U.S. patent application number 13/581904 was filed with the patent office on 2012-12-20 for elastic nonwoven cloth and fiber product.
This patent application is currently assigned to IDEMITSU KOSAN CO., LTD.. Invention is credited to Yohei Koori, Yutaka Minami, Tomoaki Takebe.
Application Number | 20120322330 13/581904 |
Document ID | / |
Family ID | 44542156 |
Filed Date | 2012-12-20 |
United States Patent
Application |
20120322330 |
Kind Code |
A1 |
Takebe; Tomoaki ; et
al. |
December 20, 2012 |
ELASTIC NONWOVEN CLOTH AND FIBER PRODUCT
Abstract
To provide an elastic nonwoven cloth that is excellent in
elastic recovery property and has pleasant texture without
stickiness, and a fiber product using the elastic nonwoven cloth,
by an elastic nonwoven cloth containing fibers that are spun at a
spinning speed of from 500 to 2,500 m/min and contain a low
crystalline polypropylene that satisfies (a) [mmmm]=20 to 60% by
mol, (b) [rrrr]/(1-[mmmm]).ltoreq.0.1, (c) [rmrm]>2.5% by mol,
(d) [mm].times.[rr]/[mr].sup.2.ltoreq.2.0, (e) weight average
molecular weight (Mw)=10,000 to 200,000, and (f) molecular weight
distribution (Mw/Mn)<4, and a fiber product using the elastic
nonwoven cloth.
Inventors: |
Takebe; Tomoaki; (Chiba,
JP) ; Minami; Yutaka; (Chiba, JP) ; Koori;
Yohei; (Chiba, JP) |
Assignee: |
IDEMITSU KOSAN CO., LTD.
Tokyo
JP
|
Family ID: |
44542156 |
Appl. No.: |
13/581904 |
Filed: |
February 28, 2011 |
PCT Filed: |
February 28, 2011 |
PCT NO: |
PCT/JP2011/054551 |
371 Date: |
August 30, 2012 |
Current U.S.
Class: |
442/329 |
Current CPC
Class: |
Y10T 442/602 20150401;
D04H 3/005 20130101; D04H 3/147 20130101; D04H 3/007 20130101; D01F
8/06 20130101 |
Class at
Publication: |
442/329 |
International
Class: |
D04H 13/00 20060101
D04H013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2010 |
JP |
2010-044492 |
Claims
1. An elastic nonwoven cloth, comprising fibers that are spun at a
spinning speed of from 500 to 2,500 m/min, said fibers comprising a
low crystalline polypropylene satisfying the following properties:
(a) a mesopentad fraction [mmmm]=20 to 60% by mol; (b)
[rrrr]/(1-[mmmm]).ltoreq.0.1, where [rrrr] is a racemic pentad
fraction; (c) a racemic-meso-racemic-meso pentad fraction
[rmrm]>2.5% by mol; (d) [mm].times.[rr]/[mr].sup.2<2.0,
wherein [mm], [rr] and [mr] are triad fractions; (e) a weight
average molecular weight (Mw)=10,000 to 200,000; and (f) a
molecular weight distribution (Mw/Mn)<4.
2. The elastic nonwoven cloth according to claim 1, wherein the
fibers are core-sheath composite fibers.
3. The elastic nonwoven cloth according to claim 2, wherein the
core-sheath composite fibers comprise a sheath component comprising
an olefin polymer, and a core component comprising from 90 to 100%
by mass of a low crystalline polypropylene, said core component
comprising the low crystalline polypropylene in a larger proportion
than the sheath component.
4. The elastic nonwoven cloth according to claim 2, wherein the
core-sheath composite fibers have a total low crystalline
polypropylene content calculated by the following expression of
from 90 to 99% by mass: total low crystalline polypropylene content
(%)=(Ws.times.Xs+Wc.times.Xc)/100 wherein Ws represents a mass
fraction of the sheath component, Wc represents a mass fraction of
the core component, Xs represents a mass fraction of the low
crystalline polypropylene in the sheath component, and Xc
represents a mass fraction of the low crystalline polypropylene in
the core component.
5. A fiber product comprising the elastic nonwoven cloth according
to claim 1.
6. The elastic nonwoven cloth according to claim 3, wherein the
core-sheath composite fibers have a total low crystalline
polypropylene content calculated by the following expression of
from 90 to 99% by mass: total low crystalline polypropylene content
(%)=(Ws.times.Xs+Wc.times.Xc)/100, wherein Ws represents a mass
fraction of the sheath component, Wc represents a mass fraction of
the core component, Xs represents a mass fraction of the low
crystalline polypropylene in the sheath component, and Xc
represents a mass fraction of the low crystalline polypropylene in
the core component.
Description
TECHNICAL FIELD
[0001] The present invention relates to an elastic nonwoven cloth
that is excellent in elastic recovery property and has pleasant
texture without stickiness, and a fiber product using the elastic
nonwoven cloth.
BACKGROUND ART
[0002] In recent years, elastic fibers and elastic nonwoven cloths
are subjected to various applications including, for example, a
disposable diaper, a sanitary product, a hygienic product, a
clothing material, a bandage and a packaging material. In
particular, a disposable diaper, a sanitary product and the like
are used directly on the skin, and thus are demanded to have
suitable elasticity and elastic recovery property from the
standpoint of good wear feeling to the body and easiness of the
body motion after wearing.
[0003] As elastic fibers having elastic recovery property imparted
thereto, Patent Document 1 discloses elastic fibers containing an
elastomer, such as an olefin copolymer or a styrene block
copolymer, having another resin component mixed therewith. However,
the elastomer has poor compatibility with polypropylene and is
noncrystalline, and in the case where elastic fibers are formed by
mixing the elastomer and polypropylene, the elastomer bleeds to the
surface of the fibers. Accordingly, there are problems that an
elastic nonwoven cloth formed of the elastic fibers has stickiness,
and a fiber product using the elastic nonwoven cloth has unpleasant
texture.
