Note: Descriptions are shown in the official language in which they were submitted.
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
Moulding Mixture for Manufacture of Mouldable Product
Field of the invention
The invention relates to a moulding mixture for manufacture of mouldable
products. More
particularly, this invention relates to a moulding mixture for manufacturing
products from
plant ~ fibers.
Background of the invention
In this specification, where a document, act or item of knowledge is referred
to or
discussed, this reference or discussion is not an admission that the document,
act or item of
1o knowledge or any combination thereof was at the priority date, publicly
available, known
to the public, part of common general knowledge, or known to be relevant to an
attempt to
solve any problem with which this specification is concerned.
Whilst the following discussion concerns moulding mixtures suitable for
moulding
products such as containers, protective packaging and shock absorbing
packaging it is to be
15 understood that the same principles apply to any products manufactured
according to the
present invention from plant matter including table tops, cups, take-away food
containers,
partitions, packing materials, golf tees and all products comprising either a
flat piece or a
container. A product formed using the moulding mixture of the invention may be
of any
convenient shape and may optionally include partitions or protrusions.
20 Many currently used products are made from plastics and petroleum based
derivatives or
natural wood. Plastics materials do not degrade and cannot be disposed of
effectively.
Such materials may be collected and often recycled. However, recycling does
not
completely solve the environmental problems posed by many plastics because the
breakdown of these compounds releases harmful gases into the atmosphere.
Plastics
25 products which are not recycled may lead to land and water pollution
causing irreparable
damage to the environment. Wood-based products, such as paper boxes and paper
pulp
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
packaging, lead to deforestation. Whilst disposal of paper products may not
have a direct
harmful effect on the environment, deforestation resulting from the need for
wood chips
for paper products causes ozone layer depletion which is equally harmful to
the
environment. Reforestation takes at least 15 years and the harmful ecological
impact
during the recovery period may not be remedied, even over an extended period
of time.
Further, some paper products, such as paper cups, have a coating that is non-
biodegradable
which can cause further ecological harm.
These adverse environmental and ecological effects caused by the disposal of
voluminous
waste give rise to a need for a substitute material to produce these products,
preferably a
to material that is derived from a biodegradable and/or readily renewable
resource.
While biodegradable materials are available, the previously known materials
may not be
useable as a substitute for some plastics products.
There are known processes which form products by binding together loose
materials. For
example, chipboard or particle board uses a compression method and adhesives.
However
it is not convenient to produce shaped articles from chipboard.
There is a process that uses a biodegradable material such as plant fibers to
form products
by thermo-foaming. In this process, steam is used to cook the raw materials,
mainly
starch, so that the starch can expand and bind with the next molecule of
starch. As the
starch is heated in the presence of moisture, it expands and creates a
multitude of small air
pockets in the product. 'This product mainly consists of starch therefore the
product
degrades or disintegrates very quickly when it contacts a liquid such as
water. As a result,
the product cannot be coated with a water-proofing material since it starts to
degrade once
it contacts the liquid.
This prior art thermo-foaming process relies on foam formation of the material
to shape the
material into receptacles. Such shaped products are soft and "cushion-like"
and so will not
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
be durable and strong enough to withstand hard knocks. As a result, the
products which
can be made via this process are limited. Another issue with this process is
the cost of
production. The methodology used is very costly and the limited uses does not
provide the
volume of production to make the production line cost effective.
We are aware of a series of prior US Patents in the names of Andersen and
Hodson and
assigned to E. Khashoggi Industries, LLC including US Patents 5,662,731;
5,783,126;
5,868,824 and 6,030,673 (the Khashoggi patents), These US Patents all refer to
manufacturing moulded articles. However, the I~hashoggi patents all teach the
addition of
at least 10 wt % of starch and quote a typical range as being 10-80 wt %. For
example,
1o Khashoggi US patent number 5,783,126 teaches a preferred starch content of
30 to 70%
which gives rise to a problem due to the relatively high cost of starch-based
binder and the
excess time and energy necessary to remove the solvent. Khashoggi therefore
teaches the
addition of inorganic fillers or aggregates. The Khashoggi patents also teach
the addition
of inorganic fillers in relatively high concentrations and quote a typical
Ieve1 of inorganic
aggregate as being greater than 20 wt %.
