JPS5930870A - Electron beam-curable coating composition - Google Patents

Abstract

PURPOSE:To provide titled composition of good processability, capable of giving coating film of high crosslinking density and rigidity, for use in precoat metal manufacturing, comprising a specific proportion of a multifunctional vinyl monomer and specific (un)saturated acrylic copolymer consisting mainly of (substituted) acrylic ester(s). CONSTITUTION:The objective composition comprising (A) 10pts.wt. of a (un) saturated acrylic copolymer with a number average molecular weight of 8,000- 400,000 and a glass transition point ranging from -50 deg.C to 20 deg.C, consisting mainly of at least one sort of (alpha-substituted) acrylic ester, (B) 1-100pts.wt. of a second (un)saturated acrylic copolymer with a number average molecular weight of 8,000-400,000 and a glass transition point of 10-70 deg.C (higher than that of the component (A) by >=2 deg.C), consisting mainly of at least one sort of (alpha-substituted) acrylic ester, and (C) 5-100pts.wt. per 100pts.wt. of the sum of the components (A) and (B), of a multifunctional vinyl monomer with a molecular weight <=2,000 and at least two radical polymerizable double bonds in one molecule. EFFECT:Giving coating film of high stain, chemical, and water resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam curable coating composition for precoated metal that has excellent mechanical properties of the coating film.

Precoated metal is a material that is painted or coated before processing, and its production has increased significantly in recent years as it provides a significantly more streamlined manufacturing method for metal products compared to conventional methods such as press working that are coated after processing. ing.

The most common method for manufacturing such pre-coated metal is to apply a thermosetting paint to a surface-treated metal plate by an appropriate means and heat cure it. Alternatively, a method of heat-pressing thin films or adhesively laminating them via an adhesive layer is also used.

Precoated metal is primarily used for both outdoor applications, such as roofing materials and side walls of houses, and indoor applications, such as interior walls, cabinets, and home appliances.
In addition to corrosion resistance, weather resistance and processability are particularly required for outdoor applications, and high processability, stain resistance, and chemical resistance are particularly required for indoor applications. Furthermore, there are many required performance items such as water resistance, boiling water resistance, hardness, and aesthetic appearance (and the level thereof is extremely high).

Among these required performances, the present inventors have continued to study workability, especially improving bending workability, and have found that the paint film has excellent stain resistance, chemical resistance, water resistance, and The present inventors have succeeded in obtaining a coating composition of the present invention that provides a coating film with high coating film hardness and excellent workability without impairing various properties such as water boiling properties.

Processability here refers to the ease of processing and the degree of damage resistance when forming a flat plate of pre-coated metal into shapes for various end uses. In other words, it can be said that the precoated metal has good workability because the coating film is less damaged in processes such as bending, drawing, extrusion, and cutting.

There are various known examples of coating compositions used therefor. However, the workability of both methods was insufficient, and improvements were desired. This is because, although it is preferable to have a high crosslinking density and high hardness in terms of durability of the coating film, from the viewpoint of processability, all of these factors act in an unfavorable direction.

In view of the above circumstances, the inventors of the present invention have conducted intensive studies on the problem of improving workability while maintaining a high level of crosslinking density and hardness, and have now completed the present invention.

That is, the present invention has a number average molecular weight in the range of A8,000 to 400,000, contains one or more of acrylic esters or α-substituted acrylic esters as a main component, and has a glass transition point of 150. A saturated or unsaturated acrylic copolymer having a number average molecular weight in the range of 8,000 to 400,000, and one or more α-substituted acrylic acid ester straddling α-substituted acrylate copolymers or A saturated or unsaturated acrylic copolymer which has the above as its main components, has a glass transition point in the range from lo to 70'C, and has a glass transition point at least 2 degrees Celsius or higher than that of component A.
1 to ioo part C A polyfunctional vinyl monomer having a molecular weight of 2,000 or less and having two or more radically polymerizable type 2 bonds in one molecule, based on 100 parts of the total of the components A and BIi'Fii 5 to 100
The gist of the invention is an electron beam curable coating composition that has excellent mechanical properties of the coating film and has a main sealant component.

