U.S. patent application number 10/633764 was filed with the patent office on 2005-02-10 for membranes with fluid barrier properties and articles containing such membranes.
Invention is credited to Chang, Yihua, Watkins, Richard L..
Application Number | 20050031816 10/633764 |
Document ID | / |
Family ID | 34115882 |
Filed Date | 2005-02-10 |
United States Patent
Application |
20050031816 |
Kind Code |
A1 |
Chang, Yihua ; et
al. |
February 10, 2005 |
Membranes with fluid barrier properties and articles containing
such membranes
Abstract
A membrane comprising at least one elastomeric material, at
least one polymeric fluid barrier material, and a laminar
nano-filler having an average platelet thickness of up to about 10
nanometers and an average aspect ratio of at least about 200
provides desirable appearance and low gas transmission
characteristics. The membrane may be a single layer, but preferably
the membrane includes at least one layer of an elastomeric material
and at least one layer of a polymeric barrier material, in which
the elastomeric material layer and/or the polymeric barrier
material layer comprises the laminar nano-filler.
Inventors: |
Chang, Yihua; (Portland,
OR) ; Watkins, Richard L.; (Portland, OR) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
34115882 |
Appl. No.: |
10/633764 |
Filed: |
August 4, 2003 |
Current U.S.
Class: |
428/35.7 |
Current CPC
Class: |
B32B 25/08 20130101;
B32B 27/18 20130101; B32B 2250/24 20130101; Y10T 428/1352 20150115;
A43B 13/026 20130101; B32B 2437/02 20130101; A43B 13/20 20130101;
B32B 2264/10 20130101; B32B 2274/00 20130101; B32B 27/306 20130101;
B32B 2250/42 20130101; A43B 13/12 20130101; B32B 27/20 20130101;
B32B 27/40 20130101 |
Class at
Publication: |
428/035.7 |
International
Class: |
B65D 001/00 |
Claims
What is claimed is:
1. A membrane, comprising an elastomeric material, a polymeric
fluid barrier material, and a laminar nano-filler having an average
platelet thickness of up to about 10 nanometers and an average
aspect ratio of at least about 200.
2. A membrane according to claim 1, comprising a mixture of the
laminar nano-filler and the polymeric fluid barrier material.
3. A membrane according to claim 2, wherein the mixture is
distributed in a continuous matrix of the elastomeric material.
4. A membrane according to claim 1, wherein the elastomeric
material is selected from the group consisting of polyurethane
elastomers, flexible polyolefins, styrenic thermoplastic
elastomers, polyamide elastomers, polyamide-ether elastomers,
ester-ether and ester-ester elastomers, flexible ionomers,
thermoplastic vulcanizates, flexible poly(vinyl chloride)
homopolymers and copolymers, flexible acrylic polymers, and
combinations thereof.
5. A membrane according to claim 1, wherein the elastomeric
material is selected from the group consisting of thermoplastic
polyester-polyurethanes, thermoplastic polyether-polyurethanes,
thermoplastic polycarbonate-polyurethanes, and combinations
thereof.
6. A membrane according to claim 1, wherein the polymeric fluid
barrier material is selected from the group consisting of
ethylene-vinyl alcohol copolymers, poly(vinyl chloride),
polyvinylidene polymers and copolymers, polyamides, acrylonitrile
polymers, polyurethane engineering plastics, poly(methyl pentene)
resins, ethylene-carbon monoxide copolymers, liquid crystal
polymers, polyesters, polyimides, and combinations thereof.
7. A membrane according to claim 1, wherein the polymeric fluid
barrier material comprises an ethylene-vinyl alcohol copolymer.
8. A membrane according to claim 1, wherein the laminar nano-filler
has an average thickness of from about 1 nm to about 10 nm and an
aspect ratio from about 200 to about 1000.
9. A membrane according to claim 1, wherein the laminar nano-filler
is a montmorillonite clay.
10. A membrane according to claim 1, wherein the membrane comprises
from about 4 to about 10 weight percent of the laminar
nano-filler.
11. A permanently sealed, inflated bladder comprising a membrane
according to claim 1.
12. A permanently sealed, inflated bladder comprising a membrane
according to claim 2.
13. A membrane, comprising at least one elastomeric layer
comprising an elastomeric material and at least one barrier layer
comprising a polymeric fluid barrier material, wherein at least one
of the membrane layers further comprises a laminar nano-filler
having an average platelet thickness of up to about 10 nanometers
and an average aspect ratio of at least about 200.
14. A membrane according to claim 13, wherein the elastomeric
material is selected from the group consisting of polyurethane
elastomers, flexible polyolefins, styrenic thermoplastic
elastomers, polyamide elastomers, polyamide-ether elastomers,
ester-ether and ester-ester elastomers, flexible ionomers,
thermoplastic vulcanizates, flexible poly(vinyl chloride)
homopolymers and copolymers, flexible acrylic polymers, and
combinations thereof.
15. A membrane according to claim 13, wherein the elastomeric
material is selected from the group consisting of thermoplastic
polyester-polyurethanes, thermoplastic polyether-polyurethanes,
thermoplastic polycarbonate-polyurethanes, and combinations
thereof.
16. A membrane according to claim 13, wherein the polymeric fluid
barrier material is selected from the group consisting of
ethylene-vinyl alcohol copolymers, poly(vinyl chloride),
polyvinylidene polymers and copolymers, polyamides, acrylonitrile
polymers, polyurethane engineering plastics, poly(methyl pentene)
resins, ethylene-carbon monoxide copolymers, liquid crystal
polymers, polyesters, polyimides, and combinations thereof.
17. A membrane according to claim 13, wherein the polymeric fluid
barrier material comprises an ethylene-vinyl alcohol copolymer.
18. A membrane according to claim 13, wherein the laminar
nano-filler has an average thickness of from about 1 nm to about 10
nm and an aspect ratio from about 200 to about 1000.
19. A membrane according to claim 13, wherein the laminar
nano-filler is a montmorillonite clay.
20. A membrane according to claim 13, wherein the membrane
comprises from about 4 to about 10 weight percent of the laminar
nano-filler.
21. A permanently sealed, inflated bladder comprising a membrane
according to claim 13.
22. A permanently sealed, inflated bladder comprising a membrane
according to claim 15.
23. A permanently sealed, inflated bladder comprising a membrane
according to claim 17.
24. A permanently sealed, inflated bladder comprising a membrane
according to claim 18.
25. A permanently sealed, inflated bladder comprising a membrane
according to claim 20.
26. A bladder according to claim 21, wherein said bladder is
inflated with a gas comprising nitrogen.
27. A bladder according to claim 24, wherein said bladder is
inflated with a gas comprising nitrogen.
28. A bladder, comprising an elastomeric barrier membrane, wherein:
said membrane comprises a microlayer polymeric composite layer
having at least about 10 microlayers, each microlayer individually
being up to about 100 microns thick, said microlayers alternating
between at least one polymeric gas barrier material and at least
one elastomeric material; and further wherein said microlayers of
polymeric fluid barrier material or said microlayers of elastomeric
material or both comprise a laminar nano-filler having an average
platelet thickness of up to about 10 nanometers and an average
aspect ratio of at least about 200.
29. A bladder according to claim 28, wherein the microlayers of
polymeric fluid barrier material comprise the laminar
nano-filler.
30. A bladder according to claim 28, wherein said elastomeric
material comprises a member selected from the group consisting of
polyurethane elastomers, flexible polyolefins, styrenic
thermoplastic elastomers, polyamide elastomers, polyamide-ether
elastomers, ester-ether elastomers, ester-ester elastomer, flexible
ionomers, thermoplastic vulcanizates, flexible poly(vinyl chloride)
homopolymers and copolymers, flexible acrylic polymers, and
combinations thereof.
31. A bladder according to claim 28, wherein said elastomeric
material includes a polyurethane elastomer.
32. A bladder according to claim 28, wherein said elastomeric
material includes a member of the group consisting of thermoplastic
polyester diol-based polyurethanes, thermoplastic polyether
diol-based polyurethanes, thermoplastic polycaprolactone diol-based
polyurethanes, thermoplastic polytetrahydrofuran diol-based
polyurethanes, thermoplastic polycarbonate diol-based
polyurethanes, and combinations thereof.
33 A bladder according to claim 32, wherein the elastomeric
material comprises a thermoplastic polyester diol-based
polyurethane.
