Process for applying a coating to a product comprising a porous three-dimensional network of material, catalyst, and catalytic reactor.

Method for applying a coating to a product containing porous three-dimensional network material, catalyst, and catalyst reactor

<p>1 . . . electrode</p><p>10. . . Colloidal fluid</p><p>15. . . container</p><p>20. . . Object to be coated</p><p>twenty one. . . Product Electrode</p><p>twenty two. . . Opposite polarity electrode</p><p>twenty three. . . Dielectric material</p><p>twenty four. . . aperture</p><p>31. . . Needle electrode</p><p>32. . . Dielectric material</p><p>41. . . Electrode containing material to be coated</p><p>42. . . Electrodes of opposite polarity</p><p>43. . . Electrodes of opposite polarity</p><p>44. . . groove</p><p>46. . . Electrophoretic coating</p><p>60. . . Flakes</p><p>61. . . Distance fixer</p><p>62. . . electrode</p><p>63. . . electrode</p><p>64. . . container</p><p>67. . . electrode</p>

Figure 1 is a simplified schematic diagram of an electrophoretic coating device;

Figure 2 is a simplified schematic diagram of an electrophoretic coating device with a device for reducing edge effects;

Figure 3 is a simplified schematic diagram of an electrode that reduces edge effects;

Figure 4 is a simplified schematic diagram of an electrophoretic coating device for reducing edge effects;

Figure 5 is a simplified electrophoretic coating device including a positioning device for the material to be coated

The owner of this application has priority of US provisional application number 60059,795 (filed on September 23, 1997) and US patent application number 60097,483 (filed on August 21, 1998).

The present invention relates to coated products and their manufacture. The present invention also relates to electrophoretic coating and the products manufactured therefrom. The present invention is further related to providing a more uniform coating by using electrophoretic coating or deposition. In a specific aspect, the present invention relates to the manufacture of a three-dimensional network of coated materials in which both the inside and the outside of the materials are coated. The present invention further relates to a coated catalyst structure, wherein the structure is formed by a plurality of fiber layers coated with a particulate paint including the catalyst.

There are a variety of techniques available to provide coated materials. One such method involves spraying and dipping to coat the material. Attempts to use this technology to coat the three-dimensional network of materials generally produce coated products where only a part of the material is coated inside.

Another coating procedure known in the art is electrophoretic coating. This type of electrophoretic coating is generally only applied to dense objects or surfaces.

In addition, in the electrophoretic coating process, there are many situations in which various difficulties may be encountered when providing the following coatings; that is, when the thickness of the coating on the edge of the material is basically the same as the thickness of the coating on the other parts of the material.

According to one aspect of the present invention, its provider is a method of depositing particles, with paint, on a product or carrier composed of a three-dimensional network of materials, and the particles are applied to the product or carrier by an electrophoretic coating process superior.

The applicant has found that by using a porous product or carrier composed of a three-dimensional network of electrophoretic coating materials, such a porous product or carrier can be effectively coated with a particulate coating, and the coating can or may not penetrate into the porous product or carrier. Inside, it is better to penetrate and the degree of penetration can be controlled. Such a three-dimensional thick material network is preferably formed by many layers of randomly oriented fibers.

Moreover, the inside of the porous product can be coated to obtain a uniform coating on the defined thickness of the porous product; however, the present invention is not limited to obtaining such a uniform coating; that is, the porous product can have a non-uniform coating on the defined thickness . Although, in the preferred embodiment, the porous product is electrophoretic coated to produce a product with a particulate coating-in which its defined thickness is uniformly coated (the interior of a multilayer product is coated), but the present invention is also applicable to Manufacture of coated products-in which there is basically no penetration into the interior of the product or the penetration is controlled and the coating is not uniform.

The applicant has surprisingly discovered that, contrary to the expectations of the art, the electrophoretic coating process can be used to deposit particles in the interior of a product composed of a three-dimensional network of materials. Moreover, the applicant has surprisingly discovered that the electrophoretic coating process can be used to deposit particles with a uniform coating in a defined thickness inside such a three-dimensional network.

By using electrophoretic coating, the provider is a coated porous product, which is different from the coated porous product made by the process previously used in this art, such as spray coating or dip coating. For example, using the technology of the present invention provides a more uniform coating, that is, the thickness of the coating has a lower variation in the defined thickness of the product. In addition, unlike previous technical procedures, the excessive accumulation of paint that blocks or closes the pores at the intersection of the materials that form the three-dimensional network structure can be reduced or eliminated. Furthermore, by applying the coating more uniformly, the "clogging" or "closing" of the pores can be reduced and/or eliminated. In addition, in terms of the defined thickness, according to the present invention, the exposed or uncoated part of the material can be reduced or eliminated.