The present applicants have found that the high levels of added starch and
inorganic
aggregate as taught by the Khashoggi patents lead to high costs and a tendency
to form a
multitude of small voids within the moulded product. The formation of the
voids also
tends to impart a "cushion-like" structure which has low structural strength.
The
2o applicants have now found that contrary to teachings of the Khashoggi
patents, moulded
products having significant structural integrity can be satisfactorily
produced with low
starch concentrations or even the absence of added starch and without the
addition of
inorganic aggregates.
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
4
Summary of the invention
According to one aspect of the invention, there is provided a moulding mixture
for use in
moulding a product including:
(i) 40 to 60 wt% plant fibre pieces optionally combined with 0 to 10 wt%
added starch; and
(ii) I O to 55 wt % water and 3 to 10 wt % one or more water-soluble binding
agents or adhesives
According to a fixrther aspect of the invention, there is provided a moulding
mixture for use
in moulding a product including:
(i) 40 to 60 wt% plant fibre pieces optionally combined with 0 to 2 wt% added
starch; and
(ii) 10 to SS wt % water and 3 to 10 wt % one or more water-soluble binding
agents or adhesives
According to a further aspect of the invention, there is provided a moulding
mixture for use
in moulding a product including:
(i) 40 to 60 wt% plant fibre pieces optionally combined with 2 to 10 wt%
added starch; and
(ii) I O to 55 wt % water and 3 to 10 wt % one or more water-soluble binding
agents or adhesives
2o According to a further aspect of the invention there is provided a moulding
mixture for use
in moulding a product including:
(i) 40 to 60 wt% plant fibre pieces combined with about 2 to 10 wt% starch;
and
(ii) 10 to 55 wt % water and 3 to I0 wt % one or more water-soluble and
biodegradable binding agents or adhesives.
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
The moulding mixture of the present invention is suitable for a range of
moulding
processes known to the person skilled in the art. The moulding mixture has
also been
found to be suitable in the following novel moulding process not hitherto
known to the
skilled person, the process comprising the following steps:
5 (a) preparing the moulding mixture of the present invention
(b) pouring the mixture into a mould, the mould being at a temperature of at
least 60°C;
(c) subjecting the mixture in the mould to a temperature in the range of 15 to
60
°C and a pressure in the range from 1000 to 7000 PSI for a period of
time
1 o such that a portion of the water in the mixture is converted to steam
which
causes the mixture to fill the mould while remaining in a mouldable state;
(d) reducing the pressure so that steam continues to form within the mould
without causing an explosion whilst maintaining the mixture in a mouldable
state;
(e) increasing the temperature and pressure to a temperature in the range from
100 to 200°C and a pressure in the range of 500 to 1500 PSI;
(f) removing the steam or allowing the steam to escape until the moulded
product is substantially dry;
(g) removing the substantially dried and moulded product from the mould.
2o The novel process suitable for use with the moulding mixture of the present
invention may
further comprises the steps of
(h) at least partially coating the moulded product with one or more binding
agents or adhesives; and
(i) heating the coated moulded product to substantially dry and cure the
coating.
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
6
Typically the action of steam forces the mixture to be distributed throughout
the mould.
.Any excess solids material will thus be forced out of the mould by the action
of the steam.
Once the action of the steam has spread the mixture throughout the mould, the
steam is
removed or escapes through the gap or a valve. Without this steam action, the
solids in the
mixture would not spread throughout the mould and would end up being
compressed at the
bottom of the mould in which case the mixture would no longer be in a readily
mouldable
state.
Preferably the aforementioned novel process comprises a further step of
trimming the
edges of the product prior to coating the product in step (h). Typically, such
trimming is
to conducted using a die-cut machine. Other methods for trimming may also be
used within
the scope of the invention including polishing and/or sanding down the edges
of the
product.
