JPS61287794A - Dryer for uv-curable ink used in printing on foamed plastic container - Google Patents

Abstract

PURPOSE:To enhance adhesion of a UV-curable printing ink, by a method wherein wetting of a container with an ink is accelerated by a low-temperature heater, prior to irradiating the container with UV rays. CONSTITUTION:Desired printing is conducted on the surface of a cup form container A by using a UV-curable printing ink, and the container A is placed upside down on a starting end part of a central part of a belt conveyor 1 in a printing ink dryer. Then, the container A is fed into a heater 7 in the state of being fixed onto the belt 1 by a suction into a suction port 1a, and is heated at a predetermined temperature for a predetermined period of time. By this, the solvent in the printing ink on the surface of the container A is evaporated, the ink is brought into a wetting condition, and affinity of the ink for the surface of the container A is enhanced, whereby the ink is securely adhered to the surface of the container A. Then, the container A is fed while turning it, is passed into a UV ray irradiator 4, and is irradiated with UV rays by a UV ray irradiation means 6 to harden the ink.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention provides a method for printing on the surface of a foamed plastic container using ink that is cured by ultraviolet light, and then hardening the printed ink by ensuring that the printing ink is brought into close contact with the surface of the container. This invention relates to an ink drying device for printing on foamed plastic containers.

(Prior art) When printing on this type of foamed plastic container, the conventional printing method is to use heat drying ink (an ink made by dissolving alkyd resin pigments in a glycol solvent) as the printing ink. After printing on the container,
Some devices dry the ink on the surface of the container using a hot air dryer at high temperature to fix and dry the ink. According to this method, the solvent evaporates sufficiently, so the ink adheres well to the container surface and the ink does not peel off. However, on the other hand, the hot air from the dryer deteriorates the container surface, causing it to lose its gloss and become mirror-like. When finishing was applied, there was a drawback that the surface became rough. Therefore, as a printing method to overcome this drawback, there is a method of printing with the same type of ink and then drying it with an electric heat dryer at a relatively low temperature, but with this method, it takes a long time to dry the ink, so It is necessary to increase the length of the drying device, thus increasing the transport path of the containers, increasing the footprint of the entire printing device, and increasing the printing (drying) time, which significantly reduces the container production efficiency. There was a drawback. Also, recently,
A method has been proposed in which a foamed plastic container is printed using an ultraviolet curable ink and then the ink is cured using an ultraviolet irradiation device. However, although this method prevents the surface of the container from deteriorating and maintains its luster, the ink does not wet the container well, resulting in poor adhesion of the ink to the surface of the container, causing the content inside the container to deteriorate. There was a drawback that printing ink peeled off during the loading and transporting processes of objects (food, etc.).

(Problems to be Solved by the Invention) This invention has been made in view of the above-mentioned points, and the surface of the foamed plastic container does not deteriorate, the mirror finish and gloss are maintained, and the adhesion of printing ink is improved. It is an object of the present invention to provide an ink drying device that is expensive and does not peel off, has a short processing time after printing, has high production efficiency, and occupies a small area of the entire device.

(Means for Solving the Problems) The basic structure of the present invention is to improve the adhesion of the ink by promoting wetting of the ink to the container using a relatively low-temperature heating device before irradiating the ultraviolet rays. The gist of this method is to cure the ink by irradiating it with ultraviolet rays.

(Function) According to the present invention, ink printed on the surface of a foamed plastic container is heated in advance at a low temperature for a short time to promote wetting of the ink to the container during the transportation process of the container. It adheres reliably and is then cured by irradiation with ultraviolet light.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a central vertical sectional view showing a printing ink drying device, and FIG. 2 is a plan view thereof. In these figures, 1 is a belt conveyor as a conveying device for cup-shaped containers A, and a belt of this conveyor 1 is provided with a gap in the longitudinal direction at the center of the belt to hold the container A in a fixed position on the belt during conveyance. A suction port 1a is opened for the purpose, and a continuous suction duct 2 is disposed below the belt along the suction port 1a. Moreover, a wire row 13 for rotating the container A along the longitudinal direction is provided on the conveyance path on the conveyor 1, for example.

