JPH0483773A - Heat expansion-resistant member - Google Patents

Abstract

PURPOSE:To improve durability by blending sepiolite mineral with treated unexpanded vermiculite, ceramics fibers and an ethylenebased multi-copolymer as an organic binder in a specific weight ratio. CONSTITUTION:3-5wt.% alpha type sepiolite mineral is blended with 49-59wt.% unexpanded vermiculite treated with an aqueous solution of NaNH4HPO4, 25-30wt.% ceramics fibers and 10-15wt.% ethylenebased multi-copolymer such as ethylene vinyl acetate acrylic acid copolymer as an organic binder to give a heat expansionresistant sheet. The sheet is suitable for four-wheel automobiles and a heat expansion-resistant sheet by partially changing the blend of 23-33wt.% treated unexpanded vermiculite and 5O-60wt.% ceramics fibers is suitable for motor-bicycles. Then a heat expansion-resistant sheet 2 is wound twice around the outer periphery of a monolithic catalyst 1 made of ceramics honeycomb, attached to a two-divided metallic casing 3 and the outer periphery of the casing 3 is fastened with a metallic band 4 to give a metallic converter.

Description

[Detailed Description of the Invention] Field of Industrial Application] The present invention purifies exhaust gas by oxidizing or reducing harmful components such as carbon monoxide, hydrocarbons, and nitrogen oxides emitted from automobile engines. The present invention relates to a thermal expansion resistant member suitable as a holding material for a ceramic honeycomb monolithic catalyst constituting a catalytic converter in a low-pollution engine.

[Conventional technology] Carbon monoxide emitted from car engines.

Ceramic honeycomb monolith catalysts, which have excellent high-temperature properties, are suitable as catalysts for purifying exhaust gas by oxidizing or reducing harmful acids such as hydrocarbons and nitrogen oxides, and for obtaining low-pollution engines. Are known.

By the way, since ceramics are brittle and have poor toughness, a retaining material with cooling properties is used to prevent them from being damaged by mechanical shocks such as vibrations that occur when a car is running. It is wound and attached to a metal casing.

Since the ceramic honeycomb monolith catalyst is exposed to high-temperature exhaust gas during engine operation, the holding material is naturally required to have excellent heat resistance, that is, conditions that do not reduce high-temperature strength. Moreover, as the engine is operated continuously and the exhaust gas gradually becomes hotter, even if the holding material expands correspondingly to each temperature range, the holding power and cushioning properties for the ceramic honeycomb monolith catalyst decrease. Conditions that do not apply are required.

Conventionally, as a holding material for a monolithic catalyst that can satisfy such conditions, for example, Japanese Patent Publication No. 61-35143
As disclosed in the publication, from 40% by weight of untreated unexpanded vermiculite to 6.
A heat-expandable sheet is known, which contains 5% by weight of a binder selected from the group consisting of 5% by weight, 25% to 50% by weight of an inorganic fiber material, and 5% to 15% by weight of a binder selected from inorganic binders.

For example, as disclosed in Japanese Patent Publication No. 62-38397, instead of the inorganic binder, natural rubber latex, styrene-butadiene latex, butadiene-
Heat-expandable sheet materials using organic binders such as acrylonitrile latex, latex of polymers or copolymers of acrylic acid esters and methacrylic acid esters are also known.

[Problems to be Solved by the Invention] However, as is clear from Table 2 and the graph in FIG. 3 below, based on the experimental results by the present inventor, the heat-expandable sheet made using the above-mentioned inorganic binder has the following problems: Around 200°C to 300°C, which corresponds to the low temperature range (for details, 200°C to 32°C)
5°C) due to the creep phenomenon, and the amount of thermal expansion corresponding to the medium temperature range of 350°C to 400°C is extremely small, resulting in rattling. It has been found that the holding power of the monolithic catalyst is significantly reduced, and the amount of thermal expansion is suppressed at temperatures above 600° C., which corresponds to the high temperature range, which significantly reduces the holding power of the ceramic honeycomb monolithic catalyst in the high temperature range. In other words, with conventional heat-expandable sheets, it is not possible to expect high holding power in both low-temperature and high-temperature regions, resulting in wobbling.Furthermore, the sheet retains its shape by being bonded only with an inorganic binder. As a result, the parts exposed to high-temperature, high-speed flowing exhaust gas gradually disappear, and the monolithic catalyst's retention function disappears over time. That is, it has problems such as extremely poor gas attack resistance.

