U.S. patent application number 10/956850 was filed with the patent office on 2005-02-24 for durable hydrophilic nonwoven wipes.
Invention is credited to Henning, Gregory Neil, Kinn, Larry L., Mathur, Ashish, Ritter, Timothy L..
Application Number | 20050042518 10/956850 |
Document ID | / |
Family ID | 22359701 |
Filed Date | 2005-02-24 |
United States Patent
Application |
20050042518 |
Kind Code |
A1 |
Kinn, Larry L. ; et
al. |
February 24, 2005 |
Durable hydrophilic nonwoven wipes
Abstract
A wipe comprising a nonwoven web of a wettable fiber matrix,
wherein the wettable fiber matrix are thermoplastic polymeric
fibers blended with at least one hydrophilic melt additive. In
alternate embodiments, the nonwoven web further includes binder
fibers which may be wettable or non-wettable or combinations of
both.
Inventors: |
Kinn, Larry L.; (Franklin,
MA) ; Mathur, Ashish; (Wilmington, DE) ;
Henning, Gregory Neil; (Charlotte, NC) ; Ritter,
Timothy L.; (Selinsgrove, PA) |
Correspondence
Address: |
OSTRAGER CHONG FLAHERTY & BROITMAN PC
250 PARK AVENUE, SUITE 825
NEW YORK
NY
10177
US
|
Family ID: |
22359701 |
Appl. No.: |
10/956850 |
Filed: |
October 1, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10956850 |
Oct 1, 2004 |
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10232480 |
Aug 30, 2002 |
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10232480 |
Aug 30, 2002 |
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09479694 |
Jan 7, 2000 |
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6444367 |
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60115172 |
Jan 8, 1999 |
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Current U.S.
Class: |
429/250 ;
429/254; 442/118 |
Current CPC
Class: |
D04H 1/4291 20130101;
D04H 1/732 20130101; Y10T 442/681 20150401; Y10T 442/637 20150401;
Y10T 442/692 20150401; Y10T 442/68 20150401; Y02E 60/10 20130101;
H01M 50/411 20210101; Y10T 442/2484 20150401; H01M 50/44 20210101;
D04H 1/5412 20200501; H01M 10/24 20130101; Y10T 442/641 20150401;
D04H 1/43835 20200501; Y10T 442/696 20150401; D04H 1/5418 20200501;
D04H 1/43828 20200501 |
Class at
Publication: |
429/250 ;
429/254; 442/118 |
International
Class: |
H01M 002/16; B32B
027/04 |
Claims
1-22. (canceled)
23. A wipe comprising a nonwoven web of a wettable fiber matrix
wherein said wettable fiber matrix are thermoplastic polymeric
fibers blended with at least one hydrophilic melt additive, said
hydrophilic melt additive comprising a mixture of hydroxy phenols
and polyethylene glycols.
24. A wipe comprising a nonwoven web of a wettable fiber matrix
wherein said wettable fiber matrix are thermoplastic polymeric
fibers blended with at least one hydrophilic melt additive, said
nonwoven web further comprising non-wettable binder fibers.
25. The wipe according to claim 23 wherein said thermoplastic
polymeric fibers are polypropylene staple fibers.
26. The wipe according to claim 23 wherein said thermoplastic
polymeric fibers are polypropylene/polypropylene bicomponent
fibers.
27. The wipe according to claim 26 wherein said
polypropylene/polypropylen- e bicomponent fibers comprise a
polypropylene sheath and a polypropylene core.
28. The wipe according to claim 24 wherein said hydrophilic melt
additive is a mixture of hydroxy phenols and polyethylene
glycols.
29. The wipe according to claim 24 wherein said non-wettable binder
fibers are polyethylene/polypropylene bicomponent fibers.
30. The wipe according to claim 29 wherein said
polyethylene/polypropylene bicomponent fibers comprise a
polyethylene sheath and a polypropylene core.
31. The wipe according to claim 23 wherein said nonwoven web
further comprises wettable binder fibers.
32. The wipe according to claim 31 wherein said wettable binder
fibers are polyethylene/polypropylene bicomponent fibers blended
with a hydrophilic melt additive.
33. The wipe according to claim 24 wherein said nonwoven web is:
30-90 wt. % of said wettable fiber matrix; and 10-70 wt. % of said
non-wettable binder fibers.
34. The wipe according to claim 24 wherein said nonwoven web has
hydrophobic and hydrophilic regions.
35. The wipe according to claim 23 wherein said nonwoven web has
enhanced wettability and increased strength.
36. The wipe according to claim 24 wherein said thermoplastic
polymeric fibers are polypropylene staple fibers.
37. The wipe according to claim 24 wherein said thermoplastic
polymeric fibers are polypropylene/polypropylene bicomponent
fibers.
38. The wipe according to claim 37 wherein said
polypropylene/polypropylen- e bicomponent fibers comprise a
polypropylene sheath and a polypropylene core.
39. The wipe according to claim 24 wherein said nonwoven web
further comprises wettable binder fibers.
40. The wipe according to claim 39 wherein said wettable binder
fibers are polyethylene/polypropylene bicomponent fibers blended
with a hydrophilic melt additive.
41. The wipe according to claim 39 wherein said nonwoven web is: up
to 40 wt. % of said wettable fiber matrix; up to 40 wt. % of said
non-wettable binder fibers; and up to 30 wt. % of said wettable
binder fibers.
42. The wipe according to claim 24 wherein said nonwoven web has
enhanced wettability and increased strength.
43. A wipe comprising a nonwoven web of a wettable fiber matrix
wherein said wettable fiber matrix are thermoplastic polymeric
fibers blended with at least one hydrophilic melt additive, and
wherein at least some of said thermoplastic polymeric fibers are
sheath/core fibers and said hydrophilic melt additive is blended
into the sheath of said sheath/core fibers.
44. The wipe of claim 23 wherein the wipe is selected from the
group consisting of general application wipes, hard surface wipes,
cleaning wipes, and automotive wipes.
Description
RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/115,172 filed Jan. 8, 1999, which is
incorporated in its entirety herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to battery separator
materials. More particularly, the invention is directed to nonwoven
webs made of a wettable fiber matrix and non-wettable binder fibers
for use in rechargeable alkaline batteries.
