U.S. patent application number 08/973533 was filed with the patent office on 2002-02-07 for non-woven fabric comprising staple fibers and an absorbent article using the same.
This patent application is currently assigned to CHISSO CORPORATION. Invention is credited to HIRABAYASHI, SHIGERU, NAGANO, KOKI.
Application Number | 20020016120 08/973533 |
Document ID | / |
Family ID | 26499651 |
Filed Date | 2002-02-07 |
United States Patent
Application |
20020016120 |
Kind Code |
A1 |
NAGANO, KOKI ; et
al. |
February 7, 2002 |
NON-WOVEN FABRIC COMPRISING STAPLE FIBERS AND AN ABSORBENT ARTICLE
USING THE SAME
Abstract
A non-woven fabric comprising staple fibers, having a fiber
length of 3 to 25 mm and a single fiber fineness of 1 to 100
denier, and is produced by the fibers being dropped while being
dispersed to be accumulated and adhered at the intersection point
of the staple fibers. The non-woven fabric has a specific volume of
40 to 200 cm.sup.3/g, and the number of fiber lumps having a volume
of not less than 1 mm.sup.3 is not more than 5 lumps per 20 g of
the non-woven fabric. The bulky non-woven fabric of the present
invention in which the sufficient contribution to bulkiness by
fibers is exhibited is suitable for sanitary materials, such as
disposable diapers, sanitary napkins, incontinence pads, nursing
pads or the like, or wipes etc.
Inventors: |
NAGANO, KOKI; (SHIGA,
JP) ; HIRABAYASHI, SHIGERU; (SHIGA, JP) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
CHISSO CORPORATION
OSAKA
JP
|
Family ID: |
26499651 |
Appl. No.: |
08/973533 |
Filed: |
December 10, 1997 |
PCT Filed: |
June 16, 1997 |
PCT NO: |
PCT/JP97/02073 |
Current U.S.
Class: |
442/352 ; 19/296;
442/353; 442/356; 442/357; 442/364; 442/409 |
Current CPC
Class: |
D04H 1/5412 20200501;
Y10T 442/633 20150401; Y10T 442/632 20150401; D04H 1/5418 20200501;
Y10T 442/69 20150401; D04H 1/62 20130101; Y10T 442/629 20150401;
D04H 1/54 20130101; D04H 1/5414 20200501; Y10T 442/627 20150401;
Y10T 442/641 20150401 |
Class at
Publication: |
442/352 ;
442/356; 442/357; 442/353; 442/364; 442/409; 19/296 |
International
Class: |
D04H 001/00; D04H
001/54 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 1996 |
JP |
8-179964 |
Dec 11, 1996 |
JP |
8-351863 |
Claims
1. A non-woven fabric comprising staple fibers, which comprises at
least one kind of staple fiber having a fiber length of 3 to 25 mm
and a single fiber fineness of 1 to 100 denier, and is produced by
said fibers being dropped while being dispersed to be accumulated
and adhered at the intersection point of the staple fibers; said
non-woven fabric has a specific volume of 40 to 200 cm.sup.3/g, a
number of fiber lumps having a volume of not less than 1 mm.sup.3
is not more than 5 lumps per 20 g of said non-woven fabric.
2. The non-woven fabric comprising staple fibers according to claim
1, wherein the fiber length of the staple fiber is in the range of
5 to 10 mm.
3. The non-woven fabric comprising staple fibers according to claim
1, wherein at least one kind of staple fiber is a staple fibers
having 3 to 20 crimps/inch (2.54 cm) of spiral type crimps.
4. The non-woven fabric comprising staple fibers according to claim
1, wherein at least one kind of staple fiber in the fabric is a
thermoplastic fiber.
5. The non-woven fabric comprising staple fibers according to claim
1, wherein at least one kind of staple fiber is olefin
thermoplastic fiber or polyester thermoplastic fiber.
6. The non-woven fabric comprising staple fibers according to claim
1, wherein at least one kind of staple fiber is a thermoplastic
conjugated staple fiber having a component which is capable of a
thermal adhesion to said fiber.
7. The non-woven fabric comprising staple fibers according to claim
1, wherein at least one staple fiber is a staple fiber having an
eccentric core and sheath type structure comprising high
crystalline polypropylene as a core component and high density
polyethylene as a sheath component.
8. An absorbent article using a non-woven fabric comprising staple
fibers according to any one of claims 1 to 7.
Description
TECHNICAL FIELD
[0001] The invention relates to a non-woven fabric comprising
staple fibers. More specifically, it relates to a non-woven fabric
comprising staple fibers, which is suitable for sanitary materials
such as disposable diapers, sanitary napkins, incontinence pads,
nursing pads or the like, or wipers, and to absorbent articles
using the non-woven fabric comprising staple fibers.
BACKGROUND ART
[0002] Hitherto, as this kind of non-woven fabric comprising staple
fibers, Japanese Patent Publication No. Sho 52-12830 discloses a
non-woven fabric produced by a process wherein thermal adhesive
conjugated fibers are aligned by the use of a carding machine and
then piled up and entangled to be adjusted to the predetermined
basis weight, followed by conducting a thermal adhesion between
fibers by a thermal treatment.
[0003] However, the above mentioned conventional non-woven fabrics
lose the bulkiness of the non-woven fabric contributed by fibers,
because the fibers of the non-woven fabric are arranged in the
machine direction by combing fibers with a card clothing having
needles of the carding machine. Therefore, the bulky non-woven
fabrics in which the sufficient contribution by fibers is exhibited
have not been produced, and the conventional non-woven fabrics are
not always satisfactory.
[0004] The object of the present invention is to provide a bulky
non-woven fabric in which the sufficient contribution to bulkiness
by fibers of the non-woven fabric is exhibited.
DISCLOSURE OF INVENTION
[0005] The non-woven fabric comprising staple fibers of the present
invention and the absorbent article using the non-woven fabric of
the present invention are as follows.
[0006] (1) A non-woven fabric formed of staple fibers, which
comprises at least one kind of staple fiber having a fiber length
of 3 to 25 mm and a single fiber fineness of 1 to 100 denier, and
is produced by the fibers being dropped and dispersed to be
accumulated and adhered at the intersection point of each staple
fiber; the non-woven fabric has a specific volume of 40 to 200
cm.sup.3/g, the number of fiber lumps having a volume of not less
than 1 mm.sup.3 is not more than 5 lumps per 20 g of the non-woven
fabric.
[0007] (2) The non-woven fabric comprising staple fibers according
to the above item (1), wherein the fiber length of the staple fiber
is in the range of 5 to 10 mm.
[0008] (3) The non-woven fabric comprising staple fibers according
to the above item (1), wherein at least one kind of staple fiber is
a staple fibers having 3 to 20 spiral type crimps per inch (2.54
cm).