Therefore, according to one aspect of the present invention, a product composed of a three-dimensional network of materials can be manufactured, in which the defined thickness inside the material is coated with particles in a uniform manner. The defined thickness of the three-dimensional network structure of the material can be a part of the entire thickness or can be the entire thickness of the three-dimensional network structure.

In a preferred embodiment of this aspect of the present invention, a coating composed of particles will form a porous coating on both the outside and the inside of the three-dimensional network structure of the material. The coating may be composed of one, two or more layers of deposited particles.

According to another aspect of the present invention, it provides a method and a coated product, wherein the non-particulate carrier system is electrophoretically coated with particles having an average particle size greater than 0.5 microns, wherein these large particles have an average particle size less than 150 millimetres. Micron particles (these small particles can be in the form of sol or colloid) are electrophoretically coated on the carrier together. The applicant has found that the electrophoretic coating of large particles (average particle size greater than 0.5 microns) can be applied more effectively if the coating bath used in the electrophoretic coating method includes particles with an average particle size of less than 150 nanometers in addition to the large particles.

Although the applicant does not wish to be bound by any theoretical inferences, it is believed that small particles can more effectively combine large particles with each other and/or with the carrier or product in the coating. In fact, small particles can be used as "sizing materials" to improve the adhesion of large particles to each other and/or to the coated product or carrier and to improve the fluidity of large particles in an electric field.

In a particularly preferred embodiment, the large particles to be coated on the product or carrier are not the catalyst carrier, the catalyst precursor, and the catalyst is the catalyst or catalyst precursor on the particulate carrier.

The small particles may be the same material as the large particles, or may be different materials.

In many cases, it is necessary to manufacture a catalyst system, in which the granular catalyst (the granular catalyst coated on the non-particulate carrier can be a coated or impregnated particulate catalyst carrier) is present in the non-particulate catalyst as a coating. On the particulate carrier, the particulate catalyst, when supported by the non-particulate carrier, has an average particle size greater than 0.5 microns. Under these circumstances, the applicant found that the electrophoresis method was used to coat a catalyst or a catalyst precursor or a catalyst carrier (with or without a catalyst or a catalyst precursor) on a non-particulate solid carrier and the catalyst, the catalyst When the average particle size of the precursor or carrier is greater than 0.5 microns, the electrophoretic coating bath containing these large particles may also include small particles (in the form of sol or colloid). Coating, large particle coating can effectively adhere to non-particulate carrier. The small particles may be composed of the same material as the large particles, or may be different materials, or may include large particles plus materials of different materials. As shown above, it is believed that small particles can be used as "sizing materials", which can improve the adhesion of large particles to each other and/or to non-particulate carriers.

As shown above, the average particle size of small particles is generally less than 150 nanometers. Generally speaking, the average particle size is at least 2 nanometers. For example, in a specific example, the average particle size is 20-40 nanometers.

The large particles to be coated on the non-particulate carrier generally have an average particle size of at least 0.5 microns, for example, at least 1.0 microns. Generally speaking, the average particle size does not exceed 20 microns.

In the coating bath, the relative amount of large particles and small particles is selected to obtain the required amount of large particles in the final coating, and the amount of small particles can make the coating containing large particles effectively adhere to the non-particulate carrier . Generally speaking, based on the total amount of large particles and small particles, the amount of small particles used in the coating bath is 0.1 to 10% by weight.

This aspect of electrophoretic coating of large particles on a carrier of the present invention is also applicable to electrophoretic coating of porous carriers (three-dimensional carriers with a certain thickness-where the coating is applied to the outside or inside of the carrier), as well as the dense or non-electrophoretic coating of electrophoretic coating. Porous support-where the coating is basically only applied to the outside of the support.

The product or carrier to which the particle coating is applied by electrophoretic coating is one that can accept electric charge. The product can be formed of only conductive materials, or a mixture of conductive and non-conductive materials. If the entire product can accept electric charges, it can be used alone or in combination to form a representative of all or part of the product composed of a three-dimensional network of materials. Examples of conductive materials include metals, carbon and conductive polymers and/or ceramics. Representative examples of preferred metals include stainless steel, Fe-Ni or Fe-Cr alloys, Fe-Cr-Al alloys, copper, nickel, brass, and so on.

The coated product or carrier may be of the type described in US Patent No. 5,304,330, 5,080,962, 5,102,745 or 5,096,663. The three-dimensional network structure of the material can be composed of fibers or iron wires, such as iron wire or fiber mesh, metal felt or gauze, metal fiber filter or paper and the like, or can be a porous metal composite formed by sintering porous metal powder . The three-dimensional structure of the material with a certain thickness can be determined by compacting the powder and/or iron wire or fiber. Generally speaking, the thickness of the three-dimensional structure of the material containing uniform metal is at least 5 microns, and generally no more than 10 mm. According to a preferred embodiment, the thickness of the net structure containing the uniform coating is at least 50 microns, and more preferably at least 100 microns, and generally does not exceed 2 mm.

