One-component moisture-curable polyurethane composition comprising titanium oxide

Abstract

To provide a one-component moisture-curable polyurethane composition comprising titanium oxide, which is used as a coating composition having excellent high weather resistance while ensuring concealability without impairing adhesion to the substrate, primer and topcoat.SOLUTION: There is provided a one-component moisture-curable polyurethane composition comprising titanium oxide which is obtained by blending an acrylate compound having a polar group, titanium oxide and a latent curing agent in at least one polyol selected from a polycarbonate polyol and an acrylic polyol and a urethane prepolymer synthesized from a polyisocyanate.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a one-component moisture-curable polyurethane composition containing titanium oxide. More specifically, the present invention relates to a one-component moisture-curable polyurethane composition containing titanium oxide, which is used as a paint excellent in hiding power and weather resistance without impairing the adhesion to a substrate, a primer, and a topcoat.

Background Art

[0002] Since titanium oxide has a high refractive index, it also has a hiding effect of hiding the color of the substrate, and thus is an indispensable white pigment for paints for formulating light colors.

[0003] Titanium oxide mainly has anatase-type crystals with high photocatalytic activity and rutile-type crystals with low photocatalytic activity. As a white pigment, rutile-type titanium oxide whose photocatalytic activity is suppressed by surface treatment using silica or alumina is used. However, even such titanium oxide whose photocatalytic activity is suppressed by surface treatment has a problem that radicals are generated when irradiated with ultraviolet rays, and the resin in the composition is deteriorated at an early stage. As a result, there is a significant decrease in the gloss of the paint, or the pigment in the paint falls off, resulting in coating film deterioration called chalking.

[0004] Here, when titanium oxide is used as a paint pigment, good weather resistance can be obtained by surface treatment of titanium oxide using inorganic substances such as alumina, silica, and zirconia, fatty acids such as stearic acid, and organic substances such as alkylsilane compounds and silicone compounds (Non-Patent Document 1).

[0005] However, even with such a method, there are still problems in obtaining a paint excellent in weather resistance at a high level.

Prior Art Documents

Non-Patent Documents

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide a titanium oxide-containing one-component moisture-curing polyurethane composition that can be used as a paint excellent in high weather resistance while ensuring concealability without impairing the adhesion to a substrate, primer, and topcoat.

Means for Solving the Problems

[0008] The object of the present invention is achieved by a titanium oxide-containing one-component moisture-curing polyurethane composition obtained by blending a urethane prepolymer synthesized from at least one polyol selected from polycarbonate polyol and acrylic polyol and polyisocyanate with an acrylate compound having a polar group, titanium oxide, and a latent curing agent.

Effects of the Invention

[0009] The titanium oxide-containing one-component moisture-curing polyurethane composition according to the present invention uses an acrylate compound having a specific structure together with titanium oxide, so that while ensuring the concealability by titanium oxide, it does not cause a decrease in weather resistance, which is regarded as an adverse effect of using titanium oxide, and has an excellent effect of being used as a paint that does not impair the adhesion to a substrate, primer, and topcoat.

Modes for Carrying Out the Invention

[0010] The titanium oxide-containing one-component moisture-curing polyurethane composition of the present invention contains at least one polyol selected from polycarbonate polyol and acrylic polyol, polyisocyanate, and titanium oxide, and an acrylate compound having a polar group and a latent curing agent.

[0011] Examples of the polycarbonate polyol include those obtained by reacting at least one aliphatic polyhydric alcohol such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, diethylene glycol, cyclohexanedimethanol with a dialkylene carbonate or a dialkyl carbonate such as diethylene carbonate, dimethyl carbonate, or diethyl carbonate. Here, the alkylene group or the dialkyl group has 2 to 10 carbon atoms. As such a polycarbonate polyol, those having a number average molecular weight Mn of 500 to 3000 are preferably used, and commercially available products such as UBE products ETERNACOLL UH-50, UH-100, UH-200, UH-300, PH-50, PH-100, PH-200, PH-300, UC-100, UM-90U, and Toray products Nipporan 981, 980R, 982R, 965, 963, 964, 968 can be used as they are.

