Note: Descriptions are shown in the official language in which they were submitted.
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HYDROENTANGLED NONWOVEN WEB CONTAINING RECYCLED SYNTHETIC
FIBROUS MATERIALS
FIELD OF THE INVENTION
The present invention relates to a hydraulically entangled nonwoven fabric
containing recycled fibers and a method for making a nonwoven composite
fabric.
BACKGROUND OF THE INVENTION
Although nonwoven webs of pulp fibers are known to be absorbent, nonwoven
to webs made entirely of pulp fibers may be undesirable for certain
applications such
as, for example, heavy duty wipers because they lack strength and abrasion
resistance.
Pulp fibers have been combined with staple length fibers and hydraulically
entangled. However, adding staple fibers increases expense. In addition,
s5 suspensions containing staple fibers can be more difficult to process
utilizing
conventional paper-making or wet-laying techniques. One known technique for
combining these materials is by hydraulic entangling. For example, U.S. patent
No.
4,808,467 to Suskind discloses a high-strength nonwoven fabric made of a
mixture
of wood pulp and textile fibers entangled with a continuous filament base web.
ao Laminates of pulp fibers with textiles and/or nonwoven webs are disclosed
in
Canadian Patent No. 841,398 to Shambelan. According to that patent, high
pressure jet streams of water, may be used to entangle an untreated paper
layer with
base webs such as, for example, a continuous filament web.
It has been proposed that bonded fibrous webs may be mechanically broken
a5 up into smaller pieces such as fiber bundles, threads and/or individual
fibers and
these pieces then be formed into a web by hydraulic entangling. This is
normally
accomplished by mechanical tearing and shredding dry material.
For example, International Application PCT/SE95/00938 states that it is known
to mechanically shred dry nonwoven and textile waste and that dry mixed waste
3o containing both synthetic and natural fibers may be used. According to
PCT/SE95/00938, a significant feature of shredding and tearing techniques is
that
the tearing or shredding operation is often incomplete so that recycled fibers
are
present partly in the form of discrete bits of the original fabric that may be
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characterized as "flocks" or fiber bundles. These flocks are described as
providing
non-uniformities that give webs containing such flocks a more textile-like
appearance.
Flocks and bits of fabric are difficult to process in subsequent operations
such
as, for example, a wet-laying process, air-laying process, hydraulic
entangling
process or other web-forming processes. Presence of these non-uniformities may
reduce the value of the recycled fibers as well as degrade the appearance,
strength,
uniformity and other desirable properties of a web or fabric made with the
recycled
fibers. Removing the non-uniformities by screening or other techniques reduces
the
so efficiency of the fiber recovery. Additional dry mechanical chopping,
shredding,
tearing, garnetting or picking operations to reduce the fiber bundles or
flocks into
fibers or fiber-like material having a length of less than 5 millimeters may
be
impractical. In addition, the additional mechanical work may transfer so much
energy
in the form of heat that the dry material may melt into unusable clumps and
may
diminish or eliminate any environmental or economic advantages initially
presented
by recycling the material. '
SUMMARY OF THE INVENTION
The present invention addresses the needs discussed above by providing a
ao hydraulically entangled nonwoven fabric that includes recycled synthetic
fibers and
fiber-like materials having at least one thread element composed of synthetic
material and with at least one irregular distortion generated by hydraulic
fracture of
the thread element to separate it from a bonded fibrous material white the
bonded
fibrous material is suspended in a liquid.
The thread element may have a length ranging from about 1 millimeter to
about 15 millimeters. For example, the thread element may have a length
ranging
from about 1.5 to about 10 millimeters. As another example, the thread element
may have a length ranging from about 2 to about 5 millimeters. The thread
element may have a diameter of less than 100 micrometers. For example, the
so ' thread element may have a diameter of less than about 30 micrometers and,
as a
particular example, may have a fiber diameter of from about 10 micrometers to
about 20 micrometers.
According to an aspect of the invention, the irregular distortions may be in
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the form of bends in the thread element, flattened segments of thread element,
expanded segments of thread element and combinations thereof. In addition,
with
recycling, the bends and/or twists provide more effective interlocking of the
fibrous
web in the entangling process.
Generally speaking, the irregular distortions cause the thread elements of
the recycled materials to have greater surface area than thread elements in
the
bonded fibrous material prior to hydraulic fracture of the thread element to
separate it from the bonded fibrous material. For example, the surface areas
of
the recycled thread elements are at least about 5 percent greater.
so In embodiments of the invention, the recycled synthetic fibers and fiber-
like
materials may be a synthetic material selected from polyesters, polyamides,
polyolefins, fiberglass and combinations thereof. In embodiments of the
invention,
the recycled synthetic fibers and fiber-like materials may be a synthetic
thermoplastic material. For example, the synthetic thermoplastic material may
be a
i5 polyolefin such as polypropylene, polyethylene and combinations of the
same. The
synthetic thermoplastic material may be in the form of multicomponent fibers,
filaments, strands or the like and may include fiber and/or filaments having
various
cross-sectional shapes, lobes or other configurations.
The hydraulically entangled nonwoven fabric may further include non-
2o recycled natural fibrous materials, non-recycled natural synthetic
materials,
recycled natural fibrous materials, particulate materials and combinations
thereof.
For example, hydraulically entangled nonwoven fabric may further include pulp
fibers. In an embodiment of the invention, the hydraulically entangled
nonwoven
fabric may contain from about 1 to about 85 percent, by weight of recycled
synthetic
25 fibers and fiber-like materials and from about 15 to about 99 percent, by
weight of
pulp.
The pulp fiber component may be woody and/or non-woody plant fiber pulp.
The pulp may be a mixture of different types and/or qualities of pulp fibers.
The present invention also contemplates treating the hydraulically entangled
3o nonwoven fabric with small amounts of materials such as, for example,
binders,
surfactants, cross-linking agents, de-bonding agents, fire retardants,
hydrating
agents, pigments and/or dyes. Alternatively and/or additionally, the present
invention contemplates adding particulates such as, for example, activated
charcoal,
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clays, starches, and superabsorbents to the nonwoven fabric. In one
embodiment,
hydraulically entangled nonwoven fabric may further include up to about 3
percent of
a de-bonding agent.
