Aqueous block polyisocyanate composition, aqueous coating composition, coating film and coating base material

Abstract

To provide: an aqueous block polyisocyanate composition which is excellent in dispersibility with respect to an aqueous main agent, curability and hardness of a cured coating film, water resistance, chemical resistance, dryness and storage stability; an aqueous coating composition; a coating film; and a coating base material.SOLUTION: An aqueous block polyisocyanate contains: polyisocyanate derived from one or more diisocyanates selected from aliphatic diisocyanate and alicyclic diisocyanate; a hydrophilic compound; and a block polyisocyanate compound derived from a thermally dissociable blocking agent. Therein: viscosity at 60°C in a state of containing no organic solvent is 1,000 mPa s or more and 30,000 Pa s or less; a molar ratio (urethane group / isocyanurate group) of a urethane group to an isocyanurate group is 0.5 / 100 or more and 20.0 / 100 or less; and a molar ratio (uretdione group / isocyanurate group) of a uretdione group to an isocyanurate group is 10.0 / 100 or more and 80.0 / 100 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an aqueous blocked polyisocyanate composition, an aqueous coating composition, a coating film, and a coated substrate. [Background technology]

[0002] Coating films obtained from two-component polyurethane compositions using a polyisocyanate composition derived from an aliphatic diisocyanate or alicyclic diisocyanate as a curing agent exhibit excellent performance in terms of weather resistance, chemical resistance, abrasion resistance, etc., and are therefore widely used as paints, inks, adhesives, etc. In recent years, as global environmental issues have become more widely recognized, proposals have been made on water-based two-component polyurethane compositions that do not use organic solvents or that use a reduced amount of organic solvents and that further have hydrophilic groups.

[0003] Also, from the viewpoint of easy handling, one-component paints are desired whose paint properties do not change even when the base agent and curing agent are mixed. These are made by protecting the isocyanate group of the curing agent with a blocking agent, and by heating after application on site, the isocyanate group is regenerated and reacts with the hydroxyl group of the base polyol to form a hardened coating film. Such isocyanates are called blocked polyisocyanates. Solvent-based blocked polyisocyanate compositions are mainly used, but water-based compositions are desired from the viewpoint of environmental protection.

[0004] For water-dispersible blocked polyisocyanate compositions, a method of introducing a hydrophilic group into a polyisocyanate is known (for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 11-512772 [Patent Document 2] Special Publication No. 2002-511507 [Patent Document 3] JP 2020-143231 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the blocked polyisocyanate compositions described in Patent Documents 1-3 have insufficient dispersibility depending on the combination with the aqueous base, and the appearance of the applied coating film may be poor, and the desired coating film properties may not be exhibited. In addition, in order to improve the dispersibility with the base, it is necessary to increase the amount of hydrophilic organic solvent, which increases the amount of solvent that evaporates during drying, and there is a concern that this is against the trend of protecting the global environment. Furthermore, when the amount of hydrophilic groups introduced is increased in order to improve the dispersibility with the base, there is a problem that the curing property of the paint, the water resistance, chemical resistance, and storage stability of the cured coating film are deteriorated.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an aqueous blocked polyisocyanate composition, an aqueous coating composition, a coating film, and a coated substrate, which have excellent dispersibility in an aqueous base agent, and which have excellent curability, hardness, water resistance, chemical resistance, drying property, and storage stability of a cured coating film. [Means for solving the problem]

[0008] That is, the present invention includes the following aspects. [1] A blocked polyisocyanate compound derived from one or more diisocyanates selected from an aliphatic diisocyanate and an alicyclic diisocyanate, a hydrophilic compound, and a thermally dissociable blocking agent, The viscosity at 60°C without containing any organic solvent is 1,000 mPa s or more and 30,000 mPa s or less. the molar ratio of urethane groups to isocyanurate groups (urethane groups / isocyanurate groups) is 0.5 / 100 or more and 20.0 / 100 or less; An aqueous blocked polyisocyanate composition having a molar ratio of uretdione groups to isocyanurate groups (uretdione groups / isocyanurate groups) of 10.0 / 100 or more and 80.0 / 100 or less. [2] The aqueous blocked polyisocyanate composition according to [1], wherein the average number of isocyanate groups bonded to a thermally dissociable blocking agent in the blocked polyisocyanate compound per molecule is 2.0 to 3.5. [3] The aqueous blocked polyisocyanate composition according to [1] or [2], wherein the blocked polyisocyanate compound has a number average molecular weight of 300 or more and 3,000 or less. [4] The aqueous blocked polyisocyanate composition according to any one of [1] to [3], wherein the content of the hydrophilic compound used to derive the blocked polyisocyanate compound is 0.1 mass % or more and 30 mass % or less, based on the aqueous blocked polyisocyanate composition. [5] The aqueous blocked polyisocyanate composition according to any one of [1] to [4], wherein the content of the hydrophilic organic solvent in the aqueous blocked polyisocyanate composition is 30 mass % or less. [6] The aqueous blocked polyisocyanate composition according to any one of [1] to [5], wherein the hydrophilic compound is a polyalkylene glycol alkyl ether having a structure represented by the following general formula (I):

[0009] [ka]

[0010] (In general formula (I), R 11 is an alkylene group having 1 to 4 carbon atoms, R 12 is an alkyl group having 1 to 4 carbon atoms, and n11 is 4.0 or more and 20 or less. [7] The aqueous blocked polyisocyanate composition according to any one of [1] to [5], wherein the hydrophilic compound is one or more sulfonic acids selected from the group consisting of sulfonic acids containing a hydroxyl group and sulfonic acids containing an amino group. [8] The aqueous blocked polyisocyanate composition according to any one of [1] to [7], wherein the polyisocyanate contains, as bonding groups, an isocyanurate group, an iminooxadiazinedione group, a uretdione group, and an allophanate group, and the molar ratio of the uretdione group is 1.0 mol% or more and 50.0 mol% or less relative to the total molar amount (100 mol%) of the bonding groups. [9] The aqueous blocked polyisocyanate composition according to any one of [1] to [8], wherein the thermally dissociable blocking agent is at least one selected from the group consisting of oxime compounds, acid amide compounds, amine compounds, active methylene compounds, and pyrazole compounds.

[10] An aqueous coating composition comprising the aqueous blocked polyisocyanate composition according to any one of [1] to [9].

[11] A coating film obtained by curing the aqueous coating composition described in

[10] .

[12] A coated substrate coated with the aqueous coating composition described in

[10] . Effect of the Invention

[0011] According to the present embodiment, it is possible to provide an aqueous blocked polyisocyanate composition having excellent dispersibility in an aqueous base, as well as an aqueous coating composition, a coating film, and a coating substrate which, when formed into a coating film using this aqueous blocked polyisocyanate composition, have excellent curability, hardness, water resistance, chemical resistance, drying property, and storage stability. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment for carrying out the present invention (hereinafter, simply referred to as "the present embodiment") will be described in detail. The present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0013] <Water-based blocked polyisocyanate composition> The aqueous blocked polyisocyanate composition of the present embodiment contains a polyisocyanate component derived from one or more diisocyanates selected from aliphatic diisocyanates and alicyclic diisocyanates, and a blocked polyisocyanate compound derived from a hydrophilic compound and a thermally dissociable blocking agent. Hereinafter, the component derived from the polyisocyanate, the hydrophilic compound, and the thermally dissociable blocking agent may be referred to as the "blocked polyisocyanate composition."

[0014] <Polyisocyanate component> The polyisocyanate component constituting the aqueous blocked polyisocyanate composition of the present embodiment contains a polyisocyanate compound derived from at least one diisocyanate selected from an aliphatic diisocyanate and an alicyclic diisocyanate.

[0015] Examples of aliphatic diisocyanates include, but are not limited to, 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, ethyl (2,6-diisocyanato)hexanoate, 1,6-diisocyanatohexane (hereinafter sometimes referred to as "HDI"), 1,9-diisocyanatononane, 1,12-diisocyanatododecane, 2,2,4- or 2,4,4-trimethyl-1,6-diisocyanatohexane, and the like.

[0016] The alicyclic diisocyanate is not particularly limited, but examples thereof include 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (hereinafter sometimes referred to as "hydrogenated XDI"), 1,3- or 1,4-diisocyanatocyclohexane, 3,5,5-trimethyl-1-isocyanato-3-(isocyanatomethyl)cyclohexane (hereinafter sometimes referred to as "IPDI"), 4-4'-diisocyanato-dicyclohexylmethane (hereinafter sometimes referred to as "hydrogenated MDI"), 2,5- or 2,6-diisocyanatomethylnorbornane, and the like.

[0017] Among these, the diisocyanate is preferably HDI, IPDI, hydrogenated XDI or hydrogenated MDI from the viewpoint of weather resistance, and more preferably HDI or IPDI.

[0018] The polyisocyanate compound may also contain an aliphatic triisocyanate, such as 1,3,6-triisocyanatohexane, 1,8-diisocyanato-4-isocyanatomethyloctane, or 2-isocyanatoethyl-2,6-diisocyanato-hexanoate.

[0019] Moreover, these polyisocyanate compounds can be used alone or in combination of two or more kinds.

[0020] <Hydrophilic compounds> The hydrophilic compound constituting the aqueous blocked polyisocyanate composition of the present embodiment is a compound having a hydrophilic group in the molecule. In order to react with one isocyanate group, the hydrophilic compound preferably has one or more active hydrogen groups for reacting with the isocyanate group contained in the polyisocyanate component per molecule of the hydrophilic compound. Specific examples of the active hydrogen group include hydrophilic groups such as a hydroxyl group, a mercapto group, a carboxylic acid group, and an amino group.

[0021] The hydrophilic compound is not particularly limited, but examples thereof include nonionic compounds, anionic compounds, cationic compounds, etc. These hydrophilic compounds may be used alone or in combination of two or more.

[0022] (Nonionic compounds) A nonionic hydrophilic compound has one or more active hydrogen groups per molecule of the hydrophilic compound to react with an isocyanate group of a polyisocyanate component. Specific examples of the active hydrogen groups include hydroxyl groups, mercapto groups, carboxylic acid groups, amino groups, and thiol groups. The nonionic hydrophilic compounds may be used alone or in combination of two or more kinds.

[0023] The nonionic hydrophilic compound is not particularly limited, but may be, for example, a polyalkylene glycol alkyl ether. The number of hydroxyl groups in the polyalkylene glycol alkyl ether is preferably one, from the viewpoint of reducing the viscosity of the polyisocyanate composition.

[0024] A preferred polyalkylene glycol alkyl ether has a structure represented by the following general formula (I):

[0025] [ka]

[0026] (In general formula (I), R 11 is an alkylene group having 1 to 4 carbon atoms, R 12 is an alkyl group having 1 to 4 carbon atoms, and n11 is 4.0 or more and 25 or less.

[0027] Polyalkylene glycol alkyl ether is not a single component, but an aggregate of substances with different numbers of n (hereinafter, sometimes referred to as "polymerization degree n" or simply "n") indicating the degree of polymerization. Therefore, the degree of polymerization n is expressed as an average value. n11 in the general formula (I) is the degree of polymerization n of the preferred polyalkylene glycol alkyl ether.

[0028] When polyisocyanate is mixed with a water-based base resin, thickening of the base resin can often be an issue. If there is a large increase in viscosity, the polyisocyanate cannot be dispersed uniformly in the base resin, which tends to lead to a decrease in the physical properties of the coating film.

[0029] Therefore, from the viewpoint of water dispersibility and dispersibility in the base agent, n is preferably 4.0 or more and 25.0 or less, more preferably 4.0 or more and 20 or less, and even more preferably 6.0 or more and 20.0 or less. When n is equal to or more than the lower limit, emulsifying power increases, so dispersibility tends to improve, while when n is equal to or less than the upper limit, viscosity increase is prevented, so dispersion tends to be easy.

[0030] The polyalkylene glycol alkyl ether may be used in combination of two or more types having different n values. The n value of the polyalkylene glycol alkyl ether may be measured by a proton nuclear magnetic resonance (NMR) method.

[0031] In general formula (I), R 11 From the viewpoint of imparting hydrophilicity, R is an alkylene group having 1 to 4 carbon atoms, and from the viewpoint of imparting greater hydrophilicity, an ethylene group having 2 carbon atoms is preferable. 11 can be independently selected and may be the same or different from each other.

[0032] Also, R 12 is an alkyl group having 1 to 4 carbon atoms from the viewpoint of imparting hydrophilicity, and a methyl group having 1 carbon atom is preferable from the viewpoint of imparting greater hydrophilicity.

