Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1997-10-17
2003-01-14
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...
C524S037000, C524S038000, C524S039000, C524S040000, C524S041000, C524S042000, C524S043000, C524S044000, C524S045000, C524S046000, C524S050000, C524S051000, C523S128000
Reexamination Certificate
active
06506824
ABSTRACT:
The present invention relates to biodegradable thermoplastic composition suitable, in particular for preparing injection moulded articles free from surface defects, comprising a starchy component and a cellulose ester or ether.
Biodegradable composition obtained starting from starch and a thermoplastic polymer are well known in the art and available from the market and are disclosed, e. g., in European patent applications EPA 32 802, 327 505, 400 532, 404 723, 404 727, 404 728, and in W090/0671, W071/02025, U.S. Pat. No. 5,095,054.
Typically, such compositions can be obtained by blending starch and a synthetic thermoplastic polymer, under extrusion cooking conditions, i.e. in the presence of limited amounts: of water (generally 0.5-40% by weight based on starch-water system) or of a plasticiser, by operating under temperature and pressure conditions sufficient to destroy the starch crystallinity and to obtain a thermoplastic molten mass (destructured starch).
From European patent application EPA 575 349, biodegradable compositions are known which comprise a starch component and a cellulose ester.
The injection moulded articles obtained starting from said compositions are affected from the drawback of displaying unpleasant surface scale due to the poor compatibility between starch and cellulose esters. European patent application EPA 542 155 discloses compositions based on starch and cellulose esters added with a compatibilizer agent (epoxidized soy bean oil and acetylated starch) in order to confer improved mechanical properties to the moulded articles. The moulded articles from the above compositions undergo considerable delamination phenomena due to the insufficient compatibilization between starch and the cellulose ester.
We have found now that it is possible to improve the mutual compatibility of starch or starch esters or ethers and cellulose esters or ethers and to obtain moulded articles free from scales unevenness, by using selected classes of compatibilizing agents.
Beside endowing the resulting compositions with better homogeneity, the use of the compatibilizing agents of the invention improves the biodegradability characteristics of the compositions.
The compositions according to the present invention comprise:
starch or a starch ester or ether with a substitution degree from about 1.2 to 2.5;
a cellulose ester or ether with a substitution degree from about 1.2 to 2.5;
a plasticizer for the starchy phase and a plasticizer for the cellulose derivatives phase or a plasticizer for both phases;
a compatibilizing agent selected from the following classes:
(A) polymers compatible with cellulose esters or ethers and/or starch or starch esters and ethers, grafted with aliphatic or polyhydroxylated chains containing from 4 to 40 carbon atoms;
(B) copolymers obtained from hydroxy acids and/or diamines with 2-24 carbon atoms and aliphatic or aromatic diisocyanates or epoxy compounds and anhydrides; copolymers obtained from aliphatic polyesters, polyamides or polyureas and aliphatic or aromatic diisocyanates; copolymers obtained from aliphatic or aromatic diisocyanates and polyalkylene glycols;
(C) copolymers obtained from polymers compatible with cellulose esters or ethers and/or starch or starch esters or ethers, by grafting starch soluble polyols or structures capable of complexing starch.
(D) polymers capable of complexing starch such as ethylene—vinyl alcohol or ethylene acrylic acid copolymers, aliphatic polyesters or polyamides.
(E) starch compatible polyols selected from the monomers and the low molecular weight polyols (Viscosity average molecular weight lower than 10,000) such as glycerol, sorbitol, erythritol, polyglycerol, dextrines, polyvinylalcohol, polyaspartates, and the above polyols grafted with alkylenoxides or polyalkylenoxides. The compatibilizer agents indicated under (A) are obtained by grafting aliphatic chains with 4-40 carbon atoms optionally containing up to three unsaturations and or heteroatoms or still other functional groups, to polymers compatible with cellulose esters or cellulose ethers. Preferably, the chains derive from animal or vegetable fats, such as oleic, lauric, myristic, palmitic, stearic, euric, linoleic, ricinoleic acids or phospholipids with terminal end groups which allow the chains to be grafted to the polymers compatible with cellulose esters or ethers.
