1. Use of synthetic resin binders based on an aqueous mixture of different phenolic resins being I) at least one phenol-resol in which at least 1.1 mole of formaldehyde per phenolic hydroxyl of the monohydric phenols has been added and/or condensed to the phenolic body and II) at least oen co-condensate of at least one monohydric phenol and at least oen polyhydric phenol with formaldehyde, with co-condensate contains per mole of monohydric phenol from 1.1 to 1.9 mole of formaldehyde and from 0.1 to 0.2 mole of a polyhydric phenol, the molar ratio of the used quantities of formaldehyde to the sum of the phenols being in the range of from 0.6:1 to 1.5:1, and optionally further additives, components I) and II) being present in the micture in a ratio of at most 95:5 and at least 70:30, for the manufacture of abrasive materials on flexible substrates, but without the use of formaldehyde donors and without application of superatmospheric pressure.
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