Note: Descriptions are shown in the official language in which they were submitted.
WO 2004/097095 CA 02523499 2005-10-24 PCT/US2004/010198
SCOURING MATERIAL
The present invention relates to nonwoven fibrous scouring materials suitable
more
especially, but not exclusively, for domestic use.
BACKGROUND
Scouring materials for domestic use are produced in many forms, including
nonwoven
webs (for example, the low density nonwoven abrasive webs described in US-A-2
958
593). Following manufacture, a web of scouring material may be cut into
individual pieces
of a size suitable for hand use (for example, the individual rectangular pads
described in
US-A-2 958 593) or it may be left to the end user to divide the web into
pieces of a
convenient size when required (as described, for example, in WO 00/006341 and
US-A-5
712 210).
Other domestic scouring pads formed using nonwoven web materials are known,
for
example the pads described in US-A-2 327 199, 2 375 585 and 3 175 331.
Nonwoven
hand pads for more general abrasive applications are also known and include,
for example,
the hand pads available under the trademark "Scotch-Brite " from 3M Company of
St.
Paul, Minnesota, USA.
Preferred nonwoven fibrous scouring materials are low density, open materials
having a
comparatively high void volume. Scouring materials of that type exhibit an
effective
cleaning action (because the voids retain material removed from a surface that
is being
cleaned) but are themselves easily cleaned simply by rinsing in water or some
other
cleansing liquid so that they can be re-used. Despite that, many scouring
materials
employed in the domestic environment are intended for limited re-use only,
following
which they are discarded. From a hygiene standpoint, discarding such products
before they
become contaminated is to be recommended since they are frequently used for
cleaning
kitchen work surfaces as well as cooking and eating utensils. However, as
consumers
become increasingly concerned with environmental issues, they are increasingly
reluctant
to use disposable products unless they know that they can be recycled or will
degrade
CA 02523499 2005-10-24
WO 2004/097095 PCT/US2004/010198
quickly without producing harmful by-products. For this reason, there is
growing interest
in the use of products based on natural materials for domestic cleaning.
Scouring materials formed solely from natural vegetable fibres are known and
include, for
example, traditional scourers formed from the fibrous parts of gourds or palm
leaves. Such
scouring materials will degrade in an environmentally-acceptable manner but
suffer from
the disadvantage that, when made in the traditional manner, they cannot be
mass produced
to a uniform standard. Moreover, natural vegetable fibres have little or no
resilience
(unlike the crimped synthetic fibres that are used to manufacture nonwoven
abrasive/scouring materials) so that, even if they are processed into a more
uniform
nonwoven web, it is difficult to incorporate abrasive mineral into the web
without
crushing the fibres and, as a result, compacting the web to an undesirable
extent.
Consequently, domestic scouring materials formed from natural fibres have
tended to be
less attractive to the consumer than those that are formed from synthetic
fibres.
SUMMARY
The present invention provides a scouring material comprising
a three-dimensional non-woven web of entangled fibres bonded to one another at
their
mutual contact points by a pre-bond resin, wherein a majority by weight of the
fibres
comprise natural fibres, and the bonded web has a maximum density of 50 kg/m3
(preferably 30 kg/m3) A plurality of abrasive particles are adhered to the
fibres of the
bonded web by a make-coat resin.
The present invention also provides a method of making a scouring material
comprising
the steps of: 1) forming a three-dimensional nonwoven web of natural fibres
contacted
with dry particulate material that includes fusible binder particles, 2)
exposing the web to
conditions that cause the binder particles to form a flowable liquid binder,
and then
solidifying the liquid binder to form bonds between the fibres of the web and
thereby
provide a pre-bonded web and 3) applying abrasive particles to the pre-bonded
web and
bonding the abrasive particles to the fibres of the pre-bonded web by at least
a make-coat
resin to provide the scouring material.
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The present invention also relates to a scouring material comprising: a three-
dimensional non-
woven web of entangled fibres bonded to one another at their mutual contact
points by a pre-
bond resin, wherein at least 80% by weight of the fibres comprise natural
fibres, and the
bonded web has a maximum density of 50 kg/m3; and a plurality of abrasive
particles adhered
to the fibres of the bonded web by a make-coat resin.
