JP2026014085A - Polyisocyanate composition, coating composition and coating film - Google Patents

Abstract

The present invention provides a polyisocyanate composition, a coating composition, and a coating film.
[Solution] The polyisocyanate composition contains a polyisocyanate derived from a diisocyanate (A), a monoalcohol (B), a polyether polyol (C), and a polyether polyol (D) and containing an allophanate group, wherein (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, (B) is a monoalcohol having 3 to 20 carbon atoms, (C) is a polyether polyol having a number average molecular weight of 400 or more and 2000 or less and having an oxypropylene group, (D) is a polyether polyol having a number average molecular weight of 2500 or more and 6000 or less and having an oxyethylene group and an oxypropylene group, and the mass % ratio of (C) to (D) is 50:50 or more and 90:10 or less.
[Selection diagram] None

Description

The present invention relates to a polyisocyanate composition, a coating composition, and a coating film.

Aliphatic polyaspartic coating compositions, which are a type of polyurea coating composition, are formed from aspartic acid ester compounds containing amino groups and aliphatic and/or alicyclic polyisocyanate compositions containing isocyanate groups. The drawback of aromatic polyurea coating compositions, yellowing of the coating film due to exposure to ultraviolet light, is significantly reduced, and polyaspartic coating compositions have traditionally been used in a wide range of applications, including various paints, flooring materials, and waterproofing materials.

Aspartic acid ester compounds have a lower viscosity than the base polyol of polyurethane coating compositions, allowing for a significant reduction in the amount of diluent solvent in polyaspartic coating compositions, making it possible to create high-solids or solvent-free formulations. Furthermore, due to the fast reactivity between the amino groups of aspartic acid ester compounds and the isocyanate groups of aliphatic and/or alicyclic polyisocyanates, polyaspartic coating compositions have the advantages of a faster curing rate even at room temperature and superior mechanical strength compared to polyurethane coating compositions.

For example, the polyaspartic paint composition disclosed in Patent Document 1 contains a polyaspartic acid ester compound and a polyisocyanate composition in which the contents (mol %) of isocyanurate groups, iminooxadiazinedione groups, uretdione groups, allophanate groups, and biuret groups are in a specified relationship. In this polyaspartic paint composition, the polyisocyanate composition has a low viscosity suitable for high-solids and solvent-free formulations, and while maintaining curability and drying properties, the coating film produced using this polyaspartic paint composition is characterized by excellent chemical resistance, hardness, and weather resistance.

Furthermore, the polyaspartic paint composition disclosed in Patent Document 2 has optimized viscosity, exhibits good viscosity and pot life under solvent-free conditions, and is characterized by excellent appearance, chemical resistance, impact resistance, and scratch resistance when formed into a coating film.

International Publication No. 2018/163953 Japanese Patent Application Laid-Open No. 2022-66853

However, the polyaspartic coating compositions disclosed in Patent Documents 1 and 2 make no mention of the elongation, stress, or alkali resistance of the coating film.

The present invention was made in consideration of the above circumstances, and aims to provide a polyisocyanate composition that can produce a coating film that has excellent weather resistance, alkali resistance, and excellent coating elongation and stress, as well as a paint composition and coating film that use the polyisocyanate composition.

That is, the present invention includes the following aspects.
[1] A polyisocyanate composition comprising a polyisocyanate derived from a diisocyanate (A), a monoalcohol (B), a polyether polyol (C), and a polyether polyol (D) and containing an allophanate group, wherein the diisocyanate (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, the monoalcohol (B) is a monoalcohol having 3 to 20 carbon atoms, the polyether polyol (C) is a polyether polyol having a number average molecular weight of 400 to 2000 and containing an oxypropylene group, the polyether polyol (D) is a polyether polyol having a number average molecular weight of 2500 to 6000 and containing an oxyethylene group and an oxypropylene group, and the mass % ratio of the polyether polyol (C) to the polyether polyol (D) is 50:50 to 90:10.
[2] The polyisocyanate composition according to [1], wherein the polyisocyanate is a polyisocyanate derived from a polyisocyanate precursor, the polyether polyol (C), and the polyether polyol (D), the polyisocyanate precursor is a dimer or higher of a diisocyanate derived from the diisocyanate (A) and the monoalcohol (B), the polyisocyanate precursor has an isocyanurate group and an allophanate group, and the molar ratio of the isocyanurate group to the allophanate group (isocyanurate group:allophanate group) is 1:99 or more and 60:40 or less.
[3] The polyisocyanate composition according to [2], wherein the ratio of the number of moles of isocyanate groups in the polyisocyanate precursor to the total number of moles of hydroxyl groups in the polyether polyol (C) and the polyether polyol (D) is 3:1 or more and 9:1 or less.
[4] The polyisocyanate composition according to any one of [1] to [3], wherein the total content of the polyether polyol (C) and the polyether polyol (D) relative to the total amount of the polyisocyanate composition is 10 to 40 mass%.
[5] The polyisocyanate composition according to any one of [1] to [4], wherein the average number of isocyanate groups in the polyisocyanate composition is 2.3 or more and 3.0 or less.
[6] The polyisocyanate composition according to any one of [1] to [5], having a viscosity at 25°C of 2000 mPa·s or more and 8000 mPa·s or less.
[7] A coating composition comprising a polyaspartic base and the polyisocyanate composition according to any one of [1] to [6].
[8] A coating film obtained by curing the coating composition according to [7].

The present invention provides a polyisocyanate composition that can produce a coating film that has excellent weather resistance, alkali resistance, and excellent coating film elongation and stress, as well as a coating composition and coating film that use the polyisocyanate composition.

<Polyisocyanate Composition>
The polyisocyanate composition of the present embodiment can be suitably used as a curing agent for a coating composition.
The polyisocyanate composition comprises a polyisocyanate derived from a diisocyanate (A), a monoalcohol (B), a polyether polyol (C), and a polyether polyol (D) and containing allophanate groups.
The diisocyanate (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.
The monoalcohol (B) is a monoalcohol having 3 to 20 carbon atoms.
The polyether polyol (C) is a polyether polyol having a number average molecular weight of 400 or more and 2000 or less and having an oxypropylene group.
The polyether polyol (D) is a polyether polyol having a number average molecular weight of 2,500 or more and 6,000 or less and containing an oxyethylene group and an oxypropylene group.
The mass % ratio of the polyether polyol (C) to the polyether polyol (D) is 50:50 or more and 90:10 or less.

The polyisocyanate composition of the present embodiment preferably has a viscosity at 25°C of 2000 mPa·s or more and 8000 mPa·s or less in a state that does not substantially contain a solvent or a diisocyanate.
The lower limit of the viscosity is more preferably 2200 mPa·s or more, even more preferably 2600 mPa·s or more, and particularly preferably 3000 mPa·s or more.
The upper limit of the viscosity is more preferably 7,500 mPa·s or less, even more preferably 7,000 mPa·s or less, and particularly preferably 6,500 mPa·s or less.
When the viscosity is equal to or higher than the lower limit, a polyisocyanate composition having sufficient crosslinkability can be obtained.When the viscosity is equal to or lower than the upper limit, a coating composition having reduced VOC components can be obtained.

<Diisocyanate (A)>
The diisocyanate (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.

Aliphatic diisocyanates are compounds that contain saturated aliphatic groups in their molecules. On the other hand, alicyclic diisocyanates are compounds that contain cyclic aliphatic groups in their molecules. Using aliphatic diisocyanates is preferred because the resulting polyisocyanate composition has a low viscosity.

Examples of aliphatic diisocyanates include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (HDI), 1,6-diisocyanato-2,2,4-trimethylhexane, and methyl 2,6-diisocyanatohexanoate (lysine diisocyanate).

Examples of alicyclic diisocyanates include 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate; hereinafter sometimes abbreviated as "IPDI"), 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated xylylene diisocyanate), bis(4-isocyanatocyclohexyl)methane (hydrogenated diphenylmethane diisocyanate), and 1,4-diisocyanatocyclohexane.

