Patent Application
20250172085
The present invention relates to a mat material, an exhaust gas conversion apparatus, and a method for producing a mat material.
Exhaust gas discharged from an internal combustion engine such as a diesel engine contains a particulate matter (hereinafter, also referred to as “PM”). Adverse effects of PM on the environment and human bodies have been problems. The exhaust gas also contains harmful gas components such as CO, HC, and NOx. This causes concerns about the effects of such harmful gas components on the environment and human bodies.
In view of the above, various exhaust gas conversion apparatuses that collect PM in exhaust gas and convert harmful gas components have been proposed. Such an exhaust gas conversion apparatus includes an exhaust gas treatment unit including porous ceramic such as silicon carbide or cordierite, a casing for housing the exhaust gas treatment unit, and a holding sealing material (mat material) between the exhaust gas treatment unit and the casing. The holding sealing material (mat material) is disposed mainly, for example, for preventing the exhaust gas treatment unit from being damaged by contact with the casing that covers the periphery of the exhaust gas treatment unit due to vibrations and impacts caused by operation of automobiles or the like, and for preventing exhaust gas leakage from a space between the exhaust gas treatment unit and the casing.
Patent Literature 1 discloses attaching of an organic binder and an inorganic binder to a mat material including inorganic fibers and use of the organic binder and the inorganic binder at a weight ratio of 1:1. Since the inorganic fibers are coated with a binder layer made of the organic binder and the inorganic binder, inorganic fiber scattering can be prevented or reduced.
When the inorganic binder and the organic binder are used at a weight ratio of 1:1, the friction between the inorganic fibers cannot be sufficiently increased, and the shear modulus is low. A mat material having a higher friction value and a higher shear modulus can more stably hold an exhaust gas treatment unit.
The present invention was made in view of the above problems and aims to provide a mat material having a high shear modulus, with inorganic fiber scattering being prevented or reduced.
Specifically, the mat material of the present invention is a mat material including inorganic fibers, with an inorganic binder and an organic binder attached to the mat material, wherein a ratio [w1B/w1A] of a weight percentage w1B of the organic binder to a weight percentage w1A of the inorganic binder satisfies the following condition (1) or (2), where w1A is the weight percentage of the inorganic binder relative to a weight of the mat material as a whole, and w1B is the weight percentage of the organic binder relative to the weight of the mat material as a whole:
0<w1B/w1A≤0.8; or (1)
9≤w1B/w1A. (2)
In the mat material of the present invention, the ratio [w1B/w1A] of the weight percentage w1B of the organic binder to the weight percentage w1A of the inorganic binder satisfies (1) 0<w1B/w1A≤0.8 or (2) 9≤w1B/w1A.
When the condition (1) is satisfied, the weight ratio of the inorganic binder is relatively high. Thus, slipping of the inorganic fibers on each other can be prevented or reduced by forming irregularities derived from the inorganic binder on a surface of each inorganic fiber.
When the condition (2) is satisfied, the weight ratio of the organic binder is relatively high, which increases the strength of a coating formed from the organic binder and the inorganic binder, so that slipping of the inorganic fibers on each other can be prevented or reduced.
When the ratio [w1B/w1A] of the weight percentage w1B of the organic binder to the weight percentage w1A of the inorganic binder is more than 0.8 and less than 9, the effect of the formation of irregularities derived from the inorganic binder on the surface of each inorganic fiber is not sufficiently exhibited, and the effect of an increased strength of the coating due to the organic binder is also not sufficiently exhibited.
Preferably, in the mat material of the present invention, the inorganic binder and the organic binder are attached in an individually dispersed state to the surface of each inorganic fiber.
When the inorganic binder and the organic binder are attached in an individually dispersed state to the surface of each inorganic fiber, the inorganic binder is in a dispersed state in the coating formed from the organic binder. The coating in such a state has excellent mechanical strength and thus can prevent the inorganic fibers from slipping on each other and increase the shear modulus of the mat material.
Preferably, the mat material of the present invention further contains a polymeric dispersant.
When the mat material further contains a polymeric dispersant, the organic binder and the inorganic binder can be easily attached in a dispersed state to the surface of each inorganic fiber.
In the mat material of the present invention, preferably, aggregates of the inorganic binder and the organic binder are attached to the surface of each inorganic fiber.
The aggregates of the inorganic binder and the organic binder can form irregularities on the surface of each inorganic fiber, which can increase the friction between the inorganic fibers and improve the holding power.
In the mat material of the present invention, preferably, the surface of each inorganic fiber is at least partially covered with a coating layer containing a mixture of the inorganic binder and the organic binder.
The coating layer containing a mixture of the inorganic binder and the organic binder has a higher mechanical strength than a coating layer containing only the organic binder. Thus, the coating layer is less likely to peel off, making it possible to increase the frictional resistance between the inorganic fibers.
In the mat material of the present invention, preferably, the coating layer is formed from a continuous flaky mixture of the inorganic binder and the organic binder.
When the coating layer is formed from the flaky mixture, many irregularities derived from the flaky mixture are formed on a surface of the coating layer, which can further increase the frictional resistance between the inorganic fibers.
In the mat material of the present invention, preferably, the coating layer has a stepped shape.
When the coating layer has a stepped shape, the frictional resistance between the inorganic fibers can be further increased.
In the mat material of the present invention, preferably, a particulate mixture of the inorganic binder and the organic binder is attached to the surface of the coating layer.
When the particulate mixture of the inorganic binder and the organic binder is attached to the surface of the coating layer, the frictional resistance between the inorganic fibers can be further increased than when no such particulate mixture is attached to the coating layer.
Preferably, the mat material of the present invention is a needle-punched mat in which at least one of a front surface or a back surface thereof is needled.
Preferably, the mat material of the present invention includes multiple entanglement points formed by needling at least one of the front surface or the back surface thereof, and a density ρ of the entanglement points is in a range of 0.5 pcs/cm2≤ρ<18 pcs/cm2.
When the density ρ of the entanglement points is in the above range, the shear modulus can be improved.
