U.S. patent application number 13/266990 was filed with the patent office on 2012-02-23 for laminated nonwoven fabric.
Invention is credited to Nobuhiro Inokuma, Norihisa Matsuo, Minoru Yoshida.
Application Number | 20120045626 13/266990 |
Document ID | / |
Family ID | 43032253 |
Filed Date | 2012-02-23 |
United States Patent
Application |
20120045626 |
Kind Code |
A1 |
Inokuma; Nobuhiro ; et
al. |
February 23, 2012 |
LAMINATED NONWOVEN FABRIC
Abstract
An object of the present invention is to provide a nonwoven
fabric having high tensile strength and high tear strength. The
laminate nonwoven fabric of the present invention is a laminated
nonwoven fabric obtained by thermally press-contacting a
thermoplastic continuous fiber layer as an outer layer with both
surfaces of an interlayer, wherein the ratio (F1/F2) between the
average oblateness (F1) of the thermoplastic continuous fiber
present on the surface side and the average oblateness (F2) of the
thermoplastic continuous fiber present on the inner side is 1.20 or
more.
Inventors: |
Inokuma; Nobuhiro; (Tokyo,
JP) ; Matsuo; Norihisa; (Tokyo, JP) ; Yoshida;
Minoru; (Tokyo, JP) |
Family ID: |
43032253 |
Appl. No.: |
13/266990 |
Filed: |
April 28, 2010 |
PCT Filed: |
April 28, 2010 |
PCT NO: |
PCT/JP2010/057624 |
371 Date: |
October 28, 2011 |
Current U.S.
Class: |
428/195.1 ;
156/324 |
Current CPC
Class: |
B32B 2307/718 20130101;
B01D 61/025 20130101; B32B 2307/5825 20130101; B32B 2307/54
20130101; B01D 69/10 20130101; B32B 5/26 20130101; B32B 2262/0261
20130101; D04H 3/009 20130101; D04H 3/011 20130101; B32B 2250/20
20130101; B32B 2307/724 20130101; B32B 2250/03 20130101; Y10T
428/24802 20150115; B32B 2262/0284 20130101 |
Class at
Publication: |
428/195.1 ;
156/324 |
International
Class: |
B41M 5/00 20060101
B41M005/00; B29C 70/08 20060101 B29C070/08 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 30, 2009 |
JP |
2009-111448 |
Claims
1-15. (canceled)
16. A laminated nonwoven fabric obtained by thermally
press-contacting a thermoplastic continuous fiber layer as an outer
layer with both surfaces of an interlayer, wherein the ratio
(F1/F2) between the average oblateness (F1) of the thermoplastic
continuous fiber present on the surface side and the average
oblateness (F2) of the thermoplastic continuous fiber present on
the inner side is 1.2 or more.
17. The laminated nonwoven fabric according to claim 16, wherein
the interlayer contains at least one or more thermoplastic
ultrafine fiber layers.
18. The laminated nonwoven fabric according to claim 16, wherein
the average oblateness (F2) of the thermoplastic continuous fiber
present on the inner side is from 0.1 to 0.8.
19. The laminated nonwoven fabric according to claim 17, wherein
the fiber diameter of the thermoplastic continuous fiber is from 5
to 30 .mu.m and the fiber diameter of the thermoplastic ultrafine
fiber is from 0.5 to 10 .mu.m.
20. The laminated nonwoven fabric according to claim 16, wherein
the total thickness of the laminated nonwoven fabric is from 15 to
300 .mu.m.
21. The laminated nonwoven fabric according to claim 16, wherein
the total basis weight of the laminated nonwoven fabric is from 10
to 250 g/m.sup.2.
22. The laminated nonwoven fabric according to claim 16, wherein
the outer layer surface is bonded over the entire surface.
23. The laminated nonwoven fabric according to claim 17, wherein
the content ratio of the thermoplastic ultrafine fiber is from 5 to
40 wt %.
24. The laminated nonwoven fabric according to claim 16, wherein
the tensile strength in the machine direction per unit basis weight
is 1.00 (N/1.5 cm)/(g/m.sup.2) or more and the tear strength in the
machine direction per unit basis weight is 0.04 N/(g/m.sup.2) or
more.
25. The laminated nonwoven fabric according to claim 16, wherein
the resin component constituting the thermoplastic continuous fiber
is present in a state of forming a structure except for a
sheath-core structure.
26. The laminated nonwoven fabric according to claim 17, wherein
the thermoplastic continuous fiber and the thermoplastic ultrafine
fiber are composed of a single component.
27. The laminated nonwoven fabric according to claim 17, wherein
the thermoplastic continuous fiber and the thermoplastic ultrafine
fiber are composed of a polyester-based resin or a polyamide-based
resin.
28. A method for producing the laminated nonwoven fabric according
to claim 17, comprising a step of, after a thermoplastic continuous
fiber layer is stacked on both surfaces of a thermoplastic
ultrafine fiber layer, pressurizing and thermally press-contacting
the surfaces one by one in two stages between a flat rigid heated
roll and a non-heated elastic roll having a Shore hardness D of 60
to 95 under a surface pressure of 30 to 200 kg/cm.sup.2 by setting
the rigid heated roll temperature to a temperature 5.degree. C. or
more lower than the melting point of the resin constituting the
thermoplastic continuous fiber, wherein a step of rapidly cooling
the laminate is provided between said pressurizing and thermally
press-contacting steps in two stages.
29. A composite membrane support comprising the laminated nonwoven
fabric according to claim 16.
30. A composite membrane obtained by forming a porous layer and a
dense layer (skin layer) having a separation function, on the
composite membrane support according to claim 29.
Description
TECHNICAL FIELD
[0001] The present invention relates to a laminated nonwoven fabric
having high tensile strength and high tear strength and being
excellent in fuzz resistance, and a production method thereof.
BACKGROUND ART
[0002] Generally, when it is intended to obtain high tensile
strength in a continuous fiber nonwoven fabric, the tear strength
tends to be reduced due to increase of bonding points, and these
two effects cannot be easily attained at the same time.
