US2755420A - Transfer inks for duplication processes - Google Patents

Description

United States Patent TRANSFER INKS FOR DUPLICATION PROCESSES Roy Clifford Locke, Salem, N. .L, assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application January 8, 1954, Serial No. 403,059

9 Claims. (Cl. 106-22) This invention relates to transfer inks for duplication processes. More particularly, this invention deals with novel oily compositions of matter adapted for use as the color bearing liquid in the manufacture of typewriter ribbon. This invention further embraces the novel typewriter ribbons thus produced.

It is an object of this invention to provide transfer inks of the aforegoing character which are essentially colorless in themselves or at least have no great tendency to produce intensely colored stains upon the fingers of a person, while yet being adapted to produce, through the medium of a typewriter ribbon, an intensely colored message on a sheet of paper. A further object of this invention is to produce an essentially non-staining typewriter ribbon of the character and for the purposes aforementioned. Various other objects and achievements of this invention will become apparent as the description proceeds.

When I speak of essentially colorless typewriter ribbon in this specification, it will be understood that I am referring to the film of the oily ink which permeates the typewriter ribbon, not to the article as a whole. For clearly, it is possible to use for the background itself a dyed ribbon, without stepping out ofthe teachings of this invention. In other words, my principal object in this invention is to produce articles of manufacture of the character and for the purposes mentioned, in which that component which normally rubs ofi onto a persons hands shall be essentially colorless or non-staining. It follows further that absolute freedom from color is not essential to this invention, inasmuch as the purpose may be fully satisfied even if the oily liquid is weakly buff colored or dark, so long as it does not produce an objectionable and tenaciously adhering stain upon the fingers.

The current general practice in duplication processes, such as the spirit hectograph process, impact-printing and ordinary typing with carbon copies, is discussed at length in copending application of Walter Jean Balon and Otto Stallmann, Serial No. 400,776, filed December 28, 1953. The noxious problem of staining arising from the customary use in said practice of polyalkyl triaminotriphenyl methane colors is also'discussed there in detail. The term polyalkyl there is defined as indicating the presence of not less than and not more than 6 lower alkyl radicals per molecule, wherein lower alkyl is typified by methyl to butyl. It will be used in the same sense throughout the instant specification and claims. As common commercially available illustrations of the colors in question are mentioned methyl violet, crystal violet and ethyl violet.

Balon and Stallmann then describe and claim novel, essentially colorless compositions of matter comprising the carbinol form of N-polyalkyl-tri(p-aminophenyl) methane colors in intimate association with a relatively smaller quantity of quaternary ammonium bases which contain alkyl, aralkyl, cycloalkyl, hydroxyalkyland epihydrin groups intheir structure, as typified by benzyl-trimethylammonium hydroxide and several other compounds named in said specification.

The compositions are prepared by heating the normally highly colored, commercial carbinol form of one of the aforementioned colors, in a secondary or tertiary alcohol which contains an excess of the mentioned quaternary base, until the intense blue color disappears, and then cooling and isolating the colorless crystals of the carbinol which presumably contain occluded quaternary base. The isolated solid is sufiiciently retarded as to color development, to permit its handling in the various processes involved, such as filtration and drying, and to permit its storing for a few days or weeks.

As specific illustrations of their invention and mode of procedure said copending application of Balon and Stallmann brings numerous detailed examples; including Example 1 which reads as follows:

To a stirred mixture of 50 g. of crude crystal violet carbinol in 3700 cc. of isopropyl alcohol at room temperature, 10 cc. of a commercial aqueous solution (36%) of benzyl trimethyl ammonium hydroxide were added. The mixture was stirred and heated during 45 min. to reflux temperature (82 C.), and held under reflux until completely discolored (about 1 hr.). The resulting pale yellow solution, after filtering at about C. and cooling, gave the product in the form of long, white, orthorhornbic prisms which melted at 194 C. to 196 C. These crystals analyzed 11.4% N; (theoretical is 10.8% They were characterized by unusual stability to color change, a sample having remained colorless for over 4 months when kept in a glass jar which was opened frequently.

