Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Process for Manufacture of Mouldable Product
and Mould for use with this Process
Field of the invention
The invention relates to a process for manufacture of mouldable products and a
mould for
use with this process. More particularly, this invention relates to a process
and to a mould
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 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 products such as containers,
protective packaging
and shock absorbing packaging it is to be 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 made using
the process or
mould of the invention may be of any convenient shape and may optionally
include
partitions or protrusions.
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 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
packaging, lead to
deforestation. Whilst disposal of paper products may not have a direct harmful
effect on the
environment, deforestation resulting from the need fox 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
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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
material that is derived from a biodegradable and/or readily renewable
xesource.
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
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 Khashoggi patents all teach the
addition of at
least 10 wt % of starch and quote a typical range as being 10-80 wt %. For
example,
Khashoggi US patent number 5,783,126 teaches a preferred starch content of 30
to 70%
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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 level
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
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.
Summary of the invention
According to one aspect of the invention, there is provided a process for
manufacturing
moulded products comprising the following steps:
(a) preparing a moulding mixture by:
(i) taking 40 to 60 wt% plant fibre pieces and optionally combining 0 to
wt% added starch with the plant fibre pieces; and
(ii) adding thereto 10 to 55 wt % water and 3 to 10 wt % one or more
water-soluble binding agents or adhesives;
(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
such that a portion of the water in the mixture is converted to steam wluch
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;
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(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.
According to a ftufiher aspect of the invention, there is provided a process
for manufacturing
moulded products comprising the following steps:
(a) preparing a moulding mixture by:
(i) taking 40 to 60 wt% plant fibre pieces and optionally combining 0 to 2
wt% added starch with the plant fibre pieces; and
(ii) adding thereto 10 to 55 wt % water and 3 to 10 wt % one or more
water-soluble binding agents or adhesives;
(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
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.
According to a further aspect of the invention, there is provided a process
for manufacturing
moulded products comprising the following steps:
(a) preparing a moulding mixture by:
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(i) taking 40 to 60 wt% plant fibre pieces and optionally combining 2 to
wt% added starch with the plant fibre pieces; and
(ii) adding thereto 10 to 55 wt % water and 3 to 10 wt % one or more
water-soluble binding agents or adhesives;
(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
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.
According to a further aspect of the invention, there is provided a process
for manufacturing
moulded products comprising the following steps:
(a) preparing a moulding mixture by:
(i) taking 40 to 60 wt% plant fibre pieces and optionally combining 2 to
10 wt% added starch with the plant fibre pieces; and
(ii) adding thereto 25 to 55 wt% water and 2 to 10 wt% one or more
water-soluble binding agents or adhesives;
(b) pouring the mixture into a mould, the mould at a temperature in the range
of
from 70 to 100°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
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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 form the mould.
In a preferred embodiment, the process 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.
The invention involves employing the action of the steam to force 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 process comprises a further step of trimming the edges of the
product prior to
coating the product in step (h). Typically, such trimming is conducted using a
die-cut
machine. Other methods for trimming may also be used within the scope of the
invention
including polishing andlor 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 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
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applied during formation of the product. Therefore, the product is liquid-
resistant enough to
withstand treatment with water-resistance agents or decorative materials.
The cured product can be further treated with a water resistance material or
decorative
materials.
The period of time for which pressure in the range of from 1000 to 7000 PSI is
applied in
step (c) is preferably in the range of from 3 to 10 seconds. Preferably, in
step (c) the mixture
in the mould is subjected to a temperature of about 29 °C.
Preferably, the pressure in step (d) is reduced to a pressure in the range of
from 500 to 1500
PSI before pressure is increased in step (e). Most preferably the pressure in
step (d) is
reduced to atmospheric and then increased in step (e) to a pressure in the
range of from 500
to 1500 PSI more preferably about 1000 PSI.
Preferably, the temperature in step (e) is increased to about
140°C.
Step (f) typically occurs for a period of time in the range of from 10 seconds
to 30 minutes
or longer till the product is dry at a temperature in the range of from
100°C to 250°C.
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
leaves, corn crops, roots, grass, flowers, recycled paper or combinations
thereof.
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 S 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.
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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
starch is
removed during the process. Once all the ingredients are combined in step
(a)(ii), 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
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 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 4000 PSI.
The strength of the product produced by the process of the present invention
will depend on
four factors:
(1) the fibre pieces.
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The finer the pieces, the higher the density and hence the greater the
strength of the product.
(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
film strength, the higher the adhesive 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 by the process 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.
The plant fibers used in the process of the present invention 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 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.
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
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objects. As a result, investigations were made into developing a mould
appropriate for such
large products.
