The invention relates to a method for producing a polymer. Said method is characterized as follows: a) a mixture (I) containing 6-aminocapronitrile and water is converted into a mixture (II) containing caprolactam, ammonia, water, high boilers and low boilers in the presence of a catalyst; then b) the ammonia is removed from mixture (II) to obtain a mixture (III) containing caprolactam, water, high boilers and low boilers; subsequently c) the water is completely or partially eliminated from mixture (III) to obtain a mixture (IV) containing caprolactam, high boilers and low boilers; and finally d) mixture (IV) is subjected to a polymerization reaction. The invention also relates to a polymer obtained according to said method, to its use in the production of fibres, flat material and moulded bodies that are obtained using a polymer of this type.