Note: Descriptions are shown in the official language in which they were submitted.
FABRIC HAVING EXCELLENT WIPING PROPERTIES
The invention relates to a nonwoven fabric having a
valuable combination of properties that makes the fabric
particularly useful as a wiping cloth.
Background of the Invention
Wiping suraces of aqueous liquids is an activity
practiced by virtually everyone, whether at home, at play;
or at work. Among the properties desired of a cloth used
for wiping aqueous liquids are the following:
(a) Sufficient capacity to be able to retain a reasonable
quantity o liquid;
(b) Adequate take-up rate so that spills can be wiped up
within a reasonable period bf time;
(c) Ability to pick up liquid while leaving little or no
residue;
(d) Abrasion resistance appropriate to the end-use
intended for the fabric;
(e) Fabric-like softness or hand so that the cloth is
comfortable to handle;
() Economy (i.e., low cost per use); and
(g) In a cloth having re-use capabilities, resistance to
staining by foods, qrease, and the like.
This invention is directed to a nonwoven fabric that has
these properties.
32~6
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Brief Summary of the Invention
The fabric of the invention comprises a substantially
isotropic web of lightly entangled rayon staple fibers
containing a small amount of adhesive binder substantially
uniformly distributed throughout said web, the amount of
said binder being sufficient to resist wet collapse of
said web, wherein the fabric has an excellent balance of
wiping properties, abrasion resistance, resistance to
staining, and softness or handle characteristics.
According to a further broad aspect, the present invention
provides a non-woven fabric comprising a substantially
isotropic web of rayon staple fibers characterized by -the
web having regions of lightly entangled fibers and also
containing a small amount of adhesive binder substantially
uniformly distributed throughout. The amount of binder
is sufficient to resist wet collapse of the web. The
fabric has an excellent balance of wiping properties,
abrasion resistance and softness. The fabric comprises
two series of fibrous bands that are substantially perpen-
dicular to each other, wherein each band in both series
contains segments in which the individual fibers are all
substantially parallel to each other, which segments
alternate with regions in which the fibers are randomly
entangled. The regions occur where an individual band
of one series intersects an individual band of the other
series, and wherein at regularly spaced intervals between
the individual bands of both of said series there are
openings in the fabric.
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The Prior Art
Brooks, in published British patent application No.
2,045,825A, November 5, 1980, discloses, in Control
Example 2, Run 1, a substantially isotropic web composed
of lightly entangled rayon staple fibers containing about
26 weight per cent, based on fibers plus binder, of
adhesive binder distributed in an intermittent pattern.
Brief Description of the Drawinqs
Fig. 1 is a schematic side elevation of one form of
apparatus suitable for producing the fabrics of the
invention,
Fig. 2 is a photomacrograph, originally taken a-t 5X with
incident light, of one preferred fabric of the invention
(the fabric of Example 2),
Fig. 3 is a photomacrograph similar to Fig. 2, except that
it was taken with transmitted light,
Figs. 4 and 5 are pho-tomacrographs, originally -taken at
lOX, of the fabric of Example 3, and
`` ~.3L 5392~
Figs. 6 and 7 are photomacrographs, originally taken at
lOX, of the fabric of Example 4.
retailed Description of the Invention
Referring first to Fig. 1, a random laid web 10 of rayon
staple fibers is passed onto a liquid pervious support
member, such as an endless woven belt 12. The belt 12
carries the web of fibers 10 under a series of high
pressure, fine, essentially columnar jets of water 14.
The high pressure water is supplied from a manifold 16.
The jets 14 are arranged in rows disposed transversely
across the path of travel of the belt 12. Preferably,
there is a vacuum means 15 pulling a vacuum of e.g., up to
5 to 10 inches of mercury, beneath the belt 12, with a
vacuum slot positioned directly under each row of jets 14.
The fibers in the web 10 are rearranged and entangled by
the jets 14 as the liquid from the jets 14 passes through
the fibrous web 10 and then through the belt 12. The
fabric 18 is carried by the belt 12 over a vacuum
dewatering station 20, and then proceeds to a series of
drying cans 22~
Evans, in ~J.S. Patent No. 3,4~5,706, describes a process
and apparatus for rearranging/entangling fibrous webs by
carrying such webs on a woven belt under a series of high
pressure, fine, columnar jets of liquid. Apparatus of the -
general type disclosed by Evans can be used in the process
oE this invention, although typically the degree of
entanglement contemplated by this invention is much less
than that generally preferred by Evans.
