KR101384796B1 - Silicon carbide filter, preparation method thereof and diesel particulate filter comprising the same - Google Patents

Abstract

The present invention relates to a silicon carbide filter, a method for manufacturing the same, and a diesel particulate filter (DPF) using the same. More specifically, a silica sintered body layer is integrated on an outer wall finish. It relates to a silicon carbide filter formed by the same, a manufacturing method thereof, and a dust filter for a diesel engine using the same. In the present invention, the thermal shock resistance of the filter can be remarkably improved by forming the silica sintered body layer by the silica sol treatment and the post-heat treatment in a state of being integrated with the silicon carbide filter separately from the outer wall finish.

Silicon Carbide Filter, Honeycomb Filter, Silica Sol, Silica Sintered Body, Exterior Wall Finish, Heat Treatment, Spraying, Impregnation, Coating

Description

Silicon carbide filter, preparation method thereof and dust filter for diesel engine comprising same

The present invention relates to a silicon carbide filter, a method for manufacturing the same, and a diesel particulate filter (DPF) using the same. More specifically, a silica sintered body layer is integrated on an outer wall finish. The present invention relates to a silicon carbide filter, a method of manufacturing the same, and a dust filter for a diesel engine using the same, the thermal shock resistance of which is improved by forming the same.

Porous honeycomb filter or candle filter is a diesel particulate filter (DPF) to remove particulate matter (PM) contained in the catalyst carrier or exhaust gas. Often used on the back.

Conventionally, cordierite-based ceramics have been mainly used as materials for such filters. The cordierite is excellent in thermal shock, and has the advantage that it can be freely manufactured in a structure of various sizes and shapes. However, since cordierite has a low melting point, there is a problem in that when used for a dust filter or the like, it is locally dissolved or destroyed in a regeneration process of a structure, that is, a high temperature process of removing adsorbed dust by applying high temperature heat.

Accordingly, recently, attention has been paid to silicon carbide (SiC) quality filters having a high melting point and excellent thermal conductivity. However, since the silicon carbide has a large coefficient of thermal expansion, cracking occurs due to stress generated during heating and cooling. Therefore, the silicon carbide filter is difficult to manufacture in monolithic form, such as cordierite, and is generally manufactured by forming a rectangular column segment and then joining a plurality of them.

International Patent Publication No. 2006-112061 discloses a honeycomb structure bonded to a seal material or coated with an outer circumferential portion, and using oxide ceramic particles such as silica and silica sol as the sealant. In addition, US Patent Publication No. 2006-216466 discloses a honeycomb structure formed by joining a plurality of honeycomb units with a sealing material, wherein the sealing material uses an inorganic binder such as an oxide particle such as silica having a specific particle diameter and a silica sol. The technique is disclosed.

The sealant treatment disclosed in the above prior patent corresponds to the outer wall finish in the manufacturing process of the honeycomb structure. That is, the honeycomb structure manufactured by joining a plurality of segments is subjected to a process of grinding the outer wall of the joint into a shape such as a circle or an ellipse, at which time the cells of the segments of the outer peripheral part are opened. Thus, the exterior wall finish treatment is performed to smoothly finish the exterior wall surface of the processed structure.

However, the conventional silicon carbide filter as described above has the following problems. That is, silicon carbide has a low thermal shock resistance because it has a large coefficient of thermal expansion and elasticity, and this property is particularly fatal when a silicon carbide filter is used in a dust filter or the like. The above-mentioned prior patents attempt to use a specific sealant (outer wall finish) to solve this problem, but such treatment alone cannot impart satisfactory thermal shock resistance to the silicon carbide filter. Accordingly, there is a demand for a fundamental solution to solve this problem and to ensure stable use of the filter over a long period of time.

The present invention has been made in consideration of the above-described prior art, and an object thereof is to impart excellent thermal shock resistance to a silicon carbide filter used for a dust filter for a diesel engine.

The present invention provides a silicon carbide filter including a silica sintered body layer formed in an integrated state with an outer wall finish as a means for solving the above problems.

The present invention also provides a means for solving the above problems,

A first step of treating the silicon carbide filter subjected to the outer wall finish treatment process with a silica brush; A second step of blowing the silicon carbide filter treated with silica brush with compressed air and then drying; And it provides a method of manufacturing a silicon carbide filter comprising a third step of heat-treating the dried silicon carbide filter.

The present invention also provides a means for solving the above problems,

Canisters; Silicon carbide filters according to the present invention; And it provides a dust filter for a diesel engine comprising a regeneration device.

In the present invention, the thermal shock resistance of the filter can be remarkably improved by forming the silica sintered body layer formed by the silica sol treatment and the post-heat treatment in an integrated state on the silicon carbide filter separately from the outer wall finish.

