阅读说明：本技术 无机纤维成型体、尾气净化装置用垫和尾气净化装置 (Inorganic fiber molded body, mat for exhaust gas purifying device, and exhaust gas purifying device ) 是由 木村祐介 森田宽一 河原一宪 于 2020-08-05 设计创作，主要内容包括：本发明提供可兼顾高面压和优异的剥离强度的无机纤维成型体、以及使用了该无机纤维成型体的尾气净化装置用垫和尾气净化装置。一种无机纤维成型体,其由无机纤维构成,具有沿厚度方向延伸的针迹,该针迹中存在沿该厚度方向延伸的由该无机纤维构成的纵丝条,其特征在于,该无机纤维成型体由规定的剥离试验测定的相对于每1个针迹的纵丝条的平均体积为1.0mm～(3)以上,或者相对于每1条纵丝条的平均体积为3.0mm～(3)以上。(The invention provides an inorganic fiber molded body which can achieve both high surface pressure and excellent peel strength, and a mat for an exhaust gas purifying device and an exhaust gas purifying device using the inorganic fiber molded body. An inorganic fiber molded article comprising an inorganic fiber and having stitches extending in a thickness direction, wherein longitudinal strands of the inorganic fiber extending in the thickness direction are present in the stitches, characterized in that the average volume of the longitudinal strands per 1 stitch measured by a predetermined peel test is 1.0mm 3 Above, or 3.0mm per 1 longitudinal filament average volume 3 The above.)

1. An inorganic fiber molded body comprising inorganic fibers and having stitches extending in a thickness direction, the stitches including longitudinal strands of the inorganic fibers extending in the thickness direction, the inorganic fiber molded body being characterized in that,

the inorganic fiber molded body had a basis weight of 1800g/m²In the above-mentioned manner,

when the following peeling test was performed, in the case where the effective longitudinal fibers were represented by the longitudinal fibers having a diameter of 100 μm or more and a protruding length of 2mm or more among all the longitudinal fibers protruding from one peeled surface and the other peeled surface in the range of 50mm × 50mm,

the inorganic fiber molded body satisfies at least one of the following characteristics (I) and (II),

(I) the average volume of the effective longitudinal threads per 1 stitch obtained by dividing the total volume of the portions of the effective longitudinal threads protruding from the release surface in the range by the number of stitches in the range is 1.0mm³The above;

(II) the average volume of the portion protruding from the peeling surface per 1 effective longitudinal yarn in the range is 3.0mm³In the above-mentioned manner,

< peeling test >

A test piece 50mm wide and 150mm long was die-cut from an inorganic fiber molded article, a 30mm deep notch was cut at the thickness center of one end face of the test piece, both ends formed by the notch were supported by a holding jig, and then the test piece was set in a tensile testing machine, and both ends of the test piece were respectively pulled in opposite thickness directions at a speed of 500mm/min to be split into 2 pieces.

2. The inorganic fiber molding according to claim 1, wherein the stitch density is 1 piece/cm²About 30 pieces/cm²。

3. The inorganic fiber molded body according to claim 1 or 2, wherein the maximum peel strength obtained by the peel test as a load peak in the unit of N is 3.0N or more.

4. The inorganic fiber molded body according to claim 1 to 3, wherein the inorganic fiber is an alumina/silica fiber.

5. A mat for an exhaust gas purifying device, comprising the inorganic fiber molded body according to any one of claims 1 to 4.

6. An exhaust gas purifying apparatus comprising a catalyst support, a housing covering the outside of the catalyst support, and a mat attached between the catalyst support and the housing, characterized in that the mat is the mat according to claim 5.

Technical Field

The present invention relates to an inorganic fiber molded body obtained by needle punching. The present invention also relates to a holding material for a catalyst support of an exhaust gas purifying device, which is an exhaust gas purifying device mat made of the inorganic fiber molded body, and an exhaust gas purifying device provided with the exhaust gas purifying device mat.

Background

Molded bodies of inorganic fibers typified by ceramic fibers have been used in applications where they are exposed to high temperatures, such as industrial heat-insulating materials, refractories, and sealing materials. And also as a mat (catalyst-holding material) for an automobile exhaust gas purifying device. The catalyst holding member is a buffer material for an exhaust gas purifying device that is wound around the catalyst support when the catalyst support is housed in the metal case and is attached between the catalyst support and the metal case (GAP).

As an inorganic fiber molded body constituting the catalyst holding member, for example, an inorganic short fiber assembly for a holding member (catalyst holding member) composed of an alumina fiber laminated body disclosed in patent document 1 is known. However, in recent years, in order to improve the catalyst efficiency, the exhaust gas purification device tends to be disposed in a higher temperature portion directly below the engine. Therefore, since the amount of movement of the catalyst holding member due to compression and release of the catalyst holding member due to the operation and stop of the engine increases, it is considered that the conventional inorganic fiber molded body is likely to have a decreased repulsive force, and cannot cope with the increase in GAP at higher temperatures.

For example, patent document 2 discloses a holding sealing material made of alumina fibers having stitches formed thereon, wherein the alumina fibers contain 85 to 98 wt% of an alumina component and 15 to 2 wt% of a silica component, in order to maintain the holding force of the holding sealing material (catalyst holding material) at a higher temperature. And a holding sealing material having a surface pressure after a heat treatment test at a test temperature of 950 ℃ in a heating step of 65 to 99% of the surface pressure of the holding sealing material after the heat treatment test at a test temperature of 800 ℃.

Documents of the prior art

Patent document

Patent document 1: international publication No. 2004/003276

Patent document 2: japanese patent laid-open publication No. 2017-110564

However, the holding sealing material of patent document 2 has a problem that peeling is likely to occur when the holding sealing material is wound around a catalyst support and stored in a metal case, and thus is not practical.

Disclosure of Invention

Problems to be solved by the invention

In the inorganic fiber molded body obtained by needle-punching the collected inorganic fibers, it is considered that the surface pressure (surface pressure after high-temperature cycle) can be increased and the bounce durability (surface pressure retention rate after high-temperature cycle) can be increased by reducing the number of needles (the number of strokes) in the needle punching treatment and the restriction of the loose fibers. However, when the number of needles in the needle punching treatment is reduced to loosen the fiber constraint, the peel strength of the inorganic fiber molded body is lowered, and the inorganic fiber molded body is likely to be peeled off when pressed into a metal shell.

As described above, in the inorganic fiber molded body obtained by the needle punching treatment, there has been no inorganic fiber molded body that can exhibit a high surface pressure without impairing the peel strength. That is, an object of the present invention is to provide an inorganic fiber molded body which achieves both high surface pressure and excellent peel strength, and an exhaust gas purifying device mat and an exhaust gas purifying device using the inorganic fiber molded body.