[0033] Examples of polyalkylene glycol alkyl ethers include, but are not limited to, polyethylene glycol (mono)methyl ether, poly(ethylene, propylene) glycol (mono)methyl ether, and polyethylene glycol (mono)ethyl ether. Among these, polyethylene glycol (mono)methyl ether is preferred from the viewpoint of imparting hydrophilicity.

[0034] Commercially available polyalkylene glycol alkyl ethers include, for example, trade names "UNIOX M-400", "UNIOX M-550", "UNIOX M-1000", and "UNIOX M-2000" manufactured by NOF Corporation, and trade names "MPG-081" and "MPG-130" manufactured by Nippon Nyukazai Co., Ltd.

[0035] The content of the hydrophilic compound used to derive the blocked polyisocyanate compound is preferably 0.1% by mass or more and 30% by mass or less with respect to the aqueous blocked polyisocyanate composition. In the aqueous blocked polyisocyanate composition, the content of the portion derived from polyalkylene glycol alkyl ether is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.2% by mass or more and 25% by mass or less, and even more preferably 0.5% by mass or more and 20% by mass or less with respect to the total solid content mass (100% by mass) of the blocked polyisocyanate composition from the viewpoint of coating film properties. When the content of the portion derived from polyalkylene glycol alkyl ether is within the above range, the isocyanate group used for crosslinking increases, and the coating film properties (hardness, water resistance, and solvent resistance) tend to be better. When a compound other than polyalkylene glycol alkyl ether is used as the hydrophilic compound, the same content (content) can be selected.

[0036] The method for controlling the content of the portion derived from polyalkylene glycol alkyl ether within the above range is not limited to the following, but for example, a method for adjusting the compounding ratio of the polyalkylene glycol alkyl ether and the polyisocyanate compound can be mentioned. The content of the portion derived from polyalkylene glycol alkyl ether can be measured by liquid chromatography-mass spectrometry (LC-MS).

[0037] In the blocked polyisocyanate composition, the proportion modified with polyalkylene glycol alkyl ether (modification rate) (hereinafter, sometimes referred to as "introduction rate of polyalkylene glycol alkyl ether") is the proportion of the portion derived from polyalkylene glycol alkyl ether introduced relative to 100 molar equivalents of isocyanate groups in the polyisocyanate component. From the viewpoint of adjusting the content rate of the portion derived from polyalkylene glycol alkyl ether to the above-mentioned preferred range, the modification rate is preferably 0.5 mol% or more and 40 mol% or less, more preferably 1.0 mol% or more and 30 mol% or less, and even more preferably 2.0 mol% or more and 20 mol% or less.

[0038] The above content and modification rate can be calculated, for example, by the following method. Specifically, the polyisocyanate precursor before the blocking reaction is used as a sample, and the peak area ratio at 220 nm of liquid chromatography (LC) for unintroduced polyisocyanate, polyisocyanate having one moiety derived from polyalkylene glycol alkyl ether introduced, polyisocyanate having two moieties introduced, and polyisocyanate having three or more moieties introduced can be determined. The measurement conditions by LC include, for example, the following conditions.

[0039] (Measurement conditions) LC device: Manufactured by Waters, UPLC (product name) Column: Waters, ACQUITY UPLC HSS T3 1.8 μm C18 Inner diameter 2.1mm x length 50mm Flow rate: 0.3mL / min Mobile phase: A = 10 mM ammonium acetate aqueous solution, B = acetonitrile Gradient conditions: The initial mobile phase composition is A / B=98 / 2, and after sample injection, the ratio of B is increased linearly to A / B=0 / 100 after 10 minutes. Detection method: Photodiode array detector, measurement wavelength is 220 nm

[0040] (anionic compounds) The anionic compound is not particularly limited, but examples thereof include compounds containing a carboxylic acid group, compounds containing a phosphoric acid group, and compounds containing a sulfonic acid group.

[0041] The compound containing a carboxylic acid group is not particularly limited, but examples thereof include monohydroxycarboxylic acids such as 1-hydroxyacetic acid, 3-hydroxypropanoic acid, 12-hydroxy-9-octadecanoic acid, hydroxypivalic acid, and lactic acid, and carboxylic acids containing a hydroxyl group such as polyhydroxycarboxylic acids such as dimethylolacetic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolpentanoic acid, dihydroxysuccinic acid, and dimethylolpropionic acid. Among these, hydroxypivalic acid or dimethylolpropionic acid is preferred.

[0042] The compound containing a phosphoric acid group is not particularly limited, but examples thereof include acid phosphoric acid esters, acid phosphorous esters, acid hypophosphite esters, and specific polyether phosphonates (for example, those commercially available under the trade name RHODAFAC (registered trademark) (Solvay Nicca Co., Ltd.)). Among these, acid phosphoric acid esters are preferred.

[0043] From the viewpoint of water dispersibility, the polyisocyanate composition preferably has a phosphorus atom content of 0.03 mass% or more, more preferably 0.05 mass% or more, and even more preferably 0.1 mass% or more, based on the total amount (100 mass%) of the polyisocyanate composition. When the phosphorus atom content is 0.03 mass% or more, the interfacial tension is reduced, and the composition tends to exhibit better water dispersibility.

[0044] From the viewpoint of coating film properties, the blocked polyisocyanate composition preferably has a phosphorus atom content of 6.0 mass% or less, more preferably 3.0 mass% or less, and even more preferably 1.0 mass% or less, relative to the total amount (100 mass%) of the blocked polyisocyanate composition. When the phosphorus atom content is equal to or less than the upper limit, the coating film properties tend to be better due to the increased amount of isocyanate groups used for crosslinking.

[0045] The method for controlling the phosphorus atom content within the above range includes, but is not limited to, a method of adjusting the compounding ratio of the compound containing the phosphoric acid group and the raw material polyisocyanate compound. The phosphorus atom content is measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0046] The compound containing a sulfonic acid group is not particularly limited, but examples thereof include sulfonic acids containing a hydroxyl group, sulfonic acids containing an amino group, etc. Examples of sulfonic acids containing a hydroxyl group include 2-hydroxyethanesulfonic acid, 3-hydroxypropanesulfonic acid, 4-hydroxybutanesulfonic acid, 5-hydroxypentanesulfonic acid, 6-hydroxyhexanesulfonic acid, hydroxybenzenesulfonic acid, hydroxy(methyl)benzenesulfonic acid, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid, 2-hydroxy-3-morpholinopropanesulfonic acid, and specific polyethersulfonates (for example, those commercially available under the trade name Tegomer (registered trademark) (The Goldschmidt AG, Essen, Germany)). Examples of sulfonic acids containing an amino group include 2-aminoethanesulfonic acid, 2-methylaminoethanesulfonic acid, 2-(cyclohexylamino)-ethanesulfonic acid, 3-(cyclohexylamino)-propanesulfonic acid, 4-aminotoluene-2-sulfonic acid, 5-aminotoluene-2-sulfonic acid, 2-aminonaphthalene-4-sulfonic acid, 4-aminobenzenesulfonic acid, and 3-aminobenzenesulfonic acid.

[0047] Among these, 2-hydroxyethanesulfonic acid, 3-hydroxypropanesulfonic acid, hydroxybenzenesulfonic acid, hydroxy(methyl)benzenesulfonic acid, 2-(cyclohexylamino)-ethanesulfonic acid, or 3-(cyclohexylamino)-propanesulfonic acid is preferred.

[0048] The acidic groups of the anionic compound, such as a carboxylic acid group, a phosphoric acid group, a sulfonic acid group, etc., are preferably neutralized with an inorganic base or an organic amine compound.

[0049] Examples of inorganic bases include alkali metals such as lithium, sodium, potassium, rubidium, and cesium; alkaline earth metals such as magnesium, calcium, strontium, and barium; metals such as manganese, iron, cobalt, nickel, copper, zinc, silver, cadmium, lead, and aluminum; and ammonia.

[0050] Examples of the organic amine compound include linear tertiary amines such as trimethylamine, triethylamine, tripropylamine, tributylamine, trioctylamine, trilaurylamine, tritridecylamine, and tristearylamine; branched tertiary amines such as triisopropylamine, triisobutylamine, tri-2-ethylhexylamine, and tribranched tridecylamine; N,N-dimethylethylamine, N,N-dimethylpropylamine, N,N-dimethylisopropylamine, N,N-dimethylbutylamine, and N,N-dimethylisobutylamine. amine, N,N-dimethyloctylamine, N,N-dimethyl-2-ethylhexylamine, N,N-dimethyllaurylamine, N,N-dimethyl(branched)tridecylamine, N,N-dimethylstearylamine, N,N-diethylbutylamine, N,N-diethylhexylamine, N,N-diethyloctylamine, N,N-diethyl-2-ethylhexylamine, N,N-diethyllaurylamine, N,N-diisopropylmethylamine, N,N-diisopropylethylamine, N,N-diisopropylbutylamine, N,N-diisopropyl-2 -ethylhexylamine and other tertiary amines having mixed hydrocarbon groups; alicyclic tertiary amines such as N,N-dimethylcyclohexylamine, N,N-diethylbenzylamine, N,N-diethylcyclohexylamine, N,N-dicyclohexylmethylamine, N,N-dicyclohexylethylamine, and tricyclohexylamine; N,N-dimethylbenzylamine, N,N-diethylbenzylamine, N,N-dibenzylmethylamine, tribenzylamine, N,N-dimethyl-4-methylbenzylamine, N,N-dimethylphenylamine, and N,N- Examples of the amines include tertiary amines having an aromatic ring substituent, such as diethylphenylamine and N,N-diphenylmethylamine; and cyclic amines, such as N-methylpyrrolidine, N-ethylpyrrolidine, N-propylpyrrolidine, N-butylpyrrolidine, N-methylpiperidine, N-ethylpiperidine, N-propylpiperidine, N-butylpiperidine, N-methylmorpholine, N-ethylmorpholine, N-propylmorpholine, N-butylmorpholine, N-sec-butylmorpholine, N-tert-butylmorpholine, N-isobutylmorpholine, and quinuclidine.These organic amine compounds may be used alone or in combination of two or more.

[0051] Among these, tertiary amines having 5 to 30 carbon atoms are preferred. Specific examples thereof include triethylamine, tripropylamine, tributylamine, trioctylamine, trilaurylamine, tridecylamine, triisopropylamine, triisobutylamine, tri-2-ethylhexylamine, tribranched tridecylamine, N,N-dimethylpropylamine, N,N-dimethylisopropylamine, N,N-dimethylbutylamine, N,N-dimethylisobutylamine, N,N-dimethyloctylamine, N,N-dimethyl-2-ethylhexylamine, N,N-dimethyllaurylamine, N,N-dimethyl(branched)tridecylamine, N,N-dimethylstearylamine, N,N-diethylbutylamine, N,N-diethylhexylamine, N, Examples of the organic amine compounds include N-diethyloctylamine, N,N-diethyl-2-ethylhexylamine, N,N-diethyllaurylamine, N,N-diisopropylmethylamine, N,N-diisopropylethylamine, N,N-dimethylcyclohexylamine, N,N-diethylcyclohexylamine, N,N-dicyclohexylmethylamine, N,N-dicyclohexylethylamine, N,N-dimethylbenzylamine, N,N-diethylbenzylamine, N,N-dibenzylmethylamine, tribenzylamine, N,N-dimethylphenylamine, N,N-diethylphenylamine, N,N-diphenylmethylamine, N-methylpiperidine, N-ethylpiperidine, N-methylmorpholine, N-ethylmorpholine, quinuclidine, pyridine, and quinoline. These preferred organic amine compounds may be used alone or in combination of two or more.

[0052] In order to disperse the blocked polyisocyanate compound in water, the compound is modified with the hydrophilic compound (the hydrophilic group derived from the hydrophilic compound is introduced into the polyisocyanate compound), but by not increasing the modification ratio too much, the deterioration of the coating film properties (hardness, water resistance, and solvent resistance) tends to be suppressed. That is, since the anionic compound has a high emulsifying power, a high emulsifying effect can be obtained with a small amount.

[0053] In the blocked polyisocyanate composition, the lower limit of the sulfur atom content is preferably 0.03 mass%, more preferably 0.05 mass%, and even more preferably 0.08 mass%, based on the total mass (100 mass%) of the polyisocyanate composition, from the viewpoint of water dispersibility. When the sulfur atom content is equal to or more than the lower limit, the interfacial tension decreases, and therefore the composition tends to exhibit better water dispersibility.

