JPH0315500B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of curing a radiation-curable resin, and when the radiation-curable resin coated on an object made of a radiation-transparent material is irradiated with radiation and cured, the inside of the resin is cured. This prevents the resin from becoming cloudy due to the whitening phenomenon and allows the resin to be uniformly and completely cured.

Radiation curing resins such as ultraviolet (UV) curing resins and electron beam (EB) curing resins have fast curing properties and
It has various excellent properties such as high physical strength and resistance to deterioration and fading.If this type of resin is used as a coating agent instead of conventional chemical paints,
Various advantages can be obtained. In other words, conventional chemical paints dry by the evaporation of the solvent contained in the paint, and not only do they take a long time to dry, but they also shrink during drying and cause minute cracks. Moisture easily enters into such cracks due to its capillary action, and this moisture accelerates deterioration, fading, and peeling of the paint, which has the drawback of losing aesthetics and the ability to protect the painted object in a short period of time. Furthermore, conventional chemical paints of this kind have the disadvantage that they tend to deteriorate and fade due to contact with the air, direct sunlight, or temperature changes, and they also tend to peel off due to physical stimulation.

On the other hand, radiation-curable resins such as ultraviolet-curable resins and electron beam-curable resins cure by causing chemical reactions such as polymerization reactions, condensation reactions, and crosslinking reactions when irradiated with radiation, and have fast curing properties. Extremely easy to work with. Furthermore, since it is cured by the above-mentioned reactions, there is no shrinkage due to curing, so almost no cracks occur during curing, and the physical strength after curing is extremely high. In addition, there is almost no deterioration or fading due to aging, and it is difficult to peel off, and it also has extremely good adhesion to objects with smooth surfaces such as glass plates and synthetic resin plates, so it maintains the aesthetics of the objects to be painted for a long time. and retains its surface protection function. In this way, we have developed a radiation-cured resin that has various superior properties compared to conventional paints.
It is possible to improve the quality of various articles by painting them.

However, conventionally, when curing this type of radiation-curable resin, after applying the resin to the object,
Volatile substances in the resin are evaporated using a drying device,
After that, radiation was irradiated from above the resin to harden it. However, when the resin 6b is applied thickly to the surface of the object 6a as shown in FIG. In that case, if radiation is applied from above the resin 6b using the radiation irradiator 6c,
Since the surface portion 6b ₁ (see the shaded line in FIG. 6b) of the resin 6b hardens first, the volatile substances 6d remaining in the resin 6b cannot volatilize out of the resin 6b, and the volatile substances 6d remain in the resin 6b.
When the resin 6b is confined inside and further irradiated with radiation, the surface portion 6b ₁ of the resin 6b is further hardened (see Fig. 6c), but the radiation does not sufficiently reach the deep portion 6b ₂ of the resin 6b, so the deep portion 6b ₂ is sufficiently hardened. Without, deep part 6b ₂
A whitening phenomenon occurs and the deep part 6b ₂ becomes cloudy, and since the deep part 6b ₂ is not sufficiently cured, it does not adhere well to the surface of the object 6a, which causes the problem that the resin 6b easily peels off from the object 6a.

Furthermore, if a coloring agent such as a pigment such as carbon black or Prussian blue is mixed into this type of radiation-cured resin, the transmittance of radiation to the resin will be greatly reduced, so that the object 7a as shown in FIG. Even if the resin 7b is applied thinly to the resin 7b, the radiation does not sufficiently reach the deep part _7b2 of the resin 7b, and only the surface part _7b1 is cured, and the deep part 7b, that is, the bonded part between the object 7a and the resin 7b, is hardened. remains uncured, and the resin 7b is easily peeled off from the object 7a.

Therefore, the present invention has been made in consideration of the above points, and in curing a radiation-curable resin coated on a radiation-transparent object,
First, radiation is irradiated from below the object through which the radiation can pass, hardening the lower part of the resin while volatilizing the volatile substances contained in the resin into the air, and then radiation is irradiated from above the object. The upper part of the resin is cured by this method, which prevents the resin from whitening.
It is designed to harden the resin uniformly and completely.

Embodiments of the present invention will be described below with reference to the drawings, taking as an example the case of forming a decorative plate.

