U.S. patent application number 10/021637 was filed with the patent office on 2003-06-12 for cleaning sheet, system and apparatus.
This patent application is currently assigned to Kimberly-Clark Worldwide, Inc.. Invention is credited to Arnold, Billy Dean, Keck, Laura Elizabeth.
Application Number | 20030106568 10/021637 |
Document ID | / |
Family ID | 21805312 |
Filed Date | 2003-06-12 |
United States Patent
Application |
20030106568 |
Kind Code |
A1 |
Keck, Laura Elizabeth ; et
al. |
June 12, 2003 |
Cleaning sheet, system and apparatus
Abstract
The present invention provides a cleaning sheet that has an
enhanced dirt, dust and/or debris pick-up and retention
characteristics, which can be used in dry applications and/or wet
applications. The cleaning sheet is prepared from a nonwoven web
containing plurality of multicomponent multilobal filaments,
wherein the multicomponent multilobal filaments have a plurality of
raised lobal regions separated by depressed regions. The cleaning
sheet also has voids between the plurality of multicomponent
multilobal filaments which allow for enhanced dirt, dust and/or
debris pick-up and retention. The nonwoven web can be a single
layer or a layer of a multilayer laminate. The nonwoven web is
optionally electret treated. Also disclosed is a cleaning implement
and cleaning kit containing the cleaning sheet.
Inventors: |
Keck, Laura Elizabeth;
(Alpharetta, GA) ; Arnold, Billy Dean;
(Alpharetta, GA) |
Correspondence
Address: |
KIMBERLY-CLARK WORLDWIDE, INC.
401 NORTH LAKE STREET
NEENAH
WI
54956
|
Assignee: |
Kimberly-Clark Worldwide,
Inc.
|
Family ID: |
21805312 |
Appl. No.: |
10/021637 |
Filed: |
December 12, 2001 |
Current U.S.
Class: |
134/6 ;
15/104.93; 15/104.94; 15/208; 15/209.1; 15/228; 15/231 |
Current CPC
Class: |
A47L 13/20 20130101;
D01F 8/06 20130101; A47L 13/16 20130101; D01D 5/253 20130101; D04H
3/16 20130101 |
Class at
Publication: |
134/6 ;
15/104.93; 15/104.94; 15/208; 15/209.1; 15/228; 15/231 |
International
Class: |
A47L 013/16; A47L
013/17; A47L 013/20 |
Claims
1. A cleaning sheet having an ability to pick-up and retain dirt,
dust and/or other debris, said cleaning sheet comprising a nonwoven
web comprising a plurality of thermoplastic multicomponent,
multilobal filaments, wherein each of the filaments comprises a
plurality of raised lobal regions separated by depressed regions
and the nonwoven web comprises voids between the plurality of
multilobal filaments which allow for dirt, dust and/or other debris
pick-up and retention within the nonwoven web.
2. The cleaning sheet according to claim 1, wherein each
multicomponent, multilobal filament comprises between 2 and 10
lobes.
3. The cleaning sheet according to claim 2, wherein each
multicomponent, multilobal filament comprises between 2 and 5
lobes.
4. The cleaning sheet according to claim 1, wherein the
thermoplastic multicomponent, multilobal filaments comprise a
thermoplastic polymer selected from the group consisting of
polyolefins, polyesters, polyamides, polycarbonates, polyurethanes,
polyvinylchloride, polytetrafluoroethylene, polystyrene, polylactic
acid and blends thereof.
5. The cleaning sheet according to claim 1, wherein the
multicomponent, multilobal filaments are bicomponent filaments
comprising a first polymer component and a second polymer
component.
6. The cleaning sheet according to claim 5, wherein the first
polymer component comprises polyethylene and the second polymer
component comprises polypropylene.
7. The cleaning sheet according to claim 6, wherein the first
polymer component and the second polymer component are arranged in
a side-by-side configuration.
8. The cleaning sheet according to claim 1, wherein the
multicomponent, multilobal filaments are crimped.
9. The cleaning sheet according to claim 1, wherein the bulk
density of the sheet is in the range of about 0.015 g/cm.sup.3 to
about 0.075 g/cm.sup.3.
10. The cleaning sheet according to claim 1, wherein the basis
weight of the sheet is between about 0.25 osy and about 25 osy.
11. The cleaning sheet according to claim 10, wherein the basis
weight of the sheet is between about 0.5 osy and about 10 osy.
12. The cleaning sheet according to claim 11, wherein the basis
weight of the sheet is between about 1.0 osy and about 5.0 osy.
13. The cleaning sheet according to claim 1, wherein the nonwoven
web further comprises a plurality of pulp fibers intermingled with
the plurality of multicomponent, multilobal filaments.
14. The cleaning sheet according to claim 1, wherein the nonwoven
web further comprises a plurality of monolobal filaments
intermingled with the plurality of the multicomponent, multilobal
filaments.
15. The cleaning sheet according to claim 14, wherein the monolobal
filaments comprise a thermoplastic polymer selected from the group
consisting of polyolefins, polyesters, polyamides, polycarbonates,
polyurethanes, polyvinylchloride, polytetrafluoroethylene,
polystyrene, polylactic acid and blends thereof.
16. The cleaning sheet according to claim 15, wherein the monolobal
filaments comprises monocomponent filaments, multicomponent
filaments or a mixture thereof.
17. The cleaning sheet according to claim 16, wherein the monolobal
filaments comprise multicomponent, monolobal filaments.
18. The cleaning sheet according to claim 17, wherein the
multicomponent, monolobal filaments are bicomponent filaments
comprising a first polymer component and a second polymer
component.
19. The cleaning sheet according to claim 18, wherein the first
polymer component comprises polyethylene and the second polymer
component comprises polypropylene.
20. The cleaning sheet according to claim 19, wherein the first
polymer component and the second polymer component are arranged in
a side-by-side configuration.
21. The cleaning sheet according to claim 1, wherein the nonwoven
web comprises a laminate structure having at least two layers, a
first layer and a second layer, wherein the first layer comprises
the plurality of multicomponent, multilobal filaments; and the
second layer comprises a plurality of monolobal filaments.
22. The cleaning sheet according to claim 21, wherein the monolobal
filaments comprises monocomponent filaments, multicomponent
filaments or a mixture thereof.
23. The cleaning sheet according to claim 22, wherein the monolobal
filaments comprise a thermoplastic polymer selected from the group
consisting of polyolefins, polyesters, polyamides, polycarbonates,
polyurethanes, polyvinylchloride, polytetrafluoroethylene,
polystyrene, polylactic acid and blends thereof.
24. The cleaning sheet according to claim 22, wherein the monolobal
filaments comprise multicomponent, monolobal filaments.
25. The cleaning sheet according to claim 24, wherein the
multicomponent filaments are bicomponent filaments comprising a
first polymer component and a second polymer component.
26. The cleaning sheet according to claim 25, wherein the first
polymer component comprises polyethylene and the second polymer
component comprises polypropylene.
27. The cleaning sheet according to claim 26, wherein the first
polymer component and the second polymer component are arranged in
a side-by-side configuration.
28. The cleaning sheet according to claim 1, wherein the
multicomponent, multilobal fibers comprises a higher melting point
polymer component, a lower melting point polymer component and an
interface between the higher melting polymer component.
29. The cleaning sheet according to claim 1, wherein the nonwoven
web is electret treated.
30. The cleaning sheet according to claim 14, wherein the nonwoven
web is electret treated.
31. The cleaning sheet according to claim 21, wherein the nonwoven
web is electret treated.
32. A cleaning implement comprising: a. a handle; b. a head; and c.
a removable cleaning sheet; wherein head is connected to the
handle, the removable cleaning sheet is removable attached to the
head and the removable cleaning sheet comprises the cleaning sheet
of claim 1.
33. A cleaning implement comprising: a. a handle; b. a head; and c.
a removable cleaning sheet; wherein head is connected to the
handle, the removable cleaning sheet is removable attached to the
head and the removable cleaning sheet comprises the cleaning sheet
of claim 14.
34. A cleaning implement comprising: a. a handle; b. a head; and c.
a removable cleaning sheet; wherein head is connected to the
handle, the removable cleaning sheet is removable attached to the
head and the removable cleaning sheet comprises the cleaning sheet
of claim 21.
35. A method of cleaning a surface comprising contacting and wiping
the surface with the cleaning sheet of claim 1.
36. A method of cleaning a surface comprising contacting and wiping
the surface with the cleaning sheet of claim 14.
37. A method of cleaning a surface comprising contacting and wiping
the surface with the cleaning sheet of claim 21.
38. A cleaning kit comprising the cleaning implement according to
claim 32 and a plurality of the cleaning sheets.
39. The cleaning kit of claim 38, wherein the cleaning sheets are
premoistened.
40. The cleaning kit of claim 38, wherein the cleaning sheets are
dry.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to cleaning sheets, implements
for cleaning surfaces and a method of cleaning surfaces. More
particularly the present invention relates to disposable cleaning
sheets, implements for use in wet surface-cleaning applications or
dry surface cleaning applications and a method of cleaning surfaces
using the disposable cleaning sheets and cleaning implements of the
present invention.