These diisocyanates may be used alone or in combination of two or more.
Among these, HDI, IPDI, hydrogenated xylylene diisocyanate, and hydrogenated diphenylmethane diisocyanate are preferred as the diisocyanate (A) because they are readily available industrially. HDI is particularly preferred because it provides excellent weather resistance and coating film flexibility.
Hereinafter, aliphatic diisocyanates and alicyclic diisocyanates may be collectively referred to as diisocyanates.

<Monoalcohol (B)>
The monoalcohol (B) is a monoalcohol having 3 to 20 carbon atoms.
The number of carbon atoms in the alcohol is preferably not more than 16, more preferably not more than 13, and even more preferably not more than 9. When the number of carbon atoms is not more than the above upper limit, the hardness of the coating film is sufficient.
When the number of carbon atoms in the alcohol is 3 or more, the dissolving power in organic solvents tends to be high.

The monoalcohol used in the present invention may also contain an ether group in the molecule, such as 1-butoxyethanol, 2-butoxyethanol, 1-butoxypropanol, 2-butoxypropanol, 3-butoxypropanol, or ethylene glycol monobutyl ether. It may also contain an ester group, a carbonyl group, or a phenyl group, such as benzyl alcohol, but monoalcohols consisting solely of saturated hydrocarbon groups are preferred. Furthermore, branched monoalcohols are more preferred. Examples of such monoalcohols include 1-hexanol, 2-propanol, 2-hexanol, 1-heptanol, 1-octanol, 2-ethylhexanol, 3,3,5-trimethyl-1-hexanol, 1-tridecanol, pentadecanol, palmityl alcohol, stearyl alcohol, cyclopentanol, cyclohexanol, methylcyclohexanol, and trimethylcyclohexanol. Among these, 1-octanol, 2-ethyl-1-hexanol, tridecanol, pentadecanol, palmityl alcohol, stearyl alcohol, and 1,3,5-trimethylcyclohexanol are more preferred. 1-hexanol, 2-hexanol, 1-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, and 3,3,5-trimethyl-1-hexanol are more preferred because they have lower viscosities. 1-hexanol, 2-propanol, 1-tridecanol, and 2-ethyl-hexanol are most preferred because they also have lower viscosities.
The monoalcohol (B) may be used alone or in combination of two or more kinds.

<Polyether polyol (C)>
The number average molecular weight of the polyether polyol (C) is 400 or more and 2000 or less. The number average molecular weight is preferably 600 or more. The number average molecular weight is preferably 1500 or less, more preferably 1200 or less. When the number average molecular weight is in the range of 400 or more and 2000 or less, the coating film obtained from the coating composition has sufficient extensibility and also sufficient curability.

The polyether polyol (C) used is a polyether polyol having an oxypropylene group. A polyether polyol having an oxypropylene group is a polyether polyol having only oxypropylene groups in the molecular chain. In this case, only oxypropylene is contained in the repeating units.

Examples of such polyether polyols include polypropylene glycols and triols. Examples of such polyether polyols include Exenol 1030 (trade name, manufactured by AGC Inc., polypropylene triol, number average molecular weight 1000) and Exenol 420 (trade name, manufactured by AGC Inc., polypropylene glycol, number average molecular weight 400).

Examples of methods for producing polyether polyols include adding propylene oxide to polyhydric alcohols, polyhydric phenols, polyamines, and alkanolamines, either alone or in combination. Specifically, examples include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, and bisphenol A; trihydric alcohols such as glycerin and trimethylolpropane; and diamines such as ethylenediamine, either alone or in combination. These methods involve the use of a strong basic catalyst such as a hydroxide, alcoholate, or alkylamine of lithium, sodium, or potassium, or a complex metal complex such as a metal porphyrin, a complex metal cyanide complex, a complex of a metal with a tridentate or higher chelating agent, or a zinc hexacyanocobaltate complex. Other methods include the dehydration condensation of polyhydric alcohols.

The amount of polyether polyol (C) used in the present invention is preferably 10 to 30% by mass relative to the polyisocyanate. The upper limit of the amount of polyether polyol (C) is more preferably 25% by mass. The lower limit is more preferably 15% by mass. When the amount of polyether polyol (C) is in the range of 10 to 30% by mass, sufficient extensibility can be imparted to the coating film obtained from the coating composition.

<Polyether polyol (D)>
The number average molecular weight of the polyether polyol (D) is 2,500 or more and 6,000 or less. The number average molecular weight is preferably 3,000 or more. The number average molecular weight is preferably 5,500 or less, more preferably 4,500 or less. When the number average molecular weight is in the range of 2,500 or more and 6,000 or less, the coating film obtained from the coating composition has sufficient extensibility and also sufficient curability.

The polyether polyol (D) is a polyether polyol having an oxyethylene group and an oxypropylene group.
The polyether polyol having an oxyethylene group and an oxypropylene group is a polyether polyol having an oxyethylene group and an oxypropylene group in the molecular chain. In this case, in addition to the oxyethylene repeating unit and the oxypropylene repeating unit, other oxyalkylene groups, specifically, oxystyrene groups, etc. may be contained. When the total content of the oxyethylene group and the oxypropylene group is preferably 60 mol% or more, more preferably 70 mol% or more, and most preferably 80 mol% or more, the solubility in organic solvents is further improved.

Such polyether polyols include so-called Pluronic (registered trademark) type polypropylene glycols or triols, in which ethylene oxide is addition-polymerized to the terminals of polypropylene glycol, polyoxypropylene-polyoxyethylene copolymer diols or triols, and polyoxypropylene-polyoxyethylene block polymer diols or triols. Particularly preferred are so-called Pluronic (registered trademark) type polypropylene glycols or triols, in which ethylene oxide is addition-polymerized to the terminals of polypropylene glycol or triol. Examples of such polyether polyols include Exenol 230 (trade name, manufactured by AGC Inc., polypropylene triol (ethylene oxide-terminated), number-average molecular weight 3000) and Exenol 510 (trade name, manufactured by AGC Inc., polypropylene glycol (ethylene oxide-terminated), number-average molecular weight 4000).

Polyether polyols can be produced by adding propylene oxide, butylene oxide, and optionally alkylene oxides such as ethylene oxide and styrene oxide, either alone or in combination, to a polyhydric alcohol, polyhydric phenol, polyamine, or alkanolamine, specifically, for example, dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, or bisphenol A, trihydric alcohols such as glycerin or trimethylolpropane, or diamines such as ethylenediamine, either alone or in combination, in the presence of a strong basic catalyst such as a hydroxide, alcoholate, or alkylamine of, for example, lithium, sodium, or potassium, or a complex metal complex such as a metal porphyrin, a complex metal cyanide complex, a complex of a metal with a tridentate or higher chelating agent, or a zinc hexacyanocobaltate complex. Other methods include dehydration condensation of polyhydric alcohols.

The amount of polyether polyol (D) used in the present invention is preferably 3 to 20% by mass relative to the polyisocyanate. The upper limit of the amount of polyether polyol (D) is more preferably 12% by mass. The lower limit is more preferably 5% by mass. When the amount of polyether polyol (D) is in the range of 3 to 20% by mass, sufficient extensibility can be imparted to the coating film obtained from the coating composition.

<Polyisocyanate precursor>
In the present embodiment, the polyisocyanate is preferably a polyisocyanate derived from a polyisocyanate precursor, a polyether polyol (C), and a polyether polyol (D). The polyisocyanate precursor is a dimer or higher of a diisocyanate derived from a diisocyanate (A) and a monoalcohol (B).
The polyisocyanate precursor has an isocyanurate group and an allophanate group, and the molar ratio of the isocyanurate group to the allophanate group (isocyanurate group:allophanate group) is preferably 1:99 or more and 60:40 or less.

A polyisocyanate precursor consisting of a dimer or higher diisocyanate has both a polyisocyanurate group represented by the following formula (1) and an allophanate group represented by the following formula (2).

The molar ratio of isocyanurate groups to allophanate groups in the polyisocyanate precursor is preferably 1:99 or more and 60:40 or less, with the upper limit being most preferably 1:99. The lower limit is more preferably 40:60 or less, and even more preferably 20:80 or less. Most preferably, it is 5:95 or less. Having a molar ratio within the above range results in better compatibility, drying properties, and extensibility. The molar ratio of isocyanurate groups to allophanate groups can be determined by the method described in the Examples.

