Process for preparation of a dendritic polyol

A process for synthesis of a dendritic polymeric polyalcohol having reactive or protected terminal hydroxyl groups, which polymeric polyalcohol has n dendritic branches emanating from a monomeric or polymeric initiator molecule having n reactive groups (A), whereby each branch comprises g branching generations each generation comprising at least one polymeric or monomeric branching chain extender having three functional groups of which at least two are reactive hydroxyl groups (B) and one is a group (C) reactive to said reactive group (A) and/or said hydroxyl groups (B), and optionally at least one spacing generation, comprising at least one spacing chain extender having two functional groups of which one is a protected hydroxyl group (B″) and one is a group (D) reactive to a hydroxyl group, and whereby n and g are integers and at least 1, said process comprising the steps of

• (i) acetal protection of the two hydroxyl groups (B) of employed monomeric or polymeric branching chain extender, said acetal protection being obtained by reaction between said two hydroxyl groups (B) and an acetalforming carbonyl compound;
• (ii) addition to the initiator molecule of a first branching generation by reaction between said reactive group (A) and said reactive group (C) at a molar ratio reactive groups (A) to reactive groups (C) of 1 to at least 1, whereby a polymeric polyalcohol having acetal protected hydroxyl groups (B′) and n dendritic branches comprising one generation is yielded, which acetal protected hydroxyl groups (B′) optionally are deprotected by means of acetal decomposition, whereby a polymeric polyalcohol having reactive hydroxyl groups (B) is yielded;
• (iii) addition of further branching generations, in g-1 repeated steps, by reaction between reactive hydroxyl groups (B), obtained after deprotection by means of acetal decomposition, and reactive group (C) at a molar ratio hydroxyl groups (B) to reactive groups (C) of 1 to at least 1, whereby a polymeric polyalcohol having acetal protected hydroxyl groups (B′) and n dendritic branches comprising two or more generations is yielded, which acetal protected hydroxyl groups (B′) optionally is deprotected by means of acetal decomposition, whereby a polymeric polyalcohol having reactive hydroxyl groups (B) is yielded;
• and wherein step (ii) and/or each repetition of Step (iii) optionally and individually is followed by
• a) a partial protection of available reactive hydroxyl groups (B), whereby a polymeric polyalcohol having at least one reactive hydroxyl group (B) for utilization in Step (iii) or a repeated Step (iii) is yielded;
• and/or
• b) addition of said optional spacing chain extender yielding, after deprotection of said protected hydroxyl group (B″), a polymeric polyalcohol having reactive hydroxyl groups (B) for utilization in Step (iii) or a repeated Step (iii) and n dendritic branches comprising one or more branching generations and at least one spacing generation being at least a partial generation.