U.S. patent application number 10/182729 was filed with the patent office on 2003-08-21 for nonwoven fabric, process for producing the same, sanitary material and sanitary supply.
Invention is credited to Ishikawa, Masahide.
Application Number | 20030157859 10/182729 |
Document ID | / |
Family ID | 18557704 |
Filed Date | 2003-08-21 |
United States Patent
Application |
20030157859 |
Kind Code |
A1 |
Ishikawa, Masahide |
August 21, 2003 |
Nonwoven fabric, process for producing the same, sanitary material
and sanitary supply
Abstract
Polyolefin resin-based non-woven fabric characterized by
containing a fatty acid amide compound, and by having a static
friction coefficient of 0.1 to 0.4. Production of such non-woven
fabric is achieved by subjecting, for example, non-woven fabric
containing 0.05 to 1 wt. % erucamide to an aging treatment at 30 to
60.degree. C. for 5 to 50 hours.
Inventors: |
Ishikawa, Masahide;
(Sanbu-gun, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
18557704 |
Appl. No.: |
10/182729 |
Filed: |
November 15, 2002 |
PCT Filed: |
February 7, 2001 |
PCT NO: |
PCT/JP01/00834 |
Current U.S.
Class: |
442/340 ;
442/382; 442/401 |
Current CPC
Class: |
A61F 13/51 20130101;
C08L 23/10 20130101; D04H 3/16 20130101; Y10T 442/66 20150401; D01F
1/10 20130101; Y10T 442/681 20150401; C08L 23/12 20130101; C08L
23/02 20130101; D04H 1/4291 20130101; Y10T 442/614 20150401; C08L
23/00 20130101; D04H 3/007 20130101; C08K 5/20 20130101; C08K 5/20
20130101; C08L 23/02 20130101 |
Class at
Publication: |
442/340 ;
442/401; 442/382 |
International
Class: |
D04H 001/00; D04H
003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2000 |
JP |
2000-33191 |
Claims
1. Polyolefin resin-based non-woven fabric characterized by that it
contains a fatty acid amide compound, and that its static friction
coefficient is 0.1 to 0.4.
2. Polyolefin resin-based non-woven fabric as described in claim 1
wherein the fatty acid amide compound is erucamide, and its content
is 0.05 to 1.0 wt. %.
3. Polyolefin resin-based non-woven fabric as described in claim 1
or 2 wherein the fiber constituting the non-woven fabric has a
diameter of 1 to 50 .mu.m.
4. Polyolefin resin-based non-woven fabric as described in any one
of claims 1 to 3 which has an mass per unit area of 5 to 200
g/m.sup.2.
5. Polyolefin resin-based non-woven fabric as described in any one
of claims 1 to 4 which is spunbonded non-woven fabric.
6. Polyolefin resin-based non-woven fabric as described in any one
of claims 1 to 5 wherein the polyolefin resin is a polypropylene
resin.
7. Polyolefin resin-based non-woven fabric as described in claim 6
wherein the polypropylene resin is crystallizable, and has an
isotactic pentad fraction of 88 to 95 mol. %.
8. Polyolefin resin-based non-woven fabric as described in claim 6
or 7 wherein the melt index (MI) of the polypropylene resin is 5 to
200 g/10 min.
9. Multi-layered non-woven fabric comprising polyolefin resin-based
non-woven fabric as described in any one of claims 1 to 8 at least
on one surface.
10. Multi-layered non-woven fabric as described in claim 9 wherein
the fabric has a three layered structure comprising a spunbonded
non-woven fabric layer/meltblown non-woven fabric layer/spunbonded
non-woven fabric layer, and those non-woven fabric layers have an
mass per unit area of 7 to 25 g/m.sup.2.
11. A method for producing polyolefin resin-based non-woven fabric
as described in any one of claims 1 to 10 comprising subjecting
non-woven fabric obtained by melting a polyolefin resin containing
a fatty acid amide compound and by spinning the melt into fiber, to
an aging treatment at 30 to 60.degree. C. for 5 to 50 hours.
12. A sanitary material comprising polyolefin resin-based non-woven
fabric as described in any one of claims 1 to 10.
13. A sanitary material as described in claim 12 wherein the
polyolefin resin is a polypropylene resin which is crystallizable
and has an isotactic pentad fraction of 88 to 95 mol. %.
14. A sanitary material as described in claim 12 or 13 wherein the
polyolefin resin is a polypropylene resin which has a melt index
(MI) of 30 to 80 g/10 min.
15. A sanitary material as described in any one of claims 12 to 14
which is applicable to a disposable diaper, sanitary napkin or
incontinence pad.
16. A sanitary article made from a sanitary material as described
in any one of claims 12 to 14.
17. A sanitary article as described in claim 16 which is applicable
to a disposable diaper, sanitary napkin or incontinence pad.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to polyolefin resin-based
non-woven fabric and a method for the production thereof,
particularly to fabric suitable as a material of sanitary articles
such as disposable diapers because of its excellent hand and touch
feeling.
