The invention relates to a method for manufacturing foamed products
according to the preamble of claim 1. Such a method is known from International
patent application WO 96/05254.
The products to be manufactured according to the invention have a
foamy structure. More particularly, the foamy material always comprises at least
three parts: two relatively dense layers on the outside, which, as it were, form
a skin, and between them a foam structure as core. The dense layers are firm and
strong and consist of substantially closed, small cells. The foam structure of
the core is generally open, which means that the cells have burst to allow the
gasses evolving during the manufacture, for instance water vapour or carbon dioxide,
to escape. The cells generally have a firm and solid cell wall due to the relatively
high pressure and temperature during the process. In the manufactured product,
the fibers extend between and possibly partly through the cells and are mainly
intricately connected to the material of the cells.
In this description, "gelatinization" is understood to mean a change
of a natural polymer from a slightly or completely loose granular or comparable
granulate form into a cohesive form which may or may not be dry and/or foamed,
in which stretched polymers are present. That is to say, a transition occurs from
a solid substance, a colloidal solution or suspension to a more homogeneous fluid
mass. Depending on the polymers used, "gelatinization" should therefore be understood
to include, for instance, gelling, gellating and the like.
In foamed products where only gelatinization occurs, as a result
of gas evolution, bubbles are formed in the mass to be foamed, substantially after
gelatinization. This process occurs at relatively low temperatures and pressures.
Over the entire cross section, such products have approximately the same structure
of relatively small cells with walls of substantially uncross-linked natural polymers.
In this description, "baking" is understood to mean a method in which
both gelatinization and cross-linking occur, at relatively high temperature and/or
pressure. As a result, the formation of gas arises relatively soon, so that bubbles
are already formed prior to or during gelatinization. As a result of
inter alia the high pressure adjacent strongly heated parts, the polymers
cross-link quickly when using a mould or like baking form with a temperature at
or above the baking temperature.
These baked products have a core with relatively large cells, enclosed
between skin parts with relatively small cells. The cell walls have a relatively
high density and the natural polymers included therein are cross-linked to a high
extent, which means that they have entered into mutual chain bonds. Such a baked
product therefore has a sandwich-like structure.
In the method known from WO 96 05254 and WO 95/20628, an open platen
set is employed, wherein products are manufactured from a batter comprising natural
polymers, inorganic filler, water and fibers. The batter is introduced into the
bottom half of an open platen set, for instance a baking iron, after which the
platen set is closed and heated, so that the batter is gelatinized. The products
obtained are thin-walled and biodegradable, which is advantageous from an environmental
point of view. The fibers added have the advantage that an increase of the product
strength is thereby obtained relative to products wherein such fibers have not
been added. Such products are for instance known from WO91/12186.
A disadvantage of the use of platen sets is that the batter is introduced
into an open mould which is subsequently closed and, for instance, is passed through
a continuous oven, where it is heated, for instance by gas burners. Energetically
speaking, this is little efficient and moreover the temperature in the baking
mould is not properly controllable and may vary strongly during the baking process,
which is not beneficial to the quality of the products. Moreover, the products
which are obtained according to this method are not particularly dimensionally
stable and allow no or only very slight differences in wall thickness, because
otherwise no homogeneous structure can be obtained. A further disadvantage of this
method is that the introduction of the batter and the removal of the product is
very laborious and will often lead to failure in the production. Moreover, with
this method no products can be manufactured that are non-withdrawable, so that
the freedom of design is limited.
In a further method according to WO 96/05254 a powderlike mixture
of natural polymers, inorganic filler, water and fibers is introduced into a conventional
EPS mould by use of an airstream through said mould. The mixture is heated inside
the mould by use of heated steam, in order to provide for gelatinization and foaming
of the mixture for forming the desired article.
In this method the mixture is introduced into the mould relatively
slowly, which results in relatively long production times and can only be used
with moulds having relatively easy designs and short flow paths. Furthermore, the
products resulting from this method have to be stabilized by conditioning them,
resulting in even longer production cycles.
European patent application 0 118 240 discloses a method for manufacturing
biodegradable medicament capsules and like products by injection-moulding from
a starch composite. To that end, a starch mixture with a low water content is introduced
into a closed space, in particular the hopper of an injection-moulding machine,
where plasticization of the mixture is provided for at a suitable specific temperature,
pressure and humidity. The temperature and pressure are increased to such an extent
that the mixture is adjusted to above the vitrification point. Thereafter the plasticized
mixture is forced into a cooled mould and maintained under pressure, until the
or each product has cooled off sufficiently, whereafter the mould is opened and
The advantage of this known method is that dimensionally stable biodegradable
products can be manufactured relatively fast. However, the possible dimensions
of products that can be manufactured with this method are limited, owing to the
flow path in the mould. In fact, the plasticized mass forced into the mould is
cooled directly, which gives rise to solidification and prevents flow of the mass
relatively soon after entry of the mould. Moreover, no cross-linking of the search
in the mass occurs, so that the products have relatively weak strength properties
and exhibit relatively poor resistance to water and moist conditions in general.
In a moist environment the products will take up a great deal of water and thereby
become slack; conversely, in a dry environment moisture will evaporate from the
products, so that they become hard and brittle. The produces obtained with this
method have a high density and have no foamy structure.
International patent application 95/04104 discloses a method for
manufacturing foamed, biodegradable products from starch-containing raw materials,
in which an amount of starch is liquefied in a pre-stage by heating to a temperature
far above the gelatinization temperature, whereafter an amount of water-saturated
ramie fibers is admixed. This mixture is thereafter passed into or through a mould
or converted to a dry granulate. Upon heating of the mixture, the water is to escape
from the ramie fibers and to function as blowing agent. When using this known
method, a substantially dry granulate of starch is to be strongly heated in the
pre-stage, which granulate therefore cannot form a liquid batter. This known method
has the disadvantage that the raw materials are to be supplied in relatively dry
form and in the pre-stage are to be mixed with the moist fibers under simultaneous
increase of the temperature in the tank, whereby the desired gelatinization occurs.
To that end, the mixture must be heated, which is difficult to effect homogeneously
in view of the relatively large mass. As a consequence, the process is relatively
poorly controllable. A further disadvantage is that the products obtained in this
way have only limited durability and are not water-resistant and moreover are
not particularly dimensionally stable. With this method, the freedom of design
is limited. Hence, this method suffers from the drawbacks mentioned in respect
of the gelatinization of the mass prior to its introduction into the mould.
