Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The present invention relates to barrier films and, in
particular, to barrier films having at least one exposed high
energy surface for receipt of a barrier coating through vapor
deposition of a barrier coating material.
Coatings produced by vapor deposition are known to
provide certain barrier characteristics to the coated
substrate. For example, an organic coating such as a
amorphous carbon can inhibit the transmission of elements such
as water, oxygen, and carbon dioxide. Accordingly, carbon
coatings have been applied to substrates (e. g., polymeric
films) to improve the barrier characteristics exhibited by the
substrate. Thus, the vapor deposited coating is often
referred to as a barrier coating.
Another example of coatings applied to substrates to
improve their barrier characteristics are coatings of
inorganic materials, such as inorganic oxides. Oxides of
silicon and aluminum are widely utilized to improve the
barrier characteristics of substrates, especially polymeric
substrates. Oxides of silicon and aluminum also provide
abrasion resistance due to their glass-like nature.
The above-described coatings can be deposited on
substrates through various techniques of vapor deposition.
Typically vapor deposition techniques can be classified as
either physical vapor deposition (PVD) or as chemical vapor
deposition (CVD). Examples of PVD processes include ion beam
sputtering and thermal evaporation. Examples of CVD processes
include glow discharge and Plasma Enhanced Chemical Vapor
Deposition (PECVD).
Of these techniques, PECVD is becoming widely utilized,
in part, because it enables the coating of temperature
sensitive substrates, such as polymeric films. Particularly,
this technique allows the deposition of a coating material at
lower reaction chamber temperatures, as compared to the
reaction chamber temperatures required in other deposition
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2
processes, e.g., glow discharge and more so, ion beam
sputtering. As a result of the lower reaction chamber
temperatures, temperature-sensitive substrates can be coated,
which might otherwise be detrimentally affected by the higher
reaction chamber temperatures found in the other coating
processes.
The PECVD process is, however, a relatively slow and
lengthy process, which in many cases renders such technique
commercially impracticable. Accordingly, there exists a need
in the art for a method that increases the rate of production
of a barrier film utilizing PECVD, while at the same time
maintaining the desirable barrier properties exhibited by the
coated substrate.
There is also a continuing need in the art to provide
barrier films with increased barrier characteristics.
Accordingly, it is an object of the present invention to
provide barrier films with improved barrier characteristics
and a method of making the same.
The present invention, which addresses the needs of the
prior art, provides a method for producing a polymeric film
having barrier characteristics. The method includes the step
of vapor depositing a barrier coating on an exposed surface of
an ethylene vinyl alcohol layer which is adhered to a
polymeric substrate.
The polymeric substrate can be any polymeric substrate as
long as its compatible with the ethylene vinyl alcohol layer.
Preferred polymeric substrates include polypropylene,
polyethylene, biaxial nylon and polyester.
The barrier coating can be an organic or inorganic
coating. Preferred inorganic oxide coatings include oxides of
silicon and aluminum, and more specifically, SiOX, in which x
is 1 _< x s 2, A1203 and mixtures thereof. Preferred organic
coatings include amorphous carbon.
- The present invention also provides a method for
increasing the production rate of a barrier film. The method
includes the step of adhering an ethylene vinyl alcohol layer
to a polymeric substrate and thereafter vapor depositing a
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barrier coating on the exposed surface of the ethylene vinyl
alcohol layer. A preferred technique of adhering the ethylene
vinyl alcohol layer to the polymeric substrate is through
coextrusion.
The present invention also provides a multilayer
polymeric film having barrier characteristics. The film has a
polymeric substrate with an ethylene vinyl alcohol layer on
one side of the polymeric substrate. A barrier coating is
situated on the outside surface of the ethylene vinyl alcohol
layer, i.e., the side opposite from the polymeric substrate.
The barrier coating preferably has a thickness from 10 to 5000
angstroms.
As a result of the present invention, the time required
to produce a polymeric film having a vapor deposited barrier
coating is greatly reduced, and thereby increases the
commercial practicality of PECVD techniques. Moreover, the
present invention provides a method of making a polymeric film
having an improved barrier to the transmission of water and
atmospheric gases when the coating time remains the same.
2o Accordingly, the barrier films of the present invention
provide improved impermeability to the elements such as water
and atmospheric gases.
In accordance with the present invention, a method is
provided for producing a polymeric film having barrier
characteristics. The method includes the step of vapor
depositing a barrier coating on an exposed surface of a
polymeric material that provides a high energy surface, which
is adhered to a polymeric substrate.
