Inorganic fiber sheet

Abstract

Provided is an inorganic fiber sheet which has, inter alia, high workability and also demonstrates excellent in tackiness or adhesiveness when a tackiness agent or an adhesive has been applied thereto. This inorganic fiber sheet is unwoven fabric including inorganic fibers, the inorganic fiber sheet containing shots with a diameter of 45 μm or more derived from the inorganic fibers, wherein the thickness T of the inorganic fiber sheet is 1 mm or more, and the shots contained in the inorganic fiber sheet are distributed as represented by formula 1 in the sheet thickness direction. Provided that formula 1 is represented by "1-Y / X ≤ 0.12," wherein X represents "total weight of shots in inorganic fiber sheet per unit area" / "total weight of inorganic fiber sheet per unit area," and Y represents "weight of shots per unit area contained in inorganic fiber sheet from which part with thickness t satisfying 0 ≤ t ≤ s (provided that 0.10 mm ≤ s ≤ 0.55 mm) is removed, with wire side surface of inorganic fiber sheet serving as reference surface" / "weight per unit area of inorganic fiber sheet from which part with thickness t is removed, with wire side surface of inorganic fiber sheet serving as reference surface."

Description

Technical Field

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

Background Art

[0002] Currently, inorganic fiber sheets such as rock wool paper and AES (alkaline earth silicate) paper are widely used as heat insulating materials, heat insulation materials, etc.

[0003] These inorganic fiber sheets are made from inorganic fibers, and in the process of fiber production, particles called shots are inevitably formed at the ends of such inorganic fibers. When the fibers with shots are made into paper by conventional methods, the shots tend to localize near the surface of the fiber sheet. As a result of the shots localizing near the surface of the fiber sheet like this, when a coating agent such as an adhesive or a bonding agent is applied to the surface of the fiber sheet, the shots fall off together with the coating agent due to impact or the like, and problems such as not being able to obtain desirable adhesiveness or bonding properties have occurred.

[0004] In Patent Document 1, with respect to the problem related to the shots in the inorganic fiber sheet, it has been proposed to separate the shots in the manufacturing process and reduce the concentration of the shots themselves in the paper sheet. In addition, in Patent Document 2, a method has been proposed in which a paper raw material liquid in which inorganic fibers are dispersed is centrifuged, passed through a screen filter or the like, and the concentration of the shots is reduced.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, upon examining the inorganic fiber sheets described in Patent Documents 1 and 2, it was found that in some cases, sufficient processability and other properties could not be obtained.

[0007] Therefore, the present invention aims to provide an inorganic fiber sheet that has high processability and excellent tackiness or adhesion when coated with an adhesive or bonding agent.

[0008] Furthermore, the inorganic fiber sheets described in Patent Document 1 and Patent Document 2 both require a process to remove shot from the inorganic fibers, which leads to problems such as reduced production efficiency and decreased raw material yield.

[0009] Therefore, the second objective of the present invention is to provide an inorganic fiber sheet that can be manufactured without reducing production efficiency and raw material yield. [Means for solving the problem]

[0010] The inventors of this invention conducted thorough research into the above-mentioned problems and discovered that these problems can be solved by limiting the distribution of shots in the inorganic fiber sheet to a specific range, thereby completing the present invention. That is, the present invention is as follows.

[0011] The present invention relates to an inorganic fiber sheet, which is a nonwoven fabric containing inorganic fibers, The thickness T of the inorganic fiber sheet is 1 mm or more. The inorganic fiber sheet contains shots derived from inorganic fibers, with a diameter of 45 μm or more. The inorganic fiber sheet is characterized in that the shots contained in the inorganic fiber sheet are distributed in the sheet thickness direction as shown in the following formula 1. (Formula 1) 1 - Y / X ≤ 0.11 (In Equation 1, X represents the "total weight of shots in the inorganic fiber sheet per unit area" / "total weight of the inorganic fiber sheet per unit area". Also, Y represents the "weight of shots per unit area contained in the inorganic fiber sheet after removing the portion with a thickness of t satisfying 0 ≤ t ≤ s (where 0.10 mm ≤ s ≤ 0.55 mm), using the wire side surface of the inorganic fiber sheet as the reference plane" / "weight per unit area of ​​the inorganic fiber sheet after removing the portion with a thickness of t, using the wire side surface of the inorganic fiber sheet as the reference plane".)

