Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – With oxygen or halogen containing chemical bleach or oxidant...
Reexamination Certificate
1999-11-02
2001-08-14
Ogden, Necholus (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
With oxygen or halogen containing chemical bleach or oxidant...
C510S372000, C510S375000
Reexamination Certificate
active
06274542
ABSTRACT:
This invention relates to percarboxylic acid solutions and more particularly to their production from precursors comprising carboxylic acid esters.
Percarboxylic acids, by virtue of their properties, are contemplated for application in a wide range of uses, for example as oxidants, as stain removers and as microbicides, amongst others. Many factors are taken into account in selecting which percarboxylic acid is employed for a particular application, including its effectiveness for the purpose, its ease of preparation, its stability, and its acceptability to the user. For example, a low molecular weight aliphatic monoperoxyacid such as peracetic acid has been the peracid of choice on a number of occasions, because it can be produced readily, is acknowledged to be effective and capable of being produced in stable solutions, and is acceptable to many users, but some producers of microbicidal compositions would prefer to employ a compound with less odour, in order to avoid possible offence or irritation to the final users of those compositions.
A number of alternative percarboxylic acids have been disclosed hitherto in the literature that are derivable from dicarboxylic acids and derivatives thereof, including diperoxycarboxylic acids, their corresponding monoperoxy acids, and ester monoperoxycarboxylic acids.
For example, European Patent application No. EP-A-0 166 571 to Unilever teaches the use of ester peracids of the general formula [RX]
m
AOOH, where R is hydrocarbyl or alkoxylated hydrocarbyl, X is a heteroatom moiety, preferably oxygen, A is a wide range of organic moieties containing one or two carbonyl groups and m is one or two, for use in bleaching and laundry applications.
European Patent Application No. EP-A-0 426 217 to Unilever teaches the use of ester peracids of the general formula X—O
2
C—A—CO
3
H where A is a C1 to C12 alkyl aryl or alkaryl radical and X is a C1 to C20 alkyl, aryl, alkyl aryl radical optionally including a heteroatom for use in bleaching and cleaning systems.
Both French Patent Application no. 2324626 and a paper by Nedelec et al, Synthesis, 1976, pp 821-3 teach a method for the preparation and isolation of ester peracids from the reaction between acid chlorides and hydrogen peroxide in organic solvents.
A paper by C. Lion et al. Bull. Soc. Chim. Belg. 1991, 100, pp.-559 discloses the preparation and isolation of ester peracids by the reaction between ester acid and hydrogen peroxide in the presence of high concentrations of sulphuric acid and quenching into ice. The ester peracids so produced are employed in the destruction of toxic organophosphorus compounds in aqueous alkaline solution.
Compositions containing ester percarboxylic acids and their preparation by reaction between a monoester of an aliphatic dicarboxylic acid and hydrogen peroxide have been described in a PCT Application, International Publication WO 95/34537 to Solvay Interox Limited. Such compositions were shown to have no discernible odour and to be effective as a microbicide. Although the compositions exhibited a level of available oxygen (avox) stability that would enable to them to remain effective during several weeks storage, there is a continuing need to find ways of improving their storage capability, for example based on the total peracid content or total peroxygen content of the composition and/or extending the range of reagents from which they or related compositions can be produced.
It is an object of at least certain aspects of the present invention to provide a new or alternative process for the production of peracids of aliphatic dicarboxylic acids and their esters.
According to the present invention, there is provided a process for the production of aqueous percarboxylic acid solutions by reaction between a peroxygen compound and a precursor of the percarboxylic acid in the presence of an acid catalyst characterised in that the peroxygen compound is hydrogen peroxide and the precursor is an aliphatic diester satisfying the general formula R
1
—O—CO—R
2
—CO—O—R
3
in which R
1
and R
3
each represents an alkyl group containing from 1 to 4 carbon atoms which may the same or different and R
2
represents an aliphatic alkylene group which may be linear or branched containing from 2 to 6 carbon atoms and optionally unsaturated.
The selection of hydrogen peroxide to effect the peroxidation avoids the neutralisation or partial neutralisation that would arise if an alternative inorganic peroxygen compound like sodium percarbonate or sodium perborate were employed.
In a further aspect there is provided a composition comprising an ester, a peracid derivative of thereof, hydrogen peroxide and water characterised in that it comprises from 2 to 30% w/w hydrogen peroxide, 5 to 90% w/w water and 3 to 90% w/w of an aliphatic diester satisfying the general formula R
1
—O—CO—R
2
—O—R
3
in which R
1
and R
3
each represents an alkyl group containing from 1 to 4 carbon atoms which may the same or different and R
2
represents an alkylene group which may be linear or branched containing from 2 to 6 carbon atoms and optionally unsaturated, the % for the diester including the peracidic derivative thereof and any acidic derivative of the ester generated in situ.
Herein the compositions are often expressed in terms of the reactants that are introduced into the reaction mixture, namely the diester and hydrogen peroxide. It will be recognised that in the reaction mixture, a number of acid catalysed hydrolysis and perhydrolysis reactions take place, resulting in a complex mixture containing a residual concentration of the reactant diester, the corresponding monoester peroxycarboxylic acid in which one or other of R
1
and R
3
groups have been substituted to convert the ester to a peroxyacid group and likewise the corresponding monoester carboxylic acid, and the corresponding diperoxycarboxylic acid in which both R
1
and R
3
groups have been substituted to convert the ester to a peroxyacid group and likewise the corresponding dicarboxylic acid. As the reactions proceed, the mixture moves towards an equilibrium at which point the relative proportions of each constituent of the mixture depend on the relative proportions and concentrations of the diester and the hydrogen peroxide employed in the mixture before equilibration commences and the extent of decomposition of the peroxygen compounds subsequently. The rate at which the composition moves towards equilibrium depends on the prevailing temperature, the concentrations of the reactants and the concentration of the catalyst.
By controlling the composition of the reaction mixture expressed in terms of its reagents, and specifically by the choice of molar ratio of the diester to hydrogen peroxide and the extent of dilution of the mixture with water, it is possible to control the ratio of monoester monopercarboxylic acid to other monopercarboxylic acid/dipercarboxylic acid constituents at equilibrium and during the move towards equilibrium. In particular the peroxygen species can be directed towards the acid/monoperacid as the main or predominant peroxyacid species by diluting the mixture with at least a significant or preferably with a major fraction of water. The peroxyacid species can be directed towards the ester monoperacid species by employing high concentrations of the diester and hydrogen peroxide, preferably at or near an equimolar ratio and comparatively low concentration of water. During the period in which the mixture is approaching equilibrium, the proportion of peroxygen species, as measured by the proportion of available oxygen (Avox), present as peroxyacid species increases. Since, for many purposes, peroxyacid species are more effective as eg a biocide or oxidant, it is desirable to store the mixture until a significant fraction of the developable peroxyacid species have been produced, such as at least 90% before use.
It will be recognised that there is a particular benefit in employing diester derivatives of dicarboxylic acids as substrate for the formation of peracid derivatives, namely that first perhydrolysi
Carr Graham
James Alun P.
Lawton Valerie
Morton Kelly J.
Sankey John P.
Larso & Taylor, PLC
Ogden Necholus
Petruncio John M
Solvay Interox Limited
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