Patent Publication Number: US-2003236322-A1

Title: Method and additive for dry coalescing and kneading powders, for the exfoliation thereof

Description:
BACKGROUND OF THE INVENTION  
       [0001] The present invention relates to a method for dry coalescing and kneading powders, for performing exfoliation thereof.  
       [0002] As is known, a very important problem occurring in several industrial fields is that of handling, processing and using powder products which, frequently, generate fumes, with consequent environmental polluting problems.  
       [0003] A drawback associated with prior powder handling methods is that the great volatility of said powders, when they are very fine, generates great processing problems.  
       [0004] This drawback, in a lot of cases, makes the use of said powders practically impossible.  
       [0005] Thus, it is not possible to make, by using said prior diffused powder processing methods, all the desired articles of manufacture.  
       SUMMARY OF THE INVENTION  
       [0006] Accordingly, the aim of the present invention is to overcome the above disclosed drawbacks, by providing a method for dry coalescing and kneading powders, for their exfoliation, which is adapted to coat said powders, with a microfibrous coating aggregating the powder particles thereby providing a material which can be easily exfoliated or reduced to a sheet form.  
       [0007] Within the scope of the above mentioned aim, a main object of the present invention is to provide such a processing method and additive which, as applied to powder materials, allow to improve said powder handling and to prevent said powders from polluting the encompassing environment, thereby a broad range of articles of manufacture can be easily produced.  
       [0008] Yet another object of the present invention is to provide such a lubricating additive providing the powder materials contacted thereby with very good sliding properties, thereby facilitating the processing of said powder materials, for example the molding and extruding thereof. 
     
    
    
     [0009] According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by a method for dry coalescing and kneading powder materials, for the exfoliation thereof, characterized in that said method comprises the steps of providing an aqueous polytetrafluoro-ethylene suspension or emulsion, stirring said emulsion to flocculate said emulsion, fully drying said emulsion and dispersing a concentrated material obtained therefrom through the powder materials to be processed.  
     [0010] Further characteristics and advantages of the present invention will become more apparent hereinafter from the following detailed disclosure of a method for dry coalescing and kneading powder materials, for the exfoliation thereof, which method generally comprises the step of starting from a commercial aqueous polytetrafluoro-ethylene (—(CF 2  CF 2 )N — ) suspension or emulsion.  
     [0011] Generally, the powder materials to be processed have a particle size range from 1 micron to 3 mm.  
     [0012] In particular, the polymer is water diluted to an amount depending on the aggregate and absorbing characteristics of the powder the polymer is applied to.  
     [0013] To provide an optimum flocculation of the polytetrafluoro-ethylene material into the aqueous suspension or emulsion, it is rotatively stirred with a very high stirring force, for example up to 2500 rpm&#39;s, the end of the flocculation treatment being indicated by the filtrate material clearness.  
     [0014] Upon filtering, said emulsion is fully dried, and the concentrate material obtained therefrom is dispersed into the powder materials to be processed.  
     [0015] It should be apparent that the polymer amount should be selected depending on the cohesion properties to be imparted to the processed powder materials.  
     [0016] In particular, said polymer amount will advantageously range from a minimum value of 0.2% to a maximum value of 30%.  
     [0017] Then the powder dispersed concentrate material is subjected to a kneading step, according to conventional kneading methods, and it can be successively exfoliated or reduced into a sheet form by lamination.  
     [0018] The thus obtained material can be used in a very broad range of applications, for example, for mixing resins with “gamma-absorbing” metals, for radiologic screen applications, packaging applications and for forming outer packaging materials.  
     [0019] Moreover, said material can also be used for providing inner coatings for cars, for antimagnetically screening electronic apparatus, for making in synthetic marble and concrete materials, “cavity walls”, roofing undertile materials, superlight bricks, light false ceilings and so on, agglomerating fine powder chemical products and very fine powder chemical products (SiO 2 , P.T.F.E. for dyes and pigment materials and so on), compound masterbatch pastes, plastics material agglomerates and PVC, inks, paints, rubbers in the cosmetic and pharmaceutical industries, and in the galvanic field and pharmaceutical and food fields.  
