Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND O~ THE INVENTION
Field of the Invention
This invention relates to methods for applying coatings
to substrates and, in particu~ar, to producing high gloss coatings
on substrates.
Description of the Prior Art
Coatings have traditionally been applied to substrates
such as paper by dissolving the coating composition in an inert
volatile carrier, directly applying it to the substrate, and
heat-curing in an oven. On the application of heat the inert
carrier is driven off and the coating composition thermoset.
This process, however, left much to be desired in regard to
desirable surface characteristics of the coated substrate.
British Patent No. 1,241,851 describes a process for coating
an article that comprises applying a film of an ethylenically
unsaturated ester and exposing it to ionizing radiation. No
liquid vehicle is used. A transfer coating process involving
the use of release paper is disclosed in Britlsh Patent No.
1,519,493.
SUMMARY OF THE INVENTION
I have now discovered a transfer coating process for
applying a high gloss coating to heretofore difficult to coat
substrates. By practice of the hereindisclosed process,
it is now possible to significantly reduce absorption of the
coating into the substrate thereby reducing the quantity of
coating needed because of reduced penetration into the substrate.
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Su~s~râtes coated by this process demons~~ate imprcved
glcss and smoot~.ess of surface texture. ?~rticularly
des r~ble surface ~ex~ures are created by a?plying the
coa ~ng composition to the substrate in va~ious patterr.s ar.d/or
fi'-. thicknesses p~ior to curing. A particularly bene .cial
_s__^~ of this prccess is that it may be carried out er.'irely
in ~ nd that -.o -nert gaseous atmosphe~e is requireQ
dur~rg the curin~ staOe.
In general, the process comprises the application
1~ of a radiation curable coating composition to â smooth surface
carrying web, the carrying web being of a nature such that
the coating composition, when polymerized, will not adhere
to its surface. The substrate to be coated is then brought
into contact with the coating composition cy passirg the
i~ substrate and the carrying web through a palr of nip rollers
to fo~m a sandwich, thèreby initiating transfer of the coating
co~.position from the carrying web to the substrate. The sandwich
is ~hen subjected to a conventional radiation curing process
~herein the coating composition is polymerized and set. Upon
removal from the radiation curing station, the carrying web
may be separated ~rom the coated subst~ate. The coated sub-
strate is then removed ~or storage and the carrying web is
either discarded or recycled for reuse in the process. It is
kr.o-~.n that radiation curable coatings differ in their ability
~^, to adnere to ~arious substrates and the essence of the present
invention comprises the selection of the carrying ~eb ~nd the
substrate such that, for any given coating composition, the
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cured coating adheres t~ the su~strate of interest but does
not adhere to the carrying web.
For the production of high gloss sur~aces on the
coated substrate, materials useful as carrying webs in this
process should be impervious to the coating composition
involved and should have a high degree of surface smoothness.
Additionally, they should be resistant to tearing and of a
composition such that they ~ill not stick to the coating.
Useful carrying webs may comprise continuous films or an
endless belt. They may be polyester film material, a metal
foil, or a polished metal belt or drum. After a coating
composition is applied to a carrying web it may then be
transferred to a number of substrates, ranging from a wide
variety of papers and film materials to wood, fiber compositions
and even to metals, depending on the nature of the carrying
web and the coating composition.
Porous substrates (e.g. coarse paper) may be particu-
larly advantageously coated by the hereindisclosed process to
give a very smooth, glossy surface. In addition, the coated
substrate may subsequently be top coated with another material
by the same or different process - for instance, coated paper
may be metallized with aluminum by conventional metallizing
technology. The advantage of such operation being that the
secondary coating will thereby exhibit surface characteristics
(smoothness, gloss, reflectance, etc.) which are significantly
superior to those achieved by the prior art.
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Other substrates co~ted as per the process o~ thiS
invention will provide a superior casting and suppoxt surface
for cast-forming plastic film material (e.g. vinyl, polyester,
polyolefin, etc.). The highly desirable surface characteristics
of the coated substrate result in a cast plastic film having
similar superior surface characteristics.
