JP2006063162A - Ultraviolet-curing type coating material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultraviolet-curing type coating material excellent in weather resistance and abrasion resistance, causing no degradation of externals and generating no crack when bent under heating. <P>SOLUTION: The ultraviolet-curing type coating material comprises bifunctional urethane acrylate oligomer (A), a mixture (B) and a photopolymerization initiator, wherein the oligomer (A) is a reaction product of an isocyanate compound, obtained by reacting a polyetherpolyol with a linear chain aliphatic or an alicyclic diisocyanate, with acrylate monomer having a hydroxy group and the mixture (B) is obtained by mixing a 6-functional aliphatic urethane acrylate oligomer with a bifunctional acrylate monomer, and wherein weight ratio of (A)/(B) is 20/80 to 70/30. And the ultraviolet-curing type coating material is obtained by adding 2-10 pts. wt. ultraviolet absorber and ≤2 pts. wt. hindered amine-based photostabilizer to 100 pts. wt. (A) and (B). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultraviolet curable coating, particularly to an ultraviolet curable coating that imparts weather resistance and abrasion resistance when applied to a plastic material, has no deterioration in appearance, and is excellent in thermoforming (thermal bending) properties.

  Various plastic materials are used for personal protective equipment such as sports goggles, helmet shields, windshields, safety glasses, safety shields, etc. from the viewpoints of lightness, transparency, workability and safety when cracked. Industrial applications such as various display devices, instrument covers, lenses, sensor covers, etc., residential use such as partitions and showcases in residential stores, transportation related applications such as partitions, shelves, instrument covers, windows, etc. It is used for. However, these plastic materials have the disadvantage of being inferior in wear resistance compared to glass.

  In order to eliminate this drawback, various studies on surface modification have been made. For example, there is a method of coating the surface of a plastic material with a thermosetting resin such as polyorganosiloxane or melamine. However, these have the disadvantage that the plastic material cannot be thermoformed (hot bending) for use as, for example, goggles or helmet shields, and have low wear resistance and practical problems. Further, although an ultraviolet curable coating has been proposed, durability and wear resistance are improved as compared with a thermosetting coating, but cracking occurs during molding due to insufficient thermoformability.

  In recent years, an ultraviolet curable coating that can be thermoformed has been proposed to solve this drawback. For example, it is a method of increasing the bifunctional acrylate monomer to lower the crosslinking density of the entire coating material and improving thermoformability (see Patent Documents 1 to 3). However, although this method improves thermoformability, the wear resistance is remarkably lowered, and there is a high possibility that problems on the appearance of the substrate such as whitening and rough skin will occur.

In addition, a proposal has been made to combine dipentaerythritol hexaacrylate (DPHA) and aromatic bifunctional polyester urethane acrylate, which are generally used for ultraviolet curable hard coats (see Patent Document 4). Although the wear resistance and appearance can be maintained to some extent, they are insufficient and structurally inflexible, so that there is a problem that cracks occur during thermoforming or punching. Further, in terms of weather resistance, there is a problem that the cured coating film is peeled off or discolored during long-term outdoor use.
JP 02-003408 JP 02-248469 A JP 10-036540 JP-A-11-342460

  An object of the present invention is to solve the above problems, and to provide an ultraviolet curable coating material that is excellent in weather resistance and wear resistance, does not deteriorate in appearance, and does not generate cracks even when thermally bent.

  This inventor discovered that the said objective can be achieved by making into a composition the specific bifunctional urethane acrylate oligomer and the mixture of a hexafunctional urethane acrylate oligomer and a bifunctional acrylate monomer.

  That is, the present invention is a bifunctional urethane acrylate oligomer (A) that is a reaction product of an isocyanate compound obtained by reacting a polyether polyol and a linear aliphatic or alicyclic diisocyanate and an acrylate monomer having a hydroxyl group, It consists of a mixture (B) of a hexafunctional aliphatic urethane acrylate oligomer and a bifunctional acrylate monomer, and a photopolymerization initiator, and the weight ratio of the above (A) / (B) is 20/80 to 70/30. The gist of the ultraviolet curable paint is as follows. Further, an ultraviolet curable coating material characterized in that 2 to 10 parts by weight of an ultraviolet absorber and 2 parts by weight or less of a hindered amine light stabilizer are added to 100 parts by weight of the above (A) and (B). And

