US 2755202 A
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United States Patent STABILIZED COLORENG COMPOSITIONS AND METHQDS OF MAKING AND USING SAME Walter Jean Balon, Carneys Point, and Otto Stallmann, Bridgeton, N. 1., assignors to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application September 17, 1954, Serial No. 456,887
19 Claims. (Cl. 117-36) :se but are adapted to develop the desired color in situ when put to a practical use. More particularly, this invention deals with novel colorless coloring agents or coloring compositions which are adapted to yield triarylmethane colors in situ after having been deposited in a suitable pattern upon paper in a process such as typing, writing or duplicating from a spirit-hectograph master sheet. In its broader aspects, this invention encompasses further novel coating inks, carbon paper, typewriter ribbon and similar transfer media containing as principal source of color a colorless coloring agent of the mentioned type.
It is an object of this invention to provide coloring agents for the purposes above indicated which are per se colorless, or at least non-staining, with the result that these coloring agents, or transfer media carrying these agents (for instance typewriter ribbon, carbon paper or hectograph master sheets) will not stain the hands or clothes of persons who necessarily have to come in contact with said coloring agents or carriers in practical use.
Another object of this invention is to provide coloring agents of the character mentioned in a physical form which will not spread noxious or staining dusts in the course of their being incorporated into the necessary carriers, such as coating inks, typewriter ribbons or duplicating paper. A still further object of this invention is to provide the coloring agents needed for preparing the coating film, in the process of making duplicating paper, in a form which will facilitate such incorporation and produce coating films of desirable viscosity or so-called working properties. ments of this invention will appear as the description proceeds.
X By spirit hectograph printing, in this specification, we mean multi-copy duplication from a master sheet which carries a heavy imprint of a reverse image of the desired writing. Copies are made from this master sheet by bringing copy sheets successively into contact with the imprinted face of the master sheet, usually in some form of a rotary-cylinder machine. Contrasted with this multicopy duplication process are the single-copy processes, as for instance in ordinary typing with carbon copies, wherein each duplicating sheet produces but one copy, although of course several copy sheets and coated transfer sheets may be stacked up behind each other so as to produce several copies by a single impression or typing.
In the carriers for producing master sheets, for instance hectograph carbons and typewriter ribbons, as well as in the transfer sheets for ordinary typing with carbon copies, the colors of the triarylmethane series have come to be recognized as the standard coloring matters. reason for this lies firstly in the intensity of their color, and secondly in their ready solubility in water and alco- Various additional objects and achieve- The 2,755,202 Patented July 17, 1956 hols, which facilitates their transfer from the master to a copy sheet moistened with these liquids.
A particularly popular group of colors within the mentioned broad family of triarylmethanes is the group of NpOIyalkyI-tri(p-aminophenyl) methanes which generally occur in commerce in the form of chlorides. Methyl violet, crystal violet and ethyl violet are common commercial members of this group, but it may embrace also other poly lower-alkyl derivatives such as propyl, isopropyl, n-butyl, isobutyl, benzyl or mixed alkyl and aralkyl radicals, the word poly being here used to indicate the presence of not less than 5 and not more than 6 such lower alkyl or aralkyl radicals per molecule. This particular subgroup of colors has gained a strong foothold in the mentioned art, because of its reasonable price,
and outstandingly high tinctorial strength, being capable of yielding as many as 500 readable hectograph copies from one master sheet.
On the other hand, the mentioned group of colors have the great drawback of coming easily ofi the coating onto the hands of the typist or the operator of the duplicating machine, and of producing tenaciously adhering stains upon their skin or clothes. Such stains do not wash oif readily with soap and water. Another vital objection is that crystal violet and methyl violet as currently produced occur on the market in the form of fine powders, which have tendency to spread noxious and staining dusts during the process of their incorporation into oily or waxy vehicles in the plants which manufacture transfer sheets and typewriter ribbon.
line 0.1. #676).
The group of colors hereinabove discussed produces copies of dark-blue to violet shades. Coloring compounds of other shades, however, are also of considerable interest in the trade. Other shades of blue are obtainable by diphenylnaphthyl-methane compounds typified by Victoria blue (C. I. #728). These compounds have dialkylamino or N-methyl-N-benzylamino radicals in the phenyl nuclei, para to the methane C-atom, and a mono or dialkylamino or a phenylamino group in the naphthyl nucleus in position para to the methane C-atom. Greens are generally obtainable by alkylated diamino-triphenyl methane compound, typified by Malachite green (C. I. #657). Reds are generally found in the non-alkylated triamino-triphenyl-methanes, as typified by para-rosani- Finally, the market is greatly interested in black duplication media, which shades are generally obtainable by mixing properly selected representatives of the reds, greens, blues and violets aforementioned, in proper proportions, sometimes with the addition of a non-triphenybmethanc type shading color, for instance an orange or yellow azo dye.
in all these cases, the practical interest is limited to colors which are compatible with waxy and oily media, these being generally the liquid or liquifiable vehicles employed for producing the coatings on the carbon sheets or similar transfer media. This implies freedom of the color from sulfo, carboxy and hydroxy groups. The colors selected are generally soluble in ethanol, methanol or dioxane, and are generally spoken of as spirit-soluble colors.
Triarylmethane colors, however, are generally watersoluble in their salt form, which is the customary commercial form of these colors. Moreover, they seem to have a strong affinity for the human skin. Consequently, the triphenylmethane colors as a class have the noxious property of producing tenacious stains upon the human skin. By contrast, the mentioned yellow and orange s shading colors of the azo classes can easily be washed ofithe skin. Accordingly, these auxiliary colors will be referred to hereinafter as non-smudging colors, whereas the various colors of the triarylmethane class must be considered as smudging colors.
This invention contemplates solving the above problems of smudging and dusting by producing the mentioned coloring substances in an intermediate, colorless form, which however will develop the desired intense color upon being transferred to the copy. More particularly, this invention contemplates coating the transfer medium (carbon paper or typewriter ribbon) with a nonsmudging coloring composition whose principal coloring component is a colorless leuco form of a triaryl methane compound, producing thus a relatively colorless, nonsmudging carbon paper or typewriter ribbon. If the transfer medium has no color of its own, and if the coloring composition contains nothing but triaryhnethane coloring matters, the sheet or ribbon will be essentially white. If the carbon paper has pigment imbedded in it, or if the typewriter ribbon has been dyed, the transfer medium will have the corresponding background color. Finally, if the coloring composition contains a nonsmudging shading color of the azo class or other nontriarylmethane type color, the transfer medium will have the respective color, which, however, will not stain the fingers tenaciously. These relatively colorless or non smudging transfer media are contemplated for use in the ordinary manner, except that provision is to be made for developing the colorless imprint into a colored image by the action of acid and oxidizing agents, as more fully set forth hereinafter.
To illustrate what we mean, we give here the formulas for ethyl violet (the color itself or salt form), its carbinol (sometimes called carbinol base) and its leuco form (sometimes referred to as leuco-base or methane form).
These forms represent in inverse order three stages in the synthesis of the color, although some processes of manufacture give directly the color without forming, or at least without isolating, either or both of the intermediate stages.
Similar formulas may be drawn for all other colors of triarylmethane class, but for the sake of clarity, the discussion hereinbelow will be confined to ethyl violet or the subclass of polyall-tyl-triarnino-triphenyl-methanes, as typical representatives of the entire class.
When isolated in pure form, in small quantities on a laboratory scale, the leuco form is colorless. This state, however, is unstable and quickly becomes converted into color, presumably by absorbing oxygen and CO2 from the atmosphere. It is known that light has a strong catalytic effect on this conversion, and the process has been referred to in the literature as a case of photochemical oxidation. Whatever the explanation be, it is a fact that the leuco bases of hexaalkyl triamino triphenyl methane colors, for instance, do not occur in commerce except in laboratory-scale quantities. When they are produced on a large scale in the plant, they are invariably obtained as violet colored products. Consequently, the use of these leuco bases as hitherto manufactured does not solve the aforementioned problems of staining and dusting.
