U.S. patent application number 14/119588 was filed with the patent office on 2014-06-26 for multilayered polyolefin-based films having a layer comprising a crystalline block copolymer composite or a block copolymer composite resin.
This patent application is currently assigned to Dow Global Technologies LLC. The applicant listed for this patent is DOW GLOBAL TECHNOLOGIES LLC. Invention is credited to Jeffrey E. Bonekamp, Lih-Long Chu, Mark G. Hofius, Yushan Hu, John A. Naumovitz, Nichole E. Nickel.
Application Number | 20140174509 14/119588 |
Document ID | / |
Family ID | 46514795 |
Filed Date | 2014-06-26 |
United States Patent
Application |
20140174509 |
Kind Code |
A1 |
Bonekamp; Jeffrey E. ; et
al. |
June 26, 2014 |
MULTILAYERED POLYOLEFIN-BASED FILMS HAVING A LAYER COMPRISING A
CRYSTALLINE BLOCK COPOLYMER COMPOSITE OR A BLOCK COPOLYMER
COMPOSITE RESIN
Abstract
Disclosed are multilayer film structures comprising a layer (B)
that comprises a crystalline block copolymer composite (CBC) or a
specified block copolymer composite (BC), comprising i) an ethylene
polymer (EP) comprising at least 80 mol % polymerized ethylene; ii)
an alpha-olefin-based crystalline polymer (CAOP) and iii) a block
copolymer comprising (a) an ethylene polymer block comprising at
least 80 mol % polymerized ethylene and (b) a crystalline
alpha-olefin block (CAOB); and a layer C that comprises a
polyolefin having at least one melting peak greater than 1255 C,
the top facial surface of layer C in adhering contact with the
bottom facial surface of layer B. Such multilayer film structure
preferably comprises (A) a seal layer A having a bottom facial
surface in adhering contact with the top facial surface of layer B.
Such films are suited for use in electronic device (ED) modules
comprising an electronic device such as a PV cell. Also disclosed
is a lamination process to construct a laminated PV module
comprising such multilayer film structures.
Inventors: |
Bonekamp; Jeffrey E.;
(Midland, MI) ; Hu; Yushan; (Pearland, TX)
; Nickel; Nichole E.; (Midland, MI) ; Chu;
Lih-Long; (Midland, MI) ; Naumovitz; John A.;
(Midland, MI) ; Hofius; Mark G.; (Midland,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DOW GLOBAL TECHNOLOGIES LLC |
Midland |
MI |
US |
|
|
Assignee: |
Dow Global Technologies LLC
Midland
MI
|
Family ID: |
46514795 |
Appl. No.: |
14/119588 |
Filed: |
June 28, 2012 |
PCT Filed: |
June 28, 2012 |
PCT NO: |
PCT/US12/44558 |
371 Date: |
November 22, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61503335 |
Jun 30, 2011 |
|
|
|
Current U.S.
Class: |
136/251 ;
438/64 |
Current CPC
Class: |
B32B 27/32 20130101;
H01L 31/049 20141201; B29C 41/003 20130101; Y02E 10/50 20130101;
B32B 37/185 20130101; B32B 27/08 20130101; B32B 2270/00 20130101;
C08L 2203/204 20130101; C08L 2205/03 20130101; C08L 2205/035
20130101; H01L 31/0481 20130101; B29K 2023/0625 20130101; C08L
2205/025 20130101; B29C 41/26 20130101; B29K 2023/06 20130101; C08L
2205/12 20130101; B29L 2009/00 20130101; B29C 41/32 20130101; B32B
2457/12 20130101; C08L 53/00 20130101; H01L 31/18 20130101; B32B
2323/04 20130101 |
Class at
Publication: |
136/251 ;
438/64 |
International
Class: |
H01L 31/048 20060101
H01L031/048; B32B 27/08 20060101 B32B027/08; H01L 31/18 20060101
H01L031/18; B32B 27/32 20060101 B32B027/32 |
Claims
1. A multilayer film structure comprising a layer (Layer B) and a
bottom layer (Layer C), each layer having opposing facial surfaces
in adhering contact with the other layer, wherein: B. Layer B
comprises a crystalline block copolymer composite (CBC) or a
specified block copolymer composite (BC), comprising: i) an
ethylene polymer (EP) comprising at least 80 mol % polymerized
ethylene; ii) an alpha-olefin-based crystalline polymer (CAOP) and
iii) a block copolymer comprising (a) an ethylene polymer block
comprising at least 80 mol % polymerized ethylene and (b) a
crystalline alpha-olefin block (CAOB), or a mixture of said
composite(s); and C. bottom Layer C comprises a polyolefin having
at least one melting peak greater than 125.degree. C. and has a top
facial layer and a bottom facial surface, the top facial surface of
Layer C in adhering contact with the bottom facial surface of Layer
B.
2. A multilayer film structure according to claim 1 wherein the i)
EP in Layer B comprises at least 80 mol % polymerized ethylene and
the balance is polymerized propylene.
3. A multilayer film structure according to claim 1 wherein the
block composite resin in Layer B is a crystalline block composite
resin.
4. A multilayer film structure according to claim 1 wherein the
Layer B block composite resin has a CAOB amount (in part (iii)) in
the range of from 30 to 70 weight % of the CAOB.
5. A multilayer film structure according to claim 3 wherein the
Layer B block composite resin has a CAOB amount (in part (iii)) in
the range of from 40 to 60 weight % of the CAOB.
6. A multilayer film structure according to claim 1 where tie Layer
B comprises a CBC having a CBCI of between 0.3 to 1.0 or a
specified BC having a BCI of between 0.1 to 1.0.
7. A multilayer film structure according to claim 1 wherein
propylene is the alpha-olefin in ii) and iii) in tie Layer B.
8. A multilayer film structure according to claim 1 wherein tie
Layer B is a blend comprising greater than 40 weight percent CBC or
specified BC.
9. A multilayer film structure according to claim 8 wherein tie
Layer B is a blend further comprising one or more polyolefin
selected from an ethylene octene plastomer, LLDPE and LDPE.
10. A multilayer film structure according to claim 1 wherein the
CBC or specified BC of Layer B has a melt flow rate of from 3 to 15
g/10 min (at 230.degree. C./2.16 Kg).
11. The multilayer film structure according to claim 1 comprising:
(A) a seal layer A having a top facial surface and a bottom facial
surface, the bottom facial surface in adhering contact with the top
facial surface of layer B.
12. A multilayer film structure according to claim 11 in which the
top layer A comprises a linear low density polyethylene
(LLDPE).
13. A multilayer film structure according to claim 12 in which the
top layer A comprises a blend formulation of a linear low density
polyethylene (LLDPE) comprising a polar ethylene copolymer in an
amount of from 10 to 45 weight %.
14. A multilayer film structure according to claim 11 in which the
top layer A comprises a BC or CBC and the layer composition is
different from layer B composition.
15. A multilayer film structure according to claim 1 in which the
bottom layer C comprises a propylene-based polymer.
16. A multilayer film structure according to claim 9 in which the
bottom layer C comprises a propylene-based polymer having a heat of
fusion value of at least 60 Joules per gram (J/g).
17. A multilayer film structure according to claim 1 wherein Layer
A is from 0 to 200 micrometer (.mu.m) in thickness; Layer B is from
25 to 100 .mu.m in thickness; and Layer C is from 150 to 350 .mu.m
in thickness.
18. A multilayer film structure according to claim 1 comprising a
top seal Layer A comprising a blend formulation of a linear low
density polyethylene (LLDPE) comprising a polar ethylene copolymer
in an amount of from 10 to 45 weight %, a bottom Layer C comprising
a propylene-based polymer and a Layer B between Layer A and Layer C
comprising a crystalline block copolymer composite (CBC) comprising
i) an ethylene polymer (EP) comprising at least 93 mol %
polymerized ethylene; ii) a crystalline propylene polymer and iii)
a block copolymer comprising (a) an ethylene polymer block
comprising at least 93 mol % polymerized ethylene and (b) a
crystalline propylene polymer block.
19. An electronic device (ED) module comprising an electronic
device and a multilayer film structure according to claim 1.
20. A lamination process to construct a laminated PV module
comprising the steps of: (1.) bringing at least the following
layers into facial contact in the following order: (a) a
light-receiving top sheet layer having an exterior light-receiving
facial surface and an interior facial surface; (b) a light
transmitting thermoplastic polymer encapsulation layer, having one
facial surface directed toward the top sheet layer and one directed
toward a light-reactive surface of a PV cell; (c) a PV cell have a
light reactive surface; (d) a second encapsulating film layer; and
(e) a backsheet layer comprising a multilayer film structure
according to claims 1; and (2.) heating and compressing the layers
of Step (1.) at conditions sufficient to create the needed adhesion
between the layers and, if needed in some layers or materials,
initiation of their crosslinking.
Description
[0001] This application claims priority from copending provisional
U.S. Patent application Ser. No. 61/503,335 filed Jun. 30, 2011
having the same title as this application; from copending U.S.
patent application Ser. No. 61/570,464 filed Dec. 14, 2011
entitled, "FUNCTIONALIZED BLOCK COMPOSITE AND CRYSTALLINE BLOCK
COMPOSITE COMPOSITIONS AS COMPATIBILIZERS" and from copending
United States patent application filed Dec. 14, 2011 Ser. No.
61/570,340 entitled, "FUNCTIONALIZED BLOCK COMPOSITE AND
CRYSTALLINE BLOCK COMPOSITE COMPOSITIONS". This application is
related to commonly assigned and copending U.S. Patent application
Ser. No. 61/503,326 filed the same date herewith and entitled
"MULTILAYERED POLYOLEFIN-BASED FILMS HAVING INTEGRATED BACKSHEET
AND ENCAPSULATION PERFORMANCE COMPRISING A LAYER COMPRISING
CRYSTALLINE BLOCK COPOLYMER COMPOSITE OR BLOCK COPOLYMER COMPOSITE"
and claiming priority from provisional U.S. Patent application Ser.
No. 61/503,326.
[0002] This invention relates to films having a layer comprising a
Crystalline Block Composite ("CBC") or a specified Block Composite
("BC") and having improved combinations of properties; being
particularly suited for use as protective layers, for example
"backsheets", in electronic device (ED) modules, e.g., photovoltaic
(PV) modules. In one aspect, the invention relates to the backsheet
films for use in such modules. In another aspect, the invention
relates to co-extruded, multilayered films of this type. In still
another aspect, the invention relates to the ED module
incorporating such a backsheet.
[0003] Thermoplastic polymeric material films, often referred to as
plastic films, are commonly used as layers in the manufacture of
modules or assemblies comprising one or more electronic devices
including, but not limited to, solar cells (also known as
photovoltaic (PV) cells), batteries, liquid crystal panels,
electro-luminescent devices and plasma display units. The modules
often comprise an electronic device in combination with one or more
substrates, often positioned between two substrates, in which one
or both of the substrates comprise, as support(s), glass, metal,
plastic, rubber or another material. The terminology for the names
and descriptions of the ED component layers varies somewhat between
different writers and different producers but polymeric film
materials are typically used as internally located "encapsulant" or
"sealant" layers for the device itself or, depending upon the
design of the device, as outer "cover" or "skin" layer components
of the module.
[0004] PV modules are well known in the art, and typically comprise
the following components that are assembled into the final module
structure:
[0005] 1. a stiff or flexible transparent cover layer,
[0006] 2. a front transparent encapsulant,
[0007] 3. a PV (solar) cell,
[0008] 4. a rear encapsulant (typically the same composition as the
front encapsulant) and
[0009] 5. a backsheet.
[0010] The present invention is concerned with improved films or
film layers utilizing a crystalline block copolymer composite or a
specific block copolymer composite in a layer that in turn provides
improved PV modules in terms of cost effectiveness and performance.
Backsheet layers, as discussed in more detail below, protect the
back surface of the cell and may have additional features that
enhance the performance of the PV module.
[0011] Examples of some of the types of backsheet products that are
currently in commercial use are TPE-type structures (a PVF/PET/EVA
laminate) available from Madico, and Icosolar 2442 (a PVF/PET/PVF
laminate) available from Isovolta; and PPE-type structures
(PET/PET/EVA) structure available from Dunmore. A number of
proposed improved and enhanced backsheets are also disclosed
including the following.
[0012] In U.S. Pat. No. 6,521,825 solar cell module backsheet
layers are disclosed having two heat and weather resistant layers
with a moisture resistant core layer.
[0013] In U.S. Pat. No. 7,713,636B2 multi-layer films comprising
propylene-based polymers are disclosed having improved peel
strength properties and comprising a core layer and a first tie
layer made from at least 5 wt % of a grafted propylene-based
polymer.
[0014] WO 2010/053936 discloses backsheet layers for electronic
device (ED) modules, e.g., photovoltaic (PV) modules, having at
least three layers including a tie layer of a glycidyl methacrylate
(GMA) graft resin joining layers that each use a maleic anhydride
modified resin (MAH-m resin) in each of the joined layers to
provide good interlayer adhesion.
[0015] US 2011/0048512 discloses backsheet layers for electronic
device (ED) modules, e.g., photovoltaic (PV) modules, comprising a
coextruded multilayer sheet that comprises: i) an inner layer
comprising a polyolefin resin; ii) a core layer comprising a
polypropylene resin, a blend of a polypropylene resin and a maleic
anhydride grafted polypropylene (MAH-g-PP), or a polypropylene
resin/MAH-g-PP multilayer structure; iii) an outer layer comprising
a maleic anhydride grafted polyvinylidene fluoride (MAH-g-PVDF), a
blend of a polyvinylidene fluoride (PVDF) and a MAH-g-PVDF, or a
PVDF/MAH-g-PVDF multilayer structure; iv) a first tie layer between
the core layer and the outer layer; and v) an optional second tie
layer between the core layer and the inner layer.
[0016] In WO/2011/009568 there are disclosed photovoltaic module
backsheets on base of preferably high molecular weight, impact
resistant, shrinkage and thermal (flow) resistant FPP (Flexible
Polypropylene) compositions preferably containing functional
particles or being coextruded with a primer adhesive layer to
obtain highly reliable adhesion on EVA adhesive layers. In one
embodiment, the backsheet has a functionalized polyolefin (PO)
adhesive layer allowing direct adhesion to cells back-contacts,
i.e. without the use of an EVA adhesive layer. In a further
embodiment, the backsheet, with functional PO adhesive layer,
allows the use of an upper adhesive layer which has s a transparent
thermoplastic polyolefin (TPO) film layer.
[0017] Noting the issues and limitations involved with the use of
the prior art components in electronic devices such as PV modules,
there is always a continuing desire for improved and lower cost
electronic devices such as PV modules that can be obtained by use
of improved components in their construction. In particular, better
interlayer adhesion of backsheet layers and substantial reduction
or elimination of interlayer failure between backsheet layers in PV
modules is expected to increase lifetime of PV modules.
SUMMARY OF THE INVENTION
[0018] Therefore, according to one embodiment of the present
invention, there is provided a multilayer film structure comprising
a layer (Layer B) and a bottom layer (Layer C), each layer having
opposing facial surfaces in adhering contact with the other layer,
wherein:
B. Layer B comprises a crystalline block copolymer composite (CBC)
or a specified block copolymer composite (BC), comprising:
[0019] i) an ethylene polymer (EP) comprising at least 80 mol %
polymerized ethylene;
[0020] ii) an alpha-olefin-based crystalline polymer (CAOP) and
[0021] iii) a block copolymer comprising (a) an ethylene polymer
block comprising at least 80 mol % polymerized ethylene and (b) a
crystalline alpha-olefin block (CAOB), or a mixture of said
composite(s); and
C. bottom Layer C comprises a polyolefin having at least one
melting peak greater than 125.degree. C. and having a top facial
layer and a bottom facial surface, the top facial surface of Layer
C in adhering contact with the bottom facial surface of Layer
B.
