U.S. patent application number 10/437170 was filed with the patent office on 2003-10-30 for spunbond nonwoven fabrics from reclaimed polymer.
This patent application is currently assigned to BBA Nonwoven Simpsonville, Inc.. Invention is credited to Alexander, Robert C., Gillespie, Jay Darrell, Kong, Daniel Deying.
Application Number | 20030203698 10/437170 |
Document ID | / |
Family ID | 25445278 |
Filed Date | 2003-10-30 |
United States Patent
Application |
20030203698 |
Kind Code |
A1 |
Gillespie, Jay Darrell ; et
al. |
October 30, 2003 |
Spunbond nonwoven fabrics from reclaimed polymer
Abstract
A spunbond nonwoven fabric useful as a topsheet is produced from
polypropylene filaments including a high level of reclaimed
polypropylene, while maintaining a product quality, including
superior formation, comparable to that obtained when using 100
percent virgin polymer. The spunbond nonwoven fabric is made with
multicomponent filaments having at least two different polymer
components occupying different areas within the filament cross
section, and wherein one of the polymer components comprises
reclaimed polypropylene recovered from previously spun
polypropylene fiber or webs comprised of previously spun
polypropylene fiber. In a specific embodiment, the filaments are
sheath-core bicomponent filaments and the reclaimed polypropylene
is present in the core component. The core of the bicomponent
filament can be comprised of up to 100% reclaimed
polypropylene.
Inventors: |
Gillespie, Jay Darrell;
(Simpsonville, SC) ; Kong, Daniel Deying;
(Vancouver, WA) ; Alexander, Robert C.; (Brush
Prairie, WA) |
Correspondence
Address: |
ALSTON & BIRD LLP
BANK OF AMERICA PLAZA
101 SOUTH TRYON STREET, SUITE 4000
CHARLOTTE
NC
28280-4000
US
|
Assignee: |
BBA Nonwoven Simpsonville,
Inc.
|
Family ID: |
25445278 |
Appl. No.: |
10/437170 |
Filed: |
May 13, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10437170 |
May 13, 2003 |
|
|
|
09921323 |
Aug 2, 2001 |
|
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Current U.S.
Class: |
442/401 ;
264/171.11; 264/172.11; 442/327; 442/361; 442/364; 442/403 |
Current CPC
Class: |
Y10T 442/697 20150401;
Y10T 442/637 20150401; Y02P 70/62 20151101; Y10T 442/638 20150401;
Y10T 442/60 20150401; Y10T 442/681 20150401; D01F 8/06 20130101;
Y10T 442/684 20150401; D01F 13/04 20130101; D04H 3/16 20130101;
Y10T 442/641 20150401 |
Class at
Publication: |
442/401 ;
442/327; 442/361; 442/364; 442/403; 264/171.11; 264/172.11 |
International
Class: |
D04H 003/00; D04H
005/00; D04H 013/00; D04H 003/16 |
Claims
That which is claimed:
1. A spunbond nonwoven fabric which includes substantially
continuous multicomponent filaments having at least two different
polymer components occupying different areas within the filament
cross section, and wherein one of the polymer components comprises
reclaimed polypropylene recovered from previously spun
polypropylene fiber or webs comprised of previously spun
polypropylene fiber, the fabric exhibiting superior formation as
indicated by a coefficient of variability for air permeability of
less than about 7%.
2. A fabric according to claim 1, wherein the reclaimed
polypropylene comprises at least 25 percent by weight of the
filament.
3. A fabric according to claim 1, wherein said one polymer
component is formed entirely of said reclaimed polypropylene.
4. A fabric according to claim 1, wherein at least one of the other
polymer components has a melt flow rate at least 5 units lower than
that of the reclaimed polypropylene.
5. A fabric according to claim 1, wherein at least one of the other
components is formed entirely of virgin polypropylene.
6. A fabric according to claim 1, wherein the multicomponent
filaments are sheath/core bicomponent filaments, and the reclaimed
polypropylene is present in the core component and the virgin
polypropylene is present in the sheath component.
7. A spunbond nonwoven fabric which includes substantially
continuous bicomponent filaments, the bicomponent filaments having
two different polypropylene polymer components within the filament
cross section arranged to form a core component and a sheath
component surrounding the core component, the sheath component
including virgin polypropylene, the core component including
reclaimed polypropylene recovered from previously spun
polypropylene fiber or webs comprised of previously spun
polypropylene fiber and having a melt flow rate at least 5 units
greater than that of the sheath component, and the fabric
exhibiting superior formation as indicated by a coefficient of
variability for air permeability of less than about 7%.
8. A fabric according to claim 7, wherein at least 25 percent by
weight of the bicomponent filament is comprised of said reclaimed
polypropylene.
