KR101403986B1 - Ultraviolet-curable coating composition and steel sheet using the same - Google Patents

Abstract

The present invention relates to an ultraviolet curable coating composition and steel sheets using the same. The ultraviolet curable coating composition according to the present invention can produce eco-friendly steel sheets with a uniform surface since an existing solvent used for coating steel sheets is not used. Moreover, an ultraviolet curing method has superior reaction rates when compared with an existing heat curing method and can provide high quality steel sheet with improved appearance, gloss, hardness, and chemical resistance.

Description

[0001] The present invention relates to an ultraviolet-curable coating composition and a steel sheet using the same,

The present invention relates to a UV-curable coating composition and a steel sheet on which the composition is cured.

Generally, steel materials such as steel sheets form a coating film on the surface thereof to provide surface protection, corrosion prevention, and material beauty.

As a typical method for forming a coating film on a steel material such as a steel sheet, a PCM (Pre Coated Metal) method in which a resin composition such as a paint is directly coated on the surface of a steel material, and a film sheet, And a laminating method of adhering to a material.

However, in the above-mentioned prior art, a resin composition for forming a coating film, that is, a coating paint is composed of a polyester or a polyurethane type and is coated on a steel material such as a steel sheet by a thermosetting method to form a coating film, And thus, the time required for the coating operation is increased and the productivity is decreased. In addition, the solvent may cause environmental pollution, and in particular, a conventional solvent volatilization type coating method, a thermosetting type coating method, an electrostatic and electrodeposition coating method, a powder coating method, and the like for forming a coating film on a metallic material such as a steel product There is a problem that the production time and energy consumption increase.

In addition, the PCM system, which occupies most of the coil coating system, has a problem of securing facility space and high cost due to a long length of the high temperature drying facility line.

In order to solve the above problems, development using ultraviolet (UV) coating method has recently been developed. The ultraviolet coating method can work in a short time, and is excellent in productivity. The problem of environmental pollution can be reduced because no solvent is used, and other coating methods such as a solvent volatilization type coating method, a thermosetting type coating method, And the electrodeposition coating method and the powder coating method, it is possible to reduce the energy consumption and the energy saving drying method even if the curing facility space is small.

However, such ultraviolet drying method has a high hardening density due to the property of ultraviolet ray curing system, and is not suitable for coating with a metallic material such as a steel sheet due to low adhesiveness. Therefore, there is a need for studies on compositions and methods for applying ultraviolet curing systems for steel sheet coating.

Korea Patent Publication No. 2010-0073809

The present invention relates to a UV-curable coating composition and a steel sheet using the same, and can provide a matte coating film applicable to a steel sheet for a building material.

The present invention can provide an ultraviolet ray curable composition for a steel sheet. As one example, it may include a modified epoxy acrylate oligomer, a urethane acrylate oligomer, a reactive acrylic monomer, a photoinitiator, an adhesion promoter, and a quencher.

Also, a steel sheet on which the composition is cured can be provided. As an example,

Steel plate; And

A coating film formed on one side of the steel sheet and being a cured product of the composition,

The coating film may include a steel sheet having an ultraviolet cured coating film having a gloss of 15 to 30% when the gloss is measured at an angle of 60 °.

For example, the coating film can be used as a steel sheet for a building material.

The ultraviolet ray curable coating composition for a steel sheet according to the present invention does not use a solvent used for coating a conventional steel sheet, and thus is environmentally friendly. It can prevent surface defects that may occur after product production, Can be produced. In addition, the ultraviolet ray curing system has a reaction rate of a few seconds to a few tens of seconds and is so fast that it can not be compared with the conventional thermosetting system. As a result, a steel sheet with excellent quality such as surface smoothness, high gloss, high hardness, .

1 is a schematic view of a steel sheet comprising a composition according to the present invention, in one embodiment.

The present invention relates to a UV-curable coating composition, a cured coating film thereof, and a steel sheet using the same.

As one example of the ultraviolet curable coating composition,

An ultraviolet curable coating composition for a steel sheet comprising a modified epoxy acrylate oligomer, a urethane acrylate oligomer, a reactive acrylic monomer, a photoinitiator, an adhesion promoter, and a quencher.