Further, European patent application 0 634 261 discloses a method
for manufacturing biodegradable products utilizing a kind of injection-moulding
technique, which starts from a mixture of a first and second biodegradable starting
material. The first has a melting temperature of above 100iC, the second
of less than 100iC. Either a substance which contains water is added
to the starting material, or water is incorporated in the starting material, in
such a manner that it can provide for the blowing of the cells. In an extruder
press, the mass is heated to above the gelatinization temperature of at least the
first starting material, mixed and pressurized and subsequently sprayed into a
mould cavity provided in a pressurized space. After introduction of the mass,
the pressure is removed, so that the water in the mass expands, blows the cells
and exits through the permeable wall of the mould cavity. Such a method requires
a complicated composition of starting materials. Further, this known apparatus
has the above-mentioned disadvantages resulting from the gelatinization of at
least a part of the mass prior to its introduction into the mould. In particular,
as a result of inter alia the porous walls, the outer wall portions of the
products manufactured according to this method will not have a dense, compact
wall but a uniform distribution of cells of uniform size throughout the product
The object of the invention is to provide a method for manufacturing
foamed products according to the preamble of claim 1, in which the supply of the
starting material is simple, in which the manufactured products are simple to remove
from the mould, which involves a relatively great moulding freedom and whereby
the manufactured products have a good dimensional stability and exhibit relatively
good resistance to different conditions, including moist environments and temperature
fluctuations, which products can moreover be integrated in a paper-reuse flow (paper
recycling). To that end, the present invention provides a method according to
Owing to the supply of the mass from which the or each product is
to be formed at a temperature which is below the gelatinization temperature, the
supply of the mass can be realized in a simple manner, for instance via pumps and
pipes. Moreover, a stock of the mass can be priorly prepared and be fed to a processing
apparatus directly from a storage tank. By subsequently passing the mass under
pressure into or through the mould and only heating it in the mould, it is ensured
that the mould is always filled sufficiently. The flow path, that is, the or each
path traversed by the mass to and in the mould can then be long to very long with
respect to the cross sections of the passages. Only in the mould, the eventual
gelatinization of the natural polymers occurs and then cross-linking of those
Due to the cross-linking that occurs, a firm product is obtained.
The natural polymer provides for a relatively firm skeleton which extends around
preferably continuous cells that form in the mould due to moisture or other blowing
agents which, as a result of the heat in the mould, attempts to escape from the
mass and due to the pressure in the mould, forms bubbles. As a result, the product
obtained has a blown foamy structure. Since the natural polymer provides for a
relatively stiff jacket, the thus obtained product is dimensionally stable upon
exiting from the mould. Depending inter alia on the extent of cross-linkage,
the product obtained is more or less flexible.
Since the mould is heated and not the mass prior to being forced
into the mould, the temperatures in the mould can be properly controlled, both
for the mould as a whole and for each separate portion thereof. As a result, products
can be manufactured with different and varying wall thicknesses and with different
mechanical properties. In fact, by heating more or less and/or for a longer or
shorter period and adjusting, for instance, the pressure, for instance the extent
of cross-linkage of the polymers can be controlled locally, so that the mechanical
and physical properties are influenced. All this can be simply determined by those
skilled in the art.
Heating the mass to the baking temperature, hence in excess of 100iC,
offers the advantage that the occurrence of fungoid growth is prevented, or at
least substantially slowed down. The addition of fibers, in particular natural
fibers, offers the advantage that the products are more dimensionally stable after
injection moulding and heating, and remain shape-retaining, also in moist conditions.
The products obtained with a method according to the invention are relatively
strong and compression-resistant, impact-resistant and relatively elastic, insulating
and can be reduced without involving fragmentation. After use, the products can
be included in an existing waste flow for, for instance, composting or, more advantageously,
in a paper-recycling flow.
By utilizing natural fibers, in particular fibers of, for instance,
annual plants and/or recycled fibers such as cellulose fibers from paper and wood
waste, significant advantages are realized in terms of environment and manufacture.
For instance, the emission of harmful substances is reduced, if not prevented,
during manufacturing as well as during waste processing. As no fossile resources
are used in the products, the processing thereof will cause no permanent increase
of CO2 in the atmosphere, so that these products do not contribute to
the so-called hothouse effect.
A further important advantage realized through the addition of fibers
is that the obtained product retains its original shape and properties longer than
it does without fibers. It is true that composting, i.e. the biological degrading
process, proceeds relatively slowly, so that the product is less suitable for inclusion
in a flow of vegetable, fruit and garden waste, but the product is thereby sufficiently
durable for being able to serve as, for instance, packaging material, also if the
articles packaged therein are stored and/or dispatched for a long time, or under
unfavorable conditions, such as high temperature and/or high air humidity. When
further preserved, products manufactured according to the invention are suitable
as constructional elements, building parts and the like. These products are durable,
light, mouldable, insulating and of sandwich-shaped composition.
A product manufactured according to the invention is in general self-extinguishing,
whereas comparable products manufactured from, for instance, (paper) pulp or EPS
are relatively combustible. Moreover, the manufacture of such pulp products is
labor-intensive and costly, the products are less strong, heavy, little resistant
to, for instance, high temperatures and moisture, and the freedom of design is
slight. A number of these and comparable drawbacks occur with comparable products
manufactured from plastic, such as polystyrene foam and the like.
In an advantageous embodiment, a method according to the invention
is further characterized by the features of claim 2.
By controlling the process conditions, in particular the feed rate
of the mass, the temperature of the mould and the pressure in the mould, a product
is manufactured in which the cells are smaller adjacent the mould wall than centrally
between the walls of the mould. In other words, in the product the cell size increases
from the inside to the outside. Thus, a relatively closed, water-tight skin is
obtained which properly protects the product from premature decline, while the
inside of the product comprises relatively large cells which can keep the product
light and flexible. Moreover, the foam-shaped inside is particularly favorable
for obtaining and increasing the insulating action. A further advantage of the
skin with a relative large density is that, as a result, a taut and smooth surface
is obtained which affords the product an agreeable appearance, has a pleasant feel,
is simply removable from the mould, is simply printable and moreover hygienic.
Accordingly, in contrast with the known methods, a cell structure is obtained
which is non-homogeneous, at least viewed across the wall thicknesses.
In a further advantageous embodiment, a method according to the invention
is further characterized by the features of claim 3.
The use of recycled fibers, for instance paper fibers or like cellulose
fibers, offers the advantage that a relatively cheap and environmentally friendly
basic material can be used. Such recycled fibers are relatively cheap and widely
available. Moreover, a product obtained according to such method can, after use,
be incorporated into the same waste flow and reused in such products.
In further elaboration, a method according to the invention is further
characterized by the features of claim 4.
By using fibers coming from annual plants, in particular by only
using fibers which preferably come from annual plants and/or from recycling, the
advantage is achieved that products can be manufactured in a particularly environmentally
friendly manner. The use of fibers from annual plants is preferred to fibers from,
for instance, trees, because these annual plants are quickly renewable, are relatively
cheap and readily available. Moreover, the use of annual plants stimulates diversification
in agriculture. In particular wood cutting is not necessary for this. Further,
annual plants produce relatively long fibers. When used, these fibers have the
advantage that the flexibility of the products obtained is considerably increased
thereby. The fibers act as a kind of reinforcement.
In a further advantageous embodiment, the invention is characterized
by the features of claim 5.
By coating at least a portion of the fibers to be used in the method,
water absorption by the fibers is limited to a minimum, at least to a favorable
low value. This limits or prevents thickening of the mass, so that the processing
thereof remains possible in an simple manner, also in the case of relatively long
paths of flow. Moreover, the baking process is accelerated thereby, because less
water needs to be evaporated, which is also favorable from an energetic viewpoint.