Since the coating composition of the present invention combines an acrylic copolymer with a low glass transition point and an acrylic copolymer with a high glass transition point, it is possible to form a flexible coating film based on the properties of the former, and has good processability. Based on the latter characteristic, good surface properties and durability obtained by a hard coating film can be successfully exhibited.

Furthermore, since the radically polymerizable polyfunctional vinyl monomer that acts as a crosslinking agent is cured by electron beam irradiation, it is possible to provide a densely crosslinked coating film with excellent IJ durability, stain resistance, and chemical resistance.

Examples of the acrylic acid or α-substituted acrylic ester in components A and B include, but are not limited to, the following. For example, alkyl acrylates such as methyl acrylate, ethyl acrylate, -propyl acrylate, isobutyl acrylate, -amyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, and n-octyl acrylate. and cycloalkyl esters, alkyl acrylate halides such as 2-chloroethyl acrylate, 3-')lolpropyl acrylate, acrylic rJIl-2
- Acrylic acid hydroxyalkyl esters with OH groups such as hydroxyethyl and 2-hydroxypropyl acrylate; acrylic esters containing ether rings such as glycidyl acrylate and tetrahydrofurfuryl acrylate; aromatic rings such as benzyl acrylate; Acrylic esters containing methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, n-amyl methacrylate, methacrylate -n-octyl acrylate, α-alkyl acrylate and cycloalkyl ester such as lauryl methacrylate, α-halogen acrylate ester such as methyl α-chloroacrylate, ethyl α-chloroacrylate, 2-chloroethyl methacrylate , α-alkyl acrylic acid halogenated alkyl esters such as 3-chloropropyl methacrylate, OH such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 1-chloro-2-hydroxyethyl methacrylate. Examples thereof include α-alkyl acrylic esters having a group, glycidyl methacrylate, ether ring-containing methacrylic esters such as tetrahydrofurfuryl methacrylate, and methacrylic esters containing an aromatic ring such as benzyl methacrylate. In the present invention, it is preferable for the acrylic copolymer of both components A and B to use one or more of these acrylic esters or α-substituted acrylic esters in an amount of 50 or more by weight based on the entire monomer. Any other polymerizable compound may be used as the remaining monomer.

The glass transition point refers to the temperature at which a polymer changes from a hard, glass-like state to a rubber-like state, and is generally a measure of the hardness or softness of a polymer. A component is -50℃ to 20℃
Preferably, it is a soft resin component having a glass transition point in the range of 10 to 20°C, and component B is a hard resin component having a glass transition temperature in the range of 10 to 70°C, preferably 10 to 50°C. These A.

When the difference in the glass transition points of both components B is preferably 2 DEG C., preferably 1-j5 DEG C. or more, the respective desirable characteristics of both components are fully exhibited. Preferable performance can be obtained when the glass transition point of the resin mixed with component A and 111 is in the range of -5°C to 40°C.

These acrylic copolymers can exhibit the effects of the present invention whether or not they have unsaturated bonds in their molecules. An unsaturated bond can be introduced into the side chain or the end of the main chain by utilizing the reactivity of the functional group. If the amount of unsaturated groups is too large, the crosslinking density will become excessive and processability will decrease, so the molecular weight should be 1.0.
It is preferable that the number of unsaturated groups is 0.3 or less per 00.

It is necessary to mix the A and B component copolymers so that the A component is 10 parts and the B component is 1 to 100 parts. If this range is exceeded, only the characteristics of one component will be exhibited, and it will be impossible to simultaneously achieve high levels of hardness and workability, which are the characteristics of the present invention.

The polymerization method for these acrylic copolymers may be any one of solution, suspension, and emulsion polymerization methods.

The molecular weight of Coholima is determined as a number average molecular weight of s, ooo to 400. It is necessary that it be relatively large, such as OOO. The molecular weight is s, oo.

If it is smaller, sufficient mechanical strength of the coating film cannot be obtained,
Poor workability. On the other hand, if it is larger than 400.000, the fluidity of the coating film will be insufficient and a coating film with good surface condition will not be obtained.

