U.S. patent application number 16/853305 was filed with the patent office on 2020-10-29 for nonwoven sheets comprising surface enhanced pulp fibers, surgical gowns and surgical drapes incorporating such nonwoven sheets, and methods of making the same.
This patent application is currently assigned to DOMTAR PAPER COMPANY, LLC. The applicant listed for this patent is DOMTAR PAPER COMPANY, LLC. Invention is credited to Harshad PANDE, Rod TIBBOLES.
Application Number | 20200340155 16/853305 |
Document ID | / |
Family ID | 1000004900166 |
Filed Date | 2020-10-29 |
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United States Patent
Application |
20200340155 |
Kind Code |
A1 |
PANDE; Harshad ; et
al. |
October 29, 2020 |
NONWOVEN SHEETS COMPRISING SURFACE ENHANCED PULP FIBERS, SURGICAL
GOWNS AND SURGICAL DRAPES INCORPORATING SUCH NONWOVEN SHEETS, AND
METHODS OF MAKING THE SAME
Abstract
A nonwoven sheet can comprise a plurality of cellulosic pulp
fibers and a plurality of synthetic polymeric fibers. The
cellulosic pulp fibers can include a plurality of cedar pulp fibers
that have a length weighted average fiber length of at least 1.0
millimeters (mm), optionally between 1.5 and 2.0 mm, and an average
hydrodynamic specific surface area of at least 4.5 square meters
per gram (m.sup.2/g), optionally at least 5 m.sup.2/g. The
cellulosic pulp fibers can also include a plurality of softwood
pulp fibers that, optionally, are NBSK pulp fibers and do not
include cedar pulp fibers. The synthetic polymeric fibers can
comprise polyester fibers.
Inventors: |
PANDE; Harshad;
(Pointe-Claire, CA) ; TIBBOLES; Rod; (Port Huron,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DOMTAR PAPER COMPANY, LLC |
Fort Mill |
SC |
US |
|
|
Assignee: |
DOMTAR PAPER COMPANY, LLC
Fort Mill
SC
|
Family ID: |
1000004900166 |
Appl. No.: |
16/853305 |
Filed: |
April 20, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62883223 |
Aug 6, 2019 |
|
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|
62840125 |
Apr 29, 2019 |
|
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62837431 |
Apr 23, 2019 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D10B 2201/01 20130101;
D04H 1/492 20130101; D10B 2331/04 20130101; D04H 1/26 20130101;
D04H 1/435 20130101; D10B 2501/04 20130101 |
International
Class: |
D04H 1/26 20060101
D04H001/26; D04H 1/435 20060101 D04H001/435; D04H 1/492 20060101
D04H001/492 |
Claims
1. A nonwoven sheet comprising: a plurality of cellulosic pulp
fibers comprising: a plurality of cedar pulp fibers that have a
length weighted average fiber length of at least 1.0 millimeters
(mm) and an average hydrodynamic specific surface area of at least
4.5 square meters per gram (m.sup.2/g); and a plurality of softwood
pulp fibers that do not include cedar pulp fibers; and a plurality
of synthetic polymeric fibers.
2. The nonwoven sheet of claim 1, wherein the softwood pulp fibers
are northern bleached softwood kraft (NBSK) pulp fibers.
3. The nonwoven sheet of claim 1, wherein by weight: between 1% and
20% of the cellulosic pulp fibers are the cedar pulp fibers; and
between 80% and 99% of the cellulosic pulp fibers are the softwood
pulp fibers.
4. The nonwoven sheet of claim 3, wherein the length weighted
average fiber length of the cedar pulp fibers is between 1.0 mm and
2.2 mm.
5. The nonwoven sheet of claim 4, wherein the length weighted
average fiber length of the cedar pulp fibers is between 1.5 mm and
2.0 mm.
6. The nonwoven sheet of claim 4, wherein the average hydrodynamic
specific surface area of the cedar pulp fibers is at least 5.0
m.sup.2/g.
7. The nonwoven sheet of claim 7, wherein the cedar pulp fibers
have a length weighted fines value that is less than or equal to
30%, when pulp fibers having a length of 0.20 mm or less are
classified as fines.
8. The nonwoven sheet of claim 8, wherein the nonwoven sheet is a
spunlace nonwoven.
9. A method of making a nonwoven sheet, the method comprising:
directing one or more jets of water onto a nonwoven precursor web
comprising a plurality of fibers, the fibers including: a plurality
of cellulosic pulp fibers that comprise: a plurality of cedar pulp
fibers that have a length weighted average fiber length of at least
1.0 millimeters (mm) and an average hydrodynamic specific surface
area of at least 4.5 square meters per gram (m.sup.2/g); and a
plurality of softwood pulp fibers that do not include cedar pulp
fibers; and a plurality of synthetic polymeric fibers; and drying
the nonwoven precursor web.
10. The method of claim 9, wherein the softwood pulp fibers are
northern bleached softwood kraft (NBSK) pulp fibers.
11. The method of claim 9, wherein by weight: between 1% and 20% of
the cellulosic pulp fibers are the cedar pulp fibers; and between
80% and 99% of the cellulosic pulp fibers are the softwood pulp
fibers.
12. The method of claim 11, wherein the length weighted average
fiber length of the cedar pulp fibers is between 1.5 mm and 2.0
mm.
13. The method of claim 9, wherein the average hydrodynamic
specific surface area of the cedar pulp fibers is at least 5.0
m.sup.2/g.
14. The method of claim 9, wherein the cedar pulp fibers have a
length weighted fines value that is less than or equal to 30%, when
pulp fibers having a length of 0.20 mm or less are classified as
fines.
