Polyisocyanate composition, mixture, coating composition, coating film, and biodegradable polyurethane cured product

Abstract

To provide a polyisocyanate composition exhibiting superior biodegradability and mechanical characteristics when being made into a coating film.SOLUTION: A polyisocyanate composition comprising a polyisocyanate having an allophanate group derived from (A), (C), and (D), wherein (A) is at least one diisocyanate selected from the group consisting of an aliphatic diisocyanate and an alicyclic diisocyanate, (C) is a polyester polyol or a polycaprolactone polyol having a number average molecular weight Mn of 500 or more and 4,000 or less and being difunctional or trifunctional, and (D) is a hydrophilic component, wherein, based on a total mass of the polyisocyanate composition, a content of (C) is more than 50 mass% and 85 mass% or less, and a content of (D) is 0.1 mass% or more and 20 mass% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyisocyanate composition, a mixture, a coating composition, a coating film, and a biodegradable polyurethane cured product. [Background technology]

[0002] In recent years, there has been an increasing demand for biodegradable resins that have a low environmental impact, and there is also a demand for biodegradable polyisocyanates. However, because high-performance urethane compositions have excellent durability and hydrolysis resistance, they may remain in the environment without decomposing even when released into the environment. To impart biodegradability to high-performance urethane compositions, it is first necessary to break down the resin particles by hydrolysis catalyzed by microbial enzymes.

[0003] For example, Patent Document 1 discloses a polyisocyanate obtained by adding a diisocyanate to a polyester polyol containing succinic acid as a carboxylic acid and triethylene glycol as an alcohol as essential components. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5263644 Summary of the Invention [Problem to be solved by the invention]

[0005] The polyisocyanate described in Patent Document 1 has room for improvement in terms of achieving both biodegradability when formed into a coating film and mechanical strength when formed into a coating film.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyisocyanate composition which, when formed into a coating film, has excellent biodegradability and mechanical properties. [Means for solving the problem]

[0007] The present invention includes the following aspects. [1] A polyisocyanate composition containing a polyisocyanate having an allophanate group, wherein the polyisocyanate is derived from (A), (C), and (D), wherein (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, and (C) is a polyester polyol or a polycaprolactone polyol, has a number average molecular weight Mn of 500 or more and 4,000 or less, and is bifunctional or trifunctional, and wherein the preceding The polyisocyanate composition has an average number of isocyanate functional groups of 1.8 or more and 3.2 or less, the polyester polyol is composed of polyol units and dicarboxylic acid units having 8 or less carbon atoms, the content of (C) relative to the total mass of the polyisocyanate composition is more than 50 mass% and 85 mass% or less, and the content of (D) relative to the total mass of the polyisocyanate composition is 0.1 mass% or more and 20 mass% or less. [2] The polyisocyanate composition according to [1], wherein the polyisocyanate is derived from (B) in addition to (A), (C), and (D), and (B) is an alcohol having 1 to 20 carbon atoms. [3] The polyisocyanate composition according to [1] or [2], wherein the isocyanate group content is 1% by mass or more and 13% by mass or less, based on the total mass of the polyisocyanate composition. [4] The polyisocyanate composition according to any one of [1] to [3], wherein the number average molecular weight Mn of (C) is 1,000 or more and 4,000 or less. [5] The polyisocyanate composition according to any one of [1] to [4], wherein the polyol unit constituting the polyester polyol is an aliphatic polyol. [6] The polyisocyanate composition according to [5], wherein the dicarboxylic acid unit is succinic acid or adipic acid. [7] The polyisocyanate composition according to [5], wherein the aliphatic polyol is diethylene glycol or triethylene glycol. [8] The polyisocyanate composition according to any one of [1] to [7], wherein (D) is a nonionic hydrophilic component having one hydroxyl group and consisting of 3 to 25 ethylene oxide repeating units. [9] The polyisocyanate composition according to any one of [2] to [8], wherein (B) is 2-ethylhexanol.

[10] The polyisocyanate composition according to any one of [1] to [9], which is a curing agent for a coating composition or a polyurethane bead composition.

[11] A mixture comprising the polyisocyanate composition according to any one of [1] to

[10] .

[12] A coating composition comprising a polyol and a curing agent, the curing agent comprising the polyisocyanate composition according to any one of [1] to

[10] .

[13] A coating film obtained by curing the coating composition according to

[12] .

[14] A biodegradable polyurethane cured product obtained by curing the polyisocyanate composition according to any one of [1] to

[10] alone or together with an acrylic polyol. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a polyisocyanate composition that, when formed into a coating film, has excellent biodegradability and mechanical properties. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The following 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 modified in various ways without departing from the gist of the present invention.

[0010] In this specification, the term "polyol" refers to a compound having two or more hydroxy groups (-OH) in one molecule. In addition, in this specification, the term "polyisocyanate" refers to a reaction product in which a plurality of monomer compounds having two or more isocyanate groups (-NCO) are bonded together.

[0011] <Polyisocyanate composition> The polyisocyanate composition of the present embodiment is a polyisocyanate composition containing a polyisocyanate having an allophanate group. The polyisocyanate is derived from (A), (C) and (D). The (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates. The (C) is a polyester polyol or a polycaprolactone polyol, has a number average molecular weight Mn of 500 or more and 4,000 or less, and is bifunctional or trifunctional. The (D) is a hydrophilic component. The polyester polyol is composed of a polyol unit and a dicarboxylic acid unit having 8 or less carbon atoms. The average number of isocyanate functional groups in the polyisocyanate composition of the present embodiment is 1.8 or more and 3.2 or less. The content of (C) relative to the total mass of the polyisocyanate composition of this embodiment is more than 50 mass % and 85 mass % or less. The content of (D) relative to the total mass of the polyisocyanate composition of the present embodiment is 0.1 mass % or more and 20 mass % or less. Here, the polyisocyanate composition means a composition consisting only of a compound component having an isocyanate group and a compound component derived from a compound having an isocyanate group, and does not include solvents, various additives, etc.

[0012] The polyisocyanate composition of the present embodiment has the above-described structure, and as will be shown in the examples below, when formed into a coating film, it has excellent biodegradability and mechanical properties.

[0013] Each of the constituent components of the polyisocyanate composition of the present embodiment will be described in detail below.

[0014] <(A)> (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.

[0015] Aliphatic diisocyanates are compounds having saturated aliphatic groups in their molecules. On the other hand, alicyclic diisocyanates are compounds having cyclic aliphatic groups in their molecules. From the viewpoint of achieving a low viscosity of the resulting polyisocyanate composition, it is preferable to use an aliphatic diisocyanate.

[0016] Examples of aliphatic diisocyanates include 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane (HDI), 1,6-diisocyanato-2,2,4-trimethylhexane, and methyl 2,6-diisocyanatohexanoate (lysine diisocyanate).

[0017] Examples of alicyclic diisocyanates include 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate; hereinafter, sometimes abbreviated as "IPDI"), 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated xylylene diisocyanate), bis(4-isocyanatocyclohexyl)methane (hydrogenated diphenylmethane diisocyanate), and 1,4-diisocyanatocyclohexane.

[0018] These diisocyanates may be used alone or in combination of two or more. Among these, the (A) diisocyanate is preferably HDI, IPDI, hydrogenated xylylene diisocyanate, or hydrogenated diphenylmethane diisocyanate because of its industrial availability, and particularly preferably HDI because of its excellent biodegradability and flexibility. Hereinafter, aliphatic diisocyanates and alicyclic diisocyanates may be collectively referred to as diisocyanates.

[0019] <(C)> (C) is a polyester polyol or a polycaprolactone polyol, and has a number average molecular weight Mn of 500 or more and 4,000 or less, and is bifunctional or trifunctional. The polyester polyol (C) is composed of polyol units and dicarboxylic acid units having 8 or less carbon atoms. In one embodiment of the present invention, (C) is preferably biodegradable in the natural environment.

[0020] The polyester polyol in this embodiment is obtained by a condensation reaction between a dibasic acid alone or a mixture thereof and a dihydric or trihydric alcohol alone or a mixture thereof.

[0021] The polycaprolactone polyol in this embodiment is obtained by ring-opening polymerization of ε-caprolactone with a dihydric or trihydric alcohol.

[0022] Examples of dibasic acids include succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and other carboxylic acids.

[0023] Examples of dihydric alcohols include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, trimethylpentanediol, 1,2-, 1,3-, and 1,4-cyclohexanediol.

[0024] Examples of trihydric alcohols include trimethylolpropane, 12-hydroxystearyldiol, diols obtained by reducing dimer acids, glycerin, pentaerythritol, 2-methylolpropanediol, and ethoxylated trimethylolpropane.

[0025] Examples of polyester polyols include Maximol (registered trademark) SDK-145 (trade name, manufactured by Kawasaki Chemical Industries, Ltd., succinic acid unit-containing polyester polyol, number average molecular weight Mn 1,250, average number of hydroxyl groups 2.0), OD-X-2693 (trade name, manufactured by DIC Corporation, adipic acid unit-containing polyester polyol, number average molecular weight Mn 3,000, average number of hydroxyl groups 2.0), and OD-X-2694 (trade name, manufactured by DIC Corporation, adipic acid unit-containing polyester polyol, number average molecular weight Mn 4,000, average number of hydroxyl groups 2.0).