[0004] Patent Document 2 discloses processing a propylene polymer
constituting a nonwoven cloth with a free radical initiator. The
process enhances the flowability of the propylene polymer, but
lowers the thermal stability of the propylene polymer.
[0005] Patent Document 3 discloses formation of fibers with a
propylene composition containing propylene and ethylene, and
formation of core-sheath composite fibers formed of the propylene
composition including propylene and ethylene as a sheath component
and high density polyethylene as a core component. However, the
propylene composition containing propylene and ethylene is not
necessarily sufficient in compatibility with a crystalline
isotactic propylene homopolymer, and thus may suffer deterioration
of the kneading property and deterioration of properties due to
bleed on the surface of the fibers.
[0006] Patent Document 4 discloses an elastic nonwoven cloth formed
of core-sheath composite fibers containing a composition containing
low crystalline polypropylene and high crystalline polypropylene as
a sheath component and low crystalline polypropylene as a core
component. However, in the case where the spinning speed is high,
the fibers may be oriented and crystallized, thereby providing such
problems that the elastic recovery property may become
insufficient, and the tensile properties, particularly the breaking
elongation, may be deteriorated.
RELATED ART DOCUMENTS
Patent Documents
[0007] Patent Document 1: JP-A-2003-129330 [0008] Patent Document
2: JP-T-2007-511680 [0009] Patent Document 3: JP-A-2007-277755
[0010] Patent Document 4: JP-A-2009-209506
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0011] The present invention has been made under the circumstances,
and an object thereof is to provide an elastic nonwoven cloth that
is excellent in elastic recovery property and breaking elongation,
and has pleasant texture without stickiness, and a fiber product
using the elastic nonwoven cloth.
Means for Solving the Problems
[0012] As a result of earnest investigations made by the present
inventors, it has been found that the object has been accomplished
by an elastic nonwoven cloth that contains a particular low
crystalline polypropylene and is obtained under a particular
formation condition. Specifically, it has been found that fibers
containing a low crystalline polypropylene having a particular
stereoregularity is excellent in elastic recovery property and
breaking elongation, has lowered stickiness, and thus is suitable
as a material for forming an elastic nonwoven cloth. The present
invention has been completed based on the findings.
[0013] The present invention provides the following.
[0014] 1. An elastic nonwoven cloth containing fibers that are spun
at a spinning speed of from 500 to 2,500 m/min and contain a low
crystalline polypropylene that satisfies the following properties
(a) to (f):
[0015] (a) [mmmm]=20 to 60% by mol,
[0016] (b) [rrrr]/(1-[mmmm]).ltoreq.0.1,
[0017] (c) [rmrm]>2.5% by mol,
[0018] (d) [mm].times.[rr]/[mr].sup.2.ltoreq.2.0,
[0019] (e) weight average molecular weight (Mw)=10,000 to 200,000,
and
[0020] (f) molecular weight distribution (Mw/Mn)<4.
[0021] 2. The elastic nonwoven cloth according to the item 1,
wherein the fibers are core-sheath composite fibers.
[0022] 3. The elastic nonwoven cloth according to the item 2,
wherein the core-sheath composite fibers contain a sheath component
containing an olefin polymer, and a core component containing from
90 to 100% by mass of a low crystalline polypropylene, and the core
component contains the low crystalline polypropylene in a larger
content than the sheath component.
[0023] 4. The elastic nonwoven cloth according to the item 2 or 3,
wherein the core-sheath composite fibers has a total low
crystalline polypropylene content calculated by the following
expression of from 90 to 99% by mass:
total low crystalline polypropylene content
(%)=(Ws.times.Xs+Wc.times.Xc)/100
wherein
[0024] Ws represents a mass fraction of the sheath component,
[0025] Wc represents a mass fraction of the core component,
[0026] Xs represents a mass fraction of the low crystalline
polypropylene in the sheath component, and
[0027] Xc represents a mass fraction of the low crystalline
polypropylene in the core component.
[0028] 5. A fiber product containing the elastic nonwoven cloth
according to any one of the items 1 to 4.
ADVANTAGES OF THE INVENTION
[0029] According to the present invention, such an elastic nonwoven
cloth may be provided that is excellent in elastic recovery
property and breaking elongation, and has pleasant texture without
stickiness. The elastic nonwoven cloth also has excellent
capabilities, for example, the elastic nonwoven cloth is excellent
in secondary processability with good releasing property from a
winding roll, is excellent in heat resistance, and is free of
contraction upon application of HMA (hot melt adhesive).
EMBODIMENTS FOR CARRYING OUT THE INVENTION
[0030] The elastic nonwoven cloth of the present invention contains
fibers that contain a low crystalline polypropylene that has
particular properties and are spun at a spinning speed of from 500
to 2,500 m/min.
[0031] A crystalline polypropylene means a polypropylene that has a
melting point observed by measurement with a differential scanning
calorimeter (DSC) described later, a high crystalline polypropylene
means a crystalline polypropylene having the melting point that is
155.degree. C. or more, and a low crystalline polypropylene means a
crystalline polypropylene having the melting point that is from 0
to 120.degree. C.
[0032] The melting point (Tm-D) is defined as a peak top of a peak
observed on the highest temperature side of a melt endothermic
curve obtained by maintaining the temperature at -10.degree. C. for
5 minutes and then increasing the temperature at 10.degree. C. per
minute by using a differential scanning calorimeter (DSC) under a
nitrogen atmosphere.
Low Crystalline Polypropylene
[0033] The low crystalline polypropylene used in the present
invention has the following properties (a) to (f), which can be
controlled by the selection of the catalyst and the reaction
conditions upon producing the low crystalline polypropylene.
