U.S. patent application number 13/147895 was filed with the patent office on 2011-12-01 for water-disintegrable nonwoven fabric.
This patent application is currently assigned to UNI-CHARM CORPORATION. Invention is credited to Takayoshi Konishi, Kenichi Sasayama, Tsutomu Shirai.
Application Number | 20110294388 13/147895 |
Document ID | / |
Family ID | 42542113 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110294388 |
Kind Code |
A1 |
Konishi; Takayoshi ; et
al. |
December 1, 2011 |
WATER-DISINTEGRABLE NONWOVEN FABRIC
Abstract
The present invention provides a water-disintegrable nonwoven
fabric having a high strength and flexibility. The
water-disintegrable nonwoven fabric includes fibers mechanically
entangled with one another and adapted to be disentangled from one
another when it is stirred in water. 10 to 50% by mass of the
fibers is occupied by ultrafine thermoplastic synthetic fibers each
having a fineness of 0.01 to 0.5 dtex and a fiber length of 3 to 10
mm. 90 to 50% by mass of the fibers is occupied by at least one of
chemical fibers each having a fineness of 1 to 2 dtex and a fiber
length of 5 to 20 mm and pulp fibers having a freeness of 600 to
770 cc.
Inventors: |
Konishi; Takayoshi; (Kagawa,
JP) ; Shirai; Tsutomu; (Kagawa, JP) ;
Sasayama; Kenichi; (Kagawa, JP) |
Assignee: |
UNI-CHARM CORPORATION
Ehime
JP
|
Family ID: |
42542113 |
Appl. No.: |
13/147895 |
Filed: |
February 3, 2010 |
PCT Filed: |
February 3, 2010 |
PCT NO: |
PCT/JP2010/051512 |
371 Date: |
August 4, 2011 |
Current U.S.
Class: |
442/414 |
Current CPC
Class: |
Y10T 442/696 20150401;
D04H 1/46 20130101 |
Class at
Publication: |
442/414 |
International
Class: |
D04H 13/00 20060101
D04H013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 6, 2009 |
JP |
2009-026718 |
Claims
1. A water-disintegrable nonwoven fabric comprising fibers
mechanically entangled with one another and adapted to be
disintegrated from one another when the water-disintegrable
nonwoven fabric is stirred in water, the water-disintegrable
nonwoven fabric being characterized in that: 10 to 50% by mass of
the above-mentioned fibers is occupied by ultrafine thermoplastic
synthetic fibers each having a fineness of 0.01 to 0.5 dtex and a
fiber length of 3 to 10 mm; and 90 to 50% by mass of the
above-mentioned fibers is occupied by at least one of chemical
fibers each having a fineness of 1 to 2 dtex and a fiber length of
5 to 20 mm and pulp fibers having a freeness of 600 to 770 cc.
2. The water-disintegrable nonwoven fabric defined by claim 1,
wherein the ultrafine thermoplastic synthetic fibers are formed by
splitting split fibers.
3. The water-disintegrable nonwoven fabric defined by claim 1,
wherein the water-disintegrable nonwoven fabric contains a
water-soluble binder in 3 to 10% by mass.
4. The water-disintegrable nonwoven fabric defined by claim 1,
wherein the water-disintegrable nonwoven fabric is obtained by
taking the following steps of mixing the ultrafine thermoplastic
synthetic fibers with at least one of the chemical fibers and the
pulp fibers to prepare a slurry, injecting high pressure water jets
to a web formed from a slurry and thereafter drying the web.
5. The water-disintegrable nonwoven fabric defined by claim 4,
wherein the slurry contains therein a water-soluble binder.
Description
TECHNICAL FIELD
[0001] The present invention relates to water-disintegrable
nonwoven fabrics adapted to be disintegrated to fragments (small
pieces) and/or individual fibers or masses of several fibers when
stirred in water.
BACKGROUND
[0002] Water-disintegrable nonwoven fabrics adapted to be
disintegrated to fragments (small pieces) and/or individual fibers
or masses of several fibers when stirred in water are known. For
example, JP1997-78919A (PTL 1) discloses a nonwoven fabric of this
kind as a water decaying nonwoven fabric. The nonwoven fabric
disclosed therein is obtained by taking the following steps; making
a web which is composed of 70 to 97% regenerated cellulose fibers
or synthetic fibers by mass each having a fiber length of 5 to 20
mm and 3 to 30% ultrafine pulp fibers by mass each having water
retention capacity of 210 to 450% by papermaking treatment,
subjecting the web to high pressure water jets treatment so that
the fibers may be mechanically entangled with one another, and then
drying it. The nonwoven fabric obtained in this manner is suitable
to be used as a material for wet tissues, sweeping wipers, diapers,
sanitary napkins or the like. Such nonwoven fabric may be easily
disintegrated in a large amount of water flow.