Generally speaking, when the product is a fibrous network of materials, the thickness or diameter of the fibers is less than 500 microns, preferably less than 100 microns, and more preferably less than 30 microns.

The coated product is preferably composed of multiple fiber layers with fibers in each layer arbitrarily oriented, and according to the present invention, the fibers inside and outside the product are coated with particulate paint to form a porous coating.

By the electrophoretic coating method, the particles applied with the coating to the three-dimensional network of the material generally have an average particle size of no more than 100 microns, and in most cases, no more than 10 microns. Generally speaking, the particle size of these particles is at least 1 nanometer, preferably at least 2 nanometers. The particles can be colloidal particles or a mixture of colloidal particles and/or a mixture of colloidal particles and one or more non-colloidal particles.

The thickness of the formed coating can vary. Generally, the thickness is at least 1 micrometer, and generally not greater than 100 micrometers.

The particles to be coated on the carrier can be composed of a single material or multiple materials (two, three or more different materials). For example, the material can be a complex of two or three materials, such as an ion or an absorption complex.

The inside of the product coated according to the present invention has a porosity sufficient to allow the particles constituting the coating to penetrate or move into the three-dimensional network. Therefore, the pore size of the three-dimensional material and the particle size of the particles constituting the coating material, in fact, determine the particle penetration and the distance within the three-dimensional network of the coating material and/or the thickness of the coating in the network. The larger the pores, the larger the thickness of the coating that can be uniformly applied according to the present invention. Generally speaking, the average pores of the coated product are at least 10 microns, preferably at least 20 microns, and preferably the void volume is 60-90% (the percentage of voids is the ratio of the open volume to the total volume multiplied by 100). Therefore, by adjusting the particle size and the pore size of the product to be coated, the penetration or migration of the paint into the porous product can be controlled by changing the pore size of the material to be coated.

The coated product or carrier can have different pore sizes throughout its thickness, and within the scope of the present invention, the coated three-dimensional product will have uniform porosity as a whole or its porosity will be different, and this The various products can be laminated and/or composed of the same or different materials and/or can have multiple layers. The material to form a three-dimensional network structure and to be electrocoated can be coated or uncoated, and such a three-dimensional network structure may have particles trapped or contained in it. Generally speaking, these particles, if any, have a particle size of 1-300 microns.

The particulate material used as a coating can be composed of a single material or a mixture of materials. When a mixture is used, the particles can be a composite composed of small particles (sol) adhered to large particles.

The choice of materials, particle size and coating conditions must be coordinated to ensure that the particles retain sufficient charge for electrophoretic coating. Therefore, in some cases, such as when the carrier is coated with large particles (such as a catalyst carrier or large particles in the form of a catalyst), the coating mixture may include a suitable sol, all or part of which adheres to the large particles to provide sufficient The charge and/or binding properties of the present invention are used to produce the particulate coating of the present invention.

It should be understood that, within the scope of the present invention, the particulate material applied with the paint may be particles larger than the sol, and the large particles may be added or not added with the sol, preferably the sol-added paint is applied.

In some cases, it may be necessary to treat the product before coating to facilitate the coating and/or improve the adhesion of the coating; for example, acid etching or gas treatment with oxygen-containing gas.

In a preferred embodiment, the particles applied to the three-dimensional network of porous materials can be catalyst particles or catalyst carriers and/or catalyst carriers and/or catalyst precursors containing active catalysts or precursors. In this specific example, the particles preferably form a uniform coating on the defined thickness of the three-dimensional network structure of the material, and the three-dimensional network structure of the material is porous (with void volume), and the particle coating on the material is also porous . In this way, the entire catalyst structure with high void volume can be provided, and the defined thickness of the catalyst is evenly distributed inside the three-dimensional network structure.

When the particles are catalyst precursors, the product is processed after the particles are deposited to convert the catalyst precursors into active catalysts. When the particles deposited in the three-dimensional network of the material are supported by the catalyst, the active catalyst or catalyst precursor can be applied to such a carrier by, for example, spraying, dipping or dipping.