BRIEF DESCRIPTION OF THE DRAWINGS
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FIGURE 1 is a schematic representation of a prior
art system for coating paper substrates.
FIGURE 2 is a schematic representation of one embodi-
ment of the present invention.
FIGURE 3 depicts another embodiment of this invention.
FIGURE 4 depicts still another embodiment especially
useful for the coating of highly porous substrates.
FIGURE 5 shows another embodiment wherein the carrying
web has been formed into an endless belt.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
, .
The process of the present invention will be described
with the aid of appended schematic drawings, which are intended
2Q to represent a typical industrial setup for coating paper
substrates. Throughout the drawings, common elements have
been numbered the same to minimize confusion.
Looking first at Figure 1, we see a typical processing
line for applying high gloss coatings to paper substrates.
The uncoated substrate sheet 100 is fed to the line from
substrate roll 1. It passes~over tensioning roller 2 and
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on to roller 3 where a coati..~ is ap?lied. C02ting G?~lication
is by means of a conventior.al offset gravure process.
Basically, the uncured coa.ir.~ co~.posi'icn is placed in
pan 4 and is then picked up oy steel gravure roll 5 ~hich,
as it rotates, transfers tre coating cc~oosition to rubber
of~set roll 6. Then, as substrate sheet 100 passes '~etween
rollers 3 and 6, the coating composition is transferred to
the surface of the substrate sheet. The raw coated substrate
sheet 101 is then fed to the curing station 7. (~or the
purposes of explaining thls process, the curing station shall
hereinafter be referred to as an "electron beam apparatus.")
As the raw coated substrate sheet 101 passes under the electron
beam, the coating composition is rapidly pol~-merized and cured.
Exiting from the electron be~m apparatus, the cured coated
sheet 102 passes over and ~rcund tensioning rollers 8 and 9
and is wound on take-up roller 10.
Moving now to Figure 2, we see one of the preferred
embodiments of the process of t~is irvention. Since it is
basically built upon the prior art process confi~uration
' of Figure 1, the explanation of the common elements shall
remain the same. In the Figure 2 embodi~.ent, ~;e see carrying
~eb roll 30 which supplies to the line a carrying web 200.
The carrying web 200 is passed over tensioning roller 31
and the coating composition is applied by the of set gravure
process as described above, ~xcept this ~ime it i3 applied
to a carrying web 200. ~.fte- the uncure~ co~tin composition
is applied to the web, both 'she web and the substrate sbeet 100
are passed between nip rollers 11 and 12 for~.ing sandwich
3112~3461
s~et 201. Sh~t 201 ~mpri~s the substrate sheet on ~p,
the carrying web on the bottcm and the un~ured cGstin~
composition bet~Yeen the two. It should be mentioned ~t
this point that in most process configurations e~bodying
the present invention, it is not signi~icant whether the
sàndwich is formed with the car-ying web Dn the bottom 2S
in the present explanation or with the carrying ~eb on the
top, i.e. the reverse of the present configuratiQn. Once
the sandwich 201 is formed, it is passed ~uickly ~o tne
curing station to minimize or eliminæte a~sorption of the
coating composition into the substrate sheet. A ter ?assing
through the electron beam where the coaling com~osition
is polymerized and cured, the sand~ich 2Ql .s then passed
around tensioning rollers 8 and 9 as in ~igure 1 and is wound
on take-up roller 10. When ready for use, the csrrying web
200 may be peeled away from the coated substrate since the
choice of materials is such that the curel coatir.g cc-.position
will not adhere to the carrying web but ~;ill a~here ~o the
paper substrate. While substantially recucing wicking of
the raw coating composition into the substrate, tnis orocess
significantly reduces the amour.t of co~tin& composit on
required to produce a suitab~y coated substrate ~heet in
relation to that required by the prior art proce~s configura-
tion of Figure 1. Also, by carefully chcosing t:~.e msterial
which is to comprise the car~y_ng ~eb 20C, one i-~ ab:e to
control the surface finish on the coated sheet with ~ fine
degree of precision. A judicious choice o~ ~.aterial for the
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c-rry'r.s web ~.ay result in a smooth and glossy ~inish on
he coating or, ,f desired, a dull and .lat fin~sh.
