Compositions: coating or plastic – Coating or plastic compositions – Carbohydrate or derivative containing
Reexamination Certificate
2002-02-20
2003-03-18
Brunsman, David (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Carbohydrate or derivative containing
Reexamination Certificate
active
06533854
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for producing a shaped body made of biodegradable material, a shaped body which is obtainable by this process and its use for packaging articles, in particular food.
2. Description of the Related Art
Currently, the avoidance, reduction and disposal of waste is one of the greatest environmental problems. This is becoming especially apparent in the case of shaped bodies, such as beakers, plates, cups, dishes, cartons and other containers which are used, for example, for packaging foods and in fast-food restaurants. Thus foods, for example, especially those which are intended for immediate consumption, are frequently purchased in voluminous packaging. Although such shaped bodies are relatively light, after their use, they increase on their disposal the amount and volume of long-lasting solid wastes. As a result these shaped bodies, owing to their considerable volume, make demands on the refuse containers and the refuse landfills. In addition, they are readily blown away by the wind. If such shaped bodies are discarded in the open after the foods contained therein have been consumed, they frequently disfigure the landscape over years.
Many of the materials used to date for producing the above-mentioned shaped bodies are not produced from renewable raw materials, which in addition represents a heavy ecological burden. As becomes clear from the circumstances described above, there is a great requirement for a material which can be used for shaped bodies, in particular packaging, which is predominantly produced from renewable raw materials and which is very rapidly biodegradable.
DE 197 06 642 A discloses a shaped body made of biodegradable material consisting of cellulose fibres, native and/or modified starch and water which is prepared by subjecting a mixture (bakeable mass) of these constituents to a baking operation with formation of the shaped body. The content of fibrous materials in the mass is from 25 to 75% by weight, the starch content is from 13 to 38% by weight and the water content is from 13 to 38% by weight.
For baking, this bakeable mass is placed (metered) into a baking mold and baked therein by heating. The baking mold can be formed here by at least two baking sheets, i.e. an upper and lower baking sheet, which are held in a baking iron, the inner surfaces of the baking sheets being spaced apart in the closed locked state of the baking mold, forming a mold cavity.
However, this process has the disadvantage that the foaming, i.e. the expansion behavior during thermoforming, is not satisfactory.
SUMMARY OF THE INVENTION
The object thus underlying the present invention is to provide a process for producing a shaped body made of biodegradable material in which the bakeable mass used shows good expansion behavior during thermoforming.
According to the invention this is achieved by a process for producing a shaped body made of biodegradable material which is distinguished in that a bakeable mass is produced by mixing from 7.8 to 8.5% by weight of cellulosic fibres, from 16.1 to 17.6% by weight of native starch, from 5.4 to 6.0% by weight of pregelatinized starch and from 68.0 to 70.6% by weight of water, in each case based on the bakeable mass, and the bakeable mass is then baked, forming a shaped body.
Surprisingly it has been found that an improved expansion behavior during thermoforming is achieved owing to the high water content, as a result of which the shaped bodies obtained are not only very light, but also, the foam-like wall structure obtained by the production process has a heat-insulating action.
The term “bakeable mass” refers to masses of any type which can be baked, i.e. can be foamed by steam which escapes during the baking.
The starch which is present in the bakeable mass can be an amylopectinaceous starch, for example selected from natural starch, chemically and/or physically modified starch, biotechnologically produced and/or genetically modified starch and mixtures thereof. Examples of the starches which are usable in the process of the invention are potato starch, maize starch, rice starch, tapioca starch and wheat starch and other starches produced from plant materials.
In the process of the invention, cellulosic fibres are used, the term “cellulosic fibres” referring to fibres of any type which contain cellulose or consist of cellulose. Plant fibres preferred here are those of differing lengths in the range from 600 &mgr;m to 3000 &mgr;m, principally from wood, hemp or cotton. The width of the cellulosic fibres can be in the range from 10 &mgr;m to 60 &mgr;m.
The expression “fibres” used here refers to fine, thin objects restricted in their length, the length being greater than the width. They can be present as individual fibres or as fibre bundles. Such fibres can be produced in a manner known to those skilled in the art.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In a preferred embodiment of the process according to the invention, the viscosity of the bakeable mass is set at a value in the range from 70,000 to 80,000 mPa.s. This can be achieved by varying the amounts of the constituents used in the process of the invention, in particular via the water content. The metering behavior of the bakeable mass is improved via this viscosity. As a result it is possible to meter the mass into the baking sheets in the form of a single large lump which, owing to its high water content, distributes itself spontaneously therein and completely fills all cavities. The reason for this is firstly the improved viscosity, but secondly also, because of the higher water content, a rapidly increasing pressure course due to the higher water evaporation which ensures that the bakeable mass is more rapidly distributed before the starch is completely baked and thus becomes solid.
As was mentioned above, in the process of the invention pregelatinized starch is used. The pregelatinized starch is preferably produced here from about 90 to 94% by weight of water and from 6 to 10% by weight of native starch, particularly preferably from about 92% by weight of water and about 8.0% by weight of native starch.
In the process, a homogeneous suspension is first produced from these two components. This can be performed, for example, by vigorously stirring water and the native starch in a conventional agitator. This homogeneous suspension is then heated and subsequently cooled.
The heating is preferably carried out to a temperature of from 68 to 70° C. It has further proved to be expedient to carry out the heating for a period of about 10 minutes, i.e. the suspension is kept at a constant temperature of 68 to 70° C. for a period of about 10 minutes.
The pregelatinized starch is subsequently cooled. The temperature to which it is cooled is preferably about 50° C.
In a preferred embodiment of the process according to the invention, the bakeable mass is prepared by combining in parallel or sequentially the cellulosic fibres, the native starch, the pregelatinized starch and the water and mixing them. This represents a considerable improvement in comparison to previously known processes for producing shaped bodies made of biodegradable material in which the components are mixed in one after the other, since this simplifies the entire mixing process.
In a further preferred embodiment of the process according to the invention, the pregelatinized starch is added to a mixture of native starch, fibres and water at a temperature of about 50° C., preferably exactly 50° C.
During mixing, the constituents cellulosic fibres, native starch, pregelatinized starch and water are mixed with one another homogeneously in the course of about 5 minutes. The mixing temperature is 40° C. After mixing the mixture is not subsequently cooled.
The bakeable mass used in the process of the invention can either consist only of the components water, fibres, native and pregelatinized starch, i.e. no other constituents are present, apart from those which are present in these components as usual accompanying materials, e.g. cont
Kaiser Norbert
Kesselring Anneliese
Köblitz Thomas
Apack AG für Biologische Verpackungen
Brunsman David
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