The present invention relates to a nonwoven fabric layered body, a stretchable
nonwoven fabric layered body, a fiber product, an absorbent article, and a sanitary mask.
BACKGROUND ART
[0002] In recent years, nonwoven fabrics are widely used in various applications because of
their excellent breathability and flexibility. Therefore, nonwoven fabrics are required to
have various characteristics depending on the application thereof, and improvement of those
characteristics is demanded.
[0003] For example, nonwoven fabrics used for sanitary materials such as disposable diapers
and sanitary napkins, backings for poultices, and the like are required to have water resistance
and excellent moisture permeability. Further, they are also required to have stretchability,
bulkiness, and wearability depending on the sites where they are used.
[0004] As a method of imparting stretchability to nonwoven fabrics, a method in which a
thermoplastic elastomer is used as a raw material for a spun bond nonwoven fabric (see, e.g.,
Japanese National-Phase Publication (JP-A) No. H07-503502), a method in which
low-crystalline polypropylene is used (see, e.g., Japanese Patent Application Laid-Open
(JP-A) No. 2009-62667 and Japanese Patent Application Laid-Open (JP-A) No. 2009-79341),
and the like have been proposed.
[0005] JP-A No. 2009-62667 or JP-A No. 2009-79341 suggests the addition of
high-crystalline polypropylene or a release agent to low-crystalline polypropylene for the
improvement of stickiness or the like of spun bond nonwoven fabrics. W020 12/070518
discloses a layered body of a nonwoven fabric comprising low-crystalline polypropylene and
an extensible spun bond nonwoven fabric.
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0006] In the method described in JP-A No. 2009-62667 or JP-A No. 2009-79341, it is
necessary to increase the amount of the high-crystalline polypropylene or the release agent to
be added to the low-crystalline polypropylene in order to prevent reduction of formability
(adhesion of the nonwoven fabric to various rotary units in an apparatus in steps of embossing
and the like or to other portions that are brought into contact with the nonwoven fabric) which
occurs when producing a spunbond nonwoven fabric using low-crystalline polypropylene.
As a result, the obtained spun bond nonwoven fabric tends to have an increase in residual
strain, thereby having poor stretchability. In the method described in W02012/070518,
stretchability is maintained by layering low-crystalline polypropylene and an extensible
spun bond nonwoven fabric. However, there is a strong demand to further improve
stretchability. There is also an additional demand to realize favorable texture and
improvement in wearability and roll blocking resistance.
[0007] Here, the term "roll blocking" refers to a phenomenon in which, when a nonwoven
fabric layered body is stored in a rolled form for a long period of time, overlapping nonwoven
fabric layered bodies adhere to each other due to storage environment temperature or pressure
applied to the nonwoven fabric layered bodies, thereby causing the roll to be solidified.
With regard to the nonwoven fabric layered body comprising low-crystalline polypropylene
disclosed in W020 12/070518, improvement in blocking resistance during long-term storage
at high temperatures is required.
[0008] In view of the above problems, an object of the invention is to provide a nonwoven
fabric layered body excellent in formability upon production, stretchability, texture,
wearability, and roll blocking resistance, and a stretchable nonwoven fabric layered body, a
fiber product, an absorbent article, and a sanitary mask using the same.
SOLUTION TO PROBLEM
[0009] Means for solving the above-described problems includes the following
embodiments.
<1> A nonwoven fabric layered body, comprising:
an elastic nonwoven fabric; and
an extensible spunbond nonwoven fabric that is disposed on at least one surface side
of the elastic nonwoven fabric and that bas a degree of m~ximum load elongation of 50% or
more in at least one direction,
the nonwoven fabric layered body satisfying the following (I) and (2):
(1) the elastic nonwoven fabric comprises a resin composition containing a
low-crystalline polypropylene satisfying the following (a) to (f), and an a-olefin copolymer A
containing an ethylene-derived constitutional unit and a propylene-derived constitutional unit,
2
and having a melting point of 100°C or more and a crystallization degree of 15% or less, and
(2) the resin composition contains from 5 patis by mass to 50 parts by mass of the
a-olefin copolymer A with respect to I 00 parts by mass of the resin composition:
(a) [mmmm] = 20 to 60 mol%
(b) [rrrr]/(1-[mmmm]) s 0.1
(c) [rmnn] > 2.5 mol%
(d) [mm] x [rr]/[mr]2 s 2.0
(e) weight average molecular weight (Mw) = 10,000 to 200,000
(f) molecular weight distribution (Mw/Mn) < 4,
wherein, in (a) to (d), [mmmm] represents a meso pentad fraction, [rrrr] represents a
racemic pentad fraction, [ m11m] represents a racemic meso racemic meso pentad fraction, and
[mm], [rr] and [mr] each represent a triad fraction.
[0010] <2> The nonwoven fabric layered body according to < 1 >, wherein the resin
composition contains from 95 patis by mass to 50 patis by mass of the low-crystalline
polypropylene with respect to 100 parts by mass of the resin composition.
[0011] <3> The nonwoven fabric layered body according to <1> or <2>, wherein the
a-olefin copolymer A has a tensile elastic modulus of I 00 MPa or less.
[0012] <4> The nonwoven fabric layered body according to any one of <1> to <3>,
wherein the a-olefin copolymer A is a copolymer comprising constitutional units derived from
ethylene, propylene, and butene.
[0013] <5> The nonwoven fabric layered body according to any one of <1> to <4>,
wherein the extensible spunbond nonwoven fabric is disposed on both surface sides of the
elastic nonwoven fabric.
[0014] <6> The nonwoven fabric layered body according to any one of to <5>,
wherein the elastic nonwoven fabric is a nonwoven fabric obtained by a spun bond method.
[0015] <7> The nonwoven fabric layered body according to any one of <1 >to <6>,
wherein the extensible spunbond nonwoven fabric is an extensible spunbond nonwoven fabric
comprising a concentric core-sheath-type composite tiber comprising, as a core portion, a
low-MFR propylene-based polymer having an MFR in a range of from I g/1 0 minutes to 200
gil 0 minutes and, as a sheath portion, a high-MFR propylene-based polymer having an MFR
in a range of from 16 g/10 minutes to 215 g/10 minutes, and wherein a difference in MFR
between the low-MFR propylene-based polymer and the high-MFR propylene-based polymer
is 15 g/1 0 minutes or more.
[0016] <8> The nonwoven fabric layered body according to any one of <1> to <7>,
3
wherein the extensible spunbond nonwoven fabric comprises an olefin-based polymer
composition containing from 80% by mass to 99% by mass of a crystalline propylene-based
polymer and from I% by mass to 20% by mass of a high-density polyethylene.
