Drying method

Details Drying method Drying method

1999-09-29

2001-09-25

Yan, Ren (Department: 2854)

Printing

Processes

With heating or cooling

C101S424100

Reexamination Certificate

active

06293200

ABSTRACT:

FIELD OF THE INVENTION
The invention concerns a method of drying the ink which is printed on to a paper web in a printing mechanism of a rotary intaglio printing machine and which has been put into a suitably liquefied form by means of a solvent.
BACKGROUND OF THE INVENTION
A typical method of that kind in which the paper web generally passes in a four-color first-form and perfecting procedure through eight printing mechanisms, downstream of each of which is provided a respective drier, provides that the solvent used to put the ink into a suitably liquid form, generally toluene, is evaporated by means of hot air which flows through the respective drier and serves as an energy carrier, at least to such an extent that, on the freshly printed side, the paper web can be passed over guide or direction-changing rollers without ink being transferred on to same, or that the paper web can be printed upon with another ink in a downstream printing mechanism, without involving smearing and smudging of the ink first applied.
In that respect, for reasons relating to safety engineering, it is not possible to exceed a maximum solvent concentration of 50% of what is known as the ‘lower explosion limit’, often referred to by the abbreviation LEL, in which case the value of that LEL is dependent on the temperature in the drier. For air which has an oxygen content of about 21%, 50% LEL at 20° C. corresponds to about 21 g/m
3
while at 80° C. it is only about 16 g/m
3
.
Further important parameters in regard to the drying methods in question are the speed at which the paper web passes through the printing mechanisms and the driers, and the length that the individual driers must be so that an adequate drying action can be achieved.
An adequate drying action in that respect not only requires fulfilment of the two conditions referred to above, but also involves a sufficiently low residual solvent content in the finished printed product as the solvent residue quantity which is still contained therein is not to exceed certain specified limits, both for health reasons and also in regard to complying generally with environmental pollution conditions, and also for the reason that otherwise, when folded printed products are laid one upon the other or when a printed paper web which has not yet been cut into pieces is wound on to an intermediate storage roll, the various sheets or layers could stick together, so that the entire production would be rendered useless.
Modern production processes seek to achieve ever increasing paper web speeds and larger and larger paper web widths, but nonetheless the lengths of the driers and the amount of hot air which can be passed through each drier per unit of time cannot be increased just as may be desired. It therefore becomes extremely difficult under those conditions to ensure a drying action which is ‘adequate’ in the above-indicated sense.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of drying ink on a paper web in a printing machine, which ensures an adequate drying action even at very high paper speeds and when wide paper webs are involved.
Another object of the present invention is to provide a method of drying ink applied to a paper web in a printing machine, without requiring driers of extreme length or without involving the passage of very large amounts of drying air through driers.
Still other object of the present invention is to provide a method of drying ink printed on a paper web in a rotary intaglio printing machine, capable of affording enhanced drying of the ink on the web without involving adverse environmental considerations.
Yet a further object of the present invention is to provide a method of drying ink on a paper web printed in a rotary intaglio printing machine, which permits close control of an ink-drying procedure to satisfy the operating demands of the printing process and the printed product.
In accordance with the principles of the present invention the foregoing and other objects are attained by a method of drying the ink which is printed on to a paper web in the printing mechanisms of a rotary intaglio printing machine, being liquefied or suitably diluted by means of a solvent. Downstream of each printing mechanism the paper web passes through a drier which includes a substantially closed housing and through which flows a gas serving to carry away the solvent. The drying gas used in at least one of the driers is an inert gas. The through-put of the inert gas through said drier is so selected that a solvent concentration which is very high in comparison with drying with air occurs in said drier.


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Werner STRAUBINGER: Sebald 2000-Projekt. In: dw—Druckwelt 6, Jun. 1998, pp. 46 and 47.
R. Mehnert, u.a.: Die Elektronenstrahlhartung von Druckfarben in Leipziger ESH-Rollenoffset-Versuchsanlage erfolgversprechend (II). In: Deutscher Drucker, Nr. 26-27, Jul. 14, 1994, pp. W8, W10, W13-W34.

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