Preferably, the mat material of the present invention includes multiple entanglement points formed by needling at least one of the front surface or the back surface thereof, and at least one of a 4 mm×4 mm first region without the entanglement points or a 3 mm×8 mm second region without the entanglement points is arranged in a 25 mm×25 mm region.
In the mat material of the present invention, preferably, at least one of the first region or the second region is arranged in a plural number in the 25 mm×25 mm region.
When at least one of the first region or the second region is arranged in a plural number in the 25 mm×25 mm region, the surface pressure of the mat material can be increased.
Preferably, the mat material of the present invention is used in an exhaust gas conversion apparatus.
The mat material of the present invention has a high shear modulus, and thus can be suitably used in an exhaust gas conversion apparatus.
Preferably, the mat material of the present invention has a shear modulus of 0.26 or more.
At a shear modulus of 0.26 or more, the mat material is less likely to shear when an exhaust gas treatment unit is pressed into a metal casing using the mat material of the present invention.
The shear modulus is determined by dividing the shear failure load by the reduced surface pressure.
Methods for measuring the shear failure load and the reduced surface pressure are described later.
Preferably, the mat material of the present invention further includes a protective sheet on at least one surface thereof.
The protective sheet, when further placed on the surface of the mat material, prevents or reduces displacement and/or dense wrinkles of the mat material and generation of a gap in a fitting portion when the mat material is wound around an exhaust gas treatment unit.
An exhaust gas conversion apparatus of the present invention includes an exhaust gas treatment unit, a metal casing for housing the exhaust gas treatment unit, and a mat material arranged between the exhaust gas treatment unit and the metal casing for holding the exhaust gas treatment unit, wherein the mat material is the mat material of the present invention.
The exhaust gas conversion apparatus of the present invention can stably hold the exhaust gas treatment unit owing to the arrangement of the mat material of the present invention between the exhaust gas treatment unit and the metal casing.
A method for producing a mat material according to a first embodiment of the present invention includes a needle-punched mat preparing step of preparing an inorganic fiber mass including inorganic fibers by needling; and an attaching step of attaching an inorganic binder and an organic binder to the inorganic fiber mass, wherein a ratio [w2B/w2A] of a weight percentage w2B of the organic binder to a weight percentage w2A of the inorganic binder satisfies the following condition (3) or (4), where w2A is the weight percentage of the inorganic binder for use in the attaching step, and w2B is the weight percentage of the organic binder for use in the attaching step:
0<w2B/w2A≤0.8; or (3)
9≤w2B/w2A. (4)
In the method for producing a mat material according to the first embodiment of the present invention, preferably, in the attaching step, a dispersion in which the inorganic binder and the organic binder are dispersed in a dispersion medium is attached to the inorganic fiber mass.
In the method for producing a mat material according to the first embodiment of the present invention, preferably, in the attaching step, an aggregated dispersion in which the inorganic binder and the organic binder are aggregated is attached to the inorganic fiber mass.
A method for producing a mat material according to a second embodiment of the present invention includes: a defibrating step of defibrating inorganic fibers; a slurry preparing step of mixing the opened inorganic fibers with a solvent, an inorganic binder, and an organic binder to prepare a slurry; and a papermaking step of subjecting the slurry to papermaking to obtain an inorganic fiber papermaking sheet; and a drying step of drying the inorganic fiber papermaking sheet, wherein a ratio [w3B/w3A] of a weight percentage w3B of the organic binder to a weight percentage w3A of the inorganic binder satisfies the following condition (5) or (6), where w3A is the weight percentage of the inorganic binder contained in the slurry to be prepared in the slurry preparing step, and w3B is the weight percentage of the organic binder contained in the slurry to be prepared in the slurry preparing step:
0<w3B/w3A≤0.8; or (5)
9≤w3B/w3A. (6)
The method for producing a mat material of the present invention can easily produce the mat material of the present invention.
Hereinafter, embodiments of the present invention are specifically described. The present invention is not limited to the embodiments described below, and suitable modifications may be made without departing from the scope of the present invention.
The mat material of the present invention is a mat material including inorganic fibers, with an inorganic binder and an organic binder attached to the mat material, wherein a ratio [w1B/w1A] of a weight percentage w1B of the organic binder to a weight percentage w1A of the inorganic binder satisfies the following condition (1) or (2), where w1A is the weight percentage of the inorganic binder relative to a weight of the mat material as a whole, and w1B is the weight percentage of the organic binder relative to the weight of the mat material as a whole:
0<w1B/w1A≤0.8; or (1)
9≤w1B/w1A. (2)
As shown in
The mat 10 shown in
Neither the protrusion nor the recess may be provided at the ends of the mat material of the present invention.
Each end of the mat may have an L-shape such that the ends fit each other when the mat material is wound around an object.
The mat thickness is not limited but is preferably 2 to 40 mm. At a mat thickness of more than 40 mm, the mat loses its flexibility, which makes handling difficult when the mat material is wound around an exhaust gas treatment unit, and which also makes the mat material prone to winding wrinkles and cracking.
At a mat thickness of less than 2 mm, the exhaust gas treatment unit easily falls out due to insufficient holding power of the mat material. In addition, when changes occur in the volume of the exhaust gas treatment unit, the mat material is less likely to absorb such changes in the volume of the exhaust gas treatment unit. Thus, the exhaust gas treatment unit becomes prone to cracking and the like.
The mat includes inorganic fibers.
Any inorganic fibers may be used, but the inorganic fibers preferably include at least one selected from the group consisting of alumina fibers, silica fibers, alumina silica fibers, mullite fibers, biosoluble fibers, and glass fibers.
The inorganic fibers including at least one selected from alumina fibers, silica fibers, alumina silica fibers, and mullite fibers have excellent heat resistance, so that the properties or the like will not change, even when the exhaust gas treatment unit is exposed to sufficiently high temperatures, and the mat material can sufficiently maintain its function. In the case where the inorganic fibers are biosoluble fibers, for example, even when a worker inhales the inorganic fibers that are scattered during production of the exhaust gas conversion apparatus using the mat material, the inorganic fibers will dissolve in vivo and thus cause no harm to the health of the worker.
