JP2001040061A - Photocurable resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a urethane (meth)acrylate resin-based photocurable resin composition having improved adhesivity to a woody substrate such as plywood, etc., even in use of exposure to light rays such as sunshine, etc., excellent luster and crack resistance. SOLUTION: This photocurable resin composition comprises a urethane (meth) acrylate resin containing a (meth)acryloyl group and an isocyanate group at the end obtained by reacting a polyisocyanate compound containing two or more isocyanate groups in one molecule with a polyester polyol, a tri- or polyhydric alcohol and a hydroxyl group-containing (meth)acrylate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocurable resin composition for woodwork paints, which has good workability and good adhesion to a substrate, and more particularly to wood and wood-based plywood as a substrate. The present invention relates to a photocurable resin composition for woodwork paints, which is capable of providing a light-cured coating film having good light resistance, which is provided for coating.

[0002]

2. Description of the Related Art Conventionally, resin compositions which are hardened by irradiation with light such as ultraviolet rays are paints such as plastics, papers, and woodwork,
It has been put to practical use for applications such as adhesives and printing inks.

Curing by light such as ultraviolet light involves designing (1) a photocurable resin composition which is fast-curing, has high productivity, and (2) does not contain a solvent, and becomes a nearly 100% cured coating film. And (3) there is no need to heat and cure, so that there is little influence of heat on the base material. As the photocurable resin composition, unsaturated polyester resin, urethane acrylate resin, epoxy acrylate resin, etc. are used. Among them, urethane is used because of its quick curing property, especially in woodwork coating, and a high degree of freedom in resin design. Acrylate resins are often used.

In recent years, wood-based plywood made of inexpensive imported wood of poor quality has been increasing in the field of woodwork coating. A photocurable resin composition using a soft urethane acrylate resin has been developed as a material applicable to such a wood-based plywood (see JP-A-10-130345). This resin composition is characterized in that the coating film cures in a short time and the coating film is unlikely to crack even under severe cold conditions. However, although a coating film obtained from a photocurable resin composition using a soft urethane acrylate resin tends to have good crack resistance, it is inferior in light resistance of the coating film under light exposure conditions such as sunlight. The point is a problem.

[0005]

SUMMARY OF THE INVENTION The present invention provides a urethane acrylate resin-based photocurable resin composition which eliminates the above-mentioned disadvantages of the prior art and has excellent light resistance even when used under exposure to light such as sunlight. The purpose is to provide.

[0006]

Means for Solving the Problems The present inventors have intensively studied to solve this problem. As a result, a polyisocyanate compound (a) having two or more isocyanate groups per molecule, a polyester polyol (b),
Urethane (meth) acrylate resin (A) having a (meth) acryloyl group and an isocyanate group at a terminal obtained by reacting a trihydric or higher polyhydric alcohol (c) and a hydroxyl group-containing (meth) acrylate (d) and a light It has been found that this problem can be achieved by using a photocurable resin composition containing the polymerization initiator (B), and the present invention has been completed.

That is, the present invention relates to a polyisocyanate compound having two or more isocyanate groups per molecule (a), a polyester polyol (b), a trihydric or higher polyhydric alcohol (c), and a hydroxyl group-containing (meth) acrylate ( Urethane (meth) acrylate resin (A) having terminal (meth) acryloyl group and isocyanate group obtained by reacting d) and photopolymerization initiator (B)
The present invention relates to a photocurable resin composition containing:

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a polyisocyanate compound (a) includes tolylene diisocyanate, hydrogenated tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tolidine diisocyanate, naphthalene diisocyanate,
Diisocyanate compounds such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate;

Further, a buret-type polyisocyanate compound obtained by reacting the above-mentioned various diisocyanate compounds with water, or a polyhydric alcohol such as the above-mentioned various diisocyanate compounds and trimethylolpropane. And a polymer obtained by subjecting various diisocyanate compounds as described above to isocyanuration.

