U.S. patent application number 14/183954 was filed with the patent office on 2015-08-20 for multilayered polyolefin films, methods of manufacture thereof and articles comprising the same.
The applicant listed for this patent is Dow Global Technologies LLC. Invention is credited to Sharon L. Baker, Christopher I. Gandy, Yushan Hu, Lori L. Kardos, Gary R. Marchand, Rajen M. Patel.
Application Number | 20150231862 14/183954 |
Document ID | / |
Family ID | 52598833 |
Filed Date | 2015-08-20 |
United States Patent
Application |
20150231862 |
Kind Code |
A1 |
Hu; Yushan ; et al. |
August 20, 2015 |
MULTILAYERED POLYOLEFIN FILMS, METHODS OF MANUFACTURE THEREOF AND
ARTICLES COMPRISING THE SAME
Abstract
Disclosed herein is a multilayer film comprising two outer
layers; where each outer layer comprises polyethylene; two tie
layers; where each tie layer comprises a crystalline block
copolymer composite; where each tie layer has a first face and a
second face that are opposed to each other, and where the first
face of each tie layer contacts at least one outer layer; and a
core layer; where the core layer comprises a polypropylene; where
the second face of each tie layer contacts the core layer.
Disclosed herein is a method comprising coextruding a multilayered
film comprising two outer layers; where each outer layer comprises
polyethylene; two tie layers; where each tie layer comprises a
crystalline block copolymer composite; where each tie layer has a
first face and a second face that are opposed to each other, and
where the first face of each tie layer contacts at least one outer
layer; and a core layer; where the core layer comprises a
polypropylene; where the second face of each tie layer contacts the
core layer; and coextruding the multilayered blown film.
Inventors: |
Hu; Yushan; (Pearland,
TX) ; Patel; Rajen M.; (Lake Jackson, TX) ;
Marchand; Gary R.; (Gonzales, LA) ; Baker; Sharon
L.; (Lake Jackson, TX) ; Gandy; Christopher I.;
(Chicago, IL) ; Kardos; Lori L.; (Sugar Land,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dow Global Technologies LLC |
Midland |
MI |
US |
|
|
Family ID: |
52598833 |
Appl. No.: |
14/183954 |
Filed: |
February 19, 2014 |
Current U.S.
Class: |
428/516 ;
264/510 |
Current CPC
Class: |
B32B 2323/10 20130101;
B32B 2323/04 20130101; B32B 7/12 20130101; B29C 48/21 20190201;
B29C 49/02 20130101; B32B 2270/00 20130101; B32B 2307/558 20130101;
B32B 27/32 20130101; B29K 2023/06 20130101; B32B 2250/05 20130101;
B32B 2250/242 20130101; B32B 2250/40 20130101; B29C 48/40 20190201;
B29K 2023/12 20130101; B32B 2307/546 20130101; B32B 2439/70
20130101; B29L 2009/00 20130101; B29L 2031/7128 20130101; B29K
2995/0077 20130101; B32B 27/08 20130101; B32B 2307/704 20130101;
B32B 2439/00 20130101; B29C 48/185 20190201; Y10T 428/31913
20150401; B29C 49/04 20130101; B32B 2274/00 20130101; B32B 2439/46
20130101; B32B 2307/54 20130101; B29C 48/22 20190201 |
International
Class: |
B32B 27/08 20060101
B32B027/08; B32B 7/12 20060101 B32B007/12; B29C 49/02 20060101
B29C049/02; B32B 27/32 20060101 B32B027/32 |
Claims
1. A multilayer film comprising: two outer layers; where each outer
layer comprises polyethylene; two tie layers; where each tie layer
comprises a crystalline block copolymer composite; where each tie
layer has a first face and a second face that are opposed to each
other, and where the first face of each tie layer contacts at least
one outer layer; and a core layer; where the core layer comprises a
polypropylene; where the second face of each tie layer contacts the
core layer.
2. The multilayer film of claim 1, where the polyethylene comprises
a linear low density polyethylene or an ethylene-.alpha.-olefin
copolymer.
3. The multilayer film of claim 2, where the linear low density
polyethylene in each outer layer has a melt index I.sub.2 of 0.25
to 2.5 g/10 minutes when measured as per ASTM D 1238 at 190.degree.
C. and 2.16 kg.
4. The multilayer film of claim 2, where the
ethylene-.alpha.-olefin copolymer is ethylene/propylene,
ethylene/butene, ethylene/1-hexene, ethylene/1-octene,
ethylene/styrene, ethylene/propylene/1-octene,
ethylene/propylene/butene, ethylene/butene/1-octene,
ethylene/butene/styrene, or a combination comprising at least one
of the foregoing ethylene-.alpha.-olefin copolymers.
5. The multilayer film of claim 3, where the outer layer further
comprises low density polyethylene and/or high density
polyethylene.
6. The multilayer film of claim 4, where the outer layer further
comprises low density polyethylene and/or high density
polyethylene.
7. The multilayer film of claim 1, where the crystalline block
copolymer composite comprises a crystalline ethylene based polymer,
a crystalline alpha-olefin based polymer, and a block copolymer
comprising a crystalline ethylene block and a crystalline
alpha-olefin block, wherein the crystalline ethylene block of the
block copolymer is the same composition as the crystalline ethylene
based polymer in the block composite and the crystalline
alpha-olefin block of the block copolymer is the same composition
as the crystalline alpha-olefin based polymer of the block
composite.
8. The multilayer film of claim 1, where each tie layer further
comprises an elastomer; and where the elastomer is a homogeneously
branched ethylene-.alpha.-olefin copolymer, a polyolefin elastomer,
a vinyl aromatic block copolymer, or a combination comprising at
least one of the foregoing elastomers.
9. The multilayer film of claim 8, where each tie layer further
comprises polypropylene and/or polyethylene.
10. The multilayer film of claim 1, where the polypropylene is
selected from the groups consisting of random copolymer
polypropylene, impact copolymer polypropylene, high impact
polypropylene, high melt strength polypropylene, isotactic
polypropylene, syndiotactic polypropylene, or a combination
comprising at least one of the foregoing polypropylenes.
11. The multilayer film of claim 10, where the core layer further
comprises polyethylene or an elastomer; and where the elastomer is
a homogeneously branched ethylene-.alpha.-olefin copolymer, a
polyolefin elastomer, a vinyl aromatic block copolymer, or a
combination comprising at least one of the foregoing
elastomers.
12. The multilayer film of claim 1, where the crystalline block
composite has a melt flow ratio 0.1 to 30 dg/min, when measured as
per ASTM D 1238 at 230.degree. C. and 2.16 kilograms.
13. The multilayer film of claim 1, where the crystalline block
composite comprises 5 to 95 weight percent crystalline ethylene
blocks and 95 to 5 wt percent crystalline alpha-olefin blocks.
14. The multilayer film of claim 1, where the crystalline block
composite has a crystalline block composite index of 0.3 to
1.0.
15. An article comprising the multilayer film of claim 1.
16. A method comprising: coextruding a multilayered film
comprising: two outer layers; where each outer layer comprises
polyethylene; two tie layers; where each tie layer comprises a
crystalline block copolymer composite; where each tie layer has a
first face and a second face that are opposed to each other, and
where the first face of each tie layer contacts at least one outer
layer; and a core layer; where the core layer comprises a
polypropylene; where the second face of each tie layer contacts the
core layer; and blowing the multilayered film.
17. The method of claim 16, further comprising laminating the film
in a roll mill.
Description
BACKGROUND
[0001] This disclosure relates to multilayered polyolefin films,
methods of manufacture thereof and to articles comprising the
same.
[0002] Multilayered films are widely used as heavy duty shipping
sacks for bagging bulk products such as chemicals, polymers,
fertilizers and animal food. These multilayers are often
polyethylene based, combining high density polyethylene (HDPE) as
stiffening layer and metallocene linear low density polyethylene
(LLDPE) sealant layer for sealability and toughness. Combinations
of different type of polyethylenes layers and proper layer ratio
selection offers desirable properties such as stiffness for
mechanical strength and machineability (i.e., bag filling
operation), toughness (good machine direction tear and dart drop)
and sealability (good heat seal property). For polyethylene based
multilayered films, incorporating more HDPE increases stiffness.
However, the tear resistance in the machine direction (MD) is
reduced. There therefore exists a need for improved high stiffness,
high toughness multilayer films and heavy duty packaging in order
to reduce the multilayered film thickness.
