CA1228204A

CA1228204A - Fountain solution

Info

Publication number: CA1228204A
Application number: CA000423922A
Authority: CA
Inventors: Richard J. Burns; Donald F. Smith, Jr.
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1982-03-29
Filing date: 1983-03-18
Publication date: 1987-10-20
Also published as: EP0091601A3; EP0091601A2; JPS58176280A

Abstract

ABSTRACT OF THE DISCLOSURE
An improved fountain solution suitable for use in a lithographic offset printing press which solution contains from about 0.5 to about 10 percent by volume of an isopropanol replacement, and between 0.005 and about 1 percent by weight of a water- soluble/miscible polymer selected from hydroxyethyl cellulose, hydroxy-propyl cellulose, methylcellulose, hydroxypropyl methylcellulose, hydroxybutyl methylcellulose, poly-(ethylene oxdel), poly(acrylamide), poly(vinyl alco-hol), guar gums, and acid thickening polymers. The fountain solution provides increased viscosity over current fountain solutions which results in improved operating latitude and decrease of problems associated with isopropanol replacements.

Description

AN IMPROVED FOUNTAIN SOLUTION

BACKGROUND OF THE INVENTION
This invention is directed to an improved fountain solution suitable for use in a lithographic printing press. This fountain solution is essentially free of volatile alcohols~ such as isopropanol. The fountain solution uses less volatile alcohols, polyols, diols, glycols, glycol ethers, and glycol ether esters of varying degrees o~ water solubility and mixtures thereof with a particular high molecular weight water-soluble/miscible polymer that increases the viscosity of the fountain solution and permits operatio~ of a printing press in a manner more like that of conven-tional alcohol-modified fountain solutions.
Lithographic printing press operations require the use of a dampening or fountain solution to achieve proper operation of the press, so as to yield good, acceptable, commercial quality prints. The purpose of the fountain solution is to keep the ink in the image area and to keep the non-image areas of the printing plate free of ink. The compositions of fountain solutions have been described in the literature and generally con~ain solutions of salts, phosphoric acid, and low molecular weight water-soluble polymers, such as gum arabic. Alcohol, such as isopropanol, is usually included at levels of 1 n to 30 percent by volume of the fountain solution. It is possible to print without alc~ol in ~he fountain solution but it is extremely difficult to do so, and constant attentlon must be given to keeping the press in adjustment. Use of alcohol increases operating latitude ? n that good quality pri~ts can be ~ade over 2 range of press adj~s~ents~ espec~al~y fountain solution feed rate.

i~2~

Considerations of toxicity of these volatile alcohols and their attendant flammability have provided the impetus to find alcohol replacements. A number of patents pertaining to alcohol substitutes for fountain solutio~s attest to the desirability of elim1nating vola~ile alcohols~ In commercial practice these alcohol substitutes may range from a single component such as Bu~yl Cellosolve to more complex mixtures as taught in ~.S. Patent 4,278,467 which describes iso-propanol-free fountain solutions utilizing glycol(s) and glycol ether(s) or mixtures thereof. Thus, the prior art enables the formulation of alcohol-free fountain solutions that can perform in commercial printing operations. However, the common problem observed in the use of the alcohol-free fountain solutions is decreased operating latitude, especially on presses equipped with a Dahlgren dampening system.
The Dahlgren dampening system is a means of transport-ing the fountain solution to the printing plate by first picking up fountain solution from a reser~oir, then mixing the fountain solution (emulsifying it) with the ink so that ink and fountain solution are carried together to the plate where the physical mixture of ink and fountain solution separate wi~h ink going to the image area and fountain solution going to the non-image area of the plate.
The Dahlgren roll (fountain solution supply roll) speed is set separately from the speed of the rolls of the ink train assembly. When alcohol sub-stitutes are used, it is commonly observed that much higher speeds are needed on the Dahlgren roll to prevent a problem known as scumming. Scumming is the deposition of excess ink on the printed surface due to insufficient fountain solution transport. The neces-sity of operating at increased Dahlgren roll speeds ~8~

reduces latitude, which is essentially the working range of Dahlgren roll speed settings over which commercial quality prints can be obtained. Latitude also includes the adjustments of gaps, and speed setting of the other rolls of the press. A low degree of latitude coupled with the need to run the Dahlgren roll at significantly higher speeds makes the continu-ing production of commer~ial quality pri~ted matter very difficult.

