WO1999059185A1

WO1999059185A1 - Structures and components thereof having a desired surface characteristic together with methods and apparatuses for producing the same

Info

Publication number: WO1999059185A1
Application number: PCT/US1999/010150
Authority: WO
Inventors: Angelo Yializis; Richard E. Ellwanger; Michael G. Mikhael; Wolfgang Decker; C. Barry Johnson; Gale Shipley; Timothy D. O'brien
Original assignee: Asten, Inc.
Priority date: 1998-05-08
Filing date: 1999-05-08
Publication date: 1999-11-18
Also published as: US6146462A; AU3893099A

Abstract

Methods and apparatus for plasma modifying a substrate are disclosed along wiht associated techniques for applying coatings to the substrate. Particular utility has been found using a hollow cathode to generate the plasma along with magnetic focusing means to focus the plasma at the surface of a substrate.

Description

STRUCTURES AND COMPONENTS THEREOF HAVING A DESIRED

SURFACE CHARACTERISTIC TOGETHER WITH METHODS AND

APPARATUSES FOR PRODUCING THE SAME

BACKGROUND OF THE INVENTION

Field Of The Invention

The present invention relates generally to structures and their components

which have been treated with equipment and techniques that produce modifications

to surface characteristics in either the structures or the components. More

particularly, the present invention relates to equipment and techniques for treating

substrates and components having commercial and industrial uses, particularly in

industrial fabrics. Most particularly, the invention relates to plasma treated

components and substrates together with equipment and techniques useful in treating

the same in an efficient and accurate manner.

The prior art has recognized the advantages to be obtained by plasma treating

and deposition techniques, at low pressure and at atmospheric pressure, to achieve

desirable characteristics in a product. Most generally, the products treated in the

prior art are single purpose products which were not intended to be exposed to a

working condition or an active environment where the treated product is subjected

to varying conditions over an extended time period. Furthermore, the prior art

products were not exposed to varied treatment over time in a work environment. For

example, industrial fabrics are frequently required to work under conditions of high

mechanical stress and hostile environments. Special applications, like papermaking,

require industrial fabrics that generally work in hot, moist and chemically hostile

environments. As such, the fabric may be exposed to high water content in a formation step, heat, pressure and relatively high water content in a pressing step, and

then, exposed to high temperatures in a drying step. Thus, the fabrics may see a

variety of conditions in the process. Industrial fabrics may also be exposed to varying

conditions in industries such as food processing, waste treatment, assembly line

processes or surface painting and treating techniques.

The art has recognized that it would be desirable to have substrates and

components with certain mechanical properties, such as strength, dimensional

stability, and flexibility over extended periods. While these characteristics are

desired as properties, it is sometimes desired to have surface properties which are

contrary to these properties. For instance, it may be desirable to have a component

which exhibits good internal resistance to moisture at its core while having an

external affinity for moisture at its surface. It is not uncommon to have a conflict

develop between the desired mechanical properties and the preferred surface

properties. The prior art has recognized and there have been attempts at producing

a mechanically robust core which supports a surface layer that has specific

characteristics for the desired application. It has been recognized that important

surface layer properties such as hydrophilicity, hydrophobicity, oleophilicity,

oleophobicity, conductivity, chemical resistance and abrasion resistance may not

necessarily be optimized in a single component which optimizes core properties such

as strength, flexibility, and the like.

The present invention addresses the shortcomings of the prior art by providing

structures and components which are treated with a highly efficient and controllable plasma treatment. If desired, the structure or component may be further enhanced or

modified by exposure to a deposition treatment.

SUMMARY OF THE INVENTION

The present invention provides substrates and components having at least one

inherent surface characteristic thereof modified by equipment and techniques which

are particularly suitable for achieving that modification. The inherent surface

property may be modified by a plasma treatment process which comprises the steps

of providing a plasma treatment chamber which includes one or more hollow

cathodes for generating a plasma within the chamber. The chamber includes means

for focusing the generated plasma at the surface to be treated as it is introduced into

the chamber and reacted with the plasma.

