U.S. patent application number 10/260955 was filed with the patent office on 2004-04-01 for nonwoven loop material and process and products relating thereto.
Invention is credited to Ahn, Jung Yeul, Bolian, Charles Edward II, Chin, JeaSeung, Forbes, Brian Stephen, Jung, SooGyung, Kim, ByungSoo, Lee, Jin Hee, Ning, Xin, You, JueYoung.
Application Number | 20040063369 10/260955 |
Document ID | / |
Family ID | 32029834 |
Filed Date | 2004-04-01 |
United States Patent
Application |
20040063369 |
Kind Code |
A1 |
Ahn, Jung Yeul ; et
al. |
April 1, 2004 |
Nonwoven loop material and process and products relating
thereto
Abstract
The present invention provides nonwoven fiber materials, and
methods for making the same, useful for loop materials in hook and
loop mechanical attachment systems, the nonwoven materials having
crimped monocomponent fibers having substantially circular cross
sections, and the webs may further contain uncrimped fibers. The
invention also provides disposable articles comprising nonwoven
loop materials including disposable personal care absorbent
articles such as diapers, feminine care sanitary napkins, and adult
incontinence articles, and disposable protective articles such as
surgical drapes and gowns and other protective apparel.
Inventors: |
Ahn, Jung Yeul; (Kumsan-gun,
KR) ; Bolian, Charles Edward II; (Buford, GA)
; Chin, JeaSeung; (SuWon-City, KR) ; Forbes, Brian
Stephen; (Alpharetta, GA) ; Jung, SooGyung;
(Seoul, KR) ; Kim, ByungSoo; (Kimcheon-City,
KR) ; Lee, Jin Hee; (Taejon-City, KR) ; Ning,
Xin; (Alpharetta, GA) ; You, JueYoung;
(Anyang-City, KR) |
Correspondence
Address: |
KIMBERLY-CLARK WORLDWIDE, INC.
401 NORTH LAKE STREET
NEENAH
WI
54956
|
Family ID: |
32029834 |
Appl. No.: |
10/260955 |
Filed: |
September 30, 2002 |
Current U.S.
Class: |
442/327 ; 428/85;
428/92; 442/352 |
Current CPC
Class: |
D04H 11/00 20130101;
Y10T 442/60 20150401; A61F 13/627 20130101; Y10T 428/23957
20150401; A44B 18/0011 20130101; Y10T 442/627 20150401; A61P 1/00
20180101; D04H 3/00 20130101 |
Class at
Publication: |
442/327 ;
442/352; 428/085; 428/092 |
International
Class: |
D04H 001/00; D04H
003/00 |
Claims
1. A nonwoven loop material for a personal care article, said loop
material comprising helically crimped continuous monocomponent
fibers having a substantially circular cross section, said nonwoven
loop material having a first plane surface and a second plane
surface, said nonwoven loop material further having a plurality of
discrete unbonded areas defined by substantially continuous bonded
areas, wherein said unbonded areas comprise about 85 to about 50
percent of said second plane surface of said nonwoven loop
material.
2. The nonwoven loop material of claim 1 wherein said helically
crimped continuous monocomponent fibers comprise thermoplastic
polymer selected from the group consisting of polyolefins and
copolymers thereof.
3. The nonwoven loop material of claim 2 wherein said thermoplastic
polymer is a random copolymer of olefins.
4. The nonwoven loop material of claim 2 wherein said nonwoven loop
material further comprises uncrimped continuous fibers.
5. The nonwoven loop material of claim 4 wherein said crimped
monocomponent fibers comprise a random copolymer of propylene and
ethylene and wherein said uncrimped fibers comprise
polypropylene.
6. The nonwoven loop material of claim 5 wherein said first plane
surface comprises a majority of said uncrimped fibers and further
wherein said second plane surface comprises a majority of said
crimped fibers.
7. The nonwoven loop material of claim 6 having a basis weight of
about 20 to about 100 grams per square meter.
8. The nonwoven loop material of claim 7 having a basis weight of
about 40 to about 80 grams per square meter.
9. The nonwoven loop material of claim 7 having a bulk of about 0.4
millimeters to about 1.2 millimeters.
10. The nonwoven loop material of claim 9 wherein said crimped
fibers are about 3 to about 6 denier and wherein said uncrimped
fibers are about 2 to about 5 denier.
11. A disposable article comprising the nonwoven loop material of
claim 1.
12. A disposable article comprising the nonwoven loop material of
claim 6.