[0009] (4) The non-woven fabric comprising staple fibers according
to the above item (1), wherein at least one kind of staple fiber is
a thermoplastic fiber.
[0010] (5) The non-woven fabric comprising staple fibers according
to the above item (1), wherein at least one kind of staple fiber is
olefin thermoplastic fiber or polyester thermoplastic fiber.
[0011] (6) The non-woven fabric comprising staple fibers according
to the above item (1), wherein at least one kind of staple fiber is
a thermoplastic conjugated staple fiber having a component which is
capable of thermal adhesion as one component.
[0012] (7) The non-woven fabric comprising staple fibers according
to the above item (1), wherein at least one staple fiber is a
staple fiber having an eccentric core and sheath type structure
comprising high crystalline polypropylene as a core component and
high density polyethylene as a sheath component.
[0013] (8) An absorbent article using the non-woven fabric
comprising staple fibers according to any one of the above items
(1) to (7).
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a side elevational view of an apparatus for
producing the non-woven fabric of the present invention.
[0015] FIG. 2 is a partial cutaway view of an air laid apparatus 1
of the apparatus shown in FIG. 1.
[0016] FIG. 3 is a cross sectional view taken on line E-E' of the
apparatus according to FIG. 2.
BEST MODE FOR CARRYING OUT THE INVENTION
[0017] As the fibers used for the non-woven fabric comprising
staple fibers of the present invention, the following examples can
be mentioned: natural fibers such as pulp, cotton and the like;
regenerated fibers such as rayon; semi synthetic fibers such as
acetate; and synthetic fibers such as nylon, vinylon, polyester,
acrylic, polyethylene, polypropylene, polystyrene and the like. The
fibers used for the non-woven fabric of the present invention are
not particularly limited as long as they are adhered in a case
where binders are used and they do not give an adverse effect on
the uniformity of the non-woven fabric. However, thermal adhesive
thermoplastic fibers being capable of thermal adhesion between
fibers at the intersection points in a short time, without using
powder-like binders that fall in the form of small particles or
water soluble binders that need to be dried, are preferable.
[0018] The fiber length of the staple fiber constituting the
non-woven fabric comprising staple fibers of the present invention
needs to be in the range of 3 to 25 mm. Preferably, it is in the
range of 3 to 15 mm, more preferably, in the range of 5 to 10 mm.
In particular, in the case of the spiral type crimps, the number of
crimps is approximately 5 crimps per inch (2.54 cm). Therefore, the
appropriate fiber length is 5 mm which corresponds to the length of
once winding of crimp and 10 mm which corresponds to the length of
twice winding of crimps. If the fiber length is less than 3 mm, the
strength of the non-woven fabric lowers. Moreover, if the fiber
length is more than 25 mm, it is difficult to produce a uniform
web, because fibers are entangled with each other before passing
through a sieve or a screen.
[0019] The fiber thickness is in the range of 1 to 100 denier,
preferably in the range of 1.5 to 35 denier. More preferably, it is
in the range of 1.5 to 20 denier. If the fiber thickness is less
than 1 denier, the density of the fiber in the cylindrical screen
increases, so that a uniform web cannot be produced. On the other
hand, if the fiber thickness is more than 100 denier, the ability
of fibers to entangle each other becomes strong, so that it is
difficult to produce a uniform web.
[0020] The specific volume of the non-woven fabric comprising
staple fibers of the present invention is in the range of 40 to 200
cm.sup.3/g. Preferably, it is in the range of 70 to 150 cm.sup.3/g.
It is not preferable for the specific volume of the non-woven
fabric to be less than 40 cm.sup.3/g, since the non-woven fabric
becomes hard. Also, it is not preferable for the specific volume of
the non-woven fabric to be more than 200 cm.sup.3/g, since the
strength of the non-woven fabric is lowered.
[0021] Moreover, in the non-woven fabric comprising staple fibers
of the present invention, the number of fiber lumps having a volume
of not less than 1 mm.sup.3 is not more than 5 lumps per 20 g of
the non-woven fabric. It is not preferable for the fiber lumps of
such size included in the non-woven fabric to be more than the
above mentioned range, since there arise some disadvantages: the
non-woven fabric becomes not-uniform, has a rough touch and becomes
non-uniform in the coloring due to fiber lumps.
[0022] In a case where the fibers used for the non-woven fabric of
staple fibers of the present invention are conjugated fibers
comprising at least two components (hereinafter, the component (A)
and the component (B) will be used for an abbreviation), the below
mentioned resins etc. can be used as materials.
[0023] As resins of the component (A), the following can be used:
polyolefins such as polypropylene, high density polyethylene,
medium density polyethylene, low density polyethylene, linear low
density polyethylene, binary copolymer or terpolymer of propylene
with other -.alpha.-olefin and the like; polyamides; polyesters
such as polyethylene terephthalate, polybutylene terephthalate, low
melting point polyester from copolymerizing diol and terephthalic
acid / isophthalic acid etc., polyester elastomer and the like;
fluororesin; the mixture of the above mentioned resins; other
resins that can be spun.
[0024] As resins of the component (B), the following can be used:
polyolefins such as polypropylene, high density polyethylene,
medium density polyethylene, low density polyethylene, linear low
density polyethylene, binary copolymer or terpolymer of propylene
with other .alpha.-olefin and the like; polyamides; polyesters such
as polyethylene terephthalate, polybutylene terephthalate, low
melting point polyester from copolymerizing diol and terephthalic
acid / isophtalic acid etc., polyester elastomer and the like;
fluororesin; the mixture of the above mentioned resins; other
resins that can be spun.
[0025] It is preferable that the difference in the melting point
between the component (A) and the component (B) is not less than
10.degree. C. Consequently, when the thermal treatment is conducted
at the temperature not less than the melting point of the low
melting point component and less than the melting point of the high
melting point component, the low melting point component of the
conjugated fiber melts and the high melting point component remains
as it is. As a result, the thermal adhesive non-woven fabric having
a three dimensional network structure can be formed. Moreover, in
the above, when the melting point is not clearly determined, the
melting point denotes the softening point. The measurement of the
softening point is conducted under the conditions specified in JIS
K 2531.
[0026] As the combination examples of the resin component (A) and
(B), the following examples can be mentioned: high density
polyethylene/polypropyl- ene, low density
polyethylene/propylene-ethylene-butene-1 crystalline terpolymer,
high density polyethylene/polyethylene terephthalate, nylon 6/nylon
66, low melting point polyester/polyethylene terephthalate,
polypropylene/polyethylene terephthalate, polyvinylidene
fluoride/polyethylene terephthalate, the mixture of linear low
density polyethylene and high density polyethylene/polyethylene
terephthalate and the like.
