Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
2001-02-27
2003-01-28
Brunsman, David (Department: 1755)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
Reexamination Certificate
active
06512108
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention, in general, relates to films or foils and products made from, or incorporating, foils or coatings and, more particularly, to such products made from aqueous solutions of starch or amylose derivatives of the kind useful as fat impervious coatings of otherwise pervious or wettable packages made of paper, card board and the like.
2. The Prior Art
Films, foils and foil products, hereinafter sometimes collectively referred to as foils, are produced in huge quantities. Since a considerable quantity of such foils is intended for single time use only and since, following such use, the foils are usually discarded, there is an increased demand for foils which can either be recycled or which are biodegradable. Recycling is, however, sometimes made difficult since such foils, because of their great variety, can often not be distinguished and sorted by laymen or consumers for subsequent recycling processes. Foils which are fully bio-degradable or compostable within a reasonable time would, of course, constitute an ideal alternative to conventional foils and would very likely eventually replace those conventional foils which are not biodegradable or compostable, such as polyvinyl chloride, polystyrene, polyethylene, etc., if they could be made to posses similar properties, especially in terms of transparency, mechanical strength and stability as well as unidirectional or bidirectional imperviousness, as the case may be, in respect of predetermined substances.
Heretofore, numerous experiments have been conducted in which starch was used as a base or raw material for producing bio-degradable films or foils. However, products made from pure starch have thus far not been able effectively to compete with conventional products made from synthetic polymers. Their low tear strength and extensibility as well as their lack of transparency and stability are drawbacks which have prevented use of those products on any significant scale.
To overcome the disadvantages and, more particularly, to improve the mechanical properties of starch-based foils, it has been proposed (see, e.g. German patent 1,745,680) to add to the starch various softeners such as sorbite, glycerine, polyvinyl alcohol and so forth. Another way of improving the mechanical properties of starch-based products of the kind here under consideration is to add polyolefin-based synthetic polymers. For Instance, WO 90/14388 discloses a biodegradable plastic formed from corn starch and low-density polyethylene. The improvements brought about by such products have not, however, been such as to result in serious alternatives to synthetic polymers.
Another attempt to avoid, or at least lessen, the mentioned disadvantages was made by using so-called special amyloses such as, for instance, chemically modified high amyloses. For example, certain hydroxyalkyl derivatives of amylose may be processed into thermoplastic articles or foils, films and membranes, or hydroxypropyl starches may be added to other polymers, with a view to attaining improvements in predetermined properties. Thus, U.S. Pat. No. 3,850,652 relates to a specific application and teaches a multi-purpose membranous material of high flexibility and mechanical strength formed at least in part of a hydroxypropyl starch. Whilst this multi-purpose membranous material may be immune from being absorbed by other materials in contact therewith or vice versa, it is neither transparent nor completely biodegradable.
As described in EP 0,417,828, hydroxypropyl starches have also been used to improve the biological degradation behavior of products made from unsaturated hydrocarbon polymer compounds which would otherwise be difficult to decompose biologically. However, the properties of such products have by no means been satisfactory. Whilst the products may be generally transparent, they nevertheless display some slight brownish tinge, and they are of insufficient mechanical strength. Furthermore, U.S. Pat. No. 3,778,392 describes a mixture of polymeric starch and hydroxypropyl starch for use in connection with high-quality papers. These products are not biodegradable and involve comparatively complex manufacturing processes.
As regards their utility, none of the known products derived from starch or amylose have developed into products which effectively compete with comparable synthetic polymer products. Moreover, additives and softeners added to the starch or amylose often prevent complete biodegradability of the final product.
OBJECTS OF THE INVENTION
It is an object of the invention to provide foils or products thereof made from starch or amylose derivatives without added synthetic materials.
Another object is to provide foils or products thereof made from starch or amylose derivatives without added softener.
Still another object is to provided foils and the like made from starch or amylose derivatives which are qualitatively significantly superior to known foils of this kind by providing improved physical and mechanical properties.
It is a particular object of the invention to provide foils and the like made from starch or amylose derivatives which are of superior tear strength and extensibility as well as high transparency.
It is also an object of the invention to provide foils and films made from starch or amylose derivatives which may be used as overhead projection slides or printable films.
Yet another object of the invention resides in the provision of foils and films which may be used as surface coatings or laminates of paper and cardboard.
Still further, it is an object of the invention to provide a compound made from starch or amylose derivatives which may be deposited on a surface by spraying, spreading or pouring to form a foil or film thereon.
It is a further object of the invention to provide a compound from starch or amylose derivatives suitable as a surface coating of paper and the like to improve the surface quality thereof.
It is yet another object of the invention to provide a compound derived from starch or amylose derivatives which is completely biodegradable.
Another important object of the invention is to provide a laminate consisting of paper coated by a compound derived from starch or amylose derivatives to provide a substantially fat impervious food wrapping material.
A still further particular object of the invention is to provide a laminate incorporating a layer of a starch or amylose derived substance to provide a high degree of imperviousness to fat or fatty substances.
Still another object of the invention resides in the provision of a material suitable for coating a support layer made of paper, cardboard or similar materials to render it substantially impervious to fat or fatty substances.
Other object will in part be obvious and will in part appear hereinafter.
SUMMARY OF THE INVENTION
In accordance with the invention, there is provided a compound derived from a starch or amylose derivative of low salt content and dissolved in ether, the derivative having a mean molecular weight of between about 10
5
and about 2×10
7
g/mol, a degree of substitution between about 0.1 and 0.5, a substantially uniform distribution of substituents between the C
2
/C
3
and C
6
within their glucose unit, a water content of less than 25% under normal climatic conditions, a polydispersity from about 2 to about 8, and a predominantly amorphous structure with a low crystalline proportion and a predominant particle size not greater than 400 nm.
In a further advantageous embodiment of the invention the basic material has an amylose content of not less than 60%.
Other advantageous embodiments will become apparent to those skilled in the art as the description unfolds.
It has surprisingly been found that foils and products made thereof possessing the above parameters and made from pure starch or amylose derivatives without any additives have excellent mechanical properties and a high degree of transparency. Due to the fact that the foils and products made from them do not incorporate any synthetic additives or softe
Albrecht Rotraut
Boettcher Silvio
Haerter Gernod
Pawlak Peter
Schwartze Erich Heinrich
Gesellschaft fuer Spezialfolien-Entwicklung m.b.H.
Hormann Karl
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