Conventionally, a coating method for a steel plate such as a PCM method and a laminating method is used. However, there is a problem that a space for securing a facility space and an expensive cost are generated, and environmental pollution is caused. On the other hand, when coating is performed on a steel sheet using the ultraviolet ray curable coating composition according to the present invention, the above problems can be solved.

Specifically, based on 100 parts by weight of the entire UV curable coating composition,

10 to 20 parts by weight of a modified epoxy acrylate oligomer,

10 to 25 parts by weight of a urethane acrylate oligomer,

35 to 50 parts by weight of a reactive acrylic monomer,

5 to 10 parts by weight of a photoinitiator,

0.1 to 2 parts by weight of an adhesion promoter, and

And 5 to 20 parts by weight of quenching.

For example, most of epoxy acrylates are produced from bisphenol A as a raw material. Epoxy acrylates prepared by using such bisphenol A have high crosslinking density, high chemical resistance, corrosion resistance and scratch resistance, There is a problem that this occurs. Recently, a modified epoxy acrylate oligomer has been developed. When the above product is used alone, the problem of yellowing can be solved, but it is difficult to use it in a steel sheet for construction material exposed to 100% outdoors. Therefore, an ultraviolet curable coating composition for a steel sheet was prepared by further including a material such as a urethane acrylate oligomer, a reactive acrylic monomer, a photoinitiator, an adhesion promoter and a quencher.

Specifically, the modified epoxy acrylate oligomer may include 10 to 18 parts by weight, 12 to 18 parts by weight, 14 to 20 parts by weight, or 14 to 17 parts by weight of the modified epoxy acrylate oligomer. Within this range, when the composition is formed into a coating film, corrosion resistance and processability can be improved. The modified epoxy acrylate oligomer is not particularly limited as long as it is a modified epoxy acrylate oligomer conventionally used in the art, and specifically, an epoxy acrylate oligomer modified with a urethane series can be used. For example, it may include at least one of Miramer ME 1201, CN 150/80 from Sartomer, EA 1580 from HS Chemtron, and 3020-A80 from AGI.

In addition, the urethane acrylate oligomer in the composition may include a bifunctional urethane acrylate oligomer and a hexafunctional urethane acrylate oligomer. For example, the bifunctional urethane acrylate oligomer and the hexafunctional urethane acrylate oligomer may be contained in a weight ratio of 5 to 15: 1 to 10, and within the above range, when the composition is formed into a coating film, , Processability, scratch resistance and chemical resistance can be realized.

Examples of the bifunctional urethane acrylate oligomer include UA-2205, UA-2890BX and UA-5221 of HS Chemtron, CN 966J75, CN 966H90 and Cytec of Sartomer Co., 0.0 > Ebecryl < / RTI > 244, Ebecryl 284.

Examples of the hexafunctional urethane acrylate oligomer include at least one of UA-800, UA-8570, Ebecryl 1290 manufactured by Cytec, and QU-1620 manufactured by Q & can do.

In addition, the reactive acrylic monomer in the composition may be a monofunctional acrylic monomer. The monofunctional acrylic monomer may be 35 to 50 parts by weight, for example, 35 to 45 parts by weight, 35 to 40 parts by weight, 40 to 50 parts by weight, or 45 to 50 parts by weight, based on 100 parts by weight of the composition . Within this range, when the composition is formed into a coating film, high adhesion and hardenability can be realized, thereby increasing productivity. The monofunctional acrylic monomer is not particularly limited but includes, for example, acryl morpholine (ACMO), tetrahydrofurfuryl acrylate (THFA), hydroxyethyl acrylate (HEA), hydroxypropyl acrylate (HPA ), N-vinylpyrrolidine (NVP), and isobornyl acrylate (IBOA).

The photoinitiator in the composition is intended to cause polymerization reaction of the resin composition when ultraviolet rays are irradiated after applying the ultraviolet resin composition to the surface of a metal material such as a steel sheet to form a coating film. Specifically, the photoinitiator may be a conventional polymerization initiator that exhibits activity by ultraviolet light. Examples of the photoinitiator include benzophenone, benzoin, benzoin ether, benzyl ketal, acetophenone, anthraquinone, and thioxanthone And may include one or more species. Examples of commercially available polymerization initiators include Irgacure 184, 500, 754, 819, Darocur 1173, TPO and Micure CP-4, MP-8, BP, TPO of MIWOO Co., Ltd. of CIBA GEIGY Specifically, since the ultraviolet curable coating composition of the present invention does not use a solvent, liquid phase initiators Irgacure 754, Irgacure 250, Darocur 1173 and Micure MP-8 can be used.

