JP2009227927A - Polyisocyanate and two-pack type coating agent - Google Patents

Abstract

Disclosed is a polyisocyanate and a two-component coating agent that can form a coating film that is sufficiently excellent in stain resistance.
[Solution]
A polyisocyanate that can be obtained by reaction of a fluorine-containing monoalcohol with an aliphatic diisocyanate, and includes an allophanate-modified product and an isocyanurate-modified product. Polyisocyanate which is contained and the content of the diallophanate body is 21 to 80 parts by weight and the content of the trialophanate body is 5 to 60 parts by weight with respect to 100 parts by weight of the monoallophanate body.
[Selection figure] None

Description

  The present invention relates to a polyisocyanate and a two-component coating agent.

  Urethane-based paints using polyisocyanates derived from aliphatic or alicyclic diisocyanates are excellent in weather resistance and abrasion resistance, coating outdoor base materials such as buildings and civil engineering structures, repairing automobiles, Used for plastic coating.

However, in recent years, the required characteristics in these coating fields have become more severe, and further improvement in contamination resistance is required. For example, in patent document 1, formation of the coating film with low surface energy using the coating composition containing fluorine-containing polyisocyanate is examined.
JP-A-10-176026

  However, the stain resistance of the coating film formed from the coating composition disclosed in Patent Document 1 has not yet reached a level that can satisfy the requirements.

  Therefore, an object of the present invention is to provide a polyisocyanate and a two-pack type coating agent that can form a coating film that is sufficiently excellent in stain resistance.

  In order to achieve the above object, the present invention is a polyisocyanate which can be obtained by a reaction of a fluorine-containing monoalcohol and an aliphatic diisocyanate, and includes an allophanate-modified product and an isocyanurate-modified product, wherein the allophanate-modified product is It contains a mono allophanate body, a di allophanate body and a triarophanate body, the content of the di allophanate body with respect to 100 parts by weight of the mono allophanate body is 21 to 80 parts by weight and the content of the trilophanate body is 5 to 60 parts by weight. A polyisocyanate is provided.

Here, the allophanate modified body is a compound represented by the following general formula (1).

In the formula, R ¹ represents a group obtained by removing an isocyanate group from an aliphatic diisocyanate, and R ² represents a group obtained by removing a hydroxyl group from a fluorinated monoalcohol. Further, n represents the number of repeating units of the allophanate group, is an integer of 1 or more, and usually has a number of repeating units of about 1 to 3. Thus, the allophanate modified body contains the allophanate body more than a di allophanate body other than a mono allophanate body.

  In general, the allophanate-modified product has a relatively low viscosity and excellent handleability, but has a tendency to be inferior in stain resistance as compared with the isocyanurate-modified product. As a result of intensive studies on the polyisocyanate obtainable by the reaction of a fluorinated monoalcohol with an aliphatic diisocyanate, the present inventors have conducted monoallophanate, diallophanate, and trialophanate in an allophanate-modified product. It was found that the contamination resistance is improved by setting the ratio of the above to a predetermined range, and the present invention has been completed.

  By providing the above configuration, the polyisocyanate of the present invention can form a coating film with sufficiently improved contamination resistance.

  Moreover, it is preferable that the polyisocyanate of this invention contains 7-20 mol% of isocyanurate modified bodies on the basis of whole quantity. Thereby, not only can a coating film more excellent in stain resistance be formed, but weather resistance is also improved.

  Further, the polyisocyanate preferably has a viscosity at 25 ° C. of 160 to 2000 mPa · s. By setting it as such a viscosity range, it is excellent in the handleability at the time of adjusting the two-pack type coating agent containing the polyisocyanate of this invention, and can make a non volatile matter content high.

  The present invention also provides a two-component coating agent containing the polyisocyanate. Since such a coating agent contains the polyisocyanate of this invention, it can form the coating film which is excellent in stain resistance sufficiently.

  According to the present invention, it is possible to provide a polyisocyanate and a two-component coating agent that can form a coating film that is sufficiently excellent in stain resistance.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

(Polyisocyanate)
The polyisocyanate of the present invention can be obtained by a reaction between a fluorine-containing monoalcohol and an aliphatic diisocyanate, and includes an allophanate-modified product and an isocyanurate-modified product. The allophanate-modified product includes a mono-allophanate product and a diallophanate product. Body and trialophanate body.

