WO1999058756A1

WO1999058756A1 - Structures and components thereof having a desired surface characteristic together with methods and apparatuses for producing the same

Info

Publication number: WO1999058756A1
Application number: PCT/US1999/010148
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: AU3892899A

Abstract

Methods and apparatus for plasma modifying a substrate are disclosed along with 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 -2- 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 mechanical properties, it is sometimes desired to have surface properties

which are contrary to these mechanical 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 -3- 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 of an apparatus in accordance with the invention

for use in treating large, continuous substrates.

Figures 2 through 5 depict individual portions of the apparatus of Figure 1

in more detail.

Figure 6 depicts an apparatus for treating an endless substrate, such as a

papermaking fabric, in accordance with the present invention. -4- Figure 7 illustrates depicts another variation of an apparauts for treating

industrial sized substrates, such as papermaking fabrics, with an accompanying

structural arrangement for supporting the apparatus.

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 mechamcal, thermal, or

chemical means or a combination thereof without braiding, weaving, or knitting.. -5- 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.

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 -6- 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 fragment, 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 -7- 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

II

^Rl C - OR⁴

\ /

C=C (I)

/ \

^R2 R

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 R\ 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 (π)

/ \ / \

R² _R3 _R5 _R6 where R¹, R², R\ 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. -8- 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. (See Table

1)

TABLE 1

R⁴ Surface Properties

-CH₂CH₂CH₂OCH₂CH₂CH₂OCH₂CH₂CH₂- Abrasion Resistance

~CH₂CH₂OCH₂CH₂OCH₂CH₂- Abrasion Resistance

-CH₂CH₂COOH Hydrophilicity

-CH₂CH₂OH Hydrophilicity

Formula I 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. -9-

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

O R²

II I

R¹CHCH₂OC-C=CH₂

I (HI)

O-C-C=CH₂

II I

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.

The formulation Sigma-MM-2116 has been developed to impart

hydrophobic/oleophobic characteristics and 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, Teflon-like, 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 -10- 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

resistance.

Figures 1-7 illustrate apparatuses for treatment of a substrate, such as a fabric,

belt or web. The apparatus 100 consists of a series of opposed entry and exit vacuum

chambers 103 and 105, 107 and 109, 111 and 113, and 115 and 117 flanking

opposed treatment chambers, 120 and 121, 122 and 123, 124 and 125, 126 and 127,

128 and 129, and 130 and 131. The flanking vacuum chambers provide a vacuum

between 1 and 10 torr. The inner flanking vacuum chambers provide a higher degree

of vacuum in a range between 10^"4 and 1 torr. The interior treatment chambers are

also under a vacuum. If desired, all of the chambers may be manifold connected and

the vacuum within each chamber controlled by a switching means. Plasma treatment

equipment may be located in the upper vacuum chambers or in the lower chambers

as desired. This makes it possible to treat only the upper surface 98, only the lower

surface 99 or both the upper and lower surfaces. As can be seen from Figure 1, the

treatment chambers are mounted on opposed rollers 140-169 which are in contact

with the substrate 97. The exterior rollers 140, 141, 160 and 161 for chambers 103,

105, 111 and 113 respectively are generally spaced apart by a distance which is less

than the fabric thickness. This causes an initial compression of the fabric and helps

to remove trapped air from the fabric. As the fabric enters a first chamber, it is -11- compressed between a first pair of large rollers, for instance 162 and 163, which

compress the fabric to almost its maximum density within the vacuum chamber. The

chamber support rollers 142, 143, 158 and 159 are set to this lower compressed

distance so as to retain the fabric in compression. The fabric may pass through an

additional pair of opposed rollers, such as 164 and 165, as it enters a second chamber

under greater vacuum. The fabric is then maintained in contact with rollers 144

through 157 at this compressed distance to retain as much vacuum as possible in the

treatment chamber(s). When the fabric reaches an exit position, it passes through a

first pair of rollers, such as 166 and 167, which are still at the lesser distance. The

fabric then passes through an additional pair of rollers, such as 158 and 159, after

which the fabric is permitted to begin relaxation before passing through the final

rollers 168, 169 and 160 and 161.

Figure 2 shows a representative upper chamber, 126 and a representative

lower chamber, 127, to illustrate one treatment arrangement. In Figure 2, upper

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

magnets 50. The arrangement of Figure 2 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 cathode 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 2 does not show a gas feed connection for introducing gas to be ionized or -12- 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 3 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 into chamber 129 to oxidize the aluminum and create

aluminum oxide (Al₂O₃).

