U.S. patent application number 10/380168 was filed with the patent office on 2004-03-25 for multilayer non-woven fabric and use thereof.
Invention is credited to Ishikawa, Masahide, Kurahashi, Akihiko.
Application Number | 20040058610 10/380168 |
Document ID | / |
Family ID | 18766631 |
Filed Date | 2004-03-25 |
United States Patent
Application |
20040058610 |
Kind Code |
A1 |
Ishikawa, Masahide ; et
al. |
March 25, 2004 |
Multilayer non-woven fabric and use thereof
Abstract
A multilayer non woven fabric having a polypropylene spun bonded
non woven fabric and a polypropylene melt blown non woven fabric,
characterized in that it has a bending resistance, the sum of the
values for longitudinal and transverse directions as measured
according to JIS L 1096 6. 19.1 A method (45 degree cantilever
method) of 70 to 120 mm, the surface of the spun bonded non woven
fabric has a static friction coefficient of 0.1 to 0.4. The
multilayer non woven fabric preferably has a polypropylene melt
brown non woven fabric layer between polypropylene spun bonded non
woven fabric layers.
Inventors: |
Ishikawa, Masahide; (Chiba,
JP) ; Kurahashi, Akihiko; (Chiba, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
18766631 |
Appl. No.: |
10/380168 |
Filed: |
September 26, 2003 |
PCT Filed: |
September 17, 2001 |
PCT NO: |
PCT/JP01/08051 |
Current U.S.
Class: |
442/401 ;
442/327 |
Current CPC
Class: |
Y10T 442/60 20150401;
B32B 5/26 20130101; D04H 1/559 20130101; B32B 27/32 20130101; D04H
1/56 20130101; Y10T 442/681 20150401; D04H 3/14 20130101 |
Class at
Publication: |
442/401 ;
442/327 |
International
Class: |
D04H 003/16 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 2000 |
JP |
2000282065 |
Claims
1. A multi layer non woven fabric having a polypropylene based
resin spun bonded non woven fabric and a polypropylene based resin
melt blown non woven fabric, characterized in that it has a bending
resistance [the sum of the values for longitudinal and transverse
directions as measured according to JIS L 1096 6. 19.1 A method
(45.degree. cantilever method)] of 70 to 120 mm, and the surface of
the spun bonded non woven fabric has a static friction coefficient
of 0.1 to 0.4.
2. The multi layer non woven fabric according to claim 1 wherein
the multi layer non woven fabric has a polypropylene based resin
melt blown non woven fabric between propylene based resin spun
bonded non woven fabrics.
3. The multi layer non woven fabric according to claim 1 or 2
wherein the spun bonded non woven fabric has an average fiber
diameter of 10 to 30 .mu.m and the mass per unit area of the multi
layer non woven fabric is from 10 to 50 g/m.sup.2.
4. The multi layer non woven fabric according to any of claims 1 to
3 wherein the spun bonded non woven fabric contains a lubricant in
an amount of 0.05 to 1.0% by weight.
5. The multi layer non woven fabric according to any of claims 1 to
4 wherein the lubricant is a fatty amide compound.
6. An absorptive article obtained by using the multi layer non
woven fabric according to any of claims 1 to 5.
7. A medical sheet obtained by using the multi layer non woven
fabric according to any of claims 1 to 5.
8. A powder wrapping material obtained by using the multi layer non
woven fabric according to any of claims 1 to 5.
Description
TECHNICAL FIELD
[0001] The present invention relates to a multi layer non woven
fabric, and relates to a multi layer non woven fabric made of a
polypropylene based resin which has a liquid barrier property, fine
powder barrier property and gas permeability, particularly is
excellent in feeling and skin touch feeling and in strength and
secondary processability, and can be suitably used for various
applications, particularly, back sheet materials and side gather
materials for absorptive articles such as dispensable diapers and
the like and medical and powder wrapping materials and the like,
and to a use thereof.
BACKGROUND ART
[0002] Spun bonded non woven fabrics are used in a lot of fields
because of excellent continuous spinning and productivity together
with properties such as excellent strength, suitable bending
resistance, gas permeability and the like. As the thermoplastic
resin used in this spun bonded non woven fabric, long fiber non
woven fabric, polyamide based resins and polyester based resins
have been used due to a melt spinning property, fiber property and
the like, however, polypropylene based resins, common resins, are
being used frequently in absorptive articles such as disposable
diapers and the like.
[0003] These polypropylene based resin non woven fabrics include a
lot of resins different in crystallinity even in the case of
homopolymers of propylene, and there are known non woven fabrics
made of resins having various properties such as melting point,
strength, elastic modulus and the like by a copolymer of propylene
with ethylene, butene-1 and the like. Such a non woven fabric using
a polypropylene based resin has, in the case of a resin having high
crystallinity, an excellent spinning property, however, is inferior
in flexibility and has a problem in feeling. In the case of a
propylene based resin having low crystallinity or melting point,
flexibility is obtained, however, there are problems that a slimy
feeing occurs, friction resistance between fibers, between fiber
and other metals and the like in spinning increases, leading to an
extremely poor spinning property.
[0004] At present, as the polypropylene based resin non woven
fabric used in absorptive articles such as disposable diapers and
the like, there are frequently used those produced by using a resin
having an isotactic pentad fraction of about 90 mol %, index of
crystallinity, due to strength, spinning property, rigidity and the
like thereof.
[0005] However, there is a problem that the use feelings such as
flexibility, feeling, skin tough and the like of the resulted non
woven fabric are not necessarily sufficient when used in absorptive
articles such as disposable diapers, sanitary napkins, incontinence
pads and the like
[0006] Though a spun bonded non woven fabric made of this
polypropylene based resin long fiber is a material excellent in gas
permeability, a liquid barrier property, in use as the absorptive
article, is an essential required property particularly in a back
sheet for absorptive articles, depending on use places. Therefore,
for satisfying the liquid barrier property and property of a
polypropylene based resin non woven fabric simultaneously,
generally used are non woven fabric complex materials obtained by
complexing with other moisture permeable water preventing
materials. Likewise, a side gather is also used in complex with
materials having excellent water pressure resistance.
