MXPA97009009A - Microencapsulation of fine and yelectromolde particle - Google Patents

Abstract

A method and apparatus for microencapsulating or coating powdered or powdered material comprising using a rotary pass through device (40) to alternately compact and electroplate the powder and reorient it before another compacting action. The invention also provides a method and apparatus (40) for forming a strip, mesh or film of the powder material, which is particularly useful for composite form of metallic powder mixed in a nickel mesh for use in metal hydride batteries.

Description

MICROENCAPSDACION DB PARTICLE FINA AND ELECTROMOLDEADO DESCRIPTION OF THE INVENTION: This application is a continuation in part of the US application Series No. 08 / 295,055 entitled "Electroplating apparatus and electroplating method for small articles" filed on August 26, 1994. The present invention relates to apparatus and methods for electroplating and electroforming, particularly by centrifugal means and for encapsulating, coating and electro-depositing powders, including mesh or film webs. The term "electro deposit" is used in the description and in the claims indicating electroplating and / or electromolding. The process of microencapsulation of metal hydride electrode powder (and other powders) has been limited in the past to metallic copper and nickel deposit without electrodes. Previous studies of electroplating on fine particles employed equipment capable of handling light materials in an aqueous solution (see Figures 1 and 2) but the results were limited due to the difficulty of obtaining a good electrical contact during the circulation of the particles, poor cathode efficiency (loss of cathode and plate contact and increase in the solution, (from ion concentration) and bipolarization, resulting in a costly and unreliable electrolytic process.Alternatively, the alternative chemical copper or the nickel process without electrode was unfeasible from the economic point of view due to the large surface areas of the powders. to Figure 1 (prior art) a first known apparatus of particle plating 11 consi of the plating solution 12 surrounding the particles 13, anode (Ni or Cu) 14, cathode 15, filter 16, propeller 17, storage tank 18, pump 19, Luggin 20 capillary, and calomel electrode 21. One second known plating apparatus 31, as shown in Figure 2 (prior art) consists of a plating bath surrounding the particles 33, anode 34, cathode 35, rotary shaft 367, storage tank 38, pump 39, and angle of inclination 40. As you can see, these devices are expensive and inefficient. However the benefits of microencapsulated metal hydride electrodes (Ishikawa and associates J. Less Common Met 120: 123 (1986), was a significant improvement in the performance and duration of metal hydride batteries, which have twice the energy and duration of NiCd cells This encapsulation had two functions: to encapsulate the metal particle Misch (Mm) to prevent premature decomposition during use but allowing the flow through the gas, and provide increased conductivity Sakai and associates Less Common Met 172-174: 1194 (1991) This requires that the encapsulations are porous and have a stable interface The difficulty of developing a cost-effective process to perform the encapsulation was a limiting factor for commercial applications, since there is a need to subsequently make compact or cold sinter the loose powder into a self-supporting flexible mesh or plug. also an apparatus and a method for centrifugal elelectromoldeado of compound powders in mesh and film, which had not been possible. The present invention is an improvement to a rotary flow electro-deposit apparatus comprising a return tray of the electro-deposit solution, comprising a plurality of solution return drains available below the solution return tray. , and a device for switching the position of the return tray of the solution between positions above each of the return drains of the solution. In the preferred embodiment, the enhancement includes a plurality of solution containers, each connected to one or more of the return drains of the solution. The switching device is preferably rotary and the return drains are arranged on an arc pierced by the device. The present invention is also an improvement to an electrodepositive rotary flow apparatus comprising an immersion anode unit, comprising a plurality of solution supply nozzles, and a coupling device for fixing one of the nozzles to give solution to the anode unit with immersion. In the preferred embodiment, the coupling device is rotary. The invention is additionally a rotary flow pass through electro-deposit apparatus comprising: an anode immersion unit, plurality of solution supply nozzles; a coupling device to fix one of the nozzles and give solution to the anode immersion unit, a rotating electrolytic cell in which the anode unit is submerged, a return tray of the electro-deposit solution under the cell rotary electrolytic; a plurality of solution return drains available below the return tray of the solution, and a device for fixing the position of the return tray between several positions above each of the return drains. In the preferred embodiment the coupling device and the fixing or switching device are rotary, preferably the switching device passes through an arc on which the return drains