U.S. patent application number 14/163377 was filed with the patent office on 2014-07-31 for cushioning device.
This patent application is currently assigned to MSD Consumer Care, Inc.. The applicant listed for this patent is MSD Consumer Care, Inc.. Invention is credited to Philip C. Yang.
Application Number | 20140209229 14/163377 |
Document ID | / |
Family ID | 51221635 |
Filed Date | 2014-07-31 |
United States Patent
Application |
20140209229 |
Kind Code |
A1 |
Yang; Philip C. |
July 31, 2014 |
CUSHIONING DEVICE
Abstract
A cushioning device including a layer of styrenic based gel
material having top and bottom surfaces, a first layer including:
i. layer of maleic anhydride and ii. layer of thermoplastic
polyurethane, wherein the first layer has a surface bonded to the
top surface of the layer of styrenic based gel material, the second
layer has a surface bonded to the bottom of the layer of styrenic
based gel material and wherein a pressure sensitive adhesive
coating is disposed on at least one of the first and second layers
opposite to the layer of styrenic based gel material.
Inventors: |
Yang; Philip C.; (Memphis,
TN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MSD Consumer Care, Inc. |
Memphis |
TN |
US |
|
|
Assignee: |
MSD Consumer Care, Inc.
Memphis
TN
|
Family ID: |
51221635 |
Appl. No.: |
14/163377 |
Filed: |
January 24, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61757901 |
Jan 29, 2013 |
|
|
|
Current U.S.
Class: |
156/60 ; 428/213;
428/337; 428/339; 428/354; 428/41.3 |
Current CPC
Class: |
Y10T 428/266 20150115;
A43B 19/00 20130101; A43B 17/006 20130101; Y10T 428/2495 20150115;
Y10T 156/10 20150115; Y10T 428/1452 20150115; A43B 17/02 20130101;
Y10T 428/2848 20150115; Y10T 428/269 20150115 |
Class at
Publication: |
156/60 ; 428/354;
428/41.3; 428/339; 428/213; 428/337 |
International
Class: |
A43B 19/00 20060101
A43B019/00 |
Claims
1. A cushioning device comprising a layer of styrenic based gel
material comprising top and bottom surfaces, a first layer
comprising: i. layer of maleic anhydride, and ii. layer of
thermoplastic polyurethane, and a second layer comprising: i. layer
of maleic anhydride, and ii. layer of thermoplastic polyurethane,
wherein the first layer has a surface bonded to the top surface of
the layer of styrenic based gel material, and the second layer has
a surface bonded to the bottom surface of the layer of styrenic
based gel material and wherein a pressure sensitive adhesive
coating is disposed on at least one of the first and second layers
opposite to the layer of styrenic based gel material.
2. The cushioning device of claim 1, further comprising a release
liner on an exposed surface of the pressure sensitive adhesive
coating.
3. The cushioning device of claim 1, wherein the styrenic based gel
material has a Shore 00 hardness of between about 10 and about
80.
4. The cushioning device of claim 1, wherein the styrenic based gel
material has a Shore 00 hardness of between about 30 and about
60.
5. The cushioning device of claim 1, wherein the styrenic based gel
material has a Shore 00 hardness of Shore 00 hardness of about
50.
6. The cushioning device of claim 1, wherein the styrenic based gel
material has a thickness of between 0.3 mm and 3 mm.
7. The cushioning device of claim 1, wherein the styrenic based gel
material comprises styrene copolymers selected from
styrene-isoprene-styrene (SIS), styrene-isobutylene-styrene (SIBS),
styrene-ethylene-butylene-styrene (SEBS), styrene-butadiene-styrene
(SBS) copolymers, and combinations of two or more thereof.
8. The cushioning device of claim 1, wherein the styrenic based gel
material comprises styrene-ethylene-butylene-styrene (SEBS).
9. The cushioning device of claim 1, wherein the i. layer to the
ii. layer has a thickness ratio of between 1:3 and 3:1.
