JP4380396B2 - UV-curable paint and transparent plastic substrate with paint film - Google Patents

Description

  The present invention relates to an ultraviolet curable coating material, particularly an ultraviolet curable coating material which imparts abrasion resistance by application 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, safety glasses, safety shields, etc. from the viewpoint of lightness, transparency, processability and safety when cracked. Used for 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 has been. 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, it has been proposed to combine dipentaerythritol hexaacrylate (DPHA) and bifunctional polyester-based urethane acrylate, which are generally used for ultraviolet curable hard coats (see Patent Document 4). However, it is inadequate and structurally inflexible, so that there is a problem that cracks occur during thermoforming or punching.
JP 02-003408 JP 02-248469 A JP 10-036540 JP-A-11-343460

  An object of the present invention is to solve the above-mentioned problems, and to provide an ultraviolet curable coating material that is excellent in 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 mixture of a specific bifunctional urethane acrylate oligomer, a hexafunctional urethane acrylate oligomer, a bifunctional acrylate monomer, and a tetrafunctional acrylate. .

That is, the present invention is an ultraviolet curable coating applied to the surface of a transparent plastic substrate,
Bifunctional urethane acrylate oligomer (A), hexafunctional urethane acrylate oligomer, bifunctional, which is a reaction product of an isocyanate compound obtained by reacting a polyether polyol with an aromatic or alicyclic diisocyanate and an acrylate monomer having a hydroxyl group a mixture of acrylate monomers, and tetrafunctional acrylate (B), and consists of a photopolymerization initiator, Ri weight ratio of 10 / 90-40 / 60 der above (a) / (B), used in (B) The content ratio of each of the 6-functional urethane acrylate oligomer, the 2-functional acrylate monomer, and the 4-functional acrylate is 5% or more in the total of (A) and (B), and the 6-functional urethane acrylate oligomer is a polyester polyol, Polyether polyol, Polycar It is a reaction product of an isocyanate compound obtained by reacting an nate diol and a diisocyanate and an acrylate monomer having a hydroxyl group, and the tetrafunctional acrylate is ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate. Oh and gist ultraviolet curable coating material, characterized in Rukoto.

  The ultraviolet curable coating material of the present invention is a bifunctional urethane acrylate oligomer (A) which is a reaction product of an isocyanate compound obtained by reacting a polyether polyol with an aromatic or alicyclic diisocyanate and an acrylate monomer having a hydroxyl group. ), A hexafunctional urethane acrylate oligomer, a mixture (B) of a bifunctional acrylate monomer, and a tetrafunctional acrylate, and a photopolymerization initiator, and the weight ratio of the above (A) / (B) is 10/90 to 40 / By setting it to 60, the wear resistance is excellent, the appearance is not deteriorated, and cracking does not occur even when thermally bent.

<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.

  Diisocyanate plays a role in maintaining abrasion resistance, and in the case of straight chain aliphatic ones, it is insufficient to maintain abrasion resistance, and it must have a cyclic structure, that is, aromatic diisocyanate or alicyclic diisocyanate. There is. Aromatic diisocyanates include tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, and alicyclic diisocyanates include isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated methylene diphenyl diisocyanate. be able to.

  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, tetraethene 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, aromatic diisocyanate and linear or cyclic aliphatic diisocyanate are used. Typical examples include hexamethylene diisocyanate, lysine isocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated xylylene diisocyanate.

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

  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, 1,10-decanediol diacrylate, 2-methyl-1,8-octanediol diacrylate, ethoxylated cyclohexanedimethanol diacrylate having an average addition mole number of ethylene oxide of 4-10, average addition mole number of ethylene oxide An ethoxylated bisphenol A diacrylate in which is 4-20.

  Examples of the tetrafunctional acrylate monomer include ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, and dipentaerythritol tetraacrylate.

The weight ratio (A) / (B) of the bifunctional urethane acrylate oligomer (A) to the mixture (B) of the hexafunctional urethane acrylate oligomer, the bifunctional acrylate monomer, and the tetrafunctional acrylate is 10/90 to 40 / 60, more preferably 20/80 to 30/70. When the ratio of (A) is less than 10%, excellent thermoforming performance cannot be imparted. When the ratio of (B) is less than 60%, thermoformability can be imparted, but sufficient wear resistance. This is because it cannot be given. Moreover, the content ratio of each of the hexafunctional urethane acrylate oligomer, the bifunctional acrylate monomer, and the tetrafunctional acrylate used in (B) needs to be 5% or more in the whole of (A) and (B). If the hexafunctional urethane acrylate oligomer is less than 5%, it is impossible to impart abrasion resistance, and if the tetrafunctional acrylate is less than 5%, the paint has a high viscosity and has poor appearance such as rough skin during curing. This is because if the bifunctional acrylate monomer is less than 5%, the adhesion to the substrate becomes insufficient.

  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, such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin. Benzoin or benzoin alkyl ethers such as 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- (4 -Isopropylphenyl Acetophenones such as 2-hydroxy-2-methyl-propan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropanone-1, 2-methylanthraquinone, 2-ethyl Anthraquinones such as anthraquinone and 2-t-butylanthraquinone, thioxanthones such as 2,4-dimethylthioxanthone, 2-isopropylthioxanthone and 2,4-diisopropylthioxanthone, 1-phenyl-1,2-propanedione-2- ( Alpha-acyl oximes such as o-ethoxycarbonyl) oxime, amines such as ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, and the like can be used. Of these, acetophenones such as 2-hydroxy-2-methyl-1-phenyl-1-propan-1-one and aromatic ketones such as benzophenone are particularly preferable.