[0012] Examples of the acrylic polyol include homopolymers or copolymers of (meth)acrylic monomers having a hydroxyl group, or those obtained by copolymerizing (meth)acrylic monomers having a hydroxyl group with other monomers having a polymerizable unsaturated bond. Here, the hydroxyl groups in the acrylic polyol preferably have an average of 2 to 8 per molecule.

[0013] As such an acrylic polyol, those having a glass transition temperature Tg of 0 to 100 °C and a hydroxyl value of 50 to 150 mgKOH / g are used. When the glass transition temperature Tg is less than 0 °C, the weather resistance tends to decrease. On the other hand, when it exceeds 100 °C, although the weather resistance is excellent, the cured product tends to become hard and brittle. Here, since the hydroxyl value of the acrylic polyol affects the viscosity of the urethane prepolymer, it also affects the workability of the paint. When the hydroxyl value is less than 50 mgKOH / g, the strength and weather resistance of the coating film tend to decrease. On the other hand, when the hydroxyl value exceeds 150 mgKOH / g, the viscosity of the prepolymer becomes high, which may cause problems in the production of the prepolymer.

[0014] Examples of other monomers having a polymerizable unsaturated bond include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate; unsaturated carboxylic acids such as (meth)acrylic acid, maleic acid, itaconic acid; unsaturated amides such as (meth)acrylamide, N-methylol(meth)acrylamide; and styrene, vinyltoluene, vinyl acetate, acrylonitrile, etc. These may be used alone or in combination of two or more. Among these, from the viewpoint of weather resistance, (meth)acrylic acid esters such as (meth)acrylic acid alkyl and / or (meth)acrylic acid alkoxyalkyl are preferably used.

[0015] Also, for property adjustment, polyols other than these polyols can be used in a proportion of less than 20% by mass in the total polyols, specifically, within a range that does not impair the weather resistance of the cured product. However, if other polyols are used in a proportion of 20% by mass or more, it may be difficult to achieve both weather resistance and impact resistance, which is not preferable.

[0016] Examples of such polyols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, trimethylolpropane, 1,2,5 - hexanetriol, 1,3 - butanediol, 1,4 - butanediol, 4,4′ - dihydroxyphenylpropane, 4,4′ - dihydroxyphenylmethane, pentaerythritol propylene oxide, ethylene oxide, butylene oxide, styrene oxide, tetramethylene glycol, polytetramethylene glycol, polyoxypropylene polyol, etc. Preferably, polytetramethylene glycol is mentioned.

[0017] As the polyisocyanate, mainly aliphatic and / or alicyclic polyisocyanates are used. For example, MDI (diphenylmethane diisocyanate), hydrogenated MDI, 1,6 - hexamethylene diisocyanate (HDI), isophorone diisocyanate, xylylene diisocyanate (XDI), hydrogenated XDI, tetramethylxylylene diisocyanate (TMXDI), 1,8 - diisocyanatomethyloctane, lysine ester triisocyanate, 1,3,6 - hexamethylene triisocyanate, 1,6,11 - undecane triisocyanate, bicycloheptane triisocyanate and their modified products (biuret, allophanate, isocyanurate form), derivatives such as trimethylolpropane adducts, etc. Preferably, from the viewpoint of weather resistance, aliphatic polyisocyanates such as isophorone diisocyanate and their derivatives are mentioned.

[0018] The polyol and the polyisocyanate are preferably used within the range of the equivalent ratio (NCO / OH) of the hydroxyl group of the polyol and the isocyanate group of the polyisocyanate being 1.4 to 3.0. If the equivalent ratio is less than 1.4, the molecular weight of the urethane prepolymer increases, and it may become difficult to handle as a paint due to an increase in viscosity. On the other hand, if it exceeds 3.0, the concentration of isocyanate in the composition increases, and problems such as delay in curing and deterioration of weather resistance occur.

