Note: Descriptions are shown in the official language in which they were submitted.
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~'aFl~~~'~~'~SES ~w~~ I~IEI'~~~S F~~' ELE~'~' '~'~S'fi'~'aTI~~~L~
Pl~~~ESSII~~ ~~L.~i~~E~ F~~I~IUL~TI~~S
~a~~~r~un~
Electrostatic processing techniques use electrostatic force to draw a
charged polymer formulation from a source to a collector. The electrostatic
field acts to accelerate the liquid from the source to the collector, on which
the electrostatically processed material is collected.
Summary
Apparatuses and methods for electrostatically processing polymer
formulations are provided. The apparatuses and methods can provide
continuous production of electrostatically processed materials.
A preferred embodiment of an apparatus for electrostatically
processing a polymer formulation comprises a feeding stage operable to
continuously eject electrostatically processed material comprising a polymer
formulation; a collection stage spaced from the feeding stage; a power
supply operable to generate an electric field, which causes the
electrostatically processed material ejected from the feeding stage to deposit
on the collection stage; and a pick-up stage including a removing device
disposed to continuously remove the electrostatically processed material
from the collection stage.
Polymer formulations that can be electrostafiically processed using
preferred embodiments of the apparatuses and methods include polymer
solutions, dispersions, suspensions, emulsions, mia~tures thereof, and
polymer melts. The electrostatically processed material can have various
forms, including fibers, droplets, beads, films, dry porous films, webs, mats
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and/or combinations thereof. The electrostatically processed material
preferably has at least one micro-scale or nano-scale dimension.
Another preferred embodiment of the apparatus comprises a
treatment stage, which is operable to treat the electrostatically processed
material at the collection stage and/or after being removed from the
collection stage. For example, the material can be heated, cured, rolled, cut,
sfiretched, and/or treated to change its surface chemical structure. The
treatment stage can also be operated fio apply one or more substances to
the electrostatically processed material.
Another preferred embodiment of the apparatus comprises at least
one thickness sensor and/or slack sensor for detecting the thickness of,
and/or the amount of slack in, the electrostatically processed material. The
apparatus can include a controller, which is operable to receive signals from
the sensors) and adjust the collection stage and/or pick-up stage, as
appropriate, to maintain a desired thickness and/or amount of slack.
A preferred embodiment of a method for electrostatically processing a
polymer formulation comprises generating an electric field; supplying a
polymer formulation to a feeding stage; continuously ejecting
electrostatically
processed material from the feeding stage through the electric field;
collecting the electrostatically processed material at a collection stage; and
continuously removing the electrostatically processed material from the
collection stage.
Brief Description of the Drawings
Figure 1 illustrates a preferred embodiment of an apparatus for
~5 electrostatic processing.
Figure ~ illustrates a preferred embodiment of a feeding device of fihe
apparatus, which includes multiple nozzles.
Figure 3 illustrates another preferred embodiment of the feeding
device, which includes dual flow passages and multiple nozzles.
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Figure 4 illustrates a preferred embodiment of the feeding device
including a brush.
Figure 5 illustrates another preferred embodiment of the feeding
device including a brush construction.
Figure 6 illustrates another preferred embodiment of the feeding
device, which includes nozzles and nobble cleaning structure.
Figure ~ illusfirafies a preferred embodiment of the apparatus including
a collection stage, a post-collection stage and sensors for monitoring the
electrostatically processed material.
Figure 8 illustrates a preferred embodiment of the apparatus, which
includes a post-collection treatment stage.
Figure 9 illustrates another preferred embodiment of the apparatus
including a rolling stand.
Figure 10 illustrates another preferred embodiment of the apparatus
including a release sheet application roll.
Figure 11 illustrates a preferred embodiment of the apparatus
including the feeding device shown in Figure 5.
Figure 12 illustrates a preferred embodiment of the apparatus
including the feeding device shown in Figure 6.
Figure 13 illustrates another preferred embodiment of the apparatus
including a target, which rotates in a liquid.
