Note: Descriptions are shown in the official language in which they were submitted.
- - 21 87055
ROLL8 HAVING PT~T~ T~ COATING~,
A MBT~OD FOR APPLYING A pT~T.~^T~ COATING TO A ROLL,
AND A ~FT~OD OF TRAN8PORTING a VI8CID ~B
FIBLD OF T~ INV D TION
The field of this invention is finishp~ coatings for rolls
used in industrial applications, and more particularly, rolls
having release coatings, methods for making such coatings, and
L0 methods for coating rolls.
The field of this invention also relates to machine elements
used to transport and process a viscid web and, a method for
transporting such a web.
BAC~GROUND OF THF INVB~TION
Covered rolls are used industrially in demanding
environments where they are subjected to high dynamic loads and
temperatures. Covered rolls are used not only for transporting
the material under process, which is in the form of a travelling
web, but also for processing the web itself into a finished
product.
Bowed rolls are a particular kind of machine element used to
correct distortions and similar problems by distributing lateral
tension evenly across a travelling sheet material. For example,
bowed rolls are used to spread out or ~Yp~n~ the travelling web
for the purposes of maintaining width, eliminating wrinkles,
eliminating baggy centers or slack edges. Bowed rolls are also
2 1 87~5~
used to control felts by maintaining their width, openness and
seams, and to eliminate interleaving of individual slit webs on
winders.
Press rolls are yet another kind of machine element used in
nip presses. Press rolls ~Gce~s the travelling web by
compressing the web at the nip. Typically this is done to remove
liquids from the web, e.g., dewatering presses, or to eliminate
high and low spots in a finished product, e.g., finish nip
presses.
United States Patent No. 2,393,191 issued to John
Robertson, discloses how the transfer of sticky viscid materials
onto the roll and ultimately into the ball bearings causes rapid
gumming of the races and failure of the roll. Robertson also
discloses an PYpAn~r roll having a rubber cover which allows
delicate web sheet fabrics to be ~oce~ce~ without tearing.
Bowed rolls with elastomeric sleeves and press rolls with
compliant elastomeric covers are machine elements used in
applications where the web under ~o~ess is coated with surface
enhancing materials that are tacky and sub~ect to transfer to any
surface in contact with the web. In general, the transfer of
viscid materials from the web to the surface of the roll results
in the degradation of the roll's surface and the web's surface.
Therefore, it is desirable to have such rolls coated with a
material that is, inter alia, self-cl~An;~g~ i.e., has high
release properties. Rolls covered with release coatings prevent
excessive sticking which ultimately allows the "release" of the
- 21 87~5
viscid material from the roll surface.
Industrial web processing applications in the paper, textile
and plastics industries, are enhanced through the use of covered
rolls with surfaces that have high resistance to abrasion,
optimum release properties, flexibility and low coefficients of
friction. At present, industrial needs are met by rolls
having surfaces treated with epoxies, ure~hAnec, Teflon polymers,
silicones or waxes. Epoxies and urethanes have desirable
abrasion resistance properties, but lack the desired high
release properties and low coefficients of friction. Teflon
polymers and silicones have high release properties and low
coefficients of friction, but lack high abrasion resistance
qualities. Waxes and silicone polish coatings do not last very
long.
lS The flexing surfaces of bowed rolls and press rolls must
have good coating release properties, low coefficients of
friction, high flexibility, and good abrasion resistance. The
materials that are presently being used to cover these machine
elements are Teflon shrink tubing, sintered Teflon polymer
coatings and silicones. These coatings are eYpensive, subject
to eYceccive wear rates, and exhibit poor adhesion to
substrates. Often, they are rendered useless by minor cut
damage from the mech~nical removal of the web coating material
which adheres to the Teflon polymer, and must be removed
manually. Thus, the need exists to develop rolls with coatings
that are harder, have lower coefficients of friction and
21 87~55
improved release properties, with lower wear rates than present
day covered rolls.
~MMARY OF TRD IN~EN~ION
The problems caused by prior art coatings, are reduced in
accordance with the present invention through the application of
a release coating to the surface of a roll or machine element.
