JP2734486B2 - Method for producing porous body composed of a plurality of particle layers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a porous body composed of a plurality of particle layers used for a dust-collecting ceramic filter or the like for collecting exhaust gas and dust in exhaust gas. It relates to a manufacturing method.

[Prior Art] A ceramic filter having high heat resistance and corrosion resistance is used for dust collection from high-temperature exhaust gas or highly corrosive wastewater. This filter has a two-layer structure consisting of a thick skeletal layer with coarse pores and large pores, and a thin dust collecting layer with small pores on the surface using finer particles than the raw material for the skeletal layer. What is said is common.

[Problems to be solved by the invention]

The production of a conventional ceramic two-layer structure is disclosed in
As described in 6206 gazette, a method of attaching a layer made of a fine slurry body applied on the core on the surface of the skeleton layer,
As disclosed in JP-A-60-61019, a ceramic powder for a dust removing layer is applied to a core mold by a spray method, and after sufficiently drying, a coarse raw material for a skeleton layer is disposed on the core to obtain a rubber / core material. A method of forming a two-layer structure by performing pressing or the like is employed.

However, with these conventional methods, it is very difficult to control the thickness of the fine dust collection layer, and the fine filtration required for ceramic dust filters in the future cannot be sufficiently achieved. That is, in the above-described conventional method, the thickness of the dust collecting layer of fine particles may change due to differences in the slurry adhesion management and the coating method. Further, when peeling or pinholes occur, it is not possible to inspect and manage these, especially for products in which a dust collecting layer is applied to the inner surface of a pipe. In addition, as the pore diameter increases, the change in the differential pressure due to the change in the layer thickness increases, and accurate management is required. In addition, instead of the conventional two-layer structure, a three-layer or four-layer structure is required for microfiltration, but this is extremely difficult with the conventional method.

An object of the present invention is to provide a method for producing a porous body composed of a plurality of particle layers, which can solve the above problems.

[Means for solving the problem]

The method for producing a porous body composed of a plurality of particle layers of the present invention is a method for producing a porous body composed of a plurality of particle layers having different pore diameters. It is formed into a tape having a predetermined thickness by extrusion molding or a doctor blade method, and then dried to form a flexible and deformable green sheet. It is characterized in that a layer composed of fine particles is formed.

[Action]

In the present invention, fine particles are kneaded with a resin and a solvent to produce a clay-like material, which is then formed into a tape-like material by an extrusion molding method or a doctor blade method, and then dried, To form a tape-like green sheet for forming a layer composed of various particles.

Since the above-mentioned green sheet is formed by the above-mentioned forming method using the above-mentioned material, it can be made flexible, deformable, and handleable.

Therefore, in particular, when forming a cylindrical porous body, after forming a layer made of fine particles by winding and forming a porous body integrated with a layer made of coarse particles,
By firing this, a porous body can be produced, and the production of the porous body becomes easy.

Further, since the formation of the green sheet is performed by an extrusion molding method or a doctor blade method, the thickness can be easily controlled, the film thickness can be reduced, and three layers using particles having different particle diameters can be formed. Formation of a four-layer structure is also facilitated, and a porous body capable of more precise filtration can be manufactured.

〔Example〕

 Hereinafter, a first embodiment of the present invention will be described.

In this embodiment, three layers of tubular ceramic porous bodies having different pore diameters are manufactured using the green sheet described below. The ceramic porous body manufactured according to the present embodiment is:
As shown in FIG. 1, the tube is formed into a tubular shape by three layers of a layer composed of fine particles 1, a layer composed of intermediate-sized particles 2, and a layer composed of coarse particles 3. The layers are arranged.

The layer composed of the fine particles 1 is intended for dust removal. For example, in order to prevent particles of about 1 μm contained in exhaust gas from entering, the raw material particle diameter is about 3 μm. If the film thickness is increased, dust removal is improved, but the flow resistance is increased and the pressure loss is too high. Therefore, it is necessary to make this film thickness as thin as possible.

In the present embodiment, a sheet having a predetermined thickness, in which the intermediate particle size 2 is a green sheet, is used.

As a method for forming the ceramic green sheet (formed body), an extrusion method and a doctor blade method are used. Either method is suitable for forming a sheet of about 100 μm to 1000 μm.

Extrusion molding uses methyl cellulose,
A plasticizer, a lubricant, and a solvent are added to an organic binder having a thickening action such as an acrylic resin binder, and the mixture is kneaded, and then a green sheet is extruded with a mold having a predetermined thickness. In the doctor blade method, a plasticizer and a solvent are added to an organic binder having a thickening effect such as methyl methacrylic resin to a ceramic powder in the same manner as in extrusion molding to produce a slurry having a lower viscosity than in extrusion molding. A green sheet is obtained by flowing on a release film while controlling the film thickness with a blade set to a predetermined film thickness.