Figure 4 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 5 shows a representative upper chamber 130 that has a bank 82 of U V

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

Figure 6 illustrates a second apparatus for treatment of a substrate 97. The

substrate is wound around two cylinders 190 and 192 of a type commonly used in

finishing industrial fabrics. In this embodiment there are again multiple chambers -13- 103, 107, 111, 115, 120, 122, 128, and 130 for various purposes as previously

described in connection with Figures 8 through 12. However, this configuration only

seeks to do single surface treatment at this location. In this embodiment, the original

fabric compression is achieved by an exterior roller 196 against roller 192. Assuming

a fabric moving from left to right as indicated by the arrow, the substrate 97 kept

compressed between rollers 160 and 192. A second large compression roller 166

acting against roller 192 is located in chamber 111. Once again the chamber support

rollers continue the compression of the substrate 97 against the opposed roller 192.

A similar arrangement is provided at the exit by rollers 162, 140, 194 and 192.

With reference to Figure 7, there is shown an illustrative embodiment of a

substrate treating apparatus which is particularly suitable for use with a papermaking

fabric. The apparatus 200 is shown as fragmented right portion thereof to recognize

the fact that such an apparatus may be required to be in excess of 10 meters (420

inches} wide. It is presently contemplated that the apparatus 200 would be mounted

in the fabric finishing area of the papermaking fabric manufacturing process. In such

an area, it is common to have a mounting block or foot 202 which moves in a track

or recess in a finishing apparatus. The mount 202 would preferably include a lifting

apparatus 204, such as a hydraulic cylinder to elevate the lower treatment array 206

to the desired height. The lower array 206 includes transverse rollers 208 and 210

which will contact the fabric when located in the desired position. In order to relieve

the strain on the elevation means 204, a support column 214 is provided with a

plurality of apertures 216 so that a pin may be inserted through an aperture 216 to -14- assist in maintaining a fixed position. The lower treatment array 206 may include a

plurality of treatment chambers within the area 212 or it may include a shielding

device which will assist in maintaining vacuum during treatment with the upper array

220. With respect to upper array 220, it includes a sleeve 222 which is dimensioned

to fit about the support 214. Sleeve 222 will assist in centering the upper array 220

so that the rollers 224 and 226 of upper array 220 will be opposed to the rollers 208

and 210 of the lower array 206. In areas where it is difficult to maintain opposed

roller alignment or positioning, it will be preferable to provide a sleeve for lower

array 206 so that support 214 may act as a centering device. The array 220 may

contain any of the previously described treatment chambers. At present, it is

contemplated that the array 220 will be raised by an overhead pragmatic crane to

allow location of a fabric between the array 206 and 220.

Example

Five samples of a papermaking press felt, of the type having a base fabric and

batt layers, were tightly mounted around a drum. Each sample was approximately 4

feet long and 12 inches wide. The drum was enclosed in a vacuum chamber, and all

samples were subjected to plasma treatment by rotating the drum for 30 minutes at

50 feet per minute (circumference speed) through a 10% argon/90% nitrogen mix

while exposed to 300 watts. After the plasma treatment, some samples were coated

with a surface deposition, by evaporation, of acrylate monomers followed by an

electron beam curing of the monomers. An acrylate monomer evaporator and an ^•15- electron beam gun were used to coat and cure the samples. One sample received a

post electron beam plasma treatment. Post plasma treatment was done in the same

manner as the initial preliminary plasma treatment.

TABLE 2

Sample Acrylate Coating Treatment

1 β-CEA:HDODA (l:l) Plasma-Acrylate

2 AUC: AA:HDODA (1:1:1) Plasma-Acrylate

3 FfDODA Plasma-Acrylate

4 None Plasma

5 β-CEA:HDODA (l:l) Plasma- Acrylate-PostAcrPlasma

The samples and their treatment are summarized in Table 2. In Table 2 the

abbreviations are as follows: β-CEA is β-carboxyethyl acrylate, FfDODA is

hexanediol diacrylate, AUC (RadCure Photomer 6210 fromRadCure, a division of

UCB Chemical Co.) is aliphatic urethane acrylate oligomer, and AA is acrylated

amine oligomer (RadCure Ebecryl 7190 from RadCure) .

The acrylate monomers in the evaporated mix are listed in the acrylate coating

column. The molar ratio of the monomers are shown in parentheses.

In the treatment column, "Plasma-Acrylate" indicates the sample underwent

plasma treatment followed by acrylate coating. "Plasma- Acrylate-PostAcrPlasma"

indicates the sample underwent plasma treatment, acrylate coating, and a second

plasma treatment. -16-

All five samples were tested for their ability to absorb water by placing a drop

of water on their surface layer and observing how quickly the drop was absorbed. All

five samples absorbed the water instantaneously upon contact whereas an untreated

control sample took several seconds to absorb the water.