The coating of the present invention is harder, and has a lower
coefficient of friction, better release properties and wear
L0 rates than those of Teflon polymers.
In accordance with this invention, it has been found that a
liquid solution of varying percentages of 2-Phenoxyethyl
Acrylate, Tetraethylene Glycol Diacrylate, Isobutyl Benzoin
Ether, l,6 Hexanediol Diacrylate, Cycloaliphatic Bis A Epoxide,
Polyurethane Acrylate, Methyl Methacrylate, Polysiloxane and
other Acrylics, Tertiary Amines, Epoxidized Novolac, Fluorinated
Alkyloxylate, Electromagnetic Wave Energy sensitive
Photoinitiators, and Electromagnetic Energy absorbers, composed
of 8% to 24% by weight of polysiloxane will produce a liquid
phase reaction of the polysiloxane and acrylated epoxy creating
a susp~n~eA precipitate of Epoxidized polysiloxane in a
predominantly Polyurethane acrylate and monomer solution.
It is an object of the present invention to provide a
coating that can be applied to metallic or nonmetallic surfaces.
Another object of this invention is to provide a method of
coating a machine element with a release coating.
21 87~55
Another object of this invention is to provide a method of
curing the coated surface of a machine element with
ElectromagnetiC Wave Energy.
Another object of this invention is to provide a method of
curing the coated surface of a machine element with Electron Beam
Bombardment.
Another object of this invention is to provide a method of
curing the coated surface of a machine element with Ultraviolet
Light Radiation.
Another object of the present invention is to provide a
coating for a machine element that is hard enough to be abrasion
resistant while having high release ~LG~e~Lies.
Another object of the present invention is to provide a
coating for a machine element that is abrasion resistant while
having a low coefficient of friction.
Another object of the present invention is to provide a
coating for a machine element that has im~oved release
properties.
Another object of the present invention is to provide a
coating for a machine element that has lower wear rates than
prior art coatings.
Another object of the present invention is to provide a
coating for a machine element that has wear rates that are lower
than that of a ~eflon polymer.
Another object of the present invention is to provide a
coating for a machine element that is abrasion resistant.
21 87~5~
Another object of the present invention is to provide a
coating for a machine element that is abrasion resistant yet
complaint enough to be applied to machine elements requiring
flexible surfaces.
Another object of the present invention is to manufacture
covered machine elements having release coatings applied as a
liquid composition of 100% solids and/or solvent th~nne~ solids.
Another object of the present invention is to apply a
release coating to machine elements located on site, i.e., at the
user's facility.
Another object of the present invention is to provide a new
and improved roll having better release properties.
Another object of the present invention is to provide an
improved method of processing a viscid web using rolls with
L5 improved release properties.
Another object of the present invention i8 a method of
applying a release coating utilizing a minimum of solvents.
2 1 8iû5~
-
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view illustrating the application
of the adhesive coating to a machine element in accordance with
the present invention.
FIG. 2 is a perspective view illustrating the step of
curing of a final release layer on a machine element to form a
release coating in accordance with the present invention.
FIG. 3 is a sectional view illustrating a machine element
covered with the release coating in accordance with the present
10 invention having a multiplicity of release layers applied over an
adhesive substrate layer.
FIG. 4A is a sectional view illustrating a nip press havinq
a lower cylindrical roll covered with the release coating of t~e
press invention.
FIG. 4B is an ~xrAn~e~ sectional view of the encircled are~3
in FIG. 4A illustrating how the flexible release coating of the
present invention can withstand a nip deformation.
FIG. 5A is a plan view of a bowed roll illustrating an
elastomeric roll cover coated with a release coating in
accordance with the present invention.
FIG. 5B is partially sectioned vLew of a bowed roll
illustrating the adhesive and multiple release layers in
accordance with the release coating of the present invention.
FIG. 6A is a side view illustrating a bowed roll covered
with the release coating in accordance with the present
invention.
21 87055
FIG. 6B is a diagram illustrating the placement of bowed
rolls in processing a viscid web in accordance with the present
invention.
