KR101517192B1 - Uv-curable coating composition and molded article comprisng a cured coating layer formed from the same - Google Patents

Abstract

The present invention relates to an ultraviolet ray curable coating composition and a molded article including cured coating layers formed from the same and, more specifically, an ultraviolet ray curable coating composition, which is painted in an air spray manner and has outstanding attachment and durability for various materials at high temperatures, and a molded article including cured coating layers formed from the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a UV-curable coating composition and a cured coating layer formed therefrom. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a UV-curable coating composition,

The present invention relates to a UV curable coating composition and a molded article comprising the cured coating layer formed therefrom. More particularly, the present invention relates to an ultraviolet curable coating composition having excellent adhesion and durability at various temperatures, And a cured coating layer formed thereon.

In automobile headlamps, the light source is being changed from halogen bulb to HID and LED headlamp, lamp design has been diversified, and structural changes such as inserting additional devices due to additional convenience such as irradiation angle adjustment have been made have. As a result, the temperature of the headlamp reflector is maintained at 200 ° C or more, resulting in detachment of the dry-plated coating film, appearance of rainbow-like phenomenon, defective appearance such as air bubbles and poor light distribution of the headlamp reflector. As a result, Difficulty of operation occurs.

There are two types of commercial paints that have high temperature durability in the market today.

The first is a paint using an acrylate resin as a UV coating of flow coating type. For example, Korean Patent Registration No. 10-1210903 discloses a process for producing a polyfunctional acrylate oligomer comprising an aliphatic urethane acrylate oligomer having at least 6 polymerizable functional groups, a polybutadiene modified aliphatic urethane acrylate oligomer, an acid functional group-containing acrylate oligomer, a monofunctional acrylate monomer and a photopolymerization initiator An ultraviolet curing type coating composition is disclosed. However, these paints are good in physical properties, but they must be equipped with a dedicated inline facility in which the pretreatment and coating facilities are all integrated, and it is difficult to maintain and manage facilities such as paint change and appearance quality control.

The second is a paint using an epoxy resin as a main component as a powder coating. This paint is good in environmental friendliness and high temperature durability but has a disadvantage that it can not be used other than a metal material as a paint for electrostatic painting. In addition, the coating method used in the domestic, Chinese, and Indian automobile industries is developed by air spray method. However, the paint is not suitable for the air spray method, so it is applied in domestic, Chinese and Indian markets it's difficult.

Accordingly, development of an ultraviolet ray curing type coating composition capable of coating with air spray and having good adhesiveness and durability to various materials at high temperatures is desired.

It is an object of the present invention to solve the problems of the prior art as described above, and it is an object of the present invention to provide an aluminum die-casting (ALDC) ) And MGC (Magnesium Die-casting) material at 230 DEG C for 72 hours at a high temperature, and a cured coating layer formed therefrom.

(A) an MMA modified thermoplastic acrylic resin having a weight average molecular weight of 40,000 to 50,000 and a glass transition temperature (Tg) of 70 to 80 ° C, (B) (C) a multifunctional acrylate having at least three polymerizable functional groups, (D) a styrene-modified thermosetting acrylic resin having a glass transition temperature (Tg) of 60 to 80 DEG C and an acid value of 100 to 130 mgKOH / g, Wherein the photocuring initiator comprises a short-wavelength initiator that absorbs ultraviolet light having a wavelength of 230 to 340 nm and a long-wavelength initiator that absorbs ultraviolet light having a wavelength of 350 nm or more, wherein the content of the photopolymerization initiator And 1 to 5% by weight based on 100% by weight of the total composition.

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.

Since the UV curable coating composition according to the present invention is capable of air spray coating, the air spray coating is suitable for mass production of automobile head lamps in domestic and overseas markets of China and India. , ALDC and MGDC materials can be provided with a good appearance, adhesion and durability at a high temperature of 230 ° C for 72 hours.

Hereinafter, the present invention will be described in more detail.

In the coating composition of the present invention, the (A) MMA modified thermoplastic acrylic resin is one having a weight average molecular weight of 40,000 to 50,000 and a glass transition temperature (Tg) of 70 to 80 ° C. If the weight average molecular weight of the thermoplastic acrylic resin is less than 40,000, there is a problem that the adhesion to the material is poor. If the weight average molecular weight is more than 50000, the leveling is poor after spraying and the compatibility with the other raw materials is poor, . If the glass transition temperature is lower than 70 캜, the heat resistance tends to deteriorate. If the glass transition temperature is higher than 80 캜, the adhesion to the material tends to deteriorate.

