KR20120097817A - Uv-curable coating composition useful as top surface coating for plastic substrate and molded article comprisng a cured coating layer formed from the same - Google Patents

Abstract

PURPOSE: A UV-curable paint composition is provided to have excellent adhesion to polycarbonate material, heat resistance, abrasion resistance, hardness, chipping resistance, and weatherability. CONSTITUTION: A UV-curable paint composition comprises polyfunctional aliphatic urethane acrylate oligomer having six or more polymerizable functional groups, a Benzotriazole-modified aliphatic urethane acrylate oligomer, a polyfunctional acrylate monomer, a photopolymerization initiator, a UV-absorbing agent, and a photostabilizer. The polyfunctional aliphatic urethane acrylate oligomer is a reaction product of a bifunctional isocyanate compound, hydroxy acrylate monomer containing three or more polymerizable unsaturated groups per a molecule.

Description

UV-CURABLE COATING COMPOSITION USEFUL AS TOP SURFACE COATING FOR PLASTIC SUBSTRATE AND MOLDED ARTICLE COMPRISNG A CURED COATING LAYER FORMED FROM THE SAME}

The present invention relates to a molded article comprising an ultraviolet curable coating composition useful for surface coating of a plastic substrate and a cured coating layer formed therefrom, and more particularly, a multifunctional aliphatic urethane acrylate oligomer or a benzotriazole modified aliphatic urethane. It includes acrylate oligomers, polyfunctional acrylate monomers, photopolymerization initiators, ultraviolet absorbers and light stabilizers, and has excellent adhesion and heat resistance to plastic materials, in particular polycarbonate (PC) materials, and abrasion resistance, high hardness, chipping resistance and The present invention relates to a molded article comprising an ultraviolet curable coating composition having excellent weather resistance and useful for surface coating of a plastic material for glass replacement products, such as a PC lens of an automobile head lamp, in particular, a cured coating layer formed therefrom.

The conventional automotive headlamp market has used glass as the headlamp cover. However, in order to reduce the weight of the material for improving fuel efficiency of the automobile and to reduce the cost for reducing the production cost, all headlamp covers that are produced are made of plastic, especially polycarbonate, which has excellent transparency and formability.

However, polycarbonate materials generally applied to automotive headlamp lenses have excellent transparency and impact resistance, but are poor in scratch resistance, weather resistance and chemical resistance. In order to compensate for the scratch resistance and weather resistance, which are weak points of the polycarbonate material, a hard coat coating process for coating with a coating composition having excellent weather resistance and scratch resistance is required.

An example of using a polyfunctional urethane acrylate oligomer for improving scratch resistance is disclosed in Korean Patent Publication No. 10-0199908. However, in the case of this composition, the shrinkage stress between molecules in the coating film causes exposure to the outdoor environment for a long time, and if left unchecked, cracks and yellowing of the coating film occur severely, resulting in damage to the appearance of the coating film, deterioration in adhesion, and discoloration.

Korean Laid-Open Patent Publication No. 10-1999-0073009 discloses a coating composition using a urethane acrylate oligomer or an unreactive thermoplastic acrylic resin. However, in the case of this composition, the original purpose of the coating film is achieved due to a decrease in scratch resistance and heat resistance. There is a problem that can not.

In short, conventional UV curable coating compositions are not suitable for surface coating applications of plastic molded articles, especially automotive headlamp lenses, which are subject to prolonged exposure to UV, heat and scratch causing materials under harsh outdoor environmental conditions.

The present invention has been made to solve the above problems of the prior art, it is coated on the surface of the molded article can prevent the deterioration of the molded article itself even when used in outdoor environment for a long time and at the same time scratch resistance, high hardness, adhesion of the coating film, Molded article (e.g. automobile headlamps) comprising a UV-curable coating composition and a cured coating layer formed thereon, which are particularly effective for the surface coating of a transparent material such as a transparent plastic lens, particularly an automotive headlamp lens due to excellent crack resistance and excellent chipping resistance. It is a technical subject to provide the PC lens for a camera.

The present invention to solve the above technical problem, (A) a polyfunctional aliphatic urethane acrylate oligomer having six or more polymerizable functional groups, (B) benzotriazole modified aliphatic urethane acrylate oligomer, (C) polyfunctional acrylate Provided are an ultraviolet curable coating composition comprising a monomer, (D) a photopolymerization initiator, (E) an ultraviolet absorber, and (F) an optical stabilizer.

