Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2079~
Wo 92/13004 PCT/EP92/00152
Process and apparatus for the preparation of a product
containing starch and/or at least one starch derivative
Technical field of the invention
The invention relates to a process and an
apparatus for the preparation of a product containing
starch and/or at least one starch derivative.
Products based on starch can be used, for
example, for replacing plastics products and, compared
with the latter, generally have the advantage of being
better degradable and/or degradable with less
environmental pollution and in particular biodegradable
and furthermore of being flame-retardant.
Prior art
Several processes for the preparation of
various starch products have already been disclosed.
In a process disclosed in US-A 4 673 438 for the
preparation of pore-free starch products, a material
consisting of starch and/or starch derivatives and
water is heated and extruded in an extruder together
with an extender, a crosslinking agent and a lubricant.
The resulting, gelled mixture is processed to capsules
and packaging containers by means of an injection
molding apparatus.
In this known process, the starch is gelled at
a temperature of 80 C to 240C in the interior of the
extruder. However, the forced transport between
successive windings of the helical rib of the screw
prevents the simultaneous mixing of the starch with the
additives introduced. Since in addition relatively
high shear forces are exerted on the mixture present in
the interior of the extruder by the movement of the
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screw, there is a danger that the mixture will
agglomerate in the interior of the extruder. This
additionally hinders homogeneous distribution of
additives in the mixture and furthermore makes it more
difficult to keep the pressure of the mixture constant
during extrusion from the interior of the extruder.
This in turn has the disadvantage that, particularly in
the production of large articles, it is virtually
impossible to produce these with a homogeneous density.
In the cited US-A-4 673 438, it is true that
the production of packaging containers for packing food
and other products is mentioned. However, it appears
doubtful whether relatively large and thin-walled
containers, such as those now conventionally used as
plastics containers for packing foods, can be produced
by gelling a starch-containing mixture and then
injection molding this mixture. Furthermore, it is
likely to be at least difficult or even impossible to
use the known process to produce containers which are
sufficiently water-resistant to pack moist or water-
containing products - such as fresh meat. In addition,
the known process can scarcely be used to produce
relatively large transparent articles, for which
homogeneous distribution of the crosslinking agent in
2~ the mixture is essential. Moreover, it is also
impossible, by means of injection molding, to produce
films such as those which are desired as intermediates
or end products for various purposes.
In a process disclosed in EP-A-0 087 847 for
the production of foamed, gelled starch products, a
material consisting of starch and/or starch derivatives
and water is heated and extruded in an extruder
together with a crosslinking agent and a blowing agent
to temperatures of 60 C to 220 C. Extrudates formed
during extrusion can then be divided into foam
particles which have a particle size of 3 cm to 5 cm
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WO 92/13004 PCT/EP92/00152
and are used as binders for foods or carriers of odor
and flavor components and also as packaging material
for protecting fragile articles.
Since the mixture formed in the interior of the
extruder contains a blowing agent and is at the above-
mentioned, relatively high temperature in the extruder,
expansion and foam formation with simultaneous
solidification of the pasty mixture already occurs in
the interior of the extruder and in the outlet, which
usually consists of a die. Because the mixture foams
in the extruder itself, it can at most foam and expand
a little further after flowing out through the outlet
of the extruder. If a sheet-like or strand-like
article is produced as an intermediate or end product
by continuous extrusion, its maximum possible cross-
sectional dimensions are at most slightly larger than
the cross-sectional dimensions of the passage of the
die of the extruder. The last-mentioned cross-
sectional dimensions are in turn limited by the cross-
sectional area of the interior of the extruder. Forexample, it is therefore scarcely possible to produce
large sheets, as required, for example, for packing
television sets and the like. Furthermore, the foaming
of the mixture in the interior of the extruder makes it
impossible or difficult to keep constant the pressure
of the mixture while it is being pressed through a
profiled die which serves for shaping or while it is
being pressed into a mold. This in turn has the
disadvantage that it is virtually impos~ible to produce
articles having the intended shapes and dimensions in
a more or less exact way.
Furthermore, this process permits exclusively
the production of foamed products but not the
production of pore-free products, such as, for example,
transparent films. Since, as mentioned above,
homogeneous distribution of the crosslinking agent in
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the mixture is essential for transparent products, the
process disclosed in EP-A-0 087 847 would be unsuitable
for the production of transparent products even if no
blowing agent were added, since a crosslinkin~ agent
added to the mixture before entry into the extruder is
likewise not homogeneously distributed in the mixture.
The process disclosed in EP-A-0 087 847 also
has the disadvantage that the starch and the water are
evidently mixed with one another only on introduction
into the extruder. In such a mixing process, the
starch particles can swell only slightly, if at all,
which in turn prevents absorption of the crosslinking
agent into the molecular structure of the starch and
hence homogeneous distribution of the crosslinking
agent.
Descri~tion of the invention
The object of the invention is therefore to
provide a process and an apparatus for the alternative
production of pore-free, for example transparent and
glass-clear or foamed and porous starch products in
which the disadvantages of the known processes and
apparatuses should be eliminated. It is desired in
particular, both in the preparation of a pore-free
product and in the preparation of a porous product,
completely to dissolve the starch during the
preparation process and to form a product which has a
very homogeneous density, structure and crosslinking.
In the preparation of an unfoamed product, this product
should accordingly actually be completely pore-free
and, if required, can be transparent and, for example,
even clear and glass-clear. In the production of a
foamed product, it should furthermore be possible to
ensure that, if required, the material can also foam
and expand after flowing out of a cavity in which it
has been gelled. In addition, it should be possible to
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ensure that the pressure of the material on passing
through an outlet or while being pressed into a mold is
as constant as possible and as far as possible has
exactly the intended magnitude so that the article
formed, or each article formed, as far as possible has
exactly the intended shape, the intended dimensions
and/or a homogeneous density.
This object is achieved by a process having the
features of claim 1 and by an apparatus having the
features of claim 33.
Particularly advantageous embodiments of the
process and of the apparatus are evident from the
dependent claims.
In an advantageous embodiment of the process
according to the invention, a material which contains
starch-containing biomass and/or pure starch and/or at
least one starch derivative and usually water and/or
alcohol can ~e introduced into a transport and/or
pressing apparatus and, in this apparatus, by means of
a movable transport and/or pressing element, can be
subjected to pressure, mixed, compacted, moved and
pressed through an outlet of the transport and/or
pressing apparatus from the interior of the latter into
the cavity of a gelling and/or mixing chamber, possibly
mixed with additives in the latter and heated, melted
; and gelled by supplying hot steam.
On introduction into the interior of the
transport and/or pressing apparatus, the material or
the starch-containing biomass and/or starch and/or the
starch derivative are usually in a particulate state
and in fact consist, for example, of already swollen
particles or grains. Furthermore, when introduced into
the interior of the transport and/or pressing
! apparatus, the material preferably contains neither a
crosslinking agent nor a blowing agent.
The trsnsport and/or pressing process which
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taXes place in the transport and/or pressing apparatus
causes heating of the material. If necessary, the
latter can be additionally heated or possibly cooled
and brought to an advantageous, relatively low
temperature in the interior of the transport and/or
pressing apparatus by means of a heating and/or cooling
apparatus. As will be explained, the starch and/or the
starch derivative of the material used may contain no
more than a small amoun~ or a relatively large amount
of amylose - depending on the type of product to be
prepared. At least when the material contains little
or no amylose, the temperature of the material in the
total interior of the transport and/or pressing
apparatus is expediently less than 60 C, preferably at
least 30 C and, for example, 40~C to 55-C. In
experiments performed, for example, a temperature of
about 50-C proved particularly advantageous. If, on
the other hand, an amylose-rich material is used, it
should preferably be at the above-mentioned
temperatures at least in the first half of the interior
of the transport and/or pressing apparatus.
If the temperature in the interior of the
transport and/or pressing apparatus is fixed in the
manner described above at an advantageous, relatively
low value and furthermore the material introduced into
the interior is advantageously both free of
crosslinking agent and free of blowing agent, it is
possible to achieve a situation where the starch and/or
starch derivative particles usually present when the
material is introduced into the interior of the
transport and/or pressing apparatus lose their cohesion
and disintegrate when the transport and/or pressing
process takes place, without there being any
significant gelling, without the starch and/or the one
or more starch derivatives agglomerating and without
! the material foaming. Furthermore, when the material
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is compressed and compacted, its viscosity decreases
again.
In a preferred embodiment of the process, an
extruder or screw extruder which has a cylindrical
S chamber which defines an elongated interior and has an
inlet at one end and an outlet at the other end is used
as the transport and/or pressing apparatus. A
rotatable, axially non-displaceable screw may be
arranged in the chamber as a transport and/or pressing
element, and a plurality of such screws may be present.
Using an extruder or screw extruder of this type, the
material is transported continuously from the inlet to
the outlet and pressed out through the latter.
