JP2020152741A - Topcoat active energy ray-curable type coating composition - Google Patents

Abstract

To provide an active energy ray-curable type topcoat coating composition that has an excellent adhesion to the primer coating and is less likely to crack, and has a high pencil strength and a good wear resistance in taper wear test.SOLUTION: Provided is a topcoat active energy ray-curable type coating composition, containing (A) a (meth)acrylate having an isocyanurate skeleton, (B) a polyfunctional (meth)acrylate excluding (A), (C) a hydrophobic nano-silica, (D) a glass filler, and (E) a photopolymerization initiator, and in which, characterized, the average particle size of (D) is 5 to 18 μm.SELECTED DRAWING: None

Description

The present invention relates to a coating composition for a top coat that is cured by active energy rays such as ultraviolet rays.

Decorative materials used in the construction field are, for example, wood materials and ceramic materials, on which a decorative sheet is attached and a decorative layer is applied, and a finishing layer that generally also protects the decorative layer is applied on top of it. As 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. In addition to having a good finished appearance, the topcoat layer is required to have various properties such as abrasion resistance, high hardness, chemical resistance, stain resistance, and slip resistance, depending on the intended use. ..

As such a resin, for example, as a deodorant top coat, a resin composition containing an acrylate-based oligomer, an ultraviolet curable and curable monomer, a photoradical polymerization initiator, and a titanium oxide fine particle deodorant component has been proposed (Patent Document 1). ). Further, as a composition having excellent stain resistance and abrasion resistance, a resin composition containing a bifunctional urethane (meth) acrylate resin, a polysiloxane-modified urethane (meth) acrylate resin, and an epoxy (meth) acrylate resin has been proposed. (Patent Document 2). However, there is room for improvement in that the finished appearance is excellent, the pencil strength is high while maintaining high adhesion to the base paint, and the taber wear test also has high wear resistance.

Japanese Unexamined Patent Publication No. 2006-9780 Japanese Unexamined Patent Publication No. 2017-0527297

An object of the present invention is to provide an active energy ray-curable coating composition suitable for a top coat, which has excellent adhesion to a base coating material, is less likely to crack, has high pencil strength and good wear resistance. There is.

The invention of claim 1 is a (meth) acrylate (A) having an isocyanurate skeleton, a polyfunctional (meth) acrylate (B) excluding (A), a hydrophobic nanosilica (C), and a glass filler (D). To provide an active energy ray-curable coating composition for a top coat, which comprises a photopolymerization initiator (E) and an average particle size of (D) of 5 to 18 μm.

The invention of claim 2 provides the active energy ray-curable coating composition for a top coat according to claim 1, wherein the (A) contains a (meth) acrylate (a1) having a urethane bond.

The active energy ray curing for a top coat according to claim 2, wherein the invention of claim 3 is a reaction product of an isocyanurate compound obtained by quantifying hexamethylene diisocyanate and 2-hydroxypropyl acrylate. Provided is a mold coating composition.

The active energy ray-curable coating composition for a top coat according to any one of claims 1 to 3, wherein the invention of claim 4 further contains tris (acryloxyethyl) isocyanurate (a2). Provide things.

The invention of claim 5 provides the active energy ray-curable coating composition for a top coat according to any one of claims 1 to 4, wherein the (D) is surface-modified with (meth) acrylate. ..

The coating composition of the present invention has excellent adhesion to the base paint, is less likely to crack, has high pencil strength and good wear resistance, and is an active energy ray-curable top coat used as a decorative material for construction applications. It is useful as a paint.

The present invention will be described in detail.

The composition of the ultraviolet curable coating composition for a top coat of the present invention comprises a (meth) acrylate (A) having an isocyanurate skeleton, a polyfunctional (meth) acrylate (B), a hydrophobic nanosilica (C), and a glass filler. (D) and the photopolymerization initiator (E). In addition, in this specification, (meth) acrylate includes both acrylate and methacrylate.