CITATION LIST
Patent Literature
[0003] {PTL 1} JP 1997-78419 A
SUMMARY
Technical Problem
[0004] The nonwoven fabric disclosed in PTL 1 uses ultrafine pulp
fibers finely beaten in a wetted condition. While such ultrafine
fibers have their surface areas enlarged and a hydrogen bonding
strength between each of the ultrafine pulp fibers is significantly
increased as they are drying compared to that of pulp fibers before
being beaten finely and consequently the nonwoven fabric being made
of such ultrafine pulp fibers increases in strength, there is a
possibility that the nonwoven fabric may become stiff and have a
poor flexibility and be deteriorated in texture. In addition,
though this nonwoven fabric is made by following the steps of a
paper making process and an injection process of high pressure
water jets, in these steps, the ultrafine pulp fibers easily fall
off from the web and/or it is difficult for the ultrafine pulp
fibers to be entangled with other types of fibers. In these
respects, manufacturing of the nonwoven fabric disclosed in the
cited invention is not necessarily easy.
[0005] An object of the present invention is to provide a
water-disintegrable nonwoven fabric adapted to be easily made and
having a desirable degree of strength and flexibility.
Solution to Problem
[0006] According to the present invention, there is provided a
water-disintegrable nonwoven fabric including fibers mechanically
entangled with one another and being adapted to be disintegrated
from one another when the nonwoven fabric is stirred in water.
[0007] The present invention is characterized as follows: 10 to 50%
by mass of the above-mentioned fibers is occupied by ultrafine
thermoplastic synthetic fibers each having a fineness of 0.01 to
0.5 dtex and a fiber length of 3 to 10 mm, and 90 to 50% by mass of
the above-mentioned fibers is occupied by at least one of chemical
fibers each having a fineness of 1 to 2 dtex and a fiber length of
5 to 20 mm and pulp fibers having a freeness of 600 to 770 cc.
[0008] According to one embodiment of the invention, the ultrafine
thermoplastic synthetic fibers are formed by splitting split
fibers.
[0009] According to another embodiment of the invention, the
water-disintegrable nonwoven fabric contains 3 to 10% water-soluble
binder by mass.
[0010] According to still another embodiment of the invention, the
water-disintegrable nonwoven fabric is obtained by taking the
following steps of mixing the ultrafine thermoplastic synthetic
fibers with at least one of the chemical fibers and the pulp fibers
to prepare a slurry, injecting high pressure water jets to a web
formed from the slurry, and thereafter drying the web.
[0011] According to yet another embodiment of the invention, the
slurry contains a water-soluble binder.
Advantageous Effects of Invention
[0012] The water-disintegrable nonwoven fabric according to the
present invention uses the ultrafine thermoplastic synthetic fibers
each having a fineness of 0.01 to 0.5 dtex and a fiber length of 3
to 10 mm and the fibers are mechanically entangled with one another
in the nonwoven fabric. Such unique arrangement allows the
water-disintegrable nonwoven fabric to be easily manufactured and,
in addition, improves a flexibility and a tensile strength of the
nonwoven fabric.
BRIEF DESCRIPTION OF DRAWINGS
[0013] FIG. 1 Diagram exemplarily illustrating a part of a process
for making a water-disintegrable nonwoven fabric.
DESCRIPTION OF EMBODIMENTS
[0014] A water-disintegrable nonwoven fabric according to the
present invention is suitable to be used, for example, as a
topsheet adapted to be come in contact with a wearer's skin, a
backsheet adapted to be come in contact with a wearer's garment,
dry wipes and wet wipes. This nonwoven fabric can be advantageously
disintegrated to fragments (small pieces) and/or individual fibers
or masses of several fibers (hereinafter referred to as
"fragments") when the nonwoven fabric is thrown in a large amount
of water and stirred. Such water-disintegrable nonwoven fabric has
a thickness of 0.15 to 0.4 mm and a basis mass of 25 to 60
g/m.sup.2 and contains 10 to 50% ultrafine thermoplastic synthetic
fibers by mass each having a fineness of 0.01 to 0.5 dtex and a
fiber length of 3 to 10 mm. 90 to 50% by mass of the nonwoven
fabric is occupied by at least one of chemical fibers having a
fineness of 1 to 2 dtex and a fiber length of 5 to 20 mm and pulp
fibers having a freeness of 600 to 770 cc. The term "thermoplastic
synthetic fibers" used herein means the fibers formed from the
thermoplastic synthetic resin adapted for melt spinning by means of
an extruder. The term "chemical fibers" used herein includes
synthetic fibers inclusive of the thermoplastic synthetic fibers,
semisynthetic fibers and regenerated fibers. One example of the
semisynthetic fibers is acetate fibers and one example of the
regenerated fibers is rayon. These fibers included in the
water-disintegrable nonwoven fabric according to the invention are
entangled with one another under the effect of high pressure water
jets. The water-disintegrable nonwoven fabric may contain a
water-soluble binder in order to restrain its liquid-perviousness
or to enhance its tensile strength depending on the intended
purposes. In contrast, the water-disintegrable nonwoven fabric may
contain a hydrophilizing agent in order to improve its
liquid-perviousness or liquid retention capacity.
