JP5956401B2 - UV curable coating composition with excellent resistance to hot water, coating film forming method, coated article - Google Patents

Description

The present invention relates to an ultraviolet curable coating composition, in particular, an ultraviolet curable coating composition suitable for application to a transparent synthetic resin molded article such as a polycarbonate substrate, a method for forming a coating film thereof, and a coated article.

Synthetic resin molded products manufactured from polymethylmethacrylate resin, polycarbonate resin, etc. are not only lightweight and excellent in impact resistance, but also have good transparency and workability, and are used for lighting windows and lenses in recent years. The use of inorganic glass as an alternative material is increasing. Specifically, it is increasingly used as a plastic material for automobiles for headlamps, glazing, instrument covers, and the like. In addition, the use of roofing materials such as carports and terraces as housing and building materials is increasing.
On the other hand, since it is a resin base material, there is a problem in that it deteriorates in weather resistance, such as a change in appearance due to light or oxygen, that is, a reduction in coloration or transparency, or a deterioration in material strength.
In addition, these synthetic resin molded products do not have sufficient wear resistance on the surface, so the surface is easily damaged by contact with other hard objects, friction, scratches, etc. There is also a need to improve the wear resistance of the surface as it significantly reduces value and renders the product unusable in a short period of time.
Furthermore, water resistance is also required in order to be suitable for applications used outdoors.

Various methods have been studied for improving the drawbacks of such synthetic resin molded products. For example, a coating material made of a resin composition such as silicon or melamine is applied to the surface of a synthetic resin molded product. A method of improving the abrasion resistance by applying heat condensation to form a crosslinked coating film, or applying a radical polymerizable monomer or a cationic polymerizable composition, and then irradiating active energy rays such as ultraviolet rays to the crosslinked coating film. There has been proposed a method for forming the film.

By these methods, the wear resistance of the surface of the synthetic resin molded article is improved to some extent. However, the former method requires a high baking temperature, so that the base material is deformed and is economically disadvantageous.
In the latter method, although durability and chemical resistance are excellent, particularly in the case of a synthetic resin molded article having essentially poor weather resistance, such as a polycarbonate substrate, the weather resistance of the cured coating film on the surface itself Even if the properties are good, the base material itself is deteriorated by active energy rays such as ultraviolet rays contained in the sunlight that has passed through the coating film, causing yellowing, cracks in the cured coating film on the surface, The film peels off.
In addition, when used as a roofing material, snow may be melted with warm water. In such a case, if there is no warm water resistance in the coating film, there is a problem that the appearance of the coating film is deteriorated by the warm water and the commercial value is remarkably lowered.

Therefore, as a coating material that does not change the base material even when used outdoors for a long time, JP-A-11-021470 proposes an ultraviolet curable liquid composition using a specific resin composition. However, the wear resistance is not sufficient, and the hot water resistance is not sufficient.
Accordingly, there has been a demand for an ultraviolet curable coating composition that is not only excellent in weather resistance but also excellent in wear resistance and warm water resistance.

Japanese Patent Laid-Open No. 11-021470

In view of the above, an object of the present invention is to provide an ultraviolet curable coating composition excellent in transparency, abrasion resistance, weather resistance, and hot water resistance, and a method for forming a coating film.
Another object of the present invention is to provide a coated article having a coating film formed on its surface using an ultraviolet curable coating composition.

That is, this invention provides the ultraviolet curable coating composition characterized by including the following components (a)-(g) and having a haze value of 2% or less when a dry film having a thickness of 10 μm is formed. .
(A) a urethane acrylate that have a 4-9 acryloyl groups in the molecule; have 20 to 70 parts by weight (b) 1 to 3 acryloyl groups in the molecule, further has a polyester skeleton in a resin skeleton Urethane acrylate : 10 to 60 parts by weight (c) Urethane acrylate having 1 to 3 acryloyl groups in the molecule and no polyester skeleton in the resin skeleton ; 2 to 18 parts by weight (d) acetophenone-based Photopolymerization initiator; 1 to 20 parts by weight with respect to 100 parts by weight of the total amount of component (a), component (b) and component (c) (e) Phosphine oxide-based photopolymerization initiator; component (a) , 0.5 to 15 parts by weight relative to 100 parts by weight of the total amount of component (b) and component (c)
(F) Ultraviolet absorber; 1 to 20 parts by weight (g) with respect to 100 parts by weight of the total amount of component (a), component (b) and component (c); light stabilizer; component (a), component (b) ) And 1 to 20 parts by weight relative to 100 parts by weight of the total amount of component (c) The present invention also relates to a method for forming a coating film using the above-described ultraviolet curable coating composition, and the above-described ultraviolet curable coating. Provided is a coated article having a coating film formed on the surface using the composition.

