CA1037184A

CA1037184A - Lithographic ink

Info

Publication number: CA1037184A
Application number: CA194,645A
Authority: CA
Inventors: Bheema R. Vijayendran
Original assignee: Pitney Bowes Inc
Current assignee: Pitney Bowes Inc
Priority date: 1973-03-12
Filing date: 1974-03-11
Publication date: 1978-08-22
Also published as: JPS5026604A; NL7403263A; GB1449361A; DE2411832A1; AU6651974A; ZA741356B; US3844994A

Abstract

Abstract of The Disclosure A novel ink formulation useful in lithographic printing processes which eliminates the necessity to dampen the litho-graphic master between printing cycles. The novel ink formula-tion of this invention is a stable emulsion comprising an oleophilic phase and a hydrophilic phase, comprising one or more polyhydric alcohols, a surfactant and polystyrene sulfonate.
The specific polymeric surfactants are: polyoxyethylene alcohols polyoxyethylene esters, polymeric condensation products of ethylene oxide - propylene oxide, the reaction product of ethylene oxide and propylene oxide with ethylene diamine, and polyvinyl pyrrolidone.

Description

Back~round of ~ e Invention Thl~ invention relates to a novel lnk formulation useful ln planographic and lithographlc printing procesHes. More psrticularly, this lnvention relates to a novel ink formulation useful in connection with lithographic printing processes, whereby the use thereof eliminates the need for ~eparate and repeated dampening of the lithographic master plate between prlnting of copies.
Basically, a lithographic master plate is prepared by producing on the surface thereof ink receptive and water re-ceptive areas, the latter being ink repellent areas. When the plate is contacted with an aqueous liqu$d, the aqueous liquid iB attracted to the water receptive areas and then when the ink i8 appliet the ink is selectively attracted by the ink re-ceptive surface of the plate and re~ected by the ink repellent areas. In the case of indirect or offset lithography, the plate bearing the ink in only those selective areas, is contacted with a printing blanket. The inked image i9 transferred to the blanket whi.ch in turn transfers the image to the sheet of paper or surface upon which the image is desired. However, in case of direct lithography, the ink bearing plate is contacted directly with the sheet of paper or other printing surface.
The various processes presently in use for preparing printing plates range from lithographic processes, where a de-slgn is made on the surface of the material with a water-repellent, ink receptive material such as crayon or lithographic chalk. Photographic processes may also be used wherein light sensitive bi-chromated gums or light sensitive diazo materials are exposed to an image pattern and the exposed materials are then treated to obtain ink receptive areas. Llthography plates may also be prepared by electrostatic copying methods. Any of .. ~k tb/~

1037~8~
these plates may be used with the printing ink of this invention.
In sltuations where many copies are to be made from the original lithographic plate, flexible plate~ are wrapped around cylinders and an aqueous solution and ink from separate fountains are supplied by rollers. In a typical printing operation, the cylinder bearing the lithographic plate is first contacted with a roller wetted by a water or other suitable aqueous solution.
The aqueous solution is absorbed by the hydrophilic surfaces but repelled by ink receptive or oleophilic surfaces. The plate is then contacted with a roller wetted with an oil base ink and the ink is adsorbed by the ink receptive surfaces and re-~ected by the ink repellent surfaceg which have been rendered oil repellent by the initial treatment with the aqueous solution.
The plate is then contacted with the printing blanket to which the ink is tran~ferred, and the blanket in turn contacts the sheet of paper upon which the design is to be printed. The ink is transferred from the blanket to the sheet and the entire process is repeated to obtain the individual sheets bearing the design. This process require~ the sequential application of water and ink each time a print is made, and this repeated ; operation decreases the useful life of the plate. Troubles are also encountered through partial comingling or emulsification of the oil and water on the plate.
In addition to the foregoing, another problem is faced in ehe case where the lithographic printing process is conducted automatically in the absence of human supervision. It is very difficult to control the water supply which is applied to the rollers to prevent print offset. Without uniform water appli-cation there occurs background print offset in the case of in-sufficlent water application, or weak print quality in the caseof a surplus of water appl~cation.