[0012] It is preferable that the fiber length of the inorganic fiber is 600 μm or more. The content of organic components in the inorganic fiber sheet is preferably 5.4 to 10.1% by mass, based on the total amount of the inorganic fiber sheet. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide an inorganic fiber sheet that has high processability and excellent tackiness or adhesion when coated with an adhesive or bonding agent. Furthermore, this inorganic fiber sheet can be manufactured without reducing production efficiency or raw material yield. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a conceptual diagram of an apparatus for manufacturing inorganic fiber sheets. [Modes for carrying out the invention]

[0015] The inorganic fiber sheet and the method for manufacturing the inorganic fiber sheet will be described in detail below, but the present invention is not limited to the following.

[0016] In this invention, unless otherwise specified, the physical properties and evaluation of inorganic fiber sheets shall be measured on samples that have been left to stand for 12 hours in an atmosphere of 23°C / 50%RH.

[0017] <<<<Inorganic fiber sheet>>>> The inorganic fiber sheet contains at least inorganic fibers and shots derived from the inorganic fibers. The inorganic fiber sheet may also contain other components. The inorganic fiber sheet may also include other layers, for example, an adhesive layer or an adhesive layer may be laminated.

[0018] <<<Structure>>> <<Density>> The density of the inorganic fiber sheet is preferably 50 to 1000 kg / m 3 and more preferably 100 to 500 kg / m 3 and particularly preferably 150 to 300 kg / m 3 By setting the density of the inorganic fiber sheet within such a range, it is possible to prevent the shots from falling off and to improve the mechanical strength and heat insulation properties.

[0019] <<Thickness>> The thickness T of the inorganic fiber sheet is preferably 1 mm or more, more preferably 1 to 50 mm, and particularly preferably 2 to 6 mm in order to optimize the distribution state of the shots described below and to obtain sufficient heat insulation properties.

[0020] <<<Components>>> <<Inorganic fibers>> The material constituting the inorganic fibers is not particularly limited as long as it can be formed into an inorganic fiber sheet. For example, metal fibers such as stainless steel fibers, nickel fibers, copper fibers, aluminum fibers, silver fibers, gold fibers, titanium fibers, etc., glass fibers, carbon fibers, silica fibers, rock wool, slag wool, alumina fibers, ceramic fibers, etc. can be used. The inorganic fibers may be only one kind or may include two or more kinds.

[0021] <Fiber length> The fiber length of the inorganic fiber is preferably 500 μm or more, more preferably 600 μm or more, even more preferably 1000 to 3000 μm, and particularly preferably 1000 to 2000 μm. By setting the fiber length of the inorganic fiber within this range, it is possible to prevent deterioration of the fabric due to entanglement of long fibers while ensuring wet strength such as wire peel resistance and tear resistance.

[0022] <Fiber diameter> The fiber diameter of the inorganic fibers is preferably 1 to 50 μm, and more preferably 1 to 30 μm. By setting the fiber diameter of the inorganic fibers within this range, it is possible to obtain the aggregate effect while preventing deterioration of the fabric, and to ensure strength through fiber entanglement.

