Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PEEL PACK PAPER
FIELD OF THE INVENTION
The field of the present invention is that of peel packs for use in the
automated
sterilization of, for example, hospital operating room instruments.
BACKGROUND OF THE INVENTION
Various medical instruments and supplies used in hospitals are subjected to
sterilization treatments such as, for example, steam sterilization) ethylene
oxide gas
sterilization, radiation sterilization, and dry-heating sterilization before
they are used in
medical treatments. In many instances) the non-sterile instruments andlor
supplies are
first packaged in what is conventionally called a "peel pack" and then the
pack and its
contents are subjected to sterilizing conditions. One of the major functions
of the peel
pack is to maintain the supplieslinstruments in a sterile condition until such
time as the
pack is opened and the supplies/instruments are utilized.
Typically) there are at least three elements to a peel pack. First) the pack
includes
a layer of a material which is impervious to pathogens. Exemplary materials of
this sort
are poiyoiefinic films or plastics. In some instances the films or plastic
materials are
molded to provide a chamber for retention of the supplies/instruments. The
second
element of a peel pack is an adhesive which is usually applied around the
outer periphery
of the pathogen impervious layer. Lastly, peel packs include a layer of a
material
{typically paper) which allows entry of sterilizing gases into the chamber
during a
sterilization procedure but prohibits entry of pathogens into the chamber
thereafter. This
peel pack paper is joined to the pathogen impervious material by the adhesive.
The
juncture of the peel pack paper with the pathogen impervious material forms
the "peel
pack". It should be noted that, in some instances, the peel pack paper can be
heat sealed
directly onto the pathogenic impervious material. These situations arise where
the
pathogenic impervious material has been especially formulated to form a heat
seal with a
peel pack paper. In such instances) naturally, the necessity of an adhesive is
eliminated.
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Conventionally, peel packs are opened by peeling the peel pack paper away from
the pathogen impervious material so as to allow access to the chamber and the
supplies/instruments contained therein.
One of the problems with which those of skill in the art have been confronted
is
that peel packs do not always easily and cleanly open. That is, the peel pack
paper may
resist separation from the adhesive/pathogen impervious material. In such
situations, the
peel pack paper may tear in a non-uniform, non-predictable manner. This can
lead to two
undesirable results. First, the peel pack paper may separate into a number of
smaller
parts which may then be inadvertently strewn about the operating field.
Secondly) the
paper's resistance to uniform tearing/separation can be a general aggravant to
operating
room personnel. In those instances where an adhesive is utilized to join the
peel pack
paper to the pathogenic impervious material) another potentially complicating
factor is that
the act of sterilizing the peel pack and contents can) in some instances, lead
to an
increase in the bond strength of the bond formed by the adhesive between the
peel pack
paper and the pathogen impervious film or molded plastic material. See) for
example,
U.S. patent number 3,995,739 to Tasch et al. which issued on December 7, 1976.
Generally speaking, to overcome these problems a desirable peel pack paper
will
have to be strong enough to resist internal tearing up to and exceeding the
amount of
force that is necessary to promote separation of the peel pack paper from the
adhesive/pathogen impervious material. That is, if the strength of the
juncture/bond
between the peel pack paper and the pathogen impervious material exceeds the
strength
of the peel pack paper) the paper will fail before separation with
unsatisfactory results.
Accordingly, peel pack papers having sufficient strength to withstand the
demands placed
upon them during the opening or peeling operation are highly desirable.
Those of skill in the art have sought to strengthen peel pack papers by
incorporating strengthening or reinforcing fibers into the paper. While
incorporation of
such reinforcing fibers did improve the strength of the resulting peel pack
paper, it was
found that the porosity of the strengthened peel pack paper had been increased
with a
subsequent and adverse decrease in the pathogenic barrier properties of the
resulting
strengthened paper. In other words, the peel pack paper was now of a
satisfactory
strength to peel (open) with reliability and consistency, but the paper no
longer performed
its primary function of maintaining a sterile filed within the peel pack.
Naturally, this result
is undesirable.
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OBJECTS OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a peel
pack paper which provides a satisfactory barrier to pathogens.
