Compositions – Preservative agents – Anti-oxidants or chemical change inhibitants
Patent
1995-07-19
1996-09-24
McKane, Joseph K.
Compositions
Preservative agents
Anti-oxidants or chemical change inhibitants
514373, 548209, A01N 4380, C07D27506
Patent
active
055588166
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB 94/0100 filed Jan. 19, 1994.
The present invention relates to a stable liquid composition comprising an alkali metal salt of 1,2-benzisothiazolin-3-one and dipropylene glycol having a lower pH and lower viscosity than those hitherto known.
1,2-benzisothiazolin-3-one (referred to hereinafter as BIT) is an established industrial biocide and is particularly effective in protecting aqueous media against microbiological spoilage. It is particularly effective as a bactericide and is especially suited to the protection of latices. Thus one of its major uses is as an in-can preservative for the preservation of acrylic and acrylate paint emulsions.
BIT has low aqueous solubility and can cause sensitization in some individuals. Consequently, for ease of handling and to reduce handling risks, it has been formulated as an aqueous dispersion and also as a stable solution in an amine solvent as disclosed in UK 1,191,253 and UK 1,330,531. For some applications, these amine formulations are not attractive and are rarely used for indirect food contact applications, such as for instance for use in water-based adhesives which may be used in the food packaging industry, because the amines are volatile and tend to have an unpleasant odour. Furthermore, amine solutions of BIT may not be suitable for use as biocides in in-can preservation of latices because amine solvents may cause yellowing of the latex. Amines are also capable of reacting with and deactivating certain biocides and this further limits the use of amine formulations of BIT when used with such biocides.
To avoid these problems associated with amines, BIT is now generally formulated as an alkali metal salt in one or more water miscible solvents such as dipropylene glycol as disclosed in U.S. Pat. No. 4,188,376. Such formulations are stable solutions which withstand freeze-thaw temperature cycling, and even if frozen recover on warming to re-generate a stable solution. Formulations of this type containing 20% BIT, and 658% dipropylene glycol, the remainder being water wherein the BIT has been converted to sodium-BIT by reacting 1.1 moles sodium hydroxide with 1 mole BIT as described in Example 1 of U.S. Pat. No. 4,188,376, have been available commercially for many years as Proxel GXL (Proxel is a registered trade mark of ICI PLC). These formulations have proved highly successful and withstand all but the most extreme of low temperatures. However, these glycol formulations suffer from high viscosity at lower temperatures even when remaining fluid, and this causes problems in metering the correct dosage, especially by pumping. A further disadvantage of such formulations is their high pH, normally pH 12 or above, which can cause `pH-shock` and coagulation when added to a medium to be protected, such as an emulsion paint or latex, owing to the different pH of the medium. The high viscosity and high pH are caused by the combination of the amount and type of solvent employed and also the amount of alkali both of which have hitherto been considered necessary to produce stable solutions of sodium-BIT. Indeed, in all the working examples of U.S. Pat. No. 4,188,376 a 10% excess of sodium hydroxide has been used relative to BIT in making the sodium salt. We have now found that the use of such high levels of sodium hydroxide is unnecessary and that stable solutions can be obtained even when using less than stoichiometric amounts of alkali. It has also been found that the amount of dipropylene glycol can also be reduced, which further reduces the viscosity without adversely affecting the storage properties.
According to the invention there is provided a stable composition comprising from 5 to 25% by weight of BIT and from 40% to 60% dipropylene glycol, wherein the BIT is present as an alkali metal salt formed by reacting from 0.75 to 1.07 moles alkali metal hydroxide with one mole of BIT.
The remainder of the composition may be water, one or more solvents selected from propylene glycol, dipropylene glycol, tripropylene glycol, C.sub.1-4 -alkyl
REFERENCES:
patent: 4188376 (1980-02-01), Payne et al.
patent: 5160666 (1992-11-01), Lindner et al.
patent: 5185356 (1993-02-01), Backhouse et al.
Cross Laura R.
McKane Joseph K.
Zeneca Limited
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