34. A bladder according to claim 33, wherein the polyester diol of
said polyurethane is a reaction product of a mixture comprising at
least one dicarboxylic acid, dicarboxylate ester, or anhydride
selected from the group consisting of adipic acid, glutaric acid,
succinic acid, malonic acid, oxalic acid, anhydrides of these
acids, and mixtures thereof and at least one diol selected from the
group consisting of ethylene glycol, diethylene glycol, triethylene
glycol, tetraethylene glycol, propylene glycol, dipropylene glycol,
tripropylene glycol, tetrapropylene glycol, 1,3-propanediol,
1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol,
and mixtures thereof.
35. A bladder according to claim 28, wherein the fluid barrier
material comprises a member selected from the group consisting of
ethylene vinyl alcohol copolymers, polyvinylidene chloride,
acrylonitrile copolymers, polyethylene terephthalate, polyamides,
crystalline polymers, polyurethane engineering thermoplastics, and
combinations thereof.
36. A bladder according to claim 28, wherein the fluid barrier
material comprises an ethylene-vinyl alcohol copolymer.
37. A bladder according to claim 28, wherein said microlayer
polymeric composite includes at least about 50 microlayers.
38. A bladder according to claim 28, wherein said microlayer
polymeric composite includes from about 10 microlayers to about
1000 microlayers.
39. A bladder according to claim 28, wherein said microlayer
polymeric composite layer includes from about 50 microlayers to
about 500 microlayers.
40. A bladder according to claim 28, wherein the average thickness
of each fluid barrier material microlayer is independently from
about 0.01 micron to about 2.5 microns thick.
41. A bladder according to claim 28, wherein the average thickness
of the microlayer polymeric composite layer is from about 75
microns to about 0.5 centimeter.
42. A bladder according to claim 28, wherein said membrane further
comprises at least one layer including an elastomeric
polyurethane.
43. A bladder according to claim 42, wherein said membrane
comprises further layers including an elastomeric polyurethane
adjacent to either side of the microlayer polymeric composite
layer.
44. A bladder according to claim 28, wherein the bladder is
inflated with a gas.
45. A bladder according to claim 28, wherein said bladder is
inflated with a gas comprising nitrogen.
46. A bladder according to claim 44, wherein the inflating gas is
at a pressure of at least about 3 psi.
47. A bladder according to claim 28, wherein the bladder is
permanently sealed.
48. A bladder according to claim 29, wherein the laminar
nano-filler has an average thickness of from about 1 nm to about 10
nm and an aspect ratio from about 200 to about 1000.
49. A bladder according to claim 29, wherein the laminar
nano-filler is a montmorillonite clay.
50. A bladder according to claim 29, wherein the membrane comprises
from about 4 to about 10 weight percent of the laminar
nano-filler.
51. A shoe, comprising at least one bladder according to claim
28.
52. A shoe according to claim 51, wherein the bladder is
incorporated as a portion of said sole.
53. A shoe according to claim 51, wherein said bladder forms at
least a part of an outer surface of said shoe.
54. A ball, comprising a bladder according to claim 28.
Description
FIELD OF THE INVENTION
[0001] This invention concerns membranes including fillers suitable
for applications that require both barrier properties and
flexibility, particularly for use in preparing bladders for
inflated objects and cushioning devices. The present invention
further relates to articles that are inflated or have inflated
elements.
BACKGROUND OF THE INVENTION
[0002] Barrier membranes and inflatable bladders formed from such
membranes have been used in a variety of products for inflation or
cushioning, including vehicle tires, balls, accumulators used on
heavy machinery, and in footwear, especially athletic shoes. It is
often desirable to use polymeric materials that are thermoplastic
to form the membranes because thermoplastic materials may be
reclaimed and reformed into new articles, thus reducing waste
during manufacturing operations and promoting recycling after the
useful life of an article. While thermoplastic barrier films may be
flexed to a certain extent due to their thinness, thermoplastic
barrier films having only barrier material layers generally do not
have sufficient elasticity for many applications, particularly for
applications in which the inflated bladder is subjected to high
strains during use. In order to overcome this problem, the barrier
materials have been blended or layered with elastomeric materials.
Elastomeric materials, or elastomers, are able to substantially
recover their original shape and size after removal of a deforming
force, even when the part has undergone significant deformation.
Elastomeric properties are important in many inflatable bladder
applications, including inflatable bladders for footwear, game
balls, and hydraulic accumulators.
[0003] One key property of a membrane that forms an inflated
bladder is that of its gas transmission rate, which quantifies its
barrier effectiveness toward an inflating gas. An accepted method
of measuring the relative permeance, permeability, and gas
transmission rates of different film materials is set forth in the
procedure designated as ASTM D-1434-82-V. It is desirable for the
inflated bladder to retain a useful amount of internal pressure
throughout its lifetime without the need to periodically
re-introduce an inflating gas. Thus, the inflated bladder could be
permanently sealed and would not need to be re-inflated. One way to
achieve the lower gas transmission rate needed for such
"permanently inflated" bladders would be to increase the thickness
of the barrier material layer of the membrane used to form the
bladder. However, because of the increased stiffness that would
result from a thicker layer of the barrier material, this is not an
attractive option. It would be preferred from the standpoint of
maintaining membrane resiliency to reduce gas transmission rate by
a method that does not substantially increase the stiffness of the
membrane.
[0004] Styling is another concern in some applications for
bladders, such as bladders for shoes or for play balls. Styling
attracts the eye of the purchaser and makes the product appealing.
One recent styling innovation for footwear is that of a transparent
element with an external surface. It is often desirable for the
transparent element to be crystal clear for a sharp, clean,
"high-tech" look. Inflated bladders, incorporated into footwear for
cushioning, can also function as an element with transparency. The
bladder must, however, maintain the elastomeric and gas barrier
properties needed to fulfill its primary function of providing
cushioning to the foot. Thus it would be desirable to reduce gas
transmission rate through the membrane by a method that does not
make a membrane that is opaque or hazy in appearance.
[0005] Membranes with layers of flexible materials and layers of
fluid barrier materials are described, for example, in U.S. Pat.
No. 6,082,025, issued Jul. 4, 2000; U.S. Pat. No. 6,013,340, issued
Jan. 11, 2000; U.S. Pat. No. 5,952,065, issued Sep. 14, 1999; and
U.S. Pat. No. 5,713,141, issued Feb. 3, 1998, each of which is
incorporated herein by reference. While the membranes disclosed in
these references provide flexible, "permanently" inflated,
gas-filled bladders, further improvements in resiliency would be
desirable.
[0006] Mica and other large aspect ratio platelet fillers have been
employed to decrease the gas transmission rate of inflated
membranes. Tokoh et al., U.S. Pat. No. 5,221,566, teaches that a
container may be made with a first layer containing 50-95% EVOH and
5-50% of an inorganic filler and a second layer of a moisture
resistant thermoplastic resin such as polyolefin. The inorganic
filler has an average flake diameter of not more than 50 microns,
an aspect ratio of at least three, and a whiteness of at least 80
(measured with Kett spectrophotometer). The Tokoh et al. materials
do not have the resiliency required for cushioning devices and many
inflated articles.
[0007] Thus a need remains for flexible barrier material
compositions that are highly impervious to the inflating gas.
SUMMARY OF THE INVENTION
[0008] The invention provides a membrane having at least one layer,
with the membrane comprising at least one elastomeric material and
at least one polymeric fluid barrier material, in which a laminar
nano-filler having an average platelet thickness of up to about 10
nanometers and an average aspect ratio of at least about 200 is
present in at least one of the membrane layers. The membrane
preferably includes at least one elastomeric layer containing an
elastomeric material and at least one barrier layer containing a
polymeric fluid barrier material. The elastomeric material provides
resiliency and dimensional stability to the membrane of the
invention, while the polymeric fluid barrier material allows the
membrane to prevent the transfer of a fluid from one side of the
membrane to the other. The laminar nano-filler increases the
ability of the membrane to prevent transfer of a fluid from one
side of the membrane to the other without appreciably increasing
the opacity or haziness of the membrane and without appreciably
decreasing the resilience of the membrane.
[0009] Such durable, elastomeric barrier membranes may be used to
prepare inflated bladders. By "durable" it is meant that the
membrane has excellent resistance to fatigue failure, particularly
that a membrane of the invention can undergo repeated flexing
and/or deformation and recover without delamination along the layer
interfaces of the membranes, preferably over a broad range of
temperatures.