One example of a polymeric material that provides what is
referred to as a "high energy surface" is amorphous nylon. It
is believed that the surface of an amorphous nylon layer
facilitates the adhesion of the vapor deposited coating
thereto, which in turn results in a better quality coating.
Particularly, the exposed surface of the amorphous nylon layer
exhibits a high "wettability" or surface energy in comparison
to other polymers. The wettability of a polymer is believed
to affect the ability of material to intimately contact
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another material. Thus, it is believed that the high
wettability o~ the amorphous nylon skin layer facilitates the
vapor deposition of a better quality barrier coating than can
be achieved by directly coating the underlying polymeric
substrate.
In this regard, it has been demonstrated herein that the
application of a polymeric layer having a high energy surface
(e. g., amorphous nylon) to a polymeric substrate greatly
reduces the time required to deposit a barrier coating via
vapor deposition, and more specifically, PECVD. The high
energy surface enables a reduction in the coating time while
maintaining barrier characteristics comparable to the prior
art films.
The use of a high energy surface (e. g., amorphous nylon)
also facilitates the production of a barrier film having
increased or improved barrier characteristics if the coating
time period remains the same. In other words, one of ordinary
skill in the art can keep the coating time period at a
constant and obtain a multilayer polymeric film with increased
barrier characteristics. The effect of utilizing a high
energy surface has also been observed to become more
pronounced during short coating times, e.g., at coating rate
of eight feet per minute (FPM) versus four FPM. This is
believed to be due to the overall barrier characteristics
exhibited by the film depending more on the quality of the
coating than the quantity of the coating material applied.
The amorphous nylon employed in the present invention is
preferably an amorphous co-polyamide synthesized from
hexamethylenediamine and a mixture of isophthalic and
terephthalic acids. One such commercially available product
is Dupont PA-3426. By reference to an amorphous nylon, a nylon
polymer that is substantially 100% amorphous is contemplated.
This can easily be ascertained by Differential Scanning
- Calorimetry (DSC) because the polymer should not exhibit any
peaks that correspond to a crystalline region. However, it is
also contemplated that blends of amorphous nylon with semi-
crystalline nylons can be utilized as long as the blend
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exhibits a wettability comparable to that of the amorphous
nylon.
The amorphous nylon layer can be adhered to the substrate
by a variety of techniques known in the art. For example, the
5 nylon layer can be laminated onto a polymeric substrate by use
of an adhesive. One particularly preferred method of securing
a nylon layer to a polymeric substrate is accomplished by co-
extruding a polymeric material with amorphous nylon, thereby
providing a polymeric substrate having a layer of amorphous
nylon on at least one side. Typically, a tie layer is
employed to adhere the amorphous nylon to the polymeric
substrate. For example, a material such as malefic anhydride
modified polypropylene can be employed as the tie layer. One
such commercially available product is Atmer QF-500A.
It is also contemplated that other polymers exhibiting a
similar wettability to that of amorphous nylon would also be
effective in providing a high energy surface for receipt of a
barrier coating by vapor deposition.
One material that has been found to exhibit a wettability
similar to that of amorphous nylon is an ethylene vinyl
alcohol copolymer (EVOH). As demonstrated herein, an EVOH
skin layer on a polymeric substrate facilitates the deposition
of a barrier coating comparable to the those produced
utilizing an amorphous nylon skin layer. The EVOH resin
employed is preferably a resin having a mole percent ratio of
ethylene to vinyl alcohol ranging from about 29:71 to about
48:52. More preferred is an EVOH resin having a mole percent
ratio ranging from about 44:56 to about 48:52. EVOH resins
that can be utilized in accordance to the present invention
are readily available from Kuraray Co., Ltd. and Nippon
Gohsei, both of Japan, and from EVAL Co., of America. One
such preferred EVOH resin is a 48 mole percent resin, ECG-
156B, produced by EVAL Company of America.
- As with the amorphous nylon layer, the EVOH layer can be
adhered to the substrate by a variety of techniques known in
the art. For example, the EVOH layer can be laminated onto a
polymeric substrate by use of an adhesive. One particularly
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preferred method of securing a EVOH layer to the polymeric
substrate is by coextrusion. Thus, a polymeric substrate
having an exposed surface of an EVOH layer on one side is
produced. A tie layer, such as those employed with the
amorphous nylon layer, can also be employed to adhere the EVOH
layer to the polymeric substrate.