TABLE 3

SAMPLE TIME TO WET TEST LIQUID #

(SEC)

1 5 1

2 1 1

3 6 2

4 <1 1

C 1 3

Four of the samples and the control were also tested for hydrophilicity using a version

of AATCC Test Method 118 modified to test for water repellency rather than oil

repellency. Test liquids #1 through #6, contain solutions of isopropanol and water

in ratios of (on a percentage by volume basis) 2:98, 5:95, 10:90, 20:80, 30:70 and

40:60 respectively. Beginning with the lowest number test liquid, drops were

carefully placed in several locations on the surface of the sample. If surface wetting

did not occur within 10 seconds, this was repeated with the next higher number liquid

until surface wetting occurred within 10 seconds (with the test liquid indicated in the

right hand column in Table 3). Results are shown in Table 3 (where "C" is the

untreated control). Test liquid #1 is the most waterlike and therefore hydrophilic.

Test liquid #6 is the least waterlike and therefore hydrophobia The results show that -17- the treated samples are substantially more hydrophilic than the untreated control.

Hydrophilicity is desirable in papermaking press fabrics because hydrophilic fabrics

have low resistence to flow allowing water to pass right through.

The samples were also tested under impulse drying conditions (see TABLES

4 and 5). Each sample was first plasma treated and then coated with a particular

coating. Sample 1 was coated with β-Carboxyethyl Acrylate (BCEA)/Hexandiol

Diacrylate (HDODA). Sample 2 was coated with Aliphatic Urethane Acrylate

Oligomer / Acrylated Amine Oligomer / HDODA. Sample 3 was coated with

Hexandiol Diacrylate (HDODA). Sample 4 was plasma treated, acrylate coated with

β-CEA/ HDODA (50:50) and then plasma treated again. Sample 5 was plasma

treated without subsequent coating.

High temperature felt conditioning trials were then conducted on the Beloit

MTS LD (Impulse Drying) simulator. Trial conditions of pressure (500 psi average),

NRT (35msec), and temperature (400F) were kept constant during the tests. These

testing conditions were chosen to typify the severe conditions the felt must survive

without a sheet in the nip during Impulse Drying operations.

The MTS LD simulator screening trial is conducted under the same conditions

for each felt candidate. Beloit "G" upper platen was used as the hot surface. A de-

ionized water-cooled bottom platen was used during felt conditioning; this keeps the

felt wet and the bottom platen cool during testing. The felt is conditioned for 50,000

cycles; at 2 cycles per second, with paper samples impulse dried at various cycle

increments. The paper sample and felt are impulse dried between the Beloit "G" -18- platen and a grooved bottom platen. Furnish used for the paper testing was a 38 gsm

C-LWC made on XPM#3 on 2/6/95, #38993. The handsheet tests are conducted at

certain established intervals by hand-feeding a sheet between the felt and the hot

platen. During the test the sheet is free to stick to either the felt, hot platen, both, or

not to either. During handsheet tests, the felt is kept essentially dry before any

impulse. Each sample was evaluated as shown in Tables 4 and 5.

TABLE 4

Sample Baseline 1 2 3 4 5

Stabilization Temperature 282F 282F 27 IF 27 IF 27 IF 270F

Caliper Drop @ 50 psi 0.34 0.39 0.38 0.38 0.41 0.41

Caliper Drop @ 300 psi 0.29 0.29 0.29 0.29 0.30 0.30

Surface Roughness Drop 0.66 0.71 0.69 0.55 0.67 0.71

CFM (start) 60.00 52.00 67.00 67.00 63.00 62.00

CFM (end) 4.00 4.00 4.00 4.00 4.00 4.00

Wt. Loss After 50,000 cycles 0.01 0.01 0.01 0.01 0.01 0.01

Water absorbed from handsheet 0.29 0.49 0.38 0.33 0.32 0.39

Solids out -6.00 -8.00 -4.00 -4.00 -4.00 -4.00

Sticking Factor 1—3 3.00 3.00 3.00 3.00 3.00

-19- TABLE 5

Sample Comments

Baseline Handsheet sticking to felt & platen first 30,000 cycles

1 Handsheet sticking to felt & platen first 30,000 cycles Handsheet sticking to felt after first 30,000 cycles Blistering throughout test. Not enough venting.

2 Sheet sticking to felt from start - heavy rewet.

MD shrinkage - 11%

No blistering/delamination.

3 Sheet sticking to felt from start - heavy rewet.

MD shrinkage - 10%

No blistering/delamination.

4 Sheet sticking to felt from start - heavy rewet.

MD shrinkage - 10%

No blistering/delamination.

Thin film on bottom platen after each conditioning increment.

5 Sheet sticking to felt from start - heavy rewet.

MD shrinkage - 10%

No blistering/delamination.