The present invention relates to a silicon carbide filter comprising a silica sinter layer formed in an integrated state with an outer wall finish. In the present invention, after the outer wall finishing process, the silica sintered body layer is formed on the surface of the silicon carbide filter to be integrated with the outer wall finishing material, thereby significantly improving the thermal shock resistance of the silicon carbide filter.

Hereinafter, the silicon carbide filter of the present invention will be described in detail.

The structure of the silicon carbide filter used in the present invention is not particularly limited. That is, in the present invention, most conventional filters made of silicon carbide can be used. Examples of such a filter include a honeycomb filter and a candle filter. Among them, a honeycomb filter is more preferable. Such silicon carbide honeycomb filters are manufactured by joining a plurality of honeycomb segments in the shape of a square bar column. An example of a honeycomb structured silicon carbide filter that can be used in the present invention will be described with reference to the accompanying drawings.

1 and 2 are a perspective view and a cross-sectional view of the segment constituting the silicon carbide filter according to an aspect of the present invention, Figure 3 is a view of a honeycomb structure formed by joining a plurality of segments according to FIG.

Segments 1 constituting silicon carbide are generally manufactured by adding an organic binder such as a polymer compound and an inorganic binder as a sintering aid to silicon carbide powder, and then extruding, cutting, drying and firing it. A plurality of channels 3 are formed in the segment 1 manufactured in this way, and the channels 3 are penetrated in the longitudinal direction, and either one of the inlet or the outlet of the channel 3 is alternately sealed by the sealing material 3a. Will be Accordingly, when the silicon carbide filter is used for a diesel particulate filter (DPF) or the like, the exhaust gas G introduced into the channel 3 passes through the porous partition wall 2 and then another adjacent channel. Outflow through (3), and thus dust contained in the exhaust gas (G) is collected in the porous partition (2).

The segment 1 as described above is joined by the bonding material 4 after the firing process, and the outer peripheral part is processed through a grinding process or the like, and then treated with an outer wall finish. The outer wall finishes typically include silicon carbide, ceramic fibers, organic and inorganic binders. The type of ceramic fiber, organic and inorganic binder used at this time is not particularly limited, and materials commonly used in this field may be used without limitation. Examples of such ceramic fibers include one or more selected from the group consisting of alumina, aluminosilicate, alumino borosilicate and mullite. In addition, examples of the organic binder include polyacrylamide (PAM), polyethylene oxide (PEO), epoxy binder (epichlorohydrin modified polyamide), polyvinyl alcohol, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl Acetates (PVA), purified starch, dextrins, polyvinylbutyral, polymethyl (meth) acrylates, paraffins, waxes and polyethyleneglycols (PEG); and one or more inorganic binders. And at least one selected from the group consisting of feldspar, alumina, silica-alumina and silica. In the above, the organic and inorganic binders include a liquid phase and a solid phase.

The silicon carbide filter of the present invention includes a silica sintered body layer formed in an integrated state with the outer wall finish as described above. At this time, the thickness of the silica sintered body layer is not particularly limited to be appropriately adjusted according to the intended use, the average technician in this field through the appropriate adjustment of the amount of raw materials and heat treatment time, the sintered body layer of the desired thickness Can be easily formed.

The present invention also relates to

A first step of treating the silicon carbide filter subjected to the outer wall finish treatment process with a silica sol;

A second step of blowing the silicon carbide filter treated with silica sol with compressed air and then drying; And

It relates to a method for producing a silicon carbide filter comprising a third step of heat-treating the dried silicon carbide filter. According to the method of this invention, the silicon carbide filter formed by integrating the sintered compact layer can be manufactured efficiently.

Hereinafter, the manufacturing method of the present invention will be described in detail.

The first step of the present invention is the step of treating the silicon carbide filter, which has undergone the outer wall finish treatment process, with a silica brush. At this time, the method of manufacturing the silicon carbide filter is not particularly limited, and methods commonly used in the art may be used without limitation.

For example, the silicon carbide filter,

(a) joining silicon carbide segments; (b) processing the outer wall surface of the segment joint prepared in step (a); And (c) treating the outer wall surface processed in step (b) with an outer wall finish.

The silicon carbide segment used in step (a) may be prepared from a sinterable silicon carbide slurry or paste incorporating silicon carbide powder, organic and inorganic binders. Specifically, the silicon carbide segment may be manufactured through general processes such as extrusion, cutting, drying, and firing using the sinterable silicon carbide slurry or paste as a raw material. Although not specifically limited, It is preferable that the diameter of the silicon carbide powder is in the range of 10-200 micrometers above. In addition, the type of the organic and inorganic binders is not particularly limited, and for example, the same ones as those contained in the above-described outer wall finishing material can be used.

