U.S. patent application number 10/736261 was filed with the patent office on 2005-06-16 for nonwoven webs manufactured from additive-loaded multicomponent filaments.
This patent application is currently assigned to Nordson Corporation. Invention is credited to Allen, Martin A., Crane, Patrick L..
Application Number | 20050130539 10/736261 |
Document ID | / |
Family ID | 34653848 |
Filed Date | 2005-06-16 |
United States Patent
Application |
20050130539 |
Kind Code |
A1 |
Allen, Martin A. ; et
al. |
June 16, 2005 |
Nonwoven webs manufactured from additive-loaded multicomponent
filaments
Abstract
Multicomponent filaments for manufacturing a hydrophilic
nonwoven web in which each filament has a sheath and a core
enclosed within the sheath that includes a concentration of an
additive, such as a surfactant. Additive removed from an external
surface of the sheath is replaced by additive migrating outwardly
from the sheath. Additive migrating outwardly from the core into
the sheath, which initially either includes a smaller additive
concentration than the core or lacks additive, serves to replenish
additive transferred from the sheath to the external surface.
Inventors: |
Allen, Martin A.;
(Dawsonville, GA) ; Crane, Patrick L.;
(Dawsonville, GA) |
Correspondence
Address: |
WOOD, HERRON & EVANS, LLP (NORDSON)
2700 CAREW TOWER
441 VINE STREET
CINCINNATI
OH
45202
US
|
Assignee: |
Nordson Corporation
|
Family ID: |
34653848 |
Appl. No.: |
10/736261 |
Filed: |
December 15, 2003 |
Current U.S.
Class: |
442/364 ;
428/373; 428/374; 428/375; 428/397 |
Current CPC
Class: |
D01F 1/02 20130101; D01F
8/04 20130101; Y10T 428/2933 20150115; D01F 8/02 20130101; D01D
5/34 20130101; D04H 3/00 20130101; Y10T 428/2929 20150115; Y10T
442/641 20150401; Y10T 428/2931 20150115; D04H 1/00 20130101; Y10T
428/2973 20150115 |
Class at
Publication: |
442/364 ;
428/373; 428/374; 428/375; 428/397 |
International
Class: |
D04H 001/00 |
Claims
1. A nonwoven web comprising a plurality of multicomponent
filaments, each of the multicomponent filaments comprising: a
sheath region including a first melt-processable polymer; and a
core region encased within said sheath region, said core region
including a second melt-processable polymer and a first additive
distributed at a first concentration in said second
melt-processable polymer, said first additive migrating outwardly
from said core region into said sheath region.
2. The nonwoven web of claim 1 wherein said first melt-processable
polymer includes a second concentration of said first additive,
said second concentration being less than said first concentration
to produce a concentration gradient.
3. The nonwoven web of claim 2 wherein said first concentration of
said first additive ranges from about 5% by weight to about 10% by
weight and said second concentration of said first additive is less
than about 3% by weight.
4. The nonwoven web of claim 1 wherein said first melt-processable
polymer includes a second concentration of a second additive
differing in chemical composition from said first additive.
5. The nonwoven web of claim 1 wherein said first concentration of
said first additive ranges from about 5% by weight to about 10% by
weight.
6. The nonwoven web of claim 1 wherein said first additive is a
surfactant selected from the group consisting of an anionic
surfactant, a cationic surfactant, an amphoteric surfactant, and a
non-ionic surfactant.
7. The nonwoven web of claim 1 wherein said sheath region and said
core region are concentrically arranged.
8. The nonwoven web of claim 1 wherein said core region has an
eccentric arrangement with said sheath region.
9. The multicomponent filament of claim 1 further comprising a
plurality of core regions within said sheath region, at least one
of said core regions including said first additive.
10. The multicomponent filament of claim 1 wherein said sheath
region has an external surface and a portion of at least said first
additive is chemically active at said external surface, after
outward migration has occurred.
11. A method of manufacturing a nonwoven web, comprising: heating a
first thermoplastic polymer to a flowable state; heating a second
thermoplastic polymer to a flowable state; adding a first
concentration of a first additive to the first thermoplastic
polymer; combining the first and second thermoplastic polymers to
form a plurality of multicomponent filaments each having a sheath
region including the second thermoplastic polymer and a core region
including the first thermoplastic polymer and the first additive;
and collecting the plurality of multicomponent filaments to form a
nonwoven web.
