Continous plasma activated species treatment process for particulate

The present invention includes methods for treating particles with plasma activated species. Through the use of the present invention, particles can be functionalized, coated or grafted.

FIELD OF THE INVENTION 
The present invention relates to an apparatus and a method for continuously 
treating particulate with a plasma activated species. The present 
invention further relates to particulate treated thereby. 
BACKGROUND OF THE INVENTION 
The use of reactive or excited gases in the treatment of particulate has 
held much promise for product development. For example, by coating 
particulate, or changing their surface chemistry, powders which would 
otherwise be incompatible with a variety of host materials may be rendered 
compatible therewith. Plasmas could be used to deposit hydrophobic 
coatings on moisture-sensitive powders to reduce degradation and increase 
storage time or, conversely, particles can be modified such that they 
disperse into liquids more readily. However, the promise of this 
technology has gone largely unfulfilled due to the rigors of the various 
methodologies employed to date. 
McCoy, U.S. Pat. No. 3,305,466 relates to a method and apparatus for 
reacting gas and solids. The method of McCoy is applicable to a reaction 
between a gaseous or vaporized reactant and a solid which could be 
comminuted therewith and which, in comminuted form, is susceptible to the 
effect of an alternating electric current. According to the method of 
McCoy, solids which are susceptible to the effect of an alternating 
electrostatic field are generally heated and introduced into a reaction 
chamber where they are agitated by the application of an alternating 
electric field and by the countercurrent flow of a reaction gas. For 
example, ferrite ore containing tungsten was heated to 300.degree. C. and 
reacted with carbon tetrachloride. This method is, however, limited. 
First, the requirement of alternating electric current susceptibility and 
the application of high temperatures significantly limits the type of 
particle which may be used and thus treated. Furthermore, this process is 
not energy efficient. Moreover, as McCoy requires agitation of its 
particles by the flowing gas, it is limited to operation at relatively 
high gas pressures. Finally, the reaction gas utilized often presents a 
safety and a disposal problem. 
Treatments using plasma activated species may eliminate many of the 
disadvantages associated with ordinary gas treatment processes and provide 
results that are otherwise unobtainable. 
Furthermore, plasma activated species treated powders, may advantageously 
be used in a number of environments. For example, ultra-high molecular 
weight polyethylene may be used as an additive for thermoplastic 
composites. Treated rubber may be used in non-slip epoxy flooring. Treated 
talc, clay, silica, carbon black and ground tires may be used as filler 
material. Treated pigments may be used for paints and coatings, treated 
micronized waxes may be used in inks, lubricants and coatings, and treated 
polymer dispersions may be used in coatings and emulsions. Unfortunately 
traditional plasma techniques for treating powders or particles are 
generally batch or modified batch procedures which are not economically 
feasible. See, for example, U.S. Pat. Nos. 4,423,303, 4,619,861, 
4,685,419, 4,810,524 and 4,867,573. In addition, the batch plasma 
treatment of certain particles is not possible due to their size, shape or 
density. 
Furthermore, particles cannot be treated uniformly in a batch mode because 
particles in the bulk receive less plasma exposure than particles at the 
surface, even though new particles are continuously moving to the surface. 
To mitigate this problem, long treatment times and/or violent agitation 
are generally necessary. However these treatments preclude the use of 
delicate or treatment-time sensitive powders and often result in the over 
exposure of a significant percentage of the treated particles. In the case 
of, for example, polymer particles, this may lead to discoloration, 
nonuniformity of structure or properties, and the like. 
The present invention makes feasible the use of plasma activated species to 
treat powders or particulate continuously, and eliminates many of the 
deficiencies in conventional batch treatments. Specifically, the present 
invention provides methods and apparatus for treating particulate in a 
continuous fashion with a plasma activated species. The present invention 
is particularly well suited for the treatment of particulate which because 
of size, delicacy, or composition, have not readily lent themselves to 
such treatments in the past. For example, the present invention is 
particularly useful for the treatment of polymer particles. 
