Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR PRODUCING A BRIGHT
METALIZED FOIL OR BOARD
The present invention relates generally to the production of
metalized paper or board products, and particularly to a
transfer technique for applying the metal coating to the
paper or board substrate, which results in the preparation
of a metalized product having improved brilliance.
In general, the use of transfer techniques to apply metallic
coatings to substrates, such as fabric, leather or plastic
surfaces, is well known. Thus, the technique of gold leaf
transfer was utilized in the l9th century by bookbinders, who
employed gold foil transfer sheets to attach gold letters to
leather bindings. The transfer sheets comprised a waxed
carrier web over which a sheet of gold foil was placed, the
gold foil coated on its free side with a heat-activated ad-
hesive layer. In practise, the transfer sheet was hot pressed
with a heated dje to adhere the metal foil to the leather, and
the carrier was thereafter stripped away. The waxy parting
layer that was coated initially over the carrier, served to
maintain the gold leaf in position on the carrier prior to its
transfer, and to permit release of the carrier after the gold
had been affixed to the leather.
In recent times, the advent of vapor deposition of metals,
such as aluminum and the like, has spurred further interest
in the use of this metalization technique for the preparation
of a variety of metalized substrates. Thus, techniques of
both direct and transfer coating have been attempted on a
variety of base materials, including porous materials such as
cloth, leather, paper and the like. The potential usefulness
for these metalized substrates is enormous, as, for example,
~ 1~65~3
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metalized paper or board is broadly used for decorative pack-
- aging, and other applications where the appearance of a metal
surface is desired.
A number of techniques for the metalization of paper and
board are known and are disclosed in the art. Thus, U.S.
Patent Number 3,043,728, to Stauffer, discloses a specific
apparatus and associated method for preparing a metalized
paper product, which relies on the initial application of the
metalized layer to a drum and the transfer of the metal layer
to the paper substrate which has been previously directly
coated with an adhesive. U.S. Patent Number 3,235,395, to
Scharf, discloses a transfer metalization technique that
patentee states is applicable to paper. A heat or pressure
sensitive adhesive is utilized ln this method.
Other transfer metalization techniques are disclosed in U.S.
Patent Numbers 2,703,772, to Keithly, 3,080,270, to Lorenz,
and U.S. Patent Number 3,589,962, to Bonjour. All of these
techniques, however, relate primarily to metalization of
fabrics, and make secondary reference to metalization of paper,
and in the instance of Lorenz, suggests that an initial coating
must be placed on the substrate prior ta the transfer of the
metal layer thereto.
Direct metalization techniques for the preparation of coated
paper products are disclosed in U.S. Patent Number 3,463,659,
to Dragoon et al., and U.S. Patent Number 3,730,752, to
Guajardo Garza et al. In both instances, however, the patentees
suggest that a preliminary coating or base coating of the
paper substrate is necessary to facilitate application of the
metal layer.
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Finally, U.S. Patent Number 4,153,494, to Oliva, discloses a
metalization technique which when carefully reviewed, appears
closer to the ancient art of gold leaf transfer. In particu-
lar, Oliva utilizes a varnish, interposed between the metal
layer and the substrate to be coated, such as paper or board,
so that the metal layer will be adhesively bound thereto.
Oliva may apply the varnish either directly to the substrate
to be coated, or to the metal layer which is subsequently
transferred to the substrate.
Oliva, as well as the remainder of the prior art techniques
discussed above, possess certain basic drawbacks, which most
of the patentees above already acknowledge. In particular,
paper and board substrates are porous materials having re-
sidual moisture. The process of applying the metalized sur-
face directly to the paper or board base is complicated bythe tendency of the base to exhibit outgassing during the
application of the metal coating, that causes coating dis-
continuities that result in the formation of a dull or matte
finish to the metal surface.
