JP2024097601A - Coating composition and coating - Google Patents

Abstract

[Problem] To provide a coating composition capable of producing a coating film with excellent coating film elongation, and a coating film produced using said coating composition. [Solution] A coating composition comprising a polyaspartic base agent and a polyisocyanate composition, the polyisocyanate composition comprising a polyisocyanate derived from (A), (B) and (C) and containing an allophanate group, (A) being at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, (B) being an alcohol having 1 to 20 carbon atoms, and (C) being an elastic component polyol. [Selected Figure] None

Description

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

Among polyurea paint compositions, polyaspartic paint compositions, which are aliphatic, 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 paint compositions, yellowing of the coating film due to exposure to ultraviolet light, is greatly reduced, and they have 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, and the dilution solvent in the polyaspartic coating composition can be significantly reduced, making it possible to formulate high solids or solvent-free formulations. In addition, since the amino groups of the aspartic acid ester compounds react quickly with the isocyanate groups of the aliphatic and/or alicyclic polyisocyanates, polyaspartic coating compositions have the advantage of being faster curing speeds even at room temperature and superior mechanical strength compared to polyurethane coating compositions.

For example, Patent Document 1 discloses a polyaspartic paint composition, which is an aliphatic polyurea paint composition, consisting of a polyamine component containing a secondary amino group having an aspartic acid ester skeleton and a polyisocyanate component containing an isocyanate group in an aliphatic polyisocyanate composition. This paint composition has a relatively long pot life and high coating hardness, and therefore has the characteristic that it can be applied without using a high-pressure impingement mixer spray machine.

Japanese Patent Application Publication No. 3-43472

The method disclosed in Patent Document 1 may result in a coating film with insufficient elongation.

The present invention has been made in consideration of the above circumstances, and aims to provide a coating composition capable of producing a coating film with excellent coating film elongation, and a coating film using the coating composition.

That is, the present invention includes the following aspects.
[1] A coating composition comprising a polyaspartic base and a polyisocyanate composition, the polyisocyanate composition comprising a polyisocyanate derived from (A), (B), and (C) and containing an allophanate group, the (A) being at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, the (B) being an alcohol having 1 to 20 carbon atoms, and the (C) being a polyol having a number average molecular weight of 400 to 20,000, the polyol being at least one elastic component polyol selected from a polyether polyol having at least one oxyalkylene group selected from an oxypropylene group and an oxytetramethylene group, a polyester polyol having a side chain, a polyolefin polyol, or a polycarbonate diol.
[2] The coating composition according to [1], wherein (B) is a monoalcohol having 6 to 20 carbon atoms, (C) is a polyol having a number average molecular weight of 3,500 to 20,000, and is at least one selected from the group consisting of polyether polyols having at least one oxyalkylene group selected from an oxypropylene group and an oxytetramethylene group, polyester polyols having side chains, and olefin polyols, and the polyisocyanate is substantially free of isocyanurate groups and has an allophanate group.
[3] The coating composition according to [1] or [2], wherein (A) is a polyisocyanate precursor consisting of a dimer or more of at least one kind of diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, 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 80:20 or less.
[4] The coating composition according to any one of [1] to [3], which is used for coating metals or plastics.
[5] The coating composition according to any one of [1] to [3], which is used 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.
[6] A coating film obtained by curing the coating composition according to any one of [1] to [5].

The present invention provides a coating composition capable of producing a coating film with excellent coating elongation, and a coating film using the coating composition.

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

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

〔式（Ｉ）中、Ｘはｎ価のポリアミンの第一級アミノ基を除去することによって得られたｎ価の有機基であり、Ｒ^１及びＲ^２は反応条件下でイソシアネート基に対して不活性である同じ又は異なった有機基であり、ｎは２以上の整数である。〕

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

(X)
In 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. n is an integer of 2 or more, as described below.

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

Examples of the cyclic aliphatic group include cycloalkylene groups.

The aromatic group may be, for example, an arylene group such as a phenylene group.

More specifically, from the viewpoint of the yellowing resistance of the polyaspartic coating composition of this embodiment, X is preferably a linear, branched or cyclic divalent aliphatic group having 2 to 20 carbon atoms. Examples of the linear, branched or cyclic divalent aliphatic group having 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 which 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 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.

<Polyisocyanate composition>
The coating composition of the present embodiment includes a polyisocyanate composition. The polyisocyanate composition acts as a curing agent for the coating composition.
The polyisocyanate composition comprises a polyisocyanate derived from (A), (B) and (C) and containing allophanate groups.
(A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.
(B) is an alcohol having 1 to 20 carbon atoms.
(C) is a polyol having a number average molecular weight of 400 or more and 20,000 or less, and is at least one type of elastic component polyol selected from a polyether polyol having at least one oxyalkylene group selected from an oxypropylene group and an oxytetramethylene group, a polyester polyol having a side chain, a polyolefin polyol, or a polycarbonate diol obtained by copolymerizing at least two types of diols selected from the group consisting of diols having 2 to 20 carbon atoms with a carbonate compound.

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

Aliphatic diisocyanates are compounds that have saturated aliphatic groups in their molecules. On the other hand, alicyclic diisocyanates are compounds that have cyclic aliphatic groups in their molecules. The use of 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), 1,4-diisocyanatocyclohexane, etc.

These diisocyanates may be used alone or in combination of two or more.
Among these, the diisocyanate (A) is preferably HDI, IPDI, hydrogenated xylylene diisocyanate, or hydrogenated diphenylmethane diisocyanate because of its industrial availability, and is particularly preferably HDI because of its excellent weather resistance and coating film flexibility.
Hereinafter, aliphatic diisocyanates and alicyclic diisocyanates may be collectively referred to as diisocyanates.

In the present embodiment, (A) may be a polyisocyanate precursor composed of a dimer or more of at least one kind of diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.
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 80:20 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 0:100 or more and 80:20 or less, and the upper limit is most preferably 1:99. The lower limit is more preferably 70:30 or less, and even more preferably 50:50 or less. Most preferably, it is 5/95 or less. The polyisocyanate precursor does not substantially contain isocyanurate groups and contains allophanate groups, and "substantially" here refers to a molar ratio of isocyanurate groups to allophanate groups of 5/95 or less. By having the molar ratio within the above range, compatibility, drying properties, and extensibility are superior. The molar ratio of isocyanurate groups to allophanate groups can be determined by the method described in the examples.

(B)
(B) is an alcohol having 1 to 20 carbon atoms, and is preferably a monoalcohol having 6 to 20 carbon atoms.
The number of carbon atoms in the alcohol is preferably not more than 16, more preferably not more than 12, 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.
Although the lower limit of the number of carbon atoms of the alcohol is not particularly limited, if it is 6 or more, the dissolving power in organic solvents tends to be high.

The alcohol used in the present invention may be, for example, methanol, ethanol, or butanol.
Also, the alcohol may contain an ether group in the molecule, for example, 1-butoxyethanol, 2-butoxyethanol, 1-butoxypropanol, 2-butoxypropanol, 3-butoxypropanol, ethylene glycol monobutyl ether, etc. Furthermore, the alcohol may contain an ester group, a carbonyl group, a phenyl group, for example, benzyl alcohol, etc., but a monoalcohol consisting only of a saturated hydrocarbon group is preferred. Furthermore, a monoalcohol having a branch is more preferred. Examples of such monoalcohols include 1-hexanol, 2-hexanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, 3,3,5-trimethyl-1-hexanol, tridecanol, pentadecanol, palmityl alcohol, stearyl alcohol, cyclopentanol, cyclohexanol, methylcyclohexanol, trimethylcyclohexanol, etc. 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 a lower viscosity. 2-hexanol, 2-octanol, 2-ethyl-1-hexanol, and 3,3,5-trimethyl-1-hexanol are most preferred because they also have a lower viscosity.

In this embodiment, (B) is preferably a monoalcohol having 6 to 20 carbon atoms.
The alcohol (B) may be used alone or in combination of two or more kinds.

(C)
(C) At least one elastic component polyol is used, which is selected from a) a polyether polyol having at least one oxyalkylene group selected from an oxypropylene group and an oxytetramethylene group, b) a polyester polyol having a side chain, and c) a polyolefin polyol, and d) a polycarbonate diol obtained by copolymerizing at least two diols selected from the group consisting of diols having 2 to 20 carbon atoms with a carbonate compound.

