DE4029383A1 - Foam body mfr. - uses prepd. foam sections to be assembled with carrier layer to form permeable and passage zones - Google Patents

Abstract

To form bodies of ceramic foam, with sepd. zones of permeable organic polymer foam impregnated with ceramic dross and then dried, the body is formed by the assembly of two or more dried foam sections. Separate flow paths are formed in the bodies by aligned connecting channels and/or foam sections and/or seals between them. The sealed carrier layer to form the flow zones is inserted between the foam sections to be bonded together, using a carrier layer of a non-woven of glass, ceramic or organic fibres satd. with dross by impregnation, in a material thickness of 0.1-1.0 (0.2-0.6) mm. The assembled foam components are dried again. USE/ADVANTAGE - The foam body allows fluid and gas media to flow through, such as filters for exhaust gases, and is assembled from sections where they join each other precisely and retain their shape and structure during firing. The body is porous and stable in use, and can be covered with a conductive layer such as for diesel exhausts. (8pp Dwg.No.1/8)

Description

The invention relates to a method for producing a Ceramic foam body and especially one Foam body through which a medium flows can.

The production of one-piece ceramic foam bodies by impregnating or coating an organic polymeric foam with a ceramic slip and a later burning of this foam under Decomposition of the organic material to a ceramic Foam structure is described in DE 28 05 611 C2. The Structure is open-celled and can be of liquid or gaseous media are flowed through.

From US-PS 44 36 538 and 45 40 535 it is known Foam ceramic body, especially filter for cleaning of exhaust gases, from several parts of different Put together porosity and between the parts one or several layers of thin-layer polyurethane foam insert. To seal off the foam layers separate parts from each other are in multiple layers layers of different porosity are used, too that z. B. a layer of higher density between two layers lower density is added, with the impregnation achieved impermeability with a ceramic slip shall be.  

Because of the use of multiple layers of foam different densities, this process is complex and cumbersome. In addition, the accuracy of the joining body composed of several parts with increasing number of liners problematic because shrinkage occurs when burning.

EP-A1 3 20 457 describes a method for coating part of the surface of a porous ceramic body known. This is a Circumferential coating made with sheet material Paper, fleece or other textile or textile Ceramic fibers is carried out. After a one-sided the thin coating of ceramic slip becomes the flat Material with the side containing the ceramic slip on the surface to be reinforced or sealed unfired ceramic body and after a Drying phase burned together with the ceramic body. Here only one to the outside is sealing if necessary electrically conductive layer, for example for Diesel exhaust filter manufactured.

The invention has for its object a to form ceramic foam body made up of several Foam parts with partially complete sealing of the Share with each other with great joining accuracy and Dimensional stability during the burning process easy and simple can be produced, the foam parts partially form separate flow zones and / or the Flow path of a medium in the body is affected and can be extended.  

This task is accomplished with a procedure according to the Features of claim 1 solved. The subclaims represent preferred developments of this method and for the production of special embodiments of Foam bodies produced according to the invention Claim 9 gives a preferred device for the Implementation of procedural measures.

According to the invention, molded, in particular cut, soaked with a ceramic slip and then dried foam parts put together. It is between the individual, separate flow zones forming foam parts a connecting the parts and at the same time against each other sealing layer with a slip sufficient impregnated carrier layer inserted. This backing layer can e.g. B. a nonwoven fabric made of glass fibers or ceramic Be fibers, including nonwovens made of organic Fibers are applicable. Such a nonwoven has preferably a thickness in the range of 0.2 to 0.6 mm and becomes even with a few mm thick layer Spread slip on both sides. The composite Part is dried again before it is burned.

