Furthermore, the present invention relates to a method for obtaining such a water based dispersion.

The water based dispersion according to the present invention has a particularly useful application for printing ink and coating industries.

BACKGROUND ART It is known in the art that effective UV absorbing materials are constituted by organic molecules which are tipically insoluble in water.

By way of example, in the cosmetic industry UV absorbing materials are normally used as creams which are constituted by oil in water emulsions, whereby W absorbing materials are dissolved in the oil phase.

This mode of application, i. e. an oil in water emulsion, is not suitable for producing printing inks; in fact, in this case solvent inks should be used in order to dissolve the UV absorbing material in the oil based solvent.

Furthermore, a very high concentration of the UV absorbing material generally used in the cosmetic industry

would be necessary to obtain printed films featuring acceptable UV absorbing properties.

Since said UV absorbing materials are rather expensive, they can hardly be used for this kind of applications.

UV absorbing materials used in sunscreens are normally constituted by liquids and include benzophenones and anthranilates for long wave length absorption and PABA derivatives and salicylates for short wave length absorption.

In the field of bottling and packaging of bottles, prior to the advent of P. E. T. (Polyethylene Terpolymer) the bottle labels were made of paper and applied at a rate of 600 to 1.000 labels a minute.

With the introduction of plastic bottles, plastic labels consisting of a layer of voided polyethylene on which an ink layer is applied have been used, whereby a polypropylene layer is then spread on said ink layer.

This results in a rather expensive product.

Owing to the limited solubility of organic molecules provided with UV absorbing properties, there is at present no effective water based ink available as UV protective coating.

Document US-A-4,945, 121 discloses a process characterized by dissolving a dye in a solution of organic solvent and an epoxy type polymer, which requires a curing agent in order to create a resultant nanosphere that will crosslink through the action of the curing agent, and not simply as the result of a solvent removal which defined each nanosphere.

The dye may be in concentration range of 1% to 50% by weight of solvent, and the organic solvent must have limited solubility in water, typically less than 20%.

An initial intermolecular mixing step dissolves dye

and epoxy resin within a solvent so as to make a homogeneous solvent/polymer/dye intermediate mixture, that then is dispersed as nanoparticles in water, and thereafter crosslinked.

Surfactants may be used to assist in dispersing the dye/polymer/solvent solution into the water continuous phase.

According to this document, the invention can also be used for UV absorbers ; however, the process according to this document involves an intermediate solvent which requires that the active ingredient and the encapsulating matrix be soluble in the solvent.

After emulsification into small liquid drops, the solvent must be extracted to form a stable dispersion of solid particles.

Although this works quite well with a number of materials for methylene chloride as a solvent, this solvent was later put on the EPA list of undesirable solvents.

This constitutes a fundamental drawback of this process, since the particles resulting from said process contain significant amounts of methylene chloride, which could not be entirely extracted.

Many searches have been carried out for several years in order to single out a substitute solvent, but no one has been found with the same desirable properties, especially for commercial production.

DESCRIPTION OF THE INVENTION The present invention aims to set aside the disadvantages and drawbacks which are typical of the background art, and to provide, thus, for a water based dispersion of solid particles containing UV absorbing components as active ingredients which can be formulated into a cost effective water based ink or coating

exhibiting very strong UV absorbing characteristics, whereby the dispersion does not contain any trace of methylene chloride.

This is achieved by means of the water based dispersion disclosed in claim 1.

The dependent claims disclose particularly advantageous forms of embodiment of the water based dispersion according to the invention.

Furthermore, the present invention aims to provide for a method for obtaining such a water based dispersion, whereby no intermediate solvent is used.

This is achieved by carrying out the steps disclosed in claim 8.

The claims dependent on this claim outline particularly advantageous forms of embodiment of the method according to the invention.

The dispersion according to the present invention consists of colloidally stable submicron particles dispersed in water, i. e. particles which have a diameter which is predominantly less than one micron, said dispersion consisting of an active ingredient, in particular a UV absorbing material, encapsulated into a protective matrix.

A typical particle size range according to the invention is 0,05 microns to 5,0 microns.

According to the invention, said active ingredient is constituted by an UV absorbing organic molecule which is not soluble in water and which can be liquid or solid at room temperature.

According to a particularly advantageous form of embodiment of the present invention, the organic UV absorber is UV-Chek AM-3000 (Polymer Additives Division Ferro Corporation - 7050, Krick Road - Walton Hills - Ohio - U. S. A.).

Organic UV absorber W-Chek AM-300@ is 2-Hydroxy-4-n- Octyloxybenzophenone and is a strong UV absorber over a wide range of the UV spectrum; it is solid at room temperature (melting point: 47°C) and is compatible with a plurality of low melting point encapsulating matrices which are very good solvent for said organic UV absorber.

UV-Chek AM-300@ is an effective UV light absorber for wide variety of polymers, and it features especially effective UV absorbing properties in polyolefins; it is normally used as costabilizer in polyolefin films for agricultural and greenhouse use, as well as light stabilizer for flexible and semi-rigid PVC coatings.

