JP4299366B2 - Holding sealing material and manufacturing method thereof - Google Patents

Description

  The present invention relates to a sheet material, a method for producing such a sheet material, an exhaust gas treatment apparatus provided with such a sheet material as a holding sealing material, and a method for producing the same.

  The number of automobiles has increased dramatically since the beginning of this century, and along with this, the amount of exhaust gas discharged from the internal combustion engine of automobiles has been increasing rapidly. In particular, various substances contained in the exhaust gas of a diesel engine cause pollution, and are now having a serious impact on the global environment.

  Under such circumstances, various exhaust gas treatment apparatuses have been proposed and put into practical use. A general exhaust gas processing apparatus is provided with a casing made of, for example, metal in the middle of an exhaust pipe connected to an exhaust gas manifold of an engine, and an exhaust having a large number of cells partitioned by cell walls therein. It has a structure in which a gas processing body is arranged. These cells often have a honeycomb structure. In this case, in particular, the exhaust gas treating body is also called a honeycomb structure. Examples of the exhaust gas processing body include a catalyst carrier and an exhaust gas filter such as a diesel particulate filter (DPF). For example, in the case of DPF, with the above-described structure, when exhaust gas passes through the exhaust gas processing body through each cell, particulates (particulates) are trapped on the cell walls, and the particulates can be removed from the exhaust gas. it can. The constituent material of the exhaust gas treating body is a metal, an alloy, ceramic, or the like. A cordierite honeycomb filter is known as a representative example of an exhaust gas treating body made of ceramic. Recently, from the viewpoint of heat resistance, mechanical strength, chemical stability, etc., porous silicon carbide sintered bodies have been used as materials for exhaust gas treatment bodies.

  Usually, a holding sealing material is installed between the exhaust gas processing body and the casing. The holding sealing material is used to prevent damage due to contact between the exhaust gas processing body and the inner surface of the casing during traveling of the vehicle, and to prevent the exhaust gas from leaking from the gap between the casing and the exhaust gas processing body. Further, the holding sealing material has a role of preventing the exhaust gas processing body from falling off due to exhaust gas exhaust pressure. Furthermore, the exhaust gas treating body needs to be kept at a high temperature in order to maintain the reactivity, and the holding sealing material is also required to have heat insulation performance. As a member satisfying these requirements, there is a holding sealing material made of inorganic fibers such as alumina fibers.

  The holding sealing material is wound around at least a part of the outer peripheral surface excluding the opening surface of the exhaust gas processing body, and, for example, the gripping portions at both ends are fitted to each other and further integrated with the exhaust gas processing body by taping or the like. Immobilized and used. Thereafter, the integrated product is accommodated in a casing to constitute an exhaust gas processing device.

  In addition, while the exhaust gas is being increased in temperature and pressure, the holding sealing material is required to further improve the heat insulating property for the following reason. (I) prevention of a decrease in holding force of the holding sealing material due to an increase in the interval between the casing and the exhaust gas processing body caused by thermal expansion of the casing due to heat transferred from the exhaust gas processing body to the casing; (ii) ) Prevention of heat deterioration of accessories (instruments, etc.) connected to the outer surface of the casing, (iii) Regeneration processing (captured particulates) performed when DPF or the like is used as an exhaust gas treatment body To improve the efficiency of processing that enables the reuse of used exhaust gas treatment bodies.

  Therefore, as a countermeasure against these problems, in order to further improve the heat insulating property of the holding sealing material, it is conceivable that the interval between the exhaust gas processing body and the casing is made wider and the holding sealing material is formed thicker. However, when such a thick holding sealing material is wound around the exhaust gas treating body, a larger circumferential length difference (difference between the outer circumferential length and the inner circumferential length) is generated in the holding sealing material. For this reason, cracks are likely to occur on the outer peripheral surface of the holding sealing material (the surface opposite to the side in contact with the exhaust gas treating body). Such cracks can lead to leakage of untreated exhaust gas.

  Therefore, in order to prevent cracks due to such a difference in circumferential length, it has been proposed to provide a large number of grooves on the surface of the holding sealing material on the side in contact with the exhaust gas treating body (that is, the inner circumferential side) ( Patent Document 1). In this method, it is disclosed that the presence of the groove provided in the holding sealing material can alleviate the influence of the circumferential length difference and suppress leakage of untreated exhaust gas.

Japanese Patent No. 3072281

  However, in the holding sealing material as in Patent Document 1, in order to prevent the occurrence of the above-described cracks, the position, shape, and / or dimensions of the groove are matched with the exhaust gas processing body that is actually wound. Need to optimize. However, actual exhaust gas treatment bodies having various specifications (shape, dimensions, etc.) are used in accordance with the use of the exhaust gas treatment apparatus and the installation object. Therefore, in the technique of Patent Document 1, it is necessary to appropriately manufacture a holding sealing material in which the dimension and shape of the groove are changed for each exhaust gas treating body, and the productivity is significantly reduced.

  The present invention has been made in view of such problems, and provides a holding sealing material that does not easily cause cracking due to a difference in circumference even when the thickness is increased, and does not cause the above-described problem of lowering productivity. The purpose is to do. Another object of the present invention is to provide a method for producing such a holding sealing material.

In the present invention, a holding sealing material constituted by laminating at least two mats, a first mat containing a first inorganic fiber and a second mat containing a second inorganic fiber,
An average fiber length of the first inorganic fiber is longer than an average fiber length of the second inorganic fiber, and a holding sealing material is provided.

  Here, the first inorganic fiber and the second inorganic fiber may be the same material.

  The average fiber length of the first inorganic fibers may be in the range of 20 mm to 120 mm.

  The average fiber length of the second inorganic fiber may be in the range of 0.5 mm to 10 mm.

  The first mat and / or the second mat may further include a binding material.

  The holding sealing material may have an interface layer at the interface between the first mat and the second mat.

  The interface layer may have a thickness in the range of about 0.05 mm to 2 mm.

  The thickness of the holding sealing material may be in the range of 6 mm to 20 mm.

Further, the present invention is a method for producing a holding sealing material in which at least two mats are laminated,
Providing a first mat comprising a first inorganic fiber;
A second step of laminating a second mat containing a second inorganic fiber on the first mat containing the first inorganic fiber;
Have
An average fiber length of the first inorganic fiber is longer than an average fiber length of the second inorganic fiber, and a method for producing a holding sealing material is provided.

