Note: Descriptions are shown in the official language in which they were submitted.
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FILM WITH ENHANCED PERFORMANCE PROPERTIES
FIELD OF THE INVENTION
This invention relates to a tough, stiff film, comprising a blend of polymeric
materials.
BACKGROUND OF THE INVENTION
to Blends comprising alkenyl aromatic polymers, for example polystyrene, and
alpha-olefin/hindered vinyl or vinylidene interpolymers, for example, ethylene-
styrene
copolymer, are known in the art. Such blends have been suggested for use in
several
applications, including films and foams.
WO 95/32095 discloses a heat-shrinkable film comprising an oriented film
15 layer comprising a homogeneous alpha-olefin/vinyl aromatic copolymer.
Further proposed is
a laminate comprising a foam sheet and a film adhered to the foam sheet which
may
comprise a polystyrene homopolymer and homogeneous alpha-olefin/vinyl aromatic
copolymer.
U.S. Patent No. 5,460,818 describes a compatibilized blend of olefinic
2 o polymers and monovinylidene aromatic polymers and an expandable
composition
comprising such a polymer blend composition and an expanding agent. The
disclosed
polymer blend composition may comprise (a) an aliphatic alpha-olefin
homopolymer or
interpolymer, (b) a homopolymer or interpolymer of monovinylidene aromatic
monomers,
and (c) a substantially random interpolymer comprising an aliphatic alpha-
olefin and a
2 s vinylidene aromatic monomer.
WO 98/10014 pertains to blends of alpha-olefin/hindered vinylidene monomer
interpolymers and vinyl aromatic polymers and foams therefrom. Specifically
disclosed are
foams comprising a general purpose polystyrene and an ethylene-styrene
substantially
random copolymer having foam densities ranging from about 40 to about 130
kg/m3.
3 o There still is the need for a film structure providing improved
performance
properties, especially in applications requiring tough and stiff film.
Particularly desirable are
films exhibiting advantageous mechanical properties in combination with good
aesthetics. It
is the object of the present invention to provide a film displaying a well
balanced combination
of performance attributes including high toughness, good stiffness, abrasion
resistance,
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crack resistance, high ultimate elongation and good tear properties in
combination with good
optical properties. Such properties are required, for example, for films
suitable for use as
envelope window films, packaging films for window boxes, greeting card
overlays and labels.
A window envelope is an envelope with one or more openings of any shape,
typically rectangular. The opening or openings allow examination of any
information, such as
a name and an address, printed on a limited area of matter within and are
sealed or closed
by a window composed of a non-opaque plastic film. Known window films are
typically
composed of oriented polystyrene, optionally with a small proportion of rubber-
reinforced
polymer.
io Typically, a label is affixed to or accompanying an article to furnish
identification or other information. For example, a label may be a component
of a packaging
material, such as a container, which component does not come into contact with
the
contents of the package. Preferably, a label is printable. A label may have a
protective
function, for example, with respect to the integrity of the article or the
packaging material.
15 Window films and films for use as labels require high stiffness to provide
excellent handling and converting in high speed printing operations, envelope
manufacturing
applications, label manufacturing and end-use application processes. In
addition, such films
require high surface gloss (for excellent appearance and printability), good
tensile strength
and toughness properties as well as good scratch or abrasion resistance.
2 o It is the object of the present invention to provide a film displaying a
well-
balanced combination of performance properties such as to render this film
particularly
suitable for the above-mentioned and related applications, and especially as
window film or
label.
2s SUMMARY OF THE INVENTION
The present invention pertains to tough and stiff films, comprising a blend
comprising (at least) Component (A) and Component (B). Component (A) is
present in an
amount of from about 45 percent by weight to about 90 percent by weight, based
on the total
weight of Components A and B, and Component (B) is present in an amount of
from about
30 10 percent by weight to about 55 percent by weight, based on the total
weight of
Components A and B. Component (A) is composed of one or more alkenyl aromatic
polymers. Component (B) is composed of one or more substantially random
interpolymers
comprising in polymerized form (i) from about 50 mole percent to 74 mole
percent of
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ethylene and/or one or more alpha-olefin monomers, and ii) from 26 mole
percent to about
50 mole percent of one or more vinyl or vinylidene aromatic monomers and/or
one or more
sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers,
and iii) from 0
mole percent to about 20 mole percent of other polymerizable ethylenically
unsaturated
monomer(s).
The blend components and their ratio are selected to provide films of high
stiffness and toughness. The superior stiffness of the films is reflected in
modulus (1 percent
secant modulus in machine direction) of at least about 85,000 psi. Toughness
is reflected in
a high tensile toughness and ultimate elongation strength.
to Further aspects of the invention relate to methods for making the films of
the
invention and the use of such films.
In another aspect, the present invention provides a window envelope having
one or more window openings, the window opening being entirely closed by a non-
opaque
plastic window, the window being formed of a film according to the present
invention.
is Furthermore, the present invention provides a label for a container, the
label
being made from a film according to the present invention.
The present invention also provides an article of manufacture comprising the
film of the invention.
2o DETAILED DESCRIPTION OF THE INVENTION
The term "polymeric materials" as used herein refers to polymeric compounds
obtainable by polymerizing one or more monomers. The generic terms "polymeric
compounds" or "polymer" embrace the term homopolymer, usually employed to
refer to
polymers prepared from only one monomer, and the term interpolymer as defined
2 s hereinafter.
The term "comprising" as used herein means "including".
The term "film" as used herein refers to a thin article and includes strips,
tapes
and ribbons.
The term "multilayer film" as used herein indicates a film consisting of two,
3 o three, four, five, six, seven or more layers.
The term foamed film as used herein refers to a monolayer or multilayer
structure wherein a layer of the structure is foamed and has a density greater
than about 300
kg/m3 and less than the non-foamed polymer.
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The term "interpolymer" as used herein refers to polymers prepared by the
polymerization of at least two monomers. The generic term interpolymer thus
embraces the
terms copolymer, usually employed to refer to polymers prepared from two
different
monomers, and polymers prepared from more than two different monomers, such as
s terpolymers.
As defined herein, the term "substantially random" in the substantially random
interpolymer of Component (B) means that the distribution of the monomers of
said
interpolymer can be described by the Bernoulli statistical model or by a first
or second order
Markovian statistical model, as described by J. C. Randall in Polymer Sequence
to Determination. Carbon-13 NMR Method, Academic Press New York, 1977, pp. 71-
78.
