JPH04209663A - Ultraviolet-curable composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. having an excellent adhesion to a thermosetting undercoating film and a good weatherability when used as a clear coat, etc., by compounding a specific polyfunctional (meth)acrylate, a specific copolymer, and specific components. CONSTITUTION:A polyfunctional (meth)acrylate having at least two radical- polymerizable double bonds, a satd. polymer comprising a copolymer contg. copolymerized dibutyl fumarate, a urethan (meth)acrylate obtd. by reacting a polyol, a polyisocyanate, and a hydroxylated (meth)acrylate, a photopolymn. initiator, a primary antioxidant, a hindered amine light stabilizer, and an ultraviolet absorber are compounded as essential components to give the title compsn., which gives a coating film excellent in interlaminar adhesion with an undercoating film and in scratch resistance, weatherability, hardness, etc., when compared with a conventional clear coat.

Description

[Detailed description of the invention]

[00011

[Industrial Application Field] The present invention relates to an ultraviolet curable composition for a clear coat applied to a thermosetting coating film for aluminum wheels, motorcycles, automobiles, etc. The present invention relates to an ultraviolet curable composition that has excellent adhesion to other objects, has excellent scratch resistance, and has excellent appearance. [0002] [Prior Art] It is a well-known fact that aluminum wheels, motorcycles, automobiles, etc. are coated with various thermosetting paints and cured for their cosmetic properties and the protection of steel plates. be. [0003] And in order to respond to the recent trend towards luxury,
For various purposes, a clear coat is applied on top of such a thermosetting coating to give it a high degree of cosmetic properties and also to provide functions such as preventing scratches.As this clear coat, Attempts have begun to be made to apply UV-curable paints. [0004] Due to its polymerization mechanism, ordinary UV-curable paints generally shrink more than ordinary thermosetting paints, and tend to have poor adhesion to the substrate due to residual stress after curing. However, when coated on top of a thermosetting coating film for the above-mentioned purposes, interlayer adhesion is poor, and in many cases it cannot be put to practical use. [00051 The present inventors previously described a specific polyfunctional (meta)
By blending acrylate with a copolymer having a specific structure, we have found that it is possible to obtain a UV-curable composition that does not have problems with interlayer adhesion, but it is also possible to obtain UV-curable compositions that do not have problems with interlayer adhesion. In such applications, weather resistance becomes an issue, and there is a need for an ultraviolet curable composition that has a good balance between glabellar adhesion with ordinary thermosetting paints and weather resistance. [0006]

[Problems to be Solved by the Invention] An object of the present invention is to provide an ultraviolet curable composition for an ultraviolet curable clear coat to be applied on a thermosetting coating film, which has a higher bond with the substrate than conventional clear coats. The object of the present invention is to provide an ultraviolet curable composition for a clear coat, which has excellent interlayer adhesion and can provide a coating film having excellent scratch resistance, weather resistance, hardness, etc. [0007]