The alumina fibers may contain, in addition to alumina, additives such as calcia, magnesia, and zirconia.
The compositional ratio of the alumina silica fibers by weight is preferably Al2O3:SiO2=60:40 to 80:20, more preferably Al2O3:SiO2=70:30 to 74:26.
The mat can be produced by needling or papermaking. The inorganic fiber mass produced by needling is also referred to as “needle-punched mat”, and the mat produced by papermaking is also referred to as “papermaking mat”.
In the case of needling, the average fiber length of the inorganic fibers is preferably 1 to 150 mm, more preferably 10 to 80 mm.
Inorganic fibers having an average fiber length of less than 1 mm are too short in length, so that such inorganic fibers are insufficiently entangled with each other and result in poor winding properties of the mat material when the mat material is wound around the exhaust gas treatment unit, making the mat material easily breakable. Inorganic fibers having an average fiber length of more than 150 mm are too long in length, so that there are fewer fibers constituting the mat material, reducing the denseness of the mat material. As a result, the mat material has a low shear strength.
In the case of papermaking, the average fiber length of the inorganic fibers is preferably 200 to 20000 μm, more preferably 300 to 10000 μm, still more preferably 500 to 1500 μm.
In the case of needling, entanglement points are formed on the front surface or back surface of the mat material.
Preferably, the density ρ of the entanglement points is in the range of 0.5 pcs/cm2≤ρ<18 pcs/cm2.
When the entanglement points are formed on both the front surface and back surface of the mat material, the density ρ of the entanglement points is the density of the entanglement points measured on a main surface, either the front surface or back surface, with a higher density of the entanglement points.
In the case of needling, preferably, at least one of a 4 mm×4 mm first region without the entanglement points or a 3 mm×8 mm second region without the entanglement points is arranged in a 25 mm×25 mm region of the front surface or back surface of the mat material.
A high surface pressure is exhibited owing to the arrangement of at least one of the first region or the second region.
The main surface of the mat material to be checked to determine whether at least one of the first region or the second region is arranged thereon is the main surface on which the density of the entanglement points is measured.
In
In
Each of the 4 mm×4 mm squares and the 3 mm×8 mm rectangles shown in
Accordingly, neither the first regions nor the second regions can be arranged in the mat material shown in
The number of the first regions and the second regions in the 25 mm×25 mm region can be counted by the following method.
(1) A 4 mm×4 mm region (first region) in which no entanglement points are formed is located. At this point, multiple first regions that do not overlap with each other are selected.
(2) A 3 mm×8 mm region (second region) in which no entanglement points are formed is located. At this point, multiple second regions that do not overlap with each other are selected. The second region and the first region may overlap with each other. When the first region and the second region overlap with each other, the area without the entanglement points increases, which can increase the surface pressure of the mat material.
(3) A 25 mm×25 mm region in which the total number of non-overlapping first regions and non-overlapping second regions is the maximum is selected.
The above operation is performed for ten samples, and the average is calculated.
The above operation may be performed using commercially available image processing software or the like.
Preferably, at least one of the first region or the second region is arranged in a plural number in the 25 mm×25 mm region.
When at least one of the first region or the second region is arranged in a plural number in the 25 mm×25 mm region, the surface pressure of the mat material can be increased.
That “at least one of the first region or the second region is arranged in a plural number” refers to a case where the total number of the first regions and the second regions is two or more, which includes, for example, a case where multiple first regions are arranged, a case where multiple second regions are arranged, and a case where multiple first regions and multiple second regions are arranged.
Preferably, a third region, which is a 4 mm×4 mm region including four or more entanglement points, is arranged in the 25 mm×25 mm region on the front surface or back surface of the mat material.
The arrangement of the third region can increase the shear strength of the mat material because the inorganic fibers in the third region are strongly entangled with each other.
The method for counting the number of the third regions in the 25 mm×25 mm region is the same as the method for counting the number of the first regions described above.
The mat material contains an inorganic binder (also referred to as “inorganic binding material”) and an organic binder (also referred to as “organic binding material”).
The ratio [w1B/w1A] of the weight percentage w1B of the organic binder to the weight percentage w1A of the inorganic binder satisfies the following condition (1) or (2), where w1A is the weight percentage of the inorganic binder relative to the weight of the mat material as a whole, and w1B is the weight percentage of the organic binder relative to the weight of the mat material as a whole:
0<w1B/w1A≤0.8; or (1)
9≤w1B/w1A. (2)
When the condition (1) is satisfied, the weight ratio of the inorganic binder is relatively high. Thus, slipping of the inorganic fibers on each other can be prevented or reduced by forming irregularities derived from the inorganic binder on the surface of each inorganic fiber.
When the condition (1) is satisfied, the ratio [w1B/w1A] of the weight percentage w1B of the organic binder to the weight percentage w1A of the inorganic binder is preferably 0<w1B/w1A≤0.5, more preferably 0<w1B/w1A≤0.3, still more preferably 0<w1B/w1A≤0.1.
When the condition (2) is satisfied, the weight ratio of the organic binder is relatively high, which increases the strength of the coating formed from the organic binder and the inorganic binder, so that slipping of the inorganic fibers on each other can be prevented or reduced.
When the condition (2) is satisfied, the ratio [w1B/w1A] of the weight percentage w1B of the organic binder to the weight percentage w1A of the inorganic binder is preferably 10≤w1B/w1A, more preferably 11≤w1B/w1A, still more preferably 13≤w1B/w1A.
When the ratio [w1B/w1A] of the weight percentage w1B of the organic binder to the weight percentage w1A of the inorganic binder is more than 0.8 and less than 9, the effect of the formation of irregularities derived from the inorganic binder on the surface of each inorganic fiber is not sufficiently exhibited, and the effect of an increased strength of the coating due to the organic binder is also not sufficiently exhibited.
The weight percentage w1A of the inorganic binder attached to the mat material and the weight percentage w1B of the organic binder attached to the mat material can be measured by the following method.
