Note: Descriptions are shown in the official language in which they were submitted.
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64536-829F
MOISTURE BARRIER FILM
This application is a divisional application of
copending application 2,106,258, filed September I5, 2993.
FIELD OF THE INVENTION
This invention relates to thermoplastic films for
packaging; and more particularly, this invention relates to
a multi-layer film having high moisture barrier
characteristics.
BACKGROUND OF THE INVENTION
Thermoplastic film, and in particular polyolefin
materials, have been used for some time in connection with
packaging of various articles including .food products which
require protection from the environment, an attractive
appearance, and resistance to abuse during the storage and
distribution cycle. Suitable optical properties are also
desirable in order to provide for inspection of the packaged
product after packaging, in the distribution chain, and
ultimately at point of sale. Optical properties such as high
gloss, high clarity, and low haze characteristics contribute
to an aesthetically attractive packaging material and
packaged product to enhance the consumer appeal of the
product.
Various polymeric materials have been used to
provide lower moisture permeability in order to reduce the
transmission of moisture through the packaging film and
thereby extend the shelf life of products such as food,
medical, electronic, and other items which are sensitive to
moisture gain or loss. For some products, maintenance of a
high
1
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moisture content is desirable, and the film ideally
minimizes loss of moisture from the package to the
environment. For other products, maintenance of a low
moisture content is desirable, and the film ideally
minimizes gain of moisture from the environment through the
packaging material.
It is also often desirable to include in a
packaging film a shrink feature, i.e. the propensity of the
film upon exposure to heat to shrink or, if restrained,
create shrink tension within the packaging film. This
property is imparted to the film by orientation of the film
during its manufacture. Typically, the manufactured film is
heated to its orientation temperature and stretched in
either a longitudinal (machine) or transverse direction
(i.e. monoaxial orientation), or both directions (i.e.
biaxial orientation), in varying degrees to impart a certain
degree of shrinkability in the film upon subsequent heating.
When biaxial orientation is done, it can be simultaneous or
sequential; that is, the orientation can be done in each of
the directions in turn, or else both the longitudinal and
transverse orientation can be done at the same time. Any
suitable technique, such as blown bubble or tenterframing,
can be used to achieve orientation of the film. After being
so stretched, the film is rapidly cooled to provide this
latent shrinkability to the resulting film. One advantage
of shrinkable film is the tight, smooth appearance of the
wrapped product that results, providing an aesthetic package
as well as protecting the packaged product from
environmental abuse. Various food and non--food items may be
and have been packaged in shrinkable films.
Tt is sometimes also desirable to orient a
packaging film and thereafter heat set the film by bringing
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the film to a temperature near its orientation temperature.
This produces a film with substantially less shrinkability,
while retaining much of the advantages of orientation,
including improved tensile strength, modulus and optical
properties.
Of interest are U.S. Patent Nos. 4,921,749
(Bossaert et al); 5,085,943 (Crighton et al); 5,091,237
(Schloegel et al); 5,128,183 (Bu2io); and 5,212,009 (Peiffer
et al) disclosing the use of hydrocarbon resins.
SUMMARY OF THE INVENTION
The present invention provides a thermoplastic
multilayer film characterized by good moisture barrier
properties. Further, the present invention provides a
thermoplastic multilayer film having an aesthetic appearance
with good clarity, and other desirable optical properties.
The present invention also provides a thin thermoplastic
multilayer film having toughness and abrasion resistance.
The present invention also provides a thermoplastic
multilayer film which may be totally coextruded, oriented,
and have good moisture barrier and, in some cases, both
moisture barrier and oxygen barrier properties.
The present invention relates to a thermoplastic
multi-layer film comprising a core layer comprising a blend
of propylene polymer or copolymer, or ethylene alpha olefin
copolymer, and a hydrocarbon resin; and two outer layers
comprising a propylene polymer or copolymer, ethylene alpha
olefin copolymer, polybutene, or blends thereof.
In another aspect, the present invention relates
to a thermoplastic mufti-layer film comprising a core layer
comprising a blend of propylene polymer or copolymer, and a
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hydrocarbon resin; two intermediate layers, on' opposite
surfaces of the core layer, comprising propylene polymer or
copolymer, or a polymeric adhesive; and two outer layers
comprising a propylene polymer or copolymer, ethylene alpha
olefin copolymer, ionomer, polybutene, or blends thereof.
The present invention also relates to a
thermoplastic mufti-layer film comprising a core. layer
comprising an ethylene alpha olefin copolymer, ethylene
propylene copolymer, rubber modified ethylene
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propylene copolymer, or ethyene propylene butene terpolymer; two
intermediate layers, on opposite surfaces of the core layer, comprising
a blend of propylene polymer or copolymer, and a hydrocarbon resin; and
two outer layers comprising a propylene polymer or copolymer, ethylene
alpha olefin copolymer, ionomer, polybutene, or blends thereof.
A film with oxygen barrier as well as moisture barrier properties
comprises a core layer comprising an oxygen barrier material; two
intermediate layers, on opposite surfaces of the core layer,. comprising
a polymeric adhesive; two outer layers comprising a blend of propylene
polymer or copolymer, or polybutene, and a hydrocarbon resin; and a
polymeric sealant layer adhered to at least one of the outer layers.
An alternative film with at least seven layers comprises a core
layer comprising~high density polyethylene; two intermediate layers, on
opposite surfaces of the core layer, comprising a polymeric adhesive,
ethylene vinyl acetate copolymer, or ethylene alpha olefin copolymer;
two outer layers comprising a blend of propylene polymer or copolymer,
and a hydrocarbon resin; and two outermost layers comprising propylene
polymer or copolymer, polybutene, or blends thereof.