[0007] However, an absorptive article using this non woven fabric
complex material comes in direct contact with skin, and with
clothes in use, or comes in contact with hands of workers in
detaching. Therefore, it is suggested that use feelings such as
flexibility, feeling, skin touch and the like and a working feeling
are not satisfactory, and its touch feeling is as of a plastic
film, and not suitable also for skin. Accordingly, non woven fabric
laminates having improved these properties are desired.
[0008] For this, there are suggested various improvements in the
feeling, skin tough feeling and the like as the surface material of
these absorptive articles. For example, (1) Japanese Patent
Application Laid Open (JP-A) No. 2-88056 suggests that a polyolefin
based melt blown non woven fabric having a fineness of less than 1
denier and having a mass per unit area (Metsuke) of 0.2 go 10
g/m.sup.2 is contacted with and laminated on a polyolefin based
spun bonded non woven fabric having a fineness of 1 to 4 denier and
having a mass per unit area of 8 to 28 g/m.sup.2 when the non woven
fabric shows stickiness. However, though an effect is observed in
the case if a spun bonded non woven fabric having a narrow fiber
diameter, when the fiber diameter decreases, the bending resistance
of a spun bonded non woven fabric lowers, and working is not stable
in steps of running of a laminate, heat sealing, and the like, and
high speed processing and automation may become difficult, in
secondary processes.
[0009] (2) JP-A No. 9-143853 suggests a laminated non woven fabric
obtained by fusing a complex spun bonded non woven fabric made of
two kinds of resins having a melting point difference of 10.degree.
C. or more to two kinds of melt blown non woven fabrics having a
melting point difference of 10.degree. C. or more, with a resin of
low melting point and a non woven fabric. However, in this case,
feeling is generated by the melt blown non woven fabric and is a
property as the surface material of the melt blown non woven
fabric, consequently, a problem of the melt blown non woven fabric
cannot be solved, and in the production of the complex non woven
fabric, an apparatus becomes complicated, and melting point and
flowability are different between the complex resins, leading to
difficulty in spinning, in some cases.
[0010] Further, (3) JP-A No. 10-16115 suggests a moisture permeable
film obtained by heat fusing a gas permeable film to a non woven
fabric (spun bonded) containing a resin having melting point lower
than or the same as that of a resin in the above mentioned gas
permeable film, at an emboss are ratio of 5 to 20% by emboss
processing of an emboss pattern having no angle. However, in this
case, resins to be combined are limited, and the spun bonded non
woven fabric itself is not particularly improved, therefore, it is
estimated that improvements in surface property and feeling are
limited.
[0011] Furthermore, (4) JP-A No. 11-972 suggests a moisture
permeable complex film obtained by laminating a polyolefin based
non woven fabric having a mass per unit area of 5 to 20 g/m.sup.2,
an average fiber diameter of 0.2 to 2 denier and a bulk specific
gravity of 0.05 or less on at least one surface of a polyolefin
based biaxially stretched moisture permeable film. However, this
complex film is composed mainly of a moisture permeable stretched
film, the non woven fabric itself is a special material that is,
the complex film is a special film which is not a general laminate
mainly composed of a spun bonded non woven fabric.
[0012] Still further, (5) JP-A No. 11-290381 discloses a back sheet
for absorptive article in which a polypropylene based wet non woven
fabric layer constitutes one of surface layers of a laminate
obtained by alternately laminating a layer made of a polypropylene
based melt blown non woven fabric and a layer made of a
polypropylene based wet non woven fabric. Namely, by adoption of a
short fiber wet non woven fabric, a surface sliding property and a
liquid barrier property are intended to be secured. However, the
fiber diameter of a wet non woven fabric is relatively narrow, and
a problem occurs that a production method becomes complicated.
[0013] As described above, the moisture permeable water preventing
non woven fabric complex material does not hold properties in
performance such as strength, flexibility, bending resistance and
the like and features in production such as a spinning property and
cheapness, of conventional polypropylene based resin spun bonded
non woven fabrics, and only provides fine fiber diameter, soft
resin use, short fiber, complex spinning and the like.
[0014] Therefore, these improvement technologies have a maximum
problem in that a secondary processability which is an important
property in use of a spun bonded non woven fabric in large amount
in disposable diapers and the like, namely, suitable bending
resistance necessary for handing a non woven fabric stably in
complexing processes such as transferring of a non woven fabric,
heat adhesion and the like is not maintained. Therefore, it is
difficult to speed up, automation and stable production in
production of an absorptive article.
[0015] Consequently, particularly due to secondary processabilities
and productivities such as a spinning property and the like,
complex materials with a polypropylene spun bonded non woven fabric
are still used in spite of insufficient feeling, skin touch and the
like, as the non woven fabric complex material, in current
conditions. Therefore, improvement of these problems of
polypropylene spun bonded non woven fabrics is strongly desired by
users and producers of absorptive articles such as disposable
diapers and the like.
[0016] An object of the present invention is to provide a moisture
permeable water preventing multi layer non woven fabric
substantially holding properties such as strength, secondary
processabilities and the like essentially revealed by polypropylene
based resin spun bonded non woven fabrics, and additionally having
excellent flexibility, feeling, skin touch feeling and the like,
particularly, a multi layer non woven fabric which can be suitably
used for back sheets and side gathers of absorptive articles such
as disposable diapers, sanitary napkins and the like, and for
medical and powder wrapping materials and the like, and a use
thereof.
