JPS6067574A - Coating composition curable with electron ray - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] A flat metal plate that is pre-painted is called pre-coated metal, and is used to assemble and process box-shaped products such as home appliances such as refrigerators and washing machines, vending machines, etc. Office equipment, etc. are manufactured. By using this pre-coated metal, home appliance manufacturers will no longer need a painting process, which will have a significant effect on streamlining and preventing pollution.

The most common method for producing pre-coated metal is to coat a surface-treated metal plate with a thermosetting paint using an appropriate method.
A method of heating and curing is used. Methods of heat-pressing thin films or adhesively laminating them via an adhesive layer are also used.

Precoated metal is mainly used for outdoor applications such as roofing materials and side walls of houses, and for indoor applications as described above. Required properties include processability, corrosion resistance, and water resistance, as well as weather resistance for outdoor use, and stain resistance and chemical resistance for indoor use, as well as hardness and aesthetics.

The inventors have continued to study to obtain a pre-coated metal mainly for indoor use that has excellent levels of hardness, workability, and stain resistance among these required performances. A coating composition of the invention was obtained.

Processability here refers to the ease with which a flat plate of precoated metal can be processed into shapes for various end uses and the resistance to damage. In other words, bending.

It can be said that precoated metal has good workability because the coating film is less damaged during processes such as drawing, extrusion, and cutting. Also, stain resistance means that the coating film is magic ink, crayon, or lipstick.

This is to see if the stain can be easily removed by appropriate means when it is stained with colored substances such as soy sauce. Needless to say, the coating film is excellent because it is resistant to contamination.

Although the inventors were able to obtain a coating film with excellent hardness, workability, and stain resistance, these performances could not be achieved in any of the known examples. The reason for this is that there is usually a relationship in which if one of these three performances is improved, one or more of the other two will necessarily be degraded. That is, increasing the hardness lowers the workability, and increasing the workability lowers the stain resistance.

In terms of the physical properties of the coating film, it is hard, has a high crosslinking density,
Furthermore, the above three performances can only be satisfied if the material has flexible characteristics. It is clear to those in the know that this is not something that can be achieved easily.

As a result of intensive study to overcome the above-mentioned difficulties, the inventors have discovered this invention.

That is, this invention has a number average molecular weight in the range of A8,000 to 4,00,000, and comprises one or more of acrylic esters or α-substituted acrylic esters, and acrylonitrile or methacrylonitrile. 100 parts of a copolymer containing at least one of them as the main component; 5 to 250 parts of a polyfunctional vinyl monomer or oligomer having a molecular weight of 5.000 or less and two or more radically polymerizable double bonds in one molecule as the main resin; The present invention relates to an electron beam curable coating composition that has excellent mechanical properties and stain resistance of the coating film.

The coating composition of this invention is an acrylic ester or α-
Good mechanical properties of the coating film due to the flexibility and toughness of the substituted acrylic acid ester polymer, and good stain resistance due to the chemical insolubility and non-staining property of the acrylonitrile or methacrylonitrile polymer. Further, the radically polymerizable polyfunctional monomer or oligomer acting as a crosslinking agent is cured by electron beams, and a densely crosslinked coating film with excellent hardness and durability can be obtained.

Examples of the acrylic acid or α-substituted acrylic ester in component A include, but are not limited to, the following. For example, methyl acrylate,
Alkyl acrylates and cycloalkyl esters such as ethyl acrylate, n-propyl acrylate, isobutyl acrylate, n-amyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 〇-octyl acrylate, acrylic 2-ethyl acrylate, halogenated alkyl acrylate such as 3-chloropropyl acrylate, hydroxyalkyl acrylate having an OH group such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, etc. ester, acrylic ester containing an ether ring such as glycidyl acrylate, and tetrahydrofurfuryl acrylate; acrylic ester containing an aromatic ring such as benzyl acrylate;
Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, n-amyl methacrylate, n-octyl methacrylate, methacrylic acid α-Alkyl acrylates and cycloalkyl esters such as lauryl, α-halogen acrylates such as methyl α-chloroacrylate, ethyl α-chloroacrylate, 2-chloroethyl methacrylate, methacrylic acid-
α-Alkyl acrylic acid halogenated alkyl esters such as 3-chloropropyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and α-containing OH groups such as 1-chloro-2-hydroxyethyl methacrylate. -Alkyl acrylic esters, methacrylic esters containing an ether ring such as glycidyl methacrylate, and tetrahydrofurfuryl methacrylate, and methacrylic esters containing an aromatic ring such as benzyl methacrylate. In this invention, one of these acrylic esters or α-substituted acrylic esters
It is preferable to use one or more species in an amount of 40 to 95% by weight of the total monomer. When copolymerized within this range, flexibility and toughness are the characteristics of acrylic esters or α-substituted acrylic esters.