Cimilarly, a design may be i~.parted to the co2ted surface
~e~ely by appropriate choice and/or modificatior. of the
c^rry'ng web.
Firure 3 of the dra~iings shows another pre~erred
e-.bodimlent of this irvention. The process line is set up
as in the Figure 2 embodiment. After the sandwich 201 is
formed and passed through the electron beam apparatus, it
is fed to separating rollers 13 and 14 where the carrying
~eb 200 is released by the coated substrate 102 and
separated therefrom. The carrying web is passed around
tensioning rollers 32 and 33 and wound on web taXe-up
roller 34, thereby enabling one to reuse the carrying l~eb
i~ the process merely by substituting the material on take-up
- roller 34 for the carrying ~eb roll 30 in another process run.
~-'ter separation of the carrying web from the cured and coated
substrate 102, the substrate 102 is passed over tensioning
roller 9 and wound on take-up roll 10 as before.
2 J The process configuration illustrated in Figure 4
demonstrates a modification of the previous embodiments
hich is particularly suitable in the coating of highly
porous substrates. In this embodiment, the nip rollers
11 and 12 which help form sandwich 201 are positioned
_, '.. media'ely before curir.g station 7 so as to minimize the
distance which the sandwich 201 must travel before being
exposed to the electron beam radiation of the curing~station.
The purpose for this modification is to enable the
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p-actioner to coat highly porous substrates which, prior to
the present invention, have been difficult or ever. impossible
to surface coat due to vhe high degree o~ substrate porosity
whlch resulted in most or all of the uncured coat~ng composition
beir.g absorbed into the substrate instead o~ remaining on
the surface thereof. After curing the coating composition
in sandwich 201 as ~efore, the sandwich is passed bet~-een
separating rollers 13 and 14 where the carrying web 200 is
released from the coated substrate 102 and recovered on take-up
roll 34. Alternately, both the coated substrate and the
carrying web may be wound on the same roll as in Figure 2.
Still another embodiment of the prccess of the present
invention is illustrated schematically in ~igure 5. In this
e~bodiment, the carrying ~eb roll 30 and carrying -leb take-up
roll 34 are completely eliminated and replaced by an endless
belt of carrying web material as depicted ~y belt 300. The
belt 300 is coated with the coating composition as descrlbed
in the previous embodiments and the substrate sheet 100
brought into contact with the coating composition via nip
rollers 11 and 12 as before to form sandw ch 301. Sandwich 301
is then passed through the electron beam, where the coating
com?osition is polymerized and cured. ~he coated substrate
102 is subsequently stripped lrom belt 300, passed over tensioning
roller 9 and wound on ta~e-up roller 10. When ut~lizing the
process configuration o~ Figure 5, one may complet~ly eliminate
the need for maintaining an inventory of carrying web ma~erial
and, at the same time, reduce the compleY.ity of the process
line.
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Suitable sources o~ radiation for curin~ t~.e cc2ting
composition co~rise electron beam radiation, ultravlolet
li~ht, or even thermal radiation. The prefer.ed ssurce
of radiavion for the initiation of polymerization and
curing is electron beam radia'ion. Such elec'rcn be~-.
