Foils and coatings

Details Foils and coatings Foils and coatings

1999-03-25

2001-04-10

Hess, Bruce H. (Department: 1774)

Stock material or miscellaneous articles

Structurally defined web or sheet

Physical dimension specified

C428S327000, C428S532000

Reexamination Certificate

active

06214452

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 starch or amylose derivatives of the kind useful in an office environment or as data carriers or image surfaces as well as teaching and learning materials such as, for instance, overhead projection slides, printing or drawing sheets, transparent folders or windows of envelopes. Other fields of application relate to the manufacture and refinement of special papers and to packaging materials as in see-through packages or parts of packages or as laminates on other web materials. Further fields of application of the foils here under consideration are in food packaging and agriculture.
2. The Prior Art
Films, foils and foil products, hereinafter sometimes collectively referred to as foils, are produced in huge quantities. Since a considerable amount of such foils are intended for one-time use only and since, following such use, they must be disposed, there is an increased demand for foils which can either be recycled or which are biodegradable. However, recycling is made difficult by the fact that these foils, because of their great variety, can often not be distinguished and sorted out by laymen for subsequent appropriate recycling processes. An alternative to such foils would be foils which are fully bio-degradable or compostible within a reasonably short time. Such foils would very likely eventually replace those foils which are not biodegradable or compostible, such as polyvinyl chloride, polystyrene, polyethylene, etc. provided they could be made to exhibit similar properties, especially in terms of transparency and mechanical strength and stability.
In the past, numerous experiments have been conducted in which starch served as the base or raw material for producing bio-degradable films or foils. Thus far, however, products made from pure starch have not been able effectively to compete with conventional products made from synthetic polymers. Their low tear strength and extensibility as well as lacking 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 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 synthetic polymers based upon polyolefines. Thus, there is known 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.
A further attempt to avoid, or at least lessen, the mentioned drawbacks was made by using so-called special amyloses such as, for instance, chemically modified high amyloses. For instance, certain hydroxyalkyl derivatives of amylose may be processed into thermoplastic articles or foils, films and membranes, or hydroxypropyl starches are 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 non-absorbable by other materials in contact therewith, it is neither transparent nor completely biodegradable.
Hydroxypropyl starches are also utilized for improving the biological degradation behavior of products made from unsaturated hydrocarbon polymer compounds which are difficult to decompose biologically. However, the properties of products thus obtained are by no means satisfactory. Whilst these products may be 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 hyydropropyl 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 been capable of competing effectively against comparable products made from synthetic polymers. Moreover, in most cases the additives and softeners added to the starch or amylose prevents 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.
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 softeners they are completely biodegradable.
Particularly advantageous results are attained if the basic material, i.e. the starch is derived from the group of high amylose starches and if its amylose content is not less than 60%.
The inventive parameters of the derivative, viz. low salt content, mean molecular weight between about 10
5
and about 2×10
7
g/mol, polydispersity of about 2 to about 8, a degree of substitution of 0.1 to 0.5 and preferably from 0.1 to 0.3, substantially uniform distribution o

Affiliated with

Also associated with

Rating

Foils and coatings does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Foils and coatings, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Foils and coatings will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2492384