JPH0467504B2 - - Google Patents

Description

Detailed Description of the Invention A. Object of the Invention (Field of Industrial Application) The present invention relates to a drying device for evaporating a solvent from an ink film in an offset rotary printing press that prints on a strip of paper using heat set ink, and a drying device for evaporating a solvent from an ink film, It is related to a cooling device that cools the strip-shaped printed material that has passed through the device.

(Prior Art) An offset rotary press has higher productivity and labor savings than a sheet-fed printing press, and is capable of printing a large amount of paper on a thin web in a short prepress preparation time. Due to its characteristics, offset rotary printing has recently been increasingly adopted, and demands for improved characteristics have also increased, leading to faster printing speeds. When four-color printing using offset rotary presses appeared, the printing speed was
What used to be about 200m/min has recently become 250m/min.
300m/min is common, and 500m/min for high-speed aircraft.
Heading towards min.

Heatset inks are used in offset rotary printing. Heat set ink consists of a colorant such as a pigment and a vehicle such as a resin or solvent, and is dried by evaporating the solvent from the printed ink film.

For this reason, as shown in FIG. 4, a drying oven 11 is generally used that blows hot air onto the strip-shaped printed matter 9. However, the temperature of the strip-shaped printed material 9 immediately after passing through the drying oven 11 is still high, and the temperature of the printed strip 9 is still high. The resin in the ink film is still softened and has not reached the so-called set state. After passing through the drying oven 11, the strip of paper is then wrapped around a water-cooled cooling cylinder 12 to cool it to near room temperature and to a so-called ``set'' state where no ink sticks to it when touched. .

In the evaporation step in the drying oven 11, it is not necessary to evaporate all of the solvent, and approximately half of the solvent remains in the ink film. Since the strip of paper that leaves the drying oven is usually at a high temperature of 100°C or higher, the solvent in the ink film has a high vapor pressure and continues to evaporate outside the drying oven. Since the ambient temperature outside the drying oven is lower than inside the oven, the vaporized solvent is cooled and becomes colored mist. If left as is, the inside of the printing chamber will become contaminated, so it is common practice to provide a hood 13 that covers the top surface of the strip-shaped printed matter 9 and the cooling cylinder 12 to suction and discharge.

(Problem to be Solved) A boundary layer exists on the upper and lower surfaces of the above-mentioned strip-shaped printed matter in close contact with the paper surface. Since the paper strip is still at a high temperature, solvent vapor continues to enter the boundary layer from the ink film on the surface of the paper strip, and the boundary layer contains a high concentration of solvent vapor in the gas phase and solvent in the form of a mist. The solvent mist is diffused from the boundary layer into the surrounding atmosphere.

When the solvent vapor in these boundary layers is cooled and liquefied, the amount adhering to the paper strip is absorbed again by capillary action since the paper strip is porous.

At conventional printing speeds, when the strip of printed material is cooled by the cooling cylinder 12, the solvent in the boundary layer is also cooled and absorbed, and the resin in the ink film also cools, increases its viscosity, and solidifies, establishing "set." I came.

However, the situation has changed as printing speeds have increased recently.

(1) Due to the increased speed, the time it takes for the strip of printed matter to leave the drying oven and come into contact with the cooling cylinder is shortened, so there is less temperature drop due to air cooling of the strip, and the solvent evaporates even after leaving the drying oven. is strongly sustained.

(2) Since the amount of printing per unit time is large, the amount of solvent evaporated per unit time is also increasing.

(3) The boundary layer up to the point of contact between the lower surface of the strip-shaped printed material and the upper surface of the cooling cylinder has mass and velocity, and its momentum causes the boundary layer between the two (the strip-shaped printed material and the cooling cylinder) after the point of contact to However, the strip-shaped printed matter 9 has a contact pressure against the cooling cylinder 12 generated by tension, and has the effect of pushing back the air that tries to enter.

As the speed increases, the momentum increases and the "wedge effect" in which an air layer enters between the two becomes stronger, while the contact pressure of the printed strip decreases due to centrifugal force.

For these reasons, an air layer containing a large amount of solvent vapor exists between the cooling cylinder 12 and the strip-shaped printed material 9. For this reason, (1) the cooling effect of printed strips is reduced due to the presence of an air layer with poor conductivity;

(2) As the side of the air layer that comes into contact with the cooling cylinder cools, the solvent vapor liquefies and adheres to the cylinder surface.

(3) The solvent that adheres to the surface of the cooling cylinder and gradually accumulates, increasing the height of the pile, dissolves the ink film of the strip of printed matter and usually consists of a black stain that is approximately parallel to the running direction of the strip of printed material. This causes so-called chill marks, which deteriorate print quality.

That is, although the drying oven maintains the necessary amount of solvent evaporation, there is a problem in that the drying is apparently not good.

As a measure to solve the above problems, there is a method (2) of designing a larger drying oven to solve the problem, but it goes without saying that this is inappropriate in terms of cost.

() Place the vicinity of the contact point between the printed material strip and the cooling cylinder in a vacuum atmosphere to limit the absolute amount of air entering due to the "wedge effect." This is also unreasonable in terms of cost.

() The so-called "Chill Jet System" which has already been disclosed
(Refer to Publication No. 153654).

() The present invention provides an apparatus that solves the problem at an extremely low cost without using the method described in () above.

B. Structure of the Invention (Means for Solving the Problems) A strip of printed matter leaves the drying oven and is wrapped around a cooling cylinder. A dog-shaped nozzle that blows cold air in the opposite direction is installed, and the cold air is ejected toward the front half of the printed strip from the center line, and flows in the opposite direction to the half opposite the center line. It blows out cool air.