The present invention also relates to a method of making a scouring material
as described
herein, comprising the steps of (i) forming a three-dimensional nonwoven web
of natural
fibres contacted with dry particulate material that includes fusible binder
particles;
(ii) exposing the web to conditions that cause the binder particles to form a
flowable liquid
binder, and then solidifying the liquid binder to form bonds between the
fibres of the web and
thereby provide a pre-bonded web; and (iii) applying abrasive particles to the
pre-bonded
web, and bonding the abrasive particles to the fibres of the pre-bonded web by
at least a
make-coat resin to provide the scouring material.
The present invention also relates to a method of making a scouring material,
comprising the
steps of (i) forming a three-dimensional nonwoven web of entangled fibers,
wherein majority
by weight of the fibers comprise natural fiber (ii) contacting the web with
dry particulate
material that includes fusible binder particles; (iii) exposing the web to
conditions that cause
the binder particles to form a flowable liquid binder, and then solidifying
the liquid binder to
form bonds between the fibers of the web forming a pre-bonded web with a
maximum density
of 50 kg/m3; and (iii) applying abrasive particles to the pre-bonded web, and
bonding the
abrasive particles to the fibers of the pre-bonded web by at least a make-coat
resin.
2a
WO 2004/097095
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Brief Description of the Drawings
By way of example only, scouring materials in accordance with the invention
and methods
for their manufacture will now be described with reference to the accompanying
drawings,
in which:
Fig. 1 is a view of a scouring pad in accordance with the invention;
Fig. 2 illustrates, diagrammatically and on an enlarged scale, the structure
of a scouring
pad in accordance with the invention;
Fig. 3 is a schematic illustration of a method of making the scouring material
of Fig. 1;
and
Fig. 4 illustrates a modification of part of the method of Fig. 3.
The present invention is directed to the problem of providing a scouring
material that is Detailed Description
capable of providing an effective cleaning action in the domestic environment
and, at the
end of its effective life, can be discarded in the knowledge that it will
degrade in an
environmentally-friendly manner.
The present invention provides a scouring material comprising an open, lofty,
three-dimensional noi
woven web of entangled fibres that are bonded to one another at their mutual
contact points by a pre
bond resin, wherein a majority by weight of the fibres comprise natural fibres
A plurality of abrasiv(
particles are adhered to the fibres of the bonded web by a make-coat resin.
The terms "open" and "lofty" indicate that the bonded web is of comparatively
low
density, having a network of many, relatively large, intercommunicated voids
that
comprise the greater amount (more than 50%, preferably substantially more than
50%) of
the volume occupied by the web. In the context of the present invention, the
terms indicate
that the bonded web has a density no greater than 50 kg/m3, preferably no
greater than 30
kg/m3. Preferably, the bonded web has a minimum thickness of 5 mm.
It has been found that a scouring material in accordance with the invention is
capable of
providing an effective scouring action despite the fact that the natural
fibres from which it
is mainly composed are traditionally associated with non-woven materials
having a low
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WO 2004/097095 CA 02523499 2005-10-24 PCT/US2004/010198
void-volume and/or a low abrasive action. After use, the scouring material can
be
discarded in the knowledge that the fibres (which are the major component of
the material)
will degrade in an environmentally acceptable manner.
Referring to the Figures, the generally rectangular scouring pad 1 shown in
Fig. 1 is
intended for hand use and comprises a three-dimensional non-woven web of
entangled
fibres 3 (see Fig. 2) that are bonded to one another at their mutual contact
points. The
bonded web preferably has a minimum thickness of 5 mm and a maximum density of
50
kg/m3 (more preferably, 30 kg/m3).
The fibres 3 of the pad 1 are bonded to one another at their mutual contact
points 5 by a
pre-bond resin as described below, and the pad additionally contains abrasive
particles 7
that are adhered to the fibres by a make-coat resin, as also described below.
The fibres 3 comprise at least 80% by weight of natural fibres, preferably
vegetable fibres
such as coco, sisal, and hemp fibres. Other natural fibres that could be used
include those
of cotton, jute, flax and wool. When synthetic fibres are present, they can be
made of any
suitable material including polyester (e.g., polyethylene terephthalate),
polyamide (e.g.,
hexamethylene adipamide, polycaprolactum and aramids), polypropylene, acrylic
(formed
from a polymer of acrylonitrile), rayon, cellulose acetate, polyvinylidene
chloride-vinyl
chloride copolymers, and vinyl chloride-acrylonitrile copolymers, as well as
carbon fibres
and glass fibres. The fibers used may be virgin fibers or waste fibers
reclaimed from
garment cuttings, carpet manufacturing, fiber manufacturing, or textile
processing, and so
forth.