10. The cushioning device of claim 1, wherein the ii. layer has a
Shore A hardness of between about 40 to about 95.
11. The cushioning device of claim 1, wherein the ii. layer has a
thickness of between 0.025 mm and 0.25 mm.
12. The cushioning device of claim 1, wherein the ii. layer has a
thickness of at least 0.025 mm.
13. The cushioning device of claim 1, wherein the ii. layer
comprises SEBS material.
14. The cushioning device of claim 1, wherein the pressure
sensitive adhesive coating comprises acrylic adhesives,
methacrylate adhesives, or rubber-based adhesives.
15. The cushioning device of claim 1, wherein the pressure
sensitive adhesive coating is an adhesive based on styrene
copolymers, silicones or combinations thereof.
16. The method of claim 1, wherein the pressure sensitive adhesive
coating has a thickness of between about 0.0125 mm and about 0.25
mm.
17. The cushioning device of claim 1, wherein probe tack of the
pressure sensitive adhesive coating to an adherend conducted in
accordance with ASTM D 2979-01 is at least about 300 g.
18. The cushioning device of claim 1, wherein probe tack of the
pressure sensitive adhesive coating to an adherend conducted in
accordance with ASTM D 2979-01 is at least about 300 g following
incubation at 50.degree. C. for at least 3 months.
19. The cushioning device of claim 1 which is a heel cushioning
device.
20. The cushioning device of claim 1, wherein each i. layer of
maleic anhydride independently comprises (i) maleic anhydride
grafted linear low density polyethylene, (ii) a terpolymer having
ethylene, butyl acrylate, butyl acetate or ethyl acetate, and
maleic anhydride, or (iii) a combination of (i) and (ii).
21. The cushioning device of claim 1, wherein at least one of the
first and second layers further comprises: iii. layer comprising
maleic anhydride.
22. The cushioning device of claim 21, wherein the iii. layer
comprises (i) maleic anhydride grafted linear low density
polyethylene, (ii) a terpolymer comprising ethylene, butyl
acrylate, butyl acetate or ethyl acetate, and maleic anhydride, or
(iii) a combination of (i) and (ii).
23. A method for providing enhanced adhesion performance of a
cushioning device in a shoe, comprising providing the cushioning
device of claim 1 wherein the pressure sensitive adhesive is
positioned so as to attach the cushioning device inside of the
shoe.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority from U.S.
Provisional Application Ser. No. 61/757,901, filed on Jan. 29,
2013, the entire contents of which are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a cushioning device
including a layer of styrenic based gel material having top and
bottom surfaces, a first layer including: i. layer of maleic
anhydride (MAH), and ii. layer of thermoplastic polyurethane (TPU),
wherein the first layer has a surface bonded to the top surface of
the layer of styrenic based gel material, and the second layer has
a surface bonded to the bottom surface of the layer of styrenic
based gel material and a pressure sensitive adhesive coating is
disposed on at least one of the first and second layers opposite to
the layer of styrenic based gel material.
BACKGROUND OF THE INVENTION
[0003] Cushioning devices made of soft gels are desirable for their
comfort, flexibility, durability and look. Generally, such
cushioning devices include a gel material having at least one layer
of polyurethane film thereon that contacts the foot, sock or
hosiery of the user and a pressure sensitive adhesive on the
opposing side of the cushioning device that is in contact with the
footwear of the user.
[0004] To effectively improve the comfort of users, soft gel
cushioning devices require a certain level of tack to stay in
place. For example, to prevent footwear from rubbing sensitive
areas of skin (e.g., the heel area) soft gel cushioning devices
must stay in place firmly during movement associated with normal
use of footwear. However, tack of cushioning devices is reduced
over time thereby rendering the cushioning device less
effective.
[0005] Thus, there is a need for improved cushioning devices having
a desirable level of tack that is retained for a greater period of
time.