In the present invention, the polyester polyol is obtained by using a polyvalent carboxylic acid and subjecting it to an esterification reaction with a polyhydric alcohol.

The polycarboxylic acids include adipic acid, sebacic acid, succinic acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, tetrahydrophthalic anhydride fumaric acid, maleic acid, maleic anhydride, Known examples include itaconic acid, trimellitic acid, trimellitic anhydride, pyromellitic acid, and pyromellitic anhydride.

The polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol,
Dipropylene glycol, neopentyl glycol,
1,4-butanediol, 1,6-hexanediol,
3-methyl-1,5-pentanediol, ethylene oxide or propylene oxide adducts of bisphenol A, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, dimethylolpropionic acid, dimethylolbutanoic acid, and the like, which are known and used. No.

In the present invention, the aliphatic dicarboxylic acid / aromatic dicarboxylic acid ratio of the polycarboxylic acid component of the polyester polyol (b) is desirably 100/0 to 20/80 (weight ratio). If the ratio of the aliphatic dicarboxylic acid / aromatic dicarboxylic acid is more than 20/80 than that of the aromatic dicarboxylic acid, the cured coating film becomes brittle, and the crack resistance of the coating film under cold conditions deteriorates.

In the present invention, the number average molecular weight of the polyester polyol (b) is preferably from 500 to 3,000. If the number average molecular weight is less than 500, the cured coating film becomes brittle, and if it exceeds 3000, the curability and the strength of the cured coating film are insufficient.

In the present invention, the trihydric or higher polyhydric alcohol (c) includes known and commonly used ones such as glycerin, trimethylolpropane, trimethylolethane and pentaerythritol.

If necessary, a dihydric polyhydric alcohol or a divalent polyamine may be used as a chain extender.

Examples of the dihydric polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, and 3-methyl-1,5-pentanediol. And known and commonly used products such as ethylene oxide or propylene oxide adduct of bisphenol A.

Examples of the divalent polyamine include ethylenediamine, hexamethylenediamine, tolylenediamine, hydrogenated tolylenediamine, diphenylmethanediamine, hydrogenated diphenylmethanediamine, tolidinediamine, naphthalindiamine, isophoronediamine, xylylenediamine, and hydrogenated xylylenediamine. Known examples include amines.

In the present invention, the hydroxyl group-containing (meth) acrylate (d) includes 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, butanediol mono (meth) acrylate, and 2-hydroxyethyl (meth) acrylate. Known examples include a caprolactone-modified acrylate, glycidol di (meth) acrylate, and pentaerythritol tri (meth) acrylate.

In the present invention, it is necessary to react a polyisocyanate compound (a), a polyester polyol (b), a trihydric or higher polyhydric alcohol (c) and a hydroxyl group-containing (meth) acrylate (d). As the method, a hydroxyl group-containing (meth) acrylate (d) is added to a molecular terminal using a hydroxyl group of a polyester polyol (b) and a trihydric or higher polyhydric alcohol (c) via a polyisocyanate compound (a). can do. At this time, a method of reacting (I) (b) and (c) with the polyisocyanate compound (a) to form a terminal isocyanate oligomer and adding a hydroxyl group-containing (meth) acrylate (d), (II) (b) And (c) and the hydroxyl group-containing (meth) acrylate (d) are mixed, and a polyisocyanate compound (a) is added and reacted.

In the present invention, the urethane (meth) acrylate resin (A) preferably has an isocyanate group content of 1 to 10% by mass based on the solid content of the resin. If the isocyanate group content is less than 1% by mass, the adhesion to the substrate is not sufficient, and if it is more than 10% by mass, the viscosity becomes high,
Curability also worsens.

In the present invention, the photopolymerization initiator (B) is benzyldimethyl ketal, benzoin, benzoin ethyl ether, benzoin isopropyl ether, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropane-1 And known ones such as -one and benzophenone. These photopolymerization initiators can be used alone or in combination of two or more.