FIG. 7 is a perspective view illustrating the application
of a release coating to a machine element in accordance with the
specific example of the present invention.
FIG. 8 is a diagram illustrating how a bowed roll located in
spaced relationship with press rolls and a size bath are used to
coat paper in the paper making industry.
FIG. 9 is a diagram illustrating a system of machine
elements used to transport a viscid web in the paper making
industry.
FIG. lO is a diagram illustrating a coating process in the
paper making industry.
FIG. ll is a diagram illustrating a system of machine
elements used to transport and laminate two viscid web~ in a
paper making laminating process.
2 1 870~5
D138CRIPTION OF T}ll~ PRISFBRRI~D 13~1BODIN~T
At the outset, a roll having a release coating, the
associated method for making the coating and applying it to the
roll, and a method for transporting a viscid web, are described
in their broadest overall aspects with a more detailed
description following.
In its broadest overall aspects, the release coating of the
present invention is a composite coating, comprising multiple
layers of release coating applied over an initial adhesive layer.
In manufacturing the initial adhesive layer of the present
invention, a liquid composition of 100% solids and/or solvent
thinned solids is prepared from what is essentially acrylated
epoxy, acrylated urethane and acrylated monomer. Then the
adhesive mix is applied to form an initial layer on the machine
element utilizing conventional methods, such as a sprayer.
In its broadest overall aspects, the release coating of the
present invention comprises the addition of acrylated
polysiloxane to the adhesive mix which produces a liguid phase
reaction of the acrylated polysiloxane and acrylated epoxy,
thereby creating a susren~e~ precipitate of epoxidized
polysiloxane in a predominantly polyurethane acrylate and
acrylated monomer solution. Thus, the release coating is a
liquid composition of 100% solids and/or solvent th i nn^~ solids
prepared to form a pre-reacted solution that is essentially an
epoxidized-siloxane matrix in acrylated urethane and acrylated
monomer. Then the pre-reacted solution is applied over the
2 1 87055
,
adhesive layer on the machine element utilizing conventional
methods, such as a sprayer.
The relea~e coating, including the initial adhesive coating,
of the present invention can be applied to machine elements
located at end-users' facilities, thus reducing manufacturing
costs and facilitating emergency repairs. The adhesive and
release layers can either be prepared CO~ LeI1~1Y in separate
mixing vats or consecutively by A~ i n~ the acrylated polysiloxane
subsequent to the application of the initial adhesive layer.
10The adhesive and pre-reacted release coatings can be applied
to flexible or rigid substrates, such as, bowed rolls, press
rolls or carrying rolls. Through the addition of photoinitiators,
both the adhesive and release coatings can be cured using
Electromagnetic Wave Energy in the wave lengths ranging from
15about 5500 A. through 006 A, i.e., long wave ultraviolet down to
short wave gamma rays. Alternatively, Electron Beam Bombardment
can be used to cure the coatings without the use of
photoinitiators.
T~RT~C 1 and 2 summarize the chemical ingredients used to
create the liquid oligomers for the adhesive and release coating
layers, Le ~e~ively. As used througho~t this specification and
the claims, all percentages are by weight unless otherwise
specified.
The chemicals listed in TABLE 1 are mixed together to make
the solution for the initial adhesive coat in the ~Lo~G~ions as
indicated. Each of the ingredients can be varied as indicated
21 87~55
~ by the range of percentage amounts in TABLES 1 and 2. However,
any increase of one ingredient must be compensated by a
COLLe~On~;n~ decrease in other components.
TABLE 1
Adhesive Coating Chemical Composition By Weight Percentage
Ingredient Range
Acrylated Monomer 35.6-59.4
Acrylated Polyurethane 14-39
Acrylated Epoxy 11-27
Free Radical Photoinitiator 2-6
2 1 87~5~
TABLE 2
Release Coating Chemical Composition By Weight Percentage
Ingredient Range
Acrylated monomer 28-52
Acrylated polyurethane 10-35
Acrylated epoxy 9-26
Polysiloxane 8-24
Cationic Photoinitiator 1-3
Free Radical Photoinitiator 1-5
Generally, 2 Phenoxyethyl Acrylate and Tetraethylene Glycol
Diacrylate and 1,6 Hexanediol Diacrylate are polyacrylates that
comprise the acrylated monomer. Cycloaliphatic Bia A epoxy
diacrylate is an example of a commonly used acrylated epoxy.
