U.S. patent application number 13/388463 was filed with the patent office on 2012-07-19 for face mask.
This patent application is currently assigned to UNI-CHARM CORPORATION. Invention is credited to Makoto Ishigami, Akira Shibata, Naohito Takeuchi.
Application Number | 20120180800 13/388463 |
Document ID | / |
Family ID | 43544357 |
Filed Date | 2012-07-19 |
United States Patent
Application |
20120180800 |
Kind Code |
A1 |
Shibata; Akira ; et
al. |
July 19, 2012 |
FACE MASK
Abstract
A mask has a mask body and a pair of ear straps. The mask body
includes an outer layer sheet and an intermediate layer sheet. The
outer layer sheet is formed of hydrophobic fibers. The intermediate
layer sheet is laid on the outer layer sheet so as to be located on
a wearer's side of the outer layer sheet when the mask is worn. The
intermediate layer sheet includes a first fiber layer which is
formed of polyolefin fibers containing an inorganic antimicrobial
agent and a second fiber layer which is formed of polyolefin fibers
and has a larger fiber diameter than the first fiber layer. The
fiber diameter of the first fiber layer is within a range of 0.5 to
2.8 .mu.m and the ratio of a particle diameter of the inorganic
antimicrobial agent with respect to the fiber diameter is within
the range of 0.1 to 6.0.
Inventors: |
Shibata; Akira;
(Kanonji-shi, JP) ; Ishigami; Makoto;
(Kanonji-shi, JP) ; Takeuchi; Naohito;
(Kanonji-shi, JP) |
Assignee: |
UNI-CHARM CORPORATION
Shikokuchuo-shi, Ehime-ken
JP
|
Family ID: |
43544357 |
Appl. No.: |
13/388463 |
Filed: |
August 3, 2010 |
PCT Filed: |
August 3, 2010 |
PCT NO: |
PCT/JP2010/063125 |
371 Date: |
April 10, 2012 |
Current U.S.
Class: |
128/863 |
Current CPC
Class: |
A41D 13/11 20130101;
A41D 2400/52 20130101; A41D 13/1192 20130101; A41D 31/305 20190201;
A41D 13/113 20130101; A62B 23/025 20130101 |
Class at
Publication: |
128/863 |
International
Class: |
A41D 13/11 20060101
A41D013/11 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 7, 2009 |
JP |
2009-184045 |
Claims
1. A mask comprising a mask body that covers at least wearer's
mouth and nose and a pair of ear straps that extend from both sides
of the mask body and are designed to be hooked around wearer's
ears, wherein: the mask body includes a first fiber sheet and a
second fiber sheet which are laid one on the other such that the
second fiber sheet is located on a wearer's side of the first fiber
sheet when the mask is worn, and the first fiber sheet comprises
hydrophobic fibers, the second fiber sheet includes a first fiber
layer which is formed of polyolefin fibers containing an inorganic
antimicrobial agent and a second fiber layer which is formed of
polyolefin fibers and has a larger fiber diameter than the first
fiber layer, wherein the fiber diameter of the first fiber layer is
within a range of 0.5 to 2.8 .mu.m and the ratio of a particle
diameter of the inorganic antimicrobial agent with respect to the
fiber diameter is within a range of 0.1 to 6.0.
2. The mask as defined in claim 1, wherein the first fiber layer of
the second fiber sheet is disposed on the first fiber sheet side of
the second fiber layer.
3. The mask as defined in claim 1, wherein the first fiber sheet is
formed of hydrophobic fibers having a fiber diameter of 10 to 40
.mu.m and a pore size of 60 to 100 .mu.m.
4. The mask as defined in claim 1, wherein the mask body includes a
bonding part which is formed between the first fiber sheet and the
second fiber sheet by applying a hot-melt adhesive in fibrous form
having a light basis weight of 1.0 to 3.0 g/m.sup.2.
5. The mask as defined in claim 1, wherein the mask body includes a
third fiber sheet that is laid on a side of the second fiber sheet
facing away from the first fiber sheet, and the third fiber sheet
is formed of fibers having a fiber diameter of 10 to 40 .mu.m and a
pore size of 60 to 100 .mu.m.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a technique of constructing
a mask to be worn on a wearer's face, and more particularly to a
mask having antibacterial and antiviral effects.
BACKGROUND OF THE INVENTION
[0002] Japanese laid-open Patent Publication No. 2007-37737
discloses a three-dimensional mask which covers wearer's mouth and
nose. Recently, responding to rising consciousness of hygienic
environment, and epidemics of colds and influenza and further to
outbreaks of new infectious diseases such as avian influenza and
coronavirus, masks having antibacterial and antiviral effects have
been actively developed.
[0003] For example, Japanese laid-open Patent Publication Nos.
1993-153874 and 1996-325915 disclose nonwoven fabric which is
formed of polyolefin fibers containing an inorganic antimicrobial
agent. In this nonwoven fabric, however, most of the inorganic
antimicrobial agent present inside of the fibers is covered with
polyolefin, so that only a small amount of the inorganic
antimicrobial agent is exposed to the fiber surface. Therefore,
even if this nonwoven fabric is used to form a mask, the
antibacterial and antiviral effects of the inorganic antimicrobial
agent against pathogens such as bacteria and viruses are not fully
achieved.
[0004] Further, when the mask is worn, the wearer may touch the
mask body (mask cup). In this case, if any bacterium or virus
adheres to the outer surface of the mask body and stays on it, the
bacterium or virus may cause secondary infection. Therefore, in
manufacturing a mask by using a fiber sheet containing an inorganic
antimicrobial agent, a technique is desired to be provided by which
antibacterial and antiviral effects of the inorganic antimicrobial
agent are reliably achieved so as to prevent any bacterium or virus
from staying on the outer surface of the mask body.
[0005] Further, in development of the mask of this type, in
addition to high antibacterial and antiviral effects, it is also
desired to realize such a high capture efficiency that the mask can
capture dust or other particles in the air, and such a high air
permeability that ease of breathing of the wearer can be enhanced,
and to realize high productivity by provision of fibers which are
unlikely to be broken during mask manufacturing.
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0006] It is, accordingly, an object of the present invention to
provide an effective technique for preventing bacteria or viruses
from staying on an outer surface of a mask body in order to achieve
high antibacterial and antiviral effects, and for improving air
permeability, capture efficiency and productivity.
Means for Solving the Problem
[0007] In order to solve the above-described problem, the present
invention as defined in each claim is provided.
[0008] A mask according to this invention is designed to be worn on
a wearer's face and includes at least a mask body and a pair of ear
straps. The mask may be of disposable type designed for a single or
multiple use which can be used once or several times, or reusable
type which can be reused by washing.
[0009] The mask body covers at least the mouth and nose (nostril)
of a wearer. The pair of ear straps extend from both sides of the
mask body and are designed to be hooked around wearer's ears. The
ear straps are preferably formed of a stretch material so as to
prevent excessive load on the ears. Further, the mask body is
preferably formed of a material which is soft and comfortable to
wear and has lower stretchiness than the ear straps so that the
mask body lends itself to be retained in shape when the mask is
worn on the face. The mask body may be planer or three-dimensional.
In the case of a three-dimensional mask, it is essential for the
mask body to take a three-dimensional shape at least when the mask
is worn. (For example, the mask body may be designed to take a
three-dimensional form when the mask is worn and to be folded into
a planar form in a predetermined manner when the mask is not worn.)
Therefore, the mask body may be designed to be three-dimensional
not only when the mask is worn but when the mask is not worn. The
mask body is a sheet-like structure formed by fixing or entangling
fibers by mechanical, chemical or heat treatment. Typically, it is
formed of nonwoven fabric which partly includes thermal melting
(thermoplastic) fibers and thus can be heat-sealed (fusion
bonded).
[0010] The mask body includes a first fiber sheet and a second
fiber sheet. The first fiber sheet is formed of hydrophobic fibers
(also referred to as "water-repellent fibers"). The second fiber
sheet is laid on the first fiber sheet such that the second fiber
sheet is located on the wearer's side of the first fiber sheet when
the mask is worn. In this construction, the first fiber sheet forms
the outer surface (side to be exposed to the air) of the mask. The
mask body may have a two-layer structure having the first and
second fiber sheets, or it may have a multilayer structure of three
or more layers having the first and second fiber sheets and one or
more additional fiber sheets.
[0011] Further, the second fiber sheet includes a first fiber layer
and a second fiber layer. The first fiber layer is formed of
polyolefin fibers containing an inorganic antimicrobial agent.
Particularly in the first fiber layer, the fiber diameter is within
a range of 0.5 to 2.8 .mu.m and the ratio of a particle diameter of
the inorganic antimicrobial agent with respect to this fiber
diameter is within the range of 0.1 to 6.0. The second fiber layer
is formed of polyolefin fibers having a larger fiber diameter than
those of the first fiber layer. The second fiber sheet as a whole
can secure desired antibacterial and antiviral effects via the
first fiber layer and can secure desired capture efficiency (also
referred to as "dust collecting efficiency") and air permeability
via the second fiber layer. In the second fiber sheet, the first
fiber layer may be disposed on the first fiber sheet side (the
outer side) of the second fiber layer, or the first fiber sheet may
be disposed on the first fiber sheet side (the outer side) of the
first fiber layer.
