Abstract:
A method of marking forms such as pharmaceutical tablest, capsules, confectionery and food with a water based ingestible ink comprising mixing pigments, a polymer, and optionally a plasticizer into water to form an ink dispersion, and printing the ink dispersion onto said forms to form a trademark, logo, or the like.

Description:
This is a continuation of co-pending application Ser. No. 191,704 filed on May 9, 1988, now abandoned. 
    
    
     TECHNICAL FIELD 
     This invention is in the field of applying indicia to pharmaceutical dosage forms, food products and confectionery items using an ink that primarily has a water base. 
     BACKGROUND OF THE INVENTION 
     This invention is concerned with a method of marking forms such as confectionery products, food, pharmaceutical tablets, and hard and soft gelatin capsules with a water based ingestible ink. 
     Reference is made to James C. Brown U.S. Pat. No. 3,258,347 issued on Jun. 28, 1966 for &#34;Edible Pharmaceutical Ink&#34;; Roy Y. Sanders, Jr. U.S. Pat. No. 2,948,626 issued on Aug. 9, 1960 for &#34;Edible Pharmaceutical Ink and Process of Using Same&#34;; Chester J. Piotrowski U.S. Pat. No. 3,694,237 issued on Sept. 26, 1972 for &#34;Edible Ink&#34;; and Stuart C. Porter et al. U.S. Pat. No. 4,543,370 issued on Sept. 24, 1985 for &#34;Dry Edible Film Coating Composition, Method and Coating Form&#34;. These patents are incorporated herein by reference. 
     Prior art ingestible inks suitable for marking forms such as confectionery products, food, pharmaceutical tablets, and hard and soft gelatin capsules have a shellac base in ethyl alcohol. One of the problems in marking such forms and one of the more important parameters for these inks is drying time. Brown U.S. Pat. No. 3,258,347, which refers to drying time as &#34;set-to-touch-time&#34;, states that the optimum transfer characteristics of the ink are obtained when the set-to-touch-time is two to four minutes. When the drying time is too slow, as is discussed in Sanders, Jr. U.S. Pat. No. 2,948,626, a tackiness problem develops resulting in spotting or smudging of the ink. Drying time is also discussed in Piotrowski U.S. Pat. No. 3,694,237 at column 1, lines 57-72 which states: &#34;Prior art edible inks are made with dry shellac, ethyl alcohol, plasticizers and/or detackifiers, pigments, or dyes, and solvents which give a desired drying time, say three minutes. As the ink ages, a process occurs wherein the acid groups of the shellac react with the ethyl alcohol to form an ethyl ester of the shellac. The presence of the shellac ester increases the drying time of the ink, and as the amount or percentage of ester increases, the drying time is increased, eventually to a point where the drying time is too long, causing offset, or pick-off, or transfer of the ink from one printed piece or tablet to another. Accordingly, it has been noted that the drying time of prior art inks increases with age, and this limits the shelf or storage life of the ink.&#34; 
     The machines presently being used to print marks onto pharmaceutical, food or confectionery products use a principle that is best described as offset gravure. An engraved cylinder picks up ink as it rotates in an ink bath. Excess ink is wiped off the engraved cylinder by a doctor blade and the ink remaining in the gravure etch of the cylinder is transferred to a rubber transfer (offset) roller which rotates with its roller surface in contact with the engraved cylinder. The ink on the transfer roller is then deposited onto the end product such as a tablet, or capsule. 