The molar ratio of allophanate groups to isocyanurate groups can be determined by 1H-NMR. An example of a method for measuring a polyisocyanate composition using HDI and an isocyanate prepolymer obtained therefrom as raw materials by 1H-NMR is shown below.
Example of 1H-NMR measurement method: A polyisocyanate compound is dissolved in deuterated chloroform at a concentration of 10% by mass (0.03% by mass of tetramethylsilane is added relative to the polyisocyanate compound). The chemical shift reference is the hydrogen signal of tetramethylsilane, which is set at 0 ppm. 1H-NMR is measured, and the area ratio of the signal of the hydrogen atom bonded to the nitrogen of the allophanate group (1 mol of hydrogen atom per 1 mol of allophanate group) at around 8.5 ppm to the signal of the hydrogen atom of the methylene group adjacent to the isocyanurate group (6 mol of hydrogen atom per 1 mol of isocyanurate group) at around 3.85 ppm is measured, and the molar ratio is calculated using the following formula:
Allophanate group/Isocyanurate group=(signal area near 8.5 ppm)/(signal area near 3.85 ppm/6)

In addition, since uretdione compounds tend to dissociate due to heat or other factors and generate HDI, it is preferable to reduce their content. The uretdione compound content is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, based on the polyisocyanate composition. The uretdione compound content can be determined by measuring the area ratio of the peak corresponding to a molecular weight of approximately 336 in gel permeation chromatography (GPC) using a parallax refractometer. If there is a peak near the 336 molecular weight peak that interferes with measurement, the content can also be determined using FT-IR, quantifying the ratio of the height of the uretdione group peak at approximately 1770 cm-1 to the height of the allophanate group peak at approximately 1720 cm-1 using an internal standard.

The GPC measurement method is described below. All measurements related to the molecular weight of polyisocyanate compounds were performed using the following measurement method. Instrument used: HLC-8120 (manufactured by Tosoh Corporation), Columns used: TSK GEL Super H1000, TSK GEL Super H2000, TSK GEL Super H3000 (all manufactured by Tosoh Corporation), Sample concentration: 5 wt/vol% (for example, dissolve 50 mg of sample in 1 ml of THF), Carrier: THF, Detection method: Parallax refractometer, Outflow rate: 0.6 ml/min, Column temperature: 40°C). The GPC calibration curve was prepared using polystyrene with molecular weights of 50,000 to 2,050 (GL Sciences PSS-06 (Mw 50,000), BK13007 (Mp = 20,000, Mw/Mn = 1.03), PSS-08 (Mw = 9,000), PSS-09 (Mw = 4,000), and 5040-35125 (Mp = 2,050, Mw/Mn = 1.05)) as standards, and a hexamethylene diisocyanate-based polyisocyanate composition (Duranate TPA-100, Asahi Kasei Corporation) containing isocyanurate trimers to heptamers (isocyanurate trimer molecular weight = 504, isocyanurate pentamer molecular weight = 840, isocyanurate heptamer molecular weight = 1,176) and HDI (molecular weight = 168).

The isocyanate group content (hereinafter referred to as NCO content) of the polyisocyanate used in the present invention is 5 to 20% by mass in a state substantially free of solvent and diisocyanate. The lower limit of the NCO content is preferably 6% by mass, even more preferably 7% by mass, and most preferably 8% by mass. The upper limit is preferably 18% by mass, more preferably 16% by mass, and most preferably 14% by mass. A content in the range of 5 to 20% by mass allows for a polyisocyanate composition to be obtained that is sufficiently soluble in organic solvents and has sufficient crosslinking properties.

<Method for producing polyisocyanate composition>
The method for producing the polyisocyanate composition used in the present invention will be described below.
There are various methods for producing the polyisocyanate used in the present invention, but a representative preferred synthesis method will be described below.

(1) A method in which a C3-20 monoalcohol and a diisocyanate are subjected to a urethane reaction, followed by, or simultaneously with, an allophanation reaction; unreacted diisocyanate is removed by purification; and then a urethane reaction with polyether polyol (C) and polyether polyol (D) is carried out to obtain the polyisocyanate used in the present invention.

(2) A method for obtaining the polyisocyanate used in the present invention by subjecting a C3-20 monoalcohol and a diisocyanate to a urethane reaction, followed by, or simultaneously with, an allophanation reaction, terminating the allophanation reaction with a reaction terminator, and then subjecting the resulting mixture to a urethane reaction with polyether polyol (C) and polyether polyol (D), and removing any unreacted diisocyanate by purification.

(3) A method for obtaining the polyisocyanate used in the present invention by subjecting a C3-20 monoalcohol, a diisocyanate, and polyether polyol (C) and polyether polyol (D) to a urethane reaction, followed by, or simultaneously with, an allophanation reaction, and then removing the unreacted diisocyanate by purification.

(4) A method for obtaining the polyisocyanate used in the present invention by mixing a polyisocyanate compound obtained by subjecting a C3-20 monoalcohol and a diisocyanate to a urethane reaction, followed by, or simultaneously with, an allophanation reaction, and removing the unreacted diisocyanate by purification, with a polyisocyanate compound obtained by subjecting polyether polyol (C) and polyether polyol (D) to a urethane reaction with a diisocyanate, and optionally removing the unreacted diisocyanate by purification.

(5) A method for obtaining the polyisocyanate compound used in the present invention by mixing a reaction liquid obtained by subjecting a C3-20 monoalcohol and a diisocyanate to a urethanization reaction, followed by or simultaneously with an allophanation reaction, and terminating the allophanation reaction with a reaction terminator, with a reaction liquid obtained by subjecting polyether polyol (C) and polyether polyol (D) and a diisocyanate to a urethanization reaction, followed by or simultaneously with an allophanation reaction as necessary, and terminating the allophanation reaction with a reaction terminator, and removing the unreacted diisocyanate by purification.

Methods (1) to (5) above may be combined.

The urethanization reaction is preferably carried out at 20 to 200°C, more preferably 40 to 150°C, and even more preferably 60 to 120°C, for 10 minutes to 24 hours, more preferably 15 minutes to 15 hours, and even more preferably 20 minutes to 10 hours. The reaction is rapid at temperatures above 20°C, while side reactions such as urethodionation are suppressed and discoloration is also suppressed at temperatures below 200°C. A reaction time of 10 minutes or more allows the reaction to be completed, while a reaction time of 24 hours or less ensures no problems with production efficiency and suppresses side reactions. The urethanization reaction can be carried out without a catalyst or in the presence of a tin-based, amine-based, or other catalyst.

The allophanation reaction is preferably carried out at a temperature of 20 to 200°C. More preferably, it is 40 to 180°C, and even more preferably, it is 60 to 160°C. Even more preferably, it is 90 to 150°C, and most preferably, it is 110 to 150°C. At temperatures above 20°C, the amount of allophanation catalyst required is reduced, and the time required to complete the reaction is short. Furthermore, at temperatures below 200°C, side reactions such as uretdione formation are suppressed, and coloration of the reaction product is suppressed.

When the allophanate formation reaction is carried out by any of methods (1) to (5), it is preferable to use a catalyst, and it is particularly preferable to select a catalyst that produces a polyisocyanate with an isocyanurate group to allophanate group ratio of 1:99 to 60:40. Examples of such catalysts include carboxylates of zinc, tin, zirconium, zirconyl, etc., and mixtures thereof.
The allophanate formation catalyst is used in an amount of preferably 0.001 to 2.0% by mass, more preferably 0.01 to 0.5% by mass, based on the total mass of the reaction solution. At an amount of 0.001% by mass or more, the catalytic effect can be fully exerted. At an amount of 2% by mass or less, the allophanate formation reaction can be easily controlled.

In the present invention, the method of adding the allophanation catalyst is not limited. For example, it may be added before the production of the compound containing urethane groups, i.e., prior to the urethanization reaction between the diisocyanate and the organic compound having a hydroxyl group, or it may be added during the urethanization reaction between the diisocyanate and the organic compound having a hydroxyl group, or it may be added after the production of the urethane group-containing compound. Furthermore, the required amount of allophanation catalyst may be added all at once, or it may be added in several installments. Alternatively, a method of adding it continuously at a constant rate may be used.