BACKGROUND OF THE INVENTION
[0002] Disposable cleaning sheets have heretofore been used in
connection with cleaning tools such as mops and brushes. As an
example, U.S. Pat. No. 5,461,749 to Ahlberg et al. discloses a
floor mop or fabric for picking-up and retaining dust. The cleaning
fabric can be attached to a mop head thereby allowing the mop to be
used in as a "duster", i.e. a tool or fabric for picking-up dust
and other particulate matter. Once the cleaning fabric is soiled,
it can be removed from the mop head and a new, clean sheet placed
therein. A similar product is disclosed in published PCT
Application WO97/04701 to Suzuki et al. This publication discloses
a flat bag-like cleaning cloth having an insertion space. The head
portion of a handle is inserted within the insertion space to form
a cleaning apparatus for use as a duster. As a further example,
published PCT Application WO98/52548 discloses a sheet material
having a macroscopically three-dimensional structure suitable for
use a duster in conjunction with a handle or other cleaning
tool.
[0003] In addition, U.S. Pat. No. 4,823,427 to Gibbs et al. teaches
the use of an absorbent elastic mop head cover that can be secured
to the mop head without fasteners. The elastic mop head cover can
comprise a meltblown fiber fabric and, in one embodiment, can
include absorbent materials such as wood pulp or synthetic staple
fibers in order to increase the water or oil absorbency of the
fabric. While Gibbs provides a durable cleaning sheet suitable for
use in wet and/or dry cleaning applications, cleaning sheets having
improved durability and an improved capacity to pick up larger
and/or coarser particulate matter are desirable. Thus, there exists
a need for cleaning sheets and implements suitable for use in dry
or wet surface-cleaning applications which are highly durable,
capable of absorbing liquids and further which are also capable of
picking up dirt and large particulate matter. Still further, there
exists a need for such a cleaning sheet that is also sufficiently
inexpensive so as to comprise a disposable product.
SUMMARY OF THE INVENTION
[0004] The present invention provides a cleaning sheet that has an
enhanced dirt, dust and/or debris pick-up and retention
characteristics, which can be used in dry applications and/or wet
applications.
[0005] It has been discovered, as a result of the present
invention, a cleaning sheet comprising a nonwoven web comprising a
plurality of multicomponent multilobal filaments, wherein the
multicomponent multilobal filaments comprises a plurality of raised
lobal regions separated by depressed regions and the nonwoven web
comprises voids between the plurality of multicomponent multilobal
filaments has enhanced dirt, dust and/or debris pick-up and
retention.
[0006] In a further aspect of the present invention, it has been
discovered that a cleaning sheet comprising a nonwoven web
comprising a mixture of a plurality of multicomponent multilobal
filaments, and a plurality of monolobal filaments, wherein the
multicomponent multilobal filaments comprises a plurality of raised
lobal regions separated by depressed regions and the nonwoven web
comprises voids between the plurality of multicomponent filaments
and/or the monolobal filaments has enhanced dirt, dust and/or
debris pick-up and retention.
[0007] Further discovered is a multilayered cleaning sheet
comprising a first layer comprising a plurality of multicomponent
multilobal filaments, wherein the multicomponent multilobal
filaments comprises a plurality of raised lobal regions separated
by depressed regions and the layer comprises voids between the
plurality of multicomponent filaments, and a second layer
comprising monolobal filaments also has enhanced dirt, dust and/or
debris pick-up and retention.
[0008] The present invention also relates to a cleaning implement
comprising a handle; a head; and a removable cleaning sheet;
wherein the head is connected to the handle, and the removable
cleaning sheet is removably attached to the head. The cleaning
sheet comprises a nonwoven web comprising a plurality of
multicomponent multilobal filaments, wherein each of the filaments
comprises a plurality of raised lobal regions separated by
depressed regions and the nonwoven web comprises voids between the
plurality of multicomponent filaments which allow for enhanced
dirt, dust and/or debris pick-up and retention.
[0009] A further aspect of the present invention relates a method
of cleaning a surface comprising contacting and wiping the surface
with the cleaning sheet of the present invention.
[0010] The present invention also relates to a kit containing the
cleaning implement of the present invention and a plurality of the
cleaning sheets of the present invention.
BRIEF DESCRIPTIONS OF THE DRAWINGS
[0011] FIG. 1 illustrates cross-section shapes of several different
multilobal fibers suitable for the nonwoven web cleaning sheet of
the present invention.
[0012] FIG. 2 illustrates one process for producing the nonwoven
web used in the cleaning sheet of the present invention.
[0013] FIG. 3 illustrates a cleaning implement of the present
invention.
DEFINITIONS
[0014] As used herein, the term "cleaning sheet" or "wiping sheet"
is intended to include any web which is used to clean an article or
a surface. Examples of cleaning sheets include, but are not limited
to, webs of material containing a single sheet of material which is
used to clean a surface by hand or a sheet of material which can be
attached to a cleaning implement, such as a floor mop or a hand
held cleaning tool, such as a duster.
[0015] As used herein, the term "fiber" includes both staple
fibers, i.e., fibers which have a defined length between about 2
and about 20 mm, fibers longer than staple fiber but are not
continuous, and continuous fibers, which are sometimes called
"continuous filaments" or simply "filaments". The method in which
the fiber is prepared will determine if the fiber is a staple fiber
or a continuous filament.
[0016] As used herein, the term "nonwoven web" means a web having a
structure of individual fibers or threads which are interlaid, but
not in an identifiable manner as in a knitted web. Nonwoven webs
have been formed from many processes, such as, for example,
meltblowing processes, spunbonding processes, and bonded carded web
processes. The basis weight of nonwoven webs is usually expressed
in ounces of material per square yard (osy) or grams per square
meter (gsm) and the fiber diameters useful are usually expressed in
microns, or in the case of staple fibers, denier. It is noted that
to convert from osy to gsm, multiply osy by 33.91.
[0017] The term "denier" is defined as grams per 9000 meters of a
fiber. For a fiber having circular cross-section, denier may be
calculated as fiber diameter in microns squared, multiplied by the
density in grams/cc, multiplied by 0.00707. A lower denier
indicates a finer fiber and a higher denier indicates a thicker or
heavier fiber. Outside the United States the unit of measurement is
more commonly the "tex," which is defined as the grams per
kilometer of fiber. Tex may be calculated as denier/9. The "mean
fiber denier" is the sum of the deniers for each fiber, divided by
the number of fibers.
[0018] As used herein, the term "bulk density" refers to the weight
of a material per unit of volume and is generally expressed in
units of mass per unit bulk volume (e.g., grams per cubic
centimeter).
[0019] As used herein, the term "spunbonded fibers" refers to
fibers which are formed by extruding molten thermoplastic material
as filaments from a plurality of fine, usually circular capillaries
of a spinneret with the diameter of the extruded filaments then
being rapidly reduced as by, for example, U.S. Pat. No 4,340,563 to
Appel et al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S.
Pat. No. 3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and
3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartman; U.S. Pat.
No. 3,542,615 to Dobo et al.; and U.S. Pat. No. 5,382,400 to Pike
et al.; the entire content of each is incorporated herein by
reference. Spunbond fibers are generally not tacky when they are
deposited onto a collecting surface. Spunbond fibers are generally
continuous and have average diameters (from a sample of at least
10) larger than 7 microns to about 50 or 60 microns, often, between
about 15 and 25 microns.
[0020] As used herein, the term "meltblown fibers" means fibers
formed by extruding a molten thermoplastic material through a
plurality of fine, usually circular, die capillaries as molten
threads or filaments into converging high velocity, usually hot,
gas (e.g. air) streams which attenuate the filaments of molten
thermoplastic material to reduce their diameter, which may be to
microfiber diameter. Thereafter, the meltblown fibers are carried
by the high velocity gas stream and are deposited on a collecting
surface to form a web of randomly dispersed meltblown fibers. Such
a process is disclosed, for example, in U.S. Pat. No. 3,849,241.
Meltblown fibers are microfibers, which may be continuous or
discontinuous, and are generally smaller than 10 microns in average
diameter, and are generally tacky when deposited onto a collecting
surface.
[0021] As used herein, the term "polymer" generally includes, but
is not limited to, homopolymers, copolymers, such as for example,
block, graft, random and alternating copolymers, terpolymers, etc.
and blends and modifications thereof. Furthermore, unless otherwise
specifically limited, the term "polymer" shall include all possible
geometrical configurations of the molecule. These configurations
include, but are not limited to isotactic, syndiotactic and random
symmetries.
[0022] As used herein, the term "conjugate fibers" refers to fibers
or filaments which have been formed from at least two polymers
extruded from separate extruders but spun together to form one
fiber. Conjugate fibers are also sometimes referred to as
"multicomponent" or "bicomponent" fibers or filaments. The term
"bicomponent" means that there are two polymeric components
making-up the fibers. The polymers are usually different from each
other though conjugate fibers may be prepared from the same
polymer, but the polymers are different from one another in some
physical property, such as, for example, melting point or the
softening point. The polymers are arranged in substantially
constantly positioned distinct zones across the cross-section of
the multicomponent fibers or filaments and extend continuously
along the length of the multicomponent fibers or filaments. The
configuration of such a multicomponent fiber may be, for example, a
sheath/core arrangement, wherein one polymer is surrounded by
another, a side-by-side arrangement, a pie arrangement or an
"islands-in-the-sea" arrangement. Multicomponent fibers are taught
in U.S. Pat. No. 5,108,820 to Kaneko et al., U.S. Pat. No.
