U.S. patent application number 09/220223 was filed with the patent office on 2002-01-17 for nonwoven fabric and method for making same.
Invention is credited to KOBAYASHI, TOSHIO, SUZUKI, MIOU, TAKEUCHI, NAOHITO.
Application Number | 20020006760 09/220223 |
Document ID | / |
Family ID | 26580898 |
Filed Date | 2002-01-17 |
United States Patent
Application |
20020006760 |
Kind Code |
A1 |
KOBAYASHI, TOSHIO ; et
al. |
January 17, 2002 |
NONWOVEN FABRIC AND METHOD FOR MAKING SAME
Abstract
A nonwoven fabric suitable to be used as a kitchen paper
including thermoplastic synthetic fibers being 7.about.30 mm long
and as fine as of 0.1.about.0.8 d, in 90.about.10% by weight and
pulp fibers being 2.about.7 mm long, in 10.about.90% by weight,
these component fibers being mixed together as homogeneously as
possible and mechanically entangled so as to have a basis weight of
10.about.80 g/m.sup.2 as a whole.
Inventors: |
KOBAYASHI, TOSHIO;
(KAGAWA-KEN, JP) ; SUZUKI, MIOU; (KAGAWA-KEN,
JP) ; TAKEUCHI, NAOHITO; (KAGAWA-KEN, JP) |
Correspondence
Address: |
Baker & Daniels
111 East Wayne Street, Ste. 800
Fort Wayne
IN
46802
US
|
Family ID: |
26580898 |
Appl. No.: |
09/220223 |
Filed: |
December 23, 1998 |
Current U.S.
Class: |
442/351 ;
162/146; 162/157.1; 162/201; 162/222; 162/223; 442/344;
442/400 |
Current CPC
Class: |
D04H 1/495 20130101;
Y10T 428/24479 20150115; Y10T 428/24636 20150115; Y10T 442/689
20150401; Y10T 428/24628 20150115; D21F 11/00 20130101; D21H 25/005
20130101; Y10T 442/68 20150401; Y10T 442/619 20150401; Y10T 442/626
20150401; D04H 1/56 20130101; D21H 13/10 20130101 |
Class at
Publication: |
442/351 ;
442/344; 442/400; 162/146; 162/157.1; 162/201; 162/222;
162/223 |
International
Class: |
D04H 001/56; D04H
013/00; D21F 011/00; D21H 017/00 |
Claims
What is claimed is:
1. A nonwoven fabric containing thermoplastic synthetic
microfibers, said nonwoven fabric comprising: thermoplastic
synthetic fibers being 5.about.30 mm long and as fine as of
0.1.about.0.8 d, in 90.about.10% by weight, mixed and mechanically
entangled with pulp fibers being 2.about.7 mm long, in 10.about.90%
by weight, so as to have a basis weight of 10.about.80 g/m.sup.2 as
a whole.
2. A nonwoven fabric according to claim 1, wherein said
thermoplastic synthetic fibers preferably is melt blown fibers.
3. A nonwoven fabric according to claim 1, wherein said nonwoven
fabric is a kitchen paper or wipe-out sheet.
4. A method for making nonwoven fabric containing thermoplastic
synthetic microfibers, said method comprising the steps of: a.
obtaining a wet sheet from slurry containing 0.5.about.20% by
weight of a fibrous mixture dispersed in water, said fibrous
mixture comprising, in 90.about.10% by weight, thermoplastic
synthetic fibers being 7.about.30 mm long and as fine as of
0.1.about.0.8 d mixed with pulp fibers being 2.about.7 mm long, in
10.about.90% by weight; and b. placing said wet sheet on a support
and then subjecting said wet sheet to high velocity water jet
streams of 50.about.200 kgf/cm.sup.2 for mechanically entangling
said fibrous mixture.
5. A method according to claim 4, wherein said thermoplastic
synthetic fibers preferably is melt blown fibers.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to nonwoven fabrics well adapting
itself to embossing and suitable for use as water-absorbent kitchen
papers, wipe-out sheets, etc. as well as a method for making such
nonwoven fabric.