     The form may have been film coated, sugar coated, or not coated at all. To date, almost all inks used for this purpose have been of a shellac base in ethyl alcohol. While some shellac based inks have incorporated some water into the formula by the modification of pH, the inks remain alcohol based for the most part. Accordingly, their closed cup flash point is less than 100° F., and, therefore, they must be labeled as a hazardous flammable liquid. 
     SUMMARY OF THE INVENTION 
     A pharmaceutically or confectionery acceptable ingestible ink for use on pharmaceutical, confectionery and food forms, such as hard and soft shell gelatin capsules, tablets, candy and the like, comprises about 3 to 15 parts polymer, 5 to 30 parts pigment, 0.0 to 20.0 parts plasticizer, 0.0 to 17.0 parts alcohol, 0.0 to 0.001 parts antifoaming agent, and sufficient water to make 100 parts, by weight of the ink. A preferred ink formulation comprises about 10 parts polymer, 22 parts pigment, 7 parts HPMC (6 cps), 12 parts alcohol, 0.001 parts anti-foaming agent, and sufficient water to make 100 parts, by weight, of the ink. 
     The polymer may be methylcellulose, hydroxypropyl methylcellulose (HPMC), hydroxypropyl cellulose (HPC), cellulose acetate phthalate, ethylcellulose, polyvinylpyrrolidone, sodium ethylcellulose sulphate, zein, polyvinylacetatephthalate, methacrylic acid-methacrylic methacrylic acid ester co-polymer, or other film forming polymer used for coating tablets and the like. 
     Any of the pigments heretofore used in making ingestible ink may be used in the ink. Examples are discussed in Porter et al. U.S. Pat. No. 4,543,370. Examples of pigments include FD&amp;C and D&amp;C lakes, titanium dioxide, magnesium carbonate, talc, pyrogenic silica, iron oxides, channel black, and insoluble dyes. Also natural pigments such as riboflavin, carmine 40, curcumin, and annatto. Other examples are listed in Jeffries U.S. Pat. No. 3,149,040 and Butler et al. U.S. Pat. No. 3,297,535, as well as in Signorino U.S. Pat. No. 3,981,984, which are incorporated herein by reference. 
     The plasticizer may be any of the polymer plasticizers discussed in Porter et al. U.S. Pat. No. 4,543,370. Exemplary of the polymer plasticizer are polyethyleneglycol, for example, polyethylene glycol having a molecular weight of 200 to 8000 (Carbowax by Union Carbide), glycerin, propylene glycol, Triacetin (Pfizer&#39;s glycerin triacetate), acetylated monoglyceride, and Citroflex 2 (triethyl citrate), Citroflex 4 (tributyl citrate), Citroflex A2 (acetyl triethyl citrate), Citroflex A4 (acetyl tributyl citrate), diethyl phthalate, and mineral oil. Citroflex 2, 4, A2 and A4 are made by Pfizer and are plasticizers adapted for use with organic solvents. 
     The polymer plasticizer, to soften the polymer and make it less brittle, may be a liquid or a solid plasticizer, and a preferred plasticizer is a liquid such as polyethylene glycol 400. 
     Small amounts of alcohol may be used as a preservative or anti-foam agent. Examples of the alcohol that may be used are methanol, ethanol, isopropanol, and n-butanol, in amounts that are not sufficient to lower the flash point of the ink below 100° F. so as not to be classified as flammable by the Department of Transportation (DOT) of the U.S. government. 
     The antifoam may be Medical Anti-Foam (A-compound simethicone by Dow Corning) or dimethyl polysiloxane. 
     The inks made from the above formula with the water soluble polymer and with small amounts of alcohol still have a flash point above 100° F., and therefore are not classified as a hazardous flammable liquid. 
     With all the water present in these inks there was concern about the ability of the ink to dry on the offset gravure printing equipment used in this process of marking tablets. Two properties of the formula indicated possible problems. One is the latent heat of vaporation and the other in the set-to-touch-time. 
     Looking at the following Table 1 of latent heats of vaporation illustrates the problem. 
     