Since the ultraviolet curable coating composition of the present invention has the above-described configuration, it is excellent in transparency, abrasion resistance, weather resistance and hot water resistance, and is a synthetic resin molded article, particularly as a surface coating for a polycarbonate substrate. Is preferred.

The present invention is described in detail below.

The urethane acrylate compound (a) (hereinafter referred to as “component (a)”) having 2 to 9 acryloyl groups in the molecule used in the present invention is a hydroxyl group (—OH group) in the resin skeleton. And an amino group (—NH ₂ group) is preferred. This is because those having a hydroxyl group and an amino group in the resin skeleton have an effect of promoting yellowing by interacting with a π-electron system such as an aromatic ring or a double bond.

The component (a) used in the present invention comprises a compound (a1) having two or more isocyanate groups in the molecule (hereinafter referred to as “component (a1)”), a hydroxyl group and 1 to 5 It is obtained by reacting a compound (a2) having an acryloyl group (hereinafter referred to as “component (a2)”), and has 2 to 9 acryloyl groups in the molecule.

The component (a1) may be aliphatic or alicyclic, such as hexamethylene diisocyanate, lysine diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), methylcyclohexane- 2,4-diisocyanate, methylcyclohexane-2,6-diisocyanate, 1,3- (isocyanatomethyl) cyclohexane, isophorone diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methylene diisocyanate, ethylene diisocyanate, butylene diisocyanate, propylene diisocyanate, octa Decylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,10-decanmethylene diisocyanate, 1,3- Isocyanurate of black hexylene diisocyanate such as diisocyanate, biuret, can be mentioned adducts and the like.

As said component (a2), the compound etc. which added the acrylic acid to the polyacrylate esterified with acrylic acid with respect to the hydroxyl group of the polyol which has a 2 or more hydroxyl group in a molecule | numerator, etc. can be mentioned. Examples of the polyol having two or more hydroxyl groups in the molecule include ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,5-pentanediol. 1,4-hexanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, triethylene glycol and the like.

The said component (a) can be manufactured as follows, for example. The said component (a1) and the said component (a2) are made to react at the temperature of 60-70 degreeC in presence of 1000 ppm of dilauric acid n-butyltin catalysts in the compounding ratio from which an isocyanate group and a hydroxyl group become equivalent. The component (a) is obtained by reacting the reaction mixture until absorption of isocyanate groups in the reaction mixture is not observed by FT-IR.
Examples of commercially available urethane acrylate compounds (a) having 2 to 9 acryloyl groups in the molecule include WJV-534 (manufactured by DIC).

The component (a) is particularly preferably an aliphatic urethane acrylate having 3 to 5 acryloyl groups. The acryloyl group is more reactive than the methacryloyl group. As a result, the curing rate is high and the reactive functional groups are less likely to remain unreacted, and the weather resistance is prevented from being lowered due to the unreacted groups, so that the weather resistance is improved.
Examples of commercially available products include KRM7804 and KRM8452 (both manufactured by Daicel Ornex).

The component (a) is more preferably a urethane acrylate in which amorphous nanosilica particles whose functional groups are modified on the surface are bonded to molecular ends. By arranging the cured coating film so as to form a nanocomposite structure and silica particles are lifted on the surface of the coating film, the wear resistance can be remarkably improved. In addition, because the silica particles are nano-sized, the coating film becomes white and cloudy due to light refraction and interference light caused by unevenness on the coating film surface, such as when silica particles with a particle size of micron size or larger are used. It is not visible and a coating film with excellent transparency can be formed. Furthermore, since the silica particles and urethane acrylate form a chemically strong bond, even if the coating film is worn, the silica particles are not easily detached from the coating film and have excellent durability.

In order to modify the surface of the amorphous nanosilica particles with a functional group, there is a method of treating with a silane coupling agent. For example, the surface of the amorphous nanosilica particles can be treated with an amino group-containing silane coupling agent to silylate the surface, and the silylated particles can be further treated with a polymer to form polymer-grafted silica particles. When the polymer is grafted onto the surface of silica, which is an inorganic compound, that is, an organic group is bonded, the affinity of the silica particles to the organic compound is improved. Therefore, the dispersibility with respect to resin which is a bulk component which forms a coating film improves, and aggregation of silica particles is suppressed simultaneously. This makes it possible to crosslink the silica particles and the resin in detail, and the wear resistance is dramatically improved. In addition, cross-linking over details increases the degree of cross-linking of the resin and contributes to improved weather resistance.
The method for imparting a functional group to the surface of the amorphous nanosilica particles is not limited to the above method, and any method may be used as long as the same effect is obtained.