The adhesion promoting agent in the composition may be acrylic phosphate and is not particularly limited, and for example, hydroxyethyl acryloyl phosphate, hydroxyethyl methacrylate phosphate and the like may be used. The adhesion promoting agent may be contained in a small amount in the composition, and when the composition is formed into a coating film, high adhesion can be realized.

Further, the quencher in the composition may be a plate-shaped aluminum silicate. A commonly used quencher is a type that can be applied to ultraviolet curing, such as a wax series and a silica series. For example, wax-based quenching agents include polyethylene (PE), polypropylene (PP), and amide wax. However, when such a wax series is applied to the development of a solventless type of the present invention, There are difficulties in controlling the timing. Also, in the case of Silica series which is most applied in solvent-free coating, a UV hardening machine with high hardening strength is used in a field requiring a high line speed such as PCM. In this case, in case of a silicate series quencher having a spherical structure It is difficult to obtain a desired light extinction effect due to a long curing time after coating, and in general, it has been difficult to apply the composition to a dental formulation because the viscosity increases during dispersion in a solution manufacturing process. On the other hand, it is possible to provide a matte coating composition having physical properties required for a steel sheet for a building material by using the aluminum silicate type matting (ASM) having a plate-like structure used in the present invention. The particle size of the plate-shaped aluminum silicate quencher may be in the range of 400 to 500 nm, and may be previously paste-used for facilitating normal injection into the manufacturing process. The paste process was prepared by dispersing the reactive acrylic monomer, ASM, and dispersant in a weight ratio of 6: 4: 0.3, respectively. At this time, the reactive acrylic monomer used may be a monofunctional reactive acrylic monomer, and thereby a quenching effect can be obtained.

For example, the plate-structured aluminum silicate quencher may be selected from the group consisting of montmorillonite, bentonite, hectorite, fluorohectorite, saponite, beidelite, ), At least one of nontronite, stevensite, vermiculite, volkonskoite, magadite, and kenyalite.

The quencher may be 5 to 20 parts by weight, for example, 5 to 15 parts by weight, 5 to 10 parts by weight, 10 to 20 parts by weight or 10 to 15 parts by weight based on 100 parts by weight of the total composition. Within the above range, it is possible to satisfy the non-light glossy (60% or less based on 30%) standard required by the steel sheet for building materials.

The ultraviolet curable coating composition for a steel sheet according to the present invention may further comprise a defoaming agent and a leveling agent. Specifically, 0.1 to 1.0 part by weight of a defoaming agent and 0.1 to 1.0 part by weight of a leveling agent may be further added based on 100 parts by weight of the entire ultraviolet curable coating composition.

First, the antifoaming agent can prevent the defects of the external appearance of the coating film by removing bubbles which may occur during the coating operation. For example, one or more of Airex 920 of TEGO, 1790 of BYK, and 2021 of AFCONA can be used have.

Further, the leveling agent can realize a beautiful appearance of the coating film and a high surface scratch resistance. For example, one or more of Glide 410, Glide 440, Rad 2250, Rad 2500 and 3510, 333 of TEGO Co., Can be used.

The present invention may include a steel sheet in which the composition is formed with a cured coating film. As an example,

Steel plate; And

A coating film formed on one side of the steel sheet and being a cured product of the ultraviolet curable coating composition for a steel sheet according to the present invention,

The coating film may have a glossiness of 15 to 30% when the glossiness is measured at an angle of 60 °.

The steel sheet is not particularly limited, and specifically, a steel sheet on which an ultraviolet curing coating film is formed by curing the ultraviolet curing type coating composition on a steel sheet with ultraviolet rays can be manufactured. When the glossiness is measured at an angle of 60 ° , And a gloss of 15 to 30%. For example, the glossiness of the coating film may be 15 to 20% or 20 to 25%, and the coating film within the above range may be applied to a non-light gloss level required by the steel sheet for building materials.

