Modified polyisocyanate, moldable polyurethane resin composition, coating material composition, and coating film

Abstract

This modified polyisocyanate is a product of an allophanation reaction between a polyisocyanate including an aliphatic polyisocyanate having an aliphatic hydrocarbon group with 4-6 carbon atoms and a polyol including poly(tetramethylene glycol), or a modified product of this reaction product, and which has a polydispersity of 1.0-2.1. The ratio of the content of urethane groups relative to the total content of allophanate groups, isocyanurate groups and urethane groups is 19 mol% or less.

Description

Modified polyisocyanate, polyurethane resin-forming composition, coating composition and coating film

[0001] The present disclosure relates to a modified polyisocyanate, a polyurethane resin-forming composition, a coating composition, and a coating film.

[0002] BACKGROUND ART Aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI) and modified polyisocyanates, which are modified products thereof, have conventionally been used as curing agents for paints, adhesives, and the like.

[0003] For example, Patent Document 1 discloses a modified polyisocyanate used as a curing agent for a coating material, which is a reaction product or a modified product thereof of a polyisocyanate component containing an organic diisocyanate or a modified product thereof, and a polyol component containing at least one member selected from the group consisting of polytetramethylene ether glycol and polycarbonate polyol, having a number average molecular weight of 200 to 750.

[0004] International Publication No. 2022 / 210289

[0005] However, polytetramethylene ether glycol-modified polyisocyanates can experience a significant increase in viscosity over time, leaving room for improvement in storage stability. Furthermore, the use of polytetramethylene ether glycol-modified polyisocyanates as curing agents can sometimes result in a decrease in the hardness of coating films.

[0006] Therefore, one aspect of the present disclosure aims to provide a modified polyisocyanate that is less likely to cause a decrease in coating film hardness and has excellent storage stability. Other aspects of the present disclosure aim to provide a urethane resin-forming composition and a coating composition using the modified polyisocyanate, as well as a coating film containing a cured product of the coating composition.

[0007] In some aspects, the present disclosure provides the following [1] to

[11] .

[0008] [1] A modified polyisocyanate, which is an allophanate reaction product of a polyisocyanate containing an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms and a polyol containing polytetramethylene ether glycol, or a modified product thereof, having a polydispersity of 1.0 to 2.1, and the proportion of the urethane group content in the total content of allophanate groups, isocyanurate groups, and urethane groups is 19 mol % or less.

[0009] [2] The modified polyisocyanate according to [1], wherein the proportion of the urethane group content in the total content of allophanate groups, isocyanurate groups, and urethane groups is 0.01 to 7 mol %.

[0010] [3] The modified polyisocyanate according to [1] or [2], wherein the proportion of the allophanate group content in the total content of allophanate groups, isocyanurate groups, and urethane groups is 75 to 98 mol %.

[0011] [4] The modified polyisocyanate according to any one of [1] to [3], wherein the proportion of the isocyanurate group content in the total content of allophanate groups, isocyanurate groups, and urethane groups is 0.1 to 7 mol%.

[0012] [5] The modified polyisocyanate according to any one of [1] to [4], wherein the average number of isocyanate groups is 6.0 to 8.0.

[0013] [6] The modified polyisocyanate according to any one of [1] to [5], having a number average molecular weight of 1500 to 2000 g / mol.

[0014] [7] The modified polyisocyanate according to any one of [1] to [6], wherein the polytetramethylene ether glycol has a number average molecular weight of 200 to 800.

[0015] [8] The modified polyisocyanate according to any one of [1] to [7], wherein the polytetramethylene ether glycol has a polydispersity of 1.00 to 1.60.

[0016] [9] A polyurethane resin-forming composition comprising the modified polyisocyanate according to any one of [1] to [8] and a polyol.

[0017]

[10] A coating composition comprising the polyurethane resin-forming composition according to [9].

[0018]

[11] A coating film comprising a cured product of the coating composition according to

[10] .

[0019] According to the present disclosure, it is possible to provide a modified polyisocyanate that is unlikely to cause a decrease in coating film hardness and has excellent storage stability. Furthermore, according to the present disclosure, it is possible to provide a urethane resin-forming composition and a coating composition that use the modified polyisocyanate, and a coating film that includes a cured product of the coating composition.

[0020] Exemplary embodiments for carrying out each aspect of the present disclosure will be described in detail below, although the present disclosure is not limited to the following embodiments.

[0021] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​written before and after "to" as the minimum and maximum values, respectively. Furthermore, unless specifically stated otherwise, the units of the numerical values ​​written before and after "to" are the same. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples. Furthermore, the upper and lower limit values ​​individually described can be arbitrarily combined. Furthermore, unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more types. When multiple substances corresponding to each component are present in the composition, the content of each component in the composition means the total amount of the multiple substances present in the composition, unless otherwise specified.

[0022] <Modified Polyisocyanate> One embodiment of the present disclosure is an allophanate reaction product or a modified product thereof between a polyisocyanate containing an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms (hereinafter referred to as "polyisocyanate (A)") and a polyol containing polytetramethylene ether glycol (hereinafter referred to as "polyol (B)"), wherein the modified polyisocyanate has a polydispersity index of 1.0 to 2.1 and the proportion of the urethane group content in the total content of allophanate groups, isocyanurate groups, and urethane groups is 19 mol % or less.

[0023] Herein, the reaction for urethanization of a polyisocyanate with a polyol and subsequent allophanation is collectively referred to as an allophanation reaction. In the allophanation reaction, other reactions such as isocyanuration may occur in addition to allophanation, and the compounds produced as a result of these reactions also constitute the modified polyisocyanate. The term "modified product" is a general term for products obtained by modifying the allophanation reaction product. Like the allophanation reaction product, the modified product has allophanate groups formed by the allophanation reaction between polyisocyanate (A) and polyol (B). Examples of modified products include block modified products. The block modified product is a reaction product of an allophanation reaction product with a blocking agent, and has a structure in which at least a portion of the free isocyanate groups in the allophanation reaction product are blocked with the blocking agent.

[0024] In addition, the term "polydispersity" in this specification means the ratio of the weight average molecular weight to the number average molecular weight. The number average molecular weight and weight average molecular weight are values ​​measured using GPC (gel permeation chromatography) under the following conditions. However, when the modified polyisocyanate is a block-modified product, the number average molecular weight and weight average molecular weight of the modified polyisocyanate in an unblocked state (a state in which the blocking agent has been dissociated) are measured. [Conditions] Measuring instrument: "HLC-8120" (manufactured by Tosoh Corporation) Column: "TSKguard column HXL-L" (manufactured by Tosoh Corporation) Particle size = 6 μm, size = 6 mm ID x 30 cm x 4 columns Carrier: tetrahydrofuran (THF) Detector: parallax refraction Sample: 0.1% THF solution Calibration curve: polystyrene

[0025] As described above, the modified polyisocyanate may be a mixture of multiple compounds having different molecular weights. Such a mixture of modified polyisocyanates may also be referred to as a modified polyisocyanate composition. That is, another embodiment of the present disclosure is a modified polyisocyanate composition comprising an allophanation reaction product of polyisocyanate (A) and polyol (B) or a modified product thereof, having a polydispersity index of 1.0 to 2.1, and in which the proportion of urethane groups in the total content of allophanate groups, isocyanurate groups, and urethane groups contained in the composition is 19 mol% or less. The phrase "the total content of allophanate groups, isocyanurate groups, and urethane groups contained in the composition" refers to the total content of allophanate groups, isocyanurate groups, and urethane groups contained in the allophanate group-containing compound, isocyanurate group-containing compound, and urethane group-containing compound, respectively, contained in the composition. Here, the allophanate group-containing compound, the isocyanurate group-containing compound, and the urethane group-containing compound refer to a compound having an allophanate group, a compound having an isocyanurate group, and a compound having a urethane group, respectively. A compound having an allophanate group and an isocyanurate group corresponds to both an allophanate group-containing compound and an isocyanurate group-containing compound, a compound having an allophanate group and a urethane group corresponds to both an allophanate group-containing compound and an urethane group-containing compound, and a compound having an isocyanurate group and an urethane group corresponds to both an isocyanurate group-containing compound and an urethane group-containing compound.