The particle size of the amorphous nanosilica particles needs to be nano-sized. Specifically, the thickness is preferably 1 to 50 nm. If it is 1 nm or more, it is effective in improving the wear resistance and can be easily prepared. On the other hand, when the thickness is 50 nm or less, the transparency of the coating film is not lowered, and a coating film having excellent transparency can be formed. Preferably, it is 20-40 nm.

Examples of commercially available components (a) include KRM85528C (manufactured by Daicel Ornex).

The content of the component (a) is such that the component (a), the urethane acrylate (b) having 1 to 3 acryloyl groups in the molecule (hereinafter referred to as “component (b)”) and the molecule. In a total amount of 100 parts by weight of urethane acrylate (hereinafter referred to as “component (c)”) different from (a) and (b) having 1 to 3 acryloyl groups, the solid content is 20 to 70 parts by weight. is there. When the amount is less than 20 parts by weight, the wear resistance is lowered. When the amount exceeds 70 parts by weight, the weather resistance is lowered and economically disadvantageous.
Preferably, it is 35-60 weight part.

The component (b) used in the present invention comprises a compound (b1) having 1 to 3 isocyanate groups in the molecule (hereinafter referred to as “component (b1)”), a hydroxyl group and 1 to 3 in the molecule. The compound (b2) having the acryloyl group (hereinafter referred to as “component (b2)”) is reacted and has 1 to 3 acryloyl groups in the molecule. Similar to component (a), the functional group having a double bond for UV curing is preferably an acryloyl group rather than a methacryloyl group because of its high reaction rate and low yellowing of the coating film.
Similar to the components (a), it is preferable in the resin backbone are those which do not have hydroxyl group (-OH group) and amino group (-NH ₂ group). This is because those having a hydroxyl group and an amino group in the resin skeleton have an effect of promoting yellowing by interacting with a π-electron system such as an aromatic ring or a double bond.

The component (b) preferably has a homopolymer glass transition temperature (Tg) of -40 to 40 ° C. When it is −40 ° C. or lower, the scratch resistance is lowered, and when it is 40 ° C. or higher, the weather resistance is lowered. Preferably it is -30 degreeC-30 degreeC, Most preferably, it is -20-20 degreeC.

The component (b1) may be either aliphatic or alicyclic, such as hexamethylene diisocyanate, lysine diisocyanate, 4,4'-methylenebis (cyclohexyl isocyanate), methylcyclohexane-2. , 4-diisocyanate, methylcyclohexane-2,6-diisocyanate, 1,3- (isocyanatomethyl) cyclohexane, isophorone diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methylene diisocyanate, ethylene diisocyanate, butylene diisocyanate, propylene diisocyanate, octade Sylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,10-decanmethylene diisocyanate, 1,3-si Isocyanurates of diisocyanates such as Rohe diisocyanate, biuret, can be mentioned adducts and the like.
An aromatic isocyanate compound is not preferable because it easily yellows.

Examples of the component (b2) include polyacrylate esterified with acrylic acid to a hydroxyl group of a polyol having 1 to 3 hydroxyl groups in the molecule, a compound obtained by adding acrylic acid to glycidyl acrylate, and the like. it can.
Examples of the polyol having 1 to 3 hydroxyl groups in the molecule include the same compounds as those having 1 to 3 hydroxyl groups in the molecule among the compounds described above as the component of component (a). be able to.

The component (b) is particularly preferably an aliphatic urethane acrylate having a structure containing a polyester skeleton. This is because the polyester structure has a small steric hindrance in the molecular skeleton and is highly flexible in the molecular skeleton, so that there are fewer reactive functional groups remaining unreacted during the curing reaction.
In order to synthesize an aliphatic urethane acrylate containing a polyester skeleton, a polyester polyol may be used as the polyol.
Examples of the polyester polyol include caprolactone-modified diol.

The said component (b) can be manufactured as follows, for example.
The said component (b1) and the said component (b2) are made to react at the temperature of 60-70 degreeC in presence of 1000 ppm of dilaurate n-butyltin catalysts in the compounding ratio from which an isocyanate group and a hydroxyl group become equivalent.
The component (b) is obtained by reacting the reaction mixture until absorption of isocyanate groups in the reaction mixture is not observed by FT-IR.