These photopolymerization initiators (B) are 100
1 to 10 parts by mass, preferably 2 to 10 parts by mass,
It is desirable to use 7 parts by mass. If the amount is less than 1 part by mass, the curability is not sufficient, and if it exceeds 10 parts by mass, the physical properties of the obtained coating film deteriorate.

The photocurable resin composition of the present invention may contain a polymerizable monomer. Examples of the polymerizable monomer include styrene, vinyltoluene, vinyl acetate, N-vinylpyrrolidone, N-vinylformamide, N-vinylcaprolactam, (meth) acryloylmorpholine, cyclohexyl (meth) acrylate, and 2-ethoxyethyl (meth). ) Acrylate, 2-ethylhexyl (meth)
Acrylate, n-hexyl acrylate, cyclohexyl acrylate, isobornyl acrylate, phenoxyethyl acrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate,
Known examples include neopentyl glycol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and dipentaerythritol hexaacrylate.

Further, various organic solvents, polymerization inhibitors and dehydrating agents can be added as required.

Examples of the organic solvent include hydrocarbons such as toluene and xylene, and esters such as ethyl acetate and butyl acetate.
Known examples such as ketones such as methyl ethyl ketone and methyl isobutyl ketone are used.

Examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, benzoquinone, pt
-Butyl catechol, 2,6-dibutyl-4-methylphenol and the like can be used.

Examples of the dehydrating agent include isocyanates (trade name: Additive TI), orthoesters such as methyl orthoformate and methyl orthoacetate, orthoborate esters, silicates, and synthetic zeolite adsorbents (trade name:
Known and commonly used materials such as molecular sieve 3A).

If necessary, various additives other than those described above, such as known antioxidants, defoamers, leveling agents, ultraviolet absorbers and pigments, may be added.

[0030]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples. Hereinafter, “parts” and “%” are “parts by mass” and “% by mass”, respectively, unless otherwise specified.

[0031]

[Production Example 1] (Synthesis of urethane acrylate resin A) In a flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet tube, "Teslac 2455" [polyester polyol (1, 1) manufactured by Hitachi Chemical Co., Ltd. 6-hexanediol, neopentyl glycol and polyester polyol of adipic acid, number average molecular weight 2000)] 20
00 parts, trimethylolpropane 402 parts, toluene 2
375 parts were charged. Next, the temperature inside the system was raised to 60 ° C. while blowing nitrogen gas, and after uniformly dissolving, 1776 parts of isophorone diisocyanate was added, the temperature was further raised to 100 ° C., and the temperature was kept for 4 hours. At this point, the isocyanate group content of the reaction solution was 3.2%. 90 ° C
The temperature was lowered to, the blowing of nitrogen gas was stopped, 232 parts of 2-hydroxyethyl acrylate and 2.2 parts of hydroquinone monomethyl ether were added, and the mixture was kept warm for 7 hours and cooled when the isocyanate group content reached 1.9%. And
I took it out. A urethane acrylate resin A having a heating residue of about 65%, an isocyanate group content of 1.9%, and a number average molecular weight of 3,800 was obtained.

[0032]

[Production Example 2] (Synthesis of urethane acrylate resin B) "Teslac 2468" [polyester polyol (1,4-butanediol, polyester polyol of adipic acid) manufactured by Hitachi Chemical Co., Ltd.] , Number average molecular weight 2000)], 2000 parts, glycerin 460 parts and toluene 3571 parts. Next, the temperature inside the system was raised to 60 ° C. while blowing nitrogen gas,
After dissolving uniformly, isophorone diisocyanate 266
4 parts were added, the temperature was further raised to 100 ° C., and the temperature was kept for 4 hours. At this point, the isocyanate group content of the reaction solution was 3.4%. The temperature was further lowered to 90 ° C., the blowing of nitrogen gas was stopped, 232 parts of 2-hydroxyethyl acrylate and 2.4 parts of hydroquinone monomethyl ether were added, and the mixture was kept warm for 7 hours to have an isocyanate group content of 2.
When it reached 5%, it was cooled and taken out. Urethane acrylate resin B having a heating residue of about 60%, an isocyanate group content of 2.4%, and a number average molecular weight of 5,400
I got

