WO2005052096A1

WO2005052096A1 - Encapsulation and dispersion method and capsule therefor

Info

Publication number: WO2005052096A1
Application number: PCT/GB2004/004597
Authority: WO
Inventors: Darrell Green; Clive Antony Marchant
Original assignee: Johnson Matthey Plc
Priority date: 2003-11-19
Filing date: 2004-10-29
Publication date: 2005-06-09
Also published as: BRPI0416688A; EP1682639A1; GB0326932D0

Abstract

A marker composition for a liquid medium comprises a tablet or capsule containing a predetermined amount of said marker which is capable of dispersing said marker when the tablet or capsule is introduced into said liquid medium. A method of tagging a liquid petroleum product using the tagging composition is also described. A capsule for dispersing a solid or liquid into a larger body of liquid is also described.

Description

Encapsulation and dispersion method and capsule therefor

The present invention relates to a method for dispersing a measured amount of a material into a liquid, and, in a particular embodiment, to a capsule adapted to contain the measured amount of material and disperse it on introduction into the liquid.

Dispersion of solid and liquid materials by encapsulation is known in e.g. laundry products, drugs and agrochemicals for example. It is known to incorporate marker compounds into commercially formulated products in order to identify the source of the product or to trace the flow of a particular chemical composition. Such marking or "tagging" of products may be used to counteract counterfeit products or simply to monitor the flow of chemicals through a process or supply chain. However, it is not known to supply a marking or tagging composition for a liquid product in the form of an encapsulated pre-measured amount of the marker compound in a package which enables dispersion of the marker in the liquid when the package is placed in contact with the liquid.

One particular application for tagging technology is in petroleum products. Petroleum products are often subject to taxes and regulations which require that the amount and composition of the products sold is monitored and recordable. In such situations any deviation from a regulated standard of purity may impact the amount of tax which is recoverable in the state in which it is sold. Petroleum products such as automotive fuel gasoline may contain hydrocarbon solvents such as toluene, xylene or hexane but the amount of solvent permitted is normally strictly controlled to avoid potential damage to engines and to limit the amount of tax lost on the non- petroleum content of such fuels. In some territories gasoline may contain a certain proportion of a non-hydrocarbon component such as ethanol. It is often difficult to separate and thus identify and measure solvents found in a petroleum mixture because the petroleum is itself a complex mixture of compounds. These petroleum products may therefore be tagged by adding the marker compound or "taggant" to the petroleum or to the solvent. Various marker compounds may be used, for example radioactive materials, dyes, fluorescent materials or other materials which are readily detectable by particular methods. However it is often relatively simple to counterfeit such a tagged material.

In order to render counterfeiting more difficult, systems may be devised that employ two or more taggants that interact, for example as described in US 6312958 where two or more interacting fluorescent dyes are employed as markers for liquids such as petroleum products, e.g. gasoline and diesel fuels.

The taggants are generally powdery solids at room temperature and are either soluble in oil or the hydrocarbon-based petroleum products or in another constituent of the petroleum product, such as a permitted solvent, e.g. methanol or ethanol if present. In use they are required at very low concentrations, typically below 500 ppb by weight. Heretofore they have been added to petroleum products through the intermediary of a concentrated stock solution. Often it is desirable to employ a known concentration of taggant, especially where mixtures of taggants are employed. Heretofore this has necessitated measuring out relatively small amounts of the concentrated stock solutions. Thus if a taggant concentration of 100 ppb by weight is required, then only 5 ml of a 10% solution of the taggant is required for every 5000 litres of liquid, e.g. gasoline, to be tagged. Accurate measurement of such small amounts of concentrated stock solutions presents handling difficulties in many practical situations. It would be advantageous to provide a more convenient method of taggant handling.

It is an object of the invention to provide a method for dispersing a predetermined amount of a solid or liquid compound in a larger volume of liquid. It is a further object of the invention to provide an improved method of adding a marker composition or "taggant" to a liquid, in particular to a non-polar liquid such as a hydrocarbon. It is still a further object of the invention to provide an improved method and capsule for dispersing a solid or liquid compound in a larger body of liquid.