The intermediate particle 2 constituting this green sheet is intended to support the finest particle 1 and to bridge the coarse particle 3 with the finest particle 1 as described below.
Preferably, the thickness of the green sheet is about 200 μm. The green sheet is formed by the extrusion molding method or the doctor blade method as described above, and has a paper-like flexibility. The thickness of the green sheet can be easily set to a predetermined value.

The coarse particles 3 forming the outermost layer are raw materials for forming a skeleton layer that maintains the strength of the structure. It is desirable that the pressure difference of this layer is as small as possible.
A coarse raw material having a diameter of about 100 to 300 μm is used. This layer can also be formed into a green sheet by the same method as the layer of the intermediate particle size 2, but it is more cost-effective to prepare the raw material as granulated powder for pressure molding.

As described above, the green sheet composed of the intermediate-size particles 2 formed by the extrusion molding method or the doctor blade method is wound into a roll while being dried. The surface is coated with ink obtained by coloring the fine particles 1 using an ink brush or the like. The sheet is dried and wound up. This completes the preparation of the intermediate layer composed of the intermediate particle particles 2 and the dust removal layer composed of the fine particles 1. According to the application of the fine particles 1, unlike the case of directly applying to the conventional porous ceramics,
This is an application to a flat sheet, and the film thickness can be controlled to be thin or an inspection such as uneven coating can be easily performed.

The sheet composed of the intermediate layer and the dust removing layer configured as described above is wound around a mold with the dust removing layer facing the mold. At the time of winding the sheet around the mold, the joint between the sheet and the mold is adhered using a solvent for forming the green sheet, such as water. Then, after attaching a rubber model forming an outer periphery around the mold, coarse particles 3 are filled in the space between the mold and the rubber model.

As described above, the sheet including the intermediate layer and the dust removing layer, the mold containing the coarse particles 3 and the rubber model are covered with a lid, and sealed so that water does not enter. Molding. As a result, the dust removing layer, the intermediate layer, and the layer of the coarse particles 3 are integrated with each other, and shape retention can be obtained.

Then, it is removed from the mold and the rubber mold to obtain a ceramic porous molded body. By firing this at a predetermined temperature,
A desired ceramic porous body is obtained.

In the present embodiment, the intermediate layer composed of the intermediate particle particles 2 is manufactured by using a green sheet formed by an extrusion molding method or a doctor blade method, and the thickness, the particle diameter, and the material can be appropriately selected. And the dust removal layer
It is formed by coating on a flat green sheet of the intermediate layer, the thickness of which can be reduced, and the coating can be inspected for unevenness to obtain a uniform thickness.

An example of manufacturing a porous ceramic body using this embodiment will be described below.

The crushed granules of the electrofused cordierant (2MgO.2Al ₂ O ₂ .5SiO ₂ ) are classified into coarse particles having a particle size range of 300 to 150 μm, intermediate particles having an average particle size of 22 μm, and fine particles having an average particle size of 8 μm. Obtain three types of raw materials.

The coarse particles are prepared by adding 2.5 parts by weight of a glaze and 3 parts by weight of polyvinyl alcohol as binders to 100 parts by weight, adding water to the mixture, kneading the mixture, and then drying and crushing to obtain a raw material for a skeleton layer.

Intermediate particle size is 1000 parts by weight, organic binder
After adding 20 parts by weight and 30 parts by weight of water and kneading with a pressure kneader, extruding it into a sheet with an extruder equipped with a mold having a width of 80 mm and a thickness of 0.2 mm, winding it into a roll, winding it up into a roll, Green sheet.

For the fine particles, a slurry was prepared by adding 3 parts by weight of polyvinyl alcohol to 100 parts by weight, a small amount of an antifoaming agent, 40 parts by weight of water, and 0.2 parts by weight of carbon black. Carbon black is a colorant for examining uneven coating and coating thickness. This slurry is used as a raw material for the dust removal layer.

The raw material slurry of the dust-removing layer is applied to one surface of a green sheet of the intermediate layer placed on a flat plate with a roll brush having a width of 100 mm.
The coating thickness of the roll brush is adjusted with a height adjusting jig of a gantry to which the roll brush is attached so that the thickness after drying is about 30 μm.

The green sheet coated with a dust layer material on one side,
It is spirally wound around a φ120 × 900 mold core surface with the dust layer raw material application surface inside. At this time, the joint between the sheets is wrapped by about 2 mm so that there is no gap between the sheets.