[0019] As the urethane prepolymer, when synthesizing the urethane prepolymer from a polyol composed of polycarbonate polyol (PC) and acrylic polyol (AC) and a polyisocyanate, a product in which a hydroxyl group-containing oxazolidine is used in a proportion of 0.5 equivalent or less with respect to the remaining isocyanate groups is also used. Preferably, at this time, the mass ratio PC / AC of these is 60 / 40 to 90 / 10, with the amount of PC exceeding the amount of AC. If these ratios deviate, it may be difficult to achieve both weather resistance and impact resistance. Also, the total amount of PC and AC in the polyol being 80% by mass or more makes it possible to provide a resin excellent in weather resistance and impact resistance.

[0020] As the titanium oxide, any of rutile type, anatase type, and brookite type may be used, but the rutile type is preferred from the viewpoint of weather resistance. Known surface treatment agents such as inorganic substances other than titanium oxide, phosphate esters, or organic substances such as organic acids, for example, silica, alumina, zirconia, silicon oxide, aluminum oxide, zinc oxide, antimony oxide, tin oxide, cerium oxide, iron oxide, sulfur, fluorine, phosphate esters, etc., preferably those surface-treated with silica, alumina, or zirconia are used. Also, any average particle size can be used, but from the viewpoints of the substrate hiding property of the coating film and the coating workability of the paint composition, those with an average particle size of 0.01 to 10 μm, preferably 0.05 to 5 μm, are preferably used in a dried state.

[0021] Titanium oxide is further surface-treated with an acrylate compound having a polar group to finally improve the weather resistance of the resulting paint. The titanium oxide used is surface-treated with an inorganic substance, a phosphate ester, an organic acid, etc. Although its photocatalytic activity is suppressed, the surface treatment is not complete, and there is a possibility of oxidative decomposition of the matrix resin due to a slight untreated portion showing photocatalytic activity. Therefore, by adding a highly polar acrylate compound, the acrylate compound strongly interacts with the untreated portion of the titanium oxide surface, the acrylate localizes in that portion, and the titanium oxide activated by light generates radicals and polymerizes the acrylate. As a result, a polyacrylate lid is formed on the untreated portion of the titanium oxide.

[0022] Examples of the acrylate compound having a polar group include groups that show hydrogen bonding or strong interaction with titanium oxide, specifically, a hydroxyl group, a glycidyl group, a carboxyl group, a urethane bond, an amide group, a urea group, a ketoester group, an epoxy group, an oxetane group, an alkoxysilyl group, etc. Preferably, acrylate compounds having a hydroxyl group are mentioned, such as hydroxyalkyl (meth)acrylate esters like 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, (meth)acrylate monoesters of triols such as glycerin (meth)acrylate monoester and trimethylolpropane (meth)acrylate monoester, resins obtained by reacting (meth)acrylic acid with the glycidyl groups of epoxy resins or acrylic resins, preferably, for example, 2-hydroxyethyl acrylate, glycidyl acrylate, pentaerythritol triacrylate, etc. These can be used alone or in combination of two or more.

[0023] The amount of acrylate is preferably used such that the number of moles of acrylate groups is 0.002 to 0.2 mol, more preferably 0.005 to 0.1 mol, per 100 parts by mass of titanium oxide. If the amount of acrylate is less than this, the required weather resistance cannot be obtained. On the other hand, if it is more than this, desired physical properties such as hardness in the initial physical properties cannot be obtained.

[0024] Titanium oxide can also obtain the desired effect by being added together with an acrylate having a polar group to a urethane prepolymer in the process of preparing the paint. Preferably, a masterbatch composed of an acrylate having a polar group and titanium oxide is added to the urethane prepolymer and used.

[0025] The masterbatch is prepared by mixing titanium oxide with an acrylate compound having a hydroxyl group and a (poly)isocyanate or a reaction product of these with a polycarbonate polyol and / or an acrylic polyol, or an acrylate compound having a polar group other than a hydroxyl group and a (poly)isocyanate, using a bead mill, a dispersing machine, etc. under an appropriate amount of solvent.

[0026] The obtained titanium oxide masterbatch is blended with a urethane prepolymer together with a latent curing agent to constitute a one-component moisture-curable polyurethane composition used for paints and the like.

