Note: Descriptions are shown in the official language in which they were submitted.
2~5232.~
The invention relates to improvements in composite
sheets in general (hereinafter called foils for short), and
more particularly to improvements in foils wherein at
least one side of a substrate (e.g., a strip or web of
plastic material) is coated with a metallic film, such
as a film of aluminum. The invention also relates to a
method of making foils which contain metallic films.
Foils of the above outlined character are in
widespread use in a number of industries, particularly
for the packing or wrapping of foadstuffs and many other
products. An advantage of foils which consist of or
include metallized substrates is that they enhance the
appearance of the packed or wrapped products. Another
advantage of such foils is that their initial as well as
processing cost is but a fraction of the cost of foils
which are made solely of a metallic material, such as
aluminum. A further important advantage of foils wherein
a usually nonmetallic substrate carries one or more films
of metallic material is that they can be provided with
one or more additional coats in a simple, time-saving and
inexpensive manner.
A drawback of presently known foils wherein a
substrate carries one or more films of metallic material
is that they are not suitable for a number of important
uses. For example, foodstuffs of many kinds, as well
as many cosmetic substances, must be packaged or
wrapped in such a way that the contents of the package
are reliably sealed from the surrounding air as well as
from moisture. Heretofore known attempts to produce foils
which satisfy such requirements include the utilization
CA 02052321 2003-05-23
28680-7
of plastic substrates which are laminated with films of a
metallic material, such as aluminum. It is also known to
coat metallized plastic foils with layers of polyvinylidene
chloride. A drawback of such foils is that they are
expensive as well as that they do not satisfy the exacting
requirements of environmental protection agencies in many
countries. Another drawback of such foils is that they are
not fluidtight, or are not sufficiently fluidtight, for a
number of purposes. Moreover, their ability to prevent the
penetration of gaseous and/or liquid fluids is not
predictable and often varies from area to area. While the
inability of such conventional foils to prevent the passage
of certain gases and/or vaporized liquids might not be
detrimental for a number of uses, their permeability to
oxygen and/or vapors (such as water vapors) renders them
unacceptable for a number of important applications in the
food processing and many other industries. Extensive and
costly research in this field has so far failed to provide a
solution which would broaden the field of application of
metallized foils. Moreover, the permeability of
conventional foils to oxygen and to certain other fluids
increases drastically if their metallic films are permitted
to rub against each other and/or against the substrates
and/or against the confined product or products.
One feature of the invention resides in the
provision of a foil having two substantially parallel
surfaces which comprises a plastic substrate having a first
side and a second side, a metallic film which adheres to at
least one of the first and second sides of the substrate and
has a surface facing away from the substrate, and a
protective layer which overlies and adheres to the entire
surface of the metallic film facing away from the substrate.
The protective layer contains or consists of an organic
3
CA 02052321 2003-05-23
28680-7
material which strongly adheres to the surface of the
metallic film. Such organic material has a molecular weight
of at least 10,000 or less than 10,000. The organic
material can be selected from the group consisting of
natural and synthetic resins, natural and synthetic waxes
and lubricants. For example, the organic material can
contain a resin for lacquers and varnishes, a nonsmearing
wax or caoutchouc. Furthermore, the organic material can
constitute a priming which facilitates the application of
printed matter to the protective layer.
The layer is thin, preferably very thin. For
example, the layer can have a thickness of 0.1 to 1 g/m2,
more preferably 0.5 to 1 g/m2. Such layer is applied to the
metallic film while the latter is still devoid of scratches
and/or other defects which would render the film permeable
to gases. The metallic material of the film can be
vaporized onto the one side of the substrate and the organic
material of the protective layer can be vaporized onto
successive increments of the freshly vaporized film.
The protective layer and the metallic film jointly
constitute a fluidtight coating at the one side of the
substrate. Furthermore, the protective layer can be
resistant to corrosion, i.e., it can prevent oxidation of
the metallic film.
The protective layer is preferably made in such a
way that its thickness is constant along the entire surface
4
2r~:~~
of the film. Furthermore, the protective layer can be
resistant to blocking. The organic material of the layer
preferably exhibits high affinity for the metallic
material of the film, and the layer is preferably made
of an imprintable material,
The foil can further include a coating which
overlies and adheres to the protective layer. The coating
can constitute an extrusion which is crystallized on and
uniformly covers the layer.
It is further desirable to make the layer of
a physiologically acceptable material and to utilize an
odorless material.
The substrate can be made of a material which
is selected from the group consisting of polypropylene,
polyethylene, polyesters, polyamides, polystyrene and
polyvinyl chloride.
The preferably thin layer is or can be made of
a material which has a low coefficient of friction,
i.e., which has a smooth exposed surface and can move
relative to an abutting surface in response to the
application of a relatively small force. The term
"protective" is intended to denote, among others, that
the layer can shield the surface of the metallic film
from scuffing.
Another feature of the invention resides in
the provision of a method of making a foil o.f the above
outlined character, The method comprises the steps of
applying a film of metallic material (e. g., aluminum)
to at least one side of a substrate so that the film has
a surface which faces away from the substrate, and bonding
J
205232
a protective layer to the surface of the film. The layer
can contain an organic material, and the bonding step can
include vaporizing the organic material onto the
surface of the film.
The method can further comprise the step of
convoluting the foil upon completion of the bonding step.