More specifically, as the (MMA) modified thermoplastic acrylic resin (A), an acrylic copolymer resin containing methyl methacrylate (MMA) as a maximum component as a polymerization unit can be used. According to one embodiment of the present invention, the thermoplastic acrylic resin includes 40 to 50 parts by weight of methyl methacrylate (MMA) as main binder, 20 to 30 parts by weight of styrene monomer (SM), n-butyl methacrylate 20 to 30 parts by weight of acrylate (n-BMA) and 1 to 10 parts by weight of acrylic acid (AA) are initially introduced or dropped in a solvent (e.g., toluene) One resin may be used, but is not limited thereto.

In the coating composition of the present invention, the content of the (A) MMA modified thermoplastic acrylic resin is preferably 15 to 30% by weight based on 100% by weight of the composition. If the content of the component (A) is less than 15% by weight, there may be a problem that the adhesion of the material and the heat resistance are poor. When the content exceeds 30% by weight, the leveling of the cured coating film is lowered and the coating film may be hazed.

In the coating composition of the present invention, the styrene-modified thermosetting acrylic resin (B) preferably has a weight average molecular weight of 5,000 to 15,000, a glass transition temperature (Tg) of 60 to 80 ° C and an acid value of 100 to 130 mgKOH / g use. When the weight average molecular weight of the styrene-modified thermosetting acrylic resin is less than 5,000, the heat resistance of the styrene-modified thermosetting acrylic resin may deteriorate. When the glass transition temperature is lower than 60 ° C, the hardness of the coating film is lowered and the heat resistance is lowered. When the glass transition temperature is higher than 80 ° C, the coating tends to become brittle and the adhesion is lowered. If the acid value is less than 100 mgKOH / g, there is a problem that the curability is deteriorated and the adhesion is deteriorated. When the acid value is more than 130 mgKOH / g, the water resistance is lowered and the yellowing of the coating film becomes weak.

More specifically, as the (B) styrene-modified thermosetting acrylic resin, an acrylic copolymer resin containing styrene as a maximum component as a polymerization unit can be used. According to one embodiment of the present invention, the styrene-modified thermosetting acrylic resin includes 40 to 50 parts by weight of a styrene monomer (SM) as a main binder, 10 to 20 parts by weight of methyl methacrylate (MMA) 10 to 20 parts by weight of hexylethyl methacrylate (2-HEMA), 1 to 10 parts by weight of acrylic acid (AA) and 10 to 20 parts by weight of an epoxy compound (e.g. Cardura E-10P) But the present invention is not limited thereto. The resin may be a resin synthesized in the presence of a thermal initiator (e.g., peroxide)

In the coating composition of the present invention, the content of the styrene-modified thermosetting acrylic resin (B) is preferably 7 to 15% by weight based on 100% by weight of the total composition. If the content of the component (B) is less than 7% by weight, heat resistance may be deteriorated. If the content of the component (B) is more than 15% by weight, adhesion may be deteriorated.

In the coating composition of the present invention, the (C) multifunctional acrylate having three or more polymerizable functional groups may include trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PETA), and combinations thereof But the present invention is not limited thereto.

In the coating composition of the present invention, the content of the polyfunctional acrylate having three or more polymerizable functional groups (C) is preferably 20 to 30% by weight based on 100% by weight of the total composition. If the content of the component (C) is less than 20% by weight, the curing property may be deteriorated and unfavorable areas may be unfavorably formed. If the content of the component (C) is more than 30% by weight, the curing coating may become brittle and the adhesion may be deteriorated.

The coating composition of the present invention includes a combination of a short wavelength initiator that absorbs ultraviolet light having a wavelength of 230 to 340 nm and a long wavelength initiator that absorbs ultraviolet light having a wavelength of 350 nm or more as the photocurable initiator (D).

Examples of the short-wavelength initiator include 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1 -hydroxy-cyclohexyl- (2-methyl-1- [4- (methylthio) phenyl] -2- (4-morpholinyl) phenyl] -1-butanone Ketone compound initiators such as methyl-1- [4- (methylthio) phenyl] -2- (4-morpholinyl) phenyl] -1-butanone, ketal compound initiators such as benzyldimethylketal, methylbenzoylformate), and a combination of these initiators can be preferably used.

Examples of the long-wavelength initiator include phenyl bis (2,4,6-trimethyl benzoyl) -phosphine oxide, diphenyl (2,4,6-trimethyl Benzoyl) -phosphine oxide (Diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide) can be preferably used.

The content ratio of the short wavelength initiator and the long wavelength initiator in the photocuring initiator (D) is preferably from 5: 1 to 15: 1, more preferably from 8: 1 to 10: 1 Is more preferable. If the relative content of the initiator for a short wavelength is smaller than the above level, the curing property may be deteriorated and unfavorable portions may become unfavorable. On the contrary, if the relative level is lower than the above range, the cured coating may become brittle and adherence may be deteriorated.