  Here, the second step may include a step of directly manufacturing the second mat on the first mat.

  The second step may include a step of laminating the first mat and the second mat after the second mat is manufactured independently.

  Further, the second step may include a step of joining an interface between the first mat and the second mat by an adhesive and / or sewing.

  The first mat may be manufactured by a needling method.

  Further, the second mat may be manufactured by a papermaking method.

  By using the sheet material of the present invention as a holding sealing material of an exhaust gas processing apparatus, it is possible to suppress cracks generated on the outer peripheral surface of the holding sealing material due to a difference in circumferential length. In addition, since this effect is equally expressed regardless of the shape and size of the exhaust gas processing body and the specifications of the exhaust gas processing apparatus, it is necessary to manufacture sheet materials appropriately according to the specifications of various exhaust gas processing apparatuses. Therefore, the effect of not impairing the productivity at the time of manufacture can be obtained.

It is an example of the shape of the sheet material by this invention. It is a conceptual diagram which shows the state when the sheet | seat material by this invention is assembled | attached in a casing with an exhaust-gas process body. It is an example of the SEM photograph image | photographed in order to measure the fiber length of an inorganic fiber. It is a figure which shows one structural example of the exhaust-gas processing apparatus of this invention. It is a flowchart for manufacturing the sheet material by this invention. It is a figure which shows schematically the cross section of the sheet | seat material of this invention manufactured by the "direct lamination method". It is a flowchart for manufacturing the exhaust-gas processing apparatus by this invention. It is the figure which showed typically the method of installing a covering waste gas processing body in a casing by a press injection system. It is the figure which showed typically the method of installing a covering waste gas processing body in a casing by a clamshell system. It is the figure which showed typically the method of installing a covering waste gas processing body in a casing by the winding method. It is the figure which showed typically the method of installing a covering waste gas processing body in a casing by a sizing system. 2 is a photograph after a winding test of a sheet material according to Example 1. FIG. It is a photograph after the winding test of the sheet material according to Comparative Example 1.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  In FIG. 1, an example of the form of the sheet | seat material by this invention is shown. However, the sheet material of the present invention is not limited to the shape of FIG. FIG. 2 shows an exploded configuration diagram of an exhaust gas processing apparatus using the sheet material according to the present invention as a holding sealing material.

  When the sheet material 30 according to the present invention is wound around an exhaust gas processing body 20 such as a catalyst carrier and used as a holding sealing material 24 of an exhaust gas processing apparatus, as shown in FIG. A pair of fitting convex portions 50 and a fitting concave portion 60 are provided on both end faces 70 and 71 perpendicular to the (X direction). When the sheet material 30 is wound around the exhaust gas processing body 20, as shown in FIG. 2, the fitting convex portion 50 and the fitting concave portion 60 are fitted, and the sheet material 30 becomes the exhaust gas processing body 20. Fixed to. Thereafter, the exhaust gas processing body 20 around which the sheet material 30 is wound is press-fitted into a cylindrical casing 12 made of metal or the like, for example, by a press-fitting method, and the exhaust gas processing device 10 is configured.

  The sheet material 30 according to the present invention is mainly composed of inorganic fibers, but may further include a binder as described later.

  Here, the sheet material 30 of the present invention is configured by laminating at least two types of mats, and each mat includes inorganic fibers having different average fiber lengths. For example, in FIG. 1, the sheet material 30 of the present invention is configured by laminating two mats, a first mat 82 and a second mat 84, and is included in the first mat 82. The average fiber length of the inorganic fibers is longer than the average fiber length of the inorganic fibers included in the second mat 84. Hereinafter, the first mat 82 is referred to as “long fiber mat” 82, and the second mat 84 is referred to as “short fiber mat” 84.

  Next, the characteristic effect obtained by the sheet material 30 according to the present invention configured as described above will be described.

  Usually, when the sheet material (holding seal material) is wound around the exhaust gas processing body, the sheet material is determined by the circumferential difference (L (= LO−LI)) between the outer periphery (LO) and the inner periphery (LI) of the sheet material. Tensile stress is generated on the outer peripheral side of. In particular, the influence of the circumferential length difference becomes more prominent as the thickness of the sheet material increases. Therefore, in a thick sheet material, when the sheet material is wound around the exhaust gas processing body, there is a high possibility that a crack will occur in the outer peripheral portion. Further, when such a crack occurs in the sheet material, the exhaust gas is not introduced into the exhaust gas processing body, and may leak from the exhaust gas processing apparatus through the crack without being processed. In order to solve this problem, a plurality of grooves perpendicular to the winding direction are formed in advance on the surface (inner surface side) that is the inner peripheral side of the sheet material during winding, and There is a way to mitigate the effects of length differences. However, in this method, in order to exert the above-described effects, it is necessary to optimize the dimensions and the like of the grooves provided in the sheet material each time according to the specifications of the exhaust gas treatment body to be used ( For example, the groove width and the pitch are usually designed such that the sum of the widths of the grooves formed on the inner surface side of the sheet material is equal to the circumferential difference L. The depth needs to be adjusted according to the thickness of the sheet material), and it is difficult to obtain a universal effect, and the productivity of the sheet material at the time of manufacture is significantly reduced.

  On the other hand, the sheet material according to the present invention is configured by laminating two mats, a long fiber mat 82 and a short fiber mat 84. In general, a mat including inorganic fibers having a large average fiber length has higher tensile strength than a mat including inorganic fibers having a small average fiber length. Therefore, by causing the sheet material 30 to be wound around the exhaust gas treating body 20 with the surface of the long fiber mat 82 of the sheet material 30 as the outer peripheral side, it is possible to easily suppress the occurrence of cracks due to the influence of the peripheral length difference. Become. Further, in the sheet material 30 according to the present invention, such an effect is always exhibited by winding the sheet material 30 around the exhaust gas treating body 20 with the surface of the long fiber mat 82 as the outer peripheral side. Unlike the method of forming a groove having an optimum specification in the sheet material by a one-piece manufacturing method, the productivity of the sheet material is not reduced during the production.