[0026] In the above-described embodiments, the allophanate reaction product and its modified product can also be referred to as a composition containing a compound having a structure formed by an allophanate reaction between an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms and polytetramethylene ether glycol (e.g., a structure containing a residue of an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms, a residue of polytetramethylene ether glycol, and an allophanate group). Another embodiment of the present disclosure is a modified polyisocyanate composition containing a compound having a structure formed by an allophanate reaction between an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms and polytetramethylene ether glycol, the modified polyisocyanate composition having a polydispersity index of 1.0 to 2.1, and the proportion of urethane groups in the total content of allophanate groups, isocyanurate groups, and urethane groups contained in the composition being 19 mol% or less. Note that the meaning of "the total content of allophanate groups, isocyanurate groups, and urethane groups contained in the composition" is the same as above. Furthermore, the above-mentioned "residue of an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms" means a group remaining after removing an isocyanate group from an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms, and the above-mentioned "residue of polytetramethylene ether glycol" means a group remaining after removing a hydroxyl group from polytetramethylene ether glycol.

[0027] In the following description, the term "modified polyisocyanate" can be read as "modified polyisocyanate composition."

[0028] The modified polyisocyanate has excellent storage stability and is unlikely to increase in viscosity over time. Furthermore, when used as a curing agent for a coating material, the modified polyisocyanate is unlikely to cause a decrease in coating film hardness. Therefore, by using the modified polyisocyanate as a curing agent for a coating material, a coating film with sufficient hardness can be formed.

[0029] Although the reason for this effect is unclear, it is believed that if urethane groups formed by the reaction of polyisocyanate (A) and polyol (B) remain in the molecule, crystallinity increases due to intermolecular hydrogen bonding, resulting in an increase in viscosity over time, whereas in the modified polyisocyanate, the proportion of urethane groups in the total content of allophanate groups, isocyanurate groups, and urethane groups is 19 mol% or less, and therefore the increase in viscosity due to the urethane groups is suppressed. Furthermore, while variations in molecular weight distribution are likely to lead to the formation of areas with low crosslink density due to molecules with large molecular weights, resulting in a decrease in coating film hardness, the modified polyisocyanate has a polydispersity of 2.1 or less and has a small variation in molecular weight distribution, and therefore is believed to be less likely to cause a decrease in coating film hardness due to a decrease in crosslink density.

[0030] The modified polyisocyanate has a polydispersity of 2.1 or less, and therefore tends to have excellent stability at low temperatures.

[0031] (Polyisocyanate (A)) The polyisocyanate (A) includes an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms (hereinafter also referred to as "aliphatic polyisocyanate (a)"). Examples of the aliphatic hydrocarbon group having 4 to 6 carbon atoms include a tetramethylene group, a pentamethylene group, and a hexamethylene group. The number of isocyanate groups in the aliphatic polyisocyanate (a) is, for example, 2 or 3, and may be 2 from the viewpoint of obtaining better storage stability. From the viewpoint of weather resistance of the coating film, the aliphatic polyisocyanate (a) may be a polyisocyanate having no unsaturated bonds. Examples of the aliphatic polyisocyanate (a) include tetramethylene diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate. Among these, when hexamethylene diisocyanate is used, a coating film having better hardness and excellent adhesion is likely to be obtained.

[0032] The polyisocyanate (A) may contain a polyisocyanate other than the aliphatic polyisocyanate (a). For example, the polyisocyanate (A) may contain a polymer of the aliphatic polyisocyanate (a). The polymer may be a dimer, a trimer or higher polymer.

[0033] The proportion of the aliphatic polyisocyanate (a) in the entire polyisocyanate (A) may be 80 to 100 mass%, 90 to 100 mass%, or 95 to 100 mass%, based on the total mass of the polyisocyanate (A), from the viewpoint of easily obtaining better coating hardness.

[0034] (Polyol (B)) The polyol (B) includes polytetramethylene ether glycol. Polytetramethylene ether glycol is a compound having an oxytetramethylene group in the molecular skeleton, and is represented by the formula (I): HO—(CH ２ CH ２ CH ２ CH ２ O)nH, where n is the number of repeating units, and the average of n is 2 or more. Polytetramethylene ether glycol is mainly obtained by ring-opening polymerization of tetrahydrofuran.

[0035] The number average molecular weight of the polytetramethylene ether glycol may be 200 to 800, 220 or more, or 250 or more, and may be 750 or less, 700 or less, 600 or less, or 500 or less, or may be 220 to 750, 250 to 700, 220 to 600, or 250 to 500. The larger the number average molecular weight of the polytetramethylene ether glycol, the more likely it is that the adhesion of the coating film will be improved, and the smaller the number average molecular weight of the polytetramethylene ether glycol, the more likely it is that the low temperature stability will be improved, and the hardness, smoothness, and appearance of the coating film will be improved.

[0036] The polydispersity of the polytetramethylene ether glycol may be 1.00 to 1.60, 1.00 to 1.58, 1.00 to 1.55, 1.00 to 1.40, 1.00 to 1.20, or 1.00 to 1.10, from the viewpoint of more easily obtaining a better coating hardness.

[0037] The content of mono- to hexamers (compounds in formula (I) where n is any of 1 to 6) in polytetramethylene ether glycol may be 80% by mass or more, 85% by mass or more, 90% by mass or more, or 95% by mass or more based on the total mass of polytetramethylene ether glycol, from the viewpoint that the crystallinity of the modified polyisocyanate is likely to be low and that storage stability and stability at low temperatures are improved. The content of mono- to hexamers (compounds in formula (I) where n is any of 1 to 6) in polytetramethylene ether glycol may be 100% by mass or less, 99% by mass or less, or 98% by mass or less, from the viewpoint that better coating hardness is likely to be obtained. From the above viewpoint, the content of monomers to hexamers (compounds in which n in the above formula (I) is any of 1 to 6) in polytetramethylene ether glycol may be, for example, 80 to 100 mass%, 85 to 99 mass%, 90 to 98 mass%, or 95 to 100 mass%, based on the total mass of polytetramethylene ether glycol.

[0038] Polytetramethylene ether glycol may contain potassium, and the amount of potassium contained in polytetramethylene ether glycol may be 0.01 ppm by mass or more, 4.5 ppm by mass or less, or 3.0 ppm by mass or less, or may be 0 to 4.5 ppm by mass or 0.01 to 3.0 ppm by mass.

[0039] The polyol (B) may contain a polyol other than polytetramethylene ether glycol. However, from the viewpoint of obtaining a coating film with better adhesion and of facilitating obtaining better coating film hardness, the proportion of polytetramethylene ether glycol in the entire polyol (B) may be 80 to 100 mass%, 90 to 100 mass%, or 95 to 100 mass%, based on the total mass of the polyol (B).

[0040] (Structure) The modified polyisocyanate contains at least a residue of polyisocyanate (A), a residue of polyol (B), and an allophanate group. The residue of polyisocyanate (A) contains a group (an aliphatic hydrocarbon group having 4 to 6 carbon atoms) obtained by removing an isocyanate group from aliphatic polyisocyanate (a). At least a portion of the residue of polyisocyanate (A) contains an unreacted isocyanate group and / or a blocked isocyanate group. The blocked isocyanate group may be a group formed by blocking an unreacted isocyanate group with a known blocking agent. The residue of polyol (B) contains a group (a polyoxytetramethylene group) obtained by removing a hydroxyl group from polytetramethylene ether glycol. The allophanate group includes, for example, an allophanate group formed by an allophanation reaction between an aliphatic polyisocyanate (a) and a polytetramethylene ether glycol (an allophanate group directly bonded to a residue of the aliphatic polyisocyanate (a) and a residue of the polytetramethylene ether glycol). When the modified polyisocyanate contains such a group, it becomes a low-viscosity liquid, and there are achieved effects such as being able to obtain a coating film that is flexible yet strong and highly adhesive, and improving handleability during coating.