The number average molecular weight of the elastic component polyol is 400 to 20,000. In a) polyether polyol having at least one oxyalkylene group selected from an oxypropylene group and an oxytetramethylene group, b) polyester polyol having a side chain, and c) polyolefin polyol, the number average molecular weight is preferably 3,500 or more. The number average molecular weight is preferably 15,000 or less, more preferably 10,000 or less, and particularly preferably 8,000 or less. If the number average molecular weight is in the range of 400 to 20,000, the coating film obtained from the coating composition has sufficient extensibility at low temperatures and also has sufficient curing properties.

a) A polyether polyol having at least one oxyalkylene group selected from an oxypropylene group and an oxytetramethylene group is a polyether polyol having an oxypropylene group and/or an oxytetramethylene group in the molecular chain. In this case, the oxyalkylene repeating unit may contain other oxyalkylene groups, specifically, oxyethylene groups or oxystyrene groups. When the oxypropylene group and/or oxytetramethylene group having a side chain 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. In addition, among oxyalkylene groups, the oxypropylene group has particularly excellent solubility in organic solvents, and the oxytetramethylene group has excellent weather resistance.

Examples of such polyether polyols include polypropylene glycol or triol, polypropylene glycol or triol of the so-called Pluronic (registered trademark) type obtained by addition polymerization of ethylene oxide to the terminal of polypropylene glycol, polyoxypropylene polyoxyethylene copolymer diol or triol, polyoxypropylene polyoxyethylene block polymer diol or triol, polytetramethylene glycol or triol, polyoxydimethylpropylene polyoxybutylene copolymer diol or triol, polyoxydimethylpropylene polyoxybutylene block polymer diol or triol, etc. In particular, polypropylene glycol or triol, and polypropylene glycol or triol of the so-called Pluronic (registered trademark) type obtained by addition polymerization of ethylene oxide to the terminal of polypropylene glycol are preferred. The so-called Pluronic (registered trademark) type polypropylene glycol or triol obtained by addition polymerization of ethylene oxide to the terminal of polypropylene glycol are more preferred because of their excellent reactivity. Examples of such polyether polyols include Exenol 840 (trade name, manufactured by Asahi Glass Co., Ltd., polypropylene triol (ethylene oxide terminal added), number average molecular weight 6500), Exenol 510 (trade name, manufactured by Asahi Glass Co., Ltd., polypropylene glycol (ethylene oxide terminal added), number average molecular weight 4000), and Preminol 3010 (trade name, manufactured by Asahi Glass Co., Ltd., polypropylene triol, number average molecular weight 12000).

Methods for producing polyether polyols include a method of adding a single or mixture of polyhydric alcohols, polyhydric phenols, polyamines, and alkanolamines, specifically, for example, 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, to the single or mixture of the dihydric alcohols, using a strong basic catalyst such as a hydroxide of lithium, sodium, or potassium, an alcoholate, or an alkylamine, or a complex metal complex such as a metal porphyrin, a complex metal cyanide complex, a complex of a metal and a chelating agent with a tridentate or higher coordination, or a zinc hexacyanocobaltate complex, and propylene oxide, butylene oxide, and, if necessary, an alkylene oxide such as ethylene oxide or styrene oxide, to the single or mixture of the dihydric alcohols, specifically, for example, 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, to the single or mixture of the dihydric alcohols, specifically, for example, ethylene glycol, diethylene 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, to the single or mixture of the dihydric alcohols, specifically, ethylene glycol, diethylene glycol, dipropylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, and bisphenol A, trihydric alcohols such as glycerin and tri

b) A polyester polyol having a side chain is one in which the dibasic acid and/or polyhydric alcohol used as the raw material has a side chain. The side chain here is not particularly limited as long as the number average molecular weight of the polyol is 3,500 to 20,000. Examples of such compounds include polyester polyols obtained from dimer acid (adipic acid or isophthalic acid as necessary) and a diol selected from ethylene glycol, hexanediol, nonanediol, and dimer diol obtained by reducing dimer acid, and polyester polyols obtained from 3-methyl-1,5-pentanediol or 2-methyl-1,8-octanediol and adipic acid. Examples of such polyester polyols include Kuraray Polyol P-4010 (trade name, manufactured by Kuraray Co., Ltd., polyester polyol using 3-methyl-1,5-pentanediol, number average molecular weight 4,000).

The polyester polyol can be produced, for example, by a known condensation reaction of a dibasic acid such as succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, or 1,4-cyclohexanedicarboxylic acid, or a mixture thereof, with a polyhydric alcohol such as ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, trimethylpentanediol, 1,2-, 1,3-, and 1,4-cyclohexanediol, trimethylolpropane, 12-hydroxystearyldiol, diols obtained by reducing dimer acids, glycerin, pentaerythritol, 2-methylolpropanediol, or ethoxylated trimethylolpropane, or a mixture thereof. For example, the above components can be combined and heated at about 160 to 220°C. Furthermore, polycaprolactones obtained by ring-opening polymerization of lactones such as ε-caprolactone, preferably with a polyhydric alcohol having a side chain, can also be used as polyester polyols. At least one of the dibasic acid and polyhydric alcohol used as raw materials must have a side chain.

c) Polyolefin polyols are compounds obtained by polymerizing a compound having two double bonds in the molecule, such as butadiene or isoprene, to obtain a polymer having terminal OH groups, and then hydrogenating the polymer to make the remaining double bonds saturated and aliphatic. There are no particular limitations on the compound having two double bonds in the molecule used here, so long as the number-average molecular weight of the resulting polyol is between 400 and 20,000. These polyolefin polyols have excellent solubility in organic solvents.

d) Polycarbonate diol is described below. Although not particularly limited, it is preferable to use a copolymer of at least two diols (hereinafter simply referred to as "two diols") selected from the group consisting of diols having 2 to 20 carbon atoms and a carbonate compound. Polycarbonate diol is described below.

The number average molecular weight of the polycarbonate diol used in this embodiment is preferably 400 to 20,000, more preferably 400 to 2,500, and even more preferably 500 to 2,000. When the number average molecular weight is within the above range, flexibility and workability tend to be superior. The number average molecular weight can be measured by the method described in the examples.

[Method for producing polycarbonate diol]
The method for producing the polycarbonate diol is not particularly limited, but for example, it can be obtained by subjecting two kinds of diols and a carbonate compound to a dealcoholization reaction, a dephenolization reaction, or the like. Alternatively, it can be obtained by subjecting a high molecular weight polycarbonate polyol to an ester exchange reaction using two kinds of diols. The method for carrying out the polymerization reaction between the diol and the carbonate compound is not particularly limited, and known methods, such as the various methods described on pages 9 to 20 of "Polymer Reviews, Vol. 9" by H. Schnell (published by Interscience Publishers, USA, in 1964), can be used.

The above two types of diols are not particularly limited, but examples thereof include diols selected from the group consisting of aliphatic diols and aromatic diols. Among these, alkylene glycols having two hydroxyl groups and 2 to 20 carbon atoms are preferred. By using such diols, the weather resistance and chemical resistance of the coating film obtained using the polyisocyanate composition tends to be superior. Here, the "alkylene group" may be branched and may contain an alicyclic structure. These bifunctional alcohols may be used alone or in combination of two or more types.

The diol is not particularly limited, but examples thereof include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 2-ethyl-1,6-hexanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 2,2'-bis(4-hydroxyethyl) Examples include di(cyclohexyl)-propane, p-xylylenediol, p-tetrachloroxylylenediol, 1,4-dimethylolcyclohexane, bishydroxymethyltetrahydrofuran, di(2-hydroxyethyl)dimethylhydantoin, diethylene glycol, dipropylene glycol, polypropylene glycol, polytetramethylene glycol, 2,6'-dihydroxyethylhexyl ether, 2,4'-dihydroxyethyl butyl ether, 2,5'-dihydroxyethyl pentyl ether, 2,3'-dihydroxy-2',2'-dimethylethyl propyl ether, and thioglycol.

Among these, diols having 2 to 11 carbon atoms are preferred, and diols having 3 to 6 carbon atoms are more preferred. As a combination of diols, a combination of a diol having 5 carbon atoms and a diol having 6 carbon atoms, a combination of two or more isomers of a diol having 4 carbon atoms, or a combination of a diol having 4 carbon atoms and a diol having 6 carbon atoms are more preferred. By using such two types of diols, the extensibility, heat resistance, and water resistance (hydrolysis resistance) of a coating film obtained using the polyisocyanate composition tend to be more excellent. Such diols are not particularly limited, but specifically, one or a combination of two or more selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 2-methyl-1,3propanediol is preferred, and a combination of 1,6-hexanediol and 1,5-pentanediol, a combination of 1,6-hexanediol and 1,4-butanediol, and a combination of 1,4-butanediol and 2-methyl-1,3propanediol are more preferred.

The carbonate compound used in the production of polycarbonate diol is not particularly limited, but examples thereof include compounds selected from alkylene carbonate, dialkyl carbonate, diaryl carbonate, and phosgene. Specific examples of such carbonate compounds include, but are not particularly limited to, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, diphenyl carbonate, etc. Among these, diethyl carbonate is preferred in terms of ease of production.

In this embodiment, (C) is a polyol having a number average molecular weight of 400 to 20,000, and is preferably at least one selected from the group consisting of polyether polyols having at least one oxyalkylene group selected from oxypropylene groups and oxytetramethylene groups, polyester polyols having side chains, and olefin-based polyols.

