inorganic binder.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a fire-resistant sheet for backing wallpaper used in interior walls of houses and other buildings. [Background technology]

[0002] The Building Standards Act and its enforcement regulations define which buildings are subject to fire protection requirements. For commercial facilities, office buildings, medical and welfare facilities, and other such buildings, new construction or renovations are subject to interior finishing restrictions on walls, ceilings, etc., requiring the use of fire-resistant wall coverings certified as non-combustible. Therefore, several wall coverings possessing flame retardancy, heat resistance, and non-combustibility have been proposed. However, currently, an inexpensive fire-resistant sheet for wallpaper backing that satisfies these performance requirements while also possessing good flatness of the polyvinyl chloride resin (foamed PVC sol) coating surface, along with the flexibility necessary for easy application, has yet to be found.

[0003] For example, as a sheet material, Patent Document 1 discloses a sheet material in which an inorganic filler (inorganic particles) and an organic synthetic resin are mixed and applied (added) to the gaps between a fiber-based sheet, which consists of 20-100% glass fibers and 80-0% pulp and / or other organic fibers. In this way, when an inorganic filler is used, the fiber-based sheet is required to have excellent coating properties when applying the inorganic filler. Furthermore, the sheet material is required to be resistant to a phenomenon called "powder shedding," where the inorganic filler falls off. The sheet material in Patent Document 1 has the problem of insufficient non-flammability because organic fibers are used, and if organic fibers are not used, it has the problem of low strength, difficulty in applying the inorganic filler, and poor coating properties. In addition, an organic synthetic resin is used as a binder for the inorganic filler, which has the problem of reduced non-flammability and heat resistance. Furthermore, the flatness of the polyvinyl chloride resin coated surface was also insufficient.

[0004] Furthermore, as a flame-retardant paper with gloss, Patent Document 2 discloses a sheet-like material made by impregnating a paper-like material of inorganic fibers with a flame-retardant coating mainly composed of inorganic powder (inorganic particles) that generates flame-extinguishing gas. However, this flame-retardant paper has several drawbacks: because an organic binder is used in the flame-retardant coating, it is not sufficiently non-flammable; release paper is used in the coating of the inorganic powder, resulting in poor productivity and high costs; and it also lacks flexibility, making it unsuitable as a backing sheet for wallpaper.

[0005] Furthermore, Patent Document 3 discloses coating the surface of glass fiber-reinforced paper, which consists of at least glass fibers, wood pulp, and binder fibers, with a resin composition containing latex. This glass fiber-reinforced paper had low fire resistance and non-flammability because it was coated with wood pulp and a resin composition such as latex. In addition, the flatness of the polyvinyl chloride resin (foamed PVC sol) coated surface was sufficient for use as a cushion flooring sheet, but insufficient for use as a wallpaper backing sheet. Moreover, the folding strength when bent at the corner of a wall was insufficient, leading to the problem of corner cracking during wallpaper installation.

[0006] Furthermore, Patent Document 4 discloses a glass nonwoven fabric in which flattened cross-section glass fibers are one of the constituent materials, containing 10% or more by weight of flattened cross-section glass fibers, and also disclosing a glass nonwoven fabric in which circular cross-section glass fibers are also constituent materials. This glass nonwoven fabric is intended to be used as a base material for electrical insulating boards and laminates for printed wiring boards. In the examples, although the glass nonwoven fabric contains 75% or more by mass of flattened cross-section glass fibers, the remaining component is a binder, and it is stated that resins such as epoxy resin, acrylic resin, melamine resin, urea resin, vinyl acetate, and polyvinyl alcohol can be used as the resin (binder) to adhere the glass fibers. As a result, the fire resistance and non-combustibility were insufficient. In addition, the density of the glass nonwoven fabric was high, resulting in significantly poor impregnation of inorganic particles. Furthermore, when polyvinyl chloride resin was coated, the polyvinyl chloride resin bled through to the back surface of the glass nonwoven fabric, causing the problem of soiling paper rolls. As a result, the flatness of the polyvinyl chloride resin coated surface was insufficient.

[0007] Furthermore, in Patent Document 5, a fire-resistant layer of a fire-resistant electric wire in which a fire-resistant layer, an insulating layer, and an outer coating layer are sequentially provided outside a conductor. The fire-resistant layer is a fire-resistant composite tape formed by laminating integrated mica and an inorganic fiber sheet. The inorganic fiber sheet serving as a reinforcing layer for holding the integrated mica is composed of 60 to 100 parts by weight of fibers having a flat cross-section with a sheet weight of 100 parts by weight and 0 to 40 parts by weight of an organic or inorganic binder. A fire-resistant insulating tape is disclosed. Since this fire-resistant insulating tape uses 60 to 100 parts by weight of inorganic fibers having a flat cross-section, it has a thin thickness and a high density, and thus is a sheet that is significantly inferior in the impregnation property of inorganic particles. Furthermore, in the examples, since a silicone-based resin adhesive is used as an adhesive for the integrated mica, the fire resistance and incombustibility are insufficient. Also, when a polyvinyl chloride resin is coated, there is a problem that the polyvinyl chloride resin penetrates through the back surface of the fire-resistant insulating tape and stains the paper roll. Therefore, the flatness of the coated surface of the polyvinyl chloride resin is insufficient.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] The object of the present invention is to provide a fire-resistant sheet for wallpaper backing that has excellent coating properties for the inorganic particle layer, good flatness of the polyvinyl chloride resin coated surface in the fire-resistant sheet for wallpaper backing, no bleed-through of the polyvinyl chloride resin, and combines flexibility, fire resistance, and non-combustibility with excellent flexural strength. [Means for solving the problem]

[0010] As a result of diligent research to solve the above problems, we have discovered the following invention.

[0011] (1) A fire-resistant sheet for wallpaper backing, characterized in that it contains a base material and an inorganic particle layer, the base material contains glass fibers, moist heat adhesive binder fibers and fibrillated fibers, the glass fibers contain at least flattened cross-section glass fibers, the fibrillated fiber content is 6% by mass or more and 12% by mass or less of the total raw materials constituting the base material, and the inorganic particle layer contains inorganic particles and an inorganic binder.

[0012] (2) The fire-resistant sheet for wallpaper backing described in (1) above, wherein the glass fiber content of the flat cross-section is 75% by mass or more and 100% by mass or less of the total amount of glass fiber.

[0013] (3) The fire-resistant sheet for wallpaper backing according to (1) or (2) above, wherein the moist heat adhesive binder fiber is a silanol-modified polyvinyl alcohol fiber. [Effects of the Invention]

[0014] The fire-resistant sheet for wallpaper backing of the present invention contains a base material and an inorganic particle layer, the base material containing glass fibers, moist heat adhesive binder fibers, and fibrillated fibers. The fibrillated fibers intertwine and bond with the glass fibers and moist heat adhesive binder fibers, and the moist heat adhesive binder film strongly fixes the fibers together, thus improving the strength of the sheet and providing excellent coating properties for the inorganic particle layer. Furthermore, because the fibrillated fibers fill the gaps between the fibers, it prevents the polyvinyl chloride resin from seeping through to the back, and because it firmly captures the inorganic particles, it can improve heat resistance and non-combustibility.

