Note: Descriptions are shown in the official language in which they were submitted.
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BREATHABLE NON-WETTABLE MELT-BLOWN NON-WOVEN
MATERIALS AND PRODUCTS EMPLOYING THE SAME
FIELD OF THE INVENTION
The present invention relates generally to non-woven materials
(e.g., fabric structures). In particularly preferred embodiments, the
present invention relates to breathable non-woven melt-blown materials
having oleophobic and/or hydrophobic properties.
BACKGROUND AND SUMMARY OF THE INVENTION
There are numerous fields of use whereby breathable fabric
o structures having oleophobic and/or hydrophobic properties are desired.
For example, such fabric structures are highly desirable to form surgical
drapes and gowns, ground dressings/bandages, outer garments, and
barrier vents.
Currently, there are several products on the market that provide
~5 breathable protective garments for use during surgery. This breathability
is typically expressed as a material's moisture vapor transmission rate
(MVTR). Typical MVTR ranges for such protective garments are between
about 1,000 to about 10,000 grams of water per square meter per 24
hours (g/m2/24hrs). However, a person's body heat tends to increase
2o beneath the garments to a point whereby they become uncomfortable to
wear. A surgical drape or gown having the ability to repel low surface
tension fluids (for example, fluids having a surface tension of less than
about 42 dynes/cm) and having an MVTR in excess of 100,000
g/m2/24hrs would be quite desirable to those wearing the garments but
25 which to date has not been made available.
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It is also known that one common problem with conventional
wound dressings is that, to provide for an adequate barrier against
airborne pathogens, barrier films with little or no MVTR are employed.,
This minimal MVTR creates a situation where sufficient amounts of
moisture produced by the human body underneath a bandage cannot be
removed and, as a result, maceration of the skin surrounding the wound
occurs. This maceration can lead to prolonged healing times. It would
therefore be quite desirable for.a bandage material to have a MVTR in
excess of about 100,000 g/m224 hrs so as to prevent such maceration
1o from occurring as well as to provide the irvearer with a more comfortable
bandage. To date, however, bandage materials which satisfy these
requirements have not been offered.
Conventional water-proof and breathable outerwear garments
provide significant improvements in wearer comfort over non-permeable
materials that may be used (e.g., polyvinylchloride (PVC) films).
However, any moderate to strenuous activity causes a rapid increase in
temperature beneath these garments thereby causing great discomfort. A
garment that was made from fabric materials that are non-wettable by
fluids having surface tensions of less than about 42 dynes/cm and having
2o MVTR's of greater than 100,000 g/m2/24hrs would be a significant
improvement in wearer comfort. Again, however, such garment fabrics
have not been provided to date.
Finally, there are many applications where fluids of various surface
tensions need to be contained or prevented from entering designated
areas while at the same time permit airflow to occur. Traditional barriers
are made from polymeric materials that have either hydrophobic and/or
oleophobic properties. Often, these properties are rendered onto a
polymeric material by a secondary process which can add cost and
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typically results in non-uniform coatings that result in an unacceptable rate
of failures. A barrier vent with inherent surface energies of less than
about 30 dynes/cm and having the ability to allow for bulk airflow (e.g.,
Gurley densiometer readings of less than 600 seconds for a one square
inch orifice, 100 cc of air and 5 ounce cylinder) would be quite desirable,
but to date has not been provided. Expressed in other units an air
permeability in excess of 0.045 ft3/ft2/min at a differential pressure of 2163
Pascals would be desirable.
As can be appreciated from the preceding discussion, what has
1o been needed are fabric structures which exhibit oleophobicity and/or
hydrophobicity characteristics while, at the same time, are capable of
allowing bulk air flow. It is towards fulfilling such needs that the present
invention is directed.
Broadly, the present invention is embodied in materials comprised
of a mass of melt-blown non-woven fibers comprised of a terpolymer of
tetrafluroethylene, hexafluoropropylene and vinylidene fluoride monomers.
Most preferably, such materials are in the form of fabric structures which
can be processed to form a variety of products for numerous end-use
applications, such as for garments, bandages, barrier vents, filter media
2o and the like. In especially preferred form, the melt-blown non-woven
fibers are comprised of a THV terpolymer formed of between about 30 to
about 70 wt.% of tetrafluoroethylene monomer, between about 10 to
about 20 wt.% of hexafluoroethylene monomer, and between about 20 to
about 65 wt.% vinylidene fluoride monomer.