Since the main component of the mixture is plant fibers which are bonded
together by an
adhesive which hardens as it cures, the cured product will not disintegrate
immediately
15 upon contact with liquid. Depending on the density of the product (and thus
the porosity
of the product), the product will take a minimum of ten minutes before it
starts
disintegrating and could last as long as one hour. The density of the product
is dependent
on the pressure applied during formation of the product. Therefore, the
product is liquid-
resistant enough to withstand treatment with water-resistance agents or
decorative
2o materials.
The cured product formed from the moulding mixture can be further treated with
a wafer
resistant material or decorative materials.
The plant fibers can come from any source. For example, suitable plant fibres
may be
chosen from the group comprising rice stalks, wheat stalks, sugar cane, corn
leaves, banana
25 leaves, corn crops, roots, grass, flowers, recycled paper or combinations
thereof.
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
7
The size of the fibers affects the texture of the final product. The
requirements of the final
product will dictate the size of the fibers required. For example, a table top
will need to be
strong and is flat so this will allow larger longer pieces of fiber to be used
than those used
in a smaller or curved item such as a cup. Preferably, the plant fiber pieces
used in the
composition and process are in the range from O.lmm to 5 mm. More preferably,
the
length should between 1 mm to 2 mm. However it is possible to use plant fibers
which
have been ground smaller than 1 mm, eg. powdered.
The binding agents or adhesives which are used to bind the fibres are water
soluble and
preferably are environmental friendly. It is preferred that non-biodegradable
plastics or
synthetic polymers are not used so that the process provides a biodegradable
product
although it is to be appreciated that biodegradability of the binding agents
or adhesives is
not essential where the end product does not need to be biodegradable.
Preferably, water
based biodegradable adhesives are used so that the end product is
biodegradable.
Preferably, latex-based adhesives, such as Neoprene, are used in accordance
with the
invention.
Preferably, any added starch used in accordance with the present invention is
selected from
the group comprising tapioca flour, ground sweet potatoes or any other root
powder, corn
starch, flour and combinations thereof. While corn starch and flour are
suitable for use as
added starch in accordance with the present invention the results are not as
good as when
other starch sources are used. There is no need to modify the added starch
prior to
processing.
The fiber and flour or other added starch are mixed together initially in step
(a)(i) to
produce an even mixture. Further, if the liquid ingredients contact the flour
before it is
evenly mixed in, the flour will form lumps and this will create holes in the
product as the
2s starch is removed during the process. Once all the ingredients are combined
in step (a)(ii),
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
8
the mixture is stored in a sealed container until required for step (b) to
prevent the mixture
from drying out. The mixture is preferably stored at room temperature prior to
use to
prevent hardening. The mixture may be stored at a temperature in the range
from the
freezing point of the mixture to about 25°C. Preferably, the mixture is
stored at a
temperature in the range from 15 to 25°C. Further, at higher
temperatures there is a
possibility that mould will form because of the combination of water and an
organic
mixture. Preferably, step (a) occurs at a temperature at or below 25°C.
The water used can be of any quality. The water quality chosen will depend on
the
intended use for the product. For example, non-potable water such as sea water
may be
to used as well as normal utility water. However, products intended for food
contact must be
made from drinking quality water. The water is converted to steam during the
process.
This aids in spreading the mixture evenly in the mould. The mixture does not
foam
because the pressure prevents the mixture from expanding, and the action of
the steam is
directed towards spreading the mixture throughout the mould. Once the
spreading is
15 complete, the steam is removed to allow the product to dry.
The amount of pressure applied to the mould will affect the density of the
final product.
The denser the product, the harder it is. Therefore, if a more flexible
product is desired
then a lower pressure should be used. When the pressure is applied to the
mould, any
excess material will be squeezed out of the mould. Preferably, the pressure is
at about
20 4000 PSI.
The strength of the product produced using the moulding mixture will depend on
four
factors:
the fibre pieces. The finer the pieces, the higher the density and hence the
greater the strength of the product.
SUBSTTTUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
9
2 the type of adhesive including the crystallization rates and viscosity of
the
adhesive. Different types and grades of adhesive contribute differently to the
strength of the products. Different crystallization rates and viscosities of
different adhesives result in different products. Crystallization determines
the rate of initial strength development. The faster the rate of
crystallization, the faster the rate of strength development. Viscosity
influences the inherent strength of the adhesive film, the solution viscosity,
and solids content. The higher the polymer viscosity, or the higher the
molecular weight, the higher the filin strength, the higher the adhesive
l0 viscosity, or the lower the solids at a given adhesive viscosity.
3. the structural design of the mould. The product design may enhance the
strength of the overall product. For example, a box with ribs will be
stronger than one without.
4. the type of fibre. For example, sugar cane fibre provides a moulded product
that is inherently resilient but not brittle. Conversely, rice husks tend to
provide a product that is hard, but comparatively brittle.
Products produced from the moulding mixture of the invention can be recycled
with very
minimal loss of original material and with no harmful by-products. In other
words, a
product can be recycled to produce an almost identical product.
When disposed of, products produced from the moulding mixture of the invention
will
breakdown and disintegrate to form substances which are not detrimental to the
environment. This is because all of the materials used are non-toxic and are
mostly natural
and edible. If the products are collected after disposal and left to
decompose, the resultant
manure can be used as a fertilizer because of the fact that the main component
of the
product is plant fibers.
Further, the plant fibers may be obtained from the unwanted parts of crops
such as rice-
stalks, sugar cane pulps or any other fibers that are not directly consumed.
This helps to
dispose of such waste from harvesting sites, factories etc. which would
otherwise be
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
disposed of by burning and thus causing air pollution. The use of such raw
material helps
to reduce this air pollution.
Further, during the process of the invention, bacteria are killed due to the
high
temperatures being applied.
5 The present invention relates to biodegradable as well as non-biodegradable
materials.
Since the manufacture of products from biodegradable materials requires that
steam be
able to escape from the mould, the use of biodegradable materials to produce
large objects,
such as table tops, has not been viable due to the extended drying time
required for such
large obj ects.
to The moulding mixture of the present invention may be used in a range of
moulds known to
the person skilled in the art. The moulding mixture is also suitable for use
in a novel
mould, comprising one or more valves in the top and/or bottom ends of the top
and/or
bottom parts of the mould to enable steam to be removed wherein the openable
valves are
closed when the mixture is placed into the mould and then the valves open when
the steam
needs to be removed.
Typically this novel mould consists of at least two parts - a top and a bottom
part and is
typically made of metal. However, it is possible to use moulds which come in
three or
more parts provided that there is still a top and a bottom part. In use, the
mould is
preferably compressed vertically, that is, in a downward and upward manner so
that the top
2o part is compressed against the bottom part.
The valves enable the steam to be removed from the mould so that the product
will dry out
faster. Further, the steam is removed more quickly and the product is less
likely to be
burnt.
The moulding mixture of the present invention enables the processing of a
certain
prescribed mixture to form products of various shapes and sizes suitable for
protective
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
11
packaging such as boxes and receptacles and coverings for electronic goods,
cushioning
packaging for delicate and fragile electronic and computer systems and
components, food
and beverage containers such as cups, plates, lunchboxes etc, building
material and
prefabricated boards such as partitions, ceiling boards and other shaped
products eg
garment hangers, horticultural and agricultural planters and pots, and
disposable golf tees.
All proportions in this specification are in percentage weight.
Description of the drawings
The moulding mixture of the present invention and its use in producing moulded
products
to will now be further explained and illustrated by reference to the
accompanying drawings in
which:
Figure 1 is a flow diagram of a moulding process suitable for use with the
moulding
mixture of the invention; and
Figure 2 is a schematic of an overview of the process referred to in figure l;
15 Figure 3 is a perspective view of an open mould, suitable for use with the
moudling
mixture of the present invention;
Figure 4 is a perspective view of the mould in Figure 3 filled with the
mixture;
Figure 5 is a perspective view of the mould in Figure 4 closed and under
pressure with the
valve closed;
2o Figure 6 is a perspective view of the mould in Figure 5 with the valve now
open;
Figure 7 is a perspective view of the mould in Figure 6 opened with the
product removed;
and
Figure 8 is a cross-sectional view of another mould suitable for use with the
moulding
mixture of the present invention.