13. A process for making a nonwoven material comprising the steps
of: a) providing a fiber forming thermoplastic polymer composition;
b) forming a plurality of molten monocomponent fibers from said
thermoplastic polymer composition, said molten monocomponent fibers
having a substantially circular cross section; c) differentially
quenching said molten fibers to form crimped monocomponent fibers
having a substantially circular cross section; d) depositing said
crimped monocomponent fibers upon a forming surface to form a
nonwoven web material; and thereafter e) bonding said nonwoven web
material with heat and pressure to form a pattern of substantially
continuous bonded areas defining a plurality of discrete unbonded
areas, and wherein said nonwoven material has an unbonded area of
from about 85 percent to about 50 percent.
14. The process of claim 13 further comprising the step of
providing upon said forming surface a plurality of uncrimped fibers
before the step of depositing said crimped fibers.
15. The process of claim 14 wherein said fiber forming
thermoplastic polymer composition is a random copolymer of olefins
and further wherein said uncrimped fibers comprise
polypropylene.
16. The process of claim 15 wherein said fiber forming
thermoplastic polymer composition is a random copolymer of
propylene and ethylene.
17. The process of claim 16 further comprising the step of
subjecting the nonwoven material to a stretching force after said
bonding step.
18. The process of claim 17 wherein said stretching force is a 5
percent to 15 percent longitudinal stretching force.
19. A disposable article comprising: an inner body contacting side
and an outer non-body contacting side, a hook material, and a
nonwoven loop material, wherein said loop material comprises at
least a portion of said outer non-body contacting side, and further
wherein said nonwoven loop material comprises a plurality of
helically crimped continuous monocomponent fibers having a
substantially circular cross section.
20. The disposable article of claim 19 wherein said nonwoven loop
material comprises first and second plane surfaces, wherein said
first plane surface comprises a majority of said uncrimped fibers
and said second plane surface comprises a majority of said crimped
fibers, and further wherein said second plane surface is exposed on
said outer non-body contacting side of said article.
21. The disposable article of claim 20 wherein said crimped fibers
comprise a random copolymer of propylene and ethylene and wherein
said uncrimped fibers comprise polypropylene.
22. The disposable article of claim 20 further comprising a tab and
wherein said hook material is located on said tab, and further
wherein said tab and said hook material are adapted to be
superposable and engagable with said loop material.
23. The disposable article of claim 21 further comprising a tab and
wherein said hook material is located on said tab, and further
wherein said tab and said hook material are adapted to be
superposable and engagable with said loop material.
24. The disposable article of claim 22 wherein said loop material
comprises on its surface a point unbonded bond pattern, said point
unbonded bond pattern comprising a plurality of discrete unbonded
areas defined by substantially continuous bonded areas.
25. The disposable article of claim 22 wherein said loop material
comprises on its surface a point bonded bond pattern, said point
bonded bond pattern comprising a plurality of discrete bonded areas
separated by substantially unbonded areas.
26. The disposable article of claim 23 wherein said loop material
comprises on its surface a point unbonded bond pattern, said point
unbonded bond pattern comprising a plurality of discrete unbonded
areas defined by substantially continuous bonded areas, wherein
said unbonded areas comprise about 85 to about 50 percent of said
second plane surface of said nonwoven loop material.
27. A disposable diaper comprising: a body contacting liner, an
outer cover, an absorbent core disposed between said liner and said
outer cover, and a mechanical fastening system, said mechanical
fastening system comprising a nonwoven loop material and a tab
comprising a hook material, said nonwoven loop material comprising
at least a portion of said outer cover and having a first plane
surface comprising a majority of uncrimped fibers and a second
plane surface comprising a majority of helically crimped continuous
monocomponent fibers having a substantially circular cross section,
and wherein said second plane surface of said nonwoven loop
material is exposed.
28. The disposable diaper of claim 27 wherein said crimped
monocomponent fibers comprise a random copolymer of propylene and
ethylene and said uncrimped fibers comprise polypropylene.
29. The disposable diaper of claim 28 wherein said loop material
comprises on a surface a point bonded bond pattern, said point
bonded bond pattern comprising a plurality of discrete bonded areas
separated by substantially unbonded areas.
30. The disposable diaper of claim 28 wherein said loop material
comprises on a surface a point unbonded bond pattern, said point
unbonded bond pattern comprising a plurality of discrete unbonded
areas defined by substantially continuous bonded areas.
31. The disposable diaper of claim 30 wherein said unbonded areas
comprise about 85 to about 50 percent of said second plane surface
of said nonwoven loop material.
Description
TECHNICAL FIELD
[0001] The present invention generally relates to the field of
nonwoven materials and webs, and processes for manufacturing the
same. More specifically, the present invention is related to
crimped fiber nonwoven materials useful as a loop material in
mechanical attachment systems, such as a hook and loop mechanical
attachment system.
