Photocurable top coat resin composition

The present invention relates to a photocurable topcoat resin composition having a stable matte appearance and adhesion.

The decorative materials used in the construction field are, for example, a decorative sheet or a decorative layer coated on a wood material or a ceramic material, and a finishing layer that generally also protects the decorative layer. As a result, a top coat layer is provided. As the resin used there, an active energy ray-curable resin having a high curing rate and excellent productivity is often selected.

When making such a top coat layer have a matte appearance, it is common to add a filler such as silica, but in the case of a solvent-free top coat resin, since it does not contain an organic solvent, when the solvent volatilizes. It was not easy to obtain a stable matte appearance because a so-called lifting effect, in which a filler such as silica floats up on the coated surface and is densely packed to change the appearance, cannot be expected.

In order to deal with these problems, for example, a coating material containing a urethane acrylate oligomer, a bifunctional acrylate oligomer, a trifunctional urethane oligomer, spherical silica having a particle size of 3 to 5 μm, and a photopolymerization initiator is used, and semi-cured by ultraviolet irradiation. A manufacturing method has been proposed in which the mixture is completely cured by irradiation with an electron beam (Patent Document 1). However, this method requires two types of light sources, ultraviolet irradiation and electron beam irradiation, which imposes manufacturing restrictions, and when the base is an acrylic paint, there is a problem that the adhesion is not stable, and there is room for improvement. was there.

<p><patcit num="1"><text>Japanese Patent No. 4876384</text></patcit></p>

<p>An object of the present invention is to provide a solvent-free photocurable topcoat resin composition having a stable matte appearance and excellent adhesion to a base coating material.</p>

<p>In order to solve the above problems, the invention of claim 1 according to the present application comprises a tetrafunctional or higher functional urethane (meth) acrylate oligomer (A) and a pentaerythritol triacrylate (B) having a hydroxyl value of 160 to 330 mgKOH / g. It contains a monofunctional (meth) acrylate monomer (C) having a hydroxyl group, inorganic fine particles (D) having an average particle diameter of 1 to 30 μm, and a photopolymerization initiator (E), with respect to the total solid content of (A). Provided is a photocurable top coat resin composition characterized by a blending amount of 8 to 50% by weight.</p><p>The invention according to claim 2 provides the photocurable topcoat resin composition according to claim 1, wherein the blending amount with respect to the total solid content of the above (B) is 3 to 40% by weight.</p><p>The invention of claim 3 further provides the photocurable topcoat resin composition according to claim 1 or 2, further comprising an antiviral agent (F).</p><p>The invention according to claim 4 is the photocurable topcoat resin composition according to any one of claims 1 to 3, wherein the blending amount with respect to the total solid content of the above (F) is 3 to 30% by weight. offer.</p><p>The invention according to claim 5 provides the photocurable topcoat resin composition according to any one of claims 1 to 4, which is used as a topcoat of a base coating material made of an acrylic resin.</p>

<p>The coating composition of the present invention has a stable matte appearance and is extremely excellent in adhesion to the undercoat paint, and is therefore useful as a solvent-free photocurable topcoat resin used in decorative materials for construction applications. be.</p>

The present invention will be described in detail.

The composition of the photocurable coating composition of the present invention comprises a tetrafunctional or higher functional urethane acrylate oligomer (A), pentaerythritol triacrylate (B), monofunctional (meth) acrylate monomer (C), and inorganic fine particles (D). ) And the photopolymerization initiator (E). In addition, in this specification, (meth) acrylate includes both acrylate and methacrylate.

The tetrafunctional or higher functional urethane acrylate oligomer (A) used in the present invention is a main component constituting a cured film, and has excellent scratch resistance due to the cohesive force of hydrogen bonds derived from urethane bonds. The number of functional groups is preferably 4 to 12 functional, and more preferably 6 to 10 functional. When the number of functionalities is 4 or more, sufficient curability and film cohesive force can be secured, and when the number of functionalities is 12 or less, curing shrinkage can be suppressed and a cured film with less strain can be easily formed.