The applying step of such method can include vaporizing
the metallic material onto the at least one side of the
substrate, and the bonding step can include vaporizing
the organic material onto the film immediately following
the applying step. The organic material can be selected
from the group consisting of natural and synthetic
resins, natural and synthetic waxes and lubricants.
The film is ready to withstand a force which is applied
to it by way of the protective layer as soon as the
making of the layer is completed.
The protective layer is preferably thin and
its thickness is preferably constant along the entire
surface of the film.
The applying step can include vaporizing the
metallic material onto the at least one side of the
substrate in a vaporizer, and the bonding step can include
vaporizing the organic material of the layer onto the
surf ace of the film while the respective portion of the
substrate is still in the vaporizer. The organic
material of the layer is preferably selected in such a
way that it exhibits high affinity for the metallic
material of the film,
If the layer contains a resin, the bonding
step can include heating the resin to vaporization
202321
temperature in a vaporizer and contacting the surface
of the film with vaporized resin in the vaporizer.
The bonding step can include a plurality of
successive stages. The method then preferably further
comprises the step of advancing the substrate and the
film thereon along a predetermined path, and each stage
can include contacting the film with vaporized organic
material in successive portions of the path. The
contacting steps can include applying a discrete stratum
of organic material to the film in each portion of the
path so that the application of a next-following stratum
begins immediately following completion of application of
a preceding stratum. Such method preferably comprises
the step of solidifying successively applied strata of
the layer, and the contacting steps can include applying
each next-following stratum subsequent to start of
solidification of the immediately preceding stratum.
Successive stages of the bonding step can be
carried out at predetermined intervals, preferably at
intervals of 30 to 120 seconds. The duration of the
intervals can depend upon the characteristics of the
corresponding strata; alternatively, such intervals can
be fixed or variable. The arrangement may be such that
the duration of intervals increases or decreases from
each preceding stage to the next-following stage of the
plurality of successive stages. Each stage can involve
the application of one and the same material to the film;
alternatively, at least one stage can involve the application
of a first material and at least one other stage can
involve the application of a different second material to
252321
the film. For example, one of the materials can be a
resin and another material can be a wax. Tf the stages
include three or more successive stages, the bonding step
can include alternatingly applying resin and wax during
successive stages of such plurality of successive stages.
A presently preferred embodiment of the method
further comprises the step of advancing the substrate
along a predetermined path in a predetermined direction
and at a predetermined.speed, and the applying step
includes vaporizing the metallic material onto the at
least one side of the advancing substrate at the
predetermined speed and while the substrate advances
along a first portion of its path. The bonding step
comprises establishing a supply of organic material
adjacent a second portion of the path downstream of the
first portion, heating the supply to vaporization
temperature, and contacting the film with vaporized
organic material in the second portion of the path. The
heating step can include electrically heating the supply
of organic material.
The novel features which are considered as
characteristic of the invention are set forth in particular
in the appended claims. The improved foil itself,
both as to its composition and the method of making the
same, together with additional features and advantages
thereof, will be best understood upon perusal of the
following detailed description of certain presently
pref erred specific embodiments with ref erence to the
accompanying drawing.
FIG. 1 is an enlarged fragmentary sectional view
_ g _
2052321
of a foil which embodies one form of the invention and
comprises a single metallic film and a single protective
layer for the metallic film;
FIG. 2 is a greatly enlarged view of a detail
in FIG. l;
FIG. 3 is an enlarged view similar to 'that of
FIG. 2 and further showing printed matter applied to the
exposed side of the protective layer;
FIG. 4 shows the application of an extruded
coating to the exposed side of the protective layer;
FIG. 5 is a fragmentary sectional view of two
convolutions of the improved foil on a core;
FIG. 6 is a diagrammatic view of an apparatus
which can be utilized for the practice of the improved
method; and
FTG. 7 is an enlarged fragmentary sectional view
of that portion of the apparatus which is indicated by
the arrow VII, the section being taken in a plane
which is parallel to the plane of FIG. 6 and being turned
through 180°.
Referring first to FIGS. 1 and 2, there is
shown a portion of a foil which includes a plastic
carrier or substrate l, a metallic film 2 which adheres
to one side 5 of the substrate and has a surface 6
which faces away from the substrate, and a thin protective
layer 3 which adheres to and overlies the entire surface
6 of the film 2. The metallic material of the film 2 is
vaporized, sprayed or otherwise applied to the adjacent
side 5 of the substrate l, The organic material of the
protective layer 3 can be vaporized onto or otherwise
_ g _
20532:1
applied to the surface ~ so that the :~ini.shed lr:~ye:c~ 3
shields the metallic film 2 from corrosion, mer_hanical
damage and other undesirable influences.
Certain presently preferred materials for the
makincJ of the protective layer 3 include natural and
synthetic resins, natural and synthetic waxes and
certain :Friction reducing acJents (hereinafter called
lubri.cants). For example, the material of the layer 3
can be a synthetic resin for lacquers and varnishes.
It is also possible to utilize caoutchouc, a mixture of
natural and synthetic resins, a mixture of natural and
synthetic waxes or any other mixture of. the above-
enumerated organic substances (for. example, a mixture
of a natural or synthetic resin with a natural or synthetic
wax).