Now we have found that the leuco-bases of triaryl methane colors may be decolorized and stabilized against discoloration on exposure in bulk to the atmosphere by associating the same with certain organic bases as more fully set forth hereinbelow under the conditions indicated hereinbelow. Furthermore, this stable composition nevertheless yields readily to simple treatment with various oxidizing agents, under acidic conditions, to produce the corresponding colors.
As a consequence, the novel leuco-base compositions of the mentioned colors, prepared according to this invention, are ideally adapted for the purposes hereinabove discussed, that is, production of non-staining coatings on transfer media for duplication processes.
The novel stabilizing treatment hereinabove indicated comprises, first of all, crystallization or precipitation of the mentioned leuco compounds from their solutions in organic solvents to obtain them in a state free of nontriarylmethane-type, colored by-products. Secondly, the purified compound is treated, in the very process of purification or in a separate step, with a small quantity of a quaternary nitrogenous base, which acts as a stabilizing agent. As convenient illustrations of quaternary nitrogenous bases suitable for this purpose may be mentioned: benzyl-trimethyl-ammonium hydroxide, tetramethyl ammonium hydroxide, phenyl-dimethyl-benzylammonium hydroxide, and choline (Z-hydroxyethyl-trimethyl-ammonium hydroxide). Other quaternary nitrogcnous bases possessing short-chain aliphatic groups are also suitable, for instance the reaction product of epichlorhydrin and ammonia produced according to U. S. P. 1,977,251. Although the patent formulates the product as a secondary amine, more recent researches have revealed that the product is essentially a quaternary base.
In general it seems that any polyalkyl ammonium hydroxide is suitable for our invention, or derivatives thereof wherein one or more of the alkyl groups are replaced by hydroxyalkyl, epihydrin, cycloalkyl, aralkyl or aryl radicals, or the N-atoms may be part of a heterocyclic ring. The only restriction upon the ammonium base is that it be soluble to a workable degree in the selected organic solvent.
The function of the quaternary nitrogenous base is not clearly understood. The base, of course, will act to convert to the colorless carbinol form any color (salt form) present in the leuco mixture as a result of photochemical oxidation. But the base apparently, or else the resulting trace of arbinol, also acts somehow to overcome the catalytic effect of light on the leuco compound and retards or totally stops the process of air oxidation of the leuco compound.
It is noted in this connection that the quantity of quaternary base required for stabilization need not be very large. A quantity of the base corresponding in weight to from 0.2 to 5% of the Weight of the leuco compound is generally sufiicient. A good rule to follow is to add sufiicient base to give the resulting coloring agent a pH of 8 or higher when measured in a 1% solution or suspension thereof in ethanol at room temperature. Larger quantities, however, may be added subject to two limiting considerations. Firstly, when the quantity of base incorporated into the leuco compounds is too large, say over 10% by weight, it is apt to have a hydrolyzing effect on the wax to be added later as filmforming vehicle for producing a coating ink for a transfer sheet. Secondly, the higher the alkalinity of the stabil ized leuco compound, the more acid or special organic reagent will be required in the subsequent reconversion of the leuco compound into color, in the process of developing the printed copy.
As concerns the leuco compound being treated, the same may be obtained from several sources:
In the case of dyes now occurring in commerce, for instance ethyl violet or crystal violet, a ready source is the dye itself. This is subjected to alkaline reduction, as for instance by means of alkaline sodium hydrosulfite or by means of zinc and acid to produce the leuco base. The treatment of the latter with quaternary ammonium base may then be incorporated in the reduction process just prior to isolation of the leuco compound, or it may he applied to the isolated compound.
A more economical and preferred process is to synthesize the leuco compound directly from lower inter mediates. This process is especially useful in the case of hexaalkyl-triamino-triphenyl methane compounds which do not occur in commerce and must be synthesized specially. It is also of special merit in the case of triarylmethanes which are otherwise difiicult to obtain in a state free of non-reducible, colored by-products. When this preferred process is used, the quaternary base may be added to the reaction mass in which the leuco compound has been produced, or the latter may be isolated and then treated with the base.
When applied to the isolated leuco compound, the treatment generally involves dissolving the leuco compound in an organic solvent, adding an aqueous solution of the selected quaternary base, heating until the color of the original solution disappears, then cooling to crystallize or precipitate the color, followed by filtering or decanting and drying. Suitable solvents for the above purpose are polar organic solvents such as the lower primary, secondary or tertiary alcohols (1 to 5 C-atoms per molecule), the lower monoalkyl ethers of ethylene glycol (Cellosolves), the lower monoalkyl ethers of diethylene glycol (Carbitols), acetone or dioxane, as well as the common non-polar solvents for instance the aromatic hydrocarbons and chlorinated hydrocarbons of the henzene series.
As in other chemical processes, heating the mass during the above treatment is desirable, because it increases the solubility of the leuco compound in the solvent chosen, thereby diminishing the required quantity of the latter. Temperatures above 120 C., however, should be avoided to prevent possible decomposition of the quaternary ammonium base. In some instances, heating may be avoided altogether, for instance by dissolving the colored crude leuco compound in benzene, adding the quaternary base in the form of an aqueous solution and then adding a limited amount of alcohol to effect precipitation of the colorless leuco compound either in the form of crystals or as a viscous, resin like product.
Combinations of the several procedures indicated, or multiple treatments of the leuco compound with the base may, of course, also be applied.
While the above modes of procedure apply in general to all commercial or specially synthesized triarylmethane compounds, it will be noted here that the intended ultimate use of the coloring agent may nevertheless influence the choice of particular compound. If the intended use is for preparing transfer sheets for spirit hectograph duplication in reddish blue or violet colors, leuco ethyl violet and compounds whose N-alkyl groups average more than 2 C-atoms per alkyl group are to be selected. The reason for this is that the film on the transfer sheet for hectograph duplication requires a very high concentration of color, often reaching 40 to 60% by weight of the entire waxy coating composition. We find that leuco ethyl violet and its hi her homologs are sufficiently soluble in the common wax vehicles for this purpose (e. g., carnauba wax, montan wax or cetyl alcohol), or else, sufficiently low melting, to permit the production of coating films of such high color content without special difficulties. To put it in different words, the working properties of leuco ethyl violet and its higher homologs are ideal for the preparation of transfer coatings, both in high color concentration and in low concentration. The leuco forms of crystal violet and methyl violet do not have this ideal property, but are suitable for coating single-copy transfer sheets, wherein the required color concentration is seldom higher than by weight, and more commonly of the order of 2 to 5%. Similar considerations will guide the choice in the case of other colors of the triarylmethane class.
As far as we have learned hitherto, the primary stabilizing effect is limited to quaternary ammonium compounds as above defined. Other bases, for instance potassium carbonate or sodium hydroxide do not achieve this effect. On the other hand, the effect of the quaternary ammonium bases named above is powerful enough to protect the leuco compound for many months and is suf icient for all practical purposes. Nevertheless, coating with additional protective agents as set forth, for instance, in our copending application Serial No. 400,776, may be resorted to if desired.
Without limiting our invention, the following examples are given to illustrate our preferred mode of operation. Parts, proportions or percentages, where mentioned, are by weight.
PART I.PREPARATION OF THE COLORING AGENTS Group A.-Vi0lets and blues-reduction of commercial color EXAMPLE 1 To a solution of 50 parts of ethyl violet (C. I. 682) in 800 parts of ethyl alcohol at reflux temperature, a solution of 63 parts of sodium hydrosulfite in 280 parts of Water and 1 part of zinc dust were added alternately in small portions. When complete decolorization was achieved, dilute aqueous ammonia (3.6%) Was fed in slowly until a total of 115 parts have been entered and the reaction mixture no longer developed cloudiness upon further addition of ammonia. The reaction mass was then cooled, and the separated white solid was filtered off, washed first with 50% ethyl alcohol, then with water and vacuum dried at 50 C.
42 parts of the above dry product were dissolved in 400 parts of boiling ethyl alcohol containing 3 parts of a 36% solution of benzyltrimethylammonium hydroxide in water. The mass was then cooled to room temperature, and the precipitated product Was filtered off and dried at 50 C. in vacuo. The white crystalline plates thus obtained melted at to 96 C., and analyzed 9.45% of nitrogen. (Theoretical content is 9.19%.) When 1 part of this product was slurried in 99 parts of 95% ethanol at 25 C. the slurry had a pH of 8.45, as measured by a Beckman pH meter. The pH of the ethanol itself was 7.5.