Content of the said component (b) is 10-60 weight part as solid content in 100 weight part of total amounts of the said component (a), the said component (b), and the said component (c).
When it is less than 10 parts by weight, the weather resistance is lowered, and when it exceeds 60 parts by weight, the hot water resistance and the wear resistance are lowered.
Preferably, it is 20-50 weight part.

The component (c) used in the present invention comprises a compound (c1) having 1 to 3 isocyanate groups in the molecule (hereinafter referred to as “component (c1)”), a hydroxyl group and 1 to 3 in the molecule. The compound (c2) having an acryloyl group (hereinafter referred to as “component (c2)”) is reacted and has 1 to 3 acryloyl groups in the molecule.

The component (c1) is preferably aliphatic or cycloaliphatic, such as hexamethylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methylene diisocyanate, ethylene diisocyanate, butylene diisocyanate, propylene. Examples include diisocyanates such as diisocyanate, octadecylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,10-decanmethylene diisocyanate, and 1,3-cyclohexylene diisocyanate, burette bodies, adduct bodies, and the like.

The component (c2) is not particularly limited. For example, one of the hydroxyl groups of a polyol having 1 to 3 hydroxyl groups in the molecule is left, and acrylic acid is added to polyacrylate and glycidyl acrylate esterified with acrylic acid. Examples include added compounds. The polyol having 1 to 3 hydroxyl groups in the molecule is not particularly limited, and examples thereof include the same compounds as the above-described compounds having 1 to 3 hydroxyl groups in the molecule as the component of component (a). be able to.

The component (c) preferably has a weight average molecular weight of 5,000 to 30,000. More preferably, it is 8000-25000. When the weight average molecular weight is 5000 or less, there is no effect in improving hot water resistance, and when it is 30000 or more, the compatibility with other components is poor and the transparency of the coating film is impaired.

The said component (c) can be manufactured as follows, for example.
The said component (c1) and the said component (c2) are made to react at the temperature of 60-70 degreeC in presence of 1000 ppm of dilaurate n-butyltin catalysts in the compounding ratio from which an isocyanate group and a hydroxyl group become equivalent.
The component (c) is obtained by reacting the reaction mixture until absorption of isocyanate groups is not observed by FT-IR.

Content of the said component (c) is 2-18 weight part as solid content in 100 weight part of total amounts of the said component (a), the said component (b), and the said component (c). When it is less than 2 parts by weight, the warm water resistance is lowered, and when it exceeds 18 parts by weight, the weather resistance and the warm water resistance are lowered. Preferably, it is 5 to 15 parts by weight.

The first photopolymerization initiator (d) used in the present invention is preferably an acetophenone type, and examples thereof include the following. 2,2-dimethoxy-2-phenylacetophenone, pt-butyltrichloroacetophenone, pt-butyldichloroacetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, and the like.
Among these, α-hydroxyacetophenone is particularly preferable to α-aminoacetophenone from the viewpoint of yellowing and odor. α-Hydroxyacetophenone has little yellowing of the cured product, and can be kept low in yellowing immediately after ultraviolet irradiation or during storage in sunlight or indoor light, and has excellent surface curability.

The addition amount of the acetophenone photopolymerization initiator is not particularly limited, but is 1 to 1 as an active ingredient with respect to 100 parts by weight of the total amount of the component (a), the component (b) and the component (c). It is preferably 20 parts by weight. More preferably, it is 2 to 12 parts by weight, and particularly preferably 3 to 10 parts by weight. If it is less than 1 part by weight, curing in the presence of the UV absorber is insufficient, and if it exceeds 20 parts by weight, yellowing of the coating film becomes large and uneconomical, so it is limited to the above range. The

The second photopolymerization initiator (e) used in the present invention is preferably a phosphine oxide type.
By adding a phosphine oxide-based photopolymerization initiator, radicals can be generated by irradiation with light having a long wavelength, so that the deep portion of the coating film can be particularly cured. Furthermore, since the phosphine oxide-based ultraviolet polymerization initiator has a photobleaching effect that eliminates absorption in the visible light region due to a photoreaction, yellowing is also extremely reduced.
Since the phosphine oxide-based photopolymerization initiator can generate radicals by irradiation with light in a wide wavelength range, those that generate radicals by irradiation with light having a wavelength shorter than 380 nm are preferable. The phosphine oxide photopolymerization initiator is preferably an acyl phosphine oxide photopolymerization initiator. For example, the following can be mentioned. 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylphenylphosphine oxide, and the like.