[0017] <9> The nonwoven fabric layered body according to any one of <1> to <8>,
wherein a weight-per-area ratio of the elastic nonwoven fabric and the extensible spunbond
nonwoven fabric (elastic nonwoven fabric: extensible spunbond nonwoven fabric) is in a
range of from 10:90 to 90:10.
[0018] <10> A stretchable nonwoven fabric layered body, obtained by drawing the
nonwoven fabric layered body according to any one of <1> to <9>.
[0019] <11> A fiber product, comprising the nonwoven fabric layered body according to
any one of to <9> or the stretchable nonwoven fabric layered body according to <1 0>.
[0020] <12> An absorbent article, comprising the nonwoven fabric layered body
according to any one of to <9> or the stretchable nonwoven fabric layered body
according to .
[0021] <13> A sanitary mask, comprising the nonwoven fabric layered body according to
any one of <1> to <9> or the stretchable nonwoven fabric layered body according to <10>.
ADVANTAGEOUS EFFECTS OF INVENTION
[0022] According to the invention, a nonwoven fabric layered body excellent in formability
upon production, stretchability, texture, wearabili!y, and roll blocking resistance, and a
stretchable nonwoven fabric layered body, a fiber product, an absorbent article, and a sanitary
mask using the same are provided.
BRIEF DESCRIPTION OF DRAWINGS
[0023] Fig. I schematically depicts a gear drawing apparatus.
Fig. 2 schematically depicts a preheating apparatus.
DESCRIPTION OF EMBODIMENTS
[0024] Embodiments for carrying out the invention will be described in detail below. Note
that the invention is not limited to the embodiments below. In the following embodiments,
the constituent elements (also including element steps) are not essential except for a case in
which they are specifically described to be essential or they are considered to be apparently
essential in principle. The same applies to the numerical values and their ranges, which are
not intended to limit the invention.
4
[0025] The term "steps" used herein includes not only separate steps but also steps that
cannot be clearly distinguished from other steps as long as the objects of the steps are
achieved. Further, the numerical range shown herein by using "to" are indicative of the
range including the respective minimum and maximum numerical values described before
and after "to". The content of each component in a composition described herein, when the
composition contains plural kinds of substances corresponding to the component, refers to the
total amount of the plural kinds of substances, unless otherwise specified.
[0026]
The nonwoven fabric layered body of the invention comprises:
an elastic nonwoven fabric; and
an extensible spunbond nonwoven fabric that is disposed on at least one surface side
of the elastic nonwoven fabric and that has a degree of maximum load elongation of 50% or
more in at least one direction,
the nonwoven fabric layered body satisfying the following (I) and (2):
(1) the elastic nonwoven fabric comprises a resin composition containing a
low-crystalline polypropylene satisfying the following (a) to (f), and an a-olefin copolymer A
containing an ethylene-derived constitutional unit and a propylene-derived constitutional unit,
and having a melting point of 100°C or more and a crystallization degree of 15% or less, and
(2) the resin composition contains from 5 parts by mass to 50 parts by mass ofthe
a-olefin copolymer A with respect to I 00 parts by mass of the resin composition:
(a) [mmmm] = 20 to 60 mol%
(b) [rm]/(1-[mmmm]) ~ 0.1
(c) [rmrm] > 2.5 mol%
(d) [mm] x [rr]/[mr]2 ~ 2.0
(e) weight average molecular weight (Mw) = 10,000 to 200,000
(f) molecular weight distribution (Mw/Mn) < 4
wherein, in (a) to (d), [mmmm] represents a meso pentad fraction, [rrrr] represents a
racemic pentad fraction, [rmrm] represents a racemic meso racemic meso pentad fraction, and
[mm], [rr] and [mr] each represent a triad fraction.
[0027] The nonwoven fabric layered body of the invention has excellent formability and
productivity because an extensible spunbond nonwoven fabric is disposed on at least one
surface side of an elastic nonwoven fabric, thereby making it possible to prevent adhesion of a
nonwoven fabric layered body to members such as various rotary units in an apparatus used in
steps of embossing and the like. Further, as the spun bond nonwoven fabric is extensible,
5
excellent stretchability of the elastic nonwoven fabric can be maintained. Furthermore, as
the elastic nonwoven fabric comprises a specific resin composition, the nonwoven fabric
layered body has a small residual strain and stretchability that has been improved compared
with that of a conventional nonwoven fabric layered body. Moreover, texture, wearability,
and roll blocking resistance are also favorable.
[0028] The nonwoven fabric layered body of the invention has preferably a structure in
which at least an extensible spunbond nonwoven fabric is disposed on a surface at a side that
is brought into contact with a rotary unit included in a nonwoven fabric manufacturing
apparatus, and more preferably a structure in which an extensible spunbond nonwoven fabric
is disposed on both surface sides of the elastic nonwoven fabric.
[0029] The nonwoven fabric layered body of the invention usually has a weight per area in a
range of 360 g/m2 or less, preferably 240 g/m2 or less, more preferably !50 g/m2 or less, and
still more preferably from 120 g/m2 to 15 g/m2 The weight per area can be determined by
the method used in the Examples described below.
[0030] The composition ratio of the elastic nonwoven fabric and the extensible spunbond
nonwoven fabric can be determined depending on various applications, if appropriate. The
ratio of the elastic nonwoven fabric: the extensible spunbond nonwoven fabric
(weight-per-area ratio) is usually in a range of from 10:90 to 90:10, preferably from 20:80 to
80:20, and more preferably from 20:80 to 50:50. In a case in which there are two or more
elastic nonwoven fabrics (or extensible spunbond nonwoven fabrics), the weight per area of
the elastic nonwoven fabrics (or extensible spunbond nonwoven fabrics) is the sum of those
of the two or more.
[0031] The nonwoven fabric layered body of the invention usually has a residual strain of
26% or less and preferably 25% or less in at least one direction. When the residual strain in
at least one direction is 26% or less, stretchability is favorable. The residual strain can be
determined by the method used in the Examples described below.
[0032] The nonwoven fabric layered body of the invention usually has a degree of
maximum load elongation of 205% or more and preferably 230% or more in at least one
direction. The degree of maximum load elongation can be determined by the method used in
the Examples described below.
[0033] The nonwoven fabric layered body of the invention has a rate of remaining bosses of
preferably 60% or more, more preferably 65% or more, and still more preferably 70% or more
after drawing. When it has a rate of remaining bosses of 60% or more after drawing, it has
favorable texture. TI1e rate of remaining bosses can be determined by the method nsed in the
6
Examples described below.
[0034] The nonwoven fabric layered body of the invention has a peel strength of preferably
ION or less, more preferably 9N or less, and still more preferably 8N or less after two
overlapping sheets of the nonwoven fabric layered bodies are stored in an oven. When it has
a peel strength of I ON or less, it has favorable roll blocking resistance. The peel strength
can be determined by the method used in the Examples described below.