[0015] FIG. 1 is a schematic diagram exemplarily illustrating a
process for making a water-disintegrable nonwoven fabric according
to the invention wherein the water-disintegrable nonwoven fabric is
denoted by reference numeral 1. The process illustrated in FIG. 1
utilizes the known process of paper making and includes a first
wire part 11, a second wire part 12, a third wire part 13, a dryer
drum 14 and a reeler 15. A slurry feeder 16 and a water jets
injector 17 are provided so as to cooperate with the first wire
part 11. The slurry feeder 16 feeds a slurry 21 containing a
fibrous mixture to form the water-disintegrable nonwoven fabric and
an appropriate amount of water onto the first wire part 11 so that
the fibrous mixture may form a web 22 on the first wire part 11.
The water jets injector 17 includes two or more nozzle rows 18 each
having a plurality of nozzles arranged intermittently in a cross
direction (CD) being orthogonal to a machine direction (MD). High
pressure water jets are injected to the web 22 and the fibers
forming the web 22 are mechanically entangled with one another
under the effect of predetermined injection energy. The water jets
injector 17 is provided with a suction box 19 so as to suck the
high pressure water jets after working thereof. The high pressure
water jets treated web 22 is transported by the second wire part 12
and then the third wire part 13 onto a peripheral surface of the
dryer drum 14. The web 22 is dried by the dryer drum 14 to become
the water-disintegrable nonwoven fabric 1 and rolled up by the
reeler 15.
[0016] When the water-disintegrable nonwoven fabric 1 obtained in
this manner is thrown into a large amount of water and stirred, the
fibers being mechanically entangled with one another can be
disintegrated from one another to fragments.
[0017] Referring to FIG. 1, the fibrous mixture to form the
water-disintegrable nonwoven fabric and the amount of water are
mixed in an appropriate proportion so that, for example, the
fibrous mixture may occupy 0.5 to 1.5% by mass of the quantity of
the slurry 21. In the fibrous mixture, two or more types of fibers
are mixed at the same ratio as that in the water-disintegrable
nonwoven fabric 1. More specifically, the fibrous mixture in both
the water-disintegrable nonwoven fabric 1 and the slurry 21 contain
the ultrafine thermoplastic synthetic fibers having a fineness of
0.01 to 0.5 dtex and a fiber length of 3 to 10 mm at a rate of 10
to 50% by mass. In addition, the fibrous mixture in both the
water-disintegrable nonwoven fabric 1 and the slurry 21 contain at
least one of (a) the chemical fibers having a fineness of 1 to 2
dtex and a fiber length of 5 to 20 mm and (b) the pulp fibers
having a freeness as an indication of the degree of beating, at a
rate of 90 to 50% by mass.
[0018] As the ultrafine thermoplastic synthetic fibers being
contained in the water-disintegrable nonwoven fabric 1 and the
slurry 21, it is possible to use, for example, fibers which are
obtained by splitting a commercially available polyester/nylon
conjugate fiber having a fineness of 3.3 dtex and being formed to
be splittable into 11 fibers. This conjugate fiber may be
mechanically treated, for example, by a grinder to split this fiber
into 11 ultrafine thermoplastic synthetic fibers having a fineness
of about 0.3 dtex. It is also possible to use ultrafine
thermoplastic synthetic fibers which are obtained by splitting a
commercially available polypropylene/polyester conjugate fiber
having a fineness of 3.3 dtex and being formed to be splittable
into 16 fibers having a fineness of about 0.21 dtex. In addition to
the above-mentioned fibers, ultrafine thermoplastic synthetic
fibers which are obtained by splitting a commercially available
polyester/nylon conjugate fiber having a fineness of 3.3 dtex and
being formed to be splittable into 16 fibers each having a fineness
of about 0.21 dtex, ultrafine thermoplastic synthetic fibers which
are obtained by splitting a commercially available
polypropylene/polyethylene conjugate fiber having a fineness of 2.0
dtex and being formed to be splittable into 16 fibers each having a
fineness of about 0.13 dtex, ultrafine thermoplastic synthetic
fibers which are obtained by splitting a commercially available
polyester/polyethylene conjugate fiber having a fineness of 2.2
dtex and being formed to be splittable into 8 fibers each having a
fineness of about 0.28 dtex are possible to be used. Furthermore,
it is also possible to use ultrafine thermoplastic synthetic fibers
such as melt blown fibers each having a fineness of 0.01 to 0.51
dtex and a fiber length of 3 to 10 mm.