Another object of the present invention is to provide a peel pack paper which
is of a satisfactory strength so that it easily delaminates from the other
portions of a
peel pack. That is, so that the peel pack can be easily and satisfactorily
opened.
Yet a further object of the present invention is to provide a peel pack which
has the peel pack paper incorporated therein.
Still another general object of the present invention is to provide a process
for
forming such a peel pack paper and for forming a peel pack having the peel
pack
paper incorporated therein.
Still further objects and the broad scope of applicability of the present
invention will become apparent to those of skill in the art from the details
given
hereinafter. However, it should be understood that the detailed description of
the
presently preferred embodiment of the present invention is given only by way
of
illustration because various changes and modifications well within the spirit
and scope
of the invention will become apparent to those of skill in the art in view of
the following
description.
DEFINITIONS
As used herein, the term "reinforcing fibers" means fibers which are
conventionally
incorporated into cellulose-based papers to impart higher strength and/or
higher
endurance and/or increased resistance to, for example, heat, light, insects
and/or
bacteria. Examples of such fibers are polyester fibers, cotton fibers, rayon
fibers and
nylon fibers. Reinforcing fibers typically have an average fiber length of
less than 25.4
millimeters. For example, in some cases, about 0.5 inch {'f 2.7 millimeters)
and, in other
instances, about 0.25 inch {6.3 millimeters).
As used herein, the term "hardwood fibers" means fibers obtained from an
angiosperm. Angiosperms typically possess true vessels in the structure of the
wood.
As used herein, the term "softwood fibers" means fibers obtained from a
gymnosperm. Gymnosperms typically lack true vessels in the structure of the
wood.
As used herein, the term "eucalyptus fibers" means any fibers obtained from a
tree
which is a member of the genus "eucalyptus". These trees are typically tall,
aromatic
evergreen trees of the myrtle family which bear pendent leaves and umbels of
white, red,
or pink flowers. Eucalyptus trees naturally occur in Austrafia,Tasmania and
South
America. However) they have been introduced into other geographic areas such
as, for
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example, the United States) by man. The fibers typically have an average fiber
length of
from 0.55 to 0.65 millimeters (mm). For example, an average fiber length of
about 0.59
millimeters.
As used herein, the term "dielectric material" refers to any material, such as
a
polymer, which is an electrical insulator or in which an electric field can be
sustained with
a minimum dissipation of power. A solid material is a dielectric if its
valence band is full
and is separated from the conduction band by at least 3 eV. This definition is
adopted
from the McGrav~i-Hill Encyclopedia of Science & Technoio~w, 7th Edition,
Copyright 1992.
As used herein, the term "high density polyethylene" refers to any
polyethylene
material having a density measured in accordance with ASTM D 2839-93 in the
range of
from about 0.941 to about 0.959 grams per cubic centimeter.
Unless otherwise stated, Gurley porosity is to be determined in accordance
with
TAPPI test method T460-1988.
Unless otherwise stated, Elmendorf tear values are to be determined in
accordance with TAPPI test method T414-1982.
Unless otherwise stated, the effectiveness of a peel pack paper in resisting
pathogenic penetration is measured by a particulate filtration test
conventionally known as
the NaCI Filter Efficiency Test (hereinafter the NaCI Test). The NaCI Test is
conducted
using an automatic filter tester, CertitestTM Model # 8110, which is available
from TSI
Inc., St. Paul, MN. The particulate filtration efficiency of the tested
material is reported as
percent (%) penetration. The percent penetration is calculated by the
following formula:
100 X (downstream particles/upstream particles). The upstream particles
represent the
total quantity of approximately 0.1 micron NaCI aerosol particles which are
introduced into
the tester. The downstream particles are those particles which have been
introduced into
the tester and which have passed through the bulk of the test material.
Therefore, the
percent penetration value reported is a percentage of the total quantity of
particles
introduced into a controlled air flow within the tester which pass through the
test material.
In all cases the face velocity was 31 liters per minute. Unless otherwise
stated percent
penetration values are the average of three such tests.
