US2215551A - Developing composition - Google Patents

Description

Patented Sept. 24, 1940 UNITED STATES.

2,215,551 DEVELOPING COMPOSITION Willy 0-. Herrmann, Deisenhofen, Upper Bavaria,

and Wolfram Haehnel, Munich, Bavaria, Germany, assignors to gesellschaft, m. b. H., poration of Germany Chemi'sche Forschungs- Munich, Germany, a'cor- I No Drawing. Application January 29, 1937, Se-

rial No. 123,066. In Germany February 6,

3 Claims.

This invention relates to printing processes,.

and, more particularly, to an improved developing composition for producing ink-receptive surfaces on printing plates, such as are used in lithography and similar printing processes.

In lithographic printing processes utilizing printing plates of zinc or other metals, it has been necessary heretofore to follow a rather elaborate procedure to render the printing surface of the plate properly receptive to the printing ink. The procedure usually employed is substantially as follows:

After the image has been formed on the plate and the plate has been etched, a fixing agent sometimes called a color magnet is rubbed into the surface of the plate and the developing composition is applied thereover. The plate is then placed in an oven and heated at a temperature of about C. for about 10 minutes, whereupon the developing composition and the underlying fixing agent become fused to the plate. When the coating composition has been fused satisfactorily, the plate is treated for about 10 minutes in a bath containing a 2 to 3% aqueous solution of acetic acid and is then rinsed with water. This is followed by treatment for several minutes in a 5% sulphuric acid bath. Only after such treatment is it possible to completely remove the film from the plate with cold water.

Aside from the time and labor consumed in the foregoing procedure, the nature and multiplicity of the operations involved make it dimapplication. Other objects and advantages of the invention will be apparent hereinafter.

The foregoing objects are accomplished in accordance with the invention by providing a developing composition containing an agent comprising a hydroxy compound which is capable of exerting a mild etching action on the zinc or other metal which forms the printing plate. As examples of substances which are particularly suitable for incorporating in the developing composition may be mentioned phenolic materials such as phenol, cresol, and their homologues. Excellent developing compositions can be made in accordance with the invention merely by adding a suitable amount of a reactive hydroxy compound to the various developing compositions now in commercial .use. For example, when phenol is used as the reactive hydroxy compound, about 10% by weight of phenol added to a commercial developing composition will produce excellent results.

As a specific example, a developing composition prepared in accordance with the invention may have the following composition:

Parts by weight Asphalt 5.42 Carbon black 5.42

Pitch 2.46 Petrolatum 25.90 Turpentine 50.80 Phenol 10.00

cult to secure good results consistently. In particular, the heating operation requires a considerable amount 'of skill and care on the part of the operator in order to avoid defects in the plates. Also, many of the available fixing agents have the disadvantage of being effective for binding the developing composition adequately only when they are freshly applied, so that any interruptions in the continuity of the treating process leads to defective results.

It is, accordingly, an object of the present invention to provide a developing composition which does not require the use of a fixing agent for its application to printing plates. A further object is to provide a developing composition which can be simply and easily applied to printing plates and which does not require treatment at elevated temperatures subsequent tb its I In preparing an off-set printing plate utilizing the above phenol-containing developing composition, the plate upon which the image has been formed is etched and thenthe developing composition is simply rubbed into the surface of the plate. Without further treatment, the film is completely removed from the plate by washing with a 5% aqueous sulphuric acid solution for a short period of time, followed by rinsing with which must be followed when using the developing compositions available heretofore.

2. A developing composition for rendering printing surfaces receptive to printing ink, having substantially the following composition:

Parts by weight Asphalt Carbon bla Pitch Petrol-atum Turpentine- Phenol 3. A developing composition for rendering printing surfaces receptive to printing ink, comprising a mixture of asphalt, carbon black, pitch, petrolatum, turpentine, and a phenol.

' WILLY O. HERRMAN'N.

WOLFRAM HAEHNEL.