U.S. patent application number 16/651132 was filed with the patent office on 2020-07-30 for spunbond nonwoven fabric.
This patent application is currently assigned to Toray Industries, Inc.. The applicant listed for this patent is Toray Industries, Inc.. Invention is credited to Masanori Endo, Yoshitsugu Funatsu, Hiroo Katsuta.
Application Number | 20200240061 16/651132 |
Document ID | 20200240061 / US20200240061 |
Family ID | 1000004807900 |
Filed Date | 2020-07-30 |
Patent Application | download [pdf] |
United States Patent
Application |
20200240061 |
Kind Code |
A1 |
Katsuta; Hiroo ; et
al. |
July 30, 2020 |
SPUNBOND NONWOVEN FABRIC
Abstract
Provided is a spunbond nonwoven fabric which is made of a
polypropylene fiber and satisfies all of the following conditions A
to E: A. the average single fiber diameter of the fiber is 6-17
.mu.m; B. the degree of crystal orientation of the fiber as
obtained by wide-angle X-ray diffraction is at least 0.91; C. the
crystallite size of the (110) plane of the fiber as obtained by
wide angle X-ray diffraction is at least 12 nm; D. the average
orientation parameter of the fiber as obtained by Raman
spectroscopy is at least 8.0; and E. the complex viscosity of the
spunbond nonwoven fabric at a temperature of 230.degree. C. is
20-100 Pasec at an angular frequency of 6.3 rad/sec.
Inventors: |
Katsuta; Hiroo; (Shizuoka,
JP) ; Funatsu; Yoshitsugu; (Otsu-shi, Shiga, JP)
; Endo; Masanori; (Otsu-shi, Shiga, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Toray Industries, Inc. |
Tokyo |
|
JP |
|
|
Assignee: |
Toray Industries, Inc.
Tokyo
JP
|
Family ID: |
1000004807900 |
Appl. No.: |
16/651132 |
Filed: |
September 27, 2018 |
PCT Filed: |
September 27, 2018 |
PCT NO: |
PCT/JP2018/035928 |
371 Date: |
March 26, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D04H 3/007 20130101;
D04H 3/16 20130101 |
International
Class: |
D04H 3/007 20060101
D04H003/007; D04H 3/16 20060101 D04H003/16 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2017 |
JP |
2017-188004 |
Jul 27, 2018 |
JP |
2018-141053 |
Claims
1. A spun-bonded nonwoven fabric comprising polypropylene fibers
wherein all of the following conditions A to E are satisfied: A.
the fibers have an average single fiber diameter of 6 .mu.m or more
and 17 .mu.m or less; B. the fibers have a crystal orientation
degree in wide-angle X-ray diffraction of 0.91 or more; C. the
fibers have a crystallite size of a (110) plane in wide-angle X-ray
diffraction of 12 nm or more; D. the fibers have an average
orientation parameter in Raman spectroscopy of 8.0 or more; and E.
the spun-bonded nonwoven fabric has a complex viscosity of 20 Pasec
or more and 100 Pasec or less at a temperature of 230.degree. C. at
an angular frequency of 6.3 rad/sec.
2. The spun-bonded nonwoven fabric according to claim 1, wherein
the spun-bonded nonwoven fabric has the complex viscosity of 40
Pasec or more and 80 Pasec or less at the temperature of
230.degree. C. at the angular frequency of 6.3 rad/sec.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is the U.S. National Phase application of
PCT/JP2018/035928, filed Sep. 27, 2018, which claims priority to
Japanese Patent Application No. 2017-188004, filed Sep. 28, 2017
and Japanese Patent Application No, 2018-141053, filed Jul. 27,
2018, the disclosures of each of these applications being
incorporated herein by reference in their entireties for all
purposes.
FIELD OF THE INVENTION
[0002] The present invention relates to a spun-bonded nonwoven
fabric which is soft and has excellent mechanical properties and
higher-order processability.
BACKGROUND OF THE INVENTION
[0003] Spun-bonded nonwoven fabrics made of polyolefin,
particularly polypropylene spun-bonded nonwoven fabrics, are low in
cost and have excellent processability, and are hence widely used
mainly in hygienic material applications.
[0004] In recent years, as for polypropylene spun-bonded nonwoven
fabrics used in hygienic material applications, further improvement
in texture, touch, softness and production efficiency is required,
and various studies have particularly been made to improve
softness.
[0005] It is known that fiber diameter reduction is effective as
means for improving softness. However, in diameter-reducing methods
in which ejection rates are reduced, production efficiency is
lowered. In methods in which spinning speeds are increased to
increase the production efficiency, filament breakage occurs
frequently, hence stable production is difficult to realize.
[0006] Therefore, a polyolefin-based long fiber nonwoven fabric, in
which fiber diameter, fiber adsorption force and friction
coefficient of the nonwoven fabric are set in specific ranges to
improve softness of the spun-bonded nonwoven fabric, and bending
flexibility and slipperiness of the fibers are both achieved, has
been proposed (see Patent Literature 1).
[0007] Meanwhile, a spun-bonded nonwoven fabric, in which
propylene-based polymers are used as raw materials, and basis
weight, melt flow rate, fineness and emboss area ratio of the
spun-bonded nonwoven fabric are set in specific ranges, and fuzzing
resistance, softness, strength and production efficiency are
excellent, has been proposed (see Patent Literature 2).
PATENT LITERATURE
[0008] Patent Literature 1: JP-A-2013-159884
[0009] Patent Literature 2: WO2007/091444
SUMMARY OF THE INVENTION
[0010] According to the method disclosed in Patent Literature 1,
the softness of the nonwoven fabric can be reliably improved.
However, since a melt flow rate of resin used therein is low, a
softness improving effect thereof is not sufficient, and nonwoven
fabrics exemplified in examples thereof are nonwoven fabrics
containing low melting point polyolefin-based resin, hence the
production efficiency may decrease due to occurrence of filament
breakage. Further, there is also a problem that the resin used is
substantially limited.
[0011] In the method disclosed in Patent Literature 2, although the
softness of the nonwoven fabric can be reliably improved, since the
melt flow rate of the resin used therein is low, a softness
improving effect thereof is not sufficient. Moreover, a hole
diameter of a spinneret exemplified in examples thereof is as large
as 0.6 mm.phi., hence spinneret pressure is difficult to be
applied, spinning cannot be performed uniformly, and filament
breakage and fiber diameter unevenness are generated, which makes
it difficult to stably obtain uniform nonwoven fabrics.
[0012] Therefore, an object of the present invention is to provide
a spun-bonded nonwoven fabric which is soft and has excellent
mechanical properties and higher-order processability.
[0013] As a result of studies performed by the present inventors,
it has been found that the softness of the spun-bonded nonwoven
fabric has a high correlation with complex viscosity thereof in a
molten state. As the complex viscosity of the spun-bonded nonwoven
fabric becomes lower, the softness is improved, while the
mechanical properties and the higher-order processability are
reduced. Therefore, as a result of intensive studies to solve the
above problems, the present inventors have found that a spun-bonded
nonwoven fabric, in which softness and excellent mechanical
properties and higher-order processability are all achieved, is
obtained by setting fineness, crystal orientation degree,
crystallite size, and orientation parameter of the spun-bonded
nonwoven fabric in specific ranges, and further by setting the
complex viscosity of the spun-bonded nonwoven fabric in a specific
range, hence the present invention was completed.