DESCRIPTION OF THE RELATED ART
[0002] The filament non-woven fabric such as spunbonded non-woven
fabric has been widely used in many applications because it has
excellent mechanical properties such as high tensile strength and
air permeability, as well as ensures the efficient production of
fabric based on continuously spun fibers. The thermoplastic resin
which has been mainly used as a material of such filament non-woven
fabric includes polyamide resins and polyester resins because they
give excellent fiber characteristics, and are easily melt into a
fiber easily yielding to spinning (spinning easiness). However,
currently, an increasingly larger amount of polyolefin resins such
as polypropylene, polyethylene, etc., or the resins, which have
been used, in general applications, come to be used as a material
of the fabric in question.
[0003] To see how a polyolefin-based resin can serve as a material
of non-woven fabric, take, for example, a polypropylene-based
resin. Even if the polypropylene resin results from a single
propylene monomer, the resulting homopolymers may have different
crystallizing activities. Or, if propylene is polymerized together
with ethylene or butene-1, the resulting copolymers will have
different properties, for example, in the melting point, mechanical
strength, elastic modulus, etc. Take non-woven fabric made of such
polypropylene resins. If it is made of a resin having a high
crystallizing activity, it will be excellent in spin easiness, but
poor in softness and problematic in hand. On the contrary, if a
polypropylene resin having a low crystallizing activity and melting
point is used as a material of the non-woven fabric, the fiber of
the fabric will be very resistant to spinning, because it shows a
high friction against adjacent fibers or metals, although it will
be excellent in softness.
[0004] If a polypropylene-based resin of which the isotactic pentad
fraction (which serves as an index representing the crystallizing
activity of the resin) is about 90 mol %, or a resin most often
used as a material of non-woven fabric, is employed, the fiber will
be comparatively good in spin easiness but the fabric based thereon
will not always have a sufficient hand and touch feel to be
effectively applied for the production of sanitary articles such as
disposable diapers, sanitary napkins, incontinence pads, etc.
[0005] To cope with these problems, the Japanese Patent Laid-Open
No. 10-88459 proposes filament non-woven fabric which is made of a
thermally bonded filament bicomponent fiber: the bicomponent fiber
is obtained by combining a first component having at least one low
melting point or one low softening point selected from olefin
double copolymers or olefin triple copolymers, and a second
component composed of a crystalliable thermoplastic resin, a
hydrocarbon lubricant being added at least to the first component,
and the combination of the two components occurring in such a way
as to make the content of the hydrocarbon lubricant in the
bicomponent fiber to be 2-20 wt. %.
[0006] This proposal employs, as a polypropylene resin, a
propylene-based random copolymer, which has a low melting point and
is soft, to enhance the softness and touch feel of the resulting
fabric, and tries to compensate for the degraded spin easiness
characteristic with such a copolymer, by adding a hydrocarbon
lubricant thereto. In the material of this fabric, however, the
features characteristic with a propylene-based homopolymer such as
high thermal resistance, high mechanical strength, etc are absent,
and a comparatively large amount of a hydrocarbon compound with a
low molecular weight and low melting point must be added to the
propylene-based random copolymer. The coexistence of such a
hydrocarbon lubricant may prove to be problematic: the heat seal
and adhesiveness of the non-woven fabric will be degraded as a
result of the brittleness introduced by the lubricant.
[0007] The Japanese Patent Laid-Open No. 8-13238 discloses a
polypropylene resin composition for fiber production which is
obtained by combining 100 parts by weight of a crystallizable
polypropylene resin of which the ratio (Mw/Mn) of the weight
average molecular weight (Mw) against the number average molecular
weight (Mn) is 2 to 15, and of which the fraction of isotactic
pentads is 96% or higher, with 0.01 to 1 part by weight of a fatty
acid amide compound added.
[0008] This patent publication introduces a highly crystallizable
polypropylene resin which ensures the production of a highly strong
fiber whose drawing is increased 6 times or more than that of the
common polypropylene resin-based fiber, with a lubricant added to
enhance the drawing and luster of the fiber as well as to
compensate for the otherwise degraded drawing of the fiber which
might result from fuzz which otherwise might develop during the
extension of the fiber. Namely, the resin has a crystallizing
activity different from that of the resin commonly used as a
material of a polypropylene resin-based non-woven fabric; but the
fabric based on the resin does not always give a good softness,
hand and touch feel. Indeed, although the patent publication
mentions that the fabric based on the resin is suitably used as a
material of non-woven fabric for industrial use, it gives no
mention regarding its applicability to the production of sanitary
materials, suggesting the fiber made from the resin is rather
adaptive for special applications.
[0009] The present invention aims at providing polyolefin
resin-based non-woven fabric which substantially retains the
features characteristic with the constituent resin represented by a
polypropylene resin, such as high thermal resistance, high
mechanical strength, etc., is excellent in softness, hand and touch
feel, and is used particularly suitably as a sanitary material for
the production of disposable diapers, sanitary napkins, etc.,
method for producing the same, and applications of the same.
DISCLOSURE OF THE INVENTION
[0010] The present inventors studied hard to find a method by which
to produce polyolefin resin-based non-woven fabric, particularly
polypropylene resin-based non-woven fabric which retains the
features characteristic with the constituent polyolefin resin such
as good vapor permeability, waterproofness, softness, and high
mechanical strength and thermal resistance, and which still
presents with, in addition to spin easiness, a good use feeling
based on hand and good touch feeling, the feature required for
finished products prepared from the fabric. As a result, they found
that the frictional property of the non-woven fabric has a grave
influence on its use feeling, and achieved the invention based on
this finding.
