KR102234354B1 - Uv curable coating composition - Google Patents

Abstract

The present invention relates to a molded article including an ultraviolet curable paint composition and a cured coating layer formed using the same, and by applying a high solid type paint, the generation of volatile organic compounds (VOC) is minimized to provide an eco-friendly ultraviolet curable paint composition. I can.

Description

UV curable coating composition {UV CURABLE COATING COMPOSITION}

The present invention relates to a molded article including an ultraviolet curable coating composition and a cured coating layer formed by using the same.

The coating composition used for the hard coating of plastic automobile molded products, for example, automotive headlamp PC lenses (polycarbonate lenses), is required to have excellent productivity, adhesion, water resistance, and weather resistance. In addition, in the case of automobile parts, excellent appearance, workability, and productivity can be secured when coating is possible by a method such as air spray coating. Coating compositions for painting such as air spray or flow coating have a low solid content (NV) and a relatively high solvent content. There is a problem that causes environmental pollution because a lot of organic compounds, VOCs) are generated.

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, resulting in the generation of photochemical oxidizing substances such as ozone and photochemical smog, and are also carcinogens. Therefore, recently, regulations on the content of volatile organic compounds have become strict in advanced countries such as Europe, and according to these regulations, it is necessary to operate facilities that remove volatile organic compounds, as well as a problem that disposal costs and environmental costs are continuously incurred. have.

Methods for reducing volatile organic compounds include water-based paints that use water as a solvent, powder paints that do not use any solvents, and high-solid-state paints that increase the solid content of the paint. However, in the case of a conventional high solid type paint, it was difficult to reduce the content of volatile organic compounds and at the same time secure workability and coating properties (appearance, drying time, adhesion, etc.).

In the present invention, by applying a high solid type paint having a solid content of 70% or more as an ultraviolet curable paint composition, the basic physical properties of the conventional paint composition are secured, while improving workability due to a decrease in the solvent content. , Provides an environment-friendly UV curable coating composition with less generation of volatile organic compounds.

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

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 a 5-functional or higher function. It includes an acrylate oligomer and a second urethane (meth) acrylate oligomer of tetrafunctional or less.

By applying the high-solid-type paint according to the present invention, the content of volatile organic compounds is reduced to reduce environmental pollution, and at the same time, it is possible to improve workability due to a decrease in solvent content, and excellent drying properties and adhesion due to high solid content It is possible to secure coating properties such as property, heat resistance, moisture resistance, cold and heat resistance, and beautiful appearance characteristics.

In addition, the high-solid-type paint according to the present invention can meet all of the reinforced overseas environmental regulations as well as the environmental regulations of domestic volatile organic compounds in the regulatory standard agreement of the Ministry of Environment, and minimize the use and management costs of conventional environmental facilities to achieve productivity. And economic feasibility can be improved.

In addition, the high solid-type paint according to the present invention can minimize the generation of paint waste by enabling the recycling of the paint, thereby improving productivity and economy.

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

In this specification, "(meth)acrylate" represents an acrylate and a methacrylate.

In addition, in the present specification, "monomer" and "monomer" have the same meaning. In the present specification, a monomer is distinguished from an oligomer and a polymer, and refers to a compound having a weight average molecular weight of 1,000 or less. In the present specification, the "polymerizable functional group" refers to an unsaturated group involved in a polymerization reaction, such as a (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 uses two kinds of polyfunctional urethane (meth)acrylate oligomers as the photocurable oligomer component. , As a photocurable monomer, a (meth)acrylate monomer is used. If necessary, conventional additives, including an ultraviolet absorber, a light stabilizer, and a leveling agent, may be further included.

According to one embodiment of the present invention, the ultraviolet curable coating composition 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 5-functional The first urethane (meth)acrylate oligomer and the second urethane (meth)acrylate oligomer of tetrafunctional 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, the 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 a 5-functional or higher function and a second urethane (meth)acrylate oligomer having a tetrafunctional or lower function are mixedly used. In the case of using two or more types of urethane (meth)acrylate oligomers, which are ground with this, the solid content in the paint increases, so that excellent properties of the coating film can be exhibited in terms of heat resistance, weather resistance and hardness.

The first urethane (meth) acrylate oligomer may have 5 or more (eg 5 to 16), for example 6 or more (eg 6 to 10), 6 or more polymerizable functional groups, which are 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 aforementioned weight average molecular weight range, it has excellent reactivity and excellent physical properties such as heat resistance, weather resistance, and hardness of the dry coating film.

