Generation of Chlorine Dioxide for Disinfection and Sterilization

United States Patent [191 Hartshorn [11] 4,104,190 [45] Aug. 1, 1978 [54] GENERATION OF CHLORINE DIOXIDE FOR DISINFECT ION AND STERILIZATION [75] Inventor: Stephen R. Hartshorn, Harlow, England [73] Assignee: Minnesota Mining and Manufacturing Company, Saint Paul, Minn. [21] App1.No.: 779,696 [22] Filed: Mar. 21, 1977 [30] Foreign Application Priority Data Mar. 23, 1976 [GB] United Kingdom ............. .. 11676/76 [51] Int. Cl.2 ....................... .. D06L 3/08; COIB 11/02 [52] U.S. C1. ............................. .. 252/ 187 R; 8/108 A; 252/95; 423/477; 423/470; 424/149 [58] Field of Search ........... .. 252/187 R, 95; 423/477, 423/478; 8/108 A; 424/149 [56] References Cited U.S. PATENT DOCUMENTS 2,131,447 9/1938 Logan ................................ .. 423/477 3,123,521 3/1964 Wehtworth et al. .. 252/187 R 3,278,447 10/1966 McNicholas ..... .. 252/187 R 3,386,915 6/1968 Rutschi et al. . ..... .. 423/477 3,585,147 6/1971 Gordon ........ .. .. 252/187 R 3,754,079 8/1973 Callerame . . . . . . . . . . .. 423/477 3,836,475 9/1974 Kirner .......... .. .. 252/187 R 4,013,761 3/1977 Ward et a1. ........................ .. 423/477 Prima/y Examiner—Benjamin R. Padgett Assistant Exam1'ner——Irwin Gluck Attorney, Agent, or Firm——Cruzan Alexander; Donald M. Sell; Mark A. Litman [57] ABSTRACT Chlorine dioxide is generated from aqueous liquids con- tainer alkali metal or alkaline earth metal chlorites, and compounds which liberate chlorine in water. Dry, sta- ble, solid compositions, in one or two parts, can be made from these and other ingredients. 25 Claims, No Drawings 4,104,190 1 GENERATION OF CHLORINE DIOXIDE FOR DISINFECTION AND STERILIZATION This invention relates to disinfecting and/or steriliz- ing. In particular the invention relates to a method of providing an aqueous disinfecting and/ or sterilizing liquid and to solid compositions which can be used to prepare that aqueous liquid. Chlorine dioxide is a very powerful oxidizing agent and is an excellent bactericide and antiseptic. In its natural state, however, chlorine dioxide is an explosive gas. Therefore, it is normally not stored as chlorine dioxide but is generated at low concentrations immedi- ately prior to use by chemical reaction from stable pre- cursors, e. g. by making sodium chlorite solutions highly acidic. According to the invention there is provided a method of generating chlorine dioxide in an aqueous liquid in which chlorine is released in an aqueous liquid containing an alkali metal of alkaline earth metal chlo- rite by adding to the aqueous liquid a water soluble solid composition containing a chlorine-releasing compound which is stable when dry but releases chlorine when dissolved in water, the chlorine released or chlorine species (as hereinafter defined) subsequently produced generating chlorine dioxide by reaction with the alkali metal or alkaline earth metal chlorite. The chlorine dioxide can be formed in this way in other than highly acidic solutions. The concentration of chlorine dioxide produced can range from low to me- dium to high concentrations. Concentrations of 5 to 10 ppm appear to be an optimum concentration in view of the toxicity of chlorine dioxide. The aqueous liquid formed is a very powerful disin- fecting and/or sterlizing liquid, the presence of both the chlorine dioxide and chlorine or chlorine species reduc- ing the chance of forming resistant strains. The chlorine generated in the solution can be present as free chlorine dissolved in the aqueous liquid or can be present as chlorine species such as chloric, chlorous or hypochlorous acid, formed by reaction of the chlorine with the aqueous liquid. It may be that these chlorine species themselves react with the alkali metal or alka- line earth metal chlorite to release chlorine dioxide or that they initially decompose to chlorine which then reacts to release the chlorine dioxide. By choice of the relative proportions of the alkali metal or alkaline earth metal chlorite and the chlorine-releasing compound the relative amounts of free chlorine and chlorine species can be to some extent predetermined. The chlorine or the chlorine species will generate the required chlorine dioxide by reaction with the alkali metal or alkaline earth metal chlorite. The aqueous liquid can initially contain chlorine di- oxide therein in the form of an alkali metal or alkaline earth metal chlorite, such solutions being commonly known as stabilized chlorine dioxide and referred to as such herein, and this solution will be quite stable pro- vided the pH is kept at neutral or above. Once, how- ever, chlorine is generated in the liquid by addition of the composition containing the chlorine-releasing com- pound there is an immediate release of chlorine dioxide, a much more immediate release than is the case when such liquids are acidified. On the other hand one can add to water or an aqueous liquid free of the chlorite a composition which contains an alkali metal or alkaline 5 10 15 20 25 30 35 45 50 55 60 65 2 earth metal chlorite and the chlorine-releasing com- pound. The water-soluble solid composition added to the aqueous liquid is preferably either in the form of a pow- der or tablet whether or not it contains the alkali metal or alkaline earth metal chlorite. The composition may if necessary contain a substantial proportion of a solid filler to ensure that it remains as a readily dispensible powder or has sufficient bulk for making into a tablet. The solid filler could be simply an inert filler. Prefera- bly, however, the solid filler is constituted