4 is an ultraviolet irradiation device, and the casing 5 has an opening for entrance and exit.
A pair of ultraviolet ray irradiation devices 6 are arranged on both sides of the container, shifted in position in the transport direction, and slightly inclined in the vertical direction. The ultraviolet irradiation device 6 includes a reflecting mirror 6a having a semicircular arc cross section.
This type has an ultraviolet light bulb 6b such as a mercury lamp placed inside, and the inside of the reflecting mirror 6a is cooled by circulating cooling air, cooling water, etc. using a cooling device (not shown).

Reference numeral 7 denotes a heating device, and this heating device 7 is disposed in front of the ultraviolet irradiation device 4, facing each other with the conveyor 1 in between. Each heating device 7 has a structure in which a heating device 7b such as an electric heater is mounted on the front surface of a support member 7a, or a structure in which hot air is circulated in a duct using steam or the like as a heat source and heated by the radiant heat.
By adjusting the electric power of the electric heater, the temperature of the hot air, the distance between container A and heating device 7, etc., the temperature in front of heating device 7 can be kept at a relatively low temperature (50 to 1
20℃).

Next, the printing process on the surface of a container will be explained using a cup-shaped container as an example.

The cup-shaped container A is made of, for example, polystyrene beads that are pre-foamed and then heated and fused using a cup molding machine.

Then, a desired print is applied to the surface of the container A using an ultraviolet curable printing ink (for example, an ink prepared by dissolving an acrylic resin pigment in an acrylic monomer solvent).

Next, the container A whose starting end at the center of the belt conveyor 1 is printed is placed upside down.

The container A is placed on the belt by the suction force into the suction port la, and a part of the container A comes into contact with the wire row 13, and the container A is conveyed between the heating devices 7 while rotating due to the resistance. When the capacity of is 460cc, the heating temperature is about 1
．． Heats for 2 seconds.

Note that the passage time in the heating device 7 is appropriately set in the range of 0.5 to 2.0 seconds in consideration of prevention of deterioration of the container surface due to heating.

As a result, the solvent of the printing ink on the surface of the container A evaporates and the ink becomes so-called wet, and the ink becomes well-familiar with the surface of the container A and securely adheres to the surface of the container A.

After passing through the heating device 7, the container A is conveyed while rotating and passes through the ultraviolet irradiation device 4.

While passing through this irradiation device 4, the printing ink on the surface of the container A is cured by irradiation with ultraviolet rays.

In addition, the total amount of ultraviolet irradiation is 150 to 250 mj/cm
is necessary.

In this way, the printing ink on the surface of container A was firmly adhered and cured. Further, no deterioration phenomenon on the surface of container A could be confirmed, and the surface of container A was maintained in a mirror-like state.

(Effects) As explained above, since the apparatus of the present invention has the above-described configuration, it has the following effects. That is, in the transportation path of the foamed plastic container, a heating device that is kept at a relatively low temperature is provided in front of the ultraviolet irradiation device,
Before curing the ultraviolet curing printing ink on the container surface by ultraviolet irradiation, heating is performed for a short time using a heating device to actively promote the wet state of the printing ink on the container surface,
By improving the adhesion of the ink to the surface of the container, the adhesion of the ink is significantly greater than when curing the ink using only ultraviolet rays, and the ink peeling off during container handling is reliably prevented. In addition, since the heating temperature is low, there is almost no deterioration of the container surface, and even in the case of mirror-finished containers, the mirror surface is maintained.

[Brief explanation of drawings]

FIG. 1 is a central longitudinal cross-sectional view showing a printing ink drying apparatus as an embodiment of the present invention, and FIG. 2 is a plan view thereof. ■...Belt conveyor, 2...Suction duct, 4...
- Ultraviolet irradiation device, 7... heating device.

Claims (1)

[Claims] A foamed plastic container printing method, characterized in that a heating device and an ultraviolet irradiation device are sequentially provided during the process of printing the surface of a foamed plastic container with an ultraviolet curable ink and then transporting the container by a belt conveyor or the like. Ink drying equipment.