JP3265049B2 - Curable coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the appearance, weather resistance, water resistance, impact resistance, solvent resistance, chemical resistance,
The present invention relates to a coating composition capable of forming a crosslinked cured coating film having excellent adhesion to a substrate and corrosion resistance.

[0002]

2. Description of the Related Art At present, transparent or colored thermosetting acrylic resin-based paints are used for many automotive exterior parts. This thermosetting paint is useful in that it is inexpensive and the baking equipment is simple, but at present, it requires about 30 minutes per coat for the curing time of the coating line process. In view of the improvement of the coating process, there is a problem that the coating process cannot be shortened with such a long curing time.

[0003] On the other hand, an ultraviolet curable coating material can cure a coating film in a very short time (for example, within one minute), and is used as a plastic base material for cosmetic containers and interior building materials. As can be seen from the above, since there is little heat energy applied to the base material, in recent years, attempts have been made to use it as a plastic product automotive exterior part. However, UV-cured coatings have few compositions with good weather resistance due to changes in internal stress over time caused by residual double bonds, and weather resistance to automotive exterior materials such as aluminum wheels and plastic bumpers. In addition to
UV-curable coating compositions with satisfactory performance, as they require performance equivalent to automotive exterior coatings such as impact resistance, water resistance, heat resistance, solvent resistance, chemical resistance, corrosion resistance, and adhesion. The thing did not exist.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an external appearance, weather resistance, water resistance, impact resistance, solvent resistance, chemical resistance, adhesion to a substrate, and corrosion resistance by irradiating ultraviolet rays. ,
An object of the present invention is to provide a coating composition capable of forming a crosslinked cured coating film having excellent weather resistance.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, a light stabilizer, an ultraviolet absorber and an antioxidant are used in combination with a specific radically polymerizable compound. By expressing good weather resistance by using this, and by using an acrylic copolymer having no hydroxyl group in the side chain and phosphoric acid (meth) acrylate, it is possible to improve the adhesion to the substrate, The inventors have found that a performance satisfying the required characteristics can be obtained, and have completed the present invention.

That is, the present invention relates to (a) a compound having two (meth) acryloyloxy groups in one molecule (only
And the following components (b) and (d) are excluded)
Parts by weight, (b) urethane (meth) acrylate having two or more (meth) acryloyloxy groups in one molecule
15 parts by weight, (c) 50 to 5 parts by weight of an acrylic copolymer having no hydroxyl group in a side chain, and (d) phosphoric acid (meth) having at least one (meth) acryloyloxy group in one molecule. 0.1-5 parts by weight of acrylate, 0.1-10 parts by weight of (e) photopolymerization initiator, 0.1-5 parts by weight of hindered amine light stabilizer, (g) 0.1-UV absorber 5 parts by weight, and (h) 0.1 to 5 parts by weight of a primary antioxidant (provided that the total amount of the components (a) to (c) is 100 parts by weight;
The amount of the component (h) indicates the amount to be further added to 100 parts by weight. ) As a main component.

[0007]

In the curable coating composition of the present invention, the compound having two (meth) acryloyloxy groups in one molecule [component (a)] is used in an amount of 50 to 80 parts by weight.
If the amount is less than 50 parts by weight, the strength of the coating film is reduced, and if it is more than 80 parts by weight, the impact resistance is reduced.

Examples of the compound [component (a)] include a reaction between a polybasic acid such as phthalic acid and adipic acid, a polyhydric alcohol such as ethylene glycol and butanediol, and a (meth) acrylic acid compound. Polyester poly (meth) acrylate obtained; epoxy poly (meth) acrylate obtained by reaction of epoxy resin with (meth) acrylic acid compound; polysiloxane poly (obtained by reaction of polysiloxane with (meth) acrylic acid compound (Meth) acrylate; polyamide poly (meth) obtained by reacting a polyamide with a (meth) acrylic acid compound
Examples include acrylate and the like, and are not particularly limited. Such a compound can sufficiently function as a component of the coating composition of the present invention, but has a polymerizable double bond equivalent [molecular weight per (meth) acryloyloxy group].
Is 450 or less, since a high degree of solvent resistance and chemical resistance can be obtained.