The blending amount of the phosphine oxide photopolymerization initiator is not particularly limited, but it is an active ingredient with respect to 100 parts by weight of the total amount of the component (a), the component (b) and the component (c). It is preferably 0.5 to 15 parts by weight. More preferably, it is 1-12 weight part, Most preferably, it is 2-8 weight part. If it is less than 0.5 part by weight, curing in the presence of the UV absorber is insufficient, and if it exceeds 15 parts by weight, the shrinkage of curing becomes too large, so that the adhesion is lowered. Moreover, since there exists a problem that coloring becomes large and it is uneconomical, it is limited to the said range.

It does not specifically limit as an ultraviolet absorber (f) used by this invention, For example, the following can be mentioned.
Phenyl salicylate, 4-t-butylphenyl salicylate, 2,4-di-t-butylphenyl-3,5'-di-t-butyl-4'-hydroxylbenzoate, 4-t- Salicylate UV absorbers such as octylphenyl salicylate; 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2-hydroxy- 4-n-octoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane, 2,2 '-Dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-di Toxibenzophenone, 2,2 ', 4,4'-tetrahydroxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2-hydroxy-4- (2- Benzophenone-based UV absorbers such as (methacryloyloxyethoxy) benzophenone.

2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- [2′-hydroxy-3 ′, 5′-bis (α, α-dimethylbenzyl) phenyl] benzotriazole, 2- ( 2'-hydroxy-3 ', 5'-di-tert-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazo 2- (2'-hydroxy-3 ', 5'-di-t-butylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3', 5'-di- t-amyl) benzotriazole, 2- (2'-hydroxy-5'-t-octylphenyl) benzotriazole, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2N-benzotria Zol-2-yl) phenol] and the like.
2- [4-[(2-hydroxy-3-dodecyloxypropyl) oxy] -2-hydroxyphenyl] 4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2- [ 4- (2-hydroxy-3-tridecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4dimethylphenyl) -1,3,5-triazine, 2- [4- [ (2-hydroxy-3- (2'-ethyl) hexyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2,4- Bis (2-hydroxy-4-butyloxyphenyl) -6- (2,4-bis-butyloxyphenyl) -1,3,5-triazine, 2- (2-hydroxy-4- [1-octyloxycarbonyl) Ethoxy ] Phenyl) -4,6-bis (4-phenylphenyl) -1,3,5-triazine, 2,2 ', 4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'- Dimethoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-acetoxyethoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4- Methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-n-octoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxy-5,5'-di Hydroxyphenyltriazine-based purple such as sulfobenzophenone disodium salt Linear absorption agents and the like.
These may be used alone or in combination of two or more.
Of these, a hydroxyphenyltriazine-based ultraviolet absorber is preferred because the ultraviolet absorber itself is stable to ultraviolet rays and heat and is excellent in absorbability.

A commercial item can be used as said ultraviolet absorber (f).
As said commercial item, Tinuvin 400, Tinuvin 477 (made by Ciba Japan) etc. can be mentioned, for example.

Content of the said ultraviolet absorber (f) is 1-20 weight part as solid content with respect to 100 weight part of total amounts of the said component (a), the said component (b), and the said component (c).
When it is less than 1 part by weight, the coating film turns yellow during the weather resistance test, and when it exceeds 20 parts by weight, the curability, adhesion, and wear resistance are reduced, so the range is limited to the above range.
The amount is preferably 2 to 15 parts by weight, particularly preferably 3 to 12 parts by weight.

The light stabilizer (g) used in the present invention is not particularly limited, and examples thereof include phenyl-4-piperidinyl carbonate, bis- (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, Bis- (n-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis- (1,2,2,6,6-pentamethyl-4-piperidyl) -2- (3,5 -Di-t-butyl-4-hydroxybenzyl) -2-n-butyl malonate, 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, 2,2,6,6-tetramethyl-4 -Hindered amine light stabilizer such as piperidyl methacrylate; ethyl-2-cyano-3,3-diphenyl acrylate, 2-ethylhexyl-2-cyano-3,3'-diphenyl acrylate, Cyanoacrylate light stabilizer such as a chill 2-cyano-3-methyl-3- (p-methoxyphenyl) acrylate, and the like.
Among these, a hindered amine light stabilizer having a larger effect in a small amount is preferable.
Among the hindered amine light stabilizers, those having a reactive group such as an acryloyl group or a methacryloyl group are particularly preferable. Since it is polymerized with the coating film-forming resin and incorporated into the coating film, it becomes difficult to bleed out and its function can be maintained for a long time.

