Organic compounds -- part of the class 532-570 series – Organic compounds – Percarboxylic acids or salts thereof
Patent
1992-08-24
1994-09-20
Dees, Jose G.
Organic compounds -- part of the class 532-570 series
Organic compounds
Percarboxylic acids or salts thereof
562 2, 562 3, C07C27910
Patent
active
053490835
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the production of dilute aqueous solutions of lower aliphatic peracids and to their use as disinfecting solutions.
The lower aliphatic peracids are effective wide-spectrum bactericides which have the particular advantage, in use, of leaving as residues only the corresponding lower aliphatic acids and therefore being particularly suitable for applications which require a non-environmentally-polluting disinfectant. While the lower aliphatic peracids in general are contemplated herein, for example those corresponding to carboxylic aliphatic acids containing 2 to 5 carbon atoms, peracetic acid is particularly envisaged since it is already a commercially important peracid for disinfectant purposes. Where the following description relates to peracetic acid it is understood that the other peracids may be read in substitution therefor provided that the technical context allows it. It is also understood that reference to a lower aliphatic acid includes a reference to the corresponding anhydride where appropriate.
Aqueous solutions of peracetic acid containing up to about 45% by weight of peracetic acid are commercially available. Such solutions may be produced by reacting appropriately concentrated hydrogen peroxide and acetic acid in an aqueous medium in the presence of an acid catalyst which is usually sulphuric acid or other strong mineral acid. The acid catalyst may be present in from about 0.1% to about 5% by weight of the reaction mixture.
Aqueous solutions of peracetic acid represent equilibrium mixtures of the reactants and the reaction products and, under relatively forcing reaction conditions, for example when using one or more of a substantial quantity of catalyst, an elevated reaction temperature and a concentrated reaction mixture, equilibrium may be substantially reached in a relatively short time. When using the strong acid catalyst in from 2% to 5% of the reaction mixture, a temperature of from 30.degree. C. to 50.degree. C. and a concentration of acid above about 20% by weight the reaction mixture may come to equilibrium within hours. For some applications, or where long storage is envisaged, it may not be desirable for there to be catalyst residues in a peracid product particularly, for example, dilute products intended for personal or domestic hygiene use. For many applications dilute solutions of peracetic acid, for example below 5% by weight but often below 2%, for example from 0.1% to 2% by weight, are required. Concentrations of peracetic acid above 0.5% by weight for example from 0.5% to 1 % by weight, are particularly effective bactericidally in, for example, toilet cleansing applications. Such dilute peracetic acid solutions may be produced directly by reacting acetic acid and hydrogen peroxide in a suitably dilute reaction medium but equilibrium can take an extremely long time to reach, particularly at the more extreme dilutions envisaged. At peracid concentrations below 1% by weight equilibrium may take a month or more to reach if the reaction is not acid catalysed or a week or more even if the reaction is acid catalysed. This entails a very heavy utilisation of plant and equipment on a large production scale.
If a concentrated equilibrium solution of peracetic acid is diluted with water the equilibrium point of the system is progressively altered, as dilution progresses, in favour of the regeneration of the original reactants. The ageing time taken to attain the new equilibrium point, after dilution, is of a similar order to that required to produce such a dilute solution directly from suitable reactants. Such a diluted solution may be used directly although it is not at equilibrium and is therefore of variable composition in storage. Such non-equilibrium diluted solutions also have a composition dictated by the equilibrium point applying at the original concentration, which may not be desired in some applications.
In 1955 Greenspan et al.(Proc. 42nd Ann. Mtg. Chem. Spec. Man. Ass. Dec. 1955), disclosed that stable dilute peracetic acid solutions can be prepare
REFERENCES:
patent: 4297298 (1981-10-01), Crommelynck
patent: 4743447 (1988-05-01), Le Rouzic
Brougham Paul
Pearce Timothy
Sanderson William R.
Conrad Joseph M.
Dees Jos,e G.
Solvay Interox Limited
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