JP2007284485A - Ultraviolet ray-curing type coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultraviolet ray-curing type coating having excellent weather resistance and abrasion resistance and adhesiveness of a coated film and having thermoforming properties hardly causing crack even by heat bending. <P>SOLUTION: The ultraviolet ray-curing type coating comprises a bifunctional urethane acrylate oligomer, a polyfunctional urethane acrylate oligomer and a polyfunctional and/or a monofunctional acrylate monomer which are a reaction product of an isocyanate compound obtained by reacting a polyether polyol with a straight-chain aliphatic or an alicyclic diisocyanate and an acrylate monomer having a hydroxy group. The coating comprises an ultraviolet ray-curing type resin (A) having 2.4-4.8 average number of functional groups and an acrylic polymer (B) prepared by using an ultraviolet light absorber and/or a light stabilizer having an unsaturated double bond as copolymerization components in (60/40) to (95/5) weight ratio (A)/(B) of the components (A) to (B). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention provides an ultraviolet curable coating, particularly a UV curable coating that can be applied to a plastic material to provide weather resistance and abrasion resistance, and to provide thermoformability that is less prone to cracking even when thermally bent. It relates to paint.

  Various transparent plastic materials are light weight, transparency, workability, and the safety of human body such as sports goggles, helmet shield, windshield, safety glasses, safety shield, etc. Applications, industrial applications such as various display devices, instrument covers, lenses, sensor covers, housing applications such as partitions and showcases in residential stores, transportation and partitions such as partitions and shelves, instrument covers, windows, etc. Used for applications. 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, the coating films obtained by these methods have the disadvantages that they cannot be thermoformed especially for use as goggles or helmet shields, especially hot bending, and have low wear resistance, which is problematic in practice. In addition, although UV curable coatings have been proposed, the coating film obtained by this method has better durability and wear resistance than thermosetting coatings, but the thermoformability is not sufficient. In particular, there is a problem that cracks occur during molding.

  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, the coating film obtained by this method has a problem that although the thermoformability is improved, the wear resistance is remarkably lowered.

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). The coating film obtained by this method has insufficient wear resistance and is not structurally flexible, 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

  The present invention provides an ultraviolet curable coating material that solves the above-mentioned problems, has excellent weather resistance, abrasion resistance, adhesion of a coating film, and has thermoformability that hardly causes cracking even when thermally bent. With the goal.

  The present inventor has developed an ultraviolet curable resin in which a specific bifunctional urethane acrylate oligomer, a polyfunctional urethane acrylate oligomer, and a polyfunctional and / or monofunctional acrylate monomer are adjusted to have a specific functional group number, and an ultraviolet absorber It was found that the above-mentioned object can be achieved by blending an acrylic polymer obtained as a copolymerization component in a specific ratio and making it an ultraviolet curable paint.

  That is, the present invention relates to a bifunctional urethane acrylate oligomer or polyfunctional urethane 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 resin (A) containing an acrylate oligomer and a polyfunctional and / or monofunctional acrylate monomer and having an average functional group number of 2.4 to 4.8, an ultraviolet absorber having an unsaturated double bond, and And / or an acrylic polymer (B) obtained using a light stabilizer as a copolymerization component, and the weight ratio (A) / (B) of (A) to (B) is 60/40 to 95/5. The gist of the ultraviolet curable paint characterized by

  The ultraviolet curable paint of the present invention is a bifunctional urethane acrylate oligomer that 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 resin (A) containing a polyfunctional urethane acrylate oligomer and a polyfunctional and / or monofunctional acrylate monomer and having an average functional group number of 2.4 to 4.8, and an ultraviolet ray having an unsaturated double bond An acrylic polymer (B) obtained by using an absorber and / or a light stabilizer as a copolymerization component, and a weight ratio (A) / (B) of (A) to (B) of 60/40 to By specifying in the range of 95/5, it is excellent in weather resistance, abrasion resistance, and adhesion of the coating film, and cracks even when thermally bent There is an effect that the thermoformability is less likely to occur.

  Hereinafter, in describing the ultraviolet curable coating material of the present invention, first, each component in the ultraviolet curable resin (A) will be described.

<Bifunctional urethane acrylate oligomer>
The bifunctional urethane acrylate oligomer of the present invention can be obtained by reacting an isocyanate compound obtained by reacting a polyether polyol with a linear aliphatic or alicyclic diisocyanate and an acrylate monomer having a hydroxyl group.