[0027] It is preferable that a thermoplastic conjugated fiber
comprises olefin resin or polyester resin, or the combination
thereof. As the combination examples of such resin components (A)
and (B), the following examples can be mentioned: high density
polyethylene/polypropylene, low density
polyethylene/propylene-ethylene-butene-1 crystalline terpolymer,
high density polyethylene/polyethylene terephthalate, low melting
point polyester/polyethylene terephthalate,
polypropylene/polyethylene terephthalate, linear low density
polyethylene/polyethylene terephthalate and the like.
[0028] The shapes of the conjugated fiber are not limited and can
be a core and sheath type, an eccentric core and sheath type, a
side-by-side type, a multi-layer type having three layers or more,
a hollow multi-layer type, a modified (non-circular) multi-layer
type etc. and other structures in which the low melting point resin
component forms at least one part of the fiber surface.
[0029] The preferable combination of the component constituting the
conjugated fibers and the shape is: the thermoplastic conjugated
fiber having an eccentric core and sheath type structure comprising
high crystalline polypropylene as a core component and high density
polyethylene as a sheath component and having spiral type crimps. A
fiber having spiral type crimps has much space per a single fiber,
so that a web formed by piling up fibers has a very high
bulkiness.
[0030] The bulkiness of the web depends much on the number of
crimps of the thermoplastic fibers used for a non-woven fabric. In
particular, it is preferable that the thermoplastic fiber has 3 to
20 spiral type crimps per an inch (2.54 cm). Herein, "3 to 20
crimps per an inch (2.54 cm)" denotes that 3 to 20 crimps are
included in an inch (2.54 cm) of fiber length. Preferably, it is a
fiber having 5 to 15 spiral type crimps per an inch (2.54 cm), more
preferably it is a fiber having 5 to 10 spiral type crimps per an
inch (2.54 cm). Preferably, the non-woven fabric using fibers
having the above mentioned range of number of crimps has high
bulkiness. If the number of the spiral type crimps is considerably
less than 3 crimps per an inch (2.54 cm), the fiber is not
different from the straight type fiber and the bulkiness tends to
be lowered. On the other hand, in a case where the spiral type
crimps are far more than 20 crimps per an inch (2.54 cm), the space
per a single fiber becomes small, and thus the bulkiness of the
non-woven fabric conversely tends to be reduced.
[0031] In the above mentioned conjugated fiber, the composition
ratio of the low melting point component to high melting point
component is: the low melting point resin component is in the range
of 10 to 90 wt. % and the high melting point resin component is in
the range of 90 to 10 wt. %. More preferably, the low melting point
resin component is in the range of 30 to 70, wt. % and the high
melting point resin component is in the range of 70 to 30 wt. %. If
the low melting point component is less than 10 wt. %, the tensile
strength of the thermal adhesive non-woven fabric comprising
conjugated fibers tends to be reduced. On the other hand, if the
low melting point component is more than 90 wt. %, too little core
component remains without melting, so that the bulkiness of the
thermal adhesive non-woven fabric comprising conjugated fibers
tends to be reduced.
[0032] In the case of the straight type staple fibers, the
non-woven fabric has a uniformity, but does not have the high
bulkiness, thus making the non-woven fabric very flat. As a result,
the applicability as commercial products is reduced. However, in a
case where the staple fiber having actual crimps is used, the
non-woven fabric having a high bulkiness can preferably be
produced.
[0033] As the shape of the crimps of staple fibers used for the
non-woven fabric comprising staple fibers, the following examples
can be mentioned: spiral (three dimensional crimps) type crimps,
zig-zag type crimps, wave type crimps or the like. The staple
fibers having any of the above mentioned shapes of crimps can be
applied to a non-woven fabric comprising staple fibers of the
present invention. The most preferable crimp is a spiral type
crimp.
[0034] In a case where the shape of crimps of staple fiber is the
spiral type crimps, fibers are not entangled with each other so
much and the bulkiness of the resultant non-woven fabric becomes
very high. This tendency is remarkably found when a fiber has the
above mentioned preferable range of fiber length and the shape of
the spiral is approximately circular.
[0035] In a case where the shape of crimps of staple fiber is the
zig-zag type crimps, the larger the number of the crimps is, the
more securely and deeply the crimps are set. As a result, the
bulkiness of the resultant non-woven fabric is higher. However, if
the number of the crimps is far more than the above mentioned
preferable range, fibers tend to be easily entangled with each
other and an uniform non-woven fabric is not obtained.
[0036] In a case where the shape of crimps of staple fiber is the
wave type crimps, the tendency of the fibers to entangle is more
remarkable, so that large fiber lumps generate and easily cause the
blocking of a sieve or screen. Consequently, the production of the
non-woven fabric becomes difficult.
[0037] However, with any type of crimp, unless the number of crimps
or the fiber length is much different from the above mentioned
preferable range, the effect of the present invention is not
harmed.
[0038] In a case where webs are produced by the use of the
conventional carding machine, fibers are entangled and then the
webs are drawn, so that the bulkiness of the web is reduced.
Therefore, as the preferable embodiment of the present invention,
methods in which a web is not drawn are to be sought. One example
of such methods is: the method in which a web is produced by fibers
that are dropped while being dispersed to be accumulated. In the
method in which fibers are successively dropped with dispersion to
be accumulated, fibers are not drawn with being entangled, and
therefore the bulkiness of the fiber itself is not lost. The
non-woven fabric in which the sufficient contribution to bulkiness
by fibers is exhibited can be produced.
[0039] In a case where webs are produced by fibers being dropped
with dispersion to be accumulated, if the fibers are long, a
uniform dispersion is difficult and the resultant non-woven fabric
has a coarse density. On the other hand, if fibers are short, a
uniform dispersion is easily obtained, and the non-woven fabric
without coarse density can be produced. Moreover, one of the
methods to enhance a uniform dispersion of fibers is to make fibers
pass through a sieve or screen. In a case where fibers are made to
pass through a sieve or screen, even staple fibers are entangled
before passing the screen or sieve and the fiber lumps of the
entangled fibers pass through the screen and are piled up in the
non-woven fabric. As a result, the resultant non-woven fabric is
sometimes not-uniform and includes fiber lumps. The non-woven
fabric contaminated with fiber lumps sometimes has a rough touch
and non-uniform coloring due to the subtle reflecting property of
the fiber lumps.
[0040] There are staple fibers that are easily entangled and staple
fibers that are less easily to be entangled. If classified, the
staple fibers having a zig-zag type crimps and having a large
number of crimps and/or having high crimp set force tend relatively
to be easily entangled. Moreover, the staple fibers having the wave
type crimps with fish-hook shaped ends tend to be easily entangled.
The staple fibers having the spiral type crimps are particularly
preferable since their ends of fibers are approximately on the same
circumference and are not easily entangled.
