INORGANIC FIBER SHEET

Abstract

To provide an inorganic fiber sheet with high workability, which is also excellent in tackiness or adhesiveness when a pressure-sensitive adhesive or an adhesive has been applied thereto. The inorganic fiber sheet is a non-woven fabric containing inorganic fibers. The inorganic fiber sheet has a thickness T of 1 mm or more and contains shots derived from inorganic fibers and having a diameter of 45 ?m or more. The shots included in the inorganic fiber sheet is distributed in a sheet thickness direction as represented by Formula 1. Provided that Formula 1 is 1?Y/X? 0.11, where X represents a total weight of the shots in the inorganic fiber sheet per unit area / a total weight of the inorganic fiber sheet per unit area, and Y represents a weight of the shots per unit area included in the inorganic fiber sheet from which a portion having a thickness t and satisfying 0?t?s is removed, provided, however, that 0.10 mm?s?0.55 mm, with a wire side surface of the inorganic fiber sheet as a reference surface / a weight per unit area of the inorganic fiber sheet from which the portion having the thickness t is removed with the wire side surface of the inorganic fiber sheet as the reference surface.

Claims

1. An inorganic fiber sheet comprising a non-woven fabric containing inorganic fibers, wherein the inorganic fiber sheet has a thickness T of 1 mm or more, the inorganic fiber sheet includes shots derived from inorganic fibers and having a diameter of 45 ?m or more, and the shots included in the inorganic fiber sheet are distributed in a sheet thickness direction as represented by Expression 1 stated below:
1?Y/X?0.11(Expression 1) where X represents a total weight of the shots in the inorganic fiber sheet per unit area / a total weight of the inorganic fiber sheet per unit area, and Y represents a weight of the shots per unit area included in the inorganic fiber sheet from which a portion having a thickness t and satisfying 0?t?s is removed, provided, however, that 0.10 mm?s?0.55 mm, with a wire side surface of the inorganic fiber sheet as a reference surface / a weight per unit area of the inorganic fiber sheet from which the portion having the thickness t is removed with the wire side surface of the inorganic fiber sheet as the reference surface.

2. The inorganic fiber sheet according to claim 1, wherein a fiber length of the inorganic fibers is 600 ?m or more.

3. The inorganic fiber sheet according to claim 1, wherein a content of an organic component in the inorganic fiber sheet is 5.4 to 10.1 mass % based on a total amount of the inorganic fiber sheet.

4. The inorganic fiber sheet according to claim 2, wherein a content of an organic component in the inorganic fiber sheet is 5.4 to 10.1 mass % based on a total amount of the inorganic fiber sheet.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0019] FIG. 1 is a conceptual diagram of an apparatus of manufacturing an inorganic fiber sheet.

DESCRIPTION OF EMBODIMENTS

[0020] Hereinafter, an inorganic fiber sheet and the method of manufacturing an inorganic fiber sheet will be described in detail, but the present invention is not limited to the following description at all.

[0021] In the present invention, the physical properties, evaluation, and the like of the inorganic fiber sheet are measured for a sample after being left to stand for 12 hours in an atmosphere of 23? C./50% RH unless otherwise specified.

<<<<Inorganic Fiber Sheet>>>>

[0022] The inorganic fiber sheet includes at least inorganic fibers and shots derived from the inorganic fibers. The inorganic fiber sheet may contain other components. The inorganic fiber sheet may include other layers, and for example, an adhesive layer or a pressure-sensitive adhesive layer may be laminated.

<<<Structure>>

<<Density>>

[0023] The density of the inorganic fiber sheet is preferably 50 to 1000 kg/m.sup.3, more preferably 100 to 500 kg/m.sup.3, and particularly preferably 150 to 300 kg/m.sup.3. The inorganic fiber sheet having a density within the above-described range can prevent shots from falling off and have the improved mechanical strength and heat insulating properties.

<<Thickness>

[0024] A 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 shots that will be described later and to obtain sufficient heat insulating properties.

<<<Components>

<<Inorganic Fiber>>

[0025] The material constituting the inorganic fibers is not particularly limited provided that it can be formed into an inorganic fiber sheet. Examples of the material include metal fibers such as stainless steel fibers, nickel fibers, copper fibers, aluminum fibers, silver fibers, gold fibers, and titanium fibers, glass fibers, carbon fibers, silica fibers, rock wool, slag wool, alumina fibers, and ceramic fibers. The inorganic fibers may include only one, or two or more of the above.