[0010] For purposes of this invention, the term "membrane" is used
to denote a free-standing film separating a fluid, particularly a
gas, preferably at higher than atmospheric pressure, from another
fluid (liquid or gas) or from the gas at a lower pressure. Films
laminated or painted onto another article for purposes other than
separating fluids are excluded from the present definition of a
membrane.
[0011] In a further aspect, the invention provides a membrane that
includes a layer of a microlayer polymeric composite that has
microlayers of at least one polymeric fluid barrier material and
microlayers of at least one elastomeric material, optionally layers
of one or more further materials, all of the different layers being
arranged in regular repeating order in the composite. The polymeric
fluid barrier material and/or the elastomeric material layers
further include a laminar nano-filler having an average platelet
thickness of up to about 10 nanometers and aspect ratio of at least
about 200.
[0012] The invention further provides enclosures formed from the
membranes of the invention, including but not limited to
permanently sealed, inflated bladders, as well as articles
containing such enclosures and bladders. The bladder may be
inflated with a gas such as nitrogen or air. The bladder may be
used to inflate or cushion, for example to inflate a sports ball or
to provide cushioning in footwear. The bladder may be combined with
other materials, such as cloth or foam outer layers, in forming a
cushioning device.
[0013] The barrier membrane preferably has a gas transmission rate
that is sufficiently low to allow a sealed bladder to remain
"permanently" inflated; that is, to retain a useful internal
pressure for the useful life of the article into which it is
incorporated. An accepted method for measuring the relative
permeance, permeability, and diffusion of different film materials
is ASTM D-1434-82-V. The gas transmission rate of a membrane is
expressed as the quantity of gas per area per time that diffuses
through the membrane. The gas transmission rate may be expressed in
units of (cc)(mil)/(m.sup.2)(24 hours), at standard temperature and
pressure. The gas transmission rate of the barrier membrane
provided by the invention is preferably less than about 1 (cc)(20
mils)/(m.sup.2)(24 hours).
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention will become more fully understood from
the detailed description and the accompanying drawing, wherein:
[0015] FIG. 1 shows a multilayer membrane of the invention;
[0016] FIG. 2 shows a multilayer membrane of the invention
including a microlayer polymeric composite layer; and
[0017] FIG. 3 shows an expanded view of a section of the multilayer
membrane of FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0019] The invention provides a membrane having at least one layer,
with the membrane comprising at least one elastomeric material and
at least one polymeric fluid barrier material, in which a laminar
nano-filler having an average platelet thickness of up to about 10
nanometers and an average aspect ratio of at least about 200 is
present in at least one of the membrane layers. The membrane may be
a single layer containing the elastomeric material, the fluid
barrier material, and the laminar nano-filler, but the membrane
preferably contains at least two layers. The membrane preferably
includes at least one layer of an elastomeric material and at least
one layer of a polymeric barrier material, in which the elastomeric
material layer and/or the polymeric barrier material layer
comprises the laminar nano-filler having an average platelet
thickness of up to about 10 nanometers and aspect ratio of at least
about 200. Preferably, the laminar nano-filler is combined with the
fluid barrier material, e.g. in islets of the fluid barrier
material in a single layer membrane or in the fluid barrier
material layer(s) of a multi-layer membrane.
[0020] The elastomeric material may be a thermoplastic elastomer or
rubber. Thermoplastic elastomers in general have a soft or flexible
segment or segments that provide elastomeric properties and hard or
rigid segments acting as thermally reversible physical crosslinks
that enable the polymer to be processed as a thermoplastic material
while retaining elastic behavior at room temperature. For example,
one kind of thermoplastic elastomer has one or more soft or rubbery
polymer segments, such as a polyester or polyether segments, and
hard or glassy polymer segments, such as polyurethane or polyurea
segments. A-B-A block copolymers such as styrene/butadiene/styrene
block copolymers have a similar structure, but the center of the
polymer chain is always the soft or elastic segment (e.g., rubbery
polybutadiene) while the ends are glassy (e.g., polystyrene).
Another suitable class of thermoplastic elastomers are dynamic
vulcanizates, in which a rubbery phase is vulcanized in a molten
thermoplastic phase under shear. Particular examples of elastomeric
materials suitable for forming elastomeric layers include, without
limitation, polyurethane elastomers, including elastomers based on
both aromatic and aliphatic isocyanates; flexible polyolefins,
including flexible polyethylene and polypropylene homopolymers and
copolymers; styrenic thermoplastic elastomers, including styrene
(ethylene-butylene) styrene block copolymer; polyamide elastomers;
polyamide-ether elastomers; ester-ether and ester-ester elastomers;
flexible ionomers; thermoplastic vulcanizates; flexible poly(vinyl
chloride) homopolymers and copolymers; flexible acrylic polymers;
and blends and alloys of these, such as poly(vinyl chloride) alloys
like poly(vinyl chloride)-polyurethane alloys. Rubbers that may be
extruded before crosslinking may also be used, with the
crosslinking being carried out after extrusion of the membrane.
Examples of rubbers include, without limitation nitrile rubber and
butyl rubber. The different elastomeric materials may be combined
as blends in a layer or may be included as separate layers of the
membrane.
[0021] Particularly suitable are thermoplastic
polyester-polyurethanes, polyether-polyurethanes, and
polycarbonate-polyurethanes, including, without limitation,
polyurethanes polymerized using as diol reactants
polytetrahydrofurans, polyesters, polylactone polyesters
(especially polycaprolactone diols) or polyesters prepared from
monocarboxylic acids containing an hydroxyl group, and polyethers
of ethylene oxide, propylene oxide, and copolymers including
ethylene oxide and propylene oxide. These polymeric diol-based
polyurethanes are prepared by reaction of the polymeric diol
(polyester diol, polyether diol, polycaprolactone diol,
polytetrahydrofuran diol, or polycarbonate diol), one or more
polyisocyanates, and, optionally, one or more chain extension
compounds. Chain extension compounds, as the term is used herein,
are compounds having two or more functional groups, preferably two
functional groups, reactive with isocyanate groups. Preferably the
polymeric diol-based polyurethane is substantially linear (i.e.,
substantially all of the reactants are di-functional).
[0022] The polyester diols used in forming the preferred
thermoplastic polyurethanes of the invention are in general
prepared by the condensation polymerization of polyacid compounds
(including anhydrides and esters thereof) and polyol compounds.
Preferably, the polyacid compounds and polyol compounds are
di-functional, i.e., diacid compounds (including anhydrides of
diacid compounds) and diols are used to prepare substantially
linear polyester diols, although minor amounts of mono-functional,
tri-functional, and higher functionality materials (perhaps up to 5
mole percent) can be included. Suitable dicarboxylic acids include,
without limitation, glutaric acid, succinic acid, malonic acid,
oxalic acid, phthalic acid, hexahydrophthalic acid, adipic acid,
maleic acid, anhydrides of these, and mixtures thereof. Suitable
polyols include, without limitation, wherein the extender is
selected from the group consisting of ethylene glycol, diethylene
glycol, triethylene glycol, tetraethylene glycol, propylene glycol,
dipropylene glycol, tripropylene glycol, tetrapropylene glycol,
cyclohexanedimethanol, 2-ethyl-1,6-hexanediol, 1,4-butanediol,
1,5-pentanediol, 1,3-propanediol, butylene glycol, neopentyl
glycol, and combinations thereof. Small amounts of triols or higher
functionality polyols, such as trimethylolpropane or
pentaerythritol, are sometimes included. In a preferred embodiment,
the carboxylic acid includes adipic acid and the diol includes
1,4-butanediol. Typical catalysts for the esterification
polymerization are protonic acids, Lewis acids, titanium alkoxides,
and dialkyl tin oxides.
[0023] Polymerization of an hydroxy carboxylic acid compound will
also produce a polyester. Such a reaction may be carried out with
or without an initiating polyol.
[0024] Polyether or polylactone diol reactants may also be used in
preparing preferred thermoplastic polyurethanes. The polyether or
polylactone diols may be prepared by reacting a diol initiator,
e.g., a diol such as ethylene or propylene glycol, with a lactone
or alkylene oxide or other oxirane chain-extension reagent.