[0041] A fiber lump that gives an adverse effect on the uniformity
of the non-woven fabric is divided into two types: one is the
entangled fibers and another is the portion where the fibers are
not sufficiently opened. In the not-opened portions, individual
fibers are spaced closely after the opening step. Therefore, the
effective method for preventing the generation of fiber lumps is to
space each fiber less closely. Specifically, not-opened portions
can be reduced by selecting a shape of crimps. When the shape of
crimps is the wave type, fibers are easily dispersed and few
not-opened portions are generated as compared with the zig-zag type
crimps. Furthermore, when the shape of crimps is the spiral type,
fibers are easily be dispersed and few not-opened portions are
generated as compared with the wave type crimps. In other words,
the entanglement of fibers and generation of the not-opening
portion can be inhibited by selecting the shape of crimps.
[0042] In other words, the object of the present invention, namely
to provide the bulky non-woven fabric in which sufficient
contribution to bulkiness by fibers is exhibited, can be attained
by producing the non-woven fabric in the following way: a web is
produced by making short fibers pass through a sieve or screen and
dropped with uniform dispersion in three dimensions to be
accumulated, and by thermally adhering the intersection point of
each fiber by thermal treatment.
[0043] In the non-woven fabric produced by the method of making
fibers pass through a sieve or screen, fibers are dropped with
dispersion in three dimensions to be accumulated. Such non-woven
fabric has a greater specific volume as compared with the non-woven
fabric in which fibers are aligned in one direction by the carding
machine. The non-woven fabric having a large specific volume has a
soft touch and is particularly suitable for products that directly
contact the users' skin, for example, absorbent articles of
disposable diapers, sanitary napkins or the like. Moreover, since
the high specific volume denotes the high bulkiness and high
cushioning property, such non-woven fabric is preferably used for
applications that requires a cushioning property, for example,
bandage or eye bandage, table linen, cooking towel, packing
materials for glass or ceramics, packing materials for fresh
products and flowers, packing materials for instruments and
furniture and the like.
[0044] The thermal adhesive conjugated fibers used for the
non-woven fabric comprising staple fibers of the present invention
can be produced by, for example, the following step.
[0045] Resins for a core component and a sheath component are
melted and discharged from, for example, the composite spinneret
having 100 to 350 holes. At this time, unstretched fibers are
cooled by cooling just below the spinneret. Unstretched fibers of 3
to 400 denier are produced by taking up at the discharging volume
of 100 to 200 g/min and at the taking up speed of 40 to 1300 m/min.
The unstretched fibers are stretched between the two rollers heated
at temperatures of 60 to 120.degree. C., while making the rotating
speed of the second roll greater than that of the first roll.
Stretched fibers of 1 to 100 denier are produced by stretching with
the ratio of the rotating speed of the first roll to the second
roll in the range of 1:2 to 1:5. Finishing agents are applied to
the stretched fibers by using a contact roller, followed by making
the stretched fibers pass through a box-type crimp processor to
produce a tow having crimps. It is preferable that the number of
crimps is 0 to 25 crimps per an inch. Since the tow contains
approximately 10 wt. % of water, it is dried by the use of a drier
at 60 to 120.degree. C. The dried tow is cut with a push-cutting
type cutter into fibers having the constant length ranging from 3
to 25 mm. Such fiber length is substantially shorter than fibers
used for the non-woven fabric produced by the conventional carding
process.
[0046] At the time of producing the non-woven fabric, a plurality
of forming heads are used and the non-woven fabric having a
different fineness or a different shape of staple fiber is used at
each forming head. Consequently, the non-woven fabric having a
density gradient in the thickness direction can be produced. The
non-woven fabric having a density gradient in the thickness
direction, produced by the above mentioned method, can be used as
non-woven fabric materials for filters, such as a liquid filter, an
air filter etc.
[0047] When the non-woven fabric comprising staple fibers produced
by the above mentioned method is used for absorbent articles such
as disposable diapers, they can be used for a non-woven fabric as a
surface material, second sheet, or back layer material sheet. In
particular, since the non-woven fabric comprising staple fibers has
a high bulkiness, it is preferably used for the second sheet that
requires the high bulkiness. Moreover, the non-woven fabric
comprising mixture of pulp, thermal adhesive fibers and high
absorptive materials is preferably used as absorbent articles which
do not lose shape when absorbing urine.
[0048] The non-woven fabric comprising staple fibers of the present
invention can be produced as follows with staple fibers having a
fiber length of 3 to 25 mm and by the use of the air laid type
apparatus.
[0049] As shown in FIG. 1 to FIG. 3, an air laid type apparatus
comprises: a casing 2 having a trapezoidal shaped cross section and
having an opening portion in its bottom face only; fiber feeding
openings 3 and 4 which are provided at both ends of the casing 2;
web forming heads 5 and 6 corresponding to the feeding openings 3
and 4, comprising cylindrical screens 5a and 6a which are
positioned parallel to the side face of the casing 2 and are
capable of rotating; needle rolls 5b and 6b which are provided in a
way to contact each inner wall of the cylindrical screens 5a and
6a, and fiber circulation zones 7 and 8 which are respectively
provided at the both ends of cylindrical screens 5a and 6a and at
the both ends of the casing 2. A net conveyor 9a is provided just
below the lower face of the air laid type apparatus. A pair of
drive rolls 17a and 17b and a suction unit 10 are attached to the
net conveyor 9a. Moreover, an apparatus for carrying out the next
step in the air laid type apparatus comprises: a suction drier 12
for thermally adhering the conjugated fibers constituting a web, a
net conveyor 9b which makes the web pass through the suction drier
12, a pair of drive rolls 17c and 17d for driving the net conveyor
9b thereunder; and a pressing roll 11 on the drive roll 17c across
the net conveyor 9b. Moreover, a feed roll 18 for feeding the
produced thermal adhesive non-woven fabric 14 and a pair of drive
rolls 19a and 19b for driving a take-up roll 14 are provided.
[0050] In the above mentioned apparatus, staple fibers are
mechanically opened by the use of an opening apparatus (not shown)
and then are fed to the fiber feeding circulation duct connected to
the fiber inserting openings 3 and 4. At this time, the fiber
bundle is nearly dissolved. Fibers 15 which are fed into the fiber
inserting openings 3 and 4 are mixed and circulated while moving in
the passage formed by cylindrical screens 5a and 6a and circulating
zones 7 and 8 in the direction of arrows C1, C2, C3, and C4 and in
the direction of arrows D1, D2, D3, and D4 of FIG. 2. The
circulated fibers are discharged through the rotating cylindrical
screens 5a and 6a by means of centrifugal force and shearing effect
generated by both the rotations of the needle rolls 5b and 6b
rotating in the direction of arrow AA' and the cylindrical screens
5a and 6a rotating in the direction of arrow BB'. The discharged
fibers are sucked by the use of the suction unit 10 from the lower
portion of the casing 2 and are collected on the net conveyor 9a.
The collected web 16 is pressed between the web pressing roll 11
and the drive roll 17c of the net conveyor 9b. At this time, the
collected fibers are oriented in random directions and form a
web.