The hydraulically entangled nonwoven fabric may be used as a heavy duty
wiper. In one embodiment, the nonwoven fabric may be a single-ply or multiple-
ply
wiper having a basis weight from about 20 to about 200 grams per square meter
(gsm). For example, the wiper may have a basis weight between about 25 to
about
150 gsm or more particularly, from about 30 to about 110 gsm. The wiper
desirably
has a water capacity greater than about 450 percent, an oil capacity greater
than
so about 250 percent, a water wicking rate (machine direction) greater than
about 2.0
cm per 15 seconds, and oil wicking rate (machine direction) greater than about
0.5
cm per 15 seconds.
The present invention also encompasses a method of making a hydraulically
entangled nonwoven fabric that includes the steps of: (a) providing a layer of
recycled synthetic fibers and fiber-like materials having at least one thread
element composed of synthetic material containing at least one irregular
distortion
generated by hydraulic fracture of the thread element to separate it from a
bonded
fibrous material white the bonded fibrous material is suspended in a liquid;
(b)
hydraulically entangling the layers to form a nonwoven web; and (c) drying the
2 o web.
According to the present invention, the step of providing the layer of
recycled
synthetic fiber and fiber-like materials may encompass depositing a layer of
the
recycled fibers on a hydraulic entangling fabric by dry forming or wet-forming
techniques.
In an embodiment of the invention, the step of providing the layer of recycled
synthetic fiber and fiber-like materials may include depositing a layer
composed of
recycled fibers and pulp fibers on a hydraulic entangling fabric by wet-
forming
techniques.
The hydraulic entangling may be carried out by conventional hydraulic
3o entangling techniques.
The hydraulically entangled nonwoven composite fabric may be dried utilizing
a non-compressive drying process. Through-air drying processes have been found
to work particularly well. Other drying processes which incorporate infra-red
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radiation, yankee dryers, steam cans, vacuum de-watering, microwaves, and
ultrasonic energy may also be used.
DEFINITIONS
The term "machine direction" as used herein refers to the direction of travel
of
the forming surface onto which fibers are deposited during formation of a
nonwoven
web.
The term "cross-machine direction" as used herein refers to the direction
which
is perpendicular to the machine direction defined above.
1o The term "pulp" as used herein refers to fibers from natural sources such
as
woody and non-woody plants. Woody plants include, for example, deciduous and
coniferous trees. Non-woody plants include, for example, cotton, flax, esparto
grass, milkweed, straw, jute, hemp, and bagasse.
The term "average fiber length" as used herein refers to an average length of
fibers, fiber bundles and/or fiber-like materials determined by measurement
utilizing
microscopic techniques. A sample of at least 20 randomly selected fibers is
separated from a liquid suspension of fibers. The fibers are set up on a
microscope
slide prepared to suspend the fibers in water. A tinting dye is added to the
suspended fibers to color cellulose-containing fibers so they may be
distinguished or
~o separated from synthetic fibers. The slide is placed under a Fisher
Stereomaster II
Microscope S19642/S19643 Series. Measurements of 20 fibers in the sample are
made at 20X linear magnification utilizing a 0-20 mils scale and an average
length,
minimum and maximum length, and a deviation or coefficient of variation are
calculated. In some cases, the average fiber length will be calculated as a
weighted
~5 average length of fibers (e.g., fibers, fiber bundles, fiber-like
materials) determined
by equipment such as, for example, a Kajaani fiber analyzer Model No. FS-200,
available from Kajaani Oy Electronics, Kajaani, Finland. According to a
standard test
procedure, a sample is treated with a macerating liquid to ensure that no
fiber
bundles or shives are present. Each sample is disintegrated into hot water and
3o diluted to an approximately 0.001 % suspension. Individual test samples are
drawn in
approximately 50 to 100 ml portions from the dilute suspension when tested
using
the standard Kajaani fiber analysis test procedure. The weighted average fiber
5
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length may be an arithmetic average, a length weighted average or a weight
weighted average and may be expressed by the following equation:
k
(x; * n;)ln
x,=o
where k = maximum fiber length
x; = fiber length
n; = number of fibers having length x;
n = total number of fibers measured.
1o One characteristic of the average fiber length data measured by the Kajaani
fiber
analyzer is that it does not discriminate between different types of fibers.
Thus, the
average length represents an average based on lengths of all different types,
if any,
of fibers in the sample.
As used herein, the term "spunbonded filaments" refers to small diameter
i5 continuous filaments which are formed by extruding a molten thermoplastic
material
as filaments from a plurality of fine, usually circular, capillaries of a
spinnerette with
the diameter of the extruded filaments then being rapidly reduced as by, for
example, eductive or mechanical drawing and/or other well-known spunbond
mechanisms. The production of spun-bonded nonwoven webs is illustrated in
ao patents such as, for example, in U.S: Patent No. 4,340,563 to Appel et al.,
and U.S.
Patent No. 3,692,618 to Dorschner et al. The disclosures of these patents are
hereby incorporated by reference.
As used herein, the term "meltblown fibers" means fibers formed by extruding
a molten thermoplastic material through a plurality of fine, usually circular,
die
a5 capillaries as molten threads or filaments into a high velocity gas (e.g.
air) stream
which attenuates the filaments of molten thermoplastic material to reduce
their
diameter, which may be to microfiber diameters. 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 disbursed meltblown fibers. Such a process is
disclosed,
3o for example, in U.S. Patent No. 3,849,241 to Butin, the disclosure of which
is hereby
incorporated by reference.
As used herein, the term "microfibers" means small diameter fibers having an
average diameter not greater than about 100 microns; for example, having a
6
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diameter of from about 0.5 microns to about 50 microns, more particularly,
microfibers may have an average diameter of from about 1 micron to about 40
microns.