There can be multiple catalyst active materials and precursors. For example, as a representative and non-limiting example, the catalyst active material may include one or more ethnic VIB, VIIB, VIII catalyst active metals, metal oxides or sulfides and mixtures thereof, and optionally include active agents such as Phosphorus, halogen or boron; or group VIB, VIIB, VIII catalyst active metals, metal oxides or metal sulfides or metal nitrates and optionally including active agents such as phosphorus, halogen or boron and their mixtures, deposited on refractory metal oxidation Substrates such as alumina, silica, silica/alumina, titania, zirconia, etc. and their mixtures, and aluminosilicates such as natural or synthetic zeolites such as zeolite X, zeolite Y, zeolite beta, ZSM- 5. Offretite, mordenite, erronite, etc. and their mixtures. Oxides, like alumina, zeolite, zirconia, silica, titania phase, vanadium oxide phase, transition lead oxide, zinc phase can all come from suspension, such as nanometers or micrometers, or from sols of these compounds Or a mixture of the two can be deposited directly. The coated particles can include carbon supports, such as carbon black, oxidized carbon supports, carbon molecular sieves, etc., porous or non-porous. The concentration of solids in the suspension can vary from 0.01 to 80% by weight.

Generally speaking, the particles applied to three-dimensional materials (catalyst, catalyst carrier, catalyst precursor) are inorganic particles.

When a coating bath is used, the coating bath may include additional agents in some cases, such as stabilizers, binders, fluidity enhancers, etc., and in some cases, a single material can perform many functions in this way. As a representative stabilizer, there can be mentioned: polymers such as polyacrylic acid, allylamine, organic quaternary ammonium compounds or other special mixtures, which are selected according to the particles to be coated.

By choosing the appropriate binder/stabilizer, different materials can be deposited at the same time, which means that they migrate to the object to be coated and deposited at the same time. The deposition is measured by the migration speed and particle concentration in the system. The advantage of the sol is that it will not be thermally decomposed during subsequent heat treatment; in most cases, heat treatment is used to achieve proper bonding between the coating and the substrate. For example, in order to obtain a gamma alumina coating with strong adhesion between the oxide and the metal wire, the alumina powder is suspended in an aqueous system and an alumina sol is added to obtain it. For example, alumina is used in such an aqueous system. The concentration is between 1 and 30% by weight. After deposition, the object is dried and calcined. The dried and calcined sol is a good binder for alumina. In addition, during the coating process, the sol acts as a stabilizer and provides alumina particle fluidity.

When preparing the catalyst according to the present invention, the catalyst can be applied to the carrier in various ways.

In a specific example, the particulate catalyst carrier can be applied to the carrier by electrophoretic coating according to the present invention, and then the catalyst solution is applied to the coated product, for example, by spraying or dipping.

In another specific example, the carrier-free catalyst particles can be applied to the carrier according to the present invention.

In a further specific example, the particulate catalyst carrier system on which the catalyst or catalyst precursor is applied is coated on the carrier according to the present invention.

In any of the above procedures, electrophoretic coating can be completed with or without a binder in the electrophoretic coating mixture.

In a further embodiment, the adhesive may be applied to the three-dimensional network before or after the application of the particulate material, and these adhesives are preferably applied according to the electrophoretic coating of the present invention.

In another embodiment, the multilayer coating can be applied to the same product in multiple coating steps, and the coatings can be the same or different from each other.

In still another specific example, during electrophoretic coating, in addition to particles applied by electrophoretic coating, a material can also be applied to a non-particle carrier.

These and other specific examples should be understood by those who are familiar with the handwriting skills from the teachings here.

A product composed of a three-dimensional network of materials has particles applied to it by using an electrophoretic coating or deposition method; the electrophoretic method may be a type known in the art. This known electrophoretic coating or deposition procedure is not expected to be effectively applied to the inside and outside of products or carriers (products with thickness) composed of a porous three-dimensional network of materials , because it was previously expected that particles can only be applied It is applied to the external surface of this three-dimensional net structure instead of both the external and internal surfaces.

According to the present invention, a product composed of a three-dimensional network of materials is connected to a power source with a positive electrode or a negative electrode, depending on the charge of the particles to be applied to the product. The particles are used as a suspension in a suitable liquid medium for application to the product or carrier. Therefore, the product to which the particles are to be applied forms one of the poles or electrodes used in the procedure.

The speed and amount of particles applied to the carrier, and therefore the thickness of the coating, can be controlled by the current (which is determined by the electrophoretic deposition parameters such as the voltage used in the procedure and the solid content of the particle suspension, and additives) and the coating process Total time control.

After the coating procedure, the coated porous body is usually dried, and if necessary, one or more treatment steps can be carried out.

More specifically, the object to be coated is immersed in the coating suspension. The electrodes are placed parallel to the geometric surface of the object considered as a sheet. The electrode may be composed of metal (for example, stainless steel). Depending on the surface charge of the suspended particles, the object to be coated is ten or one pole (cathode or anodic deposition). The deposition process is usually carried out at a constant voltage, depending on the shape of the entire system (electrode size/distance) and the nature of the suspension. Generally speaking, the correlation is as follows: I=n ₂ *g ₂ /η*Uv/dI = current n ₂ = Concentration of colloidal particles g = Charge of colloidal particles η = Viscosity of colloidal particles U = Voltage V = Volume between electrodes d = Distance between electrodes After the coating is deposited, the coated object will be baked between 0°C and 150°C Dry. Then a second heating step is performed to properly bond the coating to the surface and make the coating itself more stable against wear and other effects. The specific heating cycle and conditions depend on the coating. When using a sol, the heating cycle will cause the proper crystalline phase to form. Alumina sol, for example, can be dried at 110°C, and then processed at 550°C in an inert or oxygen-containing atmosphere to form transition-alumina.