The target excellent performance in terms of weather resistance is demonstrated.

Furthermore, regarding acrylonitrile or methacrylonitrile in component A, either or both must be copolymerized as main components. In order to obtain the target level of good stain resistance, it is preferable to use one or both of them in an amount of 5 to 60% by weight of the entire monomer. When copolymerized within this range, excellent performance in terms of stain resistance and chemical resistance, which are characteristics of acrylonitrile or methacrylonitrile, is exhibited. Any other polymerizable compound may be used as long as it does not disrupt the suitable composition range of the main component described above.

The copolymer may be polymerized by any of solution, suspension, and emulsion polymerization methods. However, when using various diluents to ultimately adjust the viscosity of the paint and make it easier to apply, it is most rational to use a solution polymerization method using the same diluent as the solvent. It can be said to be a method.

The effects of the present invention can be exerted regardless of whether the copolymer has unsaturated bonds in its molecules or not. 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 amount of unsaturated groups should be 0.00% per 1.000 molecular weight.
The number of unsaturated groups is preferably 3 or less.

The molecular weight of the copolymer is determined as a number average molecular weight of 8.0 by gel permeation chromatography, osmotic pressure method, end group determination method, etc. It is essential that it be in the range OOO to 400,000. If the molecular weight is less than 8,000, sufficient mechanical strength cannot be obtained and processability is poor. 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 or oligomer having a molecular weight of 5,000 or less as component B refers to a compound having two or more radically polymerizable double bonds in the same molecule. Although the distinction between monomers and oligomers has not been established, here we will distinguish those with a molecular weight of 500 or less as monomers, and those with a molecular weight of 500 to 5,000 as oligomers. Among these are: a ethylene glycol dimethacrylate or diacrylate.

b Molecular weight5. (Polyethylene glycol dimethacrylate or diacrylate of 1 o or less.

C Propylene glycol dimethacrylate or diacrylate.

d Polypropylene glycol dimethacrylate or diacrylate with a molecular weight of 5.000 or less.

e Trimethylolpropane trimethacrylate or triacrylate.

f Pentaerythritol tri- or tetramethacrylate, or tri- or tetraacrylate.

g Dipentaerythritol penta- or hexamethacrylate, or penta- or hexaacrylate.

h Methacrylic or acrylic ester of aliphatic polyol other than those mentioned above.

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

j A reaction between an isocyanate compound having a valence of 2 or more and a compound having an unsaturated group and an active hydrogen.

For example, a compound obtained by reacting hexamethylene diisocyanate alone or an adduct with 2-hydroxyethyl methacrylate.

0 k An oligomer with unsaturated bonds at both ends obtained by the reaction of diisocyanate, diol (aliphatic, polyester, polyether, etc.) and an unsaturated compound with active hydrogen.

■ Diallyl phthalate Allyl compounds such as diallyl maleate and dially itaconate.

m Divinyl compounds such as divinylbenzene and divinyltoluene.

n Unsaturated epoxy ester obtained by reaction of epoxy resin and unsaturated acid.

0 A polyfunctional monomer obtained by adding an unsaturated acid to glycidyl methacrylate or glycidyl acrylate.

p A polyfunctional monomer obtained by adding glycidyl methacrylate or glycidyl acrylate to a polycarboxylic acid.

q A polyfunctional monomer obtained by adding glycidyl methacrylate or glycidyl acrylate to a primary amino compound.

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

S Polyfunctional monomer or oligomer obtained by adding polyhydric alcohol and glycidyl methacrylate or glycidyl acrylate.

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

U Esterification product of OH-terminated polyester and unsaturated acid.