OBJECTIVES AND SUMMARY 
One object of the present invention is to provide an apparatus which can be 
used to treat particulate with a plasma activated species in a continuous 
fashion. 
In accordance with one aspect of the present invention there is provided an 
apparatus for continuously treating particulate with at least one plasma 
activated species comprising: means for continuously providing at least 
one plasma activated species in a treatment zone and maintaining said 
treatment zone at sub-atmospheric pressure; means for continuously 
dropping a particulate through the treatment zone thereby treating the 
particulate with at least one plasma activated species; and means for 
continuously recovering treated particulate. 
The apparatus in accordance with the present invention has advantageously, 
and unexpectedly, been found to provide an excellent arrangement for the 
treatment of particulate by at least one plasma activated species in a 
continuous fashion. The apparatus uses gravity to move particulate through 
a treatment zone containing a plasma activated species. Because the 
apparatus eliminates the need for high temperature and/or agitation of 
particulate, delicate powders which could not otherwise be treated, may be 
processed. While apparatus according to some embodiments of the present 
invention may have a relatively small throughput at any given time, its 
continuous operation can provide yields which are superior to conventional 
batch apparatus of similar size. Furthermore, because the volume of 
particulate treated in any given time is reduced in comparison to a batch 
apparatus, shorter exposure times are required and more uniform treatments 
are obtained. 
Another object of the present invention is to provide methods for treating 
particulate in a continuous fashion with at least one plasma activated 
species. 
Therefore and in accordance with another aspect of the present invention 
there is provided a continuous process of treating particulate with at 
least one plasma activated species comprising the steps of: continuously 
providing at least one plasma activated species in a treatment zone 
maintained at subatmospheric pressure; continuously dropping a particulate 
through the treatment zone thereby treating the particulate with at least 
one plasma activated species; and continuously recovering treated 
particulate. 
The method of the present invention allows for the continuous treatment of 
particulate by a plasma activated species. The method involves 
continuously providing a plasma and dropping particulate through a 
treatment zone containing the plasma activated species and continuously 
recovering the treated particles there from. The method employs the use of 
gravity as a means for transporting particulate through the system and has 
resulted from the recognition that such a simple and gentle procedure can 
often result in complete treatment of even the most delicate and difficult 
particulate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Generally speaking, the method in accordance with the present invention 
includes a step of continuously providing a plasma activated species in a 
treatment zone maintained at sub-atmospheric pressure, continuously 
dropping a particulate through the treatment zone thereby treating the 
particulate with plasma activated species, and continuously recovering 
treated particulate. 
The term "continuous" as used herein means that the length of time that any 
particular particle is treated is substantially less than the length of 
time that the apparatus is in operation. Furthermore, the term 
"continuous" as used herein means that a particle to be treated only 
traverses a treatment zone containing plasma activated species once during 
the course of that particles manipulation through an apparatus of the 
present invention. The particle may be recovered and re-introduced to the 
apparatus or may be further modified by the introduction of the 
particulate to other apparatus. 
"Plasma activated species" in accordance with the present invention 
contemplates reactive gaseous species that include, or result from the 
ionization of an ionizable gas into a primary plasma. The term "primary 
plasma" indicates the excited states of ionizable gas while that gas is 
under the direct influence of an electromagnetic field or other plasma 
generating device and also represents the highest activated states in this 
reaction system. A "plasma" or "primary plasma" is created by introducing 
an ionizable gas into a vacuum chamber and exciting the gas with, for 
example, radio frequency (RF) energy. The RF energy dissociates the gas 
into electrons, ions, free radicals and metastable excited species. See 
Cormia, "Use Plasmas To Re-Engineer Your Advanced Materials", R&D 
Magazine, Jul. 19, 1990 at page 60, the text of which is hereby 
incorporated by reference. Plasma activated species in accordance with the 
present invention may include, without limitation, electrons, ions, free 
radicals, metastable species the latter of which are commonly referred to 
as plasma afterglow. Of course, when reference is made to "a plasma 
activated species", the term should be more correctly understood as at 
least one plasma activated species. 