5,336,552 to Strack et al., and U.S. Pat. No. 5,382,400 to Pike et
al., the entire content of each is incorporated herein by
reference. For two component fibers or filaments, the polymers may
be present in ratios of 75/25, 50/50, 25/75 or any other desired
ratios.
[0023] As used herein, the term "multiconstituent fibers" refers to
fibers which have been formed from at least two polymers extruded
from the same extruder as a blend or mixture. Multiconstituent
fibers do not have the various polymer components arranged in
relatively constantly positioned distinct zones across the
cross-sectional area of the fiber and the various polymers are
usually not continuous along the entire length of the fiber,
instead usually forming fibrils or protofibrils which start and end
at random.
[0024] As used herein, the term "hot air knife" or HAK means a
process of preliminarily bonding a just produced microfiber web,
particularly spunbond, in order to give it sufficient integrity,
i.e. increase the stiffness of the web, for further processing, but
does not mean the relatively strong bonding of secondary bonding
processes like through-air bonding, thermal bonding and ultrasonic
bonding. A hot air knife is a device which focuses a stream of
heated air at a very high flow rate, generally from about 1000 to
about 10,000 feet per minute (fpm) (305 to 3050 meters per minute),
or more particularly from about 3000 to 6000 feet per minute (915
to 1830 meters per minute) directed at the nonwoven web immediately
after the nonwoven web formation. The air temperature is usually in
the range of the melting point of at least one of the polymers used
in the web, generally between about 200.degree. and 550.degree. F.
(93.degree. and 290.degree. C.) for the thermoplastic polymers
commonly used in spunbonding. However, the temperature of the air
must be adjusted accordingly for the particular polymers used to
prepare the nonwoven web. The control of air temperature, velocity,
pressure, volume and other factors helps avoid damage to the web
while increasing its integrity. The HAK's focused stream of air is
arranged and directed by at least one slot of about 1/8 to 1 inches
(3 to 25 mm) in width, particularly about 3/8 inch (9.4 mm),
serving as the exit for the heated air towards the web, with the
slot running in a substantially cross-machine direction over
substantially the entire width of the web. In other embodiments,
there may be a plurality of slots arranged next to each other or
separated by a slight gap. At least one slot is usually, though not
essentially, continuous, and may be comprised of, for example,
closely spaced holes. The HAK has a plenum to distribute and
contain the heated air prior to its exiting the slot. The plenum
pressure of the HAK is usually between about 1.0 and 12.0 inches of
water (2 to 22 mmHg), and the HAK is positioned between about 0.25
and 10 inches and more preferably 0.75 to 3.0 inches (19 to 76 mm)
above the forming wire. In a particular embodiment the HAK plenum's
cross sectional area for cross-directional flow (i.e. the plenum
cross sectional area in the machine direction) is at least twice
the total slot exit area. Since the forming wire onto which
spunbond polymer is formed generally moves at a high rate of speed,
the time of exposure of any particular part of the web to the air
discharged from the hot air knife is less a tenth of a second and
generally about a hundredth of a second in contrast with the
through-air bonding process which has a much larger dwell time. The
HAK process has a great range of variability and controllability of
many factors such as air temperature, velocity, pressure, volume,
slot or hole arrangement and size, and the distance from the HAK
plenum to the web. The HAK is further described in U.S. Pat. No.
5,707,468 to Arnold et al., the entire contents of which is
incorporated by reference.
[0025] As used herein, through-air bonding or "TAB" means a process
of bonding a nonwoven fiber web in which air, which is sufficiently
hot to melt one of the polymers of which the fibers of the web are
made, is forced through the web. The air velocity is between 100
and 500 feet per minute and the dwell time may be as long as 10
seconds. The melting and resolidification of the polymer provides
the bonding. Through-air bonding has relatively restricted
variability and since through-air bonding requires the melting of
at least one component to accomplish bonding, it is generally
restricted to webs with two components like multicomponent fibers
or those which include an adhesive. In the through-air bonder, air
having a temperature above the melting temperature of one component
and below the melting temperature of another component is directed
from a surrounding hood, through the web, and into a perforated
roller supporting the web. Alternatively, the through-air bonder
may be a flat arrangement wherein the air is directed vertically
downward onto the web. The operating conditions of the two
configurations are similar, the primary difference being the
geometry of the web during bonding. The hot air melts the lower
melting polymer component and thereby forms bonds between the
filaments to integrate the web.
[0026] As used herein "thermal point bonded" means bonding one or
more fabrics with a pattern of discrete bond points. As an example,
thermal point bonding often involves passing a fabric or web of
fibers to be bonded at a nip between a pair of heated bonding
calender rolls. One of the bonding rolls is usually, though not
always, patterned in some way so that the entire fabric is not
bonded across its entire surface, and the second or anvil roll is
usually a smooth surface. As a result, various patterns for
calender rolls have been developed for functional as well as
aesthetic reasons. One example of a pattern has points and is the
Hansen Pennings or "H&P" pattern with about a 30% bond area
with about 200 bonds/square inch as taught in U.S. Pat. No.
3,855,046 to Hansen and Pennings. The H&P pattern has square
point or pin bonding areas wherein each pin has a side dimension of
0.038 inches (0.965 mm), a spacing of 0.070 inches (1.778 mm)
between pins, and a depth of bonding of 0.023 inches (0.584 mm).
The resulting pattern has a bonded area of about 29.5%. Another
typical point bonding pattern is the expanded Hansen Pennings or
"EHP" bond pattern which produces a 15% bond area with a square pin
having a side dimension of 0.037 inches (0.94 mm), a pin spacing of
0.097 inches (2.464 mm) and a depth of 0.039 inches (0.991 mm).
Another typical point bonding pattern designated "714" has square
pin bonding areas wherein each pin has a side dimension of 0.023
inches, a spacing of 0.062 inches (1.575 mm) between pins, and a
depth of bonding of 0.033 inches (0.838 mm). The resulting pattern
has a bonded area of about 15%. Yet another common pattern is the
C-Star pattern which has a bond area of about 16.9%. The C-Star
pattern has a cross-directional bar or "corduroy" design
interrupted by shooting stars. Other common patterns include a
diamond pattern with repeating and slightly offset diamonds with
about a 16% bond area and a wire weave pattern, having generally
alternating perpendicular segments, with about a 19% bond area.
Typically, the percent bonding area varies from around 10% to
around 30% of the area of the fabric laminate web. Point bonding
may be used to hold the layers of a laminate together and/or to
impart integrity to individual layers by bonding filaments and/or
fibers within the web.
[0027] As used herein "pattern unbonded" or interchangeably "point
unbonded" or "PUB", means a fabric pattern having continuous bonded
areas defining a plurality of discrete unbonded areas. The fibers
or filaments within the discrete unbonded areas are dimensionally
stabilized by the continuous bonded areas that encircle or surround
each unbonded area, such that no support or backing layer of film
or adhesive is required. The unbonded areas are specifically
designed to afford spaces between fibers or filaments within the
unbonded areas. A suitable process for forming the pattern-unbonded
nonwoven material includes providing a nonwoven fabric or web,
providing opposedly positioned first and second calender rolls and
defining a nip there between, with at least one of said rolls being
heated and having a bonding pattern on its outermost surface
comprising a continuous pattern of land areas defining a plurality
of discrete openings, apertures or holes, and passing the nonwoven
fabric or web within the nip formed by said rolls. Each of the
openings in said roll or rolls defined by the continuous land areas
forms a discrete unbonded area in at least one surface of the
nonwoven fabric or web in which the fibers or filaments of the web
are substantially or completely unbonded. Stated alternatively, the
continuous pattern of land areas in said roll or rolls forms a
continuous pattern of bonded areas that define a plurality of
discrete unbonded areas on at least one surface of said nonwoven
fabric or web. The PUB pattern is further described in U.S. Pat.
No. 5,858,515 to Stokes et al, the entire contents of which are
hereby incorporated by reference.
[0028] As used herein, the term "debris" means items which
typically need removal during a cleaning process. This term is
intended to include, but is not limited to, hair (both human and
pet), dandruff (both human and pet), food particles, e.g. crumbs
from bread, cakes cookies and the like, grass, dirt, defoliated
skin, and other such items.