:
Alternately, when the metal layer is formed on a carrier and
a transfer to the paper or board base is attempted, the condi-
tions under which such transfer is usually conducted, i.e.
pressure and/or elevated temperature, results in the undesirable
elimination of all moisture from the porous paper or board
base, with the result that the paper or board base subsequently
absorbs moisture from the atmosphere and develops surface
discontinuities, known as "curling", "cockling", and "crowning",
- all of which substantially detract from the smooth metalized
appearance desired in the product.
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In similar fashion, the direct application of adhesives to
the paper or board base, as disclosed in certain of the prior
art references, causes the same surface discontinuities to
develop and the resulting metalized products exhibit the
same deficiencies. Attempts to overcome this problem have
centered around efforts to apply primer coatings by techniques
that subsequently surface treat the paper or board base in
an attempt to assure a smooth, sealed surface for the applica-
tion of the metal layer. Such processes, however, are un-
economical and frequently unreliable, and have enioyed limitedcommercial success, if any.
A need therefore exists for the development of a simple, in-
expensive process that results in the preparation of a metal-
ized paper or board product.offering uniform, improved
brilliance and smoothness, together with durability and hard-
ness in use.
!
In accordance with the present invention, a method for pro-
ducing a metalized paper or board product with improved surface
smoothness and brightness, together with hardness and scratch
resistance, is disclosed which comprises applying a lacquer
coating to a carrier film to serve as the outer, protective
surface of the metalized paper or board product, the lacquer
coating being one capable of adherently bonding to a deposited
metal surface, as well as receiving other display material
that may be printed or otherwise coated on the outer surface
thereof, Thereafter, a thin, continuous and adherent metal
layer is vapor deposited on the lacquer coating, and a tie
coating, preferably comprising a polyurethane film forming
composition is thereafter applied thereto~
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An adhesive coating is then applied to the tie coating, the
adhesive coating preferably comprising an emulsion.
The carrier bearing the coatings and layers just described
is then brought in contact with the paper or board base by
feeding the two, with the adhesive coated surface facing the
base, into the nip of a pair of pressure rollers while the
adhesive remains wet, so that the adhesive is wet as it con-
tacts the base, and penetrates the base after the base and
the carrier are brought together between the pressure rollers.
Finally, the carrier and the base may be separated after their
emergence from the pressure rollers, with the base having
adherently bound thereto a multi-layered article comprising
an outer coating of the lacquer, a next adjacent coating of
the metal layer, a tie coating next adiacent the metal layer
and an adhesive bond disposed between the tie coating and the
paper or board base.
Preferably, the carrier may be a conventional material such
as a polyester sheet or strip, the lacquer coating may be
selected from cellulosic resins, such as nitrocellulose, or
vinyl resins, such as vinylacetate-vinylchloride copolymers,
and other equivalent materials. The vapor deposited metal is
preferably aluminum, and the tie coat is preferably aliphatic
polyurethane compositions. The adhesive may comprise a poly-
meric emulsion including various vinyl polymers such as poly-
vinylalcohol and polyvinylacetate homopolymers and copolymersas well as polyacrylic compositions. Preferably, the adhesive
coating has an acidic pH, and more particularly a pH ranging
from about 4.5 to about 5.5.
The present method is essentially a "wet process" in that the
adhesive emulsion is wet as it contacts the paper or board
base, and remains so for a time sufficient to penetrate the
paper or board base during the bonding of the metalized layer
thereto. The penetration of the paper or board base by the
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wet adhesive is a feature of the invention that is particu-
larly noteworthy in view of the prior art caveats against
such a technique, as described earlier. Metalized paper or
board products prepared by the present technique have uniformly
smooth surfaces, and do not exhibit the prior art defects of
"cockling", "crowning" and the like, despite the penetration
of the wet adhesive into the base.
The adhesive bond formed between the base and the metalized
composite is such that the carrier may be simply stripped
away after passage of the base and carrier through the pressur-
ized rollers. There is no need for a post-curing operation,
or the application of heat together with pressure, as utilized
in the prior art. The present method, by contrast, may be
practiced with an optional final step wherein the already
formed metalized product is heated to achieve further drying,
by, for example, exposure of the coated product to a temper-
ature of about 250F, for a period of about one minute. This
is in marked contrast to the heating regimes utilized in the
prior art, which achieve curing of the adhesive b~ exposure
to higher temperatures for longer periods of time.