Means for solving the problems

The present inventors paid attention to the form of a longitudinal yarn composed of inorganic fibers extending in the thickness direction of an inorganic fiber molded body. In the past, the average volume of the longitudinal yarn per 1 stitch of the longitudinal yarn in the inorganic fiber forming body is 0.01-0.6 mm³Left and right. The average volume of the yarn per 1 effective longitudinal yarn is 0.02 to 2.5mm³Left and right. The present inventors have found that if the inorganic fiber molded body has a larger average volume of the longitudinal yarns in a specific range, the longitudinal yarns are firmly formed and two opposite physical properties, i.e., surface pressure and peel strength, can be satisfied.

The gist of the inorganic fiber molded article of the present invention is as follows.

An inorganic fiber molded body comprising inorganic fibers and having stitches extending in a thickness direction, the stitches including longitudinal strands of the inorganic fibers extending in the thickness direction, the inorganic fiber molded body being characterized in that,

in the inorganic fiber molded body, a thermoplastic resin,

when the following peeling test was performed, in the case where the effective longitudinal fibers were represented by the longitudinal fibers having a diameter of 100 μm or more and a protruding length of 2mm or more among all the longitudinal fibers protruding from one peeled surface and the other peeled surface in the range of 50mm × 50mm,

satisfies at least one of the following characteristics (I) and (II).

(I) The average volume of the effective longitudinal threads per 1 stitch obtained by dividing the total volume of the portions of the effective longitudinal threads protruding from the release surface in the range by the number of stitches in the range is 1.0mm³The above.

(II) the average volume of the portion protruding from the peeling surface per 1 effective longitudinal yarn in the range is 3.0mm³The above.

< peeling test >

A test piece 50mm wide and 150mm long was die-cut from the inorganic fiber molding. Then, a notch having a depth of 30mm was cut at the center of the thickness of one end face of the test piece, and both ends formed by the notch were supported by a holding jig and then set in a tensile tester. The both ends of the test piece were pulled in opposite thickness directions at a speed of 500mm/min, and the test piece was split into 2 pieces.

In one embodiment of the present invention, the stitch density is 1 to 30 stitches/cm²。

In one embodiment of the present invention, the maximum peel strength obtained as the load peak (N) by the above peel strength test is 3.0N or more.

In one embodiment of the present invention, the inorganic fiber is an alumina/silica fiber.

The mat for an exhaust gas purifying device of the present invention is characterized by containing the inorganic fiber molded product of the present invention.

The exhaust gas purifying apparatus of the present invention comprises a catalyst support, a casing covering the outside of the catalyst support, and the mat for an exhaust gas purifying apparatus of the present invention installed between the catalyst support and the casing.

ADVANTAGEOUS EFFECTS OF INVENTION

The inorganic fiber molded body of the present invention satisfies at least one of the characteristics (I) and (II), and therefore, the fibers in the approximate thickness direction are strongly entangled with each other inside the inorganic fiber molded body, thereby having a high surface pressure and an excellent peel strength.

Drawings

Fig. 1 is an explanatory view of a peel strength test.

FIG. 2 is an explanatory view of a peel strength test piece.

Detailed Description

The embodiments of the present invention will be described in detail below.

The description of "a to b" indicating a numerical range means "a to b inclusive".

The upper limit and the lower limit of the numerical range in the present specification are included in the equivalent range of the present invention as long as the same operation and effect as those in the numerical range are obtained even when the upper limit and the lower limit are slightly out of the specific numerical range in the present invention.

[ inorganic fiber molded article ]

The inorganic fiber molded body of the present invention is an inorganic fiber molded body comprising inorganic fibers and having stitches extending in a thickness direction, the stitches including longitudinal strands of the inorganic fibers extending in the thickness direction,

in the inorganic fiber molded body, a thermoplastic resin,

when the following peeling test was performed, in the case where the effective longitudinal fibers were represented by the longitudinal fibers having a diameter of 100 μm or more and a protruding length of 2mm or more among all the longitudinal fibers protruding from one peeled surface and the other peeled surface in the range of 50mm × 50mm,

satisfies at least one of the following characteristics (I) and (II).

(I) The average volume of the effective longitudinal threads per 1 stitch obtained by dividing the total volume of the portions of the effective longitudinal threads protruding from the release surface in the range by the number of stitches in the range is 1.0mm³The above.

(II) the average volume of the portion protruding from the peeling surface per 1 effective longitudinal yarn in the range is 3.0mm³The above.

The inorganic fiber molded body of the present invention is an inorganic fiber molded body composed of inorganic fibers and subjected to a needle punching treatment. The inorganic fiber molded body is in the form of a mat having a predetermined thickness. Hereinafter, a surface perpendicular to the thickness direction of the inorganic fiber molded body is sometimes referred to as a mat surface. In addition, a side surface (surface in the thickness direction) perpendicular to the mat surface of the inorganic fiber molded body may be referred to as an end surface.

[ method for producing inorganic fiber molded article ]

The inorganic fiber molded article of the present invention can be produced by a method comprising the steps of: a step of obtaining a mat-like aggregate of inorganic fiber precursors by a sol-gel method; a step of subjecting the obtained mat-like aggregate of inorganic fiber precursors to a needling treatment; and a firing step of firing the mat-like aggregate of the inorganic fiber precursor after the needling treatment to produce an inorganic fiber molded body. However, the inorganic fiber molded article of the present invention can be produced by another method.

The following description will exemplify a method for producing an alumina/silica-based fiber molded body, and an example of the method for producing an inorganic fiber molded body is described, but the inorganic fiber molded body of the present invention is not limited to the alumina/silica-based fiber molded body at all, and may be a molded body composed of silica, zirconia, spinel, titania, or a composite fiber thereof as described above.

< spinning step >

In the production of a mat-like assembly of alumina/silica fibers by a sol-gel method, first, a spinning solution containing an alkaline aluminum chloride, a silicon compound, an organic polymer as a thickener, and water is spun by a jet spinning method to obtain an assembly of an alumina/silica fiber precursor.

Preparation of spinning solution

Basic aluminum chloride Al (OH)_3-xCl_xFor example, it can be prepared by dissolving metallic aluminum in hydrochloric acid or an aqueous solution of aluminum chloride. The value of x in the above formula is usually 0.45 to 0.54, preferably 0.5 to 0.53. As the silicon compound, silica sol is suitably used, and in addition, a water-soluble silicon compound such as tetraethyl silicate or a water-soluble siloxane derivative can be used. As the organic polymer, for example, a water-soluble polymer compound such as polyvinyl alcohol, polyethylene glycol, polyacrylamide, or the like is suitably used. The polymerization degree of these is usually 1000 to 3000.

With respect to the spinning dope, from alkalineThe ratio of aluminum in aluminum chloride to silicon derived from silicon compound is converted to Al₂O₃With SiO₂The weight ratio of (A) to (B) is usually 99:1 to 65:35, preferably 99:1 to 70:30, preferably 170 to 210g/L of aluminum, and 20 to 50g/L of organic polymer.

When the amount of the silicon compound in the spinning solution is less than the above range, α -alumina is likely to occur in alumina constituting the short fibers, and embrittlement of the short fibers is likely to occur due to coarsening of alumina particles. On the other hand, when the amount of the silicon compound in the dope is more than the above range, the silicon compound reacts with mullite (3 Al)₂O₃·2SiO₂) Silicon dioxide (SiO) formed therewith₂) The amount of (A) is increased, and the heat resistance is liable to be lowered.