  The polyisocyanate can be synthesized by the reaction of an aliphatic diisocyanate and a fluorinated monoalcohol in the presence of an allophanatization catalyst. As a synthesis method, for example, a method described in Japanese Patent No. 3511622 can be used.

  Examples of the aliphatic diisocyanate include tetramethylene diisocyanate, hexamethylene diisocyanate, decamethylene diisocyanate, and lysine diisocyanate. These can be used individually by 1 type or in mixture of 2 or more types.

  The fluorine-containing monoalcohol is a compound having a fluorine atom and a hydroxyl group in the molecule. Specific examples of the fluorinated monoalcohol include 2,2-difluoroethanol, 2,2,3,3-tetrafluoropropanol, 2,2,3,3,4,4-hexafluorobutanol, 2,2, 3,3,4,4,5,5-octafluoropentanol, 2,2,3,3,4,4,5,5,6,6-decafluorohexanol, 2,2,3,3,4 , 4,5,5,6,6,7,7,8,8-tetradecafluorooctanol, 2,2,3,3,4,5,5,6,6,7,7,8, 8,9,9,10,10-octadecafluorodecanol, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10, 10,11,11,12,12-docosadecafluorododecanol, 3,3-difluoropropanol, 3,3,4,4- Trifluorobutanol, 3,3,4,4,5,5,6,6-octafluorohexanol, 3,3,4,4,5,5,6,6,7,7,8,8,9, 9,10,10,11,11,12,12-icosafluorododecanol, 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10, 10,11,11,12,12,13,13,14,14-tetracosafluorotetradecanol, 2,2,2-trifluoroethanol, 2,2,3,3,3-pentafluoropropanol, 1H , 1H-perfluoro-1-butanol, 1H, 1H-perfluoro-1-hexanol, 1H, 1H-perfluoro-1-octanol, 1H, 1H-perfluoro-1-decanol, 1H, 1H-perfluoro- 1-dodecanol, 3, 3, -Trifluoropropanol, 3,3,4,4,4-pentafluorobutanol, 2- (perfluoro-n-butyl) ethanol, 2- (perfluoro-n-hexyl) ethanol, 2- (perfluoro-n -Octyl) ethanol, 2- (perfluoro-n-decyl) ethanol, 2- (perfluoro-n-dodecyl) ethanol, 1H, 1H-perfluoro-1-isopropanol, 1H, 1H-perfluoro-1-iso Butanol, 1H, 1H-perfluoro-1-isohexanol, 1H, 1H-perfluoro-1-isooctanol, 1H, 1H-perfluoro-1-isodecanol, 1H, 1H-perfluoro-1-isododecanol, 2- (perfluoroisopropyl) ethanol, 2- (perfluoro-2-methylpropyl) ) Ethanol, 2- (perfluoro-3-methylbutyl) ethanol, 2- (perfluoro-5-methylhexyl) ethanol, 2- (perfluoro-7-methyloctyl) ethanol, 2- (perfluoro-9-methyldecyl) ) Ethanol and 2- (perfluoro-11-methyldodecyl) ethanol. In the present invention, 2,2,2-trifluoroethanol is preferably used from the viewpoints of reactivity with aliphatic diisocyanate and compatibility. These can be used individually by 1 type or in mixture of 2 or more types.

  The amount of the fluorinated monoalcohol is preferably 4 to 24 parts by mass, more preferably 5 to 22 parts by mass, and 8 to 20 parts by mass with respect to 100 parts by mass of the aliphatic diisocyanate. More preferably. When the amount of the fluorinated monoalcohol is less than 4 parts by mass, the stain resistance tends to be reduced, and when it exceeds 24 parts by mass, the viscosity of the polyisocyanate tends to be high and handling becomes difficult.