15. The method of claim 9, comprising forming the nonwoven
precursor web at least by: depositing the synthetic polymeric
fibers onto a moving surface; and depositing a pulp sheet
comprising the cellulosic pulp fibers onto the synthetic polymeric
fibers.
16. The method of claim 9, wherein the length weighted average
fiber length of the cedar pulp fibers is between 1.5 mm and 2.0
mm.
17. The nonwoven sheet of claim 1, wherein the length weighted
average fiber length of the cedar pulp fibers is between 1.0 mm and
2.2 mm.
18. The nonwoven sheet of claim 1, wherein the average hydrodynamic
specific surface area of the cedar pulp fibers is at least 5.0
m.sup.2/g.
19. The nonwoven sheet of claim 1, wherein the cedar pulp fibers
have a length weighted fines value that is less than or equal to
30%, when pulp fibers having a length of 0.20 mm or less are
classified as fines.
20. The nonwoven sheet of claim 1, wherein the nonwoven sheet is a
spunlace nonwoven.
Description
CROSS-REFERENCED TO RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of U.S.
Provisional Application No. 62/837,431, filed Apr. 23, 2019, U.S.
Provisional Application No. 62/840,125, filed Apr. 29, 2019, and
U.S. Provisional Application No. 62/883,223, filed Aug. 6, 2019.
The contents of the foregoing applications are incorporated herein
by reference in their respective entireties.
FIELD OF INVENTION
[0002] The present invention relates generally to nonwoven sheets
and articles incorporating the same, and more particularly but
without limitation to nonwoven sheets comprising surface enhanced
pulp fibers.
BACKGROUND
[0003] Nonwoven sheets can comprise both cellulosic pulp fibers and
synthetic polymeric fibers. Such nonwovens are used in a wide
variety of applications, such as in medical and scientific apparel,
wipes, cloths, and the like. For some applications, such as
surgical gowns and surgical drapes, the nonwoven sheet preferably
has a high air permeability and drapability for comfort while
impeding the flow of liquids (e.g., bodily fluids) therethrough to
protect a wearer. The drapability and combination of air
permeability and liquid resistance that a nonwoven sheet can
achieve depends, at least in part, on the morphological
characteristics of the nonwoven's fibers.
[0004] Typically, cellulosic pulp fibers included in such nonwoven
sheets are not fibrillated or are lightly fibrillated (e.g., have
an average hydrodynamic specific surface area that is about 2
square meters per gram), at least in part because highly
fibrillated pulp fibers may comprise a large amount of fines. Fines
can be detrimental in the hydroentangling process used to make some
nonwovens (e.g., spunlace nonwovens) and can adversely affect
barrier properties; as such, highly fibrillated pulp fibers are
generally considered undesirable for such nonwovens. Additionally,
some fiber grades, such as northern bleached softwood kraft (NBSK)
pulp fibers, may provide poor drapability and thus are also
generally considered undesirable for these nonwovens. However,
pulps having non-fibrillated or lightly refined fibers that tend to
impart a more desirable drapability and/or combination of air
permeability and liquid resistance for a nonwoven sheet are
typically more expensive to produce and/or process, while fibers of
pulps that have lower production and/or processing costs may not
provide the same level of performance.
SUMMARY
[0005] As such, there is a need in the art for nonwoven sheets that
can provide a drapability and/or a combination of air permeability
and liquid resistance that is comparable to or better than that of
conventional nonwoven sheets incorporating fibers of
expensive-to-produce pulps, but that can be made at lower cost. The
present nonwoven sheets address this need in the art by
incorporating a combination of softwood pulp fibers, such as NBSK
pulp fibers, surface enhanced pulp fibers (SEPF) that are highly
fibrillated (e.g., have a length weighted average fiber length of
at least 1.0 mm and an average hydrodynamic specific surface area
of at least 4.5 m.sup.2/g, for cedar pulp fibers), and a plurality
of synthetic polymeric fibers, such as polyester fibers.
[0006] The SEPF can be cedar pulp fibers, which have a high
collapsibility that promotes air permeability and liquid
resistance. While cedar pulp fibers can be relatively expensive to
make, due at least in part to the unique fiber morphology of cedar
SEPF, a nonwoven sheet can achieve comparable air permeability and
liquid resistance using a combination of less expensive softwood
pulp fibers that do not include cedar pulp fibers (e.g., NBSK pulp
fibers) and cedar SEPF than an otherwise similar nonwoven sheet in
which all of the cellulosic pulp fibers are cedar pulp fibers. And,
unlike highly fibrillated pulp fibers made using conventional
processes, the SEPF can be made via a mechanical refining process
in which one or more refiners expend a large amount of energy,
utilize refiner elements having a fine bar pattern, and/or operate
at a low specific edge load (SEL), which can mitigate fine
production and thereby facilitate hydroentangling and promote
desirable nonwoven barrier properties. The combination of non-cedar
softwood pulp fibers and cedar SEPF can also yield better nonwoven
drapability than if the cellulosic pulp fibers only included the
non-cedar softwood pulp fibers. Such nonwoven sheets incorporating
SEPF may be particularly suitable for articles such as surgical
gowns and surgical drapes.
[0007] Some of the present nonwoven sheets comprise a plurality of
cellulosic pulp fibers and a plurality of synthetic polymeric
fibers. The cellulosic pulp fibers, in some nonwoven sheets,
comprise a plurality of cedar pulp fibers and a plurality of other
softwood pulp fibers. The other softwood pulp fibers, in some
nonwoven sheets, do not include cedar pulp fibers. In some nonwoven
sheets, at least 50% of the fibers of the nonwoven sheet, by
weight, are the cellulosic pulp fibers. The nonwoven sheet, in some
embodiments, is a spunlace nonwoven.