The polyfunctional vinyl monomer having a molecular weight of 2.000 or less as component C refers to a compound having two or more radically polymerizable double bonds in the same molecule.

Among these are: a ethylene glycol dimethacrylate or diacrylate.

b Polyethylene glycol dimethacrylate or diacrylate with a molecular weight of 2,000 or less.

C Propylene glycol dimethacrylate or diacrylate.

d Polypropylene glycol dimethacrylate or diacrylate with a molecular weight of 2,000 or less.

e Trimethylolpropane trimethacrylate or triacrylate.

f Pentaerythritol trimethacrylate or triacrylate.

g A phosphate ester-based polyfunctional monomer such as trisacryloxyethyl phosphate.

h A polyfunctional monomer having a divalent or higher valence isocyanate and an unsaturated group. For example, a compound obtained by a 2-hydroxyethyl methacrylate reaction sequence with hexamethylene diisocyanate alone or an adduct, or with tolylene diisocyanate alone or an adduct.

i Allyl compounds such as diallyl phthalate, diallyl maleate, diallylitaconate.

j Divinylbenzene.

k An unsaturated epoxy ester obtained by the reaction of an epoxy resin and an 11th acid, with a molecular weight of 2.000 or less.

1 Glycidyl methacrylate) A polyfunctional monomer obtained by adding an unsaturated acid to glycidyl acrylate.

m A polyfunctional monomer obtained by adding glycidyl methacrylate or glycidyl acrylate to a polyvalent carboxylic acid.

A polyfunctional monomer obtained by adding glycidyl acrylate or diacrylate to an n-amino compound.

0 A polyfunctional monomer obtained by adding an unsaturated alcohol to a compound having a glycidyl group.

p A polyfunctional monomer obtained by adding polyhydric alcohol and glycidyl methacrylate or glycidyl acrylate.

q A polyfunctional monomer obtained by reacting glycerin with an unsaturated carboxylic acid.

r An esterification product of polyester with terminal OH groups and unsaturated acid, with a molecular weight of less than 2,000.

S A polyfunctional monomer obtained by the reaction of a polyhydric alcohol and an unsaturated carboxylic acid, other than those described in items a to f.

The properties required of these polyfunctional monomers include that when they are cured by electron beam irradiation, they form crosslinked network bonds with the acrylic copolymer to form a strong film structure;
It is important that the mechanical properties, stain resistance, chemical resistance, water resistance, etc. of the coating film are not adversely affected. These polyfunctional vinyl monomers must be used in an amount of 5 to 100 parts based on 100 parts of the total weight of components A and H.

If it is less than 5 parts, the coating film will be insufficiently cured and its solvent resistance will be poor, and if it exceeds 100 parts, the film's removability will decrease (
-1 The mechanical properties become inferior.

The reason why the molecular weight is 2.000 or less is because h is preferable in terms of compatibility with the acrylic copolymer and handling properties as a liquid.

In addition to the above main components A, B, and C, monofunctional vinyl monomers, volatile diluents, etc. may be added as necessary.

Monofunctional vinyl monomers and L7 are divided into volatile and non-volatile ones, but volatile ones do not become coating film components and are therefore used only as a diluent. Representative examples of these include methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, and vinyl acetate. Most of the non-volatile polymerizable diluent is mixed into the cured coating film after curing. Therefore, it has a large effect on the performance of the coating film, and it is necessary to pay sufficient attention to its selection.

Among these are cyclohexyl methacrylate,
Ethylhexyl methacrylate, indecyl methacrylate 1
/-t, higher fatty acid ester acrylates such as lauryl methacrylate, methacrylates, styrene, vinyltoluene, and the like.

Non-polymerizable diluents are limited to volatile ones.