[0026] Among the above, from the viewpoint of achieving better biodegradability when formed into a coating film, it is preferable that the polyol units constituting the polyester polyol are aliphatic polyols, and it is more preferable that the aliphatic polyol is diethylene glycol or triethylene glycol.

[0027] The dicarboxylic acid units having 8 or less carbon atoms constituting the polyester polyol are preferably succinic acid or adipic acid, from the viewpoints of preventing an increase in the viscosity of the polyisocyanate composition and providing a coating film with better mechanical properties.

[0028] Examples of polycaprolactone polyols include OD-X-2542C (trade name, manufactured by DIC Corporation, number average molecular weight Mn 850, average number of hydroxyl functional groups 3.0), OD-X-2721 (trade name, manufactured by DIC Corporation, polycaprolactone polyol, number average molecular weight Mn 1,000, average number of hydroxyl functional groups 2.0), and OD-X-2722 (trade name, manufactured by DIC Corporation, polycaprolactone polyol, number average molecular weight Mn 2,000, average number of hydroxyl functional groups 2.0).

[0029] The polyester polyol or polycaprolactone polyol can be produced by a known condensation reaction, for example, by combining the above components and heating them at about 160 to 220°C. At least one of the dibasic acid, dihydric, or trihydric alcohol used as raw materials for the polyester polyol must have a side chain.

[0030] In this embodiment, the number average molecular weight Mn of (C) is 500 or more and 4,000 or less, and preferably 1,000 or more and 4,000 or less. When the number average molecular weight Mn is equal to or more than the above lower limit, the mechanical properties of the formed coating film are more excellent. On the other hand, when the number average molecular weight Mn is equal to or less than the above upper limit, the viscosity of the polyisocyanate is less likely to increase, and the biodegradability of the formed coating film is more excellent.

[0031] The content of (C) relative to the total mass of the polyisocyanate used in this embodiment is more than 50 mass% and not more than 85 mass%, preferably 52 mass% or more and 83 mass% or less, and more preferably 54 mass% or more and 81 mass% or less. When the content of (C) is equal to or greater than the above lower limit, the coating film has better biodegradability, whereas when the content of (C) is equal to or less than the above upper limit, the coating film has better mechanical properties.

[0032] The polyisocyanate used in this embodiment contains allophanate groups, which results in a coating film with superior biodegradability. The polyisocyanate preferably has a molar ratio of isocyanurate groups to allophanate groups (isocyanurate groups:allophanate groups) of 0:100 or more and less than 25:75.

[0033] The molar ratio of allophanate groups to isocyanurate groups can be determined by H-NMR. An example of a method for measuring the polyisocyanate composition using HDI and the isocyanate prepolymer obtained therefrom as raw materials by H-NMR is shown below.

[0034] Example of 1H-NMR measurement method: Dissolve polyisocyanate in deuterated chloroform at a concentration of 10% by mass (0.03% by mass of tetramethylsilane added relative to the polyisocyanate). The chemical shift reference is the hydrogen signal of tetramethylsilane, set at 0 ppm. Measure using 1H-NMR, and measure the area ratio of the signal of the hydrogen atom bonded to the nitrogen of the allophanate group (1 mol of hydrogen atom per 1 mol of allophanate group) at around 8.5 ppm to the signal of the hydrogen atom of the methylene group adjacent to the isocyanurate group (6 mol of hydrogen atoms per 1 mol of isocyanurate group) at around 3.85 ppm, and calculate the molar ratio using the following formula: Allophanate group / Isocyanurate group=(signal area around 8.5 ppm) / (signal area around 3.85 ppm / 6)

[0035] Furthermore, since uretdione compounds tend to dissociate due to heat or other factors and generate HDI, it is preferable to reduce their content. The content of uretdione compounds is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, based on the polyisocyanate composition. The content of uretdione compounds can be determined by measuring the area ratio of the peak corresponding to a molecular weight of approximately 336 in gel permeation chromatography (hereinafter referred to as GPC) using a parallax refractometer. If there is a peak near the peak of approximately 336 that interferes with measurement, the content can also be determined by a method using FT-IR to quantify the ratio of the height of the uretdione group peak at approximately 1770 cm-1 to the height of the allophanate group peak at approximately 1720 cm-1 using an internal standard.

[0036] The GPC measurement method is described below. All measurements of the molecular weight of polyisocyanate were performed using the following method: Instrument used: HLC-8120 (manufactured by Tosoh Corporation), Columns used: TSK GEL SuperH1000, TSK GEL SuperH2000, TSK GEL SuperH3000 (all manufactured by Tosoh Corporation), Sample concentration: 5 wt / vol% (for example, dissolving 50 mg of sample in 1 ml of THF), Carrier: THF, Detection method: Parallax refractometer, Outflow rate: 0.6 ml / min, Column temperature: 40°C). The GPC calibration curve was prepared using polystyrenes with molecular weights of 50,000 to 2,050 (GL Sciences PSS-06 (Mw 50,000), BK13007 (Mp = 20,000, Mw / Mn = 1.03), PSS-08 (Mw = 9,000), PSS-09 (Mw = 4,000), and 5040-35125 (Mp = 2,050, Mw / Mn = 1.05)). The isocyanurate trimer to heptamer (molecular weight of isocyanurate trimer = 504, molecular weight of isocyanurate pentamer = 840, molecular weight of isocyanurate heptamer = 1,176) of a hexamethylene diisocyanate-based polyisocyanate composition (Duranate TPA-100, manufactured by Asahi Kasei Chemicals Corporation) and HDI (molecular weight = 168) were used as standards.

[0037] A high content of biuret compounds and other diisocyanate polymers is undesirable because they reduce the biodegradability and mechanical properties of the coating film formed. The range of the amount of biuret compounds and other diisocyanate polymers contained in the polyisocyanate composition of the present invention is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less.

[0038] <(D)> (D) is a hydrophilic component, and the content of the hydrophilic component relative to the total mass of the polyisocyanate composition is 0.1% by mass or more and 20% by mass or less.

[0039] The content of (D) relative to the total mass of the polyisocyanate composition is preferably 0.2% by mass or more and 15% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and even more preferably 0.8% by mass or more and 7% by mass or less. When the content of (D) is equal to or greater than the lower limit, microbial decomposition is promoted, and the resulting coating film has better biodegradability. On the other hand, when the content is equal to or less than the upper limit, the resulting coating film has better mechanical properties.

[0040] (D) is preferably a nonionic hydrophilic component having one hydroxyl group and consisting of 3 to 25 ethylene oxide repeating units. The nonionic hydrophilic component is a polyalkylene oxide ether alcohol containing an ethylene oxide repeating unit, and the hydrophilic component has at least one hydroxyl group. Such compounds include polyethylene glycol, Pluronic (registered trademark) type polyalkylene glycol, etc. A preferred compound is polyethylene glycol monoalkyl ether, and particularly preferred is methoxypolyethylene glycol.

[0041] The number of ethylene oxide repeating units is preferably 3 to 25, more preferably 5 to 23, and even more preferably 7 to 20. If the number of ethylene oxide repeating units is 3 or more, sufficient emulsifying ability can be obtained. If the number of ethylene oxide repeating units is 25 or less, the crystallinity is not too high and the composition is stable. The nonionic hydrophilic component, when incorporated into the polyisocyanate structure, exhibits surfactant properties.

[0042] The isocyanate group content (hereinafter also referred to as "NCO content") relative to the total mass of the polyisocyanate composition of this embodiment, in a state substantially free of solvent and diisocyanate, is preferably 1% by mass or more and 13% by mass or less, more preferably 1% by mass or more and 12% by mass or less, and most preferably 1% by mass or more and 11% by mass or less. If the NCO content is within the above range, a polyisocyanate composition can be obtained that is sufficiently soluble in a low-polarity organic solvent and has sufficient crosslinkability. The NCO content of the polyisocyanate composition of the present embodiment can be measured using the method described in the examples below.

[0043] The average number of isocyanate functional groups in the polyisocyanate composition of the present embodiment is 1.8 to 3.2, preferably 1.8 to 3.1, more preferably 1.8 to 2.8, and even more preferably 1.8 to 2.7. When the average number of isocyanate functional groups is equal to or greater than the above lower limit, the mechanical properties of the coating film are improved, whereas when the average number of isocyanate functional groups is equal to or greater than the above upper limit, the biodegradability of the coating film is improved. The average number of isocyanate functional groups in the polyisocyanate composition of the present embodiment can be measured using the method described in the examples below.

[0044] ((B)) In the polyisocyanate composition of the present embodiment, the polyisocyanate is preferably derived from (B) in addition to (A), (C), and (D). (B) is an alcohol having 1 to 20 carbon atoms.

[0045] (B) is preferably a monoalcohol having 6 to 20 carbon atoms. The number of carbon atoms in the alcohol is preferably not more than 16, more preferably not more than 12, and even more preferably not more than 9. When the number of carbon atoms is not more than the above upper limit, the hardness of the coating film is sufficient. Although the lower limit of the number of carbon atoms of the alcohol is not particularly limited, if it is 6 or more, the dissolving power in low-polarity organic solvents tends to be high. In one embodiment of the present invention, the alcohol has, for example, 6 or more and 16 or less, 6 or more and 12 or less, or 6 or more and 9 or less carbon atoms.

