Compositions: coating or plastic – Coating or plastic compositions – Proteinaceous material containing
Reexamination Certificate
2000-03-13
2002-06-18
Nutter, Nathan M. (Department: 1711)
Compositions: coating or plastic
Coating or plastic compositions
Proteinaceous material containing
C106S145100, C106S162100, C106S162500, C106S162510
Reexamination Certificate
active
06406530
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to the field of thermoplastic processing of polymeric materials. In particular, the invention relates to thermoplastic mixtures based on biopolymers, preferably starch, the preparation of mixtures of this type, and also the use of these mixtures for producing shaped biodegradable articles, such as moldings or films, which have improved properties, for example improved mechanical properties.
The industrial sector concerned with biopolymers is enjoying constantly increasing interest, due primarily to environmental factors.
Biopolymers, such as polysaccharides and proteins, are biocompatible materials and as such have the great advantage of fundamentally good biodegradability and biocompatibility. The increased use of what are known as hydrophilic polymers as natural and, together with this, physiologically compatible and biodegradable plastics for a wide variety of application sectors, is also leading to considerable efforts to process biopolymers of this type, including starch, using known plastics-processing techniques, e.g. injection molding or extrusion. However, products produced in this way, such as moldings or films, frequently have inadequate mechanical properties, for example insufficient strength, and there is also frequently a lack of cost-effective methods for preparing appropriate starting materials for the products.
Limited improvements can be made by modifying the biopolymers chemically. There are many and varied reactions used to modify, for example, starch. These include oxidative processes, polymer-analogous reactions with organic chemicals and crosslinking reactions.
In the further processing of biopolymer mixtures, in particular starch mixtures, using conventional polymer-processing technology it is in most cases of interest to melt the polymer mixture (e.g. in injection molding, blow molding, extrusion, coextrusion or extrusion with blowing). This requires thermoplastic behavior in the molding compositions based on biopolymers.
However, substances which have to be used to improve the plastification of the thermoplastic mixtures are frequently disadvantageous to the mechanical properties of the products manufactured from the thermoplastic mixture. If, for example, attempts are made to improve the thermoplastic behavior of, for example, starch by crosslinking, a process in which an important part is often played by bifunctional molecules based on aldehydes, such as glyoxal, glutaric dialdehyde or dialdehyde starch, or else those based on diisocyanates, on epoxides, or epichlorohydrin, diesters, etc., if the content of crosslinking agent is too high, the extent of the crosslinking reaction can hinder achievement of the desired effect, which is better plastification of the starch. In particular, relatively strong crosslinking results in an insoluble, though swellable, product.
For more detailed prior art regarding starch materials the following publications are cited:
WO 90/05161 (PCT/CH89/00185)=D1,
DE-A 39 31 363=D2,
DE 44 12 136=D3 and
DE 42 07 131=D4.
D1 describes the preparation of thermoplastically processable starch by admixing an additive with essentially native or natural starch and melting the mixture by introducing heat and mechanical energy. The additive is a substance which lowers the melting point of the starch, and the melting point of the starch together with this additive is therefore below the decomposition temperature of the starch. Specific examples of the additive are DMSO, 1,3-butanediol, glycerol, ethylene glycol, propylene glycol, butylene glycol, diglyceride, diglycol ether, formamide, N,N-dimethylformamide, N-methylformamide, N,N′-dimethylurea, dimethylacetamide and N-methylacetamide. D1 also proposes the addition of a crosslinking agent selected from the group consisting of the di- or polybasic carboxylic acids and/or anhydrides, the halides and/or amides of di- or polybasic carboxylic acids, the derivatives of di- or polybasic inorganic acids, epoxides, formaldehyde, the derivatives of urea, the divinyl sulfones, the isocyanates, mono- or polyfunctional oxo compounds, and also cyanamide.
D2 relates to a process for reducing the swellability of starch by modification, by adding a crosslinking reagent in a pure or encapsulated form and achieving the crosslinking reaction by subsequent annealing at elevated temperature. The crosslinking agents used are, inter alia, urea derivatives, urotropin, trioxane, di- or polyepoxides, di- or polychlorohydrins, di- or polyisocyanates, carbonic acid derivatives, diesters or else inorganic polyacids, such as phosphoric or boric acids. A feature of the mixtures described is- very high weight ratios of crosslinking agent used (from 10 to 100% by weight) in order to achieve an appropriate increase in mechanical stability through the subsequent thermal treatment.
Lignin is used, for example, in adhesives and glues, as described, for example, in D3. The heterogeneous mixture of ligninsulfonate with colophonium resin and starch gives, in an aqueous dispersion, a glue for gluing surfaces or objects.
D4 describes the use of liquid smoke flavorings in the production of tubular viscose casings or wrappings for food packaging by precipitation processes, with the aim of giving meat products in particular characteristic properties. A disadvantage is that the liquid flavoring has to be applied via further operations after the production process.
SUMMARY OF THE INVENTION
Bearing in mind the prior art described and discussed here, therefore, one object of the invention was to provide a thermoplastic mixture based on biopolymers, preferably starch, which permits the production of shaped biodegradable articles with improved properties, preferably with improved mechanical properties.
Another object of the invention was a process for preparing a thermoplastic mixture for extrudates or pelletized materials, together with the use of the thermoplastic mixture.
In a manner which is not readily foreseeable, the presence of an effective amount of lignin in a thermoplastic mixture based on biopolymers is successful in modifying the properties of materials of this type, where the proportion of lignin varies depending on the intended application. In film applications in particular, favorables effects can be seen on the mechanical properties and other performance charteristics, such as the odor of the film.
Because the lignin added is a natural material, it can also be used in the food and drink sector.
Due to its chemical nature, the lignin here gives both the the thermoplastic molding composition itself and also the shaped articles of any tape manufactured therefrom a pleasant aromatic odor. The unforeseeable effect is advantageously perceptible in particular when producing films or foils, and there is therefore a possible use as an aroma component or smoke substitute.
Alongside the effect on appearance, odor and taste, positive effects on the preservation behavior of the thermoplastic molding compositons, and also of shaped articles or films resulting therefrom, can arise.
Due to the processing temperatures required according to the invention, it was not readily foreseeable that a favorable effect of this type would result from the use of lignin or its derivatives.
The invention therefore consists primarily in the use of lignin for modifying thermoplastically processable materials, such as proteins and/or polyseccharides. Surprisingly, although lignin is omnipresent in the environment, no technical consideration has previously been given to the fact that combining a natural matrial isolated from timber, namely lignin, with proteins and/or polysaccharides, preferably polysaccharides, especially starch or its derivatives, gives an advantageous modificaton of thermoplastic mixtures in which these biopolymers are present and improves the properties of products produced therefrom.
Another advantage of the present invention, besides the improvements mentioned in the properties of the products, is that a rational use is provided for a previously unuse
Bengs Holger
Böhm Gitte
Aventis Research & Technologies GmbH & Co KG
Connolly Bove & Lodge & Hutz LLP
Nutter Nathan M.
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