Note: Descriptions are shown in the official language in which they were submitted.
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COLORED POLYOLEF1N FILM AND METHOD OF MAKING
Related Applications
This application is a continuation-in-part of Application Serial No. to be
assigned (ExxonMobil Docket No. 10234, inventors: Pang-Chia Lu, Robert
Sheppard, Don Burns, Robert Migliorini, Sal Pellingra, Karen Sheppard, Robert
Peet)), filed December 19, 2000, entitled "Colored Polyolefin Film and Method
of
Making," the entire disclosure of which is hereby incorporated herein by
reference.
to
BACKGROUND OF THE INVENTION
The present invention relates to coextruded films made of multiple layers of
thermoplastics, wherein at least one of the layers is colored using a coloring
agent,
15 and at least one of the remaining layers is opaque.
In the packaging of certain types of foods, such as snack foods like potato
chips,
cookies and the like, it is common practice to employ a mufti-layer film. A
desirable property in such a packaging film is an opacity which protects the
2o packaged product from deterioration caused by exposure to light. In
particular, it
has been found that certain wavelengths of light, up to about 450 nm cause
increased spoilage in such packaged products. Even when a degree of opacity is
present in the film, some spoilage may occur depending on how much light may
pass through.
Oriented opaque film compositions are known in the art. U.S. Pat. No.
4,377,616
discloses an opaque, biaxially oriented polymeric film structure of lustrous
satin
appearance comprising a thermoplastic core matrix having a strata of voids;
said
voids being created by the inclusion within the matrix material of spherical
void-
initiating solid particles which are incompatible with the matrix material.
The
void space occupied by the particle is substantially less than the volume of
the
void. The polymer matrix material is extruded in the form of a film and
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2
positioned on opposite surfaces of the film are void free, transparent
thermoplastic
skin layers adhering to said surfaces. The structure has excellent opacity and
extremely high gloss measurement and a lustrous satin appearance.
U.S. Pat. No. 4,632,869 discloses a resin combination comprising a
thermoplastic
polymer matrix having dispersed therein as distinct phases, a multiplicity of
small
spherical solid particles of polybutylene terephthalate, the resin combination
in
opaque biaxially oriented polymeric film form and the same oriented film
structure having on at least one surface thereof a void-free thermoplastic
skin
layer. The process for preparing a biaxially oriented opaque film comprising
providing said resin combination, forming an unoriented film of said resin
combination and biaxially orienting said film to an extent sufficient to
opacify the
same. The process also provides for the opaque film having a void-free
thermoplastic skin layer on at least one surface thereof.
U.S. Pat. No. 5,176,954 also discloses a non-symmetrically layered, highly
opaque, biaxially oriented polymer film with a core containing numerous
microscopic voids and at least about 1 % by weight of opacifying compounds; a
first skin layer on one surface of the core containing up to about 12% by
weight of
inorganic particulate material; and a second skin layer on the other surface
of the
core.
U.S. Pat. No. 5,397, 635 also a multi-layer opaque, biaxially oriented
polymeric
film structure. The film structure includes a thermoplastic polymer matrix
core
layer having a first surface and a second surface, within which is located a
strata
of voids, positioned at least substantially within a substantial number of the
voids
is at least one spherical void-initiating particle which is phase distinct and
.
incompatible with the matrix material, the void space occupied by the particle
being substantially less than the volume of the void, the population of the
voids in
3o the core being such as to cause a significant degree of opacity, a first
thermoplastic polymer skin layer having a first surface and a second surface,
the
first surface of the first skin layer adhering to the first surface of the
core layer, the
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3
first skin layer including up to about 12% by weight of titanium dioxide
contact
pigment, and a second thermoplastic polymer skin layer having a first surface
and
a second surface, the first surface of the second skin layer adhering to the
second
surface of the core layer, the second skin layer including finely divided,
uniformly
dispersed inorganic material in an amount effective to impart antiblocking
characteristics and decrease the inherent film-to-film coefficient of friction
at the
second surface of the second thermoplastic polymer skin layer.
U.S. Pat. No. 5,972,490 discloses a biaxially oriented polyolefin films
comprising
a core layer of propylene polymer, an intermediate layer of a non-voided,
substantially non-pigmented propylene polymer on the core layer, and an outer
skin layer of a polyolefin including titanium dioxide as a pigment are
disclosed.
U.S. Pat. No. 4,758,396 discloses a process for the preparation of a biaxially
stretch-oriented film having at least one opaque layer. The opaque layer is
composed essentially of propylene polymer and fillers in a quantity of about
10 to
40% by weight, relative to the total weight of propylene polymer and fillers.
In
production, the granules are melted in a screw extruder, are forced through a
die
and are formed by cooling to give a preformed film. The preformed film is then
2o stretch-oriented both along the machine direction and transversely
perpendicular
to the machine direction and is then heat-set. The fillers are added in the
form of a
masterbatch to the granules of unfilled polymers. The masterbatch should have
a
filler content of more than about 30% by weight.
U.S. Pat. No. 4,758,462 discloses an opaque, biaxially oriented film structure
which comprises: an expanded thermoplastic polymer matrix core layer within
which is located a minor amount of a light-absorbing pigment and a strata of
voids; positioned at least substantially within at least a substantial number
of said
voids is at least one void-initiating particle which is phase distinct and
incompatible with the matrix material, the void space occupied by said
particle
being substantially less than the volume of said void, with one generally
cross-
sectional dimension of said particle, at least approximating a corresponding
cross-
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sectional dimension of said void; the population of voids in said core and the
thickness of said core being such as to cause a degree of opacity of less than
15%
light transmission; and at least one void-free thermoplastic skin layer
affixed to a
surface of the core layer, said skin layers) being of a thickness such that
the outer
surfaces thereof do not, at least substantially, manifest the surface
irregularities of
said core layer.
U.S. Pat. No. 4,652,489 discloses a sealable, opaque polyolefinic multilayer
film
composed of a polypropylene base layer, a non-sealable surface layer, and a
l0 sealable surface layer, and process therefor. The sealable surface layer
has a low
minimum sealing temperature and is made from a copolymer of propylene and
ethylene or butene-1 units and/or a terpolymer of ethylene, propylene and
butene-
1 units. The non-sealable layer is a combination of a propylene homopolymer
and
a slip agent. The base layer contains an additive which is incompatible with
15 polypropylene. The process includes stretching of the film, and during the
stretching step, the polymer matrix is torn open around the additive particles
to
form vacuoles which give the base layer a degree of opacity.
U.S. Pat. No. 4,741,950 discloses a surface treated oriented polymer laminate
film
20 which possesses a comparatively rough, non-blocking first surface and a
smooth,
lustrous second surface which is particularly well suited for further film
processing operations such as metallization.
U.S. Pat. No. 4,594,211 discloses a thin polyolefine based film, having a
thickness
25 of from about 15 to about 200 microns, which is perfectly non-transparent
in spite
of its low thickness. The film is composed of polyolefine as a homopolymer, an
ethylene-vinyl acetate copolymer, and a pigment filler such as titanium
dioxide as
rutile, and aluminium powder. Color pigments and dispersing agents may also be
present. The film is made by extrusion.
Also, in the packaging of certain types of foods, such as snack foods like
potato
chips, cookies and the like, one or more colors may be printed onto the film
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packaging. A desirable property in such a packaging film is bright coloring
with a
pleasing aesthetic appearance.
U.S. Pat. No. 4,894,264 discloses a single-sheet gusset bag for photographic
photosensitive materials formed of a laminated sheet comprising a metal foil
layer
or metallized flexible sheet layer, a water-absorptive, and heat-resistant
flexible
sheet layer which resists dust formation laminated on the outside of said
metal foil
layer or metallized flexible sheet layer, and a light-shielding polyolefin
resin film
layer containing at least linear low density polyethylene resin, carbon black
and an
1o antioxidant and having a thickness of more than 50 mu m laminated on the
inside
of said metal foil layer or metallized flexible sheet layer, and the bottom
seal
portion is turned or rolled and fixed by an adhesive or adhesive tape.