The material can be introduced, i.e. pressed,
from the interior of the transport and/or pressing
apparatus through a preferably nozzle-shaped outlet
which forms a constriction, via a non-return valve,
into the cavity defined by a chamber. The chamber is,
for example, cylindrical and formed by a gelling and/or
mixing chamber of a gelling and/or mixing apparatus
which has a stirring mschanism having at least one
stirrer which can be rotatable about the axis of the
chamber, which axis is, for example, vertical or
horizontal. In addition to the feed line connected to
the outlet of the transport and/or pressing apparatus,
at least one further feed line which forms an inlet for
introducing a crosslinking agent and/or blowing agent
and/or any other additives can enter the cavity.
Furthermore, a plurality of orifices for introducing
steam and/or alcohol vapor into the cavity are also
present. The temperature in the stated cavity is
preferably greater than the temperature in the interior
of the transport and/or pressing apparatus and
depending on the type of material and on the product to
be prepared - is preferably at least 80 C, usually at
least 100C, expediently at least 140C, for example
even at least 150C or at least 160 C and, for example,
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not more than about 240~C. The cavity preferably has
a gas-tight seal with respect to the environment, so
that the material in the cavity can be kept under a
pressure which is greater than the ambient atmospheric
pressure. The pressure in the cavity is preferably at
least 50 kPa and preferably not more than 1.5 MPa
greater than the ambient atmospheric pressure and can
accordingly - measured as absolute pressure
preferably be at least 0.15 MPa and, for example, 0.3
MPa to 2.5 MPa. The material present in the cavity is
preferably heated at least in part or, for example,
completely by the supplied steam and/or alcohol vapor,
which is preferably superheated. The vapor preferably
has a temperature of more than 100 C, expediently at
least 120 C, preferably at least 140C, preferably not
more than 240 C and, for example, 150 C to 200 C. The
vapor is preferably passed into the cavity in such a
way that at least some - for example the major part -
of it is dissolved in the material as vapor or gas. At
least some of the vapor passed into the material, i.e.
preferably the major part thereof, and possibly the
total amount of steam passed into the material should
then be removed again from the material. This can be
effected, for example, if the material is passed out of
the cavity and through a vapor separator. However, it
; is also possible to remove all or some of the steam
and/or alcohol vapor from the material when the latter
flows out through an outlet, the pressure of the
material decreases to the ambient atmospheric pressure
' 30 and the material furthermore comes into contact with
the surrounding air. On flowing through a pipe
connecting the cavity to the stated outlet, the vapor
fed to the stated cavity may condense partly or
completely, so that, when the material flows out of the
outlet, the vapor-forming material is partly or
completely in the liquid state and separates from the
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gelled mixture in the form of a liquid. Under certain -
circumstances, it is even possible to remove some or
even all of the vapor passed into the cavity from the
material in the cavity itself and to pass this vapor,
for example, via a vapor outlet provided with a
pressure relief valve and out of the cavity.
The material can be processed in a relatively
dry state in the preferably present extruder or screw
extruder or at least in the first half of the distance
covered therein by the material. During this
procedure, the material may become quasi-homogeneous
and pasty. A crosslinking agent and/or a blowing agent
and possibly also at least one other additive may be
added to the homogenized, relatively free-flowing
material present in this state, in the cavity of the
gelling and/or mixing chamber. Heat energy can be fed
to the material present in the cavity by means of the
steam and/or alcohol vapor and can be uniformly
distributed in the material. It is also possible, for
example, for at least some of the steam and/or alcohol
vapor to be converted in the cavity into a liquid and
to be absorbed by the material. The liquid produced in
this manner into the material is uniformly distributed
in the material. By supplying the steam and by means
of the one or more stirrers, the free-flowing material
is homogeneously mixed with the above-mentioned
additives. The free-flowing material present in the
cavity is therefore uniformly heated, melted and gelled
by means of the steam and/or alcohol vapor and the
stirrer. The supply of steam and/or alcohol vapor
prevents in particular partial agglomeration of the
free-flowing material in the cavity of the gelling
and/or mixing chamber and deposition of said material
on the inner walls of the cavity.
The free-flowing, gelled material formed in the
cavity and preferably provided with additives is also
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WO 92/13004 PCT/EP92/00152
referred to below as the mixture and, in the still more
or less warm state, can be pressed under the action of
the pressure generated by a transport and/or pressing
apparatus and/or by the steam through a pipe which has
a closed cross-section and which may, if required, be
heated or cooled, and through a vapor separator which
for example may be present, out of an outlet. The
outlet may be formed, for example, by a slot die, a
casting head or a profiled mold. The profiled mold has
at least one passage to impart a profile to the mixture
pressed continuously through it.
The mixture formed in the stated cavity
preferably passes continuously Ollt of this cavity and,
during and/or after blowing out of an outlet, is shaped
continuously into an intermediate or end product, for
example rolled with a roll mill to give a sheet forming
a film. The gelled mixture can also be fed to a
conveyor belt through an outlet in the form of, for
example, a slot die. However, it is also possible to
pass the gelled mixture throuqh an outlet continuously
into a channel open at the top. Its base may be
formed, for example, by a conveyor belt or may have
conveying rollers so that the strand or the sheet
formed during continuous outflow of the mixture is
transported away from the outlet.
During shaping, the gelled mixture can be at
approximately the same temperature as the temperature
during gelling in the stated cavity, and the
temperature during shaping can be, for example, up to
about 220 C. However, the starch-based material can in
many and important cases also be subjected to plastic
deformation at a lower temperature, not more than about
120 C, expediently about 20 C to 80 C and preferably
40 C to 70 C, and, for example, rolled to give films or
other extrudates and/or drawn and/or cast to give
moldings. The gelled mixture which flows out, for
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11
example, via a vapor separator may therefore cool
readily during a certain period after gelling and can
then be shaped into the desired particles. If
necessary, the mixture formed in the stated cavity can,
between flowing out of the said cavity and the shaping
process, be brought to a temperature which is optimal
for the shaping process, by means of a heating and/or
cooling apparatus.
All types of starch-containing biomasses and/or
of unmodified starches and/or starch derivatives,
individually or mixed, can be used as raw material or
material for the process according to the invention.
Starch is produced in large amounts by plants.
Furthermore, byproducts or waste products which consist
completely or partly of starch and/or starch
derivatives are obtained in certain industrial
processes in which vegetable products are processed.
A starch-containing plant is, for example, the reed, in
particular the Chinese reed which grows as a wild plant
2~ in China and other Asian countries and contains about
40~ by weight to 50% by weight of starch. The Italian
reed also contains a rather large amount of starch.
Furthermore, potatoes (or more precisely potato
tubers~, rice grains, wheat grains, corn kernels and
peas contain a large amount of starch. Moreover, the
straw obtained during harvesting of various cereals
also contains some starch. The stated plants and plant
parts usually also contain water and other substances,
in particular cellulose, in addition to starch. The
material consisting of starch-containing biomass and/or
starch and/or at least one starch derivative can be
procured and provided simply, economically and in an
environment-friendly manner.
If a product to be produced is to be
transparent, glass-clear and colorless, it is
preferable to use a material which preferably contains
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WO 92/13004 PCT/EP92/00152
12
starch and/or at least one starch derivative which,
apart from the water usually present in vegetable raw
materials, is as pure as possible. The material should
then in particular also be as free as possible of
cellulose and other plant constituents which may cause
turbidity or coloration. If, on the other hand, it is
intended to produce a pore-free or porous product which
need have only a low light transmittance or can or
should be opaque and/or colored, it is possible to use
a particulate material which, in addition to the one or
more starches and/or one or more starch derivatives,
also contain cellulose and/or other plant constituents.
The material may then contain, for example, a biomass
which contains reed and/or straw which has been
converted into small particles by cutting and~or by
pulverizing and/or by milling. Since straw in
particular contains only a relatively small amount of
starch, another starch-rich material, for example more
or less pure potato starch, may be added to this
biomass.
Any starch derivative present in the material
may be formed, for example, by esterification and/or
etherification and/or oxidation and/or partial
hydrolytic degradation of starch.
For many purposes, it is possible to use a
material which contains starch and/or at least one
starch derivative and no amylose or only a relatively
small amount of amylose. Such a material, such as, for
example, potato starch, is particularly economically
obtainable and also relatively easy to gel.
