FIELD: chemistry.
SUBSTANCE: described is a composition of expandable vinyl aromatic polymers for making expanded articles or extruded expanded sheets, which contains: a) a polymeric matrix obtained by polymerising a base comprising 50-100 wt % of one or more vinyl aromatic monomers and 0-50 wt % of at least one copolymerisable monomer; b) 1-10 wt %, with respect to the polymer (a), of an expandable agent included in the polymeric matrix; and thermally non-conducting filler containing: c) 0.05-25 wt %, with respect to the polymer (a), of coke in particle form with an average diametre (d50) (size) of the particles ranging from 0.5 to 100 mcm, having a surface area, measured according to ASTM D-3037-89 (BET), ranging from 5 to 200 m2/g, and d) 0.05-10 wt %, with respect to the polymer (a), of expanded graphite in particle form with an average diametre (d50) (size) of the particles ranging from 1 to 30 mcm, having a surface area, measured according to ASTM D-3037-89 (BET), ranging from 5 to 500 m2/g Also described is an expandable article made from said composition, having density ranging from 5 to 50 g/l and thermal conductivity ranging from 25 to 50 mW/(m-K). Described is an extruded expanded sheet made from said composition, which includes a cellular vinyl aromatic polymer matrix having density ranging from 10 to 200 g/l, an average cell size ranging from 0.01 to 1.00 mm and containing from 0.1 to 35 wt % of thermally non-conducting filler comprising said coke in particle form with average diametre (d50) of the particles ranging from 0.5 to 100 mcm and surface area, measured according to ASTM D-3037-89 (BET), ranging from 5 to 200 m2/g, and said expanded graphite in particle form with average diametre (d50) of the particles ranging from 1 to 30 mcm and surface area, measured according to ASTM D-3037-89 (BET), ranging from 5 to 500 m2/g. Described is a method of producing said composition in form of spheres or granules, which involves aqueous suspension polymerisation. Also described is a method of producing said composition in form of spheres or granules by continuous bulk polymerisation. Described is a method of producing said extruded expanded sheet from vinyl aromatic polymers, involving: a1) mixing the vinyl aromatic polymer in granule form and at least one thermally non-conducting filler, comprising 0.05-25 wt %, with respect to the polymer, of said coke in particle form with an average diametre (size) of the particles ranging from 0.5 to 100 mcm, having a surface area, measured according to ASTM D-3037-89 (BET), ranging from 5 to 200 m2/g, and 0.05-10 wt %, with respect to the polymer, of said expanded graphite in particle form with an average diametre (d50) (size) of the particles ranging from 1 to 30 mcm, having a surface area, measured according to ASTM D-3037-89 (BET), ranging from 5 to 500 m2/g; b1) heating the mixture (a1) to temperature ranging from 180°C to 250°C to obtain a molten polymer which is homogenised; c1) adding at least one expanding agent and, optionally, other additives, for example said self-extinguishing system, to the molten polymer; d1) homogenising the molten polymer containing the expanding agent; e1) uniformly cooling the molten polymer (d1) to temperature not higher than 200°C and not lower than Tg of the obtained polymer composition; f1) extruding the molten polymer through an extrusion head to obtain an expanded polymer sheet.
EFFECT: obtaining a composition with improved thermal insulation properties.
29 cl, 14 ex