DISCLOSURE OF THE INVENTION
[0017] The present inventors have intensively studied use feelings
required for non woven fabric final articles, particularly, for
absorptive articles and the like, such as flexibility, feeling,
skin touch feeling and the like, regarding non woven fabric
materials endowed with a water preventing property and a powder
barrier property, while utilizing functions such as gas
permeability, flexibility, strength, heat resistance, secondary
processability, automation fitness and the like of polypropylene
based resin spun bonded non woven fabrics. As a result, the present
inventors have found that even a spun bonded non woven fabric can
remarkable improve use feelings such as flexibility, feeling, skin
touch and the like as compared with conventional multi layer non
woven fabrics even if resin used, fiber diameter and mass per unit
area are equivalent, by controlling its friction property and by
complex with a melt blown non woven fabric, leading to completion
of the invention based on this finding.
[0018] Namely, the present invention provides
[0019] (1) A multi layer non woven fabric having a polypropylene
based resin spun bonded non woven fabric and a polypropylene based
resin melt blown non woven fabric, characterized in that it has a
bending resistance [the sum of the values for longitudinal and
transverse directions as measured according to JIS L 1096 6. 19.1 A
method (45.degree. cantilever method)] of 70 to 120 mm, and the
surface of the spun bonded non woven fabric has a static friction
coefficient of 0.1 to 0.4;
[0020] (2) The multi layer non woven fabric according to (1)
wherein the multi layer non woven fabric has a polypropylene based
resin melt blown non woven fabric between propylene based resin
spun bonded non woven fabrics;
[0021] (3) The multi layer non woven fabric according to (1) or (2)
wherein the spun bonded non woven fabric has an average fiber
diameter of 10 to 30 .mu.m and the mass per unit area of the multi
layer non woven fabric is from 10 to 50 g/m.sup.2;
[0022] (4) The multi layer non woven fabric according to any of (1)
to (3) wherein the spun bonded non woven fabric contains a
lubricant in an amount of 0.05 to 1.0% by weight;
[0023] (5) The multi layer non woven fabric according to any of (1)
to (4) wherein the lubricant is a fatty amide compound;
[0024] (6) An absorptive article obtained by using the multi layer
non woven fabric according to any of (1) to (5);
[0025] (7) A medical sheet obtained by using the multi layer non
woven fabric according to any of (1) to (5); and
[0026] (8) A powder wrapping material obtained by using the multi
layer non woven fabric according to any of claims (1) to (5).
BEST MODES FOR CARRYING OUT THE INVENTION
[0027] The present invention will be illustrated in detail
below.
[0028] The multi layer non woven fabric is a multi layer non woven
fabric having a polypropylene based resin spun bonded non woven
fabric and a polypropylene based resin melt blown non woven fabric,
characterized in that it has a bending resistance [the sum of the
values for longitudinal and transverse directions as measured
according to JIS L 1096 6. 19.1 A method (45.degree. cantilever
method)] of 70 to 120 mm, and the surface of the spun bonded non
woven fabric has a static friction coefficient of 0.1 to 0.4.
[0029] Namely, it is a multi layer non woven fabric having a
polypropylene based resin spun bonded non woven fabric constituting
at least one surface of the multi layer non woven fabric, and a
polypropylene based resin melt blown non woven fabric, in which it
has a bending resistance [the sum of the values for longitudinal
and transverse directions as measured according to JIS L 1096 6.
19.1 A method (45.degree. cantilever method)] of 70 to 120 mm, and
the surface of the spun bonded non woven fabric has a static
friction coefficient of 0.1 to 0.4.
[0030] The multi layer non woven fabric of the present invention
can be produced by inline or secondary connection of a
polypropylene based resin spun bonded non woven fabric having a
static friction coefficient of 0.1 to 0.4 and a polypropylene based
resin melt blown non woven fabric. Preferable is a multi layer non
woven fabric of three layer structure having a polypropylene based
resin melt blown non woven fabric sandwiched by polypropylene based
resin spun bonded non woven fabrics.
[0031] Materials constituting the multi layer non woven fabric of
the present invention will be described below.
[0032] [Polypropylene Based Resin Spun Bonded Non Woven Fabric]
[0033] The polypropylene based resin spun bonded non woven fabric
may advantageously be that having a static friction coefficient
within a range from 0.1 to 0.4. Therefore, the means of controlling
the static friction coefficient is optional, and adoption of
various means is considered. However, the reason for a fact that
the multi layer non woven fabric of the present invention has
excellent flexibility, feeling and skin touch feeling is believed
to an effect by improvement of a sliding property of mutual long
fibers in a spun bonded non woven fabric, therefore, it is
preferable that not only a fiber sliding property of the surface
part of a non woven fabric but also a fiber sliding property of the
whole non woven fabric is improved and resultantly, the static
friction coefficient as a surface property is within a specific
range.
[0034] The fiber diameter of a polypropylene based resin spun
bonded non woven fabric constituting the multi layer non woven
fabric of the present invention is preferably from 10 to 30 .mu.m,
more preferably from 15 to 25 .mu.m. Here, when less than 10 .mu.m,
strength and bending resistance lower and secondary
processabilities lower in come cases, and its use field is
restricted significantly. While when over 30 .mu.m, flexibility,
feeling and skin tough feeling lower, and the features of the
present invention as a multi layer non woven fabric lose, and
particularly, application to absorptive articles, medical
materials, wrapping bodies and the like is difficult in some
cases.