Detailed Description
[0029] The inventors of the present invention have discovered that
nonwoven webs formed from multicomponent, multilobal shaped fibers
have an enhanced dirt, dust and/or debris pickup and retention
within the nonwoven web. Furthermore, the multicomponent,
multilobal shaped fibers are also shaped in ways meant to enhance
liquid retention. These properties provide for a cleaning sheet
which can be used in both dry and wet applications, which provide
enhance and effective dirt, dust and/or debris pickup and
retention, while, at the same time, can also provide absorbency of
liquids. The multicomponent, multilobal shaped fibers have "lobes"
separated by depressed regions which allow the nonwoven web to
absorb liquids and hold the absorbed liquids in place within the
nonwoven structure. Tips of the multicomponent, multilobal shaped
fibers increase surface area which provides for enhance surface
contact, which in turn provides for the enhanced dirt, dust and/or
debris pickup of the cleaning sheet. In addition, the multilobal
shape of the fibers also creates voids within the nonwoven web
structure which allows for dirt, dust and/or debris retention
within the nonwoven web.
[0030] The shaped fibers of the present invention may be spunbond
fibers made from at least two polymers as multicomponent fibers and
have at least one lobe capable of holding liquid. Multicomponent
fibers may be split, crimped and through-air bonded among many
other properties and bonding options. Combining the advantages of
the liquid and particle pick-up and retention of multilobal fibers
with the processing advantages of multicomponent fiber results in a
nonwoven web which has highly desirable properties needed in
cleaning sheets. In addition, the fibers of the present invention
have improved processibility and can provide a myriad of different
nonwoven webs having properties which can be tailored to the needs
of the end user.
[0031] The spunbond process generally uses a hopper which supplies
polymer to a heated extruder. The extruder supplies melted polymer
to a spinneret where the polymer is fiberized as it passes through
fine openings arranged in one or more rows in the spinneret,
forming a curtain of filaments. The filaments are usually quenched
with air at a low pressure, drawn, usually pneumatically and
deposited on a moving foraminous mat, belt or "forming wire" to
form the nonwoven web. Polymers useful in the spunbond process
commonly have a process melt temperature of between about
400.degree. F. to about 610.degree. F. (200.degree. C. to
320.degree. C.).
[0032] The fibers produced in the spunbond process are usually in
the range of from about 5 to about 50 microns in average diameter,
depending on process conditions and the desired end use for the
webs to be produced from such fibers. For example, increasing the
polymer molecular weight or decreasing the processing temperature
results in larger diameter fibers. Changes in the quench fluid
temperature and pneumatic draw pressure can also affect fiber
diameter. The fibers used in the practice of this invention usually
have average diameters in the range of from about 7 to about 35
microns, more particularly from about 15 to about 25 microns.
[0033] The fibers used to produce the web of this invention are
multicomponent fibers. As these multicomponent fibers are produced
and cooled, the differing coefficients of expansion of the polymers
can cause these fibers to bend and ultimately to crimp, somewhat
akin to the action of the bimetallic strip in a conventional room
thermostat. Crimped fibers are described in U.S. Pat. No. 5,382,400
wherein fibers are crimped with the same air as is used to draw
them. Sufficiently warm drawing air activates the latent helical
crimp of the fibers as the fibers are produced and before they are
deposited on the forming wire. Crimped fibers have an advantage
over uncrimped fibers in that they produce a more bulky web,
thereby increasing the void spacing within the nonwoven web. Larger
void spacing is a desirable characteristic for cleaning sheets,
since the larger voids will allow for the pickup and retention of
larger particles of dirt, dust and/or debris. Therefore, crimped
fibers are somewhat more desirable than uncrimped fibers in
cleaning sheets. Additionally, the degree of crimp can be
controlled by controlling the temperature of the drawing air,
thereby providing a mechanism for controlling the web density.
Generally, a higher air temperature produces a higher number of
crimps. This allows one to change the resulting bulk density, and
void size distribution of the resulting cleaning sheet by simply
adjusting the temperature of the air in the fiber draw unit.
[0034] In the present invention, the nonwoven web cleaning sheets
will typically have a bulk density of about 0.01 to about 0.2
g/cm.sup.3. Preferably, the cleaning sheets with have a bulk
density of about 0.015 to about 0.075 g/cm.sup.3 and ideally about
0.02 to about 0.05 g/cm.sup.3.
[0035] The nonwoven web cleaning sheets of the present invention
may have basis weights ranging from about 0.25 osy (8.5 gsm) to
about 25 osy (850 gsm). The actual basis weight of the nonwoven
material is dependent of the final use of the cleaning sheet. It is
desirable that the basis weight be in the range from about 0.5 osy
(17 gsm) to about 10 osy (340 gsm), and preferably about 1.0 osy
(34 gsm) to about 5 osy (170 gsm), for many applications.
[0036] The multicomponent, multilobal shape of the fibers used in
the practice of this invention must provide areas in which dirt,
dust and/or debris can be retained and/or where liquids may be
retained. Preferred shapes are those described in U.S. Pat. Nos.
5,069,970 and 5,057,368 to Largman et al., assigned to Allied
Signal, Inc., hereby incorporated by reference in their entirety,
which describe fibers with unconventional shapes. In addition,
shaped fibers are also described in U.S. Pat. Nos. 5,314,743,
5,342,336 and 5,458,963 to Meirowitz et al., hereby incorporated by
reference in their entirety. None of these patents, however,
suggest multicomponent fibers or the unique advantages of such
fibers in crimping, varying web pore size or bonding and which are
important factors determining the usefulness of such fibers when
used to create a nonwoven web cleaning sheet. Multicomponent shaped
fibers are known in the art and have been used in filter fabrics as
is shown in U.S. Pat. No. 5,707,735 to Midkiff et al, which is also
hereby incorporated by reference in its entirety. Fibers having the
shapes and configurations of the '735 patent may also be used in
the present invention. Generally, the multilobal fibers of the
present in invention will have between 2 and 10 lobes, but
preferably have between 2 and 5 lobes. Other examples of
multicomponent, shaped fibers which can be used in the present
invention are shown in FIG. 1.
[0037] Referring to FIG. 1(a), a bilobal bicomponent nonwoven fiber
100 is shown in cross-section. The fiber 100 has two lobes 112 and
114, and depressed regions 116 and 118 on both sides of fiber 110
between the lobes. A boundary line 119 indicates the interface
between a polymer component forming one of the lobes 112 and 114,
and a polymer component forming the other lobe. The polymer
components of the fiber are arranged side-by-side.
[0038] FIG. 1(b) illustrates, in cross-section, a trilobal
bicomponent nonwoven fiber 120 in which the three lobes 122, 124
and 126 are positioned at right angles to each other. A depressed
region 123 is located between the lobes 122 and 124. A depressed
region 125 is located between the lobes 122 and 126. It should be
apparent from FIG. 1(b), for instance, that the term "depressed
region" refers to a region which is concave with respect to a
straight line drawn tangential to the two adjacent lobes. In FIG.
1(b), a straight line 127 can be drawn tangential to adjacent lobes
122 and 124, with concave portion 123 underneath the straight line.
A similar straight line can be drawn tangential to adjacent lobes
122 and 126. However, no concave region exists with respect to a
straight line drawn tangential to adjacent lobes 124 and 126. In
FIG. 1(b), the dividing line 129 represents an interface between a
polymer component forming half of the fiber, and a polymer
component forming the other half of the fiber. Again, the polymer
components of the fiber are arranged in a side-by-side
configuration.
[0039] FIG. 1(c) illustrates, in cross-section, a trilobal
bicomponent nonwoven fiber 130 in which the three lobes 132, 134
and 136 are positioned at 60-degree angles to each other. A
depressed region 133 is located between lobes 132 and 134. A
depressed region 135 is located between lobes 132 and 136. A
depressed region 137 is located between lobes 134 and 136. A
dividing line 139 represents an interface between a polymer forming
half of the fiber 130, and a polymer forming the other half. Again,
the fiber 130 has a side-by-side distribution of the polymer
components.
[0040] FIG. 1(d) illustrates, in cross-section, a quadrilobal
bicomponent fiber 140 in which the four lobes 142, 144, 146 and 148
are arranged in a star-like configuration. Depressed regions 141,
143, 145 and 147 are formed between each pair of adjacent lobes. A
circular dividing line 149 represents an interface between the
polymer components. In this instance, the bicomponent fiber has a
sheath-core configuration with one polymer forming the core and the
other polymer forming the sheath.
[0041] FIG. 1(e) illustrates, in cross-section, a quadrilobal
bicomponent fiber 150 in which the four lobes 152, 154, 156 and 158
are arranged in a cross configuration. Depressed regions 151, 153,
155 and 157 are formed between each pair of adjacent lobes.
Dividing line 159 represents the interface between polymer
components, which are arranged in a side-by-side configuration.
[0042] FIG. 1(f) illustrates, in cross-section, a pentalobal
bicomponent fiber 160 having five lobes 162, 164, 166, 168 and 170
arranged at approximately 72-degree angles to each other. Depressed
regions 161, 163, 165, 167 and 169 are formed between each pair of
adjacent lobes. Dividing line 171 represents the interface between
the polymer components which are arranged in a side-by-side
configuration.
[0043] FIG. 1(g) illustrates, in cross-section, a quadrilobal
bicomponent fiber 180 in which the four lobes 182, 184, 186 and 188
are arranged in a cross configuration. Depressed regions 181, 183,
185 and 187 are formed between each pair of adjacent lobes.