DESCRIPTION OF THE INVENTION
It has now been found that incorporation of low levels of relatively high molecular weight water miscible/soluble polymers in the fountain solution allows significant reduction in Dahlgren roll speed setting and increases the latitude of press operation.
A wide variety of water miscible/soluble polymers exist which can effectively thicken alcohol-free fountain solids when used at low levels. Low levels of thic~ening are preerred so as to minimize adverse interaction between the polymer and ink. These polymers include cellulosic polymers, such as hydroxy-ethyl cellulose, hydroxypropyl cellulose, methylcellu-lose, hydroxypropyl methylcellulose, hydroxybutyl methylcellulose, carboxymethyl cellulose, and other water-soluble/miscible polymers such as poly(ethylene oxide), poly(acrylamide), poly(vinyl alcohol), and guar gums and chemically modified gums. These polymers constitute from ~bou~ 0~005 to about 1 percent by weight of the fountain solution.
The fountain solution contains between about 0 . 5 and about 10 percent by volume of the isopropanol repla~ement .

Preferably, the replacement is a mixture of a polyol and/or glycol ether partially soluble in water and a polyol and/or glycol ether completely soluble in water. The polyol and/or glycol partially soluble in water includes, for example, one or more of

2-ethyl-1,3-hexanediol, Esterdiol-204~, i.e., HO-CH2C(CH3)2CH2OCOC(CH3)2CH2OH, Hexyl Cellosolve , i.e., C6H13OCH2CH2OH, Hexyl Carbitol , i.e., C6H13O(C2H4O)2H, and the like. The polyol and/or glycol ether which is completely soluble in water includes, for example, one or more of propylene glycol, ethylene glycol, dipropylene glycol, diethylene glycol, hexylene glycol, triethylene glycol, tetraethylene glycol, tripropylene glycol, 1,5-pentanediol, Methyl Cellosolve, i.e., CH3OC2H4OH, Cellosolve solvent, i.e., C2H5OC2H~OH, Butyl Cellosolve solvent, i.e., C4HgOC2B4OHI and the like.
The solubility is measured by determing the percent by weight of the polyol and/or glycol ether which is soluble in water at 20C. A polyol and/or glycol is characterized as partially soluble in water if its solubility in water at 20C is from about 0.99 to about 28.0 weight percent.
From about 0.08 to about 10 parts by volume of the polyol and/or glycol ether, which is partially soluble in water, is used per part by volume of the polyol and/or glycol ether which is completely soluble in water.
The fountain solutions are preferably used as aqueous acidic solutions. Phosphoric acid is a preferred acid for use in acidifying the formulation.
Other acids which can be used include inorganic as well as organlc acids, such as acetic acid, nitric acid, hydrochloric acid, and the like. A buffering agent, such as ammoniu~ acetate, can also be included.

13506 *Trademark of Union Carbide Corp.

The fountain solution is generally maintained at a pH of from about 2 to about 5. However, the particular pH at which a given solution will be main-tained will depend upon factors, such as the type of water-soluble polymer used, other ingredients 'in the solution, as well as the type of substrate employed in the lithographic printing plate, and the like.
Other additives which may be used in the fountain solution include preservatives such as phenol, sodium salicylate, and the like; corrosion inhibitors such as ammonium bichromate, magnesium nitrate, zinc nitrate, and the like; hardeners, such as chromium, aluminum, and the like; organic solvents, such as cyclic ethers, e.g., 4-butyrolactone, and the like; low molecular weight aldehydes, such as formaldehyde, glutaraldehyde, and the like. These additives are generally used in amounts of from about 0.1 to about 10 percent by volume.

EXAMPLES
The following examples serve to illustrate specific embodiments of this invention and it is not intended that the invention shall be limited by the examples.
The viscosity of water, of an isopropanol/
water mixture, of a eonventional fountain solution, and of an alcohol substitute fountain solution is presented in Table 1.