[0041] The modified polyisocyanate may further contain a urethane group. The urethane group may be a urethane group derived from the raw material (a urethane group contained in the polyisocyanate) or a urethane group formed by the reaction of the polyisocyanate (A) with the polyol (B) during the allophanation reaction.

[0042] The modified polyisocyanate may further contain an isocyanurate group. The isocyanurate group may be an isocyanurate group derived from the raw material (an isocyanurate group possessed by the polyisocyanate) or an isocyanurate group formed by the isocyanuration of the polyisocyanate (A) during the allophanation reaction.

[0043] The isocyanate group content (NCO content) may be 11.0 to 23.0 mass%, 13.0 to 23.0 mass%, 14.0 to 22.0 mass%, or 15.0 to 21.0 mass%. When the NCO content is 13.0 mass% or more, the stain resistance of the coating film tends to be better, and when the NCO content is 23.0 mass% or less, the self-repairing property of the coating film tends to be better.

[0044] In this specification, the NCO content is a value measured by the method described in JIS K1603-1 (Testing methods for aromatic isocyanates used as raw materials for polyurethanes). However, when the modified polyisocyanate is a block-modified product, the NCO content of the modified polyisocyanate in an unblocked state (a state in which the blocking agent has been dissociated) is measured.

[0045] The average number of isocyanate groups may be 6.0 or more, 6.5 or more, or 7.0 or more, from the viewpoint of obtaining a coating film with superior hardness and from the viewpoint of facilitating obtaining better coating film hardness. The average number of isocyanate groups may be 8.0 or less, or may be 7.5 or less, from the viewpoint of viscosity. From the above viewpoints, the average number of isocyanate groups may be, for example, 6.0 to 8.0, 6.5 to 7.5, or 7.0 to 8.0.

[0046] In this specification, the average number of isocyanate groups means the average number of isocyanate groups (-NCO) contained per molecule of the modified polyisocyanate. The average number of isocyanate groups of the modified polyisocyanate can be calculated from the isocyanate group content (NCO content) and number average molecular weight of the modified polyisocyanate. When the modified polyisocyanate is a block modified product, the average number of isocyanate groups also includes the number of blocked isocyanate groups.

[0047] The proportion of allophanate groups in the total content of allophanate groups, isocyanurate groups, and urethane groups may be 75 mol% or more, 80 mol% or more, 85 mol% or more, or 90 mol% or more, from the viewpoint of improving the adhesion of the coating film and improving storage stability. The proportion of allophanate groups in the total content of allophanate groups, isocyanurate groups, and urethane groups may be 98 mol% or less, or even 95 mol% or less, from the viewpoint of improving the weather resistance of the coating film and making it easier to obtain better coating hardness. From the above viewpoints, the proportion of allophanate groups in the total content of allophanate groups, isocyanurate groups, and urethane groups may be, for example, 75 to 98 mol%, 80 to 98 mol%, 85 to 98 mol%, or 90 to 95 mol%.

[0048] The proportion of urethane groups in the total content of allophanate groups, isocyanurate groups, and urethane groups is 19 mol% or less, and from the viewpoint of improving the adhesion of the coating film and improving storage stability, it may be 10 mol% or less or 7 mol% or less. From the viewpoint of improving the weather resistance of the coating film and making it easier to obtain better coating film hardness, the proportion of urethane groups in the total content of allophanate groups, isocyanurate groups, and urethane groups may be 0.01 mol% or more, or may be 0.1 mol% or more, 0.2 mol% or more, 0.5 mol% or more, 1 mol% or more, 2 mol% or more, 3 mol% or more, or 4 mol% or more. The reason why the coating film hardness improves as the proportion of the urethane group content increases is not clear, but it is presumed that this is because a small amount of urethane groups increases crystallinity to an extent that does not affect storage stability, improving cohesive force and thereby suppressing a decrease in coating film hardness. From the above viewpoint, the proportion of the urethane group content in the total content of allophanate groups, isocyanurate groups, and urethane groups may be, for example, 0.01 to 19 mol%, 0.01 to 10 mol%, 0.01 to 7 mol%, 0.1 to 19 mol%, 0.2 to 19 mol%, 0.5 to 19 mol%, 1 to 19 mol%, 2 to 19 mol%, 3 to 19 mol%, or 4 to 19 mol%.

[0049] The proportion of the isocyanurate group content in the total content of allophanate groups, isocyanurate groups, and urethane groups may be 0.1 mol% or more, 0.5 mol% or more, or 1 mol% or more, from the viewpoint of improving the weather resistance of the coating film and making it easier to obtain better coating film hardness. The proportion of the isocyanurate group content in the total content of allophanate groups, isocyanurate groups, and urethane groups may be 7 mol% or less, 5 mol% or less, or 3 mol% or less, from the viewpoint of improving the adhesion of the coating film and making it easier to obtain better storage stability. From the above viewpoints, the proportion of the isocyanurate group content in the total content of allophanate groups, isocyanurate groups, and urethane groups may be, for example, 0.1 to 7 mol%, 0.5 to 5 mol%, or 1 to 3 mol%.

[0050] The contents of allophanate groups, isocyanurate groups, and urethane groups were determined by proton nuclear magnetic resonance ( １ This can be confirmed by H-NMR spectrum.

[0051] (Physical Properties) The number average molecular weight of the modified polyisocyanate may be 1500 g / mol or more, 1600 g / mol or more, or 1700 g / mol or more, from the viewpoint of improving the adhesion of the coating film. The number average molecular weight of the modified polyisocyanate may be 2000 g / mol or less, 1900 g / mol or less, or 1800 g / mol or less, from the viewpoint of easily obtaining better coating film hardness and improving low-temperature stability. From these viewpoints, the number average molecular weight of the modified polyisocyanate may be, for example, 1500 to 2000 g / mol, 1600 to 1900 g / mol, or 1700 to 1800 g / mol.

[0052] The polydispersity of the modified polyisocyanate is 1.0 to 2.1. From the viewpoint of superior heat resistance, the polydispersity of the modified polyisocyanate may be 1.5 or more or 1.6 or more. From the viewpoint of easier obtaining of better coating film hardness and superior low-temperature stability, the polydispersity of the modified polyisocyanate may be 2.0 or less or 1.9 or less. From these viewpoints, the polydispersity of the modified polyisocyanate may be, for example, 1.5 to 2.0 or 1.6 to 1.9.

[0053] The viscosity of the modified polyisocyanate at 25°C may be 500 to 10,000 mPa·s, or may be 800 to 6,000 mPa·s, or 1,000 to 3,000 mPa·s. When the viscosity of the modified polyisocyanate at 25°C is within the above range, the coating film formability is good, the coating film smoothness is even better, and the coating film appearance is even better. The viscosity of the modified polyisocyanate at 25°C is a value measured using a B-type viscometer.

[0054] (Production Method) The modified polyisocyanate can be obtained by an allophanate reaction between a polyisocyanate (A) and a polyol (B). Specifically, the modified polyisocyanate can be obtained, for example, through the following first to fourth steps.