  The ultraviolet curable paint of the present invention is a bifunctional urethane acrylate oligomer (reaction product of an isocyanate compound obtained by reacting a polyether polyol with a linear aliphatic or alicyclic diisocyanate and an acrylate monomer having a hydroxyl group ( A), a hexafunctional aliphatic urethane acrylate oligomer, a mixture with a bifunctional acrylate monomer (B), and a photopolymerization initiator, wherein the weight ratio of the above (A) / (B) is 20/80 to 70/30 As a result, the weather resistance and wear resistance are excellent, the appearance is not deteriorated, and cracks are not generated even when heat bending. Further, by adding 2 to 10 parts by weight of the ultraviolet absorber and 2 parts by weight or less of the hindered amine light stabilizer to 100 parts by weight of the above (A) and (B), more excellent weather resistance is exhibited.

<Bifunctional urethane acrylate oligomer>
The polyether polyol used in the bifunctional urethane acrylate oligomer (A) of the present invention is polyethylene oxide, polypropylene oxide, ethylene oxide-propylene oxide random copolymer, and preferably has a number average molecular weight of 400 or more. This is because if it is less than 400, sufficient thermoformability may not be obtained.

  As the diisocyanate, linear and cyclic aliphatic isocyanates are used. Examples of the alicyclic diisocyanate include isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated methylene diphenyl diisocyanate. Examples of the aliphatic diisocyanate include hexamethylene diisocyanate. From the viewpoint of maintaining abrasion resistance, alicyclic diisocyanates are preferred.

  Examples of the acrylate monomer having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl acrylate, and polyethylene glycol monoacrylate.

<Hexafunctional urethane acrylate oligomer>
The hexafunctional urethane acrylate oligomer used in the present invention is a reaction product of an isocyanate compound obtained by reacting a polyol and diisocyanate and an acrylate monomer having a hydroxyl group.

  Here, examples of the polyol include polyester polyol, polyether polyol, and polycarbonate diol.

  The manufacturing method of a polyester polyol is not specifically limited, A well-known manufacturing method can be employ | adopted. For example, the diol and dicarboxylic acid or dicarboxylic acid chloride may be subjected to a polycondensation reaction, or the diol or dicarboxylic acid may be esterified and subjected to an ester exchange reaction.

  Examples of the dicarboxylic acid include adipic acid, succinic acid, glutaric acid, pimelic acid, sebacic acid, azelaic acid, maleic acid, terephthalic acid, isophthalic acid, and phthalic acid. As the diol, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, tripropylene glycol, tetrapropylene glycol and the like are used.

  The polyether polyol is preferably a polyethylene oxide, polypropylene oxide, ethylene oxide-propylene oxide random copolymer having a number average molecular weight of 400 or more. This is because if it is less than 400, sufficient thermoformability may not be obtained.

  Examples of the polycarbonate diol include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, 2-ethyl-1,3-hexanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanediol, polyoxyethylene glycol, and the like are used, and one kind or two kinds You may use the above together.

  As the diisocyanate, a linear or cyclic aliphatic diisocyanate is used. Typical examples include hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated xylylene diisocyanate.

  Examples of the acrylate monomer having a hydroxyl group include trimethylolpropane triacrylate, pentaerythritol triacrylate, and dipentaerythritol triacrylate.

<Bifunctional acrylate monomer>
Examples of the bifunctional acrylate monomer used in the present invention include dipropylene glycol diacrylate, 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, dimethylol dicyclopentane diacrylate, 1,9-nonanediol diacrylate, Examples include 1,10-decanediol diacrylate, 2-methyl-1,8-octanediol diacrylate, and ethoxylated cyclohexanedimethanol diacrylate having an average addition mole number of ethylene oxide of 4-10.

  The weight ratio (A) / (B) of the bifunctional urethane acrylate oligomer (A) and the mixture (B) of the hexafunctional aliphatic urethane acrylate oligomer and the bifunctional acrylate monomer is 20/80 to 70/30, more preferably 40. / 60 to 60/40. When the ratio of (A) is less than 20%, excellent thermoforming performance cannot be imparted, and when the ratio of (B) is less than 30%, thermoformability can be imparted, but sufficient wear resistance. This is because it cannot be given. Further, the content ratio of each of the hexafunctional aliphatic urethane acrylate oligomer and the bifunctional acrylate monomer used in (B) needs to be 5% or more in (A) and (B) as a whole. If the hexafunctional aliphatic urethane acrylate oligomer is less than 5%, the wear resistance cannot be imparted, and if the bifunctional acrylate monomer is less than 5%, the adhesion with the substrate becomes insufficient. is there.

