U.S. patent application number 11/027390 was filed with the patent office on 2006-07-06 for nonwoven loop material.
This patent application is currently assigned to Kimberly-Clark Worldwide, Inc.. Invention is credited to Yung Hsiang Huang, Paul Theodore Van Gompel.
Application Number | 20060148359 11/027390 |
Document ID | / |
Family ID | 36123308 |
Filed Date | 2006-07-06 |
United States Patent
Application |
20060148359 |
Kind Code |
A1 |
Van Gompel; Paul Theodore ;
et al. |
July 6, 2006 |
Nonwoven loop material
Abstract
Disclosed herein are nonwoven loop materials suitable for use as
the female component of hook and loop fastening systems. In
embodiments, the loop materials may include a fibrous nonwoven web
layer and an elastic substrate layer, or may include elastic fibers
coformed with other fibers. Also disclosed herein is a process for
forming the nonwoven loop materials. Such nonwoven loop materials
are highly useful for hook and loop type closures or fastening
systems in or on personal care products, protective wear garments,
medical care products, bandages and the like.
Inventors: |
Van Gompel; Paul Theodore;
(Hortonville, WI) ; Huang; Yung Hsiang; (Appleton,
WI) |
Correspondence
Address: |
KIMBERLY-CLARK WORLDWIDE, INC.
401 NORTH LAKE STREET
NEENAH
WI
54956
US
|
Assignee: |
Kimberly-Clark Worldwide,
Inc.
|
Family ID: |
36123308 |
Appl. No.: |
11/027390 |
Filed: |
December 30, 2004 |
Current U.S.
Class: |
442/328 ;
442/329 |
Current CPC
Class: |
B32B 2437/00 20130101;
B29C 66/723 20130101; B32B 27/34 20130101; B32B 2307/5825 20130101;
B29C 66/7294 20130101; B29L 2031/729 20130101; A44B 18/0057
20130101; B29C 66/73921 20130101; B32B 2274/00 20130101; B32B 27/36
20130101; A44B 18/0011 20130101; B32B 2262/12 20130101; B32B
2555/00 20130101; B32B 2038/0028 20130101; B32B 2262/0253 20130101;
B29C 65/02 20130101; B32B 2305/20 20130101; B29C 66/344 20130101;
B32B 27/32 20130101; D04H 1/559 20130101; B29C 66/7315 20130101;
B32B 27/205 20130101; B32B 37/144 20130101; B32B 2262/0207
20130101; Y10T 442/601 20150401; B29C 66/45 20130101; B29C 66/21
20130101; B32B 27/40 20130101; B32B 2262/0261 20130101; B32B
2555/02 20130101; B32B 5/08 20130101; B32B 37/0076 20130101; Y10T
442/602 20150401; B32B 38/0012 20130101; B32B 5/022 20130101; D04H
3/14 20130101; B32B 5/26 20130101; B32B 7/05 20190101; B32B 27/12
20130101; B32B 2262/0292 20130101; B32B 2262/0276 20130101; B32B
2535/00 20130101; D04H 1/56 20130101; B32B 5/06 20130101; B29C
66/1122 20130101; B32B 2307/724 20130101; B32B 2435/00 20130101;
B32B 7/14 20130101 |
Class at
Publication: |
442/328 ;
442/329 |
International
Class: |
D04H 13/00 20060101
D04H013/00; D04H 1/00 20060101 D04H001/00; D04H 3/00 20060101
D04H003/00 |
Claims
1. A process for forming a laminate composite loop material for a
hook and loop fastening system, the process comprising: providing a
sheet-form elastic substrate layer; providing at least a first
fibrous nonwoven web, the fibrous nonwoven web comprising fibers
which are less elastic than the elastic substrate layer;
interposing the elastic substrate layer and the fibrous nonwoven
web in a face-to-face relation; bonding the elastic substrate layer
and the fibrous nonwoven web together at spaced-apart locations to
form a laminate composite material; extending the laminate
composite in at least one direction in an extension amount
sufficient to permanently elongate at least a number of the less
elastic fibers along at least a portion of the lengths of the
fibers; and retracting the laminate.
2. The process of claim 1 wherein the elastic substrate layer is a
layer selected from the group consisting of elastic meltblown
layers, elastic spunbond layers and elastic film layers.
3. The process of claim 1 wherein the fibrous nonwoven web
comprises fibers which are substantially inelastic.
4. The process of claim 1 further comprising providing a second
fibrous nonwoven web and bonding the second fibrous nonwoven web to
the elastic substrate layer on the side of the elastic substrate
layer opposite the first fibrous nonwoven web.
5. The process of claim 1 wherein the at least one direction is the
machine direction and the laminate is extended by incremental
stretching or by stretching between at least two pairs of engaged
nipped rollers.
6. The process of claim 1 wherein the at least one direction is the
cross machine direction and the laminate is extended by tentering
or incremental stretching.
7. The process of claim 1 wherein the fibrous nonwoven web
comprises fibers which are substantially continuous fibers.
8. A laminate composite loop material formed by the process of
claim 1.
9. A process for forming a coform composite loop material for a
hook and loop fastening system, the process comprising: providing a
plurality of first, elastic fibers; providing a plurality of second
fibers which are less elastic than the first, elastic fibers;
coforming the first elastic fibers and the second fibers together
to form a composite nonwoven web; bonding the composite nonwoven
web at spaced-apart locations to form a bonded composite nonwoven
web; extending the bonded composite nonwoven web in at least one
direction in an extension amount sufficient to permanently elongate
at least a number of the second fibers along at least a portion of
the lengths of the second fibers: and retracting the coform
composite.
10. The process of claim 9 wherein the first and second fibers are
coformed in a spunbonding process.
11. The process of claim 9 wherein the first and second fibers are
coformed in a meltblowing process.
12. The process of claim 9 wherein the first fibers are meltblown
fibers and the second fibers are staple fibers, and wherein the
fibers are coformed together by merging the staple fibers with the
meltblown fibers during production of the meltblown fibers.
13. The process of claim 9 wherein the at least one direction is
the machine direction and the laminate is extended by incremental
stretching or by stretching between at least two pairs of engaged
nipped rollers.
14. The process of claim 9 wherein the at least one direction is
the cross machine direction and the laminate is extended by
tentering or incremental stretching.
15. A coform composite loop material formed by the process of claim
9.
16. A composite loop material comprising at least one elastic
component and at least one loop-forming component, the loop-forming
component comprising fibers which form loops extending above the
plane of the composite loop material, the loops comprising loop
ends secured in bond points, wherein the loop-forming component
fibers are less elastic than the elastic component, and further
wherein at least a plurality of the loop-forming component fibers
comprise first length portions along the fiber having a fiber cross
sectional diameter which is at least 5 percent smaller than the
cross sectional diameter along a second length portion of the same
fiber.
17. The composite loop material of claim 16 wherein the at least
one elastic component is selected from the group consisting of
elastic meltblown, elastic spunbond and elastic films, and wherein
the loop-forming component is selected from the group consisting of
spunbond fibers and staple fibers.
18. The composite loop material of claim 16 wherein the loop
material is a laminate comprising an elastic substrate layer and a
continuous fiber nonwoven web bonded together in face-to-face
relation.
19. The composite loop material of claim 16 wherein the loop
material is a composite material comprising elastic fibers coformed
with the fibers of the loop-forming component.
20. The composite loop material of claim 18 wherein the elastic
substrate layer is an elastic film layer.
21. The composite loop material of claim 18 wherein the elastic
substrate layer is an elastic meltblown layer
22. The composite loop material of claim 19 wherein the elastic
fibers are elastic meltblown fibers and wherein the fibers of the
loop-forming component are staple fibers.
