Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1995-03-27
1999-02-23
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 10, 524 12, 524 13, 524 14, 524 29, 524 35, 524 47, 524 49, 524 50, 524 15, 524 51, C08L 300, C08L 100, C08L 508, C08K 5053
Patent
active
058744860
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a biodegradable polymeric composition of the type including starch and synthetic thermoplastics polymers, suitable for the production of biodegradable articles having satisfactory physical and mechanical properties, by means of conventional techniques applied to thermoplastics materials of synthetic origin.
Thermoplastics compositions of the type specified above are known and available commercially and are described, for example, in patent applications EP-A-0 032 802, EP-A-0 327 505, WO 90/10671, EP-A-0 400 532, EP-A-404 723, EP-A-0 404 727, EP-A-0 404 728, WO 91/02024, WO 91/02025 and U.S. Pat. No. 5,095,054.
Typically these compositions can be obtained by the mixing of a starch component with a synthetic thermoplastics polymeric component in conditions typical of the "extrusion-cooking" process, that is in the presence of a limited quantity of water (typically 5-40% by weight with reference to the starch-water system) or of a plasticizer at a high enough temperature and pressure to destroy the crystalline structure of the starch and to obtain a molten thermoplastics mass.
The object of the present invention is to provide compositions of the type specified above which have improved mechanical properties, particularly a higher rigidity, even in the presence of high humidity, and properties of processability comparable with those of conventional plastics, while retaining or surpassing the rate of biodegradability of the known compositions.
This object is achieved by virtue of a polymeric composition comprising a matrix including a starch component and at least one synthetic thermoplastics polymeric component in which a filler is dispersed, characterised in that the matrix includes a fluidising agent selected from the group consisting of: and amides of the said fatty acids, polyolefin waxes and polyglycol ethers of alditols or polyglycerols esterified with the said fatty acids and their mixtures and the said filler comprises natural fillers of an organic nature dispersed in the matrix in quantities of from 5% to 70% by weight with reference to the total weight of the composition.
The materials constituting the fillers are preferably selected from wood flour, walnut shells, cellulose, cotton, jute, raffia, rice chaff, animal bristles, chitin and granular starch and their mixtures; of these the preferred are the fibrous materials. The dimensions of the fillers may vary within wide limits according to the mechanical properties which it is intended to bestow. Typically the average dimensions are between 0.5 and 500 microns, preferably between 1.5 and 300 microns; the shape ratio L/D is generally between 1 and 100 and preferably between 2 and 50.
The preferred filler concentrations are in the range 20%-50% by weight with reference to the weight of the composition. In combination with the natural organic fillers listed above, the compositions may include inorganic fillers such as talc, mica, titanium dioxide, aluminium oxide in concentrations preferably no higher than 5% by weight. The fillers may be surface treated to improve their affinity with the matrix material, for example, by means of linking agents such as titanates or zirconates or by silanisation.
The preferred matrix materials include the starch component and the synthetic thermoplastics component typically in a ratio of from 1:9 to 9.8:0.2, preferably from 1:4 to 4:1 and more preferably from 1.5:1 to 1:1.5.
The starch used is generally a natural starch extracted from various plants such as maize, potato, tapioca and cereals; it is intended that the term starch should be understood to include starches with a high amylopectin content (waxy starches) and chemically and physically modified starches, such as for example starches whose acid values have been reduced to between 3 and 6, starches in which the type and concentration of cations associated with the phosphate groups have been modified, ethoxylated starches, starch acetates, catlonic starches, oxidated starches and cross-linked starches.
As the polymeric component, t
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patent: 5095054 (1992-03-01), Lay et al.
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Patent Abstracts of Japan, vol. 16, No. 406 (C-978)(5449) & JP,A,41 36 047 (Kuraray Co. Ltd.) (Abstract), May 1992.
Derwent Abstract AN 92-295587 & JP,A,4 202 429 (Lion Corp.), Jul. 1992.
Derwent Abstract for DE 2305150, Aug. 1974.
Bastioli Catia
Bellotti Vittorio
Lombi Roberto
Nicolini Matteo
Novamont S.p.A.
Szekely Peter A.
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