  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. Moreover, as a coating method, a roll coater, a spray coater, a curtain flow coater, a slit die coater, etc. having a horizontal type coating and conveying facility are 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.

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

<Adjustment of bifunctional urethane acrylate oligomer>
(1) 150 parts of hydrogenated tolylene diisocyanate (hydrogenated TDI) 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 300 parts of polyoxypropylene diol was charged and reacted at 80 ° C. for 5 hours in 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 (TDI) which is an aromatic diisocyanate instead of the hydrogenated TDI.
(3) Instead of the hydrogenated TDI, 1,6-hexamethylene diisocyanate (HDI), which is a linear aliphatic diisocyanate, was used in the same manner to obtain a bifunctional urethane acrylate oligomer (3).

<Examples 1-4, Comparative Examples 1-5>
Ethoxylation having an average addition mole number of ethylene oxide of 4 as the above-mentioned bifunctional urethane acrylate oligomer (1), aromatic isocyanate-based hexafunctional urethane acrylate (trade name: EB220, manufactured by Daicel UCB) and bifunctional acrylate monomer Bisphenol A diacrylate (trade name: A-BPE-4, manufactured by Shin-Nakamura Chemical Co., Ltd.), pentaerythritol tetraacrylate was prepared as a tetrafunctional acrylate.

  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. In this case, a photopolymerization initiator (1-hydroxycyclohexyl phenyl ketone, trade name: Irgacure 184, manufactured by Ciba Specialty Chemicals) previously dissolved in isopropyl alcohol was added to the polar diluent solvent so that the solid content ratio was 5% by weight. Added as part. Furthermore, 1.25 parts by weight of a silicon-based surface conditioner (polyether-modified polydimethylsiloxane solution, trade name: BYK-306, manufactured by BYK 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, a 160 W / cm high-pressure mercury lamp (manufactured by Ushio Inc.) was used to irradiate the coated and dried polycarbonate sheet with ultraviolet rays on a conveyor at a distance of 15 cm and a speed of 1.5 m / min. Cured. 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 surface of the coating is smooth and transparent from any angle ○: The surface of the coating is smooth. Things x: The surface of the coating film is rough, or even when the plane is viewed from the front, it is cloudy and has no practicality.

<Abrasion resistance>
In accordance with ASTM D1044, a Taber type wear test (CS10F wear wheel, load 500 g, 100 revolutions) was performed and evaluated as follows according to 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% or more and 10% or less (a little practically 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 removal, 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 (based on JIS K5400) was performed and evaluated as follows.
○: In 25 squares / 25 squares (having very strong adhesion)
×: Less than 25 squares / in 25 squares (practical problem)

<Example 5>
As the bifunctional urethane acrylate oligomer, the bifunctional urethane acrylate oligomer (2) was used and blended as shown in Table 1, and the same operation as in Example 1 was performed. The evaluation results are shown in Table 1.

<Comparative Example 6>
A bifunctional urethane acrylate oligomer (3) was used as a bifunctional urethane acrylate oligomer, blended as shown in Table 1, and the same operation as in Example 1 was performed. The evaluation results are shown in Table 1.

  From the results of Table 1, in Examples 1 to 4 blended according to the scope of the present invention using a bifunctional urethane acrylate oligomer obtained using an alicyclic diisocyanate, both wear resistance and moldability are good. Results are shown. 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 no tetrafunctional acrylate monomer is blended, the paint has a high viscosity and is inferior in appearance. In Comparative Example 5 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 Example 5 in which a bifunctional urethane acrylate oligomer obtained using an aromatic diisocyanate was used and blended according to the scope of the present invention, good results were obtained in both wear resistance and moldability. On the other hand, in Comparative Example 6 using a bifunctional urethane acrylate oligomer obtained using a linear aliphatic diisocyanate, the moldability is improved, but no abrasion resistance can be imparted.

Claims (3)

An ultraviolet curable paint applied to the surface of a transparent plastic substrate,
Bifunctional urethane acrylate oligomer (A), hexafunctional urethane acrylate oligomer, bifunctional, which is a reaction product of an isocyanate compound obtained by reacting a polyether polyol with an aromatic or alicyclic diisocyanate and an acrylate monomer having a hydroxyl group a mixture of acrylate monomers, and tetrafunctional acrylate (B), and consists of a photopolymerization initiator, Ri weight ratio of 10 / 90-40 / 60 der above (a) / (B), used in (B) The content ratio of each of the 6-functional urethane acrylate oligomer, the 2-functional acrylate monomer, and the 4-functional acrylate is 5% or more in the total of (A) and (B), and the 6-functional urethane acrylate oligomer is a polyester polyol, Polyether polyol, Polycar It is a reaction product of an isocyanate compound obtained by reacting an nate diol and a diisocyanate and an acrylate monomer having a hydroxyl group, and the tetrafunctional acrylate is ditrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate. UV curable coating, wherein Rukoto Oh. Apply the UV curable paint according to claim 1 to a transparent plastic substrate, and cure the coating.
A transparent plastic substrate with a coating film, characterized in that is formed. The transparent plastic substrate with a coating film according to claim 2, wherein the transparent plastic substrate is a polycarbonate sheet.