JP2007237022A - Photosetting paint composition excellent in stain-proof and method for curing paint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a final coating film which has a low gloss and is excellent in stain-proof and cracking resistance. <P>SOLUTION: The method for curing the coating film consisting of a photosetting paint composition includes: an application step of applying the photosetting paint composition containing a photosetting resin (A), a photopolymerization initiator (B) and a reactive thinner (C) onto a base material to form the coating film consisting of the photosetting paint composition; a first irradiation step of exposing the uncured coating film to the long-wavelength ultraviolet light emitted from a metal halide lamp to semi-cure the uncured coating film; and a second irradiation step of exposing the semi-cured coating film to the ultraviolet light emitted from a high-pressure mercury lamp in an inert gas atmosphere to fully cure the semi-cured coating film, in this order. Dimethylol tricyclodecane diacrylate of 30-200 parts weight on the basis of 100 parts weight photosetting resin (A) is preferably used as the reactive thinner (C) and blended. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photocurable coating composition and a coating curing method excellent in stain resistance, a coating film formed by the method, and a substrate coated with the coating film. More specifically, the present invention can increase the curing speed and the performance of the resulting coating film (especially stain resistance) when the photocurable coating composition is cured by irradiating with ultraviolet rays or the like, and can reduce the cost. The present invention relates to a possible paint curing method, a coating film formed by the method, and a substrate coated with the coating film.

  The floor surface is easily contaminated by walking or adhering to dust or dirt. Wood flooring materials used for western houses, corridors, kitchens, etc. in ordinary houses are painted with UV paints or urethane paints, but in particular in kitchens, floor contamination due to oil, seasonings, foods, etc. is likely to occur. Supermarkets, department stores, restaurants, automobile exhibition halls, etc. use vinyl chloride resin tiles such as vinyl chloride resin tiles and long flooring. Frequent cleaning to keep the floor clean. is required. Therefore, in order to reduce these efforts, the floor surface is required to be resistant to contamination. In addition, there are many accidents involving falling elderly people and children due to the slipperiness of the floor surface, and the floor surface is also required to be non-slip. In addition, low-gloss products dominate the demand for finishing wood substrates.

  As a conventional technique for enhancing the stain resistance of the floor surface, for example, an ordinary ultraviolet curable coating composition is applied to the floor surface, and then an electroded mercury lamp with an output of 80 to 120 W / cm is used in the air. A method of curing the composition by irradiating ultraviolet rays has been put into practical use. However, when ultraviolet rays are irradiated in the air, the radicals on the surface layer of the composition are stabilized by oxygen in the air, so that the inhibition of curing occurs and the crosslinking density decreases, and the stain resistance of the coating film is insufficient. Become.

In order to solve the above problems, a method has been proposed in which the composition is cured by irradiating the composition with ultraviolet rays or electron beams in an inert gas atmosphere such as nitrogen or carbon dioxide. According to this method, the curing time of the coating film can be shortened, the crosslinking density can be increased, and a coating film with good stain resistance can be obtained. However, the crosslink density expected when the oxygen concentration in the irradiation chamber exceeds 0.5% cannot be obtained.
Further, in order to keep the oxygen concentration at 0.5% or less in order to ensure a high crosslink density of the resin, a large amount of inert gas is required, so that this method is significantly expensive.

  Further, Patent Document 1 below is directed to an ultraviolet curable coating containing at least one aliphatic urethane (meth) acrylate prepolymer having at least two double bonds per molecule and at least one reactive diluent. A method for curing an uncured coating film formed on a support by exposing it to ultraviolet rays emitted from a normal electroded ultraviolet lamp under an inert atmosphere is described. Curing is important in wooden flooring. There is no mention of low gloss, anti-fouling properties, crack resistance, etc. of the coating film. In the following Patent Document 2, a first irradiation step of irradiating an active energy ray in a gas atmosphere having an oxygen concentration of 15% or more after coating an active energy ray curable composition on the surface of the substrate, and an oxygen concentration of 15 It is described that a cured film having both contamination resistance and heat cracking resistance can be obtained by a method for forming a cured film having a second irradiation step of irradiating a secant energy beam in a gas atmosphere of less than%, No mention is made of the low gloss of the coating.