As used herein, the term "thermoplastic material" refers to a polymer that
softens when exposed to heat and returns to generally its un-softened state
when
cooled to room temperature. Natural substances which exhibit this behavior are
crude rubber and a number of waxes. Other exemplary thermoplastic materials
include, without limitation, polyvinyl chlorides, some polyesters, polyamides,
polyfluorocarbons, polyolefins, some polyurethanes, polystyrenes, polyvinyl
1o alcohols, caprolactams, copolymers of ethylene and at least one vinyl
monomer
(e.g., poly(ethylene vinyl acetates), copolymers of ethylene and n-butyl
acrylate
(e.g., ethylene n-butyl acrylates), polylactic acids, thermoplastic elastomers
and
acrylic resins.
As used herein, the term "non-thermoplastic material" refers to any material
i5 which does not fall within the definition of "thermoplastic material"
above.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a photomicrograph of a detail of an exemplary recycled synthetic
fiber of the type used in the formation of an exemplary hydraulically
entangled
~o nonwoven web.
FIG. 2 is a photomicrograph of a detail of an exemplary virgin synthetic
staple fiber.
FIG. 3 is a photomicrograph of a detail of an exemplary recycled synthetic
fiber of the type used in the formation of an exemplary hydraulically
entangled
25 nonwoven web.
FIG. 4 is a photomicrograph of a detail of an exemplary recycled synthetic
fiber of the type used in the formation of an exemplary hydraulically
entangled
nonwoven web.
FIG. 5 is a photomicrograph of a detail of an exemplary recycled synthetic
30' fiber of the type used in the formation of an exemplary hydraulically
entangled
nonwoven web.
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FIG. 6 is a photomicrograph of a detail of an exemplary recycled synthetic
fiber of the type used in the formation of an exemplary hydraulically
entangled
nonwoven web.
FIG. 7 is a photomicrograph of a detail of an exemplary virgin synthetic
staple fiber.
FIG. 8 is a photomicrograph of a detail of multiple exemplary recycled
synthetic fibers of the type used in the formation of an exemplary
hydraulically
entangled nonwoven web.
FIG. 9 is a photomicrograph of a detail of an exemplary recycled synthetic
to fiber of the type that may be used in the formation of an exemplary
hydraulically
entangled nonwoven web.
FIG. 10 is a photomicrograph showing details of exemplary recycled
synthetic fibers of the type that may be used in the formation of an exemplary
hydraulically entangled nonwoven web.
15 FIG. 11 is a photomicrograph showing details of exemplary recycled
synthetic fibers of the type that may be used in the formation of an exemplary
hydraulically entangled nonwoven web.
FIG. 12 is a photomicrograph showing details of exemplary recycled
synthetic fibers of the type that may be used in the formation of an exemplary
ao hydraulically entangled nonwoven web.
DETAILED DESCRIPTION OF THE INVENTION
The present invention encompasses a hydraulically entangled nonwoven
fabric formed of recycled synthetic fibers and fiber-like materials. The
synthetic
a5 fibers and fiber-like materials are recovered from bonded fibrous materials
that are
converted into substantially individual fibers and fiber-like materials.
Importantly,
these- bonded fibrous materials are materials that include synthetic fibers
and may
be bonded fibrous materials such as, for example, woven fabrics, knitted
fabrics,
nonwoven webs and combinations thereof. As a further example, the recycled
fibers
so may come from nonwoven webs that are thermally bonded, adhesively bonded,
mechanically entangled, solvent bonded, hydraulically entangled and/or
combinations of such techniques and may contain synthetic fibrous materials,
natural fibrous materials and combinations thereof. The synthetic fibrous
material
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may include thermoplastic fibers and filaments.
In order to recover useable recycled synthetic fibers for hydraulic
entangling,
bonded fibrous webs are cut or shredded into pieces having sizes that are
adapted for suspension in a liquid. Next, the pieces are suspended in liquid
and
mechanical work is applied to the liquid suspension of discrete pieces to
generate
hydraulic pressure and mechanical shear stress conditions sufficient to
hydraulically fragment the bonded fibrous materials into fibers and fiber-like
components. Finally the substantially individual fibers and fiber-like
components
are separated from the liquid.
1o The bonded fibrous materials may be converted into discrete pieces by a
conventional operation such as, for example, mechanical shredding, mechanical
cutting, mechanical tearing', mechanical grinding, pulverizing, water jet
cutting,
laser cutting, garnetting and combinations thereof.
Importantly, a liquid suspension of these pieces is exposed to conditions of
hydraulic pressure, shear stress, and/or cavitational forces sufficient to
fragment,
rupture, rupture, burst or disintegrate pieces of bonded fibrous materials
into
useful free fibers and fiber bundles or fiber-like materials. These process
conditions used to convert the shredded material to recycled fibers are more
aggressive and stringent than those found in conventional pulping operations.
2o As an example, normal pulping operations typically use less than about 3
horsepower-day (24 hours) per dry ton of material. Embodiments of the present
invention may utilize much larger inputs of energy. According to the
invention, the
approximate amount of mechanical work applied to the liquid suspension may be
greater than about 3 Horsepower - day (24 hours) per dry ton of bonded fibrous
material - as determined by measuring the electric current drawn by the motor
providing movement to the components generating hydraulic pressure and shear
stress conditions. This number may be greater than 4 Horsepower - day per ton
and may be even greater than 6 or more. For example, the method of the
invention may be practiced utilizing 35% more energy; 50% percent more energy,
or even more to separate useful free fibers and fiber bundles from the bonded
fibrous material. It is contemplated that, in some situations or under some
conditions, the approximate amount of mechanical work may be less than 3
Horsepower - day per dry ton of bonded fibrous material.
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Although the inventors should not be held to a particular theory of
operation, it is believed that the combination of hydraulic pressure, shear
stress,
and cavitational forces breaks up the material into free fibers and fiber
bundles. It
is also thought that the content of free fibers and the average size of the
bundles
can be controlled by varying the pressure and mechanical stress. It is
generally
thought that this high level of mechanical action or work is possible without
causing significant degradation of the synthetic components of the bonded
fibrous
materials (e.g., without melting synthetic thermoplastic material) because the
water/liquid in the process absorbs the heat generated as free fibers and
fiber-like
1o materials are separated from the bonded fibrous material.