The pre-bond resin by which the fibres 3 are bonded to one another at their
mutual contact
points 5 is selected to provide the scouring material with good strength and
water/heat
resistance. The binder materials may be selected from among certain
thermosetting resins,
including formaldehyde-containing resins, such as phenol formaldehyde, novolac
phenolics and especially those with added crosslinking agent (e.g.,
hexamethylenetetramine), phenoplasts, and aminoplasts; unsaturated polyester
resins;
vinyl ester resins; alkyd resins, allyl resins; furan resins; epoxies;
polyurethanes; and
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WO 2004/097095 CA 02523499 2005-10-24 PCT/US2004/010198
polyimides. The binder materials may also be selected from among certain
thermoplastic
resins, including polyolefin resins such as polyethylene and polypropylene;
polyester and
copolyester resins; vinyl resins such as poly(vinyl chloride) and vinyl
chloride-vinyl
acetate copolymers; polyvinyl butyral; cellulose acetate; acrylic resins
including
polyacrylic and acrylic copolymers such as acrylonitrile-styrene copolymers;
and
polyamides (e.g., hexamethylene adipamide, polycaprolactum), and copolyamides.
Preferably, the pre-bond resin 5 is an epoxy, or a polyurethane, or a co-
polyamide resin.
Mixtures of the above thermosetting and thermoplastic resins may also be used.
The abrasive particles 7 can be of any type known to be suitable for use in
scouring pads,
taking into account the nature of the surfaces to be cleaned and the abrasive
action desired.
Included among the suitable abrasive materials are particles of inorganic
materials, for
example aluminum oxide including ceramic aluminum oxide, heat-treated aluminum
oxide
and white-fused aluminum oxide; as well as silicon carbide, tungsten carbide,
alumina
zirconia, diamond, ceria, cubic boron nitride, silicon nitride, garnet, and
combinations of
the foregoing. It is contemplated that abrasive agglomerates may also be used
in the
invention such as those described in U.S. Pat. Nos. 4,652,275 and 4,799,939.
Suitable
abrasive particles also include softer, less aggressive materials such as
thermosetting or
thermoplastic polymer particles as well as crushed natural products such as
crushed nut
shells, for example. Suitable polymeric materials for the abrasive particles
include
polyamide, polyester, poly(vinyl chloride), poly(methacrylic) acid,
polymethylmethacrylate, polycarbonate, polystyrene and melamine-formaldehyde
condensates. The abrasive particles preferably will have a particle size small
enough to
allow penetration of the particles into the interstices of the nonwoven
fibrous web 1.
The make-coat resin can be any resin known to be suitable for use as a make-
coat in
scouring materials, including water-based resins. Preferred binders include
phenolic resins
(more especially, for example, for harder-wearing scouring materials) and
latex resins
(more especially, for example, for scouring materials for non-scratch bathroom
cleaning).
5
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60557-7406
A first process for making the scouring pad of Fig. 1 is illustrated in Fig_
3, and will now
be described_ A process of this type is also described in WO 2004/096494.
If the selected fibres 3 are provided in bales, the latter are first opened.
The fibres are then
supplied to web-forming equipment 12 in which they are formed into a dry-laid,
open,
lofty, three-dimensional nonwoven web 13. A preferred type of nonwoven web is
an air-
laid web as described in US-A-2 958 593, in which case the web-forming
equipment 12
may be a commercially-available .Rando-Webber device, such as obtained from
Randoml
Machine Co., Macedon, N.Y., and the lengths of the fibres 3 are preferably
within the
range 3 ¨ 30 cms. The web 13 is preferably formed with a minimum thickness of
5 mm
and a maximum density of 50 kg/m3(more preferably, 30 kg/m3).