A commercial item can be used as said light stabilizer (g).
As said commercial item, ADK STAB LA-87 (made by ADEKA), Tinuvin 152 (made by Ciba Japan), etc. can be mentioned, for example.

Content of the said light stabilizer (g) is 1-20 weight part as solid content with respect to 100 weight part of total amounts of the said component (a), the said component (b), and the said component (c). If it is less than 1 part by weight, the coating film turns yellow during the weather resistance test, and if it exceeds 20 parts by weight, the curability and wear resistance decrease, so the range is limited. The amount is preferably 2 to 15 parts by weight, particularly preferably 3 to 12 parts by weight.

In the ultraviolet curable coating composition of the present invention, an organic solvent, an antioxidant, an anti-yellowing agent, a blueing agent, a pigment, a leveling agent, an antifoaming agent, a thickening agent, an anti-precipitation agent, if necessary, An antistatic agent, an antifogging agent, a slip agent and the like may be added.

The ultraviolet curable coating composition of the present invention requires a haze value of 2% or less when a dry coating film having a film thickness of 10 μm is used. It is suitable for application to a material to be coated.
A universal method for reducing the haze value to 2% or less when a dry coating film of 10 μm is not clear, and generally the coating composition becomes turbid when the compatibility between the components used in the coating composition is poor. As a result, the haze value of the coating film made from this increases. Therefore, it is necessary to use a combination of components having good compatibility.

The substrate to which the ultraviolet curable coating composition of the present invention is applied is not particularly limited. For example, polymethyl methacrylate resin, polymethacrylamide resin, polycarbonate resin, polystyrene resin, polyethylene terephthalate (PET) resin, AS resin, A synthetic resin molded product obtained by molding an ABS resin or the like can be used.
Especially, the base material which shape | molded polycarbonate resin is preferable.

The synthetic resin molded product is not particularly limited. For example, a synthetic product obtained by molding a polymethyl methacrylate resin, a polymethacrylimide resin, a polycarbonate resin, a polystyrene resin, a polyethylene terephthalate (PET) resin, an AS resin, an ABS resin, an acrylic resin, or the like. Examples include resin molded products.
Among these, it is particularly preferable to apply to a molded product formed from a polycarbonate resin or a sheet formed from a polyethylene terephthalate (PET) resin.

The method for applying the ultraviolet curable coating composition is not particularly limited, and examples thereof include spray coating, dip coating, and roll coating.
The thickness of the coating film is preferably 3 to 30 μm after curing.
When the thickness is less than 3 μm, sufficient weather resistance and wear resistance cannot be obtained, and curing inhibition by oxygen tends to occur. If it exceeds 30 μm, there is a problem that the curing shrinkage becomes large, so that the adhesiveness is lowered and the coloring of the coating film is not negligible.
More preferably, it is 4-20 micrometers, Most preferably, it is 5-15 micrometers.

The method for removing the solvent is not particularly limited, and examples thereof include preheating.
The preheating can be performed by an IR furnace, an electric furnace, a gas furnace, or the like.
In the preheating, the temperature of the synthetic resin molded product is preferably maintained at 60 to 80 ° C. for 5 to 15 minutes.
If the temperature of the synthetic resin molded product is less than 60 ° C., the organic solvent in the applied UV curable coating composition remains, causing blemishes in the initial coating film, and whitening of the coating film during the weather resistance test. Arise.

The cooling is preferably performed until the temperature of the synthetic resin molded product reaches 50 ° C. or lower.
If the temperature of the synthetic resin molded product exceeds 50 ° C., heat is further applied by ultraviolet irradiation performed after cooling, and the synthetic resin molded product is deformed.
More preferably, it is 40 degrees C or less.

As the ultraviolet light source, for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used. Irradiation conditions vary depending on each lamp, but the irradiation light amount may be about 600 to 1400 mJ / cm ² , preferably 800 to 1200 mJ / cm ² , and peak intensity is 90 to 500 mw / cm ² , preferably 110 to 400 mw. / Cm ² .

