U.S. patent application number 11/115241 was filed with the patent office on 2005-11-17 for bulky sheet and process of producing the same.
This patent application is currently assigned to Kao Corporation. Invention is credited to Otsuka, Hiroshi, Yanagida, Hiroyuki.
Application Number | 20050255297 11/115241 |
Document ID | / |
Family ID | 34935707 |
Filed Date | 2005-11-17 |
United States Patent
Application |
20050255297 |
Kind Code |
A1 |
Otsuka, Hiroshi ; et
al. |
November 17, 2005 |
Bulky sheet and process of producing the same
Abstract
A bulky sheet 1 has a network sheet 11 and a nonwoven
fabric-like fiber aggregate 10 having fibers arranged on at least
one side of the network sheet 11. The fibers of the fiber aggregate
10 is in entanglement among themselves and with the network sheet
11 to be unitary with the network sheet 11. The network sheet 11 is
three-dimensionally shaped to form a number of protrusions and
depressions, and the fiber aggregate 10 is united with the network
sheet 11 along the contour of the three-dimensionally shaped
network sheet 11 such that the bulky sheet, as a whole, has a
three-dimensional profile with a number of protrusions and
depressions.
Inventors: |
Otsuka, Hiroshi; (Haga-gun,
JP) ; Yanagida, Hiroyuki; (Haga-gun, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
Kao Corporation
Tokyo
JP
|
Family ID: |
34935707 |
Appl. No.: |
11/115241 |
Filed: |
April 27, 2005 |
Current U.S.
Class: |
428/174 |
Current CPC
Class: |
D04H 5/03 20130101; D04H
3/04 20130101; D04H 1/498 20130101; D04H 1/558 20130101; Y10T
428/24628 20150115 |
Class at
Publication: |
428/174 |
International
Class: |
B65D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2004 |
JP |
2004-134600 |
Claims
1. A bulky sheet comprising a network sheet and a nonwoven
fabric-like fiber aggregate having fibers arranged on at least one
side of the network sheet, the fibers of the fiber aggregate being
in entanglement among themselves and with the network sheet to be
unitary with the network sheet, the network sheet being
three-dimensionally shaped to form a number of protrusions and
depressions, and the fiber aggregate being unitary with the network
sheet along the contour of the protrusions and the depressions of
the network sheet such that the bulky sheet, as a whole, has a
three-dimensional profile with a number of protrusions and
depressions.
2. The bulky sheet according to claim 1, wherein the
three-dimensional shaping of the network sheet is by plastic
deformation.
3. The bulky sheet according to claim 2, wherein the plastic
deformation of the network sheet is carried out by heat embossing
using a pair of matched engraved rolls both having a number of
protrusions and depressions or a combination of an engraved roll
having a number of protrusions and depressions and a smooth roll
comprising an elastic material.
4. The bulky sheet according to claim 1, wherein the network sheet
comprises a first thermoplastic resin, and the fiber aggregate
comprises a second thermoplastic resin, the first thermoplastic
resin having a lower melting point than the second thermoplastic
resin.
5. The bulky sheet according to claim 1, which is for use as a
cleaning sheet.
6. A process of producing the bulky sheet according to claim 1,
comprising the steps of: superposing a fiber web on at least one
side of a network sheet, hydro-entangling fibers of the fiber web
among themselves and with the network sheet to convert the fiber
web into a nonwoven fabric-like fiber aggregate and to unite the
fiber aggregate with the network sheet, and heat embossing the
resulting unitary sheet by inserting the sheet between a pair of
matched engraved rolls both having a number of protrusions and
depressions or between an engraved roll having a number of
protrusions and depressions and a smooth roll comprising an elastic
material to shape the unitary sheet to the contour of the engraved
roll.
7. The process according to claim 6, wherein the network sheet
comprises a first thermoplastic resin, and the fiber aggregate
comprises a second thermoplastic resin, the first thermoplastic
resin having a lower melting point than the second thermoplastic
resin, and the step of heat embossing is carried out at a
temperature lower than the melting point of the first thermoplastic
resin.
8. The process according to claim 6, wherein the step of heat
embossing is followed by the step of cooling the resulting
sheet.
9. The process according to claim 8, wherein the step of cooling is
carried out by blowing cool air to the sheet or wrapping the sheet
around a cooling roll.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a bulky sheet having a
three-dimensional profile with numerous protrusions and depressions
and a process of producing the same.