Preferably, substantially random interpolymers do not contain more than 15
percent of the
total amount of vinyl aromatic monomer in blocks of vinyl aromatic monomer of
more than 3
units. More preferably, the interpolymer is not characterized by a high degree
of either
isotacticity or syndiotacticity. This means that in the carbon-13 NMR spectrum
of the
is substantially random interpolymer the peak areas corresponding to the main
chain
methylene and methine carbons representing either meso diad sequences or
racemic diad
sequences should not exceed 75 percent of the total peak area of the main
chain methylene
and methine carbons.
2o The present invention relates to films comprising blends comprising one or
more alkenyl aromatic homopolymers, or copolymers of alkenyl aromatic
homopolymers,
and/or copolymers of alkenyl aromatic monomers with one or more
copolymerizable
ethylenically unsaturated comonomers (other than ethylene or linear
C3 C,2 alpha-olefins) with at least one substantially random interpolymer.
2s The alkenyl aromatic polymer material (Component (A)) may further include
minor proportions of non-alkenyl aromatic polymers. The alkenyl aromatic
polymer material
may be comprised solely of one or more alkenyl aromatic homopolymers, one or
more
alkenyl aromatic copolymers, a blend of one or more of each of alkenyl
aromatic
homopolymers and copolymers, or blends of any of the foregoing with a non-
alkenyl
3 o aromatic polymer. Regardless of composition, the alkenyl aromatic polymer
material
comprises greater than 50 weight percent and preferably greater than 70 weight
percent
alkenyl aromatic monomeric units. Most preferably, the alkenyl aromatic
polymer material is
comprised entirely of alkenyl aromatic monomeric units.
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Suitable alkenyl aromatic polymers include homopolymers and copolymers
derived from alkenyl aromatic compounds such as styrene; alpha-methylstyrene,
ethylstyrene, vinyl benzene, vinyl toluene, chlorostyrene, bromostyrene, t-
butyl styrene,
including all isomers of these compounds. Suitable polymers to be employed as
Component
s (A) also include alkenyl aromatic polymers having a high degree of
syndiotactic
configuration. A preferred alkenyl aromatic polymer is polystyrene. Minor
amounts of
monoethylenically unsaturated compounds such as C2-6 alkyl acids and esters,
ionomeric
derivatives, and C4~ dienes may be copolymerized with alkenyl aromatic
compounds.
Examples of copolymerizable compounds include acrylic acid, methacrylic acid,
ethacrylic
Zo acid, malefic acid, itaconic acid, acrylonitrile, malefic anhydride, methyl
acrylate, ethyl
acrylate, isobutyl acrylate, n-butyl acrylate, methyl methacrylate, vinyl
acetate and
butadiene.
General purpose polystyrene is the most preferred alkenyl aromatic polymer
material suitable as Component (A) as defined herein. The term "general
purpose
15 polystyrene" is defined in the Encyclopedia of Polymer Science and
Engineering, Vol. 16,
1989, pages 62-71. Such polystyrene is also referred to as crystal polystyrene
or
polystyrene homopolymer.
The monoalkenyl aromatic polymers may be suitably modified by rubbers to
improve their impact properties. Examples of suitable rubbers are homopolymers
of C4-C6
2 o conjugated dienes, especially butadiene or isoprene; interpolymers of one
or more alkenyl
aromatic monomers, and one or more C4 C6 conjugated dienes; interpolymers of
ethylene
and propylene or ethylene, propylene and a nonconjugated diene, especially 1,6-
hexadiene
or ethylidene norbornene; homopolymers of CQ-C6 alkyl acrylates; interpolymers
of C,-Cs alkyl
acrylates and an interpolymerizable comonomer, especially an alkenyl aromatic
monomer or
2s a C,-CQ alkyl methacrylate. Also included are graft polymers of the
foregoing rubbery
polymers wherein the graft polymer is an alkenyl aromatic polymer. A preferred
alkenyl
aromatic polymer for use in all of the foregoing rubbery polymers is styrene.
A most
preferred rubbery polymer is polybutadiene or a styrene/butadiene copolymer.
Impact modified alkenyl aromatic polymers are well known in the art and
3 o commercially available.
Suitable polymers to be employed as Component (A) also include alkenyl
aromatic polymers having a high degree of syndiotactic configuration.
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Preferred alkenyl aromatic polymers for use as Component (A) of the present
invention include polystyrene, syndiotactic polystyrene, rubber-modified high
impact
polystyrene, poly (vinyl-toluene), and poly(alpha-methylstyrene).
The substantially random interpolymers of Component(B) as defined herein
comprise (i) from about 50 to 74 mole percent of polymer units derived from at
least one of
ethylene and/or a C3 C2o alpha (a)-olefin; (ii) from 26 to about 50 mole
percent, of polymer
units derived from (a) at least one vinyl or vinylidene aromatic monomer, or
(b)at least one
sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomer,
or (c) a
to combination of at least one aromatic vinyl or vinylidene monomer; and (iii)
from about 0 to
about 20 mole percent of polymer units derived from one or more of
ethylenically
unsaturated polymerizable monomers other than those derived from (i) and (ii).
Suitable a-olefins include, for example, a-olefins containing from 3 to about
20, preferably from 3 to about 12, more preferably from 3 to about 8 carbon
atoms. These a-
15 olefins do not contain an aromatic moiety.
Particularly suitable are ethylene, propylene, butene-1, 4-methyl-1-pentene,
hexene-1 or octene-1 or ethylene in combination with one or more of propylene,
butene-1, 4-
methyl-1-pentene, hexene-1 or octene-1.
Polymerizable ethylenically unsaturated monomers) include norbornene and
2o C,.,o alkyl or C6_,o aryl substituted norbornenes, with an exemplary
interpolymer being
ethylene/styrene/norbornene.
