JPH0645510B2 - Inorganic oxide artificial fiber honeycomb structure and method for manufacturing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a honeycomb structure made of an inorganic oxide artificial fiber used as a filter, a catalyst carrier, and an adsorbent.

[Conventional technology]

As the honeycomb structure made of ceramic, there are a ceramic powder extruded and sintered, and an inorganic oxide artificial fiber paper manufactured by a method similar to that of cardboard paper.

The ceramic powder is limited in that the thickness of the partition wall can be reduced by extrusion, so there is a limit to increase the surface area per unit volume. If the volume is increased, a portion lacking the partition wall is generated during extrusion, so that the honeycomb structure having the partition wall having a large porosity cannot be manufactured. Therefore, a catalyst carrier, a filter, or the like that is not sufficiently compatible with the situation has not been obtained.

Since the paper of the inorganic oxide artificial fiber is manufactured by the papermaking method, the bulk density is usually 0.35 g / cc or less,
If fire powder is added to increase the bulk density, the bulk density becomes large and the strength becomes strong, but the spalling resistance becomes small and the life becomes extremely short when repeatedly subjected to heating bellows. The honeycomb structure formed by bending a paper having a low bulk density into a corrugated shape and alternately stacking the flat plates on each other and adhering the paper has extremely low strength.

Therefore, to date, a honeycomb structure made of an inorganic oxide having a large surface area per unit volume, a desired bulk density of partition walls, a desired porosity and sufficient strength and spalling resistance has not been provided. It is in.

[Problems to be Solved by the Invention]

In view of such circumstances, the present invention has a large surface area per unit volume, can have desired bulk density and porosity of partition walls, and has good strength and spalling resistance. The challenge is to provide.

[Means for Solving the Problems]

The present invention has found that a honeycomb structure made of an artificial inorganic oxide fiber capable of solving the above problems can be obtained by applying extrusion molding to the artificial inorganic oxide fiber.

According to the present invention, 80% by weight or more is made of an inorganic oxide artificial fiber, the partition wall for partitioning the cell has a thickness of 1.0 to 0.1 mm, and the partition wall has a bulk density of 1.8 to 0.5 g / In cc, the open cross-sectional area of one cell is 1 mm ² or more, and the inorganic oxide artificial fiber honeycomb structure is composed of an extruded body in which the inorganic oxide artificial fibers are bonded to each other by an inorganic binder. Aspect ratio of 10% or more by weight or more
And, an inorganic oxide artificial fiber having an aspect ratio of less than 10 is 30% by weight or less and a shot content of less than 1% by weight in an inorganic content of 87% by weight or more, an inorganic binder, and a total composition other than water. A method for manufacturing an inorganic oxide artificial fiber honeycomb structure, in which a mixture containing 40 to 60 parts by weight of water with respect to 100 parts by weight is extruded and dried and fired is used as a means for solving the problem.

In the present invention, as the inorganic oxide artificial fibers, glass fibers, alumina fibers, silica fibers, silica-alumina fibers, silica-alumina-boria fibers, zirconia fibers and the like having a general fiber diameter of 2 to 12 μm are used. If the diameter of the fiber is large, the number of bonding points between the fibers is small. Therefore, when the partition wall is thin, the strength becomes small. Therefore, it is preferable to use the thickness of about this level. The commercially available fibers of these inorganic oxide artificial fibers are about 2 μm in the thinnest fiber. These may be used alone or in combination of two or more.

In the present invention, the aspect ratio means the ratio of the fiber length to the fiber diameter (fiber length / fiber diameter). Shot is a granular material generated in the process of making the molten raw material into fibrous,
Those of ordinary skill in the art will generally indicate the shot content as a 212 μm sieve residue.

These inorganic oxide artificial fibers are carboxymethyl cellulose, methyl cellulose, for facilitating molding,
Organic paste such as polyvinyl alcohol, wax, paraffin, water emulsion such as stearic acid, lubricant for smoothly extruding graphite, water as a plasticizer, water-containing salt instead of water, alcohol, Water and the same effect substances such as ketones can be used as a plasticizer, but water is the most economical.

Glycerin, amines, polyethylene glycol, etc., a wetting agent for imparting flexibility and toughness to the molded body during molding and drying, an inorganic binder such as water glass, colloidal silica, colloidal alumina, talc, bentonite, nitriding agent It is mixed with powder of boron, magnesium oxide or the like to form a paste, which is extruded into a honeycomb shape, dried, and then fired to obtain a honeycomb structure.

[Action]

In the inorganic oxide artificial fiber honeycomb structure of the present invention,
In order to make the structure itself strong, it is necessary to add an inorganic binder that alternately binds the fibers, in order to make the structure itself strong.
The lower limit of the fiber content is naturally determined from the fact that it cannot be set to 00% and the amount varies depending on the type of binder used, and the total amount with the addition amount of the binding aid for strengthening this binding. This is because of

Further, when the total amount of the binder and the binding aid exceeds 13% by weight, the spalling resistance is lowered, and the spalling resistance of the inorganic oxide artificial fiber cannot be fully utilized. This is because it is necessary to suppress the total amount of these to 13% by weight.

In the inorganic oxide artificial fiber honeycomb structure of the present invention,
The partition wall that divides the cell has a thickness of 0.1 to 1.0 mm, and the opening cross-sectional area of one cell is 1 mm ² or more. Yes, because the cross-sectional area of one opening of the cell is 1 mm ² . The reason why the upper limit of the thickness of the partition walls that define the cells is set to 1 mm is that if the thickness is increased to more than 1 mm, the surface area per unit volume becomes small, which makes it unsuitable for use as a honeycomb structure. .