Figure 14 illustrates another preferred embodiment of the apparatus
including a funnel-shaped target.
~etaited ~e~o~i~r~i~n
Preferred embodiments of apparatuses and methods for
electrostatically processing polymer formulations can provide continuous
production of electrostatically processed materials. The electrostatically
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processed materials can be in various forms, including, but not limited to,
fibers, droplets, beads, films, dry porous films, webs, mats and/or
combinations thereof.
The electrostatically processed materials can be micro-scale or nano-
scale materials. As used herein, the terms "micro-scale" and "nano-scale"
denote materials that have at least one micro-scale dimension, or at least
one nano-scale dimension, respectively. The dimension can be, for
example, a diameter, maximum transverse dimension, length, width and/or
height. The electrostatically processed materials also can have
compositions, structures and properties that can be varied by the selection of
starting materials and/or processing conditions.
As used herein, the term "electrostatic processing" denotes
electrostatic spinning (electrospinning) and electrostatic spraying
(electrospraying) techniques. Electrospinning produces fibers, and
electrospraying produces droplets or clusters of droplets. Such fibers
continuously collect on the collection stage, while the droplets or droplet
clusters collect in individual droplets on the collection stage.
An electrostatically processed material can be formed by
electrospinning or electrospraying a polymer formulation by manipulating
components of the polymer system and/or changing various process
parameters, such as applied voltage, distance from the feeding stage to the
collection stage, volumetric flow rate, and the like. In addition, whether a
polymer formulation electrospins or electrosprays can be controlled by
changing physical characteristics of the polymer formulation, such as
changes in concentration, solvent selection, polymer molecular weight,
polymer branching, and the lilee.
A preferred embodiment of an apparatus 20 for electrostatically
processing polymer formulations is depicted in Figure 1. The apparatus 20
comprises a feeding stage 30 and a collection stage 40. The apparatus 20
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prefierably also includes a pick-up stage, as described below. The apparatus
20 can optionally also include a post-collection treatment stage, as also
described below.
The feeding stage 30 is operable to continuously elect a polymer
formulation 45, which is electrostatically processed. ~4s described below, the
feeding stage 30 can comprise one feeding device, or alternatively multiple
feeding devices. The electrostatically processed material ~2 is deposited on,
and preferably continuously removed from, the collection stage 40. The
polymer formulation can be a polymer solution, dispersion, suspension,
emulsion, mixtures thereof, or a polymer melt. The polymer formulation can
comprise one-phase or two-phase systems. Exemplary polymer
formulations include, but are not limited to, cellulose acetate, poly(ethylene-
co-vinylacetate), poly(lactic acid), and blends thereof, poly(acrylonitrile),
polyaniline-sulfonated styrene, polyaniline, polyester,
poly(ethyleneterephthalate), poly(propylene), polyethylene) and blends
thereof. Exemplary suitable solvents for the polymer formulation include, but
are not limited to, water for aqueous solvent-based polymer formulations,
and organic solvents, such as acetone and alcohols, for organic solvent-
based polymer formulations.
Polymer melts can be prepared by techniques known to those skilled
in the art and electrostatically processed. Preparation techniques may
include premixing and melting the components of the polymer, such as by
melt mixing in a heated extrusion apparatus. Electrostatic processing
techniques are described, for example, in Larrondo, L. and S. John Manley,
J "Electrostatic Fiber Spinning from Polymer li/lelts, I. Experimental
~bservations on Fiber Formation and Properties," Journal of Polymer
Science, Polymer Physics Ed., vol. 19, (1931 ) 909-920, the contents of
which are incorporated herein by refierence in their entirety.