Unless otherwise stated, delamination resistance values are to be determined
by
conducting a "Delamination Test". The Delamination Test is conducted as
follows. One
inch wide (cross-machine direction) by eight inch long (machine direction)
samples of
material to be tested are obtained. Starting at one end) seven inches of each
sample is
covered on both sides with black pressure tape (#A963-02-5 from Ideal Tape Co.
of
Lowell, Mass.). The taped sample is placed on a hot plate (Thermolyne Model SP-
A1025B from the Sybron Corp. of Dubuque) Iowa) which is maintained at a
temperature in
the range from 300 degrees F. to 325 degrees F. for 20 seconds. While on the
hot plate,
six inches of the sample, starting at the taped end, is subjected to pressure
from a five (5)
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pound steel weight measuring 6 inches in length by 1.5 inches in width. Thus,
the first six
inches of sample are subjected to pressure and are taped, the next one inch of
sample is
just taped and the last inch of sample is not taped or subjected to pressure.
After its
removal from the hot plate, each sample is allowed to cool for at least 30
minutes. The
sample is then cut, lengthwise, into 15mm wide strips using a JDC Precision
Sample
Cutter (Thwing-Albert Instrument Co. of Philadelphia, Pa, Model JDC 15M-10).
Thereafter, the one inch long portion of the tape that was not subjected to
pressure while
the sample was on the hot plate is peeled back on both sides of the sample.
Each peeled
back portion is placed in the jaws of an Instron Model 5500R instrument
available from the
Instron, Inc. of Canton) Mass. and the tape is pulled away from the sample.
The gauge
length is one inch and the crosshead speed is 300 millimeters per minute
(300mm/min).
As used herein, the terminology "electret treatment" or "electreting" refers
to any
process which places a charge in and/or on a dielectric material. One
exemplary process
for placing a charge on a dielectric material involves the application of a DC
corona
discharge to the material. An exemplary conventional method of this type is
described in
detail in U.S. patent number 5,401,446 to Tsai et al. entitled "Method and
Apparatus for
the Electrostatic Charging of a Web or Film" which issued on March 28, 1995.
The
entirety of this patent is hereby incorporated by reference.
As used herein, the term "Kraft" pulp or fibers refers to conventional Kraft
pulping
processes. This alkaline pulping process typically uses a combination of
sodium
hydroxide and sodium sulfide. The term Kraft is derived from the German word
meaning
"strong" because Kraft pulp is amongst the strongest chemical pulps. Those of
skill in the
art utilize the term "sulfate pulping" alternatively or as a synonym for Kraft
pulping. The
"Handbook For Puip & Paper Technologists" by Gary A. Smook (Angus Wilde
Publications), copyright 1992, [ISBN 0-9694628-1-6] gives a detailed
description of
conventional Kraft pulping techniques at chapter 7, pages 74-83. The entirety
of this book
is hereby incorporated by reference.
As used herein, any given range is intended to include any and all lesser
included
ranges. For example, a range of from 45-90 would also include 50-90; 45-30; 46-
89; etc.
SUMMARY OF THE 1NVENT10N
In response to the foregoing problems and difficulties encountered by those of
skill
in the art, a peel pack paper has been discovered which can be utilized in
making
improved peel packs for use in automatic sterilization processes. The peel
pack paper
has a Gurley porosity of greater than 20 seconds/sheet. The paper includes (a)
from
about 45 to about 65%, by weight, of substantially fully bleached eucalyptus
Kraft pulp
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fibers; (b) from about 10 to about 45%, by weight) of a blend of substantially
fully bleached
softwood Kraft pulp fibers and substantially fully bleached hardwood Kraft
pulp fibers
wherein the softwood Kraft pulp fibers comprise at least 90%) by weight, of
the blend; and
(c) from about 10 to about 30%, by weight, of reinforcing fibers. Importantly,
substantially
all of the fibers of the paper are coated with a dielectric material with the
coating having
an average thickness of less than 1 micron.
In some embodiments, the softwood fibers may be fir fibers. For example, the
softwood fibers may be selected from the group including spruce fibers, pine
fibers and
cedar fibers.
In some embodiments, the hardwood fibers may be selected from the group
including aspen fibers) maple fibers ash fibers, poplar fibers and beech
fibers. Many
combinations of softwood and hardwood fibers are possible.