In FIG. 1, reference numeral 1 denotes a radiation-transparent synthetic resin plate, on the upper surface of which radiation-curable resin 2 is applied in thick lines to form a lattice pattern. After volatile substances contained in the resin 2 are evaporated into the air by a drying device (not shown), the resin 2 is cured by irradiation with radiation. Fig. 2 shows the situation, where 3 is a radiolucent belt conveyor made of aluminum mesh, and radiation irradiators 4 and 5 are installed at the lower front and upper rear of the conveyance path, respectively. It is arranged. When curing the resin 2 coated on the synthetic resin board 1, the synthetic resin board 1 is transferred to a belt conveyor 3.
It is placed on top and conveyed to the right by the belt conveyor 3. During this process, radiation is first applied from below the synthetic resin plate 1 by the radiation irradiator 4 . Due to the radiation irradiation, the lower part 2a of the resin 2 (see the shaded line in Fig. 3a) is hardened, and due to the sudden rise in temperature due to the radiation irradiation, the volatile substances 2c remaining in the resin 2 are released from the surface of the resin 2 into the air. It evaporates inside. Once the lower part 2a of the resin 2 has been cured in this way, the synthetic resin plate 1 is then conveyed to the lower part of the radiation irradiator 5, and radiation is irradiated from above to harden the uncured upper part 2b of the resin 2. As a result, the resin 2 is uniformly and completely cured (see FIG. 3b). In this way, first, radiation is irradiated from below the synthetic resin plate 1 through which the radiation can pass to harden the lower part 2a of the resin 2, and then radiation is irradiated from above to harden the upper part 2a.
If b is cured to cure the entire resin 2, the volatile substance 2c remaining in the resin 2 can be completely volatilized into the air, causing a whitening phenomenon inside the resin 2 and making the resin 2 cloudy. There is no problem, and the resin 2 is uniformly and completely cured, and firmly adheres to the synthetic resin plate 1. Furthermore, it is possible to make the amount of radiation irradiated appropriate and prevent deterioration of the resin 2 due to excessive radiation irradiation. Further, the synthetic resin plate 1 is not irradiated with excessive radiation only from one direction (for example, from above), but is irradiated almost evenly from above and below, so that deterioration of the synthetic resin plate 1 can be prevented.

Once the flow prevention frame 2 has been formed by curing the resin 2 in this manner, radiation-cured resins a ₁ to a ₉ colored in a desired color are painted within each frame defined by the flow prevention frame 2. (See Figure 4). in this case,
By applying a predetermined amount of resin A ₁ to _{A 9} according to the area within each frame and painting, the thickness of each resin A ₁ to A ₉ within each frame can be made uniform and color shading can be eliminated. can. In addition, since each resin a ₁ to _{a 9} is partitioned by a flow prevention frame 2, each uncured resin a ₁ to a ₉ flows and the resins a ₁ to a ₉ mix with each other, causing the pattern to collapse. You can prevent it from being put away.

Next, as shown in FIG. 5, the synthetic resin plate 1 is placed on a radiation-transparent conveyor 6. Radiation irradiators 7 and 8 are also disposed at the front lower part and rear upper part of the conveyance path of the conveyor 6, respectively. First, the radiation irradiator 7 irradiates radiation from below to each resin a ₁ to
After curing the lower part of each resin a ₁ to a ₉ while volatilizing the volatile substances remaining in a ₉ , the radiation irradiator 8
By irradiating radiation from above and curing the upper part of each resin a ₁ to a ₉ , each resin a ₁ to a ₉ is completely and uniformly cured. In other words, if pigments such as carbon black or Prussian blue are mixed into each of the resins _a1 to _a9 , the radiation irradiation rate of the resins _a1 to _a9 will decrease, as explained with reference to FIG. Therefore, if radiation is applied only from above, the deep parts of each resin a ₁ to _{a 9} will not be sufficiently cured, and each resin a ₁ to a ₉ will easily peel off from the synthetic resin plate 1. When the radiation irradiators 7 and 8 sequentially irradiate the resins with radiation from below and above, each of the resins a ₁ to a ₉ is uniformly and completely cured and firmly fixed to the synthetic resin plate 1 . Of course, in this case, each resin a ₁ to a ₉ is the synthetic resin plate 1
If it is coated relatively thinly, has sufficient radiation transmittance, and can be uniformly and completely cured only by irradiation from above, it is not necessarily necessary to irradiate it with radiation from below using the radiation irradiator 7. It may also be cured only by irradiation from above. Also in this case, it is desirable to volatilize and remove volatile substances contained in each of the resins a ₁ to a ₉ in advance using a drying device before irradiating the resins with radiation using the radiation irradiators 7 and 8 .

Although the above embodiment has been described using an example in which a decorative board is formed by forming a desired pattern on the synthetic resin plate 1 as an object, the method according to the present invention is not limited to the above embodiment. This method can be applied when a radiation-curing resin is coated on an object made of a radiation-transparent material that can be irradiated with radiation from below, and then cured by irradiating it with radiation. When applying a thick coating of radiation-curable resin on an object in a desired pattern and curing it by irradiating it with radiation, or when curing radiation-curable resin mixed with a coloring agent that reduces radiation transmittance, This is particularly effective.

As explained above, in the method according to the present invention, in curing the radiation-curable resin 2 coated on the object 1 made of a radiation-transparent material, after irradiating the radiation curable resin 2 from below the object 1, By irradiating the radiation from above the object 1, it is possible to prevent the radiation-cured resin 2 from becoming cloudy due to the whitening phenomenon, and also to uniformly spread the radiation-cured resin 2.
It also has the effect of completely curing.

[Brief explanation of the drawing]

The figure shows an embodiment of the present invention.
The figure is a perspective view, Figures 2 and 3 a and b are side views during work, Figure 4 is a perspective view, Figure 5 is a side view during work, and Figures 6 a, b, c and 7 The figure is a side view of a conventional one. 1...Synthetic resin plate as an object, 2, a ₁ to a ₉
...Radiation curing resin.

Claims (1)

[Claims] 1. When curing the radiation-curable resin 2 coated on the object 1 made of a radiation-transparent material, the object 1 is irradiated with radiation from below, and then the object 1 is irradiated with radiation from above. Method of curing radiation curing resin.