Abstract:
An ink composition comprising at least one color suitable for food use and a liquid vehicle including water and an organic solvent miscible with water in a volumetric ratio variable from 3:1 to 1:10, wherein the organic solvent is ethanol or a mixture ethanol:acetone in a volumetric ratio variable from 1:2 to 3:1; this ink composition is suitable, in particular, even though not exclusively, for surface coloring and printing on supports, wrappings and objects intended for coming into contact with foods.

Description:
FIELD OF APPLICATION  
         [0001]    The present invention relates to an ink composition practically void of toxicity, particularly suitable, even if not exclusively, for surface coloring and printing on supports, wrappings and objects which are to come into contact with foods.  
           [0002]    The materials suitable for direct contact with foods (e.g. paper or plastic material wrappings, plastic or cardboard supports or trays, etc.) are currently colored or printed by means of inks which always have a certain degree of toxicity, more or less high. For this reason, these wrappings or supports are mandatorily coated with paraffinized papers or transparent plastic films, which perform a barrier function to prevent the migration of ink components towards the foods, although allowing to appreciate, in transparency, the underlying colorings or inscriptions.  
           [0003]    It is clear that the presence of this additional barrier layer implies additional manufacturing costs and it can make the disposal of the used containers or wrappings complicated, due to the different chemical nature of the barrier layer with respect to that of the support whereon it is applied.  
           [0004]    Moreover, in case the barrier layer, for any reason, is damaged even only in a small portion thereof, the ink can come into contact with the food and this can cause also serious consequences for the consumer&#39;s health.  
           [0005]    Such an occurrence is certainly unlikely during the manufacturing step of the support or wrapping, especially if good manufacturing practices are scrupulously complied with, but it becomes likely during the using step by the final consumer. For example, the tear of the barrier layer on a picnic cardboard plate, also plastic plate, when using a knife to cut a food contained in the plate is to be considered.  
           [0006]    It is proper to finally remind that sometimes certain colored or printed supports which are not per se to come into contact with foods (and thus not coated with a barrier layer) can however come into contact with the foods. It is the case, for example, of the paper place-mats used in self-service and fast food restaurants, whereon the consumer can involuntarily let particles of food fall. Since most consumers are not aware of the fact that the above place-mats are not “for foods”—also because of the reduced size of the appropriate warning “not for foods”—the food fallen on the place-mat is often picked up again and consumed.  
           [0007]    Other fields wherein inks are often employed which may damage, in a more or less considerable extent, the consumer&#39;s or user&#39;s health are those of cosmetic products, of toys, of colors for painting or drawing (e.g. felt-tips) and of all those products that can come into contact with mouth, mucosae and skin.  
           [0008]    The problem underlying the present invention has thus been that of providing an ink composition with safety characteristics from the toxicological point of view such as to be used for surface coloring and printing of objects, wrappings and supports intended for coming into contact with foods or with the consumers&#39; skin or mucosae, without any risk of toxicity for these latter.  
         SUMMARY OF THE INVENTION  
         [0009]    Such a problem is solved, according to the invention, by an ink composition comprising at least one color suitable for food use and a liquid vehicle including water and an organic solvent miscible with water in a volumetric ratio variable from 15:1 to 1:10, wherein said organic solvent is ethanol or a mixture ethanol:acetone in a volumetric ratio variable from 1:2 to 3:1.  
           [0010]    Preferably, water and the organic solvent are in a ratio variable from 12:1 to 1:7 and said organic solvent is ethanol.  
           [0011]    The color (or dye) contained in the ink composition according to the present invention is chosen among those allowed for food use, in particular among those for which the absolute harmlessness is universally known, such as for example, among the organic ones, curcumin, riboflavin, chlorophyll and chlorophyllins and complexes thereof with copper, carotene, lycopene, xanthophylls, lutein and betanine, and, among the inorganic ones, iron oxides and hydroxides, titanium dioxide, calcium carbonate, silver, aluminum, gold.  
           [0012]    A non limiting list of the colors allowed for food use can be derived from the Italian Ministerial Decree of 21-12-1967 and from Italian Ministerial Decree of 27-12-1996, No. 684.  
           [0013]    The color is contained in an amount preferably comprised between 0,1 and 30%, conveniently 1-25%, by weight on the total weight of the composition. When an organic color is used, the composition preferably contains 1 to 6% of it by weight of the total weight and the liquid vehicle preferably contains water and ethanol in a volume ratio varying from 3:1 to 1:7.  