Generally speaking, conventional beating and/or refining equipment is used
to modify cellulose fibers to develop papermaking properties of hydration and
fibrillation. According to the present invention, conventional beaters and/or
refiners
may be configured or operated in an unconventional manner to provide the
hydraulic pressure and shear stress conditions sufficient to fragment and
fracture
the bonded fibrous material into free fibers, fiber bundles and fiber-like
materials.
Exemplary beater devices are available from manufacturers such as Beloit
Jones,
E. D. Jones, Valley, and Noble & Wood.
A liquid suspension of bonded fibrous material pieces is introduced into the
2o beater device. Alternatively and/or additionally, bonded fibrous material
pieces
may be introduced directly infio liquid in the beater vat. Various proportions
of
bonded fibrous materials and water may be used and one skilled in the art may
determine appropriate proportions.
During operation, a cylinder or beater roll is rotated at sufficient speed so
that sufficient hydraulic pressure and shear stress are produced between the
blades or vanes on the roll and separate blades mounted on a fixed plate
beneath
the roll.
Rotation speed, consistency of the suspension in the vat and clearance
between the rotating blades or vanes and the fixed blades is also adjusted to
3o coriditions that enhance "metal to fiber" interaction that cuts or controls
the length
of free fibers, fiber bundles and fiber-like particles. The term "metal to
fiber"
interaction is used to describe the contact between the bonded fibrous
material
and the fixed and/or rotating blades that may occur under conditions of
hydraulic
io
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pressure and mechanical shear stress sufficient to sever, cut or break long
fibers.
According to the invention, this interaction should be controlled to cut long
fibers
without materially affecting or lowering the length and/or freeness of pulp or
short
fibers that may be present in the suspension.
While equipment may be operated_to provide fibers, fiber bundles and fiber-
like materials having a wide range of lengths, it may also be used to generate
fiber
and fiber-like material having an average length distribution that spans
approximately 7 millimeters or less. Generally speaking, a more uniform fiber
distribution tends to enhance processing and hydraulic entangling. However, it
is
zo contemplated that a mix of longer fibers and shorter fibers may be
desirable. The
longer fibers may have advantages in providing strength and shorter fibers may
have advantages in providing other useful characteristics such as, for
example,
absorbency, hand, drape and/or bulk.
In addition to controlling length, some "metal to fiber" interaction may
15 generate deformations and distortions of synthetic components of the bonded
fibrous material. While some deformations and distortions may be generated by
hydraulic fragmentation of the bonded fibrous material others may be generated
by tearing, slicing and breaking of fiber and/or filaments. These fiber
deformations
and irregularities are thought to help wet forming (or dry forming) of a web
as well
ao as subsequent hydraulic entangling. These characteristics of the recycled
fibers
and fiber-like materials enhance their utility in hydraulic entangling
processes and
make it practical to produce hydraulically entangled fabric that may exhibit
the
same or similar physical properties as one produced from 100 percent virgin
fibers
and potentially exceed those properties.
25 A discussion of the recycled synthetic fibers is useful to understanding
the
hydraulically entangled fabrics constructed from these fibers. Referring now
to
FIGS. 1, 3-6, and 8-12~ there are shown various exemplary recycled synthetic
fibers, fiber bundles and/or fiber-like materials having at least one thread
element
composed of synthetic material having at least one irregular distortion
generated
3o by hydraulic fracture of the thread element to separate it from a bonded
fibrous
material while the bonded fibrous material is suspended in a liquid.
The thread element is discontinuous and, as an example, may have a
length ranging from about 1 millimeter to about 15 millimeters. For example,
the
m
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thread element may have a length ranging from about 1.5 to about 10
millimeters.
As another example, the thread element may have a length ranging from about 2
to about 5 millimeters. The thread element may have a diameter of less than
100
micrometers. For example, the thread element may have a diameter of less than
30 micrometers. Generally speaking, these dimensions are similar to certain
varieties of commercially available pulps and may be readily blended with
commercial pulps. In some embodiments, the thread elements may have a
diameter of less than 10 microns and may even be less than 1 micron.
The irregular distortions may be in the form of bends in the thread element,
so flattened segments of thread element, expanded segments of thread element
and
combinations thereof.
Generally speaking, the irregular distortions cause the thread elements of
the recycled materials to have greater surface area than thread elements in
the
bonded fibrous material prior to hydraulic fracture of the thread element to
separate it from the bonded fibrous material. For example, the surface areas
of
the recycled thread elements may be at least about 5 percent greater. The
increased surface area will often be the result of remaining fiber bond areas,
cross
over points, flat areas, fiber distortions and the like.
FIG. 1 is a photomicrograph (approximately 500X linear magnification)
2o showing a detail of an exemplary recycled synthetic fiber. The recycled
fiber was
recovered from a composite structure containing a thermally point bonded
continuous polypropylene filament web and pulp fibers hydraulically entangled
with
the continuous filament web. The fiber visible in the center of the
photomicrograph
is a spunbonded polypropylene thread element having bends in the filaments and
a relatively flattened segment. At least a portion of these distortions, e.g.
flattened
sections, are generated or exposed by hydraulic fracture of the thread element
from the bonded continuous polypropylene fiber web along with the cellulose
pulp
(i.e., the composite structure). The material surrounding the thread element
is
cellulose pulp.
3o FIG. 2 is a photomicrograph (approximately 500X linear magnification)
showing conventional polypropylene staple fibers appearing in a conventional
bonded carded web structure. In contrast to the thread elements of F1G. 1,
these
fibers appear relatively free of irregular distortions. The fibers have
relatively
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smooth surfaces, even or uniform diameters, and lack the twists, bends, kinks
and
other irregular distortions that are evident in the thread element shown in
FIG. 1.