[0003] Patent Document 1 describes a nonwoven fabric having
excellent fuzz resistance as well as high tensile strength and high
tear strength. This nonwoven fabric is a three-layer structure
nonwoven fabric using a thermoplastic continuous fiber composed of
a multiple component sheath-core fiber and consisting of a
thermoplastic continuous fiber layer/a thermoplastic ultrafine
fiber layer/a thermoplastic continuous fiber layer. A
low-melting-point component on the outer side of the fiber having a
sheath-core structure allows bonding of fibers to each other at a
low temperature, and a high-melting-point component on the inner
side does not participate in bonding, whereby high tensile strength
and high tear strength are realized. However, this nonwoven fabric
is liable to suffer from a problem that, for example, because of
multiple component, the heat-resisting temperature is not high; or
since a low-melting-point component is fused, a low-melting-point
component must be contained and resinification of fibers is locally
generated. For this reason, its application field is limited.
[0004] In Patent Document 2, it is proposed to use a thermoplastic
continuous fiber for suppressing fuzz on the surface, and use of a
composite thermoplastic continuous fiber composed of a plurality of
components is proposed so as to obtain an adequate effect of
suppressing fuzz and a sufficient tensile strength. However, in the
case of using a multiple component fiber, as described above, a
low-melting-point component is readily melted and this is liable to
bring about, for example, a problem in the heat resistance or a
problem of local generation of resinification. With respect to a
nonwoven fabric using a thermoplastic continuous fiber composed of
a single component, a method of laminating thermoplastic continuous
fiber nonwoven fabrics together and using the laminate has been
proposed, but in this method, interlayer separation readily takes
place and high tensile strength cannot be easily developed, or
although the separation may be suppressed by strongly
press-contacting the fabrics, local resinification is liable to
occur and it becomes difficult to obtain high tear strength.
Calendering using an elastic roll is also disclosed, but when this
technique is used, thermal pressure-contact in two stages is
usually applied so that a heated roll can be contacted with each of
the front and back surfaces, and there is a problem that in the
case of a single component, the bonding effect by calendering in
the second stage is insufficient and it is difficult to attain all
of fuzz prevention, high tensile strength and high tear strength at
the same time. This problem is presumed to be ascribable to the
fact that crystallization of the nonwoven fabric has proceeded by
the calendering in the first stage.
[0005] Patent Document 3 describes a nonwoven fabric with a
three-layer structure of thermoplastic continuous fiber
layer/thermoplastic ultrafine fiber layer/thermoplastic continuous
fiber layer, which is composed of a single component prepared using
a thermoplastic continuous fiber and has high tensile strength. It
is disclosed that the ultrafine fiber of the interlayer intrudes
into a gap between thermoplastic continuous fibers of the lower
layer and thereby the nonwoven fabric exhibits excellent tensile
strength as well as good filter and barrier properties, and that
the tensile strength is more enhanced by applying flat calendering
using a combination of a metal roll and a metal roll. However, the
nonwoven fabric produced by the spun-bonding method has problems
that dispersion of the basis weight is liable to be partially
generated, impairing the uniformity of the entirety, the range of
conditions to satisfy both fuzz prevention and high tear strength
is narrow, and local resinification readily occurs.
PRIOR ART
Patent Document
[0006] Patent Document 1: WO 2005/059219 [0007] Patent Document 2:
WO 2009/017086 [0008] Patent Document 3: WO 2006/068100
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0009] An object of the present invention is to provide a laminated
nonwoven fabric having high tensile strength and high tear strength
and being excellent in the fuzz resistance, and a production
process thereof.
Means to Solve the Problems
[0010] As a result of intensive studies on the problems above, the
present inventors have found that high tensile strength and high
tear strength can be realized by a laminated nonwoven fabric having
a specific cross-section structure where a thermoplastic continuous
fiber layer is bonded as an outer layer to both surfaces of an
interlayer and while the thermoplastic continuous fiber present on
the surface side has a large oblateness, the thermoplastic
continuous fiber present on the inner side has a small oblateness
and keeps the round shape. The present invention has been
accomplished based on this finding. Also, it has been found that
high tensile strength and high tear strength are achieved
particularly when the interlayer contains at least one or more
thermoplastic ultrafine fiber layers.
[0011] That is, the present invention is as follows.
[0012] (1) A laminated nonwoven fabric obtained by thermally
press-contacting a thermoplastic continuous fiber layer as an outer
layer with both surfaces of an interlayer, wherein the ratio
(F1/F2) between the average oblateness (F1) of the thermoplastic
continuous fiber present on the surface side and the average
oblateness (F2) of the thermoplastic continuous fiber present on
the inner side is 1.2 or more.
[0013] (2) The laminated nonwoven fabric as described in (1) above,
wherein the interlayer contains at least one or more thermoplastic
ultrafine fiber layers.
[0014] (3) The laminated nonwoven fabric as described in (1) or (2)
above, wherein the average oblateness (F2) of the thermoplastic
continuous fiber present on the inner side is from 0.1 to 0.8.
[0015] (4) The laminated nonwoven fabric as described in (2) or (3)
above, wherein the fiber diameter of the thermoplastic continuous
fiber is from 5 to 30 .mu.m and the fiber diameter of the
thermoplastic ultrafine fiber is from 0.5 to 10 .mu.m.
[0016] (5) The laminated nonwoven fabric as described in any one of
(1) to (4) above, wherein the total thickness of the laminated
nonwoven fabric is from 15 to 300 .mu.m.
[0017] (6) The laminated nonwoven fabric as described in any one of
(1) to (5) above, wherein the total basis weight of the laminated
nonwoven fabric is from 10 to 250 g/m.sup.2.
[0018] (7) The laminated nonwoven fabric as described in any one of
(1) to (6) above, wherein the outer layer surface is bonded over
the entire surface.
[0019] (8) The laminated nonwoven fabric as described in any one of
(2) to (7) above, wherein the content ratio of the thermoplastic
ultrafine fiber is from 5 to 40 wt %.
[0020] (9) The laminated nonwoven fabric as described in any one of
(1) to (8) above, wherein the tensile strength in the machine
direction per unit basis weight is 1.00 (N/1.5 cm)/(g/m.sup.2) or
more and the tear strength in the machine direction per unit basis
weight is 0.04 N/(g/m.sup.2) or more.
[0021] (10) The laminated nonwoven fabric as described in any one
of (1) to (9) above, wherein the resin component constituting the
thermoplastic continuous fiber is present in a state of forming a
structure except for a sheath-core structure.
[0022] (11) The laminated nonwoven fabric as described in any one
of (2) to (10) above, wherein the thermoplastic continuous fiber
and the thermoplastic ultrafine fiber are composed of a single
component.
[0023] (12) The laminated nonwoven fabric as described in any one
of (2) to (11) above, wherein the thermoplastic continuous fiber
and the thermoplastic ultrafine fiber are composed of a
polyester-based resin or a polyamide-based resin.
