U.S. patent application number 12/679486 was filed with the patent office on 2010-11-04 for synthetic turf with shock absorption layer.
This patent application is currently assigned to Dow Global Technologies Inc.. Invention is credited to Carolin Boehm, Jacques Carrere, Andy Cheng Chang, Loic Chereau, Christine Delabroye, Jean-Francois Xavier Koenig, Jill Minick Martin, Filip Tauson, Enrique Torres.
Application Number | 20100279032 12/679486 |
Document ID | / |
Family ID | 40019268 |
Filed Date | 2010-11-04 |
United States Patent
Application |
20100279032 |
Kind Code |
A1 |
Chereau; Loic ; et
al. |
November 4, 2010 |
SYNTHETIC TURF WITH SHOCK ABSORPTION LAYER
Abstract
A synthetic turf surface including a synthetic grass carpet
having a flexible base sheet, and a shock absorbing pad, wherein
the shock absorbing pad includes a non-crosslinked polyolefin foam
is shown and described. The foam may be recyclable, as it is
non-crosslinked.
Inventors: |
Chereau; Loic; (Zurich,
CH) ; Torres; Enrique; (Thalwil, CH) ; Chang;
Andy Cheng; (Houston, TX) ; Martin; Jill Minick;
(Pearland, TX) ; Delabroye; Christine;
(Riedisheim, FR) ; Koenig; Jean-Francois Xavier;
(Strasbourg, FR) ; Carrere; Jacques; (Strasbourg,
FR) ; Boehm; Carolin; (Menden, DE) ; Tauson;
Filip; (Freeport, TX) |
Correspondence
Address: |
The Dow Chemical Company;Osha Liang LLP
Two Houston Center, 909 Fannin Street, Suite 3500
Houston
TX
77010-2002
US
|
Assignee: |
Dow Global Technologies
Inc.
Midland
MI
|
Family ID: |
40019268 |
Appl. No.: |
12/679486 |
Filed: |
August 28, 2008 |
PCT Filed: |
August 28, 2008 |
PCT NO: |
PCT/US08/74648 |
371 Date: |
June 29, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60974812 |
Sep 24, 2007 |
|
|
|
Current U.S.
Class: |
428/17 |
Current CPC
Class: |
E01C 13/08 20130101 |
Class at
Publication: |
428/17 |
International
Class: |
E01C 13/08 20060101
E01C013/08 |
Claims
1. A synthetic turf surface comprising: a. a synthetic grass carpet
having a flexible base sheet, and b. a shock absorbing pad, wherein
the shock absorbing pad comprises a non-crosslinked polyolefin
foam.
2. The synthetic turf surface of claim 1, wherein the foam
thickness is between 8 and 30 mm.
3. The synthetic turf surface of claim 1, wherein the foam density
is between 20 and 600 kg/mm.sup.3.
4. The synthetic turf surface of claim 3, wherein the foam density
is between 30 and 150 kg/mm.sup.3.
5. The synthetic turf surface of claim 1, wherein the foam has a
cell size of between 0.2 and 3 mm.
6. The synthetic turf surface of claim 1, wherein the polyolefin
foam comprises a polyethylene foam.
7. The synthetic turf surface of claim 6, wherein the polyethylene
has a density of 0.865 and 0.96 g/cc.
8. The synthetic turf surface of claim 1, wherein the turf has a
vertical ball rebound of 0.60 to 1 m, as measured in accordance
with FIFA regulations.
9. The synthetic turf surface of claim 1, wherein the turf has a
shock absorption of 55% to 70% as measured in accordance with FIFA
regulations.
10. The synthetic turf surface of claim 1, wherein the turf has a
vertical deformation of 4 mm to 9 mm as measured in accordance with
FIFA regulations.
11. The synthetic turf surface of claim 1, wherein the polyolefin
foam comprises at least two layers of foam.
Description
BACKGROUND OF INVENTION
[0001] 1. Field of the Invention
[0002] Embodiments disclosed herein relate generally to a
thermoplastic foam shock absorbing layer. In another aspect,
embodiments described herein relate to a synthetic turf including a
thermoplastic foam shock absorbing layer, where the foam may be
recyclable.
[0003] 2. Background
[0004] Artificial turf consists of a multitude of artificial grass
tufts extending upward from a sheet substrate. The turf is usually
laid upon a prepared, flat ground surface to form a game playing
field intended to simulate a natural grass playing field
surface.
[0005] For some types of games, a resilient underpad is placed
beneath the turf and upon the firm ground support surface to
provide a shock absorbing effect. Also, in some instances, a layer
of sand or other particulate material is placed upon the upper
surface of the carpet base sheet and around the strands. An example
of this type of construction is shown in U.S. Pat. No. 4,389,435
issued Jun. 21, 1983 to Frederick T. Haas, Jr. Another example is
shown in U.S. Pat. No. 4,637,942 issued Jan. 20, 1987 to Seymour A.
Tomarin.
[0006] Further, examples of artificial turfs which are formed with
the grass-like carpet placed upon a resilient underpad are
disclosed in U.S. Pat. No. 3,551,263 issued Dec. 29, 1970 to Carter
et al., which discloses a polyurethane foam underpad; U.S. Pat. No.
3,332,828 issued Jul. 25, 1967 to Faria et al., which discloses a
PVC foam plastic or polyurethane foam plastic underpad; U.S. Pat.
No. 4,637,942 issued Jan. 20, 1987 to Seymour A. Tomarin which
discloses a rubber-like underpad; U.S. Pat. No. 4,882,208 issued
Nov. 21, 1989 to Hans-Urich Brietschidel, which illustrates a
closed cell crosslinked polyethylene foam underpad; U.S. Pat. No.
3,597,297 issued Aug. 3, 1971 to Theodore Buchholz et al., which
discloses a polyurethane underpad having voids; and U.S. Pat. No.
4,505,960 issued Mar. 19, 1985 to James W. Leffingwell, which
discloses shock absorbing pads made from elastomer foams of
polyvinyl chloride, polyethylene, polyurethane, polypropylene,
etc.
[0007] Shock absorbing layers may, of course, be more broadly used
in other applications, such as in energy dampening in floors, for
example. What is still needed, therefore, are improved materials
and methods for forming shock absorbing layers, including
recyclable shock absorbing layers.
SUMMARY OF INVENTION
[0008] In one aspect, embodiments disclosed herein relate to a
synthetic turf surface comprising a synthetic grass carpet having a
flexible base sheet, and a shock absorbing pad, wherein the shock
absorbing pad comprises a non-crosslinked polyolefin foam.
[0009] Other aspects and advantages of the invention will be
apparent from the following description and the appended
claims.
BRIEF DESCRIPTION OF FIGURES
[0010] FIG. 1 illustrates instrumentation and experimentation for a
shock absorption test using FIFA standards.
[0011] FIGS. 2 and 2c compare results of the compressive
stress-strain behavior analyses of foams according to embodiments
disclosed herein to those of crosslinked polyethylene foams.
[0012] FIGS. 3 and 3c compare compressive strain versus time test
results for foams according to embodiments disclosed herein to
those of crosslinked polyethylene foams.
[0013] FIG. 4 compare compressive creep behavior test results for
foams according to embodiments disclosed herein to those of
crosslinked polyethylene foams.
[0014] FIG. 5 illustrates synthetic turf that may be formed using
embodiments of the non-crosslinked polyolefin foams described
herein.
DETAILED DESCRIPTION
[0015] General Definitions and Measurement Methods:
[0016] The following terms shall have the given meaning for the
purposes of this invention:
[0017] "Polymer" means a substance composed of molecules with large
molecular mass consisting of repeating structural units, or
monomers, connected by covalent chemical bonds. The term `polymer`
generally includes, but is not limited to, homopolymers, copolymers
such as block, graft, random and alternating copolymers,
terpolymers, etc., and blends and modifications thereof. Further,
unless otherwise specifically limited, the term `polymer` shall
include all possible geometrical configurations of the molecular
structure. These configurations include isotactic, syndiotactic,
random configurations, and the like.
[0018] "Interpolymer" means a polymer prepared by the
polymerization of at least two different types of monomers. The
generic term "interpolymer" includes the term "copolymer" (which is
usually employed to refer to a polymer prepared from two different
monomers) as well as the term "terpolymer" (which is usually
employed to refer to a polymer prepared from three different types
of monomers). The class of materials known as "interpolymers" also
encompasses polymers made by polymerizing four or more types of
monomers.
[0019] Density of resins and compositions is measured according to
ASTM D792.
[0020] Density of foams is measured according to ASTM
D3575/W/B.