DESCRIPTION OF THE DRAWINGS

Figure 1 is a side elevation showing a plasma treatment apparatus in

accordance with the present invention in an opened condition.

Figure 2 is an elevation of the other side of the plasma treatment apparatus

of Figure 1 taken along the line 2-2 of Figure 1.

Figure 3 is an elevation of one side of the plasma treatment apparatus of

Figure 1 taken along the line 3-3 of Figure 1.

Figure 4 is a side elevation of one arrangement for treating a substrate in

accordance with the present invention. Figure 5 is a partial cutaway perspective view of a capillary drip system.

Figure 6 is a side elevation of a solution bath.

Figure 7 is an elevation, similar to Figure 2, showing a plurality of discrete

substrates being treating simultaneously.

Figure 8 shows a plurality of substrates A-F in cross-section with or without

plasma treating and secondary coating.

Figure 9 shows an alternative arrangement of the plasma treatment chamber.

Figure 10 shows a treatment chamber for metal deposition.

Figure 11 shows a treatment chamber for vapor deposition of a monomer.

Figure 12 shows a curing unit.

Glossary

A component is a structural or modular element that is capable of producing

a structure when a plurality thereof are assembled together.

A fabric structure is formed by arranging individual strands in a pattern, such

as by weaving, braiding, or knitting.

A fiber is a basic element of a textile and is characterized by having a length

at least 100 times its diameter.

A filament is a continuous fiber of extremely long length.

A hollow cathode is an energy efficient chamber for generating a plasma.

An industrial fabric is one designed for a working function such as transport

devices in the form of a moving or conveying belt. An inherent property or characteristic is one that exists prior to any treatment

by plasma or other means.

A monofilament is a single filament with or without twist.

A multifilament yarn is a yarn composed of more than one filament assembled

with or without twist.

A nonwoven structure is a substrate formed by mechanical, thermal, or

chemical means or a combination thereof without weaving, braiding, or knitting.

A plasma is a partially ionized gas; commonly ionized gases are argon, xenon,

helium, neon, oxygen, carbon dioxide, nitrogen, and mixtures thereof.

A strand is a filament, monofilament, multifilament, yarn, string, rope, wire,

or cable of suitable length, strength, or construction for a particular purpose.

A structure is an assemblage of a plurality of components.

A substrate is any structure, component, fabric, fiber, filament, multifilament,

monofilament, yarn, strand, extrudate, modular element, or other item presented for

plasma treatment or coating.

A web is an array of loosely entangled strands.

A yarn is a continuous strand of textile fibers, filaments, or material in a form

suitable for intertwining to form a textile structure.

A 100% solids solution is a fluid such as a monomer, combination of

monomers or other coating material which includes no carriers or solvent.

A 100% solids bath is a tank filled with a fluid such as a monomer, which

includes no carriers or solvent. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments will be described with reference to the drawing

Figures wherein like numerals indicate like elements throughout.

With reference to Figure 1, there is shown plasma treatment chamber 2 which

is useful in accordance with the present invention. Plasma treatment chamber 2 is

divided into a plasma generating side 4 and a plasma focusing side 6. In use, the

plasma generating side 4 and the plasma focusing side 6 are joined together in a

sealed relationship except for openings 8 and 10 at the respective upper and lower

ends. Entry and exit openings are created by the recesses 12, 14, 16 and 18. Since

the pressure in the plasma treatment chamber 2 is preferably below atmospheric

pressure, the recesses 12, 14, 16 and 18 will be provided with air locks of foam

material or loop pile material, such as is available under the trade name Nelcro®.

Presently, a closed cell polyolefin, such as polyethylene or polypropylene, foam is

preferred. When chamber 2 is closed, the walls 20 and 22 will form a channel 24

through the apparatus 2. A substrate passing between the air locks at openings 8 and

10 will pass into channel 24 and be sufficiently sealed against the atmosphere so as

to maintain the desired vacuum level within the plasma treatment chamber 2. The

vacuum in chamber 2 is drawn through the outlet ducts 30 and 32 by a suitable

vacuum generating device as will be known to those skilled in the art. Currently, the

plasma is being generated between 900 milli torr (0.900 torr) and 3 torr. In earlier

trials, plasma was generated at up to 34 torr. With reference to Figure 2, taken along line 2-2 of Figure 1, there is

illustrated a substrate 3 as it passes through the plasma treatment chamber 2 and the

hollow cathode assemblies 36. As shown in Figures 1 and 2, the hollow cathode

assemblies 36 define multiple hollow cathodes 38. The plasma generated in the

hollow cathodes 38 will be initially focused in the vicinity of the substrate 3.