BACKGROUND OF THE INVENTION
[0002] Applicant previously proposed in JP-A-5-25763 and
JP-A-5-192285 a sheet comprising a network sheet and a nonwoven
fabric-like fiber aggregate on one or both sides of the network
sheet. The fiber aggregate is formed by entanglement of a fiber
web. The fibers constituting the fiber aggregate are in
entanglement not only among themselves but with the network sheet
to form a unitary sheet. The fiber aggregate forms a large number
of protrusions and depressions.
[0003] Applicant further proposed a bulky sheet in JP-A-2001-336052
comprising a network sheet and a fiber aggregate formed by
hydro-entanglement of a fiber web and having a large number of
protrusions and depressions formed of the fiber aggregate. The
protrusions and depressions are results of second
hydro-entanglement that is performed on the fiber aggregate in such
a manner that the fibers of the fiber aggregate are rearranged and
that the fiber aggregate bends zigzag along its planar direction so
that the protrusions and depressions per se exhibit shape
retention.
[0004] In applications as a dry type cleaning sheet, all the
above-described bulky sheets are capable of catching up dust and
debris of relatively large size such as fluff, lint, and hairs,
which have been difficult to trap with conventional cleaning
sheets, with their fibers having high freedom and of surely
collecting dust from a wide area while keeping adequate strength
while in use. With high bulk, they are capable of conforming to the
grooves of floors and uneven surfaces of furniture, appliances,
etc. to remove dirt and dust from such grooves or recesses. Because
these bulky sheets as produced in continuous form are usually wound
in roll for storage before fabrication into final products, the
three dimensional profile with the protrusions and depressions is
liable to be collapsed due to the winding pressure. Collapse of the
profile can also occur when the bulky sheet in roll form is
unrolled and processed under tension or between the nip of
rolls.
SUMMARY OF THE INVENTION
[0005] The present invention provides a bulky sheet having a
network sheet and a nonwoven fabric-like fiber aggregate formed by
entanglement of fibers. The fiber aggregate is present on at least
one side of the network sheet. The fibers of the fiber aggregate
are in entanglement not only among themselves but with the network
sheet to be unitary with the network sheet. The network sheet is
three-dimensionally shaped to form a number of protrusions and
depressions, and the fiber aggregate is united with the network
sheet along the contour of the protrusions and the depressions of
the network sheet such that the bulky sheet, as a whole, has a
three-dimensional profile with a number of protrusions and
depressions.
[0006] The present invention also provides a preferred process of
producing the bulky sheet. The process includes the steps of (1)
superposing a fiber web on at least one side of a network sheet,
(2) hydro-entangling the fibers constituting the fiber web among
themselves and with the network sheet to convert the fiber web into
a nonwoven fabric-like fiber aggregate and to unite the fiber
aggregate with the network sheet, and (3) heat embossing the
resulting unitary sheet by inserting the sheet between a pair of
matched engraved rolls both having a number of protrusions and
depressions or between an engraved roll having a number of
protrusions and depressions and a smooth roll made of or covered
with an elastic material to shape the sheet to the contour of the
engraved roll.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a perspective of an embodiment of the bulky sheet
according to the present invention.
[0008] FIG. 2 is an exploded perspective view of the bulky sheet of
FIG. 1.
[0009] FIG. 3 schematically illustrates apparatus suitable for the
production of the bulky sheet shown in FIG. 1.
[0010] FIG. 4 schematically shows another configuration of the
cooling part of the apparatus shown in FIG. 3.
[0011] FIG. 5 is a schematic illustration of another apparatus
suitable for the production of the bulky sheet of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0012] The present invention will be described with reference to
its preferred embodiments by referring to the accompanying
drawings. An embodiment of the bulky sheet according to the
invention is shown in FIG. 1. FIG. 2 represents an exploded,
perspective view of the bulky sheet of FIG. 1. The bulky sheet 1 of
the embodiment has a first side 1a and a second side 1b. The bulky
sheet 1 has many protrusions 2 protruding from one side to the
other. The protrusions 2 are regularly spaced in both the machine
direction X and the cross direction Y in lines and rows,
respectively, to form a rhombic lattice pattern as a whole. Between
every adjacent protrusions 2 in every line and every row are made
depressions 3 to form a rhombic lattice pattern as a whole. With
the protrusions 2 and the depressions 3 the bulky sheet 1 has a
three-dimensional surface profile as a whole.