A product of the same quality was obtained when the hot filtration was omitted. Likewise, the use of 15 cc. and 25 cc. of the quaternary ammonium base gave the same results.

Other carbinols and dyestuffs specifically named in said copending application of Balon and Stallmann and treated by the general process therein set forth are Crystal violet itself (Col. Ind. 681);

Ethyl violet (Col. Ind. 682);

N-hexa(n-butyl -tri(p-aminophenyl) -carbinol, obtained by condensing 2 moles of N-di-n-butyl-aniline with 1 mole of p-(di-n-butyl-amino)-benzaldehyde, followed by oxidation with chloranil.

N-tetra(n-butyl)-N-diethyl tri(p aminophenyl) carbinol, obtained in similar manner except using p-diethylamino-benzaldehyde.

Other quaternary ammonium hydroxides named in said copending application are tetrarnethyl-ammonium hydroxide, phenyl-dimethyl-benzyl-ammonium hydroxide, N-methyl-pyridinium hydroxide and the reaction product of epichlorhydrin and ammonia produced according to U. S. P. 1,977,251.

Balon and Stallmann further found that the mentioned colorless carbinol composition may be further stabilized against discoloration in long storage or upon exposure to a humid atmosphere rich in CO2 fumes, by coating the crystals with a fatty substance such as carnauba wax, provided the natural, residual acidity of the Wax is first neutralized by treatment with a quaternary base of the type hereinabove discussed.

The invention of Balon and Stallman is very useful in that it produces for the first time a composition of matter readily transformable into a triphenyl methane color, yet free of color itself and free of the inevitable nuisance normally attendant upon the handling and use of these colors in spreading intensely colored dusts and in producing difficultly removable stains upon the hands and clothes of persons. The said invention is also very elfective insofar as its primary object of handling, storing and using the coloring agent per se is concerned. Samples of the coated, colorless carbinols, produced according to Balon and Stallmann, have been known to resist discoloration for many months, even when kept in the vicinity of a large chemical plant, wherein the atmosphere is apt to be laden with various acid fumes.

The color stability of the Balon and Stallmann product, however, appears to be dependent upon its crystalline form. When the product is dissolved in or ground into an oily vehicle which is then spread out through the fiber of a typewriter ribbon, the color stability essentially disappears. In other words, colorless typewriter ribbon prepared from the colorless carbinol composition of Balon et al. are not so stable to discoloration in storage or upon exposure to the atmosphere as is the crystalline coloring agent itself. Perhaps the thinness of the film and the high surfaceto-volume ratio of the ground carbinol particle are contributing factors to this reduced discoloration stability.

Now according to my invention, the above problem is solved, and stable thin films of essentially colorless N- polyalkyl-tri(p-aminophenyl) carbinols are produced by adding to the coating-ink composition, in addition to its customary vehicle and the mentioned coloring agent, a relatively large proportion of an organic nitrogenous base whose physical state is selected to match the vehicle of the ink composition, in view of its intended use. In other words, inasmuch as the vehicle generally selected for impregnating typewriter ribbon is of an oily or liquid nature, I select as nitrogenous base an aliphatic amine which is liquid at room temperature, but boils above 150 C. Other practical requisites are freedom from objectionable odor and color and absence of tendency to polymerize.

Practical examples of such oily amines, suitable for the purposes of this invention are mono-, diand triethanolamine, tri-n-propylamine, tri-isobutylamine, di-n-butylamine, nor iso-octylamine, hexamethylene diamine, diethylene triamine, triethylene tetramine and tetraethylene pentamine.

The preferred quantity of the mentioned third ingredient is preferably based on the weight of the entire ink rather than on its coloring constituent. It may vary from 5 to 50% by weight of the entire composition. For practical purposes, however, I prefer to use a quantity of the amine equal to from 20 to 40% by weight of the entire composition.