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In the embodiment, the feeding sfiage 30 is electrically connecfied to a
power supply 50, which applies a volfiage fio the feeding stage. The power
supply 50 can be eifiher D~ or an A~ power supply. In fihe embodiment, the
collecfiion stage 40 is at ground potential. Dy applying a sufficiently high
voltage to the feeding stage 30, with the collection stage 40 afi ground
potenfiial, an electric field can be generated in the space between the
feeding sfiage and collection stage. The feeding stage 30 and collection
stage 40 are sufficiently close togefiher to produce an electric field
strength
that is sufficient to initiate the electrostatic processing of the polymer
formulation. The feeding stage 30 is operable to introduce the polymer
formulation 45 into the electric field. The electric field produces an
electrostatic force, which draws the polymer formulation through the space
from the feeding stage 30 to the collection stage 40, where the polymer
formulation deposits to form fibers, droplets, and/or structures comprising
fibers and/or droplets, especially when a transition from electrospraying to
electrospinning occurs during processing of a polymer formulation.
Depending on the polymer formulation, the electrospraying to
electrospinning transition may occur or not occur as the concentration of the
polymer in the polymer formulation is increased.
A preferred embodiment of the feeding stage 30 is depicted in Figure
2. The feeding stage 30 comprises a feeding device 130 including a flow
passage 132 in fluid communication with a manifold 134. The manifold 134
can include a single nozzle, or preferably a plurality of nozzles 136, as
shown. The nozzles 136 can be arranged parallel to each other as depicted,
or alternatively can have other desired orientations. The nozzles 136 can be
positioned in a horizonfial plane as depicted, or alternatively can be
posifiioned at different angles relative to the horizontal to change the
direcfiion of impingemenfi of fihe elecfirostafiically processed material on
the
collection stage 40.
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The number of nozzles 136 in the manifold 134 can be chosen based
on different factors, such as the desired throughput of fibers from the
feeding
device 130, or the size of the collection surFace(s) of the collection siege
on
which the polymer is deposited. The number of nozzles 136 in the manifold
134 and/or the number of manifolds 134 including nozzles 136 can be
increased in the apparatus to increase throughput of electrostatically
processed material.
In addition, the size of the nozzle 136 openings of the manifold 134
can be the same as each other, or two or more nozzles can have different
sized openings. The nozzles 136 can have a suitable nozzle opening size
and length to produce a jet or spray of the polymer formulation with desired
characteristics.
The polymer formulation is supplied to the flow passage 132 of the
feeding device 130 from a source 138 in fluid communication with the flow
passage 132. The source 138 preferably has a sufficiently large capacity of
the polymer formulation to allow for the continuous production of a desired
amount of electrostatically processed material by operation of the apparatus.
The feeding stage 30 preferably comprises at least one pump 137
between the source 138 and flow passage 132. The pump 137 is operable
to supply the polymer formulation to the manifold 134, preferably at a
controlled rate, to thereby control the ejection rate of the polymer
formulation
from the nozzles) 136. The pump 137 can be used to supply a single
manifold, or alternatively two or more manifolds.
In another preferred embodiment, the polymer formulation can be fed
through the one or more nozzles 136 of the manifold 134 using various
alternative feeding techniques including, for eacample, gravity, compressed
air, piston motion, or the like.
Figure 3 depicts a feeding device 230 according to another preferred
embodiment. The feeding device 230 includes a first flow path 233 in fluid
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communication with a first source 238 of a polymer formulation, a solvent, at
least one optional active component, or a mixture of a solvent and at least
one optional active component, and a second flow path 235 in fluid
communication with a second source 239 of a polymer formulation, a
solvent, at leasfi one optional active component, or a mixture of a solvenfi
and
at least one optional active component. The first and second polymer
formulations can be the same or different formulations. The active
component can be, for example, at least one cross-linking agent,
photoinitiator, thermal initiator, or the like.
The first flow path 233 and second flow path 235 are in fluid
communication with the flow passage 232. The feeding device 230 is
operable to produce electrostatically processed materials from a single
polymer formulation or from two-component polymer formulations.
Particularly, the same or different polymer formulation can be introduced via
the first flow path 233 and second flow path 235 into the flow passage 232,
where the polymer formulations are combined together to form a mixed
polymer formulation, which is ejected from the nozzles 236. Alternatively, a
polymer formulation can be supplied from the first source 238 or second
source 239, and a solvent or active component supplied from the other of the
first source 238 or second source 239, to change the polymer formulation
composition to affect the composition and/or processing characteristics of
the polymer formulation.