FIG. 3 is a photomicrograph (approximately 120X linear magnification)
showing a detail of an exemplary recycled synthetic fiber recovered from the
same
type of composite structure as the thread element shown in FIG. 1. The fiber
visible across the central region of the photomicrograph is a polypropylene
thread
element that exhibits a loop and bends as well as relatively flattened
segments. At
least a portion of these distortions are generated or exposed by hydraulic
fracture
of the thread element from the bonded fibrous material (i.e., the composite
1o structure). The material surrounding the thread element is cellulose pulp.
FIG. 4 is a photomicrograph (approximately ~20X linear magnification)
showing a detail of an exemplary recycled synthetic fiber recovered from the
same
type of composite structure as the thread element shown in FIG. 1. The fiber
visible in the center of the photomicrograph is a polypropylene thread
element.
15 The arrow in the photomicrograph points to a sharp bend in the thread
element.
FIG. 5 is a photomicrograph (approximately 500X linear magnification)
showing a detail of an exemplary recycled synthetic fiber recovered from the
same
type of composite structure as the thread element shown in FIG. 1. The fiber
visible in the center of the photomicrograph is a polypropylene thread element
that
20 exhibits bends and/or twists as well as a roughened segment.
FIG. 6 is a photomicrograph (approximately 500X linear magnification)
showing a detail of an exemplary recycled synthetic fiber recovered from the
same
type of composite structure as the thread element shown in FIG. 1. The fiber
visible across the center of the photomicrograph is a polypropylene thread
element
25 showing a cut end of the fiber that is flattened and expanded.
F1G. 7 is a photomicrograph (approximately 500X linear magnification)
showing a detail of a conventional polypropylene staple fiber. In contrast to
the
thread element of FIG. 6, the fiber appears relatively free of irregular
distortions
and has an end that appears to be cut cleanly without evidence of expansion or
30 other distortion.
FIG. 8 is a photomicrograph (approximately 250X linear magnification)
showing a detail of two exemplary recycled synthetic fibers recovered from the
same type of composite structure as the thread element shown in FIG. 1. The
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fibers visible across the center and near the lower portion of the
photomicrograph
are polypropylene thread elements that exhibit bends as well as roughened
segments.
FIG. 9 is a photomicrograph (approximately 500X linear magnification)
showing a detail of exemplary recycled synthetic fibers. The recycled fibers
were
recovered from KimtexO brand wiper containing thermally point-bonded web of
polypropylene meltblown fibers. The relatively fine meltblown fibers visible
in the
center of the photomicrograph are polypropylene thread elements having bends,
twists, tangles and relatively flattened segments. At least a portion of these
so distortions are generated or exposed by hydraulic fracture of the thread
elements
from the bonded fibrous material (i.e., the Kimtex~ wiper). The material
surrounding the thread elements is cellulose pulp.
FIG. 10 is a photomicrograph (approximately 100X linear magnification)
showing a detail of exemplary recycled synthetic fibers recovered from the
same
type of material as the thread elements shown in FIG. 9. A bond point
approximately 500 micrometers in length is visible in the center of the
photomicrograph. Fibers radiate outward from the edges of the bond point in
the
form of polypropylene thread elements having bends, twists, tangles and
relatively
flattened segments. At least a portion of these distortions are generated or
~o exposed by hydraulic fracture of the thread elements from the bonded
fibrous
material. Some of the material in the background of the thread elements is
cellulose pulp.
FIG. 11 is a photomicrograph (approximately 500X linear magnification)
showing a detail of exemplary recycled synthetic fibers recovered from the
same
25 type of material as the thread elements shown in FIG. 10. A larger fiber-
like
material or fiber bundle is approximately 40 micrometers in width is visible
in the
center of the photomicrograph. Fibers surround and radiate outward from the
edges of the fiber-like material or fiber bundle in the form of polypropylene
thread
elements having bends, twists, tangles and relatively flattened segments. At
least
3o a portion of these distortions are generated or exposed by hydraulic
fracture of the
,thread elements from the bonded fibrous material. The larger fibrous
materials
near the thread elements are cellulose pulp fibers.
14
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FIG. 12 is a photomicrograph (approximately 500X linear magnification)
showing a detail of exemplary recycled synthetic fibers recovered from the
same
type of material as the thread elements shown in FIG. 10. A mix of cellulose
pulp
and recycled fibers in the form of polypropylene thread elements having bends,
twists, tangles and relatively flattened segments is shown.
The hydraulically entangled web of recycled fibers and fiber-like materials
may
be made by conventional hydraulic entangling techniques. For example, a dilute
suspension of recycled fibers and fiber-like materials may be supplied by a
head-box
and deposited via a sluice in a uniform dispersion onto a forming fabric of a
to conventional papermaking machine.
The suspension of fibers may be diluted to any consistency which is typically
used in conventional papermaking processes. For example, the suspension may
contain from about 0.01 to about 1.5 percent by weight fibers suspended in
water.
Water is removed from the suspension of fibers to form a uniform layer. The
recycled fibers may also include added pulp fiber and/or other types of
fibers,
particulates or other materials. It is contemplated that the recycled fibers
and these
various fibers and/or other material may be formed into a stratified or
heterogeneous
sheet or layer. Alternatively and/or additionally, these components may be
blended
or mixed to form a homogenous layer.
ao Small amounts of wet-strength resins and/or resin binders may be added to
improve strength and abrasion resistance if there is a cellulose component in
the
fibers. Useful binders and wet-strength resins include, for example, Kymene
557 H
available from the Hercules Chemical Company and Parez 631 available from
American Cyanamid, Inc. In some cases, it may be possible to add cross-linking
~5 agents and/or hydrating agents to the fibers. It is also possible to add
debonding
agents. One exemplary debonding agent is available from the Quaker Chemical
Company, Conshohocken, Pennsylvania, under the trade designation Quaker 2008.