Moreover, the coating enables in a particularly simple manner the addition of additives
to the mass. The coating can for instance consist of means for obtaining a better
bond between the fibers and, for instance, the starch from which the cells are
blown. Moreover, the coating can contain, for instance, a blowing agent, colorants,
natural anti-fungal agents, flavorings and/or fragrances, and the like.
In further elaboration, a method according to the invention is characterized
by the features of claim 6.
The addition of at least 0.5% and preferably between 2% and 25% fibers
offers the advantage that the mass can be introduced into the mold in a relatively
simple and suitable manner and results in a proper distribution thereof in the
mold, while the above-mentioned advantages are achieved. In particular when 4-15%
fibers is added, particularly favorable results are achieved.
Further, an advantageous embodiment of a method according to the
invention is characterized by the features of claim 7.
The addition of 15-75% dry substance in the mass, and more advantageously
between 20-60% dry substance yields advantageous results. In the starting condition,
i.e. at a temperature below the gelatinization temperature, a mass thus designed
has good flowing properties, while products having the above-mentioned favorable
properties are obtained thereby. In particular when using a mass containing between
30-50% dry substance, particularly favorable results are achieved thereby.
The above-mentioned percentages are in each case mentioned for suspensions
used, not for any prefoamed mass. The percentages present therein can easily be
derived from these compositions.
In a further advantageous embodiment, a method according to the invention
is characterized by the features of claim 8.
By building up the products according to the invention from dish
or sheet parts each having at least one slight thickness with regard to the other
dimensions, at least with regard to outside dimensions, voluminous products can
be manufactured which can yet be supplied at all points with so much heat during
the preparation that the desired extent of cross-linkage occurs. Thus, dish-shaped
products can be manufactured, that is, also block-shaped products, with, for instance,
a recess in which a product to be packaged can be wholly or partly received, and
filler blocks for, for instance, packages, can be manufactured. Also, for instance
through extrusion, for instance hollow or finned profiles can be manufactured.
A further advantage of the relatively thin sheet parts is that, as a result, a
relatively great flexibility is obtained while the products yet maintain the desired
strength properties and volumes.
In a first preferred embodiment, a method according to the invention
is characterized by the features of claim 9.
By making use of a batter which is liquid below the gelatinization
temperature, preferably at room temperature, supply of the batter can be realized
in a simple manner, for instance via pipes and using simple pumping means. Moreover,
a stock of the batter can be priorly prepared and be fed to a processing apparatus
directly from a storage tank. In this connection, the liquidity of the batter provides
the advantage that the flow paths in the mould can be particularly long. The water
in the batter functions as blowing agent and moreover, upon evaporating from the
mould, provides space for the expansion of the cells.
The batter preferably consists entirely of constituents coming from
renewable sources, in particular in the form of a suspension. As a result, good
flow properties of the batter are maintained and crude starting material such as
starch can be used, for instance potato starch or tapioca. Moreover, such a suspension
can be simply stored, at least better than a mixture already gelatinized.
Mentioned as suitable natural polymers are native starch, for instance
potato starch, maize starch, wheat starch, waxy maize starch, tapioca starch, pea
starch, high-amylose starch or rice starch. Preferably, however, potato starch
is used with an amolypectin content of between 75 and 100%. Starch derivatives
can also be used, for instance, starch which has been modified by etherification,
esterification, acid hydrolysis, oxidation, cross-linking and/or the action of
In an alternative embodiment, a method according to the invention
is characterized by the features of claim 12 or 13.
The use of relatively dry, optionally slightly prefoamed starting
material provides the advantage that relatively little water or other moisture
needs to evaporate in the mould, which has appreciable energetic advantages, the
more so since the mass only needs to be heated in the mould, not in the pre-stage.
The mass can for instance consist of granulate material, in particular more or
less spherical particles having small to very small dimensions with respect to
the passage openings to and in the mould. This granulate material can contain a
blowing agent, for instance in the form of water or blowing agents simply released
and/or evaporating upon heating, such as bicarbonates, which provide for gas evolution
through decomposition at elevated temperature.
As starting materials, for instance, the natural polymers mentioned
in respect of the batter can be used.
In a further advantageous embodiment, a method according to the invention
is characterized in that as mould an injection mould is used.
By making use of an injection mould in a method according to the
invention, products can be manufactured with both regular and irregular shapes,
which are dimensionally stable and can have varying wall thicknesses. Products
manufactured in this manner can, for instance, be used as sheet and dish parts,
trays and boxes and like dish-shaped packages and as filler for, for instance,
packaging products in boxes and the like, and as constructional or building part.
One of the important advantages that can be achieved with this method is that a
greater freedom in design is obtained than when platen sets are used. The products
can be manufactured in withdrawable as well as non-withdrawable manner, since divisible
cores and the like can be readily utilized. As a result, for instance undercuts
can be integrally moulded. Moreover, greater differences in height can be incorporated
in the product in that the flow path can be longer and gravity has no influence,
at least no appreciable influence, on the distribution of the mass.
In a further advantageous embodiment, a method according to the invention
is characterized in that an extrusion die is used.
When using an extrusion die in a method according to the invention,
sections and the like can be manufactured in a simple manner with the above-mentioned
advantages of the cross-linked structure of the natural polymers. Owing to the
mass being supplied in cold, preferably liquid form, the preparation thereof is
particularly simple and products with the desired properties can be manufactured
in substantially one processing pass. In this manner, for instance, sheets and
sections can be extruded which are used in great lengths or can be divided up
and, for instance, be used as loose filler in the packaging of products in boxes,
crates, bags, as decorative parts, as constructional element and as building part
and the like. Extrusion and the use of an extrusion die should herein be understood
to mean in particular forcing a moulding mass under pressure through a relatively
small orifice, this orifice determining substantially at least one cross section
of the product. The delivery pressure can, for instance, be generated with a pump
or a plunger.
Products that are manufactured with a method according to the invention
can in a general sense be designed light with respect to the volume, have sufficient
strength and elasticity and are properly resistant to different conditions, in
particular when using a "skin" with a relatively high density and a core with
a relatively low density.
During the manufacture of the products according to the invention,
gas formation through evaporation of water or under the influence of blowing agents
occurs so fast that foaming occurs concurrently with or preferably prior to the
gelatinization. At elevated pressure and/or temperature this effect is achieved,
while further more solid material is "compressed" as cell wall. This not only yields
a core made up of large cells with firm cell walls but also skin layers with a
higher degree of densification of firm small cells.
In addition, there may be a number of other conditions that must
be met to obtain the desired result.
The colloidal particles and corresponding conditions must meet requirements
to provide for the formation of foam, which requires, among other things, a particular
load and particular surface tensions, in conjunction with an internal and external
pressure in the foam bubbles.
The charging of the mould cavity must be complete within a very short
time, which entails requirements for the "flow" properties and the thrust: during
this short period the "flow" properties must remain sufficient to ensure complete
filling, while the driving force, the propellant or "foam" gas, must remain present
in a sufficient amount to advance the mass (which is increasingly hard to move).