(a) Mesopentad Fraction [mmmm]=20 to 60% by mol
[0034] When the mesopentad fraction [mmmm] is less than 20% by mol,
the solidification may be considerably delayed, and the nonwoven
cloth may be attached to or drawn to a calender roll or a belt, and
thus may not be continuously formed. When the mesopentad fraction
[mmmm] exceeds 60% by mol, the elastic recovery property may be
deteriorated due to the high crystallinity. The mesopentad fraction
[mmmm] is preferably from 30 to 50% by mol, and more preferably
from 40 to 50% by mol.
(b) [rrrr]/(1-[mmmm]).ltoreq.0.1
[0035] The value of [rrrr]/(1-[mmmm]) is an index representing the
uniformity of the regularity distribution of the low crystalline
polypropylene. When the value is too large, a mixture of a high
regularity polypropylene and an atactic polypropylene is obtained
as similar to an ordinary polypropylene produced with a
magnesium-supported titanium catalyst, and causes stickiness.
[0036] In the low crystalline polypropylene, when [rrrr]/(1-[mmmm])
is larger than 0.1, the regularity distribution is broadened to
form a mixture with an atactic polypropylene, which causes
stickiness. In this point of view, [rrrr]/(1-[mmmm]) is preferably
0.05 or less, and more preferably 0.04 or less.
(c) [rmrm]>2.5% by mol
[0037] When the racemic-meso-racemic-meso pentad fraction [rmrm] of
the low crystalline polypropylene is 2.5% by mol or less, the
randomness of the low crystalline polypropylene is lowered, and the
crystallinity thereof is increased, thereby lowering the elastic
recovery property. [rmrm] is preferably 2.6% by mol or more, and
more preferably 2.7% by mol or more. The upper limit thereof is
generally approximately 10% by mol.
(d) [mm].times.[rr]/[mr].sup.2.ltoreq.2.0
[0038] The value of [mm].times.[rr]/[mr].sup.2 is an index of the
randomness of the polymer, and when the value is close to 0.25, the
randomness is increased, and excellent elastic recovery property
may be provided. When the value is 2.0 or less, the fibers obtained
by spinning may have sufficient elastic recovery property, and the
stickiness thereof may be suppressed.
[0039] For providing the sufficient elastic recovery property, the
value of [mm].times.[rr]/[mr].sup.2 is preferably from 0.25 to 1.8,
and more preferably from 0.25 to 1.5.
(e) Weight Average Molecular Weight (Mw)=10,000 to 200,000
[0040] When the weight average molecular weight of the low
crystalline polypropylene is 10,000 or more, the viscosity of the
low crystalline polypropylene is not too low and is moderate, and
breakage of the thread upon spinning may be suppressed. When the
weight average molecular weight thereof is 200,000 or less, the
viscosity of the low crystalline polypropylene is not too high, and
the spinning property may be enhanced. The weight average molecular
weight is preferably from 30,000 to 150,000, and more preferably
from 50,000 to 150,000.
(f) Molecular Weight Distribution (Mw/Mn)<4.
[0041] The molecular weight distribution (Mw/Mn) of the low
crystalline polypropylene is less than 4, the fibers obtained by
spinning may be suppressed from suffering stickiness. The molecular
weight distribution is preferably 3 or less.
[0042] The stereoregularity properties (a) to (d) are obtained by
NMR.
[0043] In the present invention, the mesopentad fraction [mmmm],
the racemic pentad fraction [rrrr] and the
racemic-meso-racemic-meso pentad fraction [rmrm] are the meso
fraction, the racemic fraction and the racemic-meso-racemic-meso
fraction, respectively, in the pentad units of the polypropylene
molecular chain that are measured with the signal of the methyl
group in the .sup.13C-NMR spectrum according to the method proposed
by A. Zambelli, et al., Macromolecules, vol. 6, p. 925 (1973). When
the mesopentad fraction [mmmm] is increased, the stereoregularity
is increased. The triad fractions [mm], [rr] and [mr] are also
calculated by the aforementioned method.
[0044] The .sup.13C-NMR spectrum may be measured according to the
peak assignment proposed by A. Zambelli, et al., Macromolecules,
vol. 8, p. 687 (1975), with the following apparatus and
conditions.
apparatus: .sup.13C-NMR apparatus, Model JNM-EX400, produced by
JEOL, Ltd. method: proton complete decoupling method concentration:
220 mg/mL solvent: mixed solvent of 1,2,4-trichlorobenzene and
deuterated benzene at 90/10 (by volume) temperature: 130.degree. C.
pulse width: 45.degree. pulse repetition time: 4 seconds
accumulation: 10,000
Calculating Expressions
[0045] M=m/S.times.100
R=.gamma./S.times.100
S=P.beta..beta.+P.alpha..beta.+P.alpha..gamma.
S: signal intensity of carbon atoms in side chain methyl of all the
propylene units
P.beta..beta.: 19.8 to 22.5 ppm
P.alpha..beta.: 18.0 to 17.5 ppm
P.alpha..gamma.: 17.5 to 17.1 ppm
[0046] .gamma.: racemic pentad chain, 20.7 to 20.3 ppm m:
mesopentad chain, 21.7 to 22.5 ppm
[0047] The weight average molecular weight (Mw) (e) and the
molecular weight distribution (Mw/Mn) (f) are obtained by
measurement of gel permeation chromatography (GPC). The weight
average molecular weight in the present invention is a polystyrene
conversion weight average molecular weight measured with the
following apparatus and conditions, and the molecular weight
distribution is a value calculated from a number average molecular
weight (Mn) measured in the same manner and the weight average
molecular weight.
