Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1993-10-12
1995-08-08
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524 52, 524366, 524376, 524386, 524312, C08L 302, C08B 3012
Patent
active
054399530
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to improvements in the production of materials and shaped articles made therefrom, said materials being based on modified starch which is present in an intimate mixture with thermoplastic polymer compounds.
STATEMENT OF RELATED ART
Numerous proposals in recent years deal with an attempt to develop high molecular weight polymer compounds of natural origin--and among these especially starch--so that these compounds would find new fields of application. These works, more particularly, have been based on the recognition that native starch in combination with limited amounts of water and/or further auxiliary materials can be converted into a thermoplastic material by means of a thermomechanical digestion, which thermoplastic material is subsequently processable by conventional means, e.g. by procedures of injection molding. More particularly, the thermomechanical digestion using elevated temperatures and elevated pressures can be carried out in conventional extruders before the process step of molding. From the voluminous literature, here reference may be made to R. F. T. Stepto et al., "Injection Molding of Natural Hydrophilic Polymers in the Presence of Water", Chimia 41 (1987), No. 3, 76-81, and to the literature cited therein.
A great number of publications deal with the improvement of product properties in the thermoplasticized starch by the use or concomitant use of selected organic auxiliary liquids in the digestion of starch, which may be exemplified by the PCT Patent Application WO 90/05161. Here, for producing a thermoplastically processable starch it is proposed to mix additives with the native or natural starch, which additives decrease the melting temperature of the starch and are additionally characterized by some definite solubility parameter. Furthermore the vapor pressure of the additive should be less than 1 bar in the melting range of the mixture of starch plus additive. As the additives there have been especially mentioned polyfunctional lower alcohols such as ethylene glycol, propylene glycol, glycerol, 1,3-butanediol, diglyceride, corresponding ethers, but also compounds such as dimethylsulfoxide, dimethylformamide, dimethylurea, dimethylacetamide and the corresponding monomethyl derivatives.
Materials based on a starch having been thus thermoplasticized and the molded parts made therefrom are characterized by a seriously restricted utility. The cause thereof is the extreme hydrophilicity of this material. Therefore, the starch modified in such a manner is not suitable for use as a biodegradable polymer material of natural origin which could act as a substitute, much desired today, for polymer compounds of synthetic origin.
Recent proposals deal with an attempt to combine a thermoplasticized starch of the described type with synthetically produced water-resistant polymer compounds to the end that the starch-based hydrophilic polymer compound will be provided with an increased resistance to hydrophilic solvents, while nevertheless substantial proportions of the material or molded part, respectively, will be formed by the thermoplasticized starch. Reference is made to PCT Patent Application WO 90/01 043 among the pertinent literature. Therein it is described to coat hydrophilic polymers such as starch with selected aliphatic polyesters which themselves in turn are degradable, especially by bacteria or fungi. What is described therein, more specifically, is coating molded articles made of starch with polyesters of lower hydroxycarboxylic acids such as glycolic acid, lactic acid, hydroxybutyric acid and hydroxyvaleric acid. Since such layer combinations exhibit a poor mutual adhesion, it is proposed to improve the adhesion by a preceding treatment of the starch surface, and/or by the addition to the coating solution of a solvent or swelling agent for the starch.
Another approach to attain the same goal is described in the EP-A2 327 505. Therein, polymer mixed compositions have been described, which are recovered from a melt of water-containing
REFERENCES:
Chimia 41 (1987); Stepto & Tomka "Injection Moulding of Natural Hydrophilic Polymers in the Presence of Water", pp. 76-81.
Bergner Rainer
Kempf Wolfgang
Ritter Wolfgang
DeWitt LaVonda
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Michl Paul R.
Szoke Ernest G.
LandOfFree
Starch-based materials and/or molded parts modified by synthetic does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Starch-based materials and/or molded parts modified by synthetic, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Starch-based materials and/or molded parts modified by synthetic will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-971723