radiation is obtair.ed from high energy electrons ?~od~ced
by high ~olta~e electron accelera'or, rescnan transfcrr.ers,
transformer recvifiers, microwave waveguide l'near accelerator,
. and synchrotrons. The primary reason for preferring electron
_0 beam radiation is, of course, that such radiation is r.ot
limited by the physical nature of either the web or the
substrate. The electron beam will penetrate any combination
of materials and has no particular thickness limitaticn as
such. The primary limitation in an electron beam curing
:5 process is the density of the total substrate which the
beam must penetrate ti.e. the density of the sandwich in
the illustrations). Although in most applications the beam
will penevrate the entire sandwich with some of the beam
passing through the sandwich, it of course need only penetrate
as far as the coa'1ng composition, since its only purpose is
to initiate polymerization of the coating. The densi~J
limitation for any particular beam is determined by the
intensity o~ that beam. ~or example, a 200 k~ beam of
electrons will penetrate up to 10 mils of unit dersity
^~ material (material having a density of 1 gr2m per centimeter
cubed). Aluminum has a density of 3, so one can cnly penetrate
3 mils of aluminum. Since water has a density of 1, such a
beam will penetrate 10 mils of water. Co~mercial polyester
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-ilms also have a density of approximately 1. ~:eavier
.aterials, such 2S stainless steel, are ~isable in an
e'ectron beam curing setup but one must arrance the
s_nd~ich such that the stainless steel layer cor.prises
~^.e back layer of the sandwich relative to the direction
cf the electron beam radiation, thereby enablin~ the beam
to reach and cure the coating composition.
Ultraviolet radiation is usable for initiating cure
ol the coating coating composition, provided at least one
side of the sandwich is transparent to the U.V. light rays.
In practice, this requirement usually means that the
c~rrying web must be transparent thereby eliminating metal
or metallized carrying webs and materials such as polyester
film which absorb the U.V. light. However, suitably trans-
1~ parent materials (e.g. polyethylene film) may be utilized
.ith great success as carrying webs, thereby enabling the
practioner to use the process with existing or slightly
modified ultraviolet curing apparatus. Similarly, thermal
r-diation is usable with this process, as long as the
curing or drying energy is sufficient to reach and cure
the coating composition before significant absorption into
the substrate sheet. All of these sources of radiation and
rethods of generating and regulating them are well known
and practiced in the art.
2~ In addition to the foregoing, one may also employ
non-conventional means for curing the coating compositions.
Such means may include, for example,cherically induced
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polymerization, microwave ~dia~ion ox othe~ e~otic types
or sources of radiation. In sortr suitable curing mean~
for utilization in the process of the invention includes
any means, conventional or non-convent~ional, which will
successfully activate the polymerization mechanism in the
uncured coating composition of choice.
Whatever the means employed for initiating the
polymerization mechanism in the coating composition,
utilization of the disclosed process for producing coated
substrates has the unexpected advantage of totally eliminating,
or at least substantially reducing, the necessity of pro-
viding an inert gaseous atmosphere in the vicinity of the
coated substrate while the coating composition is under-
going polymerization. Prior art processes, such as that
shown in Figure 1, have required the provision of an inert
gaseous atmosphere in the area in which polymerization of
the coating composition was taking place to avoid the
undesirable effects brought about by the presence of unwanted
substances introduced via the atmosphere. Of particular
2Q concern has been the undesirable interference with the
formation of cross-linking bonds in the polymer caused by
the presence of atmospheric oxygen, the effect of which has
been that the resultant cured coating composition will
have physical characteristics less desirable than those other-
wise expected, By practice of the invention described above,
it will no longer be necessary to incur the added work and
expense involved in eliminating atmospheric oxygen since the
coating composition is no longer exposed to the atmosphere
during the curing process.
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Another i~portan-t adv~nta~e of -this invention is the
substantial savings realized in the amount of coating compo-
sition needed to be applied to the substrate in order to achieve
a given surface effect, particularly with respect to the coating
of porous substrates. Previously, "wicking" - the absorption
of the uncured coating composition into the substrate - has
been a major, if not insolvable, problem in the coating of
certain substrates. It is now possible, by applying the
coating compositions as disclosed herein, to get smooth, high
gloss coatings w-ith even the most porous of substrates (e.g.:
tissue paper and textiles) while simultaneously using substan-
tially less coating material than heretofore possible. Such
highly desirable improvement in hold-out properties is the
result of the very short contact times between the uncured
compositions and the porous substrates prior to polymerization.