Most of these non-polymerizable diluents must be evaporated by an evaporation process or forced heat drying before electron beam irradiation. If a large amount remains, serious defects often occur in the processing adhesion, water resistance, chemical resistance, etc. of the coating film. Furthermore, the polymerization solvent used in the synthesis of the acrylic copolymers of components A and H and the solvent used in the synthesis of the polyfunctional vinyl monomer of component C can also be used subsequently as diluents. Examples of such diluents include the following. Ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, methyl isobutyl ketone,
Examples include isopropyl alcohol, toluene, and xylene. The required amount of diluent is determined by the appropriate viscosity at the time of coating. Since this appropriate viscosity varies greatly depending on the coating method, type of coating machine, coating speed, film thickness, and degree of surface condition, the amount of diluent used can be adjusted to any desired ratio.

In addition to the above-mentioned components, other components can be added to the present composition as long as the gist of the present invention is not impaired. Such components include pigments, fillers, surfactants, dispersants, plasticizers, ultraviolet absorbers, antioxidants, etc. for the purpose of coloring, paint effect, etc. The proportions of these components in the composition can vary within a wide range depending on the performance required of the final product.

When this composition is used by coating on various iron plates (for example, untreated bare steel plates, zinc-treated steel plates, zinc phosphate-treated steel plates, etc.) and thin metal plates for pre-coated metal such as aluminum thin plates, the composition has the highest percentage. exhibit symptoms. When a painted film is formed on such a substrate, these coated plates can be pressed or extruded into various shapes because of the excellent workability of the cured film.

The coating structure of the present composition on a substrate can have various structures such as a single layer structure made of a single composition or a multilayer structure made of two or more layers made of different compositions. In particular, when a high degree of corrosion resistance is required, such as in the case of colored iron plates, the lower layer may contain the present composition containing a corrosion-resistant pigment or any other composition, and the upper layer may contain the present composition containing a colored pigment. It can be made into a multilayer structure using Further, when a high degree of processability is required, a primer with good adhesion to the base material can be used as the lower layer, and the present composition with good processability can be applied as the upper layer.

Various methods are possible for forming a thin film structure using this composition. For example, methods such as spraying, roller coating, curtain flow coating, casting, and knife coating are possible. It is also possible to apply heat or pressure to reduce the viscosity of the coating.

A method of curing this composition is to irradiate it with high-energy electron beams. High-energy electron beams are electron beams with acceleration energy of 0.1 to 3.0 MeV, and include Cockcroft type, Cockcroft-Walton type, Pan de Graff type, resonant transformer type, insulated core transformer type, and linear type. Refers to the books emitted from various types of electron beam accelerators, such as dynamitron type and high wave type. The irradiation amount can be freely changed within a wide range depending on the required coating hardness and coating performance, but if it is less than 0.1 M rad, the coating hardness will be insufficient.
If the temperature is higher than 20 Mrad, excessive crosslinking will occur and only a coating film lacking in flexibility will be obtained.
A range of is appropriate. The atmosphere during irradiation is preferably an inert gas such as nitrogen, carbon dioxide, helium, argon, neon, or combustion scum, since oxygen has the effect of inhibiting or suppressing curing.

The coating film made from the above-mentioned composition of the present invention can sufficiently satisfy various required properties, such as weather resistance, corrosion resistance, processability, chemical resistance, stain resistance, water resistance, and boiling water resistance. Among these, remarkable improvements were achieved that were unprecedented, especially in workability. This is because the use of two types of acrylic copolymers with relatively high molecular weights and different glass transition points causes a phenomenon in which the coating film hardness is high and the processability is good. In other words, a polymer with a high glass transition point increases hardness, and a polymer with a low glass transition point improves processability, which are both characteristics that can be clearly expressed in the present composition. It is from. This kind of performance is particularly evident in the field of pre-coated metals, which have high workability and durability.

Examples according to the present invention are shown below.

Example 1 (1) Polymerization stirrer for acrylic copolymer (A-1),
A four-bottle flask (2/2) equipped with a reflux condenser, an inert gas inlet, and a raw material inlet was prepared, and a monomer solution having the following composition was prepared and mixed.

The above mixture was stirred and polymerized at 70°C under a nitrogen stream. 3
Over time, the solution became highly viscous due to polymerization. Next, a monomer solution having the following composition was prepared and added dropwise to the above solution over 4 hours, and polymerization was continued at 70°C.

Then, [bupur acetate 182.111] was added dropwise over 2 hours, and polymerization was continued at 70°C.