In addition, the aforementioned untreated unexpanded vermiculite was mixed with phosphoric acid 2
Treatment with sodium hydrogen is also known, but although this heat expansion resistant sheet suppresses negative expansion in the low temperature region, it is expected to have sufficient holding power because the thermal expansion in the medium and high temperature regions is small. (See Table 2 and Figure 3).

Furthermore, as is clear from Table 5 below, which is based on the experimental results of the present inventors, the heat-expandable sheet material made using the above-mentioned organic binder has low tensile strength at room temperature, and Due to its lack of flexibility, it is prone to cracking over a long range when bent, making it unsuitable for this type of heat-expandable member that is often used in a bent state, such as when wound.

The present invention was made in view of these circumstances, and it is possible to secure a sufficiently large holding force from a low temperature range to a high temperature range, and to improve gas attack resistance.
Moreover, it is an object of the present invention to provide a heat expansion resistant member that can improve tensile strength and flexibility.

1. Means for Solving the Problems] In order to achieve the above object, the heat expansion resistant member according to the present invention contains sepiolite mineral, treated unexpanded vermiculite, ceramic fiber, and organic binder in a predetermined ratio. In the heat expansion resistant member, an ethylene-based multi-component copolymer is used as the organic binder.

Further, as the treated unexpanded vermiculite, untreated unexpanded vermiculite treated with an aqueous solution of sodium ammonium phosphate is used.

Further, the blending ratio of each of the constituent materials is 3 to 5% by weight of sepiolite mineral and 49 to 59% by weight of treated unexpanded vermiculite.
The ceramic fibers are set at 25-30% by weight, and the ethylene-based multi-component copolymer as an organic binder is set at 10-15% by weight.

Furthermore, the blending ratio of each of the constituent materials is 3 to 5% by weight of sepiolite mineral and 23 to 3% by weight of treated unexpanded vermiculite.
3% by weight, 50 to 60% by weight of ceramic fibers, and 10 to 15% by weight of ethylene-based multi-component copolymer as an organic binder.

[Function] According to the present invention, by blending sepiolite mineral, treated unexpanded vermiculite, shellac fiber, and organic binder in predetermined ratios, it is possible to improve the low negative expansion range in the low temperature region and the heat resistance strength in the high temperature region. It is possible to provide cushioning properties that alleviate mechanical shocks such as vibrations and shape retention properties at room temperature in a moderately balanced manner, and to ensure a sufficiently large holding force in a wide temperature range from low to high temperatures. At the same time, gas attack resistance can be improved. In particular, by using an ethylene-based multi-component copolymer as an organic binder, which has excellent elongation, adhesion, and weather resistance in a well-balanced manner, it improves tensile strength and flexibility at room temperature, and prevents cracks caused by bending. Occurrence is suppressed.

In addition, if untreated unexpanded vermiculite is treated with an aqueous solution of sodium ammonium hydrogen phosphate, Na
Those that are easily ion-exchanged with + and those that are easily ion-exchanged with NH4+ are effectively ion-exchanged by the aqueous solution containing both ions, increasing the amount of expansion and expansion power of vermiculite.

[Example] Embodiments of the present invention will be described below based on the drawings.

Fig. 1 is a schematic cross-sectional view showing an example of a catalyst converter. In the figure, 1 is a ceramic honeycomb monolith catalyst, and a heat-expandable sheet 2 is wound around the outer circumference of the monolith catalyst 1, which is divided into two metal parts. It is attached to a casing 3, and the outer periphery of the metal casing 3 is tightened with a metal band 4.