  As described above, in the sheet material 30 according to the present invention, it is possible to suppress the generation of cracks on the outer peripheral side due to the peripheral length difference when wound around the exhaust gas processing body 20. Therefore, in the exhaust gas processing apparatus using the sheet material according to the present invention as the holding sealing material, it is possible to effectively suppress the leakage of untreated exhaust gas from the holding sealing material side.

  In addition, in this application, the average fiber length of the fiber contained in the short fiber mat 84 and the long fiber mat 82 was measured as follows, respectively. In the case of the short fiber mat 84, first, 10 regions of each mat (10 cm × 10 cm size) are selected at random, and the fibers are sampled from each location, and then this is used with an SEM (scanning electron microscope). And measure the length of at least 50 fibers in each area. Next, the measurement results of all the obtained regions were averaged to determine the average fiber length of the mat. In FIG. 3, an example of the SEM photograph image | photographed in order to obtain | require the average fiber length of the short fiber mat 84 is shown. On the other hand, in the case of the long fiber mat 82, first, 10 regions of each mat (10 cm × 10 cm size) are randomly selected, and after sampling fibers from each location, this is 10 times using an optical microscope. And measure the length of at least 50 fibers in each region. Next, the measurement results of all the obtained regions were averaged to determine the average fiber length of the mat.

  In the sheet material of the present invention, the average fiber length of the inorganic fibers contained in the long fiber mat 82 is preferably in the range of 20 mm to 120 mm, more preferably in the range of 30 mm to 70 mm, and in the range of 40 mm to 60 mm. More preferably. On the other hand, the average fiber length of the inorganic fibers contained in the short fiber mat 84 is preferably in the range of 0.5 mm to 10 mm, more preferably in the range of 1 mm to 5 mm, and in the range of 2 mm to 4 mm. Is more preferable. Further, the average fiber length of the inorganic fibers contained in the long fiber mat 82 is preferably about 6 times or more, more preferably about 10 times or more the average fiber length of the inorganic fibers contained in the short fiber mat 84. preferable.

In the sheet material of the present invention, the thickness of the sheet material as a whole is not particularly limited, but for example, a thickness of 6 mm to 20 mm can be used. However, when the total thickness of the sheet material is thin (for example, 6 mm or less), the above-described cracking problem is less likely to occur by using a single-layer sheet material composed only of long fiber mats. Therefore, the necessity to use the sheet material according to the present invention is reduced. In addition, the density and basis weight of the entire sheet member is not specifically limited, as the density, for ^example, those of 0.15g / cm ³ ~0.30g / cm 3, but also as a basis weight, for example, those of 500g ^{/ m 2} ~3000g ^/ m 2 may be used. The basis weight means the total weight of fibers contained per unit area of the sheet material, but when the binding material is included in the sheet material, the total weight of the binding material and fibers contained per unit area is calculated. Say.

  In the sheet material of the present invention, the thickness, density, and basis weight of the long fiber mat and the short fiber mat are not particularly limited, and those having various thicknesses, densities, and basis weights are used. Furthermore, in the sheet material of the present invention, the ratio of the thickness of the long fiber mat to the short fiber mat is not particularly limited, and for example, the ratio of the thickness of the long fiber mat to the thickness of the short fiber mat is about 2. A sheet material configured in the range of 8 to about 5: 5 can be used.

  The sheet material 30 according to the present invention is configured by laminating at least two mats, a long fiber mat 82 and a short fiber mat 84. Therefore, in order to increase the bonding force between the long fiber mat 82 and the short fiber mat 84, an “interface layer” may be provided at the interface between them. In the present application, the term “interface layer” includes any layer that exists at the interface between adjacent layers and has a composition different from those of these layers. Accordingly, the “interface layer” includes a bonding layer such as an adhesive that is intentionally placed on the surface of one or both layers in order to bond adjacent layers. 3 includes a third layer 86 that is naturally formed at the interface between adjacent layers by concentrating the binder and the like (see FIG. 6 described later).

  As described above, the sheet material 30 according to the present invention is wound around the outer periphery of the exhaust gas treating body 20 so that the long fiber mat 82 side is the outer peripheral side (that is, the casing 12 side), and the end portion is Used by fitting and fixing. The exhaust gas processing body 20 around which the sheet material 30 is wound is then installed in the casing 12 by any one of a press-fitting method, a clamshell method, a tightening method, or a sizing method, and an exhaust gas processing device. 10 is configured. Each of these mounting methods will be described later.

  FIG. 4 shows an example of the configuration of the exhaust gas processing device 10 configured as described above. In the example of this figure, the exhaust gas treating body 20 is a catalyst carrier having a large number of through holes in a direction parallel to the gas flow. The catalyst carrier is made of, for example, porous silicon carbide having a honeycomb structure. The exhaust gas treatment device 10 of the present invention is not limited to such a configuration. For example, the exhaust gas treating body 20 may be a DPF whose end of the through hole is sealed in a checkered pattern. In such an exhaust gas processing apparatus, due to the effect of the sheet material as described above, when the sheet material is wound around the exhaust gas processing body, occurrence of cracks on the outer peripheral side is suppressed. Therefore, the exhaust gas introduced into the apparatus can be prevented from being discharged untreated through the crack of the sheet material.

  Hereinafter, an example of the manufacturing method of the sheet | seat material of this invention is demonstrated. In FIG. 5, the flowchart of the manufacturing method of the sheet | seat material of this invention is shown.

  As shown in FIG. 5, in the sheet material of the present invention, a step of providing a first mat containing the first inorganic fibers (step S110), and the second inorganic fibers are provided on the first mat. And laminating a second mat including the same (step S120).

  In the following description, a method for producing a sheet material according to the present invention will be described by taking as an example a case where a long fiber mat is manufactured in step S110 and a short fiber mat is laminated on the long fiber mat in step S120. However, the sheet material of the present invention may be manufactured by manufacturing a short fiber mat in step S110 and laminating the long fiber mat on the short fiber mat in step S120. There is a need to.

  The long fiber mat can be manufactured using, for example, a needling method. Although a detailed example of the needling method will be described later, in this application, the term “needling method” means a method for manufacturing a mat including a step of inserting and removing a fiber entanglement means such as a needle into the mat. In addition, the short fiber mat can be manufactured using, for example, a papermaking method. Although a detailed example of the papermaking method will be described later, in the present application, the term papermaking method means a method for manufacturing a mat including the steps of fiber opening, slurrying, molding, and compression drying.

