US2678278A - Anhydrous moisture-sensitive printing ink vehicle - Google Patents

Description

Patented May 11, 1954 .ANHYDROUS MOISTURE-SENSITIVE PRINT- ING INK VEHICLE Alfred F. Schmutzler, Stamford,onn.

1N0 Drawing.

8 Claims.

"This invention relates to moisture-sensitive printing'inks comprising shellac, a liquid polyhydric alcohol, and a nitrogen-containing cornpound. The present'application is av continuation-in-part of my application Serial No. 119,023, filed September '30, 1949, now Patent No. 2,597,903, while. the latter application, in turn, is a continuation-in-part of my now abandonedapplication Serial No. 573,636, filed January 19, 1945.

.I, have disclosed in my, parent application that shellac becomes solublein liquid polyhydric. alcohols when it is neutralized with ammonia or amines and that the resulting solutions can be used: as vehicles for moisture-sensitive inks. In addition, it was disclosed inmy patent application Serial No. 119,023'thatpartial or complete neutralization of the reaction products of .shellac and a polycarboxylic acid further improves the water-tolerance of the reaction product.

My present application is based on these dis closures and deals with moisture-sensitive inks comprising a vehicle of partially neutralized shellac in aliquid polyhydric alcohol. .By introducing shellac as the binder for the'coloring material in a. printing ink, excellent toughness and hardness can be provided for the printed ink film.

Shellac has heretofore been used in several types of printing inks, such aslaniline, rotogravure, stencil and silk screen inks. All of them are quick drying and can rely on methanol, ethanol, propanol, acetone, Cellosolve, similar low boiling liquids, and even water, because they are applied by a very simple ink application system which obviates drying of the ink on the rollers. For accomplishing this: purpose, the ink distribution system contains'not more than two rollers, so that the ink does not dry before reaching the paper. In addition, avery fluid ink containing a relatively small percentage of nonvolatile matteranda relatively large. percentage of solventv is used in order to. compensate for the solvent lost on the. application system during printing; the large amount of solvent replenishes the loss due to evaporation and thus. keeps the ink printable. However, when the press is stopped for just a minute, the roller and printing plate have to be wiped cleanof dried ink,

they; have to be reset and adjusted for proper printing. With aniline and rotogravure printing presses, the final proper adjustments are carried out while the press is running, resulting in losses of aboutj100 feet of web or more. Thus, the method of printing with very quick drying inks Application February 29, 1952, Serial No. 274,277

2 involves considerable waste of printed matter.

An additional disadvantage of printing with very quick drying inks is directly related to the volatility of the solvents and the simplicity of the inking mechanism; it consists of a considerably inferior quality of printing than that obtained with slow drying inks used on more elaborate ink distribution systems with about four to ten distribution and transferrollers. The slow drying inks can be picked up from the ink fountain and smoothed out into even films so that always a uniform film can be deposited on the sheet or web of printable surface. The fast drying inks cannot be operated on such presses, as the ink would become too tacky or sticky before reaching the printing plate. Theink required for such presses must consist. essentially of. slow drying liquids. For moisture-sensitive inks, the solvents for the binder must be water-miscible and they should be poor solvents, i. e.,.they should not be so strong as to resoften the top layer of binder which has been precipitated from the ink film during steam-setting.

Some of the high boiling solvents for shellac are butyl Cellosolve, carbitol, butyl carbitol, their corresponding esters, .ethers and esters of dipropylene glycol. All of them. are considered strong solvents; inks made with them have shown the tendency to resoften after steam-setting during the gradual dissipation of the contaminating water. The. resulting disadvantages usually comprise offsetting, smearing. or smudging of the printed matter, and sticking of the sheets when stacked.