U.S. Pat. No. 4,536,184 discloses overprinting a polyvinyl chloride) resin
substrate whose surface, or portion thereof, is colored by solvent soluble dye
or by
way of a mass solvent soluble dye, with a coloring agent made up of a liquid
halogenated hydrocarbon solvent having 1-4 carbon atoms, pigment dispersed in
said halohydrocarbon solvent, and a film former, dissolved in said
halohydrocarbon solvent, consisting essentially of (a) acrylic resin or (b) a
combination of acrylic resin and chlorinated polyolefin, at least 50% by
weight of
acrylic resin; and heat treating said overprinted substrate to adhere said
film
former and associated pigment.
U.S. Pat. No. 5,683,805 discloses a colored film formed of a transparent film
and
at least one colored adhesive layer arranged on one side of the transparent
film.
The adhesive layer has been colored by a colorant composed of a pigment and a
dispersant. The dispersant comprises a (meth)acrylate ester polymer formed, as
essential monomer components, of an aromatic vinyl monomer, a primary to
tertiary amino-containing (meth)acrylate ester monomer and a (meth)acrylate
ester
3o monomer containing an ammonium group quaternized with an aromatic
compound.
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U.S. Pat. No. 5,328,743 discloses a reinforced shrink wrap that has been
developed for use in alI types of environments and products or applications.
The
shrink wrap is tear resistant and can be prepared to withstand exposure from
the
sun and corrosive elements. The wrap is multilayered with reinforcing
filamentous grids in adhesive layers on either side of a shrink film with
outer
layers of olefin film.
U.S. Pat. No. 4,681,803 discloses a pigmented, heat-sealable coating
composition
for application to a primer-coated, oriented mono-layer or multilayer
polyolefin
film which comprises a blend of (a) a binding and oxygen barrier effective
amount
of a heat-sealable polyvinylidene chloride homopolymer and/or polyvinylidene
chloride copolymer containing at least about 50 weight percent copolymerized
vinylidene chloride, (b) an amount of wax sufficient to result in a
significant
reduction in the coefficient of friction of a film to which the coating
composition
is applied and (c) an amount of pigment sufficient to result in a significant
reduction in the light transmission property of a film to which the coating
composition is applied.
2o Accordingly, it is an object of the present invention to provide a colored
film with
low light transmission especially in the UV and blue wavelengths. It is a
further
object of the present invention to provide a colored film which also has,high
opacity. It is yet another object of the present invention to provide a
colored film
which may be bonded to a wide variety of substrates and coatings.
SUMMARY OF THE INVENTION
The film structure of the present invention is a opaque, biaxially oriented
polymeric film with an inner core containing numerous microscopic voids and at
least about 1% by weight of void initiating or opacifying compounds and/or
particles; a first intermediate layer on one surface of the core layer,
containing a
coloring agent; a first skin layer on the outside of the first intermediate
layer
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7
which may or may not contain a coloring agent; a second intermediate layer on
the
other surface of the core layer and a second skin layer on the outside of the
second
intermediate layer. The second intermediate layer and/or the second skin layer
may or may not contain a coloring agent.
In one family of embodiments, when relatively low concentrations of the
coloring
agents are used, the film offers a deep and vibrant color. This results from a
comparatively large portion of the incident light reaching the opaque inner
core
where it is reflected or refracted back through the first intermediate layer
to containing a coloring agent; without too much scattering. The film
typically
offers good protection against light going through the film, with an opacity
greater
than 60%, and light transmission less than 40% in the wavelength range of from
250 nm to 500 nm which is particularly damaging to a packaged food product.
15 The configuration of the layers offers great flexibility and economy in
achieving
desired film characteristics. The first intermediate and skin layers which may
be
on a package exterior allow optimum protection against water vapor
transmission
and a vibrantly colored surface which can be printed, laminated or otherwise
modified. The inner core layer has all the advantages of cavitation with
protection
2o against light transmission. The second intermediate layer can also be
colored the
same or a different color for a film with the same or different colors on each
side.
The second skin layer can be a simple, economical thin encapsulating layer or
it
can be a more elaborate heat sealable layer.
25 The composition of the layers can allow for a differential appearance when
viewed from the first skin layer or when viewed from the second skin layer. A
first color will be viewed on the first skin layer together with any printing
or other
modifications. A second color can be viewed on the second skin Layer together
with different printing or modifications, or the appearance from the second
skin
30 layer can be a plain white which would be suitable for the inside of a food
package.
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For a better understanding of the present invention, together with other and
further
objects, reference is made to the following description, taken together with
the
accompanying drawings, and its scope will be pointed out in the appended
claims.
s BRIEF DESCRIPTION OF THE DRAWINGS
The novel features believed characteristic of the invention are set forth in
the
appended claims. The invention itself however, as well as a preferred mode of
use, further objects and advantages thereof, will best be understood by
reference
to to the following detailed description of several illustrative embodiments
when
read in conjunction with the accompanying drawings, wherein:
Figure 1 is a schematic diagram of a method for determining percent light
transmission;
Figure 2 is a schematic diagram of a method for determining percent opacity;
Figure 3 is a cross sectional view of a five layered colored film;
Figure 4 is a cross sectional view of a three layered colored film;
Figure 5 is a cross sectional view of a four layered colored film; and
Figure 6 is a cross sectional view of a two layered colored film.
DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1, shows how the percent light transmission through a film is
determined
by using light source 2 to transmit light rays 3 directly through film 4 and
3o measuring at light sensor 5, value T2 which is the amount of light rays 3
which is
transmitted through film 4. The amount of light rays 3 which can be directly
transmitted, value Tl, is determined by measuring the light rays 3 directly
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9
transmitted by light source 2 with no intervening film. The percent light
transmission through the film can then be determined using the formula:
Light Transmission = T2 /T1 * 100
Referring now to Figure 2, for a measure of percent opacity of a film, light
source
2 transmits light rays 3 through film 4 onto a white surface 9 and the same
procedure used to project light onto a black surface 10. With both white and
black
surfaces, measurement at light sensor 5 is of all of the following: light
reflected
off the upper surface of the film 6; light transmitted through the film and
reflected
to by the white surface 9 or black surfaces 10 on the side of the film
opposite from
the light source 7; and, light scattered by the film 8.
The percent opacity of the film can then be determined using the formula:
Opacity =100 * RB /RW
where
RW = Reflected light+scattered light+light transmitted through the film and
reflected off a white surface
RB = Reflected light+scattered light+light transmitted through the film and
reflected off a black surface
Accordingly, a highly reflective film may provide high opacity while allowing
light transmission. This is because percent light transmission is not the
equivalent
of percent opacity.
Light transmission is the amount of light passing directly through the film.
To
prevent food spoilage decreased light transmission is desirable. Prevention of
light
transmission in shorter LTV wavelengths up to 400 nm and the blue-violet range
of
from 400 to 450 nm is particularly desirable for this purpose.
Referring now to Figure 3 is a cross sectional view of a five layered colored
film
50. The film 50 is comprised of a first surface 11, a f rst skin layer 10, a f
rst
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intermediate or transition layer 12, an opaque core layer 14, a second
intermediate
or transition layer 16, a second skin layer 18, and a second surface 19.
