KR20200054670A - Hard Coating Composition - Google Patents

Abstract

The present invention relates to a solvent-free hard coating composition with excellent weather resistance and workability, and to a molded product comprising a coating layer formed by applying the same. The hard coating composition comprises: a urethane (meth)acrylate oligomer; a (meth)acrylate monomer; and a photo-initiator.

Description

Hard coating composition {Hard Coating Composition}

The present invention relates to a molded article comprising a hard coating composition excellent in weather resistance and workability and a coating layer formed by applying the same.

The coating composition used for hard coating of automobile parts such as automobile molded products, for example, a headlamp PC lens (polycarbonate lens), requires excellent productivity, adhesion, water resistance, weather resistance, 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, volatile organic compounds (Volatile) are used when painting in places 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. Accordingly, in recent years, 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.

As a method for reducing volatile organic compounds, technologies using water-based coatings using water as a solvent, powder coatings not using solvents at all, and high-solids coatings that increase the solids content of coatings have been continuously developed. For example, Japanese Patent Application Publication JP 2006-036985 A discloses a two-liquid, room temperature curable organo polysiloxane-based coating composition capable of solvent-free and high-solidification. However, such a conventional coating composition overcomes problems such as appearance characteristics and workability, which are disadvantages of a solvent-free coating, and does not secure sufficient properties to apply a warm spray method for securing an excellent appearance.

The present invention provides a solvent-free hard coating composition excellent in weather resistance and workability without using a volatile organic compound.

In addition, the present invention provides a molded article (for example, a car headlamp lens) comprising a coating layer formed by applying the solvent-free hard coating composition.

The present invention includes a urethane (meth) acrylate oligomer, a (meth) acrylate monomer, and a photoinitiator, wherein the urethane (meth) acrylate oligomer is a 6 or more functional urethane (meth) acrylate oligomer, trifunctional urethane (meth) Provided is a hard coating composition comprising an acrylate oligomer and a bifunctional urethane (meth) acrylate oligomer.

The present invention provides a hard coating composition excellent in weather resistance and workability while reducing environmental pollution by not containing volatile organic compounds. In addition, the hard coating composition according to the present invention can be recycled paint to minimize the generation of paint waste, it is possible to improve productivity and economics. In addition, the present invention is a warm spray (Warm Spray) method is applicable, it provides a hard coating composition capable of ensuring excellent appearance of the coating film.

The lens for a car headlamp including a high weatherability coating layer to which the solvent-free hard coating composition according to the present invention is applied has excellent appearance quality and night driving stability.

The molecular weight and the weight average molecular weight of the resin used in the present invention are measured by a conventional method known in the art, and can be measured by, for example, a gel permeation chromatograph (GPC) method. In addition, the glass transition temperature of the oligomer and the monomer is measured by a conventional method known in the art, for example, it can be measured by differential scanning calorimetry (differential scanning calorimetry, DSC).

Hereinafter, the present invention will be described. However, it is not limited only by 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.

<Hard coating composition>

The hard coating composition according to the present invention comprises a urethane (meth) acrylate oligomer, a (meth) acrylate monomer, and a photoinitiator, and the urethane (meth) acrylate oligomer is a urethane (meth) acrylate oligomer of trifunctional or higher, trifunctional Sex urethane (meth) acrylate oligomers and bifunctional urethane (meth) acrylate oligomers. If necessary, UV absorbers, light stabilizers, and silicone additives may be further included. Hereinafter, the composition of the hard coating composition of the present invention will be described in detail.

Urethane (meth) acrylate oligomer

The hard coating composition according to the present invention contains a urethane (meth) acrylate oligomer as a main component forming a coating film. The urethane (meth) acrylate oligomer controls the crosslinking density of the entire coating film, and serves to express the strength, high temperature durability and adhesion of the hard coating film.

The urethane (meth) acrylate oligomer of the present invention includes a six- or more-functional urethane (meth) acrylate oligomer, a trifunctional urethane (meth) acrylate oligomer, and a bifunctional urethane (meth) acrylate oligomer. When three types of oligomers are used in combination as above, the solid content in the coating becomes high, and thus it is possible to exhibit excellent film properties in terms of heat resistance, weather resistance and hardness.