In the embodiment, the feeding device 230 preferably comprises a
first pump 237 and a first valve 241 between the first source 238 and the
flow passage 232, and a second pump 240 and a second valve 243 between
the second source 239 and the flow passage 232, to supply the contents of
the first source 238 and second source 239 to the manifold 234, preferably
at controlled flow rates, to thereby control the ejection rate of the polymer
formulation from the one or more nozzles 236 of the feeding device 230.
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_g_
The solvent alone can be flowed to the manifold 234 from the first
source 233 or second source 23g to clean the nodes, as desired.
In a preferred embodiment, an in-line mi~zer 244 can be provided
along the flow passage 232 to promote mixing of the polymer formulation
prior to being ejected from the nobbles 236.
Figure 4 depicts a feeding device 330 according to another preferred
embodiment. The feeding device 330 includes an open container 332,
which contains a polymer formulation, and a brush 340. The feeding device
330 also includes a polymer formulation supply system 344, such as shown
in Figure 3, to replenish the polymer formulation in the container 332 as it
is
consumed during electrostatic processing.
The brush 340 includes a plurality of bristles 342 made of an
electrically conductive material, such as a metal or metal alloy. The brush
340 can be connected to a suitable drive source 345, such as a variable
speed motor, which is operable to rotate the brush 340 at a desired speed
as indicated by arrow A. A power supply 346 can be electrically connected to
the brush 340, such as to the axis 347. The power supply 346 can be either
a DC or an AC power supply. During rotation of the brush 340, the bristles
342 contact, and are wetted by, the polymer formulation in the container 332,
ejecting the polymer formulation 45 into the electric field.
Figure 5 illustrates a feeding device 430 according to another
preferred embodiment. The feeding device 430 includes an alternative
brush 440, and a container 432 containing the polymer formulation 45. The
brush 440 includes a body 442 and bristle-lilts extensions 444 extending
outward from the body 442. The brush 440 is made of an electrically
conductive metal or mefial alloy. During rotation of the brush 440 as
represented by arrow D, the extensions 444 contact, and are wetted by, the
polymer formulation 45 in the container 432, causing the polymer formulation
45 to be ejected into the electric field and drawn toward the collection
stage.
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A feeding device 530 according to another preferred embodiment is
depicted in Figure 6. The feeding device 530 includes a polymer formulation
flow passage 560, a cleaning liquid flow passage 570, and a plurality of
nozzles 581-588 extending outwardly from the surface 552. The number of
nozzles of the feeding device 530 can be varied to produce a desired
ejection pattern and throughput of the polymer formulation. A polymer
formulation is supplied to the polymer formulation flow passage 560 from a
source of the polymer formulation. A cleaning liquid is supplied to the
cleaning liquid flow passage 570 from a source of the cleaning liquid.
The feeding device 530 is rotatable as represented by arrow C, such
that the nozzles 581-588 in succession come into fluid communication with
the polymer formulation flow passage 560 containing the polymer
formulation. As shown, when the feeding device 530 is at a particular
angular orientation, a nozzle, such as nozzle 581, is in fluid communication
with the polymer formulation flow passage 560, such that the polymer
formulation can be ejected from this nozzle.
The feeding device 530 includes a stationary mask 590 having an
opening 591. The mask 590 is provided to cover the inlet end of the nozzles
581-588 as they rotate over the mask 590. In the illustrated position of the
feeding device 530, the mask 590 covers the inlets of the nozzles 582-588,
preventing the flow of the cleaning liquid into these nozzles. The opening
591 supplies cleaning liquid to a nozzle as it rotates over the location of
the
opening 591. The cleaning liquid can flow into nozzle 585 in communication
with the opening 591 in the mask 590 in the illustrated position of the
feeding
device 530. Thus, cleaning liquid can be sequentially supplied to the
nozzles 581-588 as they rotate in this order over the mask 590.