When the concentration of aluminum in the dope is less than 170g/L or the concentration of the organic polymer is less than 20g/L, the dope cannot have an appropriate viscosity, and the fiber diameter of the obtained alumina/silica-based fiber becomes small. That is, the free water in the spinning solution is too much, so that the drying speed in spinning by the jet spinning method is slow, the stretching is excessively progressed, and the fiber diameter of the precursor fiber to be spun is changed, and short fibers having a predetermined average fiber diameter and a narrow fiber diameter distribution cannot be obtained. Further, when the concentration of aluminum is less than 170g/L, the productivity is lowered. On the other hand, when the concentration of aluminum exceeds 210g/L or when the concentration of the organic polymer exceeds 50g/L, the viscosity is too high, and the spinning dope cannot be formed. The preferable concentration of aluminum in the spinning solution is 180-200 g/L, and the preferable concentration of the organic polymer is 30-40 g/L.

The above spinning solution was prepared as follows: adding Al to alkaline aluminum chloride aqueous solution₂O₃:SiO₂The spinning dope is prepared by concentrating the concentrations of aluminum and the organic polymer to the above ranges in the amounts of the silicon compound and the organic polymer in proportion.

Jet spinning

Spinning (fiberization of a spinning solution) is generally carried out by a jet spinning method in which a spinning solution is supplied in a high-speed spinning gas flow, thereby obtaining an alumina short fiber precursor. The structure of the spinning nozzle used for the above-mentioned spinning is not particularly limited, and for example, as described in japanese patent No. 2602460, it is preferable that the air flow discharged from the air nozzle and the spinning liquid flow extruded from the spinning liquid supply nozzle form a parallel flow, and the parallel flow of air is sufficiently rectified to be in contact with the spinning liquid.

In addition, in spinning, it is preferable that a sufficiently drawn fiber is first formed from a spinning solution under conditions that suppress evaporation of water and decomposition of the spinning solution, and then the fiber is rapidly dried. Therefore, in the process from the formation of the fibers from the spinning solution to the arrival at the fiber catcher, it is preferable to change the atmosphere from a state in which the evaporation of water is suppressed to a state in which the evaporation of water is promoted.

The alumina/silica-based fiber precursor can be collected and accumulated as a continuous sheet-like accumulated body (thin-layer sheet) of the alumina/silica-based fiber precursor by an accumulation device having a structure in which an endless belt made of a wire mesh is provided so as to be substantially perpendicular to a spinning gas flow, and the endless belt is caused to collide with the spinning gas flow containing the alumina/silica-based fiber precursor while being rotated.

The basis weight of the thin layer sheet is 10-200 g/m²Particularly preferably 30 to 100g/m²The left and right sides are not limited thereto.

The thin-layer sheet recovered by the accumulating apparatus may be further laminated. Specifically, for example, a stacked body (stacked sheet) of inorganic fiber precursors can be formed by continuously drawing out a stacked body (thin-layer sheet) of inorganic fiber precursors, feeding the stacked body to a folding device, and continuously moving the stacked body in a direction perpendicular to the folding direction while folding the stacked body at a predetermined width. By laminating the thin-layer sheets in this manner, the basis weight (mass per unit area) of the laminated sheet becomes uniform over the entire sheet. As the folding device, the device described in Japanese patent laid-open No. 2000-80547 can be used.

The laminated sheet is formed by laminating thin-layer sheets preferably having 5 or more layers, more preferably 8 or more layers, and particularly preferably 10 to 80 layers. However, the number of layers is not limited to this.

< Process for adding needle punching Assistant >

The above-mentioned needling assistant is added to the laminated sheet of the alumina/silica-based fiber precursor obtained by spinning or the sheet surface of the laminated sheet as necessary. The needling aid is preferably attached to both sheet sides.

The needling assistant is not particularly limited as long as it has an action of reinforcing the yarn near the mat surface of the inorganic fiber precursor aggregate, and various coating agents, for example, acrylic polymer coating agents and the like can be used.

The inorganic fiber precursor mat-like assembly can be dried after the needling aid attachment. That is, the needling aid preferably forms a dry coating. The needling aid may be attached during the assembly of the inorganic fiber precursor.

A friction reducing agent (surfactant or emulsion) having an effect of reducing the friction between the needle and the fiber may be used in combination with the needle punching assistant. In this case, the order of use of the needling aid and the friction reducing agent is not particularly limited, and for example, it is preferable to perform coating (wet coating) by dissolving or dispersing the friction reducing agent in a solvent after the needling aid liquid is deposited.

< needling treatment Process >

After a needling assistant is added to the laminated sheet of the alumina/silica fiber precursor obtained by spinning as necessary, a needling treatment is performed in which a barbed needle is inserted into and pulled out of the laminated sheet. The needling treatment may be performed from either side or both sides. Preferably from both sides.

The needle is preferably inserted and extracted in a direction perpendicular to the sheet surface of the laminated sheet. The needle is inserted deeper than the center of the laminated sheet in the thickness direction. The needle may penetrate the laminated sheet in the thickness direction.

By performing the needling treatment in this manner, stitches are formed in the inorganic fiber molded body. That is, when the needle punching process of inserting and extracting the barbed needle into and from the inorganic fiber assembly is performed, at least a part of the fibers extend in the substantial thickness direction by the action of the needle at the portion where the needle is inserted and extracted. Thereby, stitches are formed on the surface of the inorganic fiber molded body. The yarn of inorganic fibers extending in the substantially thickness direction inside the inorganic fiber molded body subjected to the needle punching treatment is referred to as a longitudinal yarn.

The needling treatment is performed to adjust the bulk density, peel strength, surface pressure (surface pressure after high-temperature cycles), and durability of the repulsive force (surface pressure retention rate after high-temperature cycles) of the inorganic fiber molded body by forming longitudinal yarns.

The stitches may penetrate the inorganic fiber molded body or may penetrate from one mat surface and extend so as not to reach the other mat surface.

< firing Process >

The inorganic fiber molded body of the present invention is preferably a fired body of an inorganic fiber molded body obtained by firing an inorganic fiber precursor subjected to a needle punching treatment. Firing after the needling treatment is usually carried out at a temperature of 900 ℃ or higher, preferably 1000 to 1300 ℃. When the firing temperature is 900 ℃ or higher, crystallization is sufficiently progressed, and alumina/silica-based fibers having excellent strength can be obtained, and therefore, this is preferable. Further, when the firing temperature is 1300 ℃ or lower, the alumina/silica-based fiber having an appropriate strength can be obtained without excessively growing the grains of the fiber crystal, and therefore, it is preferable.