The fiber layer is then laid upon a foraminous entangling surface of a
conventional hydraulic entangling machine. The layer of recycled fibers and
fiber-like
3o materials (and any added pulps, fibers and/or other materials) pass under
one or
more hydraulic entangling manifolds and are treated with jets of fluid to
entangle the
recycled fibers and fiber-like materials with one another.
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It is contemplated that hydraulic entangling may take place while the fiber
layer
is on the same foraminous screen (i.e., mesh fabric) on which the wet-laying
took
place.
The hydraulic entangling may be accomplished utilizing conventional hydraulic
entangling equipment such as may be found in, for example, in U.S. Patent No.
3,485,706 to Evans, the disclosure of which is hereby incorporated by
reference.
The hydraulic entangling of the present invention may be carried out with any
appropriate working fluid such as, for example, water. The working fluid flows
through a manifold which evenly distributes the fluid to a series of
individual holes or
to orifices. These holes or orifices may be from about 0.003 to about 0.015
inch in
diameter. For example, the invention may be practiced utilizing a manifold
produced
by Honeycomb Systems Incorporated of Biddeford, Maine, containing a strip
having
0.007 inch diameter orifices, 30 holes per inch, and 1 row of holes. Many
other
manifold configurations and combinations may be used. For example, a single
15. manifold may be used or several manifolds may be arranged in succession.
In the hydraulic entangling process, the working fluid passes through the
orifices at a pressures ranging from about 200 to about 2000 pounds per square
inch gauge (psig). At about 2000 psig, it is contemplated that the composite
fabrics
may be processed at speeds of about 1000 feet per minute (fpm). The fluid
impacts
ao the fiber layer which is supported by a foraminous surface which may be,
for
example, a single plane mesh having a mesh size of from about 40 X 40 to about
100 X 100. The foraminous surface may also be a multi-ply mesh having a mesh
size from about 50 X 50 to about 200 X 200. As is typical in many water jet
treatment processes, vacuum slots may be located directly beneath the hydro-
25 needling manifolds or beneath the foraminous entangling surface downstream
of the
entangling manifold so that excess water is withdrawn from the hydraulically
entangled material.
Although the inventors should not be held to a particular theory of operation,
it
is believed that the columnar jets of working fluid which directly impact the
relatively
3o distorted, twisted and high surface area recycled fibers laying on the
entangling
surface work to entangle and intertwine those fibers with each other (and with
other
fibers that may be present such as, for example, pulp fibers).
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Generally speaking, it is thought that the various irregularities of the
central
thread element and any branching thread elements, fibrils or the like help the
recycled fibers form a coherent entangled matrix. When recycled fibers are
mixed
with pulp fibers, this matrix is thought to help secure the pulp fibers.
After the fluid jet treatment, the hydraulically entangled fabric may be
transferred to a non-compressive drying operation. A differential speed pickup
roll
may be used to transfer the material from the hydraulic needling belt to a non-
compressive drying operation. Alternatively, conventional vacuum-type pickups
and
transfer fabrics may be used. If desired, the entangled fabric may be wet-
creped
to before being transferred to the drying operation. Non-compressive drying of
the
fabric may be accomplished utilizing a conventional rotary drum through-air
drying
apparatus. The temperature of the air forced through the hydraulically
entangled
fabric by the through-dryer may range from about 200 to about 500 F. Other
useful through-drying methods and apparatus may be found in, for example, U.S.
Patent Nos. 2,666,369 and 3,821,068, the contents of which are incorporated
herein
by reference.
Although through-air drying processes have been found to work particularly
well, other drying processes which incorporate infra-red radiation, yankee
dryers,
steam cans, vacuum de-watering, microwaves, and ultrasonic energy may also be
ao used.
It may be desirable to use finishing steps and/or post treatment processes to
impart selected properties to the composite fabric. For example, the fabric
may be
lightly pressed by calender rolls, creped or brushed to provide a uniform
exterior
appearance and/or certain tactile properties. Alternatively and/or
additionally,
a5 chemical post-treatments such as, adhesives or dyes may be added to the
fabric.
In one aspect of the invention, the fabric may contain various materials such
as, for example, activated charcoal, clays, starches, and superabsorbent
materials.
For example, these materials may be added to the suspension of recycled fibers
used to form the fiber layer. These materials may also be deposited on the
fiber
30 layer prior to the fluid jet treatments so that they become incorporated
into the
hydraulically entangled fabric by the action of the fluid jets. Alternatively
and/or
additionally, these materials may be added to the hydraulically entangled
fabric after
the fluid jet treatments.
m
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Test Methods
Trapezoidal tear strengths. of samples were measured in accordance with
ASTM Standard Test D 1117-14 except that the tearing load is calculated as an
average of the first and the highest peak loads rather than an average of the
lowest
and highest peak loads.
Water and oil absorption capacities of samples were measured in accordance
with Federal Specification No. UU-T-595C on industrial and institutional
towels and
wiping papers. The absorptive capacity refers to the capacity of a material to
absorb
liquid over a period of time and is related to the total amount of liquid held
by a
material at its point of saturation. Absorptive capacity is determined by
measuring
the increase in the weight of a material sample resulting from the absorption
of a
liquid. Absorptive capacity may be expressed, in percent, as the weight of
liquid
absorbed divided by the weight of the sample by the following equation:
Total Absorptive Capacity = [(saturated sample weight - sample
weight)/sample weight] X 100.
The basis weights of samples were~determined essentially in accordance with
~o ASTM D-3776-9 with the following changes: 1) sample size was at least 20
square
inches (130 cm2); and 2) a minimum of three random specimens were tested for
each sample.
The drape stiffness of samples was measured in accordance with ASTM
D1388 except that the sample size is 1 inch by 8 inches.
~5 Bulk (i.e., thickness) of a sample was measured essentially in accordance
with
TAPPI 402 om-93 and T 411 om-89 utilizing a Emveco 200-A Tissue Caliper
Tester.
The tester was equipped with a 56.42 mm diameter foot having an area of 2500
mm2. A stack of 10 samples was tested at a load of 2.00 kPa and a dwell time
of 3
seconds.
