KR20200062130A - Uv curable coating composition - Google Patents

Abstract

The present invention relates to a UV curable paint composition, and to a molded product comprising a cured coating layer formed by using the same. The UV curable paint composition minimizes generation of volatile organic compounds (VOCs) by applying a high-solid type paint, thereby providing an eco-friendly UV curable paint composition.

Description

UV curable coating composition {UV CURABLE COATING COMPOSITION}

The present invention relates to a molded article comprising a UV curable coating composition and a cured coating layer formed using the same.

The coating composition used for hard coating of a plastic automobile molded article, for example, a headlamp PC lens (polycarbonate lens), requires excellent productivity, adhesion, water resistance, weatherability, and the like. In addition, in the case of automotive parts, it must be possible to paint by a method such as spraying (Air Spray) to ensure excellent appearance, workability and productivity. Since the coating composition for coating such as air spray or flow coating has a low solid content (NV) content and a relatively high solvent content, a volatile organic compound (Volatile) is used when painting in a place where environmental facilities are not provided. Organic Compounds (VOCs) are generated a lot, causing environmental pollution.

Volatile organic compounds refer to liquid or gaseous volatile organic compounds that evaporate easily into the atmosphere due to high vapor pressure. Volatile organic compounds cause photochemical reactions in the atmosphere, causing photochemical oxidizing substances such as ozone and causing photochemical smog, and are also carcinogens. Therefore, in recent years, the regulations on the content of volatile organic compounds have become stricter in developed countries such as Europe, and according to these regulations, it is necessary to operate a facility for removing volatile organic compounds, as well as the problem of continuous disposal and environmental costs. have.

Methods for reducing volatile organic compounds include water-based coatings using water as a solvent, powder coatings using no solvents, and techniques using high-solids coatings with increased solids. However, in the case of the conventional high solid type paint, it was difficult to secure workability and coating film properties (appearance, drying time, adhesion, etc.) while reducing the content of volatile organic compounds.

The present invention is a UV-curable coating composition, by applying a high solid type (high solid type) coating having a solids content of 70% or more, while improving the workability due to reducing the solvent content while securing the basic properties possessed by the conventional coating composition, , It provides an environmentally friendly UV curable coating composition with less generation of volatile organic compounds.

In addition, the present invention provides a molded article having a cured coating layer formed from the ultraviolet curable coating composition (for example, a lens for automobile headlamps).

The ultraviolet curable coating composition of the present invention includes a urethane (meth)acrylate oligomer, a (meth)acrylate monomer, a photoinitiator, an additive and a solvent, and the urethane (meth)acrylate oligomer is a first urethane (meth) having five or more functionalities And acrylate oligomers and second-functional urethane (meth)acrylate oligomers.

By applying the high-solid type coating according to the present invention, the content of volatile organic compounds is reduced to reduce environmental pollution, and at the same time, the workability can be improved by reducing the solvent content, and excellent dryability and adhesion due to high solid content It is possible to secure coating film properties such as resistance, heat resistance, moisture resistance, heat and cold resistance, and beautiful appearance characteristics.

In addition, the high-solid-type paint according to the present invention can meet not only the environmental regulations of domestic volatile organic compounds in the Ministry of Environment's Regulatory Standards Agreement, but also the strengthened foreign environmental regulations, and minimize the cost of using and managing conventional environmental facilities to increase productivity. And improving economic efficiency.

In addition, the high-solid type paint according to the present invention can be recycled (Recycle) of the paint to minimize the generation of paint waste, it is possible to improve productivity and economics.

Hereinafter, the present invention will be described in detail. However, the present invention is not limited only to the following contents, and each component may be variously modified or selectively mixed as necessary. Therefore, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

In the present specification, "(meth)acrylate" refers to acrylate and methacrylate.

In addition, in this specification, "monomer" and "monomer" have the same meaning. In the present specification, a monomer is a compound that is distinguished from oligomers and polymers and has a weight average molecular weight of 1,000 or less. As used herein, "polymerizable functional group" refers to an unsaturated group involved in the polymerization reaction, such as (meth)acrylate group.