[0008] Some of the present methods of making a nonwoven sheet
comprise depositing a plurality of fibers onto a moving surface to
form a nonwoven web precursor. The fibers, in some methods, include
a plurality of cellulosic pulp fibers and a plurality of synthetic
polymeric fibers. The cellulosic pulp fibers, in some methods,
comprise a plurality of cedar pulp fibers and a plurality of
softwood pulp fibers that, optionally, do not include cedar pulp
fibers. In some methods, depositing the fibers is performed such
that at least 50% of the fibers of the nonwoven precursor web, by
weight, are the cellulosic pulp fibers. In some methods, depositing
the fibers comprises depositing the synthetic polymeric fibers onto
a moving surface and depositing a pulp sheet comprising the
cellulosic pulp fibers onto the synthetic polymeric fibers. Some
methods comprise directing one or more jets of water onto the
nonwoven precursor web and, optionally, drying the nonwoven
precursor web. In some methods, the nonwoven precursor web is
substantially free of water before the water jet(s) are directed
onto the nonwoven precursor web.
[0009] In some embodiments, the cedar pulp fibers have a length
weighted average fiber length of at least 1.0 millimeters (mm),
optionally between 1.0 mm and 2.2 mm or between 1.5 mm and 2.0 mm,
and an average hydrodynamic specific surface area of at least 4.5
square meters per gram (m.sup.2/g), optionally at least 5.0
m.sup.2/g. The cedar pulp fibers, in some embodiments, have a
length weighted fines value that is less than or equal to 30%, when
fibers having a length of 0.20 mm or less are classified as fines.
The softwood pulp fibers, in some embodiments, are northern
bleached softwood kraft (NBSK) pulp fibers. In some embodiments,
the synthetic polymeric fibers are polyester fibers. In some
embodiments, between 1% and 20%, optionally between 1% and 10%, of
the cellulosic pulp fibers, by weight, are the cedar pulp fibers
and/or between 80% and 99%, optionally between 90% and 99%, of the
cellulosic pulp fibers are the softwood pulp fibers.
[0010] Some of the present articles can comprise a surgical gown or
a surgical drape. Some surgical gowns comprise a torso portion, two
sleeves coupled to the torso portion, and a neck hole defined at an
upper end of the torso portion such that, when the surgical gown is
worn, the neck hole is configured to receive a neck of a wearer and
each of the sleeves is configured to receive a respective one of
the arms of the wearer. Some surgical gowns can comprise any of the
present nonwoven sheets.
[0011] The term "coupled" is defined as connected, although not
necessarily directly, and not necessarily mechanically; two items
that are "coupled" may be unitary with each other. The terms "a"
and "an" are defined as one or more unless this disclosure
explicitly requires otherwise. The term "substantially" is defined
as largely but not necessarily wholly what is specified--and
includes what is specified; e.g., a composition substantially free
of water can have no water or can have a low amount of water (e.g.,
less than 10% of the composition, by weight, can be water)--as
understood by a person of ordinary skill in the art. In any
disclosed embodiment, the terms "substantially" and "approximately"
may be substituted with "within [a percentage] of" what is
specified, where the percentage includes 0.1, 1, 5, and 10
percent.
[0012] The terms "comprise" and any form thereof such as
"comprises" and "comprising," "have" and any form thereof such as
"has" and "having," and "include" and any form thereof such as
"includes" and "including" are open-ended linking verbs. As a
result, a product or system that "comprises," "has," or "includes"
one or more elements possesses those one or more elements, but is
not limited to possessing only those elements. Likewise, a method
that "comprises," "has," or "includes" one or more steps possesses
those one or more steps, but is not limited to possessing only
those one or more steps.
[0013] Any embodiment of any of the products, systems, and methods
can consist of or consist essentially of--rather than
comprise/include/have--any of the described steps, elements, and/or
features. Thus, in any of the claims, the term "consisting of" or
"consisting essentially of" can be substituted for any of the
open-ended linking verbs recited above, in order to change the
scope of a given claim from what it would otherwise be using the
open-ended linking verb.
[0014] Further, a device or system that is configured in a certain
way is configured in at least that way, but it can also be
configured in other ways than those specifically described.
[0015] The feature or features of one embodiment may be applied to
other embodiments, even though not described or illustrated, unless
expressly prohibited by this disclosure or the nature of the
embodiments.
[0016] Some details associated with the embodiments described above
and others are described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The following drawings illustrate by way of example and not
limitation. For the sake of brevity and clarity, every feature of a
given structure is not always labeled in every figure in which that
structure appears. Identical reference numbers do not necessarily
indicate an identical structure. Rather, the same reference number
may be used to indicate a similar feature or a feature with similar
functionality, as may non-identical reference numbers.
[0018] FIG. 1A is a top view of an embodiment of the present
nonwoven sheets.
[0019] FIG. 1B is a sectional view of the nonwoven sheet of FIG. 1A
taken along line 1B-1B.
[0020] FIG. 2 is a schematic front view of a surgical gown that can
incorporate one or more of the present nonwoven sheets.
[0021] FIG. 3 is a schematic of a system that can be used to make
some of the present nonwoven sheets, the system including a
refining unit and a nonwoven manufacturing system.
[0022] FIG. 4A is a first embodiment of a refining unit that can be
used in the system of FIG. 3 to make SEPF, the refining unit
comprising a single mechanical refiner through which pulp fibers
can be recirculated.