Examples of polymeric substrates to be utilized in
accordance with the present invention include, but are not
limited to, polypropylene, polyethylene, biaxial nylon and
polyester. It is believed that other substrates can also be
employed, as long as such substrates are compatible with the
material exhibiting the high energy surface.
The present invention also provides a method for
increasing the production rate of a barrier film. The method
includes the steps of adhering a polymeric layer having at
least one exposed high energy surface to a polymeric substrate
and, thereafter vapor depositing a barrier coating on the
exposed, high energy surface. Again, this polymeric layer is
preferably an amorphous nylon or ethylene vinyl alcohol layer.
As described earlier, the barrier coating is formed by
the vapor deposition of the barrier material. In accordance
with the present invention, any material that can be vapor
deposited and offer barrier properties can be utilized as the
barrier coating. The barrier coating can be either an organic
coating, such as a carbon coating, or an inorganic coating,
such as an oxide coating. A preferred carbon coating is
amorphous carbon, which is due in part to its barrier
characteristics and ease of application. Preferred oxide
coatings include oxides of silicon (SiOX, in which is x __<2) and
of aluminum (A1203). Moreover, mixtures of various coatings
can also be utilized, e.g., SiOx, in which 1<_ x __<2, and A1203.
Any vapor deposition technique can be utilized in
accordance with the present invention, provided that the
reaction chamber temperatures are not detrimental to the
substrate being coated. Preferably, a CVD process is utilized
because of the temperature sensitive nature of the polymeric
materials. PECVD is most preferred because the reaction
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chamber temperatures are usually well below the melting points
of the contemplated polymeric materials to be utilized as the
substrate. This is due in part due to the low temperature
plasma that is formed during the PECVD coating process.
PVD techniques usually require reaction chamber
temperatures above the melting points of the contemplated
polymeric substrates and, as a result, should normally be
avoided. However, if the reaction chamber temperatures can be
kept at a temperature that is not detrimental to the polymeric
substrate, the PVD technique can of course be utilized in
accordance with the present invention.
As will be apparent to those skilled in the art, the
source material for the barrier coating is dependent on the
type of vapor deposition process utilized. In PVD processes
the source material is usually the same chemical specie that
is being deposited as the barrier coating. For example, a
solid SiOX source is placed within reaction chamber to be
vaporized and is thereafter deposited as a SiOX coating on the
substrate.
In CVD processes, which are preferred, the source
material is not the same chemical specie that is being
deposited as the coating. For example, gaseous reactants such
as hexamethyldisiloxane (HMDSO) and oxygen (OZ) are placed in
the reaction chamber to react and thereafter provide a SiOx
coating on the substrate. Thus, the main gaseous reactant,
e.g., HMDSO, decomposes to form the desired coating on the
substrate.
Because CVD coating processes are preferred, the source
material for the barrier coating is preferably a gaseous
reactant or a mixture of gaseous reactants. Alternatively,
non-gaseous source materials can be utilized provided that
they can be transformed to a gaseous state, e.g., vaporized or
sublimed.
- The deposition of an amorphous carbon coating requires a
carbon source as the gaseous reactant. Preferably, the
gaseous reactant is a hydrocarbon having from 1 to 20 carbon
atoms. Acetylene is one such preferred gaseous reactant.
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Similarly, the deposition of a SiOx coating, in which
1~ x s2, requires a silicon-containing compound and an
oxidizing agent as the gaseous reactants. Examples of these
silicon-containing compounds include, but are not limited to,
silanes, siloxanes and silanols. Hexamethydisiloxane and
tetraethoxyl-silane (TEOS) are two such preferred gaseous
reactants. Oxidizing agents include, but are not limited,
molecular oxygen (OZ) and nitrous oxide (N20). However, other
sources for atomic oxygen can be readily utilized.
The deposition of an aluminum oxide coating requires an
aluminum-containing compound and an oxidizing agent. An
example of an aluminum-containing compound is aluminum
chloride (A1C13). The oxidizing agents can be the same as
previously described for the deposition of an SiOX coating.
Overall, once a particular barrier coating has been
selected, one of ordinary skill in the art can easily be
ascertain the gaseous reactants required to vapor deposit the
barrier coating.
Upon the introduction of the gaseous reactant to the
reaction chamber, the main gaseous reactant decomposes or
reacts with other gaseous reactants and is thereafter
deposited on the exposed high energy surface as a barrier
coating. This coating may range in thickness from 10 to 5000
angstroms, preferably from 100 to 2000 angstroms. The
thickness of the coating will be primarily dependent on the
amount of time allowed for deposition.
