PROCESS FOR COATING A SUBSTRATE BODY

Abstract

The present invention is directed to a certain method of catalytically coating a honeycomb monolith, in particular a so-called flow-through monolith. These types of monoliths can be quite precisely be coated by a method using an indirect coating via a displacement body. The present invention further improves this method through controlling the process by monitoring the certain measures.

Claims

1. A process for coating substrates for the production of exhaust gas purification catalysts, particularly for motor vehicles, which are cylindrical support bodies and each have two end faces (301), a circumferential surface (302) and an axial length L and are traversed from the first end face to the second end face by a multiplicity of channels (310), with liquid coating media, which has a cylinder (102) filled with a liquid (103) and having a piston (101), wherein the liquid-filled cylinder (102) communicates with a tank (112), in the interior of which a displacement body (111) is arranged in such a way that, when the piston (101) is moved, the displacement body (111) is moved proportionally by the liquid (103), and the tank (112) communicates with the coating device (122) for the substrate, wherein the displacement body (111) acts on the liquid coating medium (113), with the result that a proportional change in the level of liquid coating medium (113) in the coating device (122) is brought about, wherein the movement of the piston (101), which leads to deflation of the displacement body (111) is controlled in such a way that a velocity of the piston (101) is not overshot thereby avoiding the appearance of bubbles in the washcoat.

2. Process according to claim 1, characterized in that, the velocity of the piston (101)), which leads to deflation of the displacement body (111) is between 0.01-3 m/s.

3. Process according to claim 2, characterized in that, the viscosity of the liquid coating medium (113) is between 2-200 mPa*s.

4. Process according to claim 1, characterized in that, the velocity of the piston (101), which leads to deflation of the displacement body (111) is controlled in such a way that the piston is accelerated first and decelerated to the end of its backstroke.

5. Process according to claim 1, characterized in that, the sensor used to control the velocity of the piston (101) is selected from the group consisting of pressure sensor, optical sensor, conductivity sensor and vibration sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1: [0037] 100 actuator [0038] 101 piston [0039] 102 cylinder [0040] 103 liquid [0041] 104 connection [0042] 110 channels—in the substrate 121 [0043] 111 displacement body [0044] 112 tank [0045] 113 coating medium [0046] 114 line section [0047] 115 multiway valve [0048] 116 line section [0049] 117 filling flow direction [0050] 118 return flow direction to remove coating medium 113 [0051] 119 discharge pump [0052] 120 connecting line leading to the reservoir for the coating medium [0053] 121 substrate [0054] 122 coating device [0055] 123 sensor for detecting the level 130 [0056] 124 sensor for monitoring the position of the displacement body 111 [0057] 125 control unit [0058] 130 first level—of 113 in the coating device 122 [0059] 132 second level—of 113 in the substrate 121

[0060] FIG. 2: [0061] 200 actuator [0062] 201 piston [0063] 202 cylinder [0064] 203 liquid [0065] 204 connection [0066] 210 channels—in the substrate 221 [0067] 211 displacement body [0068] 212 tank [0069] 213 coating medium [0070] 214 line section [0071] 215 multiway valve [0072] 216 line section [0073] 217 filling direction [0074] 218 extraction flow direction of 213 [0075] 219 discharge and extraction pump [0076] 220 connecting line leading to the reservoir for excess coating medium 213 [0077] 221 substrate [0078] 222 coating device [0079] 223 sensor for detecting the level 230 [0080] 224 sensor for monitoring the position of the displacement body [0081] 225 control unit [0082] 230 first level—in the coating device 222 [0083] 232 second level—in the substrate 221

[0084] FIG. 3: [0085] 300 substrate [0086] 301 end face [0087] 302 circumferential surface [0088] 303 first partial length zone [0089] 304 spacing—between the two partial lengths 303 and 305 [0090] 305 second partial length zone [0091] 310 channels—in the substrate 300 [0092] 330 first coating—in the channels 310 [0093] 340 second coating—in the channels 310 [0094] L total length of the substrate 300

DETAILED DESCRIPTION OF THE DRAWINGS

[0095] FIG. 1 shows an arrangement for coating channels (110) in a substrate (121), which has a piston (101), actuated by an actuator (100), in a cylinder (102), which is filled with liquid (103) and, through a connection (104) of the cylinder (102) to the displacement body (111), allows the actuation of the displacement body (111) in the tank (112), which is filled with liquid coating medium (113) and has two line sections (114, 116) with an interposed multiway valve (115) between the tank (112) and the coating device (122), wherein the coating device (122) is provided with the substrate (121) and with sensors (123) for determining the first level (130). Additional sensors (124) are used to monitor the displacement volume of the coating medium (113) and the state of the displacement body (111) in the tank (112).

[0096] The values determined by the sensors (123, 124) are transmitted to a control unit (125) which, for its part, controls the actuator (100) and hence the piston (101).

[0097] On the one hand, the multiway valve (115) switches the filling of the coating device (122) with coating medium (113) up to the first level (130) in the filling flow direction (117) and, on the other hand, after the second level (132) in the substrate (121) is reached, switches, in the return flow direction (118), the connection to the discharge pump (119) and to the connecting line (120) leading to a storage tank for excess coating medium (113) and for holding it ready for further use.

[0098] All the control commands required for this purpose are preferably likewise output by the central control unit (125).

[0099] FIG. 2 shows an arrangement for coating channels (210) in a substrate (221), which has a piston (201), actuated by an actuator (200), in a cylinder (202), which is filled with liquid (203) and, through a connection (204) of the cylinder (202), communicates with the tank (212), in which the displacement body (211) is situated, which contains liquid coating medium (213) and is connected via two line sections (214, 216) with an interposed multiway valve (215) to the coating device (222), which is provided with a substrate (221) and sensors (223) for determining the first level (230) of coating medium (213).

[0100] By means of the additional sensors (224) on the tank (212), the displacement volume of coating medium and the state of the displacement body (211) in the tank (212) are monitored. The values determined by the sensors (223, 224) are transmitted to a control unit (225) which, for its part, controls the actuator (200) and hence the piston (201).

[0101] On the one hand, the multiway valve (215) switches the filling of the coating device (222) with coating medium (213) up to the first level (230) in the filling flow direction (217) and, on the other hand, after the second level (232) in the substrate (221) is reached, switches, in the return flow direction (218), the connection to the discharge pump (219) and to the connecting line (220) leading to a storage tank for excess coating medium (213) and for holding it ready for further use. All the control commands required for this purpose are preferably likewise output by the central control unit (225).

[0102] FIGS. 3A and 3B show in perspective a substrate (300), which has a section broken away in three planes in the central part thereof to make it possible to see into the coating structure according to the invention.

[0103] The substrate (300), which is coated in two partial length zones (303, 305), has two end faces (301), a circumferential surface (302) and a length (L) and is traversed by a multiplicity of channels (310) between the two end faces (301).

[0104] A first coating (330) is applied to a first partial length zone (303) in the channels (310), while a further partial length zone (305) is provided with a second coating (340).

[0105] Between the two partial length zones (303) and (305) or between the two coatings (330) and (340) there is a coating-free zone (304), as FIG. 3B, in particular, shows on an enlarged scale.