23. The composite loop material of claim 19 wherein the elastic
fibers are elastic spunbond fibers and wherein the fibers of the
loop-forming component are spunbond fibers.
24. The composite loop material of claim 16 wherein at least a
plurality of the loop-forming component fibers comprise first
length portions along the fiber having a fiber cross sectional
diameter which is at least 10 percent smaller than the cross
sectional diameter along a second length portion of the same
fiber.
25. The composite loop material of claim 16 wherein at least a
plurality of the loop-forming component fibers comprise first
length portions along the fiber having a fiber cross sectional
diameter which is at least 15 percent smaller than the cross
sectional diameter along a second length portion of the same
fiber.
26. The composite loop material of claim 16 wherein at least a
plurality of the loop-forming component fibers comprise first
length portions along the fiber having a fiber cross sectional
diameter which is at least 20 percent smaller than the cross
sectional diameter along a second length portion of the same fiber.
Description
BACKGROUND OF THE INVENTION
[0001] Many of the medical care products, protective wear garments,
mortuary and veterinary products, and personal care products in use
today are available as disposable products. By disposable, it is
meant that the product is used only a few times, or even only once,
before being discarded. Examples of such products include, but are
not limited to, medical and health care products such as surgical
drapes, gowns and bandages, protective workwear garments such as
coveralls and lab coats, and infant, child and adult personal care
absorbent products such as diapers, training pants, incontinence
garments and pads, sanitary napkins, wipes and the like. These
products need to be manufactured at a cost which is consistent with
single- or limited-use disposability.
[0002] Products such as the above mentioned medical, veterinary,
protective and personal care products often utilize mechanical
fastening systems such as hook-and-loop fastening systems, for
purposes of closure or attachment. Fibrous nonwoven webs formed by
extrusion processes such as spunbonding and meltblowing, and by
mechanical dry-forming process such as air-laying and carding, are
ideal candidates to be utilized in or as part of fibrous loop
components of the hook and loop fastening system of disposable
products, since the manufacture of nonwovens is often inexpensive
relative to the cost of woven or knitted loop components.
[0003] Therefore, in order to provide loop materials consistent
with use in limited- or single-use disposable products, there
remains a need for new nonwoven loop material and processes for
producing the nonwoven loop materials.
SUMMARY OF THE INVENTION
[0004] The present invention provides a process for producing
composite nonwoven loop materials that are highly suited for use in
hook and loop fastening systems. In one aspect, the process for
producing the composite loop materials produces a laminate
composite loop material and includes the steps of providing a
sheet-form elastic substrate layer and at least a first fibrous
nonwoven web, the fibrous nonwoven web including fibers which are
less elastic than the elastic substrate layer, interposing the
elastic substrate layer and the fibrous nonwoven web in a
face-to-face relation, bonding the elastic substrate layer and the
fibrous nonwoven web together at spaced-apart locations to form a
laminate composite material, and then extending the laminate
composite in at least one direction, such as, for example, the
machine direction or the cross machine direction, in an extension
amount sufficient to permanently elongate at least a number of the
less elastic fibers along at least a portion of the lengths of the
fibers, and then retracting the laminate. In embodiments, the
elastic substrate layer may be such as elastic meltblowns, elastic
spunbonds or elastic films. A second fibrous nonwoven web may
desirably be bonded to the elastic substrate layer on the side
opposite the first fibrous nonwoven web.
[0005] In another aspect, the process for producing the composite
loop materials produces a coform composite loop material and
includes the steps of providing a plurality of first, elastic
fibers and a plurality of second fibers which are less elastic than
the first, elastic fibers, coforming the first elastic fibers and
the second fibers together to form a composite nonwoven web,
bonding the composite nonwoven web at spaced-apart locations to
form a bonded composite nonwoven web, and then extending the bonded
composite nonwoven web in at least one direction, such as, for
example, the machine direction or the cross machine direction, in
an extension amount sufficient to permanently elongate at least a
number of the second fibers along at least a portion of the lengths
of the second fibers, and then retracting the composite. In
embodiments, the first and second fibers may be coformed in
spunbond processes, meltblown processes, combinations of spunbond
and meltblown processes, or in meltblown-and-staple fiber coforming
processes.
[0006] The present invention further provides composite nonwoven
loop materials such as may be made by the process embodiments
described above. The composite loop material includes at least one
elastic component and at least one loop-forming component. The
loop-forming component includes fibers which form loops extending
above the plane of the composite loop material, and the loops have
loop ends secured or anchored in bond points. The loop-forming
component fibers are less elastic than the elastic component, and
at least a plurality of the loop-forming component fibers include
first length portions along the fiber having a fiber cross
sectional diameter which is at least 5 percent smaller than the
cross sectional diameter along a second length portion of the same
fiber. In embodiments, the diameter at the first length portions on
at least some of the loop-forming fibers may be 10 percent smaller,
15 percent smaller, or even 20 percent or more smaller than the
diameter at the second length portions. In embodiments, the elastic
component may desirably be such as elastic meltblown, elastic
spunbond and elastic films, and the loop-forming component may be
spunbond fibers or staple fibers. The composite loop material may
desirably be a laminate composite material or a coform composite
material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 schematically illustrates a nonwoven loop
material.
[0008] FIG. 2A-2C schematically illustrate close up view of a
single loop-forming fiber during the process of making the nonwoven
loop material.
[0009] FIG. 3 schematically illustrates in top view a directional
orientation path of a single loop-forming fiber.
[0010] FIG. 4 schematically illustrates an enlarged view of certain
portions of the loop-forming fiber shown in FIG. 3.
DEFINITIONS
[0011] 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".
[0012] 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 material. These configurations
include, but are not limited to isotactic, syndiotactic and random
symmetries. As used herein the term "thermoplastic" or
"thermoplastic polymer" refers to polymers that will soften and
flow or melt when heat and/or pressure are applied, the changes
being reversible.
[0013] As used herein, the terms "elastic" and "elastomeric" are
generally used to refer to a material that, upon application of a
force, is stretchable to a stretched, biased length which is at
least about 133 percent, or one and a third times, its relaxed,
unstretched length, and which upon release of the stretching,
biasing force will recover at least about 50 percent of its
elongation. By way of example only, an elastic material having a
relaxed, unstretched length of 10 centimeters may be elongated to
at least about 13.3 centimeters by the application of a stretching
or biasing force. Upon release of the stretching or biasing force
the elastic material will recover to a length of not more than
11.65 centimeters.
[0014] As used herein the term "fibers" refers to both staple
length fibers and substantially continuous filaments, unless
otherwise indicated. As used herein the term "substantially
continuous" with respect to a filament or fiber means a filament or
fiber having a length much greater than its diameter, for example
having a length to diameter ratio in excess of about 15,000 to 1,
and desirably in excess of 50,000 to 1.
[0015] As used herein the term "monocomponent" fiber refers to a
fiber formed from one or more extruders using only one polymer
composition. This is not meant to exclude fibers or filaments
formed from one polymeric extrudate 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 or filaments that 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 or filament. Multicomponent fibers are also
sometimes referred to as conjugate fibers or bicomponent fibers,
although more than two components may be used. 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
concentric or eccentric sheath/core arrangement wherein one polymer
is surrounded by another, or may be a side by side arrangement, an
"islands-in-the-sea" arrangement, or arranged as pie-wedge shapes
or as stripes on a round, oval or rectangular cross-section fiber,
or other configurations. Multicomponent fibers are taught in U.S.
Pat. No. 5,108,820 to Kaneko et al. and U.S. Pat. No. 5,336,552 to
Strack et al. Conjugate fibers are also taught in U.S. Pat. No.