[0015] Furthermore, in the fire-resistant sheet for wallpaper backing of the present invention, by having a glass fiber content of 75% to 100% by mass relative to the total amount of glass fibers, the flatness of the polyvinyl chloride resin coated surface of the fire-resistant sheet for wallpaper backing can be improved. In addition, the thickness can be reduced, flexibility can be improved, and tensile strength, tear strength, and flexural strength can be significantly improved while ensuring the coating properties of the inorganic particle layer.

[0016] Furthermore, because the fire-resistant sheet for wallpaper backing according to the present invention contains an inorganic particle layer containing inorganic particles and an inorganic binder, it can achieve excellent fire resistance and non-combustibility. [Brief explanation of the drawing]

[0017] [Figure 1] This is a surface observation image of the base material of a fire-resistant sheet used as a backing for wallpaper. [Modes for carrying out the invention]

[0018] In the present invention, the fire-resistant sheet for wallpaper backing contains a base material and an inorganic particle layer, the base material contains glass fibers, moist heat adhesive binder fibers and fibrillated fibers, the glass fibers contain glass fibers with a flat cross-section, and the content of the fibrillated fibers is 6% by mass or more and 12% by mass or less of the total raw materials constituting the base material. In this specification, "fire-resistant sheet for wallpaper backing" may be abbreviated as "fire-resistant sheet".

[0019] Examples of glass fibers used in this invention include chopped strands, glass wool, and glass flakes. Any glass fiber that is resistant to breakage and capable of forming a substrate is acceptable.

[0020] In the present invention, the base material contains glass fibers. The cross-sectional shape of the glass fibers can be circular or flattened. In the present invention, the glass fibers contain glass fibers with a flattened cross-section. In the glass fibers with a flattened cross-section, the dimensions of the major axis and minor axis of the flattened cross-section are not particularly limited, and any fiber whose cross-section has a major axis and a minor axis is acceptable, however, the ratio of the major axis to the minor axis (hereinafter, the "ratio of major axis to minor axis" will be referred to as the "flattening ratio") is preferably 3 to 5. If the flattening ratio is less than 3, the effect of improving the flatness and strength of the polyvinyl chloride resin coated surface may be reduced, on the other hand, if the flattening ratio exceeds 5, spinning of the flattened glass fibers may become difficult, or in papermaking, the number of fibers decreases, which may lead to deterioration of the base material's structure, the fire-resistant sheet becoming too thin, or pinholes becoming more likely to occur.

[0021] The equivalent fiber diameter of the flattened cross-section glass fibers is preferably 5 to 17 μm, more preferably 6 to 14 μm, and even more preferably 7 to 11 μm. The minor axis is preferably 2.8 to 9.6 μm, more preferably 3.5 to 7.0 μm, and even more preferably 4.0 to 6.0 μm. The equivalent fiber diameter refers to the diameter of a circular cross-section fiber having the same area as the cross-sectional area of ​​the flattened fiber. If the equivalent fiber diameter is less than 5 μm, economical spinning becomes difficult, while if the equivalent fiber diameter exceeds 17 μm, the fibers become too thick, resulting in high rigidity and difficulty in dispersion during the papermaking process. Furthermore, the reduction in the number of glass fibers can lead to larger voids, which may reduce the coating properties and adhesion of the inorganic particle layer, or worsen the flatness of the polyvinyl chloride resin coated surface of the fire-resistant sheet.

[0022] The fiber diameter of the circular cross-section glass fibers is preferably 1 to 11 μm, more preferably 2 to 8 μm, and even more preferably 3 to 7 μm. If the fiber diameter is less than 1 μm, it may be too fine and the glass fibers may fall off the substrate during papermaking, resulting in insufficient strength and thickness of the substrate. If the fiber diameter exceeds 11 μm, the glass fibers become too thick, creating large gaps in the substrate. Even if an inorganic particle layer is formed, this may impair the flatness of the polyvinyl chloride resin coated surface, increase the shedding of inorganic particles, or worsen flexibility. When the fiber diameter of the glass fibers is 1 to 11 μm, the gaps in the substrate are fine and uniform, resulting in less shedding of inorganic particles after the inorganic particle layer is formed, making it easier to achieve a flat polyvinyl chloride resin coated surface, and also resulting in a fire-resistant sheet with excellent flexibility.

[0023] The fiber length of the glass fibers is preferably 1 to 15 mm, more preferably 3 to 13 mm, and even more preferably 5 to 10 mm. If the fiber length is less than 1 mm, the strength of the base material may be insufficient, and if the fiber length exceeds 15 mm, the base material may not form properly, or clumps and twists of glass fibers may easily occur, or the flexibility may deteriorate.

[0024] The glass fiber content is preferably 78 to 90% by mass, more preferably 80 to 88% by mass, and even more preferably 82 to 86% by mass, relative to the total raw materials constituting the base material. If the content is less than 78% by mass, the strength, fire resistance, or non-combustibility of the base material may deteriorate. If the content exceeds 90% by mass, the bonding between glass fibers is weak, which may result in weaker base material strength and deterioration of the coating properties of the inorganic particle layer. Furthermore, the gaps between the fibers in the base material become larger, which may impair the flatness of the polyvinyl chloride resin coated surface.

[0025] The content of flattened cross-section glass fibers is preferably 75% to 100% by mass, more preferably 80% to 100% by mass, and even more preferably 85% to 100% by mass, relative to the total amount of glass fibers. When the content is within this range, the tensile strength of the substrate is strong in both dry and wet conditions, and the coating properties of the inorganic particle layer are excellent. In addition, the fire-resistant sheet has excellent flexibility and high bending strength, which can prevent corner cracking during wallpaper installation. If the content is less than 75% by mass, the glass fibers may easily fall off the substrate.

[0026] The binder fibers used in the present invention are moist heat adhesive binder fibers. Moist heat adhesive binder fibers are fibers that, in a wet state, flow from a fibrous state at a certain temperature, or easily deform to exhibit adhesive function. Specifically, these are thermoplastic fibers that soften with hot water or steam (for example, around 80-120°C) to self-adhere or adhere to other fibers. Examples include polyvinyl fibers (polyvinylpyrrolidone, polyvinyl ether, polyvinyl alcohol, polyvinyl acetal, etc.), cellulose fibers (C1-3 alkylcellulose such as methylcellulose, hydroxyC1-3 alkylcellulose such as hydroxymethylcellulose, carboxyC1-3 alkylcellulose such as carboxymethylcellulose, or salts thereof), and fibers made of modified vinyl copolymers (polymers of vinyl monomers such as isobutylene, styrene, ethylene, vinyl ether, etc., and unsaturated carboxylic acids such as maleic anhydride, or their anhydrides, or salts thereof). Polyvinyl fiber is preferred as the moist heat adhesive binder fiber used in the present invention, and polyvinyl alcohol (PVA) fiber is more preferred. When polyvinyl alcohol fiber is used, the strength of the substrate is increased, a film is more easily formed between the fibers, and inorganic particles are more easily retained between the fibers. In addition, the flatness of the polyvinyl chloride resin coated surface of the fire-resistant sheet is more easily improved.

[0027] In the present invention, modified polyvinyl alcohol fibers modified with a compound having a crosslinkable functional group, and crosslinked polyvinyl alcohol fibers crosslinked under mild conditions during or after spinning using a crosslinking agent are more preferable as moist heat-adhering binder fibers, as they can impart hot water resistance properties to low-draw yarns.