Under the circumstances as described above, the conventional UV curable coating composition that can suppress the inhibition of curing by oxygen and the resulting deterioration of the stain resistance of the coating film, and further achieve low gloss of the resulting coating film. There is a need for better curing methods.
Special table 2003-507559 gazette JP 2003-236457 A

  The present invention relates to a method for curing a light (ultraviolet) curable coating composition capable of suppressing the inhibition of curing due to oxygen and the resulting decrease in the stain resistance of the coating film and further realizing a reduction in gloss of the resulting coating film. The purpose is to provide.

The paint curing method of the present invention comprises:
A photocurable coating composition containing (A) a photocurable resin, (B) a photopolymerization initiator, and (C) a reactive diluent is applied onto a substrate to form a coating film composed of the composition. Application process,
A first irradiation process in which an uncured coating film is semi-cured by exposure to long-wavelength ultraviolet light emitted from a metal halide lamp, and a semi-cured coating film is exposed to ultraviolet light emitted from a high-pressure mercury lamp in an inert gas atmosphere. The second irradiation step for full curing is performed in this order.

  The photocurable resin (A) is preferably at least one photocurable resin selected from the group consisting of urethane (meth) acrylate resins, epoxy (meth) acrylate resins, and polyester (meth) acrylate resins. .

  The photopolymerization initiator (B) is preferably a photopolymerization initiator selected from the group consisting of benzophenones, anthraquinones, thioxanthones, acetophenones, acylphosphine oxides, and methylphenylglyoxyesters. . Moreover, it is preferable to use a photoinitiator (B) in 1-25 weight part with respect to 100 weight part of photocurable resin (A).

  The reactive diluent (C) is preferably a mixture of a monofunctional reactive diluent (C1), a bifunctional reactive diluent (C2), and a polyfunctional reactive diluent (C3). Moreover, it is preferable that a reactive diluent (C) is mix | blended in the ratio of 20-300 weight part with respect to 100 weight part of photopolymerizable resins (A).

  As the bifunctional reaction diluent (C2), dimethylol tricyclodecane diacrylate is suitable. This dimethylol tricyclodecane diacrylate is preferably mixed in a proportion of 30 to 200 parts by weight with respect to 100 parts by weight of the photopolymerizable resin (A) in the reactive diluent (C).

  In the coating step, one or more of a stain coating film, an undercoat coating film, and an intermediate coating film are formed in advance in this order on the substrate, and the outermost layer of these coating films is coated. It is also preferable to apply the photocurable coating composition used in any one of claims 1 to 7 on the film.

The first irradiation step is preferably performed in air using a long wavelength metal halide lamp having an output of 60 W / cm or more.
The inert gas in the second irradiation step is preferably nitrogen gas or nitrogen-containing gas, and more preferably nitrogen / oxygen mixed gas having an oxygen concentration of 4% by volume or less.

Further, in the second irradiation step, an electroded mercury lamp having an output of 80 W / cm or more as a high-pressure mercury lamp in a nitrogen / oxygen mixed gas atmosphere having an oxygen concentration of 0.5 to 4.0% by volume, or 24 to It is preferable to use an electrodeless mercury lamp having an output of 240 W / cm.

In the first irradiation step and the second irradiation step, one or two or more lamps are disposed apart from the conveyor by a predetermined distance, and a substrate on which the photocurable coating composition is applied is disposed. It is preferable to carry out continuously by making it convey to this conveyor at the speed of 1-150 m / min. In the second irradiation step, the accumulated light amount is 20 to 1000 mJ / cm ² using a high-pressure mercury lamp having an output of 60 to 240 W / cm per one on the base material coated with the photocurable coating composition. It is preferable to be performed by irradiating in an amount.

  The photocured coating film according to the present invention is formed by the above method. The base material with a coating film according to the present invention is characterized in that the surface of the base material is coated with the photocured coating film formed by the above method. The base material is preferably a wooden floor material or a vinyl chloride floor material.

  According to the present invention, even in an inert gas atmosphere having a higher oxygen concentration than before, the resulting cured coating film has improved stain resistance and the like, and has excellent crack resistance and low glossiness. It becomes possible to manufacture a base material on which the coating film is formed. As a result, a flooring material having low gloss and good maintenance after construction is provided.