According to a further aspect of the invention, there is provided a mould for
use with the
process of the present invention, comprising one or more valves in the top
andlor bottom
ends of the top andlor 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.
There is additionally provided a process for manufacturing moulded
biodegradable products
using the mould of the present invention, the process comprising the following
steps:
(a) preparing a moulding mixture by:
(i) taking 40 to 60 wt% plant fibre pieces and optionally combining 0 to
10 wt% added starch with the plant fibre pieces; and
(ii) adding thereto 10 to 55 wt % water and 3 to 10 wt % one or more
water-soluble binding agents or adhesives;
(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
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.
There is additionally provided a process for manufacturing moulded
biodegradable products
using the mould of the present invention, the process comprising the following
steps:
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(a) preparing a moulding mixture by:
(i) taking 40 to 60 wt% plant fibre pieces and optionally combining 0 to
2 wt% added starch with the plant fibre pieces; and
(ii) adding thereto 10 to 55 wt % water and 3 to 10 wt % one or more
water-soluble binding agents or adhesives;
(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
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;
In a further aspect there is provided a process for manufacturing moulded
biodegradable
products using the mould of the present invention, the process comprising the
following
steps:
(a) preparing the moulding mixture of any one of the preceding claims:
(i) taking 40 to 60 wt% plant fibre pieces and optionally combining 2 to
wt% added starch with the plant fibre pieces; and
(ii) adding thereto 10 to 55 wt % water and 3 to 10 wt % one or more
water-soluble binding agents or adhesives;
(b) pouring the mixture into a mould the mould being at a temperature of at
least
60°C;
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(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
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 ;
(fj 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;
Typically, the valves are closed while the mixture is poured into the mould in
step (b) and
during the application of pressure to the mould in step (c).
In use the mould of the present invention may be used to manufacture a moulded
product
using a moulding mixture comprising;
(i) 40 to 60 wt% plant fibre, optionally combined with 0 to 10 wt% added
starch;
and
(ii) adding thereto 10 to 55 wt% water and 3 to 10 wt% one or more water-
soluble binding agents or adhesives.
In a further aspect, in use, the mould of the present invention may be used to
manufacture a
moulded product using a moulding mixture comprising;
(i) 40 to 60 wt% plant fibre, optionally combined with 0 to 2 wt% added
starch;
and
(ii) adding thereto 10 to 55 wt% water and 3 to 10 wt% one or more water-
soluble binding agents or adhesives.
In yet a further aspect, in use, the mould of the present invention may be
used to
manufacture a moulded product using a moulding mixture comprising;
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(i) 40 to 60 wt% plant fibre, optionally combined with 2 to 10 wt% added
starch;
and
(ii) adding thereto 10 to 55 wt% water and 3 to 10 wt% one or more water-
soluble binding agents or adhesives.
The 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 part is
compressed
against the bottom part. Typically, there is a gap of 1 mm between the top and
bottom
mould parts through which the steam and excess mixture can escape.
The surface of the mould is preferably smooth, that is the surface is not
rough or feels like
sand paper. If desired a pattern may be engraved into the mould. Any
protrusions in the
mould must not interfere with the removal of the product from the mould. The
shape and
size of the mould will depend on the product to be produced.
The mould may be heated by attaching heaters to the mould or passing the mould
through an
oven. The pressure may be provided by any known means including a hydraulic
press,
pneumatic press or mechanical press. Typically, the pressure is provided by a
hydraulic
press as these presses provide a consistent pressure.
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 valves are mechanically operated. Once the temperature in the mould has
risen above
the boiling point of the water, this indicates that mixture will be spread
evenly throughout
the mould and the valves can be opened to release the steam. By the time that
the mixture
has spread evenly throughout the mould, it will have hardened just enough so
that it does not
enter into the valve with the steam. The valves are closed when the mixture is
placed into
the mould and when the pressure is applied to the mould, thus the mould is
totally closed
except the gap between the top and bottom parts of the mould. As the water or
moisture in
the mixture is converted into steam, this steam will rush upward forcing the
mixture to move
into all the open spaces thus filling up the whole mould. Extra or excess
mixture will be
squeezed out of the mould. Normally the mould will be opened in process step
(d) when the
temperature reaches between 100 and 200 °C and preferably at about
110°C. The valves
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shorten the time for the product to be dried and thus shorten the processing
time. Further
without using this valve, the steam will take longer to escape through the
side and out
through the gap between the top and bottom parts of the mould, and if the
steam takes too
long to remove, the heat would cook or burn the center portion of the product
while the sides
are only just dry.
Preferably, there is one valve every 4 square inches. The valves cannot be
placed in the
sides of the mould as this would impede the proper spreading of the mixture to
be moulded.