The urethane (meth) acrylate oligomer having 6 or more functionalities may have 6 or more polymerizable functional groups, which are polymerizable unsaturated groups, for example 6 to 16, 6 to 10 other examples, and 6 to 6 other examples. The weight average molecular weight (Mw) of the urethane (meth) acrylate oligomer of 6 or more functionalities may be 1,000 to 3,700 g / mol, for example, 1,500 to 2,000 g / mol. When the urethane (meth) acrylate oligomer having 6 or more functionalities has the above-mentioned weight average molecular weight range, it has excellent reactivity and excellent physical properties such as heat resistance, weather resistance and hardness of the dry film.

The trifunctional urethane (meth) acrylate oligomer refers to one containing three polymerizable functional groups. The weight average molecular weight (Mw) of the trifunctional urethane (meth) acrylate oligomer may be 1,000 to 3,500 g / mol, for example, 1,500 to 2,500 g / mol. When the trifunctional urethane (meth) acrylate oligomer has the above-mentioned weight average molecular weight range, physical properties such as heat resistance, weather resistance and adhesion of the dry coating film are excellent.

The bifunctional urethane (meth) acrylate oligomer refers to one containing two polymerizable functional groups. By adjusting the content of the bifunctional urethane (meth) acrylate oligomer, it is possible to adjust the curing density of the coating layer, through which it is possible to secure excellent physical properties of the dry film. The bifunctional urethane (meth) acrylate oligomer can form a viscosity of the hard coating composition at an appropriate level to realize excellent processability, and improve the scratch resistance by controlling the curing density of the coating layer. The weight average molecular weight (Mw) of the bifunctional urethane (meth) acrylate oligomer may be 100 to 800 g / mol, for example, 100 to 500 g / mol. When the bifunctional urethane (meth) acrylate oligomer has the above-mentioned weight average molecular weight range, physical properties such as heat resistance, weather resistance and hardness of the dry coating film are excellent.

As an example, the mixing ratio of the above-mentioned six-functional urethane (meth) acrylate oligomer, trifunctional urethane (meth) acrylate oligomer and bifunctional urethane (meth) acrylate oligomer is from 1: 0.05 to 0.5: 0.05 to 0.5. It may be a weight ratio.

According to an embodiment of the present invention, the urethane (meth) acrylate oligomer is 20 to 40% by weight of a urethane (meth) acrylate oligomer of 6 or more functional groups based on the total weight of the hard coating composition. Trifunctional urethane (meth) acrylate oligomer 1 to 10% by weight and bifunctional urethane (meth) acrylate oligomer 1 to 10% by weight may be included. When the urethane (meth) acrylate oligomer is mixed at the above-mentioned compounding ratio, excellent strength and heat resistance of the coating film are exhibited, and adhesion to the substrate can be improved.

(Meth) acrylate monomer

The hard coating composition according to the present invention includes at least one of trifunctional or higher (meth) acrylate monomers and bifunctional or lower (meth) acrylate monomers. The (meth) acrylate monomer serves as a crosslinking agent for controlling the crosslinking density between polymers, and serves to assist in curing properties such as hardness, adhesion, appearance characteristics, and workability of the coating film.

The trifunctional or higher (meth) acrylate monomer may have three or more polymerizable functional groups (for example, 3 to 10), for example, 3 to 5. The molecular weight of the trifunctional or higher (meth) acrylate monomer may be 200 to 400 g / mol, and the glass transition temperature (Tg) may be 40 to 80 ° C.

Non-limiting examples of the trifunctional or higher (meth) acrylate monomer, 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 mixtures of these can be used.

The bifunctional or less (meth) acrylate monomer refers to two or less polymerizable functional groups, for example, two. The molecular weight of the bifunctional or less (meth) acrylate monomer may be 150 to 300 g / mol, and the glass transition temperature (Tg) may be 25 to 60 ° C.

