the polymers according to the invention preferably have a molecular weight m w of from 6 000 to 500 000 particularly preferably from 8 000 to 200 000 and in particular from 10 000 to 150 000 the polymers according to the invention can be obtained by known methods for example by subsequent protection of hydroxyl containing polymers comprising structural repeating units of the formulae i and ii with vinyl ether compounds or isopropenyl ether compounds for example with methyl vinyl ether ethyl vinyl ether n butyl vinyl ether tert butyl vinyl ether cyclohexyl vinyl ether isopropyl vinyl ether 2 methoxypropene and the like protection is preferably carried out in the presence of a suitable usually acidic catalyst examples of such suitable catalysts are acidic ion exchange resins acids for example sulfonic acid or salts thereof for example pyridinium tosylate the hydroxyl containing polymers comprising structural repeating units of the formulae i and ii can be prepared by known methods for example by copolymerization of the corresponding hydroxystyrene and vinylcyclohexanol derivatives with or without further commonomers such as for example acrylic acid methacrylic acid alkyl methacrylate alkyl acrylate styrene fumaronitrile maleic anhydride or maleimide and derivatives thereof a preferred process for the preparation of hydroxyl containing polymers comprising structural repeating units of the formulae i and ii is the metal catalyzed partial hydrogenation described in jp a 01 103604 of hydroxyl containing homopolymers for example poly 4 hydroxystyrene poly 4 hydroxy u03b1 methylstyrene and poly 3 hydroxystyrene or copolymers formed from phenolic vinyl.