JPH04272913A - Ultraviolet-curable composition - Google Patents

Abstract

PURPOSE:To provide the title compsn. which is used, e.g. as a clear topcoating compsn., shows an excellent adhesion to a thermosetting coating film, and is excellent in resistance to solvent and acid. CONSTITUTION:The title compsn. mainly comprises a copolymer prepd. by copolymerizing a polyfunctional (meth) acrylate having at least two radical- polymerizable double bonds with dibutyl fumarate and hence has polymerizable double bonds in the side chains.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an ultraviolet curable composition for use as a clear coat on thermosetting coatings for aluminum wheels, motorcycles, automobiles, etc. The present invention relates to an ultraviolet curable composition that has excellent adhesion to other objects, as well as excellent solvent resistance, scratch resistance, and appearance.

0002

BACKGROUND OF THE INVENTION 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.

[0003] In order to respond to the recent trend toward 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.

However, 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. When coated on thermosetting coatings such as those used in the above applications, there are many cases in which the interlayer adhesion is poor and the coating cannot be put to practical use.

[0005] The present inventors previously discovered a specific polyfunctional (meta)
It was discovered that by blending acrylate with a copolymer having a specific structure, it was possible to obtain an ultraviolet curable composition with no problem with interlayer adhesion, but with this composition, the gel fraction of the cured product was It has been found that if the resistance does not rise above a certain level and attempts are made to improve solvent resistance or acid resistance, interlayer adhesion tends to worsen.

[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 better 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 solvent resistance, acid resistance, etc.

[0007]

[Means for Solving the Problems] This problem is solved by copolymerization of (a) a polyfunctional (meth)acrylate having at least two or more radically polymerizable double bonds, and (b) dibutyl fumarate. This problem can be solved by using an ultraviolet curable composition whose main component is a polymer having a radically polymerizable double bond in its side chain.

The present invention will be explained in detail below.

The polyfunctional (meth)acrylate having at least two or more radically polymerizable double bonds, component (a), used in the present invention 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 added to ethylene oxide, tri(meth)acrylate of trimethylolpropane added to propylene oxide, tetra(meth)acrylate of ditrimethylolpropane added to ethylene oxide, tetra(meth)acrylate of ditrimethylolpropane added to propylene oxide acrylate,
Tetra(meth)acrylate of pentaerythritol added to ethylene oxide, Tetra(meth)acrylate of pentaerythritol added to propylene oxide, Penta(meth)acrylate of pentaerythritol added to ethylene oxide
meth)acrylate, propylene oxide-added dipentaerythritol penta(meth)acrylate, ethylene oxide-added dipentaerythritol hexa(
meth)acrylate, propylene oxide-added dipentaerythritol hexa(meth)acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl formal, 1,3,5-triacryloylhexahydro-S-triazine, bisphenol A - diglycidyl ether di(meth)acrylate, polypropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate,
Diacrylate of dicyclopentadiene diol, neopentyl glycol di(meth)acrylate, ethylene oxide-added neopentyl glycol di(meth)acrylate, propylene oxide-added neopentyl glycol di(meth)acrylate, neopentyl glycol and phthalic acid, adipic acid Polyester poly(meth)acrylate obtained by the reaction of polybasic acids such as (meth)acrylic acid, polybasic acids such as phthalic acid and adipic acid, polyhydric alcohols such as ethylene glycol and butanediol, and (meth)acrylic Polyester poly(
meth)acrylate, epoxy poly(meth)acrylate obtained by the reaction of an epoxy resin and (meth)acrylic acid, urethane poly(meth)acrylate obtained by the reaction of a polyol, polyisocyanate, and a hydroxyl group-containing monomer such as 2-hydroxyethyl acrylate ) acrylate, polysiloxane poly(meth)acrylate obtained by the reaction of polysiloxane and a (meth)acrylic acid compound, polyamide poly(meth)acrylate obtained by the reaction of polyamide and a (meth)acrylic acid compound, etc. .

Among these, 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.

[0011] In addition, the copolymer obtained by copolymerizing dibutyl fumarate, which is component (b) of the present invention, has a radically polymerizable double bond in the side chain. It can be obtained by addition-reacting a monomer having a reactive group capable of addition-reacting with dibutyl fumarate to a reactive group of a copolymerized polymer using a polymerization or emulsion polymerization method.