[ preferred constitution of inorganic fiber molded article ]

< inorganic fibers >

The inorganic fiber constituting the inorganic fiber molded body of the present invention is not particularly limited, and examples thereof include single or composite fibers of silica, alumina/silica, zirconia containing these, spinel, titania and the like, and alumina/silica-based fibers, particularly crystalline alumina/silica-based fibers, are preferable. The alumina/silica-based fiber preferably has an alumina/silica composition ratio (weight ratio) of 60 to 95/40 to 5, more preferably 70 to 84/30 to 16, and particularly preferably 70 to 76/30 to 24.

In addition, the inorganic fiber is preferably a short fiber. The average fiber diameter of the inorganic fibers is preferably 3 to 10 μm, and particularly preferably 5 to 8 μm. When the upper limit of the average fiber diameter of the inorganic fibers is in this range, the inorganic fiber molded article preferably has a moderate rebound force. The lower limit of the average fiber diameter of the inorganic fibers is preferably in this range because the amount of dust floating in the air can be suppressed.

< stitch Density >

Method for measuring stitch density

In one embodiment of the present invention, the inorganic fiber molded body is a fired body. In this case, the stitch density is the unit area (1 cm) of the inorganic fiber molded body after firing²) The number of stitches on the pad surface.

When visible light is irradiated to the mat surface of the inorganic fiber molded body, the amount of transmitted light at the stitches is larger than that at the regions other than the stitches, and therefore, the transmitted light is observed as a light spot on the release surface. The number of stitches is determined by counting the number of light spots and the number of longitudinal threads formed by transmission on the release surface.

That is, the number of stitches is determined by irradiating visible light to one surface of the inorganic fiber molded body and counting the number of light spots and the number of vertical yarns formed by transmission on the release surface.

Preferred range of stitch Density

In the present invention, the inorganic fiber molded article has a unit area (1 cm)²) The number of stitches (stitch density) on the pad surface of (1) is preferably 1/cm on the average value of the entire pad surface²More preferably 3 pieces/cm or more²More than or equal to, and more preferably 5/cm²More than, particularly preferably 8/cm²Above, preferably 30 pieces/cm²Less, more preferably 28 pieces/cm²The number of the molecules is preferably 25/cm²The number of the molecules is preferably 20/cm or less²The following. When the number of stitches is in such a range, the inorganic fiber molded article can maintain a high surface pressure, and is particularly preferably used for applications requiring durability of a repulsive force such as a mat for an exhaust gas purifying apparatus.

In the present invention, the average diameter of the stitches is preferably 10 to 400 times, particularly 30 to 300 times, and particularly 50 to 200 times the average fiber diameter of the inorganic fibers constituting the inorganic fiber molded body. When the average diameter of the stitches is in this range, a longitudinal yarn with less damage to the fiber can be formed, and therefore, the inorganic fiber molded body can maintain a high surface pressure, and is particularly preferably used for applications requiring durability against the elastic force, such as a mat for an exhaust gas purifying device.

< basis weight and thickness of inorganic fiber molded body >

The basis weight (mass per unit area) of the inorganic fiber molded article of the present invention is suitably determined depending on the application, and is preferably 600g/m²Above, more preferably above 700g/m²Further preferably more than 800g/m²Ultra, further preferably greater than 900g/m²Particularly preferably more than 1000g/m². The basis weight of the inorganic fiber molded article of the present invention is not particularly limited, but is preferably 5000g/m²Hereinafter, more preferably 4500g/m²The lower, more preferably 4000g/m²The lower, particularly preferred is 3500g/m²The following.

The thickness of the inorganic fiber molded article of the present invention is preferably 4mm or more, more preferably 5mm or more, and particularly 6mm or more. The thickness of the inorganic fiber molded article of the present invention is preferably 40mm or less, more preferably 35mm or less, and particularly preferably 30mm or less.

The basis weight and thickness per unit area of the inorganic fiber molded article can be adjusted to the above ranges by adjusting the amount of fibers per unit area when the inorganic fiber aggregate constituting the inorganic fiber molded article is laminated by a folding device. The inorganic fiber molded article of the present invention may be a structure in which a plurality of inorganic fiber molded articles are bonded, or may be a single structure, and is preferably a single structure in terms of handling properties and peel strength at the bonded interface.

< longitudinal yarn >

The inorganic fiber molded body of the present invention has stitches formed by a needle punching process. As described above, when the needle punching treatment for inserting and extracting the barbed needle into and from the inorganic fiber assembly is performed, at least a part of the fibers extend in the substantial thickness direction by the action of the needle at the needle-inserted and extracted portion. The yarn of inorganic fibers present inside the inorganic fiber molded body and formed substantially in the thickness direction by the needle punching treatment is referred to as a longitudinal yarn.

< effective longitudinal yarn >

In the present invention, among the longitudinal strands present inside the inorganic fiber molded body, the longitudinal strands having a specific diameter and length are used as the effective longitudinal strands. Specifically, in the case of performing a peeling test described later, the effective longitudinal fibers are all those having a diameter of 100 μm or more and a protruding length of 2mm or more in all the longitudinal fibers F (fig. 1) protruding from the two peeling surfaces (one peeling surface 1a and the other peeling surface 1b) per unit area (50mm × 50 mm). The unit area (50mm × 50mm) of each value of the longitudinal filament measured is an arbitrary region of the test piece (150mm × 50mm) that avoids a portion where a 30mm deep notch is cut at the center of the thickness.

The effective longitudinal yarn is a longitudinal yarn having a diameter and a length that function to adjust the bulk density, peel strength, and durability of the elastic repulsion force (surface pressure retention rate after high-temperature cycles) of the inorganic fiber molded article, among the longitudinal yarns existing in the approximate thickness direction inside the inorganic fiber molded article.

[ Explanation of characteristic I, II ]

< peeling test >

A test piece 1 having a width of 50mm and a length of 150mm was die-cut from the inorganic fiber molded article, and a notch having a depth of 30mm was cut in the center of the thickness of one end face 1e of the test piece 1 as shown in FIG. 2. The slit is provided so as to extend from one end to the other end in the width direction. Subsequently, as shown in fig. 1, both ends of the cut-out were supported by a holding jig 2, and then the test piece was set in a tensile tester, and was pulled at a speed of 500mm/min in the opposite direction (upper and lower directions in fig. 1) perpendicular to the pad surface, thereby splitting the test piece into 2 pieces.

< maximum peel strength >

As shown in fig. 1, the maximum value (N) of the load peak when the test piece 1 was split into 2 pieces by pulling at a speed of 500mm/min in the direction opposite to the direction perpendicular to the mat surface was defined as the maximum peel strength.

In the inorganic fiber molded article of the present invention, the maximum peel strength obtained as a load peak (N) in the above-described peel test is preferably 3.0N or more, more preferably 5.0N or more, further preferably 6.0N or more, and particularly preferably 6.5N or more. The higher the peel strength of the inorganic fiber molded product, the more advantageous it is, but it is preferably 50.0N or less, more preferably 45.0N or less, and particularly preferably 40.0N or less.

In the inorganic fiber molded body of the present invention, for example, when processed as a heat insulating material, it is preferable that the inorganic fiber molded body has excellent peel strength in order to minimize deterioration of workability and difference in density distribution during molding. Further, when the mat for an exhaust gas purifying device used in an automobile or the like is wound around a catalyst support and assembled in a metal case, it is preferable that the mat has excellent peel strength so that no displacement occurs between layers of the mat.

