Background to the invention

This invention relates to a marking method and marking formulations for use therein.

The management of cash in transit, presents a number of logistical problems, not least of which is combating theft. In an attempt to discourage theft of cash in transit, use is made of marking agents that stain bank notes accessed without authorization whilst in transit. In this method, dye is loaded into a rapid release container in a cash in transit (CIT) banknote conveyance box. The CIT box is provided with electronic sensors that will trigger the release of the dye into the cash hold of the box if there is any attempt at unauthorized opening the box or if there is any indication that the integrity of the box is or may be compromised.

A problem with dyes presently used in this method is that many of the existing dyes can be removed by washing with water to yield a bank note that is good and clean enough to pass on to an unsuspecting recipient. A further problem is that these dyes can be bleached with commonly available household bleaching agents, further to clean the notes.

It is an object of this invention to address this problem.

Summary of the invention

According to this invention, a bank note marking agent is provided, the marking agent being constituted by a water soluble dye that is adapted to be rendered water insoluble when brought into contact with water or an organic solvent.

The dye may conveniently be a quaternary dye salt.

As an alternative, the bank note marking agent may be constituted by a marking substance that is adapted to produce a colour when exposed to an oxidizing agent, such as a bleaching agent.

The marking substance may conveniently be cobalt nitrate.

In the preferred form of the invention, the bank note marking agent is constituted by a combination of the dye and the marking substance described immediately above.

The bank note marking agent described above is preferably adapted for use in a cash in transit box.

The invention includes a cash in transit box that includes a cash hold and the bank note marking agent described in the preceding paragraphs, the box including means to release the marking agent into the cash hold of the box, means to determine when, in use, the integrity of the box is or may be compromised and means to activate the release means in the event that integrity of the box is or may be compromised.

Description of embodiments of the invention

The quaternary salt dye for use as a bank note marking agent is preferably a quaternary of pthalo cyanine blue and a suitable nitrogen containing compound such as acetylated pyrrolidone.

Such a salt is water soluble and can thus penetrate the fabric of a bank note or at least the print layer and the paper and cotton fibre substrate of a paper bank note and the print layer on plastic bank notes. On such penetration the salt dissociates releasing the water insoluble pthalo cyanine blue. Further, this salt is rendered water insoluble on contact with water or an organic solvent. The salt and pthalo cyanine blue makes a dark stain on a bank note in which it comes into contact. The stain caused by the now water-insoluble pthalo cyanine blue cannot be removed by washing.

The substance for use as a bank note marking agent is preferably cobalt nitrate. Cobalt nitrate turns black on reaction with an oxidizing agent such as a bleaching agent. Should the person in possession of the stained notes attempt to bleach the stained notes, after unsuccessfully trying to wash the stained notes in water, the stains on the notes will become even darker as the cobalt nitrate reacts with the bleach.

Acetylated pyrrolidone pthalo cyanine blue can be produced by first reacting pyrrolidone with acetic acid in the presence of an acid catalyst such as a mineral acid to produce the acetylated pyrrolidone. The preferred mineral acid is sulphuric acid. Thereafter, the acetylated pyrrolidone is reacted with the pthalo cyanine blue in the presence of a pH reducing agent such a methylethanolamine to produce the salt.

The formulation may conveniently include a solvent-based resin, such as polyvinyl alcohol, that is adapted to coat the bank notes on contact therewith to render the notes even less susceptible to cleaning by washing with water or alcohol.

In use, a CIT box is provided with a staining agent container loaded with the above mentioned formulation containing both the quaternary salt of pthalo cyanine blue and cobalt nitrate. This combination of staining agents is released into the cash hold of the box to mark any notes in the cash hold should the integrity of the box be comprised in any unauthorised way.

It will not be possible to clean the bank notes so marked in any way suitable to re-introduce them into public circulation. In fact, any attempt at cleaning the notes will simply result in the staining agents turning darker, particularly if the notes are bleached so that the cobalt nitrate reacts with the bleach and turns black.

The reactions involved in producing the acetylated pyrrolidone pthalo cyanine blue are:

REACTION 1

REACTION 2

REACTION 3

The resultant dyes are less toxic than existing dyes and, being water based, present a much reduced fire hazard compared to existing staining agents. This advantage is not inconsequential in the light of the fact that CIT boxes make use of electrical devices and often make use of pyrotechnic devices to discharge the staining agent, with the concomitant risk of spark-induced ignition of the CIT box contents.

This risk is exacerbated by presently available solvent based dyes and staining agents.