9. A fabric according to claim 7, wherein at least 50 percent by
weight of the bicomponent filament is comprised of said reclaimed
polypropylene.
10. A fabric according to claim 7, wherein the core component is
formed from 100% reclaimed polypropylene recovered from previously
spun polypropylene fiber or webs comprised of previously spun
polypropylene fiber.
11. A fabric according to claim 7, wherein the sheath component is
formed from a blend of virgin polypropylene with reclaimed
polypropylene recovered from previously spun polypropylene fiber or
webs comprised of previously spun polypropylene fiber.
12. A fabric according to claim 7, which additionally includes
substantially continuous monocomponent filaments.
13. A fabric according to claim 7, wherein said monocomponent
filaments include filaments formed entirely of virgin
polypropylene.
14. An adult incontinence garment comprising a fabric according to
claim 7.
15. A baby diaper comprising a fabric according to claim 7.
16. A spunbond nonwoven fabric according to claim 1 produced by a
process comprising the steps of: separately melting two or more
polymeric components, at least one polymeric component including
reclaimed polypropylene recovered from previously spun
polypropylene fiber or webs comprised of previously spun
polypropylene fiber; separately directing the two or more molten
polymer components through a distribution plate configured so that
the separate molten polymer components combine at a multiplicity of
spinnerette orifices to form filaments containing the two or more
polymer components; extruding the multicomponent filaments from the
spinnerette orifices into a quench chamber; directing quench air
from a first independently controllable blower into the quench
chamber and into contact with the filaments to cool and solidify
the filaments; directing the filaments and the quench air into and
through a filament attenuator and pneumatically attenuating and
stretching the filaments; directing the filaments from the
attenuator into and through a filament depositing unit; depositing
the filaments from the depositing unit randomly upon a moving
continuous air-permeable belt to form a nonwoven web of
substantially continuous filaments; applying suction from a second
independently controllable blower beneath the air-permeable belt so
as to draw air through the depositing unit and through the
air-permeable belt; and directing the web through a bonder and
bonding the filaments to convert the web into a coherent nonwoven
fabric.
17. A spunbond nonwoven fabric according to claim 1 produced by a
process comprising the steps of: separately melting a first
polymeric component comprising virgin polypropylene and a second
polymeric component comprising reclaimed polypropylene recovered
from previously spun polypropylene fiber or webs comprised of
previously spun polypropylene fiber; separately directing the first
and second molten polymer components through a distribution plate
configured so that the separate molten polymer components combine
at a multiplicity of spinnerette orifices to form bicomponent
filaments containing a core of the second polymer component and a
surrounding sheath of the first polymer component; extruding the
bicomponent filaments from the spinnerette orifices into a quench
chamber; directing quench air from a first independently
controllable blower into the quench chamber and into contact with
the filaments to cool and solidify the filaments; directing the
filaments and the quench air into and through a filament attenuator
and pneumatically attenuating and stretching the filaments;
directing the filaments from the attenuator into and through a
filament depositing unit; depositing the filaments from the
depositing unit randomly upon a moving continuous air-permeable
belt to form a nonwoven web of substantially continuous filaments;
applying suction from a second independently controllable blower
beneath the air-permeable belt so as to draw air through the
depositing unit and through the air-permeable belt; and directing
the web through a bonder and bonding the filaments to convert the
web into a coherent nonwoven fabric.
18. A spunbond nonwoven fabric produced by a process comprising the
steps of: separately melting two or more polymeric components, at
least one polymeric component including reclaimed polypropylene
recovered from previously spun polypropylene fiber or webs
comprised of previously spun polypropylene fiber; separately
directing the two or more molten polymer components through a
distribution plate configured so that the separate molten polymer
components combine at a multiplicity of spinnerette orifices to
form filaments containing the two or more polymer components;
extruding the multicomponent filaments from the spinnerette
orifices into a quench chamber; directing quench air from a first
independently controllable blower into the quench chamber and into
contact with the filaments to cool and solidify the filaments;
directing the filaments and the quench air into and through a
filament attenuator and pneumatically attenuating and stretching
the filaments; directing the filaments from the attenuator into and
through a filament depositing unit; depositing the filaments from
the depositing unit randomly upon a moving continuous air-permeable
belt to form a nonwoven web of substantially continuous filaments;
applying suction from a second independently controllable blower
beneath the air-permeable belt so as to draw air through the
depositing unit and through the air-permeable belt; and directing
the web through a bonder and bonding the filaments to convert the
web into a coherent nonwoven fabric.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a divisional of Application Ser. No. 09/921,323,
filed Aug. 2, 2001.