The second urethane (meth)acrylate oligomer may have 4 or less (eg 1 to 4) polymerizable functional groups, eg 3 or less (eg 2 to 3), and 3 other examples. 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-described weight average molecular weight range, physical properties such as heat resistance, weather resistance, and adhesion of the dry coating film are excellent.

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

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

For example, in the case of mixing the first urethane (meth) acrylate oligomer and the second urethane (meth) acrylate oligomer in the present invention, the first urethane ( 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 acts as a crosslinking agent to control the crosslinking density between polymers, and serves to assist curing 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 trifunctional or higher function, a second (meth)acrylate monomer having a bifunctional or lower function, or a mixture thereof may be used. By using two or more kinds of polyfunctional acrylate monomers of difunctional or less and trifunctional or more, the workability, appearance characteristics, and degree of curing of the paint can be controlled.

The first (meth)acrylate monomer may have 3 or more (eg, 3 to 10), eg, 3 to 5, polymerizable functional groups in the molecule. 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 the first (meth)acrylate monomers that can be used 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 having two or less functions, a known (meth)acrylate monomer including two or less, for example, two polymerizable functional groups in a molecule may be used without limitation. This second (meth)acrylate monomer has a low viscosity, good dilution power, and is suitable because it has a small low shrinkage after curing.

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

Non-limiting examples of the second (meth)acrylate monomers that can be used 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), combinations thereof, and the like.

In the present invention, the above-described trifunctional or higher polyfunctional first (meth)acrylate monomer and the difunctional or lower second (meth)acrylate monomer may be mixed. At this time, the mixing ratio of the first (meth) acrylate monomer and the second (meth) acrylate monomer having a difunctional or lower level may be 1-2:1 by weight.

In the present invention, the content of the (meth)acrylate monomer is not particularly limited, and as an example may be 10 to 25% by weight based on the total weight of the UV-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 may be expressed, and adhesion to other substrates may be improved.

For example, in the case of mixing the first (meth)acrylate monomer and the second (meth)acrylate monomer in the present invention, the first (meth)acrylic based on the total weight of the ultraviolet 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 ratio of the urethane (meth)acrylate oligomer and (meth)acrylate monomer to be used 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 serves to initiate photopolymerization by being excited by ultraviolet (UV) or the like, and a conventional photopolymerization initiator in the art may be used without limitation.

Non-limiting examples of photoinitiators that can be used include, but are not limited to, 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 , 2-Choro 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 two or more of them may be used in combination.

According to one embodiment of the present invention, the photoinitiator may be used as an initiator for short wavelengths absorbing ultraviolet rays having a wavelength of 230 to 340 nm, an initiator for long wavelengths absorbing 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, the photopolymerization reaction may be sufficiently performed without deteriorating the physical properties of the coating film.

solvent

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

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

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

additive

In addition to the above-described components, the UV-curable coating composition of the present invention may use, without limitation, additives known in the art to the extent that the effect of the present invention is not impaired. By mixing one or more types of an ultraviolet absorber, a light stabilizer, a silicone-based leveling agent, and the like as an additive, the smoothness of the paint, the appearance characteristics of the coating film, and weather resistance can be improved.

The ultraviolet curable coating composition of the present invention contains a conventional ultraviolet absorber 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 UV-A, UV-B and UV-C regions), especially in the short wavelength region of 300 nm or less (e.g., UV-B and UV-C regions). ) Is a component that is added to improve the weather resistance.

In the present invention, the ultraviolet absorber may be a triazine-based ultraviolet absorber having two or more ultraviolet absorbing groups, and for example, a hydroxyphenyl 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 UV absorber is less than 500 g/mol, the UV absorber component is difficult to remain in the coating film when exposed outdoors due to high volatility and extractability, and thus 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-described range, it is difficult to obtain an effect of improving the weather resistance of the coating film, and curing disorder may occur during ultraviolet curing.

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 or silicone poly Acrylate compounds), lubricants, surface modifiers, surfactants, antifoaming agents (eg, dimethylpolysiloxane), slip agents, stain inhibitors, softeners, thickeners, polymers, and the like. These may be used alone or two or more of them may be used in combination. These additive components enhance the workability of the paint and the smoothness of the coating film.

In the present invention, the content of the additive can be appropriately adjusted within a range known in the art. As an example, it is appropriate that the amount of each of the additives used does not exceed 5% by weight based on 100% by weight of the ultraviolet curable coating composition.

