JPS5831233B2 - Electrochemical analysis of the human body using the net and light - Google Patents

Description

DETAILED DESCRIPTION OF THE PRESENTINESS The present invention relates to a coating method in which a heat and light curable coating composition that has been applied almost uniformly onto an object to be coated is cured and dried by the combined use of heat and light irradiation into a thick, completely concealing composition.

In recent years, a method of forming a coating film from a composition that is applied to an object to be coated and hardens when exposed to light, in which the formation of the coating film is promoted by irradiation with light, particularly ultraviolet light, has come into use. However, with this method, the hardening component applied to the object does not harden completely, and the surface that comes into contact with air does not harden sufficiently because of the hardening inhibition effect of oxygen. Furthermore, shaded areas and recessed areas that are not sufficiently exposed to light do not harden sufficiently and may remain unhardened.

Furthermore, when attempting to obtain a thick coating film by applying the coating composition in a single application to a thickness of about 100 μm and then irradiating it with light, a relatively large amount of unreacted low molecular weight resin or unvolatilized solvent remains inside the coating film as uncured portions. Therefore, when heat is then applied, the coating film is so thick that it does not cure uniformly all at once, but cures gradually from the surface to the inside, and in the process, the resin or solvent may escape outside the coating film, resulting in coating defects in the form of small dents on the surface.

The present invention has been made in view of the above points, and provides a method for curing and drying a coating composition using both heat and light, which comprises repeating a coating step of applying a heat- and light-curable coating composition substantially uniformly onto an object to be coated, and a light-curing step of curing the composition by irradiating the object to be coated with ultraviolet light or other light, several times, and then applying heat to the object to be coated to cure and dry uncured portions of the composition.

The method of curing and drying a coating composition using both heat and light of the present invention focuses on the fact that the method of forming a film by irradiation with light utilizes the energy of light to activate the initiator in the curing component and generate radicals, and aims to generate those radicals using thermal energy as well, thereby eliminating uncured areas, and furthermore, to obtain a thick coating film without causing any defects in the coating film.

The curing and drying method of the present invention will now be described with reference to the drawings.

A conveyor 3 is provided which transports the object to be coated 1 placed on a cart 2 in a straight line from a painting booth 4 and an ultraviolet irradiation device 5 connected thereto through a heat imparting device 6 (a device that imparts heat to an object, such as a hot air stove) and a cooling furnace 7, and the conveyor 3 has a loop-shaped section which branches off midway between the ultraviolet irradiation device 5 and the heat imparting device 6 and leads to the painting booth 4.

The object 1 to be coated is coated with a heat- and light-curable composition in a coating booth 4, and the composition is cured in an ultraviolet irradiator 5, leaving only the surface layer and areas that have not been sufficiently irradiated with light. The object 1 to be coated is then led to a loop-shaped portion of a conveyor 3, where the composition is applied again in the coating booth 4 and cured again in the ultraviolet irradiator 5. The object 1 is then transported to a hot air oven 6, where the uncured areas of the composition are cured by heat, and the coating is cured and dried.

The object 1 to be coated is then cooled naturally or forcibly in a cooling furnace 7 .

In this way, by repeating the application of the heat and light curable coating composition and the UV irradiation several times, the composition applied to the object to be coated is irradiated with UV rays by the UV irradiation device, and the curing proceeds while leaving only the surface layer and areas that are not sufficiently irradiated with light.
Finally, heat is applied by a heat application device to harden the unhardened portions, completing the hardening.

In this case, the thick coating film is cured by repeatedly applying a predetermined thin coating film and irradiating it with light multiple times, so the amount of unreacted resin and unvolatilized solvent remaining in the coating film is extremely small compared to when a thick coating film is applied all at once and then cured by irradiating it with light.

Therefore, when the coating is cured by applying heat, a thick coating film can be obtained without causing coating defects such as small depressions on the surface caused by resin or solvent escaping from the coating film.

Example 1 An automobile body moving on a conveyor was painted with 50 ml of paint (a mixture of unsaturated polyester resin as a base, methyl methacrylate, benzophenone (polymerization initiator), pigment, additives, and diluents) in a painting booth.
The film is then applied with a thickness of 1 μm, and then the UV lamps (Iwasaki Electric Co., Ltd.) are placed in the UV irradiation device in parallel with the direction of travel of the object.
UB-04A-2B model, lamp type H2O00LU-
2-OL') and irradiated with ultraviolet light for 2 minutes.

This process was repeated once more (a second UV exposure for 3 minutes) and then the object was heated to 140° C. for 7 minutes in a hot air oven to complete the curing.

Example 2 The paint was applied to an automobile body in a thickness of 50 μm and irradiated with ultraviolet light for 2 minutes. This process was repeated three more times (the second, third, and fourth UV irradiations were each for 3 minutes,
After 15 minutes (5 minutes, 10 minutes) the object was heated at 140° C. in a hot air oven to complete the curing.

According to the method of the present invention, when the paint is applied and irradiated with light, there will be a difference in the degree of cure between the surface layer and areas that have not been sufficiently irradiated with light and the other areas. However, the uncured areas will be cured by the subsequent thermal curing, resulting in uniform curing. Moreover, even if the paint is thick enough, the paint will cure sufficiently and uniformly without any defects.

The coating thickness and pencil hardness of the heat- and light-curable coating composition obtained by the method of the present invention are shown in Table 1.

Furthermore, the pencil hardness at each location when a film thickness of 100 μm was obtained is as shown in Table 2. Good results were obtained, and it can be said that this is an invention of great practical value.

[Brief description of the drawings]

The drawing shows a conceptual diagram of an apparatus for carrying out the present invention. 1: object to be coated, 2: cart, 3: conveyor, 4: coating booth, 5: ultraviolet irradiation device, 6:
Heat application device.

Claims (1)

[Claims] A method for curing and drying a coating composition using both heat and light, characterized in that a coating step in which a heat and light curable composition is applied almost uniformly to an object to be coated, and a light curing step in which the composition is cured by irradiating the object with ultraviolet light or the like are repeated several times, and then heat is applied to the object to be coated to cure and dry the uncured portions of the composition.