Dividing lines 189 represents the interface between polymer
components, which are arranged in a sheath/core configuration.
[0044] FIG. 1(h) illustrates, in cross-section, a pentalobal
bicomponent fiber 200 having five lobes 202, 204, 206, 208 and 210
arranged at approximately 72-degree angles to each other. Depressed
regions 201, 203, 205, 207 and 209 are formed between each pair of
adjacent lobes. Dividing line 211 represents the interface between
the polymer components which are arranged in a sheath/core
configuration.
[0045] It is pointed out that the shape of the fibers which can be
used in the present invention are not limited to the specific shape
or configurations shown in FIG. 1. Other shapes and configurations
of the multicomponent, multilobal shaped fibers can, so long as the
resulting nonwoven web has an ability to pick-up and retain dirt,
dust and/or debris and/or to absorb and retain fluids.
[0046] The polymers suitable for the present invention include
polyolefins, polyesters, polyamides, polycarbonates, polyurethanes,
polyvinylchloride, polytetrafluoroethylene, polystyrene,
polyethylene terephathalate, biodegradable polymers such as
polylactic acid and copolymers and blends thereof Suitable
polyolefins include polyethylene, e.g., high density polyethylene,
medium density polyethylene, low density polyethylene and linear
low density polyethylene; polypropylene, e.g., isotactic
polypropylene, syndiotactic polypropylene, blends of isotactic
polypropylene and atactic polypropylene, and blends thereof;
polybutylene, e.g., poly(1-butene) and poly(2-butene); polypentene,
e.g., poly(1-pentene) and poly(2-pentene);
poly(3-methyl-1-pentene); poly(4-methyl 1-pentene); and copolymers
and blends thereof. Suitable copolymers include random and block
copolymers prepared from two or more different unsaturated olefin
monomers, such as ethylene/propylene and ethylene/butylene
copolymers. Suitable polyamides include nylon 6, nylon 6/6, nylon
4/6, nylon 11, nylon 12, nylon 6/10, nylon 6/12, nylon 12/12,
copolymers of caprolactam and alkylene oxide diamine, and the like,
as well as blends and copolymers thereof. Suitable polyesters
include polyethylene terephthalate, polytrimethylene terephthalate,
polybutylene terephthalate, polytetramethylene terephthalate,
polycyclohexylene-1,4-di- methylene terephthalate, and isophthalate
copolymers thereof, as well as blends thereof.
[0047] Many polyolefins are available for fiber production, for
example polyethylenes such as Dow Chemical's ASPUN 6811A linear
low-density polyethylene, 2553 LLDPE and 25355 and 12350 high
density polyethylene are such suitable polymers. The polyethylenes
have melt flow rates in g/10 min. at 190.degree. F. and a load of
2.16 kg, of about 26, 40, 25 and 12, respectively. Fiber forming
polypropylenes include Exxon Chemical Company's ESCORENE PD3445
polypropylene. Many other polyolefins are commercially available
and generally can be used in the present invention. The
particularly preferred polyolefins are polypropylene and
polyethylene.
[0048] Examples of polyamides and their methods of synthesis may be
found in "Polymer Resins" by Don E. Floyd (Library of Congress
Catalog number 66-20811, Reinhold Publishing, N.Y., 1966).
Particularly commercially useful polyamides are nylon 6, nylon-6,6,
nylon-11 and nylon-12. These polyamides are available from a number
of sources such as Custom Resins, Nyltech, among others. In
addition, a compatible tackifying resin may be added to the
extrudable compositions described above to provide tackified
materials that autogenously bond or which require heat for bonding.
Any tackifier resin can be used which is compatible with the
polymers and can withstand the high processing (e.g., extrusion)
temperatures. If the polymer is blended with processing aids such
as, for example, polyolefins or extending oils, the tackifier resin
should also be compatible with those processing aids. Generally,
hydrogenated hydrocarbon resins are preferred tackifying resins,
because of their better temperature stability. REGALREZ.RTM. and
ARKON.RTM. P series tackifiers are examples of hydrogenated
hydrocarbon resins. ZONATAC.RTM. 501 lite is an example of a
terpene hydrocarbon. REGALREZ.RTM. hydrocarbon resins are available
from Hercules Incorporated. ARKON.RTM. series resins are available
from Arakawa Chemical (USA) Incorporated. The tackifying resins
such as disclosed in U.S. Pat. No. 4,787,699, hereby incorporated
by reference, are suitable. Other tackifying resins which are
compatible with the other components of the composition and can
withstand the high processing temperatures, can also be used.
[0049] In addition, the lobes may be made from particular polymers
which are hydrophilic or which may be treated for hydrophilicity
which will enhance the ability of the nonwoven web to absorb
aqueous liquids.
[0050] The polymers used to make the nonwoven web may contain
additives, such as surfactants or slip agents, to aid in the
sliding of the sensitive surface against the nonwoven material.
Other additives, such as pigments, dyes, processing aids and the
like can be added to the polymer prior to fiber formation, provided
that the additives do not adversely affect the ability of the
nonwoven web to pickup and retain dirt, dust and/or debris and/or
the ability of the nonwoven web to absorb liquids. Ferroelectric
materials, such as those disclosed in U.S. Pat. No. 6,162,535 to
Turkevich et al, assigned to the assignee of this invention, and is
incorporated in its entirety by reference, may also be added to
fibers. In addition, other polymeric additives, such as maleic
anhydride telomers may also be added, for example to provide
electret stability.
[0051] It is desirable that the particular polymers used for the
different components of the fibers in the practice of the invention
have melting points different from one another. This is important
not only in producing crimped fibers but also when through-air
bonding is used as the bonding technique, wherein the lower melting
polymer bonds the fibers together to form the fabric or web. It is
desirable that the lower melting point polymers makes up at least a
portion of the outer region of the fibers. More particularly, the
lower melting component should be located in an outer portion of
the fiber so that it comes in contact with other fibers. For
example, in a sheath/core fiber configuration, the lower melting
point polymer component should be located in the sheath portion. In
a side-by-side configuration, the lower melting point polymer will
inherently be located on an outer portion of the fiber.
[0052] The proportion of higher and lower melting polymers in the
multicomponent, multilobal fibers can range between about 10-90% by
weight higher melting polymer and 10-90% lower melting polymer. In
practice, only so much lower melting polymer is needed as will
facilitate bonding between the fibers. Thus, a suitable fiber
composition may contain about 40-80% by weight higher melting
polymer and about 20-60% by weight lower melting polymer, desirably
about 50-75% by weight higher melting polymer and about 25-50% by
weight lower melting polymer.
[0053] In a preferred embodiment, a first polymer, which is the
lower melting point polymer is polyethylene and the higher melting
point polymer is polypropylene. This embodiment is preferred from
the standpoint of cost and resulting properties of the cleaning
sheet.
[0054] After the fibers are formed and deposited on the forming
wire and create the web of this invention, the web may be passed
through a hot air knife or HAK to very slightly consolidate the web
and provide the web with enough integrity for further processing.
After deposition but before HAK treatment, the fiber web has low
stiffness which makes its difficult, if not impossible, to
successfully convert on commercially available converting equipment
commonly used to the final use. The application of the HAK allows
forming a web of fibers to deliver high stiffness by melting only a
portion of the lower melting component in the web, preferably only
that lower melting component on the side facing the HAK air, in a
pre- or primary bonding step. This HAK step creates a zone of
pre-bonded fibers located on one side of the web which then undergo
a second melting when exposed to through-air bonding or bonding
with a heated bonding roll, such as a roll which will impart a PUB
pattern to the nonwoven web or a roll which imparts a thermal point
bonded pattern to the web. The exposure of this zone to at least
two heating and melting cycles is believed to create a zone of high
stiffness in the web from the crystallization of the polymer,
however, since the zone is comprised of a small percentage of the
total web, the effect on bulk density of the web is minimized. This
differs from the commonly used method of increasing the integrity
of a web known as compaction rolls since, while compaction rolls
increase the stiffness of a web, the compaction rolls also increase
the bulk density of the web. It is noted, however, that while
compaction rolls may be used in the practice of this invention, the
HAK is generally preferred since the HAK does not reduce the void
spacing of the web while compaction rolls will reduce the void
spacing. After treatment with the HAK, the web is sufficiently
cohesive to move it to the next step of production; the secondary
bonding step. Any secondary bonding known to those skilled in the
art can be used.
[0055] The secondary bonding procedure which may be used in the
practice of this invention is preferably through-air bonding
because it does not appreciably reduce web void (pore) size. When
used with HAK pre-bonding, through-air bonding very effectively
produces high stiffness in the web since it provides a second
heating of the polymer previously heated by the HAK and provides
sufficient heat to bond fibers not bonded by the HAK. This creates
bonds at almost every fiber crossover point, thereby restricting
movement of the majority of the fibers of the web.
[0056] Other secondary bonding methods can be used without
limitation. Examples of other secondary bonding methods include PUB
bonding and thermal point bonding. In the PUB pattern, a continuous
bond area is formed with a plurality of discrete unbonded areas.