[0022] In other alternative independent embodiments related to
Layer B, there are provided multilayer film structures as described
above where: the i) EP in Layer B comprises at least 80 mol %
polymerized ethylene and the balance polymerized propylene and,
preferably wherein the block composite resin in Layer B is a
crystalline block composite resin; the Layer B block composite
resin has a CAOB amount (in part (iii)) in the range of from 30 to
70 weight % of the CAOB, preferably from 40 to 60 weight % of the
CAOB; Layer B comprises a CBC having a CBCI of between 0.3 to 1.0
or a specified BC having a BCI of between 0.1 to 1.0; propylene is
the alpha-olefin in ii) and iii) in tie Layer B; tie Layer B is a
blend comprising greater than 40 weight percent CBC or specified
BC, preferably further comprising one or more polyolefin selected
from an ethylene octene plastomer, LLDPE and LDPE; and/or the CBC
or specified BC of Layer B has a melt flow rate of from 3 to 15
g/10 min (at 230.degree. C./2.16 Kg).
[0023] In other alternative independent embodiments, there are
provided multilayer film structures as described herein comprising:
(A) a seal layer A having a top facial surface and a bottom facial
surface, the bottom facial surface in adhering contact with the top
facial surface of layer B; preferably such a film in which the top
layer A comprises a linear low density polyethylene (LLDPE) and
more preferably such a film in which the top layer A comprises a
blend formulation of a linear low density polyethylene (LLDPE)
comprising a polar ethylene copolymer in an amount of from 10 to 45
weight %. Optionally in such films the top layer A comprises a BC
or CBC and the layer composition is different from layer B
composition.
[0024] In other alternative independent embodiments, there are
provided multilayer film structures as described above where the
bottom layer C comprises: a propylene-based polymer or optionally a
propylene-based polymer having a heat of fusion value of at least
60 Joules per gram (J/g). A further independent embodiment of the
present invention is a multilayer structure as described herein
wherein Layer A is from 0 to 200 micrometer (.mu.m) in thickness;
Layer B is from 25 to 100 .mu.m in thickness; and Layer C is from
150 to 350 .mu.m in thickness.
[0025] A further independent embodiment of the present invention is
a multilayer film structure as described herein comprising a top
seal Layer A comprising a blend formulation of a linear low density
polyethylene (LLDPE) comprising a polar ethylene copolymer in an
amount of from 10 to 45 weight %, a bottom Layer C comprising a
propylene-based polymer and a Layer B between Layer A and Layer C
comprising a crystalline block copolymer composite (CBC) comprising
i) an ethylene polymer (EP) comprising at least 93 mol %
polymerized ethylene; ii) a crystalline propylene polymer and iii)
a block copolymer comprising (a) an ethylene polymer block
comprising at least 93 mol % polymerized ethylene and (b) a
crystalline propylene polymer block.
[0026] A further independent embodiment of the present invention is
an electronic device (ED) module comprising an electronic device
and a multilayer film structure as described above.
[0027] A further independent embodiment of the present invention is
a lamination process to construct a laminated PV module comprising
the steps of:
(1.) bringing at least the following layers into facial contact in
the following order:
[0028] (a) a light-receiving top sheet layer having an exterior
light-receiving facial surface and an interior facial surface; (b)
a light transmitting thermoplastic polymer encapsulation layer,
having one facial surface directed toward the top sheet layer and
one directed toward a light-reactive surface of a PV cell; (c) a PV
cell have a light reactive surface; (d) a second encapsulating film
layer; and (e) a backsheet layer comprising a multilayer film
structure according to claims 1; and
(2.) heating and compressing the layers of Step (1.) at conditions
sufficient to create the needed adhesion between the layers and, if
needed in some layers or materials, initiation of their
crosslinking.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a cross-sectional view of an exemplary three-layer
backsheet in adhering contact with an encapsulant layer on the back
surface of an electronic device.
DETAILED DESCRIPTION
[0030] One of the important features of the films of the present
invention is use of a layer that comprises a block composite resin
comprising: i) an ethylene-based polymer; ii) an alpha-olefin-based
crystalline polymer (which is preferably based on propylene) and
iii) a block copolymer comprising an ethylene block and a
crystalline alpha-olefin (preferably propylene) block. In
discussing the polymer components of the film layers and films of
present invention there are several terms that are frequently used
and are defined and understood as follows.
Polymer Resins Descriptions and Terms
[0031] "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.
[0032] "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.
[0033] "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/.alpha.-olefin polymer" and "propylene/.alpha.-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.
[0034] "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.
[0035] "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.
[0036] "(Meth)" indicates that the methyl substituted compound is
included in the term. For example, the term "ethylene-glycidyl
(meth)acrylate" includes ethylene-glycidyl acrylate (E-GA) and
ethylene-glycidyl methacrylate (E-GMA), individually and
collectively.
[0037] "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.
Layer C--High Melting Point Polyolefin Resins
[0038] The polyolefin resins useful in the bottom layer or Layer C
of the backsheet have a melting point of at least 125.degree. C.,
preferably greater than 130 C, preferably greater than 140.degree.
C., more preferably greater than 150.degree. C. and even more
preferably greater than 160.degree. C. These polyolefin resins are
preferably propylene-based polymers, commonly referred to as
polypropylenes. These polyolefins are preferably made with
multi-site catalysts, e.g., Zeigler-Natta and Phillips catalysts.
In general, polyolefin resins with a melting point of at least
125.degree. C. often exhibit desirable toughness properties useful
in the protection of the electronic device of the module.
[0039] Regarding polyolefin resins in general, such as suitable for
Layer C or for other olefin polymer components of the present
invention, the sole monomer (or the primary monomer in the case of
interpolymers) is typically selected from ethylene, propene
(propylene), 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene,
1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene
and is preferably propylyene for the Layer C polyolefin resin. If
the polyolefin resin is an interpolymer, then the comonomer(s)
different from the first or primary monomer is/are typically one or
more .alpha.-olefins. For purposes of this invention, ethylene is
an .alpha.-olefin if propylene or higher olefin is the primary
monomer. The co-.alpha.-olefin is then preferably a different
C.sub.2-20 linear, branched or cyclic .alpha.-olefin. Examples of
C.sub.2-20 .alpha.-olefins for use as comonomers include ethylene,
propene (propylene), 1-butene, 4-methyl-1-pentene, 1-hexene,
1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and
1-octadecene. The .alpha.-olefins for use as comonomers 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. Although not
.alpha.-olefins in the classical sense of the term, for purposes of
this invention certain cyclic olefins, such as norbornene and
related olefins, are .alpha.-olefins and can be used as comonomer
in place of some or all of the .alpha.-olefins described above.
Similarly, styrene and its related olefins (for example,
.alpha.-methylstyrene, etc.) are .alpha.-olefins for purposes of
comonomers according to this invention. Acrylic and methacrylic
acid and their respective ionomers, and acrylates and methacrylates
are also comonomer .alpha.-olefins for purposes of this invention.
Illustrative polyolefin copolymers include but are not limited to
ethylene/propylene, ethylene/butene, ethylene/1-hexene,
ethylene/1-octene, ethylene/styrene, ethylene/acrylic acid (EAA),
ethylene/methacrylic acid (EMA), ethylene/acrylate or methacrylate,
EVA and the like. Illustrative terpolymers include
ethylene/propylene/1-octene, ethylene/propylene/butene,
ethylene/butene/1-octene, and ethylene/butene/styrene. The
copolymers can be random or blocky.
[0040] The high melting point polyolefin resins (having a melting
point of at least 125.degree. C.), that are useful in the present
invention and preferred for use as all or most of bottom layer
Layer C in the practice of this invention include propylene-based
polymers, also referred to as propylene polymers or polypropylenes,
including e.g., polypropylene or propylene copolymers comprising a
majority of units derived from propylene and a minority of units
derived from another .alpha.-olefin (including ethylene). These
propylene-based polymers include polypropylene homopolymer,
copolymers of propylene and one or more other olefin monomers, a
blend of two or more homopolymers or two or more copolymers, and a
blend of one or more homopolymer with one or more copolymer, as
long as it has a melting point of 125.degree. C. or more. The
polypropylene-based polymers can vary widely in form and include,
for example, substantially isotactic propylene homopolymer, random
propylene copolymers, and graft or block propylene copolymers.
[0041] The propylene copolymers preferably comprise at least 85,
more preferably at least 87 and even more preferably at least 90,
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 having up to 20, preferably up to 12 and more
preferably up to 8, carbon atoms. The .alpha.-olefin is preferably
a C.sub.3-20 linear, branched or cyclic .alpha.-olefin as described
above.
[0042] In general, preferred propylene polymer resins include
hompolymer polypropylenes, preferably high crystallinity
polypropylene such as high stiffness and toughness polypropylenes.
Preferably the propylene polymer MFR (measured in dg/min at
230.degree. C./2.16 kg,) is at least 0.5, preferably at least 1.5,
and more preferably at least 2.5 dg/min and less than or equal to
25, preferably less than or equal to 20, and most preferably less
than or equal to 18 dg/min.
[0043] In general, preferred propylene polymer resins for Layer C
have heat of fusion values (reflecting the relatively higher
crystallinity) as measured by DSC of at least about 60 Joules per
gram (J/g), more preferably at least about 90 J/g, still more
preferably at least about 110 J/g and most preferably at least
about 120 J/g. For the heat of fusion measurements, as generally
known and performed by practitioners in this area, the DSC is run
as generally described below under nitrogen at 10.degree. C./min
from 23.degree. C. to 220.degree. C., held isothermal at
220.degree. C. for 3 minutes, dropped to 23.degree. C. at
10.degree. C./min and ramped back to 220.degree. C. at 10.degree.
C./min. The second heat data is used to calculate the heat of
fusion of the melting transition.
[0044] The following are illustrative but non-limiting propylene
polymers that can be used in the backsheets of this invention: a
propylene impact copolymer including but not limited to former DOW
Polypropylene T702-12N; a propylene homopolymer including but not
limited to former DOW Polypropylene H502-25RZ; and a propylene
random copolymer including but not limited to former DOW
Polypropylene R751-12N. It should be noted that the propylene
polymer products above and other that were formerly available from
The Dow Chemical Company may now be available from Braskem or
correspond to products available from Braskem. Other polypropylenes
include some of the VERSIFY.degree. polymers available from The Dow
Chemical Company, the VISTAMAXX.degree. polymers available from
ExxonMobil Chemical Company, and the PRO-FAX polymers available
from Lyondell Basell Industries, e.g., PROFAX.TM. SR-256M, which is
a clarified propylene copolymer resin with a density of 0.90 g/cc
and a MFR of 2 g/10 min, PROFAX.TM. 8623, which is an impact
propylene copolymer resin with a density of 0.90 g/cc and a MFR of
1.5 g/10 min. Still other propylene resins include CATALLOY.TM.
in-reactor blends of polypropylene (homo- or copolymer) with one or
more of propylene-ethylene or ethylene-propylene copolymer (all
available from Basell, Elkton, Md.), Shell's KF 6100 propylene
homopolymer; Solvay's KS 4005 propylene copolymer; and Solvay's KS
300 propylene terpolymer. Furthermore, INSPIRE.TM. D114, which is a
branched impact copolymer polypropylene with a melt flow rate (MFR)
of 0.5 dg/min (230.degree. C./2.16 kg) and a melting point of
164.degree. C. would be a suitable polypropylene. In general,
suitable high crystallinity polypropylene with high stiffness and
toughness include but are not limited to INSPIRE.TM. 404 with an
MFR of 3 dg/min, and INSPIRE.TM. D118.01 with a melt flow rate of
8.0 dg/min (230.degree. C./2.16 kg), (both also formerly available
from The Dow Chemical Company).
[0045] Propylene polymer blend resins can also be used where
polypropylene resins as described above can be blended or diluted
with one or more other polymers, including polyolefins as described
below, to the extent that the other polymer is (i) miscible or
compatible with the polypropylene, (ii) has little, if any,
deleterious impact on the desirable properties of the
polypropylene, e.g., toughness and modulus, and (iii) the
polypropylene constitutes at least 55, preferably at least 60, more
preferably at least 65 and still more preferably at least 70,
weight percent of the blend. The propylene polymer can be also be
blended with cyclic olefin copolymers such as Topas 6013F-04 cyclic
olefin copolymer available from Topas Advanced Polymers, Inc. with
preferred amounts when used at least 2, preferably 4, and more
preferably 8 weight percent up to and including to 40, preferably
35 and more preferably 30 weight percent. In general, propylene
polymer resins for Layer C can comprise an impact modifier such as
ethylene octene plastomers such as AFFINITY PL 1880G, PL8100G, and
PL 1850G brand resins or ethylene octene elastomers such as ENGAGE
8842, ENGAGE 8150, and ENGAGE XLT 8677 brand resins commercially
available from The Dow Chemical Company, olefin block copolymers
such as for example INFUSE 9100 and 9107 brand resins commercially
available from The Dow Chemical Company or propylene based
elastomers such as VERSIFY 2300 and VERSIFY 3300 brand resins
available from The Dow Chemical Company. In general, these are used
in amounts at least of 2 weight percent, preferably at least 5 and
more preferably at least 8 weight percent and preferably less than
45 weight %, preferably less than 35 weight percent and more
preferably less than 30 weight percent. Other candidate impact
modification or blend resins are ethylene/propylene rubbers
(optionally blended with polypropylene in-reactor) and one or more
block composites as described herein. Combinations of impact
modifiers of different types may also be used.
[0046] Other additives that could be used with the propylene
polymer resins are inorganic fillers such as talc (including epoxy
coated talc), colorants, flame retardants (halogenated and
non-halogenated) and flame retardant synergists such as
Sb.sub.2O.sub.3.
Layer B Crystalline Block Copolymer Composite and Block Copolymer
Composite Resin Components
[0047] The composition of Layer B in the films according to the
present invention, often referred to as a "tie" layer, is selected
to be adhered, either preferably by co-extrusion or alternatively
but less preferably by a lamination process (such as extrusion
lamination, thermal lamination, or adhesive lamination) to the
layers C and optionally A (or optionally another layer) in
production of the films according to the invention. As mentioned
above, Layer B comprises a Crystalline Block Copolymer Composite
Resin ("CBC") and/or certain Block copolymer Composite Resins
("BC's"), CBC's and BC's collectively referred to herein as
"Crystalline Block and Block Composite Resins" "Composite Resins"
or "(C)BC's". Layer B can alternatively comprise a blend of one or
more CBC and with one or more BC, or a blend of one or both of
these resins with one or more other resin.
[0048] The term "block copolymer" or "segmented copolymer" refers
to a polymer comprising two or more chemically distinct regions or
segments (referred to as "blocks") joined in a linear manner, that
is, a polymer comprising chemically differentiated units which are
joined (covalently bonded) end-to-end with respect to polymerized
functionality, rather than in pendent or grafted fashion. In a
preferred embodiment, the blocks differ in the amount or type of
comonomer incorporated therein, the density, the amount of
crystallinity, the type of crystallinity (e.g. polyethylene versus
polypropylene), the crystallite size attributable to a polymer of
such composition, the type or degree of tacticity (isotactic or
syndiotactic), regio-regularity or regio-irregularity, the amount
of branching, including long chain branching or hyper-branching,
the homogeneity, or any other chemical or physical property. The
block copolymers of the invention are characterized by unique
distributions of both polymer polydispersity (PDI or Mw/Mn) and
block length distribution, due, in a preferred embodiment, to the
effect of a shuttling agent(s) in combination with the
catalyst(s).