[0035] [Elastic Nonwoven Fabric]
The elastic nonwoven fabric included in the nonwoven fabric layered body of the
invention comprises a resin composition containing a low-crystalline polypropylene satisfying
(a) to (f) described below (hereinafter also simply referred to as a "low-crystalline
polypropylene") and an a-olefin copolymer A containing an ethylene-derived constitutional
unit and a propylene-derived constitutional unit and having a melting point of 1 00°C or more
and a crystallization degree of 15% or less.
[0036] According to the invention, the term "elastic nonwoven fabric" refers to a nonwoven
fabric having a feature of recovering because of its elasticity when stress is released after
drawing.
[0037] The elastic nonwoven fabric can be produced by various known methods.
Specifically, examples of such method include a spunbond method, a melt-blown method, and
a flash spinning method. Among elastic nonwoven fabrics, a spun bond nonwoven fabric
obtained by a spunbond method or a melt-blown nonwoven fabric obtained by a melt-blown
method is preferable.
[0038] The elastic nonwoven fabric usually has a weight per area in a range of 120 g/m2 or
less, preferably 80 g/m2 or less, more preferably 50 g/m2 or less, and still more preferably
from 2 g/m2 to 40 g/m2
.
A fiber as a component of the elastic nonwoven fabric usually has a fiber diameter of
50 ~m or less, preferably 40 ~m or less, and more preferably 30 ~m or less.
[0039] (Resin Composition)
A resin composition as a component of the elastic nonwoven fabric contains from 5
parts by mass to 50 parts by mass of a-olefin copolymer A with respect to I 00 patis by mass
ofthe resin composition. The resin composition further contains preferably from 95 parts by
mass to 50 patis by mass of low-crystalline polypropylene with respect to I 00 parts by mass
of the resin composition. A nonwoven fabric layered body containing an elastic nonwoven
fabric comprising such resin composition has a small residual strain, excellent stretchability, a
high degree of maximum load elongation, and excellent texture, wearability, and roll blocking
7
resistance. The resin composition more preferably contains from 5 patis by mass to 45 parts
by mass of a-olefin copolymer A and from 55 parts by mass to 95 parts by mass of
low-crystalline polypropylene with respect to 100 parts by mass of the resin composition.
[0040] From the viewpoint of effectively achieving the object of the invention, the total
content of a-olefin copolymer A and low-crystalline polypropylene in the total mass of the
resin composition is preferably 80% by mass or more, more preferably 90% by mass or more,
and still more preferably 95% by mass or more.
(0041] (a-olefin Copolymer A)
a-olefin copolymer A contains an ethylene-derived constitutional unit and a
propylene-derived constitutional unit, and has a melting point of I 00°C or more and a
crystallization degree of 15% or less.
a-olefin copolymer A is not particularly limited as long as it satisfies the
above-described conditions, and it may further contain one or more kinds of a-olefin-derived
constitutional units other than ethylene or propylene. Examples of a-olefin other than
ethylene or propylene include !-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene.
[0042] From the viewpoint of effectively achieving the object of the invention, the total
proportion of an ethylene-derived constitutional unit and a propylene-derived constitutional
unit in all the constitutional units of a-olefin copolymer A is preferably 80 mol% or more,
more preferably 85 mol% or more, and still more preferably 90 mol% or more.
[0043] The melting point of a-olefin copolymer A is defined as the peak top of a peak
observed on the highest temperature side of a melting endothe1mic curve that is obtained by
retaining the copolymer A in a nitrogen atmosphere at -40°C for 5 minutes and increasing the
temperature at a rate of 1 0°C/minute using a differential scanning calorimeter (DSC).
Specifically, it can be defined as the peak top of a peak observed on the highest temperature
side of a melting endothermic curve that is obtained by retaining 5 mg of a sample in a
nitrogen atmosphere at -40°C for 5 minutes and increasing the temperature at a rate of
10°C/minute using a differential scanning calorimeter (manufactured by PerkinElmer Inc.,
DSC-7).
(0044] a-olefin copolymer A has a melting point of preferably 130°C or more and more
preferably 150°C or more.
[0045] The crystallization degree of a-olefin copolymer A is calculated from a melting
endothermic curve derived from melting ofthe major component selected from melting
endothermic curves obtained by retaining the copolymer A in a nitrogen atmosphere at -40°C
for 5 minutes and increasing the temperature at a rate of l 0°C/minute using a differential
8
scanning calorimeter (DSC). Specifically, it can be calculated by the following equation
based on a melting endothermic curve derived from melting of the major component selected
rrom melting endothermic curves obtained by retaining 5 mg of a sample in a nitrogen
atmosphere at -40°C for 5 minutes and increasing the temperature at a rate of I 0°Ciminute
using a differential scarming calorimeter (manufactured by PerkinElmer Inc., DSC-7).
Crystallization degree ~ I\. HI 1\.HO x 1 00 (%)
[0046] In the equation, 1\.H represents a heat quantity upon melting (Jig), which is obtained
from a melting endothermic curve derived from melting of the major component of a-olefin
copolymer A comprising ethylene and propylene, and 1\.HO represents a heat quantity upon
melting (Jig) of a perfect crystal of the major component. In other words, in a case in which
the major component is ethylene, 1\.HO is 293 Jig, and in a case in which the major component
is propylene, 1\.HO is 210 Jig.
[0047] a-olefin copolymer A has a crystallization degree of preferably 10% or less and more
preferably 8% or less.
[0048] a-olefin copolymer A has a tensile elastic modulus measured by a method in
accordance with JIS K7161 (the edition ofFY2011), which is preferably 100 MPa or less,
more preferably 40 MPa or less, and still more preferably 25 MPa or less.
[0049] (Low-crystalline Polypropylene)
Low-crystalline polypropylene is a polymer satisfying the following requirements (a)
to (f).
(a) [mmmm] ~ 20 to 60 mol%:
When the meso pentad fraction [ mmmm] of low-crystalline polypropylene is 20
mol% or more, the occunence of stickiness is suppressed, and when it is 60 mol% or less, the
crystallization degree does not become excessively high, which results in favorable elastic
recovery. The meso pentad fraction [ mmmm] is preferably from 30 to 50 mol% and more
preferably from 40 to 50 mol%.
[0050] The meso pentad fraction [mmmm] and the below-mentioned racemic pentad
fraction [rnr] and racemic meso racemic meso pentad fraction [rmrm] are detem1ined in
accordance with the method suggested by A. Zan1belli eta!. in "Macromolecules, 6, 925
(1973)", and the fractions are the meso fraction, racemic fraction, and racemic meso racemic
meso fi·action of a pentad unit in a polypropylene molecule chain measured based on signals
of methyl groups in a 13C-NMR spectrum. When the meso pentad fraction [mmmm]
increases, stereoregularity becomes high. In addition, the below-mentioned triad fractions
[mm], [rr], and [mr] are also calculated by the method described above.