  The photopolymerization initiator has a function as a polymerization initiator when the photopolymerizable compound is cured by ultraviolet rays, and a known one can be used alone or in combination, benzoin, benzoin methyl ether, Benzoin or benzoin alkyl ethers such as benzoin ethyl ether and benzoin isopropyl ether, aromatic ketones such as benzophenone and benzoylbenzoic acid, alpha-dicarbonyls such as benzyl, benzyl ketals such as benzyldimethyl ketal and benzyl diethyl ketal, Acetophenone, 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propan-1-one , 1- Acetophenones such as 4-isopropylphenyl) -2-hydroxy-2-methyl-propan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1, 2-methyl Anthraquinones such as anthraquinone, 2-ethylanthraquinone and 2-t-butylanthraquinone, thioxanthones such as 2,4-dimethylthioxanthone, 2-isopropylthioxanthone and 2,4-diisopropylthioxanthone, bis (2,4,6-trimethyl) Phosphine oxides such as benzoyl) -phenylphosphine oxide, alpha-acyloximes such as 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) oxime, ethyl p-dimethylaminobenzoate, p-Dimethylaminobenzoic acid It can be used amines such as isoamyl. Among these, acetophenones such as 2-hydroxy-2-methyl-1-phenyl-1-propan-1-one, aromatic ketones such as benzophenone and bis (2,4,6-trimethylbenzoyl) -phenylphosphine The combined use of fin oxides with phosphine oxides is particularly preferred.

  As the ultraviolet curable coating material of the present invention, an ultraviolet absorber and a hindered amine light stabilizer are added to the bifunctional urethane acrylate oligomer (A) and a mixture (B) of a hexafunctional aliphatic urethane acrylate oligomer and a bifunctional acrylate monomer. It may be added.

  As the ultraviolet absorber, known ones can be used alone or in combination, and benzotriazoles such as 2- (2-hydroxy-5-tert-butylphenyl) -2H-benzotriazole, 2- [4- Hydroxyphenyl triazines such as [(2-hydroxy-3-dodecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, ultraviolet light Examples thereof include an acrylic copolymer having a skeleton having an absorption property in the side chain, a reactive ultraviolet absorber having an acryl group or a methacryl group in the molecule and an ultraviolet absorption property skeleton. The addition amount of the ultraviolet absorber is 2 to 10 parts by weight, preferably 4 to 8 parts by weight with respect to 100 parts by weight of the above (A) and (B). When it is less than 2 parts by weight, sufficient weather resistance cannot be imparted, and when it exceeds 10 parts by weight, coloring of the cured coating film and poor adhesion occur.

  As the hindered amine-based light stabilizer, known ones can be used, such as 1,1-dimethylethylhydroperoxide, octane and decandioic acid, bis (2,2,6,6-tetramethyl- Examples include a reaction product of 1- (octyloxy) -4-piperidinyl) ester. The addition amount of this light stabilizer is 2 parts by weight or less, preferably 1 part by weight or less, based on 100 parts by weight of the above (A) and (B). This is because when the amount exceeds 2 parts by weight, poor adhesion to the substrate occurs.

  In the present invention, in order to obtain wettability and uniformity of the coating film on the base material at the time of coating, surface smoothness and surface slip property of the cured coating film, the surface of a silicone system, an acrylic copolymer system, etc. It is preferable to add a regulator.

  As the silicone-based surface conditioner, polydimethylsiloxane or a modified silicone-based one obtained by modifying it is used. As the modified silicone, a polyether-modified product, an alkyl-modified product, a polyester-modified product and the like are preferable, and a polyether-modified product is particularly preferable. Moreover, it is also possible to use these in combination.

  The coating film made of the coating material of the present invention can be obtained in the steps of mixing, dilution, coating, drying and curing of the composition. The thickness of the coating film is 1 μm or more and 15 μm or less. The thermoformability becomes worse as the film thickness is increased, and if it is thicker than 15 μm, the thermoformability is lowered. As a coating method, a roll coater, a flow coater, a spray coater, a curtain flow coater, a dip coater, a slit die coater, or the like is suitable.

  After the coating material of the present invention is applied to the base material, the temperature of the base material and the atmosphere is raised, the diluted solvent is sufficiently evaporated, and then the ultraviolet ray is irradiated to cure the coating film. For the ultraviolet irradiation, a general electroded or electrodeless high-pressure ultraviolet lamp or metal halide lamp can be used.