If, however, water-resistant products are to be
prepared and in particular if they have a very thin
cross-section in at least one direction and, for
example, have a thin film, a thin-walled container or
a thin filament, it is advantageous for at least one
component of the stated material to contain a
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WO 92/13004 PCT/EP92/00152
13
relatively large amount of amylose. The material may
contain, for example, an amylose-rich starch - for
example corn starch - and/or a starch derivative - for
example slightly esterified corn starch, which starch
or starch derivative contains at least 30% by weight or
even at least 35~ by weight of amylose - based on its
own weight. The amount of this amylose-rich starch or
of the amylose-rich starch derivative in the total
material consisting of starch and/or at least one
starch derivative is preferably at least 1% by weight,
preferably not more than 60% by weight, expediently at
least 3~ by weight and expediently not more than 20~ by
weight and, for example, at least 6~ by weight to not
more than about 15~ by weight. The remaining starch
which may be present in the material then need not
contain any amylose or may contain no more than a small
amount, for example not more than 10% by weight of
amylose. The amount of amylose in the total material
consisting of starch and/or of at least one starch
derivative can accordingly be at least 0.3~ by weight,
expediently at least about 1% by weight and, for
example, at least about 2% by weight. If the material
contains a large amount of amylose, in order to effect
gelling it should be heated in the stated cavity to a
temperature which is preferably at least 140 C or
preferably higher, i.e., for example, at least 150 C
and for example up to about 180C or even up to about
200 C.
A material containing a starch-containing
biomass and/or more or less pure starch and/or at least
one starch derivative as main raw material is
preferably introduced into a mixer in a particulate
state, i.e. as bulk material consisting of granules
and/or particulate bulk material and/or pulverulent
bulk material, and mixed therein preferably at ambient
temperature - i.e. without heating - and thus usually
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14
at a temperature of about 20~C and less than 30 C, with
water andtor alcohol serving as a solvent and/or
dispersant, and possibly with extenders and/or other
materials. The biomass, starch and/or starch
derivative particles may be agitated, for example by
means of at least one mixing tool in the form of a
rotatable stirrer. The particles swell by the
absorption of water and/or alcohol, with the result
that the viscosity of the material increases.
It should be pointed out here that the starch
produced by plants has a certain moisture content, the
water content of starch obtained freshly from plants,
for example potatoes, being typically about 15 to 25%
by weight. If the starch or a starch derivative is
obtained from plants which have been stored for a
relatively long time and/or already pretreated in some
manner and/or as a byproduct of some industrial
treatment processes, the water content may be lower or
higher. The amount of water and/or alcohol added
during mixing can be adapted to the water content
already present in the starch or in the starch
derivative in such a way that the total amount of water
and/or alcohol present in the material is at least 2%
by weight, not more than 60% by weight and preferably
10% by weight to 35% by weight. For the sake of
clarity, it is noted that these percentages are based
on the total weight of the moist material which is
introduced into the cavity used for gelling. Usually,
the material may contain water as a solvent and/or
dispersant. If, however, very thin, flexible films or
tapes and/or thin, film-like jackets or hoses, bags or
containers having thin walls or thin filaments are to
be formed, it may be advantageous to add alcohol,
instead of water, to the material and possibly even to
replace the water already present in the vegetable
starch by alcohol, because the film or the articles
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otherwise produced then dries more rapidly.
If an amylose-rich material is gelled, it can
even be introduced in the completely dry state - i.e.
without water and without alcohol - into the cavity
used for gelling. In this case, water and/or alcohol
in the liquid state may also be added to the material
in the stated cavity, in addition to the steam and/or
alcohol vapor.
The crosslinking agent which is at least
usually also mixed with the gelled starch material in
the cavity may contain, for example, melamine resin
and/or melamine and/or urea and/or formaldehyde and/or
urotropine and/or glyoxal and/or qlucose. A melamine
resin formed from melamine and formaldehyde and used as
a crosslinking agent can be added to the material, for
example, as partlculate material - for example as
granules - or in solution in formaldehyde and thus in
the liquid state.
The properties of the subsequently formed
products, i.e. articles, can be adapted to the intended
use through the type and degree of crosslinking and/or
the other modifications. For example, the resistance
or - from another point of view - the rate of rotting
can be controlled through the type and amount of
crosslinking agent added. If, for example, starch left
in the natural state is introduced onto or into a humus
soil, it rots relatively rapidly under the action of
the soil bacteria. However, the resistance to rotting
can be increased, for example, by admixing and metering
a crosslinking agent which reduces the water
solubility, such as melamine resin or melamine or urea
or glyoxal, and a shelf life and resistance of at least
5 years or of at least 10 years or if necessary of even
a larger number of years can be ensured, for example,
by appropriate metering of the melamine resin and/or
melamine content and/or urea content, depending on
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16
requirements, even in the case of a thin flexible film.Particularly when amylose-free or at least low-amylose
starting materials are used, the total content of
crosslinking agent is in many cases, for example, not
more than 1~ by weight or even at most only 0.1% by
weight of the more or less dry material containing
starch and/or at least one starch derivate. Otherwise,
a product rendered durable by melamine resin and/or
melamine and/or urea and/or glyoxal can also rot in a
natural environment, but rotting then simply takes
longer.
If, in the manner described above, the material
contains amylose-rich starch or an amylose-rich starch
dexivative and is intended for the preparation of
water-resistant products, melamine resin and/or
melamine and/or urea and preferably additionally
glucose are added to the material as crosslinking
agents. For the formation of pore-free, completely
water-resistant products, the content of crosslinking
agent may then be at least 10% by weight and up to 30~
by weight of the more or less dry material or even of
the material which contains water and/or alcohol and is
; introduced into the cavity used for gelling. The
melamine resin and/or melamine and/or urea content may
be - based on the total material containing starch
and/or at least one starch derivative and water and/or
alcohol and introduced into the cavity used for gelling
- preferably at least 10% by weight and preferably not
more than 15% by weight. The glucose content may be -
based on the stated material - preferably at least 2%
by weight and preferably not more than 12~ by weight.
Of course, other additives may also be mixed
with the material no later than in the cavity used for
gelling, in order to obtain certain properties of the
products. It is possible, for example, to add at least
one additive for additionally reducing the water
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solubili'y and~or at least one curing agent. By adding
magnesium sulfate, for example, the moisture-resistant
properties of the starch products are improved.
Although products based on starch are as such already
flame-retardant and poorly flammable, it is also
possible to add at least one flame-retardant substance.
Furthermore, at least one dye may be added in order to
color the otherwise usually colorless products.
The articles formed by shaping a gel solidify
after they have been shaped and are then relatively
tough and, with a correspondingly thin cross-sectional
dimension, also flexible. In an advantageous
embodiment of the process, the articles formed from the
gel are dried by heating after they have been shaped,
in order to accelerate the solidification and
compaction process, so that at least some of the water
and/or alcohol originally present as a solvent and/or
dispersing liquid escapes. If, as mentioned above,
compact, pore-free and/or transparent articles, for
example films, are to be produced, they can be dried,
for example, at least partly by exposure to infrared
light. If a film is produced, it can be exposed, for
example, simultaneously from both sides - i.e. for
example from aboYe and from below in the case of a film
running along a horizontal plane. During drying by
exposure to infrared light, the outermost layers are
first heated and dried, so that removal of liquid thus
progresses from the outside inward. This promotes the
formation of substantially pore-free, clear and
transparent films or other articles.
For the continuous production of a web used for
the formation of a film or of a tape, the gelled
mixture can, for example, be fed through an outlet in
the form of, for example, a slot die to a roll
apparatus or an apparatus having a conveyor and/or
casting belt and at least one shaping tool which is
2~7~95
WO 92/13004 PCT/EP92/00152
18
formed by a wedge-like and/or knife-like doctor.
Extrudates and webs having any other profiles - for
example also pipes or tubes - can also be produced
continuously with the aid of suitable profile dies, by
rolling processes, pultrusion and/or extrusion and
other shaping processes. The widths and thicknesses of
the films or tapes or the other cross-sectional
dimensions of extrudates profiled in any manner can of
course be established in accordance with requirements
by appropriate dimensioning of the profile die used.
Furthermore, at least one flavor and/or odor
material may be added to a material used for producing
a film, in order, for example, to repel moths and any
other insects or other animals. A film of this type
can then be used for forming a bag or container for
storing clothes.
Transparent films or tapes based on starch can
also be used as text-bearing and/or image-bearing
transparencies for so-called daylight or "overhead"
projectors. Such films or tapes are frequently used
only once and for a short time and then discarded, so
that environment-friendly degradability of such films
or tapes is likewise very advantageous.
If compact pore-free and/or transparent, three-
dimensional moldings are to be produced, the gelledstarch mixture can first be continuously shaped into a
web. This can then be converted in a shaping apparatus
into three-dimensional shaped articles, such as
containers, for example before it has completely dried
and solidified. Such shaped articles can be used, for
example, as packaging material for foods, such as, for
example, vegetables, meat or chocolates.