More suitable high boiling liquids are ethylene glycol. propylene glycol, butylene glycol, glycerol, diethylene glycol, and dipropylene glycol. However, these polyhydric alcohols are very poor solvents for shellac. Glycerol and ethylene glycol are solvents for shellac at elevated temperatures but non-solvents at room temperatures. The other polyhydric alcohols dissolve shellac at elevated temperatures, but the resulting solutions are very sensitive to contamination by water; just traces of water in the solvent cause the. separation of shellac. When inks are made with these solutions, no satisfactory prints can be made at even moderate humidities. Such inks are not press-stable; they form cake-like masses on the printing rollers, because shellac and these solutions have not suimcient water-tolerance.

.l'. have found that the Water-tolerance of shellac can considerably be improved so that press-stable, moisture-sensitive, shellac-containing printing inks can be made. This objective can be accomplished by dissolving the shellac in a liquid polyhydric alcohol and adding certain nitrogen containing compounds to the solution. Inks made with these solutions are press-stable.

If the solution is neutral or alkaline, shellac has the tendency to remain in solution regardless of whether a small or a large amount of water is added. Inks made from such a solution remain soft when exposed to steam or water. If the solution is still acid, indicating that not all terminal carboxyl groups have been saponified, shellac will remain in solution when a small amount of water is added but will separate when a large amount of water is added. Inks made with such a solution will form a non-offsetting layer when its printed film is exposed to steam or water. Consequently, solutions of shellac having some remaining terminal carboxyl groups will impart steam-setting properties to the inks made with them. Since shellac is essentially an ester consisting of several molecules of trihydroxypalmitic acid, it is obvious that the carboxyl group in the last radical of the chain is a terminal group. When a quantity of shellac is partially neutralized, some of the carboxyl groups are reacted with the nitrogen-containing compound, while the remainder will remain as terminal carboxyl groups.

Thus, it is one of the objects of this invention to provide for a moisture-sensitive, shellac-containing printing ink vehicle.

It is a further object of this invention to provide for a press-stable, moisture-sensitive, shellac-containing printing ink.

By introducing shellac as the binder for the coloring material, excellent toughness, adhesion, and hardness can be imparted to the printed ink films, so that those inks are suitable for glassine paper, cellophane, and other hard and flexible surfaces.

By providing for a press-stable ink, it will be possible to use it on high quality printing jobs which depend on an elaborate ink distribution mechanism of about four to ten rollers between the ink fountain and the printing plate so that the deposited ink film is of uniform thickness.

By providing for moisture-sensitivity, it is possible to harden the printed film of the slow drying ink quickly by exposing it to steam or water.

These objects can be accomplished by dissolving shellac in a liquid polyhydric alcohol containing a nitrogen-containing compound in such an amount so that not all of the carboxyl groups in the shellac are neutralized. The resulting shellac solution is a vehicle suitable for pressstable, moisture-sensitive printing inks.

Orange shellac, with an acid number of about 61, requires approximately 0.066 part of guanidine carbonate per part of shellac for the complete neutralization of its terminal carboxyl groups. Vehicles for printing inks with suitable Water-tolerance can be prepared with only 0.04 part of guanidine carbonate for every part of shellac. The amount can be reduced further with an increase in the moisture-sensitivity of the vehicle. At the very low concentrations of saponified shellac, the moisture-sensitivity becomes very good at a slight impairment of the water-tolerance.

Thus, the water-tolerance of shellac solutions in polyhydric alcohols can be improved by heating them with a salt of ammonia or an aliphatic amine.

I have further found that the water-tolerance of solutions of shellac in polyhydric alcohols can be improved by heating them with amides in an amount insufiicient to condense with all the terminal carboxyl groups of the shellac. Thus, while the reaction between ammonia, ammonium salts or amines and a portion of the terminal carboxyl groups of shellac is a saponification reaction, the amides condense with such carboxyl groups to improve the water-tolerance of polyhydric alcohol solutions of shellac. The resulting solutions, having a portion only of the terminal carboxyl groups of the shellac condensed with the amide, are particularly useful in moisture-sensitive printing inks.

