Note: Descriptions are shown in the official language in which they were submitted.
~
W O 95!30713 219 0 ~J 0 S PCT/US95/05757
This invention pertains to a medium modulus polyethylene film
and a method for preparing such film. The novel film can be prepared by
variable-stalk blown extrusion. The film has surprisingly high tear and
impact properties. The film can be used in heavy-duty packaging and
shipping applications and also in hot-fill packaging applications.
Polyethylene films with tear and impact properties are needed for
packaging and shipping heavy items, such as building and construction
materials, lawn and garden materials, salt, polymer pellets. Heavy-duty
films and bags must also possess good rigidity and stiffness (modulus).
Good film strength properties are required to prevent bag ruptures and
product losses during distribution while the rigidity and stiffness provide
good dimensional stability. Dimensional stability is important during
fabrication and packaging operations because it assists in maintaining the
correct positioning of the film or bag as it is conveyed through the various
equipment stations during bag-making and product-filling operational
steps. Dimensional stability at elevated temperatures during the product-
filling step is also required in some instances when the product ( for
example, salt) is packaged hot such as, for example, in some form-fill-seal
packaging operations.
Heavy-duty packaging currently involves monolayer and multilayer
polyethylene films having a calculated film density as low as about 0.920
g/cc. Typical polyethylene film compositions for heavy-duty packaging
include (a) blends of linear low density polyethylene (LLDPE) with low
density polyethylene (LDPE), (b) high density polyethylene (HDPE) modified
1
2190005
W0 95130713 PCTIUS95/05757
by adding rubber and other elastomers ( for example, polybutylene) to
impart impact resistance, (c) LLDPE blended with a low molecular weight,
high density polyethylene (LMW-HDPE), (d) LLDPE blended with a high
melt flow rate HDPE, or (e) LLDPE blended with partially isotactic polymers.
See, For example, US Patent 5,041,401 by Shirodkar et al., US Patent 5,102,955
y
by Calabro et al. and US Patent 4,828,906 by Nishimura et al. Also known is
the polyethylene composition disclosed by Thiersault et al. in US Patent
4,786,688 which contains 80 to 98 percent by weight HDPE and 2 to 20 percent
by weight LLDPE which is alleged to be useful for thin film (20 microns) and
blow molding applications. Additionally, ternary polymer blends have been
used in this packaging application. For example, in US Patent 4,824,912, Su
et al. disclose LLDPE blended with minor amounts of a low molecular
weight HDPE (LMW-HDPE) and a high molecular weight HDPE (HMW-
HDPE) for processability and film property improvements over LLDPE used
alone.
The prior art shows that the linear ethylene polymers-currently used
in making polyethylene films provide increased tear strength as density
increases to about 0.920 g/cc and then show substantially lower tear
strengths as density increases above about 0.920 g/cc. Attempts to improve
tear strength by increasing ~ilm thickness have been only marginally
effective. When film thickness is increased to improve strength properties,
the rigidity of present art polyethylene films increases disproportionately to
impact and tear resistance properties, and thereby thicker films offer
practitioners little or no additional benefit. Thus, although a variety of
polyethylene films and film compositions are known, prior art polyethylene
films are not completely satisfactory for use in heavy-duty packaging
applications because they do not offer the desired balance of high tear and
2
W095130713 ~ C~ ~ ~ ~ j pCTIUS95/05757
impact resistance at the required film rigidity or modulus and/or they do
not have the desired dimensional stability.
Hence, it is an object of the present invention to provide a
'' polyethylene film with improved tear strength and impact resistance and
good dimensional stability, as well as a method for making the same, which
can be used in heavy-duty packaging and shipping applications and for use
in hot fill packaging applications.
Applicants have discovered a novel medium modulus, polyethylene
blown film having good impact and tear strengths, and a method for
preparing such film. The novel film comprises:
(A) from 60 to 95 weight percent, based on the combined weights
of components (A) and (B), of at least one high molecular
weight linear ethylene polymer having a density in the range
of 0.92 to 0.96 g/cc and an I5 melt index in the range of 0.1 to 3
g/10 minutes, and
(B) from 5 to 40 weight percent, based on the combined weights of
components (A) and (B), of at least . ==e substantially linear
ethylene/a-olefin interpolymer characterized as having:
i. a melt flow ratio, hp/Iy, >_ 5.63, and
ii. a molecular weight distribution, Mw/Mn, defined by the
equation:
Mw/M" 5 (hp/Iy) - 4.63
wherein the substantially linear ethylene/a-olefin
interpolymer is further characterized as containing at least one
a-olefin monomer and having a density in the range of 0.85 to
0.92 g/cc and an Iz melt index in the range of 0.3 to 3 g/10
minutes.
3
2190005
WO 95130713 PCTIUS95105757
The novel method for producing such medium modulus
polyethylene film is a variable-stalk extrusion process which comprises the
steps of:
(1) providing an extrudable thermoplastic composition containing
(A) from 60 to 95 weight percent, based on the combined
weights of components (A) and (B), of at least one high weight
molecular linear ethylene polymer having a density in the
range of 0.92 to 0.96 g/cc and an I5 melt index in the range of
0.1 to 3 g/10 minutes, and (B) from 5 to 40 weight percent,
based on the combined weights of components (A) and (B), of
at least one substantially linear ethylene/a-olefin interpolymer
characterized as having:
l. a melt flow ratio, IIp/I2, 2 5.63, and
ii. a molecular weight distribution, Mw/Mn, defined by the
equation:
Mw/Mn S (I10/Iy) -4.63
wherein the substantially linear ethylene/a-olefin
interpolymer is further characterized as containing at least one
a-olefin monomer and having a density in the range of 0.85 to
0.92 g/cc and an Iz melt index in the range of 0.3 to 3 g/10
minutes.
(2) introducing said composition of step (1) into a filin extrusion
apparatus equipped with an annular die,
(3) extruding said composition of step (1) to form a tube that is
subsequently blown-up and drawn-down through nip and
take-off rollers to form a layflat film with a thickness greater
than about 1.25 mils, and
4
CA 02190005 2005-03-07
74069-221
(4) conveying said film formed in step (3) for
subsequent use down-line of the film extrusion apparatus of
step (2) or collecting said film formed in step (3) for
subsequent use off-line.
According to one aspect of the present invention,
there is provided a medium modulus, polyethylene film
characterized as having a thickness greater than 1.25 mils
which comprises: (A) from 60 to 95 weight percent, based on
the combined weight of components (A) and (B), of at least
one high molecular weight linear ethylene polymer having a
density in the range of 0.92 to 0.96 g/cc and an IS melt
index in the range of 0.1 to 3 g/10 minutes, and (B) from 5
to 40 weight percent, based on the combined weight of
components (A) and (B), of at least one substantially linear
ethylene/a-olefin interpolymer characterized as having: i. a
melt flow ratio, Ilo/Iz >- 5.63, and ii. a molecular weight
distribution, MW/Mn, defined by the equation: Mw/Mn s (Ilo/Ia)
- 4.63, and iii. a critical shear rate at onset of surface
melt fracture at least 50 percent greater than the critical
shear rate at onset of surface melt fracture of a Ziegler
polymerized heterogeneously branched linear ethylene polymer
or homogeneously branched linear ethylene polymer having
about the same Tz and MW/Mn wherein the substantially linear
ethylene/a-olefin polymer is further characterized as
containing at least one ethylene/a-olefin monomer and having
a density in the range of 0.85 to 0.92 g/cc and an I2 melt
index in the range of 0.3 to 3 g/10 minutes.
According to another aspect of the present
invention, there is provided a method for preparing a medium
modulus, polyethylene film comprising the steps of: (1)
providing an extrudable thermoplastic composition containing
(A) from 60 to 95 weight percent, based on the combined
weight of components (A) and (B), of at least one high
5
CA 02190005 2005-03-07
74069-221
molecular weight linear ethylene polymer having a density in
the range of 0.92 to 0.96 g/cc and an IS melt index in the
range of 0.1 to 3 g/10 minutes, and (B) from 5 to 40 weight
percent, based on the combined weight of components (A) and
(B), of at least one substantially linear ethylene/a-olefin
interpolymer characterized as having: i. a melt flow ratio,
Ilo/IZ >- 5.63, and ii. a molecular weight distribution, MW/Mn,
defined by the equation: MW/Mn ~ (Ilo/IZ) - 4.63, and iii. a
critical shear rate at onset of surface melt fracture at
least 50 percent greater than the critical shear rate at
onset of surface melt fracture of a Ziegler polymerized
heterogeneously branched linear ethylene polymer or
homogeneously branched linear ethylene polymer having about
the same I2 and Mw/Mn wherein the substantially linear
ethylene/a-olefin polymer is further characterized as
containing at least one ethylene/a-olefin monomer and having
a density in the range of 0.85 to 0.92 g/cc and an I2 melt
index in the range of 0.3 to 3 g/10 minutes, (2) introducing
said composition of step (1) into a heated film extrusion
apparatus equipped with an annular die, (3) extruding said
composition through said annular die to form a molten or
semi-molten thermoplastic tube of said composition that is
subsequently blow-up beyond the die diameter and drawn-down
through nip and take-off rollers to form a layflat film with
a thickness greater than 1.25 mil (31 ~,m) and (4) conveying
said film formed in step (3) for subsequent use off-line.
