JP2010209501A - Inorganic fiber blanket and method for producing the same - Google Patents

Abstract

To provide an inorganic fiber blanket that is inexpensive and has a small variation in basis weight, and a method for producing the same.
An inorganic fiber blanket 1 includes a long fiber layer 2 mainly composed of inorganic long fibers having an average fiber length of 3000 μm or more and a short fiber mainly composed of short fibers having an average fiber length of 2000 μm or less. And a fiber layer 3. By performing the needling, a part of the long fibers of the long fiber layer 2 enter the short fiber layer 3, thereby tangling the long fiber layer 2 and the short fiber layer 3 together. As the short fibers, those obtained by defibrating the end material discharged from the long fiber sheet cutting step (may be a punching step) when manufacturing an alumina long fiber product are used.
[Selection] Figure 1

Description

  The present invention relates to a blanket of inorganic fibers such as alumina fibers and a method for producing the same.

  As a method for producing an alumina fiber, a method is known in which a spinning solution containing an aluminum compound is spun to form an alumina fiber precursor, which is fired to obtain an alumina fiber. As the spinning solution, an aluminum compound is mainly used and various auxiliary components are contained therein. Auxiliary components include those that are the constituent elements of the finally obtained alumina fibers such as metal compounds, and those that adjust the properties of the spinning solution such as water-soluble polymer compounds. For example, a spinning solution prepared by adding silica sol and polyvinyl alcohol to a basic aluminum chloride aqueous solution obtained by dissolving aluminum in hydrochloric acid is used.

  The spinning solution is generally spun by a blowing method. In this blowing method, a spinning solution is supplied from a nozzle in a high-speed spinning airflow. The spinning solution is stretched in a spinning air flow and loses moisture to solidify to become an alumina fiber precursor.

  The formed alumina fiber precursor is accumulated to obtain an alumina fiber precursor sliver which is an alumina fiber precursor sheet having a predetermined basis weight, that is, a weight per unit area. This precursor sliver is fired to obtain an alumina fiber sheet having a stable oxide state and high crystallinity. In addition, an alumina fiber sheet excellent in mechanical strength can be obtained by needling the precursor sheet before firing (see Japanese Patent Publication No. 1-38901, Japanese Patent Publication No. 6-67780, Japanese Patent Laid-Open No. 2000-80547, etc.).

  Since such an alumina fiber sheet has extremely high heat resistance, it is widely used as a gripping material for an exhaust gas purification device of an automobile (paragraph 0009 of the above Japanese Patent Laid-Open No. 2000-80547).

1-38901 JP 6-67780 JP2000-80547

i) As described above, the alumina fiber sheet obtained by spinning and accumulating the alumina fiber precursor and calcining has a slightly larger basis weight variation than the papermaking sheet due to uneven accumulation during accumulation.

  When used as a gripping material for an automobile exhaust gas purification device, in order to hold the honeycomb catalyst firmly and stably in the casing over a long period of time, the variation in the basis weight of the alumina fiber sheet constituting the gripping material is as much as possible. It is desired to make the gripping force small and uniform.

  An object of the present invention is to provide an inorganic fiber blanket having a small basis weight variation and a method for producing the same.

ii) In the process of producing an alumina fiber sheet product, the alumina fiber sheet original fabric obtained by firing is usually cut into standard dimensions (including punching). The scraps generated by this cutting are discarded and are wasted.

  In one aspect of the present invention, an object of the present invention is to provide an inorganic fiber blanket capable of reusing such offcuts and a method for producing the same.

  The inorganic fiber blanket of claim 1 is a blanket having a long fiber layer mainly composed of inorganic long fibers having an average fiber length of 3000 μm or more and a short fiber layer mainly composed of short fibers having an average fiber length of 2000 μm or less. The short fiber layer is interposed between the long fiber layers, a part of the long fibers of the long fiber layer enter the short fiber layer, and the long fiber layer and the short fiber layer are integrated. It is characterized by that.

  The inorganic fiber blanket according to claim 2 is characterized in that, in claim 1, some of the long fibers of the long fiber layer have entered the short fiber layer by needling.

