BE1026559B1 - MODIFIED FIRE RESISTANT ALUMINUM SILICATE CERAMIC FIBER, METHOD FOR THE PRODUCTION THEREOF AND SUBSTRATE CARRIER MAT FOR A VEHICLE EXHAUST GAS PURIFICATION DEVICE - Google Patents

Abstract

The present invention provides a modified refractory aluminum silicate ceramic fiber, a method of manufacturing the same, and a substrate support mat for a vehicle exhaust gas purification device. In the present invention, a granule removal treatment is first performed on the refractory aluminum silicate ceramic fiber to remove the granules that have no compliance in the fiber, then the surface of the fiber is etched with hydrofluoric acid to form more reaction sites on the surface of the fiber , then a layer of mullite crystals is formed on the surface of the fiber by calcining. The present invention greatly improves the compliance of the refractory aluminum silicate ceramic fiber by modification, and the substrate support mat for the vehicle exhaust gas purification device as manufactured using the modified refractory aluminum silicate ceramic fiber according to the present invention has excellent aging resistance and fatigue resistance.

Description

MODIFIED FIRE RESISTANT ALUMINUM SILICATE CERAMIC FIBER, METHOD FOR THE PRODUCTION THEREOF AND SUBSTRATE CARRIER MAT FOR A VEHICLE EXHAUST GAS PURIFICATION DEVICE

TECHNICAL AREA

The present invention relates to the technical field of exhaust gas treatment, in particular a modified refractory aluminum silicate ceramic fiber, a method for the production thereof and a substrate carrier mat for a vehicle exhaust gas cleaning device.

BACKGROUND

The construction of a vehicle exhaust gas purification device comprises three parts, i. H. a ceramic substrate, a substrate support mat and a metal jacket. The ceramic substrate is brittle and requires support and protection from the carrier mat. Because the difference of

Coefficient of thermal expansion of the ceramic and the metal is large, the gap between the ceramic substrate and the metal shell expands greatly under conventional working conditions, but the size of the gap returns to the original value when the

Exhaust purification device returns to room temperature. This back and forth

The nature of the gap causes the substrate support mat to tire and age and the fiber structure of the mat to break easily, as a result of which the support mat can no longer offer sufficient holding force for the substrate, with the result that the substrate moves, collides, breaks and the exhaust system is blocked and thus fails caused.

The present solution is to use a polycrystalline mullite fiber to make a substrate support mat. This fiber has sufficient compliance and tends to spring back rather than break after being pressed, so a substrate support mat made therefrom exhibits excellent anti-fatigue and anti-aging performance. However, the polycrystalline mullite fiber is very expensive and has a low yield. Fireproof aluminum silicate ceramic fibers are inexpensive and readily available, but have aging resistance and fatigue resistance that cannot meet the requirements when used directly for the manufacture of the substrate support mat.

SUMMARY

For these reasons, an object of the present invention is to provide a modified refractory aluminum silicate ceramic fiber, a method for producing the same, and a substrate support mat for a vehicle exhaust gas purification device. The modified refractory aluminum silicate ceramic fiber provided by the present invention is inexpensive and readily available, has good compliance, and provides a mat with good fatigue resistance and aging resistance when used to make the substrate support mat for the

BE2018 / 5840

Vehicle exhaust gas purification device is used.

DETAILED DESCRIPTION

The present invention provides a method of making a modified refractory aluminum silicate ceramic fiber, comprising the steps of:

(1) Performing a shot removal treatment on the refractory aluminum silicate ceramic fiber to adjust the granule content of the fiber

Bring granule removal to below 5 wt .-%;

(2) mixing the fiber after granule removal with a hydrofluoric acid solution and then performing heat treatment so that the surface of the fiber is etched by the hydrofluoric acid to obtain an etched fiber; and (3) calcining the etched fiber to obtain the modified refractory aluminum silicate ceramic fiber.