SUMMARY
[0003] Disclosed herein is a multilayer film comprising two outer
layers; where each outer layer comprises polyethylene; two tie
layers; where each tie layer comprises a crystalline block
copolymer composite; where each tie layer has a first face and a
second face that are opposed to each other, and where the first
face of each tie layer contacts at least one outer layer; and a
core layer; where the core layer comprises a polypropylene; where
the second face of each tie layer contacts the core layer.
[0004] Disclosed herein is a method comprising coextruding a
multilayered film comprising two outer layers; where each outer
layer comprises polyethylene; two tie layers; where each tie layer
comprises a crystalline block copolymer composite; where each tie
layer has a first face and a second face that are opposed to each
other, and where the first face of each tie layer contacts at least
one outer layer; and a core layer; where the core layer comprises a
polypropylene; where the second face of each tie layer contacts the
core layer; and blowing the multilayered film.
BRIEF DESCRIPTION OF THE FIGURES
[0005] FIG. 1 depicts an exemplary embodiment of the multilayered
film; and
[0006] FIG. 2 depicts an exemplary embodiment of a multilayered
film that comprises two multilayered films of the FIG. 1 that are
coextruded or laminated together.
DETAILED DESCRIPTION
[0007] "Composition" and like terms mean a mixture of two or more
materials, such as a polymer which is blended with other polymers
or which contains additives, fillers, or the like. Included in
compositions are pre-reaction, reaction and post-reaction mixtures
the latter of which will include reaction products and by-products
as well as unreacted components of the reaction mixture and
decomposition products, if any, formed from the one or more
components of the pre-reaction or reaction mixture.
[0008] "Blend", "polymer blend" and like terms mean a composition
of two or more polymers. Such a blend may or may not be miscible.
Such a blend may or may not be phase separated. Such a blend may or
may not contain one or more domain configurations, as determined
from transmission electron spectroscopy, light scattering, x-ray
scattering, and any other method known in the art. Blends are not
laminates, but one or more layers of a laminate may contain a
blend.
[0009] "Polymer" means a compound prepared by polymerizing
monomers, whether of the same or a different type. The generic term
polymer thus embraces the term homopolymer, usually employed to
refer to polymers prepared from only one type of monomer, and the
term interpolymer as defined below. It also embraces all forms of
interpolymers, e.g., random, block, etc. The terms
"ethylene/a-olefin polymer" and "propylene/a-olefin polymer" are
indicative of interpolymers as described below. It is noted that
although a polymer is often referred to as being "made of"
monomers, "based on" a specified monomer or monomer type,
"containing" a specified monomer content, or the like, this is
obviously understood to be referring to the polymerized remnant of
the specified monomer and not to the unpolymerized species.
[0010] "Interpolymer" means a polymer prepared by the
polymerization of at least two different monomers. This generic
term includes copolymers, usually employed to refer to polymers
prepared from two or more different monomers, and includes polymers
prepared from more than two different monomers, e.g., terpolymers,
tetrapolymers, etc.
[0011] "Polyolefin", "polyolefin polymer", "polyolefin resin" and
like terms mean a polymer produced from a simple olefin (also
called an alkene with the general formula C.sub.nH.sub.2n) as a
monomer. Polyethylene is produced by polymerizing ethylene with or
without one or more comonomers, polypropylene by polymerizing
propylene with or without one or more comonomers, etc. Thus,
polyolefins include interpolymers such as ethylene-.alpha.-olefin
copolymers, propylene-.alpha.-olefin copolymers, etc.
[0012] "Melting Point" as used here (also referred to a melting
peak in reference to the shape of the plotted DSC curve) is
typically measured by the DSC (Differential Scanning calorimetry)
technique for measuring the melting points or peaks of polyolefins
as described in U.S. Pat. No. 5,783,638. It should be noted that
many blends comprising two or more polyolefins will have more than
one melting point or peak; many individual polyolefins will
comprise only one melting point or peak.
[0013] The term `and/or" includes both "and" as well as "or". For
example, the term A and/or B is construed to mean A, B or A and
B.
[0014] Disclosed herein is a multilayered film that comprises a
plurality of layers and that can be used as heavy duty shipping
sacks for bagging a variety of different bulk products. The
multilayer film comprises at least five layers--a first layer or an
outer layer that comprises polyethylene, a second layer, which is a
tie layer that comprises a diblock polymer, a third layer (also
called a core layer) that comprises polypropylene, a fourth layer,
which is also a tie layer that comprises a diblock polymer, and a
fifth layer (also an outer layer that is opposedly disposed to the
first layer) that comprises polyethylene. The presence of a core
layer that comprises polypropylene in the multilayered film
provides it with improved stiffness, high creep resistance, high
temperature performance and oil/crease resistance, which enables
the multilayered film to be used for bagging and shipping large
masses of material or products. In another exemplary embodiment,
the core layer has a thickness that is less than 20% of the
thickness of the multilayered film.
[0015] FIG. 1 depicts the multilayered film 100 that comprises the
first layer or outer layer 102, the second layer or tie layer 104,
the third layer or core layer 106, the tie layer 108 and the fifth
layer 110. In one embodiment, the multilayered film 100 has a
symmetrical structure about a center line drawn through the length
of the film. While the FIG. 1 depicts a single 5-layered
multilayered film, commercial embodiments of the film can include
multiples of the 5-layered multilayered film. For example, a single
multilayered film can contain 2 or more 5-layered multilayered
films that contact each other. In one embodiment, a single
multilayered film can have 2 to 10 5-layered multilayered films,
specifically 2 to 8 multilayered films, and more specifically 2 to
5 multilayered films that contact each other. In an exemplary
embodiment, the plurality of multilayered films are coextruded. In
another exemplary embodiment, the plurality of multilayered films
are bonded together using an adhesive layer.
[0016] As may be seen in the FIG. 1, the first layer 102 and the
fifth layer 110 are outer layers or skin layers that are disposed
at opposing ends of the multilayered film and comprise a
polyethylene. The following description will refer to the first
layer 102 and the fifth layer 110 collectively as outer layers. The
polyethylene is selected from ultralow density polyethylene
(ULDPE), low density polyethylene (LDPE), linear low density
polyethylene (LLDPE), medium density polyethylene (MDPE), high
density polyethylene (HDPE), high melt strength high density
polyethylene (HMS-HDPE), ultrahigh density polyethylene (UHDPE),
and combinations thereof. In a further embodiment, the polyethylene
has a density greater than 0.950 g/cc (i.e., a HDPE). The
combinations can include blends, copolymers and blends of
copolymers. In an exemplary embodiment, the polyethylene used in
the outer layers is a linear low density polyethylene, an
ethylene-.alpha.-olefin copolymer, or a combination thereof. When
the outer layers comprise a linear low density polyethylene, an
ethylene-.alpha.-olefin copolymer, or a combination thereof, they
may also optionally contain a LDPE and/or HDPE.
[0017] In an exemplary embodiment, the outer layers 102 and 110
comprise linear low density polyethylene (LLDPE). LLDPE is a
copolymer (also referred to as an interpolymer) of ethylene and an
.alpha.-olefin having 3 to 12 carbon atoms, specifically 4 to 8
carbon atoms (e.g., propene, 1 butene, 4-methyl-1-pentene,
1-hexene, 1 octene, 1-decene, and the like), that has sufficient
.alpha.-olefin content to reduce the density of the copolymer to
that of LDPE. The term "LLDPE", includes both--resin manufactured
using the traditional Ziegler-Natta catalyst systems as well as
single-site catalysts such as metallocenes (sometimes referred to
as "m-LLDPE"). LLDPEs contain less long chain branching than LDPEs
and includes the substantially linear ethylene polymers which are
further defined in U.S. Pat. No. 5,272,236, U.S. Pat. No.
5,278,272, U.S. Pat. No. 5,582,923 and U.S. Pat. No. 5,733,155; the
homogeneously branched linear ethylene polymer compositions such as
those in U.S. Pat. No. 3,645,992; the heterogeneously branched
ethylene polymers such as those prepared according to the processes
disclosed in U.S. Pat. No. 4,076,698; and/or blends thereof (such
as those disclosed in U.S. Pat. No. 3,914,342 or U.S. Pat. No.
5,854,045). The LLDPE can be made by any process such as gas phase
polymerization, solution phase polymerization, slurry
polymerization or combinations thereof.