According to another aspect of the present invention, there is provided a molded article comprising a cured coating layer formed from the above-described ultraviolet curable coating composition of the present invention.

The UV curable coating composition according to the present invention has excellent adhesion and heat resistance to plastic materials, especially polycarbonate (PC) materials, and has excellent abrasion resistance, high hardness, chipping resistance and weather resistance, and the durability of the coating film even under severe outdoor long-term use conditions. It is very useful for surface coating of transparent plastic lens, especially transparent material such as PC lens of automobile headlamp.

Hereinafter, the present invention will be described in detail.

(A) Multifunctional  Aliphatic Urethane Acrylate Oligomer

The polyfunctional aliphatic urethane acrylate oligomer included in the ultraviolet curable coating composition of the present invention has 6 or more (eg 6 to 15) polymerizable functional groups which are unsaturated groups capable of polymerization, and is used for scratch resistance and hardness of the coating film. It is an ingredient. Oligomer (A) When the number of polymerizable functional groups in one molecule is less than 6, the hardness of the coating film becomes weak and it is difficult to obtain a coating film with pencil hardness of 2H or more, and it cannot pass the steel wool scratch resistance test, and the crack of the coating film after the chipping resistance test There is a problem that can occur.

As said polyfunctional aliphatic urethane acrylate oligomer (A), Unsaturation which can superpose | polymerize with the compound of bifunctional aliphatic isocyanate (for example, hexamethylene diisocyanate, dicyclohexyl methane diisocyanate, isophorone diisocyanate etc.) is possible, for example. Reaction products with hydroxy acrylate monomers (eg, pentaerythritol triacrylate, dipentaerythritol triacrylate, etc.) containing three or more groups per molecule can be used. As a weight average molecular weight of component (A), 1000-2000 are preferable. Specific examples of component (A) include PU610 of Miwon Corp., Ebecryl 1290 of SK-Cytec, U400 of Bayer, DM 87A of Double Bond Chemical, and the like.

In the ultraviolet curable coating composition of the present invention, the component (A) is preferably 30 to 60% by weight, more preferably 45 to 55% by weight based on the total composition of the composition excluding the organic solvent. When the content of component (A) in the composition is less than 30% by weight based on the total composition of the composition excluding the organic solvent, it is difficult to form a cured coating film, and the curability and scratch resistance are poor. This may cause cracks in the coating film.

(B) Benzotriazole  Modified aliphatic urethane Acrylate Oligomer

The benzotriazole-modified aliphatic urethane acrylate oligomer included in the ultraviolet curable coating composition of the present invention is produced by the reaction between a benzotriazole having a hydroxy group, an isocyanate and an acrylate compound, and the weather resistance and oxidation resistance of the coating film. It is an ingredient used for. In consideration of the weather resistance and oxidation resistance of the coating film, the weight average molecular weight of the component (B) is preferably 800 to 1500.

Examples of the benzotriazole-modified aliphatic urethane acrylate oligomer (B) include polymerization of a bifunctional aliphatic isocyanate compound (for example, hexamethylene diisocyanate, dicyclohexyl methane diisocyanate, isophorone diisocyanate, etc.). Hydroxy acrylate monomers containing up to 2 possible unsaturated groups per molecule (e.g., hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxybutyl acrylate, hydroxypentyl What was obtained by making the aliphatic urethane acrylate oligomer which is reaction product with acrylate, hydroxybutyl methacrylate, etc.) react with the benzotriazole modified acrylate which has a hydroxyl group can be used. Specific examples of the benzotriazole-modified acrylates usable in the present invention include RUVA-93 by Otsuka.

In the case of the benzotriazole-modified acrylate in the synthetic raw material of component (B), a weight average molecular weight in the range of 300 to 500 may be preferably used in consideration of weather resistance, oxidation resistance, in particular, compatibility and transparency. When benzotriazole-modified acrylate outside of this molecular weight range is applied, transparency and compatibility may be lowered and discoloration of the coating composition may be caused.