[0014] An object of the present invention is to solve the above
problems, and a spun-bonded nonwoven fabric according to
embodiments of the present invention contains polypropylene fibers,
in which all of the following conditions A to E are satisfied:
[0015] A. an average single fiber diameter of the fibers is 6 .mu.m
or more and 17 .mu.m or less;
[0016] B. a crystal orientation degree in wide-angle X-ray
diffraction of the fibers is 0.91 or more;
[0017] C. a crystallite size of a (110) plane in the wide-angle
X-ray diffraction of the fibers is 12 nm or more;
[0018] D. an average orientation parameter in Raman spectroscopy of
the fibers is 8.0 or more; and
[0019] E. a complex viscosity of the spun-bonded nonwoven fabric is
20 Pasec or more and 100 Pasec or less at a temperature of
230.degree. C. at an angular frequency of 6.3 rad/sec.
[0020] According to a preferred mode of the spun-bonded nonwoven
fabric according to the present invention, the complex viscosity of
the spun-bonded nonwoven fabric is 40 Pasec or more and 80 Pasec or
less at the temperature of 230.degree. C. at the angular frequency
of 6.3 rad/sec.
[0021] The fiber diameter of the fibers constituting the
spun-bonded nonwoven fabric according to the present invention is
low, and the complex viscosity thereof in the molten state is low,
hence the spun-bonded nonwoven fabric has high softness. In
addition, the crystal orientation thereof is high, the crystallite
size thereof is large, and the orientation parameter thereof is
high, hence the spun-bonded nonwoven fabric according to the
present invention exhibits excellent mechanical properties and
higher-order processability.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0022] The spun-bonded nonwoven fabric according to exemplary
embodiments of the present invention is a spun-bonded nonwoven
fabric containing polypropylene fibers, in which all of the
following conditions A to E are satisfied:
[0023] A. the fibers have an average single fiber diameter of 6
.mu.m or more and 17 .mu.m or less;
[0024] B. the fibers have a crystal orientation degree in
wide-angle X-ray diffraction of 0.91 or more;
[0025] C. the fibers have a crystallite size of a (110) plane in
wide-angle X-ray diffraction of 12 nm or more;
[0026] D. the fibers have an average orientation parameter in Raman
spectroscopy of 8.0 or more; and
[0027] E. the spun-bonded nonwoven fabric has a complex viscosity
of 20 Pasec or more and 100 Pasec or less at a temperature of
230.degree. C. at an angular frequency of 6.3 rad/sec.
[0028] The spun-bonded nonwoven fabric according to embodiments of
the present invention is explained in detail below.
[0029] [Polypropylene-Based Resin]
[0030] A spun-bonded nonwoven fabric according to embodiments of
the present invention is made of fibers of polypropylene-based
resin (polypropylene fibers). The polypropylene-based resin means
resin containing propylene units serving as main repeating units.
By using the polypropylene-based resin, a spun-bonded nonwoven
fabric which is low in cost and has excellent softness can be
obtained.
[0031] Examples of the polypropylene-based resin used in
embodiments of the present invention include propylene
homopolymers, copolymers of propylene and various .alpha.-olefins,
and the like. When a copolymer of propylene and various
.alpha.-olefins is used as the polypropylene-based resin, a
copolymerization ratio of the various .alpha.-olefins is preferably
10 mol % or less, more preferably 5 mol % or less, even more
preferably 3 mol % or less from the viewpoint of strength
improvement.
[0032] The polypropylene-based resin used in the present invention
can be blended with other component resin as long as the effects of
the present invention are not impaired. Examples of the other
component resin include polyolefin-based resin such as polyethylene
and poly-4-methyl-1-pentene whose melting points are close to
polypropylene, low melting point polyester resin and low melting
point polyamide resin. From the viewpoint of imparting softness,
low-crystalline olefin-based resin is preferably used. For example,
an ethylene-propylene copolymer, low stereoregular polypropylene,
or the like is preferably used as the low-crystalline olefin-based
resin. A mass ratio of the other component resin is preferably 20%
by mass or less, and more preferably 15% by mass or less, so as to
sufficiently exhibit characteristics of the polypropylene-based
resin.
[0033] Coloring pigments, antioxidants, lubricants such as
polyethylene wax, heat-resistant stabilizer, and the like can be
added to the polypropylene-based resin used in the present
invention as long as the effects of the present invention are not
impaired.
[0034] It is preferable not to add additives that decompose the
resin and reduce molecular weight, for example, free radical agents
such as peroxide, especially dialkylated oxide, to the resin to be
used in the polypropylene-based resin used in the present
invention. When the above additives are added to the
polypropylene-based resin, unevenness of fiber diameter occurs due
to partial viscosity unevenness, making it difficult to
sufficiently reduce fiber diameter, and in some cases, spinnability
is deteriorated by bubbles caused by the viscosity unevenness or
decomposition gas. Therefore, by not adding the above additives to
the polypropylene-based resin, uniformity of the fiber diameter is
improved, and the fiber diameter can be further reduced.
[0035] A melting point of the polypropylene-based resin used in the
present invention is preferably 120.degree. C. or more and
180.degree. C. or less. Heat resistance that can withstand
practical use can be obtained when the melting point is preferably
120.degree. C. or more, more preferably 130.degree. C. or more.
Heat bonding of spun fibers becomes easy when the melting point is
preferably 180.degree. C. or less, more preferably 170.degree. C.
or less, and hence a spun-bonded nonwoven fabric, which has good
mechanical properties and higher-order processability, is
obtained.
[0036] About 2 mg of spun-bonded nonwoven fabric is set in a
differential scanning calorimeter, differential scanning
calorimetry is performed three times in nitrogen at a heating rate
of 16.degree. C./min, and an arithmetic average value of a
temperature of an endothermic peak is taken as the melting point
(.degree. C.) of the spun-bonded nonwoven fabric according to the
present invention.
[0037] A weight average molecular weight of the polypropylene-based
resin used in the present invention is preferably 100,000 or more
and 200,000 or less. The fibers have excellent fiber diameter
uniformity when the weight average molecular weight is preferably
100,000 or more, more preferably 110,000 or more, and hence
processability of the nonwoven fabric is improved. Flowability of
the polypropylene-based resin is improved when the weight average
molecular weight is preferably 200,000 or less, more preferably
180,000 or less, hence the spinnability is improved. The weight
average molecular weight in the present invention refers to a value
calculated in terms of polystyrene and dibenzyl using gel
permeation chromatography.
[0038] A melt mass flow rate of the polypropylene-based resin used
in the present invention is preferably 155 g/10 min or more and 500
g/10 min or less. Flowability of the polypropylene-based resin is
improved when the melt mass flow rate is preferably 155 g/10 min or
more, more preferably 160 g/10 min or more, hence the spinnability
is improved. Filament breakage caused by low melt viscosity is
reduced when the melt mass flow rate is preferably 500 g/10 min or
less, more preferably 400 g/10 min or less, and hence the
spinnability is improved.
[0039] The melt mass flow rate can be controlled by the weight
average molecular weight of the polypropylene-based resin. As the
weight average molecular weight of the polypropylene-based resin
increases, the melt mass flow rate decreases.