  Next, as a method for laminating the short fiber mat on the long fiber mat, there are roughly two methods.

  One is a method in which long fiber mats and short fiber mats are produced independently, and then these mats are joined at the lamination interface to obtain a sheet material in which both are laminated (hereinafter referred to as “indirect lamination method”). It is said). In addition, in the “indirect lamination method”, the long fiber mat and the short fiber mat are joined at the interface by a method of bonding via an adhesive or the like, a method of stitching and joining both mats, and a superposition of the two mats. In a state, there is a method in which both are put into a sealed container and the inside of the container is depressurized to vacuum-compress both of them. In the method of bonding via an adhesive or the like, an acrylic adhesive, an acrylate latex or the like can be used as the adhesive. The thickness of the adhesive is not particularly limited, but is, for example, 0.05 mm to 2 mm. Note that, as described above, this adhesive layer is also called an interface layer.

  The other is a method in which a short fiber mat is directly produced on a long fiber mat to form a sheet material in which both are laminated (hereinafter referred to as “direct lamination method”). However, as described above, the long fiber mat may be formed directly on the short fiber mat. This method is superior in that it is not necessary to prepare each mat independently, and the manufacturing process can be simplified.

  Hereinafter, an example of a method for producing the sheet material of the present invention will be specifically described.

(Production of long fiber mat)
As described above, the long fiber mat can be manufactured using the needling method. In the following description, a long fiber mat containing a mixture of alumina and silica as an inorganic fiber will be described as an example. However, the fiber material of the long fiber mat is not limited to this, and for example, only one of alumina or silica is used. It may be configured. Alternatively, other inorganic fibers may be used.

  Silica sol is added to a basic aluminum chloride aqueous solution having an aluminum content of 70 g / l and Al / Cl = 1.8 (atomic ratio) so that the alumina-silica composition ratio is 60 to 80:40 to 20, for example. A fiber precursor is prepared. In particular, the alumina-silica composition ratio is more preferably about 70 to 74:30 to 26. When the alumina composition ratio is 60% or less, the composition ratio of mullite produced from alumina and silica is low, so that the thermal conductivity of the finished long fiber mat tends to be high, and the heat insulation tends to decrease. .

  Next, an organic polymer such as polyvinyl alcohol is added to the alumina fiber precursor. Thereafter, this liquid is concentrated to prepare a spinning solution. Further, this spinning solution is used for spinning by a blowing method.

The blowing method is a method in which spinning is performed by an air flow blown from an air nozzle and a spinning solution flow pushed out from a spinning solution supply nozzle. The gas flow rate per slit from the air nozzle is usually 40 to 200 m / s. The diameter of the spinning nozzle is usually 0.1 to 0.5 mm, and the amount of liquid per spinning solution supply nozzle is usually about 1 to 120 ml / h, but about 3 to 50 ml / h. preferable. Under such conditions, the spinning solution extruded from the spinning solution supply nozzle is sufficiently stretched without being sprayed (misted) and hardly welded between the fibers. A uniform alumina fiber precursor having a narrow diameter distribution can be obtained.

Here, the average diameter of the inorganic fibers is not particularly limited, but for example, those having a diameter of about 3 μm to 10 μm can be used.

  The average diameter of the fiber was measured by the following method. First, the alumina fiber obtained by the above method is put in a cylinder and pulverized under pressure at 20.6 MPa. Next, this sample is placed on a sieve net, and the sample that has passed through the sieve is used as an electron microscope observation specimen. After depositing gold or the like on the surface of the specimen, an electron micrograph at a magnification of about 1500 times is taken. The diameter of at least 40 fibers is measured from the obtained photograph. This operation was repeated for 5 samples, and the average of the measured values was taken as the average fiber diameter.

  A raw material sheet is manufactured by laminating the precursors that have been spun. Further, a needling process is performed on the raw material sheet. A needling device is usually used for the needling process.

Usually, a needling device is comprised by the needle board which can be reciprocated in the stab direction (usually up-down direction), and a pair of support plate installed in the both surfaces of the surface of a raw material sheet, and a back surface. A large number of needles for piercing the raw material sheet are attached to the needle board at a density of about 25 to 5000/100 cm ² , for example. Each support plate is provided with a number of through holes for needles. Therefore, with the raw material sheet pressed from both sides by a pair of support plates, by moving the needle board closer to or away from the raw material sheet, the needle is inserted into and removed from the raw material sheet, and many entangled points where the fibers are entangled Is formed. Here, the needling device is further provided with conveying means for conveying the raw material sheet in a constant direction (a direction substantially parallel to the front and back surfaces of the raw material sheet) at a constant feed rate (for example, about 20 mm / second). Also good. In this case, since the needling process can be performed in a state where the raw material sheet is moved at a constant speed, an operation of moving the raw material sheet is not required every time the needle board is pressed.

  As another configuration, the needling device may include two sets of needle boards. Each needle board has a respective support plate. Two sets of needle boards are disposed on the front and back surfaces of the raw material sheet, respectively, and the raw material sheet is fixed from both sides with each support plate. Here, the needles are arranged on one needle board so that the positions of the needle groups on the other needle board do not overlap during the needling process. In addition, each support plate is provided with a large number of through-holes so that the needle does not contact the support plate during the needling process from both sides of the raw material sheet in consideration of the needle arrangement of both needle boards. It has been. Using such an apparatus, a raw material sheet may be sandwiched from two sides by two sets of support plates, and needling may be performed from both sides of the raw material sheet by two sets of needling boards. By performing the needling process by such a method, the processing time is shortened. Moreover, although there is a limit to the number of needles that can be installed on the needle board, this method is significant because the number of needles installed on one needle board can be reduced.

  At the entanglement points generated by such a needling treatment, the intertwined fibers are oriented in the laminating direction, so that the raw material sheets can be strengthened in the laminating direction.

  Next, the raw material sheet thus subjected to the needling treatment is heated from room temperature and continuously fired at a maximum temperature of about 1250 ° C. for about 0.5 to 2 hours to obtain a long fiber mat.