The colorless leuco ethyl violet composition obtained above remained white on storage for more than 8 months in a bottle exposed to daylight, and did not stain the skin and clothing of people who handled it. When treated with a solution of chloranil in dioxane, the product is rapidly reconverted into the original color. Further details on this conversion and on the mode of using the novel composition of this example for producing duplicating formulations, are given in Examples 23 to 28 below.
EXAMPLE 2 The procedure of Example 1 was repeated except for using 50 parts of crystal violet (C. I. 681) in lieu of the ethyl violet there mentioned. Stabilized leuco crystal violet was obtained in the form of colorless plates, melting at 178 to 179 C. This product had the same properties and utility as that of Example 1, and its pH value, measured by the same method as in Example 1, was 8.8.
Group B.Violets and bluessynthesis from a benzaldehyde compound and 2 moles of an aniline compound EXAMPLE 3 To a rapidly stirred mixture consisting of 71 parts of p-diethylaminobenzaldehyde, 25.2 parts of urea and 125 parts of diethylaniline in 174 parts of isopropyl alcohol, 43 parts of 93% sulfuric acid were added slowly at a temperature of 25 to 30 C. The stirred mixture was heated to 79 to 80 C. and held at this temperature for a period of 16 hours, after which it was diluted with 237 parts of isopropanol and 186 parts of water. After cooling the reaction mass to 30 C., parts of 30% sodium hydroxide solution were added slowly and were followed by 1 part of a 50% aqueous choline solution. This made the reaction mass just alkaline to brilliant yellow paper. Stirring was then continued for a period of 3 /2 hours. The leuco ethyl violet which crystallized out in admixture with some sodium sulfate was filtered off, stirred for /2 hour in 700 parts of water containing 0.5 part of choline, filtered off, sucked well and dried.
The product thus obtained (143 parts) was recrystallized from 1100 parts of alcohol containing 0.5 part of EXAMPLE 4 The procedure of Example 3 was repeated, except that the 125 parts of diethylaniline were replaced by 139 parts of Ndiethyl-o-toluidine. A colorless composition of similar characteristics was obtained.
EXAMPLE 5 Calls C 2H5 A mixture of 44.3 parts of p-diethylaminobenzaldehyde, 18 parts of urea, 108 parts of N-ethyl-N-benzylaniline, 40.8 parts of 96% sulfuric acid in 160 parts of isoproponal was stirred at 83 to 84 C. for 20 hours.
The reaction mass was then diluted with 80 parts of isopropanol and 90 parts of water, cooled below 50 C., and the sulfuric acid was neutralized with 30% aqueous sodium hydroxide. The neutral mass was agitated with 2.5 parts of a 36% aqueous solution of benzyltrimethylammonium hydroxide until the separated leuco compound became essentially colorless. The aqueous layer was decanted off and the remaining viscous mass was agitated with 500 parts of hot (70 C.) water and 2 parts of 36% benzyltrimethylammonium hydroxide solution for 1 hour. After separation from the aqueous layer, the product was dissolved in 240 parts of benzene, and the solution was dried over solid NaOH and filtered. The benzene was then evaporated off, leaving 140 parts of stabilized leuco compound of the above structure, which did not solidify on standing. The product remained colorless after exposure to light and the atmosphere of the chemical laboratory for a period of several months.
The leuco compound obtained above was compatible with the usual hectograph formulations, giving colorless master sheets from which strong and bright violet-blue shade copies were obtained by the spirit duplicating process, using a 1% solution of chloranil in a 50:50 ethanol-dioxane solution as the developer.
EXAMPLE 0 To a rapidly stirred mixture of 18 parts of p-diethylaminobenzaldehyde, 6.4 parts of urea and 34 parts of N-ethyl-N-(betahydroxyethyl)-o-toluidine in 120 parts of isopropanol, 10.9 parts of 96% sulfuric acid were added slowly at a temperature of 25 to 30 C. The mixture was heated in one hour to a temperature of 79 to 80 C. and held at this temperature for a period of 16 hours, after which it was diluted with 46 parts of distilled water. After cooling the reaction mass to a temperature of 30 C., 28.5 parts of a 30% sodium hydroxide solution and 2 parts of 36% benzyltrimethylammonium hydroxide solution were added slowly.
The reaction mass, which was just alkaline to Brilliant Yellow paper, was then subjected to a steam distillation to remove the isopropanol and other volatile impurities. The cooled oily residue was extracted with 150 parts of ether containing 1 part of 36% benzyltrimethylammonium hydroxide solution. The ether extract was dried over anhydrous sodium carbonate and the ether was then evaporated off on a steam bath. The residual product was a pale yellow viscous oil, and is believed to be an unsymmetrical hexaalkyl-triamino-triphenyl methane of the following formula:
CH CH3 HOCHzCHz I l GHZCHZOH The leuco compound prepared above was stable against color formation on exposure to light and air and showed excellent compatibility in hectograph vehicles.
Unlike the leuco compounds from crystal violet or ethyl violet, the product of this example was found to be very soluble in most common solvents at room temperature, even in cold ethanol and in a mixture of 60% isopropanol and 40% water. A 1% solution of this stabilized leuco compound in ethanol showed a pH of 8.6 at 26 C., as compared with a pH of 7.8 for the solvent alone under similar conditions.
A test portion of this leuco compound when treated with chloranil in dioxane, was converted to the corresponding triphenylmethane color of a bluish violet shade.
EXAMPLE 7 To a mixture of 4-2 parts of N-beta-cyanoethyl-N- methyl aniline, 22 parts of p-diethylaminobenzaldehyde, 7.5 parts of urea and parts of isopropanol, l3.3 parts of 93% sulfuric acid were added slowly, with agitation at 30 to 40 C. The mixture was heated within 1 hour to 78 C. and held at 78 to 80 C. for 3 hours. The reaction mixture was then diluted with 100 parts of isopropanol and parts of water. To the violet solution thus obtained, 34.6 parts of 30% caustic soda were added, and followed by one-half part of 36% benzyltrirnethylammonium hydroxide. The mixture was then stirred for 3 hours, during which time a viscous, pale yellow colored substance separated out of solution. This product did not solidify, and was separated by decanting off the aqueous layer. It was then subjected to a steam distillation to remove the volatile impurities. The oily still residue formed on cooling a light colored, viscous product which weighed 67 parts. i
The product, which may be named p-diethylaminophenyl di(N-methyl-N-beta-cyanoethyl-p-aminophenyl)- methane, is soluble in hot isopropanol, tert. amyl alcohol and tert. butanol from which, on cooling. it precipitates in the form of a viscous oil. It is highly soluble in cold benzene, acetone and carbon tetrachloride, but insoluble in petroleum ether or isooctane. In diluted mineral acids, the compound dissolves readily to give pale yellow, clear solutions.
The above product does not become discolored upon being stored in daylight for long periods of time, but treatment thereof with oxidizing agents in the presence of acid converts it rapidly into the corresponding tri phenyl-methane color.
EXAMPLE 8 When the procedure of Example 7 was repeated except for replacing the p-diethylamino'benzaldehyde by its equivalent weight of p-dimethylamino-benzaldehyde, a similar leuco compound was obtained in the form of an oil which did not become discolored on storage. its solubility properties and the shade developed from it by the aid of acid and oxidizing agents were similar to those of the product of Example 7.
Group C.-Vi0lets and blues-synthesis from a diphenyl hydrol and 1 mole of an aniline compound EXAMI LE 9 To 30 parts of di(p-dimethylaminophenyl)methane were added 32 parts of 87% formic acid and 30 parts of 37% hydrochloric acid. The mixture was heated to 60 to 70 C. until a clear solution was obtained which then was diluted with 1825 parts of water. The solution was cooled to 1 to 2 C., and 94 parts of a thin aqueous paste containing 39.9% of lead peroxide was added under vigorous stirring. After stirring for 10 minutes further, a solution containing 37 parts of sodium sulfate in 100 parts of water was stirred in and the slurry was rapidly filtered through a diatomaceous earth-coated filter cloth.