[0012] The second fiber sheet can be subjected to electret
treatment as necessary. The "electret treatment" here is defined as
a treatment for creating a dielectric state by providing a
polyolefin fiber surface with a predetermined amount of positive or
negative charge and polarizing it. By forming the mask having the
electret second fiber sheet, the capture efficiency is further
improved.
[0013] As the "inorganic antimicrobial agent" here, any inorganic
antimicrobial agent can be used which is harmless to humans, not
volatilized, not decomposed and not altered or deteriorated, for
example, by heat during melt spinning of fibers, and has
antibacterial and antiviral effects which are not deteriorated in a
short period of time. Typically used are one or more kinds of an
inorganic antimicrobial agent in which metal ions having
antibacterial and antiviral effects, such as silver ions, copper
ions and zinc ions, are supported by inorganic carriers, an
inorganic antimicrobial agent of titanium oxide series, and other
similar inorganic antimicrobial agents. As for the inorganic
antimicrobial agent having antibacterial metal ions supported by
inorganic carriers, the kind of inorganic carriers is not
particularly limited, and any inorganic carrier which does not
exhibit an effect of deteriorating a fiber sheet can be used.
Suitably, inorganic carriers having ion-exchange capacity and
metal-ion adsorption capacity and having high metal-ion retention
capacity are used. Such inorganic carriers typically include
zeolite, zirconium phosphate and calcium phosphate. Particularly,
zeolite and zirconium phosphate having high ion-exchange capacity
are most suitable.
[0014] Further, the "fiber layer formed of polyolefin fibers"
widely includes not only a fiber layer formed only of polyolefin
fibers, but a fiber layer formed of polyolefin fibers and other
fibers in mixture. The polyolefin fiber typically includes
polypropylene fiber, polyethylene fiber and poly 1-butene
fiber.
[0015] With the mask having the above-described construction, when
breathing of a mask wearer creates air flow from the mask outer
surface toward the wearer's mouth, airborne droplets containing
bacteria or viruses are led to the second fiber sheet without being
absorbed by the first fiber sheet formed of hydrophobic fibers
(without staying on the mask outer surface). Therefore, even if the
wearer touches the mask body (mask cup) when putting on or off the
mask, secondary infection can be prevented. Further, the evaluation
tests conducted by inventors show that, by setting the fiber
diameter of the first fiber layer and the ratio of the particle
diameter of the inorganic antimicrobial agent with respect to the
fiber diameter within the above-described respective appropriate
ranges, high antibacterial and antiviral effects can be exerted and
the air permeability, capture efficiency and productivity can be
improved.
[0016] Particularly as for the antibacterial and antiviral effects,
by providing such that the fiber diameter of the first fiber layer
and the ratio of the particle diameter of the inorganic
antimicrobial agent with respect to the fiber diameter are within
the above-described respective appropriate ranges, compared with a
construction in which they are not within the appropriate ranges,
the inorganic antimicrobial agent can be effectively exposed onto
the fiber surface, so that the inherent antibacterial and antiviral
effects of the inorganic antimicrobial agent against pathogens such
as bacteria and viruses can be fully exerted. Further, when it is
designed and provided to have the same antibacterial and antiviral
effects as a mask not having the above-described construction, the
composition ratio of the inorganic antimicrobial agent can be
reduced. Thus, the effect of reducing the product costs can be
increased. Further, decrease of productivity due to fiber breakage
can be prevented.
[0017] In the mask according to another aspect of this invention,
the first fiber layer of the second fiber sheet is disposed on the
first fiber sheet side of the second fiber layer. With such a
construction, the inorganic antimicrobial agent in the first fiber
layer can promptly exert an antibacterial effect on droplets
containing bacteria or viruses which pass through the first fiber
sheet.
[0018] In the mask according to another aspect of this invention,
the first fiber sheet is formed of hydrophobic fibers having a
fiber diameter of 10 to 40 .mu.m and a pore size of 60 to 100
.mu.m. With such a construction, the first fiber sheet has a low
density and thus has increased air permeability, so that ease of
breathing of the wearer is increased. Further, droplets containing
bacteria or viruses are more easily led to the second fiber
sheet.
[0019] In the mask according to another aspect of this invention,
the mask body includes a bonding part which is formed between the
first fiber sheet and the second fiber sheet by applying a hot-melt
adhesive in fibrous form having a light basis weight of 1.0 to 3.0
g/m.sup.2. The "hot-melt adhesive" here refers to an adhesive which
contains no organic solvent mainly made of thermoplastic resin.
Further, in "applying in fibrous form" here, typically, hot-melt
resin fibers are applied to the bonded part at about equal
intervals in meandering form in the direction of application. The
diameter, shape and pattern of the fibers can be appropriately
selected according to the kind and application conditions of the
hot-melt resin. In a bonding part which is formed by applying an
adhesive in film form, movement of droplets containing bacteria or
viruses may be blocked so that the droplet guiding efficiency may
be reduced. In this embodiment, however, the bonding part having a
light basis weight has a function of preventing such decrease of
the droplet guiding efficiency.
[0020] In the mask according to another aspect of this invention,
the mask body includes a third fiber sheet that is laid on a side
of the second fiber sheet facing away from the first fiber sheet,
and the third fiber sheet is formed of fibers having a fiber
diameter of 10 to 40 .mu.m and a pore size of 60 to 100 .mu.m. The
third fiber sheet having a low density can be increased in air
permeability so that ease of breathing of the wearer can be
increased.
[0021] Other objects, features and advantages of the present
invention will be readily understood after reading the following
detailed description together with the accompanying drawings and
the claims.
Effect of the Invention
[0022] According to this invention, an effective technique for
preventing bacteria or viruses from staying on an outer surface of
a mask body in order to achieve high antibacterial and antiviral
effects, and for improving air permeability, capture efficiency and
productivity, can be provided in a mask to be worn on a wearer's
face.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a perspective view of a mask 1 according to an
embodiment of the invention.
[0024] FIG. 2 is a sectional view of a mask body 10 forming the
mask 1.
REPRESENTATIVE PREFERABLE EMBODIMENT FOR PERFORMING THE
INVENTION
[0025] The construction of a mask 1 is described as a
representative embodiment of the "mask" according to the present
invention with reference to FIGS. 1 and 2.
[0026] Each of the additional features and method steps disclosed
above and below may be utilized separately or in conjunction with
other features and method steps to realize manufacturing and use of
improved masks. Representative examples of this invention, which
examples utilized many of these additional features and method
steps in conjunction, will now be described in detail with
reference to the drawings. This detailed description is merely
intended to teach a person skilled in the art further details for
practicing preferred aspects of the present teachings and is not
intended to limit the scope of the invention. Only the claims
define the scope of the claimed invention. Therefore, combinations
of features and steps disclosed within the following detailed
description may not be necessary to practice the invention in the
broadest sense, and are instead taught merely to particularly
describe some representative examples of the invention.
[0027] FIG. 1 is a perspective view of the mask 1 according to this
embodiment. The mask 1 shown in FIG. 1 is designed as a disposable
mask for single or multiple use which can be used once or several
times. The mask 1 is suitably used as a safeguard against viruses
such as cold viruses, or against pollens as necessary. The mask 1
of this embodiment includes a mask body 10 and a pair of ear straps
20.
(Mask Body 10)
[0028] The mask body 10 is designed to cover the mouth and nose
(nostril) of a wearer. The mask body 10 corresponds in part or in
entirety to the "mask body" according to this invention.
[0029] The mask body 10 includes a right sheet piece 10a that
covers right half of the wearer's face and a left sheet piece 10b
that covers left half of the wearer's face. The right and left
sheet pieces 10a, 10b are bonded together by heat-sealing. A
vertically extending bonding edge 10c is formed in a bonding region
between the right and left sheet pieces 10a, 10b, so that the mask
body 10 is divided into right and left halves by the bonding edge
10c. When the mask is worn, the mask body 10 forms a
three-dimensional shape (three-dimensional structure) having a
concave or cup-like form defined by a wearing face of the mask body
10 facing the wearer. The mask body 10 is also referred to as a
"mouth covering part" or a "mask cup".
[0030] When the mask is worn, the mask body 10 is unfolded into a
three-dimensional form with the right and left sheet pieces 10a,
10b separated away from each other. When the mask is in storage or
not in use, the mask body 10 folds flat such that the right and
left sheet pieces 10a, 10b come in face contact with each other.
Further, it is essential for the mask body 10 to form a
three-dimensional form at least when the mask is worn. Therefore,
the mask body 10 may be designed to be three-dimensional not only
when the mask is worn but when the mask is not worn (not in use).
Further, preferably, the mask body 10 has lower stretchiness than
the ear straps 3 so that the mask body 10 lends itself to be
retained in a three-dimensional form when the mask is worn.