For clarity, the larger body of liquid into which it is desired to disperse a taggant, or marker composition will be referred to as a "bulk" liquid, although the use of this term is not to be taken to mean any particular volume of liquid. By marker composition we mean a composition which may contain one or more than one marker compound (or tag or taggant) and optionally one or more additional compounds such as a dispersing agent, surfactant, diluent etc. A marker compound is an individual marker such as a chemical marker or dye which is used to mark or tag a liquid product, for example to enable the liquid product to be traced and/or identified in a supply chain or process.

According to the present invention there is provided a tablet or capsule containing a predetermined amount of a marker composition, said tablet or capsule being capable of dispersing said marker composition when the tablet or capsule is introduced into a bulk liquid medium.

When the marker composition is a powder, it may simply be bound together to form a tablet, containing a known amount of the marker composition powder, with a binder. Alternatively, and preferably, the marker composition may be charged into a capsule so that the capsule contains a specified amount of the marker composition. In some cases it may be desirable to charge a marker composition which comprises a known mixture of marker compound materials to a single tablet or capsule. Alternatively it may be more preferable to charge known amounts of marker compounds or marker compositions singly to separate tablets or capsules and, where mixtures of marker compounds are required simply to add the appropriate number of different tablets or capsules to the bulk liquid to be tagged or marked. Typically each tablet or capsule contains 1 to 100 g of the marker composition.

According to a preferred aspect of the invention we provide a capsule for dispersing a measured amount of a solid or liquid compound in a larger volume of bulk liquid, said capsule comprising a compound-containing portion for containing the solid or liquid compound to be dispersed, a buoyancy portion to control the rate at which the capsule sinks within the bulk liquid and, optionally, a counterweight portion to ballast the capsule and maintain its orientation in the bulk liquid.

The compound-containing portion may comprise a matrix of soluble material in which the compound to be dispersed is incorporated or, alternatively and preferably, it comprises an enclosed chamber in which the solid or liquid compound to be dispersed is placed.

The capsule is formed from a material which is soluble in the liquid in which the solid or liquid compound it contains is to be dispersed. Thus when the capsule is placed into the volume of bulk liquid it begins to dissolve, thereby releasing the solid or liquid compound from the chamber. It is preferred that the entire capsule is formed from the soluble material, however it is essential that at least a part of the material forming the enclosed chamber is the soluble material. Preferably the container is capable of dissolving in the bulk liquid in such a way that no or minimal solid residues of the container remain which could foul the transfer lines in a subsequent transfer of the bulk liquid. When the capsule is intended to dissolve in water or an aqueous liquid then suitable soluble materials include hydrophilic, water-soluble polymers, starch, gelatin etc. When the capsule is intended to disperse a marker composition into a hydrocarbon liquid such as gasoline or diesel then the soluble material is preferably a non-polar soluble polymer or a solid hydrocarbon, e.g. a hydrocarbonaceous material selected from paraffin wax or polystyrene, compounded with or encapsulating a soluble marker composition. The hydrocarbonaceous material is preferably paraffin wax of melting point in the range 50 to 60°C. Paraffin wax is available in various grades according to its melting point, or set point. We have found that for dissolution in gasoline, a wax having a melting point of 50 - 60°C, preferably 50 - 56°C, especially 51 - 53°C is particularly suitable. Waxes of higher melting point only dissolve slowly in petroleum liquids, especially where the latter contains a significant proportion of non-hydrocarbon solvent such as ethanol, while waxes of lower melting point may soften in hot climates.

In order for the capsule to be sufficiently robust, normally the material is of a thickness which is completely soluble only after several minutes in contact with the bulk liquid. This is especially true in situations where access to the bulk liquid for mixing following contact with the capsule is difficult. Therefore in a preferred embodiment the material forming the enclosed chamber is of a non-uniform thickness. In this way one or more portions of the chamber walls may be of thinner material which can dissolve in the bulk liquid more quickly than the thicker portions of material to accelerate the release of the material within the chamber.