3o Abrasion resistance testing was conducted utilizing a TaberAbraser, Model
No. 5130 (rotary head, double head abrader) with Model No. E 140-15 specimen
holder available from Teledyne Taber of North Tonawanda, New York, generally
in
accordance with Method 5306 Federal Test Methods Standard No. 191A and ASTM
18
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Standard: D 3884 Abrasion Resistance of Textile Fabrics. Sample size measured
about 5 inches by 5 inches. Samples were subjected to abrasion cycles under a
head weight of about 250 grams. Each abradant head was loaded with a non
resilient, vitrified, Calibrade grinding wheel No. H-18, medium grain/medium
bond.
Abradant heads were vacuumed after each specimen and resurfaced after each
sample (generally about 4 specimens). Resurfacing of abradant heads was
carried
out with a diamond wheel resurfacer. The abrasion test measured the number of
cycles needed to form a 1/2 inch hole through the sample.
to Example
This example relates to recycling a bonded and entangled composite
material containing natural fibers and synthetic filaments, introducing the
material
into the furnish stream of a wet forming process, depositing the material onto
a
nonwoven continuous filament substrate and then hydraulically entangling the
materials together.
A composite hydraulically entangled material containing virgin wood pulp and
a continuous web of bonded synthetic polypropylene filaments (approximately 20
percent, by weight) (i.e., a spunbond continuous filament web) - available
from the
Kimberly-Clark Corporation, Roswell, Georgia under the trademarks WYPALL~
ao WORKHORSEO manufactured rags and HYDROKNITO fast absorbing materials -
was shredded into pieces ranging from about 10 - 350mm in length and 3 - 70mm
in width. The composite contained approximately 80% by weight pulp and about
percent, by weight, polypropylene filaments. The material was shredded
utilizing a shredder available from the East Chicago Machine Tool Company. The
pieces were transferred to a conventional Hollander-type industrial beater
manufactured by E.D. Jones & Sons, Pittsfield, MA. The beater was a "Number 3
Jones Beating Unit" equipped with a 45 degree diagonal bed plate. The beater
had a rotating roll with blades or vanes generally aligned on the roll. The
blades or
vanes were approximately 1/4 inch (~6 mm) wide, approximately 1/2 inch (~12 to
so 13 mm) high. These were spaced approximately 1/2 inch (~12 to 13 mm) apart
on
the exterior of the roll perpendicular to the direction or plane of rotation.
A fixed
plate was mounted just below the rotating roll and was equipped with blades or
"knives" that were approximately 1/8 inch (~3mm) wide, 1/4 inch (~6 mm) high,
19
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WO 02/38027 PCT/USO1/46761
spaced approximately 3/8 inches (~9 to 10 mm) apart. These were aligned at an
angle of 45 degrees to the direction or plane of rotation.
The rotating roll had a diameter of 72 inches, a width of 72 inches, 192
blades each having a length of 72 inches and spaced one-half inch apart. The
roll
s weighed approximately 16 tons. Generally speaking, the speed of rotation is
constant and the variable that is modified is the pressure or load on the
roll. The
roll was mounted such that a gauge pressure reading of 0 psi corresponded to
very little or no portion of the weight of the roll (~0 tons) counteracting
the force
generated by fibers and pieces of bonded fibrous material as they squeezed as
to they passed through the gap existing between the blades at the bottom of
the
rotating roll and the fixed blades mounted underneath the roll. A gauge
pressure
reading of 50 psi corresponded to approximately one-half of the weight of the
roll
(~8 tons) counteracting the pressure generated fibers and pieces of bonded
fibrous material as they squeezed through the gap existing between the blades
at
15 the bottom of the rotating roll and the fixed blades mounted underneath the
roll. A
gauge pressure reading of 100 psi corresponded to approximately the full
weight.
of the roll (~16 tons) counteracting the pressure generated by fibers and
pieces of
bonded fibrous material as they squeezed through the gap existing between the
blades at the bottom of the rotating roll and the fixed blades mounted
underneath
2o the roll.
Water was added to the shredded material and hydraulic pressure and shear
stress was applied to the material in the Hollander-type beater in two stages.
Hydraulic pressure and shear stress was controlled by adjusting the load on
the
roll as it rotated. In this particular arrangement, hydraulic pressure and
shear
25 stress is generated by a "paddle wheel" type pumping action produced when
the
beater roll rotates and its attached blades or vanes force liquid and wet
material
against a fixed plate with blades mounted diagonally to the direction or plane
of
rotation. Generally speaking, a greater load applied to the rotating roll
produces
less clearance between the rotating roll and the fixed plate. This corresponds
to
3o greater levels of hydraulic pressure and shear stress.
During the first stage, the pressure or load against the rotating roll was 0
pounds per square inch gauge (psig) for 10 minutes: Essentially, no load was
applied and the "paddle wheel" action of the rotating roll squeezed the pieces
in
CA 02426027 2003-04-16
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the suspension through a gap of about 1 cm or more between blades of the
rotating roll and blades mounted on the fixed plate. Generally speaking, the
first
stage was used to wet the shredded material and separate the natural fibers
from
the synthetic fibers. The consistency was adjusted to be about 3.3 percent
(the
s percentage, by weight of air or oven dry fibrous material in the
suspension).
During the second stage, conditions were adjusted to establish small zones
of very high hydraulic pressure, shear stress, and possibly cavitation forces
between the moving blades on the rotating roll and fixed blades near or at
their
closest point of contact. These small zones are thought to generate a micro-
Zo bursting action on the shredded bonded fibrous material to hydraulically
fragment
and/or blow apart and reduce the resulting synthetic fiber length. In
addition, the
hydraulic fragmentation and "metal to fiber" or "metal to bonded fibrous
material"
contact controls the length of the longer synthetic filaments. In this
example, the
specific objective was to control the length of the synthetic fibers so the
length is
i5 maximized while still producing a sheet with uniform appearance and
physical
properties and without materially lowering the length or freeness of pulp
fibers that
may be present in the suspension.