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One of the propo~ed method~ for overcomlng so~e oP the tefects of the de~cribed process has been the use of water-in-oil emulsion inks. However, the emulsion inks heretoEore sug-ge~ted for u~e posse~et drawbacks which have not made their use completely acceptable. Some of the ~nks previously pro-posed did not have the capacity to remain in an emulsive state, that is, these inks have a tentency to temulsify or break in the ink fountain or during storage. Others may not provide satis-factory prints, particularly where a great number of copies are to be produced. In order to be effective for lithographic printing the aqueous phase dispersed in the oily printing ink must not significantly change tho~e characteristics of the ink which are requisite to satisfactory printing. When an ink emulsion te-mulsifies in the ink fountain or does not properly separate or break upon application to the printing surface, the printed imsge is dull, le~s intense, ant spottet or stippled. The non-ima8e area is sometimes toned or diAcolored.
Among the methods and/or formulations heretofore sug-gestet for use in overcoming the problems associatet with the water-in-oil emulsion inks are those disclosed in U.S. Patent 3,615,750 which tiscloses a relatively anhydrou~ polyhydric alcohol-in-oil emulsion ink which can be employed in litho-graphic printing processe~ without repeated applicatlons of water to the lithographic master plate before each printing.
However, the ink formulations discloset in U.S. Patent 3,615,750 have been found to be relatively unstable ant very sensitive to heat. As a result, these prior art ink formulations requiret "curing or aging" for from about seven to thirty tays to ob-taln equilibration before they coult be successfully employed.
In addition, these prior art formulations have been fount to suffer from a further tisadvantage It often occurs that after tb¦~ ~

10371~4 repeated use of a sin~le lithographic master plate with the prlor art ink formulations, it may be necessary for one reason or another to stop the printlng process for an extended period of time, for example, for an hour or more for repairs or for some other reason. Upon restarting the printing process after this prolonged "stand down" time, it has been found that the master plate and/or the internal phase of the ink formulation on the rollers has dried out and that the prior art ink formula-tions cause ink offset to occur, i.e., ink is picked up by the previously ink repellent areas of the master plate and is trans-ferred to the paper on which the image is to be printed. This offset continues until the master plate is redampened and re-sults in poor quality reproductions which must be discarded.
Accordingly, it is an ob~ect of the invention to provide litho-graphic ink formulations which are stable over a substantial perlod of time.
It is a further ob~ect of the invention to provide litho-graphic ink formulations of the above character which require less curing or aging time than do prior art formulations.
Other ob~ects of the invention will in part be obvious ; and will in part appear hereinafter.

Summarv of the Invention I have now discovered a new and novel ink formulation suitable for use in lithographic printing processes which ob-vlates the tisadvantages experienced with the prior art formu-lations. I have found new ink formulations which eliminate the necessity for separate and repeated tampening of the lithographic master plate between copies. In atdition, the ink formulations - of thi~ lnventlon are extremely stable and may be employed after being "aget or cured" for as little as four hours. Furthermore, .

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1037~84 even after "~tand down" tlmes ln excess of 8iX hour~, it has been found that the ink formulations of this invention may be employed wlthout the necessity of redampening the lithographlc ma~ter plate and has greatly retuced ink offget problems.
The novel ink formulations of this invention comprise a ~table and persistent emulsion of two dissimilar phases; i.e., an oleophilic phase ant a hydrophilic phase. These two dis-slmilar phases are held in a stable emulsion form by the employ-ment of a polymeric surfactant and a small but effective amount of polystyrene sulfonate. The stability of the resultant emul-sions of the instant invention is such that the emulsion is storably stable even over extentet periods of time while at the same time is capable of being broken by the operation of the pre6s rollers by which they are applied to the master plate dur-ing the lithographlc printing process.
The oleophilic phase of the ink formulations of this in-; vention may be compriset of various materials which are commonly employet in inks useful in lithographic printing processes, ant includes such material as pigments, resin~, oils, varnishes, gels, waxes, drying agents such as metal soaps, antl oxitants, ant otherlike materials as are well known to the skilled worker to be use-ful for such purposes.
The hydrophilic phase of the ink formulations of this lnvention are preferably comprised of such hytrophilic substances - a~ one or more polyhydric alcohols in combination with a poly-~erlc surfactant and polystyrene sulfonate to impart stable characteri8tic8 to the lnk formulations. The polyhytric alcohols whlch may be satlsfactorlly employed elther singly or ln com-blnation, lnclude glycerine, ethylene glycol, glycerol, propylene glycol, 80rbitol, mannitol and the like. In addltlon, ln the ~practice of thi~ lnventlon, there may be adtet to the polyhytric .