In the ultraviolet curable coating composition of the present invention, the component (B) is preferably 3 to 20% by weight, more preferably 5 to 15% by weight based on the total composition of the composition excluding the organic solvent. If the content of component (B) in the composition is less than 3% by weight based on the total composition of the composition excluding the organic solvent, the weather resistance and oxidation resistance of the coating film tend to be lowered. Discoloration of the coating film may be caused by curing and the characteristics of the resin itself.

(C) Acrylate Monomer

The acrylate monomer included in the UV curable coating composition of the present invention is an acrylate monomer containing 2 to 4 polymerizable unsaturated groups per molecule, for the scratch resistance, hardness and adhesion of the coating film, and It is a component used for reacting and assisting hardened | cured material property.

Examples of the polyfunctional acrylate monomer (C) include butanediol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol diacrylate, and triethylene glycol diacrylate. Acrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, glyceryl propoxy triacrylate, and the like. Can be used in combination.

In the ultraviolet curable coating composition of the present invention, the component (C) is preferably 5 to 40% by weight, more preferably 25 to 35% by weight based on the total composition of the composition excluding the organic solvent. If the content of component (C) in the composition is less than 5% by weight based on the total composition of the composition excluding the organic solvent, the viscosity of the paint increases and the adhesion to the substrate decreases. Degradation and UV curing can cause long-term clouding of the coating depending on the presence of unreacted materials.

( D) photopolymerization Initiator

The photoinitiator contained in the ultraviolet curable coating composition of the present invention is used to cure the coating film forming component, for example, 2-hydroxy-2-methyl-1-phenylpropane-1-phenone, 1-hydroxycyclohexylphenyl Ketone, benzophenone, 1- (4-isopropylphenyl) 2-hydroxy 2-methyl 1-one, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl propane 1-one, α, α-diethoxyacetophenone, 2,2-diethoxy 1-phenyl ethanone, bis (2,4,6-trimethyl benzoyl) -phenylphosphine oxide or the like alone or in combination It can be used in combination.

In the ultraviolet curable coating composition of the present invention, the component (D) is preferably 1 to 10% by weight, more preferably 1 to 5% by weight, based on the total composition of the composition excluding the organic solvent. If the content of component (D) in the composition is less than 1% by weight, based on the total composition of the composition excluding the organic solvent, it may result in a lowering of the hardenability and a lowering of scratch resistance and adhesion due to uncuring. It may cause contamination by unreacted photopolymerization initiator, deterioration of adhesion due to low degree of polymerization, and yellowing.

(E) UV absorbers

The ultraviolet absorber included in the ultraviolet curable coating composition of the present invention is used to improve the weather resistance of the cured coating film and the durability of the plastic material. Preferred ultraviolet absorbers include triazine-based compounds, and specific examples include, but are not limited to, 6- [bis (2,4-dimethylphenyl) -1,3,5-triazine, 6- [bis (2,4-dimethylphenyl) -1,3,5 triazine, tris [2,4,6- [2- {4- (octyl-2-methylethanoate) oxy-2hydroxyphenyl}]- 1,3,5 triazine etc. can be used individually or in combination of 2 or more types.

In the ultraviolet curable coating composition of the present invention, the component (E) is preferably 0.5 to 10% by weight, more preferably 0.75 to 8% by weight based on the total composition of the composition excluding the organic solvent. If the content of the component (E) in the composition is less than 0.5 wt% based on the total composition of the composition excluding the organic solvent, the weather resistance may decrease, which may cause deterioration, yellowing, and cracking of the coating film in a long-term outdoor environment. Exceeding the% decreases the photocuring reaction, so that uncuring and water resistance are weak, which may cause cloudiness.

(F) Light stabilizer

The light stabilizer (or antioxidant) contained in the ultraviolet curable coating composition of the present invention is used to improve the weather resistance of the cured coating film and the durability of the plastic material. Preferred light stabilizers include hindered amine light stabilizers (HALS), specifically, but not limited to, bis (1-methoxy-2,2,6,6-tetra Methyl-4-piperidyl) sebacate etc. are mentioned. These light stabilizer compounds may be used alone or in combination of two or more thereof.