SUMMARY OF THE INVENTION
[0006] The present invention provides cushioning devices including
a layer of styrenic based gel material having top and bottom
surfaces, a first layer including: i. layer of MAH, and ii. layer
of TPU, and a second layer including: i. layer of MAH, and ii.
layer of TPU, wherein the first layer has a surface bonded to the
top surface of the layer of styrenic based gel material and wherein
a pressure sensitive adhesive coating is disposed on at least one
of the first and second layers opposite to the layer of styrenic
based gel material
[0007] Advantageously, such cushioning devices provide a desirable
level of tack which is retained for an extended period of time
(e.g., following at least 3-months accelerated aging at 50.degree.
C.).
[0008] Additionally, desirable film surface friction is provided by
cushioning devices wherein at least one of the first and second
layers includes: iii. layer of MAH. Notably, the friction
coefficient of the iii. layer of MAH in such cushioning devices is
less than that of ii. layer of TPU in a film material.
[0009] Further, enhanced bonding strength is exhibited by a layer
of a terpolymer having ethylene, butyl acrylate and MAH bonded to a
layer of TPU as compared to a layer of MAH grafted linear low
density polyethylene (MAH-LLDPE) bonded to a layer of TPU.
[0010] The present invention also provides methods for providing
enhanced adhesion performance of a cushioning device in a shoe
including providing the aforementioned cushioning devices wherein
the pressure sensitive adhesive is positioned so as to attach the
cushioning device inside of the shoe.
BRIEF DESCRIPTION OF THE FIGURES
[0011] FIG. 1 depicts a cross section of one embodiment of the
cushioning device of the present invention.
[0012] FIG. 2 depicts a cross section of another embodiment of the
cushioning device of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0013] Referring to FIGS. 1 and 2, cushioning devices 10 of the
present invention are shown. Cushioning device 10 is used in a
manner well known in the art to provide a barrier so as to increase
user comfort, for example, to prevent footwear from rubbing
sensitive areas of skin (e.g., the heel area). Cushioning device 10
has a styrenic based gel material 12, having a top surface 22 and a
bottom surface 24.
[0014] Referring to FIG. 1, the cushioning device has two layers of
a film material 14, each of the film material including i. layer of
MAH 16 and ii. layer of TPU 18, wherein the first layer has a
surface 26 bonded to the top surface 22 and the second layer has a
surface 26 bonded to the bottom surface 24 of the layer of styrenic
based gel material 12 and wherein a pressure sensitive adhesive
coating 20 is disposed on a surface 28 of the second layer of the
film material 14 that is opposite to the surface 26 of the film
material bonded to the layer of styrenic based gel material 12.
Optionally, a release liner 30 is present on the exposed surface of
the pressure sensitive adhesive coating.
[0015] Referring to FIG. 2, the cushioning device 10 has a first
layer of film material 32 and a second layer of film material 14.
The first layer 32 includes i. layer of MAH 16, ii. layer of TPU
18, and iii. layer of MAH 36. The second layer 14 includes i. layer
of MAH 16 and ii. layer of TPU 18. The first layer 32 has a surface
34 bonded to the top surface 22 of the layer of styrenic based gel
material 12. The second layer 14 has a surface 26 bonded to the
bottom surface 24 of the layer of styrenic based gel material 12
and the second layer 14 has a pressure sensitive adhesive coating
20 disposed on a surface 28 of the second layer of the film
material 14 that is opposite to the surface 26 of the film material
bonded to the layer of styrenic based gel material 12. Optionally,
a release liner 30 is present on the exposed surface of the
pressure sensitive adhesive coating.
[0016] Styrenic based gel materials suitable for use in the present
invention include, but are not limited to, the Kraton family of
styrene-olefin-rubber block copolymers. In certain embodiments,
elastomers are a Kraton block copolymer of styrene-isoprene-styrene
(SIS), styrene-isobutylene-styrene (SIBS),
styrene/ethylene-co-butylene/styrene (SEBS) or
styrene/butadiene/styrene (SBS), and combinations of two or more
thereof. In one embodiment, the gel material is a Kraton block
copolymer of styrene/ethylene-co-butylene/styrene (SEBS). In
certain embodiments, the styrenic based gel material includes
mineral oil incorporated into the matrix as a plasticizer.