Therefore, according to the present invention, a uniform coating can be applied to almost the entire material up to a defined thickness inside the porous three-dimensional network. For example, if such a three-dimensional network is composed of fibers or iron wires or a mixture thereof, each fiber and iron wire within the defined thickness can be uniformly coated with these particles.

Although in a preferred embodiment, almost the entire thickness of the material is coated with particles, it is also within the spirit and scope of the present invention that such particles are not coated to the entire thickness. At the same time, various coating thicknesses in the three-dimensional structure are also within the spirit and scope of the present invention.

As shown above, the present invention uses sols or colloids to more effectively electrophoretically coat larger particles on the carrier or product. This aspect is suitable for electrophoretic coating that basically only coats the outer porous carrier, as well as the inner and outer parts. Coating of porous carriers that are both coated.

The present invention further relates to a catalyst reactor, wherein the reactor contains at least one fixed catalyst bed, which is composed of the coated, porous, three-dimensional product of the present invention.

The coating of porous, three-dimensional products includes appropriate catalysts. All or part of the coating is applied to the product or carrier by the above-mentioned electrophoresis procedure. The electrophoretic coating is composed of the catalyst alone, or the combination of the catalyst and the carrier or the carrier, and only the catalyst carrier In the case of electrophoretic coating, the catalyst is applied by another procedure, such as spraying or dipping or dipping.

The void volume of the coated product is preferably at least 45%, preferably at least 55%, more preferably at least 65%. Generally speaking, the void volume does not exceed 95%, and preferably does not exceed 90%. The term "void volume", as used here, is calculated by dividing the open volume of the coated product (without catalyst and the material that forms the net) by the total volume of the coated product (opening, mesh and coating) ) Determination, there is another 100 left.

The reactor contains at least one catalyst bed, and this catalyst bed may be formed by one or more layers of the coated product of the present invention. In most cases, the catalyst bed is composed of multiple layers of such coated products.

The coated product, according to the present invention, can be formed into various shapes, and therefore can be used as a filling element of a catalytic reactor. Thus, for example, the mesh can be made into wave-shaped packing elements, wherein each wave-shaped packing element forming a fixed catalyst bed is formed of a coated product. The catalyst bed can be formed by many such wave-shaped elements, and each element can be arranged in various shapes or forms.

According to another aspect of the present invention, its provider is a catalyst structure, which is composed of many fiber layers (each layer forms a three-dimensional network structure of materials); the fibers are arbitrarily oriented in each layer, and the fibers are coated with porous particles. Layer in which the particulate coating is applied to the fibers in particulate form.

Therefore, when manufacturing the catalyst structure, the catalyst or catalyst precursor or catalyst carrier (the catalyst carrier may or may not include the catalyst or catalyst precursor) is applied to the fiber in the form of particles during the coating process .

According to one aspect of the present invention, its provider is a method (and the resulting product) for manufacturing a catalyst structure; the catalyst structure is composed of a carrier structure coated with a particulate paint containing the catalyst. The carrier structure is a porous network structure composed of multiple layers of randomly oriented fibers, in which the fibers inside the network structure and the fibers outside the network structure are coated with particulate coating. According to the present invention, the particles of the particulate coating are in the form of particles when they are applied to the fibers.

Therefore, according to one aspect of the present invention, its provider is a porous non-particulate carrier, which is composed of multiple layers of fibers (preferably arbitrarily oriented), wherein the fibers of the multiple layers are coated with a particulate coating containing a catalyst, wherein the coating The particles are applied to the fiber as particles.

The particles applied with paint may be (i) a catalyst carrier that may or may not include a catalyst or a catalyst precursor, or (ii) a catalyst or (iii) a catalyst precursor.

When the particles are a catalyst carrier without a catalyst, the catalyst can be added to the carrier particles coated on the fiber. When the particle is or includes a catalyst precursor or the particle is a catalyst carrier containing the catalyst precursor, the catalyst precursor is converted into a catalyst by a procedure known in the art.

The fibers used in the catalyst structure may be of the above-mentioned type, and the resulting catalyst structure may also have the above-mentioned properties (void volume, etc.).

The carrier structure used in this aspect of the present invention is composed of many layers of randomly oriented fibers, and is therefore not a woven mesh structure used in the art and is different. In particular, the net structure includes a single layer of material.

