| 摘要 |
<p>A biodegradable heterophase polymer composition comprises thermoplastic starch dispersed in a continuous phase of a thermoplastic polymer incompatible with starch. The composition contains an interfacial agent which is a polyol ester (I), a water soluble nonionic surfactant (II) or an isocyanate-derived polymer (III). (I) has a hydrophilic-lipophilic balance (HLB) above 8 and is an ester of a polyol with a mono- or di-carboxylic acid of dissociation constant pK below 4.5, or has a HLB of 5.5-8 and is an ester of a polyol with a mono- or d-carboxylic acid having less than 12 C atoms and pK above 4.5, or has a HLB below 5.5 and is used at 10-40 wt.% based on starch and is an ester of a polyol with a 12-22C fatty acid. (II) when added to the starch thermoplastic polymer composition suffers no more than 30% migration after 100 hours immersion in water at ambient temperature. (III) is the reaction product of an aliphatic or aromatic diisocyanate with a polymer containing terminal groups reactive with isocyanate. An alternative composition comprises starch dispersed in a thermoplastic polymer incompatible with starch which is a polyester (IV) comprising repeat units derived from a 2+C hydroxyacid and/or an aliphatic dicarboxylic acid. The ratio (R) between the viscosimetric average M.Wt. of (IV) and its melt index measured at 180[deg]C under a 5kg load is above 25000. An alternative composition comprises starch dispersed in a thermoplastic polymer incompatible with starch which is an aliphatic-aromatic copolyester (V), a polyesteramide (VI), a polyesterether, a polyesteretheramide, a polyesterurethane or a polyester urea. These compositions are obtained by extrusion. The water content of the composition during mixing is 1-5 wt.% as measured at the exit of the extruder.</p> |