[0049] As used herein, the terms "block composite" or "block
copolymer composite" resins are different from "crystalline block
composites" or "crystalline block copolymer composite resins" based
on the amount of comonomer polymerized with the ethylene polymer
and ethylene block in the composite. The term "BC" refers generally
to polymers comprising (i) a soft ethylene copolymer (EP) having
polymerized units in which the comonomer content is greater than 10
mol % and having less than 90 mol % polymerized ethylene, and
preferably greater than 20 mol % and less than 80 mol % ethylene,
and most preferably greater than 33 mol % and less than 75 mol
ethylene %, (ii) a hard or crystalline .alpha.-olefin polymer
(CAOP), in which the .alpha.-olefin monomer (preferably propylene)
is present in an amount of from greater than 90 up to 100 mol
percent, and preferably greater than 93 mol percent, and more
preferably greater than 95 mol percent, and most preferably greater
than 98 mol percent and (iii) a block copolymer, preferably a
diblock, having a soft segment and a hard segment, wherein the hard
segment of the block copolymer is essentially the same composition
as the hard .alpha.-olefin polymer in the block composite and the
soft segment of the block copolymer is essentially the same
composition as the soft ethylene copolymer of the block composite.
The block copolymers can be linear or branched. More specifically,
when produced in a continuous process, the block composites
desirably possess PDI from 1.7 to 15, preferably from 1.8 to 3.5,
more preferably from 1.8 to 2.2, and most preferably from 1.8 to
2.1. When produced in a batch or semi-batch process, the block
composites desirably possess PDI from 1.0 to 2.9, preferably from
1.3 to 2.5, more preferably from 1.4 to 2.0, and most preferably
from 1.4 to 1.8. Such block composites are described in, for
example, US Patent Application Publication Nos US2011-0082257,
US2011-0082258 and US2011-0082249, all published on Apr. 7, 2011
and incorporated herein by reference with respect to descriptions
of the block composites, processes to make them and methods of
analyzing them.
[0050] As mentioned above, alternatively or in addition to the CBC
(discussed in more detail below), certain suitable "BC" resins can
be employed in Layer B in the films according to the present
invention. The specific suitable "BC's" comprise a soft ethylene
copolymer (EP) having the comonomer content greater than 80 mol %
and up to 90 mol % and preferably greater than 85 mol % and most
preferably greater than 87 mol %, but otherwise a BC as generally
described herein.
[0051] The term "crystalline block composite" (CBC) (including the
term "crystalline block copolymer composite") refers to polymers
comprising a crystalline ethylene based polymer (CEP), a
crystalline alpha-olefin based polymer (CAOP), and a block
copolymer having a crystalline ethylene block (CEB) and a
crystalline alpha-olefin block (CAOB), wherein the CEB of the block
copolymer is essentially the same composition as the CEP in the
block composite and the CAOB of the block copolymer is essentially
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. The block copolymers can be linear
or branched. More specifically, each of the respective block
segments can contain long chain branches, but the block copolymer
segment is substantially linear as opposed to containing grafted or
branched blocks. When produced in a continuous process, the
crystalline block composites desirably possess PDI from 1.7 to 15,
preferably 1.8 to 10, preferably from 1.8 to 5, more preferably
from 1.8 to 3.5. Such crystalline block composites are described
in, for example, the following filed patent applications:
PCT/US11/41189; U.S. Ser. No. 13/165,054; PCT/US11/41191; U.S. Ser.
No. 13/165,073; PCT/US11/41194; and U.S. Ser. No. 13/165,096; all
filed on 21 Jun. 2011 and incorporated herein by reference with
respect to descriptions of the crystalline block composites,
processes to make them and methods of analyzing them.
[0052] CAOB refers to highly crystalline blocks of polymerized
alpha olefin units in which the monomer is present in an amount
greater than 90 mol %, preferably greater than 93 mol percent, more
preferably greater than 95 mol percent, and preferably greater than
96 mol percent. In other words, the comonomer content in the CAOBs
is less than 10 mol percent, and preferably less than 7 mol
percent, and more preferably less than 5 mol percent, and most
preferably less than 4 mol %. CAOBs with propylene crystallinity
have corresponding melting points that are 80.degree. C. and above,
preferably 100.degree. C. and above, more preferably 115.degree. C.
and above, and most preferably 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,
preferably between 0 mol % and 10 mol %, more preferably between 0
mol % and 7 mol % and most preferably between 0 mol % and 5 mol %.
Such CEB have corresponding melting points that are preferably
75.degree. C. and above, more preferably 90.degree. C., and
100.degree. C. and above.
[0053] "Hard" segments refer to highly crystalline blocks of
polymerized units in which the monomer is present in an amount
greater than 90 mol percent, and preferably greater than 93 mol
percent, and more preferably greater than 95 mol percent, and most
preferably greater than 98 mol percent. In other words, the
comonomer content in the hard segments is most preferably less than
2 mol percent, and more preferably less than 5 mol percent, and
preferably less than 7 mol percent, and less than 10 mol percent.
In some embodiments, the hard segments comprise all or
substantially all propylene units. "Soft" segments, on the other
hand, refer to amorphous, substantially amorphous or elastomeric
blocks of polymerized units in which the comonomer content is
greater than 10 mol % and less than 90 mol % and preferably greater
than 20 mol % and less than 80 mol %, and most preferably greater
than 33 mol % and less than 75 mol %.
[0054] The BC's and/or CBC's are preferably prepared by a process
comprising contacting an addition polymerizable monomer or mixture
of monomers under addition polymerization conditions with a
composition comprising at least one addition polymerization
catalyst, a cocatalyst and a chain shuttling agent, said process
being characterized by formation of at least some of the growing
polymer chains under differentiated process conditions in two or
more reactors operating under steady state polymerization
conditions or in two or more zones of a reactor operating under
plug flow polymerization conditions. In a preferred embodiment, the
BC's and/or CBC's comprise a fraction of block polymer which
possesses a most probable distribution of block lengths.
[0055] Suitable processes useful in producing the block composites
and crystalline block composites may be found, for example, in US
Patent Application Publication No. 2008/0269412, published on Oct.
30, 2008, which is herein incorporated by reference.
[0056] When producing a block polymer having a crystalline ethylene
block (CEB) and a crystalline alpha-olefin block (CAOB) in two
reactors or zones it is possible to produce the CEB in the first
reactor or zone and the CAOB in the second reactor or zone or to
produce the CAOB in the first reactor or zone and the CEB in the
second reactor or zone. It is more advantageous to produce CEB in
the first reactor or zone with fresh chain shuttling agent added.
The presence of increased levels of ethylene in the reactor or zone
producing CEB will typically lead to much higher molecular weight
in that reactor or zone than in the zone or reactor producing CAOB.
The fresh chain shuttling agent will reduce the MW of polymer in
the reactor or zone producing CEB thus leading to better overall
balance between the length of the CEB and CAOB segments.
[0057] When operating reactors or zones in series it is necessary
to maintain diverse reaction conditions such that one reactor
produces CEB and the other reactor produces CAOB. Carryover of
ethylene from the first reactor to the second reactor (in series)
or from the second reactor back to the first reactor through a
solvent and monomer recycle system is preferably minimized. There
are many possible unit operations to remove this ethylene, but
because ethylene is more volatile than higher alpha olefins one
simple way is to remove much of the unreacted ethylene through a
flash step by reducing the pressure of the effluent of the reactor
producing CEB and flashing off the ethylene. A more preferable
approach is to avoid additional unit operations and to utilize the
much greater reactivity of ethylene versus higher alpha olefins
such that the conversion of ethylene across the CEB reactor
approaches 100%. The overall conversion of monomers across the
reactors can be controlled by maintaining the alpha olefin
conversion at a high level (90 to 95%).
[0058] Suitable catalysts and catalyst precursors for use in
preparing BC's and/or CBC's invention include metal complexes such
as disclosed in WO2005/090426, in particular, those disclosed
starting on page 20, line 30 through page 53, line 20, which is
herein incorporated by reference. Suitable catalysts are also
disclosed in US 2006/0199930; US 2007/0167578; US 2008/0311812;
U.S. Pat. No. 7,355,089 B2; or WO 2009/012215, which are herein
incorporated by reference with respect to catalysts.
[0059] Preferably, the BC's and/or CBC's comprise propylene,
1-butene or 4-methyl-1-pentene and one or more comonomers.
Preferably, the block polymers of the BC's and CBC's 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.
[0060] Comonomer content in the resulting BC's and/or CBC's may be
measured using any suitable technique, with techniques based on
nuclear magnetic resonance (NMR) spectroscopy preferred. It is
highly desirable that some or all of the polymer blocks comprise
amorphous or relatively amorphous polymers such as copolymers of
propylene, 1-butene or 4-methyl-1-pentene and a comonomer,
especially random copolymers of propylene, 1-butene or
4-methyl-1-pentene with ethylene, and any remaining polymer blocks
(hard segments), if any, predominantly comprise propylene, 1-butene
or 4-methyl-1-pentene in polymerized form. Preferably such segments
are highly crystalline or stereospecific polypropylene, polybutene
or poly-4-methyl-1-pentene, especially isotactic homopolymers.
[0061] Further preferably, the block copolymers of the BC's and/or
CBC's comprise from 10 to 90 weight percent crystalline or
relatively hard segments and 90 to 10 weight percent amorphous or
relatively amorphous segments (soft segments), preferably from 20
to 80 weight percent crystalline or relatively hard segments and 80
to 20 weight percent amorphous or relatively amorphous segments
(soft segments), most preferably from 30 to 70 weight percent
crystalline or relatively hard segments and 70 to 30 weight percent
amorphous or relatively amorphous segments (soft segments). Within
the soft segments, the mole percent comonomer may range from 10 to
90 mole percent, preferably from 20 to 80 mole percent, and most
preferably from 33 to 75 mol % percent. In the case wherein the
comonomer is ethylene, it is preferably present in an amount of 10
mol % to 90 mol %, more preferably from 20 mol % to 80 mol %, and
most preferably from 33 mol % to 75 mol % percent. Preferably, the
copolymers comprise hard segments that are 90 mol % to 100 mol %
propylene. The hard segments can be greater than 90 mol %
preferably greater than 93 mol % and more preferably greater than
95 mol % propylene, and most preferably greater than 98 mol %
propylene. Such hard segments have corresponding melting points
that are 80.degree. C. and above, preferably 100.degree. C. and
above, more preferably 115.degree. C. and above, and most
preferably 120.degree. C. and above.
[0062] In some embodiments, the block copolymer composites of the
invention have a Block Composite Index (BCI), as defined below,
that is greater than zero but less than 0.4 or from 0.1 to 0.3. In
other embodiments, BCI is greater than 0.4 and up to 1.0.
Additionally, the BCI can be in the range of from 0.4 to 0.7, from
0.5 to 0.7, or from 0.6 to 0.9. In some embodiments, BCI is in the
range of from 0.3 to 0.9, from 0.3 to 0.8, or from 0.3 to 0.7, from
0.3 to 0.6, from 0.3 to 0.5, or from 0.3 to 0.4. In other
embodiments, BCI is in the range of from 0.4 to 1.0, from 0.5 to
1.0, or from 0.6 to 1.0, from 0.7 to 1.0, from 0.8 to 1.0, or from
0.9 to 1.0.
[0063] The block composites preferably have a Tm greater than
100.degree. C., preferably greater than 120.degree. C., and more
preferably greater than 125.degree. C. Preferably the MFR of the
block composite is from 0.1 to 1000 dg/min, more preferably from
0.1 to 50 dg/min and more preferably from 0.1 to 30 dg/min.
[0064] Further preferably, the block composites of this embodiment
of the invention have a weight average molecular weight (Mw) from
10,000 to about 2,500,000, preferably from 35000 to about 1,000,000
and more preferably from 50,000 to about 300,000, preferably from
50,000 to about 200,000.
[0065] Preferably, the block composite polymers of the invention
comprise ethylene, propylene, 1-butene or 4-methyl-1-pentene and
optionally one or more comonomers in polymerized form. Preferably,
the block copolymers of the crystalline block composites comprise
in polymerized form ethylene, propylene, 1-butene, or
4-methyl-1-pentene and optionally one or more C.sub.4-20
.alpha.-olefin comonomers. Additional suitable comonomers are
selected from diolefins, cyclic olefins, and cyclic diolefins,
halogenated vinyl compounds, and vinylidene aromatic compounds.
[0066] Comonomer content in the resulting block composite polymers
may be measured using any suitable technique, with techniques based
on nuclear magnetic resonance (NMR) spectroscopy preferred.
[0067] Preferably the crystalline block composite polymers of the
invention comprise from 0.5 to 95 wt % CEP, from 0.5 to 95 wt %
CAOP and from 5 to 99 wt % block copolymer. More preferably, the
crystalline block composite polymers comprise from 0.5 to 79 wt %
CEP, from 0.5 to 79 wt % CAOP and from 20 to 99 wt % block
copolymer and more preferably from 0.5 to 49 wt % CEP, from 0.5 to
49 wt % CAOP 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 CEP, CAOP and block copolymer
equals 100%.
[0068] Preferably, the block copolymers of the invention 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
preferably, the block copolymers comprise 25 to 75 wt % CEB and 75
to 25 wt % CAOB, and even more preferably they comprise 30 to 70 wt
% CEB and 70 to 30 wt % CAOB.
[0069] In some embodiments, the block composites of the invention
have a Crystalline Block Composite Index (CBCI), as defined below,
that is greater than zero but less than 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 in the range of from 0.1 to 0.9, from 0.1
to 0.8, from 0.1 to 0.7 or from 0.1 to 0.6. Additionally, the CBCI
can be in the range of from 0.4 to 0.7, from 0.5 to 0.7, or from
0.6 to 0.9. In some embodiments, CBCI is in the range of from 0.3
to 0.9, from 0.3 to 0.8, or from 0.3 to 0.7, from 0.3 to 0.6, from
0.3 to 0.5, or from 0.3 to 0.4. In other embodiments, CBCI is in
the range of from 0.4 to 1.0, from 0.5 to 1.0, or from 0.6 to 1.0,
from 0.7 to 1.0, from 0.8 to 1.0, or from 0.9 to 1.0.
[0070] Further preferably, the crystalline block composites of this
embodiment of the invention have a weight average molecular weight
(Mw) of 1,000 to about 2,500,000, preferably of 35000 to about
1,000,000 and more preferably of 50,000 to 500,000, of 50,000 to
about 300,000, and preferably from 50,000 to about 200,000.
[0071] The overall composition of each resin is determined as
appropriate by DSC, NMR, Gel Permeation Chromatography, Dynamic
Mechanical Spectroscopy, and/or Transmission Electron Micrography.
Xylene fractionation and high temperature liquid chromatography
("HTLC") fractionation can be further used to estimate the yield of
block copolymer, and in particular the block composite index. These
are described in more detail in US Patent Application Publication
Nos US2011-0082257, US2011-0082258 and US2011-0082249, all
published on Apr. 7, 2011 and incorporated herein by reference with
respect to descriptions of the analysis methods.
[0072] For a block composite derived from ethylene and propylene,
the insoluble fractions will contain an appreciable amount of
ethylene that would not otherwise be present if the polymer was
simply a blend of iPP homopolymer and EP copolymer. To account for
this "extra ethylene", a mass balance calculation can be performed
to estimate a block composite index from the amount of xylene
insoluble and soluble fractions and the weight % ethylene present
in each of the fractions.
[0073] A summation of the weight % ethylene from each fraction
according to equation 1 results in an overall weight % ethylene (in
the polymer). This mass balance equation can also be used to
quantify the amount of each component in a binary blend or extended
to a ternary, or n-component blend.