  Examples of polyether polyols include polyethylene oxide, polypropylene oxide, and ethylene oxide-propylene oxide random copolymers. Among them, those having a number average molecular weight of 400 or more are desirable. This is because if it is less than 400, sufficient thermoformability may not be obtained.

  Examples of the linear aliphatic diisocyanate include hexamethylene diisocyanate. Examples of the alicyclic diisocyanate include isophorone diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated methylene diphenyl 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.

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

  Examples of the polyol include polyester polyol, polyether polyol, and polycarbonate polyol.

  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.

  Dicarboxylic acids include adipic acid, succinic acid, glutaric acid, pimelic acid, sebacic acid, azelaic acid, maleic acid, terephthalic acid, isophthalic acid, phthalic acid, etc., and diols include 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.

  As the polyether polyol, polyethylene oxide, polypropylene oxide, ethylene oxide-propylene oxide random copolymerization is used.

  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, etc. are used, and one or two of them are used. 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.

<Multifunctional and / or monofunctional acrylate monomer>
Examples of the polyfunctional acrylate 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, tricyclodecane dimethanol diacrylate, ethoxylated cyclohexanedimethanol diacrylate having an average added mole number of ethylene oxide of 4-10, Examples include dipentaerythritol hexaacrylate and pentaerythritol triacrylate. Examples of the monofunctional acrylate monomer include isobornyl acrylate, isostearyl acrylate, octyl acrylate, and decyl acrylate. These acrylate monomers may be used alone or in combination of two or more.

  The ultraviolet curable resin (A) of the present invention is obtained by containing a bifunctional urethane acrylate oligomer, a polyfunctional urethane acrylate oligomer, and a polyfunctional and / or monofunctional acrylate monomer. In the present invention, the average number of functional groups in these components needs to be 2.4 to 4.8. That is, by making it in this range, weather resistance, wear resistance and thermoformability can be sufficiently imparted to the coating film. On the other hand, when the average number of functional groups of the UV curable resin (A) deviating from this is less than 2.4, sufficient wear resistance cannot be imparted, and when the average number of functional groups is higher than 4.8. Sufficient thermoformability cannot be imparted.

  The acrylic polymer (B) of the present invention is obtained by copolymerizing an acrylic monomer with an ultraviolet absorber and / or light stabilizer having an unsaturated double bond as a copolymerization component. Examples of the ultraviolet absorber having an unsaturated double bond include benzotriazole, benzophenone, and benzophenolate, and examples of the light stabilizer having an unsaturated double bond include a hindered amine. As long as each of these copolymer components has an unsaturated double bond, the basic structure is not particularly limited, and any conventionally known one can be used without limitation.

  The acrylic monomer is a monomer capable of reacting with an unsaturated double bond having an ultraviolet absorber and / or a light stabilizer, and the type thereof is not particularly limited. For example, (meth) acrylic acid, methyl Those having a linear or branched alkyl group such as (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, cyclohexyl (meth) Examples thereof include those having an alicyclic hydrocarbon group such as acrylate and methylcyclohexyl (meth) acrylate, and those having a polycyclic hydrocarbon group such as bornyl (meth) acrylate and isobornyl (meth) acrylate. However, methyl (meth) acrylate is desirable.

  The ultraviolet absorber and / or light stabilizer is preferably contained in the acrylic polymer (B) at a ratio of 10 to 90% by weight of the monomer. If it is less than 10%, sufficient weather resistance may not be exhibited, and if it exceeds 90%, molding defects may occur.

  The acrylic polymer (B) is obtained by a conventionally known polymerization method such as a solution polymerization method, a dispersion polymerization method, a suspension polymerization method, an emulsion polymerization method, etc., from an ultraviolet absorber and / or a light stabilizer and an acrylic monomer. Can do.

  The ultraviolet curable coating material of the present invention has a weight ratio (A) / (B) of the ultraviolet curable resin (A) and the acrylic polymer (B) of 60/40 to 95/5, more preferably 70 / It can be obtained by containing each in the range of 30 to 90/10. At this time, if the ratio of (B) exceeds 40%, sufficient wear resistance cannot be imparted and the adhesion of the coating film is also poor. Conversely, if the ratio of (B) is less than 5%, sufficient weather resistance cannot be imparted.

