JP2003211078A - Coating method using ultraviolet setting type powder coating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method by which a coating film having flat and smooth surface is formed by solving deficiency such as the occurrence of orange peel due to the remainder of the shape of powder on the surface of the material to be coated or appearance of the ruggedness on the surface of the coating film by the ruggedness of the material to be coated in the coating method using an ultraviolet setting type powder coating material. <P>SOLUTION: A product provided with the coating film having flat and smooth surface is obtained by applying the ultraviolet setting type powder coating material 2 on the surface of the material 1 to be coated by using an electrostatic coating apparatus 70, heating and melting by using an infrared heating apparatus 80, smoothing the surface of a coating layer 3 by using a press means 90 and setting the coating layer 3 by the irradiation of an ultraviolet ray irradiation apparatus 100. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method using an ultraviolet curable powder coating material, and more particularly to a coating method suitable for coating wood materials, and belongs to the field of coating technology.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 11-201212, Japanese Unexamined Patent Publication No. 2001-58384 and the like disclose a method of using an ultraviolet curable paint as a method of coating a decorative board used for a floor material for a house or the like. ing. This UV-curable paint is superior in quick-hardening and low-temperature curability as compared with general thermosetting paints, so it is effective in improving work efficiency and saving space, as well as in wood and plastic materials. It has the feature that it can be applied to materials that are unstable to heat such as.

Particularly, in addition to the above-mentioned features, the ultraviolet-curable powder coating material is difficult to adhere to human skin because it is a powder, and the coating material that has not adhered to the material to be coated is easy to collect. It has the advantages of high safety for human body, low environmental pollution, economical, easy setting and management of coating thickness, and capable of thick coating in one coating. In addition, in recent years, there is a tendency that the use of the material for floor materials, joinery materials, furniture materials, etc., especially for homes is expanded.

[0004]

By the way, the coating using this ultraviolet-curable powder coating material is performed by applying the powder coating material to an object to be coated by an electrostatic coating method or the like and then once melting it by heating. This is carried out in a process in which the whole is fluidized halfway and then cured by irradiation with ultraviolet rays, and the powder is once melted to achieve uniform coating on the surface of the material to be coated.

However, the UV-curable powder coating has a limit to the miniaturization of the particle size, and in the case of a coating material having a relatively low heat-resistant temperature such as a wood material or a plastic material, it causes thermal destruction or thermal deformation. It does not melt sufficiently by heating in the range that is not allowed, so after heating and melting, minute irregularities due to the powder shape remaining on the surface of the paint layer remain, which is cured by UV irradiation as it is and the surface is matte. It becomes a state called "shaped yuzu skin".

Further, since the powder coating material adheres to the material to be coated with a substantially uniform thickness, in the case of a material having a relatively large waviness-like unevenness on the surface such as wood, the coating film There is also a problem that the unevenness appears on the surface.

Therefore, the present invention provides a coating method using an ultraviolet-curable powder coating material even when the surface of the coating film is free from the rusted surface and the surface of the material to be coated has undulations. It is an object of the present invention to provide a method by which unevenness is leveled and a smooth and flat coating film surface is obtained.

[0008]

That is, the present invention is characterized by having the following constitution in order to solve the above problems.

First, the invention according to claim 1 of the present application (hereinafter referred to as "first invention") relates to a coating method using an ultraviolet-curable powder coating material, wherein the surface of a material to be coated is ultraviolet-cured. The present invention is characterized in that a mold powder coating material is applied, the coating material is heated and melted, the surface of the molten coating material layer is smoothed by a pressing means, and then the coating material layer is cured by irradiation with ultraviolet rays.

The invention according to claim 2 (hereinafter referred to as the "second invention") is the method of the first invention, wherein the smoothing treatment is performed at a pressure of 5 × 10 ^{5 to} 20 × 10 ⁵ Pa. It is characterized by performing.

The invention according to claim 3 (hereinafter referred to as "third invention") is the method of the first or second invention, wherein the smoothing treatment is carried out under heating at 90 to 120 ° C. It is characterized by

The invention according to claim 4 (hereinafter referred to as the "fourth invention") is the method according to any one of the first to third inventions, wherein the paint is applied by using a pressing means during the smoothing treatment. The layer surface is embossed.

Further, the invention according to claim 5 (hereinafter referred to as "fifth invention") is a coating material using a pressing means at the time of smoothing treatment in any one of the first to fourth inventions. It is characterized in that an ink layer having a predetermined pattern is transferred onto the layer surface.