[0031] The sectional structure of the mask body 10 (or the right
and left sheet pieces 10a, 10b) is shown in FIG. 2. As shown in
FIG. 2, the mask body 10 has an outer layer sheet 11 which is
located on the outer side (faces away from the wearer's face) when
the mask is worn, an inner layer sheet 12 which faces the wearer's
face when the mask is worn, and an intermediate layer sheet 13
disposed between the outer layer sheet 11 and the inner layer sheet
12. Specifically, the mask body 10 has a three-layer structure in
which the outer layer sheet 11 and the inner layer sheet 12 are
laid on opposite sides of the intermediate layer sheet 13. Further,
the intermediate layer sheet 13 is configured as a composite fiber
sheet having a first fiber layer 14 and a second fiber layer 15
which are both formed of nonwoven fabric. Further, bonding parts 16
are provided between the outer layer sheet 11 and the intermediate
layer sheet 13 and between the inner layer sheet 12 and the
intermediate layer sheet 13. The outer layer sheet 11, the inner
layer sheet 12 and the intermediate layer sheet 13 are features
that correspond to the "first fiber sheet", the "third fiber sheet"
and the "second fiber sheet", respectively, according to this
invention.
[0032] Each of the outer layer sheet 11, the inner layer sheet 12
and the intermediate layer sheet 13 may be formed of one piece of
nonwoven fabric sheet, or it may be formed of a plurality of
nonwoven fabric sheets stacked in layers or butted and joined
together.
[0033] The outer layer sheet 11 is formed as a low-density nonwoven
fabric sheet (fiber sheet) having high hydrophobicity or water
repellency (formed of hydrophobic fiber or water-repellent fiber).
Typically used is a low-density pointbond nonwoven fabric sheet,
containing polyethylene terephthalate fiber and polyethylene fiber
and point-bonded by a pressure roll (for example, a nonwoven fabric
sheet having an average fiber diameter of 10 to 40 .mu.m, a pore
size of 60 to 100 .mu.m and a basis weight of 20 to 40 g/m.sup.2).
By using such a low-density outer layer sheet 11, bacteria- or
virus-containing droplets adhered to the outer layer sheet 11 are
prevented from being absorbed onto the outer layer sheet 11 itself
and are more easily led to the intermediate layer sheet 13.
Further, the outer layer sheet 11 is increased in air permeability
so that ease of breathing of the wearer is increased, and it is
nice and soft. It is essential for the outer layer sheet 11 to have
high hydrophobicity or water-repellency as a whole, and it is not
necessary to be formed only of a highly hydrophobic or
water-repellent fiber sheet.
[0034] The inner layer sheet 12 is formed as a low-density nonwoven
fiber sheet. Typically used is a pointbond nonwoven fabric sheet of
the same kind as used for the outer layer sheet 11. In this case,
the nonwoven fiber sheet of the inner layer sheet 12 may have high
hydrophobicity or water repellency, or it may have low
hydrophobicity or water repellency. Such an inner layer sheet 12 is
increased in air permeability so that ease of breathing of the
wearer is increased, and it is nice and soft.
[0035] The first fiber layer 14 of the intermediate layer sheet 13
is formed as a nonwoven fabric layer formed of polyolefin fibers
which are made of a polyolefinic resin composition (typically,
polypropylene resin) containing a particulate inorganic
antimicrobial agent. The first fiber layer 14 has a higher density
than the outer layer sheet 11 and the inner layer sheet 12.
Particularly, in the intermediate layer sheet 13 of this
embodiment, the first fiber layer 14 is disposed on the outer layer
sheet 11 side or the outer side of the second fiber layer 15. With
such a construction, the particulate inorganic antimicrobial agent
in the first fiber layer 14 can promptly exert an antibacterial
effect on droplets containing bacteria or viruses which pass
through the outer layer sheet 11. The first fiber layer 14 is a
feature that corresponds to the "first fiber layer" according to
this invention.
[0036] As the inorganic antimicrobial agent to be contained in the
first fiber layer 14, any inorganic antimicrobial agent can be used
which is harmless to humans, not volatilized, not decomposed and
not altered or deteriorated, for example, by heat during melt
spinning of fibers, and has antibacterial and antiviral effects
which are not deteriorated in a short period of time. Typically
used are one or more kinds of an inorganic antimicrobial agent in
which metal ions having antibacterial and antiviral effects, such
as silver ions, copper ions and zinc ions, are supported by
inorganic carriers, an inorganic antimicrobial agent of titanium
oxide series, and other similar inorganic antimicrobial agents. As
for the inorganic antimicrobial agent having antibacterial metal
ions supported by inorganic carriers, the kind of inorganic
carriers is not particularly limited, and any inorganic carrier
which does not exhibit an effect of deteriorating a fiber sheet can
be used. Suitably, inorganic carriers having ion-exchange capacity
and metal-ion adsorption capacity and having high metal-ion
retention capacity are used. Such inorganic carriers typically
include zeolite, zirconium phosphate and calcium phosphate.
Particularly, zeolite and zirconium phosphate having high
ion-exchange capacity are most suitable. The inorganic
antimicrobial agent is a feature that corresponds to the "inorganic
antimicrobial agent" according to this invention.
[0037] The second fiber layer 15 of the intermediate layer sheet 13
is formed as a nonwoven fabric layer formed of polyolefin fibers
which do not contain an inorganic antimicrobial agent. The second
fiber layer 15 has a higher density than the outer layer sheet 11
and the inner layer sheet 12. In the intermediate layer sheet 13 of
this embodiment, the second fiber layer 15 is disposed on the inner
layer sheet 12 side or the wearer's side. Further, the second fiber
layer 15 has a larger fiber diameter (average fiber diameter) than
the first fiber layer 14. With this construction, the intermediate
layer sheet 13 as a whole can exert antibacterial and antiviral
effects via the first fiber layer 14 and can secure desired capture
efficiency (also referred to as "particle collecting efficiency")
and air permeability via the second fiber layer 15. Further, the
first fiber layer 14 having a smaller fiber diameter than the
second fiber layer 15 is securely retained by the second fiber
layer 15. The second fiber layer 15 is a feature that corresponds
to the "second fiber layer" according to this invention.
[0038] Each of the bonding parts 16 is formed by applying a
hot-melt adhesive in fibrous form having a light basis weight (for
example, 1.0 to 3.0 g/m.sup.2) to a bonded part. The "hot-melt
adhesive" here refers to an adhesive which contains no organic
solvent mainly made of thermoplastic resin. Further, in "applying
in fibrous form" here, typically, hot-melt resin fibers are applied
to the bonded part at about equal intervals in meandering form in
the direction of application. The diameter, shape and pattern of
the fibers can be appropriately selected according to the kind and
application conditions of the hot-melt resin. In contrast to a
bonding part which is formed by applying an adhesive in film form,
the bonding part 16 having the above-described construction of a
light basis weight has a function of preventing decrease of droplet
guiding efficiency which may be caused by preventing movement of
droplets containing bacteria or viruses. The bonding part 16 is a
feature that corresponds to the "bonding part" according to this
invention.
(Ear Straps 20)
[0039] The ear straps 20 extend from right and left sides of the
mask body 10 or from free ends of the right and left sheet pieces
10a, 10b. The ear strap 20 here is a feature that corresponds to
the "ear strap" according to this invention. The ear straps 20 are
formed separately from the mask body 10 and overlapped and bonded
onto the mask body 2. The ear straps 20 may be integrally formed
with the mask body 10. Further, each of the ear straps 20 has a
ring-like shape having an opening 21. When the mask is worn, the
opening 21 of the ear strap 20 is hooked around the wearer's ear
with the wearer's face, or particularly the nose and mouth, covered
with the mask body 10.
[0040] Like the mask body 10, the ear strap 20 is formed of
nonwoven fabric of thermoplastic synthetic fibers. Preferably, the
ear strap 20 is formed of a stretch material so as to prevent
excessive load on the ear. For example, the ear strap 20 suitably
has a stretch layer of inelastically extensible fibers (for
example, nonwoven fabric formed by heat-sealing propylene
continuous fibers) and an elastic layer of elastically stretchable
fibers (for example, nonwoven fabric formed by using elastic yarn
of thermoplastic synthetic fibers such as elastomer and urethane)
which are laid one on the other.
[0041] An example of a method of manufacturing the intermediate
layer sheet 13 and the mask body 10 is now described. This
manufacturing method has the following steps 1 to 4.
(Step 1)
[0042] Polypropylene (having the melt flow rate (MFR) of 700 g/10
min.) is subjected to meltblow spinning process at the spinning
temperature of 280.degree. C., the air temperature of 290.degree.
C., the air pressure of 1.2 kg/cm.sup.2 and the amount of discharge
per pore of 0.4 g/min., with a nozzle having 2,850 spinning pores
(in a linear arrangement) and at the capture distance of 30 cm by
using a conventional meltblow (or called as "meltblown") apparatus.