  As the allophanatization catalyst, for example, a zirconium salt of carboxylic acid can be used. Examples of the carboxylic acid include acetic acid, propionic acid, butyric acid, caproic acid, octylic acid, lauric acid, myristic acid, palmitic acid, stearic acid, 2-ethylhexanoic acid and other saturated aliphatic carboxylic acids, cyclohexanecarboxylic acid, Saturated monocyclic carboxylic acids such as cyclopentanecarboxylic acid, saturated polycyclic carboxylic acids such as bicyclo (4.4.0) decane-2-carboxylic acid, mixtures of the above-mentioned carboxylic acids such as naphthenic acid, oleic acid, linoleic acid , Monocarboxylic acids such as linolenic acid, soybean fatty acid, unsaturated fatty carboxylic acid such as tall oil fatty acid, aromatic aliphatic carboxylic acid such as diphenylacetic acid, aromatic carboxylic acid such as benzoic acid, toluic acid, phthalic acid, Isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, succinic acid, tartaric acid, oxalic acid, malonic acid, gluta Acid, adipic acid, pimelic acid, suberic acid, kurtaconic acid, azelaic acid, sebacic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, 1,4-cyclohexyldicarboxylic acid, α-hydromuconic acid, β-hydromcon And polycarboxylic acids such as acid, α-butyl-α-ethylglutaric acid, α, β-diethylsuccinic acid, maleic acid, fumaric acid, trimellitic acid and pyromellitic acid. These zirconium carboxylates can be used alone or in combination of two or more, and it is more preferable to use a monocarboxylic acid zirconium salt having 10 or less carbon atoms.

  The amount of the allophanatization catalyst used varies depending on the type, but is preferably 0.005 to 10 parts by mass, and 0.01 to 1 part by mass with respect to 100 parts by mass of the total amount of fluorine-containing monoalcohol and aliphatic diisocyanate. More preferably, it is a part. If the amount of catalyst is less than 0.005 parts by mass, the reaction tends to take a long time. On the other hand, when the amount of the catalyst used exceeds 10 parts by mass, the reaction tends to be difficult to control.

  The polyisocyanate of the present invention can be synthesized, for example, as follows. First, a fluorine-containing monoalcohol and an aliphatic diisocyanate are mixed and subjected to a urethanization reaction at 20 to 100 ° C., and then an allophanatization reaction is performed at 70 to 150 ° C. in the presence of an allophanate catalyst. The allophanatization reaction time varies depending on the type of catalyst, the amount added, and the reaction temperature, but is usually within 10 hours, preferably 1 to 5 hours. Next, after confirming that the predetermined isocyanate (NCO) content (mass%) has been reached, a reaction terminator is added to stop the allophanatization reaction and to remove free aliphatic diisocyanate.

  As the reaction terminator, for example, inorganic acids such as phosphoric acid and hydrochloric acid, organic acids having a sulfonic acid group, a sulfamic acid group and the like, esters thereof, and acyl halides can be used. The addition amount of the reaction terminator varies depending on the type and the type of the catalyst, but is preferably 0.5 to 2 equivalents, more preferably 0.8 to 1.5 equivalents relative to the allophanatization catalyst. . If the reaction terminator is less than 0.5 equivalent, the storage stability of the resulting polyisocyanate tends to decrease, and if it exceeds 2 equivalents, the resulting polyisocyanate may be colored.

  In addition, an organic solvent can be used for the said reaction as needed. Examples of the organic solvent include n-hexane, octane, cyclohexane, methylcyclohexane, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether. Acetate, 3-methyl-3-methoxybutyl acetate, ethyl-3-ethoxypropionate, diethyl ether, tetrahydrofuran, dioxane, methyl chloride, methylene chloride, chloroform, carbon tetrachloride, methyl bromide, methylene iodide, dichloroethane, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, hexamethylphosphonilamide may be mentioned. An organic solvent can be used individually by 1 type or in mixture of 2 or more types.

  Free aliphatic diisocyanate exists in the polyisocyanate composition after the allophanatization reaction. Since this free aliphatic diisocyanate causes odor and turbidity when it changes over time, it is preferable to remove unreacted aliphatic diisocyanate until it becomes 1% by mass or less. In addition, free aliphatic diisocyanate content can be confirmed by measuring gas chromatography.