The invention according to claim 6 (hereinafter,
The “sixth invention” is characterized in that, in the method of the fifth invention, an ultraviolet curable ink is used as the transfer ink.

The invention according to claim 7 (hereinafter,
The "7th invention") is characterized in that, in any one of the first to sixth inventions, the material to be coated is a wood material.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The ultraviolet-curable powder coating material used in each of the above inventions is a colorless transparent or colored transparent material prepared by blending a photopolymerization initiator with a polymerization-reactive polymer such as polyester or epoxy. Generally used are those for clear coating and those for colored coating in which a pigment is blended. The particle size is 20 to 30 μm, and it is currently difficult to make the particles smaller than that.

As the polymerization-reactive polymer, in addition to the polyester-based and epoxy-based polymers, acryl-based, urethane-based, vinyl-ether-based, silicon-based, and fluorine-based polymers can be used.

As the photopolymerization initiator, conventionally known ones are used, and for example, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzophenone and the like are used alone or in combination.

Further, a defoaming agent is added if necessary, and in the case of a colored coating material containing a pigment, a flow promoter is added if necessary.

The material to be coated is not particularly limited, but may be MDF (medium density fiber board), PB (particle board), composite material obtained by sticking a veneer to these materials, laminated wood, solid wood, composite wood, etc. It is possible to use a wood material or a material such as a resin sheet or a resin-impregnated paper that has been thermally destroyed or deformed in the conventional coating using a thermosetting coating material having a high curing temperature.

The UV-curable powder coating material is applied to the surface of the coating material by an electrostatic coating method in which charged powder coating material particles are sprayed and adhered to the coating material by an air stream. It is also possible to use a preheating fluidized dipping method or the like in which the powder coating particles are attached to the material to be coated which has been preheated in the suspended tank.

FIG. 1A shows a state after the powder coating material is applied by the electrostatic coating method. This electrostatic coating method makes it easy to control the coating thickness of the powder coating, and the coating thickness is almost uniform, and it is possible to coat up to about 100 μm in thickness after curing with one coating. is there.

Since the coating thickness is uniform, the coating of FIG.
As shown in (A), when the material to be coated 1 is a wood material or the like, if there are undulating irregularities on the surface, the irregularities appear on the surface of the coating layer 3 to which the powder coating material 2 is attached. Become.

For heating and melting the powder coating material, a non-contact type heating means such as an infrared heater or a hot air heating device is used.
It is heated at a temperature of 120 ° C, preferably 100-110 ° C. If the heating temperature is lower than 90 ° C., the melting of the powder coating becomes insufficient, and if it exceeds 120 ° C., the fluidity of the powder coating does not become high because the heat energy is consumed unnecessarily. When the material is a wood-based material, a resin-based material, or the like, there is a risk of causing thermal destruction or thermal deformation.

The heating time depends on the heating temperature and the conveying speed of the material to be coated, but it is several seconds to several minutes as a range in which the powder coating material is sufficiently melted and thermal destruction or thermal deformation of the material to be coated does not occur. And preferably 10 to 60 seconds.

FIG. 1B shows a state after the powder coating material 2 applied to the coating material 1 is melted. In this state, the shape of the powder coating material 2 remains on the surface 3a of the coating layer 3. By doing so, minute irregularities are generated.

After the above powder coating material melting step, a smoothing treatment is performed using a pressing means. A press plate or a press roll is generally used as this pressing means, and the surface of the coating material layer 3 in a molten state is pressed by this.

The pressure in that case is 1 × 10 ⁵ Pa to 30
× a 10 5 ^Pa, the surface of the paint layer 2 is not sufficiently smoothed is less than this, or extruded coating of molten exceeds this causes damage it when the coating material is wood-based There is a risk of A preferred range is 5 × 10 ^{5 to} 20 × 10 ⁵ Pa, as specified in the second invention.

As a result, both the minute irregularities due to the remaining shape of the powder coating material 2 and the relatively large irregularities in the case where the material 1 to be coated is a wood-based material are leveled, and FIG.
As shown in (C), the surface 3a of the paint layer 3 is formed into a flat and smooth surface.

In this smoothing treatment, heating is not required if it is carried out immediately after the melting treatment in the previous step, but a thin skin layer is formed on the surface of the paint layer 3 in a relatively short time after melting, and the moldability is improved. Therefore, it is desirable to heat at the same time as pressurizing using a heating press board or a heating press roll with a built-in heater.