[0028] Examples of crosslinkable functional groups include silanol groups, carboxyl groups, and methylol groups. By adjusting the pH, etc., polyvinyl alcohol modified with a compound having a crosslinkable functional group can be dissolved in water without crosslinking, spun, and modified polyvinyl alcohol fibers can be obtained. The modified polyvinyl alcohol fibers may be crosslinked during or after spinning. The degree of modification is preferably 0.01 to 10 mol%, and more preferably 0.1 to 5 mol%. A suitable example is a silanol-modified polyvinyl alcohol fiber obtained by dissolving silanol-modified polyvinyl alcohol (degree of modification 0.1 to 2 mol%) in an alkaline solution (pH 9 to 13), spun while crosslinking by making the solution acidic (pH 5 to 6), drying, and then heat-treating.

[0029] Furthermore, cross-linked polyvinyl alcohol fibers can also be used, which are obtained by spinning unmodified polyvinyl alcohol that does not self-crosslink, and then applying various organic or inorganic crosslinking agents to induce crosslinking. Examples of inorganic crosslinking agents include phosphoric acid, ammonium phosphate, ammonium sulfate, and titanyl sulfate. Examples of organic crosslinking agents include methylol-based, epoxy-based, isocyanate-based, and aldehyde-based crosslinking agents. Crosslinking can be advanced by adding these crosslinking agents to the unmodified polyvinyl alcohol spinning solution and spinning, or by spinning unmodified polyvinyl alcohol alone, passing it through a crosslinking agent-containing bath, and then heat-treating it. It is also possible to use these methods in combination.

[0030] The moist heat-adhesive binder fibers used in the present invention are not limited to those described above, but silanol-modified polyvinyl alcohol fibers are particularly preferred because they further enhance adhesion to glass fibers, thereby further increasing the tensile strength of the substrate.

[0031] The fineness of the moist heat-adhesive binder fibers is preferably 0.1 to 5.6 decitex, more preferably 0.4 to 2.2 decitex, and even more preferably 0.6 to 1.1 decitex. If the fineness is less than 0.1 decitex, the fibers themselves become very expensive, and the base material may become too dense and thin. On the other hand, if it exceeds 5.6 decitex, the contact points with the glass fibers decrease, making it difficult to maintain strength in a wet state. Also, a uniform form may not be obtained. The fiber length of the moist heat-adhesive binder fibers is preferably 1 to 15 mm, more preferably 2 to 10 mm, and even more preferably 3 to 5 mm. If the fiber length is less than 1 mm, the moist heat-adhesive binder fibers may fall off the papermaking wire during papermaking, and a fire-resistant sheet with sufficient strength may not be obtained. On the other hand, if the thickness exceeds 15 mm, the moist heat adhesive binder fibers may become entangled when dispersed in water, which may result in an uneven texture of the fire-resistant sheet.

[0032] The content of moist heat-adhesive binder fibers is preferably 4 to 10% by mass, more preferably 5 to 9% by mass, and even more preferably 6 to 8% by mass, relative to the total raw materials constituting the base material. If the moist heat-adhesive binder fiber content is less than 4% by mass, the strength of the base material decreases, and paper breakage or detachment of glass fibers may occur when coating the inorganic particle layer. On the other hand, if the moist heat-adhesive binder fiber content exceeds 10% by mass, the peelability from the dryer may deteriorate when the base material is made using a wet papermaking method, and the penetration into the base material may decrease when coating the inorganic particle layer, which may worsen the fire resistance of the fire-resistant sheet for wallpaper backing.

[0033] Examples of fibrillated fibers include those made from heat-resistant resins such as natural cellulose, solvent-spun cellulose, acrylic, fully aromatic polyamide, fully aromatic polyester, polyimide, polyamide-imide, polyetheretherketone, polyethersulfone, polyphenylene sulfide, polybenzimidazole, poly-p-phenylenebenzobisthiazole, poly-p-phenylenebenzobisoxazole, and polytetrafluoroethylene. Among these, fully aromatic polyamides are preferred because they have high heat resistance, high hydrophilicity, and are easily fibrillated. More preferably, pulp-like materials made from meta-aromatic polyamides such as poly(m-phenylene isophthalamide) and poly(m-phenylene terephthalamide) resins are preferred. Pulp-like materials made from meta-aromatic polyamides are thin leaf-like or scale-like pieces having numerous minute fibril portions that can be used to create paper-like structures using a paper machine, and they have the effect of filling voids in the base material and smoothing the sheet. Furthermore, when moisture present within the crystal structure is removed by heating or depressurization, it shrinks significantly, strengthening the fiber network and thus improving the wet strength of the substrate.

[0034] In the present invention, the modified filtration rate of the fibrillated fibers is preferably 0 to 300 ml, more preferably 0 to 200 ml, and even more preferably 0 to 100 ml. If the modified filtration rate exceeds 300 ml, the fiber width of the main portion of the fibrillated fiber is thick, and fibrillation has not progressed sufficiently, resulting in a smaller dense network with the glass fibers, which may reduce the tensile strength. On the other hand, if the modified filtration rate is less than 0 ml, the fine content of the fibrillated fibers increases, increasing the rate of shedding from the substrate, which may reduce the yield. Furthermore, the fibrillation treatment of the fibers takes a long time and becomes very expensive. In addition, the substrate tends to become thinner and denser, making it difficult for the coating liquid for forming the inorganic particle layer to penetrate into the interior, which may worsen the fire resistance. As fibrillation of the fibrillated fibers progresses, the modified filtration rate continues to decrease. Furthermore, even after the modified filtration rate reaches 0 ml, if fibrillation continues, the fibers will pass through the mesh, and the modified filtration rate will begin to increase in reverse. In this invention, this state in which the modified filtration rate begins to increase in reverse is referred to as "modified filtration rate less than 0 ml".

[0035] In this invention, the modified filtration rate is the value measured in accordance with JIS P8121-2:2012, except that an 80-mesh wire mesh with a wire diameter of 0.14 mm and a mesh opening of 0.18 mm was used as the sieve plate, and the sample concentration was set to 0.1%.

[0036] In the fibrillated fibers of the present invention, the mass-weighted average fiber length is preferably 0.02 mm or more and 1.50 mm or less. Furthermore, the length-weighted average fiber length is preferably 0.02 mm or more and 1.00 mm or less. If the average fiber length is shorter than the preferred range, the fibrillated fibers may detach from the substrate. If the average fiber length is longer than the preferred range, the fibers will not dissociate well, and dispersion problems are more likely to occur.

[0037] When fibrillated fibers have the above-mentioned mass-weighted average fiber length and length-weighted average fiber length, even if the fibrillated fiber content in the substrate is low, a dense network structure of fibers is formed between the fibrillated fibers and between the fibrillated fibers and glass fibers, making it easier to obtain a substrate with high tensile strength and improved penetration and liquid retention of the coating liquid for forming an inorganic particle layer.

[0038] The average fiber width of the fibrillated fibers is preferably 0.5 μm to 40.0 μm, more preferably 3.0 μm to 35.0 μm, and even more preferably 5.0 μm to 30.0 μm. If the average fiber width exceeds 40.0 μm, the entanglement between the fibrillated fibers and glass fibers decreases, which may reduce the tensile strength. If the average fiber width is less than 0.5 μm, the fibrillated fibers may detach from the substrate, and the number of intersections may increase too much, which may reduce the tensile strength unless the amount of moist heat-adhesive binder fibers is increased.