[0027] Titanium oxide is used in a proportion of 10 to 100 parts by mass, preferably 20 to 80 parts by mass, based on 100 parts by mass of the urethane prepolymer. Also, when the proportion of titanium oxide is less than this, it becomes difficult to ensure hiding power. On the other hand, when the proportion of titanium oxide is more than this, the amount of resin relatively decreases, and the adhesiveness to the substrate, primer, and topcoat deteriorates, and sufficient coating film strength cannot be obtained. In addition, as the pigment, inorganic pigments or organic pigments other than titanium oxide can also be used, for example, in an amount of about 10 to 100 parts by mass based on 100 parts by mass of the urethane prepolymer. Also, precipitated barium sulfate, zinc sulfate, etc. can be used as highly hiding pigments in these urethane resin compositions within a range that does not significantly impair the physical properties of the coating film.

[0028] As latent curing agents, ketimines, enamines, oxazolidines, etc., which are latent curing agents activated by moisture, are known. However, from the viewpoint of storage stability, oxazolidine is preferably used. Oxazolidine is hydrolyzed by moisture in the air to generate a secondary amine and a hydroxyl group, and these react by an isocyanate reaction, and curing proceeds. As catalysts for promoting the hydrolysis of oxazolidine, carboxylic acids, phosphoric acids, etc. are known. However, since they reduce the storage stability of one-component moisture-curable resins, they are not particularly essential components and can be used as appropriate.

[0029] As the oxazolidine, preferably a hydroxyl group-containing oxazolidine is used. A hydroxyl group-containing oxazolidine can also be blended with an oxazolidine compound previously reacted with a polyisocyanate, preferably a compound obtained by reacting a hydroxyl group-containing oxazolidine (OH) with an isocyanate group (NCO) at a ratio of NCO / OH = 1 / 0.1 to 1 / 1. Here, as the polyisocyanate, preferably an aliphatic polyisocyanate is used.

[0030] As the salicylic acid-containing oxazolidine, hydroxyalkyl oxazolidines such as 2-isopropyl-3-(2-hydroxyethyl)oxazolidine, 2-(1-methylbutyl)-3-(2-hydroxyethyl)oxazolidine, N-hydroxyethyl-2-phenyloxazolidine, 2-(p-methoxyphenyl)-3-(2-hydroxyethyl)oxazolidine, etc. are used. Preferably, from the viewpoints of storage stability, curability, and physical properties after curing, 2-isopropyl-3-(2-hydroxyethyl)oxazolidine is used. These hydroxyalkyl oxazolidines are synthesized from the corresponding aldehyde or ketone and hydroxyalkylamine by a known method.

[0031] The equivalent ratio of the isocyanate group (NCO) to the oxazolidine group (OX) in the urethane resin composition is preferably NCO / OX = 1.0 to 3.0. When the NCO / OX equivalent ratio is less than 1.0, the oxazolidine becomes excessive with respect to the isocyanate group, so unreacted amino groups remain during curing, which causes deterioration of weather resistance. On the other hand, when the NCO / OX equivalent ratio exceeds 3.0, the oxazolidine group as the curing agent becomes significantly less than the isocyanate group, so the curability deteriorates.

[0032] As a method of mixing the above essential components into the urethane prepolymer, a dispersion is carried out using various dispersers such as a disper, a planetary mixer, a roll, a bead mill, etc., and a one-component moisture-curable polyurethane composition containing titanium oxide is prepared.

Examples

[0033] Next, the present invention will be described with reference to examples.

[0034] Reference Example 1 250 g of an aromatic solvent (product R100 manufactured by Shin Nippon Chemical Industry Co., Ltd.) placed in a separable flask with a capacity of 500 ml equipped with a stirring blade was added with 10.4 g of a hydroxyl group-containing acrylate (product Light Ester HOA(N) manufactured by Kyoeisha Chemical Co., Ltd.), 12.1 g of isophorone diisocyanate, and 0.02 g of dibutyltin dilaurate. The temperature was gradually raised to 80°C under a nitrogen stream and reacted at 80°C for 2 hours, and then cooled to room temperature.

[0035] Next, 600 g of dried titanium oxide (product R-62N manufactured by Sakai Chemical Industry Co., Ltd., SiO2-Al2O3 surface treatment, primary average particle diameter: 0.26 μm) was added and passed through a bead mill twice to prepare titanium oxide masterbatch 1 (titanium oxide: 68.7 mass%, acrylate group: 0.015 mol / 100 g titanium oxide).