FIELD OF THE INVENTION
[0002] This invention relates to improvements in the manufacture of
spunbonded nonwoven fabrics, and more particularly to the use of
recycled polymer in the manufacture of spunbond nonwoven
fabrics.
BACKGROUND OF THE INVENTION
[0003] A major goal in the nonwovens industry is to reduce cost. At
the same time there is growing concern in society about degradation
of the natural environment. Disposal of solid waste is a major
contribution to this growing environmental concern.
[0004] During the production of polypropylene nonwoven fabrics,
significant waste polypropylene is generated during startup of the
process, from trimming left when the nonwoven web is slit to
customer's specification, and from rolls that may have been
slightly damaged or otherwise out of specifications. This
polypropylene waste, coming from previously spun polypropylene
fiber and webs comprised of previously spun polypropylene fiber,
can be safely sent to solid waste landfills. However since this is
very clean polypropylene it can also be remelted for recycling back
through the spunbonding process. Recycle thus meets two goals,
saving of the cost of wasted polypropylene and reduced solid waste
to downgrade the natural environment.
[0005] Recycling such polypropylene is well known in the nonwoven
industry. However once the polypropylene goes through the spinning
process it is partly degraded by oxidation so that the polymer
molecular weight is reduced. This effect can be partly mitigated by
the optimized addition of antioxidants. However some degradation is
always seen. Such degradation can be seen by measuring the melt
flow rate of the processed polymer. The melt flow rate will
increase. The melt flow of polypropylene can be measured as taught
in ASTM D-1238, at conditions of 230.degree. C. and 2.14 kg.
[0006] Because of the reduced molecular weight, the recycled
polypropylene is not generally suitable for being used by itself in
the manufacture of spunbond nonwoven fabrics. Therefore, it is
typically blended with virgin polypropylene. However, the amount of
recycled previously spun polypropylene that can be recycled is
limited. If too much recycled polypropylene is blended with the
virgin resin, then an increase in the number of spinning breaks
(broken filaments) will be seen. These broken filaments will cause
quality defects in the finished spunbond nonwoven fabric or, in
severe cases, a complete disruption of the manufacturing process.
Second, the presence of too much recycled polypropylene can reduce
the measured tensile strength of the resulting spunbond nonwoven
fabric. For these reasons the amount of polypropylene recycled back
through the process is usually limited to less than about 20% of
the total polypropylene by weight.
SUMMARY OF THE INVENTION
[0007] The present invention makes it possible to use a high level
of reclaim, while maintaining a product quality, including superior
formation, comparable to that obtained when using 100 percent
virgin polymer.
[0008] According to the present invention, a spunbond nonwoven
fabric is made with multicomponent filaments having at least two
different polymer components occupying different areas within the
filament cross section, and wherein one of the polymer components
comprises reclaimed polypropylene recovered from previously spun
polypropylene fiber or webs comprised of previously spun
polypropylene fiber. In a specific embodiment, the filaments are
sheath-core bicomponent filaments and the reclaimed polypropylene
is present in the core component. The core of the bicomponent
filament can be comprised of up to 100% reclaimed
polypropylene.
[0009] For producing the spunbond nonwoven fabric, we have
developed a particular process which enables producing bicomponent
filaments with high reclaimed polypropylene content and at the high
speeds which are necessary for practical and economical commercial
production. The spunbond nonwoven fabrics have superior formation
and product quality.
[0010] According to the present invention, a process for producing
spunbond nonwoven fabrics is provided, comprising the steps of:
separately melting two or more polymeric components, at least one
polymeric component including reclaimed polypropylene recovered
from previously spun polypropylene fiber or webs comprised of
previously spun polypropylene fiber; separately directing the two
or more molten polymer components through a distribution plate
configured so that the separate molten polymer components combine
at a multiplicity of spinnerette orifices to form filaments
containing the two or more polymer components; extruding the
multicomponent filaments from the spinnerette orifices into a
quench chamber; directing quench air from a first independently
controllable blower into the quench chamber and into contact with
the filaments to cool and solidify the filaments; directing the
filaments and the quench air into and through a filament attenuator
and pneumatically attenuating and stretching the filaments;
directing the filaments from the attenuator into and through a
filament depositing unit; depositing the filaments from the
depositing unit randomly upon a moving continuous air-permeable
belt to form a nonwoven web of substantially continuous filaments;
applying suction from a second independently controllable blower
beneath the air-permeable belt so as to draw air through the
depositing unit and through the air-permeable belt; and directing
the web through a bonder and bonding the filaments to convert the
web into a coherent nonwoven fabric.