If pore-free articles, such as, for example,
films, tapes or shaped articles, are produced,
polyethylene oxide may be added, during introduction
into a conveyor and/or pressing apparatus or at the
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WO 92/13004 PCT/EP92/00152
19
late~t during gelling, to the material containing
starch and/or at least one starch derivative. The
polyethylene oxide may be added to the remaining
material, for example in dissolved form. The content
of polyethylene oxide in the total mixture containing
starch and/or at least one starch derivative is
preferably not more than 30% by weight and, for
example, 0.5 to 5~ by weight. In addition to the
polyethylene oxidel a small amount of at least one
other water-soluble synthetic resin may be added to the
mixture. The content thereof in the mixture may be,
for example, 0.5 to 4.5~ by weight. Articles formed
from material containing polyethylene oxide have a
relatively smooth surface. If, for example for shaping
at least one article, the material is shaped in the
free~flowing or semisolid state by means of at least
one mold and/or at least one apparatus, for example
rolled with rollers and possibly additionally shaped by
means of a shaping apparatus or cast in a mold, the
added polyethylene oxide prevents stiffening of the
material to the mold or to the apparatus. Furthermore,
the surface of such an article can readily be provided
with at least one pattern which consists of linear
and/or dot-like indentations. These indentations can
be impressed by means of at least one, for example
heated, embossing roller or by means of a heated stamp
into the material which has already been shaped by
rolling or casting or the like to give an article but
which has not yet completely solidified. Instead, the
indentations may be burned in by means of a laser or
produced by a shrinkage process or by a cutting
process. In an advantageous embodiment, the depths of
the indentations and/or the distances from one another
are not more than 0.01 mm, preferably not more than
0.001 mm and, for example, only 1 nm to 10 nm.
Furthermore, a layer of polyethylene oxide may
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Wo 92/13004 PCT/EP92/00152
be applied to an article which consists of a starch-
containing material without polyethylene oxide. It is
also possible to apply a starch mixture containing
polyethylene oxide to a surface of an article, such as,
for example, paper, wood or textile fabric. Finally,
it is also possible to apply a thin metallic film to at
least one region of the surface of an article
containing starch and/or at least one starch
derivative, for example by vapor deposition. These
methods can be used to form articles having smooth
surfaces, which can subsequently likewise be provided
with fine, linear or dot-like indentations.
Patterns with indentations of the stated type
produce different light efPects and different colors
with different incident light as a result of
diffraction and interference processes. Articles
having such patterns representing, for example, text
characters and/or at least one image may be in the form
of, for example, packaging material, containers for
foods or possibly securities or tickets.
The gelled mixture can furthermore be shaped
continuously into filaments, which can be dried by
treatment with hot air and, for example, further
processed to give cords and ropes or to give wadding-
like starch products.
If expanded starch products are prepared, theymay have sizes and shapes which can be chosen within
wide limits. Thus, it is possible to produce, for
example, relatively large foam elements for packing
equipment or fragile articles or structured materials
for the construction of stage sets and for interior
decoration. In the production of foam elements, gelled
mixtures containing starch and/or at least one starch
derivative can be exposed to microwaves in a dryer
after more or less substantial preliminary shaping and
partial expansion in an advantageous embodiment of the
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WO 92/13004 PCT/EP92/00152
21
process. The intermediate product present in the dryer
is then progressively heated and dried from the inside
outward by the microwaves in said dryer. subbles
formed during evaporation of water and/or alcohol cause
the gel to expand and hence further shape it and make
it porous.
In the production of foam products, however, it
is also possible, for example, to produce small
expanded foam particles which can be used as packaging
material by spraying the gelled mixture dropwise into
a hot air stream.
To increase pore formation, a blowing agent can
be added to the material before the expansion process.
This may consist, for example, of at least one salt,
for example a metal carbonate, such as lime, or calcium
carbide, and/or an inorganic acid, for example
hydrochloric or phosphoric acid, and/or an organic
acid, for example citric acid, and/or hydrogen peroxide
and/or alumina and/or cement. The added amount of
blowing agent may be at least about 0.01% by weight,
not more than about 20% by weight and, for example,
about 0.1% by weight to 5% by weight of the material
containing water and/or alcohol and introduced in the
mixed state into the cavity used for gelling. The
stated percentages may be based on the amount of
starting material consisting of starch and/or at least
one starch derivative or on the amount -of mixture
containing this starting material, water and/or
alcohol, usually a crosslinking agent and possibly
additional substances and introduced into the cavity of
the gelling and/or mixinq chamber. To ensure that any
added blowing agent does not cause expansion and
; resinification of the material in the press used for
homogenization, the blowing agent of the mixture is
advantageously first added to the gelling material in
the cavity of the gelling and/or mixing chamber.
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WO 92/13004 PCT/EP92/00152
22
A foam strand formed by expansion can then be
shaped into desired articles in the more or less free-
flowing state by rolling, pressing or casting or the
like, or separated in a more or less soft state or in
the solidified state by means of a separating apparatus
into pieces, for example panels or chips.
Starch foam products or articles produced by
the process according to the invention may have a
density of at least about 5 mg/cm3, not more than about
600 mgtcm3 and, for example, 100 to 400 mg/cm3. The
starch foam articles produced may be dimensionally
stable, hard and rigid, i.e. not elastically
compressible, depending on the production process, the
composition and the shape and the dimensions. However,
it is also possible to produce film-like or tape-like
foam articles which likewise are not elastically
compressible or at least not highly elastically
compressible but are flexible. Furthermore, it is
possible to produce foam products which have at least
limited elastic compressibility.
Furthermore - particularly in the case of
porous articles based on starch - it is possible to add
sweeteners and/or flavors and/or spices and/or
nutrients of any type during production. Products of
this type can then, for example, first be used for
packing foods and/or as plates, cups or the like and
then consumed. Porous starch foam articles containing
additives of the stated type can furthermore be
provided as actual foods and thus, for example, can be
fried in oil to give crispy sticks and chips for eatlng
as snacks.
In the production of foam products, it is, for
` example, also possible to add acetyl anhydride and/or
,~ sodium acetate and/or cellulose diacetate and possibly
also a small a~ount of kieselguhr, acetic acid and/or
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WO 92/13004 PCT/EP92/00152
23
glycerol to the material. As a result of adding these
substances, the foam products become more viscous and
more stable and can be further shaped before their
final solidification, without the pores being
destroyed. Such a product may contain, for example,
0.5~ by weight to 5% by weight of cellulose diacetate,
0.5~ by weight to 3.5% by weight of kieselquhr and not
more than 0.075% by weight of glycerol. In this case,
the glycerol has the property of a plasticizer and
prevents the starch-containing material from
agglomerating.
It is also possible, by means of electrically
hydraulically or pneumatically operated piston presses,
to press a gelled, free-flowing starch mixture
containing a blowing agent through a die, for example
one which is heated, and to inject it directly into
intermediate spaces of walls or the like, so that,
after expansion and drying, they form foamed filling
and/or insulation materials.
It is also possible to produce liquid starch
products. Products of this type can, according to
requirements, be nebulized or sprayed, for example as
impregnating or coating materials, onto the articles to
be coated, by a spraying means operated with compressed
air. The starch-based coating materials which can be
prepared by this process can be used in the processing
of cardboard boxes, paper and wood and as an
environment-friendly substitute product for protective
wax coatings on road vehicles. owing to their pore-
filling properties, these products are also suitable
for mixing with water-soluble finishes and~or other
conventional impregnating agents.
It is also possible to add to the starch
material various extenders, such as water-soluble
gelatine, plastics wastes, quartz sand, lime, cement,
slate dust, ceramic dust, stone dust and/or cellulose-
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W~ 92/13004 PCT/EP92/00152
24
containing materials, for example sawdust, wood chips,
paper or straw, where the latter - as already mentioned
- may also contain a small amount of starch. These
extenders may be introduced either together with the
starch and/or with at least one material containing a
starch derivative and water and/or alcohol, by means of
a transport and/or pressing apparatus preferably
consisting of an extruder or screw extruder, or
separately and directly into the cavity of the gelling
and/or mixing cha~ber and thus added to the starch
material in the cavity at the latest. Depending on the
use, expanded and porous or pore-free and flexible and
easily moldable or rigid starch products can be
produced from the extender-containing material.
When plastics wastes are used as extenders,
granulated plastics wastes, preferably consisting of
polyvinyl chloride and polyethylene, can be added to
the starch material. The amount of plastics wastes may
be, for example, 5~ by weight to 95% by weight of the
mixture consisting of starch and/or at least one starch
derivative and the plastics waste. In order to achieve
better miscibility of the various plastics wastes,
glucose may also be added to the plastic/starch
mixture. The articles produced by this process can be
readily further processed by machining operations, such
as, for example, sawing and drilling, and can be
readily screwed. These very water-resistant and acid-
resistant articles can be used as formwork and
underwater components, for example in the building
industry, and as crash barriers.
By suitably establishing the composition of the
material and the process parameters, it is possible to
prepare both a mixture free of blowing agent and a
mixture containing blowing agent and to pass it through
an outlet into a channel, said mixture being
sufficiently free-flowing to allow it to be uniformly
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WO 92/13004 PCT/EP92/00152
distributed over the entire width of the channel even
when the latter is substantially broader than the
orifice of the outlet. If the gelled mixture contains
a blowing agent, it may be in a substantially
unexpanded state when it flows into the channel and not
expand until it is in the channel. The process
according to the invention therefore permits the
production of pore-free and expanded, porous webs which
have a large width compared to the width of the outlet.