The heat-expandable sheet 2 contains 3-5% by weight, preferably 4% by weight of sepiolite mineral, 49-59% by weight, preferably 54% by weight of unexpanded vermiculite, and 1125-35% by weight, preferably ceramic fiber. 30% by weight and 10 to 1 ethylene-based multi-component copolymer as an organic binder
It is produced by a papermaking method with a blending ratio of 5% by polymerization, preferably 12% by weight.

Then, a metal casing 3 divided into two and a metal band 4
are each made of 5US304.

There are two types of sepiolite minerals that make up the thermal expansion-resistant sheet 2, depending on their crystallinity: α-type sepiolite is a highly crystalline fibrous mineral, and -β is a powder-like one with low crystallinity or amorphous. It is called type sepiolite. Since β-type sepiolite is in powder form, it has poor entanglement with ceramic fibers, unexpanded vermiculite, etc., so α-type sepiolite is used. However, α-type and β-type may be used together, and sepiolite minerals are
It solidifies when kneaded with water and dried. Furthermore, 400 to 80
It has a light sinterability at 0℃, and α-type sepiolite in particular entangles well with ceramic fibers and vermiculite, and it does not break like glass fibers or ceramic fibers even when rubbed or tightened. The heat expansion resistant sheet 2 to which sepiolite mineral is added prevents negative expansion at around 300°C when subjected to surface pressure.

To improve the holding power of a ceramic honeycomb monolith catalyst 1.

The treated unexpanded vermiculite is treated with an aqueous solution of sodium ammonium hydrogen phosphate. In this way, by immersing the untreated unexpanded vermiculite in the aqueous solution, N
Those that are easily ion-exchanged with H4+ are effectively ion-exchanged by the aqueous solution containing both ions, increasing the amount of expansion and expansion power of vermiculite.

Ceramic fiber improves heat resistance strength and 30
It plays the role of preventing negative expansion near 0°C, and particularly functions as a binder in the high temperature range where the organic binder completely disappears, improving shape retention.

Ethylene-vinyl acetate acrylate copolymer (for example, Sumikaflex 900 manufactured by Sumitomo Chemical Co., Ltd.) is used as the ethylene-based multi-component copolymer serving as the organic binder, and if it is less than 10% by weight, the strength at room temperature and Since flexibility is insufficient, it is necessary to keep the amount in the range of 10 to 15% by weight.

Table 1: 1000g of unexpanded vermiculite from South Africa
After immersing the vermiculite in the aqueous solution shown at room temperature for 120 hours, washing with running water and drying at 105°C for 2 hours, and heating at a predetermined superheating temperature for 30 minutes, the specific volume of the vermiculite was measured using a measuring cylinder. It was measured.

The measurement results are shown in Table 2 and FIG.

Table 1 Treatment aqueous solution (blank below) Table 2 Degree of expansion of vermiculite due to heat treatment (specific volume c
c/g) In Table 2 above, the numbers in parentheses indicate the coefficient of thermal expansion (%).
It is m.

In Table 2 above, sodium ammonium hydrogen phosphate is 200 ml as seen in ammonium dihydrogen phosphate treatment.
It can be seen that there is no contraction at ~300°C, that is, no negative expansion, a higher degree of expansion (amount of expansion) than in sodium hydrogen phosphate treatment, and an early expansion start temperature of 275°C.

α-type sepiolite (Milcon MS-2 from Showa Mining Co., Ltd.)
-2) 4% by weight, treated unexpanded vermiculite (No. 0 from South Africa) 5431 (amount, ceramic fiber (new annotation)
5C1260D2) from Sumitomo Chemical Co., Ltd. and 30% by weight of ethylene vinyl acetate acrylate copolymer emulsion (Sumikaflex 900 from Sumitomo Chemical Co., Ltd.) as an organic binder.
12% by weight, thickness 4.9mm, density 0.5~0
．． A heat-expandable mat of 8 g/c, preferably 0.7 g/c, is produced by a papermaking method, and this mat/
Material A with a diameter of 15 mm and a thickness of 4.9 mm was prepared from the sheet, and as shown in Fig. 2, it was compressed to a thickness of 3 mm with quartz rods 7A and 7A in a heating furnace 5 using a load cell 6, and was compressed in about 50 minutes. The thermal expansion force was measured while the temperature was raised to 750°C. The results are shown in Table 3 below.