[0019] The ultrafine thermoplastic synthetic fibers each having a
fiber length of 3 to 10 mm assure that the water-disintegrable
nonwoven fabric 1 has a low stiffness, a high flexibility and a
high tensile strength in a dry state as well as in a wet state. The
term "stiffness" used herein is based on the value measured by
Bending Resistance A Method according to JIS L 1096. It is
preferable that an average bending resistance of
water-disintegrable nonwoven fabric 1 should be 80 mm or less, and
the average bending resistance is determined by measuring the
stiffness of two or more test pieces of water-disintegrable
nonwoven fabric 1 in the length direction corresponding to the
machine direction as well as to the cross direction in the process
of making the water-disintegrable nonwoven fabric. Assumed that the
nonwoven fabric of which the stiffness exceeds 80 mm is used as a
sheet in the bodily fluid absorbent article to be put in contact
with the wearer's skin, it will be rather difficult to put this
sheet in contact with the wearer's skin with a desired fit. A
tensile strength of the water-disintegrable nonwoven fabric 1 means
a breaking strength value which is obtained when a test piece of 25
mm in width and 150 mm in length is stretched at a tension rate of
100 mm/min with a chuck distance of a tensile tester set at 100 mm.
The test pieces of which length direction were corresponding to the
machine direction and the test pieces of which length direction
were corresponding to the cross direction were prepared and
strength of the respective test pieces measured after they had been
conditioned at a temperature of 20.degree. C. and R. H. 60% for 24
hours was measured as DRY strength. Strength after the respective
test pieces had been impregnated with ion exchanged water
corresponding to 200% by mass of the respective test pieces was
measured as WET strength. DRY strength of the water-disintegrable
nonwoven fabric 1 is 3.0 N or higher per width dimension of 25 mm
in MD as well as in CD. WET strength thereof is 2.0 N or higher per
width dimension of 25 mm in MD as well as in CD.
[0020] According to the invention, the water-disintegrable property
is evaluated in a manner as follows. The evaluation is conducted on
the basis of visual observation and measurement of dispersive
power. In the visual observation, a test piece of 100.times.100 mm
is dried at a temperature of 100.degree. C. for 2 hours and a dry
mass (W.sub.1) is determined. Then this test piece is thrown
together with 800 ml of distilled water into a vertical liquid
separatory funnel shaker (SHKV-200 manufactured by IWKI) and shaken
at a shaking speed of 240 rpm for 60 minutes and then the interior
of the separatory funnel is visually observed. The
water-disintegrable nonwoven fabric 1 according to the invention is
disintegrated beyond recognition of the original shape or at least
to three fractions. In the dispersive power measurement, the test
piece remaining within the liquid separatory funnel after having
been visually observed was transferred together with distilled
water into a basket made of 2-mesh woven metal wire (mesh size of
11.2 mm, void of 77.8% and adapted for grain diameter of 1.5 mm)
and having a longitudinal dimension.times.transverse
dimension.times.height dimension=100.times.100.times.120 mm. Then,
the quantity of the test piece remaining in the basket was dried at
a temperature of 100.degree. C. for 2 hours and dry mass (W.sub.2)
was determined. From this dry mass W.sub.2 and the dry mass W.sub.1
having been determined in the step of visual observation, the
dispersive power was obtained by a following equation:
{(W.sub.1-W.sub.2)/W.sub.1}.times.100=Dispersive power(%)
[0021] The water-disintegrable nonwoven fabric 1 according to the
invention has a dispersive power of 50% or higher.
[0022] The ultrafine thermoplastic synthetic fibers having a fiber
length of 3 to 10 mm are rarely oriented in one direction and not
intricately entangled with the fibers of the web when the web 22 is
formed from the slurry 21 in the process of FIG. 1. In consequence,
the web 22 in which the fibers are uniformly distributed and the
water-disintegrable nonwoven fabric 1 obtained from such web is
easily disintegrated in water. The ultrafine thermoplastic
synthetic fiber having a fiber length exceeding 10 mm will often
prevent the web 22 being smoothly disintegrable in water,
consequently, the water-disintegrable nonwoven fabric 1 from being
obtained. The ultrafine thermoplastic synthetic fiber having a
fiber length less than 3 mm will make it difficult for the fibers
to be entangled with one another and will be apt to fall off from
the first wire part 11.