5,382,400 to Pike et al. and may be used to produced crimp in the
fibers by using the differential rates of expansion and contraction
of the two (or more) polymers. For two component fibers, the
polymers may be present in ratios of 75/25, 50/50, 25/75 or any
other desired ratios. In addition, any given component of a
multicomponent fiber may desirably comprise two or more polymers as
a multiconstituent blend component.
[0017] As used herein the terms "biconstituent fiber" or
"multiconstituent fiber" refer to a fiber or filament formed from
at least two polymers, or the same polymer with different
properties or additives, extruded from the same extruder as a
blend. Multiconstituent fibers do not have the polymer components
arranged in substantially constantly positioned distinct zones
across the cross-section of the multicomponent fibers; the polymer
components may form fibrils or protofibrils that start and end at
random.
[0018] As used herein the terms "nonwoven web" or "nonwoven fabric"
refer to a web having a structure of individual fibers or filaments
that are interlaid, but not in an identifiable manner as in a
knitted or woven fabric. Nonwoven fabrics or webs have been formed
from many processes such as for example, meltblowing processes,
spunbonding processes, airlaying processes, and carded web
processes. The basis weight of nonwoven fabrics is usually
expressed in grams per square meter (gsm) or ounces of material per
square yard (osy) and the filament diameters useful are usually
expressed in microns. (Note that to convert from osy to gsm,
multiply osy by 33.91).
[0019] The terms "spunbond" or "spunbond nonwoven web" refer to a
nonwoven fiber or filament material of small diameter fibers 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 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., U.S. Pat. No. 3,692,618 to
Dorschner et al., and U.S. Pat. No. 3,802,817 to Matsuki et al.,
all incorporated herein by reference in their entireties.
Typically, spunbond fibers or filaments have a
weight-per-unit-length in excess of about 1 denier and up to about
6 denier or higher, although both finer and heavier spunbond fibers
can be produced. In terms of fiber diameter, spunbond fibers often
have an average diameter of larger than 7 microns, and more
particularly between about 10 and about 25 microns, and up to about
30 microns or more.
[0020] As used herein the term "meltblown fibers" means fibers or
microfibers formed by extruding a molten thermoplastic material
through a plurality of fine, usually circular, die capillaries as
molten threads or filaments or fibers into converging high velocity
gas (e.g. air) streams that attenuate the fibers of molten
thermoplastic material to reduce their 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 to Buntin. Meltblown fibers may
be continuous or discontinuous, are often smaller than 10 microns
in average diameter and are frequently smaller than 7 or even 5
microns in average diameter, and are generally tacky when deposited
onto a collecting surface.
[0021] As used herein "carded webs" refers to nonwoven webs formed
by carding processes as are known to those skilled in the art and
further described, for example, in U.S. Pat. No. 4,488,928 to
Alikhan and Schmidt which is incorporated herein in its entirety by
reference. Briefly, carding processes involve starting with staple
fibers in a bulky batt that is combed or otherwise treated to
provide a web of generally uniform basis weight. Typically, the
webs are thereafter bonded by such means as through-air bonding,
thermal point bonding, adhesive bonding, and the like.
[0022] As used herein "coform" or "coformed web" refers to
composite nonwoven webs formed by processes in which two or more
fiber types are intermingled into a heterogeneous composite web,
rather than having the different fiber types supplied as separate
or distinct web layers, as is the case in a laminate composite
material. Certain well-known coform processes are described in U.S.
Pat. Nos. 4,818,464 to Lau and 4,100,324 to Anderson et al., the
disclosures of which are incorporated herein by reference in their
entireties, wherein at least one meltblown diehead is arranged near
a chute or other delivery device through which other materials or
fiber types are added while the web is being formed. Such other
materials or fiber types disclosed in these patents include staple
fibers, cellulosic fibers, and/or superabsorbent materials and the
like.
[0023] As used herein, "thermal point bonding" involves passing a
fabric or web of fibers or other sheet layer material to be bonded
between a heated calender roll and an anvil roll. The calender roll
is usually, though not always, patterned on its surface in some way
so that the entire fabric is not bonded across its entire 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 percent bond area with about 200 bonds per
square inch (about 31 bonds per square centimeter) 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
percent. Another typical point bonding pattern is the expanded
Hansen and Pennings or "EHP" bond pattern which produces a 15
percent 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). Other common patterns
include a high density diamond or "HDD pattern", which comprises
point bonds having about 460 pins per square inch (about 71 pins
per square centimeter) for a bond area of about 15 percent to about
23 percent, a "Ramish" diamond pattern with repeating diamonds
having a bond area of about 8 percent to about 14 percent and about
52 pins per square inch (about 8 pins per square centimeter) and a
wire weave pattern looking as the name suggests, e.g. like a window
screen. As still another example, the nonwoven web may be bonded
with a point bonding method wherein the arrangement of the bond
elements or bonding "pins" are arranged such that the pin elements
have a greater dimension in the machine direction than in the
cross-machine direction. Linear or rectangular-shaped pin elements
with the major axis aligned substantially in the machine direction
are examples of this. Alternatively, or in addition, useful bonding
patterns may have pin elements arranged so as to leave machine
direction running "lanes" or lines of unbonded or substantially
unbonded regions running in the machine direction, so that the
nonwoven web material has additional give or extensibility in the
cross machine direction. Such bonding patterns as are described in
U.S. Pat. No. 5,620,779 to Levy et al., incorporated herein by
reference in its entirety, may be useful, such as for example the
"rib-knit" bonding pattern therein described. Typically, the
percent bonding area varies from around 10 percent to around 30
percent or more of the area of the fabric or web. Thermal bonding
imparts integrity to individual layers or webs by bonding fibers
within the layer and/or for laminates of multiple layers, such
thermal bonding holds the layers together to form a cohesive
laminate material.
[0024] As used herein, "loops" refers to portions of fibers in a
nonwoven web material which define an arch, semi-circle or similar
configuration extending above the flat length-width plane of the
nonwoven web material. Typically, fiber loops will have loop ends
which are anchored or secured by bond points.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present invention provides a process for producing
composite nonwoven loop materials suitable for use in hook and loop
fastening systems. The present invention further provides nonwoven
loop materials. The invention will be described with reference to
the following description and Figures which illustrate certain
embodiments. 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.
Furthermore, features described or illustrated as part of one
embodiment may be used with another embodiment to yield still a
further embodiment. It is intended that the scope of the claims
extend to all such variations and equivalents.
[0026] In one aspect, the process for producing the composite loop
materials produces a laminate composite loop material by bonding at
least a first nonwoven web layer to a sheet-form elastic substrate
layer at spaced-apart locations, to form a precursor composite
material which is a laminate of at least the two layers. The
nonwoven web layer should include fibers which are inelastic, or at
least less elastic than the elastic substrate layer. The inelastic
or less elastic fibers are the loop-forming fibers. In another
aspect, the process for producing the composite loop materials
produces a coform composite loop material by coforming together a
first type of fibers, which are elastic, and a second type of
fibers, which are either inelastic or at least less elastic than
the first fibers, and bonding the coformed web at spaced-apart
locations to form a precursor composite material. As mentioned, the
inelastic or less elastic fibers are the loop-forming fibers.