BACKGROUND OF THE INVENTION
[0003] Rechargeable alkaline batteries typically require separators
to function primarily as dielectric as well as electrolyte
reservoirs. In addition to being inert to 31% potassium hydroxide
(KOH) used as the electrolyte, separator materials should possess
durable wettability to withstand the rigors during the discharging
and recharging of the battery. Typical separator constructions
employ nonwoven structures comprising either nylon or polyolefin
fibers
[0004] Representative examples of such constructions are
illustrated in the following patents.
[0005] U.S. Pat. No. 5,389,471 to Kung discloses a separator for an
alkaline battery comprised of a porous sheet of a microporous film,
fabric or synthetic paper which sheet is saturated with a resin
containing one or more carboxyl groups neutralized with a base so
as to form a salt. The resin includes a high molecular weight
acrylic acid having one or more carboxyl groups. A particularly
preferred resin disclosed in the examples is Carbopol (a high
molecular weight acrylic acid homopolymer).
[0006] U.S. Pat. No. 5,439,734 to Everhart discloses a nonwoven
fabric formed from polyolefin blended with at least one di-fatty
acid ester hydrophilic additive. The additives in Everhart include
a dioleate ester of polyethylene oxide, ethoxylated ester of caster
oil, a blend of glycerol mono-oleate ester and ethoxylated
nonylphenol and Maypeg-400 ml monolaurate.
[0007] Palmer U.S. Pat. No. 3,847,676 teaches a battery separator
made of a non woven mat of fibers of polymeric resin, i.e., C2-C8
polyolefin thermoplastic such as polyethylene, polypropylene and
polystyrene containing a first wetting agent dispersed therein
(relatively water insoluble), the fibers having a coating on their
outer surfaces of a second wetting agent. The internally dispersed
wetting agents are surfactants and preferably C8 to C18 phenol
surfactants having 1-15 moles of ethylene oxide. The second wetting
agent which is coated on the exterior of the fibers is relatively
water soluble and relatively oil insoluble and is preferably an
anionic and/or nonionic surfactant.
[0008] Palmer U.S. Pat. No. 3,870,567 deals with battery separators
formed from nonwoven thermoplastic fiber mats, the fibers
containing an internal wetting agent that will bloom over a period
of time at ambient temperatures of the battery. Nonylphenol
ethylene oxide is an example of a suitable wetting agent.
[0009] Palmer U.S. Pat. No. 3,918,995 also involves a battery
separator produced from a nonwoven mat of plastic fibers having an
internal surfactant and a second surfactant coated on the exterior
of the fibers. This patent is a division of Palmer U.S. Pat. No.
3,847,676, the claims in the '995 patent being drawn to a battery
as contrasted with a separator.
[0010] Palmer U.S. Pat. No. 3,933,525 discloses nonwoven battery
separators comprised of polyolefin fibers having internal wetting
agents, preferably comprised of two surfactants. The preferred
surfactants are C8 and C18 phenol surfactants having 1-15 moles of
ethylene dioxide.
[0011] Broadhead U.S. Pat. No. 3,928,067 discloses polypropylene
separators for use in lithium non aqueous secondary batteries which
include as wetting agents for the polypropylene separators
polyalkylene glycol esters, tetraalkylammonium halides and certain
lithium salts and preferably combinations of certain polyalkylene
glycol ethers and tetralkyl-ammonium halides.
[0012] Bunton 3,947,537 discloses battery separators made from
nonwoven mats of thermoplastic fibers which have been wetted with a
surfactant water mixture of an anionic surfactant such as an
aliphatic sulfate or a non-ionic surfactant such as a polyethylene
oxy compound.
[0013] EP 0 450 449 B1 is directed to separator materials for
storage batteries comprising a fabric sheet made of sulfonated
conjugate fibers comprising at least first and second components
thermally bonded together, the first component being a surface
layer, the second component occupying a core portion, the first
component being an ethylene copolymer containing at least a unit
having the formula --CH.sub.2--C(SO.sub.3H) (COOH)-- and comprising
an ethylene carbonic acid monomer containing acrylic and/or nucleic
acid and possibly also an acrylic acid ester, the second component
comprising a non-sulfonated polyolefin.
[0014] EP 0 591 616 B1 is directed to a hydrophilized separator
material of a nonwoven composed of a mixture of polyamide and/or
polyolefin fibers of different softening ranges, characterized in
that the separator material is moistened with deionized water
before its use.
[0015] EP 0 680 107 B1 is concerned with a nickel-hydrogen
secondary battery including a separator formed of a sheet material
containing polyolefin based synthetic resin fibers having a first
surface which is hydrophilic and a second surface having a
hydrophilic portion and a hydrophobic portion. The polyolefin
fibers are core-sheath type composite fibers comprising a core of
polyolefin and a sheath of another polyolefin.
[0016] EP 0 710 994 A2 relates to a battery separator comprising
(1) a nonwoven web of fibers having a mean diameter of about 15
.mu.m or less and (2) a graft polymerized monomer on the surface of
the nonwoven web which renders the nonwoven web wettable.
[0017] EP 0 756 340 A1 is directed to a battery separator
comprising a nonwoven web of first and second fibers, the first
fibers corresponding to a first and second polyolefin, the second
fibers comprising a third polyolefin, treated so that the separator
preferably formed of two such nonwoven webs, is spontaneously
wettable by an electrolyte.
[0018] EP 0 795 916 A1 relates to a wet-laid nonwoven fabric formed
from three dimensional entanglement of thermoplastic staple fibers
with hot melt fibers suitable for use as a battery separator. The
resultant nonwoven fabric can be subjected to a hydrophilic
treatment with a "generally used surfactant, a sulphonation
treatment, a fluorination treatment, a plasma treatment or a corona
discharge treatment.
[0019] EP 0 834 938 A2 discloses an alkaline battery separator
formed by heat fusion and hydroentangling 1) polyolefin dividable
composite fibers 2) high strength composite fibers (polypropylene)
and 3) polyolefin heat sensitive adhesive fibers, all as more
specifically defined. This application also teaches treatment of
the resultant fabric for imparting a hydrophilic property by
employing a sulphonating treatment, a treatment with fluorine gas,
a graft polymerization treatment with vinyl monomers, a treatment
with a surface active agent, a treatment used to adhere hydrophilic
resins, a discharging treatment, or the like. As surface active
agents there are disclosed anionic surface active agents (alkali
metal salt of a higher fatty acid, alkyl sulfonate, or a salt of
sulfosuccinate).