[0011] Briefly, the present invention includes following
constitutive elements.
[0012] (1) Polyolefin resin-based non-woven fabric, which contains
a fatty acid amide compound, and whose static frictional
coefficient is 0.1 to 0.4.
[0013] (2) Polyolefin resin-based non-woven fabric as described in
the paragraph (1) wherein the above fatty acid amide compound is
erucamide and its content is 0.05 to 1.0 wt. %.
[0014] (3) Polyolefin resin-based non-woven fabric as described in
(1) or (2) wherein the fiber of the fabric has a diameter of 1-50
.mu.m.
[0015] (4) Polyolefin resin-based non-woven fabric cited in any one
of the paragraphs (1) to (3) whose mass per unit area is 5 to 200
g/m.sup.2.
[0016] (5) Polyolefin resin-based non-woven fabric cited in any one
of the paragraphs (1) to (4) which is spunbonded non-woven
fabric.
[0017] (6) Polyolefin resin-based non-woven fabric cited in any one
of the paragraphs (1) to (5) wherein the polyolefin resin is a
polypropylene resin.
[0018] (7) Polyolefin resin-based non-woven fabric cited in the
paragraph (6) wherein the polypropylene resin is crystallizable and
its isotactic pentad fraction is 88 to 95 mol. %.
[0019] (8) Polyolefin resin-based non-woven fabric cited in the
paragraph (6) or (7) wherein the melt index (MI) of the
polypropylene resin is 5 to 200 g/10 min.
[0020] (9) Multi-layered non-woven fabric comprising, at least in
one surface, polyolefin resin-based non-woven fabric as cited in
any one of the paragraphs (1) to (8).
[0021] (10) Multi-layered non-woven fabric cited in the paragraph
(9) which has a three layered structure comprising a spunbonded
non-woven layer/meltblown non-woven layer/spunbonded non-woven
layer, and in which the mass per unit area of each non-woven layer
is 7 to 25 g/m.sup.2.
[0022] (11) Method for producing polyolefin resin-based non-woven
fabric cited in any one of the paragraphs (1) to (10) comprising
submitting non-woven fabric made of fiber obtained by melting a
polyolefin resin containing a fatty acid amide compound and
spinning it into fiber, to an aging treatment at 30 to 60.degree.
C. for 5 to 50 hours.
[0023] (12) Sanitary materials made from polyolefin resin-based
non-woven fabric cited in any one of the paragraphs (1) to
(10).
[0024] (13) Sanitary materials cited in the paragraph (12) wherein
the polyolefin resin is a polypropylene resin which is
crystallizable, and whose isotactic pentad fraction is 88 to 95
mol. %.
[0025] (14) Sanitary materials cited in the paragraph (12) or (13)
wherein the polyolefin resin is a polypropylene resin whose melt
index (MI) is 30-80 g/10 min.
[0026] (15) Sanitary materials cited in any one of the paragraphs
(12) to (14) which are used for the production of disposable
diapers, sanitary napkins or incontinence pads.
[0027] (16) Sanitary articles made of a sanitary material cited in
any one of the paragraphs (12) to (14).
[0028] (17) Sanitary articles cited in the paragraph (16) which are
used for the production of disposable diapers, sanitary napkins or
incontinence pads.
BEST MODE FOR CARRYING OUT THE INVENTION
[0029] The present invention will be described in detail below.
[0030] The polyolefin resin-based non-woven fabric of this
invention is characterized by containing a fatty acid amide
compound, and by having a static friction coefficient of 0.1 to
0.4. The fatty acid amide compound is not limited to any specific
one but may include any compound selected from the fatty acid amide
compounds cited below, but preferably includes erucamide whose
content is in the range of 0.05 to 1.0 wt. %, preferably 0.1 to 0.5
wt. %, or most preferably 0.2 to 0.4 wt. %.
[0031] The static friction coefficient of non-woven fabric can be
determined in accordance with ASTM-D1894. Specifically, the
measurement was performed under following conditions:
[0032] Tester of static friction coefficient: one provided by Toyo
Seiki Manufacturing Co. (AN type);
[0033] Supportive plate: iron plate with a size of 63.6
mm.times.102.2 mm.times.19.4 mm (height), and weighing 8.87N;
and
[0034] Gradient angle developing velocity: 2.7 degree/sec.
[0035] For non-woven fabric to be tested, two test pieces were
prepared; the test surfaces were placed one over the other; the
gradient angle was increased until the overlying piece starts to
slide; and the sliding angle (?) was determined, to give tan ?
which is used as the static friction coefficient of the test
fabric. The lower the coefficient, the readier the test fabric is
to slide.
[0036] The polyolefin resin-based non-woven fabric of this
invention is not limited to any specific ones, but may include any
such non-woven fabric obtained by a variety of manufacturing
methods including the publicly known non-woven fabric such as
spunbonded non-woven fabric, spunlace non-woven fabric, hot
air-through bonding carded non-woven fabric, thermal embossing
carded non-woven fabric, meltblown non-woven fabric, etc. Among
them, what is preferred on account of mechanical strength and
productivity may include spunbonded non-woven fabric based on long
fibers, meltblown non-woven fabric adapted for a special function,
and multilayered non-woven fabric comprising layers made of the
above fabric.
