JPS6018221B2 - How to paint porous substrates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a porous substrate (hereinafter simply referred to as "base material") using a photo-curable or ionizing radiation-curable (hereinafter simply referred to as "photo-curable etc.") paint. The present invention relates to a coating method that prevents whitening of the coating film and the occurrence of pinholes during finishing, and provides a smooth coating film without wrinkles.

Conventionally, when finishing a substrate such as wood with a photocurable paint, the resulting cured coating often has significant whitening and pinholes, and has poor smoothness.

The cause of whitening, pinholes, etc. is that the air existing inside the base material expands due to the heat generated during irradiation with actinic light or ionizing radiation, pushing up the coating film on the surface of the base material from the inside. It is thought that the rapid hardening of the paint film caused by irradiation makes it difficult for the air inside Motomura to diffuse outside the paint film, and that air replacement is not carried out smoothly, which also contributes to the frequent occurrence of these paint film defects. . Therefore, for example, when applying a photocurable paint to a base material, the coating film must be gradually cured by irradiating it with low-energy active light that does not generate a large amount of heat for a long time, or it can be cured gradually using a catalytic curing type unsaturated polyester resin. After the base material has been sufficiently sealed with a surfacer such as a polyurethane resin or a cellulose lacquer, it is necessary to finish with a photocurable paint.

However, these methods significantly reduce the advantages of shortening and increasing efficiency of the coating process, which are the characteristics of the photocuring method and the ionizing radiation curing method, and are not rational countermeasures. In the case of painting finishes using opaquely colored photocurable paints, the transmittance of actinic rays to the paint film is low, resulting in a difference in the curing state between the surface and interior of the paint film, resulting in wrinkles in the cured paint film. is likely to occur.

In order to prevent stagnation, it is almost possible to reduce the thickness of the paint film and increase the number of coats, but this will drastically reduce the coating efficiency. The purpose of the present invention is to prevent the above-mentioned defects and obtain excellent aesthetic properties when finishing a base material using a photocurable paint. This is accomplished by coating a base material with a sealer such as a photo-curing material at a predetermined dry coating weight, and finishing with a top coat such as a photo-curable paint after curing.

That is, in the present invention, a sealer such as a photoresist is applied to the base material with a viscosity of 1.0 poise or less at room temperature and a dry coating weight of 20
The gist of this is a method for painting a base material, which is characterized by applying an undercoat so as not to exceed the thickness of the base material, curing this, and then finishing with a top coat such as a photocurable paint.
Use a photo-curable sealer containing a non-reactive organic solvent, and use a suitable non-reactive organic solvent selected from alcohol-based solvents, ester-based solvents, and ketone-based solvents. In an embodiment, one type or two or more types are used.

The base material in the present invention is an organic or inorganic material that has many conduits, small holes, voids, or narrow grooves extending from the surface layer to the inside, and is generally in contact with a liquid substance such as a paint. Natural wood, processed wood (e.g. plywood, laminated wood, particle board, fiberboard, etc.), plywood wood, and inorganic wood have the property of easily absorbing it and are used daily in construction, machinery, fixtures, decorations, etc. Fibrous materials (e.g. glass fiber board, rock wool board), cement and concrete materials (e.g. asbestos slate, asbestos cement board, barren cement board, concrete board, etc.),
It is typified by processed plaster materials (gypsum board).

In addition, in the sealer and top coat used in the present invention, photocurable means that radicals are formed by irradiation with active light belonging to ultraviolet rays, visible heat radiation, etc. having wavelengths in the visible range from near ultraviolet to 500 french. It refers to the property of curing by exciting a polymerization reaction, and the purpose is usually achieved by adding a small amount of photosensitizer to an unsaturated resin composition capable of radical polymerization and irradiating it with actinic rays.