[0027] In either aspect, the precursor composite is stretched or
extended by the application of one or more biasing forces in at
least one direction, such as the machine direction or the cross
machine direction, or both. During this stretching or extending
step, the composite material is extended from its original length
or width dimension to a new, extended length which is greater than
the original length. The new, longer length should represent an
extension distance which is greater than the capability of the
loop-forming fibers to elastically recover. In this way, at least
some number, and desirably a substantial majority, of the
individual loop-forming fibers are permanently deformed or
permanently elongated to a new, longer length, at least along a
portion of their individual lengths. Then, the biasing or
stretching force is relaxed and the composite material is allowed
to retract. The composite material retracts or recovers toward its
original unextended length due to the elastic stretch and recovery
properties of the elastic component, and may, depending on the type
of elastic selected and the amount of extension applied, retract
substantially to its original unextended length. As the composite
retracts to a length less than the extended length, the portions of
the loop-forming fibers which were permanently elongated now have
additional length or "slack", which provides for arcs or looped
fiber portions capable of extending from the planar surface of the
composite material.
[0028] An exemplary composite loop material is shown in FIG. 1. In
FIG. 1, the composite loop material 10 is represented as a laminate
composite loop material which includes a fibrous nonwoven web layer
20 and an elastic substrate layer 30. The fibrous nonwoven web
layer 20 may desirably be any fibrous nonwoven layer such as
spunbond, meltblown, carded webs and the like. The fibers of the
fibrous nonwoven web layer 20 are anchored or secured to the
elastic substrate layer 30 by a plurality of spaced-apart bond
points 40.
[0029] FIGS. 2A, 2B, and 2C show a highly stylized illustration of
a close-up side view of a precursor composite nonwoven material and
a single loop-forming fiber as the precursor composite nonwoven
material 100 is processed into an extended intermittent material
110 (FIG. 2B) and finally into the composite loop material 120
(FIG. 2C). The FIG. 2A shows a single fiber 130 which is
intermittently secured or anchored into the elastic substrate layer
140 of the composite precursor nonwoven web 100 at spaced-apart
bond points 150. The loop-forming fiber 130 may be an inelastic
fiber or may have some elastic stretch/recovery properties, but
should be less elastic than elastic substrate layer 140. Note that
although for the purposes of this illustration, the composite
nonwoven 100 is shown in laminate form with elastic substrate layer
140 as a separate distinct layer, the composite nonwoven 100 could
also be the coform composite web embodiment having elastic fibers
intermingled with the inelastic or less elastic loop forming
fibers.
[0030] In addition, for the purposes of this illustration only a
single fiber 130 is shown, and the fiber is shown to lie
essentially in a straight line and to be anchored to each adjacent
bond point 150. However, one skilled in the art will recognize that
due to the random nature of the directional orientation of fibers
in nonwoven webs, in practice a given single fiber would be
expected to lie along a random path in the x and y plane of the
nonwoven web rather than to follow a single straight line as
represented in this illustration.
[0031] As can be seen in FIG. 2A, the fiber 130 lies close against
the planar surface of the material 100 and is essentially flat,
with little or no extension of the fiber 130 above the planar
surface. An anchor-to-anchor distance is shown marked by bracket
160 for comparison of the length of the fiber 130 throughout
certain portions of the process shown.
[0032] Turning to FIG. 2B, the material has been extended or
stretched by the application of a biasing or stretching force such
that it is in an intermittent state of the process, where the
composite 110 as a whole has been extended to a desired level of
extension (approximately 150 percent of the original length of the
material 100 in FIG. 1) and the fiber 130 has been elongated
between anchor positions or bond points 150 to a length greater
than its ability to elastically recover. This new extended
anchor-to-anchor distance or length is shown by bracket 170. As
shown in FIG. 2B, the fiber length encompassed by bracket 170 is
approximately 150 percent of the fiber length encompassed by
bracket 160 in FIG. 2A.
[0033] Turning to FIG. 2C, the biasing or stretching force has been
removed, allowing the composite material 120 to retract due to the
elastic recovery properties of the elastic substrate layer 140. As
the elastic substrate layer 140 retracts towards or to its original
unstretched length, the loop-forming fiber 130 (FIGS. 2A and 2B),
because it has been permanently elongated by being stretched to a
length greater than its ability to recover, now has length between
anchor points or bond points 150 which is greater than the length
prior to stretching. This additional point-to-point length allows
for fiber buckling and extension of the fiber into loop elements
180 having loop ends secured or anchored into the bond points 150.
These loop elements 180 are capable of much more upward extension
(away from the planar surface) than the same anchor-to-anchor
length portion of the fiber prior to composite elongation and
retraction.
[0034] As mentioned above, due to the random nature of fiber
orientation in nonwoven web materials, a given single fiber will
typically lie along a random path in the x and y plane of a
nonwoven web instead of following a single straight line path as
was represented in FIGS. 2A-2C. Shown in FIG. 3 is a top view of a
directional orientation path of a single exemplary loop-forming
fiber 210 in or on a section of a composite web material 200. The
machine direction (generally, direction of material production or
material feed direction) is shown as arrow MD. The loop-forming
fiber 210 travels along a generally random path which intersects,
among others, the bond points 220, 230 and 240 while the fiber 210
follows a generally machine direction oriented path, and then turns
generally perpendicular (toward the cross machine direction) and
intersects bond point 250. Note that the number, size, shape,
spacing and general orientation of the bond points shown are only
for purposes of this illustration, and one skilled in the art will
recognize that the characteristics of bond points can vary
considerably.
[0035] As stated above, after the composite has been stretched and
retracted at least some number of the individual loop-forming
fibers will have been permanently elongated to a new length which
is longer than their pre-stretched length. Desirably, in order to
provide as many loop elements as possible, a substantial majority
of the fibers will have been permanently elongated. However, for a
given direction of composite elongation, such as elongation along a
line parallel to line MD, there will generally be fibers having
substantial portions of their lengths which are largely unaffected
by the composite elongation, where, for example, for a given
portion along the length of a fiber, the fiber runs between bond
points oriented substantially perpendicular to the direction of
elongation. As a specific example, in FIG. 3 there are certain
"first" portions along the length of the fiber 210 which connect
between bond points 220 and 230, and between 230 and 240, which may
be expected to be substantially extended along with the entire
composite material when the composite is extended along line MD.
However, another or "second" portion along the length of the fiber
210 which connects between bond points 240 and 250 may be expected
to be largely unaffected by composite elongation along line MD, and
therefore this second portion will have much less permanent
elongation than the first portions, and possible no permanent
elongation at all.
[0036] FIG. 4 shows an enlarged illustration of the above-mentioned
first and second portions along the length of the same loop-forming
fiber 210, i.e., those portions of the fiber 210 which in FIG. 3
intersect bond points 220, 230, 240 and 250. When the composite is
extended, the first portions of the fiber 210 which are permanently
elongated are also reduced in diameter. As shown illustrated in
FIG. 4, the first portions along the fiber length which were
subjected to substantial permanent stretching or elongation
(between bond points 220 and 230, and between 230 and 240), have a
smaller cross sectional diameter than the illustrated second
portion shown (between bond points 240 and 250). It is expected
that for any substantial permanent elongation of a given first
fiber portion, that portion of the loop-forming fiber will have a
fiber cross sectional diameter at least 5 percent smaller than the
cross sectional diameter along a second length portion of the same
fiber. Depending on the amount of permanent elongation, the
elongated or first portions of an individual fiber may have
diameters which are 5 to 10 percent smaller, or even ranging from 5
percent to 40 percent smaller, than the diameter of the second
portions.