[0039] In the present invention, the mass-weighted average fiber length, length-weighted average fiber length, and average fiber width of the fibrillated fiber are the mass-weighted average fiber length (L(w)), length-weighted average fiber length (L(l)), and fiber width measured in projected fiber length (Proj) mode using Kajaani FiberLab V3.5 (manufactured by Metso Automation).

[0040] Fibrilized fibers can be obtained by processing fibrous or pulp-like resins using refiners, beaters, mills, grinding devices, rotary homogenizers that apply shear force with high-speed rotating blades, double-cylinder high-speed homogenizers that generate shear force between a high-speed rotating inner blade and a fixed outer blade, ultrasonic crushers that pulverize materials with ultrasonic impact, and high-pressure homogenizers that apply shear and cutting forces to a suspension of heat-resistant resin by applying a pressure difference of at least 20 MPa to pass it through a small-diameter orifice at high speed, and then rapidly decelerating it by impact.

[0041] In the present invention, the fibrillated fiber content is 6% by mass or more and 12% by mass or less, more preferably 7% by mass or more and 11% by mass or less, and even more preferably 8% by mass or more and 10% by mass or less, relative to the total raw materials constituting the base material. If the fibrillated fiber content exceeds 12% by mass, fire resistance and shape retention after fire resistance testing will decrease. Also, the base material will become too thin, reducing the voids in the base material, which will decrease the permeability and liquid retention of the coating liquid for forming the inorganic particle layer, and the amount of inorganic particle layer to be coated will decrease, requiring an increase in the number of coatings. On the other hand, if the fibrillated fiber content is less than 6% by mass, the effect of the fibrillated fibers in filling the voids between the fibers constituting the base material will be insufficient, and the polyvinyl chloride resin will bleed through to the back.

[0042] In the present invention, in addition to glass fibers, moist heat adhesive binder fibers, and fibrillated fibers, various other fibers can be added as needed, within a range that does not impair performance. As a result, the number of finer voids can be increased, improving the retention of inorganic particles and the strength of the fire-resistant sheet for wallpaper backing. Such fibers can include regenerated fibers such as rayon, cupro, and lyocell; semi-synthetic fibers such as acetate, triacetate, and promix; synthetic resin fibers such as polyolefin, polyamide, polyacrylic, vinylon, vinylidene, polyvinyl chloride, polyester, benzoate, polychloral, phenol, melamine, furan, urea, aniline, unsaturated polyester, fluorine, silicone, and their derivatives; and inorganic fibers such as metal fibers, carbon fibers, alumina, silica, ceramics, and rock fibers.

[0043] The synthetic resin fiber may be a fiber made of a single resin (monofilament fiber) or a composite fiber made of two or more resins. Examples of composite fibers include core-sheath type, eccentric type, side-by-side type, sea-island type, orange type, and multi-bimetal type. Furthermore, the various fibers described above that can be included in the fire-resistant sheet for wallpaper backing of the present invention may be used individually or in combination of two or more types.

[0044] In the present invention, the thickness of the base material is preferably 0.1 mm or more, more preferably 0.2 mm or more, and even more preferably 0.3 mm or more. Furthermore, it is preferably 1.0 mm or less, more preferably 0.8 mm or less, and even more preferably 0.6 mm or less. When the thickness of the base material is within the above range, the base material in the present invention can maintain the tensile strength required in the papermaking and coating processes, resulting in good workability in each process, including the papermaking properties of the base material. If the thickness of the base material exceeds 1.0 mm, the flexibility may be impaired, making it difficult to handle as a fire-resistant sheet for wallpaper backing. If the thickness of the base material is less than 0.1 mm, the voids in the base material become larger, making coating difficult, and it may be necessary to coat a large amount of inorganic particle layer, which may increase powder shedding or worsen flexibility.

[0045] The density of the base material in this invention is 0.10 g / cm³. 3 Preferably, it should be 0.20 g / cm³ or more. 3 It is more preferable that the above is true. Also, 0.50 g / cm³ 3 Preferably, it is 0.40 g / cm³. 3 It is more preferable that the density is 0.10 g / cm³. 3 If the value is less than 0.50 g / cm³, the tensile strength of the substrate will be too weak, which may cause damage during handling or coating. 3 If this limit is exceeded, the flexibility of the substrate may deteriorate, making it difficult to wind up with a papermaking reel, or the amount of inorganic particle coating may decrease.

[0046] In the present invention, the base material is preferably a wet nonwoven fabric produced by a wet papermaking method. In the wet papermaking method, fibers are dispersed in water to form a uniform papermaking slurry, and this papermaking slurry is papermade using a papermaking machine to produce a wet nonwoven fabric. Examples of papermaking machines include cylinder papermaking machines, long screen papermaking machines, inclined papermaking machines, inclined short screen papermaking machines, and combinations thereof. It can also be produced using a papermaking machine that has multiple headboxes and stacks wet paper on a wire. In addition to the fiber raw material, dispersants, paper strength enhancers, thickeners, inorganic fillers, organic fillers, defoamers, etc., can be added to the papermaking slurry as needed. The solid content concentration of the papermaking slurry is preferably about 0.5 to 0.001% by mass. This papermaking slurry is further diluted to a predetermined concentration before papermaking to obtain a wet paper web. Next, the prepared wet paper web is nipped using a press roll or similar device, and then a Yankee dryer is used to melt the moist heat-adhesive binder fibers and develop strength. Drying with a Yankee dryer results in a flat surface with minimal surface irregularities. In addition, auxiliary drying may be performed using heating devices such as a hot air dryer, heated roll, or infrared heater. The drying temperature at this time should preferably be such that the moisture in the wet paper web is sufficiently removed and the moist heat-adhesive binder fibers develop strength.

[0047] In this invention, the inorganic particle layer is a layer containing inorganic particles and an inorganic binder. This inorganic particle layer covers the entire surface of the fibers contained in the substrate and fills the voids in the substrate, thereby providing the fire-resistant and non-combustible effects of the fire-resistant sheet. Furthermore, the penetration of polyvinyl chloride resin is suppressed, resulting in good flatness of the polyvinyl chloride resin coated surface.

[0048] Figure 1 is an electron microscope (SEM) image of the Yankee dryer surface of a fire-resistant sheet substrate for wallpaper backing. The substrate contains glass fibers with circular and flattened cross-sections, fibrillated fibers which are pulp-like materials made of meta-aromatic polyamide, and moist-heat adhesive binder fibers. The fibrillated fibers are interwoven between the glass fibers, filling the gaps. The moist-heat adhesive binder fibers, in a wet state, flow from their fibrous state at a certain temperature, or easily deform into a film, covering the intersections of the glass fibers and the fibrillated fibers. In the SEM image of Figure 1, this is observed as an irregularly shaped film on the surface. This provides adhesion, improves the flatness of the substrate, and prevents the polyvinyl chloride resin from seeping through to the back.

[0049] As inorganic particles, water-dispersible inorganic particles such as aluminum hydroxide, aluminum hydroxide oxide, magnesium hydroxide, calcium hydroxide, gypsum dihydrate, tricalcium aluminate, clay, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, barium carbonate, talc, and titanium dioxide can be used. The above inorganic particles may be used individually or in combination of two or more types.

[0050] Among inorganic particles, aluminum hydroxide oxide, clay, kaolin, calcined kaolin, and carbonate-based inorganic particles are preferred because they solidify when exposed to flames, preventing them from falling off the refractory sheet. Furthermore, aluminum hydroxide oxide, clay, kaolin, and calcined kaolin are even more preferred because they exhibit excellent fire resistance and non-combustibility, maintaining the strength of the refractory sheet even when held at high temperatures.