[0017] In one preferred embodiment, the gel material is a Kraton
block copolymer of styrene/ethylene-co-butylene/styrene (SEBS) with
mineral oil incorporated into the matrix as a plasticizer.
[0018] As used herein, TPU will be understood to encompass polymers
that contain a plurality of urethane linkages and comprise either
aliphatic or aromatic isocyanate prepolymers, and combinations
thereof, both with either di- or tri-functional polyol polymers or
prepolymers. The TPU may optionally also contain other kinds of
chemical linkages formed from the reactions of polyisocyanates,
including but not limited to urea linkages, isocyanurate linkages,
oxazolidone linkages, biuret linkages, allophanate linkages,
combinations of these, and the like.
[0019] The gel materials useful in the invention may typically have
a Shore 00 hardness of between about 10 and about 80. In certain
embodiments, the gel materials used may have a Shore 00 hardness of
between about 30 and about 60. In certain embodiments, the gel
materials used may have a Shore 00 hardness of about 50. The gel
materials may typically have a thickness of between about 1 and
about 7 mm. In certain embodiments, the gel materials used may
typically have a thickness of 2.5 mm.
[0020] The film material includes i. layer of MAH and ii. layer of
TPU. In certain embodiments, each i. layer of MAH independently
includes (i) MAH-LLDPE, (ii) a terpolymer having ethylene, butyl
acrylate, butyl acetate or ethyl acetate, and maleic anhydride, or
(iii) a combination of (i) and (ii). In one embodiment, the i.
layer includes MAH-LLDPE.
[0021] In certain embodiments, the film material has a thickness
ratio of the i. layer to the ii. layer of between 1:3 and 3:1. In
certain embodiments, the i. and ii. layers of the film material
have a thickness ratio of i. layer to ii. layer of between 1:1 and
1:2. For example, one or both of the first and second layers of the
film material may have a thickness of i. layer of MAH that is about
0.04 mm and a thickness of ii. layer of TPU that is about 0.08 mm.
Alternatively, one or both layers of the first and second layers of
the film material may have a thickness of i. layer of MAH that is
about 0.02 mm and a thickness of ii. layer of TPU that is about
0.04 mm.
[0022] In certain embodiments, the i. and ii. layers of the film
material in the cushioning device will have a thickness of about
0.5 mm. In certain embodiment, the i. and ii. layers of the film
material in the cushioning device may have a total thickness of
about 0.4 mm. In certain embodiments, the i. and ii. layers of the
film material in the cushioning device will have a thickness of 0.2
mm.
[0023] In certain embodiments, at least one of the first and second
layers of the film material further includes iii. layer of MAH. For
example, the iii. layer of MAH includes (i) maleic anhydride
grafted linear low density polyethylene, (ii) a terpolymer having
ethylene, butyl acrylate, butyl acetate or ethyl acetate, and
maleic anhydride, or (iii) a combination of (i) and (ii).
[0024] In certain embodiments, the film material has a thickness
ratio of the i. layer to the ii. layer of between 1:3 and 3:1 and a
thickness ratio of the ii. layer to the iii. layer of between 3:1
and 1:3. In one embodiment, the i. layer, ii. layer and iii. layer
of the film material in the cushioning device has a thickness ratio
of 1:1:1.