[0037] As mentioned above, the composite nonwoven loop materials
may be produced as laminate composite loop materials and coform
composite loop materials, and the loop material and the components
used in the composite loop material may have a wide range of basis
weights. Generally speaking, the basis weight of the loop-forming
component fibrous nonwoven web(s) or loop-forming component fibers
in a coform composite loop material may suitably be from about 7
gsm or less up to 100 gsm or more, and more particularly may have a
basis weight from about 10 gsm or less to about 68 gsm, and still
more particularly, from about 14 gsm to about 34 gsm. Other
examples are possible. In addition, generally, the basis weight of
elastic fibers in the coform composite loop material or of the
elastic substrate layer in the laminate composite loop material may
be from about 5 gsm or less to about 100 gsm or greater. More
desirably, the elastic component of the composite loop material may
have a basis weight from about 5 gsm to about 68 gsm, and still
more desirably from about 5 gsm to about 34 gsm. Because elastic
materials are often expensive to produce, the basis weight of
elastic material utilized is desirably of as low a basis weight as
is possible while still providing the desired properties of stretch
and recovery to the composite loop material.
[0038] Suitable laminate composite loop material constructions
include one or more sheet-form elastic substrate layers with one or
more fibrous layers, the fibrous layer or layers including the
loop-forming fibers. As mentioned above, the loop-forming fibers
should be either inelastic, or at least less elastic than the
elastic substrate layer. The two types of layers are placed in
face-to-face relation as a composite and then bonded together at
spaced-apart locations to form a bonded laminate composite.
Suitable elastic substrate layers include elastic spunbond layers,
elastic film layers, and/or elastic meltblown layers. Suitable
fibrous layers to provide loop-forming fibers include nonwoven
layers as are known in the art, such as carded and airlaid staple
fiber webs, and spunbond and meltblown meltspun fiber webs.
[0039] The production of each of these types of individual elastic
substrate layers and fibrous/loop-forming fiber containing layers
is mentioned briefly hereinabove, and well known in the art and
therefore will not be discussed here in detail. However, it should
be noted that in addition to laminating dissimilar sheet types
(such as for example an elastic film/inelastic nonwoven laminate,
or elastic meltblown/inelastic spunbond), similar types may also
beneficially be laminated together to form the laminate composite.
As a specific example, spunbonding processes as are known in the
art often employ multiple spinpack and fiber drawing unit ("FDU")
assemblies on the same spunbond machine, wherein a first
spinpack/FDU assembly deposits its fibers as a web directly onto
the collecting surface, and the second spinpack/FDU assembly
deposits its fibers onto the web deposited by the first assembly,
thereby producing a spunbond web which is formed as two layers.
Such a multi-spinpack spunbonding machine may be beneficially used
to produce the composite laminate by extruding elastic fibers for
the elastic substrate layer from one spinning assembly and
extruding the loop-forming spunbond fibers from another spinning
assembly.
[0040] It should be noted that for the laminate composite loop
material, either or both of the sheet-form elastic substrate layer
or the loop-forming fibrous nonwoven web may themselves be
multi-layer structures. Particular examples of multilayer laminate
construction for the loop-forming fibrous nonwoven web include
spunbond-meltblown laminates, spunbond-spunbond laminates,
spunbond-carded web laminates, and the like. Examples of laminate
construction for an elastic substrate layer include
spunbond-elastic layer laminates and carded web-elastic layer
laminate. Because elastic layers such as an elastic film layer or
elastic meltblown layer may feel tacky to the touch, such "faced"
elastic layers may be desirable where the loop material laminate is
to be used with the elastic substrate layer in skin contact, so
that the nonwoven facing over the elastic layer provides more of a
cloth-like feel against the skin.
[0041] Where the sheet-form elastic substrate layer for the
laminate composite loop material is an elastic film layer, it may
be desirable for the film to be breathable. Meltblown and spunbond
layers are inherently breathable; that is, meltblown and spunbond
layers are capable of transmitting gases and water vapors. Film
layers however, generally act as a barrier to the passage of
liquids, vapors and gases. An elastic layer which is breathable may
provide increased in-use comfort to a wearer by allowing passage of
water vapor and assist in reducing excessive skin hydration, and
help to provide a more cool feeling. Therefore, where a film is
used as the elastic component but a breathable composite loop
material is desired, the elastic material used may be a breathable
monolithic or microporous barrier film.
[0042] Monolithic breathable films can exhibit breathability when
they comprise polymers which inherently have good water vapor
transmission or diffusion rates such as, for example,
polyurethanes, polyether esters, polyether amides, EMA, EEA, EVA
and the like. Examples of elastic breathable monolithic films are
described in U.S. Pat. No. 6,245,401 to Ying et al., incorporated
herein by reference in its entirety, and include those comprising
polymers such as thermoplastic (ether or ester) polyurethane,
polyether block amides, and polyether esters. Microporous
breathable films contain a filler material, such as for example
calcium carbonate particles, in an amount usually from about 30
percent to 70 percent by weight of the film. The filler-containing
film (or "filled film") opens micro-voids around the filler
particles when the film is stretched, which micro-voids allow for
the passage of air and water vapor through the film. Breathable
microporous elastic films containing fillers are described in, for
example, U.S. Pat. Nos. 6,015,764 and 6,111,163 to McCormack and
Haffner, U.S. Pat. No. 5,932,497 to Morman and Milicevic, and in
U.S. Pat. No. 6,461,457 to Taylor and Martin, all incorporated
herein by reference in their entireties. In addition, multilayer
breathable films as are disclosed in U.S. Pat. No. 5,997,981 to
McCormack et al., incorporated herein by reference in its entirety,
may be useful. Another example of a film which can exhibit
breathability is a cellular elastic film, such as may be produced
by mixing an elastic polymer resin with a cell opening agent which
decomposes or reacts to release a gas that forms cells in the
elastic film. The cell opening agent can be an azodicarbonamide,
fluorocarbons, low boiling point solvents such as for example
methylene chloride, water, or other agents such as are known to
those skilled in the art to be cell opening or blowing agents which
will create a vapor at the temperature experienced in the film die
extrusion process. Cellular elastic films are described in PCT App.
No. PCT/US99/31045 (WO 00/39201 published Jul. 06, 2000) to Thomas
et al., incorporated herein by reference in its entirety.
[0043] As another example, if an elastic film layer is the selected
elastic substrate layer but liquid barrier properties are not
particularly important or are not desired, the elastic film itself
(prior to lamination) or the composite laminated with the nonwoven
loop-forming fibers may be apertured or perforated to provide a
laminate capable of allowing the passage of vapors or gases. Such
perforations or apertures may be performed by methods known in the
art such as for example slit aperturing or pin aperturing with
heated or ambient temperature pins.
[0044] Suitable coform composite loop material constructions
include elastic meltblown fibers for the elastic component which
are coformed with inelastic (or less elastic) staple fibers, such
as may be produced according to the above-mentioned U.S. Pat. No.
4,818,464 to Lau and U.S. Pat. No. 4,100,324 to Anderson et al. by
introducing staple fibers into the just-extruded meltblown fibers,
by delivering the staple fibers down a chute as the meltblown
fibers are being extruded and attenuated. Another exemplary
coforming process is described in U.S. Pat. No. 5,350,624 to
Georger et al., incorporated herein by reference in its entirety.
In U.S. Pat. No. 5,350,624, the coforming process uses multiple
meltblown dieheads arranged on either side of the delivery chute.
Such a process could be utilized by coforming elastic meltblown
fibers with a second (loop-forming) inelastic or less elastic
meltblown fibers, and/or by adding loop-forming staple fibers via
the delivery chute, and/or by meltblowing elastic fibers from both
dieheads while adding loop-forming staple fibers via the delivery
chute.