BACKGROUND OF THE INVENTION
[0002] Mechanical fastening systems, such as the type referred to
as "hook and loop" fastener systems, have become widely used in
various consumer and industrial applications. A few examples of
such applications include disposable personal care absorbent
articles, protective garments, clothing, sporting goods equipment,
and a wide variety of other miscellaneous articles. Typically, such
hook and loop fastening systems are employed in situations where a
refastenable connection between two or more materials or articles
is desired. These mechanical fastening systems have in many cases
replaced other conventional devices used for making such
refastenable connections, such as safety pins, buttons, buckles,
zippers, and the like.
[0003] Mechanical fastening systems typically employ two
components, a "male" or hook type component and a "female" or loop
type component. The hook component usually includes a plurality of
semi-rigid, hook-shaped elements anchored or connected to a base
material. The loop component generally as known in the art includes
a resilient backing material from which a plurality of loops
project. The hook-shaped elements of the hook component are
designed to engage the loops of the loop material, thereby forming
mechanical attachments between the hook and loop elements of the
two components. These mechanical attachments function to prevent
separation of the respective components during normal use.
[0004] Mechanical fastening systems can be advantageously employed
in disposable personal care absorbent articles, such as disposable
diapers, disposable garments, disposable feminine care products,
disposable incontinence products, and so forth. In addition,
mechanical fastening systems may be beneficially used in mechanical
attachment systems for other disposable articles as surgical gowns
and surgical drapes, patient exam gowns, industrial workwear and
cleanroom apparel. Because such disposable products are intended as
single-use items to be discarded after a relatively short period of
use, often only a few hours, it is important to reduce the overall
expense of materials in the design of such products and to reduce
manufacturing costs wherever possible. Thus there exists a
continuing need for an inexpensive loop fastening material for a
mechanical fastening system, particularly as such are used in
disposable personal care absorbent articles and disposable
protective articles.
BRIEF SUMMARY OF THE INVENTION
[0005] The present invention provides a nonwoven loop material
useful in disposable articles such as disposable personal care
absorbent articles and disposable protective articles. In one
aspect, the nonwoven loop material comprises monocomponent fibers
which are helically crimped and which have a substantially circular
cross section, and the nonwoven material comprises a plurality of
discrete unbonded areas defined by substantially continuous bonded
areas, wherein these unbonded areas comprise about 85 percent to
about 50 percent of the second of first and second plane surfaces
of the nonwoven loop material. The crimped fibers may comprise
random copolymers of olefins. The nonwoven loop material may
further comprise uncrimped fibers, in which case the majority of
the uncrimped fibers is located in or on the first plane surface
while the majority of the crimped fibers is located in or on the
second plane surface of the material. The invention also provides a
process for making a nonwoven material including the steps of
providing a fiber forming thermoplastic composition, forming a
plurality of molten monocomponent fibers of substantially circular
cross section from the thermoplastic composition, differentially
quenching the molten fibers to form crimped monocomponent fibers
having substantially circular cross section, depositing the crimped
fibers upon on a forming surface to form an unbonded nonwoven web,
and then bonding the unbonded web with heat and pressure to form a
pattern of substantially continuous bonded areas defining a
plurality of discrete unbonded areas, and wherein the nonwoven
material has an unbonded area of from about 85 percent to about 50
percent. In one aspect the process additionally includes providing
on the forming surface a plurality of uncrimped fibers before the
step of depositing the crimped fibers. The process may optionally
include the step of subjecting the material to a stretching
force.
[0006] The invention also provides disposable articles comprising
inner and outer sides, a hook material, and a nonwoven loop
material comprising at least a portion of the outer side of the
article, and the nonwoven loop material further comprising
helically crimped continuous monocomponent fibers of substantially
circular cross section. The hook material may be located on a tab
on or attached to the article, and the tab located on the article
in such a way as to make the hooks easily superposable and
engagable with the loop material. That is, having the tab with hook
material located in such a way as to be easily placed in
face-to-face relation with the loop material so that the hooks may
readily engage the loop material.
[0007] The invention also provides a disposable diaper comprising a
liner, outer cover, and an absorbent core disposed between the
liner and outer cover, and further comprising a mechanical
fastening system having a tab comprising a hook material, and a
loop material, wherein the loop material comprises at least a
portion of the outer cover, and further wherein the loop material
has a first plane surface having a majority of uncrimped fibers and
a second plane surface having a majority of helically crimped
monocomponent fibers of substantially circular cross section, and
wherein the second plane surface is exposed on the outer cover. In
certain aspects, the loop material is thermally pattern bonded with
a point bond pattern, while in other aspects the loop material is
thermally pattern bonded with a point-unbonded bond pattern.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a top view of an exemplary embodiment of the
nonwoven loop material of the present invention.