Hereinafter, the photocurable coating composition and the coating curing method, the coating film formed by the method and the substrate coated with the coating film in the present invention will be specifically described.
<Photocurable coating composition>
The photocurable coating composition used in the present invention contains a photocurable resin (A), a photopolymerization initiator (B), and a reactive diluent (C).

  Usually, a photocurable resin and a photopolymerization initiator that is easily photoexcited are used in combination, and radical or cation active species are generated by cleavage or hydrogen transfer of the initiator by ultraviolet rays, and the active species act on the resin. Polymerization or crosslinking reaction takes place and the resin cures in a very short time. In addition, as such a photocurable coating composition, either a solvent type or a solventless type can be used. However, the curing reaction can be rapidly advanced, the coating workability is excellent, and there is a risk of environmental pollution. In the present invention, a solvent-free paint is more desirable because it is rare and excellent in terms of environment.

In the present invention, the reactive diluent (C) is more preferably used by mixing with the photocurable resin (A).
The photocurable resin (A) used in the present invention is a resin (including a prepolymer and an oligomer) that can be cured using an ultraviolet region (200 to 600 nm, preferably 200 to 450 nm) in an electromagnetic wave. It has two or more (meth) acryloyl groups. Among such resins, urethane (meth) acrylate resin, epoxy (meth) acrylate resin, polyester (meth) acrylate resin and the like are preferable in the present invention. These photocurable resins can be used alone or in combination of two or more.

Examples of the photopolymerization initiator (B) used in the present invention include benzophenones, anthraquinones, thioxanthones, acetophenones, acylphosphine oxides, and methylphenylglyoxyesters. “Irgacure 184” used in Examples described later is a photopolymerization initiator belonging to the acetophenones. In addition, a photoinitiator may be called a reaction initiator.

The blending ratio of the photocurable resin (A) and the photopolymerization initiator (B) is based on 100 parts by weight of the photopolymerizable resin (A) from the viewpoint of the curing rate of the applied uncured coating film, etc. A photoinitiator (B) is 1-25 weight part normally, Preferably it is 5-20 weight part.

  The reactive diluent (C) is a reactive monomer having one or two or more acryloyl groups or methacryloyl groups per molecule, and serves as a diluent for reducing the viscosity of a highly viscous oligomer. In the present invention, the reactive diluent (C) includes a monofunctional reactive diluent (C1) having one acryloyl group or methacryloyl group per molecule, and two acryloyl groups or methacryloyl groups per molecule. The resulting bifunctional reactive diluent (C2) and a polyfunctional reactive diluent (C3) having three or more acryloyl groups or methacryloyl groups per molecule are used. This is preferable from the viewpoint of contamination and crack resistance. Moreover, the compounding quantity of a reactive diluent (C) is taken as the ratio of 20-300 weight part with respect to 100 weight part of photopolymerizable resins (A) from points, such as stain resistance of the cured coating film obtained. It is preferable.

  The bifunctional reaction diluent (C2) is suitable in terms of the stain resistance of the cured coating film from which dimethylol tricyclodecane diacrylate is obtained. The amount of the dimethylol tricyclodecanediacrylate mixed in the reactive diluent (C) is 30 to 200 parts by weight with respect to 100 parts by weight of the photopolymerizable resin (A). It is preferable because the viscosity of the product is appropriate and the resulting coating film has significantly improved stain resistance.

A conventionally well-known thing can be used as a reactive diluent (C). Examples of the monofunctional reaction diluent (C1) include “ACMO” (manufactured by Kojin Co., Ltd.) and “light acrylate MTG-A” (manufactured by Kyoeisha Chemical Co., Ltd.). Examples of the bifunctional reaction diluent (C2) include “Biscoat 260” (manufactured by Osaka Organic Chemical Industry), “Neomer NA-305” (manufactured by Sanyo Chemical Industries), or dimethylol cyclodecandi. “Light acrylate DCP-A” (produced by Kyoeisha Chemical Co., Ltd.), which is an acrylate, can be mentioned. Examples of the multifunctional reactive diluent (C3) include “New Frontier TEICA” (trade name, Daiichi Kogyo Seiyaku Co., Ltd.) and “Aronix M-400” (trade name, Toa Gosei Co., Ltd.). .