[0013] The individual protrusions 2 are almost hemispherical, and
so are the depressions 3. It is preferred for the bulky sheet 1 of
the present embodiment to exhibit the same performance on both
sides thereof particularly where it is used as a cleaning sheet. In
this connection, it is preferred that the shape and the spacing of
the protrusions 2 on the first side la and those on the second side
1b be substantially the same. It is preferred that the back of the
depressions 3 on the first side 1a correspond to the protrusions 2
on the second side 1b and vise versa. It is also preferred that the
shape of the individual protrusions 2 be an inversion of the
individual depressions 3.
[0014] The protrusions 2 are preferably distributed on either side
at an average density of 50 to 850, more preferably 100 to 600, per
10 cm square at any site on that side. With the density of the
protrusions 2 falling within that range, the bulky sheet 1 has
protrusions 2 and depressions 3 arranged in good balance and, when
used as a cleaning sheet, for example, exhibits still superior
performance in catching up and holding relatively large dust
including bread crumbs as well as fine dust.
[0015] As will be understood from a preferred process of producing
the bulky sheet 1 described infra, the shape and arrangement of the
protrusions 2 and the depressions 3 can be freely designed by
designing the engraved pattern on an engraved roll used in the
production.
[0016] The individual protrusions 2 preferably have an area of 1 to
100 mm.sup.2, more preferably 4 to 25 mm.sup.2, in their plan view
from the standpoint of dust trapping capabilities and stable
three-dimensional shape retention. The same preference applies to
the area of the individual depressions 3. From the same standpoint,
the distance between adjacent protrusions 2 and between adjacent
depressions 3 in the machine direction X is preferably 1 to 20 mm,
more preferably 4 to 20 mm. The same applies to the cross direction
Y.
[0017] The thickness of the bulky sheet 1, i.e., the distance from
the plane connecting the apices of the protrusions 2 on the first
side 1a to the plane connecting the apices of the protrusions 2 on
the second side 1b is preferably 0.5 to 8 mm, more preferably 1 to
4 mm. The bulky sheet 1 with that thickness encompasses ample voids
to provide high bulk and is fit for use as, for example, a cleaning
sheet. Sheet 1 thickness measurement is taken under a load of 0.3
kPa, which corresponds to the pressure applied when the sheet is
lightly pressed by a hand, using, for example, a thickness gauge
FS60DS supplied by Mitutoyo Corp.
[0018] To maintain bulk while in use, the sheet 1 preferably has a
thickness of 0.5 to 6 mm, more preferably 1 to 3 mm, under a load
of 0.7 kPa, which is greater than the above-recited measuring load
and corresponds to the load applied while the sheet 1 attached to a
cleaning tool is used to clean a floor, etc.
[0019] The bulky sheet 1 is composed of a fiber aggregate 10 formed
by hydro-entangling a fiber web and a network sheet 11 disposed
inside the fiber aggregate 10. As described infra in detail, the
fibers constituting the fiber aggregate 10 are entangled with the
network sheet 11 by hydro-entanglement so that the fiber aggregate
10 and the network sheet 11 are unitary with each other.
[0020] As is clear from FIG. 2, the network sheet 11 is shaped in
three dimensions to form a number of protrusions and depressions.
As will be apparent from a preferred process of producing the bulky
sheet 1 described later, the three dimensional shaping of the
network sheet 11 is based on plastic deformation so that the three
dimensionally uneven profile of the network sheet 11 is retained
stably.
[0021] The fiber aggregate 10 is present on both sides of the
network sheet. The fiber aggregate 10 on both sides of the network
sheet is integral with the network sheet in conformity with the
contour of the three dimensionally shaped profile of the network
sheet 11. As a result, the whole sheet 1 has a three dimensional
profile with a number of the protrusions 2 and depressions 3. In
other words, the shapes of the protrusions 2 and the depressions 3
of the bulky sheet 1 are substantially the same as those of the
network sheet 11.
