Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1996-01-26
1997-09-02
Szekely, Peter A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524 13, 524 34, 524 35, 524 47, 10616251, C08L 302, C08L 102, C08L 126
Patent
active
056632169
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a reinforced substantially biologically degradable polymer as well as a process for its production.
Biologically degradable polymers such as starch, gelatin, cellulose derivatives, etc., or mixtures thereof are in the course of establishing themselves as polymer materials in addition to the known plastics, although, to be sure, at present only for very specific uses such as the encapsulating of active principles such as drugs, as packaging materials or packaging aids without special mechanical demands, as dish ware, cups, and the like. Their use for technical purposes as so-called "engineering plastics" is greatly limited due to their relatively poor mechanical properties such as compressive and tensile strength, as compared with the known plastics.
One possibility for improving these properties consists in reinforcing biologically degradable polymers, a technique which is already known from the use of plastics. As reinforcing materials, glass fibers or beads stand, in particular, in the foreground, and recently also carbon fibers and aramid fibers have been used. These reinforcing agents, however, are not biologically degradable; on the contrary, they are extremely resistant to natural degradation processes.
It is therefore an object of the present invention to propose a solution for improving the mechanical properties of biologically degradable polymers.
Another object of the present invention is to propose a biologically degradable polymer which is suitable for use as so-called engineering plastic.
In accordance with the invention, a reinforced, substantially biologically degradable polymer characterized by thermoplastic starch or a polymer mixture containing thermoplastic starch and at least one hydrophobic biologically degradable polymer, reinforced by natural fiber which are incorporated in the polymer is provided.
In accordance with the invention, it is proposed to reinforce a substantially biologically degradable polymer by natural fibers which are incorporated in a suitable biologically degradable polymer in accordance with the methods generally customary in plastics engineering. The natural fibers can be one of the following: ramie, cotton, jute, hemp, sisal, flax, linen, silk, abaca and/or mixtures thereof.
Sisal and ramie fibers are particularly suitable. In the case of sisal, concerned are flexible leaf fibers from leaves of a length of up to 2 meters of the sisal agave native to Central America. These hard fibers, at times referred to also as "sisal hemp", are used, for example, for the production of ships' hawsers, ropes, brushes, etc. Ramie fibers, also known by the name of China grass fibers, are obtained from the ramie plant, which comes originally from China, Japan, and Southeast Asia. About 85% of the raw ramie production of a total of about 100,000 tons of raw fibers still comes today from China. The high polymer chemical structure and the special microstructure impart to the ramie fiber dynamic loadability and an extremely high tear strength in dry as well as in wet state. Under tensile load, the ramie fiber shows very little elongation as compared, for instance, with glass, metal, carbon or aramid fibers.
Due to the properties described, sisal fibers and ramie fibers are particularly suitable as reinforcement, so that it has already been proposed in the past to combine, for instance, ramie fibers with metal, aramid and carbon fibers in plaster, cement and epoxy resins. However, because of their high price--ramie fibers cost about twice as much as cotton fibers--ramie fibers have not been able to establish themselves as reinforcement.
In connection, however, with biologically degradable polymers, natural fibers, such as, in particular, sisal and ramie fibers, afford an excellent possibility for decisively improving the mechanical properties of such polymers, without, however, negatively affecting the biologically degradability of said polymers. Even more, sisal and ramie fibers represent a natural replenishing resource so that they supply, in combinati
REFERENCES:
patent: 5317037 (1994-05-01), Golden et al.
Chemical Abstracts, vol. 119, No. 181893.
Bio-Tec Biologische Naturverpackungen GmbH
Szekely Peter A.
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