[0011] In a further, more specific, aspect, the present invention
provides a process for producing a spunbond nonwoven fabric,
comprising the steps of: reclaiming polypropylene from previously
spun polypropylene fiber or webs comprised of previously spun
polypropylene fiber; separately melting a first polymeric component
comprising virgin polypropylene and a second polymeric component
comprising the reclaimed polypropylene; separately directing the
first and second molten polymer components through a distribution
system configured so that the separate molten polymer components
combine at a multiplicity of spinnerette orifices to form
bicomponent filaments containing a core of the second polymer
component and a surrounding sheath of the first polymer component;
extruding the bicomponent filaments from the spinnerette orifices
into a quench chamber; directing quench air into the quench chamber
and into contact with the filaments to cool and solidify the
filaments; directing the filaments and the quench air into and
through a filament attenuator and pneumatically attenuating and
stretching the filaments; directing the filaments from the
attenuator into and through a filament depositing unit; depositing
the filaments from the depositing unit randomly upon a moving
continuous air-permeable belt to form a nonwoven web of
substantially continuous filaments; and directing the web through a
bonder and bonding the filaments to convert the web into a coherent
nonwoven fabric.
[0012] The present invention also provides a spunbond nonwoven
fabric produced by the above-described processes.
[0013] In a further aspect, the present invention is directed to a
spunbond nonwoven fabric which includes substantially continuous
multicomponent filaments having at least two different polymer
components occupying different areas within the filament cross
section, and wherein one of the polymer components comprises
reclaimed polypropylene recovered from previously spun
polypropylene fiber or webs comprised of previously spun
polypropylene fiber. The spunbond nonwoven fabric is suitable for
being used as components in hygiene applications, such as diapers
and incontinent garments. The nonwoven fabrics show superior
formation, as indicated by a coefficient of variation for air
permeability of less than about 7 percent.
[0014] In a further specific embodiment, the spunbond nonwoven
fabric includes substantially continuous sheath/core bicomponent
filaments, the sheath component comprising polypropylene, the core
component comprising reclaimed polypropylene having a melt flow
rate at least 5 units higher than the sheath component.
[0015] In a specific embodiment, the initial handling, melting, and
forwarding of the two or more polymer components is carried out in
respective individual extruders. The separate polymer components
are combined and extruded as multicomponent filaments with the use
of a spin beam equipped with spin packs having a unique
distribution plate arrangement available from Hills, Inc. and
described in U.S. Pat. Nos. 5,162,074; 5,344,297 and 5,466,410. The
extruded filaments are quenched, attenuated and deposited onto a
moving air-permeable conveyor belt using a system known as the
Reicofil III system, as described in U.S. Pat. No. 5,814,349. The
web of filaments which is formed on the conveyor belt may be
bonded, either in this form or in combination with additional
layers or components, by passing through a bonder. The bonder may
comprise a heated calender having a patterned calender roll which
forms discrete point bonds throughout the fabric. Alternatively,
the bonder may comprise a through-air bonder. The fabric is then
wound into roll form using a commercially available take-up
assembly
BRIEF DESCRIPTION OF THE DRAWING
[0016] The drawing FIGURE shows schematically an arrangement of
system components for producing a bicomponent spunbonded nonwoven
fabric in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention now will be described more fully
hereinafter with reference to the accompanying drawing, in which a
preferred embodiment of the invention is shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiment set forth herein; rather,
this embodiment is provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like numbers refer to like
elements throughout.
[0018] The drawing FIGURE schematically illustrates the system
components for carrying out the process of the present invention.
In the illustrated embodiment, the system includes two extruders
11, 12 adapted for receiving and processing two separate
fiber-forming polymer materials, typically received from the
manufacturer in the form of polymer chip or flake. The extruders
are equipped with inlet hoppers 13, 14 adapted for receiving a
supply of polymer material in granular or flake form. The extruders
include a heated extruder barrel in which is mounted an extruder
screw having convolutions or flights configured for conveying the
chip or flake polymer material through a series of heating zones
while the polymer material is heated to a molten state and mixed by
the extruder screw. Extruders of this type are commercially
available from various sources. Alternatively, one or both of the
extruders can be fed molten polymer from polypropylene obtained
directly from polypropylene filaments or webs. For example, the
extruder which is used for supplying polymer for the core component
of a sheath/core bicomponent filament (e.g. extruder 12 in the
drawing) can be equipped with an additional auxiliary feed extruder
(not shown) which directly receives polypropylene webs or filaments
and melts the webs or filaments in order to supply molten reclaimed
polypropylene polymer to the barrel of the main extruder (e.g.
extruder 12). The main extruder can be operated with 100 percent
reclaimed polypropylene from this auxiliary feed extruder, or the
reclaimed polypropylene can be blended with virgin polypropylene
resin supplied from hopper 14.
