JPH03174472A - Ultraviolet-curable coating composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. excellent in the resistance to abrasion and water by compounding an ultraviolet-curable coating compsn. contg. a coloring pigment with a specific photoreaction initiator and a transparent glass powder. CONSTITUTION:An ultraviolet-curable coating compsn. contg. a coloring pigment, wherein a photoreaction initiator comprises an acrylphosphine oxide compd. and a transparent glass powder is contained in an amt. of 20-80wt.% (based on the total solid content of the compsn.). The glass powder has a median particle diameter of 100mum or lower and such a refractive index that the difference in refractive index between a clear coating film obtd. from the compsn. without contg. the pigment and the glass powder is not larger than 0.3. The glass power, imparting abrasion resistance to a resulting coating film and transmitting photoenergy to the inside of the film, enables the formation of a thick film and a high pigment loading even in a thin film, i.e., the formation of a thin film with a high hiding power.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention provides an ultraviolet curable coating composition containing a colored pigment, capable of being cured by ultraviolet rays, and capable of producing a film having excellent abrasion resistance, water resistance, etc. Regarding.

<Conventional technology and its problems to be solved> In recent years, pollution-free,
In line with social demands such as resource conservation, there is a tendency for some UV-curable coating compositions that are solvent-free or contain a small amount of organic solvent to be adopted. However, the mainstream of conventional UV-curable coating compositions is clear, which does not contain colored pigments, and enamels containing colored pigments have only been put into practical use in some areas because they cannot be made into thick films. situation.

As mentioned above, when an ultraviolet curable coating composition containing a colored pigment is formed into a thick film, the ultraviolet rays do not sufficiently penetrate into the coating.
This resulted in poor curing, and only the surface of the coating was cured, resulting in wrinkles, resulting in poor coating appearance and poor coating performance.

Therefore, methods have been proposed such as using pigments that do not easily absorb ultraviolet rays as coloring pigments, using highly reactive ultraviolet polymerizable compounds, and using lamps that emit light on the long wavelength side as ultraviolet lamps. However, in all cases, the film thickness is limited to about 30 μm, and if it exceeds this, curing failure occurs, and the coloring power and hiding power are inferior to that of ordinary enamels.

Recently, a method has also been proposed in which spherical glass powder is incorporated into an ultraviolet curable coating composition containing a colored pigment (eg, JP-A-62-79275). According to this method, a thick film with excellent curability to some extent can be obtained, but there have been problems such as poor water resistance and poor curability with light on the short wavelength side.

On the other hand, photoinitiators used in the UV-curable coating composition include benzophenone, acetophenone, jetoxyacetophenone, chloroacetophenone, 2,2-dimethoxy-2-phenylacetophenone, propiophenone, thioxanthone, benzoin, benzyl, Representative examples include anthraquinone, benzyl ketal, benzoin ethyl ether, benzoin isopropyl ether, and dimethoxyphenylacetophenone.

However, in the case of using a photoreaction initiator that is generally widely used, in the case of an ultraviolet curable coating composition containing a large amount of a pre-transparent component such as a colored pigment, the resulting film is This has caused problems such as not being able to cure sufficiently.

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies to develop an ultraviolet curable coating composition that is sufficiently cured even if it contains a colored pigment and can provide a film with excellent water resistance. This has led to the present invention.

Means for Solving the Problems> That is, the present invention uses an acylphosphine oxide compound as a photoreaction initiator in an ultraviolet curable coating composition containing a colored pigment, and the coating composition excluding the colored pigment. Relating to an ultraviolet curable coating composition containing 20 to 80% by weight of transparent glass powder with a refractive index difference of 0.3 or less and a center particle size of 100 μm or less in the total solid content of the coating composition. It is something.

In the present invention, the inside of the film was not sufficiently cured with many ordinary photoinitiators, but unexpectedly, by using an acylphosphine oxide compound as a photoinitiator and in combination with a specific transparent glass powder, Even a thick film of several hundred μm can be sufficiently cured and a film with excellent water resistance etc. can be obtained.
The present invention was completed based on the discovery that it is possible to add a large amount of colored pigment to a thin film of several μm to 30 μm, and therefore a cured film with hiding power can be obtained.