Therefore, according to one aspect of the present invention, its provider is a three-dimensional catalyst carrier or filler for a catalytic reactor, wherein the carrier or filler is formed by a coated, porous, three-dimensional product with the above-mentioned characteristics.

The reactor, especially the fixed bed reactor of the present invention, uses catalyst-coated packing, which can provide one or more of the following improvements: low by-product formation (improved selectivity); high volume activity per unit of reactor volume ; Increased catalyst life, reverse mixing is minimized or disappeared; bottom pressure drop; improved reactant and/or product mixing with liquid and/or gas; high catalyst geometric surface area to volume ratio; improved quality and Heat transfer and so on.

Catalytic reactors can be used for various chemical reactions. As representative examples of these chemical reactions, hydrogenation reactions, oxidation reactions, dehydrogenation reactions, catalytic or steam reforming, and alkylation reactions can be mentioned. Hydrogen treatment, condensation reaction, hydrogen cracking, etherification reaction, isomerization reaction, selective catalyst reduction, and catalyst removal of volatile organic compounds, etc.

According to another aspect of the present invention, its provider is a method for electrocoating a material by means of reducing the "edge effect" of the coating on the material.

"Edge effect" is an effect in which the material being coated receives a thicker coating around the edges than other parts, especially the middle part.

Although the ability to reduce the "edge effect" described here is particularly suitable for the electrophoretic coating of the three-dimensional materials described above, the teachings of the present invention in this respect are also applicable to the electrophoresis of porous materials (where only the surface of the material is coated) Coated.

According to this aspect of the present invention, the "edge effect" is reduced, which will result in minimizing the difference between the coating thickness around the edges of the coated material and other parts of the coated material; that is, on the same surface Above, the thickness of the coating on the edge of the material is basically equal to the thickness of the coating on the other parts of the material.

According to the specific example of reducing the edge effect of the present invention, the edge effect is reduced by electrophoretic coating material, and the method used is to make the electrode containing the material to be coated and adjacent to the electrode containing the material to be coated The field image between the electrodes of opposite polarity is interrupted. The applicant has discovered that the edge effect can be minimized by interrupting or changing the field image between the electrode containing the material to be coated and the adjacent electrode of opposite polarity. This reduction of equilateral effects can be accomplished without using interrupted balancing electrodes. Therefore, according to one aspect of the present invention, the electrophoretic coating is formed by using non-homogeneous or non-uniform field images.

In another specific example, the edge effect of the electrophoretic coating process is minimized by electrocoating a material. The method used is to make the electrode containing the material to be coated and the opposite polarity adjacent to the material to be coated The cross-section of the electrode is equal to the cross-section of the coating bath between the electrodes. Therefore, the shape and external dimensions of these electrodes and the external dimensions of the coating bath between these electrodes are basically the same. The applicant has found that the use of these sizes will reduce the edge effect.

According to another specific example, the distance between the electrode containing the material to be coated and the electrode of opposite polarity adjacent to the electrode containing the material to be coated is selected at a value, which causes the edge effect during such electrophoretic coating Minimize. The applicant has found that by reducing the distance between these electrodes, the edge effect can be reduced. In a preferred embodiment, the distance between the electrode containing the material to be coated and/or the electrodes of opposite polarity adjacent to these electrodes is less than 100 mm, generally less than 1 mm.

In another specific example, a dielectric material is placed between the electrode containing the material to be coated and the adjacent electrode of opposite polarity. This dielectric material has openings and its dielectric constant is different from that in the coating bath Suspension. Preferably, the dielectric constant of this dielectric material is at least 10 times greater than the dielectric constant of the suspension in the coating bath.

The openings in the dielectric material generally account for 10% to 90% of the area of the dielectric material. In particular, the size or area of the opening or the plurality of openings is smaller than the size or cross-sectional area of the object to be coated.

In a further specific example, the electrophoretic coating is carried out in the following manner. That is, the electrode adjacent to the electrode containing the material to be coated and the electrode with the opposite polarity is composed of a large number of separate electrodes, and each electrode is smaller than the electrode containing the material to be coated. electrode. Therefore, in fact, the polarity is opposite to the electrode containing the material to be coated, and each electrode adjacent to the material to be coated is composed of many needle-shaped electrodes, which are fixed or placed in the dielectric material, and the needle electrodes are separated from each other. open. These needle electrodes can generate non-uniform or interrupted electric fields, thereby improving the uniformity of electrophoretic coating, that is, reducing edge effects.