           [0014]    When, instead, an inorganic color is used, the composition preferably contains 7 to 25% of it by weight of the total weight and the liquid vehicle preferably contains water and ethanol in a volume ratio of 12:1 to 2:1.  
           [0015]    Conveniently, the ink composition according to the invention also contains a non-toxic thickening agent, chosen from the group comprising cellulose ethers, in particular methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose and carboxymethylcellulose, cellulose esters, in particular cellulose acetate, arabic gum, shellac, polyvinylpyrrolidone, xanthane and alginates.  
           [0016]    Preferred thickening agents are the cellulose ethers, polyvinylpyrrolidone and shellac. Methylcellulose is particularly preferred.  
           [0017]    Preferably, the amount of the thickening agent contained in the ink composition according to the present invention is comprised between 0.1% and 20% by weight of the total weight of the composition.  
           [0018]    A further possible component of the ink composition according to the invention is represented by tannins, preferably natural, in particular tannic acid, as fixers or however agents increasing the color fastness. When present, the tannins are contained in an amount variable from 0.1% to 10% of the total weight of the composition.  
           [0019]    It can be useful, under certain circumstances and with particular reference to requirements of ink-jet printing, that the composition according to the invention contains agents regulating the conductivity, such as for example ammonium or alkali salts of organic acids, such as acetic, lactic and propionic acid.  
           [0020]    The amounts of these salts in this case are generally comprised between 0.1% and 0.5% by weight on the total weight of the composition.  
           [0021]    Finally, the ink composition according to the invention can contain an antifoam agent, for preventing the foaming of the ink during the printing step. As antifoam agent silicone compounds can be used, such as for example the DC-150 of Dow Corning, or acetylenic compounds, such as for example the antifoam agents of the SURFYNOL™ series of the firm Air Product and Chemical Co. (U.S.A.) or, advantageously, natural fatty substances such as vegetal oils or animal fats.  
           [0022]    When they are used, these antifoam agents preferably constitute 0.01%-2.0% of the total weight of the ink composition according to the invention.  
           [0023]    The composition according to the invention, especially in the case in which natural fatty substances are used as antifoam agents, can also contain one or more emulsifiers, selected in particular among those suitable for use with foods, such as, for example, lecithins, mono- and diglycerides of food fatty acids and esters thereof with lactic, citric and tartaric acids, sucroesters (E 473) and sucroglycerides (E 474).  
           [0024]    For the purpose of adjusting the pH of the ink composition of the present invention and to optimize the action of certain thickening agents it may result to be convenient adding ammonia, which also has the function of regulating conductivity, and/or borax, which also acts as a preservative, and/or calcium hydroxide.  
           [0025]    Further preservatives that may be added to the ink composition according to the invention—although the latter is generally perfectly preserved even in the absence of specific preserving agents—are the parabens, in particular methyl- and propylparaben.  
           [0026]    The addition of polyols such as glycerol, polyglycols and propyleneglycols, acting as drying time regulating agents, may be convenient.  
           [0027]    Finally, according to particular application needs, further components, such as perfumes, substances conferring sweet taste (e.g. glycerol), essential oils etc. can be considered in the composition according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]    The present invention will be further described by making reference to some examples regarding ink compositions for printing on paper or cardboard but it is to be underlined that the field of application of the ink composition according to the invention is not limited to this application but it extends also to the field of the cosmetics industry, of the colors for painting and drawing, including wall paintings, and others.  
       EXAMPLE 1 
       [0029]    [0029]                                                       Erythrosin   0.35 g           Methylcellulose   12.0 g           Ethanol    350 ml           Water     50 ml                        
         [0030]    The solution obtained by mixing the above listed components has allowed to print inscriptions and drawings practically on all the types of paper and cardboard, comprised those less porous and even those which are coated or glazed.  
       EXAMPLE 2 
       [0031]    [0031]                                                       Erythrosin    0.35 g           Methylcellulose    2.7 g           Ethanol   43.75 ml           Water   31.25 ml                        
         [0032]    This solution has resulted to be suitable for printing on papers and cardboards of medium-low porosity, comprised papers and cardboards which are shiny on one side.  
       EXAMPLE 3 
       [0033]    [0033]                                                       Erythrosin    0.30 g           Methylcellulose    3.9 g           Ethanol   43.75 ml           Water   56.25 ml                        
         [0034]    This solution is suitable for printing on papers and cardboards of medium porosity.  