As the monomer having a reactive group capable of copolymerizing with dibutyl fumarate and undergoing an addition reaction, glycidyl (
meth)acrylate, isocyanatoethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4
-Hydroxybutyl (meth)acrylate, (meth)acrylic acid, and the like.

Other monomers copolymerized with dibutyl fumarate include styrene, methyl (meth)acrylate, ethyl (meth)acrylate, and n-propyl (meth)acrylate.
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, n-nonyl (meth)acrylate, dicyclopentenyl (meth)acrylate, 2-dicyclopentenoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxyethoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl ( Vinyl monomers such as meth)acrylate, 4-hydroxybutyl(meth)acrylate, (meth)acrylic acid, (meth)acryloylmorpholine, α-methylstyrene, vinyltoluene, allyl acetate, vinyl acetate, vinyl propionate, vinyl benzoate, etc. etc., and one or more of these may be used. Among them, from the viewpoint of copolymerizability,
Preferably, styrene is used as one of the comonomers.

For synthesis of the copolymer of component (b), solution polymerization is preferred from the viewpoint of ease of production, and after copolymerizing the monomers in the presence of an organic solvent and a polymerization initiator,
By performing an addition reaction, a copolymer having a radically polymerizable double bond in the side chain can be obtained.

The organic solvent used here is not particularly limited, but includes isopropyl alcohol, n-butanol,
Commonly used organic solvents such as toluene, xylene, Solvesso #100 (aromatic petroleum derivative manufactured by Esso) may be used, and as a polymerization initiator, azo compounds such as azobisisobutyronitrile and benzoyl peroxide cumene hydrocarbons may be used. A commonly used polymerization initiator such as a peroxide such as peroxide may be used.

The ratio of component (a) and component (b) affects the curing speed and performance of the cured coating film, and the more component (a) is present, the better the curability tends to be. The film has good pencil hardness and scratch resistance. On the other hand, when the amount of component (b) increases, the curing properties tend to be slow and the adhesion of the coating film to the base tends to be good. Usually, (a) component 1
It is desirable that the amount of component (b) be 5 to 70 parts by weight, preferably 10 to 50 parts by weight.

In order to cure the composition of the present invention with ultraviolet rays, a conventional photopolymerization initiator may be used, and a photosensitizer and a photoaccelerator may be used in combination with the photopolymerization initiator.

Specific examples of the photopolymerization initiator include benzoin monomethyl ether, benzoin isopropyl ether, benzophenone, benzyl dimethyl ketal, 2,
Examples include 2-diethoxyacetophenone and 1-hydroxycyclohexylphenyl ketone. The amount of the photopolymerization initiator to be blended is 0.1 to 10 parts by weight based on 100 parts by weight of the total amount of components (a) and (b).

Specific examples of photosensitizers include 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,
Examples include 4-diisopropylthioxanthone.

Specific examples of the photoaccelerator include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 2-n-butoxyethyl p-dimethylaminobenzoate, 2-dimethylaminoethyl benzoate, etc. can be mentioned.

The composition of the present invention may contain an organic solvent to adjust the viscosity to a desired level. 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; and halogenated hydrocarbons such as methylene chloride, chlorobenzene and chloroform.

[0022]Additives such as lubricants, abrasives, rust preventives, and antistatic agents may also be added to the composition of the present invention.

[0023] When applying a paint such as a clear coat using the composition of the present invention, any of the following coating equipment 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.

[0024] The present invention will be explained in more detail below with reference to Examples. In addition, "part" means "part by weight."

<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, a solution consisting of 0.6 parts of benzoyl peroxide and 20 parts of toluene was added over 30 minutes. dripped. 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. The 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 was found to be 70.
It was 000.

<Production example of thermosetting paint> The amounts of each material shown in Table 1 were placed in a stainless steel container, stirred thoroughly, and the viscosity was adjusted with a diluent mixed solvent to prepare thermosetting paint B. −
1, B-2 was manufactured.