[0024] (13) A method for producing the laminated nonwoven fabric
described in any one of (2) to (12) above, comprising a step of,
after a thermoplastic continuous fiber layer is stacked on both
surfaces of a thermoplastic ultrafine fiber layer, pressurizing and
thermally press-contacting the surfaces one by one in two stages
between a flat rigid heated roll and a non-heated elastic roll
having a Shore hardness D of 60 to 95 under a surface pressure of
30 to 200 kg/cm by setting the rigid heated roll temperature to a
temperature 5.degree. C. or more lower than the melting point of
the resin constituting the thermoplastic continuous fiber, wherein
a step of rapidly cooling the laminate is provided between the
pressurizing and thermally press-contacting steps in two
stages.
[0025] (14) A composite membrane support comprising the laminated
nonwoven fabric described in any one of (1) to (12) above.
[0026] (15) A composite membrane obtained by forming a porous layer
and a dense layer (skin layer) having a separation function, on the
composite membrane support described in (14) above.
Effects of the Invention
[0027] The laminated nonwoven fabric of the present invention has
not only high tensile strength but also high tear strength and is
excellent in fuzz resistance and uniform in air permeability and
liquid permeability.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1 is a view schematically showing one example of the
cross-section of the laminated nonwoven fabric of the present
invention.
[0029] FIG. 2 is a graph showing the relationship between the
average oblateness ratio and the tear strength with respect to
Examples and Comparative Examples in the present invention.
[0030] FIG. 3 is a graph showing the relationship between the
average oblateness ratio and the tensile strength with respect to
Examples and Comparative Examples in the present invention.
MODE FOR CARRYING OUT THE INVENTION
[0031] The present invention is described in detail below by
taking, as an example, a case using a thermoplastic ultrafine layer
for the interlayer. However, the interlayer is not limited to a
thermoplastic ultrafine fiber layer and, for example, a bonding
material having a shape of powder, nonwoven fabric, paste, binder,
resin, emulsion or the like may be also used.
[0032] The structural features of the laminated nonwoven fabric of
the present invention are as follows.
[0033] (1) The cross-section structure of the nonwoven fabric is
controlled such that only thermoplastic continuous fibers on the
surface side of the laminated nonwoven fabric are thoroughly
deformed and press-contacted to cause great flattening and
thermoplastic continuous fibers present on the inner side of the
laminated nonwoven fabric are weakly press-contacted to cause small
flattening.
[0034] (2) A thermoplastic ultrafine fiber layer present as an
interlayer is bonded with upper and lower thermoplastic continuous
fiber layers, whereby the nonwoven fabric is integrated as a
whole.
[0035] These structural features are as shown in FIG. 1.
[0036] By controlling the cross-section structure of the nonwoven
fabric in this way, the thermoplastic continuous fiber on the
surface exerts high tensile strength, and the thermoplastic
continuous fiber on the inner side exerts high tear strength.
[0037] The thermoplastic continuous fiber as used in the present
invention means a fiber by a spunbond spinning method or the like,
which is melt-spun and continuously produced by extruding a molten
thermoplastic resin usually from a circular capillary spinneret. In
view of bonding property, the diameter of the fiber by the spunbond
spinning method is preferably 30 .mu.m or less, more preferably
from 5 to 20 .mu.m. Also, the basis weight of the nonwoven fabric
composed of the thermoplastic continuous fiber is suitably from 5
to 240 g/m.sup.2, preferably from 10 to 145 g/m.sup.2, more
preferably from 10 to 125 g/m.sup.2. The thermoplastic ultrafine
fiber is generally known as a meltblown fiber and is a fiber
melt-spun by extruding a thermoplastic resin through a plurality of
capillary spinnerets into a high-velocity gas, where the resin is
fragmented by the extrusion into a high-velocity gas. Also in the
present invention, from the standpoint that fibers can be on-line
stacked on the nonwoven fabric constituting the outer layer,
spinning by a meltblown method is preferred. The diameter of the
thermoplastic ultrafine fiber for use in the present invention is
preferably from 0.5 to 10 .mu.m, more preferably from 1 to 3 .mu.m.
Also, the basis weight of the nonwoven fabric composed of the
thermoplastic ultrafine bier is suitably from 0.5 to 100 g/m.sup.2,
preferably from 1 to 60 g/m.sup.2, more preferably from 1 to 50
g/m.sup.2.
[0038] FIG. 1 is a schematic view showing an example of the
cross-section of the laminated nonwoven fabric of the present
invention. The laminated nonwoven fabric shown in this schematic
view has a three-layer structure of thermoplastic continuous fiber
layer/thermoplastic ultrafine fiber layer/thermoplastic continuous
fiber layer.
[0039] In FIG. 1, 5 is the outer layer composed of a thermoplastic
continuous fiber (3), and 6 is the interlayer composed of a
thermoplastic ultrafine fiber (4). In the present invention, the
thermoplastic continuous fiber present on the surface side of the
laminated nonwoven fabric means, as shown in FIG. 1, the fiber
group 1 on the surface side out of four parts equally divided in
the thickness direction from the cross-section of the laminated
nonwoven fabric, and the thermoplastic continuous fiber present on
the inner side of the laminated nonwoven fabric means the fiber
group 2 on the inner side out of the equally-divided four
parts.
[0040] The average oblateness ratio as used herein is the value
(F1/F2) obtained by dividing the average oblateness F1 of the
thermoplastic continuous fiber on the surface side as measured in
the following manner, by the average oblateness F2 of the
thermoplastic continuous fiber on the inner side. The cross-section
of the laminated nonwoven fabric is photographed according to the
method described in Examples later, where the longest diameter
portion in the cross-section of individual fibers is taken as the
major axis a and the longest diameter in the direction
perpendicular to the major axis a is taken as the minor axis b.
Assuming that the cross-section of each fiber is in the shape of an
ellipse with the major axis of a and the minor axis of b, the value
calculated according to the following formula is defined as the
oblateness f.
f = a - b a ##EQU00001##
[0041] With respect to the thermoplastic continuous fibers on the
surface and inner sides, the oblateness f is measured on the
cross-section of each of 50 fibers, and the average value thereof
is defined as the average oblateness F of thermoplastic continuous
fibers on the surface and inner sides.
[0042] In the present invention, a laminated nonwoven fabric having
high tensile strength and high tear strength is produced by
intentionally changing the average oblateness ratio between surface
and inside thermoplastic continuous fibers according to the
production method. That is, the laminated nonwoven fabric of the
present invention has a structure where the thermoplastic
continuous fiber on the surface side is thermally press-contacted
to deform in an average oblateness ratio of 1.20 or more, compared
with the thermoplastic continuous fiber on the inner side.