are arranged, and the apparatus includes a plurality of solution containers, each connected to one or more of the return drains of the solution. The present invention further encompasses a method for coating a powder material, comprising: depositing a powder material having a particle size of about 5 to 500 microns in an electrolytic cell having an annular cathode, circulating an electrolytic solution deposit in the cell, immerse an anode in the electro-deposit solution; rotate the cell at a speed sufficient to compact the powder material against the annular cathode, periodically stop or reverse the rotation of the cell to disperse and reorient the powder, and repeat steps d) and e) until the powder is electroplated in a pre-established condition, as desired. The present invention also concerns a method for forming a strip of powder material, comprising depositing a powder material having a particle size of approx. 5 to 500 microns in an electrolytic cell, circulate an electro-deposit solution in the cell, rotate the cell at a sufficient speed to compact the powder material against a solid at the periphery of the cell, dip an anode into the solution of Electro-deposit, and perform the electro-deposit until the powder is joined or electromolded together. In the preferred embodiment, the electro-deposit comprises continuing until the powder material is joined or conformed to a strip (preferably an approximately uniform mesh or film). For a mesh, a filler material (such as fibers, granules, beds, particles, compounds, or wires) can be deposited and then removed after the electro-deposit to increase the porosity of the mesh. The density of the amperage can also be adjusted to alter the porosity of the mesh. The solution and the anode can be changed to form a multilayer composition. To decrease the porosity of a film, powder material can be added to what follows the electro-deposit step and restart the electro-deposit. Preferably the cell is rotated at a sufficient speed to compact the powder material against an annular cathode or a conductive shape against a periphery of the cell. The present invention also seeks to manufacture a powder material coated by the following steps: depositing a powder material having a particle size of about 5 to 500 microns in an electrolytic cell having an annular cathode, circulating an electrolytic solution deposit in the cell, immerse an anode in the electro-deposit solution; rotate the cell at a speed sufficient to compact the powder material against the annular cathode, periodically stop or reverse the rotation of the cell to disperse and reorient the powder, and repeat steps d) and e) until the powder be electroplated to a pre-set condition, desired. The present invention also relates to a structure comprising powder material made in accordance with the steps of depositing a powder material having a particle size of approx. 5 to 500 microns in an electrolytic cell, circulating an electro-deposit solution in the cell, rotating the cell at a speed sufficient to compact the powder material against a solid at the periphery of the cell, immerse an anode in the electrodeposition solution, and perform the electrode - deposited until the powder material is joined or electromolded into a structure. In the preferred embodiment, the electro-deposit is made until the powder is joined or electro-molded into a strip, mesh or film. Filler material (such as fibers, granules, beds, particles, compounds, or wires) can be deposited and then removed after the electro-deposit to increase the porosity of the structure. The density of the amperage can also be adjusted to alter the porosity of the structure. The solution and the anode can be changed to form a multilayer structure composition. To decrease the porosity of a structure, powder material can be added to what follows the electro-deposit step and restart the electro-deposit. Preferably the cell is rotated at a sufficient speed to compact the powder material against an annular cathode or a conductive shape against the periphery of the cell, the structure formed can be a metal powder compound blended in a nickel mesh, platinum-plated powder, composite diamond or other abrasive, an engineered composite film for wear surfaces or bearings, dielectric films, chemically inert and non-dissolvable film composites of radioactive isotope particles, composite films for sensing or fusing devices, Membranes of the sintered type by electromolding, composite strips carrying microencapsulated reactive materials mixed with critical stoichiometry for detonating devices, composite films with projected polymer resins, or highly conductive heating elements. A primary object of the apparatus of the present invention is to allow a multi-step electroplating process without physical transfer of the plating substance and annoying manual exchange of the solutions. A principal object of the methods of the invention is to provide the effective microencapsulation of powdered materials, the mesh formation of such materials, and the electromolding of those materials. A primary advantage of the apparatus of the present invention is that particles of miera size can be microencapsulated. An important advantage of the apparatus of the invention is that the materials can be plated many times faster than with the existing technology.

