Process for preparing branched organopolysiloxanes

A process for preparing branched organopolysiloxanes O that have a glass transition temperature (Tg) of 5° C. to 100° C. and contain units of the general formula (I):

• RaSi(OR1)bO(4-a-b)/2 Formula (I)
• wherein
• R is a hydrolysis-stable C1-C18 hydrocarbon radical that is unsubstituted or substituted by heteroatoms,
• R1 is a hydrogen radical or C1-C4 hydrocarbon radical and
• a and b are 0, 1, 2 or 3, with the proviso that
• a+b≤3 and
• a in at least 70 mol % of all units of the general formula (I) has the value of 1,
• a averaged over all units of the general formula (I) has an average value of 0.7 to 1.3,
• b averaged over all units of the general formula (I) has an average value of 0.10 to 1.0,
• and at least 70 mol % of all radicals R1 are a hydrogen radical, methyl radical or ethyl radical,
• in which silanes of the general formula (II)
• RnSi(OR1)4-n (II),
• where
• n can have the values of 0, 1, 2 or 3,
• n in at least 70 mol % of the silanes of the general formula (II) has the value of 1,
• R and R1 have the definitions given for the general formula (I),
• in at most 20 mol % of the silanes of the general formula (II) all radicals R are a C1-C2 hydrocarbon radical and R1 a methyl radical,
• and per 100 mol of silanes of the general formula (II) there is at most 10 mol of further alkoxy- and/or hydroxy-functional organopolysiloxanes or alkoxy- and/or hydroxy-functional silanes,
• are reacted with water, catalytic amounts of an acidic catalyst K,
• and optionally alcohol A,
• with the proviso that no other solvent apart from alcohol A is used throughout the entire process,
• where alcohol A is selected from methanol, ethanol or a mixture of methanol and ethanol, where up to 50 parts by weight of a further alkanol may be present in each case based on 100 parts by weight of methanol and ethanol
• and that prior to the work-up of the organopolysiloxane solution the acidic catalyst is deactivated to a residual hydrochloric acid content, titratable with ethanolic potassium hydroxide solution against tetrabromophenolphthalein ethyl ester, of 100 to 0 ppm, where the organopolysiloxanes O have average molecular weights Mw in the range of 500 to 20,000 g/mol (weight average) with a polydispersity (PD) of at most 20.