  Examples of the method for removing free aliphatic diisocyanate include known methods such as distillation, reprecipitation, and extraction. Distillation methods, particularly thin film distillation methods, are preferable because they do not require the use of a solvent. Moreover, as conditions of thin film distillation, it is preferable that it is a pressure of 0.1 kPa or less and the temperature of 100-170 degreeC, and it is more preferable that it is 0.05 kPa or less and 120-160 degreeC.

  Thus, the polyisocyanate obtained contains 21 to 80 parts by mass of diallophanate and 5 to 60 parts by mass of trialophanate with respect to 100 parts by mass of the monoallophanate. The content of the diallophanate body is preferably 25 to 75 parts by mass and more preferably 35 to 75 parts by mass with respect to 100 parts by mass of the monoallophanate body. When the content of the diallophanate is less than 21 parts by mass, the stain resistance tends to decrease, and when it exceeds 80 parts by mass, the viscosity of the polyisocyanate tends to increase and it becomes difficult to handle.

  Moreover, it is preferable that it is 7-50 mass parts with respect to 100 mass parts of mono allophanate bodies, and, as for content of a trialophanate body, it is more preferable that it is 10-50 mass parts. When the content of the trialophanate body is less than 5 parts by mass, the stain resistance tends to decrease, and when it exceeds 60 parts by mass, the viscosity of the polyisocyanate tends to be high and handling tends to be difficult.

  The content ratio of the mono allophanate body, the di allophanate body, and the triarophanate body in the allophanate modified body can be calculated from the peak area of the spectrum in gel permeation chromatography (GPC) measurement. The said content rate can be set to the target range by adjusting suitably the compounding ratio of fluorine-containing monoalcohol and aliphatic diisocyanate, and synthesis conditions (temperature, time, etc.).

In addition, although polyisocyanate mainly contains the allophanate modified body which has an allophanate group, it can contain the isosinurate modified body which has an isocinurate group by preparing reaction conditions. The molar ratio of allophanate groups and isocyanurate groups in the polyisocyanate of the present invention can be adjusted in the range of 99: 1 to 70:30. The content of the isocyanurate-modified product is preferably 6 to 25 mol%, more preferably 7 to 22 mol%, based on the total amount of polyisocyanate. If the isocyanurate-modified product is less than 6 mol%, the weather resistance tends to decrease, and if it exceeds 25 mol%, the viscosity of the polyisocyanate tends to increase, making it difficult to handle. The molar ratio can be calculated by measuring ¹ H-NMR of polyisocyanate.

  The viscosity of the polyisocyanate is preferably 160 to 2000 mPa · s at 25 ° C., more preferably 190 to 2000 mPa · s or less, and further preferably 230 to 1700 mPa · s or less. When the viscosity of the polyisocyanate exceeds 2000 mPa · s, the viscosity when the two-pack type coating agent is adjusted tends to be high, and the handling tends to be difficult. On the other hand, when the viscosity is less than 160 mPa · s, the monoallophanate component tends to increase, and thus the stain resistance tends to decrease. In addition, since the isocyanurate component tends to decrease, the physical properties of the coating film tend to decrease.

(Two-component coating agent)
The two-component coating agent of the present invention is composed of a curing agent containing the polyisocyanate and a main agent containing an active hydrogen-containing resin.

  The active hydrogen-containing resin is not particularly limited as long as it is a resin having active hydrogen, and examples thereof include acrylic resins, fluororesins, acrylic silicone resins, polyester resins, alkyd resins, silicone resins, and polyester-modified acrylic resins. Among these, from the viewpoint of further improving the stain resistance, acrylic resins and fluororesins are preferable as the active hydrogen-containing resin. Examples of the group containing active hydrogen include a hydroxyl group, a thiol group, an amino group, and a carboxyl group, and a hydroxyl group is preferable. The active hydrogen-containing resin is preferably a polyol.

  In the two-component coating agent of the present invention, the polyisocyanate content is preferably 1 to 150 parts by mass, more preferably 1 to 130 parts by mass, with respect to 100 parts by mass of the active hydrogen-containing resin. 1 to 100 parts by mass is more preferable.