Additional focusing of the plasma on the substrate is accomplished by the focusing

means included in plasma focusing side 6.

Turning now to Figure 3, there is a view of the plasma focusing side 6 of

plasma treatment apparatus 2 that is taken along the line 3-3 of Figure 1. The plasma

focusing side 6 includes a plurality of focusing arrays 50 which are located in space

relative to each other so as to achieve a reinforcement of the magnetic focusing field.

Surrounding the magnets 50 (shown in Crosshatch for clarity) are the cooling ducts

52 which serve to control the temperature in the chamber, thereby protecting the

magnets from overheating.

Plasma treatment to remove low molecular weight material or surface

impurities will preferably use readily available, inexpensive, environmentally benign

gases. In some applications, plasma treatment alone may be sufficient, however, it

can be followed by coating with metals, ceramics, or polymerizable compounds.

Preferred polymerizable compounds are radiation curable organic monomers

containing at least one double bond, preferably at least two double bonds, especially

alkene bonds. Acrylates are particularly well-suited monomers. Metals suitable for

deposition include, but are not limited to Al, Cu, Mg, and Ti. Ceramics suitable for deposition include, but are not limited to, silicate-containing compounds, metal

oxides particularly aluminum oxide, magnesium oxide, zirconium oxide, beryllium

oxide, thorium oxides, graphite, ferrites, titanates, carbides, borides, suicides,

nitrides, and materials made therefrom. Multiple coatings comprising metal, ceramic

or radiation curable compound coatings are possible.

Plasma treatment leads to one or more of the following benefits: cleaning,

roughening, drying, or surface activation. Plasma treatment can also lead to chemical

alteration of a substrate by adding to a substrate or removing from a substrate,

functional groups, ions, electrons, or molecular fragments, possibly accompanied by

cross-linking.

All materials are of interest for plasma treatment or application of a secondary

coating. Those of primary interest are polymers, such as aramids, polyesters,

polyamides, polyimides, fluorocarbons, polyaryletherketones, polyphenylene sulfides,

polyolefins, acrylics, copolymers and physical blends or alloys thereof. Preferred

secondary layer coating thickness for polymers is in the range of 0.1 to 100 microns,

more preferably 20 to 100 microns, most preferably 20 to 40 microns. Preferred

metal or ceramic secondary layer coating thickness is in the range of 50 angstroms

to 5 microns, more preferably 100 to 1000 angstroms. A preferred polymer is an

acrylate of acrylic acid or its esters. The preferred acrylates have two or more double

bonds. Monoacrylates have the general formula

O

C=C (I)

/ \

R² _R3

Wherein R¹, R², R³, and R⁴ are H or an organic group.

Diacrylates are acrylates of formula I wherein either R¹, R², R³, or R⁴ is itself

an acrylate group. Organic groups are usually aliphatic, olefinic, alicyclic, or aryl

groups or mixtures thereof (e.g. aliphatic alicyclic). Preferred monoacrylates are

those where R¹, R² and R³ are H or methyl and R⁴ is a substituted alkyl or aryl group.

Preferred diacrylates have the formula

O O

II II

R¹ C R⁴ C R⁷

\ / \ / \ / \ / C=C O O C=C (II)

/ \ / \

R² _R3 _R5 _R6

where R¹, R², R³, R⁵, R⁶, R⁷ are preferably H or methyl, most preferably H.

