JPH0441190B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a photocurable rust preventive coating composition, and more specifically, a photocurable rust preventive coating composition that is useful for temporary rust preventive treatment of steel materials and is easy to remove with alkali. Regarding. [Technical background of the invention and its problems] At present, so-called steel materials such as rolled steel plates, steel pipes, wire rods, and steel bars are treated with mineral oil-type and dry-type rust prevention for the purpose of rust prevention during the period from the manufacturer to the user. The coating film formed by coating with a rust preventive agent or water-soluble resin is removed with an alkaline aqueous solution such as sodium silicate or sodium hydroxide in a pre-treatment process for painting by the user. However, the currently used mineral oil type, dry type, and water-soluble resin rust preventive agents do not dry well after curing and become sticky, take a long time to dry, and have poor corrosion resistance. There were problems such as insufficient coating performance such as moisture resistance. For this reason, there has been a strong demand for a temporary protective coating that cures in a short time, does not leave a sticky coating, and does not have to worry about solvent volatilization. Therefore, efforts are being made to develop temporary protective coating materials that suitably combine one or more monomers or oligomers with polymerizable unsaturated groups that react when irradiated with so-called active energy rays such as ultraviolet rays. Conventional temporary protective coating materials harden in a short time at room temperature and are affected by residual stress and volumetric shrinkage, resulting in poor adhesion to base materials such as metals. Currently, they are used in combination with additives. However, if additives such as adhesion promoters are used together when applying rust preventives to steel materials, the moisture resistance of the paint film and stability of the paint will be poor, so there are major restrictions on the use of these additives in combination. will receive. In addition, in the process of removing the rust preventive coating, it is necessary that the coating film be easily removed using a 1 to 10% by weight aqueous solution of sodium hydroxide or sodium orthosilicate, but conventional UV-curable coating materials However, it has been difficult to strike a balance between film removability and coating film performance such as corrosion resistance and moisture resistance. In other words, those with good coating film performance such as corrosion resistance and moisture resistance have poor film removability, while those with good film removability have the disadvantage of poor coating film performance such as corrosion resistance and moisture resistance. It was hot. Therefore, it has been desired to develop a composition for a photocurable rust preventive coating (hereinafter referred to as a photocurable rust preventive coating composition) that does not have the above drawbacks. [Object of the invention] The present invention aims to provide a photocurable rust-preventive coating composition that has a good balance of film performance such as film removability, corrosion resistance, and moisture resistance without using an adhesion promoter. purpose. [Summary of the Invention] As a result of intensive studies into the development of compositions for UV-curable temporary rust-preventing coatings, the present inventors have determined that the polymer used in UV-curable coatings has an acid value within a specific range. The inventors have discovered that it is sufficient to blend a specific amount of a copolymer of acrylic acid or methacrylic acid and its ester compound, and have completed the present invention. That is, the photocurable antirust coating composition of the present invention is a copolymer of (A) (a) acrylic acid or methacrylic acid and (b) acrylic ester or methacrylic ester, and has a weight average molecular weight of
5000~100000, and 30~
5 to 50 parts by weight of an acrylic copolymer having an acid value in the range of 300 KOHmg/g (B) 95 to 50 parts by weight of an unsaturated compound having one or more polymerizable double bonds (C) Photopolymerization initiator 1 ~10 parts by weight. The present invention will be explained in more detail below. The acrylic copolymer (A) in the present invention has a 30 to 300
It is necessary to have an acid value in the range of KOHmg/g. If the acid value of the copolymer is less than 30 KOHmg/g, it will be difficult to remove the cured coating film with alkali, and if it exceeds 300 KOHmg/g, the rust prevention properties of the coating film, that is, corrosion resistance and moisture resistance will be affected. etc. performance deteriorates. As a copolymer having an acid value within this range, an acrylic copolymer containing acrylic acid or methacrylic acid and a monomer copolymerizable with these as main components is used. Examples of monomers copolymerizable with acrylic acid or methacrylic acid include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, Isobutyl methacrylate, 2-ethylhexyl acrylate,