[0054] In addition, in the blocked polyisocyanate composition, the upper limit of the sulfur atom content is preferably 3.0 mass%, more preferably 2.5 mass%, and even more preferably 2.0 mass%, based on the total mass (100 mass%) of the polyisocyanate composition, from the viewpoint of coating film properties. When the sulfur atom content is equal to or less than the upper limit, the coating film properties tend to be better due to the increased amount of isocyanate groups used for crosslinking.

[0055] That is, in the blocked polyisocyanate composition, the content of sulfur atoms is preferably 0.03 mass% or more and 3.0 mass% or less, more preferably 0.05 mass% or more and 2.5 mass% or less, and even more preferably 0.08 mass% or more and 2.0 mass% or less, relative to the total mass (100 mass%) of the blocked polyisocyanate composition.

[0056] The method for controlling the content of sulfur atoms within the above range includes, but is not limited to, a method of adjusting the compounding ratio of the compound containing the sulfonic acid group and the raw material polyisocyanate compound. The content of sulfur atoms can be measured by ion chromatography (IC).

[0057] The method for reacting the raw material polyisocyanate compound with the anionic compound is not limited to the following, but may be, for example, a method for reacting a terminal isocyanate group of the polyisocyanate of the raw material polyisocyanate compound with an active hydrogen group of the anionic compound.

[0058] (cationic compounds) The cationic compound is not particularly limited, but examples thereof include amine compounds containing a hydroxyl group, such as dimethylethanolamine, diethylethanolamine, diethanolamine, methyldiethanolamine, N,N-dimethylaminohexanol, N,N-dimethylaminoethoxyethanol, N,N-dimethylaminoethoxyethoxyethanol, N,N,N'-trimethylaminoethylethanolamine, and N-methyl-N-(dimethylaminopropyl)aminoethanol. Among these, dimethylethanolamine, diethylethanolamine, N,N-dimethylaminohexanol, N,N-dimethylaminoethoxyethanol, or N,N-dimethylaminoethoxyethoxyethanol are preferred. The tertiary amino group (cationic hydrophilic group) introduced into the polyisocyanate derived from the cationic compound can also be quaternized with dimethyl sulfate, diethyl sulfate, or the like.

[0059] The tertiary amino group of the cationic compound is preferably neutralized with a compound having an anionic group. The anionic group is not particularly limited, but examples thereof include carboxyl group, sulfonic acid group, phosphoric acid group, halogen group, and sulfate group. The compound having the carboxyl group is not particularly limited, but examples thereof include formic acid, acetic acid, propionic acid, butyric acid, and lactic acid. The compound having the sulfonic group is not particularly limited, but examples thereof include ethanesulfonic acid. The compound having the phosphoric acid group is not particularly limited, but examples thereof include phosphoric acid and acidic phosphoric acid ester. The compound having the halogen group is not particularly limited, but examples thereof include hydrochloric acid. The compound having the sulfate group is not particularly limited, but examples thereof include sulfuric acid. Among them, a compound having a carboxyl group is preferred, and acetic acid, propionic acid, or butyric acid is more preferred.

[0060] <Thermal dissociation blocking agent> In the blocked polyisocyanate composition, at least a part of the isocyanate group is blocked by a thermally dissociable blocking agent. The thermally dissociable blocking agent is a compound having one active hydrogen in the molecule, and has the property of dissociating from the isocyanate group by heating. Specific examples of the thermally dissociable blocking agent include alcohol-based compounds, alkylphenol-based compounds, phenol-based compounds, active methylene-based compounds, mercaptan-based compounds, acid amide-based compounds, acid imide-based compounds, imidazole-based compounds, urea-based compounds, oxime-based compounds, amine-based compounds, imine-based compounds, and pyrazole-based compounds.

[0061] More specifically, examples of the thermally dissociable blocking agent include the following compounds (1) to (13). These blocking agents may be used alone or in combination of two or more.

[0062] (1) Alcohol compounds: methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, and 2-butoxyethanol.

[0063] (2) Alkylphenol compounds: mono- or di-alkylphenols having an alkyl group having 4 or more carbon atoms as a substituent, for example, monoalkylphenols such as n-propylphenol, i-propylphenol, n-butylphenol, sec-butylphenol, t-butylphenol, n-hexylphenol, 2-ethylhexylphenol, n-octylphenol, and n-nonylphenol; and dialkylphenols such as di-n-propylphenol, diisopropylphenol, isopropyl cresol, di-n-butylphenol, di-t-butylphenol, di-sec-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, and di-n-nonylphenol.

[0064] (3) Phenolic compounds: phenol, cresol, ethylphenol, styrenated phenol, and hydroxybenzoic acid esters.

[0065] (4) Active methylene compounds: dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone.

[0066] (5) Mercaptan compounds: butyl mercaptan, dodecyl mercaptan. (6) Acid amide compounds: acetanilide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam. (7) Acid imide compounds: succinimide, maleimide.

[0067] (8) Imidazole compounds: imidazole, 2-methylimidazole. (9) Urea compounds: urea, thiourea, ethyleneurea.

[0068] (10) Oxime compounds: formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, cyclohexanone oxime. (11) Amine compounds: diphenylamine, aniline, carbazole, di-n-propylamine, diisopropylamine, isopropylethylamine.

[0069] (12) Imine compounds: ethyleneimine, polyethyleneimine. (13) Pyrazole compounds: pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole.

[0070] Among these, the thermally dissociable blocking agent preferably contains at least one selected from the group consisting of oxime compounds, acid amide compounds, amine compounds, active methylene compounds, and pyrazole compounds, and from the viewpoints of curability and coating hardness, pyrazole compounds are more preferred.

[0071] <Method for producing blocked polyisocyanate composition> Examples of the method for producing the blocked polyisocyanate composition of the present embodiment include 1) a method of reacting the polyisocyanate component, the hydrophilic compound, and the thermally dissociable blocking agent all at once, 2) a method of reacting the polyisocyanate component with the hydrophilic compound in advance and then reacting the thermally dissociable blocking agent, and 3) a method of reacting the polyisocyanate component with the thermally dissociable blocking agent in advance and then reacting the hydrophilic compound. Among these, method 2) is preferred because no isocyanate group remains and the hydrophilic compound and the thermally dissociable blocking agent remain. In particular, since the hydrophilic compound does not remain in an unreacted state, the decrease in the water dispersion stability of the aqueous blocked polyisocyanate composition is more suppressed, and the decrease in curability when used as an aqueous coating composition tends to be more suppressed.

[0072] In the case of the production method 2), the reaction temperature in the reaction step between the isocyanate component and the hydrophilic compound and the reaction step between the reactant and the thermally dissociable blocking agent is preferably -20°C or higher and 150°C or lower, more preferably 30°C or higher and 100°C or lower. By keeping the reaction temperature at or above the lower limit, the reactivity tends to be higher. Also, by keeping the reaction temperature at or below the upper limit, side reactions and coloration of the composition tend to be more suppressed. In the above reaction step, for example, an organic metal salt such as tin, zinc, or lead; a tertiary amine compound; or an alcoholate of an alkali metal such as sodium may be used as a catalyst.

[0073] <Production method of polyisocyanate compound> The polyisocyanate compound derived from the above diisocyanate is not particularly limited, but examples thereof include the polyisocyanates shown in the following (a) to (h). (a): Polyisocyanate having uretdione groups obtained by cyclodimerization of two isocyanate groups. (b): Polyisocyanates having isocyanurate groups or iminooxadiazinedione groups obtained by cyclotrimerization of three isocyanate groups. (c): A polyisocyanate having a biuret group obtained by reacting three isocyanate groups with one water molecule. (d): A polyisocyanate having an oxadiazinetrione group obtained by reacting two isocyanate groups with one molecule of carbon dioxide. (e): A polyisocyanate having multiple urethane groups obtained by reacting one isocyanate group with one hydroxyl group. (f): A polyisocyanate having an allophanate group obtained by reacting two isocyanate groups with one hydroxyl group. (g): Polyisocyanate having an acylurea group obtained by reacting one isocyanate group with one carboxy group. (h): Polyisocyanates having a urea group obtained by reacting one isocyanate group with one primary or secondary amine.

[0074] Among them, the polyisocyanate compound is preferably one having an isocyanurate group and a uretdione group. That is, the polyisocyanate compound may contain a mixture of polyisocyanate compounds having one of these functional groups, or may contain a mixture of polyisocyanate compounds having two or more of these functional groups, or may contain a polyisocyanate compound having a functional group other than the above two types.

[0075] The isocyanurate group is a functional group obtained by cyclotrimerization of three isocyanate groups, and has a structure represented by the following formula (II).

[0076] [ka]

[0077] In the polyisocyanate compound used in the present embodiment, the molar ratio of the isocyanurate group to the total molar amount (100 mol%) of the isocyanurate group, allophanate group, uretdione group, and iminooxadiazinedione group is preferably 50.0 mol% or more and 90.0 mol% or less, and more preferably 60.0 mol% or more and 80.0 mol% or less. When the molar ratio of the isocyanurate group is in the above range, the hardness and water resistance of the obtained coating film are superior.

[0078] The uretdione group is a functional group obtained by cyclization dimerization of two isocyanate groups, and has a structure represented by the following formula (III).

[0079] [ka]

[0080] In the polyisocyanate compound used in the present embodiment, the molar ratio of uretdione groups relative to the total molar amount (100 mol%) of isocyanurate groups, allophanate groups, uretdione groups, and iminooxadiazinedione groups is preferably 1.0 mol% or more and 50.0 mol% or less, more preferably 10.0 mol% or more and 40.0 mol% or less, and even more preferably 15.0 mol% or more and 30.0 mol% or less.

[0081] In the polyisocyanate compound used in the present embodiment, the molar ratio of the uretdione group to the isocyanurate group (uretdione group / isocyanurate group) is from 10.0 / 100 to 80.0 / 100, and more preferably from 20.0 / 100 to 60.0 / 100, in terms of achieving both low viscosity and dispersibility, curability, coating hardness, and drying properties.

[0082] The allophanate group is a functional group formed by the reaction of a hydroxyl group of an alcohol with an isocyanate group, and has a structure represented by the following formula (IV).

[0083] [ka]

[0084] In the polyisocyanate compound used in the present embodiment, the molar ratio of allophanate groups relative to the total molar amount (100 mol%) of isocyanurate groups, allophanate groups, uretdione groups, and iminooxadiazinedione groups is preferably 1.0 mol% or more and 20.0 mol% or less, and more preferably 1.5 mol% or more and 15.0 mol% or less.

[0085] The iminooxadiazinedione group is a functional group obtained by cyclization trimerization of three isocyanate groups, and has a structure represented by the following formula (V).

[0086] [ka]

[0087] In the polyisocyanate compound used in the present embodiment, the molar ratio of iminooxadiazinedione groups relative to the total molar amount (100 mol%) of isocyanurate groups, allophanate groups, uretdione groups, and iminooxadiazinedione groups is preferably 0.05 mol% or more and 3.5 mol% or less, and more preferably 0.1 mol% or more and 3.0 mol% or less.

[0088] The urethane group is a functional group formed by the reaction of a hydroxyl group with an isocyanate group, and has a structure represented by the following formula (VI).

[0089] [ka]

[0090] The molar fraction of the urethane group and the isocyanurate group in the blocked polyisocyanate composition used in the present embodiment (urethane group / isocyanurate group) is 0.5 / 100 or more and 20.0 / 100 or less. From the viewpoint of achieving both dispersibility, coating hardness, water resistance, and solvent resistance, it is preferably 1.0 / 100 or more and 15.0 / 100 or less, and more preferably 2.0 / 100 or more and 10.0 / 100 or less.

[0091] The molar ratio of the urethane group to the isocyanurate group is, for example, 13 It can be determined by C-NMR measurement.

[0092] In the blocked polyisocyanate compound used in the present embodiment, in addition to the five types of bonds, bonds of urea groups, acylurea groups, biuret groups, oxadiazinetrione groups, etc. may be contained. The molar ratio of the bonds is preferably 0.01 mol % or more and 10.0 mol % or less in addition to the total molar amount (100 mol %) of isocyanurate groups, allophanate groups, uretdione groups, and iminooxadiazinedione groups.

[0093] (Production method of polyisocyanate compound) The polyisocyanate compound of the present embodiment can be produced from a diisocyanate using the following catalyst, alcohol, etc. Alternatively, the compound may be produced from a diisocyanate using either one of a hydrophilic compound and a thermally dissociable blocking agent. The methods for producing polyisocyanate compounds containing each bond are shown below.