[0022] The protrusions 2 and the depressions 3 of the bulky sheet 1
are formed by integrally joining the fiber aggregates 10 with the
network sheet 11 along the contour of the three dimensionally
shaped profile of the network sheet 11. Accordingly, the shapes of
the protrusions 12 and the depressions 3 are stably retained by the
three-dimensionally shaped and plastically deformed network sheet
11. Therefore, the protrusions 2 and the depressions 3 hardly
collapse to lose their shapes even under load. The bulky sheets
described in JP-A-5-25763 and JP-A-5-192285 supra, in contrast, are
more liable to lose their shapes under load because the protrusions
are formed by shrinkage of a network sheet. In applications as a
cleaning sheet, the bulky sheet 1, which is less liable to collapse
its three-dimensional shape, is superior in capabilities of
cleaning grooves of floors or uneven surfaces and of catching up
and holding such dust and debris like bread crumbs. This
superiority is particularly outstanding when the bulky sheet 1 is
used as attached to a cleaning tool.
[0023] The fiber aggregate 10 and the network sheet 11 that make up
the bulky sheet 1 will be described more specifically. The fiber
aggregate 10 has a nonwoven fabric-like structure formed by
entangling fibers constituting a fiber web among themselves through
hydro-entanglement. Formed only by entanglement of the constituent
fibers, the fiber aggregate 10 provides the constituent fibers with
more freedom to move than nonwoven fabric in which the constituent
fibers are joined by fusion or with an adhesive. For this reason,
the bulky sheet 1 is excellent in capabilities of catching up and
holding hairs, fine dust, etc. and feels soft.
[0024] The fibers making up the fiber aggregate 10 include those
recited in U.S. Pat. No. 5,525,397, cl. 4, 11.3-10. It is preferred
for the fiber aggregate 10 to contain at least 50% by weight of
fibers having a fineness of 5 dtex or smaller, more preferably at
least 70% by weight of 3.5 dtex or finer fibers, so as to avoid
holes being created during the hydro-entangling process and to
provide and retain sufficiently high bulk. The recited fiber
constitution is also advantageous in view of hair catching up and
holding capabilities in applications as a cleaning sheet. The
grammage (basis weight) of the fiber aggregate 10 and the fiber
length of the fibers used in the fiber aggregate 10 should be
determined according to the use of the bulky sheet 1 in
comprehensive consideration of processability and cost. In
applications as a cleaning sheet, for instance, it is desirable
that the fiber aggregate 10 have a grammage of 30 to 100 g/m.sup.2,
more desirably 40 to 70 g/m.sup.2, and that the constituent fibers
have a length of 20 to 100 mm, more desirably 30 to 65 mm, to avoid
holes being created during hydroentanglement and to obtain and
retain sufficiently high bulk. The fiber aggregate 10 may be
provided with a surface active agent or lubricant that can improve
the surface physical properties and dust trapping capabilities of
the fiber aggregate 10.
[0025] The network sheet 11 is a resin-made net having a lattice
mesh as illustrated in FIG. 2. The network sheet 11 preferably has
an air permeability of 0.1 to 1000 cm.sup.3/cm.sup.2.multidot.sec.
Nonwoven fabric, paper, film, etc. may also serve as a network
sheet as long as their air permeability falls within that range.
The fibers of the fiber aggregate 10 are in entanglement not only
among themselves but also with the network sheet 11 so that the
fiber aggregate 10 exhibits increased tensile strength. The
diameter of the strands making the net is preferably 50 to 600
.mu.M, more preferably 100 to 400 .mu.m. The mesh size (distance
between adjacent strands) is preferably 2 to 30 mm, more preferably
4 to 20 mm. Unlike the network sheet used in JP-A-5-25763 and
JP-A-5-192285 supra, the network sheet 11 used in the present
embodiment does not need to have thermal shrinkability. To use a
thermally shrinkable network sheet in the present invention causes
no problem of course.
[0026] Useful materials to make the network sheet 11 include those
described in U.S. Pat. No. 5,525,397, cl. 3, 11. 39-46. In
particular, various thermoplastic resins are preferred. In order
for the bulky sheet 1 to be capable of retaining its bulkiness even
with a load applied thereon, the network sheet 11 is preferably of
an elastic material. Examples of suitable materials of the network
sheet 11 include polyolefin resins, such as polyethylene,
polypropylene, and polybutene; polyester resins, such as
polyethylene terephthalate and polybutylene terephthalate;
polyamide resins, such as nylon; acrylonitrile resins; vinyl
resins, such as polyvinyl chloride; and vinylidene resins, such as
polyvinylidene chloride. Modified products or blends of these
resins are also useful.
[0027] The bulky sheet 1 preferably has a weight of 30 to 110
g/m.sup.2, more preferably 40 to 80 g/m.sup.2, for assuring both
bulkiness and processability. Where the fiber aggregate 10 is
present on both sides of the network sheet 1, the part of the fiber
aggregate 10 that is on one side and the part of the fiber
aggregate 10 that is on the other side may be the same or different
in weight per unit area.