The amount of the elastic component polyol used in the present invention is preferably 8 to 40% by mass relative to the polyisocyanate. The upper limit of the amount of the elastic component polyol is more preferably 35% by mass, and most preferably 30% by mass. The lower limit is more preferably 10% by mass. When the amount of the elastic component polyol is in the range of 8 to 40% by mass, sufficient extensibility can be imparted to the coating film obtained from the coating composition.

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 to the polyisocyanate compound). The chemical shift reference is set to the hydrogen signal of tetramethylsilane at 0 ppm. Measured by 1H-NMR, 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 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) at around 3.85 ppm is measured, and the molar ratio is calculated by the following formula.
Allophanate group/isocyanurate group=(signal area around 8.5 ppm)/(signal area around 3.85 ppm/6)

In addition, since uretdione compounds tend to dissociate due to heat or the like and generate HDI, it is preferable to reduce the content. The content of uretdione compounds 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 content of uretdione compounds can be determined by measuring the area ratio of the peak of a molecular weight of about 336 in gel permeation chromatography (hereinafter, GPC) using a parallax refractometer. If there is a peak near the peak of about 336 that interferes with the measurement, it can also be determined by a method of quantifying the ratio of the height of the uretdione group peak at about 1770 cm-1 to the height of the allophanate group peak at about 1720 cm-1 using FT-IR, 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. Equipment 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, 50 mg of sample is dissolved 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 created using polystyrene with molecular weights of 50,000 to 2,050 (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) manufactured by GL Sciences Inc.) and the trimers to heptamers of isocyanurates of a hexamethylene diisocyanate-based polyisocyanate composition (Duranate TPA-100 manufactured by Asahi Kasei Chemicals Corp.) (isocyanurate trimer molecular weight = 504, isocyanurate pentamer molecular weight = 840, isocyanurate heptamer molecular weight = 1,176) and HDI (molecular weight = 168) as standards.

It is not preferable for the content of biuret and other diisocyanate polymers to be high, since their solubility in organic solvents decreases. The range of the amount of biuret and other diisocyanate polymers contained in the polyisocyanate composition of the present invention is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

The isocyanate group content (hereinafter, NCO content) of the polyisocyanate used in the present invention is 5 to 20% by mass in a state that does not substantially contain a solvent or diisocyanate. The lower limit of the NCO content is preferably 6% by mass, more preferably 7% by mass, and most preferably 8% by mass. The upper limit is preferably 19% by mass, more preferably 18% by mass, and most preferably 17% by mass. If the content is in the range of 5 to 20% by mass, a polyisocyanate composition that is sufficiently soluble in an organic solvent and has sufficient crosslinking properties can be obtained.

The viscosity of the polyisocyanate used in the present invention at 25°C is preferably 100 to 20,000 mPa.s in a state substantially free of solvent or diisocyanate. The lower limit of the viscosity is more preferably 150 mPa.s, even more preferably 180 mPa.s, and even more preferably 200 mPa.s. The upper limit of the viscosity is more preferably 17,000 mPa.s, and even more preferably 15,000 mPa.s. If the viscosity is 100 mPa.s or more, a polyisocyanate composition having sufficient crosslinking properties can be obtained. If the viscosity is 20,000 mPa.s or less, a coating composition with reduced VOC components can be obtained.

The method for producing the polyisocyanate used in the present invention will now be described.
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 C6-20 monoalcohol and a diisocyanate are subjected to a urethane-forming reaction, followed by or simultaneously with an allophanate-forming reaction, and the unreacted diisocyanate is removed by purification, followed by a urethane-forming reaction with an elastic component polyol to obtain the polyisocyanate used in the present invention.
(2) A method for obtaining the polyisocyanate used in the present invention, comprising subjecting a C6-20 monoalcohol and a diisocyanate to a urethane reaction, followed by or simultaneously with an allophanate reaction, terminating the allophanate reaction with a reaction terminator, and then subjecting the resulting mixture to a urethane reaction with an elastic component polyol, and removing unreacted diisocyanate by purification.
(3) A method for obtaining the polyisocyanate used in the present invention by subjecting a C6-20 monoalcohol, a diisocyanate, and an elastic component polyol to a urethane reaction, followed by, or simultaneously with, an allophanate 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 C6-20 monoalcohol and a diisocyanate to a urethane reaction, followed by or simultaneously with an allophanate reaction, and removing the unreacted diisocyanate by purification, with a polyisocyanate compound obtained by subjecting an elastic component polyol and a diisocyanate to a urethane reaction, and if necessary, removing the unreacted diisocyanate by purification.
(5) A method for obtaining a polyisocyanate compound for use in the present invention, comprising mixing a reaction liquid obtained by subjecting a C6 to C20 monoalcohol and a diisocyanate to a urethane-formation reaction, followed by or simultaneously therewith, an allophanation reaction, and terminating the allophanation reaction with a reaction terminator, with a reaction liquid obtained by subjecting an elastic component polyol and a diisocyanate to a urethane-formation reaction, followed by or simultaneously therewith, as necessary, an allophanation reaction, and terminating the allophanation reaction with a reaction terminator, and removing the unreacted diisocyanate by purification.
The above methods (1) to (5) 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 fast at 20°C or higher, and side reactions such as uretdione formation are suppressed at 200°C or lower, and coloring is also suppressed. If the time is 10 minutes or more, the reaction can be completed, and if it is 24 hours or less, there is no problem with production efficiency and side reactions are suppressed. The urethanization reaction can be carried out without a catalyst or in the presence of a catalyst such as a tin-based or amine-based catalyst.

The allophanate 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 a temperature of 20°C or higher, the amount of allophanate catalyst is reduced, and the time required to complete the reaction is short. Furthermore, at a temperature of 200°C or lower, 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 the methods (1) to (5), it is preferable to use a catalyst, and in particular it is necessary to select a catalyst that produces a polyisocyanate with a molar ratio of allophanate groups/isocyanurate groups of 95/5 to 100/0. 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. When the amount is 0.001% by mass or more, the catalytic effect can be fully exerted. When the amount is 2% by mass or less, the allophanate formation reaction can be easily controlled.

In the present invention, the method of adding the allophanate catalyst is not limited. For example, it may be added before the production of a compound containing a urethane group, i.e., before the urethanization reaction of a diisocyanate and an organic compound having a hydroxyl group, during the urethanization reaction of a diisocyanate and an organic compound having a hydroxyl group, or after the production of a compound containing a urethane group. In addition, as a method of addition, the required amount of the allophanate catalyst may be added all at once, or may be added in several divided portions. Alternatively, a method of continuous addition at a constant addition rate may be adopted.

The urethanization reaction and allophanate 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 the solvent.

Catalysts for deriving polyisocyanates containing isocyanurate groups from diisocyanate monomers include commonly used isocyanurate reaction catalysts. The isocyanurate reaction catalyst is not particularly limited, but is preferably one that is generally basic, such as (1) hydroxides of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium; organic weak acid salts such as acetate, octylate, myristate, and benzoate; (2) hydroxides of hydroxyalkylammonium such as trimethylhydroxyethylammonium, trimethylhydroxypropylammonium, triethylhydroxyethylammonium, and triethylhydroxypropylammonium; organic weak acid salts 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 such as 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 compounds such as tributylphosphine.

Among these, from the viewpoint of preventing the 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 isocyanurate reaction catalyst is preferably 10 ppm by mass or more and 1000 ppm by mass or less based on 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 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 setting the isocyanurate reaction temperature to 120° C. or less, coloration of the polyisocyanate tends to be effectively suppressed.
The processes of the urethanization reaction, allophanate formation reaction and isocyanurate formation in the present invention can be followed by measuring the NCO content of the reaction liquid or measuring the refractive index.

The allophanate reaction and the isocyanurate reaction can be stopped by cooling to room temperature or by adding a reaction terminator. When a catalyst is used, it is preferable to add a reaction terminator because it can suppress side reactions. The amount of the 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. At 0.25 times or more, complete deactivation is possible. At 20 times or less, storage stability is good. Any reaction terminator that can deactivate the catalyst may be used. Examples of reaction terminators include compounds that exhibit phosphoric acidity such as phosphoric acid and pyrophosphoric acid, monoalkyl or dialkyl esters of phosphoric acid and pyrophosphoric acid, halogenated acetic acids such as monochloroacetic acid, benzoyl chloride, sulfonic acid esters, sulfuric acid, sulfate esters, ion exchange resins, and chelating agents. From an industrial point of view, 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 include monoethyl and diethyl phosphates, monobutyl and dibutyl phosphates, mono(2-ethylhexyl) and di(2-ethylhexyl) phosphates, monodecyl and didecyl phosphates, monolauryl and dilauryl phosphates, monotridecyl and ditridecyl phosphates, monooleyl and dioleyl phosphates, and mixtures thereof.
It is also possible to use an adsorbent such as silica gel or activated carbon as a terminator. In this case, the amount of the adsorbent added is preferably 0.05 to 10% by mass based on the diisocyanate used in the reaction.