[0002] It is well known to emboss/deboss nonwoven fabrics
comprising a mixture of thermoplastic synthetic fibers having a
fineness of 1.about.10 d and thereby to form an emboss/a deboss
pattern thereon so that the nonwoven fabric may be used as
water-absorbent kitchen papers or wipe-out sheets.
[0003] However, it is not necessarily easy to form irregularities
thereon by embossing the kitchen papers or the like of the prior
art because the synthetic fiber has relatively high rigidity and
elasticity. This is true particularly when it is desired to form
fine or distinctly contoured embosses/debosses.
[0004] When it is attempted to feed a web of nonwoven fabric
through an embossing machine and thereby to obtain kitchen papers
formed with apertures each having a diameter in order of 5 mm or
less, individual fibers may often extend from the aperture
periphery into this aperture, resulting in the indistinctly
contoured aperture. Probably, it is for the reason that the
individual fibers can not be smoothly rearranged around each of
projections provided on the embossing machine sufficiently to form
the desired distinctly contoured aperture. The smaller a diameter
of the aperture and/or the larger a basis weight of a nonwoven
fabric is, the greater this problem becomes. While it is obvious
that the individual fibers extending into the aperture lead to a
substantial reduction of the aperture s diameter, a degree of such
reduction is not necessarily uniform. This makes a proper design of
the aperture difficult. Accordingly, it is required for nonwoven
fabric used as material for kitchen papers or the like to have a
sufficiently high formability to facilitate formation of
embosses/debosses or apertures.
SUMMARY OF THE INVENTION
[0005] In view of the problem as has been described above, it is an
object of the invention to provide a nonwoven fabric having a
sufficiently high formability to facilitate formation of
embosses/debosses or apertures when such nonwoven fabric is
intended to be used as material for kitchen papers or the like, on
one hand, and to provide a method for making such nonwoven
fabric.
[0006] According to a first aspect of the invention, there is
provided a nonwoven fabric containing thermoplastic synthetic
microfibers, the nonwoven fabric comprising synthetic microfibers
being 5.about.30 mm long and as fine as of 0.1.about.0.8 d, in
90.about.10% by weight, mixed and mechanically entangled with pulp
fibers being 2.about.7 mm long, in 10.about.90% by weight, so as to
have a basis weight of 10.about.80 g/m.sup.2 as a whole.
[0007] According to the first aspect of the invention, melt blown
fibers are preferably selected as the thermoplastic synthetic
fibers.
[0008] According to a second aspect of the invention, there is
provided a method for making a nonwoven fabric containing
thermoplastic synthetic microfibers, the method comprising the
steps of:
[0009] a. obtaining a wet sheet from slurry containing
0.5.about.20% by weight of a fibrous mixture dispersed in water,
the fibrous mixture comprising thermoplastic synthetic fibers being
7.about.30 mm long and as fine as of 0.1.about.0.8 d, in
90.about.10% by weight, mixed with pulp fibers being 2.about.7 mm
long, in 10.about.90% by weight; and
[0010] b. placing the wet sheet on a support and then subjecting
the wet sheet to high velocity water jet streams of 50.about.200
kgf/cm.sup.2 for mechanically entangling the fibrous mixture.
[0011] According to the second aspect of the invention, melt blown
fibers are preferably selected as the thermoplastic synthetic
fibers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a plan view of a nonwoven fabric according to the
invention;
[0013] FIG. 2 is a perspective view of a kitchen paper made of the
nonwoven fabric according to the invention;
[0014] FIG. 3 is a diagram schematically illustrating the steps of
a method for making the nonwoven fabric; and
[0015] FIG. 4 is a perspective view of a drum used in the
method.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] Details of a nonwoven fabric and a method for making the
nonwoven fabric will be more fully understood from the description
given hereunder with reference to the accompanying drawings.