However, the mixture can also be passed and, for
example, pressed intermittently into a mold or
alternatively into different molds. 'rhe mold or each
mold can be closed all round or open at the top.
Analogously to the situation when the mixture is passed
into a channel, it is possible to produce relatively
large articles, for example foam panels used for
packing large apparatuses.
If the end products are to be molded by casting
in molds or by blowing, and hence discontinuously, a
screw-piston press or a pistGn press which has, as a
pressing element, a screw piston which is rotatable and
axially displaceable in its cylindrical chamber or an
axially displaceable piston can be used, instead of an
extruder or screw extruder, for feeding the starch-
containing mixture into the cavity used for gelling.
Short descri~tion of the drawing
'rhe invention will now be described with
reference to embodiments, shown in the drawings, of
apparatuses for the preparation of starch products. In
the drawings,
Figure 1 shows a schematic representation of an
; apparatus for the production of a pore-free,
film-forming web,
; Figure 2 shows a schematic representation of part of a
variant of an apparatus for the production of
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WO 92/13004 PCT/EP92/00152
26
moldings by means of a shaping apparatus,
Figure 3 shows a schematic representation of part of a
variant of an apparatus for the production of
moldings by means of a centrifugal molding
apparatus,
Figure 4 shows a schematic representation of part of a
variant of an apparatus for the production of
pore-free filaments by means of a centrifuge
and
Figure 5 shows a schematic representation of part of a
variant of an apparatus for the production of
foam articles.
Preferred embodiments of the invention
The apparatus, shown in Figure l, for the
production of a film-forming web from a free-flowing
material has a faed unit 1. This has a store 3 which
contains a material 5 which consists of starch
containing a little water. A reservoir 7 which
contains water 9 is also present. The store 3 is
connected to a mixer 15 via a metering apparatus ll.
The reservoir 7 is connected to the mixer 15 by a
metering apparatus 13. The metering apparatus 11 has,
for example, a screw and a drive apparatus which serves
for driving the latter, while the metering apparatus 13
is formed, for example, by a pump and a valve. The
mixer 15 has a container and, for example, at least one
mixing tool which can be moved in said container by
means of a drive apparatus. The outlet of the mixer 15
is connected via metering apparatus 17, having for
example a screw and a drive apparatus, to the inlet 19
of a transport and/or pressing apparatus 21. The
transport and/or pressing apparatus 21 is in the form
of a press, i.e. a screw extruder. The latter has an
elongated chamber 23 whose wall has as the main part a
cylindrical barrel with a horizontal axis 25 and
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2~7~
WO 92/13004 PCT/EP92/OOlS2
27
defines an interior space 27. At that end of the
chamber 7 which is on the left in Figure 1, an inlet 19
joins the cavity 27. An outlet 29 is present at that
end of the chamber which is on the right in Figure 1.
Furthermore, the chamber 23 may have two additional
inlets not shown in Figure 1, i.e. a liquid inlet and
a vapor inlet. The two additional inlets which may be
present enter the interior space 27 in the rear half
and even in the rear third of said interior space -
relative to the transport direction of the transport
and/or pressing apparatus 21. The liquid inlet can be
connected to the reservoir 7 via a line 28 and a
metering apparatus 14 formed by a pump and a valve. A
transport and/or presssing element 30, i.e. a screw,
which can be rotated about the axis 25 by means of a
drive apparatus 31 having a motor and, for example,
also a gear is mounted axially and nondisplaceably in
the interior space 27. The barrel is provided, at
; least in part of its length, with a heating and/or
cooling apparatus 33 which has, for example, a pipe
coil for passing through a heating or cooling fluid.
The barrel is enclosed by an outer jacket serving as
heat insulation 35. The outlet 29 of the transport
and/or pressing apparatus 21 is connected to a non-
return valve 37. The latter has a passage 37a, defined
by a preferably heat-insulating wall 37b, and a movable
locking element 37c which is formed, for example, by a
~ spring-loaded flap. A gelling and/or mixing apparatus
; 38 has a gelling and/or mixing chamb~r 43 with a barrel
which, for example, is elongated, cylindrical and
vertical and two end walls. The wall essentially
i consists of metal on the inside and is, for example,
provided on the outside with a heat insulation, which
is not shown, and defines a cavity 39. The gelling
and/or mixing apparatus 38 also has a mixer with at
; least one stirrer 41 which is rotatable in the cavity
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WO 92/13004 PCT/EP92/00152
28
39 about the vertical axis of the barrel and one drive
apparatus which serves for turning said stirrer and is
formed, for example, by an electric motor and a gear.
The gelling and/or mixing chamber 43 is provided at its
one, upper end with an inlet 43a and at its other,
lower end with an outlet 43b. The inlet 43a is
connected to the outlet of the non-return valve 37. A
vapor feed line 45 enters the cavity 39 in at least one
vapor feed orifice and is preferably provided with a
vapor distributor which enters the cavity 39 through a
plurality of vapor feed orifices distributed over the
wall of the chamber 43. The vapor feed line 45 is
connected to a part 47a of a vapor source 47, for
example via a valve. The above-mentioned, possibly
present vapor inlet of the chamber 23 of the transport
and/or pressing apparatus 21 can be connected to a part
47b of the vapor source 47 ~ia a vapor feed line 46
having, for example, a valve. This vapor source has at
least one boiler and may have at least one pump in
order to generate vapor - i.e. superheated steam - and
feed it to the cavity 39 and possibly to the interior
space 27. The cavity 39 is also connected to a feed
apparatus 49. The lat~er has a reservoir 53 for
storing a crosslinking agent 51 and possibly a
reservoir 59 which serves for storing a diluent and/or
solvent and/or dispersant 57 for the crosslinking agent
51. The feed apparatus 49 furthermore has a metering
apparatus 55 which is formed, for example, by at least
one pump and two valves and has at least one feed line
entering the cavity 39. The feed unit 1, the transport
; and/or pressing apparatus 21, the vapor source 49 and
the feed apparatus 49 together form feed means for
feeding into the cavity 39 various materials, in
particular the material containing starch and/or at
least one starch derivative and water and/or alcohol.
The chamber 43 may furthermore be provided with a
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WO 92/13004 PCT/EP92/00152
29
safety pressure valve which is usually closed and has,
for example, a bursting disk.
The outlet 43b of the cavity 39 is connected to
a line 61 which has a closed cross-section and
possesses a heatinq and cooling apparatus 63 and heat
insulation and through which the free-flowing, gelled
starch mixture formed in the cavity 39 can be pressed
out of the cavity 39. That end of the line 61 which
faces away from the cavity 39 forms an outlet 71 of
that part of the apparatus which serves for forming and
gelling the mixture containing starch and/or at least
one starch derivative. The outlet 71 is, for example,
in the form of a slot die but may also have an outlet
orifice of circular cross-section.
A unit for molding, drying and solidifying the
gelled mixture which flows out of the outlet 71 is
arranged downstream of the outlet 71. The unit has
transport and/or shaping means which are formed by a
roll apparatus having a plurality of rolls 73, i.e.
heated calendar rolls arranged in pairs. It should be
noted that two pairs of such rolls 73 are shown
schematically in Figure 1 but that a greater or smaller
number of such rollers may be present, depending on
requirements. A dryer 75 which has a support 77 which
consists of a glass plate and is transparent to
infrared light and two infrared lamps 79, 81, one of
which is mounted below the support 77 and the other
above said support, and separated from the support 77
by a free intermediate space, is arranged downstream of
the rolls 73. Furthermore, transport means 83, which
consist, for example, likewise of at least one pair of
rolls, are present downstream of the dryer 75.
During operation of the apparatus, the metering
apparatuses 11, 13 feed, respectively, a material 5
consisting of starch and water 9 to the mixer 15 from
the store 3 and from the reservoir 7. For example,
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WO 92/13004 PCT/EP92/00152
kg of starch, for example moist potato starch
containing little or no amylose and having a water
content of about 20% by weight, and additionally 0.5 kg
of water, are fed continuously per batch. It should be
noted here that feed to the mixer 15 can also take
place continuously instead of batchwise. The moist
starch is mixed with the additional water in the mixer
15. The starch/water mixture 91 is formed in the mixer
and may also be regarded as a dispersion, and it is
preferably fed continuously by the metering apparatus
17 to the inlet 19 of the transport and/or pressing
apparatus 21 and reaches the interior space 27 of the
chamber 23 via said apparatus 21.
