CA1115871A

CA1115871A - Method for preparing bleed resistant lithographic inks

Info

Publication number: CA1115871A
Application number: CA309,088A
Authority: CA
Inventors: Manohar L. Arora
Original assignee: BASF Wyandotte Corp
Current assignee: BASF Corp
Priority date: 1977-08-15
Filing date: 1978-08-10
Publication date: 1982-01-05
Also published as: JPS5444908A; IT7850737A0; FR2400543B3; DK358378A; DE2835650A1; GB2002797B; FR2400543A1; GB2002797A

Abstract

ABSTRACT OF THE DISCLOSURE

Bleed resistant lithographic ink compositions containing azo red pigments are prepared by mixing a wetting agent such as an amine, an amine oxide, an amide, an amidine, an amidoxime, an oxime, an oxazolidine, or an amino acid with a substantially dry flushed color.

Description

~115871 1 This invention relates to improved lithographic printing ink compositions and to a method for preparing them. More particularly, the invention relates to bleed-resistant inks containing an azo red pigment.
In the lithographic printing process, the printing plate is prepared by a selective etching process so that the image-producing area is water-repellent and the non-image area is water-absorbent. The surfaces of said areas are even with respect to each other, in the case of a flat plate, for example, the surfaces lle in the same plane.
Prior to the applicatlon of the ink to the plate, an aqueous solution known as a fountain solution is distributed across the plate but it is adsorbed preferentially by the non-image area. The printing ink is re~ected by the wetted area and thus only the desired image is reproduced when the plate is pressed against the paper or other material belng printed.
A lithographic ink is principally a concentrated dis-persion of a pigment in a viscous oil vehicle plus a hydro-carbon solvent. The principle underlying lithographic printing is the old adage, "oil and water do not mix." Much of the difficulty encountered in lithographic printing, how-ever, originates from the fact that lithographic inks do mix with the fountain solution to some extent depending on the vehicle and pigment in the ink and the properties of the fountain solution. The repeated intimate contact of the ink with the fountain solution on the printing plate tends to ; cause the pigment to be leached from the ink by the a~ueous fountain solution. Such transfer of the pigment is known as "bleeding in the fountain."

~115871 1 Lithographic inks are, therefore, a special class of printing inks and their ingredients must be selected care-fully to minimize emulsification during intimate contact with water and to maxlmize the coating of the pigment by the vehlcle. The structure and, therefore, the properties of the pigment are particularly important considerations when lithographic inks are formulated. Some pigments are such notorlously bad bleeders that their use in lithographic inks is avoided unless there is no satisfactory substitute to provide the particular color desired. Azo red pigments are among these.
Two United States patents teach methods for reducing the bleeding of pigments from lithographic inks. Both methods are multi-step procedures and both depend on a heat-treating step to form a coating on the pigment. U.S. 2,742,375 teaches a method comprising the coating of pigment particles with a high molecular weight pyridinium chloride by slur-rying the pigment in an aqueous dispersion of the pyridinium chloride, filtering off the treated pigment and drying it and then, as an essential feature of the method, heatlng the dried pigment to develop a hydrophobic, organophilic coating on the pigment.
U.S. 2,683,702 teaches a method for improving the re-sistance of ultramarine blue and peacock blue pigments to bleeding in a lithographic fountain solution which comprises coating the pigment with a mixture of an alkylated methylol melamine and an N-alkylol fatty acid amide, or with a low molecular weight condensate thereof, by slurrying the pig-ment in an aqueous dispersion of said mixture or condensate, drying the treated pigment and curing such coating com-position at an elevated temperature.