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
12
The use of a the moulding mixture for moulding products will now be described
in relation
to the following example of a preferred moulding mixture compositions.
Preferred Compositions
Moulding mixtures having compositions according to the present invention were
prepared.
The proportions of components present in the mixture are set out as examples 1
to 40 in the
following table:
ExampleFlour/starchBinder Water Fiber (gm) Total%
(gm) (gm) Calcium of
(gm) carbonate (gm) starch
(gm)
Tapioca Latex Tap waterSugar cane
Flour water pulp
base
(degradable)
1 6.0 10.0 30.0 40.0 0,086.0 7.0%
2 6.0 8.0 30.0 40.0 0.084.0 7.1%
3 4.0 8.0 28.0 40.0 0.080.0 5.0%
4 1,5 8.0 28.0 40.0 0.077.5 1.9%
5 1.2 8.0 28.0 40.0 0.077.2 1.6%
6 1,0 8.0 28.0 40.0 0.077.0 1.3%
7 0.0 8.0 28.0 40.0 0.076.0 0.0%
8 0.0 8.0 28.0 40.0 10.086.0 0.0%
Latex
solvent
base
9 6.0 10.0 30.0 40.0 0.086.0 7.0%
6.0 8.0 30.0 40.0 0.084.0 7.1%
11 4.0 8.0 28.0 40.0 0.080.0 5.0%
12 1.5 8.0 28.0 40.0 0.077.5 1.9%
13 1.2 8.0 28.0 40.0 0.077.2 1.6%
14 1.0 8.0 28.0 40.0 0.077.0 1.3%
0.0 8.0 28.0 40.0 0.076.0 0.0%
16 0.0 8.0 28.0 40.0 10.086.0 O.U%
Water
base
wax binder
17 6.0 10.0 30.0 40.0 0.086.0 7.0%
18 6.0 8.0 30.0 40.0 0.084.0 7.1%
19 4.0 8.0 28.0 40.0 0.080.0 5.0%
1.5 8.0 28.0 40.0 0.077.5 1.9%
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
13
21 1.2 8.0 28.0 40.0 0.0 77.21.6%
22 1.0 8.0 28.0 40.0 0.0 77.01.3%
23 0.0 8.0 28.0 40.0 0.0 76.00.0%
24 0.0 8.0 28.0 40.0 10.0 86.00.0%
Solvent
base
wax binder
25 6.0 10.0 30.0 40.0 0.0 86.07.0%
26 6.0 8.0 30.0 40.0 0.0 84.07.1%
27 4.0 8.0 28.0 40.0 0.0 80.05.0%
28 1.5 8.0 28.0 40.0 0.0 77.51,9%
29 1.2 8.0 28.0 40.0 0.0 77.21.6%
30 I.0 8.0 28.0 40.0 0.0 77.01.3%
31 0.0 8.0 28.0 40.0 0.0 76.00.0%
32 0.0 8.0 28.0 40.0 10.0 86.00.0%
Solvent
base
vinyl binder
33 6.0 10.0 30.0 40.0 0.0 86.07.0%
34 6.0 8.0 30.0 40.0 0.0 84.07.1%
35 4.0 8.0 28.0 40.0 0.0 80.05.0%
36 1.5 8.0 28.0 40.0 0.0 77.51.9%
37 1.2 8.0 28.0 40.0 0.0 77.21.6%
38 1.0 8.0 2$.0 40.0 0.0 77.01.3%
39 0.0 8.0 28,0 40.0 0.0 76.00.0%
40 0.0 8.0 28.0 40.0 10.0 86.00.0%
The moulding mixtures of examples 1 to 40 were used to make golf tees
according to the
moulding process of the present invention. The golf tees were of good quality
and suitable
for their intended use. Further moulding mixtures were prepared, analogous
with the
compositions of examples 1 to 40, except that the sugar cane pulp added as a
source of
fibre was replaced with fibre chosen from the group comprising wheat stalks,
tea leaves,
rice stalks, rice husks mixed with rice stalks, corn cobs including the leaves
and the
carbonaceous residue of burnt coconut shells.