[0033]

[Production Example 3] (Synthesis of urethane acrylate resin C) "Teslac 2455" [polyester polyol (1,6-hexanediol, neopentyl glycol and adipine) manufactured by Hitachi Chemical Co., Ltd. Polyester polyol of acid, number average molecular weight 2000)] 2000 parts, trimethylolpropane 2
68 parts, neopentyl glycol 104 parts, toluene 1
782 parts were charged. Next, the temperature inside the system was raised to 60 ° C. while blowing nitrogen gas, and after uniformly dissolving, 1554 parts of isophorone diisocyanate was added, the temperature was further raised to 100 ° C., and the temperature was kept for 4 hours. At this time, the content of the isocyanate group in the reaction solution was 3.0%. 90 ° C
, The blowing of nitrogen gas was stopped, 232 parts of 2-hydroxyethyl acrylate and 2.2 parts of hydroquinone monomethyl ether were added, and the mixture was kept warm for 7 hours and cooled when the isocyanate group content reached 1.4%. And
I took it out. A urethane acrylate resin C having a heating residue of about 65%, an isocyanate group content of 1.4%, and a number average molecular weight of 3,600 was obtained.

[0034]

[Production Example 4] (Synthesis of urethane acrylate resin D) "Teslac 2455" [polyester polyol (1, 1) manufactured by Hitachi Chemical Co., Ltd.]
6-hexanediol, neopentyl glycol and polyester of adipic acid, number average molecular weight 2000)] 2
000 parts, 312 parts of neopentyl glycol, and 1566 parts of toluene. Next, the temperature inside the system was raised to 60 ° C. while blowing nitrogen gas, and after uniformly dissolving, 1110 parts of isophorone diisocyanate was added.
And kept warm for 4 hours. At this point, the isocyanate group content of the reaction solution was 1.7%. Plus 90
C., the blowing of nitrogen gas was stopped, 232 parts of 2-hydroxyethyl acrylate and 1.8 parts of hydroquinone monomethyl ether were added, and the mixture was reacted for 8 hours. As a result of IR measurement, it was confirmed that the isocyanate had disappeared. Cooled and removed. A urethane acrylate resin D having a heating residue of about 70%, an isocyanate group content of 0%, and a number average molecular weight of 3,100 was obtained.

[0035]

[Production Example 5] (Synthesis of urethane acrylate resin E) "Teslac 2455" [polyester polyol (1,6-hexanediol, neopentyl glycol and adipine) manufactured by Hitachi Chemical Co., Ltd. Polyester of acid, number average molecular weight 200
0)] 2,000 parts, 67 parts of trimethylolpropane, 260 parts of neopropylene glycol, and 1620 parts of toluene were charged. Next, while blowing in nitrogen gas,
After heating to ℃ and dissolving uniformly, 1221 parts of isophorone diisocyanate was added, the temperature was further raised to 100 ℃ and kept for 4 hours. At this point, the isocyanate group content of the reaction solution was 2.0%. The temperature was further lowered to 90 ° C., the blowing of nitrogen gas was stopped, 232 parts of 2-hydroxyethyl acrylate and 2.0 parts of hydroquinone monomethyl ether were added, and the mixture was kept warm for 7 hours to reduce the isocyanate group content to 0.4%. By the way, it was cooled and taken out. A urethane acrylate resin E having a heating residue of about 70%, an isocyanate group content of 0.4%, and a number average molecular weight of 3,300 was obtained.

The formulations in Production Examples 1 to 5 and the isocyanate group content (% by mass) per resin solid content are shown in Table 1.