  The inorganic fiber blanket according to claim 3 is characterized in that, in claim 1 or 2, the content of the short fibers is 10 to 90% by weight of the total amount of the long fibers and the short fibers.

  The inorganic fiber blanket according to claim 4 is the inorganic fiber blanket according to any one of claims 1 to 3, wherein the blanket thickness is 4 to 70 mm, and the thickness of one long fiber layer is 0.1 to 3 mm. The short fiber layer has a thickness of 0.05 to 34 mm.

The inorganic fiber blanket according to claim 5 is characterized in that, in any one of claims 1 to 4, the basis weight of the inorganic fiber blanket is 400 to 5000 g / m ² .

The inorganic fiber blanket according to claim 6 is characterized in that, in any one of claims 1 to 5, the inorganic fiber blanket has a bulk density of 0.06 to 0.2 g / cm ³ .

The inorganic fiber blanket according to claim 7 is characterized in that, in any one of claims 1 to 7, the inorganic fiber is an inorganic fiber having an Al ₂ O ₃ content of 65% by weight or more. .

  The method for producing an inorganic fiber blanket according to claim 8 comprises: a fiber layer mainly composed of inorganic fibers is defibrated, and a short fiber layer forming step of forming a short fiber layer by wet or dry method; and a solution of an inorganic raw material compound is spun. And forming a fiber precursor, collecting the fiber precursor to form a sliver that is a sheet-like fiber precursor layer, and combining the fiber precursor layer and the short fiber layer with each other between the fiber precursor layers. A step of stacking so that a short fiber layer is interposed between them, and a step of forming a stack, and a needling step of applying a needling to the stack to integrate the fiber precursor layer and the short fiber layer , Firing the integrated stack, and converting the fiber precursor into an inorganic long fiber having an average fiber length of 3000 μm or more.

  The inorganic fiber blanket of the present invention has a long fiber layer mainly composed of inorganic long fibers having an average fiber length of 3000 μm or more and a short fiber layer mainly composed of inorganic short fibers having an average fiber length of 2000 μm or less. Since the short fiber layer can generally have a smaller basis weight variation than the long fiber layer, the inorganic fiber blanket of the present invention has a smaller basis weight variation than an inorganic fiber blanket comprising only the long fiber layer. For example, according to the present invention, when an inorganic fiber blanket is divided into a rectangular grid of 7 sections in the width direction, 3 sections in the length direction and 80 mm × 210 mm square, and the basis weight of the section is measured, The triple value of the standard deviation with respect to the average value ([3σ / weighted average value] × 100) can be reduced to about 7% or less. Moreover, since the inorganic fiber blanket has a short fiber layer that can hardly suppress the thickness of the blanket by needling, the inorganic fiber blanket having a large thickness is compared with an inorganic fiber blanket composed of only the long fiber layer. It can be configured at low cost.

  Even with short fibers alone, blankets cannot be made even if needles are applied. In addition, a binder is required for molding into a mat. However, in the case of the present invention, since the long fiber layer and the short fiber layer are integrated, the molding is easier and easier to handle than the short fiber layer alone. In addition, since the short fiber layer is sandwiched between the long fiber layers, detachment of the short fibers from the short fiber layer, such as detachment, is prevented.

  In order to allow a part of the long fibers to enter the short fiber layer, it is simple and effective to perform needling.

  In the present invention, alumina fiber is suitable as the inorganic fiber.

As the above short fiber, an inorganic long fiber having an average fiber length of 3000 μm or more is defibrated,
It is preferable that the short fiber is formed into a sheet by a dry method or a wet method. These short fiber sheets have a small basis weight variation. In this case, the inorganic fiber blanket comprises a short fiber sheet forming step of defibrating a blanket mainly composed of inorganic long fibers having an average fiber diameter of 3000 μm or more to form a short fiber sheet, and a solution of the inorganic raw material compound. Is formed into a fiber precursor, the fiber precursor is collected to form a sliver that is a sheet-like fiber precursor layer, and the fiber precursor layer and the short fiber layer are formed into a fiber precursor. A process of stacking so that a short fiber layer is interposed between the layers to form a stack, and a needling in which the fiber precursor layer and the short fiber layer are integrated by needling the stack. It can be produced by a method for producing an inorganic fiber blanket having a step and a step of firing the integrated stack and forming a fiber precursor as an inorganic long fiber layer having an average fiber length of 3000 μm or more.