The nonwoven web 13 is then fed into a powder coating booth 14 where it is
contacted by
a particulate pre-bond resin 15 supplied from a fluidizing hopper 16. Optional
dry particle
additives (such as pigment powder and flow aids) that are to be applied to the
nonwoven
web 13 at this stage may be mixed with the resin particles 15 in the hopper
16. The
nonwoven web 13 is conveyed through the powder-coating booth 14 on a grounded,
electrically-conductive, open mesh conveyor 17 and the particulate resin 15 is
directed at
it from an electrostatic powder spray gun 18, of a type known for use in
powder coating
applications, which is located above the web_ The resin particles 5 will
penetrate the whole
thickness of the web 13, under the combined effects of electrostatic
attraction, gravity and
the flow of atomizing air from the spray gun 18. Any resin powder that passes
through the
web 13 and the conveyor belt 17 is collected at the bottom of the booth 14 and
can be re-
used.
If desired, the web 13 can now be turned over and conveyed for a second time
through the
powder coating booth 14 to increase the amount of resin powder 15 that is
loaded into the
web at this stage.
The pre-bond resin 15 in the web will subsequently be activated, as described
below, to
form bonds between the fibres of the web and thus provide a pre-bonded web to
which
abrasive particles are subsequently applied. The resin particles 15 should
therefore be
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WO 2004/097095 CA 02523499 2005-10-24 PCT/US2004/010198
selected having regard to the nature of the web fibres and the subsequent
processing steps
to which the pre-bonded web will be subjected, and having regard also to the
desired
properties of the scouring material that is to be produced.
Particulate resins suitable for use in bonding nonwoven webs are known, and
include
thermosetting and thermoplastic powders that are activated by heat, as well as
powders
that are activated other ways (for example, by moisture). Particulate
materials suitable for
bonding nonwoven webs for various purposes are described, for example, in US-A-
4 053
674, 4 457 793, 5 668 216, 5 886 121, 5 804 005, 5 9767 244, 6 039 821, 6 296
795, 6 458
299, and 6 472 462. The particulate binder materials suitable for use in the
manufacture of
scouring materials are those that will provide the scouring materials with
good strength
and water/heat resistance and are capable of being activated without damaging
the web
fibres. Preferred binder materials, as described above, are epoxy,
polyurethane and co-
polyamide particulate resins.
The resin particles 15 should be of a size suitable for use in the spray gun
18, and should
be small enough to ensure that they can penetrate into the interstitial spaces
between the
fibres of the web 13. Preferably, they have a particle size no greater than
200 micrometers.
To minimize wastage, the amount of resin particles 15 applied to the web 13 in
the powder
coating booth 14 should be adjusted to the minimum amount consistent with
providing
adequate bonding of the web.
The powder-containing nonwoven web 19 from the booth 14 is then exposed to
conditions
that will liquefy the resin particles to a flowable condition, following which
the resin is
cured to form bonds between the web fibres. For example, if the resin is a
heat-activated
thermosetting material (for example, a powdered epoxy resin), the web 19 is
passed
through the oven 20 in which it is heated first to liquefy the resin so that
it will coat the
web fibres, and then to cure the resin so that it will bond the fibres
together at their mutual
contact points. If, as another example, the resin is a thermoplastice material
the web 19 is
passed through the oven 20 simply to liquefy the resin so that it will coat
the web fibres
following which the web is allowed to cool so that the resin solidifies and
binds the web
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WO 2004/097095 CA 02523499 2005-10-24 PCT/US2004/010198
fibres together at their contact points. In each case, the resin should be
selected to ensure
that the web will not be damaged by the temperatures to which it is exposed at
this stage.
When the pre-bonded web 21 has cooled, it is passed through a first spray
booth 22 in
which one surface of the web is sprayed with a slurry 23 of the abrasive
particles 7 mixed
with a liquid make-coat resin which is subsequently cured by passing the web
through an
oven 24. The web then passes through a second spray booth 25 in which the
other surface
of the web is sprayed with the same abrasive-resin slurry which is then cured
in a second
oven 26. Preferred abrasive particles are corundum and poly(vinyl chloride)
particles and
preferred resins are phenolic and latex resins, although other abrasive
materials and make
coat resins mentioned above could be used. Additives such as fillers and
pigments may
also be included used in the abrasive-resin slurry, if desired.
In an alternative to the arrangement just described, the second spray booth 25
and the
second oven 26 are omitted and, instead, the web 21 is turned over when it has
left the
oven 24 and is conveyed again through the spray booth 22 so that the other
side of the web
can be sprayed with the slurry 23. The web is then passed for a second time
through the
oven 24.