In one embodiment of a five layered film 50, the first skin layer 10 and/or
the first
5 transition layer 12 can be colored by a coloring agent. The percent light
transmission of the combination of the first skin layer 10 and the first
transition
layer 12 is relatively high, in one embodiment from 50-99%, in another
embodiment from 65-97% and in a third embodiment from 75-95%. Additionally
the percent opacity of the combination of the first skin layer 10 and the
first
to transition layer 12 is relatively low, in one embodiment from 1-50%, in
another
embodiment from 3-40% and in a third embodiment from 5-25%. This
combination of low opacity and high light transmission allows the light to
enter
the first surface 11 travel through the first skin layer 10 and the first
transition
layer 12 and reach the opaque core layer 14 from where it is reflected and
travels
back through the first transition layer 12 and the first skin layer 10 to
reach the
first surface 11 and provide for deep and vibrant color. In this embodiment,
the
percent Iight transmission of the film 50 is relatively low, in one embodiment
from 0-30%, in another embodiment from 0-20% and in a third embodiment from
0-10%. 'Additionally the percent opacity of the film 50 is relatively high, in
one
2o embodiment from 50-100%, in another embodiment from 75-100% and in a third
embodiment from 90-100%. This combination of low light transmission and high
opacity for the film 50 provides a desirable packaging material which protects
the
packaged product from deterioration caused by exposure to light.
In a second embodiment, the first skin layer 10 and/or the first transition
layer 12
can be colored by a coloring agent as in the first embodiment, and the second
skin
Iayer I8 and/or the second transition Iayer 16 can also be colored by a
coloring
agent as in the first embodiment. This film 50 allows for one deep and vibrant
color to be seen on the first surface 11 and the same or a different deep and
vibrant color to be seen on the second surface 19. In this embodiment, the
percent
light transmission of the film 50 is relatively low, in one embodiment from 0-
30%, in another embodiment from 0-20% and in a third embodiment from 0-10%.
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11
Additionally the percent opacity of the film 50 is relatively high, in one
embodiment from 50-100%, in another embodiment from 75-100% and in a third
embodiment from 90-100%. This combination of low light transmission and high
opacity for the film 50 provides a desirable packaging material which protects
the
packaged product from deterioration caused by exposure to light.
In a third embodiment of a five layered film 50, the first skin layer 10 is
essentially transparent and the first transition layer 12 is colored by a
coloring
agent. Additionally, the first surface 11 on top of the first skin layer 10 an
image
to is printed. The percent light transmission of the first transition layer 12
is
relatively high, in one embodiment from 50-99%, in another embodiment from
65-90% and in a third embodiment from 75-85%. Additionally the percent
opacity of the first transition layer 12 is relatively low, in one embodiment
from 1-
50%, in another embodiment from 5-40% and in a third embodiment from 10-
15 25%. This combination of low opacity and high light transmission allows the
light to enter the first surface 11 travel through the first skin layer 10 and
the first
transition layer 12 and reach the opaque core layer 14 from where it is
reflected
and travels back through the first transition layer 12 and the first skin
layer 10 to
reach the first surface 11 and provide for deep and vibrant color and produces
a 3-
2o D effect which makes the printed image appear to float on top of the film
50. In
this embodiment, the percent light transmission of the film 50 is relatively
low, in
one embodiment from 0-30%, in another embodiment from 0-20% and in a third
embodiment from 0-10%. Additionally the percent opacity of the film 50 is
relatively high, in one embodiment from 50-100%, in another embodiment from
25 75-100% and in a third embodiment from 90-100%. This combination of low
light transmission and high opacity for the film 50 provides a desirable
packaging
material which protects -the packaged product from deterioration caused by
exposure to light. One variation of the third embodiment has a printed image
on
the first surface 11, a first skin layer 10 made of polyethylene, a first
transition
30 layer 12 made of a colored polypropylene, a core layer 14 made of cavitated
polypropylene, a second transition layer 16 made of polypropylene, and a
second
skin layer 18 made of polypropylene.
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In a fourth embodiment of a five layered film 50, inorganic additives are
added to
the first skin layer 10 to impart a rough low-gloss paper-like feel to the
first
surface 11 to simulate kraft paper. The first transition layer 12 is colored
by a
coloring agent, with a sufficient amount of coloring agent to yield a brown
kraft
paper color. Additionally, the second skin layer 18 preferably has inorganic
additives added to impart a rough low-gloss paper-like feel to the second
surface
19 to simulate kraft paper. The second transition layer 16 may be colored by a
coloring agent, with a sufficient amount of coloring agent which could be
white.
l0 One variation of the fourth embodiment has a first surface 11 with a brown
coloring and a rough low-gloss paper-like feel and a second surface 19 with a
white coloring and a rough low-gloss paper-like feel. In this embodiment, the
percent light transmission of the film 50 is relatively low, in one embodiment
from 0-30%, in another embodiment from 0-20% and in a third embodiment from
0-10%. Additionally the percent opacity of the film 50 is relatively high, in
one
embodiment from 50-100%, in another embodiment from 75-100% and in a third
embodiment from 90-100%. This combination of low light transmission and high
opacity for the film 50 provides a desirable packaging material which protects
the
packaged product from deterioration caused by exposure to light.
A fifth embodiment has a first skin layer 10 made of an EP impact copolymer or
blend of incompatible resins such as PP homopolymer, EP copolymer, EPB
terpolymer, HDPE, or LDPE copolymer, and addition of CaC03, talc, and Si02.
In one variation of the fifth, the first skin layer 10 is 0.5 to 3.0 microns
thick. The
first transition layer 12 is brown colored and made of as PP homopolymer, EP
random copolymer, PB copolymer, EPB terpolymer, HDPE, LLDPE, or MDPE
with a blend of iron oxide, carbon black, and TiOa. In another variation, the
first
transition layer 12 is 1 to 7 microns thick. In a third variation, the core
layer 14 is
made of an isotactic cavitated polypropylene and is 5 to 50 microns thick. The
3o second transition layer 16 is non-colored (white) and made of as PP
homopolymer, EP random copolymer, PB copolymer, EPB terpolymer, HDPE,
LLDPE, or MDPE with Ti02. In another variation, the second transition layer 16
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13
is 1 to 7 microns thick. The second skin layer 18 is made of an EP impact
copolymer or blend of incompatible resins such as PP homopolymer, EP
copolymer, EPB terpolymer, HDPE, or LDPE copolymer, and the addition of
CaC03, talc, and/or SiOz. In another variation, the second skin layer 18 is
0.5 to
3.0 microns thick.
In a sixth embodiment of a five layered film S0, the first skin layer 10
and/or the
first intermediate or transition layer 12 can be colored by a coloring agent
that
absorbs and/or scatters most of the light incident on the film. The percent
light
to transmission of the first skin 10 and the first intermediate or transition
12 layers
will be relatively low, in one embodiment from 0-70%, in another embodiment
from 0-SO%, and in a third embodiment from 0-30%. In the sixth embodiment the
percent opacity will be relatively high, in one embodiment from 30-100%, in
another embodiment from SO-100%, and in a third embodiment from 70-100%.
15 Very little of the incident light will travel through the layer containing
the color
agent, reflect off the cavitated core layer, and return through the colored
layer
back to the observer without being scattered or absorbed. The overall percent
light transmission of the film 50 is low, in one embodiment from 0-30%, in
another embodiment from 0-20%; and in a third embodiment from 0-10%. The
20 overall opacity of the film 50 is relatively high, in one embodiment from
70-
100%, in a second embodiment from 80-100%, and in a third embodiment from
90-100%. This combination of low light transmission and high opacity for the
film SO without the internal reflection of light returning from the cavitated
layer
back to the observer provides a more restrained or sedate look, typical of a
paper-
25 like look or of a color-coated or printed film, and is a desirable
packaging material
which protects the packaged product from deterioration caused by exposure to
light.