[0094] (1) Method for producing polyisocyanate compound containing isocyanurate group The method for producing a polyisocyanate containing an isocyanurate group is not particularly limited, but may be, for example, a method in which a diisocyanate is subjected to an isocyanurate reaction using a catalyst or the like, the reaction is stopped when a predetermined conversion rate is reached, and the unreacted diisocyanate is removed.

[0095] The catalyst used in the isocyanurate reaction is not particularly limited, but is preferably one that exhibits basicity. Specific examples thereof include tetraalkylammonium hydroxides and weak organic acid salts, hydroxyalkylammonium hydroxides and weak organic acid salts, alkali metal salts of alkylcarboxylic acids, metal alcoholates, aminosilyl group-containing compounds, Mannich bases, combined use of tertiary amines and epoxy compounds, phosphorus-based compounds, and the like.

[0096] Examples of tetraalkylammonium include tetramethylammonium and tetraethylammonium.

[0097] Examples of the organic weak acid include acetic acid, capric acid, etc. Examples of the hydroxyalkyl ammonium include trimethylhydroxypropyl ammonium, trimethylhydroxyethyl ammonium, triethylhydroxypropyl ammonium, triethylhydroxyethyl ammonium, etc.

[0098] Examples of the alkyl carboxylic acid include acetic acid, caproic acid, octylic acid, and myristic acid.

[0099] Examples of metals constituting the alkali metal salt include tin, zinc, and lead.

[0100] Examples of the metal alcoholate include sodium alcoholate and potassium alcoholate.

[0101] An example of the aminosilyl group-containing compound is hexamethyldisilazane.

[0102] An example of the phosphorus-based compound is tributylphosphine.

[0103] The amount of these catalysts used is preferably 10 ppm or more and 1.0% or less based on the total mass of the diisocyanate (and, if necessary, alcohol) that is the raw material. In order to terminate the isocyanurate reaction, the catalyst may be inactivated by adding an acidic substance that neutralizes the catalyst, thermal decomposition, chemical decomposition, etc. Examples of acidic substances that neutralize the catalyst include phosphoric acid and acidic phosphate esters.

[0104] The yield of polyisocyanate generally tends to be 10% by mass or more and 70% by mass or less, and preferably 35% by mass or more and 60% by mass or less. Polyisocyanate obtained with a higher yield tends to have a higher viscosity. The yield can be calculated from the ratio of the mass of the obtained polyisocyanate to the total mass of the raw material components.

[0105] The reaction temperature of the isocyanurate reaction is not particularly limited, but is preferably from 50° C. to 200° C., and more preferably from 50° C. to 150° C. When the reaction temperature is equal to or higher than the lower limit, the reaction tends to proceed more easily, and when the reaction temperature is equal to or lower than the upper limit, side reactions that cause coloration tend to be more effectively suppressed.

[0106] After completion of the isocyanurate reaction, it is preferable to remove unreacted diisocyanate by thin film evaporator, extraction, etc. Even if the polyisocyanate contains unreacted diisocyanate, the content of diisocyanate is preferably 3.0 mass% or less, more preferably 1.0 mass% or less, and even more preferably 0.5 mass% or less, based on the total mass of the polyisocyanate. When the concentration of residual unreacted diisocyanate is within the above range, curability tends to be more excellent.

[0107] After completion of the isocyanurate reaction, it is preferable to remove unreacted diisocyanate by thin film evaporator, extraction, etc. Even if the polyisocyanate contains unreacted diisocyanate, the content of diisocyanate is preferably 3.0 mass% or less, more preferably 1.0 mass% or less, and even more preferably 0.5 mass% or less, based on the total mass of the polyisocyanate. When the concentration of residual unreacted diisocyanate is within the above range, curability tends to be more excellent. The concentration of the residual unreacted diisocyanate can be measured by gas chromatography analysis.

[0108] (2) Method for producing polyisocyanate compound containing uretdione groups As a method for producing a polyisocyanate containing a uretdione group, there is a method using a uretdione reaction catalyst.

[0109] Specific examples of the uretdione reaction catalyst include, but are not limited to, tertiary phosphines, such as trialkylphosphines, tri-n-butylphosphine, tri-n-octylphosphine, etc.; tris(dialkylamino)phosphines, such as tris-(dimethylamino)phosphine; and cycloalkylphosphines, such as cyclohexyl-di-n-hexylphosphine. Many of these compounds also accelerate the isocyanuration reaction at the same time, producing an isocyanurate group-containing polyisocyanate in addition to a uretdione group-containing polyisocyanate.

[0110] When the desired yield is reached, a deactivator for the uretdione-forming reaction catalyst, such as phosphoric acid or methyl paratoluenesulfonate, is added to terminate the uretdione-forming reaction.

[0111] The above-mentioned catalyst is used in an amount of preferably 10 ppm by mass to 10,000 ppm by mass, more preferably 10 ppm by mass to 1,000 ppm by mass, and even more preferably 10 ppm by mass to 500 ppm by mass, based on the mass of the charged diisocyanate.

[0112] The uretdione reaction is preferably carried out at a temperature of 20° C. or higher and 120° C. or lower. The lower limit of the reaction temperature is more preferably 25° C., further preferably 30° C., and even more preferably 35° C. The upper limit of the reaction temperature is more preferably 110° C., further preferably 100° C., and even more preferably 90° C. By keeping the uretdione reaction temperature at or below the above upper limit, changes in characteristics such as coloration tend to be further suppressed.

[0113] Also, uretdione groups can be obtained by heating diisocyanate without using the above-mentioned uretdione reaction catalyst. The heating temperature is preferably 130°C or higher and 180°C or lower. The lower limit of the heating temperature is more preferably 140°C, still more preferably 145°C, still more preferably 150°C, and still more preferably 155°C. The upper limit of the heating temperature is more preferably 170°C, still more preferably 165°C, still more preferably 162°C, and still more preferably 160°C.

[0114] The heating time is preferably 0.2 hours or more and 8.0 hours or less. The lower limit of the heating time is more preferably 0.4 hours, more preferably 0.6 hours, even more preferably 0.8 hours, and even more preferably 1.0 hours. The upper limit of the heating time is more preferably 6.0 hours, more preferably 4.0 hours, even more preferably 3.0 hours, and even more preferably 2.0 hours. By setting the heating time to the lower limit or more, there is a tendency that the viscosity can be more effectively reduced, and by setting the heating time to the upper limit or less, there is a tendency that the coloring of the polyisocyanate itself can be more effectively suppressed.

[0115] When the polyisocyanate composition of the present embodiment is obtained without using a uretdione formation reaction catalyst, it is preferable to remove unreacted diisocyanate after the uretdione formation reaction by heating alone and the above-mentioned isocyanurate formation reaction are completed, from the viewpoints of reducing the concentration of unreacted diisocyanate, reducing the rate of change in molecular weight after storage of the obtained polyisocyanate composition, and reducing yellowing during high-temperature baking.

[0116] (3) Method for producing polyisocyanate compounds containing allophanate groups A method for producing a polyisocyanate containing an allophanate group includes, for example, adding an alcohol to a diisocyanate and using an allophanate reaction catalyst.

[0117] The alcohol used to form the allophanate group is preferably an alcohol formed only from carbon, hydrogen and oxygen. Specific examples of the alcohol include, but are not limited to, monoalcohols, dialcohols, etc. These alcohols may be used alone or in combination of two or more.

[0118] Examples of monoalcohols include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, and nonanol. Examples of the dialcohol include ethylene glycol, 1,3-butanediol, neopentyl glycol, and 2-ethylhexanediol.

[0119] The molar ratio of the isocyanate group of the diisocyanate to the molar amount of the hydroxyl group of the alcohol is preferably 10 / 1 or more and 1000 / 1 or less, more preferably 100 / 1 or more and 1000 / 1 or less. When the molar ratio is equal to or more than the lower limit, the average number of isocyanate groups (average number of functional groups) can be more sufficiently secured. When the molar ratio is equal to or less than the upper limit, there is an effect of excellent surface hardness.

[0120] Examples of the allophanate reaction catalyst include, but are not limited to, alkyl carboxylates of tin, lead, zinc, bismuth, zirconium, zirconyl, and the like. Examples of tin alkylcarboxylates (organotin compounds) include tin 2-ethylhexanoate and dibutyltin dilaurate. An example of the alkyl carboxylate of lead (organic lead compound) is lead 2-ethylhexanoate. Examples of zinc alkylcarboxylates (organic zinc compounds) include zinc 2-ethylhexanoate. An example of the alkyl carboxylate of bismuth is bismuth 2-ethylhexanoate. An example of the zirconium alkylcarboxylate is zirconium 2-ethylhexanoate. An example of the zirconyl alkylcarboxylate is zirconyl 2-ethylhexanoate, etc. These catalysts can be used alone or in combination of two or more.

[0121] The above-mentioned isocyanurate-forming reaction catalyst can also serve as an allophanate-forming reaction catalyst. When the allophanate-forming reaction is carried out using the above-mentioned isocyanurate-forming reaction catalyst, an isocyanurate-type polyisocyanate is naturally produced. Among these, it is preferable from the viewpoint of economical production to carry out the allophanate formation reaction and the isocyanurate formation reaction using the above-mentioned isocyanurate formation catalyst as the allophanate formation reaction catalyst.

[0122] The upper limit of the amount of the allophanate reaction catalyst used is preferably 10,000 ppm by mass, more preferably 1,000 ppm by mass, and even more preferably 500 ppm by mass, relative to the mass of the charged diisocyanate. On the other hand, the lower limit of the amount of the isocyanurate reaction catalyst used is not particularly limited, and may be, for example, 10 ppm by mass.

[0123] The lower limit of the allophanate reaction temperature is preferably 60° C., more preferably 70° C., even more preferably 80° C., and particularly preferably 90° C. On the other hand, the upper limit of the allophanate reaction temperature is preferably 160° C., more preferably 155° C., even more preferably 150° C., and particularly preferably 145° C.

[0124] That is, the allophanate reaction temperature is preferably 60°C or higher and 160°C or lower, more preferably 70°C or higher and 155°C or lower, further preferably 80°C or higher and 150°C or lower, and particularly preferably 90°C or higher and 145°C or lower. By setting the allophanate formation reaction temperature to the above lower limit or higher, it is possible to further increase the reaction rate. By setting the allophanate formation reaction temperature to the above upper limit or lower, it is likely that changes in properties such as coloration of the polyisocyanate can be more effectively suppressed.

[0125] The lower limit of the allophanate reaction time is preferably 0.2 hours, more preferably 0.4 hours, even more preferably 0.6 hours, particularly preferably 0.8 hours, and most preferably 1 hour, while the upper limit of the allophanate reaction time is preferably 8 hours, more preferably 6 hours, even more preferably 4 hours, particularly preferably 3 hours, and most preferably 2 hours. That is, the allophanate reaction time is preferably from 0.2 to 8 hours, more preferably from 0.4 to 6 hours, even more preferably from 0.6 to 4 hours, particularly preferably from 0.8 to 3 hours, and most preferably from 1 to 2 hours. By setting the allophanate formation reaction time to be equal to or more than the above lower limit, the viscosity of the polyisocyanate can be made lower, while by setting the allophanate formation reaction time to be equal to or less than the above upper limit, changes in properties such as coloration of the polyisocyanate tend to be more effectively suppressed.

[0126] When the desired yield is reached, a deactivator for the allophanate formation catalyst, such as phosphoric acid or methyl paratoluenesulfonate, is added to terminate the allophanate formation reaction.

[0127] (4) Method for producing polyisocyanate compound containing iminooxadiazinedione group The catalyst for deriving a polyisocyanate containing an iminooxadiazinedione group from a diisocyanate is not particularly limited, but for example, the following catalyst (i) or (ii), which is generally known as an iminooxadiazinedione reaction catalyst, can be used.