[0037] However, the polyolefin resin-based non-woven fabric of this
invention should have following features: it has a static friction
coefficient in the range of 0.1 to 0.4 as described above, and
thus, even if it has a multilayered structure, at least one exposed
surface of the fabric has a static frictional coefficient of 0.1 to
0.4. If the polyolefin resin-based non-woven fabric of this
invention has a multilayered structure, the other non-woven fabric
used for concomitant layers may be made of a polyamide resin or a
polyester resin, instead of a polyolefin resin.
[0038] The polypropylene resin used for the production of the
polyolefin resin-based non-woven fabric of this invention is not
limited to any specific ones, but may include homopolymers of
propylene, or copolymers of propylene with at least one monomer
selected from the a-olefins comprising ethylene, butene-1,
4-methyl-pentene-1, hexene-1, octene-1, etc. These polypropylene
resins present with widely different crystallizing activities,
molecular weights, and molecular weight distributions depending on
the catalysts selected, and given polymerization conditions, and an
appropriate one must be chosen from among them in accordance with
the properties required from the target fabric.
[0039] In terms of the crystallizing activity, the resin used in
this invention should be selected from those that have an isotactic
pentad fraction in the range of 88 to 95 mol. %, preferably 89 to
93 mol. %, as long as the resin is used for the production of
sanitary materials suitable for disposable diapers. The isotactic
pentad fraction (IPF) is as defined in Macromolecules 28(16): 5403
(1995), that is, the fraction of isotactic species per pentad of a
test polypropylene chain which is determined by radioactive carbon
isotope-based nuclear magnetic resonance (.sup.13C-NMR).
[0040] In terms of the melt index (MI), the resin used in this
invention should be selected from those whose MI is in the range of
5 to 200 g/10 min, preferably 10 to 100 g/10 min, when determined
according to JIS K 7210 (temperature set at 230.degree. C. and load
at 21.18N). Particularly, the resin whose MI is in the range of 30
to 80 g/10 min is preferred, when it is used for the production of
sanitary materials.
[0041] Next, the preferred polyethylene resin may include
homopolymers of ethylene, and copolymers of ethylene with an
a-olefin compound(s) with 3 to 10 carbon atoms, such as propylene,
butene-1, 4-methyl-pentene-1, hexene-1, octene-1, etc.
Particularly, copolymers of ethylene with an a-olefin monomer as
described above having a density of 880 to 960 kg/M.sup.3,
preferably 900 to 950 kg/M.sup.3, a melting point of 100 to
140.degree. C., preferably 110 to 130.degree. C., and an MI of 5 to
60 g/10 min, preferably 10 to 50 g/10 min (MI being determined
according to JIS K 7210 where the temperature is set at 190.degree.
C., and load at 21.18N) are preferred on account of their melting
point and mechanical strength.
[0042] The above polypropylene resin or polyethylene resin may
occur as copolymers of two or more kinds of monomers. Or, they may
occur as a resin composition to which is added another ethylene
resin, another propylene resin or a thermoplastic elastomer, as
long as the addition is kept at 50 wt. % or lower.
[0043] The polyolefin resin-based non-woven fabric of this
invention must contain, without fail, a fatty acid amide compound.
The fatty acid amide compound used in this invention may include
fatty acid monoamide compounds, fatty acid diamide compounds,
saturated monoamide compounds, unsaturated diamide compounds, etc.
Specifically, it may include lauramide, myristamide, palmitamide,
stearamide, behenamide, oleinamide, erucamide, montamide, N,
N'-methylene-bis-lauramide, N, N'-methylene-bis myristamide, N,
N'-methylene-bis palmitamide, N, N'-methylene-bis-behenam- ide, N,
N'-methylene-bis-oleinamide, N, N'-methylene-bis-erucamide, N,
N'-ethylene-bis-oleinamide, N, N'-ethylene-bis-erucamide, etc. Two
or more of them may be combined.
[0044] Among these fatty acid amide compounds, erucamide or an
unsaturated fatty acid monoamide compound is preferably used. The
reason is ascribed to the facts that the non-woven fabric
containing such a compound is safely protected against degraded
spinning easiness which would otherwise result from the deposition
of fatty acid amide on the fiber surface during the melt being spun
into fiber, and that the non-woven fabric containing such a
compound will have a more lowered static friction coefficient as a
result of the aging as will be described later. The content of the
fatty acid amide compound with respect to the amount of the
polyolefin resin is in the range of 0.05 to 1 wt. %, preferably 0.1
to 0.5 wt. %. The content in question should be determined with due
consideration being paid to general conditions including the
species of the fatty acid amide compound, the species of the
concomitant polyolefin resin as well as the characteristics of the
latter including its crystallizing activity, MI, etc., and the
properties required from the target fabric, and the aging.
[0045] If, for example, erucamide is used in conjunction with a
propylene homopolymer whose isotactic pentad fraction is about 90
mol. %, its content should be in the range of 0.1 to 0.5 wt. %,
most preferably 0.2 to 0.4 wt. %. In such a case, if the content of
erucamide is below 0.2 wt. %, it will be difficult for the fabric
to have a static friction coefficient of 0.1 to 0.4, depending on
the aging condition. On the contrary, if the content of erucamide
is over 0.4 wt. %, its deposition on the fiber surface will become
considerable, which may result in the development of whiteness on
the fiber surface, degrading its appearance, or cause the lowered
thermal adhesiveness of fibers.
