Lightweight fiber layer and method for forming the same

Abstract

To provide a technique (a lightweight fiber layer and a method for forming a lightweight fiber layer) which causes no surface color unevenness when the surface of a fiber layer (first layer) formed using a binding material slurry containing alkali silicate and water and a granular fiber as main components is coated with a second layer using a binding material slurry having a color tone (color difference) different from that of the binding material slurry used for the formation of first layer.MEANS: All of the surface of a fiber layer of a first layer formed using a binding material slurry containing alkali silicate and water and a granular fiber as main components is covered with a fiber layer of a second layer mainly composed of a binding material slurry in which the alkali amount contained in the solid content is 5% or less in terms of Na2O and a granular fiber so that the surface of the first layer is not visible.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a lightweight fiber layer, and more particularly to a lightweight fiber layer that is made up of two or more laminated layers each containing a binder slurry and lightweight fibers as its main components, and has no visible color spots (color unevenness) on the surface. [Background technology]

[0002] A fiber layer such as rock wool is provided on the base of a structure surface or the like for the purpose of imparting fire resistance, fire prevention, sound absorption, and / or heat insulation, etc. The fiber layer is generally formed by a spraying method using granular fibers (fiber masses with a diameter of several mm to several cm) and a binder slurry whose main components are water and an inorganic binder such as cement or alkali silicate, or an organic binder made of a polymer such as vinyl acetate resin, acrylic resin, or synthetic rubber. This spraying method, known as a semi-dry method, uses rock wool granules and cement slurry (a binder slurry made from cement and water). The granular rock wool fibers are fed into a device called a rock wool sprayer or deflocculator, where they are pulverized (into fine granules (fiber clumps with diameters of several millimeters to several centimeters)) by a built-in rotary cutter or other deflocculator. The granules are then quantitatively pumped into a pressure path by a rotary feeder or other constant-feeding device, and then pressure-fed through a hose by a blower and supplied to a spray nozzle. The cement is mixed with water in a mixer to form a cement slurry, which is then pumped through a conveying pipe (a hose for pumping cement slurry) by a slurry pump to a liquid material (cement slurry) spray nozzle located on the granular fiber spray nozzle. The cement slurry is sprayed from a liquid material (cement slurry) spray nozzle located on the periphery of the granular fiber spray nozzle, or from a liquid material (cement slurry) spray nozzle located near the central axis of the granular fiber spray nozzle, and merges and mixes with the rock wool to form a fiber layer consisting of rock wool and cement hydrate (solidified cement slurry) (see, for example, Patent Documents 1 and 2).

[0003] Cement is an inexpensive and excellent inorganic binder, but because it is produced by decomposing the raw material limestone at high temperatures and then reacting it with silicon dioxide raw materials, aluminum oxide raw materials, iron oxide raw materials, etc. at high temperatures, a large amount of carbon dioxide, a representative greenhouse gas, is generated during production. For this reason, an inorganic binder (binder slurry) containing alkali silicate and water, which does not contain cement as the main component, has been proposed, and an inorganic lightweight coating material (lightweight fiber layer) consisting of this inorganic binder and rock wool granules has been disclosed (see, for example, Patent Document 3). Rock wool granular fibers are white or very close to white in color, and the inorganic binder (binder slurry containing alkali silicate and water) and inorganic lightweight coating material shown in the examples of Patent Document 1 are also white or very close to white in color (hereinafter collectively referred to as "white").