  Monofunctional reactive diluents, bifunctional reactive diluents, and polyfunctional reactive diluents having three or more functionalities are referred to as “monofunctional monomers”, “bifunctional monomers”, and “multifunctional monomers”, respectively. There is also.

In addition to the above components, the photocurable coating composition of the present invention may appropriately contain various additives such as extender pigments, antifoaming agents, leveling agents, fluidity modifiers, and the like.
The photocurable coating composition containing each of the above components is applied to a substrate using a conventional method and cured by the method described below.

<Curing method of coating film comprising photocurable coating composition>
In the coating curing method according to the present invention, after the photocurable coating composition as described above is applied to a substrate to form an uncured coating film composed of the composition,
A first irradiation process in which an uncured coating film is exposed to a long wavelength ultraviolet ray emitted from a metal halide lamp and semi-cured, and an ultraviolet ray emitted from a high-pressure mercury lamp in an inert gas atmosphere. A second irradiation step of exposing to a full cure (complete curing) is performed in this order.

  The metal halide lamp used in the first irradiation step is one in which a metal is enclosed in the form of a halide in addition to mercury and a rare gas in an arc tube, and radiates a wide range of ultraviolet rays from 200 to 450 nm. It is characterized by high output of long wavelength ultraviolet rays compared to mercury lamps, and is used mainly for curing printing inks.

  In the present invention, it is more preferable to use a metal halide lamp having an output of 60 W / cm or more in the first irradiation step. Examples of such a metal halide lamp include “CK-1” (maximum output: 80 W / cm) manufactured by IST METZ GmbH.

  On the other hand, the high-pressure mercury lamp used in the second irradiation step is a quartz glass tube in which mercury and a small amount of rare gas are enclosed, and efficiently emits ultraviolet light having a main wavelength of 365 nm. . It is characterized by higher output of short-wavelength ultraviolet light than other lamps, and is used mainly for curing clear paints.

  In the present invention, in the second irradiation step, it is preferable in terms of curing performance to use an electroded mercury lamp having an output of 80 W / cm or more or an electrodeless mercury lamp having an output of 24-240 W / cm. . The electrodeless mercury lamp is a system that emits light by exciting the mercury inside the lamp with the energy of the microwave generated by the magnetron to form a plasma state. Unlike the lamp, there is no electrode inside. Examples of the electrode mercury lamp having an output of 80 W / cm or more include “Icure Light” (maximum output: 160 W / cm) manufactured by Eye Graphic Co., Ltd. In addition, as an electrodeless mercury lamp having an output of 24 to 240 W / cm, for example, “Fusion UV systems JAPAN KK”, trade name “MODEL VSP / I600” (maximum output: 240 W / cm), “MODEL” A combination of “VSP / I250” (maximum output: 150 W / cm) and “H bulb” having a strong emission peak in the 200 to 280 nm region and around 365 nm as in the case of the mercury spectrum.

  In the present invention, it is possible to select a metal halide lamp or a high-pressure mercury lamp having a suitable emission spectrum in consideration of the type of components, curing conditions, coating thickness, type of substrate, etc. of the photocurable coating composition used. it can.

  As described above, after the coating film is semi-cured by the first irradiation process using the metal halide lamp, the coating film is completely cured by the second irradiation process using the high-pressure mercury lamp. A glossy cured coating film can be obtained. Ultraviolet rays with a long wavelength around 400 to 420 nm by the metal halide lamp in the first irradiation step are effective for curing the deep part of the coating film, and when a matting agent (fine powder silica) is added to the paint, It hardens more and pushes the matting agent onto the surface of the coating film, thereby reducing the gloss of the resulting coating film. In addition, the metal halide lamp alone has a difficulty in curing the surface of the coating film, and it is difficult to remove the adhesion of the surface. However, ultraviolet rays having a short wavelength of around 365 nm by the high-pressure mercury lamp in the second irradiation step are hardened on the surface layer of the coating film. It is effective for. In particular, when an electrodeless ultraviolet lamp having a maximum maximum output of 240 W / cm is used, an excellent one can be obtained due to the curability of the coating film surface and the crosslinking density (contamination resistance).