[0025] In one embodiment, the film material has i. layer of
MAH-LLDPE, ii. layer of TPU and iii. layer of MAH-LLDPE. In another
embodiment, the film material has i. layer of MAH-LLDPE, ii. layer
of TPU and iii. layer of a terpolymer of ethylene, butyl acrylate,
butyl acetate or ethyl acetate, and MAH. In yet another embodiment,
the film material has i. layer of a terpolymer of ethylene, butyl
acrylate, butyl acetate or ethyl acetate, and MAH, ii. layer of TPU
and iii. layer of MAH-LLDPE. In still yet another embodiment, the
film material has i. layer of a terpolymer of ethylene, butyl
acrylate, butyl acetate or ethyl acetate, and MAH, ii. layer of TPU
and iii. layer of a terpolymer of ethylene, butyl acrylate, butyl
acetate or ethyl acetate, and MAH. In yet still another embodiment,
the film material has i. layer of MAH-LLDPE and/or a terpolymer of
ethylene, butyl acrylate, butyl acetate or ethyl acetate, and MAH,
ii. layer of TPU and iii. layer of MAH-LLDPE and/or a terpolymer of
ethylene, butyl acrylate, butyl acetate or ethyl acetate, and
MAH.
[0026] In one embodiment, the i. layer, ii. layer and iii. layer of
the film material in the cushioning device each have a thickness of
about 0.08 mm. For example, in one embodiment, the film material
has i. layer of MAH-LLDPE with a thickness of 0.08 mm, ii. layer of
TPU with a thickness of 0.08 TPU and iii. layer of MAH-LLDPE with a
thickness of 0.08 mm.
[0027] Suitable materials for use in the present invention in each
layer of MAH independently include (i) MAH-LLDPE; (ii) a terpolymer
having ethylene, butyl acrylate, butyl acetate or ethyl acetate,
and maleic anhydride, or (iii) a combination of (i) and (ii). In
certain embodiments, the i. layer of MAH includes MAH-LLDPE. In
certain embodiments, the iii. layer of MAH includes a terpolymer of
ethylene, butyl acrylate, butyl acetate or ethyl acetate, and MAH.
In certain embodiments, either or both the i. layer of MAH and iii.
layer of MAH includes a combination of MAH-LLDPE and a terpolymer
of ethylene, butyl acrylate, butyl acetate or ethyl acetate, and
MAH. Such combinations can readily be achieved by blending
components as is well known to a skilled artisan.
[0028] The MAH content of MAH-LLDPE is about 1% or less. The MAH
content of suitable terpolymers of ethylene, butyl acrylate, butyl
acetate or ethyl acetate, and MAH is 1 to 4% (e.g., greater than 1
wt % to 4 wt %).
[0029] Exemplary suitable terpolymers of ethylene, butyl acrylate,
butyl acetate or ethyl acetate, and MAH include, but are not
limited to, Lotader.RTM. 3210 resin (a random terpolymer of
ethylene, butyl acrylate and MAH having a 3% MAH content),
Lotader.RTM. 3410 resin (a random terpolymer of ethylene, butyl
acrylate and MAH having a 3% MAH content), Lotader.RTM. 4210 resin
(a random terpolymer of ethylene, butyl acrylate and MAH having a
3.8% MAH content, Lotader.RTM. 2210 (a random terpolymer of
ethylene, acrylic ester and MAH having a 2.8% MAH content), and
Lotader.RTM. 2308 (a random terpolymer of ethylene, acrylic ester
and MAH having a 1.5% MAH content), all of which are available from
Arkema, Colombes, France.
[0030] In one embodiment, when an SEBS gel material is used in the
cushioning device, the ii. layer of TPU includes SEBS. The ii.
layer of TPU may typically have a Shore A hardness of between about
40 to about 95. The ii. layer of TPU may typically have a thickness
of between 0.025 mm and 0.25 mm.
[0031] In certain other embodiments, individual layers of the film
material in the cushioning device will have different thicknesses.
In practice, varying the thickness of the film material will affect
the softness and flexibility of the film material and will likewise
affect the softness and flexibility of the final cushioning
product.
[0032] As used herein, pressure sensitive adhesives (also known as
contact adhesives) are those that form viscoelastic bonds that are
aggressively and permanently tacky, adhere without the need of more
than slight pressure, and require no activation by water, solvent
or heat. Pressure sensitive adhesives are typically available in
solvent and latex or water based forms and are often based on
non-crosslinked rubber adhesives, acrylics or polyurethanes.