Another alternative is a film comprising a core layer comprising an
oxygen barrier material; two intermediate layers, on opposite surfaces
of the core layer, comprising polyamide; two tie layers, each disposed
on a respective polyami.de layer, comprising a polymeric adhesive,
ethylene alpha olefin copolymer, or ethylene vinyl acetate copolymer;
two moisture barrier layers, adhered to respective adhesive layers,
comprising a blend of propylene polymer or copolymer, and a hydrocarbon
resin; and two outermost. layers comprising a propylene polymer,
propylene copolymer, ethylene alpha olefin copolymer, or polybutene.
In another aspect of the invention, a method of making a
thermoplastic multilayer film comprises the steps of coextruding an
interior layer of a blend of propylene polymer or copolymer, and a
hydrocarbon resin, and two outer layers comprising a propylene polymer
or copolymer, ethylene alpha olefin copolymer, polybutene, or blends
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6453&-829F
thereof; cooling the coextruded m.ulti-layer film; and
collapsing the cooled film.
In one aspect, the invention of the parent
application provides a thermoplastic mufti-layer film,
comprising: (a) a core layer comprising a blend of propylene
polymer or copolymer, and a hydrocarbon resin; and (b) two
outer layers comprising a polymeric material selected from
the group consisting of: i) ethylene alpha olefin copolymer,
ii) polybutene, and iii) blends thereof.
In a further aspect, the invention of the parent
application provides a thermoplastic multi-layer film
comprising: (a) a core layer comprising a blend of propylene
polymer or copolymer, and a hydrocarbon resin; (b) two
intermediate layers, on opposite surfaces of the core layer,
comprising propylene polymer or copolymer, or' polymeric
adhesive; and (c) two outer Layers comprising a polymeric
material selected from the group consisting of: i) ethylene
alpha olefin copolymer, ii) ionomer, iii) polybutene, and
iv) blends thereof.
In one aspect, the invention in this divisional
application provides a thermoplastic multi-layer film,
comprising: (a) a core layer comprising an oxygen barrier
material; (b) two intermediate layers, on opposite surfaces
of the core layer, comprising polyamide; (c) two tie layer,
each disposed on a respective polyamide layer, comprising a
polymeric material selected from the group consisting of: i)
polymeric adhesive; ii) ethylene alpha olefin copolymer; and
iii) ethylene vinyl acetate copolymer; (d) two moisture
barrier layers, adhered to respective adhesive layers,
comprising a blend of propylene polymer or copolymer, and a
hydrocarbon resin; and (e) two outermost. layers comprising a
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' 64536-829F
polymeric material selected from the group consisting of: i)
propylene polymer, ii) propylene copolymer, iii) ethylene
alpha olefin copolymer, and iv) polybutene.
DEFINITIONS
"Hydrocarbon resin" ( "~?~C" herein) and the like as
used herein means resins made by the polymerization of
monomers composed of carbon and hydrogen only.
Thermoplastic resins of low molecular weight made from
relatively impure monomers derived from coal-tar fractions,
petroleum distillates, etc. are also inc7_uded. A discussion
of HC resins can be found e.g. in U.S. Patent Nos. 4,921,749
(Bossaert et al); 5,091,237 (Schloegel et al); and 5,128,183
(Buzio) .
"Ethylene alpha olefin copolymer" (EAO) is used
here to include such materials as linear low density
polyethylene (LLDPE); very low and ultra low density
polyethylene (VLDPE and ULDPE); and meta7_locene catalyzed
polymers such as those supplied by Exxon. Tafmer (tm)
materials supplied by Mitsui are also included. These
materials generally include copolymers of ethylene with one
or more comonomers selected from C4 to Clo alpha olefins such
as butene-1, hexene-1, octene-1, etc. in which the molecules
of the copolymers comprise long chains with relatively few
side chain branches or cross-linked structures. This
molecular structure is to be contrasted with conventional
low or medium density polyethylenes which are more highly
branched than their respective counterparts. "LLDPE" as
defined here has a density in the range of from about 0.916
grams per cubic centimeter to about 0.940 grams per cubic
centimeter. Generally, °'EAO" as used here includes both
homogeneous and heterogeneous polymers.
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64536-829F
"Intermediate layer" and the like is used herein
to define a layer in a mufti-layer film enclosed on both
sides by other layers, i.e. disposed between other layers of
the film.
The term "oriented" and the like is used herein to
define a polymeric material in which the molecules have been
aligned in the
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longitudinal and/or transverse direction by a .process such as a tenter
frame or blown bubble process.
"Propylene polymer'° and the like is used here to mean polymerized
propylene in its homopolymer form, and "propylene copolymers" means
copolymers such as ethyene propylene copolymer, where generally small
amounts of a comonomer such as ethylene are included in the copolymer.
Terpolymers are also included.
"Polymeric adhesive" and the like here means polymeric materials, of
any suitable composition, which can be used to create or enhance
interlaminar bonds in multilayer thermoplastic films. Polyolefins are
preferred, especially those which have been modified, e.g. by carboxylic
acid or acid anhydride in a graft copolymer.
"Rubber modified EPC" and the like here means an EPC which has been
modified by the inclusion of other moieties in the polymer structure.
Such material may provide improved elasticity or other properties.