[0055] Step 1: Polyisocyanate (A) and polyol (B) are charged in amounts such that the isocyanate groups are in excess relative to the hydroxyl groups, and urethane formation is allowed to proceed at 20 to 70°C to obtain an isocyanate-terminated prepolymer I. Step 2: A catalyst is charged to the isocyanate-terminated prepolymer I, and allophanation is allowed to proceed at 70 to 150°C. Step 3: The reaction is stopped by adding a reaction terminator. Step 4: Free polyisocyanate is removed by thin-film distillation or solvent extraction to obtain a modified polyisocyanate.

[0056] In the first to third steps, the reaction is carried out in a nitrogen gas or dry air stream. The first to third steps may be carried out in the presence or absence of an organic solvent.

[0057] As the organic solvent, various organic solvents that do not affect the reaction can be used. Examples of the organic solvent include aliphatic hydrocarbons such as octane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; ketones such as methyl isobutyl ketone and cyclohexanone; esters such as butyl acetate and isobutyl acetate; glycol ether esters such as ethylene glycol ethyl ether acetate, propylene glycol monomethyl ether acetate, 3-methyl-3-methoxybutyl acetate, and ethyl-3-ethoxypropionate; ethers such as dioxane; halogenated hydrocarbons such as methylene iodide and monochlorobenzene; and polar aprotic solvents such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, and hexamethylphosphonylamide. These organic solvents may be used alone or in combination of two or more.

[0058] [First Step] In the first step, the polyisocyanate (A) and the polyol (B) are reacted to obtain an isocyanate group-terminated prepolymer I. The amounts of the polyisocyanate (A) and the polyol (B) charged are set so that the isocyanate groups are in excess relative to the hydroxyl groups.

[0059] The "excess amount of isocyanate groups relative to hydroxyl groups" refers to the number of moles of isocyanate groups in the polyisocyanate (A) (M' ＮＣＯ ) and the number of moles of hydroxyl groups in the polyol (B) (M' ＯＨ ) and the ratio R' (=M' ＮＣＯ / M' ＯＨ ) may be 6 to 60, or may be an amount such that the ratio R' is 7 to 50. When the ratio R' is 6 or more, it is possible to further prevent the amount of isocyanurate groups in the resulting modified polyisocyanate from becoming excessive. When the ratio R' is 60 or less, it is possible to further prevent an increase in the amount of urethane groups contained in the resulting modified polyisocyanate, and it is possible to further prevent a decrease in the number of functional groups, thereby further improving productivity and yield.

[0060] The temperature (urethanization temperature) at which the polyisocyanate (A) and the polyol (B) are reacted is, for example, 20 to 70°C, and may be 20 to 60°C, 45 to 65°C, or 50 to 60°C. By setting the urethanization temperature to 70°C or less, the content of urethane groups in the finally obtained modified polyisocyanate can be reduced, and the content of isocyanate groups can be increased. This is thought to be because the lower the urethanization temperature, the more suppressed the occurrence of side reactions in the urethanization reaction (e.g., reactions that generate intermediate compounds having a ring structure, such as dimers and trimers of polyisocyanate (A), and the urethanization reaction between such intermediate compounds and polyol (B)). That is, among the compounds generated by side reactions, urethane compounds having a ring structure in particular have poor compatibility with the allophanation catalyst. Therefore, if the amount of such urethane compounds increases, the allophanation catalyst will not function, and urethane groups will likely remain. The reaction time for urethanization varies depending on the presence or absence of a catalyst, the type of catalyst, and the temperature, but is generally within 10 hours, and may be 1 to 5 hours.

[0061] A known urethanization catalyst can be used for the urethanization. Examples of the urethanization catalyst include organometallic compounds such as dibutyltin diacetate, dibutyltin dilaurate, and dioctyltin dilaurate; organic amines such as triethylenediamine and triethylamine, and salts thereof. These catalysts may be used alone or in combination of two or more.

[0062] [Second Step] In the second step, allophanation is carried out on the isocyanate group-terminated prepolymer I obtained in the first step. At this time, the allophanation may be carried out simultaneously (in parallel) with the urethanization, or may be carried out after the urethanization is completed.

[0063] When urethanization and allophanation are carried out simultaneously (in parallel), the reaction may be carried out in the presence of a urethanization catalyst and an allophanation catalyst. On the other hand, when allophanation is carried out after the completion of urethanization, urethanization may be carried out for a predetermined period of time in the presence of the urethanization catalyst but in the absence of the allophanation catalyst, and then the allophanation may be carried out by adding the allophanation catalyst.

[0064] The allophanate catalyst can be appropriately selected from known catalysts and includes, for example, metal salts of carboxylic acids (metal salts of alkali metals such as lithium, sodium, and potassium; metal salts of alkaline earth metals such as magnesium, calcium, and barium; metal salts of other typical metals such as tin and lead; and metal salts of transition metals such as manganese, iron, cobalt, nickel, copper, zinc, and zirconium). Examples of carboxylic acids include monocarboxylic acids and polycarboxylic acids.

[0065] Specific examples of the allophanate catalyst include zirconium octylate, etc. The allophanate catalyst may be used alone or in combination of two or more.

[0066] The amount of the allophanation catalyst used may be 0.001 to 0.1% by mass, or may be 0.005 to 0.03% by mass, relative to the total mass of the polyisocyanate (A) and the polyol (B). When the amount of the allophanation catalyst used is 0.001% by mass or more, the allophanation proceeds more easily, the content of urethane groups in the resulting modified polyisocyanate can be reduced, and a decrease in the average number of isocyanate groups can be suppressed. Furthermore, when the amount of the allophanation catalyst used is 0.1% by mass or less, storage stability is further improved.

[0067] The reaction temperature for allophanation may be 70 to 150°C, or may be 90 to 130°C. If the reaction temperature is 70°C or higher, the content of allophanate groups in the resulting modified polyisocyanate tends to be high, and the content of urethane groups can be reduced. If the reaction temperature is 150°C or lower, the content of isocyanurate can be reduced, further improving adhesion.

[0068] The allophanatization may be carried out until urethane groups are substantially absent. Here, the term "urethane groups are substantially absent" means that the allophanatization is carried out until urethane groups are substantially absent as determined by proton nuclear magnetic resonance ( １ This means that the content of the urethane-modified polyisocyanate confirmed by H-NMR spectrum is 0.01 mol % or less based on the total amount of the allophanate-modified polyisocyanate, the isocyanurate-modified polyisocyanate, and the urethane-modified polyisocyanate.

[0069] In the second step, allophanation mainly proceeds, but as described above, the ratio R' (=M') in the first step ＮＣＯ / M' ＯＨ ) can be adjusted to allow partial isocyanuration to proceed, and the proportion of the isocyanurate group content can be adjusted.

[0070] [Step 3] In Step 3, after Step 2, a reaction terminator that deactivates the catalyst is added to the reaction system to terminate the allophanation. The reaction terminator may be added when the urethane group content reaches a desired ratio. However, in order to suppress the progression of side reactions, it is preferable to add the reaction terminator promptly after the completion of the allophanation.

[0071] Examples of reaction terminators that can be used include inorganic acids such as phosphoric acid and hydrochloric acid, organic acids having a sulfonic acid group, a sulfamic acid group, and their esters, and known compounds such as acyl halides. These may be used alone or in combination of two or more.

[0072] The amount of reaction terminator added varies depending on the type of catalyst, but may be 0.5 to 10 equivalents, or 0.8 to 5.0 equivalents, relative to the amount of catalyst added. When the amount of reaction terminator added is 0.5 equivalents or more, the storage stability of the resulting modified polyisocyanate is further improved. When the amount of reaction terminator added is 10 equivalents or less, coloration can be further suppressed. After the reaction has stopped, a purification step can be performed to remove free, unreacted polyisocyanate (A).

[0073] [Step 4] In Step 4, any free, unreacted polyisocyanate (A) present in the reaction mixture is removed. If an organic solvent is used in the reaction step, it can be removed in this purification step.