In this manner, a nonwoven fabric layer (the second fiber layer 15)
having a predetermined basis weight and a predetermined fiber
diameter (average fiber diameter) is manufactured.
(Step 2)
[0043] A master batch containing a silver inorganic antimicrobial
agent is prepared by combination of 80 parts by mass of
polypropylene (.alpha.) (MFR=700 g/10 min.) and 20 parts by mass of
the silver inorganic antimicrobial agent (TOAGOSEI's "NOVARON
AG300", 1 .mu.m in average particle diameter, generally cubic) in
which silver ions are supported by inorganic ion exchangers mainly
made of zirconium phosphate. The prepared master batch and
polypropylene (.beta.) (MFR=700 g/10 min.) are mixed at the mass
ratio of 1:1 and then subjected to meltblow spinning process on the
nonwoven fabric layer (the second fiber layer 15) manufactured in
the above-described step 1, at the spinning temperature of
280.degree. C., the air temperature of 290.degree. C., the air
pressure of 1.2 kg/cm.sup.2 and the amount of discharge per pore of
0.4 g/min., with a nozzle having 2,850 spinning pores (in a linear
arrangement) by using a conventional meltblow apparatus. In this
manner, another nonwoven fabric layer (the first fiber layer 14) is
formed. Thus, a composite fiber sheet having the first fiber layer
14 and the second fiber layer 15 is manufactured.
(Step 3)
[0044] The composite fiber sheet obtained in the above-described
step 2 is subjected to electret treatment by using a conventional
electret apparatus under the conditions that the distance between a
needle electrode and a roll electrode is 25 mm, the applied voltage
is -25 KV and the temperature is 80.degree. C. In this manner, a
charged composite fiber sheet (the intermediate sheet 13) is
manufactured. By this electret treatment, the surface of the
polypropylene fiber is provided with a predetermined amount of
positive or negative charge and turns into a polarized dielectric
state. The mask formed of such an electret composite fiber sheet
can be further improved in capture efficiency or dust collecting
efficiency.
[0045] In this embodiment, because the first and second fiber
layers 14, 15 are formed of one kind of polyolefin fibers, or
particularly, polypropylene fibers, their electret treatment can be
particularly easily performed, and a low-cost mask can be provided
which is advantageous in terms of cost. Further, the first and
second fiber layers 14, 15 may be formed of polyolefin fibers other
than polypropylene fibers, such as polyethylene fibers and poly
1-butene fibers.
(Step 4)
[0046] A hot-melt adhesive is applied in fibrous form having a
light basis weight (e.g. 1.0 to 3.0 g/m.sup.2) to one side of the
charged composite fiber sheet (the intermediate sheet 13) obtained
in the above-described step 3, and then the outer layer sheet 11 is
placed on this side. Further, the hot-melt adhesive is applied in
fibrous form having a light basis weight (e.g. 1.0 to 3.0
g/m.sup.2) to the other side of the charged composite fiber sheet
(the intermediate sheet 13), and then the inner layer sheet 12 is
placed on this side. In this manner, the mask body 10 is
manufactured.
[0047] In a mask which is formed of polyolefin fibers containing a
particulate inorganic antimicrobial agent like the mask 1 of this
embodiment, most of the inorganic antimicrobial agent present
inside of the fibers is covered with polyolefin, so that only a
small amount of the inorganic antimicrobial agent is exposed to the
fiber surface. Therefore, the inherent antibacterial and antiviral
effects of the inorganic antimicrobial agent are not fully
achieved. In order to solve this problem, inventors have focused on
the relationship between the fiber diameter of the polyolefin
fibers containing the inorganic antimicrobial agent and the
particle diameter of the inorganic antimicrobial agent and
successfully found that the inherent antibacterial and antiviral
effects of the inorganic antimicrobial agent can be achieved, while
securing the capture efficiency and air permeability, by setting
values relating to the fiber diameter of the polyolefin fibers and
the particle diameter of the inorganic antimicrobial agent within
their respective specified ranges.
[0048] Performance of a mask was evaluated by varying the
construction of the mask body 10. For evaluation of mask
performance, specimens of the following examples 1 to 10 and
comparative examples 1 to 10 representing the mask body 10 were
prepared.
[0049] In each of the specimens, non-electret polyethylene
terephthalate/polyethylene pointbond nonwoven fabric sheet (average
fiber diameter: 17 .mu.m, basis weight: 32 g/m.sup.2) was used as
the outer layer sheet 11 and the inner layer sheet 12. Further, the
particle diameter of the inorganic antimicrobial agent, and the
fiber diameter, basis weight and pore size of the fiber layer were
measured as follows.
(Particle Diameter of Inorganic Antimicrobial Agent)
[0050] Water is added to the particulate inorganic antimicrobial
agent (silver-based inorganic antimicrobial agent) contained in the
first fiber layer 14 and stirred well enough for the agent to be
uniformly dispersed in the water. Particle size distribution of the
dispersed liquid is measured by using a laser
diffraction/scattering particle size distribution analyzer
(HORIBA's "LA-920"). At this time, prior to measurement of the
particle size distribution of the dispersed liquid, the dispersed
liquid is radiated with ultrasound for one minute by using an
ultrasonic homogenizer built into the measuring device. An
arithmetic mean value (.mu.m) is then calculated from the particle
size distribution on the volumetric basis and defined as an average
particle diameter of the inorganic antimicrobial agent. The
calculated average particle diameter of the inorganic antimicrobial
agent is defined as the particle diameter of the inorganic
antimicrobial agent contained in the first fiber layer 14.
(Fiber Diameter)
[0051] A square specimen (5 cm.times.5 cm) is obtained from the
first fiber layer 14 (the second fiber layer 15) made of polyolefin
fibers. The central portion (around the intersection of the
diagonal lines) of the surface of the obtained specimen is then
photographed at 1000-fold magnification by using a scanning
electron microscope (SEM). On this photo, a circle with a radius of
15 cm is drawn around the center (the intersection of the diagonal
lines) of the photo. Subsequently, the fiber diameter of all
(commonly about 50 to 100) non-heat-sealed polyolefin fibers within
this circle is measured at the middle in the length direction or
its vicinity with calipers. The mean value of the measured fiber
diameter is defined as the average fiber diameter (.mu.m) of the
polyolefin fibers. The obtained average fiber diameter of the
polyolefin fibers is defined as the fiber diameter of the first
fiber layer 14 (the second fiber layer 15).
[0052] In obtaining the average fiber diameter of the polyolefin
fibers, the fiber diameter of all polyolefin fibers in the photo is
measured without distinguishing whether the polyolefin fibers in
the photo are located on the outermost surface of the first fiber
layer 14 (the second fiber layer 15) or on its inner side, and the
average of the measurements is obtained. The specimen of the first
fiber layer 14 (the second fiber layer 15) may also have a size
other than that (5 cm.times.5 cm) described above, as
necessary.
(Basis Weight)
[0053] As for the basis weight of the second fiber layer 15, a
square specimen (20 cm.times.20 cm) is obtained from nonwoven
fabric used as the second fiber layer 15. The basis weight of the
obtained specimen is measured at three points along the width
direction of the specimen in accordance with JIS L1906 (Test
methods for nonwoven fabrics made of filament yarn), and the mean
value of the measured basis weight is defined as the basis weight
of the second fiber layer 15.
[0054] As for the basis weight of the intermediate-layer sheet 13,
a square specimen (20 cm.times.20 cm) is obtained from the
intermediate-layer sheet 13. The basis weight of the obtained
specimen is measured at three points along the width direction of
the specimen in accordance with JIS L1906 (Test methods for
nonwoven fabrics made of filament yarn), and the mean value of the
measured basis weight is defined as the basis weight of the whole
intermediate-layer sheet 13.
[0055] As for the basis weight of the first fiber layer 14, the
value obtained by subtracting the calculated basis weight of the
second fiber layer 15 from the basis weight of the whole
intermediate-layer sheet 13 is defined as the basis weight of the
first fiber layer 14.
[0056] The specimens of the second fiber layer 15 and the
intermediate-layer sheet 13 may also have a size other than that
(20 cm.times.20 cm) described above, as necessary.
(Pore Size)
[0057] As for the pore size, a circular specimen 42.5 mm in
diameter is obtained from the mask body (mouth covering part) 10.
The average pore size of the obtained specimen is measured by using
a known measuring device (Porous Materials, Inc.'s Automated Perm
Porometer), and the measured average pore size is defined as the
pore size. In this manner, the pore size of fibers forming, for
example, the outer layer sheet 11 and the inner layer sheet 12 can
be measured.
EXAMPLE 1
[0058] As for a specimen of example 1, a polypropylene meltblow
nonwoven fabric sheet (fiber diameter: 1.5 .mu.m, basis weight: 1.5
g/m.sup.2, particle diameter of the inorganic antimicrobial agent:
1.0 .mu.m, particle diameter of the inorganic antimicrobial
agent/fiber diameter: 0.7) is used as the nonwoven fabric sheet
corresponding to the first fiber layer 14 of the intermediate-layer
sheet 13. Further, a polypropylene meltblow nonwoven fabric sheet
(fiber diameter: 3.5 .mu.m, basis weight: 15 g/m.sup.2) is used as
the nonwoven fabric sheet corresponding to the second fiber layer
15 of the intermediate-layer sheet 13. This specimen has the total
basis weight of 84.1 g/m.sup.2 and contains the inorganic
antimicrobial agent of 0.15 g/m.sup.2.