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

(Optional ingredients)
The coating composition of the present embodiment may further contain an antioxidant in addition to the polyisocyanate composition and the main agent. The antioxidant may be added at the stage of producing 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 include, but are not limited to, Adeka STAB LA-52 (trade name), Adeka STAB LA-68 (trade name), Adeka STAB LA-77Y (trade name) (each manufactured by Adeka Corporation), Tinuvin 622 (trade name), Tinuvin 765 (trade name), Tinuvin 770 (trade name), Tinuvin 791 (trade name) (each manufactured by BASF), etc.

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

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 (product name) (manufactured by BASF Corporation).

Cyanoacrylate-based antioxidants are not particularly limited, but examples include Uvinul 3035 (product name) (manufactured by BASF Corporation).

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 hydroxylamine-based antioxidants.

Hindered phenol-based antioxidants include, but are not limited to, dibutyl hydroxytoluene (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), Adeka STAB AO-80 (trade name) (each manufactured by Adeka Corporation), and the like.

Examples of phosphorus-containing antioxidants include, but are not limited to, Adeka STAB PEP-8 (trade name), Adeka STAB HP-10 (trade name), Adeka STAB 1178 (trade name), Adeka STAB C (trade name) (each manufactured by Adeka Corporation), Irgafos 168, Irgafos 38 (trade name) (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 (product name) (manufactured by BASF Corporation).

Vitamin E-based antioxidants include, but are not limited to, Irganox E201 (product name) (manufactured by BASF Corporation), for example.

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

Among them, the antioxidant is preferably at least one selected from the group consisting of hindered phenol-based antioxidants, hindered amine-based 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 the present embodiment is useful as a solvent-based coating composition, and can be obtained by the production method described below.

When the coating composition of the present embodiment is a solvent-based coating composition, for example, first, add the polyisocyanate composition as a curing agent to the polyaspartic base or its solvent dilution, if necessary, to which various additives are added. Next, if necessary, add a solvent to adjust the viscosity. Then, by stirring by hand or using a stirring device such as a mixer, a solvent-based coating composition can be obtained.
In addition, the order of mixing the base component mainly composed of a polyaspartic base agent, 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 hardener component is mixed at the painting site into the base component, which has already been mixed with various additives.
2) At the painting site, the base component and the hardener component are mixed, and then various additives are mixed in.
3) The base 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.

<Applications 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, and inorganic materials, and is particularly suitable as a coating for metals or plastics.
The coating composition of the present embodiment is suitable, for example, as a coating for architecture, a heavy-duty corrosion protection coating, a coating for automobiles, a coating for information appliances, and a coating for information appliances 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 the present embodiment is obtained by curing the above-mentioned coating composition, and always exhibits stable quality and is excellent in water resistance, weather resistance, flexibility and adhesion.
Furthermore, the coating film of the present embodiment is obtained by curing the above-mentioned coating composition, and always exhibits stable quality and is excellent in acid resistance and coating film elongation.

<Method of producing coating film>
The method for producing a coating film of this embodiment is a method including a step of curing the above-mentioned coating composition.

The coating film of the present embodiment can be produced by applying the coating composition onto 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, or the like, and then curing the composition.
Examples of the substrate include the same molded articles made of the materials exemplified above in "<Uses of the coating composition>".

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

The molar ratio of allophanate groups to isocyanurate groups was determined using 1H-NMR (FT-NMR DPX-400 manufactured by Bruker) from the area ratio of the signal of hydrogen on the nitrogen atom of the allophanate group at about 8.5 ppm to the signal of hydrogen of the methylene group adjacent to the nitrogen atom of the isocyanurate ring of the isocyanurate group at about 3.8 ppm.
The NCO content was determined by reacting the isocyanate groups with an excess of 2N amine followed by back titration with 1N hydrochloric acid.

The viscosity was measured at 25° C. using an E-type viscometer (Tokimec Co., Ltd.) A standard rotor (1°34′×R24) was used, and the rotation speed was as follows.
100 rpm (less than 128 mPa.s)
50 rpm (for 128 mPa.s to 256 mPa.s)
20 rpm (for 256 mPa.s to 640 mPa.s)
10 rpm (for 640 mPa.s to 1280 mPa.s)
5 rpm (for 1280 mPa.s to 2560 mPa.s)

(Average number of isocyanate functional groups (average NCO number))
Using the polyisocyanate composition before the addition of n-butyl acetate as a sample, the average number of isocyanate functional groups (average NCO number) was calculated according to the following formula.

Average isocyanate (NCO) number = (Mn x NCO% x 0.01) / 42

In the formula, "NCO%" represents the isocyanate group content, and the value obtained in (Isocyanate group content (NCO%)) described below is used. Also, "Mn" represents the number average molecular weight, and was calculated as the molecular weight based on polystyrene by performing GPC measurement under the measurement conditions shown below.

(Measurement condition)
Equipment: HLC-8320GPC (TOSOH)
Column: TSKgel Super H2500 x 1 (TOSOH)
TSKgel Super H4000 x 1 bottle (TOSOH)
TSKgel Super H5000 x 1 bottle (TOSOH)
TSKgel Super H6000 x 1 bottle (TOSOH)
Carrier: tetrahydrofuran Flow rate: 0.6 mL/min Sample concentration: 1.0% by mass
Injection volume: 20 μL
Temperature: 40°C
Detection method: Differential refractometer

(Isocyanate group content (NCO%))
The NCO% was determined by neutralizing the isocyanate groups with an excess of 2N amine, followed by back titration with 1N hydrochloric acid.

[Synthesis Example 1A]
The inside of a four-neck flask equipped with a stirrer, a thermometer, and a condenser was replaced with nitrogen, 1200 g of HDI and 93 g of 2-ethyl-1-hexanol were charged, and a urethane reaction was carried out at 90°C for 1 hour under stirring. After heating to 130°C, 0.42 g of a 20% mineral spirit solution of 2-ethylhexanoic acid zirconyl was added as an allophanate catalyst. After 60 minutes, when the increase in refractive index of the reaction solution reached 0.0055, 3.9 g of a 10% solids 2-ethyl-1-hexanol solution of pyrophosphoric acid (manufactured by Taihei Chemical Industry, product name "Phosphoric acid (105%)" diluted with 2-ethyl-1-hexanol) was added to stop the reaction. After filtering the reaction solution, 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.
The obtained polyisocyanate compound was a transparent liquid, with a yield of 330 g, a viscosity of 100 mPa.s, and an NCO content of 17.4%. NMR analysis revealed that the molar ratio of allophanate groups to isocyanurate groups was 97/3. The obtained polyisocyanate was designated as polyisocyanate composition A-1.

[Synthesis Example 2A]
In a device similar to that of Synthesis Example 1A, 1000 g of HDI and 100 g of 2-ethyl-1-hexanol were charged, and a urethane reaction was carried out at 90° C. for 1 hour with stirring. 0.36 g of a 10% solids n-butanol solution of tetramethylammonium caprate was added as an allophanate and isocyanurate catalyst. When the NCO content of the refractive index of the reaction solution reached 35.8%, 0.58 g (4.0 times the moles of the catalyst) of an 85% solids aqueous solution of phosphoric acid was added to stop the reaction. After filtering the reaction solution, unreacted HDI was removed by the same method as in Synthesis Example 1A.
The obtained polyisocyanate compound was a transparent liquid, with a yield of 480 g, a viscosity of 450 mPa.s, and an NCO content of 17.7%. NMR analysis revealed that the molar ratio of allophanate groups to isocyanurate groups was 63/37. The obtained polyisocyanate was designated polyisocyanate composition A-2.

[Synthesis Example 3A]
In a device similar to that of Synthesis Example 1A, 600 g of HDI, 600 g of isophorone diisocyanate, and 82 g of 2-ethyl-1-hexanol were charged, and a urethane reaction was carried out at 90° C. for 1 hour under stirring. After heating to 130° C., 0.42 g of a 20% mineral spirit solution of 2-ethylhexanoic acid zirconyl was added as an allophanate catalyst. When the refractive index of the reaction solution increased to 0.0053, 3.9 g of a 2-ethyl-1-hexanol solution of pyrophosphoric acid with a solid content of 10% (manufactured by Taihei Chemical Industry Co., Ltd., product name "Phosphoric acid (105%)" diluted with 2-ethyl-1-hexanol) was added to stop the reaction. After filtering the reaction solution, unreacted HDI and isophorone diisocyanate were removed by the same method as in Synthesis Example 1A.
The obtained polyisocyanate compound was a transparent liquid, with a yield of 320 g, a viscosity of 230 mPa.s, and an NCO content of 16.3%. NMR analysis revealed that the molar ratio of allophanate groups to isocyanurate groups was 97/3. The obtained polyisocyanate was designated as polyisocyanate composition A-3.

