GB2450323A

GB2450323A - Biocidal cleaning

Info

Publication number: GB2450323A
Application number: GB0711778A
Authority: GB
Inventors: Christopher Barry; Edward Weir
Original assignee: Enviro Tech
Current assignee: Enviro Tech
Priority date: 2007-06-18
Filing date: 2007-06-18
Publication date: 2008-12-24
Also published as: GB0711778D0

Abstract

A quaternary ammonium compound is used together with a degreasing agent to clean a surface and also to eliminate, reduce or prevent microbial growth. The degreasing agent is an alkyl halide, preferably propyl bromide. The composition is used to reduce or eliminate microbial growth on a surfaces of a component of a fuel system, an electronic or electrical device, a component of a gas supply system or a medical device.

Description

* 2450323

BIOCIDAL CLEANING

The present invention relates to a cleaning treatment that can eliminate or reduce or prevent microbial (which term includes viral) growth. In preferred embodiments the present invention relates generally to molecular level cleaning of various surfaces by techniques such as vapour degreasing, ultrasonic cleaning, cold -wiping and hand cleaning.

It is known for such cleaning purposes to use degreasing agents such as solvent mixtures comprising n-propyl bromide. That material may be used together with a mixture of terpenes and a mixture of low boiling solvents. Reference may be made to US 5616549, US 5824162, US 5938859, US 6176942 and US 1/0000001. The disclosures of those specifications are incorporated herein by reference. Particularly preferred cleaning products are marketed under the Trademark "EnSolv" by Enviro Tech International, Inc. Such compositions comprise an azeotropic formulation that provides for superior stability, acid neutralisation, white metals reaction prevention, soil lifting and rust inhibition. The materials are environmentally friendly and non-flammable. One advantage of them is that they do not include chlorinated hydrocarbons, and therefore may be used where trichloroethylene and HCFC 141b are no longer allowed. These materials may have similar physical properties to those chlorinated materials, and in particular have a similar evaporation rate.

While these existing cleaning compositions are highly effective they do not in general prevent subsequent microbial growth on cleaned surfaces when contaminated fluids are later introduced. This problem can occur particularly in fuel systems, including fuel tanks and fuel lines. Many hydrocarbon fuels are susceptible to microbial growth which may affect performance of the fuel, and in any case is quite likely to cause formation of sludges which inhibit its passage through fuel lines.

This problem also occurs in many other situations, for example water systems, cooling systems, and air or other gas supply systems. Generally, therefore, the problem arises with systems whose function is to store and/or transmit fluids, but contamination can also occur in electronic or electrical or medical or other devices where contact with a fluid is merely incidental.

We have now discovered a way of overcoming this problem which involves the use of a biocide which, when applied to a vulnerable surface, is preferably retained as a thin film. The biocide is preferably applied to the surface after the surface has been cleaned, preferably after it has been cleaned by a cleaning material of the type referred to above. We particular prefer that the biocide be incorporated into the cleaning composition. It may be noted here that the cleaning composition itself preferably leaves no measurable residue after cleaning, and therefore substantially the only residue on the surface is that of the biocide.

A variety of biocides may be used, but at present we prefer quaternary ammonium compounds.

Thus, the present invention provides the use of a quaternary ammonium compound in conjunction with a degreasing, or other cleaning, agent to eliminate or reduce or prevent microbial (including viral) growth.

The present invention also provides a method of eliminating or reducing or preventing microbial (including viral) growth which comprises applying to a surface a quaternary ammoniuin compound and a degreasing or other cleaning agent.

The invention further provides a composition suitable for eliminating, reducing or preventing microbial (including viral) growth, which comprises a degreasing or other cleaning agent and a quaternary ammonium compound.

The quaternaiy ammonium compound is preferably incorporated into a formulation comprising the degreasing (or other cleaning) agent, and the resulting composition is applied to the surface in question.

We prefer that the quatemary ammonium compound comprises one or more organically-soluble compound, particularly compounds that are soluble in appropriate cleaning solvents or other agents.

The concentration of the quaternary ammonium compound or other biocide in the cleaning agent is preferably from 0.1 to 10% by weight. More preferred minimum concentrations are 0.5% and 0.75% by weight. More preferred maximum

I

concentrations are 5% and 3% by weight. For many purposes we prefer a concentration of about 1% by weight.

The cleaning agent and the biocide are preferably such that after application of the composition to the article to be treated, and subsequent removal of solvents comprising the cleaning agent, a residue of biocide remains on the treated surfaces.

The thickness of the residue is preferably in the nano to micro range, ie is, say from 0.1 nanometres to 10 microns. for example from 1 nanometre to I micron The degreasing or other cleaning agent preferably comprises an alkyl halide, particular an alkyl bromide, in particular propyl bromide, and more particularly n-propyl bromide. In particular it may be a stabilised composition, especially a stabilised n-propyl bromide. It may be noted that n-propyl bromide is not an ozone depleting material.