In either case, the resulting nonwoven scouring web can then be converted
(following
storage, if required) into scouring pads 1 as shown in Fig. 1.
Various other modifications can be made to the process described above and
illustrated in
Fig. 3. For example, the web-forming equipment 12 could be one that produces a
dry-laid
web by carding and cross-lapping, rather than by air-laying, and the powder-
coating booth
14 could be replaced by other equipment known to be suitable for achieving an
even
distribution of powder resin throughout the web (for example, equipment
employing a
metering roll (e.g., a knurled roll powder applicator), powder spraying or
sifting, or a
fluidized bed, or the like may be successfully employed).
It is also possible to modify the manner in which the abrasive particles 7 are
applied to the
pre-bonded web 21. For example, instead of mixing the abrasive particles with
a liquid
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WO 2004/097095 CA 02523499 2005-10-24 PCT/US2004/010198
binder composition to form a slurry, the liquid binder composition may be
applied alone to
the pre-bonded web (for example, by spraying or by roll-coating) following
which the
abrasive particles can be drop coated, sprinkled, sprayed, or the like, in a
dry condition
upon a surface of the web, for example by conveying the web beneath an
abrasive particle
dispenser. The binder composition is then cured to bind the abrasive particles
to the fibres
of the web. As a further alternative, the abrasive particles may be blended
with a powdered
resin binder, the blend then being applied in dry form to the pre-bonded
nonwoven web.
As a further modification, an additional resin layer may be applied to the web
after the
abrasive particles 7 have been attached. This optional resin layer (also known
as a size
coat) will serve to consolidate the nonwoven scouring material and increase
its wear
resistance.
In another modified version of the method illustrated in Fig. 3, the
particulate pre-bond
resin 15 is mixed with the web fibres 1 prior to the formation of the nonwoven
web in the
web-forming equipment 12. In that case, the powder-coating booth 14 is
omitted. In yet
another modified version, the powder-coating booth 14 is replaced by the
equipment
illustrated in Fig. 4, comprising a powder scattering unit 30 and a powder
impregnation
unit 31. In that case, the web 13 from the web-forming equipment 12 passes
into the unit
30, where the particulate pre-bond resin 15 (together with any optional dry
particle
additives) is distributed evenly from a dispenser 32 over the upper surface of
the web. Any
resin that happens to pass through the web is collected at the bottom of the
unit 30 and can
be re-used. The web then passes into the impregnation unit 31, where it passes
between
two electrode plates 33 across which an alternating voltage is applied: the
effect of this is
to distribute the resin powder 15 throughout the thickness of the web,
following which the
web passes to the oven 20 as in Fig. 1. Brushes 34, contacting the upper and
lower
surfaces of the web are located downstream of the impregnation unit 31 to
remove any
excess resin powder, which can be collected and re¨used.
A method of the type illustrated in Fig. 4 is described in EP-A-0 914 916,
while a further
alternative method of contacting a fibrous web with a powder is described in
EP-A-0 025
543.
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The use of a particulate pre-bond resin 15 as described above enables an open,
low-
density, bonded nonwoven web 21 to be produced despite the fact that the web
is
constructed from fibres that are much less resilient than the crimped
synthetic fibres that
are normally used to form nonwoven fibrous webs for scouring materials and
abrasive
materials generally. The particulate resin 15 can be distributed in the
unbonded web 13
without any compressive force being applied to the web_ A compressive force on
the un-
bonded web 13, such as would occur if the resin were applied to the web in
liquid form by
roll coating or even by spraying, would result in the web being compacted and
make it less
effective, or even ineffective, for use as a basis for a nonwoven scouring
material. Once
the fibres have been bonded by the particulate resin 15, however, the web 21
is able to
withstand the compressive forces that might arise during the application of
the abrasive
particles 7 and the make-coat resin.
Methods of producing scouring materials in accordance with the invention are
described in
greater detail in the following non-limiting examples. All parts and
percentages are by
weight unless indicated otherwise.
EXAMPLES
The examples used the following materials, equipment and test methods. -
Materials
TM
Epoxy resin powder: Beckrypox AF4 low temperature cure black thermoset powder
(mean particle size 35 microns) from Dupont of Montbrison, France.