GPC Measurement Apparatus
[0048] column: TOSO GMHHR-H(S)HT detector: Waters 150C, RI detector
for liquid chromatography
Measurement Conditions
[0049] solvent: 1,2,4-trichlorobenzene measurement temperature:
145.degree. C. flow rate: 1.0 mL/min specimen concentration: 2.2
mg/mL injection amount: 160 .mu.L, calibration curve: Universal
Calibration analysis software: HT-GPC (ver. 1.0)
[0050] The low crystalline polypropylene may be produced, for
example, by using a metallocene catalyst disclosed in
WO2003/087172. In particular, a metallocene catalyst containing a
transition metal compound having a ligand forming a crosslinked
structure through a crosslinking group is preferred, and a
metallocene catalyst obtained by combining a transition metal
compound having a crosslinked structure through two crosslinking
group, with a cocatalyst, is more preferable.
[0051] Specific examples thereof include a polymerization catalyst
containing (A) a transition metal compound represented by the
general formula (I):
##STR00001##
wherein M represents a metal element of Groups 3 to 10 in the
Periodic Table or of lanthanoid series; E.sup.1 and E.sup.2 each
represent a ligand selected from a substituted cyclopentadienyl
group, an indenyl group, a substituted indenyl group, a
heterocyclopentadienyl group, a substituted heterocyclopentadienyl
group, an amide group, a phosphide group, a hydrocarbon group and a
silicon-containing group, forming a crosslinked structure through
A.sup.1 and A.sup.2, in which E.sup.1 and E.sup.2 may be the same
as or different from each other; X represents a .sigma.-bonding
ligand, in which when there are plural ligands represented by X,
the plural ligands may be the same as or different from each other,
and may be crosslinked to another X, E.sup.1, E.sup.2 or Y; Y
represents a Lewis base, in which when there are plural Lewis bases
represented by Y, the plural Lewis bases may be the same as or
different from each other, and may be crosslinked to another Y,
E.sup.1, E.sup.2 or X; A.sup.1 and A.sup.2 are each a crosslinking
group bonding the two ligands, and each represent a hydrocarbon
group having from 1 to 20 carbon atoms, a halogen-containing
hydrocarbon group having from 1 to 20 carbon atoms, a
silicon-containing group, a germanium-containing group, a
tin-containing group, --O--, --CO--, --S--, --SO.sub.2--, --Se--,
--NR.sup.1--, --PR.sup.1--, --P(O)R.sup.1--, --BR.sup.1-- or
--AlR.sup.1--, in which R.sup.1 represents a hydrogen atom, a
halogen atom, a hydrocarbon group having from 1 to 20 carbon atoms
or a halogen-containing hydrocarbon group having from 1 to 20
carbon atoms, and A.sup.1 and A.sup.2 may be the same as or
different from each other; q represents an integer of from 1 to 5
(i.e., (valency of M)-2); and r represents an integer of from 0 to
3, and (B) a component selected from (B-1) a compound capable of
forming an ionic complex through reaction with the transition metal
compound as the component (A) or a derivative thereof, and (B-2) an
aluminoxane.
[0052] The transition metal compound as the component (A) is
preferably a (1,2') (2,1') double-crosslinked transition metal
compound, and examples thereof include (1,2'-dimethylsilylene)
(2,1'-dimethylsilylene) bis(3-trimethylsilylmethylindenyl)zirconium
dichloride.
[0053] Specific examples of the compound as the component (B-1)
include triethylammonium tetraphenylborate, tri-n-butylammonium
tetraphenylborate, trimethylammonium tetraphenylborate,
tetraethylammonium tetraphenylborate, methyl(tri-n-butyl)ammonium
tetraphenylborate, benzyl(tri-n-butyl)ammonium tetraphenylborate,
dimethylphenylammonium tetraphenylborate, triphenyl(methyl)ammonium
tetraphenylborate, trimethylanilinium tetraphenylborate,
methylpyridinium tetraphenylborate, benzylpyridinium
tetraphenylborate, methyl(2-cyanopyridinium)tetraphenylborate,
triethylammonium tetrakis(pentafluorophenyl)borate,
tri-n-butylammonium tetrakis(pentafluorophenyl)borate,
triphenylammonium tetrakis(pentafluorophenyl)borate,
tetra-n-butylammonium tetrakis(pentafluorophenyl)borate,
tetraethylammonium tetrakis(pentafluorophenyl)borate,
benzyl(tri-n-butyl)ammonium tetrakis(pentafluorophenyl)borate,
methyldiphenylammonium tetrakis(pentafluorophenyl)borate,
triphenyl(methyl)ammonium tetrakis(pentafluorophenyl)borate,
methylanilinium tetrakis(pentafluorophenyl)borate,
dimethylanilinium tetrakis(pentafluorophenyl)borate,
trimethylanilinium tetrakis(pentafluorophenyl)borate,
methylpyridinium tetrakis(pentafluorophenyl)borate,
benzylpyridinium tetrakis(pentafluorophenyl)borate,
methyl(2-cyanopyridinium) tetrakis(pentafluorophenyl)borate,
benzyl(2-cyanopyridinium) tetrakis(pentafluorophenyl)borate,
methyl(4-cyanopyridinium) tetrakis(pentafluorophenyl)borate,
triphenylphosphonium tetrakis(pentafluorophenyl)borate,
dimethylanilinium tetrakis(bis(3,5-ditrifluoromethyl)phenyl)borate,
ferrocenium tetraphenylborate, silver tetraphenylborate, trityl
tetraphenylborate, tetraphenylporphyrin manganese
tetraphenylborate, ferrocenium tetrakis(pentafluorophenyl)borate,
(1,1'-dimethylferrocenium) tetrakis(pentafluorophenyl)borate,
decamethylferrocenium tetrakis(pentafluorophenyl)borate, silver
tetrakis(pentafluorophenyl)borate, trityl
tetrakis(pentafluorophenyl)borate, lithium
tetrakis(pentafluorophenyl)borate, sodium
tetrakis(pentafluorophenyl)borate, tetraphenylporphyrin manganese
tetrakis(pentafluorophenyl)borate, silver tetrafluoroborate, silver
hexafluorophosphate, silver hexafluoro arsenate, silver
perchlorate, silver trifluoroacetate and silver
trifluoromethanesulfonate.