EXAMPLE 2
[0059] As for a specimen of example 2, a polypropylene meltblow
nonwoven fabric sheet (fiber diameter: 0.5 .mu.m, basis weight: 1.5
g/m.sup.2, particle diameter of the inorganic antimicrobial agent:
0.2 .mu.m, particle diameter of the inorganic antimicrobial
agent/fiber diameter: 0.4) is used as the nonwoven fabric sheet
corresponding to the first fiber layer 14 of the intermediate-layer
sheet 13. Further, as the nonwoven fabric sheet corresponding to
the second fiber layer 15 of the intermediate-layer sheet 13, the
same nonwoven fabric sheet as in the specimen of example 1 is used.
This specimen has the same total basis weight and contains the same
amount (g/m.sup.2) of the inorganic antimicrobial agent as the
specimen of example 1.
EXAMPLE 3
[0060] As for a specimen of example 3, a polypropylene meltblow
nonwoven fabric sheet (fiber diameter: 1.5 .mu.m, basis weight: 1.5
g/m.sup.2, particle diameter of the inorganic antimicrobial agent:
0.2 .mu.m, particle diameter of the inorganic antimicrobial
agent/fiber diameter: 0.13) is used as the nonwoven fabric sheet
corresponding to the first fiber layer 14 of the intermediate-layer
sheet 13. Further, as the nonwoven fabric sheet corresponding to
the second fiber layer 15 of the intermediate-layer sheet 13, the
same nonwoven fabric sheet as in the specimen of example 1 is used.
This specimen also has the same total basis weight and contains the
same amount of the inorganic antimicrobial agent as the specimen of
example 1.
EXAMPLE 4
[0061] As for a specimen of example 4, a polypropylene meltblow
nonwoven fabric sheet (fiber diameter: 2.0 .mu.m, basis weight: 1.0
g/m.sup.2, particle diameter of the inorganic antimicrobial agent:
0.2 .mu.m, particle diameter of the inorganic antimicrobial
agent/fiber diameter: 0.1) is used as the nonwoven fabric sheet
corresponding to the first fiber layer 14 of the intermediate-layer
sheet 13. Further, as the nonwoven fabric sheet corresponding to
the second fiber layer 15 of the intermediate-layer sheet 13, the
same nonwoven fabric sheet as in the specimen of example 1 is used.
This specimen also has the same total basis weight and contains the
same amount of the inorganic antimicrobial agent as the specimen of
example 1.
EXAMPLE 5
[0062] As for a specimen of example 5, a polypropylene meltblow
nonwoven fabric sheet (fiber diameter: 0.5 .mu.m, basis weight: 1.0
g/m.sup.2, particle diameter of the inorganic antimicrobial agent:
1.0 .mu.m, particle diameter of the inorganic antimicrobial
agent/fiber diameter: 2.0) is used as the nonwoven fabric sheet
corresponding to the first fiber layer 14 of the intermediate-layer
sheet 13. Further, as the nonwoven fabric sheet corresponding to
the second fiber layer 15 of the intermediate-layer sheet 13, the
same nonwoven fabric sheet as in the specimen of example 1 is used.
This specimen also has the same total basis weight and contains the
same amount of the inorganic antimicrobial agent as the specimen of
example 1.
EXAMPLE 6
[0063] As for a specimen of example 6, a polypropylene meltblow
nonwoven fabric sheet (fiber diameter: 2.8 .mu.m, basis weight: 1.0
g/m.sup.2, particle diameter of the inorganic antimicrobial agent:
1.0 .mu.m, particle diameter of the inorganic antimicrobial
agent/fiber diameter: 0.36) is used as the nonwoven fabric sheet
corresponding to the first fiber layer 14 of the intermediate-layer
sheet 13. Further, as the nonwoven fabric sheet corresponding to
the second fiber layer 15 of the intermediate-layer sheet 13, the
same nonwoven fabric sheet as in the specimen of example 1 is used.
This specimen also has the same total basis weight and contains the
same amount of the inorganic antimicrobial agent as the specimen of
example 1.
EXAMPLE 7
[0064] As for a specimen of example 7, a polypropylene meltblow
nonwoven fabric sheet (fiber diameter: 0.5 .mu.m, basis weight: 1.0
g/m.sup.2, particle diameter of the inorganic antimicrobial agent:
3.0 .mu.m, particle diameter of the inorganic antimicrobial
agent/fiber diameter: 6.0) is used as the nonwoven fabric sheet
corresponding to the first fiber layer 14 of the intermediate-layer
sheet 13. Further, as the nonwoven fabric sheet corresponding to
the second fiber layer 15 of the intermediate-layer sheet 13, the
same nonwoven fabric sheet as in the specimen of example 1 is used.
This specimen also has the same total basis weight and contains the
same amount of the inorganic antimicrobial agent as the specimen of
example 1.
EXAMPLE 8
[0065] As for a specimen of example 8, a polypropylene meltblow
nonwoven fabric sheet (fiber diameter: 1.0 .mu.m, basis weight: 1.0
g/m.sup.2, particle diameter of the inorganic antimicrobial agent:
6.0 .mu.m, particle diameter of the inorganic antimicrobial
agent/fiber diameter: 6.0) is used as the nonwoven fabric sheet
corresponding to the first fiber layer 14 of the intermediate-layer
sheet 13. Further, as the nonwoven fabric sheet corresponding to
the second fiber layer 15 of the intermediate-layer sheet 13, the
same nonwoven fabric sheet as in the specimen of example 1 is used.
This specimen also has the same total basis weight and contains the
same amount of the inorganic antimicrobial agent as the specimen of
example 1.
EXAMPLE 9
[0066] As for a specimen of example 9, a polypropylene meltblow
nonwoven fabric sheet (fiber diameter: 1.5 .mu.m, basis weight: 1.0
g/m.sup.2, particle diameter of the inorganic antimicrobial agent:
6.0 .mu.m, particle diameter of the inorganic antimicrobial
agent/fiber diameter: 4.0) is used as the nonwoven fabric sheet
corresponding to the first fiber layer 14 of the intermediate-layer
sheet 13. Further, as the nonwoven fabric sheet corresponding to
the second fiber layer 15 of the intermediate-layer sheet 13, the
same nonwoven fabric sheet as in the specimen of example 1 is used.
This specimen also has the same total basis weight and contains the
same amount of the inorganic antimicrobial agent as the specimen of
example 1.
EXAMPLE 10
[0067] As for a specimen of example 10, a polypropylene meltblow
nonwoven fabric sheet (fiber diameter: 2.8 .mu.m, basis weight: 1.0
g/m.sup.2, particle diameter of the inorganic antimicrobial agent:
6.0 .mu.m, particle diameter of the inorganic antimicrobial
agent/fiber diameter: 2.1) is used as the nonwoven fabric sheet
corresponding to the first fiber layer 14 of the intermediate-layer
sheet 13. Further, as the nonwoven fabric sheet corresponding to
the second fiber layer 15 of the intermediate-layer sheet 13, the
same nonwoven fabric sheet as in the specimen of example 1 is used.
This specimen also has the same total basis weight and contains the
same amount of the inorganic antimicrobial agent as the specimen of
example 1.
COMPARATIVE EXAMPLE 1
[0068] As for a specimen of comparative example 1, the
intermediate-layer sheet 13 is formed only by a nonwoven fabric
sheet having a single fiber layer, and a polypropylene meltblow
nonwoven fabric sheet (fiber diameter: 3.5 .mu.m, basis weight: 18
g/m.sup.2, particle diameter of the inorganic antimicrobial agent:
1.0 .mu.m) is used as the nonwoven fabric sheet. This specimen has
the total basis weight of 85.6 g/m.sup.2 and contains the inorganic
antimicrobial agent of 0.30 g/m.sup.2.
COMPARATIVE EXAMPLE 2
[0069] As for a specimen of comparative example 2, a polypropylene
meltblow nonwoven fabric sheet (fiber diameter: 0.4 .mu.m, basis
weight: 1.5 g/m.sup.2, particle diameter of the inorganic
antimicrobial agent: 0.1 .mu.m, particle diameter of the inorganic
antimicrobial agent/fiber diameter: 0.25) is used as the nonwoven
fabric sheet corresponding to the first fiber layer 14 of the
intermediate-layer sheet 13. Further, as the nonwoven fabric sheet
corresponding to the second fiber layer 15 of the
intermediate-layer sheet 13, the same nonwoven fabric sheet as in
the specimen of example 1 is used. This specimen has the same total
basis weight and contains the same amount of the inorganic
antimicrobial agent as the specimen of example 1.
