Inorganic fiber sheet

Abstract

Provided is an inorganic fiber sheet that has excellent processability and fire resistance. One embodiment of the present invention is an inorganic fiber sheet that includes mineral fibers and an organic binder. In this inorganic fiber sheet, the mineral fiber content in the inorganic fiber sheet is 80.0 mass% or more, the ignition loss of the inorganic fiber sheet is 2.0-10.0 mass%, and the organic binder is adhered in a webbing shape to points of entanglement between the mineral fibers.

Description

Inorganic fiber sheet

[0001] The present invention relates to an inorganic fiber sheet.

[0002] BACKGROUND ART Inorganic fiber sheets are widely used in construction materials, electrical appliances, vehicle components, etc., because they have relatively excellent fire resistance and heat resistance.

[0003] Patent Document 1 discloses an inorganic fiber sheet that uses inorganic fibers, an inorganic binder, and an inorganic fixing agent, has an organic binder content of 1 mass % or less, and exhibits little decrease in strength even when exposed to high temperatures.

[0004] Japanese Patent Application Laid-Open No. 2007-197264

[0005] In recent years, the use of inorganic fiber sheets has expanded, and inorganic fiber sheets are processed into various shapes, so inorganic fiber sheets with excellent processability are required. However, reducing the density of the inorganic fiber sheet to improve processability may result in reduced fire resistance and heat resistance, and increasing the content of an organic binder component to improve processability may result in reduced fire resistance. For example, it has been difficult to obtain an inorganic fiber sheet with excellent processability while maintaining high fire resistance.

[0006] Therefore, an object of the present invention is to provide an inorganic fiber sheet that is excellent in processability and fire resistance.

[0007] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using an inorganic fiber sheet having a specific structure.

[0008] One aspect of the present invention is an inorganic fiber sheet comprising mineral fibers and an organic binder, wherein the content of the mineral fibers in the inorganic fiber sheet is 80.0% by mass or more, the ignition loss of the inorganic fiber sheet (525°C, 30 minutes) is 2.0 to 10.0% by mass, and the organic binder is adhered in a web-like manner to the intertwining points of the mineral fibers.

[0009] The glass transition temperature of the organic binder is preferably 10°C or lower. The organic binder preferably contains an acrylic resin. The inorganic fiber sheet preferably contains an inorganic flocculant. The inorganic flocculant preferably contains one or more selected from the group consisting of aluminum sulfate, polyferric sulfate, PAC (polyaluminum chloride), and ferric chloride. The mineral fiber preferably contains one or more selected from the group consisting of rock wool, glass wool, alkaline earth silicate wool, glass fiber, and alumina fiber. The inorganic fiber sheet preferably has a density of 150 to 300 kg / m ３ The inorganic fiber sheet is preferably a sheet obtained by a wet papermaking method.

[0010] According to the present invention, an inorganic fiber sheet having excellent processability and fire resistance is provided.

[0011] Fig. 1 is a conceptual diagram of an inorganic fiber sheet according to the present disclosure, Fig. 2 is an SEM image of an inorganic fiber sheet according to Example 1, and Fig. 3 is an SEM image of an inorganic fiber sheet according to Comparative Example 4.

[0012] Hereinafter, when an upper limit value and a lower limit value are separately described, it is considered that a numerical range combining any upper limit value and any lower limit value is substantially disclosed.

[0013] In the following, unless otherwise specified, various measurements are carried out at room temperature (23° C.).

[0014] The structure / components, physical properties / properties, production method, and uses of the inorganic fiber sheet according to the present disclosure will be described below.