Flow should herein be understood to include both the flow of a liquid, such as
the liquid batter, and the flow of a granulate-form, relatively dry substance such
as small rolling and sliding granules or powder, whether or not in slightly prefoamed
Accordingly, the length of the flow path is at least dependent on
the liquidity of the starting material and, given equal conditions, will be greater
for a liquid or suspension than for granulate material. Moreover, the length of
the flow path will be positively influenced by a greater difference between the
low supply temperature and the temperature of the mould during the baking. Surprisingly,
it has been found that when fibers, in particular natural fibers, are added to
a mass for use in a method according to the invention, the flow properties are
not, or only to a very slight extent, adversely affected, particularly in the case
of relatively short to medium-length fibers. Fibers to be used will on average
have a length of between 0.5 and 10 mm, maximally a length of about 130 mm, and
average diameters between 1 and 100 µm. The fibers can be branched as well as
unbranched, open or still closed, while they may contain lignin and may comprise
fiber fibrils. Short fibers have a length of less than 1 mm, long fibers have a
length of more than 4 mm, medium-length fibers have a length of between 1 and
4 mm. Thus, if so desired, the fiber distribution in the mold, and accordingly
in each product manufactured, can be uniformly obtained, so that the product properties
are regularly obtained. The invention allows the production of a package comprising
an outer package and an inner package, at least the inner package being obtained
by a method according to the invention and the outer package being made of the
same material, paper or cardboard.
Such a package has the advantage that it can be considered a so-called
mono-material package, so that the package can as a whole be incorporated into
the same waste flow, in particular a paper, cardboard and recycling flow. To manufacturers
as well as users, this has the advantage of involving only a slight environmental
burden, while the user does not have to separate the package and present it separately,
while the manufacturer is not forced to take back the separated package parts and/or
does not have to pay a relatively high compensation for the eventual processing
of the package. The fibers in the product, manufactured according to the invention,
offer the advantage of having a paper-like or cardboard-like appearance, so that
it will be directly clear to the consumer that this package can be incorporated
into a paper-waste flow. Moreover, in view of the filling of the mold, indications
such as names and recycling symbols can readily be included, in relief, in the
product. Owing to the dense skin, it can be printed in an excellent manner.
Further advantageous embodiments of the method according to the invention
are presented in the dependent claims.
Products obtained by a method according to the invention can be
considered to be paper-like products.
To clarify the invention, exemplary embodiments will be described
with reference to the drawing.
- Fig. 1 shows a product, in particular a filler block, manufactured by injection
moulding, in perspective view with a part broken away;
- Fig. 1a shows, on an enlarged scale, twice a cross section of a wall of a product
according to Fig. 1;
- Fig. 2 schematically shows in cross-sectional view an injection-moulding apparatus
according to the invention;
- Fig. 2a shows on an enlarged scale a part of a mould, with mould cavity, in
- Fig. 3 shows a product, in particular an inner tray and a storage box, manufactured
by injection moulding, in cross section;
- Fig. 4 shows a product manufactured by extrusion, in perspective view; and
- Fig. 5 schematically shows in cross-sectional view an extrusion apparatus for
use in the invention.
The product shown in Fig. 1 is a filler block 1, for instance suitable
for locking a housing of a computer C in a box D with a proper fit. The computer
C and the box D are schematically represented in broken lines and are mentioned
only by way of example. The filler block 1 consists of a body 2 and a number of
first 3 and second ribs 4 extending downwards from the body 2. The first 3 and
second ribs 4 extend approximately at right angles to each other. Enclosed between
two first ribs 3, two second ribs 4 and the body 2 is a cavity 5 of approximately
rectangular cross section. The overall dimensions (length L, width B and height
H) of the filler block 1 are large with respect to the amount of material used,
and hence with respect to the weight, compared with a comparable solid block of
the same material and certainly with regard to a comparable block manufactured
from paper pulp or like material, which will have to be of a substantially solid
The first ribs 3 have a first part 6 which is relatively high with
respect to a second part 7 thereof. The second ribs 4 likewise have a first part
8 which is relatively high with respect to the second part 9 thereof. The relatively
high parts 6, 8 are arranged together, as are the relatively low parts 7, 9. The
low parts 7, 9 thus define an imaginary bottom surface 10. The approximately vertically
extending transition parts 11 between the high parts 6 and 8, respectively, and
the low parts 7 and 9, respectively, define two imaginary wall surfaces 12 which
include an angle with each other and with the bottom surface 10. The bottom surface
10 and the wall surfaces 12 define an imaginary space in which, for instance, a
corner of the computer C can be received.
When the computer C is accommodated in a box D, the filler block
1 is received between the computer C and three wall panels of the box D with a
proper fit. Preferably, such filler blocks 1 or comparable, suitably shaped filler
blocks 1 are fitted between the computer C and the box D at several points, so
that the computer C is prevented from shifting and moreover a shock-absorbing
capacity is obtained, so that damage is avoided. It is noted that the ribs can
be arranged in various orientations and positions with respect to each other and
the body 2, and more or fewer (groups of) ribs can be used. Thus, for instance,
the body can be arranged on the side proximal to the product to be accommodated,
so that a greater contact surface between the product and the filler block is obtained.
In addition, cavities 5 can be open in different directions, or at least locally
all or some ribs can extend in one direction only and, for instance, have a meandering,
sinusoidal or otherwise bent shape. Further, openings and recesses can be provided
in the ribs and/or in the body. These and many other modifications are considered
to fall within the scope of the invention.
The filler block 1 according to Fig. 1 is preferably manufactured
by injection moulding in a mould as will be further described hereinafter. The
manufacture of the filler block 1 will be described starting from a batter S which
comprises at least natural polymers. The batter is preferably a solution or suspension,
and in particular a suspension of starch or one or more of such natural polymers
and fibers, in particular fibers of annual plants and/or recycled fibers, for instance
cellulose from paper, cardboard or wood waste, in water. As will be further described
hereinafter, it is also possible to start from a relatively dry starting material,
for instance granulate material, and other compositions can also be used. A choice
for a batter or, for instance, granulate material, can for instance be made depending
on the desired supply means, desired energy consumption, flow paths in the mould
and in the feed track, availability of starting materials and the like. In this
description, "gelatinization" is intended to refer to a change of a natural polymer
from a slightly or completely loose granular or comparable granulate form into
a dry or non-dry and/or foamed cohesive form, in which stretched polymers are
present. That is to say, a transition occurs from a solid substance, a colloidal
solution or suspension to a more homogeneous fluid mass.
The batter is liquid at room temperature and slightly above that,
at least below the gelatinization temperature of the polymers or at least the greater
part thereof, which renders it easy to process, since the suspension has a good
flow behaviour and can simply be pumped. This provides the additional advantage
that the polymers are not damaged during supply, for instance by an extrusion
press screw. Moreover, such a suspension can be manufactured and preserved in a
simple manner. Surprisingly, it has been found that the flow behaviour is not adversely
affected by the fibers, in particular not if they have a length of between 0.05
mm and 130 mm, in particular between 0.5 mm and 20 mm. Particularly advantageous
are fibers having a length of between 1 mm and 5 mm. Preferably, the diameter of
the fibers is between 0.5 µm and 100µm, more in particular between 1 and 50 µm.