[0023] The fiber length of inorganic fibers is measured by the following method. First, 0.1 g of the sample (or, in the case of a sheet, a sample burned at 900°C) is dispersed in 10 g of water and stirred with a spatula for 1 minute. Next, one drop of the dispersion is placed onto a slide using a dropper and covered with a cover film. Then, the slide is observed under a microscope at 100x magnification, and 20 points are measured in descending order of fiber length. The average of these 20 points is taken as the fiber length of the sample. Furthermore, the fiber diameter of inorganic fibers is measured by the following method. First, 0.1 g of the sample, or in the case of a sheet, the sample burned at 900°C, is dispersed in 10 g of water and stirred with a spatula for 1 minute. Next, one drop of the dispersion is placed onto a slide using a dropper and covered with a cover film. Then, the slide is observed under a microscope at a magnification of 500x, and the fiber diameter is measured at 20 random points. The average of these 20 points is taken as the fiber diameter of the sample.

[0024] <<Shot>> The inorganic fiber sheet contains a predetermined amount of shots (shots derived from inorganic fibers) with a diameter of 45 μm or more. The upper limit of the shot diameter is not particularly limited as it depends on the diameter of the inorganic fiber, but it is 5000 μm, 1000 μm, or 500 μm, etc.

[0025] More specifically, shots with a diameter of 45 μm or more are distributed in the sheet thickness direction within the inorganic fiber sheet, as shown in Equation 1 below.

[0026] (Formula 1) 1 - Y / X ≤ 0.11 (In Equation 1, X represents the "total weight of shots in the inorganic fiber sheet per unit area" / "total weight of the inorganic fiber sheet per unit area". Also, Y represents the "weight of shots per unit area contained in the inorganic fiber sheet after removing the portion with a thickness of t satisfying 0 ≤ t ≤ s (where 0.10 mm ≤ s ≤ 0.55 mm), using the wire side surface of the inorganic fiber sheet as the reference plane" / "weight per unit area of ​​the inorganic fiber sheet after removing the portion with a thickness of t, using the wire side surface of the inorganic fiber sheet as the reference plane".) If we consider the expression to have significant figures up to the third decimal place, then "1-Y / X≦0.11" can be reinterpreted as "1-Y / X<0.115".

[0027] In Equation 1, it is even more preferable that "1-Y / X" is 0.06 or less. In Equation 1, the lower limit of "1-Y / X" is not particularly limited, but for example, it can be -0.11, -0.10, -0.5, or 0.00. By setting "1-Y / X" within such a range, it is possible to improve bending elasticity and processability of the felt side surface, and it also becomes easier to prevent delamination.

[0028] Here, the weight of shots in an inorganic fiber sheet per unit area can be measured in accordance with JIS R3311-1991. More specifically, the method for measuring the shot content in an inorganic fiber sheet is as follows: A 2g sample is burned in an electric furnace at 900°C for 30 minutes to incinerate it into ash. Measure the weight of the combustion residue and the weight of a 45μm mesh stainless steel sieve (JIS Z-8801). The combustion residue is transferred to a sieve, and the fibers are removed while the residue is crushed under pressure. The shot content is calculated from the weight of the shot and combustion residue remaining in the sieve.

[0029] Furthermore, an inorganic fiber sheet obtained by removing a portion of thickness t that satisfies 0 ≤ t ≤ s (where 0.10 mm ≤ s ≤ 0.55 mm) with the wire side surface of the inorganic fiber sheet as the reference plane is prepared as follows. A 5cm square sample is coated with No. 5000NS tape (manufactured by Nitto Denko Corporation) and laminated at a roll temperature of 80°C, a pressure of 0.05 MPa, and a speed of 0.4 m / min. Then, leave the sample at room temperature for 10 minutes, peel off the tape over 5 seconds, and remove a portion in the thickness direction.

[0030] This inorganic fiber sheet exhibits a different shot distribution within a single layer, particularly near the surface and near the center of its thickness. Specifically, a high-density region with a high shot content is formed near the center of the sheet's thickness, while a low-density region with a low shot content is formed near the surface. This optimal difference in properties between the center and surface of the inorganic fiber sheet allows for excellent thermal insulation and mechanical properties while simultaneously improving processability. Furthermore, it prevents contamination from shot shedding in production environments, improving the working environment and work efficiency.

[0031] <<Other ingredients>> Other components include known components such as binders, paper strength enhancers, and organic components such as organic fibers.