R⁴ is preferably C₂-C₂₀ alkyl, aryl, multialkyl, multiaryl, or multiglycolyl, most

preferably triethylene glycolyl or tripropylene glycolyl. The notation, C₂-C₂₀ alkyl,

indicates an alkyl group with 2 to 20 carbon atoms. R⁴ in a mono- or multiacrylate is chosen to yield the desired surface properties

after the monomer has been radiation cured to form a surface on a substrate. Table

1 contains a non-limiting list of examples.

Table 1

Formula I and II can also include triacrylate and other polyacrylate molecules.

Mixtures of diacrylates can be copolymerized, for example a 50:50 mix of two

structurally different diacrylates. Diacrylates can also be copolymerized with other

polymerizable components, such as unsaturated alcohols and esters, unsaturated

acids, unsaturated lower polyhydric alcohols, esters of unsaturated acids, vinyl cyclic

compounds, unsaturated ethers, unsaturated ketones, unsaturated aliphatic

hydrocarbons, unsaturated alkyl halides, unsaturated acid halides and unsaturated

nitriles. Diacrylates of interest also include 1,2-alkanediol diacrylate monomers of formula

O R²

II I

R¹CHCH₂OC-C=CH₂

I (in)

0-C-C=CH₂

O R² Where R¹ is in an acrylate radical having about 8 to 28 carbon atoms and R² is

hydrogen or methyl (See for example U.S. Patent 4,537,710).

The agent for promoting polymerization may be radiation, such as UV

radiation or electron beam radiation. In some instances, it may be preferred to use

a photoinitiator, such as an appropriate ketone.

Acrylate-based formulations of interest also include heterogeneous mixtures.

These formulations contain a very fine dispersion of metal, ceramic, or graphite

particles. These coatings are designed to enhance the abrasion resistance and/or the

conductivity of the surface. For the photo-curing (UV/Nisible) of these pigmented

dark acrylate-based formulations, a long wave length (> 250 nm) radiation source in

combination with a compatible photoinitiator may be preferred.

Turning now to Figures 4 and 5, there are illustrated apparatuses for

sequential plasma treatment, coating, and curing of a continuous substrate which may

most easily be thought of as a strand 3. In Figure 4, a plasma treatment apparatus

2, a coating applicator 60, and a curing unit 70, provide an integrated system for

treatment of the strand 3. The direction of movement of the strand 3 is indicated by

the in and out arrows. The strand 3 moves over a guide roller 88 and enters the plasma treatment apparatus 2 at the opening 8. To achieve uniform coverage, the

strand 3 will not touch either wall 20 or wall 22. However, the strand 3 will pass

closer to wall 22 than to wall 20. If it is desired to treat only one surface of a strand,

the surface to remain untreated may be shielded, such as by contact with wall 22.

After the strand 3 passes through channel 24, it exits the plasma apparatus 2 through

opening 10.

In the preferred embodiment, the coating applicator 60, is a capillary drip

system 400 including a reservoir 402, a pump 404, a dispensing manifold 406, a

plurality of capillary tips 408, and a separating roller 410 having a plurality of

grooves 412 dimensioned to receive a substrate as shown in Figure 5. The coating

solution 61 is pumped from the reservoir 402 into the dispensing manifold 406 and

through the plurality of capillary tips 408. Each tip 408 is associated with a groove

412 in the separating roller 410. In this arrangement, the roller 410 may rotate or be

held stationary. The strand 3 is directed to engage the roller 410 horizontally or at

an angle up to 45 ° above horizontal. The strand 3 travels around the roller 410 and

continues vertically upward into the curing unit 70. The variation in the initial angle

Θ determines how the strand 3 is coated. Depending on the angle θ, the strand

contacts 25-50% of the roller 410 circumference. Use of this capillary tip system is

accurate and efficient, requires less coating solution 61, and provides a more uniform

coating than other methods. This approach is believed to be beneficial because it

allows for remote location of the reservoir 402 away from potential curing radiation

which may impact a dip bath. Returning to Figure 4, the strand 3 then passes enters into the curing

apparatus 70 through channel 72 and passes out of the apparatus at channel 74. The

channels 72 and 74 are defined by the extensions 75 and 76. The central channel 77

is defined by the walls 78 and 79 of the curing apparatus 70. After passing the last

guide roller 88, the strand 3 is handled in the usual manner associated with normal

production of an unmodified product.