  If necessary, the long fiber mat may be impregnated with a binder such as an organic resin, so that a binder impregnation treatment may be performed. Thereby, the bulkiness of the long fiber mat can be suppressed. Moreover, it becomes possible to further suppress the detachment of the fibers from the long fiber mat. However, the binder impregnation treatment is not necessarily performed at this stage. For example, in the above-described “indirect lamination method”, after the long fiber mat and the short fiber mat are joined, the binder impregnation treatment may be performed from either side of the mat. In addition, in the case of the above-mentioned “direct lamination method”, since the long fiber mat can be impregnated with the binder when the short fiber mat is manufactured as described later, the subsequent binder impregnation treatment is omitted. Is possible. Alternatively, in the case of the “direct lamination method”, after the laminated sheet material is obtained, the binder may be impregnated from one of the mat sides.

  In the impregnation treatment, the amount of the binder impregnated is preferably in the range of 1.0 to 10.0% by weight. If the amount is less than 1.0% by weight, the effect of preventing the inorganic fibers from detaching is lowered. Moreover, when it exceeds 10.0 weight%, the quantity of the organic component discharged | emitted at the time of use of an exhaust-gas processing apparatus will increase.

  As the binder, an organic binder such as an epoxy resin, an acrylic resin, a rubber resin, or a styrene resin can be used. For example, acrylic (ACM), acrylonitrile-butadiene rubber (NBR), styrene-butadiene rubber (SBR) resin, or the like can be used.

  The long fiber mat is impregnated with the binder by spray coating using an aqueous dispersion prepared with such a binder and water. In addition, by this process, the excess adhering solid content and water added to the long fiber mat are removed as follows.

  Excess solid content is removed by a suction method using a suction device such as a vacuum pump. The excess water may be removed by heating the long fiber mat at a temperature of about 90 to 160 ° C. and / or compressing it at a pressure of 40 kPa to 100 kPa.

  Through such a process, a long fiber mat having an average fiber length of inorganic fibers of about 20 mm to 120 mm can be obtained.

(Production of short fiber mat)
As described above, the short fiber mat can be manufactured using a papermaking method. In the following description, a short fiber mat containing a mixture of alumina and silica as inorganic fibers will be described as an example. However, the fiber material of the short fiber mat is not limited to this, and for example, only one of alumina or silica is used. It may be configured. Alternatively, other inorganic fibers may be used.

  First, the opening process of inorganic fiber is performed.

  The opening process is carried out alone or in a two-stage process including a dry opening process and a wet opening process. In the dry opening process, an apparatus such as a feather mill is used to open the above-described needling sheet material. On the other hand, in the wet opening process, the cotton-like dry opening fiber obtained by the above-described dry opening process is put into a wet opening apparatus and further opened. In the wet opening process, a wet opening apparatus such as a pulper or a mixer is used. Opened raw fiber can be obtained through such fiber opening treatment.

  Next, 750 g of this raw material fiber and 75000 g of water are put into a stirrer and stirred for about 1 to 5 minutes, for example. Next, about 4 wt% to 8 wt% of an organic binder is added to the liquid and stirred for about 1 to 5 minutes. Moreover, about 0.5 wt%-1.0 wt% of inorganic binder is added to this liquid, and it stirs for about 1 to 5 minutes. Further, about 0.5 wt% of a flocculant is added to this liquid, and the mixture is stirred for about 2 minutes at maximum to prepare a raw material slurry.

  As the inorganic binder, for example, alumina sol and / or silica sol is used. Further, as the organic binder, for example, a rubber material, a water-soluble organic polymer compound, a thermoplastic resin, a thermosetting resin, or the like is used. As the aggregating agent, for example, Pacoll 292 (Ciba Specialty Chemicals) ) Etc. are used.

  Next, the obtained raw material slurry is added to a molding machine having a desired shape, a short fiber mat raw material is formed, and dehydration is further performed. In a normal case, a filtration mesh (mesh size: 30 mesh) is provided at the bottom of the molding machine, and moisture in the raw material liquid added to the molding machine is discharged through the filtration mesh. . Therefore, by using such a molding machine, the short fiber mat raw material can be simultaneously molded and dehydrated. If necessary, moisture may be forcibly sucked from the lower side of the molding machine through a mesh for filtration using a suction pump, a vacuum pump, or the like.

  Next, the obtained short fiber mat raw material is taken out from the molding machine, and compressed using a press machine or the like so that the thickness is about 0.3 to 0.5 times. The short fiber mat can be obtained by heating and drying at a temperature of 5 minutes to 1 hour.

  In addition, you may perform the above-mentioned binder impregnation process using the obtained short fiber mat. However, as described above, in the case of the “indirect lamination method”, such a binder impregnation treatment may be performed after joining the short fiber mat and the long fiber mat.

  Through such a process, a short fiber mat having an average fiber length of inorganic fibers in the range of about 0.5 mm to 10 mm can be usually obtained.

(Integration of short fiber mat and long fiber mat)
The sheet material according to the present invention can be obtained by laminating and integrating the short fiber mat and the long fiber mat thus manufactured.

  For the integration of both mats, the aforementioned “indirect lamination method” or “direct lamination method” can be used. In particular, in the case of the “direct lamination method”, in the manufacturing process of the short fiber mat described above, a long fiber mat is previously set at the bottom of the molding machine, and the short fiber mat is formed on the long fiber mat. Can be obtained in the production process of the short fiber mat. In this case, the sheet material processing step can be simplified as compared to the case where the long fiber mat and the short fiber mat are independently manufactured and then integrated.

  However, in such a “direct lamination method”, there is a concern that the bonding property at the interface between the long fiber mat and the short fiber mat is lowered in the manufactured sheet material. However, the interfacial adhesion between the long fiber mat and the short fiber mat of the sheet material obtained by directly laminating the short fiber mat on the long fiber mat as described above is determined by the “indirect lamination method” (depending on the time of bonding). Similar to the interfacial adhesion of the sheet material produced by the joining method). Further, as a result of cross-sectional observation of this sheet material, it was found that the third layer 86 (that is, the above-described interface layer) was formed at the interface between both mats as schematically shown in FIG. The interface layer 86 is expected to be a material in which the binder added to the raw slurry is condensed at the interface with the long fibers when the short fiber mat is manufactured. Further, it is considered that the bonding force at the interface between the long fiber mat and the short fiber mat is increased by the role of this layer as an adhesive layer. The thickness of the interface layer 86 is about 0.05 mm to 2 mm, although it depends on the manufacturing conditions of the sheet material.