First, a certain weight of a sample is taken out from a mat material. An organic solvent (e.g., tetrahydrofuran) that dissolves the organic binder in the sample is selected, and the organic binder is dissolved in a Soxhlet extractor to separate the organic binder from the sample. At this point, the inorganic binder is also separated, together with the dissolved organic binder, from the sample, so that the organic binder and the inorganic binder are both extracted in the organic solvent. The organic solvent containing the organic binder and the inorganic binder is placed in a crucible, and the organic solvent is removed by evaporation with heat. The weight of the residue remaining in the crucible thereafter is regarded as the total weight of the organic binder and the inorganic binder attached to the mat material. Further, the crucible is heated at 600° C. for one hour to burn out the organic binder. Since the inorganic binder remains in the crucible, the weight of the residue is regarded as the weight of the inorganic binder, and the difference in the weight of the residue before and after heating is regarded as the weight of the organic binder.
Examples of the inorganic binder include alumina sol and silica sol.
Preferably, the weight percentage w1A of the inorganic binder relative to the mat material (weight of inorganic binder/weight of mat material) is more than 0 wt % and 10 wt % or less.
When the weight percentage w1A of the inorganic binder relative to the mat material is in the above range, the holding power can be sufficiently increased.
Examples of the organic binder include water-soluble organic polymers such as acrylic resin, acrylate latex, rubber latex, carboxymethylcellulose, and polyvinyl alcohol; thermoplastic resins such as styrene resin; and thermosetting resins such as epoxy resin.
Preferably, the weight percentage w1B of the organic binder relative to the mat material (weight of organic binder/weight of mat material) is more than 0 wt % and 10 wt % or less.
When the weight percentage w1B of the organic binder relative to the mat material is in the above range, the holding power can be sufficiently increased.
The amounts of the organic binder and the inorganic binder in the mat material can be measured by the following method, for example.
First, a certain weight of a sample is taken out from a mat material in which the amounts of the organic binder and the inorganic binder therein are intended to be measured. Subsequently, an organic solvent (e.g., tetrahydrofuran) that dissolves the organic binder in the sample is selected, and the organic binder is dissolved in a Soxhlet extractor to separate the organic binder from the sample. At this point, the inorganic binder in the dissolved organic binder is also separated from the sample, so that the organic binder and the inorganic binder are both extracted in the organic solvent.
Next, the organic solvent containing the organic binder and the inorganic binder is placed in a crucible, and the organic solvent is removed by evaporation with heat. The amount (weight %) of the residue remaining in the crucible relative to the weight of the mat material is calculated, assuming that the weight of the residue is the total weight of the organic binder and the inorganic binder relative to the mat material.
Further, the crucible is heated at 600° C. for one hour to burn out the organic binder. Since the inorganic binder remains in the crucible, the amount of the inorganic binder is calculated, assuming that the amount of the residue is the amount (weight %) of the inorganic binder relative to the total of the organic binder and the inorganic binder. The balance is the amount (weight %) of the organic binder.
The weight ratio of the total of the inorganic binder and the organic binder to the mat material (total weight of inorganic binder and organic binder/weight of mat material) is preferably 0.01 wt % or more and 25 wt % or less, more preferably 0.1 wt % or more and 15 wt % or less.
Preferably, the inorganic binder and the organic binder are attached in an individually dispersed state to the surface of each inorganic fiber.
When the inorganic binder and the organic binder are attached in an individually dispersed state to the surface of each inorganic fiber, the inorganic binder is in a dispersed state in a coating formed from the organic binder. The coating in such a state has excellent mechanical strength and thus can prevent the inorganic fibers from slipping on each other and increase the holding power.
In the mat material, preferably, the surface of each inorganic fiber is at least partially covered with a coating layer containing a mixture of the inorganic binder and the organic binder.
The coating layer containing a mixture of the inorganic binder and the organic binder has a higher mechanical strength than a coating layer containing only the organic binder. Thus, the coating layer is less likely to peel off, making it possible to increase the frictional resistance between the inorganic fibers.
Preferably, the coating layer is formed from a continuous flaky mixture (mixture of the inorganic binder and the organic binder).
When the coating layer is formed from the flaky mixture, many irregularities derived from the flaky mixture are formed on the surface of the coating layer, which can further increase the frictional resistance between the inorganic fibers.
As shown in
Whether the coating layer and the particles contain a mixture of the inorganic binder and the organic binder can be confirmed by a combination of field observation under an electronic microscope and elemental analysis.
As shown in
The coating layer may or may not have a uniform thickness.
The shape of the coating layer having a non-uniform thickness is also referred to as “stepped shape”.
That the coating layer has a stepped shape means that there are irregularities on the surface of the coating layer, so that the frictional resistance between the inorganic fibers can be further increased.
Whether the coating layer has irregularities on the surface, i.e., whether the coating layer has a stepped shape, can be determined by enlarging the surface of each inorganic fiber to a magnification of 3000 times using a scanning electronic microscope and checking for the presence or absence of irregularities on the surface of the coating layer.
As shown in
The particulate mixture 40 of the inorganic binder and the organic binder is attached to the surface of the inorganic fiber 20.
Preferably, particles containing a mixture of the inorganic binder and the organic binder are attached to the surface of the coating layer.
When the particles containing a mixture of the inorganic binder and the organic binder are attached to the surface of the coating layer, the frictional resistance between the inorganic fibers can be further increased than when no such particles are attached to the coating layer.
As shown in
Preferably, the mat material further contains a polymeric dispersant.
When the mat material further contains a polymeric dispersant, the organic binder and the inorganic binder can be easily attached in a dispersed state to the surface of each inorganic fiber.
Examples of the polymeric dispersant include synthetic hydrophilic polymeric substances including anionic polymeric dispersants such as polycarboxylic acid and/or a salt thereof, a naphthalenesulfonate formalin condensate and/or a salt thereof, polyacrylic acid and/or a salt thereof, polymethacrylic acid and/or a salt thereof, and polyvinyl sulfonic acid and/or a salt thereof, and nonionic polymeric dispersants such as polyvinyl alcohol, polyvinylpyrrolidone, and polyethylene glycol; natural hydrophilic polymers such as gelatin, casein, and water-soluble starch; and semi-synthetic hydrophilic polymeric substances such as carboxymethylcellulose.