[0009] Specific examples of the compound [(a) component] is polypropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate,
Arsenate Dorokishipibarin acid neopentyl glycol di (meth) acrylate, Ne o neopentyl glycol di (meth)
Acrylates and di (meth) acrylates of dicyclopentadienyl diol are exemplified.

In the curable coating composition of the present invention, the urethane (meth) acrylate having two or more (meth) acryloyloxy groups in one molecule [component (b)] is 0 to 10%.
Use within the range of 15 parts by weight. If the amount used exceeds 15 parts by weight, the strength of the coating film decreases and the solvent resistance becomes insufficient.

The urethane (meth) acrylate [(b)
Component] includes urethane (meta) synthesized by the reaction of triisocyanate alone, polyisocyanate such as burette of di (or tri) isocyanate, multimer or adduct with polyol, and hydroxyl group-containing (meth) acrylate. A) acrylate.

The polyisocyanate used in the above synthesis is preferably a non-yellowing type containing no aromatic ring. Specific examples thereof include ethylene diisocyanate, 1,2-diisocyanatopropane, 1,3-diisocyanatopropane, hexamethylene diisocyanate,
Lysine isocyanate, 4,4′-methylenebis (cyclohexyl) isocyanate, methylcyclohexane 2,4-diisocyanate, methylcyclohexane 2,
6-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate,
Examples thereof include diisocyanates such as trimethylhexamethylene diisocyanate, tetramethylene diisocyanate, and dimer diisocyanate, simple substances of triisocyanate, burettes and multimers thereof, and adducts thereof with polyols.

Specific examples of the polyol used in the above synthesis include ethylene glycol, propylene glycol, butylene glycol, polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene glycol, trimethylolpropane, polytrimethylolpropane, and pentaerythritol. And alcohols such as polypentaerythritol, sorbitol, mannitol, glycerin and polyglycerin, and polyether polyols; polyester polyols synthesized from polyhydric alcohols and polybasic acids; and polyester polyols such as polycaprolactone polyol.

The hydroxyl group-containing (meth) used in the above synthesis
As acrylate, 2-hydroxyethyl (meth)
Hydroxyalkyl (meth) acrylates such as acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate; addition of 2-hydroxyethyl (meth) acrylate and ethylene oxide , Adducts of 2-hydroxyethyl (meth) acrylate and propylene oxide, adducts of 2-hydroxyethyl (meth) acrylate and organic lactones such as adducts of 2-hydroxyethyl (meth) acrylate and ε-caprolactone, etc. Can be mentioned.

In the curable coating composition of the present invention, an acrylic copolymer having no hydroxyl group in the side chain [component (c)]
Is mainly used to improve the weather resistance by relaxing the internal stress of the coating film and to impart good water resistance and alkali resistance by not containing a hydrophilic group, and is used in the range of 50 to 5 parts by weight. I do. If the amount is more than 50 parts by weight, the appearance and solvent resistance will be reduced, and if it is less than 5 parts by weight, the adhesion, water resistance and chemical resistance will be low.

Examples of the radical polymerizable monomer used in the acrylic copolymer [component (c)] include (meth) acrylic acid, itaconic acid, fumaric acid, crotonic acid, maleic acid, monomethyl itaconate, and monobutyl itaconate. ,
Carboxyl group-containing vinyl monomers such as monomethyl maleate and monobutyl maleate are exemplified. Furthermore,
Styrene derivatives such as styrene, α-methylstyrene and vinyltoluene; polymerizable unsaturated nitriles such as (meth) acrylonitrile; vinyl esters such as vinyl acetate and vinyl propionate; glycidyl (meth) acrylate;
Epoxy group-containing monomers such as (meth) allyl glycidyl ether and metaglycidyl (meth) acrylate, basic monomers such as dimethylaminoethyl (meth) acrylic acid and diethylaminoethyl (meth) acrylic acid, methyl (meth) acrylate, Ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, (meth) acryl (Meth) acrylates such as dodecyl acid and stearyl (meth) acrylate. However, it is not particularly limited to these.

The acrylic copolymer [component (c)] may be a polymer obtained by any known polymerization method such as a solution polymerization method, a bulk polymerization method, and an emulsion polymerization method. It is desirable that In the case of solution polymerization method,
The monomer mixture is copolymerized in the presence of an organic solvent and a polymerization initiator.