The properties required of these polyfunctional monomers or oligomers include being able to be cured by electron beam irradiation, forming a cross-linked network bond or entangled structure with the copolymer of component A, and forming a strong film structure. Mechanical properties and stain resistance as a coating film.

It is important to provide good performance in terms of chemical resistance, water resistance, etc. These polyfunctional monomers or oligomers must be used in an amount of 5 to 250 parts per 100 parts by weight of component A. If it is less than 5 parts, the coating film will be insufficiently cured and have poor solvent resistance, and if it exceeds 250 parts, the coating film will have reduced flexibility and poor mechanical properties. The reason why the amount per molecule is 5.000 or less is because it is preferable in terms of curing properties based on the mobility of one molecule that is compatible with the acrylic copolymer.

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

Monofunctional vinyl monomers are divided into volatile and nonvolatile monomers. Volatile substances do not become paint film components, so they are used only as diluents. Representative examples of these include methyl methacrylate,
Examples include methyl acrylate, ethyl acrylate, butyl acrylate, and vinyl acetate. Most of the non-volatile polymer diluent is mixed into the cured film after curing. Therefore, it has a large influence 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.

Included are higher fatty acid ester acrylates such as isodecyl methacrylate and lauryl methacrylate, 32 or methacrylate, styrene, vinyl toluene, and the like.

Non-polymerizable diluents undergo an evaporation process before electron beam irradiation,
Alternatively, most of it must be volatilized by forced heating and drying. If a large amount remains, the processing adhesion of the coating film,
Serious defects often occur in water resistance, chemical resistance, etc. It is also possible to use the polymerization solvent used in the synthesis of the acrylic copolymer of component A and the solvent used in the synthesis of the polyfunctional monomer or oligomer of component B as a diluent. Examples of such diluents include the following. These include ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, methyl isobutyl ketone, isopropyl alcohol, toluene, and xylene. The amount of diluent required is governed by the appropriate viscosity at the time of application. Since this appropriate viscosity varies greatly depending on the coating method, type of coating machine, coating speed, film thickness, and 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 as long as the gist of the invention is not impaired. Such components include pigments and fillers for coloring, hiding effects, etc., surfactants, dispersants, plasticizers, ultraviolet absorbers, and antioxidants. The proportions of these components in the composition can vary within a wide range depending on the performance required of the final product.

This composition exhibits its characteristics most when used as a coating on various types of iron plates (e.g., 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. Demonstrate. When a painted film is formed on such a substrate, it can be pressed or extruded into various shapes because of the excellent workability of the cured film.

The coating structure formed on a substrate using the present composition can be a single 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, a multilayer structure is used in which the present composition containing a corrosion-resistant pigment is placed in the lower layer, and the present composition containing a colored pigment is placed in the upper layer. be able to. In addition, if high processability and stain resistance are required, a primer with good adhesion to the base material is applied as the lower layer, and this composition with good processability and stain resistance is applied as the upper layer. be able to.

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.

The method for curing this composition is usually to irradiate it with high-energy electron beams. A high-energy electron beam has an acceleration energy of 0.1 to 3. With OMeV electron beam,
Kotsukucroft type, Kotsukucroft Walton type, bread/
Refers to what is emitted from each of the five types of electron beam accelerators, including the De Graff type, resonant transformer type, insulated core transformer type, linear type, Dynamidron type, high frequency type, and electrocurtain 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, and if it exceeds 20 M rad, excessive crosslinking will occur. The range of 0.1 to 20 Mar is suitable because the coating film is insufficient in flexibility. Oxygen inhibits or suppresses curing, so nitrogen is used as the atmosphere during irradiation.

Preferably, the reaction is carried out in an inert gas such as carbon dioxide, helium, argon, neon, or combustion gas.

The coating film made from the above-mentioned composition according to the present invention can sufficiently satisfy various required performances, such as processability, stain resistance, corrosion resistance, and water resistance. In particular, remarkable improvements were achieved in stain resistance and workability that were unprecedented. These characteristics are especially exhibited in the field of precoated metals.

Examples according to the present invention are shown below.

(Example 1) (Production of 11 copolymer 7 6 Prepare a fourth flask (21) equipped with a stirrer, reflux condenser, inert gas inlet, and raw material inlet, and prepare a monomer solution with the following composition. and mixed.