It is important to ensure that the protective
layer 3 be bonded to the surface 6 of. the metallic film 2
whi:Le the film is still .intact, i.e., while the film is
still devoid of scratches, scuffs and/or other mechanical
defects. This can be readily achieved :if. the layer 3 is
formed immediately or practically immediately follooaing
the application of metallic material oa the film 2 to
the respective side 5 of the substrate 1. One presently
preferred mode of forming the layer 3 will be described
~~aith reference to FIGS. 6 and 7. :Lt is presently
preferred to vaporize the orcJanic material of the layer
3 and to contact successive increments of the surface 6
of the :Freshly formed film 2 with vapors. As a rule, it
is desirable to provide the foil_ with a thin or extremely
thin layer 3 tahich is preferably of uniform thickness
- 10 -
2052321
adjacent each and every portion of the surface 6. Such
uniform thickness can be readily achieved by appropriate
control of vaporization of a supply of organic material
and by appropriate control of the establishment of
contact between the vaporized organic material and the
surface 6 of the film 2. Another advantage of bonding
of the layer 3 by contacting the film 2 with vaporized
organic material is that the density of the thus obtained
layer is high which is desirable in many instances, for
example, if the layer 3 is to constitute a barrier
against penetration of oxygen and/or vapors into contact
with the metallic material of the film 2. Moreover, a
dense layer 3 can shield the film 2 from scuffing,
scratching and/or other undesirable mechanical influences.
In many instances, an intact metallic film~2 is
impermeable to fluids (such as air, water and vapors).
Thus, if the film 2 is intac t prior to the application of
the protective layer 3, it will remain intact even if the
layer 3 is permeable to fluids. However, the material of
the layer 3 can be readily selected in such a way that
the combination of intact film 2 and protective layer
invariably prevents penetration of any fluids toward and
into contact trith the substrate 1 and hence into contact
with the material or materials which are to be confined
by the improved foil. Therefore, the improved foil can
be utilized with advantage for the wrapping or packing
of certain types of foodstuffs and cosmetics which should
be reliably sealed from oxygen and/or water vapors or
which should not be relieved of moisture.
The material of the layer 3 can be selected with
- 11 -
205321
a view to satisfy all of the above enumerated requirements
as well as tb form a strong mechanical barrier adjacent
the surface 6 of the film 2. This renders it possible to
apply to the film 2 a pronounced force, as long as such
force is applied by way of the protective layer 3.
Moreover, the layer 3 preferably exhibits a pronounced
resistance to blocking so that it does not adhere to an
adjacent layer 3 or to the uncoated side of a substrate 1
even if it is acted upon by a considerable force which
tends to urge it toward the surface of the film 2.
It is important to select a material which can
be vaporized at temperatures below that temperature or
below that range of temperatures which could affect the
quality of the film 2 and/or substrate 1. Thus, if the
material of the layer 3 is to be applied to the surface 6
of the film 2 in vaporized state, the material is preferably
vaporizable at temperatures between approximately 100°C,
and 150°C. The vaporized material deposits and is condensed
on the surface 6 of the film 2. A single stratum of
vaporized and condensed material often suffices to form a
reliable protective layer 3 which is not permeable to
oxygen and/or vapors, either alone or jointly with the
metallic film.,2. However, and as will be explained with
reference to FIGS. 6 and 7, the protective layer 3 can
consist of two, three or more superimposed strata which
are applied in a series of successive stages. Such mode
of forming the layer 3 is particularly desirable if
successively applied strata of the layer consist, at
least in part, of different materials each of which is to
enhance a particular characteristic of the finished product.
- 1'2 -
2052321
A material which is a proper combination of two
or more different substances can serve as a corrosion
preventing or retarding barrier in front of the surface
6 of the metallic film 2. Thus, the material of the layer
3 can be selected to prevent penetration of oxygen and/or
vapors toward and into contact with the surface 6 so that
the metallic film 2 can merely serve as a reinforcement
for the substrate 1 and/or as a decorative part of the
foil because the protective layer 3 is capable of
intercepting oxygen and/or vapors so that these substances
cannot reach the surface 6. Such protective layer can be
formed by using a selected natural or synthetic resin,
a selected natural or synthetic wax or a combination of
two or mare natural or synthetic resins and/or waxes. The
ability to prevent corrosion of the film 2 is an important
characteristic of the protective layer 3. Extensive
experiments indicate that the ability of a metallic film
to resist penetration of oxygen and/or vapors is greatly
affected by corrosion, i.e., corrosion contributes to or
causes permeability of the metallic film.
A distinguishing feature of resins is that their
molecular weight is not less than 10,000 kp whereas the
molecular weight of waxes is less than 10,000 kp. If the
protective layer 3 is a mixture of one or more waxes and
one or more resins, the resin or resins enhance the
resistance of the layer 3 to scuffing and/or other
mechanical stresses (such resistance increases if the
molecular weight of the selected resin or resins is
higher). On the other hand, the wax or waxes in such
mixture enhance the flexibility (suppleness) of the protective
- 13 -
205232 ~.
layer 3. Selection of one or more materials which are to
constitute or to form part of the protective layer 3
further depends upon the intended use of the foil. For
example, the ratio of natural and synthetic waxes and/or
resins will be selected in dependency upon the desired
or expected resistance of the layer 3 (or a combination
of film 2 and layer 3) to penetration of one or more
particular gases and/or vapors as well as in dependency
on the environment in which the foil is to be put to use.