[0023] Assumed that the content of the ultrafine thermoplastic
synthetic fibers in the water-disintegrable nonwoven fabric 1
exceeds 50% by mass, it will be difficult of the web 22 to assure a
desired freeness in the process of FIG. 1. Consequently, the
productivity of the water-disintegrable nonwoven fabric 1 will be
deteriorated.
[0024] The pulp fibers being used in the invention may be used for
making the water-disintegrable nonwoven fabric 1 liquid-pervious,
and the pulp fibers are preferably not beaten in order to make the
water-disintegrable nonwoven fabric 1 as flexible as possible or to
prevent the pulp fibers from falling off from the first wire part
11 from the web 22 in the process of FIG. 1. More specifically, the
freeness is preferably measured as indication of a degree of
beating by Canadian Standard Freeness Tester in accordance with JIS
P 2181 and the pulp fibers having the freeness of 600 to 770 cc are
preferably used. Even when the pulp fibers meet such requirement,
there is a possibility that the water-disintegrable nonwoven fabric
1 might have a high density leading to a high stiffness. The
water-disintegrable nonwoven fabric 1 containing the pulp fibers
and having a relatively high density is suitable to be used as
wipes.
WORKING EXAMPLES
[0025] In the process illustrated in FIG. 1, the composition of the
fibrous mixture contained in the slurry 21 and the injection
working conditions for the injector 17 were appropriately varied to
obtain water-disintegrable nonwoven fabrics as the working examples
and nonwoven fabrics as the comparative examples, each having a
basis mass of 35 g/m.sup.2. Compositions, evaluation items,
evaluation methods and evaluation results will be indicated in
TABLE 1 and described later in details.
TABLE-US-00001 TABLE 1 Composition, evaluation Working Working
Working Working Working Working Working Working Working items, etc.
Spec, unit, etc. Example 1 Example 2 Example 3 Example 4 Example 5
Example 6 Example 7 Example 8 Example 9 NBKP CSF 720 cc 30% 50%
NBKP CSF 400 cc Rayon 1.1 dtex .times. 7 mm 80% 50% 50% 90% 50% 80%
74% PET 1.45 dtex .times. 10 mm 30% 50% Split fiber-1 3.3 dtex
.times. 5 mm 20% 20% 20% 10% 50% 50% 50% 18% Split fiber-2 3.3 dtex
.times. 5 mm 20% Water-soluble AQ55S 8% binder Injection working
kW/m.sup.2 0.0063 0.0063 0.0063 0.0063 0.0063 0.0063 0.0063 0.0063
0.0063 condition Basis mass g/m.sup.2 35 35 35 35 35 35 35 35 38
Thickness mm 0.24 0.22 0.34 0.26 0.20 0.30 0.32 0.25 0.30 Density
g/cm.sup.3 0.146 0.159 0.103 0.135 0.175 0.117 0.109 0.140 0.127
DRY strength MD 9.39 8.42 7.85 4.35 14.01 13.56 9.86 4.14 26.24 (N)
CD 5.66 4.35 4.01 3.27 4.85 5.06 4.32 3.11 11.53 DRY extension MD
31.02 20.85 19.54 21.34 11.34 30.15 28.15 21.60 12.27 (%) CD 37.51
30.32 28.64 15.98 12.10 21.39 27.55 14.27 19.97 WET strength MD
6.75 5.46 5.04 4.26 6.47 7.99 5.52 4.73 7.72 (N) CD 4.09 2.26 2.11
2.42 2.69 3.32 2.07 2.94 4.43 WET extension MD 39.45 38.26 38.41
41.68 34.51 34.01 42.59 31.40 29.55 (%) CD 40.89 46.03 44.25 29.60
40.34 32.22 27.90 27.70 51.56 Cantilever bending mm 34 48 40 30 46
50 54 35 78 resistance Water disintegrable Visual .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. .DELTA.
