DE747690C - Agent for making the non-printing areas of planographic and offset printing forms receptive to water - Google Patents

Description

The present invention relates to an agent for rendering the non-printing ones water receptive Making flat and offset printing forms. The known means consist either of salts of phosphoric acid, the Earth metals and nitric acid or from a solution of ammonium phosphate, ammonium nitrate and nickel nitrate. Their effect is based either on pickling the metal surface, to keep them clean, or on the formation of a thin film of reaction products on the plate surface or on both factors. Furthermore, these funds had to be used in large quantities, in order to keep the printing form clean, and in addition, they were of such a composition that they could withstand the printing ink Emulsions resulted, which then also dirty the mopping rollers. Simultaneously the water-repellent property of the inking rollers has been reduced, which in turn reduces the Stripped the printing form from the required wiping water.

According to the present invention, the agent for making water receptive ₂ g consists of an aqueous solution of polyacrylic or methacrylic acid or an at least partially neutralized solution of one of these acids.

The advantages achieved by the invention are as follows:

The non-printing parts remain hygroscopic and only require a small amount Wiping water during printing. No emulsions or foam deposits form. The ink does not wash off and the shapes produce an even and clean print. the Printing press can be turned off for hours and the form remain unused without that there are any disadvantages;

The concentration of the agent according to the invention, regardless of whether it is directly related to the Printing form is applied to make it ready for printing, or whether it is the Wiper water can be used to a large extent

zen are changed, in general solutions from ι to ίο ° / o are usually sufficient. If excessively rich inks are used, a small amount of a weak organic acid of the solution of polyacrylic acid or its salts are added, said additional examples to _s wears to hold the printing plate and the wiper rolls free from foam. Suitable organic acids for this are gluconic acid or a gluconic acid solution which is in equilibrium with the lactone and pyruvic or levulinic acid.

Polyacrylic acid can be obtained in the form of viscous clear aqueous solutions with a content of 15 up to 50 percent by weight can be obtained. To make flat and often set printing forms ready for printing to make, the starting solution of the acid or the corresponding salt, e.g. B.

_{2Q of} the ammonium salt, expediently diluted to 2 to 5%. A mixture of the acid and the salt can also be used. Such a solution is easily available by neutralizing the acid solution rt until the desired i "H ~ W ^e. Appropriately, the solution should be approximately neutral, if

one also on the alkaline side up to! Pi ₁ 8 can go. As cleaning water even more dilute solution of the acid or salt j 'can be used, j ζ. B. from 0.04 to 0.10% and further up to a maximum of 1%. If a weak organic acid is added to it, then in such a way that it corresponds approximately to that of polyacrylic acid or its salts. If a soluble phosphate or chromate is used, this is done in addition to the organic salt and in a somewhat smaller amount, e.g. B. one tenth the amount of the organic salt. All quantities relate to quantities by weight.

The new means of handling printing forms is of course not limited to this Forms of the usual kind which have an albumin coating. Also the order of the Operations in the treatment of the forms can be changed, in particular that Means are used to make the form ready for printing and / or around the finished The printing forme is too damp during printing.

Examples

i. Polyacrylic acid

Water"

■ ζ. Ammonium polyacrylate ....

Polyacrylic acid

water

2a. Ammonium polyacrylate. ....

Gluconic acid

water

3. Ammonium polyacrylate ....

Ammonium hydroxide

water

4. Ammonium polymethacrylate water

For treatment
before
printing For dampening
while
of squeezing S. H 2, ou 0.04 98.00 () 9, of> 4.00 0.04 I ₁ OO 0.04 95.00 2.00 0.10 2.00 0.10 96.00 99.80 4.00 0.04 0.01 0.01 Q5.QQ QQ.Q5 2.00 0.04 98.00 99.06

Claims (2)

Patent claims: ι. Means for making water receptive the non-printing areas of flat and offset printing forms, consisting of an aqueous solution of polyacrylic or methacrylic acid or an at least partially neutralized solution one of these acids. 2. Agent according to claim 1, characterized by the addition of gluconic acid, pyruvic acid or La viii insäure. To distinguish the subject of the application from the state of the art, the granting procedure no publications were taken into account.