[0045] As stated above, other nonwoven web production methods
capable of producing a heterogeneous mixture or composite of
differing fiber types should also be considered to be coforming
production methods. For example, a coformed composite web may be
produced by orienting one or more meltblown dieheads at a slight
angle to extrude elastic meltblown fibers near the exit of a
spunbonding fiber drawing unit (or "FDU") such that the elastic
meltblown fibers intermingle into the loop-forming spunbond fibers
just prior to the loop-forming spunbond fibers being deposited onto
a collection surface. Alternatively, the spunbond fiber drawing
unit may be angled into the extrusion path of meltblown fibers, or
spunbond fibers may be deflected into the meltblown fibers after
the spunbond fibers exit the FDU. In addition, for the purposes of
this disclosure, other known processes as may be used to produce
intermingled or heterogeneous fiber type composite webs may be
considered coforming processes, for example airlaying and carding
where two or more fiber types are used, and hydraulic or mechanical
needling where two or more staple fiber types are needled together
into a composite or where one or more staple fiber types are
needled into a previously formed nonwoven web such as a spunbond,
meltblown or carded webs, for example.
[0046] Also within this usage of a "coformed" web are composite
webs formed by such processes as spunbonding, wherein two types of
spunbond fibers are spun and intermingled. Such spunbond
intermingled webs may be produced from a single spunbond spinpack
and spinneret assembly which is capable of spinning two or more
distinct polymers or fiber types separately, such as is disclosed
in U.S. Pat. No. 6,164,950 to Barbier et al. Using the method and
apparatus disclosed in U.S. Pat. No. 6,164,950, a coform composite
loop material may be produced by spinning from the one spinneret a
first spunbond fiber type which is elastic for the elastic
component, and a second spunbond fiber type for the loop-forming
fibers which is inelastic or less elastic than the elastic
component fibers. Alternatively, a coformed spunbond web may be
spun from multiple spinnerets where the fibers are intermingled at
some point prior to being deposited on the collecting surface. For
example, the elastic component fibers may be produced by one
spunbond spinpack and the loop-forming fibers by a second spinpack,
but the fibers from both spinpacks are drawn in the same fiber
drawing unit. Alternatively, the separate fiber types may be drawn
in separate fiber drawing units, where the fiber drawing units are
arranged to have the drawing unit exits close enough together to
allow fiber intermingling as the fibers exit the drawing unit and
are deposited on the collecting surface. Processes for making
coformed spunbond webs are more fully described in U.S. Pat. No.
5,853,635 to Morell et al., and U.S. Pat. No. 5,935,512 to Haynes
et al., the disclosures of which are incorporated herein by
reference in their entireties.
[0047] Polymers suitable for making the fibrous nonwoven webs to be
used in the embodiments described herein include those polymers
known to be generally suitable for making nonwoven webs such as
spunbond, meltblown, carded webs and the like, and include for
example polyolefins, polyesters, polyamides, polycarbonates and
copolymers and blends thereof. It should be noted that the polymer
or polymers may desirably contain other additives such as
processing aids or treatment compositions to impart desired
properties to the fibers, residual amounts of solvents, pigments or
colorants and the like.
[0048] 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; 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 poly(lactide) and
poly(lactic acid) polymers as well as polyethylene terephthalate,
polybutylene terephthalate, polytetramethylene terephthalate,
polycyclohexylene-1,4-dimethylene terephthalate, and isophthalate
copolymers thereof, as well as blends thereof.
[0049] Many elastomeric polymers are known to be suitable for
forming the elastic component of the laminate composite loop
material, such as elastic fibers and elastic fibrous web layers and
elastic films. As stated above, elastic polymers may also suitably
be used for forming the loop-forming fibers. However, if an elastic
polymer is used for the loop-forming fibers care should be taken to
select the polymer for the loop-forming fibers and the elastic
component of the composite loop material such that the loop-forming
fibers are less elastic than the elastic component. Thermoplastic
polymer compositions may desirably comprise any elastic polymer or
polymers known to be suitable elastomeric fiber or film forming
resins including, for example, elastic polyesters, elastic
polyurethanes, elastic polyamides, elastic co-polymers of ethylene
and at least one vinyl monomer, block copolymers, and elastic
polyolefins. Examples of elastic block copolymers include those
having the general formula A-B-A' or A-B, where A and A' are each a
thermoplastic polymer endblock that contains a styrenic moiety such
as a poly (vinyl arene) and where B is an elastomeric polymer
midblock such as a conjugated diene or a lower alkene polymer such
as for example polystyrene-poly(ethylene-butylene)-polystyrene
block copolymers. Also included are polymers composed of an A-B-A-B
tetrablock copolymer, as discussed in U.S. Pat. No. 5,332,613 to
Taylor et al. An example of such a tetrablock copolymer is a
styrene-poly(ethylene-propylene)-styrene-poly(ethylene-propylene)
or SEPSEP block copolymer. These A-B-A' and A-B-A-B copolymers are
available in several different formulations from the Kraton
Polymers of Houston, Tex. under the trade designation KRATON.RTM..
Other commercially available block copolymers include the SEPS or
styrene-poly(ethylene-propylene)-styrene elastic copolymer
available from Kuraray Company, Ltd. of Okayama, Japan, under the
trade name SEPTON.RTM..
[0050] Examples of elastic polyolefins include ultra-low density
elastic polypropylenes and polyethylenes, such as those produced by
"single-site" or "metallocene" catalysis methods. Such polymers are
commercially available from the Dow Chemical Company of Midland,
Mich. under the trade name ENGAGE.RTM., and described in U.S. Pat.
Nos. 5,278,272 and 5,272,236 to Lai et al. entitled "Elastic
Substantially Linear Olefin Polymers". Also useful are certain
elastomeric polypropylenes such as are described, for example, in
U.S. Pat. No. 5,539,056 to Yang et al. and U.S. Pat. No. 5,596,052
to Resconi et al., incorporated herein by reference in their
entireties, and polyethylenes such as AFFINITY.RTM. EG 8200 from
Dow Chemical of Midland, Mich. as well as EXACT.RTM. 4049, 4011 and
4041 from Exxon of Houston, Tex., as well as blends.
[0051] As mentioned, after formation of the elastic component(s)
with the loop-forming fiber containing component(s), the laminate
composite web or coform composite web should be bonded at
spaced-apart locations. Suitable methods for applying spaced-apart
bond locations or discrete bond "points" on either the laminate
composite loop material or the coform composite loop material
include thermal bonding methods as are known in the art, such as
the exemplary thermal point bonding methods described herein. Other
suitable methods known to those skilled in the art for imparting
discrete bonds at spaced-apart locations may also be used, for
example by point or drop deposition of adhesive materials, or by
ultrasonic bonding. After the laminate composite or coform
composite material has been bonded at spaced-apart locations, it
should be stretched or extended in one or more directions in order
to permanently deform the loop-forming fibers. That is, the
loop-forming fibers are permanently deformed by having at least
portions of their lengths permanently increased. Then, the
composite material is allowed to retract under or due to the
elastic recovery force of the elastic component. When the elastic
component retracts, the now-elongated loop-forming fibers, which
are anchored or secured at the spaced-apart bond locations, can
bunch up or flex or bow up away from the flat x-and-y plane of the
material, thereby forming loop elements capable of engaging hook
members.
[0052] Stretching or extending of the composite material may be
performed by any method as is known in the art for extending webs.
For example, a web may be stretched in the machine direction by
passing the web through two or more pairs of driven nipped rollers,
wherein an upstream pair of driven rollers is driven at a first
velocity, and a downstream pair of driven rollers is driven at a
second velocity which is greater than the first velocity. Because
the second velocity is greater than the first velocity, the
composite material will experience a machine direction tensioning
force or biasing force as it travels through the two nips. This
machine direction tensioning force will cause the composite
material to be stretched or extended in the machine direction.