In the curable coating composition of the present invention, a phosphoric acid (meth) acrylate having at least one (meth) acryloyloxy group in one molecule [component (d)]
It mainly exerts the effect of improving adhesion, and (a) to
(c) It is used in the range of 0.1 to 5 parts by weight based on 100 parts by weight of the total of the components. If the amount used is less than 0.1 part by weight, the adhesion is reduced, and if it exceeds 5 parts by weight, the appearance is reduced. Specifically, (meth) acryloyloxyethyl phosphate, di (meth) acryloyloxyethyl phosphate, tri (meth) acryloyloxyethyl phosphate, caprolactone-modified (meth) acryloyloxyethyl phosphate, caprolactone-modified diphosphate (Meth) acryloyloxyethyl, caprolactone-modified tri (meth) acryloyloxyethyl phosphate and the like.

In the curable coating composition of the present invention, the photopolymerization initiator [component (e)] is in the range of 0.1 to 10 parts by weight, preferably 100 parts by weight of the total of components (a) to (c). Is 1
Use in the range of 5 parts by weight. Specifically, benzophenone, benzoin, isobutyl ether, benzoin isopropyl ether, benzyldimethylmethal, 2,2
-Diethoxyacetophenone, 2,2-dibutoxyacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl-1- [4- (methylthio) phenyl 2-morpholino-propanone-1,
2-benzyl-2-dimethylamino1-1 (4-morpholinophenyl) -butanone-1, methylphenylglyoxylate, ethylphenylglyoxylate, 2
-Chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, 2,
4,6-trimethylbenzoyldiphenoylphosphine oxide and the like can be mentioned. These photopolymerization initiators can be used alone or in a mixture of two or more.

In the curable coating composition of the present invention, the hindered amine light stabilizer [component (f)], the ultraviolet absorber [component (g)], and the primary antioxidant [component (h)]
It is a component that greatly affects weather resistance, and by using these three components in combination, long-term weather resistance can be improved. These components (f) to (h) are the total of components (a) to (c),
0.1 to 5 parts by weight, preferably 0.5 to 3.0 parts by weight, per 100 parts by weight. The amount used is 0.
If the amount is less than 01 parts by weight, the effect of weather resistance is not recognized. If the amount exceeds 5 parts by weight, the cured coating surface becomes wrinkled and yellowing during curing becomes remarkable.

Hindered amine light stabilizer [component (f)]
Unlike UV absorbers, they do not have their own UV-absorbing ability, but supplement the radicals generated by light irradiation,
It stabilizes light. Specifically, screws (2, 2,
6,6-tetramethyl-4-piperidyl) sebacate,
Bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 4-benzoyloxy-2,2,
6,6-tetramethylpiperidine, poly [(6-morpholino-S-triazine-2,4-diyl), [(2,
2,6,6-tetramethyl-4-piperidyl) imino]
-Hexamethylene-[(2,2,6,6-tetramethyl-4-piperidyl) imino], N-2,2,6,6-tetramethyl-4-piperidyl-2- (2,2,6 6-
Tetramethyl-4-piperidylamino) 2-methylpropioamide, bis (1,2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-nbutylmalonate
2,2,6,6-pentamethyl-4-piperidyl) and the like.

The ultraviolet absorbent (component (g)) absorbs harmful ultraviolet light having a wavelength of 300 to 400 nm which causes photo-oxidative deterioration, and radiates the energy mainly as heat energy.
It does not change itself. Examples of the type include salicylic acid, benzophenone, benzotriazole, and dianoacrylate, and benzophenone is preferred from the viewpoint of yellowing during curing. Specifically, 2,4-hydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4
-Dodecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone,
Ethyl-2-cyano-3,3′-diphenylacrylate and the like.