[0037]

[Table 1]

[0038]

Example 1 To the urethane acrylate resin A obtained in Production Example 1, toluene was added in such an amount that the heating residue became 50%.
Furthermore, a photocurable resin composition for testing was prepared by adding 3% of a photopolymerization initiator (Irgacure 651 manufactured by Ciba Geigy) and uniformly mixing.

[0039]

[Examples 2 and 3],

Comparative Examples 1-2 As shown in Table 2, a test photocurable resin composition was prepared in the same manner as in Example 1.

[0040]

[Table 2]

(1) Curability test The photocurable resin composition for test was applied to a glass plate to a thickness of 25 μm with an applicator, and a high-pressure mercury lamp (80 W / cm) was used.
1 light, irradiation distance 15cm, conveyor speed 20m /
UV irradiation was performed under the conditions of minutes, and the number of passes until curing was performed was examined.

(2) Gloss test The gloss state of the coating film surface was visually evaluated.

(3) Adhesion A test photocurable resin composition was applied to a 15 cm square veneer plywood with a bar coater at a rate of 25 g / m ² , and a high pressure mercury lamp (80
W / cm) 1 lamp, irradiation distance of 15 cm, conveyor speed of 20 m / min, UV irradiation for the number of passes obtained in the above-mentioned curability test under the conditions of 15 cm, conveyor speed of 20 m / min, A test plate was used. This test plate was cut into 100 2 mm squares with a cutter knife, and a cellophane tape peeling test was performed to examine the initial adhesion. Further, the test board with the grid was continuously irradiated with ultraviolet rays by a sunshine weatherometer for 100 hours, and then the cellophane tape was peeled off, and the adhesion after the light resistance test was examined.

(4) Cracking resistance A test plate prepared in the same manner as in the adhesion test was treated twice at 80 ° C. for 2 hours and at −20 ° C. for 2 hours under repeated cold / hot conditions, and then cracks generated in the coating film were obtained. Was measured for length.

[0045]

[Table 3]

[0046]

As shown in the examples, the photocurable resin composition of the present invention cures faster by irradiation with ultraviolet light than the conventional one, and has a high gloss and adhesion both at the initial stage and after 100 hours of sunshine. The effect of good can be exhibited. In addition, from the comparison between the examples and the comparative examples in Table 2, it is understood that the coating film obtained from the photocurable resin composition of the present invention also has excellent crack resistance.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J002 AA031 BG041 CK021 EE026 FD146 GH01 4J011 SA22 SA33 SA34 SA46 SA52 TA01 UA01 WA02 4J027 AG03 AG04 AG09 AG12 AG13 AG14 AG23 AG24 AJ01 CB10 CC05 CD08 4J034 BA05 CA01 HC12 HC13 RA07 4J038 DG051 DG111 DG211 DG261 KA04 MA14 NA12 PA17 PC06

Claims (4)

[Claims] 1. A polyisocyanate compound having two or more isocyanate groups per molecule (a), a polyester polyol (b), a trihydric or higher polyhydric alcohol (c) and a hydroxyl group-containing (meth) acrylate (d). A photocurable resin composition containing a urethane (meth) acrylate resin (A) having a (meth) acryloyl group and an isocyanate group at the terminal and a photopolymerization initiator (B) obtained by the reaction. 2. The polyhydric carboxylic acid component of the polyester polyol (b) has an aliphatic dicarboxylic acid / aromatic dicarboxylic acid ratio of 100/0 to 20/80 (mass ratio). 3. The photocurable resin composition according to item 1. 3. The photocurable resin composition according to claim 1, wherein the polyester polyol (b) has a number average molecular weight of 500 to 3,000. 4. The urethane (meth) acrylate resin (A) has an isocyanate group content of 1 to 1 per resin solid content.
The photocurable resin composition according to any one of claims 1 to 3, wherein the content is 10% by mass.