COMPARATIVE EXAMPLE 3
[0070] As for a specimen of comparative example 3, a polypropylene
meltblow nonwoven fabric sheet (fiber diameter: 1.5 .mu.m, basis
weight: 1.5 g/m.sup.2, particle diameter of the inorganic
antimicrobial agent: 0.1 .mu.m, particle diameter of the inorganic
antimicrobial agent/fiber diameter: 0.07) is used as the nonwoven
fabric sheet corresponding to the first fiber layer 14 of the
intermediate-layer sheet 13. Further, as the nonwoven fabric sheet
corresponding to the second fiber layer 15 of the
intermediate-layer sheet 13, the same nonwoven fabric sheet as in
the specimen of example 1 is used. This specimen has the same total
basis weight and contains the same amount of the inorganic
antimicrobial agent as the specimen of example 1.
COMPARATIVE EXAMPLE 4
[0071] As for a specimen of comparative example 4, a polypropylene
meltblow nonwoven fabric sheet (fiber diameter: 2.5 .mu.m, basis
weight: 1.5 g/m.sup.2, particle diameter of the inorganic
antimicrobial agent: 0.2 .mu.m, particle diameter of the inorganic
antimicrobial agent/fiber diameter: 0.08) is used as the nonwoven
fabric sheet corresponding to the first fiber layer 14 of the
intermediate-layer sheet 13. Further, as the nonwoven fabric sheet
corresponding to the second fiber layer 15 of the
intermediate-layer sheet 13, the same nonwoven fabric sheet as in
the specimen of example 1 is used. This specimen has the same total
basis weight and contains the same amount of the inorganic
antimicrobial agent as the specimen of example 1.
COMPARATIVE EXAMPLE 5
[0072] As for a specimen of comparative example 5, a polypropylene
meltblow nonwoven fabric sheet (fiber diameter: 0.4 .mu.m, basis
weight: 1.5 g/m.sup.2, particle diameter of the inorganic
antimicrobial agent: 1.0 .mu.m, particle diameter of the inorganic
antimicrobial agent/fiber diameter: 2.5) is used as the nonwoven
fabric sheet corresponding to the first fiber layer 14 of the
intermediate-layer sheet 13. Further, as the nonwoven fabric sheet
corresponding to the second fiber layer 15 of the
intermediate-layer sheet 13, the same nonwoven fabric sheet as in
the specimen of example 1 is used. This specimen has the same total
basis weight and contains the same amount of the inorganic
antimicrobial agent as the specimen of example 1.
COMPARATIVE EXAMPLE 6
[0073] As for a specimen of comparative example 6, a polypropylene
meltblow nonwoven fabric sheet (fiber diameter: 3.0 .mu.m, basis
weight: 1.5 g/m.sup.2, particle diameter of the inorganic
antimicrobial agent: 1.0 .mu.m, particle diameter of the inorganic
antimicrobial agent/fiber diameter: 0.3) is used as the nonwoven
fabric sheet corresponding to the first fiber layer 14 of the
intermediate-layer sheet 13. Further, as the nonwoven fabric sheet
corresponding to the second fiber layer 15 of the
intermediate-layer sheet 13, the same nonwoven fabric sheet as in
the specimen of example 1 is used. This specimen has the same total
basis weight and contains the same amount of the inorganic
antimicrobial agent as the specimen of example 1.
COMPARATIVE EXAMPLE 7
[0074] As for a specimen of comparative example 7, a polypropylene
meltblow nonwoven fabric sheet (fiber diameter: 0.4 .mu.m, basis
weight: 1.5 g/m.sup.2, particle diameter of the inorganic
antimicrobial agent: 3.0 .mu.m, particle diameter of the inorganic
antimicrobial agent/fiber diameter: 7.5) is used as the nonwoven
fabric sheet corresponding to the first fiber layer 14 of the
intermediate-layer sheet 13. Further, as the nonwoven fabric sheet
corresponding to the second fiber layer 15 of the
intermediate-layer sheet 13, the same nonwoven fabric sheet as in
the specimen of example 1 is used. This specimen has the same total
basis weight and contains the same amount of the inorganic
antimicrobial agent as the specimen of example 1.
COMPARATIVE EXAMPLE 8
[0075] As for a specimen of comparative example 8, a polypropylene
meltblow nonwoven fabric sheet (fiber diameter: 0.9 .mu.m, basis
weight: 1.5 g/m.sup.2, particle diameter of the inorganic
antimicrobial agent: 6.0 .mu.m, particle diameter of the inorganic
antimicrobial agent/fiber diameter: 6.7) is used as the nonwoven
fabric sheet corresponding to the first fiber layer 14 of the
intermediate-layer sheet 13. Further, as the nonwoven fabric sheet
corresponding to the second fiber layer 15 of the
intermediate-layer sheet 13, the same nonwoven fabric sheet as in
the specimen of example 1 is used. This specimen has the same total
basis weight and contains the same amount of the inorganic
antimicrobial agent as the specimen of example 1.
COMPARATIVE EXAMPLE 9
[0076] As for a specimen of comparative example 9, a polypropylene
meltblow nonwoven fabric sheet (fiber diameter: 1.5 .mu.m, basis
weight: 1.5 g/m.sup.2, particle diameter of the inorganic
antimicrobial agent: 7.0 .mu.m, particle diameter of the inorganic
antimicrobial agent/fiber diameter: 4.7) is used as the nonwoven
fabric sheet corresponding to the first fiber layer 14 of the
intermediate-layer sheet 13. Further, as the nonwoven fabric sheet
corresponding to the second fiber layer 15 of the
intermediate-layer sheet 13, the same nonwoven fabric sheet as in
the specimen of example 1 is used. This specimen has the same total
basis weight and contains the same amount of the inorganic
antimicrobial agent as the specimen of example 1.
COMPARATIVE EXAMPLE 10
[0077] As for a specimen of comparative example 10, a polypropylene
meltblow nonwoven fabric sheet (fiber diameter: 3.0 .mu.m, basis
weight: 1.5 g/m.sup.2, particle diameter of the inorganic
antimicrobial agent: 7.0 .mu.m, particle diameter of the inorganic
antimicrobial agent/fiber diameter: 2.3) is used as the nonwoven
fabric sheet corresponding to the first fiber layer 14 of the
intermediate-layer sheet 13. Further, as the nonwoven fabric sheet
corresponding to the second fiber layer 15 of the
intermediate-layer sheet 13, the same nonwoven fabric sheet as in
the specimen of example 1 is used. This specimen has the same total
basis weight and contains the same amount of the inorganic
antimicrobial agent as the specimen of example 1.
(Derivation and Evaluation of Air Permeability)
[0078] For measurement of air permeability, a specimen of 40 mm or
longer in height and width was obtained from the mask body (mouth
covering part). The air permeability is preferably measured only in
a meltblow layer (filter layer), but in the case of a specimen in
which the meltblow layer is bonded with any other layer by an
ultrasonic seal, a heat seal, an adhesive or other similar bonding
methods, the measurement is conducted in a minimum number of layers
including the meltblow layer. The air permeability was measured by
using an Automatic Air-Permeability Tester (Kato Tech's
"KES-F8-AP1"). Specifically, the tester discharged air onto the
specimen (discharge mode) and sucked air from the specimen (intake
mode) at a flow rate of 4 cc/cm.sup.2/sec (area:
2.pi..times.10.sup.-4 m.sup.2). After 3 seconds of the discharge
mode and 3 seconds of the intake mode, the pressure loss was
measured by using a semiconductor type differential pressure gauge.
The air permeability (cc/cm.sup.2/sec) was then obtained from the
integral of the measurement.
[0079] Further, based on the obtained air permeability
(cc/cm.sup.2/sec), the air permeability was assessed in three
levels of .largecircle., .DELTA., .times.. The air permeability
(cc/cm.sup.2/sec) of 0.41 or lower was assessed as .largecircle.,
0.42 to 0.45 as .DELTA., and 0.46 or higher as .times..
(Derivation and Evaluation of Bacterial Filtration Efficiency
(BFE))
[0080] For measurement of bacterial filtration efficiency (BFE), a
specimen of 90 mm or longer in height and width was obtained from
the mask body (mouth covering part). When a specimen of this size
could not be obtained from the mask body (mouth covering part), a
plurality of specimens were obtained and rectilinearly bonded
together along their overlapped edges by ultrasonic sealing or heat
sealing such that a specimen of 90 mm or longer in height and width
was obtained. The bacterial filtration efficiency is preferably
measured only in a meltblow layer (filter layer), but in the case
of a specimen having a composite layer of the meltblow layer and
any other layer (e.g. spunbond layer), the measurement was
conducted in a minimum unit including the meltblow layer. The
bacterial filtration efficiency (BFE) was measured in accordance
with ASTM F2101-07. The bacterial filtration efficiency (BFE) was
obtained from the following equation:
bacterial filtration efficiency (BFE) (%)={(A-B)/A}.times.100,
where A is the average number of control colonies, and B is the
average number of sample colonies.