Because the at least one component of the composite material is
elastic, when the tension is removed or relaxed the composite will
retract toward its original machine direction length.
[0053] Machine direction drawing may also be accomplished by a
non-nipped roller assembly having multiple driven rollers in a
vertical stack, which is referred to as a "machine direction
orienter" or MDO unit. The web material travels through the roller
stack in an alternating or "S" wrap or "serpentine" wrap fashion,
such that the material contacts a first driven roller with one
planar material surface, a second driven roller with the opposite
planar material surface, a third roller with the first planar
material surface again, and so on. Each subsequent driven roller is
driven at a speed slightly higher than the previous roller. Still
another method for machine direction stretching of a moving web
includes passing the web through a nipped pair of rollers having a
gear-tooth type surface engraving which creates channels or grooves
and high points or teeth in the surfaces of the rollers which run
along the longitudinal axis of the rollers. The high points or
teeth on one roller fit or match within the grooves of the other
roller when the two rollers are nipped.
[0054] It may alternatively or also be desirable to stretch/extend
the composite material in the cross machine direction, by such
methods as tenter frames and grooved rollers. Grooved rollers may
be more desirable for cross machine direction extending because
nonwoven and film materials may have a tendency to develop
longitudinal tears under an applied transverse biasing force.
Grooved rollers may be constructed from a series of spaced disks or
rings mounted on a mandrel or axle, or may be a series of spaced
circumferential peaks and grooves cut into the surface of a roller.
A pair of matched grooved rollers is then brought together with the
peaks of one roller fitting into the grooves of the other roller,
and vice versa, to form a "nip", although it should be noted that
there is no requirement for actual compressive contact as is the
case for typical nipped rollers. Grooved rollers as are known in
the art are described as imparting an "incremental stretching"
because the whole transverse width of a web material may be
stretched by what amounts to a large number of small scale
stretches (between each peak-to-peak distance) aligned along the
transverse or cross machine direction of the web, which are less
likely to cause tears than gripping the side edges of a web
material and applying a stretching force to the web as a whole.
[0055] The overall level of stretching or extending performed on
the composite material will depend on a number of factors,
including desired amount of permanent loop-forming fiber elongation
along the above-mentioned first portions of the fibers, types of
polymers selected for the elastic and loop-forming fiber component,
and the ability of the components to extend without breaking.
Generally, the level of extending should not be so great as to
exceed the maximum stretchability of the elastic component, such
that its recovery properties are largely diminished. Also, the
level of extending should not be so great as to substantially
destroy the loop-forming fibers or the fibrous nonwoven web
containing the loop-forming fibers, although some fiber breakage is
acceptable. In broad terms, the composite may be extended in an
amount from about 5 percent of its unstretched dimension to about
300 percent or more of its unstretched dimension. More
particularly, the composite may be extended in an amount from about
20 percent of its unstretched dimension to about 200 percent of its
unstretched dimension. Still more particularly, the composite may
be extended in an amount from about 40 percent of its unstretched
dimension to about 150 percent of its unstretched dimension.
[0056] The composite loop materials described herein are highly
suitable for use as the loop component in a hook and loop fastener
system in a wide variety of applications, including uses such as
fasteners and closures for medical and health care products such as
surgical drapes, gowns and bandages, protective workwear garments
such as coveralls and lab coats, and infant, child and adult
personal care absorbent products such as diapers, training pants,
incontinence garments and pads, sanitary napkins, wipes and the
like. Because of the elastic construction components and stretch
processing the composite loop materials are inherently extensible
and/or elastic, which can provide improved product fit and body
conformance attributes. Also, the composite loop material can be
provided as a very flexible and drapeable sheet material, compared
to typical knitted loops which are often adhered to a stiff backing
material to provide anchoring for the knitted loop elements.
[0057] In addition, the composite loop material can be initially
produced in an unstretched composite state, and the unstretched
composite wound up onto a roll for storage or transport, and only
converted into the final composite loop material by stretching or
extending at the facility that manufactures the product that the
loop material is to be a component of. In this case, the loop
material may be stored and shipped in the form of the less lofty
precursor composite material, which is more convenient because
loftier or bulkier (i.e. thicker) webs require more storage space.
Also, performing the extending step at the manufacturing facility,
just prior to conversion of the loop material into or onto a
product, has the added benefit that the loop elements have not been
compressed while being stored and transported in a rolled material
form.
[0058] As stated, the composite loop materials of the invention are
highly suitable for use as the loop component in a hook and loop
fastener system in a wide variety of applications. The composite
loop materials may be used with any suitable hook-type member which
is capable of engaging the loop elements. The term "hook" or "hook
member" encompasses various shapes or geometries of protuberances
that are suitable for engaging into a loop material in order to
place or secure a fastener. Exemplary hook shapes include prongs,
stems, trees (such as the shapes connoted by "evergreen" and "palm"
trees), mushrooms, J-shaped hooks, bi-directional hooks and studs
protruding at various angles. Exemplary hook members are readily
available commercially from, for example, Velcro USA, Inc. of
Manchester, N.H. and from the 3M Company, St. Paul, Minn.
[0059] While not described in detail herein, various additional
potential processing and/or finishing steps as are known in the art
for processing of nonwoven web and film materials may be performed
on the composite loop material without departing from the spirit
and scope of the invention. Examples of further processing includes
such as slitting, treating, aperturing, printing graphics, or
further lamination of the composite with other materials, such as
other films or other nonwoven layers. General examples of web
material treatments include electret treatment to induce a
permanent electrostatic charge in the web, or in the alternative
antistatic treatments, or one or more treatments to impart
wettability or hydrophilicity to a web comprising hydrophobic
thermoplastic material. Wettability treatment additives may be
incorporated into the polymer melt as an internal treatment, or may
be added topically at some point following fiber or web formation.
Still another example of web treatment includes treatment to impart
repellency to low surface energy liquids such as alcohols,
aldehydes and ketones. Examples of such liquid repellency
treatments include fluorocarbon compounds added to the web or
fibers of the web either topically or by adding the fluorocarbon
compounds internally to the thermoplastic melt from which the
fibers are extruded.
EXAMPLES
Example 1
[0060] As a specific example of an embodiment of the foregoing, a
coform composite loop material could be produced in the following
manner. The coform composite loop material may be constructed of a
meltblown elastic component which is coformed with
polyethylene-polypropylene sheath-core type staple fibers as the
loop-forming fibers. These two components may be coformed together
substantially in accordance with the disclosure of above-mentioned
U.S. Pat. No. 4,100,324 to Anderson et al. The two components may
each be present in the coform composite loop material at a basis
weight of approximately 20 gsm so as to produce a composite
material having a basis weight of approximately 40 gsm.
[0061] To form the elastic meltblown fibers for the elastic
component of the coform composite loop material, a commercially
available polyethylene elastic polymer, available from The Dow
Chemical Company (Midland, Mich.) under the trade name
AFFINITY.RTM. EG 8200, may be melted by an extruder at
approximately 520.degree. F. (about 270.degree. C.) and supplied to
the meltblowing diehead and conveyed therethrough to be extruded as
molten polymer threads or filaments. As the elastic polymer is
extruded from the meltblown diehead, the just-extruded threads or
fibers are entrained in and drawn by converging high velocity air
streams heated to about 520.degree. F. (about 270.degree. C.) which
attenuate the polymer threads to form elastic meltblown fibers.
[0062] At the same time, the sheath-core staple fibers, such as
polyethylene/polypropylene bicomponent sheath-and-core fibers
available from ES Fibervisions of Athens, Ga., may be introduced
into the meltblown fiber flowpath by delivering the staple fibers
down a delivery chute, to be entrained into the meltblown fibers as
they are being drawn in the converging attenuation air streams.