[0051] In the present invention, the particle size of the inorganic particles is preferably 0.08 μm or more and 20.0 μm or less, more preferably 0.30 μm or more and 15.0 μm or less, and even more preferably 0.40 μm or more and 10.0 μm or less. If the particle size exceeds 20.0 μm, the fire resistance of the fire-resistant sheet for wallpaper backing may deteriorate, or powder shedding may occur, or the heat insulation performance when exposed to high temperatures may deteriorate. On the other hand, if the particle size is less than 0.08 μm, the inorganic particles tend to thicken easily when dispersed, making dispersion difficult. When coated onto a substrate, the inorganic particles may easily fall off the substrate, or it may be necessary to increase the amount of inorganic binder to prevent shedding, which may impair the flexibility of the fire-resistant sheet. The particle size of the inorganic particles was determined by diluting the inorganic particles with water, dispersing them in a stirrer, and measuring the resulting particle size using a laser scattering type particle size analyzer (Microtrac Co., Ltd., product name: MT3000). The obtained central particle size (D50, volume average) was defined as the particle size.

[0052] In the present invention, the inorganic particle layer includes an inorganic binder. Examples of inorganic binders include sepiolite, colloidal silica, water glass, alumina sol, and bentonite. The above inorganic binders may be used individually or in combination of two or more types.

[0053] In the present invention, the inorganic binder content in the inorganic particle layer is preferably 2% by mass or more and 100% by mass or less, more preferably 5% by mass or more and 50% by mass or less, and even more preferably 10% by mass or more and 30% by mass or less, relative to the total amount of inorganic particles. If the inorganic binder content is less than 2% by mass, the inorganic particles may easily fall off the substrate. Also, if the inorganic binder content exceeds 100% by mass, the coating properties of the inorganic particle layer may deteriorate or the flexibility of the fire-resistant sheet may be impaired.

[0054] The medium used to prepare the coating solution for forming an inorganic particle layer is not particularly limited, as long as it can uniformly dissolve or disperse the inorganic binder and inorganic particles. For example, 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, dimethyl sulfoxide, water, etc., can be used as needed. Furthermore, the medium used is preferably one that does not cause the substrate to swell or does not dissolve the substrate.

[0055] The inorganic particle layer content is "coating amount of inorganic particle layer (g / m²) 2 ) / base material basis weight (g / m 2 The value is calculated as "( ) × 100", and is preferably 60% by mass or more, more preferably 80% by mass or more, and even more preferably 100% by mass or more. If the inorganic particle layer content is 60% by mass or more, even if a flame is applied to the fire-resistant sheet for wallpaper backing, melting or damage to the fire-resistant sheet will hardly be observed. On the other hand, it is preferable that the inorganic particle layer content be less than 160% by mass. The higher the inorganic particle layer content, the thicker the fire-resistant sheet becomes, and the higher the fire resistance and non-combustibility, but if the inorganic particle layer content is 160% by mass or more, powder shedding may occur or the flexibility of the fire-resistant sheet may be impaired.

[0056] To form an inorganic particle layer, various coating devices can be used to coat the substrate with inorganic particles. For example, various coaters using impregnation or coating devices such as a two-roll size press, gate roll coater, gravure coater, die coater, lip coater, blade coater, curtain coater, air knife coater, rod coater, kiss touch coater, and dip coater can be used, but are not limited to these. In the present invention, if the glass fiber content of the flat cross-section of the substrate is high, the thickness will be reduced and the amount of coating liquid that the inorganic particle layer can hold will decrease. Therefore, it is preferable to adjust the concentration of the coating liquid or, if a two-roll size press is used, to use a device that has a function to precisely adjust the gap between the rolls (for example, a configuration of a cylinder and a cotter).

[0057] In the present invention, in addition to the inorganic particles and inorganic binder, the inorganic particle layer may also contain, as needed, various dispersants such as polyacrylic acid and sodium carboxymethylcellulose, various thickeners such as hydroxyethylcellulose, sodium carboxymethylcellulose, and polyethylene oxide to increase the liquid stability of the coating solution, various water-retaining agents, various wetting agents, preservatives, defoaming agents, and other additives. Generally, non-aqueous coating solutions using organic solvents as a medium have low surface tension, while aqueous coating solutions using water as a medium have high surface tension. Because the substrate of the present invention has high receptivity to coating solutions, both non-aqueous and aqueous coating solutions can be applied without problems. However, in the present invention, it is preferable to use an aqueous coating solution using only water as a medium.

[0058] In the present invention, the level difference Sk of the core portion, obtained by measuring the surface roughness of at least one side of the fire-resistant sheet for wallpaper backing using a confocal laser microscope, is preferably 55 μm or less, more preferably 50 μm or less, and even more preferably 45 μm or less. Furthermore, the Sk is preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 30 μm or more. The polyvinyl chloride resin is preferably coated on the side of the fire-resistant sheet for wallpaper backing where the Sk is 55 μm or less. The "level difference Sk of the core portion" is an index for comparing surface roughness and is the difference between the upper and lower levels of the core portion in accordance with ISO 25178. In the coating of the polyvinyl chloride resin, foamed vinyl chloride sol is coated, dried and gelled, and then foamed. When the Sk of at least one side of the fire-resistant sheet for wallpaper backing of the present invention is 55 μm or less, it means that the flatness of the polyvinyl chloride resin coated surface is good. Furthermore, when the Sk of at least one side of the fire-resistant sheet for wallpaper backing according to the present invention is 55 μm or less, powder shedding from the inorganic particle layer is reduced, making it easier to obtain a fire-resistant sheet for wallpaper backing that combines flexibility, fire resistance, and non-combustibility. If Sk exceeds 55 μm, the flatness of the polyvinyl chloride resin coated surface may deteriorate. On the other hand, if Sk is less than 20 μm, the flatness of the polyvinyl chloride resin coated surface is good, and fire resistance and non-combustibility are also good, but the flexibility as a fire-resistant sheet for wallpaper backing may be compromised.

[0059] The method for measuring Sk in this specification is described below.

[0060] (1) Photograph of fire-resistant sheet for wallpaper backing A fire-resistant sheet for wallpaper backing is cut to a size of 45 mm in width and 60 mm in length to prepare a sample. Photographs of the cut fire-resistant sheet for wallpaper backing are observed under the following conditions using a confocal laser microscope VK-X1050 (product name) manufactured by Keyence Corporation.

[0061] In the "VK Observation Application," under "Shape Measurement," use the "Simple Measurement" function to illuminate the fire-resistant sheet used for wallpaper backing with coaxial lighting and observe it at a magnification of 20x. Create a navigation image, select "Start point and length" as the "Method for specifying the linked area" in "Linked Measurement," specify the shooting size as "Width: 3000 μm × Height: 2000 μm," determine the shooting position, and start the measurement.

[0062] (2) Image correction Open the resulting photograph of the fire-resistant sheet for wallpaper backing in a "multi-file analysis application" and perform image correction processing in the following order.

[0063] Surface shape correction: Select "Waviness Removal" as the correction method, and "Correction Strength" as the specification method. Set the correction strength to "5" and perform surface shape correction.