Wt%C2.sub.Overall=W.sub.Insoluble(wt%C2.sub.Insoluble)+w.sub.soluble(wt%-
C2.sub.soluble) Eq. 1
[0074] Applying equations 2 through 4, the amount of the soft block
(providing the source of the extra ethylene) present in the
insoluble fraction is calculated. By substituting the weight %
C.sub.2 of the insoluble fraction in the left hand side of equation
2, the weight % iPP hard and weight % EP soft can be calculated
using equations 3 and 4. Note that the weight % of ethylene in the
EP soft is set to be equal to the weight % ethylene in the xylene
soluble fraction. The weight % ethylene in the iPP block is set to
zero or if otherwise known from its DSC melting point or other
composition measurement, the value can be put into its place.
Wt % C 2 Overall or xylene insoluble = w iPPHard ( wt % C 2 iPP ) +
w EP soft ( wt % C 2 EPsoft ) Eq . 2 w iPPhard = wt % C 2 overall
or xyleneinso lub le - wt % C 2 EPsoft wt % C 2 iPPhard - wt % C 2
EPsoft Eq . 3 w EPsoft = 1 - w iPPHard Eq . 4 ##EQU00001##
[0075] After accounting for the `additional` ethylene present in
the insoluble fraction, the only way to have an EP copolymer
present in the insoluble fraction, the EP polymer chain must be
connected to an iPP polymer block (or else it would have been
extracted into the xylene soluble fraction). Thus, when the iPP
block crystallizes, it prevents the EP block from solubilizing.
[0076] To estimate the block composite index, the relative amount
of each block must be taken into account. To approximate this, the
ratio between the EP soft and iPP hard is used. The ratio of the EP
soft polymer and iPP hard polymer can be calculated using Equation
2 from the mass balance of the total ethylene measured in the
polymer. Alternatively it could also be estimated from a mass
balance of the monomer and comonomer consumption during the
polymerization. The weight fraction of iPP hard and weight fraction
of EP soft is calculated using Equation 2 and assumes the iPP hard
contains no ethylene. The weight % ethylene of the EP soft is the
amount of ethylene present in the xylene soluble fraction.
[0077] For example, if an iPP-EP block composite contains an
overall ethylene content of 47 wt % C.sub.2 and is made under
conditions to produce an EP soft polymer with 67 wt % C.sub.2 and
an iPP homopolymer containing zero ethylene, the amount of EP soft
and iPP hard is 70 wt % and 30 wt %, respectively (as calculated
using Equations 3 and 4). If the percent of EP is 70 wt % and the
iPP is 30 wt %, the relative ratio of the EP:iPP blocks could be
expressed as 2.33:1.
[0078] Hence, if one skilled in the art carries out a xylene
extraction of the polymer and recovers 40 wt % insoluble and 60 wt
% soluble, this would be an unexpected result and this would lead
to the conclusion that a fraction of block copolymer was present.
If the ethylene content of the insoluble fraction is subsequently
measured to be 25 wt % C.sub.2, Equations 2 thru 4 can be solved to
account for this additional ethylene and result in 37.3 wt % EP
soft polymer and 62.7 wt % iPP hard polymer present in the
insoluble fraction.
[0079] Since the insoluble fraction contains 37.3 wt % EP
copolymer, it should be attached to an additional 16 wt % of iPP
polymer based on the EP:iPP block ratio of 2.33:1. This brings the
estimated amount of diblock in the insoluble fraction to be 53.3 wt
%. For the entire polymer (unfractionated), the composition is
described as 21.3 wt % iPP-EP Diblock, 18.7 wt % iPP polymer, and
60 wt % EP polymer. The term block composite index (BCI) is herein
defined to equal the weight percentage of diblock divided by 100%
(i.e. weight fraction). The value of the block composite index can
range from 0 to 1, wherein 1 would be equal to 100% diblock and
zero would be for a material such as a traditional blend or random
copolymer. For the example described above, the block composite
index for the block composite is 0.213. For the insoluble fraction,
the BCI is 0.533, and for the soluble fraction the BCI is assigned
a value of zero.
[0080] Depending on the estimations made of the total polymer
composition and the error in the analytical measurements which are
used to estimate the composition of the hard and soft blocks,
between 5 to 10% relative error is possible in the computed value
of the block composite index. Such estimations include the wt % C2
in the iPP hard block as measured from the DSC melting point, NMR
analysis, or process conditions; the average wt % C2 in the soft
block as estimated from the composition of the xylene solubles, or
by NMR, or by DSC melting point of the soft block (if detected).
But overall, the block composite index calculation reasonably
accounts for the unexpected amount of `additional` ethylene present
in the insoluble fraction, the only way to have an EP copolymer
present in the insoluble fraction, the EP polymer chain must be
connected to an iPP polymer block (or else it would have been
extracted into the xylene soluble fraction).
[0081] Crystalline block composites having CAOP and CAOB composed
of crystalline polypropylene and a CEP and CEB composed of
crystalline polyethylene cannot be fractionated by conventional
means. Techniques based on solvent or temperature fractionation,
for example, using xylene fractionation, solvent/non-solvent
separation, temperature rising elution fractionation, or
crystallization elution fractionation are not capable of resolving
the block copolymer since the CEB and CAOB cocrystallize with the
CEP and CAOP, respectively. However, using a method such as high
temperature liquid chromatography which separates polymer chains
using a combination of a mixed solvent/non-solvent and a graphitic
column, crystalline polymer species such as polypropylene and
polyethylene can be separated from each other and from the block
copolymer.
[0082] For crystalline block composites, the amount of isolated PP
is less than if the polymer was a simple blend of iPP homopolymer
(in this example the CAOP) and polyethylene (in this case the CEP).
Consequently, the polyethylene fraction contains an appreciable
amount of propylene that would not otherwise be present if the
polymer was simply a blend of iPP and polyethylene. To account for
this "extra propylene", a mass balance calculation can be performed
to estimate a crystalline block composite index from the amount of
the polypropylene and polyethylene fractions and the weight %
propylene present in each of the fractions that are separated by
HTLC. The polymers contained within the crystalline block composite
include iPP-PE diblock, unbound iPP, and unbound PE where the
individual PP or PE components can contain a minor amount of
ethylene or propylene respectively.
[0083] A summation of the weight % propylene from each component in
the polymer according to equation 1 results in the overall weight %
propylene (of the whole polymer). This mass balance equation can be
used to quantify the amount of the iPP and PE present in the
diblock copolymer. This mass balance equation can also be used to
quantify the amount of iPP and PE in a binary blend or extended to
a ternary, or n-component blend. For the crystalline block
composite, the overall amount of iPP or PE is contained within the
blocks present in the diblock and the unbound iPP and PE
polymers.
Wt%C3.sub.Overall=w.sub.PP(wt%C3.sub.PP)+w.sub.PE(wt%C3.sub.PE) Eq.
1
where w.sub.PP=weight fraction of PP in the polymer w.sub.PE=weight
fraction of PE in the polymer wt % C3.sub.PP=weight percent of
propylene in PP component or block wt % C3.sub.PE=weight percent of
propylene in PE component or block
[0084] Note that the overall weight % of propylene (C3) is
preferably measured from C13 NMR or some other composition
measurement that represents the total amount of C3 present in the
whole polymer. The weight % propylene in the iPP block (wt %
C3.sub.PP) is set to 100 or if otherwise known from its DSC melting
point, NMR measurement, or other composition estimate, that value
can be put into its place. Similarly, the weight % propylene in the
PE block (wt % C3.sub.PE) is set to 100 or if otherwise known from
its DSC melting point, NMR measurement, or other composition
estimate, that value can be put into its place.
[0085] Based on equation 1, the overall weight fraction of PP
present in the polymer can be calculated using Equation 2 from the
mass balance of the total C3 measured in the polymer.
Alternatively, it could also be estimated from a mass balance of
the monomer and comonomer consumption during the polymerization.
Overall, this represents the amount of PP and PE present in the
polymer regardless of whether it is present in the unbound
components or in the diblock copolymer. For a conventional blend,
the weight fraction of PP and weight fraction of PE corresponds to
the individual amount of PP and PE polymer present. For the
crystalline block composite, it is assumed that the ratio of the
weight fraction of PP to PE also corresponds to the average block
ratio between PP and PE present in this statistical block
copolymer.
w PP = wt % C 3 Overall - wt % C 3 PE wt % C 3 PP - wt % C 3 PE Eq
. 2 ##EQU00002##
where w.sub.PP=weight fraction of PP present in the whole polymer
wt % C3.sub.PP=weight percent of propylene in PP component or block
wt % C3.sub.PE=weight percent of propylene in PE component or
block
[0086] Applying equations 3 through 5, the amount of the isolated
PP that is measured by HTLC analysis is used to determine the
amount of polypropylene present in the diblock copolymer. The
amount isolated or separated first in the HTLC analysis represents
the `unbound PP` and its composition is representative of the PP
hard block present in the diblock copolymer. By substituting the
overall weight % C3 of the whole polymer in the left hand side of
equation 3, and the weight fraction of PP (isolated from HTLC) and
the weight fraction of PE (separated by HTLC) into the right hand
side of equation 3, the weight % of C3 in the PE fraction can be
calculated using equations 4 and 5. The PE fraction is described as
the fraction separated from the unbound PP and contains the diblock
and unbound PE. The composition of the isolated PP is assumed to be
the same as the weight % propylene in the iPP block as described
previously.
wt % C 3 Overall = w PP isolated ( wt % C 3 PP ) + w PE - fraction
( wt % C 3 PE - fraction ) Eq . 3 wt % C 3 PE - fraction = wt % C 3
Overall - w PPisolated ( wt % C 3 PP ) w PE - fraction Eq . 4 w PE
- fraction = 1 - w PPisolated Eq . 5 ##EQU00003##
where w.sub.PPisolated=weight fraction of isolated PP from HTLC
w.sub.PE-fraction=weight fraction of PE separated from HTLC,
containing the diblock and unbound PE wt % C3.sub.PP=weight % of
propylene in the PP; which is also the same amount of propylene
present in the PP block and in the unbound PP wt %
C3.sub.PE-fraction=weight % of propylene in the PE-fraction that
was separated by HTLC wt % C3.sub.Overall=overall weight %
propylene in the whole polymer
[0087] The amount of wt % C3 in the polyethylene fraction from HTLC
represents the amount of propylene present in the block copolymer
fraction that is above the amount present in the `unbound
polyethylene`.
[0088] To account for the `additional` propylene present in the
polyethylene fraction, the only way to have PP present in this
fraction, is that the PP polymer chain must be connected to a PE
polymer chain (or else it would have been isolated with the PP
fraction separated by HTLC). Thus, the PP block remains adsorbed
with the PE block until the PE fraction is separated.
[0089] The amount of PP present in the diblock is calculated using
Equation 6.
w PP - diblock = wt % C 3 PE - fraction - wt % C 3 PE wt % C 3 PP -
wt % C 3 PE Eq . 6 ##EQU00004##
Where
[0090] wt % C3.sub.PE-fraction=weight % of propylene in the
PE-fraction that was separated by HTLC (Equation 4) wt %
C3.sub.PP=weight % of propylene in the PP component or block
(defined previously) wt % C3.sub.PE=weight % of propylene in the PE
component or block (defined previously) w.sub.PP-diblock=weight
fraction of PP in the diblock separated with PE-fraction by
HTLC
[0091] The amount of the diblock present in this PE fraction can be
estimated by assuming that the ratio of the PP block to PE block is
the same as the overall ratio of PP to PE present in the whole
polymer. For example, if the overall ratio of PP to PE is 1:1 in
the whole polymer, then it assumed that the ratio of PP to PE in
the diblock is also 1:1. Thus the weight fraction of diblock
present in the PE fraction would be weight fraction of PP in the
diblock (w.sub.PP-diblock) multiplied by two. Another way to
calculate this is by dividing the weight fraction of PP in the
diblock (w.sub.PP-diblock) by the weight fraction of PP in the
whole polymer (equation 2).
[0092] To further estimate the amount of diblock present in the
whole polymer, the estimated amount of diblock in the PE fraction
is multiplied by the weight fraction of the PE fraction measured
from HTLC.
[0093] To estimate the crystalline block composite index, the
amount of block copolymer is determined by equation 7. To estimate
the CBCI, the weight fraction of diblock in the PE fraction
calculated using equation 6 is divided by the overall weight
fraction of PP (as calculated in equation 2) and then multiplied by
the weight fraction of the PE fraction. The value of the CBCI can
range from 0 to 1, wherein 1 would be equal to 100% diblock and
zero would be for a material such as a traditional blend or random
copolymer.
CBCI = w PP - diblock w PP w PE - fraction Eq . 7 ##EQU00005##
Where
[0094] w.sub.PP-diblock=weight fraction of PP in the diblock
separated with the PE-fraction by HTLC (Equation 6) w.sub.PP=weight
fraction of PP in the polymer w.sub.PE-fraction=weight fraction of
PE separated from HTLC, containing the diblock and unbound PE
(Equation 5)
[0095] For example, if an iPP-PE polymer contains a total of 62.5
wt % C3 and is made under the conditions to produce an PE polymer
with 10 wt % C3 and an iPP polymer containing 97.5 wt % C3, the
weight fractions of PE and PP are 0.400 and 0.600, respectively (as
calculated using Equation 2). Since the percent of PE is 40.0 wt %
and the iPP is 60.0 wt %, the relative ratio of the PE:PP blocks is
expressed as 1:1.5.
[0096] Hence, if one skilled in the art, carries out an HTLC
separation of the polymer and isolates 28 wt % PP and 72 wt % of
the PE fraction, this would be an unexpected result and this would
lead to the conclusion that a fraction of block copolymer was
present. If the C3 content of the PE fraction (wt %
C.sub.3PE-fraction) is subsequently calculated to be 48.9 wt % C3
from equations 4 and 5, the PE fraction containing the additional
propylene has 0.556 wt fraction of PE polymer and 0.444 weight
fraction of PP polymer (w.sub.PP-diblock, calculated using Equation
6).
[0097] Since the PE fraction contains 0.444 weight fraction of PP,
it should be attached to an additional 0.293 weight fraction of PE
polymer based on the iPP:PE block ratio of 1.5:1. Thus, the weight
fraction of diblock present in the PE fraction is 0.741; further
calculation of the weight fraction of diblock present in the whole
polymer is 0.533. For the entire polymer, the composition is
described as 53.3 wt % iPP-PE diblock, 28 wt % PP polymer, and 18.7
wt % PE polymer. The crystalline block composite index (CBCI) is
the estimated weight fraction of diblock present in the whole
polymer. For the example described above, the CBCI for the
crystalline block composite is 0.533.
[0098] The Crystalline Block Composite Index (CBCI) provides an
estimate of the quantity of block copolymer within the crystalline
block composite under the assumption that the ratio of CEB to CAOB
within the diblock is the same as the ratio of crystalline ethylene
to crystalline alpha-olefin in the overall crystalline block
composite. This assumption is valid for these statistical olefin
block copolymers based on the understanding of the individual
catalyst kinetics and the polymerization mechanism for the
formation of the diblocks via chain shuttling catalysis as
described in the specification.
[0099] The calculation of CBCI is based on the analytical
observation that the amount of free CAOP is lower than the total
amount of CAOP that was produced in the polymerization. The
remainder of the CAOP is bound to CEB to form the diblock
copolymer. Because the PE fraction separated by HTLC contains both
the CEP and the diblock polymer, the observed amount of propylene
for this fraction is above that of the CEP. This difference can be
used to calculate the CBCI.
[0100] Based solely on the analytical observations without prior
knowledge of the polymerization statistics, the minimum and maximum
quantities of block copolymer present in a polymer can be
calculated, thus distinguishing a crystalline block composite from
a simple copolymer or copolymer blend.