In order to produce the coating film, it can be cured at a curing intensity of 1000 to 2000 mJ / cm ² when curing with ultraviolet rays. For example, the curing strength may be ² days from 1000 to 1800 mJ / cm ^2, 1000 to 1600 mJ / cm ^2, 1300 to 2000 mJ / cm ² or 1300 to 1600 mJ / cm. The high ultraviolet hardening strength within the above range can achieve a desired gloss even when applied to a high speed, which is a PCM line characteristic.

In addition, the pencil hardness of the coating film may be 1 H or more, and may be, for example, 1 H to 5 H, 1 H to 8 H, or 3 H to 6 H. Specifically, the pencil hardness may mean the degree of scratch resistance. For example, the pencil hardness can be divided into 9B to 9H, which means that the hardness becomes weaker toward 9B and harder toward 9H.

The thickness of the coating layer may be 1 to 20 mu m. For example, the thickness may be 1 to 15 탆, 1 to 10 탆, 5 to 20 탆, or 10 to 15 탆, and a good appearance and high workability can be expected within the thickness range of the coating film.

The ultraviolet curing coating film for a steel sheet according to the present invention can be used for a steel sheet for a building material. For example, the steel sheet for construction use is a 100% steel plate used for a sandwich panel, an SGP panel, a fence, a fire door, and the like, and is excellent in appearance, Physical properties may be required. On the contrary, the ultraviolet ray hardening coating film for a steel sheet can satisfy the above properties.

Hereinafter, the present invention will be described in more detail through examples and the like, but the scope of the present invention is not limited thereto.

Example  One

15 g of modified epoxy acrylate oligomer (CN 150/80), 10 g of bifunctional urethane acrylate oligomer (UA-5221), 5 g of hexafunctional urethane acrylate oligomer (EB-1290), 1 g of monofunctional acrylic monomer 10 g of a monofunctional acrylic monomer (isobornyl acrylate, IBOA), 6 g of a photoinitiator (Darocur 1173), 2 g of a photoinitiator (Irgacure 754), 0.2 g of a leveling agent BYK 333, 0.3 g of TEGO Airex 920, 0.5 g of adhesion promoter and 12 g of aluminum silicate were mixed to prepare a UV curable coating composition for a steel sheet.

Example  2

, 16 g of modified epoxy acrylate oligomer (CN 150/80), 10 g of bifunctional urethane acrylate oligomer (CN 966J75), 4 g of hexafunctional urethane acrylate oligomer (QU-1620), 1 g of monofunctional acrylic monomer 5 g of a photoinitiator (Darocur 1173), 3 g of a photoinitiator (Irgacure 754), 0.2 g of a leveling agent Rad 2250, 10 g of a defoaming agent TEGO Airex 920, 0.5 g of adhesion promoting agent and 12 g of aluminum silicate were mixed to prepare an ultraviolet curable coating composition for a steel sheet.

Example  3

15 g of a modified epoxy acrylate oligomer (3020-A80), 10 g of a bifunctional urethane acrylate oligomer (UA-5221), 5 g of a 6-functional urethane acrylate oligomer (EB-1290), 5 g of a monofunctional acrylic monomer 5 g of a photoinitiator (Irgacure 1173), 3 g of a photoinitiator (Irgacure 754), 0.2 g of a leveling agent Rad 2500, 10 g of a defoaming agent BYK 1790 (0.3 g), adhesion promoter (0.5 g) and aluminum silicate (11 g) were mixed to prepare an ultraviolet curable coating composition for a steel sheet.

Comparative Example  One

The composition was prepared without mixing the modified epoxy acrylate oligomer.

Specifically, 10 g of bifunctional urethane acrylate (UA-5221), 5 g of hexafunctional urethane acrylate oligomer (EB-1290), 15 g of hexafunctional polyester acrylate (EB-840), 1 g of a monofunctional reactive acrylic monomer 10 g of a monofunctional acrylic monomer (isobornyl acrylate, IBOA), 5 g of a photoinitiator (Darocur 1173), 3 g of a photoinitiator (Irgacure 754), 0.2 g of a leveling agent Rad 2250, 0.3 g of defoamer TEGO Airex 920, 0.5 g of adhesion promoter and 11 g of aluminum silicate were mixed to prepare a composition.