[0021] "Melt Index (I2)" is determined according to ASTM D1238
using a weight of 2.16 kg at 190.degree. C. for polymers comprising
ethylene as the major component in the polymer. "Melt Flow Rate
(MFR)" is determined according to ASTM D1238 using a weight of 2.16
kg at 230.degree. C. for polymers comprising propylene as the major
component in the polymer.
[0022] Molecular weight distribution of the polymers is determined
using gel permeation chromatography (GPC) on a Polymer Laboratories
PL-GPC-220 high temperature chromatographic unit equipped with four
linear mixed bed columns (Polymer Laboratories (20-micron particle
size)). The oven temperature is at 160.degree. C. with the
autosampler hot zone at 160.degree. C. and the warm zone at
145.degree. C. The solvent is 1,2,4-trichlorobenzene containing 200
ppm 2,6-di-t-butyl-4-methylphenol. The flow rate is 1.0
milliliter/minute and the injection size is 100 microliters. About
0.2% by weight solutions of the samples are prepared for injection
by dissolving the sample in nitrogen purged 1,2,4-trichlorobenzene
containing 200 ppm 2,6-di-t-butyl-4-methylphenol for 2.5 hrs at
160.degree. C. with gentle mixing.
[0023] The molecular weight determination is deduced by using ten
narrow molecular weight distribution polystyrene standards (from
Polymer Laboratories, EasiCal PS1 ranging from 580-7,500,000
g/mole) in conjunction with their elution volumes. The equivalent
polypropylene molecular weights are determined by using appropriate
Mark-Houwink coefficients for polypropylene (as described by Th. G.
Scholte, N. L. J. Meijerink, H. M. Schoffeleers, and A.M.G. Brands,
J. Appl. Polym. Sci., 29, 3763-3782 (1984)) and polystyrene (as
described by E. P. Otocka, R. J. Roe, N. Y. Hellman, P. M. Muglia,
Macromolecules, 4, 507 (1971)) in the Mark-Houwink equation:
{N}=KM.sup.a where K.sub.pp=1.90E-04, a.sub.pp=0.725 and
K.sub.ps=1.26E-04, a.sub.ps=0.702.
"Molecular weight distribution" or MWD is measured by conventional
GPC per the procedure described by Williams, T.; Ward, I. M.
Journal of Polymer Science, Polymer Letters Edition (1968), 6(9),
621-624. Coefficient B is 1. Coefficient A is 0.4316.
[0024] The term high pressure low density type resin is defined to
mean that the polymer is partly or entirely homopolymerized or
copolymerized in autoclave or tubular reactors at pressures above
14,500 psi (100 MPa) with the use of free-radical initiators, such
as peroxides (see for example U.S. Pat. No. 4,599,392, herein
incorporated by reference) and includes "LDPE" which may also be
referred to as "high pressure ethylene polymer" or "highly branched
polyethylene". The cumulative detector fraction (CDF) of these
materials is greater than about 0.02 for molecular weight greater
than 1000000 g/mol as measured using light scattering. CDF may be
determined as described in WO2005/023912 A2, which is herein
incorporated by reference for its teachings regarding CDF. The
preferred high pressure low density polyethylene material (LDPE)
has a melt index MI (I2) of less than about 20, more preferably
less than about 15, most preferably less than 10, and greater than
about 0.1, more preferably greater than about 0.2, most preferably
more than 0.3 g/10 min. The preferred LDPE will have a density
between about 0.915 g/cm3 and 0.930 g/cm.sup.3, with less than
0.925 g/cm.sup.3 being more preferred.
[0025] "Crystallinity" means atomic dimension or structural order
of a polymer composition. Crystallinity is often represented by a
fraction or percentage of the volume of the material that is
crystalline or as a measure of how likely atoms or molecules are to
be arranged in a regular pattern, namely into a crystal.
Crystallinity of polymers can be adjusted fairly precisely and over
a very wide range by heat treatment. A "crystalline"
"semi-crystalline" polymer possesses a first order transition or
crystalline melting point (Tm) as determined by differential
scanning calorimetry (DSC) or equivalent technique. The term may be
used interchangeably with the term "semicrystalline". The term
"amorphous" refers to a polymer lacking a crystalline melting point
as determined by differential scanning calorimetry (DSC) or
equivalent technique.
[0026] Differential Scanning Calorimetry (DSC) is a common
technique that can be used to examine the melting and
crystallization of semi-crystalline polymers. General principles of
DSC measurements and applications of DSC to studying
semi-crystalline polymers are described in standard texts (e.g., E.
A. Turi, ed., Thermal Characterization of Polymeric Materials,
Academic Press, 1981). DSC is a method suitable for determining the
melting characteristics of a polymer.
[0027] DSC analysis was done using a model Q1000 DSC from TA
Instruments, Inc. DSC is calibrated by the following method. First,
a baseline is obtained by running the DSC from -90.degree. C. to
290.degree. C. without any sample in the aluminum DSC pan. Then 7
milligrams of a fresh indium sample is analyzed by heating the
sample to 180.degree. C., cooling the sample to 140.degree. C. at a
cooling rate of 10.degree. C./min followed by keeping the sample
isothermally at 140.degree. C. for 1 minute, followed by heating
the sample from 140.degree. C. to 180.degree. C. at a heating rate
of 10.degree. C./min. The heat of fusion and the onset of melting
of the indium sample are determined and checked to be within
0.5.degree. C. to 156.6.degree. C. for the onset of melting and
within 0.5 J/g to 28.71 J/g for the heat of fusion. Then deionized
water is analyzed by cooling a small drop of flesh sample in the
DSC pan from 25.degree. C. to -30.degree. C. at a cooling rate of
10.degree. C./min. The sample is kept isothermally at -30.degree.
C. for 2 minutes and heated to 30.degree. C. at a heating rate of
10.degree. C./min. The onset of melting is determined and checked
to be within 0.5.degree. C. to 0.degree. C.
[0028] Polymer samples were pressed into a thin film at an initial
temperature of 190.degree. C. (designated as the `initial
temperature`). About 5 to 8 mg of sample is weighed out and placed
in the DSC pan. The lid is crimped on the pan to ensure a closed
atmosphere. The DSC pan is placed in the DSC cell and then heated
at a rate of about 100.degree. C./min to a temperature (T.sub.o) of
about 60.degree. C. above the melt temperature of the sample. The
sample is kept at this temperature for about 3 minutes. Then the
sample is cooled at a rate of 10.degree. C./min to -40.degree. C.,
and kept isothermally at that temperature for 3 minutes.
Consequently the sample is heated at a rate of 10.degree. C./min
until complete melting. Enthalpy curves resulting from this
experiment are analyzed for peak melt temperature, onset and peak
crystallization temperatures, heat of fusion and heat of
crystallization, and any other DSC analyses of interest.
[0029] For a polymer comprising polypropylene crystallinity is
analyzed, T.sub.o is 230.degree. C. T.sub.o is 190.degree. C. when
polyethylene crystallinity is present and no polypropylene
crystallinity is present in the sample.
[0030] Percent crystallinity by weight is calculated according to
the following formula:
Crystallinity ( wt . % ) = .DELTA. H .DELTA. H o .times. 100 %
##EQU00001##
such that the heat of fusion (.DELTA.H) is divided by the heat of
fusion for the perfect polymer crystal (.DELTA.H.sub.o) and then
multiplied by 100%. For ethylene crystallinity, .DELTA.H.sub.o is
taken to be 290 J/g. For example, an ethylene-octene copolymer
which upon melting of its polyethylene crystallinity is measured to
have a heat of fusion of 29 J/g; the corresponding crystallinity is
10% by weight. For propylene crystallinity, .DELTA.H.sub.o is taken
to be 165 J/g. For example, a propylene-ethylene copolymer which
upon melting of its propylene crystallinity is measured to have a
heat of fusion of 20 J/g; the corresponding crystallinity is 12.1%
by weight.
[0031] "Non crosslinked" As used herein, the term non-crosslinked
refers to polymers that have between 0-10% gel, more preferably,
0-5%, and more preferably 0-1%. It should not be construed that
absolutely zero crosslinking is present, as some crosslinking may
inevitably occur during processing, but that the crosslinking
should be kept to a minimum to allow for recyclability.