Of these, synthetic hydrophilic polymeric substances are preferred, and anionic polymeric dispersants are more preferred.
One of these polymeric dispersants may be used alone or two or more of these may be used in combination. A polymeric dispersant having both a structure that exhibits properties as an anionic polymeric dispersant and a structure that exhibits properties as a nonionic polymeric dispersant may also be used.
A particularly preferred polymeric dispersant is an anionic polymeric dispersant having a number average molecular weight of 500 to 100000.
Preferably, the amount of the polymeric dispersant is 50 to 1000 ppm relative to the weight of the inorganic fibers.
In the mat material, preferably, aggregates of the inorganic binder and the organic binder are attached to the surface of each inorganic fiber.
The aggregates of the inorganic binder and the organic binder can form irregularities on the surface of each inorganic fiber, which can increase the friction between the inorganic fibers and improve the holding power.
The mat material may further contain a flocculant.
When the mat material further contains a flocculant, the organic binder and the inorganic binder can be easily attached in an aggregated state to the surface of each inorganic fiber.
Whether the inorganic binder and the organic binder attached to the surface of each inorganic fiber are either dispersed or aggregated can be checked by observing the surface of each inorganic fiber by SEM-EDX or the like.
Preferably, the mat material of the present invention has a shear modulus of 0.26 or more as determined by dividing the shear failure load by the reduced surface pressure.
At a shear modulus of 0.26 or more, the mat material is less likely to shear when an exhaust gas treatment unit is pressed into a metal casing using the mat material of the present invention.
The shear modulus is determined by dividing the shear failure load by the reduced surface pressure.
The shear failure load can be measured by a shear failure load test device shown in
A shear failure load test device 70 shown in
The specimens 1a and 1b are pierced by the protruding members 74 and are thereby fixed to the left jig 71, the right jig 72, and the stainless-steel plate 73.
In this state, the specimens are compressed to a bulk density (GBD) of 0.3 g/cm3.
Next, the stainless-steel plate 73 is moved at a rate of 5 mm/min toward the direction (upward) indicated by an arrow in
The shear force applied to the stainless-steel plate when a shear failure occurred in the specimens is determined.
The resulting shear force is divided by the area of the specimens, whereby the shear failure load (kPa) can be determined. The shear failure load may be measured using specimens obtained by cutting out portions of the mat material.
The reduced surface pressure can be measured by the following procedure.
First, the mat material is compressed to a bulk density of 0.3 g/cm3 at room temperature and kept in the state for 20 minutes. Then, the load is measured.
The resulting load is divided by the area of the specimen, whereby the reduced surface pressure (kPa) can be determined. The reduced surface pressure may be measured using specimen obtained by cutting out portions of the mat material.
The mat material of the present invention has a fiber scattering rate (wt %) of 0.35 wt % or less as measured by a scattering test.
The scattering test is performed by the following procedure.
First, the mat material was cut out into a size of 100 mm×100 mm to obtain a scattering test sample 210. The scattering rate of the inorganic fibers in the scattering test sample can be measured using a measuring device shown in
The sample supporting arms 270 are locked at a predetermined locking mechanism at a position where the sample supporting arms 270 form an angle of 90° with the supporting post 260, and the scattering test sample 210 is fixed to the sample fixing member 280 with clips 220. When the sample supporting arms 270 are unlocked, the sample supporting arms 270 and the scattering test sample 210 start falling toward the base 250 on which the supporting post 260 is fixed. Then, the falling direction changes such that the sample supporting arms 270 rotate about a junction between the sample supporting arms 270 and the supporting post 260. At the point where the sample supporting arms 270 become parallel to the supporting post 260, the sample supporting arms 270 collide with the vertical wall member 290. Due to the collision, a portion of the inorganic fibers constituting the scattering test sample 210 breaks and scatters. Thus, the fiber scattering rate can be determined by measuring the weight of the scattering test sample before and after the collision and using the following formula (1).
The mat material may further include a protective sheet on at least one surface thereof.
The protective sheet is placed on at least one surface of the mat.
The protective sheet, when further placed on the surface of the mat, prevents or reduces displacement and/or dense wrinkles of the mat material and generation of a gap in a fitting portion when the mat material is wound around an exhaust gas treatment unit.
The protective sheet may be made of any material, but, for example, a flexible resin such as polypropylene is preferred.
The protective sheet may be a non-woven fabric made of flexible resin fibers, for example.
The protective sheet may be made of a combination of two or more different materials.
The two or more materials may make up the same non-woven fabric, or two or more different non-woven fabrics may be stacked together to form the protective sheet.
The protective sheet thickness is not limited but is preferably 1 μm to 1 mm.
At a protective sheet thickness of less than 1 μm, the effect of reducing deformation of the mat may not be sufficient.
At a protective sheet thickness of more than 1 mm, the ease of handling may be reduced.
The ratio of the protective sheet thickness to the mat thickness is not limited but is preferably in the range of about 1:10 to about 1:1000, more preferably in the range of about 1:50 to about 1:200.
The protective sheet may be adhered to the mat by any method, such as one in which hot melt powder is placed between the protective sheet and the mat and is melted by heat.
Preferably, the surface on which the protective sheet is disposed is the surface that faces the outside when the mat material is wound around an exhaust gas treatment unit.
The protective sheet may include a slit formed therein.
The slit may be oriented in any direction. It may be oriented in the longitudinal or width direction of the mat material.
A mat material 2 shown in
The protective sheet may be disposed only on one surface of the mat or on each surface of the mat.
An exhaust gas conversion apparatus of the present invention includes an exhaust gas treatment unit, a metal casing for housing the exhaust gas treatment unit, and a mat material arranged between the exhaust gas treatment unit and the metal casing for holding the exhaust gas treatment unit, wherein the mat material is the mat material of the present invention.
The exhaust gas conversion apparatus of the present invention can stably hold the exhaust gas treatment unit owing to the arrangement of the mat material of the present invention between the exhaust gas treatment unit and the metal casing.