                       TABLE 1______________________________________MATERIAL     LATENT HEAT OF VAPORATION______________________________________Water        540 Calories per gramEthanol      204 Calories per gramMethanol     260 Calories per gramNormal butanol        141 Calories per gram______________________________________ 
    
     Table 1 shows that to evaporate water requires from two to four times the amount of energy that is required to evaporate alochol. 
     From Piotrowski U.S. Pat. No. 3,694,237, it is known that the ideal set-to-touch-time for a shellac-alcohol ink is two to four minutes. The set-to-touch-time for the inks disclosed in this patent application is from ten to 18 minutes. 
     Yet, in spite of all this evidence that teaches away from the present invention, the ink does perform very satisfactorily. The ink does not transfer from the tablet because of slow drying. 
     This aqueous ink adheres to problem substrates from which shellac alcohol inks rub off after drying. 
     One process of making the ink is a wet process in which the ink components are combined and run through dispersing mills in a liquid form. 
     Another process of making the ink is a dry process where the dry components are combined and run through a hammermill dry. The resulting dry material is combined with the liquid parts by mixing the dry material into the liquid in a blender. The resulting ink had the same properties as if it had been made by the wet process. 
    
    
     DETAILED DESCRIPTION 
     This invention is concerned with the composition of inks suitable for ingestion that are used to mark forms such as confectionery products, food, pharmaceutical tablets, and hard and soft gelatin capsules, including medicinal tablets, vitamin tablets, aspirin tablets, capsules, chewing gum balls, cereal, cookies, meats, fruit, pasta, and the like. 
     The following examples illustrate the invention with the ingredients being given in percent by weight and in grams. 
     
         ______________________________________EXAMPLE 1            Percent byIngredients      Weight    Grams______________________________________Water            49.00     2450Propylene Glycol 10.00     500Methanol         8.00      400Isopropanol      4.00      200HPMC (6 cps)     7.00      350Black Iron Oxide 22.00     1100______________________________________ 
    
     (a) In a wet method, the propylene glycol, HPMC and black iron oxide are mixed into the water, and the resulting mixture is run through a dispersing mill in liquid form for five minutes at room temperature until a fine dispersion is obtained. 
     (b) In a dry method, the propylene glycol, HPMC and black iron oxide are mixed together and then run through a hammermill dry. The resulting dry powder is then mixed into the water in a blender for about fifteen minutes at room temperature until a fine dispersion is obtained. 
     (c) The ink of Example 1(a) is placed into a bath of an offset gravure printing machine where an engraved cylinder picks up the ink as it rotates in the bath, the excess ink is wiped off by a doctor blade, and the remaining ink on the gravure etch of the engraved cylinder is transferred to a rubber transfer (offset) roller which transfers the ink onto tablets. 
     (d) The ink of Example 1(b) is poured into a bath of an offset gravure printing machine when an engraved cylinder picks up the ink as it rotates in the bath, the excess ink is wiped off by a doctor blade, and the remaining ink on the gravure etch of the engraved cylinder is transferred to a rubber transfer (offset) roller which contacts and transfers the ink onto tablets. 
     Other examples of ink that illustrate the invention and that are made in accordance with the wet method of Example 1(a) and are applied in accordance with Example 1(c), or made as disclosed in Example 1(b) and applied as in Example 1(d), are as follows. 
     
         ______________________________________EXAMPLE 2            Percent byIngredients      Weight    Grams______________________________________Water            49.00     2450Propylene Glycol 10.00     500Methanol         8.00      400Isopropanol      4.00      200HPMC (6 cps)     7.00      350FD&amp;C Blue        6.90      345Aluminum LakeTitanium Dioxide 15.10     755______________________________________ 
    
     
         ______________________________________EXAMPLE 3            Percent byIngredients      Weight    Grams______________________________________Water            49.00     2450Propylene Glycol 10.00     500Methanol         8.00      400Isopropanol      4.00      200HPMC (6 cps)     7.00      350FD&amp;C Red         19.30     969Aluminum LakeTitanium Dioxide 2.70      135______________________________________ 
    
     
         ______________________________________EXAMPLE 4            Percent byIngredients      Weight    Grams______________________________________Water            66.10     859.30Methyl Alcohol   9.50      123.50Black Iron Oxide 14.00     182.00HPMC (15 cps)    5.70      74.10Isopropyl        4.70      6.10Alcohol______________________________________ 
    