[0101] The upper bound on the amount of block copolymer present
within a crystalline block composite, w.sub.DB.sub.Max, is obtained
by subtracting the fraction of unbound PP measured by HTLC from one
as in Equation 8. This maximum assumes that the PE fraction from
HTLC is entirely diblock and that all crystalline ethylene is bound
to crystalline PP with no unbound PE. The only material in the CBC
that is not diblock is that portion of PP separated via HTLC.
w.sub.DB.sub.max=1-w.sub.PP.sub.isolated Eq. 8
[0102] The lower bound on the amount of block copolymer present
within a crystalline block composite, w.sub.DB.sub.Min, corresponds
to the situation where little to no PE is bound to PP. This lower
limit is obtained by subtracting the amount of unbound PP as
measured by HTLC from the total amount of PP in the sample as shown
in Equation 9.
w.sub.DB.sub.Min=w.sub.PP-w.sub.PP.sub.isolated Eq. 9
[0103] Furthermore, the crystalline block composite index will fall
between these two values:
w.sub.DB.sub.min<CBCI.ltoreq.w.sub.DB.sub.Max.
[0104] Based on the polymerization mechanism for production of the
crystalline block composites, the CBCI represents the best estimate
of the actual fraction of diblock copolymer in the composite. For
unknown polymer samples, w.sub.DB.sub.Min can be used to determine
if a material is a crystalline block composite. For a physical
blend of PE and PP, the overall weight fraction of PP should be
equal to that of the wt % PP from HTLC and the lower bound on
diblock content, Equation 9, is zero. If this analysis is applied
to a sample of PP that does not contain PE both the weight fraction
of PP and amount of PP obtained from HTLC are 100% and again the
lower bound on diblock content, Equation 9, is zero. Finally if
this analysis is applied to a sample of PE that does not contain PP
then both the weight fraction of PP and weight fraction PP
recovered via HTLC are zero and the lower bound on diblock,
Equation 9, is zero. Because the lower bound on diblock content is
not greater than zero in any of these three cases, these materials
are not crystalline block composites.
Differential Scanning calorimetry (DSC)
[0105] Differential Scanning calorimetry is used to measure, among
other things, the heats of fusion of the crystalline block and
block composites and is performed on a TA Instruments 01000 DSC
equipped with an RCS cooling accessory and an auto sampler. A
nitrogen purge gas flow of 50 ml/min is used. The sample is pressed
into a thin film and melted in the press at about 190.degree. C.
and then air-cooled to room temperature (25.degree. C.). About 3-10
mg of material is then cut, accurately weighed, and placed in a
light aluminum pan (ca 50 mg) which is later crimped shut. The
thermal behavior of the sample is investigated with the following
temperature profile: the sample is rapidly heated to 190.degree. C.
and held isothermal for 3 minutes in order to remove any previous
thermal history. The sample is then cooled to -90.degree. C. at
10.degree. C./min cooling rate and held at -90.degree. C. for 3
minutes. The sample is then heated to 190.degree. C. at 10.degree.
C./min heating rate. The cooling and second heating curves are
recorded. For the heat of fusion measurements for the CBC and
specified BC resins, as known and routinely performed by skilled
practitioners in this area, the baseline for the calculation is
drawn from the flat initial section prior to the onset of melting
(typically in the range of from about -10 to about 20.degree. C.
for these types of materials) and extends to the end of melting for
the second heating curve.
[0106] To summarize:
[0107] Suitable block composite resins (BC's) comprise: [0108] i)
an ethylene polymer (EP) comprising from about 80 to about 90 mol %
polymerized ethylene, preferably at least about 85 mol %; [0109]
ii) an alpha-olefin-based crystalline polymer (CAOP) and [0110]
iii) a block copolymer comprising (a) an ethylene polymer block
(EB) comprising from about 10 to about 90 mol % ethylene and (b) a
crystalline alpha-olefin block (CAOB).
[0111] Crystalline block composite resins (CBC's) comprise: [0112]
i) a crystalline ethylene polymer (CEP) comprising at least greater
than about 90 mol % polymerized ethylene, preferably at least about
93 mol %; [0113] ii) an alpha-olefin-based crystalline polymer
(CAOP) and [0114] iii) a block copolymer comprising (a) a
crystalline ethylene polymer block (CEB) comprising at least
greater than about 90 mol % polymerized ethylene, preferably at
least about 93 mol % and (b) a crystalline alpha-olefin block
(CAOB).
[0115] Another way to collectively summarize the suitable resin(s)
used in Layer B is as comprising a CBC or a specified BC
comprising: [0116] i) an ethylene polymer comprising at least about
80 mol % polymerized ethylene, preferably at least about 85 mol %,
more preferably at least about 90 mol %, and most preferably at
least about 93 mol % polymerized ethylene; [0117] ii) an
alpha-olefin-based crystalline polymer (CAOP) and [0118] iii) a
block copolymer comprising (a) an ethylene polymer block comprising
at least about 80 mol % polymerized ethylene, preferably at least
about 85 mol %, more preferably at least about 90 mol %, and most
preferably at least about 93 mol % polymerized ethylene and (b) a
crystalline alpha-olefin block (CAOB).
[0119] Preferred suitable BC and/or CBC resin(s) for Layer B have a
CAOB amount (in part (iii)) in the range of from about 30 to about
70 weight % (based on (iii)), preferably at least about 40 wt %,
more preferably at least about 45 wt % and most preferably about 50
wt %, and preferably up to about 60 wt %, and preferably up to
about 55 wt % (the balance in each case being ethylene polymer). It
has also been found that the BC and/or CBC resin(s) suitable for
Layer B have a (crystalline) block composite index of at least
about 0.1, preferably at least about 0.3, preferably at least about
0.5 and more preferably at least about 0.7. Another way to
characterize the suitable BC and/or CBC resin(s) essential for
Layer B is as having a MFR in the range of from about 1 to about 50
dg/min; preferably at least about 2, more preferably at least about
3; and preferably up to about 40, and preferably up to about 30
g/min.
[0120] In general, BC's that can be used in Layer B according to
the present invention will have heat of fusion values (generally
related to their ethylene content in the EP and EB) of at least
about 75 Joules per gram (J/g), more preferably at least about 80
J/g, still more preferably at least about 85 J/g and most
preferably at least about 90 J/g, as measured by DSC. In general,
CBC's that can be used in Layer B according to the present
invention will have heat of fusion values (reflecting the
relatively higher ethylene content in the CEP and CEB) as measured
by DSC of at least about 85 Joules per gram (J/g), more preferably
at least about 90 J/g. In either case, the heat of fusion values
for polymers of these types would generally have a maximum in the
area of about 125 J/g. For the heat of fusion measurements, as
generally known and performed by practitioners in this area, the
DSC is run as generally described below under nitrogen at
10.degree. C./min from 23.degree. C. to 220.degree. C., held
isothermal at 220.degree. C., dropped to 23.degree. C. at
10.degree. C./min and ramped back to 220.degree. C. at 10.degree.
C./min. The second heat data is used to calculate the heat of
fusion of the melting transition.
[0121] Blends of these resins can also be used in Layer B where
blended or diluted with one or more other polymers, including the
polyolefins as described herein. Suitable additional components
could be, for example, LDPE, LLDPE, an impact modifier such as
ethylene octene copolymer plastomers such as AFFINITY PL 1880G,
PL8100G, and PL 1850G or ethylene octene copolymer elastomers such
as ENGAGE 8842, ENGAGE 8150, and ENGAGE XLT 8677, or olefin block
copolymers such as for example INFUSE 9100 and 9107 brand polymer
or propylene based elastomers such as VERSIFY 2300 and VERSIFY 3300
brand resins available from The Dow Chemical Company. In
alternative embodiments, the CBC and/or BC polymer resins of Layer
B can be blended with other polyolefin resins that are grafted or
functionalized with glycidyl methacrylate, maleic anhydride (MAH),
amines or silane or they can be blended with polar copolymers of
ethylene such as EEA, EVA, EMA, EnBA, EAA and the like. If used,
the additional blend polymer needs to be: (i) miscible or highly
compatible with the BC and/or CBC, (ii) have little, if any,
deleterious impact on the desirable properties of the polyolefin
block copolymer composite, e.g., toughness and modulus, and (iii)
used in levels such that the BC and/or CBC resin(s) constitute from
at least 40 to 99 weight percent of the blend, preferably at least
60, more preferably at least 75, and more preferably at least 80
weight percent of the blend. If used, blend components would be
used in the Layer B resins in amounts of at least 2 weight percent,
preferably at least 5 and more preferably at least 8 weight percent
and preferably less than 30 weight percent, preferably less than 25
weight percent and more preferably less than 20 weight percent.
Blending can be used to provide: improve compatibility (adhesion)
with C and/or other layers under a range of conditions and lower
costs. In particular, blends would desirably be employed where
Layer B is employed as surface layer, as discussed below, and this
film surface needs properties sufficient for roll-up, handling,
packaging, transport and assembly into final laminate structures,
such as into electronic device modules.
[0122] In an alternative embodiment of the present invention, all
or part of the BC and/or CBC component in the Layer B are grafted
or functionalized with glycidyl methacrylate, maleic anhydride
(MAH), amines or silane to provide desired property modifications
such as improved adhesion to other films or the surfaces of
articles. In general, functionalization or grafting can be done by
techniques known to those skilled in this art area. Particularly
useful and applicable techniques are taught in copending United
States patent applications filed Dec. 14, 2011: (a) Ser. No.
61/570,464 entitled, "FUNCTIONALIZED BLOCK COMPOSITE AND
CRYSTALLINE BLOCK COMPOSITE COMPOSITIONS AS COMPATIBILIZERS and (b)
Ser. No. 61/570,340 entitled, "FUNCTIONALIZED BLOCK COMPOSITE AND
CRYSTALLINE BLOCK COMPOSITE COMPOSITIONS", which are incorporated
herein by reference.
[0123] In an alternative embodiment of the present invention, with
proper selection of the Layer B formulation, Layer B can be
designed to have sufficient physical properties and be sufficiently
adhesive to other films or articles and the films according to the
present invention are two layer structures. Such other films to
which adhesion may be desired include, for example, the
"encapsulation films" employed in the assembly of electronic
devices and discussed in more detail below, eliminating the need to
have a further, separate seal layer. Such other articles to which
Layer B adhesion may be desired include, for example, the surfaces
of photovoltaic cells (eliminating the need to have further seal or
encapsulation layers) or metal surfaces such as tin or other metals
used in photovoltaic cells, and aluminum or other metals that might
be employed in construction of lithium ion batteries. To provide
the proper balance of adhesion and other properties in Layer B, the
CBC and/or BC resin formulation employed would comprise: greater
than 20 wt % CBC and/or BC resin, preferably greater than 40 wt %
CBC and/or BC and more preferably greater than 50 wt % CBC and/or
BC and even more preferably greater than 60 wt % CBC and/or BC. In
this embodiment, the thickness of the Layer B would generally be
greater than when used as tie layer with layers A and C in a 3 or
more layer film.
Layer A Polyolefin Resin Components
[0124] Layer A, optionally employed according to the present
invention and often referred to as a "seal" layer, is selected to
be adhered, either preferably by co-extrusion or alternatively but
less preferably by a lamination process (such as extrusion
lamination, thermal lamination, or adhesive lamination) to the tie
layer (Layer B) in production of the film according to the
invention and to adhere the film to other films or articles such as
the encapsulation films employed in the assembly of electronic
devices ("encapsulation films" being discussed in more detail
below). Layer A materials can be selected from a very wide variety
of different types of materials assembled in blends and/or layers
as described in more detail below. Among other things, the relative
thinness of Layer A distinguishes it from a layer that would serve
as an "encapsulation" layer.
[0125] The wide variety of candidate seal layer materials includes
generally wide range of thermoplastic ethylene-based polymers, such
as high pressure, free-radical low density polyethylene (LDPE), and
ethylene-based polymers prepared with Ziegler-Natta catalysts,
including high density polyethylene (HDPE) and heterogeneous linear
low density polyethylene (LLDPE), ultra low density polyethylene
(ULDPE), and very low density polyethylene (VLDPE), as well as
multiple-reactor ethylenic polymers ("in reactor" blends of
Ziegler-Natta PE and metallocene PE, such as products disclosed in
U.S. Pat. No. 6,545,088 (Kolthammer et al.); U.S. Pat. No.
6,538,070 (Cardwell et al.); U.S. Pat. No. 6,566,446 (Parikh et
al.); U.S. Pat. No. 5,844,045 (Kolthammer et al.); U.S. Pat. No.
5,869,575 (Kolthammer et al.); and U.S. Pat. No. 6,448,341
(Kolthammer et al.)). Commercial examples of linear ethylene-based
polymers include ATTANE.TM. Ultra Low Density Linear Polyethylene
Copolymer, DOWLEX.TM. Polyethylene Resins, and FLEXOMER.TM. Very
Low Density Polyethylene, ELITE.TM. brand enhanced polyethylene
resin, all available from The Dow Chemical Company. Other suitable
synthetic polymers include ethylene/diene interpolymers, ethylene
acrylic acid (EAA), ethylene-vinyl acetate (EVA), ethylene ethyl
acrylate (EEA), ethylene methyl acrylate (EMA), ethylene n-butyl
acrylate (EnBA), ethylene methacrylic acid (EMAA), various types of
ionomers, and ethylene/vinyl alcohol copolymers. Homogeneous
olefin-based polymers such as ethylene-based plastomers or
elastomers can also be useful as components in blends or compounds
made with the ethylenic polymers of this invention. Commercial
examples of homogeneous metallocene-catalyzed, ethylene-based
plastomers or elastomers include AFFINITY.TM. polyolefin plastomers
and ENGAGE.TM. polyolefin elastomers, both available from The Dow
Chemical Company, and commercial examples of homogeneous
propylene-based plastomers and elastomers include VERSIFY.TM.
performance polymers, available from The Dow Chemical Company, and
VISTAMAX.TM. polymers available from ExxonMobil Chemical Company.
Suitable ethylene-propylene polymers include BC's and CBC's as
described above.
Layer A Olefinic Interpolymers
[0126] Some specific preferred examples of olefinic interpolymers
useful in this invention, particularly in the top layer of the
backsheet, include very low density polyethylene (VLDPE) (e.g.,
FLEXOMER.RTM. ethylene/1-hexene polyethylene made by The Dow
Chemical Company), homogeneously branched, linear
ethylene/.alpha.-olefin copolymers (e.g. TAFMER.RTM. by Mitsui
Petrochemicals Company Limited and EXACT.RTM. by Exxon Chemical
Company), homogeneously branched, substantially linear
ethylene/.alpha.-olefin polymers (e.g., AFFINITY.RTM. and
ENGAGE.RTM. polyethylene available from The Dow Chemical Company),
and ethylene multi-block copolymers (e.g., INFUSE.degree. olefin
block copolymers available from The Dow Chemical Company). The more
preferred polyolefin copolymers for use in the top layer of the
backsheet are the homogeneously branched linear and substantially
linear ethylene copolymers, particularly the substantially linear
ethylene copolymers which are more fully described in U.S. Pat.
Nos. 5,272,236, 5,278,272 and 5,986,028, and the ethylene
multi-block copolymers which are more fully described in U.S. Pat.
No. 7,355,089, WO 2005/090427, US2006/0199931, US2006/0199930,
US2006/0199914, US2006/0199912, US2006/0199911, US2006/0199910,
US2006/0199908, US2006/0199906, US2006/0199905, US2006/0199897,
US2006/0199896, US2006/0199887, US2006/0199884, US2006/0199872,
US2006/0199744, US2006/0199030, US2006/0199006 and
US2006/0199983.