[0054] Examples of the aluminoxane as the component (B-2) include
known linear aluminoxanes and cyclic aluminoxanes.
[0055] Furthermore, the low crystalline polypropylene may be
produced by using, in combination, an organoaluminum compound, such
as trimethylaluminum, triethylaluminum, triisopropylaluminum,
triisobutylaluminum, dimethylaluminum chloride, diethylaluminum
chloride, methylaluminum dichloride, ethylaluminum dichloride,
dimethylaluminum fluoride, diisobutylaluminum hydride,
diethylaluminum hydride and ethylaluminum sesquichloride.
High Crystalline Polypropylene
[0056] As the high crystalline polypropylene used in the present
invention, Y2000GP (a trade name, produced by Prime Polymer Co.,
Ltd.) and the like may be used, and any crystalline polypropylene
that has a melting point of 155.degree. C. or more may be used
without particular limitation. Examples thereof include a propylene
homopolymer, an ethylene-propylene random copolymer and an
ethylene-propylene block copolymer. The molecular weight of the
high crystalline polypropylene may be selected from the standpoint
of the moldability in any case. In the case of molding by a
melt-blow method, one having a melt flow rate (MFR) measured
according to JIS K7210 at a temperature of 230.degree. C. and a
load of 21.18 N of approximately from 100 to 2,000 g/10 min is
preferred, and in the case of molding by a spunbond method, one
having an MFR of approximately from 10 to 100 g/10 min is
preferred. The high crystalline polypropylene may be selected from
these ranges in consideration of the target purpose of the fibers
and the nonwoven cloth. Specifically, for the propose where the
moldability is important, a polypropylene that has a high
crystallization temperature and has high crystallinity is
preferred, and one having a crystallization temperature (Tc) of
100.degree. C. or more is more preferred.
Spinning Conditions
[0057] The spinning conditions of the fibers preferably include a
relatively low spinning speed for suppressing the orientation
crystallization of the fibers, and the spinning speed is
necessarily from 500 to 2,500 m/min, and preferably from 1,000 to
2,000 m/min. When the spinning speed exceeds 2,500 m/min, the
breaking elongation of the elastic nonwoven cloth is decreased,
thereby failing to provide sufficient elastic recovery property,
and when the spinning speed is less than 500 m/min, the nonwoven
cloth may be insufficient due to, for example, deteriorated
appearance caused by a thick thread and an insufficient fiber
amount.
Core-Sheath Composite Fibers
[0058] The fibers forming the nonwoven cloth of the present
invention are preferably core-sheath fibers. The core-sheath fibers
referred herein are fibers that has, on the cross sectional view
thereof, a core as a center portion and a sheath as an outer
layer.
1. Sheath Component
[0059] The sheath component of the core-sheath composite fibers
preferably contains a low crystalline polypropylene and a high
crystalline polypropylene, and the component amounts thereof are
preferably from 50 to 99% by mass for the low crystalline
polypropylene and from 1 to 50% by mass for the high crystalline
polypropylene, more preferably from 60 to 95% by mass for the low
crystalline polypropylene and from 5 to 40% by mass for the high
crystalline polypropylene, and further preferably from 60 to 90% by
mass for the low crystalline polypropylene and from 10 to 40% by
mass for the high crystalline polypropylene. When the amount of the
low crystalline polypropylene is 50% by mass or more, sufficient
elastic recovery property may be obtained, and when it is 99% by
mass or more, attachment to a calender roll is suppressed, thereby
enhancing the continuous moldability.
[0060] The sheath component in the present invention may contain an
internal releasing agent. The internal releasing agent is an
additive that is added to the resin raw material for enhancing the
releasing property of the nonwoven cloth, and specific examples
thereof include a high melting point polymer, an organic carboxylic
acid or a metal salt thereof, an aromatic sulfonic acid or a metal
salt thereof, an organic phosphorus compound or a metal salt
thereof, dibenzylidene sorbitol or a derivative thereof, a partial
metal salt of rosin acid, inorganic fine particles, an imide
compound, an amide compound, a quinacridone compound, a quinone
compound, and mixtures thereof.
[0061] Examples of the high melting point polymer include a
polyolefin, such as polyethylene and polypropylene.
[0062] Examples of the organic carboxylic acid include an aliphatic
acid, such as octylic acid, palmitic acid, lauric acid, stearic
acid, behenic acid, montanic acid, 12-hydroxystearic acid, oleic
acid, isostearic acid and ricinoleic acid, and an aromatic
carboxylic acid, such as benzoic acid and p-t-butylbenzoic acid.
Examples of the metal salt of an organic carboxylic acid include
salts of Li, Ca, Ba, Zn, Mg, Al, Pb and the like of the
aforementioned organic carboxylic acids and a metal soap which is a
metal salt of the carboxylic acid, and specific examples thereof
include aluminum benzoate, aluminum p-t-butylbenzoate, sodium
adipate, sodium thiophene carboxylate and sodium pyrrole
carboxylate.
[0063] Examples of the aromatic sulfonic acid include a linear
alkylbenzenesulfonic acid, a branched alkylbenzenesulfonic acid,
naphthalenesulfonic acid and dodecylbenzenesulfonic acid, and
examples of the metal salt of an aromatic sulfonic acid include
salts of Li, Ca, Ba, Zn, Mg, Al, Pb and the like of the
aforementioned aromatic sulfonic acids.