The (meth) acrylate (A) having an isocyanurate skeleton used in the present invention is a monomer having a triazine trione ring having excellent thermal stability, and is a main component constituting a cured film. The triazine trione ring and the (meth) acryloyloxy group may contain a vinyl bond, an ether bond, an ester bond, a urethane bond, or the like, or may be bonded only with a saturated hydrocarbon. Among these, it is preferable to have a structure having a urethane bond in terms of increasing the toughness of the film strength and improving the pencil hardness, and having a structure linked with saturated hydrocarbons of C1 to 3 in terms of improving heat resistance. ..

Examples of the structure (a1) having a urethane bond in (A) include an addition reaction product obtained by reacting an isocyanurate form in which diisocyanate is trimerized with a (meth) acrylate having a hydroxyl group. In this case, the number of functional groups becomes trifunctional when a (meth) acrylate having one acryloyloxy group in one molecule is reacted, and one molecule has two acryloyloxy groups (). When the meta) acrylate is reacted, it becomes hexafunctional, but trifunctional is preferable from the viewpoint of the balance between reactivity and hardness.

The diisocyanate used in (a1) is tolylene diisocyanate or diphenylmethane isocyanate as a highly reactive aromatic system, and hexamethylene diisocyanate (hereinafter HDI) or isophorone diisocyanate (hereinafter referred to as HDI) as an aliphatic system having good weather resistance. IPDI) and the like, and can be used alone or in combination of two or more. Among these, an aliphatic system is preferable, and HDI, which has higher reactivity than IPDI, is more preferable. Further, as the (meth) acrylate having a hydroxyl group, 2-hydroxypropyl acrylate is preferable.

The method of reacting the isocyanurate compound with the (meth) acrylate having a hydroxyl group is a known method using a tin compound as a catalyst, and the addition reaction is allowed to proceed at a temperature of 50 to 120 ° C. over 2 to 10 hours. If necessary, for example, a ketone-based solvent or an ester-based solvent may be added. The reaction ratio between the isocyanate group and the hydroxyl group is preferably 0.7 to 1.1 in terms of molar ratio, and more preferably 0.95 to 1.05.

Further, the (A) preferably further contains a compound having a structure in which a triazine trione ring and a (meth) acryloyloxy group are linked with a saturated hydrocarbon, and in particular, a tris (acryloyl) linked with an alkyl group of C2. It preferably contains loxyethyl) isocyanurate (a2). By including (a2), the heat resistance of the cured film can be improved.

The blending amount of the composition (A) with respect to the total solid content is preferably 45 to 68% by weight, more preferably 50 to 63% by weight. When it is 45% by weight or more, sufficient coating film strength and heat resistance can be secured, and when it is 68% by weight or less, it is easy to adjust the viscosity to be suitable for workability. Further, the ratio of (a1) in the whole (A) is preferably 60 to 80% by weight, more preferably 65 to 75% by weight. Within this range, it is possible to secure sufficient pencil strength and form a film having good heat resistance.

The polyfunctional (meth) acrylate monomer (B) used in the present invention is a monomer having two or more (meth) acryloyloxy groups in one molecule, and is a monomer that improves the reactivity of the composition and at the same time is a reactive diluent monomer. Formulate as. For example, examples of the bifunctional (meth) acrylate monomer include (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, 1.6-hexanediol diacrylate (hereinafter referred to as HDDA), and dicyclopentanyl. Examples of the trifunctional or higher functional (meth) acrylate monomer such as diacrylate include trimethyl propantri (meth) acrylate, pentaerythritol triacrylate, dipentaerythritol tri (meth) acrylate, trimethylolpropanthry (meth) acrylate, and penta. Examples thereof include erythritol tetra (meth) acrylate, dipenta erythritol tetra (meth) acrylate, dipenta erythritol penta (meth) acrylate, and dipenta erythritol hexa (meth) acrylate, which can be used alone or in combination of two or more. .. Among these, a combination of a bifunctional (meth) acrylate monomer (hereinafter (b1)) that does not cause excessive curing shrinkage and a trifunctional or higher (meth) acrylate monomer (hereinafter (b2)) that increases the toughness of the cured film. It is preferable to mix them. In particular, tripropylene glycol diacrylate and HDDA are preferable for bifunctional (b1), and pentaerythritol triacrylate and pentaerythritol tetraacrylate are preferable for trifunctional or higher (b2).