[0074] The polyisocyanate (A) is preferably removed to a residual content of 1.0 mass% or less, more preferably to a residual content of less than 1.0 mass%. When the residual content is 1.0 mass% or less, odor is further reduced and storage stability is further improved.

[0075] The removal of the polyisocyanate (A) is preferably carried out by thin film distillation, which can be carried out, for example, under a high vacuum of 10 to 100 Pa at a temperature of 120 to 140°C.

[0076] After the fourth step, a step of modifying (blocking) a portion of the isocyanate groups with a blocking agent may be carried out. Examples of the blocking agent include phenol-based blocking agents such as phenol, cresol, xylenol, nitrophenol, chlorophenol, ethylphenol, p-hydroxydiphenyl, t-butylphenol, o-isopropylphenol, o-sec-butylphenol, p-nonylphenol, p-t-octylphenol, hydroxybenzoic acid, and hydroxybenzoic acid esters; lactam-based blocking agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam; active methylene-based blocking agents such as diethyl malonate, dimethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone; methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol, n-amyl alcohol, t-amyl alcohol, lauryl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and diethylene glycol monomethyl ether. alcohol-based blocking agents such as ethylene glycol monoethyl ether, propylene glycol monomethyl ether, benzyl alcohol, methoxymethanol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate and other glycolic acid esters; lactic acid, methyl lactate, ethyl lactate, butyl lactate and other lactate esters; methylol urea, methylol melamine, diacetone alcohol, ethylene chlorohydrin, ethylene bromohydrin, 1,3-dichloro-2-propanol, ω-hydroperfluoroalcohol, acetocyanhydrin and other alcohol-based blocking agents; mercaptan-based blocking agents such as butyl mercaptan, hexyl mercaptan, t-butyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, ethylthiophenol and other mercaptan-based blocking agents; acid amide-based blocking agents such as acetanilide, acetanisidide, acetotoluide, acrylamide, methacrylamide, acetic amide, stearic acid amide, benzamide and other acid amide-based blocking agents; imide-based blocking agents such as succinimide, phthalic acid imide, maleic acid imide and otherExamples of suitable blocking agents include amine-based blocking agents such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, and butylphenylamine; imidazole-based blocking agents such as imidazole and 2-ethylimidazole; urea-based blocking agents such as urea, thiourea, ethyleneurea, ethylenethiourea, and 1,3-diphenylurea; carbamate-based blocking agents such as N-phenylphenylcarbamate and 2-oxazolidone; imine-based blocking agents such as ethyleneimine and propyleneimine; oxime-based blocking agents such as formamidoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, and cyclohexanone oxime; and sulfite-based blocking agents such as sodium bisulfite and potassium bisulfite. These blocking agents may be used alone or in combination of two or more.

[0077] <Curing Agent> Another embodiment of the present disclosure is a curing agent containing the modified polyisocyanate. The curing agent is used in combination with a compound (e.g., a polyol) that is reactive with polyisocyanate. The modified polyisocyanate of this embodiment may be the modified polyisocyanate composition of the above embodiment. That is, in the following description, the modified polyisocyanate may be read as the modified polyisocyanate composition.

[0078] The curing agent may consist solely of a modified polyisocyanate. The curing agent may contain a component other than the modified polyisocyanate (for example, a polyisocyanate other than the modified polyisocyanate). However, from the viewpoint of enhancing the effect of the modified polyisocyanate, the content of the modified polyisocyanate may be 80% by mass or more, 90% by mass or more, or 95% by mass or more, based on the total mass of the polyisocyanate contained in the curing agent.

[0079] The curing agent may further contain an additive. The additive may be any additive that does not have reactivity with polyisocyanate, and for example, the same additives that can be used in the polyurethane resin-forming composition described below can be used.

[0080] <Polyurethane Resin-Forming Composition> Another embodiment of the present disclosure is a polyurethane resin-forming composition containing the modified polyisocyanate and a polyol. This polyurethane resin-forming composition forms a polyurethane resin by reacting the modified polyisocyanate with the polyol. The modified polyisocyanate of this embodiment may be the modified polyisocyanate composition of the above embodiment. That is, in the following description, the term "modified polyisocyanate" may be read as the modified polyisocyanate composition.

[0081] The polyol may be a known polyol used in forming polyurethane resins. From the viewpoint of easily obtaining a coating film excellent in adhesion and hardness, the polyol may contain an acrylic polyol. Here, "acrylic polyol" refers to a polymer containing (meth)acrylic monomers as monomer units and having multiple hydroxyl groups. Furthermore, "(meth)acrylic" refers to at least one of acrylic and its corresponding methacrylic.

[0082] The acrylic polyol may be a homopolymer obtained by polymerizing one kind of (meth)acrylic monomer, or may be a copolymer obtained by copolymerizing two or more kinds of (meth)acrylic monomers. The acrylic polyol may contain a monomer other than the (meth)acrylic monomer as a monomer unit, but from the viewpoint of achieving both a predetermined glass transition temperature and a predetermined hydroxyl value, the acrylic polyol may contain only the (meth)acrylic monomer as a monomer unit.

[0083] Examples of homopolymers obtained by polymerizing one type of (meth)acrylic monomer include homopolymers of (meth)acrylic acid hydroxy compounds. Examples of copolymers obtained by copolymerizing two or more types of (meth)acrylic monomers include copolymers obtained by copolymerizing a (meth)acrylic acid ester and a (meth)acrylic acid hydroxy compound.

[0084] Here, the (meth)acrylic acid ester is at least one selected from the group consisting of acrylic acid esters and methacrylic acid esters, and the (meth)acrylic acid hydroxy compound is at least one selected from the group consisting of acrylic acid hydroxy compounds and methacrylic acid hydroxy compounds, each having one or more hydroxyl groups that can serve as reaction sites in its molecule.

[0085] The glass transition temperature (glass transition point, Tg) of the acrylic polyol may be 5 to 30°C. When the glass transition temperature of the acrylic polyol is 5°C or higher, the self-repairing property against repeated scratches and the contamination resistance when used outdoors are improved. Furthermore, when the glass transition temperature of the acrylic polyol is 30°C or lower, the self-repairing property at room temperature (e.g., 5 to 35°C) and low temperature (e.g., below 5°C) is improved. The glass transition temperature of the acrylic polyol may be 10°C or higher or 15°C or higher, from the viewpoint of improving the self-repairing property against repeated scratches and the contamination resistance when used outdoors. The glass transition temperature of the acrylic polyol may be 25°C or lower or 20°C or lower, from the viewpoint of improving the self-repairing property at room temperature and low temperature. From the above viewpoint, the glass transition temperature of the acrylic polyol may be 10 to 25°C or 15 to 20°C. A polyol having a glass transition temperature within the above range can be synthesized by adjusting the types and compounding ratios of the monomer components. For example, when the acrylic polyol is a copolymer, the glass transition temperature can be estimated by Fox's equation and the compounding ratios of the monomer components can be set to obtain an acrylic polyol having a glass transition temperature within the above range.

[0086] The glass transition temperature of the acrylic polyol can be determined by measuring the inflection point of DSC in accordance with JIS K7121.

[0087] The hydroxyl value of the acrylic polyol may be 50 mgKOH / g or more and 150 mgKOH / g or less. When the hydroxyl value of the acrylic polyol is within this range, adhesion, coating hardness, and smoothness are improved. The hydroxyl value of the acrylic polyol may be 80 mgKOH / g or more or 100 mgKOH / g or more from the viewpoint of improving coating hardness and smoothness. The hydroxyl value of the acrylic polyol may be 130 mgKOH / g or less or 110 mgKOH / g or less from the viewpoint of improving adhesion. From the above viewpoints, the hydroxyl value of the acrylic polyol may be 50 to 150 mgKOH / g, 80 to 150 mgKOH / g, 100 to 150 mgKOH / g, 80 to 130 mgKOH / g, 100 to 130 mgKOH / g or less, or 100 to 110 mgKOH / g or less. The hydroxyl value of the acrylic polyol is a value measured by a method in accordance with JIS K1557.