The invention also provides a method of tagging or marking a liquid petroleum product comprising adding one or more tablets or capsules as described above containing a marker composition to a known amount of a bulk liquid petroleum product.

The counterweight portion is preferably present but may be omitted. It is preferred to maintain a particular orientation of the capsule within the bulk liquid in order to ensure that certain parts of the capsule, particularly thinner parts of the wall of the chamber are maintained in contact with the bulk liquid so that they dissolve quickly. In this way the dissolution of the wall of the chamber and thus the release of its contents may be controlled. The counterweight portion preferably comprises the same soluble material from which the remainder of the capsule is formed. Therefore the counterweight may be provided by a thicker portion of the chamber or a solid part of the capsule in the region of the base of the capsule.

The buoyancy portion is provided to control the rate at which the capsule sinks within the bulk liquid and to enable the capsule to float within the bulk liquid for at least some of the time taken to dissolve sufficient of the material to release a significant proportion of the compound which is to be dispersed. It will be appreciated that if the capsule sinks to the bottom of the bulk liquid before the compound has been dispersed from the capsule, then dispersion of the compound within the liquid is less easy and may require agitation. The buoyancy portion may comprise a portion of the capsule formed from or containing a material which is less dense than the bulk liquid into which the material contained in the capsule is to be dispersed. Examples of such less-dense materials include gases and foams. The buoyancy portion preferably comprises an air-filled chamber. The capsule may optionally comprise fins or grooves to control its orientation within the bulk liquid medium. For example fins may be supplied which induce spinning of the capsule in order to assist in dispersion of the contents.

The tablet or capsule may be of various proportions but is preferably of suitable size and shape to be handled easily, e.g. from about 20mm to about 200 mm. The tablet or capsule may incorporate a small amount of visible pigment or dye to identify different types or amounts of taggant material. Alternatively, or additionally, the capsule or tablet may be marked, e.g. by printing or embossing in order to identify the type of contents or a batch number etc.

It is preferred to supply the tablet or capsule in a protective packaging to avoid breakage or tampering with its contents. Various marker compounds or tags may be used, for example radioactive materials, dyes, fluorescent materials or other materials which are readily detectable by particular methods, including chemical analysis and chromatography. The marker composition may comprise one or more than one marker compound, each marker compound being detectable by similar or by different means.

A first group of particularly suitable marker compounds are fluorophores which absorb radiation at one or more wavelengths and re-emit the radiation at one or more characteristic, longer, wavelengths. Examples of fluorophores are fluorescent dyes such as quinone-imine dyes, especially oxazine dyes, and xanthene dyes, particularly the Rhodamine dyes and coumarin dyes, 4-(butylamino)-N-butyl-1 ,8-naphthalimide, and Glowbug Invisible Red S- Organic Europium Complex, Glowbug Invisible Lemon S- Organic Non-longenic Oxazine Derivative, and Glowbug Invisible Cyan S -Organic Pyrazoline Derivative supplied by Capricorn Chemicals. Suitable dyes are well known, for example in the field of laser dyes or histopathology and characteristics of suitable dyes may be found in manufacturers literature, for example

"Lambdachrome® Laser Dyes" by U. Brackmann published by Lambda Physik AG. Preferably the fluorophore absorbs in the ultra-violet and/or visible parts of the electromagnetic radiation spectrum and re-emit in the visible and/or near infra-red parts.