The terminal group can be carboxy, ester or salt groups; the chains can also be modified in order to obtain terminal groups such as alcohol, aldehyde, amine, amide, acid chloride, isocyanate, mercaptan epoxy and anhydride groups. The polymers to which the above said lipidic chains are grafted can display different degrees of affinity with cellulose derivatives and starch esters or ether; some of them can even be miscible with said cellulose derivatives and starch ester or ethers; others, with a lower compatibility degree, can anyway result to be interesting because they can be easily transformed into compatible derivatives.
Such polymers can be of either natural or synthetic origin. Furthermore, they can be used as such, or modified or depolymerized to trimer level by hydrolysis, saponification, cracking or by means of enzymatic reactions.
Examples of the above polymers are:
(a) cellulose esters with various DS (Degree of Substitution);
(b) cellulose ethers with various DS;
(c) cellulose ethers/esters with various DS values;
(d) starch ester with various DS values, as acetates;
(e) starch ethers with various DS values, such as the reaction products of starch with ethylene or propylene glycols;
(f) starch ethers/esters with various DS values;
(g) partially hydrolysed polyvinyl acetate;
(h) aliphatic polyesters and copolyesters, optionally also grafted with those products as listed under (a)-(g) above. In this case, polymers are preferred which are obtained by grafting low molecular weight(350-1000) polycaprolactone (PCL) to polyvinyl alcohol copolymer or, also, by grafting PCL to regenerated cellulose or starch;
(i) aliphatic/aromatic or aromatic copolyesters optionally grafted with above (a)-(g) products;
(j) polymers from natural origin such as cellulose, hemicellulose, lignin, cellulose ethers and xanthates, regenerate cellulose, pullulan, chitin, chitosan,pectins, proteins, vegetable and animal gelatines, zein, gluten, casein, albumen, natural or modified rubbers, alginates, rosin derivatives.
The aliphatic chains can be grafted by means of any known type of reaction, and generally by:
(1) transesterification of ester group;
(2) esterification of hydroxy groups;
(3) urethanizing hydroxy groups by means of isocyanates;
(4) epoxidizing hydroxy groups with aliphatic epoxides;
(5) acetilization of hydroxy groups with aliphatic aldehydes.
The compatible polymers with the cellulose derivatives and starch esters or ethers, polyols soluble in starch, or capable of complexing starch, can be grafted for example with following polyols: modified amylose and its hydrolysis product; polyvinyl alcohol with various hydrolysis degrees, ethylene-vinyl alcohol copolymers, polyols of glycerol, polyglycerol, saccharides, oligosaccharides, trimethylol propane, pentaerythritol.
The number of grafted chains are comprised within the range of from 0.1 to 30 grafted chains per each 100 monomeric units in the polymer chain, preferably from 0.2 to 20, and still more preferably, from 0.3 to 10 grafted chains for each 100 monomeric units.
Besides the compatibilizers of above (A) type which require that polymeric products are modified by grafting lipidic chains, also copolymers of above (B) type can be advantageously used, particularly those obtained from such aliphatic polyesters such as polycaprolactone with various molecular weight and polyethylene succinates, from alipathic or aromatic diisocyanates or copolymers obtained from C
2
-C
24
hydroxy acids, or aliphatic or aromatic diisocyanates, or copolymers of above (C) type.
For the preparation of copolymers of above (B) type, preferred diisocyanates are:
4,4′-diphenylmethane diisocyanate, hydrogenated 4,4′-diphenylmethane diisocyanate, toluid
Bastioli Catia
Bellotti Vittorio
Lombi Roberto
Perego Gabriele
Cave LLP Brian
Novamont S.p.A.
Szekely Peter
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