In addition to containing one or more afore-
mentioned materials (such as natural and/or synthetic
waxes and/or natural and/or synthetic resins), the
protective layer 3 can also contain one or more friction
reducing substances which act as lubricants. The
addition of one or more lubricants enables the exposed
surface of the protective layer 3 to readily slide
along the exposed surface of a neighboring layer 3 or
along the uncoated side of a substrate 1 or along the
adjacent surface of a product which is to be packed or
wrapped. FIGS. 5 and 6 show a roll 18 of convoluted foil
wherein the exposed surface of the protective layer 3
forming part of an inner convolution is in contact with
the uncoated side of the substrate 1 forming part of the
neighboring outer convolution. The addition of one or
more lubricants ensures that the layer 3 is not damaged as
a result of sliding contact ~~~ith the adjacent substrate 1.
The innermost convolution of the roll 18 surrounds a core 8.
The lubricant is selected in such a v~ay that it
does not.promote the separability of the layer 3 from the
surface 6 of the metallic film 2; on the contrary, the
- 14 -
2052321
selected lubrican or lubricants can enhance the ability
of the layer 3 to strongly adhere to the film 2. P4ore-
over, the selected lubricant can enhance the afore-
discussed desirable characteristics of the protective
layer 3, such as flexibility, resistance to penetration
of oxygen and/or vapors, mechanical strength and/or
others. The percentage of lubricant in the layer 3 is or
can be small so that the addition of lubricant does not
contribute to thickness of the layer to any significant
extent. The lubricant can but need not constitute the
outermost stratum of a protective layer 3 which consists
of two or more superimposed strata.
Another advantage of a lubricant is that it
enables the thus obtained protective layer 3 to constitute
a highly satisfactory priming which enhances the ability
of the foil to accept and retain printed matter. This
is shown in FIG. 3 wherein the exposed surface 3a of the
protective layer 3 carries printed matter 3b. FIGS. 1, 2
and 3 further show that the ratio of thicknesses of the
metallic film 2 and protective layer 3 need not be ffixed,
Thus, the thickness of the layer 3.in FIG. 1 matches or
approximates the thickness of the metallic film 2. On
the other hand, the metallic film 2 which is shown in
FIGS. 2 and 3 is thicker than the protective layer 3.
The presence of lubricant in the protective
layer 3 is often desirable on the additional ground that
such protective layer can be more readily bonded to a
coating 3c of extruded plastic or other material (see
FIG. 4). FIG. 4 further shows that the abutting surfaces
of the film 2 and layer 3 can form a number of hills and
- 15 -
valleys 7.
As already mentioned above, the protective layer
3 can be selected and bonded to the film 2 with a view
to prevent corrosion of the metallic. material of the foil.
The material of the layer 3 can be selected with a view
to prevent corrosion of the film 2 for any desired interval
of time, as long as the layer 3 remains at least
substantially intact. The constituent or constituents
of the layer 3 can be selected with a view to constitute
an anticorrosion barrier for a particular metallic material
as well as in dependency upon the intended use of the foil
and in dependency upon the anticipated mechanical and/or
other stressing of the layer 3 in actual use of the foil.
The lubricant or lubricants in the layer 3 can be
selected in such a way that they do not affect the
ability of the layer 3 to prevent corrosion of the
metallic film 2; on the contrary, certain lubricants can
enhance such ability of the protective layer.
Still further, the material of the protective
layer 3 is preferably selected in such a way that it
exhibits high affinity for the metallic material of the
film 2. Thus, and if the material of the layer 3 is
vaporized prior to contacting the surface 6 of the film 2,
the vaporized material should exhibit pronounced affinity
for the metallic material to thus ensure the establishment
of a reliable and lasting bond which will remain intact
in actual use of the foil. Moreover, such affinity
ensures that the layer 3 overlies and adheres to the
entire surface 6 of the metallic film 2 so that the
quality of each and every portion of the finished product
- 16 -
I ~H~~l.~ ~~
is equally satisfactory. zn addition, such selection of
the material of the layer 3 ensures or contributes to
uniform application of vaporized material o.f the layer 3
to the surface 6 of the film 2.
It is further desirable to select the material
of the protective layer 3 with a view to ensure that the
surface 3a (FIG.3) of the finished layer can readily
accept and retain printed matter 3b which is applied in
accordance with available printing techniques. This can
be readily achieved if the material of the layer 3
contains one or more organic substances of the above
enumerated character, such as one or more natural and/or
synthetic resins and/or one or more natural and/or
synthetic waxes with or without one or more lubricants.
As mentioned above, a properly composed protective layer
3 can serve as a highly satisfactory priming for the
printed matter fib. This renders it possible to dispense
with the application of a priming to the exposed surface
3a of the protective layer 3 prior to the application of
printed matter 3b. A protective layer 3 can serve as a
satisfactory priming for printed matter 3b and/or as an
adhesion-promoting substrate for the extruded coating 3c
of FIG. 4. Such selection of the protective layer 3 (to
serve as a priming for printed matter 3b and/or for the
coating 3c) enhances the versatility of the foil and
reduces its cost because it is not necessary to apply a
specially produced priming over the surface 3a of the
layer 3. It has been found that low-molecular olefin
waxes are particularly suitable for use in a protective
layer 3 which is to serve as an adhesion-promoting priming
- 17 -
21~~2321
for an extruded coating 3~.
Still further, the material of the protective
layer 3 can be selected with a view to ensure that its
surface 3a will accept and retain an adhesive or a solvent
which is to be applied preparatory to the making of a
laminate including the improved foil and one or more
additional sheet-, strip- or web-like materials which are
to be bonded to the layer 3, Moreover, the material of
the extruded coating 3c should be capable of satisfactory
crystallization on the surface 3a of the layer 3.