An example is believed to be Himont KS - 052 P, or those available from
Rexene (E1 Paso).
"Ethylene ,propylene butene terpolymer" and the like is used here to
mean a terpolymer incorporating these three comonomers in various
percentages. An example is KT - 021 from Himont, o:r those available
from Sumitomo.
"Core layer" as used herein means an intermediate layer of a
multilayer film, and the central layer where the film has. an odd number
of layers.
BRIEF DESCRIPTION OF THE DRAWINGS
Further details are given below with reference to the drawing
figures wherein Figure 1 is a schematic cross section of a preferred
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64 536°829
embodiment of a mufti-layer moisture barrier film of the
invention, and Figures 2 and 3 are alternai:.ive embodiments of the
invention.
DESCRIPTIOP1 OF THE PREFERRED EMHODIMEAITS
Referring specifically to the drawings, in Figure 1, a
schematic cross section of a preferred embodiment of the multi-
layer moisture barrier film of the invention is shown. Ttie multi-
layer film 10 has the generalized structure of .A/B/A where A is an
outer layer, and B is a core layer comprising a moisture barrier
material.
Core layer 12 preferably comprises a blend of a
propylene polymer or copolymer, and a hydrocarbon resin~ this
blend shown as a spotted/striped Iayer. A typical example of a
propylene homopolymer is Exxon PD 4062 E7*,, or those available
from Fina, or Himont PD 064*. A preferred propylene copolymer is
ethylene propylene copolymer sold under the designation Fina 8473*
or Fina 8473X*. This material has an ethylene content of about
40. A preferred hydrocarbon resin is Rega:lrez 1128* or 1239 from
Hercules. The HC resin preferably comprises between about 30o and
50's by weight of the blend.
Outer layers 14 and 16 are preferably ethylene propylene
copolymer (EPC), polypropylene (PP), or blends thereof. If only
polypropylene resin is used, the film can be difficult to use for
packaging applications involving heat sealing. Therefore, it is
preferable to use EPC alone, or the blend of the two materials.
Commercial resin examples are those discussed above for core layer
12. An alternative polypropylene for the outer layers 14 and Z6
*Trade-mark 7
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64536-829
is Himont PD 064. These blend layers may include from 0-100% EPC
and 100%-0% PP, although preferably the blend layers include
between about 96% and 85% EPC and between about 4% and l5% PP;
even more preferably, the blend layer. inclLides about 92% EPC and
8% PP. EAO and polybutene can alse be used in the outer layers.
7a
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In Figure 2, a schematic cross section of another embodiment of the
mufti-layer .moisture barrier film of the invention is generally~shown.
The mufti-layer film has the structure of A/B/C/~3/A where A is an outer
layer, B is:-.=-an intermediate adhesive layer, and C is a core layer
comprising a moisture barrier material.
The core layer preferably comprises a blend of a propylene polymer
or copolymer, and.'a hydrocarbon resin. ~ Suitable .mat.erials are those
described above for core layer 12 of film 10.
The outer layers are preferably the materials discussed above for
outer layers 14 and 16 of film 10. The outer layers also preferably
include an HC such as described for core layer 12 of film 10.
The intermediate layers preferably comprise a propylene polymer or
copolymer, or blends thereof, optionally blended with hydrocarbon resin.
An alternative A/B/C/B/A structure is also within the scope of this
invention, and specifically shown by the pos9.tion of the moisture
barrier layers in the film of Fig.2.
In this alternative, core layer 24 preferably comprises an ethylene
alpha olefin copolymer,. more preferably a linear EAO. Very low density
polyethylene (VhDPE), and linear low density polyethyene (hLDPE) are
preferred. A suitable T.T-nPE is I7owlex 2045TM The core layer 24 can also
comprise EPC, a rubber modified EPC, or an ethylene terpolymer,
especially an ethylene propylene butene terpolymer such as KT 021 P from
Himont.
Outer layers 20 and 28 are preferably the materials discussed above
for outer layers 14 and 16 of film 10.
Intermediate layers 22 and 26 preferably comprise a blend of a
propylene polymer or copolymer, and ~ hydrocarbon :resin. Suitable
materials are those described above for core layer 12 of film 10. An
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alternative material for layers 22 and 26 is Exxon 6042, which is
believed to be a blend of polypropylene and hydrocarbon resin.
In Figure 3, a schematic cross section of another embodiment of the
multi-layer moisture barrier film of the invention is shown. The
multi-layer film 30 has the generalized. structure of A/B/C/D/C/B/A where
A is an outer layer, B is a moisture barrier layer, C is an intermediate
adhesive layer, and D is a core layer comprising a.n oxygen barrier
material.
Core layer 38 preferably comprises an oxygen barrier material such
as ethylene vinyl alcohol copolymer, vinylidene chloride copolymer,
polyester, or polyamide.
Outer layers 32 and 44 are preferably the materials discussed above
for outer layers 14 and l6 of film 10.
Intermediate layers 36 and 40 preferably comprise a propylene
polymer or copolymer, such as Exxon PD 4062 E7. Alternative materials
are polymeric adhesives, especially carboxylic acid or malefic
anhydride-modified pclyolefins and more preferably polypropylene-based
carboxylic acid or malefic anhydride-modified adhesives. Conventional
lamination or other suitable methods may sometimes be necessary,
depending on the nature of the respective layers, to ensure adequate
interlaminar bond strength.