  The two-component coating agent can contain an organic solvent, if necessary. Examples of the organic solvent include methylcyclohexane, ethylcyclohexane, mineral spirit, turpentine oil, High Aromatic White Spirit (hereinafter referred to as “HAWS”) (manufactured by Shell Chemicals Japan, trade name), Low Aromatic White Spirit (hereinafter, “ LAWS ”) (manufactured by Shell Chemicals Japan, trade name), Essonaphtha No. 6 (ExxonMobil, product name), Pegasol 3040 (ExxonMobil, product name), A Solvent (New Japan Oil, product name), Clensol (New Japan Oil, product name), Mineral Spirit A (made by Nippon Oil Corporation, trade name), Hyalom 2S (made by Nippon Oil Corporation, trade name), Solvesso 100 (made by ExxonMobil, trade name), Solvesso 150 (made by ExxonMobil, trade name), Swazol 100 (manufactured by Maruzen Petrochemical Co., Ltd., trade name), SWAZOL 200 (manufactured by Maruzen Petrochemical Co., Ltd., trade name), SWAZOL 1000 (manufactured by Maruzen Petrochemical Co., Ltd., trade name), SWAZOL 1500 (manufactured by Maruzen Petrochemical Co., Ltd., trade name) , Swazol 1800 (trade name, manufactured by Maruzen Petrochemical Co., Ltd.), Idemitsu Ipsol 100 (product name, manufactured by Idemitsu Kosan Co., Ltd.), Idemitsu Ipsol 150 (Idemitsu Kou Pegasol ARO-80 (ExxonMobil, trade name), Pegasol R-100 (ExxonMobil, trade name), Akishiro Toshiki Hyzol (Shell Chemicals Japan, trade name), Japan Stone Hysol (trade name) manufactured by Nippon Oil Corporation. These organic solvents can be used individually by 1 type or in mixture of 2 or more types.

  The two-component coating agent may contain various additives that can be used for general paints. Examples of additives include plasticizers, antiseptics, antifungal agents, algaeproofing agents, antifoaming agents, leveling agents, pigment dispersants, anti-settling agents, anti-sagging agents, catalysts, curing accelerators, dehydrating agents, and gloss. Examples include quenchers, ultraviolet absorbers, antioxidants, pigments, and surfactants.

  Moreover, as a coating method of the two-pack type coating agent of this invention, methods, such as brush coating, roller coating, and spray coating, can be used, for example. Moreover, when coating a dry-type building material, it is also possible to pre-coat in a factory etc. with a flow coater or a roll coater.

  Examples of the substrate to be applied include concrete, mortar, siding board, extruded plate, porcelain tile, metal, glass, wood, and plastic.

  The above-mentioned two-component coating agent may be applied directly to the base material. When the base material is a metal, iron phosphate treatment or phosphorous may be applied to the base material, electrodeposition or undercoating (primer application), intermediate coating (coloring, etc.). You may apply | coat on the base material with which surface treatments, such as a zinc acid treatment, were given.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not restrict | limited to this.

  Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited thereto.

[Synthesis of polyisocyanate]
(Synthesis Example 1)
To a 1 L four-necked flask equipped with a stirrer, a thermometer, a condenser and a nitrogen gas inlet tube, 950 g of hexamethylene diisocyanate (trade name “HDI”, manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanate content: 49.9%) and 2, After adding 50 g of 2,2-trifluoroethanol and heating to 60 ° C. with stirring, 0.2 g of zirconyl octylate (Daiichi Rare Element Chemical Co., Ltd.) as an allophanatization catalyst was added to this solution, and 110 ° C. After confirming that the desired isocyanate (NCO) content (%) was reached, 0.3 g of phosphate ester “JP-508” (trade name, manufactured by Johoku Chemical Co., Ltd.) as a reaction terminator was added. The reaction was stopped by stirring at 50 ° C. for 1 hour. After completion of the reaction, the obtained reaction solution was subjected to thin-film distillation at 140 ° C. and 0.04 kPa, an NCO content of 18.4%, a viscosity at 25 ° C. of 190 mPa · s, unreacted free hexamethylene diisocyanate (hereinafter “ A polyisocyanate having a content of 0.1% (denoted as “F-HDI”) was obtained. This was designated as “S-1.”