12. The method of claim 11 further comprising: adding a second
concentration of the first additive to the sheath region, the
second concentration being smaller than the first
concentration.
13. The method of claim 11 further comprising: adding a second
concentration of a second additive to the sheath region.
Description
FIELD OF THE INVENTION
[0001] The invention relates generally to nonwoven webs and, more
particularly, to nonwoven webs of multicomponent filaments loaded
with surfactant and methods of manufacturing such nonwoven
webs.
BACKGROUND OF THE INVENTION
[0002] Nonwoven webs and their manufacture in meltspinning devices
have been the subject of extensive development resulting in a wide
variety of materials for numerous commercial applications. Nonwoven
webs consist of a sheet of overlapped or entangled filaments or
fibers of melt-processable thermoplastic polymers manufactured
using spunbond and meltblown processes. A spunbond process
generally involves extruding a curtain of semi-solid filaments of
one or more thermoplastic polymers from multiple rows of fine
orifices in a spinneret and attenuating or drawing the extruded
filaments with drag forces created by a high-velocity flow of
process air. Spunbond filaments are generally continuous and may
have average diameters in the range of about 10 to 20 microns. A
meltblown process generally involves pumping a thermoplastic
polymer from an extruder through a die to form a curtain of fibers
and directing a high pressure gas stream at the exit of a die to
attenuate the fibers while they are in their extensible molten
state. Meltblown fibers may be continuous or discontinuous and are
usually smaller than 10 microns in average diameter. The filaments
or fibers are deposited on a moving collector in a substantially
random manner thereby forming a continuous-length nonwoven web.
[0003] As many thermoplastic polymers are normally hydrophobic, the
thermoplastic filaments or fibers must be modified to produce a
nonwoven web that is water permeable or hydrophilic. One
modification technique involves mixing a surfactant with the
thermoplastic polymer before extrusion so that the fibers or
filaments are impregnated with surfactant upon extrusion. The
surfactant migrates or diffuses to the external surface of the
impregnated fibers or filaments in a process called blooming.
Surfactant migration may occur during and/or after filament
formation and may be coerced by heating. Alternatively, the
filaments or fibers may be surface-treated with a chemical agent by
a conventional post-deposition topical treatment. One type of
post-deposition surface treatment involves dipping the nonwoven web
in a treatment bath containing a surfactant. Another type of
post-deposition surface treatment involves coating or spraying the
nonwoven web with a treatment solution containing a surfactant.
[0004] Surfactant-treated nonwoven webs in an article are
susceptible to surfactant loss when exposed to stresses capable of
removing the surfactant. Surfactant may be transferred from the
external surface of a surfactant-treated nonwoven web to a
contacting hydrophobic material, such as when an article containing
the surfactant-treated nonwoven web is packaged and stored. As a
specific example, surfactant is transferred from top sheets in
hygienic articles to contacting hydrophobic surfaces of the
hygienic article and/or to the product packaging when compression
packaged and stored before use. As a result, the hygienic article
will not perform as expected when used or has a shortened shelf
life the top sheet gradually loses its ability to transfer liquids,
and. Elevated temperatures experienced during shipping and storage
may accelerate surfactant migration to contacting hydrophobic
surfaces rendering them hydrophilic with a concomitant loss of
barrier properties. The incremental conversion of hydrophobic
surfaces further reduces product shelf life.
[0005] Surfactant also tends to be removed from the
surfactant-treated nonwoven web by recurring exposure to an aqueous
medium. For example, washing cycles gradually diminish the
hydrophilicity of a surfactant-treated nonwoven web. As another
example, when used as a top sheet in a hygienic absorbent article,
a surfactant-treated nonwoven web loses its aqueous permeability
with accumulating exposures to soilings by aqueous body fluids.
[0006] It would be desirable, therefore, to provide a nonwoven web
treated with a chemical agent or additive, such as a surfactant,
that can better withstand stresses and adverse conditions such as
those discussed above.