[0023] FIG. 4B is a second embodiment of a refining unit that can
be used in the system of FIG. 3 to make SEPF, the refining unit
comprising a first mechanical refiner and a second mechanical
refiner through which pulp fibers can be recirculated.
[0024] FIG. 5 is a schematic, sectional view of refining elements
that can be used in each of the refiner(s) in the refining units of
FIGS. 4A and 4B, each of the refining elements having a plurality
of bars and grooves.
[0025] FIG. 6 is a schematic of a nonwoven manufacturing system
that can be used in the system of FIG. 3, the nonwoven
manufacturing system configured to hydroentangle softwood pulp
fibers, SEPF, and synthetic polymeric fibers.
DETAILED DESCRIPTION
[0026] Referring to FIGS. 1A and 1B, shown is an embodiment 10 of
the present nonwoven sheets. Nonwoven sheet 10 can have a
composition that facilitates air permeability and impedes the flow
of liquids through the sheet, rendering the sheet suitable for use
in, for example, surgical gowns and drapes. To illustrate, nonwoven
sheet 10 can comprise fibers 14 that include cellulosic pulp fibers
18 and synthetic fibers 22. Cellulosic pulp fibers 18 can comprise
softwood pulp fibers 26 (e.g., originating from spruce, pine, fir,
hemlock, redwood, and/or the like) and a plurality of highly
fibrillated pulp fibers 30, referred to herein as "surface enhanced
pulp fibers" (SEPF), that can be softwood pulp fibers, hardwood
pulp fibers (e.g., originating from oak, gum, maple, poplar,
Eucalyptus, aspen, birch, and/or the like), or non-wood pulp fibers
(e.g., originating from kenaf, hemp, straws, bagasse, and/or the
like). Preferably, SEPF 30 are softwood pulp fibers, particularly
cedar pulp fibers. Cedar pulp fibers can have high collapsibility,
which may promote air permeability while impeding the ingress of
liquids through the sheet.
[0027] Softwood pulp fibers 26 can be unrefined or lightly
fibrillated (compared to SEPF 30) (e.g., the softwood pulp fibers
can have an average hydrodynamic specific surface area that is less
than any one of, or between any two of, 3 square meters per gram
(m.sup.2/g), 2 m.sup.2/g, 1 m.sup.2/g, or less (e.g., less than 2
m.sup.2/g)). SEPF 30 can have higher surface areas compared to
conventionally-refined pulp fibers and can be made in a manner
(described below) that mitigates reductions in fiber length and the
production of fines. For example, SEPF 30 can have a length
weighted average fiber length that is greater than or equal to any
one of, or between any two of, 0.20 millimeters (mm), 0.30 mm, 0.40
mm, 0.50 mm, 0.60 mm, 0.70 mm, 0.80 mm, 0.90 mm, 1.0 mm, 1.5 mm,
2.0 mm, or larger (e.g., when cedar, greater than or equal to 1.0
mm, such as between 1.0 mm and 2.0 or 2.2 mm, or between 1.5 mm and
2.0 or 2.2 mm), and an average hydrodynamic specific surface area
that is greater than or equal to any one of, or between any two of,
4.5 m.sup.2/g, 5 m.sup.2/g, 6 m.sup.2/g, 7 m.sup.2/g, 8 m.sup.2/g,
9 m.sup.2/g, 10 m.sup.2/g, 12 m.sup.2/g, 14 m.sup.2/g, 16
m.sup.2/g, 18 m.sup.2/g, 20 m.sup.2/g, or larger (e.g., for cedar,
at least 4.5 or 5.0 m.sup.2/g). And, SEPF 30 can have a length
weighted fines value that is less than or equal to any one of, or
between any two of, 40%, 35%, 30%, 25%, 20%, or less (e.g., less
than or equal to 30%), when fibers having a length of 0.20 mm are
classified as fines. Optionally, the number of SEPF 30 can be at
least 12,000 per milligram on an oven-dry basis (e.g., based on a
sample of the SEPF that is dried in an oven set at 105.degree. C.
for 24 hours). A description of SEPF and processes by which SEPF
can be made are set forth in further detail in U.S. patent
application Ser. No. 13/836,760, filed Mar. 15, 2013, and published
as Pub. No. US 2014/0057105 on Feb. 27, 2014, which is hereby
incorporated by reference. Softwood pulp fibers 26 and SEPF 30 can
be of any suitable grade, e.g., those pulp fibers can originate
from a chemical process (e.g., a kraft process), a mechanical
process, a thermomechanical process, a chemi-thermomechanical
process, and/or the like, and can be bleached or unbleached. For
example, softwood pulp fibers 26 can be northern bleached softwood
kraft (NBSK) pulp fibers.
[0028] Incorporating both softwood pulp fibers 26, which can be
non-cedar pulp fibers (e.g., NBSK pulp fibers), and cedar SEPF 30
can reduce the cost of producing nonwoven sheet 10 while providing
a comparable or better drapability and/or combination of air
permeability and liquid resistance, compared to conventional
nonwoven sheets in which all of the cellulosic pulp fibers are
cedar pulp fibers. Pulps having cedar fibers--which may have good
collapsibility--can be more expensive to produce than other pulps
such as NBSK pulps, which typically comprise pine, spruce, and/or
larch pulp fibers. For example, chips used to make cedar pulp can
have a low packing density which can reduce productivity and the
cost of chemicals and/or bleaching when making cedar pulp may be
relatively high. Due at least in part to the unique characteristics
of cedar SEPF 30, incorporating softwood pulp fibers 26 can reduce
the amount of cedar SEPF required to achieve desired performance.