A wide variety of physical characteristics and numerous combinations and
permutations thereof are possible with the peel pack paper of the present
invention. For
example, the paper may have a Gurley porosity of greater than 25 seconds/sheet
andlor a
delamination resistance of at least 200 grams/15mm. In some instances the peel
pack
paper may have a delamination resistance of at least-900 grams/15mm.
In some embodiments the peel pack paper may have an Elmendorf tear of greater
than 145 grams. For example, the peel pack paper may have an Elmendorf tear of
greater than 180 grams.
One of the important aspects of the present invention is that the peel pack
paper
provides a satisfactory barrier to pathogens. This barrier capability is
evidenced by the
paper having an average 0.1 micron sodium chloride particulate penetration of
less than 5
percent. For example, the paper may have an average 0.1 micron sodium chloride
particulate penetration of less than 2 percent.
In some embodiments, the reinforcing fibers are selected from the group of
polyester fibers, nylon fibers, cotton fibers and rayon fibers.
in some embodiments the dielectric coating is selected from the group of
polyolefins and polyolefin copolymers. For example,the dielectric material is
selected
from the group of high density polyethylenes, natural rubbers, synthetic
rubbers and
ethylene acrylic acid copolymers.
In some embodiments, the peel pack paper includes: (a} from about 50 to about
60%, by weight, of eucalyptus fibers; (b) from about 10 to about 30%, by
weight, of the
blend of northern softwood and hardwood pulp fibers; and (c) from about 20 to
about
30%, by weight, of the reinforcing fibers. For example, the peel pack paper
can include:
(a) about 55%, by weight, of eucalyptus fibers; (b) about 20%, by weight, of
the blend of
northern softwood and hardwood pulp fibers; and (c) about 25%) by weight) of
the
reinforcing fibers.
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In some desirable embodiments) the coated peel pack paper may be subjected
electreting. For example, to treatment with a DC corona charge apparatus(DC
corona
discharge treatment). The present invention is also directed toward a method
for
forming the peel pack paper where the method includes the steps of: (a)
providing a paper
comprising ( 1 ) from about 45 to about 65°l°, by weight, of
substantially fully bleached
eucalyptus Kraft pulp fibers; {2) from about 10 to about 45%, by weight) of a
blend of
substantially fully bleached softwood Kraft pulp fibers and substantially
fully bleached
hardwood Kraft pulp fibers wherein the softwood fibers comprise at least 90%,
by weight,
of the blend; and (3) from about 10 to about 30%, by weight, of reinforcing
fibers; and (b)
coating substantially all of the fibers of the paper with a dielectric
material wherein the
average thickness of the coating is less than 1 micron.
In some embodiments, the dielectric coating may be applied by an emulsion
coating process. In further embodiments the method may include the additional
step of
electreting the emulsion coated paper. An exemplary method of electreting the
emulsion
coated paper is to apply a DC corona charge to the coated fibers.
DETAILED DESCRIPTION OF THE INVENTION
Turning now to the drawings where like numerals represent like or equivalent
structure or process steps, it can be seen that Fig.1 is a schematic
representation of a
process for forming a peel pack in accordance with the present invention.
Fig. 1 reveals that the first step in the process, step 10, is to form a
liquid
dispersion, desirably from water, containing the desired cellulosic component
fibers.
Thereafter, as step 20 illustrated, a reinforcing fiber material is added to
the dispersion.
At this point) the celluiosic fibrous portion of the dispersion will include
(a) from about 45
to about 65%, by weight, of substantially fully bleached eucalyptus Kraft pulp
fibers and
(b) from about 10 to about 45%, by weight, of a blend of substantially fully
bleached
softwood Kraft pulp fibers and substantially fully bleached hardwood Kraft
pulp fibers
wherein the softwood Kraft pulp fibers comprise at least 90%, by weight, of
the blend and
(c) from about 10 to about 30°l°, by weight, of reinforcing
fibers. For example, the
celiulosic portion of the dispersion may include (a) from about 50 to about
fi0%, by weight,
of eucalyptus fibers; (b) from about 10 to about 30%, by weight) of the blend
of softwood
and hardwood pulp fibers and (c) from about 20 to about 30%, by weight, of the
reinforcing fibers. More particularly, the cellulosic portion of the
dispersion may include:
(a) about 55%, by weight, of eucalyptus fibers; (b) about 20%, by weight, of
the blend of
softwood and pulp fibers and (c) about 25%, by weight; of the reinforcing
fibers. The
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amount of water or other appropriate liquid in the dispersion will vary with
the amount and
type of cellulosic fibers as is well known to those of skill in the paper
making art.