[0064] Examples of the organic phosphorus compound include
trimethyl phosphate, triethyl phosphate, tributyl phosphate,
2-ethylhexyl phosphate, butoxyethyl phosphate, triphenyl phosphate,
tricresyl phosphate, trixylenyl phosphate, cresyldiphenyl
phosphate, 2-ethylhexyldiphenyl phosphate,
cresyldi-2,6-xylenylphosphate, resorcinoldiphenolphosphate, various
aromatic condensed phosphate esters, 2-chloroethyl phosphate,
chloropropyl phosphate, dichloropropyl phosphate, tribromoneopentyl
phosphate, a halogen-containing condensed phosphoric acid,
bis-2-ethylhexyl phosphate, diisodecyl phosphate,
2-methacryloyloxyethyl acid phosphate,
diphenyl-2-methacryloyloxyethyl phosphate, methyl acid phosphate,
butyl acid phosphate, monoisodecyl phosphate, 2-butylhexyl acid
phosphate, isodecyl acid phosphate, triphenyl phosphate, dibutyl
hydrogen phosphate, dibutyl hydrogen phosphate, polyoxyethylene
lauryl ether phosphoric acid, polyoxyalkyl ether phosphoric acid,
polyoxyethylene alkyl phenyl ether phosphoric acid and
polyoxyethylene dialkyl phenyl ether phosphoric acid, and examples
of the metal salt of an organic phosphoric acid compound include
metal salts of Li, Ca, Ba, Zn, Mg, Al, Pb and the like of the
aforementioned organic phosphorus compounds. Examples of the
commercially available products thereof include Adeka Stab NA-11
and Adeka Stab NA-21, produced by ADEKA Corporation.
[0065] Examples of dibenzylidene sorbitol or a derivative thereof
include dibenzylidene sorbitol,
1,3:2,4-bis(o-3,4-dimethylbenzylidene)sorbitol,
1,3:2,4-bis(o-2,4-dimethylbenzylidene)sorbitol,
1,3:2,4-bis(o-4-ethylbenzylidene)sorbitol,
1,3:2,4-bis(o-4-chlorobenzylidene)sorbitol and
1,3:2,4-dibenzylidene sorbitol, and examples of the commercially
available products thereof include Gel All MD and Gel All MD-R,
produced by New Japan Chemical Co., Ltd.
[0066] Examples of the partial metal salt of rosin acid include
Pine Crystal KM1600, Pine Crystal KM1500 and Pine Crystal KM1300,
produced by Arakawa Chemical Industries, Ltd.
[0067] Examples of the inorganic fine particles include talc, clay,
mica, asbestos, glass fibers, glass flakes, glass beads, calcium
silicate, montmorillonite, bentonite, graphite, aluminum powder,
alumina, silica, diatom earth, titanium oxide, magnesium oxide,
pumicite, pumice balloons, aluminum hydroxide, magnesium hydroxide,
basic magnesium carbonate, dolomite, calcium sulfate, potassium
titanate, barium sulfate, calcium sulfite and molybdenum sulfide.
Examples of the commercially available products thereof include
Sylysia, produced by Fuji Sylysia Chemical Ltd., and Mizukasil,
produced by Mizusawa Industrial Chemicals, Ltd.
[0068] The internal releasing agent may be used solely or as a
combination of two or more kinds thereof. In the present invention,
among these internal releasing agents, dibenzylidene sorbitol,
1,3:2,4-bis(o-3,4-dimethylbenzylidene)sorbitol,
1,3:2,4-bis(o-2,4-dimethylbenzylidene)sorbitol,
1,3:2,4-bis(o-4-ethylbenzylidene)sorbitol,
1,3:2,4-bis(o-4-chlorobenzylidene)sorbitol and
1,3:2,4-dibenzylidene sorbitol are preferred.
[0069] The content of the internal releasing agent is preferably
from 10 to 10,000 ppm by mass based on the composite of the sheath
component resin as a standard, and more preferably from 100 to
5,000 ppm by mass. When the content of the internal releasing agent
is 10 ppm by mass or more, the function of the releasing agent may
be exhibited, and when the content thereof is 10,000 ppm by mass or
less, good balance may be obtained between the function of the
releasing agent and the cost.
2. Core Component
[0070] The core component of the core-sheath composite fibers
preferably contains a low crystalline polypropylene, and the
content thereof is preferably from 90 to 100% by mass of the low
crystalline polypropylene and from 0 to 10% by mass of a high
crystalline polypropylene. When the content of the low crystalline
polypropylene is 90% by mass or more, sufficient elastic recovery
property may be obtained, and the content of the low crystalline
polypropylene is preferably 100% by mass for providing the highest
elastic recovery property.
3. Composite Fibers
[0071] The core-sheath composite fibers preferably satisfy the
following conditions. In the following description, the parameters
are abbreviated as follows.
[0072] Ws: mass fraction of the sheath component (%)
[0073] Wc: mass fraction of the core component (%)
[0074] Xs: mass fraction of the low crystalline polypropylene in
the sheath component (%)
[0075] Xc: mass fraction of the low crystalline polypropylene in
the core component (%)
[0076] In the core-sheath composite fibers of the present
invention, the ratio of the sheath component and the core component
(Ws/Wc) is preferably in a range of from 50/50 to 10/90. When the
condition is satisfied, good elastic recovery property may be
obtained.
[0077] The core-sheath composite fibers of the present invention
preferably has a larger content of a low crystalline polypropylene
in the core component than in the sheath component. In other words,
Wc.times.Xc is preferably larger than Ws.times.Xs. When the
core-sheath composite fibers satisfy the condition, both high
elastic recovery property and good continuous moldability may be
obtained simultaneously.