Foam Shock Absorbing Layer
[0032] In one aspect, embodiments described herein relate to a
thermoplastic foam shock absorbing layer. In another aspect,
embodiments described herein relate to a synthetic turf including a
thermoplastic foam shock absorbing layer. In selected applications,
embodiments described herein relate to a thermoplastic
non-crosslinked polymer foam shock absorption layer having the
following characteristics:
[0033] 1) Foam thickness: between 8 and 30 mm;
[0034] 2) Foam density: between 30 and 150 kg/m3;
[0035] 3) Foam cell size: between 0.2 and 3 mm; and
[0036] 4) % Open cell volume is low, so as to avoid water uptake:
typically less than 35%.
[0037] Polymer
[0038] The thermoplastic polymer used to form the shock absorbing
layer may vary depending upon the particular application and the
desired result. In one embodiment, for instance, the polymer is an
olefin polymer. As used herein, an olefin polymer, in general,
refers to a class of polymers fanned from hydrocarbon monomers
having the general formula C.sub.nH.sub.2n. The olefin polymer may
be present as a copolymer, such as an interpolymer, a block
copolymer, or a multi-block interpolymer or copolymer.
[0039] In one particular embodiment, for instance, the olefin
polymer may comprise an alpha-olefin interpolymer of ethylene with
at least one comonomer selected from the group consisting of a
C.sub.3-C.sub.20 linear, branched or cyclic diene, or an ethylene
vinyl compound, such as vinyl acetate, and a compound represented
by the formula H.sub.2C.dbd.CHR wherein R is a C.sub.1-C.sub.20
linear, branched or cyclic alkyl group or a C.sub.6-C.sub.20 aryl
group. Examples of comonomers include propylene, 1-butene,
3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene,
1-heptene, 1-hexene, 1-octene, 1-decene, and 1-dodecene.
[0040] In other embodiments, the polymer may be an alpha-olefin
interpolymer of propylene with at least one comonomer selected from
the group consisting of ethylene, a C.sub.4-C.sub.20 linear,
branched or cyclic diene, and a compound represented by the formula
H.sub.2C.dbd.CHR wherein R is a C.sub.1-C.sub.20 linear, branched
or cyclic alkyl group or a C.sub.6-C.sub.20 aryl group. Examples of
comonomers include ethylene, 1-butene, 3-methyl-1-butene,
4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-hexene,
1-octene, 1-decene, and 1-dodecene. In some embodiments, the
comonomer is present at about 5% by weight to about 25% by weight
of the interpolymer. In one embodiment, a propylene-ethylene
interpolymer is used.
[0041] Other examples of polymers which may be used in the present
disclosure include homopolymers and copolymers (including
elastomers) of an olefin such as ethylene, propylene, 1-butene,
3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene,
1-heptene, 1-hexene, 1-octene, 1-decene, and 1-dodecene as
typically represented by polyethylene, polypropylene,
poly-1-butene, poly-3-methyl-1-butene, poly-3-methyl-1-pentene,
poly-4-methyl-1-pentene, ethylene-propylene copolymer,
ethylene-1-butene copolymer, and propylene-1-butene copolymer;
copolymers (including elastomers) of an alpha-olefin with a
conjugated or non-conjugated diene as typically represented by
ethylene-butadiene copolymer and ethylene-ethylidene norbornene
copolymer; and polyolefins (including elastomers) such as
copolymers of two or more alpha-olefins with a conjugated or
non-conjugated diene as typically represented by
ethylene-propylene-butadiene copolymer,
ethylene-propylene-dicyclopentadiene copolymer,
ethylene-propylene-1,5-hexadiene copolymer, and
ethylene-propylene-ethylidene norbornene copolymer; ethylene-vinyl
compound copolymers such as ethylene-vinyl acetate copolymers with
N-methylol functional comonomers, ethylene-vinyl alcohol copolymers
with N-methylol functional comonomers, ethylene-vinyl chloride
copolymer, ethylene acrylic acid or ethylene-(meth)acrylic acid
copolymers, and ethylene-(meth)acrylate copolymer; styrenic
copolymers (including elastomers) such as polystyrene, ABS,
acrylonitrile-styrene copolymer, methylstyrene-styrene copolymer;
and styrene block copolymers (including elastomers) such as
styrene-butadiene copolymer and hydrate thereat, and
styrene-isoprene-styrene triblock copolymer; polyvinyl compounds
such as polyvinyl chloride, polyvinylidene chloride, vinyl
chloride-vinylidene chloride copolymer, polymethyl acrylate, and
polymethyl methacrylate; polyamides such as nylon 6, nylon 6,6, and
nylon 12; thermoplastic polyesters such as polyethylene
terephthalate and polybutylene terephthalate; polycarbonate,
polyphenylene oxide, and the like. These resins may be used either
alone or in combinations of two or more.
[0042] In particular embodiments, polyolefins such as
polypropylene, polyethylene, and copolymers thereof and blends
thereof, as well as ethylene-propylene-diene terpolymers may be
used. In some embodiments, the olefinic polymers include
homogeneous polymers described in U.S. Pat. No. 3,645,992 by
Elston; high density polyethylene (HDPE) as described in U.S. Pat.
No. 4,076,698 to Anderson; heterogeneously branched linear low
density polyethylene (LLDPE); heterogeneously branched ultra low
linear density (ULDPE); homogeneously branched, linear
ethylene/alpha-olefin copolymers; homogeneously branched,
substantially linear ethylene/alpha-olefin polymers which can be
prepared, for example, by a process disclosed in U.S. Pat. Nos.
5,272,236 and 5,278,272, the disclosure of which process is
incorporated herein by reference; heterogeneously branched linear
ethylene/alpha olefin polymers; and high pressure, free radical
polymerized ethylene polymers and copolymers such as low density
polyethylene (LDPE).
[0043] In another embodiment, the polymers may include an
ethylene-carboxylic acid copolymer, such as, ethylene-vinyl acetate
(EVA) copolymers, ethylene-acrylic acid (EAA) and
ethylene-methacrylic acid copolymers such as, for example, those
available under the tradenames PRIMACOR.TM. from the Dow Chemical
Company, NUCREL.TM. from DuPont, and ESCOR.TM. from ExxonMobil, and
described in U.S. Pat. Nos. 4,599,392, 4,988,781, and 59,384,373,
each of which is incorporated herein by reference in its entirety.
Exemplary polymers include polypropylene, (both impact modifying
polypropylene, isotactic polypropylene, atactic polypropylene, and
random ethylene/propylene copolymers), various types of
polyethylene, including high pressure, free-radical LDPE, Ziegler
Natta LLDPE, metallocene PE, including multiple reactor PE ("in
reactor") blends of Ziegler-Natta PE and metallocene PE, such as
products disclosed in U.S. Pat. Nos. 6,545,088, 6,538,070,
6,566,446, 5,844,045, 5,869,575, and 6,448,341. Homogeneous
polymers such as olefin plastomers and elastomers, ethylene and
propylene-based copolymers (for example polymers available under
the trade designation VERSIFY.TM. available from The Dow Chemical
Company and VISTAMAXX.TM. available from ExxonMobil) may also be
useful in some embodiments. Of course, blends of polymers may be
used as well. In some embodiments, the blends include two different
Ziegler-Natta polymers. In other embodiments, the blends may
include blends of a Ziegler-Natta and a metallocene polymer. In
still other embodiments, the thermoplastic resin used herein may be
a blend of two different metallocene polymers.
[0044] In one particular embodiment, the polymer may comprise an
alpha-olefin interpolymer of ethylene with a comonomer comprising
an alkene, such as 1-octene. The ethylene and octene copolymer may
be present alone or in combination with another polymer, such as
ethylene-acrylic acid copolymer. When present together, the weight
ratio between the ethylene and octene copolymer and the
ethylene-acrylic acid copolymer may be from about 1:10 to about
10:1, such as from about 3:2 to about 2:3. The polymer, such as the
ethylene-octene copolymer, may have a crystallinity of less than
about 50%, such as less than about 25%. In some embodiments, the
crystallinity of the polymer may be from 5 to 35 percent. In other
embodiments, the crystallinity may range from 7 to 20 percent.
[0045] In one particular embodiment, the polymer may comprise at
least one low density polyethylene (LDPE). The polymer may comprise
LDPE made in autoclave processes or tubular processes. Suitable
LDPE for this embodiment is defined elsewhere in this document.
[0046] In one particular embodiment, the polymer may comprise at
least two low density polyethylenes. The polymer may comprise LDPE
made in autoclave processes, tubular processes, or combinations
thereof. Suitable LDPEs for this embodiment are defined elsewhere
in this document.
