Yeda Research and Develpment & Co. Ltd

Makhteshim Chemical Works Ltd.

Stephen L Daren

David Vofsi

Moshe Levy

Ella Cohen

Meir Asscher

Aurelia Finkels

The invention relates to the stabilization of monobromostyrene of dibromostyrene and of mixtures of these. The stabilization is effected by means of hydroxy-benzene derivatives, where the benzene ring contains at least two substituents, one of these being a hydroxy group. The process is advantageously carried out by heating the styrene material with an excess of the inhibitor, distilling the monomer and adding an additional quantity of the inhibitor. The distilled monomer is preferably dried prior to the addition of the further quantity of inhibitor.

Stabilization of bromostyrenes

The invention relates to an improved process for the production of crystalline tribromostyrene. The process involves removal of hydrogen bromide in a two phase system with the aid of phase transfer catalysts. One of the phases used is an aqueous one containing an alkali metal hydroxide whereas the second comprises .beta.-bromoethyltribromobenzene in an alcohol as solvent.

Production of crystalline tribromostyrene

The present invention relates to the production of ring-halogenated styrene monomers of high purity. These are of value in the production of polymers which possess flame retardance. The process of the invention comprises reacting heterogenously ring halogenated beta-bromoethyl benzene with a strong aqueous alkali base in the presence of a quaternary phase transfer catalyst until substantially all the bromoethyl benzene has undergone reaction, separating the phases, washing and neutralizing the organic phase and recovering the ring-halogenated styrene monomer, which is the desired product.

Process for preparing ring halogenated styrenes

A process for the simultaneous production of bromostyrene or dibromostyrene and of an alkyl bromide, which comprises reacting bromoethyl bromobenzene or bromoethyl dibromobenzene with an alkanol at an elevated temperature. When only these reactants are reacted, the temperature is between 400.degree.C and 550.degree.C; when the reaction is effected in the presence of a source of free radicals, the temperature used can be lower, and temperatures of about 300.degree.C are adequate.

Production of bromostyrene, dibromostyrene and alkyl bromides

A process for the production of mono-, di-, and/or tribromostyrene which comprises reacting .beta.-bromomethyl-mono-, di- and/or tribromobenzene at a temperature between 280.degree.C to 470.degree.C in the presence of a free radical source and either a lower alkanol or water.

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Ness Ziona, Israel

Stephen L Daren