The urethanization reaction and allophanation reaction can be carried out without a solvent. If necessary, ester solvents such as ethyl acetate and butyl acetate, ketone solvents such as methyl ethyl ketone, aromatic solvents such as toluene, xylene, and diethylbenzene, organic solvents that do not react with isocyanate groups such as dialkyl polyalkylene glycol ether, and mixtures of these can be used as solvents.

Catalysts for deriving polyisocyanates containing isocyanurate groups from diisocyanate monomers include commonly used isocyanuration reaction catalysts. The isocyanuration reaction catalyst is not particularly limited, but is preferably a catalyst that is generally basic. Examples include: (1) hydroxides of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium; and organic weak acid salts thereof such as acetate, octylate, myristate, and benzoate; (2) hydroxides of hydroxyalkylammonium such as trimethylhydroxyethylammonium, trimethylhydroxypropylammonium, triethylhydroxyethylammonium, and triethylhydroxypropylammonium; and organic weak acid salts thereof such as acetate, octylate, myristate, and benzoate; (3) metal salts of alkylcarboxylic acids such as tin, zinc, and lead, such as acetate, caproic acid, octylate, and myristic acid; (4) metal alcoholates of sodium and potassium; (5) aminosilyl group-containing compounds such as hexamethylenedisilazane; (6) Mannich bases; (7) combinations of tertiary amines and epoxy compounds; and (8) phosphorus-based compounds such as tributylphosphine.

Among these, from the viewpoint of less generation of unnecessary by-products, preferred are weak organic acid salts of quaternary ammonium, and more preferred are weak organic acid salts of tetraalkylammonium.
The amount of the isocyanurate formation reaction catalyst is preferably 10 ppm by mass or more and 1000 ppm by mass or less, relative to the mass of the charged diisocyanate monomer. The upper limit is more preferably 500 ppm by mass, and even more preferably 100 ppm by mass. The isocyanurate formation reaction temperature is preferably 50° C. or more and 120° C. or less, and more preferably 60° C. or more and 90° C. or less. By keeping the isocyanurate formation reaction temperature at 120° C. or less, coloration of the polyisocyanate tends to be effectively suppressed.
The processes of the urethane-forming reaction, allophanate-forming reaction and isocyanurate-forming reaction in the present invention can be followed by measuring the NCO content of the reaction liquid or measuring the refractive index.

The allophanatization reaction and isocyanurate formation reaction can be terminated by cooling to room temperature or by adding a reaction terminator. When a catalyst is used, adding a reaction terminator is preferable because it can suppress side reactions. The amount of reaction terminator added is preferably 0.25 to 20 times the molar amount of the catalyst, more preferably 0.5 to 16 times the molar amount, and even more preferably 1.0 to 12 times the molar amount of the catalyst. Complete deactivation is possible at 0.25 times or more. Storage stability is improved at 20 times or less. Any reaction terminator that deactivates the catalyst may be used. Examples of reaction terminators include compounds exhibiting phosphoric acidity such as phosphoric acid and pyrophosphoric acid, monoalkyl or dialkyl esters of phosphoric acid and pyrophosphate, halogenated acetic acids such as monochloroacetic acid, benzoyl chloride, sulfonate esters, sulfuric acid, sulfate esters, ion exchange resins, and chelating agents. From an industrial viewpoint, phosphoric acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, and monoalkyl and dialkyl phosphates are preferred because they are less likely to corrode stainless steel. Examples of monoesters and diesters of phosphoric acid include monoethyl phosphate, diethyl phosphate, monobutyl phosphate, dibutyl phosphate, mono(2-ethylhexyl) phosphate, di(2-ethylhexyl) phosphate, monodecyl phosphate, didecyl phosphate, monolauryl phosphate, dilauryl phosphate, monotridecyl phosphate, ditridecyl phosphate, monooleyl phosphate, dioleyl phosphate, and mixtures thereof.
It is also possible to use an adsorbent such as silica gel or activated carbon as a terminator, preferably in an amount of 0.05 to 10% by mass based on the diisocyanate used in the reaction.

After the reaction is complete, unreacted diisocyanate and solvent may be separated from the polyisocyanate. From a safety perspective, it is preferable to separate the unreacted diisocyanate. Examples of methods for separating unreacted diisocyanate and solvent include thin-film distillation and solvent extraction.

<Coating composition>
The coating composition of the present embodiment contains a polyaspartic base resin and a polyisocyanate composition.
Each component will be described below.

<Polyaspartic main ingredient>
The polyaspartic base agent is an aspartic acid ester compound represented by the following formula (I).

[In formula (I), X represents an n-valent organic group obtained by removing a primary amino group from an n-valent polyamine, ^R1 and ^R2 represent the same or different organic groups that are inert to isocyanate groups under reaction conditions, and n represents an integer of 2 or greater.]

(X)
In general formula (I), X is an n-valent organic group.

The n-valent organic group may be an aliphatic group or an aromatic group. The aliphatic group may be linear, branched, or cyclic. Furthermore, n is an integer of 2 or greater, as described below.

Examples of the linear or branched aliphatic group include an alkanediyl group (an alkylene group), an alkylidene group, an alkylidyne group, and the like.

Examples of the cyclic aliphatic group include cycloalkylene groups.

Examples of the aromatic group include arylene groups such as phenylene groups.

More specifically, from the viewpoint of the yellowing resistance of the polyaspartic paint composition of this embodiment, X is preferably a linear, branched, or cyclic divalent aliphatic group having from 2 to 20 carbon atoms. Examples of the linear, branched, or cyclic divalent aliphatic group having from 2 to 20 carbon atoms include an n-butylene group, an n-pentylene group, an n-hexylene group, a 2,2,4-trimethylhexamethylene group, a 2,4,4-trimethylhexamethylene group, a 3,3,5-trimethyl-5-methylcyclohexylene group, a dicyclohexylmethylene group, and a 3,3'-dimethyldicyclohexylmethylene group.

( ^R1 and ^R2 )
In general formula (I), R ¹ and R ² are each independently an organic group that is inert to an isocyanate group under reaction conditions.

In this specification, "inert to isocyanate groups under reaction conditions" means that ^R1 and ^R2 do not have Zerewitinoff active hydrogen-containing groups (CH acidic compounds) such as hydroxyl groups, amino groups, or thiol groups.

R ¹ and R ² are each preferably an alkyl group having 1 to 10 carbon atoms, and more preferably a methyl group, an ethyl group, a propyl group, or a butyl group.

R ¹ and R ² may be the same or different.

(n)
In general formula (I), n is an integer of 2 or more.
Among these, n is preferably an integer of 2 or more and 6 or less, more preferably an integer of 2 or more and 4 or less, even more preferably 2 or 3, and particularly preferably 2.

<<Method for producing an aspartic acid ester compound represented by formula (I)>>
The aspartic acid ester compound represented by formula (I) can be produced by the method described in WO 2018/163959.

(optional ingredient)
The coating composition of this embodiment may further contain an antioxidant in addition to the polyisocyanate composition and the main component. The antioxidant may be added during the production of the coating composition, or may be added to the polyisocyanate composition in advance. The antioxidant may be used alone or in combination of two or more.

Antioxidants are not particularly limited, but examples include substances with antioxidant properties that are used as light stabilizers, heat stabilizers, etc.

Antioxidants used as light stabilizers are not particularly limited, but examples include hindered amine antioxidants, benzophenone antioxidants, benzotriazole antioxidants, triazine antioxidants, and cyanoacrylate antioxidants.

Hindered amine antioxidants are not particularly limited, but examples include Adeka STAB LA-52 (trade name), Adeka STAB LA-68 (trade name), and Adeka STAB LA-77Y (trade name) (all manufactured by Adeka Corporation), Tinuvin 622 (trade name), Tinuvin 765 (trade name), Tinuvin 770 (trade name), and Tinuvin 791 (trade name) (all manufactured by BASF).

Benzophenone-based antioxidants are not particularly limited, but examples include Chimassorb 81 (trade name) (manufactured by BASF).