Suitable vinyl or vinylidene aromatic monomers which can be employed to
prepare the substantially random interpolymers include, for example, those
represented by
the following formula:
Ar
I
( i H2)n
Rl - C = C(R2)2
wherein R' is selected from the group of radicals consisting of hydrogen and
alkyl radicals
containing from 1 to about 4 carbon atoms, preferably hydrogen or methyl; each
R2 is
independently selected from the group of radicals consisting of hydrogen and
alkyl radicals
3 o containing from 1 to about 4 carbon atoms, preferably hydrogen or methyl;
Ar is a phenyl
group or a phenyl group substituted with from 1 to 5 substituents selected
from halo, C,
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WO 00/66651 PCT/US00/10946
alkyl, and C,~ haloalkyl; and n has a value from zero to about 4, preferably
from zero to 2,
most preferably zero. Exemplary vinyl aromatic monomers include styrene, vinyl
toluene, a-
methylstyrene, t-butyl styrene, chlorostyrene, also including all isomers of
these compounds
. Particularly suitable such monomers include styrene and lower alkyl- or
halogen-
substituted derivatives thereof. Preferred monomers include styrene,
a-methylstyrene, the lower alkyl-(C,- C,) or phenyl-ring substituted
derivatives of styrene,
such as for example, ortho-, meta-, and para-methylstyrene, the ring
halogenated styrenes,
para-vinyl toluene or mixtures thereof. The most preferred aromatic vinyl
monomer is
styrene.
to By the term "sterically hindered aliphatic or cycloaliphatic vinyl or
vinylidene
compounds", it is meant polymerizable vinyl or vinylidene monomers
corresponding to the
formula:
A'
R1- C = C(R2)2
is wherein A' is a sterically bulky, aliphatic or cycloaliphatic substituent
of up to
20 carbons, R' is selected from the group of radicals consisting of hydrogen
and alkyl
radicals containing from 1 to about 4 carbon atoms, preferably hydrogen or
methyl; each R2
is independently selected from the group of radicals consisting of hydrogen
and alkyl
radicals containing from 1 to about 4 carbon atoms, preferably hydrogen or
methyl; or
2 o alternatively R' and A' together form a ring system. Preferred aliphatic
or cycloaliphatic vinyl
or vinylidene compounds are monomers in which one of the carbon atoms bearing
ethylenic
unsaturation is tertiarily or quaternarily substituted. Examples of such
substituents include
cyclic aliphatic groups such as cyclohexyl, cyclohexenyl, cyclooctenyl, or
ring alkyl or aryl-
substituted derivatives thereof, tert-butyl, or norbornyl. Most preferred
aliphatic or
2s cycloaliphatic vinyl or vinylidene compounds are the various isomeric vinyl-
ring substituted
derivatives of cyclohexene and substituted cyclohexenes, and 5-ethylidene-2-
norbornene.
Especially suitable are 1-, 3-, and 4-vinylcyclohexene. Simple linear non-
branched a-olefins
including for example, a-olefins containing from 3 to about 20 carbon atoms
such as
propylene, butene-1, 4-methyl-1-pentene, hexene-1 or octene-1 are not examples
of
3 o sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene
compounds.
One method of preparation of the substantially random interpolymers includes
polymerizing a mixture of polymerizable monomers in the presence of one or
more
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WO 00/66651 PCT/US00/10946
metallocene or constrained geometry catalysts in combination with various
cocatalysts, as
described in EP-A-0,416,815 by James C. Stevens et al. and U.S. Patent No.
5,703,187 by
Francis J. Timmers, both of which are incorporated herein by reference in
their entirety.
Preferred operating conditions for such polymerization reactions are pressures
from
s atmospheric up to 3000 atmospheres and temperatures from -30°C to
200°C.
Polymerizations and unreacted monomer removal at temperatures above the
autopolymerization temperature of the respective monomers may result in
formation of
some amounts of homopolymer polymerization products resulting from free
radical
polymerization.
so Examples of suitable catalysts and methods for preparing the substantially
random interpolymers are disclosed in EP-A-514,828); as well as U.S. Patents:
5,055,438;
5,057,475; 5,096,867; 5,064,802; 5,132,380; 5,189,192; 5,321,106; 5,347,024;
5,350,723;
5,374,696; 5,399,635; 5,470,993; 5,703,187; and 5,721,185, all of which
patents and
applications are incorporated herein by reference.
15 The substantially random a-olefin/vinyl aromatic interpolymers can also be
prepared by the methods described in JP 07/278230 employing compounds shown by
the
general formula
CP1 R1
R3
M
CP2~ ~ R2
wherein Cp' and Cp2 are cyclopentadienyl groups, indenyl groups, fluorenyl
groups, or
substituents of these, independently of each other; R' and R2 are hydrogen
atoms, halogen
atoms, hydrocarbon groups with carbon numbers of 1 to 12, alkoxyl groups, or
aryloxyl
groups, independently of each other; m is a group IV metal, preferably Zr or
Hf, most
2s preferably Zr; and R3 is an alkylene group or silanediyl group used to
crosslink Cp' and Cpz.
The substantially random a-olefin/vinyl aromatic interpolymers can also be
prepared by the methods described by John G. Bradfute et al. (W. R. Grace &
Co.) in WO
95/32095; by R. B. Pannell (Exxon Chemical Patents, Inc.) in WO 94/00500; and
in Plastics
Technoloay, p. 25 (September 1992), all of which are incorporated herein by
reference in
3 o their entirety.
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WO 00/66651 PCT/US00/10946
Also suitable are the substantially random interpolymers which comprise at
least one a-olefin/vinyl aromatic/vinyl aromatic/a-olefin tetrad disclosed in
U.S. Application
No. 08/708,869 filed September 4, 1996 and WO 98/09999 both by Francis J.
Timmers et al.
These interpolymers contain additional signals in their carbon-13 NMR spectra
with
s intensities greater than three times the peak-to-peak noise. These signals
appear in the
chemical shift ranges of 43.70 to 44.25 ppm and 38.0 to 38.5 ppm.
Specifically, major
peaks are observed at 44.1, 43.9, and 38.2 ppm. A proton test NMR experiment
indicates
that the signals in the chemical shift region 43.70 to 44.25 ppm are methine
carbons and the
signals in the region 38.0 to 38.5 ppm are methylene carbons.
to It is believed that these new signals are due to sequences involving two
head-to-tail vinyl aromatic monomer insertions preceded and followed by at
least one a-
olefin insertion, for example, an ethylene/styrene/styrene/ ethylene tetrad
wherein the
styrene monomer insertions of said tetrads occur exclusively in a 1,2 (head to
tail) manner.
It is understood by one skilled in the art that for such tetrads involving a
vinyl aromatic
15 monomer other than styrene and an a-olefin other than ethylene that the
ethylene/vinyl
aromatic monomer/vinyl aromatic monomer/ethylene tetrad will give rise to
similar carbon-13
NMR peaks but with slightly different chemical shifts.