[0043] In the present invention, the average oblateness ratio
(F1/F2) must be 1.20 or more and is preferably from 1.25 to 2.50,
more preferably from 1.30 to 2.00. If the average oblateness ratio
(F1/F2) is less than 1.20, as described later, it is impossible to
satisfy both high tensile strength and high tear strength. Also,
when the ratio is 2.50 or less, resinification of the thermoplastic
continuous fiber on the surface side scarcely occurs and the
tensile strength is advantageously increased.
[0044] At this time, the average oblateness of the thermoplastic
continuous fiber on the inner side is preferably 0.1 or more,
because generation of interlayer separation or decrease in the
tensile strength is reduced. The oblateness is more preferably 0.2
or more. Also, when the oblateness is 0.8 or less, resinification
of the fiber is suppressed and high tear strength is advantageously
obtained. The oblateness is more preferably 0.7 or less.
[0045] FIG. 2 shows the relationship between the average oblateness
ratio (F1/F2) and the tear strength in the present invention. As
shown in FIG. 2, there is a relationship such that as the average
oblateness ratio is increased, the tear strength in the machine
direction is enhanced.
[0046] The present inventors estimate the cause of enhancing the
tear strength in the machine direction to be attributable to the
fact that the thermoplastic continuous fiber present on the inner
side is less deformed, decrease in the strength is reduced, the
bonding area of fibers to each other due to deformation is small
compared with the surface side, and the fiber itself has high
degree of freedom and is easily movable. In short, it is estimated
that the fiber shifts at tearing and the stress is relieved.
[0047] FIG. 3 shows the relationship between the average oblateness
ratio (F1/F2) and the tensile strength, and even when the average
oblateness ratio is increased, the tensile strength is nearly
constant, which reveals that in the present invention, the tear
strength can be enhanced without impairing the tensile
strength.
[0048] In the laminated nonwoven fabric of the present invention,
as shown in FIG. 1, the average oblateness F of the thermoplastic
continuous fiber 3 is intentionally varied between the surface side
and the inner side. For creating such a characteristic structure,
it is preferred to thermally press-contact the surfaces one by one
in two stages under a specific surface pressure by using a specific
elastic roll in the production step described later. Also, between
the steps of thermally press-contacting the surfaces one by one in
two stages, a step of rapidly cooling the nonwoven fabric is
preferably present. By rapidly cooling the nonwoven fabric, the
heat obtained by the thermoplastic continuous fiber on the surface
side in the first stage can be removed, and crystallization of the
fiber can be prevented from proceeding. In turn, the surface
thermoplastic continuous fiber on the heated roll side in the
second stage is liable to be effectively deformed and bonded, and
the above-described nonwoven fabric structure can be easily
obtained.
[0049] On the other hand, the thermoplastic ultrafine fiber layer
as the interlayer is thought to be readily bonded due to the large
surface area. This enables the thermoplastic continuous fibers on
the inner side to be bonded through the thermoplastic ultrafine
fiber. From these results, it is considered that high tensile
strength is obtained thanks to bonding of thermoplastic continuous
fibers to each other on the surface side and since the
thermoplastic continuous fiber on the inner side is kept from
bonding of continuous fibers to each other, high tear strength is
obtained by the thermoplastic continuous fiber on the inner side.
If the average oblateness ratio (F1/F2) is less than 1.20, this
indicates that the laminate is in the state of being thoroughly
press-contacted and deformed even in the inside or being not
press-contacted at all, and it is impossible to satisfy both high
tensile strength and high tear strength.
[0050] Also, this structure has, as one characteristic feature,
many portions allowing a void to be present between the
thermoplastic continuous fiber group 1 on the surface side and the
thermoplastic continuous fiber group 2 on the inner side. This is
because the thermoplastic continuous fiber group on the inner side
and the thermoplastic continuous fiber group on the surface side
are not bonded with respect to the width direction of the nonwoven
fabric. Nevertheless, interlayer separation does not occur, because
the thermoplastic continuous fiber on the inner side becomes a
surface-side thermoplastic continuous fiber in a certain portion in
the machine direction and is bonded.
[0051] In the present invention, the nonwoven fabric has strong
strength such that the tensile strength in the machine direction
per unit basis weight is 1.00 (N/1.5 cm)/(g/m.sup.2) or more and
the tear strength in the machine direction per unit basis weight is
0.04 N/(g/m.sup.2) or more. The tensile strength in the machine
direction per unit basis weight is preferably 1.05 (N/1.5
cm)/(g/m.sup.2) or more, and the tear strength in the machine
direction per unit basis weight is preferably 0.04 N/(g/m.sup.2) or
more. The upper limit of each strength is preferably higher, but as
the practically possible range, the tensile strength in the machine
direction is about 10.0 (N/1.5 cm)/(g/m.sup.2) or less, and the
tear strength in the machine direction is about 5.0 N/(g/m.sup.2)
or less.
[0052] The "bonded over the entire surface" as used in the present
invention indicates a state where, for example, by a treatment with
a flat calendering roll, thermoplastic continuous fibers on the
surface side are thermally press-contacted over the entire surface
and thereby adhesively bonded to each other. Thanks to bonding over
the entire surface, a laminated nonwoven fabric reduced in fuzzing
of the thermoplastic continuous fiber on the outer layer surface
and endowed with high fuzz resistance is obtained.
[0053] The resin constituting the fiber for use in the present
invention may be composed of multiple components but is preferably
composed of a single component. This is because in the case of a
single component resin, the nonwoven fabric is kept from local
resinification due to a low-melting-point component and the
above-described structure is easily obtained, making it possible to
effectively satisfy both high tensile strength and high tear
strength. Incidentally, the single component as used herein
indicates a component having the same molecular structure and may
have any melt viscosity, reduced viscosity or molecular weight
distribution.