The degree of fiber entanqlement contemplated by this
invention is preferably that obtained by the use of jet
pressures of from about 200 to abo~lt 700 psi, and up to
about 20 to 25 rows of orifices, with the orifices being
` :\ (I j
spaced such that there are about 30 to 50 per linear inch.
The orifices are usually about o.nO5 to 0.007 inch in
diameter. The web is usually positioned about 1/2 to 1-
1/2 inches below the orifices. With web speeds of from
about 8 to about 100 yards per minute, fibrous webs of
from about 1/2 to about 5 ounces per square yard are
conveniently processed.
The Examples below illustrate typical conditions.
ln Selection ox conditions in specific cases is dependent
upon a number of interrelated factors. For instance,
heavier webs usually require more energy to entangle, and
therefore usually require higher pressure and/or more rows
of orifices. Also, the number of rows of orifices
required is directly related to the web speeds. Thus,
slower web speeds (as illustrated in the Examples) require
only a few rows of orifices, while faster speeds require
more rows of orifices. It is within the skill of the art
to select specific entangling conditions for specific
cases. As a general rule, the pressure is maintained
between ahout 50n and 700 psi, and adjustments are made to
web speed and/or number of rows of orifices to control the
degree of entangling.
After the fibrous web 23 has been entangled and then dried
by the drying cans 22, the dried web 23 proceeds to a
honding station 25 wherein an aqueous resin hinder compo-
sition is applied uniformly to the dried web 23, as by a
padder (shown schematically in Fig. 1).
The padder includes an adjustable upper rotatable top roll
24 mounted on a rotatable shaft 26, in light pressure
contact, or stopped to provide a 1 or 2 mil gap between
the rolls, with a lower pick-up roll 28 mounted on a rotat-
able shaft 30. The lower pick-up roll 28 is partially
immersed in a bath 3h of aqueous resin hlnder composition
. .~
38. The pick-up roll 28 has a smooth rubhér surface and
the top roll 24 has a steel surface, which may be smooth
or enqraved. The pick-up roll 28 picks up resin binder
composition 38 and transfers it to the web 23 at the nip
between the two rolls 24,28.
After the web has passed through the padder 25, the
binder-containing web 39 is then subjected to elevated
temperature, as by passing around a set of drying cans 40,
to dry and/or cure the resin binder, and the web l con-
taining the driec and/or cured binder is then collected,
as on a conventional wind-up 42.
It is not essential to dry the web prior to the applica-
tion of binder, as was described above. However, unlessthe vacuum de-watering is quite efficient, better control
over the binder application is obtained by drying the web
before applying binder because there is less dilution of
binder and less migration of binder to the surface of the
web during drying.
The fibers used in the invention are rayon staple fibers,
i.e., rayon fiber; having lengths of at least one-half
inch up to ahout three inches. Some of the rayon fibers
can be replaced with other fibers such as polyester staple
fibers. However, the fibers used are predominantly rayon,
c at least about 70 weight per cent rayon and
preferably at least 80 weight per cent rayon.
The resin binder composition can be the conventional aque-
ous latex compositions, such as acrylic latexes, polyvinyl
acetate latexes, ethylene-vinyl acetate latexes, carhoxy-
lated styrene-butadiene rubher latexes, or the like.
Acrylic latex hinders are preferred for maximum resistance
to staining. One important difference compared with
conventional procedures is that the resin hinder
composition will usually be quite dilute, e.g., prom about
1/2 to about 5 weight per cent solids, when applies by
padding or dipping onto a dry web. Slightly higher solids
may be needed when applying to a wet web.
s
The amount of resin binder employed is a small amount,
e.g., up to about 10 weight per cent, based on weight of
fibers plus binder. The minimum amount is that amount
that is sufficient to impart wet collapse resistance to
the fabric. The exact amount used will depend, to a
degree, on factors such as weight of fabric, presence or
absence of polyester, polypropylene, or other water-
resistant fibers (when polyester fibers are used, the
amount of bincler can be slightly less), exact end use
intended, and the like. The amount o binder used will
usually be within the range of from about 0.8 to about 10
weight per cent, based on fibers plus binder.
An important feature of the fabrics of the invention is
that they are relatively isotropic, that is, their tensile
strengths are not more than ahout three, and preferably
about two, times their tensile strengths in the cross
direction. Such isotropicity is obtained by employing a
random laid web as the starting web 10. Thus, the start-
ing weh can be produced by air laying by known p~oceclures,as by using a "Rando ~ebber" or a clual rotor as disclosed
in U.S. Patent Nos. 3,9h3,392; 3,768,118; 3,7~0,797;
3,772,73n; and 3,895,n89.