To illustrate, by weight, less than or equal to any one of, or
between any two of, 20%, 18%, 16%, 14%, 12%, 10%, 8%, 6%, 4%, 2% or
less (e.g., between 1% and 20% or between 1% and 10%) of cellulosic
pulp fibers 18 can be SEPF 30 and greater than or equal to any one
of, or between any two of, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%,
96%, 98%, 99%, or more (e.g., between 80% and 99% or between 90%
and 99%) of the cellulosic pulp fibers can be softwood pulp fibers
26. The comparatively large surface area and low fines content of
SEPF 30 can promote nonwoven sheet 10's barrier properties--e.g.,
promoting liquid resistance while maintaining good air
permeability--for use in articles such as surgical gowns and
surgical drapes in which these barrier properties are desirable.
The relatively low fines content of SEPF 30 can also mitigate poor
hydroentangling (described below) attributable to fines, a
challenge that rendered conventional highly fibrillated pulp fibers
undesirable in conventional nonwovens. And the combination of SEPF
30 with non-cedar softwood pulp fibers 26 (e.g., NBSK fibers) can
yield a desirable drapability for nonwoven sheet 10, something that
may not be achievable if the cellulosic fibers included the
non-cedar softwood pulp fibers alone.
[0029] Synthetic fibers 22 can comprise any suitable polymeric
fibers, such as, for example, polyester, polyethylene,
polypropylene, polyvinyl chloride, polyethylene terephthalate,
nylon, polycarbonate, and/or polysulfone fibers; as shown, the
synthetic fibers are polyester fibers. And in some embodiments,
synthetic fibers 22 can comprise fibers derived from cellulose,
such as viscose and/or lyocell.
[0030] Nonwoven sheet 10 can comprise any suitable proportion of
cellulosic pulp fibers 18 and synthetic fibers 22. For example, at
least a majority of the fibers of nonwoven sheet 10 can be
cellulosic pulp fibers 18, e.g., by weight, greater than or equal
to any one of, or between any two of, 50%, 60%, 70%, 80%, 90%, or
more of the fibers of the nonwoven sheet can be the cellulosic pulp
fibers and less than or equal to, or between any two of, 50%, 40%,
30%, 20%, 10%, or less of the fibers of the nonwoven sheet can be
the synthetic fibers. The combination of cellulosic pulp fibers 18
and synthetic fibers 22 can promote nonwoven sheet 10's air
permeability and resistance to liquids.
[0031] A wide variety of articles, such as, for example, surgical
gowns and surgical drapes, can incorporate at least a portion of
nonwoven sheet 10. Referring to FIG. 2, shown is a surgical gown 34
having a torso portion 38, two sleeves 42 coupled to the torso
portion, and a neck hole 46 defined at an upper end of the torso
portion such that, when the surgical gown is worn, the wearer's
neck can be received through the neck hole and each of the wearer's
arms can be received in a respective one of the sleeves. Surgical
gown 34 can comprise one or more of the present nonwoven sheets
(e.g., 10). For example, at least one of (up to and including each
of) torso portions 38 and sleeves 42 can comprise at least a
portion of nonwoven sheet 10. The relatively high air permeability
of nonwoven sheet 10 can promote comfort, and the nonwoven sheet
can function as a barrier to impede the flow of liquids (e.g.,
bodily fluids) through the gown and to the wearer. These advantages
can also be beneficial for surgical drapes, among other articles.
For example, while nonwoven sheet 10 is, as shown, incorporated
into a surgical gown, in other embodiments the nonwoven sheet can
be used to make articles such as clean room apparel, masks, gloves,
sheets, cloths, and/or the like.
[0032] Nonwoven sheet 10 can be made in any suitable process; for
example, the nonwoven sheet can be a spunlace nonwoven. Referring
to FIG. 3, shown is a system 50 that can be used to perform some of
the present methods of making a nonwoven sheet (e.g., 10). While
some methods are described with reference to system 50, system 50
is not limiting on those methods, which can be performed using any
suitable system.
[0033] Some methods include a step of making the SEPF (e.g., 30) in
a refining unit (e.g., 54). To make the SEPF, a first pulp feed
comprising SEPF precursor pulp fibers (e.g., 58)--which can be any
of the cellulosic fiber types discussed above (e.g., softwood or
cedar pulp fibers)--can be refined using one or more mechanical
refiners (e.g., 62a and/or 62b) (FIGS. 4A and 4B). Referring
additionally to FIG. 5, each of the refiner(s) can comprise at
least two refining elements (e.g., 66), each including a plurality
of bars (e.g., 70) that extend outwardly from a surface (e.g., 74)
of the refining element and define a plurality of grooves (e.g.,
78). For example, each of the refiner(s) can be a disk refiner
(e.g., a single-disk refiner, a double-disk refiner, or a
multi-disk refiner) (e.g., in which the refining elements are
refiner plates) or a conical refiner (e.g., in which the refining
elements are conical refiner fillings).