The present invention will be explained in detail below.

The ultraviolet curable coating composition of the present invention contains an ultraviolet polymerizable vehicle, a photoreaction initiator, a transparent glass powder, and a colored pigment as essential components, and further contains extender pigments, organic solvents, additives, etc. as necessary. It is something.

As the vehicle component, a compound having an unsaturated double bond capable of radical polymerization in the molecule can be used. Specifically, unsaturated polyester resins, unsaturated acrylic resins, unsaturated urethane resins, unsaturated epoxy resins, unsaturated polyamide resins, or these resins and ethylenic resins are used in ordinary UV-curable paints. A typical example is a mixture with a reactive diluent having an unsaturated group. Particularly suitable are the following vehicles which have excellent weather resistance and recoatability, that is, excellent interlayer adhesion even under a wide range of ultraviolet irradiation conditions.

The vehicle has an acrylic urethane oligomer as a main component, and the acrylic urethane oligomer has a urethane bond in the molecule and an unsaturated double bond capable of radical polymerization, and has an average molecular weight of about several hundred to several hundred. This includes a wide range of substances that are viscous at room temperature.

For example, polyisocyanate and hydroxyl group-containing (meth)
In addition to oligomers obtained by reaction with acrylic esters, polyether-based acrylic urethane oligomers,
Also included are polyester-based acrylics, urethane oligomers, polybutadiene-based acrylic urethane oligomers, and the like.

Specifically, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, their isomers or excess polyisocyanate and polyester polyol, polyoxymethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, caprolactone polyol. A reaction product of a polyisocyanate (preferably a non-yellowing type polyisocyanate), such as a compound having an isocyanate end, which is a reaction product of trimethylolpropane or pentaerythritol with a polyhydric alcohol, and a compound having a hydroxyl group and an unsaturated group. Examples include things. Typical examples of the compound having a hydroxyl group and an unsaturated group include hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyethyl (meth)acrylate, and glycidyl (meth)acrylate.

The vehicle consists of these acrylic urethane oligomers and a reactive diluent. As reactive diluents, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (
meth)acrylate, isobornyl(meth)acrylate, tripropylene glycol diacrylate), 1.6
-Hexanediol diacrylate, tetraethylene glycol diacrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(
meth)acrylate, ditrimethylolpropane pentaacrylate, dipentaerythritol hexaacrylate, vinyl acetate, N-vinylpyrrolidone, dimethyl(
Typical examples include methacrylamide, vinyltoluene, divinylbenzene, etc., and these reaction diluents are
It is suitable to mix 10 to 100 parts by weight.

As a photoreaction initiator, an acylphosphine oxide compound is used. This acylphosphine oxide compound is a compound represented by the following general formula.

[In the formula, R1 is a linear or branched alkyl group having 1 to 6 carbon atoms, cyclohexyl having a total of 6 to 12 carbon atoms,
Cyclobenyl, aryl-, halogen-, alkyl-1 or alkoxy-substituted aryl group, or S- or N
- represents a 5- or 6-membered heterocyclic group (containing other carbon atoms); R2 has the same meaning as R1, and R1 and R2 may be the same or different, or Number 1
represents an alkoxy group having ~6 carbon atoms, an aryloxy group or an arylalkoxy group having a total carbon number of 6 to 12, or R1 and R2 together with the phosphorus atom represent an alkoxy group having a total carbon number of 6 to 12;
and R3 has 2 carbon atoms.
Linear or branched alkyl group having ~18 carbon atoms, 3 to 1 carbon atoms
represents an alicyclic group, a phenyl group or a naphthyl group having 0, or an S-1○-1 or N-containing 5- or 6-membered heterocyclic group (containing other carbon atoms), and the R3 group represents 1 wherein R' and R2 are as defined above, and X is a phenylene group or an aliphatic or alicyclic divalent group having 2 to 6 carbon atoms. and one or more of R'-R' may be olefinically unsaturated.] Specifically, 2,2-dimethylpropioyldiphenylphosphine oxide, 2,2-dimethylpentanoyldiphenylphosphine oxide, 2,2-dimethyloctanoyldiphenylphosphine oxide, methyl 2,2-dimethyloctanoyl phenylphosphine oxide, 2-methyl-2-ethylhexanoyldiphenylphosphine oxide, 2,6-dimethylbenzoyldiphenyl Phosphin oxide, 2,6-cymethoxybenzoyldiphenyl phosphin oxide 1()', 2
．． 6-cyclobenzoyldiphenylphosphinoxide, 2,4.6-dolimethylbenzoyldiphenylphosphine oxide, methyl 2,4.6-dolimethylbenzoylphenylphosphinate, 2,3.6-
) Limethylbenzoyldiphenylphosphine oxide, 2゜4.6-) Limethoxybenzoyldiphenylphosphine oxide, 2,4.6-) Lichlorobenzoyldiphenylphosphine oxide, 2゜4.6-
) Limethylbenzoylnaphthyl phosphonate and the like are representative examples.