In a seventh embodiment of a five layered film S0, the first skin layer 10
and/or
3o the first intermediate or transition layer 12 can be colored by a coloring
agent as
described in the sixth embodiment, and the second skin layer 18 and/or the
second
transition or intermediate layer 16 can also be colored by a coloring agent as
in the
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first or sixth embodiment. In this embodiment, most of the light incident on
the
colored layer or layers having coloring agents which absorb or scatter most of
the
light incident upon them will be absorbed by the coloring agent. The percent
light
transmission of such layers will be relatively low, in one embodiment from 0-
70%, in another embodiment from 0-50%, and in a third embodiment from 0-
30%. The percent opacity will be relatively high, in one embodiment from 30-
100%, in a second embodiment from 50-100%, and in a third embodiment from
70-I00%. Very little of the incident light will travel through the layer or
layers
containing such a coloring agent, reflect off the cavitated core layer, and
return
1 o through the colored layer back to the observer without being scattered or
absorbed. The overall percent light transmission of the film 50 is low, in one
embodiment from 0-30%, in another embodiment from 0-20% and in a third
embodiment from 0-10%. The overall opacity of the film opacity of the film 50
is
relatively high, in one embodiment from 70-100%, in another embodiment from
80-100%, and in a third embodiment from 90-100%. This combination of low
light transmission and high opacity for the film 50 provides a more restrained
or
sedate look, typical of a paper-like look or of a color coated or printed
film, on
one or both sides without the internal reflection of light returning from the
cavitated layer back to the observer, and can, alternatively, have the deep
and
2o vibrant look on a side selected as described in the first embodiment, and
is a
desirable packaging material which protects the packaged product from
deterioration caused by exposure to light.
Referring now to Figure 4 is a cross sectional view of a three layered colored
film
30. The film 30 is comprised of a first surface 11, a first skin layer 10, a
first
transition layer 12, an opaque core layer 14, and a second surface 19.
In one embodiment of a three layered film 30, the first skin layer 10 and/or
the
first transition layer 12 can be colored by a coloring agent. The percent
light
3o transmission of the combination of the first skin layer 10 and the first
transition
layer 12 is relatively high, in one embodiment from 50-99%, in another
embodiment from 65-90% and in a third embodiment from 75-85%. Additionally
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the percent opacity of the combination of the first skin layer 10 and the
first
transition layer 12 is relatively low, in one embodiment from 1-50%, in
another
embodiment from 5-40% and in another embodiment from 10-25%. This
combination of low opacity and high light transmission allows the light to
enter
5 the first surface 11 travel through the first skin layer 10 and the first
transition
layer 12 and reach the opaque core layer 14 from where it is reflected and
travels
back through the first transition layer 12 and the first skin layer 10 to
reach the
first surface 11 and provide for deep and vibrant color. In this embodiment,
the
percent light transmission of the film 30 is relatively low, in one embodiment
to from 0-30%, in another embodiment from 0-20% and in a third embodiment from
0-10%. Additionally the percent opacity of the film 30 is relatively high, in
one
embodiment from 50-100%, in another embodiment from 75-100% and in a third
embodiment from 90-100%. This combination of low light transmission and,high
opacity for the film 30 provides a desirable packaging material which protects
the
15 packaged product from deterioration caused by exposure to light.
In a second embodiment of a three layered film 30, the first skin layer 10 is
essentially transparent and the first transition layer 12 is colored by a
coloring
agent. Additionally, the first surface 11 on top of the first skin layer 10 is
printed
on with an image. The percent light transmission of the first transition layer
12 is
relatively high, in one embodiment from 50-99%, in another embodiment from
65-90% and in a third embodiment from 75-85%. Additionally the percent
opacity of the first transition layer 12 is relatively low, in one embodiment
from 1-
50%, in another embodiment from 5-40% and in a third embodiment from 10-
25%. This combination of low opacity and high light transmission allows the
light to enter the first surface 11 travel through the first skin layer 10 and
the first
transition layer 12 and reach the opaque core layer 14 from where it is
reflected
and travels back through the first transition layer 12 and the first skin
layer 10 to
reach the first surface 11 and provide for deep and vibrant color and make the
3o printed image appear to float on top of the film 30. In this embodiment,
the
percent light transmission of the film 30 is relatively low, in one embodiment
from 0-30%, in another embodiment from 0-20% and in a third embodiment from
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16
0-10%. Additionally the percent opacity of the film 30 is relatively high, in
one
embodiment from 50-100%, in another embodiment from 75-100% and in a third
embodiment from 90-100%. This combination of low light transmission and high
opacity for the film 30 provides a desirable packaging material which protects
the
packaged product from deterioration caused by exposure to light.
Referring now to Figure 5 is a cross sectional view of a four layered colored
film
40. The film 40 is comprised of a first surface 11, a first skin layer 10, a
first
transition layer 12, an opaque core layer 14, a second skin layer 18, and a
second
to surface 19.
There are multiple possible embodiments with the four layered colored hlm 40.
The first skin layer 10, the first transition layer 12, and/or the second skin
layer 18
can all be colored by a coloring agent to yield a single colored film or a
dual
15 colored film as seen on the first surface 11 and the second surface 19.
Additionally, the first skin layer 10 and/or the second skin layer 18 can be
printed
on or treated with inorganic additives to impart a rough low-gloss paper-like
feel
to the first surface 11 and/or the second surface 19.
2o Referring now to Figure 6 is a cross sectional view of a two layered
colored film
20. The film 20 is comprised of a first surface 11, a f rst skin layer 10, an
opaque
core layer 14, and a second surface 19.
There are multiple possible embodiments with the two layered colored film 20.
25 The first skin layer 10 can be colored by a coloring agent to yield a
single colored
film as seen on the first surface 11 and the second surface 19. Additionally,
the
first skin layer 10 can be printed on or treated with inorganic additives to
impart a
rough low-gloss paper-like feel to the first surface 11.
3o In one embodiment, the opaque core layer 14 of film 50, film 30, film 40,
and film
20 is a thermoplastic polymer matrix material within which is preferably
located a
stratum of voids. From this it is to be understood that the voids create the
matrix
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17
configuration. The opacity and low light transmission of the film are
preferably
enhanced by the addition to the core layer 14 of at least about 1 % by weight
and
up to about 10% by weight of void initiating on opacifying compounds, which
are
added to the melt mixture of the core layer 14 before extrusion. Opacifying
compounds which may be used include iron oxides, carbon black, aluminum,
Ti02, and talc. Although one embodiment has a strata of voids located in the
opaque core layer 14, it is possible to form an opaque core layer 14 that is
substantially free of voids where the opacity is achieved by the addition of
opacifying compounds.
In another embodiment, to aid in providing the film with low light
transmission,
especially in the UV and blue wavelengths, iron oxide is added to the core
layer
14 in an amount of from about 1 to about 8% by weight, or in another
embodiment about 2% to 4% by weight. Carbon black or other compounds may
also be used. In another embodiment, aluminum is also added in an amount of
from about 0 to about 1.0% by weight, in another embodiment from about 0.25%
to about 0.75% by weight, and in another embodiment about 0.5% by weight. In
another embodiment, the core layer 14 also contains from about 0.5% by weight
to about 3% by weight of TiOa and/or talc.
In one embodiment, from about 3% to about 9% by weight of inorganic
particulate material such as Ti02 and/or talc is added to the melt mixture of
the
core layer 14 before extrusion.
As a result of the additions to the first skin layer 10, first transition
layer 12,
opaque core layer 14, second transition layer 16, and/or second skin layer 18,
the
film presents a differential appearance. The term "differential" as applied to
the
film of this invention is intended to convey the concept of the distinctly
dissimilar
composition and appearance of each exposed film surface: the first surface 11
and
3o the second surface 19. When viewed from the first surface 11, the film can
have
vibrant coloration, a printed image that appears to float on a colored film,
or a
kraft paper like finish, a general color-coated or paper-like film appearance,
the
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18
typical appearance of a film printed with a high opacity ink, or a more
restrained
or sedate looking appearance. It is contemplated that when the subject film is
used in packaging, the second surface 19 is preferably positioned on the
interior of
a package and the first surface 11 is preferably positioned on the package
exterior.