[0020] WO98/31060 discloses a battery separator useful in batteries
of the recombinant or sealed type made from extremely fine
meltblown fibers self-bonded in a cohesive, uncompressive mass.
This fiber mat is made wettable by battery acid by addition of a
surface active agent to the polymer prior to extrusion or by
covalently bonding hydrophilic groups to the surface of the fibers
after formation. Suitable additives are polytetrahydrafuran, mono
& diglycerides from fatty acids & dimethylsilicone
oxyalkylene copolymer. WO99/00447 discloses a product and process
for making wettable fibers prepared from an olefin polymer,
polyester or polyamide including a wetting agent consisting
essentially of a monoglyceride or a combination of a monoglyceride
and a mixed glyceride with the monoglyceride amounting to at least
85% by weight in the case of the combination.
[0021] The monoglyceride corresponds to the formula 1
[0022] wherein --OR.sub.1, OR.sub.2, and --OR.sub.3 are hydroxyl or
a fatty acid ester group, but only one of them is a fatty acid
ester group (C.sub.12-22). The mixed glyceride (di- or tri-)
corresponds to the formula 2
[0023] wherein --OR.sub.4, OR.sub.5, and --OR.sub.6 are hydroxyl or
a fatty acid ester group (C.sub.12-22). The combination of this di-
or tri-glyceride with the monoglyceride constitutes the wetting
agent in accordance with one embodiment.
[0024] As is shown in the prior art both nylon and polyolefins have
inherent property limitations, which lead to shorter battery life.
While nylon is susceptible to alkaline degradation, polyolefins,
though being chemically inert, are hydrophobic in nature.
[0025] It is known in the art to convert polypropylene fiber, which
is hydrophobic, into a hydrophilic fiber by chemically modifying
its surface. However, topical chemical applications are not
entirely satisfactory as they are not durable, and other types of
surface modifications may need extra processing steps and tend to
be expensive. In addition, some of these modifications age with
time, especially in the presence of 31% potassium hydroxide (KOH)
electrolyte solution used in alkaline batteries. The few processes
known to render the polyolefins wettable are environmentally
unfriendly, very slow processes and are not durable enough.
[0026] An alternative and improvement over chemical modification is
to directly melt blend a hydrophilic additive into the
polypropylene or thermoplastic polymer rendering the fibers
themselves hydrophilic. The invention solves the forgoing problems
and provides such a product by incorporating one or more
hydrophilic melt additives into polyolefin resin (polypropylene
(PP) or polyethylene (PE) or bicomponent) fibers to produce
nonwoven constructions for use as battery separators. The
hydrophilic melt additives are incorporated into PP polymer fiber
which is then converted into nonwoven separator materials by wet
laid and carding/thermal bonding processes. Alternatively, the PP
polymer and additives may be converted directly from the polymer
into nonwoven form by spunbonding or meltblowing, or a combination
of the two.
[0027] The preferred melt additives are an admixture of hydroxy
phenols and polyethylene glycols. The hydroxy phenol is
characterized in that it contains the functional group
HOC.sub.6H.sub.4--. According to the preferred embodiments of the
invention, the nonwoven battery separator is fabricated employing
wet laid and carded thermal bonding processes. An advantage of the
invention is obtained by use of combinations of hydrophobic and
hydrophilic fibers in the battery separator fabric, i.e., all
fibers in the separator need not be permanently wettable. In the
preferred embodiment, the separator includes bicomponent fibers in
which the melt additive is incorporated into the sheath
constituent(s) of the fiber. Use of bicomponent fibers, as well as
combinations of hydrophobic and hydrophilic fibers, reduces costs
and permits optimization of the separator for diverse
applications.
[0028] A broad aspect of the invention is to provide a nonwoven web
that is durable and has the wettability and strength for use in
rechargeable alkaline batteries by directly incorporating melt
additives into the polymeric component during melt processing to
form a wettable fiber matrix. This fiber matrix can be meltblown,
spunbonded or made into staple fibers to form a 100% wettable web.
Alternatively the wettable fiber matrix can be mixed with binder
fibers that are wettable or non-wettable or mixtures of both which
are then made into a nonwoven web.
[0029] An object of the invention is to provide a nonwoven web with
increased wettability and strength for use as battery separator
material.
[0030] Another broad object of the invention is to provide a
nonwoven that is durable and wettable in harsh environments.
[0031] A further object of the invention is to provide a nonwoven
web that has both hydrophilic and hydrophobic regions.
[0032] Another further object of the invention is to provide a
method for producing products that can be designed to have varied
wettablility and strength properties depending on the desired end
use applications.
[0033] A specific object of the invention is to provide a lower
cost battery separator material including bicomponent fibers,
wherein melt additives are incorporated in the fiber sheath of the
bicomponent fiber and not the core.
[0034] Another specific object of the invention is to provide an
economical battery separator material made of both wettable and
non-wettable polymeric fibers.
[0035] A more specific object of the invention is to provide a
nonwoven web that can be used for other applications such as
diapers and feminine care products, and medical applications which
would require durable wettability.
[0036] Another object of the invention is to provide a nonwoven web
that can be used in clothing applications, wherein products
produced remain durable and hydrophilic after multiple machine
washings.
[0037] Another object of the invention is to provide a nonwoven
that can be used in filtration applications, wherein durable and
wettable properties are required.
SUMMARY OF THE INVENTION
[0038] In the present invention, these purposes, as well as others
which will be apparent, are achieved generally by providing a
battery separator material comprising a nonwoven web of a wettable
fiber matrix, wherein the wettable fiber matrix are thermoplastic
polymeric fibers blended with a hydrophilic melt additive. The
fiber matrix furnish can be meltblown, spunbonded or made into
staple fibers to form a nonwoven web that is 100% wettable.
[0039] The thermoplastic polymeric fibers are preferrably either
polypropylene staple fibers or polypropylene/polypropylene
bicomponent fibers having a polypropylene sheath and a
polypropylene core.
[0040] The hydrophilic melt additives are a mixture of at least one
or more hydroxy phenols and polyethylene glycols.