The acylphosphine oxide compound is suitably blended in an amount of 0.1 to 5 parts by weight, preferably 0.2 to 3 parts by weight, per 100 parts by weight of the vehicle component.

The photoreaction initiator may be an acylphosphine oxide compound alone, but it is also possible to use the photoreaction initiator conventionally used in boat fishing.

The transparent glass powder used in the present invention has the function of imparting abrasion resistance to the resulting coating and allowing light energy to propagate inside the coating. Therefore, it is possible to form a thick coating, and also to form a thin coating. Even in this case, since it is possible to add a large amount of colored pigment, it is possible to form a thin film coating with high hiding power.

In order for the transparent glass powder to have the above function, it must satisfy the following conditions.

(a) The central particle size is 100 μm or less, preferably 0.5 to
It is 60 μm. If the center particle size exceeds 100 μm, it does not affect the hardening properties of the coating, but the glass powder becomes noticeable in the resulting coating, causing roughness, etc., which is unfavorable in terms of coating appearance.

In addition, a decrease in physical properties such as tensile strength is observed. On the other hand, there is no particular limit to the lower limit of the particle size, but it is preferably within the above range since the transmittance tends to decrease substantially. Note that if a thin film of about 30 μm or less is desired, the center grain size is preferably 10 μm or less.

(b) The difference between the refractive index of the transparent glass powder and the refractive index of the clear coating of the ultraviolet curable coating composition excluding the colored pigment is 0.
．． It is within 3. It should be noted that if the difference in refractive index exceeds 0.3, the light energy for curing the film will be significantly attenuated in the deep part of the film when the film is thickened, resulting in poor curing, which is not suitable.

The shape of the glass powder is preferably spherical when forming a thick film of several tens of μm to several hundred μm, and irregular when forming a thin film of uniformly dispersed μm to several tens of μm. Good too.

The transparent glass powder used in the present invention can be used without particular limitations as long as it satisfies the above conditions.

Usually, the refractive index No of the clear film of the ultraviolet curable coating composition is about 1.4 to 1.6, so the refractive index No
Soda lime glass with a D of around 1.5, soda lime glass
Specific examples include, but are not limited to, lead glass, potash/lead glass, potash/lead glass, potash/soda/lead glass, borosilicate glass, high alumina glass, potash/soda/barium glass, etc. That should be obvious.

The amount of glass powder blended is 20 to 80% by weight in the resulting coating film, especially when making a single layer coating thicker than 100 μm.
0 to 70% by weight is suitable.

As the coloring pigment used in the present invention, ordinary inorganic/organic pigments and dyes can be used. Specifically, titanium oxide,
Zinc sulfide, zinc white, lead white, IJ) carbon, carbon black, oil smoke, navy blue, phthalocyanine blue, ultramarine blue, carmine FB, yellow lead, zinc yellow, hand yellow, ocher,
Typical examples include red iron oxide and insoluble metal-containing azo dyes.

In particular, in the present invention, zinc sulfide, oil smoke, ultramarine blue, phthalocyanine blue, carmine FB, which has a low ultraviolet absorption rate,
Preferred are yellow lead, ocher, red iron, insoluble metal-containing azo dyes, and the like. It is also possible to use other metallic pigments, colorant particles, etc., if necessary.

The amount of the colored pigment to be blended is suitably 40% by weight or less in the resulting coating film, and the lower limit is arbitrarily determined depending on the desired hiding power and coloring power of the coating film.