- 2 -1 The use of amine salts and quaternary ammonium salts, each having at least one long chain aliphatic residue, as plgment flushing aids ls taught in U.S. 2,192,954. The flushlng ald must be a water-soluble salt and is added to the water phase of a pigment either as the salt or, when the water contains a sufficient amount of free acid to form a soluble salt of the amine, as the free base. A related patent, U.S. 2,192,956, characterizes the action of the salts in the '954 patent as a coating of the pigment with a hydrophobic layer. The invention disclosed and claimed in the '956 patent, on the other hand, is the use of said salts as flocculation aids in the washing and filtering of aqueous slurries of pigments.
Various other treatments of pigments and printing inks are known in the pigment art. U.S. 3,244,734 teaches that stearamides are used as adheslon, anti-block, antl-tack, and viscoslty-control additives in printing lnks. The vlscoslty, adheslon, tack and blocklng propertles of an lnk are at-trlbutes of the vehlcle rather than of the pigment and there is no correlation between such properties and the bleeding of lithographic inks. Moreover, it has been found that stearamide has no effect on the tack or blocklng properties of a lithographic printing ink, thus pointing up the special nature of this class of printing inks.
The full development of a pigment's color in thermo-plastic and thermoset resins is ach~eved by coating the pigment particles with a melted fatty acid amide, according to U.S. 3,953,218. Extremely high pigment loadings are also said to be obtained. The patent teaches that the su-perior wetting action of the amide permits the formulation of resin compositions in which the amide-coated pigments 1 are highly dispersed. The properties of molded and cast resins are discussed but the effect of water on the resins is not discussed.
U.S. 3,905,825 teaches the treatment of azo-acyl-acetaryl pigments with heterocyclic amines having a long aliphatic chain attached to the ring or with aliphatic diamines which are precursors of such heterocyclic amines.
The azo-acyl-acetaryl pigments are exemplified by Yellow Pigment Nos. 12 and 13. The treated pigment is taught to be easily dispersed in organic media and to be advantage-ously useful in rotogravure inks. Bleeding in the fountain is not a problem with such pigments, however. Almost no bleeding occurs when a lithographic ink containing Yellow Pigment No. 12 is contacted with a fountain solution. No difference in bleeding is observed when the yellow pigment is treated with a wetting agent according to the method described and claimed hereinbelow.
The 1825 patent refers to two other patents, Brltish Patent No. 1,080,115 and French Patent No. 1,538,270, for their teaching about the treatment of pigments with certain amines to make them easily dispersible. The French patent also relates to azo-acyl-acetaryl pigments. The British patent teac~es the treatment of organic pigments, including azo red pigments, with amine salts in the presence of water.
A possible explanation of the improved dispersibility of pigments so treated, as offered by the patentee, is that there is a transfer (~lushing) of the pigment from the aqueous phase to the amine phase. The patentee teaches that aqueous suspensions of pigments may be treated simultaneously with the amine and resins such as wood rosin and maleinized IllS871 1 natural resins.
Cycloaliphatic amlnes are taught in U.S. Patent No.

3,573,946 as agents for treating either dry pigments or aqueous suspensions of pigments in order to make said pigments more dispersible in organlc or aqueous media.
The coating of pigments with a special cationic surface-active combination of a quaternary ammonium com-pound and a tertiary aliphatic amine containing up to ten ethoxy groups is ~aught in U.S. Patent No. 3,014,810.
The treatment is said to enhance dispersion of the pig-ments in organophilic media, e.g., oil systems, and oleo-resinous materials. The coating of the pigment may be accomplished by adding the special surface-active agent to the organophilic media and then adding a dry pigment to said media or by flushing a water-wet pigment cake with said media.
Printing inks and varnishes whose components comprise amine salts of acidic resins and of acidic modifled drylng olls are taught ln U.S. 3,412,053. Sald amlne salts are miscible with water-soluble organic solvents but the acidic resins and drying oils from which they are made are not miscible with such solvents. Decomposition of the amine salts after deposition of the printing ink on paper causes the precipitation of the insoluble binders.
Now, it has been discovered that lithographic printing ink compositions containing an azo red pigment and at least one lithographic vehicle selected from the class consisting of an aromatic petroleum hydrocarbon, an alkali refined linseed oil, a pentaerythritol ester of phenolic modified 3o ~115871 rosin, a heat-bodied linseed oil, and a pentaerythritol ester of maleic modified rosin are made resistant to bleeding of the pigment into the fountain solution by mixing the ink vehicle and pigment with at least one pigment wetting agent selected from the class consisting of:
an aliphatic monoamine having from 2 to about 20 carbon atoms;
an aliphatic polyamine having from 2 to about 36 carbon atoms wherein the ratio of carbon atoms to amino groups is from about 1 to about 18, an amine oxide having the formula ~Rl R_ N ~ 0 wherein R, R' and R2 are aliphatic groups having from 1 to about 20 carbon atoms but wherein the total number of carbon atoms is about 36 or less;
dehydroabietylamine or tetrahydroabietylamine;
an amide having the formula H
wherein R3 is an aliphatic group containing from about 12 to about 20 carbon atoms and R4 is an aliphatic group containing from 1 to about 7 carbon atoms;
an amide having the formula o R~ - C - NR6R7 III