2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, acrylic acid 2
-Hydroxyethyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,
Acrylic acid esters or methacrylic acid esters such as 2-hydroxypropyl methacrylate, 1-hydroxybutyl acrylate, 1-hydroxybutyl methacrylate, benzyl acrylate, and benzyl methacrylate; By arbitrarily blending one or more monomers selected from these monomers, various coating film performances can be exhibited. The weight average molecular weight of the above copolymer is 5000 to 100000
If it is less than 5,000, performance such as corrosion resistance and moisture resistance tends to deteriorate, and if it exceeds 100,000, the viscosity of the composition becomes too high, making it impractical. These copolymers can be obtained by generally known polymerization methods, but because the blending ratio of acid monomers is high, these copolymers cannot be produced by suspension polymerization or emulsion polymerization. It is difficult to do so. For this reason, it is preferable to manufacture by a solution polymerization method or a bulk polymerization method. Such an acrylic copolymer is blended in the coating composition in an amount of 5 to 50 parts by weight; if it is less than 5 parts by weight, the coating film will not be easily removed by alkali, and if it exceeds 50 parts by weight, it will be difficult to remove the coating film. Corrosion resistance of the resulting coating film,
Performance such as moisture resistance deteriorates, and the purpose of rust prevention cannot be achieved. Examples of the unsaturated compound (B) having one or more polymerizable double bonds in the present invention include () tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate. , isodecyl acrylate, isodecyl methacrylate, monofunctional unsaturated compounds such as acrylic acid or methacrylic acid adducts of phenyl glycidyl ether; () ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol Polyfunctional unsaturated compounds such as di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate; () Polyester-forming component or polyester , a reaction product with an acryloyloxy group-forming component or a compound containing an acryloyloxy group, which is a polyester polyacrylate having an average of one or more acryloyloxy groups per molecule; a reaction product between an epoxy resin and acrylic acid; Examples include oligomers such as epoxy polyacrylates having an average of one or more acryloyloxy groups per molecule, and urethane polyacrylates having a urethane bond in the main chain and having an average of one or more acryloyloxy groups per molecule. Various combinations of such unsaturated compounds can be considered in order to maintain a balance between film removability and coating performance, but as a yarn with a good balance, an acrylic acid adduct of phenyl glycidyl ether is preferred. These unsaturated compounds are blended in the coating composition in an amount of 95 to 50 parts by weight; if the amount exceeds 95 parts by weight, the coating film will not be easily removed by alkali, and if it is less than 50 parts by weight, the coating composition will not be easily removed. Corrosion resistance, moisture resistance, and other properties of the paint film deteriorate. Examples of the photopolymerization initiator (C) in the present invention include benzoin, benzoin methyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyl (diphenyl diketone), benzophenone, 2-methylanthraquinone, benzyl dimethyl ketal, and the like. .
These may be used alone or in combination of two or more, and are blended in an amount of 1 to 10 parts by weight per 100 parts by weight of the total amount of the acrylic copolymer and unsaturated compound. It is also possible to modify the coating composition of the present invention into a coating composition suitable for various performances by optionally blending other resins that can be normally blended, such as epoxy resins and butyral resins. Furthermore, if necessary, commonly used phosphoric acid-based or amine-based rust inhibitors may be used in combination to further improve the rust prevention properties. The coating composition of the present invention is applied to the surface of steel material and cured by irradiation with so-called active energy rays such as ultraviolet rays, and then provided to the user, and the film is removed by alkaline treatment in the pre-painting process at the user. be done. [Effects of the Invention] The coating composition of the present invention has excellent adhesion to steel materials even though it does not contain an adhesion promoter, and has excellent coating performance such as corrosion resistance and moisture resistance, as well as alkali resistance. Excellent film removability through treatment. Therefore, the coating composition is useful as a temporary rust-preventive protective coating for steel materials, and its industrial value is extremely large. [Examples of the Invention] In the following examples, parts and % represent parts by weight and % by weight, respectively. Example 1 30 parts of methyl methacrylate, butyl methacrylate
Add 0.4 parts of azobisisobutyronitrile as a polymerization initiator to a mixed solution consisting of 50 parts of acrylic acid and 20 parts of acrylic acid.