<Fiber Length>

[0026] The fiber length of the inorganic fibers is preferably 500 ?m or more, more preferably 600 ?m or more, still more preferably 1000 to 3000 ?m, and particularly preferably 1000 to 2000 ?m. With the fiber length of the inorganic fibers set within the above-described range, wet strength such as durability against wire release and tear resistance can be secured while preventing deterioration of formation due to entanglement of long fibers.

<Fiber Diameter>

[0027] The fiber diameter of the inorganic fibers is preferably 1 to 50 ?m, and more preferably 1 to 30 ?m. With the fiber diameter of the inorganic fibers set within the above-described range, aggregate effect can be obtained, and the strength attributable to entanglement of fibers can be secured while preventing deterioration of formation.

[0028] The fiber length of the inorganic fibers is measured by the following method. First, 0.1 g of a sample or a sample burned at 900? C. in the case where the sample is a sheet is dispersed in 10 g of water, and the dispersion liquid is stirred with a spatula for 1 minute. Next, one drop of the dispersion liquid is dropped on the preparation using a dropper, and the dropped dispersion liquid is covered with a cover film. Thereafter, fibers are observed with a microscope at a magnification of 100 times, 20 fibers are measured in descending order of fiber length, and an average value of the 20 fibers is taken as the fiber length of the sample.

[0029] The fiber diameter of the inorganic fibers is measured by the following method. First, 0.1 g of a sample or a sample burned at 900? C. in the case where the sample is a sheet is dispersed in 10 g of water, and the dispersion liquid is stirred with a spatula for 1 minute. Next, one drop of the dispersion liquid is dropped on the preparation using a dropper, and the dropped dispersion liquid is covered with a cover film. Thereafter, fibers are observed with a microscope at a magnification of 500 times, 20 fibers are randomly selected and measured, and an average value of the 20 fibers is taken as the fiber diameter of the sample.

<<Shot>>

[0030] The inorganic fiber sheet includes a predetermined amount of shots (shots derived from inorganic fibers) having a diameter of 45 ?m or more. The upper limit of the diameter of the shot is not particularly limited because the diameter of the shot depends on the diameter of the inorganic fiber, and is 5000 ?m, 1000 ?m, 500 ?m or the like.

[0031] More specifically, shots each having a diameter of 45 ?m or more are distributed in the sheet thickness direction in the inorganic fiber sheet as represented by the following Expression 1.

1?Y/X?0.11(Expression 1) [0032] where X represents a total weight of the shots in the inorganic fiber sheet per unit area / a total weight of the inorganic fiber sheet per unit area, and Y represents a weight of the shots per unit area included in the inorganic fiber sheet from which a portion having a thickness t and satisfying 0?t?s (provided, however, that 0.10 mm?s? 0.55 mm) is removed, with a wire side surface of the inorganic fiber sheet as a reference surface / a weight per unit area of the inorganic fiber sheet from which the portion having the thickness t is removed with the wire side surface of the inorganic fiber sheet as the reference surface.

[0033] When 1?Y/X is valid to the third decimal place in terms of significant figures, 1?Y/X? 0.11 can be replaced with 1?Y/X<0.115.

[0034] In Expression 1, 1?Y/X is more preferably 0.06 or less.

[0035] In Expression 1, the lower limit value of 1?Y/X is not particularly limited, but is, for example, ?0.11, ?0.10, ?0.5, or 0.00. With 1?Y/X set within the above-described range, bending elasticity, workability of the felt side surface, and the like can be improved, and prevention of the occurrence of delamination can be facilitated.

[0036] Here, the weight of the shot in the inorganic fiber sheet per unit area can be measured in accordance with JIS R 3311-1991.

[0037] More specifically, the method of measuring the shot content in the inorganic fiber sheet is as follows.

[0038] A sample having a weight of 2 g is burned in an electric furnace at 900? C. for 30 minutes and incinerated.

[0039] The weight of the combustion residue and the weight of a stainless steel sieve with a sieve opening size of 45 ?m (JIS Z-8801) are measured.

[0040] The combustion residue is transferred to the sieve, and the fibers are dropped while being pressurized and pulverized.