As mentioned hereinabove, the process of this
invention can be used to advantage in the manufacture of
metalized papers and plastic films. Of particular concern
in metallizing applications is the achievement of optimum
surface characteristics in the metal layer. This is
especially prob~ematic when the substrate to be metallized
is a porous material such as paper. The basic shortcoming
in the metallization of porous materials is that, since the
metallized layer is so very thin (typically on the order
of a fraction of a micron), any and all surface imperfections
in the substrate will be reproduced~on-the metallized
surface. In order to get a good, smooth, reflective,
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mirror-like surface on the ~let211ized layer it is a~solutely
essential that the surface receivin~ the metâllized layer
be s~ooth and free of imperfectlons. Tn~s is mo~t ~ter.
dor.e by applying a base coat to the s~lbstrate to fill
minor imperfections and provide ~ suit~le hi6h-alo~s
surface to receive the metal deposit. ~12stic ~ateri21s,
~hich are substantially non-porous and usua~ly alre~dy have
reasonably smooth surfaces, are commonly base ccated with
lacquer, acrylic resins, alkyd resins Cpure and ~odified),
polyesters, conventional Yarnishes, urea-lor~aldehyde
resins, vinyl poly~.ers, acrylonitrile polymers, phenolic
resins, cellulosic resins, polyure~es, butyl rubber and
chlorinated butyl rubber, sllicone resirs, mela~.ine-
formâldehyde resins, polystyrenes, natural rubbe~, and
modified phenolic resins, either individually or in various
combinations.
Porous substrate materials preser.t consicerably greater
problems, both in degree and in kind, than do non-porous
subst~ates because the sealing and fill'ng-in of the
surface at reasonable cost and without ubstantially al~ering
or destroying the desirable physical characteristics of the
substrate create no small challenge for one desiring to
metallize such material. Compositions suit~ble for use as
a base coat do not pose any particular vrob~ems with regard
to their chemistry in metallizing applications. Ge~erally,
any of the types of materials enumerated above, as ~.ell as
any o~her composition normally used to coat and Oive a high
gloss finish to paper, would be suitable. The cnly criteria
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is that the coating block the ?ores o~ the substrate;
:ave good holdout character'st~cs to giVQ a ~moo h, ~igh-
loss surface; and not be toG hard or sll?pery so as to
~nhib~ t:~e adhesion o~ the mQtcl atoms to the surface. As
stated a~ove, these characte~istics can normally ~e achieved
.i th most conventional coating for~.ulations. klthough no
?articular chemistry is requ'red in the coating composition,
it ls pre~erable that silicone lubricants on the surface of
t~e cured coating be kept at a minlmum since such material
m2y tend to interfere with tne depositior. of the metal atoms.
It has been found that,in metallizing applications,
utilizaticn of the hereindisclosed invention to apply a base
coat to a porous substrate prior to deposition of the metal
^toms will result in a surpr's'ngly improved and very desir-
able metallized surface. The base coat is applied and cured
as taught above and, after removal from the carrying web,
the coated surface is metallized using conventional techno1ogy.
Suitable techniques include, for example, vacuum metallizing,
electroplating and sputterin~. A descri~tion o~ the vacuum
metallizction process ~ill be ~ound in E~TRUSION AND OTHER
PLASTICS OPERATIONS, N.M. Bikales editor ~Wiley-Interscience,
1971) pa~es 249-260. A similar descript on of the electro-
platinO process ~ill be found at pages 2~1-277 o~ the same
reference. Ihe so-called "sputtering" technique is relatively
r.ew in the art and involves the ejection of atoms or groups
of atoms from the surface of the cathode as the result of
heavy-ion impact to deposit a ~hin layer of metal on ~lass 3
plastic, metal, paper or other sur~ace in vacuum.