[0015] <<Structure / Components>> Figure 1 shows a conceptual diagram of an inorganic fiber sheet according to the present disclosure. As shown in Figure 1, the inorganic fiber sheet according to the present disclosure includes an organic binder (OB) that is attached in a web-like manner to the intertwining points between the mineral fibers (MF). In other words, as shown in Figure 1, the inorganic fiber sheet according to the present disclosure has a web-like film A1 that is provided near the intertwining points between the mineral fibers (MF) and exists only in a portion of the area partitioned by the intertwining of the mineral fibers (MF). By providing this web-like organic binder (OB) film, the bonding strength between the mineral fibers (MF) is effectively increased even when the content of the organic component is reduced, making it easier to obtain an inorganic fiber sheet that combines punching processability with thermal insulation / fire resistance, etc.

[0016] The inorganic fiber sheet according to the present disclosure may have a film A2 that exists across all of the regions partitioned by the entanglement of mineral fibers, as shown in FIG.

[0017] <Mineral Fiber> The mineral fiber may be a natural mineral fiber such as sepiolite, but is preferably an artificial mineral fiber. More specifically, the mineral fiber preferably includes one or more fibers selected from the group consisting of rock wool, glass wool, alkaline earth silicate wool, glass fiber, and alumina fiber. The use of such mineral fibers makes it easy to improve the heat insulating property / fire resistance.

[0018] The fiber diameter of the mineral fibers is preferably 1.0 μm or more, 2.0 μm or more, or 3.0 μm or more, and is preferably 50 μm or less, 30 μm or less, or 20 μm or less. The average fiber diameter of the mineral fibers is calculated as the average diameter of 50 mineral fibers observed under an optical microscope in the inorganic fiber sheet.

[0019] The fiber length and aspect ratio of the mineral fibers are not particularly limited as long as they are long enough to form an inorganic fiber sheet. The fiber length of the mineral fibers (average fiber length of 50 fibers) is, for example, 0.1 mm or more, 0.5 mm or more, or 1.0 mm or more.

[0020] The content of mineral fibers in the inorganic fiber sheet is preferably 80.0 mass% or more, 85.0 mass% or more, or 90.0 mass% or more, and is preferably 96.0 mass% or less, or 95.0 mass% or less. By setting the content in such a range, it is easy to improve fire resistance and heat insulation properties.

[0021] <Organic Binder> The organic binder is not particularly limited, and any appropriate one can be used.

[0022] Examples of organic components constituting the organic binder include resins such as acrylic resin, polyurethane, polyolefin, polyacrylamide, polyvinyl chloride, polyester, styrene-acrylic acid ester copolymer, vinyl acetate-(meth)acrylic acid ester copolymer, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol copolymer. Furthermore, the organic component constituting the organic binder may be a rubber component such as styrene-butadiene rubber (SBR) or nitrile rubber (NBR). These may be used alone or in combination of two or more.

[0023] The organic binder preferably contains an acrylic resin. By using an acrylic resin as the organic binder, an inorganic fiber sheet having excellent durability can be easily obtained.

[0024] Examples of the acrylic resin include conventionally known acrylic resins.

[0025] Examples of monomers constituting the acrylic resin include (meth)acrylic acid ester monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and polypropylene glycol mono(meth)acrylate.

[0026] The monomer constituting the acrylic resin may be a monomer having a carboxyl group such as (meth)acrylic acid; a monomer having a hydroxyl group such as 4-hydroxybutyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, or tetrahydrofurfuryl(meth)acrylate; a monomer having a glycidyl group such as glycidyl(meth)acrylate; a monomer having an amide group such as hydroxyethyl(meth)acrylamide, isopropyl(meth)acrylamide, or dimethylaminopropyl(meth)acrylamide; a monomer having a nitrile group such as (meth)acrylonitrile; or other monomers.

[0027] The monomers constituting the acrylic resin can be used alone or in combination of two or more.

[0028] The organic binder may contain a component (e.g., polyacrylamide) that functions as a paper strength enhancer. When the organic binder contains the paper strength enhancer, the structure of the fiber sheet becomes favorable, and it is easy to improve the effects of mechanical properties, heat insulation, etc. Furthermore, it is preferable that the organic binder contains an acrylic resin and a paper strength enhancer (e.g., polyacrylamide).