When viewed from the second surface 19, the film can also have a different
vibrant coloration, a different printed image that appears to float on a
colored film,
or a different kraft paper like finish. If the film is being used in
packaging, and
the second surface 19 is on the interior, then the second surface 19 can be
plain
white, unprinted and unfinished. But when viewed from the first surface 11,
the
to film presents an excellent printable surface and an appealing appearance
desirable
for a package exterior.
When viewed from the second surface 19, the film can also have a different
vibrant coloration, a different printed image that appears to float on a
colored film,
or a different kraft paper like finish, a general color-coated or paper-like
film
appearance, the typical appearance of a film printed with a high opacity ink,
or a
more restrained or sedate looking appearance.
The film has very high opacity and very low light transmission. A distinction
2o must be made between opacity and light transmission for the purposes of
this
invention. Opacity is the opposite of transparency and is a function of the
scattering and reflection of light transmitted through the film. Opacity is
the
ability, for example, to block out writing below it.
Through a combination of opacity resulting from cavitation of the core layer
14
and the addition of metal compounds, pigment, and inorganic particulate
material,
the present invention provides a high opacity, and a low light transmission in
the
UV range measured at 250 nm and low light transmission in the 450 nm blue
range.
In one embodiment, when forming the core layer 14, as in U.S. Pat. Nos.
4,377,616; 4,632,869; 5,176,954; 5,397,635; 5,972,490; 4,758,396; 4,758,462;
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19
4,652,489; 4,741,950; 4,594,21 l; and 6,004,664 the disclosures of which are
incorporated herein by reference in their entirety, a master batch technique
can be
employed by either forming the void initiating particles in situ or in adding
preformed spheres to a molten thermoplastic matrix material. After the
formation
of a master batch, appropriate dilution of the system can be made by adding
additional thermoplastic matrix material until the desired proportions are
obtained.
However, the components may also be directly mixed and extruded instead of
utilizing a master batch method.
l0 The void-initiating particles which are added as filler to the polymer
matrix
material of the core layer 14 can be any suitable organic or inorganic
material
which is incompatible with the core material at the temperature of biaxial
orientation such as polybutylene terephthalate, nylon, solid or hollow
preformed
glass spheres, metal beads or spheres, ceramic spheres, calcium carbonate,
COC's
15 (cyclic olefin polymers and cyclic olefin copolymers), etc. COC's are
described in
U.S. Patent No. 6,048,608 issued to Peet, et al; this patent is incorporated
herein
by reference in its entirety.
The polyolefin contemplated as the material in the core layer 14 includes
20 polypropylene, polyethylene, polybutene and copolymers and blends thereof.
One
embodiment uses an isotactic polypropylene containing at least about 80% by
weight of isotactic polypropylene, wherein it is preferred that the
polypropylene
have a melt flow index of from about 2 to 10 g/10 min. Another embodiment uses
a high density polyethylene, with a density of 0.95 or greater.
In one embodiment, the average diameter of the void-initiating particles is
from
about 0.1 to about 10 microns. These particles may be of any desired shape
although it is preferred that they be substantially spherical in shape. This
does not
mean that every void is the same size. It means that, generally speaking, each
void
tends to be of like shape when like particles are used even though they vary
in
dimensions. These voids may assume a shape defined by two opposed and edge
contacting concave disks.
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In one embodiment, characteristics of opacity and appearance are obtained when
the two average major void dimensions are greater than about 30 microns.
In another embodiment, the void-initiating particle material, is incompatible
with
the core material, at least at the temperature of biaxial orientation.
The core layer 14 has been described above as being a thermoplastic polymer
matrix material within which is located a stratum of voids. From this it is to
be
0
l0 understood that the voids create the matrix configuration. The term
"stratum" is
intended to convey the understanding that there .are many voids creating the
matrix. In one embodiment, the voids themselves are oriented so that the two
major dimensions are aligned in correspondence with the direction of
orientation
of the polymeric film structure. After each void has been formed through the
15 initiation of the described particle, the particle generally contributes
little else to
the system. This is because its refractive index can be close enough to the
matrix
material that it makes no contribution to opacity. When this is the case, the
opacity
is principally a function of the light scattering effect which occurs because
of the
existence of the voids in the system. In another embodiment, iron oxide in an
2o amount of from about 1 to about 8% by wt.; in another embodiment from about
2% to 4% ; and in one embodiment aluminum in an amount from about 0 to about
1.0% by wt., in another embodiment from about 0.25% to 0.75% are added to the
core matrix. Carbon black or other compounds may also be used in lieu of some
or
all of the iron oxide.
A typical void of the core is defined as having major dimensions X and Y and
minor dimension Z; where dimension X is aligned with machine direction
orientation, dimension Y is aligned with transverse direction orientation and
dimension Z approximately corresponds to the cross-sectional dimension of the
3o spherical particle which initiated the void.
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21
In one embodiment, the orientation conditions are such that the X and Y
dimensions of the voids of the core are major dimensions in comparison to the
Z
dimension. Thus, while the Z dimension generally approximates the cross-
sectional dimension of the spherical particle initiating the void, X and Y
dimensions are significantly greater. By way of illustration, room temperature
biaxial orientation of a polypropylene matrix containing polybutylene
terephthalate (PBT) spheres of the size and amount contemplated herein, would
not be effective for this embodiment. Either void splitting would occur, or,
voids
of insignificant size would result. Polypropylene should be oriented at a
to temperature significantly higher than its glass transition temperature. The
temperature conditions will permit X and Y to be at least several multiples of
the
Z dimension without void splitting at least to any significant degree. When
this is
accomplished, optimum physical characteristics, including low water vapor
transmission rates and a high degree of light scattering are obtained without
void
splitting or film fibrillating.
As indicated above, the matrix polymer and the void initiating particle must
be
incompatible and this term is used in the sense that the materials are two
distinct
phases. The spherical void initiating particles constitute a dispersed phase
2o throughout the lower melting polymer which polymer will, ultimately, upon
orientation, become a void-filled matrix with the spherical particles
positioned
somewhere in the voids.
As a result of the biaxial orientation of the film structure herein, in
addition to
opacifying the core layer 14 of the structure, the orientation improves other
physical properties of the composite layers such as flex-crack resistance,
Elmendorff tear strength, elongation, tensile strength, impact strength and
cold
strength properties. The resulting film can have, in addition to a rich high
quality
appearance and excellent opacifying characteristics, low water vapor
transmission
3o rate characteristics and low oxygen transmission rate characteristics. This
makes
the film ideally suited for packaging food products including liquids. The
film
also has attractive utility as a decorative wrap material.
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22
It is believed that because of comparative sphericity of the void-initiating
particles, the voids are closed cells. This means that there is virtually no
path
open from one side of the core to the other through which liquid or gas can
transverse.
The polymers contemplated herein for the first skin layer 10, first transition
layer
12, second transition layer 16, and second skin layer 18 can be selected from
those
polymers typically employed in the manufacture of mufti-layered films.
l0
Typical examples of materials which are suitable for use as the skin layers
are
coextrudable materials which form a seal upon application of elevated
temperatures and, at least slight pressure. Examples of polymeric materials
which
can be used for the sealing layer include olefinic homo-, co- or terpolymers.
The
15 olefinic monomers can comprise 2 to 8 carbon atoms. Specific examples
include
polypropylene, ethylene-propylene random copolymer, ethylene-butene-1
copolymer, ethylene-propylene-butene-1 terpolymer, propylene-butene
copolymer, high density polyethylene, low density polyethylene, linear low
density polyethylene, very low density polyethylene, metallocene-catalyzed
2o polyethylene, metallocene-catalyzed polymers known by the term plastomer,
metallocene-catalyzed ethylene-hexene copolymer, metallocene-catalyzed
ethylene-butene copolymer, metallocene-catalyzed ethylene-octene copolymer,
ethylene-methacrylic acid copolymer, ethylene-vinyl acetate copolymer and
ionomer resin. A blend of the foregoing materials is also contemplated such as
a
25 blend of the plastomer and ethylene-butene copolymer.