To the filtrate, containing di(p-dimethylaminophenyl) hydrol, 23.6 parts of diethylaniline were added, and the solution was heated slowly to 80 C. and held at this temperature for 3 hours. After cooling to 60 C., 50.5 parts of 30% caustic soda were stirred in, which caused the precipitation of the unsymmetrical leuco di(p-dimethylaminophenyl) -p diethylarninophenyl methane in the form of a grayish, gummy mass which, on continued stirring, became granular. The leuco product was then filtered off and the cake was washed with water, dried at 50 C. in vacuo, and recrystallized from 1460 parts of isopropanol containing 1.08 parts of benzyltrimethylammonium hydroxide. The stabilized leuco compound thus obtained was in the form of colorless plates which melted at 130 to 132 C. its nitrogen content was found to be 10.50%; its pH, 8.7.
Regeneration of color from this leuco with a 1% solution of chloranil in dioxane gave a very strong violet color practically identical in shade with that from leuco crystal violet, prepared according to Example 2.
EXAMPLE 10 45 parts of di(p di n butylaminophenyl)methane, which was prepared as described in J. A. C. S. 58, 1430 (1936), were dissolved in a mixture of 23 parts of 87% formic acid and 21.5 parts of 37% hydrochloric acid solution. The clear, pale yellow solution thus obtained was added to 1825 parts of water under vigorous stirring at room temperature. The solution was cooled to 0 C., and 67 parts of a freshly prepared aqueous paste containing 29.9% lead peroxide was added within 2 minutes. The slurry was stirred for 10 minutes at 0 to +2 C., and 26.5 parts of sodium sulfate dissolved in 70 parts of water were added. After stirring for 10 minutes at 2 to C., the precipitated lead sulfate was filtered oif, and the cake was washed with 200 parts of water. The combined filtrates amounted to 2175 parts in which the hydrol, formed by the lead oxidation, remained dissolved. The isolated hydrol melted at 128 to 129 (1., contained 6.64% N (theory 6.39%) and gave a deep blue color with acetic acid, typical of hydrols.
To-1087 parts of the above solution, were added 11.6 parts of di-n-butylaniline. The mixture was stirred and slowly heated to 80 C. It was held at this temperature for 2.5 hours and then allowed to cool to 30 to 35 C., whereupon 180 parts of a 30% caustic soda solution was added. This rendered the reaction mass neutral to Congo red paper. The mass was then extracted with 300 parts of benzene containing 0.5 part of 36% by weight aqueous solution of benzyltrimethylammonium hydroxide, and the benzene extract was steam distilled until free of solvent and small amounts of volatile impurities. The still residue was extracted with 100 parts of ether containing 0.5 part of 36% by weight aqueous solution of benzyltrimethylammonium hydroxide and the ether was evaporated off in an atmosphere of nitrogen on the steam bath to give 11 parts of a light brownish colored viscous oil which did not solidify, but on standing for 2 weeks a small amount of unreacted, crystalline hydrol separated out. The crys- -10 tals melted at 128 to 129 C., and analyzed 6.38 The oil remaining after filtering oif these crystals was found to consist mainly of the desired leuco compound, namely tn(p-di-n-butylaminophenyl) methane. A test portion treated with a solution of chloranil in dioxane was completely converted into the bluish-violet hexa-n-butyltriamino-triphenylmethane dye.
The above leuco compound had a pH of 8.3, was stable against color formation on exposure to light and air, and showed excellent compatibility in the waxy vehicles customarily employed for making the transfer film in hectograph carbon paper.
EXAMPLE 11 A mixture of 6.5 parts of the isolated hydrol described in Example 10, 2.4 parts of diethylaniline, 3.2 parts of 87% formic acid and parts of isopropanol was stirred and heated within 1% hours to 80 C. where it was kept for 3 hours. To the hot (60 C.) violet-colored solution were added 5 parts of 30% caustic soda and 0.5 part of a 36% aqueous solution of benzyltrimethylammonium hydroxide. The excess of unreacted diethylaniline and the isopropanol were then removed by steam distillation, and the still residue was cooled and extracted with ether. After separating the ether layer, 0.5 part of the same quaternary ammonium hydroxide solution was added thereto and the mass was dried over anhydrous sodium carbonate. The ether solution was then decanted olf and evaporated, to yield 7.8 parts of a pale-yellowish viscous oil which did not solidify on storage at room temperature. The product, which is believed to be an unsymmetrical hexaalkyl-triamino-triphenyl methane of the structure:
di(p-dibutylaminophenyl) p-diethylaminophenyl is readily soluble in ethanol, isopropanol, t-butanol, acetone, benzene, carbon tetrachloride and chloroform. On long storage in light and air, it did not change in color.
EXAMPLE 12 By the procedure of Example 10, 543 parts of the same hydrol solution were condensed with 3.8 parts of N-ethyl- N-methyl-aniline. The leuco compound was thus obtained in the form of a brownish oil which did not solidify and did not show any precipitate on storage at room temperature. Its pH was 8.6. The new product may be designated as N-methyl-N-ethyl-p-aminophenyl-di(dibutylp-aminophenyD-methane. A test portion of this compound when treated with a 1% solution of chloranil in dioxane, gave the corresponding new triphenyl methane dye.
The above leuco compound was stable against color formation on exposure to light and air, and showed excellent compatibility with the customary, waxy hectograph vehicles.
EXAMPLE 13 543 parts of hydrol solution obtained in Example 10 above were condensed by the procedure of Example 10 with 4.5 parts of lSI-beta-cyanoethyl-N-methyl aniline. The leuco compounri hus obtained was a light brownish oil. It was stable against color formation on exposure to light and air, but was readily converted into a bluishviolet color upon treatment with a solution of chloranil in dio'xane.
In manners similar to the above examples, other leucopolyalkyl-triamino-triphenyl-methane compounds may be synthesized, decolorized and stabilized against spontaneous color development. For instance, in the synthesis typified by Examples 3, 6 and 7, various other dialkyl anilines may be condensed with p-diethylaminobenzaldehyde, to give symmetrical or unsymmetrical triphenylmethane compounds. Of particular interest in this con nection are dimethyl aniline, N-methyl-N-ethyl aniline, N-methyl-N-benzyl aniline, N-ethyl-N-benzyl aniline, dimethylor diethylortho-toluidine, dimethylr diethylmetatoluidine, Nmethyl-N-hydroxyethyl aniline, N- methyl-N-hydroxyethyl orthotoluidine, N-methyl-N-betameta-toluidine, N-methyl-N-hydroxyethyl aniline, N- methyl-N-hydroxyethyl ortho-toluidine, N-methyl-N-betacyanoethyl aniline, N-ethyl-N-cyanoethyl aniline, N- ethyl-N-beta-cyanoethyl ortho-toluidine, di-beta-hydroxyethyl aniline, di-beta-cyanoethyl aniline, etc.
The p-diethylaminobenzaldehyde itself, in the mentioned examples may be replaced by pdimethylaminobenzaldehyde, or p-N-methyl-N-ethyl-amino benzaldehyde.
In the synthesis typified by Examples 9 to 13, the dialkyl-anilines named in the examples may be replaced by any of the symmetrical or unsymmetrical, substituted or unsubstituted dialkyl anilines hereinabove indicated, and the di(p-dibutyl-aminophenyl)-methane itself may be replaced by the corresponding di-(p-di-n-propyl), di(p-diisopropyl) and di(p-diethyl) compounds.
The quaternary ammonium base named in the examples may be replaced by any of the other bases indicated hereinabove, and larger or smaller quantities thereof may be used, within the limits hereinabove indicated.