[0078] In the core-sheath composite fibers of the present
invention, the content of the total low crystalline polypropylene
calculated by the following expression is preferably from 90 to 99%
by mass. When it is 90% by mass or more, sufficient elastic
recovery property may be obtained, and when it is 99% by mass or
less, deterioration of the moldability due to attachment to a
calender roll and stickiness of the nonwoven cloth may be
prevented.
total low crystalline propylene content
(%)=(Ws.times.Xs+Wc.times.Xc)/100
[0079] The mass fraction of the sheath component and the mass
fraction of the core component may be controlled by changing the
resin ejection amounts for the core part and the sheath part in the
core-sheath composite nozzle used for forming the nonwoven
cloth.
[0080] Various additives may be added depending on necessity to the
resin compositions of the sheath component and the core component
used for producing the core-sheath composite fibers of the present
invention. Examples of the additives include an antioxidant, a
neutralizing agent, a slipping agent, an antiblocking agent, an
antifoggant and an antistatic agent. The additives may be used
solely or as a combination of two or more kinds thereof. Examples
of the antioxidant include a phosphorus antioxidant, a phenol
antioxidant and a sulfur antioxidant. These may be added upon
preparing the resin compositions of the sheath component and the
core component, or may be added upon producing the low crystalline
polypropylene.
Elastic Nonwoven Cloth and Fiber Product
[0081] The elastic nonwoven cloth of the present invention may be
produced by such a method as a melt-blow method, a spunbond method
and the like, and the production method may be appropriately
selected depending on the purpose of the elastic nonwoven
cloth.
[0082] In the melt-blow method, the elastic nonwoven cloth may be
produced in such a manner that a molten resin is extruded from a
nozzle and then made in contact with a high-speed heated gas flow
to form fine fibers, and the fine fibers are collected on a moving
collecting surface to form a nonwoven cloth. A nonwoven cloth
produced by the melt-blow method contains fibers with a small
average diameter, which constitute the nonwoven cloth, and thus has
pleasant texture.
[0083] In the spunbond method, the elastic nonwoven cloth may be
produced in such a manner that a resin having been melt-kneaded is
spun, stretched and filamentized to form continuous long fibers,
and continuously in the subsequent process step, the continuous
long fibers are accumulated and entangled on a moving collecting
surface. In the spunbond method, an elastic nonwoven cloth may be
produced continuously, and an elastic nonwoven cloth produced by
the spunbond method has a large strength since the fibers
constituting the nonwoven cloth are stretched continuous long
fibers.
[0084] The fiber product using the elastic nonwoven cloth of the
present invention is not particularly limited, and examples thereof
include the following fiber products. Specifically, examples
thereof include a material for a diaper cover, an elastic material
for a diaper cover, an elastic material for a sanitary product, an
elastic material for a hygienic product, an elastic tape, an
adhesive plaster, an elastic material for a clothing material, an
electric insulating material for a clothing material, a thermal
insulating material for a clothing material, a protective garment,
a headwear, a face mask, a glove, an athletic supporter, an elastic
bandage, a base cloth for a wet dressing, an antislipping base
cloth, a vibration dampener, a finger stall, an air filter for a
clean room, an electret filter having been subjected to an electret
treatment, a separator, a thermal insulating material, a coffee
bag, a food packaging material, a ceiling surface material for an
automobile, an acoustic insulating material, a cushioning material,
a dust proof material for a speaker, an air cleaner material, a
insulator surface material, a backing material, an adhesive
nonwoven cloth sheet, various automobile member, such as a door
trim material, various cleaning material, such as a cleaning
material for a duplicator, a surface material and a backing
material of a carpet, an agricultural rolled cloth, a wood draining
material, a shoe material, such as a surface material for sport
shoes, a member for a bag, an industrial sealant, a wiping
material, and a bed sheet.
EXAMPLE
[0085] The present invention will be described in more detail with
reference to examples, but the present invention is not limited to
the examples.
Example 1
(1) Production of Low Crystalline Polypropylene
[0086] To a stainless steel vessel having an inner capacity of 20 L
equipped with a stirrer, n-heptane at 20 L/h, triisobutylaluminum
at 15 mmol/h, and a catalyst component, which was obtained by
making dimethylanilinium tetrakis(pentafluorophenyl)borate,
(1,2'-dimethylsilylene) (2,1'-dimethylsilylene)
bis(3-trimethylsilylmethylindenyl)zirconium dichloride,
triisobutylaluminum and propylene at a mass ratio of 1/2/20, at 6
.mu.mol/h in terms of zirconium were continuously fed.
[0087] Polymerization reaction was performed at a polymerization
temperature set at 67.degree. C. while continuously feeding
propylene and hydrogen to maintain the hydrogen concentration in
the gas phase of the reactor to 2% by mol and the total pressure in
the reactor to 0.8 MPaG.
[0088] To the resulting polymerization solution, Irganox 1010
(produced by Ciba Specialty Chemicals Co., Ltd.) as a stabilizer
was added to make the content ratio thereof of 500 ppm by mass, and
then n-heptane as a solvent was removed, thereby providing a low
crystalline polypropylene (LMPP).
[0089] The resulting low crystalline polypropylene was measured for
a melting point (Tm-D), a stereoregularity index ([mm]), a
mesopentad fraction [mmmm], a racemic-meso-racemic-meso pentad
fraction [rmrm], [rrrr]/(1-[mmmm]), [mm].times.[rr]/[mr].sup.2, a
weight average molecular weight (Mw) and a molecular weight
distribution (Mw/Mn) according to the aforementioned methods. The
results are shown in Table 1.
TABLE-US-00001 TABLE 1 Low Crystalline Polypropylene (LMPP) melting
point (Tm-D) 70 [mm] (% by mol) 65 [mmmm] (% by mol) 44.6 [rmrm] (%
by mol) 2.7 [rrrr]/(1 - [mmmm]) 0.036 [mm] .times. [rr]/[mr].sup.2
1.4 Mw 110,000 Mw/Mn 2.0
(2) Formation of Nonwoven Cloth
[0090] As the sheath component, a mixture in a pellet form obtained
by mixing 90% by mass of the low crystalline polypropylene (LMPP)
obtained in the item (1) and 10% by mass of a high crystalline
polypropylene (PP, Moplen HP561S, produced by Basell Polyolefins
Company) having a melt flow rate (MFR) measured according to JIS
K7210 at a temperature of 230.degree. C. and a load of 21.18 N of
33 g/10 min was used, and as the core component, only the low
crystalline polypropylene was used.