[0128] (i) (Poly)hydrogen fluorides represented by the general formula M[Fn] or the general formula M[Fn(HF)m], such as tetramethylammonium fluoride hydrate and tetraethylammonium fluoride (wherein m and n are integers satisfying the relationship m / n>0, and M represents an n-charged cation (mixture) or one or more radicals having a valence of n in total). (ii) 3,3,3-trifluorocarboxylic acids, 4,4,4,3,3-pentafluorobutanoic acid, 5,5,5,4,4,3,3-heptafluoropentanoic acid, 3,3-difluoroprop-2-enoic acid, etc. of the general formula R 1 -CR' 2 -C(O)O- or general formula R 2 =CR'-C(O)O-(wherein, R 1 , and R 2represents a branched, cyclic, and / or unsaturated perfluoroalkyl group having 1 to 30 carbon atoms as necessary, and R' is the same or different and is selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and an aryl group, and optionally contains a heteroatom.) and a quaternary ammonium cation or a quaternary phosphonium cation.

[0129] From the viewpoint of availability, the above (i) is preferred, and from the viewpoint of safety, the above (ii) is preferred. The amount of the iminooxadiazinedione reaction catalyst is preferably 10 ppm or more and 1,000 ppm or less based on the mass of the charged diisocyanate. The lower limit is more preferably 20 ppm, even more preferably 40 ppm, and even more preferably 80 ppm. The upper limit is more preferably 800 ppm, further preferably 600 ppm, and even more preferably 500 ppm or less.

[0130] The iminooxadiazinedione reaction temperature is preferably 40° C. or higher and 120° C. or lower. The lower limit is more preferably 50° C., and even more preferably 55° C. The upper limit is more preferably 100° C., and even more preferably 90° C., and even more preferably 80° C. By setting the iminooxadiazinedione reaction temperature to 40° C. or higher, it tends to be possible to maintain a high reaction rate. By setting the iminooxadiazinedione reaction temperature to 120° C. or lower, it tends to be possible to effectively suppress coloration of the polyisocyanate.

[0131] <Physical properties of polyisocyanate component> The viscosity at 25°C of the polyisocyanate compound produced by the above production method is preferably 300 mPa s or more and 5,000 mPa s or less, from the viewpoint of achieving both dispersibility in the aqueous base of the coating composition, and curability, water resistance, solvent resistance, and moist heat resistance. The lower limit of the viscosity is more preferably 350 mPa·s, and even more preferably 450 mPa·s, from the viewpoint of improving curability and water resistance, while the upper limit of the viscosity is more preferably 4,000 mPa·s, and even more preferably 3,000 mPa·s, from the viewpoint of improving dispersibility in the aqueous base resin. The viscosity of the polyisocyanate compound can be measured, for example, at 25° C. with an E-type viscometer (manufactured by Tokimec Co., Ltd.) using a standard rotor (1°34′×R24).

[0132] The isocyanate group content (NCO%) of the polyisocyanate compound, excluding unreacted aliphatic diisocyanate, is preferably 18% by mass or more and 25% by mass or less, more preferably 19% by mass or more and 24% by mass or less, and even more preferably 20% by mass or more and 24% by mass or less. By making the isocyanate group content equal to or more than the lower limit, the water resistance and weather resistance of the coating film formed can be improved, whereas by making the isocyanate group content equal to or less than the upper limit, the dispersibility of the coating composition can be improved. The isocyanate group content (NCO%) of the polyisocyanate compound can be measured by the titration method described in the Examples below.

[0133] The number average molecular weight of the polyisocyanate compound is preferably from 450 to 4,000, more preferably from 500 to 3,500, and even more preferably from 550 to 3,000, from the viewpoints of dispersibility in the aqueous base resin and curability. The number average molecular weight can be measured, for example, by using gel permeation chromatography (GPC).

[0134] The average number of functional groups of the polyisocyanate compound is preferably from 1.8 to 6.2, more preferably from 2.0 to 5.6, and even more preferably from 2.5 to 4.6, from the viewpoints of curability, hardness and water resistance of the coating film. The average number of functional groups is the number of isocyanate functional groups statistically contained in one molecule of a polyisocyanate compound, and can be calculated from the number average molecular weight (Mn) and isocyanate group content (NCO%) of the polyisocyanate compound using the following formula.

[0135] [Average number of functional groups] = Mn×NCO% / 4,200

[0136] <Physical properties of blocked polyisocyanate composition> In the blocked polyisocyanate composition of the present embodiment, the effective NCO content per solid content is not particularly limited, but is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 18% by mass or less, and even more preferably 3% by mass or more and 16% by mass or less, in order to improve the curability, coating hardness, and solvent resistance of the blocked polyisocyanate composition. The effective NCO content can be calculated using the method described in the Examples below.

[0137] The blocked polyisocyanate composition of this embodiment has a viscosity at 60°C in the absence of an organic solvent of 1,000 mPa·s or more and 30,000 mPa·s or less. From the viewpoint of maintaining curability and moist heat resistance, the lower limit is more preferably 2,000 mPa·s or more, and even more preferably 3,000 mPa·s or more. From the viewpoint of dispersibility in the aqueous base, the upper limit is more preferably 20,000 mPa·s or less, and even more preferably 15,000 mPa·s or less. The viscosity can be measured by the method described in the Examples below. To obtain a state free of organic solvents, the blocked polyisocyanate composition may be desolvated at a temperature equal to or lower than the viscosity measurement temperature (60° C.) under atmospheric pressure or reduced pressure. For example, an evaporator may be used to remove the solvent.

[0138] The average number of isocyanate groups bonded to a thermally dissociable blocking agent in one molecule of the blocked polyisocyanate composition is preferably 2.0 to 3.5 in terms of curability, hardness and water resistance of the coating film.

[0139] The number average molecular weight of the blocked polyisocyanate composition is preferably 300 or more and 3,000 or less, from the viewpoints of dispersibility in the aqueous base resin and curability.

[0140] <Acid phosphate esters> The blocked polyisocyanate composition of the present embodiment may further contain an acidic phosphoric acid ester in addition to the blocked polyisocyanate compound. Examples of acidic phosphate esters include, but are not limited to, methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, dibutyl pyrophosphate, butoxyethyl acid phosphate, 2-ethylhexyl acid phosphate, alkyl (C 12 , C 14 , C 16 , C 18 ) acid phosphate, isodecyl acid phosphate, isotridecyl acid phosphate, lauryl acid phosphate, stearyl acid phosphate, oleyl acid phosphate, tetracosyl acid phosphate, ethylene glycol acid phosphate, 2-hydroxyethyl methacrylate acid phosphate, dibutyl phosphate, bis(2-ethylhexyl) phosphate, and the like.

[0141] The content of the acidic phosphate esters in the blocked polyisocyanate composition is 5 ppm by mass or more, preferably 10 ppm by mass or more, and more preferably 15 ppm by mass or more, and 95 ppm by mass or less, preferably 92 ppm by mass or less, and more preferably 90 ppm by mass or less, in terms of the lower limit.

[0142] <Other components> The aqueous blocked polyisocyanate composition of the present embodiment may contain other components in addition to the blocked polyisocyanate compound. The other components are not particularly limited, but examples thereof include organic solvents, preservatives, antioxidants, light stabilizers, polymerization inhibitors, surfactants, and antioxidants.

[0143] (Organic solvent) The organic solvent may be a hydrophilic organic solvent or a hydrophobic organic solvent, and these organic solvents may be used alone or in combination.

[0144] The hydrophobic organic solvent is not particularly limited, but examples thereof include mineral spirits, solvent naphtha, LAWS (Low Aromatic White Spirit), HAWS (High Aromatic White Spirit), toluene, xylene, cyclohexane, esters, ketones, and amides.

[0145] Examples of esters include ethyl acetate and butyl acetate.

[0146] Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

[0147] Examples of amides include N,N-dimethylformamide and N,N-dimethylacetamide.

[0148] The hydrophilic organic solvent is not particularly limited, but examples thereof include alcohols, ethers, and esters of ether alcohols.

[0149] Examples of the alcohols include methanol, ethanol, propanol, isopropanol, and 2-ethylhexanol.

[0150] Examples of the ethers include diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, and dipropylene glycol dimethyl ether.

[0151] Examples of esters of ether alcohols include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol monomethyl ether acetate.

[0152] In the aqueous blocked polyisocyanate composition of the present embodiment, the content of the organic solvent is preferably from 0 mass % to 90 mass %, more preferably from 0 mass % to 50 mass %, and even more preferably from 0 mass % to 30 mass %, relative to the total mass of the aqueous blocked polyisocyanate composition of the present embodiment, from the viewpoint of ease of dispersion.

[0153] (Antioxidants and light stabilizers) Examples of the antioxidant and light stabilizer include the following (a) to (e), which may be contained alone or in combination of two or more. (a) Aliphatic, aromatic or alkyl-substituted aromatic esters of phosphoric or phosphorous acid, and hypophosphorous acid derivatives. (b) Phosphorus compounds such as phenylphosphonic acid, phenylphosphinic acid, diphenylphosphonic acid, polyphosphonates, dialkyl pentaerythritol diphosphites, and dialkyl bisphenol A diphosphites. (c) Phenolic derivatives (especially hindered phenol compounds). (d) Compounds containing sulfur, such as thioether compounds, dithioacid salt compounds, mercaptobenzimidazole compounds, thiocarbanilide compounds, and thiodipropionic acid esters. (e) Tin compounds such as tin maleate and dibutyltin monoxide.

[0154] (Polymerization inhibitor) Examples of the polymerization inhibitor include hydroquinones, phenols, cresols, catechols, and benzoquinones. Specific examples of the polymerization inhibitor include benzoquinone, p-benzoquinone, p-toluquinone, p-xyloquinone, naphthoquinone, 2,6-dichloroquinone, hydroquinone, trimethylhydroquinone, catechol, p-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, monomethylhydroquinone, p-methoxyphenol, 2,6-di-tert-butyl-p-cresol, and hydroquinone monomethyl ether. These may be contained alone or in combination of two or more.

[0155] (Surfactant) Examples of the surfactant include known anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0156] In the blocked polyisocyanate composition of the present embodiment, the total content of the antioxidant, the light stabilizer, the polymerization inhibitor, and the surfactant is preferably 0% by mass or more and 10% by mass or less, more preferably 0% by mass or more and 5% by mass or less, and even more preferably 0% by mass or more and 2% by mass or less, relative to the total mass of the blocked polyisocyanate composition of the present embodiment.

[0157] <Water-based coating composition> The aqueous coating composition of the present embodiment contains the above-mentioned blocked polyisocyanate composition and a base agent. The aqueous coating composition contains the above-mentioned blocked polyisocyanate composition, and thus when formed into a coating film, it has excellent curability, hardness, and water resistance.

[0158] <Main ingredient> The main agent used in the water-based coating composition is preferably an aqueous polyol.The aqueous polyol includes all of those that contain hydroxyl groups and are expressed as latex, emulsion, dispersion, and water-soluble resin.Specific examples of the aqueous polyol include polyvinylidene chloride copolymer, polyvinyl chloride copolymer, vinyl acetate copolymer, water-soluble acrylic resin, water-soluble polyester resin, urethane dispersion, acrylic emulsion, fluorine copolymer emulsion, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer, rubber-based latex, polybutadiene copolymer, urethane-acrylic emulsion, and copolymers or mixtures thereof. Among these, the aqueous polyol is preferably one that is expressed as a latex, emulsion, or dispersion because of its excellent operability and water resistance, and among these, an acrylic emulsion, a fluorocopolymer emulsion, a urethane dispersion, or a polymer thereof is particularly preferred because of its excellent weather resistance, gloss, and toughness when formed into a coating film.

[0159] When an aqueous polyol expressed as a latex, emulsion or dispersion is used, the lower limit of the particle size is preferably 5 nm, more preferably 10 nm, and even more preferably 40 nm, while the upper limit of the particle size is preferably 1.0 μm, more preferably 500 nm, and even more preferably 300 nm. That is, the particle size is preferably 5 nm or more and 1.0 μm or less, more preferably 10 nm or more and 500 nm or less, and even more preferably 40 nm or more and 300 nm or less. When the particle size is within the above range, the resulting coating film has higher gloss and better water resistance, and the latex, emulsion or dispersion has more sufficient stability.

[0160] The lower limit of the hydroxyl value of the aqueous polyol is preferably 1 mgKOH / g, more preferably 5 mgKOH / g, and even more preferably 10 mgKOH / g, while the upper limit of the hydroxyl value is preferably 300 mgKOH / g, more preferably 200 mgKOH / g, and even more preferably 150 mgKOH / g. That is, the hydroxyl value of the aqueous polyol is preferably from 1 mgKOH / g to 300 mgKOH / g, more preferably from 5 mgKOH / g to 200 mgKOH / g, and even more preferably from 10 mgKOH / g to 150 mgKOH / g. When the hydroxyl value of the aqueous polyol is within the above range, the number of crosslinking points becomes more sufficient, and a more flexible and tough coating film can be obtained.