[0034] The first pulp feed can be refined at least by, for each of
the refiner(s), introducing the first pulp feed between the
refining elements and rotating at least one, optionally each, of
the refining elements. The bars can thereby impart compression and
shearing forces on the SEPF precursor pulp fibers to increase the
fibrillation, and thus the average hydrodynamic specific surface
area, thereof. To facilitate a high degree of fibrillation while
mitigating undesired reductions in fiber length, each of the
refining elements can have a fine bar pattern and, optionally, the
refiner(s) can be operated at a low intensity (e.g., at a low
specific edge load (SEL)), compared to conventional refining
processes. For example, for each of the refining elements, each of
the bars can have a width (e.g., 80) that is less than or equal to
any one of, or between any two of, 1.4 millimeters (mm), 1.3 mm,
1.2 mm, 1.1 mm, 1.0 mm, 0.9 mm, 0.8 mm, or less (e.g., less than or
equal to 1.4 mm, 1.3 mm, or 1.0 mm) and each of the grooves can
have a width (e.g., 84) that is less than or equal to any one of,
or between any two of, 2.5 mm, 2.3 mm, 2.1 mm, 1.9 mm, 1.7 mm, 1.5
mm 1.3 mm, or less (e.g., less than or equal to 2.5 mm, 1.6 mm, or
1.3 mm). For cedar SEPF precursor pulp fibers, the bar width is
preferably less than or equal to 1.4 mm or 1.3 mm and the groove
width is preferably less than or equal to 2.5 mm or 2.4 mm. And,
refining the first pulp feed can be performed such that each of the
refiner(s) operates at a SEL that is less than or equal to any one
of, or between any two of, 1.5 Watt-seconds per meter (Ws/m), 1.0
Ws/m, 0.50 Ws/m, 0.45 Ws/m, 0.40 Ws/m, 0.35 Ws/m, 0.30 Ws/m, 0.25
Ws/m, 0.20 Ws/m, 0.15 Ws/m, 0.10 Ws/m, or less (e.g., less than or
equal to 0.45 Ws/m, at least for cedar SEPF precursor pulp
fibers).
[0035] The first pulp feed can be refined using a large amount of
refining energy, compared to conventional processes, to achieve a
high degree of fibrillation. For example, refining the first pulp
feed can be performed such that, per ton of fiber in the first pulp
feed, the refiner(s) consume greater than or equal to any one of,
or between any two of, 300 kilowatt-hours (kWh), 400 kWh, 500 kWh,
600 kWh, 700 kWh, 800 kWh, 900 kWh, 1,000 kWh, or more (e.g.,
greater than or equal to 300 kWh or 600 kWh per ton of fiber in the
first pulp feed). The refining energy expended can depend at least
in part on the type of pulp fibers in the first pulp feed and the
desired degree of fibrillation. Without limitation, when the SEPF
precursor pulp fibers are hardwood pulp fibers, the refining energy
can be between 300 kWh and 600 kWh per ton of fiber and when the
SEPF precursor pulp fibers are softwood pulp fibers (e.g., cedar
pulp fibers), the refining energy can be at least 600 kWh per ton
of fiber (e.g., because softwood pulp fibers, which are typically
longer than hardwood pulp fibers, may be subjected to more refining
than hardwood pulp fibers before fiber shortening and fines
production adversely affects fiber quality).
[0036] Such refining energies can be reached in any suitable
manner. For example, each of the refiner(s) can consume, per ton of
fiber in the first pulp feed, less than or equal to any one of, or
between any two of, 110 kWh, 100 kWh, 90 kWh, 80 kWh, 70 kWh, 60
kWh, 50 kWh, 40 kWh, 30 kWh, or less each time the first pulp feed
is passed through the refiner. To reach the total desired refining
energy, the first pulp feed can be recirculated through at least
one of the refiner(s) and/or passed through multiple refiners such
that the cumulative energy consumed by the refiner(s) reaches the
desired level (e.g., at least 300 kWh or at least 600 kWh per ton
of fiber). Referring to FIG. 4A, for example, the one or more
refiners can consist of a single refiner (e.g., 62a) (e.g., where,
for each of the refiner's refining elements, each of the bars has a
width that is less than or equal to 1.4 mm or 1.3 mm and each of
the grooves has a width that is less than or equal to 2.5 mm or 2.4
mm) and the first pulp feed can be passed through the refiner a
plurality of times (e.g., greater than or equal to any one of, or
between any two of, 2, 6, 10, 14, 18, 22, 26, or more times) until
the refiner consumes the desired refining energy. Alternatively,
and referring to FIG. 4B, the one or more refiners can comprise one
or more first refiners (e.g., 62a) (e.g., a single first refiner)
and one or more second refiners (e.g., 62b) such that the first
pulp feed passes through multiple refiners. Each of the first
refiner(s) can be configured to fibrillate the first pulp fibers
with less refinement than the second refiner(s). For example, for
each of the first refiner(s), each of the bars can have a width
that is greater than or equal to 1.0 mm, each of the grooves can
have a width that is greater than or equal 1.6 mm, and the first
refiner can operate at a SEL between 0.2 and 0.45 Ws/m. The first
pulp feed can be introduced into the second refiner(s) after
passing through the first refiner(s) and, for each of the second
refiner(s), each of the bars can have a width that is less than or
equal to 1.0 mm, each of the grooves can have a width that is less
than or equal to 1.6 mm, and the second refiner can operate at a
SEL between 0.1 and 0.2 Ws/m. The first pulp feed can be
recirculated through at least one of the second refiner(s) (e.g.,
as described with respect to FIG. 4A). In other embodiments, the
first and second refiners can provide a similar level of refinement
(e.g., each can have the same bar width, such as less than or equal
to 1.4 mm or 1.3 mm, and groove width, such as less than or equal
to 2.5 mm or 2.4 mm, and/or operate at the same SELs).
[0037] The first pulp feed can have any suitable consistency to
promote runnability in the refining unit. For example, the first
pulp feed can be a slurry in which less than or equal to any one
of, or between any two of, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%,
or less of the slurry, by weight, is the SEPF precursor pulp
fibers.