  The second irradiation step of the present invention is performed in an inert gas atmosphere. Examples of the inert gas include noble gases such as nitrogen, carbon monoxide, carbon dioxide, and argon, and mixed gases thereof. In particular, use of nitrogen gas or nitrogen-containing gas is preferable. These inert gases may contain oxygen gas. The oxygen concentration in the inert gas is preferably 4% by volume or less.

In the present invention, for example, the oxygen concentration in the inert gas used exceeds 0.5% by volume,
Even in a high concentration of 4% by volume, that is, in the presence of a mixed gas containing such a high concentration of oxygen gas and the remaining amount (96 to 98% by volume) of an inert gas (eg, nitrogen gas). In addition, by irradiating a high-pressure mercury lamp to completely cure the uncured coating film composed of the photocurable coating composition, a cured coating film having excellent characteristics such as stain resistance and crack resistance can be obtained. Is possible.

On the other hand, in the conventional technique, the oxygen concentration exceeds 0.5% (eg, 2 to 4% by volume).
In an inert gas atmosphere contained in the above, a high resin crosslink density as expected cannot be obtained, and an oxygen concentration of 0.5% or less is to be maintained in order to maintain a high crosslink density of the resin. Then, although a large amount of inert gas was required, the problem in the prior art is solved by the present invention.

In the first irradiation step and the second irradiation step in the present invention, one or two or more lamps (for example, a high-pressure mercury lamp having an output of 60 to 240 W / cm in the second irradiation step) In order to keep the distance from the coating film to about 5 to 10 cm, it is arranged apart from the belt conveyor, and the substrate with the coating film is conveyed at a speed of about 1 to 150 m / min on this belt conveyor. It is preferable to carry out continuously. The integrated light quantity in the second irradiation step is preferably ²⁰ to 1000 mJ / cm ² in consideration of the fact that the curing speed is greatly improved in an inert gas atmosphere.

<Formation of laminated coating film>
In the present invention, if necessary, one or more of a stain coating, an undercoat coating, and an intermediate coating are formed in advance in this order on the surface of the base material, and the photocurable coating composition is applied to those coatings. You may apply | coat on the outermost layer of a film | membrane. When all of the stain film, the undercoat film, and the intermediate coat film are applied, the stacking order is “coating composed of substrate / stain film / undercoat film / intercoat film / photocurable coating composition”. Film ". In addition, when any coating film is excluded / omitted, it is sufficient to apply the coating while maintaining this order. For example, when excluding / omitting the undercoating film, “substrate / stain coating / intermediate coating” is used. The order of lamination is “film / photocurable coating composition made of photocurable coating composition”.

  The paint for the stain coating can be either water-based or solvent-based, but water-based stain is preferable from the viewpoint of environmental measures. Both the undercoat paint and the intermediate coat paint can be either solvent-type or solvent-free. However, because the curing reaction can proceed quickly, the coating workability and the environment are excellent. The solvent-free type is desirable. In applying the paint, any known method such as a roll coater, a flow coater, an air spray, an airless spray, or a brush may be used.

  When any one or more of a stain coating film, an undercoat coating film, and an intermediate coating film is formed on the substrate in advance, the coating film for each coating film is usually applied and then 70 for the stain coating film. By drying in a drying oven at -100 ° C for 1 to 3 minutes, and for an undercoating film or an intermediate coating film, irradiation with a high-pressure mercury lamp, metal halide lamp, electrodeless UV lamp, etc. in the air Cure the coating.

In addition, a stain coating film, an undercoat coating film, and an intermediate coating film are normally used when the base material is woody, and is not common when the base material is a vinyl chloride resin.
<Hardened coating film and substrate with the coating film>
The photocured coating film according to the present invention is formed by the above method. As described above, the coating film is formed, for example, in the order of “base material / stain coating film / undercoat coating film / intermediate coating film / coating film made of a photocurable coating composition”. In this case, the thickness of each layer (coating film) varies depending on the type and application of the final product and is not unconditionally determined. For example, it is a dry film thickness, a stain coating film: about 3 to 10 μm (thickness), and an undercoat The film is about 10 to 50 μm (thickness), the intermediate coating film is about 10 to 30 μm (thickness), and the coating film made of the photocurable coating composition is about 10 to 100 μm (thickness).