While any eucalyptus pulp fibers may be utilized; one desirable source of such
fibers is Aracruz Cellulose SA, Rio De Janerio, Brazil. Eucalyptus base sheet
may be
obtained from this source under the trade designation "Aracruz Eucalyptus".
Aracruz
Eucalyptus is fully bleached Brazilian hardwood Kraft pulp (100%) with an
average fiber
length of about 0.59 millimeters.
In some embodiments) the softwood fibers may be fir fibers. For example, the
softwood fibers may be selected from the group including spruce fibers, pine
fibers and
- cedar fibers.
in some embodiments, the hardwood fibers may be selected from the group
including aspen fibers, maple fibers ash fibers, poplar fibers and beech
fibers. Many
combinations of softwood and hardwood fibers are possible.
One desirable blend of softwood and hardwood fibers can be obtained from the
Kimberly-Clark Corporation of Dallas, Texas under the trade designation
"Longloc-19"
(LL-19). LL-19 is fully bleached northern softwood Kraft pulp (approximately
95%, by
weight spruce) with a trace amount of fully bleached northern hardwood (mainly
aspen).
The average fiber length of LL-19 is approximately 1.07 millimeters.
In some embodiments, the reinforcing fibers may be selected from the group of
polyester fibers, nylon fibers, cotton fibers and rayon fibers.
Fig. 1, at step 30) reveals that, after the reinforcing fibers and the
cellulosic paper
making fibers have been satisfactorily combined, the dispersion is formed into
a paper
product in any of a number of conventional and well known paper forming
methods.
Step 40 illustrates that, after the paper has been formed, it is coated with a
dielectric material. In some embodiments, the coating can be accomplished
through use
of conventional emulsion coating techniques. For example, the emulsion coating
can be
accomplished by passing the paper through a nip formed by nip rollers with the
nip being
flooded by the dielectric emulsion. Those of skill in the art will readily
recognize that the
amount of dielectric emulsion applied to the paper can be easily and readily
varied by
condensing or dilution of the emulsion. Additionally, this amount can be
easily increased
by passing the paper through the flooded nip two or more times since, with
each passage,
the paper tends to pick up more dielectric material. The amount of material
picked up and
retained by the peel pack paper (add-on) desirably is within the range of 25-
200%, by
weight, of the paper. For example the amount of dielectric add-on may vary
within the
range of from 50-150%, by weight) of the paper. More particularly, the amount
of
dielectric add-on may vary within the range of from 50-100%, by weight, of the
paper.
The emulsion coating processes is carried out, in conventional fashion, so
that
substantially all of the fibers of the paper are coated with the dielectric
material with the
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coating having an average thickness of less than 1 micron. For example, the
coating may
have an average thickness of less than 0.5 microns.
In some embodiments the dielectric coating is selected from the group of
polyolefins and polyolefin copolymers. For example, the dielectric material is
selected
from the group of high density poiyethyienes, natural rubbers, synthetic
rubbers and
ethylene acrylic acid copolymers. One particular dielectric emulsion coating
may be
obtained under the trade designation Michem Emulsion 93135 (Michelman, Inc.
Cincinnati
Ohio). Michelman information states that Michem 93135 is a high density
polyethylene
emulsion which is a tan colored translucent liquid, having a pH of 10.0 - 11.5
and a
specific gravity of 0.99 - 1.01. Another dielectric coating material may also
be obtained
from Michelman, Inc. under the trade designation Michem Prime 4983. Michelman
information states that Michem 4983 is a dispersion of ethylene acrylic acid
which is a
translucent liquid having a pH of 8.3 - 10.