The partition wall bulk density of 1.8 to 0.5 g / cc is 0.5
If it is less than g / cc, the porosity of the partition wall becomes large, but it does not have the strength to withstand handling, and if it exceeds 1.8 g / cc, the ratio of the inorganic oxide artificial fiber having a small aspect ratio becomes large, so the strength is high. In order to achieve this, the amount of binder that bonds the contact points of the fibers also increases, and the porosity of the partition wall is about 25.
This is because it becomes less than 100% and becomes unsuitable for use as a honeycomb structure.

In the method for manufacturing a honeycomb structure of the present invention, most of the inorganic oxide artificial fibers have an aspect ratio of 10 to 300.
If the aspect ratio is less than 10, the bulk density is greater than 1.8 g / cc, and if it exceeds 3000, extrusion molding becomes difficult. Also, if the aspect ratio is less than 10 and more than 30% by weight, the bulk density will exceed 1.8 g / cc.

Further, in the case of fibers containing a shot, if the shot content exceeds 1% by weight, the bulk density of the partition walls becomes large and the extrusion molding machine becomes clogged, so less than 1% by weight, preferably 0.5% by weight. It is good to be less than.

The extruded material needs to be extruded as a paste, and if the water content is too high, the paste needs to be formed in a large amount in order to give the paste moldability. Not only does the shrinkage increase, but it becomes difficult to remove oils and fats added as a lubricant, cracks occur during firing, and the bulk density becomes less than 0.5 g / cc. Therefore, it is necessary to add 40 to 60 parts by weight of water to 100 parts by weight of the total composition other than water.

〔Example〕

The shot content of silica-alumina fibers having an average fiber diameter of 2.8 μm was reduced to 0.05% by weight, most of the aspect ratios were set to 100 to 200, and the aspect ratio was set to 10
Was used in an amount of 8 wt% (bulk a), and most of the same fiber had an aspect ratio of 10 to 50 and an aspect ratio of less than 10 was 18 wt% (bulk b).

This bulk was premixed with a stirrer in the composition shown in the table below, thoroughly kneaded with a kneader, and each mixture was left to stand for 24 hours and extruded with an auger type vacuum extruder.

In Example 1 using the bulk a, each cell has a square shape having an opening size of 3 × 3 mm, a partition wall thickness of 0.5 mm, and an outer diameter of about 2 mm.
Extruded into a 5 × 25 mm square.

In the second embodiment using the bulk b, the opening size of one cell is a square of 1.5 × 1.5 mm, and the partition wall thickness is 0.2.
mm, and an outer diameter of about 26 × 26 mm was extruded into a square.

This extruded compact is dried and degreased and then heated in an electric furnace at 200 ° C.
The temperature was raised to 1350 ° C. at a heating rate of / hr, and the temperature was maintained for 1 hour for firing.

Comparative Example 1 A honeycomb structure was obtained in the same manner as in Examples 1 and 2 except that the alumina powder having a central particle size of 5 μm was compounded as shown in the table and the firing temperature was 1650 ° C.

Comparative Example 2 A silica-alumina fiber having an average fiber diameter of 2.8 μm and a length of 1 was used.
0mm or less, 8% bulk with a shot content of 30% by weight
0 parts by weight and 20 parts by weight of kibushi clay were dispersed in 5000 parts by weight of water, and after adding polyvinyl acetate as an organic binder to this, polyacrylamide was added to perform coagulation treatment, and papermaking was performed by a papermaking method. A sheet having a thickness of about 0.6 mm was prepared. After drying this sheet, corrugated sheets with a continuous corrugation with a wave pitch of 5 mm and a wave height of 1.8 mm and a flat sheet are alternately laminated in the same manner as corrugated paper and baked at 1250 ° C. for 1 hour. , External dimensions approx. 30 x 30
A honeycomb structure with a size of 30 mm was obtained.

The above composition and the physical properties of the obtained honeycomb structure are shown in the following table.

In the table, partition bulk density is g / cc, compressive strength is in the opening direction kg.
f / cm ² , cell number is 25 mm square, spalling resistance is 100
The results obtained by alternately moving up and down at 0 ° C. and room temperature 10 times are shown.

〔The invention's effect〕

Advantageous Effects of Invention According to the present invention, it is possible to provide a honeycomb structure made of an inorganic oxide artificial fiber, which has a large surface area per unit volume, can have desired bulk density and porosity of partition walls, and has good strength and spalling resistance.

Claims (2)

[Claims] 1. 87% by weight or more is made of an inorganic oxide artificial fiber, and the partition wall partitioning the cell has a thickness of 1.0 to 0.1 mm.
The partition wall has a bulk density of 1.8 to 0.5 g / cc, one opening cross-sectional area of the cell is 1 mm ² or more, and the inorganic oxide artificial fibers are bonded to each other with an inorganic binder. An inorganic oxide artificial fiber honeycomb structure consisting of an extruded body. 2. Aspect ratio of 70% by weight or more of the fiber is 1
An inorganic oxide artificial fiber having an aspect ratio of 0 to 30 and an aspect ratio of less than 10 is 30% by weight or less and a shot content of less than 1% by weight in an inorganic content of 87% by weight or more, an inorganic binder, and a content other than water. 40 to 100 parts by weight of the total formulation
A method for producing an inorganic oxide artificial fiber honeycomb structure, which comprises extruding a mixture containing 60 parts by weight of water and drying and firing the mixture.