Abstract: There is disclosed a process for the preparation of expandible particles of styrene-based polymers which are useful for the production of molded bodies, especially large blocks, having a uniform cellular structure, and with a particularly short time of residence in the mold.

Abstract: Expandible particles of styrene particles for producing molded bodies, particularly large blocks having a homogeneous fine-cell structure, and having improved characteristics, are obtained by polymerizing styrene or a mixture of styrene and one or more different monomers copolymerizable with styrene, in the presence of at least one compound of the following general formulae (I) or (II) ##STR1## wherein R.sub.1 and R.sub.4, either like or unlike each other, are an optionally halogen-substituted alkyl radical containing 1 to 30 carbon atoms;R.sub.2 and R.sub.3, like or unlike each other, are an alkyl, cycloalkyl or phenyl radical, optionally halogen-substituted;X is a halogen or an alkyl radical having 1 to 8 carbon atoms;M is an integer from 0 to 4; andN is an integer from 0 to 5.

Abstract: Expandible polystyrene particles useful for making molded bodies, particularly large blocks having a uniform cellular structure and a particularly short residence time in the mold, are prepared by polymerizing styrene in the presence of at least one ether having the general formula (III) or (IV): ##STR1## wherein: R.sub.1 and R.sub.2, which may be the same or different, are alkyl or cycloalkyl radicals and/or phenyl radicals, optionally halogen-substituted;R.sub.5 is a non-halogenated alkyl radical having 4 to 30 carbon atoms or a fully or partially halogenated alkyl radical having 9 to 30 carbon atoms;X is a halogen or an alkyl radical, optionally halogenated, having 1 to 8 carbon atoms;N is an integer from 0 to 4;M is an integer from 0 to 5, andR.sub.3 and R.sub.4, which may be the same or different, are alkyl radicals, optionally halogenated, having 1 to 30 carbon atoms, with the exception that, when R.sub.1 and R.sub.2 are alkyl radicals, X is bromine and n is 2, R.sub.3 and R.sub.

Abstract: Polymers of styrene or copolymers thereof with monomers copolymerizable therewith are obtained in the form of expandable particles by polymerizing the styrene or mixture of monomers comprising styrene in the presence of an elastomeric olefinic copolymer or terpolymer, incorporating an expanding agent during or after the polymerization, ageing the preexpanded particles, and molding the pre-expanded and aged particles in a pressure-resistant mold which is not gas tight to obtain molded articles having very desirable characteristics.

Abstract: Expandible particles of styrene polymers are prepared by a process in which the polymerization of styrene, or of mixtures of styrene and monomers copolymerizable with it, and/or treatment of the expandible particles prior to expansion thereof, are (is) carried out in the presence of dimers or trimers of unsaturated fatty acids or their esters with C.sub.1 -C.sub.18 alcohols.