9
[0051] 13C-NMR spectrometry can be performed in compliance with the peak attribution
proposed by A. Zambelli et al. in "Macromolecules, 8, 687 (1975)" using the apparatus under
the conditions described below.
[0052] Apparatus: JNM-EX400 13C-NMR apparatus manufactured by JEOL Ltd.
Method: Proton complete decoupling method
Concentration: 220 mg/ml
Solvent: Mixed solvent of 1,2,4-trichlorobenzene and heavy benzene at a ratio of90:10
(volume ratio)
Temperature: 130°C
Pulse widtb: 45°
Pulse repetition time: 4 seconds
Integration: l 0000 times
[0053] [Calculation Formulae]
M=m/S x 100
R = y/S X 100
S = Pflfl+Pafl+Pay
S: Signal intensity of side-chain methyl carbon atoms of all propylene units
Pflfl: 19.8 to 22.5 ppm
Pafl: 18.0 to 17.5 ppm
Pay: 17.5 to 17.1 ppm
y: Racemic pentad chain: 20.7 to 20.3 ppm
m: Meso pentad chain: 21.7 to 22.5 ppm
[0054] (b) [rrrr]/(1-[mmmm]) :<; 0.1
The value of[rrrr]/[1-mmmm] is calculated from the pentad unit fraction described
above, and it is an index of uniformity of the regularity distribution of! ow-crystalline
polypropylene. When this value increases, a mixture of high-regularity polypropylene and
atactic polypropylene is formed as in the case of conventional polypropylene that is produced
using an existing catalyst system, which causes stickiness.
When low-crystalline polypropylene has a [rrrr]/(1-[mmmm]) value ofO.l or less,
stickiness of the obtained elastic nonwoven fabric is suppressed. In view of this,
[mr]/(1-[mmmm]) is preferably 0.05 or less and more preferably 0.04 or less.
[0055] (c) [rmrm] > 2.5 mol%
When the racemic meso racemic meso fraction [rmrm] oflow-crystalline
polypropylene exceeds 2.5 mol%, randomness of the low-crystalline polypropylene increases,
10
resulting in further improvement of elastic recovery of the elastic nonwoven fabric. [rmrm J
is preferably 2.6 mol% or more and more preferably 2. 7 mol% or more. The upper limit
thereof is usually about I 0 mol%.
[0056] (d) [ mm] x [ rr]/[ mr ]2 :<': 2.0
[mm] x [rr]/[mr]2 represents an index of randomness oflow-crystalline
polypropylene. When this value is 2.0 or less, the elastic nonwoven fabric has sufficient
elastic recovery, and stickiness is also suppressed. As [mm] x [rr]/[mrf becomes closer to
0.25, randomness increases. From the viewpoint of obtaining sufficient elastic recovery
described above, [mm] x [rr]/[mr]2 is preferably from more than 0.25 to 1.8 and more
preferably from 0.5 to 1.5.
[0057] (e) Weight average molecular weight (Mw) = 10,000 to 200,000
When low-crystalline polypropylene has a weight average molecular weight of
10,000 or more, viscosity of the low-crystalline polypropylene is at an appropriate level,
which is not excessively low, thereby suppressing yarn breakage upon manufacturing of the
elastic nonwoven fabric. In addition, when the weight average molecular weight is 200,000
or less, viscosity of the low-crystalline polypropylene does not become excessively high,
resulting in improvement of spinnability. The weight average molecular weight is preferably
from 30,000 to 150,000 and more preferably from 50,000 to 150,000. The method of
measuring the weight average molecular weight will be described below.
[0058] (f) Molecular weight distribution (Mw/Mn) < 4
When low-crystalline polypropylene has a molecular weight distribution (Mw/Mn)
of less than 4, the occurrence of stickiness of the elastic nonwoven fabric is suppressed. The
molecular weight distribution is preferably 3 or less.
The weight average molecular weight (Mw) is a weight average molecular weight in
terms of polystyrene measured by the gel penneation chromatography (GPC) method using
the apparatus under the conditions described below. The molecular weight distribution
(Mw/Mn) is a value calculated from the number average molecular weight (Mn) and the
weight average molecular weight (Mw) measured in the same manner.
[0059] [GPC measuring Device]
Column: TOSO GMHHR-H (S) HT
Detector: RI detector WATERS 150C for liquid chrom"atogram
[Measurement Conditions]
Solvent: I ,2,4-trichlorobenzene
Measurement temperature: 1 45°C
II
Flow rate: 1.0 mL!minute
Sample concentration: 2.2 mg/mL
Injection volume: 160 111
Calibration curve: Universal Calibration
Analysis program: HT-GPC (Ver.1.0)
[0060] It is preferable for low-crystalline polypropylene to further satisfy the following (g).
(g) The melting point (Tm-D) defined as the peak top of a peak observed on the highest
temperature side of a melting endothermic curve obtained by retaining the polypropylene in a
nitrogen atmosphere at -1 ooc for 5 minutes and increasing the temperature at a rate of
1 0°C/minute using a differential scanning calorimeter (DSC) is ooc to l20°C.
[0061] When low-crystalline polypropylene has a melting point (Tm-D) of 0°C or more, the
occun·ence of stickiness of the elastic nonwoven fabric is suppressed, and when it is 120°C or
less, sufficient elastic recovery can be achieved. In view of this, the melting point (Tm-D) is
more preferably from ooc to 1 oooc, and still more preferably from 30°C to 1 00°C.
[0062] The melting point (Tm-D) described above can be defined as the peak top of a peak
observed on the highest temperature side of a melting endothermic curve obtained by
retaining 1 Omg of sample in a nitrogen atmosphere at -1 0°C for 5 minutes and increasing the
temperature at a rate of 1 0°C/minute using a differential scanning calorimeter (manufactured
by PerkinElmer Inc., DSC-7).
[0063] Low-crystalline polypropylene can be synthesized using a homogeneous catalyst
referred to as "metallocene catalyst" described in, for example, W02003/087172.
[0064] The resin composition, a-olefin copolymer A, and low-crystalline polypropylene may
contain, as optional components, various known additives such as an antioxidant, a heat
stabilizer, a weathering stabilizer, an antistatic agent, a slip agent, an anti fog agent, a lubricant,
a dye, a pigment, a natural oil, a synthetic oil, and a wax within a range that does not impair
the object of the invention.
[0065] [Extensible Spunbond Nonwoven Fabric]
An extensible spunbond nonwoven fabric as a component of the nonwoven fabric
layered body of the invention is a nonwoven fabric that has a degree of maximum load
elongation in at least one direction of 50% or more, preferably 70% or more, and more
preferably 100% or more, and still more preferably exhibits substantially no elastic recovery.