[0051] The web 16 is pressed by using the pressing roll 11 and
provided to the suction drier 12 and then thermally treated at a
temperature not less than the melting point of the low melting
point component and not more than the melting point of the high
melting point component, for example, in the range of 90 to
170.degree. C., for 3 to 10 seconds. By this thermal treatment, the
low melting point component of the conjugated fiber is melted and
the high melting point component of the conjugated fiber remains as
it is. Thus, the thermal adhesive non-woven fabric 13 having a
three dimensional network structure is formed and taken up by the
take-up roll 14.
[0052] In order to arrange the air carried staple fibers more
randomly, the production method of making the staple fibers pass
through a sieve or net which comprises a wide variety of mesh is
conducted. Specifically, it is preferable that the method of making
the staple fibers pass through a screen with dispersion to be
accumulated is conducted.
[0053] The shape of holes of the screen of the cylindrical screens
5a and 6a is generally a laterally longer rectangle. It is
preferable that the laterally longer rectangle having the
longitudinal length of which is 1 to 3 mm and the lateral length of
which is 15 to 30 mm. The shape of the holes is not limited to a
laterally longer rectangle and may be circle, triangle, quadrangle,
polygon and oval besides a laterally longer rectangle. It is
preferable that the rate of the hole area of the screen is 20 to
50%. By selecting the above mentioned hole shape and the rate of
hole area, a uniform web can be produced.
[0054] Among the non-woven fabrics comprising staple fibers of the
present invention, the non-woven fabric comprising thermal adhesive
conjugated fibers is thermally adhered in the intersection point of
each fiber by thermal treatment using the suction drier 12 after
the formation of web. This thermal treatment may be conducted by
the use of heating apparatus such as a thermal calendar roll etc.
instead of the suction drier 12. The basis weight of the resultant
non-woven fabric is not particularly limited. However, it is
preferable that the basis weight is about 10 to 1000 g/m.sup.2. In
the case of surface materials for disposable diapers, the basis
weight is about 10 to 60 g/m.sup.2; in the case of wipes, about 10
to 500 g/m.sup.2; in the case of filters, about 10 to 1000
g/m.sup.2. Moreover, the apparent density of the non-woven fabric
is not particularly limited. However, it is preferably about 0.017
to 0.10 g/cm.sup.3 when the hand feeling is taken into
consideration.
[0055] The non-woven fabric having higher density can be produced
by carrying out a thermal pressing process or thermal rolling
process or the like as an after-processing treatment.
[0056] In a case where the thermal adhesive non-woven fabric
comprising staple fibers of the present invention is thermally
adhered at the intersection point of each fiber by the use of a
thermal calendar roll, it is preferable to make the rate of the
thermo-compression area be in the range of 10 to 30%. By selecting
the above range of the rate of thermo-compression area, the
non-woven fabric which is excellent in resistance against falling
off of fibers and strength and has a soft hand feeling and touch
can easily be provided.
[0057] The non-woven fabrics comprising staple fibers of the
present invention can be used for a wide variety of applications by
themselves, or after being laminated, sewn, or thermally adhered
with another material. For example, when they are used as a member
of pants type disposable diapers, they can be used for the portion
where both hand feeling and strength are required, for example, as
front surface materials, back sheets etc. As a matter of course,
when the non-woven fabric is used for the pants type disposable
diapers and the like, they can be used in combination with other
members or thermal adhesive non-woven fabric such as a stretchable
and contractable material for closely contacting with the trunk or
legs portions. Moreover, the thermal adhesive non-woven fabric can
be used as cover materials of the above mentioned front surface
materials or back surface materials or the like, by laminating
other non-woven fabric or tissue papers, webs, films or the
like.
[0058] The non-woven fabric comprising staple fibers of the present
invention can be used as wipes for furniture, cars and the like by
applying various kinds of lubricant.
[0059] Further, the non-woven fabric comprising staple fibers can
be made into filter materials by subjecting the non-woven fabrics
to an after-processing treatment such as a pleat processing,
forming into a cylindrical shape, winding the thermal adhesive
non-woven fabric to form into a cylindrical shape, and winding
while heating to form into a thermally adhered cylindrical
shape.
[0060] Hereinafter, the present invention will be further described
by referring to the Examples but is not limited to them alone.
[0061] The definition of values of the physical properties etc. of
the thermal adhesive non-woven fabric in the Examples and the
measuring method for determining the values are as follows.
[0062] The specific volume of the non-woven fabric comprising
staple fibers of Table 1 is determined and measured in the below
mentioned method.
[0063] (1) Specific Volume
[0064] The basis weight and the thickness of the non-woven fabric
were measured and the value calculated by the following equation
was defined as the specific volume.
Specific Volume=(Y.times.100.times.100)/X
[0065] wherein X denotes the basis weight of the non-woven fabric
(g/m.sup.2) and Y denotes the thickness of the non-woven fabric
(cm).
[0066] Moreover, the size of the non-woven fabric sample used
herein was 25 cm.times.25 cm.
[0067] The number of the fiber lumps of the non-woven fabric
comprising staple fibers of Table 1 was determined and measured by
the below mentioned method.
[0068] (2) Number of Fiber Lumps
[0069] The number of fiber lumps having a volume not less than 1
mm.sup.3 existing in 20 g of the non-woven fabric was defined as
the number of fiber lumps.
[0070] However, ten pieces of 20 g of non-woven fabric were sampled
and the average value of each number of fiber lumps observed in
each sample was defined as the number of fiber lumps.
[0071] (3) Hand Feeling and Appearance of Non-Woven Fabric
[0072] Five panelists evaluated the hand feeling of the non-woven
fabric in the viewpoints of uniformity, a rough feeling, and
non-uniformity in the color phase, the color phase becoming
non-uniformity due to the fiber lumps. The hand feeling and
appearance of the non-woven fabric were judged based on the
following standards. When three or more panelists evaluated that
the non-woven fabric had at least one defect among the following
items: that is, the non-woven fabric had a non-uniformity; the
non-woven fabric had a rough feeling; and the non-woven fabric is
not uniform in color phase, then the hand feeling was regarded as
"bad". In any other cases, the hand feeling of the non-woven fabric
was judged as "good".
