Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-10-27
2001-08-21
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S010000, C524S012000, C524S013000, C524S014000, C524S029000, C524S035000, C524S047000, C524S414000, C524S430000, C524S449000, C524S451000
Reexamination Certificate
active
06277899
ABSTRACT:
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-0 404 723, 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 presence of a limited quantity of water (typically 5-40% by weight with reference to the starch-water system) or of a plastisizer 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, characterized in that the matrix includes a fluidising agent selected from the group consisting of: C
12
-C
22
fatty acids, C
12
-C
22
fatty alcohols, esters 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, cationic starches, oxidated starches and cross-linked starches.
As the polymeric component, the polymers described in the patent literature mentioned in the introduction to the present specification may be used.
The synthetic polymeric component is preferably selected from the following polymers and copolymers and their mixtures:
(A) Polyvinyl alcohol, polyvinyl acetate and copolymers of an olefin selected from ethylene, propylene, isobutene and styrene with one or more monomers selected from acrylic acid, methacrylic acid, C
1
-C
4
alchylacrylate, C
1
-C
4
alkylmethacrylate, vinyl alcohol, vinyl acetate and maleic acid, such as ethylene-acrylic acid, ethylene-vinyl alcohol, ethylene-vinyl acetate, ethylene-maleic anhydride copolymers and their mixtures; the particularly preferred compounds are ethylene-vinyl alcohol copolymers with an ethylene content of from 10-44% by weight produced by the hydrolysis of the corresponding poly-ethylene-vinyl acetate with a degree of hydrolysis of between 50 and 100;
(B) Thermoplastics polyesters such as, in particular, homopolymers and copolymers of hydroxyaliphatic acids having from 2 to 24 carbon atoms, preferably 2 to 8 carbon atoms, the corresponding lactones or lactides and polyesters derived from bifunctional carboxylic acids with aliphatic diols.
(C) Graft copolymers of polysaccharides and their derivatives, such as starches, cellulose, modified cellulose, rubbers, alginates, pectins, dextrins and pullulans with monomers such as styrene, methylmethacrylate, methylacrylate, butylacrylate, butadiene, isoprene, acrylonitrile; graft copolymers of polysaccharides are described in the Encyclopedia of Polymer Science and Engineering, John Wiley & Sons, Volume 3, 1986. In particular, in group B the preferred polymers and mixtures of polymers selected are:
B1) poly-epsilon-caprolactone, copolymers of epsilon-caprolactone with isocyanates such as, in particular, 4,4′-diphenylmethane diisocyanate, toluylene diisocyanate, isophorone diisocyanate or hexamethylene diisocyanate;
B2) polymers of lactic acid or polylactides, of glycolic acid or polyglycolides, copolymers of lactic acid and glycolic acid;
B3) polyhydroxybutyrrate, polyhydroxybutyrrate/valerate;
B4) polymers derived from dicarboxylic acids with aliphatic diols such as, in particular, polyethylene and polybutylene adipate or sebacate;
B5) block or graft copolymers formed between homopolymers and copolymers of hydroxyacids, in particular poly-epsilon-caprolactone, and one or more of the following components:
i) cellulose or modified cellulose, for example, carboxymethylcellulose and cellulose acetate;
ii) amylose, amylopectin, natural or modified starches;
iii) polymers resulting from the reaction of a compound selected from aliphatic diols (such as ethylene glycol, propylene glycol, butylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, neopentyl glycol, 1,4-butanediol, cyclohexanediol), prepolymers or polymers of polyesters having terminal diol groups with monomers selected from:
bifunctional aromatic or aliphatic isocyanates,
bifunctional aromatic or aliphatic epoxides,
dicarboxylic aliphatic acids (such as malonic, succinic, maleic, fumaric, itaconic, glutaric, adipic, pimelic, suberic, azeleic and sebacic acids),
dicarboxylic cycloaliphatic acids (such as cyclohexanedicarboxylic acid, 2,2,2-dicyclooctanedicarboxylic acid) or
aromatic acids or anhydrides (such as phthalic acid),
iv) polyurethanes, polyamides-urethanes from diisocyanates and aminoalcohols, polyamides, polyesters-amides from dicarboxylic acids and aminoalcohols, polyester-urea from aminoacids and diesters of glycols,
v) polyhydroxy polymers (such as polyvinyl alcohol, ethylene-vinyl alcohol copolymers, totally or partially hydrolysed),
vi) polyvinyl pyrrolidone, polyvinyl pyrrolidone-vinyl-acetate copolymers and polyethyloxazoline,
B6) polyesters obtained from monomers of hydroxyacids upgraded with chain lengtheners such as isocyanates, epoxides, phenylesters and aliphatic carbonates;
B7) polyesters obtained from monomers of hydroxya
Bastioli Catia
Bellotti Vittorio
Lombi Roberto
Nicolini Matteo
Bryan Cave LLP
Novamont S.p.A.
Szekely Peter
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