The blending amount of the composition (B) with respect to the total solid content is preferably 15 to 40% by weight, more preferably 20 to 35% by weight. Sufficient curability can be ensured when the content is 15% by weight or more, and cracking of the coating film due to being too hard can be prevented from occurring when the content is 40% by weight or less. Further, the ratio of (b1) in the whole (B) is preferably 35 to 75% by weight, more preferably 40 to 70% by weight. Within this range, it is possible to adjust to a coating film having a high hardness in which cracks are unlikely to occur.

The nanosilica (C) used in the present invention is hydrophobic silica whose particle surface is methacrylate-treated, and is blended for the purpose of improving the pencil hardness of the cured film. If the surface is not treated, it becomes hydrophilic and the compatibility with other components decreases, which is not suitable. The average particle size is preferably 1 to 30 nm, more preferably 5 to 20 nm, and particularly preferably 10 to 15 nm as measured by the BET method. Within this range, it is possible to balance pencil hardness and good appearance.

The blending amount of the composition (C) with respect to the total solid content is preferably 2 to 12% by weight, preferably 3 to 10% by weight, and particularly preferably 3.5 to 8% by weight. When the content is 2% by weight or more, sufficient pencil hardness can be ensured, and when the content is 12% by weight or less, an increase in the viscosity of the paint is suppressed and the coating performance is improved. Examples of commercially available products include Optisol-ASAM3100 (trade name: manufactured by RANCO, average particle size of 10 to 15 nm, diluted with TMPTA 50%) and the like.

The glass filler (D) used in the present invention is blended for the purpose of improving the wear resistance of the cured film in the Taber wear test. A hydrophobic glass filler in which the particle surface is methacrylate-treated is preferable, and when the particle surface is not treated, the particles become hydrophilic and the compatibility with other components tends to decrease. The average particle size of (D) is 5 to 18 μm, preferably 8 to 15 μm, and even more preferably 10 to 13 μm. If it is less than 5 μm, the wear resistance in the Taber wear test may be insufficient, and if it exceeds 18 μm, the appearance of the coating film tends to be whitened. The average particle size of the glass filler can be measured by a laser diffraction method based on JISZ8825-1.

The blending amount of the composition (D) with respect to the total solid content is preferably 0.5 to 15% by weight, more preferably 1 to 10% by weight, and particularly preferably 2 to 8.5% by weight. When it is 0.5% by weight or more, sufficient wear resistance can be ensured, and when it is 15% by weight or less, a good coating film appearance can be ensured. Examples of commercially available products include CF0023-05C (trade name: manufactured by Nippon Frit Co., Ltd., average particle size 12 μm, methacrylate surface treatment).

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, and is benzylketal-based, acetophenone-based, or phos. A general-purpose photopolymerization initiator such as a fin oxide 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-diphenylethane-1-one as a benzyl ketal system, 1-hydroxy-cyclohexyl-phenyl-ketone and 1- [4- (2- (2- (2-)) as an α-hydroxyacetophenone system. Hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one is a 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1 as an α-aminoacetophenone system. -On includes 2.4.6-trimethylbenzoyl-diphenyl-phosphine oxide and bis (2.4.6-trimethylbenzoyl) -phenylphosphine oxide as acylphosphine oxide systems, alone or in combination of two or more. Can be used in combination. Among these, it is preferable to include an acylphosphine oxide system having excellent internal curability, and examples of commercially available products include Omnirad TPO (trade name: manufactured by IGM).

The ratio of the active energy ray-curable resin component (E) to 100 parts by weight is preferably 1 part to 10 parts by weight, more preferably 2 to 8 parts by weight. When the amount is 1 part by weight or more, sufficient curability is exhibited, and when the amount is 10 parts by weight or less, yellowing of the coating film and deterioration of storage stability can be prevented without excessive addition.

Further, the resin composition of the present invention contains a leveling agent, an ultraviolet absorber, an antioxidant, a colorant, an antifoaming agent, a thickener, a precipitation inhibitor, an antistatic agent, an antifogging agent, and a non-slip agent, if necessary. , Antibacterial agent, organic fine particles and the like may be added.