Typically, Urethane Diacrylate is combined with 1,6 ~Y~ne~i
Diacrylate to lower viscosity in the acrylated polyurethane.
Isobutyl Benzoin Ether is an example of a commonly used free
radical initiator, while a Triarylsulfonium Hexaflouroantimonate
salt is commonly used as a cationic photoinitiator.
Other equivalent ingredients can be used to augment or
substitute the ingredients listed ~ABT~S 1 and 2. Epoxidized
Novolac is an alternative epoxy which imparts further abrasion
resistance and hardness to the final product, if so desired, as
12
21 87~55
for example in a press roll. Tertiary amines are additive
adjuncts to photoinitiators which extend the curing beyond the
Ultraviolet Cure Phase. A Methacrylate, such as
Glycidylmethacrylate, for example, can be used as an alternative
highly reactive monomer, and when added, Flourinated Alkyloxylate
imparts additional release properties to the coatings.
In general, to manufacture a coated machine element of the
present invention, 9 to 26 by percentage weight acrylated epoxy,
10 to 35 by percentage weight acrylated urethane, 8 to 24 by
weight acrylated polysiloxane, 28 to 52 by percentage weight
acrylated monomer, and 2 to 8 by percentage weight of cationic
and free radical photoinitiators are initially mixed together to
form a mixture of liquid oligomers in a mixing vat.
In its broadest overall terms, the release coating of the
present invention comprises oligomers of acrylated epoxy,
acrylated urethane, acrylated siloxane and acrylated monomer.
Ultimately, it is the acrylated epoxy and acrylated urethane
components which provide abrasion resistance properties to the
coating while the acrylated urethane and acrylated monomer
components add compliance and flexibility. The epoxidized
siloxane precipitate further imparts haL~,~s3 and high release
o~e~ie~ to the coating.
Photoinitiators are added to the oligomers to cross-link the
pre-reacted solution upon the application of Electromagnetic
Energy. Electromagnetic Radiation of a machine element covered
with the release coating of the present invention, causes the
13
21 87~5~
photoinitiators to generate free radicals and cationic particles
which initiat~ the formation of cross-linking bonds among the
polymers and the siloxane. Several different kinds and
combinations of photoinitiators can be used as described in the
text, "Radiation Curing Science and Technology," Edited by S.
Peter Papas, (1992 Plenum Press), the teachings of which are
hereby incG~GLated by reference.
FIG.l illustrates how the adhesive coating of the present
invention is applied to a roll 10 mounted rotatably in bearings
11 and 12. Arrow 13 indicates the direction of roll 10, which is
arbitrary. A traverse carriage 1 travels back and forth
alongside roll 10. For ~ oses of illustration, traverse
carriage 1 i8 shown moving in the direction of arrow 2. M;Ying
vessel 3 which contains the oligomers comprising the adhesive
coating, and ultraviolet lamps 6 are mounted on top of traverse
carriage 1. Sprayhead 4 applies liquid adhesive coating 5 to coat
roll 10 to form a first layer 14 for cllh-qquent ho~ g of
additional release coating layers thereto. Ultra-violet lamps 6
radiate long wave-length Electromagnetic E1.eLYY 7 to effect a
partial cure of the adhesive layer 14. This create~ good
adhesion between the initlal adhesive layer 14 and roll 10, and
provides a partially reacted reactive film 15 on the outer
surface for ~-lh-qquent bonding with additional layer~ of release
coating. `
The pre-reacted liquid oligomer miYture comprising the
release coating is applied in the same manner as with the
14
21 87~5
adhesive coating. Similar to FIG. 1, FIG. 2 shows how a roll lo
of the ~ t invention is finally cured with ultraviolet lamps
5 which radiate Electromagnetic Wave Energy 6. Arrow 13
indicates the rotational direction of roll 10, which is
arbitrary. FIG. 2 further shows symbolically how final layer 16
is cured to form a fini ~h~ release coating 17 which is a matrix
com~ of hard sites of cross-linked Epoxidized Polysiloxane
Acrylate dispersed in a flexible lower modulus binder of cross-
linked polyurethane acrylate and acrylated monomer.