Group D.Bluesdiphenyl-naphthyl-methane type EXAMPLE 14.-LEUCO VICTORIA PURE BLUE BO mnm-OqznGmmmn To a stirred and heated solution of 52 parts of technical Victoria Pure Blue BO (U. S. P. 2,422,445) in 950 parts by weight of ethyl alcohol, there were added over a period of one hour at reflux, a concentrated sodium hydrosulfite solution (containing 63 parts of sodium hydrosulfite dissolved in 280 parts of water) and, in small portions, a total of 4 parts of zinc dust. After refluxing for an additional period of 20 minutes, the original color of the charge changed to a pale yellow olive color. The charge was then diluted carefully with a solution containing 34 parts of 28% ammonia and 3 parts of a 36% aqueous benzyltrimethylammonium hydroxide solution in 300 parts of water. The charge was allowed to cool slowly while stirring for a period of 4 hours. The reaction product which crystallized out, was filtered off, and the cake was washed with 200 parts of a 50% alcoholic solution containing 3 parts of benzyltrimethylammonium hydroxide, sucked well and dried in a vacuum oven at 50 C. for 6 hours.
The crude product weighing 44 parts (yield 908%) was purified by recrystallization from 500 parts of isoamyl alcohol containing 3 parts of 36% aqueous benzyltrimethylammonium hydroxide to give the pure leuco Victoria Pure Blue B0 of the above shown structure in colorless crystals which melted at 161 to 163 C.
By analysis the leuco product showed a nitrogen content of 8.76% as compared with the calculated nitrogen value of 8.77%.
The compound was found to be soluble in benzene, dioxane and hot isoamyl alcohol; and moderately soluble in methyl, ethyl, or isopropyl alcohol.
In dioxane the compound readily oxidized with a chloranil-dioxane developer to give a bright and strong blue color.
Group E.-Greensdiamino-triaryl-methane type EXAMPLE 15.-DIETHYLDIBENZYL-DIAMINO TRI- PHENYLMETHANE To 315 parts by weight of isopropanol were added under stirring 53 parts of benzaldehyde and 30 parts of urea. After stirring for 15 minutes at room temperature there was added 221 parts of N-ethyl-N-benzylaniline. After stirring another /2 hour, 54 parts of 96% sulfuric acid were added slowly. After stirring for /2 hour longer at room temperature, the reaction mixture was gradually heated to reflux (82 to 83 C.) and held at this temperature for a period of 21 hours.
The hot reaction mass was then diluted carefully first with 160 parts of isopropanol and then with 170 parts of water. The mass was cooled to 40 C., and then neutralized by adding slowly 144 parts of 30% sodium hydroxide solution, followed by 5 parts of a 36% aqueous solution of benzyltrimethylammonium hydroxide.
The reaction product, mixed with sodium sulfate, separated out as a colorless heavy viscous mass. After decanting off the alcoholic layer, the viscous product was stirred for A2 hour at 85 to C. with 1000 parts of water containing 3 parts of the 36% benzyltrimethylammonium hydroxide solution and separated by decanting oflf the hot aqueous layer. The viscous product weighing 286 parts was then added to 1400 parts of acetone, containing 3 parts of the 36% benzyltrimethylammonium hydroxide solution and heated under stirring to reflux until all was in solution which was then cooled. The product crystallized out in the form of small colorless needles, melting at to 116 C. By analysis, the product showed a nitrogen content of 5.36% as compared with the calculated nitrogen value of 5.49%
The product was soluble in benzene, acetone and acetic acid and slightly soluble in ethanol, isopropanol and isoamyl alcohol, but insoluble in petroleum ether.
Infrared determination of a sample oxidized by means of a chloranil-dioxane solution showed that the dye obtained from this leuco has its adsorption peak at 6325 A. It was a yellower green than Malachite Green.
EXAMPLE 16.-o-CHLORO-LEUCO BRILLIANT GREEN This compound was prepared by refluxing for a period of 20 hours a mixture of 70 parts of distilled o-chlorobenzaldehyde, 45 parts of urea, 164 parts of N,N-tliethylaniline and 52 parts of 96% sulfuric acid in 350 parts of isopropanol.
The completed reaction mass was then diluted with 191 parts of water, neutralized with parts of 30% sodium hydroxide solution and stirred at room temperature for 2 hours allowing the product to crystallize out of solution.
After filtration, the crude product was treated first with 300 parts of 50% ethyl alcohol containing 2 parts of 36% aqueous solution of benzyltrimethylammonium hydroxide and then with 1500 parts of water containing 5 parts of 36% aqueous solution of benzyltrimethylammonium hydroxide to give, after vacuum drying, 227 parts of the crude colorless leuco compound.
One recrystallization from ethyl alcohol (containing a small amount of the 36% benzyltrimethylammonium hydroxide) gave the product as colorless plates which 13 melted at 109 to 110 C. By analysis the product contains 8.43% of nitrogen as compared with the calculated value of 8.44%.
A small sample of the leuco compound oxidized with chloranil in dioxane gave a bluish-green color having its maximum absorption band at 6500 A.
EXAMPLE 17.p-CHLORO-LEUCO MALACHITE GREEN This leuco compound was prepared by refluxing for 20 hours a mixture of 70 parts of p-chlorobenzaldehyde, -45 parts of urea, 133 parts of N,N-dimethylaniline and 52 parts of 96% sulfuric acid in 350 parts of isopropanol.
The reaction mass was then diluted with 191 parts of water, neutralized with 140 parts of 30% sodium hydroxide solution and the product was stabilized and isolated as follows: The aqueous layer was decanted from the viscous product which solidified upon standing. 192 parts of a colorless solid were obtained. The latter was dissolved, by heating at reflux temperature, in 2250 parts of ethanol containing 24 parts of a 36% aqueous solution of benzyltrimethylammonium hydroxide. The hot solution was clarified by filtration and the filtrate was cooled, filtered and the cake was dried, thus yielding 161 parts of the stabilized leuco compound in the form of colorless needles which melted at 99 to 100 C.
By analysis the product contains 9.78% of nitrogen as compared with the calculated value of 9.74%.
A sample of the leuco compound, oxidized in dioxane with chloranil, gave a yellowish-green color having its maximum absorption band at 6350 A.
The purified leuco thus obtained showed very good stability when exposed to air for a long storage period.
EXAMPLE 18.p-CHLOROPHENYL-BIS (p-N-ETHYL-N- BENZYL-AMINO-PHENYL) -METHANE This compound was prepared by refluxing for a period of 24 hours a mixture of 71 parts of p-chlorobenzaldehyde, 30 parts of urea, 221 parts of N-ethyl-N-benzylaniline and 54 parts of 96% sulfuric acid in 310 parts of isopropanol. The reaction mass was diluted with 180 parts of isopropanol and 170 parts of water. The sulfuric acid was then neutralized with 145 parts of 30% aqueous sodium hydroxide. The neutral slurry was agitated at room temperature for 3 hours with parts of a 36% aqueous solution of benzyltrimethylammonium hydroxide. The aqueous layer was decanted from the viscous reaction product, which was essentially colorless. The viscous product was agitated for 2 hours at room temperature with 900 parts of a solution containing equal parts by volume of water and ethanol and 3 parts of 36% aqueous benzyltrimethylammonium hydroxide. The alcohol-water layer was decanted from the viscous product, and the latter was washed by slurrying with 1300 parts of hot (75 C.) water containing 5 parts of the quaternary ammonium stabilizer solution. The stabilized, viscous leuco compound was dried and contained by analysis 4.81% nitrogen as compared with the theoretical value of 5.07%.
A sample of the above leuco, oxidized in dioxane with chloranil, gave a yellowish-green dye having its maximum light absorption band at 6350 A.
The stabilized compound was found to possess exceptionally good stability on prolonged air exposure and excellent compatibility in the conventional hectograph for mulations. Because of its very yellowish-green (devel oped) shade, this leuco compound is of particular value when used in mixtures with other selected stabilized leuco compounds, disclosed in this application, for the preparation of colorless hectograph or one-time carbon formulations which are designed to give on treatment with a chloranil type developer useful black copy shades.
EXAMPLE 19.LEUCO BRILLIANT GREEN This leuco compound was prepared by the general method described in Examples 1, 2 and 14 above, by reducing 50 parts of Brilliant Green (C. I. 662) with a i4 saturated sodium hydrosulfite solution (63 parts of Sodium hydrosulfite in 280 parts of water) in 950 parts of boiling ethyl alcohol with the aid of a small amount (3 parts) of zinc dust.
The colorless, hot reduction mass was then diluted with a solution of 300 parts of water containing 38 parts of 28% ammonia, and the bottom oily layer together with some zinc salts was separated after cooling. The mass was then agitated with 350 parts of benzene, and dried over caustic and filtered to remove the zinc salts.
