Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1998-01-12
2000-01-04
Szekely, Peter A.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
523128, 524 50, 524 51, 525 5425, 527300, 527301, 527311, C08L 304, C08L 306, C08L 308, C08L 317
Patent
active
060110929
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process according to the preamble of claim 1 for plasticizing starch.
The invention also relates to a melt-processible polymer composition according to the preamble of claim 6. A composition of this kind generally comprises a starch-based component and a thermoplastic polymer component.
Furthermore, the invention concerns a method according to the preamble of claim 25 for preparing a melt-processible polymer composition.
Environmental concerns and green concepts are creating new markets for products based on renewable resources. These trends are seen e.g. in the industrial sectors of packaging, hygiene and glue, for which recyclability, reusability, compostability, biodegradability and nonstressability of the environment are contemporary requirements. There is also an increasing trend to substitute petrochemically derived products with refined biopolymers.
Thermoplastization of natural polymers, in particular starch, is discussed in a large number of patents and patent applications (e.g. GB 2 190 093 A, U.S. Pat. No. 4,673,438, EP 282 451 A3, EP 0 298 920 A3, EP 0 304 401 A2, EP 0 326 517 A1), which disclose opening of the granular structure of starch by melt processing generally in the presence of water and some plastisizer such as glycerol, ethylene glycol and oligomers thereof, and other adjuvants. Even if the products thus obtained are thermoplastic and biodegradable, their water resistance is poor which considerably limits their use. These kinds of thermoplastic starch products tend to absorb water when the humidity of air is high, which changes their mechanical properties. On the other hand, at low moisture contents, the water contained in the product evaporates and the products become more brittle. Attempts have been made to improve the properties (water resistance and mechanical properties) of thermoplastic starches by blending them with synthetic polymers, as disclosed, e.g., in the following applications: EP 0 404 723 A2, EP 0 409 788 A3, EP 0 404 727 A3, EP 0 404 728 A3, EP 0 408 501 A3, EP 0 408 502 A3, EP 0 409 782 A3 and EP 0 409 781 A3, FI 902662, WO 92/19680, FI 921264 and EP 0 519 367 A1. Often the used synthetic polymers are hydrophilic and even if they do improve the mechanical properties the water resistance of the products still remains poor. The above-mentioned patent applications describe improvement of the water resistance of thermoplastic starches by blending them with traditional thermoplastic polymers, polyolefins and polyesters, prepared from the raw materials of petrochemistry. The thus obtained blends and mixtures are hetero phasic and their biodegradability is impaired when the amount of non-degradable components increases.
Starch has been mixed also with biodegradable synthetic polymers in addition to synthetic, nondegradable polymers (e.g. poly(caprolactone), polylactide), as has been described in the following patent applications and articles: WO 92/19680, EP 0 530 987 A1, EP 0 535 994 A1, Koenig, M. F. and Huang, S. J., Biodegradable Polymers/Starch Blends, Composites and Coatings, Polymer Materials Science Engineering 67(1992) s. 290-291. Starch has increased the biodegradability of the mixture, but essentially diminished the mechanical properties of the blends. The blended material has also often been non-homogeneous, consisting of dispersed or lamellar structures.
Various coupling reactions have been used to improve the blending of the starch component and the synthetic polymer. The patent application DE 41 16 404 A1concerns a mixture of a thermoplastic starch with polyolefines and an ethylene-acrylatemaleic anhydride copolymer. In the mixture, the copolymer is coupled by ester bonds to the thermoplastic starch and contributes to the compatibilization of the blend. The content of non-biodegradable polyethylene in the blend was 10-35% and the content of copolymer was 10-40%.
According to the patent application WO 93/23456, reactive blending of natural polymers and synthetic polymers has resulted in compositions in which two polymers ha
REFERENCES:
patent: 5412005 (1995-05-01), Bastioli et al.
patent: 5756576 (1998-05-01), Bruls et al.
patent: 5780568 (1998-07-01), Vuorenpaa et al.
patent: 5847027 (1998-12-01), Marten et al.
Heikkila Elina
Malin Minna
Peltonen Soili
Seppala Jukka
Vuorenpaa Jani
Szekely Peter A.
Valtion teknillinen tutkimuskeskus
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