Sodium hypochlorite and chlorine gas are commonly used as circulating water slimicides. Upon reaction with organic system components, these materials can produce adsorbable organic halogen (AOX) by-products which are environmentally undesirable. In addition, the bactericidal efficacy of these materials is substantially reduced in high organic component systems because of rapid reactions of free halogen with organic materials. In high organic component recirculating waters such as pulp and paper processing and oil field applications, these deleterious effects are pronounced.
U.S. Pat. No. 3,328,294 teaches reaction of sulfamic acid with hypochlorite solutions, forming N-chlorosulfamate solutions which are used to disinfect paper-processing streams. The stated advantage is reduced reactions with paper-processing components. Enhanced biocidal efficacy is demonstrated over a non-oxidizing biocide containing N-methyldithiocarbamate and cyanodithioimidocarbonate with bacterial concentrations of 10.sup.3 cfu/ml being achieved at residual chlorine concentrations of 1.6 ppm as Cl.sub.2. Unfortunately, as a practical matter, N-chlorosulfamic acid provides reduced biocidal efficacy relative to hypochlorite, thus limiting its usefulness as a papermaking slimicide.
U.S. Pat. No. 3,749,672 teaches the use of N-hydrogen materials to formulate bleaching solutions with enhanced stability to spontaneous decomposition. The claimed formulations contain (A) a hypohalite, (B) an N-hydrogen compound, (C) N-halo relation product of (A) with (B) at concentrations of 1.0.times.10.sup.-3 to 1.0 molar, and (D) a buffer to maintain pH 4-11. The preferred compositions are liquid formulations containing a phosphate buffer, sulfamic acid and sodium hypochlorite buffered at pH 10. Use of such formulations containing the N-hydrogen compound is discussed, as is fighting microorganisms in paper mills. The essence of the invention is the production of stable formulations which can be handled and shipped without the loss of active halogen. This is effected by the incorporation of a buffer. The invention is not concerned with the on-site combination of hypochlorite-containing solutions or process streams with N-hydrogen compounds, but only with shelf-stable formulations.
While this patent teaches reduced yellowing when the formulations are used as bleaches, neither the reduction of AOX nor the unexpected biocidal activity enhancement of active halogen by N-hydrogen compounds in pulp slurries is revealed.