[0004] When considering using a fiber layer for the interior of a building such as a house or a store, it is conceivable that a color different from the white fiber layer to be formed may be required. The inventors thought that this problem could be solved by covering the surface of the formed fiber layer with a layer of binder slurry (a layer made of solidified binder slurry) of a color different from that of the white fiber layer. Therefore, in an experiment, the inventors applied black or gray binder slurry to the surface of a fiber layer made of rock wool granular fibers and a binder slurry containing alkali silicate (sodium silicate) not primarily composed of cement and water. When they examined the surface, white-appearing crystals were precipitated on the surface of the black or gray binder slurry layer (the layer made of solidified binder), causing the surface to become mottled. Analysis of these crystals revealed that they were sodium carbonate hydrate crystals. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-070546 [Patent Document 2] Japanese Patent Publication No. 2020-159093 [Patent Document 3] Japanese Patent Publication No. 2022-031022 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide a technology that prevents uneven color on the surface when the surface of a fiber layer (first layer) formed mainly from a binder slurry containing alkali silicate and water and granular fibers is covered with a second layer using a binder slurry of a different color (having a color difference) from the binder slurry used to form the first layer. The present invention aims to provide a lightweight fiber layer that does not produce color unevenness on the surface when the surface of a fiber layer (first layer) formed mainly from a binder slurry containing alkali silicate and water and granular fibers is covered with a second layer using a binder slurry of a different hue (having a color difference) from the binder slurry used to form the first layer. Another object of the present invention is to provide a lightweight fiber layer that is unlikely to peel off when applied to a ceiling surface or the like. Another object of the present invention is to provide a method for forming a lightweight fiber layer that does not cause color unevenness on the surface when the surface of a fiber layer (first layer) formed mainly from binder slurry and granular fibers is covered with a second layer using a binder slurry of a different hue (having a color difference) from the binder slurry used to form the first layer.A further object of the present invention is to provide a method for forming a lightweight fiber layer that is unlikely to peel off when formed on a ceiling surface or the like. [Means for solving the problem]

[0007] The inventors have found that the above-mentioned problems can be solved by completely covering the surface of a first fibrous layer formed mainly from granular fibers and a binder slurry containing alkali silicate and water with a second fibrous layer mainly from granular fibers and a binder slurry containing 5% or less alkali in solid content calculated as Na2O, thereby concealing the surface of the first layer, and have completed the present invention. That is, the present invention relates to the lightweight fibrous layers represented by the following items (1) to (3) and a method for forming a lightweight fibrous layer represented by item (4). (1) A lightweight fiber layer comprising a first layer mainly composed of a binder slurry containing alkali silicate and water and granular fibers, and a second layer mainly composed of a binder slurry containing granular fibers and an alkali content of 5% or less in terms of Na2O in the solid content, the second layer covering the surface of the first layer. (2) The lightweight fiber layer of (1) above, wherein the binder slurry forming the second layer is a slurry mainly composed of water and one or more binders selected from organic binders consisting of cement and polymers. (3) The second layer has an oven-dry bulk density of 0.12 to 1.0 g / cm 3 The lightweight fiber layer according to (1) or (2) above, which has a thickness of 5 to 60 mm. (4) A method for forming a lightweight fiber layer, comprising forming a first layer mainly composed of a binder slurry containing alkali silicate and water and granular fibers, and covering the surface of the first layer with a second layer mainly composed of a binder slurry and granular fibers, the alkali content of which is 5% or less in terms of Na2O in the solid content. [Effects of the Invention]

[0008] According to the present invention, when the surface of a fiber layer (first layer) formed mainly from a binder slurry containing alkali silicate and water and granular fibers is coated with a second layer using a binder slurry of a different hue (having a color difference) from the binder slurry used to form the first layer, a lightweight fiber layer is obtained that does not produce color unevenness on the surface.Furthermore, according to the present invention, when the surface of a fiber layer (first layer) formed mainly from a binder slurry containing alkali silicate and water and granular fibers is coated with a second layer using a binder slurry of a different hue (having a color difference) from the binder slurry used to form the first layer, a lightweight fiber layer is obtained that does not produce color unevenness on the surface and is not easily peeled off when applied to a ceiling surface or the like. Furthermore, according to the present invention, a method for forming a lightweight fiber layer can be obtained in which, when the surface of a fiber layer (first layer) formed primarily from binder slurry and granular fibers is covered with a second layer using a binder slurry of a different hue (having a color difference) from the binder slurry used to form the first layer, color unevenness does not occur on the surface. Furthermore, according to the present invention, a method for forming a lightweight fiber layer can be obtained in which when the surface of a fiber layer (first layer) formed mainly from binder slurry and granular fibers is covered with a second layer using a binder slurry of a different hue (having a color difference) from the binder slurry used to form the first layer, color unevenness does not occur on the surface and the lightweight fiber layer is not easily peeled off when applied to a ceiling surface or the like. According to the present invention, the surface of the lightweight fiber layer does not become spotty or have uneven color, and the surface of the lightweight fiber layer can be made to have a desired color. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing an example of a spraying device used in a semi-dry rock wool spraying method. [Figure 2] FIG. 2 shows photographs of the surface of the specimen of Test No. 15 in the example immediately after spraying and after 28 days of use. [Figure 3] FIG. 3 shows photographs of the surface of the specimen of Test No. 16 in the example immediately after spraying and after 28 days of use. [Figure 4] FIG. 4 shows photographs of the surface of the specimen of Test No. 17 in the example immediately after spraying and after 28 days of use. DETAILED DESCRIPTION OF THE INVENTION