Moisture barrier layers 34 and 42 preferably comprise a blend of a
propylene polymer or copolymer, and a hydrocarbon resin. Suitable
materials are those described above for core layer 12 of film 10. An
alternative material for layers 34 and 42 is Exxon 6042.
An alternative film with at least seven layers comprises a core
layer 38 comprising high density polyethylene; two intermediate layers
36 and 40, on opposite respective surfaces of the core layer, comprising
a polymeric adhesive, ethylene vinyl acetate copolymer, or ethylene
alpha olefin copolymer; two moisture barrier layers 34 .and 42 comprising
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a blend of propylene polymer or copolymer and a hydrocarbon resin; and
two outermost layers 32 and 44 comprising propylene polymer or copolymer.
A multilayer film of four or six layers, a.nd/or possessing both
moisture barrier and oxygen barrier properties, can also be made in
accordance with the present invention. In such alternative
constructions, a blend of HC resin with propylene polymer or copolymer
can be present in any of the layers of the multilayer film.
The core, intermediate, and ~isture barrier layers of such a film
can be like that of film 30. A sealant layer i.s coextruded with, or
extrusion coated, extrusion laminated, or adhesive laminated, by means
and methods well known in the art, to one of the moisture barrier
layers. The 'sealant layer, which can be disposed on one or both outer
surfaces of the film structure, preferably comprises an ethylene alpha
olefin copolymer, more preferably a linear EAO. Very low density
polyethylene (VhDPE), and linear low density polyethyene (LLDPE) are
preferred. A suitable T.T,nPE is Dowlex 2045. The sealant layer can also
comprise EPC, a rubber modified EPC, an ethylene propylene butene
terpolymer such as KT 021 P from Himont, an ethylene vinyl acetate
copolymer, an ethylene alkyl acrylate copolymer, an ethylene acrylic or
methacrylic acid copolymer, or an ionomer.
The films of the present invention can be made by coextrusion,
extrusion coating, extrusion laminating, and conventional adhesive
lamination techniques well known in the art, using annular or slot die
extrusion equipment as appropriate.
The beneficial low moisture transmission rates (high moisture
barrier) and other properties associated with exemplary filans of the
present invention are demonstrated in the Tables.
The resins used in these examples are identified in Table 1, and the
films made from these resins are identified in Tables 2 through 8.
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Physical properties of these films are itemized in the remaining
Tables. Values given are typically average values obtained from four
replicate measurements; values for MVTR are average obtained from three
samples.
The terms and abbreviations In the Tables have the following meaning:
"PP" = polypropylene.
"EPC" = ethylene propylene copolymer.
°'EAO" = ethylene alpha olefin copolymer.
"EPB" = ethylene propylene butane terpolymer.
''EVOH" = ethylene vinyl alcohol copolymer.
"ADH" - polymeric adhesive; ADH 1 is an ethylene butane - based
adhesive from Du Pont; ADH 2 is an EPC-based adhesive from Mitsui.
"AB" = antiblock.
°'M0" = mineral oil.
"Tensile" = tensile at break and 73° F, in PSI (ASTM D 882-81).
'°PSI" = pounds per square inch (ASTM 882-81).
"Unshrunk°' - a film sample. or samples that were not shrunk by
exposure to heat at the time of testing for the stated property.
"Shrunk" = a film sample or samples that were shrunk by exposure to
heat at the time of testing for the stated property.
°'LD" = longitudinal orientation direction.
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"TD" = transverse orientation direction.
"Modulus" = modulus of elasticity (ASTM 882-81) in PSI at 73°F.
"Haze" = haze (ASTM D 1003-61 (reapproved 1977)) in per cent.
"Clarity" - total light transmission (ASTM D 1003 Method A} in
percent.
°'Gloss" - gloss measured at 45° angle to film surface (ASTM D
2457-70 (reapproved 1977) )
°'MVTR 1" = moisture (water) vapor transmission rate (ASTM F 372) in
grams/24 hours, 100 square inches at 100% relative humidity and 100°F.
°'MVTR 2" = moisture (water) vapor transmission rate (ASTM F 372} in
grams/24 hours, 100 square inches at 90o relative humidity and 100°F.
vo~rjrRn = oxygen transmission rate (ASTM D 3985-81) in cc at standard
temperature and pressure, in 24 hors, per square meter, at one
atmosphere, at 0% relative humidity.
,'Tear" = tear propagation in grams at 73°F (ASTM ~ 1938-79).
°'Filrn Thickness" = the average thickness (gauge) of the film samples
in mils (_ .001 inches).
"Tensile'° = tensile strength at break (ASTM L) 882-81} in psi.
"Elongation" = elongation at break (ASTM D 882-81) in percent.
"Ball Burst" - ball burst impact in centimeters-kilograms at 73°F
(ASTM D 3420-80).
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TABLE 1
MATERIAL TRADENAME SUPPLIER
PP 1 Profax PD-064 Himont
PP 2* [see footnote
PP 3 PD 4062 Exxon
PP 4** Escorene PD 6042 Exxon
[see footnote)
EPC 1. Fina 8473 or Fina
Fina 8473 X
EPC 2***
[see footnote
EPC '~ PD 9302 Exxon
EPB 1 KT-021 Himont
HC I Regalrez 1128 Hercules
HC 2 Escorez 5340 Exxon
HC 3 Regalrez 1139 Hercules
EAO 1 Dowlex 2045.03 Dow
EAO 2 Dowlex 2045.04 Dow
ADH 1 Bynel CXA 4104 Du font
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ADH 2 Admer QF 551 A Mitsui
EVOH 1 EVAL~SC H-103 Evalca
EVOH 2 EVAL hC F-101 A Evalca
EVOH 3 EVAL LC H-103 Evalca
MO 1 Kaydol Witco
*PP 2 is a masterbatch blend of PF 1 with about 4%, by weight of the
blend, of a silica-containing anti-blocking agent, about 5% by .i~eight of
amide waxes, and about to of a lubricating agent. The amide waxes and
lubricating agent.are well known in the art as slip agents.