Accordingly, it is a principal object of the present invention
to provide a method for the rapid and inexpensive manufacture
of a metalized paper or board product.
It is a further object of the present invention to provide a
method as aforesaid that results in the preparation of a prod-
uct having improved surface smoothness, brilliance and hard-
ness.
,:
It is a yet further object of the present invention to provide
a method as aforesaid which utilizes a transfer technique em-
ploying a wet adhesive without adversely effecting the coatedpaper or board base.
1 ~7~553
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It is a still further object of the present invention to pro-
vide a method as aforesaid which does not require the imposi-
tion of a post-treatment to cure the adhesive binding the
metalized layer to the base.
Other objects and advantages will become apparent to those
skilled in the art from a review of the ensuing description
which prGceeds with reference to the following illustrative
drawings.
FIGURE 1 is a schematic plan view sequentially illustrating
the various steps of the present method.
FIGURE 2 is a schematic fragmentary sectional view partly in
phantom, illustrating the various layers of the metalized
paper or board product prepared in accordance with the present
invention.
In its broadest aspect, the present invention comprises the
preparation of a metalized paper or board product having im-
proved surface smoothness and brightness, and resistance to
fracture upon flexure. The method comprises providing and
feeding a carrier film, applying a lacquer coating to the
carrier film, the lacquer coating to serve as the outer, pro-
tective surface of the metalized paper or board product. The
lacquer coating should preferably be capable of adherently
bonding to a deposited metal layer, as well as receiving other
display material that may be printed or otherwise coated on
its outer surface.
After the application of the lacquer coating, a thin, con-
tlnuous and adherent metal layer is deposited on the lacquer
coating, to provide the brilliant metalized appearance to
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the resulting paper or board product. A tie coating prefer-
ably comprising a polyurethane composition, is thereafter
applied to the outer surface of the metal layer, and is per-
mitted to dry. Thereafter, an adhesive coating preferably
comprising a wet emulsion, is applied over the tie coating
to prepare the composite structure for transfer.
The next step in the method comprises feeding the carrier
prepared as described above, and a base such as paper or
board into the nip of a pair of pressure rollers, with the
surface of the carr;er bearing the wet adhesive emulsion facing
the paper or board base. As the carrier and the base are
united between the rollers, the adhesive coating penetrates
the base as it adheres thereto. Subsequently, the carrier
may be stripped from the base, leaving the base having ad-
herently bound thereto a multi-layered article, comprising an
outer coating of the lacquer, a next adjacent coating of the
metal layer, a tie coating next adjacent to the metal layer
and an adhesive bond disposed between the tie coating and the
base.
The carriers useful in the present invention includes those
materials conventionally employed, that may be capable of
withstanding repeated use in accordance with the present
method. Thus, the carrier should be capable of successive
coating and stripping, and recoating without exhibiting de-
terioration during metalizing or under the tension of delamin-
ation during the release of the transferred composite to the
base. Suitable materials employed in accordance with the
present invention as the carrier, include polyester films,
various cellulose derivatives, vinyl compounds, elastomers and
i 30 others. Preferably, a polyester film is employed. While the
thickness of the carrier is not critical, a thickness of 1 mil
is preferred.
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The lacquer coating useful in the present invention may be
selected from a variety of materials capable of providing
a durable outer surface for the coated paper or board product,
that is receptive to printed, coated and embossed display
material. The lacquer must also be capable of cleanly
stripping away from the carrier in use, so that a smooth,
continuous surface is left. A variety of lacquers are suit-
able for this purpose, and include cellulose derivatives
such as nitrocellulose, and vinyl polymers, including vinyl-
chlor~de and vinylacetate polymers and copolymers. In par-
ticular, a vinylchloride-vinylacetate copolymer may be uti-
lized. The lacquer coat may be applied in various thicknesses,
and is preferably applied in a thickness ranging from about
0.0005 to about 0.005 thousandths of an inch. The lacquer
coat may be prepared with conventional organic solvents such
as methyl ethyl ketone, ethyl alcohol, toluol and the like.