[0017] FIG. 1 is a plan view of a nonwoven fabric. The nonwoven
fabric 1 has a basis weight of 10.about.80 g/m.sup.2 and the
nonwoven fabric 1 comprises thermoplastic synthetic fibers 3 being
7.about.30 mm long and as fine as of 0.1.about.0.8 d, in
90.about.10% by weight, and pulp fibers 4 (e.g., NBKP), in
10.about.90% by weight. These fibers 3, 4 are mixed with each other
as homogeneously as possible so that they are mechanically
entangled to maintain the form of a nonwoven fabric. Individual
fibers are randomly distributed or slightly oriented in the machine
direction during a manufacturing process of the nonwoven fabric 1
as will be described later. It should be understood that none of
binding agents such as poval is employed in making the nonwoven
fabric.
[0018] FIG. 2 is a perspective view of a nonwoven fabric 1A having
a plurality of protuberances 51 obtained by embossing or depossing
the nonwoven fabric of FIG. 1, which is adapted to be used as a
kitchen paper. As seen in FIG. 2, the nonwoven fabric 1A is formed
with the protuberances 51 having a height h and arranged at a pitch
y in the longitudinal direction and at a pitch x in the transverse
direction. The height h is in a range of 0.2.about.5 mm and the
pitches y, x are in a range of 1.about.10 mm. While the synthetic
fibers 3 and the pulp fibers 4 are observed to be slightly oriented
so far as regions defined from bases toward crests of the
respective protuberances 51 are concerned, they are randomly
distributed in regions defined between each pair of the adjacent
protuberances 51 just as in the nonwoven fabric of FIG. 1.
[0019] FIG. 3 is a diagram exemplarily illustrating the steps of
the inventive method for making the nonwoven fabric 1 and the
kitchen paper 1A obtained therefrom. The method starts from the
left in FIG. 3. Slurry containing 0.5.about.20% by weight of the
fibrous mixture which comprises, in turn, the thermoplastic
synthetic fibers 3 and the pulp fibers 4 at a weight ratio of
10:90.about.90:10 is supplied through a feed pipe 11 to a slurry
tank 12. From the slurry tank 12, slurry is then fed onto a first
endless belt 13 in a suction zone 14 in which the first endless
belt 13 describes a rightward ascending slope. In the suction zone
14, the slurry is dehydrated by a vacuum pump 16 and thereby a wet
sheet 17 is obtained. The wet sheet 17 is then subjected, in a
first zone 18, to high velocity water jet streams injected from a
first nozzle 19 to stabilize a texture of the wet sheet 17 which is
then transferred to a rotary drum 23 installed in a second zone 22.
The amount of water injected in the first zone 18 is drawn by a
suction mechanism 20. In the second zone 22, the wet sheet 17
supported on a smooth surface of the rotary drum 23 is subjected to
high velocity water jet streams injected from a second nozzle 24 to
ensure that component fibers of the wet sheet 17 are mechanically
entangled together. Now the wet sheet 17 is transferred to a second
endless belt 28 and subjected, in a third zone 26, to high velocity
water jet streams injected from a third nozzle 27. Thereafter, the
wet sheet 17 is dehydrated and dried by dehydrator/drier means 29
to obtain a nonwoven fabric 31. As will be apparent, the nonwoven
fabric 31 may be cut into an appropriate size to obtain the
nonwoven fabric 1 of FIG. 1. If desired, the nonwoven fabric 31 may
be further transported so as to pass between a pair of embossing
rolls 32, 33. The embossing roll 32, one of these rolls, is formed
on its peripheral surface with forming elements 34 comprising a
plurality of conical or pyramidal projections so that a continuous
sheet of kitchen paper 1A having the protuberances 51 as shown in
FIG. 2 is obtained as the forming elements 34 are pressed against
the nonwoven fabric 31. The continuous sheet of nonwoven fabric 31
or kitchen paper 1A obtained in this manner may be taken up in the
form of a roll 36. If necessary, such continuous sheet of nonwoven
fabric 31 or kitchen paper 1A may be further processed, using an
embossing machine or the like, to be formed with a plurality of
apertures each having a diameter of 0.5.about.5 mm.