[0038] Such high-energy refining (e.g., at least 300 kWh or 600 kWh
per ton of fiber) performed using refining elements having a fine
bar pattern (e.g., any of those described above) and/or at low
intensity (e.g., at a SEL between 0.1 and 0.45 Ws/m) can yield
larger increases in the average hydrodynamic specific area of the
SEPF precursor pulp fibers than conventional refining processes
while mitigating reductions in fiber length. For example, the first
pulp feed can be refined such that the average hydrodynamic
specific surface area of the SEPF precursor pulp fibers increases
by at least 300% (e.g., at least 700%) while the length weighted
average fiber length of the SEPF precursor pulp fibers decreases by
less than 30%. The resulting SEPF can thereby have any of the
above-described length weighted average fiber lengths and average
hydrodynamic specific surface areas.
[0039] Some methods include a step of combining the refined first
pulp feed and a second pulp feed comprising softwood pulp fibers
(e.g., 26) that are unrefined or lightly fibrillated (e.g., any of
those described above) (e.g., non-cedar, NBSK pulp fibers) to
produce a third pulp feed that comprises both of the cellulosic
pulp fibers (e.g., 18). The refined first pulp feed and second pulp
feed can be combined such that at least a majority of the
cellulosic pulp fibers in the third pulp feed are unrefined or
lightly fibrillated. For example, the refined first pulp feed and
the second pulp feed can be combined such that less than or equal
to any one of, or between any two of, 20%, 19%, 18%, 17%, 16%, 15%,
14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or
less (e.g., between 1% and 10% or between 1% and 20%) of the pulp
fibers of the third pulp feed, by weight, are the SEPF and/or
greater than or equal to any one of, or between any two of, 80%,
81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%,
94%, 95%, 96%, 99%, or more (e.g., between 80% and 99% or between
90% and 99%) of the pulp fibers of the third pulp feed, by weight,
are the softwood pulp fibers. As a result, a nonwoven sheet
incorporating the cellulosic pulp fibers can comprise those
proportions of softwood pulp fibers and SEPF and, as set forth
above, can thereby achieve a suitable combination of air
permeability and liquid resistance.
[0040] The third pulp feed can be prepared for delivery to a
nonwoven manufacturing system (e.g., 82) where the cellulosic pulp
fibers can be used to make the nonwoven sheet. For example, the
third pulp feed can be dried (e.g., by draining, pressing, and/or
heating the third pulp feed) (e.g., in a Fourdrinier machine) to
form one or more cellulosic sheets (e.g., 84) (e.g., one or more
pulp sheets) comprising the cellulosic pulp fibers. Substantially
all of the moisture of the third pulp feed can be removed when it
is dried, e.g., such that less than or equal to any one of, or
between any two of, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%,
5%, 4%, 3%, 2%, 1%, or less (e.g., less than or equal to 15% or
10%) of the cellulosic sheet(s), by weight, is liquid. The
cellulosic sheet(s) can be baled and/or at least some of the
cellulosic sheet(s) can be wound into a roll.
[0041] Referring additionally to FIG. 6, the cellulosic pulp fibers
and a plurality of synthetic fibers (e.g., 22) (e.g., any of the
synthetic fibers described above) can be used to make the nonwoven
sheet in the nonwoven manufacturing system. Some methods include a
step of depositing the fibers (e.g., 14) (e.g., the cellulosic and
synthetic fibers) onto a moving surface (e.g., 86), such as a
moving surface of a foraminous carrier belt (e.g., 90) or of one or
more drums, to form a nonwoven precursor web (e.g., 94). The fibers
can be deposited and used to form the nonwoven precursor web in any
suitable manner, such as by airlaying, carding, or wetlaying the
fibers, and such that the nonwoven precursor web, and thus the
nonwoven sheet resulting therefrom, has any of the above-described
proportions of cellulosic pulp fibers and synthetic fibers (e.g.,
such that at least a majority of the fibers are the cellulosic pulp
fibers). To illustrate, the fibers can be deposited such that the
nonwoven precursor web comprises two or more layers, at least one
of which includes the cellulosic pulp fibers and at least one of
which includes the synthetic fibers. To do so, the synthetic fibers
can be deposited onto the moving surface (e.g., using an apertured
drum 98) to form a layer of the synthetic fibers thereon and each
of the cellulosic sheet(s) (e.g., each of the pulp sheet(s)) can be
deposited onto the synthetic fiber layer (e.g., such that the
cellulosic sheet(s) define one of the nonwoven precursor web's
layers). In other embodiments, the cellulosic sheet(s) can be
broken apart and the cellulosic pulp fibers of the broken-apart
sheet(s) can be deposited onto the moving surface to form a
cellulosic pulp fiber layer. The cellulosic sheet(s) and/or
polymeric fibers can be wetted prior to the below-described bonding
process (e.g., before and/or while being deposited). In other
embodiments, the order in which the synthetic fibers and cellulosic
pulp fibers are deposited onto the moving surface can be reversed
(e.g., by depositing the cellulosic pulp fibers on the moving
surface and thereafter depositing the synthetic fibers onto the
cellulosic pulp fibers, such as when using a drum system) or (e.g.,
when the cellulosic sheet(s) are broken apart) the cellulosic pulp
fibers and synthetic fibers (e.g., polyester fibers) can be
deposited after mixing the fibers (e.g., such that the nonwoven
precursor web comprises a single layer of the mixed fibers).
[0042] The nonwoven precursor web can, but need not, be compacted
(e.g., to remove air pockets from the nonwoven precursor web). For
example, the nonwoven precursor web can be pressed between two
moving belts (e.g., 90 and 102), at least one of which can, but
need not, be the carrier belt onto which the fibers are deposited.
In other embodiments, however, the nonwoven precursor web can be
compacted in any suitable manner (e.g., by pressing the nonwoven
precursor web with two or more pressing elements).