[0010] The lightweight fiber layer of the present invention is characterized by comprising a first layer mainly composed of granular fibers and a binder slurry containing alkali silicate and water, and a second layer mainly composed of granular fibers and a binder slurry containing 5% or less of alkali in terms of Na2O in the solid content, the second layer covering the surface of the first layer. Here, "lightweight" means a bulk density of 1.0 g / cm3 in an oven-dry state. 3 Here, the bone dry bulk density is determined by finding the volume (V) of a specimen from the outer dimensions of a fiber layer specimen obtained by cutting out a cylindrical shape from the formed fiber layer using a rock wool cutter with an inner diameter of 80 mm, placing the specimen in a dryer and drying it at 105°C until it reaches a constant weight, and then calculating the bulk density (ρ) from the mass (M) of the specimen after drying using the following formula (1), which is the bone dry bulk density. ρ=M / V (1)

[0011] The granular fibers used in the present invention include organic and inorganic granular fibers, such as synthetic fibers (e.g., cellulose fibers, nylon fibers, and polypropylene fibers), and cellulose fibers. Non-metallic inorganic fibers are preferred in terms of fire resistance. For example, inorganic granular fibers selected from rock wool, glass wool, and ceramic wool are preferred in terms of durability, sound absorption, and heat insulation. Rock wool and ceramic wool are more preferred because they can maintain their shape without melting even when exposed to temperatures above 800°C and have excellent heat resistance and fire resistance. Here, rock wool refers to a material (mineral fiber) produced by rapidly cooling a material primarily composed of rock or blast furnace slag melted in a melting furnace and then fiberizing it. For example, rock wool also includes slag wool produced from a material primarily composed of blast furnace slag. The granular fibers used in the present invention are preferably agglomerated (granular), such as rock wool granular cotton, because the resulting rock wool composition layer has low thermal conductivity and the resulting first layer (first fiber layer) has excellent shape retention. The granular fibers used in the present invention are preferably in a lump form (granular, fiber masses with a diameter of several mm to several cm) such as the granular rock wool cotton used in rock wool-based fire-resistant coating materials, because the thermal conductivity of the formed rock wool composition layer is low and the formed base material layer has excellent ability to retain its shape. The rock wool aggregate is preferably a granular cotton obtained by subjecting raw cotton consisting of fiberized mineral fibers to one or a combination of two or more processes, such as crushing, deflocculating, cutting, sorting (e.g., sieving), and granulation. Examples of the rock wool granular cotton include fine and micro-sized rock wool granules, and commercially available rock wool granules, fine and micro-sized rock wool granules, such as "S-Fiber Granular Cotton" (product name) manufactured by Japan Rock Wool Co., Ltd., "Locceram Granular Cotton" (product name) manufactured by JFE Rock Fiber Corporation, and "Pacific Mineral Fiber Granular Cotton" (product name) manufactured by Pacific Materials Corporation, can be suitably used. When such rock wool granular cotton is used, heat is less likely to be transmitted to the substrate covering the rock wool, providing thermal insulation, fire resistance, or non-combustibility, as well as sound absorption.

[0012] The binder slurry used in the first layer of the present invention (hereinafter sometimes referred to as "first binder slurry") is a binder slurry containing an alkali silicate and water. Here, the alkali silicate is preferably one or more selected from sodium silicates such as sodium metasilicate, sodium orthosilicate, and water glass, lithium silicate, and potassium silicate. It may also be an aqueous solution, such as water glass. In addition to the alkali silicate and water, the first binder slurry may contain an SiO2-containing inorganic powder other than cement and alkali silicate (hereinafter sometimes referred to as "SiO2-containing inorganic powder"), an alkali hydroxide, other inorganic components, and organic components, and the inclusion of an SiO2-containing inorganic powder is preferred from the viewpoint of the strength of the first layer. Here, the SiO2-containing inorganic powder refers to an inorganic powder containing SiO2 as the main chemical composition other than cement and alkali silicate, and preferred examples include blast furnace slag powder, fly ash, metakaolin, silica fume, volcanic ash, igneous rock powder, powder of burned igneous rock, powder of burned sewage sludge slag, and powder of molten slag from municipal waste. The SiO2-containing inorganic powder is preferably an inorganic powder having a Blaine specific surface area of ​​2000 cm 2 / g or more is preferred because the binder hardens quickly, and more preferably 2500 cm 2 The upper limit of the Blaine specific surface area of ​​the SiO2-containing inorganic powder used in the present invention is 12000 cm2, since this allows the time during which the fluidity of the binder can be maintained to be long. 2 / g or less, and more preferably 10000 cm 2 / g or less. The other inorganic components may be contained in an amount of 10% by mass or less relative to the mass of the SiO2-containing inorganic powder, and in this case, the cement mainly acts as a stimulant for the SiO2-containing inorganic powder. Since the amount of carbon dioxide generated during the production of the raw materials is small, the content of cement in the first layer of the present invention is more preferably 5% by mass or less, and even more preferably 2% by mass or less, relative to the mass of the SiO2-containing inorganic powder.