As shown in
The exhaust gas treatment unit 130 has a pillar shape in which many cells 131 are arranged in parallel in a longitudinal direction with cell walls 132 between the cells. If necessary, an inlet tube for introducing exhaust gas discharged from an internal combustion engine and an outlet tube for discharging the exhaust gas that has passed through the exhaust gas conversion apparatus are connected to ends of the casing 120.
In the exhaust gas conversion apparatus 100 shown in
As shown in
A method for producing a mat material according to a first embodiment of the present invention includes a needle-punched mat preparing step of preparing an inorganic fiber mass including inorganic fibers by needling; and an attaching step of attaching an inorganic binder and an organic binder to the inorganic fiber mass, wherein a ratio [w2B/w2A] of a weight percentage w2B of the organic binder to a weight percentage w2A of the inorganic binder satisfies the following condition (3) or (4), where w2A is the weight percentage of the inorganic binder for use in the attaching step, and w2B is the weight percentage of the organic binder for use in the attaching step:
0<w2B/w2A≤0.8; or (3)
9≤w2B/w2A. (4)
In the needle-punched mat preparing step, an inorganic fiber mass including inorganic fibers is prepared by needling. The inorganic fiber mass obtained by needling is also referred to as “needle-punched mat”.
Examples of methods for preparing an inorganic fiber mass by needling include a method that includes a spinning step of spinning a spinning mixture containing at least an inorganic compound and an organic polymer to produce an inorganic fiber precursor; a compressing step of compressing the inorganic fiber precursor to produce a sheet; a needle-punching step of needle-punching at least one surface of the sheet to produce a needle-punched article; and a firing step of firing the needle-punched article.
In the spinning step, the spinning mixture containing at least an inorganic compound and an organic polymer is spun to produce an inorganic fiber precursor.
In the spinning step, for example, a spinning mixture containing an aqueous solution of basic aluminum chloride, silica sol, and the like as raw materials is spun by blowing, whereby an inorganic fiber precursor having an average fiber diameter of 3 to 10 μm is produced.
In the compressing step, the inorganic fiber precursor obtained in the spinning step is compressed to produce a continuous sheet having a predetermined size.
In the needle-punching step, at least one surface of the sheet obtained in the compressing step is needle-punched to produce a needle-punched article.
In the needle-punching step, preferably, the needle arrangement density is set to 0.5 needles/cm2 or more and less than 18 needles/cm2.
In the needle-punching step, the positions where the needles are arranged correspond to the entanglement points in the mat material. Thus, when the needle arrangement density is set to 0.5 needles/cm2 or more and less than 18 needles/cm2, a mat material in which the density ρ of the entanglement points is in the range of 0.5 pcs/cm2≤ρ<18 pcs/cm2 can be obtained by single needle-punching.
The needle arrangement density is not limited to the above range when the same sheet is needle-punched several times.
By intentionally unevenly arranging the needles in the needle-punching step, the arrangement of the entanglement points to be formed on the needle-punched article can be varied in density so as to form a 4 mm×4 mm region without the entanglement points (first region) and/or a 3 mm×8 mm region without the entanglement points in a 25 mm×25 mm (second region) in a 25 mm×25 mm region, while the density ρ of the entanglement points is in the range of 0.5 pcs/cm2≤ρ<18 pcs/cm2.
Examples of methods for intentionally unevenly arranging the entanglement points include a method that includes needle-punching such that the entanglement points are evenly arranged and then additionally needle-punching some portions. Other examples include a method that includes performing needle-punching several times while moving the inorganic fiber precursor, and a method that include performing needle-punching using a needle board on which needles are not arranged at equal intervals.
In the needle-punching step, the needles may or may not penetrate in the thickness direction of the sheet.
In the firing step, the needle-punched article is fired to obtain an inorganic fiber mass including inorganic fibers.
The firing temperature of the needle-punched article is not limited but is preferably 1000° C. to 1600° C.
Neither an inorganic binder nor an organic binder is attached to the inorganic fiber mass (needle-punched mat) prepared by needling.
Subsequently, the attaching step is performed in which an inorganic binder and/or an organic binder is attached to the inorganic fiber mass.
Examples of methods for attaching an inorganic binder and an organic binder to the inorganic fiber mass include a method that includes bringing a binder mixture of a solvent, an inorganic binder, and an organic binder into contact with the inorganic fiber mass and then drying the binder mixture.
Examples of methods for bringing a binder mixture into contact with the inorganic fiber mass include a method that includes immersing the inorganic fiber mass in a binder mixture and a method that includes dropping a binder mixture onto the inorganic fiber mass by curtain coating or the like.
A mat constituting the mat material can be obtained by attaching an inorganic binder and/or an organic binder to the inorganic fiber mass.
The weights of the inorganic binder and the organic binder for use in the attaching step are set such that the ratio [w2B/w2A] of the weight percentage w2B of the organic binder to the weight percentage w2A of the inorganic binder satisfies the following condition (3) or (4), where w2A is the weight percentage of the inorganic binder relative to the binder mixture, and w2B is the weight percentage of the organic binder relative to the binder mixture:
0<w2B/w2A≤0.8; or (3)
9≤w2B/w2A. (4)
In the method for producing a mat material according to the first embodiment of the present invention, an inorganic binder and an organic binder are attached to the inorganic fiber mass to which neither an inorganic binder nor an organic binder is attached. Thus, the mat material of the present invention can be obtained by adjusting the ratio [w2B/w2A] of the weight percentage w2B of the organic binder to the weight percentage w2A of the inorganic binder such that the condition (3) or (4) is satisfied.
When the binder mixture for use in the attaching step satisfies the condition (3), the ratio [w2B/w2A] of the weight percentage w2B of the organic binder to the weight percentage w2A of the inorganic binder is preferably 0<w2B/w2A≤0.5, more preferably 0<w2B/w2A≤0.3, still more preferably 0<w2B/w2A≤0.1.