EXAMPLE 1
[0073] A method for producing a non-woven fabric where rayon staple
fibers and thermal adhesive fibers are mixed and the intersection
points of fibers are adhered by thermal treatment:
[0074] 40 wt. % of rayon fibers having 12 zig-zag type crimps per
inch (2.54 cm), the fiber fineness of 1.5 d/f and the fiber length
of 5 mm (hereinafter, the expression like "1.5 d/f.times.5 mm" will
be used for an abbreviation) and 60 wt. % of an eccentric core and
sheath type conjugated fiber comprising polypropylene as a core
component and high density polyethylene as a sheath component,
having 7 spiral type crimps per inch (2.54 cm) and being 3
d/f.times.5 mm were fed into and made to pass through an opening
apparatus and thereby fibers were opened mechanically. Then, the
opened fibers were fed into an air laid type apparatus shown in
FIG. 1 to FIG. 3 and treated therein. Specifically, rayon fibers
and thermal adhesive fibers 15, which were made to pass through the
opening apparatus, were inserted into the fiber insertion openings
3 and 4 by way of the fiber feeding circulation duct and discharged
from the rotating cylindrical screens 5a and 6a. The discharged
fibers were collected on the net conveyor 9a having the suction
apparatus 10 moving at the speed of 90 m/min to form the web 16.
After the web 16 was compressed with the web compressing roll 11,
it was thermally treated at 150.degree. C. for three seconds by the
use of the suction drier 12, and thereby high density polyethylene
of the sheath component was melted and adhered to produce the
non-woven fabric 13. Then the non-woven fabric 13 was taken up into
the take-up roll 14.
[0075] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 3.6 mm,
specific volume of 143 cm.sup.3/g, and the number of the fiber
lumps of 2.1 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 2
[0076] A method for producing thermal adhesive staple fibers:
[0077] High crystalline polypropylene having MFR (melt flow rate)
of 11 g per 10 minutes (the conditions 14 specified in JIS K7210)
as a core component and high density polyethylene having MI (melt
index) of 16.5 g per 10 minutes (the conditions 4 specified in JIS
K7210) were spun out of an eccentric core and sheath type spinneret
having 621 holes at the discharging ratio of high crystalline
polypropylene to high density polyethylene of 5:5 and at the
discharging volume of 450 g/min, and then taken up at the speed of
592 m/min to produce 11 denier unstretched fibers. When spinning
was conducted, fibers were cooled by air cooling just below the
spinneret, and then finishing agent comprising lauryl phosphate
potassium salt as a main component was applied by using a contact
roll.
[0078] This unstretched fiber was stretched between the first roll
and the second roll to produce a stretched fiber having the
fineness of 3 denier and spiral type crimps. At this time, the
first roll was 90.degree. C. and the second roll was 20.degree. C.,
and the rotating ratio of the first roll to the second roll was set
to be 1:4.5. This stretched fiber having spiral type crimps was cut
into fibers of 5 mm in length by using the push-cutting type
cutter.
[0079] Hereinafter, the method for producing a non-woven fabric
comprising the thermal adhesive fibers will be explained.
[0080] The conjugated fibers were fed into and made to pass through
an opening apparatus and opened mechanically, and then treated by
feeding the opened fibers to the air-laid type apparatus shown in
FIG. 1 to FIG. 5. Specifically, the opened conjugated fiber 18 was
fed into the fiber inserting openings 3 and 4 by way of the fiber
feeding circulation duct and discharged from the rotating
cylindrical screen 5a and 6a. The discharged fibers were collected
on the net conveyor 9a having the suction apparatus 10 moving at
the speed of 90 m/min to form into the web 16. After the web was
compressed with the web compressing roll 11, it was thermally
treated at 150.degree. C. for three seconds by the use of suction
drier 12, and thereby high density polyethylene of a sheath
component was melted and adhered to produce the non-woven fabric
13. Then the non-woven fabric 13 was taken up by the take-up roll
14.
[0081] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 4.6 mm,
specific volume of 185 cm.sup.3/g, and the number of the fiber
lumps of 1.2 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 3
[0082] The non-woven fabric was produced under the same conditions
as Example 2 except that the fiber length of the conjugated fiber
was made to be 10 mm.
[0083] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 4.4 mm,
specific volume of 176 cm.sup.3/g, and the number of the fiber
lumps of 1.9 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 4
[0084] The non-woven fabric was produced under the same conditions
as Example 2 except that the fiber length of the conjugated fiber
was made to be 15 mm.
[0085] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 4.25 mm,
specific volume of 170 cm.sup.3/g, and the number of the fiber
lumps of 3.8 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 5
[0086] A method for producing the non-woven fabric using polyester
staple fibers and side-by-side type conjugated fiber: 30 wt. % of
polyester fibers having 14 zig-zag type crimps per inch (2.54 cm),
and being 2 d/f.times.5 mm and 70 wt. % of side-by-side type
conjugated fibers comprising a polypropylene component and a high
density polyethylene component, having 6 spiral type crimps per
inch (2.54 cm) and being 2 d/f.times.5 mm were fed into and made to
pass through an opening apparatus, thus opening the fibers
mechanically. Then, the opened fibers were fed into an air laid
type apparatus shown in FIG. 1 to FIG. 3 and treated therein.
Specifically, the opened polyester fibers and side-by-side type
conjugated fibers 15 were inserted into the fiber insertion
openings 3 and 4 by way of the fiber feeding circulation duct and
discharged from the rotating cylindrical screens 5a and 6a. The
discharged fibers were collected on the net conveyor 9a having the
suction apparatus 10 moving at the speed of 90 m/min to form into
the web 16. After the web was compressed with the web compressing
roll 11, it was thermally treated at 150.degree. C. for three
seconds by the use of the suction drier 12, and thereby high
density polyethylene of the sheath component was melted and adhered
to produce the non-woven fabric 13. Then the non-woven fabric 13
was taken up by the take-up roll 14.
[0087] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 3.4 mm,
specific volume of 137 cm.sup.3/g, and the number of the fiber
lumps of 2.2 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 6
[0088] A method for producing thermal adhesive staple fibers:
[0089] The non-woven fabric was produced under the same conditions
as Example 2 except that high crystalline polypropylene having MFR
of 11 g per 10 minutes (the conditions 14 specified in JIS K7210)
and high density polyethylene having MI of 16.5 g per 10 minutes
(the conditions 4 specified in JIS K7210) were spun out of a
side-by-side type composite spinneret having 621 holes at the
discharging ratio of high crystalline polypropylene to high density
polyethylene of 5:5 and at the discharging volume of 450 g/min, and
then taken up at the speed of 592 m/min to produce 8.1 denier
unstretched fibers.
[0090] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 4.5 mm,
specific volume of 181 cm.sup.3/g, and the number of the fiber
lumps of 1.3 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 7
[0091] Fibers were produced under the same conditions as Example 6
except that the number of holes of the spinneret was 60, the
discharging volume was 200 g/min, the taking-up speed was 417
m/min, the unstretched fiber was 72 denier, the stretched fiber was
18 denier and the number of spiral crimps was 6 crimps per inch
(2.54 cm).
[0092] The conditions for producing non-woven fabrics were made to
be the same as Example 5.