Layer A Polar Ethylene-Copolymers
[0127] One preferred polar ethylene copolymer for use in the top
layer of the claimed films is an EVA copolymer, including blends
comprising EVA copolymers, that will form a sealing relationship
with other films or layers, e.g., encapsulant, a glass cover sheet,
etc. when brought into adhesive contact with the layer or other
component. The ratio of units derived from ethylene to units
derived from vinyl acetate in the copolymer, before grafting or
other modification, can vary widely, but typically the EVA
copolymer contains at least about 1, preferably at least 2, more
preferably at least 4 and even more preferably at least 6, wt %
units derived from vinyl acetate. Typically, the EVA copolymer
contains less than about 33 wt % units derived from vinyl acetate,
preferably less than 30, preferably less than 25, preferably less
than 22, preferably less than 18 and more preferably less than 15
wt % units derived from vinyl acetate. The EVA copolymer can be
made by any process including emulsion, solution and high-pressure
polymerization.
[0128] The EVA copolymer before grafting or other modification
typically has a density of less than 0.95, preferably less than
0.945, more preferably less than 0.94, g/cc. The same EVA copolymer
typically has a density greater than 0.9, preferably greater than
0.92, and more preferably greater than 0.925, g/cc. Density is
measured by the procedure of ASTM D-792. EVA copolymers are
generally characterized as semi-crystalline, flexible and having
good optical properties, e.g., high transmission of visible and
UV-light and low haze.
[0129] Another preferred polar ethylene copolymer useful as top
layer of the backsheet is an ethylene acrylate copolymer such as
ethylene ethyl acrylate (EEA) and ethylene methyl acrylate (EMA)
copolymers, (including blends comprising either) that can also form
a sealing relationship with the adjacent layer, such as an
encapsulant layer in an electronic device module, when they are
brought into adhesive contact. The ratio of units derived from
ethylene to units derived from ethyl acrylate or methyl acrylate in
the copolymer, before grafting or other modification, can vary
widely, but typically the EEA or EMA copolymer contains at least 1,
preferably at least 2, more preferably at least 4 and even more
preferably at least 6, wt % units derived from the ethyl acrylate
or methyl acrylate. Typically, the EEA or EMA copolymer contains
less than 28, preferably less than 25, more preferably less than
22, and more preferably less than 19, wt % units derived from ethyl
acrylate or methyl acrylateacrylate.
[0130] These polar ethylene copolymers (e.g., EVA, EEA or EMA
copolymers) typically have a melt index (MI as measured by the
procedure of ASTM D-1238 (190C/2.16 kg) of less than 100,
preferably less than 75, more preferably less than 50 and even more
preferably less than 30, g/10 min. The typical minimum MI is at
least 0.3, more preferably 0.7, and more preferably it is at least
1 g/10 min.
[0131] One preferred top layer of the backsheet is a blend
formulation of a linear low density polyethylene (LLDPE) comprising
polar ethylene copolymer in an amount of from 10 to 45 weight %,
the weight % depending upon the polar ethylene copolymer being
used.
Layer A MAH-m-Polyolefins
[0132] MAH-m-polyolefins are another preferred seal layer material
and include MAH-g-polyolefins and MAH interpolymers, i.e., the MAH
functionality is present in the polyolefin either by grafting onto
the polymer backbone or incorporating the functionality into the
backbone through copolymerization of MAH with the olefin
monomer.
[0133] In one embodiment of the invention, the polyolefin is
graft-modified to enhance the interlayer adhesion between the top
layer and the bottom layer of the multilayer structure through a
reaction of the grafted functionality with the reactive group
present in the middle tie layer. Any material that can be grafted
to the polyolefin and can react with the reactive group present in
the tie layer can be used as the graft material.
[0134] Any unsaturated organic compound containing at least one
ethylenic unsaturation (e.g., at least one double bond), at least
one carbonyl group (--C.dbd.O), and that will graft to the
polyolefin polymer and more particularly to EVA, EEA, EMA or
polypropylene, can be used as the grafting material. Representative
of compounds that contain at least one carbonyl group are the
carboxylic acids, anhydrides, esters and their salts, both metallic
and nonmetallic. Preferably, the organic compound contains
ethylenic unsaturation conjugated with a carbonyl group.
Representative compounds include maleic, fumaric, acrylic,
methacrylic, itaconic, crotonic, .alpha.-methyl crotonic, and
cinnamic acid and their anhydride, ester and salt derivatives, if
any. Maleic anhydride is the preferred unsaturated organic compound
containing at least one ethylenic unsaturation and at least one
carbonyl group.
[0135] The unsaturated organic compound content of the graft
polyolefin is at least 0.01 wt %, and preferably at least 0.05 wt
%, based on the combined weight of the polyolefin and the organic
compound. The maximum amount of unsaturated organic compound
content can vary to convenience, but typically it does not exceed
10 wt %, preferably it does not exceed 5 wt %, and more preferably
it does not exceed 2 wt %. This unsaturated organic content of the
graft polyolefin is measured by a titration method, e.g., a grafted
polyolefin/xylene solution is titrated with a potassium hydroxide
(KOH) solution. The MAH functionality can be present in the
polyolefin e.g., by grafting, or even by copolymerization with the
olefin monomer.
[0136] The unsaturated organic compound can be grafted to the
polyolefin by any known technique, such as those taught in U.S.
Pat. Nos. 3,236,917 and 5,194,509. For example, in the '917 patent
the polymer is introduced into a two-roll mixer and mixed at a
temperature of 60.degree. C. The unsaturated organic compound is
then added along with a free radical initiator, such as, for
example, benzoyl peroxide, and the components are mixed at
30.degree. C. until the grafting is completed. In the '509 patent,
the procedure is similar except that the reaction temperature is
higher, e.g., 210 to 300.degree. C., and a free radical initiator
is not used or is used at a reduced concentration.
[0137] An alternative and preferred method of grafting is taught in
U.S. Pat. No. 4,950,541 by using a twin-screw devolatilizing
extruder as the mixing apparatus. The polymer and unsaturated
organic compound are mixed and reacted within the extruder at
temperatures at which the reactants are molten and in the presence
of a free radical initiator. Preferably, the unsaturated organic
compound is injected into a zone maintained under pressure within
the extruder.
Layer A Silane Grafted Ethylene-Based Polymers
[0138] In another preferred embodiment, a suitable material for
Layer A can be provided by a silane grafted polyolefin as described
below for use as the encapsulation layer, particularly as provided
by silane grafting in the thermoplastic ethylene-based polymers
described above, including in an olefinic interpolymer or polar
ethylene copolymer described above. If used as Layer A in a
backsheet film according to the present invention, as discussed
below, the silane grafted polyolefin layer thickness would
generally be less than 200 micron (.mu.m), and more preferably less
than 100 .mu.m and not sufficient to serve as a typical
encapsulation layer that is commonly a film 450 .mu.m thick. It
will, however, in layer A of the present films provide good sealing
with such materials used in encapsulation films.
Layer A Crystalline Olefin Block Composite
[0139] In another preferred embodiment of the present invention and
depending upon the nature of the encapsulant film layer, a suitable
sealing layer can be provided by a crystalline block copolymer
composite as described above. In a backsheet according to the
present invention, depending upon the specific selection of this
type of crystalline block copolymer composite as the B layer, the B
layer can serve as both Layers B and A. In a preferred embodiment,
the present invention is a novel film comprising Layers B and C. In
this embodiment, it may also be desirable to incorporate a minor
amount (e.g., less than 25%) of a polar ethylene copolymer in such
crystalline block copolymer composite.
Blends
[0140] Blends comprising these polyolefin resins with others as
described above can also be used in Layer A of films according to
the invention. In other words, Layer A polyolefin polymers can be
blended or diluted with one or more other polymers to the extent
that the polyolefin is (i) compatible with the other polymer, (ii)
the other polymer has little, if any, deleterious impact on the
desirable properties of the polyolefin polymer, e.g., toughness and
modulus, and (iii) the polyolefin polymer of this invention
constitutes at least 55, preferably at least 70, preferably at
least 75 and more preferably at least 80, weight percent of the
blend.
Crosslinking in Layer A
[0141] Although crosslinking would preferably be avoided, due to
the low density and modulus of the polyolefin resins used in the
practice of this invention, these polymers can be cured or
crosslinked at the time of lamination or after, usually shortly
after, assembly of the layers into the multilayered article, e.g.,
PV module. Crosslinking can be initiated and performed by any one
of a number of different and known methods, e.g., by the use of
thermally activated initiators, e.g., peroxides and azo compounds;
photoinitiators, e.g., benzophenone; radiation techniques including
Electron-beam and x-ray; vinyl silane, e.g., vinyl tri-ethoxy or
vinyl tri-methoxy silane; and moisture cure.
Additives in Layers A, B, or C
[0142] The individual layers of the multilayered structure can
further comprise one or more additives. Exemplary stabilizer
additives include UV-stabilizers, UV-absorbers, and antioxidants.
These stabilizer additives are useful in, e.g., reducing the
oxidative degradation and improving the weatherability of the
product. Suitable stabilizers include hindered amines and hindered
benzoates such as Cynergy A400, A430, R350 and R350-a4, Cyasorb
UV-3529, Cyasorb UV-3346, Cyasorb UV-3583, Hostavin N30, Univil
4050, Univin 5050, Chimassorb UV-119, Chimassorb 944 LD, Tinuvin
622 LD and the like; UV absorbers such as Tinuvin 328 or Cyasorb
UV-1164 and the like and; primary and secondary antioxidants such
as Cyanox 2777, Irganox 245, 1010, 1076, B215, B225, PEPQ, Weston
399, TNPP, Irgafos 168 and Doverphos 9228. The amounts and
combinations of stabilizers needed depend on the type, aging
environment and longevity desired and are used in the manner and,
as is commonly known in the art, the amounts typically range
between greater than 0.01 and less than 3% weight percent based on
the polymer weight being stabilized.
[0143] Other additives that can be used include, but are not
limited to ignition resistance additives, anti-blocks such as
diatomaceous earth, superfloss, silicates, talc, mica, wolastonite,
and epoxy coated talcs, and the like; slip additives such as
erucamide and stearamide and the like, polymer process aids such as
Dyneon fluoropolymer elastomers like Dynamar FX5930, pigments and
fillers such as TiO2 R960, R350, R105, R108, R104, graphites,
carbon blacks such as used in Dow DNFA-0037 masterbatch or provided
by Cabot. Also, pigments commonly used to create colored plastics
may be employed, especially those known to have greater light
stability. These and other potential additives are used in the
manner and amount as is commonly known in the art.
Multilayer Film Structures and ED Modules
[0144] In describing the use of the polymer components above to
make laminate or layered structures, there are a number of terms
that are regularly used and defined as follows.
[0145] "Layer" means a single thickness, coating or stratum
continuously or discontinuously spread out or covering a
surface.
[0146] "Multi-layer" means at least two layers.
[0147] "Facial surface", "planar surface" and like terms as related
to films or layers mean the surfaces of the layers that are in
contact with the opposite and adjacent surfaces of the adjoining
layers. Facial surfaces are in distinction to edge surfaces. A
rectangular film or layer comprises two facial surfaces and four
edge surfaces. A circular layer comprises two facial surfaces and
one continuous edge surface.
[0148] "In adhering contact" and like terms mean that one facial
surface of one layer and one facial surface of another layer are in
touching and binding contact to one another such that one layer
cannot be removed for the other layer without damage to the
in-contact facial surfaces of both layers.
[0149] "Sealing relationship" and like terms mean that two or more
components, e.g., two polymer layers, or a polymer layer and an
electronic device, or a polymer layer and a glass cover sheet,
etc., join with one another in such a manner, e.g., co-extrusion,
lamination, coating, etc., that the interface formed by their
joining is separated from their immediate external environment.
[0150] The polymeric materials as discussed above can be used in
this invention to construct multilayer structure film or sheet,
which is used in turn to construct and electronic device modules in
the same manner and using the same amounts as is known in the art,
e.g., such as those taught in U.S. Pat. No. 6,586,271, US Patent
Application Publication US2001/0045229 A1, WO 99/05206 and WO
99/04971. These materials can be used to construct "skins" for the
electronic device, i.e., multilayered structures for application to
one or both face surfaces of the device, particularly the back
surface of such devices, i.e., "backsheets". Preferably these
multilayered structures, e.g., backsheets, are co-extruded, i.e.,
all layers of the multilayered structures are extruded at the same
time, such that as the multilayered structure is formed.
[0151] Depending upon their intended use, the multilayer film or
sheet structures according to the present invention can be designed
to meet certain performance requirements such as in the areas of
physical performance properties including toughness, transparency,
tensile strength, interlayer adhesion, and heat resistance;
electrical properties such as insulation, dielectric breakdown,
partial discharge and resistance; reflectance; and appearance.
Layer C--Comprising High Melting Point Polyolefin Resins
[0152] In general, Layer C in the multilayer backsheet structures
according to the present invention is prepared from the "Layer C
High Melting Point Polyolefin Resins" as discussed above. In one
preferred embodiment, it is preferably a highly crystalline
homopolymer polypropylene resin. Depending upon the specific
performance requirements for the film and/or a module structure in
which it is intended for use, the thickness of Layer C is typically
in the range of from 100 .mu.m to 400 .mu.m. As for minimum
thickness, Layer C is preferably at least 125 .mu.m, more
preferably at least 150 .mu.m, more preferably at least 160 .mu.m
and most preferably at least 170 .mu.m thick. As for maximum
thickness, the thickness of Layer C can be up to and including 375
.mu.m; 350 .mu.m, preferably 300 .mu.m, more preferably 275 .mu.m
and most preferably 250 .mu.m.
Layer B--Comprising Polyolefin Block Copolymer Composite Resin
[0153] In general, Layer B in the multilayer backsheet film
structures according to the several embodiments of the present
invention is prepared from the "Layer B Polyolefin Block Composite
Resins" as discussed above. In one preferred embodiment, it is
preferably a crystalline block copolymer composite resin. Depending
upon the specific performance requirements for the film and/or a
module structure in which it is intended for use, the thickness of
Layer B is typically in the range of from 1 .mu.m to 500 .mu.m. In
the alternative embodiment of the present invention where Layer B
is sufficiently strong and adhesive and the films according to the
present invention are two layer structures of Layers B and C for
use in the electronic device embodiment, the thickness of the Layer
B would generally be at least 10 um, more preferably at least 15
um, even more preferably at least 25 um and preferably less than or
equal to 500 um, more preferably less than or equal to 400 um and
even more preferably less than or equal to 350 um. With Layer B
serving as both a surface seal layer it is preferably a blend
comprising the CBC and one or more other components such as polymer
process aids, colorants, and slip or anti-block additives. As for
minimum thickness when used as tie layer with at least an A and C
layer, Layer B is only as thick as needed to tie the adjacent
Layers A and C together and can preferably be at least 2 .mu.m,
preferably at least 3 .mu.m, preferably at least 4 .mu.m, more
preferably at least 10 .mu.m, more preferably at least 15 .mu.m,
more preferably at least 20 .mu.m and most preferably at least 25
.mu.m thick. As for maximum thickness when a tie layer for A and C,
the thickness and cost of Layer B are desirably minimized but are
preferably up to and including 150 .mu.m, preferably 100 .mu.m,
more preferably 75 .mu.m and most preferably up to and including 50
.mu.m thick.
Layer A--Seal Layer
[0154] As mentioned above, in one multilayered article embodiment
of the present invention, the top or seal Layer A adheres the films
according to the present invention to an encapsulating film.
Depending upon the specific performance requirements for the film
and/or a module structure in which it is intended for use, the
thickness of Layer A is typically in the range of from 15 .mu.m to
200 .mu.m. As for minimum thickness, Layer A is only as thick as
needed to adhere the backsheet to the encapsulation film layer and
should be at least 17 .mu.m, preferably at least 20 .mu.m, more
preferably at least 23 .mu.m and most preferably at least 25 .mu.m
thick. As for maximum thickness, the thickness and cost of Layer A
are desirably minimized but can be up to and including 175 .mu.m,
preferably 150 .mu.m, more preferably 130 .mu.m, and most
preferably up to and including 125 .mu.m.
