The present invention relates to a method for dry coalescing
and kneading powders, for performing exfoliation thereof.
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.
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.
This drawback, in a lot of cases, makes the use of said
powders practically impossible.
Thus, it is not possible to make, by using said prior diffused
powder processing methods, all the desired articles of manufacture.
The document EP-A-0 770 659 discloses "the mechanical stability
of aqueous PTFE emulsion(s)" (page 1, lines 17-21) does not disclose or suggest
to disperse such a PTFE material through powders.
The document US-A-3 551 205 discloses the simultaneous
coagulation and precipitation of a PTFE aqueous emulsion by vigorous mechanical
agitation and thus forming a binder for a mixtures of fibers and conducting material
(column 4, lines 14-22).
Though this latter document teaches substeps of the characterizing
step of the present method, it is not quite clear if "dried flocculated polytetrafluoroethylene"
is explicitly disclosed by this document. "Precipitation and coagulation of polytetrafluoroethylene
in the slurry can be facilitated by addition of acetone to the aqueous slurry during
the mechanical agitation. When the slurry is cast to form a web, polytetrafluoroethylene
extends throughout the web binding the carbon particles with fibers. Ounce dried,
the polytetrafluoroethylene is resistant to most organic solvents and is an insoluble
component suitable for use in many organic and aqueous electrolyte systems" (column
4, lines 19-28). In any case, this document does not disclose or suggest the steps
of present claim 1, let alone in combination with subsequent steps thereof.
SUMMARY OF THE INVENTION
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.
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.
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.
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, according to the main claim.
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 (-(CF2 CF2)N-) suspension
Generally, the powder materials to be processed have a
particle size range from 1 micron to 3 mm.
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.
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's, the end of the flocculation
treatment being indicated by the filtrate material clearness.
Upon filtering, said emulsion is fully dried, and the concentrate
material obtained therefrom is dispersed into the powder materials to be processed.
It should be apparent that the polymer amount should be
selected depending on the cohesion properties to be imparted to the processed powder
In particular, said polymer amount will advantageously
range from a minimum value of 0.2% to a maximum value of 30%.
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.
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
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 (SiO2, 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.
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.
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.
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.
From the above discussion, it should be apparent that the
application fields of the invention can be very different.
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
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.
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.
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.
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.
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.
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.
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.
It is also possible to make rigid foamed cellular constructions,
by including foaming agents.
Moreover, it is also possible to make reinforcement screen,
gauze or fiber materials, of multilayered construction with decorated glossy outer
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.
Said powders, furthermore, can be further subjected to
embossing and the like processing operations.
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.
The inclusion of the aqueous curing material would be controlled
by the reaction stechiometry, and these article of manufactures can also contain
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.
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.
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
Thus, said articles of manufacture will be characterized
by an evenly distributed construction.
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.
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.
Yet another application of the invention is in making filler
materials for high density polyethylene or polypropylene polymers.
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.
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.
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.
A panel of 10 cm of thickness, in particular, would have
a unit weight for unit surface less than 80 Kg/m2, and a sound damping
power of R(dV)= 40, as well as a low thermal transmittance.
In making outer plasters, the optimum particle size distribution
of the aggregates would facilitate to embed air therein, without problems.
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.
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.
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.
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.
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.
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.
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
In such a case, a sand 300 and a high density polyehtylene
polymer 100 would be used.
In particular, foamed polypropylene panels, having a density
from 0.2 to 0.3 g/cm3, could replace conventional wood chip panels in
furniture, automobilistic and railway fields.
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.
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.
Modern batteries, in particular, could have their bipolar
plate elements and electrodes made by the same technology.
From the above disclosure it should be apparent that the
invention fully achieves the intended aim and objects.
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.
The invention, as disclosed, is susceptible to several
modifications and variations, all coming within the scope of the invention.
Moreover, all the constructional details can be replaced
by other technically equivalent elements.
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.