3n The fahrics of the invention are relatively bulky, which
enhances their absorbent capacities. Their bulk densities
are usually within the range of from ahout n.n7 to about
~.13 qrams/cc.
..
The examples below illustrate the invention:
Fxample l
Avte~ S~119i3, l.5 denier, l-l/8 inch staple rayon was
processed through an opener/blender and fed to a random
air layinq unit, which deposited a snn 15~ qrains per
square yead web onto a forming belt woven of n. 0157 - inch
diameter polyester monofilaments. It is a dual layer
fabric havinq two superimposed layers each having 42 warp
monofilaments per inch, and 32 shute monofilaments per
inch woven through the warp monofilaments in the following
repeating pattern: under two, between the two, over two,
between the two, etc. It is available commercially rom
Appleton wire Division of Alhany International as Type
5710 Duotex polyester belt.
Using an apparatus similar to that shown in FigO l, the
web was passed under a water weir to wet the fiber, and
was then carried at a speed of 23 yards per minute under
12 orifice strips, each of which contained a row of holes,
sn holes per inch, of o.nO5 inch diameter. water, at
l2nF., was jetted through the holes in the orifice strips
at lOn psi for the first three strips and 600 psi for the
remainder.
The web was dewatered by passing over a vacuum slot, and
then passed over two stacks of steam cans to dry it. The
stacks of steam cans were operated at 90 psi and 85 psi
3n steam pressure, respectively.
The dried weh was then run throuqh a padder similar to the
one shown in the Fix. l, and the following binder
formulation was impreqnated in the web:
l8~
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- Table I -
Table _
Component Weight
Water 360 Pounds
Acrylic Resin Latex( ) 30 Pounds
Antifoarn agent (Y-30) 0.1 Pounds
Wetting agent (NS-5199) 1.4 Pound
Diammonium Phosphate 54 Grams
Ammonia to pH 7-8 As Required
__________________ _________________________________________
(1) National Starch 4260, 51 % solids
_____________________________________________________________
There is about 190 weight per cent wet pick-up in the
padder, based on weight of fibers. The web containing the
binder composition was then passed over two stacks of drying
cans, operated at 60 and 98 psi, respectively.
The finished fabric had a binder content of about 7.5 weight
per cent, based on weight of fibers plus binder, and a grain
weight of about 875 grains per square yard.
Representative properties of this fabric, and properties of
the fabric of Example 2, are displayed below in Table III.
_ ample _
By a procedure analogous to that described in Example 1, a
mixture of 88 weight per cent Avitex SM1913 rayon staple
fibers and 12 weight per cent Celanese Fortrel Type 310,
1.5 denier, 1-1/2 inch staple polyester, was processed
through an opener/blender and fed to a random air laying
unit, which deposited a web having a grain weight of 866 +
15% per square yard onto a forming belt. The forming belt
* Registered trademark
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was woven ox 0.0~0 inch polyester monofilaments in a plain
lxl single layer weave, having 6 warps per inch and 6
shutes per inch. The belt had an open area of 57.8 per
cent.
The processing conditions under the water jets were the
same as in Example 1. After dewatering, the entangled web
was passed over two stacks of steam cans operated at 40
psi.
The dried web was then rum through a padder similar to
that shown in Fig. 1, and the following binder formulation
was impregnated in the web:
Table II
Component Weight
Water 380 pounds
2n IS 4260 Acrylic Latex 3.9 pounds
Antifoam Agent (581-B)(2) 0.2 pounds
Deceresol O.T. Spec.(3) 1.4 pounds
Diammonium Phosphate 0.15 gram
Pigment - Inmont Yellow N2G 9883 0.33 pouncl
Ammonia to pH 7-8 As required
_________________________________________ ________________
(2) 581-B antifoam is a silicone oil.
(3) Deceresol O.T. Spec. is a surfactant (rewe-tting
agent).
___________________________________________________________
The wet pick-up of the hinder composition is 20~ weight
per cent, hased on weight of fibers. The web containing
the hincler composition was then passed over two stacks
of drying cans, the firs-t stack of which was operated at
.
--10--
increasing pressures of 2n to 60 psi, and the second at 90
psi .
The finished fabric had a hinder content of about 1 weight
per cent, based on weiqht of fibers plus binder, and a
qrain weight of ahout ~75 grains per square yard.
This Example 2 illustrates one preferred fabric of the
invention. This fabric is shown in Figs. 2 and 3. It is
characterized by two series of bands 50 and 52 that are
substantially perpendicular to each other. As seen most
clearly in Fig. 3, each band in both series contains seg-
ments in which the individual fibers are all substantially
parallel to each other, which segments alternate with
regions 54 in which the fibers are randomly entangled.