;;~z~

(Measured with an Ubbelhode Capillary Viscometer) 1) Deionized Water D.87 2) 20% Volume ~ixture of 1.67 Isopropanol/Deionized Water

3) Conventional Fountain Solution 1.66 2.0 oz Varn Wonderline(a) etch per qallon of 20% Volume Isopropanol/Water Solution

4) Alcohol Substitute I(b) 1.1 oz/gal of water 0.87 2.2 oz/gal of water 0.90 3.4 oz/gal of water 0.9~
a~ Varn Wo~derline: A comercially available .
solution of a mixture of acid, salts, gum ~olution~ etc. (Tra~emark of Varn Products, Inc.) b) Composition of Alcohol Substitute Io Wei~ht Percent Dipropylene glycol 32 2-~thyl 1-3-hexanediol 18 n-Hexyl Cellosolve Water 45 The finding from the data of Table 1 is that water or al~ohol substitute-based ~ountain solution has only half the viscosity of alcohol solution or alcohol-modified ~ountain solution.
A number o~ water-miscibleJ~oluble poly~ers were ~ested at low concen~rations ~o d~termine the ~is~osity o~ the resul~ing water ~olutivns. Data are pre~ented in ~able 2 .. . .. . ... ... . . .... . .

~Z8~

Dilute Solution Viscosity of Selected Grades of Poly(Vinyl Alcohol) and Hy~roxyethyl Cellulose Concentration Viscosity~*
in Water Centistokes Polymers Weight_% _ 29-C

~a) Gelvatol 20/90 0.1 0.9~
0~2 1.05 0.5 1.37 ~b) Cellosi~e QP-100M 0.05% 1.37~C) QP-52M 0.07% 1.92(c) QP-4400 0.05~ 1.25(C) QP-4400 0.08% 1.56(C) QP-09 0.08% ~.96(c) QP-3L 0.31~ 1.52 QP-3L 0.31% 1.50(C) ~Measured with an Ubbelhode Capillary Viscometer.

a) Gelvatol 88% hydrolyzed poly(vinyl alcohol). Trademark of Monsanto b) Hydroxyethyl Cellulose fro~ Union Carbide ' Corporat~n.
~) With 1.0 oz/gal of Alcohol Substitute I fr~m Tabl~ 1.

.. . ,, .. ~ . ~, ... . . . . .. . .. ...... ... . .

~ 2 ~

Using the polymer concentration/viscosity data of Table 2 as a guide, other water-soluble/miscible polymers were evaluated to determine the concentration required to approximate the viscosity of the conven-tional fountain solution.
Appropriate concentrations of polymer solution were then blended with a commercially available etch and an alcohol substitute to prepare fountain solutions for evaluation on a printing press. Formulations are shown in Table 3. The viscosity of each formulation is shown in Table 4.
~ he fountain solutions of Table 3 were evalu-ated on a Miehle Favorite 25-inch sheetfed press.
Table 5 presents a listing of results of the press trial. Example 1 amply illustrates the wide operating latitude of a conventional isopropanol-modified foun-tain colutionO Example 2 illustrates the performance of another isopropanol substitute with thickener.
Example 3 illustrates the low viscosity and narrow latitude of a commercial quality alcohol substi-tute~ Examples 4 and 5, and 8 through 14 show a significant increase in press operation latitude compared to Example 3. Examples 6 and 7, which yielded poor ~uality prints, illustrate that viscosity control alone is not the sole reason for improved performance, but that the polymers must have an affinity for the ink, etch, and the alcohol subs~itute in order to realize an improvement.
The foregoing has amply illustrated the interdepend~nce of thickener, ink, etch, and ~the organic components of alcohol subs~itutes on overall performance. It further shows that as any component is varied, so alqo may print quality vary, and fountain ~olution formulation adjustment may be needed along ~Z~8~

with a proper matching of thickener species. Operating latitude is but one aspect involved in press perfor-mance. Other characteristics such as dot spread, optical density, tinting, banding, scumming, selection of ink, etc., determine the optimum choice of f~untain solution components.

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ountain Solution Composition in Fluid Ounces Example 1 2 3 4 Water 140 111 123 ~ 114 Varn Wonderline etch 2 - - -*Prisco R855A etch - 3 3 3 Butyl Cellosolve - 5 - -~*Alcohol Substitute I - - 2 2 1~ Soln. Cellosi(ze)QP-4400 - 9 - 9 Isopropanol 26 - - -!