The lacquer coat may be clear, in the instance where it is
desired to obtain a purely metallic appearance, or may be
colored by incorporation of pigments, dyes and the like, to
give various decorative appearances to the final paper or
board product.
The application of the metal layer to the coated carrier may
be accomplished by conventional techniques, and is preferably
accomplished by vapor deposition. The invention does not re-
late to the manner in whlch the metal coating is applied perse, and thus the techniques of vapor deposition of metal as
are known in the art, may be utilized herein, and such con-
ventional techniques are incorporated herein by reference.
As is known in the art, the number of metals that may be
applied by this technique to form a tightly adherent, continuous
coating is broad, and would include both precious and non-
precious metals, such as gold, silver, tin, zinc, chromium
and aluminum. In accordance with the present invention,
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aluminum is the preferred metal and is applied by vapor depo-
sition to a thickness that may range, for example, up to about
7 mils or greater. The exact thickness of the layer is dis-
cretionary, and may vary with the intended application of the
paper or board product.
The tie coating as noted earlier, provides improved hardness
and scratch resistance to the paper or board product. Suit-
able tie coatings include polyurethane compositions, and in
particular, flexible polyurethanes formed with a polyol and
an aliphatic isocyanate. Naturally, polyurethanes produced
by the reaction of a polyol with an aromatic isocyanate such
as toluene di-isocyanate, may be utilized as well, however,
polyurethane compositions produced by the reaction of an ali-
phatic isocyanate with a polyol have been found to result
in a tie coating having improved resistance to yellowing
or aging.
The polyurethane compositions may possess coatings ranging
in thickness from about 0.005 thousandths of an inch to about
0.008 thousandths of an inch. The polyurethane tie coatings
are particularly receptive and compatible with a subsequently
applied emulsion adhesive, and thus fav~rably coact therewith,
in addition to imparting improved hardness and scratch re-
sistance to the resulting paper or board product.
.,
The adhesive coating of the present invention is preferably
applied as a liquid emulsion and as noted earlier, is com-
patible with the tie coating so that the bond between the
metallic layer and the base will be firmly formed. Suitable
adhesives include vinyl polymers, such as vinylacetate homo-
polymers and copolymers, polyvinylalcohol emulsions, shellac
emulsions and acrylic emulsions. In accordance with the present
invention, the adhesive emulsion may preferably possess a pH
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in the acidic range, and more particularly a pH ranging from
about 4.5 to 5.5~ It has been found that the employment of
an adhesive emulsion of this pH range reduces the incidence
of attack and deterioration of the metal layer during the life
of the paper or board product.
As noted earlier, the adhesive is preferably applied as a
wet emulsion, and the present process is accordingly charac-
terized as a "wet process". By this it is meant that the
adhesive remains wet from the time of its application, until
it is applied against the adjacent surface of the paper or
board base, as the base and the carrier are united between
the nip of the pressure rollers. In this way, the wet adhesive
emulsion may thoroughly penetrate the base, and preferably
must do so, to assist in the formation of the improved bond
between the metalized composite and the paper or board base
that is characteristic of the present product. The ability
Gf the present product to emerge from the pressure rollers
in its completed form, without the exhibition of surface de-
fects or dullness is one of the primary features of the present
invention.
Referring now to FIGURE 1, the producti4n of ~he paper or
board product proceeds in the following manner. A supply
roll 11 delivers a sheet, strip or film of a carrier 12 to
a series of coaters. The carrier 12 may, as noted earlier,
comprlse a polyester film.
A lacquer coating 10 is then applied by coater 13, and may
be applied to the thicknesses suggested earlier herein.
Carrier 12 then passes through the vacuum furnace 14 where a
vapori~ed metal layer 15, which may comprise aluminum, is con-
densed on its upper surface. The exact thickness of layer 15may vary as indicated earlier.