In one embodiment, curing apparatus 70 has one section 80 with a plurality

of UN lamps (one lamp is noted as 82) and an opposed section 84 with a plurality of

opposing mirrors (one mirror is noted as 86). In a preferred arrangement for curing

certain monomer coatings, there are up to four lamps, in opposed pairs. Each lamp

is preferably adjustable for controlling their combined output. The sections 80 and

84 are hinged relative to each other to allow access for startup and repair. The UV

light used for curing preferably emits radiation between 150 and 400 nanometers.

The series of guide rollers 88 change the direction of the strand 3 so it passes

continuously through plasma treatment apparatus 2, coating applicator 60, and curing

apparatus 70.

The system components, plasma treatment apparatus 2, coating applicator 60,

curing apparatus 70, and rollers 88, are secured in a stable manner to preserve the

spacial relationship between them.

Figure 7 illustrates the case for multiple strands 3, such as monofilaments,

passing through the plasma treatment apparatus 2. The strands are spaced across the

width, preferably in individual paths, so that the entirety of the strand is exposed to treatment. The individual strands are preferably guided by grooves cut in the rollers

88. Using a series of grooved rollers 88 keeps the strands in the desired relationship

as they move through the treatment process.

The treated substrate is tested according to Test Method 118 developed by the

American Association of Textile Chemists and Colorists (AATCC). Drops of

standard test liquids, consisting of a selected series of hydrocarbons with varying

surface tensions, are placed on the surface and observed for wetting, wicking, and

contact angle. The oil repellency grade is the highest numbered liquid which does

not wet the surface. The method was modified to test for water repellency, using test

liquids of isopropanol and water in ratios of 2:98, 5:95, 10:90, 20:80, 30:70, and

40:60 (in percent by volume) numbered one through six respectively. If surface

wetting does not occur within 10 seconds, the next test liquid is applied. Lower

ratings indicate oleo-or hydrophilicity while higher ratings indicate oleo-or

hydrophobicity.

Example 1

Using a continuous treatment system shown in Figures 1-5, a plurality of

strands are treated. An extruder is adjusted to produce 10 ends of a polyethylene

terephthalate monofilament with a nominal size of 0.26mm X 1.06mm. These sizes

have a tolerance of 0.22-0.304mm and 1.01-1.11mm respectively, with an expected

yield of 2900 denier. Additionally the yarn would have a relative elongation at 3

grams per denier of 19%, and a free shrinkage at 200 degrees Centigrade of 6.5%. The production speed of the extruder line is set at 216.8 fpm, with the godet rolls and

oven temperatures appropriately adjusted to give the specified yarn.

Immediately after exiting the extruder, nine of the ten strands are introduced

into the plasma chamber, which is at 1.01 Torr, with constant induction of 400

ml/min of commercial grade Argon. The amplifier and tuner are adjusted to

introduce 1326 Watts to the hollow cathode, with less than 10 Watts of reflected

power. An external chiller is used, which maintains the temperature near room

temperature, but above the dew point.

Upon exiting the plasma chamber, the nine ends are then directed to a grooved

separator roll where monomer is applied. From a one inch manifold being supplied

formulation MM2116 by a diaphragm pump, nine capillaries drop to individual

grooves spaced evenly across the roller. The air-operated pump is adjusted with a

micro air valve to supply a steady state of monomer to the monofilament. A

weighing device is used to continually monitor the amount delivered. Coating

thickness can be controlled by increasing or decreasing pump pressure, fiber speed

or stopping the rotation of the roller.

After coating, the yarn proceeds directly upward, and enters the ultra violet

cure box, which has three lamps operating. Two lamps are set on medium, and one

is set on high, providing an immediate and complete cure of the monomer. In the

upper section, two of the lamps are opposed to each other rather than having one

lamp opposed by a mirror. Other applications may demand more or fewer lamps. Af ter the yarn exits the UV chamber, it continues down the line through a nip

roll and onto the spools mounted on a conventional spool winder.