[0066] The extensible spunbond nonwoven fabric has a weight per area in a range of usually
120 g/m2 or less, preferably 80 g/m2 or less, more preferably 50 g/m2 or less, and still more
preferably from 40 g/m2 to 5 g/m2
.
12
[0067] A fiber as a component of the extensible spun bond nonwoven fabric has a fiber
diameter of usually 50 11m or less, preferably 40 11m or less, and more preferably 30 11m or
less.
[0068] An example ofthe extensible spunbond nonwoven fabric is a nonwoven fabric that is
obtained by using one kind or two or more kinds of olefin-based polymers described below.
Examples of a nonwoven fabric that is obtained using olefin-based polymers include:
(I) a spunbond nonwoven fabric made of a core-sheath-type composite fiber, a parallel-type
composite fiber (side-by-side type composite fiber), or a crimped composite fiber comprising
two or more kinds of olefin-based polymers having a difference in the flow-induced
crystallization induction period of 100 seconds or more (a propylene-based polymer having a
high melting point and a propylene-based polymer having a low melting point); (2) a
spunbond nonwoven fabric made of a core-sheath-type composite fiber, a parallel-type
composite fiber, or a crimped composite fiber comprising a propylene-based polymer and an
ethylene-based polymer; and (3) a spunbond nonwoven fabric made of a concentric core
sheath composite fiber comprising, as a core portion, a low-MFR propylene-based polymer
having a melt flow rate (hereinafter also referred to as "MFR", ASTMD-1238, 230°C, 2160 g
load) in a range offrom I g/1 0 minutes to 1000 g/1 0 minutes and, as a sheath portion, a
high-MFR propylene-based polymer having an MFR in a range offrom I g/1 0 minutes to
I 000 g/1 0 minutes, the polymers having an MFR difference of 1 g/1 0 minutes or more,
preferably 15 g/1 0 minutes or more, more preferably 30 g/1 0 minutes or more, and still more
preferably 40 g/1 0 minutes or more.
[0069] Specific examples include: (I) a spun bond nonwoven fabric obtained using an
olefin-based polymer composition comprising 80% by mass to 99% by mass of a propylene
homopolymer and 20% by mass to 1% by mass of high-density polyethylene; (2) a spun bond
nonwoven fabric made of a core-sheath-type composite fiber, a parallel-type composite fiber,
or a crimped composite fiber comprising a high-melting-point propylene-based polymer
(preferably propylene homopolymer) having a melting point in a range of from 157°C to
165°C and a low-melting-point propylene-a-olefin random copolymer having a melting point
in a range of from 130°C to 150°C, which have the same or different MFR; and (3) a
spunbond nonwoven fabric made of a concentric core-sheath-type composite fiber comprising,
as a core portion, a low-MFR propylene-based polymer (preferably propylene homopolymer)
having an MFR in a range of from 1 g/1 0 minutes to 200 g/1 0 minutes and, as a sheath
portion, a high-MFR propylene-based polymer (preferably propylene homopolymer) having
an MFR in a range of from 16 g/10 minutes to 215 g/10 minutes, the polymers having an
13
MFR difference of 15 g/1 0 minutes or more.
[0070] A preferable example of the extensible spun bond nonwoven fabric is: (1) a spunbond
nonwoven fabric made of a concentric core-sheath-type composite fiber comprising, as a core
portion, a low-MFR high-melting-point propylene-based polymer (preferably propylene
homopolymer) having an MFR in a range of from I 0 g/1 0 minutes to 200 g/1 0 minutes and a
melting point in a range of from 157°C to 165°C and, as a sheath portion, a high-MFR
low-melting-point propylene-a-olefin random copolymer having an MFR in a range of from
I 0 g/1 0 minutes to 200 g/1 0 minutes and a melting point in a range of from 130°C to 150°C,
the polymers having an MFR difference of 1 g/1 0 minutes or more, a parallel-type composite
fiber, or a crimped composite fiber; or (2) a spun bond nonwoven fabric made of a concentric
core-sheath-type composite fiber comprising, as a core portion, a low-MFR propylene-based
polymer (preferably propylene homopolymer) having an MFR in a range of rrom 1 g/1 0
minutes to 200 gil 0 minutes and, as a sheath portion, a high-MFR propylene-based polymer
(preferably propylene homopolymer) having an MFR in a range of from 31 g/1 0 minutes to
230 gil 0 minutes, the polymers having an MFR difference of 30 g/1 0 minutes or more.
These extensible spunbond nonwoven fabtics have particularly excellent extensibility when
they have a degree of maximum load elongation in at least one direction of 110% or more.
[0071] (Olefin-based polymer)
In a case in which the extensible spunbond nonwoven fabric is formed rrom one kind
or two or more kinds of olefin-based polymers, examples of olefin-based polymers include
ethylene-based polymers, propylene-based polymers, and crystalline polymers that are
homopolymers or copolymers of a-olefins such as ethylene, propylene, !-butene, 1-hexene,
4-methyl-1-pentene, and 1-octene.
Specific examples of ethylene-based polymers include ethylene homopolymers such
as high-pressure low-density polyethylene, linear low-density polyethylene (i.e., LLDPE), and
high-density polyethylene (i.e., HDPE), and ethylene-a-olefin random copolymers.
Specific examples of propylene-based polymers include polypropylene (propylene
homopolymer), and propylene-a-olefin random copolymers such as a propylene-1-butene
random copolymer, a propylene-ethylene random copolymer, and a
propylene-ethylene· 1 -butene random copolymer.
Specific examples of crystalline polymers include poly-1-butene and
poly-4-methyl-1-pentene.
[0072] (Propylene-based Polymer)
The propylene-based polymer described above is usually a crystalline resin that is
14
manufactured and sold under the name of polypropylene. Specific examples include: a
propylene homopolymer or a copolymer comprising, as the major component, propylene and,
as a copolymerization component, one kind or two or more kinds of a-olefins having 2 or
more carbon atoms (except 3 carbon atoms) and preferably 2 to 8 carbon atoms (except 3
carbon atoms) such as ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and
4-methyl-1-pentene, which usually has a melting point (Tm) in a range of l55°C or more and
preferably from 157°C to l65°C; and a copolymer of propylene and one or two or more kinds
of a-olefins having 2 or more carbon atoms (except 3 carbon atoms) and preferably 2 to 8
carbon atoms (except 3 carbon atoms) such as ethylene, !-butene, 1-pentene, 1-hexene,
1-octene, and 4-methyl-1-pentene, which usually has a melting point (Tm) in a range of from
130°C to less than 155°C and preferably from 130°C to 150°C. Examples of copolymers
include random copolymers and block copolymers.