Unless foam body with separate, - too partially or entirely - parallel flow zones are to be produced, at least one of the Foam parts one in the main flow direction trending channel. In this case, that a support layer between two foam parts is used with at least one through opening. Such through openings of the sealing Backing can connect to a sequel  of the channel from a first foam part into one second result. They can preferably serve a channel continuing in the second foam part to interrupt and force the flow through the Flow foam structure. Becomes a channel that a Through channel in one of the assemblies Foam parts is, for example, at its end a soaked fiber fleece is closed, so it is expedient, this closure by a pre-dried Soaked foam washer to support that by means of added slip into the end of the channel is used. Such a disc reinforces itself proportionate from the impregnated carrier layer thin ceramic wall. In this way, channels can also be closed off from or to one end of the composite body, but not the Introduction or the exit of the medium at its Flow through the ceramic body should serve. These openings to be closed, or the inserted washers, are soaked by a Carrier layer, which expediently covers the entire End face covered, sealed.

The assembly of a foam body according to the invention This can be done from several pre-dried foam parts used, large or irregularly shaped Form foam body. It can also be used for this foam parts of different porosity, including different pore structure and itself according to different resulting Flow resistance to assemble. The between the fleece used is u. a. suitable, with several over the whole cross section  distributed openings or passages (including Perforations).

Furthermore, the method can be used if a ceramic foam body to be produced, the various provided inside Flow channels, between them Foam structures as well as only in certain places Cross-section openings to flow through in should contain substantial dense partitions.

It may also be appropriate to consider the full scope of the joined body by a slip impregnated carrier layer, such as a Glass fiber fleece, to be sealed and sealed. About the thickness of the layer applied to the fleece Unevenness in the peripheral surface compensated and undesirable for installation in an envelope Tolerances are corrected. That way Manufactured, fired ceramic body is one exception an inlet and an outlet, which too Inlet and outlet channel pieces such. B. Diffusers May contain, sealed, so that the Medium only in the ways provided in the body, d. H. through existing channels, openings in the connecting carrier layers and the open cell ceramic foam structure can flow.

The shrinkage that occurs when burning leaves a thin one Fleece tears as a result of tension or causes too large fleece thickness lifting off the surface. It does both Leak that affects the functions of the body affect. A fleece thickness in the specified range  advantageously offers the drying and firing stresses arising from the shrinkage of the slip enough resistance to prevent cracks. Favored this effect is preferably achieved by adding ceramic fibers to form a slip monolithic structure from the inner area to the edge down including the fleece layer.

An existing of a porous mineral building material Body with a number of inside it arranged partially closed against each other Channels is described in DE 37 29 219 A1 and is said to be Exhaust silencer with the function of a reflection or resonance silencer. DE 32 24 224 A1 shows another with a through channel through a porous ceramic material provided exhaust silencer, the should act as an adsorption silencer here. In both However, the flow of the Exhaust gas through the open-cell ceramic structure, than on sound absorption by adsorption or Reflection in the open pores that flowed through Surround spaces. The present invention, however, provides the possibility, e.g. B. a silencer shape that the exhaust gases the ceramic foam structure even without an incompatible increase in Flow resistance can flow through and the sound energy in the pores considerably is reduced.

An application for the invention With a suitable design, the foam body is the use as a silencer for internal combustion engines and compressors. Another application is as a filter for gases and  e.g. B. also as a diesel soot filter. As a further use it is also used as a filter for water and others Liquids as well as for reducing Flow noise from liquids in question. Further can the foam body according to the invention as Catalyst carrier in the treatment of exhaust gases are used, the catalysts after Burn the foam body to be stored in it. Even oxidation and Reduction catalysts in different Flow zones of the same foam body applied will.

The slip to be used according to the invention is in essentially the same as for the impregnation of the Foam parts and made of aluminum oxide, Cordierite, mullite and their mixtures. However preferably this slip, the two pre-dried Foam parts connects, a share of 0.1 to 10 % By weight preferably 1 to 3% by weight of ceramic or organic fibers added. As a foam expediently used polyurethane, depending on Use a suitable pore diameter is to be selected. The invention creates the possibility also foam parts of different porosity put together.