In more general terms, the cleaning agent is preferably a solvent showing high solubility for fuels and diesel oils or other relevant materials. The solvent generally needs to evaporate to allow a residue of the biocide to coat the surface to be treated.

Also, the solvent will in general need to show high solubility for the biocide.

Furthermore, we prefer that the solvent is not flammable. The most important group of materials that meet thess requirements are halogenated hydrocarbons. Chlorinated hydrocarbons may be used, for example trichloroethylene, methylene chloride, perchloroethylene. HFEs and HCEs in general may be mentioned. However, as indicated above, we currently prefer n-propyl bromide.

As noted above, by means of the invention microbial growth is particularly usefully eliminated, reduced or prevented on a surface of a component of a fuel system, on a surface of an electronic or electrical device (such as a printed circuit board), on a surface of a component of a cooling system, or on a surface of a component of an air or other gas supply system.

The composition may additionally comprise one or more additives. Preferred additives neutralise acids, inhibit or prevent corrosion of iron or other metals, enhance solvency or enhance soil-lifting performance.

The precise nature of the cleaning agent will of course depend on the nature of the surface to be treated and on the conditions under which it will be used. The cleaning agent preferably has good soil- lifting performance, particularly in terms of its capacity to carry materials such as solder fluxes, waxes, adhesives, metal working lubricants, anti-seize compounds, coolants, greases and oils. In general, we prefer that the cleaning agent be any of the compositions claimed or disclosed in US 5616549.

US 5616549 claims a solvent mixture for use in a vapour degreasing system, said solvent mixture comprising: 90% to about 96.5% n-propyl bromide; an effective amount of up to about 6.5% of a mixture of terpenes, said terpene mixture comprising 35% to about 50% cis-pinane and 35% to about 50% trans-pinane; and 3.5% to about 5% of a mixture of low boiling solvents, said solvent mixture comprising 0.5% to about 1% nitromethane, 0.5% to about 1% 1,2-butylene oxide and 2.5% to about 3% 1,3-dioxolane.

(The percentages are preferably by weight.) That specification also claims a method for cleaning an article in a vapour degreaser, said method comprising: (a) providing a vapour degreaser system; (b) adding to the solvent reservoir of said vapour degreaser system a solvent mixture, said solvent mixture comprising: 90% to about 96.5% n-propyl bromide; an effective amount of up to about 6.5% of a mixture of terpenes, said terpene mixture comprising 35% to about 50% cis-pinane and 35% to about 50% trans-pinane; and 35% to about 5% of a mixture of low boiling solvents, said solvent mixture comprising 0.5% to about 1% nitromethane, 0.5% to about 1% l,2-butyleneoxide and 2.5% to about 3% I,3-dioxolane; (c) boiling said solvent mixture to form a vapour layer; (d) introducing into said vapour layer said article to be cleaned, said vapour layer condensing on said article thereby subjecting the surface of said article to a solvent-flashing action; and (e) removing said article from the said vapour layer.

(The percentages are preferably by weight.) An analogous method maybe used for the purpose of the present invention, the only difference necessary being the presence in the present invention of the quaternaiy ammonium compound or other biocide.

A solvent mixture as claimed in US 5938859 may be used in the present invention. That solvent mixture comprises: (a) about 85% by weight to less than about 96.5% by weight n-propyl bromide; (b) about 3.5% by weight to less than about 15% by weight of a mixture of low boiling solvents, said solvent mixture comprising about 0.5% by weight to about 1% by weight nitromethene, about 0.5% by weight to about 1% by weight I,2-butylene oxide, and about 2.5% by weight to about 3% by weight I,3-dioxolane; and (c) an effective amount of up to about 5% by weight of at least one additive selected from the group consisting of sec-butanol, ethanol and methanol, provided that sec-butanol comprises 0% by weight to about 3% by weight of said solvent mixture.

The present invention may also employ a solvent mixture as claimed in US 5824162. That solvent mixture comprises: 90% to about 96.5% n-propyl bromide; and 3.5% to about 5% of a mixture of low boiling solvents, said solvent mixture comprising 0.5% to about 1% nitromethane, 0.5% to about 1% 1,2 butylene oxide and 2.5% to about 3% 1,3-dioxolane.

(The percentages are preferably by weight.) The present invention may also employ a solvent mixture as disclosed in US 6 176942. That specification claims a solvent mixture comprising: (a) about 85 wt% to less than about 96.5 wt % n-propyl bromide; (b) about 3.5 wt % to less than about 15 wt % of a mixture of low boiling solvents, said mixture of low boiling solvents comprising about 0.5 wt % to about 1 wt % nitromethane, based on the solvent mixture, about 0.5 wt % to about I wt % I,2-butylene oxide based on the solvent mixture, and the balance of said mixture of low boiling solvents being 1,3-dioxolane; and (c) an effective amount of up to about 5 wt % of at least one additive selected from the group consisting of sec-butanol, ethanol and methanol, provided that the sec-butanol comprises 0 wt % to about 3 wt % of said solvent mixture.