In this case, the heating temperature is preferably in the range of 90 to 120 ° C., and preferably 100 to 110 ° C. for the same reason as in the melting, as limited by the third invention.

Next, the coating layer 3 is cured by irradiation with ultraviolet rays. In this curing treatment, a mercury lamp, a xenon lamp, a metal halide lamp, or the like can be used as an ultraviolet irradiation means, and the wavelength of the lamp can be, for example, an ultraviolet region of 100 to 400 nm.

The irradiation dose is 1000 to 6000 mj / c.
m ² range, preferably 2500-3000 mj / cm
^The irradiation time is in the range of 1 second to 1 minute, preferably in the range of 1 to 30 seconds, although it depends on the transport speed of the material to be coated 1 and the wavelength of ultraviolet rays.

When the irradiation dose is less than 1000 mj / cm ² and when the irradiation time is less than 1 second, the coating layer 3 is not sufficiently cured and when the irradiation dose exceeds 6000 mj / cm ² and the irradiation time is 1 If it exceeds minutes, not only the energy is unnecessarily consumed but also the discoloration and brittleness of the coating film due to overirradiation occur.

As described above, a coating film having a flat surface and a smooth surface is formed on the material to be coated. This coating has a hardness (about 2 in terms of pencil strength) when an ultraviolet curable liquid coating is used.
It has a hardness of about 4H, which is higher than that of H).

Then, particularly as in the seventh invention, the coated material 1
When wood is used and there are waviness-like irregularities on the surface, the irregularities are evened out and a coating surface with high flatness and gloss is obtained, and at the time of heating and melting the powder coating material. And the temperature when heating during smoothing treatment is 1 at the maximum.
Since the temperature is 20 ° C., even when the material to be coated 1 is a wood material, a resin material, or the like that is unstable to heat, a good coating film is formed without causing thermal destruction or thermal deformation, which has high commercial value. The product will be obtained.

In the smoothing process, the fourth
As in the invention, the surface of the paint layer 3 can be embossed.

In this case, as the press board or the press roll, a press surface having a pattern such as a wood grain pattern or irregularities for surface processing is used, whereby the coating layer surface is smoothed at the same time. However, the surface will be given a pattern or given a surface treatment.

Further, as in the fifth aspect of the invention, in the smoothing process, a predetermined pattern such as a pattern or a pattern can be transferred to the surface of the paint layer 3 by the transfer ink by using a pressing means.

As this transfer method, first, there is a method using a transfer sheet 10 as shown in FIG. This transfer sheet 10 has a release layer 1 on one surface of a base film 11.
2, the ink layer 13 and the adhesive layer 14 are laminated in this order, and the ink layer 13 forms a pattern such as a pattern or a pattern to be transferred using the transfer ink.

Then, as shown in FIG. 3, the transfer sheet 10 is coated with an adhesive layer 14 between the coating layer 3 of the coating material 1 and the pressing surface of the press board 20 containing the heater 21. The material is supplied toward the material 1 side, and the surface of the paint layer 3 is pressed by the press board 20 and at the same time, the transfer sheet 10 is pressed against the surface of the paint layer 3.

At this time, due to heat and pressure, the ink layer 13 of the transfer sheet 10 is transferred to the surface of the paint layer 3 of the material 1 to be coated through the adhesive layer 14, and the press board 20 is retracted and then transferred. When the base film 11 of the sheet 10 is peeled off and removed, a pattern of a predetermined pattern or a pattern is formed by the transfer ink on the surface of the smoothed paint layer 3.

FIG. 4 shows a transfer sheet in a method in which a heating type press roll 30 is used as a press means and the press roll 30 is rotated in synchronization with the conveyance of the material 1 to be coated to smooth the coating layer 3. It shows a method of transferring an ink layer having a predetermined pattern from the to the surface of the paint layer 3.

In this method, the transfer sheet 10 continuous in a strip shape is supplied from the supply roll 31 between the paint layer 3 of the material 1 to be coated and the press roll 30, and the press roll 30 smoothes the surface of the paint layer 3. At the time of conversion, the transfer sheet 10 is pressed against the surface of the paint layer 3, and the ink layer 13 of the transfer sheet 10 is transferred to the surface of the paint layer 3 by the pressure and heat at that time. Then, the base film 11 of the transfer sheet 10 is peeled off and taken up by a take-up roll 32 to transfer the ink layer having a predetermined pattern onto the surface of the paint layer 3.

