DE2113452A1 - Damp process for offset printing - Google Patents

Description

DR. BERG DIPL.-ING. STAPF

PATENT LAWYERS
8 MUNICH 8O, MAUERK1RCHERSTR. 45

Dipl.-Ing. Stapf, 8 MOnehen 80, MauerkircherstroSe 45 Your letter Our sign date

2o 8o5 March 1, 1971

Kabushiki Kaisha Ricoh, Tokyo / Japan

Moisture process for offset printing

The invention relates to a dampening method for offset printing and, in particular, relates to a method for Water supply in offset printing using new types of printing inks in which one was previously enclosed in microcapsules Wetting or moisturizing liquid is dispersed 1st.

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Conventional offset presses rotate between the Side walls of the same a forme cylinder, a blanket cylinder and a printing cylinder. The one around the forme cylinder The tensioned form plate prints the inked image on the surface of the blanket cylinder. That on it The printed image is then offset onto a sheet of material or transferred while this is under pressure runs through the press by means of the pressure cylinder.

The inking unit usually comprises a form roller, a vibrating roller, an ink distribution roller, a guide roller, a Ink application roller and a squeegee arrangement on which the printing ink is applied. Next to the inking unit is a Dampening provided, with a container for the wetting liquid, a take-up roller and one between the Pick-up roller and the vibrating roller of the inking unit vibrating vibrating roller to transfer the wetting liquid to the Vibrating roller of the inking unit and for mixing it with the printing ink on its surface.

The wetting liquid usually consists of water with or without suitable additives. It serves to reduce the fat-repelling properties of the non-printing ones To preserve parts of the plate. This process step is essential for producing high quality prints.

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In conventional offset printing presses of the type described the plate clamped around the forme cylinder was moistened mechanically. The amount of the to be applied Wetting liquid be precisely regulated, so that the dampening system and in particular the drive devices of the Dampening rollers have a complicated structure, which in turn leads to an offset press of large dimensions, complicated Structure and complex operation leads.

The inking unit and the dampening unit preferably produce an approximately 50% water-oil emulsion so that it does not printing surfaces of the plate are sufficiently moistened and the printing surfaces supplied with a sufficient amount of ink obtain. For this purpose, a method has been proposed that uses the offset press directly with the approximately 50% water-oil emulsion to be charged as printing ink. However, it is not possible to use an emulsion of more than 3o2 of the printing ink to be kept for a long time. In addition, it is not with a dispersion of 5o to 7οΐ water in the printing ink possible to achieve the stated water-oil emulsion.

The invention is intended to eliminate the disadvantages of conventional offset printing described above and thus a Simplification of the structure of the facilities concerned allow an offset printing press.

According to the invention, there is a novel offset printing ink

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Use. It consists of conventional printing ink in connection with dampening or wetting liquid enclosed in microcapsules. When feeding the offset press with the printing ink, the microcapsules mixed with the grease ink are deposited on the ink distribution roller or the The vibrating roller of the press is destroyed or crushed and the wetting liquid is dispersed in the grease paint. the Dispersed printing ink is then applied to the plate clamped onto the forme cylinder of the press, whereby the liquid fed in the same way as in the conventional method is the liquid repelling the fat color Maintains property of the non-printing areas of the plate.

Further features, details and advantages of the invention emerge from the following description of exemplary embodiments based on the drawing. In this shows:

Flg. 1 is a schematic representation of an offset press operating according to the method according to the invention and

2 is an enlarged sectional view of a wetting · solution containing microcapsule according to the invention.

According to the invention, a new type of printing ink is used in which a dampening or wetting liquid containing microcapsules with conventional offset printing fat

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color are mixed. The wetting liquid W is enclosed in a capsule 21 in a chemical process (Fig. 2). The microcapsules are the printing ink before Loading of the inking unit of the offset press in a predetermined one Ratio mixed. The microcapsules 21 are then destroyed on the paint distribution roller or on the vibrating roller, and the liquid is dispersed in the fat color, whereby the most suitable water-oil emulsion can be achieved in each case is.

The wetting liquid W used in the present invention is Water or an aqueous solution with suitable additives. Such are for example:

1. The wetting liquid for the Electrofax offset process contains ferrocyanides such as potassium ferrocyanide and sodium ferrocyanide, phosphates such as tribasic sodium phosphate, monobasic or dibasic ammonium phosphate, sodium pyrophosphate, sodium triphosphate and sodium ammonium hydrogen phosphate as the main component, organic acids such as oxalic acid, citric acid and dibasic ammonium citrate as well as glycols such as ethylene glycol and propylene glycol.

2. Another wetting liquid for the electrofax offset printing process contains ferrocyanides and phosphates as Main component as well as organic acids such as citric acid and glycerin.

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3. The wetting liquid for offset printing with Aluminum plates contain phosphates and glycols such as ethylene glycol.