** PP 4 is Escorene PD 60'42T; believed to be a blend of polypropylene
and hydrocarbon resin.
***EPC 2 is a blend of EPC 1 blended with about 1:5%, by weight of
the blend, of an antiblock agent, and 0.5~, by weic_tht of the blend, of
a mineral oil.
14
E. 4 5 3 6 - 8 2 9 F ~ 02417182 2003-06-30
TABLE 2 ( CONTROL )
Initial efforts r_o make a moisture barrier
material involved the use of homopo:lymer polypropylene in a
core layer, with sealant layers of propylene copolymer on
both surfaces of the core :Layer. The objer_t was to maximize
thickness of the core layer to minimize the moisture vapor
transmission rate (MVTR), while still maintaining adequate
free shrink and :~ealability properties of the film. The
IvIVTR did not prove adequate :for at least some moisture
barrier packaging applications. An example of this film i:~
given below:
1=;XAMPLE FILM S'TRUC'TURE
1. . 92 % EPC 1 + 8 % PP 2 / PP 1 / 92 % EPC 1 + 8 % PP 2
The generalizeo :structure of she film of Example 1
was A/B/A.
Relative layer thickness ratios:
A =-. 1.0; B - 2.0; A = 1Ø
'TABLE 3
The fi:Lms of Table 3 were made in an effort to
make a moisture barrier nrav~~eria.l with lower MVTR. This was
achieved using hydrocarbon resin blended with homopolymer
polypropylene. :Ct was fc,und t:hat these formulations had
much lower moisture vapor transmission :rate (MVTR) than
those of Table 2. However, they could not be oriented much
over 4.5 X 4.5 racking (c:~ri.entation) ratio because of
equipment limita.t~ions. Cin other equipment, e.g. a modified
bubble process or tenterframing, higher orientation
;racking) rates can be achieved. They also could not be
CA 02417182 2003-02-19
made into heavier gauge films because of relatively poor tear
properties. Examples of these films are given below:
EXAMPLE FILM STRUCTURE
2. 90%j92% EPC 1 + 8% PP 2] + 10% HC 1
PP 3
84.5% PP 3 + 15% HC 1 + 0.5% MO 1
PP 3
90%j92% EPC 1 + 8% PP 2] + 10% HC 1
The generalized structure of the film of Example 2 was
A/B/C/B/A.
Relative layer thickness raties:
2.5 : 0.8 : 3.7 . 0.6 : 2.4.
3. 92% EPC 1 + 8% PP 2 / PP 4 / 92 % EPC 1 + 8% PP 2
The generalized structure of the film of Example 3 was
A/B/A.
Relative layer thickness ratios:
1 : 2 : 1
4 . 92 % EPC 1 + 8~ PP 2 / PP 4 / 92 % EPC 1 -t- 8% PP 2
The generalized structure of the film of Example 4 was
A/B/A.
Relative layer thickness ratios:
1 : 3 : 1.
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TABLE 4
Alternative films of Table 4 were made in which, in effect, the core
layer of the films of Table 3 (i.e. the layer containing the hydrocarbon
resin) were '°split" into two substrate (intermediates layers. A
'°new°'
core layer of e.g. LLDPE or EPC is introduced. The practical effect of
this is to improve tear properties of the film, related to tape creasing
during the orientation process, so that it can he oriented at e.g. 6 x 6
ratio. The film was in fact oriented at 4 x 4.5 because of the
equipment limitations discussed for the Examples of Table 3. Examples
of these films are given below:
EXAMPLE FILM STRUCTURE
. 92% EPC. 1 + 8% PP 2 / PP 4 / EAO 1 / PP 4 / 92 % EPC 1 + 8% PP 2
The generalized structure of the film of Example 5 was A/B/C/B/A.
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1.5.
6. 92% EPC 1 + 8 % PP 2 / PP 4 / EPC 1 / PP 4 / 92 % EPC 1 + 8% PP 2
The generalized structure of the film of Example 6 was
A/B/C/B/A.
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 3.5
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TABLE 5
The inventor took the basic constructions of Table 4, and oriented
them at generally higher racking ratios of 6 x B. The result was a film
showing improvements in (i.e. lower) MVTR. Examples of these films are
given below:
EXAMPLE FILM STRUCTURE
7 . 92 o EPC 1 + 8 % PP 2 / PP 4 / EAO 1 / PP ~ / 92 % EPC 1 + 8% Pp 2
The generalized structure of the film of Example 7 was
A/B/C/B/A. This film was like that of Example 5, but with both
MD and TD racking ratios of about 6 x 6 in the longitudinal and
transverse directions respectively.
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1.5.
8. 92 ~ EPC 1 + 8% PP 2 / . PP 4 / EAO 1 / PP 4 / 92% EPC 1 + 8 % PP 2
The generalized structure of the film of Example 8 was
A/B/C/B/A. This film was like 'that of Example 7, but
oriented at a higher temperature compared to Example 7.