[0027]

[Table 1]

*1) to *5) in Table 1 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 Solvesso 150 (aromatic petroleum derivative manufactured by Esso) 20
% mixture. *1) Manufactured by Degussa *2) Aluminum paste, manufactured by Toyo Aluminum Co., Ltd. *3) Manufactured by Mitsui Toatsu Chemical Co., Ltd., butyl etherified melamine resin (nonvolatile content 60%) *4) Manufactured by Mitsui Cyanamid Co., Ltd., Methyl butyl mixed etherified melamine resin (100% non-volatile content) *5) KI
Manufactured by NG, sulfonic acid catalyst

<Synthesis example of component (b) polymer> 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. The temperature was increased to 100°C. Next, styrene 3
0 parts, 2-hydroxyethyl methacrylate 30 parts, dibutyl fumarate 20 parts, glycidyl methacrylate 2
After dropping 100.5 parts of a solution consisting of 0 part of azobisisobutyronitrile and 0.5 parts of azobisisobutyronitrile over 4 hours, 0.5 parts of azobisisobutyronitrile was added, and the mixture was further stirred and heated for 2 hours. The conversion was increased to 100% and the reaction was terminated. After this, the temperature of the reaction vessel was lowered to 60°C, 2 parts of triethylamine was added as an addition reaction catalyst, 10 parts of acrylic acid and 0.5 parts of hydroquinone monomethyl ether were added as a polymerization inhibitor to carry out an addition reaction, and the acid value 3
The reaction was completed below to obtain Polymer F-1. Hereinafter, by changing the monomers etc. to be added dropwise as shown in Table 2, polymer F
-2 to F-6 were synthesized and the resin solution characteristic values were measured. The results are also shown in Table 2.

[0030]

[Table 2]

<Examples 1 to 9 and Comparative Examples 1 to 3> Thermosetting paints B-1 and B-2 were spray-coated onto a mild steel plate to a thickness of 20 μm, and heated at 150° C. for 30 minutes. After curing, a clear coat consisting of Examples and Comparative Examples according to the formulations in Tables 3 and 4 of the present invention was applied on this coating film, and the coating was heated at 60°C.
After setting for 5 minutes, UV irradiation was performed using a UV irradiation device UV-5003 manufactured by Mitsubishi Rayon Engineering under the conditions of 80 W/cm, 3 lamps, lamp height 30 cm, and conveyor speed of 4 m/min.

[0032] In the formulations in Tables 3 and 4, *1 to *10
is as follows. *1: Dipentaerythritol hexaacrylate *2
: Pentaerythritol triacrylate *3: Neopentyglycol diacrylate *4: Manufactured by Nippon Kayaku Co., Ltd. *5: Urethane acrylate manufactured by Mitsubishi Rayon Co., Ltd. *
6: Urethane acrylate manufactured by Mitsubishi Rayon Co., Ltd. *7
: Irgacure 184 manufactured by Ciba Geigy *8: Toluene/isopropanol/butyl vinegar = 1/1/1 *9: Polyester acrylate manufactured by Mitsubishi Rayon Co., Ltd. *10: Water-added bisphenol A epoxy acrylate

These samples were evaluated for adhesion, pencil hardness, 60° gloss, solvent resistance, acid resistance, scratch resistance, etc., and are shown in Tables 3 and 4.

[0034]

[Table 3]

[0035]

[Table 4]

[0036] 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 coating 10 times with #0000 steel wool, and solvent resistance was determined by soaking methyl ethyl ketone. Acid resistance was evaluated based on the change in appearance after rubbing the coating film 100 times with a dry cloth.Acid resistance was evaluated by dropping a 5% aqueous sulfuric acid solution onto the coating film and evaluating the change in appearance after standing for 24 hours.

As is clear from Tables 3 and 4, the clear coat made of the ultraviolet curable composition of the present invention exhibits excellent adhesion to thermosetting coatings, and also has excellent solvent resistance and acid resistance. It can be seen that it is excellent, and also has good hardness, gloss, and scratch resistance.

[0038]

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 solvent resistance and acid resistance. It has good hardness, gloss, and scratch resistance.

Claims (2)

[Claims] Claim 1: Radical polymerization is performed on the side chain of a copolymer obtained by copolymerizing (a) a polyfunctional (meth)acrylate having at least two or more radically polymerizable double bonds, and (b) dibutyl fumarate. 1. An ultraviolet curable composition comprising as a main component a polymer having possible double bonds. 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.