Water 118118 120 116 119 Prisco R855A etch 3 3 3 3 3 Alcohol Subs~itute I 2 2 2 2 2 1% Soln. ~csllosize QP-4400 5 1% Hercul~s 7M CMC - 5 3 1% Polyox Coag Soln. - - - 7 4 Water 120115 120 116 115 Prisco R855A etch 3 3 3 3 3 1~ Jagua~ ~07 Guar Gum 5 10 - - -t% Klucel M Hydroxy- - - S 9 '' propyl(fCellulo~e 1% Tylo e ~ethyl. - - 10 Cellulose Sol~.

. *Commercially availabl~ etch solution containing a mixture of acid, salts, gum~ etc.
**From Table Io (a) trademark of Printer's Service,Inc.
(b) trademark of UCC
(c) trademark of Hercules, Inc.
135~ (d) trademark o Celanese, Inc.
(e~ trademark of l~ercules, Inc.
(f) trademark of Kalle/Hoechst ~' .
- ~ - - _ ,, .

2~!~

Viscosi~y of Fountain Solutions*

Example Viscosity,_Centistokes, 19C
r 1 .66 2 1.71 3 0.89 1 .5Y

1.15 6 1.07 7 1.09 8 1.43 9 1.16 1.20 11 1.65 12 1.20 13 1.~5 14 1.11 ~Formulations shown in Table 3. Viscosity measured with an t~bbelhode capillary viscometer.

lZ2~ C~4 Press Trial ~esults of Fountain Solution Evaluation ExamPle~ (a) Latitude(b) l 33-90 5r 2 60~100 40 3 70-~0 10 4 <60-B0 20+
<70-100 30~
6 -very poor print quality 7 -very poor print quality <80-100 20+
9 <85-100 15+
<40-100 60+
ll <60-100 40+
12 ~70-100 30+
13 >60-80 15+
14 <80-100 20+

(a) Dahlgren roll speed settings over which good quality prints were obtained. Settings below lower speed limit tend towards scumming, values higher than upper limit tend to wash out or develop banding.

(b) Total operating range over which good quality prints are made.

35g6

Claims

1. An improved fountain solution suitable for use in a lithographic offset printing press wherein the improvement comprises an aqueous acidic solution from of at least about 1.5 centistoke viscosity, about 0.5 to about 10 percent by volume of an isopropanol replacement selected from polyols, glycol esters, and glycol ether esters and from about 0.005 to about 1 percent by weight of a water-soluble/miscible polymer selected from hydroxyethyl cellulose, methylcellulose, hydroxypropyl methylcellulose, hydroxybutyl methylcellulose, guar gums, and chemically modified gums.

2. A fountain solution as defined in claim 1 wherein the iopropanol replacement comprises a mixture of one or more polyols and/or glycol ethers partially soluble in water and one or more polyols and/or glycol ethers completely soluble in water.

3. A fountain solution as defined in claim 1 or 2 wherein the water-soluble polymer is hydroxy-ethylcellulose, guar gum, hydroxypropyl cellulose, or methylcellulose.

4 . A fountain solution as defined in claims 1 or 2 wherein the water-soluble polymer is hydroxyethyl cellulose, hydroxypropyl cellulose or methylcellulose.

5. A fountain solution as defined in claim 1 wherein said alcohols are polyols.

6. A fountain solution as defined in claim 5 wherein said polyols are diols.

7. A fountain solution as defined in claim 6 wherein said diols are glycols.

8. A fountain solution as defined in claim 1 which additionally contains 0.1 to about 20 percent by volume of isopropanol.

9. A fountain solution as defined in claim 1 or 2 wherein the isopropanol replacement is Butyl Cellosolve, dipropylene glycol, 2-ethyl-1,3-hexanediol, or N-Hexyl Cellosolve.

10. A fountain solution as defined in claim 1~ wherein the isopropanol replacement is Butyl Cellosolve.

ABSTRACT OF THE DISCLOSURE
An improved fountain solution suitable for use in a lithographic offset printing press which solution contains from about 0.5 to about 10 percent by volume of an isopropanol replacement, and between 0.005 and about 1 percent by weight of a water-soluble/miscible polymer selected from hydroxyethyl cellulose, hydroxy-propyl cellulose, methylcellulose, hydroxypropyl methylcellulose, hydroxybutyl methylcellulose, poly-(ethylene oxide), poly(acrylamide), poly(vinyl alco-hol), guar gums, and acid thickening polymers. The fountain solution provides increased viscosity over current fountain solutions which results in improved operating latitude and decrease of problems associated with isopropanol replacements.