[Synthesis Example 4A]
100 g of the polyisocyanate polyisocyanate composition A-1 obtained in Synthesis Example 1A and 39 g of Exenol 510 (trade name, polypropylene glycol (EO-terminated type), number average molecular weight = 4000, manufactured by Asahi Glass Co., Ltd.) were added to an apparatus similar to that used in Synthesis Example 1A, and a urethane reaction was carried out at 120°C for 6 hours with stirring. The obtained polyisocyanate compound had a viscosity of 700 mPa.s and an NCO content of 10.8%. NMR measurement revealed that the molar ratio of allophanate groups/isocyanurate groups was 97/3. This polyisocyanate was designated polyisocyanate composition A-4.

[Synthesis Example 5A]
In a device similar to that of Synthesis Example 1A, 1000 g of HDI, 100 g of 2-ethyl-1-hexanol, and 80 g of Exenol 840 (trade name, polypropylene glycol (terminal EO-added type), number average molecular weight = 6500, manufactured by Asahi Glass Co., Ltd.) were charged, and a urethane reaction was carried out for 1 hour at 130 ° C. with stirring. 0.50 g of a 20% solids solution of 2-ethylhexanoic acid zirconyl in mineral spirits (manufactured by Nippon Kagaku Sangyo Co., Ltd., trade name "Nikka Octix Zirconium 12%" diluted with mineral spirits) was added as an allophanate catalyst. When the refractive index of the reaction solution increased to 0.007, 4.6 g (14.0 times the moles of the catalyst) of a 10% solids solution of pyrophosphoric acid in 2-ethyl-1-hexanol (manufactured by Taihei Chemical Industry Co., Ltd., trade name "Phosphoric acid (105%)" diluted with 2-ethyl-1-hexanol) was added to stop the reaction. The reaction solution was filtered, and then unreacted HDI was removed in the same manner as in Synthesis Example 1A.
The polyisocyanate obtained was a transparent liquid, with a yield of 400 g, a viscosity of 420 mPa.s, and an NCO content of 13.5%. NMR analysis revealed that the molar ratio of allophanate groups to isocyanurate groups was 97/3. The polyisocyanate obtained was designated polyisocyanate composition A-5.

[Synthesis Example 6A]
Into an apparatus similar to that of Synthesis Example 1A, 700 g of HDI, 60 g of 3,3,5-trimethyl-1-hexanol, and 50 g of Exenol 510 (trade name, polypropylene glycol (terminal EO added type), number average molecular weight = 4000, manufactured by Asahi Glass Co., Ltd.) were charged, and a urethane reaction was carried out for 1 hour at 90°C with stirring. After raising the temperature to 130°C, 0.20 g of a mineral spirit solution with a solid content of 20% zirconyl 2-ethylhexanoate (manufactured by Nippon Chemical Industry Co., Ltd., trade name "Nikka Octix Zirconium 12%" diluted with mineral spirit) was added as an allophanate formation catalyst. When the increase in the refractive index of the reaction solution reached 0.007, 1.8 g (14.0 times the moles of the catalyst) of a 2-ethyl-1-hexanol solution of pyrophosphoric acid with a solid content of 10% (manufactured by Taihei Chemical Industry Co., Ltd., product name "Phosphoric Acid (105%)" diluted with 2-ethyl-1-hexanol) was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed in the same manner as in Synthesis Example 1A.
The polyisocyanate obtained was a transparent liquid, with a yield of 240 g, a viscosity of 720 mPa.s, and an NCO content of 10.5%. NMR analysis revealed that the molar ratio of allophanate groups to isocyanurate groups was 97/3. The polyisocyanate obtained was designated polyisocyanate composition A-6.

[Synthesis Example 7]
300 g of Polyisocyanate A-5 obtained in Synthesis Example 5A and 19 g of Polyisocyanate A-2 obtained in Synthesis Example 2A were mixed. The resulting polyisocyanate had a viscosity of 430 mPa.s and an NCO content of 13.7%. NMR measurement revealed that the molar ratio of allophanate groups/isocyanurate groups was 95/5. This polyisocyanate is designated as Polyisocyanate Composition A-7.

[Synthesis Example 8A]
100 g of the polyisocyanate composition A-3 obtained in Synthesis Example 3 and 25 g of Exenol 510 (trade name, polypropylene glycol (EO-terminated type), number average molecular weight = 4000, manufactured by Asahi Glass Co., Ltd.) were added to an apparatus similar to that of Synthesis Example 1A, and a urethane reaction was carried out at 120°C for 6 hours with stirring. The obtained polyisocyanate compound had a viscosity of 900 mPa.s and an NCO content of 11.0%. NMR measurement revealed that the molar ratio of allophanate groups/isocyanurate groups was 97/3. This polyisocyanate is designated as polyisocyanate composition A-8.

[Synthesis Example 9A]
Polyisocyanate composition A-9 was prepared by adding 1 part by mass of TINUVIN765 to the total amount of polyisocyanate A-4 obtained in Synthesis Example 4A.

[Synthesis Example 10A]
Into the same apparatus as in Synthesis Example 1A, 1000 g of HDI, 100 g of 2-ethyl-1-hexanol, and 80 g of Exenol 510 (trade name, polypropylene glycol (terminal EO-added type), number average molecular weight = 4000, manufactured by Asahi Glass Co., Ltd.) were charged, and a urethane reaction was carried out for 1 hour at 90°C with stirring. 0.55 g of a 20% solids solution of bismuth 2-ethylhexanoate in mineral spirits (manufactured by Nippon Kagaku Sangyo Co., Ltd., trade name "Nikka Octix Bismuth 25%" diluted with mineral spirits) was added as an allophanate/isocyanurate catalyst. When the increase in the refractive index of the reaction solution reached 0.01, 2.3 g (4.0 times the moles relative to the catalyst) of 2-ethylhexyl phosphoric acid ester (manufactured by Johoku Chemical Industry Co., Ltd., trade name "JP-508") was added to stop the reaction. After filtering the reaction solution, unreacted HDI was removed by the same method as in Synthesis Example 1A.
The polyisocyanate obtained was a transparent liquid, with a yield of 500 g, a viscosity of 450 mPa.s, and an NCO content of 14.7%. NMR analysis revealed that the molar ratio of allophanate groups to isocyanurate groups was 85/15. The polyisocyanate obtained is designated as polyisocyanate composition A-10.

[Synthesis Example 11A]
Into an apparatus similar to that used in Synthesis Example 1A, 53 g of polyisocyanate composition A-1 obtained in Synthesis Example 1A, 87 g of polyisocyanate A-2 obtained in Synthesis Example 2A, and 60 g of Exenol 840 (trade name, polypropylene glycol (EO-terminated type), number average molecular weight = 6500, manufactured by Asahi Glass Co., Ltd.) were charged, and a urethane reaction was carried out for 5 hours at 120°C with stirring. The resulting polyisocyanate had a viscosity of 1200 mPa.s and an NCO content of 13.2%. NMR measurement revealed that the molar ratio of allophanate groups/isocyanurate groups was 76/24. This polyisocyanate was designated polyisocyanate composition A-11.

<Production of Coating Composition>
The base agent used was "Desmophen 1420" (an aspartic acid ester compound, a product name of Covestro, an amine value of 201 mg KOH/g resin). In Table 1, the aspartic acid ester compound is referred to as "PAE".
As the curing agent, the polyisocyanate compositions A-4 to A-11 obtained above were used.
The base agent and the curing agent were mixed in a ratio of NCO/NH = 1.1, and the paint solids content was adjusted to 90 mass% with n-butyl acetate to obtain the paint compositions of Examples 1A to 5A and Comparative Examples 1A to 2A, respectively.

The impact resistance and coating elongation of each of the resulting coating compositions were evaluated using the methods described below. The results are shown in Table 1.

[Impact resistance]
Each coating composition was applied to a mild steel plate using an applicator so that the film thickness after drying was 40 μm, and the coating film was cured for one week under conditions of 20° C. and 63% humidity. After that, the impact resistance of the coated plate was evaluated. The impact resistance was evaluated by measuring the height at which the coating film broke using a 1/4 iron core and a weight of 1000 g.
(Evaluation criteria)
◎: Higher than 50 cm.
○: Higher than 40 cm and less than 50 cm.
×: Less than 40 cm.