If the valve was fixed to the side of the mould, steam would escape through
it, thus reducing
the pressure inside. This reduced steam pressure may cause the mixture not to
flow to the
space above the valve and create an incomplete product.
This invention enables the processing of a certain prescribed mixture to form
products of
various shapes and sizes suitable for protective 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 invention will now be further explained and illustrated by reference to
the
accompanying drawings in which:
Figure 1 is a flow diagram of the process according to the invention; and
Figure 2 is a schematic of an overview of the process.
Figure 3 is a perspective view of one embodiment of the mould of the present
invention in
the open position;
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;
Figure 6 is a perspective view of the mould in Figure 5 with the valve now
open;
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Figure 7 is a perspective view of the mould in Figure 6 opened with the
pioduct removed;
and
Figure 8 is a cross-sectional view of a mould according to another embodiment
of the
invention.
The use of a mould as shown in the drawings will now be described in relation
to following
example of a preferred embodiment of the process provided by the invention.
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 I.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 0.0 86.0 7.0%
I 6.0 8.0 30.0 40.0 0.0 84.0 7.1
0
11 4.0 8.0 28.0 40.0 0.0 80.0 5.0%
I 1.5 8.0 28.0 40.0 0.0 77.5 1.9%
Z
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13 1.2 8.0 28.0 40.0 0.0 77.2 1.6%
14 1.0 8.0 28.0 40.0 0.0 77.0 1.3%
I S 0.0 8.0 28.0 40.0 0.0 76.0 0.0%
16 0.0 8.0 28.0 40.0 10.0 86.0 0.0%
Water base
wax binder
17 6.0 10.0 30.0 40.0 0.0 86.0 7.0%
18 6.0 8.0 30.0 40.0 0.0 84.0 7.1%
19 4.0 8.0 28.0 40.0 0.0 80.0 5.0%
20 1.5 8.0 28.0 40.0 0.0 77.5 1.9%
21 1.2 8.0 28.0 40.0 0.0 77.2 1.6%
22 1.0 8.0 28.0 40.0 0.0 77.0 1.3%
23 0.0 8.0 28.0 40.0 0.0 76.0 0.0%
24 0.0 8.0 28.0 40.0 10.0 86.0 0.0%
Solvent base
wax binder
25 6.0 10.0 30.0 40.0 0.0 86.0 7.0%
26 6.0 8.0 30.0 40.0 0.0 84.0 7.1%
27 4.0 8.0 28.0 40.0 0.0 80.0 5.0%
28 1.5 8.0 28.0 40.0 0.0 77.5 1.9%
29 1.2 8.0 28.0 40.0 0.0 77.2 1.6%
30 1.0 8.0 28.0 40.0 0.0 77.0 1.3%
31 0.0 8.0 28.0 40.0 0.0 76.0 0.0%
32 0.0 8.0 28.0 40.0 10.0 86.0 0.0%
Solvent base
vinyl binder
33 6.0 10.0 30.0 40.0 0.0 86.0 7.0%
34 6.0 8.0 30.0 40.0 0.0 84.0 7.1%
35 4.0 8.0 ' 28.0 40.0 0.0 80.0 5.0%
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36 1.5 8.0 28.0 40.0 0.0 77.5 1.9%
37 1.2 8.0 28.0 40.0 0.0 77.2 1.6%
38 1.0 8.0 28.0 40.0 0.0 77.0 1.3%
39 0.0 8.0 28.0 40.0 0.0 76.0 0.0%
40 0.0 8.0 28.0 40.0 10.0 86.0 0.0%
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 golf
tees according to the moulding process of the present invention. The golf tees
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.
Preparation of the Mixture
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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 S.0 mm. The ground fiber was
combined
with the starch of tapioca flour, sweet potato flour and corn flour thoroughly
in a mixer (a
container with fan like blade spinning at a speed of S00 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 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.
The top mould part 21 has a valve 23 located in its upper surface 24. The
bottom mould part
has a cavity 2S 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 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 l, the process commences at A with pre-heating
the mould 20
to 70°C. This heating is only required the first time that the mould 20
is used because 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
(about 2S °C) or at Ieast within the range of I S 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
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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 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 G) for about 3 to 10 seconds until
excess mixture
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
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 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).
When it has been observed that the escape of steam has effectively ceased,
approximately
after one to five minutes at a temperature of 140°C (depending the
number of valves), the
mould 20 is opened and the substantially dried article 28 removed (see I). As
there is
overflow, the edge of the article has to be trimmed using a die cutting
machine or manually
(see ~.
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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 for 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.
Figure 8 shows a top part of a mould (100) 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 in
the art. Such modifications and improvements are intended to be within the
scope of this
invention.
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