[0035] The mass per unit area of the polypropylene based resin spun
bonded non woven fabric in the multi layer non woven fabric is
preferably from 5 to 40 g/m.sup.2, more preferably from 7 to 30
g/m.sup.2. Here, when the mass per unit area is less than 5
g/m.sup.2, strength is not sufficient, bending resistance is low,
and secondary processabilities are inferior in some cases, while
when over 40 g/m.sup.2, flexibility, gas permeability, skin touch
feeling and the like decrease, the features of the present
invention as a multi layer non woven fabric lose, and depending on
applications, use is difficult in some cases. This mass per unit
area of the polypropylene based resin spun bonded non woven fabric
is that when the spun bonded non woven fabric exists as a single
layer in the multi layer non woven fabric, and in the case of two
layers, the above mentioned mass per unit area is the sum of the
mass per unit area of the two layers.
[0036] The second feature of the multi layer non woven fabric of
the present invention is that the polypropylene based resin spun
bonded non woven fabric has a static friction coefficient of 0.1 to
0.4, preferably 0.12 to 0.35. Here, when the static friction
coefficient is less than 0.1, processabilities decrease due to
excess sliding in secondary processing, and because of decrease in
the static friction coefficient, the use amount of additives or
surface treatment agents generally adopted is required to be large,
deteriorating in economy, in some cases. Further, a connecting
property by heat seal, additives and the like in secondary
processing tends to decrease undesirably, in some cases. When over
0.4, an effect of improving use feelings such as flexibility,
feeling, skin touch feeling and the like is insufficient.
Polypropylene based resin spun bonded non woven fabrics can be
appropriately selected and combined based on applications in which
a multi layer non woven fabric is used, necessary conditions, gas
permeability, water resistance (non water permeability) and the
like.
[0037] The static friction coefficient of the surface of the multi
layer non woven fabric of the present invention can be measured
according to ASIM-D1894. Specifically, based on the following
measurement conditions:
[0038] Static friction coefficient measuring apparatus: AN type
manufactured by Toyo Seiki Seisakusho K.K.
[0039] Load plate: iron plate of 63.6 mm.times.102.2 mm.times.19.4
mm (height) and load: 8.87 N
[0040] Inclination speed: 2.7.degree./second,
[0041] measurement surfaces of non woven fabrics are mutually
overlaid, sliding angle (.theta.) is measured, tan .theta. is
measured, to give a static friction coefficient. When the numerical
value is smaller, a sliding property is more excellent.
[0042] The polypropylene based resin used in the polypropylene
based resin spun bonded non woven fabric used in the multi layer
non woven fabric of the present invention is not particularly
restricted, and listed are homopolymers of propylene, and
copolymers of propylene with at least one of .alpha.-olefins such
as ethylene, butene-1,4-methyl-pentene-1, hexane-1, octane-1 and
the like. As these polypropylene based resins, various resins
different in crystallinity, molecular weight and molecular weight
distribution are appropriately selected based on conditions
required for a non woven fabric, depending on selection,
polymerization conditions and the like of a catalyst in
polymerization. This selection is investigated from the standpoints
of the strength, flexibility, application and the like of a non
woven fabric, and as described above, there are used homopolymers
of propylene or polypropylene copolymers having a copolymerization
ratio of preferably 5 wt % or less, more preferably 3 wt % or less,
in view of a spinning property, flexibility, slimy feeling and the
like.
[0043] Here, regarding crystallinity, when a non woven fabric is
used as a material for absorptive article such as disposable
diapers and the like, the isotactic pentad fraction is preferably
selected in the range of from 88 to 95 mol %, more preferably from
89 to 93 mol %. Here, the isotactic pentad fraction (IPF) is an
isotactic pentad fraction in pentad unit in a polypropylene
molecule chain measured using nuclear magnetic resonance spectrum
(.sup.13C-NMR) by isotope carbon described, for example, in
"Macromolecules", vol. 28, no. 16, p. 5403 (1995).
[0044] The melt flow rate (MFR) [according to JIS K 7210,
measurement temperature: 230.degree. C., measurement load: 21.18 N]
of a polypropylene based resin is in the range of from 5 to 200
g/10 minutes, preferably from 10 to 100 g/10 minutes. Particularly,
as the absorptive article, those having a melt flow rate in the
range of from 30 to 80 g/10 minutes are suitable.
[0045] Next, the means for obtaining a polypropylene based resin
spun bonded non woven fabric having a static friction coefficient
of 0.1 to 0.4, which is a feature of the present invention, is not
particularly restricted, and various means are listed.
Specifically, these are roughly classified into (1) methods of
compounding a lubricant in a polypropylene based resin for
spinning, conducting melt spinning, then, effecting aging, (2)
methods of conducting surface treatment on fibers after spinning,
and the like, for example.
[0046] Here, the lubricant is not particularly restricted, and
there are mentioned fatty amide compounds, fatty acid compounds,
paraffin and hydrocarbon resins, silicone based compounds, silicone
based polymers, fluorine based compounds, fluorine based polymers
such as copolymers of tetrafluoroethylene with propylene,
copolymers of vinylidene fluoride with hexafluoropropylene, and the
like; or mixtures thereof. Of them, fatty amide compounds are
preferably used.
[0047] As the fatty amide compound, listed are fatty monoamide
compounds, fatty diamide compounds, saturated fatty monoamide
compounds, and unsaturated fatty diamide compounds. Specifically
listed are lauric amide, myristic amide, palmitic amide, stearic
amide, behenic amide, oleic amide, erucic amide, montanic amide,
N,N'-methylene-bis-lauric amide, N,N'-methylene-bis-myristic amide,
N,N'-methylene-bis-palmitic amide, N,N'-methylene-bis-behenic
amide, N,N'-methylene-bis-oleic amide, N,N'-methylene-bis-erucic
amide, N,N'-ethylene-bis-oleic amide, N,N'-ethylene-bis-erucic
amide and the like, and it is also possible to use two or more of
them in combination.