Comparative Example  2

The composition was prepared without mixing the modified epoxy acrylate oligomer.

Specifically, 25 g of a bifunctional urethane acrylate oligomer (UA-5221), 5 g of a hexafunctional urethane acrylate oligomer (EB-1290), 30 g of a monofunctional acrylic monomer (tetrahydroperfuryl acrylate, THFA) 5 g of a photoinitiator (IBOA), 5 g of a photoinitiator (Darocur 1173), 3 g of a photoinitiator (Irgacure 754), 0.2 g of a leveling agent BYK 333, 0.3 g of a defoamer TEGO Airex 920, And 11 g of aluminum silicate were mixed to prepare a composition.

Comparative Example  3

A composition was prepared using a quartz agent instead of an aluminum silicate quencher in a silica type quencher.

Specifically, 15 g of a modified epoxy acrylate oligomer (CN 150/80), 10 g of a bifunctional urethane acrylate oligomer (UA-5221), 5 g of a hexafunctional urethane acrylate oligomer (EB-1290) (Tetrahydrofurfuryl acrylate, THFA), 10 g of monofunctional acrylic monomer (isobornyl acrylate, IBOA), 6 g of photoinitiator (Darocur 1173), 2 g of photoinitiator (Irgacure 754), leveling agent BYK 333 0.2 , 0.3 g of antifoaming agent TEGO Airex, 0.5 g of adhesion promoter and 12 g of quencher (Silica).

Experimental Example

The compositions of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1 below. Each content is expressed in parts by weight with respect to 100 parts by weight of the total composition.

The ultraviolet curable coating layer 50 of the steel sheet as shown in Fig. 1 was formed using the ultraviolet curable coating composition for a steel sheet prepared in Examples 1 to 3 and Comparative Examples 1 to 3. 1 shows a structure in which a material layer 10, a zinc plating layer 20, a surface treatment layer 30, an oily color layer 40, and an ultraviolet curing coating layer 50 are sequentially laminated. When forming the ultraviolet-cured coating layer shown in FIG. 1, the coating layer is coated to a thickness of 5 to 10 μm through a bar coating, and then irradiated with ultraviolet rays at a curing intensity of 1500 mJ / cm ² using a UV- .

The properties of the respective steel sheets on which the ultraviolet cured coating layer was formed using the compositions of Examples 1 to 3 and Comparative Examples 1 to 3 were tested. Specifically, experiments were conducted to measure appearance, gloss, corrosion resistance, workability, impact resistance, adhesion and pencil hardness. The results are shown in Table 2 below.

Exterior Glossiness Corrosion resistance Processability Impact resistance Attachment Pencil hardness Example 1 ○ 22% ◎ 3T ○ ◎ 2H Example 2 ○ 20% ◎ 3T ○ ◎ 2H Example 3 ○ 25% ◎ 3T ○ ◎ 2H Comparative Example 1 ○ 21% ○ 6T × ○ 3H Comparative Example 2 ○ 22% ○ 4T ○ ◎ F Comparative Example 3 ○ 50% ◎ 3T ○ ○ 1H

- Appearance: It is evaluated whether it is good without foreign substance and uncoated area of appearance.

(?: No abnormality,?: Little Ti,?: Some cratering, X: multiple cratering and yellowing)

- Glossiness: Evaluated by measuring with a BYK polisher at 60 ° angle.

(Standard for construction materials: 30% or less)

- Corrosion resistance: Evaluate initial dryness by continuously spraying the coated specimen with 5% saline at a temperature of 35 ° C and a humidity of 95%.

(⊚: no more than 480 hours, ∘: initial screening after 240 hours, △: initial screening after 120 hours, ×: early screening before 72 hours, specifications for building materials: over 480 hours)

- Workability: When the test piece thickness is bent by using a VISE, the crack of the coating on the bent portion is visually observed.

- Impact resistance: After dropping at a height of 50 cm with a 500 g impact rod, observe cracking and peeling of the coating film surface.