[0018] In one embodiment, the LLDPE used in the outer layers 102
and 100 comprises the linear low density polyethylene having a melt
index I.sub.2 of 0.25 to 2.5 g/10 minutes when measured as per ASTM
D 1238 at 190.degree. C. and 2.16 kg. An exemplary LLDPE for use in
the outer layers 102 and 110 is ELITE.TM. 5100, which is an
ethylene-octene copolymer with melt index of 0.85 g/10 min
(measured as per ASTM D1238 at 190.degree. C. and 2.16 kg), density
0.920 g/cc (measured as per ASTM D 792), polydispersity index (PDI)
Mw/Mn=3.45 and Mw=130,300 grams per mole, and commercially
available from The Dow Chemical Company. Other exemplary LLDPE's
that can be used in the outer layers 102 and 110 are linear
ethylene-based polymers such as DOWLEX.TM. Polyethylene Resins,
ELITE.TM. and ELITE AT.TM. brand enhanced polyethylene resin, all
available from The Dow Chemical Company, and EXCEED.TM. metallocene
polyethylenes, available from ExxonMobil Chemical Company.
[0019] Another exemplary polyethylene for use in the outer layers
is homogeneously branched ethylene-.alpha.-olefin copolymers. These
copolymers can be made with a single-site catalyst such as a
metallocene catalyst or constrained geometry catalyst, and
typically have a melting point of less than 105, specifically less
than 90, more specifically less than 85, even more specifically
less than 80 and still more specifically less than 75.degree. C.
The melting point is measured by differential scanning calorimetry
(DSC) as described, for example, in U.S. Pat. No. 5,783,638. The
.alpha.-olefin is preferably a C.sub.3-20 linear, branched or
cyclic .alpha.-olefin. Examples of C.sub.3-20 .alpha.-olefins
include propene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene,
1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and
1-octadecene. The .alpha.-olefins can also contain a cyclic
structure such as cyclohexane or cyclopentane, resulting in an
.alpha.-olefin such as 3-cyclohexyl-1-propene (allyl cyclohexane)
and vinyl cyclohexane.
[0020] Illustrative homogeneously branched ethylene-.alpha.-olefin
copolymers include ethylene/propylene, ethylene/butene,
ethylene/l-hexene, ethylene/l-octene, ethylene/styrene, and the
like. Illustrative terpolymers include ethylene/propylene/l-octene,
ethylene/propylene/butene, ethylene/butene/1-octene, and
ethylene/butene/styrene. The copolymers can be random copolymers or
block copolymers.
[0021] Examples of commercially available homogeneously branched
ethylene-.alpha.-olefin interpolymers useful in the outer layers
102 and 110 include homogeneously branched, linear
ethylene-.alpha.-olefin copolymers (e.g. TAFMER.RTM. by Mitsui
Petrochemicals Company Limited and EXACT.RTM. by Exxon Chemical
Company), and the homogeneously branched, substantially linear
ethylene-.alpha.-olefin polymers (e.g., AFFINITY.TM. and ENGAGE.TM.
polyethylene available from the Dow Chemical Company). Blends of
any of these interpolymers can also be used in the outer layers 102
and 110. An exemplary ethylene-.alpha.-olefin copolymer that may be
used in the outer layers 102 and 110 is AFFINITY PL1880G,
commercially available from the Dow Chemical Company.
[0022] Low density polyethylene (LDPE) may also be used in the
outer layers 102 and 110. The term "LDPE" may also be referred to
as "high pressure ethylene polymer" or "highly branched
polyethylene" and is defined to mean that the polymer is partly or
entirely homopolymerized or copolymerized in autoclave or tubular
reactors at pressures above 14,500 psi (100 MPa) with the use of
free-radical initiators, such as peroxides. LDPE and the methods of
manufacturing LDPE are described in U.S. Pat. No. 4,599,392,
incorporated herein in its entirety by reference.
[0023] The preferred LDPE for use in the outer layers 102 and 110
has a density in the range of from 0.915 to 0.930 g/cm.sup.3 and a
melt index of from 0.1 to 2.5 g/10 min, preferably less than or
equal to 1 g/10 min.
[0024] High density polyethylene (HDPE) can also be used in the
outer layers 102 and 110. The term "HDPE" refers to polyethylenes
having densities greater than about 0.940 g/cm3, which are
generally prepared with Ziegler-Natta catalysts, chrome catalysts
or even metallocene catalysts. The HDPE has a melt index of from
0.4 to 2.5 g/10 min.
[0025] In one embodiment, the outer layers 102 and 110 can comprise
a blend of LLDPE and LDPE, LLDPE and HDPE or a combination of LLDPE
with LDPE and HDPE. When the outer layer comprise LLDPE with LDPE
and/or HDPE, the LLDPE is used in an amount of 25 to 95 wt %,
specifically 40 to 90 wt %, based on the total weight of the outer
layer. The LDPE and/or HDPE may be used in amounts of 5 to 75 wt %,
specifically 10 to 60 wt %, based on the total weight of the outer
layer.
[0026] Each of the outer layers 102 and 110 has a thickness of 20
to 44%, specifically 30 to 40%, of the total thickness of the
multilayer film 100.
[0027] The tie layers 104 and 108 are disposed on opposing sides of
the third layer 106. With reference to the FIG. 1, each tie layer
104 and 108 has a first face and a second face that are on opposite
sides of the tie layer. The tie layer 104 has a first face 103 that
contacts the outer layer 102 and a second face 105 (that is
opposedly disposed to the first face 103) that contacts the core
layer 106. The tie layer 108 has a first face 109 that contacts the
outer layer 110 and a second face 107 (that is opposedly disposed
to the first face 109) that contacts the core layer 106. The tie
layers 104 and 108 are operative to bond the outer layers 102 and
110 respectively to the core layer 106.
[0028] The tie layers 104 and 108 each comprise a crystalline block
copolymer composite. In addition to the crystalline block copolymer
composite, the tie layers 104 and 108 can optionally comprise
either an ethylene-.alpha.-olefin copolymer or a polyolefin that
comprises polypropylene and polyethylene.
[0029] Each of the tie layers comprises a crystalline block
copolymer composite (CBC). The term "crystalline block composite"
(CBC) refers to polymers having three components: a crystalline
ethylene based polymer (CEP) (also referred to herein as a soft
polymer), a crystalline alpha-olefin based polymer (CAOP) (also
referred to herein as a hard polymer), and a block copolymer
comprising a crystalline ethylene block (CEB) and a crystalline
alpha-olefin block (CAOB), wherein the CEB of the block copolymer
is the same composition as the CEP in the block composite and the
CAOB of the block copolymer is the same composition as the CAOP of
the block composite. Additionally, the compositional split between
the amount of CEP and CAOP will be essentially the same as that
between the corresponding blocks in the block copolymer. When
produced in a continuous process, the crystalline block composites
desirably have a polydispersity index (PDI) from 1.7 to 15,
specifically 1.8 to 10, specifically from 1.8 to 5, more
specifically from 1.8 to 3.5. Such crystalline block composites are
described in, for example, US Patent Application Publication Nos.
2011/0313106, 2011/0313108 and 2011/0313108, all published on Dec.
22, 2011, incorporated herein by reference with respect to
descriptions of the crystalline block composites, processes to make
them and methods of analyzing them.
[0030] CAOB refers to highly crystalline blocks of polymerized
alpha olefin units in which the monomer is present in an amount
greater than 90 mol percent, specifically greater than 93 mol
percent, more specifically greater than 95 mol percent, and
specifically greater than 96 mol percent. In other words, the
comonomer content in the CAOBs is less than 10 mol percent, and
specifically less than 7 mol percent, and more specifically less
than 5 mol percent, and most specifically less than 4 mol %. CAOBs
with propylene crystallinity have corresponding melting points that
are 80.degree. C. and above, specifically 100.degree. C. and above,
more specifically 115.degree. C. and above, and most specifically
120.degree. C. and above. In some embodiments, the CAOB comprise
all or substantially all propylene units. CEB, on the other hand,
refers to blocks of polymerized ethylene units in which the
comonomer content is 10 mol % or less, specifically between 0 mol %
and 10 mol %, more specifically between 0 mol % and 7 mol % and
most specifically between 0 mol % and 5 mol %. Such CEB have
corresponding melting points that are specifically 75.degree. C.
and above, more specifically 90.degree. C., and 100.degree. C. and
above.
[0031] In one embodiment, the crystalline block composite polymers
comprise propylene, 1-butene or 4-methyl-1-pentene and one or more
comonomers. Specifically, the block composites comprise in
polymerized form propylene and ethylene and/or one or more
C.sub.4-20 .alpha.-olefin comonomers, and/or one or more additional
copolymerizable comonomers or they comprise 4-methyl-1-pentene and
ethylene and/or one or more C.sub.4-20 .alpha.-olefin comonomers,
or they comprise 1-butene and ethylene, propylene and/or one or
more C.sub.5-C.sub.20 .alpha.-olefin comonomers and/or one or more
additional copolymerizable comonomers. Additional suitable
comonomers are selected from diolefins, cyclic olefins, and cyclic
diolefins, halogenated vinyl compounds, and vinylidene aromatic
compounds. Preferably, the monomer is propylene and the comonomer
is ethylene.