[0161] In the coating composition of the present embodiment, the lower limit of the molar ratio of the isocyanate group of the polyisocyanate composition to the hydroxyl group of the aqueous polyol (isocyanate group / hydroxyl group) is preferably 0.3, more preferably 0.5, and even more preferably 0.6, while the upper limit of the molar ratio is preferably 5.0, more preferably 3.0, and even more preferably 2.5. That is, the molar ratio of the isocyanate groups of the polyisocyanate composition to the hydroxyl groups of the aqueous polyol (isocyanate groups / hydroxyl groups) is preferably 0.3 to 5.0, more preferably 0.5 to 3.0, and even more preferably 0.6 to 2.5. When the molar ratio (isocyanate group / hydroxyl group) is within the above range, the number of crosslinking points becomes more sufficient, and a more flexible and tough coating film can be obtained.

[0162] <Other ingredients> The coating composition of the present embodiment may further contain additives that are generally added to paints, in addition to the above-mentioned blocked polyisocyanate composition and resins. Examples of such additives include inorganic pigments, organic pigments, extender pigments, silane coupling agents, titanium coupling agents, organic phosphates, organic phosphites, thickeners, leveling agents, thixotropic agents, defoamers, freeze stabilizers, matting agents, crosslinking reaction catalysts (catalysts for promoting curing), antiskinning agents, dispersants, wetting agents, fillers, plasticizers, lubricants, reducing agents, preservatives, antifungal agents, deodorants, anti-yellowing agents, ultraviolet absorbers, antistatic agents or charge regulators, antisettling agents, etc. These additives may be contained alone or in combination of two or more.

[0163] The crosslinking reaction catalyst (catalyst for promoting curing) is not limited to the following, but examples thereof include those shown in (a) or (b) below. (a) Metal salts such as dibutyltin dilaurate, tin 2-ethylhexanoate, zinc 2-ethylhexanoate, and cobalt salts. (b) Tertiary amines such as triethylamine, pyridine, methylpyridine, benzyldimethylamine, N,N-dimethylcyclohexylamine, N-methylpiperidine, pentamethyldiethylenetriamine, N,N'-endoethylenepiperazine, and N,N'-dimethylpiperazine.

[0164] The aqueous coating composition of the present embodiment may further contain a surfactant in addition to the above-mentioned blocked polyisocyanate composition and resins in order to improve dispersibility in paint.

[0165] The aqueous coating composition of the present embodiment may further contain an antioxidant, a light stabilizer, and a polymerization inhibitor in addition to the above-mentioned blocked polyisocyanate composition and resins in order to improve the storage stability of the coating material.

[0166] <Method of producing water-based coating composition> The aqueous coating composition of the present embodiment can be obtained by mixing the blocked polyisocyanate composition and the base material, and, if necessary, other components, etc., using a known method.

[0167] For example, in the case of a water-based coating composition, the additives exemplified in the above-mentioned other components are added to the resin or its water dispersion or water solution as necessary. Then, the polyisocyanate composition or its water dispersion is added as a curing agent, and water or a solvent is further added as necessary to adjust the viscosity. Then, the water-based coating composition can be obtained by forced stirring with a stirring device.

[0168] When preparing a solvent-based coating composition, first, the additives exemplified in the above-mentioned other components are added to the main agent or its solvent dilution as necessary. Then, the above-mentioned blocked polyisocyanate composition is added as a curing agent, and a solvent is further added as necessary to adjust the viscosity. Then, the solvent-based coating composition can be obtained by stirring by hand or using a stirring device such as a mixer.

[0169] <Coating film and coating substrate> The coating film of the present embodiment is a coating film formed by curing the above-mentioned coating composition. The coated substrate of the present embodiment is a substrate coated with the above-mentioned coating composition. The coated substrate of the present embodiment preferably has a coating layer containing the above-mentioned coating composition.

[0170] The coated substrate of the present embodiment has a coating film formed by curing the above-mentioned coating composition, and therefore has excellent appearance, water resistance and hardness.

[0171] The coated substrate of the present embodiment can be obtained by applying the above-mentioned coating composition onto a substrate by a known method such as roll coating, curtain flow coating, spray coating, bell coating, electrostatic coating, or the like, and then curing the composition through a room temperature drying or baking process.

[0172] The coating substrate of this embodiment may comprise a desired substrate and, optionally, a conventional primer prior to coating. Examples of the substrate include metal, wood, glass, stone, ceramic materials, concrete, rigid and flexible plastics, textiles, leather products, paper, and the like.

[0173] <Usage> The aqueous coating composition of the present embodiment can be particularly used for architectural paints, automotive paints, automotive repair paints, construction and agricultural machinery paints, plastic paints, pressure sensitive adhesives, bonding agents, building materials, household aqueous paints, other coating agents, sealants, inks, casting materials, elastomers, foams, plastic raw materials, and fiber treatment agents. EXAMPLES

[0174] 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 as follows. Unless otherwise specified, "parts" and "%" mean "parts by mass" and "% by mass".

[0175] <Measurement method> [Physical Properties 1] (Viscosity of polyisocyanate component) The viscosity of the polyisocyanate component was measured at 25° C. using an E-type viscometer (manufactured by Tokimec Co., Ltd.). A standard rotor (1°34′×R24) was used. The rotation speeds were as follows:

[0176] (Rotation Speed) 100rpm (less than 128mPa·s) 50 rpm (128 mPa s or more but less than 256 mPa s) 20 rpm (256 mPa s or more but less than 640 mPa s) 10 rpm (640 mPa s or more but less than 1280 mPa s) 5 rpm (1280 mPa s or more but less than 2560 mPa s) 2.5 rpm (for values ​​between 2560 mPa s and 5120 mPa s)

[0177] [Physical Properties 2] (Isocyanate group content (NCO%)) The polyisocyanate component obtained in the synthesis example was used as a sample to measure the isocyanate group content according to the method described in JIS K7301-1995 (Test method for tolylene diisocyanate type prepolymer for thermosetting urethane elastomer). A more specific method for measuring the isocyanate group content (NCO%) is shown below.

[0178] (1) 1 g (Wg) of sample was placed in a 200 mL Erlenmeyer flask, and 20 mL of toluene was added to the flask to dissolve the sample. (2) Then, 20 mL of 2.0 N di-n-butylamine-toluene solution was added to the flask and allowed to stand for 15 minutes. (3) 70 mL of 2-propanol was added to the flask and dissolved to obtain a solution. (4) The solution obtained in (3) above is titrated with 1 mol / L hydrochloric acid to obtain the sample titer (V 1 mL) was calculated. (5) Even if no sample is added, the measurement is carried out in the same manner as in (1) to (3) above, and the blank titer (V 0 mL) was calculated.

[0179] From the sample titration amount and blank titration amount obtained above, the isocyanate group content (NCO%) was calculated using the following formula.

[0180] Isocyanate group content (mass%) = (V 0 -V 1 )×42 / [W(1g)×1000]×100

[0181] [Physical Properties 3] (Number Average Molecular Weight of Blocked Polyisocyanate Composition) The number average molecular weight of the blocked polyisocyanate composition (abbreviated as "number average molecular weight" in Tables 1 and 2) is the number average molecular weight based on polystyrene measured by gel permeation chromatography (GPC). The specific measurement conditions for the GPC measurement were as follows:

[0182] Equipment: Tosoh Corporation, HLC-802A Columns: Tosoh Corporation, G1000HXL x 1, G2000HXL x 1, G3000HXL x 1 Carrier: Tetrahydrofuran Detection method: Differential refractometer

[0183] [Physical Properties 4] (Average number of ethylene oxide (EO) repeat units (EO number)) The average number of ethylene oxide (EO) repeating units (EO number) introduced into the polyisocyanate component was calculated by the following method. It was determined by proton nuclear magnetic resonance (NMR) under the measurement conditions shown below. Here, the average number of ethylene oxide repeating units (EO number) in the polyisocyanate composition was determined by matching the integral value of the relative intensity corresponding to the alkylene group with the integral value of the relative intensity corresponding to the alkyl group.

[0184] (Measurement conditions) NMR device: Bruker Biospin Avance600 (product name) Observation kernel: 1 H Frequency: 600MHz Solvent: CDCl 3 Number of times accumulated: 256

[0185] [Physical Properties 5] (Proportion of polyalkylene glycol alkyl ether modified (modification rate)) Using a polyisocyanate component modified with polyalkylene glycol alkyl ether as a sample, the modification rate is the proportion of polyalkylene glycol alkyl ether modified relative to 100 molar equivalents of isocyanate groups in the raw polyisocyanate component, and was determined from the peak area ratio of unmodified isocyanurate trimer, 1-modified isocyanurate trimer, 2-modified isocyanurate trimer, and 3-modified isocyanurate trimer at a measurement wavelength of 220 nm by liquid chromatography (LC). The apparatus and conditions used are as follows.

[0186] (Measurement conditions) LC device: Manufactured by Waters, UPLC (product name) Column: Waters, ACQUITY UPLC HSS T3 1.8 μm C18, inner diameter 2.1 mm x length 50 mm Flow rate: 0.3mL / min Mobile phase: A = 10 mM ammonium acetate aqueous solution, B = acetonitrile Gradient conditions: The initial mobile phase composition was A / B=98 / 2, and after sample injection, the ratio of B was increased linearly to A / B=0 / 100 after 10 minutes. Detection method: Photodiode array detector, measurement wavelength is 220 nm

[0187] [Physical Properties 6] (Content of portion derived from polyalkylene glycol alkyl ether) Using a polyisocyanate component modified with a polyalkylene glycol alkyl ether as a sample, the content of the portion in the polyisocyanate component derived from the polyalkylene glycol alkyl ether of the modified polyisocyanate (referred to as the "hydrophilic compound content" in Tables 1 and 2) was calculated as follows from the isocyanate group content measured in [Physical Property 2], the molecular weight of the polyalkylene glycol alkyl ether calculated from the average number n of the polyalkylene glycol alkyl ether determined in [Physical Property 4], and the modification rate determined in [Physical Property 5].

[0188] "Content rate (%)" = (Isocyanate group content (mass%)) / 100 / 42 / {(100)-(Modification rate (%))}×(Modification rate (%))×(Molecular weight of polyalkylene glycol alkyl ether)×100

[0189] Regarding the molecular weight of the polyalkylene glycol alkyl ether, for example, when the polyalkylene glycol alkyl ether used was polyethylene glycol (mono)methyl ether, it was determined as follows.

[0190] "Molecular weight of polyethylene glycol (mono)methyl ether" = (Molecular weight of methyl group (15)) + (Molecular weight of hydroxyl group (17)) + {(Molecular weight of ethylene oxide (44)) × (average number of n)}

[0191] [Physical Properties 7] (Blocked isocyanate group content (effective NCO content)) The effective NCO content of the obtained blocked polyisocyanate composition was determined as follows. The effective NCO content (mass%) here quantifies the amount of blocked isocyanate groups present in the blocked polyisocyanate component after the blocking reaction that can participate in the crosslinking reaction, and is expressed as mass% of isocyanate groups. The effective NCO content was calculated using the formula shown below. In the formula shown below, "S" represents the non-volatile content (mass%) of the blocked polyisocyanate component. "W1" represents the mass (g) of the polyisocyanate used in the reaction. "A" represents the isocyanate group content (mass%) of the polyisocyanate. "W2" represents the mass (g) of the blocked polyisocyanate after the blocking reaction.

[0192] Effective NCO content (mass%) = {S × (W1 × A)} / W2

[0193] [Physical Properties 8] (Viscosity of Blocked Polyisocyanate Composition) The viscosity of the blocked polyisocyanate composition was measured in the absence of an organic solvent using a rheometer (RS-1 manufactured by HAAKE) at 60° C. A rotor of 2°×R10 was used.

