Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N3/00—Preparing for use and conserving printing surfaces
  • B41N3/08—Damping; Neutralising or similar differentiation treatments for lithographic printing formes; Gumming or finishing solutions, fountain solutions, correction or deletion fluids, or on-press development

Definitions

• 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 of 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 operation of a printing press in a manner more like that of conventional 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 contain 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 10 to 30 percent by volume of the fountain solution. It is possible to print without alcohol in the fountain solution but it is extremely difficult to do so, and constant attention must be given to keeping the press in adjustment. Use of alcohol increases operating latitude in that good quality prints can be made over a range of press adjustments, especially fountain solution feed rate.
• the Dahlgren dampening system is a means of transporting the fountain solution to the printing plate by first picking up fountain solution from a reservoir, 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 with 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 substitutes 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 necessity of operating at increased Dahlgren roll speeds 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 continuing production of commercial quality printed matter very difficult.
• These polymers include cellulosic polymers, such as hydroxyethyl cellulose, hydroxypropyl cellulose, methylcellulose, 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 about 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 replacement.
• the fountain solution of this invention contains a polymer selected from poly(ethylene oxide) with a possible range of molecular weight between 8000 and 100 000, poly(acrylamide) with a possible range of molecular weight between 500 000 and 2 000 000 and poly(vinyl alcohol) with a possible range of molecular weight between. 120 000 and 300 000.
• a polymer selected from poly(ethylene oxide) with a possible range of molecular weight between 8000 and 100 000, poly(acrylamide) with a possible range of molecular weight between 500 000 and 2 000 000 and poly(vinyl alcohol) with a possible range of molecular weight between. 120 000 and 300 000.
• chemically modified gums are used as water-soluble/ miscible polymers preferably gums etherified with non-ionic, cationic or anionic reagents usually providing hydroxyalkyl modifications are used.
• 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 ) 2CH2 0COC(CH 3 ) 2 CH 2 0H, Hexyl Cellosolve, Hexyl Carbitol, Propasol B, 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,. Cellosolve solvent, Butyl Cellosolve solvent, Propasol B, Propasol M, and the like.
• the solubility is measured by determining the percent by weight of the polyol and/or glycol ether which is soluble in water at 20 .
• C. A polyol and/or glycol is characterized as partially soluble in water if its solubility in water at 20'C is from about 0.99 to about 28.0 weight percent.
• 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 organic acids, such as acetic acid, nitric acid, hydrochloric acid, and the like.
• a buffering agent, such as ammonium acetate, can also be included.
• the fountain solution is generally maintained at a pH of from about 2 to about 5.
• the particular pH at which a given solution will be maintained 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.
• 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.
• Example 1 amply illustrates the wide operating latitude of a conventional isopropanol-modified fountain solution.
• 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 substitute.
• Examples 4 and 5, and 8 through 14 show a significant increase in press operation latitude compared to Example 3.

Landscapes

• Printing Plates And Materials Therefor (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=23428795

Family Applications (1)

Country Status (3)

Cited By (11)

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• 1983
  • 1983-03-18 CA CA000423922A patent/CA1228204A/en not_active Expired
  • 1983-03-28 EP EP83103080A patent/EP0091601A3/de not_active Ceased
  • 1983-03-28 JP JP5056083A patent/JPS58176280A/ja active Pending

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