[0032] Comonomer content in the crystalline block composite
polymers may be measured using any suitable technique, with
techniques based on nuclear magnetic resonance (NMR) spectroscopy
preferred.
[0033] The block composites and crystalline block composites have a
melting point Tm greater than 100.degree. C. specifically greater
than 120.degree. C., and more specifically greater than 125.degree.
C. In an embodiment, the Tm is in the range of from 100.degree. C.
to 250.degree. C., more specifically from 120.degree. C. to
220.degree. C. and also specifically in the range of from
125.degree. C. to 220.degree. C. Specifically the melt flow ratio
(MFR) of the block composites and crystalline block composites is
from 0.1 to 1000 dg/min, more specifically from 0.1 to 50 dg/min
and more specifically from 0.1 to 30 dg/min.
[0034] In an embodiment, the block composites and crystalline block
composites have a weight average molecular weight (Mw) from 10,000
to about 2,500,000 grams per mole (g/mole), specifically from 35000
to about 1,000,000 and more specifically from 50,000 to about
300,000, specifically from 50,000 to about 200,000 g/mole.
[0035] The crystalline block composite polymers comprise 0.5 to 95
wt % soft copolymer, from 0.5 to 95 wt % hard polymer and from 5 to
99 wt % block copolymer. More specifically, the crystalline block
composite polymers comprise from 0.5 to 79 wt % soft copolymer,
from 0.5 to 79 wt % hard polymer and from 20 to 99 wt % block
copolymer and more specifically from 0.5 to 49 wt % soft copolymer,
from 0.5 to 49 wt % hard polymer and from 50 to 99 wt % block
copolymer. Weight percents are based on total weight of crystalline
block composite. The sum of the weight percents of soft copolymer,
hard polymer and block copolymer equals 100%.
[0036] In an embodiment, the crystalline block composite polymers
comprises 0.5 to 95 wt % CEP, from 0.5 to 95 wt % CAOP and from 5
to 99 wt % block copolymer. More specifically, the crystalline
block composite polymers comprise 0.5 to 79 wt % CEP, 0.5 to 79 wt
% CAOP and 20 to 99 wt % block copolymer and more specifically 0.5
to 49 wt % CEP, 0.5 to 49 wt % CAOP and 50 to 99 wt % block
copolymer. Weight percents are based on total weight of crystalline
block composite. The sum of the weight percents of CEP, CAOP and
block copolymer equals 100%.
[0037] In an embodiment, the block copolymers of the crystalline
block composite comprise from 5 to 95 weight percent crystalline
ethylene blocks (CEB) and 95 to 5 wt percent crystalline
alpha-olefin blocks (CAOB). They may comprise 10 wt % to 90 wt %
CEB and 90 wt % to 10 wt % CAOB. More specifically, the block
copolymers comprise 25 to 75 wt % CEB and 75 to 25 wt % CAOB, and
even more specifically comprise 30 to 70 wt % CEB and 70 to 30 wt %
CAOB.
[0038] In some embodiments, the crystalline block composites have a
Crystalline Block Composite Index (CBCI that is greater than zero
but less than about 0.4 or from 0.1 to 0.3. In other embodiments,
CBCI is greater than 0.4 and up to 1.0. In some embodiments, the
CBCI is 0.1 to 0.9, from about 0.1 to about 0.8, from about 0.1 to
about 0.7 or from about 0.1 to about 0.6. Additionally, the CBCI
can be in the range of from about 0.4 to about 0.7, from about 0.5
to about 0.7, or from about 0.6 to about 0.9. In some embodiments,
CBCI is in the range of from about 0.3 to about 0.9, from about 0.3
to about 0.8, or from about 0.3 to about 0.7, from about 0.3 to
about 0.6, from about 0.3 to about 0.5, or from about 0.3 to about
0.4. In other embodiments, CBCI is in the range of from about 0.4
to about 1.0, from about 0.5 to about 1.0, or from about 0.6 to
about 1.0, from about 0.7 to about 1.0, from about 0.8 to about
1.0, or from about 0.9 to about 1.0.
[0039] The tie layers 104 and 108 may also comprise in addition to
the crystalline block composite (CBC), an optional elastomer and/or
an optional polypropylene or polyethylene. The optional elastomer
can be an ethylene-.alpha.-olefin copolymer (which is already
detailed above), a polyolefin elastomer (e.g., a propylene based
elastomer), a vinyl aromatic block copolymer, or the like, or a
combination comprising at least one of the foregoing
elastomers.
[0040] The polyolefin elastomers may also comprise random or block
propylene polymers (i.e., polypropylenes). The random polypropylene
elastomer typically comprises 90 or more mole percent units derived
from propylene. The remainder of the units in the propylene
copolymer is derived from units of at least one .alpha.-olefin.
[0041] The .alpha.-olefin component of the propylene copolymer is
preferably ethylene (considered an .alpha.-olefin for purposes of
this invention) or a C.sub.4-20 linear, branched or cyclic
.alpha.-olefin. Examples of C.sub.4-20 .alpha.-olefins include
1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene,
1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene. The
.alpha.-olefins also can contain a cyclic structure such as
cyclohexane or cyclopentane, resulting in an .alpha.-olefin such as
3-cyclohexyl-1-propene (allyl cyclohexane) and vinyl cyclohexane.
Although not .alpha.-olefins in the classical sense of the term,
certain cyclic olefins, such as norbornene and related olefins,
particularly 5-ethylidene-2-norbornene, are .alpha.-olefins and can
be used in place of some or all of the .alpha.-olefins described
above. Similarly, styrene and its related olefins (for example,
.alpha.-methylstyrene, and the like) are .alpha.-olefins for
purposes of this invention. Illustrative random propylene
copolymers include but are not limited to propylene/ethylene,
propylene/l-butene, propylene/l-hexene, propylene/l-octene, and the
like. Illustrative terpolymers include ethylene/propylene/l-octene,
ethylene/propylene/l-butene, and ethylene/propylene/diene monomer
(EPDM).
[0042] In one embodiment the random polypropylene copolymer has a
T.sub.m greater than 120.degree. C., and/or a heat of fusion
greater than 70 J/g (both measured by DSC) and preferably, but not
necessarily, made via Ziegler-Natta catalysis.
[0043] In another embodiment, the polyolefin elastomer is a
propylene-.alpha.-olefin interpolymer and is characterized as
having substantially isotactic propylene sequences. The
propylene-.alpha.-olefin interpolymers include propylene-based
elastomers (PBE). "Substantially isotactic propylene sequences"
means that the sequences have an isotactic triad (mm) measured by
.sup.13C NMR of greater than 0.85; in the alternative, greater than
0.90; in another alternative, greater than 0.92; and in another
alternative, greater than 0.93. Isotactic triads are well-known in
the art and are described in, for example, U.S. Pat. No. 5,504,172
and International Publication No. WO 00/01745, which refers to the
isotactic sequence in terms of a triad unit in the copolymer
molecular chain determined by .sup.13C NMR spectra.
[0044] The propylene-.alpha.-olefin copolymer comprises units
derived from propylene and polymeric units derived from one or more
.alpha.-olefin comonomers. Exemplary comonomers utilized to
manufacture the propylene-.alpha.-olefin copolymer are C.sub.2 and
C.sub.4 to C.sub.10 .alpha.-olefins; for example, C.sub.2, C.sub.4,
C.sub.6 and C.sub.8 .alpha.-olefins.
[0045] The propylene-.alpha.-olefin interpolymer comprises 1 to 40
percent by weight of one or more alpha-olefin comonomers. All
individual values and sub-ranges from 1 to 40 weight percent are
included herein and disclosed herein. The propylene-.alpha.-olefin
interpolymer may have a melt flow rate in the range of 0.1 to 500
grams per 10 minutes (g/10 min), measured in accordance with ASTM
D-1238 (at 230.degree. C./2.16 Kg). The propylene-.alpha.-olefin
interpolymer has crystallinity in the range of from at least 1
percent by weight (a heat of fusion (H.sub.f) of at least 2
Joules/gram (J/g)) to 30 percent by weight (a H.sub.f of less than
50 J/g). The propylene-.alpha.-olefin interpolymer has a density of
typically less than 0.895 g/cm.sup.3. The propylene-.alpha.-olefin
interpolymer has a melting temperature (T.sub.m) of less than
120.degree. C. and a heat of fusion (H.sub.f) of less than 70
Joules per gram (J/g) as measured by differential scanning
calorimetry (DSC) as described in U.S. Pat. No. 7,199,203. The
propylene-.alpha.-olefin interpolymer has a molecular weight
distribution (MWD), defined as weight average molecular weight
divided by number average molecular weight (Mw/Mn) of 3.5 or less;
or 3.0 or less; or from 1.8 to 3.0.