[0047] In one particular embodiment, the polymer may comprise an
alpha-olefin interpolymer of ethylene with a comonomer comprising
an alkene, such as 1-octene. The ethylene and octene copolymer may
be present alone or in combination with another polymer, such as a
low density polyethylene (LDPE). When present together, the weight
ratio between the ethylene and octene copolymer and the LDPE may be
from about 60:40 to about 97:3, such as from about 80:20 to about
96:4. The polymer, such as the ethylene-octene copolymer, may have
a crystallinity of less than about 50%, such as less than about
25%. In some embodiments, the crystallinity of the polymer may be
from 5 to 35 percent. In other embodiments, the crystallinity may
range from 7 to 20 percent. Suitable LDPEs for this embodiment are
defined elsewhere in this document.
[0048] In one particular embodiment, the polymer may comprise an
alpha-olefin interpolymer of ethylene with a comonomer comprising
an alkene, such as 1-octene. The ethylene and octene copolymer may
be present alone or in combination with at least two other polymers
from the group: low density polyethylene, medium density
polyethylene, and high density polyethylene (HDPE). When present
together, the weight ratio between the ethylene and octene
copolymer, the LDPE, and the HDPE are such that the composition
comprises one component from 3 to 97% by weight of the total
composition and the remainder comprises the other two components.
The polymer, such as the ethylene-octene copolymer, may have a
crystallinity of less than about 50%, such as less than about 25%.
In some embodiments, the crystallinity of the polymer may be from 5
to 35 percent. In other embodiments, the crystallinity may range
from 7 to 20 percent.
[0049] Embodiments disclosed herein may also include a polymeric
component that may include at least one multi-block olefin
interpolymer. Suitable multi-block olefin interpolymers may include
those described in U.S. Provisional Patent Application No.
60/818,911, for example. The term "multi-block copolymer" or refers
to a polymer comprising two or more chemically distinct regions or
segments (referred to as "blocks") preferably joined in a linear
manner, that is, a polymer comprising chemically differentiated
units which are joined end-to-end with respect to polymerized
ethylenic functionality, rather than in pendent or grafted fashion.
In certain embodiments, the blocks differ in the amount or type of
comonomer incorporated therein, the density, the amount of
crystallinity, 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
multi-block copolymers are characterized by unique distributions of
polydispersity index (PDI or M.sub.w/M.sub.n), block length
distribution, and/or block number distribution due to the unique
process making of the copolymers. More specifically, when produced
in a continuous process, embodiments of the polymers may possess a
PDI ranging from about 1.7 to about 8; from about 1.7 to about 3.5
in other embodiments; from about 1.7 to about 2.5 in other
embodiments; and from about 1.8 to about 2.5 or from about 1.8 to
about 2.1 in yet other embodiments. When produced in a batch or
semi-batch process, embodiments of the polymers may possess a PDI
ranging from about 1.0 to about 2.9; from about 1.3 to about 2.5 in
other embodiments; from about 1.4 to about 2.0 in other
embodiments; and from about 1.4 to about 1.8 in yet other
embodiments.
[0050] One example of the multi-block olefin interpolymer is an
ethylene/.alpha.-olefin block interpolymer. Another example of the
multi-block olefin interpolymer is a propylene/.alpha.-olefin
interpolymer. The following description focuses on the interpolymer
as having ethylene as the majority monomer, but applies in a
similar fashion to propylene-based multi-block interpolymers with
regard to general polymer characteristics.
[0051] The ethylene/.alpha.-olefin multi-block interpolymers may
comprise ethylene and one or more co-polymerizable .alpha.-olefin
comonomers in polymerized form, characterized by multiple (i.e.,
two or more) blocks or segments of two or more polymerized monomer
units differing in chemical or physical properties (block
interpolymer), preferably a multi-block interpolymer. In some
embodiments, the multi-block interpolymer may be represented by the
following formula:
(AB).sub.n
where n is at least 1, preferably an integer greater than 1, such
as 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, 100, or
higher; "A" represents a hard block or segment; and "B" represents
a soft block or segment. Preferably, A' s and B' s are linked in a
linear fashion, not in a branched or a star fashion. "Hard"
segments refer to blocks of polymerized units in which ethylene is
present in an amount greater than 95 weight percent in some
embodiments, and in other embodiments greater than 98 weight
percent. In other words, the comonomer content in the hard segments
is less than 5 weight percent in some embodiments, and in other
embodiments, less than 2 weight percent of the total weight of the
hard segments. In some embodiments, the hard segments comprise all
or substantially all ethylene. "Soft" segments, on the other hand,
refer to blocks of polymerized units in which the comonomer content
is greater than 5 weight percent of the total weight of the soft
segments in some embodiments, greater than 8 weight percent,
greater than 10 weight percent, or greater than 15 weight percent
in various other embodiments. In some embodiments, the comonomer
content in the soft segments may be greater than 20 weight percent,
greater than 25 eight percent, greater than 30 weight percent,
greater than 35 weight percent, greater than 40 weight percent,
greater than 45 weight percent, greater than 50 weight percent, or
greater than 60 weight percent in various other embodiments.
[0052] In some embodiments, A blocks and B blocks are randomly
distributed along the polymer chain. In other words, the block
copolymers do not have a structure like:
AAA-AA-BBB-BB
[0053] In other embodiments, the block copolymers do not have a
third block. In still other embodiments, neither block A nor block
B comprises two or more segments (or sub-blocks), such as a tip
segment.
[0054] The multi-block interpolymers may be characterized by an
average block index, ABI, ranging from greater than zero to about
1.0 and a molecular weight distribution, M.sub.w/M.sub.n, greater
than about 1.3. The average block index, ABI, is the weight average
of the block index ("BI") for each of the polymer fractions
obtained in preparative TREF from 20.degree. C. and 110.degree. C.,
with an increment of 5.degree. C.:
ABI=.SIGMA.(w.sub.iBI.sub.i)
where BI.sub.i is the block index for the i.sup.th fraction of the
multi-block interpolymer obtained in preparative TREF, and w.sub.i
is the weight percentage of the i.sup.th fraction.
[0055] Similarly, the square root of the second moment about the
mean, hereinafter referred to as the second moment weight average
block index, may be defined as follows:
2 nd moment weight average B I = .SIGMA. ( w i ( B I i - ABI ) 2 )
( N - 1 ) .SIGMA. w i N ##EQU00002##
[0056] For each polymer fraction, BI is defined by one of the two
following equations (both of which give the same BI value):
B I = 1 / T X - 1 / T XO 1 / T A - 1 / T AB or B I = - Ln P X - Ln
P XO Ln P A - Ln P AB ##EQU00003##
where T.sub.x is the analytical temperature rising elution
fractionation (ATREF) elution temperature for the i.sup.th fraction
(preferably expressed in Kelvin), P.sub.x is the ethylene mole
fraction for the i.sup.th fraction, which may be measured by NMR or
IR as described below. P.sub.AB is the ethylene mole fraction of
the whole ethylene/.alpha.-olefin interpolymer (before
fractionation), which also may be measured by NMR or IR. T.sub.A
and P.sub.A are the ATREF elution temperature and the ethylene mole
fraction for pure "hard segments" (which refer to the crystalline
segments of the interpolymer). As an approximation or for polymers
where the "hard segment" composition is unknown, the T.sub.A and
P.sub.A values are set to those for high density polyethylene
homopolymer.
[0057] T.sub.AB is the ATREF elution temperature for a random
copolymer of the same composition (having an ethylene mole fraction
of P.sub.AB) and molecular weight as the multi-block interpolymer.
T.sub.AB may be calculated from the mole fraction of ethylene
(measured by NMR) using the following equation:
Ln P.sub.AB=.alpha./T.sub.AB+.beta.
where .alpha. and .beta. are two constants which may be determined
by a calibration using a number of well characterized preparative
TREF fractions of a broad composition random copolymer and/or well
characterized random ethylene copolymers with narrow composition.
It should be noted that .alpha. and .beta. may vary from instrument
to instrument. Moreover, one would need to create an appropriate
calibration curve with the polymer composition of interest, using
appropriate molecular weight ranges and comonomer type for the
preparative TREF fractions and/or random copolymers used to create
the calibration. There is a slight molecular weight effect. If the
calibration curve is obtained from similar molecular weight ranges,
such effect would be essentially negligible. In some embodiments,
random ethylene copolymers and/or preparative TREF fractions of
random copolymers satisfy the following relationship:
Ln P=-237.83/T.sub.ATREF+0.639
[0058] The above calibration equation relates the mole fraction of
ethylene, P, to the analytical TREF elution temperature,
T.sub.ATREF, for narrow composition random copolymers and/or
preparative TREF fractions of broad composition random copolymers.