[0009] FIG. 2 is a schematic side view of an exemplary process and
apparatus for producing a nonwoven web of spunbond fibers.
[0010] FIG. 3 is a partial perspective view of a pattern roll that
can be used within the process of FIG. 2.
[0011] FIG. 4 is a perspective view of a disposable diaper
employing the nonwoven loop material of the present invention as a
loop patch.
DEFINITIONS
[0012] As used herein and in the claims, the term "comprising" is
inclusive or open-ended and does not exclude additional unrecited
elements, compositional components, or method steps. Accordingly,
the term "comprising" encompasses the more restrictive terms
"consisting essentially of" and "consisting of".
[0013] 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
spatial configurations of the material. These configurations
include, but are not limited to isotactic, syndiotactic and random
symmetries.
[0014] As used herein the term "fibers" refers to both staple
length fibers and continuous filaments, unless otherwise
indicated.
[0015] As used herein the term "monocomponent" fiber refers to a
fiber formed from one or more extruders using only one component.
Monocomponent fibers are distinct from multicomponent fibers in
that they do not comprise multiple substantially constantly
positioned distinct zones of different components across the
cross-section of the fiber. This is not meant to exclude fibers
formed from one polymer to which small amounts of additives have
been added for color, anti-static properties, lubrication,
hydrophilicity, etc.
[0016] As used herein the term "multicomponent fibers" refers to
fibers which have been formed from at least two component polymers,
or the same polymer with different properties or additives,
extruded from separate extruders but spun together to form one
fiber. Multicomponent fibers are also sometimes referred to as
conjugate fibers or bicomponent fibers. The polymers are arranged
in substantially constantly positioned distinct zones across the
cross-section of the multicomponent fibers and extend continuously
along the length of the multicomponent fibers. The configuration of
such a multicomponent fiber may be, for example, a sheath/core
arrangement wherein one polymer is surrounded by another, or may be
a side by side arrangement or other arrangements as are known in
the art. By way of example, 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.
[0017] As used herein the term "nonwoven web" or "nonwoven
material" means a web having a structure of individual fibers or
filaments which are interlaid, but not in an identifiable manner as
in a knitted or woven fabric. Nonwoven webs have been formed from
many processes such as for example, meltblowing processes,
spunbonding processes, air-laying processes and carded web
processes.
[0018] The term "spunbond" nonwoven web or material refers to a
nonwoven fiber or filament material of small diameter fibers or
filaments that are formed by extruding molten thermoplastic polymer
as fibers from a plurality of capillaries of a spinneret. The
extruded fibers are cooled while being drawn by an eductive or
other well known drawing mechanism. The drawn fibers are deposited
or laid onto a forming surface in a generally random, isotropic
manner to form a loosely entangled fiber web, and then the laid
fiber web is subjected to a bonding process to impart physical
integrity and dimensional stability. The production of spunbond
fabrics is disclosed, for example, in U.S. Pat. No. 4,340,563 to
Appel et al. and U.S. Pat. No. 3,802,817 to Matsuki et al.
[0019] As used herein, "pattern bonding" refers to bonding by one
or more means known in the art by a means which does not bond the
entire surface area of the material. As an example, thermal pattern
bonding involves passing a fabric or web of fibers or other sheet
layer material to be bonded between a calender roll and an anvil
roll, at least one of which is heated. The calender roll is
generally patterned in some way so that the entire fabric is not
bonded across its entire surface. Alternatively, both rolls may be
patterned. Various patterns for calender rolls have been developed
for functional as well as aesthetic reasons. Examples of thermal
pattern bonding include, but are not limited to, thermal point
bonding patterns such as that taught in U.S. Pat. No. 3,855,046 to
Hansen and Pennings, herein incorporated by reference, which is
known as the "H&P" pattern and which has about a 30 percent
bond area with about 200 bonds/square inch. Another exemplary
thermal point bonding pattern is the expanded Hansen and Pennings
or "EHP" bond pattern which produces about a 15 percent bond area.
Another useful example of thermal pattern bonding is the
pattern-unbonded or point-unbonded thermal bonding method described
in U.S. Pat. No. 5,858,515 to Stokes et al., herein incorporated by
reference, in which one or both of the calender rolls is engraved
such that its surface comprises a continuous pattern of land areas
defining a plurality of discrete openings, apertures or holes. Each
of the openings in the surface of the roll or rolls forms a
discrete unbonded area in the surface of the nonwoven web material
in which the fibers of the web are substantially or completely
unbonded.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Disclosed herein is a nonwoven material suitable as a loop
material for a mechanical attachment system, such as a hook and
loop mechanical attachment system. Also disclosed herein is a
method for making the nonwoven loop material of the invention. The
invention will be described with reference to the drawings
illustrating certain embodiments and with reference to certain
other exemplary embodiments as described hereinbelow. It will be
apparent to those skilled in the art that these embodiments do not
represent the full scope of the invention which is broadly
applicable in the form of variations and equivalents as may be
embraced by the claims appended hereto. It is intended that the
scope of the claims extend to all such variations and
equivalents.