To the benzene filtrate, 2 parts of a 36% aqueous solution of benzyltrimethylammonium hydroxide were added, and the benzene was evaporated off on a steam bath, under nitrogen, to give in the residue the crude leuco compound as a pale yellow viscous oil. By analysis, the product contains 7.29% of nitrogen as compared with the theoretical value of 7.25%.
A portion of the leuco brilliant green, oxidized in dioxane with chloranil, gave a bluish-green color having its maximum absorption band at 6325 A.
The leuco compound could not be converted to a solid by means of solvent treatment. It was found to possess very good stability to air exposure and excellent compatibility in the conventional hectograph formulations.
Group F.-Inc0mpletely alkylated or non-alkylated triamino triphenyl-methane type. (Mostly reds) EXAMPLE 20.LEUCO NEW FUCHSINE (TRT-p-AMINO- 'lRIail-M'ETHYL TRIPHENYL-METHANE) This leuco compound was prepared by reducing parts of the commercial dye known as New Fuchsine (C. I. 678) with a saturated sodium hydrosulfite solution (183.5 parts of sodium hydrosulfite in 810 parts of water) in 1600 parts of boiling ethyl alcohol with the aid of 5 parts of zinc dust. The light amber colored reduction mass was then diluted with a solution of 200 parts of water containing 50 parts of 28% aqueous ammonia, and filtered from the insoluble zinc salts. The upper alcoholic layer of the filtrate was separated from the lower sodium sulfate layer and was cooled to 20 C. While passing in nitrogen, a solution of 50 parts of 28% ammonia and 5 parts of a 36% aqueous solution of benzyltrimethylammonium hydroxide in 3000 parts of water was entered gradually into the mass, over a period of 2 hours. The leuco compound which crystallized out, was filtered oil and the cake was sucked well and dried at 70 C. The crude product (84 parts) was obtained in the form of slightly pinkish crystals.
49 parts of the crude leuco product above obtained were purified by dissolving in 850 parts of boiling toluene which contained 2 parts of a 36% aqueous solution of benzyltrimethylammonium hydroxide, and filtering hot. Upon cooling the filtrate to 20 C. and diluting it with 800 parts of petroleum ether, the pure leuco compound separated out in small pale yellow crystals, which were filtered off, sucked well, and vacuum dried at 50 C. The pure product was obtained in the form of yellow crystals, which melted at 157 to 160 C.
By analysis the product contains 12.35% nitrogen as compared with a theoretical value of 12.67%.
A small portion of the product, treated with chloranil in dioxane, gave a bright magenta color having its maximum absorption band at 5650 A.
The leuco compound is soluble in alcohol, ether, benzene and toluene but insoluble in petroleum ether, isooctane or water. It is also soluble in dilute acetic acid and hydrochloric acid. The stable leuco compound of this example was found to be sufficiently compatible with the vehicles of hectograph and one-time carbon formulations to serve as a very useful shading component in mixtures with the products of Examples 1 and 18 to produce improved black copy shades.
EXAMPLE 21.PARALEUCANILINE (TRI-rrAMINO- PI-IENYL-METHANE) To a solution of 10 parts of Para Magenta (C. I. 676) in 100 parts of ethanol at reflux temperature, a solution of 19 parts of sodium hydrosulfite in 84 parts of water and 2 parts of zinc dust were added alternately in small portions. When decolorization was achieved, the mass was cooled to C., and the White, crystalline precipitate was filtered off and dried, giving 6.5 parts of a product contaminated with zinc. The filtrate was diluted with 160 parts of 5% ammonia, cooled to 15 C., and the precipitate was filtered off and dried, giving 8.1 parts. The combined dry products were dissolved by heating in 160 parts of benzene containing 1 part of a 36% aqueous solution of benzyltrimethylammonium hydroxide. After filtration, 160 parts of petroleum ether were added to the cooled filtrate, and the stabilized, crystalline leuco compound was filtered off and dried. The product obtained melted at 187 to 192 C. and remained essentially colorless after storage for several months. A portion of this material, when treated in dioxane with chloranil, gave at first a bluish color which turned to the intense red color of the final dye.
EXAMPLE 22.LEUCO FUCHSINE (m-MONOMETHYL- TRI-p-AMINOPHENYL-METHANE) To a solution of 50 parts of technical Fuchsine (C. I. 677) in 800 parts of ethanol at reflux temperature, a solution of 63 parts of sodium hydrosulfite in 280 parts of water and 3 parts of zinc dust were added alternately in small portions. When decolorization was achieved, 125 parts of 6.5% aqueous ammonia were added and the mass was filtered at 60 C. The lower, aqueous-salt layer of the filtrate was removed, and the oily reduction prod uct remaining was agitated at room temperature with 2600 parts of water containing 5 parts of choline (2-hydroxyethyltrimethylammonium hydroxide) until the prod uct solidified in the form of prismatic crystals having a 4 pale buff color. The filtered and dried product, amounting to 36.5 parts, melted at 91 to 97 C.
A portion of the stabilized leuco Fuchsine was treated with chloranil in dioxane and gave at first a dark blue color which turned to the intense red color of the final dye, having its maximum absorption band at 5650 A.
In manners similar to the above examples, numerous other leuco triarylmethane compounds may be prepared, purified from color and stabilized against photochemical discoloration, the following being an abbreviated list of suitable compounds suggested for treatment, to supplement the products obtained in the various groups of examples above.
16 N ethyl-N-sec. butyl analog of leuco crystal violet (M. P. 113 C.) (By condensing Michlers hydrol with N-ethyl- N-sec. butyl aniline. Ger. 741,008).
Leuco Victoria blue R (M. P. 172-173 C.)
(By reduction of the commercial dye, C. I. 728). Leuco Victoria blue B (M. P. 167168 C.)
(By reduction of the commercial dye, C. I. 729). p dimethylaminonaphthyl tetramethyl diaminodiphenylmethane (M. P. 172 C.)
(By reduction of the corresponding dye or by condensing Michlers hydrol with N,Ndimethy1-1- naphthylamine; Ber. 41, 582).
The ethyl analogs of the three items last mentioned.
Z-methyl leuco malachite green (M. P. 102103 C.) (From o-tolualdehyde and dimethylaniline; Ber.
39, 2042). 3-dimethylamino-4-rnethyl leuco malachite green (M. P. 113 C.) (From Michlers hydrol and N,N-dimethyl-otoluidine; Ger. 109,664). p-nitro leuco brilliant green (M. P. 113 C.) (From p-nitrobenzaldehyde and diethylanilinc; Ber. 19, 746). Group F:
Tetraethyl-para-leucaniline (M. P. 118' C.)
(By reduction of corresponding nitro compound; Ber. 19, 747.) Tribenzyl-triamino-triphenylmethane (M. P. 106- 107 C.) (I. prakt. Chem. , 79, 565.) Diphenylated paraleucaniline homolog (M. P. 116
C.) (By reduction of Spirit Blue 2B, C. I. 689, according to Ber. 40, 254.)
It will be clear from the above examples that our ir1- vention is of a general nature and may be applied to the stabilization of leuco triarylmethane compounds in general, to produce essentially colorless, or in any event, non-smudging coloring agents which are adapted, upon development with an oxidizing agent (e. g., chloranil) to give violets, blues, greens, reds and blacks, useful in the manufacture of transfer media, copying sheets and simi lar articles of practical use. In particular, the class of coloring agents to which this invention is applicable may be defined as spirit-soluble, diamiuoand triaminoaryl methanes of the formula wherein X designates a member of the group consisting of hydrogen and methyl; wherein R is a radical of the group consisting of phenyl, tolyl, xylyl, mononitrophenyl, monoand dichlorophenyl, aminophenyl, aminotolyl, acetylamino-phenyl, l-p-phenylamin0-naphthyl, and 1-pmonoalkylaminoand dialkylamino-naphthyl, and wherein the N-atoms of said aminophenyl and aminotolyl radi cals and the N-atoms shown in the above formula in position para to the CH group have their second and third valencies satisfied by members of the group consisting of hydrogen, lower alkyl, 2-hydroxyethyl, Z-cyanoethyl, henzyl and phenyl, said leuco compound being in a state of purity whereby it is essentially free of color, and being devoid of sulfo, carboxy and phenolic hydroxy groups.