T.sub.XO is the ATREF temperature for a random copolymer of the
same composition and having an ethylene mole fraction of P.sub.x.
T.sub.XO may be calculated from Ln P.sub.X=.alpha./T.sub.XO+.beta..
Conversely, P.sub.XO is the ethylene mole fraction for a random
copolymer of the same composition and having an ATREF temperature
of T.sub.X, which may be calculated from Ln
P.sub.XO=.alpha./T.sub.X+.beta.
[0059] Once the block index (BI) for each preparative TREF fraction
is obtained, the weight average block index, ABI, for the whole
polymer may be calculated. In some embodiments, ABI is greater than
zero but less than about 0.4 or from about 0.1 to about 0.3. In
other embodiments, ABI is greater than about 0.4 and up to about
1.0. Preferably, ABI should be in the range of from about 0.4 to
about 0.7, from about 0.5 to about 0.7, or from about 0.6 to about
0.9. In some embodiments, ABI is in the range of from about 0.3 to
about 0.9, from about 0.3 to about 0.8, or from about 0.3 to about
0.7, from about 0.3 to about 0.6, from about 0.3 to about 0.5, or
from about 0.3 to about 0.4. In other embodiments, ABI is in the
range of from about 0.4 to about 1.0, from about 0.5 to about 1.0,
or from about 0.6 to about 1.0, from about 0.7 to about 1.0, from
about 0.8 to about 1.0, or from about 0.9 to about 1.0.
[0060] Another characteristic of the multi-block interpolymer is
that the interpolymer may comprise at least one polymer fraction
which may be obtained by preparative TREF, wherein the fraction has
a block index greater than about 0.1 and up to about 1.0 and the
polymer having a molecular weight distribution, M.sub.w/M.sub.n,
greater than about 1.3. In some embodiments, the polymer fraction
has a block index greater than about 0.6 and up to about 1.0,
greater than about 0.7 and up to about 1.0, greater than about 0.8
and up to about 1.0, or greater than about 0.9 and up to about 1.0.
In other embodiments, the polymer fraction has a block index
greater than about 0.1 and up to about 1.0, greater than about 0.2
and up to about 1.0, greater than about 0.3 and up to about 1.0,
greater than about 0.4 and up to about 1.0, or greater than about
0.4 and up to about 1.0. In still other embodiments, the polymer
fraction has a block index greater than about 0.1 and up to about
0.5, greater than about 0.2 and up to about 0.5, greater than about
0.3 and up to about 0.5, or greater than about 0.4 and up to about
0.5. In yet other embodiments, the polymer fraction has a block
index greater than about 0.2 and up to about 0.9, greater than
about 0.3 and up to about 0.8, greater than about 0.4 and up to
about 0.7, or greater than about 0.5 and up to about 0.6.
[0061] Ethylene .alpha.-olefin multi-block interpolymers used in
embodiments of the invention may be interpolymers of ethylene with
at least one C.sub.3-C.sub.20 .alpha.-olefin. The interpolymers may
further comprise C.sub.4-C.sub.18 diolefin and/or alkenylbenzene.
Suitable unsaturated comonomers useful for polymerizing with
ethylene include, for example, ethylenically unsaturated monomers,
conjugated or non-conjugated dienes, polyenes, alkenylbenzenes,
etc. Examples of such comonomers include C.sub.3-C.sub.20
.alpha.-olefins such as propylene, isobutylene, 1-butene, 1-hexene,
1-pentene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-nonene,
1-decene, and the like. 1-Butene and 1-octene are especially
preferred. Other suitable monomers include styrene, halo- or
alkyl-substituted styrenes, vinylbenzocyclobutane, 1,4-hexadiene,
1,7-octadiene, and naphthenics (such as cyclopentene, cyclohexene,
and cyclooctene, for example).
[0062] The multi-block interpolymers disclosed herein may be
differentiated from conventional, random copolymers, physical
blends of polymers, and block copolymers prepared via sequential
monomer addition, fluxional catalysts, and anionic or cationic
living polymerization techniques. In particular, compared to a
random copolymer of the same monomers and monomer content at
equivalent crystallinity or modulus, the interpolymers have better
(higher) heat resistance as measured by melting point, higher TMA
penetration temperature, higher high-temperature tensile strength,
and/or higher high-temperature torsion storage modulus as
determined by dynamic mechanical analysis. Properties of infill may
benefit from the use of embodiments of the multi-block
interpolymers, as compared to a random copolymer containing the
same monomers and monomer content, the multi-block interpolymers
have lower compression set, particularly at elevated temperatures,
lower stress relaxation, higher creep resistance, higher tear
strength, higher blocking resistance, faster setup due to higher
crystallization (solidification) temperature, higher recovery
(particularly at elevated temperatures), better abrasion
resistance, higher refractive force, and better oil and filler
acceptance.
[0063] Other olefin interpolymers include polymers comprising
monovinylidene aromatic monomers including styrene, o-methyl
styrene, p-methyl styrene, t-butylstyrene, and the like. In
particular, interpolymers comprising ethylene and styrene may be
used. In other embodiments, copolymers comprising ethylene, styrene
and a C.sub.3-C.sub.20 .alpha. olefin, optionally comprising a
C.sub.4-C.sub.20 diene, may be used.
[0064] Suitable non-conjugated diene monomers may include straight
chain, branched chain or cyclic hydrocarbon diene having from 6 to
15 carbon atoms. Examples of suitable non-conjugated dienes
include, but are not limited to, straight chain acyclic dienes,
such as 1,4-hexadiene, 1,6-octadiene, 1,7-octadiene, 1,9-decadiene,
branched chain acyclic dienes, such as 5-methyl-1,4-hexadiene;
3,7-dimethyl-1,6-octadiene; 3,7-dimethyl-1,7-octadiene and mixed
isomers of dihydromyricene and dihydroocinene, single ring
alicyclic dienes, such as 1,3-cyclopentadiene; 1,4-cyclohexadiene;
1,5-cyclooctadiene and 1,5-cyclododecadiene, and multi-ring
alicyclic fused and bridged ring dienes, such as tetrahydroindene,
methyl tetrahydroindene, dicyclopentadiene,
bicyclo-(2,2,1)-hepta-2,5-diene; alkenyl, alkylidene, cycloalkenyl
and cycloalkylidene norbornenes, such as 5-methylene-2-norbornene
(MNB); 5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene,
5-(4-cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene,
5-vinyl-2-norbornene, and norbornadiene. Of the dienes typically
used to prepare EPDMs, the particularly preferred dienes are
1,4-hexadiene (HD), 5-ethylidene-2-norbornene (ENB),
5-vinylidene-2-norbornene (VNB), 5-methylene-2-norbornene (MNB),
and dicyclopentadiene (DCPD).
[0065] One class of desirable polymers that may be used in
accordance with embodiments disclosed herein includes elastomeric
interpolymers of ethylene, a C.sub.3-C.sub.20 .alpha.-olefin,
especially propylene, and optionally one or more diene monomers.
Preferred .alpha.-olefins for use in this embodiment are designated
by the formula CH.sub.2.dbd.CHR*, where R* is a linear or branched
alkyl group of from 1 to 12 carbon atoms. Examples of suitable
.alpha.-olefins include, but are not limited to, propylene,
isobutylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and
1-octene. A particularly preferred .alpha.-olefin is propylene. The
propylene based polymers are generally referred to in the art as EP
or EPDM polymers. Suitable dienes for use in preparing such
polymers, especially multi-block EPDM type polymers include
conjugated or non-conjugated, straight or branched chain-, cyclic-
or polycyclic-dienes comprising from 4 to 20 carbons. Preferred
dienes include 1,4-pentadiene, 1,4-hexadiene,
5-ethylidene-2-norbornene, dicyclopentadiene, cyclohexadiene, and
5-butylidene-2-norbornene. A particularly preferred diene is
5-ethylidene-2-norbornene.
[0066] The polymers (homopolymers, copolymers, interpolymers and
multi-block interpolymers) described herein may have a melt index,
I.sub.2, from 0.01 to 2000 g/10 minutes in some embodiments; from
0.01 to 1000 g/10 minutes in other embodiments; from 0.01 to 500
g/10 minutes in other embodiments; and from 0.01 to 100 g/10
minutes in yet other embodiments. In certain embodiments, the
polymers may have a melt index, I.sub.2, from 0.01 to 10 g/10
minutes, from 0.5 to 50 g/10 minutes, from 1 to 30 g/10 minutes,
from 1 to 6 g/10 minutes or from 0.3 to 10 g/10 minutes. In certain
embodiments, the melt index for the polymers may be approximately 1
g/10 minutes, 3 g/10 minutes or 5 g/10 minutes. In other
embodiments, the polymers may have a melt index greater than 20
dg/min; greater than 40 dg/min in other embodiments; and greater
than 60 dg/min in yet other embodiments.