Another advantage is that in the apparatus of the present invention only the inner side of the cell is wetted by the chemical process and all solutions are changed using high speed rotation for removal. Another advantage is that both anionic and cathodic modes can be used, anodic for electro-cleaning, electro-polishing, anodizing materials, and electrodialysis, cathodic for the electro-deposit. An essential advantage in the methods of the invention is that a wide variety of articles can be made with them, including but not limited to metallic powder compound blended in nickel mesh, platinum plated powder mesh, composite diamond or other abrasive, film composite designed for wear guide surfaces or bearings, dielectric films, chemically insoluble inert film composites of radioactive isotope particles, composite films for sensing or fusing devices, membranes of the type sintered by electromolded reactive raicroencapsulated materials mixed into strips with a stoichiometry critical for detonation devices for weapons, films made of composite alloy with thermoformable cast polymer resins later, and high conductivity heating elements. Other advantages and novel features, as well as greater scope of the applicability of the invention, will be established in the description that follows with the appended claims and drawings, and may also appear to the technicians, and be found by the practice of the invention. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated and form part of the description, illustrate several modalities, and together with the description, serve to explain the principles of the invention. They are seen in the drawings: Figure 1 illustrating a prior art apparatus for microencapsulation of powders; Figure 2 illustrates a second prior art apparatus for microencapsulation of powders; Figure 3 is a sectional view of the preferred apparatus of the invention; Figure 4 is a sectional view of the preferred apparatus of the invention, but the boom and supply nozzles are removed prior to rotation; Figure 5 is a sectional view of the preferred apparatus of the invention, absent the boom and supply nozzles, during rotation; Figure 6 is a perspective view of the preferred apparatus of the invention; The invention relates to an automated centrifugal apparatus and to a method for electrolytically encapsulating loose conductive powder materials with nickel or other electroplated metal and then making a unit of the loose powders within a self-supporting flexible and flexible strip or film by electromolding. under centrifugal force. The rotary flow-through plating cell of the invention provides for the microencapsulation of particles of the size of 5- 500 microns and for example a coating thickness of 1 micron in nickel. The applications in metal hydride batteries require that the tank has a porous surface to allow hydration and dehydration that occurs during the loading / unloading cycles. The present invention employs a high efficiency electrolytic process and observes kinetic trajectories to control the porosity and the coating of the encapsulation. the present invention uses centrifugal force to separate and compact loose fine particles of material that are in a solution, against the contact of an electrolytic cathode. The pulverized material is charged through an upper opening and the plating cell is rotated with sufficient rpm to centrifugally cast or empty the powder against the contact of the cathode. The electrodeposited solution is introduced into the upper opening of the rotating cell and flows through the cell, exiting through a porous ring (eg, a sintered plastic ring) layered between the top of the dome, the cathode contact ring, and a base plate. Electroplating is carried out with a cycle of periodic stop and / or counter rotation and sequential switching of DC supply to the cell to circulate the position of the particles for a uniform coverage and prevent agglomeration (bridge formation). An advantage of the present invention is that pulverized, lightweight fine, micrometric materials with low conductivity (or high resistivity) can electroplate efficiently under centrifugal force. Another advantage is that the process solutions circulate freely through the cell to provide optimum electrolyte conditions, ion concentration, pH, temperature, and purity of the solution, another advantage is the ability of the molecular bonding of the powders to each other , in a conductive electro-deposited network that has superior conductivity and mechanical stability than cold-sintered formations. Considering Figures 3-5, the through-flow rotating veneer apparatus (cell) of the present invention 40, comprises a truncated cone 41, mounted vertically on a rotating shaft 62 capable of high rotational speed that is driven by an engine 66. The cell is operated within a concentric