Electromagnetic Wave Energy trAnspArent reinforcing fillers
(not shown) may be used to increase individual coating film
thic~ness and reduce production costs.
FIG. 3 shows one embodiment of the ~L~-ent invention is a
cylindrical machine element covered with multilayers of release
coating. Metal roll 10 is coated with an initial adhesive
layer 11 that has been partially cured. This is followed by the
application of multiple layers of release coating con~A~n1ng
polysiloxane, layers 12 through 16, until a flexible, abrasion
resistant release layer of desired thic~nea~ is formed.
With respect to FIGS. 1-3, the final coating comprised of
all layers i~ cured with more intense and shorter wave length
energy. ~ hout the application ~ t-^, multiple coating
layers and multiple frequencies of wave energy are employed to
cure the coatings in order to achieve optimum adhesion to
substrates combined with optimum release, flexibility, hardness,
low friction, and abrasion resistance of coatings.
21 870~5
The degree of flexibility or rigidity of the cured coating
can be cofl~rolled by the percentages of acrylated epoxy and
acrylated urethane used in the solutions. The reacted liquid
phase of the coating contains 1-4% of a combination of free
radical and cationic particle generating photo-initiators which
react with electromagnetic wave energy (e.g., ultraviolet light)
to effect a hard cure of the liquid coating.
With further reference to FIGS. 1-3, the initial adhesive
coat 11 is composed of acrylated polyurethane, acrylated epoxy
and acrylated monomers. The subsequent additional multiple
layers, layers 12-16, contain the epoxidized polysiloxane
precipitate matrix susp~n~ in polyurethane acrylate and
acrylated monomer. This combination provide~ extremely good
adhesion to substrates combined with a thick multi-layered
coating with good hardness, and release properties throughout
the depth of the coating, instead of the poorly adhered silicone
rich surface which results from small additions of polysiloxane,
0.5-2% by weight for example, and which does not last long in a
web processing application.
FIGS. 4A and 4B show a nip press 10 having upper and lower
cylindrical machine elements 1 and 2 respectively. The lower
machine element 2 is coated with a flexible release coating 4 of
the present invention. (For illustrative ~ , the
travelling web or sheet under ~GCe3S is not shown.) FIG. 4B,
which is an enlargement of encircled area 3 in FIG. 4A, show~
lower machine element 2 coated with the release coating of the
21 87055
present invention comprising initial adhesive layer 11 and
multiple layers of release coating 16 which have been applied as
described above. FIG. 4B also shows how the release coating of
the present invention must have enough flexibility to withstand a
nip deformation 20.
FIG. 5A shows generally how a bowed roll 10 consists of
three basic elements. A non-rotating axle 12 that is curved to
provide the degree of bow required for a specific application. A
plurality of specially designed ball bearing assemblies 14
mounted on axle 12 so that the outer races (not shown) of ball
bearing assemblies 14 are free to turn, while inner races of the
ball bearing assemblies (not shown) are held stationary on axle
12. With further reference to FIG SA, outer shell 15, or spool
as commonly referred to in the art, is affixed to the outer race
of each bearing assembly 14. A special elastomeric sleeve 18
made out of flexible rubber is assembled over the outer shells 15
of ball bearing assemblies 14. Bowed roll 10 has concave side 26
and convex side 28 with an apex shown approximately by arrow 30.
Although not shown, bowed roll 10 is mounted in special mounting
brackets which allow the roll to be mounted at any angle to vary
the location of the roll's apex 30 with ~e~ye~ to the traveling
web under ~L oce_3 .