In the present invention, the granule removal treatment is carried out on the refractory aluminum silicate ceramic fiber to bring the granule content of the fiber after granule removal to less than 5% by weight, and preferably to 3% by weight. The refractory aluminum silicate ceramic fiber is a commercially available ordinary refractory aluminum silicate ceramic fiber; and has aluminum silicate as the main component (40% by weight to 60% by weight of Al ₂ O ₃ and 60% by weight to 40% by weight of SiO ₂ ), the mean diameter being 2-5 μm.

In the present invention, the granule removal treatment is preferably carried out using the device of the patent CN201520062324.8, the granules being separated from the fiber by the difference in the sedimentation rate of the fiber and the granules.

In the present invention, the wet fiber is preferably dried after removing the granules to obtain the fiber after removing the granules.

The granule content of the commercially available refractory aluminum silicate ceramic fiber is about 50% by weight, and the granules that cannot offer compliance are reduced by the granule removal treatment in the fibers, so that the relative content of the fibers increases and the grinding damage by the Granules for the surrounding fibers are reduced when the mat is compressed.

In the present invention, after the granule removal treatment is completed, the etching treatment is carried out by mixing the fiber with the hydrofluoric acid solution after granule removal to obtain the etched fiber. In the present invention, the mass concentration of the hydrofluoric acid solution is preferably 4-6% by weight, more preferably 5% by weight; the etching treatment is carried out at a temperature of preferably below 40 ° C.,

BE2018 / 5840 more preferably 20-40 ° C, carried out over a period of preferably 5-120 min, more preferably 10-30 min; the etching treatment is preferably carried out with stirring at a rotation speed of the stirring of preferably 5-60 rpm; and the volume of the hydrofluoric acid solution only has to immerse the fiber after granule removal. Carrying out the etching treatment under the conditions mentioned can ensure that the reaction is sufficient and the fiber is not broken by excessive damage.

Hydrofluoric acid is highly corrosive and can react with SiO ₂ . In the present invention, the surface of the fiber is etched by hydrofluoric acid to enrich the defects on the surface of the fiber and thus provide enough active sites for the crystallization reaction on the surface of the fiber during the subsequent crystallization process so that the crystallization reaction occurs at a faster rate and can be carried out under milder conditions. On the one hand, this makes surface crystallization the main reaction compared to a bulk-phase crystallization reaction and improves the effect of calcination, and on the other hand, it can lower the calcining temperature, shorten the calcining time, improve the production efficiency and reduce the cost.

In the present invention, the etched fiber is calcined after the completion of the etching treatment to obtain the modified refractory aluminum silicate ceramic fiber. The calcination is carried out at a temperature of preferably 950-1,000 ° C, more preferably 960-980 ° C, for a period of preferably 10-20 minutes, more preferably 15 minutes. The calcination is preferably carried out in a batch type muffle furnace or in a continuous tunnel furnace.

When the aluminum silicate fiber is calcined under the conditions mentioned, the amorphous aluminum silicate is converted to SiO ₂ and mullite phase by a solid-solid reaction, the reaction taking place on the surface of the fiber being a surface reaction which comprises a layer of uniform and fine mullite crystals forms the surface of the fiber and is critical to improving the compliance of the fiber; while the reaction taking place in the bulk phase (the interior) of the fiber is a bulk phase reaction, which has no significant effect on improving the flexibility of the fiber. In the present invention, by the etching treatment and by controlling the calcining conditions, the surface reaction becomes the main reaction, so that the mullite crystal formed on the surface of the fiber achieves sufficient crystallinity to precipitate a mullite phase; in the present invention, the mullite crystal obtained by calcining has a crystallinity of preferably 40-60%, more preferably 50%, and the crystallite size of the mullite crystal is preferably less than 500 Å. In the present invention, calcining creates a layer of uniform, dense and fine

BE2018 / 5840

Mullite crystals are formed on the surface of the fiber to greatly improve the compliance of the fiber.

After the completion of the calcination, the present invention preferably further comprises: performing a heat treatment on the calcined fiber. The heat treatment is preferably carried out at a temperature of 800-900 ° C, more preferably 850 ° C, for a period of preferably 30-60 min, more preferably 40-50 min. In the present invention, the temperature is preferably lowered to 800-900 ° C after the completion of the calcination, then the temperature is held for 30-60 min; and the tension created in the fiber is removed by the heat treatment, so that the internal tension of the fiber in the hot state is completely released to increase the compliance of the fiber.