According to yet another aspect of the present
invention, there is provided a film produced according to
the method recited herein.
5a
CA 02190005 2005-03-07
74069-221
The film of the present invention has improved tear and impact
performance that is not ordinarily expected for medium modulus,
polyethylene films. The novel films have at least a 30 percent, and
preferably 50 percent, improvement in impact and tear properties relative to
prior .art polyethylene .films. having..abaut the .same film density,.~elt
index ..
and thickness. The benefit of the higher performing novel film is
practitioners can now meet speed heavy-duty Film requirements at
substantially lower costs by down-gauging and/or by using higher diluent
and recycled material loadings.
~~e 1 plots data describing the relationship between Mw/Mn and
ho/I2 for three distinct polymer types: substantially linear polyethylene,
heterogeneous linear polyethylene and homogeneous linear polyethylene.
Figures 2-4 are used to graphically summarize data presented in the
Examples.
Figwre 2 plots the relationship between tear strength and film
thickness for Inventive Films and Comparative Films. Inventive Films are
prepared from Film Compositions A, B and C and Comparative Films are
prepared from Film Compositions D, E and F.
Figure 3 plots the relationship between impact resistance at 3 mils
and measured film density for Inventive F'~lms and Comparative Films.
Inventive Films are prepared from Film Composition G-J and P-V.
Comparative Films are prepared from Film Compositions F, L, M and N.
Figure 4 plots the relationship between tear strength at 3 mils and
measured film density for Inventive Films and both actual and predicted
5b
W095/30713 ~ PCT/US95105757
Comparative Films. Inventive Films are prepared from Film Composition
G, H and I. Comparative Films are prepared from Film Compositions E, F
and K-O. The calculated or predicted tear strengths of compararive blend
compositions are based on a 0.951 g/cc HMW-HDPE and a 0.870 g/cc SLED of
various ratios.
"Substantially linear ethylene polymer" (SLEP) herein designates an
ethylene polymer having a polymer back-bone that is substituted with from
0.01 long chain branches/1000 carbons to 3 long chain branches/1000
carbons, more preferably from 0.01 long chain branches/1000 carbons to 1
long chain branches/1000 carbons, and especially from 0.05 long chain
branches/1000 carbons to 1 long chain branches/1000 carbons.
"Long chain branching" is defined herein as a chain length of at least
6 carbons, above which the length cannot be distinguished using 13C nuclear
magnetic resonance spectroscopy. The long chain branch can be as long as
about the same length as the length of the polymer back-bone.
Long chain branching is determined by using 13C nuclear magnetic
resonance (NMR) spectroscopy and is quantified using the method described
by Randall (Rev. Macromol. Chem. Phys., C29~ V. 2&3, p. 285-297).
The terms "ultra low density polyethylene" (ULDPE), "very low
density polyethylene" (VLDPE) and "linear very low density polyethylene"
(LVLDPE) have been used interchangeably in the polyethylene art to
designate the polymer subset of linear low density polyethylenes having a
density less than or equal to about 0.915 g/cc The term "linear low density
polyethylene" (LLDPE) is then applied to those linear polyethylenes having
a density above about 0.915 g/ca
The terms "heterogeneous" and "heterogeneously branched" are
used herein in the conventional sense in reference to a linear ethylene/a-
olefin polymer having a comparatively low short chain branching
6
2190005
a W095130713 PCTIUS95/05757
distribution index. The short chain branching distribution index (SCBDI) is
defined as the weight percent of the polymer molecules having a
comonomer content within 50 percent of the median total molar
comonomer content. The short chain branching distribution index of
polyolefins can be determined by well-known temperature rising elution
fractionation techniques, such as those described by Wild et al., Tournal of
Polymer Science, Poly. Phys. Ed., Vol. 20, p. 441 (1982), L. D. Cady, "The
Role
of Comonomer Type and Distribution in LLDPE Product Performance;' SPE
Regional Technical Conference, Quaker Square Hilton, Akron, Ohio,
October 1-2, pp. 107-119 (1985), or US Patent 4,798,081. Heterogeneous linear
ethylene/a-olefin polymers typically have a SCBDI less than about 30
percent.
The terms "homogeneous" and "homogeneously branched" are used
herein in the conventional sense in reference to an ethylene/a-olefin
polymer having a comparatively high short chain branching distribution
index (SCBDI) as determined by well-known temperature rising elution
fractionation techniques. Homogeneous ethylene/a-olefin polymers
typically have a SCBDI greater than or equal to about 30 percent.
The term "medium modulus" is used herein in reference to the
novel film to mean the calculated film density is in the range of 0.923 to
0.95 g/cc. The term "calculated film density" is used herein to mean the
density of film when calculated from the known weight fractions and the
measured annealed densities of the component polymers or layers.
The term "thick" is used herein in reference to the novel film to
mean a film thiclrness greater than about 1.25 mils (31 microns).
The term "variable-stalk extrusion" is a new term of art used herein
to express the distance between the annular film die and stalk height or
bubble expansion point which can be varied from 0 inches (0 centimeters) to
7
2190005
WO 95130713 PCTIUS95105757
greater than 144 inches (366 centimeters) during blown film fabrication. The
term includes both well-known pocket blown film extrusion and stalk
blown film extrusion. The term "high stalk extrusion" is used herein in the
conventional sense to mean a distance between the annular film die and
the air ring that is greater than or equal to 30 inches (76 centimeters). The
term "low stalk extrusion" is used herein in the conventional sense to
mean a distance in the range of 5 inches (12.7 centimeters) to 30 inches (76
centimeters).
The term "hot-fill" herein refers to a packaging or product-filling
operation where the product temperature is greater than 45°C. The term
"heavy-duty" herein refers generally to industrial items packaged in bulk or
having a single-package weight greater than 10 pounds (4.5 kilograms).
The density of the polymers used to make the medium modulus film
of the present invention is measured in accordance with ASTM D-792 and is
reported as grams/cubic centimeter (g/cc). The measurements reported in
the Examples below are determined after the polymer samples have been
annealed for 24 hours at ambient conditions.
Melt index measurements are performed according to ASTM D-1238,
Condition 190°C/2.16 kilogram (kg) and Condition 190°C/5 kg,
and are
known as Iy and Ig, respectively. Melt index is inversely proportional to the
molecular weight of the polymer. Thus, the higher the molecular weight,
the lower the melt index, although the relationship is not linear. Melt
index is reported as g/10 minutes. For purposes of this invention, in
calculating certain values in the Examples, I5 and Iy values roughly relate to
one another by a factor of about 5.1; for example, a 1.0 I2 index melt is
equivalent to about a 5.1 Ig melt index. Melt index determinations can also
be performed with even higher weights, such as in accordance with ASTM
8
2190005
W 0 95130713 PCTIUS95105757
D-1238, Condition 190°C/10 kg and Condition 190°C/21.6 kg,
and are known
as ho and I21.6, respectively.
The term "melt flow ratio" is defined herein in the conventional
sense as the ratio of a higher weight melt index determination to a lower
weight determination. For measured ho and I2 melt index values, the melt
flow ratio is conveniently designated as ho/I2. For I21.6 and hp values, the
ratio is designated I21.6/Ilo. Other melt flow ratios are occasionally used
respecting polyethylene compositions, such as, for example, Ig/Iy based on I5
and I2 melt index measurements. In general, I21.6/Ilo and IS/I2
determinations provide similar melt flow values and ho/IZ values are
usually greater than I21.6/Il0 values by a factor of about 4.4 and this factor
is
used for purposes of this invention in calculating certain values in the
Examples.
The tear resistance of the film of the present invention is measured
I5 in accordance with ASTM D1922 and is reported in grams. Tear resistance
in measured both the machine direction (MD) and in the cross direction
(CD). The term "tear strength" is used herein to represent the average
between MD and CD tear resistance values and, likewise, is reported in
grams. The impact resistance of the film of the instant invention is
measured in accordance with ASTM D1709. Where indicated and according
to the relationship of higher thicknesses yield increased performance
values, tear and impact results are normalized to exactly 3 mils by
proportionate increases or decreases based on actual measured (micrometer)
film thickness; however, such normalization calculations are only
performed and reported where thickness variations are less than 10 percent,
that is, where the measured thickness is in the range of 2.7 - 3.3 mils.