It is noteworthy, that this is the first time in my experience that a coating ink for a transfer medium is finishcd on the alkaline side. Hitherto, the triphenyl methane colors themselves have been employed, for instance methyl violet, crystal violet or ethyl violet. These being salts, more particularly chlorides, care has always been taken to produce a coating ink composition of acid reaction. My novel compositions, however, when tested by dissolving a sample in aqueous alcohol, are alkaline to Brilliant Yellow. This test may indeed be taken as defining the lower limit of said third ingredient in my novel ink compositions.

The mode of incorporation of the several ingredients with each other is not critical. The colorless carbinol composition may be incorporated into the mixture of vehicle and base by grinding on an ink mill, or the carbinol composition may be dissolved in a solvent such as benzene, then added to the oily vehicle and base mixture, whereupon the resulting composition may be sprayed onto the ribbon. To my knowledge, the latter mode of incorporating the coloring agent is also novel.

In other details, the mode of preparing the typewriter ribbon, may follow customary practice in this art.

Without limiting this invention, the following examples are given to illustrate mypreferred mode of procedure. Parts mentioned are by weight.

Example 1 Materials: Parts White mineral oil (Nujol") 71.4 Monoethanolamine 25.7

Colorless carbinol composition from the above reproduced Example 1 of copending application of Balon and Stallmann, Ser. No.

Total 100.0

Mix the ingredients together thoroughly by stirring 15 minutes at room temperature. Grind by passing 6 times through a three roll ink mill. Coat on typewriter ribbon in the usual manner.

The pure white ink and ribbon thus obtained stays uncolored during lengthy storage periods and does not stain the hands objectionably. A typewritten impression on a copy sheet which had a natural acidity due to acid aluminum compounds incorporated in its manufacture, developed to a good lcgibility in 20 minutes. The intensity of the impression then progressively increased to a very strong copy after 2 hours.

Example 2 Use the materials same as in Example 1, except substitute lard oil for the mineral oil.

The pure white ink obtained develops to the colored copy impression more readily than does the product of Example 1.

Example 3 Same materials as in Example 1, except substitute castor oil for the mineral oil.

The pure white copy ink is much more readily developed under identical conditions or by heat than the inks of Examples 1 and 2, but still possesses remarkably superior properties over the prior art products.

Example 4 Materials: Parts Lard oil 14.6 Castor oil 26.3 Monoethanolamine 17.5 Coloring agent as in Example 1 41.6

Total 100.0

possesses the advantage of cleaner handling properties than the conventional hectograph ribbons in which basic dye chlorides have been used as the color component.

Example 5 Materials: Parts White mineral oil 35.7 Monoethanolamine 12.8 Coloring agent as in Example 1 2.5 Benzene 49.0 Total 100.0

Dissolve the color ingredient in the benzene by stirring at room temperature. Add the remaining two components. Stir well. Run the typewriter ribbon through the colorless solution. Squeeze to a practicable dryness. Allow to stand overnight in order to evaporate the benzene.

The above solution can also be applied to the ribbon by spraying through a pressure gun.

The pure-white, inked ribbon obtained is stable against color development while on the ribbon. When transferred by impact to copy sheets of sufiiciently high acidity, copies of readable intensity are obtained immediately.

A further advantage is the elimination of the grinding operation.

Example 6.C0ating hot Add all the ingredients together. Heat to 200 C. with good agitation and maintain this temperature until a colorless clear solution is obtained. Immerse the ribbon in the clear solution. Withdraw the ribbon after complete impregnation is reached and squeeze as dry as practicable.

The ribbon thus obtained is suitable for use in preparing the master sheet for hectograph duplication. The pure-white ink impregnated in the ribbon remains colorless until contacted with acid media.

The hot application technique of this example attains the advantage of eliminating the grinding operation in the preparation of the colorless ink. The ink of this example can also be applied by spraying the same from a heated pressure gun, at 200 C., directly onto the ribbon fabric, and then passing the latter over heated rolls at the same temperature.