Suitable chain-extension reagents for preparing polylactones are
lactones that can be ring opened by an active hydrogen. Examples of
suitable lactones include, without limitation,
.epsilon.-caprolactone, .gamma.-caprolactone, .beta.-butyrolactone,
.beta.-propriolactone, .gamma.-butyrolactone,
.alpha.-methyl-.gamma.-butyrolactone,
.beta.-methyl-.gamma.-butyrolactone- , .gamma.-valerolactone,
.delta.-valerolactone, .gamma.-decanolactone, .beta.-decanolactone,
.gamma.-nonanoic lactone, .gamma.-octanoic lactone, and
combinations of these. In one preferred embodiment, the lactone is
.epsilon.-caprolactone. Lactones useful in the practice of the
invention can also be characterized by the formula: 1
[0025] wherein n is a positive integer of 1 to 7 and R is one or
more H atoms, or substituted or unsubstituted alkyl groups of 1-7
carbon atoms. Useful catalysts include, those mentioned above for
polyester synthesis. Alternatively, the reaction can be initiated
by forming a sodium salt of the hydroxyl group on the molecules
that will react with the lactone ring.
[0026] In another embodiment of the invention, a diol initiator is
reacted with an oxirane-containing compound to produce a polyether
diol to be used in the polyurethane polymerization. The
oxirane-containing compound is preferably an alkylene oxide or
cyclic ether, especially preferably a compound selected from
ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran,
and combinations of these. Alkylene oxide polymer segments include,
without limitation, the polymerization products of ethylene oxide,
propylene oxide, 1,2-cyclohexene oxide, 1-butene oxide, 2-butene
oxide, 1-hexene oxide, tert-butylethylene oxide, phenyl glycidyl
ether, 1-decene oxide, isobutylene oxide, cyclopentene oxide,
1-pentene oxide, and combinations of these. Ethylene oxide,
propylene oxide, and combinations of these are particularly
preferred. The alkylene oxide polymerization is typically
base-catalyzed. The polymerization may be carried out, for example,
by charging the hydroxyl-functional initiator and a catalytic
amount of caustic, such as potassium hydroxide, sodium methoxide,
or potassium tert-butoxide, and adding the alkylene oxide at a
sufficient rate to keep the monomer available for reaction. Two or
more different alkylene oxide monomers may be randomly
copolymerized by coincidental addition and polymerized in blocks by
sequential addition. Homopolymers or copolymers of ethylene oxide
or propylene oxide are preferred.
[0027] Tetrahydrofuran polymerizes under known conditions to form
repeating units
--[CH.sub.2CH.sub.2CH.sub.2CH.sub.2O]--
[0028] Tetrahydrofuran is polymerized by a cationic ring-opening
reaction using such counterions as SbF.sub.6.sup.-,
AsF.sub.6.sup.-, PF.sub.6.sup.-, SbCl.sub.6.sup.-, BF.sub.4.sup.-,
CF.sub.3SO.sub.3.sup.-, FSO.sub.3.sup.-, and ClO.sub.4.sup.-.
Initiation is by formation of a tertiary oxonium ion. The
polytetrahydrofuran segment can be prepared as a "living polymer"
and terminated by reaction with the hydroxyl group of a diol such
as any of those mentioned above.
[0029] Aliphatic polycarbonate diols are prepared by the reaction
of diols with dialkyl carbonates (such as diethyl carbonate),
diphenyl carbonate, or dioxolanones (such as cyclic carbonates
having five- and six-member rings) in the presence of catalysts
like alkali metal, tin catalysts, or titanium compounds. Useful
diols include, without limitation, any of those already mentioned.
Aromatic polycarbonates are usually prepared from reaction of
bisphenols, e.g., bisphenol A, with phosgene or diphenyl
carbonate.
[0030] The polymeric diol, such as the polymeric polyester diols
described above, that are used in the polyurethane synthesis
preferably have a number average molecular weight (determined for
example by the ASTM D-4274 method) of from about 300 to about
4,000; more preferably from about 400 to about 3,000; and still
more preferably from about 500 to about 2,000. The polymeric diol
generally forms a "soft segment" of the elastomeric
polyurethane.
[0031] The synthesis of the elastomeric polyurethane may be carried
out by reacting one or more of the above polymeric diols, one or
more compounds having at least two isocyanate groups, and,
optionally, one or more chain extension agents. The elastomeric
polyurethanes are preferably linear and thus the polyisocyanate
component preferably is substantially di-functional. Useful
diisocyanate compounds used to prepare the thermoplastic
polyurethanes of the invention, include, without limitation,
isophorone diisocyanate (IPDI), methylene bis-4-cyclohexyl
isocyanate, cyclohexylene diisocyanate (CHDI), m-tetramethyl
xylylene diisocyanate (m-TMXDI), p-tetramethyl xylylene
diisocyanate (p-TMXDI), ethylene diisocyanate,
1,2-diisocyanatopropane, 1,3-diisocyanatopropane,
1,6-diisocyanatohexane (hexamethylene diisocyanate or HDI),
1,4-butylene diisocyanate, lysine diisocyanate, 1,4-methylene
bis-(cyclohexyl isocyanate), the various isomers of toluene
diisocyanate, meta-xylylenediioscyanate and
para-xylylenediisocyanate, 4-chloro-1,3-phenylene diisocyanate,
1,5-tetrahydro-naphthalene diisocyanate, 4,4'-dibenzyl
diisocyanate, and 1,2,4-benzene triisocyanate, xylylene
diisocyanate (XDI), and combinations thereof. Particularly useful
is diphenylmethane diisocyanate (MDI).
[0032] Useful active hydrogen-containing chain extension agents
generally contain at least two active hydrogen groups, for example,
diols, dithiols, diamines, or compounds having a mixture of
hydroxyl, thiol, and amine groups, such as alkanolamines,
aminoalkyl mercaptans, and hydroxyalkyl mercaptans, among others.
The molecular weight of the chain extenders preferably range from
about 60 to about 400. Alcohols and amines are preferred. Typical
examples of useful diols that are used as polyurethane chain
extenders include, without limitation, 1,6-hexanediol,
cyclohexanedimethanol (sold as CHDM by Eastman Chemical Co.),
2-ethyl-1,6-hexanediol, Esterdiol 204 (sold by Eastman Chemical
Co.), 1,4-butanediol, ethylene glycol and lower oligomers of
ethylene glycol including diethylene glycol, triethylene glycol and
tetraethylene glycol; propylene glycol and lower oligomers of
propylene glycol including dipropylene glycol, tripropylene glycol
and tetrapropylene glycol; 1,3-propanediol, 1,4-butanediol,
neopentyl glycol, dihydroxyalkylated aromatic compounds such as the
bis (2-hydroxyethyl) ethers of hydroquinone and resorcinol;
p-xylene-.alpha.,.alpha.'-diol; the bis (2-hydroxyethyl) ether of
p-xylene-.alpha.,.alpha.'-diol; m-xylene-.alpha.,.alpha.'-diol and
the bis (2-hydroxyethyl) ether and mixtures thereof. Suitable
diamine extenders include, without limitation, p-phenylenediamine,
m-phenylenediamine, benzidine, 4,4'-methylenedianiline,
4,4'-methylenibis (2-chloroaniline), ethylene diamine, and
combinations of these. Other typical chain extenders are amino
alcohols such as ethanolamine, propanolamine, butanolamine, and
combinations of these. Preferred extenders include ethylene glycol,
diethylene glycol, triethylene glycol, tetraethylene glycol,
propylene glycol, dipropylene glycol, tripropylene glycol,
tetrapropylene glycol, 1,3-propylene glycol, 1,4-butanediol,
1,6-hexanediol, and combinations of these.
[0033] In addition to the above-described di-functional extenders,
a small amount of tri-functional extenders such as
trimethylolpropane, 1,2,6-hexanetriol and glycerol, and/or
mono-functional active hydrogen compounds such as butanol or
dimethyl amine, may also be present. The amount of tri-functional
extenders and/or mono-functional compounds employed would
preferably be 5.0 equivalent percent or less based on the total
weight of the reaction product and active hydrogen containing
groups employed.
[0034] The reaction of the polyisocyanate(s), polymeric diol(s),
and, optionally, chain extension agent(s) is typically conducted by
heating the components, for example by melt reaction in a twin
screw extruder. Typical catalysts for this reaction include
organotin catalysts such as stannous octoate or dibutyl tin
dilaurate. Generally, the ratio of polymeric diol, such as
polyester diol, to extender can be varied within a relatively wide
range depending largely on the desired hardness of the final
polyurethane elastomer. For example, the equivalent proportion of
polyester diol to extender may be within the range of 1:0 to 1:12
and, more preferably, from 1:1 to 1:8. Preferably, the
diisocyanate(s) employed are proportioned such that the overall
ratio of equivalents of isocyanate to equivalents of active
hydrogen containing materials is within the range of 0.95:1 to
1.10:1, and more preferably, 0.98:1 to 1.04:1. The polymeric diol
segments typically are from about 35% to about 65% by weight of the
polyurethane polymer, and preferably from about 35% to about 50% by
weight of the polyurethane polymer.