These interpolymers can be prepared by conducting the polymerization at
temperatures of from about -30°C to about 250°C in the presence
of such catalysts as those
2 o represented by the formula
Cp
m ~ R~2
CP
wherein: each Cp is independently, each occurrence, a substituted
cyclopentadienyl group
~-bound to M; E is carbon or Si; M is a group IV metal, preferably Zr or Hf,
most preferably
2s Zr; each R is independently, each occurrence, hydrogen, hydrocarbyl,
silahydrocarbyl, or
hydrocarbylsilyl, containing up to about 30 preferably from 1 to about 20 more
preferably
from 1 to about 10 carbon or silicon atoms; each R' is independently, each
occurrence,
hydrogen, halo, hydrocarbyl, hydrocarbyloxy, silahydrocarbyl, hydrocarbylsilyl
containing up
to about 30, preferably from 1 to about 20, more preferably from 1 to about 10
carbon or
3o silicon atoms or two R' groups together can be a C,.,o hydrocarbyl
substituted 1,3-butadiene;
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WO 00/66651 PCT/US00/10946
M is 1 or 2; and optionally, but preferably in the presence of an activating
cocatalyst.
Particularly, suitable substituted cyclopentadienyl groups include those
illustrated by the
formula:
(R)3
wherein each R is independently, each occurrence, hydrogen, hydrocarbyl,
silahydrocarbyl,
or hydrocarbylsilyl, containing up to about 30, preferably from 1 to about 20,
more preferably
from 1 to about 10 carbon or silicon atoms or two r groups together form a
divalent
Zo derivative of such group. Preferably, R independently each occurrence is
(including where
appropriate all isomers) hydrogen, methyl, ethyl, propyl, butyl, pentyl,
hexyl, benzyl, phenyl
or silyl or (where appropriate) two such R groups are linked together forming
a fused ring
system such as indenyl, fluorenyl, tetrahydroindenyl, tetrahydrofluorenyl, or
octahydrofluorenyl.
15 Particularly preferred catalysts include, for example, racemic-
(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl) zirconium dichloride,
racemic-
(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl) zirconium 1,4-diphenyl-1,3-
butadiene,
racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl) zirconium di-
C,~,alkyl, racemic-
(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl) zirconium di-C,~alkoxide,
or any
2 o combination thereof.
It is also possible to use the following titanium-based constrained geometry
catalysts, [N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-r~)-1,5,6,7-
tetrahydro-s-indacen-
1-yl]silanaminato(2-)-N]titanium dimethyl; (1-indenyl)(tert-
butylamido)dimethylsilane titanium
dimethyl; ((3-tert-butyl)(1,2,3,4,5-rf)-1-indenyl)(tert-butylamido)
dimethylsilane titanium
2s dimethyl; and ((3-isopropyl)(1,2,3,4,5-rl)-1-indenyl)(tert-butyl
amido)dimethylsilane titanium
dimethyl, or any combination thereof.
Further preparative methods for the interpolymers used in the present
invention have been described in the literature. Longo and Grassi (Makromol.
Chem.,
Volume 191, pages 2387 to 2396 [1990]) and D'Anniello et al. (Journal of
Applied Polymer
3 o Science, Volume 58, pages 1701-1706 [1995]) reported the use of a
catalytic system based
on methylalumoxane (MAO) and cyclopentadienyltitanium trichloride (CpTiCl3) to
prepare an
ethylene-styrene copolymer. Xu and Lin (Polymer Preprints, Am. Chem. Soc..
Div. Poem.
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WO 00/66651 PCT/US00/10946
Chem.) Volume 35, pages 686-687 [1994]) have reported copolymerization using a
MgClz/TiCl4/NdCh/ AI(iBu)3 catalyst to give random copolymers of styrene and
propylene. Lu
et al. (Journal of Applied Polymer Science, Volume 53, pages 1453 to 1460
[1994]) have
described the copolymerization of ethylene and styrene using a TiCl4/NdCh/
MgCl2/AI(Et)3
s catalyst. Sernetz and Mulhaupt, (Macromol. Chem. Phvs., Vol. 197, pp. 1071-
1083, 1997)
have described the influence of polymerization conditions on the
copolymerization of styrene
with ethylene using Me2Si(Me4Cp)(n-tert-butyl)TiCh/methylaluminoxane Ziegler-
Natta
catalysts. Copolymers of ethylene and styrene produced by bridged metallocene
catalysts
have been described by Arai, Toshiaki and Suzuki (Polymer Preprints, Am. Chem.
Soc.. Div.
so Polym. Chem.) Vol. 38, pages 349-350 [1997]) and in U.S. Patent No.
5,652,315, issued to
Mitsui Toatsu Chemicals, Inc. The manufacture of a-olefin/vinyl aromatic
monomer
interpolymers such as propylene/styrene and butene/styrene is as described in
U.S. Patent
No. 5,244,996, issued to Mitsui Petrochemical Industries Ltd or U.S. Patent
No. 5,652,315
also issued to Mitsui Petrochemical Industries Ltd, or as disclosed in
15 DE 197 11 339 A1 to Denki Kagaku Kogyo KK. All the above methods disclosed
for
preparing the interpolymer component are incorporated herein by reference.
Also, although
of high isotacticity and therefore not "substantially random", the random
copolymers of
ethylene and styrene as disclosed in Polymer Preprints Vol. 39, No. 1, March
1998 by Toru
Aria et al. can also be employed as component (B) for the films of the present
invention.
2o While preparing the substantially random interpolymer, an amount of atactic
vinyl aromatic homopolymer may be formed due to homopolymerization of the
vinyl aromatic
monomer at elevated temperatures. The presence of vinyl aromatic homopolymer
is in
general not detrimental for the purposes of the present invention and can be
tolerated.
The most preferred substantially random interpolymers for use as
2s Component(B) are interpolymers of ethylene and styrene and interpolymers of
ethylene,
styrene and at least one alpha-olefin containing from 3 to 8 carbon atoms.
Preferably, the substantially random interpolymer comprises in copolymerized
form about 70 mole percent or less of ethylene and/or one or more alpha-olefin
monomers.
A preferred upper limit is about 60 mole percent or less of ethylene and/or
one or more
3 o alpha-olefin monomers.
Preferably, the substantially random interpolymer comprises about 30 mole
percent or more of one or more vinyl or vinylidene aromatic monomers and/or
one or more
sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers
in copolymerized
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WO 00/66651 PCT/CTS00/10946
form. A preferred lower limit is about 40 mole percent or more of one or more
vinyl or
°vinylidene aromatic monomers and/or one or more sterically hindered
aliphatic or cyclo-
aliphatic vinyl or vinylidene monomers.
The presence of other polymerizable ethylenically unsaturated monomers) is
optional. Preferably, Component B does not contain such monomer.