[Means for solving the problem] The problem is (a)
Polyfunctional (meth)acrylate having at least two radically polymerizable double bonds, (b) copolymer obtained by copolymerizing dibutyl fumarate as a saturated polymer, (c) polyol, polyisocyanate, and hydroxyl group-containing (meth)acrylate obtained by synthesizing (meth)acrylate, (d) photopolymerization initiator, (e
) A primary antioxidant, (f) a hindered amine light stabilizer, and (g) an ultraviolet absorber. [00081 Hereinafter, the present invention will be described in detail. [00091 Component (a) used in the present invention, a polyfunctional (meth)acrylate having at least two or more radically polymerizable double bonds, constitutes a curing component of the ultraviolet curable composition of the present invention, Specific examples include trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate dipentaerythritol penta(meth)acrylate,
dipentaerythritol hexa(meth)acrylate,
Tri(meth)acrylate of trimethylolpropane with ethylene oxide, tri(meth)acrylate of trimethylolpropane with propylene oxide. Tetra(meth)acrylate of ditrimethylolpropane added to ethylene oxide, Tetra(meth)acrylate of ditrimethylolpropane added to propylene oxide, Tetra(meth)acrylate of pentaerythritol added to ethylene oxide, Tetra(meth)acrylate of pentaerythritol added to propylene oxide,
Penta(meth)acrylate of dipentaerythritol added with ethylene oxide, penta(meth)acrylate of dipentaerythritol added with propylene oxide. Hexa(meth)acrylate of dipentaerythritol added with ethylene oxide, hexa(meth)acrylate of dipentaerythritol added with propylene oxide,
triallyl formal, triallyl isocyanurate,
Triallyl formal, 1. 3. 5-Triacryloylhexahydro-5-h lyazine, bisphenol A
- diglycidyl ether di(meth)acrylate, polypropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, dicyclopentadiene diol diacrylate, neo Pentyl glycol di(meth)acrylate, ethylene oxide-added neopentyl glycol di(meth)acrylate, propylene oxide-added neopentyl glycol di(meth)acrylate, neopentyl glycol and polybasic acids such as phthalic acid and adipic acid (meth) Polyester polyester obtained by reacting with acrylic acid (meth)acrylate, polyester polyester obtained by reacting polybasic acids such as phthalic acid and adipic acid with polyhydric alcohols such as ethylene glycol and butanediol, and (meth)acrylic acid. (meth)acrylate, epoxy poly obtained by the reaction of an epoxy resin and (meth)acrylic acid; Examples include meth)acrylate, polysiloxane poly(meth)acrylate obtained by the reaction of polysiloxane and a (meth)acrylic acid compound, and polyamide poly(meth)acrylate obtained by the reaction of polyamide and a (meth)acrylic acid compound. It will be done. [Among 00101, compounds having a neopentyl structure as a molecular skeleton are preferred in consideration of adhesion to the underlying thermosetting coating film. In addition, these monomers may be used alone or in combination.
A mixture of more than one species can be used. [00111] In addition, the component (b) of the present invention, a saturated copolymer containing dibutyl fumarate as an essential copolymerization component, can be obtained by a conventional solution polymerization, emulsion polymerization, or suspension polymerization method. Other monomers copolymerized with dibutyl fumarate include styrene, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate,
n-butyl (meth)acrylate, i-butyl (meth)
Acrylate, t-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate
Acrylate, n-nonyl (meth)acrylate, dicyclopentenyl (meth)acrylate, 2-dicyclopentenoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate Acrylate, methoxyethoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylatetetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate Acrylate, (meth)acrylic acid, monofunctional (meth)acrylate monomers such as (meth)acryloylmorpholine, N-vinyl-2- and lolidone, N-vinylimidazole, N-
Vinyl monomers such as vinyl caprolactam, α-methylstyrene, vinyltoluene, allyl acetate, vinyl acetate, vinyl propionate, vinyl benzoate, methacrylic acid,
Acrylic acid, itaconic acid, citraconic acid, maleic acid,
Examples include fumaric acid, crotonic acid, itaconic acid, etc., and one or more of these may be used. Among these, from the viewpoint of copolymerizability, copolymers with styrene, OH group-containing monomers, and carboxyl group-containing monomers are preferred, and styrene is preferably used as one of the comonomers. (0012) The copolymer of component (b) is preferably produced by a solution polymerization method from the viewpoint of ease of production, and the monomers are copolymerized in the presence of an organic solvent and a polymerization initiator. (0013) The solvent used is: Although not particularly limited,
Isopropyl alcohol, n-butanol, toluene,
Commonly used organic solvents such as xylene, Trupetz #100 (aromatic petroleum derivative manufactured by Esso) may be used, and as a polymerization initiator, azo compounds such as azobisisobutyronitrile and benzoyl peroxide cumene hydroperoxide can be used. Any commonly used polymerization initiator may be used, such as peroxides such as . [0014] The urethane (meth)acrylate used as component (c) of the present invention is an organic isocyanate (A) having at least two isocyanate groups in one molecule.
, a polyol (B) having at least two or more hydroxyl groups in one molecule, and a hydroxyl group-containing (meth)acrylate (c
) by a known method. [0015] Specific examples of the organic isocyanate (A) having at least two isocyanate groups in one molecule include 2. 6-tolylene diisocyanate, 2. 4-
Tolylene diisocyanate, diphenylmethane-4,4
゛Diisocyanate, dicyclohexylmethane-4,4
゛-diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, phenylene diisocyanate, lysine diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, 3,3 dimethyldiphenylmethane-4,4゛-diisocyanate, 1, Examples include 3-bis(isocyanatomethyl)cyclohexane, trimethylhexamethylene diisocyanate, isophorone diisocyanate, adduct compounds of these compounds with water, trimethylolpropane, etc., and trimeric ring compounds. [0016] Specific examples of the polyol (B) having at least two or more hydroxyl groups in one molecule include polyether polyol compounds, such as polyalkylene glycols (such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, Alternatively, alkylene oxides such as ethylene oxide, propylene oxide, tetrahydrofuran, etc. can be mixed with polyhydric alcohols (such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerol,
1,3-butanediol, 1,4-butanediol, 1
．． 5-hexanediol, bisphenol A) and polyester polyol compounds, such as polybasic acids (e.g., phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, tetrachlorophthalic acid, tetrabromide). phthalic acid, hexahydrophthalic acid, hemic acid, het acid, succinic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, dodecenylsuccinic acid, trimellitic acid, pyromellitic acid) or their anhydrides and polyhydric alcohols, e.g. , ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerol, 1
．． 3-butanediol, 1,4-butanediol, 1.
Polyester polyol obtained by condensation reaction with 6-hexanediol, neopentyl glycol, bisphenol A, the above polyhydric alcohol and epoxy compound such as Cardura E, n-butyl glycidyl ether, allyl glycidyl ether, etc. by reaction with the above polybasic acid. Polyester polyols obtained, polyester polyols obtained by reaction of the above epoxy compound and the above polybasic acid, and polybutadiene polyols such as hydrogenated or unadded 1,4 polybutadiene diol and 1,2-polybutadiene diol. , polycaprolactone polyol, and the like. [0017] Furthermore, a reaction product of a monocarboxylic acid and an amino alcohol, a reaction product of a carboxylic acid ester and an amino alcohol, a hydroxycarboxylic acid and a compound containing at least one primary or secondary amine nitrogen; reaction products of internal esters of hydroxycarboxylic acids, such as lactones, with ammonia or compounds containing at least one primary or secondary amino nitrogen,
Mention may also be made of amidohydroxy compounds such as polyamide polyols. [0018] Hydroxyl group-containing (meth)acrylate compound (
Specific examples of c) include 2-hydroxyethyl (meth)
Acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate,
ε-caprolactone-β-hydroxyethyl (meth)acrylate adduct, 2-hydroxy-3-chloro-propyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 2-hydroxy-3 phenyloxypropyl (meth) Examples include acrylate. [0019] These (A), (B), (c)
Among the components, preferred are isophorone diisocyanate and dicyclohexylmethane as component (A).
4,4' diisocyanate, tetramethylxylylene diisocyanate, and the component (B) is polytetramethylene glycol, γ-butyrolactone, and N-
A reaction product with methylethanolamine and polycaprolactone diol, and component (c) is 2-