  In addition to the above components, an ultraviolet absorber and / or a light stabilizer may be added to the ultraviolet curable paint of the present invention. For example, benzotriazole or hydroxyphenyl triazine can be used as the ultraviolet absorber, and hindered amine can be used alone or in combination as the light stabilizer. The ultraviolet absorber is added in an amount of 10 parts by weight or less, preferably 2 to 4 parts by weight, based on 100 parts by weight of the ultraviolet curable paint. This is because if it exceeds 10 parts by weight, coloring of the cured coating and poor adhesion may occur. The light stabilizer is added in an amount of 2 parts by weight or less, preferably 1 part by weight or less. It is because the adhesion failure of a coating film may arise when it exceeds 2 weight part.

  When the ultraviolet curable coating material of the present invention is applied to a substrate such as a plastic sheet, the wettability and uniformity of the coating film to the substrate, the smoothness of the surface, and the surface slip property of the cured coating film are obtained. In consideration of the above, it is preferable to add a surface conditioner such as a silicone type or an acrylic copolymer type.

  As the silicone-based surface conditioner, polydimethylsiloxane or a modified silicone-based material obtained by modifying it can be 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 UV curable coating material of the present invention is applied to a substrate such as a plastic sheet by diluting with a solvent and then using a conventional method such as a roll coater, a flow coater, a spray coater, a curtain flow coater, a dip coater, or a slit die coater. Made. At that time, the thickness of the coating is preferably about 1 to 15 μm. This is because when the film thickness is thicker than 15 μm, the thermoformability deteriorates.

  In order to cure the ultraviolet curable coating material of the present invention, for example, after the ultraviolet curable coating material of the present invention is applied to a substrate, the temperature of the substrate and the atmosphere is raised, the diluting solvent is sufficiently evaporated, and then the ultraviolet light is cured. Can be performed. For the ultraviolet irradiation, a general electroded or electrodeless high-pressure ultraviolet lamp or metal halide lamp can be used.

  As a base material to which the ultraviolet curable paint of the present invention is applied, a general transparent plastic sheet is applicable, but sports goggles, helmet shields, safety glasses, windshields, safety shields, etc. that are assumed as uses of the present invention. Applications for personal protective equipment, industrial applications such as various display devices, instrument covers, lenses, sensor covers, residential applications such as partitions and showcases in residential stores, partitions and shelves for automobiles, railway vehicles, instrument covers, windows In transportation-related applications such as the above, the polycarbonate resin is preferable from the viewpoints of lightness, transparency, workability, and resistance to cracking and safety when cracked. Of course, other transparent plastics such as polymethyl methacrylate, polyethylene terephthalate, and polyvinyl chloride are also applicable.

<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. Then, it cooled to 40 degreeC, 150 parts of 2-hydroxyethyl acrylate was added next, and it was made to react at 80 degreeC by air atmosphere for 4 hours, and bifunctional urethane acrylate oligomer (1) was obtained.
(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 tolylene diisocyanate.
(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).

<Adjustment of acrylic polymer>
In a 1 liter four-necked flask equipped with a thermometer, stirrer, inert gas inlet, air inlet and reflux condenser, 2- [2-hydroxy-5-metyloyloxyethyl] phenyl] -2H-benzo 18 parts of triazole, 4-methacryloyloxy-1,2,2,6,2 parts of 6-pentamethylpiperidine, 80 parts of methyl methacrylate and 120 parts of propylene glycol monomethyl ether were charged and heated to 90 ° C. with stirring in a nitrogen atmosphere. As an initiator, a mixture of 0.5 part of t-butylperoxy-2-ethylhexanoate and 30 parts of propylene glycol monomethyl ether was added dropwise to the charged product over 2 hours, followed by further heating for 2 hours. Next, the temperature was raised to 120 ° C. and heated for 1 hour to obtain a 40% solution of an acrylic polymer.

<Examples 1-5, Comparative Examples 1-2, 5-6>
As a UV curable resin (A), a bifunctional urethane acrylate oligomer (1), an aliphatic isocyanate-based hexafunctional urethane acrylate (trade name: EB1290, manufactured by Daicel UC), and a 1,6-hexanediol as a bifunctional acrylate monomer Each diacrylate was prepared. The average functional group numbers in these total components are as shown in Tables 1 and 2.