The melt index (1z) according to ASTM D 1238 Procedure A, condition E,
generally is from about 0.01 to about 50 g/10 minutes, preferably from about
0.01 to about
20 g/10 minutes, more preferably from about 0.1 to about 7 g/10 minutes, and
most
preferably from about 0.3 to about 5 g/10 minute.
so The density of the substantially random interpolymer is generally about
0.930
g/cm3or more, preferably from about 0.930 to about 1.045 g/cm3, more
preferably from about
0.930 to about 1.040 g/cm3, most preferably from about 0.930 to about 1.030
g/cm3. The
molecular weight distribution, M~/M~, is generally from about 1.5 to about 20,
preferably from
about 1.8 to about 10, more preferably from about 2 to about 5.
15 The substantially random interpolymers may be modified by typical grafting,
hydrogenation, functionalizing, or other reactions well known to those skilled
in the art. The
polymers may be readily sulfonated or chlorinated to provide functionalized
derivatives
according to established techniques. The substantially random interpolymers
may also be
modified by various chain-extending or crosslinking processes including, but
not limited to
2o peroxide-, silane-, sulfur-, radiation-, or azide-based cure systems. A
full description of the
various crosslinking technologies is described in U.S. Patent No. 5,869,591
and EP-A-
778,852, the entire contents of both of which are herein incorporated by
reference. Dual
cure systems, which use a combination of heat, moisture cure, and radiation
steps, may be
effectively employed. For instance, it may be desirable to employ peroxide
crosslinking
as agents in conjunction with silane crosslinking agents, peroxide
crosslinking agents in
conjunction with radiation, sulfur-containing crosslinking agents in
conjunction with silane
crosslinking agents. The substantially random interpolymers may also be
modified by
various crosslinking processes including, but not limited to the incorporation
of a diene
component as a termonomer in its preparation and subsequent crosslinking by
the
3 o aforementioned methods and further methods including vulcanization via the
vinyl group
using sulfur for example as the crosslinking agent.
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The above-mentioned substantially random interpolymer suitable as
component (B) as defined herein is preferably thermoplastic, which means it
may be molded
or otherwise shaped and reprocessed at temperatures above its melting or
softening point.
The blend comprising polymeric materials for use in the present invention is
obtainable according to methods known in the art, such as but not limited to,
dry blending in
a screw extruder, or a Banbury mixer. The dry blended pellets may be directly
melt
processed into a final solid state article.
Preferred are blends, wherein Component (A) is present in an amount of from
about 60 weight percent or more, more preferably in amount of from about 70
weight
to percent or more. The preferred upper limit for the amount of Component (A)
is about 80
weight percent or less. The preferred lower limit for the amount of Component
(B) in the
blend is about 20 weight percent or more. The preferred upper limit for the
amount of
Component (B) in the blend is about 40 weight percent or less, more preferably
about 30
percent or less.
The film according to the present invention has a thickness of less than about
350 microns (p.m), preferably less than about 300 p.m and most preferably less
than about
250 p.m (10 mils).
The film according to the present invention may include one or more
2 o additives, for example but not limited to, antioxidants, light
stabilizers, processing aids,
plasticizers, pigments, fillers, slip additives, antiblock materials, antifog
agents, cling agents,
tackifiers, blowing agents, nucleators, clarifiers, flame retardant additives.
The film provided herein has little or no free shrink at 90°C. This
means that
the film has a free shrink, at 90°C, of less than about 20 percent,
more preferably of less
than about 10 percent. The film of the present invention may be a monolayer or
a multilayer
film. One or more layers of the film may be oriented or foamed. A multi-layer
film of the
present invention may contain one, two or more layers comprising a blend as
defined herein.
Most preferably, the film according to the invention has a thickness of about
0.5 to about 10
mils. Preferably, the present invention pertains to a tough and stiff film,
comprising a blend
of polymeric materials consisting essentially of Component (A) and Component
(B), as
described herein. The film of the invention may be printed. Particularly
preferred is a film
wherein component (A) is composed of one or more polystyrenes) and component
(B) is
composed of one or more substantially random ethylene-styrene interpolymer(s).
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The film of the invention is obtainable according to methods known in the art.
The film may be made using a blown or a cast film extrusion process, including
co-extrusion
and extrusion coating. One or more layers of the film may be expanded, for
example with a
conventional blowing agent, to make foamed film. One or more films may be
laminated to
s form a multi-layer structure. The films may be (further) oriented after
forming via tenter
frame, double-bubble or blown film techniques.
In one embodiment, the film of the present invention is an oriented film. The
term "orientation" as used herein refers to a process of stretching a hot
polymeric article to
align the molecular chains in the directions) of stretching. When the
stretching is applied in
to one direction, the process is called uniaxial orientation; when the
stretching is applied in two
(perpendicular) directions, the process is called biaxial orientation.
Orientation can be
uniaxial or, preferably, biaxial. Orientation may be accomplished according to
conventional
methods, such as blown film processes, "double-bubble" film processes,
cast/tentered film
processes or other techniques known in the art to provide orientation.
15 Preferably, the oriented film according to the invention has a modulus (2
percent secant modulus in the machine direction) of more than 150,000 psi
(1034 MPa).
Preferred oriented films comprise a blend, wherein component (A) is a
polystyrene and
component (B) is an ethylene-styrene interpolymer. Preferably, Component (A)
is present in
an amount of more than about 50 to less than about 80, more preferably in
amount of about
a o 70 to about 77, most preferably about 75, weight percent, and Component
(B) is present in
an amount of more than about 20 to less than about 50, more preferably in an
amount of 23
to about 30 weight percent, most preferably about 25 weight percent.
Preferably, the
substantially random ethylene-styrene interpolymer contains from about 60
weight percent to
about 75 weight percent, preferably about 70 percent copolymerized styrene.
The melt
2s index (condition E) is preferably from about 0.3 to about 5 g/10 minute.
The oriented films of the invention are particularly suitable for use in
window
envelope and related applications. For window envelope and related
applications, high
modulus, good cuttability and lower haze are desired properties. The oriented
films
according to the present invention advantageously combine these properties.
The oriented
3 o films provided herein are characterized by unexpected changes or
improvements in film
performance, including toughness, modulus and abrasion resistance.
Additionally, optical
properties of the blend film of the invention are enhanced compared to
conventional rubber
modified polystyrene films, especially with respect to gloss (higher) and haze
(lower). The
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films also demonstrate improved dead-fold characteristics as shown by high
stress relaxation
properties. Furthermore, tear properties are advantageously affected. When
blended with a
crystalline syndiotactic polystyrene resin (Component (A)) in a ratio
described herein
ethylene-styrene interpolymer resins provide films with good optical
characteristics and
unexpected elongation, under suitable biaxial orientation conditions.
In another aspect, the present invention relates to a foamed film. Such film
is
especially suitable for use as label or in thermoformable articles of
manufacture.