[0041] In another embodiment the wettable fiber matrix is blended
with non-wettable binder fibers. Preferably these binder fibers are
polyethylene/polypropylene bicomponent fibers having a polyethylene
sheath and a polypropylene core.
[0042] In another embodiment of the invention the nonwoven web
further includes wettable binder fibers. The wettable binder fibers
are prefereably polyethylene/polypropylene bicomponent fibers
blended with a hydrophilic melt additive. Where the hydrophilic
melt additive is incorporated into the polyethylene sheath of the
bicomponent fiber.
[0043] In a preferred embodiment the nonwoven web is 30-90 wt. % of
the wettable fiber matrix; and 10-70 wt. % of the non-wettable
binder fibers. In a more preferred embodiment the nonwoven web is
50% wettable fiber matrix and 50% non-wettable binder fibers.
[0044] In another preferred embodiment the nonwoven web is up to 40
wt. % of the wettable fiber matrix; up to 40 wt. % of the
non-wettable binder fibers; and up to 30 wt. % of the wettable
binder fibers. Although preferred ranges are described, any
combination of wettable fiber matrix, non-wettable binder fibers
and wettable binder fibers are encompassed by the invention with
the amounts of each component depending on the desired wettability
and strength properties of the resulting web.
[0045] In general the battery separator materials of the invention
have enhanced wettability and strength and provide good
permeability to gases.
[0046] The invention also includes the related process for making
nonwoven webs which can be used as battery separators and in other
applications which require durability and wettability. In general a
fiber furnish comprising wettable thermoplastic polymeric fibers
blended with at least one hydrophilic melt additive is formed into
a nonwoven web by meltblowing, spunbonding or made into staple
fibers. In a preferred embodiment the furnish is further mixed with
binder fibers which are then laid on a papermaking machine to form
a wet-laid web The water is removed from the wet-laid web, thermal
bonded and calendered to form the nonwoven.
[0047] The nonwoven mats produced, in addition to use as battery
separators, can be used in other applications such as absorbent and
hygiene products, medical products, clothing and filtration
products which require durable wettability and strength.
[0048] Other objects, features and advantages of the present
invention will become apparent from the following detailed
description of the best mode of practicing the invention as
follows:
DETAILED DESCRIPTION OF THE INVENTION
[0049] In general, a battery separator material comprising a
nonwoven web of a wettable fiber matrix made of thermoplastic
polymeric fibers blended with at least one hydrophilic melt
additives.
[0050] The hydrophilic melt additives are incorporated into the
thermoplastic polymer and subsequently converted into fiber form
and later into a nonwoven using any of the various forming
technologies. Alternatively the material can be converted directly
from the polymer into a nonwoven by spunbonding, meltblowing or a
combination of the two. By combining the melt additives and the
nonwoven process, a permanently wettable battery separator is
produced and is able to withstand up to 31% KOH and prolong the
lifetime of NiCd and NiMH rechargeable alkaline batteries.
[0051] In an embodiment of the invention the hydrophilic melt
additives are blended with a polypropylene staple fibers to form a
wettable fiber matrix. This matrix is then further combined with
non-wettable binder fibers and wet-laid to form the nonwoven
material of the invention. The non-wettable binder fibers used
include a bicomponent fiber comprising a polyethylene sheath and a
polypropylene core, commercially available as Chisso fibers from
Chisso, Japan. The nonwoven material formed has both discrete
hydrophobic and hydrophilic regions due to the different types of
fibers used in making the web.
[0052] In an alternate embodiment the hydrophilic melt additives
are blended with bicomponent fibers comprising a polypropylene
sheath and a polypropylene core to form the wettable fiber matrix.
The bicomponent sheath/core fiber proportions used in the invention
vary from 50/50 sheath/core to 60/40 sheath/core. Essentially the
melt additives are incorporated into the outer polypropylene sheath
of the fibers. Use of bicomponent fibers having 60/40 sheath/core
permit higher incorporation of the melt additive into the sheath
portion. The wettable fiber matrix formed is then further combined
with non-wettable binder fibers to form the nonwoven web.
[0053] In all embodiments, the durable hydrophilic mat is
manufactured by blending a concentrate of hydrophilic melt
additives with the thermoplastic polymer and converting the polymer
into a nonwoven form directly or through an intermediate fiber
formation process. The chemistry and physical properties of the
additives, its compatibility with the thermoplastic resin, as well
as the process conditions and constructional features of the
nonwoven separator are necessary to yield the desired performance.
The type of melt additive and proportion are important to the
durable wettability of the nonwoven fabric.
[0054] In general the melt additives used in the invention are an
admixture of hydroxy phenols and polyethylene glycols. Examples of
melt additives used are commercially available from Techmer PM,
California under the product designations PPM 11211, PPM 11249, PPM
11212, PPM 11267 and PPM 11268. The technical brochures of each of
these materials are incorporated herein by reference.
[0055] A variety of different melt additive formulations can be
used to form the wettable fiber matrix. Specific formulations are
illustrated in Examples 1 to 5 herein. In general, the formulas
include an active chemical which is an admixture of hydroxy phenols
and polyethylene glycols. This active or functional chemical is
provided in a carrier resin, preferably polypropylene, of a given
melt flow rate (MFR) suitable for meltblowing, spunbonding or
staple fiber manufacture. Accordingly, the formulations have
different melt flow rates depending on the end use applications.
The MFR listed in the formulations below were measured at
230.degree. C., 2.16 kg. Melt blown grade polpropylene resins
typically have a much higher melt flow rate (MFR 800-1200), whereas
spunbond and staple fiber grade polypropylene resins have a lower
melt flow rate (MFR 7-35). The base chemicals in the formulations
include durable hydrophilic materials or non-durable hydrophilic
materials depending on the desired wettability properties and end
use applications.
[0056] The non-durable hydrophilic materials provide initial
wetting of the fibers to enhance and maximize incorporation of the
durable hydrophilic materials. The durable hydrophilic materials
impart the wettability and strength properties to the fiber
materials. In particular, in battery separator applications, the
more durable chemical loaded, absorbency and wicking increase and
the longer the life of the battery.
[0057] Melt Additive formulations 1 to 5 are illustrative of the
types of melt additive formulations used in the invention and shown
in Examples 1 to 5.
[0058] Melt Additive 1 contains approximately 30% of the active
chemical and includes the same durable hydrophilic materials as in
Melt Additive formulation 4 but a different melt flow rate. This
additive is commercially available as PPM 11211 from Techmer PM,
California.