[0035] It may be desirable in certain applications to include
blends of polyurethanes in the elastomeric layer or layers of the
membrane, such as when susceptibility to hydrolysis is of
particular concern. For example, a polyurethane including soft
segments of polyether diol or polyester diol wherein the repeating
units of the reaction product has more than eight carbon atoms can
be blended with a polyurethane including polyester diol having
repeating units of eight or fewer carbon atoms or products of
branched diols. Preferably, the polyurethanes other than those
including polyester diol repeating units having eight or fewer
carbon atoms or with oxygen atoms connected to tertiary carbons
will be present in the blends in an amount up to about 30 wt. %,
(i.e. 70.0 wt. % polyethylene glycol adipate based polyurethane
30.0% isophthalate polyester diol based polyurethane). Specific
examples of the polyester diols wherein the reaction product has
more than eight carbon atoms include poly(ethylene glycol
isophthalate), poly(1,4-butanediol isophthalate) and
poly(1,6-hexanediol isophthalate).
[0036] Instead of blends of various thermoplastic polyurethanes, a
single polyurethane having various soft segments may be used. In
one embodiment, the soft segments may include soft segments of
polyester or polyether polyol having repeating units with a total
of eight or fewer carbon atoms combined with soft segments of
polyester or polyether polyol having repeating units with a total
of more than eight carbon atoms. It is preferred that the total
amount of soft segment having repeating units with a total carbon
atom count of more than eight be present in an amount of up to
about 30 wt. % of the total weight of soft segments included in the
polyurethane. One preferred embodiment includes at least about 70
wt. % of the soft segment with repeating units having eight or
fewer carbon atoms.
[0037] Specific examples of suitable commercial elastomeric
materials include polyamide-ether elastomers marketed under the
trademark PEBAX.RTM. by Elf Atochem, ester-ether elastomers
marketed under the trademark HYTREL.RTM. by DuPont, ester-ester and
ester-ether elastomers marketed under the trademark ARNITEL.RTM. by
DSM Engineering, thermoplastic vulcanizates marketed under the
trademark SANTOPRENE.RTM. by Advanced Elastomeric Systems,
elastomeric polyamides marketed under the trademark GRILAMID.RTM.
by EMS-Chemie, Sumter, S.C., and elastomeric polyurethanes marketed
under the trademark PELLETHANE.RTM. by Dow Chemical Company,
Midland, Mich., ELASTOLLAN.RTM. polyurethanes marketed by BASF
Corporation, Mt. Olive, N.J., TEXIN.RTM. and DESMOPAN.RTM.
polyurethanes marketed by Bayer, MORTHANE.RTM. polyurethanes
marketed by Huntsman, and ESTANE.RTM. polyurethanes marketed by
Noveon.
[0038] The membrane also includes a polymeric barrier material. The
polymeric barrier material may be blended with the elastomer
material, for example to form a single-layer membrane or as one
layer of a multi-layer membrane. In this case, the polymeric
barrier layer material is preferably present in a minor amount and
the elastomer material in a major amount, so that the elastomer
material is a continuous matrix.
[0039] The polymeric barrier material, however, is preferably in at
least one layer separate from a layer containing the elastomeric
material. In general, the polymeric barrier material layers will be
thinner than the elastomeric material layers so that the membrane
will be flexible and durable.
[0040] Suitable polymeric fluid barrier materials include, without
limitation, ethylene-vinyl alcohol copolymers; poly(vinyl
chloride); polyvinylidene polymers and copolymers, including
polyvinylidene chloride; polyamides including amorphous polyamides;
acrylonitrile polymers, including acrylonitrile-methyl acrylate
copolymers; polyurethane engineering plastics; poly(methyl pentene)
resins; ethylene-carbon monoxide copolymers; liquid crystal
polymers; polyesters such as polyethylene terephthalate;
polyimides, including polyether imides and polyacrylic imides; and
other such polymeric materials known to have relatively low gas
transmission rates. Blends and grafts of these materials, such as
combinations of polyimides and crystalline polymers such as liquid
crystal polymers, polyamides and polyethylene terephthalate, and
combinations of polyamides with styrenics, are also suitable. The
membrane may have a layer or layers with combinations of different
fluid barrier materials, or the different fluid barrier materials
may also be included as separate layers of the membrane.
[0041] Ethylene-vinyl alcohol copolymers are preferred,
particularly those copolymers in which the ethylene comonomer unit
content is from about 25 mole percent to about 50 mole percent, and
more particularly from about 25 mole percent to about 40 mole
percent. Ethylene-vinyl alcohol copolymers are prepared by
hydrolyzing ethylene-vinyl acetate copolymers, as is
well-known.
[0042] Examples of suitable specific commercial products include
acrylonitrile copolymers such as BAREX.RTM., available from BP
Chemicals, Inc.; polyurethane engineering plastics such as
ISOPLAST.RTM., available from Dow Chemical Corp., Midland, Mich.;
ethylene vinyl alcohol copolymers marketed under the trademarks
EVAL.RTM. by EVAL Company of America (EVALCA), Lisle, Ill.,
SOARNOL.RTM. by Nippon Goshei Co., Ltd. (U.S.A.) of New York, N.Y.,
CLARENE.RTM. by Solvay, and SELAR.RTM. OH by DuPont;
polyvinylidiene chloride available from Dow Chemical under the
tradename SARAN.RTM., and from Solvay under the tradename
IXAN.RTM.; liquid crystal polymers such as VECTRA.RTM. from Hoechst
Celanese and XYDAR.RTM. from Amoco Chemicals; MXD6 nylon, available
from Mitsubishi Gas Chemical Co., Ltd, Solvay, and Toyobo and
amorphous nylons such as NOVAMID.RTM. X21 from Mitsubishi,
SELAR.RTM. PA from DuPont, and GELON A-100 from General Electric
Company; KAMAX.RTM. polyacrylic-imide copolymer available from Rohm
& Haas; polyetherimides sold under the tradename ULTEM.RTM. by
General Electric; VINEX poly(vinyl alcohol) available from Air
Products; and polymethylpentene resins available from Phillips 66
Company under the tradename CRYSTALOR and from Mitsui Petrochemical
Industries under the tradename TPX.RTM.. Highly preferred
commercially available copolymers of ethylene and vinyl alcohol,
such as those available from EVALCA, will typically have an average
ethylene content of between about 25 mol % to about 48 mol %.
[0043] At least one layer of the membrane, or at least one
polymeric material of a single-layer membrane, contains a laminar
nano-filler having an average platelet thickness of up to about 10
nanometers and an aspect ratio of at least about 200. In the
preferred membrane containing an elastomeric layer and a barrier
material layer, the elastomeric layer, the barrier material layer,
or both include a laminar nano-filler having an average platelet
thickness of up to about 10 nanometers and an aspect ratio of at
least about 200. Preferred laminar nano-fillers have a thickness of
from about 1 nm to about 10 nm and height and width each
independently from about 0.1 micron to about 1.5 microns. The
aspect ratio is preferably from about 200 to about 1000 and more
preferably from about 200 to about 500. One preferred laminar
nano-filler is a montmorillonite clay.
[0044] In another preferred membrane, a single layer includes a
thermoplastic material, such as nitrile rubber or thermoplastic
polyurethane elastomer, in a major amount, a gas barrier polymeric
material, such as a polyamide, in a minor amount, and the laminar
nano-filler in an amount of up to about 10% by weight of the total
composition. In one preferred embodiment, the elastomer is a
dynamic vulcanizate rubber in a thermoplastic material, such as in
another elastomer or in the polymeric barrier material. Covalent
bonding between the rubber and the polymeric barrier material or
the other thermoplastic elastomer may be used to promote good
interfacial adhesion.
[0045] The laminar nano-fillers may be used with hydrophilic
polymers without modification or preferably may be modified to
increase their affinity for the polymer (e.g., to aid in
exfoliating and dispersing the nano-fillers) or to help prevent
re-agglomeration. In one preferred modification octadecyl trimethyl
ammonium chloride or bromide is mixed with a clay laminar
nano-filler to replace sodium ions initially on the surface of the
clay. In general, a laminar nano-filler may be surface-modified by
wetting the nano-filler, adding the treating material, and then
drying the nano-filler.