3o 1 wherein R~ is an aliphatic group having from about 12 to about 20 carbon atoms and R6 and R7 are indepen-dently hydrogen, lower alkyl, or lower aminoalkyl;
an amide having the formula O / (R9 - O)~ H

\ (Rl- O)~ H
wherein R3 is an aliphatic group having from about 12 to about 20 carbon atoms, R9 and Rl are alkylene groups having from 2 to about 4 carbon atoms, m is from 0 to about 5 and n is from about 1 to about 5 but m + n i8 from about 1 to about 5, an amidine having from about 12 to about 20 carbon atoms;
an amidoxime having from about 12 to about 20 carbon atoms;
an oxime having from about 12 to about 20 carbon atoms;
an oxazolidine having the formula Rll - N O V

wherein ~1l is a polyacrylate residue having a molec-ular weight of from about 800 to about 3000;
an amino acid having the formula Rl2 - CH(NRl3) - (CH )p - COOH VI
wherein Rl 2 iS an aliphatic group containing from about 12 to about 20 carbon atoms, Rl 3 iS independently hy-drogen, methyl or ethyl, and p is from 0 to about 4;

3o ~115871 1 an N-acyl amino acid having the for~ula o Rl~
Rl 4 _ C - N - CH - COOH VII
W}!ereill Rl 4 iS an alkyl group having from about 12 to about 20 carbon atoms and Rl' is an alkyl group having from 1 to about 4 carbon atoms;
an alkyl imidazoline having the formula N - CH

N ~ ( ~H 2 [(CH2)X - O]y H

wherein Rl 6 iS an alkyl group having from about 12 to about 20 carbon atoms, x is from 2 to about 4, and y is from 0 to about ~; and an aliphatic substituted aniline or naphtylamine wherein the aliphatic substituent contains from about 6 to about 20 carbon atoms.
Saltæ of the foregoing amines with organlc and in-organic acids are also useful. The salts of lower alkyl carboxyllc acids are preferred.
The term "aliphatic" is used in the description of this invention herein to mean a hydrocarbon group. Thus, for example, an aliphatic monoamine is an amine having a hydrocarbon group attached to the nitrogen atom and there are no other substituents on the hydrocarbon chain.
~epresentatives of the azo red pigment include tol-uidine red, chlorinated para red, permanent red 2B, lithol rubine red, red lake C, lithol red, Molora red and Macatawa 3o 1 red. Molora and Macatawa trademarks of ~hemetron Corp-poration for the manganese and calcium salts, respectively, of the diazo couple from C-amine and ~-hydroxy naphthoic acid.
The composition and properties of the lithographic vehicles which may be employed in the method and com-positlon of this invention are well known in the printing and pigment arts. Included among such vehicles are aromatic petroleum hydrocarbon resins, alkali-refined linseed oil, pentaerythritol esters of phenolic-modified rosins, maleic acid-modified rosin esters and mixtures thereof with each other and with tung oil.
The amount of pigment wetting agent which is effective to impart bleed resistance varies somewhat depending upon the particular agent employed but it is generally within the range of from about 0.5% to about 60% based on the weight of the pigment. The effective amount of the various types of agent is as follows:
aliphatic monoamines and salts thereof - from about 0.5% to about 25%, preferably from about 0.75 to about 12%; amounts ranging from about 1.5~ to about 12% are especially effective;
aliphatic polyamines and salts thereof - from about 0.5% to about 25%, preferably from about 1% to about12%;
aliphatic substituted aniline or naphthylamine and salts thereof - from about 1% to about 20%, pre-ferably from about 2% to about 15%;