[0054] The thermoplastic ultrafine fiber may be used in combination
with a bonding material within the range not impairing the effects
of the present invention. In the case of using the bonding
material, examples of the shape thereof include powder, nonwoven
fabric, paste, binder, resin and emulsion, but powder or nonwoven
fabric is preferred. The material constituting the powdered bonding
substance is a thermobondable substance, and examples thereof
include a polyester, a saponified copolymer of ethylene and vinyl
acetate, an ethylene vinyl alcohol copolymerized resin, a
polyolefin, a nylon and an acryl. Incidentally, the powder as used
herein means a fine powdered solid and includes a particulate
matter where a solid becomes a particle and many particles are
aggregated. A nonwoven fabric is also preferred from the standpoint
that it exhibits strong strength when bonded and has appropriate
air permeability at the same time. Examples of the material of this
nonwoven fabric include a polyester, a polypropylene, a
polyethylene, a nylon and an acryl. Among these, a polyester and a
polypropylene are preferred because of their water resistance,
chemical resistance and lower melting point.
[0055] In the laminated nonwoven fabric of the present invention,
the laminated structure may be formed on-line by stacking, in
order, a first nonwoven fabric layer and a second layer on a
collecting net, or respective fiber layers may be individually
formed, then stacked and bonded to form a laminated structure.
However, from the standpoint that high tensile strength is
obtained, on-line formation is preferred. Also, in view of high
bonding property to the upper and lower layers, the laminated
structure is preferably a three-layer structure of continuous fiber
layer/ultrafine fiber layer/continuous fiber layer. The calendering
treatment of the present invention may be applied on-line to the
nonwoven fabrics stacked, but it is preferred to apply calendering
as a separate step after temporarily joining the stacked nonwoven
fabrics by means of a metal heated roll.
[0056] The total basis weight of the laminated nonwoven fabric of
the present invention is suitably from 10 to 250 g/m.sup.2. When
the total basis weight is 10 g/m.sup.2 or more, the nonwoven fabric
is not easily subject to a heat history during calendering and fuzz
prevention on the surface is advantageously facilitated. Also, when
it is 250 g/m.sup.2 or less, heat is transmitted even to the inside
and this advantageously makes it difficult to generate interlayer
separation. In particular, from the standpoint that fuzz prevention
and no occurrence of interlayer separation are easily achieved at
the same time, the total basis weight is preferably from 20 to 150
g/m.sup.2, more preferably from 20 to 130 g/m.sup.2. Also, for the
same reason, the total thickness of the laminated nonwoven fabric
is suitably from 15 to 300 .mu.m. When the total thickness is 15
.mu.m or more, the nonwoven fabric is not susceptible to the effect
of heat during calendering, facilitating fuzz prevention on the
surface, and also, the above-described cross-section structure of
the nonwoven fabric is easily configured. Furthermore, when the
total thickness is 300 .mu.m or less, heat is transmitted even to
the inside and this advantageously makes it difficult to generate
interlayer separation. In particular, from the standpoint that fuzz
prevention and no occurrence of interlayer separation are easily
achieved at the same time, the total thickness is preferably from
25 to 200 .mu.m, more preferably from 25 to 170 .mu.m.
[0057] The ratio of the thermoplastic ultrafine fiber layer in the
total basis weight of the web after lamination is suitably from 5
to 40 wt %. When the ratio is 5 wt % or more, bonding property to
the upper and lower layers is increased, and therefore interlayer
separation does not easily occur. Also, when the ratio is 40 wt %
or less, the ultrafine fiber is less likely to steep out of the
upper and lower continuous fiber layers and at the production, the
roll is advantageously kept from severe contamination.
[0058] In order to obtain the effects of the present invention, it
is important to control the cross-section structure of the nonwoven
fabric, and the structure or resin of the thermoplastic continuous
fiber used is not responsible. However, from the standpoint that
local resinification can be suppressed, the resin component
constituting the thermoplastic continuous fiber is preferably
present in a state of forming a structure except for a sheath-core
structure. Also, in view of heat resistance and the like, the
thermoplastic resin is preferably a polyester-based resin or a
polyamide-based resin. Examples of the polyester-based resin
include polyethylene terephthalate, polybutylene terephthalate and
polytrimethylene terephthalate. Among these, a polyethylene
terephthalate resin has also high dimensional stability and is
excellent as a material. Examples of the polyamide-based resin
include nylon 6, nylon 66, nylon 610 and nylon 612.
[0059] Although this is not particularly limited, the laminated
nonwoven fabric of the present invention is preferably used as a
composite membrane support used for water treatment or gas
separation. The method for producing a composite membrane using the
support of the present invention is not particularly limited, and a
conventionally known method may be used. For example, a porous
layer is first formed by a so-called nonsolvent phase separation
method where a film-forming solution obtained by dissolving a
polymer in a solvent is cast on the support surface layer,
solidified with a nonsolvent such as water and then deliquored and
washed, and on this porous layer, a dense layer (skin layer) having
a separation function is formed, for example, by coating or
interfacial polymerization, whereby a composite membrane such as
reverse osmosis membrane or nanofiltration membrane is
produced.
[0060] The material of the porous layer for use in the present
invention is not particularly limited, but examples thereof include
polysulfone, polyethersulfone, polyphenylsulfone, polyvinylidene
fluoride, polyimide, polyacrylonitrile, ethylene-vinyl alcohol
copolymer, and cellulose acetate. In particular, polysulfone and
polyethersulfone are excellent in the mechanical strength, chemical
resistance and heat resistance and suitably used.
[0061] As for the characteristics of a membrane where the composite
membrane support of the present invention and a porous layer formed
on the support are integrated, for example, of an ultrafiltration
membrane, the cut-off molecular weight is from 10,000 to 200,000
Daltons, preferably from 20,000 to 100,000 Daltons, and the
permeate flow rate is, under 0.1 MPa, from 1 to 15
m.sup.3/m.sup.2day, preferably from 3 to 10 m.sup.3/m.sup.2day.
Incidentally, the cut-off molecular weight and the permeate flow
rate are terms indicating membrane characteristics defined in JIS K
3802 (Terms of Membrane).
[0062] The dense layer (skin layer) is also not particularly
limited, and a conventionally known dense (skin layer) can be used
without any limitation. For example, as described above, this layer
may be formed by interfacial polymerization. In particular, for
example, a crosslinked polyamide obtained by condensation
polymerization or the like of a polyfunctional acid halide and a
polyfunctional amine is preferably used for the dense layer (skin
layer), and a crosslinked polyamide typically composed of
metaphenylenediamine and trimesic acid chloride is more preferably
used. A polyamide composite reverse osmosis membrane can be
produced by the method disclosed, for example, in Japanese
Unexamined Patent Publication Nos. 8-224452 and 9-253455.
[0063] The laminated nonwoven fabric provided by the present
invention is preferably produced by the following method.