[0019] A spin beam assembly, generally indicated at 20, is
communicatively connected to the discharge end of each extruder for
receiving molten polymer material therefrom. The spin beam assembly
20 extends in the cross-machine direction of the apparatus and thus
defines the width of the nonwoven fabric to be manufactured. The
spin beam assembly is typically several meters in length. Mounted
to the spin beam assembly is one or more replaceable spin packs
designed to receive the molten polymer material from the two
extruders, to filter the polymer material, and then to direct the
polymer material through fine capillaries formed in a spinnerette
plate. The polymer is extruded from the capillary orifices under
pressure to form fine continuous filaments. It is important to the
present invention to provide a high density of spinnerette
orifices. Preferably the spinnerette should have a density of at
least 3000 orifices per meter of length of the spin beam, and more
desirably at least 4000 orifices per meter. Hole densities as high
as 6000 per meter are contemplated.
[0020] Each spin pack is assembled from a series of plates
sandwiched together. At the downstream end or bottom of the spin
pack is a spinnerette plate 22 having spinnerette orifices as
described above. At the upstream end or top is a top plate having
inlet ports for receiving the separate streams of molten polymer.
Beneath the top plate is a screen support plate for holding filter
screens that filter the molten polymer. Beneath the screen support
plate is a metering plate having flow distribution apertures formed
therein arranged for distributing the separate molten polymer
streams. Mounted beneath the metering plate and directly above the
spinnerette plate 22 is a distribution plate 24 which forms
channels for separately conveying the respective molten polymer
materials received from the flow distribution apertures in the
metering plate above. The channels in the distribution plate are
configured to act as pathways for the respective separate molten
polymer streams to direct the polymer streams to the appropriate
spinnerette inlet locations so that the separate molten polymer
components combine at the entrance end of the spinnerette orifice
to produce a desired geometric pattern within the filament cross
section. As the molten polymer material is extruded from the
spinnerette orifices, the separate polymer components occupy
distinct areas or zones of the filament cross section. For example,
the patterns can be sheath/core, side-by-side, segmented pie,
islands-in-the-sea, tipped profile, checkerboard, orange peel, etc.
The spinnerette orifices can be either of a round cross section or
of a variety of cross sections such as trilobal, quadralobal,
pentalobal, dog bone shaped, delta shaped, etc. for producing
filaments of various cross section.
[0021] The thin distributor plates 24 are easily manufactured,
especially by etching, which is less costly than traditional
machining methods. Because the plates are thin, they conduct heat
well and hold very low polymer volume, thereby reducing residence
time in the spin pack assembly significantly. This is especially
advantageous when extruding polymeric materials which differ
significantly in melting points, where the spin pack and spin beam
must be operated at temperatures above the melting point of the
higher melting polymer. The other (lower melting) polymer material
in the pack experiences these higher temperatures, but at a reduced
residence time, thus aiding in reducing degradation of the polymer
material. Spin packs using distributor plates of the type described
for producing bicomponent or multi-component fibers are
manufactured by Hills Inc. of W. Melborue Fla., and are described
in U.S. Pat. Nos. 5,162,074, 5,344,297 and 5,466,410, the
disclosures of which are incorporated herein by reference.
[0022] Upon leaving the spinnerette plate, the freshly extruded
molten filaments are directed downwardly through a quench chamber
30. Air from an independently controlled blower 31 is directed into
the quench chamber and into contact with the filaments in order to
cool and solidify the filaments. As the filaments continue to move
downwardly, they enter into a filament attenuator 32. As the
filaments and quench air pass through the attenuator, the cross
sectional configuration of the attenuator causes the quench air
from the quench chamber to be accelerated as it passes downwardly
through the attenuation chamber. The filaments, which are entrained
in the accelerating air, are also accelerated and the filaments are
thereby attenuated (stretched) as they pass through the attenuator.
The blower speed, attenuator channel gap and convergence geometry
are adjustable for process flexibility.
[0023] Mounted beneath the filament attenuator 32 is a
filament-depositing unit 34 which is designed to randomly
distribute the filaments as they are laid down upon an underlying
moving endless air-permeable belt 40 to form an unbonded web of
randomly arranged filaments. The filament-depositing unit 34
consists of a diffuser with diverging geometry and adjustable side
walls. Beneath the air-permeable belt 40 is a suction unit 42 which
draws air downwardly through the filament-depositing unit 34 and
assists in the lay-down of the filaments on the air-permeable belt
40. An air gap 36 is provided between the lower end of the
attenuator 32 and the upper end of the filament depositing unit 34
to admit ambient air into the depositing unit. This serves to
facilitate obtaining a consistent but random filament distribution
in the depositing unit so that the nonwoven fabric has good
uniformity in both the machine direction and the cross-machine
direction.