In operation, flexible sleeve 18 YpAn~ with rotation from
the concave side 26 of eur ved axle 12 to the co~.vex side 28. The
bowed roll is set so the web approaches the roll on concave side
26 and leaves on convex side 28. In this way the web is spread
- 2 1 870~5
out in the cross machine direction. Setting of the bow direction
is easily accomplished by rotating axle 12 in special mounting
brackets, (not shown).
FIG. 5B is a partial cutaway of bowed roll 10 of the present
invention which shows a flexible sleeve 18 covered with an
adhesive layer 20 and a multiplicity of release layers 21-25
according to the present invention.
Although not shown, bowed rolls without elastomeric sleeves
may have each outer shell 15 of each individual bearing assembly
14 covered with the coating of the present invention.
FIG. 6A is a side view of a bowed roll covered with the
release coating of the present invention. FIG. 6B and phantom
lines 12 show how bowed roll 10 may be located between guide
rolls, lead-in 30 and lead-out 32, re~e~ively, to eYpAn~
travelling web 34. The spreA~in~ of travelling web 34, (or
felt), starts when the web 34 leaves lead-in roll 30 which is
directly before bowed roll 10. As the web 34 leaves bowed roll
10, spreA~ing is complete. To prevent the web's tenAency of
reverting back to its original state, lead-out roll 32 is
proximally located after bowed roll 10. The closer bowed roll
10 is to the next roll in process, the better the job of "locking
in" the spr~AA~n~ that is accomplished. Also by varying the
configuration of bowed roll 10, web 34 can be spread evenly
from the center to both outside edges of the roll, or spread more
at the center than the edges to ~G~Lect baggy centers, or more at
the edges to correct slacking edges.
18
2 1 87055
The present invention is further illustrated by the
following non-limiting example.
In this specific example, the adhesive and release coatings,
are comprised of the solutions t~bulAted by percentage weight in
TABLES 3 and 4, respectively. As a corollary to TABLE 4 and as
used throughout this specification and claims, TABLE 5 lists the
various chemicals of TABLE 4 with their average molecular weights
and chemical structures using Lewis structures as is known in the
art. Where applicable, commonly used acronyms are also listed in
lo parenthesis.
19
21 87055
TABLE 3, (SPECIFIC EXAMPLE)
Adhesive Coating Chemical Composition By Weight Percentage
Ingredient %
2 Phenoxyethyl Acrylate 44
Tetraethylene Glycol Diacrylate 4.4
1,6 Hexanediol Diacrylate 20
Cycloaliphatic Bis A Epoxy Diacrylate 20
Polyurethane Diacrylate 6
L0 Isobutyl Benzoin Ether 5.6
21 87055
TABLE 4, (SY~ 1C EXAMPLE)
Release Coating Chemical Composition By Weight Percentage
Ingredient %
2 Phenoxyethyl Acrylate 36
Tetraethylene Glycol Diacrylate 3
1,6 Hexanediol Diacrylate 16
Cycloaliphatic Bis A Epoxy Diacrylate 16
Polyurethane Diacrylate 5
Polysiloxane 16
(Poly)Methoxy(Neth)acrylate Siloxane
Triarylsulfonium Hexaflouroantimonate 3
Isobutyl Benzoin Ether 5
21 87055
-
TABLE 5
AVQrage Mol-cular Weight (AMW) and Chemical StructurQ
2 Phenoxyethyl Acrylate, (2-PEA)
AMM: 192
~o_ ~_f _o_c_ CN-CNz
H _ 2
TetraethylQn- Glycol Diacrylat~, (TEGDA)
AMM: 302
O H H H H H H O
CH2-~CH--C--O--C--C--O----C--C--O-- C--C--O--C--CH--CH2
H H H ~ _ 2 H H
1,6 ReY~re~tol Diacrylat-, (HDODA)
AMM: 226
CH2 -CH- C -O ~ O - C - CH CH2
_ H - 6 H
2 1 87055
TABLE 5, (CC~.. . lNU~SV)
Averag~ Mol~ Ar Weight (AMM) and Chemical Structure
cycloaliphatic Big A Epoxy Diacrylate;
AMM: 525 + 252, (BLEND/MIXTURE)
OH ~ OH
CH2~CH-l-O-CH2-cH-cH2-o ~ c ~ o-cH2-cH-cH2-o-c-cH=cH2
O O
0 ~ ~
CH2--o--
(Poly)urethane Diacrylate
AMM: 1500