[0064] That is, the nonwoven fabric after lamination is subjected
to thermal pressure-contact using a combination of a non-heated
elastic roll having a Shore hardness D of 60 to 95 and a flat rigid
heated roll. This is because the elastic roll having a Shore
hardness D of 60 or more has high pressure-resisting performance
and therefore, can reduce fuzzing on the nonwoven fabric surface,
and also its effect of deforming and fusing thermoplastic
continuous fibers on the surface side is high, whereas an elastic
roll having a Shore hardness D of more than 95 is not present. The
non-heated elastic roll satisfying this hardness range includes,
for example, a cotton paper roll and a polyamide paper roll, and a
polyamide paper roll strongly resistant against deformation of the
roll due to mingling of an extraneous matter is preferably used at
the production. The flat rigid heated roll is preferably a metal
heated roll.
[0065] The nonwoven fabric surfaces are pressurized and thermally
press-contacted one by one in twice by the combination of these
flat rolls under a surface pressure of 30 to 200 kg/cm.sup.2,
preferably from 50 to 140 kg/cm.sup.2. The surface pressure is
preferably 30 kg/cm.sup.2 or more, because fuzzing on the nonwoven
fabric surface can be reduced, and the surface pressure is
preferably 200 kg/m.sup.2 or less, because resinification of the
nonwoven fabric can be suppressed.
[0066] The roll temperature is preferably a temperature 5.degree.
C. or more lower than the melting point of the resin. When the roll
temperature is lower than that, the nonwoven fabric can be
effectively prevented from, for example, resinification or winding
around the roll.
[0067] At the time of pressurizing and thermally press-contacting
the nonwoven fabric in twice, a step of rapidly cooling the
nonwoven fabric immediately after calendering is preferably
provided between the pressurizing and thermally press-contacting
steps. In the case of applying thermal pressure-contact to the
surfaces one by one in separate steps, when the heated roll is set
to a high temperature for increasing the adhesive force in the
central part, melting and resinification of the fiber is readily
generated, and when thermal pressure-contact is performed at a low
temperature so as to prevent the melting and resinification,
sufficiently high strength can be hardly obtained. However, when
heat obtained by the nonwoven fabric is removed by rapidly cooling
immediately after thermal pressure-contact in the first stage and
then, the same thermal pressure-contact is performed in the second
stage, the thermal pressure-contact can be very effectively applied
and high bonding property can be obtained on both front and back
surfaces, as a result, the above-described nonwoven fabric
structure is easily obtained. This is considered to result because
the thermoplastic ultrafine fiber interlayer and the thermoplastic
continuous fiber layer on the non-heated elastic roll side are kept
from crystallization due to heat history of calendering in the
first stage.
EXAMPLES
[0068] The present invention is described below by referring to
Examples, but the present invention is not limited to these
Examples. The characteristic values referred to in Examples and
Comparative Examples were obtained by the following measurement
methods. In this Example, physical properties were measured on a
test piece produced with a width of 1 m, excluding 10 cm at both
end parts.
[0069] (1) Measurement of Total Basis Weight [g/m.sup.2]:
[0070] In accordance with the method specified in JIS-L-1906, a
test piece of 20 cm in length.times.25 cm in width was sampled at 3
portions per 1 m of width and measured for the mass, and the
average value thereof was converted into the mass per unit area
(rounded to whole number) to determine the total basis weight.
[0071] (2) Measurement of Oblateness:
[0072] The cross-section photograph of the laminated nonwoven
fabric for performing the measurement of oblateness was taken in
the following manner.
[0073] Test pieces selected from 5 portions at regular intervals in
the width direction were impregnated with cyclohexane. Each test
piece was then frozen in liquid nitrogen and immediately cut in the
direction perpendicular to the machine direction of the fabric, and
the cross-section of the fiber was used as a sample for
observation. The observation was performed using a scanning
electron microscope, and the photograph was taken at a
magnification of 1,000 times with an accelerating voltage of 3.0
kV. In the image, the cross-section was sandwiched between two
parallel straight lines. Each of two parallel lines was drawn to
contact with the most protruded portion on the surface side in the
cross-section. With respect to these two parallel lines, the
cross-section was equally divided into four parts in the thickness
direction and, as shown in FIG. 1, each part was designated as the
surface side or the inner side. The oblateness was measured on 50
fibers in each portion on the surface side and the inner side
observed in the image, and the average value of 50 fibers was
determined (rounded to second decimal place) from the obtained
oblateness on the surface side or the inner side. The values
obtained were designated as the average oblateness F1 and the
average oblateness F2, and the average oblateness ratio F1/F2 was
calculated from these average oblatenesses F1 and F2 (rounded to
second decimal place).
[0074] (3) Measurement of Fiber Diameter [.mu.m]:
[0075] A 1 cm-square test piece was cut out from each section of 20
cm in width, excluding 10 cm in both end parts of the laminated
nonwoven fabric sample, and used as the sample for measurement. In
each test piece, the fiber diameter was measured at 50 points by a
microscope at the magnification of 1,000 times, and the average
value thereof (rounded to whole number) was defined as the fiber
diameter. In this Example, test pieces at 5 points in the width
direction were sampled, and the diameter was measured on 250 fibers
in total and taken as the fiber diameter.
[0076] Apparatus used: VT-8000 manufactured by Keyence Corp.
[0077] (4) Measurement of Tensile Strength [(N/1.5
cm)/(g/m.sup.2)]:
[0078] A test piece of 3 cm.times.20 cm was sampled per 20 cm of
width, excluding 10 cm in both end parts of the laminated nonwoven
fabric sample, where one sheet was sampled in each of the machine
direction and the width direction. A load was applied to each test
piece until the sheet was ruptured, and the average value of the
strength of the test piece at a maximum load was determined in the
machine direction and the width direction. The value obtained was
converted into a value per 1.5 cm of width, and this value was
divided by the total basis weight (g/m.sup.2) to calculate the
tensile strength per unit basis weight [(N/1.5 cm)/(g/m.sup.2)]
(rounded to second decimal place). In this Example, test pieces at
5 points in each of the machine direction and width direction were
sampled and measured, and the average value thereof was
calculated.