A rubber mold of φ170 × 900 is attached to the mold base on which the mold core is attached around the mold around which the sheet is wound. Here, after filling the coarse particle raw material into the gap between the rubber mold and the core, a mold lid is attached and sealed so that water does not enter.

This mold is placed in a CIP molding apparatus having an internal volume of φ500 × 1200, and then molded under pressure at a pressure of 1000 kgf / cm ² . Then, the rubber mold and the metal mold are removed to obtain a molded body. After firing this molded body in the air at 1350 ° C. × 4 hr, the outer surface is cut to form an outer diameter of 150 mm and an inner diameter of 120 mm × 800 m
m porous ceramic body is obtained.

For evaluation of the ceramic porous body, a test piece in which one end was sealed after cutting the product into a length of 100 mm was used. Pressure loss performance to read the pressure by flowing air at room temperature at a flow rate of 5 cm / sec from one end of this test piece, dust removal performance for cross-sectional observation of ash penetration by similar air flow including ash with an average diameter of 10 μm, and inside the test piece A vinyl film was applied and sealed, and pressure was applied until the internal pressure of the tube became 5 kgf / cm ² , and tests for internal pressure durability were performed to check for damage. The results are as follows, and the porous body showed good performance.

 5cm / sec pressure drop performance 180mmAq Dust removal performance (× 100 observation) No penetration.

5kgf / cm ² internal pressure durability performance No damage.

Next, a second embodiment of the present invention in which a dust removing layer is provided on the outer surface of a tubular ceramic porous body will be described.

In this embodiment, only a dust layer formed of fine particles 1 and a green sheet of an intermediate layer formed of intermediate particles 2 and a layer formed of coarse particles 3 formed in the same manner as in the first embodiment are pipe-shaped. An extruded and then dried green single layer tube is provided. A green sheet is wound around the green single-layer tube in the same manner as in the first embodiment, with the dust removal layer facing outward. Thereafter, this is placed in a CIP mold in the same manner as in the first embodiment, subjected to CIP molding, and then separated and fired to form a tubular ceramic porous body having a dust removal layer made of fine particles 1 on the outer surface. Get.

Next, a third embodiment of the present invention in which a dust removing layer is provided on one surface of a plane will be described.

In this embodiment, after the green sheet comprising the dust removal layer and the intermediate layer of the first and second embodiments is placed on the bottom of the mold, the coarse particles as the skeleton layer material are filled thereon, In the same manner as in the second embodiment, a metal mold is formed, and this is released and fired to obtain a porous ceramic body.

The second and third embodiments are different from the first embodiment only in the arrangement of the dust removal layer or the shape of the ceramic molded body, and have the same effects as the first embodiment. it can.

The porous body in each of the above embodiments has a three-layer structure, but the present invention is not limited to this, and may have a two-layer structure or a four-layer structure or more. In addition, although ceramic particles are used in each of the above embodiments, the present invention can produce a porous body in the same manner even with a metal in the form of particles.
The present invention can also be applied to an inclined configuration of a ceramic and a mold.

〔The invention's effect〕

In the method for producing a porous body composed of a plurality of particle layers according to the present invention, a fine sheet is kneaded with a resin and a solvent to form a clay, and the green sheet is formed into a tape by an extrusion molding method or a doctor blade method. By forming a layer composed of fine particles using this green sheet, the green sheet is flexible and deformable, and can be handled easily, so that a porous body can be easily formed. By firing this, a porous body can be easily manufactured.

Further, since the green sheet is formed by the extrusion molding method or the doctor blade method, the thickness of the green sheet can be easily controlled, the film thickness can be reduced, and three or four layers using particles having different particle diameters can be obtained. A structure can be easily formed, and a porous body capable of more precise filtration can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a porous ceramic body manufactured according to an embodiment of the present invention. 1 ... fine particles, 2 ... medium-sized particles, 3 ... coarse particles.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masaki Akiyama 1-1, Akunouracho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (72) Inventor Yoshiharu Watanabe 1-1, Akunoura-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Shipyard (56) References JP-A-61-2616 (JP, A)

Claims (1)

(57) [Claims] 1. A method for producing a porous body comprising a plurality of particle layers having different pore diameters, wherein a resin and a solvent are added to fine particles to form a clay, which is extruded or a doctor blade method. After forming into a tape-shaped thing having a predetermined film thickness by drying, a flexible and deformable green sheet is formed by drying, and a layer made of fine particles is formed using this green sheet. A method for producing a polyporous body composed of a plurality of particle layers.