  As the inorganic long fiber to be defibrated, a blanket end material composed of a long fiber layer discharged from a cutting process in producing an inorganic long fiber product is suitable. Since this scrap has been discarded almost without being used in the past, reusing it as a short fiber layer eliminates waste of resources and reduces the amount of industrial waste. be able to.

It is typical sectional drawing of the inorganic fiber blanket which concerns on embodiment of this invention. Both (a) and (b) are schematic cross-sectional views of the mat before firing. It is explanatory drawing of the stacking method of the mat | matte before baking. It is explanatory drawing of the stacking method of the mat | matte before baking. It is sectional drawing which shows another formation method of a laminated body. It is a SEM photograph of a blanket.

  Hereinafter, the present invention will be described in more detail.

  FIG. 1 is a schematic cross-sectional view of an inorganic fiber blanket according to an embodiment of the present invention. The inorganic fiber blanket 1 includes a long fiber layer 2 mainly composed of inorganic long fibers having an average fiber length of 3000 μm or more and a short fiber layer 3 mainly composed of short fibers having an average fiber length of 2000 μm or less, which are alternately stacked. And have. The outermost layer (the uppermost layer and the lowermost layer in FIG. 1) is the long fiber layer 2.

  In this embodiment, by performing needling, a part of the long fibers of the long fiber layer 2 enters the short fiber layer 3, thereby entangled the long fiber layer 2 and the short fiber layer 3, It is united.

  The content of short fibers in the inorganic fiber blanket of the present invention is preferably 10 to 90% by weight of the total amount of long fibers and short fibers. Preferably it is 20 to 80 weight%, More preferably, it is 30 to 70 weight%.

Alumina fibers are preferred as the inorganic long fibers, but are not limited thereto. In addition to the alumina fibers, ceramic fibers are also suitable as the inorganic short fibers. In addition, as a representative example of the alumina fiber, in addition to the alumina fiber having an SiO ₂ content of 5 wt% or less, that is, an Al ₂ O ₃ content of 95 wt% or more, the SiO ₂ content is 5 to 30 wt%. Alumina-silica-based polycrystalline short fibers whose remainder is Al ₂ O ₃ can be mentioned. In particular, mullite fibers having a SiO ₂ content of about 28% by weight and an Al ₂ O ₃ content of 72% by weight are one of the most frequently used alumina fibers because of their excellent high-temperature thermal stability. In general, ceramic fiber is a general term for amorphous alumina-silica fiber produced by a melting method, Al ₂ O ₃ content is approximately 40 to 60% by weight, the balance is silica, and zirconia or chromium. Are added in small amounts, and these are also suitably used as inorganic short fibers after defibration to a desired size.

  The long fiber layer only needs to be mainly composed of inorganic long fibers having an average fiber length of 3000 μm or more (for example, 98% or more by weight), and may contain some other inorganic fibers. The short fiber layer may be mainly composed of inorganic short fibers having an average fiber length of 2000 μm or less (for example, 98% or more by weight), and may contain some other inorganic fibers.

The fiber length of the long fibers of this inorganic fiber blanket is preferably 3 mm or more, particularly preferably 150 mm or more. Further, the fiber length of the short fibers is preferably 20 μm or more, particularly 100 μm or more. The thickness is preferably 4 to 70 mm, and in the case of an inorganic fiber blanket having this thickness, the number of long fiber layers is preferably 2 or more, particularly 4 or more, and the thickness per layer is 0.00. 1 to 3 mm, particularly about 0.2 to 2 mm is preferable. The thickness of each short fiber layer is preferably 0.05 to 34 mm, particularly preferably about 0.1 to 5 mm. The blanket weight is preferably 400 to 5000 g / m ² , and the density is preferably 0.06 to 0.2 g / cm ² .

