Thermoplastic starch
Described is a method for producing a thermoplastic starch, wherein a mixture is extruded comprising starch and a polyol, preferably selected from the group comprising polyethylene glycol, monosaccharides, sugar alcohols and mixtures thereof, in a quantity of 0 to 9.9 wt. % of the mixture, and an epoxide, selected from the group comprising epoxidised vegetable oils, and mixtures thereof, in a quantity of 0.1 to 6 wt. % of the mixture, the mixture further containing an acid, preferably a carboxylic acid selected from the group consisting of citric acid, malic acid or tartaric acid, in a quantity of 0.1 to 1 wt. % of the mixture, and being devoid of polyester urethane. The invention also describes a thermoplastic starch produced in this way, a compound produced with the aid of the thermoplastic starch, and a film produced from such a compound or an injection-moulded item produced from such a compound.
1 . A method for producing thermoplastic starch, comprising extruding a mixture comprising starch and a polyol in a quantity of from 0 to 9.9 wt. % of the mixture, and an epoxidised plant oil in a quantity of from 0.1 to 6 wt. % of the mixture, wherein the mixture also contains an acid in a quantity of from 0.1 to 1 wt. % of the mixture, and is free from polyester urethane, wherein the thermoplastic starch has a bulk density of 70 to 90 g/100 ml.
2 . The method of claim 1 , wherein the mixture contains a polyol selected from the group consisting of sorbitol, erythritol, xylitol, mannitol and mixtures thereof, in a quantity of up to 7 wt. %.
3 . The method of claim 1 , wherein the mixture contains sorbitol or erythritol in a quantity of up to 6 wt. %.
4 . The method of claim 1 , wherein the acid is a carboxylic acid selected from the group consisting of citric acid, malic acid and tartaric acid.
5 . The method of claim 1 , wherein the mixture comprises an epoxidized plant oil selected from the group consisting of soybean oil, linseed oil, sunflower oil, rapeseed oil and mixtures thereof in a quantity of from 1 to 4.5 wt. % of the mixture.
6 . The method of claim 1 , wherein the mixture contains epoxide to polyol in a ratio of 1:1 to 1:4.
7 . The method of claim 6 , wherein the mixture contains epoxide to polyol in a ratio of 1:1 to 1:3.
8 . The method of claim 1 , wherein the mixture additionally contains lactic acid in a quantity of 2 to 9 wt. % of the mixture.
9 . The method of claim 8 , wherein the mixture contains lactic acid in a quantity of 4 to 7 wt. % of the mixture.
10 . The method of claim 1 , wherein the mixture is extruded at a temperature of 100-175° C.
11 . A compound containing a thermoplastic starch obtainable by a method for producing thermoplastic starch, comprising extruding a mixture comprising starch and a polyol in a quantity of from 0 to 9.9 wt. % of the mixture and an epoxidised plant oil in a quantity of from 0.1 to 6 wt. % of the mixture, wherein the mixture also contains an acid in a quantity of from 0.1 to 1 wt. % of the mixture and is free from polyester urethane, wherein the thermoplastic starch has a bulk density of 70 to 90 g/100 ml.
12 . A method for producing a compound according to claim 11 , wherein the mixture is extruded with at least one thermoplastic polymer at a temperature of 100-175° C.
13 . A film produced by blown or flat film extrusion according to a compound of claim 11 .
14 . An injection moulded article produced by injection moulding a compound according to claim 11 .
15 . The compound of claim 11 , wherein the mixture contains a polyol selected from the group consisting of sorbitol, erythritol, xylitol, mannitol and mixtures thereof, in a quantity of up to 7 wt. %.
16 . The compound of claim 11 , wherein the mixture contains sorbitol or erythritol in a quantity of up to 6 wt. %.
17 . The compound of claim 11 , wherein the acid is a carboxylic acid selected from the group consisting of citric acid, malic acid and tartaric acid.
18 . The compound of claim 11 , wherein the mixture comprises an epoxidized plant oil selected from the group consisting of soybean oil, linseed oil, sunflower oil, rapeseed oil and mixtures thereof in a quantity of from 1 to 4.5 wt. % of the mixture.
19 . The compound of claim 11 , wherein the mixture contains epoxide to polyol in a ratio of 1:1 to 1:4.
20 . The compound of claim 19 , wherein the mixture contains epoxide to polyol in a ratio of 1:1 to 1:3.
21 . The compound of claim 11 , wherein the mixture additionally contains lactic acid in a quantity of 2 to 9 wt. % of the mixture.
22 . The compound of claim 21 , wherein the mixture contains lactic acid in a quantity of 4 to 7 wt. % of the mixture.
23 . The compound of claim 11 , wherein the mixture is extruded at a temperature of 100 to 175° C.