The term "treatment zone" refers to a region within the apparatus in which 
the powder or particulate material to be treated comes into contact with 
the primary plasma and/or other plasma activated species. In some 
embodiments, such as that illustrated in FIG. 1, particulate will first 
contact an ionizable gas. Thereafter, as the particulate move into the 
region of influence of a plasma generating RF electrode, the particles 
will come in contact with a primary plasma as previously defined. The 
particulate will remain in contact with the primary plasma for the entire 
length of the plasma generating electrode, and possibly for some short 
distance thereafter. 
However, as the particulate move further down the treatment chamber and 
away from the plasma generating electrode, the plasma begins to return to 
less excited states forming other plasma activated species. These species 
are likely to still be reactive and the treatment zone encompasses them to 
the extent that they are. Therefore, if the treatment chamber is long 
enough, the treatment zone may be that portion of the treatment chamber in 
which the particulate may react with or be acted upon by plasma activated 
species. Thus the treatment zone may be shorter than the treatment 
chamber. If however, the treatment chamber is short, then the treatment 
zone extends roughly from the point at which a primary plasma is formed, 
or just there before, through the point at which the particulate is 
separated from the plasma activated species. It should also be mentioned 
that the rate of the flow of ionizable gas may have an influence in 
defining the length and extent of the treatment zone. If, for example, the 
treatment chamber is long, but the rate of flow of ionizable gas is 
significantly high, plasma activated species may extend through a greater 
length of the treatment chamber than would otherwise be apparent. 
The method, broadly described above, may be used to alter the surface, or 
to surface treat particulate by "functionalization", "coating", or 
"grafting". In "functionalization", the gases that are used to create the 
plasma and plasma activated species cannot be polymerized. The electrons 
and the active species generated in the plasma by the ionization of the 
gas interact with the particle surface. The plasma activated species are 
thought to extract atoms such as hydrogen or molecules such as methyl 
groups from the surface of the material, thereby leaving an active site. 
Active sites created on the surface react with other active species to 
form various chemical functional groups on the particle's surface. 
In a plasma coating, complex gases such as methane or propylene or volatile 
monomers are introduced into a chamber and ionized. This creates various 
active fragments that re-combine as a film on the surface of the particle 
and conform very accurately to the contour of the particle surface. 
Finally, grafting is a hybrid of plasma functionalization and conventional 
chemistry. In this process, a noble-gas plasma such as argon or helium 
creates free radicals on the surface of the particulate. After plasma 
activation, and before exposure to the atmosphere the particle's surface 
is exposed to, for example, a vapor of an unsaturated monomer. The free 
radicals on the surface react with the unsaturated monomer causing a 
polymer layer to be grafted on to the activated particle's surface. 
When coating particulate, it is not necessary, in all applications, that 
the coating be uniform. Generally speaking, a partial coating as thin as 
50 angstroms may be sufficient for certain applications such as 
harmonizing particulate with a specific polymer binder. However, to obtain 
a uniform coating of material on a particle, generally the coating will 
have a thickness of at least about 500 angstroms and will range up to 
about 1 micron in thickness. The exact thickness of the applied coating 
will vary with the size and composition of the particle being coated, the 
composition of the coating being applied, and the extent to which the 
particle is exposed to the primary plasma or plasma activated species. 