[0073] The melt flow rate (MFR: ASTM D-1238, 230°C, 2160 g load) of the
propylene-based polymer is not particularly limited as long as the polymer can be melt-spun.
The melt flow rate is usually in a range of from 1 to I 000 g/1 0 minutes, preferably from 5 to
500 gil 0 minutes, and more preferably from l 0 to 100 g/10 minutes.
(0074] (Olefin-based Polymer Composition)
It is preferable for the extensible spunbond nonwoven fabric according to the
invention to be formed from an olefin-based polymer composition comprising an
ethylene-based polymer and a propylene-based polymer. The olefin-based polymer
composition usually includes tbe propylene-based polymer in a range of from 80% to 99% by
mass and preferably 84% to 96% by mass, and the ethylene-based polymer in a range of from
1% to 20% by mass and preferably 4% to 16% by mass (wherein the propylene-based
polymer+ the ethylene-based polymer= 100% hy mass).
(0075] The ethylene-based polymer contained in the olefin-based polymer composition is
not particularly limited; however, it is preferably a high-density polyethylene having a density
in a range of from 0.94 to 0.97 g/cm3
, more preferably from 0.95 to 0.97 g/cm3
, and still more
preferably from 0.96 to 0.97 g/cm3
. In addition, the melt flow rate (MFR: ASTM D 1238,
l90°C, 2160 g load) of the ethylene-based polymer is not pa~iicularly limited as long as the
polymer has spinnability. From the viewpoint of exhibition of extensibility, the melt flow
rate is usually in a range of from 0.1 to 100 gil 0 minutes, more preferably 0.5 to 50 g/1 0
minutes, and still more preferably I to 30 g/1 0 minutes.
[0076] The olefin-based polymer, ethylene-based polymer, and propylene-based polymer
described above may contain, as optional components, various publicly known additives such
15
as an antioxidant, a heat stabilizer, a weathering stabilizer, an antistatic agent, a slip agent, an
antifog agent, a lubricant, a dye, a pigment, a natural oil, a synthetic oil, a wax, and a
hydrophilic agent within a range that does not impair the object of the invention.
[0077] [Other Layers]
The nonwoven fabric layered body of the invention may have one layer or two or
more layers other than layers of the elastic nonwoven fabric and the extensible spunbond
nonwoven fabric depending on applications.
[0078] Specific examples of other layers include knitted fabrics, woven fabrics, nonwoven
fabrics other than elastic nonwoven fabrics and extensible spunbond nonwoven fabrics, and
films. A method of further layering (bonding) other layers on the nonwoven fabric layered
body of the invention is not particularly limited. A variety of methods, including thermal
fusion bonding methods such as hot embossing and ultrasonic fusion bonding, mechanical
entangling methods such as needle punching and water jetting, methods using adhesives such
as hot melt adhesives and urethane adhesives, and extrusion lamination, can be employed.
[0079] In a case in which the nonwoven fabric layered body of the invention has a
nonwoven fabric other than the elastic nonwoven fabric and the extensible spunbond
nonwoven fabric, examples of such nonwoven fabric include various known nonwoven
fabrics such as spun bond nonwoven fabrics, meltblown nonwoven fabrics, wet nonwoven
fabrics, dry nonwoven fabrics, dry pulp nonwoven fabrics, flash-spun nonwoven fabrics, and
split-fiber nonwoven fabrics. These nonwoven fabrics may be stretchable or non-stretchable
nonwoven fabrics. Here, the term "non-stretchable nonwoven fabrics" refers to nonwoven
fabrics which do not produce recovery stress after elongation in MD (machine direction or
longitudinal direction of nonwoven fabric) or CD (cross direction or direction perpendicular
to the machine direction of nonwoven fabric).
[0080] In a case in which the nonwoven fabric layered body of the invention has a film, a
breathable (moisture permeable) film is preferable in order to maintain breathability and
hydrophilicity that are characteristics of the nonwoven fabric layered body of the invention.
Examples of such breathable film include various known breathable films such as films of
moisture permeable thermoplastic elastomers such as polyurethane elastomers, polyester
elastomers, and polyamide elastomers, and porous films obtained by drawing thermoplastic
resin films containing inorganic or organic fine particles to create pores in the films.
Preferable thermoplastic resins used for the porous films are polyolefins such as high-pressure
low-density polyethylene, linear low-density polyethylene (i.e., LLDPE), high-density
polyethylene, polypropylene, a polypropylene random copolymer, and any combination
16
thereof. Note that in a case in which it is not necessary to maintain breathability and
hydrophilicity of the nonwoven fabric layered body, thermoplastic resin films of, for example,
polyethylene, polypropylene, and any combination thereof may be used.
[0081] [Method for Producing Nonwoven Fabric Layered body]
The nonwoven fabric layered body of the invention can be produced by a known
method of producing a nonwoven fabric using a low-crystalline polypropylene and a-olefin
copolymer A that are used as raw materials for the elastic nonwoven fabric, an olefin-based
polymer that is used as a raw material for the extensible spun bond nonwoven fabric, and
additives to be used if necessary.
[0082] As an example of the method of producing a nonwoven fabric layered body, a
method using a nonwoven fabric manufacturing apparatus equipped with at least two lines of
spinning units is described below.
At first, an olefin-based polymer, or two or more kinds of olefin-based polymers, if
necessary, are molten in an extruder, or two or more extruders, if necessary, provided at the
first-line spinning unit, and are introduced to a spinneret (die) fitted with a large number of
spinning orifices (nozzles) or sheath-core spinning orifices, if necessary, and ejected.
Thereafter, the continuous fibers comprising an olefin-based polymer that have been melt
spun are introduced into a cooling chamber and cooled with cooling air. Then, the
continuous fibers are drawn (towed) with drawing air and the extensible spunbond nonwoven
fabric is deposited on the mobile collecting face.
Meanwhile, a resin composition comprising low-crystalline polypropylene and
a-olefin copolymer A is molten in an extruder provided at the second-line spinning unit, and
is introduced to a spinneret (die) fitted with a large number of spinning orifices (nozzles), and
the resin composition is ejected. Thereafter, the continuous fibers comprising a resin
composition that have been melt spun are introduced into a cooling chamber and cooled with
cooling air. Then, the continuous fibers are drawn (towed) with drawing air and the resultant
is deposited on the extensible spunbond nonwoven fabric, thereby forming an elastic
nonwoven fabric.
The extensible spunbond nonwoven fabric may be deposited on the elastic nonwoven
fabric using the third-line spinning unit, if necessary.