<Ultraviolet (UV) curable coating composition>

The ultraviolet curable coating composition according to the present invention is a photocurable composition comprising a photocurable oligomer, a photocurable monomer, and a photoinitiator, and two polyfunctional urethane (meth)acrylate oligomers are used as the photocurable oligomer component. , (Meth)acrylate monomer is used as the photocurable monomer. If necessary, it may further include conventional additives such as ultraviolet absorbers, light stabilizers, leveling agents.

According to one embodiment of the present invention, the ultraviolet curable coating composition includes a urethane (meth)acrylate oligomer, (meth)acrylate monomer, photoinitiator, additive and solvent, and the urethane (meth)acrylate oligomer is 5-functional The first urethane (meth) acrylate oligomer and the second urethane (meth) acrylate oligomer of 4 or less are included.

Hereinafter, the composition of the ultraviolet (UV) curable coating composition will be described in detail.

Urethane (meth)acrylate oligomer

In the ultraviolet curable coating composition of the present invention, urethane (meth)acrylate oligomer is a main component that forms a coating film, and controls the crosslinking density of the entire coating film to express the strength, high temperature durability and adhesion of the hard coating film. Play a role.

In the present invention, as the urethane (meth)acrylate oligomer, a first urethane (meth)acrylate oligomer having 5 or more functionalities and a second urethane (meth)acrylate oligomer having 4 or lower functionalities are mixed. When two or more types of urethane (meth)acrylate oligomers are used, the solid content in the paint becomes high, and thus, excellent heat-resistance, weather resistance, and hardness can exhibit excellent coating film properties.

The first urethane (meth) acrylate oligomer may have 5 or more polymerizable functional groups (for example, 5 to 16), for example, 6 or more (for example 6 to 10), and 6 for other polymerizable unsaturated groups. have. The weight average molecular weight (Mw) of the first urethane (meth)acrylate oligomer may be 800 to 2,500 g/mol, for example, 1,000 to 2,000 g/mol. When the first urethane (meth)acrylate oligomer has the above-mentioned weight average molecular weight range, it is excellent in reactivity and excellent in physical properties such as heat resistance, weather resistance and hardness of a dry coating film.

The second urethane (meth)acrylate oligomer may have 4 or less polymerizable functional groups (eg 1 to 4), for example 3 or less (eg 2 to 3), and 3 as another example. The weight average molecular weight (Mw) of the second urethane (meth)acrylate oligomer may be 1,500 to 3,000 g/mol, for example, 1,700 to 2,300 g/mol. When the second urethane (meth)acrylate oligomer has the above-mentioned weight average molecular weight range, it is excellent in physical properties such as heat resistance, weather resistance and adhesion of the dry coating film.

According to one embodiment of the present invention, the mixing ratio of the first urethane (meth) acrylate oligomer having 5 or more functionalities and the second urethane (meth) acrylate oligomer having 4 or lower functionalities may be 1-3:1 weight ratio.

In the present invention, the content of the urethane (meth)acrylate oligomer is not particularly limited, and for example, may be 30 to 50% by weight based on the total weight of the UV curable coating composition. When the content of the urethane (meth)acrylate oligomer falls within the aforementioned range, excellent strength and heat resistance of the coating film are exhibited, and adhesion to the substrate is improved.

For example, in the present invention, when the first urethane (meth) acrylate oligomer and the second urethane (meth) acrylate oligomer are mixed, the first urethane (based on the total weight of the ultraviolet curable coating composition) The content of the meth)acrylate oligomer may be 20 to 30% by weight, and the content of the second urethane (meth)acrylate oligomer may be 10 to 20% by weight.

(Meth)acrylate monomer

In the ultraviolet curable coating composition of the present invention, the (meth)acrylate monomer serves as a crosslinking agent for controlling the crosslinking density between polymers, and serves to assist the cured properties such as hardness, adhesion, appearance characteristics, and workability of the coating film. .

In the present invention, as the (meth)acrylate monomer, a first (meth)acrylate monomer having a trifunctionality or more, a second (meth)acrylate monomer having a bifunctionality or less, or a mixture thereof may be used. By using two or more types of polyfunctional acrylate monomers having bifunctional or lower and trifunctional or higher functionalities, it is possible to control the workability, appearance characteristics, and curing degree of the paint.

