US3459594A - Process of conditioning the surface of a lithographic press member - Google Patents

Description

Aug. 5, 1969 D. N. ADAMS 5 PROCESS OF CONDITIONING THE SURFACE OF A LITHOGRAPHIC PRESS MEMBER Filed Jan. 28. 1966 INVENTOR DOLOR N. ADAMS ATTORNEYS nited States Patent 3,459,594 PROCESS OF CONDITIONING THE SURFACE OF A LITHOGRAPHIC PRESS MEMBER Dolor N. Adams, Cleveland Heights, Ohio, assignor, by mesne assignments, to Riddet Company, Philadelphia, Pa., a corporation of Illinois Filed Jan. 28, 1966, Ser. No. 523,615 Int. Cl. BOSb 3/08, 9/00 11.8. Cl. 134-42 2 Claims ABSTRACT OF THE DISCLOSURE Conditioning the elastomeric surface of a lithographic press member by treating it with ethylene glycol monoethyl ether acetate not only removes lithographic ink adhered thereto but also causes the surface to be capable of immediately carrying a thin, substantially uniform film of aqueous lithographic dampening film, without having to wait before use and without resulting in a waste of the first few sheets after such cleaning.

This invention relates to a process for conditioning the surface of a lithographic press member.

In lithographic offset or planographic printing, the printing plate is chemically treated to provide a printing area and a nonprinting area, with the printing area, of course, being ink receptive and the nonprinting area being hydrophilic or water receptive. Pursuant to such treatment, a film of moistening or dampening fluid is applied to the surface of the plate the fluid being retained by the hydrophilic area but repelled by the ink-receptive printing area, thus separating and isolating the nonprinting area from the ink which is applied to the printing areas. As a result, only the image of the printing area is transferred to the blanket cylinder and onto the paper on which the image is printed.

To achieve successful printing by this method, it is necessary that the moistening fluid be applied to the surface of the printing plate in uniform and evenly distributed quantities and in regulated amounts to assure uniformly good quality reproduction of the printed image. To achieve such application of fluid, an arrangement of rollers is employed which transfers the moistening fluid onto the nonprinting areas of the cylinder.

For reasons which are well known in the lithographic art, the quantity of water which is applied is desirably kept at a minimum and only a sutficient amount is applied to form a minimum thickness of film on the nonprinting area to repel the ink and maintain that area ink free. Such regulation of the water or mOiStening fluid in correlation with the quantity of ink applied is commonly referred to as the ink-water balance, and proper control of this balance is essential to successful printing.

In some types of dampening mechanisms, in transferring the moistening fluid onto the printing cylinder, one of the rollers carrying such fluid comes in contact with a roller or other member carrying lithographic ink, as will be explained in more detail hereinafter. To regulate the quantity of water which is to be applied, a metering mechanism is used, which is most typically a roller having a soft elastomeric surface positioned adjacent a roller with a hard surface so that the film of water will pass between the rollers, the metering occurring by regulating the pressure exerted by the one roller against the other. Due to the contact of the water-carrying roller with the ink-carrying roller, particles of ink will occasionally be carried back from the inking roller to the surface of the elastomeric metering roll where it will adhere. The presence of ink on this roller obviously adversely affects the 'ice metering action of the roller and accordingly must be removed periodically.

To remove the adhered ink, it has been the practice prior to the present invention to treat the surface of the roller with acetone which is a suitable solvent for most inks. Although acetone effectively removes the ink, it does not, however, leave the surface of the roll in a water receptive condition, and this condition is only reestablished after running a number of sheets or permitting the roller to idle for a period of time. The use of acetone as the cleaning agent thus makes it considerably more difficult to establish the desired ink-water balance and accordingly materially reduces production.

It is an object of the present invention therefore to provide a process of conditioning the surface of such lithographic press member in a manner that effectively removes the adhered ink and also leaves the surface in a water-receptive condition.

The invention constitutes a process of conditioning the surface of such a lithographic press member by the use f ethylene glycol monoethyl ether acetate, otherwise known as Cellosolve acetate.