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.Q.nother desirable use of the prc~ucts and process
c~ this invention is in the cast-forming OL P1 as~ic Gr
ovher sheet materi 21 ~here high quality surface characteristics
of the cast sheet is of ma~or concern. ~y a?plying a coating
to the support substrate by this process prior to castinæ
tne f'lm, one may impart to the subs~ratc a smoo'her
surf2ce than previously obtainable. A7terna'ely, one may
employ the instant process to give heretofore unuseable
substrates a superior surface quality suitable for use in
cast-formin~, thereby enabling the practioner to use much
less eY.pensive, but previously unsuitable, substrate
materials as support surfaces for castin~ films. Most of
the kinds of coating compositions mentioned previously will
be employable in this type of applicatior., but with certain
added limitations concerning imperviousness to solvents and
temperature stability. Basically, if the sheet or film to
be cast-formed is to be cast from the melt - i.e. the molten
resin is to be applied directly to the support surface and
alloNed to cool - the cured coating composition lhich
comprises the casting surface of the substrate must be
substantially unaffected by the temperature of the molten
resin. Likewise, if the sheet or film is to be solvent-cast -
i.e. a solution of the resin is laid down on the support sur-
face and the solvent subsequently removed - the cured
coating composition must be totally im.. ur.e tc the solvent.
Such limitations are considered to be primarily technical
and readily overcome by a Judicious selection of coating
composition based on the exigencies of the applicaticn
of interest.
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In view o~ the fact that the coating com?~sition
is applied to a ca-rying web and then tr~nsfer~ed to vhe
substrate, ore may advantageously coal; any cf 2 numrer
of substra~es by this process. Conterr.pl_ved substra~es
r2nge fro~ a wide range of papers, both pcrous 2n~ nonporous,
as well as coated and uncoated ?apers, tG ~ilm materials and
even to mevals, depending primzrily on the choice of carrying
web material and coating composition. I~ith su,table modifi-
cation, the baslc concept disclosed herein may è~-en be
used to apply desirable coatlngs to open weave fabrics,
hardboard material, and even wood paneling and metal.
Although there are no specific requireme~ts as to
what would constitute a suitable carry'n~ web material,
there are certain general recuirements fcr the web. To
be useful, a web should be impervlous to the raw coating
composition and shoul`d be chosen from amon~ suitable materials
which w~ll r.ot stick to the cured coatin~ composition,
thereby allowing the web to release the cured surface of
the coated substrate. Also, the carrying web should be
resist~nt to tearing since it ~ill be under some degree
of tension during the operation. Contemplated materials
include, for example, polyester film (e.g., the material
sold by the Dupont Company under the trademark ~YLAR film),
metal foil material, plastic film., and pslished metal belt
or drum. Another requiremen~ ~or suit_ble carrying ~eb
material is that it must be resistant to (i.e. not
deteriorated by~ the type of curing radiation utiiized.
If a high degree of surface smcothness is desired in the
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finished coated substrate,it is paxticularly impo~tant that the
carrying web be chosen for its surface characteristics. In
contrast, by imparting a design to the surface of the carrying
web, it is possible to transfer the design to the coated sub-
strate.
Althou~h in the discussion of the preferred embodiments
the raw coatin~ composition i5 supplied to the carrying web by
means of the known offset gravure application method, it will
of course be obvious that any conventional method of applying
a coating to the surface of the carrying web is utilizable.
Examples of such application methods include~ but are not limited
to, for instance, direct gravure coating, roll coating applica-
tion, brushing, flow coating, and 50 forth.
A choice of coating composition to be used in this
process will be determined primarily by the considerations
normally encountered in the coatings arts. That is to say,
the nature of the substrate to be coated and the quality,
texture and other characteristics which one desires to achieve
in the final coated substrate. Other considerations include,
2Q of course, the nature of the means used to initiate polymeri-
zation in curin~ the coating. For example~ if one is using
electron beam radiation, it is necessary to have an electron
beam curable coating. Such a coating compri$es a mixture of
one or more materials CQntaining one or more ethylenically
unsaturated functional groups. Similarly, if the coating
composition is to be cured b~ means of ultraviolet radiation
a photoinitiator should be present in the coating composition.