  FIG. 7 shows a flowchart of a method for manufacturing an exhaust gas treatment apparatus using the sheet material of the present invention. First, in step S210, a sheet material configured by laminating long fiber mats and short fiber mats by the above-described method is provided. Next, in step S220, the sheet material is wound around the exhaust gas processing body. At this time, the sheet material is wound around the exhaust gas treating body such that the long fiber mat side is the outer peripheral side. Next, in step S230, the exhaust gas processing body around which the sheet material is wound is accommodated in the casing by any one of the press-fitting method, the clamshell method, the tightening method, and the sizing method, and the exhaust gas processing is performed. The device is configured.

  Hereinafter, each mounting method will be described with reference to the drawings. 8, FIG. 9, FIG. 10 and FIG. 11 respectively show an exhaust gas treating body 20 (hereinafter referred to as “coated exhaust”) in which a holding sealing material 24 is wound by a press-fitting method, a clamshell method, a tightening method and a sizing method. This schematically shows a method of mounting the gas processing body “210”) in the casing.

  The press-fitting method is a method of configuring the exhaust gas processing apparatus 10 by mounting the coated exhaust gas processing body 210 at a predetermined position by pushing the coated exhaust gas processing body 210 from one of the opening surfaces of the casing 121. . In order to facilitate the insertion of the coated exhaust gas treatment body 210 into the casing 121, the inner hole diameter is shaped so as to decrease from one to the other as shown in FIG. 8, and the minimum inner hole diameter is the inner diameter of the casing 121. In some cases, a press-fitting jig 230 adjusted so as to have substantially the same dimensions as the above is used. In this case, the coated exhaust gas treating body 210 is inserted from the wide inner hole diameter side of the press-fitting jig 230 and is mounted in the casing 121 through the minimum inner hole diameter side.

  Further, in the clamshell method, as shown in FIG. 9, when facing each other, the casing member is divided so that a pair of casings are completed (for example, divided into two in the example shown in the figure) (122A 122B) is used. After the coated exhaust gas treating body 210 is installed in one of these casing members, the remaining casing members are combined, and these members are further welded together by, for example, flange portions 220 (220A, 220B) to form the casing 122. By configuring the above, it is possible to obtain the exhaust gas processing apparatus 10 in which the coated exhaust gas processing body 210 is mounted at a predetermined position.

  Further, as shown in FIG. 10, the winding method is to wind a metal plate 123 as a casing member around the coated exhaust gas treatment body 210, and then tighten the metal plate 123 using a wire rope or the like. In this method, the metal plate 123 is brought into contact with the periphery of the coated exhaust gas treatment body 210 with a predetermined surface pressure. Finally, one end portion of the metal plate 123 is welded to the other end portion or the surface of the lower metal plate 123, whereby the exhaust gas treatment device 10 in which the covered exhaust gas treatment body 210 is mounted inside the casing 123. Is obtained.

  Further, as shown in FIG. 11, the sizing method includes inserting the coated exhaust gas treating body 210 into the metal shell 124 having an inner diameter larger than the outer diameter, and then using a press or the like to move the metal shell 124 to the outer peripheral side. And uniformly compressing (sizing (JIS-z2500-2002)). By the sizing process, the inner diameter of the metal shell 124 is accurately adjusted to a desired dimension, and the coated exhaust gas processing body 210 can be installed at a predetermined position.

  In addition, as a material of the casing used in these mounting methods, a metal such as a heat-resistant alloy is usually used.

  As described above, in the present invention, since the average fiber length of the inorganic fibers is larger, that is, the first mat having higher strength is wound so as to be on the outer peripheral side of the sheet material, a thick sheet material is used. Even in this case, it is difficult to be affected by the difference in circumferential length, and an effect that cracks are hardly generated on the outer peripheral side of the sheet material can be obtained. In addition, since such an effect is effectively exhibited as long as the sheet material is wound around the exhaust gas treatment body so that the long fiber mat side is the outer peripheral side, a groove that is produced in one piece in the sheet material. Unlike the case where the sheet is provided, it is possible to avoid a decrease in productivity at the time of manufacturing the sheet.

  In the above description, the case where the sheet material according to the present invention is composed of two layers of a long fiber mat and a short fiber mat has been described as an example. However, in the present invention, it is obvious that the sheet material may be configured by laminating three or more mats. That is, in the present invention, what is important is that when the sheet material is wound around the exhaust gas treating body, the laminated sheet material is provided so that a mat including the fibers having the longest average fiber length is provided on the outermost peripheral side. Is to configure. Therefore, it should be noted that any exhaust gas treatment apparatus in which the sheet material is used in such a manner belongs to the scope of the present invention.

  The effects of the present invention will be described below with reference to examples.

  In order to verify the effect of the present invention, a sheet material according to the present invention was produced and various tests were performed. The sheet material was manufactured according to the following procedure.

  First, a long fiber mat was produced according to the following procedure.

Silica sol is added to a basic aluminum chloride aqueous solution having an aluminum content of 70 g / l and Al / Cl = 1.8 (atomic ratio) so that the composition of the alumina fiber is Al ₂ O ₃ : SiO ₂ = 72: 28. Blended to form an alumina fiber precursor. Next, an organic polymer such as polyvinyl alcohol was added to the precursor of the alumina fiber. Further, this solution was concentrated to obtain a spinning solution, and this spinning solution was used for spinning by a blowing method. Thereafter, the precursors of the alumina fibers were folded and laminated to produce an alumina fiber material sheet. Next, a needling process was performed on the raw material sheet. The needling treatment was performed from both sides of the raw material sheet by arranging two sets of needle boards each having 50 needles / 100 cm ² needles arranged on the front and back surfaces of the raw material sheet. As a result, a raw material sheet having an entanglement point density of about 1 piece / cm ² was obtained.

Thereafter, the obtained raw material sheet was continuously baked at an ordinary temperature to a maximum temperature of 1250 ° C. for 1 hour to obtain a long fiber mat having a basis weight of 950 g / m ² and a thickness of 4 mm. The average fiber length of the alumina fibers was about 50 mm. Moreover, the average diameter of the alumina fiber was 6.2 μm, and the minimum diameter was 3.2 μm.

  Next, a short fiber mat was produced directly on the long fiber mat by the following procedure to obtain a sheet material.