The cleaning liquid can be any suitable liquid that is effective to
remove polymer material fihat may deposit in the flow passages of the
nozzles 581-588 during operation of the feeding device 530. For example,
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the cleaning liquid can be water for water-based polymer formulations, or
scat~nes, alcohols, or other organic solvents for solvent-based polymer
formulations. The cleaning liquid is preferably flowed Through the nozzles
531-533 at a high pressure to enhance removal of deposited polymer
material from the flow passages of the nozzles. Accordingly, the nozzles
531-533 can be cleaned during operation of the feeding device 530 to
achieve more consistent and uniform election of the polymer formulation
from the nozzles.
The feeding stage 30 can include one or more feeding devices, such
as the feeding devices 130, 230, 330, 430 and 530 described above, to
enable the production of electrostatically processed material structures, such
as mats or webs, composed of different polymeric materials, or to produce
structures having different compositional andlor density characteristics. The
relative spatial locations of the different feeding devices of the feeding
stage
30 can be chosen relative to each other and to the collection stage 40 to
produce fibrous structures having different densities, morphologies, or other
characteristics.
The electric field can be generated between the feeding stage 30 and
collection stage 40 according to various preferred arrangements. For
example, the polymer formulation feeding device can include an electrically
conductive portion electrically connected to a pole of a power supply. The
electrically conductive portion can be, for example, the manifolds 134 (Figure
2) and 234 (Figure 3) of the feeding devices 130 and 230, respectively, or
the brushes 340 (Figure 4) and 440 (Figure 5) of the feeding devices 330
and 430, respectively. f~lternatively, the polymer formulation can be charged
by placing an electrode in the polymer formulation flow passage 560 of the
feeding device 530.
However, it will be understood by those skilled in the art that the
collection stage 40 can alternatively be charged, with the feeding stage 30
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being grounded, in order to generate the electric field between fibs feeding
stage and fhe collection stage.
A preferred embodiment of the apparatus 100 is shown in Figure 7.
The apparatus 100 includes a feeding device, such as the feeding device
230 described above, a collection stage 40, and a post-collection stage 60
downstream from the collection stage 40. As shown, the polymer
formulation 45 is ejected from the feeding device 230 onto a target 70 of fibs
collection stage 40, electrostatically processed material 72 is formed on the
outer surface 74 of the target 70, and the electrostatically processed
material
is collected at the pick-up stage 60.
The target 70 includes a body 76, which can have various shapes and
sizes. As depicted, the body 76 can be cylindrical roll having a cylindrical
outer surface 74. Alternatively, the outer surface 74 of the body 76 can have
other shapes, such as oval or the like. The outer surface 74 can include one
or more flat portions and/or contoured portions (e.g., including
protuberances, as well as depressions, grooves, channels, or the like). The
shape and/or surface configuration of the outer surface 74 can be selected
based on factors, such as the desired shape of the deposited polymer
material.
The body 76 of the target 70 can be solid, or alternatively can be
hollow to reduce the weight of the target 70. The body 76 can comprise a
suitable electrically conductive material, such as aluminum, aluminum alloys,
or like metals. The target 70 can be made entirely of the electrically
conductive material, or alternatively can include an outer portion, such as an
electrically conductive coating, formed over the body 76 and including the
outer surface 74.
Anofiher preferred embodiment of the target 70 can be made of a non-
conductive material. In such embodiment, the target 70 is positioned
sufficiently close to a member made of a conductive material and connected
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to a pole of a power supply, which can be either a DC or an A~ power
supply, or alternatively grounded with voltage applied to the feeding stage,
in
order to generate the electric field. The polymer formulation is elected from
the feeding stage 30, drawn toward the conductive member and deposited
on the target 70.
The apparatus 100 can include one feeding stage and one target 70,
or alternatively can include one or more feeding stages and two or more
targets. By incorporating more than one target, the apparatus 100 can
produce different electrostatically processed material structures, having the
same or different polymeric compositions and/or structures, on the different
targets. The different structures can be produced in any desired order on
the different targets, such as simultaneously or sequentially.