The molding mixtures comprising each of the listed sources of fibre were used
to make
to golf tees according to the moulding process of the present invention. The
golf tees
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
14
comprising each different type of fibre were compared with the aforementioned
golf tees
comprising sugar cane pulp. While there were differences in quality of the
golf tees
depending on the type of fibre used, these differences did not have any
significant effect on
the performance of the golf tees.
Of the aforementioned sources of fibre, only rice husks have any inherent
starch content.
The rest of the listed fibre sources have no inherent starch content and
therefore make no
contribution to the starch content of the moulding mixture. Accordingly, when
rice husks
were used to make the moulding mixtures of examples 1 to 40, the proportion of
starch
present was slightly greater than the quantities listed in the table.
It is noted that for examples comprising a given type of fibre, varying the
nature of the
binder does not affect the quality of the product produced according to the
present
invention. However, based on environmental considerations, water soluble
binders are
preferred for use in the moulding mixture because they are biodegradable,
whereas binders
soluble in non-aqueous solvents are generally not biodegradable.
1S Preparation of the Mixture
Individual mixtures were prepared using fibers of wheat stalks or rice stalks
or sugar cane
pulp or corn leaves in combination with corn pulp. The mixtures were ground by
a
grinding machine to a size in the range of from O.lmm to 5.0 mm. The ground
fiber was
combined with the starch of tapioca flour, sweet potato flour and corn flour
thoroughly in a
2o mixer (a container with fan like blade spinning at a speed of 500 to 700
rpm) to form a
moulding mixture. Care was taken to ensure that the starch did not form into
lumps when
the liquid ingredients were added. Any lumps which do form should be broken up
because
when the water forms steam, such lumps of starch will be cooked and will foam
which will
cause an air trap or hole in the mould product. A water soluble adhesive with
a latex base
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
is then added together with water and the mixture further stirred until the
whole mixture is
mixed evenly. This mixture can be used to produce a cup, box or tray.
The Mould
The mould 20 shown in the drawings has a top mould part 21 and a bottom mould
part 22.
5 The top mould part 21 has a valve 23 located in its upper surface 24. The
bottom mould
part has a cavity 25 to receive mixture 26. When mould 20 is closed, there is
a gap 27 of
about 1 mm between the top mould part 21 and the bottom mould part 22. Once
closed,
pressure is applied to upper surface 24. The valve 23 is operated either
manually or
automatically via a controller (not shown). Typically, the valve 23 is opened
(see Figure
l0 6) when the temperature of the mould 20 is at about 110°C. Once the
article 28 has dried,
the mould 20 is opened and the article 28 removed.
Manufacturing an Article from the Mixture
In the flow diagram of Figure 1, the process commences at A with pre-heating
the mould
to 70°C. This heating is only required the first time that the mould 20
is used because
15 in a continuous process the mould 20 would be at about 140°C from
forming the last article
28 and is actually cooled to 70°C at B. Once formed the article 28 is
removed from the
mould 20 at C to be trimmed, sealed and further treated as desired.
Once the mould 20 is brought to about 70°C, the mould 20 is opened (see
D of Figure 2)
and overfilled with mixture 26 (see E). Ideally the mixture is kept at ambient
temperature
20 (about 25 °C) or at least within the range of 15 to 40 °C.
The mould 20 is intentionally
overfilled to ensure that there is sufficient mixture to evenly and completely
fill the mould
20. The mould 20 is not left cold because when the mixture 26 is compressed
under
pressure, the solids in the mixture would be forced and compressed to the
bottom of the
mould and water would separate from the mixture and be squeezed out through
the gap or
air vent. If the temperature goes above 100°C, the moisture will turn
into steam too
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
16
quickly and can cause an explosion. However when the mould 20 is hot
(70°C to 100°C)
and the materials are compressed, the moisture will immediately transform into
vapor and
start to look for a space or gap to escape. This action will move the solids
in the mixture
into all the open spaces in the mould 20 with excess mixture seeping out of
the mould 20.