The following examples serve to illustrate preferred embodiments of moisture-sensitive printing inks formed by condensing amides with shellac in a polyhydric alcohol solution. The proportions in the examples denote parts by weight:

Example I 6.0 parts of urea, 20.0 parts of shellac, 34.0 parts of diethylene glycol are heated together at about C. The resulting solution is mixed with 15.0 parts of Victoria blue toner and 15.0 parts of diethylene glycol, and the mixture is milled until it is suitable for a printing ink.

Example II 3.5 parts of formamide, 25 parts of shellac, and 53 parts of diethylene glycol are stirred at C.,until a uniform solution is formed. The time required is about 5 hours. The cooled solution can be mixed and milled with 20 parts of carbon black for making a suitable black printing ink.

Example III 0.6 part of dicyandiamide, 20 parts of shellac, and 39.4 parts of diethylene glycol are stirred at 90 C. until a uniform liquid is formed. The resulting solution is cooled to room temperature and mixed with 15 parts of diethylene glycol and 25 parts of Lithol red.

Example IV '1.5 parts of acetamide, 20.0 parts of shellac, and 38.5 parts of diethylene glycol are heated for about two hours at 150 C. until a uniform solution is formed. The resulting solution is a suitable ink vehicle, with a water-tolerance and press-stability better than that of a shellac solution without acetamide. The modified shellac in this solution is reactive with aldehydes.

Example V 6.0 parts of diethylformamide, 20.0 parts of shellac, and 34.0 parts of butylene glycol are heated at C. until a uniform solution is formed. The resulting solution is cooled and mixed with 30.0 parts of chrome yellow pigment; and the mixture is milled until suitable for an ink.

Example VI 3.0 parts of butyramide, 20.0 parts of shellac, and 27.0 parts of diethylene glycol are heated at 120 C. until a uniform solution is formed. The resulting solution is cooled, mixed with 40.0 parts molybdate orange, and the mixture is milled until homogeneous.

Example VII 3.0 parts of N, N-diethyloxamide, 20.0 parts of shellac, and 27.0 parts of propylene glycol are heated at 120 C. until a uniform solution is formed. The resulting solution is cooled, mixed with 15.0 parts of carbon black, 5.0 parts of poW- dered alkali blue toner, and 30 parts of propylene -glycol,.:and'-the mixture is milled .until homoeneous.

' Example 'VIII ei.0' -parts.ofphthalamide, 20.0 partsof shellac,

.and 136.0 parts of dipropylene glycol arev heated -6.0.- parts ofurea, 20.0-parts of shellac, and 34.;0 parts-of propylene glycol areiheated together at about 110 C. The resulting solution is cooled and mixed-With.15-.0 parts of phtha-locyanine blue pigment, 4.5 parts of powdered paraformaldehyde, ,and 10.5 partspropylene glycol; and the mixture is milled until suitable for a printing: ink.

The resulting ink can beused as a. steam-set, heat-set or air drying ink, or it can be used for printing on pie-moistened paper which, after printing, is exposed to heat with theobiect of evaporating excessmoisture in the paper. Dur-' ing the formation of steam on the surface of the paper, the printed film will be hardened by the water vapor, and fast setting of theprint Will be accomplished. In additiomto the steam-setting hardening, urea and paraformaldehyde will react in the presence of! the moistureto cure to a very hard resin.

Instead of urea, some other amide such as dicyandiamide may .beincorporated in such an ink. Instead of. paraiormaldehyde, .othercondensation products .of aldehydes, such as hexamethylenetetramine, trioxane, furfuramide, hydroxymeth- 'ylnitromethane, .hydroxymethyl-Zenitroethane, or other condensation, productsof nitroalkanes and an aldehyde, or the like. Such condensation products have the tendency :to regenerate the aldehyde. When incorporated in a printing ink, which is hardened by heat or steam or a combination of moisture and heat, the regeneratedaldehyde will react with compounds like urea, dicyandiamide, -melamine, guanidine, phenol, and amides with the formation of resinous products.