tert-dodecyl mercaptan as chain transfer agent 0.3
80
Polymerization was carried out for 3 hours in a constant temperature water bath at 0.degree. C. to obtain a copolymer consisting of three components with an acid value of 156 KOH mg/g and a weight average molecular weight of 20,000. Dissolve 20 parts of this copolymer [ ] in 70 parts of tetrahydrofurfuryl acrylate, and add Diabeam UK-6123 (epoxy polyacrylate, manufactured by Mitsubishi Rayon Co., Ltd.) to this solution.
A coating composition was obtained by mixing 10 parts and 4 parts of benzoin butyl ether. This coating composition was coated onto a degreased mild steel plate using a bar coater to a film thickness of 15 to 20 μm, and a high-pressure mercury lamp (manufactured by Mitsubishi Rayon Engineering Co., Ltd.) was used.
UK-2501) Irradiated for about 2 seconds with one 80w/cm lamp. The obtained coated steel plate was tested for adhesion, pencil hardness, impact resistance, corrosion resistance, moisture resistance, and film removability. The results are shown in the table. Example 2 A coated steel plate was obtained in the same manner as in Example 1, except that 20 parts of the copolymer obtained in Example 1 was dissolved in 70 parts of an acrylic acid adduct of phenyl glycidyl ether. This coated steel plate was subjected to the same tests as in Example 1, and the results are listed in the table. Example 3 To 90 parts of a solution of the acrylic acid adduct of phenyl glycidyl ether of the copolymer [ ] obtained in Example 2, 5 parts of Diabeam UK-6123 (epoxy polyacrylate, manufactured by Mitsubishi Rayon Corporation) and epoxy were added. A coating composition was obtained by mixing 5 parts of a resin (Epicoat #828, manufactured by Yuka Ciel Chemical Co., Ltd.) and 4 parts of benzoin butyl ether. A coated steel plate was obtained using this coating composition in the same manner as in Example 1, and the same tests as in Example 1 were conducted on the steel plate, and the results are listed in the table. Example 4 50 parts of the copolymer obtained in Example 1 was mixed with 30 parts of an acrylic acid adduct of phenyl glycidyl ether.
1 part and 10 parts of an adduct of phthalic anhydride and hydroxyethyl acrylate, and 1,6-
5 parts of hexanediol diacrylate and 5 parts of benzoin butyl ether were dissolved and mixed to obtain a coating composition. Example 1 Using this coating composition
A coated steel plate was obtained in the same manner as in Example 1, and the same test as in Example 1 was conducted on the steel plate, and the results are shown in the table. Example 5 5 parts of the copolymer [ ] obtained in Example 1 were dissolved in 45 parts of tetrahydrofurfuryl acrylate and 30 parts of an acrylic acid adduct of phenyl glycidyl ether, and trimethylolpropane was added to this solution. Acrylate 5 parts, Diamond Beam UK-6105
(Epoxy polyacrylate, manufactured by Mitsubishi Rayon Co., Ltd.) 5 parts, 10 parts of an adduct of phthalic anhydride and hydroxyethyl acrylate, and 5 parts of benzoin isobutyl ether were mixed to obtain a coating composition. A coated steel plate was obtained using this coating composition in the same manner as in Example 1, and the same tests as in Example 1 were conducted on the steel plate, and the results are shown in the table. Example 6 0.3 parts of benzoyl peroxide as a polymerization initiator was dissolved in a mixed solution consisting of 75 parts of butyl methacrylate, 5 parts of 2-hydroxyethyl methacrylate, and 20 parts of methacrylic acid, and polymerization was carried out in the same manner as in Example 1. A copolymer [] having an acid value of 130 KOHmg/g and a weight average molecular weight of 50,000 was obtained. 20 parts of this copolymer [ ] was dissolved in 60 parts of an acrylic acid adduct of phenyl glycidyl ether. To this solution, 5 parts of epoxy resin (manufactured by Yuka Ciel Chemical Co., Ltd., Epicoat #828), 5 parts of Diabeam UK-6123 (epoxy polyacrylate, manufactured by Mitsubishi Rayon Co., Ltd.)