FIG. 5 shows that the press layer 40 having a relatively flexible pad on the pressing surface is used to smooth the paint layer 3 of the coating material 1 and at the same time transfer the ink layer to the paint layer 3. The press board 40 is configured to move in a gate shape between a press position of the material 1 to be coated with respect to the paint layer 3 and a plate 41 installed in the vicinity thereof.

Then, in a state where the grooves forming the transfer pattern provided on the plate 41 are filled with ink, the press board 4 is pressed.
By pressing 0 on the plate 41, the ink of the above pattern is attached to the pressing surface of the press board 40, and in this state, the press board 40 is pressed against the paint layer 3 of the material 1 to be coated.
As a result, the surface of the paint layer 3 is smoothed, and at the same time, an ink layer having a predetermined pattern is transferred onto the surface.

Further, FIG. 6 shows the press roll 50 as a press roll 50 in the method of smoothing the coating layer 3 while rotating the press roll 50 in synchronization with the conveyance of the material 1 to be coated, as in the method of FIG. It shows a method of using a plate cylinder provided with protrusions of a transfer pattern on the peripheral surface.

A coating roll 52, the lower portion of which is immersed in an ink tray 51, is brought into rolling contact with the press roll 50, and ink is applied to the projections on the peripheral surface of the press roll 50 via the coating roll 52. Then, in this state, the peripheral surface of the press roll 50 is pressed against the paint layer 3 of the coating material 1, whereby the surface of the paint layer 3 is smoothed, and at the same time, an ink layer having a predetermined pattern is formed on the surface. Transcribed.

By each of the above methods, as shown in FIG.
The surface 3a of the coating layer 3 of the coating material 1 is smoothed, and at the same time, a predetermined pattern of the transfer ink 4 is applied to the surface 3a. In this case, the pattern is transferred to the surface of the molten paint layer 3 by applying pressure, so that the ink 4 is embedded in the surface of the paint layer 3 as shown in the figure. When the ink 4 is hardened, the ink 4 is firmly bonded to the coating film to obtain a transfer pattern having excellent releasability, which improves the design of the product.

In each of the above transfer methods, when the ultraviolet curable ink is used as the transfer ink 4 as in the sixth invention, the transfer ink is cured at the same time as the coating layer 3 is cured by the irradiation of ultraviolet rays. Dry the ink again,
The step for curing is unnecessary.

On the other hand, the powder coating material used in the present invention can be applied uniformly not only to a flat surface but also to a complicated uneven surface, a curved surface, or other three-dimensional surface. The present invention can be applied to the coated material having the same.

That is, as shown in FIG. 8, the ultraviolet-curable powder coating material is applied to the coating material 1 having a non-planar surface by an electrostatic coating method or the like, and the powder coating material is heated and melted. Adheres evenly to the surface to be coated and has a relatively large viscosity even after melting, so that a uniform coating layer 3 does not flow.
Is retained. Then, when the surface of the paint layer 3 is pressed by using the press board 60 having the pressing surface 61 corresponding to the surface of the material to be coated, the surface of the non-planar paint layer 3 is smoothed, and in this state. By curing the paint layer 3 by irradiating with ultraviolet rays, along with the shape of the surface of the material to be coated 1, the yuzu-skin state is eliminated, and a glossy coating film having a uniform thickness is formed. Become.

[0053]

EXAMPLES Next, examples of the coating method according to the present invention will be described.

In this embodiment, the material to be coated is 250 m
An MDF (medium density fiber board) having a size of m × 300 mm and a thickness of 7 mm was used and subjected to the following steps.

First, as shown in FIG. 9A, the UV-curable powder coating material 2 was electrostatically coated on the surface of the coated material 1 by using a well-known electrostatic coating device 70.

The powder coating material 2 used here is a powder coating material for clear coating in which a polyester resin is used as a polymerization-reactive polymer and a photopolymerization initiator and a defoaming agent are added thereto. The particle size is 20 to 30 μm.
It was attached to the surface of the to a thickness capable of electrodeposition.

Next, as shown in FIG. 9B, this coating material 1 was supplied to the infrared heating furnace 80, and the powder coating material 2 applied to the surface of the coating material 1 was heated and melted.

The convey speed of the material 1 to be coated by the conveyor 81 is 0.75 m / min, and the infrared lamp 82 of the heating furnace 80 is used.
Was 160 W, the heating temperature was 110 ° C. corresponding to the melting temperature of the powder coating material 2 at the surface temperature of the material to be coated 1, and the heating time was about 40 seconds.