Benzotriazole-based antioxidants are not particularly limited, but examples include Tinuvin P (trade name) and Tinuvin 234 (trade name) (both manufactured by BASF).

Triazine-based antioxidants are not particularly limited, but examples include Tinuvin 1577ED (trade name) (manufactured by BASF).

Cyanoacrylate antioxidants are not particularly limited, but examples include Uvinul 3035 (trade name) (manufactured by BASF).

Antioxidants used as heat stabilizers are not particularly limited, but examples include hindered phenol-based antioxidants, phosphorus-containing antioxidants, sulfur-containing antioxidants, vitamin E-based antioxidants, and hydroxyamine-based antioxidants.

Hindered phenol-based antioxidants include, but are not limited to, dibutylhydroxytoluene (hereinafter sometimes abbreviated as "BHT"), Irganox 1010 (trade name), Irganox 1135 (trade name), Irganox 1330 (trade name), Irganox 3114 (trade name), Irganox 565 (trade name), Irganox 1520L (trade name) (each manufactured by BASF), Adeka STAB AO-20 (trade name), Adeka STAB AO-30 (trade name), Adeka STAB AO-50 (trade name), Adeka STAB AO-60 (trade name), and Adeka STAB AO-80 (trade name) (each manufactured by Adeka Corporation).

Phosphorus-containing antioxidants are not particularly limited, but examples include Adekastab PEP-8 (trade name), Adekastab HP-10 (trade name), Adekastab 1178 (trade name), and Adekastab C (trade name) (each manufactured by Adeka Corporation), Irgafos 168 and Irgafos 38 (trade names) (manufactured by BASF), and Sumilizer GP (trade name) (manufactured by Sumitomo Chemical Co., Ltd.).

Sulfur-containing antioxidants are not particularly limited, but examples include Irganox PS800FL (trade name) (manufactured by BASF).

Vitamin E-based antioxidants are not particularly limited, but examples include Irganox E201 (trade name) (manufactured by BASF).

Hydroxyamine-based antioxidants are not particularly limited, but examples include Irgastab FS042 (trade name) (manufactured by BASF).

Among these, the antioxidant is preferably at least one selected from the group consisting of hindered phenol antioxidants, hindered amine antioxidants, sulfur-containing antioxidants, and phosphorus-containing antioxidants. Furthermore, the antioxidant is more preferably at least one selected from the group consisting of Tinuvin 765 (trade name), BHT, Irganox 565 (trade name), Adekastab C (trade name), and Sumilizer GP (trade name).

<<Method for producing coating composition>>
The coating composition of this embodiment is useful as a solvent-based coating composition, and can be obtained by the production method described below.

When the coating composition of this embodiment is a solvent-based coating composition, for example, first, the polyisocyanate composition is added as a curing agent to a polyaspartic base or its solvent dilution, to which various additives are added as needed. Next, if needed, a solvent is further added to adjust the viscosity. Next, a solvent-based coating composition can be obtained by stirring by hand or using a stirring device such as a mixer.
Furthermore, the order of mixing the base component mainly composed of a polyaspartic base, the curing agent component mainly composed of the polyisocyanate composition, and the various additives is not particularly limited, and they can be mixed, for example, in the following order:
1) The curing agent component is mixed at the painting site with the base component, which has been mixed in advance with various additives.
2) After mixing the main component and the hardener component at the painting site, various additives are mixed.
3) The main component, which has been mixed with various additives in advance, is mixed with the hardener component, which has been mixed with various additives in advance, at the painting site.

[Uses of the coating composition]
The coating composition of the present embodiment can be used as a coating material for, but not limited to, spray coating, air spray coating, brush coating, immersion coating, roll coating, curtain flow coating, bell coating, electrostatic coating, and the like.
The coating composition of the present embodiment is also useful as a coating for molded articles made of materials such as metals (steel plates, surface-treated steel plates, etc.), plastics, wood, films, inorganic materials, etc., and is particularly suitable as a coating for metals or plastics.
The coating composition of the present embodiment is suitable for use as, for example, architectural coatings, heavy-duty corrosion-resistant coatings, automotive coatings, coatings for information appliances, and coatings for information devices such as personal computers and mobile phones, and is particularly suitable as a top clear coating for architectural structures, automobile bodies, metal parts for automobiles, plastic parts for automobiles, metal parts for information appliances, or plastic parts for information appliances.

<Coating film>
The coating film of this embodiment is obtained by curing the above coating composition, and always exhibits stable quality, and is excellent in weather resistance, alkali resistance, coating elongation, and coating stress.

<Coating film manufacturing method>
The method for producing a coating film of this embodiment is a method including a step of curing the coating composition.

The coating film of this embodiment can be produced by applying the coating composition to a substrate using a known coating method such as spray coating, air spray coating, brush coating, immersion coating, roll coating, curtain flow coating, bell coating, electrostatic coating, etc., and then curing the composition.
Examples of the substrate include molded articles made from materials exemplified above in "<Uses of the coating composition>".

The present invention will be explained in more detail below by way of examples and comparative examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.
In the examples and comparative examples, the physical properties of the polyisocyanate compositions were measured and evaluated as follows. Unless otherwise specified, "parts" and "%" mean "parts by mass" and "% by mass".

<Method of measuring physical properties>
[Property 1] NCO Content The NCO content (isocyanate content, mass %) of the polyisocyanate composition was measured as follows. After accurately weighing (Wg) 1 g to 3 g of the polyisocyanate composition prepared in the Production Example into an Erlenmeyer flask, 20 ml of toluene was added to completely dissolve the polyisocyanate composition. Then, 10 ml of a 2 N toluene solution of di-n-butylamine was added, and after thorough mixing, the solution was left at room temperature for 15 minutes. Furthermore, 70 ml of isopropyl alcohol was added to this solution, and the solution was thoroughly mixed. This solution was titrated with a 1 N hydrochloric acid solution (Factor F) using an indicator to obtain a titration value V2 mL. A similar titration operation was performed without using polyisocyanate, and a titration value V1 mL was obtained. From the obtained titration values V2 mL and V1 mL, the NCO content (mass %) of the polyisocyanate was calculated according to the following formula:
(NCO content (mass%)) = (V1-V2) x F x 42/(W x 1000) x 100

[Physical properties 2] Viscosity (mPa.s))
The viscosity of the polyisocyanate composition was measured at 25°C using an E-type viscometer (product name: RE-85R, manufactured by Toki Sangyo Co., Ltd.). A standard rotor (1°34' x R24) was used for the measurement. The rotation speed was set as follows:
(rotation speed)
100 rpm (less than 128 mPa·s)
50 rpm (128 mPa・s or more and less than 256 mPa・s)
20 rpm (256 mPa・s or more and less than 640 mPa・s)
10 rpm (640 mPa・s or more and less than 1280 mPa・s)
5 rpm (for viscosity between 1280 mPa·s and 2560 mPa·s)
2.5 rpm (2560 mPa・s or more and less than 5120 mPa・s)
1.0 rpm: 5120 mPa·s or more and less than 10240 mPa·s
0.5 rpm (for viscosity of 10,240 mPa·s or more and less than 20,480 mPa·s)

[Physical Property 3] Number Average Molecular Weight The number average molecular weight of the polyisocyanate composition was determined as the number average molecular weight based on polystyrene by gel permeation chromatography (hereinafter abbreviated as "GPC") using the following apparatus. The measurement conditions are as follows:
(Measurement conditions)
Apparatus: "HLC-8120GPC" (product name) manufactured by Tosoh Corporation
Column: Tosoh Corporation "TSKgel Super H1000" (trade name) x 1, "TSKgel Super H2000" (trade name) x 1, "TSKgel Super H3000" (trade name) x 1 Carrier: Tetrahydrofuran Detector: Differential refractometer

[Property 4] Average Number of Isocyanate Groups The average number of isocyanate groups in the polyisocyanate composition was calculated based on the following formula using the NCO content obtained in Property 1 and the number average molecular weight obtained in Property 3.
(Average number of isocyanate groups)=(Number average molecular weight)×(NCO content)/100/42