[0036] Reference Example 2 In Reference Example 1, the amount of hydroxyl group-containing acrylate was changed to 52.0 g, the amount of isophorone diisocyanate was changed to 56.5 g, and the amount of titanium oxide was changed to 500 g, respectively, to prepare titanium oxide masterbatch 2 (titanium oxide: 58.2 mass%, acrylate group: 0.090 mol / 100 g titanium oxide).

[0037] Reference Example 3 In Reference Example 1, 7.1 g of 1,3-bis(aminomethyl)cyclohexane was slowly added dropwise to a solution prepared by dissolving 15.5 g of 2-isocyanatoethyl acrylate in 250 g of an aromatic solvent (R100), and the mixture was stirred at room temperature for 1 hour under a nitrogen stream. Then, 600 g of dried titanium oxide (R-62N) was added, and similarly, titanium oxide masterbatch 3 (titanium oxide: 68.8 mass%, acrylate group: 0.018 mol / 100 g titanium oxide) was prepared.

[0038] Reference Example 4 In a separable flask with a capacity of 500 ml having a stirring blade, 600 g of dried titanium oxide (R-62N) was added to a solution prepared by dissolving 12.8 g of glycidyl acrylate and 1.2 g of isophorone diisocyanate in 250 g of an aromatic solvent (R100). After stirring at room temperature for 1 hour under a nitrogen stream, the mixture was passed through a bead mill twice, and titanium oxide masterbatch 4 (titanium oxide: 69.4% by mass, acrylate group: 0.017 mol / 100 g of titanium oxide) was prepared.

[0039] Reference Example 5 In Reference Example 4, 9.9 g of pentaerythritol triacrylate was used instead of glycidyl acrylate, and the amount of isophorone diisocyanate was changed to 4.8 g, and titanium oxide masterbatch 5 (titanium oxide: 69.4% by mass, acrylate: 0.017 mol / 100 g of titanium oxide) was prepared.

[0040] Reference Example 6 In Reference Example 1, an aromatic solvent in which 50.0 g of dried polycarbonate diol (ETERNACOLL PH-200, hydroxyl value 56 mgKOH / g) was dissolved was used, the amount of isophorone diisocyanate was changed to 18.0 g, and the amount of titanium oxide was changed to 800 g, respectively, and titanium oxide masterbatch 6 (titanium oxide: 70.9% by mass, acrylate group: 0.011 mol / 100 g of titanium oxide) was prepared.

[0041] Reference Example 7 In Reference Example 4, 10.0 g of n-butyl acrylate was used instead of glycidyl acrylate, and titanium oxide masterbatch 7 (titanium oxide: 69.7% by mass, acrylate group: 0.013 mol / 100 g of titanium oxide) was prepared.

[0042] Reference Example 8 Into a separable flask with a capacity of 500 ml equipped with a stirring blade, 3.0 g of isophorone diisocyanate and 0.02 g of dibutyltin dilaurate were placed together with 250 g of an aromatic solvent (R100), and after stirring for 10 minutes, 600 g of dried titanium oxide (R-62N) was added and further stirred. Then, after passing through a bead mill twice, a titanium oxide masterbatch 8 (titanium oxide: 70.3% by mass) was prepared.

[0043] Example 1 (1) 66.7 g of propylene glycol monobutyl ether acetate was charged into a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, and the temperature was raised to 92 °C while purging with nitrogen. Next, a mixed solution of 59.0 g of cyclohexyl methacrylate, 14.5 g of n-butyl acrylate, 14.0 g of 2-hydroxyethyl methacrylate, 12.5 g of 2-hydroxyethyl acrylate, and 2.9 g of tert-butyl peroxy-2-ethylhexanoate was fed over 4 hours. One hour and two hours after the feeding was completed, 0.2 g of tert-butyl peroxy-2-ethylhexanoate was added respectively, and the reaction was further carried out for 2 hours to obtain an acrylic polyol A (number average molecular weight Mn 1830, hydroxyl value 120 mgKOH / g, Tg 28 °C, 60% by mass solution of propylene glycol butyl ether acetate).