[0046] Specific examples of (B) include methanol, ethanol, butanol, and the like. Furthermore, (B) may be one containing an ether group in the molecule, such as 1-butoxyethanol, 2-butoxyethanol, 1-butoxypropanol, 2-butoxypropanol, 3-butoxypropanol, ethylene glycol monobutyl ether, and the like.

[0047] Although (B) may contain an ester group, a carbonyl group, a phenyl group, such as benzyl alcohol, a monoalcohol consisting solely of saturated hydrocarbon groups is preferred. Furthermore, a branched monoalcohol is more preferred. Examples of such monoalcohols include 1-hexanol, 2-hexanol, 1-heptanol, 1-octanol, 2-ethyl-1-hexanol, 3,3,5-trimethyl-1-hexanol, tridecanol, pentadecanol, palmityl alcohol, stearyl alcohol, cyclopentanol, cyclohexanol, methylcyclohexanol, and trimethylcyclohexanol. Among these, 1-octanol, 2-ethylhexanol, tridecanol, pentadecanol, palmityl alcohol, stearyl alcohol, and 1,3,5-trimethylcyclohexanol are particularly preferred due to their excellent solubility in low-polarity organic solvents. 1-Hexanol, 2-hexanol, 1-heptanol, 1-octanol, 2-octanol, 2-ethylhexanol, and 3,3,5-trimethyl-1-hexanol are more preferred because they provide a polyisocyanate composition with a lower viscosity. 2-Hexanol, 2-octanol, 2-ethylhexanol, and 3,3,5-trimethyl-1-hexanol are particularly preferred because they have excellent solubility in low-polarity organic solvents and provide a polyisocyanate composition with a lower viscosity.

[0048] In this embodiment, (B) may be one type of alcohol or a mixture of two or more types of alcohols.

[0049] The viscosity of the polyisocyanate composition of this embodiment at 25°C is preferably 100 to 10,000 mPa·s in a state substantially free of solvent or diisocyanate. The lower limit of the viscosity is more preferably 150 mPa·s, even more preferably 180 mPa·s, and even more preferably 200 mPa·s. The upper limit of the viscosity is more preferably 8,000 mPa·s, and even more preferably 16,000 mPa·s. A viscosity of 100 mPa·s or higher can provide a polyisocyanate composition with sufficient crosslinkability. The viscosity of the polyisocyanate composition of the present embodiment at 25°C can be measured at 25°C using, for example, an E-type viscometer (Tokimec Co., Ltd.).

[0050] <Production of Polyisocyanate> A method for producing the polyisocyanate used in this embodiment will be described below. There are various methods for producing the polyisocyanate used in the present invention, but a representative preferred synthesis method will be described below. (1) A method in which the above (A) and (B) are subjected to a urethane-forming reaction, followed by or simultaneously with an allophanation reaction, and unreacted diisocyanate is removed by purification to obtain a prepolymer, and the obtained prepolymer is mixed with the above (C) and (D), followed by a urethane-forming reaction to obtain the polyisocyanate used in this embodiment. (2) A method for obtaining a polyisocyanate for use in this embodiment by subjecting (A) and (B) to a urethane reaction, followed by or simultaneously with an allophanation reaction, and then terminating the allophanation reaction with a reaction terminator to obtain a prepolymer, mixing the obtained prepolymer with (C) and (D) and subjecting them to a urethane reaction, and removing unreacted diisocyanate by purification. (3) A method for obtaining the polyisocyanate used in the present embodiment by subjecting the above (A), (B), (C), and (D) to a urethane reaction, followed by, or simultaneously with, an allophanation reaction, and then removing the unreacted diisocyanate by purification. (4) A method for obtaining a polyisocyanate for use in this embodiment by subjecting (A) and (B) to a urethane reaction, followed by or simultaneously with an allophanation reaction, and removing unreacted diisocyanate by purification to obtain a prepolymer. The obtained prepolymer is mixed with (A), (C), and (D) above, subjected to a urethane reaction, and, if necessary, the unreacted diisocyanate is removed by purification to obtain a prepolymer. (5) A method for obtaining the polyisocyanate used in the present embodiment by mixing the above (A) and (B), carrying out a urethanization reaction, and then or simultaneously carrying out an allophanation reaction, and terminating the allophanation reaction with a reaction terminator, and then mixing the resulting reaction liquid with the above (A), (C), and (D), carrying out a urethanization reaction, and then or simultaneously carrying out an allophanation reaction, as necessary, and terminating the allophanation reaction with a reaction terminator, and then removing the unreacted diisocyanate by purification. The above methods (1) to (5) may be combined.

[0051] Any method may be used to produce the polyisocyanate used in this embodiment, as long as (C) and (D) are mixed in such a manner that the content of (C) relative to the total mass of the polyisocyanate composition of this embodiment is more than 50 mass% and not more than 85 mass%, and the content of (D) relative to the total mass of the polyisocyanate composition is 0.1 mass% or more and 20 mass% or less.

[0052] The urethanization reaction temperature is preferably 20 to 200°C, more preferably 40 to 150°C, and even more preferably 60 to 120°C. At temperatures above 20°C, the reaction is rapid, while at temperatures below 200°C, side reactions such as urethodionation are suppressed and coloration is also suppressed. The urethanization reaction time is preferably 10 minutes to 24 hours, more preferably 15 minutes to 15 hours, and even more preferably 20 minutes to 10 hours. A reaction time of 10 minutes or more allows the reaction to be completed, while a reaction time of 24 hours or less does not pose a problem in production efficiency and suppresses side reactions. The urethanization reaction can be carried out without a catalyst or in the presence of a catalyst such as a tin or amine catalyst.

[0053] The allophanate formation reaction is preferably carried out at a temperature of 20 to 200°C. More preferably, it is 40 to 180°C, and even more preferably, it is 60 to 160°C. Still more preferably, it is 90 to 150°C, and most preferably, it is 110 to 150°C. At a temperature of 20°C or higher, the amount of allophanate formation catalyst is reduced, and the time required to complete the reaction is short. Furthermore, at a temperature of 200°C or lower, side reactions such as urethodionation are suppressed, and coloration of the reaction product is suppressed.

[0054] When the allophanate formation reaction is carried out by any of methods (1) to (5), it is preferable to use a catalyst, and it is particularly necessary to select a catalyst that will result in a molar ratio of allophanate groups to isocyanurate groups in the resulting polyisocyanate of 95 / 5 to 100 / 0. Examples of such catalysts include carboxylates of zinc, tin, zirconium, zirconyl, etc., and mixtures thereof. The allophanate formation catalyst is used in an amount of preferably 0.001 to 2.0% by mass, more preferably 0.01 to 0.5% by mass, based on the total mass of the reaction solution. At 0.001% by mass or more, the catalytic effect can be fully exerted. At 2% by mass or less, the allophanate formation reaction can be easily controlled.

[0055] In the present invention, the method of adding the allophanate formation catalyst is not limited. For example, the allophanate formation catalyst may be added before the production of a compound containing a urethane group, i.e., prior to the urethanization reaction between a diisocyanate and an organic compound having a hydroxyl group, or may be added during the urethanization reaction between a diisocyanate and an organic compound having a hydroxyl group, or may be added after the production of the urethane group-containing compound. Furthermore, as a method of addition, the required amount of the allophanate formation catalyst may be added all at once or may be added in several divided portions. Alternatively, a method of continuous addition at a constant addition rate may be employed.

[0056] Examples of catalysts for deriving polyisocyanates containing isocyanurate groups from diisocyanate monomers include commonly used isocyanuration reaction catalysts. The isocyanurate reaction catalyst is not particularly limited, but is preferably generally basic, and examples thereof include: (1) hydroxides of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium; and organic weak acid salts thereof such as acetates, octylates, myristates, and benzoates; (2) hydroxides of hydroxyalkylammonium such as trimethylhydroxyethylammonium, trimethylhydroxypropylammonium, triethylhydroxyethylammonium, and triethylhydroxypropylammonium; and organic weak acid salts thereof such as acetates, octylates, myristates, and benzoates; (3) metal salts of alkylcarboxylic acids such as tin, zinc, and lead, such as acetic acid, caproic acid, octylate, and myristic acid; (4) metal alcoholates of sodium and potassium; (5) aminosilyl group-containing compounds such as hexamethylenedisilazane; (6) Mannich bases; (7) combinations of tertiary amines and epoxy compounds; and (8) phosphorus-based compounds such as tributylphosphine.

[0057] Among the isocyanurate reaction catalysts, organic weak acid salts of quaternary ammonium are preferred, and organic weak acid salts of tetraalkylammonium are more preferred, from the viewpoint of being less likely to produce unwanted by-products. The amount of the isocyanurate formation catalyst is preferably 10 ppm by mass or more and 1000 ppm by mass or less relative to the mass of the charged diisocyanate monomer. The upper limit is more preferably 500 ppm by mass, and even more preferably 100 ppm by mass. The isocyanurate formation reaction temperature is preferably 50°C or more and 120°C or less, and more preferably 60°C or more and 90°C or less. By keeping the isocyanurate formation reaction temperature at 120°C or less, coloration of the polyisocyanate tends to be effectively suppressed.