This action typically takes 5 to 10 seconds.
The mould 20 is then closed (see F of Figure 2). When closed, there is
typically a gap 27
of about 1 mm between the top 21 and bottom 22 parts of the mould through
which steam
and excess mixture can escape. Once the mould 20 is closed, a pressure of
about 4000 PSI
is applied to the top of the mould 20 (see Cl) for about 3 to 10 seconds until
excess mixture
to starts coming out of the gap 27 between the mould parts 21 and 22. The
appearance of the
excess material indicates that the mixture 26 has spread evenly throughout the
mould 20 -
this is especially important where the product is not flat and the mixture
will need to move
up the sides of the mould 20. The pressure also ensures that the shape of the
product is
maintained (that is, there is no foaming), and controls the desired
density/porosity of the
15 product.
Upon seeing the mixture stop overflowing out of the mould 20, the pressure is
reduced to
atmospheric and then increased back to a pressure in the range of from 500 to
1500 PSI. In
the examples we used a pressure of about 1000 PSI. Then the temperature was
increased
to about 140°C. The pressure is reduced to prevent an explosion due to
the water turning
2o into steam too quickly.
At this point, the steam will be rushing out through all openings and the
faster the steam
can escape, the faster the product will cure and this reflects the importance
of having a
valve 23 being operated to let the steam escape. Once the temperature has
reached about
110°C, the valve 23 is opened to increase the rate of steam escaping
(see H).
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
17
When it has been observed that the escape of steam has effectively ceased,
approximately
after one to five minutes at a temperature of I40°C (depending the
number of valves), the
mould 20 is opened and the substantially dried article 28 removed (see 1]. As
there is
overflow, the edge of the article has to be trimmed using a die cutting
machine or manually
(see ~.
The article is then optionally coated with further adhesive by spraying or
dipping (see K)
and heated at 100°C to 140°C for about 10 seconds to 10 minutes
to cure the adhesive. In
the example we used temperature of about 130°C fox about 8 minutes.
The article may be further coated with Neoprene to further enhance its water
resistance
(see L). Typically about 3 grams of Neoprene is used per square foot of the
product. The
coating is applied by spraying or dipping.. In addition, a decorative painting
or print can
be added to the surface of the product.
The following mixtures were prepared by the above method and the suitability
for
moulding assessed by applying the above process to them.
Mixture A B C
Flour 3 % 10% 6%
Adhesive 2% 10% 4.7%
Fiber 52% 40% 47.6%
Water 43 % 40% 41.7%
Mixture B provided a workable product. Mixture C is useful for packaging for
heavy
products such as televisions or table tops or as a special cushioning with
greater porosity.
Mixture A is economical and good for products which do not need a high density
such as
cups, bowls, industrial packaging for appliances.
SUBSTITUTE SHEET (RULE 26)
CA 02427527 2003-04-30
WO 02/20665 PCT/SGO1/00178
18
Figure 8 shows a fop part of a mould (I00) comprising mould part (101) and
valve (102).
Valve (102) sits in a complementarily shaped cavity (103) in mould part (101)
and is free
to move relative to mould part (101). Cavity (103) end in release hole (104)
and valve end
(105) is adapted to seal release hole (104) when the valve (102) in its closed
position (not
shown). Valve (102) is closed by pressure being applied to top end (106). When
valve
(102) is in its open position as shown in Figure 8, steam can escape from the
mould (100).
The word 'comprising' and forms of the word 'comprising' as used in this
description and
in the claims does not limit the invention claimed to exclude any variants or
additions.
Modifications and improvements to the invention will be readily apparent to
those skilled
to in the art. Such modifications and improvements are intended to be within
the scope of this
invention.
SUBSTITUTE SHEET (RULE 26)