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Carrier 12 now bearing lacquer coating 10 and vaporized metal
layer 15 thereover is then fed past a second coater 16 where
a tie coat, preferably a polyurethane composition, is applied
thereover. After the application of the tie coat, the carrier
12 passes to a coater lg where an emulsion coat or adhesive
19 is applied over the tie coat 17. The emulsion coat remains
wet, as indicated earlier, and carrier 12 is then directed
into the nip of opposed rollers 9, 9 simultaneously with the
introduction of a sheet or strip of paper or board 20 from a
supply roller 21 as illustrated. Thus, carrier 12 and paper
; or board 20 meet at the nip of rollers 9, 9, and the wet
emulslon coat 19 makes contact with and thereafter penetrates
the adjacent surface of the paper or board 20. At this point,
the bond between the paper or board 20 and the multi-layered
composite comprising the lacquer coating 10, the vaporized
metal layer 15, the tie coat 17 and the emulsion coat 19 is
complete, and the carrier 12 may be stripped away from the
base so that it parts cleanly from lacquer coating 10 and may
thereafter be retrieved for reuse in the present method. In
such instance, carrier 12 may be a continuous band~
-` The paper or board base may be used in the form received,
as prepared above, or may be given a heat treatment to hasten
the drying of the adhesive coat 19. In such instance, the
metalized paper or board product is heated in an oven at
; 25 approximately 250F for about one minute. This heating step,
; however, is optional.
The resulting product exhibits improved brilliance and scratch
resistance, and ls capable of a variety of uses, including
imprinting with colored inks, embossing and the like.
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Further, though the present invention has been described pri-
marily with respect to the disposition of a metallic coating,
it is to be understood that other coatings, such as pearl
coatings and paint coatings including irridescent coatings
such as "day-glo" may be utilized and the resulting products
will possess the same brilliance, smoothness and scratch re-
sistance.
The following examples illustrate the preparation of certain
of the coatings useful in the method of the present invention.
EXAMPLE I
A lacquer coat was prepared having the following ingredients
in the following amounts.
INGREDIENTS PARTS BY WEIGHT
Nitrocellulose
(1/2 second viscosity)
(70% wet in alcohol-
Hercules Powder Company) 20
Methyl ethyl ketone 50
Denatured ethyl alcohol 30
TOTAL 100
A second formulation was prepared with a vinyl polymer as
follows:
'
INGREDIENTS PARTS BY WEIGHT
Y~nylacetate-vinylchloride
copolymer (VAGH-Union
Carbide Corp.3 15
~ethyl ethyl ketone 50
Toluol 35
TOTAL 1 00
~ 1765~3
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1 EXAMPLE II
The tie coats were prepared from polyurethane materials
and poarticularly a material identified such as Mobay
Chemical-DESMOCOLL* E 471, and DESMOCOLL* E 477.
Preferably, the tie coat is a flexible polyurethane
derived from an aliphatic isocyanate and a polyol.
EXAMPLE II_
Two formulations of adhesive coats were prepared which
are preferably applied to a weight of approximately 3.5
pounds per 1500 square feet. The coating compositions
were as follows:
INGREDIENTS PARTS BY WEIGHT
Vinyl alcohol emulsion
(Franklin Chemical Industries-FH2) 50
Water 50
TOTAL 100
, A second formulation was prepared as follows:
` INGREDIENTS PARTS BY WEIGHT
Polyvinylacetate homopolymer
(AMSCO* Res 3 or AMSCO* Res 4
non-ionic manufactued by
Union Chemical Company) 50
Water 50
TOTAL 100
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. This invention may be embodied in other forms or carried
out in other ways without departing from the spirit or
essential characteristics thereof. The present disclosure
is therefore to be considered as in all respects illustrative
and not restrictive, the scope of the invention being indi-
cated by the appended claims, and all changes which come
within the meaning and range of equivalency are intended to
be embraced therein.