  As the base material, general transparent plastics can be used, but assumed as the application of the present invention are sports goggles, helmet shields, safety glasses, windshields, safety shields and other human protective equipment, and various display devices and Polycarbonate resin is used in industrial applications such as instrument covers, lenses, and sensor covers, in residential applications such as partitions and showcases in residential stores, and in transportation-related applications such as partitions and shelves, instrument covers, windows, etc. It is most preferable to use a base material from the viewpoint of lightness, transparency, workability, and resistance to cracking and safety when cracked. Other common transparent resins such as polymethyl methacrylate, polyethylene terephthalate, and polyvinyl chloride can also be used.

<Adjustment of bifunctional urethane acrylate oligomer>
(1) Polyoxypropylene diol 300 having 150 parts of hydrogenated tolylene diisocyanate and a number average molecular weight of 600 in a 1 liter four-necked flask equipped with a thermometer, stirrer, inert gas inlet, air inlet and reflux condenser The parts were charged and reacted at 80 ° C. for 5 hours under a nitrogen atmosphere. Thereafter, the mixture was cooled to 40 ° C., 150 parts of 2-hydroxyethyl acrylate was then added, and the mixture was reacted at 80 ° C. for 4 hours in an air atmosphere to obtain a bifunctional urethane acrylate oligomer (1).
(2) A bifunctional urethane acrylate oligomer (2) was obtained by performing the same operation using tolylene diisocyanate which is an aromatic diisocyanate instead of the hydrogenated TDI.
(3) After reacting polyester diol composed of adipic acid and 1,6-hexanediol with hydrogenated tolylene diisocyanate, 2-hydroxypropyl acrylate was reacted to obtain urethane acrylate (3).

<Examples 1-3, Comparative Examples 1-4>
The above-mentioned bifunctional urethane acrylate oligomer (1), aliphatic isocyanate-based hexafunctional urethane acrylate (trade name: EB1290, manufactured by Daicel UCB), and 1,6-hexanediol diacrylate were prepared as a bifunctional acrylate monomer.

  Each of the above components were blended as shown in Table 1, and diluted with a polar diluent solvent so as to be 20% by weight in the solution. At this time, a photopolymerization initiator (1-hydroxycyclohexyl phenyl ketone, trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals) dissolved in isopropyl alcohol in advance is polar diluted so that the solid content ratio is 4% by weight. Added as part of the solvent. Furthermore, 1.25 parts by weight of a silicon-based surface conditioner (polyether-modified polydimethylsiloxane solution, trade name: BYK-306, manufactured by Big Chemie) was added to 100 parts by weight of the composition. The composition was sufficiently stirred and mixed, and then stored in a sealed container.

  A polycarbonate sheet having a plate thickness of 1.5 mm (“Polyca Ace” manufactured by Chuchu Plastic Industry Co., Ltd.) was prepared as a base material, and the composition was applied using a metal bar coater so that the dry film thickness was 10 μm. Next, the coated polycarbonate sheet was put into a hot air circulation oven at 60 ° C. and dried. After drying for 10 minutes, using a 160 W / cm metal halide lamp (made by USHIO INC.), The coated and dried polycarbonate sheet is irradiated with ultraviolet rays on a conveyor with a distance of 15 cm and a speed of 1.5 m / min, and the composition is cured. I let you. The following evaluation was performed about the obtained sheet | seat, and the result is shown in Table 1.

<Appearance>
The coating film was visually observed and evaluated as follows.
○: The coating film surface is smooth and transparent from any angle. ×: The coating film surface is rough, or even when the flat surface is viewed from the front, it is cloudy and has no practicality.

<Weather resistance>
In accordance with JIS K5600, an acceleration test was conducted using a carbon arc sunshine weatherometer, and the appearance and yellowing degree (ΔYI) after 1000 hours were evaluated as follows.
A: No peeling or clouding occurs in the coating film, and ΔYI is 3 or less ○: No peeling or clouding occurs in the coating film, and ΔYI is 3 or more and 7 or less Δ: Coating film There is no occurrence of peeling or clouding, and ΔYI is 7 or more ×: Appearance, ΔYI has practical problems

<Abrasion resistance>
In accordance with ASTM D1044, a Taber abrasion test (CS10F wear wheel, load 500 g, 100 revolutions) was performed, and the following evaluation was made based on the generated haze.
A: Change in haze (ΔH) is less than 5% / very excellent wear resistance ○: ΔH is 5% to 7% / excellent wear resistance Δ: ΔH is 7% to 10% / Slightly insufficient wear resistance ×: ΔH exceeds 10% / practically insufficient wear resistance