[0059] Melt Additive 2 contains approximately 30% of the active
chemical and includes the same non-durable hydrophilic materials as
in Melt Additive formulation 5 but a different melt flow rate. This
additive is commercially available as PPM 11212 from Techmer PM,
California.
[0060] Melt Additive 3 contains approximately 20% of the active
chemical and includes non-durable hydrophilic materials. This
additive is commercially available as PPM 11249 from Techmer PM,
California.
[0061] Melt Additive 4 contains approximately 25% of the active
chemical and includes the same durable hydrophilic materials as in
Melt Additive formulation 1. This additive has a MFR of 54 grams/10
minutes and is commercially available as PPM 11267 from Techmer PM,
California.
[0062] Melt Additive 5 contains approximately 20% of the active
chemical and includes the same non-durable hydrophilic materials as
in Melt Additive formulation 2. This additive has a MFR of 109
grams/10 minutes and is commercially available as PPM 11268 from
Techmer PM, California.
[0063] For melt blown nonwoven structures, in preferred
applications, Melt Additive formulations 1, 2 and 3 are used.
Preferred proportions for melt blown structures include use of
15-35% of Melt Additive 1 formulation, i.e, 4-10% of the active
chemical or up to 10% of Melt Additive 2 formulation, i.e., up to
3% of the active chemical. Most preferred proportions for melt
blown structures include 30% of Melt Additive formulation 1, i.e.
9% of the active chemical and 5% of Melt Additive 2 formulation,
i.e. 1.5%. of the active chemical.
[0064] For spunbond and nonwoven mats containing staple fibers, in
preferred applications, Melt Additive formulations 4 and 5 are
used. Preferred proportions for such structures include use of
15-30% of Melt Additive 4 formulation, i.e, 4-8% of the active
chemical or up to 10% of Melt Additive 5 formulation, i.e., up to
2% of the active chemical. Most preferred proportions for these
structures include 25% of Melt Additive formulation 4, i.e. 6% of
the active chemical and 5% of Melt Additive 5 formulation, i.e. 1%
of the active chemical.
[0065] The hydrophilic melt additives can be used in the following
preferred forms of nonwovens, namely meltblown, spunbond, SMS
(spunbond/meltblown/spunbond), wet-laid, dry-laid or a combination
of these forms. While meltblown, spunbond and SMS nonwoven
structures consist of 100% polypropylene fibers, dry-laid and
wet-laid nonwovens comprise polypropylene, polyethylene or
polypropylene/polyethylene bicomponent fibers in various
proportions where the polyethylene components may or may not
contain the hydrophilic melt additive.
[0066] Fiber deniers for melt blown structures typically range from
0.1 to 2.0 deniers, with less than 1.0 most preferred. In the case
of staple fiber and spunbond filaments deniers, fiber deniers of
less than 3.0 are used, but less than 2.0 are most preferred.
[0067] Although it is preferred that the nonwoven mat of the
invention is a single-ply layer other multi-ply structures are
possible.
[0068] For spunbond and staple fiber nonwoven structures, in
preferred applications Melt Additive formulations 4 and 5 are
used.
[0069] To understand the present invention more fully, the
following examples of the invention are described below. These
examples are for purposes of illustration only and this invention
should not be considered to be limited by any recitation used
therein. The examples demonstrate the preparation of various
battery separator materials in accordance with the process of the
invention.
[0070] As in the examples below, unless otherwise specified, the
test procedures for testing electrolyte initial wet out time,
retention (absorbency %) and wicking in battery separator fabric
are as follows:
[0071] Preparation of 31% KOH solution: Ingredients: Distilled
water and potassium hydroxide pellets (KOH). Procedure: The
distilled water is freed of dissolved carbon dioxide by boiling and
covering with a watch glass. The boiled water is allowed to cool to
room temperature. The solution should be 31% KOH by weight. Since
solid KOH contains approximately 10% water, 34.5 g of solid KOH is
used for every 100 g of solution required. The solution is made by
slowly adding the 34.5 g of KOH to 65.5 g of water.
[0072] Wet Out Time
[0073] 10 ml of 31% potassium hydroxide (KOH) was placed in a five
inch watch glass. One 5/8" diameter disc sample was placed on the
surface of the KOH. The time in seconds was recorded for initial
wet out time up to 120 secs. These measurements were taken of the
sample "as is" (WET OUT BEFORE) and of the sample after 7 days
aging in the 31% KOH (WET OUT AFTER). The average time in seconds
was reported for the samples. In some examples, the samples were
only aged for 5 days.
[0074] Electrolyte Retentively (Absorbency %)
[0075] Retentively refers to the amount of potassium hydroxide
solution that will be retained by a specimen. Values are obtained
by determining the amount of solution of KOH that is retained by a
specimen soaked in the solution.
[0076] Specifically, three (3) specimens from each sample are cut
(such that the "V" shaped portion of the die runs in the MD
direction). The specimens are conditioned by drying in an oven at
70.degree. C. (158.degree. F.) for 1 minute, removed from the oven,
and conditioned to the lab environment for 15 minutes prior to
testing.
[0077] Each specimen of the fabric is weighed ("dry weight") and
then is soaked in a 31% solution of KOH. The amount of solution
retained by the specimen is measured after 1 hour. The specimen was
removed, allowed to drip for 10 minutes, and weighed and recorded
as "wet weight". The percent retention was calculated using the
following formula: 1 ( Weight weight - Dry weight ) ( Dry weight
.times. 100 ) = % Retention
[0078] Electrolyte Absorbing (Wicking)
[0079] Wicking refers to the ability of a fabric to absorb a liquid
through capillary action. Wicking values are obtained by
determining the distance a solution of potassium hydroxide (KOH) is
absorbed (wick) by a fabric specimen held vertically.
[0080] Specifically, three (3) specimens from each sample are cut
1" CD.times.7" MD. The specimens are conditioned by drying in an
oven at 70.degree. C. (158.degree. F.) for 1 minute, removed from
the oven, and conditioned to the lab environment for 15 minutes
prior to testing. Each specimen of the fabric was suspended
vertically in a 31% solution of KOH and the distance the liquid is
absorbed by the specimen is measured after 30 minutes.