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1.5
9. 92 ~ EPC 1 + 8 % PP .2 / PP 4 / EAO 2 / PP 4 / 92% EPC 1 + 8% PP 2
7/930727.1 TXTMBQ 18
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The generalized struoture of the film of Example 9 was
A/B/C/B/A.
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1.5.
10. 92 % EPC 1 + 8% PP 2 / PP 4 / EPB 1 / PF 4 / 92% EPC 1 + 8% PP 2
The generalized structure of the film of Example 10 was
A/B/C/B/A.
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1.5.
11. 92% EPC 1 + 8% pp 2
70 % PP 3 + 30 % HC 2
EAO 2
70 % PP 3 + 30 % HC 2
92 % EPC 1 + 8 % PP 2
The generalized structure of the film of Example 11 was
A/B/C/B/A.
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1:5.
12 . 90 % EPC 1 + 10% PP 2 / PP 4 / EPC 1 / PP 4 / 90 % EPC 1 + 10 % PP 2
The generalized structure of the film of: Example 12 was
A/B/C/B/A.
7/930727.1 TXTMBQ 19
CA 02417182 2003-02-19
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1.5.
13 . 90% EPC 1 + 10 % PP 2 / PP 4 / EPC 1 / PP 4 / 90% EPC 1 + 10% PP 2
The generalized structure of the film of Example 13 was
A/B/C/B/A. This film was like -that of Example 12, but lower
racking ratios of 4.5 x 4.5 to produce a film of 132 gauge
thickness.
Relative layer thickness ratios:
1.5 :- 3 : 1 : 3 : 1.5.
14 . 90% EPC 1 + 10 % PP 2 / PP 4 / EPC 1 / PP 4 / 90 % EPC 1 + 10% PP 2
The generalized structure of the film of Example 14 was
A/B/C/B/A. This film was like that of Example 13, but with
slightly higher racking ratios {4.5 x 5.0) and a final film
thickness of 155 gauge.
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1.5.
15. 87.5% EPC 3 + 12.5% PP 2
PP 4
EPC: 3
PP 4
87.5% EPC 3 + 12.5% PP 2
The generalized structure of the film of Example 15 was
A/B/C/B/A.
7/930727.1 TXTMBQ 20
CA 02417182 2003-02-19
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1.5.
16. 84~ EPC 3 + 16~ PP 2
PP 4
EPC 3
PP 4
84 o EPC 3 + 16 ~ PP 2
The generalized structure of the film of Example 16 was
A/B/C/B/A.
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1.5.
17. 86% EPC 3 + 14o PP 2
PP 4
EPC 3
PP 4
86o EPC 3 + 14% PP 2
The generalized structure of the film of Example 17 was
A/B/C/B/A.
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1.5.
TABLE 6
The inventor made a seven layer film (Example 18) as a control and
then made two moisture/oxygen barrier seven-laye~_~~fihr~s (Examples 1g and
20) with good results. Examples of these films are given below:
7/930727.1 TXTMBQ 21
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ExArgPLE Fzr~ sTRUCTURE
18. 92% EPC 1 + 8~ PP 2
PP 3
ADH 2
EVOH 1
ADH 2
PP 3
92% EPC 1 + 8% PP 2
The generalized structure of the film of Example 18 was
A/B/C/D/C/B/A.
Relative layer thickness ratios:
1 : 2.5 : 1 : 1 : 1 : 2.5. . 1
19 . 92 % EPC 1 + 8 % PP 2
PP 4
ADH 1
EVOH 2
ADH 1
PP 4
92 % EPC 1 + 8 % PP 2
The generalized structure of the film o:~ Example 19 was
A/B/C/D/C/B/A.
Relative layer thickness ratios:
1.5 : 2 : 1 : 1 : 1 : 2 : 1.5
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20. 92% EPC 1 + 8% PP 2
PP' 4
ADH 2
EVOH 3
ADH 2
PP 4
92 % EPC 1 + 8 % PP 2
The generalized structure of the film of Example 20 was
A/B/C/D/C/B/A.
Relative layer thickness ratios:
1.5 : 2 : 1 : 1 : 1 : 2 : 1.5
TABIsE 7
Two alternative films of seven layers have the structure:
21. 92% EPC 1 + 8a PP 2
PP 4
EVA 1
HDPE 1
EVA 1
PP 4
92% EPC 1 + 8% pP 2
The generalized structure of the film of Example 21 is
A/B/C/D/C/B/A.
Relative layer thickness ratios:
1 : 2.5 : 1 : 1 : 1 : 2.5 .: 1
7/930727.1 TXTMBQ 23
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22. 92% EPC 1 + 8% PP 2
PP 4
VLDPE 1
HDPE 1
VLDPE 1
PP 4
g2% EPC 1 + 8 % PP 2
The generalized structure of the i:ilm of Example 22 is
A/B/C/DeC/B/A.
Relative layer thickness ratios:
1 : 2.5 : 1 : 1 : 1 : 2.5 : 1
TABLE 8
Two additional alternative films of five layers were made, and are
compared in Table 13 with the film of Example 17. These two
additional films have the following structures:
23. 86% EPC 3 + 14% P'P 2
PP 4
85 % EPC 3 + 15 % HC 3
PP 4
86% EPC 3 + 14% PP 2
The generalized structure of the film of Example 23 is
A/B/c/B/~.
Relative layer thickness ratios:
1.5 : 3 : 1 . 3 : 1.5
7/930727.1 TXTMBQ 24
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24. 86% 85% EPC 3 + 15o HC 3] + 19% PP 2
PP 4
85% EPC 3 + 15% HC 3
pp 4
85% EPC 3 + 15~ HC 3
The generalized structure of the film of Example 24 is
A/B/c/s/c.