  In the present invention, although not limited to profit, from the viewpoint of eliminating waste of resources and reducing the amount of industrial waste, as a short fiber, side cutting for width adjustment when producing an alumina fiber product What was obtained by defibrating the end material discharged from the process (may be a punching process) is preferable. Furthermore, as the short fiber, a general ceramic fiber containing alumina can be suitably used. Any ceramic fiber can be suitably used as long as the average fiber length is 2000 μm or less, regardless of the product shape. A method for producing an alumina long fiber product having an average fiber length of 3000 μm or more will be described.

  The alumina fiber precursor obtained by spinning a solution mainly composed of an aluminum compound is accumulated so as to be deposited on the accumulating device to form a sliver of the alumina fiber precursor, and this sliver is left as one layer or A plurality of layers or continuously drawn out from the stacking device and sent to a folding device, folded to a predetermined width and stacked to form a laminated sheet made of an alumina fiber precursor, and then fired to obtain an alumina fiber sheet.

Preparation of the spinning solution and production of the alumina fiber precursor from the spinning solution can be performed according to conventional methods. As the spinning solution, for example, in a basic aluminum chloride aqueous solution prepared by dissolving aluminum in hydrochloric acid, the composition of the finally obtained alumina fiber is preferably 65 as Al ₂ O ₃ : SiO ₂ (weight ratio). Silica sol is added so as to be in a range of ˜98: 35 to 2, particularly preferably 70 to 97:30. This is because if the silicon component is too much, fiberization is easy, but the heat resistance is remarkably lowered. On the other hand, if the silicon component is too little, the fiber tends to become brittle. Further, in order to improve the spinnability, preferably, a water-soluble organic polymer such as polyvinyl alcohol, polyethylene glycol, starch, cellulose derivative or the like is added, and in some cases, a concentration operation is appropriately performed, so that the viscosity is usually 1 to 1000 poise. The adjusted one is used.

  The formation of the alumina fiber precursor from the spinning solution is preferably performed by a blowing method in which the spinning solution is supplied in a high-speed spinning airflow. There are two types of blowing method nozzles, one with a spinning fluid nozzle installed in an airflow nozzle that generates a spinning airflow, and one with a spinning fluid nozzle installed to supply spinning fluid from outside the spinning airflow. Any of them can be used. When spinning by the above-mentioned blowing method, an endless belt made of wire mesh is installed so as to be substantially perpendicular to the spinning air flow, and the spinning including the alumina fiber precursor formed thereon is rotated. It is preferable to collect and accumulate the alumina fiber precursor by colliding with an air flow.

  The sliver of the alumina fiber precursor formed on the accumulation device is continuously pulled out from the accumulation device, sent to the folding device, folded to a predetermined width and stacked, and continuously in a direction perpendicular to the folding direction. It is good also as a laminated sheet. Thereby, since the both ends of the width direction of a sliver are arrange | positioned inside the lamination sheet formed, the fabric weight of a lamination sheet becomes uniform over the whole lamination sheet.

  The laminate sheet of the alumina fiber precursor thus produced is converted into an alumina fiber sheet by firing by a conventional method. Firing is usually performed at 500 ° C. or higher, preferably 1000 to 1300 ° C. Further, when needling is applied to the laminated sheet prior to firing, an alumina fiber sheet having high mechanical strength in which the alumina fibers are also oriented in the thickness direction of the sheet can be obtained.

  When this alumina fiber sheet is cut to produce an alumina fiber product having a standard size, scraps such as cut scraps are produced.

  In order to produce a short fiber sheet from the end material, there is no particular limitation. For example, in the case of a dry method, first, the end material is defibrated by a defibrator to form short fibers, which are then used for pneumatic transportation. And send it out. In contrast, an endless belt made of wire mesh is installed so as to be substantially perpendicular, and while rotating this, an air stream containing short fibers is collided with this to collect the short fibers and convey them while pressing them with a roll. To make a sheet.