This particular run experienced an increase in the minor axis of 0.0274mm and

in the major axis of 0.1486mm, causing an increase in weight of 178 grams per 9000

meters or approximately a 5.8% add on.

The resulting yarn has an oil, water rating of 4, 6 when tested with AATCC

Test Method #118. The yarn was then woven into a filling float fabric using

conventional processing methods. The yarn survives the rigors of warping and

weaving without abrasion, or flaking indicating the coating is securely affixed.

Resulting fabrics also have an oil, water rating of 4, 6 on one surface designated as

the face. The untreated PET control has an oil, water rating of 0, 2-3.

In this particular example, a series of acrylate-based fluorinated

monomer/oligomer formulations have been tested for this application. These

materials cover a broad range of surface energies (hydrophobic/hydrophilic and

oleophobic/oleophilic), crosslinking densities, abrasion resistance and adhesion to the

substrate.

The formulation Sigma-MM-2116 is a solvent-free, acrylate based

monomer/oligomer mix which contains 50-95% perfluorinated monoacrylate with

fluorine content ranging from 30-64%. The formulation also contains 3-50% multi-

functional, compatible crosslinking agents, e.g. di- and tri-acrylate monomers. Also

1-20% of an adhesion promoter was added to enhance diacrylate monomers

functionalized with hydroxyl, carboxyl, carbonyl, sulfonic, thiol, or amino groups. The high fluorine content lowers the surface energy of the cured coating and turns the

coated yarn into hydrophobic and oleophobic material. Combining the plasma

treatment of the surface of the substrate with the functionalization of the coating with

a specialty adhesion promoter formulation helps to achieve an excellent adhesion

between the coating and the substrate while keeping the energy low, making the

surface of the substrate both hydrophobic and oleophobic.

In addition to the formulation for hydrophobicity/oleophobicity, formulations

are also contemplated in applications for electrostatic dissipation and abrasion

resistence.

Although the presently preferred embodiment uses the capillary drip

applicator, initial efforts called for a monomer bath. As shown in the sectional view

of Figure 6, the bath 418 is essentially a tub 420 for holding the monomer solution

61 and a submersible frame 422 for controlling passage through the monomer

solution 61. The frame 422 moves horizontally on shaft 424 and vertically on shaft

425. The depth of roller 426 in the monomer solution 61 may be controlled by fixing

the position of shaft 425. When the roller 426 is submerged in the monomer solution

61, each strand 3 is passed around the roller 426 so that it will exit vertically from the

bath as indicated by the broken line.

Example 2

Using a continuous treatment system as shown in Figures 1 to 5, a

polyethylene terephthalate (PET) monofilament of 0.5 mm diameter is treated. In this example, a sample monofilament is fed from the final extrusion process directly

to the plasma treatment apparatus. The control sample is fed from the final extrusion

process directly to a wind up roll. As used herein, directly means the absence of

intermediate processing steps or storage between processing steps for an extrudate.

The line speed in the test system is 200 ft/min but speeds up to 700 feet/min are

employed during production. The gas in the plasma treatment apparatus may be 10%

argon and 90% nitrogen but is more preferably 20% oxygen and 80% argon. The gas

is introduced into the treatment chamber at a rate sufficient to achieve a stable

plasma. The vacuum pressure is 10^"1 - 10^"4 torr. Power supplied to the plasma

chamber is about 2 kW (kilowatts). The power is created with direct current or

alternating current but is preferably created with an alternating current in the range

of 10 to 100 kHz, with 40 kHz being preferred. The monomer bath contains a

solution of triethyleneglycol diacrylate. The lamps in the UV treatment apparatus are

15 inch Hanovia high pressure Hg lamps that generate 300 W/inch.

The treated monofilament is compared to the control monofilament by surface

tension measurements using the oil and water tests described above.

It is preferred to use continuous or in-line processing where the substrate

moves through the base processing step, such as extrusion, and plasma/coating

treatment at the same speed.