Polyethylene and polypropylene constitute satisfactory
substrates for a polyolefine coextrusion.
The material of the protective layer 3 is
preferably selected with a view to ensure that it is
physiologically acceptable and that it is preferably
odorless. Thus, the material of the layer 3 should
not affect the c;uality of the products which are to
be wrapped or packed in the improved foil, and such
material should not be harmful to human beings and/or
animals.
The substrate 1 can be made of a wide variety
of materials. Certain presently preferred materials
include polypropylene, polyethylene, polyesters, polyamides,
polystyrene and polyvinyl chloride.
The layer 3 is preferably thing its thickness
can be in the range of 0.5 to 1 g/m2.
FIGS. 6 and 7 show certain parts of a presently
preferred apparatus which can be utilized for the practice
of the improved method, i.e., for the making of the improved
foil. An organic material 22 (which can be a natural or
- 18 -
20~232~.
synthetic wax, a natural or synthetic resin, each with or
without a lubricant, or any combination of such materials
at a desired ratio) is fed into a vaporizer 19 wherein a
heated wall 25 surrounds a bath 23 of organic material
22. The wall 25 is formed with a slot or outlet 24
which enables vapors of organic material 22 to contact
successive increments of the film 2 at the underside of a
substrate 1 which is advanced in the direction of arrow
from a source 13. to the station for the roll 18 of
convoluted foil. The vaporizer 19 is installed in a
vaporizing unit 9 for metallic material which is to form
the film 2. The inlet to the unit 9 is shown at 14,
the peripheral surface of a rotary back support l5 for
the uncoated side of the substrate 1 is shown at 16, and
the character 17 denotes a guide for the substrate 1 and
film 2 during advancement past the vaporizer 19 and a
second vaporizer 35 downstream of the vaporizer 19.
The back support 15 and the guide 17 are installed in the
internal chamber 10 of the vaporizing unit 9, and the
reference characters 1l and 12 denote standard parts of
the unit 9, i.e., of the means for applying the
metallic film 2 to successive increments of the underside
of the substrate 1 which is advanced at a predetermined
speed, namely at a speed which is required to form a film
2 of acceptable guality.
The guide 17 ensures that successive increments
of the freshly formed film 2 advance past the slot 24 of
the wall 25 which is heated by an electric heating element
26 in circuit with an energy source 20 to ensure that the
organic material which enters the internal space 34 of
- 19 -
2n52~'~1
the wall 25 at the inlet 28 of a replenishing device 33
is vaporized to an extent which is necessary to provide the
surface 6 of the metallis film 2 with a layer 3 of
requisite thickness. The cloud or flow of vapors issuing
from the internal space 34 of the wall 25 through the
slot 24 is shown at 21, and such vapors condense on the
surface 6 of the metallic film 2 to form the protective
layer 3. The thickness of the layer 3 depends on a
plurality of parameters, such as the composition of the
bath 23, the rate at which the bath 23 is heated by the
heating element 26 (through the medium of the wall 25),
the speed of advancement of the substrate 1 from the
source 13 toward the roll 18 of convoluted foil, the
rate at which the organic material 22 is fed into the
bath 23, and others. The rate of feed of organic material
23 and the rate of evaporation of such material in the
internal space 34 of the wall 25 are related to the
speed of advancement of the substrate l and film 2 in
order to ensure the formation of a protective layer 3
which has a required thickness and covers the entire
surface 6 of the film 2. On the other hand, the speed
of movement of the substrate 1 from the source 13 toward
the roll 18 depends on the desired thickness of the film
2 which is applied between the back support 15 and the
parts 11, 12 of the vaporizing unit 9.
The heating element 26 is designed to heat the
wall 25 which, in turn, heats the organic material 22 in
the internal space 34 to a temperature above the boiling
or melting point so that the bath 23 discharges vapors
which rise into the slot 24 in the form of a flow or cloud
- 20 -
21 and are converted into the protective layer 3.
FIG. 6 further shows that the layer 3 can be
applied in several successive stages, i.e., such layer
can consist of two or more strata one of which overlies the
surface 6 of the film 2 and each other of which overlies
the previously applied stratum. The second vaporizer 35
is located immediately or closely downstream of the
vaporizer 19, and the vaporizer 35 can be followed by one
or more additional vaporizers (not shown), depending on
the desired number of strata in the layer 3 of the foil
which forms the roll 18, The vaporizer 35 receives an
organic material 38 which is or which can be different
from the organic material 22. The arrangement can be such
that the organic material 22 consists of or contains one
or more natural and/or synthetic resins whereas the organic
material 38 consists of or contains one or more natural
and/or synthetic waxes. Alternatively, each of the '
organic materials 22, 38 can consist of or contain one
or more natural and/or synthetic waxes or one or more
natural and/or synthetic resins, i.e., the composition of
the material 22 can be the same as that of the material 38.
The stratum which is applied by the vaporizer 35 is
shown at 39. The reference character 36 denotes in FIG.
6 the energy source for the electric heater of the vaporizer
35, and the character 37 denotes the cloud or flow of
vapors which are discharged by the vaporizer 35 to form the
stratum 39. It is clear that the vaporizers 19 and 35 can
employ a common energy source 20 or 36; in fact, the
vaporizer 35 can be identical with the vaporizer 19, and
the same applies for one or more additional vaporizers
- 21 -
202321
(if used) downstream of the vaporizer 35. If the apparatus
of FIG. 6 employs three or more vaporizers, the first,
third, etc. vaporizers can receive vaporizable material
of a first composition, and the second, fourth, etc.
vaporizers can receive vaporizable material of a different
second composition.