In the case of a wet method, the mill ends are first defibrated by a defibrator to form short fibers and then dispersed in a liquid, preferably water. In addition, it is preferable to contain a dispersing agent in this water. To prepare a water slurry the short fibers of about 3% by weight, the pulp was added to about 10% by weight relative to the short fibers as the binder, the sheet making method, a thickness of about 0.4 mm, a basis weight of about 70 g / m ² The short fiber sheet was obtained.

The basis weight of the short fiber sheet is preferably about 5 to 1000 g / m ^2, particularly about 10 to 300 g / m ² . In addition, the average fiber length of the alumina fiber is 2000 μm or less by the above defibrating treatment.

  Next, an alumina fiber precursor sliver that is an alumina long fiber precursor sheet laminated so as to sandwich the short fiber sheet will be described.

  The sliver which is this alumina long fiber precursor sheet | seat is formed by the same method as the alumina fiber precursor layer at the time of manufacturing said alumina fiber product.

The basis weight of the sliver 1 layer which is an alumina long fiber precursor sheet is preferably about 10 to 200 g / m ^2, particularly about 30 to 100 g / m ² . The above short fiber sheet is laminated so as to be sandwiched between the alumina long fiber precursor sliver to obtain a laminate having a desired basis weight, for example, about 400 to 5000 g / m ^2, particularly about 800 to 3500 g / m ² .

  As shown in FIG. 2, a mat 4 having a structure in which an alumina long fiber precursor sliver 2p and a short fiber sheet 3 narrower than the alumina long fiber precursor sliver are stacked is used. It is preferable that the mat 4 before firing is moved to the left and right as shown in FIG.

  For continuous stacking, as shown in FIG. 4, the pre-firing mat 4 is transferred from the transfer conveyor 7 to the swing conveyor 8, and the swing conveyor 8 is moved back and forth in the direction of the arrow X. It may be deposited on the heavy conveyor 9. By adjusting the feed speed of the mat 4 before firing, the swing speed of the swing conveyor 8, and the feed speed of the stacking conveyor 9, the number of stacked stages of the mat 4 before firing on the stacking conveyor 9 can be adjusted. it can.

  Instead of the method of stacking the pre-firing mats 4 having a two-layer structure shown in FIGS. 2 and 3, as shown in FIG. 5, a required number of alumina long fiber precursor slivers 11 on the stacking conveyor 10 and The stacked body 13 is also manufactured by a method of sequentially supplying and stacking the short fiber sheet 12 having a smaller number of sheets so that the short fiber sheet 12 is interposed between the alumina long fiber precursor sliver 11. Can do.

The stack formed as shown in FIG. 4 or FIG. 5 above is needled in the stacking direction so that the needle is inserted into each layer, and a part of the long fibers in the long fiber layer is contained in the short fiber layer. The long fiber precursor layer and the short fiber layer are entangled and integrated. The number of needling strokes may be about 1 to 50 strokes / cm ² .

  Thereafter, the laminated integrated product of the long fiber precursor layer and the short fiber layer is fired at 500 ° C. or more, preferably about 1000 to 1300 ° C. Thereby, the long fiber sheet and the short fiber sheet are alternately laminated and the respective layers are integrated by needling, and an inorganic fiber blanket with good handleability is obtained.

  The inorganic fiber blanket produced in this way includes not only the long fiber layer but also the short fiber layer, and the basis weight variation is smaller than that of the inorganic fiber blanket made of only the long fiber layer. In addition, the basis weight variation of a commercially available alumina long fiber laminate (inorganic fiber blanket is 7 sections in the width direction, 3 sections in the length direction, rectangular grid shape of 80 mm × 210 mm square, 80 mm × 210 mm square rectangular grid) In this case, the triple value of the standard deviation with respect to the average weight per unit area ([3σ / weight per unit area] × 100, hereinafter the same) is about 6 to 8%. In Example 1, it is 7.7%. On the other hand, according to the present invention, this variation can be 4 to 7% or less.

  Moreover, in this embodiment, since the short fiber layer is formed using the end material of the alumina long fiber product, the material cost of the short fiber layer is low, and the resource saving and the amount of industrial waste are reduced. be able to.