[0041] The shot content is calculated from the shot weight remaining on the sieve and the combustion residue weight.

[0042] The inorganic fiber sheet from which a portion having a thickness t and satisfying 0?t?s (provided, however, that 0.10 mm?s? 0.55 mm) is removed, with a wire side surface of the inorganic fiber sheet as a reference surface is prepared as follows.

[0043] No. 5000NS (tape manufactured by Nitto Denko Corporation) is attached to a 5 cm-square sample, and the sample and the tape are laminated at a roll temperature of 80? C., a pressure of 0.05 MPa, and a speed of 0.4 m/min.

[0044] Thereafter, the sample is left to stand in a room temperature environment for 10 minutes, and the tape is peeled off over 5 seconds to remove a part in the thickness direction.

[0045] In this inorganic fiber sheet, the distribution of shots is different between the surface or the vicinity thereof and the center of thickness or the vicinity thereof in a single layer. That is, in the inorganic fiber sheet, a high density region having a high shot content is formed at or near the center of thickness, whereas a low density region having a low shot content is formed at or near the surface. In a single layer of the inorganic fiber sheet, properties at or near the center of thickness and properties at or near the surface are optimally different. As a result, the workability and the like can be improved while excellent heat insulating properties and mechanical properties are exhibited. Furthermore, contamination and the like at the production site due to dropping off of shots can be prevented, and the working environment and workability can be improved.

<<Other Components>>

[0046] Examples of other components include organic components such as a binder, a paper strength enhancer and an organic fiber, and other known components.

[0047] The content of the organic component in the inorganic fiber sheet is preferably 1.0 to 15.0 mass %, more preferably 2.0 to 12.5 mass %, and particularly preferably 5.4 to 10.1 mass %, based on the total amount of the inorganic fiber sheet. With the content of the organic component set within the above-described range, the occurrence of cracking of the inorganic fiber sheet can be prevent, and the flame retardancy can be enhanced.

[0048] The content of the organic component in the inorganic fiber sheet is measured by the method in accordance with JIS-P 8252. More specific description will now be given.

[0049] A sample having a weight of 2 g is placed in a crucible and dried at 120? ? C. for 10 minutes, and then the weight of the sample is measured.

[0050] Thereafter, the sample is burned in an electric furnace at 900? ? C. for 30 minutes and incinerated.

[0051] The weight reduction rate is calculated from the weight of the combustion residue and the weight after drying.

<<<<Method of Manufacturing Inorganic Fiber Sheet>>>>

[0052] Hereinafter, preferred examples of the method of manufacturing an inorganic fiber sheet will be described, but the method of manufacturing an inorganic fiber sheet is not limited thereto at all.

[0053] The inorganic fiber sheet can be manufactured by wet papermaking, and preferably can be manufactured using an inclined paper-making machine.

[0054] As an example, a specific method of manufacturing an inorganic fiber sheet using the inclined paper-making machine illustrated in FIG. 1 will be described.

[0055] First, a paper-making material solution containing a dispersion medium and inorganic fibers is guided into a headbox.

[0056] Next, the paper-making material solution is supplied to the headbox while controlling the supply amount of the paper-making material solution with a pump (not illustrated) to form a pool of the paper-making material solution.

[0057] Next, the paper-making material solution is convected by a water flow generator provided in a pool of the paper-making material solution.

[0058] The paper-making material solution in the pool comes into contact with a forming wire traveling obliquely upward, and is dewatered (dispersion medium is sucked) from below the forming wire, whereby a solid content (inorganic fiber) is deposited on the paper-making material solution, and an inorganic fiber sheet in a wet paper state is formed. As illustrated in FIG. 1, the dewatering start position can be controlled by providing a plurality of legs (No. 1 leg, No. 2 leg, and the like) in dewatering.

[0059] Finally, the inorganic fiber sheet in a wet paper state is passed through a drying device (dryer or the like) to obtain base paper of the inorganic fiber sheet.

[0060] The base paper of the inorganic fiber sheet may be wound into a roll shape, as necessary.

[0061] The inorganic fiber sheet may be appropriately cut into a desired size.

[0062] In order to set the shot distribution (1?Y/X) in the inorganic fiber sheet to a predetermined range, it is sufficient that the following operation be performed: [0063] (1) Bring the dewatering start position close to the raw material charging opening, whereby 1?Y/X can be reduced; and [0064] (2) Increase the blowing pressure of the water flow generation mechanism (increase the flow velocity of the water flow), whereby 1?Y/X can be reduced.