~ he rotating screw forming the transport and/or
pressing element 30 transports the mixture 91 in
interior space 27 from the inlet 19 to the outlet 29
and compacts and homogenizes the mixture. The mixture
91 is heated by the transport, pressing and compaction
process and is heated or cooled by heating and cooling
apparatus 33 so that the mixture 91 has a temperature
of less than 60C, for example 40C to 50 C in the
interior space 27. The resulting pasty material is
pressed through the outlet 29 and through the non-
return valve 37 into the cavity 39. Hot vapor for
gelling and mixing is added to the pasty starch mixture
via the feed line 45, the vapor being supplied from the
vapor source part 47a at a temperature of, preferably,
150 C to 200C and, for example, 160~C to l90~C. The
feed apparatus 49 feeds crosslinking agent 51 to the
cavity 39. The crosslinking agent 51, for example
melamine resin, is metered by the metering apparatus 55
and fed continuously to the starch in the cavity 39.
Depending on the water content of the starch in the
cavity and on the type of crosslinking agent 51 added,
for example, diluent and/or solvent and/or dispersant
57 consisting of water may be added to the crosslinking
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WO 92/13004 PCT/EP92/00152
31
agent. The mixture containing water, starch and
crosslinking agent and present in the cavity 39 is
heated therein by the vapor to a temperature above the
temperature in the interior space 27 of the transport
and/or pressing apparatus 21 and is gelled, and the
vapor may cool down slightly. The temperature of the
mixture in the cavity 39 may be, for example, about
150 C to 180 C. Furthermore, a pressure which is
greater than the ambient atmospheric pressure and whose
absolute value is expediently 0.3 NPa to 2.S MPa and
typically about 0.8 MPa to 1.2 MPa is generated in the
cavity by the vapor and by the mixture pressed through
the inlet 43a into the cavity 39. Since the vapor
releases energy to the mixture, some of the vapor in
the cavity may condense to liquid water. This can
likewise be a~sorbed by the gel formed in the cavity.
However, the remaining, preferably major part of the
vapor fed in remains in the cavity 39, preferably as
vapor - i.e. in the gaseous state.
~o ensure optimum mixing, the starch mixture
can be mixed during gelling by the stirrer 41 arranged
rotatably in the cavity 39. The stirrer 41 is of such
a form and is operated in such a way that it produces
no more than slight compaction and no more than small
gravitational [sic] forces compared with the compaction
and with the gravitational [sic] forces produced by the
transport and/or pressing element 30 consisting of a
screw. Furthermore, the stirrer 41 results in no
transport or at most in very little transport compared
with the screw and in any case in no forced transport.
The free-flowing, gelled starch mixture is pressed
continuously through the outlet 43f of the cavity 39
and through the line 61 having a closed cross-section
and out of the outlets 71 consisting, for example, of
a slot die, by means of the transport and/or pressing
apparatus 21 consisting of a screw extruder, and the
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wo ~2/13004 PCT/EP92/00152
32
pressure generated by the steam in the cavity 39.
In apparatuses for large-scale industrial
manufacture, the plant which serves for molding, drying
and solidifying the mixture and has rolls 73 and the
dryer 75 may be relatively far away from the gelling
and/or mixing appparatus 38, so that the line 61 may be
several meters long. With the aid of the heating
and/or cooling apparatus 63, the gelled mixture flowing
through the line 61 can be brought to a temperature
which is advantageous for further processing and
shaping and which is dependent on the composition of
the mixture and on the method of further processing.
If, for example, a relatively thin film is to be
produced, it is advantageous if the mixture is fed from
lS the outlet 71 to the first pair of rolls 73 used for
further processing, at a temperature which is, for
example, about 60'C to 70~C. If a relatively thick
sheet is to be produced, the stated temperature may be
lower and, for example, about 40 C to 55 C or up to
60 C. If, when flowing through the line 61, the
mixture cools to such a temperature in the range from
40~C to 70AC, the vapor present in the mixture may
condense to liquid water. However, this water is bound
by the mixture consisting of a gel at most to a small
extent and can drip from the outlet 71 when the mixture
flows out. If necessary, the line 61 and/or the outlet
71 may furthermore be provided with a water separator
and/or water collector (not shown) for separating
and/or collecting the water not bound by the gel.
The moist and soft mixture forming a web and/or
a strand and flowing out of the outlet 71 is then
passed continuously to the heated rolls 73 and rolled
by these into a web 9S which forms a sheet having an
even cross-section. This web is already dried to some
extent during rolling and is then transported over the
support 77 of the dryer 7~, which support consists of
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WO 92/13004 PCT/EP92/00152
33
a glass sheet, and between the two lamps 79, 81. The
web 95 or sheet is exposed from below through the glass
sheet and from above to infrared light and thus further
dried and solidified. The transport means 83 which
has, for example, at least one pair of rolls draws the
web through the dryer 75 and transports it further, and
it may also smooth the web. The flexible web 95 or
sheet which is now dry and forms the manufactured
article can then be wound on a reel or further
processed in any manner in order to form, for example,
bags, pockets or wall parts of a container. The sheet
95 may be pore-free and, for example, transparent to
light and even completely clear and glass-clear. If a
dye or the like is added to the mixture on introduction
into the transport and/or pressing apparatus 21 and/or
by the feed apparatus 49 in the cavity 39, it is also
possible, however, to produce a colored, only partially
transparent or opaque sheet.
If the sheet to be produced is to be water-
resistant and, for example, furthermore very thin and
also transparent, a starch or a starch derivative which
contains a large amount of amylose may be added to the
mi~ture to be gelled - as already mentioned in the
introduction~ For this purpose, for example, some of
the potato starch fed by the feed unit 1 through the
inlet 19 to the interior space 27 of the transport
and/or pressing apparatus 21 can be replaced by
amylose-rich corn starch or an amylose-rich corn starch
derivative. ~he material fed through the inlet 19
should then preferably contain a realti~ely small
amount of water. For example, it is advantaqeous if
the water content - based on the weight of the material
introduced through the inlet 19 into the interior space
27 of the transport and/or pressing apparatus 21 - is
not more than 10% by weight and for example about 5~ to
8% by weight. If the starting material which contains,
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WO g2/1300~ PCT/EP92/00152
34
for example, potato starch and corn starch already has
a water content which is above the above-mentioned
advantageous range, no water is fed to the mixer 15
from the reservoir. If necessary, the starting
material can even be dried before being introduced into
the interior space 27. The relatively dry grains or
other particles of starch and/or a starch derivative
can then be thoroughly pulverized and comminuted in the
initial part of the interior space 27 of the screw
extruder forming the transport and/or pressing
apparatus 21. The mixture may remain in this
relatively dry state as far as the outlet 29 and until
entry into the cavity 39. In this case, the amount of
water required for gelling can first be fed to the
material in the cavity 39 by the feed apparatus 49, in
the form of the steam supplied by the vapor source 47
and/or in the liquid state.
However, it is also possible to feed liquid
water and/or possibly alcohol and/or even better from
the part 47b of the vapor source 47 via the vapor feed
line 46, steam and/or possibly alcohol vapor to the
material in the last half passed through and namely,
for example, in the last third passed through, of the
elongated internal space 27 of the transport and/or
pressing apparatus 21 via the metering apparatus 14.
In that region of the cavity 27 which extends from the
entry of the inlet 19 almost to the entry of the vapor
feed line 46 - i.e. at least in the first half and, for
example, at least or approximately in the first two
thirds of this cavity 27 - the temperature of the
amylose-rich mixture, like the temperature of the low-
amylose mixture, may be less than 60 C. In the final
region of the interior space 27, which region extends
from the entry of the vapor feed line 64 to the outlet
29, the mixture may then have a higher temperature
which is possibly more than 60C. However, the amount
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Wo 92/13004 PCT/EP92/00152
and temperature of the vapor introduced into the
interior space 27 through the vapor feed line 46 is
preferably such that the temperature of the mixture
even in the stated final region of the interior space
27 is lower ~han downstream in the cavity 39. The
temperature of the mixture in the stated final region
of the interior space 27 of the transport and/or
pressing apparatus 21 is preferably less than 140 C
and, for example, about 100C to 13ûC. Glucose and
melamine resin and/or melamine and/or urea are
preferably added as crosslinking agents to the mixture
with the aid of the feed apparatus 49 in the cavity 39
- as alxeady mentioned in the introduction.