A'further group of moisture-sensitiveprinting inks may be prepared by-condensing an imide with a portion of the terminal carboxyl groups of shellac,-theshellac being dissolved in a liquid polyhydric alcohol. 'The following examples illustrate preferred types of printing inks thusprepared:

Example X 1.13-parts of guanidine carbonate, 201parts of shellac/and 88.7 partsof diethylene-glycol are agitated -at:6-0 C.untilithe liquid 'becomes uniform. This process will take aboutthreehours with regular flakes'oforangeshellac. It-can considerably be shortened'by using powdered shellac or by using a moreelevated temperature.

The-resulting solution can be-used as anrink vehicle for a redink by mixing andmilling-it with parts of diethylene glycoland. parts of the: pigment Lithol red.

Example XI 0.6 part of guanidine carbonate, "20.0 parts of orange shellac and'39A parts diethylene glycol are stirred at 60 C. until a uniform'liquid is formed. This process will take about'four' hours with regular flakes of .orangeshellac. It canv considerably be shortened by using powdered shellac or by usinga more elevated-temperature.

The resulting .solution can be used. l in an :ink as. shownv in ExampleX.

The ink made with Example XIwas nearly :as press-stable as thatmadewith-Example X; however, the ink of Example XI set more readily than that of E xampleX.

It is understoodthat the imido groupecontaining compound, tne polyhydric alcohol and the pigment may be substituted, thus permitting many difierentvariations in the vehicles and inks which can be made. Additional variationsare possible by changing the type of shellac; instead of orange shellac, white, bleached, or dewaxed shellac can be used. Further variations canbe made in the different ratios, suchas shellacto diethylene glycol, pigment to shellac, and. pigment to .polyhydric alcohol.

Example XII 6.0 parts of Nebutyl phthalimide,20.0 parts of shellac, and 34.0 parts of diethylene glycol are heated at 180 C. for 2 hours. The resulting solu- Example XIII 0.3,part of ammonia is passed bymeans ,of .a gasrdelivery tube into a-Warm solution of. 20 parts of. shellac in 30.0 parts. of diethylene. glycol. The resulting solution is mixed with18.0 parts phthallocyanine green pigment and.32.0 parts of ethylene glycol.

Thev resulting printing, inkhasexcellent pressstability; it can belhardenedby steam or water or it-can be dried by letting theglycols dissipate by evaporation andpenetration into the paper.

Other nitrogenecontaining compounds which react withthe carboxyl groups oijshellacto yield a moisture-sensitive printing ink include amines, specifically aliphatic amines and aralkyl amines. Anamount of an: amine insufl'lcient to saponify all the terminal carboxyl. groups of shellac is employed. The reaction appears to be a saponification reaction as distinguished from the condensation reactionoi amides and imides. .Thefollow. ing examples illustrate printinginks prepared by reacting amines polyhydric alcoholsolutions of shellac:

Example XIV 0.5 part of ethylene diamine, 25.0 parts of shellac, and 53 parts of diethylene glycol are agitated at 140C. for hour or until solution has taken place. The resulting solution is mixed with 20 parts of carbonblack, and the mixture is milled until suitable for a printing ink.

Example XV 0.6 part of ethylenediamine, 20.0 parts of shellac, and 39.4 parts of ethylene glycol are stirred at about "C. until a homogeneous solution is formed. The resulting solution is mixed with 18.0partsofcarbon' black, 2=0-parts 7 of iron blue pigment, and 20.0 parts of ethylene glycol; and the mixture is milled until suitable for a printing ink.

Example XVI 1.8 parts of triethylamine. 20.0 parts of shellac, and 38.2 parts of propylene glycol are stirred at about 50 C. until a uniform solution is formed. The resulting solution is a suitable vehicle for heatand steam-setting printing inks.

Example XVII 1.9 parts of cyclohexylamine, 20.0 parts of shellac, and 38.1 parts of glycerol are heated and mixed at 90 C. for 2 hours. The resulting solution is mixed with 15 parts of Victoria blue dyestuff and 5.0 parts of glycerol. The resulting dye solution is a suitable moisture-sensitive printing ink.

Example XVIII 1.8 parts of cyclohexylamine, 20.0 parts of shellac, and 38.2 parts of diethylene glycol are stirred at 60 C. until a homogeneous solution is formed.