Particularly advantageous are fibers having a diameter of between 10 µm and 40
µm. As fibers, for instance wood, straw, grass, cane, reed, bamboo, jute, hemp,
bast, leaf, seed fibers are suitable, but also other fibers such as coleseed fibers
or the like. These examples should not be given a limitative interpretation. A
further advantage is that starch is a raw material which is simple to obtain, cheap,
and present in abundance, which, moreover, in contrast with, for instance, products
based on mineral oil and the like, is continuously replenished (renewable resources).
The same holds for the natural fibers used. The water at low temperatures serves
as solvent or suspending agent and as liquefier and, upon strong heating, as blowing
agent. As desired, additives can be added to the suspension, such as for instance
emulsifiers, liquefiers, other blowing agents and colouring and flavouring substances.
In addition, ingredients conventional in the paper industry can also be added,
such as resin glues, natural and chemical retention agents, biocides (mold and
bacteria inhibitors), antifoaming agents, paraffin emulsions and the like. If necessary,
for instance thermoplastic plastics can be added in relatively small amounts,
for instance for a further improvement of the strength properties or for a further
improvement of the resistance to moisture and temperature influences or to wear.
In an alternative embodiment, the starting material is a substantially
dry, granulate-form mass M, which will be further explained hereinafter.
Fig. 2 schematically represents an injection-moulding apparatus for
use with a method according to the invention, together with a mould suitable for
the manufacture of a product according to Fig. 1.
The injection-moulding apparatus 20 comprises a supply device 21
for a batter S, a spray nozzle 22 and a mould 23. The supply device 21 comprises
a cylindrical wall 24 with a plunger 25 movable therein with a proper fit. At a
first end the cylindrical wall 24 connects to the spray nozzle 22, and remote
from the spray nozzle 22 a supply opening 26 is provided in the wall 24, to which
a supply pipe 27 for batter is connected. The batter S is for instance supplied
from a storage tank 28 utilizing a pump 29.
In the exemplary embodiment shown, the spray nozzle 22 consists of
a conically shaped first part 30, tapering in the direction away from the wall
24, and a second part 31, connecting thereto, of circular cross section, which
second part 31 is narrow with respect to the cylindrical wall 24. Via a thermally
separating connecting piece 32, the second part 31 connects to a gate 33 of the
mould 23. Further included are means, not specifically shown in the drawing, for
shutting off the supply opening 33, after the introduction of a suitable amount
of batter into the mould. These means can for instance be part of a plunger 25
or be formed by valve means or the like. The thermal separation between the supply
means and the mould and the or each product to be formed therein should be maintained
by these means.
Provided in the mould 23 are a number of mould cavities 34, which
will be further described hereinafter and two of which are depicted. Different
numbers of mould cavities can be provided, which are identical or different. The
mould cavities 34 are connected to the gate 33 via mould channels 35 (Fig. 2a).
Connecting to the or each mould cavity 34 at a point remote from the mouth 36
where the relevant mould channel 35 opens into the mould cavity 34 are one or more
deaeration channels 37 which are in communication with the environment. This communication
is preferably free, but may also be adapted to be shut off, for instance by a
pressure relief valve. The mould 23 is suitably divisible along a plane V which
intersects the or each mould cavity, in such a manner that products formed in the
or each mould cavity can be simply removed therefrom. Further, for the or each
mould cavity 34, withdrawal or eject means 38 may be provided for pushing clear
the products formed.
Arranged around the cylindrical wall 24 are means 39 for cooling
the batter S. Cooling should herein be understood to mean maintainance at a temperature
which is below the temperature at which gelatinization of the natural polymers
in the batter occurs. These cooling means can for instance consist of coolant-conveying
pipes 39. Such cooling means 39' are likewise arranged around the spray nozzle
22. The mould 23 is entirely and/or locally heated utilizing heating means 40
incorporated therein. The thermally separating connecting piece 32 contributes
to a thermal uncoupling of the supply device 21 and the mould 23. Cooling of the
section 21, 22 of the apparatus upstream of the mould 23 prevents the occurrence
of gelatinization, cross-linkage or chemical change in the suspension in the supply
device, which would adversely effect the flow properties thereof in particular.
The mould 23, of which Fig. 2a shows a part with a mould cavity 34
on an enlarged scale, contains different heating means 40. In the exemplary embodiment
shown, the mould cavity 34 is defined by a number of slotted recesses 41 intersecting
each other approximately at right angles, in a first part 42 of the mould 23,
and a trough-shaped hollowing 43 in a second part 44 movable against the first
part 42 of the mould. The depth of the hollowing 43 is small with respect to the
width and the length thereof; the width of the recesses 41 is small with respect
to the depth and the length thereof. When the first part 42 is clamped against
the second part 44, the mould cavity defines a space corresponding with the shape
of the product according to Fig. 1.
In the projections 45 formed between the recesses 41, a heating element
46 is included, for instance an electric heating element. It is noted that the
mould parts can also be heated indirectly. On the side of the hollowing 43 remote
from the dividing plane V, likewise heating elements 46 are included. The temperature
of the different heating elements is preferably controllable individually, but
several or all heating elements may also be coupled. In addition, the mould can
be heated externally from one or more sides, for instance electrically or by steam
or gas burners. Through the heating elements 46 and optional other means, the temperature
of the mould can be raised in such a manner that in the mould cavity 34 during
use, as desired, at all times and at all points the desired high baking temperature
is achieved and maintained.
The injection-moulding apparatus according to Figs. 2, 2a can be
used as follows.
The mould parts 42, 44 are clamped against each other and the eject
means 38, if any, are set in the rearmost position, outside the mould cavity or
mould cavities 34. The plunger 25 is moved in the direction away from the spray
nozzle 22, beyond the supply opening 26. As a result, the supply opening 26 is
cleared and the interior of the supply device 21 and the spray nozzle 22 are filled
with batter S. The cooling means 39, 39' and the heating means 40, 46 are switched
on in such a manner that the different parts are adjusted to the desired temperature
and so maintained. To that end, the temperature can be maintained constant or
be varied during the baking and/or cooling time. The plunger 25 is moved forwards
over a short distance, so that an amount of batter is pressed into the mould and
into the mould cavities 34 under high pressure, whereafter the gate 33 is shut
off, under a suitable thermal separation. In the mould cavities 34 the batter
is brought to the desired temperature, for instance between 150°C and 350°C, and
maintained at that temperature for a "baking time" of, for instance, 2 minutes.
As a result, gelatinization and subsequent cross-linking of the (natural) polymers
occurs, and bonding to the fibers. In addition, the strongly heated water and/or
other liquids evaporate from the batter, giving rise to the formation of bubbles.
In the batter, bubbles are formed which are partly encapsulated by the cross-linked
structure. This yields a foam structure, which can be further enhanced by adding
extra blowing agent. In order to allow substantially all of the evaporating moisture
to escape from the mould, a sufficiently large number of vents are provided. After
the baking time, the mould 23 is opened in two or more parts and the products are
taken from the mould cavities 34 or pushed out of them using the ejectors 38.