[0021] FIG. 1 is a top view which illustrates an exemplary nonwoven
loop material of the invention. Use of the term "loop" is not
intended to limit the loop material of the present invention to
only materials in which discrete, separately formed loops of
material are employed to receive and engage the hook elements of a
complementary hook material. Rather, the loop material of the
present invention includes fibrous nonwoven fabrics or webs in
which the individual fibers are crimped fibers forming an open web
structure with substantial void portions between the fibers such
that the fibers function to engage the hook elements without such
fibers necessarily being formed into discrete loops. Various types
of hook materials and hook elements, such as inverted J shapes,
inverted T shapes, and generally mushroom-shaped hooks are known in
the art. Referring again to FIG. 1, the nonwoven loop material 4
comprises, in its simplest form, a nonwoven material having
continuous bonded areas 6 which define a plurality of discrete,
dimensionally-stabilized unbonded areas 8. Within the continuous
bonded areas 6, the fibers of the nonwoven material are bonded or
fused together and desirably are substantially non-fibrous and may,
for example, comprise a film-like area. In the unbonded areas 8 the
fibers of the nonwoven material are substantially or completely
free of bonding or fusing such that they retain their open fibrous
structure. The nonwoven loop material of the invention may have
basis weights ranging from about 20 to about 100 grams per square
meter ("gsm"), and more particularly from about 40 gsm to about 80
gsm. In a further aspect, the nonwoven loop material may have a
fabric thickness or bulk of from about 0.4 millimeter to about 1.2
millimeter, or greater.
[0022] FIG. 2 schematically illustrates a process for forming the
nonwoven loop material of the present invention. In FIG. 2, process
line 10 includes an extruder 12 for melting and extruding polymer
fed into the extruder 12 from polymer hopper 14. The polymer is fed
from extruder 12 through polymer conduit 16 to a spinneret 18. The
spinneret 18 has defined openings that are commonly arranged in one
or more rows. The spinneret openings form a downwardly extending
curtain of fibers 20 when molten polymer is extruded through the
spinneret.
[0023] Polymers suitable for the present invention include the
known polymers suitable for production of nonwoven webs and
materials such as for example polyolefins, polyesters, polyamides,
polycarbonates and copolymers and blends thereof. Suitable
polyolefins include, but are not limited to, 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; 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, but are not limited to, random and
block copolymers prepared from two or more different unsaturated
olefin monomers, such as ethylene/propylene, butylene/propylene and
ethylene/butylene copolymers. Exemplary copolymers of olefins
include those containing from about 99.5 to about 90 percent, by
weight, propylene and from about 0.5 to about 10 percent, by
weight, of ethylene or another alpha-olefin co-monomer having at
least 4 carbon atoms such as 1-butene, 4-methyl-1 pentene,
1-hexene, or 1-octene.
[0024] Suitable polyamides include, but are not limited to, 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, but are not limited to, polyethylene
terephthalate, polybutylene terephthalate, polytetramethylene
terephthalate, polycyclohexylene-1,4-di- methylene terephthalate,
and isophthalate copolymers thereof, as well as blends thereof.
[0025] The exemplary process line 10 also includes a quench blower
22 positioned adjacent the curtain of fibers 20 extending from the
spinneret 18. Air from the quench air blower 22 quenches the fibers
20 extending from the spinneret 18. The quench air can be directed
from one side of the curtain of fibers as shown in FIG. 2, or both
sides of the curtain of fibers. As used herein, the term "quench"
generally means reducing the temperature of the fibers using a
medium that is cooler than the fibers such as using, for example,
chilled air streams, ambient temperature air streams, or slightly
to moderately heated air streams.
[0026] In order to produce crimped fibers, a differential quench is
applied to the fibers 20 when they are substantially molten. As
used herein, "differential quench" means applying the quenching
medium in such a fashion as to impart differential stress from one
side of the cross section of a fiber to the other side while the
fibers are being drawn from the spinneret. Imparting differential
stress causes the fibers to twist or curl, i.e. "crimp", in a
helical fashion. The differential stress may be created by, for
example, use of a single quench air blower as shown in FIG. 2 which
delivers the quench air at a relatively high air velocity, such as
for example at about 600-700 feet per minute (about 183-213 meters
per minute). The quench air velocity required in a given process to
impart helical crimp may be higher or lower and will depend on a
number of processing factors such as for example polymer selection,
polymer melt temperature, quench air temperature, fiber velocity,
distance of the quench air blower to the curtain of fibers and
number of spinneret holes (and thus fibers) per unit area.