[0046] Such propylene-.alpha.-olefin interpolymers are further
described in the U.S. Pat. Nos. 6,960,635 and 6,525,157, the entire
contents of which are incorporated herein by reference. Such
propylene-.alpha.-olefin interpolymers are commercially available
from The Dow Chemical Company, under the trade name VERSIFY.TM., or
from ExxonMobil Chemical Company, under the trade name
VISTAMAXX.TM..
[0047] The term vinyl aromatic block copolymer means a polymer
having at least one block segment of a vinyl aromatic monomer in
combination with at least one saturated or unsaturated elastomeric
monomer segment, and more preferably not having a block of polymer
that is neither elastomeric nor vinyl aromatic. Examples of vinyl
aromatic block copolymers are "styrene block copolymer or styrenic
block copolymer". The term `styrene block copolymer" or "styrenic
block copolymer" means a polymer having at least one block segment
of a styrenic monomer in combination with at least one saturated or
unsaturated elastomer (rubber) monomer segment, and more preferably
not having a block of polymer that is neither rubber or styrenic.
Suitable styrene block copolymers having unsaturated rubber monomer
units include styrene-butadiene (SB), styrene-isoprene (SI),
styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS),
.alpha.-methylstyrene-butadiene-.alpha.-methylstyrene,
.alpha.-methylstyrene-isoprene-.alpha.-methylstyrene, and the
like.
[0048] The term "styrene butadiene block copolymer" is used herein
inclusive of SB, SBS and higher numbers of blocks of styrene (S)
and butadiene (B). Similarly, the term "styrene isoprene block
copolymer" is used inclusive of polymers having at least one block
of styrene and one of isoprene (I). The structure of the styrene
block copolymers can be of the linear or radial type, and of the
diblock, triblock or higher block type. In some embodiments, the
styrenic block copolymers having at least four different blocks or
a pair of two repeating blocks, for example, repeating
styrene/butadiene or styrene/ethylene propylene blocks are
desirable. Styrene block copolymers are commercially available from
Dexco Polymers under the trademark VECTOR.RTM., from KRATON
Polymers under the trademark KRATON.TM., from Chevron Phillips
Chemical Co. under the trademark SOLPRENE.TM. and K-Resin, and from
BASF Corp. under the trade designation STYROLUX.TM.. The styrene
block copolymers are optionally used singly or in combinations of
two or more.
[0049] The styrenic portion of the block copolymer is preferably a
polymer or interpolymer of styrene or its analogs or homologs,
including .alpha.-methylstyrene, and ring-substituted styrenes,
particularly ring-methylated styrenes. Preferred styrenics are
styrene and .alpha.-methylstyrene, with styrene being especially
preferred.
[0050] The elastomer portion of the styrenic block copolymer is
optionally either unsaturated or saturated. Block copolymers with
unsaturated elastomer monomer units may comprise homopolymers of
butadiene or isoprene and copolymers of one or both of these two
dienes with a minor amount of styrenic monomer. When the monomer
employed is butadiene, it is preferred that between about 35 and
about 55 mole percent of the condensed butadiene units in the
butadiene polymer block have a 1,2-configuration. When such a block
is hydrogenated, the resulting product is, or resembles, a regular
copolymer block of ethylene and 1-butene (EB). If the conjugated
diene employed is isoprene, the resulting hydrogenated product is
or resembles a regular copolymer block of ethylene and propylene
(EP). Preferred block copolymers have unsaturated elastomer monomer
units, more preferably including at least one segment of a styrenic
unit and at least one segment of butadiene or isoprene, with SBS
and SIS most preferred. Among these, SIS is preferred because it
has been found to be particularly effective to compatibilize
polypropylene with other polymers in the composition. Furthermore,
it is preferred because of a lower tendency to crosslink forming
gels during manufacture as compared to SBS. Styrene butadiene block
copolymers are alternatively preferred when a cast tenter line is
used in manufacturing a film when its higher clarity and lower haze
are advantageous.
[0051] Elastomeric styrene block copolymers provide toughness and
lower stiffness than would be obtained in the absence of the block
copolymer. Elastomeric behavior is indicated by a property of
tensile percent elongation at break of advantageously at least
about 200, specifically at least about 220, more specifically at
least about 240, most specifically at least about 260 and
specifically at most about 2000, more specifically at most about
1700, most specifically at most about 1500 percent as measured by
the procedures of ASTM D412 and/or ASTM D882. Industrially, most
polymers of this type contain 10-80 wt % styrene. Within a specific
type and morphology of polymer, as the styrene content increases
the elastomeric nature of the block copolymer decreases.
[0052] The block copolymers desirably have a melt flow rate (MFR)
of at least about 2, specifically at least about 4 grams per 10
minutes (g/10 min), specifically 20 g/10 min, and more specifically
30 g/10 min. Measure MFR according to ASTM method D1238 Condition
G.
[0053] Preferred styrenic block copolymers include
styrene-isoprene-styrene block copolymers ("SIS"),
styrene-butadiene-styrene block copolymers ("SBS"),
styrene-ethylene-propylene block copolymers ("SEP"), and
hydrogenated styrenic block copolymer such as styrene-(ethylene
butylene)-styrene block copolymers ("SEBS") (e.g., the SEBS
commercially available from Kraton Polymers LLC under the trade
designation KRATON.TM. 1657). Preferably, the styrenic block
copolymer used in the tie layer is SBS.
[0054] In one embodiment, the styrene butadiene block copolymer has
a radial or star block configuration with polybutadiene at the core
and polystyrene at the tips of the arms. Such polymers are referred
to herein as star styrene butadiene block copolymers and are within
the skill in the art and commercially available from Chevron
Phillips Chemical Co. under the trade designation K-Resin. These
polymers contain about 27% butadiene or more in a star-block form
and often feature a bimodal molecular weight distribution of
polystyrene. The inner polybutadiene segments are of about the same
molecular weight while the outer polystyrene segments are of
different molecular weight. This feature facilitates control of
polybutadiene segment thickness, to obtain improved clarity. For
high clarity, the polybutadiene segment thickness is preferably
about one-tenth of the wavelength of visible spectrum or less.
[0055] The ethylene-.alpha.-olefin copolymer has been described
above as has the polyethylene and will not be detailed again. The
polypropylene will be detailed below with reference to the core
layer 106.
[0056] The CBC can be used in the tie layers in an amount of 100 wt
%. When the tie layers 104 and 108 comprise the crystalline block
composite (CBC) and the optional elastomer and/or an optional
polypropylene or polyethylene, the CBC may be used in amounts of 10
to 90 wt %, specifically 20 to 80 wt %, and more specifically 30 to
70 wt %, based on the total weight of the tie layers 104 and 108.
If the elastomer is used, it is present in amounts of up to 50 wt
%, specifically 5 to 45 wt %, based on the total weight of the tie
layers 104 and 108. If polypropylene and/or polyethylene are used
in the tie layers, they can be used either individually or in
combination in amounts of up to 50 wt %, specifically 5 to 45 wt %,
based on the total weight of the tie layers 104 and 108.
[0057] The tie-layers 104 and 108 each have a thickness of 1 to
20%, specifically 2 to 10%, specifically 3 to 8% and more
specifically 4 to 6% of the total thickness of the multilayer
film.
[0058] The core layer 106 comprises polypropylene. It may also
optionally comprise an elastomer and polyethylene in addition to
the propylene. The polypropylene is selected from random copolymer
polypropylene (rcPP), impact copolymer polypropylene (hPP+at least
one elastomeric impact modifier) (ICPP) or high impact
polypropylene (HIPP), high melt strength polypropylene (HMS-PP),
isotactic polypropylene (iPP), syndiotactic polypropylene (sPP), or
a combination comprising at least one of the foregoing
polypropylenes.
