Aqueous polyurethane

Abstract

The present disclosure provides, for example, an aqueous polyurethane which is excellent in terms of storage stability and quick-drying property and which, even when a film is formed therefrom in a short time, enables the formation of a urethane film having excellent chemical resistance, and a method for producing the aqueous polyurethane. This aqueous polyurethane is an aqueous polyurethane dispersion comprising a polyurethane and water, and is characterized in that: the polyurethane includes a main chain having a urethane bond and a structure represented by formula (1) and a side chain branching off from the main chain and having a hydrophilic group; the content of the structure represented by formula (1) is 35 mass% or higher with respect to the total mass of the polyurethane; the polyurethane contains carboxyl groups and carboxylate groups in an amount of 0.00-0.85 mass% with respect to the total mass of the polyurethane; and the solid concentration of the polyurethane is 35 mass% or higher with respect to the aqueous dispersion. (In the formula: the R moieties may be the same as or different from each other and each independently represent an optionally heteroatom-substituted divalent hydrocarbon group that has 2 to 20 carbon atoms, and is a linear or branched group or an alicyclic group; n is an integer of 1-50; and * indicates a bond.)

Description

Water-based polyurethane

[0001] The present invention relates to water-based polyurethanes and the like.

[0002] Polyurethane resins are used in a wide range of applications, including synthetic leather, artificial leather, adhesives, furniture paints, and automotive paints. Polyurethane resins are typically obtained as addition polymerization products of polyisocyanate and polyol components. Polyurethane resins are required to have various durability properties, such as heat resistance, water resistance, weather resistance, hydrolysis resistance, solvent resistance, sunscreen resistance, and scratch resistance. Therefore, among the raw materials for polyurethane resins, the use of polyol components having a skeletal structure such as polyether, polyester, or polycarbonate has been investigated as the polyol component to be reacted with the polyisocyanate component.

[0003] Generally, polyurethane resins are used in a diluted state with a solvent, and after being applied to a desired substrate, a film is formed by removing the solvent. However, in recent years, regulations on organic solvent emissions have been strengthened in order to reduce environmental impact, and development of polyurethanes that do not use organic solvents is progressing. One such example is water-based polyurethane. Water-based polyurethanes are aqueous dispersions in which polyurethane resins are dispersed in water, and because they do not contain organic solvents, they are materials that can form polyurethane coating films without emitting organic solvents into the atmosphere.

[0004] Specifically, Patent Document 1 discloses an aqueous polyurethane emulsion paint (aqueous urethane) obtained by reacting (i) isophorone diisocyanate, (ii) an active hydrogen group-containing compound containing a polyester polyol in which the low-molecular-weight polyol is ethylene glycol and neopentyl glycol, the aromatic polycarboxylic acid is isophthalic acid, the aliphatic polycarboxylic acid is azelaic acid, and the mass ratio of the aromatic polycarboxylic acid to the aliphatic polycarboxylic acid is 35 / 65 to 65 / 35, and (iii) 2,2-dimethylolpropionic acid and / or 2,2-dimethylolbutanoic acid.

[0005] Patent No. 3896578

[0006] Water-based polyurethanes are environmentally friendly materials that do not release organic solvents during film formation, and research into them has been actively conducted in recent years. When forming a urethane film using water-based polyurethanes, water must be evaporated. However, because the latent heat of evaporation of water is relatively large, a relatively large amount of thermal energy is required during film formation. Possible methods for reducing the energy required for film formation include increasing the solids concentration of the water-based polyurethane and shortening the baking time during film formation.

[0007] However, simply increasing the solids concentration of the aqueous polyurethane reduces the dispersion stability of the aqueous polyurethane, resulting in poor storage stability. While it is possible to reduce energy consumption by shortening the processing time required for water evaporation, this approach can result in insufficient film formation, potentially resulting in reduced strength and chemical resistance of the resulting urethane film.

[0008] Therefore, an object of the present invention is to provide a water-based polyurethane that has excellent storage stability and quick-drying properties and is capable of forming a urethane film that has excellent chemical resistance even when formed in a short period of time, and a method for producing the same.

[0009] As a result of intensive investigations aimed at solving the above-mentioned problems, the present inventors have found that by using a polyurethane precursor having a predetermined content of a carbonate-derived skeletal structure represented by formula (1) in its main chain, hydrophilic groups in its side chains, and, if necessary, predetermined contents of carboxyl groups and carboxylate groups, it is possible to overcome the trade-off between the solids concentration of the polyurethane in an aqueous dispersion and its storage stability, thereby solving the above-mentioned problems and have completed the present invention. That is, the present invention provides various specific embodiments as shown below.