SUMMARY
[0007] The invention provides a multicomponent filament having a
sheath region of a first melt-processable polymer and a core region
of a second melt-processable polymer encased within the sheath
region. The core region includes an additive distributed with a
first concentration that, over time and with the occurrence of
stresses, migrates outwardly from the core region to the sheath
region due to the presence of a concentration gradient decreasing
in a radially outward direction. The first melt-processible polymer
of the sheath region operates to impede the radial migration of
additive from the core region to the filament's external
surface.
[0008] In certain embodiments of the invention, the sheath region
may initially contain a concentration of the additive that is
smaller than the first concentration of the additive in the core
region. Alternatively, the additive may be absent from the sheath
region when the filaments are formed. In other embodiments of the
invention, the sheath region may contain a second concentration of
an additive that differs in chemical composition from the additive
in the core region, where the additives produce the same web
characteristic. The additive(s) may be a concentration gradient of
surfactant that produces a hydrophilic web or other non-surfactant
additives, such as colorants, anti-static agents, lubricants, flame
retardants, antibacterial agents, softeners, ultraviolet absorbers,
and polymer stabilizers in which the non-surfactant additive
migrates from the core region to the sheath region and external
filament surface.
[0009] In accordance with the principles of the invention, a
nonwoven web is manufactured by heating two thermoplastic polymers
to a flowable state and adding a concentration of an additive, such
as a surfactant, to at least one of the two thermoplastic polymers.
The thermoplastic polymers are combined to form multicomponent
filaments each having a core region of the additive-containing
thermoplastic polymer and a sheath region of the other
thermoplastic polymer, which may also include a concentration of an
additive. The multicomponent filaments are collected to form the
nonwoven web. If the additive is a surfactant, the period over
which the non-woven web exhibits effective hydrophilicity may be
extended as the sheath region impedes the radial migration of
additive from the core region to the filament's external
surface.
[0010] The nonwoven web of the invention may be used in diverse
commercial product applications including, but not limited to,
hygienic articles such as diapers, adult incontinence products, and
feminine hygiene products. Nonwoven webs loaded with surfactant in
accordance with the principles of the invention may be used as a
top sheet for an absorbent medium in a hygienic article. Articles
formed from nonwoven webs of such surfactant-loaded filaments will
demonstrate a lengthened shelf life and an improved performance
when subject to successive wettings by liquids. Additionally, high
fiber basis weight nonwoven webs require an internal surfactant or
bloom additive to insure hydrophilicity without the need to fully
wet the material with a conventional topical treatment. Such
topical treatments are disadvantageous as these relatively-thick
nonwoven webs must be dried throughout their full thickness, which
is time consuming and adds needless cost to the production of a
hydrophilic nonwoven web. In accordance with the invention, the
surfactant is not applied topically as a surface treatment and, as
a result, the nonwoven web does not have to be dried.
[0011] These and other objects and advantages of the present
invention shall become more apparent from the accompanying drawings
and description thereof.
BRIEF DESCRIPTION OF THE FIGURES
[0012] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention and, together with a general description of the
invention given above, and the detailed description given below,
serve to explain the principles of the invention.
[0013] FIG. 1 is a diagrammatic view of an apparatus for forming a
nonwoven web in accordance with the principles of the
invention;
[0014] FIG. 2 is a multicomponent filament in accordance with the
principles of the invention;
[0015] FIG. 3 is an axial cross-sectional view of the
multicomponent filament of FIG. 2;
[0016] FIGS. 4-6 are end views of multicomponent filaments in
accordance with alternative embodiments of the invention; and
[0017] FIG. 7 is a perspective view of a hygienic article in
accordance with the principles of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] The invention is directed to nonwoven webs having a
lengthened property, such as hydrophilicity, formed from
multicomponent filaments including a sheath and a core embedded in
the sheath, in which the core has a concentration of an additive,
such as surfactant, that serves as a reservoir for replenishing
additive depleted from the sheath. Although the invention will be
described herein as being manufactured by an exemplary meltspinning
system, it should be understood that modifications to the exemplary
system described herein could be made so as to conform any portion
or the entire system to produce any type of airlaid nonwoven web or
a collection of unbonded filaments or fibers without departing from
the intended spirit and scope of the invention.