These regions 54 occur where an individual band of one
series 50 intersects an individual band of the other
series 52. Also, at regularly spaced intervals between
the individual hands of both of said series of bands 50
and 52, there are openings or holes 56 in the fabric.
This preferred fabric of the invention is produced by a
procedure analogous to that describecl in Example I', the
significant feature being the -forming belt. The Eorming
belt is a single layer, plain weave belt woven of
monofilaments~
Table III, below displays representative physical
properties of the fabrics of Examples 1 and 2.
Table III
PropertyExample 1 Example 2
~Jei~ht, grains/yd2 875 875
S Softress(1), grams 65 25
Bulk, mils 20 30
Dry Grab Tensile(2), Pounds
RID 18 16.4
CD 13 ll.l
l0 Elongation,
MD20, dry; 2n wet 36, dry; 34, wet
CD80, dry; 60, wet 88, dry; 70, wet
Wet Tensile(2)
MD 8.5 8.2
CD 6 5.8
Absorbent Capacity, %t3) 850 930
Absorbent Time(3), Sec. l.6 1.5
jet Abrasion( 4 ), Cycles
Bottom Side 500 479
20 Launderability(5), cycles 25 5
___________________________________________________________
(l) Standard "Handle-O-Meter" test on a 4-inch square
(Ex. l) or 6-inch square (Ex. 2) sample using a 3/8-
inch slot. Machine direction of fabric is
perpendicular to slot.
(2) l x 6 inch (example l) or 4 x 6 inch (Example 2)
sample tested in an Instron tensile tester at a pull
rate ox 12 inches per minute. One qripper is l inch
wide and the other is l-l/2 inches wide.
(3) Absorhent capacity - A five qram sample of fabric
held in a three gram wire basket is immersed in a
container of tap water. absorbent time is the time
for the sample to sink. The sample is immersed for
25~6 f
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10 more seconds, the hasket with the sample is
removed and allowed to drip for 10 seconds, and is
then weighed. Absorbent capacity is calculated as
follows:
wet weight - dry weight
x 100
dry weight of fabric
0 (4) Standard abrasion test on a 3 x 9 inch sample, using
a 5 pound head weight. "Bottom side" refers to the
side adjacent to the forming belt during the water
jet entangling step
5 ~5) Wash durability - each cycle in the wash durability
test is a complete agitated wash for ln minutes in
hot water at ahout 140F. containing detergent),
rinse yin warm water - about 100F.), and spin cycle
in a Maytag home washing machine containing an eight-
pound load of laundry. The fabric is considered to
fail when it develops a holy anywhere in the fabric.
Two samples of each fabric are used, with the sample
size being at least 13 x 18 inches. An accelerated
test may be used in order to save time. Instead of
10-minute agitated wash cycles, 2-hour, 4-hour, and
24-hour agitated wash cycles may be usecl. The
results reported in Tahle III are the equivalent in
the standard 10-minute wash cycles.
___________________________________________________________
The fahrics of this invention have an excellent combina-
tion of properties that make them useful as wiping cloths.
The data presented in Tahle III, above, illustrate the
excellent combination of softness, ahsorhent capacity,
abrasion resistance, and durability (launderability)
- exhibited by these fabrics. simulated u'se testing has
~9~2~6
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demonstrated that the fabrics resist staining by foods
such as catsup, mustard, coffee, and greasy materials,
so that when the fabrics are used to wipe up such
materials, the fabrics rinse clean with little or no
residual discoloration. This makes the fabrics excellent
for use as wipes in places such as kitchens, restaurants,
fast food establishments, and ice cream counters, wherein
it is advantageous for the fabrics to remain unstained
after repeated uses and rinses.
The absorbent capacity, take-up rate, and the amount of
residue left after wiping (or, more precisely, blotting),
of the fabrics of Examples 1 and 2 were determined using
a gravimetric absorbency tester ("GAT"). The GAT is
described in detail in commonly assigned U.S. patent No.
4,357,827 which issued on November 9, 1982. Briefly,
the GAT is an apparatus for determining the weight and
rate of liquid flowing to or from a test site. The
apparatus comprises, in combination:
A vessel for containing liquid, said vessel being
supported solely by weighing means,
Indicating means for indicating the weight sensed by
said weighing means'
A test surface to receive a specimen to be tested, said
test surface includlng said test site,
Conduit means operatively connecting said vessel to said
test site for directing a flow of liquid between said
vessel and said test site, and
Means -for vertically positioning said test site.