Another organic UV absorbing material which can be used for carrying out the present invention is constituted <BR> <BR> <BR> by Escalol 567@, i. e. 2-Hydroxy-p-methoxybenzophenone (produced by ISP Van Dyk Corporation - 11 Williams Sts. - Belleville - NJ 07109 - U. S. A.).

Yet, another organic UV absorbing material which can be used for carrying out the present invention is constituted by Escalol 587@, i. e. Octyl-Salicylate (ISP Van Dyk Corporation - 11 Williams Sts. - Belleville - NJ 07109 - U. S. A.).

According to the invention, the encapsulating matrix consists of a material having a relatively low melting point, i. e. less than 100°C, which is not soluble in water and compatible with the active ingredient, or at least a very good solvent for it.

Typically, said material can be constituted by, e. g. commercial paraffin, bees wax, low molecular weight polyethylene.

According to a particular form of embodiment of the invention the UV absorber to encapsulating matrix ratio range is 1/20 to 10/1.

The method for obtaining a water based dispersion including the UV material encapsulated in the matrix comprises the following steps.

An encapsulating matrix, insoluble in water and solid at room temperature, and preferably made of, e. g. commercial paraffin, bees wax, low molecular weight polyethylene is heated above its melting point.

Then the active ingredient, i. e. the UV absorbing material, is dissolved in the melted encapsulating matrix.

A suitable surfactant like, e. g. Triton X-100@, i. e.

Octylphenooxypolyethoxyethanol (Union Carbide Corporation - 39 Old Ridgebury Road - Danbury - CT 06817-0001 - U. S. A.), or Span 80@, i. e. Sorbitan monooleate (ICI Surfactants - Concord Plaza/Bedford Building - 3411 Silverside Road - P. O. Box 15391 - Wilmington - DE 19850 - U. S. A.), or Span 85@, i. e. Sorbitan trioleate (ICI Surfactants - Concord Plaza/Bedford Building - 3411 Silverside Road - P. O. Box 15391 - Wilmington - DE 19850 - U. S. A.), is added to water which is heated to the same temperature as the encapsulating matrix.

Then the heated solution, which contains the UV absorbing material dissolved in the encapsulating matrix, is emulsified in water by a suitable emulsifier apparatus, e. g. an ultra-sonic probe or a Mantin Gaulin homogenizer.

The combination of the surfactant, which controls the surface tension, and the emulsifying apparatus, which controls the energy input, dictates the particle size distribution of the initial emulsion.

A subsequent cooling phase results in the formation of solid predominanty submicron particles which have been formulated to be of a controlled particle size and stable in water.

Such a water based dispersion consists of solid particles which contain an uniform mixture of active

ingredient, i. e. UV absorbing material, at a cost effective concentration in the encapsulating matrix.

According to the invention, such a dispersion has a particularly interesting application in the bottle labels printing industry, since the dispersion is either suitable for formulation into a gravure ink, or may be added to a gravure ink which does not contain pigment, or may also be incorporated into a coating which would then offer both physical and UV protections.

The invention will be better explained and understood by reading the following examples of different forms of embodiment.

EXAMPLE I 10 g of W -CHEK AM-300@ is dissolved into 20 g of a commercial paraffin which has been melted at 60°C.

This solution is emulsified for two minutes by means of an ultra-sonic probe in a water solution containing 0,1 g of Triton X-100@ which is heated to 60°C.

The resulting emulsion is cooled to room temperature to form a stable dispersion in water of solid, but relatively soft, particles which absorb UV radiation.

Microscopic examination reveals that the particles are predominantly less than one micron.

The active ingredient to matrix ratio for this formulation is 1/2, and has been varied over the range of 1/20 to 10/1.

EXAMPLE II 10 g of W -CHEK AM-300@ is dissolved into 20 g of a commercial bee wax which has been melted at 90°C.

This solution is emulsified for two minutes by means of an ultra-sonic probe in a water solution containing 0.1 g of Span 800 which is heated to 90°C.

The resulting emulsion is cooled to room temperature to form a stable dispersion in water of solid, but relatively hard, particles which absorb UV radiation.

Microscopic examination reveals that the particles are predominantly less than one micron.

The active ingredient to matrix ratio for this formulation is 1/2, and has been varied over the range of 1/20 to 10/1.

EXAMPLE III 10 g of Escalol 567@ is dissolved into 20 g of a commercial paraffin which has been melted at 60°C.

This solution is emulsified for two minutes by means of an ultra-sonic probe in a water solution containing 0,1 g of Triton X-100@ which is heated to 60°C.

The resulting emulsion is cooled to room temperature to form a stable dispersion in water of solid, but especially soft, particles which absorb UV radiation.

Microscopic examination reveals that the particles are predominantly less than one micron.

The active ingredient to matrix ratio for this formulation is 1/2, and has been varied over the range of 1/20 to 1/5.