The plasma utilized with the present invention is
preferably generated by the application of a primary radio
frequency to a first electrode. This radio frequency excites
the gas mixture flowing through the chamber, thereby forming a
plasma. This gas mixture is preferably a mixture of the
gaseous reactants mentioned above, e.g., acetylene or TEOS and
oxygen, and an inert or noble gas such as argon or helium.
Apparatuses adapted for vapor deposition, and more
specifically PECVD, are well known and commercially available.
Such apparatuses generally include a chamber sized for receipt
of a substrate. The apparatus additionally includes a vacuum
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pump for evacuating the chamber, means for introducing a gas
mixture to the chamber under controlled conditions, and means
for generating a plasma within the chamber.
In one particularly preferred embodiment, the plasma
generation means includes distally spaced first and second
electrodes, which together can be employed to introduce
independent dual energy sources into the reaction chamber. A
primary radio frequency of 13.56 MHZ is applied to the first
electrode and a secondary radio frequency of between 90 KHz to
450 KHz is applied to the second electrode. Preferably, the
chamber serves as the ground for both radio frequencies.
The primary frequency generates the plasma (by exciting
the gas mixture), while the secondary frequency is believed to
facilitate the deposition of the carbon on the high energy
surface by exciting the molecules of the coating material
being deposited. This rationale is supported by the fact that
a visible change in the plasma is observed upon application of
this second radio frequency.
Other means of generating the plasma are also
contemplated. For example, a primary frequency in the
microwave range, e.g., 2.45 GHz, can also be utilized. In
addition, photometric means such as lasers can be employed to
excite the gas mixture. Magnets can also be utilized to aid
in directing the coating material to the substrate.
The chamber also includes a substrate holder plate for
supporting the polymeric substrate to be coated. This
substrate holder plate is preferably integral with the second
electrode. In.addition, the substrate holder plate may
include either a flat or an arcuate support surface. It is
contemplated that the use of an arcuate support surface would
facilitate commercial production of the present invention.
F~CAMPLE 1
Two amorphous carbon coated control films were produced.
A 1 mil thick oriented polypropylene film approximately 27.94
cm (11") long by 39.37 cm (15.5") wide was placed on a 25.4 cm
(10") long by 39.37 cm (15.5") wide substrate holder plate
attached to the second electrode. The substrate holder plate
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included an arcuate surface having a 101.6 cm (40") radius of
curvature. The film overhung the substrate holder plate along
the length of such film to allow the film to be secured to the
holder.
5 The chamber was pumped down to 1 mTorr. An acetylene/
argon gas mixture was then introduced into the chamber at a
flow rate of 100 sccm, 70% of the mixture being acetylene.
The pressure within the chamber was increased to a reaction
pressure of 100 mTorr by use of a gate valve located at the
10 inlet of the vacuum pump. A primary frequency of 13.5 MHZ at
a power level of 100 watts was applied to the first electrode
and a secondary frequency of 95 kHz at a power level of 25
watts was applied to the second electrode.
The substrate was coated for approximately 300 seconds.
Thereafter, the gas mixture was shut off and the chamber was
pumped down again to 1 mTorr. The chamber vacuum was then
broken by bleeding in dry nitrogen gas and the respective
coated substrate was removed.
The two control films were thereafter tested. The first
control film exhibited an oxygen transmission rate (T02) of 0.4
cc 02/645.26 cm2(100in2)/atm/24hr at 23°C and 0% relative
humidity and a water vapor transmission rate (WVTR) of 0.02 g
H20/645.16 cm2(100in2)/atm/24hr at 37.8°C (100°F) and 90%
relative humidity. The second control film exhibited an
oxygen transmission rate of 0.6 cc 02/645.16
cm2(100in2)/atm/24hr at 23°C and 0% relative humidity and a
water vapor transmission rate of 0.09 g H20/645.16
cm2(100in2)/atm/24hr at 37.8°C (100°F) and 90% relative
humidity.
Accordingly, the average control oxygen transmission rate
was 0.5 cc 02/645.16 cm2(100in2)/atm/24hr at 23°C and 0%
relative humidity and the average control water vapor
transmission rate was 0.055 g H20/645.16 cm2(100in2)/atm/24hr
at 37.8°C (100°F) and 90% relative humidity.