[0081] Alkali Proof Character
[0082] A pre-weighed specimen of the fabric is soaked in a 31%
solution of potassium hydroxide (KOH) for 7 days at a temperature
of 70.degree. C. (158.degree. F.) and then re-weighed to determine
weight loss. This method is used to determine the effects on the
fabric when subjected to a long term exposure in a solution of KOH,
at an elevated temperature.
[0083] Specifically, three (3) specimens from each sample are cut
2" CD.times.8" MD. The specimens are conditioned by drying in an
oven at 70.degree. C. (158.degree. F.) for 1 minute, removed from
the oven, and conditioned to the lab environment for 15 minutes
prior to testing. Each specimen of the fabric was weighed and then
submerged in the KOH solution and soake for 7 days. After 7 days
the samples were removed and rinsed thoroughly with distilled water
to remove all the KOH solution (6 or 7 times in a beaker with
distilled water). The specimens were dried and re-weighed to
determine weight loss.
EXAMPLE 1
[0084] A wettable battery separator material was prepared from a
mixture of a wettable fiber matrix and non-wettable binder
fibers.
[0085] The wettable fiber matrix comprised a polypropylene staple
fiber containing combinations of Melt Additive formulations 4 and
5. The polypropylene staple fibers are 1.8 denier.times.12 mm and
are commercially available from American Extrusion.
[0086] The non-wettable binder fibers comprised a bicomponent fiber
having a polyethylene sheath and a polypropylene core. The binder
fibers are 2.0 denier.times.5 mm and are commercially available as
Chisso fibers from Chisso, Japan.
[0087] The wettable fiber matrix was mixed with varying amounts of
the non-wettable binder fibers, samples 1 to 4. The total weight of
the handsheets are indicated next to each sample.
[0088] Sample 1--50% Wettable fiber matrix; and 50% Non-wettable
binder fiber (30 gsm)
[0089] Sample 2--50% Wettable fiber matrix; and 50% Non-wettable
binder fiber (50 gsm)
[0090] Sample 3--60% Wettable fiber matrix; and 40% Non-wettable
binder fiber (50 gsm)
[0091] Sample 4--70% Wettable fiber matrix; and 30% Non-wettable
binder fiber (50 gsm)
[0092] Each fiber furnish mixture was dispersed and wet-laid into
handsheets which were evaluated before and after calendering for
wettability performance. The substrates were tested for absorbency,
wicking and wet-out to KOH. The tests were also done after 7 days
exposure to KOH at 70.degree. F. The results are summarized in
Tables I & II below.
1 TABLE I BASIS TENSILES ELONG. AIR WT. THICKNESS MD CD MD CD
PERMEABILITY SAMPLE gsy mils lbs/in % cfm 1 UNC 28 9.7 2 1 8 7 750
1 CAL 27 4.5 1.8 1.6 6 14 325 2 UNC 45.3 14.8 4 4 7 6 538 2 CAL
45.5 5.4 5.8 7.3 13 14 293 3 UNC 43 13.5 3 2.3 7 5 588 3 CAL 47 6 6
5.8 13 11 101 4 UNC 41 14 2 1.7 4 5 631 4 CAL 47.5 6 3.6 3.6 5 7 99
UNC--uncalendered; CAL--calendered
[0093] Table I illustrates the effect of calendaring on the
nonwoven web. Calendering increases the fiber tie down of the
nonwovens, specifically, it is shown that the thickness of the webs
decrease after calendering. Further as seen in the increase in
tensile values in Table I, calendering maximizes the strength of
the nonwovens.
2TABLE II WETTABILITY BEFORE AND AFTER AGING BEFORE AFTER WICKING
WET- WICKING WET cm/ OUT cm/ OUT WT. SAMPLE ABSORB % 10 min sec
ABSORB % 10 min sec LOSS % 1 UNC 801 1.0 I 674 1.2 3 2.7 1 CAL 350
4.5 I 349 1.3 I 1.9 2 UNC 770 1.3 I 790 1.6 1.7 0 2 CAL 192 6.2 I
208 2.5 I 0 3 UNC 592 1.3 I 778 1.7 3.1 0.7 3 CAL 242 6.7 I 255 7.3
I 1.1 4 UNC 831 1.4 I 815 1.7 3.6 0 4 CAL 230 6.3 I 236 6.3 I 0
UNC--uncalendered; CAL--calendered; I--immediate
[0094] For battery separator applications, target measurements for
wettability are absorbency greater than 200%, wicking greater than
3.0 cm/10 min and wet-out of less than 2 minutes. In general, all
the samples tested meet these targets. The aging data in Table II
demonstrated that the nonwovens formed were durable and wettable.
Further, the absorbency values after calendering indicated that the
nonwovens were acceptable for use as battery separator
materials.
EXAMPLE 2
[0095] A wettable battery separator material was prepared from a
mixture of a wettable fiber matrix and non-wettable binder
fibers.
[0096] The wettable fiber matrix comprised a polypropylene staple
fiber containing combinations of Melt Additive formulations 4 and
5. The polypropylene staple fibers are 1.8 denier.times.12 mm and
are commercially available from American Extrusion.
[0097] The non-wettable binder fibers comprised a bicomponent fiber
having a polyethylene sheath and a polypropylene core. The binder
fibers are 2.0 denier.times.5 mm and are commercially available as
Chisso fibers from Chisso, Japan.
[0098] 50% of the wettable fiber matrix was mixed with 50% of the
non-wettable binder fibers. The fiber furnish mixture was dispersed
and wet-laid into handsheets having a caliper of 6 mil and 7 mil,
Samples 5 and 6 respectively. The substrates were evaluated after
calendering for absorbency, wicking and wet-out to KOH. The tests
were also done after 7 days exposure to KOH at 70.degree. F. The
results are summarized in Tables III & IV below.
3 TABLE III BASIS TENSILES ELONG. AIR WT. THICKNESS MD CD MD CD
PERMEABILITY SAMPLE gsy mils lbs/in % cfm 5 (6 mil) 43 6.0 8.4 5.1
28 40 217 6 (7 mil) 44 6.9 9.1 5.4 28 42 204
[0099]
4TABLE IV WETTABILITY BEFORE AND AFTER AGING BEFORE AFTER WICKING
WET WICKING WET cm/ OUT cm/ OUT WT. SAMPLE ABSORB % 10 min sec
ABSORB % 10 min sec LOSS % 5 (6 mil) 224 96 I 277 85 I 0.4 6 (7
mil) 254 90 I 290 87 I 1.0 I--immediate
EXAMPLE 3
[0100] A wettable battery separator material was prepared from a
mixture of a wettable fiber matrix and non-wettable binder
fibers.
