DESCRIPTION

The present invention relates to a composition which is useful for protecting ink inscriptions from removal.

It is well known that ink inscriptions can be removed, even if only partially, when treated with appropriate means among which may be listed laser light, solvents (alone or in mixtures), agents which ■ remove colour by oxidation/reduction such as ink-eradicators -and the like. Abrasives, metal blades and like mechanical means may also be used for erasure.

These means can remove writing, whatever ink has been used, without damaging the substrate on which it has been formed and hence without leaving any obvious trace of the removal.

In order to protect ink inscriptions, particularly but not exclusively on official documents, cheques and other like documents, from accidental or intentional removal, particularly when the latter is not "authorised", many methods and devices have been proposed among which is that of covering the inscription with a transparent film which is very adhesive to the paper substrate, which works equally well whatever type of ink is used for the writing itself and which is insoluble in the solvents for the

ink.

However, at least with regard to intentional and "unauthorised" removal, the methods and devices used until now have had limited success in the long

term in that the results have been useful until counte measures had been found for overcoming their protective effect.

A great need has thus been felt for protecting ink inscriptions, both when it is effected manually with a fountain pen, ball-point pen, felt pen, stamp and the like and when it is effected mechanically by typewriters, printers, ink jet printers, stamping machines and the like, against removal even if only partial, whether carried out accidentally or intentionally.

The problem at the root of the present invention is that of providing a system, a method, a protection for ink inscriptions which is able to satisfy the said requirement completely.

This problem is resolved by a composition for protecting inscriptions in ink of the type used in fountain pens, ball-point pens, printers, inked or oiled stamps and the like, against removal, characterised in that it includes at least one film-forming substance which is insoluble in water,

dissolved in at least one solvent having a low solubility for the ink but sufficient to make the ink penetrate the structure of the paper.

By penetrating the paper, the inscription made with the said ink' is protected from abrasion which, to be effective, must necessarily remove the paper layer; is protected from solvents since the ink particles of which it is composed are bonded physically to the cellulose; is protected from oxidising agents since the composition is watet—repellant.

To advantage, the composition, of the invention includes at least one energy-absorbing substance such as a lasei—light filter, which is iscible with the at least one solvent. Preferably the- lasei—light filter used in the composition of the invention is soluble in the solvent for the film-forming substance.

A film-forming substance with is useful for the composition of the invention is selected from the group comprising:

- acrylate-acrylamide copolymers,

- cellulose ethyl ethers,

- esters of cellulose with organic acids,

- esters of cellulose with nitric acid,

- polymers and copolymers of .

vinylpyrrolidone,

- long and very long alkyd resins, modified with a drying oil,

- and mixtures thereof.

Particularly effective results are achieved as regards the protection if ink inscriptions from removal with the use of very long alkyd resins, modified with linseed oil.

The solvent useful for the composition of the invention, which makes the ink penetrate the structure of the paper, is selected from the group comprising trichloromethane, trichloroethane, trichloroethylene, C _j ~ ^c ₁₈ alkylbenzenes and their mixtures.

In particular, for certain uses and with particular mixtures of film-forming substances from the group given above, the said solvents or their mixtures are, to advantage, accompanied by acetone, linear- hydrocarbons, isopropyly alcohol, isobutyl alcohol, alkyl esters of citric acid, isopropyl myristate, butyl acetate, ethyl acetate.

A particularly effective lasei—light filter which is widely available and soluble in the solvents listed above is 3-benzophenone.

In order to improve the watei—repellant characteristics, necessary to prevent watei—soluble

oxidising agents, such as ink-eradicators, from being effective, an organic derivate of silicone, for example dimethylsilicone, may be added.

The solution of the film-forming substance and the light filter which constitutes the composition of the invention may be formulated for use, with a brush, with a pad, by direct application and by means

of a spray. It may be prepared at the moment of use in which case the selected film-forming substance, the light filter and the selected solvent or mixture of solvents, are kept in respective containers, preferably within a single package.

Several- examples of formulations of the composition of the invention for different methods of application are given below.

EXAMPLE 1

A COMPOSITION FOR USE WITH A BRUSH

20g of cellulose acetobutyrate were dissolved in a mixture of the solvents including 40g of dodecylbenzene, 35g of trichloromethane and 5g of isobutyl alcohol.