[0044] (2) 50.0 g (equivalent to 30.0 g) of the obtained acrylic polyol A was dissolved in 79.0 g of an aromatic solvent (R100) together with 70.0 g of dried polycarbonate diol (PH-200) in a separable flask with a capacity of 500 ml equipped with a stirring blade. Then, 36.4 g of isophorone diisocyanate and 0.02 g of dibutyltin dilaurate were added, and after stirring at room temperature for 1 hour, 5.0 g of 2-isopropyl-3-(2-hydroxyethyl)oxazolidine was added. The temperature was gradually raised to 80 °C under a nitrogen stream and reacted at 80 °C for 2 hours to obtain 240.4 g of a urethane prepolymer A (viscosity at 25 °C at 100 rpm of an E-type viscometer: 273 mPa·S, isocyanate group / oxazolidine group (NCO / OX) equivalent ratio = 3.80).

[0045] (3) A mixture consisting of the following components was thoroughly stirred to obtain a one-component moisture-curing urethane resin composition. 240.4 g of urethane prepolymer A 120 g of titanium oxide masterbatch 1 0.2 g of a leveling agent (BYK-UV3576, product of BYK Chemie Japan) 5 g of an ultraviolet absorber (UV1164, product of Ciba Geigy) 5 g of a light stabilizer (HALS292, product of Ciba Geigy) 13.9 g of a curing agent [2-isopropyl-3-(2-hydroxyethyl)oxazolidine Adduct of 2 moles and 1 mole of hexamethylene diisocyanate, [Molecular weight 486.68] 0.03 g of octylic acid Incidentally, the equivalent ratio of isocyanate group / oxazolidine group (NCO / OX) is 1.40.

[0046] Example 2 In Example 1, 155 parts by mass of titanium oxide masterbatch 2 was used instead of titanium oxide masterbatch 1.

[0047] Example 3 In Example 1, the same amount (120 parts by mass) of titanium oxide masterbatch 3 was used instead of titanium oxide masterbatch 1.

[0048] Example 4 In Example 1, 130 parts by mass of titanium oxide masterbatch 4 was used instead of titanium oxide masterbatch 1.

[0049] Example 5 In Example 1, the same amount (120) parts by mass of titanium oxide masterbatch 5 was used instead of titanium oxide masterbatch 1.

[0050] Example 6 In Example 1, instead of Titanium Oxide Masterbatch 1, Titanium Oxide Masterbatch 6 was used in the same amount (120 parts by mass).

[0051] Comparative Example 1 In Example 1, instead of Titanium Oxide Masterbatch 1, Titanium Oxide Masterbatch 7 was used in the same amount (120 parts by mass).

[0052] Comparative Example 2 In Example 1, instead of Titanium Oxide Masterbatch 1, 117.2 parts by mass of Titanium Oxide Masterbatch 8 was used.

[0053] A urethane-based primer was applied onto a ceramic siding board (product of Nichiha) with a thickness of 0.15 mm and dried in an environment of 23 (±2)°C and 50 (±10)% RH for 16 hours to form a primer layer. As the urethane-based primer, a product obtained by reacting 3.0 g of 3-aminopropyltriethoxysilane with a reaction product of 200.0 g of acrylic polyol (Alphon UH2041, product of Toagosei Co., Ltd.), 200.0 g of aromatic solvent (R100), 94.1 g of isophorone diisocyanate, and 0.3 g of dibutyl dilaurate was used. Next, the titanium oxide-containing one-component moisture-curing polyurethane composition obtained in Examples 1 to 6 and Comparative Examples 1 to 2 was applied onto the primer layer with a thickness of 0.3 mm, cured and cured in an environment of 23 (±2)°C and 50 (±10)% RH for 2 weeks to obtain a siding board with a paint cured layer formed.