[0024] The quench chamber, filament attenuator and
filament-depositing unit are available commercially from
Reifenhauser GmbH & Company Machinenfabrik of Troisdorf,
Germany. This system is described more fully in U.S. Pat. No.
5,814,349, the disclosure of which is incorporated herein by
reference. This system is sold commercially by Reifenhauser as the
"Reicofil III" system.
[0025] The web of filaments on the continuous endless moving belt
may be subsequently directed through a bonder and bonded to form a
coherent nonwoven fabric. Bonding may be carried out by any of a
number known techniques such as by passing through the nip of a
pair of heated calender rolls 44 or a through-air bonder.
Alternatively, the web of filaments may be combined with one or
more additional components and bonded to form a composite nonwoven
fabric. Such additional components may include, for example, films,
meltblown webs, or additional webs of continuous filaments or
staple fibers.
[0026] The polymer components for multicomponent filaments are
selected in proportions and to have melting points, crystallization
properties, electrical properties, viscosities, and miscibilities
that will enable the multicomponent filament to be melt-spun and
will impart the desired properties to the nonwoven fabric. At least
one of the component is formed from reclaimed polypropylene
recovered from previously spun polypropylene fiber or webs
comprised of previously spun polypropylene fiber. The reclaimed
polypropylene will have been subjected to at least two heat
histories in which the polypropylene has been melted and
resolidified: once when the virgin polypropylene resin (in pellet
or flake from as received from the polymer manufacturer) was
originally melted and extruded to form the original filaments and
webs, and at least once again when the reclaimed polypropylene was
remelted and formed into the filaments and webs of the present
invention. In many instances, the polypropylene will have undergone
an additional melting and resolidification when the waste
polypropylene, in the form of the filaments or webs which are being
reclaimed, is remelted and formed into pellets or flake suitable
for processing in the extruders of the spunbond equipment. As a
result of the prior heat histories, the reclaimed polypropylene
exhibits a melt flow rate higher than that of virgin polypropylene,
typically at least 5 melt flow units greater.
[0027] In one preferred embodiment, the multicomponent filaments
are sheath-core bicomponent filaments, and the component containing
the reclaimed polypropylene is present in the core of the
sheath-core filament. This component can contain up to 100 percent
by weight of the reclaimed polypropylene, thus making it possible
to significantly increase the amount of reclaimed polypropylene
incorporated into the filament. The sheath can contain 100 percent
by weight virgin polypropylene resin, or blends of virgin
polypropylene resin with a smaller amount of the reclaimed
polypropylene than is present in the core. Because of the higher
content of reclaimed polypropylene, the core component will have a
melt flow rate higher than that of the sheath, typically at least 5
melt flow units greater than the sheath.
[0028] Preferably, the core component of the bicomponent filament
will comprise from 25% to 75% of the filament by weight, and more
desirably from 40% to 60% by weight of the filament. In such event,
the reclaimed polypropylene will comprise 25 percent or more of the
total filament, by weight.
[0029] By incorporating the reclaimed polypropylene in the core of
the filament and surrounding it with a sheath of virgin
polypropylene or a blend of virgin with reclaimed polypropylene,
the spinning behavior of the filaments is comparable to that of
monocomponent filaments formed entirely of the sheath composition.
The process may be operated at speeds comparable to what is used in
the normal production of a spunbond fabric formed of monocomponent
filaments, and the operating efficiency and incidence of filament
breaks is comparable. Also, the fabric physical properties and
formation remain comparable to fabrics formed of conventional
monocomponent filaments of virgin polymer. The nonwoven fabrics
show superior formation, as indicated by a coefficient of variation
for air permeability of less than about 7 percent.
[0030] Formation quality is a major concern for nonwoven fabrics
used as components in baby diapers or adult incontinent diapers or
briefs. Good formation allows manufacture to proceed at high speed
without concern, for example, of adhesive bleeding through one
layer of nonwoven fabric into another part of the diaper. One
measure of formation is the ratio of the standard deviation of air
permeability divided by the average of the air permeability,
multiplied by 100 percent. This ratio is sometimes called the
coefficient of variation. A nonwoven fabric showing a low
coefficient of variation for air permeability will show a uniform
distribution of the fibers in the web making up the nonwoven. A
nonwoven fabric showing a poor distribution of fibers in the web
would show a higher value for the coefficient of variation of the
air permeability.
[0031] The spunbond fabrics of the present invention may be
produced entirely of multicomponent or bicomponent filaments, or
may be formed with a blend of reclaim-containing multicomponent or
bicomponent filaments and conventional monocomponent filaments.
[0032] The following examples are provided to illustrate the
present invention.