[0079] (5) Measurement of Tear Strength [N/(g/m.sup.2)]:
[0080] In accordance with JIS L1085 5.cndot.5C Method (pendulum
method), a test piece with a size of 65 mm.times.100 mm was sampled
per 20 cm of width of the nonwoven fabric, excluding 10 cm in both
end parts of the laminated nonwoven fabric sample, where one sheet
was sampled in each of the machine direction and the width
direction. Each test piece was measured using an Elmendorf's
tearing tester, and the average value of the measured values was
calculated and divided by the total basis weight (g/m.sup.2) to
calculate the tear strength per unit basis weight [N/(g/m.sup.2)]
(rounded to second decimal place). Incidentally, the measured data
in the machine direction indicate the value when the nonwoven
fabric was torn in the machine direction. In this Example, test
pieces at 5 points in each of the machine direction and width
direction were sampled and measured, and the average value thereof
was calculated.
[0081] (6) Measurement of Air flow Resistance [kPas/m]:
[0082] The air flow resistance was measured at 3 portions in the
machine direction at intervals of 5 cm in the entire width
direction, excluding 10 cm in both end parts of the laminated
nonwoven fabric sample, and the average value of the measured
values and the standard deviation thereof were calculated. In this
Example, three test pieces were sampled in the machine direction at
20 points in the width direction, and air flow resistance was
measured for test pieces at 60 points in total.
[0083] Measurement apparatus: An air permeability tester,
KES-F8-AP1, manufactured by Kato Tech Co., Ltd.
[0084] Measurement Conditions: [0085] Piston speed: 2.0 cm/s [0086]
Integration method: Standard [0087] Sensitivity: L (200 Pa/V)
[0088] Air hole area: 2.pi. (cm.sup.2)
[0089] (7) Measurement of Fluffing Grade (Fuzz Resistance) of
Nonwoven Fabric:
[0090] The following measurement method was devised and used in
accordance with the friction fastness test of JIS L 0849.
[0091] A test piece of 300 mm in length and 25 mm in width was
sampled in the machine direction per 20 cm of fabric width,
excluding 10 cm in both end parts of the laminated nonwoven fabric
sample. Using a fastness tester of JSPS (Japan Society for the
Promotion of Science), the load of the friction probe was set to
200 g, and the test piece sampled was fixed also to the friction
probe side with the intervention of cotton cloth between the test
piece and the friction probe. The laminated nonwoven fabrics were
moved (back and force) 200 times in the machine direction to rub
their surfaces against one another, and the fluffing grade on the
frictioned surface of each test piece was rated according to the
following criteria. The average value (rounded to first decimal
place) of grade values was determined and defined as the fluffing
grade of the nonwoven fabric. In this Example, test pieces at 5
points in the width direction were sampled and measured, and the
average value thereof was taken as the fluffing grade.
[0092] Grade 1: Fibers were ripped off to an extent of damaging the
test piece.
[0093] Grade 2: Fibers were ripped off to a significant extent of
thinning the test piece.
[0094] Grade 2.5: A large pill was clearly observed, and fibers
began to rise in a plurality of portions.
[0095] Grade 3: A small pill was observed.
[0096] Grade 3.5: A pill was not observed but fuzz was
observed.
[0097] Grade 4: No fuzz was observed.
[0098] (8) Measurement of Thickness [.mu.m]:
[0099] In accordance with the method specified in JIS-L-1906, the
sample was measured at equally-spaced 10 portions in the width
direction under a contact pressure load of 100 g/cm.sup.2, and the
average value thereof was defined as the thickness. A thickness
meter, No. 207, manufactured by PEACOCK was used. Since the minimum
scale value was 0.01 mm, the thickness was read to the third
decimal place and after averaging, expressed in as two significant
figures. In this Example, the sample was measured at 10 portions in
total for every 10 cm in the width direction, and the average value
thereof was taken as the thickness.
Examples 1 to 6 and Comparative Examples 1 to 3
[0100] Using general-purpose PET for the outer layer, a filament
group was extruded by a spunbond method toward the surface of a
mobile collecting net at a spinning temperature of 310.degree. C.
and a spinning speed of 4,500 m/min, and the spun fibers were
sufficiently opened through charging to about 1.5 mA by corona
charging to produce a thermoplastic continuous fiber web on the
collecting net. Incidentally, the fiber diameter was adjusted by
changing the discharge rate, and the basis weight was adjusted by
changing the moving speed of the collecting net.
[0101] Next, as the interlayer, PET (reduced viscosity: 0.49
.eta.sp/c) was spun by a meltblown method under the conditions of a
spinning temperature of 300.degree. C. and a heated air of 1,600
Nm.sup.3/hr and blown on the thermoplastic continuous fiber web
produced above. At this time, the distance from a meltblown nozzle
to the thermoplastic continuous fiber web was set to 100 mm, and
the suction air velocity on the collecting surface just beneath the
meltblown nozzle was set to 14.5 m/s. The fiber diameter was
adjusted by changing the discharge rate.
[0102] On the laminated web obtained above, a thermoplastic
continuous fiber web was further stacked to have predetermined
fiber diameter and fiber level by the same method as that for the
first thermoplastic continuous fiber web to obtain a laminated
nonwoven fabric consisting of an upper layer: thermoplastic
continuous fiber layer (SB)/an interlayer: meltblown fiber layer
(MB)/a lower layer: thermoplastic continuous fiber layer (SB). The
fiber diameter, fiber level and the like of each layer of the
laminated nonwoven fabric obtained are shown in Table 1.
TABLE-US-00001 TABLE 1 Interlayer Upper Layer Fiber Lower Layer
Fiber Fiber Melting Fiber Fiber Melting Level Fiber Fiber Melting
Fiber Diameter Level Point Fiber Diameter Level Point Ratio Fiber
Diameter Level Point Species (.mu.m) (g/m.sup.2) (.degree. C.)
Species (.mu.m) (g/m.sup.2) (.degree. C.) (wt %) Species (.mu.m)
(g/m.sup.2) (.degree. C.) Example 1 PET SB 11 13 260 PET MB 1.7 5
260 17 PET SB 12 13 260 Example 2 PET SB 11 40 260 PET MB 1.7 16
260 17 PET SB 12 40 260 Example 3 PET SB 11 31 260 PET MB 1.7 8 260
12 PET SB 12 31 260 Example 4 PET SB 11 29 260 PET MB 1.7 12 260 17
PET SB 12 29 260 Example 5 PET SB 11 29 260 PET MB 1.7 12 260 17
PET SB 12 29 260 Example 6 PET SB 11 31 260 PET MB 1.7 8 260 12 PET
SB 12 31 260 Comparative PET SB 11 31 260 PET MB 1.7 8 260 12 PET
SB 12 31 260 Example 1 Comparative PET SB 11 29 260 PET MB 1.7 12
260 17 PET SB 12 29 260 Example 2 Comparative PET SB 11 35 260 --
-- -- -- 0 PET SB 12 35 260 Example 3
[0103] The laminated nonwoven fabric obtained was then temporarily
press-contacted between flat rigid heated rolls under the
conditions of a linear pressure of 30 kg/cm and a roll temperature
of 180.degree. C. Subsequently, in a calendering step using a flat
rigid heated roll and a non-heated elastic roll, the laminated
nonwoven fabric produced above was treated under the conditions
shown in Table 2 by calendering the surfaces one by one in two
stages. At this time, immediately after calendering in the first
stage, the nonwoven fabric was rapidly cooled with a water-cooled
roll and subsequently, calendering in the second stage was
performed.