Fig. 1, at optional step 45, further illustrates that, in some desirable
embodiments,
the coated peel pack paper may desirably be subjected to electreting in order
to instill a
charge on the dielectric coating. Electreting may be accomplished by, for
example,
application of a DC corona charge (DC corona discharge treatment) in a
conventional
manner. The method described in U.S. patent number 5,401,446 is a conventional
method for DC corona discharge treatment. The contents of this patent are
hereby
incorporated by reference.
The invention will now be described in mare detail with reference to specific
examples and embodiments. However, in no way should the invention be taken to
be
limited to the specific examples disclosed 'and discussed below.
COMPARATIVE EXAMPLE A
This example was prepared in order to establish a baseline for conventional
peel
pack paper manufactured in a conventional matter from eucalyptus. pulp fibers
and a
blend of substantially fully bleached, northern softwood Kraft pulp with a
trace amount of
substantially fully bleached northern hardwood pulp.
Approximately 75%) by weight, of eucalyptus pulp fibers (Aracruz Eucalyptus
Sheet
from Aracruz Cellulose SA, Rio De Janeiro, Brazil) was combined with about
25%, by
weight of a blend of substantially fully bleached northern softwood Kraft pulp
fibers (about
95%, by weight, spruce) with a trace of substantially fully bleached northern
hardwood
(mainly aspen) pulp fibers (Kimberly-Clark Corporation Longloc 19 sheet) in a
Valley
Beater (Valley Laboratory Equipment Serial # 109-F-1461, V5-04649, Voith Inc.,
Appfeton,
WL). The Beater was run for approximately one (1 ) minute with the roll off,
then for about
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five (5) minutes with the roll on. Thereafter, the Beater was run for an
additional five (5)
minutes with a 12.3 pound weight on the bed plate.
At this point, the pulp slurry was diluted with water at least ten fold and
stirred with a
mixer (Model 1024 Faucett Co., RichField, OH.) to obtain a good dispersion.
Seven hundred {700) milliliters of the dispersion was then transferred to a
Hand
Sheet Mold and Wet Press (Williams Apparatus Co., Watertown, NY). A sheet of
paper
was formed in the press unit. The sheet was then pressed in a wet press at 200
pounds
per square inch (psi) for five (5) minutes to remove water. The sheet was then
dried on a
drum which consists of a steam heated (about 7 psi steam pressure) Teflon
cover drum
which has a felt sheet press cloth. The thus formed paper was then conditioned
for about
twenty four (24) hours at 73.4 degrees F. ( 23 degrees C.) and 50% relative
humidity
before measuring its properties. The properties of this conventional peel pack
paper are
reported in Table I under "A".
COMPARATIVE EXAMPLE B
Comparative Example A was repeated with the exception that after the 700
milliliters
of dispersion had been transferred to the Hand Sheet Mold and Wet Press,
polyester
(PET) reinforcing fibers having a denier of three and a length of about 0.25
inch (Mini
Fiber, Inc. of Johnson City, TN.) were added until the composition of the
dispersion was
56.25%, by weight, eucalyptus, 18,75%) by weight, LL-19 and 25%, by weight,
PET. The
properties of this reinforced conventional peel pack paper are reported under
"B" in Table
EXAMPLE 1
Comparative Example B was repeated with the exception that after the peel pack
paper had been formed) the paper was emulsion coated with a dielectric
polyethylene
(Michem 93135). The emulsion was coated onto the peel pack paper by flooding a
nip
formed by two nip rollers and passing the peel pack paper through the flooded
nip. fn this
example one of the nip rolls was hard rubber and the other was steel. The
amount of
dielectric material coated onto the peel pack paper is measured as a percent
of the dry
weight of the paper. That is, the paper is weighed before its emulsion coating
and after
the coating. The percent add-on is the weight of the amount of dielectric
material added to
the paper divided by the uncoated weight of the paper. Those of skill in the
art will
recognize that the amount of add-on can be varied by (a) condensing or
diluting the
emulsion and/or (b) passing the paper through the flooded nip more than one
time. In this
example the paper was passed through the flooded nip once to achieve a 63%, by
weight)
to
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add-on of dielectric polyethylene. Percent add on in all cases is determined
from the
formula:
coated weight - uncoated weight x 100 = % add on
uncoated weight
EXAMPLE 2
Example 1 was repeated with the exception that the paper was passed through
the
flooded nip twice to achieve a 99%) by weight, add-on of dielectric
polyethylene.