They are hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 4-hydroxybutyl acrylate. When obtaining the urethane poly(meth)acrylate which is the component (c) of the present invention using the raw materials of these components, the ratio of the components (A) / (B) / (c) is 11
It is preferably from 0.5 to 0.91 and from 0.2 to 1.1. [00201 reaction can easily proceed by mixing and stirring the three components at room temperature to 80°C using a catalyst used in general urethane reactions, for example, a tin-based catalyst such as dibutyltin laurate, and the desired urethane ( meth)acrylate is obtained. This reaction can be carried out without a solvent, or, if necessary, in a solvent or monomer that is inert to isocyanates. [00211 The photopolymerization initiator as component (d) in the present invention is for curing the composition of the present invention with ultraviolet rays, and in addition to this photopolymerization initiator, it is also combined with a photosensitizer and/or photoacceleration. Agents can be used in combination. [0022] Specific examples of the photoinitiator include benzoin monomethyl ether, benzoin isopropyl ether, benzophenone, benzyl dimethyl ketal, 2°2-jetoxyacetophenone, and 1-hydroxycyclohexylphenyl ketone. [0023] Specific examples of the photosensitizer include 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2°4-diisopropylthioxanthone, and the like. [0024] Specific examples of the photoaccelerator include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 2-n-butoxyethyl p-dimethylaminobenzoate, 2-dimethylaminoethyl benzoate, etc. can be mentioned. [00251 (e), (f), (g) of the present invention
The ingredients have a large effect on weather resistance, and they must be
By using these ingredients in combination, long-term weather resistance can be improved. [0026] Here, the primary antioxidant of component (e) is:
It prevents oxidative deterioration caused by oxygen in the air, and contains phenolic antioxidants, monophenolic antioxidants,
Bisphenol-based, polymeric phenolic antioxidants,
These are called radical chain inhibitors such as amine-based antioxidants, and peroxide decomposers (secondary antioxidants) such as sulfur-based antioxidants and phosphorus-based antioxidants reduce yellowing and weather resistance during curing. Due to poor yellowing during the test, it is not suitable for use. [0027] Of these, among the blowing antioxidants, phenolics, that is, fully hindered phenols such as 2,6-di-t-butylphenol derivatives, and 2-methyl-6-t-butylphenol derivatives are preferred. Partially hindered phenols such as [0028] Specific examples include 2-t-butyl-6-(
3'-t-butyl-5"-methyl-2°-hydroxybenzyl)-4methylphenyl acrylate, 2,2"methylene-bis-(4-methyl-6-t-butylphenol), 4.4'- Butyridien-bis-(3-methyl-6-t-butylphenol), 3.9-bis[2-[
3-(3-t-butyl-hydroxy-5-methylphenyl)propionyloxy)-1,1'-dimethylethyl]
-2,4,8,10-tetraoxaspiro [5°5]
Examples include undecane. [00291 The hindered amine photostabilizer, which is the component (f) of the present invention, differs from an ultraviolet absorber in that it does not itself have ultraviolet absorbing ability, but it captures radicals generated by light irradiation and stabilizes the photostabilizer. Specifically, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-bentamethyl-4-piperidyl) sebacate, 4 -benzoyloxy-2,2,6,6-tetramethylbiperidine, bo[(6-morpholino-s-triazine-2,4-diyl)[(2,2,6,6-tetramethyl-4- piperidylimino]-hexamethylene-C(2,2,6,6-tetramethyl-4-piperidyl)imino)], N-2゜2
, 6. 6-tetramethyl-4-piperidyl 2- (
2゜2, 6. 6-tetramethyl-4-piperidylamino)2methylpropioamide, 2-(3,5-di-
t-Butyl-4-hydroxybenzyl)-2-n-butylmalonic acid bis(1,2,2,6,6-bentamethyl-4
-piperidyl), etc. [00301 The ultraviolet absorber, which is the component (g) of the present invention, literally has harmful UV 300 to 4
It absorbs ultraviolet rays of 00 μm and re-radiates the energy mainly as harmless thermal energy, and does not change its quality in any way. [0031] Examples of ultraviolet absorbers include salicylic acid-based, benzophenone-based, benzotriazole-based, and cyanoacrylate-based ultraviolet absorbers, but benzophenone-based ultraviolet absorbers are preferred from the viewpoint of yellowing during curing. Specifically, 2
．． 4-hydroxybenzophenone, 2-hydroxy-4
-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybesizophenone, 2,2'-dihydroxy-4
Methoxybenzophenone, 2,2゛-dihydroxy4
．． 4“-dimethoxybenzophenone, 2-hydroxy-
4-methoxy-5-sulfobenzophenone, ethyl-2
-cyano-3,3-diphenyl acrylate and the like. (0032) Regarding the amount of the above-mentioned components (a) to g), the ratio of component (a), component (b), and component (c) is 10 to 70 parts (parts by weight, The same applies hereafter), (b) component is 70 to 30 parts, (c
) component is preferably 10 to 50 parts; (c)
If the amount of the component is less than 10 parts, the coating film will not stretch properly and cracks will occur easily during the weather resistance test, and if the amount is more than 50 parts,
The viscosity of the system becomes too high and painting workability deteriorates. (0033) (d) Ingredients are (a), (b)
, (c) 0.01 to 1 per 100 parts in total of component
It is necessary to add 0 parts, and if it is less than 0.01 part, the curability upon irradiation with ultraviolet rays will be poor, and it will not be cured substantially. If the amount is more than 10 parts, yellowing during curing will worsen and weather resistance will deteriorate. (0034] Also, (e), (f), (g)
The blending amounts of the ingredients are the aforementioned (a), (b),
0.0 of each component (c) per 100 parts of the blend.
Preferably, the amount is 1 to 5 parts; if it is less than 1, no effect of improving weather resistance will be observed, and if it is more than 5 parts, the cured painted surface will wrinkle or yellowing will occur during curing. Therefore, it cannot be used as a protective coat for white goods. [0035] As mentioned above, in the present invention, (e), (f
). By using component (g) in combination, a balance between long-term weather resistance and yellowing during curing can be achieved. [OQ 36] The composition of the present invention may contain an organic solvent in order to adjust the viscosity to a desired value. Examples of organic solvents include ketone compounds such as acetone, methyl ethyl ketone, and cyclohexanone; ester compounds such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, and methoxyethyl acetate; ether compounds such as diethyl ether, ethylene glycol dimethyl ether, and dioxane. ;Aromatic compounds such as toluene and xylene;Aliphatic compounds such as pentane and hexane;Methylene chloride, chlorobenzene,
Examples include halogenated hydrocarbons such as chloroform. [0037]Additives such as lubricants, abrasives, rust preventives, and antistatic agents may also be added to the compositions of the present invention. [00381 When applying a paint such as a clear coat using the composition of the present invention, any of the coating apparatuses described below can be used. That is, when performing spray painting, the composition of the present invention is adjusted to the spray coating viscosity with the above-mentioned solvent, then sprayed, the solvent is removed with far infrared rays, a hot air drying oven, etc., and then ultraviolet rays are irradiated. good. Further, in the case of a continuous film or sheet, a roll coater or a gravure coater may be used. [00391 Hereinafter, the present invention will be described in more detail with reference to Examples. Note that "parts" means "parts by weight." [00401 <Production Example of Thermosetting Paint> 40 parts of toluene and 10 parts of n-butanol were charged into a reaction vessel equipped with a stirrer, a temperature control device, and a condenser. The contents of the reaction vessel were heated with stirring to raise the temperature to 100°C. Next, 5 parts of styrene, 2 parts of methacrylic acid, 35 parts of methyl methacrylate, 46 parts of ethyl acrylate,
After dropping 101.5 parts of a solution consisting of 12 parts of 2-hydroxyethyl acrylate and 1.5 parts of benzoyl peroxide over 4 hours, 0.0 parts of benzoyl peroxide was added dropwise. 6 parts and toluene 2
A solution consisting of 0 parts was added dropwise over 30 minutes. The reaction solution was further stirred and heated at 100° C. for 2 hours to increase the conversion rate to resin, and then 30 parts of toluene was added to terminate the reaction. Obtained acrylic copolymer solution (non-volatile content 50%)
) is hereinafter referred to as acrylic resin varnish. The weight average molecular weight of this acrylic copolymer was measured by gel permulation chromatography and found to be 70.
,000. [00411 <Production example of thermosetting paint> The amounts of each material shown in Table 1 are placed in a stainless steel container, stirred thoroughly, and the viscosity is adjusted with a diluent mixed solvent to prepare thermosetting paint B-
1, B-2 was manufactured. [0042]