The dried ones after soaking for about 24 hours Foam parts are sufficiently firm that they can be used with the By hand or with mechanical grippers without changing the shape or damage can be taken. After one aligned assembly of individual foam parts with the help of fresh slip on a carrier layer  however, these should match each other exactly Lay at a temperature for at least two hours be dried between about 70 to 80 ° C before additional outer surfaces sealing layers on the manufactured body can be attached. In the case of Use of medium frequency or microwave drying the drying times are reduced accordingly to times under 20 minutes. On the intermediate drying can, however be waived in the event that the assembled Parts in a dimensionally aligned position can be held during application.

The invention is described once again with reference to the accompanying drawings, which illustrate preferred exemplary embodiments in a simplified manner. These examples are only intended to illustrate the principle and are not to be interpreted restrictively with regard to the plastic parts to be used or their shape or the channels, flow zones, etc. to be arranged in them. A preferred device is also shown in FIG. 8 in conjunction with the drawings.

In Figs. 1 to 7 according to the invention various assembled ceramic foam body are shown.

Referring to FIG. 1, a foam body of the dried plastic parts 1 and 2 is assembled by means of a slurry-impregnated fiber unwoven fabric 3. Each foam part has two foam channels 4 , 5 and 6 , 7 . The channel 4 , 7 is interrupted by the carrier layer 3 . In the area of the channel 5 , 6 , the carrier layer 3 has an opening corresponding to the dimension of the channel. The channel 5 is closed at one end by a pre-dried disc 8 inserted with slip. A disc 9 is also inserted into the other end of the channel 6 . Such a disc 10 is also inserted at the inner end of the inlet channel 4 , lying against the carrier layer 3 . A medium introduced into the channel 4 flows through the ceramic foam into the channel 5 , from there it enters the channel 6 , in turn flows through the ceramic foam into the channel 7 and can exit from it. A foam body according to FIG. 1 can be inserted into a housing made of metal, plastic, ceramic or other material that tightly encloses its circumference.

FIG. 2 shows a development of the foam body shown in FIG. 1. The front of the body is covered with impregnated surfaces 11 and 12 , which only leave the openings to the channels 4 and 7 free. Furthermore, the body is wrapped in an envelope 13 made of an impregnated fiber fleece. All outer sides of the body are sealed with ceramic.

FIG. 3 shows a section III-III through the foam body according to FIG. 2.

Fig. 4 shows a ceramic foam body which is formed of two foam parts 21, 22, which are joined together by a layer 23 of ceramic slurry. A through channel 24 extends straight through the parts 21 , 22 . These parts can be of foam of different porosity and the entire molded body can be used as an adsorption muffler or part of such.

FIG. 5 shows another foam body consisting of the foam parts 31 , 32 with channels 34 , 35 which run essentially coaxially, but are separated from one another by a ceramic wall 33 formed from a nonwoven fabric. The wall 33 has an opening 36 so that a medium can pass from the channel 34 through the foam of the part 31 , through the opening and through the foam of the part 32 into the channel 35 .

FIG. 6 shows an embodiment in which two foam parts 41 , 42 are connected by a layer 43 made of a ceramic slip, which may soak through a nonwoven fabric. This foam body is optionally housed in a housing 44 indicated by dash-dotted lines. A supplied medium flows through the foam part 41 in one direction, is deflected in the housing 44 and flows into the foam part 42 in the opposite direction.

In FIG. 6 a, the layer 43 a made of nonwoven fabric and impregnated with ceramic slip and connecting the two foam parts 41 a and 42 a contains several openings 45 . Through these openings 45 , the medium flowing through the two foam parts 41 a and 42 a, respectively from left to right, can pass from one part 41 a to the other 42 . Due to the inclined introduction of the layer 43 a z. B. a - by the larger number of openings 45 related to the cross section - for the flow favorable resistance.

