Patent ID: 7371397

Claim:
A composition having microbiocidal activity, which composition comprises water to which has been added a microbiocidally effective quantity of at least one 1,3-dibromo-5,5-dialkylhydantoin selected from the group consisting of: (a) 1,3-dibromo-5-isobutyl-5-methylhydantoin, (b) 1,3-dibromo-5-n-propyl-5-methylhydantoin, (c) 1,3-dibromo-5-ethyl-5-methylhydantoin, and (d) a mixture of two or more 1,3-dibromo-5-5-dialkylhydantoins in which one of the alkyl groups in the 5-position is a methyl group and in which the other alkyl group in the 5-position has in the range of 1 to 4 carbon atoms, (i) the molar quantity of said at least one 1,3-dibromo-5,5-dialkylhydantoin added being less than the molar quantity of N,N′-bromochloro-5,5-dimethylhydantoin required to effect the same degree of microbiocidal activity in said water, (ii) the quantity of said at least one 1,3-dibromo-5,5-dialkylhydantoin added releasing an amount of “free chlorine” that is greater than the amount of “free chlorine” that would be released in said water by an equimolar quantity of N,N′-bromochloro-5,5-dimethylhydantoin, and (iii) the amount of “free chlorine” released by the quantity of said at least one 1,3-dibromo-5,5-dialkylhydantoin added being greater than the amount of “free chlorine” that could be predicted to be released by that quantity of said at least one 1,3-dibromo-5,5-dialkylhydantoin on the basis of the amount of “free chlorine” that would be released in said water by an equimolar quantity of N,N′-bromochloro-5,5-dimethylhydantoin.