       EXAMPLE 4 
       [0035]    [0035]                                                       Erythrosin    0.30 g           Methylcellulose    3.15 g           Water   53.12 ml           Ethanol   21.88 ml                        
         [0036]    This solution is suitable for printing on papers and cardboards of high porosity.  
       EXAMPLE 5 
       [0037]    [0037]                                                       Erythrosin   0.35 g           Methylcellulose    8.0 g           Tannic Acid    2.0 g           Ethanol    300 ml           Water     50 ml                        
         [0038]    This solution is particularly suitable for printing on papers and cardboards of low porosity.  
       EXAMPLE 6 
       [0039]    [0039]                                                       Erythrosin   0.35 g           Ethanol     44 ml           Water     31 ml                        
         [0040]    This solution has resulted to be suitable for printing on papers and cardboards of medium-low porosity, comprised papers and cardboards which are shiny on one side.  
       EXAMPLE 7 
       [0041]    [0041]                                                       Erythrosin   0.35 g           Methylcellulose    8.0 g           Ethanol    200 ml           Acetone    100 ml           Water     50 ml                        
         [0042]    This solution is particularly suitable for printing on papers and cardboards of low porosity.  
       EXAMPLE 8 
       [0043]    [0043]                                                       Red iron oxide   19.2 g           Waxy shellac   17.5 g           Water   53.1 ml           Ethanol    5.0 ml           Borax    3.2 g           Lard    0.8 g           Soya lecithin    0.6 g           Multi-seed oil    0.4 g                        
         [0044]    This composition is suitable for printing on all kinds of paper and cellulose derivatives.  
         [0045]    The ink composition according to the invention is suitable for coloring and printing objects, supports and wrappings of paper or plastic material, of fabrics or non-woven fabrics, in particular for use in relation with foods, both when they have to directly bear or contain foods (trays, tubs, plates, etc.) and when they can accidentally come into contact with foods (e.g. table-cloths and serviettes).  
         [0046]    This because the ink components according to the invention are all non-toxic or even edible. Also if a certain amount of acetone had to be used for color stabilization reasons, the non-toxicity of the ink composition according to the invention would be guaranteed since the acetone is however a natural metabolite in the human body.  
         [0047]    Another possible field of application of the ink composition according to the present invention, not strictly linked to the use in relation with foods but always within a context wherein adequate hygiene conditions are required, is represented by the printing on kitchen rolls paper, toilet paper an the like, such as on disposable coats and on disposable bed sheets of paper or of non-woven fabric.  
         [0048]    The ink composition according to the invention is suitable for coloring or printing on materials of different porosity, being always possible to select a ratio between the aqueous solvent and the organic one such that it suits the particular porosity of the substrate to be colored or printed. To the same purpose it is also possible to carry out a proper selection of the thickening agent and/or of the stabilizing agent for the color and of the respective amounts contained in the composition.  
         [0049]    As it has been pointed at above, the ink composition according to the invention is also suitable to be used in the field of cosmetics and of the colors for painting and drawing, including wall paintings.  
         [0050]    As regards cosmetics, the ink composition according to the present invention, thanks to its absolute non-toxicity, is effective to be used in the production of make-up, colored lip-sticks or to carry out temporary tattoos, colorings for nails, etc.  
         [0051]    In the field of the colors for painting or drawing the ink composition can be used inside felt-tips, in particular those to be used by children. In this case, a composition free of or poor in thickening agent will be used.  
         [0052]    The ink composition according to the invention is also particularly effective for the production of watercolors and tempera. The possible presence of a suitable amount of methylcellulose or of another thickening agent inside the ink composition according to the invention contributes to give body and thickness to the brush stroke.  
         [0053]    It is worth reminding also of the possibility of using the ink composition according to the present invention for the coloring of wood or cardboard toys, obviously subject to being brought into contact with the mouth of children.  
         [0054]    Always as regards wood items, the ink composition according to the invention can be used for coloring chopping boards and similar wood tools used in the kitchen, such as wood trays, also thanks to the good capacity of impregnation that it has demonstrated towards the wood.  
         [0055]    Finally, the composition according to the present invention, thanks to its absolute harmlessness and “naturalness”, could be used for coloring any item, object or packaging, even if not expressly intended for being used in relation with foods, by those firms which desire to convey a message of maximum respect for the environment and for health to the potential buyers.