[Coating film elongation]
Each coating composition was applied with an applicator to a film thickness of 50 μm after drying. After application, each coating film was cured for 7 days under conditions of 23° C. and 50% humidity to obtain each coating film. A tensile test was performed using the obtained coating film. The elongation of the coating film was measured at a temperature of 23° C., a humidity of 50%, and a temperature of −20° C. using a tensile tester (Shimadzu Corporation, AGS 500G) at a tensile speed of 20 mm/min and a grip interval of 20 mm. The coating film elongation of each coating film was evaluated according to the following evaluation criteria.
(Evaluation criteria)
⊚: Coating elongation is 200% or more.
◯: Coating elongation is 100% or more and less than 200%.
×: Coating elongation is 0% or more and less than 100%.

As shown in the above results, the coating films formed using the coating compositions of Examples 1A to 6A had excellent impact resistance and coating elongation.

<Number average molecular weight of polycarbonate diol>
The number average molecular weight of the polycarbonate diols obtained in Synthesis Examples 7B to 14B described later was calculated according to the following formula.
Number average molecular weight=2/(OH value of polycarbonate diol×10/56.11)

<Polycarbonate diol OH value>
The OH value of the polycarbonate diol obtained in Synthesis Examples 7B to 14B was determined according to JIS K 0070:1992. Specifically, 12.5 g of acetic anhydride was diluted with 50 mL of pyridine to prepare an acetylation reagent. Next, 2.5 to 5.0 g of the polycarbonate diol produced in the Synthesis Examples was precisely weighed into a 100 mL eggplant flask. 5 mL of the acetylation reagent and 10 mL of toluene were added to the eggplant flask using a whole pipette, and then a cooling tube was attached and the mixture was heated and stirred at 100°C for 1 hour. 2.5 mL of distilled water was added using a whole pipette, and the mixture was further heated and stirred for 10 min. After cooling for 2 to 3 minutes, 12.5 mL of ethanol was added, and 2 to 3 drops of phenolphthalein were added as an indicator, followed by titration with 0.5 mol/L ethanolic potassium hydroxide.

On the other hand, as a blank test, 5 mL of the acetylation reagent, 10 mL of toluene, and 2.5 mL of distilled water were placed in a 100 mL recovery flask, heated and stirred for 10 minutes, and then titrated in the same manner. Based on this result, the OH value was calculated using the following formula.
OH number (mg-KOH/g) = {(b-a) x 28.05 x f}/e
a: titer of sample (mL)
b: Blank titer (mL)
e: sample weight (g)
f: factor of titrant

<Polycarbonate diol copolymer composition>
The copolymer composition of the polycarbonate diol was measured as follows.
1 g of sample was taken in a 100 ml eggplant flask, 30 g of ethanol, and 4 g of potassium hydroxide were added, and the mixture was reacted at 100°C for 1 hour. After cooling to room temperature, 2 to 3 drops of phenolphthalein were added as an indicator, and the mixture was neutralized with hydrochloric acid. After cooling in a refrigerator for 1 hour, the precipitated salt was removed by filtration, and the mixture was analyzed by gas chromatography. The analysis was performed using a gas chromatograph GC-14B (manufactured by Shimadzu Corporation) equipped with a DB-WAX (manufactured by J&W) column, with diethylene glycol diethyl ester as the internal standard and an FID detector. The temperature rise profile of the column was held at 60°C for 5 minutes, and then heated to 250°C at 10°C/1 minute.

<Synthesis Example of Polyisocyanate Precursor>
[Synthesis Example 1B]
(Synthesis of polyisocyanate precursor a)
The inside of a four-neck flask equipped with a stirrer, a thermometer, and a cooling tube was replaced with nitrogen. 1200 g of HDI and 0.6 g of isobutanol were charged, and the temperature inside the reactor was set to 80° C. and stirred for 2 hours to carry out a urethane reaction. Then, 0.1 g of tetramethylammonium caprylate was added as an isocyanurate catalyst to carry out an isocyanurate reaction, and when the conversion rate reached 12%, 0.2 g of phosphoric acid was added to stop the reaction. After filtering the reaction liquid, a falling thin film distillation apparatus was used to remove unreacted HDI at 160° C. (27 Pa) for the first time and at 150° C. (13 Pa) for the second time, thereby obtaining a polyisocyanate precursor a. The obtained polyisocyanate precursor a was a pale yellow transparent liquid, with a yield of 230 g, a viscosity at 25° C. of 400 mPa·s, and an isocyanate content of 22.6%. 1H-NMR measurement revealed that the molar ratio of isocyanurate groups to allophanate groups was 78/22.

[Synthesis Example 2B]
(Synthesis of polyisocyanate precursor b)
In a device similar to that of Synthesis Example 1B, 1000 g of HDI and 30 g of 2-ethylhexanol were charged, and the temperature inside the reactor was set to 80° C. and stirred for 1 hour to carry out a urethane reaction. With the temperature inside the reactor maintained at 80° C., 0.36 g of a 10% solids n-butanol solution of tetramethylammonium caprate was added as an allophanate and isocyanurate catalyst. After stirring for another 3 hours, 0.58 g of an 85% solids aqueous solution of phosphoric acid was added to stop the reaction. After filtering the reaction solution, unreacted HDI was removed in the same manner as in Synthesis Example 1B to obtain polyisocyanate precursor b. The obtained polyisocyanate precursor b was a pale yellow transparent liquid, with a yield of 300 g, a viscosity at 25° C. of 450 mPa·s, and an isocyanate content of 20.6%. 1H-NMR measurement revealed that the molar ratio of isocyanurate groups to allophanate groups was 65/35.

[Synthesis Example 3B]
(Synthesis of polyisocyanate precursor c)
In a device similar to that of Synthesis Example 1B, 1000 g of HDI and 30 g of 2-ethylhexanol were charged, and the temperature inside the reactor was set to 90° C. and stirred for 1 hour to carry out a urethane reaction. With the temperature inside the reactor maintained at 90° C., 0.6 g of a 5% solids isobutanol solution of tetramethylammonium caprate was added as an allophanate and isocyanurate catalyst. After stirring for another 2 hours, 0.06 g of an 85% aqueous solution of phosphoric acid was added to stop the reaction. After filtering the reaction solution, unreacted HDI was removed in the same manner as in Synthesis Example 1B to obtain a polyisocyanate precursor c. The obtained polyisocyanate precursor c was a transparent liquid, with a yield of 210 g, a viscosity at 25° C. of 340 mPa·s, and an isocyanate content of 20.3%. When 1H-NMR was measured, the molar ratio of isocyanurate groups/allophanate groups was 50/50.

[Synthesis Example 4B]
(Synthesis of polyisocyanate precursor d)
In the same apparatus as in Synthesis Example 1B, 561.9 g of HDI and 38.1 g of isobutanol were charged, and the temperature in the reactor was set to 90° C. and stirred for 1 hour to carry out a urethane reaction. After raising the temperature in the reactor to 120° C., 0.28 g of a 20% solids solution of 2-ethylhexanoic acid zirconyl in mineral spirits was added as an allophanate catalyst. After stirring for another 60 minutes, 0.097 g of an 85% aqueous solution of phosphoric acid was added to stop the reaction. After filtering the reaction liquid, unreacted HDI was removed in the same manner as in Synthesis Example 1B to obtain polyisocyanate precursor d. The obtained polyisocyanate precursor d was a pale yellow transparent liquid, with a yield of 203 g, a viscosity at 25° C. of 130 mPa·s, and an isocyanate content of 18.8%. When 1H-NMR was measured, the molar ratio of isocyanurate groups/allophanate groups was 3/97.

[Synthesis Example 5B]
(Synthesis of polyisocyanate precursor e)
In a device similar to that of Synthesis Example 1B, 500 g of HDI was charged, the temperature inside the reactor was set to 60° C., and 0.08 g of tetramethylammonium caprylate was added under stirring. The reaction was allowed to proceed at a reactor temperature of 60° C., and after 4 hours, the isocyanate group content and refractive index of the reaction solution were measured, and when the conversion rate to polyisocyanate reached 20%, 0.2 g of phosphoric acid was added to stop 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 obtained polyisocyanate precursor e was a pale yellow transparent liquid, with a yield of 102 g, a viscosity at 25° C. of 1400 mPa·s, and an isocyanate content of 23.4%. When 1H-NMR was measured, the molar ratio of isocyanurate group/allophanate group was 100/0.

[Synthesis Example 6B]
(Synthesis of polyisocyanate precursor f)
Polyisocyanate precursors d and e synthesized in Synthesis Examples 4B and 5B were mixed in a ratio of d/e = 54/46 (mass ratio) to obtain polyisocyanate precursor f. Polyisocyanate precursor f was a pale yellow transparent liquid with a viscosity of 770 mPa s at 25°C and an isocyanate content of 21.3%. When 1H-NMR was measured, the molar ratio of isocyanurate groups/allophanate groups was 50/50.