[0013] The first layer has a bone dry bulk density of 0.14 to 1.0 g / cm 3It is preferable to set the density to 0.14 g / cm 3 If it is less than 1.0g / cm, there is a risk of peeling. 3 If the temperature exceeds this range, there is a risk that the performance of fire resistance, fire prevention, sound absorption, heat insulation, etc. may be insufficient.

[0014] The binder slurry forming the second layer in the present invention (hereinafter, sometimes referred to as the "second binder slurry") is a binder slurry having an alkali content of 5% or less, calculated as Na2O, in the solid content. The second binder slurry is a slurry mainly composed of water and one or more binders selected from the group consisting of Portland cements such as ordinary Portland cement and white Portland cement, cements such as blast furnace cement, inorganic binders such as latent hydraulic substances such as blast furnace slag powder, and organic binders made of polymers such as vinyl acetate resins, acrylic resins, and synthetic rubbers, and may contain one or more additives (admixtures) within a range that does not impair the effects of the present invention. Examples of the additive materials (admixtures) include thickeners, cement dispersants, expansive agents, waterproofing agents, rust inhibitors, shrinkage reducing agents, pigments, fibers other than rock wool, water repellents, anti-efflorescence agents, quick-setting agents, quick-hardening agents, retarders, foaming agents, antifoaming agents, gypsum, pozzolans such as silica fume and fly ash, water repellents, surface hardeners, etc. Organic binders made of cements such as Portland cement and blended cement, blast furnace slag powder, and polymers such as acrylic resins and synthetic rubbers usually contain an alkali content of 1% or less in terms of Na2O, and one or more binders selected from these are preferred as binders for the second binder slurry.

[0015] If the amount of alkali contained in the solid content of the second binder slurry (the content ratio of the mass of alkali to the mass of the solid content) exceeds 5% (mass %) in terms of Na2O, there is a risk that crystals of alkali metal salts such as sodium carbonate hydrate will form on the surface of the second layer, causing uneven color on the surface. The amount of alkali contained in the solid content of the second binder slurry is preferably 2% or less in terms of Na2O, and more preferably 1% or less, because this reduces the risk of alkali metal salt crystals forming on the surface of the second layer.

[0016] The second binder slurry preferably has a different color from the first binder slurry, i.e., has a color difference. Here, "different color (has a color difference)" refers to a color difference before curing or solidification, i.e., before curing, where the uncured color difference is a difference in lightness of 2 or more, a difference in saturation of 4 or more, and / or a difference in hue of 4 or more in the Munsell color system. The mass ratio (mass ratio) "W / RW" of the mass of water (W) in the second binder slurry to the mass of rock wool (RW) is preferably 0.6 to 5.0, more preferably 0.8 to 4.0. If W / RW is less than 0.6, there is a risk that the second layer will peel off when the lightweight fiber layer is formed on a ceiling surface or the like, and if W / RW is more than 5.0, there is a risk that the second binder slurry will drip when the lightweight fiber layer is formed on a ceiling surface or the like.

[0017] The granular fibers used in the second layer in the present invention can be the same as those used in the first layer, and it is preferable to use the same granular fibers as those used in the first layer.