To make foamed film structures, either physical or chemical blowing agents
may be used to achieve foam densities of more than about 300 kg/m3, preferably
more than
io about 350 kg/m3 and most preferably more than about 400 kg/m3. Typically,
the foam
density is less than about 1000 kg/m3, preferably less than about 950 kg/m3,
and most
preferably less than 900 kg/m3. The cell sizes of the macrocellular foams will
be from about
0.01 to about 5.0 mm, preferably about 0.02 to 2.0 mm, and most preferably
0.02 to about
1.8 mm according to ASTM D3576. The cell sizes of microcellular foams will be
less than
15 0.1 mm. The foams may be open or closed cell, according to ASTM D2856.
A multilayer film of the invention comprising one or more foamed layers
comprising a blend comprising Components (A) and (B) as defined herein is
obtainable
according to methods known in the art, for example, using a co-extrusion
process. Preferred
are two-layer or three-layer films with one or two surface layers and the
foamed layer being
2 o the core layer. The surface layer may or may not comprise a blend of
polymeric materials
consisting essentially of Components (A) and (B) as defined herein. Preferred
is a film
comprising a foamed layer comprising a blend of Components (A) and (B) as
defined herein
and one or two non-foamed layers made from Component (A) as described herein,
particularly from a polystyrene. In a three-layer structure, preferably, the
foamed layer is the
2s core or middle layer.
The label film may be constructed from printed, slit to width, rolls of film
with
the labels glued to a container, for example a bottle, using conventional
adhesives and glues
known to the industry. In addition, the films of this invention may be
printed, coated with
pressure sensitive adhesives, laminated to release papers or films and applied
to bottles,
3 o containers or other surfaces by conventional pressure sensitive
techniques.
Preferred foamed films comprise a blend, wherein Component (A) is a
polystyrene and Component (B) is an ethylene-styrene substantially random
interpolymer.
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Preferably, Component (B) is present in an amount of from about 25 to about 35
weight
percent.
The bottle may be a glass bottle or a PET bottle. Covering or affixed to a
glass bottle; the label may also serve a protective purpose.
If the bottle is a PET bottle, the preferred label is a wrap-around label
showing
more than about 8 g tear in machine direction, and more than about 25 g tear
in cross-
direction. Elongation of the foamed film according to the invention should be
between about
4 to about 5 percent.
The properties of the polymers, blends and films useful for the purpose of the
io present invention can be determined by the following test procedures. These
procedures
were used in the Examples.
Melt Index (MI) is determined according to ASTM D-1238, condition E
(190°C,
2.16 kg).
Secant Modulus, ultimate elongation, and ultimate tensile strength are
i5 determined according to ASTM-D-882-91.
Haze is determined according to ASTM D-1003.
Gloss is determined according to ASTM D-2457.
Styrene Analv sr is: Interpolymer or copolymer styrene content and content of
atactic polystyrene in the interpolymer of Component (A) can be determined
using proton
2o nuclear magnetic resonance ('H-NMR). All proton NMR samples are prepared in
1,1,2,2-
tetrachloroethane 2D (TCE?D). The solutions contain 1.6 -to 3.2 weight percent
polymer.
Melt index (12) is used as a guide for determining sample concentration. Thus
when the 12 is
greater than 2 g/10 minutes, 40 mg of interpolymer are used; with an Iz
between 1.5 and 2
g/10 minutes, 30 mg of interpolymer are used; and when the IZ is less than 1.5
g/10 minutes,
2s 20 mg of interpolymer are used. The interpolymers are weighed directly into
5 mm sample
tubes. A 0.75 mL aliquot of TCE?D is added by syringe and the tube is capped
with a tight-
fitting polyethylene cap. The samples are heated in a water bath at
85°C to soften the
interpolymer. To provide mixing, the capped samples are occasionally brought
to reflux
using a heat gun.
3o Proton NMR spectra are accumulated on a Varian VXR 300 with the sample
probe at
80°C, and referenced to the residual protons of TCE?D at 5.99 ppm. The
delay times are
varied between 1 second, and data are collected in triplicate on each sample.
The following
instrumental conditions are used for analysis of the interpolymer samples:
Varian VXR-300,
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standard'H; Sweep Width, 5000 Hz; Acquisition Time, 3.002 seconds; Pulse
Width, 8
Nseconds; Frequency, 300 MHz; Delay, 1 second; Transients, 16.
The total analysis time per sample is about 10 minutes.
Initially, a'H NMR spectrum for a sample of polystyrene, STYRONT"" 680
s (available form The Dow Chemical Company, Midland, MI) is acquired with a
delay time of
one second. The protons are "labeled": b, branch; a,alpha; o, ortho; m, meta;
p, para, as
indicated in the formula below.
P
m
0
b
to
Integrals are measured around the protons labeled in the formula; the 'A'
designates aPS. Integral A,., (aromatic, around 7.1 ppm) is believed to be the
three
ortho/para protons; and integral A6.6 (aromatic, around 6.6 ppm) the two meta
protons. The
two aliphatic protons labeled ~ resonate at 1.5 ppm; and the single proton
labeled b is at 1.9
is ppm. The aliphatic region is integrated from about 0.8 to 2.5 ppm and is
referred to as Aa,.
The theoretical ratio for A,.,: A6.6: Aa, is 3:2:3, or 1.5:1:1.5, and
correlates very well with the
observed ratios for the STYRONT"" 680 sample for several delay times of 1
second. The
ratio calculations used to check the integration and verify peak assignments
are performed
by dividing the appropriate integral by the integral A6.6 ratio A~ is A,.,: /
A6.6.
z o Region A6.6 is assigned the value of 1. Ratio AI is integral Aa, / As.s.
All spectra
collected have the expected 1.5:1:1.5 integration ratio of(o+p ): m:(a+b). The
ratio of
aromatic to aliphatic protons is 5 to 3. An aliphatic ratio of 2 to 1 is
predicted based on the
protons labeled ~ and b, respectively, in the above formula. This ratio is
also observed when
the two aliphatic peaks are integrated separately.