[0083] The temperature for melting the polymers that are used as raw materials for the
elastic nonwoven fabric and the extensible spunbond nonwoven fabric is not particularly
limited as long as the temperature is equal to or higher than the softening temperature or the
melting point and is less than the thennal decomposition temperature of each polymer. The
17
die temperature may vary depending on the polymers used. For example, the die
temperature may be set to usually from 1 80°C to 240°C, preferably from 1 90°C to 230°C, and
more preferably from 200°C to 22S°C in the case of using a propylene-based polymer.
[0084] The temperature of the cooling air is not particularly limited as long as the polymer
can be solidified. However, it is usually in a range of from soc to S0°C, preferably 1 0°C to
40°C, and more preferably 1 S°C to 30°C. The speed of the drawing air is usually in a range
of from 100 to 10,000 m/minute and preferably SOO to 10,000 m/minute.
[OOSS] It is preferable for the nonwoven fabric layered body of the invention to have a
structure in which at least one part of the elastic nonwoven fabric and at least one part of the
extensible spun bond nonwoven fabric are thermal-fusion-bonded. At such time, at least one
part of the elastic nonwoven fabric and at least one part of the extensible spunbond nonwoven
fabric may be pressed together using a nip roll before thermal fusion bonding.
[0086] A method of thermal fusion bonding is not particularly limited and it can be selected
from various known methods. Exemplary prebonding methods include ultrasonic methods,
hot embossing with embossing rolls, and hot air through methods. Of these, hot embossing
is preferable because continuous fibers can be drawn efficiently upon drawing. The
temperature range for hot embossing is preferably from 60°C to ll5°C.
[0087] ln the case where the layered body is partially thermal-fusion-bonded by hot
embossing, the embossing area rate is usually in a range of from S% to 30% and preferably
from S% to 20%, and the non-embossing unit area is O.S mm2 or more and preferably in a
range of from 4 to 40 rnm2
• The non-embossing unit area is the maximum area of a tetragon
inscribed in bosses in the minimum unit of non-embossed portion surrounded by embossed
portions. Examples of the embossing shapes include circles, ellipses, ovals, squares,
rhomboids, rectangles, tetragons and continuations of shapes based on these shapes.
[0088]
The stretchable nonwoven fabric layered body of the invention is a nonwoven fabric
layered body having stretchability, which is obtained by drawing the nonwoven fabric layered
body described above.
[0089] The stretchable nonwoven fabric layered body of the invention can be obtained by
drawing the nonwoven fabric layered body described above. A method of drawing is not
particularly limited, and a conventionally known method can be used. In the method of
drawing, partial drawing or overall drawing may be conducted. In addition, the method may
involve monoaxial drawing or biaxial drawing. An example of a method of drawing in the
machine direction (MD) is a method wherein a partially fusion-bonded mixed fiber is allowed
18
to pass through two or more pairs of nip rolls. In this process, the partially fusion-bonded
nonwoven fabric layered body may be drawn by operating the nip rolls at increasing
rotational speeds along the machine direction. Alternatively, gear drawing may be
performed using a gear drawing apparatus depicted in Fig. I.
[0090] The drawing rate is preferably 50% or more, more preferably 100% or more, and still
more preferably 200% or more, and it is preferably 1000% or less, and more preferably 400%
or less.
[0091] The above drawing rate is preferably satisfied in the machine direction (MD) or the
cross direction (CD) in the case ofmonoaxial drawing. In the case of biaxial drawing, the
above drawing rate is preferably satisfied in at least one of the machine direction (MD) or the
cross direction (CD).
[0092] Upon drawing at the above drawing rate, all the (continuous) fibers forming the
elastic nonwoven fabric and the extensible spunbond nonwoven fabric are drawn. The
continuous fibers forming the extensible spunbond nonwoven fabric layer (s) are plastically
deformed to become extended (longer) in accordance with the drawing rate.
[0093] Thus, when the stress is released after the nonwoven fabric layered body is drawn,
the (continuous) fibers forming the elastic nonwoven fabric undergo elastic recovery while
the continuous fibers forming the extensible spunbond nonwoven fabric are folded without
undergoing elastic recovery. As a result, the nonwoven fabric layered body exhibit bulkiness.
Further, the continuous fibers forming the extensible spunbond nonwoven fabric become
thinner, thereby improving softness and texture and imparting a function as an extension
stopper.
[0094]
The fiber product of the invention comprises the nonwoven fabric layered body or
stretchable nonwoven fabric layered body of the invention. Examples of the fiber product
include, but are not particularly limited to, absorbent articles such as disposable diapers and
sanitary napkins, hygiene materials such as sanitary masks, and medical atiicles such as
bandages, clothing materials, and packaging materials. It is preferable for the fiber product
of the invention to include, as a stretchy member, the nonwoven fabric layered body or
stretchable nonwoven fabric layered body of the invention.
EXAMPLES
[0095] The invention will be described in greater detail based on the Examples hereinbelow
without limiting the scope of the invention to such examples. Physical property values and
19
the like were determined by the methods described below in the Examples and Comparative
Examples.
[0096] (I) Weight per Area [g/m2
]
Six sheets of test pieces each having a length of200 mm in the machine direction
(MD) and a length of 50 mm in the cross direction (CD) were collected from a nonwoven
fabric layered body. The sites of collection were randomly determined 3 sites in each of MD
and CD (6 sites in total). Subsequently, the mass (g) of each collected test piece was
measured using a top pan electronic balance (manufactured by Kensei Co., Ltd.). The mean
value of mass of each test piece was calculated. The calculated mean value was converted to
mass (g) per 1 m2
, and rounded to the nearest whole number to obtain the weight per area
[g/m2].
[0097] (2) Maximum Load [N/50 mm] and Degree of Maximum Load Elongation[%]
Five sheets of test pieces each having a length of200 mm in the machine direction
(MD) and a length of 50 mm in the cross direction (CD) were collected from a nonwoven
fabric layered body. Tensile test was conducted for the test pieces using a constant-rate
extension type tensile tester at a chuck interval of 100 mm and a tensile speed of 100
mm/minute. The maximum load [N/50 mm J applied to each test piece was measured. In
addition, the extension rate [%] of each test piece at the maximum load was determined.
The mean value of five test pieces was calculated so that the maximum load and the degree of
maximum load elongation were determined. The degree of maximum load elongation [%]
of an extensible spunbond nonwoven fabric was determined by measurement according to the
same method as described above.
[0098] (3) Residual Strain [%]
Five sheets of test pieces each having a length of200 mm in the machine direction
(MD) and a length of 50 mm in the cross direction (CD) were collected from a nonwoven
fabric layered body. Each test piece was drawn using a constant-rate extension type tensile
tester at a chuck interval of 100 mm, a tensile speed of 100 mm/minute, and a drawing rate of
I 00%, and then, the length of each test piece was immediately allowed to recover to the
original length at the same speed. Further, each test piece was immediately drawn at the
same speed and a drawing rate of l 00%. Then, the length of each test piece was
immediately allowed to recover to the original length at the same speed, and the strain upon
recovery was determined. The mean value of five sheets of the nonwoven fabric layered
bodies was evaluated as the residual strain (unit: %).