[0027] Alternatively, where the quenching medium is directed at the
curtain of fibers from both sides, the differential stress may be
created by setting the quench blower on one side of the curtain of
fibers at a significantly higher air velocity, and/or significantly
cooler air temperature, than the quench blower on the other side of
the curtain of fibers. Differential quenching of molten fibers is
disclosed, for example, in U.S. Pat. No. 5,427,845 to Sawyer et
al., herein incorporated by reference. Although it is known in the
art to produce helically crimped bicomponent fibers or helically
crimped fibers having shaped or lobed cross sections, neither of
these expedients is required to produce helical crimp when
differential quenching is utilized, and bicomponent and shaped
fiber processes require more specialized fiber production apparatus
than for monocomponent circular fibers.
[0028] As stated above, a wide variety of polymers and copolymers
may be utilized to form the crimped monocomponent fibers by
differentially quenching the molten fibers. Depending on processing
variables such as melt temperature and available quench air
temperature and quench air flow rate, it may be desirable to select
polymers which more readily form crimped fibers under differential
quenching conditions. In this regard, copolymers, especially
copolymers of olefins such as for example random and block
copolymers prepared from two or more different unsaturated olefin
monomers, such as for example random copolymers of propylene and
ethylene, and random copolymers of propylene and butylene, readily
develop crimp under differential quenching conditions.
[0029] Referring again to FIG. 2, a fiber draw unit or aspirator 24
to receive the quenched fibers is positioned below the spinneret 18
and the quench blower 22. Fiber draw units or aspirators for use in
melt spinning polymers are well known in the art. Suitable fiber
draw units for use in the method of the present invention include,
but are not limited to, linear fiber aspirators of the types shown
in U.S. Pat. No. 3,802,817 to Matsuki et al. and U.S. Pat. Nos.
4,340,563 and 4,405,297 to Appel et al., all herein incorporated by
reference. Generally described, the fiber draw unit 70 includes an
elongate vertical passage through which the fibers are drawn by
aspirating air entering from the sides of the passage and flowing
downwardly through the passage. Aspirating air is supplied by a
blower (not shown). The fiber draw unit 24 attenuates the fibers,
that is, applies a downward force upon the fibers thereby reducing
their diameter from the diameter initially extruded through the
spinneret 18. Generally speaking, the fibers may have a
denier-per-fiber ("denier" or "dpf") of about 1 to 10 denier, and
desirably are about 2 to about 6 denier. Denier is a measure of
fiber mass to unit length wherein 1 denier equals 1 gram per 9000
meters of fiber.
[0030] An endless foraminous forming surface 26 is positioned below
the fiber draw unit 24 to receive the fibers from the outlet
opening of the fiber draw unit 24. A vacuum source 28 positioned
below the foraminous forming surface 26 may be beneficially
employed to pull the attenuated fibers onto foraminous forming
surface 26. The fibers received onto foraminous forming surface 26
comprise a nonwoven web 30 of loose continuous fibers, which are
initially consolidated using consolidation means 32 to assist in
transferring the web to a bonding means. Consolidation means 32 may
desirably be, for example, a mechanical compaction roll as is known
in the art.
[0031] The process line 10 further includes a pattern bonding
assembly 40 such as the thermal pattern calender rolls shown in
FIG. 2 which are used to thermally bond the nonwoven web into a
coherent bonded web 44. As described above, pattern bonding is a
process by which the fibers are fused together such as by the
application of heat and pressure to form bonds. The pattern
selected may be a point bonding pattern or point-unbonded pattern,
depending on particular end-use application and the tolerance for
fiber "pull-outs" for that application. Upon disengagement or
removal of the hook material during normal use of a hook and loop
fastening system the fibers acting as loops with which the hooks
are engaged may have a tendency, to greater or lesser extent, to be
pulled out of the fibrous nonwoven web structure. An exemplary
pattern-unbonded or point-unbonded thermal bonding method is
described in U.S. Pat. No. 5,858,515 to Stokes et al., herein
incorporated in its entirety by reference. The pattern-unbonded
method described in Stokes et al. reduces fiber pull-outs and
therefore is a particularly useful bonding method for applications
where it is desirable to minimize occurrence of fiber
pull-outs.