[0058] The urethanization reaction, allophanation reaction, and isocyanuration reaction can be carried out without a solvent. In addition to the low-polarity organic solvents described above, organic solvents that are not reactive with isocyanate groups, such as ester solvents (e.g., ethyl acetate and butyl acetate), ketone solvents (e.g., methyl ethyl ketone), aromatic solvents (e.g., toluene, xylene, and diethylbenzene), and dialkyl polyalkylene glycol ethers, as well as mixtures thereof, can be used as the solvent, if necessary. The processes of the urethanization reaction, allophanate formation reaction, and isocyanurate formation reaction in the present invention can be followed by measuring the NCO content of the reaction liquid or measuring the refractive index.

[0059] The allophanatization reaction and isocyanuration reaction can be terminated by cooling to room temperature or by adding a reaction terminator. When a catalyst is used, adding a reaction terminator is preferred because it can suppress side reactions. The amount of reaction terminator added is preferably 0.25 to 20 times the molar amount of the catalyst, more preferably 0.5 to 16 times the molar amount, and even more preferably 1.0 to 12 times the molar amount of the catalyst. Complete deactivation is possible at 0.25 times or more. Storage stability is improved at 20 times or less. Any reaction terminator that can deactivate the catalyst may be used. Examples of reaction terminators include compounds exhibiting phosphoric acidity such as phosphoric acid and pyrophosphoric acid, monoalkyl or dialkyl esters of phosphoric acid and pyrophosphate, halogenated acetic acids such as monochloroacetic acid, benzoyl chloride, sulfonate esters, sulfuric acid, sulfate esters, ion exchange resins, and chelating agents. From an industrial viewpoint, phosphoric acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid, and monoalkyl and dialkyl phosphates are preferred because they are less likely to corrode stainless steel. Examples of monoesters and diesters of phosphoric acid include monoethyl phosphate, diethyl phosphate, monobutyl phosphate, dibutyl phosphate, mono(2-ethylhexyl) phosphate, di(2-ethylhexyl) phosphate, monodecyl phosphate, didecyl phosphate, monolauryl phosphate, dilauryl phosphate, monotridecyl phosphate, ditridecyl phosphate, monooleyl phosphate, dioleyl phosphate, and mixtures thereof. It is also possible to use an adsorbent such as silica gel or activated carbon as a terminator, in which case the amount added is preferably 0.05 to 10% by mass based on the diisocyanate used in the reaction.

[0060] After the reaction is complete, the unreacted diisocyanate and the solvent may be separated from the polyisocyanate. From the viewpoint of safety, it is preferable to separate the unreacted diisocyanate. Examples of methods for separating the unreacted diisocyanate and the solvent include thin film distillation and solvent extraction.

[0061] In one embodiment of the present invention, the polyisocyanate composition is a curing agent for a coating composition or a polyurethane bead composition. In one aspect of the present invention, a coating composition containing a polyol and a curing agent contains the polyisocyanate composition of this embodiment as the curing agent. In one aspect of the present invention, a polyurethane bead composition containing a polyol and a curing agent contains the polyisocyanate composition of this embodiment as the curing agent. In one aspect of the present invention, a mixture contains the polyisocyanate composition of the present embodiment. Examples of the mixture include a coating composition and a polyurethane bead composition. Components contained in the mixture other than the polyisocyanate composition are not particularly limited, and may include a solvent, a base resin, various additives, and the like.

[0062] Examples of the polyol contained in the coating composition or polyurethane bead composition include aliphatic hydrocarbon polyols, polyether polyols, polyester polyols, epoxy resins, fluorine-containing polyols, and acrylic polyols, with acrylic polyols being preferred.

[0063] [Aliphatic hydrocarbon polyols] Examples of the aliphatic hydrocarbon polyols include hydroxyl-terminated polybutadiene and its hydrogenated products.

[0064] [Polyether polyols] Examples of polyether polyols include those obtained by any of the following methods (1) to (3). (1) Polyether polyols or polytetramethylene glycols obtained by adding alkylene oxides, either singly or in mixture, to polyhydric alcohols, either singly or in mixture. (2) Polyether polyols obtained by reacting alkylene oxide with a polyfunctional compound. (3) Polymer polyols obtained by polymerizing acrylamide or the like using the polyether polyols obtained in (1) or (2) as a medium.

[0065] Examples of the polyhydric alcohol in (1) above include glycerin and propylene glycol. Examples of the alkylene oxide in (2) above include ethylene oxide and propylene oxide. Examples of the polyfunctional compound in (2) above include ethylenediamine and ethanolamines.

[0066] [Polyester polyols] Examples of the polyester polyols include the following polyester polyols (1E) and (2E). (1E) Polyester polyol resins obtained by a condensation reaction between a dibasic acid alone or a mixture of two or more kinds and a polyhydric alcohol alone or a mixture of two or more kinds. (2E) Polycaprolactones obtained by ring-opening polymerization of ε-caprolactone with polyhydric alcohols. Examples of the dibasic acid include carboxylic acids such as succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, and 1,4-cyclohexanedicarboxylic acid.

[0067] Examples of the polyhydric alcohol in (1E) include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, trimethylolpropane, glycerin, pentaerythritol, 2-methylolpropanediol, and ethoxylated trimethylolpropane.

[0068] [Epoxy resins] Examples of epoxy resins include novolac-type epoxy resins, β-methylepicro-type epoxy resins, cyclic oxirane-type epoxy resins, glycidyl ether-type epoxy resins, glycol ether-type epoxy resins, epoxy-type aliphatic unsaturated compounds, epoxidized fatty acid esters, ester-type polycarboxylic acids, aminoglycidyl-type epoxy resins, halogenated epoxy resins, and resorcinol-type epoxy resins, as well as resins obtained by modifying these epoxy resins with amino compounds, polyamide compounds, or the like.

[0069] [Fluorine-containing polyols] Examples of fluorine-containing polyols include copolymers of fluoroolefins, cyclohexyl vinyl ethers, hydroxyalkyl vinyl ethers, and monocarboxylic acid vinyl esters, which are disclosed in Reference Document 1 (JP-A-57-34107) and Reference Document 2 (JP-A-61-275311), etc.

[0070] [Acrylic polyols] Acrylic polyols can be obtained by polymerizing a polymerizable monomer having one or more active hydrogen atoms in one molecule, or by copolymerizing a polymerizable monomer having one or more active hydrogen atoms in one molecule with, as needed, another monomer copolymerizable with the polymerizable monomer.

[0071] Examples of polymerizable monomers having one or more active hydrogen atoms in one molecule include the following (i) to (iii), which may be used singly or in combination of two or more. (i) Acrylic acid esters having active hydrogen, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate. (ii) Methacrylates having active hydrogen, such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 2-hydroxybutyl methacrylate. (iii) (meth)acrylic acid esters having polyvalent active hydrogen, such as acrylic acid monoester or methacrylic acid monoester of glycerin, and acrylic acid monoester or methacrylic acid monoester of trimethylolpropane.

[0072] Examples of other monomers copolymerizable with the polymerizable monomer include the following (i) to (v), which may be used singly or in combination of two or more. (i) Acrylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate. (ii) Methacrylates such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, and glycidyl methacrylate. (iii) Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid. (iv) Unsaturated amides such as acrylamide, N-methylolacrylamide, and diacetoneacrylamide. (v) Styrene, vinyl toluene, vinyl acetate, acrylonitrile, etc.

[0073] Other examples include acrylic polyols obtained by copolymerizing polymerizable ultraviolet-stable monomers disclosed in Reference 3 (JP-A No. 1-261409) and Reference 4 (JP-A No. 3-006273).

[0074] Examples of polymerizable ultraviolet-stable monomers include 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, and 2-hydroxy-4-(3-methacryloxy-2-hydroxypropoxy)benzophenone.

[0075] For example, the above-mentioned monomer components are solution polymerized in the presence of a known radical polymerization initiator such as a peroxide or an azo compound, and the resulting solution is diluted with an organic solvent or the like as needed to obtain an acrylic polyol.

[0076] Aqueous-based acrylic polyols can be produced by known methods such as solution polymerization of an olefinically unsaturated compound followed by conversion into an aqueous phase, emulsion polymerization, etc. In this case, water solubility or water dispersibility can be imparted by neutralizing the acidic moiety of a carboxylic acid-containing monomer such as acrylic acid or methacrylic acid, or a sulfonic acid-containing monomer, with an amine or ammonia.

[0077] In one embodiment of the present invention, the coating composition is obtained by the production method shown below.

[0078] When the coating composition of this embodiment is a solvent-based coating composition, for example, first, the polyisocyanate composition is added as a curing agent to a polyol or its solvent dilution, to which various additives are added as needed. Next, if needed, a solvent is further added to adjust the viscosity. Next, the solvent-based coating composition can be obtained by stirring by hand or using a stirring device such as a mixer. Furthermore, the order of mixing the base component containing a polyol as a main component, the curing agent component containing the polyisocyanate composition as a main component, and the various additives described above is not particularly limited, and they can be mixed, for example, in the following order: 1) The main component, which has been mixed with various additives in advance, is mixed with the hardener component at the painting site. 2) At the painting site, the main agent component and hardener component are mixed, and then various additives are mixed. 3) The main component, which has been mixed with various additives in advance, is mixed with the hardener component, which has been mixed with various additives in advance, at the painting site.