[0101] In Samples 7, 8 and 10 the wettable fiber matrix used is a
bicomponent fiber comprised of a polypropylene sheath and a
polypropylene core. Combinations of Melt Additive formulations 4
and 5 were incorporated into the polypropylene sheath with
essentially none of the additives migrating to the fiber core. The
bicomponent fibers are 1.5 denier.times.1/2 inch and are
commercially available from Fiber Inovation Technologies, Johnson
City, Tenn.
[0102] Specifically in Samples 7, 8 and 10, 20% of the melt
additive (30% active material) was incorporated into the
polypropylene sheath (6% active material). The proportion of
sheath/core in the bicomponent fiber is 50/50, thus the amount of
active material in the total fiber was 3%.
[0103] In Samples 9 and 11 the wettable fiber matrix used is a
polypropylene staple fiber containing combinations of Melt Additive
formulations 4 and 5. The polypropylene staple fibers are 1.8
denier.times.12 mm and are commercially available from American
Extrusion.
[0104] Specifically in Samples 9 and 11, 20% of the melt additive
(30% active material) was incorporated into the polypropylene
staple fiber (6% active material).
[0105] The non-wettable binder fibers comprised a bicomponent fiber
having a polyethylene sheath and a polypropylene core. The binder
fibers are 2.0 denier.times.5 mm and are commercially available as
Chisso fibers from Chisso, Japan.
[0106] In each sample 50% of the wettable fiber matrix was mixed
with 50% of the non-wettable binder fibers. The fiber furnish
mixture was dispersed and wet-laid to form the nonwoven substrates.
The substrates were evaluated after calendering for absorbency,
wicking and wet-out to KOH. The tests were also done after 7 days
exposure to KOH at 70.degree. F. The results are summarized in
Table V below.
5TABLE V WICKING WET-OUT BASIS ABSORB. % mm sec WT. WT. THICKNESS
BEFORE/ BEFORE/ BEFORE/ LOSS SAMPLE gsy mils AFTER AFTER AFTER % 7
27.09 4.52 230.8/ 13 3 50.18/ 0.123 247.6 6 min 58 sec 8 26.26 3.6
193.6/ 19 3 55/ 0.862 213.7 4 min 29 sec 9 26.18 3.68 181.3/ 39 12
immed/ 0.186 198.5 1 min 21 sec 10 44.24 6.12 237.8/ 13 4 1 min 40
sec/ 0.333 261.1 8 min 4 sec 11 43.78 6.42 261.4/ 64 19 immed/
1.043 277.4 2 min 32 sec
EXAMPLE 4
[0107] A wettable battery separator material was prepared from a
mixture of a wettable fiber matrix and non-wettable binder
fibers.
[0108] In Samples 12, 13 and 14 the wettable fiber matrix used is a
bicomponent fiber comprised of a polypropylene sheath and a
polypropylene core. The proportion of sheath/core in the
bicomponent fiber is 60/40. Combinations of Melt Additive
formulations 4 and 5 were incorporated into the polypropylene
sheath with essentially none of the additives migrating to the
fiber core. The bicomponent fibers are 1.5 denier.times.1/2 inch
and are commercially available from Fiber Inovations Technologies,
Johnson City, Tenn. In particular the samples were as follows.
[0109] Sample 12 the fiber sheaths are 77.5% 12 mfr polypropylene,
20% Melt Additive 4 and 2.5% Melt Additive 5. The fiber core is 18
mfr polyproylene.
[0110] Sample 13 the fiber sheaths are 73.5% 12 mfr polypropylene,
24% Melt Additive 4 and 2.5% Melt Additive 5. The fiber core is 18
mfr polyproylene.
[0111] Sample 14 the fiber sheaths are 71.5% 12 mfr polypropylene,
26% Melt Additive 4 and 2.5% Melt Additive 5. The fiber core is 18
mfr polypropylene.
[0112] In Samples 12, 13 and 14, 50% of the wettable fiber matrix
were combined with 50% of non-wettable binder fibers comprised a
bicomponent fiber having a polyethylene sheath and a polypropylene
core. The binder fibers are 2.0 denier.times.5 mm and are
commercially available as Chisso fibers from Chisso, Japan.
[0113] Sample 15 was prepared from a mixture of a wettable fiber
matrix and a wettable binder fiber. The wettable fiber matrix used
is a polypropylene staple fiber containing combinations of Melt
Additive formulations 4 and 5. The polypropylene staple fibers are
1.8 denier
EXAMPLE 4
[0114] A wettable battery separator material was prepared from a
mixture of a wettable fiber matrix and non-wettable binder
fibers.
[0115] In Samples 12, 13 and 14 the wettable fiber matrix used is a
bicomponent fiber comprised of a polypropylene sheath and a
polypropylene core. The proportion of sheath/core in the
bicomponent fiber is 60/40. Combinations of Melt Additive
formulations 4 and 5 were incorporated into the polypropylene
sheath with essentially none of the additives migrating to the
fiber core. The bicomponent fibers are 1.5 denier.times.1/2 inch
and are commercially available from Fiber Inovations Technologies,
Johnson City, Tenn. In particular the samples were as follows.
[0116] Sample 12 the fiber sheaths are 77.5% 12 mfr polypropylene,
20% Melt Additive 4 and 2.5% Melt Additive 5. The fiber core is 18
mfr polyproylene.
[0117] Sample 13 the fiber sheaths are 73.5% 12 mfr polypropylene,
24% Melt Additive 4 and 2.5% Melt Additive 5. The fiber core is 18
mfr polyproylene.
[0118] Sample 14 the fiber sheaths are 71.5% 12 mfr polypropylene,
26% Melt Additive 4 and 2.5% Melt Additive 5. The fiber core is 18
mfr polypropylene.
[0119] In Samples 12, 13 and 14, 50% of the wettable fiber matrix
were combined with 50% of non-wettable binder fibers comprised a
bicomponent fiber having a polyethylene sheath and a polypropylene
core. The binder fibers are 2.0 denier.times.5 mm and are
commercially available as Chisso fibers from Chisso, Japan.