[0046] The laminar nano-fillers have advantageous properties when
used in the membranes. First, the laminar nano-fillers improve gas
barrier properties of the membrane at a loading (e.g., about 4 to
about 10 weight percent) that does not substantially affect the
clarity of the membrane, while use of traditional fillers such as
talc or mica will cause an increase in haze or opacity at levels
high enough to affect the gas transmission rate of the membrane. In
addition, the lower loading levels and smaller flakes of the
laminar nano-fillers improve modulus and toughness of the membranes
compared to membranes made with traditional fillers. Incorporating
the laminar nano-filler into the polymeric barrier material appears
in at least some cases to promote crystallization of the polymeric
barrier material. Incorporating the laminar nano-filler into the
elastomeric material can provide gas barrier properties to a layer
that essentially does not contribute to the gas barrier property of
the membrane without the laminar nano-filler.
[0047] The laminar nano-filler may be incorporated into the layer
material, for example, by well-known compounding methods.
Alternatively, the laminar nano-filler may be incorporated by
combining the laminar nano-filler with a monomer or other reactant
used to form the polymer before polymerization. As mentioned, the
laminar nano-filler may be treated with a compatabilizing agent to
aid in their dispersion in the layer material.
[0048] Additional materials that may be in one or more of the
layers include modifiers and other additives, preferably in minor
amount. Examples of such modifiers and additives include, without
limitation, plasticizers, light stabilizers, hydrolytic
stabilizers, thermal stabilizers, brighteners, antioxidants,
rheology modifiers, organic anti-block compounds, fungicides,
antimicrobials (including bacteriocides and the like), mold release
agents, waxes such as Montan esters or bis-amide waxes, processing
aids, and combinations of these. Tinted transparent membranes may
be formed with transparent colorants, such as dyes or transparent
pigments. Special effects in the transparent membrane, e.g.
iridescence, may be achieved by using special effect pigments.
[0049] Examples of hydrolytic stabilizers include two commercially
available carbodiimide based hydrolytic stabilizers known as
STABAXOL P and STABAXOL P-100, which are available from Rhein
Chemie of Trenton, N.J. Other carbodiimide- or
polycarbodiimide-based hydrolytic stabilizers or stabilizers based
on epoxidized soy bean oil may be useful. The total amount of
hydrolytic stabilizer employed will generally be less than 5.0 wt.
% of the total weight of the layer.
[0050] Plasticizers can be included for purposes of increasing the
flexibility and durability of the final product as well as
facilitating the processing of the material from a resinous form to
a membrane or sheet. By way of example, and without intending to be
limiting, plasticizers such as those based on butyl benzyl
phthalate (which is commercially available, e.g. as Santicizer 160
from Monsanto) have proven to be particularly useful. Regardless of
the plasticizer or mixture of plasticizers employed, the total
amount of plasticizer, if any, should generally be less than 20.0
wt. % of the total layer, preferably less than about 5% by weight
of the total layer.
[0051] The membrane of the invention may include a layer of a
microlayer polymeric composite. A microlayer polymeric composite
layer has alternating microlayers of at least one fluid barrier
material, as described above, and at least one elastomeric
material, as described above. Also contemplated are microlayer
polymeric composite layers that include microlayers of different
fluid barrier materials and/or microlayers of different elastomeric
materials, the different layers being arranged in regular repeating
order. Other layers in addition to elastomeric layers and fluid
barrier layers that alternate along with them in a regular,
repeating order may optionally be included. The microlayer
polymeric composite layer should have at least about 10
microlayers. Preferably, the microlayer polymeric composite layer
has at least about 20 microlayers, more preferably at least about
30 microlayers, and still more preferably at least about 50
microlayers. The microlayer polymeric composite layer can have
thousands of microlayers, and the skilled artisan will appreciate
that the number of microlayers will depend upon such factors as the
particular materials chosen, thicknesses of each layer, the
thickness of the microlayer polymeric composite layer, the
processing conditions for preparing the multilayers, and the final
application of the composite. The microlayer polymeric composite
layer preferably has from about 10 to about 1000 microlayers, more
preferably from about 30 to about 1000 and even more preferably it
has from about 50 to about 500 microlayers.
[0052] In the microlayer polymeric composite layer, the average
thickness of each individual microlayer of the fluid barrier
material may be as low as a few nanometers to as high as several
mils (about 100 microns) thick. Preferably, the individual
microlayers have an average thickness of up to about 0.1 mil (about
2.5 microns). Average thicknesses of about 0.0004 mil (about 0.01
micron) to about 0.1 mil (about 2.5 microns) are particularly
preferable. For example, the individual barrier material
microlayers can be, on average, about 0.05 mils (about 1.2
microns). Having thinner microlayers of the fluid barrier material
improves the ductility of the membrane. The microlayer polymeric
composite layer is preferably on average from about 0.25 mil (about
6.35 microns) to about 102 mils (2600 microns) thick, more
preferably on average from about 3 mils (about 75 microns) to about
200 mils (about 0.5 cm) thick, even more preferably from about 3
mils (about 75 Microns) to about 40 mils (about 0.1 cm).
[0053] The alternating layers of the structural polymer and the
fluid barrier polymer have their major surfaces aligned
substantially parallel to the major surfaces of the composite.
There are a sufficient number of layers of the fluid barrier
polymer so that the microlayer composite has the desired fluid
transmission rate.
[0054] The microlayer polymeric composite layer may be formed by
using a two-layer, three-layer, or five-layer feed block that
directs the layered stream into a static mixer or layer multiplier.
The static mixer has multiple mixing elements, preferably at least
about five elements, that increases the number of layers
geometrically. A preferred method for forming the microlayer
polymeric composite layer is described in detail in Schrenk, et
al., U.S. Pat. No. 5,094,793, issued Mar. 10, 1992, which is
incorporated herein in its entirety by reference. Protective
boundary layers may be incorporated according to the method of
Ramanathan et al., U.S. Pat. No. 5,269,995, issued Dec. 14, 1993,
which is incorporated herein in its entirety by reference. The
protective layers protect the elastomer and fluid barrier layers
from instability and breakup during the layer formation and
multiplication. The protective layers are provided by a steam of
molten thermoplastic material which is supplied to the exterior
surfaces of the composite stream to form a protective boundary
layer at the wall of the coextrusion apparatus. The protective
layer may add special optical or physical attributes to the
microlayer polymeric composite material, such as special
coloration, including metallic coloration obtained by including
metallic or other flake pigments in the protective boundary
layer.
[0055] Although it is not necessary for all of the microlayers to
be complete layers, that is to extend in the plane of that
microlayer to all edges of the membrane, it is desirable for most
microlayers to be substantially complete layers, that is to extend
to the edges of the membrane.
[0056] The membrane having the elastomeric material, fluid barrier
material, and nano-filler may be formed into a sealed, inflated
bladder. The membrane may be of any convenient length and width for
forming the desired inflated bladder.
[0057] The membrane of the invention can include the microlayer
polymeric material as one or more layers. Any number of microlayer
layers, preferably from one to about 5, more preferably one to
three can be used as layers of the membrane. The membrane
preferably includes at least one further layer that is a layer of
an elastomer, preferably a thermoplastic polyurethane. One
preferred membrane of the invention includes at least one layer A
of an elastomeric polyurethane and at least one layer B of the
microlayer polymeric composite. More preferably the membrane has
layers A-B-A or layers A-B-A-B-A. In another embodiment, the
membrane also contains layers C containing a blend of materials
that include at least a thermoplastic polyurethane elastomer and a
barrier material, such as ethylene-vinyl alcohol copolymer. The
membrane layers may be arranged as C-A-B-A-C or A-C-A-B-A-C-A.
[0058] It is especially beneficial to include the laminar
nano-filler of the invention in one or more of the materials used
to make the microlayers of the microlayer polymeric composite. The
process of forming the microlayers tends to align the nano-filler
generally parallel to the faces of the microlayer polymeric
composite. For a given amount of nano-filler in a membrane, the gas
transmission rate is less in the case where the nano-filler is more
parallel to the face of the membrane. The method of forming a
microlayer polymeric composite membrane or layer of a membrane
promote the desired generally parallel arrangement of the
nano-filler relative to the face of the membrane.
[0059] One further feature of some of the membranes of the present
invention is an enhanced bonding that can occur between layers of
elastomeric material and fluid barrier material of the membrane or
of a microlayer polymeric composite layer of the membrane. This
enhanced bonding is generally accomplished by using materials for
adjacent layers that have available functional groups that can
participate in hydrogen bonding such as hydrogen atoms in hydroxyl
groups or hydrogen atoms attached to nitrogen atoms in polyurethane
groups that can hydrogen bond with various receptor groups such as
oxygen atoms in hydroxyl groups, carbonyl oxygens in polyurethane
groups and ester groups, and chlorine atoms in PVDC, for example.