The wetting solutions specified above with the compositions described can be enclosed in microcapsules in the order of magnitude TOn 1 to 100 μια in the following processes:

(I) Encapsulation by spray drying in the liquid bath: By emulsifying 30 cm ^{5 of} the above

Wetting liquid in 15o cm of a lozenge solution of A water-oil emulsion was made from polystyrene in benzene. This was 1 1 with vigorous stirring aqueous 2-strength gelatin solution in the form of a fine jet added. In this way a complex water-oil-water emulsion was obtained. The temperature of the The system was raised to 40 ° C. with continued stirring. With further stirring at this temperature for about two Hours were obtained polystyrene capsules with a diameter of about 100 µm with the wetting liquid enclosed therein.

(II) Encapsulation by boundary layer polymerization:

5ο cm of the specified wetting solution were one Solution of 0.4 mol of 1,6-hexamethylenediamine and 0.45 mol Sodium carbonate is added to 100 cm of water. This mixture

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was emulsified in a mixed solvent consisting of chloroform and cyclohexane by volume ratio 1: 3. A solution of 0.6 g of phthaloyl dichloride in 75 cnr of the same solvent mixture was slowly added to the resulting emulsion. The temperature was kept at 0 + * l \ ° C , microcapsules with a diameter between 10 and 5 ° jum, in which the wetting liquid was enclosed. The microcapsules were separated by centrifugation.

(III) Encapsulation by coacervation:

100 cm of the above-mentioned wetting liquid was added 100 cm of a mixture of xylene and carbon tetrachloride in a ratio of 1: 1 with an addition of 5 % ethyl cellulose to prepare an emulsion. The emulsion was diluted by adding 10,000 carbon tetrachloride, and petroleum ether was slowly added to the diluted emulsion. The temperature of the system was maintained at Io ~ 12 ° C with continued stirring. After the addition of 800 cnr petroleum ether, a thick solution of ethyl cellulose precipitated and enveloped the wetting liquid. The microcapsules containing the wetting liquid obtained in this way were decanted off.

The microcapsules containing the wetting liquid were dispersed in printing ink or emulsified printing ink.

Exemplary embodiments of the invention are explained below:

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Example I.

The following ingredients were evenly mixed and dispersed:

Conventional offset printing ink 50 parts

Aqueous ammonium hydrogen phosphate

Solution 25 parts

Surface active agent 0.4 parts.

The emulsion of the above constituents was then given 40 parts of microcapsules with the contained therein Wetting liquid added and dispersed evenly in it. The microcapsules were produced by the above method (III) and their membrane walls were made of Ethyl cellulose.

The printing ink thus obtained was applied to the plate by means of the vibrating roller. The prints were with better and more accurate image reproduction achieved. The improved results were with both the paper die of the Elektrofax system as well as with conventional P.S. plates.

Example 2

First, an emulsion was made from the following ingredients:

Conventional ink 50 parts

Ammonium hydrogen phosphate 25 parts

Surface active agent 0.4 parts.

1 0 9 8 A 2/1 1 8 1 »._

To this emulsion, ko parts of the microcapsules containing the wetting liquid were added and uniformly dispersed therein. The microcapsules were produced by the above process (II) and their membrane walls were made of polyamide.

The printing ink was applied to the plate by means of the vibrating roller, which improved as in the case of Example 1 Set results.

The microcapsules used according to the invention are on the The vibrating roller is destroyed and remains on it and the plate clamped on the forme cylinder. Your diameter or your However, the grain size is so small that its presence does not affect the pressure in any way.

According to the invention, therefore, the wetting solution in the form of encapsulated in microcapsules is applied to the one to be used Printing ink supplied with a matched composition, so that the dampening system of the conventional offset press is more advantageous Way can come to omission. You can determine the composition of the wetting solution enclosed in the microcapsules Prepare so that even if the ink emulsion is less than £ 30 when the ink is applied to the The correct emulsion of the printing ink is formed in each case. Furthermore, the printing ink remains, in which the wetting solution is dispersed in encapsulated form according to the invention,

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unchanged in their properties, so that they can be used over a long period of time even with changing temperatures can be stored and is suitable for loading in the form of color cartridges.

The invention thus provides a dampening process for offset printing using microcapsules containing conventional printing ink and dampening or wetting liquid composite printing ink. The microcapsules are placed on the ink distribution roller or on the vibrating roller of the offset press destroyed or crushed so that the wetting liquid is dispersed in the printing ink before the Printing ink on the on the forme cylinder of the offset press Clamped plate is applied.

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Claims (1)

Claim Damp process for offset printing, characterized in that the ink distribution roller or the vibrating roller of an offset press an offset printing ink is applied, in which beforehand from a wall membrane and the wetting liquid contained therein existing microcapsules were dispersed that the microcapsules on said roller are destroyed and the Wetting liquid is dispersed in the ink and that the printing ink in which the wetting liquid is dispersed is, on a clamped around the forme cylinder of an offset press Plate is applied. 109842/1 181 Lee r side