GB2384185A

GB2384185A - Cleaning method and apparatus comprising the use of dinitrogen tetraoxide

Info

Publication number: GB2384185A
Application number: GB0129238A
Authority: GB
Inventors: Barrie Mellor
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-12-06
Filing date: 2001-12-06
Publication date: 2003-07-23
Anticipated expiration: 2021-12-06
Also published as: GB0129238D0; WO2003047777A3; WO2003047777A2; AU2002352360A1; WO2003047777B1; GB2384185B

Abstract

A cleaning method for an article or surface comprising treating the article or surface with a working fluid 15 comprising dinitrogen tetraoxide (having the chemical formula N 2 O 4, , synonyms being dinitrogen tetroxide, nitrogen tetraoxide, and liquid nitrogen dioxide). The fluid may comprise dinitrogen tetraoxide either alone or in the form of a mixture with at least one other constituent which may be nitric acid, ethyl acetate or nitromethane. The invention also comprises apparatus 11 for undertaking the cleaning of an article or surface comprising an enclosure 12 and control means 19 adapted to undertake the method and utilising the working fluid. The article may be immersed in the working fluid, and the apparatus may comprise ultrasonic generating means 16, a heater 17 and a stirrer 18. The invention is preferably for use in the sterilisation of surgical equipment or other medical apparatus, and in particular the destruction of the prion which causes nCJD.

Description

2384 1 85

CLEANING PROCESS AND APPARATUS

This invention relates to a cleaning process and to apparatus for undertaking the process. It is particularly concerned with a chemical process providing for the removal or destruction of organic residues on the surfaces of components and structural materials. Surgical equipment and other medical apparatus is frequently contaminated with organic residues during use. Gross contaminants can arise including blood and tissue, and infectious agents such as bacteria, virus's, priors; and other agent may be left on the surface of the equipment. It is essential that infectious agents shall be completely removed from the equipment before it is used on other patients. Failure to remove or destroy these agents can readily lead to the spread of infection from patient to patient.

There are a number of existing methods for decontaminating (sterilizing) medical equipment involving the use of heating (including steaming). While these are effective in removing gross contaminants, current methods may not be wholly effective in the elimination of some infectious agents. Notably, it has been reported that the prion which causes nCJD, is particularly difficult to destroy with existing methods.

According to a first aspect of the present invention there is provided a cleaning method for an article or surface comprising treating the article or surface with a working fluid comprising dinitrogen tetraoxide (having the chemical formula N Og synonyms being dinitrogen tetroxide, nitrogen tetroxide, and liquid nitrogen dioxide) either alone or in the form of a mixture with at least one other constituent.

According to a first preferred version of the first aspect of the present invention the working fluid involves a mixture of dinitrogen tetraoxide and the other constituent is selected from the group comprising nitric oxide, ethyl acetate or nitromethane.

According to a second aspect of the present invention there is provided apparatus for undertaking cleaning of an article or surface comprising an enclosure and control means adapted to undertake the method of the first aspect or of the first preferred version thereof using the working fluid.

According to a first preferred version of the second aspect of the present invention the enclosure provides for the immersion of the article or surface in the working fluid Typically the enclosure and control means provides for temperature control of working fluid contained therein.

According to a second preferred version of the second aspect of the present invention the enclosure and the control means provides for ultrasonic cleaning of articles or surfaces immersed in the working fluid.

The new process described herein, makes use of a particular chemical (and its mixtures) which has not previously been used as a sterilising agent. This material is known as dinitrogen tetraoxide). Chemicals which may be mixed with the DNTO to achieve specific benefits include (but are not limited to) nitric oxide, ethyl acetate and nitromethane. Hereafter, dinitrogen tetraoxide, together with any of its mixtures, will be referred to simply as DNTO.

DNTO may be used to sterilise apparatus by methods including (but not limited to) the following examples; Simple immersion.

Surgical equipment made of corrosion resistant metals including stainless steels and titanium alloys can be immersed in DNTO for periods of several days at ambient temperatures, or shorter period at temperature of up to 130 C.

When removed from the liquid, residual traces of DNTO may be removed in either a current of warm nitrogen gas, or by positioning in a vacuum

Ultrasonic cleaning Because ONTO is a very dense liquid, ultrasonic agitation is particularly effective in achieving effective cleaning, even at ambient temperature An exemplary embodiment of the invention will now be described with reference to the accompanying drawing of which the sole figure is a diagram of a cleaning apparatus utilising the present invention.