[0032] In point-unbonded bonding, one or both of the calender rolls
is engraved such that its surface comprises a continuous pattern of
land areas defining a plurality of discrete openings, apertures or
holes. Each of the openings in the surface of the roll or rolls
defined by the continuous land areas forms a discrete unbonded area
in the surface of the nonwoven web material in which the fibers of
the web are substantially or completely unbonded. In FIG. 3 is
shown an exemplary calender roll 60 having a point-unbonded surface
engraving having continuous land areas 62 defining a plurality of
discrete openings or apertures 64. The size, shape, number and
configuration of openings 64 can be varied to meet the particular
end-use requirements of the nonwoven loop material. The degree of
bonding imparted to the nonwoven loop material by the continuous
land areas 62 can be expressed as a percent bond area, i.e. the
portion of the area of at least one surface of nonwoven loop
material occupied by the continuous bonded areas designated in FIG.
1 by reference numeral 6. Alternatively this may be expressed in
terms of the percent unbonded area, that is, the percent portion of
the nonwoven loop material comprising loose fibers available to act
as loops. Stated generally, the lower limit on the percent bond
area suitable for a nonwoven loop material (or, alternatively the
upper limit on the percent unbonded area) is the point at which
fiber pull-out excessively reduces the surface integrity and
durability of the pattern-unbonded material. For applications where
a low to moderate amount of fiber pull-outs is acceptable, this
percent unbonded area may suitably be as high as about 85 percent.
For other applications where pull-outs are less desirous nonwoven
loop materials having percent unbonded areas ranging from about 80
percent to about 50 percent have been found suitable.
[0033] Although FIG. 2 and process line 10 are hereinabove
described with respect to a single fiber spinning apparatus or
"spin bank", in certain embodiments more than one spin bank may be
employed. For example, the process line may employ multiple spin
banks wherein each spin bank produces crimped fibers by the use of
differential quench, and at each spin bank the crimped fibers from
each subsequent (or "downstream") bank are deposited at the
foraminous forming surface atop the fibers of the previous (or
"upstream") spin bank, and after the last spin bank has deposited
its fibers the web is then transported further downstream through
the consolidation means and through a bonding assembly as described
above. However, where multiple spin banks are employed it should be
noted that it is not necessary that all of the spin banks form
crimped fibers. Rather, it is only necessary that the surface of
the nonwoven loop material which is intended to be used to engage
the hooks of the mechanical fastening system contain crimped
fibers.
[0034] In addition, other variations are possible. Where multiple
spin banks are employed the individual spin banks may all spin the
same polymer, such as polypropylene, or a random copolymer of
propylene and ethylene, or a polyester. Alternatively, all the spin
banks need not all use the same polymer, for example, and
additionally the individual spin banks need not produce fibers of
the same size. As an example of an embodiment which combines the
foregoing, a two spin bank process line may be utilized wherein the
first or upstream spin bank spins uncrimped polypropylene fibers
and the second or downstream spin bank spins crimped random
copolymer fibers, the second spin bank depositing the crimped
fibers atop the uncrimped fibers from the first spin bank. The
uncrimped fibers may for example be from about 2 to about 5 denier
and the crimped fibers from about 3 to about 6 denier. The web,
containing fibers from the two spin banks, is then transported
further downstream through the consolidation means and bonding
assembly to form a nonwoven loop material having a majority of the
crimped fibers on one surface of the material, and having a
majority of the uncrimped fibers on the opposite surface of the
material. It should also be noted that although the individual spin
banks may produce fibers at about equal mass production rates, they
may alternatively produce the fibers at significantly unequal mass
production rates wherein one spin bank produces, for example, two
thirds of the basis weight of the final nonwoven loop material
while the other spin bank produces one third.
[0035] Referring again to FIG. 2, the process line 10 further
includes a winding roll 50 for taking up the bonded web 44. While
not shown here, various additional potential processing and/or
finishing steps known in the art such as for example web slitting,
stretching, treating, printing on the nonwoven loop material,
and/or other operations may be performed without departing from the
spirit and scope of the invention. As an example, it may be highly
desirable to print the nonwoven loop material with color graphics
to provide a more visually appealing material. In addition, as an
alternative to taking the nonwoven web up on winding roll 50, the
nonwoven web may be directed immediately to various converting or
integrated product forming operations.
[0036] As another particular example, it may be beneficial to
subject the nonwoven material to a small amount (about 5 percent to
about 15 percent) of stretching to further provide additional loft
or bulk to the fibers in the unbonded areas, allowing for increased
engageability with hooks. This stretching may be performed in
either the material longitudinal direction (that is, the direction
in which the material is produced, also known as the machine
direction) or in the material transverse direction (the direction
perpendicular to the direction of material production, also known
as the cross-machine direction) and may be accomplished by means as
are well known in the art such as for example use of tenter frames
for transverse stretching, or by draw speed differential between in
a series of driven nipped rollers for longitudinal stretching. As a
specific example, about a 10 percent longitudinal stretching force
may be applied to the material by transporting the material through
a series of driven nipped rollers wherein the second pair of driven
nipped rollers is driven at a speed 10 percent faster than first
pair of rollers.