An example of a photosensitizer is Q-carbonyl alcohol (
(e.g. penzoin), acyloin ethers (e.g. penzoin ethyl ether), Q-substituted acyloin (e.g. Q-methylbenzoin), quinones (e.g. 9,
10-anthraquinone), polyketones (e.g. diacetyl), mercaptans (e.g. 2-mercaptopenzothiazole), disulfides (e.g. diphenyl disulfide), thiols (e.g. thiophenol), phenylketones (e.g. penzophenol), etc. There are compounds that belong to Furthermore, ionizing radiation curability means that an unsaturated resin composition capable of radical polymerization is cured by X-rays, y-rays,
It refers to the property of curing by exciting a radical polymerization reaction by irradiation with 8-rays, accelerated electron beams, etc., and the method using accelerated electron beams is particularly useful industrially, and the irradiation energy is 50 to 1000 KV. The range of energy is appropriate, and preferably one having an energy of 100 to 100 KV. . The polymerizable unsaturated resin that is to be the base of the photocurable sealer and top coat used in the present invention contains an ethylenic or polyene unsaturated group that can be polymerized and cured by irradiation with the above-mentioned actinic rays or ionizing radiation. The polymer compounds present in the molecule include, for example, unsaturated polyester resins, unsaturated acrylic resins, unsaturated urethane resins, unsaturated eboxy resins, unsaturated butadiene resins, unsaturated polyamide resins, One or two selected from unsaturated alkyd/amino resins, etc.
Although there are more than one species, it is not limited to only these types.

The above polymerizable unsaturated resin is dissolved in an ethylenically unsaturated monomer as a polymerizable diluent, and if necessary, a polymerizable resin having a saturated bond, a plasticizer, a coloring agent (pigment, dye, etc.) ) A photocurable sealer or top coat is made by blending photosensitizers, additives, etc.

In addition, by replacing a portion of the polymerizable diluent in the sealer with a polar organic additive that is inert (non-reactive) in the photo-curing system or ionizing radiation curing system, it is possible to apply it to the base material of the sealer during painting. Penetration and absorption are significantly enhanced. Examples of the polymerizable diluent include acrylic ester, methacrylic ester, divinylstyrene, diacryl phthalate, triallyl cyanurate, ethylene glycol diacrylate, ethylene glycol dimethacrylate,
Trimethylolpro/guntrimethacrylate, trimethylolpropane triacrylate, bentaerythritol triacrylate, bentaerythritol tetramethacrylate, 1,6 hexanediol diacrylate, 1,6 hexanediol dimethacrylate, 1,3 butylene dimethacrylate One or two ethylenically unsaturated monomers such as methacrylate, vinyl acetate, styrene, vinyltoluene, etc.
More than one species is selected.

Furthermore, the above-mentioned non-reactive polar organic solvent has a dielectric constant (2
0) One or more types of volatile organic solvents of about 5 or more, generally have good dissolving power for polymeric unsaturated resins, and have good permeability to base materials and volatilization after permeation and absorption. alcohol-based solvents (e.g. ethanol), ester-based solvents (e.g. butyl acetate, ethyl acetate, etc.),
Ketone solvents (eg, acetone, methyl ethyl ketone, etc.) and mixtures thereof are used. In the present invention, emphasis is placed on the step of surface-treating the base layer using a photocurable sealer or the like. That is, in order to prevent the curing component contained in the sealer from forming a continuous coating film on the surface of the substrate, the viscosity of the sealer is kept at room temperature at 1.0 poise or less, preferably at 0.5 poise or less, and the dry coating is Membrane weight 2
The sealer is applied at a temperature of less than 0.000 m/m to allow it to penetrate well from the surface of the base material to the inside, and the air in the voids in the base material is replaced and filled with the sealer. If active light or ionizing radiation is applied in this state,
It is possible to prevent the above-mentioned coating film defects caused by air expansion inside the base material due to heat generated during irradiation. In order to further improve the permeability of the sealer inside the substrate, it is effective to replace a portion of the polymerizable diluent contained in the sealer with a non-reactive polar organic solvent.

In particular, when the base material is natural wood, processed wood, etc., the sealer's permeability is significantly improved, and the organic solvent evaporates smoothly due to the heat generated during irradiation, so it is adversely affected by the residual solvent. Never. When applying the sealer, if the weight of the dry coating exceeds 20 mm/day, a continuous coating will tend to form on the surface of the substrate, making it impossible to prevent whitening of the finished coating and generation of pinholes.

Further, if the viscosity of the sealer is 1.0 poise or more, the permeability of the sealer into the inside of the base material is reduced, which is not in accordance with the purpose of the present invention. On top of the base material treated with the above-mentioned method, apply a top coat such as a photocurable paint to an arbitrary film thickness (usually 30 to 500
r) and irradiated with active light or ionizing radiation.

According to this coating method, the thermal expansion of the air in the voids is extremely small due to the effect of the surface treatment, and a smooth finished coating film without whitening or pinholes can be obtained. Motomura's painting often requires a translucent or opaque colored finish in addition to a transparent finish.

