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Patent US8410199
Issued 2013-04-02
Biodegradable Polymeric Compositions Comprising Starch And A Thermoplastic Polymer
The present invention provides polymeric compositions containing thermoplastic starch and a thermoplastic polymer incompatible with starch, in which the starch constitutes the dispersed phase and the thermoplastic polymer constitutes the continuous phase, selected: A) from compositions comprising an agent with an interfacial effect selected from esters of polyols with mono- or polycarboxylic acids with dissociation constants within certain limits, the esters having specific values of the hydrophilic/lipophilic balance index HLB or being amongst the non-ionic surfactants which are soluble in water but cannot significantly be extracted by water from the compositions which contain them; B) from compositions wherein the thermoplastic polymer is an aliphatic or aliphatic-aromatic copolyester wherein the ratio (R) between the average viscometric molecular weight and the melt index is greater than 25,000 and C) from compositions wherein the thermoplastic polymer is selected from aliphatic-aromatic copolyesters, polyester-amides, polyester-esters, polyester-ether-amides, polyester-urethanes and polyester-ureas and wherein the compositions are obtained by extrusion of the component maintaining a water content during the mixing stage from 1 to 5% by weight.
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- 1. A biodegradable heterophase polymeric composition having good resistance to ageing and to low humidity conditions, the composition comprising a thermoplastic starch and a thermoplastic polymer incompatible with starch, wherein the starch is in the form of particles having an average numerical dimension of less than 1 μm and is in a dispersed phase and the thermoplastic polymer is in a continuous phase, wherein
the thermoplastic polymer incompatible with starch is a polyester comprising repeating units deriving from hydroxyacids with more than 2 carbon atoms and/or from aliphatic dicarboxylic acids, and in which the ratio R between the average viscosimetric molecular weight and the melt index, measured at 180° C. under a 5 kg load, is greater than 25,000.
- 11. A biodegradable heterophase polymeric composition having good resistance to ageing and to low humidity conditions, the composition comprising a thermoplastic starch and a thermoplastic polymer incompatible with starch, wherein the starch is in the form of particles having an average numerical dimension of less than 1 μm and is in a dispersed phase and the thermoplastic polymer is in a continuous phase, wherein the thermoplastic polymer is a copolyester selected from the group consisting of aliphatic-aromatic copolyesters comprising from 30 to 70% by moles of aliphatic structure and wherein the aromatic structure derives from terephthalic acid and/or isophthalic acid, polyester-amides deriving from 30-70% by weight from an aliphatic amide, polyester-ethers, polyester- ether-amides, polyesterurethanes, and polyester-ureas,
wherein the composition is an extruded composition having a water content of from 1 to 5% by weight measured at the exit of the extruder, prior to any conditioning, and wherein the decrease of the molecular weight of the thermoplastic copolyester is negligible.