The above (A) can be obtained, for example, by reacting a polyisocyanate with a (meth) acrylate having a hydroxyl group. Examples of the polyisocyanate used include hexamethylene diisocyanate (hereinafter HDI), isophorone diisocyanate (hereinafter IPDI), diphenylmethane diisocyanate, tolylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, hydrogenated xylylene diisocyanate, and methylcyclohexylene diisocyanate. Examples thereof include HDI isocyanurate and IPDI isocyanurate, which may be used alone or in combination of two or more. Among these, aliphatic and alicyclic diisocyanates having high weather resistance and resistance to yellowing are preferable, and among them, HDI having high stretchability is particularly preferable.

As the hydroxy (meth) acrylate used in the above (A), for example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like are bifunctional in monofunctional. Then, trimethylolpropane di (meth) acrylate, glycerin di (meth) acrylate, pentaerythritol di (meth) acrylate, diglycerin di (meth) acrylate, trimethylolpropane di (meth) acrylate, dipentaerythritol di (meth) acrylate, etc. , Diglycerintri (meth) acrylate, dimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipenta for trifunctional or higher Elythritol penta (meth) acrylate can be mentioned. Among these, pentaerythritol triacrylate, which has three functionalities (corresponding to six functional groups in the synthesized (A)) and has high curability, is preferable.

The blending amount of the composition (A) with respect to the total solid content is 8 to 50% by weight, preferably 9 to 45% by weight, more preferably 9 to 40% by weight. If it is less than 8% by weight, sufficient paintability and good appearance cannot be ensured, and if it exceeds 50% by weight, a stable matte appearance cannot be ensured. The blending amount of the resin component with respect to the solid content is preferably 10 to 65% by mass, more preferably 13 to 60% by weight. Within this range, good workability, sufficient film strength and good appearance can be ensured.

Since the pentaerythritol triacrylate (B) used in the present invention has a hydroxyl value of 160 to 330 mgKOH / g and is extremely high, it is possible to secure good adhesion to the underlying resin while maintaining high curability. .. In particular, when the base resin is an acrylic resin, the adhesion can be remarkably improved. (B) is produced by reacting pentaerythritol with acrylic acid, and is a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate due to the production method. Since the characteristics can be changed by the ratio of the triacrylate having a hydroxyl group, (B) having a different hydroxyl value can be selected depending on the purpose. The hydroxyl value is more preferably 170 to 330 mgKOH / g, and particularly preferably 180 to 330 mgKOH / g. Sufficient adhesion to the substrate cannot be ensured at 160 mgKOH / g or less, and economically sufficient availability cannot be obtained at 330 mgKOH / g or more.

The blending amount of the composition (B) with respect to the total solid content is preferably 5 to 50% by weight, more preferably 8 to 45% by weight. When it is 5% by weight or more, sufficient adhesion with the base material can be ensured, and when it is 50% by weight or less, sufficient pencil hardness can be secured and penetration into the base resin can be suppressed.

The monofunctional (meth) acrylate monomer (C) used in the present invention has a hydroxyl group and is blended for the purpose of improving the adhesion with the base resin. For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 1,4- Cyclohexanedimethanol monoacrylate, 4-hydroxycyclohexyl (meth) acrylate and the like can be mentioned, and can be used alone or in combination of two or more. Among these, 2-hydroxypropyl methacrylate, which is not designated as a poisonous or deleterious substance and has a low cost, is preferable.

The blending amount of the composition (C) with respect to the total solid content is preferably 2 to 15% by weight, more preferably 3 to 12% by weight, and particularly preferably 5 to 10% by weight. When it is 2% by weight or more, sufficient adhesion with the base resin can be ensured, and when it is 15% by weight or less, sufficient pencil hardness can be secured and penetration into the base resin can be suppressed.