[0032] The content of organic components in the inorganic fiber sheet is preferably 1.0 to 15.0% by mass, more preferably 2.0 to 12.5% ​​by mass, and particularly preferably 5.4 to 10.1% by mass, based on the total amount of the inorganic fiber sheet. By setting the content of organic components within this range, it is possible to suppress the occurrence of cracking in the inorganic fiber sheet and to enhance its flame retardancy.

[0033] The organic component content in the inorganic fiber sheet is measured according to the method compliant with JIS-P8252. More specifically, it is as follows: Place 2g of the sample in a crucible, dry at 120°C for 10 minutes, and then measure its weight. Afterward, it is burned in an electric furnace at 900°C for 30 minutes to reduce it to ash. The weight loss rate is calculated from the weight of the combustion residue and the weight after drying.

[0034] << The following describes preferred examples of methods for manufacturing inorganic fiber sheets, but the methods for manufacturing inorganic fiber sheets are not limited to these.

[0035] Inorganic fiber sheets can be manufactured by wet papermaking, and preferably using an inclined paper machine.

[0036] As an example, we will explain a specific method for manufacturing an inorganic fiber sheet using the inclined paper machine shown in Figure 1. First, the papermaking raw material liquid, which contains the dispersion medium and inorganic fibers, is guided into the headbox. Next, the papermaking raw material liquid is supplied to the headbox while controlling the supply rate of the papermaking raw material liquid using a pump (not shown in the diagram), forming a pool (water reservoir) of the papermaking raw material liquid. Next, a water flow generator installed in the pool (puddle) of papermaking raw material liquid is used to create convection in the papermaking raw material liquid. The papermaking liquid in this pool comes into contact with a forming wire that runs diagonally upward, and dewatering (the dispersion medium is sucked in) occurs from below the forming wire. As a result, solid components (inorganic fibers) accumulate on the papermaking liquid, forming a wet inorganic fiber sheet. As shown in Figure 1, the dewatering start position can be controlled by providing multiple legs (No. 1 leg, No. 2 leg, etc.) during the dewatering process. Finally, the wet inorganic fiber sheet is passed through a drying device (such as a drying dryer) to obtain the base paper for the inorganic fiber sheet. The base paper for the inorganic fiber sheet may be wound into a roll as needed. The inorganic fiber sheet may be cut as appropriate to the desired size.

[0037] To set the shot distribution (1-Y / X) in an inorganic fiber sheet within a predetermined range, the following procedure should be performed. (1) By bringing the dewatering start position closer to the raw material input opening, the "1-Y / X" ratio can be reduced. (2) The "1-Y / X" can be reduced by increasing the discharge pressure of the water flow generation mechanism (increasing the flow velocity of the water flow). [Examples]

[0038] Next, the inorganic fiber sheets according to the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited thereto.

[0039] <<Raw materials>> <Inorganic Fibers> (Inorganic fiber A) Superwool Plus, manufactured by Shin Nippon Thermal Ceramics Co., Ltd. Material: Alkali Earth Silicate (AES) Fiber diameter: 2.0~14.8μm Fiber length: 530-3000 μm (Inorganic fiber B) IsoWool BSSR1300, manufactured by Isolite Industries Co., Ltd. Material: Alkali Earth Silicate (AES) Fiber diameter: 2.7~13μm Fiber length: 450-3000 μm (Inorganic fiber C) Isoflax Bulk S17, manufactured by Isolite Industries Co., Ltd. Material: Alkali Earth Silicate (AES) Fiber diameter: 1.5~11μm Fiber length: 850-3200 μm <Other ingredients> Acrylate-based latex (binder)

[0040] <<Manufacturing method>> Using the apparatus shown in Figure 1, inorganic fiber sheets according to the examples and comparative examples were manufactured, with the inorganic fibers used, the papermaking raw material liquid in the headbox (concentration of the aqueous dispersion of the above components), the blowing pressure of the water flow generator ("left side": far side of Figure 1, "right side": near side of Figure 1), the valve opening (adjustment of the supply speed of the papermaking raw material liquid), and the dewatering start position as shown in Table 1.