When the binder mixture for use in the attaching step satisfies the condition (4), the ratio [w2B/w2A] of the weight percentage w2B of the organic binder to the weight percentage w2A of the inorganic binder is preferably 10≤ w2B/w2A, more preferably 11≤w2B/w2A, still more preferably 13≤w2B/w2A.
The binder mixture for use in the attaching step may contain a polymeric dispersant.
When the binder mixture contains a polymeric dispersant, the inorganic binder and the organic binder are in a dispersed state in the binder mixture. In other words, the binder mixture is a dispersion in which the inorganic binder and the organic binder are dispersed in a dispersion medium. When the binder mixture (dispersion) in such a state is brought into contact with the inorganic fiber mass, the inorganic binder and the organic binder can be attached in a dispersed state to the surface of each inorganic fiber.
The binder mixture for use in the attaching step may contain a flocculant.
When the mixture contains a flocculant, the inorganic binder and the organic binder are in an aggregated state in the mixture. In other words, the binder mixture is an aggregated dispersion in which the aggregates of the inorganic binder and the organic binder are dispersed in a dispersion medium. When the mixture (aggregated dispersion) in such a state is brought into contact with the inorganic fiber mass, the inorganic binder and the organic binder can be attached in an aggregated state to the surface of each inorganic fiber.
In the attaching step, the attaching of an inorganic binder and the attaching of an organic binder may be separately performed.
Examples of methods for separately performing the attaching of an inorganic binder and the attaching of an organic binder include a method that includes bringing an inorganic binder mixture containing an inorganic binder into contact with the inorganic fiber mass to attach the inorganic binder thereto and then further bringing an organic binder mixture containing an organic binder into contact with the inorganic fiber mass to attach the organic binder thereto. The inorganic binder and the organic binder may be attached in any order. The inorganic binder may be attached first, or the organic binder may be attached first.
A method for producing a mat material according to a second embodiment of the present invention includes: a defibrating step of defibrating inorganic fibers; a slurry preparing step of mixing the opened inorganic fibers with a solvent, an inorganic binder, and an organic binder to prepare a slurry; and a papermaking step of subjecting the slurry to papermaking to obtain an inorganic fiber papermaking sheet; and a drying step of drying the inorganic fiber papermaking sheet, wherein a ratio [w3B/w3A] ratio of a weight percentage w3B of the organic binder to a weight percentage w3A of the inorganic binder satisfies the following condition (5) or (6), where w3A is the weight percentage of the inorganic binder contained in the slurry to be prepared in the slurry preparing step, and w3B is the weight percentage of the organic binder contained in the slurry to be prepared in the slurry preparing step:
0<w3B/w3A≤0.8; or (5)
9≤w3B/w3A. (6)
In the defibrating step, the inorganic fibers are made into short fibers (referred to as defibrating) with a grinder such as a feather mill or an agitator such as a pulper to adjust the fiber length to a desired length.
The inorganic fibers that were made into short fibers may be classified as needed. Preferably, the classification is performed such that the inorganic fibers having a fiber length of 200 μm or less are partially or entirely removed.
The classification may be performed by, for example, using a dry centrifugal classifier (also referred to as “dry cyclone”), a wet centrifugal classifier (also referred to as “wet cyclone”), or the like.
In the slurry preparing step, the opened inorganic fibers are mixed with a solvent, an inorganic binder, and an organic binder, whereby a slurry is prepared.
In the slurry preparing step, a slurry is prepared such that the ratio [w3B/w3A] of the weight percentage w3B of the organic binder to the weight percentage w3A of the inorganic binder satisfies the following condition (5) or (6), where w3A is the weight percentage of the inorganic binder contained in the slurry to be prepared, and w3B is the weight percentage of the organic binder contained in the slurry contained in the slurry to be prepared.
0<w3B/w3A≤0.8 (5)
9≤w3B/w3A (6)
The inorganic binder and the organic binder may be mixed in any order. Yet, preferably, the inorganic fibers and the inorganic binder are mixed first and left to stand for a while, and the organic binder is then added to the mixture. When the inorganic fibers and the inorganic binder are mixed first, the inorganic binder is certainly attached to the surface of each inorganic fiber. This can increase the friction between the inorganic fibers and improve the surface pressure. Further, aggregates in which the organic binder and the inorganic binder are aggregated by a flocculant may be added to the slurry.
In the papermaking step, the slurry is poured into a molding machine having a mesh for filtering on its bottom to remove the solvent in the slurry, whereby an inorganic fiber papermaking sheet is obtained.
The solvent may be removed by any means as long as the solvent contained in the inorganic fiber papermaking sheet can be removed. For example, the solvent can be removed by means such as compression, rotation, suction, decompression, or the like.
In the drying step, the inorganic fiber papermaking sheet is dried while being compressed by a method such as compression drying with a hot plate using a press dryer or the like.
A mat including the inorganic fibers with at least one of the inorganic binder or the organic binder attached thereto can be obtained by the above steps.
In the method for producing a mat material according to the second embodiment of the present invention, the step of attaching an inorganic binder and/or an organic binder to the mat after drying is not required.
However, when the ratio [w1B/w1A] of the weight percentage w1B of the organic binder attached to the mat to the weight percentage w1A of the inorganic binder attached to the mat satisfies the following condition (1) or (2) after the attaching step, the inorganic binder and/or the organic binder may be attached to the mat after the drying step:
0<w1B/w1A≤0.8; or (1)
9≤w1B/w1A. (2)
The following describes Examples that more specifically disclose the present invention. In the following Examples, the inorganic fiber mass is produced by needling, but the present invention is not limited to these Examples.
(a-1) Spinning Step
To an aqueous solution of basic aluminum chloride prepared to have an Al content of 70 g/L and an Al:Cl ratio of 1:1.8 (atomic ratio) was added silica sol to give a compositional ratio of Al2O3:SiO2 of 72:28 (weight ratio) in inorganic fibers after firing. Then, an organic polymer (polyvinyl alcohol) was further added thereto in an appropriate amount, whereby a mixture was prepared.
