Process and apparatus for the production of expanded polyester, in particular pet
AssigneeB.C. Foam S.r.l.
InventorRenato Crana
Life of this patent
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Abstract
A process for the production of expanded polyester, in particular PET, is performed by extrusion of polyester starting material have an intrinsic vircosity of at least 0.8 dl/g and an added expanded agent. To this end a twin screw extruder (14) is utilized provided with two interpenetrating screws (26) having a ratio between their axial separation and diameter lying between 0.6 and 0.8 and co-rotating at a speed of between 15 and 40 rpm. Preferably the ratio between the axial separation and diameter of the screws (26) lies between 0.69 and 0.78 and the ratio between the length and diameter of the screws (26) lies between 20 and 26.
Claims16
A process for production of expanded polyester by means of extrusion from a twin screw extruder (14) of a polyester starting material having an intrinsic viscosity of at least 0.8 dl/g and an added expanding agent, the said process being characterised in that said twin screw extruder (14) is provided with two inter-penetrating screws (26) having a ratio between axial separation and diameter lying between 0.6 and 0.8 and co-rotating at a speed lying between 15 and 40 rpm, wherein that the length-to-diameter ratio of the screws (26) lies between 20 and 26.
An apparatus for the production of expanded polyester comprising extrusion means, said apparatus being characterised in that said extrusion means consists of a single twin extruder provided with two interpenetrating screws having a ratio between axial separation and diameter lying between 0.6 and 0.8 and co-rotating at a speed lying between 15 and 40 rpm, said extrusion means including a nozzle having two facing lips of rectilinear shape in a direction transverse to the extruding direction so as to define a rectangular extrusion orifice which causes the formation of a sheet extruded product, a calibration device is located downstream of the nozzle through which the extruded sheet product is made to pass allowing its thickness to be regulated, said calibration device comprising a pair of belts comprised of glass wool clad in fluorinated polymer rotating in closed loops and having respective facing sides defining a space of adjustable height through which the sheet product passes.
Dependencies are inferred from the claim text.