[0079] (optional ingredient) In one embodiment of the present invention, the coating composition may further contain an antioxidant in addition to the polyisocyanate composition and the main component. The antioxidant may be added during the production of the coating composition, or may be added to the polyisocyanate composition in advance. The antioxidant may be used alone or in combination of two or more.

[0080] The antioxidant is not particularly limited, but examples thereof include substances having antioxidant properties that are used as light stabilizers, heat stabilizers, etc.

[0081] The antioxidant used as the light resistance stabilizer is not particularly limited, but examples thereof include hindered amine-based antioxidants, benzophenone-based antioxidants, benzotriazole-based antioxidants, triazine-based antioxidants, and cyanoacrylate-based antioxidants.

[0082] The hindered amine antioxidant is not particularly limited, but examples thereof include ADK STAB LA-52 (trade name), ADK STAB LA-68 (trade name), ADK STAB LA-77Y (trade name) (each manufactured by Adeka Corporation), Tinuvin 622 (trade name), Tinuvin 765 (trade name), Tinuvin 770 (trade name), Tinuvin 791 (trade name) (each manufactured by BASF).

[0083] The benzophenone-based antioxidant is not particularly limited, but examples thereof include Chimassorb 81 (trade name) (manufactured by BASF).

[0084] The benzotriazole-based antioxidant is not particularly limited, but examples thereof include Tinuvin P (trade name) and Tinuvin 234 (trade name) (both manufactured by BASF).

[0085] The triazine-based antioxidant is not particularly limited, but examples thereof include Tinuvin 1577ED (trade name) (manufactured by BASF).

[0086] The cyanoacrylate antioxidant is not particularly limited, but examples thereof include Uvinul 3035 (trade name) (manufactured by BASF).

[0087] The antioxidant used as the heat stabilizer is not particularly limited, but examples thereof include hindered phenol-based antioxidants, phosphorus-containing antioxidants, sulfur-containing antioxidants, vitamin E-based antioxidants, and hydroxyamine-based antioxidants.

[0088] The hindered phenol-based antioxidant is not particularly limited, but examples thereof include dibutylhydroxytoluene (hereinafter, may be abbreviated as "BHT"), Irganox 1010 (trade name), Irganox 1135 (trade name), Irganox 1330 (trade name), Irganox 3114 (trade name), Irganox 565 (trade name), Irganox 1520L (trade name) (each manufactured by BASF), Adeka STAB AO-20 (trade name), Adeka STAB AO-30 (trade name), Adeka STAB AO-50 (trade name), Adeka STAB AO-60 (trade name), Adeka STAB AO-80 (trade name) (each manufactured by Adeka Corporation).

[0089] The phosphorus-containing antioxidant is not particularly limited, but examples thereof include ADK STAB PEP-8 (trade name), ADK STAB HP-10 (trade name), ADK STAB 1178 (trade name), ADK STAB C (trade name) (each manufactured by Adeka Corporation), Irgafos 168, Irgafos 38 (trade name) (manufactured by BASF), and Sumilizer GP (trade name) (manufactured by Sumitomo Chemical Co., Ltd.).

[0090] The sulfur-containing antioxidant is not particularly limited, but examples thereof include Irganox PS800FL (trade name) (manufactured by BASF).

[0091] The vitamin E-based antioxidant is not particularly limited, but examples thereof include Irganox E201 (trade name) (manufactured by BASF).

[0092] The hydroxyamine-based antioxidant is not particularly limited, but examples thereof include Irgastab FS042 (trade name) (manufactured by BASF).

[0093] Among them, the antioxidant is preferably at least one selected from the group consisting of hindered phenol antioxidants, hindered amine antioxidants, sulfur-containing antioxidants, and phosphorus-containing antioxidants, and more preferably at least one selected from the group consisting of Tinuvin 765 (trade name), BHT, Irganox 565 (trade name), Adekastab C (trade name), and Sumilizer GP (trade name).

[0094] The coating composition of the present embodiment can be used as a coating material for, but not limited to, spray coating, air spray coating, brush coating, immersion coating, roll coating, curtain flow coating, bell coating, electrostatic coating, and the like. The coating composition of the present embodiment is also useful as a coating for molded articles made of materials such as metals (steel plates, surface-treated steel plates, etc.), plastics, wood, films, inorganic materials, etc., and is particularly suitable as a coating for metals or plastics. The coating composition of the present embodiment is suitable for use as, for example, architectural coatings, heavy-duty corrosion-resistant coatings, automotive coatings, coatings for information appliances, and coatings for information devices such as personal computers and mobile phones, and is particularly suitable as a top clear coating for architectural structures, automobile bodies, metal parts for automobiles, plastic parts for automobiles, metal parts for information appliances, or plastic parts for information appliances.

[0095] In one embodiment of the present invention, the polyurethane bead composition is obtained by the production method described below.

[0096] As a representative example of a method for producing a polyurethane bead composition, a method for producing polyurethane beads will be described below. The method for producing polyurethane beads is not particularly limited, and examples thereof include the following two production methods (first production method and second production method) using suspension polymerization. That is, the polyurethane beads obtained by these production methods are crosslinked polyurethane beads obtained by suspension polymerization. Among them, the first production method is preferred as the method for producing polyurethane beads because of its simplicity.

[0097] [First manufacturing method] The first method for producing polyurethane beads comprises a step of dispersing bead raw materials in water in a particulate form and reacting them to prepare a polyurethane bead suspension (hereinafter sometimes referred to as the "first bead preparation step"), and a step of separating the polyurethane bead suspension into solid and liquid (hereinafter sometimes referred to as the "first post-treatment step").

[0098] (First bead preparation step) In the first bead preparation step, bead raw materials are dispersed in water in the form of particles and reacted to prepare a polyurethane bead suspension. The bead raw materials in the first bead preparation step include the above-mentioned polyol and the polyisocyanate composition of the present embodiment.

[0099] The molar ratio (NCO / OH) of the isocyanurate groups in the polyisocyanate composition of the present embodiment to the hydroxyl groups of the polyol is preferably from 1 to 20. When the NCO / OH ratio is equal to or greater than the above-mentioned lower limit, unreacted polyol is less likely to remain, while when the NCO / OH ratio is equal to or less than the above-mentioned upper limit, the amount of soft segments in the polyurethane beads increases, and the glass transition temperature appears more clearly.

[0100] Furthermore, the raw material for the beads may contain a colorant such as a dye or pigment in addition to the above-described polyol and the polyisocyanate composition of the present embodiment, provided that the colorant used here does not inhibit the urethanization reaction. The inclusion of a colorant allows for the production of colored polyurethane beads, which can be added to paint to produce coating films with designs such as velvet or suede textures.

[0101] If the suspension has a high viscosity and is difficult to handle, the bead raw material may contain a diluent solvent, as long as it does not inhibit the polymerization reaction. The raw material for the beads may also contain a catalyst, such as dibutyltin dilaurate. Furthermore, in order to improve the physical properties of the polyurethane beads obtained, the raw materials for the beads may contain ultraviolet absorbers, antioxidants, metal powders, perfumes, etc.

[0102] In the first bead preparation step, the water to which the bead raw materials are added may contain a suspension stabilizer. The suspension stabilizer is not particularly limited as long as it is one that is commonly used in suspension polymerization, and may be organic or inorganic. Specific examples of the suspension stabilizer include cellulose-based water-soluble resins, polyvinyl alcohol, polyacrylates, polyethylene glycol, polyvinylpyrrolidone, polyacrylamides, and tertiary phosphates. Examples of the cellulose-based water-soluble resin include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, and carboxymethyl cellulose. These suspension stabilizers may be used alone or in combination of two or more.

[0103] The suspension stabilizer may be used in combination with a surfactant. The surfactant used in combination with the suspension stabilizer may be any of anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants.

[0104] The amount of suspension stabilizer added is preferably 0.5 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the bead raw material. When the amount of suspension stabilizer added is within the above range, the average particle size of the polyurethane beads tends to be more likely to fall within the range of 1 μm or more and 100 μm or more, which is appropriate for use as a filler.

[0105] Furthermore, by setting the amount of suspension stabilizer to the upper limit or less, it is possible to more effectively prevent the average particle size from becoming smaller than 1 μm, and also to more effectively prevent the viscosity of the suspension from increasing, thereby preventing solid-liquid separation and washing from becoming difficult. Furthermore, by setting the amount of suspension stabilizer to the lower limit or more, it is possible to more effectively prevent aggregation of particles, and prevent the particle size from becoming larger than 100 μm.

[0106] The amount of water in which the suspension stabilizer is dissolved or dispersed is preferably 30 parts by mass or more and 1,000 parts by mass or less per 100 parts by mass of the bead raw materials. When the amount of water is equal to or more than the lower limit, the bead raw materials can be dispersed more stably, while when the amount of water is equal to or less than the upper limit, the amount of polyurethane beads produced per suspension polymerization can be more sufficiently ensured.

[0107] To disperse the bead raw material into particles after adding it to water containing a suspension stabilizer, a stirring method is usually used. The stirring speed is preferably adjusted appropriately so that droplets containing the polyol and the polyisocyanate composition of the present embodiment have a predetermined particle size. After the droplet size adjustment is completed, the mixture is heated to a temperature of 30° C. to 90° C., and the polyol or water and the polyisocyanate composition of the present embodiment are reacted for 1 hour to 6 hours to carry out suspension polymerization, thereby obtaining a polyurethane bead suspension.