Film Structure and Thickness
[0155] The composition of the layers can be selected and optimized
along the lines discussed herein depending upon the intended film
structure and usage of the film structure. For example, for use in
electronic device laminate structures multilayer films according
the present invention, the films can be employed as a 2 layer
backsheet or a 3 layer backsheet (comprising both a tie layer and a
top seal layer). The films according to the present invention are
suitable to be employed as, among other things, backsheet layers
for direct use in laminate electronic device structures, such as,
for example PV modules.
[0156] In all cases, the top facial surface of the multilayered
film structure exhibits good adhesion for the facial surfaces of
the encapsulation layer material that encapsulates the device.
[0157] Depending somewhat upon the specific structure and process
for utilizing the film or sheet that structures according to the
present invention, such film structures can be prepared by any of a
large number of known film production processes including but not
limited to extrusion or co-extrusion methods such as blown-film,
modified blown-film, calendaring and casting, as well as sheet
extrusion using a roll stack. There are many known techniques which
can be employed for providing multilayer films (up to and including
microlayer films), including for example in U.S. Pat. No.
5,094,788; U.S. Pat. No. 5,094,793; WO/2010/096608; WO 2008/008875;
U.S. Pat. No. 3,565,985; U.S. Pat. No. 3,557,265; U.S. Pat. No.
3,884,606; U.S. Pat. No. 4,842,791 and U.S. Pat. No. 6,685,872 all
of which are hereby incorporated by reference herein. Layers A, B
and C of the films according to the present invention, are selected
to be adhered simultaneously together preferably by co-extrusion or
alternatively but less preferably by a lamination process (such as
extrusion lamination, thermal lamination, or adhesive lamination)
into the films according to the invention. Alternatively but less
preferably, a sequential process can be employed to adhere pairs of
layers together and to the third and any optional layers.
[0158] The overall thickness of the multilayered films and, in
particular backsheet structures, according to the present
invention, prior to attachment to other layers such as encapsulant
layers, electronic devices and/or anything else, is typically
between 50 .mu.m and 825 .mu.m. Preferably to provide sufficient
physical properties and performance, the film thickness is at least
75 .mu.m, and more preferably at least 125 .mu.m. To maintain light
weight and low costs, but retain the requisite electrical
properties, the film thickness is preferably 775 .mu.m or less,
more preferably 575 .mu.m or less. This includes any optional,
additional layers that form and are an integral part of the
multilayer structure comprising layers A, B and C.
[0159] FIG. 1, not to scale, is a cross-sectional view of an
electronic device comprising a three-layer backsheet 14 comprising
"A" Layer 14A, "B" Layer 14B and "C" Layer 14C all in adhering
contact with each other, further in adhering contact with an
encapsulant layer 12b adhered or laminated to the back surface of
an electronic device, e.g., a PV cell.
PV Module Structures and Terms
[0160] "Photovoltaic cells" ("PV cells") contain one or more
photovoltaic effect materials of any of several inorganic or
organic types which are known in the art and from prior art
photovoltaic module teachings. For example, commonly used
photovoltaic effect materials include one or more of the known
photovoltaic effect materials including but not limited to
crystalline silicon, polycrystalline silicon, amorphous silicon,
copper indium gallium (di)selenide (CIGS), copper indium selenide
(CIS), cadmium telluride, gallium arsenide, dye-sensitized
materials, and organic solar cell materials.
[0161] As shown by the diagram of a PV module in FIG. 1, PV cells
(11) are typically employed in a laminate structure and have at
least one light-reactive surface that converts the incident light
into electric current. Photovoltaic cells are well known to
practitioners in this field and are generally packaged into
photovoltaic modules that protect the cell(s) and permit their
usage in their various application environments, typically in
outdoor applications. As used herein, PV cells may be flexible or
rigid in nature and include the photovoltaic effect materials and
any protective coating surface materials that are applied in their
production as well as appropriate wiring and electronic driving
circuitry (not shown).
[0162] "Photovoltaic modules" ("PV Modules"), such as represented
by the example structure shown in FIG. 1, contain at least one
photovoltaic cell 11 (in this case having a single light-reactive
or effective surface directed or facing upward in the direction of
the top of the page) surrounded or encapsulated by a light
transmitting protective encapsulating sub-component 12a on the top
or front surface and protective encapsulating sub-component 12b on
the rear or back surface, which is optionally light transmitting.
Combined, 12a and 12b form an encapsulating component 12, shown
here as a combination of two encapsulating layers "sandwiching" the
cell. The light transmitting cover sheet 13 has an interior surface
in adhering contact with a front facial surface of the
encapsulating film layer 12a, which layer 12a is, in turn, disposed
over and in adhering contact with PV cell 11.
[0163] Multilayer backsheet films 14 according to the present
invention act as a substrate and supports a rear surface of the PV
cell 11 and optional encapsulating film layer 12b, which, in this
case is disposed on a rear surface of PV cell 11. Back sheet layer
14 (and even encapsulating sub-layer 12b) need not be light
transmitting if the surface of the PV cell to which it is opposed
is not effective, i.e., reactive to sunlight. In the case of a
flexible PV module, as the description "flexible" implies, it would
comprise a flexible thin film photovoltaic cell 11.
[0164] In the electronic device (and especially the PV module)
embodiments of the present invention, the top layer or coversheet
13 and the top encapsulating layer 12a generally need to have good,
typically excellent, transparency, meaning transmission rates in
excess of 90, preferably in excess of 95 and even more preferably
in excess of 97, percent as measured by UV-vis spectroscopy
(measuring absorbance in the wavelength range of 250-1200
nanometers. An alternative measure of transparency is the internal
haze method of ASTM D-1003-00. If transparency is not a requirement
for operation of the electronic device, then the polymeric material
can contain opaque filler and/or pigment.
[0165] The thicknesses of all the electronic device module layers,
described further below, both in an absolute context and relative
to one another, are not critical to this invention and as such, can
vary widely depending upon the overall design and purpose of the
module. Typical thicknesses for protective or encapsulate layers
12a and 12b are in the range of 0.125 to 2 millimeters (mm), and
for the cover sheet in the range of 0.125 to 1.25 mm. The thickness
of the electronic device can also vary widely.
Light transmitting Encapsulation Component or Layer These layers
are sometimes referred to in various types of PV module structures
as "encapsulation" films or layers or "protective" films or layers
or "adhesive" films or layers. So long as sufficiently light
transmitting, these layers can employ the same resins and resin
compositions as described above in connection with their use as
Layer A for backsheet embodiments of the present invention.
Typically, these layers function to encapsulate and protect the
interior photovoltaic cell from moisture and other types of
physical damage and adhere it to other layers, such as a glass or
other top sheet material and/or a back sheet layer. Optical
clarity, good physical and moisture resistance properties,
moldability and low cost are among the desirable qualities for such
films. Suitable polymer compositions and films include those used
and in the same manner and amounts as the light transmitting layers
used in the known PV module laminate structures, e.g., such as
those taught in U.S. Pat. No. 6,586,271, US Patent Application
Publication US2001/0045229 A1, WO 99/05206 and WO 99/04971. These
materials can be used as the light transmitting "skin" for the PV
cell, i.e., applied to any faces or surfaces of the device that are
light-reactive. Suitable films are known and commercially available
including ENLIGHT.TM. brand polyolefin encapsulant films
commercially available from The Dow Chemical Company. Light
transmitting Cover Sheet
[0166] Light transmitting cover sheet layers, sometimes referred to
in various types of PV module structures as "cover", "protective"
and/or "top sheet" layers, can be one or more of the known rigid or
flexible sheet materials. Alternatively to glass or in addition to
glass, other known materials can be employed for one or more of the
layers with which the lamination films according to the present
invention are employed. Such materials include, for example,
materials such as polycarbonate, acrylic polymers, a polyacrylate,
a cyclic polyolefin such as ethylene norbornene,
metallocene-catalyzed polystyrene, polyethylene terephthalate,
polyethylene naphthalate, fluoropolymers such as ETFE
(ethylene-tetrafluoroethlene), PVF (polyvinyl fluoride), FEP
(fluoroethylene-propylene), ECTFE
(ethylene-chlorotrifluoroethylene), PVDF (polyvinylidene fluoride),
and many other types of plastic or polymeric materials, including
laminates, mixtures or alloys of two or more of these materials.
The location of particular layers and need for light transmission
and/or other specific physical properties would determine the
specific material selections. As needed and possible based upon
their composition, the down conversion/light stabilizer
formulations discussed above can be employed in the transparent
cover sheets. However, the inherent stability of some of these may
not require light stabilization according to the present
invention.
[0167] When used in certain embodiments of the present invention,
the "glass" used as a light transmitting cover sheet refers to a
hard, brittle, light transmitting solid, such as that used for
windows, many bottles, or eyewear, including, but not limited to,
soda-lime glass, borosilicate glass, sugar glass, isinglass
(Muscovy-glass), or aluminum oxynitride. In the technical sense,
glass is an inorganic product of fusion which has been cooled to a
rigid condition without crystallizing. Many glasses contain silica
as their main component and glass former.
[0168] Pure silicon dioxide (SiO2) glass (the same chemical
compound as quartz, or, in its polycrystalline form, sand) does not
absorb UV light and is used for applications that require
transparency in this region. Large natural single crystals of
quartz are pure silicon dioxide, and upon crushing are used for
high quality specialty glasses. Synthetic amorphous silica, an
almost 100% pure form of quartz, is the raw material for the most
expensive specialty glasses.
[0169] The glass layer of the laminated structure is typically one
of, without limitation, window glass, plate glass, silicate glass,
sheet glass, float glass, colored glass, specialty glass which may,
for example, include ingredients to control solar heating, glass
coated with sputtered metals such as silver, glass coated with
antimony tin oxide and/or indium tin oxide, E-glass, and
Solexia.TM. glass (available from PPG Industries of Pittsburgh,
Pa.).
Laminated PV Module Structures
[0170] The methods of making PV modules known in the art can
readily be adapted to use the multilayer backsheet film structures
according to present invention. For example, the multilayer
backsheet film structures according to present invention can be
used in the PV modules and methods of making PV modules such as
those taught in U.S. Pat. No. 6,586,271, US Patent Application
Publication US2001/0045229 A1, WO 99/05206 and WO 99/04971.
[0171] In general, in the lamination process to construct a
laminated PV module, at least the following layers are brought into
facial contact: [0172] a light-receiving top sheet layer (e.g., a
glass layer) having an "exterior" light-receiving facial surface
and an "interior" facial surface; [0173] a front light transmitting
thermoplastic polymer film having at least one layer of light
transmitting thermoplastic polymers comprising the down
conversion/light stabilizer formulations according to present
invention, having one facial surface directed toward the glass and
one directed toward the light-reactive surface of the PV cell and
encapsulating the cell surface, provided that this layer can be
optional in some module structures where the PV cell material may
be directly deposited on the light receiving layer (e.g., glass);
[0174] a PV cell; [0175] a second encapsulating film layer; and
[0176] a back layer comprising glass or other back layer
substrate.
[0177] With the layers or layer sub-assemblies assembled in desired
locations the assembly process typically requires a lamination step
with heating and compressing at conditions sufficient to create the
needed adhesion between the layers and, if needed in some layers or
materials, initiation of their crosslinking. If desired, the layers
may be placed into a vacuum laminator for 10 to 20 minutes at
lamination temperatures in order to achieve layer-to-layer adhesion
and, if needed, crosslinking of the polymeric material of the
encapsulation element. In general, at the lower end, the lamination
temperatures need to be at least 130.degree. C., preferably at
least 140.degree. C. and, at the upper end, less than or equal to
170.degree. C., preferably less than or equal to 160.degree. C.
[0178] The following examples further illustrate the invention.
Unless otherwise indicated, all parts and percentages are by
weight.
EXPERIMENTS
[0179] Experimental multilayer sample films (layers indicated by
letters, e.g., A, B, and C), as summarized below in the Tables
below, are made using the thermoplastic resin materials summarized
below in Tables 1 and 2. Where indicated, the Melt Flow Rates (MFR)
are measured according to ASTM D1238 (230 C/2.16 kg) and reported
in grams per 10 minutes (g/10 min) and Melt Index values (MI) are
measured according to ASTM D1238 (190 C/2.16 kg) and reported in
g/10 min. The density is measured according to ASTM D792 and given
in grams per cubic centimeter (g/cc). The polypropylene polyolefins
all have at least one melting peak greater than 125.degree. C. and
heat of fusion values greater than 60 J/g.
TABLE-US-00001 TABLE 1 Resins Used in Examples Density Resin ASTM
D792 Resin Product name Supplier MFR/MI (g/cc) PP 1 H314-02Z PP Dow
2.0 MFR 0.900 PP 2 D118.01 PP Dow 8.0 MFR 0.900 PP3 INSPIRE 404 Dow
3.0 MFR 0.900 LLDPE DOWLEX .TM. Dow 2.3 MI 0.917 2247G Plastomer
AFFINITY .TM. PL Dow 1.0 MI 0.902 1880G EVA 1 ELVAX 3150 DuPont 2.5
MI 0.940 15% VA EVA 2 ELVAX 3128 DuPont 2.0 MI 0.930 8.9% VA
EVA-g-MAH BYNEL 30E783 DuPont 5.7 MI 0.934 7% VA Elastomer1 ENGAGE
8402 Dow 30 MI -- Elastomer2 ENGAGE 8200 Dow 5 MI -- LDPE 1 LDPE
501i Dow 1.9 MI 0.922 LDPE 2 LDPE 681i Dow 1.15 MI 0.922
[0180] The crystalline block copolymer composites (CBC's) below are
developmental materials prepared as described above and are
summarized in Table 2. They have the following general
characteristics:
i) an ethylene-based polymer (EP) that is crystalline (CEP); ii) a
propylene-based crystalline polymer (CPP) and iii) a block
copolymer comprising
[0181] (a) an ethylene polymer block (EB) that is a crystalline
ethylene block CEB) and
[0182] (b) a crystalline propylene polymer block (CPPB).
[0183] As also shown in Table 2, the CBC samples are further
characterized by the indicated: [0184] Wt % PP--Weight percentage
propylene polymer in the CBC as measured by HTLC Separation as
described above. [0185] Mw--the weight average molecular weight of
the CBC in Kg/mol as determined by GPC as described above. [0186]
Mw/Mn--the molecular weight distribution of the CBC as determined
by GPC as described above. [0187] Wt % C2 in CBC--the weight
percentage of ethylene in the CBC as determined by NMR, the balance
being propylene. [0188] Tm (.degree. C.) Peak 1 (Peak 2)--Peak
melting temperature as determined by the second heating curve from
DSC. Peak 1 refers to the melting of CPPB or CPP, whereas Peak 2
refers to the melting of CEB or CEP. [0189] Tc (.degree. C.)--Peak
crystallization temperature as determined by DSC cooling scan.
[0190] Heat of Fusion (J/g)--the heat of fusion of the CBC measured
as described above. [0191] Mol % C2 in CEB--the mole percentage of
ethylene in the crystalline ethylene block component (iii)(a) (and
also the crystalline ethylene polymer component (1) of the CBC),
the balance of comonomer in both cases being propylene. [0192] Wt %
CPPB in block copolymer--the weight percentage of crystalline
propylene polymer in the block copolymer component (iii). [0193]
CBCI--the crystalline block copolymer composite index which
reflects the content of the block copolymer (iii) in the CBC
composition.