The coating film formation method of this invention can be performed as follows, for example.
The synthetic resin molded product after molding is coated with an ultraviolet curable coating composition so that the film thickness after curing is 3 to 30 μm, and then the coated synthetic resin molded product is subjected to IR furnace, electric furnace, gas In an oven or the like, the organic solvent is volatilized by preheating at 60 to 80 ° C. for 5 to 15 minutes. The synthetic resin molded product may be annealed before painting.
Thereafter, the coating film is sufficiently cooled to 50 ° C. or less, and irradiated with ultraviolet rays in the air or in a nitrogen atmosphere at a lamp height of 10 to 30 cm using a lamp such as a high-pressure mercury lamp or a metal halide lamp. Form.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Each component was mixed according to the composition shown in Table 1 and Table 2 to obtain an ultraviolet curable coating composition.
The following (1)-(12) was used for the component in Table 1 and Table 2.
In addition, the number of the mixing | blending in Table 1 and Table 2 is a value after converting into solid content.
(1) KRM8528C (tetrafunctional aliphatic urethane acrylate oligomer that forms a nanocomposite in which amorphous nanosilica is dispersed, solid content: 95% by weight, manufactured by Daicel Ornex)
(2) KRM7804 (9-functional aliphatic urethane acrylate oligomer, manufactured by Daicel Ornex)
(3) GENOMER6083 / HD (bifunctional acrylate monomer, manufactured by RAHN AG)
(4) Sartomer CN2921 (bifunctional aliphatic urethane acrylate having a polyester skeleton, glass transition temperature of homopolymer: −13 ° C., manufactured by Sartomer)
(5) Purple light UV-7510B (trifunctional urethane acrylate oligomer, glass transition temperature of homopolymer: 17 ° C., manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
(6) EBECRYL 8701 (trifunctional urethane acrylate oligomer, manufactured by Daicel Ornex)
(7) Etacure DR-065A (bifunctional aliphatic urethane acrylate oligomer, weight average molecular weight: 10,000-20000, manufactured by ETERNAL CHEMICAL)
(8) Irgacure 184 (1-hydroxy-cyclohexyl-phenyl-ketone, manufactured by Ciba Japan)
(9) Irgacure 819 (Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, manufactured by Ciba Japan)
(10) Tinuvin 479 (hydroxyphenyltriazine-based ultraviolet absorber, manufactured by Ciba Japan)
(11) ADK STAB LA-87 (2,2,6,6-tetramethyl-4-piperidyl methacrylate, manufactured by ADEKA)
(12) Methyl ethyl ketone (organic solvent)

The transparency, adhesion, warm water resistance, abrasion resistance, and weather resistance of the initial coating film of each ultraviolet curable coating composition obtained were evaluated.
The results are shown in Tables 1 and 2.

Test piece preparation method A polycarbonate plate (LS2-111, manufactured by Suzuki Kako Co., Ltd., thickness: 3 mm) was applied by spray coating so that the film thickness after curing was 10 to 14 µm.
Then, it preheated for 5 minutes at 70 degreeC, and the organic solvent contained in an ultraviolet curable coating composition was volatilized.
Subsequently, ultraviolet irradiation was performed using a high pressure mercury lamp under irradiation conditions of a peak intensity of 350 mW / cm ² and an integrated light quantity of 1000 mJ / cm ² to form a cured coating film.

Transparency of initial coating film The haze value (ΔHAZE value) of the unpainted material and the obtained test piece was measured.
○ (Practical level): ΔHAZE value <2%
X (unsuitable for practical use): ΔHAZE value ≧ 2%

Adhesiveness of initial coating film A crosscut reaching the base material at intervals of 1 mm is put in the obtained test piece, and 100 grids of 1 mm ² are made, and cellophane tape is pasted thereon, and then peeled off rapidly. Then, the peeled grids were counted.
○: No peeling at all ×: The number of peeled grids is 1 or more

Abrasion resistance test Based on the JIS K7204 standard, a Taber abrasion test was performed using a Taber abrasion tester (device name: rotary abrasion tester, manufactured by Taber Inc.), and a change in haze value before and after the test (ΔHAZE value) was measured.
Test conditions: Wear wheel ... CS-10F
Load: 500g
Rotation speed ... 60rpm
Number of rotations: 500 times Evaluation criteria ○ (practical level): ΔHAZE value <40%
X (unsuitable for practical use): ΔHAZE value ≧ 40%