EXAMPLES

[0065] Next, the inorganic fiber sheet 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.

<<Raw Materials>>

<Inorganic Fiber>

(Inorganic Fiber A)

[0066] Superwool Plus manufactured by Shin-Nippon Thermal Ceramics Corporation, Material: alkaline earth silicate (AES) [0067] Fiber diameter: 2.0 to 14.8 ?m [0068] Fiber length: 530 to 3000 ?m

(Inorganic Fiber B)

[0069] ISOWOOL BSSR 1300 manufactured by Isolite Insulating Products Co., Ltd. [0070] Material: alkaline earth silicate (AES) [0071] Fiber diameter: 2.7 to 13 ?m [0072] Fiber length: 450 to 3000 ?m

(Inorganic Fiber C)

[0073] ISOFRAX BULK S17 manufactured by Isolite Insulating Products Co., Ltd. [0074] Material: alkaline earth silicate (AES) [0075] Fiber diameter: 1.5 to 11 ?m [0076] Fiber length: 850 to 3200 ?m

<Other Component>

[0077] Acrylate latex (binder)

<<Manufacturing Method>>

[0078] Inorganic fiber sheets according to examples and comparative examples were manufactured by using the apparatus illustrated in FIG. 1. The inorganic fibers to be used, the paper-making material solution in the headbox (concentration of the aqueous dispersion of the above-described components), the blowing pressure of the water flow generator (Left side: back side of the page of FIG. 1, Right side: front side of the page of FIG. 1), the valve opening degree (adjustment of the supply rate of the paper-making material solution), and the dewatering start position were set as listed in Table 1.

<<<Evaluation>>>

[0079] Measurement of the shot content, calculation of 1?Y/X, and measurement of the organic content (ig. loss A (%)) for the inorganic fiber sheet were performed in accordance with the above-described method.

[0080] Furthermore, the workability, flame retardancy, bending suitability, and wet strength (durability against wire release) of the inorganic fiber sheet were measured in accordance with the following methods.

[0081] The results are listed in Table 2.

<<Workability>>

[0082] No. 5000NS (tape manufactured by Nitto Denko Corporation) is attached to a 5 cm-square sample, and the sample and the tape are laminated at a roll temperature of 80? C., a pressure of 0.05 MPa, and a speed of 0.4 m/min.

[0083] Thereafter, the sample is left to stand in a room temperature environment for 10 minutes, and the tape is peeled off over 5 seconds to remove a part in the thickness direction.

[0084] The initial sample thickness is assumed to be A (mm), and the thickness transferred to No. 5000NS is assumed to be B (mm).

[0085] When the transfer rate is defined as C (%)=B/A*100, workability is determined for the value of C on the basis of the following numerical criteria. [0086] ?: C is 16 or more [0087] ?: C is 9.0 or more and less than 16 [0088] ?: C is less than 9.0

<<Flame Retardancy>>

[0089] A sample having a weight of 2 g is placed in an electric furnace at each specified temperature and burned for 5 minutes to be incinerated.

[0090] The temperature zone in which the sample is ignited until the sample is incinerated after being put into the electric furnace is recorded. [0091] ?: Not ignited before reaching 900? C., or not ignited [0092] ?: Ignited at 700? C. [0093] ?: Ignited at 500? C.

<<Bending Suitability>>

[0094] A sample having a size of 25 mm?250 mm is prepared, and a surface thereof on the wire side at the time of papermaking is wound around a cylindrical object having a specified diameter for 1 minute.

[0095] At that time, the diameter of the cylindrical object when the sample is cracked is recorded. [0096] ?: No crack is generated at ? 60 (mm) [0097] ?: No crack is generated at ? 100 (mm) [0098] ?: Crack is generated at @ 100 (mm)

<<Wet Strength (Wire Releasability)>>

[0099] At the time of papermaking, moisture was removed by a dewatering suction, the sample was then released from the wire, and thereafter the end was gripped at two points and the state when the sample was lifted was checked (sample size: 25 cm square). [0100] ?: There is no remaining portion of the sheet obtained by papermaking on the wire, and breaking of paper does not occur at the time of lifting. [0101] ?: There is no remaining portion of the sheet obtained by papermaking on the wire, or breaking of paper does not occur at the time of lifting. [0102] ?: There is a remaining portion of the sheet obtained by papermaking on the wire, and breaking of paper occurs at the time of lifting.