[0029] The organic binder preferably contains an organic binder having a glass transition temperature (Tg) of 10°C or lower, 5°C or lower, 0°C or lower, -5°C or lower, or -10°C or lower. The lower limit of the glass transition temperature is not particularly limited, but is, for example, -70°C, -50°C, or -30°C. By setting the glass transition temperature within this range, an inorganic fiber sheet with excellent processability is easily obtained. Furthermore, by setting the glass transition temperature within this range, the flexibility and fluidity of the organic binder become appropriate, making it easier to form a web-like film in the inorganic fiber sheet manufacturing method described below. The glass transition temperature can be measured using a DSC device. More specifically, when the total amount of organic binder is 100.0 mass%, the organic binder having such a glass transition temperature is preferably contained in an amount of 50.0 mass% or higher, 60.0 mass% or higher, 70.0 mass% or higher, 80.0 mass% or higher, or 90.0 mass% or higher.

[0030] The content of the organic binder in the inorganic fiber sheet is preferably 2.0 mass% or more, 3.0 mass% or more, or 4.0 mass% or more, and is preferably 10.0 mass% or less, 9.0 mass% or less, or 8.0 mass% or less. By setting the content of the organic binder within such ranges, it is easy to obtain an inorganic fiber sheet that is excellent in heat resistance / fire resistance and punching processability.

[0031] <Other Components> The inorganic fiber sheet may contain other components. Examples of other components include conventionally known additives that can be blended into inorganic fiber sheets. Specific examples of other components include inorganic flocculants, dispersants, thickeners, antifoaming agents, inorganic binders, inorganic fibers other than mineral fibers, organic fibers, etc. These other components are present in the inorganic fiber sheet in a form held by an organic binder or in a form attached to the surface of the mineral fibers.

[0032] The inorganic fiber sheet preferably contains an inorganic flocculant as another component. The inorganic flocculant is preferably one or more selected from the group consisting of aluminum sulfate, polyferric sulfate, PAC (polyaluminum chloride), and ferric chloride. The use of these inorganic flocculants facilitates the production of inorganic fiber sheets with excellent punching processability. Furthermore, since these inorganic flocculants are acidic in liquid, adding these inorganic flocculants to a raw material composition containing water and an organic binder during the production of an inorganic fiber sheet lowers the pH, making the organic binder unstable in the liquid (causing emulsification breakdown of the emulsion). This allows the organic binder to adhere appropriately to the mineral fibers, making it easier to obtain an inorganic fiber sheet with a web-like organic binder.

[0033] The content of the inorganic flocculant in the inorganic fiber sheet is, for example, preferably 0.1 mass% or more, 0.5 mass% or more, or 1.0 mass% or more, and is preferably 10.0 mass% or less, 8.0 mass% or less, or 5.0 mass% or less.

[0034] <<Physical Properties / Characteristics>> <Ignition Loss> The ignition loss of the inorganic fiber sheet is preferably 2.0 to 10.0% by mass. By setting the ignition loss in this range, it is easy to obtain an inorganic fiber sheet with excellent strength, fire resistance, etc. The ignition loss is measured as follows: (1) After holding the test sample in a thermostatic chamber at 130°C for 15 minutes, the mass of the test sample (pre-test sample mass) is measured. (2) The test sample is heated in a small electric furnace (tabletop electric furnace) at 525°C for 30 minutes (the small electric furnace is heated to 525°C in advance, and the test sample is placed in after the temperature inside the furnace has stabilized). (3) After holding the test sample in a desiccator for 60 minutes, the mass of the test sample (post-test sample mass) is measured. (4) The ignition loss (mass %) is calculated using the following formula: Ignition Loss = [(Pre-test sample mass - Post-test sample mass) / Pre-test sample mass] x 100

[0035] <Density> The density of the inorganic fiber sheet is 150 kg / m ３ Above, 180kg / m ３ or more, or 200 kg / m ３The upper limit of the density is, for example, 500 kg / m or more. ３ , 400 kg / m ３ , or 300 kg / m ３ By setting the density within this range, it is easy to ensure the desired sheet strength and stiffness.

