Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Coating predominantly nonmetal substrate
Reexamination Certificate
2000-10-30
2002-08-06
Valentine, Donald R. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Coating predominantly nonmetal substrate
C134S021000, C205S150000, C205S161000, C205S220000, C427S350000, C429S234000, C429S235000
Reexamination Certificate
active
06428674
ABSTRACT:
This application claims the priority of 199 52 094.1, filed Oct. 29, 1999, the disclosure of which is expressly incorporated by reference herein.
DISCUSSION OF BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a process for the removal of galvanic electrolytic residues from electrode frames or electrode frame webs with fiber structure.
For a number of years the field of alkaline storage systems for electric energy (Ni/Fe, Ni/Cd, Ni/metal hydride or nickel/hydrogen systems) has used for at least one polarity the type of fiber structure electrode that is well known and whose popularity has continued to grow. In the case of the fiber structure electrode a three dimensional lattice or network of metal filaments is provided as the frame for conducting current and for fixing the active material in position or for rendering the active material dimensionally stable. These metal filaments can be designed from solid metal or comprise synthetic fibers, whose surface is metallized by depositing either chemically and/or galvanically a metal layer. In everyday practice what has prevailed in industry are those fiber structure electrodes, where the electrically conducting fiber structure-based electrode frame, which stores the active material so as to be stable, is produced by metallizing synthetic fibers, which have solidified beforehand into a felt or fleece. Such fiber structure electrodes can be easily processed and are advantageously dimensioned and are inexpensive.
With respect to the state of the art relating to the production of fiber structure electrode frames made of metallized synthetic fiber-based fleeces or felts, reference is made, for example, to the German Patent DE 36 31 055 C2, which describes a process for continuous impregnation of fleece material or needled felt webs having a thickness ranging from 1 mm to 10 mm and a porosity ranging from 50% to 97%.
A process for chemical metallization of large area textile substrates, in particular fleece material and needled felt webs, is disclosed in German Patent DE 37 10 895 C2.
A process and a device for galvanic reinforcement or metal deposition of fiber structure electrode frames for accumulators and voltaic cells are described in the German Patent DE 42 16 966.
These metallically conducting fiber structure electrode frames are provided with a current discharge lug by welding technology after their production and optionally calibration (cf. German Patents DE 40 18 486 C2, DE 42 25 708 C2, DE 41 04 865 C1, DE 39 35 368 C1, DE 36 32 352 C1, DE 36 32 351 C1).
The fiber structure electrode frame, which is permanently connected to a current discharge lug, is provided with an active material. Three variants of these processes are described in the DE 38 22 197 C1, DE 40 40 017 C2 and DE 41 03 546 C2.
If the method of galvanic reinforcement of the chemically metallized textile substrate based on fleece material or needle felt is chosen for the metallizing process of the fleece material or needled felt strips or webs, then the fleeces or felts are usually transferred into a drip station after removal from the plating bath, brought into contact for a short period with the wash water and then separated into manipulable substrips having a length ranging from approximately 50 cm to 100 cm. In a wash centrifuge with integrated jets for wash water contact, these substrips can then be freed of the galvanic electrolytic residues present in the pores of the fiber structure electrode frame by centrifuging multiple times and then rinsing.
However, this prior art process has several disadvantages. The pores of such galvanically reinforced porous frame strips with fiber structure have a porosity ranging from approximately 50% to 90% after cutting to the width of the electrode. This metallized porous substrate-based textile substrate results in a pore size distribution, which can reach from a few &mgr;m to about 45 &mgr;m. Naturally the galvanic electrolyte is more difficult to remove from the smaller pores than from the larger pores. This means that a series of rinse and wash steps of the kind described in the prior art must be performed to reliably remove the last residues of the galvanic electrolyte. If, on the other hand, the rinse and wash steps, which are to be repeated several times, and the subsequent necessary centrifuging steps are ignored, there is the risk that residues of the galvanic electrolyte will remain in the frame strips, which result in salt crusts after the drying process. These salt crusts prevent the transfer of heat when welding the current discharge lug with the frame and thus result in increased rejects. If an inadequate weld joint between the current discharge lug and the frame does not break immediately after the welding step, but rather in a subsequent production step, such as filling the frame with active material, separating the cell stacks or even during operation of the finished cells, the damage is correspondingly greater.
If, due to incomplete removal of the galvanic electrolyte, the pores and wedges of the fiber structure frame are completely or partially clogged or filled with salt crusts, they can no longer be filled with the anticipated quantity of active material. This has a negative impact on the performance properties of the finished storage cell. Furthermore, the galvanic electrolyte that is thus dragged out can no longer be recycled into the galvanic water circulation or be properly disposed, which results in increased costs. In addition, if the galvanic electrolyte is dragged out as far as the finished cell, the buffer substance, which is present in the customary acidic nickel electrolyte, such as boric acid, may interfere with the cell operation. Finally the kind of centrifuging described in the prior art is expensive, since it cannot be done continuously and cannot be automated, especially for a smaller number of items. The frame strips must usually be placed by hand into the centrifuge and removed again by hand, which add to the expensive, in particular with respect to organization and handling.
Thus, the object of the invention is to further improve a process of the kind described above in such a manner that it can be continuous, requires fewer handling steps and decreases the quantity of water required for rinsing and the drag-out losses of the dissolved galvanic electrolytic salts.
The present invention provides that the galvanic electrolytic residues are removed by suction from the fiber structure frame and, then the fiber structure frame makes contact at least once under high pressure with the wash liquid in a wash station. Finally the wash liquid is removed by suction from the fiber structure frame. To remove the galvanic electrolytic residues or the wash liquid by suction, the fiber structure frame is transported into a suction station, which has at least one suction device with at least one suction port. Between the suction port and a main area of the fiber structure frame there is inserted a strip-shaped porous support area. The second main area and the face sides of the fiber structure frame are provided with a closed cover beyond the spread of the suction port. With the suction device the galvanic electrolytic residues or the wash liquid can be removed by suction through the supporting area from the fiber structure frame.
It is a surprising advantage that washing under high pressure is also suitable for fiber structure frames or the fiber structure frame strips, which are not very mechanically stable and which are filled with galvanic electrolytes. This feature is especially unexpected since the coalescence of the metal layers at the intersecting and contact points of the fibers of the textile substrate is only a few &mgr;m thick. Nevertheless, the galvanically reinforced fiber structure frames or the fiber structure frame strips are so dimensionally stable that they can also be subjected to such a process step as high pressure washing. The stability is most likely due to the fact that the fiber structure frame at the intersecting and contact points of the individual t
Imhof Otwin
Kistrup Holger
Noreikat Karl-Ernst
Daimler-Chrysler AG
Leader William T.
Valentine Donald R.
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