TABLE-US-00001 TABLE 1 Concen- Blowing Sheet Fiber tration in Pressure (MPa) Dewatering Leg Valve Thickness on Classi- Inorganic Density Length Headbox Left Side/ Start Opening Adhesive Side fication Fiber (kg/m.sup.3) (?m) (mass %) Right Side Position Degree (?m) X Y 1 ? Y/X Example 1 A 202 1151 0.339 0.10/0.10 No. 1 Leg ? Opening 357 0.326 0.312 0.043 Degree Example 2 A 196 1053 0.191 0.08/0.09 No. 1 Leg 2/6 Opening 307 0.424 0.377 0.111 Degree Example 3 B 221 1029 0.231 0.07/0.07 No. 1 Leg ? Opening 456 0.279 0.301 ?0.079 Degree Example 4 C 206 1242 0.199 0.13/0.13 No. 1 Leg ? Opening 440 0.444 0.438 0.014 Degree Example 5 C 201 1289 0.208 0.07/0.07 No. 1 Leg ? Opening 283 0.486 0.457 0.060 Degree Example 6 B 230 1054 0.231 0.07/0.07 No. 1 Leg ? Opening 371 0.321 0.311 0.031 Degree Example 7 B 238 1033 0.231 0.07/0.07 No. 1 Leg ? Opening 295 0.283 0.277 0.042 Degree Example 8 B 227 1001 0.230 0.07/0.07 No. 1 Leg ? Opening 518 0.298 0.294 0.013 Degree Example 9 B 244 1167 0.230 0.07/0.07 No. 1 Leg ? Opening 462 0.351 0.337 0.040 Degree Example 10 B 216 625 0.230 0.07/0.07 No. 1 Leg ? Opening 491 0.381 0.36 0.055 Degree Example 11 B 245 515 0.230 0.07/0.07 No. 1 Leg ? Opening 451 0.384 0.365 0.049 Degree Example 12 B 239 559 0.231 0.07/0.07 No. 1 Leg ? Opening 531 0.288 0.277 0.039 Degree Comparative B 218 1075 0.231 0.00/0.00 No. 2 Leg ? Opening 135 0.351 0.299 0.149 Example 1 Degree Comparative B 229 1112 0.230 0.00/0.00 No. 2 Leg ? Opening 179 0.331 0.271 0.181 Example 2 Degree Comparative C 209 1192 0.198 0.00/0.00 No. 2 Leg ? Opening 219 0.371 0.321 0.135 Example 3 Degree Comparative B 233 1015 0.231 0.00/0.00 No. 2 Leg ? Opening 168 0.411 0.346 0.158 Example 4 Degree Comparative B 251 533 0.231 0.00/0.00 No. 2 Leg ? Opening 231 0.365 0.323 0.116 Example 5 Degree Comparative B 245 965 0.165 0.10/0.10 No. 2 Leg ? Opening 230 0.433 0.378 0.127 Example 6 Degree Comparative B 243 589 0.231 0.00/0.00 No. 2 Leg ? Opening 256 0.388 0.341 0.121 Example 7 Degree

TABLE-US-00002 TABLE 2 Flame Workability Igloss Retardancy Bending Wet Classification Evaluation A (%) (Ignitability) Suitability Strength Example 1 ? 6.9 ? ? ? Example 2 ? 6.1 ? ? ? Example 3 ? 6.4 ? ? ? Example 4 ? 7.3 ? ? ? Example 5 ? 7.9 ? ? ? Example 6 ? 10.1 ? ? ? Example 7 ? 5.4 ? ? ? Example 8 ? 2.1 ? X ? Example 9 ? 11 ? ? ? Example 10 ? 7.2 ? ? ? Example 11 ? 3.5 ? X X Example 12 ? 15 X X X Comparative X 4.5 ? X ? Example 1 Comparative X 7.6 ? ? ? Example 2 Comparative X 7.2 ? ? ? Example 3 Comparative X 11.4 ? ? ? Example 4 Comparative X 3.6 ? X X Example 5 Comparative X 5.8 ? ? ? Example 6 Comparative X 13.1 ? ? X Example 7