The target 70 is preferably selectively rotatable (as represented by
arrow D), and/or translatable in x, y and/or z directions, to change the
location of the target at which the polymer formulation impacts during
operation of the apparatus 100. To provide rotation capabilities, the target
70 can be mounted on a shaft 78, which is operatively connected to a motor
80 (preferably a variable speed motor) operative to rotate the target 70 in
one direction, or in oscillating rotation, during set-up and/or operation of
the
apparatus 100 to control the formation of electrostatically processed material
on the target. For example, the target 70 is preferably selectively rotatable
by complete and/or partial reverse rotations.
To provide translation capabilities, the target 70 can be mounted on a
translatable target support, which can be translated in x, y and/or ~
directions.
The target 70 preferably is rotatable and/or translatable at different
speeds during electrostatic processing to control the thickness of the
electrostatically processed material deposited on the target.
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The pick-up stage 50 of the apparatus 100 is operative to remove the
electrostatically processed material 72 from the target 70. The pick-up stage
60 preferably is operative to continuously remove the electrostatically
processed material 72 from the target 70, to enable continuous production
by operation of fibs apparatus 100. The pick-up stage 60 preferably also
collects the removed electrostatically processed material 72. The collected
electrostatically processed material 72 can be subjected to one or more
post-processing treatments to alter its structure and/or properties.
The pick-up stage 60 includes a suitable device for removing the
electrostatically processed material 72 from the target. For example, the
pick-up stage 60 can include one or more doctor blades 62 positioned
relative to the target 70 to operatively interact with the target 70 to remove
the electrostatically processed material 72 from the target surface 74.
Alternatively, the pick-up stage can include mechanical, vacuum, or gas
assist devices to transfer the removed electrostatically processed material
72 from the target 70 to a desired location.
The pick-up stage 60 can comprise one roll, such as roll 64, or
alternatively two or more rolls. The roll 64 is rotated as represented by
arrow
E to wind the electrostatically processed material 72 removed from the target
70 onto the roll. The roll 64 is preferably operatively connected to a motor
68 operative to rotate the roll 64 during operation of the apparatus 100 to
control coiling of electrostatically processed material 72 onto the roll. In
addition, the roll 64 is preferably rotatable at different speeds depending on
the rotation rate of the target 70.
In preferred embodiments of the pick-up stage 60 that include multiple
rolls, the rolls can be vertically stacked, for example, to provide for
uninterrupted changeover during processing.
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The roll G4 preferably is also translatable to follow translational
movements of the target 70. For eazample, the target 70 and roll can be
mounted on a common translatable support.
The rate of pick-up of the removed electrostatically processed
material 72 on the roll 64 can be the same or different from the rate at which
the electrostatically processed material 72 is deposited on fibs target 70. In
preferred embodimenfis of the pick-up stage 60 that include multiple rolls,
fibs
rolls preferably can be operated at different speeds from each other to
process the removed electrostatically processed material 72 to change its
characteristics, such as its density and/or morphology.
The apparatus 100 preferably includes at least one thickness sensor
110 positioned to detect the thickness of the electrostatically processed
material 72 on the target 70. The thickness sensor 110 can be, for example,
a reflective laser sensor, which emits light onto the material. Such thickness
sensor 110 determines the thickness of the electrostatically processed
material 72 on the target 70 based on the amount of time required for the
light 112 to impinge on the electrostatically processed material 72 and
reflect
back to the thickness sensor 110. Other types of sensors, such as light
sensors or the like, can alternatively be used in the apparatus 100 to
determine the thickness of the electrostatically processed material 72 on the
target 70.