[0067] The polymers described herein may have molecular weights,
M.sub.w, from 1,000 g/mole to 5,000,000 g/mole in some embodiments;
from 1000 g/mole to 1,000,000 in other embodiments; from 10,000
g/mole to 500,000 g/mole in other embodiments; and from 10,000
g/mole to 300,000 g/mole in yet other embodiments. The density of
the polymers described herein may be from 0.80 to 0.99 g/cm.sup.3
in some embodiments; for ethylene containing polymers from 0.85
g/cm.sup.3 to 0.97 g/cm.sup.3; in some embodiments between 0.87
g/cm.sup.3 and 0.94 g/cm.sup.3.
[0068] In some embodiments, the polymers described herein may have
a tensile strength above 10 MPa; a tensile strength >11 MPa in
other embodiments; and a tensile strength >13 MPa in yet other
embodiments. In some embodiments, the polymers described herein may
have an elongation at break of at least 600 percent at a crosshead
separation rate of 11 cm/minute; at least 700 percent in other
embodiments; at least 800 percent in other embodiments; and at
least 900 percent in yet other embodiments.
[0069] In some embodiments, the polymers described herein may have
a storage modulus ratio, G'(25.degree. C.)/G'(100.degree. C.), from
1 to 50; from 1 to 20 in other embodiments; and from 1 to 10 in yet
other embodiments. In some embodiments, the polymers may have a
70.degree. C. compression set of less than 80 percent; less than 70
percent in other embodiments; less than 60 percent in other
embodiments; and, less than 50 percent, less than 40 percent, down
to a compression set of 0 percent in yet other embodiments.
[0070] In some embodiments, the ethylene/.alpha.-olefin
interpolymers may have a heat of fusion of less than 85 J/g. In
other embodiments, the ethylene/.alpha.-olefin interpolymer may
have a pellet blocking strength of equal to or less than 100
pounds/foot.sup.2 (4800 Pa); equal to or less than 50 lbs/ft.sup.2
(2400 Pa) in other embodiments; equal to or less than 5
lbs/ft.sup.2 (240 Pa), and as low as 0 lbs/ft.sup.2 (0 Pa) in yet
other embodiments.
[0071] In some embodiments, block polymers made with two catalysts
incorporating differing quantities of comonomer may have a weight
ratio of blocks formed thereby ranging from 95:5 to 5:95. The
elastomeric interpolymers, in some embodiments, have an ethylene
content of from 20 to 90 percent, a diene content of from 0.1 to 10
percent, and an .alpha.-olefin content of from 10 to 80 percent,
based on the total weight of the polymer. In other embodiments, the
multi-block elastomeric polymers have an ethylene content of from
60 to 90 percent, a diene content of from 0.1 to 10 percent, and an
.alpha.-olefin content of from 10 to 40 percent, based on the total
weight of the polymer. In other embodiments, the interpolymer may
have a Mooney viscosity (ML (1+4) 125.degree. C.) ranging from 1 to
250. In other embodiments, such polymers may have an ethylene
content from 65 to 75 percent, a diene content from 0 to 6 percent,
and an .alpha.-olefin content from 20 to 35 percent.
[0072] In certain embodiments, the polymer may be a
propylene-ethylene copolymer or interpolymer having an ethylene
content between 5 and 20% by weight and a melt flow rate
(230.degree. C. with 2.16 kg weight) from 0.5 to 300 g/10 min. In
other embodiments, the propylene-ethylene copolymer or interpolymer
may have an ethylene content between 9 and 12% by weight and a melt
flow rate (230.degree. C. with 2.16 kg weight) from 1 to 100 g/10
min.
[0073] In some particular embodiments, the polymer is a
propylene-based copolymer or interpolymer. In some embodiments, a
propylene/ethylene copolymer or interpolymer is characterized as
having substantially isotactic propylene sequences. The term
"substantially isotactic propylene sequences" and similar terms
mean that the sequences have an isotactic triad (mm) measured by
.sup.13C NMR of greater than about 0.85, preferably greater than
about 0.90, more preferably greater than about 0.92 and most
preferably greater than about 0.93. Isotactic triads are well-known
in the art and are described in, for example, U.S. Pat. No.
5,504,172 and WO 00/01745, which refer to the isotactic sequence in
terms of a triad unit in the copolymer molecular chain determined
by .sup.13C NMR spectra. In other particular embodiments, the
ethylene-.alpha. olefin copolymer may be ethylene-butene,
ethylene-hexene, or ethylene-octene copolymers or interpolymers. In
other particular embodiments, the propylene-.alpha. olefin
copolymer may be a propylene-ethylene or a
propylene-ethylene-butene copolymer or interpolymer.
[0074] The polymers described herein (homopolymers, copolymers,
interpolymers, multi-block interpolymers) may be produced using a
single site catalyst and may have a weight average molecular weight
of from about 15,000 to about 5 million, such as from about 20,000
to about 1 million. The molecular weight distribution of the
polymer may be from about 1.01 to about 80, such as from about 1.5
to about 40, such as from about 1.8 to about 20.
[0075] In some embodiments, the polymer may have a Shore A hardness
from 30 to 100. In other embodiments, the polymer may have a Shore
A hardness from 40 to 90; from 30 to 80 in other embodiments; and
from 40 to 75 in yet other embodiments.
[0076] The olefin polymers, copolymers, interpolymers, and
multi-block interpolymers may be functionalized by incorporating at
least one functional group in its polymer structure. Exemplary
functional groups may include, for example, ethylenically
unsaturated mono- and di-functional carboxylic acids, ethylenically
unsaturated mono- and di-functional carboxylic acid anhydrides,
salts thereof and esters thereof. Such functional groups may be
grafted to an olefin polymer, or it may be copolymerized with
ethylene and an optional additional comonomer to form an
interpolymer of ethylene, the functional comonomer and optionally
other comonomer(s). Means for grafting functional groups onto
polyethylene are described for example in U.S. Pat. Nos. 4,762,890,
4,927,888, and 4,950,541, the disclosures of which are incorporated
herein by reference in their entirety. One particularly useful
functional group is maleic anhydride.
[0077] The amount of the functional group present in the functional
polymer may vary. The functional group may be present in an amount
of at least about 1.0 weight percent in some embodiments; at least
about 5 weight percent in other embodiments; and at least about 7
weight percent in yet other embodiments. The functional group may
be present in an amount less than about 40 weight percent in some
embodiments; less than about 30 weight percent in other
embodiments; and less than about 25 weight percent in yet other
embodiments.
[0078] The foam sheets according to embodiments disclosed herein
may include a single layer or multiple layers as desired. The foam
articles may be produced in any manner so as to result in at least
one foam layer. The foam layers described herein may be made by a
pressurized melt processing method such as an extrusion method. The
extruder may be a tandem system, a single screw extruder, a twin
screw extruder, etc. The extruder may be equipped with multilayer
annular dies, flat film dies and feedblocks, multi-layer feedblocks
such as those disclosed in U.S. Pat. No. 4,908,278 (Bland et al.),
multi-vaned or multi-manifold dies such as a 3-layer vane die
available from Cloeren, Orange, Tex. A foamable composition may
also be made by combining a chemical blowing agent and polymer at a
temperature below the decomposition temperature of the chemical
blowing agent, and then later foamed. In some embodiments, the foam
may be coextruded with one or more barrier layers.
[0079] One method of producing the foams described herein is by
using an extruder, as mentioned above. In this case, the foamable
mixture (polymer+blowing agent) is extruded. As the mixture exits
an extruder die and upon exposure to reduced pressure, the fugitive
gas nucleates and forms cells within the polymer to create a foam
article. The resulting foam article may then be deposited onto a
temperature-controlled casting drum. The casting drum speed (i.e.,
as produced by the drum RPM) can affect the overall thickness of
the foam article. As the casting roll speed increases, the overall
thickness of the foam article can decrease. However, the barrier
layer thickness at the die exit, which is where foaming occurs, is
the diffusion length for the system. As the foam article is
stretched and quenched on the casting drum, the barrier layer
thickness may decrease until the foam article solidifies. In other
words, it is the barrier layer diffusion length (i.e., thickness)
at the die exit that is the important factor in controlling the
diffusion of the fugitive gas.