[0019] With reference to FIG. 1, a spunbonding apparatus 10 is
equipped with a pair of extruders 12, 14 that each convert a solid
thermoplastic polymer into a molten state and provide the molten
thermoplastic polymers under pressure to a corresponding set of
gear pumps 16,18. Extruder 12 is provided initially with a solid
mass of Polymer A from a bulk source 20, and extruder 14 is
provided initially with a solid mass of Polymer B from a bulk
source 22, which are replenished from bulk sources 20, 22 as
consumed during the melt spinning process. The gear pumps 16, 18
pump metered amounts of each thermoplastic polymer to an extrusion
die or spinneret 24, which has a spin pack that combines the
thermoplastic polymers and discharges a curtain of multicomponent
filaments 26 constituted collectively by the two thermoplastic
polymers. For ease of reference, one thermoplastic polymer provided
to spinneret 24 will be referred to as Polymer A, while the second
thermoplastic polymer provided to spinneret 24 will be referred to
as Polymer B. As will be understood in accordance with the
principles of the invention, other embodiments may utilize more
than two thermoplastic polymers. An exemplary multiple-component
spin pack for a spinneret 24 is disclosed in U.S. Pat. No.
5,162,074, which is hereby incorporated by reference herein in its
entirety.
[0020] The descending airborne curtain of multicomponent filaments
26 are quenched with cross-flow cooling air, as represented by
arrows 28, from a quench blower (not shown) to accelerate
solidification and drawn through a filament-drawing device 30. The
filament-drawing device 30 applies a tangential high velocity flow
of process air, as represented by arrows 31, in a direction
substantially parallel to the length of the multicomponent
filaments 26. Because the multicomponent filaments 26 are
extensible, the drag force of the spunbonding process pneumatically
attenuates and molecularly orients the multicomponent filaments 26.
The multicomponent filaments 26 discharged from the
filament-drawing device 30 are deposited in a substantially random
manner as a nonwoven web 32 on a horizontally and linearly moving
perforated collector 34. The collector 34 moves in a machine
direction, represented by the arrow labeled MD, that represents the
length of the nonwoven web 32 in the direction in which it is
produced. The collector 34 also spans the width of the curtain of
multicomponent filaments 26 in a cross-machine direction
perpendicular to the machine direction and into and out of the
plane of the page of FIG. 1.
[0021] Additional spunbonding apparatus, not shown but similar to
spunbonding apparatus 10, and meltblowing apparatus (not shown) may
be provided downstream of spunbonding apparatus 10 for depositing
one or more spunbond and/or meltblown nonwoven webs of either
monocomponent or multicomponent filaments on nonwoven web 32. An
example of such a multilayer laminate in which some of the
individual layers are spunbond and some meltblown is a
spunbond/meltblown/spunbond (SMS) laminate made by sequentially
depositing onto a moving forming belt first a spunbond fabric
layer, then a meltblown fabric layer and last another spunbond
layer.
[0022] With continued reference to FIG. 1, a surfactant from a
surfactant source 36 is added along with the mass of Polymer B from
bulk source 22 to the hopper of extruder 14. A mass or volume of
the surfactant is blended, preferably homogenously, with Polymer B
to create a mixture that is pumped by gear pump 18 from the
extruder 14 to the spinneret 24. The surfactant may be any suitable
chemical agent that increases the hydrophilicity of the
multicomponent filaments 26 so that nonwoven web 32 is wettable by
and has the strong ability to absorb an aqueous medium containing
water or another liquid. A mass or volume of a surfactant from a
different surfactant source 38 may be mixed with the mass of
Polymer A from bulk source 20 added to the hopper of extruder 12
and pumped by gear pump 18 from extruder 12 to spinneret 24. In
this manner and consistent with the principles of the invention,
each of the thermoplastic polymers provided to the spinneret 24 may
include a surfactant concentration.
[0023] The surfactant may be blended with the thermoplastic polymer
in a dry form, such as powder or pellets, using conventional
mechanical mixing techniques before being placed into the hopper of
either extruder 12, 14. Mechanical mixing techniques using devices
for homogenizing an admixture of powders and pellets, such as
V-blenders or double cone blenders, are familiar to persons of
ordinary skill.