[0018] The second layer in the present invention has an oven-dry bulk density of 0.12 to 1.0 g / cm 3 The thickness of the second layer is preferably 5 to 60 mm. The bulk density of the second layer in an oven-dry state is 1.0 g / cm. 3 If the thickness of the second layer is more than 60 mm, there is a risk that a part or all of the lightweight fiber layer will fall off when the lightweight fiber layer of the present invention is formed on a ceiling surface or the like by spraying or troweling. 3If the second layer has a bulk density of 0.14 to 0.8 g / cm or a thickness of 5 mm or less, there is a risk of alkali metal salt crystals forming on the surface of the second layer. 3 The thickness should be 5 to 50 mm.

[0019] The surface of the second layer may be covered with a third layer mainly composed of a binder slurry. The binder slurry forming this third layer (hereinafter sometimes referred to as "third binder slurry") is preferably the same as the second binder slurry, and more preferably the same as the second binder slurry.

[0020] The method for forming a lightweight fiber layer of the present invention is characterized by forming a first layer mainly composed of a binder slurry containing alkali silicate and water and granular fibers, and coating the surface of the first layer with a second layer mainly composed of a binder slurry containing granular fibers and an alkali content of 5% or less in terms of Na2O in the solid content. Here, the binder slurry forming the first layer is the first binder slurry described above, and the binder slurry forming the second layer is the second binder slurry. Also, the granular fibers are the granular fibers described above. The surface of the second layer may be coated with a third layer mainly composed of a binder slurry. Here, the binder slurry forming the third layer is the second binder slurry.

[0021] The first, second, and third layers can be suitably formed using a spraying device such as the spraying device used in the semi-dry construction method used in the rock wool spraying method, an example of which is shown in the schematic diagram of Figure 1. The first and second layers can also be formed by mixing binder slurry and granular fibers and then filling a formwork or applying the mixture to a substrate with a trowel, roller, or the like. The substrate used for forming the first layer can be concrete, mortar, steel, wood, or the like. The substrate used for forming the second layer is the surface of the first layer. The third layer can also be formed by applying the mixture to the surface of the second layer with a trowel, roller, or the like.

[0022] An example of a spraying device used in a semi-dry construction method, which is suitably used in the rock wool spraying method, is shown in a schematic diagram in Figure 1, and is a spraying device 10 whose main components are a cotton defibrator 20, a blower (air blower) 14, a granular fiber pressure-feed hose 9, a binder slurry storage tank 8, a binder slurry pressure-feed pump 7, a binder slurry pressure-feed hose 6, and a spray gun 1. Granular fiber (rock wool granular cotton) 11 is fed into a hopper 23 of the cotton defibrator 20, disintegrated in a first cotton defibrator section 21 of the cotton defibrator 20, and then sent by a screw feeder 24 to a second cotton defibrator section 22 for further disintegration. The disintegrated granular fiber enters a rotary feeder (quantitative supply device) 25 and is supplied in a fixed amount to a granular fiber pressure-feed pipe 26. The unraveled granular fibers 5 sent to the granular fiber pressure-transfer pipe 26 are pressurized by air sent from a blower (air blower) 14 connected to the granular fiber pressure-transfer pipe 26 into a granular fiber pressure-transfer hose 9 connected to the granular fiber pressure-transfer pipe 26, and are sprayed from a granular fiber nozzle 2 of a spray gun 1 connected to the tip of the granular fiber pressure-transfer hose 9.

[0023] The produced binder slurry 4 (first binder slurry or second binder slurry) is stored in a binder slurry storage tank 8, and is pumped by a binder slurry pressure pump 7 through a binder slurry suction hose 15, a binder slurry pressure pump 7, and a binder slurry pressure feed hose 6 to the binder slurry nozzle 3 of the spray gun 1, where it is sprayed from the binder slurry nozzle 3. The loosened granular fibers 5 sprayed from the granular fiber nozzle 2 of the spray gun 1 and the binder slurry 4 sprayed from the binder slurry nozzle 3 of the spray gun 1 are mixed together at the tip of the spray gun 1, forming a first layer (first fiber layer) or a second layer (second fiber layer) composed mainly of granular fibers and binder slurry. When forming the second layer, the second layer is formed on the surface of the first layer. The third layer is preferably formed using the same equipment as the first and second layers. In this case, the granular fibers are not pumped, and the third binder slurry 4 is sprayed onto the surface of the second layer from the binder slurry nozzle 3 of the spray gun 1. The third layer may be formed by a spraying method using a different spraying device (e.g., a mortar spraying device or a paint spraying device) instead of the spraying device 10 used in the semi-dry construction method. Alternatively, the third binder slurry may be filled into a formwork installed on the surface of the second layer or the base of the first layer, or applied to the second surface with a trowel or roller. A fourth layer may also be formed on the surface of the third layer to enhance its design, light resistance, weather resistance, water repellency, or mildew resistance. The fourth layer may be formed by applying the fourth layer to the surface of the third layer with a trowel, roller, spraying device, or the like, depending on the properties of the material constituting the fourth layer. [Example]