A second group of suitable marker compounds are chemical markers which are detectable by chemical analysis. Preferably such marker compounds may be conveniently detected by gas chromatography apparatus coupled with a suitable detector which is capable of distinguishing the marker compound from compounds forming the bulk liquid composition. Alternative methods of identifying a chemical marker compound, such as X-ray fluorescence spectroscopy (XRF), inductively-coupled plasma analysis (ICP) or gas chromatography-mass spectrometry (gc/MS) in addition to or instead of XRF and/or ICP analysis. Suitable chemical marker compounds include a halogenated hydrocarbon, or other compound which is not a natural or usual component of the petroleum product to which the marker composition is to be added. Suitable halogenated hydrocarbons include halogenated aliphatic or aromatic compounds, such as bromopropane, iodobenzene, bromobenzene, a dichlorobenzene, trichloro ethylene ,1 ,1 ,2- trichloro ethane, tetrachloroethylene, 1 ,1 ,2,2-tetrachloro ethane, pentachloro ethane, hexachloro ethane, 1 ,2,4-trichloro benzene, 1 ,2,4,5-tetrachloro benzene, pentachloro benzene, dichloro-1 ,2-dibromoethane, dichlorotribromethane, hexafluoro benzene, difluoro-1- chloroethane, trifluoro-1 ,1 ,2-trichloroethane, tetrabromoethylene , tribromopropane , dibromobutane , a dibromobenzene , diiodobutane. Other suitable marker compounds include octafluoronaphthalene, 2,3,4,5,6-petafluorobenzhydrol, 3,9-dibromocamphor, perfluoroindan, lindane, aldrin, 2-fluoro-3-(thfluoromethyl)benzophenone, or 1 ,4-diiodobenzene. In one embodiment, where the petroleum product contains an organic polar solvent, especially an alcohol such as methanol or ethanol, the marker compounds, e.g. dyes are selected to be soluble in the polar solvent. This increases the range of marker compounds which may be used. Preferred marker compounds for use in such petroleum products are polar, most preferred are dyes or other marker compounds which are capable of dissolving fully in ethanol at a concentration of up to 500 ppb at ambient temperatures and pressures.

The marker composition may be solid or liquid. Both solid and liquid forms of suitable marker compounds are known. Preferably, the marker compound(s) which comprise the marker composition are selected to be sufficiently soluble in the bulk liquid to be marked that they are dispersed homogeneously with no or only mild to moderate mixing. In the preferred form of the invention in which petroleum liquids are marked according to the method of the invention, the marker compound(s) should preferably be capable of dissolving to provide a homogeneous solution in the petroleum when the mixing action is provided by the movement of the liquid in a road or rail tanker, over a period of a few hours.

The invention will be further described with reference to the drawings, which show alternative embodiments of examples of the invention. Fig 1 depicts a tablet 10 comprising particles 12 of a marker compound dispersed in a soluble matrix of a hydrocarbon wax 14. In use the tablet is introduced into the liquid to be marked and, on dissolution of the wax matrix, the solid marker particles are released into the liquid.

Fig 2 shows a capsule 20 formed of a soluble paraffin wax material. The capsule contains a measured amount of a marker compound 22 contained within an enclosed chamber 24 within the capsule. The walls 26 of the chamber, are of variable thickness, as shown in Fig 2a in which a transverse section along line A—A is shown. Portions 36 of the interior wall are fluted to provide thinner sections which dissolve on the liquid more quickly so that the marker ^• compound 22 may be released. Chamber 28 is sealed by wall 30 and lid 32 and is filled with air to provide buoyancy to the capsule to enable it to float in the liquid. The base portion 34 of the capsule 20 is relatively dense, being formed from thicker material. The channels 38 adjust the density of the base portion so that the capsule is sufficiently buoyed by the buoyancy chamber and also provide for more rapid dissolution of the base portion than would be possible if the base were completely solid.

Fig 3 shows an alternative capsule 40, also formed from a solid wax material. In this version the marker compound 42 is contained within chamber 44 which extends into the base portion 46 of the capsule. Chamber 44 has a chamfered section 48 to enable the marker powder to flow into the base portion. At the lower end of the chamber, region 50 of the base portion is relatively thin so that it may dissolve rapidly in the liquid and release the marker compound 42. The buoyancy chamber 52 is separated from the marker-containing chamber 44 by separating wall 54.

The method of the invention is particularly useful for marking petroleum products so that they may be identified and/or traced through the supply chain from source to consumer. Thus the method of the invention may be used to mark a genuine product when there is a risk of adulteration or of substitution with a similar product, e.g. for the avoidance of tax or duty on petroleum fuels. Thus petroleum products in which the marker composition may be used include gasoline, diesel, and paraffin fuels such as kerosene etc. However, the method may be used to add a marker composition to hydrocarbon solvents such as toluene, xylene or hexane, for example in order that dilution of petroleum products with such marked solvents may be detected and quantified. In other applications the marker composition may be added to a petroleum product in order that it may be traced in the subsequent transport or refining processes, e.g. so that fuel removed (lawfully or unlawfully) from a pipeline containing the fuel may be identified and traced. The marking of a petroleum product may, alternatively, be used to trace the source of a spillage or in process monitoring applications.