  Next, each resin component obtained above and an acrylic polymer were blended as shown in Tables 1 and 2, and diluted with a polar diluent solvent so that they would be 20% by weight in the solution. At this time, a photo-polymerization initiator (1-hydroxycyclohexyl phenyl ketone, trade name: Irgacure 184 (manufactured by Ciba Specialty Chemicals)) previously dissolved in isopropyl alcohol is a polar diluent solvent so that the solid content ratio is 4% by weight. As part of 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 total solution. The resulting solution was sufficiently stirred and mixed, and then stored in a sealed container.

  Next, a polycarbonate sheet having a plate thickness of 1.5 mm ("Polyca Ace" manufactured by Chuchu Plastic Industry Co., Ltd.) is prepared as a base material, and the above solution is prepared using a metal bar coater so that the dry film thickness is 10 μm. It was applied to the material. Next, the polycarbonate sheet coated with the solution was placed in a hot air circulation oven at 60 ° C. and dried for 10 minutes. After drying, using a 160 W / cm metal halide lamp (USHIO INC.), The coated and dried polycarbonate sheet was irradiated with ultraviolet rays by a conveyor at a distance of 15 cm and a speed of 1.5 m / min to cure the coating film. The following evaluation was performed using the obtained sheet as a sample. The results are shown in Tables 1 and 2.

<Weather resistance>
In accordance with JIS K5600, an acceleration test was conducted with a carbon arc type sunshine weatherometer, and the appearance and yellowing degree (ΔYI) after 1000 hours were evaluated as follows.
◎: 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 ΔII is 3 or more and 7 or less △: Coating film No exfoliation or cloudiness, and △ YI is 7 or more ×: Appearance, △ YI 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 performed 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% / somewhat practical Insufficient wear resistance ×: ΔH exceeds 10% / practical wear resistance <thermoformability>
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.
○: There is no occurrence of cracks or peeling of the coating film and no change in appearance (good thermoformability)
X: Changes in appearance such as occurrence of cracks or peeling of the coating film, white turbidity or rough skin (the thermoformability is inferior)
<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 K5600) was performed and evaluated as follows.
○: 25 squares / 25 squares (having strong adhesion)
×: Less than 25 squares / in 25 squares (problem is practical)

<Comparative Example 3>
It replaced with the bifunctional urethane acrylate oligomer (1) in Example 2, and performed operation similar to Example 2 using the bifunctional urethane acrylate oligomer (2). The evaluation results are shown in Table 2.

<Comparative example 4>
It replaced with the bifunctional urethane acrylate oligomer (1) in Example 2, and performed operation similar to Example 2 using the bifunctional urethane acrylate oligomer (3). The evaluation results are shown in Table 2.

  From the results of Table 1, in Examples 1 to 5 blended according to the scope of the present invention, good results are shown in terms of weather resistance, abrasion resistance, adhesion of the coating film, and thermoformability. On the other hand, from the results in Table 2, in Comparative Example 1 where the blending amount of the acrylic polymer is less than the range of the present invention, the weather resistance is insufficient. Further, in Comparative Example 2 in which the blending amount of the acrylic polymer exceeds the range of the present invention, it is a result that the abrasion resistance cannot be sufficiently provided, and the adhesion of the coating film is also inferior. . Moreover, in the comparative example 3 which is outside the scope of the present invention using the bifunctional urethane acrylate oligomer (2) obtained using tolylene diisocyanate which is an aromatic diisocyanate, the weather resistance is inferior. Moreover, it is outside the scope of the present invention using urethane acrylate (3) obtained by reacting 2-hydroxypropyl acrylate after reaction with polyester diol composed of adipic acid and 1,6-hexanediol and hydrogenated tolylene diisocyanate. In Comparative Example 4, the weather resistance is inferior as in Comparative Example 3. Further, in Comparative Example 5 in which the average number of functional groups is outside the scope of the present invention, which is less than the scope of the present invention, the result is insufficient wear resistance. Moreover, in the comparative example 6 which is outside the range of this invention in which an average functional group number is less than the range of this invention, it has resulted in inadequate weather resistance.

Claims (1)

  Bifunctional urethane acrylate oligomer, polyfunctional urethane acrylate oligomer, and multifunctional product, 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 And / or an ultraviolet curable resin (A) containing a monofunctional acrylate monomer and having an average functional group number of 2.4 to 4.8, an ultraviolet absorber having an unsaturated double bond, and / or a light stabilizer. It contains an acrylic polymer (B) obtained as a copolymerization component, and the weight ratio (A) / (B) between (A) and (B) is 60/40 to 95/5. UV curable paint.