The step (b) is a step of processing the outer wall surface to form a cylindrical or oval shape according to the use of the bonded silicon carbide segment bonded in step (a), it is usually carried out through a grinding process or the like.

Subsequently, in step (c), the processed outer wall surface is treated with an outer wall finish, which is usually performed by applying and drying the finish on the outer wall. After the outer wall processing process of the segment joint in step (b), the channel of the outer peripheral part may be opened, which requires the finishing treatment with the outer wall finishing material. The outer wall finish may generally be prepared by appropriately mixing silicon carbide powder, ceramic fibers, organic and inorganic binders with a solvent such as water, and specific types of ceramic fibers, organic and inorganic binders are as described above. The present invention may further include a step of applying a heat treatment such as calcining or baking to the silicon carbide filter at a suitable temperature after the above steps (a) to (c).

In the first step of the present invention, the silicon carbide filter prepared as described above is treated with silica sol (SiO ₂ sol, colloidal SiO ₂ ). In this case, the silica sol may be prepared by diluting the silica solid in an appropriate solvent such as water, wherein the concentration of the silica solid is preferably 5 to 50% by weight, and 20 to 40% by weight based on the total weight of the silica sol. It is more preferable that is. When the concentration is less than 5% by weight, there is a fear that the thermal shock resistance of the finished silicon carbide filter is lowered, and when the concentration exceeds 50% by weight, the economy is inferior.

The method of treating the silicon carbide filter with the silica brush in the first step of the present invention is not particularly limited. For example, the treatment may include applying a silica sol to a silicon carbide filter; It can be carried out by spraying a silica sol on the silicon carbide filter or by impregnating the silicon carbide filter on the silica sol.

The second step of the present invention is to blow the silicon carbide filter treated with silica sol with compressed air. By going through this step, the thickness of the silica sol present in the silicon carbide filter can be kept uniform for all surfaces. The method of performing the blowing process is not particularly limited, and an average person skilled in the art may easily select appropriate blowing conditions according to the thickness of the desired silica sintered layer.

The third step of the present invention is to heat-treat the silicon carbide filter treated as above to form a silica sintered body layer in an integrated state with the outer wall finish of the filter. This heat treatment is usually carried out in a furnace. The heat treatment is preferably carried out at a temperature of 900 to 1500 ℃, more preferably carried out at a temperature of 1000 to 1400 ℃. In addition, the heat treatment is preferably performed for 1 to 5 hours. If the temperature is less than 900 ° C or the heat treatment time is less than 1 hour, the sintering may proceed insufficiently to obtain the desired sintered compact layer, and if the temperature exceeds 1500 ° C or the heat treatment time exceeds 5 hours, There is a fear that cracking occurs in the filter or the porosity is reduced.

The present invention also relates to

Canister; The silicon carbide filter according to the present invention described above; And a diesel particulate filter (DPF) including a regeneration device.

The dust filter (DPF) for diesel engines is an automotive part that collects, burns and removes particulate matter (PM) emitted from automobile diesel engines. Since high thermal stress is applied to such vehicle parts due to rapid temperature change due to rapid heat at engine start, rapid cool at stop, and the like, excellent thermal shock resistance is required. The dust filter for a diesel engine is usually composed of a canister, a filter, a regeneration device, and the like containing a filter, and as the filter, a silicon carbide filter according to the present invention may be used. As described above, the silicon carbide filter of the present invention has excellent thermal shock resistance, and thus, it is possible to impart excellent thermal shock resistance to the dust filter including the same.

Hereinafter, the present invention will be described in more detail with reference to examples according to the present invention and comparative examples not according to the present invention, but the scope of the present invention is not limited to the examples given below.

Example  One

A conventional silicon carbide honeycomb filter with a finished outer wall finish was manufactured using a 2 × 2 unit filter (diameter × height = 80mm × 40mm), sprayed onto a silica sol, and then blown with compressed air. Subsequently, the silica-treated filter was placed in a furnace and heat-treated at a temperature of 1300 ° C. to prepare a silicon carbide filter sample in which a silica sintered body layer was formed.

Example  2

A silica sol was sprayed onto the residue (length: 270 mm) after the outer wall of the 4 liter (4 x 5) filter was blown with compressed air. Subsequently, the above was put into a furnace and heat-treated at the temperature of 1300 degreeC, and the silica sintered compact layer was formed.

Example  3

A silicon carbide filter in which a silica sintered body layer was formed was manufactured in the same manner as in Example 1, except that silica sol was injected into a silicon carbide filter inserted into a dust filter (DPF) mounted on a GM Daewoo winstorm.

For the examples prepared as above, the thermal shock was tested by the method given below. In addition, the same filters as used in Examples 1 and 2 were used as Comparative Examples 1 and 2 in which the silica sol treatment and the heat treatment process were omitted.