In the ultraviolet curable coating composition of the present invention, the component (F) is preferably 0.1 to 5% by weight, more preferably 0.2 to 2.5% by weight based on the total composition of the composition excluding the organic solvent. If the content of the component (F) in the composition is less than 0.1% by weight based on the total composition of the composition excluding the organic solvent, the weather resistance may deteriorate, which may cause deterioration, yellowing, and cracking of the coating film in a long-term outdoor environment. Exceeding the% decreases the photocuring reaction, so that uncuring and water resistance are weak, which may cause cloudiness.

The amount of the ultraviolet absorber: light stabilizer used is preferably 2: 1 to 4: 1 by weight.

In addition to the above components, the ultraviolet curable coating composition of the present invention may further include a solvent, a wetting agent, a leveling agent, an antifoaming agent, and the like, which are conventionally added to the coating composition. These additional ingredients enhance the workability of the paint and the smoothness of the coating.

Examples of the solvent usable in the present invention include conventional solvents alone or mixtures such as ketones such as acetone, acetates such as ethyl acetate, and aromatic compounds such as toluene. In the case of using the solvent, if the content is less than 30% by weight based on 100% by weight of the coating composition, workability and leveling may be reduced, and when the content exceeds 80% by weight, coating film formation is likely to be lowered. The wetting agents usable in the present invention include polyether-modified polydimethylsiloxanes, antifoaming agents, dimethylpolysiloxanes, and leveling agents include silicone diacrylate-based and silicone polyacrylate-based compounds. It is preferable not to exceed 1% by weight relative to 100% by weight.

There is no particular limitation on the method for producing the UV curable coating composition of the present invention. After entering the equipment, it can be prepared according to conventional methods of mixing at a suitable temperature (eg room temperature).

According to another aspect of the present invention, there is provided a molded article comprising a cured coating layer formed from the ultraviolet curable coating composition of the present invention as described above.

As a material of the molded article to which the ultraviolet curable coating composition of this invention is applicable, plastic (for example, polycarbonate (PC)) is preferable. According to a preferred embodiment of the present invention, the ultraviolet curable coating composition of the present invention is coated on the surface of the molded article of such a material, and the solvent is dried, and then cured by ultraviolet irradiation to form a hard coat layer for protecting the molded article surface. The ultraviolet curable coating composition of the present invention is preferably applied to automobile molded articles, more preferably to PC lenses for automotive headlamps.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, these examples are only to aid the understanding of the present invention, and the present invention is not limited thereto.

[ Example ]

(1) Preparation of UV Curable Coating Composition

Example  And Comparative example

To the UV curable coating composition was prepared in the composition as shown in Table 1, respectively.

Table 1

(2) Evaluation of Properties of UV Curable Coating Composition

UV curable coating compositions prepared in the above Examples and Comparative Examples were air spray coated on a transparent polycarbonate specimen (trade name: 3022 L3, Samyang Co., Ltd.) at a thickness of about 10 microns (Top layer, based on dry film thickness), and 80 ° C. After drying the solvent by hot air drying for about 300 seconds at a temperature condition of 300 mW / ㎠ and irradiated with energy of 3500mj / ㎠ at a position of about 20cm in the air with a high-pressure mercury lamp of 300mW / ㎠ to evaluate the following items for the hard coating specimen It carried out, and the results are shown in Table 2 below.

1) Adhesion test: evaluation by cross cut tape test according to ASTM D3359

2) Pencil Hardness: According to ISO 15184 and JIS K 5600-5-4, not less than HB.

3) Scratch resistance test: Check the coating damage after rubbing 10 times with 500g force using Steelwool 0000 grade.

4) Moisture resistance test: After leaving for 240 hours at 50 ± 2 ℃, 98 ± 2% of the test temperature, and then removed for 1 hour, significant discoloration, discoloration, swelling, cracking, gloss reduction in the coating Evaluate whether there is no back and no abnormality in adhesion.

5) Water resistance test: The specimen was immersed in tap water (TAP WATER, test temperature 40 ℃) for 240 hours, then removed, and the surface moisture was removed by AIR BLOW. After 1 hour at room temperature, remarkable discoloration, fading, Evaluate whether there is no swelling, cracking, gloss decrease, etc., and whether the adhesion is abnormal.

6) Heat resistance test: After leaving for 300 hours at the test temperature (80 ± 2 ℃) condition, taken out and left for 1 hour at room temperature, there is no noticeable discoloration, discoloration, swelling, cracking, gloss reduction, etc. Evaluate if there is.