In addition to the above (B) and (C), other (meth) acrylate monomers may be blended as an improvement in curability and a reactive diluent. Polyfunctional (meth) acrylate monomers are particularly preferable in terms of curability, and for example, in bifunctionality, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, (poly) tetramethylene glycol di (poly) tetramethylene glycol di (poly) Meta) acrylate, 1.4-butanediol di (meth) acrylate, 1.6-hexanediol di (meth) acrylate, dimethyloltricyclodecanediacrylate, dicyclopentanyldiacrylate, trimethylolpropane tri (meth) in trifunctionality Acrylate, dipentaerythritol tri (meth) acrylate is tetrafunctional, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, diglycerin tetra (meth) acrylate. However, pentaerythritol penta (meth) acrylate may be used for the 5-functionality, dipentaerythritol hexa (meth) acrylate or the like for the 6-functionality, and the like can be used alone or in combination of two or more. Among these, bifunctional is preferable from the viewpoint of the balance between curability and curing shrinkage, and 1.6-hexanediol di (meth) acrylate having a moderately long molecular chain, low odor and good reactivity is particularly preferable.

The inorganic fine particles (D) used in the present invention are blended for the purpose of making the appearance of the coating film stable and matte, suppressing the resin penetration into the underlying layer, and at the same time improving the durability of the cured film. The presence or absence of surface treatment is not particularly specified, and may be hydrophilic or hydrophobic. The average particle size of (D) is 1 to 30 μm, preferably 2 to 15 μm, and more preferably 3 to 10 μm. When it is 1 μm or more, a matte appearance can be effectively obtained, and when it is 30 μm or less, sufficient coating stability and appearance can be ensured. The average particle size can be measured by the laser diffraction method conforming to JIS Z 8825-1.

The blending amount of the composition (D) with respect to the total solid content is preferably 3 to 20% by weight, more preferably 4 to 15% by weight, and particularly preferably 5 to 13% by weight. When it is 3% by weight or more, it is possible to secure sufficient matting effect and durability, and when it is 20% by weight or less, it is possible to secure sufficient total light transmittance.

The photopolymerization initiator (E) used in the present invention generates radicals by irradiation with active energy rays such as ultraviolet rays and electron beams, and the radicals trigger a polymerization reaction. Intramolecular cleavage type photopolymerization initiators such as fin oxide type and hydrogen extraction type photopolymerization initiators such as benzophenone and phenylglycylyl acid ester type can be used. By arbitrarily selecting the light absorption wavelength of the polymerization initiator, curability can be imparted over a wide wavelength range from the ultraviolet region to the visible light region. Specifically, 2.2-dimethoxy-1.2-diphenylethan-1-one as a benzyl ketal system, 1-hydroxy-cyclohexyl-phenyl-ketone and 1- [4- (2-hydroxyethoxy)-) as an α-hydroxyacetophenone system. Phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one as an α-aminoacetophenone system, 2.4.6-trimethylbenzoyl-diphenyl-phosphinoxide and bis (2.4.6-trimethylbenzoyl) -phenylphosphine oxide are available as acylphosphine oxide systems, and 2-phenylglycoxylate methyl is available as the phenylglycoxylate ester system. , Can be used alone or in combination of two or more. Among these, it is preferable to contain a phenylglyoxylic acid ester system that causes less yellowing even when exposed to ultraviolet rays for a long period of time and provides flexibility of the coating film when cured, and Omnirad MBF-S (trade name: trade name:) is commercially available. IGM) and so on.

The ratio of (E) to 100 parts by weight of the photocurable resin component is preferably 1 to 20 parts by weight, more preferably 5 to 15 parts by weight. When the amount is 1 part by weight or more, curability is exhibited, and when the amount is 20 parts by weight or less, yellowing of the coating film and deterioration of storage stability can be prevented without excessive addition.