[0037] The nonwoven loop material of the invention is useful in a
mechanical attachment system in a wide variety of disposable
personal care absorbent articles and disposable protective
articles. Disposable personal care absorbent articles include but
are not limited to infant and child care absorbent articles such as
diapers and training pants, disposable swimwear, adult care
incontinent garments, feminine care articles such as sanitary
napkins, bandages and wound dressings, and the like. Disposable
protective articles include but are not limited to such articles as
surgical gowns and surgical drapes, patient examination gowns,
industrial workwear and cleanroom apparel. Such disposable personal
care and protective articles generally have a body facing side
which is worn or placed against or towards the body of the user and
a non-body facing side facing away from the body of the user. The
nonwoven loop material of the invention, when used as part of a
mechanical attachment system for such disposable personal care and
protective articles, would generally be placed on or attached to
the outer or non-body facing side of the article, or alternatively
the outer or non-body facing side of the article may be composed
wholly of the nonwoven loop material of the invention. The hook
material would generally be placed on or comprise a tab on the
article which is conveniently located on the article such that the
user or wearer is able to superpose the hook tab with the nonwoven
loop material, that is, is easily able to place the hook tab in
face to face relation with the nonwoven loop material, such that
hook components can engage the fibers of the loop material.
[0038] Turning to FIG. 4 there is shown an exemplary personal care
article such as the diaper 70. Diaper 70, as is typical for most
personal care absorbent articles, includes a liquid permeable body
side liner 74, i.e., a body-facing or inner side, and a liquid
impermeable outer cover 72, i.e., a non-body facing or outer side.
Various woven or nonwoven fabrics can be used for body side liner
74 such as a spunbond nonwoven web of polyolefin fibers, or a
bonded carded web of natural and/or synthetic fibers. Outer cover
72 is formed of a thin liquid barrier material such as for example
a spunbond-meltblown layer, spunbond-meltblown-spunbond layer, or a
thermoplastic polymer film layer. A polymer film outer cover may be
embossed and/or matte finished to provide a more aesthetically
pleasing appearance, or may be a laminate formed of a woven or
nonwoven fabric and thermoplastic film. Outer cover 72 may
optionally be composed of a "breathable" material that is permeable
to vapors or gas yet substantially impermeable to liquid, such as
is known in the art. Examples of outer cover materials include but
are not limited to those disclosed in U.S. Pat. No. 6,309,736 to
McCormack et al., the disclosure of which is incorporated herein by
reference in its entirety
[0039] Disposed between liner 74 and outer cover 72 is an absorbent
core (not shown) formed, for example, of a blend of hydrophilic
cellulosic wood pulp fluff fibers and highly absorbent gelling
particles (e.g., superabsorbent material). Diaper 70 may further
include optional containment flaps 76 made from or attached to body
side liner 74. Suitable constructions and arrangements for such
containment flaps are described, for example, in U.S. Pat. No.
4,704,116 to Enloe, the disclosure of which is incorporated herein
by reference in its entirety. Still further, the diaper can
optionally include additional elements known to those skilled in
the art, including but not limited to, elasticized leg cuffs,
elastic waist band, and so forth.
[0040] To secure the diaper 70 about the wearer, the diaper will
have some type of fastening means attached thereto. As shown in
FIG. 4, the fastening means is a hook and loop fastening system
including hook elements 78 attached to the inner and/or outer
surface of outer cover 72 in the back waistband region of diaper 70
and one or more loop elements or patches 80 made from the nonwoven
loop material of the present invention attached to the outer
surface of outer cover 72 in the front waistband region of diaper
70. The nonwoven loop material can be secured to outer cover 72 of
diaper 70 by known attachment means, including but not limited to
adhesives, thermal bonding, ultrasonic bonding, or a combination of
such means. As an alternative embodiment, the nonwoven loop
material may cover substantially all or all of the outer surface of
outer cover 72. An example of this would be an outer cover material
constructed of a thermoplastic film/nonwoven loop material
laminate.
[0041] While various patents have been incorporated herein by
reference, to the extent there is any inconsistency between
incorporated material and that of the written specification, the
written specification shall control. In addition, while the
invention has been described in detail with respect to specific
embodiments thereof, it will be apparent to those skilled in the
art that various alterations, modifications and other changes may
be made to the invention without departing from the spirit and
scope of the present invention. It is therefore intended that the
claims cover all such modifications, alterations and other changes
encompassed by the appended claims.
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