Montedison S.p.a.

Montedison Fibre S.p.a.

Guido Bertazzoni

Antonio Alvares

Gianfranco Biglione

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.

Process for preparing expandible particles of styrene-based polymers

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;

Expandible particles of styrene polymers and process for preparing same

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;

Process for preparing expandible poly-styrene particles useful for

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.

Process for producing particles of expandable styrene polymers and

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.

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Campitello di Marcaria, Italy

Guido Bertazzoni