The medium modulus, polyethylene film of the present invention
has a calculated film density in the range of 0.923 g/cc to 0.95 g/cc,
9
2190005
WO 95/30713 PCTI'dJS95/05757
espetially, 0.926 g/cc to 0.948 g/cc, and more especially, 0.93 g/cc to 0.945
g/cc
The a film thickness is generally greater than about 1.25 mil,
especially, in the range of 1.5 mil to 8.75 mils, and more especially, in the
range of 2 mils to 8 mils
These novel films have tear strength or, alternately, impact
resistance, at least 30 percent greater than the tear strength or impact
resistance of a comparative prior art polyethylene film having about the
same film density, melt index and film thickness.
The tear strength of the novel film is also characterized by the
following equation:
tear strength (grams) = Ax + Bx2 + C
where A, B and C are numerical values and x is film thickness (mils); when
A is less than or equal to about 150, B is greater than or equal to about
12.5,
preferably greater than or equal to about 13.5, and more preferably greater
than or equal to about 14.5; and when A is greater than about 150, B is in the
range of -80 to 40, preferably -70 to 20, and more preferably -60 to 0. For
example, the expression 307.18x - 26.219x2 - 98.134 is thought to represent
the tear strength of the film of the present invention, whereas the
expression 13822x + 4.8116x2 -19.364 does not.
The strength of the novel film can be alternately characterized by the
following equation:
tear strength (grams) = Ax2 - Bx + C
where A, B and C are numerical values and x is measured film density
(g/cc), wherein A is greater than or equal to 1.5 x 106, preferably greater
than
or equal to 1.7 x 106 and B is greater than or equal to 2.75 x 106, preferably
greater than or equal to 3.0 x 106. For example, the following expression is
representative of 30 percent greater tear strength than a comparative
IO
WO 95!30713 219 0 0 0.~ PCT~S95/05757
polyethylene film having about the same melt index, film density and
thickness:
tear strength (grams) = 1.565 x 106(x2) - 2.971 x 10'(x) + 1.41 x 106.
The film can be even further or alternately characterized by the
following equation:
impact resistance (grams) = Ax2 - Bx + C
where A, B and C are numerical values and x is measured film density
(g/cc), where A is greater than or equal to 1.4 x 106, preferably greater than
or
equal to 1.5 x 106 and B is greater than or equal to 2.5 x 106, preferably
greater
than or equal to 2.75 x 106. For example, the following expression is
representative of 30 percent greater impact resistance than a comparative
polyethylene film having about the same melt index, film density and
thickness:
impact resistance (grams) = 1.415 x 106(x2) - 2.676 x 106(x) + 1.265 x 106.
This novel film can be conveniently formed into bags and is useful in
heavy-duty packaging and shipping applications as well as in hot-fill
packaging applications where films with a good property balance, that is,
high strength and medium modulus with good tear, impact and
dimensional stability, are needed.
The high molecular weight linear ethylene polymers, Component
(A), for use in preparing the medium modulus, polyethylene film of the
instant invention are a known class of compounds which can be produced
by any well-known particle-form polymerization process, such as slurry
polymerization and gas phase polymerization. Preferably, the high
molecular weight linear ethylene polymers are produced using well-known
Phillips or Ziegler type coordination catalysts, although metallocene catalyst
systems can also be used. Although preferred, with conventional Ziegler
11
2190005
WO 95130713 PCTIUS95105757
type catalysts, slurry polymerization processes are generally limited to
polymer densities greater than about 0.940 g/cc and especially limited to
polymer densities greater than about 0.935 g/cc, that is, about 0.935 g/cc is
the practical lower commercial limit for slurry polymerization.
The high molecular weight linear ethylene polymer can be an ,
ethylene homopolymer or a copolymer of ethylene with at least one a-olefin
of from 3 to 20 carbon atoms. However, preferably, the high molecular
weight linear polymer is a copolymer with at least one C3-Czp a-olefin, such
as 1-propylene, 1-butene, 1-isobutylene, 4-methyl-1-pentene, 1-hexene, 1-
heptene and 1-octene. Most preferably, the high molecular weight linear
ethylene polymer is an ethylene/1-butene copolymer prepared by a low
pressure slurry polymerization process. The novel Film comprises from 60
to 95 weight percent high molecular weight linear ethylene polymer,
preferably 65 to 90 weight percent, and more preferably 70 to 85 weight
I5 percent.
Component (A) can also be a blend of linear ethylene polymers. Such
blends can be prepared in-situ ( for example, by having a mixture of catalysts
in a single polymerization reactor or by using different catalysts in separate
reactors connected in parallel or in series) or by physical blending of
polymers.
The high molecular weight linear ethylene polymer has an I5 melt
index in the range of 0.1 g/10 minutes to 3 g/10, preferably, 0.1 g/10
minutes to 2 g/10 minutes and, more preferably, O.IS g/10 minutes to 1
g/10 minutes. Additionally, the linear polymer preferably has a bimodal
molecular weight distribution (MWD) and an I21.6/Il0 ratio in the range of
from 1 to 12, preferably in the range of from 3.5 to 10, more preferably in
the range of from 4 to 8, and most preferably in the range of from 4.5 to 6.
12
290005
W 0 95130713 PCTIITS95/05757
The high molecular weight linear ethylene polymer, which includes,
but is not limited to, LLDPE, LMDPE and HDPE, and mixtures thereof,
preferably has a density in the range of from 0.92 g/cc to 0.96 g/cc, more
preferably, in the range of from 0.93 g/cc to 0.96 g/cc, and most preferably,
in the range of from 0.935 g/cc to 0.958 g/cc.
The substantially linear ethylene/a-olefin polymers used in the
present invention Component (B), are a unique class of compounds that are
defined in US 5,272,236 and US Patent 5,278,272 by Lai et al. Lai et al. teach
that such polymers are preferably prepared by a continuous, solution phase
IO polymerization process using the constrained geometry catalyst discovered
by Stevens et al. US Patent 5,055,438. The substantially linear ethylene/a-
olefin interpolymers contain ethylene interpolymerized with at least one
C3-C2p a-olefin, such as 1-propylene, 1-butene, 1-isobutylene, 1-hexene, 4-
methyl-1-pentene, 1-heptene and 1-octene, as well as other monomer types
such as styrene, halo- or alkyl-substituted styrenes, tetrafluoro-ethylene,
vinyl benzocyclo-butane, 1,4-hexadiene, 1,7-octadiene, and cycloalkenes, for
example, cyclopentene, cyclohexene and cyclooctene. Although the
substantially linear ethylene/a-olefin interpolymer can be a terpolymer
where at least two a-olefin monomers are polymerized with ethylene,
preferably the interpolymer is a copolymer with one a-olefin monomer
copolymerized with ethylene and most preferably the substantially linear
ethylene/a-olefin interpolymer is a copolymer of ethylene and 1-octene.
Substantially linear ethylene/a-olefin polymers are not the
conventional homogeneously branched linear ethylene/a-olefin
copolymers described inUS Patent 3,645,992 (Elston)nor are they the same
class as conventional Ziegler polymerized linear ethylene/a-olefin
copolymers (for example, linear low density polyethylene or linear high
density polyethylene made, for example, using the technique disclosed by
13
2190005
W0 95130713 PCTIUS95105757
Anderson et al. in US Patent 4,076,698), nor are they the same as traditional
highly branched LDPE. The substantially linear ethylene/a-olefin polymers
useful in this invention are indeed a unique class of polymers which have
excellent processability, even though they have relatively narrow molecular
weight distributions (typically, about 2). Even more surprisingly, as
described in US Patent 5,278,272 by Lai et al., the melt flow ratio (hp/Iy) of
the substantially linear ethylene homopolymers or interpolymers can be
varied essentially independently of the polydispersity index (that is, the
molecular weight distribution, Mw/M"). As Figure 1 illustrates, the
rheological behavior of substantially linear ethylene polymers constitutes a
dramatic contradistinction over to the homogeneous linear ethylene/a-
olefin polymer described by Elston and to conventional Ziegler polymerized
heterogeneous linear polyethylene in that both heterogeneous linear and
homogeneously linear ethylene polymers have rheological properties such
that as the polydispersity index increases, the Iip/I2 value also increases.
The "rheological processing index" (PI) is the apparent viscosity (in
kpoise) of a polymer measured by a gas extrusion rheometer (GER). The gas
extrusion rheometer is described by M. Shida, R.N. Shroff and L.V. Cancio
in Polymer Eneineering Science, Vo1.,17, No. 11, p. 770 (1977), and in
"Rheometers for Molten Plastics" by John Dealy, published by Van
Nostrand Reinhold Co. (1982) on pp. 97-99. GER experiments are performed
herein at a temperature of 190°C, at nitrogen pressures between 250 to
5500
psig using a 3.81 cm diameter die and a 20:1 L/D rheometer with an entrance
angle of 180°. The processing index is measured herein at 3,000 psig.