rotating tray 74 which can align a drain port 75 to the motor 60 on multiple return drainages 72 distributed in the radius of the cell, which return the solution 82 to one of the multiple Solution vessels 70. The electro-tank solution 82 is then recirculated to the cell by the circulation pump 68 and the recirculation line 82 (preferably plastic tubing). The drum 41 comprises an open ended dome 56, an annular cathode contact ring 76 (preferably titanium), a porous annular ring 78 (preferably sintered plastic) and a circular base plate 79. The cell also includes a rotary accessory head 45 with multiple nozzles of supply 56 that give solution to the anode 46 (in position for immersion) and 48 (raised for the passage) to allow the steps in sequence of the chemical process to be carried out in the same cell without complicated switching steps of material and equipment during the process. The rotating accessory head 45 moves up and down from the boom 42 by the motor 44. Upon lowering to the operating position 50, the anode acts as a positive terminal 52 for the electrolytic process carried out in the cell in conjunction with the Negative Terminal 64. Escutcheon 80 provides protection to the environment from the fumes of the process and contains process solutions during operations. Optionally, the anode and the cathode can be switched to operate the apparatus in an anodic rather than a cathodic form. Figure 4 illustrates material to be veneered 58 before rotation distribution on the circular base plate 79. Figure 5 shows material 58 during rotation compacting against cathode 76 contact ring. Sequential placement of nozzles, anodes (the anode can be easily removed and commuted to provide the deposit of different metals) and the drainage port offer a method to expose the materials to be plated to a multi-step chemical process without intermixing the different chemical processes. In addition, the continuous immersion of the work that is veneered prevents the oxidation that normally occurs when performing all the steps in the same cell. The chemical solutions are returned in sequence through the porous ring to the proper drainage for a discrete circulation of each chemical solution. Then, when introducing the rinse water during the rapid rotation, the chemical solutions are exchanged with a minimum dilution due to the different specific weights. The following steps are carried out in the same way until the sheeting is deposited. the preferred cell shown in the perspective view of figure 6 has important advantages over the above apparatuses for electroplating. The cells preferably have a stainless steel frame, a seamless thermoformed cell and escutcheon, programmable logic control with screen interface (not shown), an AC inverter for the drive and pumps, precision linear guides, robotic actuators, redundant safety interlockers, total shielding for safety , complete automation or manual control, and a separate control panel (not shown) for the modular configuration of the multiple unit, When using two anodes (soluble or insoluble for two metal tanks (four chemical tank tanks, seven return drains of solution, and three nozzles (although indeed any number of these components is possible) the cell provides up to 16 sequential process steps.The process is enclosed for effective smoke control, has a high volume solution flow for a plating with high speed, and has a large cathode contact area, a cell that has a footprint of 42 x 78 inches (103 cm x 195 cm) has the ability to process approximately 1 liter of material having particle sizes from 5 microns to 5 mm with an efficiency of 100% cathode, provides approximately 5 times more plywood speeds than horizontal barrel appliances due to the high current parameters allowed by the hydrodynamic conditions within the cell and the rotating cathode, and you can use as little as 250ml of rinse solution for each rinse cycle. The preferred process flow for the cell for the encapsulation of discrete particles with nickel plating (as an example) is as follows: Conductive powder charging Rinsing Hot wetting Nickel plating with run and stop cycle Rinsing Hot rinse Vacuum drying The apparatus of the invention can also be used to produce a porous mesh or a solid film of conductive or non-conductive pulverized materials carried out in a high-speed rotating (centrifugal) plating cell. A composite of powder or granular material is measured and placed in the rotating cell. An electrodeposition solution is circulated through the cell and by centrifugal force the loose powder material forms a compact bed covering the inner surface of the annular annulus of the cathode contact. A soluble anode is placed inside the cell and under continuous rotation, the electro-deposit is carried out until the composite powder is bonded or electromolded together in a uniform band.