In this case, add dye to the extent that it does not interfere with the transmission of actinic rays
If you use a photo-curable sealer that is colored with a pigment, etc., and then finish with a photo-curable top coat that is colored with a dye or pigment that does not block the transmission of active light. good. The use of a non-reactive polar organic solvent, coating viscosity, and dry coating weight in a colored photo-curable sealer are in accordance with the conditions set for the photo-curable sealer described above. After applying this sealer to the base layer and curing it by irradiating it with active light or ionizing radiation, you can apply the above-mentioned colored photo-curable top coat and cure it by irradiating it in the same way. There is no difference in the hardening state between the surface and the inside, and the occurrence of wrinkles is prevented.

Furthermore, whitening and pinholes do not occur due to the surface treatment effect of the sealer. Furthermore, in this coating method, it is of course possible to apply a colorless and transparent top coat that does not contain a colorant, depending on the degree of coloring of the substrate. No particular coating device or equipment is required to carry out the present invention.

After spray painting as appropriate depending on the material, shape, size, etc. of the base material, spray. - Conventionally known devices and methods such as coating method, bond coating method, roll coating method, etc. may be selected. Furthermore, active light can be obtained from a light source such as a high-pressure mercury lamp, a poppy lamp, a light lamp, a xenon lamp, or an arc lamp. As described above, by implementing the present invention in painting substrates using photocurable paints, etc., whitening and pinholes in the finished coating can be prevented, and photocurable resin paints using carbon black etc. It has the advantage that it can also solve problems such as curing and sagging in coatings. That is, it is possible to exhibit the features of the photocuring method and the ionizing radiation curing method without any deterioration in mounting performance or coating efficiency. Next, production examples, examples, and comparative examples will be given to specifically explain the present invention.

In addition, parts in the examples mean parts by weight, and % means weight %. Production example: An acid value of 20 obtained by adding 2 moles of acrylic acid to 1 mole of bisphenol A type jepoxy compound (manufactured by Shell Chemical Company, Epiquat 82 & Molecular Power 380) by a conventional method.
The polymerizable unsaturated resin of product (1), maleic anhydride 6
mol, phthalic anhydride 4 mol, neobentyl glycol 5
Product (0) is a polymerizable unsaturated resin having an acid value of 45, which is obtained by condensing 6 moles of 1,6-hexanediol using a conventional method.

Seven types of photocurable sealers were manufactured using products (1) and (0) according to the formulations shown in Table 1. Also,
Four types of photocurable topcoat paints, including one containing carbon black, were manufactured according to the formulations shown in Table 2. Table 1
(Sheeler) West Germany. Black dye manufactured by BASF Co., Ltd. Table 2 (Top coat paint) In production examples 10 and 11. The particles were dispersed in a steel ball mill with a particle size of 10K.

Example 1 A piece of birch plywood (approximately 300 x 150 x 15 sides) was used as a base material, and this was submerged in the sealer of Production Example 3 at room temperature to provide an undercoat.

At this time, the dry coating weight of the sealer applied to the substrate was actually measured to be 15 days/day. After lifting the base material from the sealer and leaving it for 1 minute, irradiation was performed using a 2KW high-pressure mercury lamp (manufactured by Tokyo Shibaura Electric Company) at a distance of 30 cm, resulting in a cured coating film that was continuous on the surface of the base material. No paint film was formed, the wood grain was embossed, and no whitening or pinholes were observed. Next, the top coat of Production Example 8 was applied on top of this using a 10-yen bar coater, and immediately irradiated with ultraviolet rays under the same irradiation conditions as the undercoat, resulting in a glossy finish with the hardness of a pencil with no whitening or pinholes. was gotten. The dry coating weight of the top coat was 68 mm/m. Comparative Example 1 The top coat of Production Example 8 was applied to the same birch plywood as in Example 1 using a 10-misaki bar coater, and immediately irradiated with ultraviolet rays according to the irradiation method of Example 1.

The resulting cured coating film had severe whitening and pinholes, and had a completely impractical finish. In addition, after applying the above top coat paint, we left it at room temperature for 10 minutes to allow it to penetrate into the base material, and then we irradiated it with ultraviolet rays under the same conditions as above, but the resulting paint film showed some whitening, and it was Many holes also occurred.

This was due to the fact that the top coat in Production Example 8 had a high viscosity and did not penetrate sufficiently into the wood grain of the base material, and the weight of the dry paint film was too large, resulting in the formation of a continuous paint film on the surface of the base material. . Examples 2 to 4 and Comparative Examples 2 to 4 Using the various sealers and top coats shown in Table 3, finishing was carried out using the same base material, coating method, and ultraviolet irradiation conditions as in Example 1.