Thermal point bonding by contrast results has discrete bonding
points, and a continuous unbonded area.
[0057] Through-air bonding is preferred secondary bonding because
it does not appreciably reduce void size when compared, for
example, to thermal point bonding. Through-air bonding creates
small bonds at almost every fiber crossover point, minimally
effecting the void size within the nonwoven web structure. Thermal
point bonding by contrast results in comparatively large bonds at
discrete points, compressing the web in areas around the bond
points which decreases the void size at or near the bond
points.
[0058] After the secondary bonding, the nonwoven web may be
electret treated. Electret treatment further increases ability of
the nonwoven web to pick-up and retain dirt, dust and/or debris by
drawing the dirt, dust and/or debris into the nonwoven web by
virtue of their electrical charge. Electret treatment can be
carried out by a number of different techniques. One technique is
described in U.S. Pat. No. 5,401,446 to Tsai et al. assigned to the
University of Tennessee Research Corporation and incorporated
herein by reference in its entirety. Tsai describes a process
whereby a web or film is sequentially subjected to a series of
electric fields such that adjacent electric fields have
substantially opposite polarities with respect to each other. Thus,
one side of the web or film is initially subjected to a positive
charge while the other side of the web or film is initially
subjected to a negative charge. Then, the first side of the web or
film is subjected to a negative charge and the other side of the
web or film is subjected to a positive charge. Such webs are
produced with a relatively high charge density without an attendant
surface static electrical charge. The process may be carried out by
passing the web through a plurality of dispersed non-arcing
electric fields which may be varied over a range depending on the
charge desired in the web. The web may be charged at a range of
about 1 kVDC/cm to about 30 kVDC/cm or more particularly about 4
kVDC/cm to about 12 kVDC/cm and still more particularly about 7
kVDC/cm to about 8 kVDC/cm.
[0059] Electret charge stability can be further enhanced by
grafting polar end groups onto the polymers of the multicomponent
fibers. In addition, barium titanate and other polar materials may
be blended with the polymers to enhance the electret treatment.
Suitable blends are described in U.S. Pat. No. 6,162,535 to
Turkevich et al, assigned to the assignee of this invention and in
PCT Publication WO 00/00267 to Myers et al.
[0060] Other methods of electret treatment are known in the art
such as that described in U.S. Pat. No. 4,215,682 to Kubik et al,
U.S. Pat. No. 4,375,718 to Wadsworth, U.S. Pat. No. 4,592,815 to
Nakao and U.S. Pat. No. 4,874,659 to Ando, each hereby incorporated
in its entirety by reference.
[0061] Electret treatment is desirable if the cleaning sheet is to
be used as a dry wiping sheet, since the charge in the cleaning
sheet will tend to attract the dirt, dust and/or other debris to
the cleaning sheet. In contrast, if the cleaning sheet is to be
used as a wet cleaning sheet, then electret treatment is generally
not desired. It is pointed out, however, that a dry wiping sheet
does not have to be electret treated and a wet cleaning sheet may
be electret treated.
[0062] The multicomponent, multilobal shaped fibers of the nonwoven
web used as a cleaning sheet in the present invention can
optionally be split or fibrillated. Split or fibrillated fine
fibers exhibit highly desirable properties, including textural,
visual and strength properties. There are different known processes
for producing split fine fibers, and in general, split fibers are
produced from multicomponent fibers which contain two or more
incompatible polymer components or from an axially oriented film.
For example, a known method for producing split fibrous structures
includes the steps of forming splittable multicomponent filaments
into a fabric and then treating the fabric with an aqueous emulsion
of benzyl alcohol or phenyl ethyl alcohol to split the
multicomponent filaments. Another known method has the steps of
forming splittable multicomponent filaments into a fibrous
structure and then splitting the multicomponent filaments by
flexing or mechanically working the filaments in the dry state or
in the presence of a hot aqueous solution. Yet another commercially
utilized method for producing split fine denier fibers is a
needling process. In this process, multicomponent fibers are
hydraulically or mechanically needled to separate the different
polymer components of the multicomponent fibers. Further yet
another method for producing fine fibers, although it may not be a
fiber splitting process, utilizes multicomponent fibers that
contain a solvent or water soluble polymer component. For example,
a fibrous structure is produced from sheath-core multicomponent
fibers and then the fibrous structure is treated with a solvent
that dissolves the sheath component to produce a fibrous structure
of fine denier fibers of the core component. For the purposes of
this invention, split multicomponent fibers may be produced from
any method which is effective.
[0063] The nonwoven web of this invention may be produced from the
multicomponent, multilobal shaped fibers alone, or in combination
with other fibers, such as thermoplastic monolobal fibers. The
addition of the monolobal fibers to the multicomponent, multilobal
shaped fibers helps improves the strength of the resulting nonwoven
web. The monolobal fibers can be monocomponent fibers or can be
multicomponent fibers. Preferably, the monolobal fibers are
multicomponent fibers made from the same components as the
multicomponent multilobal shaped fibers. As with the multicomponent
multilobal shaped fibers, a portion of the outer layer should have
a lower melting point polymer. The preferred monolobal fibers
desirably have a substantially circular cross-sectional shape.
[0064] When the monolobal fibers are present in the nonwoven web,
the nonwoven web cleaning sheet comprises from about 1 to about 99%
by weight of the multicomponent, multilobal shaped fibers and about
99 to about 1% of the monolobal fibers. Preferably, the nonwoven
web cleaning sheet comprises from about 5 to about 95% by weight of
the multicomponent, multilobal shaped fibers and about 95 to about
5% of the monolobal fibers More preferably, the nonwoven web
cleaning sheet contains from about 30 to about 75% by weight of the
multicomponent multilobal shaped fibers and about 70 to about 25%
of the round shaped fibers.
[0065] The cleaning sheets of the present invention have a surface
area of at least 0.210 m.sup.2/g. Generally, the surface are
generally in the range of about 0.220 m.sup.2/g to about 0.500
m.sup.2/g, and more particularly, in the range of about 0.250
m.sup.2/g to about 0.350 m.sup.2/g.
[0066] Other fibers such as natural fibers may also be incorporated
into the thermoplastic multicomponent, multilobal shaped fibers.
Examples of such natural fibers include, for example, cellulosic,
such as pulp fibers. The addition of natural fibers can improve the
liquid absorbency of the cleaning sheet. Various pulp fibers can be
utilized including, but not limited to, thermomechanical pulp
fibers, chemithermomechanical pulp fibers, chemimechanical pulp
fibers, refiner mechanical pulp fibers, stone groundwood pulp
fibers, peroxide mechanical pulp fibers and so forth. If other
fibers are included in the nonwoven web cleaning sheet of the
present invention, these fibers should make up less than 50% by
weight of the nonwoven web.
[0067] Turning to FIG. 2, a process line 10 for preparing an
embodiment of the present invention is disclosed. The process line
10 is arranged to produce multicomponent continuous filaments, but
it should be understood that the present invention comprehends
nonwoven fabrics made with multicomponent filaments having more
than two components. For example, the fabric of the present
invention can be made with filaments having three or four
components. The process line 10 includes a pair of extruders 12a
and 12b for separately extruding a polymer component A and a
polymer component B. Polymer component A is fed into the respective
extruder 12a from a first hopper 14a and polymer component B is fed
into the respective extruder 12b from a second hopper 14b. Polymer
components A and B are fed from the extruders 12a and 12b through
respective polymer conduits 16a and 16b to a spinneret 18. The
spinneret 18 has openings arranged in one or more rows. The
spinneret openings form a downwardly extending curtain of filaments
when the polymers are extruded through the spinneret. For the
purposes of the present invention, spinneret 18 may be arranged to
form side-by-side or eccentric sheath/core multicomponent
filaments, for example.
[0068] The process line 10 also includes a quench blower 20
positioned adjacent the curtain of filaments extending from the
spinneret 18. Air from the quench air blower 20 quenches the
filaments extending from the spinneret 18. The quench air can be
directed from one side of the filament curtain as shown in FIG. 2,
or both sides of the filament curtain.
[0069] A fiber draw unit or aspirator 22 is positioned below the
spinneret 18 and receives the quenched filaments. Fiber draw units
or aspirators for use in melt spinning polymers are well-known as
discussed above. Suitable fiber draw units for use in the process
of the present invention include a linear, fiber aspirator of the
type shown in U.S. Pat. No. 3,802,817 or U.S. Pat. No. 4,340,563
and eductive guns of the type shown in U.S. Pat. Nos. 3,692,618 and
3,423,266, each hereby incorporated by reference in its entirety.
Generally described, the fiber draw unit 22 includes an elongate
vertical passage through which the filaments are drawn by
aspirating air entering from the sides of the passage and flowing
downwardly through the passage. A blower 24 supplies hot aspirating
air to the fiber draw unit 22. The hot aspirating air draws the
filaments and ambient air through the fiber draw unit.
[0070] An endless forming surface 26 is positioned below the fiber
draw unit 22 and receives the continuous filaments from the outlet
opening of the fiber draw unit. The forming surface 26 travels
around guide rollers 28. A vacuum 30 positioned below the forming
surface 26 where the filaments are deposited draws the filaments
against the forming surface.