PART IIAPPLICATION IN PRACTICE As concerns the utility of our novel compositions and the modes of developing their colors in situ, we have already mentioned that our novel compositions are applicable in general to the manufacture of typewriter ribbon Yellow vazo dye obtained by coupling 19 lization from iso-octane which contained (1% by weight) benzyl-trimethylaammonium hydroxide; The leuco compound thus obtained melted at ll4-116 C.
EXAMPLE 27 Parts Cetyl alcohol 6.00 Technical stearylamine 10.50
Petrolatum No. 5 9.00 Aluminum stearate 4.50 Stabilized leuco ethyl violet of Example 1 5.00 Stabilized leuco Victoria pure blue B0 of Example l4 m. 5.00 Stabilized leuco green of Example 10.00 Stabilized leuco pyronine G of Example 26 4.00 Stabilized leuco new fuchsine of Example 1.00
Paper coated with the above composition gave a colorless carbon paper having good stability and non-smudging properties.
A single reproduction on a chloranil-pretreated paper gave a very dark blue-black image. Hectograph copies prepared from a typed master transfer sheet, on develop- .ment with the chloranil-dioxane-alcohol solution, gave sharp blue-black reproductions.
I EXAMPLE 2s The following ingredients were heated at steam bath temperature until a uniform, clear solutionwas obtained:
Parts Stabilized leuco ethyl violet of Example 1 15.5 Stabilized leuco p-chloro malachite green of Example l7 13.0 Chrysoidine R Base (C. I. 21) 19.0 Technical 'stear'ylam'iiie 20.0 Vaseline; 15.0 Cetyl alcohol 10.0 Aluminum -stearate 7.5
The molten composition was coated in the conventional manner onto a hectograph carrier sheet, producing a dark orange colored hectograph carbon from which more than 100 strong black shade copies were obtained by the spirit duplication process, using the above described chloranil solution as the developer for the leuco compounds. The
azo dye remains unchanged and thus serves as a shading color to produce the desired black shade. The number of copies obtainable from a master sheet of thistype, and
the-intensity and shade'of the reproduction, can be varied by altering'the ratios of the two color producing constituents within a 1:2 to 2: 1 range.
In asimilar manner, various other coloring compositions containing non-smudging, shading components may be put together and used. As practical additional illustrations of such auxiliary, non-smudging components the following are suggested:
Oil yellowN C. I. 19)
diazotizecl 2,5-dichloroaniline .to N-,methyl-N.-2-,cyanoethyl-aniline Phthaloperinone. (made by condensing 1, 8-diaminonaph- .thalene with 'phthalic anhydride; Beilst. XXIV, 232).
Safranine T Base (,6. 1. 841) Oil scarlet (C.,I. 73)
Oil red (C. I. 258) Brown disazo dye obtained by coupling 2 moles of diazotized technical Xylidine to 1 mole of l-naphthol For instance, the proportion of coloring agent in the coat: ing ink may be varied from 2 to 60% by weight on the intended form of the carrier and its intended use; The consistency of the coating ink may be modified by using cetyl alcohol as part of the waxy vehicle, or by adding plasticizers. Non-quaternary nitrogenous bases, such as mono-, diand tri-ethanolamine, stearylamine or dimethyl-stearylamine oxide may be added to the ink composition. In general, any of the modifiers and variants mentioned in copending application of Webber and Locke, Serial No. 403,040 (following Example 16 thereoflmay be applied in our invention, without departing from the spirit thereof as defined by the subjoined claims.
We claim as our invention:
1. A coloring agent for producing a triarylmethane coloring matter in situ upon the surface of a stratum, said coloring agent comprising at least one leuco compound selected from the group consisting of spirit soluble, polyamino-triarylmethanes of the formula wherein X designates a member of the group consisting of hydrogen and methyl: wherein R is a radical of the group consisting of phenyl, tolyl, xylyl, mononitrophenyl, monoand dichlorophenyl, aminophenyl, aminotolyl, acetylamino-phenyl, l-p-phenylamino-naphthyl, and l-p-monoalkylaminoand dialkylamino-naphthyl, and wherein the N-atoms of said aminophenyl and aminotolyl radicals and the N-atoms shown in the above formula in position para to the CH group have their second and third valencies satisfied by members of the group consisting of hydrogen, alkyl, 2-hydroxyethyl, Z-cyanoethyl, benzyl and phenyl, said leuco compound being devoid of sulfo, carboxy and phenolic hydroxy groups and all the alkyl radicals therein being radicals of not more than 4 C-atoms each, said leuco compound being in a state of purity whereby it is essentially free of color, and having incorporated therewith a quaternary ammonium hydroxide in suflicient quantity to give the coloring agent an alkaline reaction of pH not less than 8, when measured in a 1% solution of the coloring agent in ethanol at room temperature.
2. A coloring agent as in claim 1, the quaternary ammonium hydroxide being an ammonium hydroxidewhose nitrogen valencies are satisfied by substituents of thegroup consisting of alkyl, aralkyl, aryl, cycloalkyl, hydroxyalkyl and epihydrin, and which is soluble in primary, second ary and tertiary alcohols of l to 5 carbonatoms, and the quantity of said quaternary base being not less than 0.2% and not more than 10% by weight of said .colorless crystals.
3. A coloring agent as in claim 1, the quaternary ammonium hydroxide being benzyl-trimethyl ammonium hydroxide.
4. A composition of matter adapted for use as coloring agent for transfer media in duplicating processes, comprising substantially colorless crystals of the leuco form of a hexaalkyl-triamino-triphenyl methane whose alkyl radicals contain not more than 4 C-atoms each, said crystals having occluded within them a quartenary nitrogenous base, the latter being a quaternary ammonium hydroxide whose nitrogen valencies are satisfied by substituents of the group consisting of alkyl, aralkyl, aryl, cycloalkyl, hydroxyalkyl and epihydrin, and which is soluble in primary, secondary and tertiary alcohols of l to 5 carbon atoms, and the quantity of quaternary base being not less than 0.2% and not more than 10% by weight of said colorless crystals.
5. A composition of matter adapted for use as coloring agent for transfer media in duplicating processes, comprising substantially colorless crystals of leuco-ethyllviolet, said crystals having occluded within them a quaternary nitrogenous base, the latter being a quaternary ammonium 17 and of duplicating carbons, both for the spirit-hectograph process and for single-copy carbon paper. Their application to the ribbons and sheets will in general follow ordinary procedure as practiced heretofore with triarylmethane coloring matters. In other words, our novel, non-smudging coloring agents will first be incorporated into a suitable oily vehicle, for impregnation of ribbon, or into a suitable waxy composition for coating the transfer sheets. Because the transfer sheets for spirit hectograph duplication require an exceedingly high concentration of color (usually 40 to 60% by weight of the coating ink), low melting or highly soluble leuco compounds are to be preferred for this purpose, for instance, the hexaethyl product of Example 3 and its higher homologs, as well as its hydroxy-alkyl and cyano-alkyl analogs. Higher melting or less soluble compounds on the other hand, for instance, the tetramethyl-diethyl derivative of Example 9, and the corresponding hexamethyl compound are useful in the preparation of single-copy carbons, inasmuch as these generally do not require a concentration of more than 5 to color in their coating. These coloring agents may also be used in admixture with the hexaethyl or higher homologs, in various proportions, to control the working properties of the latter, if desired.
The next problem is to provide for development of the color on the ultimate copy after typing or duplication. This may be achieved by providing means and conditions for contacting the color with an oxidizing agent and acid during the duplication process or subsequently thereto. In the case of hectograph duplication, this provision can be achieved by adding a mildly acid oxidizing agent, for instance chloranil or 2,6-dichloro-benzoquinone chlorimide, to the moistening medium (alcohol, dioxane, or other low-boiling polar solvents) employed in producing the copies. In single-copy processes of printing, an acid clay and an oxidizing agent or a special agent such as triphenyl chloromethane, may be incorporated in the transfer coating (properly insulated by a waxy film from the colorless coating containing the coloring agent, until the instant of impact), or in the paper used for the copy. Or an oxidizing agent alone may suflice in such cases, advantage being taken of the fact that many papers naturally contain aluminum silicates or similar acid clays in their fibers as a result of their process of manufacture.