The core and transition layers of the present invention may be any one of the
coextrudable, biaxially orientable film-forming resins known in the art. Such
materials include, but are not limited to, isotactic polypropylene high
density
3o polyethylene, low density polyethylene, linear low density polyethylene,
very low
density polyethylene, metallocene-catalyzed polyethylene and polypropylene,
metallocene-catalyzed polymers known by the terplastomer syndiotactic
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23
polypropylene, propylene copolymers and terpolymers which include other
monomers such as ethylene and/or butene-l, ethylene copolymers and terpolymers
which include other monomers such as propylene and/or butene-1. Typical
copolymers are ethylene-propylene copolymers, ethylene-butene-1 copolymers,
butene-1-propylene random copolymers, and ethylene-propylene block
copolymers. Typical terpolymers are ethylene-propylene-butene-1 terpolymers.
Alternative and useful thermoplastic materials include, but are not limited to
nylon, polyester, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol
copolymer. Blends of any of the foregoing homopolymers, copolymers and
terpolymers are contemplated.
Ethylene-propylene-butene-1 random terpolymers appropriate for use in the core
of the present invention include those containing 1-5 weight percent random
ethylene and 10-25 weight percent random butene-l, with the balance being made
up of propylene. The amounts of the random ethylene and butene-1 components
in these terpolymers are typically in the range of 10 to 25 weight percent
(ethylene
plus butene-1) based on the total amount of the copolymer.
The copolymers and terpolymers typically have a melt flow rate in the range of
2o about 1.5 to 15 g/10 min, with a density of about 0.9 and a melting point
in the
range of about 115 to about 170°C.
In one embodiment, the exposed first surface 11 and/or second surface 19 are
treated in a known and conventional manner, e.g., by corona discharge to
improve
its receptivity to inks and/or its suitability for such subsequent
manufacturing
operations as lamination.
In one embodiment, the exposed treated or untreated first surface 11 and/or
second surface 19 have applied to it, coating compositions or substrates such
as
3o another polymer film or laminate; a metal foil such as aluminum foil;
cellulosic
webs, e.g. numerous varieties of paper such as corrugated paperboard, craft
paper,
glassine, cartonboard; non- woven tissue, e.g., spunbonded polyolefin fiber,
melt-
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24
blown microfibers, etc. The application may employ a suitable adhesive, e.g.,
a
hot melt adhesive such as low density polyethylene, ethylene-methacrylate
copolymer, water-based adhesive such as polyvinylidene chloride latex, and the
like.
The film of the present invention may be laminated to another polyolefm film
(eg:
thermal, adhesive, extrusion, etc).
In one embodiment, the first skin layer 10, first transition layer 12, second
to transition layer 16, and second skin layer 18 includes up to about 90% by
wt., in
another embodiment from about 2% to about 20% by wt., and in a third
embodiment from about 3% to about 10% by wt. of a coloring agent is used. U.S.
Patent Nos. 5,894,048; 4,894,264; 4,536,184; 5,683,805; 5,328,743; and
4,681,803 disclose the use of coloring agents, the disclosures of which are
15 incorporated herein by reference in their entirety. Suitable coloring
agents include
pigments and dyes. In one embodiment, pigments and dyes include organic
pigments and dyes such as phthalocyanine, azo, condensed azo, azo lake,
anthraquinone, perylene/perinone, indigo/thioindigo, isoindolinone,
azomethineazo, dioxazine, quinacridone, aniline black, triphenylmethane and
2o carbon black pigments; and inorganic pigments and dyes such as titanium
oxide,
iron oxide, iron hydroxide, chrome oxide, spinel-form calcination type,
chromic
acid, chrome vermilion, iron blue, aluminum powder and bronze powder
pigments. These pigments may be provided in any form or may be subjected in
advance to various dispersion treatment in a manner known per se in the art.
25 Depending on the material to be colored, the coloring agent can be added
with one
or more of various additives such as organic solvents, film-forming resins (in
not a
large proportion), flame retardants, antioxidants, ultraviolet absorbers,
plasticizers
and surfactants. Colored compounded thermoplastics which are commercially
available are easier to use with this invention, although direction addition
of a dye
30 or pigment to the extrusion is possible. In another embodiment colored
compounded thermoplastic concentrates are used. (For example from Schulman:
Polybatch Blue P4021, Polybatch Blue P4535, Polybatch Red P50346, Polybatch
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Yellow P2214F, Polybatch Green P3510F, Polybatch Brown P1028F, and
Polybatch Orange P10307; from Ampacet: LR-92396 (blue), LR-92011 (blue),
LR-92397 (green), LR-92398 (yellow), and LR-92010 (red); from Milliken Clear
Tint Blue 9805, Clear Tint Red 9803, Clear Tint Amber 9808, and Clear Tint
Green 9807.) In a third embodiment colored compounded thermoplastic
concentrates contain lower amounts of titanium dioxide or are otherwise lower
in
opacity. Furthermore, a color on the first surface 11 or second surface 19 of
the
film allows printing of laminated or unlaminated structures without requiring
a
base colored ink.
to
The first skin layer 10 and/or the second skin layer 18 may be heat sealable
or non
heat sealable. In one embodiment, if the first skin layer 10 and/or the second
skin
layer 18 are not heat sealable, then a heat sealable layer (not shown) may be
applied to the first skin layer 10 and/or the second skin layer 18. A heat
sealable
15 layer (not shown) may be, for example, vinylidene chloride polymer or an
acrylic
polymer; or heat sealable layer (not shown) may be coextruded from any of the
heat sealable materials described for the first skin layer 10 and/or the
second skin
layer 18. Vinylidene chloride polymer or acrylic polymer coating may also be
applied to the exposed first surface 11 or the second surface 19.
In another embodiment, if the first skin layer 10 and/or the second skin layer
18
are heat sealable, it can be fabricated from any of the heat sealable
copolymers,
blends of homopolymers and blends of copolymers) and homopolymer(s)
heretofore employed for this purpose. Illustrative of heat sealable copolymers
which can be used for the first skin layer 10 and/or the second skin layer 18
of the
present film are ethylene-propylene copolymers containing from about 1.5 to
about 12, and alternatively from about 3 to about 7 weight percent ethylene
and
ethylene- propylene-butene terpolymers containing from about 1 to about 10,
and
alternatively from about 1 to about 6 weight percent ethylene and from about
70 to
3o about 97. In another embodiment, heat.sealable blends of homopolymer can be
utilized for the first skin layer 10 and/or the second skin layer 18 which
include
from about 1 to about 99 weight percent polypropylene homopolymer, e.g., one
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26
which is the same as, or different from, the polypropylene homopolymer
constituting core layer 14 blended with from about 99 to about 1 weight
percent of
a linear low density polyethylene (LDPE). If the first skin layer 10 andlor
the
second skin layer 18 are heat-sealable, corona or flame treatment of that
layer is
optional.
In another embodiment, heat sealable blends of copolymers) and homopolymer(s)
which may be used for the first skin layer 10 and/or the second skin layer 18
include: a blend of from about 5 to about 19 weight percent of polybutylene
and
l0 from about 95 to about 81 weight percent of a copolymer of propylene (80 to
about 95 mole percent) and butylene (20 to about 5 mole percent); a blend of
from
about 10 to about 90 weight percent of polybutylene and from about 90 to about
weight percent of a copolymer of ethylene (2 to about 49 mole percent) and a
higher olefin having 4 or more carbon atoms (98 to about 51 mole percent); a
blend of from about 10 to about 90 weight percent polybutylene and from about
90 to about 10 weight percent of a copolymer of ethylene (10 to about 97 mole
percent) and propylene (90 to about 3 mole percent); and, a blend of from
about
90 to about 10 weight percent of polybutylene, and from about 10 to about 90
weight percent of a copolymer of propylene (2 to about 79 mole percent) and
2o butylene (98 to about 21 mole percent).