< Total volume V of portions of effective longitudinal filaments protruding from releasing surface >

After the above-described peeling test, the number (number) N of effective longitudinal threads protruding from the peeling surfaces 1a and 1b, the diameter (thickness) D, and the length (protruding length from the peeling surface 1a or 1b) L were measured by a digital microscope. The measurement magnification of the digital microscope is preferably 10 to 20 times. The length L is a length of a portion protruding from the release surface 1a or 1b, and is measured as a portion having a diameter of 100 μm or more. The diameter D is a value measured at a longitudinal direction intermediate portion of a portion protruding from the peeling surface 1a or 1 b.

The total volume V of the portions of the effective longitudinal filaments protruding from the stripping surface in the range of 50mm × 50mm is a volume (π D) calculated for each of the N effective longitudinal filaments protruding from the stripping surface 1a or 1b²L/4) and the sum.

In the inorganic fiber molded body of the present invention, the total volume (sum of volumes) V of the effective longitudinal filaments in the portion protruding from the release surface is preferably 2.0mm³/cm²Above, more preferably 4.0mm³/cm²Above, more preferably 8.0mm³/cm²Above, particularly preferably 12.0mm³/cm²The above. The total volume of the effective longitudinal filaments in the above range means that the effective longitudinal filaments are inside the inorganic fiber molded bodyThe longitudinal strands are more firmly present, and the interlayer peel strength in the approximate thickness direction can be further improved.

The value of the total volume (sum of volumes) V is preferably 50mm in terms of per unit area (50 mm. times.50 mm)³Above, more preferably 100mm³Above, more preferably 200mm³Above, particularly preferably 300mm³The above.

< average volume of portion of effective longitudinal yarn protruding from release surface per 1 stitch (characteristic I) >

The number of stitches n in the above-described 50mm × 50mm range was measured by the above-described measurement method. The average volume of the portion of the effective longitudinal yarn protruding from the release surface for each 1 stitch (hereinafter, sometimes referred to as "average volume of the effective longitudinal yarn for each 1 stitch") is determined by dividing the total volume V determined by the peeling test by n.

That is, the average volume of the effective longitudinal threads per 1 stitch is a value V/n obtained by dividing the sum (total volume) V of the volumes of the portions protruding from the release surfaces of all the effective longitudinal threads present on the two release surfaces (one release surface and the other release surface) per unit area (50mm × 50mm) in the release test by the number of stitches n per unit area. The larger the average volume V/n of the effective longitudinal filaments per 1 stitch, the more effective the needling treatment can be performed, and stronger effective longitudinal filaments can be formed.

In the inorganic fiber molded article of the 1 st aspect, the average volume V/n of the effective longitudinal filaments per 1 stitch is 1.0mm³Above, more preferably 1.3mm³Above, more preferably 1.6mm³Above, particularly preferably 1.9mm³The above. When the average volume of the effective longitudinal filaments per 1 stitch is in the above range, the fibers in the approximate thickness direction are strongly entangled with each other inside the inorganic fiber molded body, and high surface pressure and excellent peel strength can be achieved at the same time. Further, when the catalyst support for an exhaust gas purifying device and the holding member (mat for an exhaust gas purifying device) are press-fitted into the metal case, the mat can be prevented from being peeled off. In the inorganic fiber molded body of embodiment 1, the phaseThe average volume V/n of the effective longitudinal filament for each 1 stitch is preferably 50mm³Preferably 40mm or less³Below, particularly preferably 30mm³The following.

< average volume of the portion protruding from the peeling surface for each 1 effective longitudinal yarn (characteristic II) >

The average volume of the portion protruding from the release surface for each 1 of the effective longitudinal threads (hereinafter, sometimes referred to as "average volume for each 1 of the effective longitudinal threads") is determined by dividing the total volume V by the number N of effective longitudinal threads.

That is, the average volume per 1 effective longitudinal yarn is a value V/N obtained by dividing the sum (total volume) V of the volumes of the portions of all effective longitudinal yarns protruding from the peeled surface, which are present on the two peeled surfaces (one peeled surface and the other peeled surface) per unit area (50mm × 50mm) in the peeling test, by the number N of effective longitudinal yarns per unit area. The larger the average volume V/N per 1 effective longitudinal yarn in the inorganic fiber molded article, the more effective the needling treatment can be made, and stronger effective longitudinal yarns can be formed.

In the inorganic fiber molded article of the 2 nd aspect, the average volume V/N per 1 effective longitudinal yarn is 3.0mm³Above, more preferably 3.5mm³Above, more preferably 4.0mm³The above. When the average volume V/N per 1 effective longitudinal yarn is in the above range, the peel strength can be improved. Further, when the catalyst support for an exhaust gas purifying device and the holding member (mat for an exhaust gas purifying device) are press-fitted into the metal case, the mat can be prevented from being peeled off. The average volume V/N of the effective longitudinal filaments per 1 effective longitudinal filament of the inorganic fiber molded article is preferably 100mm³Preferably 50mm or less³Below, particularly preferably 40mm³The following.

In order to improve the surface pressure and the durability of the elastic repulsion force of the inorganic fiber molded body, a method of relaxing the fiber constraint by reducing the number of needles in the needle punching process and reducing the stitch density is considered. However, when the stitch density is decreased, other physical properties such as peel strength may be decreased. Therefore, in the present invention, focusing on the form of the longitudinal yarn, the average volume V/n of the effective longitudinal yarn per 1 stitch is 1.0mm in embodiment 1³As described above, in embodiment 2, the average volume V/N per 1 effective longitudinal yarn is 3.0mm³The above. This makes it possible to form the longitudinal yarn more firmly.

In the present invention, by satisfying at least one of the characteristics (I) and (II), the longitudinal yarn formed by the needle punching treatment can be made stronger, and yarn breakage due to the needle punching treatment can be reduced.

The means for making the longitudinal filament stronger is not particularly limited, and specific means (i) and (ii) listed below can be exemplified.

(i) The thick yarn of the inorganic fiber precursor is arranged on the surface of the aggregate of the inorganic fiber precursors, and the thick yarn is pressed into the aggregate of the inorganic fiber precursors by a needle at the time of needle punching treatment to form a longitudinal yarn.

The type of needle for needling a thick thread is not particularly limited, and a fork needle is preferable. The thick yarn is preferably made of the same material as the inorganic fiber precursor, and particularly preferably a thick rope-like yarn in which precursor fibers are oriented in one direction, which is by-produced in the collecting device when the aggregate of the inorganic fiber precursors is collected. The thick string-like filaments are preferably an aggregate of short fibers. The average diameter of the thick-string filaments is preferably 1.2 times or more, particularly 1.5 times or more, and 4 times or less, particularly 3 times or less, the average diameter of the effective longitudinal filaments.