TABLE-US-00002 TABLE 2 Pressure- Shore Surface Contact Combination
of Hardness Pressure Temperature Press Rolls D (kg/cm.sup.2)
(.degree. C.) Example 1 metal/polyamide 88 74 230 Example 2
metal/polyamide 88 74 250 Example 3 metal/polyamide 88 78 245
Example 4 metal/cotton 75 75 245 Example 5 metal/polyamide 88 54
245 Example 6 metal/polyamide 88 133 245 Comparative metal/metal --
88 230 Example 1 Comparative metal/silicon 51 20 245 Example 2
Comparative metal/polyamide 88 74 245 Example 3
[0104] The measurement results of physical properties of the
laminated nonwoven fabric obtained in each of Examples and
Comparative Examples are shown in Table 3. Also, FIGS. 2 and 3 show
the relationship of the average oblateness ratio with the tear
strength and tensile strength, respectively. In this Example, it
can be confirmed that the tear strength and tensile strength per
basis weight are high and the fuzz resistance is also high.
TABLE-US-00003 TABLE 3 Average Total Average Oblateness Tensile
Strength Tear Strength Fuzz Basis Thick- Oblateness Ratio ((N/1.5
cm)/(g/m.sup.2)) (N/(g/m.sup.2)) Resis- Air Flow Resistance Weight
ness Surface Inner Surface Side/ Machine Width Machine Width tance
(kPa s/m) (g/m.sup.2) (.mu.m) Side Side Inner Side Direction
Direction Direction Direction (grade) ave. .sigma. .sigma./Ave
Example 1 30 44 0.53 0.41 1.29 1.64 0.67 0.04 0.07 4 1.2 0.3 0.25
Example 2 95 128 0.39 0.28 1.39 1.19 0.52 0.22 0.32 4 61 32 0.52
Example 3 71 91 0.48 0.31 1.55 1.44 0.56 0.11 0.28 4 7.0 1.5 0.21
Example 4 70 90 0.57 0.40 1.42 1.46 0.60 0.11 0.21 4 19 4.3 0.23
Example 5 70 97 0.36 0.28 1.30 1.53 0.53 0.09 0.24 4 7.1 1.7 0.24
Example 6 71 85 0.41 0.22 1.88 1.52 0.50 0.14 0.27 4 11 4.1 0.36
Comparative 71 88 0.28 0.26 1.08 1.52 0.70 0.03 0.04 3.5 9.9 4.5
0.46 Example 1 Comparative 70 80 0.37 0.42 0.87 1.67 0.68 0.01 0.03
3.2 49 -- -- Example 2 Comparative 70 112 0.28 0.22 1.24 0.75 0.32
0.42 0.50 4 0.7 0.2 0.28 Example 3
[0105] Incidentally, in Comparative Example 1, when the
cross-section of the nonwoven fabric was observed, a portion where
the fiber was excessively crushed and the fiber diameter could not
be measured was present. Accordingly, the average oblateness ratio
of Comparative Example 1 in Table 3 is a reference value obtained
by measuring only the portion where the fiber shape could be
confirmed in the cross-section photograph.
[0106] In Comparative Example 1, it can be confirmed that the fuzz
resistance is bad and many fuzzes are present. Also, in observation
of the cross-section, a portion where heat and pressure are
excessively applied and filming is caused, and a portion where the
heat and pressure applied are small and fuzzing is caused, were
observed. In the method of producing a nonwoven fabric by using a
spunbond method, basis weight dispersion is present in the width
direction of the nonwoven fabric, and it is seen that when such
basis weight dispersion is present in the nonwoven fabric, uniform
contact-pressure using a combination of metal rolls is very
difficult. Furthermore, in Comparative Example 1, resinification
was also generated in a portion and this reveals that the tear
strength is low.
[0107] In Comparative Example 2 where a press roll having low
hardness was used, the surface pressure for suppressing fuzz is
insufficient and fuzzing cannot be prevented. Also, although the
line speed was decreased so as to suppress fuzz, resinification
proceeded and in turn, the tear strength was reduced.
[0108] As described above, in the method of the present invention,
an elastic roll is used and therefore, pressure is uniformly
applied in the width direction of the nonwoven fabric at
calendering. Accordingly, the nonwoven fabric produced by the
method of the present invention is characterized by having uniform
air permeability. When Example 3 is compared with Comparative
Example 1, it can be confirmed that in Example, the dispersion of
air flow resistance is small and the nonwoven fabric has uniform
air permeability.
[0109] In Comparative Example 3 where a thermoplastic ultrafine
fiber layer as an interlayer was not provided, the tear strength is
high but the tensile strength is extremely low. It is understood
that the thermoplastic ultrafine fiber of the interlayer is
necessary for bringing out high tensile strength.
INDUSTRIAL APPLICABILITY
[0110] The laminated nonwoven fabric of the present invention can
be suitably used in a field requiring not only high tensile
strength but also high tear strength and also in a field requiring
surface smoothness. For example, the laminated nonwoven fabric can
be suitably used in a building material such as house wrap, walling
and underroofing cover, a sound insulating or sound absorption
material, a filtering material such as food filter, air filter,
liquid filter, vacuum cleaner filter, membrane support and
separation membrane support, an industrial or agricultural material
including filter materials, a hygiene or medical material such as
protective clothing, disposable diaper, sterilization rap and
medical filter, a packaging material, a desiccant pack, a body
warmer wrap, a tape base material having tackiness, a daily-living
product material such as a down holding member and shoe material,
and an electronic material such as an electronic field.
DESCRIPTION OF REFERENCE NUMERALS
[0111] 1 Fiber group on the surface side [0112] 2 Fiber group on
the inner side [0113] 3 Thermoplastic continuous fiber [0114] 4
Thermoplastic ultrafine fiber [0115] 5 Outer layer
* * * * *