Next, as shown in FIG. 9 (C), a smoothing process is performed by applying heat and pressure to the molten paint layer 3 on the surface of the material to be coated 1 by using a hot press machine 90. .

The heating temperature at this time is 1 at the press surface temperature.
The temperature was 00 ° C., the pressure was about 8 × 10 ⁵ Pa, and the treatment time was 5 seconds.

After that, as shown in FIG. 9D, the material to be coated 1 was supplied to the ultraviolet irradiation device 100 to cure the coating layer 3 in a molten state.

The conveying speed of the material 1 to be coated by the conveyor 101 is 1.5 m / min, and the mercury lamp 102 is used for ultraviolet irradiation.
With a dose of 2500 mj / cm ² and an irradiation time of about 2
It was 0 seconds.

As described above, the surface of the material to be coated 1 has a thickness of about 10
A 0 μm coating film was formed.

Product thus coated (Example)
The flatness of the surface of the coating film was measured, and the flatness of the surface of a product (Comparative Example) coated under the same conditions as above except that the smoothing treatment was not performed by the pressing means was measured.

As a result, the maximum height H of the surface irregularities shown in FIG. 10 was 30 μm in the comparative example and 8 μm in the example.

[0066]

As described above, according to the coating method using the ultraviolet-curable powder coating material according to the present invention, the powder coating material applied to the surface of the material to be coated is heated and melted, and then the coating layer is formed. Since the surface of the coating is smoothed by pressing means and then cured by ultraviolet irradiation, the shape of the powder remains on the surface of the coating layer after heating and melting, and the surface of the coating film after curing has a smooth surface. The conventional problem that the surface of the coating material becomes uneven or irregularities on the surface of the material to be coated appear on the surface of the coating film, and a coating film having a flat and smooth surface is formed.

In particular, in the present invention, the heating temperature at the time of melting the powder coating material and the temperature at the time of heating during the smoothing treatment are both relatively low, and the material to be coated is not subject to thermal destruction of wood-based materials or resin-based materials. Even when it is likely to undergo thermal deformation, etc., it becomes possible to form a coating film satisfactorily without causing these problems. For example, as a floor material for homes using wood materials, joinery material, furniture material, etc. Products with high commercial value can be obtained.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view sequentially showing changes in a paint layer due to each step of the method of the present invention.

FIG. 2 is an enlarged cross-sectional view showing the structure of a transfer sheet used when transferring an ink layer to a paint layer in the method of the present invention.

FIG. 3 is a schematic explanatory diagram of a first method of transferring an ink layer.

FIG. 4 is a schematic explanatory diagram of the same second method.

FIG. 5 is a schematic explanatory diagram of the same third method.

FIG. 6 is a schematic explanatory diagram of the same method.

FIG. 7 is an enlarged cross-sectional view of a paint layer onto which an ink layer has been transferred.

FIG. 8 is a schematic explanatory diagram when the present invention is applied to a non-planar coated surface.

FIG. 9 is a schematic explanatory diagram of each step constituting the embodiment of the present invention.

FIG. 10 is an explanatory diagram of smoothness.

[Explanation of symbols] 1 Coating material 2 UV-curable powder coating 3 paint layers 4 Transfer ink 20, 30, 40, 50, 60, 90 Pressing means

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Claims (7)

[Claims] 1. An ultraviolet curable powder coating material is applied to the surface of a material to be coated, the coating material is melted by heating, and the surface of the molten coating material layer is smoothed by a pressing means, and then the coating material layer. A coating method using an ultraviolet-curable powder coating material, which comprises curing the resin by ultraviolet irradiation. 2. The smoothing process is 5 × 10 ^{5 to} 20 × 10.
^The coating method using the ultraviolet-curable powder coating material according to claim 1, wherein the coating method is performed at a pressure of ⁵ Pa. 3. The coating method using the ultraviolet-curable powder coating material according to claim 1 or 2, wherein the smoothing treatment is performed under heating at 90 to 120 ° C. 4. The coating using the ultraviolet curable powder coating material according to claim 1, wherein the surface of the coating layer is embossed by using a pressing means during the smoothing treatment. Method. 5. The ultraviolet curable powder according to claim 1, wherein an ink layer having a predetermined pattern is transferred onto the surface of the coating layer by using a pressing means during the smoothing treatment. Painting method using paint. 6. The coating method using an ultraviolet curable powder coating material according to claim 5, wherein an ultraviolet curable ink is used as the transfer ink. 7. The coating method using the ultraviolet-curable powder coating material according to claim 1, wherein the material to be coated is a wood material.