[Table 1] (*1) to *5) in Table 1 of 00431 are as follows. In addition, mixed solvent a for dilution is toluene 40%
b is a mixture of 20% butyl acetate and 40% cellosolve acetate, and b is a mixture of 40% toluene, 40% ethyl acetate, and Tsurpetz 150 (aromatic petroleum derivative manufactured by Esso) 2
0% mixture. *1) Degussa binding 2) Aluminum paste, manufactured by Toyo Aluminum Co., Ltd. *3) Butyl etherified melamine resin (nonvolatile content 60%), manufactured by Mitsui Toatsu Chemical Co., Ltd. *4) Methyl butyl, manufactured by Mitsui Cyanamid Co., Ltd. Mixed etherified melamine resin (100% non-volatile content) $5) KI
Synthesis example of saturated polymer using sulfonic acid catalyst manufactured by NG Co., Ltd.
60 parts of toluene and 40 parts of butyl acetate were charged into a reaction vessel equipped with a stirrer, a temperature control device, and a condenser, and the contents of the reaction vessel were heated while stirring to bring the temperature to 100°C.
It was raised to . Next, a solution consisting of 30 parts of styrene, 30 parts of 2-hydroxyethyl methacrylate, 0.5 part of methacrylic acid, 39.5 parts of dibutyl fumarate, and 2 parts of azobisisobutyronitrile was added dropwise for 4 hours. 0.5 part of isobutyronitrile was added, and then azobisisobutyronitrile was added so that the polymerization rate was 100% to obtain a saturated polymer H-1. Hereinafter, the monomers added dropwise were changed as shown in Tables 2 and 3, and saturated polymers H-2 to H-7 were synthesized, and the resin solution characteristic values were measured. The results are also shown in Table 2. [0044]