The first (meth)acrylate monomer may have three or more polymerizable functional groups in the molecule (for example, 3 to 10), for example, 3 to 5. The molecular weight of the first (meth)acrylate monomer may be 100 to 300 g/mol, and the glass transition temperature (Tg) may be 40 to 80°C.

Non-limiting examples of usable first (meth)acrylate monomers include trimethylolpropane triacrylate (TMPTA), trimethylolpropane trimethacrylate (TMPTMA), trimethylolpropaneethoxy triacrylate (TMPEOTA), Pentaerythritol triacrylate (PETA), glyceryl propoxylated triacrylate (GPTA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA), dipentaerythritol hexaacrylate (DPHA) Or combinations thereof.

As the second (meth)acrylate monomer of the bifunctional or less, a known (meth)acrylate monomer containing two or less polymerizable functional groups in the molecule, such as two, can be used without limitation. The second (meth)acrylate monomer has a low viscosity and good dilution, and is suitable because it has a small polymerization shrinkage (low shrinkage) after curing.

The molecular weight of the second (meth)acrylate monomer may be 100 to 250 g/mol, and the glass transition temperature (Tg) may be 30 to 100°C.

Non-limiting examples of usable second (meth)acrylate monomers include 1,6-hexanediol diacrylate (HDDA), 1,6-hexanediol dimethacrylate (HDDMA), butanediol diacrylate (BDDA ), tripropylene glycol diacrylate (TPGDA), triethylene glycol diacrylate (TEGDA), neopentyl glycol diacrylate (NPGDA), polyethylene glycol 400 diacrylate (PEG400DA), polyethylene glycol 200 diacrylate (PEG200DA) ), dipropylene glycol diacrylate (DPGDA), tetraethylene glycol diacrylate (TTEGDA), tetraethylene glycol dimethacrylate (TTEGDMA), 9-ethylene glycol diacrylate (9-EGDA), triethylene glycol di Methacrylate (TEGDMA) and combinations thereof.

In the present invention, the aforementioned trifunctional or higher polyfunctional first (meth)acrylate monomer and bifunctional or lower second (meth)acrylate monomer can be mixed. At this time, the mixing ratio of the first (meth) acrylate monomer and the second (meth) acrylate monomer of bifunctional or less may be 1-2:1 weight ratio.

In the present invention, the content of the (meth)acrylate monomer is not particularly limited, and for example, may be 10 to 25% by weight based on the total weight of the ultraviolet curable coating composition. When the content of the (meth)acrylate monomer falls within the above-described range, high-temperature adhesion of the coating film is improved, excellent strength, heat resistance and appearance characteristics can be expressed, and adhesion with other substrates can be improved.

For example, in the present invention, when mixing the first (meth) acrylate monomer and the second (meth) acrylate monomer, the first (meth) acrylic based on the total weight of the UV curable coating composition The content of the rate monomer may be 5 to 13% by weight, and the content of the second (meth)acrylate monomer may be 5 to 12% by weight.

According to an embodiment of the present invention, the use ratio of the urethane (meth)acrylate oligomer and (meth)acrylate monomer may be 1-4:1 weight ratio, for example, 1-3:1 weight ratio. .

Photoinitiator

In the ultraviolet curable coating composition of the present invention, the photoinitiator is a component that is excited by ultraviolet rays (UV) or the like to initiate photopolymerization, and a conventional photopolymerization initiator in the art can be used without limitation.

Non-limiting examples of photoinitiators that can be used include Irgacure 184, Irgacure 369, Irgacure 651, Irgacure 819, Irgacure 907, Benzionalkylether, Benzophenone, Benzyl dimethyl katal, Hydro Hydroxycyclohexyl phenylacetone, chloroacetophenone, 1,1-dichloro acetophenone, diethoxy acetophenone, hydroxyacetophenone, hydroxyacetophenone , 2-Chloro thioxanthone, 2-ETAQ (2-EthylAnthraquinone), 1-hydroxy-cyclohexyl-phenyl-ketone (1-Hydroxy-cyclohexyl-phenyl-ketone), 2-hydroxy -2-methyl-1-phenyl-1-propanone (2-Hydroxy-2-methyl-1-phenyl-1-propanone), 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl ]-2-methyl-1-propanone (2-Hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone), methylbenzoylformate, and the like. These may be used alone or in combination of two or more.