     [0020] Furthermore, said material can be also used for processing silica, pigments and dyes, anti-flame materials, lubricating additives, zinc borate, molybdenum, disulphide, graphite, micronized sodium benzoate, powder hard rubber, micronized polyethylene, micronized PVC, powder iron or carbon, micronized waxes, talc, titanium dioxide, aluminium silicate, metal powders, such as aluminium, bronze, copper, gold and the like, pharmaceutical intermediate products and toner products.  
     [0021] Another possible application is in the furniture industry, for making foamed panels, directly printed upon half-finished products, synthetic marbles articles, washbasin parts and so on.  
     [0022] In this connection it should be pointed out that the above mentioned products would be very safe from a polluting standpoint, thereby they can be used for disposing of ash materials, for example embedding them therein.  
     [0023] From the above discussion, it should be apparent that the application fields of the invention can be very different.  
     [0024] For example, as a novel application thereof, the invention can be used for making micronized silica, for paints, polyester resins, rubber and elastomeric material adhesives, plastics materials, PVC, paper materials, cables, cosmetic and food products, tooth pastes and RTV and HTV compounds  
     [0025] In particular, the use of the invention in this field allows to eliminate silica powders which would be susceptible to pollute the environment, as well as provide savings in storing said materials, packaging and shipping them, and improving the environmental conditions.  
     [0026] Moreover, the above mentioned products allow to improve machining and processing properties, because of the lubrication power provided by the inventive additive, thereby allowing to use shorter processing cycles and greater processing speeds, with a less power and a better efficiency.  
     [0027] Another particular application field is in preparing of composite materials since the inventive products allow to make batches of different additives, in powder form, to be intimately mixed and dispersed in other media, such as resins, solvents, plastics materials and the like, without handling polluting, dangerous and large volume powders.  
     [0028] That same method and products, moreover, allow to greatly reduce the storing, shipping and any other costs related to raw materials for making a desired formulation.  
     [0029] For preparing pigment masterbatches and coloring and additive materials, it is possible to provide large dosages of the active portion, since the inventive additive can agglomerate and remove air entrapped in granulated and other raw materials.  
     [0030] Moreover, for processing pigments and dyes, the subject product can be added with different doses, to advantageously provide not powdery agglomerate, paste and other composite materials.  
     [0031] Furthermore, in processing sintering powders such as polyethylene, polypropylene, polyamide, PVC and the like, it is possible to provide article of manufactures devoid of elastic memory and tension properties, which, accordingly, can be easily patterned and molded.  
     [0032] It is also possible to make rigid foamed cellular constructions, by including foaming agents.  
     [0033] Moreover, it is also possible to make reinforcement screen, gauze or fiber materials, of multilayered construction with decorated glossy outer sheet elements.  
     [0034] In processing curing powders such as concrete, gypsum, lime oxide materials and the like, said powders can be patterned before soaking them to provide thin configurations.  
     [0035] Said powders, furthermore, can be further subjected to embossing and the like processing operations.  
     [0036] A main feature of the subject kneaded material is the possibility of die-cutting the made sheet elements made thereby to provide alveolar constructions of small density.  
     [0037] The inclusion of the aqueous curing material would be controlled by the reaction stechiometry, and these article of manufactures can also contain foaming agents.  
     [0038] In processing hydrosensible powder materials, such as titanium hexafluoride or polysaccharides, it is also possible to provide a dry treatment and forming, and this without any problems.  
     [0039] Yet another use example of the novel technology according to the invention is its application for making, by a novel type of method, different article series, such as washbasins, objects and the like, of synthetic marble materials.  
     [0040] In such a method, after having made a die or matrix according to the above disclosed process, and properly selected the mineral materials, the subject product allows to properly compact said materials by using a resin: in this connection it should be pointed out that the different densities and specific weights of the used mineral materials would prevent any suspension and layering phenomena from occurring.  