The outer shape of the foam body to be produced can be of any type and is expediently adapted to the application and the channels present in the foam body. Thus, FIG. 7 is a foam body of essentially triangular cross-section, which is made of three foam members 51, 52, 53. Each of these parts has three through channels 55 , 56 , 57 . A medium is introduced, for example, into the channel 55 , which is closed at the end of the part 51 by a carrier layer and an inserted disc. The channels 56 , 57 are closed on the end face 54 . In part 51 , the medium flows out of the channel 55 through the foam ceramic into the channels 56 , 57 . The sealing carrier layer 58 has openings in the region of these two channels and the medium reaches the part 52 in these channels. Here, the channels 56 , 57 are closed off by the carrier layer 59 . The medium in turn flows through the foam ceramic and reaches the channel 55, which continues into the part 53 but is closed at the end thereof. The medium in turn migrates through the foam ceramic into the channels 56 , 57 , from the ends of which it can exit. Such a body is also expediently ceramic-sealed on the end faces and on the circumference by a nonwoven fabric impregnated with slip.

FIG. 8 shows an assembly device for joining two foam parts together, for example according to FIG. 1, which, however, are only indicated here by dash-dotted lines. The frame shown has two rods. The part 2 is first pushed with its channel 6 onto the rod 61 and with further movement against the stop plate 60 with the channel 7 onto the rod 62 . The side of part 2 to be connected can be coated with slip. A nonwoven fabric which has been impregnated with slip is then placed on this side, this nonwoven having an opening corresponding to the rod 61 . In the part 1 , the washer 10 , which is coated with slip at least on its circumference, is inserted into the channel 4 and this part 1 is then pushed onto the rod 61 until it abuts the connecting layer 3 . If it is necessary that the channels 4 and 7 are in an exactly aligned position, a part (not shown) can engage the rod 61 from above, which precisely aligns the channel 4 with respect to the rod 61 , so that, for example, also the outer surfaces of parts 1 and 2 are exactly aligned.

Claims (9)

1. A process for the production of bodies made of ceramic foam with zones through which media can flow separately from cut, impregnated with a ceramic slip and then dried parts from an organic, polymeric foam, the bodies then being fired, characterized in that

• the bodies are composed of two or more individually dried foam parts,
• separate flow zones in the bodies are formed by channels and / or foam areas which are aligned with one another and / or seals provided between them,
• a sealing carrier layer forming the flow-through zones is inserted between the foam parts to be connected,
• - The carrier layer 0.1 to 1 mm, preferably 0.2 to 0.6 mm thick nonwoven fabric made of glass fibers, ceramic or organic fibers and is sufficiently impregnated with slip and
• - The assembled foam parts are dried again.

2. The method of claim 1 using at least a foam part with at least one Through channel, characterized in that a  Carrier layer with at least one through opening is used. 3. The method according to claim 1 or 2, characterized characterized in that foam parts of different Porosity can be put together. 4. The method according to one or more of claims 1 to 3, characterized in that in a too closing end one in a single Foam part existing through channel one pre-dried disc made of impregnated foam by means of added slip. 5. The method according to one or more of claims 2 to 4, characterized in that at least two opposite end faces one out Foam parts joined together by a body 0.1 to 1 mm impregnated with slip, preferably 0.2 to 0.6 mm thick carrier layer covered and be sealed. 6. The method according to any one of claims 2 to 5, characterized characterized that the scope of the assembled Body sealing by a soaked with slip 0.1 to 1 mm, preferably 0.2 to 0.6 mm thick Carrier layer is wrapped. 7. Method according to one or more of the preceding Claims, characterized in that for the Impregnation of the backing layer uses a slip is 0.1 to 10 wt .-%, preferably 1 to  3 wt .-% ceramic or organic fibers added are. 8. Method according to one or more of the preceding Claims, characterized in that the assembled foam parts with the as Grout used slip at least two Hours at a temperature of about 70 to 80 ° C to be dried before further sealing carrier layers on the manufactured Body attached. 9. Device for producing a body provided with at least one channel, in particular by carrying out the method according to one of claims 2 to 8, characterized in that for the foam parts to be joined ( 1 , 2 ) and the support layer ( 3 ) to be inserted between them, a mounting frame It is provided which has rods ( 61 , 62 ) onto which the parts with their ducts to be brought into alignment with one another can be attached.