According to one embodiment of the present invention, the photoinitiator may be used for a short wavelength initiator that absorbs ultraviolet rays having a wavelength of 230 to 340 nm, an initiator for long wavelengths that absorbs wavelengths exceeding 300 nm, or a combination of both.

In the present invention, the content of the photoinitiator may be 1 to 5% by weight based on the total weight of the UV curable coating composition. When the content of the photoinitiator falls within the above-described range, a photopolymerization reaction may be sufficiently performed without deteriorating physical properties of the coating film.

solvent

The ultraviolet curable coating composition of the present invention includes an organic solvent commonly used in the coating composition in the art. These solvents serve to dilute the above-mentioned coating composition to a predetermined viscosity so that coating is possible.

Non-limiting examples of the solvent that can be used include methoxy propanol, alcohols such as isopropyl alcohol, ketones such as acetone, acetates such as ethyl acetate, or aromatic compounds such as toluene, which can be used alone or in combination. have.

In the present invention, the content of the solvent may be a range of the residual amount that satisfies 100% by weight of the UV curable coating composition, for example, may be 20 to 40% by weight based on the total weight of the composition. When the content of the solvent is outside the above-mentioned range, workability and leveling may be deteriorated, and coating film formation is likely to be deteriorated.

additive

In addition to the above-mentioned components, the ultraviolet curable coating composition of the present invention can be used without limitation, additives known in the art within a range that does not impair the effects of the invention. By adding one or more UV absorbers, light stabilizers, and silicone leveling agents as additives, it is possible to improve the smoothness of the paint, the appearance properties of the coating film, weather resistance, and the like.

The ultraviolet curable coating composition of the present invention includes conventional ultraviolet absorbers known in the art. The UV absorber has weather resistance in both the long and short wavelength regions of the coating film (e.g., including the UV-A, UV-B and UV-C regions), particularly short wavelength regions of 300 nm or less (e.g., UV-B and UV-C regions) ) To improve the weather resistance.

In the present invention, the ultraviolet absorber may be a triazine-based ultraviolet absorber having two or more ultraviolet absorbers, for example, a hydroxy phenyl triazine derivative having two or more ultraviolet absorbing ester groups may be used alone or in combination of two or more. .

The molecular weight of the ultraviolet absorber may be 500 g/mol or more (eg, 500 to 2,000 g/mol). When the molecular weight of the ultraviolet absorber is less than 500 g/mol, volatility and extractability are large, and thus, when exposed to the outdoors, the ultraviolet absorber component is difficult to remain in the coating film, and accordingly, durability and weather resistance of the coating film may be deteriorated.

In the present invention, the content of the ultraviolet absorber may be 1 to 5% by weight based on the total weight of the ultraviolet curable coating composition. When the content of the ultraviolet absorber is out of the above-mentioned range, it is difficult to obtain an effect of improving the weather resistance of the coating film, and curing failure may be caused when curing the ultraviolet light.

Other additives that can be used include light stabilizers (e.g. HALS), antioxidants (e.g. phenolic antioxidants), wetting agents (e.g. polyether modified polydimethylsiloxane), leveling agents (e.g. silicone diacrylate based or silicone poly Acrylate-based compounds), lubricants, surface conditioners, surfactants, antifoaming agents (eg, dimethylpolysiloxane), slip agents, anti-staining agents, softeners, thickeners, polymers, and the like. These may be used alone or in combination of two or more. These additive components enhance the workability of the paint and the smoothness of the coating.

In the present invention, the content of the additive can be appropriately adjusted within a range known in the art. In one example, the amount of each of the additives is appropriate not to exceed 5% by weight relative to 100% by weight of the UV curable coating composition.