Acid alone also may suflice in some cases for instance where the imprint on the final copy paper is exposed to the atmosphere in daylight. Such color development by the aid of atmospheric oxygen may be greatly accelerated by exposing the imprint for a few seconds to a source of heat.
The following additional examples will serve to illustrate this aspect of our invention, without, however, any intended limitation thereon.
EXAMPLE 23 Materials Parts Stearylamine wax (a commercial mixture of octadecyl and hexa-decyl amines) 30 Petrolatum No. 5 (a commercial parafiin) Aluminum stearate (technical grade) 10 Stabilized leuco-ethyl violet from Example 1 above 40 Total 1,00
The leuco compound was added to the molten mixture of the other ingredients at 100 C. The highly fluid, colorless composition thus obtained was coated onto a sheet of paper to produce a colorless transfer sheet. A master copy of printed words was produced from this transfer sheet on a typewriter in ordinary manner, except that the print was colorless and essentially invisible against the white background.
The colorless master sheet was then placed over the cylinder in a Ditto machine in which the regular Ditto liquor had been replaced by a special developer prepared by diluting 25 parts of a 1% solution of chloranil in dioxane with 75 parts of ethanol. A total of 650 copies were then run off on the machine in the usual manner. Each copy was initially colorless but developed, almost immediately and without any further treatment, easily readable reproductions of the original type in a color shade similar to (but somewhat weaker in strength than) that produced from standard crystal violet. The last copy was just about as strong as the first few copies.
EXAMPLE 24 One gram of stabilized leuco ethyl violet from Example 1 was added to 3 g. of Carnauba wax and 1 g. of a commercial stearylamine wax. The resulting coating composition possessed good fluidity at steam bath temperature. A sheet of ordinary paper was then coated with this mass and used in the same manner as ordinary carbon paper. It showed excellent transfer properties, producing on a typewriter, or with a stylus or pencil, colorless carbon copies which were readily developed in situ to a very strong violet shade when the surface of the copy sheet was slightly wetted with a 1% solution of chloranil in dioxane.
Equally good results were obtained when the stearylamine used in the above formulation was replaced by a commercial mixture of mono-, diand triethanolamine.
Similar results were obtained when the above procedure was repeated in all detail except using as coloring agent the leuco crystal violet prepared in Example 2 above.
EXAMPLE 25 Parts Stearylamine wax 25 Petrolatum No. 5 20 Aluminum stearate l0 Leuco ethyl violet, as obtained in the first paragraph of Example 1, prior to stabilization 40 BenZyLtrimethyl-ammOnium hydroxide solution in methanol (36%) 5 Total The leuco .compound was added to the molten mixture of the first three ingredients at 100 C. The quaternary compound was then stirred into the hot melt, allowing the methanol to evaporate. The mass was allowed to stand at 100%110 C., to settle out an insoluble impurity, and the clear liquid mass was decanted off and coated onto a sheet of paper to produce a colorless transfer sheet.
Testing and development of the color were then carried out by the same procedure as in Example 23, with essen tially the same results.
EXAMPLE 26 Parts Cetyl alcohol 2.00 Technical stearylamine 3.50 Petrolatum No. 5 3.00 Aluminum stearate 1.50 Stabilized leuco ethyl violet of Example 1 4.00 Stabilized leuco green of Example 15 4.00 Stabilized leuco pyronine G (see below) 1.60
hydroxide whose nitrogen valencies are satisfied by substituents of the group consisting of alkyl, aralkyl, aryl, cycloalkyl, hydroxyalkyl and epihydrin, and which is soluble in primary, secondary and tertiary alcohols of 1 to 5 carbon atoms, and the quantity of quaternary base being not less than 0.2% and not more than by weight of said colorless crystals.
6. A composition of matter adapted for use as coloring agent for transfer media in duplicating processes, comprising substantially colorless crystals of a leuco ethyl violet having occluded within them benzyl trimethyl ammonium hydroxide in quantity of 0.2 to 5% by weight of said colorless crystals.
7. A process of producing a colorless composition adapted for use as coloring agent in transfer coatings for duplication processes, which comprises treating a leuco polyaminotriarylmethane compound to purify it from by-product, non-triarylmethane coloring matters, and to re-convert any triarylmethane type coloring matters present to the leuco stage, and intimately associating the purified leuco compound thus produced with a quaternary nitrogenous base in quantity suflicient to impart to said coloring agent an alkaline reaction of pH not less than 8, when measured in a 1% solution of the coloring agent in ethanol at room temperature, said leuco polyamino triarylmethane compound being a compound of the formula wherein X designates a member of the group consisting of hydrogen and methyl, R is a radical of the group consisting of phenyl, tolyl, xylyl, mononitrophenyl, monoand dichlorophenyl, aminophenyl, aminotolyl, acetylaminophenyl, I-p-phenyl-amino-naphthyl, and 1p-monoalkylaminoand dialkylamino-naphthyl, and wherein the N- atoms of said aminophenyl and aminotolyl radicals and the N-atoms shown in the above formula in position para to the CH group have their second and third valencies satisfied by members of the group consisting of hydrogen, alkyl, 2-hydroxyethyl, 2-cyanoethyl, benzyl and phenyl, said leuco compound being devoid of sulfo, carboxy and phenolic hydroxy groups and all the alkyl radicals therein being radicals of not more than 4 C-atoms each.
8. A process as in claim 7, wherein the treatment is effected by stirring together a solution of said purified leuco compound in an organic solvent with an aqueous solution of said base, then treating the solution to precipitate the colorless coloring agent, and separating the latter from the solvent.
9. A process as in claim 7, wherein the treatment is eifected by heating a solution of said leuco compound in an organic solvent containing said quarternary nitrogenous base, then cooling the solution to crystallize out the color- 22 less coloring agent, and separating the latter from the solvent.
10. A process as in claim 7, wherein the treatment is effected by stirring a solution of said leuco compound in an organic solvent containing said quarternary nitrogenous base, then diluting said solvent with a liquid which is a non-solvent for said leuco compound, whereby to cause separation of said leuco compound, and recovering the latter from said mixture of liquids.
11. A process as in claim 7, wherein the leuco compound is formed by alkaline reduction of the corresponding dyestufi and is treated in situ with an aqueous solution of said base.
12. A process as in claim 7, wherein the leuco compound is formed by synthesis from lower intermediates and is treated in situ with an aqueous solution of said base.
13. A process as in claim 7, the quaternary base being benzyl-trimethyl-ammonium hydroxide.
14. A process of producing a colorless composition adapted for use as coloring agent in transfer coatings for duplication processes, which comprises treating a leuco hexa-alkyl-triamino-triphenyl-methane whose alkyl radicals contain not more than 4 C-atoms each with a quaternary nitrogenous base in quantity sufiicient to impart to said coloring agent an alkaline reaction of pH not less than 8, when measured in a 1% solution of the coloring agent in ethanol at room temperature.
15. A process of producing a colorless composition adapted for use as coloring agent in transfer coatings for duplication processes, which comprises treating a solution of leuco ethyl violet in an organic solvent with an aqueous solution of benzyl-trimethyl-ammonium hydroxide, the quantity of said hydroxide being not less than 0.2% and not more than 10% by weight of the ethyl violet, then treating the solution to precipitate the colorless coloring agent, and separating the latter from the solvent.
16. A process of producing a non-staining transfer medium adapted for use in duplication processes, which comprises coating a transfer sheet with a waxy film containing a non-smudging coloring composition as defined in claim 1.
17. A transfer sheet adapted for use in duplication processes, said sheet being coated with a waxy film containing an essentially non-smudging coloring composition as defined in claim 1.
18. A process for producing a non-staining, essentially colorless typewriter ribbon, which comprises impregnating a ribbon of textile material with an oily matrix containing a non-smudging coloring composition as defined in claim 1.
19. A typewriter ribbon containing as principal color producing medium a non-smudging composition as defined in claim 1.
No references cited.