CA2079095A1

CA2079095A1 - Process and equipment for the production of a product containing starch and/or at least one starch derivative

Info

Publication number: CA2079095A1
Application number: CA002079095A
Authority: CA
Inventors: Wolfgang Bartsch
Original assignee: Individual
Current assignee: CAPITAL MARKETING INVEST CMI AG
Priority date: 1991-01-25
Filing date: 1992-01-24
Publication date: 1992-07-26
Also published as: EP0522126A1; WO1992013004A1; AU1167692A; JPH05505211A

Abstract

Abstract A material (5) consisting at least partly of starch and/or starch-containing biomass and/or at least one starch derivative, and normally also including water (9) and/or alcohol is homogenized and compressed in a feed and/or compression device (21), preferably a worm-gear (30). The paste-like material thus produced is forced into the hollow interior (39) of a gelling and/or mixing chamber (43) in which it is mixed with a cross-linking agent (51) and heated, melted and gelled by means of steam. This enables a highly homogeneous gelled mixture to be produced wich can be further processed to give a wide variety of products, such as a transparent continuous strip (95) or a foam.

(Fig. 1)

Description

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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WO 92/13004 PCT/EPg2/00152 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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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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2~79~95 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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2~7g~5 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 , 2~7~S

WO 92/13004 PCT~EP92/00152 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, , , 2~79~9~

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 '':' .' ` ~ :

2~79~

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 2 ~

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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2~79a93 -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 ~ ~ 7 ~

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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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 2 ~ 7 ~

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 , . ' ,` ~

, 2~7~5 Wo 92/13004 PCT/EP9~/00152 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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Wo 92/13004 PCT/EP~2/00152 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 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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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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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.

2~79~95 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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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-:
- ' , 2~7~Q~3 W~ 92/13004 PCT/EP92/00152 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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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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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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WO 92/13004 PCT/EP92/OOlS2 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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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 2~9~

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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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 2 ~

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 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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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 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 ~, 2~7~
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 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 2 ~

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 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 ~7Y~

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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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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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 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, ':, 2~79~

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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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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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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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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Claims

PATENT CLAIMS

1. A process for the preparation of a product containing starch or at least one starch derivative, a material containing starch-containing biomass or starch or at least one starch derivative being gelled in a cavity, which comprises feeding steam or alcohol vapor into the material in the cavity.

2. A process as claimed in claim 1, wherein heating of the material in the cavity is effected at least partly and, for example, completely by the vapor, and the material in the cavity is heated to a temperature which is at least 80 C and at which the vapor fed in remains at least partly and, for example, at least for the major part in the gaseous state.

3. A process as claimed in claim 1 or 2, wherein the material in the cavity is at a pressure which is greater than the ambient atmospheric pressure, preferably at least 0.15 MPa and, for example, 0.3 MPa to 2.5 MPa.

4. A process as claimed in any of claims 1 to 3, wherein at least some, for example the major part, of the vapor fed in is removed, still in the vapor state, from the material.

5. A process as claimed in claim 4, wherein the material gelled in the cavity is passed through a vapor separator to an outlet or at least one mold, and at least some of the vapor fed to the material beforehand in the cavity is removed from the material in the vapor separator, the material in the vapor separator preferably being kept at a pressure which is greater than the ambient atmospheric pressure.

6. A process as claimed in any of claims 1 to 5, wherein a crosslinking agent is added to the material in the cavity.

7. A process as claimed in any of claims 1 to 6, wherein the material containing biomass or starch or at least one starch derivative is introduced into the cavity by means of a transport or pressing apparatus and is heated therein to a temperature which is above the temperature of the material in the transport or pressing apparatus.

8. A process as claimed in claim 7, wherein the material is passed into an elongated interior space of the transport or pressing apparatus and is transported by a screw along the interior space, and the material is kept at a temperature which is less than 60 C, at least in that half of the interior space which is first passed through and, for example, in the entire interior space.

9. A process as claimed in claim 7, wherein the material is passed into an elongated interior space of the transport or pressing apparatus and is transported by at least one screw along the interior space, and steam or alcohol vapor is fed to the material in that half of the interior space which is passed through last.

10. A process as claimed in any of claims 1 to 9, wherein the material is agitated in the cavity by means of at least one stirrer.

11. A process as claimed in any of claims 1 to 10, wherein the material is composed, molded and dried in such a way that the product produced forms at least one pore-free, or transparent and, for example, even clear and glass-clear article.

12. A process for the production of a product containing starch or at least one starch derivative, in particular as claimed in claim 11, a material containing starch-containing biomass or starch or at least one starch derivative being gelled in a cavity and then being shaped into at least one article, wherein the article is at least partly dried by exposure to infrared light after the molding process.

13. A process as claimed in any of claims 1 to 12, wherein the material is dried at least partly with warm air conveyed past it or by means of heated rolls after the molding process.