[0120] Sample 15 was prepared from a mixture of a wettable fiber
matrix and a wettable binder fiber. The wettable fiber matrix used
is a polypropylene staple fiber containing combinations of Melt
Additive formulations 4 and 5. The polypropylene staple fibers are
1.8 denier.times.12 mm and are commercially available from American
Extrusion. The wettable binder fiber is a bicomponent fiber wherein
the fiber sheath is 77.5% low density polyethylene, 20% Melt
Additive 4 and 2.5% Melt Additive 5. The fiber core is 18 mfr
polypropylene. The binder bicomponent fibers are 1.5
denier.times.1/2 inch and are commercially available from Fiber
Inovations Technologies, Johnson City, Tenn.
[0121] As a control, 50% of the non-wettable bicomponent binder
fibers having a polyethylene sheath and a polypropylene core
(Chisso fibers) were mixed with 50% of a polypropylene fiber matrix
(American Extrusion fibers) without melt additives.
[0122] The fiber furnish mixtures in each sample was dispersed and
wet-laid to form the nonwoven substrates. The handsheets were
evaluated after calendering for absorbency, wicking and wet-out to
KOH. The tests were also done after 5 days exposure to KOH at
70.degree. F. The results are summarized in Table VI below.
6TABLE VI STRIP Initial 5 days TENSILE WICK Initial WICK 5 days
SAMPLE lbs/1" mm ABSORB. % mm ABSORB. % CONTROL 3.58 70 257 75 237
12 4.06 84 338 82 370 13 4.07 73 283 80 308 14 3.95 72 305 91 357
15 1.43 68 302 78 378
[0123] As illustrated in Table VI the tensile and absorbency of the
handsheet samples increased. The strength and wettability fo the
nonwovens remained even after aging. These results indicate that
the separate properties of tensile and absorbency can be provided
in a nonwoven. In addition, nonwovens are produced that have both
increased tensile and absorbency.
EXAMPLE 5
[0124] A wettable battery separator material was prepared from a
mixture of a wettable fiber matrix, non-wettable binder fibers and
wettable binder fibers.
[0125] In Samples 16 and 17 the wettable fiber matrix used is a
bicomponent fiber comprised of a polypropylene sheath and a
polypropylene core. The proportion of sheath/core in the
bicomponent fiber is 60/40. Combinations of Melt Additive
formulations 4 and 5 were incorporated into the polypropylene
sheath with essentially none of the additives migrating to the
fiber core. The bicomponent fibers are 1.8 denier.times.1/2 inch
and are commercially available from Fiber Inovations Technologies,
Johnson City, Tenn.
[0126] The non-wettable binder fibers are bicomponent fibers having
a polyethylene sheath and a polypropylene core. The binder fibers
are 2.0 denier.times.5 mm and are commercially available as Chisso
fibers from Chisso, Japan.
[0127] The wettable binder fibers used are bicomponent fibers
comprised of a polyethylene sheath and a polypropylene core.
Combinations of Melt Additive formulations 4 and 5 were
incorporated into the polyethylene sheath with essentially none of
the additives migrating to the fiber core. The bicomponent fibers
are 1.6 denier.times.1/2 inch and are commercially available from
Fiber Inovations Technologies, Johnson City, Tenn.
[0128] The fiber furnish in each of the samples are as follows.
[0129] Sample 16 40% wettable fiber matrix; 40% non-wettable binder
fiber; and 20% wettable binder fiber
[0130] Sample 17 30% wettable fiber matrix; 30% non-wettable binder
fiber; and 40% wettable binder fiber
[0131] The fiber furnish mixtures in each sample was dispersed and
wet-laid to form the nonwoven substrates. The substrates were
evaluated after calendering for absorbency, wicking and wet-out to
KOH. The tests were also done after 7 days exposure to KOH at
70.degree. F. The results are summarized in Tables VII and VIII
below.
7TABLE VII MD CD AIR AIR BASIS WT. TENSILE TENSILE PERMEABILITY
PERMEABILITY SAMPLE gsm kg/50 mm kg/50 mm cfm cm3/cm3/s 16 59.4
11.2 6.3 84.2 42.4 17 57.4 9.7 5.6 134.8 68.9
[0132]
8TABLE VIII WETTABILITY BEFORE AND AFTER AGING BEFORE AFTER WICKING
WICKING ALKALI PROOF SAMPLE ABSORB % mm ABSORB % mm % loss 16 226.8
85.3 237.9 93 0.67 17 297.2 79.3 333.9 100.7 0.5
[0133] It is known that current nylon based battery separators
degrade in the presence of the potassium hydroxide electrolyte. The
nonwoven mats of the invention present a replacement for the nylon
based battery separators by providing separator materials that have
been made permanently wettable, or if desired only partially
wettable. Polypropylene is naturally hydrophobic. Known methods to
make polypropylene wettable involves surface grafting of acrylic
acid by ultraviolet radiation or by other surface modification
methods such as plasma which are slow and expensive.
[0134] For fibrous battery separator applications the polypropylene
needs to be resistant to the KOH and exhibit permanent wettability
throughout the life of the product. Wettability is quantified by
contact angle measurements in the case of a film and additionally
by the rate of wicking and % absorbency in the case of a fibrous
web used as the battery separator.
[0135] The process of the present invention provides advantages
over prior practice by providing a nonwoven having both hydrophilic
and hydrophobic regions as opposed to hydrophilic topical
treatments. Additional wettability is achieved with incorporation
of the surfactant that has more resistance to KOH solution than
surfactants used in the prior art. Increased wettability is
achieved simultaneously with an increase in strength. The
wettability claimed in the invention is permanent and durable in a
KOH solution as opposed to the prior art.
[0136] Finally, variations from the examples given herein are
possible in view of the above disclosure. Therefore, although the
invention has been described with reference to certain preferred
embodiments, it will be appreciated that other processes may be
devised, which are nevertheless within the scope and spirit of the
invention as defined in the claims appended hereto.
[0137] The foregoing description of various and preferred
embodiments of the present invention has been provided for purposes
of illustration only, and it is understood that numerous
modifications, variations and alterations may be made without
departing from the scope and spirit of the invention as set forth
in the following claims.
* * * * *