The solvent mixture claimed in US 2001/0000001 may also be used. That

specification claims a solvent mixture comprising:

(a) about 85 wt % to less than about 96.5 wt % n-propyl bromide; (b) about 3.5 wt % to less than about 15 wt % of a mixture of low boiling solvents, said solvent mixture comprising about 0.5 wt % to about I wt % nitromethane, about 0.5 wt 5 to about I wt % 1,2-butylene oxide, and about 2.5 wt % to about 3 wt % 1,3-dioxolene; and (c) an effective amount of up to about 5 wt % of at least one additive selected from a group consisting of sec-butanol, ethanol and methanol.

In general various methods of treatment may be used depending on the size and nature of the objects to be cleaned and protected.

For large, installations cleaning can be done in situ. This will often be appropriate in the case of fuel systems in aircraft and other vehicles. In such cases, fuel lines and tanks are flushed with a composition of the cleaning agent and biocide.

An initial application will usually remove oil and sludge that is soluble in the cleaning agent. The system is then drained and flushed again with clean composition. This may be repeated an appropriate number of times. Finally, when the desired degree of cleaning has been achieved, the system is dried by ventilating usually with high pressure or high volumes of air. The solvent that comprises the cleaning agent evaporates, leaving a residue of the quaternary ammonium or other biocide on the surfaces of the cleaned system. The biocide will usually be bonded to the surfaces, particularly where, as is usually the case, the surfaces are of metals or plastics materials. This bonding means the lifetime of the biocide on the treated surfaces is high, and recleaning intervals are much increased by means of the invention.

The contaminated composition can usually be treated using simple ambient pressure distillation or by using a more sophisticated vacuum still. Thus, the cleaning solvents may be recovered.

For smaller systems or for individual components of systems or for small assemblies of components, an immersion technique may be used. This is often the preferred method for metal or plastic pipe fittings, electronic components, and medical devices. It is particularly preferred where such components are to be sourced from external suppliers or imported from non-critical production areas, and therefore where clean conditions cannot be ensured. Often one will employ at least two tanks, which tanks may but need not have ultrasonic cleaning devices or forced flow immersed jets. The parts are immersed in each tank in turn for cleaning and rinsing.

The composition in the cleaning tank must be regularly changed. An extractor may be used for final drying to evaporate residual solvent, leaving a protective coating of the biocide on the surfaces.

Vapour degreasing or other vapour cleaning techniques may be used. This usually incorporates the above-mentioned immersion process, but with a vapour blanket above the tanks. The treated parts emerge dry. This process can reduce consumption of the composition.

In the case of a vapour process, but also optionally in other processes, the quaternary ammonium compound or other biocide is selected to produce an azeotropic or constant boiling mixture with the cleaning composition. This allows the final drying process conveniently to deposit the reside of biocide on the desired surfaces.

Claims

I. The use of a quarternary ammoniuin compound or other biocide in conjunction with a degreasing or other cleaning agent to eliminate or reduce or prevent microbial growth.
2. The use according to claim 1, in which the quarternary ammonium compound is incorporated into a formulation comprising the degreasing agent, and the resulting composition is applied to a surface.
3. The use according to claim 1 or 2, in which the quarternary ammonium compound comprises an organically-soluble compound.
4. The use according to claim 1, 2 or 3, in which the degreasing agent comprises an alkyl halide.
5. The use according to any preceding claim, in which microbial growth is eliminated, reduced or prevented on a surface of a component of a fuel system, on a surface of an electronic or electrical device, on a surface of a component of a cooling system, on a surface of a component of a gas supply system, or on a surface of a medical device.
6. A method of eliminating or reducing or preventing microbial growth, which comprises applying to a surface a quarternary ammonium compound or other biocide and a degreasing or other cleaning agent.
7. A method according to claim 6, in which a composition comprising the degreasing agent and the quarternary ammonium composition is applied to the surface.
8. A method according to claim 6 or 7, in which the quarternary ammonium compound comprises an organically-soluble compound.
9. A method according to claim 6, 7 or 8, in which the degreasing agent comprises an alkyl halide.
10. A method according to any of claims 6 to 9, in which the surface is a surface of a component of a fuel system, a surface of an electronic or electrical device, a surface of a component of a cooling system, a surface of a component of a gas supply system, or a surface of a medical device.
11. A composition suitable for eliminating, reducing or preventing microbial growth, which comprises a degreasing or other cleaning agent and a quarternary ammonium compound or other biocide.
12. A composition according to claim 10, in which the quarternary ammonium compound comprises an organically-soluble compound.
13. A composition according to claim 11 or 12, in which the degreasing agent comprises an alkyl halide.
14. A composition according to claim 13, in which the alkyl halide comprises propyl bromide.
15. A composition according to any of claims 11 to 14, which additionally comprises one or more additives.
16. A composition according to claim 15, in which the one or more additives neutralize acids, inhibits or prevents corrosion of metal, enhances solvency, or enhance soil-lifting performance.