(Synthesis Examples 2 to 12)
Except that the blending ratio of HDI and 2,2,2-trifluoroethanol was changed as shown in Table 2, the same operations as in Synthesis Example 1 were performed, and the polyisocyanates “S-2” to “S-12” Were synthesized respectively.

(Synthesis Examples 13 and 14)
Polyisocyanates of “S-13” and “S-14” were prepared in the same manner as in Synthesis Example 1 except that ethanol was used in the mixing ratio shown in Table 2 instead of 2,2,2-trifluoroethanol. Were synthesized respectively.

<Viscosity measurement>
Each of the polyisocyanates obtained in Synthesis Examples 1 to 14 was placed in a 200 mL bottle, adjusted to a liquid temperature of 25 ° C., and then the viscosity was measured with a B-type viscometer.

<GPC measurement>
The polyisocyanate GPC obtained in Synthesis Examples 1 to 14 was measured under the following conditions using a trade name “HLC-8220” manufactured by Tosoh Corporation. Subsequently, the content ratio of the mono allophanate body, the diallophanate body, and the triarophanate body was computed from the GPC measurement result.
(Measurement condition)
Detector: Refractive index (RI) detector Column: TSKgel G3000H _XL , G2500H _XL , G1000 _XL
Eluent: Tetrahydrofuran (THF)
Measurement temperature: 40 ° C
Flow rate: 1.0 mL / min Calibration curve: Tosoh standard polystyrene shown in Table 1 is used. Solution concentration: Sample 0.05 g / THF 10 g

<NMR measurement>
¹ H-NMR of the polyisocyanate obtained in Synthesis Examples 1 to 14 was measured under the following conditions using a product name “ECX400M” manufactured by JEOL Ltd. The molar ratio of the allophanate modified product to the isocyanurate modified product in the polyisocyanate is the hydrogen signal adjacent to the nitrogen atom of the allophanate group near 8.55 ppm and the methylene group adjacent to the nitrogen atom of the isocyanurate group near 3.85 ppm. It calculated from the area ratio with the signal of the hydrogen couple | bonded with. The results are shown in Table 2.
(Measurement condition)
Measuring solvent: deuterated chloroform,
Sample concentration: 0.2 g / 1 mL
Magnetic field: 400MHz (9.389T)
Measurement temperature: 25 ° C
Integration count: 16 times Relaxation time: 5 seconds Chemical shift criteria: Hydrogen signal of deuterium chloroform is 7.24 ppm.

[Adjustment of two-component coating agent]
(Examples 1-9)
Acrylic polyol “Acridic HU-596” (trade name, hydroxyl value: 30 mgKOH / g, nonvolatile content: 50% by mass, manufactured by Dainippon Ink & Chemicals, Inc.), which is the main ingredient, with the composition (parts by mass) shown in Table 3. Synthesis Examples 1-9 as a curing agent in a solution in which titanium oxide “CR-90” (trade name, manufactured by Ishihara Sangyo Co., Ltd.), which is a white pigment, and an organic solvent “Solvesso 100” (trade name, manufactured by Exxon Chemical) were mixed. The polyisocyanate obtained in (1) was mixed at a ratio (unit: part by mass) shown in Table 3 to prepare a two-component coating agent.

(Comparative Examples 1-5)
In the composition (parts by mass) shown in Table 4, the polyisocyanate obtained in Synthesis Examples 10 to 14 as a curing agent was added to a solution obtained by mixing “Acridic HU-596”, “CR-90”, and “Solvesso 100”. A two-component coating agent was prepared by mixing at a ratio (unit: part by mass) shown in Table 4. In Comparative Example 3 in which the polyisocyanate obtained in Synthesis Example 12 was used, evaluation could not be performed because the viscosity of the adjusted two-component coating agent was too high.