[0081] Further, based on this bacterial filtration efficiency
(BFE), the filtration efficiency was assessed in three levels of
.largecircle., .DELTA., .times.. The bacterial filtration
efficiency (BFE) of 95% or higher was assessed as .largecircle.,
the bacterial filtration efficiency of 90 to 94% as .DELTA., and
the bacterial filtration efficiency of 89% or lower as .times..
(Testing for Antibacterial Activity)
[0082] For testing for antibacterial activity, 0.4 gram of an
antibacterial finished portion of the mask body (mouth covering
part) was obtained as a specimen. This testing was conducted in
accordance with the absorption method of JIS L1902, and the
antibacterial efficacy (activity value) was measured. This testing
was considered valid when the growth value of the viable bacteria
count is 1.0 or higher, and the bacteriostasis activity value was
measured as the above-described activity value. It was considered
as having antibacterial effects when the bacteriostasis activity
value is 2.0 or higher.
(Derivation and Evaluation of Virus Decrease Rate)
[0083] In an influenza virus inactivation test relating to virus
decrease rate, when a specimen is water-repellent, it must be
impregnated with sterile distilled water. Therefore, a specimen
obtained from the mask body (mouth covering part) was subjected to
a hydrophilizing process in advance by using Tween 80 as an
activator in the following procedure. Tween 80 having the solution
concentration of 0.05% is used. Tween 80 is hard to dissolve, so
that it should be melted over low heat by using a magnetic stirrer
with a heater, or first dissolved in hot water. Then the specimen
to be hydrophilized is immersed in this liquid and dried in an oven
at 90.degree. C.
[0084] This testing was conducted as follows:
[0085] Influenza virus A/H1N1 was used as the virus being
tested.
[0086] The influenza virus was inoculated into the allantoic cavity
of an embryonated chicken egg and cultured in an incubator. Then
the allantoic fluid was removed and the virus liquid was purified
from the allantoic fluid by density gradient centrifugation and
used as the virus being tested. The virus culture time setting was
24 hours.
[0087] The specimen cut into 4 cm squares was placed in a plastic
petri dish, and 0.2 ml of the virus liquid being tested was added
to the specimen. Further, the upper side of the specimen was
covered with a film of 4 cm squares, so that the contact efficiency
of the virus and the specimen is enhanced. After letting the virus
sit (culture) for 24 hours at room temperature, the specimen and
the film were transferred into a centrifuging tube containing 5 ml
of phosphate buffered saline (PBS). Then it was mixed for 30
seconds with a vortex mixer, so that the test virus was washed away
from the specimen. In this manner, a quantitative test specimen was
obtained.
[0088] The specimen may also have a size other than that (4
cm.times.4 cm) described above, as necessary.
[0089] A ten-fold serial dilution of the above-described
quantitative test specimen as stock solution in PBS was performed.
The diluted virus solution and MDCK (Madin-Darby canine kidney)
cells were seeded in a 96-well plate and cultured for five days in
a carbon dioxide incubator of 37.degree. C. Subsequently, the cells
in the wells were fixed and stained with 4% formalin and 0.1%
crystal violet and rinsed in water. The wells were then dried and
50 ml of ethanol was added to each well. The absorbance (585 nm of
peak wavelength) of crystal violet eluted from stained uninfected
cells was determined, and the virus infectivity titer TCID50
(median tissue culture infectious dose) was obtained. Thus the
TCID50 per one specimen was calculated.
[0090] Based on the ratio of the calculated infectivity titer of
the virus obtained after 24 hours with respect to a blank value,
the virus decrease rate was obtained from the following
equation:
virus decrease rate (%)=100-{(virus infectivity titer after 24
hrs)/(blank value)}
[0091] Further, based on the calculated virus decrease rate (%),
the antiviral efficacy was assessed in three levels of
.largecircle., .DELTA., .times.. The virus decrease rate of 90% or
higher was assessed as .largecircle., 11 to 89% as .DELTA., and 10%
or lower as .times..
[0092] Based on the above-described various derived measurements,
the specimens of examples 1 to 10 and comparative examples 1 to 10
were evaluated as follows:
EVALUATION RESULTS OF EXAMPLES 1 TO 10
[0093] The specimen of example 1 has the virus decrease rate of
99.9%, air permeability of 0.413 cc/cm.sup.2/sec and BFE of
99.1%.
[0094] The specimen of example 2 has the virus decrease rate of
99.9%, air permeability of 0.421 cc/cm.sup.2/sec and BFE of
99.3%.
[0095] The specimen of example 3 has the virus decrease rate of
90.2%, air permeability of 0.414 cc/cm.sup.2/sec and BFE of
99.1%.
[0096] The specimen of example 4 has the virus decrease rate of
90.0%, air permeability of 0.409 cc/cm.sup.2/sec and BFE of
99.0%.
[0097] The specimen of example 5 has the virus decrease rate of
99.9%, air permeability of 0.422 cc/cm.sup.2/sec and BFE of
99.3%.
[0098] The specimen of example 6 has the virus decrease rate of
94.5%, air permeability of 0.401 cc/cm.sup.2/sec and BFE of
98.1%.
[0099] The specimen of example 7 has the virus decrease rate of
99.9%, air permeability of 0.420 cc/cm.sup.2/sec and BFE of
99.0%.
[0100] The specimen of example 8 has the virus decrease rate of
99.9%, air permeability of 0.416 cc/cm.sup.2/sec and BFE of
99.1%.
[0101] The specimen of example 9 has the virus decrease rate of
99.9%, air permeability of 0.413 cc/cm.sup.2/sec and BFE of
99.3%.
[0102] The specimen of example 10 has the virus decrease rate of
99.9%, air permeability of 0.402 cc/cm.sup.2/sec and BFE of
97.0%.
[0103] All of the specimens of examples 1 to 10 were assessed as
.largecircle. in all of antiviral efficacy, air permeability and
capture efficiency. Specifically, it was verified that they are
effective in providing a mask having high antibacterial and
antiviral effects and high air permeability and capture efficiency.
Further, all of the specimens of examples 1 to 10 also provide high
enough production efficiency without causing such a problem of
fiber breakage which may decrease the production efficiency.
EVALUATION RESULTS OF COMPARATIVE EXAMPLE 1
[0104] The specimen of comparative example 1 has the virus decrease
rate of 15.0%, air permeability of 0.412 cc/cm.sup.2/sec and BFE of
96.1%. Specifically, in the specimen of comparative example 1, the
antimicrobial agent is particularly hard to be exposed to the fiber
surface and the nonwoven fabric surface, and the antiviral efficacy
was assessed as .DELTA.. Therefore, it was verified that the
specimen of comparative example 1 has lower antibacterial and
antiviral effects than examples 1 to 10.
EVALUATION RESULTS OF COMPARATIVE EXAMPLE 2
[0105] The specimen of comparative example 2 has the virus decrease
rate of 10.0%, air permeability of 0.433 cc/cm.sup.2/sec and BFE of
97.3%. Specifically, in the specimen of comparative example 2, the
antimicrobial agent is particularly hard to be exposed to the fiber
surface and the nonwoven fabric surface, and the antiviral efficacy
was assessed as .times.. Therefore, it was verified that the
specimen of comparative example 2 has lower antibacterial and
antiviral effects than examples 1 to 10. Further, fibers of the
specimen of comparative example 2 having a small fiber diameter are
easy to break, so that stable productivity cannot be obtained.
EVALUATION RESULTS OF COMPARATIVE EXAMPLE 3
[0106] The specimen of comparative example 3 has the virus decrease
rate of 10.0%, air permeability of 0.414 cc/cm.sup.2/sec and BFE of
97.1%. Specifically, in the specimen of comparative example 3, the
antimicrobial agent is particularly hard to be exposed to the fiber
surface and the nonwoven fabric surface, and the antiviral efficacy
was assessed as .times.. Therefore, it was verified that the
specimen of comparative example 3 has lower antibacterial and
antiviral effects than examples 1 to 10.
EVALUATION RESULTS OF COMPARATIVE EXAMPLE 4
[0107] The specimen of comparative example 4 has the virus decrease
rate of 12.0%, air permeability of 0.405 cc/cm.sup.2/sec and BFE of
96.0%. Specifically, in the specimen of comparative example 4, the
antimicrobial agent is particularly hard to be exposed to the fiber
surface and the nonwoven fabric surface, and the antiviral efficacy
was assessed as .DELTA.. Therefore, it was verified that the
specimen of comparative example 4 has lower antibacterial and
antiviral effects than examples 1 to 10.
EVALUATION RESULTS OF COMPARATIVE EXAMPLE 5
[0108] The specimen of comparative example 5 has the virus decrease
rate of 70.0%, air permeability of 0.434 cc/cm.sup.2/sec and BFE of
97.0%. Specifically, in the specimen of comparative example 5, the
antimicrobial agent is particularly hard to be exposed to the fiber
surface and the nonwoven fabric surface, and the antiviral efficacy
was assessed as .DELTA.. Therefore, it was verified that the
specimen of comparative example 5 has lower antibacterial and
antiviral effects than examples 1 to 10. Further, fibers of the
specimen of comparative example 2 having a small fiber diameter are
easy to break, so that stable productivity cannot be obtained.