[0024] The melt-processable thermoplastic polymer or polymers used
to fabricate the multicomponent filaments 26 may be any of the
commercially available spunbond grades of a wide range of
thermoplastic polymer resins, copolymers, and blends of
thermoplastic polymer resins, including without limitation
polyolefins such as polyethylene and polypropylene, polyesters such
as polyethylene terephthalate, polybutylene, polyamides, nylons,
polyvinyl acetate, polyvinyl chloride, polyvinyl alcohol, cellulose
acetate, and blends and copolymers thereof. The invention
contemplates that each of the thermoplastic polymers (Polymers A
and B) constituting the multicomponent filaments 26 may be
identical in base composition and differ only in the concentration
of the added surfactant. For example, the core may be formed from
polypropylene containing a concentration of surfactant and the
sheath may be formed from polypropylene having identical material
characteristics and a lower concentration of surfactant. Most of
these thermoplastic polymer resins are hydrophobic and, therefore,
are rendered hydrophilic (wettable) by the presence of the
surfactant at the external surface. The surfactant may also be
added to normally hydrophilic thermoplastic resins for enhancing
their wettability.
[0025] Typically, the surfactants supplied by the surfactant
sources 36, 38 may be identical, although the invention is not so
limited. Each surfactant may be classified as a fast wetting
surfactant that causes liquids to permeate the nonwoven web 32 at a
fast rate or, alternatively, as a low wetting surfactant which
causes liquids to permeate the nonwoven web 32 at a relatively slow
rate. Each surfactant must be miscible with the associated
thermoplastic polymer so as to be capable of forming homogeneous
mixtures. Each surfactant may be anionic, cationic, amphoteric or
non-ionic, in which non-ionic surfactants are believed to be less
irritating to human skin tissue. Preferred non-ionic surfactants
include, but are not limited to, sorbitan esters, ethoxylated
sorbitan esters, silicone copolymers, fluorochemical-based
surfactants, alcohol ethoxylates, alkylphenol ethoxylates,
carboxylic acid esters, glycerol esters, polyoxyethylene esters of
fatty acids, polyoxyethylene esters of aliphatic carboxylic acids
related to abietic acid, anhydrosorbitol esters, ethoxylated
anhydrosorbitol esters, ethoxylated natural fats, oils, and waxes,
glycol esters of fatty acids, carboxylic amides, diethanolamine
condensates, monoalkanolamine condensates, polyoxyethylene fatty
acid amides, and polyalkyleneoxide block copolymers.
[0026] With reference to FIGS. 2 and 3, the thermoplastic polymers
constituting each multicomponent filament 26 are arranged a
sheath/core configuration in which one thermoplastic polymer
(Polymer B) is disposed in a core 40 surrounded by a sheath 42 of
the other thermoplastic polymer (Polymer A). The core 40 and sheath
42 each extend continuously along the length of each multicomponent
filament 26 and are coextensive along an annular or cylindrical
interface 43. The core 40 and sheath 42 may be arranged coaxially
in a concentric configuration with the sheath 42 radially outward
of the core 40.
[0027] In accordance with the principles of the invention and with
reference to FIGS. 2 and 3, a surfactant 44a is present in the core
40 in a greater concentration than a surfactant 44b in sheath 42.
Preferably, the concentration of surfactant 44a in Polymer B
constituting the core 40 is about 5% by weight to about 10% by
weight, and the concentration of surfactant 44b in Polymer A
constituting the sheath 42 ranges up to about 3% by weight,
typically about 1% by weight to about 3% by weight. In certain
specific embodiments of the invention, Polymer A may be the same
thermoplastic polymer as Polymer B and the chemical composition of
the surfactant in each of the polymers may be identical.
[0028] In accordance with the principles of the invention, the
surfactant 44a initially present in the core 40 will tend to
diffuse or migrate from the region of high concentration across the
interface 43 to the region of low concentration in the sheath 42,
as represented by the arrows labeled with reference numeral 41.