The present invention is useful on a broad variety of powders or 
particulate. These may include the class of compositions broadly known as 
polymers and more specifically may include powders or particulate of 
polyolefins such as polyethylene, polypropylene, polyisobutylene, and 
ethylene-alpha-olefin copolymers; acrylic polymers and copolymers such as 
polyacrylate, polymethylmethacrylate, polyethylacrylate; vinyl halide 
polymers and copolymers such as polyvinyl chloride; polyvinyl ethers such 
as polyvinyl methyl ether; polyvinylidene halides, such as polyvinylidene 
fluoride and polyvinylidene chloride; polyacrylonitrile; polyvinyl 
ketones; polyvinyl amines; polyvinyl aromatics such as polystyrene; 
polyvinyl esters, such as polyvinyl acetate; copolymers of vinyl monomers 
with each other and olefins, such as ethylene-methyl methacrylate 
copolymers, acrylonitrile-styrene copolymers, ABS resins, and 
ethylene-vinyl acetate copolymers; natural and synthetic rubbers, 
including butadiene-styrene copolymers, polyisoprene, synthetic 
polyisoprene, polybutadiene, butadiene-acrylonitrile copolymers, 
polychloroprene rubbers, polyisobutylene rubber, ethylene-propylene 
rubber, ethylene-propylene-diene rubbers, isobutylene-isoprene copolymers, 
and polyurethane rubbers; polyamides such as Nylon 66 and polycaprolactam; 
polyesters, such as polyethylene terephthalate; polycarbonates; 
polyimides; polyethers; fluoropolymers such as polytetrafluoroethylene and 
fluorinated ethylenepropylene. 
Inorganic materials that can be surface modified in accordance with the 
present invention, include minerals such as talc and clay; elemental 
oxides such as silica, alumina, titania; carbon black; pigments; metal 
oxides such as iron oxides, and ceramics. 
Powder or particulate, in accordance with the present invention, generally 
includes a size range of from about 0.1 microns to about 1.0 centimeter. 
However particulate most often treated in accordance with the present 
invention generally range in size from about 1 micron to about 1000 
microns. 
Typical gases which are used for functionalization of, for example, polymer 
powders include room air, synthetic air, oxygen, nitrogen, ammonia, inert 
or noble gases, sulphur dioxide, methane, nitrous oxide, halogenated 
hydrocarbons, and water vapor. Typical gases useful for coating powders 
include alkanes, including ethane, propane, and butane; alkenes such as 
ethylene, or propylene; fluorocarbons such as tetrafluoarethylene, 
hexafluoropropylene and hexafluoropropane; organosilicons such as 
hexamethyldisiloxane, tetramethyldisiloxane and tetraethoxysilane. The 
organosilicones may optionally be mixed with oxidizers such as oxygen and 
nitrous oxide. Mixtures of the aforementioned gases such as the use of 
propylene and a noble gas is also contemplated. Of course, the choice of 
gas is virtually limitless so long as it is ionizable to form plasma 
activated species. 
The apparatus and method of the present invention will be better understood 
with reference to FIG. 1 which illustrates a preferred embodiment of the 
present invention. This apparatus is configured to facilitate powder 
functionalization. However, if the coating desired is thin enough, the 
apparatus may also be used for particle coating. Untreated powder or 
particulate is first loaded into at least one hopper 1, such as a 10 inch 
diameter conical discharge hopper. The hopper 1 may be fabricated from 
material sufficient to withstand full vacuum. A vacuum ball valve 2 such 
as those available from the A & N Corporation, Inglis, Fla. (such as model 
2"100TQF) controls the flow of powder from feed hopper 1. Without the ball 
valve 2, untreated powder would discharge into treatment chamber 10 due to 
expansion of air in feed hopper 1 as vacuum is initially applied. A feed 
screw assembly is disposed at the other side of valve 2 to receive the 
powder or particulate after it passes through the valve. The feed screw 
assembly consists of a 1.3-inch diameter auger 5 with a 1-inch pitch 
connected to variable speed motor 3 through a rotary motion feedthrough 4 
(A&N Corporation, Model 125-FTR-S) and supported by a bearing at the end 
that empties into treatment chamber 10. 
The feed screw assembly discharges into treatment chamber 10 which is 
fabricated from 4-inch inside diameter by 36-inch long glass process pipe 
available from O-I/Schott Process Systems, Inc., Vineland, N.J. (Model No. 