3 5 ~E 2
Amorphous carbon coated barrier films in accordance with
the present invention were produced utilizing a base sheet
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11
formed by co-extruding amorphous nylon with polypropylene that
was subsequently biaxially oriented. Resin pellets of Dupont
nylon PA-3426 were employed, along with a tie layer of Atmer
QF-500A. The oriented film was approximately 1 mil thick, the
amorphous nylon layer representing approximately 6% or .06
mils of the total film thickness.
A polymeric sample approximately 27.94 cm (11") long by
39.37 cm (15.5") wide was placed on the substrate holder plate
attached to the second electrode and described above in
Example 1.
The chamber was pumped down to 1 mTorr. An acetylene/
argon gas mixture was then introduced into the chamber at a
flow rate of 60 scan, approximately 83% of the mixture being
acetylene. The pressure within the chamber was increased to a
reaction pressure of 100 mTorr by use of a gate valve located
at the inlet of the vacuum pump. A primary frequency of 13.5
MHZ at a power level of 100 watts was applied to the first
electrode and a secondary frequency of 95 kHz at a power level
of 25 watts was applied to the second electrode.
The substrate was coated for approximately 60 seconds.
Thereafter, the gas mixture was shut off and the chamber was
pumped down again to 1 mTorr. The chamber vacuum was then
broken by bleeding in dry nitrogen gas and the respective
coated substrate was removed.
The polymeric sample was thereafter tested. The sample
film exhibited an oxygen transmission rate of 0.42 cc 02/645.16
cm2(100in2)/atm/24hr at 23°C and 0% relative humidity and a
water vapor transmission rate of 0.024 g H20/645.16
cm2(100in2)/atm/24hr at 37.8°C (i00°F) and 90% relative
humidity.
Additional polymeric samples were prepared under varying
test conditions. The measured results from all of the poly-
meric samples, i.e., samples 1-8, are set forth in Table 1.
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12
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13
It is readily apparent from the test data set forth above
that a barrier film can be produced by the deposition of
carbon on an exposed high energy surface of an amorphous nylon
layer. It is particularly significant that the rate of
producing such a barrier film can be increased by approxi-
mately a factor of 10, i.e., the coating time is decreased
from approximately 300 seconds to 15 to 60 seconds. It is
also significant that the resultant film exhibits a markedly
decreased oxygen transmission rate, while improving, or at the
minimum maintaining, the level of water transmission.
Example 3
A SiOX control film was produced, in which is x s2,
utilizing the stock 1 mil OPP film material described in
Example 1. After the coating process, samples from the film
were thereafter tested for oxygen and water vapor trans-
mission. The SiOX coated film exhibited an oxygen transmission
rate of 1.54 cc/645.16 cm2(100in2)/atm/24hr at 23°C and 0%
relative humidity (hereinafter cc/645.16 cmz(100in2)/atm/24hr),
and a water vapor transmission rate of 0.06 g/645.16
cm2(100in2)/atm/24hr at 37.8°C (100°F) and 90% relative
humidity (hereinafter g/645.16 cm2(100inz)/atm/24hr).
Examcle 4
A SiOX coated film in accordance with the present
invention was produced, in which 1< x s2, utilizing the stock
amorphous nylon-OPP film material described in Example 2. The
reaction parameters and coating time were identical to those
utilized in Example 3. After the coating process, samples
from the film were thereafter tested for oxygen and water
vapor transmission. The SiOX coated film exhibited an oxygen
transmission rate of 0.13 cc/645.16 cm2(100in2)/atm/24hr, and a
water vapor transmission rate of 0.07 g/645.16
cm2(100in2)/atm/24hr.
From the results in Examples 3 and 4, it is readily
apparent that the use of a high energy surface, such as that
provided by the amorphous nylon layer, is applicable to other
vapor deposited coatings, such as inorganic oxides. In
particular, the oxygen permeability of the barrier film
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14
decreased by a factor of 10 through the use of the amorphous
nylon skin. The SiOX coated OPP film in Example 3 exhibited an
oxygen transmission rate of 1.54 cc/645.16
cm2(100in2)/atm/24hr. While on the other hand, the SiOX coated
amorphous nylon-OPP film in Example 4 exhibited an oxygen
transmission rate of 0.13 g/645.16 cm2(100in2)/atm/24hr.
Accordingly, Examples 3 and 4 illustrate that when reaction
parameters are kept at a constant, barrier films with
increased barrier characteristics are obtained.
