Basf Aktiengesellschaft

Werner Georg Metzger

Franz Brandstetter

Guenther Schweier

Wolfgang Gruber

Klaus Pfleger

Peter Hennenberger

Klaus Boettcher

Paulus Schmaus

A process for the distillation of vinylaromatic monomers in the presence of 4-tert-butylcatechol (TBC) and oxygen, wherein no aromatic nitro or amino compound is present in any effective amount. The process is particularly suitable for destabilizing and purifying styrene which has been stabilized with 4-tert-butylcatechol (TBC) for transportation.

Distillation of styrene

Copolymers of ethylene containing not more than 4 moles, based on 100 moles of ethylene, of copolymerized C.sub.3 -C.sub.6 -alkenecarboxylic acids are prepared in a continuously operated tubular polymerization system under high pressures and temperatures in the presence of a polymerization initiator by a process in which a mixture of ethylene, the alkenecarboxylic acid, if required a further monomer which is copolymerizable with ethylene, an initiator and, if required, a regulator is fed into the polymerization system at its entrance and at the same time at a second point downstream of the entrance, along the polymerization system, where the reaction temperature has exceeded a maximum, the amount of alkenecarboxylic acid at the entrance of the polymerization system being not more than 0.3, preferably less than 0.28, mole, based on 100 moles of ethylene, and the remainder being metered in at the second feed point.

Preparation of copolymers of ethylene with carboxyl-containing

Propylene/ethylene block copolymers are prepared by a process in which, in an agitated fixed bed comprising small polymer particles and in each case in the presence of hydrogen, first (I) propylene is homopolymerized from the gas phase, in a first polymerization zone, by feeding in a Ziegler-Natta catalyst, and then (II) the product obtained in the first polymerization zone is fed into a second polymerization zone, where a mixture of propylene and ethylene is polymerized with the propylene homopolymer present in the product from the first polymerization zone. The process has the following features: (a) in the first polymerization zone, polymerization is carried out at a particular total pressure and at a particular temperature, with the proviso that the ratio of the partial pressure of propylene to that of hydrogen (P/H-I) has a specific value, (b) in the second polymerization zone, polymerization is carried out at a particular total pressure and at a particular temperature, with the provisos that (i) the ratio of the partial pressure of propylene to that of ethylene and (ii) the ratio of the partial pressure of propylene to that of hydrogen (P/H-II) have specific values, (c) the total pressure in the first polymerization zone is kept substantially higher than that in the second polymerization zone, (d) the temperature in the second polymerization zone is chosen to be substantially lower than that in the first polymerization zone, and (e) the ratio of P/H-I to P/H-II has a specific value. Polymers having high impact strength and good morphological properties are obtained.

Preparation of propylene/ethylene block copolymers

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Hessheim, Germany

Werner Georg Metzger