Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1993-02-18
1994-05-24
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 51, C08L 306
Patent
active
053149343
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a polymer mixture essentially consisting of starch and a polyolefin, a process to produce a polymer mixture, a film of at least a single ply, consisting essentially of a polymer mixture, along with the use of the process for the purpose of producing single or multi-ply films, as well as the use of the process to produce a foam-type film.
Polymer mixtures comprising starch are known, where starch or other biopolymers are being used, preferably because of their biodegradability, their suitable price and their independence from petroleum products.
The use of biopolymers as technical material has been described in several patents. In EP-011 82 40, EP-28 24 51, EP-29 89 20, EP-30 44 01, EP-32 65 14, GB-22 14 919 and in EP-32 75 05, it is described how natural starch, gelatine or other biopolymers are modified or destructured respectively so that they can be used as technical polymers. This is accomplished by way of extrusion or by kneading of the starch or the biopolymer while utilizing the moisture content normally present in the biopolymer or in the starch, or by adding more water, in which case, however, just this relatively high water content for instance in the process of extrusion of the thus destructured biopolymers is extremely undesired. In contrast thereto, PCT-WO90-05 161 proposes to take the water out of natural starch and by means of additives or plasticizing agents such as glycerine to convert it into a technically useful polymer, that is, a so-called thermoplastically processable starch. The workability as well as the moisture resistance of this starch polymer are of course considerably better than of those starch polymers that are produced in accordance with the above-mentioned processes. However, the mechanical properties and in particular the moisture resistance are still unsatisfactory for many technical uses and in particular for the production of films.
For this reason, numerous patents, such as EP-040 28 26, EP-04047 23, EP-40 47 27, EP-40 27 28 and EP-40 73 50 propose to mix the starch with thermoplastic material such as polyolefins, polyalcohols, ABS copolymers, ethylene acrylic acid copolymers, copolymers of vinylpyrrolidines, copolymers having amino groups etc. respectively, to produce so-called polymer blends. This creates, however, the problem of a poor compatibility between the starch and the further polymers, and results in a poor phase mixing of the individual polymers.
This can for instance be seen in films produced from these materials, where the non-starch proportion of polymer present in this mixture, when used by itself to produce a film, i.e. having a corresponding thinner sheet-thickness, exhibits better tensile strength than the thicker film produced from the total polymer mixture.
According to Patents EP-40 05 31 and EP-40 05 32 it is proposed to treat the starch analogous to W090-05 161 by means of a high boiling plasticizing agent, such as glycerine, urea, or sorbitol, in order to obtain thermoplastically processable starch in order to subsequently mix it with ethylene acrylic acid and/or polyvinyl alcohol copolymers. Films produced from these starch-polymer mixtures do exhibit a greater tensile strength; however, they are still not sufficiently moisture-resistant.
The same applies to the starch-polymer mixtures prepared in accordance with W090-14 388, where polyethylene and ethylene acrylic acid copolymers are added to the glycerine starch.
It is, therefore, the purpose of this invention to propose a polymer mixture essentially consisting of starch, which is particularly well-suited to the production of films and which in moulds and extrudates, as for instance in films, exhibits good mechanical properties, as well as moisture-resistance.
Proposed is a polymer mixture essentially consisting of starch and polyolefin, obtained by mixing essentially moisture-free thermoplastically processable starch with at least one polyolefin and at least one ethylene acrylate maleic acid anhydride terpolymer and/or one vinyl compound carrying anhydride-f
REFERENCES:
patent: 2676929 (1954-04-01), Duddy
patent: 4133784 (1979-01-01), Otey et al.
patent: 5026745 (1991-01-01), Weil
patent: 5087650 (1992-02-01), Willett
patent: 5162392 (1992-10-01), Wool et al.
Michl Paul R.
Szekely Peter
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