In the coating composition of the present invention, the total content of the photocurable initiator (D) is 1 to 5 wt%, more preferably 1 to 3 wt%, based on 100 wt% of the total composition. If the content of the component (D) is less than 1% by weight, there is a problem that unhardening occurs. When the content exceeds 5% by weight, the cured coating film becomes brittle and the adhesion is deteriorated.

In the coating composition of the present invention, the solvent (E) may be an acetate solvent (e.g., ethyl acetate, butyl acetate), a ketone solvent, an aromatic solvent (e.g., BTX, i.e., benzene, toluene, xylene) But the present invention is not limited thereto.

In the coating composition of the present invention, the content of the (E) solvent is preferably 40 to 55% by weight based on 100% by weight of the total composition. If the content of the component (E) is less than 40% by weight, the air spray workability and leveling may be deteriorated. If the content of the component (E) exceeds 55% by weight, the coverage of the coating material is lowered, It is difficult to form a uniform coating film because the coating film flows well and there is a problem that the amount of paint consumption increases.

The coating composition of the present invention may further include one or more conventional additive components in addition to the above-mentioned components. For example, a silicon-based additive and / or a non-silicon-based additive may be further included. The amount of the silicone-based additive may be 0.1 to 1% by weight based on 100% by weight of the composition.

The coating composition of the present invention exhibits the strength and the high-temperature durability of a coating film due to the thermoplastic acrylic resin component when applied to a metal or plastic material, particularly an automobile head lamp, and the flexibility of the coating film the flexibility and the adhesion to the material can be improved. Thus, 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. The material of the molded article is preferably a metal or plastic material, and a car head lamp is particularly preferable as the molded article.

Hereinafter, the present invention will be described more specifically by way of examples. However, these examples are provided only for the understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

[ Example ]

(1) Preparation of Coating Composition

The coating compositions of Examples 1 to 8 were prepared using the ingredients shown in Table 1 below in the amounts indicated and the coating compositions of Comparative Examples 1 to 14 were prepared using the ingredients shown in Table 2 below in the amounts indicated.

[Description of raw materials used (hereinafter, all molecular weights are weight average molecular weights)

A-1: MMA modified thermoplastic acrylic resin, molecular weight 40000 to 50000, Tg 78 ° C [KCC]

A-2: thermoplastic acrylic resin, molecular weight 10500, Tg 75 DEG C [trade name: BR87]

A-3: Thermoplastic acrylic resin, molecular weight 40000, Tg 109 占 폚 [Product name: LP50 / 01]

B-1: styrene-modified thermosetting acrylic resin, molecular weight 5000 to 15000, Tg 60 to 70 占 폚, acid value 120 to 130 mg KOH / g [KCC]

B-2: Thermosetting acrylic resin, molecular weight 5000 ~ 15000, Tg 60 ~ 80 ℃, acid value 70 ~ 80 mgKOH / g [KCC]

B-3: thermosetting acrylic resin, molecular weight 5000 ~ 15000, Tg 20 ~ 40 ℃, acid value 110 ~ 130 mgKOH / g [KCC]

C-1: Photo-curing initiator for short wavelength, 2-hydroxy-2-methyl-1-phenyl-

C-2: Photo-curing initiator for short wavelength, benzyl dimethyl ketal

C-3: Photo-curing initiator for short wavelength, 1-hydroxy-cyclohexyl-phenyl-ketone

C-4: Photo-curing initiator for short wavelength, methyl benzoyl formate

C-5: A photocuring initiator for short wavelength, 2-methyl-1- [4- (methylthio) phenyl] -2- (4-morpholinyl) phenyl]

C-6: Photocuring initiator for long wavelength, phenyl bis (2,4,6-trimethylbenzoyl) phosphine oxide

C-7: Photocuring initiator for long wavelength, diphenyl (2,4,6-trimethylbenzoyl) -phosphine oxide

D: Multifunctional acrylate monomer [TMPTA]

E: Polyfunctional acrylate monomer [PETA]

F: wetting and leveling agent: BYK 333

G: Solvent (mixed solvent of 50% ethyl acetate, 20% butyl acetate and 30% xylene)

(2) Evaluation of Physical Properties of Coating Composition

The ultraviolet curable coating compositions prepared in the above Examples and Comparative Examples were applied to the reflector of automobile headlamps by metal vapor deposition to evaluate their physical properties. The photocurable coating composition prepared in each of the above Examples and Comparative Examples was applied to a die casting material of AL (aluminum) or MG (magnesium) metal which is a reflecting mirror material of a head lamp projection lamp using a sprayer And the film was cured by irradiation with energy of 3000 mJ / cm 2 at a position of about 20 cm in air with a high pressure mercury lamp of 150 mW / cm 2 to remove the solvent. Aluminum was vacuum deposited in Torr. Then, HMDSO4 was applied on the deposited aluminum surface in a vacuum evaporator chamber to prepare test specimens. Properties of the following items were evaluated on the prepared specimens, and the results are shown in Tables 3 and 4, respectively.