.DELTA. .largecircle. .DELTA. property observation Dispersive 78 79
74 87 72 58 63 76 53 power (%) Liquid retention % 24.7% 27.0% 19.1%
26.9% 22.3% 16.1% 7.0% 10.7% 8.1% Liquid absorbing sec 1 sec 1 sec
1 sec 1 sec 1 sec 1 sec 3 sec 1 sec 7 sec time Dispersion area
mm.sup.2 2256 2585 1974 2500 2116 1680 1260 1520 306 Composition,
evaluation Comparative Comparative Comparative Comparative
Comparative Comparative items, etc. Spec, unit, etc. Example 1
Example 2 Example 3 Example 4 Example 5 Example 6 NBKP CSF 720 cc
NBKP CSF 400 cc 20% Rayon 1.1 dtex .times. 7 mm 100% 40% 80% 80%
80% PET 1.45 dtex .times. 10 mm Split fiber-1 3.3 dtex .times. 5 mm
60% 100% 20% 20% Split fiber-2 3.3 dtex .times. 5 mm Water-soluble
AQ55S binder Injection working kW/m.sup.2 0.0063 0.0063 0.0063
0.0063 0.0012 0.0131 condition Basis mass g/m.sup.2 35 35 35 35 35
35 Thickness mm 0.36 0.25 0.23 0.24 0.22 0.25 Density g/cm.sup.3
0.097 0.140 0.152 0.146 0.159 0.140 DRY strength MD 2.15 14.16
19.52 20.33 2.74 14.23 (N) CD 1.68 2.55 3.66 12.29 1.20 8.58 DRY
extension MD 10.40 39.37 38.35 7.30 17.57 35.11 (%) CD 8.30 14.95
18.89 4.30 16.03 38.93 WET strength MD 3.00 5.72 5.52 6.57 2.55
8.24 (N) CD 1.92 2.76 2.16 3.66 1.59 5.10 WET extension MD 29.60
33.91 30.17 27.90 29.82 42.77 (%) CD 18.40 34.65 30.22 25.80 39.08
44.29 Cantilever bending mm 38 52 33 86 resistance Water
disintegrable Visual .largecircle. X X .largecircle. .largecircle.
X property observation Dispersive 97 14 3 99 91 34 power (%) Liquid
retention % 30.8% 18.6% 10.0% 31.3% Liquid absorbing sec 1 sec 1
sec 12 sec 1 sec time Dispersion area mm.sup.2 2736 1764 304
3021
(Composition in TABLE 1)
[0026] 1. NBKP is abbreviated name of Nadelholz Bleached Kraft Pulp
(bleached softwood kraft pulp). This type of pulp having a freeness
of 720 cc as measured by Canadian Freeness Standard Filter was used
in the working examples and the same type of pulp having a freeness
of 400 cc was used in the comparative examples. 2. PET is
abbreviated name of polyethylene terephthalate fiber. 3. An
ultrafine fiber, which has a fineness of about 0.3 dtex and is
obtained by splitting a PET/nylon conjugate fiber having a fineness
of 3.3 dtex and a fiber length of 5 mm and being formed to be
splittable into 11 fibers, was used as a split fiber-1. 4. An
ultrafine fiber, which has a fineness of about 0.21 dtex and is
obtained by splitting a polypropylene/PET conjugate fiber having a
fineness of 3.3 dtex and a fiber length of 5 mm and being formed to
be splittable into 16 fibers, was used as a split fiber-2. 5.
Sulfopolyester resin (AQ5SS of Eastman Chemical Company) was used
as a water-soluble binder.
(Conditions for Injection Working Shown in FIG. 1 and TABLE 1)
[0027] 1. The injector 17 shown in FIG. 1 includes four nozzle rows
18 which have injection nozzles each having an orifice diameter of
95.mu. and lining up in the cross direction at a pitch of 0.5 mm
are arranged in the machine direction. 2. The conditions for
injection working being set on the respective nozzle rows 18 were
adjusted by varying a working energy quantity in accordance with an
equation below:
Working energy quantity(kW/m.sup.2)=1.63.times.injection
pressure(kg/cm.sup.2).times.injection flow rate
(m.sup.3/min)/working speed(m/min)/60
Injection flow rate(m.sup.3/min)=750.times.total orifice
area(m.sup.2).times.injection pressure(kg/cm.sup.2).sup.0.495
[0028] Injection nozzles: having an orifice diameter of 95.mu. and
arranged at a pitch of 0.5 mm
[0029] First, second and third wire parts: LL-70E manufactured by
Nippon Filcon Co., Ltd.
(Evaluated Items in TABLE 1)
1. Basis Mass
[0030] A basis mass indicates an average value of each basis mass
of three test pieces each dimensioned in 100.times.100 mm.
2. Thickness
[0031] A thickness indicates an average value of each thickness of
three test pieces under measuring pressure of 3 g/cm.sup.2 by a
dial thickness gauge.
3. Density
[0032] A density was calculated from the basis mass and the
thickness.