EXAMPLE 1
Control
[0033] A spunbond machine was employed equipped with three
successively arranged spinning beams (identified A, B and C), each
spinning beam having an independent polymer distribution system and
equipped with spinnerettes capable of producing sheath-core
bicomponent filaments. In each of beams A, B and C the polymer
component that formed the sheath of the bicomponent filament and
the polymer component that formed the core of the bicomponent
filament was comprised of virgin polypropylene resin (EXXON Resin
PP 3155) so that the resulting filaments were comprised of 100%
virgin polypropylene. The polymer feed rate to beams A, B and C was
such that the beams produced a web of 0.40 ounces per square yard
(13.8 grams per square meter) overall basis weight. The resulting
web, which is not part of our invention, was composed of 100%
virgin polypropylene polymer. The web was calender bonded with a
patterned calender roll having 210 embossing points per square inch
and having a 25% bond area. The fabric was then treated with
surfactant to make the fabric fit for use as topsheet for adult
incontinence diapers. The fabric was submitted to physical testing
and the results are given in Table 1.
[0034] For the data given in Table 1, basis weight was measured
generally following the method of ASTM D3776-96. MD and CD Tensile
elongation, and toughness or TEA were measured generally following
ASTM D5035-95 for testing 1-inch wide strips of nonwoven. The
liquid transport properties of the fabric, important for fabrics
used as topsheet for baby diapers or adult incontinent diapers or
briefs, were evaluated using strike-through and rewet tests.
Strike-through and rewet, or surface rewet, were evaluated by
methods similar to those described in U.S. Pat. Nos. 4,041,951 and
4,391,869, incorporated herein by reference. Strike-through was
measured as the time for 5 ml of a synthetic urine solution, placed
in the cavity of the strike-through plate, to pass through the
sample fabric into an absorbent pad. Surface rewet, reported in
grams, was evaluated by adding synthetic urine through the sample
fabric into the absorbent pad until the absorbent pad was nearly
saturated. Thus, the sample was wet at the beginning of the test. A
loading factor of approximately 4 grams of synthetic urine per gram
of absorbent sample was used. a uniform pressure loading of 0.5 psi
was then applied and the procedure was concluded as described in
the above patents. Rewet in grams measures the weight of liquid
that is transferred back through the topsheet from the core to a
sheet of filter paper facing the topsheet when compressed under the
0.5 psi loading. The Hunter color of the fabric was measured
generally following ASTM E-308 to yield an "L" value related to the
lightness reflected off the surface, an "a" value related to
redness (+) or greenness (-) reflected off the sheet and a "b"
value related to yellowness (+) or blueness (-) reflected off the
sheet. Formation is a measure of the uniformity of the fiber
distribution through the web of the bonded nonwoven fabric. A
skilled tester visually compared control samples (standards) of
nonwovens exhibiting different degrees of fiber distribution
uniformity with the fabric to be evaluated. A score was given
between 5 for very good formation to 1 for very poor formation. Air
permeability was measured generally according to ASTM D-737. Air
permeability is the rate of airflow through a material under a
pressure differential between the two fabric surfaces.
EXAMPLE 2
15% Reclaim Control
[0035] The spunbond machine described in Example 1 was used to
produce a spunbond nonwoven fabric of approximately 0.4 ounce per
square yard (13.8 grams per square meter) overall basis weight. In
beams A and C the polymer component that became the sheath of the
bicomponent filament was comprised of virgin polypropylene resin
(EXXON PP 3511). In beam A and C the polymer component that became
the core of the bicomponent filament was also comprised of virgin
polypropylene resin (EXXON PP 3155). Beam B was supplied with a
homogeneous blend of 85% virgin polypropylene (Exxon PP 3155) and
15% reclaimed polypropylene recovered from previously spun
polypropylene fiber or webs comprised of previously spun
polypropylene fiber. This polymer was supplied to both the sheath
and the core of the resulting spun filaments. The resulting web,
not part of our invention, was bonded as in Example 1 and was
tested to obtain the data provided in Table 1 labeled Example
2.
EXAMPLE 3
Bicomponent With 100% Reclaim in Core
[0036] The spunbond machine described in Example 1 was used to
produce a spunbond nonwoven web of 0.4 ounce per square yard (13.9
gram per square meter) overall basis weight containing reclaimed
polypropylene. In beam A and B the polymer component that became
the sheath of the bicomponent filament was comprised of virgin
polypropylene resin (EXXON PP 3155). In beam A and B the polymer
component that became the core of the bicomponent filament was
comprised of 100% reclaimed polypropylene recovered from previously
spun polypropylene fibers or webs comprised of previously spun
polypropylene fiber. Beam C was operated with virgin polypropylene
resin (Exxon PP 3155) supplied to both the sheath and core portion,
so that the resulting filaments were comprised of 100% virgin
polypropylene. The resulting web, a product of our invention, after
bonding and surfactant treatment as in Example 1, was tested to
supply the data shown in Table 1 to compare with the control fabric
of Example 1 made under the same conditions but with 100% virgin
polypropylene. The results summarized in Table 1 show that the web
of Examples 1 and 3 are similar in critical properties. Thus, the
product of Example 3 is fit for use as topsheet in adult
incontinent products.