The dry coating weight, coating condition, hardness, and adhesion of the sealer are shown in Table 3. Table 3 Note: (1) Whitening. It is a pinhole, and the distortion and color tone are as seen by the naked eye. The word white bow represents the next enemy grandson.

◎Excellent, 〇Good. ◎Available. △Slightly poor. × Defective (2
The pencil hardness test was conducted according to JISK5400, 6.14. (3) Adhesion: Cut the coating surface with a knife. The condition of the base material of the coating film was evaluated as follows. ◎Excellent.
○Good. @Available. △Slightly poor. *Defective In Examples 2 and 3 in which a non-reactive polar organic solvent with good permeability into the substrate was used, no whitening or pinholes were observed. On the other hand, a sealer with a viscosity of 160 centipoise (2500) (
In Comparative Example 2 using Production Example 1), the sealer did not penetrate sufficiently into the base material and the applied amount was excessive, resulting in severe whitening and pinholes, resulting in a finished coating film lacking in practicality. When applying an opaque colored finish to the base coat, apply a translucent top coat (Production Example 10) on top of the sealer containing the colorant (Production Example 6) in Example 4 to obtain a good color tone with no coating defects. A cured coating film was obtained.

However, as in Comparative Example 3, if an attempt is made to provide Bay concealment with only the top coat without coloring the sealer, the ultraviolet transmittance to the top coat decreases and sagging occurs. Furthermore, in Comparative Example 4, which used a topcoat paint whose wisteria properties were adjusted to such an extent that sagging did not occur, the color tone was insufficient due to the lack of base coloring, and a good finish was not obtained.

Example 5 The sealer of Production Example 5 was applied to cover plywood (same as Example 1)
After applying an undercoat using the same coating method as in Example 1, the irradiation distance was 1 using a 30-plate V electron beam accelerator in a nitrogen gas flow.
It is cured by irradiation under the conditions of 5 arcs and an irradiation dose of 5 megarads, and then the top coat of Production Example 9 is applied according to the coating method of Example 1.

This was cured by electron beam irradiation under the same irradiation conditions as the undercoat. The finished coating film obtained was smooth and had no whitening or pinholes.

The dry coating weight of the sealer in this case was 122/m. Comparative Example 5 Using the sealer of Production Example 2 and the top coat of Production Example 9, the finished coating film obtained by painting and electron beam irradiation in the same manner as in Example 5 had an excessive amount of sealer applied. Because of the large size and insufficient penetration into the base material, whitening and pinholes were generated, making it impractical.

The dry coating weight of the sealer in this case was 25 mm. Example 6 The sealer of Production Example 6 was undercoated on the surface of gypsum Motomura (approximately 150 x 150 The dry coating weight is approximately 12 mm).

Next, the following electron beam curable paint was applied to the gypsum base layer by airless spray painting at a coating amount of approximately 130 mm/cm (film thickness approximately 130 mm/cm), and the same coating as the sealer was applied. It was cured by electron beam irradiation under irradiation conditions.

The resulting finished coating had a glossy tile-like finish with no whitening, pinholes, or wrinkles, and no pencil hardness spots.

Preparation of electron beam curable paint: Methyl methacrylate-butyl acrylate-glycidyl acrylate copolymer (number average molecular weight approximately 10,000
) with acrylic acid to obtain an unsaturation degree of 1.0 (resin 100
An unsaturated acrylic resin varnish (methyl methacrylate solution containing 70% resin) was obtained (number of moles of unsaturated groups per unit).

Claims (1)

[Scope of Claims] 1. A photo-curable or ionizing radiation-curable sealer is applied to a porous substrate with a viscosity of 1.0 poise or less at room temperature and a dry coating weight not exceeding 20 g/m^2. Undercoat,
A method for coating a porous substrate, which comprises curing the material and then finishing with a photo-curable or ionizing radiation-curable top coat. 2. The method for coating a porous substrate according to claim 1, wherein the photo-curable or ionizing radiation-curable sealer contains a non-reactive polar organic solvent. 3 The non-reactive polar organic solvent is one or two selected from alcohol solvents, ester solvents, and ketone solvents.
3. The method for coating a porous substrate according to claim 2, wherein the porous substrate is coated with a porous substrate.