It is encompassed by the present invention that a combination of the above techniques to reduce the edge effect can be used. Therefore, two or more of these techniques can be used to improve the uniformity of the coating. In this regard, for example, when using a technique in which the size of the electrodes and the bath between the electrodes have substantially the same size, the distance between the electrodes must be selected so that the distance between the material to be coated and the adjacent electrodes of opposite polarity is reduced. To the smallest, in order to improve the uniformity of the coating. Similarly, in some cases, the above two techniques can be combined with the use of dielectric materials with appropriate openings between two adjacent electrodes.

When using dielectric materials with appropriate openings, the uniformity of the coating thickness can be controlled to provide various coating thickness differences. Therefore, the opening of the dielectric material can be controlled so that the middle part of the material in the coating has a larger coating thickness than the side part, and the side part has a larger coating thickness than the middle part. However, in a preferred embodiment, by appropriately controlling the opening of the dielectric material, the edge effect can be reduced, and a uniform coating can be obtained on a certain plane cross-sectional area of the coating material.

Schematic description

Figure 1 is a simplified schematic diagram of an electrophoretic coating device;

Figure 2 is a simplified schematic diagram of an electrophoretic coating device with a device for reducing edge effects;

Figure 3 is a simplified schematic diagram of an electrode that reduces edge effects;

Figure 4 is a simplified schematic diagram of an electrophoretic coating device for reducing edge effects;

Figure 5 is a simplified electrophoretic coating device including a positioning device for the material to be coated

Symbol description of main components

1 . . . electrode

10. . . Colloidal fluid

15. . . container

20. . . Object to be coated

twenty one. . . Product Electrode

twenty two. . . Opposite polarity electrode

twenty three. . . Dielectric material

twenty four. . . aperture

31. . . Needle electrode

32. . . Dielectric material

41. . . Electrode containing material to be coated

42. . . Electrodes of opposite polarity

43. . . Electrodes of opposite polarity

44. . . groove

46. . . Electrophoretic coating

60. . . Flakes

61. . . Distance fixer

62. . . electrode

63. . . electrode

64. . . container

67. . . electrode

Figure 1 shows an example of a deposition device. The electrode (1) made of a conductive plate (such as stainless steel) is immersed in the colloidal fluid (10), and then all of it is placed in the container (15). The object to be coated with colloidal particles is placed between the two electrodes. The shape of the configuration can be changed, so one electrode or more than two electrodes can be used. The object (20) to be coated can be placed between two electrodes, or on the opposite side of a single electrode, or between two or more electrode configurations.

Figure 2 shows a schematic diagram of a coating device that includes a dielectric material between an electrode containing the product to be coated and an electrode of opposite polarity. As shown in FIG. 2, the product electrode is 21, the opposite polarity electrode is 22, and the dielectric material is 23, which includes a gap 24. Although as shown above, the dielectric material has gaps.

However, the dielectric material can also have other openings and are within the scope of the present invention. For example, the opening may be a square or rectangular opening, or there may be many openings in the dielectric material.

Please refer to Fig. 3, which shows the electrode. The electrode is composed of a large number of separate and independent electrodes. The electrodes are used as an electrode, the polarity of which is opposite to that of the electrode containing the material to be electrophoresed. As shown in FIG. 3, this type of electrode is composed of many needle-shaped electrodes 31 in a dielectric material 32.

Figure 4 shows a schematic diagram of an electrophoretic coating design, in which the electrode containing the material to be coated, the electrode with the opposite polarity and the coating bath between the electrodes have basically the same size. As shown in FIG. 4, the electrode containing the material to be coated is denoted by 41, and the two electrodes with opposite polarities are denoted by 42 and 43. As shown, the electrodes 41, 42 and 43 are substantially the same size, and the height and width of the tank 44 for holding the electrophoretic coating paint 46 should be such that the height of the electrophoretic coating material in the tank can be maintained substantially equal to that of the electrode. high.

As shown above, the technique for reducing the edge effect of the present invention is particularly suitable for the coating of porous three-dimensional network structure of materials by electrophoretic coating. The method is that in addition to the outside of the material, the inside of the three-dimensional network should be at least one Partially coated. However, these techniques can also be used to coat the surface of non-porous materials.

In a preferred but non-limiting example of the present invention, the electrophoretic coating is applied in such a way that the distance between the sheet and each electrode of the opposite polarity is 50 mm, and the size of the test piece and bath section is 30×30 cm . In this regard, this configuration can be used to fix the sheet to be coated at a desired distance from the other electrode by using a fixer. The sheet is fixed in a movable container box. The container is then placed in the coating device and the drying device. The movable container is equipped with electrodes, and its design enables the mesh sheet to "position itself by gravity" (distance holder). The electrical contact is guided via a distance holder, so no external electrical contact is required. This makes the process easy to handle, reliable and simple to automate.