[0059] The polypropylene is generally in the isotactic form of
homopolymer polypropylene, although other forms of polypropylene
can also be used (e.g., syndiotactic or atactic). Polypropylene
impact copolymers (e.g., those wherein a secondary copolymerization
step reacting ethylene with the propylene is employed) and random
copolymers (also reactor modified and usually containing 1.5-7%
ethylene copolymerized with the propylene), however, can also be
used in the TPO formulations disclosed herein. A complete
discussion of various polypropylene polymers is contained in Modern
Plastics Encyclopedia/89, mid October 1988 Issue, Volume 65, Number
11, pp. 86-92, the entire disclosure of which is incorporated
herein by reference. The molecular weight and hence the melt flow
rate of the polypropylene for use in the present invention varies
depending upon the application. The melt flow rate for the
polypropylene useful herein is generally from about 0.1 grams/10
minutes (g/10 min) to about 100 g/10 min specifically 0.5 g/10 min
to about 80 g/10 min, and specifically 4 g/10 min to about 70 g/10
min (measured as per ASTM D1238 at 230.degree. C. and 2.16 kg). The
propylene polymer can be a polypropylene homopolymer, or it can be
a random copolymer or even an impact copolymer (which already
contains a rubber phase). Examples of such propylene polymers
include VISTAMAX (made by Exxon Mobil), VERSIFY (made by The Dow
Chemical Co.), INSPIRE (made by Braskem), and PROFAX (made by
Lyondell).
[0060] The core layer 106 may contain polypropylene in an amount of
40 to 100 wt %, specifically 50 to 90 wt %, based on the total
weight of the core layer 106.
[0061] The core layer 106 may optionally contain an elastomer in an
amount of up to 40 wt %, specifically 10 to 35 wt %, based on the
total weight of the core. The elastomer can be an
ethylene-.alpha.-olefin copolymer (which is already detailed
above), a polyolefin elastomer (e.g., a propylene based elastomer),
a vinyl aromatic block copolymer, or a combination thereof as
detailed above. The core layer may also contain polyethylene in an
amount of up to 40 wt %, specifically 10 to 35 wt %, based on the
total weight of the core. The polyethylenes have been described
above, and will not be detailed here again.
[0062] The core layer 106 has a thickness of 10 to 40%,
specifically 15 to 30%, based on the total thickness of the
multilayered film 100. In an exemplary embodiment, the core layer
106 always has a thickness that is less than 20% of the total
thickness of the multilayered film 100. Each layer of the
multilayer film 100 may contain other additives such as waxes,
antioxidants, antiozonants, mold release agents, biocides, thermal
stabilizers, pigments, dyes, infrared absorption agents,
ultraviolet stabilizers, or the like, or a combination comprising
at least one of the foregoing additives.
[0063] As noted above, one of more layers of the multilayer can
optionally comprise a wax that may reduce the melt viscosity in
addition to reducing costs. Non-limiting examples of suitable waxes
include petroleum waxes, polyolefin waxes such as low molecular
weight polyethylene or polypropylene, synthetic waxes, paraffin and
microcrystalline waxes having melting points from about 55 to about
110.degree. C., Fischer-Tropsch waxes, or a combination comprising
at least one of the foregoing waxes. In some embodiments, the wax
is a low molecular weight polyethylene homopolymer or interpolymer
having a number average molecular weight of about 400 to about
6,000 g/mole.
[0064] In further embodiments, each of the layers of the multilayer
film can optionally comprise an antioxidant or a stabilizer.
Non-limiting examples of suitable antioxidants include amine-based
antioxidants such as alkyl diphenylamines,
phenyl-.alpha.-naphthylamine, alkyl or aralkyl substituted
phenyl-.alpha.-naphthylamine, alkylated p-phenylene diamines,
tetramethyl-diaminodiphenylamine and the like; and hindered phenol
compounds such as 2,6-di-t-butyl-4-methylphenol;
1,3,5-trimethyl-2,4,6-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)benzene;
tetrakis[(methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane
(e.g., IRGANOX.TM. 1010, from Ciba Geigy, New York);
octadecyl-3,5-di-t-butyl-4-hydroxycinnamate (e.g., IRGANOX.TM.
1076, commercially available from Ciba Geigy) and combinations
thereof. Where used, the amount of the antioxidant in the
composition can be up to about 1 wt %, specifically 0.05 to 0.75 wt
%, and specifically 0.1 to 0.5 wt %, based on the total weight of
any particular layer.
[0065] In further embodiments, the compositions disclosed herein
optionally can comprise an UV stabilizer that may prevent or reduce
the degradation of the compositions by UV radiation. Non-limiting
examples of suitable UV stabilizers include benzophenones,
benzotriazoles, aryl esters, oxanilides, acrylic esters,
formamidine carbon black, hindered amines, nickel quenchers,
hindered amines, phenolic antioxidants, metallic salts, zinc
compounds, or the like, or a combination comprising at least one of
the foregoing UV stabilizers. Where used, the amount of the UV
stabilizer in any particular layer can be from about greater than 0
to about 1 wt %, specifically 0.05 to 0.75 wt %, and specifically
0.1 to 0.5 wt %, based on the total weight of a particular
layer.
[0066] In further embodiments, the compositions disclosed herein
optionally can comprise a colorant or pigment. Any colorant or
pigment known to a person of ordinary skill in the art may be used
in the adhesion composition disclosed herein. Non-limiting examples
of suitable colorants or pigments include inorganic pigments such
as titanium dioxide and carbon black, phthalocyanine pigments, and
other organic pigments such as IRGAZIN.RTM., CROMOPHTAL.RTM.,
MONASTRAL.RTM., CINQUASIA.RTM., IRGALITE.RTM., ORASOL.RTM., all of
which are available from Ciba Specialty Chemicals, Tarrytown, N.Y.
Where used, the amount of the colorant or pigment in any particular
layer can be present in an amount of up to 10 wt %, specifically
0.1 to 5 wt %, and more specifically 0.5 to 2 wt %, based on the
total weight of any particular layer of the multilayered film.
[0067] In one embodiment, in one method of manufacturing the film
100, the respective compositions for each of the layers 102, 104,
106, 108 and 110 of the multilayered film 100 is fed to a separate
device in which it is subjected to shear, extensional and
elongational forces. The device that exerts the foregoing forces on
the composition can be conducted in an extruder (single screw or
twin screw), a Henschel mixer, a Waring blender, a Buss Kneader, a
Banbury, a roll mill (two or more rolls), high shear impeller
disperser, dough mixer, or the like. The ingredients for any layer
in the multilayered film may be dry mixed or solution blended in
either a Henschel mixer, a Waring blender, a high shear impeller
disperser, or the like, prior to being extruded.
[0068] In an exemplary embodiment, the composition for each of the
respective layers is fed to separate extruders. The composition for
the outer layer 102 is fed to a first extruder, the composition for
the tie layer 104 is fed to a second extruder, the composition for
the core layer 106 is fed to a third extruder, the composition for
the tie layer 108 is fed to a fourth extruder and the composition
for the outer layer 110 is fed to the fifth extruder. The
compositions from the respective extruders are fed to a single die
and are coextruded to form the multilayered film. The coextruded
film is then blown to form a multilayered film of the desired
thickness. In an embodiment, the multilayered film after being
coextruded is laminated in a roll mill having two or more
rolls.
[0069] As detailed above, a plurality of multilayered films may be
laminated together to form a single multilayered film. When two or
more multilayered films are laminated together, at least one of the
common layers may be omitted if desired. For example, if two
multilayered films are laminated together as shown in the FIG. 2,
then at least one of the outer layers 102 or 110 may be omitted.
Thus while a single multilayered film contains 5 layers, two
multilayered films laminated together will contain 9 layers, and
three multilayered films will contain 13 layers.
[0070] The multilayered films disclosed herein are advantageous in
that the presence of a core layer that comprises polypropylene in
the multilayered film provides it with improved stiffness, high
machine direction tear resistance, strong heat seal strength
without interlayer delamination, high creep resistance, high
temperature performance and oil/crease resistance, which enables
the multilayered film to be used for bagging and shipping large
masses of material or products.
[0071] The multilayered films disclosed herein and the method of
manufacturing the films is exemplified in the following
examples.
EXAMPLES
Example 1
[0072] This example demonstrates the disclosed multilayered films
and methods of manufacture thereof. These examples were also
conducted to demonstrate the properties of the multilayered films
over comparative multilayered films.
[0073] Dart Drop Impact: This test measures the energy, as a
function of mass and drop height, required to cause failure of 50%
of the specimens tested. The result is given in grams. Type A darts
have heads 1.5 inches in diameter and drop from a height of 26
inches. Type B darts have heads 2 inches in diameter and drop from
a height of 60 inches. Specimen failure is defined as any break
through the film that can be observed readily by feeling or by
viewing under back lighted conditions. Type A and Type B Dart
Impact cannot be directly correlated. The test is based upon ASTM
STM D 1709.
[0074] Elmendorf Tear test: This test is based upon ASTM D 1922.