In the second stage, pressure on the gauge for the rotating roll was
increased to 50 psig and the clearance between the blades of the rotating roll
and
ao the fixed plates decreased to between 1 and 10 mm and approximately one-
half of
the weight of the 16 ton roll (~8 tons) was available to counteract the
pressure
generated by fibrous pieces as they were squeezed through the gap between the
roll and the fixed plate. These conditions were maintained for 50 minutes.
After treatment, samples of the free fibers, fiber bundles and fiber-like
materials were examined microscopically. Natural or pulp fibers were separated
and measured separately from the synthetic fibers. In this example, average
fiber
length was determined as previously described - by manually separating a
random
sample of 20 synthetic fibers and 20 pulp fibers, measuring the length of
individual
fibers utilizing a microscope, and then calculating an average length. The
resulting
3o recycled fibers and fiber-like materials had the following characteristics:
~ The average length of the synthetic fiber was approximately the same length
as the wood pulp fibers. Average length of the synthetic fibers was 4.21 mm.
21
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The length of individual fibers in the sample ranged from 2.54 to 7.11 mm. It
should be noted that, prior to processing, the synthetic fibers initially were
substantially continuous polypropylene filaments having indeterminate lengths
or lengths at least far exceeding 7.11 mm. The average fiber length for the
pulp
component was 2.7 mm. The length of individual pulp fibers in the sample
ranged from 1.52 to 3.94 mm.
~ The wood pulp fiber freeness shows a slight reduction (about 10%) indicating
that some additional surface area was developed on the wood pulp fiber
Zo component of the composite. However the fiber length was not affected.
~ Substantial numbers of synthetic fibers have increased surface area as a
result
of the remaining individual fiber bond areas, cross overs, and flat areas.
The treated recycled fiber stream (containing wood pulp fibers and synthetic
fibers) were introduced into the furnish stream of a wet forming process. The
recycled fibers were blended inline with virgin radiata pine pulp fibers (Laja
10
available from CMPC Celulosa of Chile) at a level of 20% by dry weight.
This blend of fibers was formed into a wet sheet having a basis weight of 50
ao grams per square meter (gsm) utilizing a forming wire available from Albany
International under the designation 84M. The wet sheet was then laid on top of
a
layer of continuous filament polypropylene spunbond having a basis weight of
approximately 24 gsm. The two layers were supported on ari hydroentangling
wire
available from Albany International under the designation 90 BH. The layers
were
a5 entangled utilizing five manifolds. Each manifold was equipped with a jet
strip having
one row of 0:005 inch holes at a density of 40 holes per inch. The water
pressure
was 1100 pounds per square inch gauge and the total time the web was exposed
to
pressure was 213 microseconds.
The resulting composite sheet was then dried to a final product. The
3o resulting product was compared to a control hydroentangled material made
with
the same wood pulp and spunbond in the same ratios and under the same
conditions but without the recycled fibers. These results are shown in Table 1
below:
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TABLE 1
PROPERTIES Product Without Product With
Recycled Material20! Recycled
Material
Basis Wt 65.7 sm 66.0 sm
Thickness 12.88 mils 12.64 mils
CD Tra Tear 1068 rams 1070 rams
MD Tra Tear 1805 rams 1868 rams
CD Dra a 3.75 cm 4,21 cm
MD Dra a 6.11 cm. 6.09 cm
Pul Side Abrasion 13.2 c cles 7 c cles
12.
Water Capacity 18.4 grams ~ _
_
19.77 grams
A second run was carried out utilizing the same materials and conditions
except that pressure used to hydraulically entangle the sample containing the
20%
recycled material was increased to 1200 psig. The material was dried in the
same
manner as before. The resulting properties are shown below in Table 2:
1 o TABLE 2
PROPERTIES Product Without Product With
Rec cled Material20%
Rec cled Material
Basis Wt 65.7 sm 63.5.0 sm
Thickness 12.88 mils 12.7 mils
CD Tra Tear 1068 rams 1179 rams
MD Tra Tear 1805 rams 2147 rams
CD Dra a 3.75 cm 4.31 cm
MD Dra a 6.11 cm. 6.16 cm
Pulp Side 13.2 cycles 17.3 cycles
Abrasion
Water Ca acit 18.4 rams 19.10 rams
It is evident from Table 2 that higher entangling pressures may be used with
x5 the recycled fibers. While these samples were entangled utilizing a carrier
fabric or
substrate (i.e., the spunbond webs), it is believed the Examples demonstrate
that
recycled fibers may be entangled without such a carrier fabric or substrate
and
directly on a hydroentangling wire.
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The recycled fibers that have been hydraulically fragmented provide
advantages because they are generally uniform and can be readily hydraulically
entangled into a tough, coherent fabric without the flocks and non-
uniformities of
previous recycled materials formed from bonded fibrous webs. The relatively
distorted, twisted and irregular nature of the recycled materials used in the
present
invention is thought to result in greater efficiency because less material is
washed
out by the high pressure jets. This is believed to be due, at least in part,
to the higher
surface area and fiber morphology causing less fiber loss. The structure of
the
recycled fibers and fiber-like materials offer additional advantages because
they are
io readily adapted to wet-forming processes and have good retention in the
forming
section. Furthermore, the relative ease with which these recycled fibers can
be
processed by wet-forming techniques provides a suitably uniform starting
material
for hydraulic entangling.
A highly uniform fabric offers advantages. A fabric that is highly uniform in
appearance tends to be aesthetically pleasing. Less pulp material and/or
lighter
basis weight substrates may be used without sacrificing the material's ability
to mask
or cover. In some cases, certain tensile properties and other physical
characteristics
may be less likely to have strong variations or localized spots of non-
uniformity.
While the present invention has been described in connection with certain
ao preferred embodiments, it is to be understood that the subject matter
encompassed
by way of the present invention is not to be limited to those specific
embodiments.
On the contrary, it is intended for the subject matter of the invention to
include all
alternatives, modifications and equivalents as can be included within the
spirit and
scope of the following claims.
24