For example, hydrogen bonding is believed to occur when the
elastomeric material comprises a polyester diol based polyurethane
and the fluid barrier material includes a polymer selected from the
group consisting of copolymers of ethylene and vinyl alcohol,
polyvinylidene chloride, copolymers of acrylonitrile and methyl
acrylate, polyethylene terephthalate, aliphatic and aromatic
polyamides, crystalline polymers and polyurethane engineering
thermoplastics. In addition to the hydrogen bonding, there may be a
certain amount of covalent bonding between the layers. Still other
factors such as orientation forces and induction forces, otherwise
known as van der Waals forces, which result from London forces
existing between any two molecules and dipole-dipole forces which
are present between polar molecules are believed to contribute to
the bond strength between contiguous layers. Besides the physical
forces and chemical bonds, the interfacial structure also
contributes significantly to the bond strength.
[0060] Referring now to the figures, FIG. 1 shows membrane 10
having layers 12, 14, 18, and 20 of elastomeric material and layer
16 of polymeric fluid barrier material. Layers 12 and 20 are
thicker, e.g. 12-14 mils, having polymeric material composed
predominantly of polymeric elastomer, e.g. thermoplastic
polyurethane elastomer, but which may include small amounts of
other polymeric materials, such as the polymeric fluid barrier
material of layer 16. Layers 14 and 18 are thinner, e.g. 1-3 mils,
and functions as tie layers between outer layers 12 and 20 and the
inner, barrier layer 16. The polymeric material of layers 14 and
18, for instance, consists essentially of thermoplastic
polyurethane elastomer. The thermoplastic polyurethane elastomer
can hydrogen bond with the material of polymeric fluid barrier
material of layer 16, which is preferably an ethylene-vinyl alcohol
copolymer. Hydrogen bonding takes place between the urethane groups
of the polyurethane and the alcohol groups of the ethylene-vinyl
alcohol copolymer. At least one of the layers contains the laminar
nano-filler, preferably layer 16.
[0061] FIG. 2 illustrates a membrane 110 having as a core, barrier
layer a microlayer polymeric composite layer 124. Microlayer
polymeric composite layer 124 may be 5-7 mils thick and has
alternating layers of a polymeric barrier layer material and an
elastomer material. Layers 112 and 120 may be, e.g. 25-27 mils,
with polymeric material composed predominantly of polymeric
elastomer, e.g. thermoplastic polyurethane elastomer, but which may
include small amounts of other polymeric materials, such as a
polymeric fluid barrier material. Layers 114 and 118 are thinner,
e.g. 1-3 mils, with polymeric material consisting essentially of
thermoplastic polyurethane elastomer. The membrane 110 has outer
skin layer 122 and 126, 1 to 2 mils thick, with polymeric material
that also consists essentially of thermoplastic polyurethane
elastomer. At least one of the layers contains the laminar
nano-filler. Preferably, the laminar nano-filler is included in one
or more of layers 112, 124, and 120.
[0062] FIG. 3 shows an expanded view of a section of the multilayer
membrane of FIG. 2. A portion of layer 114 borders a portion of
microlayer polymeric composite layer 124. Microlayer polymeric
composite layer is shown with alternating thinner layers containing
a polymeric fluid barrier material, preferably a copolymer of
ethylene and vinyl alcohol, such as layer 140, and thicker layers
of elastomer material, preferably thermoplastic polyurethane
elastomer, such as layer 142. The laminar nano-filler may be
included in both kinds of layers, but preferably the laminar
nano-filler is included in at least the polymeric fluid barrier
material layers.
[0063] The invention further provides bladders, especially inflated
bladders, prepared from the membranes of the invention and articles
including such bladders. The membranes of the invention offer
flexibility and resistance to undesirable transmission of fluids
such as an inflationary gas. These membranes can be inflated with a
gas such as nitrogen and preferably provide a gas transmission rate
value of about 10 cubic centimeters per square meter per atmosphere
per day (cc/m.sup.2.multidot.atm.multidot.day) or less. The
durable, elastomeric membranes of the inflated bladders can be used
in many applications, particularly for inflation or cushioning
applications. By "durable" it is meant that the membrane has
excellent resistance to fatigue failure, which means that the
membrane can undergo repeated flexing and/or deformation and
recover without cracking or other failures, preferably over a broad
range of environmental conditions such as temperature and relative
humidity. For purposes of this invention, the term "membrane" is
used to denote a free-standing film separating one fluid (whether
gas or liquid) from another fluid. Films laminated or painted onto
another article for purposes other than separating fluids are
excluded from the present definition of a membrane.
[0064] While the membrane may be thin or thick, the membrane should
be thick enough to provide adequate wall strength and yet thin
enough to provide adequate flexibility. Membrane thicknesses are
preferably from about 20 mils to about 70 mils, more preferably
from about 20 mils to about 40 mils thick. In a preferred
five-layer structure, it is desirable for a central fluid barrier
material layer and for elastomeric material layers adjacent on
either side of the fluid barrier layer to individually be at least
about 0.4 mil thick, preferably at least about 0.5 mil thick, more
preferably at least about 0.6 mil thick, and still more preferably
at least about 1 mil thick, and up to about 3 mils thick,
preferably up to about 2.5 mils thick, more preferably up to about
2 mils thick, and yet more preferably up to about 1.6 mils thick.
The outermost layers are preferably blend layers of predominantly
elastomeric material with a minor amount of fluid barrier material
that are preferably at least about 7 mils thick, more preferably at
least about 8 mils thick, and still more preferably at least about
9 mils thick; and preferably up to about 20 mils thick, more
preferably up to about 15 mils thick.
[0065] In particular, the present invention provides an inflatable
bladder for applications such as footwear, hydraulic accumulators,
or for inflating objects such as sports balls, the bladder having a
membrane that includes at least one elastomeric material and at
least one polymeric fluid barrier material, preferably in separate
layers, in which a laminar nano-filler having an average platelet
thickness of up to about 10 nanometers and an average aspect ratio
of at least about 200 is present in at least one of the membrane
layers. The membrane of the invention has elastomeric mechanical
properties that allows it to repeatedly and reliably absorb high
forces during use without degradation or fatigue failure. It is
particularly important in these kinds of applications for the
membrane to have excellent stability in cyclic loading. The barrier
membrane has a low gas transmission rate that allows it to remain
inflated, and thus to provide cushioning or inflation, for
substantially the expected life of the article without the need to
periodically re-inflate and re-pressurize the bladder; thus it is
permanently sealed.
[0066] A bladder may be produced by RF (radio frequency) welding
two sheets of the microlayer material or microlayer-containing
membrane, particularly when one layer is a polar material such as a
polyurethane. Nonpolar materials such as polyolefins can be welded
using ultrasound or heat sealing techniques. Other well-known
welding techniques may also be employed.
[0067] The membrane may be formed into a bladder by a blow molding
process. In general, the bladders may be formed by a first step of
coextruding the layers, or plies, in a membrane of flat or tubular
shape, then blow molding the flat membrane or tube into a desired
final shape. For example, melt materials of the layers may be
co-extruded as a parison. A mold having the desired overall shape
and configuration of the bladder is in position to receive the
parison and is closed around the parison. The parison is cut at the
edge of the mold. The mold is moved back to a position away from
the extrusion die. The open portion of the parison above the mold
is then fitted with a blow tube through which pressurized air or
other gas, such as nitrogen, is provided. The pressurized air
forces the parison against the inner surfaces of the mold. The
material is hardened in the mold to form a bladder having the
preferred shape and configuration. The blown, shaped membrane is
allowed to cool and harden in the mold, which may be at about
30.degree. F. to 80.degree. F., before it is removed from the mold.
Meanwhile, a new mold is moved into place to accept the next
section from the parison that has been cut away from the first
mold.
[0068] Besides blow molding using continuous extrusion, the forming
step may use intermittent extrusion by reciprocating screw systems,
ram accumulator-type systems, or accumulator head systems;
co-injection stretch blow molding; extruded or co-extruded sheet,
blown film tubing, or profiles. Other forming methods include
injection molding, thermoforming, vacuum molding, transfer molding,
pressure forming, heat-sealing, casting, melt casting, RF welding
and so on. For example, a flat film may be cut into a desired
shape. Two portions of the flat film may be sealed at the edges to
form a bladder. The film may alternatively be rolled into a tube
and RF welded at the edges to form a bladder.