[0048] These fatty amide compounds, among them, erucic amide which
is an unsaturated fatty monoamide compound is preferably used. The
reason for this is that because of decrease in a spinning property
by unnecessary projection of a fatty amide onto the surface in melt
spinning of a non woven fabric, and of aging of a non woven fabric
containing a fatty amide compound described later, erucic amide is
suitable for decrease in the static friction coefficient of a non
woven fabric. The content of this fatty amide compound is in the
range of from 0.05 to 1 wt %, preferably from 0.1 to 0.7 wt % in a
polypropylene based resin. This content is determined by totally
judging the kind of a polypropylene based resin, resin properties
thereof such as crystallinity, MFR and the like, the kind of a
fatty amide compound, required conditions of the resulting non
woven fabric, aging conditions and the like.
[0049] Therefore, for example, as a homopolymer of propylene, the
isotactic pentad fraction is about 90 mol %, and when erucic amide
is used, it is in the range of from 0.1 to 1.0 wt %, preferably
from 0.2 to 0.6 wt %. In this case, depending on aging treatment
conditions, when less than 0.1 wt %, it may be difficult to control
the static friction coefficient of a non woven fabric in the range
from 0.1 to 0.4, and when over 1.0 wt %, the amount of erucic amide
on the surface of a non woven fabric increases, and deteriorations
in appearance such as white powder generation and the like and
decrease in a heat fusion property and secondary processabilities
are caused, in some cases.
[0050] In a polypropylene based resin, there can be added known
additive components generally used in non woven fabrics for
applications of a multi layer non woven fabric, endowment of
properties, and the like. As these known additive components,
listed are neutralization agents such as calcium stearate,
hydrotalcite and the like, phenol based, phosphorus based and
sulfur based antioxidants and the like, heat stabilizers,
nucleating agents, ultraviolet absorbers, light stabilizers,
antistatic agents, flame retardants, pigments, dyes, or inorganic
powders such as silica, talc, calcium carbonate, calcium oxide,
magnesium oxide and the like.
[0051] In one example of a method of producing a spun bonded non
woven fabric constituting the present invention, a polypropylene
based resin is melt spun with a mixture obtained by dry blending a
given amount of lubricant such as a fatty amide and the like with
additive components added if necessary.
[0052] The polypropylene based resin spun bonded non woven fabric
use in the multi layer non woven fabric of the present invention is
not particularly restricted, and can be produced by known various
production methods. For example, a primary non woven fabric can be
obtained by a known production method in which a polypropylene
based resin, raw material for the above mentioned compounding, is
melt extruded from an extrusion molding machine, spun through a
spinning mouth ring, and the spun fiber is drawn by a gas flow
traction apparatus such as an air sucker and the like, if
necessary, fibers are opened and fiber are collected by a web
collecting apparatus together with gas flow, and if necessary,
partially welded by heating means such as heated air, heat roll and
the like, particularly by a heat roll, then, taken.
[0053] As the bonding mode, heat adhesion such as emboss, calender,
hot air and the like, adhesion with adhesives, and mechanical
entangling such as needle punch, water punch and the like can be
adopted. However, heat adhesion by embossing is preferable from the
standpoint of productivity or the like.
[0054] This polypropylene based resin spun bonded non woven fabric
is usually a non woven fabric made of a polypropylene based resin
single body, and at least 50% or more of the outer surface of
fibers may also be a complex fiber non woven fabric made of a
polypropylene based resin.
[0055] These complex fiber non woven fabric can also be a complex
fiber of core sheath structure composed of a polypropylene based
resin as a sheath component and a resin other than the
polypropylene based resin, such as a polyamide based resin,
polyester based resin and the like, or a complex fiber of side by
side structure in which usually 50 wt % or more of fibers are made
of a polypropylene based resin and remaining parts are made of
other resins. This core sheath structure complex fiber and side by
side structure complex fiber may comprise a combination of two
different polypropylene based resins among polypropylene based
resins, of course.
[0056] Thus obtained primary non woven fabric is excellent in a
spinning property, however, depending on the kind of a lubricant,
particularly in the case of a fatty amide compound, it does not
itself a static friction coefficient specified in the non woven
fabric of the present invention, in some cases. In this case, for
controlling the static friction coefficient of a non woven fabric
in the range of from 0.1 to 0.4, it cannot be controlled in the
range of static friction coefficient specified in the present
invention until treatment of this non woven fabric under heat by an
aging treatment. In conventional non woven fabric production
apparatuses, such an aging apparatus is not incorporated, and aging
is not usually conducted.
[0057] Here, the aging treatment conditions vary depending on the
kind of a polypropylene based resin, resin properties thereof such
as crystallinity, density, melting point and the like, the kind of
a fatty amide compound contained, melting point and solubility in a
polypropylene based resin (compatibility) thereof, and the like.
Therefore, in view of the properties of a polypropylene based
resin, raw material for a non woven fabric and the properties of a
fatty amide compound as a lubricant, the static friction
coefficient is in the range from 0.1 to 0.4, and specifically
determined experimentally in view of properties such as
flexibility, feeling, skin tough feeling and the like required for
the final product, and bending resistance thereof.
[0058] For example, the polypropylene based resin spun bonded non
woven fabric used in the present invention is obtained by an aging
treatment at temperatures of 30 to 60.degree. C. for about 1 to 50
hours of a spun bonded non woven fabric obtained by melt spinning
of a polypropylene based resin containing a fatty amide
compound.
[0059] For example, the following aging treatment conditions can be
set specifically when a homopolymer of propylene is used, the
isotactic pentad fraction thereof is about 90 mol % and the content
of erucic amide is 0.4 wt %.
[0060] When the aging temperature is 40.degree. C., the aging time
is from about 5 to 50 hours, preferably from about 8 to 24 hours.
When the aging time is 24 hours, the aging temperature is from
about 32 to 50.degree. C., preferably from about 33 to 45.degree.