<Moldability>
The sample was softened by heating in a hot air circulation oven set at 170 ° C for 7 minutes, and immediately after taking out, the sample was cooled to near room temperature by attaching it to a wooden cylinder with a radius of 10 mm through a flannel cloth with the coating surface facing outward. The single curved surface was molded by keeping it as it was, and then the appearance was observed and evaluated as follows.
○: No occurrence of cracks or peeling of coating film or change in appearance (excellent moldability)
X: Changes in appearance such as occurrence of cracks or peeling of the coating film, white turbidity or rough skin (no formability)

<Adhesiveness of coating film>
After immersing the sample in boiling water for 60 minutes, the moisture was wiped off and dried at room temperature for 2 hours or more, and then a cross-cut tape peeling test (conforming to JIS K5600) was performed and evaluated as follows.
○: In 25 squares / 25 squares (has very strong adhesion)
×: Less than 25 squares / in 25 squares (practical problem)

<Example 4>
As shown in Table 1, an ultraviolet absorber and a hindered amine light stabilizer were blended, and the same operation as in Example 1 was performed. As an ultraviolet absorber, (2- [4-[(2-hydroxy-3-dodecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3, 5-Triazine and 2- [4-[(2-hydroxy-3-tridecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5 -Using a mixture with triazine (trade name: Tinuvin 400, manufactured by Ciba Specialty Chemicals), as light stabilizer, 1,1-dimethylethyl hydrodoperoxide, octane and decandioic acid, bis (2, Reaction product of 2,6,6-tetramethyl-1- (octyloxy) -4-piperidinyl) ester (trade name: Tinuvin 123, Ciba Specialty Chemi Manufactured by LUZ, Inc.) was used. The evaluation results are shown in Table 1.

<Comparative Example 5>
Using the bifunctional urethane acrylate oligomer (2) as the bifunctional urethane acrylate oligomer, the same UV absorber and hindered amine light stabilizer as in Example 4 were blended as shown in Table 1, and the same operation as in Example 4 was performed. . The evaluation results are shown in Table 1.

<Comparative Example 6>
Using the bifunctional urethane acrylate oligomer (3) as the bifunctional urethane acrylate oligomer, the same UV absorber and hindered amine light stabilizer as in Example 4 are blended as shown in Table 1, and blended as shown in Table 1. The same operation as in Example 4 was performed. The evaluation results are shown in Table 1.

  From the results in Table 1, in Examples 1 to 3 blended according to the scope of the present invention using a bifunctional urethane acrylate oligomer obtained using an alicyclic diisocyanate, weather resistance, wear resistance and moldability Both show good results. Furthermore, in Example 4, the weather resistance was further improved by adding an ultraviolet absorber and a light stabilizer. On the other hand, even if the same bifunctional urethane acrylate oligomer is used, in Comparative Examples 1 and 2 in which the blending is outside the scope of the present invention, the result is that the moldability is insufficient or sufficient wear resistance cannot be imparted. ing.

  In Comparative Example 3 in which no hexafunctional urethane acrylate is blended, the moldability is good, but the wear resistance is poor. In Comparative Example 4 in which the bifunctional acrylate monomer is not blended, the result is that the adhesion between the coating film and the substrate is insufficient.

  In Comparative Example 5 in which the bifunctional urethane acrylate oligomer obtained using aromatic diisocyanate was used and blended according to the scope of the present invention, good results were obtained in both wear resistance and moldability. Even if a light stabilizer is added, the weather resistance is poor. In Comparative Example 6 using a bifunctional aliphatic polyester urethane acrylate oligomer, the weather resistance is inferior to that of the bifunctional aliphatic polyether polyol urethane acrylate despite the addition of an ultraviolet absorber and a light stabilizer. It is the result.

Claims (2)

  Bifunctional urethane acrylate oligomer (A), hexafunctional aliphatic urethane acrylate, which is a reaction product of an isocyanate compound obtained by reacting a polyether polyol with a linear aliphatic or alicyclic diisocyanate and an acrylate monomer having a hydroxyl group An ultraviolet curable type comprising a mixture (B) of an oligomer and a bifunctional acrylate monomer, and a photopolymerization initiator, wherein the weight ratio (A) / (B) is 20/80 to 70/30. paint.   An ultraviolet curable coating material, wherein 2 to 10 parts by weight of an ultraviolet absorber and 2 parts by weight or less of a hindered amine light stabilizer are added to 100 parts by weight of the above (A) and (B).