Example XIX Example XX 1.5 parts of amylamine, 200 parts of shellac, and 38.5 parts of ethylene glycol are stirred at about 100 C. until a uniform solution is formed. This process takes about hour. The resulting solution is diluted with 20.0 parts of ethylene glycol and mixed with 20.0 parts of benzidine yellow pigment. The resulting mixture is milled until suitable as a printing ink.

This ink is suitable as a moisture-sensitive printing ink; and it can also be used as an ink which can be dried by exposure to moderate heat. Its water tolerance is high enough so that it can be printed on premoistened paper with the object of hardening the printed ink Example XXI 1.5 parts of amylamine, 20.0 parts of shellac, and 38.5 parts of diethylene glycol are stirred at about 100 C. until a uniform solution is formed. This process takes about 20 minutes. The resulting solution, diluted with more diethylene glycol and mixed with any of the aforementioned pigments can be used in a moisturesensitive ink.

Example XXII 1.3 parts of butylamine, 20.0 parts of shellac, and 38.7 parts of propylene glycol are heated at about 90 C. until a homogeneous solution is formed. Theresulting solution is mixed and milled with 27.0 parts of iron blue pigment and 13.0 parts of propylene glycol.

The resulting ink can be used as a moisturesensitive ink to be hardened by exposure to steam or as a heat-setting ink to be hardened by exposure to high temperatures for a short period of time or it can be used as a combination of moisture-set and heat-set by printing it on premoistened paper and then exposing it to a high temperature for a short time.

Example XXIII 5.0 parts N-acetylbenzylamine, 20.0 parts of shellac, and 35.0 parts of diethylene glycol are heated for about two hours at 150 C. for the formation of a uniform solution. The resulting solution is a suitable printing ink vehicle.

I have further found that the water-tolerance of shellac in polyhydric alcohols may be improved by heating them with salts of ammonia. Examples of printing inks thus prepared are as follows:

Example XXIV 2.0 parts of ammonium nitrate, 20.0 parts of shellac, and 38.0 parts of diethylene glycol are agitated at 140 C. for two hours. The resulting solution is cooled, mixed with 25 parts of Rhodamine phosphotungstic toner, and the mixture is milled until suitable for a printing ink.

Example XXV 2.0 parts of ammonium thiocyanate, 20.0 parts of shellac, and 38.0 parts of diethylene glycol are stirred at C. until a homogeneous dispersion is formed. The time required is about 5 hours. The resulting dispersion is mixed and milled with 15.0 parts of diethylene glycol and 25.0 parts of benzidine yellow pigment for making a yellow printing ink.

Example XXVI 2.0 parts ammonium oxalate, 20.0 parts of shellac, and 38.0 parts of diethylene glycol are stirred at C. until a homogeneous dispersion is formed. The time required is about one hour. After cooling, the dispersion is mixed and milled with 10 parts of diethylene glycol and 30 parts of iron blue pigment, in order to make a blue ink.

In steam-setting printing inks, diethylene glycol is the preferred solvent, though dipropylene glycol, butylene glycol, propylene glycol, ethylene glycol, and glycerol can also be used. Among these polyhydric alcohols, the simple glycols are useful for printing inks which are interchangeable for steam-setting or heat-setting or for a combination of both methods.

The principle of steam-setting inks depends upon a vehicle which is stable when it is diluted with a small amount of water, such as will be absorbed by the polyhydric alcohol on a humid day, but which is unstable when a large amount of water is added. In order to satisfy this condition, not all of the free carboxyl groups in shellac should be reacted but some should remain as terminal carboxyl groups. When such a solution is diluted with a small amount of water, the resulting hydrogen ion concentration will correspond to a pH of less than 7.0.

The nitrogen-containing compounds, present in an amount insufiicient to react with all the free carboxyl groups present in shellac, react with the shellac to give a product having a pH less than 7.0 suitable for use in moisture sensitive printing inks, although the mechanism of the reaction with different classes of compounds is different. Thus, the reaction with amines and ammonia is a saponification or neutralization reaction, while the amides and imides condense with the free carboxyl groups.