(ii) By adhering (attaching) the needle-punching assistant liquid to the surface of the aggregate of the inorganic fiber precursors by spraying or the like before the needle-punching treatment, the physical properties of the inorganic fiber precursors constituting the longitudinal filaments can be enhanced. Suitable needling aids are described above.

< average thickness of effective longitudinal yarn >

In the present invention, the average thickness (diameter) of the effective longitudinal filaments is preferably 500 μm or more, more preferably 600 μm or more, and particularly preferably 700 μm or more. The average thickness of the effective longitudinal filaments is preferably 3000 μm or less, more preferably 2800 μm or less, and particularly preferably 2500 μm or less. When the average thickness of the effective longitudinal filaments is within the above range, the effective longitudinal filaments are less likely to break when an external force is applied thereto, and the carpet has a high peel strength.

< average length of effective longitudinal yarn >

In the longitudinal filaments of the inorganic fiber molded article of the present invention, the average length L' of the effective longitudinal filaments in one of the split surfaces is preferably within a specific ratio to the thickness z of the other split surface (i.e., 1/2 of the total thickness of the inorganic fiber molded article). That is, in the case of the peeling test, the ratio (L '/z) · 100 (%) of the average length L' of the effective longitudinal filaments of one peeled surface divided by the thickness z of the other peeled surface per unit area (50mm × 50mm) is preferably 50% or more, more preferably 60% or more, and particularly preferably 70% or more. When the ratio (L'/z) · 100 (%) is in the above range, the peel strength can be further improved, which is preferable. On the other hand, the ratio (L'/z) · 100 (%) is preferably 200% or less, and more preferably 150% or less. When the ratio (L'/z) · 100 (%) is within the above range, the protrusion of the closed loop can be suppressed to a small extent, and thus, the process trouble can be reduced.

< number of effective longitudinal threads per unit area >

The total number of the effective longitudinal filaments present on both the release surfaces per unit area (50mm × 50mm) of the inorganic fiber molded article of the present invention is preferably 20 or more, more preferably 40 or more, and particularly preferably 60 or more. When the number of effective longitudinal strands is in the above range, the peel strength can be further improved, which is preferable. On the other hand, the number of effective longitudinal threads per unit area is preferably 500 or less, more preferably 400 or less, and particularly preferably 250 or less. When the upper limit of the number of effective longitudinal strands is in the above range, the peel strength can be improved without lowering the surface pressure of the inorganic fiber molded article, and therefore, the upper limit is particularly preferable in applications requiring surface pressure.

< durability of surface pressure and rebound force >

In the inorganic fiber molded body of the present invention, the surface pressure (surface pressure after high-temperature cycle) and the repulsion durability (surface pressure retention after high-temperature cycle) can be determined by the following measurement tests. The inorganic fiber molded body was compressed at GBD (bulk density) of 0.30 for 30 minutes, and then the upper and lower plates were heated to 600 ℃ to repeat releasing and compressing 1000 times at GBD 0.27 for releasing and 0.30 for compressing. At this time, the contact pressure value at the time of the 1 st release (GBD 0.27) and the contact pressure value at the time of the 1000 th release (GBD 0.27) were measured. In this case, the surface pressure value (kPa) at the 1000 th release was defined as the surface pressure (surface pressure after high-temperature cycle). Further, the high-temperature cycle back pressure retention (%) which is an index of the degree of deterioration of the surface pressure was obtained by the following formula based on the surface pressure value (kPa) at the 1000 th release and the surface pressure value (kPa) at the 1 st release, and this was taken as the rebound force durability.

High-temperature cycle back pressure retention (%) ([ surface pressure value at 1000 th time ]/[ surface pressure value at 1 st time ]) × 100

The inorganic fiber molded article of the present invention can have an excellent holding power as the surface pressure (surface pressure after high-temperature cycle) is higher. Therefore, the surface pressure of the inorganic fiber molded article of the present invention is preferably 30(kPa) or more, more preferably 33(kPa) or more, and particularly preferably 36(kPa) or more. The higher the surface pressure, the more advantageous, but generally the interlayer peel strength tends to decrease, and the larger the effective longitudinal yarn volume, the greater the effect of the present invention. In the inorganic fiber molded article of the present invention, the upper limit of the surface pressure is not particularly limited, but is preferably 1000(kPa) or less, more preferably 900(kPa) or less, and particularly preferably 800(kPa) or less.

In the inorganic fiber molded article of the present invention, the higher the rebound resilience durability (the surface pressure retention after high-temperature cycles) is, the more preferable is 60 (%) or more, the more preferable is 65 (%) or more, and the particularly preferable is 70 (%) or more. The higher the durability of the repulsive force is, the more advantageous is the higher is the durability of 100 (%) or less, more preferably 99 (%) or less, and particularly preferably 98 (%) or less.

[ use of inorganic fiber molded article ]

The inorganic fiber molded article of the present invention is not particularly limited in its application, and various kinds of heat insulating materials, gaskets, and the like are available, and is particularly useful as a mat for an exhaust gas purifying device.

< mat for exhaust gas purifying apparatus >

The mat for an exhaust gas purifying device is a holding member for a catalyst support of the exhaust gas purifying device, and is a cushion material for the exhaust gas purifying device that is wound around the catalyst support when the catalyst support is housed in a metal case and is interposed between the catalyst support and the metal case (GAP). The mat for an exhaust gas purifying device of the present invention is composed of the inorganic fiber molded product of the present invention. Specifically, the inorganic fiber molded article of the present invention is subjected to shape processing such as cutting to produce a mat for an exhaust gas purifying device. The inorganic fiber molded body constituting the mat for an exhaust gas purifying device of the present invention may contain an organic binder. The content of organic binder is preferably less than 10% by weight, more preferably less than 5% by weight, and particularly preferably less than 2.5% by weight.

When the content of the organic binder is 10% by weight or more, NO may be generated due to decomposition of the organic binder caused by high heat of exhaust gas during combustion in an engine_xAnd decomposition gases such as CO and HC increase in problems.

As the organic binder, various rubbers, water-soluble high molecular compounds, thermoplastic resins, thermosetting resins, and the like can be used.

Aqueous solutions, water-dispersed emulsions, latexes, or organic solvent solutions containing the above organic binders as the active ingredients are commercially available. These organic binders can be used as they are or diluted with water or the like, and can be suitably used for containing the organic binder in the mat. It is not always necessary to use 1 type of organic binder in the mat, and even a mixture of 2 or more types does not cause any problem.

Among the above organic binders, synthetic rubbers such as acrylic rubber and nitrile rubber are preferable; water-soluble high molecular compounds such as carboxymethyl cellulose and polyvinyl alcohol; or an acrylic resin, and among them, acrylic rubber, nitrile rubber, carboxymethyl cellulose, polyvinyl alcohol, and acrylic resins not contained in acrylic rubber are particularly preferable. These binders can be suitably used because they are easily prepared or obtained as an organic binder solution, are easy to handle for penetrating into a mat, exhibit sufficient thickness-constraining force even at a low content, and are flexible and excellent in strength, and are easily decomposed or burned out under use temperature conditions.