Relative layer thickness ratios:
1.5 : 3 : 1 : 3 : 1.5
7/930727.1 TXTMBQ ' 25
CA 02417182 2003-02-19
. TABLE ~
Example 1 . ExamPr. ~-y-- Fxam~le 3 E-~-
(COntrol)
Modulus
030 336.820
316
ZD 239,480 279,920 , 316,820
240
260 298,930
214,690 ,
Fry hrink/S~Te
at 200F:
10/315 -11/408
ZD 7/396 9/321 17/504
14/381 17/528
TD 12/388
at 220F:
14/361 15/439
LD 12/435 14j335 25/548
/383 24/540
19
TD 18/432 ,
at 240F:
20/443 22/494
ZD 18/451 20/364 33/516
281413 33/591
TD 26/469
at 260~':
33/429 33/511
LD 31/473 31/397 44/561
' 39/441 45/538
3
TD 35/4
26
7/930727.1 TXTMBQ
CA 02417182 2003-02-19
Haze
Unshrunk 1.2 1.7 1.3 1.3
Shrunk 1.6 2.3 3.2 2.1
Clarit
Unshrunk 81 87 87 88
Shrunk 80 84 83 87
Gloss
87 84 87 88
Film Thickness (mils)
( related to MVTR data giver! belo~r)
Unshrunk
Actual
0.96 0.80 0.77 0.75
MVTR 1
Unshrunk
0.60 0.67 0.60 0.55
Corrected
for '75 gauge
0.77 0.71 0.62 0.55
7/930727.1 TXTMBQ 27
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MVTR 2
Unshrunk-
0.49 0.55 0.48 0.45
Corrected
for 75 gauge
0.63 0.59 0.49 0.45
7/930727.1 TXTMBQ 28
CA 02417182 2003-02-19
TABLE 10
Example 7 Examg~le 8 . E_xampl_e 9 Example 10
Modulus
LD 271,200 299,200 -------- -_-__-_
TD 292,100 337,900 ------ -_---_-
Free Shrink
at 220F:
LD -- -- 13 13
TD -- -- 19 20
at 290F:
LD 20 17 20 18
TD 28 23 30 27
at 260F:
LD - -- 2? 28
TD -- -- 37 38
Haze
I)nshrunk --- --- 1.7 1.8
Clarity
Unshrunk -- -- 82 84
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Gloss
__ __ 84 85
Film Thickness (mils)
(related to MVTR data given below)
Unshrunk
0.86 0.76 0.86 0.77
Shrunk
1.00 0.97 ____ ____
MVTR 1
Unshrunk
0.51 0.56 ---- ----
Shrunk
0.41 0.46 ---- ----
Corrected
for 75 gauge
Unshrunk
0.58 0.57 ____ ____
Shrunk
0.55 0.59 ---- ----
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T~3VTR 2
Unshrunk
0.45 0.47 0.42 0.43
Shrunk
0.35 0.38 ---- ---
Corrected
for 75 gauge
Unshrunk
0.52 0.48 0.48 0.44
Shrunk
0.47 0.49 ____ ____
Tear (grams)
LD -- -- 8.6 5.0
TD -- -- 8 . 4 f~ .1
7/930727.1 TXTNiBQ 31
CA 02417182 2003-02-19
TABLE 11
Example 11 Example 12 Exa~pm 1e 13 Example 14
Modulus
LD 345,750 352,880 322,9x0 320,470
TD 374,990 392,020 334,660 319,420
Free Shrink
at 240F:
20. 17 18 14
TD 29 23 24 25
Ha22
Unshrunk
48.5 1.3 3.3 5.3
Clarity
Unshrunk
21 85 74 64
Gloss
107 89 73 64
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Film Thickness (mils)
(related to hSS~TR data given below)
Unshrunk
0.85 0.81 1.40 1.60
I~VTR 2
Unshrunk
0.36 0.36 0.23 0.19
Corrected for
~75 Gauge
0.41 0.39 0.43 0.41
Tear (grams)
ZD -- -- 8.6 5.0
TD -- -- 8.4 6.1
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TABLE 12
Example 19 Example 20
Modulus
LD 300,890 307,380
TD 315,460 291,480
Free Shrink/Shrink
Tension
at 220F:
LD 8/440 14,/395
fiD 19/632 20/595
at 240F:
LD 18/477 21/439
TD 28/654 27/611
at 260F:
LD 28/446 29/436
TD 38/621 35/601
at 280F:
LD 44/467 43/487
TD 52/600 46/587
at 300F:
LD 59/-__ 60/--_
TD 62/--- 61/--_
7/930727.1 TXTMBQ 34
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daze
Unshrunk 1.6 1.8
Clarity
Unshrunk 76 76
Gloss
89 86
Film Thickness (mils)
(related to MVTR data given below
Unshrunk
1.09 1.12
MVTR 2
Non-shrunk
0.35 0.33
Corrected for
75 gauge 0.51 0.49
Tear
LD 6 6
TD 6 7
7/930727.1 TXTMBQ . 35
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Tensile
LD 19,415 20,407
TD 19:296 16,990
Elonc~at'ion
LD 63 62
TD 71 77
12 12
0TR
3.0 4.5
7/930727.1 TXTNBQ 36
CA 02417182 2003-02-19
TABLE 13
Example 17 Example 23 .. Exam 1e 24
Modulus
LD 398,000 420,000 437,0'00
TD 442,000 473,000 48$,000
Free Shrink
at 220F:
LD 15 14 15
TD 19 19 22
at 240F:
LD 20 19 19
TD 26 26 28
at 260F:
LD 30 30 26
TD 38 36 38
at 280F:
LD 44 44 44
TD 51 51 52
at 30bF:
LD 64 63 62
TD 68 67 68
7/930727.1 TXTMBQ 37
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Hale
Unshrunk 1.8 2.0 1.2
Clarity
Unshrunk 82 83 81
Gloss
86 83 89
Film Thickness (mils)
(related to MVTR data given below)
Unshrunk
0.89 0.91 0.82
MVTR 2
Unshrunk
0.33 0.36 0.33
Corrected for
75 gauge 0.39 0.4~ 0.36
Tear
LD 1 7 4
TD 5 7 6
7/930727.1 TXTMBQ 38
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Tensile
DD 28,000 310000 28,000
TD 29,000 33,000 29,0(?0
Elongation
LD 80 86 84
TD 71 52 73
7/930727.1 TxTMBQ 39
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In a typical working example of making the film of the present
invention:
An ethylene propylene copolymer (Fine 8473) containing about 4% by
weight ethylene, was blended with the polypropylene in a blend ratio of
about 92% by weight EPC and 8% by weight PP. (The PP percentage
includes the additives discussed above).