[Physical Property 5] 1H-NMR Measurement Method Polyisocyanate precursors a to h prepared in Synthesis Examples 1 to 8 were dissolved in deuterated chloroform at a concentration of 10% by mass. The solution contained 0.03% by mass of tetramethylsilane relative to the polyisocyanate precursor. The chemical shift reference was the hydrogen signal of tetramethylsilane, set at 0 ppm. 1H-NMR was measured, and the areas of the signal of the hydrogen atom bonded to the nitrogen of the allophanate group (1 mol of hydrogen atom per 1 mol of allophanate group) around 8.5 ppm and the signal of the hydrogen atom of the methylene group adjacent to the isocyanurate group (6 mol of hydrogen atom per 1 mol of isocyanurate group) around 3.8 ppm were measured. Based on the obtained areas, the molar ratio of isocyanurate groups to allophanate groups in the polyisocyanate precursor was calculated using the following formula:
Isocyanurate group:allophanate group=(signal area around 3.8 ppm/6):(signal area around 8.5 ppm)

The abbreviations shown in the Synthesis Examples, Examples and Tables of Examples are as follows.
HDI: Hexamethylene diisocyanate aspartic acid ester compound: Product name "Feispartic F420" manufactured by Feiyang Co., Ltd., amine value 192 mg KOH/g resin, viscosity 1450 mPa s (representative value measured at 25°C)
Polyether polyol (C): Polyether polyol having oxypropylene groups C1: Exenol 1030: Number average molecular weight 1000, average functionality 3, manufactured by AGC Inc. C2: Exenol 430: Number average molecular weight 430, average functionality 3, manufactured by AGC Inc. C3: Sannix GP1500: Number average molecular weight 1500, average functionality 3, manufactured by Sanyo Chemical Industries, Ltd. C4: Exenol 4030: Number average molecular weight 4000, average functionality 3, manufactured by AGC Inc. C5: Exenol 1020: Number average molecular weight 1000, average functionality 2, manufactured by AGC Inc. Polyether polyol (D): Polyether polyol having oxyethylene groups and oxypropylene groups D1: Exenol 230: Number average molecular weight 3000, average functionality 3, manufactured by AGC Inc. D2: Exenol 820: number average molecular weight 4900, average functionality 3, manufactured by AGC Inc. D3: Preminol 7012: number average molecular weight 10000, average functionality 3, manufactured by AGC Inc. D4: Exenol 510: number average molecular weight 4000, average functionality 2, polycarbonate diol manufactured by AGC Inc. E1: T5650E: number average molecular weight 500, average functionality 2, manufactured by Asahi Kasei Corporation

<Production of Polyisocyanate Precursors a to h>
Synthesis Example 1: Production of Polyisocyanate Precursor a A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with a nitrogen atmosphere, and 1,000 g of HDI and 60 g of 2-ethylhexanol were charged. The temperature inside the reactor was raised to 90°C and the mixture was stirred for 1 hour to carry out a urethanization reaction. After raising the temperature inside the reactor to 120°C, 0.28 g of a 20% solids solution of zirconyl 2-ethylhexanoate in mineral spirits was added as an allophanate formation catalyst. After stirring for an additional 60 minutes, 0.097 g of an 85% aqueous solution of phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and then unreacted HDI was removed using a falling thin-film distillation apparatus at 160°C (27 Pa) for the first time and 150°C (13 Pa) for the second time, yielding polyisocyanate precursor a. The obtained polyisocyanate precursor a was a transparent liquid, with a yield of 250 g, a viscosity of 150 mPa s at 25° C., and an isocyanate content of 17.5%. 1H-NMR measurement revealed that the molar ratio of isocyanurate groups to allophanate groups was 3/97.

Synthesis Example 2: Production of Polyisocyanate Precursor b A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with a nitrogen atmosphere, and 1,000 g of HDI and 90 g of 1-tridecanol were charged. The temperature inside the reactor was raised to 90°C and the mixture was stirred for 1 hour to carry out a urethanization reaction. After raising the temperature inside the reactor to 120°C, 0.28 g of a 20% solids solution of zirconyl 2-ethylhexanoate in mineral spirits was added as an allophanate formation catalyst. After stirring for an additional 60 minutes, 0.097 g of an 85% aqueous solution of phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and then unreacted HDI was removed using a falling thin-film distillation apparatus, first at 160°C (27 Pa) and then at 150°C (13 Pa), to obtain polyisocyanate precursor b. The obtained polyisocyanate precursor b was a transparent liquid, with a yield of 280 g, a viscosity of 200 mPa s at 25° C., and an isocyanate content of 15.8%. 1H-NMR measurement revealed that the molar ratio of isocyanurate groups to allophanate groups was 3/97.

Synthesis Example 3: Production of Polyisocyanate Precursor c A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with a nitrogen atmosphere, and 1,000 g of HDI and 40 g of 1-hexanol were charged. The temperature inside the reactor was raised to 90°C and the mixture was stirred for 1 hour to carry out a urethanization reaction. After raising the temperature inside the reactor to 120°C, 0.28 g of a 20% solids solution of zirconyl 2-ethylhexanoate in mineral spirits was added as an allophanate catalyst. After stirring for an additional 60 minutes, 0.097 g of an 85% aqueous solution of phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and then unreacted HDI was removed using a falling thin-film distillation apparatus, first at 160°C (27 Pa) and then at 150°C (13 Pa), to obtain polyisocyanate precursor c. The obtained polyisocyanate precursor c was a transparent liquid, with a yield of 240 g, a viscosity of 130 mPa s at 25° C., and an isocyanate content of 19.4%. 1H-NMR measurement revealed that the molar ratio of isocyanurate groups to allophanate groups was 3/97.

Synthesis Example 4: Production of Polyisocyanate Precursor d A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with a nitrogen atmosphere, and 1,000 g of HDI and 35 g of 2-propanol were charged. The temperature inside the reactor was raised to 90°C and the mixture was stirred for 1 hour to carry out a urethanization reaction. After raising the temperature inside the reactor to 120°C, 0.28 g of a 20% solids solution of zirconyl 2-ethylhexanoate in mineral spirits was added as an allophanate formation catalyst. After stirring for an additional 60 minutes, 0.097 g of an 85% aqueous solution of phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and then unreacted HDI was removed using a falling thin-film distillation apparatus, first at 160°C (27 Pa) and then at 150°C (13 Pa), to obtain Polyisocyanate Precursor d. The obtained polyisocyanate precursor d was a transparent liquid, with a yield of 235 g, a viscosity of 130 mPa s at 25° C., and an isocyanate content of 21.0%. 1H-NMR measurement revealed that the molar ratio of isocyanurate groups to allophanate groups was 3/97.

Synthesis Example 5: Production of Polyisocyanate Precursor e A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with a nitrogen atmosphere, and 1,000 g of HDI and 100 g of 2-ethylhexanol were charged. The temperature inside the reactor was raised to 90°C and the mixture was stirred for 1 hour to carry out a urethanization reaction. While maintaining the temperature inside the reactor at 90°C, 0.6 g of a 5% solids isobutanol solution of tetramethylammonium caprate was added as an allophanation and isocyanuration catalyst. After stirring for an additional 2 hours, 0.06 g of an 85% aqueous solution of phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed in the same manner as in Synthesis Example 1 to obtain polyisocyanate precursor e. The resulting polyisocyanate precursor e was a transparent liquid with a yield of 400 g, a viscosity at 25°C of 400 mPa·s, and an isocyanate content of 17.6%. 1H-NMR measurement revealed that the molar ratio of isocyanurate groups to allophanate groups was 30/70.

Synthesis Example 6: Production of Polyisocyanate Precursor f A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with a nitrogen atmosphere, and 1,000 g of HDI and 36 g of 2-ethylhexanol were charged. The temperature inside the reactor was raised to 90°C and the mixture was stirred for 1 hour to carry out a urethanization reaction. While maintaining the temperature inside the reactor at 90°C, 0.6 g of a 5% solids isobutanol solution of tetramethylammonium caprate was added as an allophanation and isocyanuration catalyst. After stirring for an additional 2 hours, 0.06 g of an 85% aqueous solution of phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed in the same manner as in Synthesis Example 1 to obtain polyisocyanate precursor f. The resulting polyisocyanate precursor f was a transparent liquid with a yield of 210 g, a viscosity at 25°C of 400 mPa·s, and an isocyanate content of 20.1%. 1H-NMR measurement revealed that the molar ratio of isocyanurate groups to allophanate groups was 50/50.