[0064] (3) Surface roughness measurement Specify "entire area" as the measurement area and measure Sk. For one fire-resistant sheet used as wallpaper backing, perform this measurement at 5 locations and calculate the average value of Sk at the 5 locations.

[0065] The detailed settings for surface roughness measurement are shown in Table 1.

[0066] [Table 1]

[0067] Methods for reducing the Sk of a fire-resistant sheet used as wallpaper backing to 55 μm or less include: (I) Use glass fibers with a fine fiber diameter. (II) Use glass fibers with a flattened cross-section. (III) Increase the amount of moist heat adhesive binder fibers. (IV) Increase the amount of fibrillated fibers. (V) Increase the amount of inorganic particle layer applied. (VI) The inorganic particle layer is applied using a surface coating method such as a gravure coater or a rod coater. One or more methods selected from the following are examples.

Example

[0068] The present invention will be described below with reference to examples, but the present invention is not limited to these examples in any way. In the examples, percentages (%) and parts are all based on mass unless otherwise specified. Also, the coating amount is the completely dry coating amount.

[0069] Example 1 <Production of fibrillated fiber 1> 10 parts of poly(m-phenylene isophthalamide) with an intrinsic viscosity of 1.5 in sulfuric acid was dissolved in 90 parts of N,N-dimethylacetamide containing 15 parts of lithium chloride. This solution was introduced into an aqueous glycerol solution in a homomixer being stirred at high speed to obtain a pulp-like material. This pulp-like material was passed through a single disk refiner to be fibrillated and the modified drainage degree was adjusted to obtain a pulp-like material (modified drainage degree: 65 ml) made of a meta-aramid. <Production of base material> 85 parts of flat glass fiber (manufactured by Nitto Boseki Co., Ltd., major axis: 28 μm, minor axis: 7 μm, fiber length: 13 mm, flat cross-section), 8 parts of silanol-modified PVA fiber (a wet heat-adhesive binder fiber, trade name: SPG056-11, manufactured by Kuraray Co., Ltd., fineness: 0.6 dtex, fiber length: 3 mm), and 7 parts of fibrillated fiber 1 were dispersed in water using a pulper to prepare a uniform papermaking slurry with a concentration of 0.5%. A wet paper web was obtained using a cylinder mold paper machine and dried by a Yankee dryer with a surface temperature of 120°C to produce a base material with a basis weight of 52.1 g / m 2 , thickness: 0.181 mm.

[0070] <Preparation of coating liquid for forming inorganic particle layer> A kaolin dispersion was prepared by mixing 100 parts of kaolin (product name: ASP® NC X-1, manufactured by BASF CORPORATION) and 0.4 parts of a water-soluble acrylic acid dispersant (product name: Aron® T-50, manufactured by Toagosei Co., Ltd.) in water and stirring thoroughly. Next, a sepiolite dispersion was prepared by mixing 20 parts of sepiolite (product name: Milcon® SP-2, manufactured by Showa KDE Co., Ltd.) and 1.0 part of a water-soluble acrylic acid dispersant (Aron T-50) in water and stirring thoroughly. Finally, the entire kaolin dispersion and the entire sepiolite dispersion were mixed and stirred, and the concentration was adjusted with water to prepare a coating solution with a solid content of 40%.

[0071] <Preparation of fire-resistant sheets for wallpaper backing> The substrate is impregnated with a coating liquid for forming an inorganic particle layer, and the gap between the rolls is adjusted using a two-roll size press with a gap adjustment function (cotter) to adjust the amount of wet coating, then dried, resulting in an oven-dry coating amount of 68.0 g / m². 2 , total basis weight 120.1g / m 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.185 mm.

[0072] Example 2 In the fiber formulation, the same method as in Example 1 was used, except that 66 parts of the flattened glass fibers used in Example 1 were used, 22 parts of glass fibers (manufactured by Nitto Boseki Co., Ltd., fiber diameter 6.5 μm, fiber length 6 mm, circular cross-section) were used, 5 parts of the silanol-modified PVA fibers used in Example 1 were used, and 7 parts of the fibrillated fiber 1 used in Example 1 were used. The basis weight was 52.6 g / m². 2 A substrate with a thickness of 0.205 mm was fabricated.

[0073] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 73.0 g / m². 2 , total basis weight 125.6g / m 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.211 mm.

[0074] Example 3 In the fiber formulation, the following was used: 76 parts of the flattened glass fibers used in Example 1, 12 parts of the glass fibers (circular cross-section) used in Example 2, 5 parts of the silanol-modified PVA fibers used in Example 1, and 7 parts of the fibrillated fiber 1 used in Example 1. The result was obtained using the same method as in Example 1, with a basis weight of 52.3 g / m². 2 A substrate with a thickness of 0.194 mm was fabricated.

[0075] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 70.0 g / m². 2 , total basis weight 122.3g / m 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.199 mm.

[0076] Example 4 In the fiber formulation, the same method as in Example 1 was used, except that 84 parts of the flattened glass fibers used in Example 1, 10 parts of the silanol-modified PVA fibers used in Example 1, and 6 parts of the fibrillated fiber 1 used in Example 1 were used, resulting in a basis weight of 52.0 g / m². 2 A substrate with a thickness of 0.173 mm was fabricated.

[0077] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 67.0 g / m². 2 , total basis weight 119.0g / m 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.177 mm.

[0078] Example 5 In the fiber formulation, the same method as in Example 1 was used, except that 84 parts of the flattened glass fibers used in Example 1, 4 parts of the silanol-modified PVA fibers used in Example 1, and 12 parts of the fibrillated fiber 1 used in Example 1 were used, resulting in a basis weight of 52.4 g / m². 2 A substrate with a thickness of 0.185 mm was fabricated.

[0079] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 69.0 g / m². 2 Total basis weight 121.4 g / m² 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.190 mm.

[0080] Example 6 In the fiber formulation, the following was used: 62 parts of the flattened glass fibers used in Example 1, 26 parts of the glass fibers (circular cross-section) used in Example 2, 5 parts of the silanol-modified PVA fibers used in Example 1, and 7 parts of the fibrillated fiber 1 used in Example 1. The result was obtained using the same method as in Example 1, with a basis weight of 51.9 g / m². 2 A substrate with a thickness of 0.207 mm was fabricated.

[0081] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 74.0 g / m². 2 Total basis weight 125.9 g / m² 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.213 mm.

[0082] Example 7 In the fiber formulation, the amount of flattened glass fiber used in Example 1 was 76 parts, the glass fiber (circular cross-section) used in Example 2 was 9 parts, the silanol-modified PVA fiber used in Example 1 was 8 parts, and the fibrillated fiber 1 used in Example 1 was 7 parts. Otherwise, the formulation was done in the same manner as in Example 1, resulting in a basis weight of 52.0 g / m². 2 A substrate with a thickness of 0.190 mm was fabricated.

[0083] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 70.0 g / m². 2 , total basis weight 122.0g / m 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.195 mm.

[0084] Example 8 In the fiber formulation, 76 parts of the flattened glass fibers used in Example 1, 9 parts of the glass fibers (circular cross-section) used in Example 2, 8 parts of PVA fibers (moist heat adhesive binder fibers, trade name: VPB(registered trademark) 107-1, manufactured by Kuraray Co., Ltd., 1.1 decitex, 3 mm) were used, and 7 parts of the fibrillated fiber 1 used in Example 1 were used, otherwise the formulation was carried out in the same manner as in Example 1, resulting in a basis weight of 51.8 g / m². 2 A substrate with a thickness of 0.190 mm was fabricated.

