JP3073816B2 - UV curable paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet-curable paint, and more particularly, to a coating which does not cause yellowing or discoloration for a long period of time when used in various coating agents and printing inks. The present invention relates to a UV-curable paint that can be used.

[0002]

2. Description of the Related Art Heretofore, UV-curable paints containing a polymerizable oligomer, a polymerizable monomer and a photopolymerization initiator have been known, and these UV-curable paints have other necessary properties so as to be suitable for various uses. Various additives have been used. For example, clear ultraviolet curable paints are widely used for the purpose of improving the surface hardness and strength of plastic molded products such as films, sheets and three-dimensional molded products, and protecting metal surfaces. However, there is a problem that a coating film made of a conventional UV-curable coating material changes color from yellow to brown when left for a long period of time, which significantly reduces the product value of the coated product. Most of the causes of such coloring and discoloration are often caused by the photopolymerization initiator used. First of all, the photopolymerization initiator is decomposed by irradiation with ultraviolet rays to generate free radicals, and the free radicals which are formed and do not contribute to the initiation of the polymerization are generated by the free radicals. Recoupling will result in a colored substance. In addition, some of the photopolymerization initiators do not decompose due to the ultraviolet rays irradiated at the time of curing and remain as they are, and the remaining photopolymerization initiator is used during storage, display, or use of the product. In addition, it is decomposed by ultraviolet rays in external light, and causes the formed coating film to be similarly colored or discolored.

[0003]

The problems of coloring and discoloration as described above occur mainly when the photopolymerization initiator is used in an unnecessarily large amount as compared to the theoretical amount. If the amount of the photopolymerization initiator used is reduced in order to solve such a problem, the required coating film curing speed, coating film strength and hardness cannot be obtained, and excessive use of the photopolymerization initiator cannot be avoided. Also, after curing of the coating film, it is conceivable to increase the amount of ultraviolet irradiation so that excess photopolymerization initiator does not remain in the coating film.However, in this case, coloring occurs at an early stage of the curing treatment, and furthermore, There is a problem that the coating film itself is deteriorated by excessive ultraviolet rays. Further, in order to prevent coloring and discoloration, an ultraviolet absorber or a light stabilizer may be added to the coating material. In this case, since these ultraviolet absorbers absorb the ultraviolet light, the coating film may be coated. Curing speed, strength, hardness, etc. decrease. Accordingly, an object of the present invention is to solve the above-mentioned conventional problems, and to provide a coating film which does not cause yellowing or discoloration for a long period of time when used in various coating agents and printing inks. It is to provide a curable coating.

[0004]

The above object is achieved by the present invention described below. That is, the present invention provides an ultraviolet-curable paint comprising a film-forming component and a photopolymerization initiator,
Film-forming component and at least a urethane Accession Li rate oligomer, 2-ethylhexyl acrylate, Tetorahi
Drofurfuryl acrylate, neopentyl glycol
Diacrylate, bisphenol A polyoxyethylene
Diacrylate and dipentaerythritol hexaac
It is a mixture composed of a reactant, and the photopolymerization initiator is 1
-An ultraviolet-curable paint having excellent light resistance, characterized by being hydroxycyclohexyl phenyl ketone.

[0005]

By using a photopolymerization initiator having a specific structure and using it in combination with a specific film-forming component, it is possible to give a coating film which does not cause yellowing or discoloration even for a long period of time. It is possible to provide an ultraviolet-curable paint that can be used.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. The ultraviolet-curable coating material referred to in the present invention includes a film-forming component and a photopolymerization initiator as essential components, and, if necessary, a non-reactive polymer, a leveling agent, an antistatic agent, a coloring agent, an extender, Solvents and the like can be included. The main component of the film-forming component is a polymer, oligomer, monomer or the like having a radically polymerizable double bond or epoxy group in its structure.
In the present invention, a particularly preferred film-forming component in combination with the photopolymerization initiator described below is a urethane (meth) acrylate-based oligomer.
Other oligomers, for example, (meth) of polyfunctional compounds such as relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiolpolyene resins, and polyhydric alcohols Oligomers such as acrylates can also be used in combination.

