Polyisobutene and polyisobutene derivatives for use in lubricant compositions

A process for preparing a polyisobutenyl derivative which comprises the steps of:

• (I) polymerizing isobutene in the presence of an initiator system comprising
• a) a Lewis acid selected from covalent metal chlorides and semimetal chlorides,
• b) and at least one compound II having at least one functional group FG which forms a carbocation or a cationic complex under polymerization conditions and is selected from halogen, acyloxy and alkoxy which are bonded to a secondary or tertiary aliphatic carbon atom, or to an allylic carbon atom or to a benzylic carbon atom,
• in a solvent which is inert toward the Lewis acid at a molar ratio of Lewis acid to compound II in the range from 10:1 to 1:100 to obtain a polyisobutene having an olefinic end group content of at least 80 mol % whose molecular weight distribution has a maximum MP in the range from 500 to 1,000 and a polydispersity MW/MN below 1.4, and
• (II) reacting the polyisobutene obtained in step (I) successively with maleic acid or maleic anhydride and then with a compound I which has at least one primary or secondary amine group and/or OH group.