[0046] The polyolefin resin-based non-woven fabric of this
invention may contain a publicly known additive, so as to be
adaptive for a given application or to be provided with a certain
desired property. Such publicly known additives may include
neutralizers such as calcium stearate, hydrotalcite, etc.;
antioxidants such as phenol-, phosphate-, sulfate-based compounds;
thermal stabilizers; nucleating agents; UV absorbers; photic
stabilizers; anti-statistics; flame-retarders; pigments; dyes; and
inorganic powders such as silica, talc, calcium carbonate, calcium
oxide, magnesium oxide, etc.
[0047] The polyolefin resin-based non-woven fabric of this
invention may exist as primary non-woven fabric which is obtained
by adding, in addition to an additive which is introduced as
needed, a specified amount of fatty acid amide to a polyolefin
resin, dry-blending the mixture, melting the yield, spinning the
melt into fiber, and combining the fibers. The method by which the
melt is turned into fibers and the fibers combined into fabric may
include spunbonding, meltblowing, spunlacing, carding with hot
air-through bonding, carding with thermal embossing, etc. Among
them, the spunbonding and the meltblowing, particularly the
spunbonding may be profitably employed because the fabric produced
by the method presents with an excellent mechanical strength,
functionality and productivity.
[0048] The spunbonded non-woven fabric may be obtained as primary
non-woven fabric, for example, by the following publicly known
method: a polyolefin resin having a composition as mentioned above
is melted in an extrusion molding device, and extruded therefrom;
spinning extruded from a spinneret is spun; the spun fibers are
pulled with an air current-based collecting device such as an air
sucker, while the collected fibers being opened as needed; the
fibers are collected on a web catcher such as an air current-based
net conveyer; the fibers are partially bonded with a heating means
based on hot blowing or on a heating roll, and the resulting fabric
is wound around a cylinder.
[0049] The above polyolefin resin-based non-woven fabric is
normally made of fibers composed of a polyolefin homopolymer, but
the fabric may be made of bicomponent fiber, as long as 50% or more
of the surface of each fiber is accounted for by a single
polyolefin resin.
[0050] The non-woven fabric made of bicomponent fiber may include
the one in which each fiber has a skin-core structure in which the
skin is made of a polyolefin resin and the core of a resin other
than the polyolefin resin such as a polyamide resin or a polyester
resin having a higher melting point than does the polyolefin resin,
or the one with a side-by-side structure in which fibers made of an
polyolefin resin and fibers made of another resin are placed side
by side in such a way as to make the former fibers account for 50%
or more wt. % of the fabric. Needless to say, two different
polyolefin resins may be utilized for the formation of the above
two kinds of fabric based on complicated fibers: they may form the
skin and the core of each fiber for the former fabric, while they
may form one and the other kinds of fibers for the latter
fabric.
[0051] As regards the diameter of the fibers constituting the
polyolefin resin-based non-woven fabric of this invention, it is
not limited to any specific value. However, it may be in the range
of 1-50 .mu.m, preferably 5-40 .mu.m. Particularly, when the fabric
is used as a sanitary material, the diameter in question is most
preferably in the range of 10 to 25 .mu.m. The mass per unit area
of the constitutive fiber is not limited to any specific value, but
usually it is in the range of 5 to 200 g/m.sup.2, preferably 10 to
100 g/m.sup.2. If the fabric is used as a sanitary material for the
production of disposable diapers, and produced by spin bonding, and
consists of a single layer, its mass per unit area is preferably in
the range of 10 to 30 g/m.sup.2, most preferably 18 to 25
g/m.sup.2. If the fabric has a three-layered structure comprising
spunbonded fabric/meltblown fabric/spunbonded fabric layers, its
mass per unit area is preferably in the range of 7 to 25 g/m.sup.2,
particularly preferably 12 to 17 g/m.sup.2.
[0052] The primary non-woven fabric produced as above, however,
does not give a static friction coefficient as specified for the
fabric of this invention unless otherwise treated, even though it
presents with excellent spinning easiness. The above primary
non-woven fabric will give a static friction coefficient falling
within the range as specified for the polyolefin resin-based
non-woven fabric of this invention, if it receives an aging
treatment under heating. Generally, aging has not been conducted
for this purpose.
[0053] The conditions for the aging treatment vary according to the
species of the polyolefin resin, its characteristics such as the
crystallizing activity, density and melting point, and the species
of the coexistent fatty acid amide compound, its melting point, and
solubility to the polyolefin resin. The conditions in question
should be determined with due consideration being paid to the
characteristics of the polyolefin resin serving as a material of
the fabric, the characteristics of the coexistent fatty acid amide,
the likeliness of the fabric to give a static friction coefficient
of 0.1 to 0.4, and the hand and touch feeling required for the
final product. For details, the conditions must be determined
experimentally.