[0080] Blowing agents suitable for use in forming the foams
described herein may be physical blowing agents, which are
typically the same material as the fugitive gas, e.g., CO.sub.2, or
a chemical blowing agent, which produces the fugitive gas. More
than one physical or chemical blowing agent may be used and
physical and chemical blowing agents may be used together.
[0081] Physical blowing agents useful in the present invention
include any naturally occurring atmospheric material which is a
vapor at the temperature and pressure at which the foam exits the
die. The physical blowing agent may be introduced, i.e., injected
into the polymeric material as a gas, a supercritical fluid, or
liquid, preferably as a supercritical fluid or liquid, most
preferably as a liquid. The physical blowing agents used will
depend on the properties sought in the resulting foam articles.
Other factors considered in choosing a blowing agent are its
toxicity, vapor pressure profile, ease of handling, and solubility
with regard to the polymeric materials used. Non-flammable,
non-toxic, non-ozone depleting blowing are preferred because they
are easier to use, e.g., fewer environmental and safety concerns,
and are generally less soluble in thermoplastic polymers. Suitable
physical blowing agents include, e.g., carbon dioxide, nitrogen,
SF.sub.6, nitrous oxide, perfluorinated fluids, such as
C.sub.2F.sub.6, argon, helium, noble gases, such as xenon, air
(nitrogen and oxygen blend), and blends of these materials.
[0082] Chemical blowing agents that may be used in the present
invention include, e.g., a sodium bicarbonate and citric acid
blend, dinitrosopentamethylenetetramine, p-toluenesulfonyl
hydrazide, 4-4.sup.1-oxybis(benzenesulfonyl hydrazide,
azodicarbonamide (1,1'-azobisformamide), p-toluenesulfonyl
semicarbazide, 5-phenyltetrazole, 5-phenyltetrazole analogues,
diisopropylhydrazodicarboxylate,
5-phenyl-3,6-dihydro-1,3,4-oxadiazin-2-one, and sodium borohydride.
Preferably, the blowing agents are, or produce, one or more
fugitive gases having a vapor pressure of greater than 0.689 MPa at
0.degree. C.
[0083] The total amount of the blowing agent used depends on
conditions such as extrusion-process conditions at mixing, the
blowing agent being used, the composition of the extrudate, and the
desired density of the foamed article. The extrudate is defined
herein as including the blowing agent blend, a polyolefin resin(s),
and any additives. For a foam having a density of from about 1 to
about 15 lb/ft.sup.3, the extrudate typically comprises from about
18 to about 1 wt of blowing agent. In other embodiments, 1% to 10%
of blowing agent may be used.
[0084] The blowing agent blend used in the present invention
comprises less than about 99 mol % isobutane. The blowing agent
blend generally comprises from about 10 mol % to about 60 or 75 mol
% isopentane. The blowing agent blend more typically comprises from
about 15 mol % to about 40 mol % isopentane. More specifically, the
blowing agent blend comprises from about 25 or 30 mol % to about 40
mol % isobutane. The blowing agent blend generally comprises at
least about 15 or 30 mol % of co-blowing agent(s). More
specifically, the blowing agent blend comprises from about 40 to
about 85 or 90 mol % of co-blowing agent(s). The blowing agent
blend more typically comprises from about 60 mol % to about 70 or
75 mol % of co-blowing agent(s).
[0085] A nucleating agent or combination of such agents may be
employed in the present invention for advantages, such as its
capability for regulating cell formation and morphology. A
nucleating agent, or cell size control agent, may be any
conventional or useful nucleating agent(s). The amount of
nucleating agent used depends upon the desired cell size, the
selected blowing agent blend, and the desired foam density. The
nucleating agent is generally added in amounts from about 0.02 to
about 20 wt % of the polyolefin resin composition.
[0086] Some contemplated nucleating agents include inorganic
materials (in small particulate form), such as clay, talc, silica,
and diatomaceous earth. Other contemplated nucleating agents
include organic nucleating agents that decompose or react at the
heating temperature within an extruder to evolve gases, such as
carbon dioxide, water, and/or nitrogen. One example of an organic
nucleating agent is a combination of an alkali metal salt of a
polycarboxylic acid with a carbonate or bicarbonate. Some examples
of alkali metal salts of a polycarboxylic acid include, but are not
limited to, the monosodium salt of 2,3-dihydroxy-butanedioic acid
(commonly referred to as sodium hydrogen tartrate), the
monopotassium salt of butanedioic acid (commonly referred to as
potassium hydrogen succinate), the trisodium and tripotassium salts
of 2-hydroxy-1,2,3-propanetricarboxylic acid (commonly referred to
as sodium and potassium citrate, respectively), and the disodium
salt of ethanedioic acid (commonly referred to as sodium oxalate),
or polycarboxylic acid such as 2-hydroxy-1,2,3-propanetricarboxylic
acid. Some examples of a carbonate or a bicarbonate include, but
are not limited to, sodium carbonate, sodium bicarbonate, potassium
carbonate, potassium bicarbonate, and calcium carbonate.
[0087] It is contemplated that mixtures of different nucleating
agents may be added in the present invention. Some more desirable
nucleating agents include talc, crystalline silica, and a
stoichiometric mixture of citric acid and sodium bicarbonate (the
stoichiometric mixture having a 1 to 100 percent concentration
where the carrier is a suitable polymer such as polyethylene). Talc
may be added in a carrier or in a powder form.
[0088] Gas permeation agents or stability control agents may be
employed in the present invention to assist in preventing or
inhibiting collapsing of the foam. The stability control agents
suitable for use in the present invention may include the partial
esters of long-chain fatty acids with polyols described in U.S.
Pat. No. 3,644,230, saturated higher alkyl amines, saturated higher
fatty acid amides, complete esters of higher fatty acids such as
those described in U.S. Pat. No. 4,214,054, and combinations
thereof described in U.S. Pat. No. 5,750,584.
[0089] The partial esters of fatty acids that may be desired as a
stability control agent include the members of the generic class
known as surface active agents or surfactants. A preferred class of
surfactants includes a partial ester of a fatty acid having 12 to
18 carbon atoms and a polyol having three to six hydroxyl groups.
More preferably, the partial esters of a long chain fatty acid with
a polyol component of the stability control agent are glycerol
monostearate, glycerol distearate or mixtures thereof. It is
contemplated that other gas permeation agents or stability control
agents may be employed in the present invention to assist in
preventing or inhibiting collapsing of the foam.
[0090] Additives
[0091] If desired, fillers, colorants, light and heat stabilizers,
anti-oxidants, acid scavengers, flame retardants, processing aids,
extrusion aids, and foaming additives may be used in making the
foam. The foam of the invention may contain filler materials in
amounts, depending on the application for which they are designed,
ranging from about 2-100 percent (dry basis) of the weight of the
polymer component. These optional ingredients may include, but are
not limited to, calcium carbonate, titanium dioxide powder, polymer
particles, hollow glass spheres, polymeric fibers such as
polyolefin based staple monofilaments and the like.
[0092] In selected embodiments, foams useful for disclosed
embodiments may have thickness between 1 and 500 mm, and in some
embodiments, 5 to 100 mm, and in some embodiments 8 and 30 mm. In
selected embodiments foams may have a density between about 20 and
600 kg/m.sup.3, preferably 25 to 300 kg/m.sup.3, and more
preferably, 30 to 150 kg/m.sup.3. In selected embodiments, foams
may have a cell size between about 0.1 to 6 mm, preferably 0.2 to
4.5 mm, and more preferably 0.2 to 3 mm.
[0093] In some embodiments, the foam layer may be perforated in
order to facilitate drainage, so that in the event of rain, water
may drain off of the playing surface.
[0094] In some embodiments, the above described foams may be used
as a shock absorbing layer in a synthetic turf. Additionally, tests
may be performed to analyze temperature performance and aging, as
well as the bounce and spin properties of the resulting turf.
Briefly, the significant tests & desired results for artificial
turf performance as specified by the FIFA Quality Concept Manual
(March 2006 Edition) are shown in the below table. Those having
ordinary skill in the art will appreciate that this is but one use
of the foams described herein, and that the artificial turf and
foams described herein may be useful in a number of other
applications an a number of other sports, such as rugby and field
hockey, for example.