[0085] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 71.0 g / m². 2 , total basis weight 122.8g / m 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.195 mm.

[0086] Example 9 In the fiber formulation, 84 parts of the flattened glass fibers used in Example 1, 8 parts of the silanol-modified PVA fibers used in Example 1, and 8 parts of fibrillated cellulose fibers obtained by refining solvent-spun cellulose fibers with an average fiber diameter of 12 μm and a fiber length of 5 mm using a refiner, and then beating them to a modified filtration degree of 100 ml, were used, except that the method was the same as in Example 1, resulting in a basis weight of 52.0 g / m². 2 A substrate with a thickness of 0.189 mm was fabricated.

[0087] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 70.0 g / m². 2 , total basis weight 122.0g / m 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.194 mm.

[0088] Comparative Example 1 In the fiber formulation, 90 parts of the flattened glass fibers used in Example 1 and 10 parts of the silanol-modified PVA fibers used in Example 1 were used, except that the method was the same as in Example 1, resulting in a basis weight of 52.1 g / m².2 A substrate with a thickness of 0.173 mm was fabricated.

[0089] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 64.5 g / m². 2 , total basis weight 116.6g / m 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.176 mm.

[0090] Comparative Example 2 In the fiber formulation, 66 parts of the flattened glass fibers used in Example 1, 22 parts of the glass fibers (circular cross-section) used in Example 2, 7 parts of the silanol-modified PVA fibers used in Example 1, and 5 parts of the fibrillated fiber 1 used in Example 1 were used, otherwise the basis weight was 52.0 g / m² using the same method as in Example 1. 2 A substrate with a thickness of 0.202 mm was fabricated.

[0091] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 72.0 g / m². 2 , total basis weight 124.0g / m 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.207 mm.

[0092] Comparative Example 3 In the fiber formulation, the same method as in Example 1 was used, except that 62 parts of the flattened glass fibers used in Example 1, 20 parts of the glass fibers (circular cross-section) used in Example 1, 5 parts of the silanol-modified PVA fibers used in Example 1, and 13 parts of the fibrillated fiber 1 used in Example 1 were used, resulting in a basis weight of 52.2 g / m². 2 A substrate with a thickness of 0.199 mm was fabricated.

[0093] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 70.2 g / m². 2 Total basis weight 122.4 g / m² 2We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.204 mm.

[0094] Comparative Example 4 In the fiber formulation, the same method as in Example 1 was used, except that 85 parts of the glass fiber (circular cross-section) used in Example 2, 8 parts of the silanol-modified PVA fiber used in Example 1, and 7 parts of the fibrillated fiber 1 used in Example 1 were used, resulting in a basis weight of 52.5 g / m². 2 A substrate with a thickness of 0.280 mm was fabricated.

[0095] The substrate was impregnated with the coating solution used in Example 1, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 75.0 g / m². 2 , total basis weight 127.5g / m 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.286 mm.

[0096] Comparative Example 5 As a coating liquid for forming an inorganic particle layer, 100 parts of kaolin used in Example 1, 0.4 parts of a water-soluble acrylic acid-based dispersant, and 20 parts of a vinyl chloride-based emulsion (product name: Vinibran® 278, solid content concentration 43%, manufactured by Nisshin Chemical Industry Co., Ltd.) were mixed in water and thoroughly stirred to prepare a coating liquid with a solid content concentration of 40%.

[0097] This coating solution was prepared in Example 7 with a basis weight of 52.0 g / m². 2 The material was impregnated onto a substrate with a thickness of 0.190 mm, and the amount of wet coating was adjusted by adjusting the gap between the rolls using a two-roll size press with a cotter, then dried, resulting in an oven-dry coating amount of 69.0 g / m². 2 , total basis weight 121.0g / m 2 We manufactured a fire-resistant sheet for wallpaper backing with a thickness of 0.193 mm.

[0098] The following physical properties were measured and evaluated for the substrates and fire-resistant sheets for wallpaper backing used in the examples and comparative examples, and the results are shown in Tables 2 and 3.

[0099] <Basis weight of fire-resistant sheets for base materials and wallpaper backing> The basis weight of the substrate and the total basis weight of the fire-resistant sheet were measured in accordance with JIS P8124:2011. The oven-dry coating weight of the inorganic particle layer was calculated by subtracting the basis weight of the substrate from the basis weight of the fire-resistant sheet.

[0100] <Thickness of base material and fire-resistant sheet for wallpaper backing> The thickness under a 5N load was measured using an outside micrometer as specified in JIS B7502:2016.

[0101] <Tensile strength of the base material> For each substrate, five sample pieces measuring 250 mm in the flow direction and 50 mm in the width direction were cut out so that the longer side was in the flow direction. Tensile tests were performed using a benchtop universal testing machine (manufactured by A&D Co., Ltd., product name STB-1225S) at a tensile speed of 100 mm / min in accordance with JIS P8113:1998. The maximum tensile stress was defined as the "tensile strength," and the average value of the five samples was used.

[0102] <Folding strength of fire-resistant sheets> For each fire-resistant sheet, sample pieces measuring 110 mm in the flow direction and 15 mm in the width direction were cut out, enough for 10 measurements, with the longer side facing the flow direction. Using an MIT testing machine, a load of 9.8 N was applied, and a folding strength test in the flow direction was performed according to JIS P8115:2001. The folding strength value was the average of 10 measurements. A higher folding strength indicates better resistance to corner cracking in the product. For fire-resistant sheets used as wallpaper backing, a folding strength of 20 or more is preferable, as it reduces the likelihood of corner cracking during installation.

[0103] <Coating properties of inorganic particle layers> The ease of coating when forming an inorganic particle layer on a substrate was evaluated using the following criteria.

[0104] ○: When applying the coating liquid, no breaks, cracks, or splits occur in the substrate. △: When applying the coating liquid, no breaks, cracks, or splits occur in the substrate, but even after adjusting the tension, wrinkles and unevenness occur in the substrate when wet, and these wrinkles and unevenness remain in the substrate even after drying. ×: When applying the coating liquid, even if the tension is adjusted, breaks, cracks, or splits may occur in the substrate.

[0105] <Fire resistance> To evaluate the fire resistance of the fire-resistant sheets for wallpaper backing, three test pieces measuring 100 mm in width and 100 mm in flow direction were cut from each sheet, and the flame of a burner (product name: Lab Burner APTL, manufactured by Phoenix Dent Co., Ltd.) was applied to the center of each test piece for 5 minutes. After that, the surface of the fire-resistant sheet on the side where the flame was applied was visually observed and evaluated according to the following evaluation criteria. The flame temperature of the burner was 1000°C.

[0106] ○: The fire-resistant sheet has no holes, cracks, or melting. △: Slight melting or indentation is visible on the surface of the fire-resistant sheet after being exposed to flame. ×: The fireproof sheet has holes or cracks.

[0107] <Nonflammable> For evaluating the non-combustibility of the fire-resistant sheets used as wallpaper backing, two test specimens measuring 100 mm in width and 100 mm in flow direction were cut from each sheet. Each test specimen was placed in a heated electric furnace capable of maintaining a temperature of 750°C ± 5°C and evaluated according to the following criteria.

[0108] ○: Does not ignite after insertion. △: It ignites momentarily after insertion. ×: After insertion, the sheet surface ignites.