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alcohol many other hydrophilic atdltives ~uch as an alkanol, for example methanol or ethanol, and/or water. Although the formulatlons of this inve~tion may be anhydrous, ~t has been found that satisfactory results are obtained even when about up to 20% by weight of water or up to 10% by weight of an alkanol ls incorporated in the polyhydric alcohol fraction.
The classes of surfactants are Polyoxyethylene esters of fatty acits; Polyoxyethylene alcohols, polymeric polyols and Polyvinyl Pyrrolidone, each having specific characteristics as more fully set forth below.
The preferred range for the surfactants is from about 1 to 10 percent of the hydrophilic phase of the ink formulation and preferably from about 2 to about 7.5 percent by weight. A
polystyrene sulfonate is employed in a smaIl but effective amount as a stabilizer. For those formulations set forth in Examples I
and II below it has been found that said stabilizer in an amount from about .05 to about 1 percent by weight of the hydrophilic phase of the ink formulation, ant preferably from about .I to about .5 percent by weight of the hydrophilic phase may be used.
~'' Detailed Description of the Invention The lithographic ink of the invention is made by emul-slfication of the hydrophilic and oleophilic phases by any known manner of creating emulsions. The hydrophilic phase of the ink should comprlse from about 15 to about 60 parts with the oleo-phllic pha~e comprising from about 85 to about 40 parts of the ink formulation.
The poly~eric surfactants which are preferred are as follows:
- - ~1) Polyoxyethyiene alcohols of the formula C~3(CH2)nO(CH2CH20)2-OH wherein n is equal to or ; 6 .... . .

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~0371~4 greater than 12. An example of ~uch a surfactant ic "BRIJ~ 92" which is commercially available from Atlas Chemical Co.

(2) Polyoxyethylene esters of saturated fatty acids of

3(CH2)mC (CH2 CH2)n CH20H wherein m 18 equal to or greater than 8 and n is greater than 50.
An example of such a surfactant which is commercially available i~ "MYR ~ 59" from Atlas Chemical Co.
(3~ Polymeric polyol condensation products of Ethylene Oxide - Propylene Oxide having a molecular weight of from 1,000 to 5,000 and preferably less than 29000 with the Hydrophilic Ethylene Oxide units com-prising less than 50 percent of the polymer.
Examples of commercially available polymeric sur-~actants are Pluronic~ L-35, Pluronic~ lO-R5 and Pluronic~ P-75 from BASF Wyandotte Corp.

(4) Reaction product of Ethylene Oxide and Propylene Oxide with Ethylene Diamine and having a molecular weight of around 4,000 with the hydrophilic poly-oxyethylene unit making up about 10 percent of the polymer.
Examples of such commercially available surfactants are Tetronic~ 701 and Tetronic~ 90l from BASF
Wyandotte Corp.

(5) Polyvinyl Pyrrolidone having a molecular we$ght of le~s than 200,000. Examples of commercially avail-able polyvinyl Pyrrolidone are mate by GAF Corporation under the designation PVP-R-60 and PVP-R-30. Other 30urces for the above surfactants may also be used wlthin the scope of the invention. Examples of db/~
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1037~84 commercially available polystyrene guifonate made by National Starch and Chemical Corp. and sold under the trademark "Versa TL", as shown in the following examples, Versa TL 700, Versa TL 500 and Ver~a TL 70 may be used. These polystyrene sul-fonates have a molecular weight of 6 to 8 million, 800>000 and 80,000 respectively.
The invention may be further illustrated by the follow-ing examples:

~XAMPLE I
A. The oleophilic phase of the ink formulation of the instant invention may be prepared as follows:
The following materials in the requisite amounts are employed:

Material Amount Carbon Black ("Regal~ 400R", Cabot Corp.) 25.0 gms.
Alkyd Resin CSyntex~ 3409"; Celane~e Corp.) 33.0 gms.

Alkyd motified urethane resin ("Uroset~ Resin"; Lawter Chemical Co.) 16.5 gms.