[0194] [Physical Properties 9] (Mole fraction of each bond group) The obtained polyisocyanate composition was subjected to polymerization using Biospin Avance 600 (trade name) manufactured by Bruker. 13 C-NMR measurements were performed under the following specific measurement conditions:

[0195] (Measurement conditions) 13 C-NMR device: AVANCE600 (manufactured by Bruker) Cryoprobe (Bruker) CryoProbe® CPDUL 600S3-C / HD-05Z Resonance frequency: 150MHz Concentration: 60wt / vol% Shift reference: CDCl 3 (77 ppm) Accumulation count: 10,000 times Pulse program: zgpg30 (proton complete decoupling method, waiting time 2 sec)

[0196] Isocyanurate group: (integral value around 148.6 ppm) ÷ 3 Uretdione group: (integral value around 157 ppm) ÷ 2 Allophanate group: (integral value around 154 ppm) ÷ 1 Iminooxadiazinedione group: (integral value around 137.3 ppm) ÷ 1 Urethane group: {(integral value around 156-157 ppm)-(integral value around 154 ppm)}÷1

[0197] The integral values ​​of the above signals were divided by the number of carbons being measured to determine the respective molar fractions relative to the total (100 mol%) of isocyanurate groups, iminooxadiazinedione groups, allophanate groups, and uretdione groups, the molar ratios of urethane groups and isocyanurate groups, and the molar fractions of uretdione groups and isocyanurate groups.

[0198] [Physical Properties 10] (Average number of isocyanate groups bonded to thermally dissociable blocking agents per molecule) In the obtained blocked polyisocyanate composition, the average number of isocyanate groups bonded to the thermally dissociable blocking agent per molecule (abbreviated as "average number of blocked isocyanate groups" in Tables 1 and 2) can be calculated in the same manner as the above-mentioned [average number of functional groups] using the blocked isocyanate group content (effective NCO content) determined in [Property 7] and the number average molecular weight (Mn) of the blocked polyisocyanate composition. The number average molecular weight (Mn) of the blocked polyisocyanate composition can be measured in the same manner as the number average molecular weight of the polyisocyanate component in [Property 3].

[0199] (Production of Water-Based Coating Composition) The acrylic resin water dispersion (solid content 42%, resin content hydroxyl value 66 mgKOH / g, acid value 16 mgKOH / g) obtained in Synthesis Example 2 described later was mixed with the blocked polyisocyanate compositions obtained in the Examples and Comparative Examples at a ratio such that the functional group ratio (NCO / OH) was 1.0. Further, deionized water was added to this mixture at a ratio such that the solid content was 40%, and the mixture was stirred at 1000 rpm for 5 minutes using a dispersing blade to prepare a water-based coating composition.

[0200] <Evaluation method> [Rating 1] (Compatibility with water-based base agents) Each water-based coating composition was applied to a 7 cm x 15 cm glass plate with an air spray gun to a dry thickness of 40 μm. It was dried at 23° C. for 30 minutes, then dried at 130° C. for 30 minutes, and cooled at 23° C. The coating was visually observed and the compatibility with the water-based base agent was evaluated according to the following criteria.

[0201] (Evaluation Criteria) ◎: Transparent, no foreign matter ○: Transparent, the number of visible foreign matter on the entire coating is 5 or less △: Slightly cloudy, with 10 or less visible foreign particles on the entire coating ×: Cloudy, 10 or more foreign objects visible on the entire coating

[0202] [Rating 2] (Curability of Water-Based Blocked Polyisocyanate Composition) Each water-based coating composition was applied onto a polypropylene plate, dried at 23°C for 30 minutes, and then dried at 130°C for 30 minutes to prepare a coating film with a thickness of 40 μm. The prepared coating film was then immersed in acetone at 23°C for 24 hours, and the mass of the coating film that remained undissolved was divided by the mass before immersion to calculate the proportion (mass%) of the coating film that remained undissolved. The curability was evaluated according to the following criteria. Hardening of coating film (%) = (mass of coating film that remained undissolved) / (mass of coating film before immersion in acetone) x 100

[0203] (Evaluation Criteria) ◎: 90% or more ○: 85% or more △: 80% or more but less than 85% ×: Less than 80%

[0204] [Rating 3] (Chemical resistance of coating film) Each aqueous coating composition was applied onto a glass plate, dried at 23°C for 30 minutes, and then dried at 130°C for 30 minutes to obtain a coating film with a thickness of 40 μm. After storing the obtained coating film at 23°C for one week, a cotton ball soaked in an 80% aqueous ethanol solution was placed on the coating film, and the change in appearance of the coating film after 60 minutes was visually confirmed. Chemical resistance was evaluated according to the following criteria.

[0205] (Evaluation Criteria) ◎: No change in appearance of coating film ○: There is a slight change in the appearance of the coating film. △: Appearance of the coating has changed, with slight cracks and peeling of the coating. ×: Cracks and peeling occurred on the entire coating

[0206] [Rating 4] (Coating film hardness) Each water-based coating composition was applied onto a glass plate, dried at 23°C for 30 minutes, and then dried at 130°C for 30 minutes to obtain a coating film having a thickness of 40 μm. The obtained coating film was stored at 23°C for 1 week, and then the Konig hardness (times) was measured using a Konig hardness tester (manufactured by BYK Garder, product name "Pendulum hardness tester"). The hardness of the coating film was evaluated according to the following criteria.

[0207] (Evaluation Criteria) ◎: 100 times or more ○: 80 to less than 100 times △: 50 to less than 80 times ×: Less than 50 times

[0208] [Rating 5] (Water resistance of coating film) Each water-based coating composition was applied onto a glass plate, dried at 23°C for 30 minutes, and then dried at 130°C for 30 minutes to obtain a coating film having a thickness of 40 μm. The obtained coating film was stored at 23°C for one week, and then immersed in water at 40°C for 72 hours, after which the change in appearance of the coating film was visually observed. The water resistance of the coating film was evaluated according to the following criteria.

[0209] (Evaluation Criteria) ◎: Almost no whitening or blisters were observed ○: Blisters were observed in some of the immersed areas. △: A slight whitening was observed in the immersed area. ×: Whitening of the immersed area is evident

[0210] [Rating 6] (Drying property of coating film (blocking resistance)) The drying property (blocking resistance) of the coating film was evaluated by a method according to JIS K5600-3-5. A 50μm thick PET film coated to a dry thickness of 30μm was baked at 120℃ for 15 minutes, then left to stand at 23℃ for 24 hours and allowed to cool. This coated film was cut to 40mm×40mm, and the coated and uncoated surfaces of the two resulting films were stacked together and a 40mm diameter weight (500g) with a smooth bottom was placed on top. The film was placed in an oven at 40℃ / 60%RH, and after 72 hours, it was left to stand at 23℃ for 24 hours and allowed to cool. The stacked coated films were peeled off and the remaining marks were visually observed to evaluate the drying properties (blocking resistance) of the coating film.

[0211] (Evaluation Criteria) ◎: No traces of paint remaining ○: Less than 10% of the coating remains on the unpainted surface △: 10% to less than 30% of the coating remains on the unpainted surface ×: 30% or more of the coating film remains on the uncoated surface.

[0212] [Rating 7] (Storage Stability of Water-Based Blocked Polyisocyanate Composition) The aqueous blocked polyisocyanate composition was sealed in a glass bottle under a nitrogen atmosphere and stored for 2 months in an environment at 40° C. After cooling to an environment at 23° C., the aqueous blocked polyisocyanate composition was evaluated for viscosity change according to the following evaluation criteria.

[0213] ◎: Viscosity change is within ±10% ○: Viscosity change is within ±10~20% △: Viscosity change is within ±20~30% ×: Viscosity change is ±30% or more

[0214] <Synthesis of polyisocyanate component>

[0215] [Synthesis Example 1-1] (Synthesis of polyisocyanate component P-1) A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was conditioned with nitrogen, and 1,000 g of HDI and 1.5 g of 2-ethylhexanol were charged. The temperature inside the reactor was kept at 70°C for 2 hours while stirring. Tetramethylammonium caprylate was then added as an isocyanurate catalyst to carry out the isocyanurate reaction. When the conversion rate reached 18%, phosphoric acid was added to stop the reaction. The reaction liquid was further kept at 160°C for 1 hour. This heating produced a polyisocyanate containing uretdione groups. The reaction liquid was cooled and filtered, and unreacted HDI was removed using a thin-film evaporator to obtain polyisocyanate component P-1. The viscosity of the obtained polyisocyanate component P-1 at 25°C was 500 mPa·s, and the NCO content was 23.3% by mass.

[0216] [Synthesis Example 1-2] (Synthesis of polyisocyanate component P-2) In a reaction vessel similar to that of Synthesis Example 1-1, 1000 g of HDI was charged, and the temperature inside the reactor was kept at 70°C for 2 hours under stirring. Then, 1 g of a solution of tetramethylammonium caprate diluted to 5% by mass with isobutanol was added as an isocyanurate catalyst to carry out an isocyanurate reaction. When the conversion rate reached 24%, phosphoric acid was added to stop the reaction. After filtering the reaction liquid, the reaction liquid was purified twice using a thin-film distillation apparatus at 160°C and 0.2 Torr to obtain polyisocyanate component P-2. The viscosity of the obtained polyisocyanate component P-2 at 25°C was 1,300 mPa·s, and the NCO content was 23.1% by mass.

[0217] [Synthesis Example 1-3] (Synthesis of polyisocyanate component P-3) Into a reaction vessel similar to that of Synthesis Example 1-1, 1000g of HDI and 3.2g of 2-ethylhexanol were charged, and the temperature inside the reactor was maintained at 70°C for 2 hours with stirring. Then, tetramethylammonium caprylate, an isocyanurate reaction catalyst, was added, and when the yield reached 41%, phosphoric acid was added to stop the reaction. After filtering the reaction liquid, unreacted HDI was removed using a thin-film evaporator to obtain polyisocyanate component P-3. The viscosity of the obtained polyisocyanate component P-3 at 25°C was 2,700mPa·s, and the NCO content was 21.7%.

[0218] [Synthesis Example 1-4] (Synthesis of polyisocyanate component P-4) In a reaction vessel similar to that of Synthesis Example 1-1, 600 g of HDI was charged, and the temperature inside the reactor was maintained at 60° C. under stirring. 9 g of tri-n-butylphosphine (Cytop™ 340, Cytec), a catalyst for uretdione formation, was added thereto, and uretdione formation and isocyanurate formation were carried out. When the conversion rate reached 40%, 12 g of methyl-p-toluenesulfonate was added to stop the reaction. After cooling the reaction liquid, it was filtered and the unreacted HDI was removed using a thin-film evaporator to obtain polyisocyanate component P-4. The viscosity of the obtained polyisocyanate component P-4 at 25° C. was 200 mPa·s, and the NCO content was 21.8% by mass.

[0219] [Synthesis Example 1-5] (Synthesis of polyisocyanate component P-5) Into a reaction vessel similar to that of Synthesis Example 1-1, 83 parts by mass of the polyisocyanate component P-2 synthesized in Synthesis Example 1-2 and 17 parts by mass of the polyisocyanate component P-4 synthesized in Synthesis Example 1-4 were added, respectively, and stirred until homogenous to obtain polyisocyanate component P-5. The viscosity of the obtained polyisocyanate component P-5 at 25°C was 1,000 mPa s, and the NCO content was 22.9% by mass.

[0220] [Synthesis Example 1-6] (Synthesis of polyisocyanate component P-6) In a reaction vessel similar to that of Synthesis Example 1-1, 1,000 g of HDI, 3.5 g of 2-ethylhexanol, and 1 part of isobutanol were charged, and the temperature inside the reactor was kept at 70°C for 2 hours under stirring. Then, tetramethylammonium caprylate was added as an isocyanurate catalyst to carry out an isocyanurate reaction, and when the conversion rate reached 15%, phosphoric acid was added to stop the reaction. This reaction liquid was further kept at 160°C for 1 hour. This heating produced a polyisocyanate containing uretdione groups. After cooling and filtering the reaction liquid, unreacted HDI was removed using a thin-film evaporator to obtain polyisocyanate component P-6. The viscosity of the obtained polyisocyanate component P-6 at 25°C was 300 mPa·s, and the NCO content was 23.0 mass%.

[0221] [Synthesis Example 1-7] (Synthesis of polyisocyanate component P-7) In a reaction vessel similar to that of Synthesis Example 1-1, 1000 g of HDI was charged, and the temperature inside the reactor was maintained at 70°C for 2 hours under stirring. Then, 1 g of a solution of tetramethylammonium caprate diluted to 5% by mass with isobutanol was added as an isocyanurate catalyst to carry out an isocyanurate reaction. When the conversion rate reached 21%, phosphoric acid was added to stop the reaction. The reaction liquid was filtered and purified using a thin-film distillation apparatus to obtain polyisocyanate component P-7. The viscosity of the obtained polyisocyanate component P-7 at 25°C was 800 mPa·s, and the NCO content was 23.2% by mass.