  In this inorganic fiber blanket, the outermost layer is a long fiber layer, so that the separation of short fibers is prevented. In addition, a short fiber alone cannot be used to form a blanket even if a needle is applied, and a binder or the like is required for molding into a mat shape. However, in the case of the present invention, since the long fiber layer and the short fiber layer are integrated, it has excellent shape retention even in the absence of a binder and is easy to handle.

  EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to description of these Examples, unless the summary is exceeded.

[Example 1]
<Fabrication of alumina fiber blanket edge material>
Alumina fiber blanket manufactured by Mitsubishi Plastics Co., Ltd. (trade name; Maftech MLS-2, composition is Al ₂ O ₃ 72 wt%, SiO ₂ 28 wt%). (Same product) was defibrated by a defibrating machine (feather mill defibrating machine) to obtain short fibers.

  As a result of microscopic observation, this short fiber had an average fiber length of about 400 μm.

To prepare a water slurry the short fibers of about 3% by weight, the pulp was added to about 10% by weight relative to the short fibers as the binder, the sheet making method, a thickness of about 0.4 mm, a basis weight of about 70 g / m ² The short fiber sheet was obtained.

<Formation of alumina long fiber precursor layer (sliver)>
An alumina long fiber precursor sliver was formed as follows.

The composition of the alumina fiber finally obtained silica sol in an aqueous solution of basic aluminum chloride (aluminum content 70 g / L, Al / Cl = 1.8 (atomic ratio)) is Al ₂ O ₃ : SiO ₂ = 72: 28 (Weight ratio), and after adding polyvinyl alcohol, it is concentrated to prepare a spinning solution having a viscosity of 20 poise and an alumina / silica content of about 30% by weight, and a blowing method using the spinning solution. Was spun in. A spinning airflow containing the formed alumina fiber precursor is collided with an endless belt made of a wire mesh to accumulate the alumina fiber precursor, and is relatively non-uniform with a basis weight of about 90 g / m ² , and the alumina fiber precursor is in-plane An alumina long fiber precursor sliver that was randomly oriented in the direction was obtained.

<Lamination and firing>
This alumina long fiber precursor sliver and a short fiber sheet having a narrower width were used as a mat before firing having a two-layer structure as shown in FIG. The mats before firing were alternately folded and stacked in 10 layers.

Then, it was needled at the number of shots of 8 shots / cm ² and fired under conditions of 1200 ° C. × 30 minutes to produce the inorganic fiber blanket of the present invention.

The inorganic fiber blanket has a thickness of 18.4 mm, a basis weight of 2290 g / m ² , and a basis weight variation of the inorganic fiber blanket is 7 sections in the width direction, 3 sections in the length direction, and a rectangular grid shape of 80 mm × 210 mm square In the case of partitioning into 80 mm × 210 mm square rectangular grids, the standard deviation was 3 times the standard deviation ([3σ / weight per unit area] × 100; hereinafter the same), which was 4.1%.

  Moreover, it has confirmed that the average fiber length of the long fiber of a long fiber layer was 3000 micrometers or more on average by SEM observation (photograph 1) of a cross section. The degree of crystallinity (mullite conversion) of the alumina fiber blanket after firing was 3%. The proportion of short fibers in the blanket is about 70% by weight.

The surface pressure of the blanket was 2.02 kgf / cm ² when the sample size was 50 mm × 50 mm and the sample was compressed to a density of 0.3 g / cm ³ . Further, the repulsive force when compressed to a density of 0.4 g / cm ³ was 5.27 kgf / cm ² .

The alumina fiber blanket had a tensile strength of 0.11 kgf / cm ² . Moreover, the tensile strength of the alumina fiber blanket after firing in the air at 800 ° C. for 2 hours was 0.10 kgf / cm ² . The shape retention after firing of this blanket was exactly the same as before firing and was good.

  The density of the long fibers in the thickness direction was confirmed by SEM observation (FIG. 6) to penetrate the long fibers in the thickness direction.

  The properties of this blanket are summarized in Table 1.

[Example 2]
An alumina fiber blanket was produced in the same manner as in Example 1 except that the mixing ratio of short fibers was 55% by weight and the basis weight of the alumina fiber blanket was 1752 g / m ² . Table 1 shows the properties of this blanket.