Polymerization was further continued at 70° C. for 5 hours to complete polymerization of unreacted monomers.

After the polymerization was completed, the following were added.

The solid content of the obtained acrylic copolymer solution was 315%.
The number average molecular weight of the polymer was determined to be 78,000 by gel-noise migration chromatography. The glass transition temperature of this copolymer was determined by differential calorimetry to be 5°C.

(2) Polymerization of acrylic copolymer (B-1) A-
Polymerization was carried out in the same manner as in 1.

First, a Motsuma solution having the following composition was polymerized at 70° C. for 5 hours.

A monomer solution with the following composition was then heated with E for 6 hours.
The solution was added dropwise to the above solution, and polymerization was continued at 70'C.

Then, was added dropwise over 2 hours, and polymerization was continued at 70°C.

Polymerization was further continued at 70° C. for 5 hours to complete polymerization of unreacted monomers.

After the polymerization was completed, the following were added.

The solid content of the obtained acrylic copolymer solution was 33.6%, the number average molecular weight of the polymer was 75.000, and the glass transition point was 21°C.

(3) Comparative Example Polymerization of acrylic copolymer (X-1) Polymerization was carried out in the same manner as in the polymerization of A-1 described above.

1-First, a monomer solution having the following composition was polymerized at 70°C for 4 hours.

Next, a monomer solution having the following composition was added dropwise to the above solution over 5 hours, and polymerization was continued at 70°C.

Then, was added dropwise over 2 hours, and polymerization was continued at 70°C.

Polymerization was further continued at 70° C. for 5 hours to complete polymerization of unreacted monomers.

After the polymerization was completed, the following were added.

The solid content of the obtained acrylic copolymer bath liquid was 33.6%, the number average molecular weight of the polymer was 74.000, and the glass transition point was 13°C.

(3) Production of paint Using the acrylic copolymer obtained above, a paint was produced using a three-roll type paint forming apparatus. The composition of the paint is shown in Table 1.

(Margins below) Table 1 (4) Manufacture of coated plate The above paint was applied using a bar coater to an electrogalvanized steel plate (thickness Q, 6 mm') that had been coated with an epoxy primer to a thickness of 2μ and cured by heat. Then, it was placed in a hot air oven at 130°C for 3 minutes to volatilize the thinner.

Next, this coated plate was applied under a nitrogen stream at a voltage of 300 KV and a current of 6
A 2 M rad electron beam was irradiated with a 5 mA ICT electron beam accelerator.

(5) Performance evaluation table 2 As can be seen from the data in the table, acrylic copolymer A-
1 and B-1 (the measured glass transition point of the mixed copolymer is 13°C). It is superior to

Example 2 (1) Comparative example acrylic copoly-r (x-2)
'D Polymerization Polymerization was carried out in the same manner as the polymerization of A-1 described above.

First, a monomer solution having the following composition was polymerized at 70'C for 4 hours.

Polymerization was then continued at 70''C while a monomer solution having the following composition was added dropwise to the above solution over 5 hours.

Methyl autoacrylate 142.9 // was then added dropwise over 2 hours, and polymerization was continued at 70°C.

The polymerization was further continued at 70° C. for 5 hours, and unreacted monomers were polymerized to complete the polymerization.

After the polymerization was completed, the following were added.

The solid content of the obtained acrylic copolymer solution was 33.6, the number average molecular weight was 76.000, and the glass transition point was 16°C. (2) Acrylic copolymer A obtained in the production of paint 1,B-1゜X-2
A paint was produced using a three-roll paint forming apparatus. The composition of the paint is shown in Table 3.

Table 3 (3) Manufacture of coated plate A coated steel plate cured by electron beam was prepared using the paint shown in Table 3 in exactly the same manner as in Example 1.

(4) Performance evaluation table 4 As can be seen from the data in Table 4, acrylic copolymer A-
The bending processability of the coating film obtained by mixing A.
It is superior to other paint films.