The particles can be made or agglomerated under a controlled process with predictable results. The resulting strip can be processed further by burning the filler material such as carbon fiber or plastic granules to increase the porosity of the mesh. Using the same process, the non-porous composite films can be electromolded with stratified layer formations of different compositions by introducing additional pulverized materials of various specific weights or establishing a subsequent bed of powder on an electromoded composition and then continuous electro-deposit. The cross-sectional profile and the thickness of the resulting mesh are determined by the amount of loose powder, the size and density of the particles and the coating of the mixed composition. The shape, width and surface finish of the surface of the inner diameter of the contact ring of the cathode will determine the profile and width of the outer surface of the mesh or electromolded film. A composition of several conductive and non-conductive particles is possible by the electro-deposit on subsequent layers of material, the porosity of the metal mesh is determined by the density of amperage used during the electro deposit and by the selection and proportion of a burnable fiber or material in particle, the primary benefit of this method of electroforming is that several components, both condutive and non-conductive, can be mixed and then joined in a mesh or composite film, which is improved by the collective properties of the composition presenting a robust, flexible support or rigid that can be incorporated into many applications. The process flow that is preferred for the electro formation of a wide-band composite film or film, is as follows: Loading of composite powders, particles, or fibers (conductive or nonconductive) Hot treatment rinse Continuous rotation plating Rinse Cold and hot alternating rinse Removal or removal of the mesh or film from the cathode surface; and Burning the fibers for the mesh, or other final operation. The present invention is particularly useful for the following applications: mixing metallic powder composed of a nickel mesh to be used in a metal hydride battery as a negative electrode. Platinum plated powder mesh for use in fuel cells; diamond or abrasive compounds for grinding and cutting tools; film designed for engineering for wear support guide and bearings; dielectric films for capacitance or resistance components of electronics and industrial power; Composed of chemically inert film, not soluble of radioactive isotope particles for industrial and medicinal processes; composite films for sensing and fusing devices; sintered electro-formed membranes and three-dimensional articles; composite mesh films carrying mixed microencapsulated radioactive materials that exhibit a critical stoichiometry for detonation devices; alloy films composed of thermo-formable engineering polymer resins that can be used in injection molding to improve contact or wear surfaces of the molded parts; and high conductivity film or mesh in heating elements. Although the invention has been described in detail with particular reference to the preferred embodiments, other embodiments may achieve the same results. Modifications and alterations are possible without departing from the spirit and scope of the present invention.

Claims (19)

1. REIVINDI CA CI ON 1.- A method for covering powdered material, which comprises the steps of: a) depositing a powder material having a particle size of approximately 5 to 500 microns in an electrolytic cell having a cathode cancel; b) circulating an electro-deposit solution inside the cell; c) immerse an anode in the electrolytic solution; d) rotating the cell at a sufficient speed to compact the powder material against the annular cathode; e) periodically stopping the rotation of the cell or reversing the rotation to disperse and reorient the pulverized material; f) repeat steps d) and e) until the powder material has been electroplated to the desired condition.
2. 2. A method for forming a strip of pulverized material, which comprises the steps of: a) depositing a powder material having a particle size of about 5 to 500 microns in an electrolytic cell; b) circulating an electro-deposit solution inside the cell; c) rotating the cell at a sufficient speed to compact the powder material against the annular cathode; d) immerse an anode in the electrolytic solution; e) electrodeposing until the powder material is joined or electroformed together.
3. 3. - The method according to claim 3 wherein the electro-deposit step comprises the electrodeposite until the powder material is joined or electro-molded together in a strip.
4. 4. The method according to claim 2, wherein the passage of electro deposit comprises the electrodeposite until the powder material is joined or electromolded together in an approximately uniform mesh.
5. 5. The method according to claim 4, comprising the step of adjusting an amperage density to alter the porosity of the mesh.
6. 6. The method according to claim 2 further comprising the step of changing the solution and the anode to form a multilayer composition.
7. 7. The method according to claim 2 wherein the rotation step comprises rotating the cell at a rate sufficient to compact the powder material against an annular cathode against the periphery of the cell.