Synthesis Example 7 Production of Polyisocyanate Precursor g A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel was conditioned with a nitrogen atmosphere, and 1,000 g of HDI and 30 g of 2-ethylhexanol were charged. The temperature inside the reactor was raised to 80°C and the mixture was stirred for 1 hour to carry out a urethanization reaction. While maintaining the temperature inside the reactor at 80°C, 0.36 g of a 10% solids n-butanol solution of tetramethylammonium caprate was added as an allophanation and isocyanuration catalyst. After stirring for an additional 3 hours, 0.58 g of an 85% solids aqueous solution of phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed in the same manner as in Synthesis Example 1 to obtain polyisocyanate precursor g. The obtained polyisocyanate precursor g was a pale yellow, transparent liquid, with a yield of 300 g, a viscosity of 600 mPa s at 25° C., and an isocyanate content of 20.5%. 1H-NMR measurement revealed that the molar ratio of isocyanurate groups to allophanate groups was 70/30.

Synthesis Example 8: Production of Polyisocyanate h A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with a nitrogen atmosphere, and 1,000 g of HDI and 3 g of 2-ethylhexanol were charged. The temperature inside the reactor was raised to 80°C and the mixture was stirred for 1 hour to carry out a urethanization reaction. While maintaining the temperature inside the reactor at 80°C, 0.36 g of a 10% solids n-butanol solution of tetramethylammonium caprate was added as an allophanation and isocyanuration catalyst. After stirring for an additional 3 hours, 0.58 g of an 85% solids aqueous solution of phosphoric acid was added to terminate the reaction. The reaction solution was then maintained at 160°C for an additional 1 hour. After filtering the reaction solution, unreacted HDI was removed in the same manner as in Synthesis Example 1, yielding Polyisocyanate Precursor h. The obtained polyisocyanate precursor h was a pale yellow, transparent liquid, with a yield of 200 g, a viscosity of 450 mPa s at 25° C., and an isocyanate content of 23.0%. 1H-NMR measurement revealed that the molar ratio of isocyanurate groups to allophanate groups was 97/3.

<Synthesis Example of Polyisocyanate Composition>
Example 1
100 g of polyisocyanate precursor a, 31.0 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 7.8 g of polyol D1 having an oxyethylene group by addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out for 5 hours at 110°C with stirring. The resulting polyisocyanate compound had a viscosity of 3000 mPa s and an NCO content of 9.7%.

Example 2
100 g of polyisocyanate precursor a, 27.4 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 18.2 g of polyol D1 having an oxyethylene group by addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out with stirring at 110°C for 5 hours. The resulting polyisocyanate compound had a viscosity of 3200 mPa s and an NCO content of 9.2%.

Example 3
100 g of polyisocyanate precursor a, 44.8 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 11.2 g of polyol D1 having an oxyethylene group by addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out with stirring at 110°C for 5 hours. The resulting polyisocyanate compound had a viscosity of 4400 mPa s and an NCO content of 7.5%.

Example 4
100 g of polyisocyanate precursor a, 19.2 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 4.8 g of polyol D1 having an oxyethylene group formed by the addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out for 5 hours at 110°C with stirring. The resulting polyisocyanate compound had a viscosity of 2500 mPa s and an NCO content of 12.1%.

Example 5
100 g of polyisocyanate precursor a, 13.0 g of polyol C2 (Exenol 430, polypropylene glycol manufactured by AGC Inc., molecular weight = 430), 3.3 g of polyol D1 having an oxyethylene group by addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out with stirring at 110°C for 5 hours. The resulting polyisocyanate compound had a viscosity of 2200 mPa s and an NCO content of 11.6%.

Example 6
100 g of polyisocyanate precursor a, 42.9 g of polyol C3 (SANNICS GP1500, polypropylene glycol manufactured by Sanyo Chemical Industry Co., Ltd., molecular weight = 1500), 10.7 g of polyol D1 having an oxyethylene group by addition of ethylene oxide (EXCENOL 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out with stirring at 110°C for 5 hours. The resulting polyisocyanate compound had a viscosity of 3600 mPa s and an NCO content of 8.8%.

Example 7
100 g of polyisocyanate precursor a, 32.0 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 8.0 g of polyol D2 having an oxyethylene group by addition of ethylene oxide (Exenol 820, polypropylene glycol manufactured by AGC Inc., molecular weight = 4900), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out with stirring at 110°C for 5 hours. The resulting polyisocyanate compound had a viscosity of 3100 mPa s and an NCO content of 9.6%.

Example 8
100 g of polyisocyanate precursor b, 28.0 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 7.0 g of polyol D1 having an oxyethylene group by addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out with stirring at 110°C for 5 hours. The resulting polyisocyanate compound had a viscosity of 2800 mPa s and an NCO content of 9.0%.

Example 9
100 g of polyisocyanate precursor c, 34.4 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 8.6 g of polyol D1 having an oxyethylene group by addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out with stirring at 110°C for 5 hours. The resulting polyisocyanate compound had a viscosity of 3200 mPa s and an NCO content of 10.4%.

Example 10
100 g of polyisocyanate precursor d, 37.2 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 9.3 g of polyol D1 having an oxyethylene group formed by the addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out for 5 hours at 110°C with stirring. The resulting polyisocyanate compound had a viscosity of 3300 mPa s and an NCO content of 11.0%.

Example 11
100 g of polyisocyanate precursor e, 15.2 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 3.8 g of polyol D1 having an oxyethylene group by addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out with stirring at 110°C for 5 hours. The resulting polyisocyanate compound had a viscosity of 3800 mPa s and an NCO content of 13.3%.

Example 12
100 g of polyisocyanate precursor f, 17.3 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 4.3 g of polyol D1 having an oxyethylene group formed by the addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out for 5 hours at 110°C with stirring. The resulting polyisocyanate compound had a viscosity of 5800 mPa s and an NCO content of 14.8%.

Example 13
100 g of the polyisocyanate precursor, 22.7 g of Polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 5.7 g of Polyol D1 having an oxyethylene group by addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out for 5 hours at 110°C with stirring. The resulting polyisocyanate compound had a viscosity of 5500 mPa s and an NCO content of 13.8%.

Example 14
100 g of polyisocyanate precursor h, 25.7 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 6.4 g of polyol D1 having an oxyethylene group by addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out for 5 hours at 110°C with stirring. The resulting polyisocyanate compound had a viscosity of 9000 mPa s and an NCO content of 15.2%.

Comparative Example 1
100 g of polyisocyanate precursor a, 33.7 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out for 5 hours at 110°C with stirring. The obtained polyisocyanate compound had a viscosity of 2700 mPa s and an NCO content of 10.1%.

Comparative Example 2
100 g of polyisocyanate precursor a, 59.6 g of polyol D1 having an oxyethylene group by addition of ethylene oxide (EXCENOL 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out for 5 hours at 110°C with stirring. The obtained polyisocyanate compound had a viscosity of 4500 mPa s and an NCO content of 9.4%.

Comparative Example 3
100 g of polyisocyanate precursor a, 18.6 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 43.3 g of polyol D1 having an oxyethylene group by addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight = 3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out for 5 hours at 110°C with stirring. The resulting polyisocyanate compound had a viscosity of 5000 mPa s and an NCO content of 8.3%.

Comparative Example 4
100 g of polyisocyanate precursor a, 36.4 g of Polyol C4 (Exenol 4030, polypropylene glycol manufactured by AGC Inc., molecular weight=4000), 24.3 g of Polyol D1 having an oxyethylene group formed by the addition of ethylene oxide (Exenol 230, polypropylene glycol manufactured by AGC Inc., molecular weight=3000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out for 5 hours at 110°C with stirring. The resulting polyisocyanate compound had a viscosity of 5000 mPa s and an NCO content of 9.7%.