[0222] <Synthesis of amine sulfonate> [Synthesis Example 2-1] (Synthesis of HES / TPA) 10 parts by mass of 1-propanol was added to 20 parts by mass of a 70% by mass aqueous solution of 2-hydroxyethanesulfonic acid (hereinafter sometimes abbreviated as "HES") and stirred to obtain a solution. Furthermore, tripropylamine (hereinafter sometimes abbreviated as "TPA") was weighed out in a ratio such that the molar equivalent ratio to HES was 1, and a liquid obtained by diluting with the same part by mass of 1-propanol was added dropwise to the above solution while stirring. One hour after the start of the dropwise addition, the stirring was stopped, and the solution was dehydrated and desolvated in an evaporator to obtain 2-hydroxyethanesulfonic acid tripropylamine salt (hereinafter sometimes abbreviated as "HES / TPA") with a solid content of 99.8% by mass.

[0223] <Synthesis of blocked polyisocyanate composition>

[0224] [Synthesis Example 3-1] (Synthesis of blocked polyisocyanate composition PB-1) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-7, 19.0 parts by mass of methoxypolyethylene glycol (MPG-081, ethylene oxide repeating unit: 15, manufactured by Nippon Nyukazai Co., Ltd.), and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 51.4 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 37.8 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain a blocked polyisocyanate composition PB-1. The physical properties of the obtained blocked polyisocyanate composition PB-1 are shown in Table 1.

[0225] [Synthesis Example 3-2] (Synthesis of blocked polyisocyanate composition PB-2) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-1, 3.8 parts by mass of methoxypolyethylene glycol (MPG-081, ethylene oxide repeating unit: 15, manufactured by Nippon Nyukazai Co., Ltd.), and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 53.8 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 37.8 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain a blocked polyisocyanate composition PB-2. The physical properties of the obtained blocked polyisocyanate composition PB-2 are shown in Table 1.

[0226] [Synthesis Example 3-3] (Synthesis of blocked polyisocyanate composition PB-3) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-1, 11.5 parts by mass of methoxypolyethylene glycol (MPG-081, ethylene oxide repeating unit: 15, manufactured by Nippon Nyukazai Co., Ltd.), and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 52.7 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 39.5 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain blocked polyisocyanate composition PB-3. The physical properties of the obtained blocked polyisocyanate composition PB-3 are shown in Table 1.

[0227] [Synthesis Example 3-4] (Synthesis of blocked polyisocyanate composition PB-4) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-1, 19.1 parts by mass of methoxypolyethylene glycol (MPG-081, ethylene oxide repeating unit: 15, manufactured by Nippon Nyukazai Co., Ltd.), and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 51.6 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 41.2 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain blocked polyisocyanate composition PB-4. The physical properties of the obtained blocked polyisocyanate composition PB-4 are shown in Table 1.

[0228] [Synthesis Example 3-5] (Synthesis of blocked polyisocyanate composition PB-5) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-1, 38.3 parts by mass of methoxypolyethylene glycol (MPG-081, ethylene oxide repeating unit: 15, manufactured by Nippon Nyukazai Co., Ltd.), and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 48.9 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 45.4 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain blocked polyisocyanate composition PB-5. The physical properties of the obtained blocked polyisocyanate composition PB-5 are shown in Table 1.

[0229] [Synthesis Example 3-6] (Synthesis of blocked polyisocyanate composition PB-6) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-5, 18.8 parts by mass of methoxypolyethylene glycol (MPG-081, ethylene oxide repeating unit: 15, manufactured by Nippon Nyukazai Co., Ltd.), and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 50.7 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 40.9 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain blocked polyisocyanate composition PB-6. The physical properties of the obtained blocked polyisocyanate composition PB-6 are shown in Table 1.

[0230] [Synthesis Example 3-7] (Synthesis of blocked polyisocyanate composition PB-7) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-6, 18.9 parts by mass of methoxypolyethylene glycol (MPG-081, ethylene oxide repeating unit: 15, manufactured by Nippon Nyukazai Co., Ltd.), and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 50.9 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 41.0 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain blocked polyisocyanate composition PB-7. The physical properties of the obtained blocked polyisocyanate composition PB-7 are shown in Table 1.

[0231] [Synthesis Example 3-8] (Synthesis of blocked polyisocyanate composition PB-8) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-1, 11.8 parts by mass of methoxypolyethylene glycol (MPG-130, ethylene oxide repeating unit: 9, manufactured by Nippon Nyukazai Co., Ltd.), and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 51.6 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 39.4 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain blocked polyisocyanate composition PB-8. The physical properties of the obtained blocked polyisocyanate composition PB-8 are shown in Table 1.

[0232] [Synthesis Example 3-9] (Synthesis of blocked polyisocyanate composition PB-9) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-1 and 3.0 parts by mass of HES / TPA synthesized in Synthesis Example 2-1 were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 51.7 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 37.4 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain a blocked polyisocyanate composition PB-9. The physical properties of the obtained blocked polyisocyanate composition PB-9 are shown in Table 1.

[0233] [Synthesis Example 3-10] (Synthesis of blocked polyisocyanate composition PB-10) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-3, 17.8 parts by mass of methoxypolyethylene glycol (MPG-081, ethylene oxide repeating unit: 15, manufactured by Nippon Nyukazai Co., Ltd.), and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 48.0 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 40.0 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain blocked polyisocyanate composition PB-10. The physical properties of the obtained blocked polyisocyanate composition PB-10 are shown in Table 2.

[0234] [Synthesis Example 3-11] (Synthesis of blocked polyisocyanate composition PB-11) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-4, 17.9 parts by mass of methoxypolyethylene glycol (MPG-081, ethylene oxide repeating unit: 15, manufactured by Nippon Nyukazai Co., Ltd.), and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 48.2 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 40.2 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain blocked polyisocyanate composition PB-11. The physical properties of the obtained blocked polyisocyanate composition PB-11 are shown in Table 2.

[0235] [Synthesis Example 3-12] (Synthesis of blocked polyisocyanate composition PB-12) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-1 and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 54.3 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 37.1 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain a blocked polyisocyanate composition PB-12. The physical properties of the obtained blocked polyisocyanate composition PB-12 are shown in Table 2.

[0236] [Synthesis Example 3-13] (Synthesis of blocked polyisocyanate composition PB-13) In a reaction vessel similar to that of Synthesis Example 1-1, 100 parts by mass of polyisocyanate component P-1, 76.6 parts by mass of methoxypolyethylene glycol (MPG-081, ethylene oxide repeating unit: 15, manufactured by Nippon Nyukazai Co., Ltd.), and 0.01 parts by mass of 2-ethylhexyl acid phosphate (JP-508, manufactured by Johoku Chemical Industry Co., Ltd.) were mixed and stirred at 100°C for 4 hours to carry out a urethane reaction. The reaction liquid was cooled to 80°C, and 43.4 parts by mass of 3,5-dimethylpyrazole was added as a thermally dissociable blocking agent and stirred. After confirming that the characteristic absorption of the isocyanate group had disappeared in the infrared spectrum, 53.6 parts by mass of dipropylene glycol monomethyl ether was added and stirred to obtain blocked polyisocyanate composition PB-13. The physical properties of the obtained blocked polyisocyanate composition PB-13 are shown in Table 2.

[0237] [Preparation Example] A water-based acrylic polyol (Setaqua (registered trademark) 6515 (trade name) manufactured by Allnex, OH (on solids): 3.3 mass%, acid value: 9.9 mg KOH / g, resin content 45 mass%) and a water-based acrylic polyol (Setaqua (registered trademark) 6522 (trade name) manufactured by Nuplex, OH (on solids): 2.4 mass%, acid value: 48 mg KOH / g, resin content 42 mass%) were mixed so that the molar ratio of hydroxyl groups was 1: 1, and each blocked polyisocyanate composition was blended so that the ratio of the molar amount of isocyanate groups to the molar amount of hydroxyl groups (isocyanate groups / hydroxyl groups) was 1.0, and deionized water was added at a ratio of 40% solids, and the mixture was stirred at 1,000 rpm for 5 minutes using a dispersing blade to prepare a water-based coating composition.

[0238] [Examples 1 to 10, Comparative Examples 1 to 5] The blocked polyisocyanate compositions PB-1 to PB-13 synthesized in Synthesis Examples 3-1 to 13 were used to measure and evaluate various physical properties according to the evaluation methods described above. The evaluation results are shown in Tables 1 and 2.

[0239] [Table 1]

[0240] [Table 2]

[0241] In Examples 1 to 9, the compositions had excellent dispersibility (compatibility) with the aqueous base resin, and when formed into a coating film, they had excellent curability, hardness, water resistance, chemical resistance, drying properties (blocking resistance), and storage stability.

[0242] Comparative Example 1 was poor in dispersibility (compatibility) with the aqueous base resin, drying property (blocking resistance), and storage stability. In Comparative Example 2, the coating film was poor in curability, water resistance, and chemical resistance. In Comparative Example 3, the dispersibility (compatibility) with the water-based base resin was poor, and the physical properties of the coating film formed were unmeasurable. Comparative Example 4 was poor in drying properties (blocking resistance). [Industrial Applicability]

[0243] According to the aqueous blocked polyisocyanate composition of the present embodiment, it is possible to provide an aqueous coating composition, a coating film, and a coated substrate which have excellent dispersibility in an aqueous base agent and which, when formed into a coating film using this aqueous blocked polyisocyanate composition, have excellent curability, hardness, water resistance, chemical resistance, drying property, and storage stability.

Claims

1. The present invention comprises a polyisocyanate derived from one or more diisocyanates selected from an aliphatic diisocyanate and an alicyclic diisocyanate, a hydrophilic compound, and a blocked polyisocyanate compound derived from a thermally dissociable blocking agent, The viscosity at 60°C in a state containing no organic solvent is 1,000 mPa·s or more and 30,000 mPa·s or less, a molar ratio of urethane groups to isocyanurate groups (urethane groups / isocyanurate groups) of 0.5 / 100 or more and 20.0 / 100 or less; An aqueous blocked polyisocyanate composition, in which the molar ratio of uretdione groups to isocyanurate groups (uretdione groups / isocyanurate groups) is 10.0 / 100 or more and 80.0 / 100 or less.

2. 2. The aqueous blocked polyisocyanate composition according to claim 1, wherein the average number of isocyanate groups bonded to a thermally dissociable blocking agent in the blocked polyisocyanate compound per molecule is 2.0 or more and 3.5 or less.

3. 3. The aqueous blocked polyisocyanate composition according to claim 1, wherein the blocked polyisocyanate compound has a number average molecular weight of 300 or more and 3,000 or less.

4. 3. The aqueous blocked polyisocyanate composition according to claim 1, wherein the content of the hydrophilic compound used to derive the blocked polyisocyanate compound is 0.1% by mass or more and 30% by mass or less based on the aqueous blocked polyisocyanate composition.

5. 3. The aqueous blocked polyisocyanate composition according to claim 1, wherein the content of the hydrophilic organic solvent in the aqueous blocked polyisocyanate composition is 30% by mass or less.

6. 3. The aqueous blocked polyisocyanate composition according to claim 1, wherein the hydrophilic compound is a polyalkylene glycol alkyl ether having a structure represented by the following general formula (I): 【Chemistry 1】 (In general formula (I), R １１ is an alkylene group having 1 to 4 carbon atoms; R １２ is an alkyl group having 1 to 4 carbon atoms, and n11 is 4.0 or more and 20 or less.

7. 3. The aqueous blocked polyisocyanate composition according to claim 1, wherein the hydrophilic compound is at least one sulfonic acid selected from the group consisting of sulfonic acids containing a hydroxyl group and sulfonic acids containing an amino group.

8. 3. The aqueous blocked polyisocyanate composition according to claim 1 or 2, wherein the polyisocyanate contains an isocyanurate group, an iminooxadiazinedione group, a uretdione group, and an allophanate group as a bonding group, and the molar ratio of the uretdione group is 1.0 mol% or more and 50.0 mol% or less with respect to the total molar amount (100 mol%) of the bonding groups.

9. 3. The aqueous blocked polyisocyanate composition according to claim 1, wherein the thermally dissociable blocking agent is at least one selected from the group consisting of oxime compounds, acid amide compounds, amine compounds, active methylene compounds, and pyrazole compounds.

10. A water-based coating composition comprising the water-based blocked polyisocyanate composition according to claim 1 or 2.

11. A coating film obtained by curing the aqueous coating composition according to claim 10.

12. A coated substrate coated with the water-based coating composition according to claim 10.

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