If the coating is to be thermally cured, then the composition ~l
must by its nature be thermosettable. As me~tioned before, it
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is of primary importance -that the com~ination o~ coating compo-
sition and carrying web material chosen be such that the cured
coating will not adhere to the carrying web, thereby allowing
transfer of the surface characteristics of the carrying web to
the surface of the coating once polymerization has taken place.
Substrates coated in this manner may, in addition, be
top-coated with other coating compositions by the same or
different application process. Such top-coatings may be trans-
parent and serve primarlly a protective function, or they may
be pigmented to provide additional decoratin~ function - for
example, wrapping paper or decorative wall coverings having
multi-colored patterns and designs.Or the other coatea;substrate
may be subsequently imprinted with written or printed messages
or with designs using printing inks - for instance, labels or
packaging materials carrying information of value to the user
of the package. Another application would be to decorate or
print on the uncoated substrate and subsequently apply a clear
protective coating by the process of this invention.
The following examples will serve to illustrate the
2Q general concept of this invention without limiting the scope
thereof.
EXAMPLE l
Using the process configuration of Figure 2, a
commercially obtaina~le 28 pound CIS paper stock (obtained from
the Consolidated Paper Company~ was coated with a white pigmented
coating having a viscoslty of 2000 cp using a 150 quad gravure
roll for application of the composition in the offset mode.
The ingredients in the coating composition are given in the
table below.
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CQ~TING COMPQ$ITION
Component gt.
l* 1 mole EPQN-828** reacted with
2 moles hydroxy ehtyl acrylate 19.25
2* HEA-5PO
1 mole hydroxy ethyl acrylate
reacted with 5 moles of pro-
pylene oxide 19.25
3 Trimethylol propane triaarylate
(TMPTA) 16.5
4 Silicone internal lubricant
(BYK-300)*** 0.2
Titanium dioxide (pigment) 44.8
* The combination of components 1 and 2 is disclosed
in U. S. Patent No. 4,064,025.
** Trademark. "Epon" resins are a series of synthetic
resins possessing terminal epoxide groups, formed
by the condensation of epichlorohydrin and bisphenol-A.
"Epon 828" is one of the lower molecular weight members
of the series: it is a viscous liquid.
*** Trademark.
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The coating composition was applied to a 0.5 mil thick carrying
eb comprising a sheet of polyester film material. The coated
carrying web was then brought into contact with the substrate
and the sandwich formed by passing the two sheets between a
pair of nip rollers. The sandwich, with the coating composition
between the two layers, was then fed to an electron beam curing
apparatus at a speed of lQQ feet per minute. The voltage of
the beam ~as 176 kv with a current vf 10 ma and the dosage of
2 MR. After curing, the carrying web was peeled from the
coated substrate to reveal a coating surface having a high gloss
and excellent smoothness.
EXAMPLE 2
Using the same paper substrate and coating composition
of Example 1, a superior matte finish was achieved by applying
the coating composition to a carrying web comprising a 1.0 mil
t~ick sheet of matte finish aluminum foil. The sand~ich was
then formed with the paper substrate as before and the coating
composition cured by means of electron beam radiation using
the parameters given above. Upon removal from the curing
2a station the aluminum foil t~as peeled from the coated substrate
to reveal the cured coating sur,face on the substrate having
superior smooihness with a matte finish.
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_ PLE 3
The porous side of the CIS 28# paper stock was
coated with the coating composition and cured as in Example
1 using a polyester carrying web. After removal of the
carrying web the cured coating composition could be seen to
reside substantially on -the surface of the paper and imparted
a smooth, high gloss, reflective finish thereto.
EXAMPLE 4
Using the same paper, coating composition, curing
speed and E.B. dosage parameters as in Example 3, the coating
was applied directly to the sur~ace of the paper using con-
ventional technology and methods. Upon inspection after
curing, it was seen that substantially all of the composition
had been drawn into the interstices of the paper and that the
coated surface had~a flat appearance with substantially no
greater gloss or reflectivity than it had before coating.