The apparatus shown in part in Figure 2 has a
gelling and/or mixing apparatus 138 with a gelling
and/or mixing chamber 143 which defines the cavity 139
and has an inlet 143a connected to a transport and/or
pressing apparatus (not shown), as well as an outlet
143b, and in which a stirrer 141 is arranged. The
cavity 139 is furthermore connected by a vapor feed
line 145 to a vapor source 147 and to a feed apparatus
149 which corresponds to the feed apparatus 49 and of
which only a section of the feed line is shown. These
parts and the parts not shown in Figure 2 may be
;~ 25 identical or similar to the apparatus described with
reference to Figure 1. However, the apparatus shown in
Figure 2 differs from the apparatus according to Figure
1 inter alia in that the outlet 143b is tightly
connected to a vapor separator 165 by the line 161
which has a closed cross-section and is provided with
a heating and/or coolîng apparatus 163. Said vapor
separator is provided with a pressure relief valve
arranged in its top, preferably manually adjustable and
forming a vapor outlet 167 and has, in its base, an
; 35 orifice which is connected to an outlet 167 in the form
~ of, for example, a molding head and/or slot die. The
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Wo 92/13004 PCT/EP92/00152
36
conveyor belt and/or casting belt 171 is arranged below
the outlet 169. A shaping tool 173 which consists of
a knife-like doctor and whose distance from the belt
171 is preferably adjustable is arranged above said
belt, after the outlet 169 - relative to the conveying
direction of said belt. Transport means 175 and a
shaping apparatus 177 are also present. These have a
female mold 181 which defines a mold cavity 179 and
whose mold cavity-enclosing edges form a plane and are
preferably provided with an elastically deformable seal
182 which is, for example, almost elastomeric. The
shaping apparatus furthermore has a pressure part 183
which can be alternatively pressed against the female
mold 181 or raised from it by means of a control
apparatus. A suction and blowing apparatus 185 having
at least one orifice leading to the mold cavity 179 is
also present.
During operation of the apparatus, which is
shown in part in Figure 2, a material containing starch
and/or at least one starch derivative can be fed
continuously through the inlet 143a to the cavity 139
of its gelling and/or mixing apparatus 138. Said
material can be gelled in the cavity 139 with the
addition of a crosslinking agent and of vapor,
analogously to the explanation in the description of
~igure 1. Thereafter, the mixture formed can be
pressed to the conveyor belt and/or casting belt 171
through the line 161, the vapor separator 165 and the
outlet 169. On passing through the vapor separator
167, the mixture is preferably so hot that the vapor
added to it in the cavity 139 is still partly in the
gaseous state in the vapor separator, and that the
mixture flows out of the outlet 169 at a relatively
high temperature of, for example, 80 C to 120 C and
reaches the conveyor belt and/or casting belt 171. In
order to achieve an advantageous temperature in the
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WO 92/13004 PCT/EP92/00152
37
vapor separator 165 and during outflow from the outlet
169, the mixture can, if necessary, be heated or cooled
in the line 161 by the heating and/or cooling apparatus
163. In the vapor separator 165, at least some of the
5vapor present in the mixture escapes via the pressure
relief valve of the vapor outlet 167. By means of the
pressure relief valve, a pressure which is higher than
the surrounding atmospheric pressure is obtained in the
cavity of the vapor separator 165, said higher pressure
10forcing the gelled mixture through the outlet 169. The
mixture flowing continuously from outle~ 169 onto the
conveyor belt and/or casting belt 171 is transported
away from the outlet 169 by the belt. By means of the
shaping tool 173, the mixture forming a still readily
15deformable web l9S is smoothed and is brought to an
adjustable layer thickness. The preshaped, film-like
web 195 is then fed to the shaping apparatus 177 by the
transport means 175. The pressure part 183 is first
lifted from the female mold 181. When the web 195
20covers the mold cavity 179, the pressure part 183 is
pressed against the female mold 181 and thus presses
the web 195 against the seal 182 in such a way that the
web tightly seals the mold cavity 179 from the
environment. A vacuum is now generated in the mold
25cavity by the suction and blowing apparatus 185. By
means of this vacuum, the section of the web l9S which
is present in the shaping apparatus 177 is shaped into
a three-dimensional, for example container-like and/or
shell-like molding 197. After this shaping process,
30the pressure part 183 is lifted from the female mold
181. The molding 197 can then be ejected from the mold
cavity 179 by means of an air impact generated by the
suction and blowing apparatus 185. The section of the
web 195 present in the shaping apparatus 177 comes
35temporarily to a stop for a short time for the shaping
process. However, the mixture can nevertheless be
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WO 92~13004 PCT/EP92/00152
38
passed continuously out of the outlet 169 and processed
to a web 195, and the web 195 can temporarily form a
loop for compensation between the conveyor belt and/or
casting belt 171 and the shaping apparatus 177, for
example during the shaping process. The completed
moldings 197 can be separated from the web by cutting
means arranged at or downstream of the shaping
apparatus 177, relative to the transport direction.
The moldings 197 produced may have a relatively small
wall thickness compared with their size and may serve,
for example, as containers for food, such as
vegetables, fruits, milk products, meat and the like.
The containers can, if necessary, be closed with a flat
film after the food has been introduced. Otherwise,
the moldings can, as required, be transparent, clear
and colorless or only of limited transparency and
colored or opaque.
The apparatus shown in part in Figure 3 is
partly identical or similar to the apparatuses
described with reference to Figures 1 and 2 and has,
inter alia, a gelling and/or mixing apparatus 238 with
a cavity 239 defined by a ~elling and/or mixing
chamber, an inlet 243a, an outlet 243b and a stirrer
241 arranged in the cavity 239. However, the chamber
has a horizontal axis about which the stirrer 241 is
rotatable. The inlet 243a is in turn connected to a
transport and/or pressing apparatus, which is not
shown. Furthermore, the cavity 239 is in turn
connected by means of a vapor feed line 245 to a vapor
source 247 and to a line of a feed apparatus 249. The
outlet 243b is connected, via a line 261 provided with
a heating and/or cooling apparatus 263, to the inlet
266 of a vapor separator 265, which has a vapor outlet
267 with a pressure relief valve and an outlet 269 for
the gelled mixture. The apparatus according to Figure
3 furthermore has a centrifugal molding apparatus 271
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WO 92/13004 PCT/EP92/00152
39
having a rotor which can be rotated by a drive
apparatus, which is not shown. The rotor carries at
least one mold 273 and, for example, a plurality of
molds 273, the mold or each mold being detachably and
replaceably fastened. The outlet 269 of the vapor
separator 265 is connected to the inlet of the
centrifugal molding apparatus 271 via a line and an
isolating apparatus drawn as a valve. This inlet can
be formed, for example, by a rotary leadthrough or
rotary coupling which tightly seals the connection
between the gas separator and the centrifugal molding
apparatus from the environment, so that the mixture can
be pressed into the molding apparatus at a pressure
above the ambient atmospheric pressure. However, the
inlet of the molding apparatus may also be open to the
environment, so that the pressure of the mixture on
flowing into the centrifugal molding apparatus is
approximately equal to the ambient atmospheric
pressure.
During operation of the apparatus shown partly
in Fi~ure 3, the mixture containing a starch and/or a
starch derivative is gelled continuously in the cavity
239 and then pressed out of this cavity through the
vapor separator 265 and fed to the centrifugal molding
apparatus 271. The temperature of the mixture in the
vapor separator should in turn be sufficiently high to
ensure that a large part of the vapor fed into the
cavity 239 and not bound by the gelled mixture i5 still
in the gaseous state and can be removed as vapor
through the vapor outlet 267. In the production of
pore-free articles, such as, for example, transparent
moldings or hollow articles, by means of the
centrifugal molding apparatus 271, the gelled mixture
pressed out of the outlet 265 is introduced into the
one or more molds 273 via the stated valve. In this
apparatus, the centrifugal force is used for producing
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WO 92/13004 PCT/EP92/00152
moldings from the starch-containing mixture, and the
rotary speed must be sufficiently large to ensure that
the gravitationa~ force is cancelled. Depending on the
form and arrangement of the molds used, solid or hollow
shapes can be produced. At the end of a molding
process, the isolating apparatus present between the
outlet 269 and the centrifugal molding apparatus 271 is
temporarily closed during removal of the moldings. The
vapor separator 265 may serve not only for separating
off vapor but additionally as a buffer or compensating
container for the gelled mixture, in order to release
intermittently the mixture fed continuously to it from
the cavity 239. However, it is also possible to
provide a separate buffer or compensating container
downstream of the vapor separator. Furthermore, the
outlet 269 can be connected to a branch having two or
more branch lines, each of which has an isolating
apparatus and each of which is connected to a
centrifugal molding apparatus. In this case, the
mixture fed from the cavity 39 via the vapor separator
265 can be transported alternately to the various
centrifugal molding apparatuses. The gelled mixture
may flow at least approximately continuously from the
outlet of the vapor separator and be passed alternately
into different centrifugal molding apparatuses.