2s For the ethylene/styrene interpolymers, the'H- NMR spectra using a delay
time of one second, have integrals C,.,, C6.6, and Ca, defined, such that the
integration of the
peak at 7.1 ppm includes all the aromatic protons of the copolymer as well as
the o and p
protons of aPS. Likewise, integration of the aliphatic region Ca, in the
spectrum of the
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interpolymers included aliphatic protons from both the aPS and the
interpolymer with no
clear baseline resolved signal from either polymer. The integral of the peak
at 6.6 ppm C6.6 is
resolved from the other aromatic signals and it is believed to be due solely
to the aPS
homopolymer (probably the meta protons). (The peak assignment for atactic
polystyrene at
s 6.6 ppm (integral A6.6) is made based upon comparison to the authentic
sample of
STYRONT"" 680.) This is a reasonable assumption since, at very low levels of
atactic
polystyrene, only a very weak signal is observed here. Therefore; the phenyl
protons of the
copolymer must not contribute to this signal. With this assumption, integral
A6.6 becomes the
basis for quantitatively determining the contents of aPS (atactic
polystyrene).
to The following equations are then used to determine the degree of styrene
incorporation in the ethylene/styrene interpolymer samples:
(C Phenyl) = C,., + A,., - (1.5 x A6.s)
(C Aliphatic) = Ce, - 1 5 x As_6)
s~ _ (C Phenyl) /5
15 e~ _ (C Aliphatic - (3 x s~)) /4
E=e~/(e~+s~)
S~ = s~ / (e~ + s~)
and the following equations are used to calculate the mole percent ethylene
and styrene in
the interpolymers.
E 2s
Wt%E = (E * 28) + (S~ * 104) 100)
and
S~*104
we%s = {E * 2g) + ~s~ * t<o4) ~ loo)
2s wherein s~ and e~ are styrene and ethylene proton fractions in the
interpolymer,
respectively, and S~ and E are mole fractions of styrene monomer and ethylene
monomer in
the interpolymer, respectively.
The weight percent of aPS in the interpolymers can be determined using the
3 o following equation:
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As.62
(Wt%S~
s<
Wt%aPS = * 100
A6.s2
100 + ~Wt%S~
s<
The total styrene content is also determined by quantitative Fourier Transform
Infrared Spectroscopy (FTIR).
s The following Examples are illustrative of the invention, but are not to be
construed as limiting the scope thereof in any manner. The following
abbreviations are used
in the Examples: PS means polystyrene; ESI means ethylene-styrene
substantially random
interpolymer; MD means machine direction; CD means cross direction.
io Example 1 - Oriented Film Comprising Polystyrene/Ethylene-Styrene
Substantially Random
Interpolymer Blend
The polystyrene is STYRONTM 665 available from The Dow Chemical
Company.
i5 The ESI was obtained as follows: the interpolymer was prepared in a
continuously operating loop reactor (36.8 gal, 140 L). The reactor runs liquid
full at 475 psig
(3,275 kPa) with a residence time of approximately 25 minutes. Raw materials
and
catalyst/cocatalyst flows were fed. Solvent feed to the reactor was supplied
by two different
sources. A fresh stream of toluene from a diaphragm pump with rates measured
was used
2o to provide flush flow for the reactor seals (20 Ib./hour (9.1 kg/hour).
Recycle solvent was
mixed with uninhibited styrene monomer on the suction side of five diaphragm
pumps in
parallel. These five pumps supply solvent and styrene to the reactor at 650
psig (4,583
kPa). Fresh styrene flow was measured by flowmeter, and total recycle
solvent/styrene flow
was measured by a separate flowmeter. Ethylene was supplied to the reactor at
687 psig
2s (4,838 kPa). The ethylene stream was measured by a mass flowmeter. A
flowmeter/controller was used to deliver hydrogen into the ethylene stream at
the outlet of
the ethylene control valve. The ethylene/hydrogen mixture combines with the
solvent/styrene stream at ambient temperature. The temperature of the entire
feed stream
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as it enters the reactor loop was lowered to 2°C by an exchanger with -
10°C glycol on the
jacket. Preparation of the three catalyst components take place in three
separate tanks:
fresh solvent and concentrated catalyst/cocatalyst premix were added and mixed
into their
respective run tanks and fed into the reactor via variable speed diaphragm
pumps. The
s three component catalyst system enters the reactor loop through an injector
and static mixer
into the suction side of the twin screw pump. The raw material feed stream was
also fed into
the reactor loop through an injector and static mixer downstream of the
catalyst injection
point but upstream of the twin screw pump suction.
Polymerization was stopped with the addition of catalyst kill (water mixed
with
io solvent) into the reactor product line after the flowmeter measuring the
solution density. A
static mixer in the line provides dispersion of the catalyst kill and
additives in the reactor
effluent stream. This stream next enters post reactor heaters that provides
additional energy
for the solvent removal flash. This flash occurs as the effluent exits the
post reactor heater
and the pressure was dropped from 475 psig (3,275 kPa) down to 450 mmHg (60
kPa) of
is absolute pressure at the reactor pressure control valve. This flashed
polymer enters the first
of two hot oil jacketed devolatilizers. The volatiles flashing from the first
devolatilizer were
condensed with a glycol jacketed exchanger, passed through the suction of a
vacuum pump,
and were discharged to the solvent and styrene/ethylene separation vessel.
Solvent and
styrene were removed from the bottom of this vessel as recycle solvent while
ethylene
2 o exhausted from the top. The ethylene stream was measured with a mass
flowmeter. The
measurement of vented ethylene plus a calculation of the dissolved gases in
the
solvent/styrene stream were used to calculate the ethylene conversion. The
polymer and
remaining solvent separated in the devolatilizer was pumped with a gear pump
to a second
devolatizer. The second devolatizer was operated at 5 mmHg (0.7 kPa) absolute
pressure
2 s to flash the remaining solvent. This solvent was condensed in a glycol
heat exchanger,
pumped through another vacuum pump, and exported to a waste tank for disposal.
The dry
polymer (less than 1000 ppm total volatiles) was pumped with a gear pump to an
underwater
pelletizer with a 6-hole die, pelletized, spin-dried, and collected in 1000
pound (454 kg)
boxes.
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The aluminum catalyst component was a commercially available modified
methalumoxane Type 3A (MMAO-3A).
The boron cocatalyst type 1 was tris(pentafluorophenyl) borane.
The titanium catalyst was (1 H-cyclopenta[I]phenanthrene-2-yl)dimethyl(t-
s butylamido)-silanetitanium 1,4-diphenylbutadiene).
The PS and the ESI were dryblended.
Films C, D, and F were produced using a down-ward blown-orientation process.
The die
diameter was 2 inches and the melt temperature was about 230°C (line
speed of 45 fpm
(13.7 m/minute)). The blow-up ratio (circumference of the bubble-shaped film
divided by that
to of the die) was about 12. Film E was a commercial oriented polystyrene
window film DWF
Clear LD, available from The Dow Chemical Company.