For the substantially linear ethylene/a-olefin interpolymers used
herein, the PI is the apparent viscosity (in kpoise) of a material measured by
GER at an apparent shear stress of 2.15 x 106 dyne/cm2. The substantially
linear ethylene/a-olefin interpolymers used herein preferably have a PI in
14-
WO 95!30713 219 0 0 0 ~ PCTIUS95/05757
the range of 0.01 kpoise to 50 kpoise, preferably 15 kpoise or less. The
substantially linear ethylene/a-olefin interpolymers used herein have a PI
less than or equal to 70 percent of the PI of a comparative linear ethylene
polymer (either a Ziegler polymerized polymer or a linear uniformly
branched polymer as described by Elston in US Patent 3,645,992) at about the
same I2 and Mw/Mn.
An apparent shear stress versus apparent shear rate plot can be used
to identify the melt fracture phenomena. According to Ramamurthy in the
Tournal of RheologX 30(2), 337-357,1986, above a certain critical flow rate,
the observed extrudate irregularities may be broadly classified into two main
types: surface melt fracture and gross melt fracture.
Surface melt fracture occurs under apparently steady flow conditions
and ranges in detail from loss of specular film gloss to the more severe form
of "sharkskin." In this disclosure, the onset of surface melt fracture (OSMF)
is characterized at the beginning of losing extrudate gloss at which the
surface roughness of the extrudate can only be detected by 40x magnification.
The critical shear rate at the onset of surface melt fracture for the
substantially linear ethylene/a-olefin interpolymers is at least 50 percent
greater than the crifical shear rate at the onset of surface melt fracture of
a
comparative linear ethylene polymer (either a Ziegler polymerized
heterogeneously branched polymer or a homogeneously branched polymer
as described by Elston in US Patent 3,645,992) having about the same I2 and
Mw/Mn.
Gross melt fracture occurs at unsteady extrusion flow conditions and
ranges in detail from regular (alternating rough and smooth, helical, etc.) to
random distortions. For commercial acceptability, (for example, in blown
films and bags therefrom), surface defects should be minimal, if not absent,
for good film quality and properties. The critical shear rate at the onset of
CA 02190005 2005-03-07
74069-221
surface melt fracture (OSMF) and the onset of gross melt fracture (OGMF)
will be used herein based on the changes of surface roughness and
configurations of ~ the extrudate.
To more fully characterize the theological behavior of the unique
substantially linear ethylene/a-olefin interpolymers, S. Lai and G.W.
Knight introduced f'ANTEC '93 Proceedings, INSTTETM Technology
Polyolefins (TTP) - New Rules in the Structure/Rheology Relationship of
Ethylene a-0lefin Copolymers, New Orleans, La., May 1993) another
theological measurement, the D.ow Rheology.I~dex (DRI), which expresses a
polymer's "normalized relaxation time as the result of long chain
branching." DRI ranges from 0 for polymers which ~do not have any
rM tei
measurable long chain branching ( for example, "TAFMER" and "EXACT"
products sold commercially by Mitsui Chemical and Exxon Chemical
Company, respectively) to about 15 and is independent of melt index. In
general, for low to medium density ethylene polymers (particularly at lower
densities) DRI provides improved corrclations to melt elasticity and high
shear flowability relative to correlations of the same attempted with melt
flow ratios. For the substantially linear ethylene/a-oleFui polymers used in
this invention, DRI is preferably at least about 0.1, and especially at least
about 0.5, and most especially at least 0.8. DRI can be calculated from the
equation:
DRI = (3652879 *'Lol~°o6~t9~o _1)/10
where 'Lo is the characteristic relaxation time of the material
and '1"~o is the zero shear viscosity of the material. Both 'Lo and
1"1o are the "best fit" values to the Cross equation, that is
~~o = 1/(1 +(Y *'Lo)~'~ )
16
WO 95f30713 219 0 0 0 5 PCT~S95/05757
where n is the power law index of the material, and'1'~ and y
are the measured viscosity and shear rate, respectively.
Baseline determination of viscosity and shear rate data are
obtained using a Rheometric Mechanical Spectrometer (RMS-
800) under dynamic sweep mode from 0.1 to 100
radians/second at 160°C and a Gas Extrusion Rheometer (GER)
at extrusion pressures from 1,000 psi to 5,000 psi (6.89 to 34.5
MPa), which corresponds to shear stress from 0.086 to 0.43 MPa,
using a 3.81 centimeter diameter die and 20:1 L/D rheometer at
190°C. Speck material determinations can be performed from
140 to 190°C as required to accommodate melt index variations.
Substantially linear ethylene/a-olefin interpolymers are considered
to be "homogeneous" in composition distribution since substantially all of
the polymer molecules have the same ethylene-to-comonomer ratio.
Moreover, the substantially linear ethylene polymers have a narrow short
chain (homogeneous) branching distribution, as defined by US Patent
3,645992. The distribution of comonomer branches for the substantially
linear ethylene/a-olefin interpolymers is characterized by its SCBDI (Short
Chain Branch Distribution Index) or CDBI (Composition Distribution
Branch Index) and is defined as the weight percent of the polymer
molecules having a comonomer content within 50 percent of the median
total molar comonomer content. The CDBI of a polymer is readily
calculated from data obtained from techniques known in the art, such as, for
example, temperature rising elution fractionation (abbreviated herein as
"TREE'). The SCBDI or CDBI for the substantially linear ethylene/a-olefin
interpolymers used in the present invention is preferably greater than 30
percent, especially greater than 50 percent.
The substantially linear ethylene/a-olefin polymers used in this
invention essentially lack a measurable "high density" fraction, as
measured by the TREF technique. Preferably, the substantially linear
17
2190005
WO 95130713 PCT/US95I05757
ethylene/a-olefin interpolymers do not contain a polymer fraction with a
degree of branching less than or equal to 2 methyls/1000 carbons. The "high
density polymer fraction" can also be described as a polymer fraction with a
degree of branching less than 2 methyls/100Qcarbons.
The molecular weight and molecular weight distribution, MW/M"
ratio, of substantially linear ethylene/a-olefin interpolymers can be
analyzed by gel permeation chromatography (GPC) on a Waters 150 high
temperature -chromatographic unit equipped with differential refractometer
and three columns of mixed porosity. The columns are supplied by
Polymer Laboratories and are commonly packed with pore sizes of 103, 104,
105 and 106th. The solvent is 1,2,4-trichlorobenzene, from which 0.3 percent
by weight solutions of the samples are prepared for injection. The flow rate-
is 1.0 milliliters/minute, unit operating temperature is 140°C and the
injection size is 100 microliters.
The molecular weight determination with respect to the polymer
back-bone is deduced by using narrow molecular weight distribution
polystyrene standards (from Polymer Laboratories) in conjunction with
their elution volumes. The equivalent polyethylene molecular weights are
determined by using appropriate Mark-Houwink coefficients for
polyethylene and polystyrene (as described by Williams and Ward in
jgurnal of Po_lgmer Science, Polymer Letters, Vol. 6, p. 621, 1968) to derive
the following equation:
Mpolyethylene = a "' (T'lpolystyrene)b.
In this equation, a = 0.4316 and b = 1Ø Weight average molecular
weight, Mw, is calculated in the usual manner according to the following
formula: M,N = R wi* ML where wi and Mi are the weight fracfion and
18
WO 95130713 219 0 D 0 5 PCT/US95/05757
molecular weight, respectively, of the ith fraction eluting from the GPC
column.
For the substantially linear ethylene/a-olefin interpolymers used in
the present invention, the MW/Mn is preferably less than 3, especially from
1.5 to 2.5.
The novel film comprises from 5 to 40 weight percent, based on the
combined weight of components (A) and (B), of the substantially linear
ethylene/a-olefin interpolymer, preferably from 10 to 35 weight percent,
and more preferably from 15 to 30 weight percent.
The substantially linear ethylene/a-olefin interpolymer used to
prepared the film of the present invention has an Iy melt index in the range
of 0.3 g/10 minutes to 3 g/10, preferably, 0.3 g/10 minutes to 2.5 g/10
minutes and, more preferably, 0.4 g/10 minutes to 2 g/10 minutes. The
substantially linear ethylene/a-olefin interpolymer has a density less about
0.92 g/cc, more preferably, in the range of 0.85 g/cc to 0.916 g/cc, and most
preferably, in the range of 0.86 g/cc to 0.91 g/cc. The IIp/Iy ratio of the
substantially linear ethylene/a-olefin interpolymers is in the range from
5.63 to 30, preferably less than about 20, especially less than about 15, and
most especially less than about 10.
Component (B) can be a blend of substantially linear
ethylene/a-olefin interpolymers or, optionally, a blend of an SLEP
interpolymer with at least one heterogeneous or homogeneous linear
ethylene polymers selected from the group consisting of LTLDPE and LLDPE.
When the substantially linear ethylene/a-olefin interpolymer is employed
in such blends, a blend of an SLEP with a heterogeneous ULDPE,
component (C), is preferred.