The extender pigments that may be added as necessary include silica sand, silicates, talc, kaolin, barium sulfate, calcium carbonate, flaky or fibrous or hollow glass,
Representative examples include resin powders such as polyurethane, polyester, polyethylene, and polystyrene.

The solvent is used to appropriately adjust the viscosity of coating or printing, and representative examples include toluene, xylene, acetone, methyl ethyl ketone, and ethyl acetate.

The colored ultraviolet curable coating composition used in the present invention consists of the components described above.

The ultraviolet curable coating composition of the present invention is coated or printed on a coated substrate using a conventional coating means or printing means, and then irradiated with ultraviolet rays to induce a photopolymerization reaction and cure the coating.

Note that as a light source used for irradiating ultraviolet rays, a low pressure mercury lamp, a high pressure mercury lamp, a metal halide lamp, a carbon arc lamp, a xenon lamp, a chemical lamp, etc. are used.

It can be applied to various base materials such as metal, wood, plastic, glass, ceramics, concrete, and paper as coating base materials. In particular, it can be used favorably for building interiors because it provides a coating that is excellent in abrasion resistance, impact resistance, scratch resistance, flame retardance, sound insulation, etc. It should be noted that these substrates may be subjected to surface treatments such as sealing treatment, polishing treatment, coloring treatment, etc., as necessary, and may also have an uneven surface.

<Effects of the Invention> As described above, since the ultraviolet curable coating composition of the present invention contains the specific photoreaction initiator and the specific glass powder, the UV-curable coating composition of the present invention does not have the same effect when it contains a colored pigment. Even in a thick film of several hundred μm (for example, 500 μm),
It can be sufficiently cured by ultraviolet irradiation, and can be made thicker, providing a film with water resistance, hiding power, and coloring power. Furthermore, in the case of a thin film of several μm to 30 μm, even if a large amount of coloring pigment is added, it will be sufficiently cured, so that a film with hiding power and coloring power can be obtained. Furthermore, because it contains glass powder, the resulting coating has excellent abrasion resistance, impact resistance, scratch resistance, flame retardancy, sound insulation, adhesion, etc., and when irradiated with ultraviolet light, It does not easily generate heat, so it can be applied to heat-sensitive substrates.
It also contains main ingredients that can prevent the coating from wrinkles caused by heat.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In the examples, "parts" and "%" are expressed on a weight basis.

[Preparation of acrylic urethane oligomer (I)] 2 moles of isophorone diisocyanate and 2 moles of 2-hydroxyethyl acrylate are subjected to an addition reaction using a conventional method to obtain an acrylic urethane oligomer (1,) having an average molecular weight of about 500.
was prepared.

[Preparation of acrylic urethane olicomer (n)] 1.6-
2.1 moles of hexanediol, 1 mole of ethylene glycol, and 2.4 moles of adipic acid were subjected to a condensation reaction to produce a polyester having a molecular weight of 1000. The polyester 1
mol, 2 mol of isophorone diisocyanate, and 2 mol of 2-hydroxyethyl acrylate in a conventional manner to prepare a polyester type acrylic urethane oligomer (II) having an average molecular weight of about 1,700.

[Preparation of acrylic epoxy oligomer (III)] A bisphenol A-type jepoxy compound (trade name "Ebiko" manufactured by Yuka Shell Epoxy Co., Ltd.) 828J with a molecular weight of about 38,011 mol and 2 mol of acrylic acid were subjected to an addition reaction using a conventional method to obtain an acid value of 20. Acrylic epoxy oligomer (III) was prepared.

Example 1 An ultraviolet curable coating composition having the following formulation was applied to a black hard vinyl chloride resin material using a 3 mil applicator.
120 W/cm of Fe after 1 minute flash-off at 0°C
-2 UV rays from a distance of 15 cm using an 8N halide lamp
The coating was cured by irradiation for seconds.

Table 1 shows the results of performance tests on the obtained coatings. In addition, the refractive index N of the clear coating film obtained by excluding soda glass powder and zinc sulfide pigment from the following formulation.

was 1.5.

