Process for the preparation of granules based on expandable thermoplastic polymers and relative product
AssigneeVersalis S.P.A.
InventorsAlessandro Casalini, Riccardo Felisari
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Abstract
A process for the continuous production of granules based on thermoplastic polymers includes at least one expandable agent and, optionally, other polymers or additives, among which inorganic pigments insoluble in the polymeric matrix, wherein a first main stream is prepared, in the molten state, and a second stream in the molten state, which englobes the additives and which is added to the first stream. The mixture is extruded through a die which is cooled by means of water jets from nozzles positioned behind the cutting blades.
Claims17
A process for preparing expandable granules based on thermoplastic polymers through a granulation die, comprising:
- i) bringing a stream of molten vinyl aromatic polymer to a selected temperature, wherein said selected temperature ranges from a critical temperature of an expanding system minus 25′C and a critical temperature of the expanding system plus 25° C.;
- ii) incorporating into a second stream of molten polymeric material, from 0 to 60% by weight, with respect to the weight of a resulting stream of inorganic and organic additives containing, less than 10 percent by weight of particles having a size larger than half of the diameter of holes of the die;
- iii) incorporating an expanding system in a polymeric composition in a molten state (ii) at a selected pressure, wherein said selected pressure is higher than a critical pressure of the expanding system;
- iv) incorporating the polymeric composition (iii) in the stream of vinyl aromatic polymer (i);
- vii) granulating the expandable polymeric composition thus obtained in a cutting chamber of a device for hot granulation of thermoplastic polymers, comprising:
- a) a die comprising a cylindrical body including to series of extrusion holes on an external surface and polymer adduction channels positioned inside the cylindrical body, in correspondence with and connected to the holes;
- b) a set of knives situated in correspondence with the die holes, rigidly connected to a rotating shaft;
- c) a set of nozzles situated behind the set of knives which generates a liquid jet directed against the die;
- d) an inlet from which a stream of gas is fed;
- and in which the stream of gas coming from said inlet (d) prevents flooding of the cutting chamber.
Dependencies are inferred from the claim text.