Biocidal compositions and treatments

Details Biocidal compositions and treatments Biocidal compositions and treatments

2000-09-05

2004-08-31

Padmanabhan, Sreeni (Department: 1617)

Drug, bio-affecting and body treating compositions

Designated organic active ingredient containing

Phosphorus containing other than solely as part of an...

C514S104000, C514S107000, C514S108000, C514S114000, C514S136000

Reexamination Certificate

active

06784168

ABSTRACT:

The present invention relates to synergistic biocidal mixtures of hydroxymethyl phosphonium biocides with certain non-foaming biopenetrants.
GB 2 145 708 describes biocidal uses of tetrakis (hydroxymethyl) phosphonium salts. which, together with their parent base, tris(hydroxymethyl)phosphine, are referred to herein collectively as “THP”. U.S. Pat. No. 4,778,813 describes the biocidal use of quaternary ammonium polymers. GB 2 178 960 describes synergism between THP and surfactant. GB 2 228 680 describes synergism between THP and certain aldehydes.
THP formulations are increasingly widely used as biocides for water treatment in treating cooling water, process water e.g. in pulp and paper manufacture, drilling fluids and other aerobic water systems, as well as in anaerobic systems such as oil field formation water, injection water, produced water and water used in hydrostatic testing. Advantages include rapid and effective bactericidal activity and environmental acceptability. Particularly in systems where slime forming bacteria proliferate (e.g. in aerobic systems such as cooling water) it has been found desirable to use THP formulations containing synergistic amounts of a surfactant according to GB 2 178 960, in order to improve cost effective biocidal action. It is believed that the surfactant aids the penetration of the biomass by the THP. However such formulations cause foaming problems. Attempts to combine THP with other biocides (e.g. aldehydes), which do not cause foaming, have not been able to provide such effective biocidal action against slime forming bacteria, and/or have detracted from the favourable environmental profile of THP.
We have now discovered that combinations of THP with certain non-surfactant biopenetrants provide strongly synergistic biocidal formulations which give excellent penetration of bacterial slime and improved activity against planktonic bacteria without causing excessive foam. We have further discovered that mixtures of THP with a surfactant, and with a non-surfactant biopenetrant give a marked ternary synergism, permitting improved biocidal efficiency with reduced foaming.
Our invention provides a biocidally synergistic mixture comprising THP and at least one THP-compatible, non-surfactant, biopenetrant synergist together optionally with a surfactant The non-surfactant biopenetrant may be selected from quaternary ammonium polymers and copolymers, hydrotropes and syntans.
According to a second embodiment the invention provides a method of treating aqueous systems contaminated, or liable to contamination, with microbes such as bacteria. fungi or algae which comprises applying thereto separately or together a biocidally active amount of the components of a synergistic mixture as aforesaid.
The aqueous system may, for instance, be contaminated with bacterial slime and/or planktonic bacteria. The invention is of use for treating aerobic systems such as cooling towers and also for anaerobic systems, such as oil wells, e.g. during secondary recovery.
The THP is conveniently present in the formulation as a salt, but is preferably used at a pH sufficient to form the base. The salt is preferably the sulphate, chloride or phosphate. However any water soluble salt may be used including the phosphite, bromide, fluoride, carbonate, acetate, formate, citrate, borate, or silicate In fact any counter ion which is chemically compatible with THP may be used, the main criteria for selection being economic. Oxidation of THP to tris(hydroxymethyl)phosphine oxide (THPO) should be avoided and oxidising agents for THP are preferably substantially absent. The composition may contain oxygen scavengers to minimise oxidation by atmospheric oxygen. The pH of the composition may be below 3.5 to avoid THPO formation during storage but the pH on addition to aqueous systems is preferably between 3.5 and 9 and more preferably less than 8, e.g. 4 to 7.5. High alkalinity, e.g. above 10, is preferably avoided. The pH of the aqueous system may optionally be adjusted by addition of alkali or acid as appropriate.