_ _
CH2=CH-C-- -O--C4~0-1CI-N~I--~cH2~NH--C-- O- I_CH=CH2
O ~ . O _4 O
2 1 87~5
TAB~E 5, (CON~l~u~.~)
Average Molecular Weight (AMW) and Chemical Structure
(Poly)Methoxy(Meth)acrylate Siloxane
AMW: 244
H3C1 11
H2C - C - C -0 - (CH2)3 - Si - (0-CH3)3
Triarylsulfonium Hexaflouroantimonat-; AMW: 607 + 1028
SbF6 +S ~ ~ SbF6 +S ~ ~ S+ SbF6
15 ~ ~ ~
Isobutyl Benzoin Eth-r, (IBBE); AMW: 268;
IC4Hg
~CN-90~
24
21 87055
The solutions which comprise the adhesive and release
coatings, respectively, are mixed in separate mixing vessels
for lS minutes before use and continuously thereafter, throughout
the application of the coating to the machine element. Both
coating materials, adhesive and release coating solutions, are
held at elevated temperature, preferably on the order of about
150F, and are continuously-mixed in their respective pressure
vessels, preferably at a mixing speed of 200 rpm. The
preferred cationic photoinitiator is Triarylsulfonium
Hexaflouroantimonate and the preferred Free Radical
Photoinitiator is Isobutyl Benzoin Ether.
With reference to FIG. 7, roll 1 is mounted rotatably in
bearings 2 and 3. The adhesive and release coating chemical
compositions of Tables 3 and 4 are contAine~ in reservoirs 5 and
6 respectively having sprayheads 7 and 8 respectively and
supported on a traversing carriage 11. Curing energy S~ULCe_ 9
and 10 are mounted on both sides of spray heads 7 and 8 to allow
coating and curing in both traversing directions. The spray
application system is composed of low pressure, pressurized
liquid feed vessel and a high volume head applicator gun.
In this specific example and with further reference to FIG.
7, the adhesive coating admixture, (TABLE 3), is applied with a
gun pressure of 50 psi from mixing vessel 5 through sprayhead 7
to form an initial substrate layer on the surface of the
rotating roll with a film thickness of approximately .003".
Both coating materials, adhesive and release coating solutions,
- ` 21 87(~55
are held at elevated temperature, preferably on the order of
about 150F, and are continuously-mixed in their respective
pressure ve~sel~, 7 and 8, preferably at a mixing speed of 200
rpm. As indicated by arrow 15, the rotational surface speed of
roll 1 is approximately 30 feet per minute while the speed of
carriage traverse 11 varies with the diameter of roll 1. In this
specific example, a roll having a diameter of 7" requires the
traverse speed to be 60" per minute. The adhesive layer
application starts at end 20 of roll 1 and procee~c beyond the
lo end 30 while following curing energy source 9 is activated to
effect a partial cure of the applied coating layer. Each energy
source 9 and 10 consists of 12" long forllc~ ultraviolet lamps
that deliver 450 watts per inch of lamp length.
Then the second coating layer which is the first release
layer is applied over the initial adhesive layer in the
opposite direction from end 30 to end 20, using second
traversing energy source 10 to partially cure that layer.
Traversing from end to end, the procedure of applying additional
layers of the release coating is repeated until a desired coating
thickness of .060" is applied and partially cured. After
applying the final layer of release coating, the carriage
traverse speed iQ reduced to 20~ per minute and both curing
energy sources 9 and 10 are used to increase radiation energy per
square inch of coating by a factor of six to complete the radiant
energy curing of the coating. Further post cure is accomplished
by moisture, and room temperature thermal curing for several
26
2 1 87055
days. The over spray is removed from the air through a filtered
exhaust system.