[0040] The melt mass flow rate in the present invention refers to a
value measured at a temperature of 230.degree. C. and a load of
2,160 g in accordance with JIS K7210-1: 2014, "Chapter 8, Method A:
Mass Measurement".
[0041] The melt mass flow rate of the polypropylene-based resin
used in the present invention can also be adjusted by blending two
or more types of resin having different melt mass flow rates at any
ratio. In this case, the melt mass flow rate of the resin blended
with the main polypropylene-based resin is preferably 10 g/10 min
or more and 1000 g/10 min or less. Unevenness of fiber diameter and
spinnability deterioration caused by partial viscosity unevenness
generated in the blended polypropylene-based resin can be inhibited
when the melt mass flow rate of the blended resin is preferably 10
g/10 min or more, more preferably 20 g/10 min or more, even more
preferably 30 g/10 min or more. A spun-bonded nonwoven fabric which
has excellent mechanical properties is obtained when the melt mass
flow rate of the blended resin is preferably 1000 g/10 min or less,
more preferably 800 g/10 min or less, even more preferably 600 g/10
min or less.
[0042] [Polypropylene Fiber]
[0043] It is important that polypropylene fibers which constitute
the spun-bonded nonwoven fabric according to embodiments of the
present invention have an average single fiber diameter of 6 .mu.m
or more and 17 .mu.m or less. Feel when touching a surface of the
spun-bonded nonwoven fabric obtained from the polypropylene fiber
becomes smooth when the average single fiber diameter is 17 .mu.m
or less, preferably 16 .mu.m or less, and more preferably 15 .mu.m
or less. In addition, the average single fiber diameter is reduced,
so that a low cross-sectional secondary moment is also exhibited,
hence the softness is further improved. Process passability at the
time of post processing is improved when the average single fiber
diameter is 6 .mu.m or more, preferably 7 .mu.m or more, and more
preferably 8 .mu.m or more, hence a spun-bonded nonwoven fabric
which has a small number of defects is obtained.
[0044] A small amount is cut out from the spun-bonded nonwoven
fabric, and diameters of the polypropylene fibers are acquired from
microscopic observation of a side surface of the polypropylene
fibers constituting the spun-bonded nonwoven fabric at a portion
other than an emboss bonding portion, and the measurement is
performed 10 times per level, and an arithmetic average value
thereof is referred to as the average single fiber diameter (.mu.m)
of the polypropylene fibers in the present invention.
[0045] It is important that a crystal orientation degree in
wide-angle X-ray diffraction of the polypropylene fibers which
constitute the spun-bonded nonwoven fabric according to embodiments
of the present invention is 0.91 or more. A crystal C-axis is
arranged along a fiber axis when the crystal orientation degree is
0.91 or more, preferably 0.92 or more, and more preferably 0.93 or
more, hence fibers which have excellent strength and higher-order
processability are obtained. An upper limit of the crystal
orientation degree that can be achieved by the present invention is
1.00.
[0046] The crystal orientation degree can be controlled by melt
mass flow rate and spinning speed, and cooling conditions during
spinning. As the melt mass flow rate decreases while the spinning
speed increases, or as cooling efficiency during spinning
increases, the crystal orientation degree is increased.
[0047] It is important that a crystallite size of a (110) plane in
the wide-angle X-ray diffraction of the polypropylene fibers which
constitute the spun-bonded nonwoven fabric according to embodiments
of the present invention is 12 nm or more. Fibers which have
excellent strength and higher-order processability are obtained
when the crystallite size of the (110) plane is 12 nm or more,
preferably 13 nm or more, and more preferably 14 nm or more. An
upper limit of the crystallite size that can be achieved by the
present invention is about 25 nm.
[0048] The crystallite size can be controlled by melt mass flow
rate and spinning speed. As the melt mass flow rate decreases while
the spinning speed increases, the crystallite size is
increased.
[0049] The crystal orientation degree and the crystallite size (nm)
in the wide-angle X-ray diffraction in the present invention
respectively refer to values measured and calculated by the
following method.
[0050] (1) 20 polypropylene fibers cut from the spun-bonded
nonwoven fabric are bundled such that fiber axes thereof are in the
same direction.
[0051] (2) The sample bundled in (1) is subjected to wide-angle
X-ray diffraction measurement using an X-ray diffraction
device.
[0052] (3) An X-ray diffraction profile in a circumferential
direction and an X-ray diffraction profile in an equatorial line
direction of a peak corresponding to the (110) plane are
obtained.
[0053] (4) Based on a peak half-value width H (.degree.) of the
X-ray diffraction profile in the circumferential direction and a
peak half-value width .beta..sub.e (.degree.) of the X-ray
diffraction profile in the equatorial line direction, values are
calculated using the following equations, respectively.
Crystal orientation degree .pi.=(180-H)/180
Crystallite size L
(nm)=0.9.lamda./(((.beta..sub.e.sup.2-.beta..sub.0.sup.2).sup.0.5.times.c-
os .theta.)
[0054] (In the equation, .lamda. represents an incident X-ray
wavelength (0.15418 nm in the present device), .beta..sub.0
represents a half-value width correction value (0.46.degree. in the
present device), and .theta. represents a peak top Bragg angle
(.degree.).)
[0055] It is important that an average orientation parameter in
Raman spectroscopy of the polypropylene fibers which constitute the
spun-bonded nonwoven fabric according to embodiments of the present
invention is 8.0 or more. Molecular chains in amorphous portions
and crystal portions are oriented in a fiber axis direction when
the average orientation parameter is 8.0 or more, preferably 8.5 or
more, more preferably 8.8 or more, hence fibers which have
excellent strength and higher-order processability are obtained. An
upper limit of the average orientation parameter that can be
achieved by the present invention is about 13.0.
[0056] The average orientation parameter can be controlled by melt
mass flow rate and spinning speed, and cooling conditions during
spinning. As the melt mass flow rate decreases while the spinning
speed increases, or as cooling efficiency during spinning
increases, the orientation parameter is increased.
[0057] The average orientation parameter in the present invention
refers to a value measured and calculated by the following
method.
[0058] (1) A single fiber is cut out from the spun-bonded nonwoven
fabric and set in a holder.
[0059] (2) A laser Raman spectroscopy is used to obtain polarized
Raman spectra under a parallel condition when a polarization
direction coincides with the fiber axis and under a perpendicular
condition when the polarization direction is perpendicular to the
fiber axis.
[0060] (3) Raman band intensity around 810 cm.sup.-1 attributed to
coupling modes of CH.sub.2 bending vibration and C--C stretching
vibration is defined as I.sub.810, while Raman band intensity of
840 cm.sup.-1 attributed to the CH.sub.2 bending vibration mode is
defined as I.sub.840, and the orientation parameter is calculated
using the following equation.
Orientation
parameter=(I.sub.810/I.sub.840).sub.parallel/(I.sub.810/I.sub.840).sub.pe-
rpendicular
[0061] (In the equation, parallel represents an intensity ratio
under the parallel condition, and perpendicular represents an
intensity ratio under the perpendicular condition.)
[0062] (4) The measurement is performed six times per level, and an
arithmetic average value thereof is taken as the average
orientation parameter.