It will be understood that the details of the above examples may be varied within wide limits. Thus in lieu of the particular colorless carbinol named in each example any other of the products mentioned in said copending Balon and Stallmann application, or their equivalents, may be employed, for instance, tri-(p-diethylaminophenyl) carbinol, tri-(p-n-propylaminophenyl) carbinol, di (p dimethylaminophenyl) p diethylaminophenylcarbinol.

The first of these will be recognized as the carbinol of ethyl violet. The other two are not at present commercial products, but were prepared specially for these tests by the mentioned inventors.

In lieu of the oils or oil-mixtures indicated in the above examples, any other non-drying oil or mixture of oils customarily employed in the art as vehicles for typewriter ribbon inks may be employed in this invention. The oily vehicle may also be modified by adding thereto plasticizers or agents for controlling their hygroscopicity. Solid or waxy amines, for instance stearylamine or some of the other amines named in the copending application of T. G. Webber and Roy C. Locke, Serial No. 403,040 (of even date herewith), may be added in limited proportions to adjust the consistency of the ink composition, if desired.

The quantity of colorless carbinol incorporated into the coating ink formulation, will naturally vary according to the purpose of the ink, but may otherwise follow the corresponding practice in the art when using the colored dyes. In other words, for ordinary typing, the quantity of coloring agent is generally from 1 to by weight of the entire coating ink. But for preparing master sheets for hectograph printing, 10 to 50% by weight is the quantity of coloring agent commonly used in the typewriter ribbon.

Because of the remarkable stability of the colorless coatings in the transfer sheets and ribbons hereinabove discussed, it is necessary that the paper upon which the copy is to be developed should come in contact with acidic agents during the development stage. In the case of hectograph duplication in a rotary machine using an alcoholic moistening agent, the acidic agent can be readily added to the moistening fluid. In the case, however, of typing from one of the aforegoing typewriter ribbons it is desirable that the paper itself have an acid reaction.

Many commercial papers have a natural acid reaction by virtue of clays, aluminum silicates or' acid-reacting salts incorporated into the paper fiber during manufacture. On the other hand, paper intended for use with the typewriter ribbons of this invention, may be treated with certain acids, whereby to give it a weak acid reaction. The treatment will usually consist of impregnating the paper with an aqueous, alcoholic, or aqueousalcoholic solution of an organic acid, and allowing the vehicle to evaporate. As organic acid is preferably chosen one which is solid at room temperature, soluble in water, alcohols or mixtures of the two, has no color of its own and is free from bad odors or toxicity. As examples of suitable acids may be mentioned acetic, oxalic, citric, tartaric, benzoic, salicylic, pyr'ogallic, naphthalene sulfonic, p-tolue'ne sulfonic, and various others.

Moreover, it has been observed that the shade of the color developed upon the copy paper can be varied to some extent by the choice of the acid. Thus, using the carbinol of crystal violet as coloring agent, stearic, citric and tartaric acids developed purple impression; oxalic acid gives a blue; and pyrogallic acid gives a jet black.

The speed of color development also can be varied to some extent by the choice of acid. Of the acids tested by me thus far, citric, tartaric and salicylic develop most rapidly and give intensely colored imprints.

The following additional examples will illustrate the preparation and use of such acidic paper, insofar as it is pertinent to my present invention.

Example 7 A sheet of white paper is impregnated With a 5% solution of oxalic acid in alcohol and allowed to dry thoroughly under normal conditions.

A record made on this paper using the typewriter ribbon of Example 1 above, develops a strong violet shade immediately after typing. This intensity increases somewhat during the next 24-hour period. Thereafer a progressive shade-change takes place to an ultimate black impression.

Example 8 The procedure is the same as in Example 7, except that citric acid is used in place of oxalic acid.

The treated paper thus obtained gives a violet copy which is many times stronger within 15 minutes than the untreated sheet gives after several days.

It is distinguished over the product of Example 7 by a more rapid development of a high intensity print, which does not change its violet shade in storage.