By blending the antiviral agent (F) in the resin composition of the present application, it is possible to impart antiviral properties. Examples of the inorganic material having antiviral properties include compounds containing copper, silver, titanium, tin, iron, nickel, zinc and the like, and examples of the organic material include hydroxyapatite, a polymer having a sulfonic acid group or a salt thereof and the like. Be done.

The blending amount of the composition (F) with respect to the total solid content is preferably 3 to 30% by weight, more preferably 5 to 15% by weight. When the content is 3% by weight or more, antiviral properties can be imparted, and when the content is 30% by weight or less, sufficient appearance and coating film performance can be ensured.

Further, in the coating composition of the present invention, if necessary, a dispersant, a leveling agent, an ultraviolet absorber, an antioxidant, a colorant, a defoaming agent, a thickener, an anti-precipitation agent, an antistatic agent, and an antifogging agent. , Non-slip agent, flame retardant and the like may be added.

The dispersant is an additive used to uniformly disperse an inorganic / organic pigment in a medium to prepare a stable dispersion, and is a surfactant that stabilizes a solid-liquid interface. In particular, a copolymer type having an acidic group is preferable because the dispersibility of silica is excellent. The blending amount of the dispersant with respect to the total solid content of the composition is preferably 0.05 to 3% by weight, more preferably 0.1 to 1% by weight. Commercially available products include Disper BYK 102 (trade name: Big Chemy Japan, copolymer having an acidic group), BYK2008 (trade name: Big Chemy Japan, modified acrylic block copolymer).

The method for applying the coating composition of the present invention is not particularly limited, and is a coating method such as a known spray coating, roll coating, die coating, air knife coating, blade coating, spin coating, reverse coating, gravure coating, wire bar, or gravure. Printing, screen printing, offset printing, inkjet printing, etc. can be used. The coating amount is 5 ~ 100g / m.²Is exemplified, but it can be selected at any time depending on the application.

After applying the coating composition of the present invention, it is cured by irradiation with light such as ultraviolet rays. Examples of the light source for irradiating ultraviolet rays include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, xenon lamps, metal halide lamps, LED lamps, and electrodeless ultraviolet lamps. 50 ~ 1000mW / cm²With the irradiation intensity of 100 to 2,000 mJ / cm as the integrated light intensity²Is exemplified. The atmosphere to be irradiated may be air or an inert gas such as nitrogen or argon.

Hereinafter, the present invention will be described in detail based on Examples and Comparative Examples, but only specific examples thereof are shown and the present invention is not particularly limited thereto. Unless otherwise stated, measurements were taken under conditions of room temperature of 25 ° C and relative humidity of 65%. The unit of the formulation table is the part by weight.

<u style="Single">Examples 1 to 6</u>As the above (A), a hexafunctional urethane acrylate (a reaction product of HDI and pentaerythritol triacrylate) was used, and as the above (B), MT-3548 (trade name: manufactured by Toa Synthetic Co., Ltd., hydroxyl value 250 to 300 mgKOH / g) was used. Light ester HOP (N) (trade name: Kyoeisha Chemical Co., 2-hydroxypropyl methacrylate) as C), ACEMATT OK607 (trade name: Ebonic, hydrophobic silica, average particle size 4.4 μm) as (D) , (E) as Omnirad MBF-S (trade name: IGM, phenylglycylyl ester), (F) as Allerbuster (trade name: Sekisui Material Solutions) and Wiltaker (trade name: Sekisui Material). Solutions), MIRAMER M201B (trade name: MIWON, 1.6 hexanediol diacrylate) as other monomers, BYK2008 (trade name: Big Chemy Japan) as a leveling agent, uniformly in the formulation shown in Table 1. The photocurable coating composition of Examples 1 to 6 was prepared by stirring until it was dissolved and dispersed in.