In one embodiment, the first skin layer 10, first transition layer 12, core
layer 14,
second transition layer 16, and second skin layer 18 are coextruded.
Thereafter,
the film is preferably biaxially oriented. For example, when employing
polypropylene for the core matrix and the skin layers and employing PBT as the
void initiating particles, a machine direction orientation is preferably from
about 4
to about 8 and a transverse orientation is preferably from 4 to about 10 times
at a
drawing temperature of about 100 degrees C. to 170 degrees C. to yield a
biaxially
oriented film. A preferred film thickness is from about 0.5 mil to about 3.5
mils.
Although various embodiments have been disclosed for the five layer film 50,
three layer film 30, four layer film 40, and two layer film 20, additional
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27
embodiments of films with two or more layers are possible by interchanging
elements of coloring agents, printing, and inorganic and organic additives
that
would be clear to one with ordinary skill in the art.
In another embodiment the first skin layer 10 and/or the second skin layer 18
has a
coating or metal layer applied. U.S. Patents 6,077,602; 6,013,353; 5,981,079;
5,972,496; 6,074,762; 6,025,059; and 5,888,648 disclose the use of coatings
and/or metal layers on a film, and are disclosed herein by reference. In one
embodiment, suitable coatings may include PVdC's or acrylics which serve to
to boost gloss, enhance machineability, and / or enhance ink adhesion;
suitable
metals may include aluminum.
The following examples illustrate the present invention:
EXAMPLE 1
Samples were produced having the following structure:
Corona Treatment
L1 EP impact copolymer
L2 Homopolymer PP or Terpolymer with color concentrate
L3 Homopolymer core ( + cavitating agent )
L4 Homopolymer PP or Terpolymer with opacifier
L5 EP impact copolymer
corona treatment
2o Thickness of the uncavitated film was 0.80 mils.
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28
The following materials were run using this structure:
Run L1 and L5 Skin Layer 4 resin L4 Layer 2 resin L2
Resin L1 thick thick
and (ga) (ga)
L5
thick
(ga)
1 Montell 0.5 Fina 3371 w/40% 8 Fina 3371 w/30%4
8523 ga ga
Schulman CTW5050 Schulman P10204/5
2 Montell 0.5 Chisso XPM7880 8 Chisso XPM7800 4
8523 ga ga
w/40% Schulman w/30% Schulman
P8555-SC P10204/5
Before
producing
sample
3
and
4
-
add
8%
Ticona
Celenex
1300A
PBT
to
the
core
3 Montell 0.5 Chisso XPM7880 8 Chisso XPM7800 4
8523 ga ga
w/40% Schulman w/30% Schulman
P8555-SC P10204/5
4 Montell 0.5 Fina 3371 w/40% 8 Fina 3371 w/30%4
8523 ga ga
Schulman CTW5050 Schulman P10204/5
Material Descriptions:
Montell 8523 is an EP impact copolymer
Schulman P8555-SC (50% Ti02 in EP random copolymer (Fina 8573))
Schulman CTW5050 referred above is 50% Ti02 (Millenium RCL4) in PP
homopolymer
Schulman P10204/5 is a brown masterbatch containing a total of 35% pigment
(iron oxide, carbon black, Ti02) in PP homopolymer.
Chisso XPM7880 is an EPB terpolymer
Fina 3371 is a 3 MF PP homopolymer
The films produced during the experiment had the brown and white kraft paper
type of color and fiber-like appearance to them.
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29
EXAMPLE 2
A second set of runs was made having the following structure:
Corona Treatment
L 1 Propylene or ethylene colymers + additives
L2 Homopolymer with color concentrate
L3 Homopolymer core + cavitating agent
L4 Homopolymer with opacifier
LS Propylene or ethylene copolymers + additives
Corona Treatment
The core homopolymer was cavitated in all cases.
Run Skin Resin SkinLayer 4 resin L4 Layer 2 resin L2
(L1 & L5 L1 thick thick
layers) and (ga) (ga)
L5
thick
(ga)
Montell 85236 Chisso XPM7880 8 Chisso XPM 5-8
+ ga ga 7800 ga
16% Schulman w/40% Schulman w/30% Schulman
T4448/50 CTW50/50 P10204/5
6 Montell 85231 Chisso XPM7880 8 Chisso XPM78805 ga
ga + ga +
20% T4448/5 + 20% T4448/5
40% +
CTW5050 30% P10204/5
Material Description:
Schulman Papermatch T4448/50 (NW HDPE w/high CaC03 loading and Ti02)
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Properties of the films produced in Examples 1 and 2 are given in Table 1.
Table 1
SampleSkins Core OpticalYieldTreatmentHaze GlossGloss
Gauge Both COF COF
sides
BrownWhiteBrawn white
side sideside side
1 BrownlwhiteClear 75.6 4040038 49.4 30.7 33.40.421 0.430
2 BrownlwhiteClear 80.9 3780037 48.6 33.5 34.50.671 0.765
3 Brown/whiteCavitated110.73720036 29.2 35.9 36.40.619 0.765
4 Brown/white~ Cavitated109 38200~ 37 27.1 30.8 36.60.421 0.430
~ ~ ~ ~
Light
Trans
5 White PP 99 3717739 31 13.4 15.10.28 0.27
matte/
tan matte
(uniform(cavitated)
surface
look)
6 White PP 96 3884537 30.4 28.1 25.30.32 0.33
matte/
tan matte
(fiber-likeCavitated
surface
look)
Brown 5.1
kraft
paper
bag
White 5
bleached
paper
bag
The films of Example 2, produced during the second experiment had the brown
and white paper type of color and also lower gloss and a rougher surface
finish to
more closely resemble the look and texture of kraft paper. Sample 5 had a
10 uniform type of surface appearance, whereas Sample 7 was produced with a
non-
uniform "fiber-like" surface appearance that more closely resembles the "fiber-
like" look of kraft paper. All these films are surface printable on either the
white
kxaft or brown kraft side. The side opposite the print side is also surface
treated
and hence suitable for either adhesive or extrusion lamination to a high
barrier
15 clear or high barrier metallized film.
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31
EXAMPLE 3
A third set of samples was produced to evaluate color concentrates for
potential
use in flex-pack applications, using the following structure:
Ll 3 ga. Dow Dowlex 2027A MDPE
L2 14 or 27 Exxon 4612 Homopolymer PP + color
ga. concentrate (see Table 2)
L3 40 or 53 Exxon 4612 Homopolymer PP + Celanese
ga. 1300A cavitating agent
L4 27 ga. Exxon 4612 Homopolymer PP
~LS ~ 3 ga. Exxon 4612 Homopolymer PP
Corona Treatment
The films had a thickness of ~ 1.4 mils when cavitated, and a polymer
thickness
equivalent to X1.0 mils if no cavitation had occurred. The core layer
thickness,
l0 L3, shown above is based on the thickness that would be obtained if the
film were
not cavitated. The color concentrates were run at a 2:1 let down.ratio.
Color concentrates used, colored layer thicknesses, color measurements, using
a
HunterLab UltraScan XE, and gloss measurements are summarized in Table 2 and
15 Table 3.
Table 2
Sample Color mater batch a* b* L* Opacity
used in L2
ThicknessThickness
S 27 40 ga. Ampacet LR-92010 46.79-8.39 56.04 67.76
ga. (flex-pack red)
9 14 53 ga. Ampacet LR-92010 44.48-9.73 59.69 70.80
ga. (flex-pack red)
10 27 40 ga. Ampacet LR-92011 -17.12-40.6046.13 66.38
ga. (flex-pack blue)
11 ~ 14 ~ . Ampacet LR-92011 -24.70-40.5154.52 73.37
ga. 53 (flex-pack blue)
ga.