C. When the aging conditions are gentler than the above mentioned
ranges, decrease in static friction coefficient requires too much
time, leading to lowering of productivity, in some cases. When the
aging conditions are stricter than the above mentioned ranges, the
static friction coefficient increases conversely, being undesirable
in some cases.
[0061] This aging treatment can be usually conducted in an aging
room in which non woven fabrics are wound in the form of roll and
arranged on core tubes and heated air is circulated. In this aging,
even if non woven fabrics are wound in the form of roll, the non
woven fabric can get a uniform aging treatment effect due to the
gas permeability of the non woven fabric. Further, not in the
condition of wound non woven fabric, but aging can also be
conducted by roll heating and/or heated air while running between
rolls.
[0062] Next, another method of imparting a static friction
coefficient to the polypropylene based resin spun bonded non woven
fabric constituting the multi layer non woven fabric of the present
invention is a method of surface treating fibers of the resulting
non woven fabric by spinning. As the surface treatment agent, for
example, dimethylsiloxane, methylhydrogenpolysiloxane, fatty amide
containing compounds, and the like can be used. However, this
surface treatment has problems such as that treatment of inside is
impossible, and the like, depending on wet treatment processes,
drying processes and the thickness of a non woven fabric, and the
above mentioned method of melt mixing of a lubricant is preferable
in may cases depending on the form, application and the static
friction coefficient range of a non woven fabric, and the like.
[0063] The spun bonded non woven fabric made of a polypropylene
based resin constituting the non woven fabric laminate of the
present invention is usually hydrophobic, and depending on
applications of absorptive articles and the like, for example, in
the case of use as a top material of disposable diapers and
sanitary napkins, hydrophilicity is required for permeation of
water, in some cases. In this case, a non woven fabric cannot be
subjected to hydrophilicity imparting treatment.
[0064] Though this hydrophilicity imparting treatment includes
introduction of a hydrophilic group such as a carboxyl group and
the like by treatment with ozone, and surface treatment with a
hydrophilic compound, and from the standpoint of an effect,
treatment with a hydrophilic compound solution is preferable. As
the imparting treatment method, a spray method, coating method,
immersion method and the like are exemplified. As the hydrophilic
compound, for example, alkyl ester based compounds such as
polyhydric alcohols having 8 to 26 carbon atoms containing
polyoxyethylene, alkyl ether based compounds, fatty amide group
containing polyethers, fatty monoglycerides, sorbitan ester
derivatives, alkyl phosphate metal salts, alkyl sulfate metal
salts, polyoxyethylene alkyl ether sulfate metal salts, alkyl
sulfosuccinate metal salts, saccharide derivatives having a glucose
ring, and the like are exemplified.
[0065] The spun bonded non woven fabric made of a polypropylene
based resin can get remarkably improved touch feelings such as
flexibility, feeling, skin touch feeling and the like, and improved
use feeling while maintaining essential properties of a non woven
fabric of the polypropylene based resin itself, namely, strength,
heat resistance, bending resistance and the like, by decrease in
static friction coefficient by this aging treatment and surface
treatment.
[0066] Next, the polypropylene based resin melt blown non woven
fabric constituting the multi layer non woven fabric of the present
invention is a non woven fabric made of extremely fine fibers, and
usually made of fibers having a fiber diameter of 0.1 to 10 .mu.m,
preferably 0.2 to 6 .mu.m, and has a mass per unit area of 1 to 45
g/m.sup.2, preferably 2 to 30 g/m.sup.2. These fiber diameter and
mass per unit area significantly affect the moisture permeability,
gas permeability, water resistance of a multi layer non woven
fabric, the leak resistance of fine powders, and the like, and can
be appropriately selected within the above mentioned ranges so that
the required properties are satisfied by applications of the multi
layer non woven fabric. For example, in the case of a side gather
of disposable diapers, it is from 1 to 5 g/m.sup.2, and in the case
of a diaper back sheet and medical sheet, it is from 5 to 30
g/m.sup.2.
[0067] The polypropylene based resin melt blown non woven fabric
can be obtained by a known method in which heated gas flow of high
seed is blown to fine stream of a melt polypropylene based resin,
and by the action of this gas flow, the melted resin is drawn to
give extremely fine fibers which are collected to be made into a
sheet.
[0068] As the polypropylene based resin constituting this melt
blown non woven fabric, the above mentioned polypropylene based
resins used in the spun bonded non woven fabric can be used
likewise. This polypropylene based resin melt blown non woven
fabric cannot necessarily be specified easily, depending on the gas
permeability, moisture permeability and water preventing property
of a multi layer non woven fabric and applications of the multi
layer non woven fabric of the present invention, and in general,
the moisture permeability as the multi layer non woven fabric is
usually 1000 g/m.sup.2.multidot.24 hours or more, preferably 2000
g/m.sup.2.multidot.24 hours or more. The water preventing property
(water pressure resistance) is, though different depending on
applications thereof, 1 kPa or more, preferably 10 kPa or more.
[0069] The multi layer non woven fabric of the present invention is
composed of a plurality of layers of the specific polypropylene
based resin spun bonded non woven fabric and polypropylene based
resin melt blown non woven fabric as described above. The method of
laminating the both non woven fabrics is not particularly
restricted, and various methods can be adopted.
[0070] In the lamination method, usually, the above mentioned
polypropylene based resin spun bonded non woven fabric, for
example, having been subjected to the aging treatment and having a
static friction coefficient of 0.1 to 0.4 is laminated on and
adheres to the polypropylene based resin melt blown non woven
fabric so that the spun bonded non woven fabric is situated at
least one surface of the melt blown non woven fabric. However, in
some cases, it is also possible the laminate the spun bonded non
woven fabric and the melt blown non woven fabric before the aging
treatment. In this case, listed is an inline lamination method in
which, for example, in spinning a melt blown non woven fabric on a
spun bonded non woven fabric, and if necessary, further
continuously producing spun bonded non woven fabrics on this in a
several stages, a fatty amide is contained in the polypropylene
based resin for the spun bonded non woven fabric and a multi layer
non woven fabric is previously produced, then, this multi layer non
woven fabric is subjected to aging treatment.