Composition/Blend> Acrylic urethane oligomer (I) 22 parts N-
Vinylpyrrolidone 6 parts 2.4.6
-) Limethylbenzoyl diphenylphosphine oxide 1 part soda glass powder Note 1) 40 parts zinc sulfide pigment
148n-butyl acetate
17 parts Note 1) Comparative example 1 of transparent amorphous powder with refractive index Nn-1.52 and center particle size 5 μm In Example 1, instead of soda glass powder, refractive index No.
2.2, coated under the same conditions as Example ① except for using transparent amorphous lead glass powder with a center particle size of 5 μm,
Irradiated with ultraviolet light.

Table 1 shows the results of performance tests on the obtained coatings.

Comparative Example 2 A film obtained by applying under the same conditions as in Example 1 except that the zinc sulfide pigment was removed and calcium carbonate was used as an extender pigment instead of glass powder, and irradiated with ultraviolet rays. Table 1 shows the results of the performance tests. However, the obtained coating was a cloudy clear coating.

Comparative Example 3 In Example 1, 2,4.6-)! The coating was applied under the same conditions as in Example 1 except that an acetophenone photoreaction initiator was used instead of J methylbenzoyl diphenylphosphine oxide, and the resulting film was irradiated with ultraviolet rays. Shown in the table.

Comparative Example 4 Table 1 shows the results of a performance test on the film obtained by coating under the same conditions as in Example 1 and irradiating it with ultraviolet rays, except that calcium carbonate was used instead of glass powder in Example 1. show.

As is clear from Table 1, the composition of the present invention had excellent coating performance.

On the other hand, in Comparative Example 1, in which a glass powder having a refractive index difference of 0.4 or more with respect to the clear coating was used, each performance decreased, and in Comparative Example 2, in which the clear coating did not use glass powder, the resistance Comparative Example 3, which used a commonly used acetophenone photoreaction initiator, had poor water resistance, and Comparative Example 4, which was a colored film that did not use glass powder, had poor adhesion. and water resistance was poor.

Example 2 An ultraviolet curable coating composition having the following formulation was applied using a 10 mil applicator, and the coating was cured in the same manner as in Example 1, except that ultraviolet rays were irradiated for 2 seconds. In addition, the refractive index N of the clear coating film obtained by excluding soda glass beads and zinc sulfide pigment from the following formulation. was 1.5.

Composition/Blend> Acrylic urethane oligomer (I[) 25 parts N
-Vinylpyrrolidone 7 parts 2.6-Simethoxybenzoyldiphenylphosphine oxide ■Part Soda glass beads Note 6)
55 parts titanium oxide pigment 1
2 copies Note 6) Refractive index Nfl = 1.52, central grain size 60 μm
The resulting coating of transparent spherical beads showed no abnormalities in the water resistance test and had good adhesion.

Comparative Examples 5 to 7 Same as Example 2 except that an acetophenone photoinitiator, a benzoyl photoinitiator, and an azobisisobutyronitrile photoinitiator were used as photoinitiators in Example 2, respectively. It was applied under the following conditions and irradiated with ultraviolet rays.

In the water resistance test, all of the obtained films exhibited blistering, poor water resistance, and poor adhesion.

Example 3 Acrylic urethane oligomer (II) in Example 2
acrylic epoxy oligomer (III) instead of and 2.6-simethoxybenzoyldiphenylphosphinoxide as photoinitiator.
- Coated under the same conditions as Example 2 except for using cyclobenzoyl diphenylphosphine oxide,
Irradiated with ultraviolet light.

The resulting coating showed no abnormalities in the water resistance test and had good adhesion.

Claims (3)

[Claims] (1) In an ultraviolet curable coating composition containing a colored pigment, an acylphosphine oxide compound is used as a photoreaction initiator, and the difference in refractive index between the coating composition excluding the colored pigment and the clear coating is 0. An ultraviolet curable coating composition containing 20 to 80% by weight of transparent glass powder having a median particle diameter of 100 μm or less in the solid content of the total coating composition. (2) The ultraviolet curable coating composition according to claim 1, wherein the vehicle component contains an acrylic urethane oligomer as a main component. (3) The ultraviolet curable coating composition according to claim 1, wherein the glass powder has a central particle size of 10 μm or less.