[ exhaust gas purifying apparatus ]

The exhaust gas purifying device includes a catalyst support, a housing covering the outside of the catalyst support, and a mat attached between the catalyst support and the housing. In the exhaust gas purifying device of the present invention, the mat for an exhaust gas purifying device of the present invention is used as the mat, and since the mat has high peel strength, the mat is excellent in handling property and workability at the time of assembling the exhaust gas purifying device, and the holding property of the catalyst carrier after assembling is also good.

The configuration itself of the exhaust gas purifying apparatus is not particularly limited, and the present invention can be applied to various exhaust gas purifying apparatuses including a catalyst support, a housing, and a mat as a holder of the catalyst support.

Examples

The present invention will be described more specifically with reference to the following examples and comparative examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Hereinafter, the methods for measuring or evaluating various physical properties and characteristics of the obtained inorganic fiber molded article are as follows.

< peeling test >

A test piece 50mm wide and 150mm long was cut out from the inorganic fiber molding die, and a notch 30mm deep was cut out at the center of the thickness of one end face 1e of the test piece. As shown in fig. 1, both ends formed by the slits were held by a clamp 2, and then the test piece 1 was split into 2 pieces by placing the test piece in a tensile tester and stretching the test piece in the opposite direction perpendicular to the pad surface at a speed of 500mm/min, and the maximum value (N) of the load peak at this time was measured.

< Total volume of effective longitudinal filaments V >

After the above-described peeling test, the effective longitudinal filaments in this range were determined to be the longitudinal filaments having an average diameter of 100 μm or more and a protruding length of 2mm or more among all the longitudinal filaments protruding from the two peeling surfaces (one peeling surface 1a and the other peeling surface 1b) per unit area (50mm × 50 mm). The number (number of filaments), diameter (thickness) and length were measured to determine the total volume of the effective longitudinal filaments. The diameter, length, number, and the like of the effective longitudinal filaments were measured by observing the peeled surface with a digital microscope (VHX-5000, manufactured by keyence corporation) at a magnification of 10 times.

< average length ratio (L'/z) & 100% >, of effective longitudinal filaments

After the above-described peeling test, the average length L' of the effective longitudinal filaments per unit area (50mm × 50mm) of one peeled surface was divided by the thickness z of the other peeled surface (1/2 of the thickness of the inorganic fiber molded body to be tested), and the average length ratio of the effective longitudinal filaments was determined.

< method for measuring number of stitches >

The inorganic fiber molded article was cut into a square of 50mm × 50mm, and as a sample, visible light was irradiated to one surface of the inorganic fiber molded article, and the number of light spots and the number of longitudinal threads formed by transmission on the release surface were counted, thereby counting the number of all stitches per unit area.

< method for measuring durability against contact pressure and rebound force >

The surface pressure and the rebound resilience durability were determined by the following methods.

The inorganic fiber molded body was compressed at GBD (bulk density) of 0.30 for 30 minutes, and then the upper and lower plates were heated to 600 ℃ to repeat releasing and compressing 1000 times at GBD 0.27 for releasing and 0.30 for compressing. At this time, the contact pressure value at the time of the 1 st release (GBD 0.27) and the contact pressure value at the time of the 1000 th release (GBD 0.27) were measured.

The surface pressure value (kPa) at the 1000 th release was set as the surface pressure (surface pressure after high-temperature cycle).

The high-temperature cycle back pressure retention (%) which is an index of the degree of deterioration of the surface pressure was obtained by the following formula based on the surface pressure value (kPa) at the 1000 th release and the surface pressure value (kPa) at the 1 st release, and this was taken as the rebound force durability.

High-temperature cycle back pressure retention (%) ([ surface pressure value at 1000 th time ]/[ surface pressure value at 1 st time ]) × 100

Comparative example 1

To an aqueous alkaline aluminum chloride solution (aluminum content 165g/L, Al/Cl: 1.8 (atomic ratio)) was added silica sol so that the composition of the finally obtained alumina fiber was Al₂O₃：SiO₂After polyvinyl alcohol was further added thereto at a weight ratio of 72:28, the mixture was concentrated to prepare a dope having a viscosity of 70 poise (25 ℃ C.) and an alumina silica content of about 35% by weight, and the dope was used to spin by a jet spinning method. The fibers were collected to obtain an aggregate of alumina/silica-based fiber precursor fibers.

And spinning the spinning solution by a jet spinning method. As the spinning nozzle, a spinning nozzle having the same structure as that of the spinning nozzle described in fig. 6 of japanese patent No. 2602460 is used. In the collection of cotton, the cotton is collected as a continuous sheet (thin-layer sheet) by a collecting device having a structure in which an endless belt made of a wire mesh is disposed substantially at right angles to a spinning gas flow, and the endless belt is rotated while being collided with the spinning gas flow containing the alumina short fiber precursor.

The thin-layer sheet collected by the collecting apparatus is continuously drawn out after the friction reducing agent is applied by spraying, and is sent to a folding apparatus, and is continuously moved in a direction perpendicular to the folding direction while being folded and stacked at a predetermined width, thereby forming a laminated sheet (inorganic fiber collection body). As the folding device, a folding device having the same structure as that of the folding device described in Japanese patent laid-open No. 2000-80547 is used.

The needling process is performed by punching the sheet with a needling apparatus.

Then, firing was carried out at 1200 ℃ to obtain a basis weight of 2800g/m²The inorganic fiber molded body (fired cotton) comprising crystalline alumina/silica fibers. The firing is carried out by raising the temperature to 1200 ℃ at a rate of 5 ℃/min in an electric furnace, holding the temperature at 1200 ℃ for 30 minutes, and then naturally cooling the temperature.

The composition ratio of the crystalline alumina/silica-based fibers was 72/28 (weight ratio), and the average fiber diameter (average of 100 pieces) of the crystalline alumina/silica-based fibers measured by microscopic observation of the inorganic fiber molded body was 5.5 μm.

The results of measuring the peel strength of the obtained inorganic fiber molded article and the like are shown in tables 1 and 2.

[ example 1]

An inorganic fiber molded body of example 1 was obtained in the same manner as in comparative example 1, except that a needling assistant was added before the needling treatment. Specifically, after the friction reducer was attached to the inorganic fiber assembly, the inorganic fiber assembly was passed through a line of 32g/m²A 10% ethanol solution of yukaforder (registered trademark) 301 manufactured by mitsubishi chemical corporation as a needling assistant was spray-applied, followed by needling treatment. After the needling assistant is added, the inorganic fiber assembly is not dried. The expression "WET" in tables 1 and 3 refers to WET coating. The results of measuring the peel strength of the inorganic fiber molded article of example 1 and the like are shown in tables 1 and 2.

[ example 2]

An inorganic fiber molded body of example 2 was obtained in the same manner as in example 1, except for the treatment with the needling assistant. As a treatment based on a needling aid, specifically, 34g/m was added²A5% ethanol solution of "Diafomer (registered trademark) Z-631" manufactured by Mitsubishi chemical corporation as a needling assistant was dried at 50 ℃ for 60 minutes and then subjected to a needling treatment. The results of measuring the peel strength and the like are shown in tables 1 and 2. The expression "DRY" in table 1 refers to DRY coating.