TABLE-US-00001 LABORATORY TESTS - BALL/SURFACE INTERACTION
Requirements FIFA Test Test Test Conditions Recommended** FIFA
Property Method Method Preparation Temp Condition (best ranking)
Recommended* Vertical ball FIFA Pre- 23.degree. C. Dry 0.60 m-0.85
m 0.60 m-1 m rebound 01/05-01 & conditioning Wet -- FIFA
Simulated 23.degree. C. Dry 0.60 m-1 m 09/05-01 Wear Shock FIFA
Flat foot Pre- 23.degree. C. Dry 60%-70% 55%-70% absorption
04/05-01 & Mean conditioning Wet -- FIFA 2.sup.nd/3.sup.rd
Simulated 23.degree. C. Dry 55%-70% 10/05-01 impact Wear --
40.degree. C. Dry -- Flat Foot -- -5.degree. C. Frozen 60%-70% --
1.sup.st impact Vertical FIFA Flat foot Pre- 23.degree. C. Dry 4
mm-8 mm 4 mm-9 mm deformation 05/05-01 & Mean conditioning Wet
-- FIFA 2.sup.nd/3.sup.rd Simulated 23.degree. C. Dry 4 mm-9 mm
10/05-01 impact Wear
[0095] Shock Absorption
[0096] Principle: A mass (20 Kgs) falls, as discussed in the FIFA
Quality Concept Manual (March 2006 Edition), which is incorporated
by reference in its entirety. The maximum force applied is
recorded. The % reduction in this force relative to the maximum
force measured on a concrete surface is reported as `Force
Reduction`.
[0097] FIFA Requirement:
[0098] FIFA 2 Star: 60%-70%
[0099] FIFA 1 Star: 55%-70%
[0100] Vertical Deformation
[0101] Principle A mass is allowed to fall onto a spring that rests
and the maximum deformation of the surface is determined.
[0102] FIFA Requirement:
[0103] FIFA 2 Star: 4 mm-8 mm
[0104] FIFA 1 Star: 4 mm-9 mm
EXAMPLES
[0105] The usefulness of polyolefin resins having selected foam
densities and thicknesses is investigated. Specifically, a number
of polyethylene resins, commercially available from The Dow
Chemical Company, Midland, Mich. are studied. Table 1 and Table 2
show a number of the compounds used. In Table 1, the performance of
crosslinked polyethylene (comparative examples 1c-4c) versus
non-crosslinked polyethylene (examples 1-4) is investigated.
Specifically, with respect to Table 1, (LDPE 300E, and LDPE PG
7004, and blends thereof, LDPE 6201, and XU 60021.24 are used to
generate the data. The formulations used in creating the Table are
shown below.
TABLE-US-00002 Resin Foam Thick- Density Density ness Cross-
Example Resin A/B (kg/m.sup.3) (kg/m.sup.3) (mm) linked 1 XU
60021.24* 0.922 33 10 No 2 90/10 (LDPE 300E/ 0.923 45 10 No LDPE
PG7004) 3 70/30 (LDPE 300E/ 0.923 64 10 No LDPE PG7004) 4 LDPE 620I
0.923 144 51 No
TABLE-US-00003 TABLE 1 Resin A Resin B Density Density (g/cm.sup.3)
(g/cm.sup.3) Foam Polymer (ASTM I.sub.2 Polymer (ASTM I.sub.2
Density Thickness Example (wt. %) Type D792) (g/10 min) (wt. %)
Type D792) (g/10 min) (kg/m.sup.3) (mm) Crosslinked 1 100 LDPE
0.922 3.3 -- -- -- -- 33 10 No 2 90 LDPE 0.9235 0.8 10 LDPE 0.9215
4.1 45 10 No 3 70 LDPE 0.9235 0.8 30 LDPE 0.9215 4.1 64 10 No 4 100
LDPE 0.9239 1.85 -- -- -- -- 144 51 No Comparative Examples. Foam
Comparative Density Thickness Crosslinked Example Designation
(kg/m.sup.3) (mm) (yes/no) 1c Qycell T-20* 33 10 yes 2c Qycell
T-30* 45 10 yes 3c Qycell T-40* 64 10 yes 4c Qycell T-80* 119 11.5
no `*` denotes foam commercially available from Qycell Corporation
(Ontario, California, USA)
[0106] Turning to the shock absorption, vertical deformation, and
energy restitution, the performance of non-crosslinked polyethylene
foams of Table 1, which are commercially available from The Dow
Chemical Company, Midland, Mich. was investigated. The results of
this investigation are summarized in FIG. 1. With respect to Table
1, the compressive stress-strain, compressive creep, and
compressive stress-strain behavior is analyzed using an Instron
Model 5565 Universal Testing Machine (Norwood, Mass.) fitted with
compression plates and a 2 kN load cell. When the tests are
performed at 65.degree. C., an Instron environmental chamber (Model
3119-405-21) is also used.
[0107] Samples 2.5 to 5 cm wide by 5 cm deep are cut from sheets of
the foam. To measure compressive stress-strain behavior, the
samples are inserted between the centers of the compressive plates.
The thickness direction of the foam is aligned parallel to
crosshead movement. A pre-load of 2.5 N was applied at 5 mm/min,
and the crosshead position is re-zeroed. The sample is then
compressed at 10 mm/min until the load approached the capacity of
the load cell. Stress is calculated by dividing the measured
compressive force by the product of the width and depth of the
foam. Stress is quantified in units of megapascals (MPa). Strain in
terms of percent is calculated by dividing the crosshead
displacement by the starting thickness of the foam and multiplying
by one hundred. Results for the compressive stress-strain behavior
tests are illustrated in FIGS. 2 and 2c (comparative samples).
[0108] To measure the compressive hysteresis behavior, a foam
sample is loaded into the Instron in the same manner as above. A
pre-load of 2.5N is applied at 5 mm/min, and the crosshead position
is re-zeroed. Then the sample is compressed at 10 mm/min until the
stress reaches 0.38 MPA, designated as the compression step.
Immediately, the crosshead is then reversed until a load of 0.0038
MPa is reached, designated as decompression. Without interruption,
the sample is compressed and decompressed for 10 cycles.
[0109] To measure the compressive creep behavior, a foam sample is
loaded into the Instron in the same manner as above, except that
the environmental chamber is in place and preheated to a
temperature of 65.degree. C. The sample is placed in between the
compression plates, at 65.degree. C. After allowing the foam sample
to equilibrate inside the chamber for one hour, a pre-load of 2.5 N
is applied at 5 mm/min, and the crosshead position is re-zeroed.
Load is then applied at 0.16 MPa. Crosshead position is then
adjusted automatically by the Instron computer, to maintain a
stress of 0.16 MPa for 12 hours. Compressive strain versus time is
measured, the results of which are presented in FIGS. 3 and 3c.
After 12 hours, the crosshead returns to its starting position.
After another two hours, the foam is removed and allowed to cool to
ambient conditions (20.degree. C., 50% relative humidity). The foam
thickness is then remeasured. The corresponding strain is
designated "strain at release, 2 hr." The compressive creep
behavior test results are presented in FIG. 4.
[0110] To measure the energy absorption behavior of the foams FIFA
quality concept methodology as described in the "March 2006 FIFA
Quality Concept Requirements for Artificial Turf Surfaces," the
FIFA handbook of test methods and requirements for artificial
football turf; which is fully incorporated herein by reference.
These foams are tested according to this methodology and it is
found that foams having a density of 144 kg/m.sup.3, as an example,
perform acceptably. More detailed test results on shock absorption
are provided below. Returning to compressive performance, the below
graphs illustrate that the performance of the foam is not
compromised by the elimination of crosslinking. In addition,
embodiments of the present invention may be useful for any field
that may use artificial turf, such as rugby and field hockey.
[0111] FIGS. 3, 3c, and 4 illustrate that essentially the same
compressive creep performance and subsequent recovery may be
achieved despite the elimination of crosslinking.
[0112] Synthetic turf, using embodiments of the present invention,
is shown in FIG. 5. Specifically, a non-crosslinked polythene foam
is provided as a shock absorption layer, which may be bonded to a
backing. Artificial grass is attached to the backing, and the
spaces between the grass may be filled with an infill.
[0113] Embodiments using non-crosslinked polyethylene may be
advantageous as non-crosslinked polyethylene is recyclable, and,
thus, there are no environmental issues. Embodiments of the polymer
foams described herein may also be useful as heavy layers for noise
and vibration dampening, among others.
[0114] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention
as disclosed herein. Accordingly, the scope of the invention should
be limited only by the attached claims.
[0115] All priority documents are herein fully incorporated by
reference for all jurisdictions in which such incorporation is
permitted. Further, all documents cited herein, including testing
procedures, are herein fully incorporated by reference for all
jurisdictions in which such incorporation is permitted to the
extent such disclosure is consistent with the description of the
present invention.
* * * * *