Non-limiting examples of the (meth) acrylate monomer of the bifunctional or less, 1,6-hexanediol diacrylate (HDDA), 1,6hexanediol 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 Methaacrylate (TEGDMA) or mixtures thereof can be used.

As an embodiment of the hard coating composition according to the present invention, the trifunctional or higher (meth) acrylate monomer and bifunctional or lower (meth) acrylate monomer may be used in combination. When the mixture of the trifunctional or higher (meth) acrylate monomer and the bifunctional or lower (meth) acrylate monomer is used, the workability, appearance characteristics, and curing degree of the paint can be adjusted. As an example, the mixing ratio of the trifunctional or higher (meth) acrylate monomer and the bifunctional or lower (meth) acrylate monomer may be 1: 0.2 to 1 by weight.

In the present invention, the content of the (meth) acrylate monomer is not particularly limited, and for example, may be 30 to 75% by weight based on the total weight of the hard 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. When a trifunctional or higher (meth) acrylate monomer and a bifunctional or lower (meth) acrylate monomer are mixed, the content of the trifunctional or higher (meth) acrylate monomer based on the total weight of the hard coating composition is 20 to 45 weight. %, The content of the (meth) acrylate monomer having a difunctional or less function may be 9 to 30% by weight.

Photoinitiator

The hard coating composition according to the present invention includes a photoinitiator. The photoinitiator is a component that is excited by ultraviolet rays (UV) or the like to initiate photopolymerization, and a conventional photoinitiator in the field 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), bis (2,4,6-trimethylbenzoyl) phenylphosphine Fine oxides (Bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide), methylbenzoylformate, and the like can be used alone or in combination of two or more.

In the present invention, the content of the photoinitiator may be 1 to 10% by weight based on the total weight of the hard 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.

additive

In addition to the above-mentioned components, the hard 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 present 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 hard coating composition of the present invention includes conventional ultraviolet absorbers known in the art. 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 the ultraviolet absorber component is difficult to remain in the coating film during outdoor exposure, 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 hard coating composition. When the content of the ultraviolet absorber is outside 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 during ultraviolet curing.

Other additives that can be used include light stabilizers (eg HALS), antioxidants (eg phenolic antioxidants), wetting agents (eg polyether modified polydimethylsiloxane), leveling agents (eg silicone diacrylate based and silicone poly Acrylate-based compounds), lubricants, surface conditioners, surfactants, antifoaming agents (such as 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 may be 1 to 10% by weight based on the total weight of the hard coating composition.

<Molded product>

The present invention provides a molded article (for example, a headlamp for an automobile) including a coating layer formed from the above-mentioned hard coating composition.

According to an embodiment of the present invention, the automobile headlamp is formed on a plastic substrate and one or both surfaces of the plastic substrate, and includes a coating layer formed from the above-mentioned hard 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 hard coating composition of the present invention is excellent.

The thickness of the coating layer made of the composition can be variously adjusted according to the use, 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.

The method of applying the hard coating composition on the plastic substrate may employ a conventional coating method in the art, such as spray coating, brushing, flow coating, dip coating, spin coat, and the like. For example, the hard coating composition may be applied to a plastic substrate by applying a warm spray method. Although the hard coating composition does not contain a solvent, it has a viscosity capable of applying a worm spray coating method, and can secure an excellent appearance when applied.

The coating layer formed of the hard coating composition according to the present invention is not only excellent in adhesion to a plastic substrate (eg, PC material), but also excellent in terms of overall physical properties of a coating film such as appearance, heat resistance, moisture resistance, and heat and cold resistance. Therefore, the lens for a vehicle headlamp including such a high weatherability coating layer has excellent appearance quality and secures driving stability at night.

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 1-10]

According to the composition shown in Table 1 below, a six-functional urethane acrylate oligomer (A), a trifunctional urethane acrylate oligomer (B), a bifunctional urethane acrylate oligomer (C), an acrylate monomer (D), and a photoinitiator (E and F), the ultraviolet absorber (G), light stabilizer (H), using a silicone additive (I), to prepare a hard coating composition of Example 1-10.