The drawing shows a cleaning apparatus 11 comprising a closable tank 12 with a hinged sealable access lid 12A in which is suspended a tray 13 of open-work mesh containing a number of used surgical instruments to be sterilised to enable the instruments to be safely re-used for further surgical functions. The tank 12 contains up to level 14 a working fluid 15 composed, in this case, of dinitrogen tetraoxide which at room temperature is a relatively dense liquid. The lid 12A is closed to seal off the tank 12, when in use, since dinitrogen tetroxide is volatile and toxic and consequently a user of the apparatus needs to be protected from the effects of the working fluid.

For a given sterilising process the working fluid can contain, in addition to the dinitrogen tetraoxide, at least one other agent to enhance the sterilising process. The tank 12 includes an ultrasonic wave generator 16 disposed around the tray 11. A heater 17 is provided to enable the temperature of the working fluid 15 to be regulated.

A stirrer 18 provides for a controlled agitation and directing of the working fluid around the contents of the tray 13. Generator 16, heater 17 and stirrer 18 are regulated by means of a control unit 19 which in this case is manually controlled. However in an alternative version the control unit 19 can include or be connected to a processor to enable operation of the generator 16, heater 17 or stirrer 18 to accord with a preselected program stored with the processor.

In use the cleaning apparatus 11 is filled with working fluid loaded with filled tray 12 and filled with working fluid 15 up to level 14. The control unit 19 is then operated to ensure the generator 16, heater 17 and stirrer 18 provide the required input to

undertake the required sterilizing cycle. On completion the tray 12 is removed and the sterilised contents removed for re-use.

The present invention provides for a readily established cleaning process which can be used on a wide range of types of articles or surfaces of a number of materials including metals, alloys, polymers, ceramics and glasses to remove or destroy microscopic residues of organic matter. The exemplary embodiment involves a liquid phase working material. It may be that the same material may be conveniently used when in a vapour phase and consequently the present invention envisages the use of a working material in the most suitable phase for a given cleaning application.

Claims

1 A cleaning method for an article or surface comprising treating the article or surface with a working fluid comprising dinitrogen tetraoxide (having the chemical formula N204,synonyms being dinitrogen tetroxide, nitrogen tetroxide, and liquid nitrogen dioxide) either alone or in the form of a mixture with at least one other constituent.

2 A cleaning method as claimed in Claim 1 wherein the working fluid involves a

mixture of dinitrogen tetraoxide and the other constituent is selected from the group comprising nitric oxide, ethyl acetate or nitromethane.

3 Apparatus for undertaking cleaning of an article or surface comprising an enclosure and control means adapted to undertake the method of Claims 1 or 2 utilising the working fluid.

4 Apparatus as claimed in Claim 3 wherein the enclosure provides for the immersion of the article or surface in the working fluid.

5 Apparatus as claimed in Claim 3 or Claim 4 wherein the enclosure and control means provides for temperature control of working fluid contained therein.

6 Apparatus as claimed in Claim 4 or Claim 5 the enclosure and the control means provides for ultrasonic cleaning of articles or surfaces immersed in the working fluid.

7 Apparatus as hereinbefore described with reference to the accompanying drawing. 8 A method of cleaning as hereinbefore described with reference to the accompanying drawing.

b Amendments to the claims have been filed as follows 1. Use of a working fluid comprising liquid dinitrogen tetraoxide or the vapour phase thereof, either alone or in the form of a mixture with at 5 least one other constituent, for the removal or destruction of organic residues on the surface of articles.

2. The use as claimed in claim 1 wherein the at least one other constituent is selected from nitric oxide, ethyl acetate and nitromethane.

3. The use as claimed in claim 1 or 2 wherein the working fluid is in the liquid phase.

4. The use as claimed in claim 1 or 2 wherein the working fluid is in 15 the vapour phase.

5. The use as claimed in any preceding claim which is used in combination with ultrasonic agitation.

20 6. The use of a working fluid as defined in any preceding claim as a sterilizing agent.

7. A sterilising agent which comprises dinitrogen tetraoxide and another chemical selected from nitric oxide, ethyl acetate and 25 nitromethane.

8. Apparatus as hereinbefore described with reference to the accompanying drawing.