Before calcining, it preferably further comprises: loading one

Nucleation accelerator on the surface of the etched fiber. Of the

Nucleation accelerator is a metal oxide or a metal oxide precursor; wherein the metal oxide is preferably one or more of zirconium dioxide, titanium dioxide and aluminum oxide; wherein the metal oxide is preferably a metal oxide nanoparticle, wherein the metal oxide precursor is preferably one or more of zirconium hydroxide, titanium hydroxide and aluminum hydroxide; wherein in the subsequent calcination process, the metal oxide precursor is pyrolyzed to a metal oxide; and the loading amount of the nucleation accelerator is not more than 1.0% by weight, preferably 0.4-0.6% by weight, of the total mass of the fiber.

When the nucleation accelerator is the metal oxide, the method of loading the nucleation accelerator preferably comprises the following steps:

Mixing the etched fiber and an aqueous dispersion of the metal oxide to perform loading, and then dewatering the loaded fiber. The aqueous dispersion of the metal oxide has a concentration of preferably 0.05-0.5 mol / l, more preferably 0.1-0.3 mol / l; in the present invention, in particular, the etched fiber and the aqueous dispersion of the metal oxide are mixed with stirring; the speed of rotation of the stirring is preferably 5-60 rpm; the metal oxide adhering to the surface of the fiber during stirring to accomplish the loading.

In the present invention, a surfactant is preferably added to the mixture of the fiber and the aqueous dispersion of the metal oxide to promote adhesion of the metal oxide to the surface of the fiber. The surfactant is preferably added in an amount of 0.02% by weight of the total amount of fiber and the aqueous dispersion of the metal oxide; wherein the surfactant is a conventional surfactant capable of

BE2018 / 5840

To promote adhesion of the metal oxide to the fiber.

When the nucleation accelerator is the metal oxide precursor, the method of loading the nucleation accelerator preferably comprises the following steps:

Mixing the etched fiber and a metal salt solution to obtain a mixed material; Adjusting the pH of the mixed material to 5-7 with aqueous ammonia so that the metal oxide precursor is precipitated in situ on the surface of the etched fiber; and then dewatering the resulting loaded fiber. The metal salt is a salt which corresponds to the metal oxide of the solution mentioned, preferably a nitrate; wherein the concentration of the metal salt solution is preferably 0.05-0.5 mol / l, more preferably 0.1-0.3 mol / l; in the present invention, the etched fibers and the metal salt solution are preferably mixed with stirring; wherein the rotation speed of the stirring corresponds to that of said solution.

In the present invention, the pH of the mixed material is preferably adjusted with aqueous ammonia. In the present invention, the pH of the mixed material is adjusted to 5-7, so that the metal oxide precursor is precipitated by adjusting the pH and adhered to the fiber.

In the present invention, by loading the nucleation accelerator on the surface of the fiber, more active sites for the surface crystallization reaction of the fiber during the calcining process can be provided to improve the calcining effect.

The present invention provides a modified refractory aluminum silicate ceramic fiber made by the method described above. The modified refractory aluminum silicate ceramic fiber provided by the present invention has good compliance and is therefore a good material for the manufacture of the substrate support mat for the vehicle exhaust gas purification device.

The present invention provides a substrate support mat for a

Vehicle exhaust gas purification device ready which contains the modified refractory aluminum silicate ceramic fiber described in the above solution. It is only necessary to manufacture the substrate support mat using the above-described modified refractory aluminum silicate ceramic fiber as a raw material by a conventional method in the prior art.

The present invention is described in detail with reference to the following examples, but these should not be considered as limiting the scope of the present invention.

In this example, the refractory aluminum silicate ceramic fiber used was the Fiberfrax fiber purchased from Unifrax.

BE2018 / 5840 (1) The untreated refractory aluminum silicate ceramic fiber became the

Granule removal treatment was carried out using the device of CN201520062324.8, wherein the granule content of the fiber after the treatment was 3% by weight.