EXAMPLE 3
Example 2 was repeated with the exception that a different dielectric
material, a
dispersion of ethylene acrylic acid was utilized. In this example the
dielectric ethylene
acrylic acid used was Michem 4983. The paper was passed through the flooded
nip twice
to achieve a 80%, by weight, add-on of dielectric ethylene acrylic acid.
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TABLE 1
PHYSICAL PROPERTIES OF SHEETS
TEST METHOD A B 1 2 3 TAPPI TEST
Basis Weight 23.69 23.86 39.63 47.52 43.16 T412-1983
(Ib/rm)
Caliper 8.36 11.96 11.44 11.49 12.6 T411-1984
Dry Tensile 1.996 1.143 2.55 2.663 14.473 T494-1981
(kg/15 mm)
Dry Stretch (%) 0.989 0.95 1.049 1.217 8.983 T494-1981
Elmendorf Tear 41 60 140 148 185 T414-1982
Delamination 31 26 160 242 916 See definition
(grams)
Sheffield Smoothness375 >400 >400 >400 >400 T538-1982
Gurley 0.75 0.23 2.12 20.85 27.9 T460-1988
Porosity (1 sheet)
Opacity TAPPI 90 86 81 84 75 T425-1986
A. 75% Eucalyptus, 25% LL-19.
B. 56.25% Eucalyptus, 18.75% LL-19, 25% PET.
1. Same as B coated with 63% Michem Emulsion 93135 (1 pass).
2. Same as B coated with 99°Jo Michem Emulsion 93135 (2 passes).
3. Same as B coated with 80% Michem Prime 4983 (2 passes).
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Table I demonstrates that the strength of the peel pack paper having the
reinforcing
fibers (Comparative Example B) improved, as evidenced by the increased
Elmendorf Tear
value as compared to the non-reinforced peel pack paper (Comparative Example
A).
However, and as has been previously stated, the addition of such reinforcing
fibers
resulted in a deterioration of the pathogenic barrier properties of the peel
pack paper as
evidenced by the decreased Gurley Porosity of Comparative Example B as
compared to
Comparative Example A.
In stark contrast, the Example 1 peel pack paper has over three times the
strength
of Comparative Example A and over twice that of Comparative Example B (per
Elmendorf
values) and a Gurley porosity increase of almost three times that of
Comparative Example
A and about nine times that of Comparative Example B. Substantially equivalent
or even
superior improvement is noted in Examples 2 and 3 as compared to Comparative
Examples A and B. Further evidence of the enhancement in strength of Example
1, 2 and
3 as compared to the Comparative Examples, can be noted by comparing the
extraordinary improvement in deiamination resistance of the Examples.
In summary, the peel pack papers of Examples 1, 2 and 3 have clearly superior
strength and pathogenic penetration resistance as compared to Comparative
Examples A
and B.
ELECTRET TREATMENT EXAMPLES
Samples of each of the peel pack papers were subjected to DC corona discharge
treatment. The corona discharge was produced by using a Model No. PIN 25A -
120 volt,
50I60 Hz reversible polarity power unit (Simco Corp., Hatfield, PA.), which
was connected
to a RC-3 Charge Master charge bar (Simco Corp.), and a Model No. P16v 120
volt,. 25 A
50l60 Hz power unit (Simco Corp.) which was connected to a solid, three inch
diameter,
aluminum roller. The corona discharge environment was 72.8 degrees F. and 70%
relative humidity. As described in U.S. patent no 5,401,446, two sets of
charge
bars/rollers were used. The voltage applied to the first charge baNroller set
was 20 Kv/0.0
Kv, respectively. The voltage applied to the second charge bar/roller set was
12 Kv/0.0
Kv, respectively.