Other alternative coating means may be used such as U shaped applicators, a

kiss roll, eyelet applicators, and clamshell eyelet applicators. In a more traditional

finishing device, the strand passes through a liquid-filled U-shaped device, and emerges with a coating around its entire perimeter. Where capillary action can be

used to carry a coating around the strand, a kiss roll applicator may be used. In this

technique, the strand is coated when it "kisses" a liquid covered roller which is

rotating with or against the strand's direction of travel. In yet another embodiment,

the strand passes through an eyelet through which the coating is pumped. The eyelet

may have a clam-shell design to avoid the need for threading the strand through the

eyelet.

Figures 8A through 8G illustrate exemplary cross-sections of coated strands

which are producible in accordance with the above example. All cross-sections are

greatly exaggerated to permit demonstration of the point. In Figure 8A, the substrate

302 has a plasma-treated outer surface 303 surrounded by a coating layer 304. More

than one type of coating may be applied through repeated coating techniques. In

Figure 8B, the usually preferred embodiment, the first coating layer 304 and a

secondary coating 306 surround the core 302. In Figure 8C, the outer layer 306 is

disposed only partly around the first coating layer 304. In Figure 8D, the first

coating 304 and the secondary coating 306 are disposed only partly around core 302.

In Figure 8E, the coating layer 304 is only partly around the core 302 but the coating

306 is completely around the core 302.

Figure 8F illustrates exemplary cross-sections of rectangular strands. In

Figure 8F, the plasma-treated substrate 302, like in 7B, is coated with a first layer

304, such as a metal or polyacrylate, and a second layer, 306, such as a metal or

polyacrylate. In Figure 8G, like 7D, the substrate 302 is covered for a portion thereof by a first layer 304 and a second layer 306. Depending on the substrates

dimensions, the cross-section in Figure 8G can resemble that of a thin film.

In general, the coating is nonconformational. That is, it will tend to be self-

leveling and will not conform to the geometry of the substrate.

Figures 9 - 12 show alternative plasma treatment chambers and coating and

curing units.

Figure 9 shows a representative upper chamber, 126 and a representative

lower chamber, 127, to illustrate one treatment arrangement. In Figure 9, upper

chamber 126 has the hollow cathodes arrays 36 and 36, and lower chamber 127 has

focusing magnets 50. The arrangement of Figure 9 will plasma treat only the upper

surface 98 of a substrate 97 when it is relatively dense. For an open, less dense

substrate, like a web or open fabric, it may be possible to treat surfaces 98 and 99 at

one time.

If desired, additional hollow cathodes arrays 36 may be located in the adjacent

lower chamber and additional focusing magnets 50 may be located in the adjacent

upper chamber 126, to simultaneously treat upper surface 98 and lower surface 99.

Figure 9 does not show a gas feed connection for introducing gas to be ionized or

electrical connections linked to the cathodes as these connections will be known to

those skilled in the art as a matter of design choice.

Figure 10 shows a representative upper chamber 128 and a representative

lower chamber 129 in an arrangement for metal deposition. Lower chamber 129 has

resistively heated boats 171 and a supply of aluminum wire 173 on spool 175. As the wire 173 contacts the resistively heated boats 171, the wire is vaporized. It then

condenses on the lower surface 99. Alternatively, one can create a ceramic coating

by introducing oxygen in to chamber 129 to oxidize the aluminum and create

aluminum oxide (A1₂0₃).

Figure 11 shows a representative upper chamber 124 and a representative

lower chamber 125 for creating a monomer layer on surface 98. A monomer

vaporizer 180 creates a cloud of monomer vapor which will be deposited through

condensation on the upper surface 98. If desired, a vaporizer 180, shown in phantom

could be located as a mirror image in lower chamber 125.

Figure 12 shows a representative upper chamber 130 that has a bank 82 of

UN emitting lights that irradiate and cure the monomers on surface 98. Alternatively,

the radiation device can be one that emits an electron beam. If the substrate is treated

on both surfaces a second bank 190, as shown in phantom will be located in chamber

131. * * *

Claims

CLAIMSWe claim:

1. A method of modifying at least one characteristic of a substrate, the

method comprising the steps of:

providing a plasma treatment chamber;

generating a plasma in the chamber;

providing a means to focus the plasma within the chamber;

introducing the substrate into the chamber; and

reacting the plasma with a substrate surface.