[0108] (First post-treatment step) In the first post-treatment step, the polyurethane bead suspension is subjected to solid-liquid separation. As a method for solid-liquid separation in the first post-treatment step, for example, filtration or centrifugation is applied. can be. After solid-liquid separation, washing and drying are preferably carried out. In the washing step, the separated and recovered polyurethane beads are washed with water or the like to remove the suspension stabilizer and the like remaining in the polyurethane beads. Drying methods that can be used include, for example, heat drying, flash drying, vacuum drying, infrared drying, etc. For example, when heat drying is used, the drying temperature can be 40°C or higher and 110°C or lower, and the drying time can be 2 hours or higher and 40 hours or lower.

[0109] When the suspension is subjected to solid-liquid separation and washing, the suspension may be treated with an enzyme such as a cellulose-degrading enzyme or a polyvinyl alcohol-degrading enzyme that decomposes the suspension stabilizer, or a reagent such as hypochlorite. Treatment with the enzyme or reagent reduces the viscosity of the suspension, making the solid-liquid separation easier and also facilitating washing.

[0110] [Second manufacturing method] The second production method includes a step of reacting a polyol with the polyisocyanate composition of the present embodiment to obtain a prepolymer having an isocyanate group terminal (hereinafter, this step may be referred to as a "prepolymer preparation step"); a step of dispersing a bead raw material containing the isocyanate group-terminated prepolymer in water in the form of particles and reacting the bead raw material to prepare a polyurethane bead suspension (hereinafter, this step may be referred to as a "second bead preparation step"); and a step of performing solid-liquid separation of the polyurethane bead suspension (hereinafter, this step may be referred to as a "second post-treatment step").

[0111] (Prepolymer preparation process) In the prepolymer preparation step, the polyol and the polyisocyanate composition of the present embodiment are reacted in advance to obtain a prepolymer having an isocyanate group at its end. This prepolymer preparation step can be carried out using a commonly known method and is not particularly limited. If the viscosity is too high, the reaction may be carried out by diluting with a solvent that does not contain active hydrogen that reacts with isocyanate groups. The reaction temperature during synthesis of the isocyanate-terminated prepolymer is preferably 30°C or higher and 90°C or lower. When synthesizing the isocyanate-terminated prepolymer, a urethanization catalyst may be added, such as a metal catalyst such as dibutyltin laurate, or an amine catalyst such as triethylamine. The molar ratio (NCO / OH) of the isocyanurate groups in the polyisocyanate composition of the present embodiment to the hydroxyl groups in the polyol is not particularly limited, but is preferably in the range of 2 or more and 10 or less.

[0112] (Second Bead Preparation Step and Second Post-Treatment Step) The second bead preparation step in the second manufacturing method is the same as the "(first bead preparation step)" in the above-mentioned "(first manufacturing method)," in which the isocyanate-terminated prepolymer is reacted with water to undergo suspension polymerization. In this suspension polymerization, urea bonds are formed by the reaction of the isocyanate-terminated prepolymer with water, thereby producing polyurethane beads. Therefore, a polyurethane bead suspension can be obtained by this suspension polymerization. Furthermore, the second post-treatment step in the second manufacturing method is similar to the "(first post-treatment step)" in the above-mentioned "(first manufacturing method)," and polyurethane beads can be recovered by carrying out the post-treatment step.

[0113] In one aspect of the present invention, the polyurethane bead composition is suitably used, for example, as a coating agent, a thermoplastic resin, polyurethane beads, etc., without any particular limitation. In particular, the polyurethane bead composition of the present embodiment is suitably used as polyurethane beads. Polyurethane beads made from the polyurethane bead composition of the present embodiment can be used as a filler for paints, plastics, adhesives, cosmetics, etc., and can exhibit high elasticity and high durability. In addition, polyurethane beads made from the polyurethane bead composition of the present embodiment have high flexibility, a low specific gravity, high affinity with binder resins, and excellent water resistance.

[0114] There is no particular upper limit to the average particle size of the polyurethane beads, but it is preferably 20 μm, more preferably 15 μm, even more preferably 12 μm, and particularly preferably 10 μm. On the other hand, the lower limit of the average particle size of the polyurethane beads is not particularly limited, but is preferably 0.1 μm from the viewpoint of ease of production. That is, the average particle size of the polyurethane beads is preferably 0.1 μm or more and 20 μm or less, more preferably 0.1 μm or more and 15 μm or less, even more preferably 0.1 μm or more and 12 μm or less, and particularly preferably 0.1 μm or more and 10 μm or less.

[0115] In this specification, the term "average particle size" refers to the volume-based average particle size (volume average particle size) measured using a laser diffraction particle size distribution analyzer (e.g., SALD2100 manufactured by Shimadzu Corporation) when the volume average particle size is 0.1 μm or more. The average particle size of polyurethane beads can be easily adjusted by adjusting the amount of suspension stabilizer used during production and the type of isocyanate used. Specifically, the larger the amount of suspension stabilizer, the smaller the average particle size, and the smaller the amount of suspension stabilizer, the larger the average particle size. Furthermore, by increasing the proportion of the polyisocyanate composition of this embodiment used in the polyurethane bead composition, the average particle size can be reduced and water resistance can be improved.

[0116] The coating film of this embodiment is obtained by curing the coating composition described above, and has excellent biodegradability and mechanical properties.

[0117] In one embodiment of the present invention, a method for producing a coating film is a method comprising a step of curing the coating composition.

[0118] In one embodiment of the present invention, the coating film can be produced by applying the coating composition to a substrate using a known coating method such as spray coating, air spray coating, brush coating, immersion coating, roll coating, curtain flow coating, bell coating, or electrostatic coating, and then curing the applied coating composition. Examples of the substrate include molded articles made from the materials exemplified above as applications of the coating composition.

[0119] The biodegradable polyurethane cured product of this embodiment is obtained by curing the polyisocyanate composition alone or together with an acrylic polyol, and has excellent biodegradability and mechanical properties.

[0120] In one embodiment of the present invention, the cured product can be produced by applying the polyisocyanate composition alone or together with an acrylic polyol to a substrate using a known coating method exemplified in the above-mentioned method for producing a coating film, and then curing the applied coating. Examples of the substrate include molded articles made from the materials exemplified above as applications of the coating composition. [Example]

[0121] The present invention will be explained in more detail below by way of examples and comparative examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.

[0122] <Measurement method> [Physical property 1: Number average molecular weight (Mn)] The number average molecular weight Mn of the isocyanate prepolymer and the polyisocyanate composition was obtained by measuring the number average molecular weight Mn using polystyrene as a standard by GPC measurement under the measurement conditions shown below.

[0123] (Measurement conditions) Equipment: Tosoh Corporation HLC-8120GPC (product name) Column: Tosoh Corporation TSKgel SuperH1000 (product name) x 1 TSKgel SuperH2000 (product name) x 1 TSKgel SuperH3000 (product name) x 1 Carrier: Tetrahydrofuran Detection method: differential refractometer

[0124] [Property 2: Isocyanate group content (NCO%)] The isocyanate group content (NCO%) (mass%) was determined by neutralizing the isocyanate groups in each polyisocyanate with an excess of 2N amine and then back-titrating with 1N hydrochloric acid.

[0125] [Property 3: Average number of isocyanate groups] The average number of functional groups of the isocyanate prepolymer and the polyisocyanate composition is the number of isocyanate functional groups statistically contained in one molecule of polyisocyanate, and can be calculated using the following formula from the number average molecular weight (Mn) and isocyanate group content (NCO%) of the polyisocyanate. Average number of functional groups=Mn×NCO% / 4200

[0126] <Evaluation method> [Rating 1: Biodegradable] The polyisocyanate compositions obtained in the Examples and Comparative Examples were blended with an acrylic polyol (Setlax 1184 (trade name) manufactured by Nuplex) so that the equivalent ratio of isocyanate groups to hydroxy groups was 1.1, and toluene was added so that the total solids mass of the polyisocyanate composition and acrylic polyol was 45 mass %, yielding a coating composition. The resulting coating composition was applied to a PP coated panel with an applicator to a film thickness of 40 μm after drying, baked at 120°C for 30 minutes, and then the coating was aged for one week at 20°C and 63% humidity.

[0127] 0.1 g of the resulting coating film was weighed out and buried in 8 cm of potting soil, and then stored in a small environmental testing machine at 60°C and 50% humidity for 40 days. The coating film was then removed and dried, after which the remaining amount (mass) of the coating film was weighed. The percentage obtained by dividing the remaining amount of the coating film after removal by the mass of the coating film before burial was calculated as the residual rate (mass%), and the biodegradability of each coating film was evaluated according to the following evaluation criteria. The lower the residual rate, the better the biodegradability, and the higher the residual rate, the worse the biodegradability.