[0028] A preferred process of producing a bulky sheet according to
the present invention will be described with reference to FIG. 3.
In this process, a fiber web is superposed on one or both sides of
a network sheet 11. The superposed three layers are hydroentangled
to entangle the fibers of the fiber web(s) among themselves and
with the network sheet 11 thereby to convert the fiber web(s) into
a nonwoven fabric-like fiber aggregate 10 and at the same time to
unite the fiber aggregate 10 and the network sheet 11. The
resulting unitary sheet is subsequently heat embossed between a set
of matched engraved rolls having a number of protrusions and
depressions. As a result of heat embossing, the unitary sheet is
shaped to have a three dimensional profile corresponding to the
shape of the nip of the engraved rolls.
[0029] FIG. 3 schematically shows apparatus 20 that is preferably
used to make the bulky sheet 1 of the present embodiment. The
apparatus 20 is sectioned into a superposing part 20A, an
entangling part 20B, a shaping part 20C, and a cooling part
20D.
[0030] The superposing part 20A has cards 21A and 21B for forming
fiber webs 10a and 10b, respectively, feed rolls 22 for feeding the
fiber webs 10a and 10b, and a feed roll 24 for feeding a network
sheet 11.
[0031] The entangling part 20B has an endless belt 25 for
supporting webs and a group of water jet nozzles 26.
[0032] The shaping part 20C has a pair of matched engraved rolls 27
each having a number of protrusions and depressions. Each engraved
roll 27 rotates in the direction indicated with the arrow shown in
FIG. 3. Each engraved roll 27 is made of metal and is equipped with
a heater (not shown) for heating the roll to a prescribed
temperature.
[0033] The cooling part 20D includes an air blow duct 28 facing one
side of a laminate sheet and a vacuum conveyor 29. The air blow
duct 28 blows cool air to the sheet. The vacuum conveyor 29 has an
endless mesh belt for conveying the sheet and is designed to vacuum
up the cool air from the air blow duct 28 through the mesh
belt.
[0034] The apparatus 20 operates as follows. In the superposing
part 20A, the cards 21A and 21B continuously feed the respective
fiber webs 10a and 10b via the respective feed rolls 22. Between
the cards 21A and 21B is placed a roll 23 of a network sheet 11,
from which the network sheet 11 is fed via a feed roll 24 and
sandwiched in between the fiber webs 10a and 10b with the aid of
the feed rolls 22 to form a three-ply composite 5.
[0035] In the entangling part 20B, the water jet nozzles 26 eject
high-pressure water jets against the composite 5, whereby the
fibers of each of the fiber webs 10a and 10b are entangled among
themselves to convert the fiber webs into a fiber aggregate 10 and,
at the same time, the fibers of the two fiber webs are entangled
with the network sheet 11 to provide a unitary laminate 6.
[0036] The laminate 6 is dried in a drier 30 and then forwarded to
the shaping part 20C, where the laminate 6 is embossed between the
nip of the engraved rolls 27. Since the engraved rolls 27 engage
with each other, that is, they are matched steel engraved rolls,
the laminate 6 is shaped to the profile of the engraved rolls 27.
It is preferred that the rolls 27 be preheated to a prescribed
temperature so that the network sheet 11 in the laminate 6 may
undergo thermal plastic deformation and be thereby shaped without
fail and with stable shape retention. From this viewpoint, the heat
embossing between the engraved rolls 27 is preferably carried out
at a temperature lower than the melting point of the thermoplastic
resin making the network sheet 11. It is also effective to conduct
the heat embossing at or above the softening point of the
thermoplastic resin. By making a clearance between the engraved
rolls 27 it is possible to set the temperature of the engraved
rolls 27 at or above the melting point of the thermoplastic resin
of the network sheet 11 provided that the heat transmitted to the
network sheet 11 is lower than the melting point. The shaping part
may be designed to fold the laminate 6 into two, three or four and
then heat emboss the folded laminate.
[0037] It is preferred that the heat embossing step be effected
under such conditions that do not cause the fiber aggregate in the
laminate 6 to reduce its dust trapping capabilities. For example,
when the fiber aggregate contains a thermoplastic resin, should
heat embossing be conducted at temperatures causing the resin to
melt, the fiber aggregate would reduce its dust trapping
performance. Where both the network sheet and the fiber aggregate
contain a thermoplastic resin, it is preferred that the melting
point of the thermoplastic resin making the network sheet be lower
than that of the thermoplastic resin making the fiber aggregate and
that the heat embossing be carried out at a temperature lower than
the melting point of the thermoplastic resin of the network
sheet.