in part or completely by other desirable components for the com- position which have additional functions but which will, in the dry solid form of the composition, act as the required filler. Other such desirable components which can constitute the filler partially or completely include one or more buffering components to bring the pH of the aqueous liquid which may initially be tap water and so of very variable hardness to the desired pH and thereafter preserve a pH, a dessicent to ensure storage stability, one or more effervescent reagents which dis- solve in water with effervescence to promote dissolu- tion of the composition or as an altemative a tablet disintegrant component, a surfactant to aid in wettin g of surfaces and to provide better contact between solu- tions and the organisms to be destroyed, and in compo- sitions to be made into tablet form a lubricant to assist in release from the tablet die. Therefore, according to another aspect of the inven- tion there is provided a stable solid composition for addition to water to give a disinfecting and/or steriliz- ing solution comprising: (a) a chlorine-releasing component which will release chlorine when in contact with water, (b) an alkali metal or alkaline earth metal chlorite, (c) a buffer, and optionally: (d) a dessicant to prevent premature chlorine release from the solid composition, (e) one or more effervescent reagents which will react to give effervescence when dissolved in water or altematively or additionally a tablet disintegrant com- ponent, (f) a surfactnat which is stable in the presence of oxidizing agents, (g) a lubricant to assist in release from a tableting machine, the lubricant optionally being constituted in part or completely by one or more of the other compo- nents a to f and h, and (h) a filler to maintain the composition as a readily dispensible powder or provide sufficient bulk for the composition to be made into a tablet, the filler being constituted by one or more of the components c to g optionally together with an inert filler which does not impair the action of components a and b. This solid composition is suitable for addition to water or aqueous liquids which do not contain any stabilized chlorine dioxide. For addition to stabilized chlorine dioxide solutions the solid composition need not contain the alkali metal or alkaline earth metal chlo- rite component b and so according to a further aspect of the invention there is provided a stable solid compo- sition for addition to aqueous stabilized chlorine dioxide solutions to give a release of chlorine dioxide and so give a disinfecting and/ or sterilizing solution, compris- mg: (a) a chlorine-releasing component which will release chlorine when in contact with water, (c) a buffer, and optionally: 4,104,190 3 (d) a dessicant to prevent premature chlorine release from the solid composition, (e) one or more effervescent reagents which will react to give effervescence when dissolved in water or alternatively or additionally a tablet disintegrant com- 5 ponent, (f) a surfactant which is stable in the presence of oxidizing agents, (g) a lubricant to assist in release from a tableting machine, the lubricant optionally being constituted in 10 part or completely by one or more of the other compo- nents a to f and h, and (h) a filler to maintain the composition as a readily dispensible powder or provide sufficient bulk for the composition to be made into a tablet, the filler being 15 constituted by one or more of the components c to g optionally together with an inert filler which does not impair the action of components a and b. These solid compositions, whether or not they incor- porate component b can be prepared, stored and used in the form of a dry powder or can be compressed into tablet form which has the advantage of providing exact amounts of the composition for adding to specified amounts of an aqueous liquid. The solid composition, whether as a dry powder or as 25 tablets, can be prepared as a two-part formulation with the components a to h divided between the two parts in various ways. This has the advantage particularly from the point of view of stability that, for example compo- nent a can be separated until use from any other compo- nent which may be hydrated, e.g. because it is difficult or expensive to obtain in an anhydrous form, or other- wise contain or attract traces of water. Additionally it may be desirable for best stability for component a to be kept separate from component b until use and in this 35 case component a and say half of components c to h can constitute one part of the composition which compo- nent b and the other half of components c to h will constitute the other part of the composition. Irrespec- tive of how the components a to h are divided between the parts of the two-part formulation the total solid composition, when added to water or stabilized chlo- rine dioxide solutions will have the same characteristics as a one-part formulation. The two-part formulations can be provided in separate compartments of a single two-compartment pack so that the correct relative pro- portions of the two-parts are available. The solid compositions are stable when protected from moisture and so can be stored for long periods until required for use provided they are kept dry and anhydrous components are used. Immediately after they are added to water, however, chlorine followed by chlorine dioxide is released. The solid compositions can be formulated so that the concentration for chlorine dioxide in solution is high enough to exhibit excellent 55 bactericidal properties, e.g. usually