[0099] (4) Spinnability
20
The spinning state in the vicinity of the nozzle face of a spunbond nonwoven fabric
manufacturing apparatus was visually observed and the number oftimes of yarn breakage per
5 minutes (unit: number oftimes/5 minutes) was counted. When the number of times of
yarn breakage was 0 times/5 minutes, it was evaluated as "A". When yam breakage
occurred and it resulted in a failure of nonwoven fabric collection, it was evaluated as "C".
[0 I 00] (5) Formability
A metal roll was operated for 5 minutes in the embossing step so that a state of
adhesion occurring during passage ofthe nonwoven fabric layered body through a pair of
embossing rolls was evaluated.
A: State in which no adhesion is visually confirmed.
B: State in which substantially no adhesion is visually confirmed.
C: State in which adhesion is visually confirmed or the nonwoven fabric layered
body is wound around the embossing roll.
[0101] (6) Texture
One sheet of a test piece having a length of 250 mm in the machine direction (MD)
and a length of200 mm in the cross direction (CD) was collected from a nonwoven fabric
layered body. The test piece was inserted in a manner so as to allow the CD direction to
coincide with the roll rotation direction of a preheating apparatus as shown in Fig. 2. Thus,
the preheated nonwoven fabric layered body was obtained. T11e obtained nonwoven fabric
layered body was immediately inserted in a manner so as to allow the CD direction to
coincide with the roll rotation direction of a gear processing machine as shown in Fig. I.
Thus, the nonwoven fabric layered body that had been gear-drawn in the MD direction
(machine direction of the nonwoven fabric layered body) was obtained. Preheating was
controlled so as to adjust the roll surface temperature to 60°C, and gear rolls each mounted on
the gear processing machine was set to have a diameter of200 mm, a gear pitch of2.5 mm,
and a roll engagement depth of5.5 mm. Ten evaluators evaluated texture of the nonwoven
fabric layered body obtained by gear drawing described above by checking hand feeling based
on the following criteria.
3: Ten out of I 0 persons evaluated that there was no roughness.
2: Seven to nine out of I 0 persons evaluated that there was no roughness.
1: Three to six out of 1 0 persons evaluated that there was no roughness.
0: Zero to two out of 10 persons evaluated that there was no roughness.
[0102] (7) Rate of Remaining Bosses[%]
A nonwoven fabric layered body that had been gear-drawn by the same method as in
21
texture evaluation was evaluated in terms of the rate of remaining bosses via shape
observation by SEM. It was determined that texture was more favorable with a higher rate
of remaining bosses. The rate of remaining bosses was calculated by the following equation.
Rate of remaining bosses= Number of non-damaged bosses I Number of observed
bosses x 100
It was determined that embossed portions, for which hole formation or fiber
elimination in embossed portions and fiber breakage in embossed portions and the boundary
therebetween had not been observed, were designated as "non-damaged bosses" via SEM
observation of embossed portions of the nonwoven fabric layered body that had been
gear-drawn.
[0103] (8) Diaper Wearability
A test piece having a length of 250 mm in the machine direction (MD) and a length
of 200 mm in the cross direction (CD) was collected from a nonwoven fabric layered body.
The test piece was inserted in a manner so as to allow the CD direction to coincide with the
roll rotation direction of a preheating apparatus as shown in Fig. 2. Thus, the preheated
nonwoven fabric layered body was obtained. The obtained nonwoven fabric layered body
was immediately inserted in a manner so as to allow the CD direction to coincide with the roll
rotation direction of a gear processing machine as shown in Fig. I. Thus, the nonwoven
fabric layered body that had been gear-drawn in the MD direction (machine direction of the
nonwoven fabric layered body) was obtained. Preheating was controlled so as to adjust the
roll surface temperature to 60°C, and gear rolls each mounted on the gear processing machine
was set to have a diameter of 200 mm, a gear pitch of 2.5 mm, and a roll engagement depth of
3.5 mm. A nonwoven fabric was removed from a commercially available diaper, and the
nonwoven fabric layered body obtained by gear drawing described above was bonded thereto.
Ten evaluators wore the diaper and evaluated wearability based on the following criteria.
3: Ten out of 10 persons evaluated that there was no looseness.
2: Seven to nine out of I 0 persons evaluated that there was no looseness.
1: Three to six out of I 0 persons evaluated that there was no looseness.
0: Zero to two out of 1 0 persons evaluated that there was no looseness.
[0104] (9) Peel Strength [N] (roll blocking resistance)
Roll blocking resistance of a nonwoven fabric layered body was evaluated by the
method described below.
A 4-kg weight (1 0 em x 1 0 em in square size) was placed on two overlapping sheets
of nonwoven fabric layered bodies and stored in an oven at 90°C for 2 hours. After storage
22
tor 2 hours, peel strength of the nonwoven fabric layered bodies taken from the oven was
measured. As a result of this measurement, the peel strength was designated as an index of
the ease of blocking due to storage environment temperature or pressure, in a case in which a
nonwoven fabric layered body was stored in the roll form. In other words, smaller peel
strength means more difficult blocking and higher blocking resistance. Peel strength was
measured by the method described below.
Two test pieces having a length of I 0.0 em in the machine direction (MD) and a
length of 5.0 em in the cross direction (CD) were collected from the overlapping sheets of
nonwoven fabric layered bodies, which had been taken from the oven. Next, a 15.0-cm
piece was cut from packing tape, which was "Fabric tape No. 159 with a width of 50 mm
manufactured by Teraoka Seisakusho Co., Ltd.", and bonded to the entire surface of the test
piece in a manner so as to allow the machine direction (MD) ofthe test piece to coincide with
the longitudinal direction of the packing tape. The packing tape was bonded to both sides of
the test piece, thereby preparing a three-layer structure of packing tape/overlapping sheets of
nonwoven fabric layered bodies/packing tape. Next, peel strength [N] of overlapping sheets
of the nonwoven fabric layered bodies was measured by attaching the packing tapes bonded
to the both sides of the three-layer structure to the upper and lower chucks of a low-rate
extension type tensile tester and pulling at a chuck interval of 50 mm and a tensile speed of
100 mm/minute. Peel strength was calculated by rounding the mean of the values obtained
for two sheets of test pieces off to two decimal places. In a case in which fixation was
strong to an extent that caused a failure of adherend, peel strength of the overlapping sheets of
the nonwoven fabric layered bodies was determined to be "adherend failure".
[0 1 05] [Example I]