Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – By gas forming or expanding
Reexamination Certificate
2000-09-25
2003-11-04
Kuhns, Allan R. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
By gas forming or expanding
C264S053000, C264S328100
Reexamination Certificate
active
06641758
ABSTRACT:
The invention resides in the field of molded bodies manufactured from a mass comprising at least natural polymers, and in particular starch, and water.
The molded bodies have a blown, foamy structure. More particularly, the foamy material always comprises at least three parts: two relatively dense layers on the outside, which as it were form a skin, and between them a foam structure as core layer. The dense layers are firm and strong and consist of substantially closed, small cells. The foam structure of the core is generally open; the cells have burst to allow the gases evolving during the manufacture, for instance water vapor or carbon dioxide, to escape. Generally, the cells have a firm and solid cell wall due to the relatively high pressure and temperature in the mold or die during the manufacturing process.
These products can be manufactured in many manners, for instance according to the methods described in WO-A-95/20628, NL-A-1004138 and WO-A-96/30186.
These known methods start from a mass or batter which substantially consists of a mixture of modified or non-modified biopolymers, and particularly starch, and water, to which processing aids and additives for influencing the properties of the finished product are added. This has advantages particularly if fibrous material is added thereto to increase the dimensional stability and reinforce the finished product.
Generally, such batters comprise, for instance, 500-1500 parts by weight of starch or starch derivatives, 0.5-50 parts by weight of xanthan gum, 5-250 parts by weight of a reactive siloxane and 0-300 parts by weight of an inert filler in water. Additionally, preferably 0.5-50 parts by weight of a salt are further included, and 0-25 wt. % of fibers calculated on the weight of the complete batter mass.
The above embodiments are applicable for the present invention, yet should not be construed as being limitative in this context. Other batter compositions on the basis of water and natural polymers, in particular starch or starch derivatives, can likewise be used. In this respect, it is within the scope of a skilled artisan to set optimum processing conditions, such as pressure, temperature and residence time, depending on the batter and the molding apparatus to be used and within the framework of the invention.
In the known methods used for forming foamed molded bodies to which the present invention is directed, a starch or starch derivative is in each case used, in practice.
Starch is usually obtained from crops having a high starch content, in particular from cereals, including rice and maize, and from potatoes. The parts of these vegetable sources that possess high starch contents are washed and subsequently ground. From the ground plant parts, the protein fraction can then be separated, when necessary. After that, the starch granules are separated from fibrous material present and from other impurities by means of, for instance, sieves and/or hydrocyclones. This so-called starch refining requires much water. The obtained and washed starch granules are subsequently dehydrated with a vacuum filter and dried with hot air of, for instance, about 120° C.
When the molded bodies are not intended for consumption, relatively crude starch may usually suffice.
European patent application 0 474 095 concerns a method wherein starch-containing natural products are used in starting substances of molded bodies. For starch-containing fruits and potatoes, a pre-drying step is preferably used. Next, a pre-heating step is performed which, depending on the water content, takes place at a temperature below the glass transition temperature or at a temperature above 80-90° C. This results in the formation of a plastic or gelatinized product which can subsequently be shaped.
Nowhere, a link is made between a faster and more homogeneous gelatinization and the use of undried, crude vegetable material. Further, no reference is made to the removal of protein-containing material and/or salt so as to limit the disadvantageous influence during the baking process in the mold.
DE-OS-42 11 888 describes molded bodies manufactured from dough or batter prepared from complete plants. The use of only plant parts that have a starch content of at least 50 wt. % calculated on the dry substance and the advantages involved is neither described, nor suggested, and neither is the separation of protein and salt.
It is an object of the present invention to further optimize the method for manufacturing molded bodies on the basis of natural polymers, in particular starch and/or starch derivatives. In particular, there is a need for a method in which the required gelatinization can be performed more quickly and preferably more homogeneously. Moreover, there is a need for a method in which, if additives are used for improving the properties of the finished end product, such as cross-linking agents, these additives are distributed more properly, in particular more homogeneously, between the different starch chains. A further object is to cause the baking process to proceed in a more controlled manner.
Surprisingly, these objectives can be accomplished by applying in the batter starch that has not been subjected to a drying step.
More in particular, the invention relates to a method for manufacturing a molded body having a blown, foamy structure, wherein a mass comprising a suspension of at least starch, starch derivatives or mixtures thereof in water, is pressurized in or through a mold and the mass is heated in the mold in a manner such as to give rise to at least cross-linking of the starch, the starch derivatives or the mixture thereof, wherein the mass in the mold is brought at least to the baking temperature, characterized in that the suspension is prepared from vegetable material which has not been subjected to an artificial drying step and which contains at least 50 wt. % of starch, calculated on the dry substance, which vegetable material is ground to particles of a suspendable size.
In addition, the invention relates to the use of ground vegetable material, which vegetable material has not been subjected to an artificial drying step and which contains at least 50 wt. % of starch, calculated on the dry substance, which vegetable material is ground into particles of a suspendable size, in a mass subjected to a thermal molding step under pressure, to effect a quicker and more homogeneous gelatinization.
Further, the invention relates to the application in which, further, at least one additive for improving the properties of the product to be formed is added to the mass, to obtain a homogeneous distribution of the additive in and between the starch chains of the vegetable material that has not been subjected to an artificial drying step. Via this application, in particular, better reaction possibilities for the additives are created.
In this description, “gelatinization” is understood to mean a change of starch and/or starch derivative from a slightly or completely loose granular or comparable granulate form into a form in which stretched starch and/or starch derivative chains are present, which chains are interconnected only slightly, if at all. That is to say, there occurs a transition of starch or starch derivative from a solid form, a colloidal solution or suspension to a more homogeneous fluid mass. In this description, the term “gelatinizing” is synonymous to terms like “gelling”, “gellating” and the like.
In this description, by “baking” is understood to mean a method in which both gelatinization and cross-linking occur, at relatively high temperature and/or pressure. As a result, the formation of gas arises relatively soon, so that bubbles are already formed prior to or during gelatinization. Due to inter alia the high pressure adjacent strongly heated parts, the polymers cross-link quickly when using a mold or like baking form with a temperature at or above the baking temperature.
These baked products have a core with relatively large cells, enclosed between skin parts with relatively small cells. The cell walls have a relatively high density. Such a
Arentsen Jan Hendrik Adolf
Huisman Jan Wietze
Hoffmann & Baron , LLP
Kuhns Allan R.
Vertis B.V.
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