These and other aspects and advantages will become more
apparent after careful consideration is given to the following detailed
description of the preferred exemplary embodiments thereof. '
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DETAILED DESCRIPTION OF THE INVENTION
1. Definitions
As used herein and in the accompanying claims, the following
terms are intended to have the definitions which follow:
"Breathable" or "breathability" mean that a fabric structure is
capable of exhibiting a moisture vapor transmission rate (MVTR) of
greater than about 100,000 g/m2/24hrs.
"Non-Wettable" or "non-wettability" means that a fabric structure is
not wetted by a fluid having a surface tension of less than about 42
1o dyne/cm. Thus, for example, "non-wettable" fabric structures in
accordance with the present invention will have an oil rating according to
AATCC Test Method 118-1997 of at least 1.
"Bulk airflow" means that a fabric structure exhibits a porosity of
less than about 600 Gurley-seconds, when employing a Gurley
~5 densiometer having a one square inch orifice, 100 cc of air and 5 ounce
cylinder. Alternatively, the term "bulk airflow" means that a fabric
structure exhibits an air permeability in excess of 0.045 ft31ft2/min at a
differential pressure of 2163 Pascals.
II. Detailed Description of Preferred Exemplary Embodiments
2o The non-woven materials (e.g., fabric structures) of the preferred
embodiments according to the present invention may be prepared from a
terpolymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene
fluoride (hereinafter referred to as "THV polymer"). Preferably, the
terpolymer includes from about 20 or less to about 65 wt. % or more
25 vinylidene fluoride, more preferably from about 25, 30, or 35 to about 40,
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45, 50, 55, or 60 wt. % vinylidene fluoride, and most preferably about 36.5
wt. % vinylidene fluoride. Preferably, the terpolymer includes from about
30 or less to about 70 wt. % or more tetrafluoroethylene, more preferably
from about 35 or 40 to about 45, 50, 55, 60, or 65 wt.
tetrafluoroethylene, and most preferably about 44.6 wt.
tetrafluoroethylene. Preferably, the terpolymer includes from about ~ 0 or
less to about 20 wt. % or more hexafluoropropylene, more preferably from
about 11, 12, 13, 14, 15, 16, 17, or 18 to about 19 wt.
hexafluoropropylene, and most preferably about 18.9 wt.
o hexafluoropropylene.
Suitable THV polymers that may be employed in the practice of the
present invention include DyneonT"" Fluorothermoplastics available from
Dyneon LLC of Oakdale MN. Particularly preferred is Dyneon THV Grade
E-15125 "O". This grade has a melting point of 164 C, a melt flow rate of
15. >200 (265 C/5Kg), a specific gravity of 2.004 g/cm3, a tensile at break of
9.9 Mpa, and an elongation at break of 273 %. Other DyneonT""
fluorothermoplastic terpolymers include DyneonT"' THV 220, DyneonT""
THV 410, DyneonT"" THV 500, and DyneonT"~ THV X 610. The DyneonT"~
fluorothermoplastic terpolymers with higher melt flow rates are preferred
2o due to the ease with which satisfactory melt blown webs may be , _
prepared. The DyneonT"" fluorothermoplastic terpolymers with higher
numbers, e.g., THV 410, THV 500, and THV X 610, have progressively
higher percentages of tetrafluoroethylene. The higher the percentage of
tetrafluoroethylene, the tougher it is to melt the polymer hence making it
25 more difficult to melt blow.
The melt-blown fibers may include a single THV polymer or
combinations or blends of a THV polymer and one or more additional
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polymers. Alternatively (or additionally) discrete fibers formed of such
other polymers may be melt-blown concurrently with or subsequently to
the THV polymer so as to form a non-woven fibrous blend of THV and
such other polymers or fibrous layers formed predominantly of the THV
~ and such other polymers, respectively.
The additional polymers that may be employed in the practice of
the present invention include another fluorothermoplastic terpolymer, or
any other suitable polymer. Suitable polymers may include any suitable
homopolymer, copolymer, or terpolymer, including but not limited to
o polysulfone, polyethersulfone (PES), polyarylsulfone, fluorinated polymers
such as polyvinylidene fluoride (PVDF), polyolefins including polyethylene
and polypropylene, polytetrafluoroethylene (PTFE or TefIonT~~),
poly(tetrafluoroethylene-co-ethylene) (ECTFE or Halarr~~), acrylic
copolymers, polyamides or nylons, polyesters, polyurethanes,
polycarbonates, polystyrenes, polyethylene-polyvinyl chloride,
polyacrylonitrile, cellulose, and mixtures or combinations thereof.