6300-40036) 
The flow of ionizable treatment gas from cylinder 9 to inlet 6 of chamber 
10 is monitored by rotameter 8 (Cole-Parmer, Chicago, Ill., No. 
N-03227-00) and controlled by metering valve 7 (Nupro Company, Willoughby, 
Ohio, No. S-SS4). 
A plasma electrode 11 is provided and consists of 16 turns of 1/4-inch 
diameter copper tubing wrapped around the outside diameter of treatment 
chamber 10 over a length of about 28 inches. Plasma electrode 11 in 
combination with 13.56 megahertz RF power supply 13 (ENI, Inc., Rochester, 
N.Y., No. ACG-5) and matching network 12 (ENI, Inc., No. MW-5) generate a 
primary plasma activated species by electromagnetic activation of the 
ionizable treatment gas. In this embodiment of the present invention the 
length of treatment zone 30 is roughly coextensive with the length of 
plasma electrode 11 and is generally defined thereby. However, as is 
explained in more detail herein, treatment zone 30 may actually extend 
downstream from the electrode 11 toward the cyclone separator 17 and the 
tee 14. While it is unlikely that a primary plasma exists far downstream 
from electrode 11, plasma activated species may still be present and 
active. 
Surface functionalization of the powder is accomplished as the powder falls 
by gravity down through treatment chamber 10 and contacts the activated 
species. Treated powder exits the treatment zone 30 and the treatment 
chamber 10 and pass through tee 14. A majority of the powder passes 
straight through tee 14 directly into a 10-inch diameter discharge hopper 
16. A minority of the treated powder and the exiting ionizable gas pass 
through the leg of tee 14 into cyclone separator 17. The cyclone separator 
is 5 inches in diameter with a 10-inch straight section, a 10-inch long 
cone section, a 1.5-inch diameter inlet, a 1.5-inch diameter powder 
outlet, and a 2-inch diameter gas outlet. The powder separated in cyclone 
separator 17 discharges into hopper 16 through tee 15 and gases are 
conveyed to vacuum pump 24. (Leybold, Inc., Export, Pa., No. D60A) 
The pressure of the system is monitored by capacitance manometer 20 (MKS 
Instruments, Inc., Andover, MA., No. 122A) and pressure display 21, (MKS 
Instruments, Inc., No. PDR-D-1) and controlled by throttle valve 22 (MKS 
No. 253A-1-40-1) and throttle valve controller 23 (MKS No. 252C). 
Tee 18 and vacuum line 19 evacuate gasses from feed hopper 1 when the 
system is initially pumped-down with ball valve 2 closed. Without this 
connection, differential pressure may cause uncontrolled discharge of 
powder in feed hopper 1 when ball valve 2 is opened. 
In operation, untreated powder is loaded into feed hopper 1 with the system 
initially at atmospheric pressure and ball valve 2 closed. The apparatus, 
including the feed hopper is then evacuated to a stable base pressure, 
generally around about 0.01 Torr through about 0.1 Torr, depending on the 
composition of the untreated powder. Operating pressure is generally 
maintained between about 0.01 and 10.0 Torr and more preferably between 
about 0.01 and 1.0 Torr using vacuum pump 24. The ionizable gas flow rate 
usually between 10 and 1000 standard cubic centimeter per minute (sccm) 
and more preferably between about 10 and about 100 sccm is established and 
maintained. The RF power supply 13 is energized to create a plasma and 
plasma activated species of the ionizable gas in the treatment chamber 10 
and, more specifically, in treatment zone 30. The RF power supply provides 
power which generally ranges from about 50 to about 5000 watts and, more 
preferably from about 100 to about 300 watts. The feed screw assembly is 
set to the desired rotational speed to provide for a feed rate of powder 
of between about 0.1 and about 2.0 pounds per minute and, more preferably, 
between about 0.1 and 1.0 pounds per minute. Ball valve 2 is then opened 
to permit powder to flow from the hopper 1 to treatment chamber 10 and to 
treatment zone 30. These process parameters are generally relative to the 
apparatus described in detail herein and illustrated in FIG. 1. However, 
these parameters may vary widely as the dimensions of the apparatus change 
to accommodate, for example, a higher through-put. Thus a 4 foot diameter 
tube could accommodate a particulate throughput as high as 200 pounds per 
minute. Of course, pressures, flow rates of ionizable gases, and power 
levels will have to be scaled up accordingly. Furthermore, a particle 
distribution system may be necessary to insure uniform particle 
distribution though the entire cross section of the treatment chamber. 