The leveling agent has the effect of uniforming the surface tension by spreading the leveling agent itself in the form of a thin film on the surface of the coating film against the non-uniformity of the surface tension that occurs on the surface of the coating film, and repairing defects before forming the coating film. There is. Examples thereof include silicone-based, fluorine-based, and acrylic-based, but silicone-based is preferable because it has a high ability to reduce surface tension. The ratio of the active energy ray-curable resin component to 100 parts by weight is preferably 1 part or less, and examples of commercially available products include BYK378 (trade name: manufactured by Big Chemie Japan Co., Ltd., polyether-modified polydimethylsiloxane).

The method for applying the resin 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 preferably 50 to 200 g / m ^2, but can be selected at any time depending on the application.

After applying the resin composition of the present invention, it is cured by using an electron beam, an active energy ray of an ultraviolet irradiator or the like. Examples of the light source for irradiating ultraviolet rays include a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, an LED lamp, and an electrodeless ultraviolet lamp. in the irradiation intensity of ^{50~1000mW / cm 2, 100~2,000mJ / cm} 2 is exemplified as a cumulative amount of light. 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 specific examples are shown and the present invention is not particularly limited thereto. Unless otherwise specified, the measurement was performed under the conditions of room temperature of 25 ° C. and relative humidity of 65%. The unit of the recipe is the part by weight.

Synthesis method of (a1) 100 g of Duranate TPA-100 (trade name: isocyanurate product of hexamethylene diisocyanate manufactured by Asahi Kasei Co., Ltd.) and 0.08 g of 2,6-ditershally butyl cresol as a polymerization inhibitor in a four-necked flask. , 0.006 g of dibutyltin dilaurate was charged as a urethanization catalyst, and the flask was rotated and stirred at 180 rpm while bubbling a 5% oxygen-nitrogen mixture at a temperature of 80 ° C., and 71.5 g of 2-hydroxypropyl acrylate was added to this flask over 2 hours. Dropped (isocyanate / hydroxyl group molar ratio 1.0). After the dropping, the mixture was further stirred at a temperature of 80 ° C. for 4 hours, and it was confirmed by the measurement of infrared absorption that the peak of 2260 cm- ¹ had disappeared from the sampled contents, and (a1) was adjusted.

Example : A reaction product (a1) of HDI isocyanurate and 2HPA synthesized above as the above (A) and GX8430 (trade name: manufactured by Daiichi Kogyo Seiyaku Co., Ltd., tris (acryloxyethyl) isocyanurate) as the above (a2). As the above (b1), MIRAMER M200 (trade name: MIWON, HDDA) and M220 (trade name: MIWON, tripropylene glycol diacrylate), and as the above (b2), MIRAMER M340 (trade name: MIWON). As the above (C), ASAM-3100 (trade name: RANCO, average particle size 10 to 15 nm, surface methacrylate surface treatment, TMPTA 50% dilution) was used as the above (manufactured by Pentaerythritol tri / tetraacrylate mixture). Leveling CF0023-05C (trade name: Nippon Frit Co., Ltd., average particle size 12 μm, with surface methacrylate surface treatment) as D) and Omnirad TPO (trade name: IGM Co., Ltd., acylphosphine oxide) as the above (E). BYK378 (trade name: manufactured by Big Chemie Japan Co., Ltd., polyether-modified polydimethylsiloxane) was stirred as an agent until uniformly dissolved and dispersed in the formulation shown in Table 1 to prepare the coating compositions of Examples 1 to 5.

Comparative Example In addition to the materials used in Examples, CF093-03 (trade name: manufactured by Nippon Frit Co., Ltd., average particle size 3.7 μm, with methacrylate surface treatment) and CF00903-10 (trade name:) as glass fillers. The coating compositions of Comparative Examples 1 to 4 were prepared by stirring a mixture (manufactured by Nippon Frit Co., Ltd., average particle size 19 μm, with methacrylate surface treatment) until uniformly dissolved and dispersed with the formulation shown in Table 1.