[Table 2] [0045]

[Table 3] [0046] <Synthesis of urethane acrylate UA-1>
222.3 g (1 mol) of isophorone diisocyanate and 437.95 g (0.5 mol) of polytetramethylene glycol were added to a No. 11 flask equipped with a stirrer, thermometer, and condenser, and after reacting at 60°C for 4 hours, 2- Add 116 g (1 mol) of hydroxyethyl acrylate and 0.02 g of hydroquinone monomethyl ether, and heat at 60°C.
The reaction was carried out for a period of time to obtain urethane acrylate UA-1. (0047] (Synthesis of urethane acrylate UA-2)
264.8 g (1 mol) of dicyclomethane-4,4' diisocyanate and 418.1 g (0.8 mol) of polycaprolactone diol were added to the same apparatus as UA-1, and after reacting at 60°C for 4 hours, -Hydroxyethyl acrylate58. 1 g (0.5 mol) and 0.02 g of hydroquinone monomethyl ether were added and reacted at 60° C. for 6 hours to obtain urethane acrylate UA-2. <Synthesis of urethane acrylate UA-3> Tetramethylxylylene diisocyanate 24 was added to the same apparatus as UA-1 instead of the isocyanate used in the synthesis of UA-1.
Urethane acrylate UA-3 was obtained in the same manner except that 4.3 g (1 mol) was used. [0048] <Synthesis of urethane acrylate UA-4>
Urethane acrylate UA-4 was prepared using the same apparatus as UA-1 except that 1 mol of toluene diisocyanate was used instead of the isocyanate used in the synthesis of UA-1.
I got it. [00491<Synthesis of urethane acrylate UA-5>
Using the same apparatus as UA-2, as the polyol component, 0.25 mol of polycaprolactone diol and 0.25 mol of a compound of γ-butyrolactone and N-methylethanolamine were used instead of polycaprolactone diol, but otherwise the same. Urethane acrylate UA-5 was obtained. [00501 <Examples 1 to 13 and Comparative Examples 1 to 6> Thermosetting paints B-1 and B-2 were spray-coated onto a mild steel plate to a thickness of 20 ILm, and cured at 150°C for 30 minutes. After that, a clear coat consisting of Examples and Comparative Examples according to the formulations of Tables 4 to 7 of the present invention was applied on this coating film, and a clear coat of 60
After setting for 5 minutes at ℃, 80 W/c using UV irradiation equipment UV-5003 manufactured by Mitsubishi Rayon Engineering.
m, 3 lamps, lamp height 30cm, conveyor speed 4
UV irradiation was carried out under the condition of 300 ml/min. [00511 In the formulations shown in Tables 4 to 7, (d
2 parts of Ciba-Geigy's "Irgacure 184" was used as a photopolymerization initiator for component (e), and 2,2'-methylene-bis(4-methyl-6) was used as a primary antioxidant for component (e).
-2**butylphenol) to 0. 3 parts, bis(2,2
, 6,6-tetramethyl-4-piperidyl) sebacate at 0. 3 parts, 2,4 as component (g) ultraviolet absorber
'-dihydroxybenzophenone at 0. 3 parts and 70 parts of an isothermal mixture of toluene/isopropyl alcohol/butyl acetate as a solvent were used in common for all examples. However, in Comparative Examples 5 and 6, (e), (f),
(g) Components were not added. [0052] This sample was used to evaluate adhesion, pencil hardness, 60° gloss, weather resistance, scratch resistance, etc., and the results are shown in Tables 4 to 7. [0053]