[0088] The acrylic polyol can be obtained, for example, by applying energy (light energy such as ultraviolet light or electron beam, or thermal energy) to a mixture of a (meth)acrylic monomer and a polymerization initiator to polymerize the (meth)acrylic monomer. In other words, the acrylic polyol may be a thermal polymer or a photopolymer. The acrylic polyol may be a thermal polymer because it is likely to become a polymer in which the polymerization reaction and crosslinking reaction are completed.

[0089] The acrylic polyol may contain one kind of acrylic polyol alone or two or more kinds of acrylic polyols in combination.

[0090] Next, the (meth)acrylic acid ester and (meth)acrylic acid hydroxy compound, which can be reaction raw materials for the acrylic polyol, and the polymerization initiator will be described.

[0091] [(Meth)acrylic acid esters] Examples of (meth)acrylic acid esters include alkyl esters having an alkyl group having 1 to 20 carbon atoms. Examples of such (meth)acrylic acid esters include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate; (meth)acrylic acid cycloalkyl esters (products obtained by esterification of (meth)acrylic acid with an alicyclic alcohol) such as cyclohexyl (meth)acrylate; and (meth)acrylic acid aryl esters such as phenyl (meth)acrylate and benzyl (meth)acrylate. These (meth)acrylic acid esters may be used alone or in combination of two or more.

[0092] [(Meth)acrylic Acid Hydroxy Compound] The (meth)acrylic acid hydroxy compound has one or more hydroxyl groups in the molecule that can serve as a reaction site with the polyisocyanate composition. Examples of the (meth)acrylic acid hydroxy compound include acrylic acid hydroxy compounds such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 3-hydroxy-2,2-dimethylpropyl acrylate, and pentaerythritol triacrylate; and methacrylic acid hydroxy compounds such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 3-hydroxy-2,2-dimethylpropyl methacrylate, and pentaerythritol trimethacrylate. These (meth)acrylic acid hydroxy compounds may be used alone or in combination of two or more.

[0093] [Polymerization initiator] Examples of the polymerization initiator include a thermal polymerization initiator and a photopolymerization initiator. The polymerization initiator is appropriately selected depending on the polymerization method.

[0094] Examples of the thermal polymerization initiator include peroxydicarbonates such as di-2-ethylhexyl peroxydicarbonate; peroxyesters such as t-butylperoxybenzoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisopropyl carbonate, and t-hexylperoxyisopropyl carbonate; and peroxyketals such as di(t-butylperoxy)-2-methylcyclohexane, di(t-butylperoxy)3,3,5-trimethylcyclohexane, and di(t-butylperoxy)cyclohexane.

[0095] Examples of the photopolymerization initiator include acetophenones such as acetophenone, methoxyacetophenone, 2,2-diethoxyacetophenone, p-dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, α-hydroxy-α,α'-dimethylacetophenone, 2-hydroxy-2-cyclohexylacetophenone, and 2-methyl-1[4-(methylthio)phenyl]-2-montmorillonite-1; benzoin ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl butyl ether; and benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl butyl ether. ketones such as benzophenone, 2-chlorobenzophenone, p,p'-dichlorobenzophenone, N,N'-tetramethyl-4,4'-diaminobenzophenone, and 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone; thioxanthones such as thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone; phosphine oxides such as bisacylphosphine oxide and benzoylphosphine oxide; ketals such as benzyl dimethyl ketal; and quinones such as camphane-2,3-dione and phenanthrenequinone.

[0096] (Other Components) The polyurethane resin-forming composition may contain a polyisocyanate other than the modified polyisocyanate described above. However, from the viewpoint of enhancing the effect of the modified polyisocyanate, the content of the modified polyisocyanate may be 80% by mass or more, 90% by mass or more, or 95% by mass or more based on the total mass of the polyisocyanate.

[0097] The polyurethane resin-forming composition may contain various additives depending on its intended use, such as antioxidants such as 2,6-di-tert-butyl-4-methylphenol, ultraviolet absorbers, pigments, dyes, solvents, flame retardants, hydrolysis inhibitors, lubricants, plasticizers, fillers, antistatic agents, dispersants, catalysts, storage stabilizers, and thickeners.

[0098] The catalyst may be a known urethanization catalyst. Examples include organometallic compounds such as dibutyltin diacetate, dibutyltin dilaurate, and dioctyltin dilaurate, and organic amines and salts thereof such as triethylenediamine, triethylamine, diazabicycloundecene, and diazabicyclononene. These catalysts may be used alone or in combination of two or more.

[0099] (M ＮＣＯ / M ＯＨ ) the number of moles of hydroxyl groups in the hydroxyl group-containing compound contained in the polyurethane resin-forming composition (M ＯＨ ) relative to the number of moles (M ＮＣＯ ) ratio R (= M ＮＣＯ / M ＯＨ ) may be 0.8 or more, 0.9 or more, or 1.0 or more, from the viewpoint of further suppressing excessive hydroxyl groups and further improving water resistance and moist heat resistance, and from the viewpoint of further suppressing a decrease in crosslink density and further improving durability (stain resistance, etc.) and the mechanical strength of the coating film. The ratio R may be 1.3 or less, 1.2 or less, or 1.1 or less, from the viewpoint of further suppressing excessive isocyanate groups, suppressing excessive production of isocyanurate groups and urea groups, and further improving the flexibility and self-repairing ability of the coating film. From the above viewpoints, the ratio R may be 0.8 to 1.3, 0.9 to 1.2, or 1.0 to 1.1.

[0100] From the same viewpoint as above, the ratio of the number of moles of isocyanate groups in the modified polyisocyanate to the number of moles of hydroxyl groups in the polyol may be 0.8 to 1.3.

[0101] The polyurethane resin-forming composition may be a one-component composition in which all of the constituent components are contained in one component, or a multi-component composition in which the constituent components are present in multiple components. The polyurethane resin-forming composition may, for example, contain a first component containing a modified polyisocyanate and a second component containing a polyol. The polyurethane resin-forming composition may contain the first component, the second component, and a third component other than these. When the polyurethane resin-forming composition is a multi-component composition, the other constituent components (such as a catalyst) may be contained in the first component, the second component, or the third component.

[0102] <Coating composition> Another embodiment of the present disclosure is a coating composition containing the polyurethane resin-forming composition. This coating composition cures while forming a polyurethane resin by reacting a modified polyisocyanate with a polyol.

[0103] The coating composition can provide a coating film with sufficient hardness. Furthermore, the coating composition can easily provide a coating film with excellent self-repairing properties, contamination resistance, smoothness, and adhesion. Therefore, the coating composition can be used for forming surface coatings on automotive exterior components and plastic molded products, which require fine processing, high designability, and lightweight exterior components.

[0104] <Coating Film> Another embodiment of the present disclosure is a coating film comprising a cured product of the coating composition. This coating film may be a so-called self-repairing coating film.

[0105] The coating film can exhibit self-repairing properties within 1 hour at room temperature (e.g., 5 to 35°C) or when heated to 40 to 60°C. The coating film can also exhibit good smoothness and good stain resistance under high humidity conditions. The inventors speculate that the improved smoothness is due to improved drying properties and humidity resistance, and that the improved stain resistance is due to improved crosslink density.

[0106] The cured product of the coating composition contains a polyurethane resin having a urethane structure formed by urethanization of a modified polyisocyanate and a polyol. The urethane structure contained in the polyurethane resin contains, in addition to the urethane group (—CONH—), reaction residues of the modified polyisocyanate and reaction residues of the polyol.