In operation, there is little mechanical interaction between the particles 
as they pass through the treatment zone. The degree of mechanical 
interaction between particles, and the degree of mechanical interaction 
between particles and the surrounding gas is far less than is typically 
encountered in a fluidized bed or similar reactor. Thus, the downward 
motion of each particle through the treatment zone approximates free fall, 
with acceleration and velocity approaching those achieved by particles 
falling in a vacuum(with some lighter particles. The vacuum may also 
influence velocity). Moreover, the ionizable gas and plasma activated 
species within the treatment zone flow downwardly, concurrent with the 
particles. To the extent there is any mechanical interaction between the 
plasma activated species and the particles, this interaction tends to 
accentuate the downward motion of the particles. The residence time of 
each particle in the treatment zone is relatively short, typically less 
than about 3 seconds, preferably less than about 1 second depending upon 
the length of the treatment zone and treatment chamber. Moreover, the 
residence time of the particles within the treatment zone is substantially 
uniform. These factors aid in providing substantially uniform treatment of 
the particles, and in processing relatively delicate particles without 
appreciable damage. 
Finally, the functionalized particulate is recovered and collected in 
discharge hopper 16, either directly or after being separated from the 
ionizable treatment gas or plasma activated species via the cyclone 
separator 17. In some circumstances, where, for example, absolute 
uniformity is essential, it may be advantageous to continue to segregate 
the particles that fall through tee 14 and those which must first be 
separated by, for example, cyclone separator 17. In this case, the 
separator can feed into a separate hopper (not shown) so the particles are 
not recombined. 
Of course, it may be useful to use more than one feed hopper 1 each of 
which may include the same or different particulate. The use of a 
plurality of hoppers containing the same particulate is one way of 
providing a continuous source of untreated starting material. The use of a 
plurality of different hoppers containing different particulate will allow 
for the formation of hybrid treated mixtures of varying powder content. 
The feed hopper may also be eliminated entirely and replaced with other 
forms of fee devices. Thus the plasma activated species treatment 
apparatus of the present invention could be directly fed by, for example, 
a grinder. Similarly, such particulate creating devices may feed into 
intermediate holding devices, such as feed hopper 1 by using alternating 
slide gates such as those described in Application Bulletin No. SR 1.31 
from the Red Valve Company, Inc., Carnegie, Pa., entitled "Red Valves Used 
As Rotary Air Lock Feeders". 
While the length of the treatment zone 30 may vary with the type of 
particulate and the type of application, it may be impractical to build a 
single apparatus that is long enough for every application. In such cases, 
it is possible to convey the once treated particles from the discharge 
hopper 16 of a first apparatus to the feed hopper 1 of a second apparatus 
so that treatment may continue. Similarly, it may be advantageous to vary 
the treatment by first subjecting untreated particulates to one type of 
plasma activated species treatment and then processing the once treated 
particulate a second time with a different plasma activated species. 
Subsequent processing by plasma activated species, or otherwise is also 
contemplated hereby. 