[0063] A density of the polypropylene fibers which constitute the
spun-bonded nonwoven fabric according to the present invention is
preferably 0.88 g/cm.sup.3 or more and 0.93 g/cm.sup.3 or less.
Fibers which have high crystallinity and excellent strength and
higher-order processability are obtained when the density is
preferably 0.88 g/cm.sup.3 or more, more preferably 0.89 g/cm.sup.3
or more. Heat bonding performance and processability during
embossing or calendering are improved when the density is
preferably 0.93 g/cm.sup.3 or less, more preferably 0.92 g/cm.sup.3
or less.
[0064] The density in the present invention refers to a value
measured by the following method.
[0065] (1) Water and ethanol are mixed in a room whose temperature
is controlled to 15.degree. C. A mass fraction of the ethanol is
40% to 70%, and 31 levels of aqueous ethanol solutions having
different concentrations at 1% intervals are prepared.
[0066] (2) A small amount of spun-bonded nonwoven fabric, from
which impurities are removed by ultrasonic cleaning, is cut out,
the cut-out spun-bonded nonwoven fabric is immersed in the aqueous
ethanol solution so as to prevent air bubbles and is left for 6
hours or more.
[0067] (3) The density is calculated by using the following
equation based on a mass fraction X.sub.E of an aqueous ethanol
solution having the lowest ethanol mass fraction among aqueous
ethanol solutions in which the spun-bonded nonwoven fabric did not
sink to the bottom.
Density of polypropylene fibers
(g/cm.sup.3)=-0.000005.times.X.sub.E.sup.2-0.0017.times.X.sub.E+1.0153
[0068] A cross-sectional shape of the polypropylene fibers which
constitute the spun-bonded nonwoven fabric according to the present
invention is preferably circular. When the cross-sectional shape is
flat or irregular, there is a bending direction in which
cross-sectional secondary moment of the same cross-sectional area
is larger than that in the case of the circular cross-section,
hence rigidity of the spun-bonded nonwoven fabric is increased, and
the softness may be impaired.
[0069] [Spun-Bonded Nonwoven Fabric]
[0070] It is important that complex viscosity of the spun-bonded
nonwoven fabric according to embodiments of the present invention
is 20 Pasec or more and 100 Pasec or less at a temperature of
230.degree. C. at an angular frequency of 6.3 rad/sec. Softness of
the fibers which constitute the spun-bonded nonwoven fabric is
improved when the complex viscosity is 100 Pasec or less,
preferably 90 Pasec or less, and more preferably 80 Pasec or less,
hence a spun-bonded nonwoven fabric having excellent softness is
obtained. Strength reduction and deterioration of higher-order
processability of the obtained nonwoven fabric can be inhibited
when the complex viscosity is 20 Pasec or more, preferably 30 Pasec
or more, and more preferably 40 Pasec or more.
[0071] The complex viscosity of the spun-bonded nonwoven fabric can
be controlled by the weight average molecular weight of the
polypropylene-based resin. As the weight average molecular weight
of the polypropylene-based resin increases, the complex viscosity
of the spun-bonded nonwoven fabric decreases.
[0072] A cut-out spun-bonded nonwoven fabric is set in a measuring
jig, a measurement using a rotary rheometer is performed three
times per level at a temperature of 230.degree. C. at an angular
frequency of 6.3 rad/sec, and an arithmetic average value thereof
is referred to as the complex viscosity (Pasec) in the present
invention.
[0073] A melting point of the spun-bonded nonwoven fabric according
to the present invention is preferably 120.degree. C. or more and
190.degree. C. or less. Troubles, such as reduction in strength and
higher-order processability caused by holes opened during emboss
bonding, can be prevented when the melting point is preferably
120.degree. C. or more, more preferably 130.degree. C. or more, and
even more preferably 140.degree. C. or more. Heat bonding
performance during embossing or calendering is improved when the
melting point is preferably 190.degree. C. or lower, more
preferably 180.degree. C. or lower, and even more preferably
175.degree. C. or lower, hence the strength and higher-order
processability of the spun-bonded nonwoven fabric are improved.
[0074] The melting point (.degree. C.) in the present invention is
obtained from a peak temperature of an endothermic peak obtained by
performing differential scanning calorimetry with a differential
scanning calorimeter at a heating rate of 16.degree. C./min in
nitrogen.
[0075] A heat of crystal melting of the spun-bonded nonwoven fabric
according to the present invention is preferably 70 J/g or more and
105 J/g or less. The fibers which constitute the spun-bonded
nonwoven fabric have appropriate crystallinity when the heat of
crystal melting is preferably 70 J/g or more, more preferably 80
J/g or more, hence a spun-bonded nonwoven fabric having high
strength and higher-order processability is obtained. The heat
bonding performance during embossing or calendering is improved
when the heat of crystal melting is preferably 105 J/g or lower,
and more preferably 100 J/g or lower, hence the strength and
higher-order processability of the spun-bonded nonwoven fabric are
improved. The heat of crystal melting (J/g) in the present
invention refers to a value obtained based on a peak area of the
endothermic peak obtained by performing the differential scanning
calorimetry with the differential scanning calorimeter at the
heating rate of 16.degree. C./min in the nitrogen.
[0076] A basis weight of the spun-bonded nonwoven fabric according
to the present invention is preferably 5 g/m.sup.2 or more and 50
g/m.sup.2 or less. A spun-bonded nonwoven fabric, which has less
breakage in succeeding processes and has excellent processability,
is obtained when the basis weight is preferably 5 g/m.sup.2 or
more, more preferably 10 g/m.sup.2 or more. The softness of the
spun-bonded nonwoven fabric can be appropriately exhibited when the
basis weight is preferably 50 g/m.sup.2 or less, more preferably 30
g/m.sup.2 or less.
[0077] A stress per basis weight at 5% elongation of the
spun-bonded nonwoven fabric according to the present invention
(hereinafter, may also be referred to as 5% modulus per basis
weight) is preferably 0.06 (N/25 mm)/(g/m.sup.2) or more and 0.33
(N/25 mm)/(g/m.sup.2) or less. A spun-bonded nonwoven fabric which
has practically usable strength is obtained when the 5% modulus per
basis weight is preferably 0.06 (N/25 mm)/(g/m.sup.2) or more, more
preferably 0.13 (N/25 mm)/(g/m.sup.2) or more, and even more
preferably 0.20 (N/25 mm)/(g/m.sup.2) or more. A spun-bonded
nonwoven fabric which has excellent softness is obtained when the
5% modulus per basis weight is preferably 0.33 (N/25
mm)/(g/m.sup.2) or less, more preferably 0.30 (N/25 mm)/(g/m.sup.2)
or less, and even more preferably 0.27 (N/25 mm)/(g/m.sup.2) or
less.
[0078] In the present invention, the 5% modulus per basis weight of
the spun-bonded nonwoven fabric adopts a value measured by the
following procedures in accordance with "6.3 Tensile Strength and
Elongation Ratio (ISO method)" of JIS L1913: 2010.
[0079] (1) Three test pieces of 25 mm.times.300 mm are taken for
each width of 1 m in a lengthwise direction (a longitudinal
direction of the nonwoven fabric) and a widthwise direction (a
transverse direction of the nonwoven fabric) of the nonwoven
fabric.
[0080] (2) The test pieces are set in a tensile tester at grip
intervals of 200 mm.