4. DRY Strength
[0033] After leaving each test piece having a width dimension of 25
mm and a length dimension of 150 mm in a humidity controlled
condition for 24 hours at a temperature of 20.degree. C. and R.H.
of 60%, a tensile test was conducted at an inter-chuck distance of
100 mm and a tension rate of 100 m/min to determine a tensile
strength at break. Three test pieces being dimensioned to be
coincident with one another in the machine direction (MD) and in
the cross direction (CD) were prepared, and the tensile strength
was determined on these test pieces, respectively, in both
directions. Then an average value thereof was calculated as the DRY
strength. The water-disintegrable nonwoven fabric according to the
present invention preferably has DRY strength of 3 kg or higher in
both directions MD, CD.
5. DRY Extension Percentage
[0034] A DRY extension percentage is an average value of each
extension percentage of the test pieces of when DRY strength at
break is measured. The water-disintegrable nonwoven fabric
according to the present invention preferably has DRY extension
percentage of 10% or higher in both directions MD, CD.
6. WET Strength
[0035] A WET strength was determined under the same conditions as
those of DRY strength except that an amount of ion-exchanged water
corresponding to 200% of the mass of the test piece was sprayed
onto the test piece and thereby the test piece was impregnated with
the ion-exchanged water. The water-disintegrable nonwoven fabric
according to the present invention preferably has WET strength of 2
kg or higher in both directions MD, CD.
7. WET Extension Percentage
[0036] A WET extension percentage is an average value of each
extension percentage of the test pieces of when WET tensile
strength at break is measured. The water-disintegrable nonwoven
fabric according to the present invention preferably has WET
extension percentage of 20% or higher in both directions MD,
CD.
8. Stiffness
[0037] A stiffness was measured in accordance with Bending
Resistance A Method (45.degree. cantilever method) specified by
Section 8.19.1 of JIS L 1096. Test results are indicated by average
values of measured values which are obtained from three test pieces
each having the longitudinal direction thereof aligned in the MD
and other three test pieces each having the longitudinal direction
thereof aligned in the CD.
9. Water-Disintegrable Properties
(Visual Observation Method)
[0038] A single test piece of 100.times.100 mm was dried at a
temperature of 100.degree. C. for 2 hours to measure a dry mass
(W.sub.1). The dried test piece was introduced together with 800 ml
of distilled water into a vertical separatory funnel shaking
apparatus (SHKV-200 manufactured by IWKI) and shaken at a shaking
speed of 240 rpm for 60 minutes. Thereafter the inside of the
separatory funnel was visually observed. The water-disintegrable
property was ranked as highly disintegrable (circle-mark) if the
test piece was observed to be disintegrated beyond recognition,
ranked as moderately disintegrable (triangle-mark) if the test
piece was observed to be disintegrated to at least three fractions
or to visually countable number of fibers, and ranked as poorly
disintegrable (x-mark) if disintegration of the test piece was
observed to come short of the moderately disintegrable property.
The water-disintegrable nonwoven fabric according to the present
invention has the highly or moderately water-disintegrable
properties.
(Measuring Method of Dispersive Power)
[0039] The test piece remaining within the liquid separatory funnel
after having been visually observed was transferred together with
distilled water into a basket made of 2-mesh woven metal wire (mesh
size of 11.2 mm, void of 77.8% and adapted for grain diameter of
1.5 mm) and having longitudinal dimension.times.transverse
dimension.times.height dimension=100.times.100.times.120 mm. Then,
the quantity of the test piece remaining in the basket was dried at
a temperature of 100.degree. C. for 2 hours and dry mass (W.sub.2)
was determined. With this dry mass W.sub.2 and the dry mass W.sub.1
having been determined in the step of visual observation, the
dispersive power was obtained by a following equation:
Dispersive power(%)={(W.sub.1-W.sub.2)/W.sub.1}.times.100
10. Liquid Retention Percentage
[0040] Five 100.times.100 mm dimensioned paper filters in
accordance with JIS P 3801 were layered one on another and a
100.times.100 mm dimensioned test piece (having a mass W.sub.0) was
placed on the layer. A burette was used to drop 1 cc of physiologic
saline water from a height of 10 mm onto the test piece at a rate
of 1 cc/2 sec. After 30 seconds had elapsed from dropping, a mass
of the test piece (W.sub.1) was determined and the liquid retention
percentage was calculated according to a following equation:
Liquid retention(%)={(W.sub.1-W.sub.0)/W.sub.0}.times.100
[0041] The water-disintegrable nonwoven fabric 1 according to the
present invention tends to have a high liquid retention percentage
by containing pulp fibers and/or rayon fibers. The disintegrable
nonwoven fabric 1 having a liquid retention percentage of 20% or
higher is suitable to be used as dry wipes or wet wipes.