TABLE-US-00002 [0193] TABLE 2 CBC and BC Resins Used in
Experimental Film Wt % Tm (.degree. C.) Heat of Mol % Wt % Density
Wt % Mw Mw/ C.sub.2 In Peak 1 Tc fusion C.sub.2 in CPPB Resin MFR
(g/cc) PP Kg/mol Mn CBC (Peak 2) (.degree. C.) (J/g) CEB in (iii)
CBCI CBC 1 3.6 0.9055 13.2 146 2.8 46.7 130 97 126 93 50 0.729
(114) CBC 2 3.5 0.9007 34.0 209 3.3 28.9 136 97 91 93 70 0.516
(101) CBC 3 1.4 0.9120 7.2 133 4.6 68.6 122 99 123 93 30 0.702
(114) CBC 4 7.0 0.9052 14.2 128 4.0 46.9 132 91 97 93 50 0.707
(108)
[0194] As also further indicated in the Tables below, other
commercially available additives and stabilizers are employed in
the formulation: [0195] Antiblock: Ampacet 10799A masterbatches
which consists of 50% talc in a 20 MI LLDPE carrier. [0196] Slip
Additive/Antiblock ("S/AB"): Supplied by Ampacet Corporation as
Ampacet 102854 that contains 5% erucamide and 2.5% stearamide slip
and 20% silicate antiblock in polyethylene carrier [0197] White
Color 1: Supplied by Ampacet Corporation as Ampacet 110456
masterbatch which contains 50% TiO2 in a 20 MI LLDPE carrier [0198]
White Color 2: Supplied by Ampacet Corporation as Ampacet 110443
concentrate which contains 50% TiO2 in a 8 MFR homopolymer
polypropylene [0199] UV 1 & 2 (stabilizer) masterbatches:
Produced by Dow Chemical according to Table 3. [0200] Polymer
Processing Additives ("PPA"): Supplied by Ampacet Corporation as
Ampacet 102823 that contains a fluoropolymer elastomer process aid
in 2 Ml LLDPE carrier [0201] Vinyltrimethoxysilane ("VTMS"):
Supplied by Dow Corning, Xiameter OFS-6300 Silane [0202] Peroxide:
Supplied by Arkema, Luperox 101
TABLE-US-00003 [0202] TABLE 3 UV Stabilizer masterbatch
formulations. All amounts are based on weight percent. Type of UV 1
UV 2 Component additive Supplier (Wt %) (Wt %) LDPE2 Resin Dow
Chemical 89.5 PP2 Resin Dow Chemical 87.5 Cyasorb UV stabilizers
Cytec Industries, 1.0 UV1164 Inc Cyasorb UV stabilizers Cytec
Industries, 4.0 UV3853S Inc Cyasorb UV stabilizers Cytec
Industries, 6.0 UV3853PP5 Inc Cyasorb UV stabilizers Cytec
Industries, 2.0 UV3346 Inc Cyasorb UV stabilizers Cytec Industries,
2.0 UV3529 Inc Cyasorb UV stabilizers Cytec Industries, 3.0 THT7001
Inc Uvinul 5050H UV stabilizers BASF Corporation 2.0 Tinuvin 770 UV
stabilizers BASF Corporation 1.0 Irganox 1010 Antioxidant BASF
Corporation 0.75 0.25 Irganox 168 Antioxidant BASF Corporation
0.75
[0203] The films are prepared using the indicated processing
conditions in Table 4 on a pilot scale cast film line using a
standard type of feedblock configuration to produce 3 layers and
providing the PP side of the film against cast roll. The cast film
components and structures are summarized in Table 5 below.
TABLE-US-00004 TABLE 4 Fabrication conditions for Experimental Cast
Films 1-14 Condition 1 Condition 2 Overall thickness, micron 381
200 Layer A B C A B C RPM 41 25 99 40 20 100 Feed zone, .degree. C.
166 193 202 166 177 199 Zone 2, .degree. C. 182 204 210 177 191 204
Zone 3, .degree. C. 188 216 216 191 199 213 Transfer line, screen,
188 216 216 191 204 213 adapters, .degree. C. Feedblock, .degree.
C. 216 210 Die, .degree. C. 216 210 Cast roll, .degree. C.
(nominal) 50 85
TABLE-US-00005 TABLE 5 Summary of Experiment Cast Film Formulations
1 and 2. Experiment No. 1 2 Sample ID # MC 2017-8 MC 2017-9 Nominal
Film Thickness 200 200 Layer A B C A B C Layer vol % 25 12.5 62.5
25 12.5 62.5 PP2 90 90 Plastomer 10 10 EVA1 21.0 LDPE1 16.5 LLDPE
64.0 EVA-g-MAH 68.5 Antiblock 15.0 15.0 CBC1 100 100 Conditions 2
2
[0204] The films are tested for their sealing and interlayer
strengths. The two A (top) layers are sealed together by heat
sealing at 204.degree. C. for 10 seconds at 30 psi (207 kPa, 2.07
bar) pressure. The films are thus sealed as CBA-ABC. The sealed
films are then tested by a peel strength test according to ASTM
F88/8F88-09 for 180.degree. peel at 23.degree. C. on an
INSTRON.RTM. tester (model 5500R) at 50 mm gap at a rate of 50
mm/min. Peel strengths are recorded below. For films exhibiting a
delamination failure, the location of the delamination is noted and
the sample is tested in the INSTRON tester in a similar manner but
by peeling the film layers that are then separating by
delamination. This second peel test is the interlayer adhesion
strength test done at 23.degree. C. The layers that delaminate are
recorded along with their interlayer adhesion strength values.
[0205] In some cases, the entire film thickness breaks, tears or
greatly elongates as only failure and there is no delamination
failure observable. In those cases, all the interlayer adhesion
strength values are clearly excellent but there is no interlayer
adhesion strength value measurable or recorded.
[0206] The experimental films are compared against a commercial
backsheet film available from Madico and referred to as a TPE film.
As indicated in the Madico technical datasheet, the TPE film
thickness is 191 microns and has polyvinylfluoride (PVF) in the
outside or bottom layer, PET in a core layer and EVA/LDPE blend in
the top or seal layer. In the Table below, unless otherwise
indicated, all amounts are based on weight percent.
TABLE-US-00006 TABLE 6 Peel test results comparing Madico film with
Inventive Examples Madico Experiment Number TPE 1 2 Seal-seal (A-A)
peel strength Number of samples 15 5 5 Average seal strength, N/cm
20.3 20.5 39.1 Percent samples with no delamination 60% 100% 100%
Number of samples with delamination 6 0 0 Location of interlayer
delamination B-C -- -- Interlayer peel Avg interlayer strength of
2.2 N/A N/A delaminating samples, N/cm
[0207] As can be seen in Table 6 above, backsheet can be made using
crystalline block composite that has better interlayer adhesion and
no delamination within the backsheet structure as compared to
commercial backsheet.
[0208] As shown below in Tables 7 and 8, Experimental Cast Films 3
through 8 having the noted formulations are similarly prepared
according to the film process conditions and are similarly
tested.
TABLE-US-00007 TABLE 7 Summary of Formulations and Structures of
Experimental Cast Films 3 through 8 Expt. No. 3 4 5 6 7 8* Sample
ID # MC 2034-13 MC 2034-7 MC 2034-8 MC 2034-9 MC 2034-10 MC 2034-6
Nominal Thickness (.mu.) 381 381 381 381 381 381 Layer A B C A B C
A B C A B C A B C A B C Approx 25 15 60 25 15 60 25 15 60 25 15 60
25 15 60 25 15 60 Layer Vol % PP1 0 82 82 82 82 82 PP2 82 LLDPE 30
30 30 30 30 30 Plastomer 80 CBC 1 80 CBC2 80 CBC3 80 CBC4 80 80
EVA2 60 60 60 60 60 60 UV1 10 10 10 10 10 10 UV2 10 10 10 10 10 10
Color1 20 20 20 20 20 20 Color 2 8 8 8 8 8 8 Fab 1 1 1 1 1 1
Condition *Comparative Experiment - not an example of the present
invention.
TABLE-US-00008 TABLE 8 Peel Test Results for Experimental Cast
Films 3 through 8 Experiment Number 3 4 5 6 7 8* Number of samples
tested 6 3 7 2 3 3 Seal-seal (A-A) peel Average seal strength, N/cm
67.1 63.0 49.8 9.7 49.2 20.8 % Samples without 83% 100% 86% 0% 0%
0% delamination Interlayer peel Location of interlayer B-C N/A B-C
B-A B-C B-C delamination Avg interlayer strength of 15.8 N/A 15.3
10.7 18.7 6.5 delaminating samples, N/cm *Comparative Experiment -
not an example of the present invention.
[0209] The film examples prepared according to the present
invention all exhibit good to excellent interlayer strength. In
comparative Experimental Film 8, instead of a tie layer Layer B
comprising CBC according to the present invention, the tie layer
for the polypropylene film layer C is a plastomer that is commonly
sold and used for this purpose and is considered suitable in many
applications. It is noteworthy, therefore, that all the films
according to the present invention have higher interlayer strength
than comparative Experimental Film 8.
[0210] As summarized below in Tables 9 and 10, further Experimental
Films 9 through 12 are prepared on a mini-scale blown film line and
evaluated for their sealing and interlayer strengths. Table 9
summarizes the process conditions. Experimental films 9-12 show,
among other things, that films which have more CBC in the tie layer
Layer B results in less delamination.
TABLE-US-00009 TABLE 9 Process Conditions for Experimental Blown
Films 9 to Ex. 12 Fabrication Process Conditions Condition 3
Mini-Blown Co-extrusion Line, Larkin 200 Midland MI RPM 55 41 100
Feed zone 1, .degree. C. 166 182 202 Zone 2, .degree. C. 177 188
207 Zone 3, .degree. C. 182 193 210 Transfer line, screen, 193 193
210 adapters, .degree. C. Feedblock, .degree. C. 193 Die, .degree.
C. 193 Air ring speed, % 60 Nominal Nip speed 914 (mm/minute)
Nominal Layflat (mm) 152
TABLE-US-00010 TABLE 10 Summary of Formulations, Structures and
Test Results for Expt. Blown Films 9-12 Expt. Film No. 9 10 11 12
Sample MB 2045-2 MB 2045-3 MB 2045-4 MB 2045-5 Nominal thickness,
mil (.mu.m) 8 (200) 8 (200) 8 (200) 8 (200) Layer A B C A B C A B C
A B C Approximate 25 25 50.0 25 25 50.0 25 25 50.0 25 25 50.0 Layer
vol % PP1 30 100 20 100 10 100 100 LLDPE 40 30 40 20 40 10 40 CBC4
40 60 80 100 EVA2 60 60 60 60 Conditions 3 3 3 3 Seal-seal (A-A)
No. Samples 10 10 10 10 Interlayer Testing Avg seal 14.1 16.4 19.2
40.1 strength, N/cm % Samples w/o 10% 40% 70% 100% delamination
Location of B-C B-C B-C N/A delamination
[0211] As shown in Table 11 below, further evaluations of
Experimental Films are performed under conditions reflecting
lamination and high temperature use of the film structures. For
testing at 85.degree. C. the same procedures of sample preparation
and testing are followed as above but the test is conducted at 85 C
rather than at 23.degree. C. To achieve this condition a hot-cold
chamber from INSTRON (model 3119-005) is heated to 85.degree. C.,
samples are loaded into the jaw grips and the door closed. When
chamber returns to 85.degree. C., the samples are heat soaked for 2
minutes and the peel test is then started.
[0212] Demonstrating performance under higher, annealing
temperature conditions employed in assembling backsheet films into
electronic devices such as photovoltaic modules, annealed samples
are prepared by heat sealing samples in the same manner as
described above, separating the unsealed tabs with Teflon film to
prevent sticking of tabs and heating the samples for 15 minutes in
an air oven operating at 150.degree. C., removing the samples and
then testing peel strengths as described above at 23.degree. C.
TABLE-US-00011 TABLE 11 Higher Temperature Peel Test Results Madico
Experiment Number TPE 2 5 8* Seal-seal (A-A) peel @23.degree. C.
Average seal strength, N/cm 20.3 20.7 49.8 20.8 % Samples without
delamination 60% 100% 86% 0% Interlayer peel @23.degree. C.
Location of interlayer delamination B-C -- B-C B-C Avg interlayer
strength of 6.6 No 15.3 6.6 delaminating samples, N/cm delam
Seal-seal (A-A) peel @85.degree. C. Average seal strength, N/cm
14.6 11.6 14.7 9.7 % Samples without delamination 60% 100% 100% 0%
Interlayer peel @85.degree. C. Location of interlayer delamination
B-C -- -- B-C Avg interlayer strength of 11.3 No No 6.7
delaminating samples, N/cm delam delam Seal-seal (A-A) peel
@23.degree. C. after annealing at 150.degree. C. for 15 minutes
Average seal strength, N/cm 78.3 34.8 60.2 15.6 % Samples without
delamination 60% 100% 100% 0% Interlayer peel @23.degree. C. after
annealing Location of interlayer delamination -- -- -- B-C Avg
interlayer strength of -- No No 1.4 delaminating samples, N/cm
delam delam
[0213] The results given in Table 11 show that films made using B
layer comprising CBC shows no delamination at 85.degree. C.
reflecting PV module use temperatures. Similarly, films made using
B layer comprising CBC shows no delamination after annealing at
150.degree. C. for 15 minutes reflecting lamination conditions
commonly used for construction of PV modules. For these tests TPE
shows no improvement in resistance to delamination. Conversely, in
comparative Experimental Film 8, where the B layer comprises
plastomer, the interlayer adhesion decreases after annealing at
150.degree. C. for 15 minutes.
[0214] Unless stated to the contrary, implicit from the context, or
customary in the art, all parts and percents are based on weight
and all test methods are current as of the filing date of this
disclosure. For purposes of United States patent practice, the
contents of any referenced patent, patent application or
publication are incorporated by reference in their entirety (or its
equivalent US version is so incorporated by reference) especially
with respect to the disclosure of synthetic techniques, definitions
(to the extent not inconsistent with any definitions specifically
provided in this disclosure), and general knowledge in the art.
[0215] The numerical ranges in this disclosure are approximate, and
thus may include values outside of the range unless otherwise
indicated. Numerical ranges include all values from and including
the lower and the upper values, in increments of one unit, provided
that there is a separation of at least two units between any lower
value and any higher value. As an example, if a compositional,
physical or other property or process parameter, such as, for
example, molecular weight, viscosity, melt index, temperature,
etc., is from 100 to 1,000, it is intended that all individual
values, such as 100, 101, 102, etc., and sub ranges, such as 100 to
144, 155 to 170, 197 to 200, etc., are expressly enumerated. For
ranges containing values which are less than one or containing
fractional numbers greater than one (e.g., 1.1, 1.5, etc.), one
unit is considered to be 0.0001, 0.001, 0.01 or 0.1, as
appropriate. For ranges containing single digit numbers less than
ten (e.g., 1 to 5), one unit is typically considered to be 0.1.
These are only examples of what is specifically intended, and all
possible combinations of numerical values between the lowest value
and the highest value enumerated, are to be considered to be
expressly stated in this disclosure. Numerical ranges are provided
within this disclosure for, among other things, density, melt index
and relative amounts of components in various compositions and
blends.
[0216] The term "comprising" and its derivatives are not intended
to exclude the presence of any additional component, step or
procedure, whether or not the same is specifically disclosed. In
order to avoid any doubt, any process or composition claimed
through use of the term "comprising" may include any additional
steps, equipment, additive, adjuvant, or compound whether polymeric
or otherwise, unless stated to the contrary. In contrast, the term,
"consisting essentially of" excludes from the scope of any
succeeding recitation any other component, step or procedure,
excepting those that are not essential to operability. The term
"consisting of" excludes any component, step or procedure not
specifically delineated or listed. The term "or", unless stated
otherwise, refers to the listed members individually as well as in
any combination.
Although the invention has been described in considerable detail
through the preceding description and examples, this detail is for
the purpose of illustration and is not to be construed as a
limitation on the scope of the invention.
* * * * *