Essentially similar results are obtained with paper which had been impregnated with any of the other acids named above, except for the individual differences in rate of color development and ultimate shade, as already noted above. In the case of tannic acid, a special further improvement obtained in that the impression is non-bleeding in water. That is, water flowed over the sheet shows no evidence of bleed from the letters into the adjacent uncolored areas.

Numerous other changes and variations in the details of my invention will be readily apparent to those skilled in the art.

I claim as my invention:

1. An ink composition for producing non-staining typewriter ribbons, comprising an oily ink vehicle and a color producing agent, said color producing agent comprising the carbinol of an N-polyalkyl-tri(p-aminophenyl) methane dye in a state of purity essentially free of the corresponding color, and said ink composition comprising further a nitrogenous organic base which is miscible with said oily vehicle, said base being a non-drying aliphatic amine which is liquid at room temperature but does not boil below C., said base being present in quantity not less than 5% and not greater than 50% by weight of the entire composition.

2. An ink composition as in claim 1, the organic nitrogenous base being an alkylamine.

3. An ink composition as in claim 1, the organic nitrogenous base being an alkylolamine.

4. An ink composition as in claim 1, the organic nitrogenous base being a polyalkylene-polyamine.

5. A composition of matter as in claim 1 the quantity of said color producing agent being from 1 to 10% by weight of the entire composition.

6. A composition of matter as in claim 1 the quantity of said color producing agent being from 10 to 50% by weight of the entire composition.

7. The process of preparing an ink composition adapted for producing non-staining typewriter ribbon, which comprises incorporating into an oily ink-vehicle a coloring agent and an organic nitrogenous base, said coloring agent being the carbinol of an N-polyalkyl-tri(p-aminophenyl) methane dye in a state of purity essentially free of the corresponding color, and the nitrogenous base being an amine which is liquid at room temperature but does not boil below 150 C., the quantity of said base being not less than 5% and not more than 50% by weight of the entire composition.

8. The process of preparing a non-staining typewriter ribbon for typing with acidic paper, which comprises impregnating a textile ribbon with an ink composition comprising an oily vehicle, a coloring agent and an organic nitrogenous base, the coloring agent being the carbinol of an N-polyalkyl-tri(p-aminophenyl) methane color in a state of purity essentially free of the corresponding color, and the nitrogenous base being a compound which is liquid at room temperature and is miscible with said oily vehicle, the quantity of said base being from 5 to and the quantity of coloring agent being from 1 to 50% by weight of the ink composition.

9. A non-staining typewriter ribbon comprising a textile ribbon impregnated with a basic, essentially colorless, ink composition as defined in claim 8.

References Cited in the file of this patent UNITED STATES PATENTS 1,198,442 Hochstetter Sept. 19, 1916 2,306,863 Bour Dec. 29, 1942 2,392,658 Geopfert Jan. 8, 1946 2,427,921 Pfaelzer Sept. 23, 1947

Claims (1)

1. AN INK COMPOSITION FOR PRODUCING NON-STAINING TYPEWRITER RIBBONS, COMPRISING AN OILY INK VEHICLE AND A COLOR PRODUCING AGENT, SAID COLOR PRODUCING AGENT COMPRISING THE CARBINOL OF AN N-POLYALKYL-TRI(P-AMINOPHENYL) METHANE DYE IN A STATE OF PURITY ESSENTIALLY FREE OF THE CORRESPONDING COLOR, AND SAID INK COMPOSITION COMPRISING FURTHER A NITROGENOUS ORGANIC BASE WHICH IS MISCIBLE WITH SAID OILY VEHICLE, SAID BASE BEING A NON-DRYING ALIPHATIC AMINE WHICH IS LIQUID AT ROOM TEMPERATURE BUT DOES NOT BOIL BELOW 150* C., SAID BASE BEING PRESENT IN QUANTITY NOT LESS THAN 5% AND NOT GREATER THAN 50% BY WEIGHT OF THE ENTIRE COMPOSITION .