  The base material with a coating film according to the present invention is one in which the surface of the base material is coated with the photocured coating film formed by the above method. The type of the base material is not particularly limited, but for use as a flooring material, woody materials such as wood, plywood, and laminated wood or vinyl chloride resins are suitable.

<Examples and Comparative Examples>
EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited at all by this Example.

In Tables 1 to 10 showing the composition of various paints used in Examples and Comparative Examples, the units in the “Formulation” column are parts by weight.
In addition, the electroded ultraviolet lamp, electrodeless ultraviolet lamp and metal halide lamp used in the examples and comparative examples, and the irradiation conditions in a nitrogen atmosphere are as follows.・ Electrode ultraviolet lamp Irradiation device: High pressure mercury lamp manufactured by iGraphic Co., Ltd. Output: 120W / cm
Irradiation distance: 15cm
Irradiation dose: 100 to 110 mJ / cm ²
・ Electrodeless ultraviolet lamp Irradiation device: Electrode high-pressure mercury lamp manufactured by Fusion, H bulb Output: 240 W / cm
Irradiation distance: 10cm
Irradiation dose: 170-180 mJ / cm ²
・ Metal halide lamp Irradiation device: Metal halide lamp manufactured by IST METZ Gmbh Output: 80 W / cm
Irradiation distance: 15cm
Irradiation dose: 60-70 mJ / cm ²
・ Irradiation conditions in nitrogen Insert a nozzle to blow nitrogen gas to the lower part of each irradiation device (ultraviolet lamp), blow nitrogen from a nitrogen cylinder, and when the oxygen concentration reaches a predetermined value, UV light is applied to the semi-cured coating film. To complete curing.

<Preparation Example> Preparation of Stain Coating Film, Undercoat Coating Film, and Substrate with Intermediate Coating Film Commercially available floor veneer plywood having a width of 30 cm, a length of 180 cm, and a thickness of 1.2 cm has a width of 30
A test substrate was cut to a length of cm and a length of 60 cm. A colored stain having the composition shown in Table 1 was continuously applied to this substrate with a sponge roll coater, a reverse roll coater, and a natural roll coater, and then dried by heating at 100 ° C. for 1 minute. Subsequently, the undercoat paint of the composition shown in Table 2 was applied with a natural roll coater, a reverse roll coater, and a natural roll coater so that the coating amount per 1 m ² was 40 g. Immediately after curing by irradiation with ultraviolet rays from an electroded ultraviolet lamp in the air, the intermediate coating material A shown in Table 3 was applied with a natural roll coater so that the coating amount per 1 m ² was 20 g. After being cured by irradiation with ultraviolet rays from an electroded ultraviolet lamp in the air, the surface was polished and smoothed with No. 360 polishing paper to remove the abrasive powder adhering to the surface.

[Example 1]
On the surface of the substrate obtained by the preparation example (upper surface of the intermediate coating film), the top coating material D shown in Table 7 was applied with a natural roll coater so that the coating amount per 1 m ² was 10 g.
Immediately after painting, it was semi-cured by irradiating with ultraviolet rays from a metal halide lamp in the air. Subsequently, the film was cured by irradiation with ultraviolet rays from an electroded ultraviolet lamp in a nitrogen / oxygen mixed gas having an oxygen concentration of 0.5%, and then left at room temperature for 24 hours to be subjected to various tests described below.

[Example 2]
A test plate was prepared in the same manner as in Example 1 except that the top coating material was changed to the top coating material E shown in Table 8.

[Example 3]
A test plate was prepared by the same method except that the top coating material was changed to the top coating material F shown in Table 9 in the method described in Example 1.

[Example 4]
A test plate was prepared by the same method except that the top coating material was changed to the top coating material G shown in Table 10 in the method described in Example 1.

[Example 5]
A test plate was prepared in the same manner as in Example 1 except that the topcoat paint was changed to the topcoat E shown in Table 8 and the oxygen concentration of the oxygen / nitrogen mixed gas was changed to 4.0%. .