14. A process as claimed in any of claims 1 to 13, wherein the starch or at least one starch derivative contains at least 0.3% by weight and preferably at least 1% by weight of amylose, glucose and urea or melamine or melamine resin are added to the material in the cavity at the latest, and the material in the cavity is heated to a temperature which is at least 140°C and, for example, at least 150°C.

15. A process as claimed in any of claims 1 to 14, wherein the mixture gelled in the cavity is continuously molded to give a web which forms a film having an even cross-section.

16. A process as claimed in claim 15, wherein at least one three-dimensional molding, for example a container, is formed from the web by shaping.

17. A process as claimed in any of claims 1 to 14, wherein a plurality of filaments are simultaneously formed from the free-flowing material gelled in the cavity.

18. A process as claimed in claim 17, wherein at least one mineral salt, for example in the form of slate dust, stone dust or ceramic dust, or phosphate or calcium carbonate, is added to the material used for forming the filaments, and a wadding-like product is formed from the filaments.

19. A process as claimed in any of claims 1 to 13, wherein the material gelled in the cavity is sprayed in the free-flowing state onto a surface of an article in order to coat or to impregnate this surface with the product.

20. A process for the preparation of a product containing starch or at least one starch derivative, in particular as claimed in any of claims 1 to 19, a material containing starch-containing biomass or starch or at least one starch derivative being gelled in a cavity, wherein polyethylene oxide is mixed with the material at the latest during gelling, or polyethylene oxide is applied to a surface of an article formed using the material.

21. A process for the preparation of a product containing starch or at least one starch derivative, in particular as claimed in any of claims 1 to 20, a material containing starch-containing biomass or starch or at least one starch derivative being gelled in a cavity, wherein the material is shaped into an article, and at least one region forming the surface of the article is provided with a metallic film.

22. A process as claimed in claim 20 or 21, wherein the surface of the article is provided with at least one pattern which has indentations whose depths or spacings are not more than 0.01 mm.

23. A process as claimed in any of claims 1 to 10, wherein a blowing agent is added to the material in the cavity, and the free-flowing, gelled material formed in the cavity is passed out of the cavity, expanded and dried so that the product produced is porous.

24. A process for the preparation of a product containing starch or at least one starch derivative, in particular as claimed in claim 23, a material containing starch-containing biomass or starch or at least one starch derivative being gelled in a cavity, wherein the product is heated with microwaves for expansion or drying.

25. A process as claimed in claim 23, wherein the gelled, free-flowing material formed in the cavity is sprayed into a hot air stream so that the material forms drops on atomization and these expand in the hot air stream to give porous particles.

26. A process as claimed in claim 23, wherein the gelled, free-flowing material formed in the cavity is applied to a flat heated surface and is molded into at least one expanded sheet.

27. A process as claimed in any of claims 23 to 26, wherein the blowing agent contains at least one of the following materials: salt, cement, acid, hydrogen peroxide and alumina, the salt consisting, for example, of a metal carbonate, such as lime, or calcium carbide.

28. A process as claimed in any of claims 23 to 27, wherein natural, water-soluble gelatine is added to the material, as an extender, in the cavity at the latest.

29. A process for the preparation of a product containing starch or at least one starch derivative, in particular as claimed in any of claims 23 to 27, a material containing starch-containing biomass or starch or at least one starch derivative being gelled in a cavity, wherein acetic anhydride or sodium acetate or cellulose diacetate is added to the material in the cavity at the latest.

30. A process as claimed in any of claims 1 to 29, wherein magnesium sulfate is added to the material in the cavity at the latest.

31. A process as claimed in any of claims 1 to 30, wherein at least one cellulose-containing substance, for example sawdust, wood chips, straw or paper, is added to the material in the cavity at the latest.

32. A process as claimed in any of claims 1 to 31, wherein plastic particles, preferably consisting of polyvinyl chloride or polyethylene, are added to the material in the cavity at the latest.

33. An apparatus for carrying out the process as claimed in any of claims 1 to 32, having a chamber defining a cavity and having feed means for feeding starch-containing biomass or starch or at least one starch derivative into the cavity, which comprises a vapor source connected to the chamber, for passing steam or alcohol vapor into the cavity for gelling the material present in the cavity.

34. An apparatus as claimed in claim 33, wherein the feed means have a transport or pressing apparatus which is connected to an inlet of the chamber and has a rotatable screw.

35. An apparatus as claimed in claim 33 or 34, wherein a vapor separator is present, which has an inlet connected tightly to an outlet of the cavity, and an outlet for the gelled material and a vapor outlet and is designed for removing vapor from the material fed into it from the cavity during operation and passed through it, the vapor outlet having, for example, a pressure relief valve.

36. An apparatus as claimed in any of claims 33 to 35, which comprises a stirring mechanism having at least one rotatable stirrer arranged in the cavity.

37. An apparatus as claimed in any of claims 33 to 36, which comprises a dryer for generating infrared light or microwaves or hot air and thus drying at least one article formed from the material.