Weather resistance test Weather resistance was evaluated using a super accelerated weather resistance tester (product name: iSuper UV Tester, manufactured by Iwasaki Electric Co., Ltd.).
Test conditions:
Lamp: Metal halide lamp irradiation intensity: 100 mW / cm ²
Test temperature: Black panel temperature 63 ° C
Test cycle: Irradiation 8 hours → Condensation 4 hours (Shower 15 seconds, before and after condensation) → Condensation (50 ° C., 90% humidity) 4 hours → Shower 15 seconds )
Evaluation method: Changes in yellowness (ΔYI value) and haze values (ΔHAZE value) before and after the test were confirmed. The yellowness was measured using a color difference meter CR-400 manufactured by Konica Minolta Sensing.
Evaluation criteria of weather resistance ○ (practical level): ΔYI value <20% and ΔHAZE value <35%
X (unsuitable for practical use): ΔYI value ≧ 20% or ΔHAZE value ≧ 35%

Hot water resistance test (1)
The obtained test piece was immersed in a constant temperature water bath at 80 ° C. for 96 hours, and then the change in appearance was visually confirmed.
Evaluation criteria ○ (practical level): no appearance abnormality △ (practical level): slight appearance abnormality × (practical inappropriate): appearance abnormality

Hot water resistance test (2)
After the obtained test piece was immersed in a constant temperature water bath at 80 ° C. for 144 hours, the change in appearance was visually confirmed.
Evaluation criteria ○ (practical level): no appearance abnormality △ (practical level): slight appearance abnormality × (practical inappropriate): appearance abnormality

Hot water resistance test (3)
After the obtained test piece was immersed in a constant temperature water bath at 100 ° C. for 12 hours, a change in appearance was visually confirmed.
Evaluation criteria ○ (practical level): no appearance abnormality △ (practical level): slight appearance abnormality × (practical inappropriate): appearance abnormality

Since the ultraviolet curable coating composition according to the present invention is excellent in transparency, abrasion resistance, weather resistance, and hot water resistance, as a plastic material for automobiles, a headlamp, glazing, etc., carport, It is suitable as a coating composition for protecting the surface of roofing materials such as terraces.

Claims (9)

An ultraviolet curable coating composition comprising the following components (a) to (g) and having a haze value of 2% or less when a dry film having a thickness of 10 μm is formed.
(A) a urethane acrylate that have a 4-9 acryloyl groups in the molecule; have 20 to 70 parts by weight (b) 1 to 3 acryloyl groups in the molecule, further has a polyester skeleton in a resin skeleton Urethane acrylate : 10 to 60 parts by weight (c) Urethane acrylate having 1 to 3 acryloyl groups in the molecule and no polyester skeleton in the resin skeleton ; 2 to 18 parts by weight (d) acetophenone-based Photopolymerization initiator; 1 to 20 parts by weight with respect to 100 parts by weight of the total amount of component (a), component (b) and component (c) (e) Phosphine oxide-based photopolymerization initiator; component (a) , 0.5 to 15 parts by weight relative to 100 parts by weight of the total amount of component (b) and component (c)
(F) Ultraviolet absorber; 1 to 20 parts by weight (g) with respect to 100 parts by weight of the total amount of component (a), component (b) and component (c); light stabilizer; component (a), component (b) ) And 1 to 20 parts by weight per 100 parts by weight of the total amount of component (c) The ultraviolet curable coating composition according to claim 1 , wherein the resin skeleton of the component (a) does not have a hydroxyl group or an amino group. The ultraviolet curable coating composition according to claim 1 or 2, wherein the component (a) is an aliphatic urethane acrylate that forms a nanocomposite structure in which amorphous nanosilica fine particles are dispersed. A component (b) is a 1-3 acryloyl groups in the molecule, a further aliphatic urethane acrylates having a polyester skeleton in a resin skeleton, the glass transition temperature of the homopolymer is -40 to 40 ° C. The ultraviolet curable coating composition according to any one of claims 1 to 3. The ultraviolet curable coating composition according to any one of claims 1 to 4 , wherein the resin skeleton of the component (b) does not have a hydroxyl group or an amino group. Component (c) has a 1-3 acryloyl groups in the molecule, and does not have a polyester skeleton in the resin skeleton, in addition, Weight average molecular weight is aliphatic urethane acrylate 5,000 to 30,000 The ultraviolet curable coating composition according to any one of claims 1 to 5. Coating which is one of a polycarbonate resin, a polyethylene terephthalate (PET) resin, an ABS resin and an acrylic resin having a coating film formed on the surface using the ultraviolet curable coating composition according to any one of claims 1 to 6. Goods. An automobile headlamp cover, a glazing, a sunroof, a building material, a carport roofing material, or a terrace, the surface of which is coated with the ultraviolet curable coating composition according to any one of claims 1 to 6 Roofing material. A method of forming a coating film using the ultraviolet curable coating composition according to claim 1.