[0038] The thus shaped laminate 6, i.e., a bulky sheet 1 has an
elevated temperature due to the heat of the embossing. If the bulky
sheet 1 continues to have the elevated temperature after the
shaping, there is a possibility that the bulk of the network sheet
having been three-dimensionally deformed by the embossing may be
reduced. Hence, the bulky sheet 1 is preferably passed through the
cooling part 20D, where the three-dimensional deformation of the
network sheet in the bulky sheet 1 is set. The cooling step makes
it possible to stably maintain the bulk of the network sheet and
therefore the bulky sheet 1. Accordingly, the cooling step is not
required under some heat embossing conditions, for instance, when
the heating temperature is low enough.
[0039] In the present embodiment, the cooling step is conducted by
blowing cool air to the bulky sheet 1. Cool air is blown from the
air blow duct 28 toward one side of the sheet 1, pushed through the
sheet 1, and vacuumed up from the other side by the vacuum conveyor
29. Note that the cooling mode is not limited to the means shown in
FIG. 3. For example, the bulky sheet I from the shaping part 20C
may be cooled by wrapping around cooling rolls 30 cooled to a
prescribed temperature. The cooling rolls 30 include water-cooled
rolls having cooling water flowing therein and perforated suction
rolls that suck in air from their peripheral surface.
[0040] When needed, the resulting bulky sheet 1 can be napped on
both sides thereof. Napping is desired when the freedom of movement
of the fibers making up the fiber aggregate has been reduced by the
nip pressure of the engraved rolls in the preceding shaping step.
Where the bulky sheet 1 is used as a cleaning sheet, reduction in
freedom of fiber movement can result in reduction of dust trapping
performance. Napping can be carried out by rubbing or brushing with
sandpaper, a metallic file, raising wires, a brush, etc.
[0041] In addition to, or in place of, the nap finish, a textile
oil may be applied to the bulky sheet 1. Textile oils containing at
least one of a mineral oil, a synthetic oil, a silicone oil, and a
surface active agent are preferably used. Examples of the mineral
oil include paraffinic hydrocarbons, naphthenic hydrocarbons, and
aromatic hydrocarbons. Examples of the synthetic oil include
alkylbenzene oils, polyolefin oils, and polyglycol oils. Examples
of the silicone oil are acyclic dimethyl polysiloxane, cyclic
dimethyl polysiloxane, methylhydrogen polysiloxane, and various
modified silicones. Examples of the surface active agent include
cationic ones, such as mono(long-chain alkyl)trimethylammonium
salts, di(long-chain alkyl)dimethylammonium salts, and
mono(long-chain alkyl)dimethylbenzylammonium salts each having an
alkyl or alkenyl group having 10 to 22 carbon atoms; and nonionic
ones, such as polyethylene glycol ethers, e.g., polyoxyethylene (6
to 35 mol) long-chain, primary or secondary, C8-C22 alkyl or
alkenyl ethers and polyoxyethylene (6 to 35 mol) C8-C18 alkyl
phenyl ethers, polyoxyethylene-polyoxypropylene block copolymers,
and polyhydric alcohol derivatives, e.g., glycerol fatty acid
esters, sorbitan fatty acid esters, and alkyl glycosides. The
textile oil can be applied either before or after the heat
embossing step.
[0042] The above-described process of producing the bulky sheet 1
can also be carried out using apparatus shown in FIG. 5. The
apparatus of FIG. 5 has basically the same configuration as the
apparatus of FIG. 3, except for the following. In FIG. 3, the parts
from the superposing part 20A to the cooling part 20D make a single
assembly, whereas the apparatus of FIG. 5 has two divided
assemblies: a first assembly 201 including the superposing part 20A
and the entangling part 20B and a second assembly 202 including the
shaping part 20C and the cooling part 20D. The system shown in FIG.
5 is advantageous in that the first assembly 201 and the second
assembly 202 may be installed at different sites, which allows for
division of work, and that the freedom of production design is
increased. More specifically, in the first assembly 201, the
laminate 6 dried in the drier 30 is once taken up in roll form 6A.
