FIELD: organic syntheses. SUBSTANCE: aqueous mobile medium is first dehydrated and heated to form essentially anhydrous melt capable to be agitated. The aqueous mobile medium contains dissolved substance selected from the group including dimethyloldimethylhydantoin, hydantoin reagent, formaldehyde source, or any combination of indicated components; and optionally a catalyst. Molten system is further prepared by adding to apt-to-agitation melt a reactive mixture containing the same or another hydantoin reagent, essentially anhydrous the same or another formaldehyde source, or their combination; and optionally the same or another catalyst. Finally, molten system contains at least one hydantoin reagent and at least one dehydrated formaldehyde source or essentially anhydrous formaldehyde source. At least one hydantoin reagent in molten system is allowed to react with at least one dehydrated or essentially anhydrous formaldehyde source, which reaction is accompanied by withdrawal of water and results in formation of anhydrous molten methylolhydantoin which is further solidified. Alternative version of invention consists in preparing solid anhydrous methylolhydantoin by reaction of reaction mixture containing the same or another hydantoin reagent, essentially anhydrous the same or another formaldehyde source, or their combination optionally in presence of the same or another catalyst in the above-indicated apt-to-agitation medium containing at least one hydantoin reagent and at least one formaldehyde source or essentially anhydrous formaldehyde reagent. Reaction is carried out at heating to a temperature at least equal to melting temperature of methylolhydantoin, while removing essentially all water, to form molten methylolhydantoin. The two methods may be performed both in periodical and semicontinuous modes. EFFECT: enhanced efficiency of preparation procedure. 23 cl
