Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Reexamination Certificate
2001-06-26
2003-09-09
Barr, Michael (Department: 1762)
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
C428S680000, C428S457000, C427S436000, C427S437000, C427S438000, C427S443100, C427S404000, C427S405000, C427S419100, C427S239000
Reexamination Certificate
active
06617047
ABSTRACT:
The present invention relates to a process for coating apparatuses and apparatus parts for chemical plant construction—which are taken to mean, for example, apparatus, tank and reactor walls, discharge devices, valves, pumps, filters, compressors, centrifuges, columns, dryers, comminution machines, internals, packing elements and mixing elements—wherein a metal layer or a metal/polymer dispersion layer is deposited in an electroless manner on the apparatus(es) or apparatus part(s) to be coated by bringing the parts into contact with a metal electrolyte solution which, in addition to the metal electrolyte, comprises a reducing agent and optionally the polymer or polymer mixture to be deposited in dispersed form, where at least one polymer is halogenated. This is optionally followed by conditioning. The invention furthermore relates to surfaces of apparatuses and apparatus parts for chemical plant construction which have been coated by the process according to the invention, and to the use of the coating comprising a metal component, at least one halogenated polymer and optionally further polymers for reducing the tendency of the coated surfaces to bind solids from fluids, with formation of deposits. Finally, the present invention relates to apparatuses and apparatus parts for chemical plant construction which have been coated by the process according to the invention.
Deposits in apparatuses and apparatus parts for the chemical plant construction represent a serious problem in the chemical industry. They particularly affect apparatus, tank and reactor walls, discharge devices, valves, pumps, filters, compressors, centrifuges, columns, dryers, comminution machines, internals, packing elements and mixing elements. These deposits are also known as fouling.
The coatings can have a variety of damaging or hindering effects for the process and may result in the necessity repeatedly to shut down and clean corresponding reactors or processing machines.
Measurement devices encrusted with coatings can result in incorrect and misleading results through which operating errors can occur.
A further problem arising through the formation of deposits is due to the fact that, in particular in coatings in polymerization reactors, the molecular parameters, such as molecular weight or degree of crosslinking, differ significantly from the product specification. If deposits detach during running operation, they may contaminate the product (for example specks in paints, inclusions in suspension beads). In the case of reactor walls, packing elements or mixing elements, undesired deposits can furthermore result in an undesired change in the residence-time profile of the apparatus or impair the effectiveness of the internals or mixing elements as such. Relatively large parts of coatings breaking off can result in blockage of discharge and processing devices, while small parts can result in impairment of the resultant product.
The deposits whose formation is to be prevented are coatings which can be caused, for example, by reaction with and on surfaces. Further reasons are adhesion to surfaces, which may be caused by van der Waals forces, polarization effects or electrostatic double layers. Other important effects are stagnation of movement at the surface and possibly reactions in said stagnating layers. Finally, mention should also be made of the following: precipitates from solutions, evaporation residues, cracking on locally hot surfaces and microbiological activities.
The causes are dependent on the respective material combinations and can be effective alone or in combination. While the processes resulting in the undesired coatings have been investigated quite well (for example A. P. Watkinson and D. I. Wilson, Experimental Thermal Fluid Sci. 1997, 14, 361 and literature cited therein), there are only few uniform concepts for preventing the above-described deposits. The processes disclosed hitherto have technical disadvantages.
Mechanical solutions have the disadvantage that they may cause considerable increased costs. Additional reactor internals may furthermore significantly change the flow profile of fluids in the reactors and consequently make expensive redevelopment of the process necessary. Chemical additives may result in undesired contamination of the product and in some cases pollute the environment.
For these reasons, there is an increasing search for ways of directly reducing the fouling tendency by modification of chemical reactors, reactor parts and processing machines for chemical products.
It is an object of the present invention to provide a process for the surface modification of apparatuses and apparatus parts for chemical plant construction
which firstly reduces the tendency of the surfaces to bind solids with formation of deposits,
where the surfaces treated by the process should have good durability,
and where it should also be possible to use the process according to the invention in an inexpensive manner for surfaces which are not readily accessible, and secondly
ensures that the product or products is (are) not contaminated by additives.
It is a further object of the present invention to provide protected surfaces of apparatuses and apparatus parts for chemical plant construction, and finally to use apparatuses and apparatus parts for chemical plant construction.
We have found that this object is achieved by a process for coating the surface of apparatuses and apparatus parts for chemical plant construction, wherein a metal layer or a metal/polymer dispersion layer is deposited in an electroless manner on the apparatus(es) or apparatus part(s) to be coated by bringing the parts into contact with a metal electrolyte solution which, in addition to the metal electrolyte, comprises a reducing agent and optionally the polymer or polymer mixture to be deposited in dispersed form, where at least one polymer is halogenated.
This solution according to the invention is based on a process for the electroless chemical deposition of metal/polymer dispersion layers which is known per se (W. Riedel: Funktionelle Vernickelung, Verlag Eugen Leize, Saulgau, 1989, pp. 231 to 236, ISBN 3-750480-044-x). The deposition of the metal layer or metal/polymer dispersion phases serves to coat the apparatuses and apparatus parts known per se in chemical plant construction. The metal layer according to the invention comprises an alloy or alloy-like mixed phase of a metal and at least one further element. The metal/polymer dispersion phases which are preferred in accordance with the invention comprise a polymer, for the purposes of the invention a halogenated polymer, which is dispersed in the metal layer. The metal alloy is preferably a metal/boron alloy or a metal/phosphorus alloy having a boron or phosphorus content respectively of from 0.5 to 15% by weight.
A particularly preferred embodiment of the coatings according to the invention involves so-called “chemical nickel systems”, i.e. phosphorus-containing nickel alloys having a phosphorus content of from 0.5 to 15% by weight; very particular preference is given to phosphorus-containing nickel alloys having a phosphorus content of from 5 to 12% by weight.
The metal/polymer dispersion layer which is preferred in accordance with the invention and is also referred to as the composite layer comprises a metal component and at least one polymer, for the purposes of the present invention at least one halogenated polymer, and optionally further polymers which are dispersed in the metal component.
In contrast to electrodeposition, the electrons necessary for this purpose in chemical or autocatalytic deposition are not provided by an external current source, but instead are generated by chemical reaction in the electrolyte itself (oxidation of a reducing agent). The coating is carried out, for example, by dipping the workpiece into a metal electrolyte solution, which has optionally been mixed in advance with a stabilized polymer dispersion.
The metal electrolyte solutions used are usually commercially available or freshly prepared metal electrolyte solutions to wh
Diebold Bernd
Franke Axel
Hüffer Stephan
Korkhaus Juergen
Krebs Thilo
Barr Michael
BASF - Aktiengesellschaft
Keil & Weinkauf
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