<u style="Single">Comparative Examples 1 to 3</u>In addition to the materials used in the examples, MIRAMER M340 (trade name: MIWON, pentaerythritol triacrylate, hydroxyl value 130 to 140 mgKOH / g) using bifunctional urethane acrylate (polycaprolactone skeleton) as a monomer is shown in Table 1. The photocurable coating composition of Comparative Examples 1 to 3 was prepared by stirring until the mixture was uniformly dissolved and dispersed.

table 1<img file="JP2022055408A_D0001.tif" />

The evaluation method was as follows.

<u style="Single">Preparation of test piece</u>Aitron Z-140 (trade name: Aica Kogyo Co., Ltd., urethane type) is applied as a sealer on a 6 mm thick calcium silicate plate (trade name: Hishitaika Aica Tech Kenzai Co., Ltd.), and Aitron is used as a sealing layer on it. Z-983S-13 and Z-983W-14 (trade name: manufactured by Aica Kogyo Co., Ltd., epoxy acrylate type) are used to form two sealing layers, and acrylic urethane paint is used on them to form 85 g / m.²After forming the decorative layer in, apply the above paint composition at 10 g / m.²After that, use Eye Grandage ECS4011GX / N (high pressure mercury lamp manufactured by Eye Graphics) as a light source, and the irradiation intensity is 200mW / cm.², Integrated light intensity 400mJ / cm²It was cured under the exposure conditions and used as a test piece.

Viscosity: Measured at 25 ± 1 ° C, rotation speed 60, 6 rpm with No. 4 or 3 rotor using BM type viscometer TVB-10 manufactured by Toki Sangyo.

Curability: Using Eye Grandage ECS4011GX / N (high pressure mercury lamp manufactured by Eye Graphics), irradiation intensity 200mW / cm², Integrated light intensity 400mJ / cm²After irradiation under the exposure conditions, it was evaluated by touch whether there was any tack residue on the surface of the coating film. The case without tack was marked with , and the case with tack was marked with ×.

Appearance: The appearance of the coating film was visually confirmed, and the case where it was flat and had no unevenness was evaluated as , the case where there was no noticeable unevenness was evaluated as , and the case where there was an abnormality due to the top coat layer such as streaks was evaluated as ×.

Initial adhesion: According to the old JIS K5400, a grid test of 100 1 mm squares was performed, and the peeling state of the coating film was confirmed with cellophane tape (specified in JIS Z 1522). When the cellophane tape attached to the coating film side was peeled off, the case where the peeled mass was 0 was evaluated as , and the case where even 1 cell was peeled off was evaluated as x.

Pencil hardness: Using a pencil scratch coating film hardness tester (type P) manufactured by Toyo Seiki Seisakusho, evaluate with a 750 g load according to JIS K 5600-5-4 (1999 version), and 2H or more is , H And F was set to Yes, and HB or less was set to x.

Glossiness: In accordance with JIS Z 8741, the glossiness (60 °) was measured several times using a digital variable angle gloss meter manufactured by Suga Test Instruments, and the matte appearance of 30 or less was marked as and over 30 was marked as ×.

Antiviral phage test: Measured by the plaque measurement method of ISO 21702: 2019. Bacteriophage Qβ was used as a test virus as a substitute for feline calicivirus, and bacteriophage φ6 was used as a substitute for influenza virus, and the virus infectivity titer was measured after 24 hours. The difference in virus infectious titer from the blank film was defined as the antiviral activity value, and 2.0 or more was marked with and 2.0 or less was marked with x. The antiviral phage test was performed only in Example 4 on behalf of all Examples.

Evaluation results<img file="JP2022055408A_D0002.tif" />

The examples were good in all aspects of curability, appearance, initial adhesion, pencil hardness, and glossiness without any problems.

On the other hand, Comparative Example 1 in which (D) was not blended had a high glossiness, and Comparative Example 2 using pentaerythritol triacrylate having a low hydroxyl value had low initial adhesion and blended a bifunctional urethane acrylate. In No. 3, the curing itself was insufficient, and none of them was suitable for the present invention.