Molecules of surfactant 44b initially present at an external
surface 48 of the sheath 42 produce hydrophilicity or wettability.
Surfactant molecules at the external surface 48 of the sheath 42
are lost, as represented by the arrows labeled with reference
numeral 47, by contact with another hydrophobic surface or by
repeated wetting with liquid. Amounts of surfactant 44b and
surfactant 44a present in sheath 42 migrate to the external surface
48 as represented by the arrows labeled with reference numeral 49.
The radially outward migration reduces the surfactant concentration
in the sheath 42. As the surfactant concentration drops in the
sheath 42, surfactant 44a migrating from the core 40 into the
sheath 42 replenishes the depleted concentration of surfactant 44a
and surfactant 44b. As a result, the nonwoven web 32 (FIG. 1) will
remain hydrophilic for a, longer period after manufacture when
packaged and with repeated exposure to liquids. The surfactant 44a
in the core 40 serves as a reservoir for surfactant transfer, as
required or otherwise on a time-delayed basis due to the difference
in concentration, across the annular interface 43 to the sheath 42
and subsequently to the external surface 48.
[0029] With reference to FIG. 4 and in accordance with an
alternative embodiment of the invention, sheath 42 may contain no
surfactant 44b at least at the moment of discharge from the
spinneret 24 (FIG. 1). Surfactant 44a migrates from the core 40
into the sheath 42 and subsequently to the external surface 48
makes the multicomponent filament 26 hydrophilic. The initial
migration occurs subsequent to discharge of the multicomponent
filament 26 from the spinneret 24, such as during web processing to
complete web formation, during web processing to form an article,
and while the web and/or article are stored before the time of
use.
[0030] The invention contemplates that the chemical composition of
the surfactant 44a may differ from the chemical composition of the
surfactant 44b. In this alternative embodiment, surfactant 44a is
not present in the sheath 42 (i.e., has a zero concentration) at
least at the moment of discharge from the spinneret 24 (FIG. 1).
The hydrophilicity of the multicomponent filament 26 is supplied
initially by molecules of surfactant 44b present at the external
surface 48. Due to the concentration disparity, surfactant 44a
migrates radially outwardly from the core 40 into the sheath 42 and
amounts of surfactant 44a eventually reach the external surface 48.
Eventually, surfactant 44a is lost from the external surface 48
along with with surfactant 44b. Amounts of surfactant 44b lost from
the external surface 48 are replenished by the outward migration of
stored amounts of surfactant 44b from the sheath 42. Surfactant 44a
lost from the external surface 48 is replenished by amounts of
surfactant 44a migrating from the underlying sheath 42. The store
of surfactant 44a in the sheath 42 is replenished by migration of
amounts of surfactant 44a from core 40. The migration and loss of
surfactant 44a may be independent of the migration and loss of
surfactant 44b or the migration and loss of surfactants 44a,b may
be interrelated.
[0031] By adjusting the relative concentrations of the surfactants
44a,b in the two thermoplastic polymers (Polymers A and B), the
shelf life of the surfactant-treated nonwoven web 32 may be
significantly extended as the hydrophilic nature of the external
surface 48 is lengthened by the net transport or migration of
surfactant 44a from the relatively-high surfactant concentration
present in the core 40 into the sheath 42 and to the external
surface 48. In addition to the gradient in surfactant
concentration, the migration rate from the core 40 to the sheath 42
and from the sheath 42 to the external surface 48 is also
influenced by other factors, including the sheath thickness, the
chemical properties of the surfactant(s), the environmental
temperature, extrusion conditions, and the characteristics of the
thermoplastic polymer(s). In particular, the diffusion of a
surfactant in a thermoplastic polymer depends upon the affinity
between the surfactant and the thermoplastic polymer. The affinity
varies among the different possible combinations of thermoplastic
polymer and surfactant, which will influence transfer of surfactant
44a from the core 40 to the sheath 42 and surfactant 44a and
surfactant 44b from the sheath 42 to the external surface.