Heterogeneously branched ULDPE and LLDPE are well known and
commercially available materials. They are typically prepared using Zsegler-
19
vJ0 95/30713 ~ PCT/US95105757
Natta catalysts in solution or gas phase polymerization processes Anderson
et al., U.S. Pat. 4,076,698, is illustrative. These traditional Ziegler-type
linear
polyethylenes are not homogeneously branched and they do not have any
long-chain branching. Heterogeneously branched ULDPE and LLDPE typical
having molecular weight distributions, MH./MI" in the range of from 3.5 to
4.1.
Homogeneously branched ULDPE and LLDPE are also well known.
Elston disclosure in U.S. Pat. 3,645,992 is illustrative. Homogeneously
branched ULDPE and LLDPE can be prepared in conventional
polymerization processes using Ziegler-type catalysts such as, for example,
zirconium and vanadium catalyst systems as well as using metallocene
catalyst systems such as, for example, those based on hafnium. Ewen et al.
disclosure in U.S. Pat. 4,937,299 and Tsutsui et al. disclosure in U.S. Pat.
5,218,071 are illustrative. This second class of linear polyethylenes are
homogeneously branched polymers, and like traditional Ziegler-type
heterogeneous linear polyethylenes, they do not have any long-chain
branching. Homogeneously branched ULDPE and LLDPE typical having
molecular weight distributions, MW/M", of about 2. Commercial examples
of homogeneously branched linear polyethylenes include those sold by
Mitsui Petrochemical Industries under the designation "TAFMER" and by
Exxon Chemical Company under the designation "EXACT".
The preparation of polyethylene Film by blown film extrusion is well-
known. See, for example, U.S. Patent 4,632,801 by Dowd which described a
typical blown film extrusion process. In the typical process, a polyethylene
composition is introduced into a screw extruder wherein it is melted and
forwarded through the extruder under pressure. The molten polymer
composition is forced through an annular film die to form a molten tube.
Air is then provided through the annular die to inflate the tube into a
WO 95/30713 219 0 0 0 5
PCT'/US95/05757
"bubble" with the desired diameter. Air is contained within the bubble by
the annular die and nip rollers downstream of the die where thereafter the
bubble is collapse into layflat film. The final thickness of the film is
controlled by extrusion rate, bubble diameter and nip speed which can be
controlled by such variables as screw speed, haul-off rate and winder speed.
Increasing the extrusion rate at a constant bubble diameter and nip speed,
will increase final film thickness.
The typical blown extrusion process can be generally classified as
either "stalk" or "pocket" extrusion. In stalk extrusion, bubble inflation and
expansion are controlled or occur at a significant distance above the annular
die. The air ring, usually of single-lip construction, provides air flow
external to the tube and parallel to the machine direction such that the
molten tube maintains the approximate diameter of the annular film die
until it is inflated at a height at least 5 inches (12.7 centimeters) above
the
annular die. Internal bubble cooling can also be used as well as an internal
bubble stabilizer to insure optimum bubble stability during fabrication.
Stalk extrusion is known to allow improved molecular relaxation
and, as such, mitigates excessive orientation in one direction and thereby
allows balanced film physical properties. Increasing the stalk or expansion
height generally provides higher cross direction (CD) properties and,
thereby, higher average film properties. Stalls extrusion, and particularly
high-stalk extrusion, is very useful for preparing blown films from vigh
molecular weight polyethylene compositions such as, for example, high
molecular high density polyethylene (HMW-HDPE) and high molecular
low density polyethylene (HMW-LDPE) which possess sufficient melt
strength to insure adequate bubble stability.
In pocket extrusion, air is supplied by an air ring disposed
immediately adjacent to the annular die to cause the bubble leaving the die
21
R'O 95130713 PCTIUS95105757
to immediately inflate and expand. The air ring is typically a dual-lip type
to
insure added bubble stability. Pocket extrusion is more widely employed
than stalk extrusion and is generally preferred for lower molecular weight,
lower melt strength polyethylene compositions such as, for example, linear
low density polyethylene (LLDPE) and ultra low density polyethylene
(LJLDPE).
Both monolayer and multilayer films can be prepared by stalk and
pocket extrusion and the films of the present invention can be monolayer
or multilayer structures. Multilayer films can be prepared by any known
technique in the art, including, for example, coextrusion, lamination or
combinations of both. However, the preferred medium modulus, thick
polyethylene film of the present invention is a monolayer film structure.
Although the film of this invention can be prepared by variable stalk
extrusion, pocket extrusion and low-stalk extrusion are preferred where the
high molecular weight linear ethylene polymer, Component (A), has an IS
melt index greater than about 0.5 g/10 minutes, particularly greater than
about 0.6 g/10 minutes, and most particularly greater than about 0.7 g/10
minutes. High stalk extrusion, where the distance between the die and the
occurrence of bubble expansion is usually from 30 to 42 inches (76 to 107
centimeters), that is, from 6 to 10 die diameters, is preferred for preparing
of the film of this invention where the high molecular weight linear
ethylene polymer, component (A), has an Ig melt index less than or equal to
about 0.5 g/10 minutes, particularly less than about 0.4 g/10 minutes, and
most particularly less than about 0.3 g/10 minutes.
Components (A) and (B), and optional Component (C), used to
prepare the film of this invention, can be individually blended ( that is,
where a component itself is a polymer blend of two or more subcomponent
polymers) or admixed together by any suitable means known in the art.
22
W095f30713 2 ~ g p ~ ~ 5 PCTlUS95105757
Suitable means are thought to include tumble dry-blending the components
together prior to charging the blown film extruder, weigh-feeding the
components directly into the blown film extruder, melt-blending the
components via compound or side-arm extrusion prior to introduction into
the blown film extruder, multiple reactor polymerization of the
components with reactors in series or in parallel and optionally with
different catalyst and/or monomer types in each reactor, or the like as well
as combinations thereof.
In addition to the above equations respecting the tear and impact
performance of the film of this invention, temperature rising elution
fractionation (TREF) can also be used to" fingerprint" or identify the novel
film of this invention as well as the film compositions used to make the
novel film.
Additives, such as antioxidants ( for example, hindered phenolics,
such as Irganox~ 1010 or Irganox~ 1076 supplied by Ciba Geigy), phosphites
for example, Irgafos~ 168 also supplied by Ciba Geigy), cling additives ( for
example, PIB), Standostab PEPQTM (supplied by Sandoz), pigments,
colorants, and fillers can also be included in the film of the present
invention, or the polymer compositions used to make the same, to the
extent that such additives or ingredients do not interfere with the improved
tear and impact resistance performance discovered by Applicants. Although
generally not required, the film of the present invention can also contain
additives to enhance antiblocking and coefficient of friction characteristics
including, but not limited to, untreated and treated silicon dioxide, talc,
calcium carbonate, and clay, as well as primary, secondary and substituted
fatty and amides, release agents, silicone coatings, etc. Still other
additives,
such as quaternary ammonium compounds alone or in combination with
ethylene-acrylic and (EAA) copolymers or other functional polymers, can
23
2190005
W O 95130713 PCTIUS95105757
also be added to enhance the antistatic characteristics of the film of this
invention and allow, for example, heavy-duty packaging of electronically
sensitive goods.
Advantageously, because of the improved strength properties of the
novel film, recycled and scrap materials as well as diluent polymers can be
incorporated or admixed into the film compositions used to make the novel
film at higher loadings than is typically possible with prior art polyethylene
film compositions and still provide or maintain the desired performance
properties for successful use in heavy-duty packaging and shipping
applications. Suitable diluent materials include, for example, elastomers,
rubbers and anhydride modified polyethylenes ( for example, polybutylene
and malefic anhydride grafted LLDPE and HDPE) as well as with high
pressure polyethylenes such as, for example, low density polyethylene
(LDPE), ethylene/acrylic acid (EAA) interpolymers, ethylene/vinyl acetate
(EVA) interpolymers and ethylene/methacrylate (EMA) interpolymers, and
combinations thereof.
24
2 ~ gooo~
W0 95130713 PCTIUS95105757
Examples
The following examples illustrate some of the particular
embodiments of the present invention, but the following should not be
construed to mean the invention is limited only to the particular
embodiments shown.
Table 1 lists various resin types for use in investigating the
requirements for improved medium modulus films.
Table 1
Resul Types and Pro~ertieg
- g/l0ming/- Ratio Shear Shear Type Type
Rate
I/sec Stress
d e/~Z
HMW- D2618 0.9425.5I21.6/110NA NA NA ButeneSlurry
PE
HMW-HDPE0.75180.951NA NA NA NA ButeneShury
HMW-MDPE0261; 0.93553I21,6/IypNA NA NA ButeneSlurry
MDPE 1.0 0.9357.711p/12NA NA 24 x O<teneSolution
I2 106
1JLDPE 0.8 0.9058.71fp/I23.Sh.DNA 3.6 OctaneSdutton
I2 x 106
LLDPE 1.0 0.9207.6110/123.53bNA 3.9 DeteneSduHort
I2 x 106
SLEP 0.8 0.91110.9 NA 1,1H4 43 x OctanetSoluHon
I2 Itp/I2 106
SLEP 1.0 0$TD 7.4 h0/121.98 SLID 3.0 OctaneSduHaat
I2 x 106
SLED 0.9 0.8~ 10.8110/122.17 258 24x OctaneSolution
I2 106
SLEP 1.0 0.9027-S h0/122.12 NA 43 x OctaneSolution
I2 106
SLEP L0 0.9099.6Iyp/I22.06 1,766 45 x OctaneSdulion
I2 106
RM-HDPE O.lI2 0.935NA NA NA NA NA NA
-H HMYV- ALL SLEPandMDPEreainsareeuppEedby a OtemicalConpany. RM-HDPEdmoresa
Polybutylme Rubber-Modified HDPE is supplied by Allied-Signal under the
deefgnatton'PAXON3208".