3o _ g _ l dehydro - and tetrahydroabietylamine and salts thereof - from about 3% to about 30%, preferably from about 5% to about 25% and especially from about 12%
to about 25%;
amides of formula II, III or IV - from about 4%
to about 12%, preferably from about 5% to about 10%, especially from about 6% to about 9%;
amine oxides - from about 1% to about 25%, pre-ferably from about l to about 12%;
amidines - from about 4% to about 15%, prefer-ably from about 6% to about 10%;
amidoximes - from about 4% to about 15%, prefer-ably ~rom about 6% to about 10%;
oximes - from about 4% to about 15%, preferably from about 6% to about 10%;
oxazolidines - from about 3% to about 60%, pre-ferably from about 4% to about 36%, more preferably from about 6% to about 25%;
amino acids of formula VI - from about 4% to about 12%, preferably from about 5% to about 10%;
N-acyl amino acids of formula VII - from about 4%
to about 12%, preferably from about 5% to about 10%, imidazolines of formula VIII - from about 1.5% to about 5%.
An aliphatic monoamines may be primary, secondary or tertiary amines and the carbon chain thereof may be straight or branched, saturated or unsaturated. Examples of such amines include ethylamine, isopropylamine, butylamine, 3o . .

lil5871 octyla~.ine, N, N-diethyl propylamine, decylamine, n-dodecylamine, n-octadecylamine, hydrogenated di-tallow amine, N, N-dimethyl dodecylamine, di-dodecyl amine, N, N-diethyl octadecylamine and the like. Amines having f~om about 12 to about 20 carbon atoms are preferred, particul-arly the primary amines having such chain lenghts.
The polyamines, likewise, may contain straight-or branched-chains. Included among examples of such amines r A / 4 -o/;q~ "to b~ t~ne, are N-methyl ethylenediamine, ~, diaminobuta~e, 1, 12-diaminododecane, N-oleyl-l, 3-diaminopropane 3 triethylene-tetramine, and diamines derived from dimer acids. Several of the last-mentioned diamines are available from Humko-Sheffield Chemical under the trademark Kemamine. The preferred polyamines have a carbon atom/amino group ratio of from about 12:1 to about 18:1. Polyamines having from about 24 to about 36 carbon atoms are preferred especially.
The aliphatic substituents in the operative anilines and naphthylamines of this invention are ring substituents including such groups as dodecyl and dodecenyl. Mixtures of alkylated anilines in which some of the side chains are unsaturated are prepared by alkylating nitrobenzene with a~
commercial mixtures of long olaim olefins and hydrogenating the resulting alkylated nitrobenzene. Such olefin mixtures are available in various cuts such as C10-Cl2, C12-C16, C16-C18 and so on. It is preferred that the ring sub-stituent have from about 10 to about 20 carbon atoms.
Amides prepared from a fatty amine and a lower ali-phatic carboxylic acid are represented by formula II and 3o 1 are exemplified by N-octadecyl acetamide, N-lauryl propion-amide and the like.
Stearamide, N, N-dimethyl oleamide, lauramine, N-methyl palmitamide and N, N-dimethylaminopropyl oleamide are among the amides represented by formula III that are contemplated for ùse ln the method of this invention.
Ethoxylated amides of fatty acids are the preferred compoùnds represented by formula IV. Among such compounds are N, N-di(hydroxyethyl) amides of oleic acid, lauric acid and myristic acid and polyethoxylated amides such as those available from Emery Industries, Inc. under its Emid trade-mark. Expecially preferred are thos having from about 1 to about 3 ethoxy groups.
A resin available from Rohm & Haas under its product designation QR 568 is representative of the oxazolidine of formula V. Such compounds are preferred wetting agents in the method and composition of this invention.
N-Coco aminobutyric acid, a product sold by Armak under its trademark Armeen and designated Armeen Z is an example of the amino acids of formula VI contemplated in this invention.
An N-oleyl sarcosine sold by Ciba-Geigy under the trademark Sarkosyl 0 exemplifies the amino acids of formula VII.
An ethoxylated oleic imidazoline sold by Ciba-Geigy as Amine 0 is an example of the imidazolines of formula VIII.
The wetting agent is incorporated into the litho-3o ~15871 1 graphic lnk compositions of this invention by adding the agent to the flushed color at or near to the end of the dispersion process, l.e., when the flushed color is sub-stantially dry. In this context, "substantially dry" means 0.5% or less water. It is especially preferred to add the wetting agent during the let down step of the dispersion process.
The treatment of the pigment vehicle dispersion with the wetting agent does not require any heating but heat may be applied to evaporate residual water in the flushed color to the deslred level. The mlxing time is not critical.
The compositions contemplated in this invention are resistant to bleeding into so-called "regular" fountain solutions and alcoholic fountain solutions. A "regular"
solution is essentially an acidic solution of gum arabic in water. Phosphoric acid is often used to ad~ust the pH
of the solution and various surfactants and etching com-pounds may be present, also. The alcoholic solutions contain up to about 40~ isopropyl alcohol in addition to the components of the "regular" solutions.
The solvents used in formulating the inks of this invention are aliphatic hydrocarbon solvents having a kauributanol value of from 23 to 30 and a distillation range from 380F. to 600F. The in~s may also contain waxes such as a polyethylene wax, anti-oxidants and various other additives.
The following examples illustrate the method of this invention and also demonstrate the advantage of the com-positions of this invention.