TM
Copolyamide resin powder: Vestamelt 350 PI thermoplastic powder 0-80 microns
from Degussa of Marl, Germany
Powder flow aid: Aerosil 200 hydrophilic fumed silica powder from Degussa of
Marl, TM
Germany. -
Sisal fibre: cut fibre from Caruso of Ebersdorf, Germany.
Coco fibre: cut fibre from Caruso of Ebersdorf, Germany.
Poly(vinyl chloride) particles: Etinox 631 from Aiscondel, Spain
TM
= 10
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Corundum particles: Very fine grade (average particle size approximately 50
microns)
brown fused aluminium oxide from Pechiney, France.
Latex resin: Styrofan ED609 from BASF, Spain.TM TM
TM
Cross-linking agents: (i) Cymel 303 and (ii) Cymel 307 from Dyno Cytec,
Norway.
Phenolic resin: "7983SW" from Bakelite AG of Iserlohn-Letmathe, Germany.
Equipment
Fiber opener: available from Laroche of Cours La Ville, France_
"Rando Webber": an air-lay nonwoven web forming machine available from Rando
Machine Co. of Macedon, NY, USA.
Web humidifier: a water spray head of a type used for room humidification,
available
from Hydrofog of Chanteloup les Vignes, France. TM
Powder coating equipment: Nersaspray IC electrostatic spray gun(s) from
Nordson of
Westlake, Ohio, USA, installed in a powder coating booth (also available from
Nordson)
and directed downwards towards a 30 cm wide horizontal metallic open mesh
conveyor
belt, which was electrically-grounded. The/each gun was fitted with a 2.5 mm
flat spray
nozzle. The powder coating booth was provided with a fluidizing hopper to
contain
powder (the hopper being fitted with a venturi pump to supply the powder to
the gun(s)); a
recovery drum to collect waste powder at the bottom of the booth; and an air
control unit
for regulating the supply of fluidizing air to the hopper, and of flow and
atomizing air to
the pump and gun(s). The hopper, pump and recovery drum are all available from
Nordson. The powder booth incorporated features that enabled the safe handling
of fine
powders (including air extraction through cartridge and HEPA filters, and a
fire detection
system).
Infra-red oven: a Curemaster Supeli.4 oven with three 1 kW short-wave infra-
red heaters,
available from Trisk of Sunderland, Tyne and Wear, UK.
Through-air ovens: a gas oven (4 meters long) and an electric oven (2 meters
long), both
available from Cavitec of Munchwilen, Switzerland.
Abrasive spray equipment: a spray booth equipped with one reciprocating spray
gun,
available from Charvot of Grenoble, France; and a spray booth equipped with
four guns,
available as Model 21 from Binks of Illinois, USA.
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Example 1
A 30 cm wide air-laid nonwoven web weighing 190 g/m2 was formed from the sisal
fibres
on the "Rando Webber" machine at a rate of 2 m/min. The fibre bales had
previously been
pre-opened using the Laroche fibre opener. The web was conveyed in line
through the
powder coating booth on the open mesh conveyor belt, where copolyamide resin
powder
(blended with 0.5% by weight of flow aid) was directed at the web by two
"Versapray II"
spray guns, arranged one behind the other, that were fixed 30 cm above the web
and
inclined on opposite sides of the vertical at an angle in the range of 20 -
30 . The resin
powder was supplied to the guns from the hopper, in which it was fluidized
until gently
bubbling using air at a pressure of 1.5 bar. The air pressure settings for the
gun were 2 bar
for the flow air and 1 bar for the atomizing air, and the maximum voltage (100
kV) was
applied. Resin powder was deposited in the web at a weight of about 60 g/m2
and any
resin powder that passed through the web was collected in the recovery drum,
positioned
underneath the open mesh conveyor belt. The powdered web was then heated in
line, first
in the infra-red oven at a temperature in the range of 150 ¨ 160 C with the
heaters
positioned 3 cm above the web to pre-set the resin powder and then in the
electric oven at
a temperature of 160 C using a low-speed setting for the recirculating air.
The total
residence time in the oven was 1 min.
The web was then turned over and conveyed again through the powder coating
booth and
the ovens with the other surface of the web uppermost.