To the acomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail a certain illustrative embodiment of the invention, thi being indicative of but one of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

The figure is a fragmentary schematic view illustrating a typical arrangement of rollers for transferring dampening fluid to a printing plate.

Referring particularly to the drawing to facilitate an understanding of the environment to which the present invention relates, the numeral 1 designates a typical plate cylinder which, in operation, is rotated in the direction of the arrow. Ink is continuously supplied to the cylinder by means of an ink train which constitutes a plurality of ink distributing rollers 2, only one of which is illustrated, which distributes a film of ink to form rollers 3 and 4. A pan 5 is provided in which the ink-repellent dampening fluid is retained. Roller 6 is preferably a metallic pan roller having a highly polished surface which is usually chrome-plated to make it hydrophilic and is rotatably disposed in the pan so that the surface thereof rotates in the fluid 7, picking up fluid from the pan and transferring it to form roller 4 after passing through a nip between roller 6 and metering roller 8. The roller 8 has a soft elastomeric surface which may be of various materials with the most common material being a rubber-like composition, such as neoprene rubber. The surface of such roller is thus smooth, but resilient and slightly deformable by the exertion of pressure. The roller is, of course, capable of having its relationship to roller 6 varied which in turn varies the pressure exerted by the roller 8 against roller 6 and accordingly controls or meters the quantity of dampening fluid passing between the two rollers and onto the cylinder.

Thus, it will be appreciated that fine particles of ink can readily come in contact with the soft surface of the metering roll 8 and adhere thereto. Since the presence of ink on the surface will obviously adversely affect the ability of the surface to pick up and retain a uniform film of water, the roller must be cleaned when this situation occurs.

Pursuant to the present invention, it has been discovered that highly desirable results can be achieved if the surface of this roller is cleaned with Cellosolve acetate, which not only effectively removes the ink but also leaves the surface in a water-receptive and thus ink-rejecting condition. As is known, Cellosolve acetate is an accepted name for ethylene glycol monoethyl ether acetate, the formula being This material is, of course, generally available commercially and has a boiling point of about 156.3 C. at 760 mm. pressure. Its molecular weight is 132.16, and its solubility in water is approximately 22 grams per 100 ml. at room temperature.

In order to clean the metering roll, it is only necessary to apply the Cellosolve acetate either to the surface of the roll or to a cloth, sponge, etc., and scrub the roll to remove the adhering ink, After such cleaning, the roll will automatically have its surface in a condition where it will readily accept a uniform film of fountain solution.

The use of this material also has other advantages in that it has a good evaporation rate which is slower than acetone and thus permits more effective cleaning with a smaller quantity of material. Moreover, it does not have an objectionable odor and is not toxic. It has also been found that this material does not have a noticeable damaing effect on the surface of the rolls.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A process of conditioning the elastomeric surface of a lithographic press member, comprising treating said surface with ethylene glycol monoethyl ether acetate to remove undried lithographic ink adhered thereto and to cause such surface to be capable immediately after treatment of carrying a thin, substantially uniform film of aqueous lithographic dampening fluid.

2. A process for cleaning the elastomeric surface of a lithographic metering roll, used in lithographic presses to bear against a metal roll which picks up ink-repellent dampening fluid and applies such fluid to a form roller, said metering roll exerting pressure on the metal roll to govern the amount of dampening fluid carried thereby and tending to have its function impaired by the presence of undried lithographic ink on its surface, comprising cleaning said metering roll as needed with ethylene glycol monoethyl ether acetate to remove said ink from said elastomeric surface and then, at any time after the completion of cleaning and evaporation of the ethylene glycol monoethyl ether acetate, using said metering roll to perform its intended function.

References Cited UNITED STATES PATENTS 1,858,437 5/1932 Dufford 134- -29 XR 1,935,911 11/1933 Neilson.

2,284,142 5/ 1942 Gray.

2,393,875 1/1946 Van Dusen 10l451 2,780,168 2/ 1957 Nichols.

3,351,008 11/1967 Lincoln et al. 101465 3,373,115 3/1968 Steppan 1( 1--465 MORRIS O. WOLK, Primary Examiner J. T. ZATARGA, Assistant Examiner US. Cl. X.R.

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