[0036] <Thickness> The thickness of the inorganic fiber sheet may be adjusted appropriately depending on the intended use and the like.

[0037] <<Manufacturing Method>> The inorganic fiber sheet is preferably a sheet obtained by a wet papermaking method. Hereinafter, a method for manufacturing an inorganic fiber sheet using the wet papermaking method will be described.

[0038] The wet papermaking method is obtained by carrying out a papermaking process and a drying process. The wet papermaking method preferably includes a preparation process of preparing a raw material composition to be used in the papermaking process. Each of these processes will be described below.

[0039] <Mixing Step> The mixing step is a step of dispersing mineral fibers and an organic binder in water, and further adding other components (such as a paper strength agent or an inorganic flocculant) as necessary to prepare a raw material composition.

[0040] Here, the organic binder is preferably an emulsion in which fine particles of an organic component (polymer) are dispersed in water, and a predetermined inorganic flocculant is further used in combination. In this case, as described above, the pH of the raw material composition decreases, causing the emulsion of the organic binder to be demulsified. As a result, the fine particles of the organic component aggregate to form an organic binder film. It is believed that during the papermaking process, the organic binder film dispersed in the raw material composition and the mineral fibers become entangled, and the organic binder film adheres to the intertwining points between the mineral fibers, or part of the organic binder film attached across multiple mineral fibers is destroyed, resulting in an inorganic fiber sheet in which web-like organic binders are attached to the intertwining points between the mineral fibers.

[0041] <Papermaking Process> The papermaking process is a process in which the raw material composition is made into paper using a known papermaking machine to form a moisture-containing fiber sheet (wet sheet).

[0042] The paper machine used in the papermaking process is not particularly limited and may be any paper machine that is applied to general papermaking techniques, but examples include Fourdrinier paper machines, short wire paper machines, cylinder paper machines, tilting paper machines, twin-wire paper machines, and combination paper machines made by combining the same or different types of paper machines from these.

[0043] After the papermaking step, a pressing step may be carried out in which pressure is applied to the obtained wet sheet to perform mechanical preliminary dewatering and adjust the thickness and density of the wet sheet.

[0044] <Drying Step> The drying step is a step of drying the moisture contained in the wet sheet to obtain an inorganic fiber sheet.

[0045] The drying device used in the drying step is not particularly limited and may be a general device used for drying inorganic fiber sheets. Examples of the drying device include Yankee dryers, rotary dryers, hand dryers, air dryers, cylinder dryers, suction drum dryers, and infrared dryers. These may be used alone or in combination of two or more.

[0046] The drying temperature and time may be set so that the moisture content of the wet sheet falls within a predetermined range (for example, less than 1% by mass of the total weight of the sheet). The drying temperature is, for example, 100 to 200°C.

[0047] The inorganic fiber sheet obtained by the drying step may be subjected to a processing step (for example, a step of punching or corrugating) to form it into a desired shape.

[0048] <<Applications>> The inorganic fiber sheet according to the present disclosure can be applied to various applications because it is easy to process and has excellent heat insulating properties, etc. The inorganic fiber sheet according to the present disclosure is preferably used, for example, as a heat insulating material for construction, home appliances, industrial equipment, etc., a sealing material for gas water heaters, oil water heaters, etc.

[0049] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0050] <<Example 1>> <Mixing Step> A raw material composition was prepared by mixing mineral fibers, an organic binder, and an inorganic flocculant in the blending ratios shown in Table 1. In Table 1, the acrylic resin used was in the form of an acrylic emulsion.

[0051] <Papermaking Process> A paper sheet was obtained from the raw material composition using an inclined short wire papermaking machine.

[0052] <Drying Step> The sheet was dried using a Yankee dryer (140°C, 2 minutes) and an air dryer (200°C, 4 minutes) to obtain an inorganic fiber sheet according to Example 1.