10 parts of an adduct of phthalic anhydride and hydroxyethyl acrylate and 5 parts of benzoin isobutyl ether were mixed to obtain a coating composition. A coated steel plate was obtained using this coating composition in the same manner as in Example 1, and the same tests as in Example 1 were conducted on the steel plate, and the results are shown in the table. Example 7 Instead of the copolymer [] in Example 6, 50 parts of methyl methacrylate, 43 parts of butyl methacrylate,
A copolymer [ ] having an acid value of 33 KOH mg/g and a weight average molecular weight of 20,000 was copolymerized by bulk polymerization using 2 parts of 2-hydroxyethyl acrylate and 5 parts of methacrylic acid. A coating composition was obtained in the same manner as in Example 6 except that this copolymer [ ] was used. Example 1 using this coating composition
A coated steel plate was obtained in the same manner as in Example 1, and the same test as in Example 1 was conducted on the steel plate, and the results are shown in the table. Example 8 Instead of the copolymer [ ] in Example 6, 40 parts of methyl methacrylate, 20 parts of ethyl methacrylate, and 35 parts of acrylic acid were used to copolymerize by bulk polymerization, with an acid value of 273 KOH mg/g. Weight average molecular weight
10000 copolymer [] was used. A coating composition was obtained in the same manner as in Example 6 except that this copolymer [ ] was used. A coated steel plate was obtained using this coating composition in the same manner as in Example 1, and the same tests as in Example 1 were conducted on the steel plate, and the results are listed in the table. Comparative Example 1 A copolymer having a weight average molecular weight of 4000 and consisting of 80 parts of methyl methacrylate and 20 parts of butyl methacrylate was produced by a suspension polymerization method. A coating composition was obtained using this copolymer in the same manner as in Example 6. A coated steel plate was obtained using this coating composition in the same manner as in Example 1, and the same tests as in Example 1 were conducted on the steel plate, and the results are listed in the table. Comparative example 2 30 parts of methyl methacrylate, butyl methacrylate
A copolymer consisting of 20 parts of methacrylic acid and 50 parts of methacrylic acid was produced by a bulk polymerization method, and the acid value was 326 KOHmg/g.
A copolymer with a weight average molecular weight of 150,000 was obtained. A coating composition was obtained using this copolymer in the same manner as in Example 6. A coated steel plate was obtained using this coating composition in the same manner as in Example 1, and the same tests as in Example 1 were conducted on the steel plate, and the results are listed in the table. Comparative Example 3 Styrene-maleic anhydride copolymer (manufactured by ARCO) was used instead of the copolymer [] in Example 6.
A coating composition was obtained in the same manner as in Example 6 using SMA1000). A coated steel plate was obtained using this coating composition in the same manner as in Example 1, and the same tests as in Example 1 were conducted on the steel plate, and the results are listed in the table.

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Claims (1)

[Scope of Claims] 1 (A) A copolymer of (a) acrylic acid or methacrylic acid and (b) acrylic ester or methacrylic ester, which has a weight average molecular weight of
5000~100000 and 30~300KOH
5 to 50 parts by weight of an acrylic copolymer having an acid value in the range of mg/g (B) 95 to 50 parts by weight of an unsaturated compound having one or more polymerizable double bonds (C) Photopolymerization initiator 1 A photocurable rust-preventive coating composition comprising 10 parts by weight. 2 Claim 1 in which the unsaturated compound (B) is an acrylic acid adduct of phenyl glycidyl ether
The photocurable rust-preventing coating composition described in 1.