Abstract: A biocide composition is provided as an addition to substances that can be infected by harmful microorganisms, in which the biocide composition has at least two active biocidal substances, one of which is 2-methylisothiazolin-3-one. The composition is characterized in that it contains 1,2-benzisothiazolin-3-one, compositions containing 5-chloro-2-methylisothiazolin-3-one being excluded. In comparison with its individual components, the composition of the invention has a synergistic biocidal activity.

Abstract: There is provided a method for the production of improved biocidal compositions which comprise at least one 3-isothiazolinone of the general formula ##STR1## Y is a hydrogen atom or an unsubstituted alkyl radical having 1 to 18 carbon atoms, a cylo alkyl radical having 5 to 8 carbon atoms, an aralkyl radical having 7 to 11 carbon atoms or an aryl radical having 6 to 10 carbon atoms and R and R' are in each case a hydrogen atom or halogen atom or a C.sub.1 to C.sub.4 -alkyl radical, or, when taken together, R and R' contain an alkylene group to form a hydrocarbon ring, the 3-isothiazolinone being produced in known manner and then stabilized by the addition of a nitrate. The method is characterized by the fact that the mixture obtained upon the production of the 3-isothiazolinone is subjected to an additional stabilization after the addition of the nitrate by storing it at a pH of 0.2 to 2.0 and a temperature of at most 40.degree. C.

Abstract: There is indicated a method for the production of qualitatively improved biocidal or biostatic compositions which comprise water and/or a polar organic solvent and contain at least one 3-isothiazolinone of the general formula ##STR1## in which Y, R and R' have the meanings indicated, the 3-isothiazolinone being produced in known manner and then stabilized by the addition of a nitrate. The method is characterized by the fact that the mixture obtained upon the production of the 3-isothiazolinone is subjected to an additional stabilization after the addition of the nitrate in the manner that it is stored at a pH of 0.2 to 1.5 and a temperature of at most 40.degree. C. for a period of at least 48 hours and then again brought to a higher pH. The compositions produced in this manner have an improved appearance and increased storage stability.

Abstract: A method for preserving a polymer emulsion comprising intimately admixing with the polymer emulsion a polymer emulsion preserving amount of a stabilized composition comprising in intimate admixture an aqueous solution of one or more 3-isothiazolones and an effective stabilizing amount of a hydroperoxide-free organic and/or manganese-free inorganic oxidizing agent, and, optionally, a stabilizer for the oxidizing agent.

Abstract: Stabilized aqueous solutions of one or more 3-isothiazolones of the general Formula I or II ##STR1## are given, characterized in that they contain at least 0.1 wt. % taken on the total solution of a 3-isothiazolone, of a hydroperoxide-free organic and/or manganese-free inorganic oxidizing agent, as well as optionally a stabilizer for the oxidizing agent.

Abstract: Stabilized aqueous solutions of one or more 3-isothiazolones of the general Formula I or II ##STR1## are given, characterized in that they contain at least 0.1 wt. % taken on the total solution of a 3-isothiazolone, of a hydroperoxide-free organic and/or manganese-free inorganic oxidizing agent, as well as optionally a stabilizer for the oxidizing agent.