[0128] (Evaluation criteria) A: Residual rate less than 95% by mass B: Residual rate 95% by mass or more and less than 98% by mass C: Survival rate 98% by mass or more

[0129] [Evaluation 2: Mechanical properties] The polyisocyanate compositions obtained in the Examples and Comparative Examples were blended with an acrylic polyol (Setlax 1152 (trade name) manufactured by Nuplex) so that the equivalent ratio of isocyanate groups to hydroxy groups was 1.0, and toluene was added so that the total solids mass of the polyisocyanate composition and acrylic polyol was 45 mass %, yielding a coating composition. The coating composition was applied to a PP coated panel with an applicator to a film thickness of 40 μm after drying, baked at 80°C for 30 minutes, and then the coating was aged for one week at 20°C and 63% humidity.

[0130] The obtained coating film was cut into a test piece 10 mm wide and 100 mm long, and the test piece was set in a tensile tester (manufactured by Shimadzu Corporation, product name: AGS-X) so that the gripping distance was 20 mm. A tensile test was performed at a speed of 20 mm / min to measure the elongation and tensile breaking stress. The obtained results were evaluated according to the following evaluation criteria. The higher the elongation and breaking stress, the better the mechanical properties, and the lower the elongation and breaking stress, the worse the mechanical properties.

[0131] (Evaluation criteria) A: Elongation rate is 200% or more and breaking stress is 5 MPa or more B: Elongation rate is 100% or more and less than 200%, and breaking stress is 3 MPa or more and less than 5 MPa C: Elongation is less than 100% and breaking stress is less than 3 MPa

[0132] <Materials used> As (C) polyester polyol or polycaprolactone polyol, the following materials were used. Polycaprolactone polyol CB-1: OD-X-2542C (trade name, manufactured by DIC Corporation, number average molecular weight 850, average number of hydroxyl groups 3.0). Polyester polyol C-1: Maximol (registered trademark) SDK-145 (trade name, manufactured by Kawasaki Chemical Industries, Ltd., succinic acid unit-containing polyester polyol, number average molecular weight 1,250, average number of hydroxyl groups 2.0). Polycaprolactone polyol C-2: OD-X-2721 (trade name, manufactured by DIC Corporation, polycaprolactone polyol, number average molecular weight Mn 1,000, average number of hydroxyl groups 2.0). Polyester polyol C-3: OD-X-2693 (trade name, manufactured by DIC Corporation, adipic acid unit-containing polyester polyol, number average molecular weight Mn 3,000, average number of hydroxyl groups 2.0). Polyester polyol C-4: A synthetic product described in Synthesis Example 8 below (sebacic acid unit-containing polyester polyol, number average molecular weight 2,000, average number of hydroxyl groups 2.0). Polyester polyol C-5: OD-X-2694 (trade name, manufactured by DIC Corporation, adipic acid unit-containing polyester polyol, number average molecular weight Mn 4,000, average functionality of hydroxyl groups 2.0). Polyester polyol C-6: a synthetic product described in Synthesis Example 9 below (dodecanedioic acid unit-containing polyester polyol, number average molecular weight 2,000, average functionality of hydroxyl groups 2.0). Polycaprolactone polyol C-7: OD-X-2722 (trade name, manufactured by DIC Corporation, polycaprolactone polyol, number average molecular weight Mn 2,000, average number of hydroxyl groups 2.0).

[0133] (D) The following materials were used as hydrophilic components: Nonionic hydrophilic component D-1: MPG-081 (trade name, manufactured by Nippon Nyukazai Co., Ltd., methoxypolyethylene glycol, number of ethylene oxide repeating units: 16.0).

[0134] <Synthesis of isocyanate prepolymer> [Synthesis Example 1] A four-neck flask equipped with a stirrer, thermometer, and condenser was purged with nitrogen. 1,000 g of HDI and 77.5 g of 2-ethylhexanol (B) were added, and the urethane reaction was carried out at 90°C for 1 hour with stirring. The temperature was then raised to 130°C, and 0.3 g of ZrO 2-ethylhexanoate was added as an allophanate catalyst. The reaction was continued for approximately 2 hours. 2.8 g of a 10% 2-ethylhexanol solution of phosphoric acid (105%) was then added, and the mixture was post-treated at 130°C for 1 hour to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed using a thin-film evaporator to obtain isocyanate prepolymer P-1 with allophanate groups. The resulting isocyanate prepolymer P-1 had an NCO content of 17.2% and an average functionality of 2.0.

[0135] [Synthesis Example 2] A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with nitrogen and charged with 1,000 g of HDI and 337 g of polycaprolactone polyol CB-1. The temperature inside the reactor was maintained at 95°C for 90 minutes with stirring to carry out a urethane reaction. The reaction solution was filtered, and unreacted HDI was removed using a thin-film evaporator to obtain isocyanate prepolymer P-2. The resulting isocyanate prepolymer P-2 had an NCO content of 9.0% by mass and an average functionality of 3.3.

[0136] [Synthesis Example 3] A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with nitrogen and charged with 1,100 g of HDI and 500 g of polyester polyol C-1. The temperature inside the reactor was maintained at 100°C for 2 hours with stirring to carry out a urethane reaction. The reaction solution was filtered, and unreacted HDI was removed using a thin-film evaporator to obtain isocyanate prepolymer P-3. The resulting isocyanate prepolymer P-3 had an NCO content of 6.0% by mass and an average functionality of 2.2.

[0137] [Synthesis Example 4] A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was purged with nitrogen and charged with 1,000 g of HDI and 100 g of 2-ethylhexanol. The temperature inside the reactor was maintained at 80°C for 60 minutes with stirring to carry out the urethane reaction. Next, 0.06 g of tetramethylammonium caprylate was added as a nurate catalyst. After 4 hours, the isocyanate group content and refractive index of the reaction solution were measured. When the conversion rate to polyisocyanate reached 45%, 0.14 g of phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed using a thin-film evaporator to obtain isocyanate prepolymer P-4. The resulting isocyanate prepolymer P-4 had an NCO content of 17.8% by mass and an average functionality of 2.7.

[0138] [Synthesis Example 5] The isocyanate prepolymer P-1 obtained in Synthesis Example 1 was added to the apparatus described in Synthesis Example 1 so that the mass ratio of the isocyanate prepolymer P-4 obtained in Synthesis Example 4 to the isocyanate prepolymer P-1 obtained in Synthesis Example 1 was 8 / 2, and they were mixed to obtain an isocyanate prepolymer P-5 having allophanate groups. The obtained isocyanate prepolymer P-5 was a transparent liquid with an NCO content of 17.5% and an average functionality of 2.5.

[0139] [Synthesis Example 6] The isocyanate prepolymer P-1 obtained in Synthesis Example 1 was added to the apparatus described in Synthesis Example 1 so that the mass ratio of the isocyanate prepolymer P-4 obtained in Synthesis Example 4 to the isocyanate prepolymer P-1 obtained in Synthesis Example 1 was 5 / 5, and they were mixed to obtain an isocyanate prepolymer P-6 having allophanate groups. The obtained isocyanate prepolymer P-6 was a transparent liquid with an NCO content of 17.4% and an average functionality of 2.3. [Synthesis Example 7] A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet, and dropping funnel was conditioned with a nitrogen atmosphere, and 1,100 g of HDI and 500 g of polyester polyol C-1 were charged. The temperature inside the reactor was maintained at 100°C for 2 hours with stirring to carry out a urethane reaction. The temperature inside the reactor was then maintained at 140°C for 4 hours with stirring to carry out allophanation. The reaction solution was filtered, and unreacted HDI was removed using a thin-film evaporator to obtain isocyanate prepolymer P-7. The resulting isocyanate prepolymer P-7 had an NCO content of 5.4% by mass and an average functionality of 2.2.

[0140] <Synthesis of polyester polyol> [Synthesis Example 8] A flask equipped with a stirrer, temperature sensor, and distillation tube was charged with 100 g of 1,3-butylene glycol, 150 g of 1,6-hexanediol, 160 g of 2-ethyl-1,3-hexanediol, and 600 g of sebacic acid (carbon number: 8). Dry nitrogen was introduced into the flask, and the mixture was heated to 180°C or higher and 210°C or lower while stirring, to carry out an esterification reaction. The reaction was stopped when the acid value reached 0.5 mgKOH / g or lower, yielding polyester polyol C-4 with a number average molecular weight Mn of 2,000, a hydroxyl value of 60 mgKOH / g, and an average functionality of 2.0 hydroxyl groups.

[0141] [Synthesis Example 9] A flask equipped with a stirrer, temperature sensor, and distillation tube was charged with 100 g of 1,3-butylene glycol, 140 g of 1,6-hexanediol, 150 g of 2-ethyl-1,3-hexanediol, and 650 g of dodecanedioic acid (carbon number 10). Dry nitrogen was introduced into the flask, and the mixture was heated to 180°C or higher and 210°C or lower while stirring, to carry out an esterification reaction. The reaction was stopped when the acid value reached 0.5 mgKOH / g or lower, yielding polyester polyol C-6 with a number average molecular weight Mn of 2,000, a hydroxyl value of 60 mgKOH / g, and an average functionality of 2.0 hydroxyl groups.

[0142] <Production of Polyisocyanate Composition> [Example 1] 39 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1, 60 g of polyester polyol C-1, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PA-1.

[0143] [Example 2] 39 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1, 60 g of polyester polyol C-2, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PA-2.

[0144] [Example 3] 44 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1, 55 g of polyester polyol C-1, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PA-3.

