Chemistry: electrical and wave energy – Processes and products – Electrophoresis or electro-osmosis processes and electrolyte...
Reexamination Certificate
1998-09-17
2001-04-17
Mayekar, Kishor (Department: 1741)
Chemistry: electrical and wave energy
Processes and products
Electrophoresis or electro-osmosis processes and electrolyte...
C204S491000
Reexamination Certificate
active
06217732
ABSTRACT:
The invention relates to coated products and the production thereof. The invention also relates to electrophoretic coating and to products produced thereby. This invention further relates to providing a more uniform coating by the use of electrophoretic coating or deposition. In a particular aspect, the present invention relates to the production of a coated three-dimensional network of material in which interior and exterior portions of the material are coated. The invention further relates to a coated catalyst structure wherein the structure is formed from a plurality of layers of fibers that are coated with a particulate coating that includes a catalyst.
There is a wide variety of technologies available for providing coated materials. One such method involves coating of materials by spraying or dipping. Attempts to employ such technology for coating a three dimensional network of material generally resulted in a coated product wherein only a portion of the interior of the material is coated.
Another coating procedure which is known in the art is electrophoretic coating. Such electrophoretic coating has generally been applied only to dense bodies or surfaces.
In addition, in electrophoretic coating procedures, in many cases, difficulties are encountered in providing a coating in which the thickness of the coating at the edges of the material is essentially the same as the coating thickness in other portions of the material.
In accordance with one aspect of the present invention, there is provided a process for depositing particles, as a coating, on a product or support comprised of a three dimensional network of material, with the particles being applied to such a product or support by an electrophoretic coating procedure.
Applicant has found that by electrophoretic coating of a porous product or support comprised of a three-dimensional network of material, such porous product or support can be effectively coated with a particulate coating with or without penetration of the coating into the interior of the porous product or support, preferably with penetration and that the degree of penetration can be controlled. Such three dimensional network of material is preferably formed from a plurality of layers of fibers that are randomly oriented.
Moreover, it is possible to coat the interior of the porous product to obtain a uniform coating over a defined thickness of the porous product; however, the invention is not limited to achieving such a uniform coating; i.e., the porous product may have a non-uniform coating over a defined thickness. Although in a preferred embodiment a porous product is coated electrophoretically to produce a product having a particulate coating in which a defined thickness thereof is uniformly coated (the interior portion of the multilayered product is coated), the present invention is also applicable to producing a coated product in which there is no essential penetration into the interior of the product or in which there is a controlled penetration and in which the coating is not uniform.
Applicant has surprisingly found that contrary to expectations in the art, an electrophoretic coating procedure may be employed for depositing particles within the interior of a product comprised of a three dimensional network of material. Moreover, Applicant has surprisingly found that an electrophoretic coating procedure may be employed for depositing particles as a uniform coating for a defined thickness of the interior portion of such a three dimensional network.
By the use of electrophoretic coating, there is provided a coated porous product which differs from coated porous products produced by procedures previously employed in the art such as spray coating or dipping. For example, the use of the technique of the invention provides a more uniform coating, i.e., there is a lower variation in coating thickness over a defined thickness of the product. In addition, unlike the prior art procedures, at intersections of the material forming the three-dimensional network an excess buildup of coating material that blocks or closes pores can be reduced or eliminated. Furthermore, by a more uniform application of the coating, “blocking” or “closing” of pores is reduced and/or eliminated. In addition, over a defined thickness, by proceeding in accordance with the invention, “bare” or uncoated portions of material are reduced or eliminated.
Thus, in accordance with an aspect of the present invention, a product comprised of a three dimensional network of materials may be produced in which a defined thickness of the interior portion of the material is coated with the particles in a uniform manner. The defined thickness of the three dimensional network of material may be a portion of the overall thickness or may be the entire thickness of such three dimensional network.
In a preferred embodiment of this aspect of the invention, the coating comprised of particles forms a porous coating on both the exterior and the interior portion of the three dimensional network of material, which coating may be comprised of one, two or more layers of the deposited particles.
In accordance with another aspect of the present invention, there is provided a process and coated product wherein a non-particulate support is electrophoretically coated with particles that have an average particle size greater than 0.5 micron wherein such larger particles are electrophoretically coated onto the support in conjunction with smaller particles that have an average particle size less than 150 nanometers (such smaller particles can be in the form of a sol or colloid). Applicant has found that an electrophoretic coating of larger particles (particles of an average particle size of greater than 0.5 micron) may be applied more effectively if the coating bath employed in such electrophoretic coating process includes particles having an average particle size of less than 150 nanometers in addition to the larger particles.
Although applicant does not intend to be bound by any theoretical reasoning, it is believed that the smaller particles function to more effectively bind the larger particles to each other and/or to the support or product that is being coated. In effect, the smaller particles function as a “glue” to improve the adherence of the larger particles to each other and/or to the coated product or support and increase the mobility of the larger particles in the electric field.
In a particularly preferred embodiment, the larger particles that are to be coated onto the product or support are either a catalyst support, catalyst precursor, a catalyst, or a catalyst or catalyst precursor on a particulate support.
The smaller particles may be the same material as the larger particles or may be a different material.
In many cases, it is desirable to produce a catalyst system in which a catalyst in particle form (the particle form of the catalyst coated on the non-particulate support may be a particulate catalyst support coated or impregnated with a catalyst) is present as a coating on a non-particulate support in which the particulate catalyst, when supported on the non-particulate support, has an average particle size greater than 0.5 micron. In such cases, applicant has found that in using an electrophoretic process for coating particles of a catalyst or catalyst precursor or catalyst support (with or without a catalyst or catalyst precursor) onto a non-particulate solid support which catalyst, catalyst precursor or support has an average particle size greater than 0.5 micron, it is desirable that the electrophoretic coating bath that contains such larger particles also includes smaller particles (in the form of a sol or colloid) in an amount that provides for a coating of the larger particles onto the non-particulate support such that the coating of the larger particles effectively adheres to the non-particulate support. The smaller particles may be comprised of the same material as the larger particles or may be a different material or materials or may include the material of the larger particle plus a differe
Gutzeit Heidemarie
Herschel Philipp
Schuh Lothar
ABB Business Services Inc.
Lillie Raymond J.
Mayekar Kishor
Olstein Elliot M.
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