Upon heating of the suspension to a temperature above the gelatinization
temperature, and at least above the gas formation or vaporization temperature of
the or a blowing agent, within the suspension gelatinization of the polymers occurs
and moreover bubble formation as a result of evaporation of the water. For starch,
the gelatinization temperature is for instance in the range of 54-65°C. Upon further
heating of the suspension, cross-linking of the polymers occurs, yielding a firm,
relatively dense structure around cells that result from the evaporation of the
water and optional other blowing agents and around the fibers extending within
the wall of the product.
The injection-moulded product has an at least substantially closed
skin 13 of closed cells and a foamy core 14 which comprises open cells 15 between
and through which fibers extend that have a relatively great length relative to
the cells. In Fig. 1a, on an enlarged scale, a cross section through one of the
ribs 3 is shown. The closed skin 13 provides for a good resistance to external
influences, such as for instance moisture and temperature, while the core 14 provides,
among other things, for a large volume combined with a relatively small weight
and for good resilience. Further, the skin 13 has a rigidity- and strength-enhancing
effect. The walls 14', as a result of the baking, have a firm skeleton.
The fibers 16 extend within the wall of the product relatively at
random, while, because of the flow behaviour during the filling of the mould, a
preference occurs for orientation approximately parallel to the skin 13 and along
the cell walls. Hence, each fiber 16 is in contact with a series of cells in the
skin 13 and/or the core 14. Consequently, the cell acquires a relatively high bending
strength and tensile strength. Moreover, in the event of an overload, the wall
may tear without directly involving breaking. That is to say, in the event of an
overload, the different parts of the product remain interconnected, so that no
fragmentation occurs. This prevents large amounts of loose, separate waste parts.
However, the product can nevertheless easily be reduced through flattening, so
that the product as waste takes up relatively little space.
The fibers 16 are always completely surrounded by the batter, or
at least the mass, so that they are not exposed in the surface, yet a part of the
fibers is in fact visible in the surface, which may give the product a fibrous,
paper- or cardboard-like appearance. This has as an advantage that it is clear
to the user that, after use, the product can be included in a paper-recycling flow
as if it were old paper, which is preferred from an environmental viewpoint. If
so desired, for instance by coating the fibers, this effect can be enhanced or,
by contrast, prevented.
The skin is dimensionally stable, which enables, for instance, its
being printed on, as well as the provision of relief using the or each mould cavity.
As long as the skin 13 remains closed, moisture absorption by the
product is adequately prevented or at least slowed down to a great extent. Through
a suitable choice of the ingredients, the temperature build-up and the pressure
build-up in the mould cavity, the properties of the product can be influenced,
for instance in that the skin 13 is thinner or thicker with respect to the core
14 and in that the core 14 and the skin 13 are cross-linked to a greater or lesser
extent ("well-done"). By variation of the temperature in time and/or in the different
parts of the mould, and in particular by changing the temperatures of the different
projections 45, the properties of the different parts of the product can be changed,
so that, for instance, the elasticity of the parts can be different.
In contrast with the known method in which use is made of platen
sets, with injection moulding, first the mould cavity is closed and only then is
the batter introduced into the mould. As a consequence, the total volume of the
mould cavity can be greater than the volume of the separate mould cavity parts
as contained in the mould's first 42 and second part 44, respectively. In fact,
in the known method, the batter is to be introduced into a cup-shaped cavity and
held therein until the mould is closed. When the mould is being closed, the batter
moreover cannot be allowed to be pressed away across the edges because it will
then flow between the land areas and prevent closure of the mould or at least render
it more difficult. In the known method, therefore, the total volume of the closed
mould cavity should be considerably smaller than the volume of the cup mould,
which moreover initially includes all of the moisture which subsequently evaporates.
Further, the use of platen sets entails the risk that the mass standing still in
the open mould causes separation, as a result of which the properties of the product
will vary and, moreover, will not be equal for all products. In a method according
to the invention, the pressure during the introduction into the mold prevents
this, so that a constant distribution is realized, in particular also of the fibers,
or at least the desired distribution is always realized.
Fig. 3 shows a cross section of an inner tray 50 in a storage box
51, in which inner tray 50 for instance a household appliance 52 can be accommodated.
The inner tray 50 is dish-shaped, that is, at least for the most part thin-walled,
and has a receiving cavity 53. Situated adjacent the upper edges 54 of the receiving
cavity 53, on opposite sides, is a clamping projection 55 which is formed integrally
therewith and has an undercut 56 under which the shaver 52, which is shown in broken
lines, can be pressed down. The inner tray has been formed by injection moulding,
utilizing a divisible core. As a consequence, the clamping projections 55 can be
integrally injection moulded. Accordingly, the method according to the invention
also enables the manufacture of non-withdrawable products in one processing pass,
which renders such products particularly suitable, for instance, as packaging material,
storage material and the like, but also as filling material, for instance for
sandwich-shaped construction parts, for housings and the like.
The inner tray 50 and the storage box 51, which is for instance manufactured
as outer package from cardboard, can together be incorporated into the paper-recycling
flow, so that the total package can be regarded as monomaterial package.
Fig. 4 shows a filler product 60, in the form of a so-called "loose
fill material", a filler product 60 which is used for packaging products in a shock-absorbing
manner in, for instance, boxes, cases, crates or like packages. To that end, a
multiplicity of the filler products 60 are loosely poured into the space between
a product (or products) to be packaged and the package, whereafter the package
can be closed and movements of the packaged product within the package are prevented
or at least accommodated in a shock-absorbing manner. To that end, the loose fill
material is slightly elastically deformable.
The filler product 60 as shown in Fig. 4 comprises an approximately
cylindrical core 61 and a number of fins 62 extending approximately radially from
the core, and which extend throughout the length of the core. The fins are relatively
thin with respect of their height and length, so that they exhibit a measure of
bending slackness. The circumference of the filler product 60, measured along the
tops of the fins 62, is largely determinative of the volume the filler product
occupies, so that a favourable volume-to-weight ratio is obtained.
The filler products according to Fig. 4 and similar for instance
lengthwise symmetrical products can be formed by extrusion on an apparatus according
to Fig. 5. The extrusion apparatus comprises a supply device comprising means 80
for the (semi)continuous pressurized supply of batter S or a granulate-form mass
M, whether or not pre-foamed to some extent, from a storage tank to a spray nozzle
81, for instance utilizing one or more pumps. Connecting to the spray nozzle 81
in this extrusion apparatus is an extrusion die 63 which comprises one or more
extrusion orifices 64 of a cross section which substantially corresponds to, at
least is similar in shape to, the cross section of the filler product to be obtained.
The supply device 80, and in particular the spray nozzle 81 are provided with
cooling means 82, for instance as described in the foregoing. The extrusion die
comprises heating means 65 which are arranged in such a manner that at least in
the extrusion orifices the temperature can be accurately controlled, for instance
to 210°C to 255°C. Arranged on the side of the extrusion die 63 remote from the
supply device 80 is a cutter 66 by which extruded sections can be cut into short
lengths upon exiting from the extrusion orifices.
The apparatus according to Fig. 5 can be used as follows.