1) Adhesion test: Evaluated by performing a cross cut tape test according to ASTM D3359.

2) Moisture resistance test: The sample was allowed to stand for 240 hours at a test temperature and relative humidity of 50 ± 2 ° C. and 98 ± 2%, and after being taken out for 1 hour, there was remarkable discoloration, discoloration, swelling, And whether there is any abnormality in adhesion.

3) Water resistance test: The specimens were immersed in tap water (TAP WATER, test temperature 40 ℃) for 24 hours, and then taken out to remove water on the surface by air blow. After left for 1 hour at room temperature, the discoloration, , Cracking, gloss reduction, etc., and whether there is any abnormality in adhesion.

4) Heat resistance test: It was left for 72 hours under the test temperature (230 ± 2 ° C) and then left for 1 hour at room temperature. Thereafter, it was evaluated whether there was no discoloration, discoloration, swelling, .

5) Heat and cold cycle test: After leaving the specimen for 4 hours at 80 ± 2 ℃ and 95% RH, change the temperature condition to -40 ± 2 ℃ and 95% RH and leave for 4h. It is evaluated whether there is no discoloration, discoloration, swelling, cracking, gloss reduction, or the like of the deposited film.

Claims (10)

(A) an MMA modified thermoplastic acrylic resin having a weight average molecular weight of 40,000 to 50,000 and a glass transition temperature (Tg) of 70 to 80 ° C,
(B) a styrene-modified thermosetting acrylic resin having a weight average molecular weight of 5,000 to 15,000, a glass transition temperature (Tg) of 60 to 80 DEG C and an acid value of 100 to 130 mgKOH / g,
(C) a multifunctional acrylate having three or more polymerizable functional groups,
(D) a photocurable initiator and
(E) a solvent,
Wherein the photocuring initiator comprises a short wavelength initiator that absorbs ultraviolet light having a wavelength of 230 to 340 nm and a long wavelength initiator that absorbs ultraviolet light having a wavelength of 350 nm or more,
Wherein the photocurable initiator content is 1 to 5 wt% based on 100 wt% of the composition,
UV curable coating composition. The method of claim 1, wherein the MMA modified thermoplastic acrylic resin comprises 40 to 50 parts by weight of methyl methacrylate (MMA) as a main binder, 20 to 30 parts by weight of a styrene monomer (SM) Modified acrylic copolymer resin which is synthesized in the presence of a heat initiator by initially injecting or dropping 20 to 30 parts by weight of acrylate (n-BMA) and 1 to 10 parts by weight of acrylic acid (AA) Based coating composition. The thermosetting acrylic resin composition according to claim 1, wherein the thermosetting acrylic resin (B) is a main binder comprising 40 to 50 parts by weight of a styrene monomer (SM), 10 to 20 parts by weight of methyl methacrylate (MMA) 10 to 20 parts by weight of a styrene-modified thermosetting acrylic copolymer (2-HEMA), 1 to 10 parts by weight of acrylic acid (AA) and 10 to 20 parts by weight of an epoxy compound in a solvent, Wherein the ultraviolet curable coating composition is a resin. The ultraviolet curable composition according to claim 1, wherein (C) the polyfunctional acrylate having three or more polymerizable functional groups is selected from the group consisting of trimethylolpropane triacrylate, pentaerythritol triacrylate, Coating composition. The ultraviolet curable coating composition according to claim 1, wherein the short wavelength initiator is selected from the group consisting of a ketone compound initiator, a ketal compound initiator, an ester compound initiator, and combinations thereof. The ultraviolet curable coating composition according to claim 1, wherein the initiator for the long wavelength is a trimethylbenzoyl compound initiator. The ultraviolet curable coating composition according to claim 1, wherein the (E) solvent is selected from the group consisting of an acetate solvent, a ketone solvent, an aromatic solvent, and combinations thereof. A molded article comprising a cured coating layer formed from the ultraviolet curable coating composition according to any one of claims 1 to 7. The molded article according to claim 8, wherein the molded article is a metal or a plastic material. The molded article according to claim 8, wherein the molded article is an automobile head lamp.