[Synthesis Example 7B]
(Synthesis of polyisocyanate precursor g)
The inside of a four-neck flask equipped with a stirrer, a thermometer, and a cooling tube was replaced with nitrogen, 1000 g of HDI was charged, and 0.1 g of tetramethylammonium caprylate, 1.0 g of isobutanol, and 5.0 g of 2-ethylhexanol were added simultaneously as catalysts while stirring at 60°C. After 4 hours, when the conversion rate to polyisocyanate reached 25% by measuring the refractive index of the reaction solution, 0.2 g of phosphoric acid was added to stop the reaction. Thereafter, the reaction solution was filtered, and unreacted HDI was removed by a thin-film distillation apparatus to obtain polyisocyanate precursor g. The obtained polyisocyanate precursor g was a pale yellow transparent liquid, with a yield of 253 g, a viscosity at 25°C of 800 mPa·s, and an isocyanate content of 22.8%. When 1H-NMR was measured, the molar ratio of isocyanurate groups/allophanate groups was 89/11.

<Synthesis Example of Polycarbonate Diol>
[Synthesis Example 8B]
(Synthesis of Polycarbonate Diol A)
382 g of 1,5-pentanediol, 433 g of 1,6-hexanediol, and 650 g of ethylene carbonate were charged into a 2 L separable flask equipped with a stirrer, a thermometer, and a vacuum jacketed Oldershaw flask with a reflux head on top, and after stirring and dissolving at 70°C, 0.015 g of lead acetate trihydrate was added as a catalyst. The flask was heated in an oil bath set at 175°C, and the reaction was carried out for 12 hours at an internal temperature of 140°C and a vacuum degree of 1.0 to 1.5 kPa while removing a part of the fraction from the reflux head at a reflux ratio of 4. The Oldershaw flask was then replaced with a simple distillation apparatus, and the flask was heated in an oil bath set at 180°C, and the internal temperature of the flask was reduced to 140 to 150°C and the vacuum degree to 0.5 kPa, and the diol and ethylene carbonate remaining in the separable flask were removed. Thereafter, the oil bath was set to 185°C, and the reaction was continued for another 4 hours at an internal temperature of the flask of 160-165°C while removing the diol produced. A viscous liquid was obtained at room temperature from this reaction. The OH value of the obtained polycarbonate diol A was 56.1 (molecular weight 2000), and the copolymerization composition was 1,5-pentanediol/1,6-hexanediol=50/50 (molar ratio).

[Synthesis Example 9B]
(Synthesis of Polycarbonate Diol B)
Polycarbonate diol B was synthesized in the same manner as in Synthesis Example 8B, except that the Oldershaw distillation apparatus was replaced with a simple distillation apparatus, the oil bath was set to 185°C, the internal temperature of the flask was set to 160-165°C, and the time for removing the produced diol was set to 2.3 hours. The OH value of the obtained reaction product was 113.2 (molecular weight 1000), and the copolymer composition was 1,5-pentanediol/1,6-hexanediol=50/50 (molar ratio).

[Synthesis Example 10B]
(Synthesis of Polycarbonate Diol C)
Polycarbonate diol C was synthesized in the same manner as in Synthesis Example 8B, except that the Oldershaw distillation apparatus was replaced with a simple distillation apparatus, the oil bath was set to 185°C, the internal temperature of the flask was set to 160-165°C, and the time for removing the produced diol was set to 1.5 hours. The OH value of the obtained reaction product was 224.4 (molecular weight 500), and the copolymer composition was 1,5-pentanediol/1,6-hexanediol=50/50 (molar ratio).

[Synthesis Example 11B]
(Synthesis of Polycarbonate Diol D)
Polycarbonate diol D was synthesized in the same manner as in Synthesis Example 8B, except that 330 g of 2-methyl-1,3-propanediol and 330 g of 1,4-butanediol were used instead of 382 g of 1,5-pentanediol and 433 g of 1,6-hexanediol. The OH value of the resulting reaction product was 56.1 (molecular weight 2000), and the copolymer composition was 2-methyl-1,3-propanediol/1,4-butanediol=50/50 (molar ratio).

[Synthesis Example 12B]
(Synthesis of Polycarbonate Diol E)
In Synthesis Example 8B, 330 g of 2-methyl-1,3-propanediol and 330 g of 1,4-butanediol were used instead of 382 g of 1,5-pentanediol and 433 g of 1,6-hexanediol, the Oldershaw was replaced with a simple distillation apparatus, the oil bath was set to 185° C., the internal temperature of the flask was set to 160 to 165° C., and the time for removing the produced diol was set to 2.0 hours, but in the same manner, polycarbonate diol E was synthesized. The OH value of the obtained reaction product was 141.1 (molecular weight 800), and the copolymerization composition was 2-methyl-1,3-propanediol/1,4-butanediol=50/50 (molar ratio).

[Synthesis Example 13B]
(Synthesis of Polycarbonate Diol F)
Polycarbonate diol F was synthesized in the same manner as in Synthesis Example 8B, except that 462 g of 1,4-butanediol and 260 g of 1,6-hexanediol were used instead of 382 g of 1,5-pentanediol and 433 g of 1,6-hexanediol. The OH value of the resulting reaction product was 56.1 (molecular weight 2000), and the copolymer composition was 1,4-butanediol/1,6-hexanediol=70/30 (molar ratio).

[Synthesis Example 14B]
(Synthesis of Polycarbonate Diol G)
Polycarbonate diol G was synthesized in the same manner as in Synthesis Example 8B, except that 594 g of 1,4-butanediol and 87 g of 1,6-hexanediol were used instead of 382 g of 1,5-pentanediol and 433 g of 1,6-hexanediol. The OH value of the resulting reaction product was 56.1 (molecular weight 2000), and the copolymer composition was 1,4-butanediol/1,6-hexanediol=90/10 (molar ratio).

[Synthesis Example 15B]
(Synthesis of Polycarbonate Diol H)
A 2L reactor equipped with a stirrer was charged with 520g of 1,6-hexanediol and 410g of ethylene carbonate, then 0.009g of lead acetate trihydrate was added as a catalyst, and the reactor was connected to a fractionation column filled with structured packing. The reactor was immersed in an oil bath at 210°C, and the reaction was carried out for 20 hours at a reaction temperature of 170°C while extracting a part of the distillate. Thereafter, the reactor was directly connected to a condenser, and the temperature of the oil bath was lowered to 190°C, after which the pressure was gradually lowered and the reaction was carried out for another 8 hours. From this reaction, 517g of aliphatic polycarbonate diol H, which is a white solid at room temperature, was obtained. The OH value of the obtained reaction product was 56.1 (molecular weight 2000).

<Synthesis Example of Polyisocyanate Composition>
[Polyisocyanate Composition 1B]
The polyisocyanate precursor a of Synthesis Example 1B was used as the polyisocyanate precursor, and the polycarbonate diol A of Synthesis Example 8 was used as the copolymerized polycarbonate diol. These were mixed in a ratio of 5 equivalents of isocyanate groups in the polyisocyanate precursor to 1 equivalent of active hydrogen in the polycarbonate diol, and reacted at 100° C. The reaction was terminated when the isocyanate content in the reaction solution reached 8.7%, to obtain polyisocyanate composition 1B.

[Polyisocyanate composition 2B]
A polyisocyanate composition 2B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor b of Synthesis Example 2B was used as the polyisocyanate precursor. The isocyanate content of the obtained polyisocyanate composition was 8.3%.

[Polyisocyanate Composition 3B]
A polyisocyanate composition 3B was obtained in the same manner as for the polyisocyanate composition 1B, except that the polyisocyanate precursor c of Synthesis Example 3 was used as the polyisocyanate precursor. The isocyanate content of the obtained polyisocyanate composition was 8.3%.

[Polyisocyanate Composition 4B]
A polyisocyanate composition 4B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor d of Synthesis Example 4B was used as the polyisocyanate precursor. The isocyanate content of the obtained polyisocyanate composition was 7.9%.

[Polyisocyanate Composition 5B]
A polyisocyanate composition 5B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor f of Synthesis Example 6B was used as the polyisocyanate precursor. The isocyanate content of the obtained polyisocyanate composition was 8.5%.

[Polyisocyanate Composition 6B]
A polyisocyanate composition 6B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor b in Synthesis Example 2B was used as the polyisocyanate precursor and the polycarbonate diol B in Synthesis Example 9B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 11.1%.

[Polyisocyanate Composition 7B]
A polyisocyanate composition 7B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor d of Synthesis Example 4B was used as the polyisocyanate precursor and the polycarbonate diol B of Synthesis Example 9B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 10.4%.

[Polyisocyanate Composition 8B]
A polyisocyanate composition 8B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor b in Synthesis Example 2B was used as the polyisocyanate precursor and the polycarbonate diol C in Synthesis Example 10B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 13.2%.

[Polyisocyanate Composition 9B]
A polyisocyanate composition 9B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor d of Synthesis Example 4B was used as the polyisocyanate precursor and the polycarbonate diol C of Synthesis Example 10B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 12.3%.