Thereafter, the intermingled elastic meltblown fibers and
loop-forming fibers staple fibers are collected onto a moving
foraminous forming surface to form an integrated elastic
meltblown/staple fiber composite web. The composite web may then be
transported by the moving foraminous forming surface to a thermal
point bonding calender roll assembly, such as the above-described
expanded Hansen and Pennings or "EHP" bond pattern to bond the
composite web at spaced-apart locations over about 15 percent of
its planar surface area.
[0063] After bonding, the coformed composite material is stretched
in the machine direction by passing the web through two pairs of
driven nipped rollers, wherein the first or upstream pair of driven
rollers is driven at a first velocity, and the second or downstream
pair of driven rollers is driven at a second velocity which is 150
percent of the first velocity. That is, for a first roller pair
velocity of about 300 feet per minute (about 91 meters per minute),
the second roller pair velocity is about 450 feet per minute (about
137 meters per minute). Because the second velocity is greater than
the first velocity, the composite material will experience a
machine direction tensioning force or biasing force as it travels
through the two nips and be stretched or extended along its machine
direction. This machine direction stretching of the coformed
composite causes the spaced-apart locations of the bonds along the
machine direction to become farther apart.
[0064] Because the spaced-apart locations of these bonds anchor the
loop-forming staple fibers, those staple fibers and/or portions of
the staple fibers traveling a generally machine direction path from
bond location to bond location are thereby elongated past their
deformation limit, causing them to become permanently elongated.
Then, after stretching or extending, the tension is removed or
relaxed by rolling the coformed composite up onto a material
winding roller which is turning at a linear velocity that is less
than that of the second roller pair, for example at about the same
linear velocity as the first pair of rollers, to allow the elastic
meltblown component of the composite to retract toward its original
machine direction length. Those portions of the loop-forming staple
fibers which have been permanently elongated between the
spaced-apart bond locations will have additional length available
to form arcs or loop elements.
Example 2
[0065] As another specific example of an embodiment of the
foregoing, a laminate composite loop material could be produced in
the following manner. The laminate composite loop material may be
formed in a spunbonding operation, wherein the first bank of
spunbond fibers are formed from an elastic polymeric composition,
and the second bank of spunbond fibers is formed from an inelastic
polymeric composition. As an example, an elastic polymer such as
the AFFINITY.RTM. EG 8185 brand polyolefin plastomer from Dow
Chemical of Midland, Mich. may be supplied to a first extruder to
be melted at about 120.degree. C. (about 250.degree. F.) and pumped
through a first polymer supply pipe to a first spunbond
spinneret/capillary assembly to be extruded as a plurality of
molten fibers in a curtain. The molten fibers may be quenched with
air from an air blower located adjacent the curtain of fibers and
the fibers may then be fed through a pneumatic fiber draw unit or
aspirator such as is described in U.S. Pat. No. 3,802,817 to
Matsuki et al. to draw or attenuate the fibers, that is, reduce
their diameter. An endless foraminous forming surface may be
positioned below the fiber draw unit to receive the drawn elastic
fibers from the outlet opening of the fiber draw unit and a vacuum
apparatus may be positioned below the foraminous forming surface to
facilitate the proper placement of the elastic fibers onto the
forming surface. The rate of extrusion of the elastic spunbond
fibers, combined with the speed of the foraminous forming surface,
may desirably make the first (elastic) spunbond layer have a basis
weight of about 14 grams per square meter.
[0066] While the elastic component fibers are being formed in the
first spunbond bank, an inelastic polypropylene polymer such as the
polypropylene designated 3155 from the ExxonMobil Chemical Company,
Houston, Tex. may be supplied to a second extruder to be melted at
about 232.degree. C. (about 450.degree. F.) and pumped through a
second polymer supply pipe to a second spunbond spinneret/capillary
assembly to be extruded as a plurality of molten fibers in a
curtain. The molten fibers may be quenched with air from an air
blower located adjacent the curtain of fibers and the fibers may
then be fed through a second pneumatic fiber draw unit or aspirator
such as the above-mentioned draw unit disclosed in U.S. Pat. No.
3,802,817 to Matsuki et al. The second, inelastic spunbond fibers
may then exit the fiber draw unit to be deposited on top of the
first elastic spunbond fibers, which are on the endless foraminous
forming surface. As mentioned above with respect to spunbond bank
1/elastic fibers, a vacuum apparatus may also be positioned below
the foraminous forming surface under spunbond bank 2, to facilitate
the proper placement of the inelastic fibers. The rate of extrusion
of the second, inelastic spunbond fibers, combined with the speed
of the foraminous forming surface, may desirably make the second
(inelastic) spunbond layer have a basis weight of about 26 grams
per square meter, such that the entire laminate composite material
has a basis weight of about 40 grams per square meter, and the
laminate composite material therefore contains about 65 weight
percent of the loop-forming fibers and about 35 weight percent of
the elastic layer.
[0067] After the two layers of spunbond (elastic from the first
spunbond bank, inelastic from the second spunbond bank) have been
formed into a laminate construction (that is, the two layers as
formed are already in a face-to-face relation), the two layers may
be bonded together by a suitable thermal calendering method, such
as by use of the HDD pattern mentioned above. After bonding, the
laminate composite material is stretched in the cross machine
direction by passing the laminate through a pair of nipped grooved
rollers. As mentioned above, the grooved roller nip may be formed
between spaced circumferential peaks and grooves cut into the
surfaces of each matching roller. Then, the grooved rollers may be
brought together with the peaks of one roller fitting into the
grooves of the other roller, and vice versa, to form a "nip",
although in this example there is no compressive contact between
the top of a peak on one roller and the bottom or nadir of a groove
on the other roller. The matching or fitting peaks and grooves may
desirably be constructed such that the pitch (peak-to-peak
distance) is about 4 millimeters. The laminate material will
experience a cross machine direction tensioning force or biasing
force as it travels through the grooved roller nip and will be
stretched or extended along its cross machine direction or
transverse axis. This transverse or cross machine direction
stretching of the laminate composite causes the spaced-apart
locations of the bonds which are primarily aligned along the cross
machine direction to become farther apart. Because the spaced-apart
locations of these bonds anchor the loop-forming inelastic spunbond
fibers, those inelastic spunbond fibers and/or portions of the
inelastic spunbond fibers traveling a generally cross machine
direction path from bond location to bond location are thereby
elongated past their deformation limit, causing them to become
permanently elongated. Then, after the laminate composite exits the
grooved rolling nip, it retracts under the power of the elastic
spunbond layer toward its original cross machine direction width or
dimension. Those portions of the loop-forming inelastic spunbond
fibers which have been permanently elongated between the
spaced-apart bond locations will have additional length available
to form arcs or loop elements.
[0068] The composite loop materials disclosed herein are highly
suitable for use in medical care products, protective wear
garments, personal care products and other products or applications
utilizing hook and loop attachment or fastening systems. Examples
of such products include, but are not limited to, medical and
health care products such as surgical drapes, gowns and bandages,
protective workwear garments such as coveralls and lab coats, and
infant, child and adult personal care absorbent products such as
diapers, training pants, incontinence garments and pads, sanitary
napkins, wipes and the like. The composite loop materials provide
the benefits of ease of storage and transport prior to conversion
into a fastener, potentially improved loop element loft after
conversion into a fastener, and have enhanced comfort qualities
such as superior material drape and flexibility properties, as well
as providing a loop material capable of elastic extensibility.
[0069] 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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