[Example 6]
In the method described in Example 1, the top coating material was changed to the top coating material E shown in Table 8, the oxygen concentration of the oxygen / nitrogen mixed gas was changed to 4.0%, and ultraviolet rays were irradiated by an electrodeless mercury lamp. A test plate was prepared in the same manner except for the above.

[Comparative Example 1]
On the surface of the substrate (upper surface of the intermediate coating film) obtained by the preparation example, the top coating material A having the composition shown in Table 4 was applied with a natural roll coater so that the coating amount per 1 m ² was 10 g.
After being cured by irradiation with ultraviolet rays from an electroded ultraviolet lamp in the air, it was left at room temperature for 24 hours and subjected to various tests described below.

[Comparative Example 2]
A test plate was prepared by the same method except that the top coating material was changed to the top coating material B shown in Table 5 in the method described in Comparative Example 1.

[Comparative Example 3]
A test plate was prepared by the same method except that the top coating material was changed to the top coating material C shown in Table 6 in the method described in Comparative Example 1.

[Comparative Example 4]
A test plate was prepared in the same manner as in the method described in Comparative Example 1 except that the top coating material was changed to the top coating material E shown in Table 8.

[Comparative Example 5]
A test plate was prepared in the same manner as in the method described in Comparative Example 1, except that the top coat was changed to the top coat E shown in Table 8 and the coating consisting of this top coat was cured using an electrodeless mercury lamp. did.

[Comparative Example 6]
In the method described in Comparative Example 1, the topcoat paint was changed to the topcoat B shown in Table 5, and the coating film composed of this topcoat paint was subjected to an electroded mercury lamp in a nitrogen / oxygen mixed gas having an oxygen concentration of 0.5% by volume. A test plate was prepared in the same manner except that it was cured using

[Comparative Example 7]
In the method described in Comparative Example 1, the topcoat paint was changed to the topcoat E shown in Table 8, and the coating film made of this topcoat paint was applied to an electroded mercury lamp in a nitrogen / oxygen mixed gas having an oxygen concentration of 0.5% by volume. A test plate was prepared in the same manner except that it was cured using

[Comparative Example 8]
In the method described in Comparative Example 1, the topcoat paint was changed to the topcoat F shown in Table 9, and the coating film composed of this topcoat paint was used in an electrodeless mercury lamp in a nitrogen / oxygen mixed gas having an oxygen concentration of 0.5% by volume. A test plate was prepared in the same manner except that it was cured using

<Test example>
The luster, stain resistance and crack resistance of the wooden floor coverings obtained from Examples 1 to 6 and Comparative Examples 1 to 8 were evaluated by the following test methods. The results are shown in Table 11.

  Gloss: The gloss of the coating film was measured for 60-degree specular reflectance according to 7.6 specular gloss of JIS K-5400. “Precision gloss meter GM-20D” (manufactured by Murakami Color Research Laboratory) was used as a measuring instrument.

  Contamination resistance: Draw a line 10 mm wide x 50 mm long with a commercially available hair dye solution (Vigen Co., Ltd., Hair Color 7G), leave it at room temperature for 30 minutes, and then use a cloth soaked in water or alcohol. This line was wiped off. After drying, the presence or absence of color remaining on the coated surface and the degree of darkness were observed. Evaluation criteria (score / content) are as follows: 5 / no trace at all; 4 / thin trace; 3 / thin trace; 2 / slight trace; 1 / dark trace.

Crack resistance: According to the Ministry of Agriculture, Forestry and Fisheries Notification No. 233 “Japanese Agricultural Standard for Plywood” dated February 27, 2003, a cold heat A test was carried out. The details are as follows;
A) A test piece was prepared from each sample plywood, each having a square shape with a length of 150 mm, and a hole with a diameter of 3 mm was made in the center of the test piece.
B) The test piece is fixed to a metal frame as shown in FIG. 1 and left in an incubator at 80 ± 3 ° C. for 2 hours and then left in an incubator at −20 ± 3 ° C. for 2 hours. And left to reach room temperature.

The fixing method of the test piece in a crack resistance test is shown.