One. Thermal shock  Test (1)

The unit filter of 2 × 2 was put in a heating furnace and maintained at a temperature of 800 ° C. for a predetermined time, and then taken out and immediately put in a 20 ° C. cooling water.

2. Thermal shock  Test (2)

In the case of a 4 liter filter, the resultant was heat-treated at 1300 ° C., and then cooled to visually check for cracks and the like.

The results observed through the above test are summarized in Tables 1 and 2, respectively.

[Table 1]

Thermal shock  Visual observation result after test (1) Example  One Segment confirmed Comparative Example  One Sample is shattered

[Table 2]

Thermal shock  Visual observation result after test (2) Example  2 No crack Example  3 No crack Comparative Example  2 Long cracks occur on the outer wall of the filter

As shown in Table 1, in Comparative Example 1, which undergoes only a conventional exterior wall finish treatment, the thermal shock resistance is remarkably degraded, so that its shape cannot be recognized after the thermal shock test, whereas in the case of Example 1 according to the present invention, I could confirm the form. Experimental results of Table 1 can be seen from FIG. The results of Table 1 and FIG. 6 show that the heat shock resistance of the filter cannot be improved only by treatment with a conventional outer wall finish including silicon carbide powder, ceramic fibers and binders (such as SiO ₂ and Al ₂ O ₃ ). The silicon carbide filter of the present invention shows that excellent thermal shock resistance is obtained.

In addition, as shown in Table 2, in Comparative Example 2 subjected to only the outer wall finish treatment including silica and alumina, etc., cracks occurred in the outer wall during the cooling process after heat treatment at 1300 ° C., but after the outer wall finish treatment, silica brush and heat In Examples 2 and 3 treated, no cracking occurred in the outer wall under the same conditions. As described above, the filter of the present invention has excellent thermal shock resistance, so that defects that may occur in a catalyst coating process or actual use state for use as a dust filter (cracking of the outer wall and breakage due to thermal shock) can be minimized. Therefore, this suggests that stable use for a long time is possible.

1 is a perspective view of a honeycomb segment constituting a silicon carbide filter.

2 is a perspective view of the honeycomb segment of FIG.

3 is a diagram illustrating a honeycomb structure in which the honeycomb segment of FIG. 1 is bonded.

4 is a photograph showing a silicon carbide filter manufactured according to Example 1 of the present invention.

5 is a photograph showing a silicon carbide filter manufactured according to Example 2 of the present invention.

6 is a photograph showing the results of thermal shock tests performed on the silicon carbide filters of Example 1 and Comparative Example 1. FIG.

≪ Description of reference numerals &

1: honeycomb segment

2: bulkhead

3: channel

3a: sealing material

4: bonding material

5: finishing material

Claims (14)

A silica sintered body layer formed in an integrated state with an outer wall finish made of silicon carbide, ceramic fiber, an organic binder and an inorganic binder, The ceramic fiber is at least one selected from the group consisting of alumina, aluminosilicate, alumino borosilicate and mullite, The organic binder is polyacrylamide, polyethylene oxide, epoxy binder, polyvinyl alcohol, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinylacetate, purified starch, dextrin, polyvinyl butyral, polymethyl At least one selected from the group consisting of (meth) acrylate, paraffin, wax and polyethylene glycol, Wherein said inorganic binder is at least one selected from the group consisting of clay, feldspar, alumina, silica-alumina and silica. The silicon carbide filter according to claim 1, wherein the filter is a honeycomb filter or a candle filter. delete delete delete delete A first step of treating the silicon carbide filter subjected to the outer wall finish treatment process with a silica brush; A second step of blowing the silicon carbide filter treated with silica brush with compressed air and then drying; And a third step of heat treating the dried silicon carbide filter. The silica sol of the first step is prepared by diluting the silica solids in a solvent, the silica solids are contained in an amount of 5 to 50% by weight relative to the total weight of the silica sol, The heat treatment of the third step is a manufacturing method, characterized in that performed for 1 to 5 hours at a temperature of 1200 to 1400 ℃. The method of claim 7, wherein The silicon carbide filter includes: (a) joining silicon carbide segments; (b) processing the outer wall surface of the joint prepared in step (a); And (c) treating the outer wall surface processed in step (b) with an outer wall finish. 9. A process according to claim 8, wherein after the step (c) the filter is further subjected to a calcination or firing process. delete delete 8. The process of claim 7, wherein the treatment with the silica brush of the first step comprises: applying the silica sol to the silicon carbide filter; A process for producing a silica sol by spraying a silicon carbide filter or impregnating a silicon carbide filter with a silica sol. delete Canisters; A silicon carbide filter according to any one of claims 1 and 2; And a dust filter for a diesel engine comprising a regeneration device.

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