Claims

1. A tablet or capsule containing a pre-determined amount of a solid or liquid material, said tablet or capsule being capable of dispersing said solid or liquid material when the tablet or capsule is introduced into a bulk liquid medium.

2. A tablet or capsule as claimed in claim 1 , wherein the solid or liquid material comprises a pre-determined amount of a marker composition, said tablet or capsule being capable of dispersing said marker composition when the tablet or capsule is introduced into a bulk liquid medium.

3. A tablet or capsule according to 'claim 1 or claim 2, wherein the tablet or capsule is formed from a non-polar soluble polymer or a solid hydrocarbon.

4. A tablet or capsule according to any one of claims 1 to 3 in the form of a capsule of the hydrocarbonaceous material containing the solid or liquid material.

5. A tablet or capsule according to any one of claims 2 to 4 wherein said marker composition comprises a mixture of two or more marker compounds.

6. A tablet or capsule according to any one of claims 2 to 5 containing from 1 to 100 g of a marker composition.

7. A tablet or capsule according to any one of claims 1 to 6 wherein the tablet or capsule comprises a capsule comprising a compound-containing portion for containing the solid or liquid compound to be dispersed, a buoyancy portion to control the rate at which the capsule sinks within the liquid and, optionally, a counterweight portion to ballast the capsule and maintain its orientation in the larger volume of liquid.

8. A tablet or capsule according to any one of claims 2 to 7 wherein the marker composition comprises

(i) a fluorophore and/ or

(ii) a chemical compound which is capable of being detected by gas chromatography apparatus^* coupled with a detector which is capable of distinguishing the marker compound from compounds forming the bulk liquid composition and/or

(iii) a chemical marker compound which is detectable by X-ray fluorescence spectroscopy (XRF) and/or

(iv) a chemical marker compound which is detectable by inductively-coupled plasma analysis

(ICP) and/or (v) a chemical marker compound which is detectable by gas chromatography-mass spectrometry (gc/MS).

9. A method of tagging a liquid petroleum product comprising adding one or more tablets or capsules of a hydrocarbonaceous material compounded with, or encapsulating, an oil- soluble marker composition to a known amount of a liquid petroleum product.

10. A method according to claim 9 wherein at least one tablet or capsule containing a first marker composition and at least one tablet or capsule containing a second marker composition is added to a known amount of liquid petroleum product.

11. A method according to claim 9 or claim 10, wherein the tablet or capsule is formed from a non-polar soluble polymer or a solid hydrocarbon.

12. A method according to any one of claims 9 to 11 , wherein the tablet or capsule is in the form of a capsule of the hydrocarbonaceous material containing the marker composition.

13. A method according to any one of claims 9 to 12, wherein said marker composition comprises a mixture of two or more marker compounds.

14. A method according to any one of claims 9 to 13, wherein said tablet or capsule contains from 1 to 100 g of a marker composition.

15. A method according to any one of claims 9 to 14, wherein said tablet or capsule comprises a capsule comprising a compound-containing portion for containing the solid or liquid compound to be dispersed, a buoyancy portion to control the rate at which the capsule sinks within the liquid and, optionally, a counterweight portion to ballast the capsule and maintain its orientation in the larger volume of liquid.

16. A method according to any one of claims 9 to 15, wherein the marker composition comprises

(i) a fluorophore and/ or

(ii) a chemical compound which is capable of being detected by gas chromatography apparatus coupled with a detector which is capable of distinguishing the marker compound from compounds forming the bulk liquid composition and/or

17. A method according to any one of claims 9 - 16, wherein said liquid petroleum product comprises gasoline, diesel or a paraffin fuel.