Tables 2 - 7 summarize the various component resins and film
compositions for use in determining the requirements for medium
modulus, polyethylene films with improved strength properties. The tables
also summarize the fabrication conditions for use in investigating
improved medium modulus, polyethylene film. Except for Inventive
Example 43 which involves side-arm extrusion preparation, all blend
compositions used in the investigation were performed by tumble-blending
2190005
WO 95/30713 PCTIUS95105757
the individual polymer components together according to the weight
percentage amounts shown in the various Tables.
Inventive Films 2-4, 6-8 and 10-12 as well as Comparative Films 1, 5,
7, 9 and 13-24 were fabricated by using a seven-zone Kiefel high stalk blown
film line equipped with a grooved-barrel extruder, a decompression screw
and no internal bubble cooling. Inventive Films 25-28, 34-40, 42 and 43 as
well as Comparative Films 29-33 and 41 were fabricated utilizing a
conventional pocket blown film line equipped a LLDPE barrier screw. With
the exception of Comparative Films prepared from Compositions F and L,
which were fabricated using an incline extruder temperature profile, all film
fabrications employed a reverse temperature profile. The physical
properties of the resultant Inventive Films and Comparative Films from
Compositions A - W as a funciion of thickness are also summarized in
Table 2 - 7.
The Tables report both measured and calculated film density. Like
calculated film density determinations, the composition I5 values reported
in the tables were also derived from weight-fraction calculations. For
purposes of this invention and for component polymers, all reported Iz
values less than 0.5 g/10 minutes and I5 values greater than 1.0 g/10
minutes are calculated values based on the following relationship:
1.0 IZ = 5.1 I5.
Additionally, for component polymers, reported Iyl.6/Ilp values less
than 4.0 and hp/I2 values greater than 15 are also calculated values based on
the following relationship:
4.4 Il0/IZ = 1.0 Izi.6/Ilp.
For purposes of this invention, and as an example, the following
computation is the weight-fraction calculation for determining the
calculated film density of Inventive Example 1 which comprises 80 weight
26
2190005
WO 9513D713 PCT/US95105757
percent of a HDPE having a density of 0.942 g/cc and 20 weight percent of a
SLEP having a density of 0.902 g/cc:
calculated film density (g/a) _ (0.8)(0.942 g/cc) + (0.2)(0.902 g/cc) = 0.934
g/cc .
The following computation example is the weight-fraction
calculation for determining the calculated composition I5 of Inventive
Example 25 which comprises 80 weight percent of a HDPE having an I5 of
0.75 g/10 minutes and 20 weight percent of a SLEP having an I2 of L0 g/10
minutes:
calculated composition IS (g/10 min.) _ (0.8)(0.75 IS) + (0.2)(1.0I2)(5.1
Is/LO Ip) = 1.62 IS .
The following computation example is the factor-based calculation
for determining the I5 melt index of the SLEP having a 0.77 g/10 minutes I2
that used to prepared Composition B:
calculated component polymer IS (g/10 min.) _ (0.77I2HS.l l,5/10 I2) = 3.93 I5
.
The following computation example is the factor-based calculation
for determining the I21,6/Ii0 ratio of the SLED having a 10.9 Iip/I2 ratio
that
used to prepared Composition B:
calculated component polymer IZt.6/Ito=_ (10.9 ho/ IZ)(LOIZlb/ItD+ 4.4 ho/ IZ)
= 2.47Iylb/ ItD.
The following computation example is the normalization calculation
for determining the tear strength of Inventive Example 10 at 3 mils where
the tear strength is 762 grams at 2.94 mils:
tear strength at 3 mils (grams) _ (762 g)(3.0 mils/2.94 mils) = 777 grams .
27
W095/30713 21 ~~ ~ ~ PCTIUS95105757
Table 2
Fllm Compositions, Fabrication Conditions and Film Properties
COMPOSITfON A I B
COMPONENT (A)
Type HDPE HDPE HDPE HDPE HDPEHDPE HDPE HDPE
PolymeduHon 9mry 9tary9mry 9tary9mrySherry9tmy Stuny
Pr~ac
C~onoma~ Butene ButeneButeneButeneButeneButeneButeneButene
lygrems/l0minutes026 026 026 026 026 026 026 026
-
I,7, gapts/10 0.05 0.05 0.05 0.05 0.050.05 OAS 0.05
minutes -
Dmslty, g/cc 0942 0.9420.9420.9420.9420.9420942 0.942
I2L6/Ilo 5.5 5.5 55 55 5b 55 5S 5.5
Iy0/I2 242 242 242 242 242 242 242 242
COMPONENT B)
Type SLED SLEP SLEP SLED SGEPSLEP SLEP SLEP
PolymefaaHon
Proce%SolutionSolutionSolutionSolutionSolutionSolutionSolutionSolution
Comononte OctaneOctaneOctaneOctaneOctaneOctaneOctaneOctane
Iy grams/10 minutes5.1 5.1 5.1 5.1 3.9 3.9 3.9 3.9
Iygams/70minutes 1.00 1.00 1.00 1.00 O.T70.77 0.T7 0.77
Density,g/cc 0.9020.9020.9020.9020.9110.9110.9110.911
121.6/110 1.7 1.7 1.7 1.7 2.5 2.5 2.5 2.5
Iy0/I2 7.5 7b Z5 7.5 10.910.9 10.9 10.9 -
(A)1(B) BLEND WI. 80/20HO/20BO/2080/2080/2080/2080/2080/20
percent
FABRICATION CONDIT10NS
Amular Die Diameter,113 113 113 113 113 113 113 113
atm
Exnuda Dtameter, 70 70 TD 7C1 70 70 70 70
mm
Extuda Latgth/Diameter24/1 24/1 24/1 24/1 24/124/7 24/1 24/1
Dle Cap, mm ~ 12 12 1.2 - 12 1.2 12 12
1.2
Output, kg/hr 71 100 100 100 100 100 100 100 -
Blow-Up Ratio 3.3/133/1 33/1 33/1 33/13.31133/1 33/1
Stalk Hdghy ~t 104 104 104 ~ 104 104 104 104
104
Target Melt Temperature,213 213 213 213 213 213 213 213
C
PHYSICAL PROPERTIES
F~lm ThidateR, mils 0.48 3.00 5.10 8.14 0.60 221 3.70 5.(19
Ca1 Frlm Density, 0934 0934 0934 0934 0.9350.9350935 0.935
g/x
CamposiHonIS,g/lOmin.120 120 120 -120 0.71 0.71 0.77 On
CD Tear,grmu - 105 801 1205 >1600127 763 799 816
MD Tmr, grams 11 642 1253 >16008 199 499 777
TearShength,gama 58 722 1229 ->160068 481 649 797
'Detotes Comparative Examples only, that is the examples are not examples of
the present'vtvenHon
CaL Fdm Density denotes calculated Blm datsity.
1~
28
~i WO 95130713 219 0 0 0 5 PCT/US95/05757
Table 3
Film Comyoaitions, Fabrication Conditions and Fitm Proyertiea
COMPOSTIION C D
.. t
COMPONENT (A)
TYPe HDPE HDPE HDPE HDPE HDPE HDpE HDpE HDPE
Polymerlaatkm Process SlimySlurrySlutry9urry9tnry Shiny9mry gurry
Comonomer ButeneButeneButeneButeneButeneButeneHuteneButene
IS grams/10 minutes 0.26 0.26 026 026 0.2G 026 026 026
-
Iy grams/10 minutes 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05
~4% 8/cc 0.9420.9420.9420.9420.935 0.9350.9350935
121.6/110 55 55 5.5 55 525 525 525 5.25
110/12 242 242 242 242 23.1 23.t 23.1 23.1
COMPONENT (B)
TYPe I1LDPEULDPEULDPEIJLDPENone None None None
Polymedration Prooss SolutionSolutionSolutionSolution. _ _
Comonomer OcteneOcteneOcteneC)<tene_ _
_
Iygams/l0minutes 4.1 4.1 4.1 4.1 . _
_
12&'ams/IOminutes 0.8 08 0.8 0.8 _ _ _
s'tY, 8/a 0.9050.9050905 0.905_ _
_
121.6/110 2.0 2.0 2.0 2.0
It0/I2 8.7 87 8.7 87 _ _ _ _
COMPONENT (C)
TYPe SLED SLED SLED SLEP None None None None
Polymedratlon Pmoe9s SolutionSolutionSolutionSolution_ _
_
~~~er OctaneOctaneOctaneOctane_ _ _
ISgtams/lOminutes 3.9 39 39 39 _ _
'
Ib8~/lOminutes 0.77 0.77 0.77 0.77 _ _ _
_
~~ty.8/~ 0911 0.9110.9:?0.917_ _ -
121.6/110 25 25 2. 25 _ _
110/12 10.9 10.9 10.y 10.9 _ _ _ _
(A)!B)!(C)BLENDiVT.
percent80/10/1080/10/1080/10/1080/10/10100/0/0100/0/0100/0/0100/0/0
FABRICATION CONDITIONS
Annular DieI)iameter,mm 113 113 113 113 113 113 113 113
Fxttvder Diameter, mm 70 70 70 70 70 70 70
70
Extruder Ixitgth/Diameter24/1 24/1 24/1 24/1 24/1 24/1 24/1 24/1
1Xe Gal % ~ 12 12 12 12 12 12 12 1
2
Output kg/hr 77 100 100 100 77 100 100 .