[0054] The method provided by this invention comprises submitting
non-woven fabric which is obtained after having melted a polyolefin
resin containing a fatty acid amide compound and spun it into
fiber, to an aging treatment at 30 to 60.degree. C. for 5 to 50
hours. However, the method for producing the polyolefin resin-based
non-woven fabric of this invention is not limited to the ranges
given above.
[0055] Take, for illustration, a case where, to produce non-woven
fabric of this invention, fiber is utilized which is made of a
propylene homopolymer, has an isotactic pentad fraction of about 90
mol. %, and contains 0.3 wt. % erucamide. Then, the preferred
conditions for aging are as follows.
[0056] If aging occurs at 40.degree. C., the aging time is about 5
to 50 hours, preferably eight to 12 hours. Conversely, if the aging
time is 24 hours, the aging temperature should be 32 to 50.degree.
C., preferably 33 to 40.degree. C. If the aging condition is milder
than above, the lowering speed of the static friction coefficient
of the fabric may become so low as to interfere with the
productivity. On the contrary, if the aging condition is sterner
than above, the fabric may give a higher static friction
coefficient than specified, which is undesirable.
[0057] The aging treatment normally occurs in an aging chamber
where fabric pieces are rolled around cylindrical cores, the pieces
are neatly arranged with the cores being placed side by side, and
hot air is allowed to circulate round the fabric pieces. During
aging, even if the fabric piece is wound around a core, it has such
a sufficient air permeability as to permit its entire mass to be
essentially uniformly subject to aging.
[0058] The polyolefin resin-based non-woven fabric of this
invention, because of its lowered static friction coefficient due
to the aging, is greatly improved in its hand and touch feeling,
while maintaining the features characteristic with the non-woven
fabric based on the polyolefin resin fiber. Accordingly, it may be
used for the production of various sanitary materials as well as of
clothing materials.
[0059] The touch feeling is only determined by the features of the
surface of the fibers constituting the non-woven fabric. Thus, it
is possible to improve the characteristics of the original fabric
such as its strength, vapor permeability, dust shielding activity,
thermal adhesiveness, etc., by adding, as appropriate, common
polyolefin resin-based fabric, thermoplastic resin-based fabric,
etc., or other sheet materials such as a vapor permeable film,
water proof film, water repellent film, etc., neither of which,
however, contains fatty acid amide compound, so as to allow the
resulting fabric to have a multilayered structure, as long as the
addition does not affect the surface characteristics of the fibers
of the original fabric.
[0060] If such addition is made, the layering should be normally
conducted in such a manner as to make the polyolefin resin-based
non-woven fabric having undergone aging be exposed at least on one
side of the layered fabric. However, in certain cases, it is
possible to overlap a layer of the polyolefin resin-based non-woven
fabric with another layer of different fabric, and then to submit
the resulting layered fabric complex to aging. The different fabric
suitable to be incorporated in such a layered structure may include
spunbonded non-woven fabric, meltblown non-woven fabric, and staple
non-woven fabric. For example, take non-woven fabric having a
multilayered structure obtained by overlapping a meltblown
non-woven fabric layer over a spunbonded non-woven fabric layer,
and then by placing another spunbonded non-woven fabric layer over
the foregoing assembly. To produce such non-woven fabric, it is
recommended to firstly prepare multilayered fabric of which at
least one spun bound non-woven fabric layer made of a polyolefin
resin is allowed to contain fatty acid amide, and then to submit
this multilayered fabric to aging.
[0061] Besides non-woven fabric made of a polyolefin resin, the
non-woven fabric according to this invention may include a fabric
layer made of, for example, a polyester resin or a polyamide resin,
particularly the one having a melting point of 150.degree. C. or
higher, more preferably 150 to 300.degree. C. The preferred
polyester resin may include homopolymers such as
polyethylenetelephthalate, polybutylenetelephthalate,
polytrimethylenetelephthalate, polynaphtalenetelephthalate, etc.,
and the copolymers of the above constitutive monomers with other
monomers, and the combinations of such copolymers.
[0062] The preferred polyamide resin may include, to mention a few
for illustration, nylon 6 (polycaprolactamide), nylon 6,6
(polyhexamethyleneadipoamide), nylon 6,10
(polyhexamethylenecebacamide), nylon 11 (polyundecanamide), nylon 7
(poly-?-aminoheptanate), nylon 9 (poly-?-aminononate), nylon 12
(polylaurinamide), etc. Among them, nylon 6 and nylon 6,6 are
preferred.
[0063] For laminating non-woven fabric layers to produce non-woven
fabric with a multilayered structure, various methods including
thermal bonding or adhesive bonding may be applicable. However,
emboss rolling under heating is particularly recommendable because
of its simplicity and low cost. The emboss rolling under heating
may occur with a publicly known laminating device based on the
combination of an emboss roll and a flat roll. The emboss rolling
may occur by any patterned rolling including, for example, grid
patterned rolling by which adhesive continuous lines form a grid
pattern, independent pattern rolling, or desired pattern rolling.
The patterned bonded area may account for 5 to 40% of the total
area.
[0064] The polyolefin resin-based non-woven fabric of this
invention may have a multilayered structure comprising, in addition
to other non-woven fabric layers, a layer such as a vapor permeable
layer (film), water impermeable layer (film) or water repellent
layer (film). For the production of such non-woven fabric,
extrusion lamination, emboss rolling under heating or dry
lamination may be employed.