     
         ______________________________________EXAMPLE 5            Percent byIngredients      Weight    Grams______________________________________Water            66.00     924.00Methyl alcohol   11.30     158.20Propylene glycol 2.00      28.00Black Iron Oxide 14.00     196.00HPMC (15 cps)    5.00      70.00HPMC (3 cps)     0.70      9.80HPC (LF)         1.00      14.00______________________________________ 
    
     
         ______________________________________EXAMPLE 6            Percent byIngredients      Weight    Grams______________________________________Water            55.00     770.00Methyl Alcohol   14.00     196.00Propylene Glycol 2.00      28.00Normal Butyl     3.00      42.00AlcoholBlack Iron Oxide 14.00     196.00HPMC (15 cps)    3.00      42.00HPMC (5 cps)     3.00      42.00HPMC (3 cps)     3.00      42.00(HPC) Klucel LF  3.00      42.00______________________________________ Klucel LF is the LF grade of a hydroxypropyl cellulose made by Hercules, Inc. 
    
     
         ______________________________________EXAMPLE 7              Percent byIngredients        Weight    Grams______________________________________Water              80.29     1846.67Black Iron Oxide   14.00     322.00HPMC (15 cps)      5.70      131.10Anti-foaming       0.01      0.23agent (10% solution)Medicinal Antifoam(A-compound simethiconeby Dow Chemical)______________________________________ 
    
     
         ______________________________________EXAMPLE 8             Percent byIngredients       Weight    Grams______________________________________Water             61.16     795.08HPMC (15 cps)     5.70      74.10FD&amp;C Red 40 Lake  17.50     227.50Titanium Dioxide  2.50      32.50Methanol          8.79      114.27Isopropanol       4.35      56.55______________________________________ 
    
     
         ______________________________________EXAMPLE 9             Percent byIngredient        Weight    Grams______________________________________Water             61.16     856.24HPMC (15 cps)     5.70      79.80FD&amp;C Blue 1 Lake  6.21      89.94Titanium Dioxide  13.79     193.06Methanol          8.79      123.06Isopropanol       4.35      60.90______________________________________ 
    
     
         ______________________________________EXAMPLE 10            Percent byIngredients      Weight    Grams______________________________________Water            61.16     1,039.72HPMC (15 cps)    5.70      96.90Black Iron Oxide 20.00     340.00Methanol         8.79      149.43Isopropanol      4.35      73.95______________________________________ 
    
     
         ______________________________________EXAMPLE 11             Percent byIngredients       Weight   Grams______________________________________Water             66.20    926.80Methanol          9.50     133.00Isopropanol       4.70     65.80HPMC (15 cps)     5.70     79.80Titanium Dioxide  14.00    196.00______________________________________ 
    
     
         ______________________________________EXAMPLE 12            PercentIngredients      by Weight Grams______________________________________SURELEASE (E-7-  84.99     1,104.877050)polymericdispersionBlack Iron Oxide 15.00     195.00(Pigment)Anti-foaming     0.01      0.13agent (as inExample 7)______________________________________ 
    
     The ink of example 12 is heat treated at 40° C. for one hour for the film to form completely. Also, any of the commercially available suspension polymer systems may be substituted for the SURELEASE dispersion, such as Aquacoat (from FMC corporation) and Eudragit (from Rohm Pharma GmbH, Darmstadt). 
     SURELEASE dispersion is a product of Colorcon, Inc., West Point, Pa., and is a polymeric dispersion comprising ethylcellulose, dibutyl sebacate, oleic acid, and fumed silica. 
     