The above mixture was stirred and polymerized at 70° C. under a nitrogen stream. After 5 hours, the solution became highly viscous due to polymerization. Next, a monomer solution having the following composition was added dropwise to the above polymerization solution over a period of 6 hours, and the polymerization was continued at 70°C.

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

Furthermore, polymerization was continued at 70° C. for 5 hours to increase the polymerization rate.

Polymerization was terminated by adding the following:

The solid content of the obtained copolymer solution was 32.6%, and the number average molecular weight of the polymer was 45,000 (measured by GPC).

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

Table 1 (Paint composition) Ma.

<31 Manufacture of coated plate An epoxy primer containing a corrosion-resistant pigment was applied to a thickness of 2 μm, and then the resulting paint was applied to a heat-cured electrogalvanized steel plate (thickness 9 mm and length 0.6 mm) to a solid content film thickness (primer (including) is 27μ, coated with a bar coater,
It was placed in a hot air oven at 30°C for 3 minutes to volatilize the thinner. Next, this coated plate was exposed to a voltage of 300 KV under a nitrogen stream.
2 M r a with an ICT electron beam accelerator with a current of 65 mA
d electron beam was irradiated.

(4) Performance evaluation Table 2 (Coating film performance) 1 0 It can be seen that all of them show satisfactory values.

(Example 2) f, 1) Production of copolymer A monomer solution having the following composition was prepared and polymerized in the same manner as in Example 1. After 5 hours at 70°C under a nitrogen stream, the solution became highly viscous. Then, a monomer solution having the following composition was added dropwise over 5 hours to continue polymerization.

2 Next, the following solution was added dropwise over 2 hours, and polymerization was continued at 70°C.

Polymerization was further continued at 70° C. for 5 hours to increase the polymerization rate. Polymerization was terminated by adding the following:

The number average molecular weight of the obtained copolymer was 52,000.

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

(Left below) Table 3 (Paint composition) An electrogalvanized steel sheet (0.0mm thick) coated with an epoxy primer containing zinc chromate to a thickness of 2μ and heat cured.
The above-obtained paint was coated onto a 6 mm thick film using a bar coater so that the solid content film thickness (including the primer) was 27 μm, and an electron beam-cured coated plate was obtained in the same manner as in Example 1.

(4) Performance Evaluation Table 4 (Coating Film Performance) The results in Table 4 show that hardness, workability, and stain resistance all show satisfactory values.

(Comparative Example 1) +11 Manufacture of copolymer In the copolymer manufacturing method of Example 1, polymerization was carried out by not using acrylonitrile as the monomer and replacing it with methyl methacrylate of the same weight, which has approximately the same Tg of the polymer. did.

First, a monomer solution having the following composition was stirred and polymerized in the same manner as in Example 1.

Next, a monomer solution having the following composition was added dropwise in the same manner as in Example 1 and polymerized.

6 and polymerized.

Furthermore, polymerization was continued in the same manner as in Example 1, and the following was added to complete the polymerization.

The solid content of the obtained copolymer solution was 33.0%, and the number average molecular weight of the polymer was 56,000.

(2) Production of paint and painted board Using the copolymer obtained above, paints having the compositions shown in Table 5 were produced.

(Hereafter, extra white) A coated steel plate cured by electron beam was obtained.

(Margins below) 7 (3) Performance Evaluation Compared to the results in Table 2, the results of this comparative example, in which a copolymer without acrylonitrile copolymerized was used as component A, did not have sufficient stain resistance.

This shows that by using the composition of the present invention, a coating film with excellent mechanical properties and stain resistance can be obtained.

Agent: Patent Attorney Takehiko Matsumoto 9 8

Claims (1)

[Scope of Claims] A number average molecular weight in the range of 8,000 to 400,000, and at least one of acrylic esters or α-substituted acrylic esters, and acrylonitrile or methacrylonitrile. 100 parts of a copolymer having either one of them as the main component B. 5 to 250 parts of a polyfunctional vinyl monomer or oligomer having a molecular weight of 5.000 or less and having two or more radically polymerizable double bonds in one molecule as the main resin component. An electron beam curable coating composition with excellent mechanical properties and stain resistance.