Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1990-11-05
1993-11-16
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523128, C08L 300
Patent
active
052624587
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to biodegradable formed articles and films based on starch and to a process for producing them.
The term "formed articles", whenever used in the present description and in the claims, includes all the products having a thickness higher than 0.2 mm, such as boxes, containers in general, plates, packing articles, rods and the like.
In the latest years, several attempts have been made to produce biodegradable articles.
Among the various materials which have been suggested for producing formed articles and films, starches are no doubt, the most desirable ones, as they are natural, inexpensive and fully biodegradable products, which are widely available in nature.
U.S. Pat. No. 4,591,475 describes an injection molding process starting from non-destructurized starch. In this case, a high process instability was observed due to the fact that the viscosity of the product in the molten state was depending on the shear strain rate, wherefore the molding process is strictly depending on conditions such as screw speed, temperature, pressure and/or water content, and worsens the quality of the obtained articles.
In published European patent application No. 304,401, a process for the injection molding of capsules starting from destructurized starch is described. The articles obtained by means of this process, however, exhibit poor mechanical properties, besides being highly water-soluble.
It has been also suggested to combine the starch with other materials in order to produce articles endowed with satisfactory characteristics. Polyethylene is the material usually proposed to the purpose. The various attempts, which have been made to produce formed articles starting from starch-polyethylene mixes, have not given, however, satisfactory results. In fact, the products appear shapeless and weak because of the presence of several voids due to the conversion of humidity to vapour during the molding process. Furthermore, the resulting products have touch properties like those of paper.
U.S. Pat. No. 4,133,784 described compositions, which consist of starch and of an ethylene-acrylic acid copolymer (EAA), which are suitable for being transformed into films, and are flexible, water-resistant, thermoweldable and biodegradable.
Said compositions are transformed into films by means of techniques such as casting, simple extrusion or milling. However, these processes are slow and very expensive. Furthermore, at certain starch contents, as are necessary to obtain the desired mechanical properties, the biodegradability degree and the ultraviolet-ray stability of the products are strongly impaired.
On the other hand, the several attempts made by the Applicant in order to mold these compositions by injection were not successful due to the poor physico-mechanical properties of the products obtained; in fact, products exhibiting a low rigidity and a high elongation under load were obtained.
U.S. Pat. No. 4,337,181 proposed to add a sufficient amount of a neutralizing agent, such as ammonia or an amine, to the starch-EAA copolymer composition, in order to neutralize a part of all of the acid groups of EAA, and then to blow mold the resulting formulation with a humidity content ranging from 2 to 10%.
The addition of a neutralizing agent permits to overcome some drawbacks depending on the low rigidity of the products obtained remain or increase.
In Ind. Eng. Chem. Res. 1987, 26, pages 1659-1663 it was also proposed to add urea and/or polyols to the starch-EAA copolymer compositions in order to favor the preparation and to improve the economic and qualitative features of the resulting films. The effect of the presence of the urea is to enable the crystalline structure of the starch to be destroyed by small quantities of water and hence to enable granules for filming to be produced directly from a composition with a water content of around 16%, as well as of eliminating the necessity to premix the starch-EAA copolymer mixture in a very complex mixer with a great water amount before the extrusion process. Therefore,
REFERENCES:
patent: 3652542 (1972-03-01), Hjermstad
patent: 4133784 (1979-01-01), Otey et al.
patent: 4337181 (1982-06-01), Otey et al.
patent: 4454268 (1984-06-01), Otey et al.
patent: 4673438 (1987-06-01), Wittwer
Chemical Abstracts, vol. 7, No. 8, p. 47, Abstract No. 60151n, F. H. Otey et al., "Starch-based blown films" (Aug. 24, 1987).
Otey, F. H. et al., Ind. Eng. Chem. Res. 26(8):1659-63 (1987), "Starch-Based Blown Films".
Bastioli Catia
Bellotti Vittorio
del Giudice Luciano
Del Tredici Gianfranco
Lombi Roberto
Barnhard Elizabeth M.
DeWitt LaVonda
Michl Paul R.
Novamont S.p.A.
LandOfFree
Biodegradable articles based on starch and process for producing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Biodegradable articles based on starch and process for producing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Biodegradable articles based on starch and process for producing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-23089