Example 3 (1) Polymerization of acrylic copolymer Using the monomer composition shown in Table 5, the fourth flask
Polymerization was carried out in 5 (21) with 350 g of butyl acetate and 0.46 g of azobisisobutyronitrile while stirring at F70°C in a nitrogen stream. After 4 hours, add 150 g of butyl acetate and 0.16 g of azobisisobutyronitrile.
g was added, and the polymerization was continued for an additional 6 hours. Then, 150 g of butyl acetate, 0.2 g of hydroquinone methyl ether
211 was added and stirred well. The number average molecular weight and glass transition point of the obtained acrylic copolymer are shown in Table 6.

Table 6 (2) Manufacture of paint Acrylic cobo IJ ma A-2, 8-2 obtained above.

A paint was produced using a three-roll paint forming apparatus using X and -3. The coating composition is shown in Table 7.

(Margins below) Table 7 (3) Manufacture of coated plate A coated steel plate cured by electron beam was prepared using the paint shown in Table 7 in exactly the same manner as in Example 1.

(4) Performance evaluation wise 8 As can be seen from Table 8, acrylic copolymers A-2 and B-
Bending of the coating film using Aku1 Norcobo 1 Tsuma X-3 having the same glass transition point It's better than that.

Example 4 (1) Production of unsaturated acrylic copolymer Acrylic copolymer A-2゜B- obtained in Example 3
A 1-da copolymer was produced by introducing a double bond into the side chain using 2.X-3.

That is, 0.25 parts of glycidyl methacrylate and 0.002 parts of triethylbenzylammonium chloride were added to 100 parts of each copolymer solution (solid content 34.0%).
The reaction was carried out at 110°C for 8 hours. Before the reaction started, the acid value was 1.95, but as a result of the reaction, the acid value decreased to 0.4.
It was 9. This indicates that the carboxyl group in the copolymer and glycidyl methacrylate reacted, 2 and a double bond was introduced into the side chain.

(2) Paint manufacturing A paint was manufactured using the unsaturated acrylic copolymer obtained above. The coating composition is shown in Table 9.

(3) Production of coated plate The primer obtained above was coated onto an electrogalvanized steel plate (thickness: 0°6 mm) to a solid film thickness of 3 μm. This was placed in an open oven at 130°C for 1 minute to volatilize the thinner. Further on top of the primer, the resulting top coat f:
It was applied to a solid film thickness of 25 μm. This is 130
The thinner was volatilized by placing it in an open oven at ℃ for 3 minutes. Next, electron beam irradiation was performed in the same manner as in Example 1.

(4) Performance evaluation Table 10 shows performance evaluation data of Examples and Comparative Examples.

(Margin below) Table 10 From Table 10 above, acrylic copolymer A-21), B-2D
It can be seen that the bending processability of the coating film produced by the mixed system is superior to that of a single copolymer having the same glass transition temperature.

that's all 2-6 Otemachi, Chiyoda-ku, Tokyo number 3 ■Applicant: Nippon Paint Co., Ltd. 2-1 Oyodokita, Oyodo-ku, Osaka City '2 No. ■Applicant: Dainippon Elio Co., Ltd. Ichigaya Kagacho-chome, Shinjuku-ku, Tokyo Number 12

Claims (1)

[Scope of Claims] A It has a number average molecular weight in the range of 8,000 to 400,000, contains one or more types of acrylic acid esters, α-[transformed heptaacrylic esters, etc. as a main component, and has a glass transition property. 10 parts of a saturated or unsaturated acrylic copolymer having a point in the range of 150 to 20'C Is having a number average molecular weight in the range of 8,000 to 400,000 and containing acrylic ester or α-substituted acrylic acid It contains one or more esters as a main component, has a glass transition point in the range of 1O to 70'C, and further contains the above-mentioned A
A saturated or unsaturated acrylic copolymer with a glass transition point at least 2°C or higher than its constituents.
1 to 100 parts C 5 to 100 parts of a polyfunctional vinyl monomer having a molecular weight of 2.000 or less and having two or more radically polymerizable type 2 bonds in one molecule, per 100 parts of the sum of both components A and B. An electron beam curable coating composition with excellent mechanical properties of the coating film, which has a main resin component.