The roll 6A is then set on the second assembly 202 installed at a
different site. The laminate 6 is unwound from the roll 6A and
shaped in the second assembly 202.
[0043] The bulky sheet thus produced is fit for use as a dry type
cleaning sheet. It is particularly suited as a cleaning sheet that
is to be attached to a cleaning tool having a flat head and a stick
handle connected to the head. Because the bulky sheet stably
retains its uneven profile and therefore shows a reduced degree of
collapse on getting wet, it is also suitable as a wet type cleaning
sheet impregnated with various cleaning fluids. The bulky sheet is
also preferably applicable to absorbent articles such as disposable
diapers and sanitary napkins and hygiene articles such as masks and
gauze.
[0044] The present invention is by no means limited to the
foregoing embodiment. For example, while the fiber aggregate is
present on both sides of the network sheet in the foregoing
embodiment, a bulky sheet having the fiber aggregate on only one
side of the network sheet is useful for some applications.
[0045] While in the foregoing embodiment the type of the nip of the
two matched engraved rolls 27 used in the shaping part 20C is
steel-to-steel, it can be paper-to-steel. Otherwise, a combination
of an engraved roll with an engraved pattern and a smooth roll made
of or covered with an elastic material is employable. In this case,
the surface of the engraved roll bites the elastic material of the
opposing roll in the embossing nip to deform the laminate 6.
[0046] The present invention will now be illustrated in greater
detail with reference to Examples, but it should be understood that
the invention is not limited thereto. Unless otherwise noted, all
the percents are by weight.
EXAMPLE 1
[0047] A bulky sheet was produced using the apparatus shown in FIG.
3. Polyester fiber (a 70%/30% mixture of polyester fiber with a
fineness of 0.8 denier (0.9 dtex) and a length of 38 mm and
polyester fiber with a fineness of 1.45 denier (1.6 dtex) and a
length of 51 mm) was carded in a usual manner into a fiber web
having a weight of 29 g/m.sup.2. The fiber web was superposed on
each of the upper and the lower sides of a polypropylene net having
a lattice mesh (distance between adjacent strands: 8 mm; strand
diameter: 300 .mu.m) as a network sheet. The superposed three
layers were entangled with water jets ejected from nozzles under
water pressure of 1 to 5 MPa to obtain a unitary laminate having a
fiber aggregate on its both sides. The laminate was embossed
between the nip of matched steel-to-steel engraved rolls heated to
105.degree. C. to become a bulky sheet having a three-dimensional
profile with a number of protrusions and depressions. Cool air at
20.degree. C. was blown at a speed of 10 m/sec for 0.2 seconds to
the bulky sheet from the engraved rolls to cool the sheet. After
the cooling, each side of the sheet was rubbed once with #1200
sandpaper to have the fibers napped. Finally, a textile oil
consisting of 90% liquid paraffin and 10% nonionic surface active
agent (polyoxyethylene alkyl ether) was applied to the sheet in an
amount of 5% based on the sheet.
COMPARATIVE EXAMPLE 1
[0048] Polyester fiber (1.5 denier, 51 mm) was carded in a usual
manner into a fiber web having a weight of 8 g/m.sup.2. Five carded
fiber webs thus prepared were lapped to make a 5-ply fiber
aggregate having a weight of 40 g/m.sup.2. The fiber aggregate was
superposed on each side of a biaxially shrinkable polypropylene net
(distance between adjacent strands: 9 mm; strand diameter: 0.2 mm)
as a network sheet. The superposed three layers were hydroentangled
under conditions of a water pressure of 40 kg/cm.sup.2, a nozzle
pitch of 1.6 mm, and a water jet speed of 5 m/min. Hot air at
130.degree. C. was applied to the resulting unitary laminate for 50
seconds to dry the laminate and simultaneously shrink the network
sheet. The percent shrinkage was about 10% in both the MD and CD.
An uneven bulky sheet was thus obtained.
[0049] Evaluation:
[0050] The bulky sheets obtained in Example 1 and Comparative
Example 1 were measured for thickness under a load of 0.3 kPa and
0.7 kPa. The bulky sheets were evaluated for (1) soil dust trapping
capabilities, (2) hair trapping capabilities, (3) yam trapping
capabilities, and (4) conformability to grooves in accordance with
the following methods. The results of measurement and evaluation
are shown in Table 1 below.