[0069] The bladder may be inflated with a fluid, preferably a gas,
and permanently sealed. The durable, elastomeric membranes of the
inflated bladders may be incorporated into the sole of an article
of footwear, for example. By "durable" it is meant that the
membrane has excellent resistance to fatigue failure, which means
that the membrane can undergo repeated flexing and/or deformation
and recover without delamination along the layer interfaces of
composite barrier membranes, preferably over a broad range of
temperatures. Footwear, and in particular shoes, usually include
two major components: a shoe upper and a sole. The general purpose
of the shoe upper is to snugly and comfortably enclose the foot.
Ideally, the shoe upper should be made from an attractive, highly
durable, comfortable materials or combination of materials. The
shoe upper can be formed form a variety of conventional materials
including, but not limited to, leathers, vinyls, nylons, and other
generally woven materials. The sole, constructed from a durable
material, is designed to provide traction and to protect the foot
during use. The sole also typically serves the important function
of providing enhanced cushioning and shock absorption during
athletic activities to protect the feet, ankles, and legs of the
wearer from the considerable forces generated. The force of impact
generated during running activities can amount to two or three
times the body weight of the wearer, while other athletic
activities such as playing basketball may generate forces of
between six and ten times the body weight of the wearer. To provide
these functions, the sole typically has a midsole or insole having
cushioning and an outsole having a traction surface. The bladder
preferably is applied to the insole portion of a shoe, which is
generally defined as the portion of the shoe upper directly
underlying the plantar surface of the foot. Use of a bladder for
cushioning in a shoe is known in the art.
[0070] Because of the desirable low haze and high clarity of the
membrane containing the nano-filler, the bladder may form at least
a part of the exterior of the shoe.
[0071] The membranes preferably are capable of containing a captive
gas for a relatively long period of time. In a highly preferred
embodiment, for example, the membrane should not lose more than
about 20% of the initial inflated gas pressure over a period of
approximately two years. In other words, products inflated
initially to a steady state pressure of between 20.0 to 22.0 psi
should retain pressure in the range of about 16.0 to 18.0 psi for
at least about two years.
[0072] The bladder or cushioning device may be inflated with air or
components of air such as nitrogen, or with supergases. When used
as cushioning devices in footwear such as shoes, the bladder may be
inflated, preferably with nitrogen, to an internal pressure of at
least about 3 psi, preferably at least about 5 psi, and up to about
50 psi. Preferably the bladder is inflated to an internal pressure
of from about 5 psi to about 35 psi, more preferably from about 5
psi to about 30 psi, still more preferably from about 10 psi to
about 30 psi, and yet more preferably from about 10 psi to about 25
psi. It will be appreciated by the skilled artisan that in
applications other than footwear applications the desired and
preferred pressure ranges may vary dramatically and can be
determined by those skilled in that particular field of
application. Accumulator pressures, for example, can range up to
perhaps 1000 psi. Accumulator pressures are preferably up to about
500 psi. A preferred range of pressure for accumulator applications
is from about 200 psi to about 1000 psi, but pressures as low as
about 25 psi are possible depending upon the design of the
accumulator. Typical pressures for bladders used in sports balls
are from about 8 to about 40 psi. After being inflated, the
inflation port is sealed, for example by RF welding, for a
permanently sealed inflated bladder.
[0073] For the bladders to remain permanently inflated, the gas
transmission rate must be suitably low. In one preferred
embodiment, the membrane of the bladder has a gas transmission rate
toward the inflationary gas, which is preferably air or nitrogen
gas, should be less than about 15 cubic centimeters per square
meter per atmosphere per day
(cc/m.sup.2.multidot.atm.multidot.day), preferably less than about
6 cc/m.sup.2.multidot.atm.multidot.day, particularly less than
about 4 cc/m.sup.2.multidot.atm.multidot.day, more preferably less
than about 2.5 cc/m.sup.2.multidot.atm.multidot.day, yet more
preferably less than about 1.5
cc/m.sup.2.multidot.atm.multidot.day, and particularly preferably
less than about 1 cc/m.sup.2.multidot.atm.multidot.day. An accepted
method of measuring the relative permeance, permeability, and
diffusion of different film materials is set forth in the procedure
designated as ASTM D-1434. While nitrogen gas is the preferred
captive gas for many embodiments and serves as a benchmark for
analyzing gas transmission rates in accordance with ASTM D-1434,
the membranes can contain a variety of different gases and/or
liquids.
[0074] Accumulators, and more particularly, hydraulic accumulators
are used for vehicle suspension systems, vehicle brake systems,
industrial hydraulic accumulators or for other applications having
differential pressures between two potentially dissimilar fluid
media. The membrane separates the hydraulic accumulator into two
chambers or compartments, one of which contains a gas such as
nitrogen and the other one of which contains a liquid.
[0075] In addition to use for cushioning devices for footwear and
for accumulators, it should be appreciated that the membranes of
the present invention have a broad range of applications, including
but not limited to bladders for inflatable objects such as balls,
including footballs, basketballs, and soccer balls; inner tubes;
flexible floatation devices such as tubes or rafts; as a component
of medical equipment such as catheter balloons; as part of an
article of furniture such as chairs and seats, as part of a bicycle
or saddle, as part of protective equipment including shin guards
and helmets; as a supporting element for articles of furniture and,
more particularly, lumbar supports; as part of a prosthetic or
orthopedic device; as a portion of a vehicle tire, particularly the
outer layer of the tire; and as part of certain recreation
equipment such as components of wheels for in-line or roller
skates.
[0076] The invention is further described in the following
examples. The examples are merely illustrative and do not in any
way limit the scope of the invention as described and claimed. All
parts are parts by weight unless otherwise noted.
EXAMPLE 1
[0077] Two single-layer sheets of ethylene-vinyl alcohol copolymer
[EVOH] containing 5% by weight of a laminar non-filler are prepared
using ETC-133 from Kuraray/Evalca as the EVOH and Cloisite 15A (a
nano-filler clay treated with dimethyl, dihydrogenated tallow,
quaternary ammonium chloride) and Cloisite 30A (a nano-filler clay
treated with methyl, tallow, bis-2-hydroxyethyl, quaternary
ammonium chloride) as the filler. These samples were produced in a
concentrate then diluted as follows: First, a high clay containing
polymer sample was produced via extrusion. Then, the concentrate
was re-extruded with the desired amount of polymer to achieve the
5% by weight clay content. The extrudate from this second extrusion
was pelletized to produce extruded ETC-133 clay nanocomposite
pellets.
[0078] The increased barrier properties of the barrier
nanocomposite layer was determined as follows. The extruded ETC-133
clay nanocomposite pellets were extruded to produce 1 mil-thick
cast film for gas transmission rate measurement. The gas
transmission rate measurement was conducted at 20.degree. C. and
65% relative humidity in 100% oxygen with nitrogen as carrier gas.
The gas transmission rates of the two nanocomposite films were
compared to the gas transmission rate of unfilled ETC-133 as
reported by the manufacturer. The results are summarized in Table
1.
1TABLE 1 Oxygen transmission rate Sample OTR
(cc-mil/m.sup.2-day-atm) 95 wt. % ETC-133/5 wt. % Cloisite 15A 5.16
95 wt. % ETC-133/5 wt. % Cloisite 30A 4.07 ETC-133 (as reported by
Kuraray) 5.76
[0079] The extruded ETC-133 clay nanocomposite pellets are then
co-extruded with a thermoplastic polyurethane to form multi-layer
construction membranes and the membranes are formed into sealed
bladders and inflated with a gas as described in U.S. Pat. No.
5,952,065. The bladders are incorporated into a sole of a shoe as
described in U.S. Pat. No. 5,952,065.
EXAMPLE 2
[0080] The extruded ETC-133 clay nanocomposite pellets of Example 1
are extruded to form a microlayer polymeric composite according to
Example 1 of Bonk et al., U.S. Pat. No. 6,082,025, with the
extruded ETC-133 clay nanocomposite pellets of Example 1 replacing
the LCF 101A material of the patent example. The microlayer
polymeric composite is formed into a sealed, inflated bladder,
which is then incorporated into a sole of a shoe as described in
Example 1.
[0081] The invention has been described in detail with reference to
preferred embodiments thereof. It should be understood, however,
that variations and modifications can be made within the spirit and
scope of the invention and of the following claims.
* * * * *