2. The method of Claim 1 further comprising the step of providing a

hollow cathode as the plasma generator.

3. The method of Claim 1 wherein the focusing means is magnetic.

4. The method of Claim 1 wherein the focusing means comprises an

electromagnetic field generator.

5. The method of Claim 1 further comprising the step of coating the

plasma treated substrate.

6. The method of Claim 5 further comprising the step of providing a

means for curing the coating.

7. An apparatus for plasma treating a substrate, the apparatus comprising:

a housing having entry and exit positions, plasma generating and

plasma target sides, a substrate receiving channel therebetween and air locks at the

entry and exit positions for maintaining vacuum under operating conditions;

a hollow cathode plasma generator mounted on the plasma generating

side; and

a means for focusing the plasma at a surface of the substrate as it passes

through the channel.

8. The apparatus of Claim 7 wherein the plasma focusing means is located

on the plasma target side.

9. The apparatus of Claim 7 wherein the plasma focusing means is

magnetic.

10. The apparatus of Claim 7 wherein the focusing means comprises an

electromagnetic field generator.

11. An apparatus for modifying at least one surface characteristic of a

substrate, the apparatus comprising:

a housing having entry and exit positions, a plasma generating side, a

plasma target side, a channel therebetween for passing the substrate between the sides

of the housing when they are in an opposed relationship to each other and air locks

at the entry and exit positions for maintaining vacuum under operating conditions;

a hollow cathode plasma generator mounted on the plasma generating

side;

a means for focusing the plasma at the surface of the substrate to be

treated; and

means for coating the plasma treated substrate.

12. The apparatus of Claim 11 wherein the coating means comprises a

coating solution bath through which the substrate passes.

13. The apparatus of Claim 11 wherein the coating means comprises a

capillary drip system including:

a coating solution reservoir;

a delivery manifold in communication with the reservoir; and

a plurality of capillary tips for delivering the solution from the manifold

to the substrate.

14. The apparatus of claim 13 wherein the coating means further

comprises:

a roller having a plurality of grooves, equal in number to the plurality

of capillary tips for positioning substrate beneath one of the plurality of capillary tips.

15. The apparatus of Claim 11 further comprising means for curing the

coating.

16. A method of modifying at least one surface characteristic of a substrate,

the method comprising the steps of:

providing a plasma treatment chamber;

generating a plasma in the chamber;

providing a means to focus the plasma within the chamber;

introducing the substrate into the chamber;

reacting the plasma with a selected surface of the substrate; and

directly coating the plasma treated substrate.

17. The method of Claim 16 wherein the plasma generator is a hollow

cathode.

18. The method of Claim 16 wherein the coating deposited on the substrate

is an organic compound containing a double bond.

19. The method of Claim 16 wherein the coating is an acrylate.

20. The method of Claim 16 further comprising the steps of:

providing a means for curing the coating; and

curing the coating.

21. The method of Claim 20 wherein the coating is cured by radiation.

22. The method of claim 21 wherein the coating is cured by UV radiation.

23. The method of Claim 21 wherein the coating is cured by electron beam

radiation.

24. The method of Claim 16 wherein the coating is a metal condensate.

25. The method of Claim 16 wherein the coating is a ceramic condensate.

26. The method of Claim 16 wherein the coating is applied by vapor

deposition.

27. The method of Claim 26 wherein the coating is an acrylate.

28. A method of directly treating an extrudate, comprising the steps of:

providing a ductile material;

forcing the ductile material through a die;

providing a plasma treatment chamber;

generating a plasma in the chamber;

providing a means to focus a plasma within the chamber;

introducing the extrudate into the chamber; and

reacting the plasma with a selected surface of the extrudate.

29. The method of Claim 28 wherein the plasma generator is a hollow

cathode.

30. The method of Claim 28 further comprising the step of coating the

plasma treated substrate.

31. The method of Claim 28 further comprising the steps of:

providing a means for curing the coating; and

curing the coating.