[Table 4] [0054]

[Table 5] [0055]

[Table 6] [0056]

[Table 7] [0057] The coating film evaluation method is based on the pencil hardness of JIS-H.
5400, adhesion was determined by a cross-cut cellophane tape peel test, abrasion resistance was determined by the change in appearance after rubbing the paint film back and forth 10 times with #0000 steel wool, and weather resistance was determined by Sanshan W-0- The appearance change after 2000 hours and the 60° gloss were evaluated. [0058] As is clear from Tables 3 to 7, the clear coat made of the ultraviolet curable composition of the present invention exhibits excellent adhesion to thermosetting coatings and has excellent weather resistance. Moreover, it can be seen that the hardness, gloss, and scratch resistance are also good. [0059]

Effects of the Invention As explained above, the clear coat made of the ultraviolet curable composition of the present invention has excellent adhesion to the underlying thermosetting coating film, etc., as well as excellent weather resistance. Moreover, the hardness, gloss, and scratch resistance are also good.

Claims (2)

[Claims] Claim 1: (a) a polyfunctional (meth)acrylate having at least two radically polymerizable double bonds; (b) a copolymer obtained by copolymerizing dibutyl fumarate as a saturated polymer; (c) ) Urethane (meth)acrylate obtained by synthesizing polyol, polyisocyanate, and hydroxyl group-containing (meth)acrylate, (d) Photopolymerization initiator, (e) Primary antioxidant, (f) Hindered amine light stabilizer, ( g) An ultraviolet curable composition comprising as a main component an ultraviolet absorber. 2. The ultraviolet curable composition according to claim 1, wherein the polyfunctional (meth)acrylate having at least two radically polymerizable double bonds has a neopentyl skeleton.