[Example 3]
An alumina fiber blanket was produced in the same manner as in Example 1 except that the mixing ratio of short fibers was 40% by weight and the basis weight of the alumina fiber blanket was 1478 g / m ² . Table 1 shows the properties of this blanket.

[Comparative Example 1]
An alumina fiber blanket was made in the same manner as in Example 1 except that no needling was performed. Table 1 shows the properties of this blanket.

[Comparative Example 2]
After making the short fiber layer in the same manner as in the short fiber layer making process in Example 1, a water-soluble latex as a binder was attached at a ratio of 4% by weight to produce a mat (thickness 5 mm) consisting only of short fibers. did. Table 1 shows the properties of this mat.

[Comparative Example 3]
Only about 30 layers of the alumina long fiber precursor layer obtained in the step of forming the alumina long fiber precursor layer in Example 1 were laminated, and similarly needling was performed at 8 strokes / cm ² and fired at 1200 ° C. for 30 minutes. An alumina fiber blanket consisting only of a long fiber layer was prototyped. Table 1 shows the properties of this blanket.

  As shown in Table 1, the alumina fiber blankets of Examples 1 to 3 have a smaller basis weight variation than Comparative Example 3 consisting only of long fibers. Moreover, the surface pressure characteristics of the alumina fiber blankets of Examples 1 to 3 are much better than those of the alumina fiber blanket made of only short fibers.

DESCRIPTION OF SYMBOLS 1 Blanket 2,11 Long fiber layer 2P Long fiber precursor layer 3,12 Short fiber layer 4 Mat before baking 13 Stack

Claims (9)

A blanket having a long fiber layer mainly composed of inorganic long fibers having an average fiber length of 3000 μm or more and a short fiber layer mainly composed of short fibers having an average fiber length of 2000 μm or less,
The short fiber layer is interposed between the long fiber layers, a part of the long fibers of the long fiber layer enter the short fiber layer, and the long fiber layer and the short fiber layer are integrated. An inorganic fiber blanket characterized by that.   The inorganic fiber blanket according to claim 1, wherein some long fibers of the long fiber layer have entered the short fiber layer by needling.   The inorganic fiber blanket according to claim 1 or 2, wherein the content of the short fibers is 10 to 90% by weight of the total amount of the long fibers and the short fibers.   In any 1 item | term of Claim 1 thru | or 3, blanket thickness is 4-70 mm, the thickness of one long fiber layer is 0.1-3 mm, and the thickness of one short fiber layer is 0.05. An inorganic fiber blanket characterized by being -34 mm. In any one of claims 1 to 4, the inorganic fiber blanket basis weight of the inorganic fiber blanket, characterized in that a 400~5000g / ^{m 2.} The inorganic fiber blanket according to any one of claims 1 to 5, wherein a bulk density of the inorganic fiber blanket is 0.06 to 0.2 g / cm ³ . The inorganic fiber blanket according to any one of claims 1 to 6, wherein the inorganic fiber is an inorganic fiber having an Al ₂ O ₃ content of 65% by weight or more. Short fiber layer forming step of defibrating a fiber layer mainly composed of inorganic fibers and forming a short fiber layer by a wet or dry method;
Spinning a solution of an inorganic raw material compound into a fiber precursor, collecting the fiber precursor and forming a sliver that is a sheet-like fiber precursor layer;
Stacking the fiber precursor layer and the short fiber layer so that the short fiber layer is interposed between the fiber precursor layers to form a stacked body;
A needling step of needling the stack to integrate the fiber precursor layer and the short fiber layer;
Firing the integrated stack, and making the fiber precursor an inorganic long fiber having an average fiber length of 3000 μm or more;
The manufacturing method of the inorganic fiber blanket which has this.   In Claim 8, the long fiber layer fibrillated in the said short fiber layer formation process is an end material of the inorganic fiber layer discharged | emitted from the process of cut | disconnecting an inorganic long fiber sheet and manufacturing an inorganic fiber product of a standard dimension. A method for producing an inorganic fiber blanket, characterized in that:

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