When a steam-setting or moisture-sensitive ink is printed with a vehicle which has a pH of less than 7.0 when diluted with water, it is laid down on the printable surface as a soft plastic film. Upon the exposure to steam or moisture, a solid non-offsetting, thin layer is formed on top of the otherwise soft plastic film, thus preventing the ink from smearing, smudging and trans ferring.

While I have described my invention in its preferred embodiments, it will be apparent that various modifications and departures may be made by those skilled in the art, and it is intended that all such variations be included within the spirit and scope of the appended claims.

I claim:

1. A substantially anhydrous moisture-sensitive printing ink vehicle stable to small amounts of water but insoluble in an unlimited amount of water comprising a liquid polyhydric alcohol and a reaction product of shellac and a nitrogen- I containing compound selected from the class consisting of amides and imides, amines, said nitrogen-containing compound being present in an amount insufficient to react with all the free terminal carboxyl groups of said shellac and said nitrogen-containing compound being an organic compound containing no elements other than nitrogen, hydrogen, oxygen and carbon and having a molecular weight of from about 17 to 220.

2. A moisture-sensitive printing ink vehicle set forth in claim 1 wherein said liquid polyhydric alcohol is diethylene glycol.

3. A moisture-sensitive printing ink vehicle set forth in claim 1 wherein said nitrogencontaining compound is an amide.

4. A moisture-sensitive printing ink vehicle set forth in claim 1 wherein said nitrogen-containing compound is an imide.

5. A moisture-sensitive printing ink vehicle set forth in claim 1 wherein said nitrogen-containing compound is an amine.

6. A substantially anhydrous moisture-sensitive printing ink vehicle stable to small amounts of water but insoluble in an unlimited amount of water comprising diethylene glycol and the reaction product of shellac and urea, the urea being present in an amount insufficient to react with all the free terminal carboxyl groups of said shellac.

7. A substantially anhydrous moisture-sensitive printing ink vehicle stable to small amounts of water but insoluble in an unlimited amount of water comprising diethylene glycol and the reaction product of shellac and guanidine carbonate, the guanidine carbonate being persent in an amount insufficient to react with all the free terminal carboxyl groups of said shellac.

8. A substantially anhydrous moisture-sensitive printing ink vehicle stable to small amounts of water but insoluble in an unlimited amount of water comprising diethylene glycol and the reaction product of shellac and cyclchexylamine, the cyclohexylamine being present in an amount insuflicient to react with all the free terminal carboxyl groups of said shellac.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 199,883 Wells Jan. 29, 1878 2,245,100 Bernstein June 10, 1941 2,323,710 Erickson et al July 6, 1943 FOREIGN PATENTS Number Country Date 376,413 Great Britain July 14, 1932

Claims (1)

1. A SUBSTANTIALLY ANHYDROUS MOISTURE-SENSITIVE PRINTING INK VEHICLE STABLE TO SMALL AMOUNTS OF WATER BUT INSOLUBLE IN AN UNLIMITED AMOUNT OF WATER COMPRISING A LIQUID POLYHYDRIC ALCOHOL AND A REACTION PRODUCT OF SHELLAC AND A NITROGENCONTAINING COMPOUND SELECTED FROM THE CLASS CONSISTING OF AMIDES AND IMIDES, AMINES, SAID NITROGEN-CONTAINING COMPOUND BEING AN ORGANIC AN AMOUNT INSUFFICIENT TO REACT WITH ALL THE FREE TERMINAL CARBOXYL GROUPS OF SAID SHELLAC AND SAID NITROGEN-CONTAINING COMPOUND BEING AN ORGANIC COMPOUND CONTAINING NO ELEMENTS OTHER THAN NITROGEN, HYDROGEN, OXYGEN AND CARBON AND HAVING A MOLECULAR WEIGHT OF FROM ABOUT 17 TO 220.