[0071] As the lamination means for obtaining this multi layer non
woven fabric, various lamination means such as heat adhesion,
adhesion with adhesives and the like are mentioned, and there can
be adopted the above mentioned inline lamination heat adhesion
means which are simple and cheap, particularly, a heat emboss roll
method. In this heat emboss roll method, lamination can be
conducted using a known lamination apparatus having an emboss roll
and a flat roll. Here, as the emboss roll, emboss patterns of
various forms can be adopted, and lattice form in which fusion
parts are continuous, lattice form in which fusion parts are
dependent, arbitrary distribution and the like are mentioned. The
emboss area ratio is in the range of from about 5 to 40%. These
emboss patterns, emboss area ratio, temperature, pressure and the
like can be appropriately selected depending on the fiber diameter,
thickness, mass per unit area, layer ratio, gas permeability,
processing speed and the like of a non woven fabric.
[0072] In the dry laminate method, it is important to secure the
moisture permeability and gas permeability of the non woven fabric
laminate of the present invention at certain levels or more, and it
is necessary to control them by the coated amount of a hot melt
adhesive coated on the lamination surface, the existence ratio of
adhesion points, and the like. Specifically, the amount of a hot
melt adhesive is from 0.1 to 5 g/m.sup.2, and as the coating
method, it is preferable to adopt not a usual coating means but a
means capable of spraying in the form of fiber to give partial
adhesion. As the adhesive in this case, ethylene vinyl acetate
based adhesives, polyurethane based adhesives, polyester based
adhesives and the like are used. A method of coating an adhesive in
the form of patterns and conducting dry laminating can also be
adopted.
[0073] The multi layer non woven fabric of the present invention is
mainly composed of a polypropylene based resin spun bonded non
woven fabric, and specifically, spun bonded non woven fabric:melt
blown non woven fabric (mass per unit area) is 95:5 to 60:40,
preferably 90:10 to 75:25. Namely, the main part of the multi layer
non woven fabric is made of a spun bonded non woven fabric, and
flexibility, feeling and skin touch thereof are remarkably improved
by basic properties such as the strength, elastic modulus and the
like of a spun bonded non woven fabric and by complexing of a
slight proportion of melt blown non woven fabric.
[0074] The multi layer non woven fabric of the present invention
can also be made of two layers as described above. In this case,
however, the problems of surface conditions of a melt blown non
woven fabric still remain. For this, use positions and applications
thereof are naturally limited. Therefore, it is preferable to give
a three layer structure in which a melt blown non woven fabric is
sandwiched by spun bonded non woven fabrics. In this case,
depending on applications, the layer ratio of the spun bonded non
woven fabrics in the both outer layers can be appropriately
changed.
[0075] The multi layer non woven fabric of the present invention
can be made as a multi layer non woven fabric having various
properties by selection and combination of the kinds, mass per unit
area, thickness, gas permeability, moisture permeability and the
like of a polypropylene based resin spun bonded non woven fabric
and a polypropylene based resin melt blown non woven fabric.
Therefore, gas permeability, moisture permeability, water
preventing property and finer powder barrier resistance are
established simultaneously, and additionally, excellent properties
such as strength, flexibility, feeling, skin touch feeling and the
like and secondary processabilities because of excellent stiffness
are satisfied together, and development into various applications
is possible. Specifically, the multi layer non woven fabric can be
effectively used for back sheets and side gathers of absorptive
articles (hygienic articles) such as disposable diapers, sanitary
napkins, incontinence pads and the like, powder wrapping materials,
medical sheets and the like having functions such as moisture
absorbing agents, de-oxygen agents, de-odoring agents and the
like.
[0076] The multi layer non woven fabric of the present invention
will be illustrated in detail below based on one production
example, but the scope of the invention is not limited to the
examples.
EXAMPLE 1
Inline Production of Multi Layer Non Woven Fabric
[0077] As the non woven fabric production apparatus, that of multi
stage mode was used. Into 100 parts by weight of a crystalline
polypropylene resin [isotactic pentad fraction: 91 mol %, MFR: 60
g/10 minutes, melting point: 160.degree. C.] was dry blended 0.035
parts by weight of a phenol based antioxidant (manufactured by
Chiba Specialty Chemicals, Irganox 1010), 0.035 parts by weight of
a phosphorus based antioxidant (manufactured by Sand, Sandstub
P-EPQ), 0.025 parts by weight of a neutralization agent
(manufactured by Kyodo Yakuhin K.K., calcium stearate) and 0.4
parts by weight of erucic amide, by a super mixer, then, the
mixture was melt kneaded at 220.degree. C. using a 65 mm .phi.
extrusion molding machine, and extruded through a spinning mouth
ring, for melt spinning. The spinning mouth rings in this case have
a caliber of 0.3 mm and 200 rings were arranged along the width
direction and 15 rings were arranged along the extrusion
direction.
[0078] Then, the spun fibers were introduced into an air sucker and
traction stretched, and collected on a belt having a suction
apparatus. On this polypropylene spun bonded non woven fabric, a
melt blown non woven fabric was formed by the above mentioned
crystalline polypropylene resin containing no erucic amide, then,
further, on this was laminated the same polypropylene spun bonded
non woven fabric as described above, subsequently, transferred to a
heat emboss roller, and emboss adhered under emboss conditions
shown in Table 1, and taken on a paper tube, to obtain a primary
multi layer non woven fabric composed of three layers of spun
bonded non woven fabric/melt blown non woven fabric/spun bonded non
woven fabric.