The fluorothermoplastic terpolymer may be subjected to a
pretreatment, for example grafting or crosslinking, prior to melt blowing, or
may be subjected to a post-treatment, for example grafting or crosslinking,
after a melt blown web is made. There is no particular molecular weight
range limitation for the THV polymer. Likewise, there is no particular
limitation on the weight ratio of the tetrafluoroethylene,
hexafluoropropylene, and vinylidene fluoride monomers in the THV
polymer. Various molecular weights and/or different monomer ratios may
be preferred for melt blown webs to be used for certain applications.
The materials of the present invention are melt-blown non-woven
structures. In this regard, the preferred THV polymers may be melt-blown
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using virtually any conventional melt-blowing technique to make sheets,
tubes, cylinders and like structural forms for a variety of end use
applications. Thus, for example, the materials of the present invention are
most preferably a mass of melt-blown non-woven fibers, which fibers as
noted above are most preferably formed of a THV polymer. Non-woven
materials of the present invention may be made using conventional melt-
blowing techniques described more fully in U.S. Patents Nos. 3,776,796;
3,825,379; 3,904,798; 4,021,281; and 5,591,335.(the entire content of
each such cited patent being incorporated expressly hereinto by
o reference).
The diameters of the melt-blown THV fibers forming the non-woven
materials of the present invention are not critical. Thus, average fiber
diameters of less than 500 Nm, and preferably less than 100 pm, and
typically less than 50 Nm may be melt-blown if desired. Most preferably,
the fibers have an average diameter which is greater than about 1 pm,
and more preferably greater than about 5 pm.
Following production, the non-woven fabrics may be fashioned into
a variety of products, for example, garments (e.g., surgical or other similar
medical gowns, drapes and the like), bandages, and bulk airflow barrier
vents. Thus, the fabrics of this invention may be mated (e.g., by sewing,
gluing and the like) to one or more other woven, non-woven or knit fabric
structures to suit virtually any end use application where the non-wettable
and breathable properties of the fabric structures of this invention are
needed.
The present invention will be further understood from a review of
the following non-limiting Examples.
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III. Examples
A THV polymer (Grade E-15125 "O") obtained commercially from
Dyneon, LLC and having the following properties was employed in the
Examples:
THV Polymer Properties:
Form: Pellets
Melting range: 164°C - ASTM D4591 )
Melt Flow Index: >200 (265°Cl5 kg) - ASTM D1238
Specific Gravity: 2.004 g/cc - ASTM D792
Tensile _~ break: 9.9 Mpa (1,435 psi) - ASTM D638
(film)
Elongation C break: 273% - ASTM D638
Seven melt-blown fabric samples, identified below by Sample Nos.
1.1 through 1.7, were made using the process conditions in Table 1 A
using a melt-blowing die having a width of 152 mm and a die temperature
of 249°C.
Table 1 A
Sample Polymer Line Die to Air Air Temp,Die
No. Throughput, Speed, Coll. Pressure, C Pressure,
kg/hr m/min Distance,Kpa (1.52 Kpa
m mm air
gap, 60)
1.1 3.46 6.1 0.254 41.4 248 1159
1.2 3.90 6.1 0.356 13.8 256 1063
1.3 3.90 6.1 0.356 13.8 247 1132
1.4 3.90 3.96 0.356 13.8 248 1159
1.5 3.90 3.96 0.203 13.8 247 1311
1.6 5.40 3.35 0.203 13.8 239 2677
~1.7 ~ 5.40 3.35 0.203 27.6 243 2415
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Samples 1.1, 1.5, 1.6 and 1.7 were subjected to physical property
measurements. The results appear in Table 1 B below.
Table 1 B
Sample Na: Air Permeability,Basis Wt., Thickness, Avg, Fii
m31m2/min g/m mm a
Diameter,
~m
1.1 60.43 76.9 0.3556 8.05
1.5 98.35 93.1 0.4064 --
1.6 74.15 ~ 165.1 _ --
__~.- 0.6756
1.7 40.49 174.2 0.7620 __
******.~.k***
While the invention has been described in connection with what is
presently considered to be the most practical and preferred embodiment,
it is to be understood that the invention is not to be limited to the
disclosed
embodiment, but on the contrary, is intended to cover various.
1o modifications and equivalent arrangements included within the spirit and
scope of the appended claims.