The apparatus 100 preferably also includes a controller 115, which is
operable to receive signals from the thickness sensor 110 and determine the
electrostatically processed material 72 thickness. If the controller
determines that the electrostatically processed material 72 thickness is
either
above or below a desired thickness, the controller 115 can send a signal to
the motor ~0, causing ad~usfiment of the rotational and/or translational speed
of fibs fiarget 70, so as to increase or decrease the residence time of the
deposition surfaces) of the target 70 in the deposition zone. Accordingly,
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the apparafius 100 can control fibs fihichness of the deposited
electrostatically
processed mafierial 72 on the target 70. The rofiafiional and/or
firanslafiional
speed of fibs fiargefi 70 can fih~as be adjusted to confirol the rate of
prod~acfiion
of electrostatically processed mafierial by the apparatus.
The apparatus 100 preferably also includes afi least one slack sensor
120 positioned to detect the amount of slack in the electrostatically
processed mafierial 72 at one or more selected locations between fibs fiarget
70 and the roll 64. The slack sensor 120 can also be a reflecfiive laser
sensor, such as described above, which determines the amount of slack of
the electrostatically processed material based on the amount of time
required for the light 122 to impinge on the electrostatically processed
material 72 and reflect back to the slack sensor 120.
The slack sensor 120 is also electrically connected to the controller
115. The slack sensor 10 sends signals to the controller 115, which then
determines the amount of slack in the electrostatically processed material
72. If the amount of slack differs from a desired value, the controller 115
sends a signal to the motor 68, causing adjustment of the rotational and/or
translational speed of the roll 64, depending on the rotational and/or
translational speed of the target 70, in order to maintain a desired level of
slack in the electrostatically processed material 72.
The electrostatically processed material 72 removed from the target
70 can be transferred to the pick-up stage 60 either through the air, or
alternatively through another fluid medium. For example, the removed
electrostatically processed material can be transferred through one or more
liquids to treat the polymer material. For example, the liquid can be an
adhesive formulafiion (e.g., PVA glue, polyacrylate glue, or the like), or a
solvent effective to form interfiber bonds in the electrostatically processed
material 72.
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As shown in Figure 5, an apparatus 200 according to another
preferred embodiment includes a post-collection treatment stage 125 located
between the collection stage ~~0 and the picle-up stage 60. The treatment
stage 125 is operable to impart desired physical, chemical and/or electrical
properties to the polymer material. For example, the electrostatically
processed material can be heated, cured, or subjected to corona treatment.
For example, the treatment stage 125 can include a radiation emitting
device operable to heat the material to a desired temperature. The radiation
emitting device can be, for example, a heater, such as a conventional heater
or an infrared heater, or a furnace. The heater can heat the material to a
suitably high temperature to, for example, dry or cure the electrostatically
processed material 72. Drying can be performed if the electrostatically
processed material 72 has already been transferred through a liquid, as
described above. The treatment stage 125 can include an ultraviolet (UV)
light or electron beam source, which can be used to cure some polymer
formulations. If it is desired to effect changes to the chemical structure of
the
electrostatically processed material, the treatment stage 125 can include a
corona treatment device operable to subject the electrostatically processed
material to a corona treatment to create surface functional groups.
The treatment stage 125 can also, or alternatively, be operable to
deposit one or more desired substances on the electrostatically processed
material. For example, the treatment stage 125 can include a source of one
or more dopants and/or catalysts, which can be applied to the
electrostatically processed material. Alternatively, the treatment stage 125
can include a source of one or more drugs or acfiive ingredients, which can
be applied to the material.
Alternatively, the treatment stage can apply one or more coating
layers on the removed polymer material. For example, a coating having
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desired chemical and/or physical properties can be deposited on fibs
removed elecfirosfiafiically processed material.
The one or more substances, or coafiings, can be applied to the
elecfirosfiatically processed material afi fibs fireafiment stage 125 by a
suifiable
application process, such as spraying, dipping, rolling, brushing, deposition
processes, or the like, using a suitable applicator device.
Figure 9 depicfis an apparatus 300 according to another preferred
embodiment. The apparatus 300 includes a rolling stand including rolls 65,
through which the electrostatically processed material 72 is transferred. The
rolls 64 can reduce the thickness of the electrostatically processed material
72 to a desired thickness. In addition, by varying the rotation rates of the
roll
64 and rolls 65, the electrostatically processed material can be stretched to
impart directional stress in the material.