[0024] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0025] [Example 1] <Formation of the first layer> The inorganic lightweight insulation material, which uses the inorganic binder (first binder slurry) of Test No. 12 described in Table 1 of JP 2022-031022 A and rock wool granules, was sprayed onto the plywood substrate at a thickness of 50 mm using a spraying device used in the semi-dry construction method used in the rock wool spraying method to form the first layer. The materials used are shown below, and the mixing conditions, the color of the first binder slurry, and the bone-dry bulk density of the formed first layer are shown in Table 1. In Table 1, RW, S, and W respectively represent the mass of rock wool, the solids in the inorganic binder of Test No. 12, and the water in the inorganic binder of Test No. 12. "S / RW" in Table 1 represents the mass ratio (mass ratio) of the solids in the inorganic binder of Test No. 12 to the mass of rock wool. "W / RW" in Table 1 represents the mass ratio (mass ratio) of the water in the cement slurry to the mass of the water in the inorganic binder of Test No. 12 to the mass of rock wool. "W / (S+RW)" in Table 1 represents the mass ratio (mass ratio) of the water in the inorganic binder of Test No. 12 to the total mass of the rock wool and the solids in the inorganic binder of Test No. 12. Rockwool: Rockwool granules manufactured by Pacific Materials Alkali silicate: No. 3 water glass (SiO2: 29.03 mass%, Na2O: 9.47 mass%, H2O: 61.50 mass%) SiO2-containing inorganic powder other than cement and alkali silicate: Blast furnace slag powder (ground blast furnace slag 4000, Blaine specific surface area: 4130 cm 2 / g) Water: Water supply from Sakura City, Chiba Prefecture

[0026] [Table 1]

[0027] <Formation of the second layer> The following slurries 1 to 10 were prepared as second binder slurries. The following materials were used in addition to the above. Slurry 7 was prepared by adding the following black pigment to the inorganic binder (first binder slurry) used in forming the first layer to color the slurry black. · Cement: Ordinary Portland cement (commercially available). Black pigment: TOMATEC Color (composite oxide pigment for coloring) 42-302A (available from TOMATEC Corporation) Sodium sulfate: Reagent (special grade): Kanto Chemical Co., Ltd. Sodium carbonate: Reagent (special grade): Kanto Chemical Co., Ltd. Water: Sakura City, Chiba Prefecture Using the semi-dry construction method, the surface of the first layer was covered with a second fiber layer consisting of the prepared second binder slurry and rock wool granules within one hour of forming the first layer. The plywood substrate was treated as the ceiling surface, and the first and second layers were formed. The rock wool granules used were the same as those used to form the first layer. Table 2 shows the mixing ratio of the second binder slurry used to form the second layer, the types of binders and additives contained in the slurry, the amount of alkali contained in the solid content of the slurry (in terms of Na2O), the color of the slurry at the time of preparation, and the thickness of the second layer. After the second layer had hardened (after 7 days of use), the surface was visually inspected to check for any unevenness in color on the surface and evaluated. The results are shown in Table 2. If there was no unevenness in color on the surface, it was evaluated as "○" (good), and if there was unevenness in color on the surface, it was evaluated as "×" (poor). In addition, if the formed fiber layer did not peel off during the formation of the second layer or within 24 hours after formation, it was evaluated as "○" (good), and if it peeled off, it was evaluated as "×" (bad).The results are also shown in Table 2.

[0028] [Table 2]

[0029] In Test Nos. 1 to 9 and 12 to 14, which correspond to examples of the present invention, the surface of the second layer was observed after hardening, and a lightweight fiber layer was obtained that had a different color tone (color difference) from the first layer without any color unevenness. In addition, the bone dry bulk density of the second layer was 0.12 to 1.0 g / cm. 3In addition, in Test Nos. 1 to 7 and Test Nos. 13 and 14, which had thicknesses of 5 to 60 mm, a lightweight fiber layer was formed to resemble a ceiling, but no peeling occurred.