[0093] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 3.9 mm,
specific volume of 156 cm.sup.3/g, and the number of the fiber
lumps of 0.5 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 8
[0094] A method for producing thermal adhesive staple fibers:
[0095] Polypropylene having MFR of 16 g per 10 minutes (the
conditions 14 specified in JIS K7210) as a core component and high
density polyethylene having MI of 16.5 g per 10 minutes (the
conditions 4 specified in JIS K7210) were spun out of a core and
sheath type spinneret having 621 holes at the discharging ratio of
high crystalline polypropylene to high density polyethylene of 5:5
and at the discharging volume of 450 g/min and taken up at the
speed of 919 m/min, to thus produce 7.1 denier of unstretched
fibers. When spinning was conducted, fibers were cooled by air
cooling just below the spinneret.
[0096] This unstretched fiber was stretched between the first roll
and the second roll to form 2 denier stretched fiber. At this time,
the first and second rolls were heated at 90.degree. C.
respectively and the rotating ratio of the first roll to the second
roll was set to be 1:4. A finishing agent comprising lauryl
phosphate potassium salt as a main component was applied to this
stretched fiber by using a contact roll. Then, they were made to
pass through a box type crimp processing apparatus to produce a tow
having 14 zig-zag type crimps per inch.
[0097] Since this tow contained a water component, it was dried at
the temperature of 90.degree. C. by using a drier and then it was
cut into fibers of 10 mm in length by using a push-cutting type
cutter.
[0098] The conditions for producing the non-woven fabrics were made
to be the same as Example 5.
[0099] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 2.8 mm,
specific volume of 79 cm.sup.3/g, and the number of the fiber lumps
of 4.5 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 9
[0100] A method for producing the thermal adhesive fibers
comprising staple fibers:
[0101] 114 denier of unstretched fibers were produced by the use of
a spinneret having 60 holes by taking up at the discharging volume
of 200 g/min and at the taken-up speed of 263 m/min, then they were
produced into 32 denier stretched fibers. Thermally adhesive
conjugated fibers were produced under the same conditions as
Example 8 except that 10 crimps per inch of zig-zag type crimps
were provided and the fiber length was 10 mm.
[0102] The conditions for producing a non-woven fabric were made to
be the same as Example 5.
[0103] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 2.6 mm,
specific volume of 45 cm.sup.3/g, and the number of the fiber lumps
of 3.6 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 10
[0104] Fibers were produced under the same conditions as Example 8
except that 340 denier unstretched fibers were produced by the use
of a spinneret having 100 holes by taking up at the discharging
volume of 200 g/min and at the taken-up speed of 53 m/min while
cooling the fibers with water at the time of spinning, then they
were produced into 100 denier stretched fibers, and the 10 zig-zag
type crimps per inch were provided and the fiber length was 25
mm.
[0105] The conditions for producing a non-woven fabric were made to
be the same as Example 5.
[0106] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 2.65 mm,
specific volume of 58 cm.sup.3/g, and the number of the fiber lumps
of 2.4 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 11
[0107] A method for producing thermal adhesive staple fibers:
[0108] High crystalline polypropylene having MFR of 11 g per 10
minutes (the conditions 14 specified in JIS K7210) as a core
component and high density polyethylene having MI of 16.5 g per 10
minutes (the conditions 4 specified in JIS K7210) as a sheath
component were spun out of a core and sheath type spinneret having
621 holes at the discharging ratio of high crystalline
polypropylene to high density polyethylene of 5:5 and at the
discharging volume of 350 g/min, and then taken up at the speed of
995 m/min to produce 5.1 denier of unstretched fibers. When
spinning was conducted, fibers were cooled by air cooling just
below the spinneret.
[0109] The unstretched fibers were stretched between the first roll
and the second roll. At this time, the first roll was heated at
90.degree. C. and the second roll was heated at 20.degree. C. and
the rotating ratio of the first roll to the second roll was set to
be 1:4.5. After a finishing agent comprising lauryl phosphate
potassium salt as a main component was applied to this stretched
fiber by using a contact roll, they were made to pass through a
box-type crimps processing apparatus to produce a tow having 9 wave
type crimps per inch. The stretched fibers having wave type crimps
were cut into fibers of 5 mm in length by using a push-cutting type
cutter.
[0110] The conditions for producing the non-woven fabric were made
to be the same as Example 5.
[0111] As to the physical properties, the resultant non-woven
fabric had a basis weight of 23 g/m.sup.2, a thickness of 3.75 mm,
specific volume of 163 cm.sup.3/g, and the number of the fiber
lumps of 1.8 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 12
[0112] A method for producing the thermal adhesive staple
fibers:
[0113] Polypropylene having MFR of 10 g per 10 minutes (the
conditions 14 specified in the JIS K7210) and polypropylene having
MI of 23 g per 10 minutes (the conditions 14 specified in the JIS
K7210) were spun out of a side-by-side type spinneret having 350
holes at the discharging ratio of each polypropylene of 5:5 and at
the discharging volume of 200 g/min, and then taken up at the speed
of 635 m/min to produce 8.1 denier unstretched fibers. When
spinning was conducted, fibers were cooled by air cooling just
below the spinneret. A finishing agent containing lauryl phosphate
potassium salt as a main component was applied by using a contact
roll.
[0114] The unstretched fibers were stretched between the first roll
and the second roll to produce 2 denier stretched fibers having
spiral type crimps. At this time, the first roll was heated at
90.degree. C. and the second roll was heated at 20.degree. C. and
the rotating ratio of the first roll to the second roll was set to
be 1:4.5. The unstreteched fiber having spiral type crimps was cut
into fibers of 10 mm in length by using a push-cutting type
cutter.
[0115] The conditions for producing the non-woven fabric were made
to be the same as Example 5.
[0116] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 3.25 mm,
specific volume of 130 cm.sup.3/g, and the number of the fiber
lumps of 1.4 lumps per 20 g. The results are shown in Table 1.
EXAMPLE 13
[0117] A method for producing the thermal adhesive staple
fibers:
[0118] High crystalline polyethylene terephthalate having the
intrinsic viscosity of 0.68 dl/g as a core component and high
density polyethylene having MI of 16.5 g per 10 minutes (the
conditions 4 specified in JIS K 7210) as a sheath component were
spun out of a core and sheath type spinneret having 621 holes at
the discharging ratio of high crystalline polyethylene
terephthalate to high density polyethylene of 5:5 and at the
discharging volume of 450 g/min and taken up at the speed of 1035
m/min to produce 6.3 denier unstretched fibers. When spinning was
conducted, fibers were cooled by air cooling just below the
spinneret.
[0119] The unstretched fibers were stretched between the first roll
and the second roll. At this time, the first and second rolls were
heated at 90.degree. C. respectively and the rotating ratio of the
first roll to the second roll was set to be 1:3.3. A finishing
agent comprising lauryl phosphate potassium salt as a main
component was applied to the stretched fibers by using a contact
roll. Then, they were made to pass through a box-type crimps
processing apparatus to produce a tow having 5 wave type crimps per
an inch (2.54 cm). The stretched fiber having wave type crimps was
cut into fibers of 10 mm in length by using a push-cutting type
cutter.