It is of ten desirable to place the vaporizers 19
and 35 into close or immediate proximity to each other.
This might be desirable and advantageous if the vapors 37
are to contact the material of the preceding stratum
before the material of the preceding stratum sets, i.e.,
the materials tahich are applied by the vaporizers 19 and
35 can be caused or permitted to mix and to form a layer
3 which has been produced in several successive stages
but its composition is at least substantially homogeneous
all the way between the surface 6 of the film 2 and the
exposed surface 3a of the finished protective layer.
Such layer can serve as a fluidtight barrier against
penetration of oxygen and/or vapors into contact with the
metallic film 2.
The distance of successive vaporizers from each
other will depend on the desired nature of the protective
layer 3. Thus, if such layer is to be composed of two
or more discrete superimposed strata (such as the
stratum 39 in FIG. 6), the distance of neighboring
vaporizers from each other will be increased to lengthen
the intervals between the application of successive
vaporized organic materials. The length of such intervals
can vary between, for example, 30 and 120 seconds. The
length of intervals will also depend upon the nature of
- 22 -
vaporized materials and can be constant from vaporizer
to vaporizer or variable, e.g., by increasing or reducing
the speed of advancement of the substrate 1 and metallic
film 2 .
The present invention is based on the recognition
that a metallic film which is applied to a substrate is
subjected to friction practically immediately following
the application of such film to the substrate because, as
a rule, the thus obtained foil is rolled onto a core or the
like as soon as the application of the metallic film is
completed. The neighboring convolutions of a roll 18 of
convolutions forming part of a rolled up foil rub against
each other and, in the absence of any remedial action,
the exposed surface of the metallic film bears against the
adjacent side of the substrate, against the adjacent
surface of a metallic film or against the surface of a
product to be packed or wrapped. Shifting of neighboring
convolutions relative to each other can result in a
minute displacement in the range of one or more tenths
of one millimeter; however, such minor displacements
suffice to affect the integrity of the metallic film,
i.e., the film is likely to be scuff ed and/or otherwise
adversely influenced and to thus suffer damage which affects
its resistance to penetration of oxygen and/or vapors
and/or other desirable characteristics. The quality of
the metallic film is or can be affected regardless of
whether the film is caused to contact another metallic
film, the substrate or any other material. The damage to
metallic film is or can be minute so that it can be
ascertained only as a result of inspection with a
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2052321
microscope; however, such minute damage often suffices
to greatly affect certain desirable characteristics of
the foil, particularly the ability of the metallic film
to prevent the penetration of oxygen and/or vapors there-
through. The exact reasons for an often pronounced drop
of impermeability of the metallic film, even in response
to minute shifting of neighboring convolutions of a
rolled up foil (namely a shifting in the range of one or
more tenths of one millimeter) are still unknown.
However, it is known that the extent of impermeability
or lack of permeability of the metallic film is a function
of several parameters including the extent of shifting
of neighboring convolutions of the roll of foil relative
to each other, the tensional stress upon the convolutions,
the diameter of the roll, the roughness of the surface
which is in contact with the exposed surface of the
metallic film, and certain other factors such as the
temperature of vaporized metallic material which is
being applied to a substrate, the speed of forward
movement of the substrate and the speed of convoluting
the metallized substrate onto a core or the like.
The metallic film on a substrate can be damaged
during rolling of the foil onto a core as well as during
unwinding of the foil and/or during other processing of
the normally convoluted foil, e.g., while the foil is
being severed into sections of desired size and/or shape.
Surprisingly enough, experiments with foils consisting of
metallized~substrates indicate that the permeability of
the metallic film is not dependent upon the thickness
of such film.
_ 2~ _
205232
Heretofore known attempts to reduce the proneness
of a foil, wherein a substrate carries a metallic film,
to damage as a result of rubbing of the exposed surface
of the metallic film against an adjacent surface include
the utilization of a friction reducing layer which is
applied to the exposed surface of the metallic film.
Such experiments have met with auite satisfactory results
if the friction reducing layer was applied to the exposed
surf ace of the metallic film prior to conversion of a
freshly metallized substrate (i.e., a foil) into a roll
of superimposed convolutions. Reference may be had to
commonly otmed U.S. Pat. No, 4,818,609 granted April 4,
1989 for "Packaging comprising substrate metallic layer
and antifriction film". However, such foils also exhibit
a number of serious drawbacks. For example, the friction
reducing layers o~ presently known composition contribute
significantly to the overall thickness of the foil. The
reason is that heretofore known materials which are used
to make friction reducing coatings cannot be applied in a
manner to ensure that they do not significantly increase
the thickness of the foil, i.e., the combined thickness
of a substrate, a metallic film and a friction reducing
layer or coating. This prevents the thus obtained foil
from being utilized in a number of fields, particularly
in connection with the wrapping or packing of certain
foodstuffs and/or cosmetics. Moreover, heretofore known
layers which are intended to reduce friction between
neighboring layers of a foil and/or between a foil and
a material to be packed or wrapped are not capable of
ensuring convenient application of printed matter by
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2052321
resorting to heretofore known printing procedures. The
same applies when a foil which is provided with a
conventional friction reducing layer is to be laminated
with a further foil or with any other sheet-, web- or
strip-like material and/or when a coating is to be
extruded onto the friction reducing layer. Therefore,
the makers of metallized substrates often desist from
utilizing a friction reducing layer on top of the
metallic film in spite of the aforediscussed advantages
of such layers. The reason is that the application of a
conventional friction reducing layer limits the fields
of application of the foils and also that the application
of a conventional friction reducing layer contributes
significantly to the cost of the foil. The cost is
increased because it is very difficult to control the
application of a conventional friction reducing layer in
such a way that the layer does not contribute significantly
to the thickness of the thus obtained foil. Moreover,
if the thickness of the friction reducing layer exceeds
a certain value, the layer is likely to peel off the
adjacent surface of the metallic film so that the
metallic film is exposed to the action of oxygen, water
vapors and/or other undesirable influences. '
The improved foil exhibits a number of important
advantages. Thus, the protective layer 3 shields the
metallic film 2 even before the web or strip including
the substrate 1 and the metallic film 2 is converted into
a roll 18, and the layer 3 also protects the f_Llm 2
during each and every stage of un~,rinding of the foil
from the roll 18, during subdivision of the foil into
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2052321
sections of desired size and/or shape as well as in actual
use as a packaging, wrapping or like material. The film
2 is protected from scuffing, chafing and/or other
mechanical damage, and its flexibility is not affected
by the protective layer since the latter can be more
readily flexible than the film 2 and/or the substrate 1.