Table 3 Thermal Expansion Force (kgf) From Table 3 above, it can be seen that high expansion force is obtained even in the high temperature range. In particular, vermiculite (No. 0), which has a small particle size, has a higher expansion power and has a smaller decrease in expansion power at high temperatures, so it is required to have high expansion power even at high temperatures, such as in holding materials for ceramic catalysts for automobiles. It is suitable for those with large particle size, such as 8-miculai) (No. 1),
Although the expansion force is slightly lower than that of vermiculite (No. 0), which has a small particle size, as shown in Table 2 above, the one with a large expansion amount is, for example, the outer periphery of a power transmission cable inserted into a through hole in a construction wall. It can be said that it is suitable for fireproof sealing materials that are wrapped around.

The heat-expandable sheet 2 according to the present invention or the conventional example (
A heat-expandable sheet (Japanese Patent Publication No. 61-35143) was wound and loaded into a metal cylindrical casing 11 with an inner diameter of φ82-2 mm and subjected to heat treatment. The cylindrical catalyst 10 was pressed in the direction of the arrow by the load cell 14 at a compression speed of 5 m/min, and the pressing force required to extrude the cylindrical catalyst 10, that is, the holding force of the heat-expandable sheet 2 was measured. The results are shown in Table 4 below and the graph in FIG.

Table 4 Pressing Force of Cylindrical Catalyst (kg f) According to Table 4 and the graph in FIG. Although the holding force in the high temperature range of 600°C or higher is small, according to the thermal expansion resistant sheet 2 according to the present invention, the holding force remains significantly low even in the negative expansion range of 325°C, and the holding force is low in the high temperature range of 600°C or higher. It can be seen that a large holding force can be secured. This can be said to be due to the synergistic effect of the expansion amount and expansion power possessed by the octa-miculite treated with sodium ammonium hydrogen phosphate and the sepiolite mineral, which is not included in conventional sheets.

In addition, mer 2 manufactured by the papermaking method with the above-mentioned blending ratio
(Example) and NBR latex (Example) as an organic binder.
The tensile strength and bending resistance of conventional mats (Comparative Examples 1 and 2) manufactured using Nippon Zeon Co., Ltd.'s 1562 and 1571) at the same blending ratio were measured. The effectiveness of using vinyl acetate acrylate copolymer was confirmed.

The test results are shown in Table 5.

The tensile test was conducted using a test mat with a diameter of 25 mm, a length of 160 mm, and a thickness of 4.9 mm, with a gage distance of 100 mm.
mm, and was pulled at a pulling speed of 20 mm/min.

In addition, the bending resistance test was conducted using a pine specimen with a radius (W) of 25 mm x length (L) of 80 mm x thickness (t) of 4.9 mm).
As shown in FIG. 6, when A was bent 180', the crack length (JL) generated on the outer surface of the bent portion was measured.

Table 5 Test Results It was found that the cloth 5 increased the tensile strength by about 2.3 to 3.5 times compared to conventional heat-expandable mats, and also had significantly superior bending resistance.

In the above example, like the exhaust system of a four-wheeled vehicle, the distance from the engine exhaust port to the catalytic converter is long and the exhaust gas is exposed to a slightly slower speed, so that the gas attack on the heat-expandable sheet is compared. We have shown a heat expansion resistant component with a compounding ratio suitable for use in small and highly rigid catalytic converters. In addition, in cases where the catalytic converter is exposed to exhaust gas flowing down at high speed and the gas attack on the thermal expansion resistant seal is severe, use a thermal expansion resistant material with a blending ratio that emphasizes gas attack resistance rather than the amount of expansion. is requested. The blending ratio of each constituent material for this is 3 to 5% by weight of Seviolite mineral, preferably 4% by weight, and 23 to 33% by weight of unexpanded vermiculite.
, preferably 28% by weight, ceramic ml & 50-60
% by weight, preferably 56% by weight, 10-15% by weight of ethylene multi-component copolymer as organic binder, preferably 1
2% by weight, and in this case, compared to the example suitable for the exhaust system of a four-wheeled vehicle, the blending ratio of unexpanded vermiculite is lowered to suppress the amount of expansion, while contributing to an improvement in heat resistance strength. By increasing the blending ratio of ceramic fibers, cracking of the monolithic catalyst 1 and abnormal deformation of the metal casing 3 due to excessive expansion can be prevented.