  First, raw material fibers in which inorganic fibers are opened are prepared. In this example, raw material fibers (hereinafter referred to as “raw cotton bulk”) composed of alumina fibers having a mixing ratio of alumina: silica = 72: 28 were used.

  790 g of this raw cotton bulk was added to 79000 g of water and stirred for 5 minutes using a stirrer. Next, 39.5 g of an organic binder (latex) was added to this liquid and stirred for 5 minutes, and then 7.9 g of an inorganic binder (alumina sol) was added and further stirred for 5 minutes. Further, 3.95 g of a flocculant (Pacol 292) was added to this solution and stirred for 1 minute to prepare a raw material slurry.

Next, the above-mentioned long fiber mat was placed on the bottom of a molding machine having a length of 930 × width 515 × depth of 400 mm provided with a filtration mesh (30 mesh) at the bottom. The length of the long fiber mat is 930 × width 515 mm × thickness 4 mm. The raw material slurry was poured from above the long fiber mat, and then dehydrated to form a short fiber mat on the long fiber mat. The dehydration process was performed by forcibly sucking the water of the raw material slurry through the mesh for filtration from the bottom side of the molding machine using a suction pump. Next, the short fiber mat integrated with the long fiber mat was taken out of the molding machine and compressed and dried at 120 ° C. and 70 kPa for 30 minutes. By such a process, a short fiber mat having a basis weight of 1750 g / m ² and a thickness of 9 mm was formed on the long fiber mat. The average fiber length of the fibers contained in the short fiber mat was about 3 mm.

Through these steps, a sheet material having an overall thickness of 13 mm and an overall density of 0.21 g / cm ³ was finally obtained. This is Example 1.

A long fiber mat was produced in the same manner as in Example 1. However, in this example, the precursor amount of the alumina fiber to be laminated was changed, and the basis weight of the obtained long fiber mat was 1350 g / m ² and the thickness was 6 mm. The average fiber length of the alumina fibers was about 50 mm. Moreover, the average diameter of the alumina fiber was 6.2 μm, and the minimum diameter was 3.2 μm.

  To 61000 g of water, 610 g of an alumina fiber raw cotton bulk having a mixing ratio of alumina: silica = 72: 28 was added, and the mixture was stirred for 5 minutes using a stirrer. Next, 30.5 g of an organic binder (latex) was added to this liquid and stirred for 5 minutes, and then 6.1 g of an inorganic binder (alumina sol) was added and stirred for another 5 minutes. Further, 3.05 g of a flocculant (Pacol 292) was added to this solution and stirred for 1 minute to prepare a raw material slurry.

Next, the above-mentioned long-fiber mat (having a basis weight of 1350 g / m ² ) was placed on the bottom of a molding machine having a length of 930 × width of 515 × depth of 400 mm provided with a mesh for filtration (30 mesh) at the bottom. The length of the long fiber mat is 930 × length 515 mm × thickness 6 mm. The raw material slurry was poured from above the long fiber mat, and then dehydrated to form a short fiber mat on the long fiber mat. The dehydration treatment was performed by forcibly sucking water in the raw material slurry from the bottom side of the molding machine through the filtration mesh using a suction pump. Next, the short fiber mat integrated with the long fiber mat was taken out of the molding machine and compressed and dried at 120 ° C. and 70 kPa for 30 minutes. By such a process, a short fiber mat having a basis weight of 1350 g / m ² and a thickness of 7 mm was formed on the long fiber mat. The average fiber length of the fibers contained in the short fiber mat was about 3 mm.

Through these steps, a sheet material having an overall thickness of 13 mm and an overall density of 0.21 g / cm ³ was finally obtained. This is Example 2.

A long fiber mat was produced in the same manner as in Example 1. However, in this example, the precursor amount of the alumina-based fibers to be laminated was changed, and the basis weight of the obtained long fiber mat was 950 g / m ² and the thickness was 4 mm. The average fiber length of the alumina fibers was about 50 mm. Moreover, the average diameter of the alumina fiber was 6.2 μm, and the minimum diameter was 3.2 μm.

  To 43,000 g of water, 430 g of raw cotton bulk of alumina fibers having a mixing ratio of alumina: silica = 72: 28 was added, and the mixture was stirred for 5 minutes using a stirrer. Next, 21.5 g of an organic binder (latex) was added to this liquid and stirred for 5 minutes, and then 4.3 g of an inorganic binder (alumina sol) was added and stirred for another 5 minutes. Further, 2.15 g of a flocculant (Pacol 292) was added to this solution and stirred for 1 minute to prepare a raw slurry.

Next, the above-mentioned long-fiber mat (having a basis weight of 950 g / m ² ) was placed on the bottom of a molding machine having a length of 930 × width of 515 × depth of 400 mm provided with a mesh for filtration (30 mesh) at the bottom. The length of the long fiber mat is 930 × width 515 mm × thickness 4 mm. The raw material slurry was poured from above the long fiber mat, and then dehydrated to form a short fiber mat on the long fiber mat. The dehydration treatment was performed by forcibly sucking water in the raw material slurry from the bottom side of the molding machine through the filtration mesh using a suction pump. Next, the short fiber mat integrated with the long fiber mat was taken out of the molding machine and compressed and dried at 120 ° C. and 70 kPa for 30 minutes. Through such a process, a short fiber mat having a basis weight of 950 g / m ² and a thickness of 5 mm was formed on the long fiber mat. The average fiber length of the fibers contained in the short fiber mat was about 3 mm.

Through these steps, a sheet material having an overall thickness of 9 mm and an overall density of 0.21 g / cm ³ was finally obtained. This is Example 3.

Comparative Example 1

  To 122,000 g of water, 1220 g of a raw cotton bulk of alumina fiber having a mixing ratio of alumina: silica = 72: 28 was added and stirred for 5 minutes using a stirrer. Next, 61 g of an organic binder (latex) was added to this liquid and stirred for 5 minutes, and then 12.2 g of an inorganic binder (alumina sol) was added and further stirred for 5 minutes. Further, 6.1 g of a flocculant (Pacol 292) was added to this solution and stirred for 1 minute to prepare a raw material slurry.