From the supply device 80, a continuous flow of batter S or a mass
M in granulate form, whether or not in a slightly pre-foamed condition, is fed
via the spray nozzle 81 to the heated extrusion die 63 and forced through the or
each extrusion orifice 64. The leading part of the batter gelatinizes and proceeds
to cross-link, whereby the moisture evaporates from the batter and provides for
the foaming of the product, optionally together with additional blowing agents
and other additives, while the fibers will extend within the fins and the core,
substantially in the longitudinal direction of the core and radially and in the
longitudinal direction in the fins. As a result, also in the case of tearing, the
fins will not come loose from the core. The filler products are relatively strong
and resilient particularly because of the fibers. Preferably, the cross section
of the or each extrusion orifice 64 widens slightly in the direction of extrusion,
in such a manner that during the foaming of the product, as the baking batter S
is being passed through the extrusion orifice, the pressure that is exerted on
the filler product 60 is sufficient to obtain the desired skin and core properties,
without the cross-linked structure thereof being broken or otherwise damaged by
the extrusion die.
As a result of the continuous supply of batter, the "baked" part
of the extruded section is pushed forward, in such a manner that it leaves the
corresponding extrusion orifice 64. On the leading side, each time a part of the
section is cut off, whereby the cut surface is closed. In this manner, at a relatively
high rate and at relatively low cost a large amount of loose fill material can
be manufactured from a liquid batter or sections in great lengths, and can for
instance also be in sheet form. These filler products are environmentally friendly.
When the batter is liquid, preferably in the form of a solution or
suspension, manufacture, storage, transport and dosage thereof are particularly
simple and in a method according to the invention use can be made of a simple apparatus,
which renders these methods relatively cheap. Further, in most embodiments the
natural polymers need not be subjected to any expensive pretreatments before they
can be used. They only need to be included in the batter.
In the foregoing, methods and apparatuses have been described for
manufacturing products with a foamed structure using an injection-moulding technique
and an extrusion technique, the starting material being a liquid batter, in particular
a solution or suspension. However, as indicated, it is also possible to start from
a substantially dry mass consisting of, or at least comprising, for instance, a
granulate material. The granulate material can, for instance, comprise more or
less spherical particles having small dimensions with respect to the orifices in
the moulds and supply means. Like a liquid, these particles can display a certain
flow behaviour, as a result of which, under pressure of the supply means, they
can fill the mould or be conveyed through it. The particles used have dimensions
and shapes such that, together with the other ingredients, they can form aggregates
The particles which can contain, for instance, water or a different
blowing agent in relatively small amounts, are heated after being introduced into
the mould and will swell as a result, since the blowing agent present will blow
up the particles, just as in the case of the particles included in the solution
or suspension. With such a starting mass too, the polymers will provide for a high
degree of cross-linkage and hence a firm cell wall of the blown cells. The fibers
will adhere to one another and to the batter to form one or more networks. It
is true of such a method too, that the mould as hot part together with the pressure
and the blowing agent will lead to a high degree of densification of the outer
parts of the walls of a product, the so-called skin, while the core will contain
Due to the fact that in this method less moisture is included in
the starting mass, relatively little energy is necessary therefor, in that less
heat is needed for the evaporation. This is precisely what is of particular importance
for the manufacture of products according to the invention, foamed paper-formed,
in view of the environmental advantages that can be achieved with such products.
Partly as a consequence of relatively cheap raw materials and high production rates
that can be achieved, thus a low-energy, environment-friendly and economically
advantageous production method has been obtained for products that present few
environmental problems, if any, also in the downstream stage, that is, as waste.
For that reason too, products manufactured by a method according to
the invention are practical for use as packaging material or construction material,
while moreover they do not present any problems regarding static charge.
The paper-like products manufactured by a method according to the
invention have for instance a density of less than 1000 g/l, more in particular
a density of between 100 and 800 g/l. However, other densities are also possible.
When a mass M in granulate form is used, of course a different flow
behaviour occurs than if a batter S is used. Moreover, not every starting material
is suitable for use as or in granulate form, at least not advantageously so. Moreover,
when using granulate material together with fillers, or combinations of granulate
materials, it is sometimes not easy to prevent separation or to obtain and/or to
maintain a good constant mixing.
In order to improve the appearance of the products, a colorant can
be added to the batter. For that purpose, the fibers can for instance be coated
completely or partly, Also, a surface layer can be formed, for instance through
texture differences or by variation in temperature of the mould at different positions
across the surface, so that local changes occur in the skin as a result of different
baking conditions. Naturally, it is also possible, after manufacture, to provide
parts of the product with a coating, coloration or printing. Furthermore, it is
possible to mould in, for instance, inserts in the product.
By way of illustration, examples are given of methods according to
the invention, which should not be construed as being limitative in any way.
From 644 g tap water, 6 g polymethyl hydrogen siloxane, and 50.5
g recycled cellulose, a solution was prepared. The recirculated cellulose consisted
on average for 75% of short cellulose fibers and for 20% of fiber binders. The
other parts were various inert fillers. This raw material was introduced in the
form of a selected type of old paper (newsprint). To the solution, 251 g potato
starch (FoodGrade PotatoStarch, 80% dry substance (80% amylopectin, 20% amylose)
and 20% water) were added with continuous stirring, followed by 0.8 g xanthan gum
(Keltrol F), 0.9 g calcium hydroxyorthophosphate, 17 g kaolin (China Clay Spes),
20 g calcium carbonate, and 0.5 g acidity regulator (sodium dihydrogen phosphate).
After all components had been added, stirring was continued for about 10 minutes.
Through the thus obtained suspension, 8.5 g hemp fiber (2-5 mm) and 0.8 g blowing
agent (sodium - bicarbonate) were mixed.
After a liquid batter was stirred from this, it was introduced into a supply device
of an injection-moulding machine. The injection-moulding machine employed is of
the type EPS-10, from the firm Thermoware of Barneveld. This apparatus comprised
a mould with ten mould cavities for forming products, each product having a size
of 210 x 65 x 45 mm (L x W x H) and a wall thickness of 3.0 mm. The injection-moulding
machine comprised electric heating elements and a plunger-injection device with
a shut-off thermally uncoupled from the mould. Per mould cavity, about 70 cc batter
was injected under a pressure of 0.5 bar and at a temperature of 20°C. The mould
was heated to 300°C, with a temperature tolerance of between 297°C and 303°C and
the mould was closed with a force of 35 kN per mould cavity. The mould was closed
for 90 s and maintained at the required temperature, while each mould cavity was
filled entirely with foamed product. During heating, 98% of the water escaped,
substantially in the form of vapour, via vents in the mould; this water acted as
blowing agent. After 90 s, the mould was opened and the injection-moulded products
were pressed from the mould cavities by means of ejectors.
The thus formed products were directly ready for use. Each product has a core of
a thickness of about 2.5 mm, covered on opposite sides by a skin of a thickness
of about 0.2 mm. Each product had a moisture content of about 2% and a weight
of 31 g. The obtained product was firm, form-retaining, and had a smooth surface.
After use, the material can be processed in the paper-recycling flow, and is also
biodegradable by means of composting.