Castor Oil ("Castung~ 103 G-H"; Baker Castor 7.0 gms.
Oil Corp.) Gel Vehicle (Lawter Chemical)18.0 gms.
Hydroquinone 0.5 ~ms.
TOTAL 100.0 gms.
All of the above materials except for the carbon black pigment are charged into a change can mixer, and are mixed until a uniform consistency is obtained. The carbon black is then atded slowly with constant stirring. The resultant mixture is then dlspersed in a 3 roll mill until the particle slze thereof is reduced to less than 10 microns as determined by a Hegman's gauge. The reYultant mixture ls then employed as the oleophilic db/~ ~

phase in the preparation of the varlous lnk formulatlons of the lnstant $nvention.
B. The hydrophilic phase of the ink formulation of the ln~tant invention may be prepared as follows:
The following materials in the requisite amounts are employed:
Formulation No. Material Amount 1Ethylene Glycol 175.0 gms.
MYR ~ 59 (Atlas Chemical Co.) 9.0 gms.
BRI ~ 92 (Atlas Chemical Co.) 1.0 gms.
Yersa-TL 500 (National Starch ant Chemical Co.) 1.0 ~ms.
TOTAL 186.0 gms.
; The above materials are charged into a 600 ml. container and thoroughly mixed with stirring and heat (140-160F.) for about ten minutes until a composition of smooth consistency is obtained.
C. The final ink formulation of the instant invention is prepared as follows:
Slxty-five grams of the oleophilic composition prepared ln Part A above are mixed with 35 grams of the hydrophilic composi-tion prepared in Part B above, in a high shear disperser for ten to fifteen minu~es, at a temperature of from about 150 to about 160 F. The resultant mixture is then cooled and tested as a lithographic ink after two hours.

EXAMPLE II
The procedure set forth in Example 1 is followed ex-cept that the following hydrophilic compositions are substituted for the hydrophilic composition set forth in Example 1, Part B.

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1037~4 Formulatlon No. Materlal Amounts 2 Ethylene Glycol 125.0 gms.
Water 50.0 gms.
MYR ~ 59 9.0 gms.
BRI ~ 92 1.0 gms.

3 Ethylene Glycol 175.0 gms.
Pluronic~ L-35 (BASF Wyandotte Corp.) 9.0 gms.
Tetronic~ 701 (BASF Wyandotte Corp.) 1.0 gms.
Versa-TL 70 O.S gms.

4 Ethylene Glycol 175.0 gms.
PVP K-30 (GAF Corp.) 9.0 gms.
Te~ronic~ 701 1.0 gms.
Versa-TL 70 0.75 gms Ethylene Glycol 175.0 gms.
PVP K-30 lO.0 gms.
Versa-TL 700 0.9 gms.

6 Glycerine 125.0 gms.
Water S0.0 gms.
MYR ~ 59 9.0 gms.
BRI ~ 92 1.0 gms.
Versa-TL 700 ~ 0.3 gms.

7 Ethylene Glycol 60.0 gms.
Glycerine 60.0 gms.
Water 55.0 gms.
~YR ~ 59 9.0 gms.
- BRI ~ 92 l.0 gms.
Ver6a-TL 700 0.4 gms.

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8 Ethylene Glycol 60.0 gms.
Glycerine 60.0 gms.
Water 55.0 gms.
PVP-K-30 6.0 gms.
Versa-TL 700 0.4 gms.
The ink for~ulations prepared in accordance with the pro-cedure set forth in Examples I and II above, were tested and evaluated. The testing was done on a lithographic press employ-ing Zinc Oxide coated paper to make lithographic master plates by means of an electrostatic copying process. The lithographic master plate is etched and placed on the master cylinder of the press and prints were made employing the various ink formulations without any water unit in the press to dampen the master plate between printings. The print quality, clean background in the non-imaged areas and ease of ink control in a long run are some of the factors considered in evaluating the ink formulations. The re~ults obtained are tabulated in Table I below:

TABLE I
Formulatlon No. Agin~ Period (hours) No. of acceptable copies 1 2 1000 +

2 4 1000 +

3 3 1000 +
4 ~ 1000 +
4 1000 +

6 3 1000 +

7 4 1000 +

8 3 1000 +

Formulation No. 2 did not contain polyRtyrene sulfonate , . , , _ ant dried on the press in 3-4 hours. All of the other formula-tions containing polystyrene sulfonate were usable for more than tb/ P ~