The resulting mixture was concentrated to obtain a spinning mixture, and the spinning mixture was spun by blowing, whereby an inorganic fiber precursor having an average fiber diameter of 5.1 μm was produced.
(a-2) Compressing Step
The inorganic fiber precursor obtained in the spinning step (a-1) was compressed to produce a continuous sheet.
(a-3) Needle-Punching Step
The sheet obtained in the compressing step (a-2) was continuously needle-punched under the following conditions, whereby a needle-punched article was produced.
First, a needle board with needles attached thereto at a density of 9 pcs/cm2 was provided. Next, this needle board was set above one surface of the sheet. Then, the needle board was moved up and down once in the thickness direction of the sheet to perform needle-punching, whereby a needle-punched article was produced. At this point, the needles were allowed to penetrate the sheet until barbs formed on the tips of the needles had completely penetrated the sheet from one surface to the other surface.
(a-4) Firing Step
The needle-punched article obtained in the needle-punching step (a-3) was continuously fired at a maximum temperature of 1250° C., whereby a fired sheet containing inorganic fibers including alumina and silica at a ratio of parts by weight of 72:28 was produced. The average fiber diameter of the inorganic fibers was 5.1 μm. The minimum fiber diameter was 3.2 μm. The thus-obtained fired sheet had a bulk density of 0.15 g/cm3 and a basis weight of 1400 g/m2. The density ρ of the entanglement points was 9 pcs/cm2.
The fired needle-punched article was cut to produce an inorganic fiber mass (needle-punched mat). Neither an inorganic binder nor an organic binder was attached to the inorganic fiber mass.
(a-5) Attaching Step
Subsequently, an inorganic binder and an organic binder were attached to the inorganic fiber mass.
(a-5-1) Organic Binder Mixture Preparing Step
Acrylate latex was diluted with water, whereby an organic binder mixture having a solids concentration of 0.20 wt % was prepared.
(a-5-2) Inorganic Binder Mixture Preparing Step
Alumina was diluted with water and blended with a polymeric dispersant, followed by sufficient stirring. Thereby, an inorganic binder mixture was prepared in which the solids concentration of the inorganic particles was 2.0 wt % and the concentration of the polymeric dispersant was 1000 ppm.
(a-5-3) Binder Mixture Preparing Step
The organic binder mixture obtained in the organic binder mixture preparing step (a-5-1) was added to the inorganic binder mixture obtained in the inorganic binder mixture preparing step (a-5-2) to give a weight ratio of 1:1, followed by sufficient stirring. Thereby, a binder mixture was prepared in which the solids concentration of the organic binder was 0.10 wt %, the solids concentration of the inorganic binder was 1.0 wt %, and the concentration of the polymeric dispersant was 500 ppm.
(a-5-4) Contacting Step
The binder mixture obtained in the binder mixture preparing step (a-5-3) was added by curtain coating to the inorganic fiber mass obtained in the firing step (a-4).
(a-5-5) Dehydrating Step
The inorganic fiber mass to which the binder mixture was added, which was obtained in the contacting step (a-5-4) above, was sucked and dehydrated by a dehydrator such that the amount of the binder mixture added was adjusted to 100 parts by weight relative to 100 parts by weight of the inorganic fibers, whereby a mat was obtained.
(a-5-6) Drying Step
The mat that underwent the dehydrating step (a-5-5) was dried, whereby a mat material according to Example 1 was produced.
A mat material according to Example 2 was produced by the same procedure as in Example 1, except that the solids concentration of the organic binder mixture prepared in the organic binder mixture preparing step (a-5-1) was changed to 0.66 wt %.
A mat material according to Example 3 was produced by the same procedure as in Example 1, except that the solids concentration of the organic binder mixture to be prepared in the organic binder mixture preparing step (a-5-1) was changed to 1.60 wt %.
A mat material according to Example 4 was produced by the same procedure as in Example 1, except that the solids concentration of the organic binder mixture to be prepared in the organic binder mixture preparing step (a-5-1) was changed to 18.0 wt %.
A mat material according to Example 5 was produced by the same procedure as in Example 1, except that the solids concentration of the organic binder mixture to be prepared in the organic binder mixture preparing step (a-5-1) was changed to 20.0 wt %.
A mat material according to Comparative Example 1 was produced by the same procedure as in Example 1, except that the solids concentration of the organic binder mixture to be prepared in the organic binder mixture preparing step (a-5-1) was changed to 0 wt %.
A mat material according to Comparative Example 2 was produced by the same procedure as in Example 1, except that the solids concentration of the organic binder mixture to be prepared in the organic binder mixture preparing step (a-5-1) was changed to 2.0 wt %.
A mat material according to Comparative Example 3 was produced by the same procedure as in Example 1, except that the solids concentration of the organic binder mixture to be prepared in the organic binder mixture preparing step (a-5-1) was changed to 4.0 wt %.
A mat material according to Comparative Example 4 was produced by the same procedure as in Example 1, except that the solids concentration of the organic binder mixture to be prepared in the organic binder mixture preparing step (a-5-1) was changed to 10.0 wt %.
A mat material according to Comparative Example 5 was produced by the same procedure as in Example 1, except that the solids concentration of the organic binder mixture to be prepared in the organic binder mixture preparing step (a-5-1) was changed to 16.0 wt %.
The shear failure load and the reduced surface pressure were measured for each of the mat materials of Examples and Comparative Examples, and the shear modulus of each mat material was determined. The shear failure strength and the reduced surface pressure were measured by the methods described in the description of the embodiments of the present invention. Table 1 shows the results.
Each of the mat materials produced in Examples and Comparative Examples was subjected to an inorganic fiber scattering test.
The method of the inorganic fiber scattering test is as described in the description of the embodiment of the present invention. A mat material with a fiber scattering rate of 0.35 wt % or less was evaluated as good “o”, and a mat material with a fiber scattering rate of more than 0.35 wt % was evaluated as poor “x”. Table 1 shows the results.
As shown in Table 1, the mat materials of the present invention were found to have a high shear modulus, with inorganic fiber scattering being prevented or reduced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-029961 | Feb 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2023/006349 | 2/22/2023 | WO |