100
Blow-Up Ratio 33/1 33/1 3.3/133/1 33/1 33/1 33/1 33/1
Stalk Height, or 104 104 104 104 104 104 104 104
Melt Temperature, C 213 213 213 213 273 213 213 213
PHYSICAL PROPERTIES
Film lludmess, mils 0.50 294 476 7.76 OSS 2.88 5.1 6.17
Ca1 Film L~lty, g/cc 0935 0.9350935 0935 0.935 0935 0.9350
935
Composition Iy g/lOmin. 0.71 071 071 0.71 026 026 Q26 .
026
CD Tear, grams 141 1120 1491 >16D095 573 828 1100
MD Tear,Bmms 10 404 923 >16009 306 726 969
Tear Strength, grams - 76 762 1197 >160052 440 7T7 1035
Denotes Comparative Examples
only, that is, the examples
are not examples of the
present invention.
CaL Film Density denotes
calculated tllm density.
29
WO 95130713 PCT/ITS95105757
Table 4
Film ComyosiHons, Fabrication Conditions and Film Properties
COMPOSITION E _ _ _ .
rr
COMPONENT (A)
Type HDPE HDPE HDPE HDPE MDPE MDPE MDPE MDPE
p~ym~~ p~ ~, r~~y gi~yy,g~.5.Soludon5oludonSotudonSoludon
-
Comonomer ButaneButaneHuteneButaneOctaneOctaneOctaneOctane
Iy gams/10 minutesQ26 026 026 0.26 5.1 5.1 5.1 5.1
Iy gnms/10 adnutes0.05 0.05 0.05 0.0$ t.0 L0 1.0 L0
Density, g/cc 0.9420.9420.9420942 0.935 0.9350.9350.935
121.6/11o 55 55 55 55 1.8 1.8 1.8 1.8
Itp/12 242 24.2 242 242 77 7.7 77 77
COMPONENT (B)
Type None None None None Norse None None None
Polymerlration _ _ _ . _ _ _ _
process
C~~~er _ _ _ _ _ _ _
lygams/lDatinutes_ _ _ _ _ _ _ _
-
1y gamsllD minutes_ _ _ _ _ _ _ _
D~,~ty,8/a _ _ _ _ _ _ _ _
Izt.s/tto _ _ _ _ _ _ _ _
11D/j2 _ _ _ _ _ _ _ _
(A)/DI) BLEND 100/0100/01D0/0100/0100/0 100/0100/0IOD/0
WT. percent
FABRICATION CONDITIONS
Annular DIe Diameter,113 113 113 113 152 152 152 152
mm
Extruder Diameter,70 70 7(1 70 64 64 64 64
mm
Extruder Lmgth/Diameter24/1 24/I 24/1 24/1 24/1 24/t 24/1 24/1
DieGep,mm 12 12 12 12 !b 1b 1.6 1.6
Output, kg/hr 77 100 100 100 64 64 64 64
Blow-Up Ratio 3.3/133/1 33/I 33/1 25/1 2.5/125/I 25/1
Stalk Height, 104 104 104 104 <I2.7 <127 <127 <127
~
Target Melt Temperature,213 213 213 213 213 2t3 213 213
C
PHYSICAL PROPERTIES
Film Tlddmess, 0.86 2.78 473 732 0.62 2.86 3.48 822
mils
CaLFHsDensity,g/a0.9420.9420.9420942 0.935 0.9350935 0.935
Composflion Iy 0.26 026 026 D26 5.1 5.1 5.1 5.1
g/lOmin.
CD Tear, gems 89 263 454 931 323 441 556 1359
MD Tear, gams 28 224 514 1054 31 305 333 1027
TearStratgth,gams59 244 484 993 171 3T3 445 1193
Impact Resistance,NA NA NA NA 50 165 185 505
gam
'Denotes Comparative Examples only, that Is, the examples are not examples of
the present invention. Cal. Film
Density denotes micvlated film density.
1~
WO 95130713
2 ~ 9 0 0 0 5 PCT/US95/05757
Table 5
Film Compositions, Fabrintion Conditions and Film Properties
COMPOSITION G H I J K L M N
EXAMPLE 25 26 27 28 29' 30' 31' 32' 33'
COMPONENT (A)
Type HDPE HDPEIiDPEHDPENoneMDPEHDPENoneHDPE
PolymairafionProcessSlurrySlurrySlurry_ SolutionSlurry- Slimy
Shury
Comonomer Butene ButeneButeneButene- OcteneButene- Butene
Iy g/10 min. 0.75 0.750.75 0.75- 5.1 0.75- 0.3
IZ g/10 min. 0.15 0.150.15 0.15- 1.0 0.15-
De<uaty,g/ 0.951 0.9510.9510.951- 0.9350.951- 0.950
It0/I2 NA NA NA NA - 7.7 NA - 24
COMPONENT B)
Type SLEP SLEPSLED SLEDSLEDNoneNoneLLDPENone
PolymerirationPmcessSolutionSolutionSolutionSolution- - Solution-
Solution
Contonomer Octane OctaneOctaneOctaneOctane- - Oetene-
Iy g/10 min. 5.1 5.1 5.7 5.1 5.1 - - 5.1 -
12, g/10 min. L0 1.0 1.D 1.0 1.0 - - 1.0 -
I)mtsity, g/ 0$70 0$700$70 0.8700.870- - 0.920-
170/12 7.4 7.4 7.4 7.4 7.4 - - 7.6 -
(A)J(B) BLEND IYT.75/2585/1590/100/100i00/0100/00/100100/0
80/20 ~
percent
FABRICATtON
CONDTTIONS
Annulu Die laameter,203 203 152 152 152 152 t52 113
mm 152
Fxtruder Diameter,89 89 64 64 64 64 64 70
mm 64
Fxtruder Length/Dlameter30/130/1 24/724/124/t24/124/124/1
24/1
Dle Gap, mm 1.6 2.8 2$ 1.6 1.6 1.6 1.6 1.6 12
Output, kg/hr 64 68 68 42 31 64 64 64 100
Hlow-Up Ratio 25/125/125/1 2.0/12.0/12.5/12.5/125/I3.3/1
Stalk Helgh4 mt <12.7<I27 <127d27 <I27<127<12.7104
<I2.7
VitonPmoesSingAid NoneNane NoneNoneYes NoneNoneNone
None
Extntder Amps 58 NA NA 58 NA 71 58 65 NA
Melt Temperature, 236 236 238 229 226 235 225 NA
C 229
Die Pressure, psi 34503450 465114170317034203130NA
3170
PHYSICAL PROPERTIES
Hlm Tlddmess atils3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0
3.0
Meas. Fdm Density,0.9360.9~ 0.9410$700.9350.9510.920.950
g/ 0.934
Compositionlyg/70m(n.7$ 1.4 12 5.1 5.1 0.755.1 030
1.6
CDTear,grams 324 73911826 464 91 328 80 1558228
MD Tear, grams 362 126 110 62 593 284 >1600125s
1419
Tear Strength, 876 976 287 77 461 182 1580177
grams 8T2
Impact Reslstan, 432 198 185 >850250 125 800 NA
grams 425
'Denotes Comparative Examples only, that is, the examples are not examples of
the present Invention.
Mess. Him Den9ty denotes measured film density. NA denotes data not available.
Viton is a fiuoropolymer
proarsing aid supplied by Dupont Chemical Company.