[ example 3]

An inorganic fiber molded article of example 3 was obtained in the same manner as in example 2 except that the drying step (wet coating) was not performed after the needling assistant was added. Namely, 34g/m of the adhesive is attached²A5% ethanol solution of "Diafomer (registered trademark) Z-631" manufactured by Mitsubishi chemical corporation as a needling assistant. The results of measuring the peel strength and the like are shown in tables 1 and 2.

[ example 4]

The needle punching treatment was carried out in the same manner as in comparative example 1,the precursor fiber filaments (by-products in the production of the above-mentioned assembly) having an average diameter of 1300 μm and an average length of 80mm were aligned at 5.7 filaments/cm²The inorganic fiber assembly thus obtained is disposed on the inorganic fiber assembly. Thereafter, the yarn was pushed in the vicinity of the center of the arranged yarn by a fork needle, and needle punching was performed again. Thereafter, in the process after firing, the same procedure as in comparative example 1 was carried out to obtain an inorganic fiber molded article of example 4. The results of measuring the peel strength and the like are shown in tables 1 and 2.

[ example 5]

As the yarn arranged on the inorganic fiber assembly, the yarn of the precursor fiber having an average diameter of 1000 μm and an average length of 80mm (by-product in the production of the above-mentioned assembly) was arranged at 1.1 yarn/cm²Except for the arrangement, the inorganic fiber molded article of example 5 was obtained in the same manner as in example 4. The results of measuring the peel strength and the like are shown in tables 1 and 2.

Comparative example 2

To an aqueous alkaline aluminum chloride solution (aluminum content 165g/L, Al/Cl: 1.8 (atomic ratio)) was added silica sol so that the composition of the finally obtained alumina fiber was Al₂O₃：SiO₂After polyvinyl alcohol was further added thereto at a weight ratio of 72:28, the mixture was concentrated to prepare a dope having a viscosity of 70 poise (25 ℃ C.) and an alumina silica content of about 35% by weight, and the dope was used to spin by a jet spinning method. The fibers were collected to obtain an aggregate of alumina/silica-based fiber precursor fibers.

And spinning the spinning solution by a jet spinning method. As the spinning nozzle, a spinning nozzle having the same structure as that of the spinning nozzle described in fig. 6 of japanese patent No. 2602460 is used. In the collection of cotton, the cotton is collected as a continuous sheet (thin-layer sheet) by a collecting device having a structure in which an endless belt made of a wire mesh is disposed substantially at right angles to a spinning gas flow, and the endless belt is rotated while being collided with the spinning gas flow containing the alumina short fiber precursor.

The thin-layer sheet collected by the collecting apparatus is continuously drawn out after the friction reducing agent is applied by spraying, and is sent to a folding apparatus, and is continuously moved in a direction perpendicular to the folding direction while being folded and stacked at a predetermined width, thereby forming a laminated sheet (inorganic fiber collection body). As the folding device, a folding device having the same structure as that of the folding device described in Japanese patent laid-open No. 2000-80547 is used.

Regarding the needling treatment, a needling machine is utilized to make the fired needle trace density be 15-30 needles/cm²The punching is performed to perform the needle punching process.

Then, firing was carried out at 1200 ℃ to obtain a basis weight of 2800g/m²An inorganic fiber molded body (fired cotton) comprising crystalline alumina/silica fibers (hereinafter, sometimes referred to as "substrate"). The firing is carried out by raising the temperature to 1200 ℃ at a rate of 5 ℃/min in an electric furnace, holding the temperature at 1200 ℃ for 30 minutes, and then naturally cooling the temperature.

The composition ratio of the crystalline alumina/silica-based fibers was 72/28 (weight ratio), and the average fiber diameter (average of 100 pieces) of the crystalline alumina/silica-based fibers measured by microscopic observation of the inorganic fiber molded body was 5.5 μm.

The results of measuring the peel strength of the obtained inorganic fiber molded article and the like are shown in tables 1 and 2.

Comparative example 3

Except that the fired needle trace density is 5-15 needles/cm²The inorganic fiber molded article of comparative example 3 was obtained in the same manner as in comparative example 2 except that the punching was performed by punching and the needle punching treatment was performed. The results of measuring the peel strength of the obtained inorganic fiber molded article and the like are shown in tables 1 and 2.

[ example 6]

The same method as in comparative example 1 was used, and the stitch density after firing was 8 to 20 stitches/cm²The precursor fiber filaments (by-products in the production of the above-mentioned integrated body) having an average diameter of 1300 μm and an average length of 80mm were punched and needle-punched in such a manner that 1.3 filaments/cm were obtained²In the obtained inorganic fiberDimension set integration. Thereafter, the yarn was pushed into the vicinity of the center of the arranged yarn by a fork needle, and needle punching was performed again. Thereafter, in the process after firing, the same procedure as in comparative example 1 was carried out to obtain an inorganic fiber molded article of example 1. The results of measuring the peel strength and the like are shown in tables 1 and 2.

[ example 7]

According to the fired stitch density of 5-15 needles/cm²The precursor fiber filaments (by-products in the production of the assembly) having an average diameter of 1000 μm and an average length of 80mm were punched and needle-punched as filaments arranged on the assembly of inorganic fibers in an amount of 1.0 filament/cm²Except for the arrangement, the inorganic fiber molded article of example 2 was obtained in the same manner as in example 1. The results of measuring the peel strength and the like are shown in tables 1 and 2.

[ example 8]

According to the fired stitch density of 3-10 needles/cm²The precursor fiber yarn (by-product in the production of the assembly) having an average diameter of 1500 μm and an average length of 80mm was punched out and needle-punched as a yarn arranged on the assembly of inorganic fibers at 1.0 yarn/cm²Except for the arrangement, the inorganic fiber molded article of example 8 was obtained in the same manner as in example 1. The results of measuring the peel strength and the like are shown in tables 1 and 2.

[ Table 2]

As shown in tables 1 and 2, the inorganic fiber molded bodies of examples had a large average volume per 1 stitch. In addition, the average volume of the inorganic fiber molded body of the example was increased for 1 effective longitudinal yarn. And thus exhibits high peel strength.

The surface pressure after the high-temperature cycle and the retention rate of the surface pressure after the high-temperature cycle of examples 6 to 8 and comparative examples 2 and 3 are shown in table 1.

As shown in Table 1, the inorganic fiber molded bodies of examples 6 to 8 can achieve both of excellent surface pressure (surface pressure after high-temperature cycle) and high peel strength. On the other hand, the surface pressure of comparative example 2 molded by the conventional manufacturing method was insufficient. In addition, the peel strength of comparative example 3 was insufficient.

While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes can be made therein without departing from the spirit and scope thereof.

The present application is based on japanese patent application 2019-.

Description of the symbols

1 test piece of inorganic fiber molded article

2 clamping fixture