[0033] In certain embodiments of the invention, the pressure
sensitive adhesives may comprise acrylic and methacrylate
adhesives, rubber-based pressure sensitive adhesives, styrene
copolymers such as styrene-isoprene-styrene (SIS) and
styrene-butadiene-styrene (SBS) copolymers with at least one
tackifier, and silicones. Acrylic adhesives often use an acrylate
system such as ethylene ethyl acrylate (EEA) or ethylene methyl
acrylate (EMA) copolymers, which are used to form hot melt PSA
adhesives. Natural rubber, synthetic rubber or elastomer adhesives
may typically comprise a variety of materials such as silicone,
polyurethane, chloroprene, butyl, polybutadiene, isoprene or
neoprene. Rubber and elastomers are characterized by their high
degree of flexibility and elasticity.
[0034] In certain embodiments, the pressure sensitive adhesive
material may include acrylate-based adhesive materials. The
thickness of the layer of the pressure sensitive adhesive material
may be varied by those of ordinary skill in the art according to
the adhesive material used and the desired tack. In certain
embodiments, the pressure sensitive adhesive may have a thickness
of between about 0.012 mm and about 0.075 mm. In certain
embodiments, the pressure sensitive adhesive will have a thickness
of 0.012 mm.
[0035] In one embodiment, probe tack is at least about 300 g. In
certain embodiments, probe tack is at least about 300 g following
incubation at 50.degree. C. for at least 3 months.
[0036] Although desirable for use in cushioning devices, it is
known that gel materials such as SEBS do not readily bond to a TPU
film. To overcome this limitation, a film material, including a
layer of TPU and layer of MAH, was utilized. The film material was
manufactured by a co-extrusion process. The layer of MAH serves as
an anchoring layer for the SEBS gel so that the SEBS gel can be
bonded to the film material having a TPU layer on the opposing
surface to that bound to the SEBS gel. The film material is used as
a covering for the SEBS gel. Desirably, the delamination strength
between a gel material comprising SEBS and a film material
including a layer of MAH and a layer of TPU was found to be about
1.5 lb/in which is sufficient for applications associated
therewith.
[0037] An injection molding process may be used in a manner well
known in the art to bond the layer of MAH of the film material to
the SEBS gel. Specifically, in preparation for injection molding, a
film material is placed next to the SEBS gel with the layer of MAH
of the film material facing the SEBS gel. Additionally, prior to
injection molding, a pressure sensitive adhesive is applied to one
TPU layer side of the film material. The mold can be treated to
resist bonding of the pressure sensitive adhesive or a release
liner material can be applied in the mold before application of the
pressure sensitive adhesive. Typically, the mold temperature is
between 160.degree. C. and 210.degree. C. and the cycle time is
approximately 1 min.
[0038] The products of the invention can be formed into any shape
suitable for use as a cushioning device, for example for insertion
into footwear to prevent rubbing between sensitive skin and hard or
exposed surfaces of the footwear. The cushioning elements can also
be applied to other garments (e.g., hats, helmets, protective
sporting gear such as elbow and knee pads and other garments
requiring extra padding for comfort, sizing and/or safety).
Cushioning elements according to the invention may also be applied
to surfaces which come in contact with body parts to provide
protection from injury (e.g., chairs, desks, cabinets, tables,
doors and door frames, among others). Depending on the size and
shape of the object to which the cushioning element is applied,
certain shapes will better protect different areas of the body from
contact with the object. In certain example embodiments, the
products are molded in the shape of circles, parabolas, stars,
squares, rectangles, rounded rectangles, half-moon, among others.
The appropriate shape of the cushioning element can be determined
based on the size and surface of the object to which the cushioning
element will be applied. In alternative example embodiments, the
cushioning element can be provided as a sheet of material that the
user can cut to a desired shape. The sheet of material can also be
provided with preformed shapes that can be removed as desired for
the appropriate protection from contact with the object.