[0071] The process line 10 as shown also includes a hot-air knife
34 which provides a degree of integrity to the web. In addition,
the process line includes a bonding apparatus which is a
through-air bonder 36. After passing through the through-air
bonder, the web is passed between a charging wire or bar 48 and a
charged roller 42 and then between a second charging wire or bar 50
and roller 44. As is stated above, the electret treatment is an
optional process step and is not required.
[0072] Lastly, the process line 10 includes a winding roll 42 for
taking up the finished fabric.
[0073] To operate the process line 10, the hoppers 14a and 14b are
filled with the respective polymer components A and B. Polymer
components A and B are melted and extruded by the respective
extruders 12a and 12b through polymer conduits 16a and 16b and the
spinneret 18. Although the temperatures of the molten polymers vary
depending on the polymers used, when polypropylene and polyethylene
are used as components A and B respectively, the preferred
temperatures of the polymers range from about 370.degree. to about
530.degree. F. and preferably range from 400.degree. to about
450.degree. F.
[0074] As the extruded filaments extend below the spinneret 18, a
stream of air from the quench air blower 20 at least partially
quenches the filaments to develop a latent helical crimp in the
filaments at an air temperature of about 45.degree. to about
90.degree. F. and a velocity from about 100 to about 400 feet per
minute.
[0075] After quenching, the filaments are drawn into the vertical
passage of the fiber draw unit 22 by a flow of hot air from the
heater 24 through the fiber draw unit. The fiber draw unit is
preferably positioned 30 to 60 inches below the bottom of the
spinneret 18. The temperature of the air supplied from the heater
24 is sufficient that, after some cooling due to mixing with cooler
ambient air aspirated with the filaments, the air heats the
filaments to a temperature required to activate the latent crimp.
The temperature required to activate the latent crimp of the
filaments ranges from about 110.degree. F. to a maximum temperature
less that the melting point of the lower melting component which
for through-air bonded materials is the second component B. The
temperature of the air from the heater 24 and thus the temperature
to which the filaments am heated can be varied to achieve different
levels of crimp. Generally, a higher air temperature produces a
higher number of crimps. The ability to control the degree of crimp
of the filaments is a particularly advantageous feature of the
present invention because it allows one to change the resulting
density, pore size distribution and drape of the fabric by simply
adjusting the temperature of the air in the fiber draw unit.
[0076] The crimped filaments are deposited through the outlet
opening of the fiber draw unit 22 onto the traveling forming
surface 26. The vacuum 30 draws the filaments against the forming
surface 26 to form an unbonded, nonwoven web of continuous
filaments. The web is then given a degree of integrity by the
hot-air knife 34 and through-air bonded in the through-air bonder
36.
[0077] In the through-air bonder 36, air having a temperature above
the melting temperature of component B and below the melting
temperature of component A is directed from the hood 40, through
the web, and into the perforated roller 38. Alternatively, the
through-air bonder may be a flat arrangement wherein the air is
directed vertically downward onto the web. The operating conditions
of the two configurations are similar, the primary difference being
the geometry of the web during bonding. The hot air melts the lower
melting polymer component B and thereby forms bonds between the
multicomponent filaments to integrate the web. When polypropylene
and polyethylene are used as polymer components A and B
respectively, the air flowing through the through-air bonder
usually has a temperature ranging from about 230.degree. F. to
about 325.degree. F. (110.degree. C. to 162.degree. C.) and a
velocity from about 100 to about 500 feet per minute. It should be
understood, however, that the parameters of the through-air bonder
depend on factors such as the type of polymers used and thickness
of the web. The web may optionally then be passed through the
charged field between the charging bar or wire 48 and the charging
drum or roller 42 and then through a second charged field of
opposite polarity created between charging bar or wire 50 and
charging drum or roller 44. The web may be charged at a range of
about 1 kVDC/cm to 30 kVDC/cm.
[0078] Lastly, the finished web is wound onto the winding roller 42
and is ready for further processing or use.
[0079] As is noted above, the HAK may be replaced with a compacting
roll, however a HAK is preferred to the compacting roll for the
reasons stated above.
[0080] The cleaning sheet of this invention may be a multilayer
laminate and may be formed by a number of different techniques
including but not limited to using adhesive, needle punching,
ultrasonic bonding, thermal calendering and through-air bonding.
Such a multilayer laminate may be an embodiment wherein some of the
layers are spunbond and some meltblown such as a
spunbond/meltblown/spunbond (SMS) laminate as disclosed in U.S.
Pat. No. 4,041,203 to Brock et al. and U.S. Pat. No. 5,169,706 to
Collier, et al., each hereby incorporated by reference. The SMS
laminate may be made by sequentially depositing onto a moving
conveyor belt or forming wire first a spunbond web layer, then a
meltblown web layer and last another spunbond layer and then
bonding the laminate in a manner described above.
[0081] Alternatively, the three web layers may be made
individually, collected in rolls and combined in a separate bonding
step.
[0082] In a preferred multilayer laminate, two layers of spunbond
webs are joined together, with or without the meltblown layer. One
of the spunbond layers is a layer of multicomponent multilobal
shaped fibers and another of the layers is a layer of monolobal
fibers. The layer of multicomponent multilobal shaped fibers gives
the resulting nonwoven web the ability to pick-up and retain dirt,
dust and/or debris, and the layer of monolobal fibers imparts
strength to the laminate. Preferably, the layer of the
multicomponent multilobal shaped fibers is adjacent to the layer of
monolobal fibers. It is further pointed out that the layer of
monolobal fibers may be monocomponent fibers or multicomponent
fibers. In addition, the layer of multicomponent, multilobal fibers
may optionally contain other fibers described above.
[0083] In another alternative laminate structure of the present
invention, the cleaning sheet may also have a barrier layer. The
liquid barrier layer desirably comprises a material that
substantially prevents the transmission of liquids under the
pressures and chemical environments associated with surface
cleaning applications. Desirably, the liquid barrier layer
comprises a thin, monolithic film. The film desirably comprises a
thermoplastic polymer such as, for example, polyolefins (e.g.,
polypropylene and polyethylene), polycondensates (e.g., polyamides,
polyesters, polycarbonates, and polyarylates), polyols, polydienes,
polyurethanes, polyethers, polyacrylates, polyacetals, polyimides,
cellulose esters, polystyrenes, fluoropolymers and so forth.
Desirably, the film is hydrophobic. Additionally, the film
desirably has a thickness less than about 2 mil and still more
desirably between about 0.5 mil and about 1 mil. As a particular
example, the liquid barrier layer can comprise an embossed,
polyethylene film having a thickness of approximately 1 mil.
[0084] The liquid barrier layer can be bonded together with the
other layer or layers of the cleaning sheet to form an integrated
laminate through the use of adhesives. In a further aspect, the
layers can be attached by mechanical means such as, for example, by
stitching. Still further, the multiple layers can be thermally
and/or ultrasonically laminated together to form an integrated
laminate. The method of bonding is not critical to the present
invention.
[0085] The size and shape of the cleaning sheet can vary with
respect to the intended application and/or end use of the same.
Desirably, the cleaning sheet has a substantially rectangular shape
of a size which allows it to readily engage standard cleaning
equipment or tools such as, for example, mop heads, duster heads,
brush heads and so forth. As one particular example, in order to
fit a standard mop head, the cleaning sheet may have a length of
about 28 cm and a width of about 22 cm. However, the particular
size and/or shape of cleaning sheet can vary as needed to fit upon
or otherwise conform to a specific cleaning tool. In an alternative
configuration, the cleaning sheet of the present invention could be
formed into a mitten shaped article for wiping and cleaning, which
would fit over the users hand.
[0086] As indicated herein above, the cleaning sheets of the
present invention are well suited for use with a variety of
cleaning equipment and, more particularly, is readily capable of
being releasably-attached to the head of a cleaning tool. As used
herein, "releasably-attached" or "releasably-engaged" means that
the sheet can be readily affixed to and thereafter readily removed
from the cleaning tool. In reference to FIG. 3, cleaning tool 240
can comprise handle 248, head 244 and fasteners 246. Cleaning sheet
243 can be superposed with and placed against head 244 such that
the liquid barrier layer, if present, faces head 244. If the
cleaning sheet is a multilayer laminate, the side of the sheet with
the multicomponent, multilobal fibers should face away from the
head. Flaps 247 can then be wrapped around head 244 and
releasably-attached to head 244 by fasteners 246, e.g. clamps. With
cleaning sheet 243 affixed to head 244, cleaning tool 240 can then
be used in one or more wet and/or dry cleaning operations.
Thereafter, when the cleaning sheet becomes heavily soiled or
otherwise spent, the used sheet can be quickly and easily removed
and a new one put in its place. The specific configuration of the
cleaning tool can vary in many respects. As examples, the size
and/or shape of the handle can vary, the head can be fixed or
moveable (e.g. pivotable) with relation to the handle, the shape
and/or size of the head can vary, etc. Further, the composition of
the head can itself vary, as but one example the head can comprise
a rigid structure with or without additional padding. Further, the
mechanism(s) for attaching the cleaning sheet can vary and
exemplary means of attachment include, but are not limited to, hook
and loop type fasteners (e.g. VELCRO.TM. fasteners), clamps, snaps,
buttons, flaps, cinches, low tack adhesives and so forth.