Although the apparatus described herein use radio frequency powered 
external coil electrodes, other electrode designs and power sources may be 
employed. Radio frequency coupling of energy through the dielectric wall 
of treatment chamber permits the use of an external coil, band, clamshell 
or helical resonator electrodes. External electrodes are preferred in some 
applications to prevent coating build-up on the electrode and to eliminate 
the need for vacuum electrical feed throughs. Internal electrodes can be 
employed with radio frequency and are required when audio frequency is 
used since audio frequency will not couple through the wall of the 
treatment chamber. Internal electrodes normally must be liquid cooled 
because heat dissipation is poor in a vacuum. Coating material may build 
up on the internal electrodes. Such built-up material may be dislodged and 
may contaminate the product being treated. Microwave power sources may be 
used with a metal treatment chamber, but microwave generators normally are 
expensive and not energy efficient. When used in coating processes, the 
quartz window required in microwave systems can become coated thus 
reducing the transmission of microwave energy to the treatment chamber and 
thus to the treatment zone. 
With reference to FIG. 2, another preferred embodiment of the present 
invention is the use of a socalled plasma afterglow or "afterglow plasma" 
as the plasma activated species for the treatment of powders or other 
particulate. The structure of the treatment chamber 10, the particulate 
feed apparatus, vacuum system and control, and particulate and gas 
separators are identical to those disclosed in connection with FIG. 1. 
However, in accordance with this aspect of the present invention ionizable 
treatment gas is ionized into a primary plasma by being conveyed through a 
chamber 31 having an RF plasma generating electrode 11' coiled about it. 
After ionization, the plasma activated species are introduced into 
treatment chamber 10' where they interact with untreated powder which is 
dropping, under the influence of gravity therethrough. In this 
configuration, treatment zone 30' is not co-extensive or coaxial with the 
plasma generating electrode 11' as is the case with the apparatus of FIG. 
1. Rather, the treatment zone 30' extends from the point at which the 
plasma activated species are introduced and intermix with the untreated 
powder and continues downwardly along the length of treatment chamber 10' 
until the plasma activated species have reached a state where they can no 
longer influence the structure of, or provide coating to the powder or 
until the powder is recovered and separated therefrom. 
Grafting of unsaturated monomers to a particulate which has been activated 
by exposure to a primary plasma and/or other plasma activated species can 
be accomplished using the apparatus illustrated in FIG. 3. Active sites 
are created on particulate surfaces by exposure thereof to plasma 
activated species in treatment zone 30. The downwardly flowing inert gas 
is diverted toward the vacuum pump through the leg of tee 14. A controlled 
flow of grafting monomer vapor stored in flask 60 is introduced into tee 
15 at inlet 70 using a rotameter 50 and a metering valve 40 as previously 
described. The grafting monomer vapor flow is balanced with the inert gas 
flow so as to maintain a region of monomer vapor in a grafting zone within 
pipes 71 and 72' such that the monomer vapor does not rise substantially 
above tee 14 into treatment zone 30. In this arrangement, the particles 
drop continuously and directly from the treatment zone into the grafting 
zone and the particles are maintained under a blanket of the plasma 
activated species and/or decay products of the plasma activated species 
from the time that the particles leave the treatment zone to the time they 
encounter the monomer vapor in the grafting zone or just shortly 
therebefore. The upwardly flowing grafting monomer vapor contacts the 
downwardly flowing particulate which has been surface activated or, 
functionalized, and grafting of the monomer to the activated sites on the 
surface of the particulate is accomplished. 
Where the ionizable gas used to form the plasma activated species is an 
"inert" gas, the particles are maintained under inert gas protection 
during this conveyance to the grafting zone. As much as the particles are 
protected and are conveyed quickly into the grafting zone, relatively 
short lived active sites on the particles remain active until they react 
with the monomer vapor in the grafting zone. For certain materials which 
may have long-lived reactive sites, grafting can be accomplished at 
atmospheric pressure by contacting the activated particle surface with a 
liquid grafting monomer. The grafting monomers must contain an unsaturated 
vinyl or allyl group. 