The results from Examples 3 and 4 also illustrate the
synergistic effect produced by the high energy surface of the
amorphous nylon layer. This effect is seen by comparing the
magnitudes of reduction in the oxygen transmission rates for
the OPP film versus the amorphous nylon-OPP film. The stock
OPP film has an oxygen transmission rate of 100 cc/645.16
cm2(100in2)/atm/24hr, which was reduced to 1.54 cc/645.16
cm2(100in2)/atm/24hr after the application of the SiOX coating.
The stock amorphous nylon-OPP film has an oxygen transmission
rate of 50.5 cc/645.15 cm2(100in2)/atm/24hr, which was reduced
to 0.13 cc/645.16 cm2(100in2)/atm/24hr after the application of
the SiOx coating. Stated otherwise, the OPP film exhibited
approximately a 65-fold reduction in its oxygen transmission
rate. The amorphous nylon-OPP film exhibited approximately a
388-fold reduction in its oxygen transmission rate. Thus, the
high energy surface of the amorphous nylon layer facilitated
the deposition of a barrier coating approximately 600% less
permeable than could be achieved by directly coating the
underlying polymeric material.
Exam 1c1 a 5
Amorphous carbon coated control films were produced
utilizing the stock amorphous nylon-OPP material described in
Example 2 to provide a standard for the EVOH embodiment of the
present invention. Overall, two sets of four film samples
were coated with an amorphous carbon coating following the
procedure of Example 2. One set of the amorphous nylon-OPP
samples were coated for approximately 22.5 seconds. The other
CA 02249394 1998-09-18
WO 97137054 PCT/US97/05143
set of amorphous nylon-OPP samples were coated for approxi-
mately 11.25 seconds.
The samples were thereafter tested for oxygen and water
vapor transmission. The samples coated for 22.5 seconds on
5 average exhibited an average oxygen transmission rate of
0.070 cc/645.16 cm2(100in2)/atm/24hr, and an average water
vapor transmission rate of 0.015 g/645.16 cmz(100in2)/atm/24hr.
The samples coated at 11.25 seconds exhibited an average
oxygen transmission rate of 0.210 cc/645.16 cmz(100in2)/
10 atm/24hr, and an average water transmission rate of 0.100
g/645.16 cm2(100in2)/atm/24hr.
Examrle 6
Amorphous carbon coated films in accordance with the EVOH
embodiment of the present invention were produced by coextrud
15 ing an EVOH resin with polypropylene to form a base sheet that
was subsequently biaxially oriented. Resin pellets of EVAL
EVOH resin, ECG-156b, were employed along with a tie layer of
Atmer QF-500A. The oriented film was approximately 1 mil
thick, in which the EVOH layer represented approximately 6% or
.06 mils of the total film thickness. Overall, two sets of
four film samples of the EVOH-OPP film were coated with an
amorphous carbon coating. The reaction parameters were
identical to those utilized in Example 5. As in Example 5,
the two sets of samples were coated for 22.5 and 11.25
seconds, respectively.
The polymeric samples were thereafter tested. The
samples coated for 22.5 seconds exhibited an average oxygen
transmission rate of 0.020 cc/645.16 cm2(100in2)/atm/24hr, and
an average water vapor transmission rate of 0.013 g/645.16
cm2(100in2)/atm/24hr. The samples coated for 11.25 seconds
exhibited an average oxygen transmission rate of 0.190
cc/645.16 cm2(100inz)/atm/24hr, and an average water vapor
transmission rate of 0.160 g/645.16 cm2(100inz)/atm/24hr.
As can be seen from the results in Examples 5 and 6 the
EVOH-OPP films coated with amorphous carbon provided barrier
properties comparable, if not better than, the amorphous
nylon-OPP samples. For example, the oxygen transmission rate
CA 02249394 1998-09-18
WO 97/37054 PCT/US97/05143
16
for the coated EVOH-OPP films were in fact better than the
oxygen transmission rates of the amorphous nylon-OPP films.
The amorphous nylon-OPP films exhibited an average oxygen
transmission rate of 0.070 and 0.210 cc/645.16
cm2(100in2)/atm/24hr, after the coating time periods of 22.5
and 11.25 seconds, respectively.
The EVOH-OPP films exhibited an average oxygen trans-
mission rate of 0.020 and 0.190 cc/645.16 cm2(100in2)/atm/24hr,
after the coating time periods of 22.5 and 11.25 seconds,
respectively. Therefore, the results of Examples 5 and 6
illustrate that EVOH resins can also be utilized in accordance
with the present invention.