[0041] <<<Rating>>> Following the method described above, the shot content of the inorganic fiber sheet was measured, the "1-Y / X" ratio was calculated, and the organic content (Igloss A (%)) was measured. Furthermore, the processability, flame retardancy, bending suitability, and wet strength (wire peel resistance) of the inorganic fiber sheet were measured according to the method described below. The measurement results are shown in Table 2.

[0042] <<Workability>> A 5cm square sample is coated with No. 5000NS tape (manufactured by Nitto Denko Corporation) and laminated at a roll temperature of 80°C, a pressure of 0.05 MPa, and a speed of 0.4 m / min. Then, leave the sample at room temperature for 10 minutes, peel off the tape over 5 seconds, and remove a portion in the thickness direction. Let A (mm) be the initial sample thickness, and B (mm) be the thickness after transferring to No. 5000NS. When the transfer rate C(%) = B / A * 100, the processability of C will be judged based on the following numerical criteria. ◎:C=16 or more ○: C = 9.0 or higher and less than 16 ×: C = less than 9.0

[0043] <<Flame-retardant>> Place a 2g sample into an electric furnace at the specified temperature and burn it for 5 minutes to turn it into ash. Record the temperature range at which the sample ignites before it is turned to ash after being placed in the electric furnace. ○: Does not ignite up to 900℃, or does not ignite at all. △: Ignites at 700℃ ×: Ignites at 500℃

[0044] <Flexibility in bending> Prepare a sample with dimensions of 25 mm × 250 mm, and during the papermaking process, wrap the wire side around a cylindrical object with a specified diameter for 1 minute. At that time, record the diameter of the cylinder when cracks occur in the sample. ○: No cracks occur at Φ60 (mm). △: No cracks occur at Φ100 (mm). ×: Cracks occur at Φ100 (mm).

[0045] <<Wet strength (wire peeling resistance)>> During papermaking, after removing moisture by dehydration suction, after peeling the sample from the wire, hold the two ends and check the state when lifted (sample size: 25 cm square). ○: There is no remaining papermaking sheet on the wire, and it does not tear when lifted. △: There is no remaining papermaking sheet on the wire, or it does not tear when lifted. ×: There is remaining papermaking sheet on the wire, and it tears when lifted.

[0046] [[ID=​​​​​​​​​​​​

Claims

1. An inorganic fiber sheet which is a nonwoven fabric containing inorganic fibers, The thickness T of the inorganic fiber sheet is 1 mm or more. The inorganic fiber sheet contains shots derived from inorganic fibers, with a diameter of 45 μm or more. The inorganic fiber is a metal fiber, silica fiber, rock wool, slag wool, alumina fiber, or ceramic fiber. An inorganic fiber sheet characterized in that the shots contained in the inorganic fiber sheet are distributed in the sheet thickness direction as shown in the following formula 1. (Formula 1) 1-Y / X≦0.11 (In Equation 1, X represents the "total weight of shots in the inorganic fiber sheet per unit area" / "total weight of the inorganic fiber sheet per unit area". Also, Y represents the "weight of shots per unit area contained in the inorganic fiber sheet after removing the portion with a thickness t satisfying 0 ≤ t ≤ s (where 0.10 mm ≤ s ≤ 0.55 mm) with the wire side surface of the inorganic fiber sheet as the reference plane" / "weight per unit area of ​​the inorganic fiber sheet after removing the portion with a thickness t, with the wire side surface of the inorganic fiber sheet as the reference plane".)

2. The inorganic fiber sheet according to claim 1, wherein the fiber length of the inorganic fiber is 600 μm or more.

3. The inorganic fiber sheet according to claim 1 or 2, wherein the content of organic components in the inorganic fiber sheet is 5.4 to 10.1% by mass, based on the total amount of the inorganic fiber sheet.

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