6 hour~. 10371~

EXAMPLE III
~ he same procedure as set forth in Example 1 was followed except that a hydrophllic composition according to the prior art was used in~tead of the composition of Example I, part B as follow~;
Ethylene Glycol 20.0 grams Glycerine 15.0 gram~
Atlas~ G-1300 (Atlas Chemical Co.) 1.8 grams Arlacel~ 186-A ~Atlas Chemical Co.) 0.2 grams According to U.S. Patent No. 3,615,750 Atlas~ G-1300 is a polyoxyethylene glyceride ester and Arlacel~ 186-A is a mix-ture of mono and di-glycerides of fat forming fatty acids.
Por comparative purposes the ink formulations as set forth ln Example III were tested in the same manner and by the same criterla as those tested for Examples I ant II. The re-~ult~ are set forth in Table II below:
TABLE II
; A8lng Period (Hours) No. of Acceptable Copies Aa will be noted, less than 100 acceptable copie~ coultbe made and even with extended aging of thes2 prior art ink formu-latlons there was no substantial lncrease in the number of ac-ceptable copies produced. Thus the ink formulations of the in-vention provide a substantial number of lithographic coples with lea~ a8ing ant more ink stabillty.
- It will thus be seen that the ob~ect~ set forth above, among tho~e ~ade apparent from the preceding description, are efficiently attained and, since certain change~ may be made in tb/~ ~

1~371~34 the above compositions ant formulatlons wlthout departing from the scope of ~he inventlon, it ls lntended that all matter contained in the above description shall be interpreted as il-lustrative and not in a limiting 8ense.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A lithographic ink emulsion comprising a 40 to about 85 parts by weight oleophilic phase and a is to about 60 parts by weight hydrophilic phase, the hydrophilic phase further com-prising A. an amount of at least one polymeric surfactant equal to 1-10% of the hydrophilic phase and taken from the group con-sisting of (1) Polyoxyethylene alcohols of the formula CH3(CH2)nO(CH2CH2O)2-OH wherein n is equal to or greater than 12;
(2) Polyoxyethylene esters of saturated fatty acids of the formula CH3(CH2)m.COO(CH2CH2O)nCH2OH wherein m is equal to or greater than 8 and n is greater than 50;
(3) Polymeric polyol condensation products of Ethylene Oxide-Propylene Oxide having a molecular weight of from 1,000 to 5,000 with the hydrophilic Ethylene Oxide units comprising less than 50 percent of the polymer;
(4) The polymeric polyol reaction product of Ethylene Oxide and Propylene Oxide with Ethylene Diamine and having a molecular weight of about 4,000, with the hydrophilic poly-oxyethylene unit making up about 10 percent of the polymer; and (5) Polyvinyl Pyrrolidone having a molecular weight of less than 200,000;
B. an amount of a polystyrene sulfonate equal to 0.05 to 1% of the hydrophilic phase; and C. a polyhydric alcohol.

2. The ink formulation claimed in claim 2 wherein said surfactant comprises from about 2 to about 7.5 percent by weight of said hydrophilic phase.

3. The ink formulation claimed in claim 1 wherein said polystyrene sulfonate comprises from about .1 to about .5 percent by weight of said hydrophilic phase.

4. A lithographic ink emulsion comprising a 40 to about 85 parts by weight oleophilic phase, a 15 to about 60 parts by weight hydrophilic phase, the hydrophilic phase further com-prising a polyhydric alcohol and a 1 to 10 percent polymeric sur-factant taken from the group consisting of at least one of A. polyoxyethylene esters of fatty acids;
B. polyoxyethylene alcohols;
C. polymeric polyol condensation products of ethylene oxide-propylene oxide;
D. a polymeric polyol reaction product of ethylene oxide and propylene oxide with ethylene diamine;
E. polyvinyl pyrrolidone; and an amount of polystyrene sulfonate equal to 0.005 to 1% of the hydrophilic phase.

5. The ink formulation claimed in claim 4 wherein said polystyrene sulfonate comprises from about .1 to about .5 per-cent by weight of said hydrophilic phase.

6. The ink formulation claimed in claim 4 wherein said polymeric surfactant is taken from the group consisting of A. Polyoxyethylene alcohols of the formula CH3(CH2)nO(CH2CH2O)2-OH wherein n is equal to or greater than 12;
B. Polyoxyethylene esters of saturated fatty acids of the formula CH3(CH2)m.COO(CH2CH2O)nCH2OH wherein m is equal to or greater than 8 and n is greater than 50;
C. Polymeric polyol condensation products of Ethylene Oxide-Propylene Oxide having a molecular weight of from 1,000 to 5,000 with the hydrophilic Ethylene Oxide units comprising less than 50 percent of the polymer;
D. the polymeric polyol reaction product of Ethylene Oxide and Propylene Oxide with Ethylene Diamine and having a molecular weight of about 4,000, with the hydrophilic poly-oxyethylene unit making up about 10 percent of the polymer; and E. Polyvinyl Pyrrolidone having a molecular weight of less than 200,000.