Next, the above raw material slurry is injected from above into a molding machine having a length of 930 × width 515 × depth of 400 mm, which is provided with a filtration mesh (30 mesh) at the bottom, and then subjected to a dehydration treatment, whereby short fibers A mat was formed. The dehydration treatment was performed by forcibly sucking water in the raw material slurry from the bottom side of the molding machine through the filtration mesh using a suction pump. Next, this short fiber mat was taken out from the molding machine and compressed and dried at 120 ° C. and 70 kPa for 30 minutes. By such a process, a single-layer sheet material consisting of only short fiber mats and having a basis weight of 2700 g / m ² , a thickness of 13 mm, and an overall density of 0.21 g / cm ³ was obtained. The average fiber length of the fibers contained in the single layer sheet material was about 3 mm. This is referred to as Comparative Example 1.

Comparative Example 2

  To 86000 g of water, 860 g of raw fiber bulk of alumina fiber having a mixing ratio of alumina: silica = 72: 28 was added and stirred for 5 minutes using a stirrer. Next, 43 g of an organic binder (latex) was added to this liquid and stirred for 5 minutes, and then 8.6 g of an inorganic binder (alumina sol) was added and stirred for another 5 minutes. Further, 4.3 g of a flocculant (Pacol 292) was added to this solution and stirred for 1 minute to prepare a raw material slurry.

Next, the above raw material slurry is injected from above into a molding machine having a length of 930 × width 515 × depth of 400 mm, which is provided with a filtration mesh (30 mesh) at the bottom, and then subjected to a dehydration treatment, whereby short fibers A mat was formed. The dehydration treatment was performed by forcibly sucking water in the raw material slurry from the bottom side of the molding machine through the filtration mesh using a suction pump. Next, this short fiber mat was taken out from the molding machine and compressed and dried at 120 ° C. and 70 kPa for 30 minutes. By such a process, a single-layer sheet material having a basis weight of 1900 g / m ² , a thickness of 9 mm, and an overall density of 0.21 g / cm ^{3 made} of only a short fiber mat was obtained. The average fiber length of the fibers contained in the single layer sheet material was about 3 mm. This is referred to as Comparative Example 2.

  Table 1 shows the basis weight, thickness, and density of the laminated sheet materials according to Examples 1 to 3 and the single-layer sheet materials according to Comparative Examples 1 and 2. In this table, the basis weight, thickness, and density of the long fiber mat and the short fiber mat included in each sheet material are also shown.

[Evaluation test]
Next, a winding test was performed using each sheet material manufactured by the above-described method. In the winding test, each sheet material was wound around a cylinder having an outer diameter of 5 inches, and when the ends were fitted and fixed as described above, whether or not the sheet material cracked was visually evaluated. . In addition, in the sheet | seat material which concerns on Examples 1 thru | or 3, it wound around the cylinder so that the side of the long fiber mat might be the outer peripheral side.

[Test results]
Table 1 summarizes the results of the winding test obtained for each sheet material. FIGS. 12 and 13 show photographs taken of the situation of the sheet materials according to Example 1 and Comparative Example 1 after the test, respectively. As a result of the winding test, in the sheet materials of Examples 1 to 3, no crack occurred in the sheet material after the winding test. On the other hand, in the single-layer sheet material according to Comparative Examples 1 and 2, a crack occurred on the outer peripheral side after the winding test. As described above, it was confirmed that the sheet material obtained by laminating the long fiber mat and the short fiber mat according to the present invention has sufficient strength even when the thickness is increased.

  The sheet material of the present invention can be used for a vehicle exhaust gas treatment device or the like.

2 Introduction pipe 4 Exhaust pipe 10 Exhaust gas treatment device 12 Casing 20 Exhaust gas treatment body 24 Holding sealing material 30 Sheet material 50 Fitting convex part 60 Fitting concave part 82 First mat (long fiber mat)
84 Second mat (short fiber mat)
86 Third layer (interface layer)
121, 122, 123, 124 Casing 210 Coated exhaust gas treatment body.

Claims (14)

A holding sealing material formed by laminating at least two mats, a first mat containing a first inorganic fiber and a second mat containing a second inorganic fiber, and wound around an exhaust gas treating body Because
The average fiber length of the first inorganic fibers is rather long than the average fiber length of the second inorganic fibers,
The holding sealing material is wound around the exhaust gas processing body such that the first mat is on the outermost peripheral side .   The holding sealing material according to claim 1, wherein the first inorganic fiber and the second inorganic fiber are made of the same material.   The holding sealing material according to claim 1 or 2, wherein an average fiber length of the first inorganic fibers is in a range of 20 mm to 120 mm.   4. The holding sealing material according to claim 1, wherein an average fiber length of the second inorganic fiber is in a range of 0.5 mm to 10 mm.   The holding sealing material according to any one of claims 1 to 4, wherein the first mat and / or the second mat further include a binding material.   6. The holding sealing material according to claim 1, further comprising an interface layer at an interface between the first mat and the second mat.   The holding sealing material according to any one of claims 1 to 6, wherein the interface layer has a thickness in a range of about 0.05 mm to 2 mm.   The thickness of the said holding sealing material exists in the range of 6 mm-20 mm, The holding sealing material as described in any one of Claim 1 thru | or 7 characterized by the above-mentioned. A method for producing a holding sealing material in which at least two mats are laminated and wound around an exhaust gas treating body ,
Providing a first mat comprising a first inorganic fiber;
A second step of laminating a second mat containing a second inorganic fiber on the first mat containing the first inorganic fiber;
Have
The average fiber length of the first inorganic fibers is rather long than the average fiber length of the second inorganic fibers,
The method of manufacturing a holding sealing material, wherein the holding sealing material is wound around the exhaust gas treating body such that the first mat is on the outermost peripheral side .   The manufacturing method according to claim 9, wherein the second step includes a step of directly manufacturing the second mat on the first mat.   10. The manufacturing method according to claim 9, wherein the second step includes a step of stacking the first mat and the second mat after the second mat is manufactured independently. .   Furthermore, the said 2nd step has the step which joins the interface of the said 1st mat and the said 2nd mat by an adhesive agent and / or sewing, The manufacturing method of Claim 11 characterized by the above-mentioned.   The manufacturing method according to claim 9, wherein the first mat is manufactured by a needling method.   The manufacturing method according to claim 9, wherein the second mat is manufactured by a papermaking method.