[Effects of the Invention] As described above, according to the present invention of claim (1), the low range of negative expansion in the low temperature region, the improvement in heat resistance strength in the high temperature region, and the effective mitigation of mechanical shocks such as vibrations are achieved. Cushioning properties and shape retention properties are imparted in a moderately well-balanced manner, and therefore the ceramic honeycomb monolithic catalyst, which has brittle characteristics with poor toughness, is properly held without wobbling with a large holding force regardless of low temperature and high temperature ranges. Therefore, it is possible to prevent the inconvenience of damage to the ceramic honeycomb monolith catalyst due to mechanical shocks such as vibrations generated when the automobile is running.

Moreover, by using an ethylene-based multi-component copolymer that has excellent elongation, adhesiveness, and weather resistance in a well-balanced manner as an organic binder, it is possible to improve tensile strength at room temperature and flexibility. As a result, the bending resistance can be increased, the occurrence of cracks due to bending during actual use can be suppressed, and durability can be significantly improved.

In the thermal expansion resistant component of claim (2), the expansion amount and expansion force of unexpanded vermiculite can be further increased from a low temperature region, and the holding force can be further increased.

In the thermal expansion resistant component of claim (3), the blending ratio of treated unexpanded vermiculite is made sufficiently higher than the blending ratio of sepiolite mineral to particularly increase the amount of expansion and expansion force, and to achieve appropriate gas resistance. Since the attack property is ensured, the compressive strength of the honeycomb monolith catalyst is high.
Further, although the metal casing is formed with a thick wall and has high rigidity, it is suitable for a catalytic converter for a four-wheeled vehicle that is exposed to exhaust gas whose flow velocity is slightly slower.

In the thermal expansion resistant member of claim 0, the blending ratio of treated unexpanded vermiculite is lowered, while the blending ratio of ceramic fibers is increased to suppress the amount of expansion and expansion force, while improving heat resistant strength, Because it has sufficient gas attack resistance, the compressive strength of the honeycomb monolith catalyst is low, and the metal 1 casing is formed with a thin wall, so it has low rigidity, but it is suitable for motorcycles that are exposed to high-velocity exhaust gas. Suitable for catalytic converters.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of a catalytic converter to which the thermal expansion resistant member of the present invention is applied, FIG. 2 is a schematic front view showing a thermal expansion force measuring device, and FIG. A graph showing the degree of expansion, Fig. 4 is an explanatory cross-sectional view of the holding force measuring device for heat-expandable sheets, Fig. 5 is a comparison graph showing the holding force measurement results, and Fig. 6 is a perspective view showing the state of the bending test. It is. 2... Heat expansion resistant member.

Claims (4)

[Claims] (1) In a heat expansion resistant member formed by blending sepiolite mineral, treated unexpanded vermiculite, ceramic fiber, and an organic binder in a predetermined ratio, an ethylene-based multi-component copolymer is used as the organic binder. A heat expansion resistant member characterized by: (2) The heat expansion resistant member according to claim 1, wherein the treated unexpanded vermiculite is obtained by treating untreated unexpanded vermiculite with an aqueous solution of sodium ammonium hydrogen phosphate. (3) 3-5% by weight of sepiolite mineral, 49-59% by weight of treated unexpanded vermiculite, and 2% by weight of ceramic fibers.
The heat expansion resistant member according to claim 1, which contains 5 to 30% by weight of the organic binder and 10 to 15% by weight of the organic binder. (4) 3-5% by weight of sepiolite mineral, 23-33% by weight of treated unexpanded vermiculite, and 5% by weight of ceramic fibers.
The thermal expansion resistant member according to claim 1, which contains 0 to 60% by weight of the organic binder and 10 to 15% by weight of the organic binder.