Typical vapors used for grafting include grafting monomers that contain an 
unsaturated vinyl or allyl group. Therefore, acryl, methacryl, unsaturated 
amide, diene and trienes in monomeric form may be used for grafting. 
Examples of plasma initiated grafting can be found in U.S. Pat. No. 
4,845,132. 
The foregoing will be better understood with reference to the following 
examples. These examples are for the purpose of illustration. They are not 
to be considered limiting as to the scope and nature of the present 
invention. 
EXAMPLE 1 
An otherwise non-dispersible polyolefin powder was rendered dispersible in 
water by treating the powder with an air plasma using a prototype 
apparatus to functionalize the powder surface with polar groups. 
The prototype apparatus was configured using a 25 millimeter outside 
diameter by 18-inch long quartz tube for the treatment chamber and an 
external coil electrode comprising 14 turns of 1/8-inch copper tubing 
wrapped over a 9-inch length. A 0.75-inch diameter, 0.75-inch pitch, auger 
rotating at 8 RPM was used to feed the powder into the treatment chamber. 
A 90 degree elbow was installed in place of tee 14 illustrated in FIG. 1. 
The treated powder was collected directly in an Edwards High Vacuum (Grand 
Island, N.Y.) model ITF20 dust filter installed in place of cyclone 
separator 17 illustrated in FIG. 1. 
The 2-inch diameter feed hopper was loaded with polyethylene with a 
viscosity average molecular weight of 4 million and an average particle 
size of 120 microns (Hoechst Hostalen (tm) GUR-412). A controlled 18 sccm 
flow of air was admitted to the treatment chamber maintained at 
approximately 120 millitorr. RF power at 50 watts and 13.56 megahertz was 
applied to the coil electrode to generate a primary plasma and other 
plasma activated species. 
The resulting functionalized powder was dispersible in water. A sample of 
reactive gas treated, but otherwise identical, material was obtained from 
Air Products and Chemicals (Primax (tm) UH1080) for comparison and ESCA 
(Electronic Spectroscopy for Chemical Application) indicated the following 
compositions: 
TABLE 1 
______________________________________ 
Atomic Concentration (percent) 
C.sub.1s O.sub.1s 
F.sub.1s 
______________________________________ 
Untreated 97 3 0 
Air Plasma Treated 
91 9 0 
Reactive Gas Treated 
69 14 17 
______________________________________ 
It appears that hydroxyl and carboxylic acid functionality was added to the 
surface by exposure to the air plasma thus improving dispersibility in 
water. 
Five gram samples of each powder were placed in an oven at 175.degree. C. 
for 45 minutes. The untreated sample showed no discoloration after 
melting. The treated sample prepared in accordance with the present 
invention showed very slight discoloration after melting. The reactive gas 
treated sample showed severe discoloration after heating with 
decomposition resulting in a porous appearance. 
EXAMPLE 2 
In this example the apparatus was configured as in FIG. 1 using a 4-inch 
inside diameter by 36-inch long glass process pipe for the treatment 
chamber and a coil electrode comprising 16 turns of 1/4-inch copper tubing 
wrapped over a 28-inch length. A 1-inch diameter, 1-inch pitch, auger 
rotating at 17 RPM was used to feed the powder into the treatment chamber. 
The treated powder was recovered using a cyclone separator. 
The feed hopper was loaded with a high density polyethylene powder (Quantum 
Microthene (tm) FA15000) with an average particle size of 20 microns. A 
controlled 15 sccm flow of air was admitted to the treatment chamber 
maintained at approximately 80 to 150 millitorr. RF power at 200 watts and 
13.56 megahertz was applied to the coil electrode to generate a plasma 
active species. 
The untreated powder was not dispersible in water. The functionalized 
powder resulting from the use of the present invention was water 
dispersible. 
EXAMPLE 3 
Ground tire was treated as described in Example 2. The untreated ground 
tire was not dispersible in water. The functionalized ground tire 
resulting from the use of the present invention was dispersible in water.