[0109] <Core level difference Sk> Using the measurement method described above, the surface Sk of each fire-resistant sheet for wallpaper backing was evaluated, with the surface that was in contact with the Yankee dryer during the drying of the substrate being considered the surface.

[0110] <Bleed-through of polyvinyl chloride resin> Each fire-resistant sheet for wallpaper backing was cut to 15 cm in width and 20 cm in length. The fire-resistant sheets were placed on a PPC paper laid on a glass plate, with the surface facing upwards, and the top of the fire-resistant sheets was secured with adhesive tape. A black-colored foamed PVC sol for wallpaper was applied to the fire-resistant sheets using an applicator bar with a gap of 0.15 mm. The PPC paper and fire-resistant sheets were heated together in a 150°C constant temperature hot air dryer for 25 seconds to gel. After removing the adhesive tape and the fire-resistant sheets, the adhesion of the black foamed PVC sol on the PPC paper was visually observed and evaluated according to the following evaluation criteria.

[0111] ○: No adhesion. △: Very small black spots are visible. ×: Numerous distinct black spots are visible.

[0112] <Flexibility> In the case of fire-resistant sheets for wallpaper backing, after applying the inorganic particle layer, the sheets were wound onto a paper tube with an outer diameter of 10 cm using a coater's reel. The appearance of the sheets was then visually observed and evaluated according to the following criteria.

[0113] ○: Can be neatly wrapped around a cardboard tube. △: Immediately after winding the sheet onto the paper tube, it may appear slightly lifted or wrinkled from the outer edge of the tube, but it will wind neatly after a while. ×: It is not possible to wrap it neatly around the cardboard tube, resulting in large gaps, cracks, and wrinkles.

[0114] <Fiberglass detachment> For each fire-resistant sheet, five sample pieces measuring 200 mm in the flow direction and 100 mm in the width direction were cut out so that the longer side was in the flow direction. 25 mm wide cellophane tape was applied to the surface of each sample piece for 100 mm in the flow direction, and a 3 kg cylindrical metal roll was rolled over it once back and forth. The cellophane tape was then peeled off, and its condition was visually observed and evaluated according to the following criteria.

[0115] ○: There are almost no glass fibers attached to the cellophane tape. △: A thin layer of glass fiber is attached to the cellophane tape. ×: The glass fibers are firmly attached to the cellophane tape.

[0116] [Table 2]

[0117] [Table 3]

[0118] As shown in Tables 2 to 3, the fire-resistant sheets produced in Examples 1 to 9 contained a base material and an inorganic particle layer. The base material contained glass fibers, moist heat-adhesive binder fibers, and fibrillated fibers. The glass fibers contained flattened cross-section glass fibers, and the fibrillated fiber content was 6% to 12% by mass relative to the total raw materials constituting the base material. The inorganic particle layer contained inorganic particles and an inorganic binder. The fibrillated fibers fixed the glass fibers, and the moist heat-adhesive binder fibers further fixed the fixed intersections. As a result, the base material had high tensile strength, and even when the inorganic particle layer forming coating liquid was applied, paper breakage and other issues did not occur.

[0119] Comparing Examples 1 to 9, when the content of flattened cross-section glass fibers was 75% to 100% by mass relative to the total amount of glass fibers, the substrate became thinner and denser, resulting in increased tensile strength and significantly improved bending strength. In addition, the coating of flattened glass fibers and moist heat-adhesive binder fibers, along with the fibrillated fibers, improved the flatness of the fire-resistant sheet, filled the voids in the fire-resistant sheet, and prevented the polyvinyl chloride resin from seeping through to the back.

[0120] In Example 6, the glass fiber content of the flattened cross-section was less than 75% by mass of the total amount of glass fibers, but a tendency for the glass fibers to easily fall off was observed.

[0121] Comparing Example 7 and Example 8, it was found that using silanol-modified polyvinyl alcohol fibers as the moist heat-adhering binder fibers resulted in higher tensile strength, superior flexural strength, and improved coating properties of the inorganic particle layer.

[0122] Comparing Example 1 and Example 9, it was found that the meta-aromatic polyamide, which has higher heat resistance, exhibits higher non-flammability.

[0123] In Comparative Example 1, the fire-resistant sheet did not contain fibrillated fibers. However, because the fire-resistant sheet was thin and the gaps between the glass fibers were not filled, when polyvinyl chloride resin was applied, its penetration could not be suppressed, resulting in see-through. Furthermore, because a dense network structure was not formed between the fibrillated fibers and glass fibers, the glass fibers were prone to falling off.

[0124] In Comparative Example 2, where the fibrillated fiber content was less than 6% by mass, the formation of a dense network structure between the fibrillated fibers and glass fibers was insufficient. As a result, the voids between the fibers were not completely filled even when an inorganic particle layer was applied, causing the polyvinyl chloride resin to seep through and slight shedding of glass fibers. On the other hand, in Comparative Example 3, where the fibrillated fiber content was more than 12% by mass, the non-flammability deteriorated because the amount of organic fibers relative to the total raw materials constituting the base material increased.

[0125] When comparing Example 1 with Comparative Example 4, using glass fibers with a flat cross-section resulted in surface adhesion with the moist heat-adhesive binder fibers, leading to superior tensile strength and flexural strength, as well as reduced glass fiber shedding. As a result, the coating properties of the inorganic particle layer were also superior. Furthermore, it was found that the reduced thickness resulted in superior flexibility. On the other hand, when using glass fibers with a circular cross-section, the adhesion with the moist heat-adhesive binder fibers became point adhesion, resulting in increased thickness, decreased tensile strength and flexural strength, reduced flexibility, and glass fiber shedding.

[0126] In Comparative Example 5, the fire-resistant sheet used an organic binder in the inorganic particle layer, but when inserted into a heated electric furnace at 750°C, the surface ignited, indicating insufficient fire resistance. [Industrial applicability]

[0127] The fire-resistant sheet for wallpaper backing of the present invention relates to a wallpaper backing sheet for interior use in houses and the like, and is suitably usable as a wallpaper backing sheet coated with foamed polyvinyl chloride resin (foamed PVC sol).

Claims

1. A fire-resistant sheet for wallpaper backing, characterized in that it contains a base material and an inorganic particle layer, the base material contains glass fibers, moist heat adhesive binder fibers and fibrillated fibers, the glass fibers contain at least flattened cross-section glass fibers, the glass fiber content is 78 to 90% by mass of the total raw materials constituting the base material, the moist heat adhesive binder fiber content is 4 to 10% by mass of the total raw materials constituting the base material, the fibrillated fiber content is 6% by mass or more and 12% by mass or less of the total raw materials constituting the base material, the inorganic particle layer contains inorganic particles and an inorganic binder, the inorganic binder content in the inorganic particle layer is 2% by mass or more and 100% by mass or less of the total amount of inorganic particles, and the inorganic particle layer content, calculated as "amount of inorganic particle layer coating (g / m²) / basis weight of base material (g / m²) × 100", is 60% by mass or more and less than 160% by mass.

2. The fire-resistant sheet for wallpaper backing according to claim 1, wherein the glass fiber content of the flat cross-section is 75% by mass or more and 100% by mass or less relative to the total amount of glass fibers.

3. The fire-resistant sheet for wallpaper backing according to claim 1 or 2, wherein the moist heat-adhesive binder fibers are silanol-modified polyvinyl alcohol fibers.

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