EXAMPLE IV 10 g of W -CHEK AM-300@ is dissolved into 20 g of a low molecular weight polyethylene which has been melted at 90°C.

This solution is emulsified for two minutes by means of an ulta-sonic probe into 70 g of a water solution containing 0,1 g of Span 85 which is heated to 90°C.

The resulting emulsion is cooled to room temperature to form a stable dispersion in water of solid and very hard particles which absorb UV radiation.

Microscopic examination reveals that the particles are predominantly less than one micron.

The active ingredient to matrix ratio for this formulation is 1/2, and has been varied over the range of 1/20 to 2/1.

EXAMPLE V 10 g of Escalol 567@ is dissolved into 20 g of a low molecular weight polyethylene which has been melted at 90°C.

This solution is emulsified for two minutes by means of an ultra-sonic probe into 70 g of a water solution containing 0,1 g of Span 85 which is heated to 90°C.

The resulting emulsion is cooled to room temperature to form a stable dispersion in water of solid and very hard particles which absorb UV radiation.

Microscopic examination reveals that the particles are predominantly less than one micron.

The active ingredient to matrix ratio for this formulation is 1/2, and has been varied over the range of 1/20 to 2/1.

EXAMPLE VI 10 g of liquid Escalol 587@ is dissolved into 20 g of a commercial paraffin which has been melted at 60°C.

This solution is emulsified for two minutes by means of an ultra-sonic probe into 70 g of a water solution containing 0,1 g of Triton X-100@ which is heated to 60°C.

The resuling emulsion is cooled to room temperature to form a stable dispersion in water of solid but especially soft particles which absorb UV radiation.

Microscopic examinatlon reveals that the particles are predominantly less than one micron.

The active ingredient to matrix ratio for this formulation is 1/2, and has been varied over the range of 1/20 to 5/1.

EXAMPLE VII

10 g of Escalol 587@ is dissolved into 20 g of a low molecular weight polyethylene which has been melted at 90°C.

This solution is emulsified for two minutes by means of an ultra-sonic probe into 70 g of a water solution containing 0,1 g of Span 85@ which is heated to 90°C.

The resulting emulsion is cooled to room temperature to form a stable dispersion in water of solid and very hard particles which absorb UV radiation.

Microscopic examination reveals that the particles are predominantly less than one micron.

The active ingredient to matrix ratio for this formulation is 1/2, and has been varied over the range of 1/20 to 2/1.

EXAMPLE VIII 5 g of Escalol 587@ and 5 g of Escalol 567 () are dissolved into 20 g of a commercial paraffin which has been melted at 60°C.

This solution is emulsified for two minutes by means of an ultra-sonic probe into 70 g of a water solution containing 0,1 g of Triton X-100@ which is heated to 60°C.

The resulting emulsion is cooled to room temperature to form a stable dispersion in water of solid but especially soft particles which absorb UV radiation.

Microscopic examination reveals that the particles are predominantly less than one micron.

The active ingredient to matrix ratio for this formulation is 1/2, and has been varied over the range of 1/20 to 5/1.

EXAMPLE XI 5 g of liquid Escalol 587@ and 5 g of Escalol 567@ are dissolved into 20 g of a low molecular weight polyethylene which has been melted at 90°C.

This solution is emulsified for two minutes by means of an ultra-sonic probe into 70 g of a water solution containing 0,1 g of Span 85 which is heated to 90°C.

The resulting emulsion is cooled to room temperature to form a stable dispersion in water of solid and very hard particles which absorb UV radiation.

Microscopic examination reveals that the particles are predominantly less than one micron.

The active ingredient to matrix ratio for this formulation is 1/2, and has been varied over the range of 1/20 to 2/1.

EXAMPLE X 5 g of W -CHEK AM-300@ and 2,5 g of Escalol 587 are dissolved into 20 g of a commercial paraffin which has been melted at 60°C.

This solution is emulsified for two minutes by means of an ultra-sonic probe into 70 g of a water solution containing 0,1 g of Triton X-100@ which is heated to 60°C.

The resulting emulsion is cooled to room temperature to form a stable dispersion in water of solid but especially soft particles which absorb UV radiation.

Microscopic examination reveals that the particles are predominantly less than one micron.

The active ingredient to matrix ratio for this formulation is 1/2, and has been varied over the range of 1/20 to 5/1.

EXAMPLE XI 5 g of W-CHEK AM-300@ and 2,5 g of Escalol 587@ and 2,5 g of Escalol 567@ are dissolved into 20 g of a low molecular weight polyethylene which has been melted at 90°C.

This solution is emulsified for two minutes by means of an ultra-sonic probe into 70 g of a water solution containing 0,1 g of Span 85@ which is heated to 90°C.

The resulting emulsion is cooled to room temperature to form a stable dispersion in water of solid and very hard particles which absorb UV radiation.

Microscopic examination reveals that the particles are predominantly less than one micron.

The active ingredient to matrix ratio for this formulation is 1/2, and has been varied over the range of 1/20 to 2/1.