A-1: 6-functional urethane acrylate oligomer (CN968NS, Sartomer, weight average molecular weight: 2,000 g / mol)

A-2: 6-functional urethane acrylate oligomer (CN9010, Sartomer, weight average molecular weight: 2,500 g / mol)

A-3: 6-functional urethane acrylate oligomer (EB8301, Sartomer, weight average molecular weight: 1,300 g / mol)

A-4: 6-functional urethane acrylate oligomer (EB9310, Cytec, weight average molecular weight: 3,600 g / mol)

B: trifunctional urethane acrylate oligomer (EB8301, Cytec, weight average molecular weight: 1,350 g / mol)

C: bifunctional urethane acrylate oligomer (UO-HE02, KCC, weight average molecular weight: 275 g / mol)

D-1: trifunctional (meth) acrylate monomer (Trimethylolpropane triacrylate, TMPTA, molecular weight: 296 g / mol)

D-2: bifunctional (meth) acrylate monomer (1,6-hexanediol diacrylate, molecular weight: 226 g / mol)

E: Photoinitiator (1-hydroxy-cyclohexyl-phenyl-ketone, Micure CP-4, Miwon Corporation)

F: photoinitiator (bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, Irgacure 819, BASF)

G: UV absorber (Hydroxyphenyl Triazines, HPT)

H: Light stabilizer (HALS, TINUVIN123, BASF)

I: Silicone additive (BYK-333, BYK)

[Comparative Example 1-3]

A hard coating composition of Comparative Example 1-3 was prepared in the same manner as in Example 1-10, except that the composition was mixed according to the composition shown in Table 2 below.

[Experimental Example-Property evaluation]

After the hard coating composition prepared in Examples 1-10 and Comparative Examples 1-3 was coated with a worm spray to a transparent polycarbonate (PC) specimen with a thickness of about 12 μm (top layer, dry film thickness), a temperature condition of 80 ° C. After drying for 30 minutes, the mixture was naturally dried for 24 hours. Physical properties were measured by the method described in Table 3, and the results are shown in Tables 4 and 5.

As shown in Table 4 and Table 5, Examples 1-10 applying a hard coating composition comprising all three types of a 6- or higher-functional urethane acrylate oligomer, a 3-functional urethane acrylate oligomer, and a 2-functional urethane acrylate oligomer It was confirmed that the coating film of showed excellent physical properties in all measured items. On the other hand, the coating film of Comparative Example 1-3 in which a hard coating composition containing only two of the six or more functional urethane acrylate oligomer, the trifunctional urethane acrylate oligomer and the bifunctional urethane acrylate oligomer is applied has at least one of measured properties. It turned out to be poor.

Claims (6)

Urethane (meth) acrylate oligomer, (meth) acrylate monomers and photoinitiators, and
The urethane (meth) acrylate oligomer is a hard coating composition comprising a six-functional urethane (meth) acrylate oligomer, a trifunctional urethane (meth) acrylate oligomer and a bifunctional urethane (meth) acrylate oligomer. According to claim 1, Based on the total weight of the coating composition, 20 to 40% by weight of a urethane (meth) acrylate oligomer of 6 or more functional. Hard coating composition comprising 1 to 10% by weight of a trifunctional urethane (meth) acrylate oligomer and 1 to 10% by weight of a bifunctional urethane (meth) acrylate oligomer. The hard coating composition of claim 1, wherein the (meth) acrylate monomer comprises at least one of a trifunctional or higher (meth) acrylate monomer and a bifunctional or lower (meth) acrylate monomer. The hard coating composition according to claim 3, wherein a mixing ratio of the trifunctional or higher (meth) acrylate monomer and the bifunctional or lower (meth) acrylate monomer is 1: 0.2 to 1 by weight. According to claim 1, Based on the total weight of the hard coating composition, 22 to 60% by weight of the urethane (meth) acrylate oligomer and 30 to 75% by weight of the (meth) acrylate monomer and 1 to 10% by weight of the photoinitiator Hard coating composition. A molded article comprising a coating layer formed by applying the hard coating composition according to any one of claims 1 to 5.