An essential component of the invention is a non-surfactant biopenetrant. Surfactants are amphiphilic compounds which, even when present in low concentrations in water (e.g. 0.1% by weight), substantially reduce the interfacial free energy of a water/hydrophobe interface. Surfactants may be identified by their effect on surface tension of water. Non-surfactants do not appreciably reduce surface tension at low concentrations. Typically the reduction of surface tension by a non-surfactant at concentrations of the order of 0.1% does not amount to more than about 5% of the value for pure distilled water. At the same concentrations typical surfactants would reduce surface tension by 50% or more. For the purposes of this specification a compound is considered non-surfactant if it lowers the surface tension of water by less than 20% at a concentration of 0.1% by weight. Preferably the reduction is less than 15%, e.g. less than 10%, especially less than 5%.
The non-surfactant biopenetrant may for example be a quaternary ammonium polymer or copolymer. The quaternary ammonium polymer may for example be any of those described in U.S. Pat. No. 4,778,813. Particularly preferred is poly[oxyethylene(dimethyliminio)ethylene (dimethyliminio)ethylene dichloride]. This a copolymer of NNN′N′-tetramethyl-1,2-diamino ethane with bis (2-chloroethyl) ether, which is referred to herein as “WSCP”. The latter is the commercial name of the product used in example 1, which is sold by Buckman Laboratories. However any other water soluble polymer containing a plurality of quaternary ammonium groups may be used. Such compounds typically comprise a polymeric cation of the formula:
wherein: each R is a divalent organic group constituting with the ammonium group a monomeric residue or separately selected from two or more comonomeric residues; each R
1
is an alkyl or hydroxy alkyl group, typically having from 1 to 4 carbon atoms and preferably methyl or ethyl; X is hydrogen or a monovalant inorganic or organic end capping group; and n is from 2 to 3000, e.g. 5 to 2000, especially 8 to 1000, e.g. 10 to 500, most preferably 20 to 100. The counter ion may be any convenient THP-compatible anion e.g. chloride, sulphate, phosphate, bromide, fluoride, carbonate, formate, acetate, citrate, lactate, tartrate, methosulphate, borate or silicate.
R may for example be a C
1-6
alkylene, oxyalkylene, polyoxyalkylene, haloalkylene, halooxyalkylene, halopolyoxyakylene or a
group wherein R
2
may be a C
1-6
alkylene, oxyalkylene polyoxyalkylene, haloalkylene, halooxyalkylene or halopolyoxyalkylene group and R
3
represents a covalent bond or an R
2
group. The polymer may for example be a methylated polyethylene polyamine of the formula
where n is 2 to 10.
Some other typical examples include:
Poly[hydroxyethylene(dimethyliminio)ethylene(dimethyliminio)methylene dichloride]
Poly[hydroxyethylene(dimethyliminio)-2-hydroxypropylene(dimethyliminio)-methylene dichloride]
N-[3-(dimethylammonio)propyl]-N[3-(ethyleneoxyethylenedimethylammonio) propyl]urea dichloride
-4-[1-tris(2-hydroxyethyl)ammonium chloride-2-butenyl]poly[1-dimethyl-ammonium chloride-2-butenyl]tris(2-hydroxyethyl)ammonium chloride
The non-surfactant biopenetrant may alternatively be a hydrotrope. Hydrotropes are sometimes confused with surfactants because they are also amphiphilic. However hydrotropes do not significantly affect surface tension at low concentrations. Hydrotropes act as solubilisers. When present in relatively high concentrations (e.g. greater than about 1%) they increase the water solubility of sparingly or moderately soluble solutes.
A preferred class of hydrotropes includes water soluble glycol ethers. The glycol ether is preferably a water soluble compound of the formula HO[CR
2
CR
2
O])
n
R′ where each R is methyl, ethyl or preferably H, provided that the total number of carbon atoms per [CR
2
CR
2
O] group does not exceed 4, more pr

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