[0054] Using the obtained siding board, a weather resistance test, a hiding power test, and an adhesion evaluation with the primer were conducted. 〔Weather Resistance Test〕 Testing Machine: Eye Super UV Tester manufactured by Iwasaki Electric Co., Ltd. Test Conditions: Ultraviolet Irradiance: 150 ± 8 mW / cm 2 Temperature: 63°C Wavelength: 295 - 450 nm Cycle: 63°C ± 3°C, 50% RH, 4-hour irradiation ⇒ 4-hour condensation Test result evaluation: ◎ indicates no change in 1200 hours, 〇 indicates no change in 1000 hours, × indicates choking or crack occurs in less than 1000 hours. 〔Concealment test〕 The test was conducted in accordance with 7.8 Concealment rate in 7. Test methods of JIS K5658 (2010). Note that for the test piece, the sample was applied to the siding board using a film applicator with a 150 μm gap, and after curing with the coating surface placed horizontally for 72 hours, the sample was applied again to the same location using the same film applicator, and the one cured with the coating surface placed horizontally for 72 hours was used. 〇 indicates a concealment rate (%) of 90 or more, and × indicates less than 90. 〔Adhesion to primer〕 The test was conducted in accordance with 7.11 Adhesion (cross-cut method) in 7. Test methods of JIS K5658 (2010), and the evaluation was carried out according to the following criteria. 0 indicates that the cut edge is completely smooth and there is no peeling in any grid cell. There is only a small peeling of the coating film at the intersection of the cuts, and the influence at the cross-cut part is clearly not more than 5%. The coating film peels along the cut edge and / or at the intersecting locations, and the influence at the cross-cut part is clearly more than 5% but not more than 15%. This is rated as 2. 〇 indicates 0 - 1, and × indicates 2 or more.

[0055] The obtained results are shown in the following table. Table Examples Comparative Examples Evaluation Items 1 2 3 4 5 6 12 Weather resistance ◎ ◎ ◎ ◎ ◎ ○ × × Concealability ○ ○ ○ ○ ○ ○ ○ ○ Adhesion ○ ○ ○ ○ ○ ○ ○ ○

Claims

1. A one - component moisture - curable polyurethane composition containing titanium oxide, which is obtained by blending a urethane prepolymer synthesized from at least one polyol selected from polycarbonate polyol and acrylic polyol and a polyisocyanate with an acrylate compound having a polar group, titanium oxide, and a latent curing agent.

2. The one - component moisture - curable polyurethane composition containing titanium oxide according to Claim 1, wherein the polar group of the acrylate compound is a hydroxyl group, glycidyl group, carboxyl group, urethane bond, amide group, urea group, keto - ester group, epoxy group, oxetane group, or alkoxysilyl group.

3. The one - component moisture - curable polyurethane composition containing titanium oxide according to Claim 1, wherein the acrylate compound is 2 - hydroxyethyl acrylate, glycidyl acrylate, or pentaerythritol triacrylate.

4. The one - component moisture - curable polyurethane composition containing titanium oxide according to Claim 1, wherein the titanium oxide is titanium oxide surface - treated with an inorganic substance or an organic substance other than titanium oxide.

5. The one - component moisture - curable polyurethane composition containing titanium oxide according to Claim 1, wherein the titanium oxide is 10 - 100 parts by mass with respect to 100 parts by mass of the urethane prepolymer, and the acrylate group in the acrylate compound is 0.002 - 0.2 mol with respect to 100 parts by mass of the titanium oxide.

6. The one - component moisture - curable polyurethane composition containing titanium oxide according to Claim 1, wherein the titanium oxide is mixed with an acrylate compound having a hydroxyl group and (poly) isocyanate or a reaction product of these with polycarbonate polyol and / or acrylic polyol, or an acrylate compound having a polar group other than a hydroxyl group and (poly) isocyanate, and is used as a masterbatch.

7. The one - component moisture - curable polyurethane composition containing titanium oxide according to Claim 1, wherein the latent curing agent is a hydroxyl - containing oxazolidine.

8. The one - component moisture - curable polyurethane composition containing titanium oxide according to Claim 1, which is used as a paint.

9. A titanium oxide masterbatch in which titanium oxide is mixed with an acrylate compound having a hydroxyl group and (poly) isocyanate or a reaction product of these with polycarbonate polyol and / or acrylic polyol, or an acrylate compound having a polar group other than a hydroxyl group and (poly) isocyanate.