Comparative Example 5
100 g of polyisocyanate precursor a, 32.9 g of polyol C1 (Exenol 1030, polypropylene glycol manufactured by AGC Inc., molecular weight = 1000), 8.2 g of polyol D3 having an oxyethylene group by addition of ethylene oxide (Preminol 7012, polypropylene glycol manufactured by AGC Inc., molecular weight = 10000), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out with stirring at 110°C for 5 hours. The resulting polyisocyanate compound had a viscosity of 4800 mPa s and an NCO content of 9.5%.

Comparative Example 6
100 g of polyisocyanate precursor a, 24.0 g of polycarbonate diol E1 (Duranol T5650E, manufactured by Asahi Kasei Corporation, molecular weight=500), and 0.02 g of 2-ethylhexyl phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were placed in the same apparatus as in Synthesis Example 1, and a urethane reaction was carried out for 5 hours at 110°C with stirring. The obtained polyisocyanate compound had a viscosity of 3,400 mPa s and an NCO content of 10.9%.

[Application Example 1]
A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with a nitrogen atmosphere, and 1,000 g of HDI and 400 g of polycaprolactone triol (OD-X-2542C, manufactured by DIC Corporation, molecular weight = 1,000) were charged. The temperature inside the reactor was raised to 100°C and the mixture was stirred for 1 hour to carry out a urethanization reaction. Using a falling thin-film distillation apparatus, unreacted HDI was removed at 160°C (27 Pa) in the first run and 150°C (13 Pa) in the second run, yielding polycaprolactone-modified adduct F. The resulting polyisocyanate F was a transparent liquid with a yield of 500 g, a viscosity of 5,500 mPa·s at 25°C, and an isocyanate content of 10.0%.
Example 1 Polyisocyanate and Polycaprolactone-modified Adduct F were mixed at a ratio of 8:2. The resulting polyisocyanate compound had a viscosity of 3760 mPa·s and an NCO content of 9.9%.

[Application Example 2]
The polyisocyanate of Example 1 and the polyisocyanate of Comparative Example 6 were mixed at a ratio of 8:2. The resulting polyisocyanate compound had a viscosity of 3,240 mPa·s and an NCO content of 10.0%.

<Evaluation method>
[Evaluation 1]
(weather resistance)
Five minutes after preparation, each polyaspartic coating composition was applied to a white enamel-coated panel with an applicator to a dry film thickness of 80 μm to 100 μm. The coating was then dried at 23°C for 7 days to obtain a cured coating. Weather resistance was evaluated using a Dew Panel Weather Meter (manufactured by Suga Test Instruments). The evaluation conditions were in accordance with JIS D0205, with an irradiation illuminance of 30 W/m2, a panel temperature of 60°C, and irradiation and condensation times cycled every 4 hours. Weather resistance was evaluated according to the following criteria.
(Evaluation criteria)
A: Gloss retention rate after 1000 hours of exposure is 80% or more. B: Gloss retention rate after 1000 hours of exposure is 70% or more but less than 80%. C: Gloss retention rate after 1000 hours of exposure is 60% or more but less than 70%. D: Gloss retention rate after 1000 hours of exposure is less than 60%.

[Evaluation 2]
(alkali resistance)
Five minutes after preparation, each polyaspartic coating composition was applied to a glass plate with an applicator so that the dry film thickness was 80 μm to 100 μm. The coating was then dried at 23°C for 7 days to obtain a cured coating. A cotton ball soaked in 10% aqueous sodium hydroxide solution was then placed on the coating for 24 hours, after which the change in appearance of the coating was visually observed, and the alkali resistance was evaluated according to the following criteria.
(Evaluation criteria)
A: No change in appearance of the coating film B: Slight change in appearance of the coating film C: Change in appearance of the coating film, slight cracks and peeling of the coating film D: Cracks and peeling of the coating film over the entire surface

[Evaluation 3]
(Coating film elongation and stress)
Five minutes after preparation, each polyaspartic coating composition was applied to a glass plate with an applicator so that the dry film thickness was 80 μm or more and 100 μm or less. The coating was then dried at 23°C for 7 days to obtain a cured coating. Measurements were performed using a tensile tester (Shimadzu Corporation, AGS 500G) at a temperature of 23°C and a humidity of 50% RH, with a pulling speed of 20 mm/min and a grip spacing of 20 mm.
(Evaluation criteria: coating elongation)
A: 300% or more B: 200% or more but less than 300% C: 100% or more but less than 200% D: Less than 100% (Evaluation criteria: coating stress)
A: 35 MPa or more B: 25 MPa or more, less than 35 MPa C: 15 MPa or more, less than 25 MPa D: less than 15 MPa

<Formulation of Polyaspartic Coating Composition>
The aspartic acid ester compound and the polyisocyanate composition obtained above were blended so that the molar ratio of the amino groups of the aspartic acid ester compound to the isocyanate groups of the polyisocyanate composition was 1.1, thereby obtaining a polyaspartic coating composition.

The main agent was "Feispartic F420" (an aspartic acid ester compound, a trade name of Feiyang Co., Ltd., an amine value of 201 mg KOH/g resin; in formula (I), X is a dicyclohexylmethylene group, R1 is an ethyl group, R2 is an ethyl group, and n is 2).
was used.

Each of the resulting coating compositions was evaluated using the methods described above. The results are shown in Tables 4 and 5.

Tables 4 and 5 confirm that the use of the polyisocyanate compositions of Examples 1 to 14 results in polyaspartic coating films with excellent weather resistance, alkali resistance, coating elongation, and stress.

According to this embodiment, when a coating composition is formed with a polyaspartic base, a polyisocyanate composition can be provided that exhibits excellent weather resistance, alkali resistance, coating elongation, and stress. Furthermore, the coating composition of this embodiment can be used as a raw material for paints, inks, adhesives, casting materials, elastomers, foams, and plastic materials. The coating composition of this embodiment is suitable for architectural paints, heavy-duty corrosion protection paints, automotive paints, paints for home information appliances, and paints for information devices such as personal computers and mobile phones.

Claims (8)

A polyisocyanate composition comprising a polyisocyanate derived from a diisocyanate (A), a monoalcohol (B), a polyether polyol (C), and a polyether polyol (D) and containing an allophanate group,
The diisocyanate (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates,
The monoalcohol (B) is a monoalcohol having 3 to 20 carbon atoms,
the polyether polyol (C) is a polyether polyol having a number average molecular weight of 400 or more and 2000 or less and having an oxypropylene group,
The polyether polyol (D) is a polyether polyol having a number average molecular weight of 2,500 or more and 6,000 or less and having an oxyethylene group and an oxypropylene group,
The polyisocyanate composition, wherein the mass% ratio of the polyether polyol (C) to the polyether polyol (D) is 50:50 or more and 90:10 or less. the polyisocyanate is a polyisocyanate derived from a polyisocyanate precursor, the polyether polyol (C), and the polyether polyol (D),
the polyisocyanate precursor is a dimer or higher of a diisocyanate derived from the diisocyanate (A) and the monoalcohol (B),
2. The polyisocyanate composition according to claim 1, wherein the polyisocyanate precursor has an isocyanurate group and an allophanate group, and the molar ratio of the isocyanurate group to the allophanate group (isocyanurate group:allophanate group) is 1:99 or more and 60:40 or less. The polyisocyanate composition according to claim 2, wherein the ratio of the number of moles of isocyanate groups in the polyisocyanate precursor to the total number of moles of hydroxyl groups in the polyether polyol (C) and the polyether polyol (D) is 3:1 or more and 9:1 or less. The polyisocyanate composition according to claim 1 or 2, wherein the total content of the polyether polyol (C) and the polyether polyol (D) is 10 to 40 mass% relative to the total amount of the polyisocyanate composition. The polyisocyanate composition according to claim 1 or 2, wherein the average number of isocyanate groups in the polyisocyanate composition is 2.3 or more and 3.0 or less. The polyisocyanate composition according to claim 1 or 2, having a viscosity at 25°C of 2,000 mPa·s or more and 8,000 mPa·s or less. A coating composition comprising a polyaspartic base and the polyisocyanate composition described in claim 1 or 2. A coating film formed by curing the coating composition described in claim 7.