According to an embodiment of the present invention, the ultraviolet curable coating composition is based on 100% by weight of the composition, urethane (meth)acrylate oligomer 30-50% by weight, (meth)acrylate monomer 10-25% by weight, It contains 1-5% by weight of the photoinitiator, 2-10% by weight of the additive, and a residual amount of solvent satisfying 100% by weight of the composition.

According to another embodiment of the present invention, the ultraviolet curable coating composition, based on 100% by weight of the composition, based on 100% by weight of the first urethane (meth) acrylate oligomer 20-30% by weight, less than or equal to 4 10-20% by weight of the second urethane (meth)acrylate oligomer, 5-15% by weight of the first (meth)acrylate monomer of trifunctional or higher, 5-10% by weight of the second (meth)acrylate monomer of bifunctional or lower, 1-5% by weight of photoinitiator, 1-5% by weight of ultraviolet absorber (eg HPT), 0.5-3% by weight of light stabilizer (eg HALS), 0.5-3% by weight of wetting agent (eg polyether-modified polydimethylsiloxane), and 20-40% by weight of a solvent (eg 1-methoxy-2-propanol).

The ultraviolet curable coating composition of the present invention comprising the above-described components, may have a high solids content of 70% or more solid content.

There is no particular limitation on the method for producing the ultraviolet curable coating composition of the present invention, and for example, the two types of urethane (meth)acrylate oligomer, (meth)acrylate monomer, photoinitiator, solvent, and one or more additives are dissolved. , After putting in the mixing equipment such as a stirrer, it may be prepared according to a conventional method of mixing at an appropriate temperature (eg, room temperature).

The UV curable coating composition of the present invention can be applied to the components of automobile headlamps, such as a headlamp lens. However, it is not particularly limited and is applicable to various process steps and uses.

<Molded product>

The present invention provides a molded article comprising a cured coating layer formed from the aforementioned ultraviolet curable coating composition. The molded article may be a molded article for automobiles, for example, an automobile headlamp (PC lens).

According to one embodiment of the present invention, the automotive headlamp is formed on a plastic substrate and one or both surfaces of the plastic substrate, and includes a curing coating layer formed from the above-mentioned ultraviolet curable coating composition.

The plastic substrate may be used without limitation, a common substrate component used in the field of headlamps, for example, thermoplastic plastics, thermosetting plastics, and the like. Non-limiting examples of plastic substrates that can be used include polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), triacetylcellulose (TAC), polycarbonate (PC), polyimide ( PI), polyethylene (PE), polypropylene (PP), polyethersulfone (PES), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), or a combination of two or more thereof. When the plastic substrate of the above-described component is used, initial and high-temperature adhesion with the ultraviolet curable coating composition of the present invention is excellent.

The thickness of the cured coating layer made of the composition can be variously adjusted depending on the application, and for example, may be in the range of 5 to 25 μm, and in another example, 5 to 20 μm. When it has the above-mentioned thickness range, it is excellent in adhesion to the surface of the plastic substrate and it is possible to prevent poor appearance.

According to one embodiment of the present invention, the ultraviolet curable coating composition is applied and dried on a plastic substrate surface, and then cured by ultraviolet irradiation to form a cured coating layer.

As a method of applying the ultraviolet curable coating composition on a plastic substrate, a conventional coating method in the art, for example, spray coating, brushing, flow coating, dip coating, spin coating, or the like may be employed. The ultraviolet irradiation amount is not particularly limited, and may be, for example, 500 to 3,000 mJ/cm ² .

The plastic substrate on which the hardened coating layer is formed may be an automobile headlamp, for example, a lens of the headlamp on which the hardened coating layer is formed. Such a headlamp is excellent in adhesion to a plastic substrate (for example, a PC material), and is excellent in terms of overall physical properties of a coating film such as appearance, heat resistance, moisture resistance, and heat resistance.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are only to aid the understanding of the present invention, and the scope of the present invention is not limited to the examples in any sense.

[Example 1-12]

According to the composition shown in Table 1 below, 6-functional urethane acrylate oligomer (A), trifunctional urethane acrylate oligomer (B), bifunctional or trifunctional (meth)acrylate monomer (C), photoinitiator (D), ultraviolet light The ultraviolet curable coating composition of Example 1-12 was prepared using an absorbent (E), a light stabilizer (F), a silicone additive (G), a solvent (H), and the like. In Table 1, the unit of use of each composition is% by weight.