[0091] The nonwoven cloth was produced by using a spunbond machine
(Reicofil 4, produced by Reicofil GmbH). The raw materials of the
sheath component resin and the core component resin were spun in
such a manner that the materials were each separately melt-extruded
with a single screw extruder at a resin temperature of 220.degree.
C., and were ejected from a core-sheath composite nozzle having a
nozzle diameter of 0.6 mm (number of pores: 5,800 pores/m) at a
rate of 0.60 g/min per single pore at a ratio of the sheath
component to the core component of 20/80.
[0092] The fibers obtained by spinning were accumulated at a
temperature of 16.degree. C. and a cabin pressure of 2,000 Pa on a
net surface moving at a line speed of 40 m/min. The fiber bundle
thus accumulated on the net surface was embossed with an embossing
roll heated to 65.degree. C. at a line pressure of 20 N/mm, and
wound to a winding roll.
[0093] The resulting elastic nonwoven cloth was measured and
evaluated as follows. The results are shown in Table 2.
(3) Measurement of Elastic Recovery Rate
[0094] A test piece having a length of 200 mm and a width of 25 mm
was taken from the resulting elastic nonwoven cloth in each of the
machine direction (MD) and a transversal direction (TD)
perpendicular to the machine direction. By using a tensile tester
(Autograph AG-I, produced by Shimadzu Corporation), the test piece
set at an initial length L.sub.0 of 100 mm was elongated by 100% at
a tensile speed of 300 mm/min and then immediately retracted at 300
mm/min, and the length L (mm) at the time when the stress became 0
was measured. The elastic recovery rate (%) was calculated
according to the following expression.
elastic recovery rate (%)=(2-L/L.sub.0).times.100
(4) Measurement of Breaking Strain and Maximum Stress
[0095] A test piece having a length of 200 mm and a width of 25 mm
was taken from the resulting elastic nonwoven cloth in each of the
machine direction (MD) and a transversal direction (TD)
perpendicular to the machine direction. By using a tensile tester
(Autograph AG-I, produced by Shimadzu Corporation), the test piece
set at an initial length L.sub.0 of 100 mm was elongated at a
tensile speed of 300 mm/min until the test piece was broken, and
the maximum stress immediately before the breakage and the length L
(mm) at that point were measured. The breaking strain (%) was
calculated according to the following expression.
breaking strain (%)=(L-L.sub.0)/L.sub.0.times.100
(5) Measurement of Areal Weight
[0096] The mass of the resulting nonwoven cloth of 5 cm.times.5 cm
was measured, and the areal weight (g/m.sup.2) was calculated.
(6) Measurement of Fineness
[0097] The fibers in the nonwoven cloth were observed with a
polarizing microscope for measuring an average value (d) of the
fiber diameters of five fibers that were randomly selected, and the
fineness of the specimen of the nonwoven cloth was calculated from
the density of the resin (.rho.=900,000 g/m.sup.3) according to the
following expression.
fineness
(g/9,000m)=.rho..times..pi..times.(d/2).sup.2.times.9,000
(7) Spinning Speed
[0098] The spinning speed was calculated from the fineness in terms
of denier obtained by the aforementioned manner according to the
following expression.
spinning speed (m/min)=single pore ejection amount (g/min)/fineness
(denierg/9,000m).times.9,000(m)
Examples 2 to 4 and Comparative Example 1
[0099] Elastic nonwoven cloths were formed in the same manner as in
Example 1 except that the sheath component and the spinning
conditions in Example 1 were changed as shown in Table 2, and were
measured and evaluated in the same manners. The results are shown
in Table 2.
TABLE-US-00002 TABLE 2 Comparative Example 1 Example 2 Example 3
Example 4 Example 1 Sheath LMPP 90 90 90 component PP 10 10 10 (%
by mass) Engage 100 40 ASPUN 60 Cabin pressure (Pa) 2,000 3,500
4,000 3,500 6,000 Embossing roll temperature (.degree. C.) 65 65 65
65 80 Line pressure (N/mm) 20 20 45 90 20 Areal weight (g/m.sup.2)
68 66 179 68 60 Fineness (g/9,000 m) 4.2 2.7 3.4 2.2 2.0 Ejection
amount per single pore (g/min) 0.60 0.60 0.60 0.60 0.60 Spinning
speed (m/min) 1,286 2,000 1,588 2,455 2,700 MD Breaking strain (%)
194 186 133 151 70 Maximum stress (N) 21.9 29.7 43.0 24.7 20.7
Elastic recovery rate (%) 84.2 83.9 84.1 76.2 -- TD Breaking strain
(%) 368 271 258 192 75 Maximum stress (N) 8.5 12.1 22.0 10.2 4.8
Elastic recovery rate (%) 81.5 82.0 82.1 71.9 --
LMPP: low crystalline polypropylene produced in Example 1 (1) PP:
Moplen HP561S, produced by Basell Polyolefins Company, melting
point: 160.degree. C. Engage: ethylene polymer, Engage 8401,
produced by Dow Chemical Company ASPUN: ethylene polymer, ASPUN
6834, produced by Dow Chemical Company
INDUSTRIAL APPLICABILITY
[0100] The elastic nonwoven cloth of the present invention may be
favorably used, for example, as various fiber products including a
disposable diaper, a sanitary product, a hygienic product, a
clothing material, a bandage and a packaging material.
* * * * *