[0030] [Example 2] Test No. 15 Using the same materials as in Example 1, a first layer was formed to a thickness of 40 mm in the same manner as in Example 1, and within one hour of forming the first layer, the surface of the first layer was coated with the first binder slurry used in forming the first layer to prepare a test specimen. The surface was observed immediately after spraying and after 28 days. As a result, no color unevenness was visible on the surface. Therefore, the evaluation of "color unevenness" was "○" (good). Figure 2 shows photographs of the surface immediately after spraying and after 28 days. Figure 2 (a) is a photograph of the surface immediately after spraying, and Figure 2 (b) is a photograph of the surface after 28 days.

[0031] Test No. 16 Using the same materials as in Example 1, a first layer was formed to a thickness of 40 mm in the same manner as in Example 1, and within one hour of the formation of the first layer, the surface of the first layer was coated with the second binder slurry (Slurry 2) used in Test No. 2 in Example 1 to prepare a test specimen. The surface was observed immediately after spraying and after 28 days. As a result, color unevenness on the surface was visually confirmed. Therefore, the evaluation of "color unevenness" was "×" (poor). Photographs of the surface immediately after spraying and after 28 days are shown in Figure 3. Figure 3(a) is a photograph of the surface immediately after spraying, and Figure 3(b) is a photograph of the surface after 28 days.

[0032] Test No. 17 Using the same material as in Example 1, a first layer was formed to a thickness of 40 mm in the same manner as in Example 1, and within one hour of the formation of the first layer, a second layer of Test No. 3 of Example 1 was formed to a thickness of 10 mm on the surface of the first layer in the same manner as in Example 1 to prepare a test specimen. The surface was observed immediately after spraying and after 28 days. As a result, no color unevenness was visible on the surface. Therefore, the evaluation of "color unevenness" was "○" (good). Figure 4 shows photographs of the surface immediately after spraying and after 28 days. Figure 4(a) is a photograph of the surface immediately after spraying, and Figure 4(b) is a photograph of the surface after 28 days.

[0033] In Test No. 17, which corresponds to an example of the present invention, observation of the surface of the second layer after curing revealed that there was no uneven color and that the lightweight fiber layer had a different color tone (color difference) from the first layer. [Industrial Applicability]

[0034] The present invention can be suitably applied to coating the surfaces of components of structures or constructions made of concrete, steel, wood, etc., for the purpose of imparting fire resistance, fire prevention, sound absorption, and / or heat insulation properties to the components. [Explanation of symbols]

[0035] 1 Spray gun (center gun) 2 Granular fiber nozzle 3. Binder slurry injection nozzle 4. Binder Slurry 5. Disintegrated granular fibers 6. Binder slurry pressure feed hose 7. Pressure pump for binder slurry 8. Storage tank for binder slurry 9 Granular fiber pressure feeding hose 10 Spraying equipment (spraying system) 11 Granular Fiber 12. A fiber layer consisting of a mixture of granular fiber and binder slurry. 13 Base (wall) 14 Blower 15 Suction hose for binder slurry 20 Cotton opening machine 21 First Cotton Decomposition Department 22 Second cotton opening section 23 Hopper 24 Screw feeder 25 Rotary feeder (quantitative feeder) 26 Granular fiber pressure pipe 31 Binder slurry pipeline 32 Granular fiber pipe 33 Central axis of granular fiber pipe

Claims

1. The first layer is mainly composed of a binder slurry containing alkali silicate and water and granular fibers, and the amount of alkali contained in the solid content is Na ２ A lightweight fiber layer comprising a binder slurry having an O content of 5% or less and a second layer mainly composed of granular fibers, the second layer covering the surface of the first layer.

2. 2. The lightweight fiber layer according to claim 1, wherein the binder slurry forming the second layer is a slurry containing water as the main components and one or more binders selected from the group consisting of cement and organic binders made of polymers.

3. The second layer has an oven-dry bulk density of 0.12 to 1.0 g / cm ３ 3. The lightweight fiber layer according to claim 1 or 2, which has a thickness of 5 to 60 mm.

4. The first layer is formed by using a binder slurry containing alkali silicate and water and granular fibers as the main components, and the amount of alkali contained in the solid content is Na ２ 1. A method for forming a lightweight fiber layer, comprising: covering the surface of the first layer with a second layer having as its main components a binder slurry having an O content of 5% or less and granular fibers.

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