Please refer to FIG. 5, which shows a container or chamber 64 formed by a first wall in the form of an electrode 62, a second wall in the form of an electrode 63, and a bottom non-conductive wall 66. As shown in Figure 5, the sheet 60 to be coated is placed in the deposition container 64 (Figure 5a); and (the sheet 60 is "unfixed" and rests in the deposition chamber or container 64 (Figure 5b). The container is tilted to 45°C. (Figure 5C), and the sheet 60 falls on the distance holder 61, which includes an electrode 67 of opposite polarity to the electrodes 62 and 63.

The current transport during electrophoretic deposition is governed by the charge transport and ion transport of colloidal particles. The latter is undesirable, because it is a kind of current delivery without any benefit. Therefore, the ion concentration should be kept to a minimum.

The present invention is further illustrated by the following examples; however, the scope of the present invention is not limited by them:

Example 1: The configuration and method of incorporating gamma alumina on and in a piece of metal felt.

The tank is filled with alumina sol, the particle size of which is from 1 to 60 mm, preferably 10 to 30 mm. The system is stabilized by adding nitric acid or acetic acid to establish a sufficiently long shelf life. Aqueous solution is preferred, so the system is easy to handle. The solid concentration of alumina in the sol is between 1 and 30% by weight, compared with 5-10% by weight. The positive electrode of the stainless steel plate is better, when the negative electrode is the object to be coated; the positive electrode can be composed of, for example, 1 mm thick metal felt, and the metal felt is made of 20 micron thick metal fibers with 90% voids The volume and average void opening are 20 microns. The size of the object to be coated is 10×10 cm. The current is applied during the deposition, and the voltage is between 10 and 20 volts, and the current is between 0.1 and 100 mA/cm² surface of the test piece, preferably 10-40mA/cm² area. After depositing for 1 to 10 minutes, remove the test piece from the tank, dry it to evaporate the water, and then sinter (for example, at a temperature of 500°C-550°C for 1 to 3 hours, preferably 500°C for 1 hour) to form a Mala alumina, which is properly bonded to the metal surface and has a suitable active surface between 100 and 300 square meters/g. Depending on the concentration current and the deposition time, up to 30% alumina loading can be incorporated into the metal felt.

Example 2: Co-deposition of sol and particles

The suspension of grain rice particles has electrophoretic fluidity, and the solid particles move into the fiber network of the object to be coated. These micron-sized particles, preferably 0.5-10 microns in size, can be titanium oxide, alumina, pumice or any other compound. Depending on the nature of the particles, the co-deposition of the particles and the sol can improve the adhesion of the particles on the surface of the metal wire. The sol system is used as an adhesive to connect the particles to the fiber surface and the particles to each other. The process starts with a stable suspension containing sol (nano-micron particles) with a concentration of less than 1% up to 20% or even higher micron particles. Subjecting the suspension/sol mixture to electrophoretic deposition will cause both nanometer particles (ie sol) and micrometer particles to move to the fiber network. The co-deposition on the fiber surface begins. As a result, the micron particles are more firmly attached to the metal surface by the sol; after heating to a temperature higher than 100°C, the dried coating begins to solidify, and the sol begins to form a crystalline state. The micron particles are embedded in the porous film coating, thereby firmly attaching to the metal.

The coated product of the present invention can be used for many purposes, including, but not limited to, being used as a catalyst, a diaphragm, a special distillation column filling material (non-catalyst or catalyst type); sensors; isolation devices other than diaphragms ; Absorbent for absorption tower. These and other uses should be understood by those who are familiar with the art from the teachings here.

Example 3: Coating to eliminate edge effect

The coating deposition chamber contains two plate-shaped stainless steel electrodes of the same shape as the cross section of the bath: 30 cm x 30 cm. The distance between the electrodes is 100 mm.

Mix water and alumina sol binder (40 nanometers): the amount of sol-binder is dominated by the total amount of lead oxide (&lt;3 microns) in the oxide powder, which is 10 weight in this example %. The amount of sol binder is 2% by weight of the amount of solid powder. The mixture was stirred vigorously, and 1% by weight (based on the amount of the oxide powder) of the fourth amine was added. Then adjust the pH to pH4-4.5 by adding dilute nitric acid. Finally, alumina (&lt;3 microns) powder is gradually added, while further stirring the suspension.

After the suspension is transferred to the deposition device, the fiber mesh (30×30 cm) that has been annealed at 300°C for 1 hour is inserted into the middle plane between the two electrodes. A voltage of 10 volts is applied to the electrodes and the fiber mesh. The deposition time of 60 seconds is sufficient to load 25% by weight of oxide powder inside the fiber network structure.

After deposition, remove the mesh from the bath, blow away the attached droplets with a hair dryer, and dry with hot air. The final step is sintering in air at 500°C for 1 hour. It can be known from the above teachings that the present invention can have various modifications and changes, and therefore, within the scope of the appended patent application, the present invention does not need to be implemented as specifically described.