<Formation of coating film>
The obtained two-pack type coating agent was degreased with methyl ethyl ketone, and a 0.8 mm thick steel plate (JIS G3141, manufactured by Nippon Test Panel Industry Co., Ltd., trade names “SPCC-SB”, PF-1077 treatment) was used with an applicator of 100 μm. It applied by thickness. After coating, the film was cured in an environment of 20 ° C. and 65% RH for 7 days to form a coating film having a dry film thickness of 40 to 50 μm.

<Various evaluations>
The coating film produced as described above was evaluated by the following method. The evaluation results of Examples 1 to 9 are shown in Table 3, and the evaluation results of Comparative Examples 10 to 14 are shown in Table 4, respectively.

(Flexibility)
Use a cylindrical mandrel with a diameter of 2 mm to check for cracks in the coating and / or peeling from the steel sheet when bent by a cylindrical mandrel, and comply with the flex resistance test of JIS K-5600-5-1. And evaluated. Those in which no cracking or peeling of the coating film occurred were regarded as acceptable.

(Copping resistance)
The presence or absence of cracking of the coating film and / or peeling from the steel sheet when subjected to partial deformation by indentation was evaluated using an indenter in accordance with the cupping resistance test of JIS K-5600-5-2. The indentation depth (mm) at which the coating film was cracked or peeled off by the indenter was defined as cupping resistance. The cupping resistance is a value indicating the substrate followability and flexibility of the coating film, and it can be said that the greater the numerical value of the indentation depth, the higher the followability and flexibility.

(Weight resistance)
Use a weight of 10.3 mm in diameter and a weight of 1.0 kg to determine whether the coating film cracks and / or peels from the steel sheet when it is deformed due to weight drop, and is resistant to JIS K-5600-5-3. Evaluation was made in accordance with a weight drop test. The lowest drop height at which cracking and peeling of the coating film occurred was defined as the weight drop resistance.

(Adhesion)
The adhesion of the coating film is determined according to JIS K-5600-5-6, which evaluates the resistance of the coating film against peeling from the substrate when a right-angle lattice pattern is cut into the coating film and penetrates to the substrate. Evaluation was performed according to a test (cross-cut method). The results are shown in Tables 2 and 3. “0” in the table means that the edge of the cut is completely smooth and there is no peeling in the eyes of any grid.

(Measurement of coating film hardness)
The hardness of the coating film surface was measured in accordance with the scratch hardness test (pencil method) of JIS K-5600-5-4. The hardness of the hardest pencil with no scratch marks on the coating film surface was defined as the coating film hardness. did.

(Contamination resistance)
The stain resistance of the coating film is determined by observing the coating film surface visually after dripping aqueous black ink onto the coating film surface, leaving it to stand at a temperature of 20 ° C. and a humidity of 65% RH for 1 day, and washing with water. evaluated. The notation regarding contamination resistance in the table is as follows.
◎: There is almost no dirt ○: Slight dirt remains △: The dirt is slightly noticeable ×: The dirt is quite noticeable

  From the results of Tables 3 and 4, the coating films produced in Examples 1 to 9 have good flex resistance, cupping resistance, weight drop resistance and adhesion, and have sufficiently high mechanical strength. In addition, it can be seen that the coating film prepared in Comparative Examples 1 to 5 is sufficiently excellent in stain resistance. From this, it was confirmed that the coating film formed using the two-component coating agent containing the polyisocyanate of the present invention has sufficiently high contamination resistance.

Claims (4)

A polyisocyanate comprising an allophanate-modified product and an isocyanurate-modified product, which can be obtained by a reaction between a fluorine-containing monoalcohol and an aliphatic diisocyanate,
The allophanate modified body contains a mono allophanate body, a diallophanate body and a trialophanate body,
The polyisocyanate whose content of the said di allophanate body with respect to 100 mass parts of said mono allophanate bodies is 21-60 mass parts and whose content of the said trialophanate body is 5-60 mass parts.   The polyisocyanate according to claim 1, comprising 6 to 25 mol% of the isocyanurate-modified product based on the total amount.   The polyisocyanate of Claim 1 or 2 whose viscosity in 25 degreeC is 160-2000 mPa * s.   The two-component coating agent containing the polyisocyanate as described in any one of Claims 1-3.