[0081] (3) A tensile test is conducted at a tensile speed of 100
mm/min, and a stress at 5% elongation (5% modulus) is measured.
[0082] (4) An average value of the 5% modulus in the lengthwise
direction and the transverse direction measured for each test piece
is calculated, the 5% modulus per basis weight is calculated based
on the following equation, and the calculated value is rounded off
to the nearest hundredth.
5% modulus per basis weight ((N/25 mm)/(g/m.sup.2))=[average value
of 5% modulus (N/25 mm)]/basis weight (g/m.sup.2).
[0083] The spun-bonded nonwoven fabric according to embodiments of
the present invention has excellent softness since the average
single fiber diameter of the polypropylene fibers constituting the
spun-bonded nonwoven fabric is as thin as 6 .mu.m or more and 17
.mu.m or less while the complex viscosity of the spun-bonded
nonwoven fabric is low. As a result of intensive studies, the
present inventors have found that when the complex viscosity is 20
Pasec or more and 100 Pasec or less under the above conditions,
production stability is improved, which is one of the problems to
be solved for obtaining fibers with small average single fiber
diameters, and in addition, that the heat bonding performance is
improved, hence the strength and processability of the spun-bonded
nonwoven fabric are improved. Meanwhile, there is a concern that
the strength may be reduced when the average single fiber diameter
is reduced. However, it has been surprisingly found that a nonwoven
fabric which has excellent processability without reducing strength
thereof is obtained when the crystal orientation degree in the
wide-angle X-ray of the polypropylene fibers constituting the
spun-bonded nonwoven fabric is 0.91 or more, the crystallite size
of the (110) plane is 12 nm or more and the average orientation
parameter in Raman spectroscopy is 8.0 or more.
[0084] [Method for Preparing Spun-Bonded Nonwoven Fabric]
[0085] Next, a method for preparing the spun-bonded nonwoven fabric
according to exemplary embodiments of the present invention will be
described in specific examples.
[0086] A raw material used in the present invention is the
polypropylene-based resin whose copolymers other than propylene,
melting point, melt mass flow rate, and the like are as described
above.
[0087] The polypropylene-based resin is used for melt spinning
without performing drying or the like.
[0088] In the melt spinning, a melt spinning method using an
extruder, such as a single-screw or twin-screw extruder, can be
applied. The extruded polypropylene-based resin is passed through
piping, metered by a metering device such as a gear pump, passed
through a filter for removing foreign substances, and guided to a
spinneret. At this time, a temperature from the resin piping to the
spinning spinneret (spinning temperature) is preferably 180.degree.
C. or more and 280.degree. C. or less, so as to increase
flowability.
[0089] A hole diameter D of a spinneret hole of the spinning
spinneret used for ejection is preferably 0.1 mm or more and 0.6 mm
or less. L/D defined by a quotient obtained by dividing a land
length L of the spinneret hole (length of a straight pipe portion
having diameter equal to the hole diameter of the spinneret hole)
by the hole diameter D is preferably 1 or more and 10 or less.
[0090] Filaments ejected from the spinneret hole are cooled and
solidified by blowing air. A temperature of the cooling air can be
determined from the viewpoint of cooling efficiency based on a
balance between the temperature of the cooling air and a speed of
the cooling air, and is preferably 0.degree. C. or more and
20.degree. C. or less from the viewpoint of uniformity of fineness.
Dew condensation and freezing at air piping and cooling air
discharge portions can be prevented by setting the temperature of
the cooling air to preferably 0.degree. C. or more, more preferably
2.degree. C. or more, hence the cooling air can be supplied stably.
The crystal orientation degree and orientation parameter of the
polypropylene fibers are improved when the temperature of the
cooling air is preferably 20.degree. C. or less, more preferably
16.degree. C. or less, and even more preferably 12.degree. C. or
less, hence a spun-bonded nonwoven fabric having excellent
mechanical properties and higher-order processability is
obtained.
[0091] Cooling gas is flowed in a substantially vertical direction
relative to the filaments to cool the filaments. At that time, the
speed of the cooling air is preferably 10 m/min or more and 100
m/min or less. The crystal orientation degree and orientation
parameter of the polypropylene fibers are improved when the speed
of the cooling air is preferably 10 m/min or more, more preferably
20 m/min or more, and even more preferably 25 m/min or more, hence
a spun-bonded nonwoven fabric having excellent mechanical
properties and higher-order processability is obtained. Filament
vibration caused by the cooling air can be reduced by setting the
speed of the cooling air to preferably 100 m/min or less, more
preferably 80 m/min or less, and even more preferably 70 m/min or
less, hence the filament breakage during spinning is reduced.
[0092] A distance from the spinning spinneret to the start of the
cooling is preferably 20 mm or more and 500 mm or less. When the
distance from the spinning spinneret to the start of the cooling is
preferably 20 mm or more, more preferably 25 mm or more, and even
more preferably 30 mm or more, a surface temperature of the
spinneret is not excessively decreased, and the ejection is
stabilized, so that the filament breakage during spinning is
reduced. The crystal orientation degree and orientation parameter
of the polypropylene fibers are improved when the distance from the
spinning spinneret to the start of the cooling is preferably 500 mm
or less, more preferably 300 mm or less, and even more preferably
200 mm or less, hence a spun-bonded nonwoven fabric having
excellent mechanical properties and higher-order processability is
obtained.
[0093] The filaments ejected from the spinneret hole are drawn by
an air flow that is accelerated at a position preferably within a
range of 400 mm or more and 7000 mm or less from the spinning
spinneret. Although the accelerated air flow can be obtained by
sealing a region where the cooling air is blown and accelerating
air flow velocity by gradually reducing a cross-sectional area of
the sealed region toward downstream of a spinning line, it is
preferable to use an ejector to obtain a higher air flow velocity.
The filaments are accelerated by this air flow velocity, and a
spinning speed, which is a traveling speed of the fibers, also
reaches a speed that is close to the air flow velocity.
[0094] The spinning speed is preferably 3 km/min or more, and is
more preferably 4 km/min so as to reduce the average single fiber
diameter. Similarly, the air flow velocity is preferably 3 km/min
or more. An upper limit of the spinning speed is about 12
km/min.
[0095] The spinning speed refers to a value calculated by the
following equation.
Spinning speed
(km/min)=Q1000/((W/2).sup.2.times..pi..times..rho.)
[0096] (In the equation, Q represents a single-hole ejection rate
(g/min), W represents an average single fiber diameter (.mu.m), and
.rho. represents a density (g/cm.sup.3).)
[0097] The filaments drawn by the air are spread by being passed
through a spreading unit which reduces surrounding air flow
velocity, then land on a net conveyor which suctions air from a
back surface thereof, and are collected as a fiber web. The
collected fiber web is conveyed by a conveyor at a speed of 10
m/min or more and 1000 m/min or less, and heat bonding processing
is performed to obtain the spun-bonded nonwoven fabric.
[0098] Examples of methods for uniting the fiber web by heat
bonding include methods of heat bonding performed by various rolls
such as: hot embossing rolls which are a pair of upper and lower
rolls that have an engraved surface (have recesses and protrusions)
respectively; hot embossing rolls which include a combination of a
roll having a flat (smooth) surface and a roll having an engraved
surface (has recesses and protrusions); and hot calendar rolls
which include a pair of upper and lower flat (smooth) rolls.