3o ~11587~

EXAMPLE l A ~acatawa red presscake weighing 337 grams and con-talning 91 grams of the dry plgment is flushed with 72 grams Or a lithographic grade hydrocarbon varnish (60% solids).
Upon completion of the phase transfer, the flushed color i8 heated under a reduced pressure to about 200F. until 0.5% or less water remains. The temperature is then lowered to about 150F., the pressure is allowed to return to atomspheric and 132 grams Or hydrocarbon resin, 5 grams of a . solution Or an antioxidant (2,6-di-t-butyl-4-methylphenol) and 3 grams Or octadecylamine are added ln a letdown operation.
A mixture of 2 grams of the resulting product, 1.6 grams Or oleoresinous varnish and 0.4 gram of a polyethylene wax is then tested for its bleed resistance by shaking it wlth 12 mls. of Dahlgren fountain solution in a one ounce ~ar on a Red Devil shaker for three minutes. The fountain ~olution is filtered and the color of the filtrate is then checked visually for evidence of bleed. On a scale of O to 5 in which O means no bleed and 5 means severe bleed, the filtrate is rated 0.5 whereas a control sample containing no wetting agent is rated 4.5.

~15871 The general procedure of Example 1 is repeated except that 15 grams of the hydrocarbon resin is replaced in the flushing step with Triple 0 Litho varnish and the Macatawa red i8 replaced by Lithol Rubine to give a lithographic lnk having a bleed resistance similar to that of the product of Example 1.
Similar results showing the advantageous bleed re-sistance of the compositions of this invention are obtained when the various other wetting agents and vehicles dis-closed herein are employed according to the method of this invention. A rating of about 3.0 for the fountain solutlon after intimate contact with the lithographic ink is con-sidered to be the maximum acceptable bleed for the com-positions of this invention and that rating is consistently better than the untreated ink.
Inks prepared according to this invention have printing properties which are equal to those of control inks which do not contain the pigment wetting agents.
While the invention has been described with reference to cerkain specific embodiments, lt will be recognized by those skilled in the art that many variations are posslble without departing from the spirit and scope of the invention claimed herein.