11. Liquid Absorption Time Length
[0042] In the step of measuring the liquid retention percentage, a
time length from completion of dropping of physiologic saline water
to a moment at which all drops of physiologic saline water
disappeared from the surface of the test piece was measured. In
TABLE 1, a record "measuring time length: 1 sec" means that the
time length until all drops of physiologic saline water disappear
was 1 second or shorter.
[0043] The water-disintegrable nonwoven fabric 1 according to the
present invention may be used in a bodily fluid-absorbent article
as a liquid-pervious water-disintegrable nonwoven fabric if the
liquid absorption time length is 3 seconds or shorter. If the
liquid absorption time length is a range of 6 to 8 seconds due to
water-soluble binder contained therein, the water-disintegrable
nonwoven fabric 1 according to the present invention may be used in
the bodily fluid-absorbent article as a poorly liquid-pervious
water-disintegrable nonwoven fabric.
12. Dispersion Area
[0044] In the step of measuring the liquid retention percentage, a
dimension ML (mm) over which the physiologic saline water dispersed
on the surface of the test piece in MD direction and a dimension CL
(mm) over which the physiologic saline water dispersed on the
surface of the test piece in CD direction were measured and the
dispersion area was determined according to a following
equation:
Dispersion area=ML.times.CL
[0045] The water-disintegrable nonwoven fabric 1 according to the
present invention contains rayon and/or pulp fibers both of which
are hydrophilic and apt to enlarge the dispersion area. The
water-disintegrable nonwoven fabric 1 assuring the dispersion area
larger than 2000 mm.sup.2 is suitable to be used as dry wipes or
wet wipes. In contrast, the water-disintegrable nonwoven fabric 1
of which the dispersion area is smaller than 1800 mm.sup.2 is
suitable to enhance a spot absorption property of the bodily
fluid-absorbent article.
Working Example 1
[0046] In the process illustrated in FIG. 1, a fibrous mixture
including the split fibers-1 of ultrafine thermoplastic synthetic
fibers in 20% by mass and chemical fibers in 80% by mass,
specifically, rayon fibers each having a fineness of 1.1 dtex was
used in a slurry. The injection working was carried out under the
conditions that four rows of nozzles each having an injection
energy of 0.0063 kW/m.sup.2 may be used to obtain a
water-disintegrable nonwoven fabric having the same composition as
that of the fibrous mixture, a basis mass of 35 g/m.sup.2 and a
thickness of 0.24 mm. Evaluation results of the water-disintegrable
nonwoven fabric are indicated in TABLE 1.
<Working Example 2> Through <Working Example 8>
[0047] In the working examples 2 through 8, water-disintegrable
nonwoven fabrics were obtained by the same process as in the
working example 1 except that the composition of the fibrous
mixture in a slurry and the composition of the fibrous mixture in
the water-disintegrable nonwoven fabrics were differentiated from
those in the working example 1 as indicated in TABLE 1. Evaluation
results of these water-disintegrable nonwoven fabrics according to
the working examples 2 through 8 are indicated in TABLE 1. The
water-disintegrable nonwoven fabrics according to the working
examples 2 and 5 have a relatively high density and stiffness and
are suitable to be used particularly as liquid-absorbent wipes.
Working Example 9
[0048] In the working example 9, a water-disintegrable nonwoven
fabric having a composition similar to that of the
water-disintegrable nonwoven fabric according to the working
example 1 except that the slurry being used in the working example
1 contains a water-soluble binder so that the water-disintegrable
nonwoven fabric contains the water-soluble binder in 8% by mass is
obtained. Evaluation results of the water-disintegrable nonwoven
fabric are indicated in TABLE 1. Specifically, being high in DRY
strength as well as in WET strength and assuring significant long
liquid-absorption time, the water-disintegrable nonwoven fabric
according to this working example is suitable to be used as a
water-disintegrable backsheet material for bodily fluid-absorbent
articles.
Comparative Example 1> Through <Comparative Example 4>
[0049] The nonwoven fabrics according to these comparative examples
were made under the same working conditions as those for the
working example 1 except that the composition of the fibrous
mixture in the slurry used in the process of FIG. 1 was different
from the composition of the fibrous mixture in the working example
1. Evaluation results of the nonwoven fabrics according to these
comparative examples are indicated in TABLE 1.
<Comparative Example 5> and <Comparative Example 6
[0050] The nonwoven fabrics according to these comparative examples
were made under the same working conditions as those for the
working example 1 except the injection working condition.
Evaluation results of the nonwoven fabrics according to the
comparative examples 5, 6 are indicated in TABLE 1.
REFERENCE SIGNS LIST
[0051] 1 water-disintegrable nonwoven fabric [0052] 21 slurry
[0053] 22 web
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