[0099] A proportion of embossed bonding area during the heat
bonding is preferably 5% or more and 30% or less. Practically
usable strength and higher-order processability can be imparted to
the spun-bonded nonwoven fabric when the bonding area is preferably
5% or more, more preferably 10% or more. Meanwhile, sufficient
softness can be imparted to the spun-bonded nonwoven fabric,
especially for use as hygienic materials, when the bonding area is
preferably 30% or less, more preferably 20% or less.
[0100] The term "bonding area" in the present invention has the
following meanings. In the case of heat bonding with a pair of
rolls having recesses and protrusions, that term means a proportion
of portions of the fiber web, with which both protrusions of the
upper roll and protrusions of the lower roll have come into
contact, to the whole nonwoven fabric. In the case of heat bonding
with a roll having recesses and protrusions and a flat roll, that
term means a proportion of portions of the fiber web, with which
protrusions of the roll having recesses and protrusions have come
into contact, to the whole nonwoven fabric.
[0101] The shape of the engraving applied to the hot embossing
rolls can be circular, elliptic, square, rectangular,
parallelogrammic, rhombic, regularly hexagonal, and regularly
octagonal shapes and the like.
[0102] A linear pressure of the hot embossing roll during the heat
bonding is preferably 5 kgf/cm or more and 50 kgf/cm or less. The
heat bonding can be sufficiently performed when the linear pressure
is 5 kgf/cm or more, more preferably 10 kgf/cm or more, and even
more preferably 15 kgf/cm or more. Meanwhile, roll stress is not
excessively applied when the linear pressure is 50 kgf/cm or less,
more preferably 40 kgf/cm or less, and still more preferably 30
kgf/cm or less, hence texture hardening of the spun-bonded nonwoven
fabric can be prevented.
[0103] An important point in the process of producing the
spun-bonded nonwoven fabric according to the present invention is
that the average single fiber diameter can be reduced by high-speed
spinning while stable production thereof can be made possible.
Although this mechanism is not clear, the spun-bonded nonwoven
fabric according to the present invention inevitably uses the
polypropylene-based resin having low viscosity as the raw material,
hence deformation followability of the polypropylene-based resin is
improved in thinning behavior during the spinning process, so that
filament breakage defects are significantly reduced.
[0104] Meanwhile, when only the above point is considered, the
strength and higher-order processability of the obtained
spun-bonded nonwoven fabric may be reduced due to the low
viscosity. Therefore, another important point in the process of
producing the spun-bonded nonwoven fabric according to the present
invention is to sufficiently cool and solidify the filaments
ejected from the spinneret within a range that does not affect
application of high-speed spinning and spinnability, so as to form
a specific fiber structure. When such a process is applied, since
high spinning stress is applied to the filaments from the spinning
spinneret to an entrance of the ejector, the crystal orientation
degree and the orientation parameter of the polypropylene fibers
constituting the spun-bonded nonwoven fabric can be improved.
[0105] In addition to excellent softness, the spun-bonded nonwoven
fabric obtained in this manner has sufficient mechanical properties
and higher-order processability to be used as a spun-bonded
nonwoven fabric for hygienic materials.
[0106] The spun-bonded nonwoven fabric according to the present
invention can be widely used in medical hygienic materials, living
materials, industrial materials, and the like, and can be suitably
used particularly for hygienic materials, since the spun-bonded
nonwoven fabric according to the present invention has excellent
softness and good touch feeling, and has few product defects, hence
processability thereof is also excellent. Specific examples thereof
include base fabrics of disposable diapers, sanitary articles, and
poultice materials.
EXAMPLES
[0107] Next, the spun-bonded nonwoven fabric according to the
present invention will be described more specifically with
reference to examples. Characteristic values in the examples were
obtained by the following methods. Unless otherwise specified, it
is assumed that the measurement was performed by the methods
described above.
[0108] A. Melting Point of Polypropylene-Based Resin:
[0109] About 2 mg of spun-bonded nonwoven fabric was set in a
differential scanning calorimeter (DSCQ2000, manufactured by TA
Instruments), differential scanning calorimetry was performed in
nitrogen at a heating rate of 16.degree. C./min, and a temperature
of an endothermic peak was taken as the melting point (.degree.
C.).
[0110] B. Average Single-Fiber Diameter and Spinning Speed:
[0111] The average single fiber diameter of the polypropylene
fibers used for measurement was measured by cutting a small amount
from the spun-bonded nonwoven fabric and observing a portion other
than an emboss bonding portion with a microscope. An optical
microscope BH2 manufactured by Olympus Corporation was used for the
measurement. The spinning speed (km/min) was obtained from the
obtained average single fiber diameter.
[0112] C. Crystal Orientation Degree:
[0113] The crystal orientation degree was measured and calculated
using the following devices under the following conditions. [0114]
Device: SmartLab manufactured by Rigaku Corporation (sealed tube
type) [0115] X-ray Source: CuK.sub..alpha. ray (Ni filter used)
[0116] Output: 40 kV 50 mA [0117] Detector: D/teX one-dimensional
detector [0118] Entrance Slit: 2 mmh.times.2.2 mmw [0119]
Light-Receiving Slit: 5 mm-5 mm.
[0120] D. Crystallite Size:
[0121] The crystallite size was measured and calculated using the
following devices under the following conditions. [0122] Device:
SmartLab manufactured by Rigaku Corporation (sealed tube type)
[0123] X-ray Source: CuK.alpha. ray (Ni filter used) [0124] Output:
40 kV 50 mA [0125] Detector: D/teX one-dimensional detector [0126]
Entrance Slit: 2 mmh.times.2.2 mmw [0127] Light-Receiving Slit: 15
mm-20 mm.
[0128] E. Average Orientation Parameter:
[0129] The orientation parameter was measured and calculated using
the following devices under the following conditions. [0130]
Device: inVia manufactured by Renishaw [0131] Measurement Mode:
Microscopic Raman (beam diameter 1 .mu.m) [0132] Light Source: YAG
2nd 532 nm [0133] Laser Power: 10 mW [0134] Diffraction Grating:
Single-3000 gr/mm [0135] Slit: 65 .mu.m [0136] Detector: CCD
1024.times.256 pixels.
[0137] F. Complex Viscosity:
[0138] The complex viscosity was measured and calculated using the
following devices under the following conditions. [0139] Device:
Rheosol-G3000 manufactured by UBM Co., Ltd [0140] Plate: 20 mm
parallel plate [0141] Gap: 0.5 mm [0142] Strain: 34.9% [0143]
Angular Frequency: 6.3 rad/sec [0144] Temperature: 230.degree.
C.
[0145] G. Defects of Spun-Bonded Nonwoven Fabric:
[0146] A region of 10 cm square at a center in a width (CD)
direction of the spun-bonded nonwoven fabric was visually observed
with a loupe, fibers whose fiber diameter is at least three times
larger than an average fiber diameter due to filament breakage, and
fibers whose cut ends are round and appear to be at least three
times larger than the average fiber diameter are defined as
defects, and the number of the defects is counted. This observation
was repeated five times in a longitudinal (MD) direction of the
nonwoven fabric, and a total number thereof was taken as the number
of defects (pieces) of the spun-bonded nonwoven fabric.