The film 2 remains impermeable to fluids, either because
it is shielded from mechanical damage or because its
resistance to penetration of gases and/or other fluids
is enhanced by the protective layer 3.
Another. important advantage of the improved
foil is that the material of the protective layer 3 can
be readily selected and applied in such a way that the
layer exhibits no tendency to become separated from the
metallic film 2, even if the thickness of the layer
matches or exceeds the thickness of the film. Since the
flexibility of the layer 3 can be determined in advance
by appropriate selection of the material or materials which
are to be bonded to the surface 6 of the metallic film,
the f~.nished foil can exhibit a desired flexibility
which is best suited for unwinding from the roll 18, for
severing and/or for conversion into packages of desired
size and/or shape.
Still further, the metallic film 2 can remain
intact for any desired period of time because it is not
subjected to the corrosive action of oxygen and/or vapors.
All that is necessary is to ensure that the protective
layer 3 is applied before the exposed surface 6 of the
metallic film 2 is subjected to any rubbing, scuff ing,
grinding or other mechanical action which would be likely
- 27
2!052321
to render it permeable to fluids. In fact, if the layer
3 is applied before the foil is converted into a roll 18,
the layer 3 contributes to a reduction of friction between
neighboring convolutions of the roll 18 so that the
likelihood of excessive mechanical stressing of the film
2 and/or of the layer 3 is even more remote. Moreover,
and since the layer 3 strongly adheres to the surface of
the metallic film 2, even pronounced pressures between
neighboring convolutions of the roll l8 cannot result in
separation of the layer from the film and/or in mechanical
damage to the layer and/or film. This holes true even
if the protective layer is extremely thin, e.g., in the
range of one or more hundredths of one micron. The
provision of a relatively thin protective layer is
desirable and advantageous in many or most instances
because this entails savings in the material of the
protective layer, a reduction of the thickness of the foil
and a reduction of the dimensions of the roll 18. The
nature of the method of bonding the layer 3 to the
surface 6 of the metallic foil 2 can be readily selected
in such a way that it is not even necessary to continuously
monitor the thickness of the applied protective layer.
This, too, contributes to simplicity and lower cost of
the improved method and apparatus as well as to lower
cost of the finished product.
Though it is possible to make the protective
layer of a material other than an organic material,
organic materials (including the above-enumerated waxes,
resins and lubricants) are preferred at this time because
such organic materials are relatively inexpensive, they
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2052321
can be selected to exhibit pronounced affinity for the metal
of the film 2, and they are effective as protective layers
even if their thickness is minimal. Moreover, it is not
necessary to monitor the application of protective
layer to the film 2 with a high degree of accuracy
because, though it is preferred to apply a protective
layer of predetermined constant thickness, fluctuations
of the thickness of the protective layer are of no great
importance as long as the layer covers the entire surface
6 of the metallic film 2.
The utilization of a lubricant as a constituent
of the material of the protective layer 3 constitutes an
optional but often highly desirable and advantageous
feature of the improved method and of the improved foil,
However, care should be taken to ensure that the
protective layer 3 which contains a lubricant will not
exhibit the drawbacks of aforediscussed friction reducing
layers which are utilized on the metallic films of
certain conventional foils. Thus, the lubricant should
be selected in such a way that it does not tend to smear
the surface of an adjacent foil, metallic film or product
to be wrapped or packed. Lubricants which are applied
directly to the metallic films of conventional metallized
substrates often exhibit a pronounced tendency to
smearing. Lubricants which are present in the protective
layer 3 can be readily distributed in the other material
or materials of the layer 3 in such a way that they can
perform their friction reducing function but are
incapable of smearing the surfaces of adjacent foils
and/or other parts. In fact, the aforementioned organic
- 29 -
202321
materials of the protective layer 3 (including natural
and synthetic resins and/or natural and synthetic
waxes) often exhibit highly satisfactory rriction reducing
characteristics so that the utilization of a typical
lubricant (i.e., of a substance which is to be utilized
solely on account of its friction reducing characteristics)
can be dispensed with.