[0065] The condition suitable for proper lamination by emboss
rolling under heating may vary depending on the melting points of
the polyolefin resin-based fabric layer and of the other
concomitant non-woven fabric layers, and on which one among plural
films is exposed to embossing, and should be determined with due
consideration being paid to those involved factors. Thus, the
emboss pattern and relative emboss area, and the temperature and
pressure under which embossing occurs should be determined as
appropriate according to the diameter of the fibers constituting
individual fabric layers, the thickness, mass per unit area, air
permeability and processing speed of individual fabric layers, and,
in addition, the melting point and thickness of concomitant
films.
[0066] The polyolefin resin-based non-woven fabric of this
invention, method for producing the same, and examples produced by
the method will be described in detail below. However, it should be
understood that the present invention is not restricted in any way
in its scope by those examples.
EXAMPLE 1
[0067] A crystallizable polypropylene resin (IPF: 91 mol. %, MI: 60
g/10 min, melting point: 160.degree. C.) 100 parts by weight, 0.035
part by weight of a phenol antioxidant (Ilganox 1010, Chiba Special
Chemicals Co.), 0.035 part by weight of a phosphate antioxidant
(Sandstab P-EPQ, Sand Co.), 0.035 part by weight of a neutralizer
(Kyodo Pharmaceutical Co.), 0.025 part by weight of calcium
stearate, and erucamide having a weight as specified in Table 1
were dry-blended with a super mixer; the mixture was melted and
kneaded at 220.degree. C. in an extrusion molding device with 65
mmF; the melt was extruded through spinneret to be spun into fiber.
Arrays of spinneret are arranged as follows: the diameter of each
spinneret is 0.3 mm, and the spinnerets number 200 in the width
direction while they number 15 in the extrusion direction. The spun
fiber had an average diameter of 18 .mu.m (ten fibers were
arbitrarily chosen, and placed under a microscope with a scale for
measurement).
[0068] A group of fibers were introduced into an air sucker to be
stretched; the fibers were then collected on a belt equipped with
an aspirator to be inserted between a pair of rolls for heat
embossing (an embossed roll kept at 140.degree. C. and a flat roll
kept at 140.degree. C.) to be partially bonded; and then the
resulting sheet was wound around a paper cylinder to produce
spunbonded non-woven fabric. The non-woven fabric wound around the
paper cylinder was submitted to aging, which consisted of keeping
the fabric at a specified temperature for a specified period, to
produce the polyolefin resin-based non-woven fabric of this
invention. Following the above procedures, a number of non-woven
fabric samples were obtained with the content of erucamide slightly
varied, and they were evaluated for their mass per unit area, spin
easiness and other involved characteristics. The results are shown
in Table 1.
[0069] For a given non-woven fabric sample, its spin easiness and
physical characteristics were evaluated as follows.
[0070] (1) Spin Easiness
[0071] The non-woven fabric sample was evaluated as excellent (?),
good (?) and normal (?), according to the behavior of the fiber
during spinning, that is, whether it was not broken, whether it did
not show any fluctuation, and whether it stably yielded to
spinning.
[0072] (2) Static Friction Coefficient
[0073] The static friction coefficient of the non-woven fabric
sample was determined according to ASTM-D1894. The detail of the
method was described above.
[0074] (3) Tensile Strength
[0075] It was measured according to JIS L 1906.
[0076] (4) Stiffness
[0077] It was determined according to JIS L 1096 (45.degree.
cantilever method).
[0078] (5) Touch Feeling/Hand
[0079] Twenty testers touched the test fabric samples, and
evaluated the samples according to the touch feel they gave as
excellent (.circleincircle.), good (.largecircle.) and normal
(.DELTA.).
[0080] The results are shown in Table 1.
[0081] From Table 1, it is apparent that the fabric samples (2),
(3) and (4) present with static friction coefficients which fall
within the range specified for the non-woven fabric of this
invention, and thus they are more suitable as a sanitary material
for disposable diapers, as compared with the fabric samples (1) and
(5).
1 TABLE 1 Example 1 (1) (2) (3) (4) (5) Addition amount of 0.1 0.2
0.3 0.4 -- erucamide (weight part) Mass per unit area (g/m.sup.2)
20 20 20 20 20 Spin easiness .circleincircle. .circleincircle.
.circleincircle. .circleincircle. .circleincircle. Aging
temperature (.degree. C.) 40 40 40 40 40 Aging time (hours) 24 24
24 24 24 Static friction coefficient 0.45 0.28 0.19 0.18 0.65
Stiffness (cm) 6.0 5.9 5.3 5.3 6.4 Touch feeling .DELTA.
.largecircle. .circleincircle. .circleincircle. .DELTA. Hand
.DELTA. .largecircle. .circleincircle. .circleincircle. .DELTA.
EXAMPLE 2
[0082] Non-woven fabric samples were obtained by the same method as
used in Example 1, except that the content of erucamide was made
constant, the aging temperature was kept constant and the aging
time was varied. The non-woven fabric samples were evaluated for
their mass per unit area, spin easiness, and other involved
characteristics. The results are shown in Table 2.