The primary antioxidant [component (h)] prevents oxidative deterioration caused by oxygen in the air. For example, it is a so-called radical chain inhibitor such as a phenolic antioxidant, a monophenolic / bisphenolic / polymeric phenolic antioxidant, and an amine-based antioxidant. On the other hand, those called secondary antioxidants such as peroxide decomposers such as sulfur-based antioxidants and phosphorus-based antioxidants have poor yellowing during curing and yellowing during weathering tests, and are not suitable for use. Not suitable. Examples of the primary antioxidant [component (h)] include phenol-based, that is, completely hindered phenols such as 2,6-di-t-butylphenol derivatives, and partially hindered phenols such as 2-methyl-6-t-butylphenol derivatives. Phenolics are mentioned. As a specific example, 2-t
-Butyl-6- (3'-t-butyl-5'-methyl-
2'-hydroxybenzyl) -4-methylphenyl acrylate, 2,2'-methylenebis (4-methyl-6-
t-butylphenol), 4,4'-butylidene-bis (3-methyl-6-t-butylphenol), 3,9
-Bis [2- [3- (3-t-butylhydroxy-5-
Methylphenyl) propionyloxy-1,1′-dimethylethyl] -2,4,8,10-tetraoxaspiro [5,5] undecane.

The curable coating composition of the present invention may contain a leveling agent, a slip agent, an antifoaming agent, an anti-repellent agent, a wetting agent, a dispersant, an anti-settling agent, a dripping inhibitor, a polymerization inhibitor, if necessary. Various additives such as an agent and a coupling agent, and a volatile organic solvent for viscosity adjustment can be used.

The curable coating composition of the present invention is rapidly cured by irradiating ultraviolet rays such as a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, a gallium lamp, a metal halide lamp, and sunlight. be able to.

The curable coating composition of the present invention can be used, for example, as a top coat material for aluminum wheels and plastic bumpers, and is formed by coating and curing an enamel dye obtained by mixing a metallic pigment and / or a coloring pigment with a thermosetting paint. Can be applied on top.

[0027]

The present invention will be described below in more detail with reference to examples and comparative examples. In the following description, “parts” means “parts by weight” unless otherwise specified.

<Synthesis example of urethane (meth) acrylate (b-1) having two or more (meth) acryloyloxy groups in one molecule> 2 mol of isophorone diisocyanate, 1 mol of polytetramethylene glycol, 2-hydroxyethyl 2 mol of acrylate and 2-ethylhexyl acrylate were charged with dibutyltin dilaurate in an amount of 0.02 parts per 100 parts by weight, and 1 mol of polytetramethylene glycol was added dropwise while maintaining the temperature at 40 ° C., and the reaction was allowed to proceed for a sufficient time. After that, 0.1 part of hydroquinone was added, and heating and stirring were continued for a further sufficient time to obtain urethane acrylate (b-1).

<Synthesis example of urethane (meth) acrylate (b-2) having two or more (meth) acryloyloxy groups in one molecule> 2 mol of 4,4'-diisocyanatocyclohexylmethane, polypropylene glycol 1
Using 2 mol of 2-hydroxypropyl acrylate and the same method as in (b-1), urethane acrylate (b-2) was obtained.

<Synthesis Example of Acrylic Copolymer (c-1) Having No Hydroxyl Group in Side Chain> Solvesso # 100 was placed in a container equipped with a stirrer, a temperature controller, and a condenser.
53.3 parts by weight were charged. 120 with stirring
Then, 2 parts by weight of azobisisobutyronitrile and 2 parts by weight of t-butylperoxyisopropyl carbonate were added to 100 parts by weight of the following monomer mixture, and the mixture was added dropwise over 3 hours. Next, 0.1 parts by weight of azobisisobutyronitrile was added four times at 30 minute intervals. Furthermore, after heating and stirring at 120 ° C. for 2 hours to increase the reaction rate, 13.3 parts by weight of n-butyl acetate was added to terminate the reaction to obtain an acrylic copolymer (c-1).

(Monomer mixture) Styrene 25 parts Methacrylic acid 20 parts n-butyl methacrylate 20 parts N-methoxymethylacrylamide 8 parts 2-ethylhexyl methacrylate 9 parts Methyl methacrylate 18 parts

<Synthesis Example of Acrylic Copolymer (c-2) Having No Hydroxyl Group in Side Chain> In the same manner as in the production example of (c-1), except that the following monomer mixture is used. An acrylic copolymer (c-2) was obtained.

(Monomer mixture) Styrene 27 parts Methacrylic acid 10 parts n-butyl methacrylate 20 parts Methyl methacrylate 15 parts 2-ethylhexyl methacrylate 10 parts i-butyl methacrylate 18 parts.