[0120] The conditions for producing the non-woven fabrics were made
to be the same as Example 5.
[0121] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 3.0 mm,
specific volume of 101 cm.sup.3/g, and the number of the fiber
lumps of 2.6 lumps per 20 g. The results are shown in Table 1.
Comparative Example 1
[0122] The non-woven fabric was produced under the same conditions
as Example 2 except that the fiber length was 38 mm and a carding
apparatus was used at the time of production of a web.
[0123] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 0.9 mm,
specific volume of 36 cm.sup.3/g, and the number of the fiber lumps
of 0.9 lumps per 20 g.
[0124] The resultant non-woven fabric had a smaller specific volume
as compared with other Examples, because of the non-woven fabric
produced by the carding process. The results are shown in Table
1.
Comparative Example 2
[0125] The non-woven fabric was produced under the same conditions
as Example 2 except that the fiber length was 30 mm.
[0126] As to the physical properties, the resultant non-woven
fabric had a basis weight of 25 g/m.sup.2, a thickness of 2.75 mm,
specific volume of 110 cm.sup.3/g, and the number of the fiber
lumps of 8.5 lumps per 20 g.
[0127] The non-woven fabric was produced by an air laid method.
[0128] However, the fiber length was longer than 25 mm, so that
fibers are easily entangled and the resultant non-woven fabric had
many fiber lumps. Therefore, the resultant non-woven fabric was
inferior in uniformity; had a rough touch; and had not uniformed
hue, namely, many white portions were found remarkably in the
non-woven fabric due to fiber lumps. Therefore, this non-woven
fabric was evaluated as bad in hand feeling and appearance. The
results are shown in Table 1.
EXAMPLE 14
[0129] In a commercially available disposable diaper having roughly
an "I" shape in a plan view like the side cross sectional shape of
a rail of railway, only the front surface material of the paper
diaper was replaced by the thermal adhesive non-woven fabric
substantially prepared in Example 2.
[0130] The commercially available disposable diaper comprised; a
front surface material which was produced from the non-woven fabric
comprising polyethylene/polypropylene thermal adhesive conjugated
staple fibers and the intersection points of the fibers were
thermally adhered; a water absorptive material comprising a pulp
and high absorptive resin as main components; and back surface
material comprising polyethylene film. Only the front surface
material was cut off with a knife and removed, followed by
laminating the thermal adhesive non-woven fabric obtained in the
above mentioned Example 3 to the same place where the front surface
material had been placed. Moreover, the thermal adhesive non-woven
fabric and the remaining non-woven fabric which was located near
the leg portions were thermally adhered. Further, the remaining
thermal adhesive non-woven fabric was cut off with scissors and
removed, to thus produce a disposable diaper in which thermal
adhesive non-woven fabric was laminated as a front surface
material. This diaper had a great strength in the lateral direction
(opposite to the longitudinal direction) of the non-woven fabric, a
high bulkiness and soft hand feeling, and was usable for a
preferable disposable diaper.
1 TABLE 1 Fiber Specific Number of Number of Denier Length Volume
Fiber Lumps Crimps Crimps Hand Feeling d/f mm cm.sup.3/g Lumps/20 g
shape Crimps/2.54 cm Appearance Example 1 3 5 143 2.1 spiral 7 good
1.5 5 zig-zag 12 Example 2 3 5 185 1.2 spiral 7 good Example 3 3 10
176 1.9 spiral 8 good Example 4 3 15 170 3.8 spiral 7 good Example
5 2 5 137 2.2 spiral 6 good 2 5 zig-zag 14 good Example 6 2 5 181
1.3 spiral 7 good Example 7 18 5 156 0.5 spiral 6 good Example 8 2
10 79 4.5 zig-zag 14 good Example 9 32 3 45 3.6 zig-zag 12 good
Example 10 100 25 58 2.4 zig-zag 10 good Example 11 1.5 5 163 1.8
wave 9 good Example 12 2 10 130 1.4 spiral 8 good Example 13 2 10
101 2.6 zig-zag 5 good Comparative 3 38 36 0.9 spiral 7 good
Example 1 Comparative 3 30 110 8.5 spiral 7 bad Example 2
[0131] As is apparent from Table 1, by selecting the denier, the
fiber length, the shape of crimps and the number of crimps of the
present invention, the non-woven fabric having a high bulkiness
well contributed to the fibers and little generation of fiber
lumps, and having good surface properties can be obtained. In
addition, the fiber length of the fiber used for the thermal
adhesive non-woven fabric of the present invention was shorter than
that of the non-woven fabrics produced by the carding method.
Consequently, as the number of fibers constituting fabric
increases, uneven dispersion of the fibers was prevented to thus
produce a uniform non-woven fabric. Moreover, since the non-woven
fabric of the present invention is produced by fibers being fallen
with dispersing to accumulate, the non-woven fabric of the present
invention has smaller density and greater ventilation degree as
compared with the non-woven fabric produced by the carding process
in which fibers are combed and oriented in one direction.
[0132] The non-woven fabric comprising staple fibers of the present
invention is produced by short fibers being dropped while being
dispersed to be accumulated. As a result, this non-woven fabric
overcomes the defects: the non-woven fabric produced by the carding
process lose the bulkiness because fibers are drawn, to thus
provide the non-woven fabric having a high bulkiness and
softness.
[0133] In addition, the non-woven fabric comprising staple fibers
of the present invention has shorter fiber length than the
non-woven fabric produced by the carding process, so that fibers
are laminated in a random dispersion state. As a result, the
uniform non-woven fabric having little non-uniformity in the
density can be obtained. Moreover, the non-woven fabrics are
produced by fibers which are dropped with dispersion in the three
dimensional direction to be accumulated, so that it has a smaller
density, higher ventilation, more excellent soft feeling and touch
as compared with the non-woven fabric produced by the carding
process in which fibers are carded and oriented.
Industrial Applicability
[0134] As the effects mentioned above, the non-woven fabric of the
present invention has a soft feeling and is particularly suitable
for such application as directly contacts with users' skin, for
example, absorbent articles for disposable diapers, sanitary
napkins, incontinence pads, nursing pads or the like. Moreover,
since the non-woven fabric of the present invention has a high
specific volume, high bulkiness and an excellent cushioning
property, it is preferably used for applications that require an
excellent cushioning property, for example, bandage or eye bandage,
or table linen, cooking towel, packing materials for glass
ceramics, packing materials for fruits and vegetables and flowers,
packing materials for instruments and furniture etc. The non-woven
fabric having a density inclination in the thickness direction
produced by the above mentioned method can be used as non-woven
fabric materials for filters, such as a liquid filter, an air
filter etc.
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