Table 1
Properties of oriented PS/ESI Films (C, D and F)
is and DWF Clear LD (MD)
Film F C D E*
ESI copolymer 60 70 70 -
s rene content
wt
M I 0.5 1.0 1.0 -
PS/ESI Ratio wt 75/25 75/25 50/50 100/0
%
Film Thickness 30.5 30.5 38 33
microns
Ultimate Elongation75 41 57 26
Ultimate Tensile 53.1 53.8 45.5 82.7
MPa
Tou hness J/cc 18.3 18.6 21.4 17.9
2% Sec. Modulus 1724 1724 1344 2758
MP
Initial Haze % 7.9 6 13 5
Gloss at 60 114 130 84 150
No. of scratch 27 32 not visible> 150
lines
Haze Change (%) 0.0 8.5 1.7 ~ 82.0
*Not an example of the present invention.
In sample C, a combination of high gloss and high clarity(low haze), high
modulus, high tensile strength and toughness was obtained compared to the
conventional
2o polystyrene homopolymer film sample E. Sample D demonstrated the effect of
increased
levels of ESI above the most preferred levels, resulting in reduced gloss,
reduced tensile
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WO 00/66651 PCT/US00/10946
strength and lower stiffness. Sample F demonstrated the effect of lower
styrene content of
the ESI material resulting in lower gloss and higher haze. Samples D and F
exhibited an
unusual, unexpected combination of high toughness, high modulus, high tensile
strength and
superior optical properties, but were not as good as the most preferred Film
C.
s Scratch-resistance is very important in window film use. The scratch
resistance of films C, D and F was tested and compared to film E as reference.
In the test,
the haze level of each film was measured and recorded. The films were then
subjected to a
relative motion against a LF Smithe 527 bronze drum under a vacuum of 10 in.
Hg to cause
scratch on the film. Next, the haze level of each film was again measured and
recorded.
io The extent of scratch on the film was then measured by calculating the
change in the
measured haze value of each film before and after scratching. A film is
considered more
scratch resistant when the change in film optical haze due to scratching is
less than a film
with more haze changes by scratching under the same condition.
Film C, D and F showed significant improvement over film E. The PS/ESI
is films showed very little abrasion-whitening and haze increase as commonly
seen in Clear
LD.
Example 2 - Tough and Stiff Foamed Films Made from PS/ESI Blends
2o A blown film co-extrusion process was used to make a polystyrene-based
foam core with two surface layers of unfoamed polystyrene. The foam core was
made
without ESI resin and with varying amounts of ESI. No ESI was added to the
surface layers.
The ESI was produced as described in Example 1 above and had a content of
copolymer
styrene of 69 weight percent and a MI of 4.6. The polystyrene was Krasten 144
(Kaucuk
2s Corp.; Mw: 260,000; Mn: 104,000; MI: 6 to 8 g/10 minutes; 1.5 to 2 percent
mineral oil). The
PS and the ESI were dry blended. The foamed films had a total thickness or
gauge of 130
p.m ~ 20 p.m.
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Table II
Foamed Film Properties
Foamed Film TEAR TEAR 20 2% Secant
MD (g) CD gloss Modulus,
(g)
MD (MPa)
8 25 20.1 850
0 wt% ESI
com arative
wt% ESI 8 42 27.4 674
wt% ESI 8 40 38.4 660
wt% ESI 8 56 46.4 658
~
The films made with PS/ESI blends were tough and stiff with improved tear and
gloss.
Example 3 - Tough and Stiff Films Made from PS/ESI blends
Films were made as described in Table III using a commercial polystyrene
resin, STYRONT"" 665 available from The Dow Chemical Company, and ESI
materials having
copolymer styrene contents of 60.6, 67.5 and 71.3 weight percent,
respectively.
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Table III
ESI/Polystyrene Film Blends and Film Properties
ESI Sam 1e 1 2 3
wt % ESI 30 30 30
wt % P S 70 70 ' 70
ESI MI 0.55 0.5 0.9
ESI % Copolymer S 71.3 60.6 ~ 67.5
Extrusion Parameters (1.25 in.(3.2 cm) Killion Extruder with 3 inch (7.6 cm)
blown film Die)
Temperatures (F) Melt 478 478 484
Screw S eed r m 50.3 50.3 50.3
Screw Am s 15 15 15
Ni Roll S eed m/min. 7.6 7.7 7.6
Layflat width (cm) 22.9 24.3 ~ 24.3
s Film Properties
Avg. Thickness (microns) 38 38 38
Optical Properties
Haze % 8.0 15.0 17.0_
45 Degree Gloss 84 ~ 75 ~ 71
Secant Modulus (MPa)
1 % Secant, MD, (MPa) 1441 1193 ~ 1586
to
Film TancilPC l9 in /min 1
Ultimate Tensile, MD si 36 24.7 25.4
Ultimate Elon ation, MD 4 3 6
%
Tensile Toughness, MD 1.1 0.3 1.2
J/cc
As can be seen from the data, higher copolymer styrene contents led to
improved gloss,
increased modulus, improved tensile strength and increased toughness,
indicating a most
15 preferred styrene content in the area of 67 to 72 percent styrene.
Films were fabricated as described in Table IV from dry blends of ESI and
polystyrene
(STYRONTM 678 available from The Dow Chemical Company) with increasing amounts
of
polystyrene.
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Table IV:
Extrusion Parameters (1.25 in. (3.2cm) Killion Extruder with 3 inch (7.6 cm)
blown film diel
Temperatures (F) Melt 446 447 447
Screw S eed r m 50 49.7 49.8
Screw Am s 13 12 12
Ni Roll S eed m/min. 7.7 6.5 9.1
Layflat width (cm) 23 j 24 24
Table V:
ESI/Polystyrene Blends and Film Properties
ESI 40 10
Pol s rene 60 90 100
ESI MI 0.95 0.95 -
ESI wt % Copolymer Styrene 71.5 ~ 71.5 -
Film Properties
Avg. Thickness (microns) 84 69 76
1o Optical Properties
Haze % 24.7 6.3 1.5
45 De ree Gloss 104 98 109
Secant Modulus (MPa)
1 % Secant, MD, MPa 1296 1696 1862
Film Tensiles (2 in./min.)
Ultimate. Tensile, MD 4 40.
si 6 3.1 6
Ultimate Elon ation, MD 15 3 2
%
Tensile Toughness, MD 4.8 0.8 0.4
J/cc
From Table V, it can be seen that even low levels of ESI (10 percent) affected
tensile elongation and toughness, while higher levels (40 percent) result in
improved
toughness and tensile elongation while retaining high gloss and stiffness as
indicated by 45
degree gloss and 1 percent secant modulus.
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