Composition comprising thermoplastic starch and aliphatic polyester

Abstract

The invention relates to a thermoplastic composition comprising at least one polyester (A) which is an aliphatic polyester; at least one starch (B); at least one organic plasticiser (C) for starch; and at lest one monoester compound (D) of fatty monoacid comprising at least 12 carbon atoms and glycerol. The composition is characterised in that the amount by weight of compound (D) varies between 0.05 and 1.7 parts per 100 parts of the dry weight of the different constituents (A), (B) and (C).

Description

FIELD OF THE INVENTION[0001]A subject of the invention is a thermoplastic composition comprising thermoplastic starch, an aliphatic polyester and at least one monoester of a fatty acid and of glycerol. Another subject of the invention is a granule of the composition, a manufacturing process for manufacturing said composition and a process for manufacturing a film by film blowing using the composition.TECHNICAL BACKGROUND OF THE INVENTION[0002]Because of their numerous advantages, plastics have become inescapable in the mass manufacture of objects. Indeed, because of their thermoplastic nature, it is possible to manufacture objects of any type from these polymers, at a high rate. To manufacture these objects, small pieces of these thermoplastic polymers are used, that are melted by providing heat and mechanical stresses in forming machines. For example, it is possible to manufacture film by introducing these pieces into a blown film extruder or a flat die extruder (cast extrusion) or...

AI Technical Summary

Benefits of technology

The invention relates to a thermoplastic composition that includes a mixture of polyester, starch, a plasticizer for starch, and a specific compound called a monoester. When this composition is in blown tube form, it has a less tacky feel than compositions without this monoester. Additionally, the patent text describes the use of a monoester in other thermoplastic compositions based on starch and a compatible thermoplastic polymer. The monoester improves water resistance and ageing resistance. Other documents describe the use of other compounds and compositions with improved properties, but none describe the use of the specific monoester described in this patent.

Problems solved by technology

Because of their numerous advantages, plastics have become inescapable in the mass manufacture of objects.

However, these plastics are still today not recycled a great deal.

Thus, this causes environmental problems since they are generally incinerated and this incineration can cause toxic gases to be given off.

However, one of the problems of these polyesters is that they are relatively expensive.

However, these thermoplastic starches have insufficient properties, in particular in terms of water resistance.

Furthermore, transforming starch into thermoplastic starch is not easy since it requires the use of substantial constraints and / or temperatures during the thermomechanical mixing, which has a tendency to degrade the thermoplastic starch thus formed.

The applicant has been able to note that one of the problems of these compositions based on thermoplastic starch and aliphatic polyester is that they can, at high rate, be tacky during the forming of the film by extrusion blow molding.

This creates problems of separation of the blown tube during or after manufacture, once this blown tube is in the form of a spool.

This problem is specific to compositions comprising aliphatic polyester since, contrary to other polyesters such as semi-aliphatic polyesters, they have a slow crystallization speed.

The blown tube remains in the molten state and has a tendency to stick during the extrusion blow molding process.

These problems are worsened when the amount of thermoplastic starch in the composition and / or the amount of plasticizer in the thermoplastic starch are high.