Accordingly, the affinity between the selected surfactant and the
thermoplastic material forming the core 40 should permit surfactant
transfer from the core 40 to the sheath 42. Likewise, the affinity
between the thermoplastic polymer forming sheath 42 and surfactant
44a will influence migration of surfactant 44a from the sheath 42
to the external surface 48. Similarly, the affinity between the
thermoplastic polymer forming sheath 42 and surfactant 44b will
influence migration of surfactant 44b from the sheath 42 to the
external surface 48.
[0032] The invention contemplates that one or more non-surfactant
additives, such as compatibilizing agents, colorants or pigments,
optical brighteners, ultraviolet light stabilizers, antistatic
agents, abrasion resistance enhancing agents, nucleating agents,
fillers and/or other additives and processing aids, may be added in
a concentration gradient to one or more of the polymers
constituting multicomponent filaments 26. In these various
alternative embodiments, the non-surfactant additive is added to
filaments 26 with a greater concentration in the core 40 than in
the sheath 42, as described herein with specific regard to
surfactant. The subsequent additive migration of the non-surfactant
additive(s) radially outward from the core 40 lengthens or sustains
the manifestation of a corresponding property(ies) or a
characteristic(s) of the filaments 26. The invention contemplates
that one or more of the non-surfactant additives may be distributed
in multicomponent filaments 26 in a manner similar to the
concentration gradient of surfactant, as described herein, either
jointly with the surfactant or in the absence of surfactant.
[0033] With reference to FIG. 5 and in accordance with an
alternative embodiment of the invention, multicomponent filament 26
may have a core 50 that is offset or non-concentric within a sheath
52 so as to have an eccentric or asymmetrical configuration. With
reference to FIG. 6 and in accordance with another alterative
embodiment of the invention, the thermoplastic polymers of
multicomponent filament 26 may have an "islands-in-the-sea"
configuration in which multiple core regions 60 of Polymer B reside
inside a sheath 62 of Polymer A. Although the components of
filament 26 are depicted in FIGS. 2-6 as having round
cross-sections, the invention contemplates that the nonwoven web 32
might be formed from filaments (not shown) of different
cross-sectional shapes.
[0034] With reference to FIG. 7, a disposable hygienic article 70
generally includes a top sheet 72, a back sheet 74, a fluid storage
layer 76 separating the top sheet 72 from the back sheet 74, and a
fluid acquisition and transfer layer 78 separating the fluid
storage layer 76 from the top sheet 72. The top sheet 72, which
faces and contacts the wearer, is fluid previous so that aqueous
body fluids may readily penetrate through its thickness to the
fluid storage layer 76. Fluid acquisition and transfer layer 78
distributes aqueous body fluids transferred from top sheet 72 to
the underlying fluid storage layer 76, which includes an absorbent
material capable of absorbing large quantities of aqueous body
fluids and retaining the absorbed body fluids under moderate
applied pressures. The back sheet 74 prevents aqueous body fluids
absorbed in the fluid storage layer 76 from wetting items in the
surrounding environment, such as pants, pajamas and undergarments.
Loop-type fasteners 80 on the back sheet 74 cooperate with
hook-type fasteners 82 on corresponding attachment tabs 84
extending laterally of the back sheet 74 cooperate for attaching
the hygienic article 70 to a wearer.
[0035] In accordance with the principles of the invention, all or
part of the components of hygienic article 70, including but not
limited to the top sheet 72 and the back sheet 74, may incorporate
portions of a nonwoven web formed from the multicomponent filaments
of the invention. The invention contemplates that various other
consumer and commercial articles may incorporate a portion of a
nonwoven web formed from the multicomponent filaments of the
invention.
[0036] While the present invention has been illustrated by a
description of various embodiments and while these embodiments have
been described in considerable detail, it is not the intention of
the applicants to restrict or in any way limit the scope of the
appended claims to such detail. Additional advantages and
modifications will readily appear to those skilled in the art. For
example, the multicomponent filaments from which the nonwoven web
of this invention is made may be produced by meltblown processes as
well known to persons of ordinary skill in the art. The invention
in its broader aspects is therefore not limited to the specific
details, representative apparatus and methods, and illustrative
examples shown and described. Accordingly, departures may be made
from such details without departing from the spirit or scope of
applicants' general inventive concept. The scope of the invention
itself should only be defined by the appended claims, wherein we
claim:
* * * * *