8. 8. The method according to claim 2, wherein the rotation step comprises rotating the cell at a speed sufficient to compact the powder material against an annular cathode of titanium and against the periphery of the cell.
9. 9. A coated powder material manufactured by the steps of: a) depositing a powder material having a particle size of about 5 to 500 microns in an electrolytic cell having an annular cathode; b) circulating an electro-deposit solution inside the cell; c) immerse an anode in the electrolytic solution; d) rotating the cell at a sufficient speed to compact the powder material against the annular cathode; e) periodically stopping the rotation of the cell or reversing the rotation to disperse and reorient the pulverized material; f) repeat steps d) and e) until the powder material has been electroplated to the desired condition.
10. 10. A structure comprising a powder material made according to the steps of: a) depositing a powder material having a particle size of about 5 to 500 microns in an electrolytic cell; b) circulating an electro-deposit solution inside the cell; c) rotating the cell at a sufficient speed to compact the powder material; d) immerse an anode in the electrolytic solution; e) electrodeposing until the powder material is joined or electroformed together in a structure.
11. 11. A method of coating a powder material comprising the steps of: a) depositing a powder material having a particle size of about 5 to 500 microns in an electrolytic cell having an annular cathode; b) circulating an electro-deposit solution inside the cell; c) immerse an anode in the electrolytic solution; d) rotating the cell at a sufficient speed to compact the powder material against the annular cathode; e) periodically stopping the rotation of the cell or reversing the rotation to disperse and reorient the pulverized material; f) repeat steps d) and e) until the powder material has been electroplated to the desired condition.
12. 12. A method for forming a strip of powder material, comprising the steps of: a) depositing a powder material having a particle size of about 5 to 500 microns in an electrolytic cell; b) circulating an electro-deposit solution inside the cell; c) rotating the cell at a sufficient speed to compact the powder material, against a solid and against the periphery of the cell; d) immersing an anode in the electrodeposite solution; and e) electrodeposing until the powder is joined or electroformed together.
13. 13. The method according to claim 12, wherein the passage of electro deposit comprises electrodepositing until the powder material is joined or electroform in a strip.
14. 14. The method according to claim 12, wherein the electrode pitch step comprises electrodeposing until the powder material is joined or electroformed together in an approximately uniform mesh.
15. 15. The method according to claim 14 further comprising the step of adjusting the density of 1 amperage to alter the porosity of the mesh.
16. 16. The method according to claim 12, further comprising the step of changing the solution and the anode to form a multilayer composition.
17. 17. The method according to claim 12, wherein the step of rotating comprises rotating the cell at a speed sufficient to compact the powder material against an annular cathode against a periphery of the cell.
18. 18. A coated powder material manufactured by the steps of: a) depositing a powder material having a particle size of about 5 to 500 microns in an electrolytic cell having an annular cathode; b) circulating an electro-deposit solution inside the cell; c) immerse an anode in the electrolytic solution; d) rotating the cell at a sufficient speed to compact the powder material against the annular cathode; e) periodically stopping the rotation of the cell or reversing the rotation to disperse and reorient the pulverized material; f) repeat steps d) and e) until the powder material has been electroplated to the desired condition.
19. 19. A structure comprising powdered or powdered material manufactured by the steps of: a) depositing a powder material having a particle size of about 5 to 500 microns in an electrolytic cell; b) circulating an electro-deposit solution inside the cell; c) rotating the cell at a sufficient speed to make the powder compact, d) immersing an anode in the solution of the electrodeposite; and e) electrodeposing until the powder material is joined or electroformed together in a structure. R E S U M E N A method and apparatus for microencapsulating or coating powdered or powdered material comprising using a rotary pass through device (40) to alternately compact and electroplate the powder and reorient it before another compacting action. The invention also provides a method and apparatus (40) for forming a strip, mesh or film of the powder material, which is particularly useful for forming metal powder compound blended in a nickel mesh for use in metal hydride batteries.