~
Table 3
Gloss les of
at Different Incident
Ang Light
SampleFilm Type Color 20 45 60 85
8 Cavitated WhiteDark 43.1 63.0 87.4 97.6
Red
9 Cavitated WhiteLight 39.9 68.4 88.8 97.2
Red
10 Cavitated WhiteDark 44.1 53,9 85.2 97.9
Blue
11 Cavitated WhiteLight 38.2 54.5 83.1 97.3
Blue
ReferenceNon-cavitated Solid 33.0 30.0 51.4 93.7
White White
ReferenceClear No color104.8 85.3 130.4 104.2
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32
Gloss vs. Angle of Incident Light
140
130
120
110
~ Dark
0 Red
gp o Light
Red
$p o
~ Dark
Blue
60 o Light
Blue
50
~ Solid
White
40
30 o Clear
Film
20
0
10
0 10
20
30
40
50
60
70
80
90
Angle
of
Incident
Light
(Deg.)
Gloss is a ratio of incident light to reflected light. The data shows that the
gloss is higher
for the cavitated colored samples versus the non-cavitated white sample (solid
white
sample) at all angles of incident light. The design of the cavitated colored
samples allows
more light to be reflected back to the observer than a non-cavitated white
film. The
incident light is scattered by the white pigment in the non-cavitated white
film, which
results in less reflected light and a lower gloss value. However, more
incident light is
reflected by the cavitated colored film, which results in a higher gloss
value.
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33
EXAMPLE 4
A fourth set of runs was made having the following structure:
L1
L2
L3
L4
L5
The colorant was located in a relatively thin tie layer sandwiched between a
clear
skin and a white, cavitated core. In some cases, the thickness of L2 was
doubled.
In some other cases, L2 was made half as thick. To maintain a constant film
to thickness, the difference in thickness was made up by changing the core
thickness
to compensate for the thicker or thinner L2.
Schulman % Loading L2 Thickness
Polybatch Blue P4021 10 25 Normal
10 '/2X normal
10 2X normal
Polybatch Red P50346 8 15 25
5
Normal
Polybatch Yellow P2214F10 22
5
normal
Polybatch Green 3510F 10 25 50 75 Normal
5
Polybatch Brown P1028F 10 25 50 75 Normal
5
Ampacet
LR-92396 (blue) 10 25 50 75 Normal
LR-92397 (green) 10 25 50 75 Normal
LR-92398 (yellow) 21 50 75 Normal
The a*, b* and L* valuesall of films have been measured
for these along with all
their light transmissionloss The data are given in
and g values. Table 3.
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34
Table 3
L2 layer a* b* L* GlossLT
gauge
10% Polybatch Blue P4021/90% Normal -14.51 -24.8978.0367 27.2
4612E2
10% Polybatch Blue P4021/90% 0.5Xnormaf-7.61 -12.3487.3271.5 29.6
4612E2
10% Polybatch Blue P4021/90% 2X normal -17.91 -32.6771.4865.4 25.3
4612E2
25% Polybatch Blue P4021/90% Normal -17.07 -39.6463.6848.9 18.5
4612E2
5% Polybatch Red P50346/95% Normal 23.56 6.84 68.8172.6 26
Exxon 4612E2
8% Polybatch Red P50346/92% Normal 33.78 11.93 61.8763.4 21.4
Exxon 4612E2
15% Polybatch Red P50346/85% Normal 44.65 51.52 53.3651 13.4
Exxon 4612E2
25% Polybatch Red P50346/75% Normal 47.49 27.47 49.0141.8 6.8,
Exxon 4612E2
5% Polybatch Yellow P2214F/95%Normal -3.3 22.52 83.7278.3 33.9
Exxon 4612E2
10% Polybatch Yellow P2214F/90%Normal -0.27 0.69 86.4768.1 31
Exxon 4612E2
22% Polybatch Yellow P2214F/78%Normal 0,28 60.33 82.6354 25
Exxon 4612E2
5% Polybatch Green P3510F/95%Normal -13.19 14.83 82.2 79.3 27.5
Exxon 4612E2
10% Polybatch Green P3510F/90%Normal -20.48 22.8 77.2269 28
Exxon 4612E2
25% Polybatch Green P3510F/75%' Normal ~ -33.3234.53 66.4645.5 18.6
Exxon 4612E2
50% Polybatch Green P3510F/50%Normal -35.4 31.82 59.0731.6 12.6
Exxon 4612E2
75% Polybatch Green P3510F/25%Normal -32.77 27.03 54.9115 7.3
Exxon 4612E2
5% Polybatch Brown P1028F/95%Normal 4.93 8.08 67.3 66 22.4
Exxon 4612E2 '
10% Polybatch Brown P1028F/90%Normal 8.06 11.02 54.1952.8 15.1
Exxon 4612E2
25% Polybatch Brown P1028F/75%Normal 6.83 7.37 35.9635.5 3.9
Exxon 4612E2
50% Polybatch Brown P1028F/50%Normal 5.5 5.98 33.2826 0.2
Exxon 4612E2
75% Polybatch Brown P1028F/25%Normal 5.27 5.41 31.8823.4 0
Exxon 4612E2
10% LR-92396 (blue)/90% ExxonNormal -33.83 -28.4975.8364.8 24.3
4612E2
25% LR-92396 (blue)/75% ExxonNormal -38.62 -40.0564.6958.6 23.6
4612E2
50% LR-92396 (blue)/50% ExxonNormal -32.18 -44.9357.0546.6 9.5
4612E2
75% LR-92396 (blue)/25% ExxonNormal -27.39 -45.3452.9640.2 7.7
4612E2
10% LR-92397 (green)/90% ExxonNormal -24.49 -1.21 87.9280.6 28.9
4612E2
25% LR-92397 (green)/75% ExxonNormal -42.73 0.22 82.2768.5 25.9
4612E2
50% LR-92397 (green)/50% ExxonNormal -58.37 3.74 76.7259.5 22.4
4612E2
75% LR-92397 (green)/25% ExxonNormal -66.93 7.18 72.5546.8 21.4
4612E2
21 % LR-92398 (yellow)/79% Normal -9 40.35 93.1889.7 31.7
Exxon 4612E2
50% LR-92398 (yellow)/50% Normal -9.93 67.02 91.6575.2 29.7
Exxon 4612E2
75% LR-92398 (yellow)/25% Normal -8.32 80.86 90.5961.5 29.8
Exxon 4612E2
10% Polybatch Biue P4021/90% Normal -0.39 -14.5565.1244.9 12.4
4612 E2 +
10% Polybatch Red P50346/90% Normal 44.75 21.9 49.0252.5
4612E2
For the last entry in Table 3, a blue colorant was coextruded in L2 with a red
colorant in L4. There was very little influence of the color on either side
affecting
the color on the other side.
Those films that were made in such a manner that much of the incident light on
the film surface passed into the film, reflected off the cavitated core
surface, and
passed back through the entry surface had a very vibrant, deep appearing look
to
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them. Many of the films that have been produced have a more "vibrant"
appearance than do some of the others. The color concentrates that contain
lower
amounts of titanium dioxide or are otherwise lower in opacity correlate to
this
aesthetic preference
5
Example 5
In a fifth experimental run, L2 of Example 4 was set up to consist of two
separate
coextruded layers. Red color concentrate was fed into one layer and blue was
fed
1o into the other. A purple color was produced.
Example 6
In a sixth experimental run, the following film structure was set up:
('nrnna TrPatmant
L 1 10 ga. MDPE ( + color concentrate)
L2 112 ga. HDPE + CaC03
L3 8 ga. MDPE
~.urvma rrea~rnem
A yellow color concentrate, Polybatch Yellow P20287, purchased from A.
Schulman, Inc., was introduced into the Ll layer at 10%. An aesthetically
pleasing film, yellow on one side and white on the other was obtained.