Then, a series of devices is installed that sucks the scavenged cold air on the outside of both edges of the strip-shaped printed matter where the cool air after scavenging reaches, and sucks the scavenged air containing the solvent, and sends it to a mist collector for processing. be.

(Operation of the present invention) Since the present invention has the above configuration, the boundary layer on the upper and lower surfaces of the printed strip is stripped off by blowing cold air onto the upper and lower surfaces of the printed strip at a high temperature after leaving the drying oven. , the solvent vapor contained in the boundary layer is cooled and turned into mist, and the solvent mist outside the boundary layer is also sucked in by a suction duct.
It can be captured and processed with a mist collector.

(Embodiments of the present invention) The present invention will be described based on embodiments and with reference to the drawings.
FIG. 1 is a system diagram of the embodiment, FIG. 2 is a perspective view of essential parts of the embodiment, and FIG. 3 is a schematic plan view of FIG. 2.

In FIGS. 1 to 3, 1 is a blower for supplying cooling jet air, which sends cool air to upper and lower nozzle boxes 4 and 4' via duct hoses 2. The duct hose 2 branches upward and downward in the middle, and after each branch, a butterfly valve 3,
3' is provided so that each individual wind speed can be adjusted.

The nozzle boxes 4 and 4' have nozzles 10 that blow out diagonally upstream toward the printed material strip 9, and the nozzle boxes 4 and 4' have a substantially dogleg shape when viewed from the vertical direction of the printed material strip 9. It is bent so that cold air is blown diagonally outward toward the front and opposite sides of the center line of the paper strip. In this example, the speed of the cold air was set at a high speed of 50 to 60 m/sec.

Suction chambers 5, 5' for sucking in the scavenged air are provided on the outside of the edge of the paper strip where the blown cold air is thought to scavenge the printed material strip and come off the edge of the paper strip. These are connected to a mist collector 8 via their respective ducts and a duct hose 7 after they are combined. Each duct has a butterfly damper 6, 6' so that the suction force can be adjusted.

As the mist collector 8, a commercially available finished product can be used, and it has primary and secondary filters and an ionized charged section.After relatively coarse particles are captured by the primary and secondary filters, Fine particles are charged in the ionization charging section and adsorbed in the dust collection section. The collected and liquefied solvent is discharged from the bottom, and the purified air is released into the room.

The mist collector 8 has a dedicated suction fan, and its capacity is about twice as large as that of the cold air blower 1, so that it can suck the entire amount of scavenging air.

Since the present invention has the above-described configuration, it solves the problem by the operation as described above (function of the present invention).

C. Effects of the Invention In the present invention, (1) By blowing cold air from a nozzle onto a strip-shaped printed matter, most of the boundary layer containing solvent vapor can be stripped off, and much of the solvent vapor and mist can be removed.

(2) Blowing high-speed cold air onto the printed material strip also promotes material transfer from the printed material strip, so the solvent that had a high vapor pressure in the area hit by the cold air is evaporated, and the evaporation rate is increased. The latent heat cools the strip-shaped printed material, and in addition to the temperature drop due to heat transfer from the cold air, subsequent solvent evaporation is greatly suppressed.

(3) Conventionally, solvent mist has tended to stagnate on the underside of strip-shaped printed matter, but this can be removed with the present invention.

(4) Therefore, the amount of solvent in the air layer between the printed material strip and the cooling cylinder can be made extremely small, preventing the solvent from adhering to the surface of the cooling cylinder, and eliminating causes of deterioration in print quality.

(5) The direction of the cold air blown from the nozzle onto the printed strip is oriented diagonally between the upstream direction and the outer edge direction of the paper strip, and the boundary layer of the printed strip runs downstream. The direction of the scavenged cold air is almost perpendicular to the direction in which the belt-shaped printed matter travels, and is directed toward the outer edge. Therefore, it is possible to provide a scavenging air suction chamber in a location where it does not interfere with the running of the strip-shaped printed matter, and if the scavenging air is directed upstream, it is sucked into the drying oven, cooling the inside of the drying oven, and cooling the inside of the drying oven. It is also possible to prevent the negative effect of the surrounding atmosphere being cooled and the solvent contained therein being condensed and dripping onto the strip of printed matter passing through the exit section, causing contamination.

It has the following effects.

[Brief explanation of drawings]

Fig. 1 is a system diagram of an embodiment of the present invention, Fig. 2 is a perspective view of main parts of the embodiment, Fig. 3 is a schematic plan view of Fig. 2, and Fig. 4 is a conventional general offset rotary printing system. FIG. 3 is an explanatory diagram of the vicinity of the drying oven. 1...Blower, 2...Duct hose, 3,3'
... Butterfly valve, 4, 4' ... Nozzle box, 5, 5' ... Chamber, 6, 6' ... Butterfly damper, 7 ... Duct hose, 8 ... Mist collector, 9 ... Band-shaped printed matter , 10... Nozzle, 1
1... Drying oven, 12... Cooling cylinder, 13...
Hood.

Claims (1)

[Claims] 1. A device for collecting solvent mist on the surface of printed material strips, which blows a jet of air onto the upper and lower surfaces of printed material strips between the time they leave the drying oven and reach the cooling cylinder, thereby blowing off the solvent mist carried along with the printed material strips.
An abbreviation of "ku" which is bent backwards toward the upstream side of the strip-shaped printed matter with the center line in the width direction of the above-mentioned strip-shaped printed matter as the axis of symmetry.
A cooling air means having a nozzle that generates jets of air from a square-shaped nozzle scavenges the surface of the strip-shaped printed matter and also generates jets directed toward both edges of the strip-shaped printed material on the diagonal upstream side; 1. A device for collecting solvent mist on the surface of a strip-shaped printed matter, comprising a collecting means capable of sucking in solvent mist from both edges, collecting, purifying, and discharging the solvent mist contained therein.