[0107] The thickness of the coating is, for example, 5 to 40 μm. The coating may be a thin film with a thickness of less than 20 μm.

[0108] The coating film can be formed by a method comprising applying the above-described coating composition to an adherend and curing the composition, thereby obtaining an article comprising the adherend and the coating film formed on the adherend.

[0109] Examples of the adherend include molded articles made from materials such as stainless steel, phosphate-treated steel, zinc-coated steel, iron, copper, aluminum, brass, glass, acrylic polyol, polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene phthalate resin, polystyrene resin, AS resin, ABS resin, polycarbonate-ABS resin, 6-nylon resin, 6,6-nylon resin, MXD6 nylon resin, polyvinyl chloride resin, polyvinyl alcohol resin, polyurethane resin, phenolic resin, melamine resin, polyacetal resin, chlorinated polyolefin resin, polyolefin resin, polyamide resin, polyether ether ketone resin, polyphenylene sulfide resin, NBR resin, chloroprene resin, SBR resin, and SEBS resin, as well as surface-treated articles of such molded articles. The surface-treated article may be a molded article (surface-treated molded article) made from an olefin resin such as polyethylene or polypropylene that has been subjected to a surface treatment such as corona discharge treatment.

[0110] The adherend may have another coating film on its surface that can serve as an intermediate layer. In other words, the coating composition may be applied directly to the surface of the molded body described above, or may be applied on top of another coating film that has been applied as a base coat on the surface of the molded body described above. The other coating film may be a single layer or multiple layers.

[0111] The coating composition may be applied by spraying, brushing, dipping, or the like.

[0112] The coating composition may be cured, for example, by heating. The heating for curing may be heating for drying. That is, when the coating composition contains a solvent, the coating composition may be cured simultaneously (in parallel) with drying for removing the solvent. The heating temperature may be, for example, 60 to 150°C. The heating time may be, for example, 1 to 10 hours.

[0113] Examples of the present disclosure will be described below, but the present disclosure should not be construed as being limited to these examples.

[0114] <Preparation of Polytetramethylene Ether Glycols> The following polytetramethylene ether glycols (PTMG1 to 6) were prepared: PTMG1 (polytetramethylene ether glycol, manufactured by Mitsubishi Chemical Corporation, trade name: PTMG-250, number average molecular weight (Mn) = 225, polydispersity (Mw / Mn) = 1.04, content of monomers to hexamers = 99 mass%, potassium content = 0.1 mass ppm) PTMG2 (polytetramethylene ether glycol, manufactured by BASF, trade name: PolyTHF250, number average molecular weight (Mn) = 250, polydispersity (Mw / Mn) = 1.04, content of monomers to hexamers = 98 mass%, potassium content = 1.4 mass ppm) PTMG3 (manufactured by PTG, polytetramethylene ether glycol, trade name: PTMEG-220, number average molecular weight (Mn) = 220, polydispersity (Mw / Mn) = 1.03, content of monomers to hexamers = 99 mass%, potassium content = 4.3 mass ppm) PTMG4 (manufactured by Hodogaya Chemical Co., Ltd., polytetramethylene ether glycol, trade name: TERATHANE PTMEG250, number average molecular weight (Mn) = 250, polydispersity (Mw / Mn) = 1.65, content of monomers to hexamers = 81 mass%, potassium content = 2.4 mass ppm, TERATHANE is a registered trademark) PTMG5 (polytetramethylene ether glycol, manufactured by Mitsubishi Chemical Corporation, trade name: PTMG1000, number average molecular weight (Mn) = 1000, polydispersity (Mw / Mn) = 1.67, content of monomers to hexamers = 8 mass%, potassium content = 0.1 mass ppm) PTMG6 (polytetramethylene ether glycol, manufactured by Mitsubishi Chemical Corporation, trade name: PTMG-650, number average molecular weight (Mn) = 650, polydispersity (Mw / Mn) = 1.55, content of monomers to hexamers = 18 mass%, potassium content = 0.1 mass ppm)

[0115]

[0116] <Example 1> (Synthesis of modified polyisocyanate) A 1 L four-necked flask equipped with a stirrer, thermometer, condenser and nitrogen gas inlet tube was charged with 890 g of hexamethylene diisocyanate (manufactured by Tosoh Corporation, NCO content: 49.9% by mass, hereinafter referred to as "HDI") and 110 g of PTMG1, and heated to 60 ° C. under a nitrogen stream, and then 0.05 g of zirconium octylate (trade name: zirconyl octylate, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., hereinafter referred to as "OctZr") was added and stirred for 2 hours at 110 ° C. Then 0.5 g of JP-508 (trade name, manufactured by Johoku Chemical Industry Co., Ltd., acidic phosphate ester) was added as a reaction terminator, and the mixture was stirred at 80 ° C. for 2 hours. After cooling the reaction solution, excess HDI was removed by thin-film distillation (conditions: 130°C, 0.04 kPa), yielding 370 g of modified polyisocyanate P1. The properties of the resulting modified polyisocyanate P1 are shown in Table 2. In this example, the properties of the modified polyisocyanate were measured by the following methods.

[0117] (Measurement of allophanate group / isocyanurate group / urethane group molar ratio) The molar ratio of each functional group (isocyanurate group, allophanate group, and urethane group) relative to the total of 100 mol% of isocyanurate group, allophanate group, and urethane group in the modified polyisocyanate was measured using ECX400M (trade name) manufactured by JEOL Ltd. １ Specifically, the measurement sample was １Measurement was performed by H-NMR, and the signal area of ​​the hydrogen atom of the methylene group adjacent to the nitrogen atom of the isocyanurate ring was determined, and the molar ratio of the isocyanurate group, allophanate group, and urethane group was calculated using the following formula. The measurement sample was prepared by dissolving the modified polyisocyanate in deuterated chloroform containing 0.2 mass% of tetramethylsilane. The sample concentration was 0.02 g / 1 mL mass%. The chemical shift reference was set to the signal of the hydrogen atom of tetramethylsilane at 0 ppm. Isocyanurate group molar ratio (mol %) = (signal area around 3.9 ppm / 6) / (signal area around 3.9 ppm / 6 + signal area around 8.6 ppm / 1 + signal area around 4.6 ppm / 1) × 100 Allophanate group molar ratio (mol %) = (signal area around 8.6 ppm / 1) / (signal area around 3.9 ppm / 6 + signal area around 8.6 ppm / 1 + signal area around 4.6 ppm / 1) × 100 Urethane group molar ratio (mol %) = (signal area around 4.6 ppm / 1) / (signal area around 3.9 ppm / 6 + signal area around 8.6 ppm / 1 + signal area around 4.6 ppm / 1) × 100

[0118] (Molecular Weight Measurement) The number average molecular weight (Mn) and weight average molecular weight (Mw) disclosed in this example were measured under the following conditions, and the polydispersity index (Mw / Mn) was calculated from these measured values. [Conditions] Measuring instrument: "HLC-8120" (manufactured by Tosoh Corporation) Column: "TSKguard column HXL-L" (manufactured by Tosoh Corporation) Particle size = 6 μm, size = 6 mm ID x 30 cm x 4 columns Carrier: tetrahydrofuran (THF) Detector: differential refractive index Sample: 0.1% THF solution Calibration curve: polystyrene

[0119] (Measurement of Monomer to Hexamer Content of Polytetramethylene Ether Glycol) The content of monomer to hexamer of polytetramethylene ether glycol was determined from the area of ​​the differential refractive index peak on the GPC chromatogram obtained by the above molecular weight measurement. Specifically, the differential refractive index peak of the monomer appears at a retention time of about 37.6 minutes, the differential refractive index peak of the dimer appears at a retention time of about 37.1 minutes, the differential refractive index peak of the trimer appears at a retention time of about 36.1 minutes, the differential refractive index peak of the tetramer appears at a retention time of about 34.9 minutes, the differential refractive index peak of the pentamer appears at a retention time of about 33.9 minutes, the differential refractive index peak of the hexamer appears at a retention time of about 33.1 minutes, and the differential refractive index peak of the heptamer or higher multimer appears in the range of about 27.6 to about 32.5 minutes. Therefore, the content of monomer to hexamer was calculated based on the following formula: Content of monomers to hexamers (mass%)=(peak area at retention time 37.6 minutes+peak area at retention time 37.1 minutes+peak area at retention time 36.1 minutes+peak area at retention time 34.9 minutes+peak area at retention time 33.9 minutes+peak area at retention time 33.1 minutes) / total area of ​​all peaks×100

[0120] (Measurement of NCO Content) The NCO content disclosed in the examples was measured according to the method described in JIS K1603-1 (Testing method for aromatic isocyanates as raw materials for polyurethane).