Table 1

The evaluation method was as follows.

Preparation of test piece A sealing layer is formed on a calcium silicate plate (trade name: Hishitaika Aica Tech Kenzai Co., Ltd.) with a thickness of 6 mm using a moisture-curable urethane paint VP9383470 (manufactured by KLEIBERIT), and inkjet printing is performed on the sealing layer. After performing cosmetic printing at 9 g / m ² using a machine, the paint composition is applied to a thickness of 100 g / m ² , and then Eye Grandage ECS4011GX / N (manufactured by Eye Graphics, high-pressure mercury lamp) is used as a light source. The test piece was cured under the conditions of irradiation intensity 100 mW / cm ² and integrated light intensity 800 mJ / cm ² exposure conditions.

Painted appearance: The appearance was visually confirmed, and the case where there was no abnormality was evaluated as ◯, and the case where there was an abnormality due to the top coat layer such as whitening was evaluated as x.

Adhesion: According to the old JIS K5400, a grid test of 100 1 mm square was performed, and the peeled state of the coating film was confirmed with cellophane tape (specified in JIS Z1522). 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 one cell was peeled off was evaluated as x.

Crack resistance: Two types of paint compositions, 140 g / m ² and 100 g / m ² , were prepared from the above test pieces, and after the paper gum tape was adhered, they were forcibly peeled off and the presence or absence of cracks was visually confirmed. .. Further, the 100 g / m ² test piece was further left in a constant temperature bath at 105 ° C. for 24 hours and then returned to room temperature, and the presence or absence of cracks was visually confirmed.

Pencil hardness: Using a pencil scratch coating film hardness tester (type P) manufactured by Toyo Seiki Seisakusho, evaluate with a load of 750 g according to JIS K 5600-5-4 (1999 version), and 4B or more is ○, 5B. The following was set as x.

Taber wear test: Taber testing machine rotary dresser RNo. Made by Toyo Seiki Seisakusho. Using 410, the area where the base material is exposed within the worn range is under the condition that the weight is 9.8 N (1 kg), the rotation speed is 60 rpm, and the polishing paper S-42 is wrapped around the wear wheel CS-0 according to JIS K 7204. The case where the rotation speed reached 50% was 350 times or more was evaluated as ◯, and the case where the number of rotations reached 50% was less than 350 times was evaluated as x.

Evaluation results

In the examples, there were no problems in all aspects of coating appearance, adhesion, crack resistance, pencil hardness, and Taber wear test, and the results were good. On the other hand, Comparative Example 1 without a glass filler has a low abrasion resistance, Comparative Example 2 without a nanosilica has a low pencil hardness, and Comparative Example 3 with a glass filler having a small particle system has a low abrasion resistance. In Comparative Example 4 in which a glass filler having a large particle system was used, the appearance was whitened to x, and none of them was suitable for the present invention.

The active energy ray-curable coating composition of the present invention has excellent adhesion to the base coating, is less likely to crack, has high pencil strength, and has good wear resistance. Therefore, it can be used as a top coating agent coating material for cosmetic materials. It is useful.

Claims (5)

A (meth) acrylate (A) having an isocyanurate skeleton, a polyfunctional (meth) acrylate (B) excluding (A), a hydrophobic nanosilica (C), a glass filler (D), and a photopolymerization initiator ( An active energy ray-curable coating composition for a top coat, which comprises E) and, wherein the average particle size of (D) is 5 to 18 μm. The active energy ray-curable coating composition for a top coat according to claim 1, wherein the (A) contains a (meth) acrylate (a1) having a urethane bond. The active energy ray-curable coating composition for a top coat according to claim 2, wherein the (a1) is a reaction product of an isocyanurate compound obtained by quantifying hexamethylene diisocyanate and 2-hydroxypropyl acrylate. The active energy ray-curable coating composition for a top coat according to any one of claims 1 to 3, wherein the (A) further contains a tris (acryloxyethyl) isocyanurate (a2). The active energy ray-curable coating composition for a top coat according to any one of claims 1 to 4, wherein the (D) is surface-modified with (meth) acrylate.