         ______________________________________EXAMPLE 13             Percent byIngredients       Weight    Grams______________________________________Water             60.66     788.60HPMC (6 cps)      5.70      74.00Propylene glycol  0.50      6.48FD&amp;C Red No. 40   17.50     227.50Aluminum LakeTitanium Dioxide  2.50      32.50Methanol          8.79      114.27Isopropanol       4.35      56.55______________________________________ 
    
     The vehicle for the pigment is the polymer, which acts as a binder and carrier for the pigment. 
     The preferred quantity of polymer, such as HPMC, used in producing the ingestible inks of this invention is from about 3% to 15% by weight of the ink. 
     The percentage by weight of the inks of the polymer may vary due to the viscosity ranges of the polymer. For example, hydroxypropyl methylcellulose (HPMC) has common viscosity types of 3 cps, 6 cps, 15 cps and 50 cps. The higher the viscosity, the more viscous (thicker) the ink is. By weight of the ink, 7 percent by weight of the ink of 6 cps hydroxypropyl methylcellulose has been found to be advantageous. 
     Preferably, the quantity of the pigment in the ink is approximately 5% to 30% by weight of the ink. Below 5%, printed ink is weak. Above 30%, the color of the printed ink is weak since a higher pigment-to-polymer ratio affects the ability of the ink to transfer properly. Preferably, the pigment-to-polymer ratio when using 6 cps hydroxypropyl methylcellulose is 7 parts of the 6 cps hydroxypropyl methylcellulose to 22 parts of pigment. For different grades of hydroxypropyl methylcellulose, the pigment-to-polymer ratios differ. 
     The plasticizer softens the polymer and makes it less brittle. The plasticizer also modifies the drying rate. 
     I have also found that my inks may be made without adding the customary plasticizers, propylene glycol or polyethylene glycol; the water in the system may act as a plasticizer. 
     Alcohol may be used in my ink to modify the drying rate, to help reduce foaming, to help preserve the ink, and to increase the wetability of the ink or reduce the surface tension. Above 17% by weight of the ink, the alcohol causes the ink to have a closed cup flash point below 100 degrees Farenheit, thus requiring the ink to be labeled as a hazardous flamable liquid as defined by the Department of Transportation. Methanol, ethanol, isopropynol and n-butanol are the only alcohols approved for use by the Food and Drug Administration. 
     In addition to alcohol, other preservatives may be used, such as sodium benzoate. 
     The anti-foaming agent reduces foaming while the ink is on the printing machine. The Food and Drug Administration limits the use of anti-foaming agents above 0.001% by weight of the finished ink. In addition to Medicinal Antifoam (A-compound simethicone by Dow Corning) and dimethyl polysiloxane, any acceptable food grade anti-foamer may be used in the ink, if needed. 
     When making the ink, a wet process may be used, such as the method used to make shellace type ink, disclosed in Brown U.S. Pat. No. 3,258,347. 
     Another process of making the ink is a dry process where the dry components are combined and run through a hammermill dry. The resulting dry material is combined with the liquid parts by mixing the dry material into the liquid in a blender. Previous shellac inks have not been made dry since the shellac could soften and prevent it from getting through the hammermill. 
     Advantages 
     Performance of this aqueous ink is equal to and sometimes superior to the performance of shellac based alcohol inks. Moreover, it is easier to clean this aqueous ink from the printing machine because, unlike shellac based alcohol inks which require cleaning by alcohol solvents or by highly caustic solutions, only water is needed to clean-up my inventive water-based inks from the printing machines. Accordingly, the operator exposure to alcohol cleaning solvents and their fumes is greatly reduced. 
     The inventive inks are not flammable at below 100° F. and are therefore shipped more easily. 
     The wet and dry components of my ink may be kept separate from one another until ink is needed, and this extends the shelf life of the ink. Further, the settling out problem associated with prior art liquid ink suspensions is eliminated. 
     Inks made with the shellac alcohol system that uses aluminum lakes for pigments sometimes gel in a short period of time (less than a week). This is probably due to a reaction between the shellac and the aluminum. Inks produced in my water based system have not exhibited this disadvantage.