Tear strength is measured using a pendulum impact tester to measure
the force required to propagate an existing slit a fixed distance
to the edge of the test sample. Fifteen samples are prepared using
a specific die cutter. These samples are positioned in the tester
and clamped in place. A cutting knife in the tester is used to
create a slit in the sample which ends 43 mm from the far edge of
the sample. The pendulum is released to propagate the slit through
the remaining 43 mm. The energy loss by the pendulum is used to
calculate an average tearing force. This test is a Constant Radius
test.
[0075] Secant Modulus testing: This test, also based upon ASTM D
882, covers the determination of the tensile, or extension,
properties of plastics in the form of thin sheeting, including
film, which is less than 1 mm (0.04 in) in thickness. Film is
defined as having a nominal thickness not greater than 0.25 mm
(0.010 in). In this test, the plastic material is pulled until in
breaks in order to measure elongation, modulus, tensile yield
strength, and tensile strength at break. All specimens are prepared
and tested in exactly the same way. For this test, the samples are
rectangular and are prepared using a die cutter. For testing
tensile strength, the separation speed on the tensile tester is set
to 2 in/min. All tests are done on an Instron-type piece of
equipment. The secant modulus measurement is a sub-measurement of
this test. The modulus is calculated by dividing the tensile stress
by the corresponding strain for the linear portion of the curve, or
for an extension of the linear line. If there is no linear
behavior, a tangent is drawn at the inflection point, to provide
toe compensation by using the intersection of the tangent line with
the strain axis as zero strain. The secant modulus can then be
calculated as the ratio of stress to corrected strain at any point
on the curve. Values for secant modulus are reported at 1 and 2%
strain.
[0076] Tensile Strength: This test, also based upon ASTM D 882,
covers the determination of the tensile, or extension, properties
of plastics in the form of thin sheeting, including film, which is
less than 1 mm (0.04 in) in thickness. Film is defined as having a
nominal thickness not greater than 0.25 mm (0.010 in). In this
test, the plastic material is pulled until in breaks in order to
measure elongation, modulus, tensile yield strength, and tensile
strength at break. All specimens are prepared and tested in exactly
the same way. For this test, the samples are rectangular and are
prepared using a die cutter. For testing tensile strength, the
separation speed on the tensile tester is set to 20 in/min. All
tests are done on an Instron-type piece of equipment.
[0077] Haze test: The total haze of films is measured per ASTM
D-1003. A Hazeguard Plus (BYK-Gardner USA; Columbia, Md.)
instrument is used to measure the haze. Specimens of 8''.times.8''
size are used, ensuring there are no wrinkles in the films and an
average of at least 5 readings is reported.
[0078] Heat Seal test: This work instruction is based upon ASTM
Standard Test Method F88, STM for Seal Strength of Flexible Barrier
Materials. It measures the force required to separate a test strip
of material containing the seal. It also identifies the mode of
specimen failure. Specimens are die cut strips that are one inch in
width. The test result is a measure of the force required to pull
apart the heat seal, or the force required to break the film in
cases where the film breaks before the heat seal parts.
[0079] The materials used in the various layers of the multilayered
film (for this example and for succeeding examples) are detailed in
Table 1 below.
TABLE-US-00001 TABLE 1 Material Description CBC1 50/50 EP/iPP, 90
wt % C2 in EP, 6.7 melt flow ratio (MFR)* CBC2 50/50 EP/iPP, 90 wt
% C2 in EP, 6.8 MFR INSPIRE 114 Impact copolymer polypropylene, 0.5
MFR, Braskem INSPIRE 118 High crystallinity polypropylene, 8.0 MFR,
Braskem PP 6D83K Polypropylene random copolymer, 1.9 MFR, Braskem
PP H110-02N Polypropylene homopolymer, 2.0 MFR, Braskem ADSTIF High
crystallinity polypropylene, 2.3 MFR, HA802H LyondellBasell
Industries ELITE 5100G Enhanced Polyethylene Resin, 0.920
g/cm.sup.3, 0.85 melt index (MI)**, The Dow Chemical Company ELITE
5400G Enhanced Polyethylene Resin, 0.916 g/cm.sup.3, 1.0 MI, The
Dow Chemical Company LDPE 133A LDPE, 0.923 g/cm.sup.3, 0.25 MI, The
Dow Chemical Company AFFINITY Polyolefin plastomer, 0.902
g/cm.sup.3, 1.0 MI, The Dow PL1880 Chemical Company ENGAGE 8100
Polyolefin elastomer, 0.870 g/cm.sup.3, 1.0 MI, The Dow Chemical
Company ENGAGE 8150 Polyolefin elastomer, 0.870 g/cm.sup.3, 0.5 MI,
The Dow Chemical Company VERSIFY 3000 Propylene-ethylene copolymer,
0.888 g/cm.sup.3, 8 MFR, The Dow Chemical Company VERSIFY 2200
Propylene-ethylene copolymer, 0.876 g/cm.sup.3, 2 MFR, The Dow
Chemical Company *Melt flow rate (MFR): measured as per ASTM D1238
at 230.degree. C. and 2.16 kg **Melt index (MI): measured as per
ASTM D1238 at 190.degree. C. and 2.16 kg
[0080] The properties for crystalline block copolymer (CBC1) and
(CBC2) from Table 1 are shown in the Table 1A.
TABLE-US-00002 TABLE 1A Wt % PP Crystalline MFR from Total Tm
(.degree. C.) Melt Block (230.degree. C./ HTLC Mw Mw/ Wt % Peak 1
Enthalpy Composite Example 2.16 kg) Separation Kg/mol Mn C.sub.2
(Peak 2) (J/g) Index CBC1 6.7 19.6 114 2.90 48.3 131 (105) 90 0.579
CBC2 6.8 21.3 117 3.14 46.7 128 (105) 88 0.560
[0081] Table 2 below shows a series of multilayered films some of
which are films that exemplify the invention, while others are
comparative films. Comparative film samples are identified with
letters (See Samples A-B and D-E), while samples that exemplify the
invention are identified with numerals (See Samples 1-5). The core
layer 106 comprises Inspire 114. The total film thickness is 5 mils
(where 1 mil= 1/1000 of an inch).
TABLE-US-00003 TABLE 2 (Outer layers) (Tie layers)
102/104/106/108/110 Layer 102/Layer Layer 104/Layer (Core layers)
(percentage of total Sample Structure 110 108 Layer 106 thickness)
A 3 Layer ELITE 5100 No tie layer INSPIRE 114 40/20/40 B 5 Layer
ELITE 5100 AFFINITY INSPIRE 114 35/5/20/5/35 PL1880G 1 5 Layer
ELITE 5100 CBC1 INSPIRE 114 35/5/20/5/35 2 5 Layer ELITE 5100 60%
CBC1 + 40% INSPIRE 114 35/5/20/5/35 ENGAGE 8150 3 5 Layer ELITE
5100 60% CBC1 + 20% INSPIRE 114 35/5/20/5/35 ENGAGE 8150 + 20%
ELITE 5100 D 3 Layer ELITE 5100 No tie layer INSPIRE 114
37.5/25/37.5 4 5 Layer ELITE 5100 CBC1 INSPIRE 114 32.5/5/25/5/32.5
E 3 Layer ELITE 5100 No tie layer INSPIRE 114 35/30/35 5 5 Layer
ELITE 5100 CBC1 INSPIRE 114 30/5/30/5/30
[0082] As can be seen in the Table 2, some of the comparative
layers have 3 layers (Samples A, D and E). The multilayered films
of the invention all have 5 layers. The layers are identified with
numerals used in the FIG. 1. The outer layers are referred to by
numerals 102 and 110, while the tie layers are referred to by
numerals 104 and 108 and the core layer is referred to by numeral
106. Note that the core layer (Layer 106) is 20% of the total
multilayer film thickness for Samples A-B and Samples 1-3, 25% for
Samples D and 4, and 30% for Samples E and 5.
[0083] Inventive samples 1-5 and comparative samples A-B and D-E
were manufactured on a LabTech 5-layer blown film line. The
diameter of the extrusion die is 75 millimeters (mm) and the die
gap is 2 mm. The blow-up ratio (BUR) was 2.4 to 2.5 and lay-flat
width 11.4 to 11.6 inch. The nip speed was 10.5 to 12.0 ft/min. The
total film thickness was 5 mils (1 mil= 1/1000 of an inch). The
line had 5 extruders. For 5-layer structures, extruders 1 and 5
were used for the outer layers (102 and 110), extruders 2 and 4 for
tie layers (104 and 108) and extruder 3 for core layer 106. A
typical extruder temperature profile is shown in Table 2A. When a
blend was used in certain layer, the ingredients were typically
dry-blended and fed to the feeder.
TABLE-US-00004 TABLE 2A Extruders Zones Temperature (.degree. F.)