The apparatus shown in part in Figure 4 is
partially identical or similar to the apparatuses
described with reference to Figures 1 to 3 and has a
line 361 which is provided with a heating and/or
cooling apparatus 363 and connects the cavity of a
gelling and/or mixing apparatus (not shown) to the
inlet 366 of a vapor separator 365. The latter has a
vapor outlet 367 with a pressure relief valve and an
outlet 369 for the gelled mixture. Furthermore, a
rotatable, preferably heatable centrifuge 371 is
connected to the outlet 369 of the vapor separator 365
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WO 92/13004 PCTJEP92/00152
41
via an isolating apparatus drawn as a valve. This
centrifuge 371 has a chamber 373 whose wall 375
possesses a plurality of hair nozzles 377 through which
the gelled mixture is forced when the centrîfuge
rotates, so that a plurality of filaments 395 are
formed simultaneously. These filaments can be dried by
treatment with hot air and, for example, braided and/or
twisted to give a cord and/or a rope. However, it is
also possible to convert the filaments 395 into a
wadding-like product which can be used as filler or
packaging material. In this case, at least one mineral
salt, for example in the form of slate dust, stone
dust, ceramic dust, phosphate and/or calcium carbonate,
is preferably added to the starting material, at the
latest in the cavity of the gelling and/or mixing
apparatus. Instead of a heated centrifuge for the
production of the filaments 395, it is also possible to
use a fixed multihole die which serves as a shaping
tool. The gelled mixture is pressed and/or sucked
through the multihole die so that a plurality of
filaments are simultaneously formed.
The apparatus shown in part in Figure 5 is
substantially identical or similar to the apparatuses
described with reference to Figures 1 to 4 and has, in
particular, a transport and/or pressing apparatus which
is not shown and which is formed by an extruder or
screw extruder having a chamber and a screw which is
rotatable in its interior space about an axis and
serves as a transport and/or pressing element. A
gelling and/or mixing apparatus 438 possesses a gelling
and/or mixing chamber 443, which defines a cavity 439,
and has an inlet 443a and an outlet 443b. At least one
stirrer 441 of a stirring mechanism is arranged in the
cavity 439. The outlet of the transport and/or
: 35 pressing apparatus (not shown) is connected to the
inlet 443a via a nonreturn valve, which is likewise not
.
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Wo ~2/13004 PCT/EP92/001~2
42
shown. A vapor source 447 is connected to the cavity
439 via a vapor feed line 445, a valve and preferably
a vapor distributor having a plurality of orifices
leading into the cavity 439. Furthermore, a feed
apparatus 449 formed similarly to the feed apparatus 49
is connected to the cavity 439 and has, for example, a
reservoir 453, a reservoir 459 and a metering apparatus
having at least one pump and valves. The reservoir 453
stores a mixture 451 which contains both a crosslinkin~
agent and a blowing agent. The reservoir 453 can also
be provided with a rotatable mixing tool which is not
shown, in order to mix the said components of the
mixture 451 homogeneously with one another. The
reservoir 459 in turn contains a diluent and/or solvent
and/or dispersant 457 which contains, for example,
water or additionally or instead alcohol.
The outlet 443b of the gelling and/or mixing
chamber 443 is connected, via a line 461 provided with
a heating and/or cooling apparatus 463, to the inlet
466 of a vapor separator 465 which has a vapor outlet
467 with a pressure relief valve and an outlet 469 for
the mixture. This is in the form of, for example, a
molding head having an outlet orifice with a circular
cross-section or in the form of a slot die and leads
into a channel 471. To ensure that the mixture pressed
from the cavity 439 to the outlet 469 during operation
foams as little as possible between the outlet 443 of
the cavity 439 and the outlet 469, the line 461 should
be as short as possible. If space allows, the outlet
443b may be connected virtually directly to the vapor
separator 465. Moreover, the outlet orifice of the
outlet 469 should be located as close as possible to
the vapor separator 465. However, the connection which
connects the gelling and/or mixing chamber 443 to the
vapor separator 465 should form a constriction between
the cavities of the chamber and of the vapor separator,
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WO 92/13004 PCT/EP92/00152
43
i.e. should have a narrower cross-section transverse to
the direction of flow of the mixtures than the two
stated cavities, so that these are defined with respect
to one another. The channel 471 leads through a dryer
473 which has a microwave emitter 475. The bottom of
the channel 471 may also be provided with transport
means (not shown), for example at least one conveyor
belt and/or conveyor rollers.
When the apparatus shown partially in Figure 5
is operated, the inlet (not shown) of the transport
and/or pressing apparatus consisting of a screw
extruder is loaded, for example, with a material which
is the same as or similar to that described for the
apparatus according to FIgure 1. The material
introduced into the screw extruder should in particular
contain no blowing agent and preferably also no
crosslinking agent. The material is homogenized in the
screw extruder by the rotating screw forming the
transport and/or pressing element, to give a pasty
material. The mixture 451 containing a crosslinking
agent, for example melamine resin, and a blowing agent,
i.e. citric acid or another acid, is then added to said
mass in the cavity 439, the amount of blowing agent
being, for example, about 1% by weight of the mixture
formed in the cavity 439. The various components of
the mixture are mixed homogeneously with one another in
; the cavity 43g analogously to the apparatuses described
above and are gelled under the ac~ion of the vapor fed
in from the vapor source 447. ~he gelled mixture -
i.e. the material containing starch and/or a starch
derivative and a blowing agent - is then pressed, by
means of the pressure generated by the screw and by the
vapor, into the vapor separator 465, in which at least
a major part of the vapor present in the mixture is
removed. Thereafter, the mixture or the free-flowing
material passes through the outlet 469 into the channel
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2~79~
WO 92/13004 PCT/EP92/00152
44
471. There, the mixture or the material comes into
contact with the ambient air and can freely expand.
Depending on its flow and the dimensions of outlet 469
and of the channel 471, the mixture can be more or less
shaped by the outlet and/or the channel, so that the
channel may to a certain extent serve as a mold. The
mixture or the material then moves in the channel in
the form of a viscous liquid and/or a semisolid strand
into the dryer 473 and is heated therein by the
microwaves generated by the microwave emitter 475. The
material containing a blowing agent expands and
solidifies to a solid article, i.e. a porous foam web
495, which can be cut, for example, into pieces.
The transport and/or pressing apparatuses in
the form of screw extruders can, in all apparatuses
described with reference to Figures 1 to S, be loaded
with the material to be processed in such a way that
they can homogenize this material continuously.
Furthermore, in all these apparatuses, the materials
can be pressed continuously through the cavity of the
gelling and/or mixing chamber and gelled therein.
The processes which can be carried out by means
of the various apparatuses permit economical production
of articles or products based on starch and can be also
carried out in particular substantially or completely
automatically without problems.
The apparatuses and processes can also be
modified in various respects. For example, features of
different apparatuses and processes described can be
combined with one another.
Furthermore, the gelling and/or mixing chamber
may, for example, also be provided with a heating
apparatus which has, for example, a heating coil or an
electrical heating element. The mixture present in the
chamber and flowing through it can then be heated both
by the vapor introduced and by the heating apparatus.
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WO 92/13004 PCT/EP92/00152
The gelling and/or mixing chamber may be
provided with fixed baffle plates or the like instead
of with a rotating s~irrer, in order thoroughly to mix
the material containing starch and/or a starch
derivative and water and/or alcohol, which is forced
through the chamber, with components fed into the
chamber.
The line arranged between the transport and/or
pressing apparatus and the qelling and/or mixing
chamber may be omitted, so that the pasty material
pressed out of the interior space of the transport
and/or pressing apparatus passes directly into the
cavity of the gelling and/or mixing chamber.
If a pore-free web or film, which has a
relatively great thickness, is to be produced, the
dryer having infrared lamps may be omitted in the
apparatus shown in Figure 1. The web or film can then
be dried exclusively by the heated rolls 175 or by
these and by a hot air dryer.
The apparatus which is shown partially in
Figure 5 and is used for the production of porous foam
products, and the operation thereof, can be modified so
that the crosslinking agent and the blowing agent are
stored in separate reservoirs, then metered by at least
one metering apparatus and fed through a common line or
through separate lines to the cavity of the gelling
and/or mixing chamber.
The transport and/or pressing apparatus 21 may
consist not of a screw extruder or extruder but of a
different apparatus which is suitable for forcing the
material containing starch and/or at least one starch
derivative and water and/or alcohol into the gelling
and/or mixing chamber by overcoming the pressure
generated by the vapor in the cavity of the gelling
and/or mixing chamber. The transport and/or pressing
apparatus may be, for example, in the form of pumps, as
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WO 92/13004 PCT/EP92/00152
46
are known for pumping sludge and other dispersions.
The apparatus may also be designed for
injection molding. In this case, the outlet of the
gelling and/or mixing chamber be connected, via the
vapor separator or without an intermediate vapor
separator and/or via a compensating and buffer
container, to a screw extruder or screw-piston press or
a piston press which is suitable for pressing or
injecting the mixture formed in the cavity
intermittently into a mold.
However, the transport and/or pressing
apparatus 21 consisting of a screw extruder may also be
operated intermittently for injection molding or may be
replaced by a screw-piston press. In this case, the
material containing starch and/or a starch derivative
: and water and/or alcohol is forced intermittently
through the cavity of the gelling and/or mixing
apparatus.
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