According to an embodiment of the present invention, the UV-curable coating composition is based on 100% by weight of the composition, 30-50% by weight of urethane (meth)acrylate oligomer, 10-25% by weight of (meth)acrylate monomer, It contains 1-5% by weight of a photoinitiator, 2-10% by weight of an additive, and a residual amount of a solvent that satisfies 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, 20-30% by weight of a first urethane (meth)acrylate oligomer having a 5-functional or higher function, 10-20% by weight of a second urethane (meth)acrylate oligomer, 5-15% by weight of a first (meth)acrylate monomer having a trifunctional or higher function, 5-10% by weight of a second (meth)acrylate monomer having a difunctional or lower level, 1-5% by weight of a photoinitiator, 1-5% by weight of an ultraviolet absorber (e.g., HPT), 0.5-3% by weight of a light stabilizer (e.g., HALS), 0.5-3% by weight of a wetting agent (e.g., polyether-modified polydimethylsiloxane), and It contains 20-40% by weight of a solvent (eg, 1-methoxy-2-propanol).

The ultraviolet curable coating composition of the present invention including the above-described components may be of a high solid type having a solid content of 70% or more.

There is no particular limitation on the method of preparing the ultraviolet curable coating composition of the present invention, for example, the two types of urethane (meth)acrylate oligomers, (meth)acrylate monomers, photoinitiators, solvents, and one or more additives are dissolved. , After being introduced into 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 ultraviolet curable coating composition of the present invention can be applied to a component of an automobile headlamp, for example, to paint a headlamp lens. However, it is not particularly limited thereto, and can be applied to various process steps and uses.

<Molded product>

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

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

The plastic substrate may use a conventional substrate component used in the field of headlamps without limitation, and examples thereof include thermoplastic plastics and thermosetting plastics. 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 using the plastic substrate of the above-described component, the initial and high temperature adhesion to 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 according to the use, for example 5 to 25 ㎛, other examples may be in the range of 5 to 20 ㎛. In the case of having the above-described thickness range, adhesion to the surface of the plastic substrate may be excellent and defects in appearance may be prevented.

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

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

The plastic substrate on which the cured coating layer is formed as described above may be an automobile headlamp, and for example, the cured coating layer may be a lens of a headlamp formed on the surface thereof. These headlamps are not only excellent in adhesion to plastic substrates (eg, PC materials), but are also excellent in the overall physical properties of the coating film, such as appearance, heat resistance, moisture resistance, and cold and heat resistance.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are only intended to aid 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 rays Using an absorbent (E), a light stabilizer (F), a silicone additive (G), a solvent (H), and the like, an ultraviolet curable coating composition of Examples 1-12 was prepared. In Table 1 below, 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 rays An absorbent (E), a light stabilizer (F), a silicone additive (G), a solvent (H), and the like were used to prepare an ultraviolet curable coating composition of Comparative Example 1-8.

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, brand 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 paint composition for automobile headlamps]

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

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

Through the above-described experimental results, the molded article having a cured coating layer formed from the ultraviolet curable coating composition according to the present invention not only has good appearance, initial adhesion, heat resistance, moisture resistance, and heat resistance, but also volatile because it is a high-solid coating material. It was found that it was eco-friendly by minimizing the content of organic compounds (VOC).

Claims (3)

As an ultraviolet curable coating composition comprising a urethane (meth) acrylate oligomer, (meth) acrylate monomer, a photoinitiator, an additive and a solvent,
The urethane (meth) acrylate oligomer includes a first urethane (meth) acrylate oligomer having a 5-functional or higher function and a second urethane (meth) acrylate oligomer having a 4-functional or lower function,
The use ratio of the first urethane (meth) acrylate oligomer and the second urethane (meth) acrylate oligomer is 1-3: 1 weight ratio,
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 trifunctional or higher first (meth)acrylate monomer and a difunctional or lower second (meth)acrylate monomer,
The first (meth) acrylate monomer and the second (meth) acrylate monomer are mixed in a 1-2:1 weight ratio,
Ultraviolet curable coating composition with a high solid content of 70% or more. The ultraviolet curable coating composition according to claim 1, wherein the urethane (meth)acrylate oligomer and the (meth)acrylate monomer are used in a ratio of 1-4:1 by weight. A molded article comprising a cured coating layer formed from the ultraviolet curable coating composition according to claim 1 or 2.