PREPARATION OF NOVOLAK MOULDING COMPOUNDS FOR THE MANUFACTURING OF COMMUTATORS

摘要

Described are asbestos-free moulding compounds based on phenol-formaldehyde resins, also known as phenolic resins, which are prepared in a turbo mixer with the addition of water. The moulding compounds include up to 30 % by wt. of a novolak resin plus short glass fibres and long glass fibres, the total glass-fibre content being about 30 % by wt. The glass fibres are preferably mixed in the ratio, by weight, of short fibres to long fibres of 2:1. The mineral fillers preferred for the moulding compounds are chalk and clays, together making up about 30 % by wt. Other components are cross-linking agents, mould-release agents, accelerators and, optionally, colorants, in most cases in quantities less than 3 % by wt. The moulding compounds are obtained as granular products with a low dust content. They can be plasticized and further processed using automatic production machinery. The moulding compounds thus obtained have properties which make them suitable for use in the manufacture of commutators for electric motors.