7) Chemical resistance test: After using glass cleaner and engine oil separately, reciprocating 20 times with 3 N force, rubbing the surface of the coating film to visually inspect the appearance, and leaving it at room temperature for 24 hours to observe significant discoloration and fading of the coating film. Evaluate whether there is no swelling, cracking, glossiness deterioration, or any abnormality in adhesion.

8) Cold-resistant cycle test: test specimen (3 h at 80 ± 2 ℃ → 1 h at room temperature → 3 h at room temperature → 1 h at room temperature → 7 ~ 15 h at 50 ± 2 ℃, 95% RH) * 5 times After standing at room temperature for 1 hour, it was evaluated whether there was no noticeable discoloration, discoloration, swelling, cracking, gloss reduction, etc. of the coating film, and no abnormality in adhesion.

9) Accelerated weathering test: Five test specimens were simultaneously examined under the conditions of the following xenon arc furnace as defined in SAE J 2527, and the discoloration of the coating film (color difference (ΔE *): 3.0 or less), fading, swelling, cracking, gloss Evaluate whether there is no degradation or the like and that there is no abnormality in adhesion.

Xenon arc furnace setting conditions

: 4000KJ / ㎡ [340nm], BLACK PNL Temperature-(LIGHT) 38 ± 2 ℃ (DARK) 40 minutes irradiation (50 ± 5% RH), cycle-60 minutes irradiation (50 ± 5% RH) 60 minutes unirradiated ( 95 ± 5% RH, Table / Rear SPRAY), Irradiance-0.55 ± 0.02W / (㎡ · nm) [340nm]

10) Chipping resistance test: After the test piece is subjected to chipping resistance test under the following conditions by a test stone machine (GRAVELO METER: SAE J 400 standard product), there is no significant cracking, scratches, etc. evaluation.

of mine Chipping Sex test conditions

1) Shooting Distance: 150mm; 2) Shooting Angle: 45 ° 3) Shooting Pressure: 3.0 Kgf / cm2; 4) Test Temperature: -40 ° C; 5) Headstone: 50g (JIS Crushed gravel No 7 stone, 2.5 ~ 5mm, 350 ~ 400 pieces)

[Table 2]

Claims (9)

(A) a polyfunctional aliphatic urethane acrylate oligomer having six or more polymerizable functional groups, (B) benzotriazole-modified aliphatic urethane acrylate oligomer, (C) polyfunctional acrylate monomer, (D) photopolymerization initiator, (E) An ultraviolet curable coating composition comprising a ultraviolet absorber and (F) light stabilizer. The polyfunctional aliphatic urethane acrylate oligomer (A) is a reaction product according to claim 1, wherein the polyfunctional aliphatic urethane acrylate oligomer (A) is a reaction product with a compound of a bifunctional aliphatic isocyanate and a hydroxy acrylate monomer containing 3 or more unsaturated groups per molecule. UV curable coating composition. The reaction product according to claim 1, wherein the benzotriazole-modified aliphatic urethane acrylate oligomer (B) is a reaction product with a compound of bifunctional aliphatic isocyanate and a hydroxy acrylate monomer containing not more than two unsaturated groups per molecule. An ultraviolet curable coating composition obtained by reacting a phosphorus aliphatic urethane acrylate oligomer with a benzotriazole-modified acrylate. The polyfunctional acrylate monomer (C) according to claim 1, wherein the polyfunctional acrylate monomer (C) is butanediol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol diacrylate, tetraglycol. Diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate, trimethylolpropane methacrylate, propoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane trimethacrylate, trimethylolpropane It is trimethacrylate, pentaerythritol triacrylate, glyceryl propoxy triacrylate, tris isocyanurate triacrylate, or a mixture thereof, The ultraviolet curable coating composition characterized by the above-mentioned. The ultraviolet curable coating composition according to claim 1, wherein the ultraviolet absorbent (E) is a triazine-based compound. The ultraviolet curable coating composition according to claim 1, wherein the light stabilizer (F) is a hindered amine light stabilizer. A molded article comprising a cured coating layer formed from the ultraviolet curable coating composition according to any one of claims 1 to 6. 8. The molded article of claim 7, wherein the molded article is made of polycarbonate. The molded article according to claim 8, which is a polycarbonate lens for an automobile headlamp.