EXAMPLE 4
Control
[0037] The product of Example 4 was made as described in Example 1
above using 100% virgin polypropylene resin (Exxon PP 3155), except
that bonding was achieved using a calender roll comprising 144
embossing points per square inch and 18% bond area. The three beams
cooperated to produce approximately equal output to yield a final
web basis weight of 0.7 ounces per square yard (23 grams per square
meter). The fabric properties of Example 4 are summarized in Table
1. This product is supplied for use as topsheet in the manufacture
of baby diapers.
EXAMPLE 5
15% Reclaim Control
[0038] The product of Example 5 was made as described in Example 2
above, except that bonding was achieved using a calender roll
having 144 embossing points per square inch and 18% bond area. The
three beams cooperated to produce approximately equal output to
yield a final basis weight of 0.65 ounce per square yard (22.1
grams per square meter). Properties of the product of Example 5 are
summarized in Table 1.
EXAMPLE 6
Bicomponent With 100% Reclaim in Core
[0039] Example 6, a product of our invention, was made as described
in Example 3 above, except that bonding was achieved using a
calender roll having 144 embossing points per square inch and 18%
bond area. The three beams cooperated to produce approximately
equal output to yield a final basis weight of 0.65 ounce per square
yard (22.1 grams per square meter). Properties of the product of
Example 6 are summarized in Table 1.
[0040] Many modifications and other embodiments of the invention
will come to mind to one skilled in the art to which this invention
pertains having the benefit of the teachings presented in the
foregoing descriptions and the associated drawings. Therefore, it
is to be understood that the invention is not to be limited to the
specific embodiments disclosed and that modifications and other
embodiments are intended to be included within the scope of the
appended claims. Although specific terms are employed herein, they
are used in a generic and descriptive sense only and not for
purposes of limitation.
1 TABLE I EXAMPLE-1 EXAMPLE-2 EXAMPLE-3 EXAMPLE-4 EXAMPLE-5
EXAMPLE-6 STD. STD. STD. STD. STD. STD. PRODUCT AVER. DEV AVER DEV.
AVER DEV AVER DEV. AVER DEV. AVER DEV. BASIS WEIGHT (g/m.sup.2)
13.79 0.33 13.85 0.32 13.86 0.31 22.98 0.41 22.13 0.46 21.95 0.58
STRIP TENSILE - MD (g/cm) 523 70 500 73 490 64 749 86 735 80 608 69
STRIP ELONGATION - MD (%) 43 9 44 7 55 8 60 8 58 8 55.6 8 STRIP TEA
TOUGHNESS - (cm-gm/cm.sup.2) 197 39 191 43 202 52 207 66 297 63 248
52 MD STRIP TENSILE - CD (gm/cm) 238 45 247 66 275 61 493 77 486 73
400 66 STRIP ELONGATION - CD (%) 46 8 47 10 56 10 58 11 60 9 57 9
STRIP TEA TOUGHNESS- (cm-gm/cm.sup.2) 98 25 105 32 118 38 198 52
198 46 164 41 CD STRIKE THROUGH (seconds) 2.18 0.42 2.13 0.19 2.26
0.4 2.11 0.26 1.99 0.21 2.07 0.24 REWET (gm) 0.14 0.03 0.13 0.02
0.16 0.02 0.11 0.02 0.11 0.01 0.12 0.02 HUNTER COLOR - L 96.6 0.33
96.32 0.41 96.52 0.38 97.08 0.34 97.04 0.46 96.76 0.46 HUNTER COLOR
- a -0.38 0.09 -0.27 0.05 -0.31 0.05 -0.39 0.11 -0.33 0.04 -0.48
0.34 HUNTER COLOR - b 0.52 0.08 1.04 0.28 0.95 0.15 0.46 0.22 0.88
0.2 1.02 0.26 FORMATION 3.66 0.48 3.17 0.4 3.1 0.3 3.98 0.2 3.95
0.25 3.99 0.08 AIR PERMEABILITY (f.sup.3/f.sup.2/min) 917 53 930 48
884 46 693 30 672 26 701 37 AIR PERMEABILITY 5.8 5.2 5.2 4.3 3.9
5.3 COEFFICIENT OF VARIATION AIR PERMEABILITY 88 >20 >20 152
>20 >20 NO. OF TESTS
* * * * *