CS241844B1 - Printing varnish for offset forme on an aluminium pad - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing varnish with increased hydrophobicity and brick resistance for making an offset printing form on an aluminum substrate, in particular on an anodized surface.

In the production of an offset printing mold on an aluminum substrate, the ink transfer printing elements are formed by coating a template that has been prepared by a photomechanical process.

The durability of the printing form in printing and its ability to transfer ink is determined by the quality of the printing lacquer, by its good adhesion - anchoring on the surface of the aluminum printing pad. Further, its oleophilicity and hydrophobicity, resistance to the chemical preparations used in the preparation of the printing form and the printing process, and to the aggressiveness of the inks are also required.

Perfect removal of water from the surface of anodized aluminum plates is difficult. When water-miscible solvents (or only slightly miscible, eg ethyl acetoacetate according to CSR AO 200 041) are applied in the lacquer, the lacquer is imperfectly anchored on the insufficiently dried surface of the anodized aluminum plates and thus the service life of the printing form is reduced.

The chemical preparations used in the preparation of the printing form and which have strongly oxidizing effects reduce the oleophilicity of the printing varnish.

In addition to lacquer-forming resins, colorants and water-immiscible or very poorly miscible solvents, a certain amount of water-miscible solvents and paraffinic substances, the above-described deficiencies are solved.

The substance according to the invention is based on an addition of 5 to 50% by weight. % water-miscible solvents from the group of ethylene glycol alkyl ethers and derivatives thereof; of paraffinic oil, solid paraffinic hydrocarbons, low molecular weight polyethylene or atactic polypropylene, based on the total weight of the lacquer.

In addition to water-miscible solvents, higher boiling solvents are also used in the printing varnish to dissolve paraffinic components such as toluene, xylene, ethyl acetate, propyl acetate, butyl acetate, isobutyl acetate, amylacetate and the like.

For good control of the printing lacquer, it is advantageous to color the lacquer with a suitable dye. Preferably, fat soluble dyes can be used for this purpose.

Example 1 wt. parts tér. % of a vinyl chloride-vinyl acetate-maleic acid polymer of 85 wt. and a K value of 43 wt. part paraffin oil wt. part of Sudan rot G parts xylene wt. parts by weight of ethylene glycol monobutyl ether, 15 wt. parts by weight of butyl acetate; parts of ethylene glycol monomethyl ether acetate

Example 2

10.5 wt. parts of a vinyl chloride / vinyl acetate copolymer having a content of 85% of vinyl chloride and a value of 42

0.7 wt. parts of paraffin 52/54, pour point 52 ° C

0.8 wt. parts of Ceresrot dye mass. parts xylene wt. parts by weight of butyl acetate; parts by weight of ethylene glycol monobutyl ether 17 parts by weight, parts by weight of ethylene glycol monomethyl ether acetate

Example 1 and d 3 wt. parts of epoxy resin, softening point 93-103 ° C epoxy equivalent 870-1050

0.8 wt. parts of low molecular weight polyethylene

0.7 wt. parts of dye Sudan rot G wt. parts xylene wt. parts by weight of ethylene glycol monoethyl ether 10 wt. parts of butyl acetate

8.5 wt. parts of ethylene glycol monobutyl ether Example 4

Paint application:

A printing plate coated with a polyvinyl alcohol-based, polyvinylpyrrolidone-based copy layer and sensitized with diazidostylbendisulfonate is exposed to a positive film film by a xenon copy lamp. After exposure, the latent obrais is induced by water. The resulting template is dried and lacquered by rubbing the lacquer according to the instructions of Example 1, 21 or 3 with a swab. The spread lacquer is dried at 70 ° C for 10 minutes and then a protective paint is applied over it.

The template is delaminated by immersing the printing plate in a 4% potassium permanganate solution acidified with 1% phosphoric acid followed by immersion in a solution of 3% hydrogen peroxide acidified with 1% phosphoric acid and wiping with a brush.

The layered printing form is rinsed thoroughly and coated with a preservative. The printing form is then used in a printing machine. The acceptability of the ink is very good and the printing form lasts for more than 50,000 prints.

The advantage of the lacquer according to the invention is, in addition to said excellent resistance to the auxiliary chemical agents used in the production of the aluminum offset printing form and to the aggressive effects of the inks, its increased affinity for the inks is also good ^! Spreadability and optimum paint drying speed.

Claims (1)

SUBJECT ¹ print varnish for offset printing plates on aluminum pad • lakotvorné comprising resins, pigments and organic solvents immiscible with water characterized in that it includes the addition of '5-50 ® / o by weight. water - miscible solvents from the group of OF THE INVENTION ethylene glycol alkyl ethers and derivatives thereof and 0.2 to 5 wt. paraffinic from the group comprising paraffin oil, solid paraffinic hydrocarbons, low molecular weight polyethylene or atactic polypropylene based on the total weight of the lacquer.