Thin film on bottom platen after each conditioning increment.

Definitions of terms used in Tables 4 and 5:

1) Stabilization temperature - the temperature the felt should reach without a

sheet in the nip.

2) Caliper drop - the percentage change in felt caliper during conditioning. A

Beloit C-Frame caliper-measuring apparatus was used to measure felt

thickness at 50 psi and at 300 psi.

3) Surface roughness - measurement of the caliper of a foil impression of the felt

surface. -20-

4) CFM - air permeability measurement in CFM/ft² using a portable Albany

permeability tester.

5) Water absorbed from handsheet - the amount of water being absorbed from

the handsheet during Impulse Drying. A weight decrease indicates that the

felt is densifying and is losing its dewatering capabilities.

6) Solids out - the average change of percent solids (ingoing solids was

controlled).

7) Sheet sticking factor - see Table 6

TABLE 6

Factor Description

_0_ Sheet not sticking at all

1 Sheet lifting with hot plate, but fell off by itself

_2_ Sheet clinging to hot plate, just have to nudge sheet off

_3_ Sheet sticking harder to hot plate, may have to peel sheet off, no "picking"

4 Sheet sticking hard to hot plate, have to peel sheet off, may be some sheet "picking"

Sheet sticking very hard to hot plate, hard to peel sheet off platen, sheet "picking"

Sheet sticking occurred in each of the fabrics, and may be due to any of a number of

factors unrelated to the plasma treatment. More importantly, none of the treated

samples showed signs of surface fusing as was seen in untreated fabrics. This result

is a positive indication that the plasma treatment altered the exterior surface

characteristics of the sample fabrics as intended.

Claims

-21- CLAIMS

1. A method of modifying at least one characteristic of a fabric, 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 fabric into the chamber; and

reacting the plasma with a fabric 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 is comprised of an

electromagnetic field generator.

5. The method of Claim 1 wherein the fabric is braided.

The method of Claim 1 wherein the fabric is woven.

7. The method of Claim 1 wherein the fabric is knitted. -22-

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

plasma treated substrate.

9. The method of Claim 8 further comprising the steps of:

providing means for curing the coating; and

curing the coating.

10. A fabric comprising a plurality of inherent chemical and physical

surface properties and at least one property modified by a plasma treatment .

11. The fabric of Claim 10 wherein the fabric is produced by a process

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 fabric into the chamber; and

reacting the plasma with a fabric surface.

12. The method of Claim 11 further comprising the step of providing a

hollow cathode as the plasma generator. -23-

13. The process of Claim 11 wherein the modification process further

comprises the step of coating the plasma treated fabric.

14. A method of modifying at least one surface characteristic of a fabric,

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 fabric into the chamber; and

reacting the plasma with a fabric surface; and

directly coating the plasma treated substrate with a 100% solids

coating.

15. The method of Claim 14 further comprising the step of providing a

hollow cathode as the plasma generator.

16. The method of Claim 14 wherein the coating deposited on the substrate

is an organic compound containing a double bond.

17. The method of Claim 14 wherein the coating is an acrylate.

18. The method of Claim 14 further comprising the steps of: -24- providing means for curing the coating; and

curing the coating.

19. The method of Claim 18 wherein the curing means is radiation.

20. The method of claim 19 wherein the curing means is UV radiation.

21. The method of Claim 19 wherein the curing means is electron beam

radiation.

22. The method of Claim 14 wherein the coating is a metal condensate.

23. The method of Claim 14 wherein the coating is a ceramic condensate.

24. The method of Claim 14 wherein the coating is a vapor deposited

acrylate.

25. An apparatus for treatment of a papermaker's fabric comprising:

opposed upper and lower treatment chambers;

a pair of spaced apart base supports for securing the lower treatment

chamber at a predetermined height;

a pair of vertical supports, for mounting the upper chamber; and -25- at least one plasma generating means for generating plasma in a selected one of the

upper and lower treatment chambers.

26. The apparatus of Claim 25 including;

a plurality of paired upper and lower treatment chambers.

27. An apparatus for plasma treatment of a papermaking fabric comprising :

a fabric support means for supporting the fabric at a predetermined

position;

a plasma treatment means secured in a position adjacent to a surface of

the fabric; and

plasma generating means positioned within the plasma treatment

means.

28. A papermaker's fabric having sheet side and machine side surfaces

wherein at least one surface has been plasma treated and coated.

29. The fabric of claim 28 wherein the coating is an acrylate.

30 The fabric of claim 29 wherein the acrylate is radiation cured.

31. The fabric of claim 28 wherein the coating in metallic condensate. -26-

32. The fabric of claim 28 wherein the coating is a ceramic condensate.