[0079] The resulted taken multi layer non woven fabric was
subjected to aging treatment under aging conditions [temperature:
40.degree. C., 24 hours] to obtain a three layer non woven fabric
of the present invention. Thread cut and rolling were not found in
the spinning process, and an excellent spinning property was shown.
Further, controlling the spinning conditions, a three layer non
woven fabric was obtained composed of a spun bonded non woven
fabric [average fiber diameter: 17 .mu.m, mass per unit area: 7
g/m.sup.2] and a melt blown non woven fabric [average fiber
diameter: 1 .mu.m, mass per unit area: 3 g/m.sup.2] and having a
total mass per unit area of 17 g/m.sup.2. The multi layer non woven
fabric, production conditions are shown in table 1 and property
evaluation results and secondary processabily are shown in Table 2.
The evaluation of the multi layer non woven fabric was conducted
based on the following descriptions.
[0080] (1) Static Friction Coefficient
[0081] It was measured according to the static friction coefficient
measurement method of ASTM-D1894. For details, see the above
mentioned descriptions.
[0082] (2) Bending Resistance [Total of Longitudinal and
Transversal]
[0083] It was measured according to JIS L 1096 6. 19. 1 A method
(45.degree. cantilever method).
[0084] (3) Feeling
[0085] A functional test was conducted by skin tough and hand tough
by 20 monitors, and evaluated by .circleincircle., .largecircle.
and .DELTA.. In the functional test, the same three layer non woven
fabric using a usual spun bonded non woven fabric containing no
erucic amide (Comparative Example 1) was evaluated as .DELTA..
[0086] (4) Water Pressure Resistance
[0087] It was measured according to JIS L 1092 (high water pressure
method).
[0088] (5) Secondary Procesability
[0089] A hot melt type adhesive containing ethylene vinyl acetate
"H-6805" [manufactured by Nitta Findray K.K.] was sprayed in the
form of fiber on a polypropylene multi layer non woven fabric using
a fiber spray die of nozzle discharge mode so that the coating
amount was 4 g/m.sup.2. Then, on this, an inorganic filler
containing stretched PE moisture permeable film "Polam PU35"
(thickness: 35 .mu.m) manufactured by Tokuyama K.K. was pasted
overlapping to product a non woven fabric laminate. In establishing
this pasting, wrinkling, meandering and powdering was evaluated as
.DELTA. and processing without problems was evaluated as
.circleincircle..
COMPARATIVE EXAMPLE 1
[0090] A three layer non woven fabric was obtained in the same
manner as in Example 1 except that addition of erucic amide and
aging treatment were not conducted in Example 1. The multi layer
non woven fabric, production conditions according to Example 1 are
shown in Table 1, and the property evaluation results and secondary
processability are shown in Table 2.
COMPARATIVE EXAMPLE 2
[0091] Using the polypropylene based resin containing no erucic
amide used in Example 1, a single layer spun bonded non woven
fabric (no aging treatment) was obtained. The non woven fabric,
production conditions according to Example 1 are shown in Table 1,
and the property evaluation results and secondary processability
are shown in Table 2.
COMPARATIVE EXAMPLE 3
[0092] A single layer spun bonded non woven fabric (no aging
treatment) was obtained except that the fiber diameter and mass per
unit area were changed in Comparative Example 2. The non woven
fabric, production conditions are shown in Table 1, and the
property evaluation results and secondary processability are shown
in Table 2.
[0093] These results show that the present invention shows
significantly lowered bending resistance and significantly improved
flexibility, feeling and skin tough as compared with Comparative
Example 1. This is more than a non woven fabric obtained by
compounding a thermoplastic elastomer in fair amount into a
polypropylene based resin. Additionally, the secondary
processability is equivalent. In comparison with the single layer
spun bonded non woven fabric of Comparative Example 2, it is
apparent that when the fiber diameter is decreased, the bending
resistance can be decreased, however, simultaneous satisfaction
with the secondary processability is impossible. Further, in
comparison with Comparative Example 3, it is apparent that it is
necessary to maintain fiber diameter and mass per unit area at
certain levels for satisfying the secondary processbaility, and it
is apparent that it is difficult to satisfy the secondary
processability and flexibility, feeling and skin touch feeling
simultaneously by these methods.
1 TABLE 1 Layer Emboss conditions constitution Temperature * Mass
per Area (.degree. C.) Fiber diameter unit area ratio Pressure
Emboss side/ (.mu.m) (g/m.sup.2) % N/cm flat side Example 1 S/M/S
7/3/7 20 500 135/135 17/1/17 Comparative S/M/S 7/3/7 20 500 135/135
example 1 17/1/17 Comparative S 17 20 500 130/130 example 2 14
Comparative S 18 20 500 135/135 example 3 18 * S: spun bonded non
woven fabric M: melt blown non woven fabric
[0094]
2 TABLE 2 Bending Water Static resistance(mm) pressure Secondary
friction Longi- Trans- Feel- resistance process- coefficient
tudinal versal Total ing mmH.sub.2O ability Example 1 0.29 42 39 81
.circleincircle. 105 .circleincircle. Comparative 0.60 65 35 100
.DELTA. 108 .circleincircle. example 1 Comparative 0.55 43 20 63
.circleincircle. 60 .DELTA. example 2 Comparative 0.62 57 38 95
.DELTA. 68 .circleincircle. example 3
INDUSTRIAL APPLICABILITY
[0095] The multi layer non woven fabric obtained by complexing a
spun bonded non woven fabric and a melt blown non woven fabric,
made of polypropylene based resins can be suitably used for various
applications, particularly, back sheet materials and side gather
materials for absorptive articles such as disposable diapers,
sanitary napkins and the like, and for medical materials, powder
wrapping materials and the like.
* * * * *