     [0041] Thus, said articles of manufacture will be characterized by an evenly distributed construction.  
     [0042] In this novel methods it is possible to use quartz and natural stone materials having of different thicknesses and weights, while holding the resin/mineral material ratio within a greatly improved range, thereby providing products of very good aesthetic characteristics.  
     [0043] A further important advantage is that it is possible to make finished products having all the above disclosed characteristics, and this by using a simple casting process, i.e. very low cost molds, and without the need of performing complex processing or handling operations of mineral materials.  
     [0044] Yet another application of the invention is in making filler materials for high density polyethylene or polypropylene polymers.  
     [0045] In this connection, it is to be pointed out that, at present, polypropylene is filled with wood materials, by using the Solvay technique or the so-called “Woodstock” method.  
     [0046] In particular the invention allows to include said filler materials up to a maximum rate of 70 parts per 100 parts of high density polyethylene, for making, for example, filled polyethylene panels and the like.  
     [0047] The invention, moreover, can also be used for making foamed cellular reinforced concrete materials, by using a processing autoclave, and starting from a silica sand base and powder CaO and aluminium.  
     [0048] A panel of 10 cm of thickness, in particular, would have a unit weight for unit surface less than 80 Kg/m 2 , and a sound damping power of R(dV)=40, as well as a low thermal transmittance.  
     [0049] In making outer plasters, the optimum particle size distribution of the aggregates would facilitate to embed air therein, without problems.  
     [0050] In an exemplary composition, a base  270 , a sand  1000  and a concrete material  350  are used with the addition of a film forming adhesive material.  
     [0051] In forming tile elements for false ceilings, a laminated plaster or gypsum material, in thin thicknesses (2-3 mm), to be in situ curved and cured would be, on the other hand, used.  
     [0052] Such a composition would present a base  100  and a plaster or gypsum material  400  and could be mass colored and reinforced by reinforcement metal gauzes or microfibers, with optional embossing operations.  
     [0053] For coating walls, it would be possible to prepare a CaO based formulation with colored pigments and mineral small stones, to be applied and sprayed with water.  
     [0054] Such a mixture would include a base  100 , minerals  200  and CaO  100 , and it could be used for making wall coatings by coupling it with electrically conductive sheet elements made of graphite, or special carbon black materials.  
     [0055] For making corrugated sheet elements for roofs, the most suitable polymeric material would be a high density polyethylene powder, to be kneaded with a sand material according to the invention.  
     [0056] In such an application, a foil material on a tubular grid would be processed in an IR oven, to provide therein a continuous cross corrugated pattern.  
     [0057] In such a case, a sand  300  and a high density polyehtylene polymer  100  would be used.  
     [0058] In particular, foamed polypropylene panels, having a density from 0.2 to 0.3 g/cm 3 , could replace conventional wood chip panels in furniture, automobilistic and railway fields.  
     [0059] In such an application, sintering, foaming and molding processes would be simultaneously carried out, with the advantage of providing small cost, increased stiffness, easily made products of small thermal conductivity.  
     [0060] In making special filters, a vegetable carbon material can be easily kneaded and exfoliated to form, for example, capsules for absorbing noxious gases and photovoltaic and fuel cell applications for advanced batteries including salt materials, such as titanium hexafluoride, stiffened by thermoplastic powders and coupled to a carbon electrode.  
     [0061] Modern batteries, in particular, could have their bipolar plate elements and electrodes made by the same technology.  
     [0062] From the above disclosure it should be apparent that the invention fully achieves the intended aim and objects.  
     [0063] In particular, the invention provides a method for dry coalescing and kneading powder materials, for the exfoliation thereof, allowing to optimize all the operating steps, and to obtain end results which could not be obtained by prior methods.  
     [0064] The invention, as disclosed, is susceptible to several modifications and variations, all coming within the scope of the invention.  
     [0065] Moreover, all the constructional details can be replaced by other technically equivalent elements.  
     [0066] In practicing the invention, the used materials, provided that they are compatible to the intended application, as well as the contingent size and shapes, can be any, depending on requirements.