The resistance to pathogenic penetration as indicated by NaCI particulate
testing
was determined for samples of each material both before and after a charge was
instilled
upon the dielectric material by electreting the material through application
of DC corona
discharge treatment. The results of these test are reported in Table 2.
13
CA 02271389 1999-OS-11
WO 98/249?0 _ _ PCT/US97I22363
TABLE 2
FILTRATION TESTING
(TSI, 0.1 micron
NaCI)
Sample Saturant Electret 0.1 micron NaCI
%Pick-Up) Penetration*
A None No 17.67
A None Yes 14.00
B None No 55.70
B None Yes 38.70
1 63% Michem No 25.7
93135
1 63% Michem Yes 24.70
93135
2 99% Michem No 1.84
93135
2 99% Michem Yes 1.59
93135
3 80% Michem No 2.55
4983
3 80% Michem Yes 1.85
4983
* - Average of three
samples
Table 2 demonstrates
that even further
improvement in resistance
to pathogenic
penetration is provided
by application of
an electret treatment
to the dielectric
emulsion
coated peel pack papers.
14
CA 02271389 1999-05-11
WO 98/24970 PCT/US97/22363
FORMATION OF PEEL PACKS
In order to demonstrate the efficacy of the peel pack paper of the present
invention,
peel packs were formed in a conventional manner utilizing the present peel
pack paper.
fn particular, pee! packs of approximately 23 centimeters by 14 centimeters in
size were
made from the peel pack paper of Example 3. The clear polyethylene portion of
a Medi-
Plus Self-Seal Pouch (Medi Plus Laboratories, Hargo Health Care Packaging,
Chicago,
Illinois) was used for the pathogenic impervious material.
Prior to formation of the peel packs, electron microscopy was conducted on the
peel pack paper and the thickness of the polyethylene dielectric coating was
found to be
less than 0.5 microns. The eVectron microscopy was accomplished by
cryomicrotoming
the peel pack paper samples using a Reichert-Juung Ultra cryomicrotome at -110
degrees
C. The samples were mounted on 600 mesh grids using a Gatan cold transfer
stage. A
Jeo1 2000fx transmission electron microscope was used for the observations.
The
accelerating voltage was 200Kv with a 10 micron condenser aperture and a
condenser
spot size of 8. A low dose MDD system was used to take the micrographs at very
fast
exposure speeds of about 0.3 seconds. This reduced the electron beam damage
and
overall_exposure of the samples to the electron beam. The samples were
observed at
various magnifications from 1000x to 20,000x.
The peel packs were formed by heat sealing the peel pack paper to the clear
polyethylene with an indicator strip being located inside the thus formed peel
pack.
Five (5) packs with indicator strips for steam sterilization (Tower Steam
Indicator
Strips, Baxter Health Care Corporation, Deerfield, Illinois) were steam
sterilized in a
conventional manner in an Amsco 2021 Gravity Sterilizer (American Sterilizer
Co, Erie,
PA.). In all packs the indicator turned from white to black indicating that
sterilization had
taken place.
An additional five (5) packs with indicator strips for peroxide plasma
sterilization
(Sterrad Chemical Strips, Code 14100 from Advanced Sterilization Products,
Arlington,
Texas) were peroxide plasma sterilized in a conventional manner in a Sterrad
Plasma
Sterilizer Model 100, from Advanced Sterilization Products, Irvine,
California. Hydrogen
peroxide was used as the chemical precursor of the active species in the
plasma. In all
packs the indicator turned from red to yellow indicating that sterilization
had taken place.
Lastly, in order to determine whether the peel pack paper of the present
invention
could adversely affect the plasma sterilization apparatus, a sample size as
large as 5,000
square centimeters was run without shutdown of the unit.
While the invention has been described in detail with respect to specific
preferred
embodiments thereof, it will be appreciated that those skilled in the art,
upon attaining an
CA 02271389 1999-OS-11
W0:98/24970 PCT/US97/22363
understanding of the foregoing, may readily conceive of alterations to and
variations of the
preferred embodiments. Such alterations and variations are believed to fall
within the
scope and spirit of the invention and the appended claims.
16