[0039] It will be appreciated by those skilled in the art that
changes could be made to the embodiments described above without
departing from the broad inventive concept thereof. It is
understood, therefore, that this invention is not limited to the
particular embodiments disclosed, but is intended to cover
modifications that are within the spirit and scope of the
invention, as defined by the appended claims.
EXAMPLES
Example 1
[0040] The cushioning device of the present invention in accordance
with the embodiment depicted in FIG. 1 wherein the layer of MAH is
a layer of MAH-LLDPE was compared to a cushioning device having a
linear low density polyethylene single layer film bound to a SEBS
gel with a pressure sensitive adhesive bound to an exposed surface
of the linear low density polyethylene single-layer film. In
particular, a probe tack test was conducted on both cushioning
devices in accordance with ASTM D 2979-01 to measure the force
required to separate an adhesive and adherend shortly after they
have been contacted under a defined load of known duration and at a
specified temperature. The results of the probe tack test are
reflected in Table 1.
TABLE-US-00001 TABLE 1 Probe Tack (g) after 3-month accelerated
Film in cushioning device Probe Tack (g) aging Multi-layer film 317
.+-. 15 321 .+-. 17 Single-layer film (comparative 187 .+-. 24 32
.+-. 1 example)
Unexpectedly, the probe tack of the cushioning device employing a
multi-layer film was much higher than that of the single-layer
linear low density polyethylene single-layer film. Further,
following a 3-month accelerated aging period during which the
cushioning devices were incubated in a 50.degree. C. oven, the
probe tack of the pressure sensitive adhesive of the cushioning
device was much better retained in the multi-layer film as compared
to the single-layer film. In fact, whereas the probe tack in the
cushioning device of the multi-layer film was maintained at a
desirable level, that of the single-layer film was insufficient for
applications such as for use in a heel cushioning device.
Example 2
[0041] The film surface friction was assayed in cushioning devices
of the present invention in accordance with the embodiments
depicted in FIGS. 1 and 2 wherein each of the layers of MAH is a
layer of MAH-LLDPE. In particular, the film surface friction of the
skin/sock-contact layer, that is the ii. layer of TPU 18 of the
film material in accordance with FIG. 1 and the iii. layer of MAH
36 of the film material in accordance with FIG. 2 was assessed. The
assay was conducted in accordance with (ASTM D 1894) to quantify
the friction coefficient of the film surfaces. The results of this
film surface friction assay are reflected in Table 2.
TABLE-US-00002 TABLE 2 Skin/sock-contact layer Friction coefficient
of the film surface TPU layer 0.98 .+-. 0.05 MAH-LLDPE layer 0.69
.+-. 0.02
[0042] The lower the film surface friction, the better the rubbing
relief. Accordingly, cushioning devices having a layer of MAH-LLDPE
as the skin/sock-contact layer provide much better rubbing relief
than those having a layer of TPU as the skin/sock-contact layer.
Further, the low level of friction coefficient of the film surface
achieved by a layer of MAH-LLDPE could not be achieved by a single
layer of TPU film.
Example 3
[0043] The bonding strength was assayed in a film material having a
layer containing Lotader.RTM. 3210 (available from Arkema,
Colombes, France) and a TPU layer. In particular, the film material
had a layer of Lotader.RTM. 3210 with a thickness of 0.04 mm and a
layer of TPU with a thickness of 0.14 mm. The bonding strength was
assayed in accordance with (ASTM D 3807). The bonding strength
between the layers of the film material was so strong that the
layers could not be delaminated from each other. Such bonding
strength may provide a more durable film material in applications
associated therewith. In comparison, the typical bonding strength
between a layer of MAH-LLDPE and a TPU layer is about 1.5 lb/in
which is sufficient for applications associated with cushioning
devices. Comparable delamination strength would be expected between
a layer of other terpolymers having ethylene, butyl acrylate, butyl
acetate or ethyl acetate, and MAH and a TPU layer.
* * * * *