[0051] 1) Soil Dust Trapping Capabilities
[0052] The bulky sheet was attached to a cleaning tool Quickle
Wiper available from Kao Corp. JIS test powder class 7 (fine
particles of the Kanto loam) weighing 0.4 g was uniformly spread on
a 100 cm side square of a floor (NEW Woody Super Z, available from
Matsushita Electric Works, Ltd.) with a brush. The dusted area of
the floor was imaginarily divided into 4 parallel sections (25
cm.times.100 cm each) and cleaned by sliding the Quickle Wiper back
and forth once on each of the sections. Without removing the soil
dust caught on the cleaning sheet, spreading dust and cleaning the
dusted area were repeated 6 times in total. The amount of dust
trapped on/in the bulky sheet was obtained by subtracting the
weight of the intact bulky sheet from the weight of the soiled
bulky sheet detached from the cleaning tool. The percentage of the
weight of the dust trapped to the total weight of the dust spread
(6.times.0.4 g=2.4 g) was taken as a dust trapping ratio.
[0053] 2) Hair Trapping Capabilities
[0054] The bulky sheet was attached to Quickle Wiper. Ten human
hairs of about 20 cm in length were scattered over an area of 30 cm
by 60 cm of a floor (NEW Woody Super Z). The hairs were wiped up by
sliding the Quickle Wiper back and forth twice with a stroke of 60
cm, and the number of hairs caught on the bulky sheet was counted.
The same operation was successively carried out 6 times using the
same bulky sheet. The percentage of the total number of hairs
caught up to the total number of hairs scattered (60) was taken as
a hair trapping ratio (%).
[0055] 3) Yarn Trapping Capabilities
[0056] The bulky sheet was attached to Quickle Wiper. Three
millimeter long cut pieces of commercially available 100% acrylic
yarn weighing 0.4 g were scattered over an area of 30 cm by 60 cm
of a floor (NEW Woody Super Z). The area of the floor with yarn was
cleaned by sliding the Quickle Wiper back and forth 30 times. The
amount of yarn caught up on the bulky sheet was obtained by
subtracting the weight of the intact bulky sheet from the weight of
the bulky sheet detached from the cleaning tool. The percentage of
the weight of the yarn trapped to the total weight of the yarn
scattered (0.4 g) was taken as a yam trapping ratio.
[0057] 4) Conformability to Grooves
[0058] An acrylic resin plate having six grooves at a 3 cm interval
was used as an object to be cleaned. Each groove had an inverted
triangle-shaped cross section with an opening width of 3.0 mm and a
depth of 1.5 mm. JIS test powder class 7 was spread in the grooves
over a length of 20 cm each in an amount of 0.01 g per groove
(total amount of dust=0.06 g). The bulky sheet was attached to
Quickle Wiper and slid on the acrylic plate back and forth twice
along the grooves. The weight of the dust trapped on/in the sheet
was measured, and a dust trapping ratio was calculated as a
percentage of the weight of the dust trapped to the weight of the
dust spread in the grooves. The conformability of the bulky sheet
to the grooves was graded A (dust trapping ratio of 70% or higher),
B (dust trapping ratio of 50% to 70%) or C (dust trapping ratio of
less than 50%).
1 TABLE 1 Comparative Example 1 Example 1 Thickness (mm) under 0.3
kPa 1.97 1.35 under 0.7 kPa 1.63 1.11 Trapping test powder class 7
76/A 70/A Capabilities hairs 88/A 64/B (trapping yarn 93/A 80/A
ratio/grade) conformability to 95/A 70/A grooves
[0059] As is apparent from the results in Table 1, the bulky sheet
of Example 1 is endurable against loads applied as compared with
that of Comparative Example 1. It is seen that the bulky sheet of
Example 1 is superior to that of Comparative Example 1 in
capabilities of trapping all kinds of dust and debris from fine
dust to relatively large one.
[0060] The bulky sheet according to the present invention stably
retains its three-dimensional profile, being supported by the
three-dimensionally shaped network sheet. Therefore the bulky sheet
undergoes reduced loss of its bulk even when stored in roll form or
processed under tension or between the nip of rolls. Having a
three-dimensional profile with numerous protrusions and
depressions, the bulky sheet applied as a cleaning sheet
effectively catches up dust and debris and conforms to the
unevenness of a surface to be cleaned, such as grooves of floors.
Having an increased surface area because of the protrusions and
depressions, the bulky sheet as a cleaning sheet exhibits increased
dust collecting capacity.
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