31
CA 02190005 2005-03-07
74069-221
Table 6
Film Compositions. Fabrication Conditions and Film Proptrties
COMPOSTriON P O R -S T U V . W
EXAMPLE 34 35 36 39 38 39 10 41'
COMPONENT (A)
Type HDPE HDPE HDPE HDPE HDPE HDPE HDPE RM-HDPE
Polymairation ProcessSlurryShnrySlvurySluaySlaa:y9vaayRubber
3urry
Coavanomver (or RubberButaveButeneButafeButeneButaneButenePblybutylene
Type) Butene
is gno ~. o.75 o.75 o.75 o.7s o.75 0.75 oaS os1
1~ g/10 min. 0.15 0.15 015 0.15 0.15 0.15 0.15 0.10
Density, g/ 0.951 0.9510951 0.9510.9510.9510951 0935
110/1Z NA NA NA NA NA NA NA NA
COMPONENT (B)
Type ~ ~ ULDPE LthDPESLEP SLEP SLED SLEP SLED None
Pblymalratiav PmoessSobaliotvSdvrtionSdutionSohationSa~ionSoiution-
Sdutiorv
Comotvomer Oetene OcteneOeteneOctaveOctaveOctaveOctave-
15,g/l0min. 4.1 4.1 4b 4b 5.1 5.1 4.6 -
ll, g/10 thin. 0.8 OB 0.9 0.9 1.0 1:0 0.9 - -
Dervsity, g/ 0.905 0.9050.8980.898Q909 0.9090.898-
l10/1~ 87 8.7 lOB 10.8 9.6 9b 70.8 -
COMPON1:NT (C)
Type None NotveNone None None None ULDPENone
p,~~~ p_ _ . _ _ _ Sa,v,~,v_
_ _ _ _ _ Octave-
Iy 8110 avin. _ _ _ _
4.1
l?, g/10 avin. . _ _ _ _ _ O,g -
Density, g/ _ _ . - _ - 0,905-
110/12 - _ _ _ _ _ _ 8.7 -
(A~B~(C) BLEND WT. 80/20/090/10/010/20/090/10/0!0/20/080/)0/10100/0
90/10/0
percent
FABRIGTION
COND1T10NS
Arunalar Die Daaovettr,152 152 152 152 15Z 152 152
avm 152
Extruder Dianveter, 64 64 64 64 61 64 64
avm 64
Extruder La~lv/Dlanveta24/1 24/1 24/1 34/1 24/1 24/1 24/1
24/1
Die Gap, avav 1.6 lb 1.6 1.6 lb 1 1.6 1.6
b
Output kg/ht 31 31 31 31 31 31 31 31
Blow-Up Ratio 2.0/1 2.0/120/1 2.0/12.0/12.0/120/I 2.0/1
Stalk Hdght, w <127 <12.T<12.?<12.7<12.7<12.T<I2? <12.7
Target Melt Teavperatvue,229 229 229 229 229 229 229
C 229
Die Preasae psi 417041?0 4170 4170 4170 4170 4170 4170
- PHYSIGL PROPERTIES
Fibs Thidavess, sails3.0 3:0 3:0 3.0 3D 3.0 3.0
3.0
Mess. Film Density, 0.9410950 0.9400.9450.9420.9410.934
g/ce 0.944
Cnmpositiotv Iy g/l0avirv.1.4 1.1 15 1.2 1b IS 051
1.1
CD Tear, grains 372 411 318 506 266 328 312 544
MD Tear, grams 115 138 114 131 94 112 110 110
Tavr Strength, ~ratns275 216 319 180 220 211 327
219
Iavpact Resisettce, 173 164 175 163 164 164 403
gams 175
'Denotes Comparstive Examples only, that is, the examples aro not examples of
the presavt invention. rM
Mess. Film Dervsity dmota measured filnv davsity. NA denotes dab root
avaBalite. RM-HDPE daates PAXON 3208
polybutylene rubber modified HDPE
32
WO 95!30713 ~ ~ ~ ~ ~. pCT/US95/05757
Table 7
Effect of Stalk Hei)5lit on Imyact Prayertiea
COMPOSITION Gt Gt
COMPONENT (A)
TYPe HDPE I-IDPE
PdymeriraHon Pmcess 9uxry Sturry
Comonomer Butene Butene
IS.g/lOmin. 0.75 0,75
I2, g/10 min.
0.t5 0.15
l~ty, g/ 0.951 0.951
I10/I2 NA NA
COMPONENT (B)
Ype SLEP SLEP
PdymetiaaNon Pmccg Solution Solution
Ca~mon~er Octane Octane
Iy g/t0 min.
5.1 5.1
I2, g/10 min. 1.D 1.0
~tY, 8/ 0970 0.870
170/12 7.4 7.4
(A)!(B) BLEND WT. 80/20 80/20
percent
FABRICATION CONDITIONS
Annular Die iameter,152 152
mm
ExrNda lhameter, 64 64
mm
Extruder Length/Diameter24/1 24/1
Die Gap, mm 2.8 2.8
Output, kg/hr 64 64
Blow-Up Ratio 25/1 2S/
1
Stalk Height cm <I27 102
Frost Line Height, 76 tZ7
~
Target Melt Temperature,232 I 232
C
PHY51CAL PROPERTTES
Thidmess,miLs 3.0 3.0
Mean Film Dmstty. g/« 0.934 ~ 0.934
Impact Resistance, grams 400 425
'1>enotes Comparative Examples only, that is, the examples are not examples of
the present
invention. Mess. Frlm Density denotes measured film density. NA denotes data
not available.
iDatotes Composition G is prepared in a mmmerdal-scale slurry polymniTation
manufachuing plant by skle-anti extrusion incorporation of the substanHaBy
liner
ethytene/a"olefin interpolymer,
1~
The physical property data in Tables 2 - 7 and Figures 2 - 4
demonstrate that films prepared in accordance with the present invention
exhibit substantially improved tear strength and impact resistance in
comparisons with other filins prepared from individual component
polymers that have the same film density, film thickness and similar melt
33
WO 95/30713 219 0 0 0 5 PCTIUS95105757
index. The tables also show Inventive Films exhibit superior tear strength
and impact resistance over PAXON 3208 (Comparative Example 41), a
polybutylene rubber modified HDPE used commercially for a variety of
heavy-duty packaging applications. The superior performance of the
Inventive Films of the present invention allow practitioners down-gauging
savings while still providing polyethylene films that meet the demanding
requirements of heavy-duty packaging.
Figure 2 specifically illustrates that Inventive Films prepared from
Composition A, B and C exhibit superior tear strength at film thicknesses
greater than 1.25 mils (31 microns), particularly in the range of 1.5 to 8.75
mils, and especially in the range of 2 mils to 8 mils in comparison to
Comparative Films prepared from Compositions D, E and F.
Figure 2 also shows Inventive Films comprising Components (A)
and (B) as well as those comprising Components (A), (B) and (C) as three-
component blends, exhibit exceptional comparative tear performance. A
comparison between the Inventive Films prepared using Compositions B
and C indicates a substantially linear ethylene/a-olefin interpolymer,
Component (B), having an hp/Iy ratio less than about 10 is most preferred
for film thicknesses greater than about 3 mils. In direct comparisons,
Inventive Films show from 30 percent greater tear strength at 3 mils
(comparison between films based on Compositions B and D) to as high as
about 180 percent greater tear strength at 5 mils (comparison between films
based on Compositions C and E).
Figure 3 shows at equivalent densities, Inventive Films (Inventive
Examples 25-28 and 34-38) exhibit superior impact resistance at 3 mils over
Comparative Films (Comparative Examples 22 and 30-32 where
Comparative Examples 22 and 30 are averaged and plotted as a single data
point). Figure 3 also indicates Inventive Examples 25 and 26 show more
34
WO 95!30713 2 1 9 0.0 0 5
PCTIUS95105757
than 100 percent greater impact resistance than is ordinarily expected for
their respective measured densities. These Inventive Films also indicate
that substantially linear ethylene/a-olefin interpolymers, Component (B),
having densities less than 0.89 g/cc are most preferred for preparing the
novel film of the present invention.
Figure 4 illustrates Inventive Examples 25, 26 and 27 exhibit
synergistically superior tear strength relative to predicated or calculated
performance based on their respective component polymers, a 0.951 g/cc
HMW-HDPE and a 0.87 g/cc SLEP at 100 percent/0 percent, 90 percent/10
percent, 80 percent/20, 70 percent/30 percent and 0 percent/100 percent,
respectively. Figure 4 also shows that Inventive Films can exhibit more
than about 90 percent greater tear strength than comparative films having
about the same melt index, film thickness and measured film density.
Table 7 specifically indicates, although low-stalls and pocket extrusion
I5 are preferred for fabricating Inventive Film comprising a Component (A)
polymer having a IS greater than 0.5 g/10 minutes, Inventive Films can also
be successfully fabricated using variable-stalk extrusion, that is pocket and
stalk extrusion. Even more surprisingly, is these Inventive Examples
indicate the novel film can be fabricated with a high-stalk on conventional
pocket extrusion lines. This feature of the invention allows Practitioners
the significant commercial benefits of equipment selection flexibility and
equipment utilization efficiency.
n s~ ' ~tx~ ~,; ;~; !.i','~' ~;,. .
.) r~~