Figure 10 depicts an apparatus 400 according to another preferred
embodiment. The apparatus 400 includes an applicator, such as a roll 67 of
a release sheet 69, which applies the release sheet to the electrostatically
processed material 72 at the collection stage to prevent blocking and allow
easier separation of the coiled material.
According to another preferred embodiment, the electrostatically
processed material 72 can be cut after it is removed from the target 70. For
example, a cutting stage can be disposed to cut the removed
electrostatically processed material 72 into mats of a desired length as an
alternative to coiling a continuous lengfih of the electrostatically processed
material 72 onfio the roll 64.
Figure 11 illustrafies an apparatus 500 according to another preferred
embodimenfi. The apparatus 500 includes fibs feeding device 430 shown in
Figure 5. t~s shown, fibs apparafius 500 can include a treatment sfiage 225
disposed to treat the electrostatically processed material 72 while on the
target 70. For example, one or more substances can be applied to the
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elecfirostafiically processed material 72 at the target 70, as opposed to, or
in
addition fio, at the treatment stage 125, as described above.
Figure 12 illustrates an apparatus 600 according to another preferred
embodiment, which includes the feeding device 530 shown in Figure 6.
Figure 13 illustrates an apparatus 700 according to other preferred
embodiment. The apparatus 700 includes a feeding stage 30 and a
collection stage 40. The feeding stage 30 can include a multiple-nozzle
feeding device, such as depicted. However, the feeding stage 30
alternatively can include, for example, the feeding device 330, 430 or 530,
as described above.
The collection stage 40 includes a target 70, and a container 90 of a
liquid 92. As the target 70 is rotated, a portion of the target 70 comes into
contact with and is wetted by, the liquid 92. A source 91 of the liquid 92 is
in
fluid communication with the container 90 to replenish the liquid consumed
during processing.
In an alternative preferred embodiment, the apparatus 700 can
include a cascade liquid source to apply the liquid to electrostatically
processed material deposited on the target 70.
As the target 70 is rotated, electrostatically processed material on the
target comes into contact with the liquid. The liquid 92 preferably has a
composition effective to impart desired properties, characteristics and/or
morphologies to the electrostatically processed material, or to promote
bonding of the electrostatically processed material, such as inter-fiber
bonding. For example, the liquid 92 can be a phase separation-producing
solution that causes phase separation of the electrostatically processed
material, resulting in different fiber morphologies, or liquid absorption. The
liquid 92 can alternatively be an active agent that is adsorbed within the
electrostatically processed material, such as a cross-linking agent, catalyst,
or the like. As another example, the liquid 92 can be a binder effective to
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produce bonded structures, such as webs or mats, from electrostatically
processed material deposited on the target 70.
Figure 14 illustrates an apparatus 800 according to another preferred
embodiment. The apparatus 800 includes a feeding stage 30 and a
collection stage 40. The feeding stage 30 can include a multi-orifice feeding
device, such as depicted. Alternatively, the feeding stage 30 can include, for
example, a feeding device 330, 430 or 530, as described above.
The collection stage 40 includes a funnel-shaped target 95, which
may be stationary or movable. The target 95 includes a conical portion 96
and a passage 97 extending through the target. As depicted, the polymer
formulation 45 is ejected from the feeding device 30 and electrostatically
processed material 72 is collected on the inner surface of the conical portion
96 of the target 95. The collected electrostatically processed material 72 can
be removed from the conical portion 96 using a suitable gas emitting device
98, such as a gas gun or the like. A vacuum is created in the passage 97 by
the vacuum system to draw the fibers as a continuous thread 99 through the
passage. The thread 99 may be collected on a spool, or the like.
The above are exemplary modes of carrying out the invention and are
not intended to be limiting. It will be apparent to those of ordinary skill in
the
art that modifications thereto can be made without departure from the spirit
and scope of the invention as set forth in the accompanying claims.