[0020] Along the line of production as has been described above, it
is preferably that the second and third zones 22, 26 are also
provided with the suction mechanisms 20 similar to those provided
in the first zone 18. The high velocity water jet streams injected
in the first, second and third zones 18, 22, 26 is preferably
columnar streams and pressure of these water jet streams is
preferably adjusted within a range of 50.about.200 kgf/cm.sup.2. It
is not always necessary to use all of the first, second and third
zones but any one or more of these zones may be eliminated from the
line of production.
[0021] FIG. 4 is a perspective view of a drum 230 provided on its
peripheral surface with a flat zone 232, a plurality of projections
231 and a plurality of drain holes 233. The drum 23 having the
smooth peripheral surface used in the line of production as
illustrated by FIG. 3 may be replaced by the drum 230 to obtain the
continuous sheet of kitchen paper 1A similar to that shown in FIG.
2. The drum 230 is disclosed in Japanese Patent Application
Disclosure Gazettes Nos. Sho61-176346 and Sho62-69867. When the
high velocity water jet streams impinge against the wet sheet 17
placed on the drum 230, the component fibers 3, 4 are reoriented so
as to follow the configurations of the projections 231 and
consequently the sheet 17 is formed with the protuberances 51. The
protuberances 231 are distributed on the drum 230 in conformity
with the distribution pattern of the forming elements 34 in FIG. 3.
Accordingly, the step of forming the protuberances by the pair of
rolls 32, 33 in FIG. 3 can be eliminated so far as the drum 230 is
employed. The drum 230 may be in the form of a drum having its
peripheral surface formed by a mesh screen when knuckles of the
mesh screen are used as protuberance forming elements.
[0022] The nonwoven fabric 31 obtained by the method illustrated in
FIG. 3 can reproduce the configurations of the forming elements 34
with a relatively high precision because both component fibers 3, 4
are relatively short, on one hand, and the synthetic fibers 3 has a
relatively low fineness as well as a relatively low rigidity. When
the forming elements 34 have a height h as small as 1.about.3 mm
and/or the forming elements 34 are polygons having sharp
ridgelines, an excellent formability of the nonwoven fabric 31 can
be particularly effective. Such nonwoven fabric 31 preferably has a
basis weight of 10.about.80 g/m.sup.2 and the synthetic fibers 3
preferably comprises melt blown fibers.
[0023] In the line of production illustrated in FIG. 3, the slurry
containing relatively short fibers 3, 4 is fed onto the endless
belt 13 describing an ascending slope and thereby orientation of
these fibers 3, 4 in the direction in which the belt 13 travels,
i.e., in the machine direction is effectively prevented. As a
result, the fibers 3, 4 are slightly oriented in the machine
direction or randomly distributed between each pair of the adjacent
protuberances 51 on the kitchen paper 1A. In this manner, the
kitchen paper 1A is relatively isotropic.
[0024] It is possible to form a nonwoven fabric having
protuberances by subjecting a web fed from a card of prior art to
the processing steps illustrated in FIG. 3 starting from the first
zone 18. However, the fibers which can be effectively processed by
the conventional card is limited to that approximately 30 mm or
longer and therefore it is difficult for the prior art to make the
nonwoven fabric 1 or 31 presenting a high formability as realized
by the invention.
[0025] The nonwoven fabric according to the invention comprises the
pulp fibers of a relatively short fiber length mechanically
entangled with the thermoplastic synthetic fibers also of a
relatively short fibers length and a low fineness. Such unique
composition enables the nonwoven fabric to precisely reproduce the
configurations of the forming elements and thereby to have an
excellent formability. It is possible to provide such nonwoven
fabric with a desired water absorbability by properly selecting a
mixture ratio of the synthetic fibers and the pulp fibers. This
nonwoven fabric can be made useful particularly as kitchen papers
or wipe-out sheets after its surface has been formed with a
plurality of protuberances or apertures.
[0026] By utilizing the inventive method for making the nonwoven
fabric, it is possible to obtain even from fibrous material having
a fiber length too short to be processed by the conventional
card.
* * * * *