(2) The fiber after granule removal and a dilute solution of hydrofluoric acid were mixed to carry out the etching treatment at a temperature of 25 ° C for 20 minutes.

(3) The etched fiber was mixed with an aqueous dispersion of alumina, stirred evenly in a reaction vessel, and dewatered after removal.

(4) Calcining was carried out using a continuous tunnel kiln, heating to 950 ° C for 15 minutes, then cooling to 850 ° C and held at that temperature for 45 minutes, and finally rapidly cooling to room temperature to obtain the modified refractory aluminum silicate Get ceramic fiber.

The obtained modified aluminum silicate refractory ceramic fiber, a dispersant and water were mixed and dispersed to obtain a dispersion of the modified fiber; the modified fiber dispersion, a binder, a surfactant and a flocculant were mixed to form a slurry; the slurry was subjected to dip molding to obtain a wet blank mat; the moist blank mat was dried to form the substrate support mat for the

Obtain vehicle exhaust gas purification device.

The mat sample was cut into 40 × 40 mm squares and placed in a test bench of a compression testing machine. After weighing, the thickness to which the square is compressed was calculated according to a density of 0.4 g / cm ³ . After compressing the square to said thickness at a rate of 10 mm / min, the upper surface of the mat sample was heated to 900 ° C and the lower surface of the mat sample was heated to 700 ° C. The gap was then expanded to 110% of the original gap at a rate of 10 mm / min, held for 10 s and then reduced to the original value at a rate of 10 mm / min. The above procedure was repeated 1,000 times and the lowest surface pressure provided by the mat sample was considered the aged surface pressure.

As demonstrated, the aged surface pressure could reach 51.6 kPa.

Claims (2)

Expectations: 1. A method for producing a modified refractory aluminum silicate ceramic fiber, comprising at least the following steps: (1) Perform granule removal treatment on the refractory Aluminum silicate ceramic fiber, the granule content of the fiber after granule removal being less than 5% by weight; (2) mixing the fiber after granule removal with a hydrofluoric acid solution and then performing heat treatment to obtain an etched fiber; and (3) calcining the etched fiber to obtain the modified refractory aluminum silicate ceramic fiber. 2. A method of manufacturing according to claim 1, wherein the concentration of Hydrofluoric acid solution in step (2) is 0.05-0.5 mol / l; and the heat treatment in step (2) is carried out at a temperature of 40 ° C for 5-120 minutes. 3. The method for producing according to claim 1, wherein the calcination of step (3) is carried out at a temperature of 950-1,000 ° C for 10-20 minutes. 4. A method of making according to claim 1, the method prior to calcining further comprising: Loading a nucleation accelerator onto the surface of the etched fiber, the nucleation accelerator being a metal oxide or a metal oxide precursor. 5. A method of manufacture according to claim 4, wherein the metal oxide is one or more of zirconium dioxide, titanium dioxide and aluminum oxide; and the metal oxide precursor is one or more of zirconium hydroxide, titanium hydroxide and aluminum hydroxide. 6. A method of manufacturing according to claim 4 or 5, wherein the method of loading the nucleation accelerator comprises the following steps: if the nucleation accelerator is the metal oxide, mixing the etched fiber and an aqueous dispersion of the metal oxide to perform loading, and then dewatering the resulting loaded fiber; and when the nucleation accelerator is the metal oxide precursor, mixing the etched fiber and a metal salt solution to obtain a mixed material; Adjusting the pH of the mixed material to 5-7 with aqueous ammonia so that the metal oxide precursor is precipitated in situ on the surface of the etched fiber; and then dewatering the resulting loaded fiber. BE2018 / 5840 7. The method for producing according to claim 1 or 3, wherein the method after calcining further comprises: performing heat treatment of the calcined fiber, the heat treatment being carried out at a temperature of 800-900 ° C for 30-60 min. 5 8. Modified refractory aluminum silicate ceramic fiber made by the process of Manufacture according to one of claims 1-7. 9. A substrate support mat for a vehicle exhaust gas purification device comprising the modified aluminum silicate ceramic fiber according to claim 8.