Degreasing composition and methods using same

Details Degreasing composition and methods using same Degreasing composition and methods using same

2001-01-25

2002-11-05

Kopec, Mark (Department: 1751)

Cleaning and liquid contact with solids

Processes

Oils, grease, tar, or wax removal, by dissolving

C134S002000, C134S039000, C134S041000, C134S042000, C510S110000, C510S245000, C510S252000, C510S267000, C510S271000, C510S272000, C510S421000, C510S435000, C510S436000, C510S475000

Reexamination Certificate

active

06475296

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The present invention relates to a degreasing composition, as well as to a gel and a degreasing foam which comprise said composition.
The present invention also relates to a process for degreasing and/or decontamination of a surface using said composition, said gel and/or said degreasing foam.
The present invention finds for example, but without being limited to, an application for degreasing surfaces, in particular metallic surfaces such as equipment, components, floors, etc. of a reprocessing plant for irradiated nuclear fuels. These surfaces are, or can be, in contact with one or several greasy substances, which can be contaminated. It is therefore necessary to clean these surfaces regularly with the aim of purification and/or radioactive decontamination.
For example, one of these substances is a solvent called tributyl phosphate (TBP) which is used in extraction cycles of radioactive metals such as, for example, uranium or plutonium. During these extraction cycles this solvent acquires a particularly high radiochemical activity, since it can contain up to several tens of grams of uranium and/or plutonium per litre. This solvent can thus become a high activity solvent (HA solvent) or a very high activity solvent (THA solvent). The presence of these HA and THA solvents on certain components of reprocessing plants for irradiated fuels, such as mixer-settlers, extraction columns etc. often leads to the formation of particularly organophilic metallic surfaces which encourage ulterior greasy deposits. These greasy deposits are almost insensible to rinsing by the classic aqueous solutions used in reprocessing and thus require a specific treatment.
On the other hand, the degradation products of TBP obtained by radiolysis of the solvent, for example hydrogenodibutyl phosphate (HDBP) form precipitates with most metallic cations such is iron III, thorium IV, uranium IV, plutonium IV, europium III, neodymium III, zirconium IV etc. which can be present during reprocessing of nuclear wastes, in particular irradiated fuels. These metals often deposit on the surfaces of the components of the reprocessing plants in contact with them, in the form of colloids. Decontamination of these surfaces requires erosion of a depth of 2 to 10 &mgr;m to be able to eliminate all traces of radiochemical activity. This erosion can only be efficient after elimination of the greasy solvent covering these surfaces. It is therefore necessary, in order to decontaminate these surfaces, to use products and processes appropriate for degreasing, first of all.
The composition, the gel and the foam as well as the degreasing and/or decontamination process of objects according to the present invention constitute efficient means for degreasing and/or decontamination of these surfaces.
In general, the invention is evidently not limited to the applications cited above, and can find an application in all the fields where rapid and efficient degreasing of an installation is necessary. Examples of such applications will be given below in the explanation of the invention.
STATE OF THE ART
In the case of degreasing a metallic surface which has been in contact with a solvent such as TBP and/or its derivatives such as HDBP, dihydrogenomonobutyl phosphate (H
2
MBP), and tetrapropylenehydrogen (TPH), the technique usually used consists of a succession of rinsing sequences of the surface to be degreased using rinsing solutions which are concentrated solutions of caustic soda and nitric acid. These sequences have to be repeated 5 or 10 times and the concentrations of the solutions used are of the order of 3 to 10 mol.l
−1
, for example 5.5 mol.l
−1
.
However, this technique is not very efficient and brings about numerous inconveniences. In fact, the nitric acid is not able to solubilize completely the precipitates formed on the surfaces which are still greasy, in particular precipitates composed of metal dibutyl phosphate.
In addition, results of radioactivity analyses of rinsing solutions, after rinsing, show that there is no important radioactivity peak showing efficient and rapid rinsing, but a slightly higher radioactivity after two or three rinsing sequences tending after that towards a limit, with greater activity when the rinsing solutions are renewed.
Moreover, in this technique, the rinsing solutions are used in large quantities, up to five or ten times the volume of the equipment to be degreased, and at a very high concentration, of the order of 3 to 10 mol. l
−1
. This technique, even though it is widely used, thus leads to a significant rise in wastes from reprocessing of spent nuclear fuels.
Finally, it can be difficult to separate the greases from the rinsing solutions of prior art efficiently, for example during reprocessing procedures of these effluents.
By reading the following description, it will be easily understood that the present invention not only makes it possible to solve the inconveniences cited above in the domain of reprocessing nuclear waste, but also in the different industrial and domestic domains in which degreasing of surfaces is necessary.
DESCRIPTION OF THE INVENTION
The present invention has precisely the aim of providing a composition, a liquid, a gel and a degreasing foam which allow efficient and rapid degreasing of a surface, and a reduction of the volume of effluents formed in comparison with prior art techniques.
The surfaces concerned can be any type of surface resistant to the degreasing composition according to the invention, for example a metallic surface, a glass surface, a plastic surface, a concrete surface etc. The metallic surface can, for example, be a steel surface, an austenitic steel surface, a uranus, aluminium zirconium surface etc.
These surfaces can be degreased with a greasy substance which can be a greasy solvent such as TBP, HDBP, H
2
MBP, TPH, or a mixture of these solvents, diverse oils such as alimentary oils, lubrication oils etc.
The degreasing composition according to the invention is characterised in that it comprises a base, a polyethoxylated fatty alcohol, saturated or unsaturated, a copolymer of ethylene oxide and propylene oxide, and water.
According to the invention, the base can, for example, be caustic soda or an equivalent base such as alcoholic potash, sodium or potassium carbonate, etc.
According to the invention, the base can have, for example, a concentration in OH
−
ions chosen from among a range from 0.1 to 1.5 mol.l
−1
in said composition.
According to the invention, the polyethoxylated fatty alcohol can be a compound of the general formula:
in which R is an alkyl with a long carbonaceous chain, saturated or unsaturated, comprising between 10 to 24 carbon atoms, and in which n represents the number of monomeric units of ethylene oxide, n being able to vary between 10 and 30.
The fatty alcohol can for example be lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, arachidyl alcohol, palmitic alcohol, oleic alcohol, linoleic alcohol, or a mixture of these.
According to the invention, n can be, for example, equal to 10 or 20.
According to the invention, the polyethoxylated fatty alcohol can for example be an ether of oleic alcohol and an ethylene polyoxide at 20 monomeric units of ethylene oxide.
In the composition according to the invention, the polyethoxylated fatty alcohol, saturated or unsaturated, can be at a concentration within a range from about 0.01 to 1.5% by weight, or at a concentration chosen in a range from about 0.05 to 0.8% by weight in said composition or yet again at a concentration chosen in a range from about 0.05 to 0.4% by weight in the composition following the utilisation of the composition according to the invention for making a degreasing liquid, foam or gel.
According to the invention, the copolymer of ethylene oxide and propylene oxide can for example be a block copolymer. It can comprise monomeric units of the ethylene oxide type and monomeric units of the propylene oxide type, respectively referred to hereinafter as OE and OP. This copolymer wi

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