[0147] H. Softness of Spun-Bonded Nonwoven Fabric:
[0148] Sensory evaluation of touch feeling of the spun-bonded
nonwoven fabric was performed, and scores were given in an absolute
evaluation based on the following criteria, in which 5 points
represents excellent softness while 1 point represents poor
softness. [0149] 5 points: There is no stiffness when the
spun-bonded nonwoven fabric is gripped, the surface of the
spun-bonded nonwoven fabric is smooth and has excellent softness.
[0150] 4 points: Although there is slight stiffness when the
spun-bonded nonwoven fabric is gripped, the surface of the
spun-bonded nonwoven fabric is smooth. [0151] 3 points: There is
slight stiffness when the spun-bonded nonwoven fabric is gripped,
and a sense of resistance is shown when the spun-bonded nonwoven
fabrics are rubbed against each other. [0152] 2 points: There is
apparent stiffness when the spun-bonded nonwoven fabric is gripped,
and a sense of resistance is shown when the spun-bonded nonwoven
fabrics are rubbed against each other. [0153] 1 point: There is
apparent stiffness when the spun-bonded nonwoven fabric is gripped,
and there is apparent unevenness when the spun-bonded nonwoven
fabrics are rubbed against each other, so the softness thereof is
poor.
[0154] This evaluation was performed by 10 participants, and an
average score is taken as the softness (point). A spun-bonded
nonwoven fabric having an average score of 4.0 or more was judged
as a spun-bonded nonwoven fabric having excellent softness.
[0155] I. Processability of Spun-Bonded Nonwoven Fabric:
[0156] The spun-bonded nonwoven fabric was run at 20 m/min for 5
minutes using a rubber nip roller. At this time, matter adhered to
the roll and the state of the spun-bonded nonwoven fabric were
observed, and scores were given as the processability (point) based
on the following criteria. A spun-bonded nonwoven fabric having a
score of 4 or more was judged as a spun-bonded nonwoven fabric
having excellent processability. [0157] 5 points: There is no fiber
adhered to the roll, and no nonwoven fabric fluff and tear was
observed. [0158] 4 points: Although there are fibers adhered to the
roll, no nonwoven fabric fluff and tear was observed. [0159] 3
points: Although there are fibers adhered to the roll and nonwoven
fabric fluff, no tear was observed. [0160] 2 points: There are
fibers adhered to the roll, nonwoven fabric fluff, and tears.
[0161] 1 point: Sheet tearing causes the nonwoven fabric to wrap
around the roll.
Example 1
[0162] A polypropylene-based resin, which is a propylene
homopolymer and has a melt mass flow rate of 200 g/10 min and a
melting point of 160.degree. C., was melt-extruded by a
single-screw extruder, and the polypropylene-based resin was
supplied to a spinning spinneret while being measured by a gear
pump. A spinning temperature (spinneret temperature) was set to
230.degree. C., and the polypropylene-based resin was ejected from
a spinneret hole having a hole diameter D of 0.30 mm and a land
length L of 0.75 mm at a single-hole ejection rate of 0.6 g/min.
The used spinning spinneret included an introduction hole which was
a straight hole located directly above the spinneret hole, and a
connecting portion between the introduction hole and the spinneret
hole had a tapered shape. Ejected fibrous resin was cooled and
solidified by applying an air flow of 12.degree. C. from an outer
side of the filaments (fibrous resin) at a speed of 30 m/min, the
air flow being started from a distance of 40 mm from the spinning
spinneret. Then the fibrous resin was drawn by a rectangular
ejector at a speed of 4.4 km/min, and collected on a moving net to
obtain a fiber web composed of polypropylene fibers.
[0163] Subsequently, a pair of hot embossing rolls composed of an
upper roll, which was a metallic embossing roll having dots formed
by engraving and having a proportion of bonding area of 16%, and a
lower roll, which was a metallic flat roll, was used to heat-bond
the fiber web composed of polypropylene fibers obtained as
described above, at a temperature of 130.degree. C. Thus, a
spun-bonded nonwoven fabric having a basis weight of 18 g/m.sup.2
was obtained. Evaluation results of the obtained spun-bonded
nonwoven fabric are shown in Table 1. It can be seen from Table 1
that the obtained spun-bonded nonwoven fabric has an average single
fiber diameter of 13.8 .mu.m, a crystal orientation degree thereof
is 0.921, a crystallite size of a (110) plane is 16.2 nm, an
orientation parameter thereof is 8.37, and complex viscosity
thereof is 55 Pasec, and that the spun-bonded nonwoven fabric has
few defects, and is excellent in softness and processability.
Examples 2, 3, Comparative Example 1
[0164] Spun-bonded nonwoven fabrics were obtained by the same
method as Example 1 except that inflow air pressure of the ejector
was changed and the spinning speed was changed to 6.9 km/min in
Example 2, 3.1 km/min in Example 3, and 2.6 km/min in Comparative
Example 1.
[0165] Results thereof are shown in Table 1. It can be seen from
Table 1 that the spun-bonded nonwoven fabric obtained in Example 2
has an average single fiber diameter of 11.0 .mu.m, the crystal
orientation degree thereof is 0.942, the crystallite size of the
(110) plane is 19.4 nm, the orientation parameter thereof is 8.83,
and the complex viscosity thereof is 53 Pasec, that the spun-bonded
nonwoven fabric obtained in Example 3 has an average single fiber
diameter of 16.5 .mu.m, the crystal orientation degree thereof is
0.913, the crystallite size of the (110) plane is 14.5 nm, the
orientation parameter thereof is 8.05, and the complex viscosity
thereof is 57 Pasec, and that both of the spun-bonded nonwoven
fabrics have few defects, and are excellent in softness and
processability.
[0166] On the other hand, it can be seen that the complex viscosity
of the spun-bonded nonwoven fabric obtained in Comparative Example
1 is 57 Pasec, and the nonwoven fabric has few defects. However,
the average single fiber diameter thereof is as large as 18.0
.mu.m, hence softness thereof is poor. The crystal orientation
degree thereof is as low as 0.902, the crystallite size of the
(110) plane is as low as 10.8 nm, and the orientation parameter
thereof is as low as 7.43, hence processability thereof is
poor.
Comparative Example 2
[0167] A spun-bonded nonwoven fabric was obtained by the same
method as Example 1 except that the temperature of the cooling air
flow at the time of spinning was 25.degree. C., and the air flow
velocity was 8 m/min.
[0168] Results thereof are shown in Table 1. It can be seen from
Table 1 that the spun-bonded nonwoven fabric obtained in
Comparative Example 2 has an average single fiber diameter of 14.1
.mu.m and complex viscosity of 55 Pasec, hence the nonwoven fabric
has few defects and is soft. However, the crystal orientation
degree thereof is as low as 0.906, the crystallite size of the
(110) plane is as low as 11.8 nm, and the orientation parameter
thereof is as low as 6.98, hence processability thereof is
poor.
Examples 4, 5, Comparative Example 3
[0169] Spun-bonded nonwoven fabrics were obtained by the same
method as Example 1 except that the melt mass flow rate of the used
polypropylene-based resin was changed to 170 g/10 min in Example 4,
450 g/10 min in Example 5, and 60 g/10 min in Comparative Example
3.