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The liquid used was water, and the test surface used for
determining absorbent capacity and take-up or absorbency
rate was a flat plate with a point source of liquid
connected to the vessel.
To determine the residue left after wiping, the test
surface used was a flat glass plate having a 6 centimeter
in diameter circular test area circumscribed by a groove
in the surface of the glass. A quantity of water equal to
10 5n per cent of the calculated ahsorbent capacity of the
specimen to be tested was placed in the test area. The
specimen (10 centimeters in diameter), mounted on a flat,
circular specimen holder 8 centimeters in diameter was
brought into contact with the test area containing the
water. A contact pressure of about 3.5 gramsjcm2 was
used, and the contact time was about 30 seconds. The test
specimen was then removed, and the weight of the residue
was determined.
The results of these three tests are shown below in
Table IV:
Table IV
Absorbent Absorbency Residue,
Capacity - Rate- gm.
weight of gm/gm/sec
water absorhed
divided hy weight
3n of fabric)
example 1 66n 0.11 0.01
Example 2 790 0.11 0.01
For comparison purposes, the tested values for several
other types oE wipes are displayed below in Table V:
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Table V
Absorbent Absorbency Residue,
Capacity Rate- gm.
gm/qm/sec
Paper Towel 880 0.17 n.n4
(Bounty)
woven Terry 485 0.07 0.02
Towel
Scott Paper 690 0.13 0.23
(Toilet tissue)
Examples 3 and 4
By a procedure similar to that described in Examples 1 and
2 (with the differences dlscussed below), two fabrics were
made from blends of 70 weight per cent Enka 8172 rayon
20 staple (1-1/4 inches; 1.5 denier) and 30 weight per cent
Celanese Fortrel Type 310 polyester staple. The total
weight of the weh was 600 + 10% grains per square yard.
Two different forming belts were use. Roth were plain
lxl single layer weaves woven of monofilament. The thread
counts and monofilament sizes were as follows:
Table VI
Warp Shute
Threats Filament Threads Filament
per inch Diameter, per inch Diameter,
mils mlls
example 3. 12 28 12 28
35 Example 4 22 20 24 17
.
... ...... ... . .. , .
96.
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All the threads were polyester monofilaments, except for
the shute in Example 4, which was stainless steel.
The conditions under the wa-ter jets were similar to that
of Example l, except that only 6 instead of 9 strips at
600 psi were used.
After dewaterinq, the weh was passed over two stacks of
steam cans operated at 20 and 40 psi, respectively.
The dried web was then run through a bonding station that
differed from the padder shown in Fig. 1 in the following
respects:
lS The pick-up roll was an enqraved steel roll engraved with
a pattern of 23 continuous lines per inch. The lines were
inclined 15 from the long axis of the roll. Each line
was 4 mils deep and 18 mils wide, The top roll had a hard
rubber face and it was wrapped with a 3/4-inch thick layer
of open celled urethane foam. The two rolls were stopped
to a gap of l or 2 mils. A doctor blade was used to wipe
excess binder formulation from the pick-up roll. The
ollowing hinder formulation was applied:
Table VII
Component Weiqht,pounds
Water 434.1
Oiammonium Phosphate n.75
30 ~nti-~oa~ aqent (y-3n) 0.0l
Acrylic resin latex(l) 14.85
~eceresol OT 0.45
___________________________________________________________
3S (l) Rohm & Elaas ~IA-8
___________________________________________________________
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jet pick-up was 100 weight per cent. The Eabric was then
dried by passing over two stacks of steam cans operated at
40 psi. The finished fabric had a binder content oE about
1.5 weight per cent, base on weight of fibers plus
binder, with the binder beinq dis-trihuted substantially
uniformly throughout the webs.
The two fabrics had very similar physical properties.
Representative physical properties are shown below in
Table VIII:
Table VIII
Weight, grains/yd 612
Bulk, mils 80
Softness, grams 24
Dry Tensile, Pounds
MD 15
CD 11
2~ ret Tensile, Pounds
MD 12
CD 8
Dry Elongation, %
MD 30
CD 85
Absorbent Capacity, % 660
Absorbent Time, seconds 1.5
(The tensile tests were carried out on 4x6 inch samples.)
Figs. 4 and 5 show the fahrlc of Example 3 and Figs. 6 and
7 show the fabric of Example 4. As can best be seen in
Fiqs. 5 and 7, which were taken with transmitted light,
the fabrics have the same hasic morphology as the fabric
of Example 2, differinq only in scale.