[0145] [Example 4] 19 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1, 80 g of polyester polyol C-3, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PA-4.

[0146] [Example 5] 33 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1, 63 g of polyester polyol C-1, and 5 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PA-5.

[0147] [Example 6] 39 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1, 60 g of polyester polyol C-4, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PA-6.

[0148] [Example 7] 39 g of the isocyanate prepolymer P-5 obtained in Synthesis Example 5, 60 g of polyester polyol C-4, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PA-7.

[0149] [Example 8] 39 g of the isocyanate prepolymer P-6 obtained in Synthesis Example 6, 60 g of polyester polyol C-4, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PA-8.

[0150] [Example 9] 99 g of the isocyanate prepolymer P-7 obtained in Synthesis Example 7, 76 g of polyester polyol C-1, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to produce polyisocyanate composition PA-9.

[0151] [Comparative Example 1] 49 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1, 50 g of polyester polyol C-2, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PB-1.

[0152] Comparative Example 2 13 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1, 86 g of polyester polyol C-5, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PB-2.

[0153] Comparative Example 3 36 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1, 63 g of polyester polyol C-2, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PB-3.

[0154] Comparative Example 4 99 g of the isocyanate prepolymer P-2 obtained in Synthesis Example 2 and 1 g of the nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PB-4.

[0155] Comparative Example 5 39 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1, 60 g of polyester polyol C-6, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PB-4.

[0156] Comparative Example 6 The isocyanate prepolymer P-3 obtained in Synthesis Example 3 was used to prepare a polyisocyanate composition PB-6.

[0157] Comparative Example 7 40 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1 and 60 g of the polyester polyol C-2 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PB-7.

[0158] [Comparative Example 8] 38 g of the isocyanate prepolymer P-1 obtained in Synthesis Example 1 and 62 g of the polyester polyol C-7 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain a polyisocyanate composition PB-8.

[0159] Comparative Example 9 39 g of the isocyanate prepolymer P-4 obtained in Synthesis Example 4, 60 g of polyester polyol C-2, and 1 g of nonionic hydrophilic component D-1 were added to the apparatus described in Synthesis Example 1 and mixed, and a urethane reaction was carried out at 90°C for 4 hours to obtain polyisocyanate composition PB-9.

[0160] The physical properties and evaluation results of the obtained polyisocyanate compositions PA-1 to 9 and PB-1 to 9 are shown in Tables 1 and 2, respectively.

[0161] [Table 1]

[0162] [Table 2]

[0163] As shown in Table 1 above, the polyisocyanate compositions PA-1 to PA-9 (Examples 1 to 9) of this embodiment were evaluated as A or B in biodegradability and mechanical properties, confirming that they have excellent biodegradability and mechanical properties when formed into a coating film.

[0164] On the other hand, as shown in Table 2 above, polyisocyanate composition PB-1 (Comparative Example 1), in which the content of polyester polyol relative to the total mass of the polyisocyanate composition was 50 mass% or less, was evaluated as C for poor biodegradability when made into a coating film.

[0165] As shown in Table 2 above, polyisocyanate composition PB-2 (Comparative Example 2), in which the content of polyester polyol relative to the total mass of the polyisocyanate composition was 86 mass%, was evaluated as C, as poor in mechanical properties when formed into a coating film.

[0166] As shown in Table 2 above, the polyisocyanate composition PB-3 (Comparative Example 3), in which the average number of isocyanate functional groups in the polyisocyanate composition was 1.4, was evaluated as C, i.e., poor, in mechanical properties when formed into a coating film.

[0167] As shown in Table 2 above, polyisocyanate composition PB-4 (Comparative Example 4), in which the average number of isocyanate functional groups in the polyisocyanate composition is 3.3, and polyisocyanate composition PB-9 (Comparative Example 9), in which the average number of isocyanate functional groups in the polyisocyanate composition is 3.4, were evaluated as C for biodegradability when formed into coating films, which was poor.

[0168] As shown in Table 2 above, the polyisocyanate composition PB-5 (Comparative Example 5), in which the dicarboxylic acid unit of the polyester polyol had 10 carbon atoms, was evaluated as C, which was poor, as a result of mechanical properties evaluation when formed into a coating film.

[0169] As shown in Table 2 above, the polyisocyanate compositions PB-6, 7, and 8 (Comparative Examples 6, 7, and 8) that did not contain a hydrophilic component were evaluated as C in biodegradability when formed into coating films, which was poor.

[0170] As shown in Table 2 above, the polyisocyanate compositions PB-4, PB-6 and PB-8 (Comparative Examples 4, 6 and 8) having no allophanate groups were evaluated as C, poor in biodegradability, when formed into coating films.

[0171] Furthermore, as shown in Table 1 above, polyisocyanate compositions PA-1 and 2 (Examples 1 and 2), in which the content of polyester polyol relative to the total mass of the polyisocyanate composition was 60 mass%, tended to have better biodegradability when formed into a coating film than polyisocyanate composition PA-3 (Example 3), in which the content of polyester polyol relative to the total mass of the polyisocyanate composition was 55 mass%.

[0172] As shown in Table 1 above, polyisocyanate compositions PA-1 and 2 (Examples 1 and 2), in which the content of polyester polyol relative to the total mass of the polyisocyanate composition was 60 mass%, tended to have better mechanical properties when formed into a coating film than polyisocyanate composition PA-4 (Example 4), in which the content of polyester polyol relative to the total mass of the polyisocyanate composition was 80 mass%.

[0173] As shown in Table 1 above, polyisocyanate compositions PA-1 and 2 (Examples 1 and 2), in which the average number of isocyanate functional groups in the polyisocyanate composition is 2.0, tended to have better mechanical properties when formed into a coating film than polyisocyanate composition PA-5 (Example 5), in which the average number of isocyanate functional groups in the polyisocyanate composition is 1.8.

[0174] As shown in Table 1 above, polyisocyanate compositions PA-1 and 2 (Examples 1 and 2), in which the average number of isocyanate functional groups in the polyisocyanate composition is 2.0, tended to have better biodegradability when formed into a coating film than polyisocyanate composition PA-7 (Example 7), in which the average number of isocyanate functional groups in the polyisocyanate composition is 3.1.

[0175] As shown in Table 1 above, polyisocyanate composition PA-1 (Example 1), in which the dicarboxylic acid unit of the polyester polyol has 2 carbon atoms, tended to have better mechanical properties when formed into a coating film than polyisocyanate composition PA-6 (Example 6), in which the dicarboxylic acid unit of the polyester polyol has 8 carbon atoms. [Industrial Applicability]

[0176] The polyisocyanate composition of the present invention is useful as a polyisocyanate composition that, when formed into a coating film, has excellent biodegradability and mechanical properties.

Claims

1. A polyisocyanate composition comprising a polyisocyanate having an allophanate group, The polyisocyanate is derived from (A), (C), and (D), (A) is at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, (C) is a polyester polyol or a polycaprolactone polyol, has a number average molecular weight Mn of 500 or more and 4,000 or less, and is bifunctional or trifunctional; (D) is a hydrophilic component, the average number of isocyanate functional groups of the polyisocyanate composition is 1.8 or more and 3.2 or less; The polyester polyol is composed of a polyol unit and a dicarboxylic acid unit having 8 or less carbon atoms, the content of (C) relative to the total mass of the polyisocyanate composition is more than 50 mass% and 85 mass% or less, A polyisocyanate composition, wherein the content of (D) relative to the total mass of the polyisocyanate composition is 0.1 mass% or more and 20 mass% or less.

2. 2. The polyisocyanate composition according to claim 1, wherein the polyisocyanate is derived from (B) in addition to (A), (C), and (D), and (B) is an alcohol having 1 to 20 carbon atoms.

3. The polyisocyanate composition according to claim 1 or 2, wherein the content of isocyanate groups relative to the total mass of the polyisocyanate composition is 1% by mass or more and 13% by mass or less.

4. The polyisocyanate composition according to claim 1 or 2, wherein the number average molecular weight Mn of the (C) is 1,000 or more and 4,000 or less.

5. The polyisocyanate composition according to claim 1 or 2, wherein the polyol unit constituting the polyester polyol is an aliphatic polyol.

6. 3. The polyisocyanate composition according to claim 1, wherein the dicarboxylic acid unit is succinic acid or adipic acid.

7. 6. The polyisocyanate composition of claim 5, wherein the aliphatic polyol is diethylene glycol or triethylene glycol.

8. 3. The polyisocyanate composition according to claim 1, wherein the component (D) is a nonionic hydrophilic component having one hydroxyl group and comprising 3 to 25 ethylene oxide repeating units.

9. The polyisocyanate composition according to claim 2, wherein (B) is 2-ethylhexanol.

10. 3. The polyisocyanate composition according to claim 1, which is a curing agent for a coating composition or a polyurethane bead composition.

11. A mixture comprising the polyisocyanate composition of claim 1 or 2.

12. A coating composition comprising a polyol and a curing agent, the coating composition comprising the polyisocyanate composition according to claim 1 or 2 as the curing agent.

13. A coating film obtained by curing the coating composition according to claim 12.

14. A biodegradable polyurethane cured product obtained by curing the polyisocyanate composition according to claim 1 or 2 alone or together with an acrylic polyol.

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