[0170] Results thereof are shown in Table 1. It can be seen from
Table 1 that the spun-bonded nonwoven fabric obtained in Example 4
has an average single fiber diameter of 13.8 .mu.m, the crystal
orientation degree thereof is 0.922, the crystallite size of the
(110) plane is 16.5 nm, the orientation parameter thereof is 9.37,
and the complex viscosity thereof is 83 Pasec, and that the
spun-bonded nonwoven fabric has few defects, and is excellent in
softness and processability. It can be seen that the spun-bonded
nonwoven fabric obtained in Example 5 has an average single fiber
diameter of 13.6 .mu.m, the crystal orientation degree thereof is
0.912, the crystallite size of the (110) plane is 12.9 nm, the
orientation parameter thereof is 8.21, and the complex viscosity
thereof is 31 Pasec, and that the spun-bonded nonwoven fabric has
few defects, and is excellent in softness and processability.
[0171] On the other hand, it can be seen that the spun-bonded
nonwoven fabric obtained in Comparative Example 3 has an average
single fiber diameter of 13.9 .mu.m, the crystal orientation degree
thereof is 0.922, the crystallite size of the (110) plane is 17.3
nm, the orientation parameter thereof is 9.95. However, the complex
viscosity thereof is as large as 206 Pasec, hence the softness
thereof is poor. The spun-bonded nonwoven fabric has a large number
of defects, hence processability thereof is also poor.
TABLE-US-00001 TABLE 1 Example Example Example Comparative
Comparative Example Example Comparative 1 2 3 Example 1 Example 2 4
5 Example 3 Resin Resin Propylene Homopolymer Melt Mass Flow 200
200 200 200 200 170 450 60 Rate (g/10 min) Spinning Speed (km/min)
4.4 6.9 3.1 2.6 4.2 4.4 4.5 4.3 Characteristics of Average Single
13.8 11.0 16.5 18.0 14.1 13.8 13.6 13.9 Fiber/Nonwoven Fiber
Diameter Fabric (.mu.m) Crystal Orientation 0.921 0.942 0.913 0.902
0.906 0.922 0.912 0.922 Degree Crystallite Size of 16.2 19.4 14.5
10.8 11.8 16.5 12.9 17.3 (110) Plane (nm) Orientation 8.37 8.83
8.05 7.43 6.98 9.37 8.21 9.95 Parameter Complex Viscosity 55 53 57
57 55 83 31 206 (Pa sec) Nonwoven Fabric 0 0 0 0 0 1 1 12 Defects
(Piece) Evaluation Nonwoven Fabric 4.6 4.7 4.3 3.5 4.6 4.2 4.3 2.2
Softness (Point) Nonwoven Fabric 5 5 4 2 2 4 4 1 Processability
(Point)
Example 6
[0172] A spun-bonded nonwoven fabric was obtained by the same
method as Example 1 except that a resin obtained from kneading
resin A having a mass ratio of 88% and resin B having a mass ratio
of 12% was used, in which a propylene homopolymer having a melt
mass flow rate of 200 g/10 min was used as the resin A while an
ethylene-propylene copolymer having a melt mass flow rate of 20
g/10 min ("Vistamaxx6202" manufactured by ExxonMobil) was used as
the resin B.
[0173] Results thereof are shown in Table 2. It can be seen from
Table 2 that the spun-bonded nonwoven fabric obtained in Example 6
has an average single fiber diameter of 13.8 .mu.m, the crystal
orientation degree thereof is 0.927, the crystallite size of the
(110) plane is 15.7 nm, the orientation parameter thereof is 9.32,
and the complex viscosity thereof is 68 Pasec, and that the
spun-bonded nonwoven fabric has few defects, and is excellent in
softness and processability.
Comparative Example 4
[0174] A spun-bonded nonwoven fabric was obtained by the same
method as Example 6, except that the resin A was changed to a
propylene homopolymer having a melt mass flow rate of 60 g/10
min.
[0175] Results thereof are shown in Table 2. It can be seen from
Table 2 that the spun-bonded nonwoven fabric obtained in
Comparative Example 4 has an average single fiber diameter of 13.9
.mu.m, the crystal orientation degree thereof is 0.932, the
crystallite size of the (110) plane is 15.9 nm, the orientation
parameter thereof is 10.48. However, the complex viscosity thereof
is as large as 228 Pasec, hence the softness thereof is poor. The
spun-bonded nonwoven fabric has a large number of defects, hence
processability thereof is also poor.
TABLE-US-00002 Comparative Example 6 Example 4 Resin Resin A
Propylene Homopolymer Melt Mass Flow Rate (g/10 min) 200 60 Mass
Ratio (%) 88 88 Resin B Ethylene-Propylene Copolymer Melt Mass Flow
Rate (g/10 min) 20 20 Mass Ratio (%) 12 12 Spinning Speed (km/min)
4.4 4.3 Characteristics of Average Single Fiber Diameter (.mu.m)
13.8 13.9 Fiber/Nonwoven Crystal Orientation Degree 0.927 0.932
Fabric Crystallite Size of (110) Plane (nm) 15.7 15.9 Orientation
Parameter 9.32 10.48 Complex Viscosity (Pa sec) 68 228 Nonwoven
Fabric Defects (Piece) 0 6 Evaluation Nonwoven Fabric Softness
(Point) 4.7 2.9 Nonwoven Fabric Processability (Point) 5 2
[0176] Examples 1 to 6 have excellent softness since the average
single fiber diameter of the fibers constituting the spun-bonded
nonwoven fabrics is small while the complex viscosity is low. In
addition, the spun-bonded nonwoven fabrics have excellent
processability since the fibers constituting the spun-bonded
nonwoven fabrics have high crystal orientation degree, high
crystallite size of the (110) plane and high orientation parameter
while there are few defects in the spun-bonded nonwoven fabric.
[0177] On the other hand, as shown in Comparative Example 1, in a
case where the average single fiber diameter of the fibers
constituting the spun-bonded nonwoven fabric is large, the softness
of the spun-bonded nonwoven fabric is poor. As shown in Comparative
Examples 1 and 2, in cases where the crystal orientation degree,
the crystallite size of the (110) plane, and the orientation
parameter are low, the processability of the spun-bonded nonwoven
fabric is poor. As shown in Comparative Examples 3 and 4, in cases
where the complex viscosity of the spun-bonded nonwoven fabric is
high, the softness of the spun-bonded nonwoven fabric is poor, and
the processability is also deteriorated due to an increase in the
defects of the nonwoven fabric.
[0178] Although the present invention has been described in detail
with reference to specific examples, it will be apparent to those
skilled in the art that various changes and modifications can be
made without departing from the spirit and scope of the present
invention. This application is based on a Japanese patent
application filed on Sep. 28, 2017 (patent application No.
2017-188004), and a Japanese patent application filed on Jul. 27,
2018 (patent application No. 2018-141053), the contents of which
are incorporated herein by reference.
obtained by wide angle X-ray diffraction is at least 12 nm; D. the
average orientation parameter of the fiber as obtained by Raman
spectroscopy is at least 8.0; and E. the complex viscosity of the
spunbond nonwoven fabric at a temperature of 230.degree. C. is
20-100 Pasec at an angular frequency of 6.3 rad/sec.
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