[0083] From Table 2 it is apparent that the fabric samples (2), (3)
and (4), particularly samples (3) and (4) present with static
friction coefficients which fall within the range specified for the
non-woven fabric of this invention, and thus they are more suitable
as a sanitary material for disposable diapers, as compared with the
fabric sample (1).
2 TABLE 2 Example 2 (1) (2) (3) (4) Addition amount of 0.3 0.3 0.3
0.3 erucamide (weight part) Mass per unit area (g/m.sup.2) 20 20 20
20 Spin easiness .circleincircle. .circleincircle. .circleincircle.
.circleincircle. Aging temperature (.degree. C.) 40 40 40 40 Aging
time (hours) 0 6 12 24 Static friction coefficient 0.55 0.35 0.22
0.19 Stiffness (cm) 6.1 5.9 5.8 5.3 Touch feeling .DELTA.
.DELTA..largecircle. .largecircle. .circleincircle. Hand .DELTA.
.DELTA..largecircle. .circleincircle. .circleincircle.
EXAMPLE 3
[0084] Non-woven fabric samples were obtained by the same method as
used in Example 1, except that the content of erucamide was made
constant, the aging time was kept constant and the aging
temperature was varied. The non-woven fabric samples were evaluated
for their mass per unit area, spin easiness, and other involved
characteristics. The results are shown in Table 3.
[0085] From Table 3 it is apparent that the fabric samples (3),
(4), and (5) present with static friction coefficients which fall
within the range specified for the non-woven fabric of this
invention, and thus they are more suitable as a sanitary material
for diapers, as compared with the fabric samples (1) and (2). It is
observed by inspecting the results of the sample (5) that the
fabric sample exposed to a higher temperature during aging tends to
develop a higher static friction coefficient.
3 TABLE 3 Example 3 (1) (2) (3) (4) (5) Addition amount of 0.3 0.3
0.3 0.3 0.3 erucamide (weight part) Mass per unit area (g/m.sup.2)
20 20 20 20 20 Spin easiness .circleincircle. .circleincircle.
.circleincircle. .circleincircle. .circleincircle. Aging
temperature (.degree. C.) 23 28 35 40 45 Aging time (hours) 24 24
24 24 24 Static friction coefficient 0.50 0.45 0.19 0.18 0.25
Stiffness (cm) 6.1 6.0 5.3 5.3 5.8 Touch feeling .DELTA. .DELTA.
.circleincircle. .circleincircle. .largecircle. Hand .DELTA.
.DELTA. .circleincircle. .circleincircle. .largecircle.
EXAMPLE 4
[0086] In stead of the device for producing spunbonded non-woven
fabric used in Example 1, a multi-stage device was employed, and
erucamide containing polypropylene used in Example 1 and
erucamide-free polypropylene were introduced as materials to
produce non-woven fabric having a two layered structure each layer
having an mass per unit area of 10 g/m.sup.2, or the density
different from those of Examples 1 to 3. The non-woven fabric was
submitted to aging, which consisted of keeping the fabric at
40.degree. C. for 24 hours. A number of non-woven fabric samples
were obtained, and they were evaluated for their mass per unit
area, spin easiness and other involved characteristics. The results
are shown in Table 4.
[0087] From Table 4 it is apparent that the layered non-woven
fabric also presents with excellent characteristics.
EXAMPLE 5
[0088] Three layered non-woven fabric was obtained by the same
method as used in Example 4, except that the mass per unit area of
each layer was varied to 7 g/m.sup.2, and that a layer (mass per
unit area being 3 g/m.sup.2) comprising meltblown non-woven fabric
made of an erucamide free polypropylene resin was laid over the
spunbonded non-woven fabric layer produced in the foregoing stage.
The multi-layered non-woven fabric thus obtained was submitted to
aging, which consisted of keeping the fabric at 40.degree. C. for
24 hours. A number of multi-layered non-woven fabric samples were
obtained, and they were evaluated for their mass per unit area,
spin easiness, and other involved characteristics. The results are
shown in Table 4.
[0089] From Table 4 it is apparent that the non-woven fabric of
this invention presents with excellent characteristics, even when
it is modified so as to have a layered structure.
4 TABLE 4 Example 4 Example 5 (1) (2) (1) (2) Addition amount of
Layer A 0.3 0.3 0.3 0.3 erucamide Layer B no no 0 0 (weight part)
Layer C 0.3 0 0.3 0 Mass per unit area (g/m.sup.2) 20 20 17 17 Spin
easiness .circleincircle. .circleincircle. .circleincircle.
.circleincircle. Static friction Surface A 0.19 0.22 0.25 0.22
coefficient Surface B 0.20 0.57 0.27 0.60 Stiffness (cm) 5.3 5.5
5.5 5.8 Touch feeling Surface A .circleincircle. .circleincircle.
.circleincircle. .circleincircle. Surface B .circleincircle.
.DELTA. .circleincircle. .DELTA. Hand Surface A .circleincircle.
.circleincircle. .circleincircle. .circleincircle. Surface B
.circleincircle. .DELTA. .circleincircle. .DELTA.
[0090] Industrial Applicability
[0091] This invention provides a method for producing polyolefin
resin-based non-woven fabric excellent in hand and touch feeling.
That fabric can be suitably used as sanitary articles such as
disposable diapers, or as a material of such sanitary articles.
* * * * *