(?: No abnormality,?: Cracking)

- Adhesion: 100 coated specimens of 1 mm in length and width are peeled off with 3M tape, and the adhesion of the coated film is evaluated.

(⊚: no abnormality, ∘: no more than 10 pieces, △: less than 50 pieces, ×: complete elimination)

- Pencil hardness: Indicates scratch resistance, measured according to JIS K5600-5-4KS. (Measurable from 9B to 9H, and stronger at 9H.)

Table 2 shows that most of the properties were satisfied in Examples 1 to 3 in which modified epoxy acrylate oligomer was the main constituent. On the other hand, in the case of Comparative Example 1 having a polyester acrylate oligomer as the main constituent, the processability and impact resistance were unfavorable. In Comparative Example 2 using the urethane acrylate oligomer alone, the pencil hardness was low, I could confirm a good thing. Also, in the case of Comparative Example 3 using a silica quencher, when a UV curing machine having a high hardening strength suitable for a high speed, which is a PCM line characteristic, was used, it was found that the desired gloss was out of the specification.

Therefore, when the ultraviolet curing coating compositions according to Examples 1 to 3 are applied to a steel sheet, desired physical properties can be expected, energy saving can be achieved instead of conventional heat curing type, and maintenance cost can be reduced. It does not require a solvent and can prevent environmental pollution.

10: Material layer
20: Zinc plated layer
30: Surface treatment layer (lower surface)
40: Oily color layer (top)
50: ultraviolet cured coating layer

Claims (15)

A modified epoxy acrylate oligomer, a urethane acrylate oligomer, a reactive acrylic monomer, a photoinitiator, an adhesion promoter, and a quencher,
Wherein the quencher is a plate-shaped aluminum silicate.
The method according to claim 1,
Based on 100 parts by weight of the total UV curable coating composition,
10 to 20 parts by weight of a modified epoxy acrylate oligomer,
10 to 25 parts by weight of a urethane acrylate oligomer,
35 to 50 parts by weight of a reactive acrylic monomer,
5 to 10 parts by weight of a photoinitiator,
0.1 to 2 parts by weight of an adhesion promoter, and
And 5 to 20 parts by weight of light-extinguishing agent.
The method according to claim 1,
Wherein the modified epoxy acrylate oligomer is an urethane-modified acrylate oligomer.
3. The method of claim 2,
The urethane acrylate oligomer comprises a bifunctional urethane acrylate oligomer and a hexafunctional urethane acrylate oligomer,
Wherein the bifunctional urethane acrylate oligomer and the 6-functional urethane acrylate oligomer are contained in a weight ratio of 5 to 15: 1 to 10.
3. The method of claim 2,
Wherein the reactive acrylic monomer is a monofunctional acrylic monomer.
The method according to claim 1,
Wherein the photoinitiator comprises at least one of benzophenone, benzoin, benzoin ether, benzyl ketal, acetophenone, anthraquinone, and thioxanzone.
The method according to claim 1,
Wherein the adhesion promoter is acrylic phosphate.
delete The method according to claim 1,
The flaky aluminum silicate quencher may be selected from the group consisting of montmorillonite, bentonite, hectorite, fluorohectorite, saponite, beidelite, nontronite, wherein the coating composition comprises at least one of nontronite, stevensite, vermiculite, volkonskoite, magadite and kenyalite. .
The method according to claim 1,
An antifoaming agent, and a leveling agent.
11. The method of claim 10,
Based on 100 parts by weight of the total UV curable coating composition,
0.1 to 1.0 part by weight of an antifoaming agent and
And 0.1 to 1.0 part by weight of a leveling agent.
Steel plate; And
A coating film formed on one side of the steel sheet and being a cured product of the ultraviolet curable coating composition for a steel plate according to any one of claims 1 to 7 and 9 to 10,
Wherein the coating film has a gloss of 15 to 30% when measured for a glossiness at an angle of 60 [deg.].
13. The method of claim 12,
Wherein the coating film has a pencil hardness of 1 H or more.
13. The method of claim 12,
Wherein the coating layer has a thickness of 1 to 20 占 퐉.
13. The method of claim 12,
Wherein the ultraviolet curing coating film is used as a steel sheet for building materials.

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