3o

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for imparting bleed resistance to a litho-graphic printing ink composition containing an azo red pigment and at least one vehicle selected from the class consisting of an aromatic petroleum hydrocarbon, an alkali refined linseed oil, a pentaerythritol ester of phenolic modified rosin, a heat-bodied linseed oil, a pentaerythritol ester of maleic modified rosin and tung oil, said method comprising mixing a substantially dry flushed dispersion of the ink vehicle and pigment with an effective amount of at least one pigment wetting agent selected from the class consisting of:
an aliphatic monoamine having from 2 to about 20 carbon atoms;
an aliphatic polyamine having from 2 to about 36 carbon atoms wherein the ratio of carbon atoms to amino groups is from about 1 to 18;
an aliphatic substituted aniline or naphthylamine wherein the aliphatic substituent contains from about 6 to about 20 carbon atoms;
an amine oxide having the formula wherein R, R1 and R2 are aliphatic groups having from 1 to about 20 carbon atoms but wherein the total number of carbon atoms is about 36 or less; dehydroabietylamine or tetrahydrobietylaimine;
an amide having the formula Claim 1 continued wherein R3 is an aliphatic group containing from about 12 to about 20 carbon atoms and R4 is an aliphatic group containing from 1 to about 7. carbon atoms;
an amide having the formula wherein R5 is an aliphatic group having from about 12 to about 20 carbon atoms and R6 and R7 are independently hydrogen, lower alkyl, or lower aminoalkyl;
an amide having the formula wherein R8 is an aliphatic group having from about 12 to about 20 carbon atoms, R9 and R10 are alkylene groups having from 2 to about 4 carbon atoms, m is from 0 to about 5 and n is from about 1 to about 5 but m * n is from about l to about 5;
an amidine having from about 12 to about 20 carbon atoms;
an amidoxime having from about 12 to about 20 carbon atoms;
an oxime having from about 12 to about 20 carbon atoms;
an oxazolidine having the formula wherein R11 is a polyacrylate residue having a molecular weight of from about 800 to about 3000;

Claim 1 continued an amino acid having the formula wherein R12 is an aliphatic group containing from about 12 to about 20 carbon atoms, R13 may be independently hydrogen, methyl or ethyl, and p is from 0 to about 4;
an N-acyl amino acid having the formula wherein R14 is an alkyl group having from about 12 to about 20 carbon atoms and R15 is an alkyl group having from 1 to about 4 carbon atoms;
an alkyl imidazoline having the formula wherein R16 is an alkyl group having from about 12 to about 20 carbon atoms, x is from 2 to about 4, and y is from 0 to about 5; and salts of the aforesaid amines, with the proviso that when the wetting agent is an amide, the effective amount is from about 6 percent to about 9 percent of the weight of the pigment.
2. The method of claim 1 wherein the wetting agent is an aliphatic monoamine.
3. The method of claim 1 wherein the wetting agent is dehydroabietylamine.
4. The method of claim 1 wherein the wetting agent is an amide having the formula wherein R8 is an aliphatic group having from about 12 to about 20 carbon atoms, R9 and R10 are alkylene groups having from 2 to about 4 carbon atoms, m is from 0 to about 5, n is from about 1 to about 5 but m + n is from about 1 to about 5.
5. The method of claim 1 wherein the wetting agent is an oxazolidine.
6. The method of claim 2 wherein from about 0.75% to about 12% of the amine, based on the weight of the pigment, is mixed with the vehicle and pigment.
7. The method of claim 6 wherein the amine is octadecylamine.
8. The method of claim 3 wherein from about 6% to about 25% of dehydroabietyl amine, based on the weight of the pigment, is used.
9. The method of claim 4 wherein from about 5% to about 10% of the amide, based on the weight of the pigment, is used.
10. The method of claim 5 wherein from about 4% to about 36% of the oxazolidine, based on the weight of the pigment, is used.