EVALUATION RESULTS OF COMPARATIVE EXAMPLE 6
[0109] The specimen of comparative example 6 has the virus decrease
rate of 10.0%, air permeability of 0.402 cc/cm.sup.2/sec and BFE of
96.8%. Specifically, in the specimen of comparative example 6, the
antimicrobial agent is particularly hard to be exposed to the fiber
surface and the nonwoven fabric surface, and the antiviral efficacy
was assessed as .DELTA.. Therefore, it was verified that the
specimen of comparative example 6 has lower antibacterial and
antiviral effects than examples 1 to 10. Further, the capture
efficiency of comparative example 6 was assessed as .DELTA., and it
was verified that the specimen of comparative example 6 has lower
capture efficiency than examples 1 to 10.
EVALUATION RESULTS OF COMPARATIVE EXAMPLE 7
[0110] The specimen of comparative example 7 has the virus decrease
rate of 98.0%, air permeability of 0.408 cc/cm.sup.2/sec and BFE of
95.0%. Specifically, the specimen of comparative example 7 has high
antivirus efficacy, air permeability and capture efficiency, but it
has demerits that fibers having a small fiber diameter are easy to
break, so that stable productivity cannot be obtained.
EVALUATION RESULTS OF COMPARATIVE EXAMPLE 8
[0111] The specimen of comparative example 8 has the virus decrease
rate of 99.0%, air permeability of 0.407 cc/cm.sup.2/sec and BFE of
91.3%. Specifically, the capture efficiency of comparative example
8 was assessed as .DELTA., and it was verified that the specimen of
comparative example 8 has lower capture efficiency than examples 1
to 10.
EVALUATION RESULTS OF COMPARATIVE EXAMPLE 9
[0112] The specimen of comparative example 9 has the virus decrease
rate of 99.0%, air permeability of 0.411 cc/cm.sup.2/sec and BFE of
92.0%. Specifically, the capture efficiency of the comparative
example 9 was assessed as .DELTA., and it was verified that the
specimen of comparative example 9 has lower capture efficiency than
examples 1 to 10. Further, fibers of the specimen of comparative
example 9 having a small fiber diameter are easy to break, so that
stable productivity cannot be obtained.
EVALUATION RESULTS OF COMPARATIVE EXAMPLE 10
[0113] The specimen of comparative example 10 has the virus
decrease rate of 99.0%, air permeability of 0.401 cc/cm.sup.2/sec
and BFE of 95.9%. Specifically, the capture efficiency of the
comparative example 10 was assessed as .DELTA., and it was verified
that the specimen of comparative example 10 has lower capture
efficiency than examples 1 to 10.
[0114] By provision of the above-described construction, when
breathing of a mask wearer creates air flow from the mask outer
surface toward the wearer's mouth, airborne droplets containing
bacteria or viruses are led to the intermediate-layer sheet 13
without being absorbed by the outer layer sheet 11 formed of
hydrophobic fibers or water-repellent fibers (without staying on
the mask outer surface). Therefore, even if the wearer touches the
mask body (mask cup) when putting on or off the mask, secondary
infection can be prevented.
[0115] Further, from the above-described evaluation results of
specimens of examples 1 to 10 and comparative examples 1 to 10, in
order to realize high antibacterial and antiviral effects and to
improve air permeability, capture efficiency and productivity, the
fiber diameter of the first fiber layer 14 of the
intermediate-layer sheet 13 is set within the range of 0.5 to 2.8
.mu.m and the ratio of the particle diameter of the inorganic
antimicrobial agent with respect to the fiber diameter is set
within the range of 0.1 to 6.0, or the fiber diameter of the first
fiber layer 14 of the intermediate-layer sheet 13 is set within the
range of 0.5 to 2.8 .mu.m and the particle diameter of the
inorganic antimicrobial agent is set within the range of 0.2 to 6.0
.mu.m.
[0116] Particularly as for the antibacterial and antiviral effects,
by provision of the above-described construction, the inorganic
antimicrobial agent can be effectively exposed onto the fiber
surface, so that the inherent antibacterial and antiviral effects
of the inorganic antimicrobial agent against pathogens such as
bacteria and viruses can be fully exerted. Further, when it is
designed and provided to have the same antibacterial and antiviral
effects as a mask not having the above-described construction, the
composition ratio of the inorganic antimicrobial agent can be
reduced. Thus, the effect of reducing the product costs can be
increased.
[0117] Further, with the above-described construction, productivity
and performance can be improved. For example, when the fiber
diameter of the first fiber layer 14 is set within the
above-described range, compared with a construction in which it is
smaller than the above-described range, decrease of productivity
due to fiber breakage can be further prevented. Further, when the
fiber diameter of the first fiber layer 14 is set within the
above-described range, compared with a construction in which it is
larger than the above-described range, the inorganic antimicrobial
agent can be effectively exposed onto the fiber surface, so that
the antibacterial and antiviral effects of the inorganic
antimicrobial agent can be fully exerted. Further, when the
particle diameter of the inorganic antimicrobial agent of the first
fiber layer 14 is set within the above-described range, compared
with a construction in which it is larger than the above-described
range, decrease of productivity due to fiber breakage can be
further prevented. Further, when the particle diameter of the
inorganic antimicrobial agent of the first fiber layer 14 is set
within the above-described range, compared with a construction in
which it is smaller than the above-described range, the inorganic
antimicrobial agent can be effectively exposed onto the fiber
surface, so that the antibacterial and antiviral effects of the
inorganic antimicrobial agent can be fully exerted.
Other Embodiments
[0118] The present invention is not limited to the above
embodiment, but rather, may be added to, changed, replaced with
alternatives or otherwise modified. For example, the following
provisions can be made in application of this embodiment.
[0119] In the above embodiment, the outer layer sheet 11 and the
inner layer sheet 12 are described as being formed as a low-density
pointbond nonwoven fabric sheet point-bonded by a pressure roll,
but it is essential for the outer layer sheet 11 and the inner
layer sheet 12 to be formed of nonwoven fabric having the fiber
diameter of 10 to 40 .mu.m. Thus, nonwoven fabric sheets other than
the pointbond nonwoven fabric sheet may be used. For example, the
outer layer sheet 11 and the inner layer sheet 12 may also be
formed by a spun lace nonwoven fabric sheet manufactured by a
spunlacing method, an air-through nonwoven fabric sheet
manufactured by an air-through bonding method, or a spunbond
nonwoven fabric sheet manufactured by a spunbonding method.
[0120] Further, in the above embodiment, the first fiber layer 14
of the intermediate layer sheet 13 is described as being disposed
on the outer layer sheet 11 side (the outer side) of the second
fiber layer 15, but in accordance with product specifications or
the like, the second fiber layer 15 may be disposed on the outer
layer sheet 11 side (the outer side) of the first fiber layer
14.
[0121] Further, in the above embodiment, both of the outer layer
sheet 11 and the inner layer sheet 12 are described as being formed
of fibers having a fiber diameter of 10 to 40 .mu.m and a pore size
of 60 to 100 .mu.m, but the fiber diameter and the pore size of the
outer layer sheet 11 and the inner layer sheet 12 do not
necessarily have to be set within these ranges.
[0122] Further, in the above embodiment, the bonding parts 16 are
described as being provided between the outer layer sheet 11 and
the intermediate layer sheet 13 and between the inner layer sheet
12 and the intermediate layer sheet 13, but both or at least one of
the bonding parts 16 may be dispensed with.
[0123] Further, in the above embodiment, the intermediate layer
sheet 13 is described as being subjected to electret treatment in
order to improve the capture efficiency of the mask, but whether it
is subjected to electret treatment or not can be appropriately
selected as necessary. For example, if it can achieve desired
capture efficiency without being subjected to electret treatment,
it does not necessarily have to be subjected to electret
treatment.
[0124] Further, in the above embodiment, the mask body 10 is
described as being formed by bonding the right and left sheet
pieces 10a, 10b by heat-sealing, but the mask body can be formed by
bonding at least one sheet in its entirety or in part by using
various bonding methods including heat sealing.
[0125] Further, in the above embodiment, the mask is described as
being of disposable type designed for a single or multiple use
which can be used once or several times, but this invention can
also be applied to a mask of reusable type which can be reused by
washing, provided that the materials of the mask body and the ear
straps are appropriately selected. Further, in this embodiment, the
mask body is described as being three-dimensional, but this
invention can also be applied to a mask having a planar mask
body.
DESCRIPTION OF NUMERALS
[0126] 1 mask [0127] 10 mask body [0128] 10a right sheet piece
[0129] 10b left sheet piece [0130] 10c bonding edge [0131] 11 outer
layer sheet [0132] 12 inner layer sheet [0133] 13
intermediate-layer sheet [0134] 14 first fiber layer [0135] 15
second fiber layer [0136] 16 bonding part [0137] 20 ear strap
[0138] 21 opening
* * * * *