Poly(vinyl chloride) particles were then applied to the bonded web in the
following
manner. An abrasive-resin slurry was prepared by mixing together thoroughly
the particles
(25%) and the latex resin (68.5%) with the cross-linking agents (1.2% of (i)
and 5.3% of
(ii)). The slurry was then transferred to the supply tank of the spray booth
having a single
spray gun. The bonded web was passed through the spray booth at a speed of 2
m/min, and
sprayed on one side with the slurry from the gun which was reciprocated across
the web to
ensure even coverage of the web with the slurry at a coating weight of about
300 g/m2.
The web was then passed through the gas oven in which it was heated at 180 C
for 2 min.
to cure the latex resin. The web was then turned over and conveyed again
through the
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spray booth so that it was sprayed with slurry on the other side in the same
manner. It was
then again passed through the gas oven.
The resulting nonwoven scouring web contained 150 g/m2 of the poly(vinyl
chloride)
particles and was cut into pads having dimensions of about 75 x 90mm.
Example 2
Example 1 was repeated, with the following modifications:
The nonwoven web weighed 150 ¨ 170 g/m2 and was formed from the coco fibres on
the
"Rando Webber" machine at a slower rate (1 m/min) to enable the curing time
for the
resin powder to be increased (see later). Before entering the powder coater,
the web was
humidified to increase its conductivity and, thereby, its uptake of resin
powder. The web
was humidified using the water spray head which was supplied with water at a
pressure of
1 bar and atomizing air at a pressure of 2.5 bar. The powder coater used a
single
"Versapray II" spray gun to direct the epoxy resin powder at the web from a
distance of 30
cm. The resin powder was fluidized in the hopper of the powder coater using
air at a
pressure of 1.8 bar. The air pressure settings for the guns were 1 bar for the
flow air and
0.8 bar for the atomizing air. Resin powder was deposited in the web at a
weight of 250
g/m2. The infra-red heater was omitted and the powdered web was heated in the
electric
oven only, at a temperature of 170 C for 2 min., using a low speed setting for
the
recirculating air.
Corundum particles were then applied to the bonded web in the following
manner. An
abrasive-resin slurry was prepared by mixing together thoroughly the particles
(25%) and
the phenolic resin (75%). The slurry was then transferred to the supply tank
of the spray
booth having four spray guns. The bonded web was passed through the spray
booth at a
speed of 2 m/min, and sprayed on one side with the slurry from the guns to
provide even
coverage of the web with the slurry at a coating weight of about 230 ¨ 260
g/m2. The web
was then passed through the gas oven in which it was heated at 180 C for 2
min. to cure
the phenolic resin. The web was then turned over and conveyed again through
the spray
booth so that it was sprayed with slurry on the other side in the same manner.
It was then
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WO 2004/097095 PCT/US2004/010198
again passed through the gas oven to yield a nonwoven scouring web which was
cut into
domestic scouring pads.
Results
Samples of the domestic scouring pads resulting from Examples 1 and 2 were
used for
cleaning soiled dishes in a simulated domestic environment and, based on a
visual
assessment, were found to offer a performance comparable to that of
conventional
synthetic scouring pads and, generally, better than that of traditional
scouring pads made
from natural fibres.
An advantage of the processes described in Examples 1 and 2 is that no
volatile organic
compounds (VOCs) are produced in the formation of the pre-bonded webs 21. In
addition,
the energy required in these processes to produce the pre-bonded webs may be
less than
that required if a liquid pre-bond resin were used. Consequently, the
environmental effects
of the processes can be substantially less than those conventionally used to
produce
synthetic scouring materials.
The scouring pads produced by the processes of Examples 1 and 2 offer the
advantage that
they can more easily be recycled after use since they are formed using natural
vegetable
fibres. Despite that, the homogeneity of the scouring pads is high compared
with
traditional natural fibre scourers making it possible to offer, to the
consumer, an
environmentally-friendly but comparatively standardized product. In addition,
the
scouring pads exhibit the advantageous openness of both traditional natural
fibre scourers
and conventional synthetic scourers, together with the abrasive performance of
the latter.
These advantages are considered to be a consequence of the fact that the
scouring pads
comprise a mechanically-formed (dry-laid) web of natural fibres which is pre-
bonded in a
way that does not involve the web being subjected to pressure (e.g. as a
result of contact
by rollers) that could irreversibly compress or damage the web fibres.
It will be appreciated that, although the above Examples describe the
manufacture of
domestic scouring pads, other scouring materials and articles could be
produced in a
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similar way with appropriate changes where necessary in the materials and
process steps
employed.
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