Examples 3 and 4 demonstrate the superior holdout
and surface characteristics of a coating composition apPlied
to a porous substrate by the hereindisclosed transfer coating
process as compared to conventional coating practices.
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EXAMPL~ 5
The coating composition of EY.Z~.~1e 1 ~aS zp~l'ed ~o
a polyester lilm carrylng web using a 150 quad offset
gr2vure roll at 110 ~t/min. The ccated s~rface c~ the
carrying web ~as ihen brought into ccnt2ct with a sheet
of 60# lithographic grade paper stock and the coatin_
composition cured by electron beam at lOma, 185kv and a
dosage of 2.0 MR. After removal of the polyester web
the coated paper was visually examined ~or the ~uality of
the cured coating. The surface was very smooth and
exceptionally reflective.
EXAMPLE 6
Using curing speed and parameters identicsl to those
of Example 5, the coating was applied directly to the 60~'
litho stock in the conventional way. Upon inspection it ~as
seen that, although the reflectivity of ~he coated surface
- had been improved, a substantial amount o~ the co...position
had been absorbed into the paper prior to polymerization and
as a result the gloss and smoothness of the coat~ng was
23 substantially less than that of Example 5.
Examples 5 and 6 again demonstrate the su~erior holdout
ar.d substantially enhanced surface characteristics of a
ccating applied by the transfer coatin~ ~rocess.
.
~.z~3461
EXAMPLE 7
Under conditions ldentical to thcse of Ex~mple 5,
the reverse (non-smooth) side of the 60# litho stsck :as
coated by the transfer method at 100 ft/r..in. The sur~ace
r.a-~-ing the cured coating composition was -lery smosth and
well sealed, having a gloss and reflectiYity co~p~rabie to
that of Example 5, thereby demonstrating ~hat coa ings may
successfully be applied by the process of this in-Jention to
either the usual calendered side of a cor~ercially useful
grade of paper or to the reverse, relatively non-smoo~h side
with equally desirable result.
EXAMPLE 8
Identical in all respects to Exa~.?le 7 except that
the coating was applied at the rate of 50 ft/min. and thé
E.B. radiation cure had a current of 5ma. At the slower
- operating speed the polymerized coating w2s not as smooth
as that of Example 7, although reflectivity and holdout were
st~ll substantially better than that of the con~entional
application method to the prepared side of the paper as in
Example 6.
EXAMPLE 9
.
Medium grade brown kraft paper w2s ccated with the
coating composition of Example 1 at the rate of 130 ft~min.
The uncured coating was applied to a polyester carrying web
using a 150 quad gravure roll in the offset mode and the
kraft paper brought into contact with the coated surface.
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~%84~1
Curing was by Electron Beam radiation at 10 ma ard lc~ kv
with a dosage of 2.0 MR. The polymerized coatinS ~as
- smooth and glossy with a very high deg~ee of reflectivity
and very little of the brown paper color sho~Jing thr-ugh
the white coating.
EXAMPLE 10
Using the same substrate and coating composit~on
as Example 9, the kraft paper was coated in the conventional
manner (i.e. direct application of the coating composition
to the paper) at 100 ft/min. Subsequent curing ~:as ~y
Electon Beam radiation at 185 kv and 30 ~.a with c dosage
- rate of 6.0 MR. The coated and.cured surface was flat and
was neither substantially smoother nor more reflecti-;e than
the uncoated paper. Additionally, although the coat ng
lightened the color of the paper somewhat, the ma~or ty
- of the composition had been absorbed into the pa~er ~ith the
result that t~e coated paper was of substantially the same
brown color as the uncoated kraft paper.
It is to be understood that although the fore~oing
description has been with reference to specific embodiments
and examples, such reference is intended merely to i-~lustrate
the most preferred embodiments of the instant process and
to disclose the generic principle behind this in-~rent'on.
Many modifications and variations may be made by those
skilled in the art without departing from the spirit of
the invention as disclosed herein and, as such, are
intended to fall within the scope of the followin.g claims.
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