[0043] The fibers of the nonwoven precursor web can be bonded by
hydroentanglement, e.g., by directing one or more jets of water
(e.g., 106), such as, for example, greater than or equal to any one
of, or between any two of, one, two, three, four, five, six, seven,
eight, nine, ten, or more jets of water, onto the nonwoven
precursor web using one or more injectors (e.g., 110). For each of
the jet(s) of water, the portion of the nonwoven precursor web onto
which the jet is directed can be supported by a surface such as a
belt (e.g., the foraminous carrier belt onto which the fibers are
deposited or another carrier belt) and/or a roller (e.g., 114). To
illustrate, a first water jet can be directed onto a portion of the
nonwoven precursor web that is disposed on carrier web 90
(optionally, while that portion is being compacted), the nonwoven
precursor web can be passed partially around each of one or more
rollers (e.g., 114), and, for each of the roller(s), an additional
water jet can be directed onto the portion of the nonwoven
precursor web being passed partially around the roller. At least
one of the surface(s) supporting the nonwoven precursor web can be
configured to facilitate removal of the water from the nonwoven
precursor web (e.g., to prevent oversaturation thereof); for
example, each of the supporting surface(s) can be a mesh or
apertured such that a vacuum can draw water from the nonwoven
precursor web through the supporting surface during
hydroentanglement. And, hydroentanglement can be performed such
that at least one jet of water is directed onto each of opposing
first and second surfaces (e.g., 118a and 118b) of the nonwoven
precursor web, which can facilitate uniform entanglement. In other
embodiments, however, the jet(s) of water can be directed onto only
one of the nonwoven precursor web's surfaces (e.g., onto a surface
defined by a layer of the cellulosic pulp fibers).
[0044] The injector(s) can operate at a relatively high pressure to
achieve hydroentanglement. For example, a pressure of each of the
jet(s) of water (e.g., at the injector) can be greater than or
equal to any one of, or between any two of, 100 pounds per square
inch (psi), 400 psi, 700 psi, 1,000 psi, 1,300 psi, 1,600 psi,
1,900 psi, 2,200 psi, 2,500 psi, or higher. When multiple jets of
water are used, the jets can have the same or different pressures.
For example, the first jet can have a comparatively low pressure
(e.g., to pre-wet the nonwoven precursor web and facilitate removal
of air pockets) while subsequent downstream jets can have a
pressure that is higher than that of the first jet. In other
embodiments, however, the jets can have the same pressure.
[0045] In conventional hydroentangling processes, highly
fibrillated pulp fibers are generally considered undesirable
because such pulp fibers can comprise a large amount of fines that
can impede fiber entanglement. The SEPF, due at least in part to
the unique process by which they are made, can comprise a
relatively low amount of fines, compared to pulp fibers that have
been highly fibrillated using conventional refining techniques. As
such, hydroentanglement of the SEPF with the softwood and synthetic
fibers may not suffer from the same detrimental effects that may
result when hydroentangling conventional, highly fibrillated pulp
fibers. In this manner, the nonwoven sheet can have a combination
of air permeability and liquid resistance that is comparable to or
better than that of an otherwise similar nonwoven sheet in which
all of the cellulosic pulp fibers are unrefined or lightly refined
cedar pulp fibers, at a lower cost (e.g., due to the use of
softwood pulp fibers, such as NBSK pulp fibers, that are less
expensive to produce in conjunction with the SEPF).
[0046] Some methods include a step of drying the nonwoven precursor
web in a drying unit (e.g., 122). The nonwoven precursor web can be
dried in any suitable manner, such as, for example, by passing the
nonwoven precursor web partially around each of one or more rollers
(e.g., 126) (each, optionally, comprising a vacuum to draw water
from the nonwoven precursor web), heating the nonwoven precursor
web, and/or directing a gas (e.g., air) onto the nonwoven precursor
web. All or almost all of the water can be removed from the
nonwoven precursor web during the drying, e.g., such that less than
or equal to any one of, or between any two of, 15%, 13%, 11%, 9%,
7%, 5%, 3%, 1%, or less (e.g., less than or equal to 10%) of the
nonwoven sheet, by weight, is water. The resulting nonwoven sheet
can thereafter be used in the production a variety of articles,
such as, for example, a surgical gown or a surgical drape, where
the nonwoven sheet's combination of air permeability and liquid
resistance may be desirable.
[0047] The above specification and examples provide a complete
description of the structure and use of illustrative embodiments.
Although certain embodiments have been described above with a
certain degree of particularity, or with reference to one or more
individual embodiments, those skilled in the art could make
numerous alterations to the disclosed embodiments without departing
from the scope of this invention. As such, the various illustrative
embodiments of the products, systems, and methods are not intended
to be limited to the particular forms disclosed. Rather, they
include all modifications and alternatives falling within the scope
of the claims, and embodiments other than the one shown may include
some or all of the features of the depicted embodiment. For
example, elements may be omitted or combined as a unitary
structure, and/or connections may be substituted. To illustrate,
while some methods can include a step of producing the SEPF and
combining the SEPF with the softwood pulp fibers, in other
embodiments the SEPF and softwood pulp fibers can be provided
(e.g., such that the refining and combining steps need not be
performed). Further, where appropriate, aspects of any of the
examples described above may be combined with aspects of any of the
other examples described to form further examples having comparable
or different properties and/or functions, and addressing the same
or different problems. Similarly, it will be understood that the
benefits and advantages described above may relate to one
embodiment or may relate to several embodiments.
[0048] The claims are not intended to include, and should not be
interpreted to include, means-plus- or step-plus-function
limitations, unless such a limitation is explicitly recited in a
given claim using the phrase(s) "means for" or "step for,"
respectively.
* * * * *