[Comparative Example 1-8]

According to the composition shown in Table 2 below, 6-functional urethane acrylate oligomer (A), trifunctional urethane acrylate oligomer (B), bifunctional or trifunctional (meth)acrylate monomer (C), photoinitiator (D), ultraviolet light An ultraviolet curable coating composition of Comparative Example 1-8 was prepared using an absorbent (E), a light stabilizer (F), a silicone additive (G), a solvent (H), and the like.

A-1: 6-functional urethane acrylate oligomer (Mw: 1,800, viscosity (25°C): 100,000 cps, specific gravity: 1.19, NV: 100, refractive index: 1.496)

A-2: 6-functional urethane acrylate oligomer (Mw: 1,000, viscosity (60°C): 2,000 cps, glass transition temperature: 69°C, density: 1.15 g/m ³ )

B: trifunctional urethane acrylate oligomer (Mw: 2,000, acid value: 1 mgKOH/g, density: 1.15 g/m ³ , NV: 100)

C-1: bifunctional (meth)acrylate monomer (1,6-hexanediol diacrylate)

C-2: Trifunctional (meth)acrylate monomer (Trimethylolpropane triacrylate, TMPTA)

D: Photoinitiator (1-Hydroxy-cyclohexyl-phenyl-ketone, trade name: Micure CP-4, Miwon Corporation)

E: UV absorber (Hydroxyphenyl Triazines, HPT)

F: light stabilizer (HALS, TINUVIN123, BASF)

G: Silicone additive (BYK-333, BYK)

H: Solvent (1-Methoxy-2-propanol)

[Experimental example. Evaluation of physical properties of UV curable coating composition for automobile headlamps]

The UV curable coating composition prepared in Examples 1-12 and Comparative Examples 1-8 was air-spray coated with a transparent polycarbonate specimen (PC) with a thickness of about 12 μm (top layer, based on dry coating thickness), and then the temperature was 80° C. After drying under conditions for about 300 seconds to remove the solvent, a specimen for physical property test was prepared by irradiating with energy of 3,500 mJ/cm 2 at a location of about 20 cm in air with a high pressure mercury lamp of 180 mW/cm 2.

The properties of the items shown in Table 3 were evaluated for the prepared specimens, and the results are shown in Tables 4 and 5 below.

Through the above-mentioned experimental results, the molded article having a cured coating layer formed from the ultraviolet curable coating composition according to the present invention is not only good in appearance, initial adhesion, heat resistance, moisture resistance and cold and heat resistance, but also is a high-solid type paint, making it volatile It was found that the content of organic compounds (VOC) was minimized to be environmentally friendly.

Claims (3)

As a UV curable coating composition comprising a urethane (meth) acrylate oligomer, (meth) acrylate monomer, photoinitiator, additives and solvents,
The urethane (meth) acrylate oligomer comprises a first urethane (meth) acrylate oligomer of 5 or more functionalities and a second urethane (meth) acrylate oligomer of 4 or less functionalities,
The use ratio of the first urethane (meth)acrylate oligomer and the second urethane (meth)acrylate oligomer is 1-3:1 by weight,
The first urethane (meth) acrylate oligomer has a weight average molecular weight of 800 to 2,500 g/mol, and the second urethane (meth) acrylate oligomer has a weight average molecular weight of 1,500 to 3,000 g/mol,
The (meth)acrylate monomer includes a first (meth)acrylate monomer having a trifunctionality or higher and a second (meth)acrylate monomer having a bifunctionality or lower,
The first (meth) acrylate monomer and the second (meth) acrylate monomer are mixed in a 1-2:1 weight ratio,
High solids UV curable coating composition having a solids content of 70% or more. According to claim 1, The urethane (meth) acrylate oligomer and the (meth) acrylate monomer is used in a ratio of 1-4: 1 weight ratio of the ultraviolet curable coating composition. A molded article comprising a cured coating layer formed from the ultraviolet curable coating composition according to claim 1.