In this example, a solution of 514 g tap water and 20 g polymethyl
hydrogen siloxane formed the basis for the batter. Added to this - with continuous
stirring - were 219 g potato starch (FoodGrade PotatoStarch, 80% dry substance
(80% amylopectin, 20% amylose) and 20% water), 100 g acetylated potato starch
(perfectamyl AC), 0.7 g xanthan gum (Keltrol F), 0.8 g calcium hydroxyorthophosphate,
20 g kaolin (China Clay Spec), 24 g calcium carbonate, and 0.5 g sodium dihydrogen
phosphate. This mixture was well stirred for 10 minutes. In the suspension now
obtained, 1.7 g of the retention agent Amylofax and 96 g coated cellulose fiber
(coating-comprising crystalline parafine wax) were subsequently mixed. The coated
fiber (about 1.5 mm) was to a high degree water-repellent, and minimally water-absorbent.
Moreover, the coating provided for the bonding of fibers relative to each other
and to the other ingredients, which increased the firmness and strength of the
product; even in moist conditions, the product changed minimally as far as size
and shape are concerned. Finally, 1.9 g flocculant (aluminum chloride (AlCl3))
and 1.4 g blowing agent (sodium bicarbonate) were stirred through the mixture
to obtain a homogeneously smooth raw material.
This raw material was processed as in Example 1, but now with an injection volume
of 50 cc per mould cavity, under a pressure of 1 bar. The mould was set at 275
degrees Celsius and was closed for 110 s.
The result was a product comparable with Example 1, in which the water and moisture
resistance now became much better: the product was water-resistant for a much longer
period, i.e. the firmness and form stability were maintained for a long time.
The recyclability in paper, and the biodegradability remained guaranteed.
A solution of 698 g tap water, 5 g glycerol, and 20 g cellulose fibers
(about 2.5 mm) was prepared. During continuous stirring, 65 g potato starch (FoodGrade
PotatoStarch, 80% dry substance (80% amylopectin, 20% amylose) and 20% water),
60 g tapioca starch (FoodGrade TapiocaStarch), 30 g lecithin, 18 g 60 mesh wood
flour, 0.4 g xanthan gum (Keltrol F) and 0.5 g acidity regulator (sodium dihydrogen
phosphate) were successively added.
After stirring for 10 minutes, 1.7 g amylofax as retention agent, 80 g hemp fiber
(2-3 mm), 20 g coated (elastic) fiber (about 3 mm) (coating: polyethene, elastomer),
and, finally, 1.4 g sodium bicarbonate followed. Stirring was again continued
for 10 minutes until a proper distribution was brought about.
The mixture was processed as in Example 1, while the injection volume was 85 cc
at an injection pressure of 2.5 bar. As mould temperature 240 degrees Celsius was
maintained, during the cycle period of 180 s.
A product of great strength was obtained: only in the case of heavy point loads
did the product eventually tear, without breaking into loose parts. For specific
applications, this tearing instead of breaking is a highly important condition.
A solution of 722 g tap water, 10 g melamine, 14.5 g resin glue (urea
formaldehyde resin), and 80 g cellulose (about 1.5 mm) was prepared. After that,
during stirring, 112 g potato starch (FoodGrade PotatoStarch, 80% dry substance
(80% amylopectin, 20% amylose) and 20% water), 0,3 g xanthan gum (Keltrol F),
0.9 g calcium hydroxyorthophosphate, 5.5 g kaolin (China Clay Spec), 6.5 g calcium
carbonate, and 0.7 g sodium dihydrogen phosphate were added. After mixing for about
15 minutes, a smooth suspension was formed, in which the following was admixed:
2.5 g AKD (Alkyl Ketene Dimer), 42 g coated fiber (coating: polyethene elastomer)
as used in Example 2, 1.7 g flocullant (aluminum chloride (AlCl3) and
1.4 g blowing agent sodium bicarbonate.
The suspension was processed as in Example 1. As injection volume 90 cc was needed,
at a pressure of 2 bar. The mould temperature was 280 degrees Celsius. The cycle
time was 150 s before a finished product was injection-moulded.
As to its functional properties, the product was comparable with the result of
Example 2. The rate and degree of biodegradability were lower. The processing in
the paper-recycling flow remained guaranteed. The major advantages were found
in the durable practical possibilities of the product, at acceptable prices for
the raw materials used.
A batter was prepared in the same manner as in Example 1. At a pressure
of 5.5 bar, this batter was continuously fed to an extrusion die with a star-shaped
aperture of a cross section of 250 mm2 and a length of 50 mm, which
aperture was 150 mm long in the downstream direction. The die was heated to a
temperature of 255°C, so that approximately 95% of the water evaporated from the
batter to form cells, while in the batter gelatinization and cross-linkage of the
starch polymers around the cells occurred. Upon leaving the die, a section had
been formed with a foam core, covered by a skin of a thickness of approximately
0.1 mm, the product formed being pushed out of the die by the batter being introduced.
The thus formed section had a specific weight of approximately 150 g per dm3
and could simply be cut into short lengths for the formation of loose fill material.
64 g jute fiber (about 1 mm) was mixed in dry form with 18 g cotton
threads (3 mm). With continuous stirring, 811 g native starch (FoodGrade PotatoStarch,
80% dry substance (80% amylopectin, 20% amylose) and 20% water) was added. Next,
107 g water, wherein 2 g blowing agent (sodium bicarbonate) and 5 g polymethyl
hydrogen siloxane were dissolved, was added. Due to the slight moisture content,
a dry, homogeneous granulate material was obtained with the moistened starch granules
(having an average diameter of 50 micron) bonding to the moistened fibers: these
aggregates of the mixed composition were further processed as granulate material.
The granulate material was introduced into a closed pretreatment apparatus, then
brought to a slightly raised temperature of about 50 degrees Celsius, and under
a pressure of 5 bar. Through the sudden application of a reduced pressure, in
this case through a rapid pressure drop from 5 bar to 1 bar, the starch granules
swelled to a diameter of about 100 micron, without involving a significant form
of gelatinization. Due to this pre-foaming, the moisture content decreased to about
By means of an airpressure plunger system, 85 cc pre-foamed granulate material
with a density of about 100-180 g/l was pressed in an injection mould. The injection
mould had a box-shaped cavity with the dimensions 190 x 125 x 18 mm and a wall
thickness of 3 mm. The mould was kept closed with a force of about 15 kN per cavity
and was then heated for about 55 s to about 270°C, whereby gelatinization and
cross-linkage of the natural polymers occurred, while the water substantially evaporated
from the granules with further foam formation. The thus obtained tray was contiguously
removed from the mould.
The tray was dimensionally stable and had a water content of about 1%. The wall
of the thus baked product had a core of open, blown and relatively large cells,
while the outer sides of the wall had a structure of compact, relatively small
and substantially closed cells.
The invention is not in any way limited to the embodiments shown
or described. Many variations are possible without departing from the scope of
the invention as defined in the appended claims. Thus all kinds of other products
can be manufactured with a method according to the invention, such as for instance
trays for chips or snacks, edible containers such as ice-cream cups, sheet, bar
and profiled material for all kinds of uses, plate-shaped or preshaped construction
material, and, in particular after further preservation, cups for cold and hot
beverages, packages for freezer and airplane meals, presentation material and like
and many other comparable products.