Extruders 1 and 5: Zone 01 Set point 350 Outer layer Zone 02 Set
point 400 Zone 03 Set point 375 Zone 04 Set point 375 Die Set point
420 Extruders 2 to 4: Zone 01 Set point 390 Tie layers and Zone 02
Set point 420 core layer Zone 03 Set point 375 Die Set point
420
[0084] The properties of the multilayered films shown in the Table
2 are detailed in the Table 3.
TABLE-US-00005 TABLE 3 Dart 1% MD 2% MD MD A Sec Mod Sec Mod tear
Heat seal fail Sample (g) (psi) (psi) (g) mode A 832 58896 48507
1400 Delamination B 836 60961 51185 1194 Delamination 1 720 61384
52051 2388 No Delamination 2 808 59917 50888 1588 No Delamination 3
764 54457 47448 1492 No Delamination D 756 64755 54782 980
Delamination 4 560 68993 56651 1952 No Delamination E 700 75032
61460 639 Delamination 5 532 76226 62812 862 No Delamination
[0085] From Table 3, it may be seen the inventive Examples 1-3 show
improved MD tear and no delamination in the heat seal test when
compared with comparative samples A-B. Similarly, compared to
Example D, inventive Example 4 has enhanced MD tear and MD modulus
without any delamination.
Example 2
[0086] In this example, a different core layer 106 is used in the
multilayered film as compared with the samples demonstrated in the
Example 1. These samples are manufactured in a manner similar to
those films of the Example 1. In this example, INSPIRE 118 is used
as the core layer 106. The total film thickness is 5 mils. The
compositions of the multilayered films are shown in the Table 4 and
the properties are shown in the Table 5. Comparative film samples
are identified with letters (See Sample F), while samples that
exemplify the invention are identified with numerals (See Samples
6-7).
TABLE-US-00006 TABLE 4 Layer 102/Layer Layer 104/Layer
102/104/106/108/110 110 108 Layer 106 (percentage of total Sample
Structure (Outer layers) (Tie layers) (core layer) thickness) F 3
Layer ELITE 5100 No tie layer INPSIRE 118 40/20/40 6 5 Layer ELITE
5100 CBC1 INPSIRE 118 35/5/20/5/35 7 5 Layer ELITE 5100 CBC1 80%
INPSIRE 118 + 35/5/20/5/35 20% ENGAGE 8100
[0087] The properties are shown in Table 5.
TABLE-US-00007 TABLE 5 Dart 1% MD 2% MD MD A Sec Mod Sec Mod tear
Heat seal fail Sample (g) (psi) (psi) (g) mode F 404 80268 68099
802 Delamination 6 500 81705 69324 1921 No Delamination 7 680 72519
60207 2624 No Delamination
[0088] Once again, it may be seen that the comparative sample
(Sample F) undergoes delamination, while the inventive compositions
(Samples 6 and 7) does not show any delamination. In addition, it
can be seen that Samples 6 and 7 show a much higher tear strength
in the machine direction.
Example 3
[0089] In this example, the composition of the tie layers 104 and
108 and the composition of the core layer 106 are changed. Table 6
shows the composition of the comparative multilayered samples and
those of the inventive samples. Table 7 shows the properties.
Comparative film samples are identified with letters (See Samples G
and I), while samples that exemplify the invention are identified
with numerals (See Samples 8-10). These samples are produced in a
similar manner to the samples of Example 1. The total film
thickness is 5 mils.
TABLE-US-00008 TABLE 6 Layer 102/Layer Layer 104/Layer
102/104/106/108/110 110 108 Layer 106 (percentage of total Sample
Structure (Outer layers) (Tie layers) (core layer) thickness) G 3
Layer ELITE 5100 No tie layer PP HA802H 40/20/40 8 5 Layer ELITE
5100 80% CBC2 + 20% PP HA802H 35/5/20/5/35 ENGAGE 8100 9 5 Layer
ELITE 5100 80% CBC2 +20% PP HA802H 35/5/20/5/35 VERSIFY 2200 I 3
Layer ELITE 5100 No tie layer 80% PP HA802H + 20% 40/20/40 ENGAGE
8100 10 5 Layer ELITE 5100 CBC2 80% PP HA802H + 20% 35/5/20/5/35
ENGAGE 8100
[0090] The properties are shown in the Table 7.
TABLE-US-00009 TABLE 7 Dart 1% MD 2% MD MD A Sec Mod Sec Mod tear
Heat seal fail Sample (g) (psi) (psi) (g) mode G 883 73822 57381
1485 Delamination 8 967 70935 56905 2024 No Delamination 9 874
74780 58564 2176 No Delamination I 1150 60564 46834 1404 No
Delamination 10 1000 64953 50206 2238 No Delamination
[0091] As can be seen from the Table 7, the comparative sample G
shows delamination, while comparative samples 8-10 show no
delamination. Compared to comparative Examples G, inventive
Examples 8 and 9 shows significantly improved MD tear at equivalent
modulus while overcoming the delamination issue observed in Example
G. Inventive Example 10 demonstrates superior MD tear with
excellent modulus as compared to Example I.
Example 4
[0092] In this example, the outer layers 102 and 110, the tie
layers 104 and 108, and the core layer 106 all utilized different
compositions from those in the Examples 1-3. The compositions are
shown in the Table 8A. The layer structure for inventive samples
11-12 are tabulated in Table 8A. The multilayer film has a total
thickness of 4.25 mils. Inventive samples 11 and 12 show higher MD
tear and higher modulus as compared to an all polyethylene 5 layer
structure (Sample J).
TABLE-US-00010 TABLE 8A Layer 102/Layer Layer 104/Layer
102/104/106/108/110 110 108 Layer 106 (percentage of total Sample
Structure (Outer layers) (Tie layers) (core layer) thickness) 11 5
Layer ELITE 5100 + CBC1 80% HA802H + 35/5/20/5/35 10% LDPE 133A 20%
ENGAGE 8100 12 5 Layer ELITE 5100 + CBC1 PP H-110 35/5/20/5/35 10%
LDPE 133A
[0093] Samples 11-12 (inventive samples) are prepared on an Alpine
7-layer blown film line. The diameter of the extrusion die is 200
mm and die gap is 2 mm. The die output is 12.13 lb per inch die
circumference. The total throughput is 350 lb per hour. The blow-up
ratio (BUR) is 1.73 and draw down ratio was 9.09. The total film
thickness of 4.25 mil is made. The line has 7 extruders. Extruders
1 and 2 and extruders and 6 and 7 were used for the outer (skin)
layers 102 and 110, extruders 3 and 5 were used for tie layers 104
and 109, and extruder 4 for layer 106. Typical extruder temperature
profiles are shown in Table 8B.
TABLE-US-00011 TABLE 8B Extruders Zones Temperature (.degree. F.)
(.degree. C.) Extruders 1 and 2 Zone 1 Set point 70 21 Extruders 6
and 7 Zone 2-5 Set point 380 193 Zone 6-8 Set point 450 232
Extruders 3 and 5 Zone 1 Set point 70 21 Zone 2-5 Set point 380 193
Zone 6-7 Set point 450 232 Extruder 4 Zone 1 Set point 70 21 Zone
2-5 Set point 380 193 Zone 6-8 Set point 450 232 Die Set point 450
232
[0094] The properties are shown in the Table 9.
TABLE-US-00012 TABLE 9 CD CD MD MD 1% MD 2% MD Tensile Strain CD
Tensile Strain MD Sec Sec Break at Stress at Break at Stress at
Dart Mod Mod MD Stress Break Yield Stress Break Yield Example A (g)
(psi) (psi) tear (g) (psi) (%) (psi) (psi) (%) (psi) 11 706 75571
59611 1611 5753 632 2385 6100 544 2491 12 610 78392 65113 1393 5543
645 2663 6057 561 2700
[0095] From the Table 9, it may be seen that samples having a
polypropylene core layer show a significantly greater 2% secant
modulus than the comparative samples which have a core layer that
comprises polyethylene.
[0096] In summary, it may be seen that the use of a core layer that
contains polypropylene performs significantly better than core
layers that contain polyethylene. In addition, the use of tie
layers that comprise a crystalline block copolymer composite to
bond the core layer to the outer layers perform better than
multilayer films that do not have elastomeric tie layers.
[0097] The inventive samples show no delamination in the heat seal
fail test and display a machine direction tear of 850 to 2500
grams, specifically 1000 to 2300 grams when tested as per ASTM D
1922, and display a 2% machine direction modulus greater than 50000
psi when tested as per ASTM D 882. The multilayered film may be
used to produce articles. The articles include bags for
transporting large quantities of commercial goods, foods, grains,
and the like.
* * * * *