The release coating manufactured in accordance with the
above has the properties indicated in TABLES 5 ~ 6.
TABLE 5
Release values in pounds per inch of bond line using
Scotch brand No. 230 3M Drafting and Universal Brand No.
51301 Masking Tape.
3M 230 Universal 51301
W Release Coating .08 .25
Teflon polymer Tube .11 .38
TABLE 6
Coefficient of Friction of Kraft Paper on Coating Surface
W Release Coating .07
Teflon Polymer Tube .09
This coating can also be applied to rolls that are installed
in process machines located at end users production facilities
using transportable portable application and over spray
accumulating filtered exhaust systems.
Rolls having release coatings in accordance with the present
invention are advantageously employed in mills for making sized,
27
2 1 87055
filled and coated paper. Referring to FIG. 8, a process is shown
diagrammatically for coating paper including press and bowed rolls
covered with the release coating of the present invention. As
shown in FIG 8, web 1 from the direction indicated by arrow 2
enters size bath 3 cont~in;ng viscid liquid coating 4. As Web 1
is completely coated it is proc~ss ~ under and over several
carrying rolls 5a-5c respectively, and pACceA through nip press 6
comprised of press rolls 7a and 7b. Then web 1 is spread by
bowed roll 8 and carrying roll 9 prior to the removal of moisture
and curing by heated roll 10 rotating in the direction indicated
by arrow 11. Arrow 12 and circles 13 and 14, represent bowed
roll 8 and form a symbol well known in the art used to indicate
bow direction. This conventional symbol of a double circled arrow
is used throughout FIGS. 8 through 11. With specific reference to
FIG. 8, the double circled arrow symbolically indicates bow
direction from side 13 to apex 14 of bowed roll 8. As known in
the art, the higher the apex 14 with respect to side 13,
indicated by arrow 12 being rotated into web 1, the greater the
amount of spreading to eliminate baggy centers. Conversely, as
apex 14 of bowed roll 8, (or arrow 12), is rotated away from web
1, the greater the degree of spreading towards the edges of the
web 1 to eliminate slacking edges. When the release coating of
the present invention is applied to the machine elements described
above, the travelling web 1 does not stick to the various roll
surfaces.
FIG. 9 shows diagrammatically how feed roll 1 supplies web 2
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over carrying rolls 3a and 3b in the direction shown by arrows 4a,
4b and 4c. Bowed roll 5a covered with the release coating of the
present invention, is located before size press 6 and maintains
web 2 under even crosswise tension before saturation with viscid
matter. Bowed rolls 5b and 5c are covered with the release
coating of the present invention, and in conjunction with drier
rolls 7a, 7b and 7c, are used to eliminate wet wrinkles and
control baggy centers and slack edges. FIG. 10 illustrates
diagrammatically how web 1 travelling in the direction indicated
by arrows 2a and 2b passes over carrying roll 3, bowed roll 4 and
through coating station 5 comprising press rolls 6a and 6b, and
coating bath 7 which contains viscid matter 8. Bowed roll 4 which
is covered with the release coating of the present invention, is
located ahead of a coating station to eliminate wrinkles.
Although not shown, bowed roll 4 can be alternatively located
after the coating station. FIG. 11 illustrates the lamination of
sheets 1 and 2 and shows how bowed rolls 3 and 4 and carrying
rolls 5, 6, 7 and 8, covered with the release coating of the
present invention, can be arranged to keep sheets 1 and 2 wrinkle
free and under even tension thereby avoiding air bubbles in the
lamination. Also shown are supply rolls 9 and 10, and press rolls
11 and 12.
In accordance with the present invention, the web 1 under
process does not stick to the rolls and the machine elements
involved do not gum up.
In the foregoing specification, the invention has been
29
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described with reference to specific exemplary embodiments
thereof. It will, however, be evident that various modifications
and changes may be made thereunto without departing from the
spirit and scope of the invention as set forth in the appended
claims. The drawings and specification are, accordingly, to be
regarded in an illustrative rather than in a restrictive sense.