<Preparation of conventional thermosetting paint> A resin prepared from the following monomer mixture (synthesized by the same method as in c-1) and Uvan 20SE (Melamine resin manufactured by Mitsui Toatsu Chemicals, Inc.) were mixed at a ratio of 70/30. At a weight ratio of

(Monomer mixture) Ethyl acrylate 15 parts Styrene 20 parts Methacrylic acid 18 parts Methyl acrylate 29 parts 2-hydroxyethyl methacrylate 18 parts

<Examples 1 to 9 and Comparative Examples 1 to 9> Each of the compositions shown in Table 1 was placed on a degreased aluminum plate in an amount of 10 μm.
m, and preliminarily dried at 60 ° C. for 5 minutes, and then irradiated with ultraviolet rays to form a crosslinked coating film. Further, with respect to the conventional thermosetting paint, a cured coating film was formed at 140 ° C. for 30 minutes. As shown in the evaluation results of the coating films in Table 2, the composition of each example was more excellent than that of the comparative example.
Excellent in various performances.

[0037]

[Table 1] (Abbreviations in Table) a-1: neopentyl glycol diacrylate a-2: neopentyl glycol ester diacrylate hydroxypivalate d-1: biscoat 3PA (manufactured by Osaka Organic Chemical Co., Ltd.) d-2: biscoat 3PMA ( E-1: Irgacure 184 (manufactured by Ciba Geigy) e-2: benzophenone f-1: bis (1,2,2,6,6-pentamethyl-4)
-Piperidyl) sebacate f-2: bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate g-1: 2,4-hydroxybenzophenone g-2: 2-hydroxy-4-methoxybenzophenone h- 1: 2,2′-methylenebis (4-methyl-6-t
-Butylphenol) h-2: 2-t-butyl-6- (3'-t-butyl-
5'-methyl-2'-hydroxybenzyl) -4-methylphenyl acrylate

[0038]

[Table 2] (Evaluation method) Appearance: Visual evaluation Water resistance: Visual evaluation after 120 H at 40 ° C. Impact resistance: DuPont impact test, Visual evaluation at a height of 15 cm with a 500 g load Solvent resistance: Visual evaluation after immersion in gasoline at 20 ° C. for 1 H Ability: Visual evaluation after immersion in 5% sodium carbonate, 40 ° C., 8H Adhesion: Bombardment test, visual evaluation Corrosion resistance: Visual evaluation after spraying 5% sodium chloride, 35 ° C., 300H Weather resistance: Sunshine weather meter (Suga tester ( Co., Ltd.)

[0039]

As described in detail above, the composition of the present invention can be cured by ultraviolet rays, and the resulting coating film has an appearance, weather resistance, water resistance, impact resistance, solvent resistance, It is excellent in chemical resistance, adhesion to a substrate, corrosion resistance, and weather resistance, and its industrial significance is extremely high.

Continuation of the front page (56) References JP-A-4-209966 (JP, A) JP-A-5-17706 (JP, A) JP-A-58-219272 (JP, A) (58) Fields studied (Int .Cl. ⁷ , DB name) C09D 4/00-4/06

Claims (1)

(57) [Claims] (1) A compound having two (meth) acryloyloxy groups in one molecule (provided that the following component (b) and
And (b) the following components (d) are excluded): 50 to 80 parts by weight; (b) 0 to 15 parts by weight of a urethane (meth) acrylate having two or more (meth) acryloyloxy groups per molecule; (c) side chain Acrylic copolymer having no hydroxyl group
5 parts by weight, (d) phosphoric acid (meth) acrylate having at least one (meth) acryloyloxy group per molecule 0.1 to 0.1 parts by weight
5 parts by weight, (e) 0.1 to 10 parts by weight of a photopolymerization initiator, (f) 0.1 to 5 parts by weight of a hindered amine light stabilizer, (g) 0.1 to 5 parts by weight of an ultraviolet absorber, and (h) 0.1 to 5 parts by weight of primary antioxidant (provided that (a) to
The total amount of the component (c) is 100 parts by weight, and the amounts of the components (d) to (h) indicate the amount to be added to 100 parts by weight. ) As the main component.