[0053] <<Examples 2-10, Comparative Examples 1-4>> Mineral fibers, an organic binder, and an inorganic flocculant were mixed in the blending ratios shown in Tables 1 and 2 to prepare raw material compositions, and inorganic fiber sheets were produced in the same manner as in Example 1.

[0054] <<Structure / Physical Properties / Characteristics>> Tables 1 and 2 show the density, thickness, and ignition loss of the inorganic fiber sheets according to each of the examples and comparative examples.

[0055] Fig. 2 shows an SEM image of the inorganic fiber sheet according to Example 1, and Fig. 3 shows an SEM image of the inorganic fiber sheet according to Comparative Example 4. As shown in Fig. 2, the inorganic fiber sheet according to Example 1 had web-like films formed near the intertwining points of the mineral fibers, while the inorganic fiber sheet according to Comparative Example 4 did not have web-like films formed near the intertwining points of the mineral fibers. The inorganic fiber sheets according to Examples 2 to 10 and Comparative Examples 1 to 3 had web-like films formed near the intertwining points of the mineral fibers, similar to Example 1.

[0056] <<Evaluation>> <Punching processability> After punching the inorganic sheet with a Thomson die, the surface of the piece was visually inspected and evaluated as follows. The evaluation results are shown in Tables 1 and 2. A: No cracks were observed. B: Fine cracks were observed within a range that would not cause problems in practical use. C: Cracks that could cause problems in practical use were observed.

[0057] <Fire resistance> The condition of the inorganic fiber sheet was visually inspected after applying a flame from a gas burner to the inorganic fiber sheet for 5 seconds, and evaluated as follows. The evaluation results are shown in Tables 1 and 2. A: No dents were observed in the area where the flame was applied. B: Dent was observed in the area where the flame was applied, but no through holes were observed. C: Through holes were observed in the area where the flame was applied.

[0058] <Overall Evaluation> A rating for each evaluation was assigned an "overall evaluation of A+," a rating that included a B in any evaluation and no C in any evaluation was assigned an "overall evaluation of B," and a rating that included a C in any evaluation was assigned an "overall evaluation of C."

[0059]

[0060]

[0061] The inorganic fiber sheet according to the present disclosure is easy to process and has excellent heat insulating properties, and is therefore useful as a heat insulating material used in construction, home appliances, industrial equipment, etc., and as a sealing material used in gas water heaters, oil water heaters, etc. CROSS-REFERENCE TO RELATED APPLICATIONS

[0062] This application claims priority based on Japanese Patent Application No. 2024-23346, filed with the Japan Patent Office on February 20, 2024, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. An inorganic fiber sheet comprising mineral fibers and an organic binder, wherein the content of the mineral fibers in the inorganic fiber sheet is 80.0% by mass or more, the ignition loss of the inorganic fiber sheet (525°C, 30 minutes) is 2.0 to 10.0% by mass, and the organic binder is adhered in a web-like manner to the intertwining points of the mineral fibers.

2. The inorganic fiber sheet according to claim 1, wherein the glass transition temperature of said organic binder is 10°C or lower.

3. The inorganic fiber sheet according to claim 1, wherein said organic binder comprises an acrylic resin.

4. The inorganic fiber sheet according to claim 1, which contains an inorganic flocculant.

5. The inorganic fiber sheet according to claim 4, wherein the inorganic flocculant comprises at least one selected from the group consisting of aluminum sulfate, polyferric sulfate, PAC (polyaluminum chloride), and ferric chloride.

6. The inorganic fiber sheet according to claim 1 or 2, wherein the mineral fibers comprise at least one type selected from the group consisting of rock wool, glass wool, alkaline earth silicate wool, glass fiber, and alumina fiber.

7. Density: 150-300 kg / m ３ 3. The inorganic fiber sheet according to claim 1 or 2, wherein 8. The inorganic fiber sheet according to claim 1 or 2, which is a sheet obtained by a wet papermaking method.

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