The protective layer 3 is capable of taking up
all mechanical and/or other stresses which are applied
directly to the metallic films of many heretofore known
foils. This contributes significantly to the useful
life as well as to impermeability and/or other desirable
characteristics of the metallic foil. Furthermore, the
protective layer 3 prevents direct contact between the
metallic foil 2 and the product or products to be packed,
wrapped and/or otherwise protected by the improved foil,
a feature which is often highly desirable and advantageous,
for example, when the improved foil is to contact a
substance containing acids or other ingredients which are
likely to attack the metallic film.
The toughness of the protective layer 3, including
the resistance to scratching, tearing, scuffing and/or
other influences.can be selected practically at will by
the simple expedient of selecting the thickness and/or
the composition of the protective layer. It has been
found that a protective layer 3 which contains or consists
of an artificial resin is especially suited to ensure the
establishment of a highly reliable intimate bond between
the protective layer and the surface 6 of the metallic film
2. On the other hand, a protective layer which contains
- 30 -
20~23~~
one or more natural resins can be used with particular
advantage when the improved foil is to be employed as a
packing or wrapping material for foodstuffs; such
protective layers exhibit a highly satisfactory flexibility
and a highly satisfactory resistance to scuffing and other
undesirable mechanical influences.
The lubricants which are to be utilized as
constituents of the protective layer can include various
oils, greases, graphite and/or others. These Lubricants
can be selected in such a way that they reduce friction
between the Layer 3 and a neighboring layer as well as
that they contribute to the corrosion-preventing or
corrosion~reducing characteristics of the protective layer.
As mentioned above, the metallic film 2 can be
applied to the substrate l, and the protective layer 3
can be bonded to the surface 6 of the metallic film 2,
in any well known manner as long as the selected
procedures ensure proper adherence of the film to the
substrate and to the protective layer. Vaporization of
metallic material preparatory to making of the film 2,
and vaporization of the material or materials of the
protective layer prior to bonding to the surface 6 of the
film 2 are preferred at this time because they permit
simple, inexpensive and reliable regulation of the thi~.kness
of the film 2 and of the layer 3 as well as proper
adherence of the film to the substrate and proper
bonding of the layer 3 to the metallic film. All that
is necessary is to control the speed of advancement of the
substrate 1 past the metallizing station and to control
the temperature and/or other parameters of the material
- 31 _
CA 02052321 2003-05-23
28680-7
or materials which are to form the protective layer 3.
The lubricant in the protective layer of the
improved foil can be the same as that disclosed in the
aforementioned commonly owned U.S. Pat. No. 4,818,609,
and the methods of bonding the protective layer 3 to the
surface 6 of the metallic film 2 can be the same as
those discussed in the aforementioned commonly owned
patent for the application of antifriction film to the
metallic layer.
EXAMPLE 1
A substrate of polyethylene was provided with a
film of aluminum in a standard vaporizing unit. A
vaporizer (such as 19) was used in the vaporizing unit
for metallic material to apply a protective layer to
successive increments of the freshly formed metallic film.
The material of the protective layer was a readily
meltable resin which was heated in the vaporizer to a
temperature of 210°C. This resulted in the development
of vapors which were directed against the exposed surfac a
of the metallic film. Condensation of such vapors on
the film resulted in the development of a protective layer
with a thickness of 0.05 ~. The resin was of the type
known as PENTALYN 255 which is produced by Hercules Inc.,
Wilmington, Delaware. The thickness of the protective
layer was uniform, and such layer covered the entire exposed
surface of the metallic film, i.e., that surface which
faces away from the substrate. Cooling of the vapors
on the surface of the metallic film was rapid, practically
instantaneous, so that the thus obtained foil was ready for
conversion into a roll of superimposed convolutions without
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28680-7
in any way affecting the integrity of the protective layer ,
FYAMDT.F 7
A running substrate of polyethylene was provided
with a film of aluminum at a customary temperature and
pressure. The application of metallic film was immediately
followed by the application of vaporized organic material,
namely a resin known as PEXIGRUP°~~M 52which is produced
and sold by Rohm GmbH, Darmstadt, Federal Republic Germany.
The organic material was heated to a temperature of 23S°C
and the thus developed vapors were caused to contact the
exposed surface of the aluminum film. The thus obtained
protective layer adhered firmly to the aluminum film and
had the thickness of approximately 0.04 u. The hardness
of the protective layer was sufficient to permit
conversion of the foil into a roll inunediately following
the formation of the protective layer.
FYAMDT.F' Z
A substrate of polyester was provided with a
film of aluminum in a vaporizing unit at a customary
temperature and pressure. A protective layer of organic
material was bonded to the exposed surface of the
aluminum film immediately after completion of application
of aluminum to one side of the substrate. The organic
material was a mixture of a resin of tl:e type known as
HALLOLYN 104 which is produced by Hercules Inc., Plilmington,
Delaware and a wax known as E-Wachs 20R 6149 produced by
BASF. The ratio of resin to wax in the material which was
used to form the protective layer was approximately nine-
to-one. The two ingredients were mixed in a single
vaporizer and were heated to vaporization temperature to
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CA 02052321 2003-05-23
28680-7
develop vapors which were contacted by successive increments
of the freshly applied aluminum film. The flexibility of
the protective layer containing I-IALLOLYN 104*and E-Wachs*
20R was improved by applying first a stratum of wax in a
first vaporizer directly onto the aluminum film and by
thereupon applying in a second vaporizer a second stratum
of resin over the stratum of wax. The second stratum
was applied prior to complete setting of the material of
the stratum of wax.
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