[0007] Preferable specific examples of the above-mentioned urethane acrylate oligomer include Gossellac UV7500B
(Nippon Synthetic Chemical) and Ebecryl 220 (UCB)
In the present invention, it is particularly preferable to use a mixture of both. The preferred range of the mixing ratio is the former / weight ratio.
The latter = 1-9 / 9-1. In addition, since the viscosity of the ultraviolet-curable coating composition is often too high with only the above oligomer, a monomer is usually used in combination as a reactive diluent. These monomers include, for example, monofunctional monomers such as ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone and polyfunctional monomers such as trimethylolpropane tri (meth) acrylate , Hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol (meth) acrylate, pentaerythritol tri (meth)
Acrylate, dipentaerythritol hexa (meth)
Acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol (meth) acrylate and the like can be mentioned.

A particularly preferred reactive diluent system in the present invention is 2-ethylhexyl acrylate (8-12),
Tetrahydrofurfuryl acrylate (5-8), neopentyl glycol diacrylate (8-12), bisphenol A polyoxyethylene diacrylate (3-
6) and dipentaerythritol hexaacrylate (8 to 12) (the numerical value in parentheses is a preferable compounding weight ratio when the whole is 100). The photopolymerization initiator used in the present invention is 1-hydroxycyclohexylphenyl ketone, and the photopolymerization initiator can be obtained from the market as Irgacure 184 (manufactured by Ciba Geigy) and used. The ultraviolet-curable coating composition of the present invention can be obtained by simply mixing the above components. In the UV-curable coating composition of the present invention, the mixing ratio of each component is, when the total weight of the oligomer, the monomer and the photopolymerization initiator is 100, the oligomer is 40 to 60, the monomer is 40 to 60, and the photopolymerization is started. The preferred range is 1-8 agents. The method for using the ultraviolet-curable coating material of the present invention and the method for curing the same are exactly the same as those in the prior art, and are not particularly limited.

[0009]

Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following, "parts" and "%" are based on weight unless otherwise specified. Example 1 Urethane acrylate oligomer {a mixture of GOSELAC UV7500B (manufactured by Nippon Gohsei) and Ebecryl 220 (manufactured by UCB)} 100 parts 2-ethylhexyl acrylate 20 parts tetrahydrofurfuryl acrylate 13 parts neopentyl glycol diacrylate 20 parts bisphenol A polyoxy Ethylene diacrylate 9 parts Dipentaerythritol hexaacrylate 17 parts Irgacure 184 (manufactured by Ciba Geigy) 7.4 parts Surface conditioner trace amount The above components were uniformly mixed to obtain an ultraviolet curable coating material of the present invention.

Comparative Example 1 Aronix M-8100 (manufactured by Toa Gosei Chemical) 100 parts Urethane-modified Aronix M-8100 75 parts N-vinylpyrrolidone 20 parts 2-ethylhexyl acrylate 22.5 parts Neopentyl glycol diacrylate 21 parts Irgacure 184 ( Ciba Geigy Co.) 10 parts Surface conditioner trace amount The above components were uniformly mixed to obtain a UV curable paint of Comparative Example. The UV curable paints of the above Examples and Comparative Examples were applied on a substrate to a coating thickness of 100 μm, and 80 W / cm × 1
5 m / min. The coating film was cured by irradiating ultraviolet rays under the conditions of × 4 pass. Next, the two types of coating films obtained were irradiated with a mercury lamp for 24 hours and then subjected to a light resistance test with a sunshine weatherometer for 24 hours. As a result, the coating film of the present invention showed little change and no coloring was observed. On the other hand, in the case of the comparative example, remarkable yellowing was observed.

[0011]

According to the present invention as described above, the photopolymerization initiator having a specific structure is employed and used in combination with a specific film-forming component, so that yellowing can be achieved for a long period of time. UV curable paint capable of providing a coating film that does not cause discoloration or discoloration can be provided. Particularly when a thick coating film is formed, the discoloration of the coating film is conspicuous, and therefore, the ultraviolet curable coating of the present invention is particularly useful for forming a thick coating film.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 4/02 C09D 5/00 CA (STN) CAOLD (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A ultraviolet-curable coating material comprising a film-forming component and a photopolymerization initiator, a coating film forming component and at least a urethane Accession Li rate oligomer, 2- Echiruhe
Xyl acrylate, tetrahydrofurfuryl acryle
, Neopentyl glycol diacrylate, bisulfate
Enol A polyoxyethylene diacrylate and dipe
Mixture consisting of antaerythritol hexaacrylate
, And the and light resistance excellent UV curable coating, wherein the photoinitiator is 1-hydroxycyclohexyl phenyl ketone.