[0087] The cleaning sheets of the present invention are well suited
for a variety of dry and wet cleaning operations such as: mopping
floors; cleaning of dry surfaces: cleaning and drying wet surfaces
such as counters, tabletops or floors (e.g. wet surfaces resulting
from spills); sterilizing and/or disinfecting surfaces by applying
liquid disinfectants; wiping down and/or cleaning appliances,
machinery or equipment with liquid cleansers; rinsing surfaces or
articles with water or other diluents (e.g. to remove cleaners,
oils, etc.), removing dirt, dust and/or other debris and so forth.
The cleaning sheets have numerous uses as a result of its
combination of physical attributes, especially the uptake and
retention dirt, dust and/or debris. Additionally, the cleaning
sheet provides a durable cleaning surface with good abrasion
resistance. This combination of physical attributes is highly
advantageous for cleaning surfaces with or without liquids such as
soap and water or other common household cleaners. Further, the
cleaning fabrics of the present invention are of a sufficiently low
cost to allow disposal after either a single use or a limited
number of uses. By providing a disposable cleaning sheet it is
possible to avoid problems associated with permanent or multi-use
absorbent products such as, for example, cross-contamination and
the formation of bad odors, mildew, mold, etc.
[0088] The cleaning sheets of the present invention are also
effective in cleaning floors used for athletics, such as gym
floors, indoor basketball courts, aerobic floors and the like,
which usually become slippery due to the presence of dust, dirt
and/or other debris on the floor, as well as liquids such as water
and/or sweat. The cleaning sheets of the present invention are very
effective in cleaning such floor surfaces since the sheet has the
ability to pick-up and retain dirt, dust, debris and liquids.
[0089] The cleaning sheets can be provided dry or pre-moistened. In
one aspect, dry cleaning sheets can be provided with dry or
substantially dry cleaning or disinfecting agents coated on or in
the multicomponent multilobal fiber layer. In addition, the
cleaning sheets can be provided in a pre-moistened and/or saturated
condition. The wet cleaning sheets can be maintained over time in a
sealable container such as, for example, within a bucket with an
attachable lid, sealable plastic pouches or bags, canisters, jars,
tubs and so forth. Desirably the wet, stacked cleaning sheets are
maintained in a resealable container. The use of a resealable
container is particularly desirable when using volatile liquid
compositions since substantial amounts of liquid can evaporate
while using the first sheets thereby leaving the remaining sheets
with little or no liquid. Exemplary resealable containers and
dispensers include, but are not limited to, those described in U.S.
Pat. No. 4,171,047 to Doyle et al., U.S. Pat. No. 4,353,480 to
McFadyen, U.S. Pat. No. 4,778,048 to Kaspar et al., U.S. Pat. No.
4,741,944 to Jackson et al., U.S. Pat. No. 5,595,786 to McBride et
al.; the entire contents of each of the aforesaid references are
incorporated herein by reference. The cleaning sheets can be
incorporated or oriented in the container as desired and/or folded
as desired in order to improve ease of use or removal as is known
in the art.
[0090] With regard to pre-moistened sheets, a selected amount of
liquid is added to the container such that the cleaning sheets
contain the desired amount of liquid. Typically, the cleaning
sheets are stacked and placed in the container and the liquid
subsequently added thereto. The sheet can subsequently be used to
wipe a surface as well as act as a vehicle to deliver and apply
cleaning liquids to a surface. The moistened and/or saturated
cleaning sheets can be used to treat various surfaces. As used
herein "treating" surfaces is used in the broad sense and includes,
but is not limited to, wiping, polishing, swabbing, cleaning,
washing, disinfecting, scrubbing, scouring, sanitizing, and/or
applying active agents thereto. The amount and composition of the
liquid added to the cleaning sheets will vary with the desired
application and/or function of the wipes. As used herein the term
"liquid" includes, but is not limited to, solutions, emulsions,
suspensions and so forth. Thus, liquids may comprise and/or contain
one or more of the following: disinfectants; antiseptics; diluents;
surfactants, such as nonionic, anionic, cationic, waxes;
antimicrobial agents; sterilants; sporicides; germicides;
bactericides; fungicides; virucides; protozoacides; algicides;
bacteriostats; fungistats; virustats; sanitizers; antibiotics;
pesticides; and so forth. Numerous cleaning compositions and
compounds are known in the art and can be used in connection with
the present invention.
[0091] The cleaning sheets of the present invention can be provided
in a kit form, wherein a plurality of cleaning sheets and a
cleaning tool are provided in a single package.
EXAMPLE
[0092] Cleaning sheets from multilobal multicomponent fibers were
produced and compared to cleaning sheets produced from
multicomponent round fibers and commercially available nonwoven
cleaning sheets. The multilobal multicomponent fibers were prepared
using a pentalobal shaped spinneret and contain 60% by weight
polypropylene and 40% by weight polyethylene in a side-by-side
configuration, using the process disclosed in U.S. Pat. No.
5,597,645 to Pike et al, assigned to the assignee of the present
application. The fibers were through-air-bonded and were electret
treated. The basis weight of the resulting nonwoven web cleaning
sheet was 1.5 osy (51 gsm) and the surface area is about 0.275
m.sup.2/g
[0093] The cleaning sheets from round multicomponent fibers were
prepared using a round spinnerett and contain 50% by weight
polypropylene and 50% by weight polyethylene in a side-by-side
configuration, using the process disclosed in U.S. Pat. No.
5,382,400 to Pike et al, assigned to the assignee of the present
application. The fibers were through-air-bonded and were electret
treated. The basis weight of the resulting nonwoven web cleaning
sheet was 1.8 osy (61 gsm) and the surface area is about 0.219
m.sup.2/g.
[0094] The prepared cleaning sheets were compared to commercially
available cleaning sheets using the following test. The Swiffer.TM.
had a surface area of about 0.154 m.sup.2/g, the Pledge Grab-It.TM.
had a surface are of about 0.206 m.sup.2/g and the Vileda.TM.
Exstatic Cloth had a surface area of about 0.3075 m.sup.2/g. Ten
samples of each sheet were compared. A tray having a 18".times.24"
linoleum floor surface with Lexan polycarbonates sides which were
1.5" high was used to test the pick-up of the cleaning sheets. A
8.5".times.11" sample of each cleaning sheet was attached to the
same mop head and handle assembly. A measured amount of debris,
mixed hair clippings from a barbershop or commercially dried and
packed bread crumbs were place onto the tray. The amount of hair
clipping in the each of the 10 samples tested for each cleaning
sheet ranged from 0.1 g to 0.14 g and the bread crumbs ranged from
0.2 g to 0.28 g. The tray was swept twice in the same fashion with
each cleaning sheet and carefully removed from the cleaning
implement. The amount of debris pick-up was calculated for each
sample. The results are shown in Table 1 for the hair pick-up and
Table 2 for the bread crumb pick-up. As can be seen from the Tables
below, the cleaning sheet of the present invention has an enhanced
debris pick-up as compared to the commercially available cleaning
sheets and the cleaning sheet prepared from monolobal round fibers.
It is further shown in the Tables that the pick-up of the cleaning
sheets of the present invention is superior to cleaning sheets
having smaller, larger or about the same surface area as the
cleaning sheets of the present invention.
1TABLE 1 Cleaning Sheet Sample Average % of hair pick-up Present
invention from bicomponent, 86.6% multimodal shaped fibers
Comparative example from round 57.9% bicomponent fibers Swiffer
.TM..sup.1 79.0% Pledge Grab-It .TM..sup.2 80.8% Vileda .RTM.
Exstatic Cloth .TM..sup.3 35.1% .sup.1Available from Procter &
Gamble Company, Cincinnati, Ohio .sup.2Available from S.C. Johnson,
Racine, Wisconsin .sup.3Available from Freudenberg Household
Products, River Grove, Illinois
[0095]
2TABLE 2 Cleaning Sheet Sample Average % of crumb pick-up Present
invention from bicomponent, 63.4% multilobal shaped fibers
Comparative example from round 50.5% bicomponent fibers Swiffer
.TM..sup.1 39.2% Pledge Grab-It .TM..sup.2 36.1% Vileda .RTM.
Exstatic Cloth .TM..sup.3 22% .sup.1Available from Procter &
Gamble Company, Cincinnati, Ohio .sup.2Available from S.C. Johnson,
Racine, Wisconsin .sup.3Available from Freudenberg Household
Products, River Grove, Illinois
[0096] While the invention has been described in detail with
respect to specific embodiments thereof, and particularly by the
example described herein, it will be apparent to those skilled in
the art that various alterations, modifications and other changes
may be made without departing from the spirit and scope of the
present invention. It is therefore intended that all such
modifications, alterations and other changes be encompassed by the
claims.
* * * * *