[Polyisocyanate Composition 10B]
A polyisocyanate composition 10B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polycarbonate diol D of Synthesis Example 11B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.7%.

[Polyisocyanate Composition 11B]
A polyisocyanate composition 11B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor b in Synthesis Example 2B was used as the polyisocyanate precursor and the polycarbonate diol D in Synthesis Example 11B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.3%.

[Polyisocyanate Composition 12B]
A polyisocyanate composition 12B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor c in Synthesis Example 3B was used as the polyisocyanate precursor and the polycarbonate diol D in Synthesis Example 11B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.3%.

[Polyisocyanate Composition 13B]
A polyisocyanate composition 13B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor d of Synthesis Example 4B was used as the polyisocyanate precursor and the polycarbonate diol D of Synthesis Example 11B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 7.9%.

[Polyisocyanate Composition 14B]
A polyisocyanate composition 14B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor f of Synthesis Example 6B was used as the polyisocyanate precursor and the polycarbonate diol D of Synthesis Example 11B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.5%.

[Polyisocyanate Composition 15B]
A polyisocyanate composition 15B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor b in Synthesis Example 2B was used as the polyisocyanate precursor and the polycarbonate diol E in Synthesis Example 12B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 11.9%.

[Polyisocyanate Composition 16B]
A polyisocyanate composition 16B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor d of Synthesis Example 4B was used as the polyisocyanate precursor and the polycarbonate diol E of Synthesis Example 12B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 11.1%.

[Polyisocyanate Composition 17B]
A polyisocyanate composition 17B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polycarbonate diol F of Synthesis Example 13B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.7%.

[Polyisocyanate Composition 18B]
A polyisocyanate composition 18B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor b in Synthesis Example 2B was used as the polyisocyanate precursor and the polycarbonate diol F in Synthesis Example 13B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.3%.

[Polyisocyanate Composition 19B]
A polyisocyanate composition 19B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor d of Synthesis Example 4B was used as the polyisocyanate precursor and the polycarbonate diol F of Synthesis Example 13B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 7.9%.

[Polyisocyanate composition 20B]
A polyisocyanate composition 20B was obtained in the same manner as in Polyisocyanate Composition Example 1B, except that the polyisocyanate precursor f of Synthesis Example 6B was used as the polyisocyanate precursor and the polycarbonate diol F of Synthesis Example 13B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.5%.

[Polyisocyanate Composition 21B]
A polyisocyanate composition 21B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polycarbonate diol G of Synthesis Example 14B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.7%.

[Polyisocyanate Composition 22B]
A polyisocyanate composition 22B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor b in Synthesis Example 2B was used as the polyisocyanate precursor and the polycarbonate diol G in Synthesis Example 14B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.3%.

[Polyisocyanate Composition 23B]
A polyisocyanate composition 23B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor d of Synthesis Example 4B was used as the polyisocyanate precursor and the polycarbonate diol G of Synthesis Example 14B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 7.9%.

[Polyisocyanate Composition 24B]
A polyisocyanate composition 24B was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor f of Synthesis Example 6B was used as the polyisocyanate precursor and the polycarbonate diol G of Synthesis Example 14B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.5%.

[Polyisocyanate Composition 25B]
The polyisocyanate precursor c of Synthesis Example 3B was used as the polyisocyanate precursor, and the polycarbonate diol A of Synthesis Example 8B was used as the copolymerized polycarbonate diol. These were mixed in a ratio of 20 equivalents of isocyanate groups in the polyisocyanate precursor to 1 equivalent of active hydrogen in the polycarbonate diol, and reacted at 100° C. The reaction was terminated when the isocyanate content in the reaction solution reached 15.5%, to obtain polyisocyanate composition 25B.

[Polyisocyanate Composition 26B]
A polyisocyanate composition 26B was obtained in the same manner as in the polyisocyanate composition 25B, except that the polycarbonate diol D of Synthesis Example 11B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 15.7%.

[Polyisocyanate Composition 27B]
To the total amount of the polyisocyanate composition 4B obtained above, 1 part by mass of TINUVIN765 was added to prepare polyisocyanate composition 27B.

[Polyisocyanate composition Bb-1]
A polyisocyanate composition Bb-1 was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor e in Synthesis Example 5B was used as the polyisocyanate precursor and the polycarbonate diol A in Synthesis Example 8B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.8%.

[Polyisocyanate composition Bb-2]
A polyisocyanate composition Bb-2 was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor e in Synthesis Example 5B was used as the polyisocyanate precursor and the polycarbonate diol D in Synthesis Example 11B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.8%.

[Polyisocyanate composition Bb-3]
A polyisocyanate composition Bb-3 was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor e in Synthesis Example 5B was used as the polyisocyanate precursor and the polycarbonate diol F in Synthesis Example 13B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.8%.

[Polyisocyanate composition Bb-4]
A polyisocyanate composition Bb-4 was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor e of Synthesis Example 5B was used as the polyisocyanate precursor and the polycarbonate diol G of Synthesis Example 14B was used as the copolymerized polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.8%.

[Polyisocyanate composition Bb-5]
A polyisocyanate composition Bb-5 was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor g of Synthesis Example 7B was used as the polyisocyanate precursor and the polycarbonate diol A of Synthesis Example 8B was used as the polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.7%.

[Polyisocyanate composition Bb-6]
A polyisocyanate composition Bb-6 was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor g of Synthesis Example 7B was used as the polyisocyanate precursor and the polycarbonate diol D of Synthesis Example 11B was used as the polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 8.7%.

[Polyisocyanate composition Bb-7]
A polyisocyanate composition Bb-7 was obtained in the same manner as in the polyisocyanate composition 17B, except that the polyisocyanate precursor c of Synthesis Example 3B was used as the polyisocyanate precursor and the polycarbonate diol H of Synthesis Example 15B was used as the polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 15.5%.

[Polyisocyanate composition Bb-8]
A polyisocyanate composition Bb-8 was obtained in the same manner as in the polyisocyanate composition 1B, except that the polyisocyanate precursor d of Synthesis Example 4B was used as the polyisocyanate precursor and the polycarbonate diol H of Synthesis Example 15B was used as the polycarbonate diol. The isocyanate content of the obtained polyisocyanate composition was 13.5%.

<Production of Coating Composition>
The base agent used was "Desmophen 1420" (an aspartic acid ester compound, a product name of Covestro, amine value 201 mg KOH/g resin). In Tables 2 to 5, the aspartic acid ester compound is referred to as "PAE."
As the curing agent, the polyisocyanate compositions 1B to 27B and Bb-1 to Bb-8 obtained above were used.
The base agent and the curing agent were mixed in a ratio of NCO/NH = 1.1, and the paint solids content was adjusted to 90 mass% with n-butyl acetate to obtain the paint compositions of Examples 1B to 27B and Comparative Examples 1B to 28B, respectively.

The impact resistance and coating elongation of each of the resulting coating compositions were evaluated using the methods described above. The results are shown in Tables 2 to 5.

As shown in the above results, the coating films formed using the coating compositions of Examples 1B to 27B had excellent impact resistance and coating elongation.

According to this embodiment, a coating composition can be provided that has excellent coating film elongation when formed into a coating film. In addition, the coating composition of this embodiment can be used as a raw material for coatings, inks, adhesives, casting materials, elastomers, foams, and plastic materials. The coating composition of this embodiment is suitable for architectural coatings, heavy-duty corrosion protection coatings, automotive coatings, coatings for information appliances, and coatings for information devices such as personal computers and mobile phones.

Claims (6)

A coating composition comprising a polyaspartic base and a polyisocyanate composition,
The polyisocyanate composition comprises a polyisocyanate derived from (A), (B), and (C) and containing allophanate groups;
The (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates,
(B) is an alcohol having 1 to 20 carbon atoms;
The coating composition includes (C), which is a polyol having a number average molecular weight of 400 or more and 20,000 or less, and which is at least one elastic component polyol selected from a polyether polyol having at least one oxyalkylene group selected from an oxypropylene group and an oxytetramethylene group, a polyester polyol having a side chain, a polyolefin polyol, or a polycarbonate diol. (B) is a monoalcohol having 6 to 20 carbon atoms;
The (C) is a polyol having a number average molecular weight of 3,500 or more and 20,000 or less, and is at least one selected from the group consisting of polyether polyols having at least one oxyalkylene group selected from an oxypropylene group and an oxytetramethylene group, polyester polyols having side chains, and olefin polyols;
2. The coating composition of claim 1, wherein the polyisocyanate is substantially free of isocyanurate groups and has allophanate groups. The (A) is a polyisocyanate precursor comprising a dimer or more of at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates,
3. The coating 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 80:20 or less. The coating composition according to claim 1 or 2, which is used for coating metals or plastics. The coating composition according to claim 1 or 2, which is used 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. A coating film formed by curing the coating composition according to claim 4.