<p>Petroleum Resins particularly effective for use as tackifiers for hot melt adhesives and in tackifiers for solvent-based pressure sensitive adhesives are prepared by a process</p><p>Wherein (1) a C<Sub>8</Sub>- and/or C<Sub>9</Sub> aromatic unsaturated hydrocarbon-containing feed (optionally containing up to 18 wt.% or C<Sub>4</Sub> or C<Sub>5</Sub> unsaturated aliphatic hydrocarbons( is first polymerised completely and thereafter a C<Sub>s</Sub>-aliphatic unsaturated hydrocarbon-containing feed is added, polymerisation continued and the reactor effluent stripped to obtain the resin. The order of polymerisation may be reversed.</p>