[0121] (Average Number of Isocyanate Groups) The average number of isocyanate groups disclosed in the examples was calculated by the following formula: Average Number of Isocyanate Groups = Number Average Molecular Weight × NCO Content / (42 × 100)

[0122] (Measurement of Viscosity) The viscosity values ​​disclosed in the examples were obtained by measuring the viscosity at 25° C. using a B-type viscometer (manufactured by Tokyo Keiki Co., Ltd., model "DVL-BII") with a No. 4 rotor.

[0123] (Measurement of Turbidity) The turbidity disclosed in the present examples was obtained by measuring the kaolin turbidity (visual method) according to JIS-K0101 for a polyisocyanate composition stored at 5° C. for 24 hours. A turbidity of 2 or less can be said to have good low-temperature stability.

[0124] (Measurement of Potassium Content) The potassium content disclosed in the present examples was obtained by ashing a sample (polytetramethylene ether glycol or polyisocyanate composition) and then dissolving it in acid, and measuring the potassium ion concentration of the resulting solution using ICP-AES (Optima 8300, manufactured by PerkinElmer).

[0125] Example 2 Except for using PTMG2 instead of PTMG1, 360 g of modified polyisocyanate P2 was obtained in the same manner as in Example 1. The properties of the obtained modified polyisocyanate P2 are shown in Table 2.

[0126] Example 3 Except for changing the stirring time after adding 0.05 g of OctZr to 1 hour, the same procedure as in Example 2 was repeated to obtain 320 g of modified polyisocyanate P3. The properties of the obtained modified polyisocyanate P3 are shown in Table 2.

[0127] Example 4 Except for changing the stirring time after adding 0.05 g of OctZr to 3 hours, the same procedure as in Example 2 was repeated to obtain 390 g of modified polyisocyanate P4. The properties of the obtained modified polyisocyanate P4 are shown in Table 2.

[0128] Example 5 Except for using PTMG3 instead of PTMG1, 360 g of modified polyisocyanate P5 was obtained in the same manner as in Example 1. The properties of the obtained modified polyisocyanate P5 are shown in Table 2.

[0129] Example 6 Except for using PTMG6 instead of PTMG1, 360 g of modified polyisocyanate P6 was obtained in the same manner as in Example 1. The properties of the obtained modified polyisocyanate P6 are shown in Table 2.

[0130] Comparative Example 1 Except for using PTMG4 instead of PTMG1, 360 g of modified polyisocyanate P7 was obtained in the same manner as in Example 1. The properties of the obtained modified polyisocyanate P7 are shown in Table 2.

[0131] Comparative Example 2 Except for changing the stirring time after adding 0.05 g of OctZr to 30 minutes, the same procedure as in Example 2 was repeated to obtain 250 g of modified polyisocyanate P8. The properties of the obtained modified polyisocyanate P8 are shown in Table 2.

[0132] Comparative Example 3 Except for using PTMG5 instead of PTMG1, 360 g of modified polyisocyanate P9 was obtained in the same manner as in Example 1. The properties of the obtained modified polyisocyanate P9 are shown in Table 2.

[0133]

[0134] <Evaluation 1: Measurement of coating film hardness> (Preparation of coating composition) An acrylic polyol (trade name: Acrydic A-801, glass transition temperature: 50°C, hydroxyl value: 50 mg KOH / g resin, solids content: 50 mass%, manufactured by DIC Corporation) and the modified polyisocyanate of each example (P1 to P9) were blended so that the equivalent ratio of hydroxyl groups to isocyanate groups was 1:1. Then, butyl acetate was added to prepare a coating composition with a coating solids content of 40 mass%.

[0135] (Preparation of coating film) The obtained coating composition was applied to a steel plate (JIS G3141, product name: SPCC-SB, treatment method: PF-1077, manufactured by Paltec Co., Ltd.) as an adherend, and after curing at 23°C and 50% RH for 1 hour, the coating composition was cured by baking at 80°C for 10 hours. This gave a coating film with a thickness of 20 μm.

[0136] The Martens hardness of the resulting coating film was measured in accordance with JIS Z2255 using HM2000 (trade name, manufactured by Fisher Instruments). The evaluation criteria are shown below, and the evaluation results are shown in Table 3. A: Martens hardness of 90 or more B: Martens hardness of 60 or more but less than 90 C: Martens hardness less than 60

[0137] <Evaluation 2: Evaluation of storage stability> The coating composition prepared in Evaluation 1 was stored at 45°C for 24 hours. The viscosity of the coating composition was measured before and after storage, and the rate of change in viscosity (initial viscosity and viscosity after storage) before and after storage was calculated using the following formula, and storage stability was evaluated based on this rate of change. The viscosity was measured at 25°C using a B-type viscometer. Viscosity change rate (%) = (viscosity after storage - initial viscosity) / initial viscosity x 100 The evaluation criteria are shown below, and the evaluation results are shown in Table 3. A: Viscosity change rate less than 120% B: Viscosity change rate 120% or more but less than 250% C: Viscosity change rate 250% or more

[0138]

Claims

1. A modified polyisocyanate which is an allophanate reaction product or a modified product thereof between a polyisocyanate containing an aliphatic polyisocyanate having an aliphatic hydrocarbon group having 4 to 6 carbon atoms and a polyol containing polytetramethylene ether glycol, and which has a polydispersity index of 1.0 to 2.1, and in which the proportion of urethane groups in the total content of allophanate groups, isocyanurate groups, and urethane groups is 19 mol% or less.

2. The modified polyisocyanate according to claim 1, wherein the proportion of the urethane group content in the total content of allophanate groups, isocyanurate groups, and urethane groups is 0.01 to 7 mol %.

3. The modified polyisocyanate according to claim 1, wherein the proportion of the allophanate group content in the total content of allophanate groups, isocyanurate groups, and urethane groups is 75 to 98 mol %.

4. The modified polyisocyanate according to claim 1, wherein the proportion of isocyanurate groups in the total content of allophanate groups, isocyanurate groups, and urethane groups is 0.1 to 7 mol %.

5. The modified polyisocyanate according to claim 1, wherein the average number of isocyanate groups is 6.0 to 8.

0.

6. The modified polyisocyanate according to claim 1, having a number average molecular weight of 1,500 to 2,000 g / mol.

7. The modified polyisocyanate according to claim 1, wherein the polytetramethylene ether glycol has a number average molecular weight of 200 to 800.

8. The modified polyisocyanate according to claim 1, wherein the polytetramethylene ether glycol has a polydispersity of 1.00 to 1.

60.

9. A polyurethane resin-forming composition comprising the modified polyisocyanate according to any one of claims 1 to 8 and a polyol.

10. A coating composition comprising the polyurethane resin-forming composition according to claim 9.

11. A coating film comprising a cured product of the coating composition according to claim 10.

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