Claims (19)

A photocurable coating composition containing (A) a photocurable resin, (B) a photopolymerization initiator, and (C) a reactive diluent is applied onto a substrate, and an uncured coating film comprising the composition After the coating process to form
A first irradiation process in which an uncured coating film is semi-cured by exposure to long-wavelength ultraviolet light emitted from a metal halide lamp, and a semi-cured coating film is exposed to ultraviolet light emitted from a high-pressure mercury lamp in an inert gas atmosphere. A paint curing method in which the second irradiation step of full curing is performed in this order.   The photocurable resin (A) is at least one photocurable resin selected from the group consisting of urethane (meth) acrylate resins, epoxy (meth) acrylate resins, and polyester (meth) acrylate resins. The paint curing method according to claim 1.   The photopolymerization initiator (B) is a photopolymerization initiator selected from the group consisting of benzophenones, anthraquinones, thioxanthones, acetophenones, acylphosphine oxides, and methylphenylglyoxyesters. The paint curing method according to claim 1 or 2.   The photocuring resin (A) is used in a range of 1 to 25 parts by weight of the photopolymerization initiator (B) with respect to 100 parts by weight of the photocurable resin (A). Method.   The reactive diluent (C) is a mixture of a monofunctional reactive diluent (C1), a bifunctional reactive diluent (C2), and a trifunctional or higher polyfunctional reactive diluent (C3). The paint curing method according to any one of claims 1 to 4, wherein   Reactive diluent (C) is mix | blended in the ratio of 20-300 weight part with respect to 100 weight part of photopolymerizable resins (A), The coating material in any one of Claims 1-5 characterized by the above-mentioned. Curing method.   6. The paint curing method according to claim 5, wherein the bifunctional reactive diluent (C2) is dimethylol tricyclodecane diacrylate.   In the reactive diluent (C), dimethylol tricyclodecane diacrylate is mixed in a proportion of 30 to 200 parts by weight with respect to 100 parts by weight of the photopolymerizable resin (A). The paint curing method as described.   The paint curing method according to any one of claims 1 to 8, wherein the first irradiation step is performed in air using a metal halide lamp having an output of 60 W / cm or more.   The paint curing method according to any one of claims 1 to 9, wherein the inert gas in the second irradiation step is nitrogen gas or nitrogen-containing gas.   The paint curing method according to claim 10, wherein the inert gas in the second irradiation step is a nitrogen / oxygen mixed gas having an oxygen concentration of 4% by volume or less.   The second irradiation step is performed using an electroded mercury lamp having an output of 80 W / cm or more as a high-pressure mercury lamp in a nitrogen / oxygen mixed gas atmosphere having an oxygen concentration of 0.5 to 4.0% by volume. The paint curing method according to claim 1, wherein: The second irradiation step is performed using an electrodeless mercury lamp having an output of 24 to 240 W / cm as a high-pressure mercury lamp in a nitrogen / oxygen mixed gas atmosphere having an oxygen concentration of 0.5 to 4.0% by volume. The paint curing method according to claim 1, wherein:   In the first irradiation step and the second irradiation step, one or two or more lamps are arranged spaced apart from the conveyor by a predetermined distance, and the substrate coated with the photocurable coating composition is disposed on the conveyor. The paint curing method according to any one of claims 1 to 13, wherein the coating is continuously carried out by transporting at a speed of 1 to 150 m / min. In the second irradiation step, the integrated light quantity is 20 to 1000 mJ / cm ² using a high-pressure mercury lamp having an output of 60 to 240 W / cm per one on the substrate on which the photocurable coating composition is applied.
The paint curing method according to claim 1, wherein the paint curing method is performed by irradiating with an amount of   In the coating step, one or more of a stain coating film, an undercoat coating film, and an intermediate coating film are previously formed in this order on the substrate, and the outermost coating film among these coating films. The photocurable coating composition used in any one of Claims 1-15 is apply | coated on the top, The coating-curing method in any one of Claims 1-15 characterized by the above-mentioned.   The photocuring coating film formed by the method as described in any one of Claims 1-16.   The base material with a coating film by which the surface of a base material is coat | covered with the photocuring coating film formed by the method as described in any one of Claims 1-17.   The base material with a coating film of Claim 18 whose base material is a wooden flooring or a vinyl chloride flooring.

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