The EPC/PP blend was then blended with a hydrocarbon resin (Regalrez
1128 from Hercules) in a blend ratio of about 90% by weight EPC/PP and
10% by weight HC.
A second blend was also prepared, in a blend ratio of about 84..5 by
weight PP (Exxon PD 4062 E7), 15% by weight HC (Regalrez 1128), and 0.5%
white mineral oil (Kaydol from Witco Chemical).
A circular coextrusion die was fed with three extruders to prepare a
five layer shrink film. One extruder was used t.o fee~3 the blend of EPC
or polypropylene, and HC, as a melt to the extrusion die to form the
outer layers. Another extruder fed a polypropylene (Exxon PD 4062 E7)
to the extrusion die to provide the intermediate layers in the
multi-layer film. The third extruder provided the second blend of PP
and HC to the extrusion die.
The extruded tape was rapidly cooled to room temperature and
collapsed by pinch rolls. The tape was subsequently heated to an
orientation temperature. Using a bubble technique well known in the
art, internal air pressure stretched the tape to about 4.5 times its
unstretched dimensions in the longitudinal (machiraQ) direction and about
4.0 times its unstretched dimensions in the transverse direction to form
a bubble which provided biaxial orientation to the resulting film. The
bubble was then rapidly cooled by chilled air in order to maintain the
oriented state of the film. Finally, the bubble was collapsed and the
expanded film gathered on a take-up roll. After orientation, the total
wall thickness of the film was about one mil with 50 0 of the structure
being the blend of ethylene propylene copolymer and polypropylene; 15%
7/930727.1 TXTMBQ . 40
CA 02417182 2003-02-19
of the structure being the intermediate layers; and the remainder or 35%
of the structure being the core layer.
It will be clear to one skilled in the art that the degree of
stretching may be to obtain the desireddegree of film gauge
varied or
thickness and to regulate of shrink tension,
the desiret~ amount free
shrink, and other propertiesof the
shrink final
film,
depending
on the
packaging application.Preferred stretching.or racking ratios
are
between about 3.0 8.0 in both the machine and transverse
and
directions.
The multi°layer film of the present invention is preferably not
irradiated. However, the sealant material, if extrusion laminated,
extrusion coated, or conventionally laminated to the substrate m~isture
barrier film, can itself be irradiated or eleci~ronic~ally or chemically
crosslinked prior to lamination. Irradiation may be accomplished by
means well known in the art.
The blend ratios of the EPC and PP may be varied according to
desired properties or end-use of the multi-layer film. For example,
increasing the polypropylene in the blend wil:L add stiffness to the
film, but also increase the sealing temperature of the film.
Conversely, increasing the EPC in the blend tends to lower the shrink
temperature of the oriented film, or to increase shrink at the same
temperature, and also lowers the sealing temperature of the film. A
preferred blend includes between about 4% and 15% PP and between about
96% and 85% EPC.
The multilayer film of the present invention is preferably oriented
either monoaxially or biaxially, and preferably used as a shrink film.
Optionally, the oriented film may be further processed by reheating the
film to a temperature near its orientation temperature, i.e. either
somewhat below, at, or somewhat about its orientatican temperature, to
heat set the film. This future processing step has the advantage of
substantially retaining many of the favorable physical characteristics.
of an oriented film, such as higher tensile strength, modulus and
7/930727.1 TXTMBQ ~1
CA 02417182 2003-02-19
improved optical properties, while providing a substantial shrink°free
film in applications where a shrink feature is undesirable.
The film of the present invention can utilize hydrocarbon resin in
at least one or more, or even all the layers of the film, as long as the
HC resin in any given layer is compatible from a process and performance
point of view with the resin with which it is blended.
Films in accordance with this invention are .preferably oriented~ and
preferably heat shrinkable. Preferred films exhibit a free shrink at
240° F of at least 10 % (LD) and 15 0 ( TD) , more preferably at least
15%
(LD) and 22% (TD).
Obvious modifications to the invention as described may be made by
one skilled in the art without departing from the spirit and scope of
the claims as presented below.
7/930727.1 TXTMBQ 42
