Feinzellige Polyolefinschaumstoffe, deren Herstellverfahren und Verwendung
Fine-celled polyolefin foam with high heat distortion temperature and stiffness and a foam density of 10-600 kg/m consists of polypropylene (PP) and polyethylene (PE). It is made from mixtures of 10-90, preferably 60-80 wt.% PP and 90-10, preferably 40-20 wt.% PE in 2 reactive process stages (1, 2)...
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Zusammenfassung: | Fine-celled polyolefin foam with high heat distortion temperature and stiffness and a foam density of 10-600 kg/m consists of polypropylene (PP) and polyethylene (PE). It is made from mixtures of 10-90, preferably 60-80 wt.% PP and 90-10, preferably 40-20 wt.% PE in 2 reactive process stages (1, 2) and a foaming stage (3), as follows. (1) The PP-PE mixture is partly reacted with 0.05-2 wt.% bifunctional ethylenically unsaturated monomers (I) and/or 0.5-1 wt.% hydrolysable, ethylenically unsaturated organo-silane compounds (II) in the presence of 0.01-0.85 wt.% thermal free radical initiator (III), so that 5-35 wt.% of the (I) used and 10-40 wt.% of the (III) used are unreacted at the end of this stage. Reaction is carried out (1.a) with a powder mixture in the solid phase at 55-105 degrees C in a continuous screw mixer, using (III) based on acyl peroxides (IIIA), alkyl peroxides (IIIB), hydroperoxides (IIIC) and/or peresters (IIID) with a half life of 0.2-5 minutes at the reaction temperature; or (1.b) in the solid/melt transition phase at 105-190 degrees C in a twin screw extruder, using (III) based on (IIIA), (IIIB), (IIIC), peroxycarbonates, (IIID), ketone peroxides, peroxyketals and/or azo compounds with a half life of 0.2-2 minutes at the reaction temperature. (2) The unreacted components in the mixture are coupled at 195-270 degrees C in a twin screw extruder, with addition of 0.3-8 wt.% blowing agent and, if necessary, 0.01-0.35 wt.% peroxide with respect to the polyolefins. (3) The mixture is foamed by extrusion and hauled off as film, tube or profile or as a strand that is immediately cut into particles. Before and/or during stage (1) and/or (2), 0.01-1 wt.% nucleating agent, 0.1-1 wt.% antistatic, 0.2-3 wt.% pigment, 5-40 wt.% filler and/or reinforcement, 2-20 wt.% flame retardant, 0.1-5 wt.% silanol condensation catalyst and/or 0.01-5 wt.% processing aid, all with respect to PP-PE mixture, may be added. Also claimed is the production of the foam in this way. |
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