To this mixture of solvents was added 1 gram of 3-benzophenone as a light filter for absorbing laser radiation.

A brush was used for the application of this

composition, and was kept immersed in the solution

itself until the moment of use.

EXAMPLE 2 20g of cellulose acetobutyrate were dissolved in a mixture of solvents ^' including 40g of trichloroethylene, 35g of trichloromethane and 5g of dimethyls!licone.

To this mixture was added 1 gram of 3-benzophenone as a light filter for absorbing laser radiation.

A brush was again used for the application of this composition and was kept immersed in the solution itself until the moment of use.

EXAMPLE 3 lOg of PVP-VA-crotonic acid copolymer were dissolved in 30g of a mixture of C ₁₂ ~ ^c ιs linear paraffins and 50g of trichloroethylene, and lOg of dodecylbenzene.

A sponge pad for stamps was impregnated with this solution and was suitably protected against evaporation by appropriate means known per se.

EXAMPLE 4 50g of a very long alkyd resin, modified with drying linseed oil and sold by N. BENASEDO S.p.A. (ITALIAN FIRM) with the name of BENASOL LI 85, were

dissolved in ethyl acetate and to this solution 12,5gof linear C ₁₆ - C ₁₈ paraffins, 12,5g of albyl (C ₁₆ - C , _Q ) benzenes and lg of 3-benzophenone were added.

Furhter 1.5g of a metalorganic catalyst

comprising Co, Mn and Pb were added to the above solution.

A brush was used for the application of this composition and was kept immersed in the solution itself until the moment of use.

EXAMPLE 5 COMPOSITION FOR USE WITH A PAD lOg of PVP-VA-crotonic acid copolymer were dissolved in 40g of trichloromethane, 40g of trichloroethylene, 8g of ethyl citrate, and 2g of dimethylsilicone.

A sponge pad for stamps was impregnated with this solution and was suitably protected against evaporation by appropriate means known oe r se.

EXAMPLE 6 A COMPOSITION FOR DIRECT APPLICATION lOg of ethyl cellulose were dissolved in a solvent mixture including 30g of trichloroethane, 4g of water and 56g of acetone. A conventional feed device used for example for coloured indicators was filled with this solution. The composition of the invention

was spread directly on to the ink writing with this indicator forming a strip.

EXAMPLE 7

COMPOSITION FOR DIRECT APPLICATION lOg of ethyl cellulose were dissolved in a solvent mixture including 30g of trichloroethylene, 4g of dimεthylsilicone and 56g of trichloromethane. A conventional feed device used for example for coloured indicators was filled with this solution. The composition of the invention was spread directly on the ink writing with this indicator forming a strip.

EXAMPLE 8 SPRAY COMPOSITION 3g of acrylate-acrylamide copoly er marketed by BASF under the name ULTRAHOLD 8 where dissolved in 47g of trichlorethylene. This solution was metered into a suitable cylinder charged with 50g of propane/butane under pressure.

EXAMPLE 9 INK JET PRINTERS A solution of 4g of vinylpyrrolidone-hexadecane copolymer in 76g of isopropyl myristate and 20g of tricholomethane were used in suitable apparatus in a position in parallel with the jet printer so as to superpose the protective

liquid on the characters which had just been printed.

EXAMPLE 10 A solution of 16g of vinylpyrrolidone-hexadecane copolymer in 84g of isopropyl yristate was prepared and microencapsulated with ethyl cellulose to obtain a 40-60 mesh powder which was used by means of the printing technology for self-copying paper. A strip of this microencapsulated liquid was provided on those parts of the cheques or documents which were to receive writing and which needed protection. The movement of the tip of the pen during writing ruptured the microcapsules with the consequent protection and penetration of the writing.

As a result of repeated and accurate evaluations of the effectiveness of the protection achieved by the application of the composition of the invention, it was ^' found, surprisingly that, with the single exception of fountain pen ink, the inscriptions were made to penetrate the structure of the paper without any blurring of the ink.

Consequently, even after the removal of the protective film formed by the selected film-forming substance, it was impossible to remove- the writing without destroying the paper.

For inscriptions in fountain-pen ink, the

protection was due completely to the film formed thereon and was very effective against attempts to remove it with water.

The invention thus conceived can be varied and modified within the capability of the expert in the art while remaining within the scope of protection defined bv the followinα claims.