[0010] <1> An aqueous polyurethane dispersion containing polyurethane and water, wherein the polyurethane comprises a main chain having a urethane bond and a structure represented by the following formula (1), and a side chain branched from the main chain, the side chain having a hydrophilic group; the content of the structure represented by the following formula (1) relative to the total mass of the polyurethane is 35 mass% or more; the polyurethane contains 0.00 to 0.85 mass% of carboxyl groups and carboxylate groups relative to the total mass of the polyurethane; and the solids concentration of the polyurethane in the aqueous dispersion is 35 mass% or more. (In the formula, R may be the same or different and is a linear, branched or alicyclic divalent hydrocarbon group having 2 to 20 carbon atoms, which may be optionally substituted with a heteroatom; n is an integer of 1 to 50; and * represents a bond.)

[0011] <2> The aqueous polyurethane according to <1> above, wherein the polyurethane is an addition polymerization product of a polyol (A) and a polyisocyanate (B), the polyol (A) includes a polyol (a-1) including a main chain having a structure represented by the following formula (1) and a side chain branched from the main chain, the side chain having a hydrophilic group, and the content of the structure represented by the following formula (1) relative to the total mass of the polyol (a-1) is 50 mass% or more: (In the formula, R may be the same or different and is a linear, branched or alicyclic divalent hydrocarbon group having 2 to 20 carbon atoms, which may be optionally substituted with a heteroatom; n is an integer of 1 to 50; and * represents a bond.)

[0012] <3> The aqueous polyurethane according to <2> above, wherein the hydrophilic group of the polyol (a-1) is a nonionic hydrophilic group, and the polyol (A) further includes a polyol (a-2) having a carboxyl group or a carboxylate group.

[0013] <4> The aqueous polyurethane according to the above <2> or <3>, wherein the hydrophilic group of the polyol (a-1) is a polyalkylene glycol.

[0014] <5> The aqueous polyurethane according to any one of <2> to <4>, wherein the polyol (a-1) has at least one skeleton Z selected from the group consisting of an isocyanurate skeleton, an iminooxadiazinedione skeleton, an allophanate skeleton, and a biuret skeleton in the main chain, and the side chain having the hydrophilic group is branched from the skeleton Z.

[0015] <6> The water-based polyurethane according to the above <5>, wherein the skeleton Z includes at least one isocyanurate skeleton.

[0016] <7> The aqueous polyurethane according to any one of <1> to <6>, wherein the polyurethane has an average particle size of 300 nm or less.

[0017] <8> A method for producing an aqueous polyurethane, comprising a step of reacting a polyol (A) with a polyisocyanate (B) to synthesize an aqueous polyurethane dispersion containing polyurethane and water, wherein the polyol (A) comprises a polyol (a-1) having a main chain having a structure represented by the following formula (1) and a side chain branched from the main chain, the side chain having a hydrophilic group, the content of the structure represented by the following formula (1) relative to the total mass of the polyol (a-1) being 50 mass% or more, and the solids concentration of the polyurethane in the aqueous dispersion being 35 mass% or more. (In the formula, R may be the same or different and is a linear, branched or alicyclic divalent hydrocarbon group having 2 to 20 carbon atoms, which may be optionally substituted with a heteroatom; n is an integer of 1 to 50; * represents a bond.) Here, it is preferable that the production method of <8> above further has the technical feature described in any one of <2> to <7> above.

[0018] <9> A water-based polyurethane obtained by reacting a polyol (A) with a polyisocyanate (B), the polyurethane comprising a main chain having a urethane bond and a structure represented by the following formula (1), and a side chain branched from the main chain, the side chain having a hydrophilic group; the content of the structure represented by the following formula (1) relative to the total mass of the polyurethane is 35% by mass or more; the polyurethane contains 0.00 to 0.85% by mass of carboxyl groups and carboxylate groups relative to the total mass of the polyurethane; and the solids concentration of the polyurethane in the water dispersion is 35% by mass or more. (In the formula, R may be the same or different and is a linear, branched or alicyclic divalent hydrocarbon group having 2 to 20 carbon atoms, which may be optionally substituted with a heteroatom; n is an integer of 1 to 50; * represents a bond.) Here, it is preferable that the water-based polyurethane of above <9> further has the technical feature described in any one of above <1> to <7>.

[0019] <10> A water-based polyurethane obtained by reacting a polyol (A) with a polyisocyanate (B), wherein the polyol (A) comprises a polyol (a-1) having a main chain having a structure represented by the following formula (1) and a side chain branched from the main chain, the side chain having a hydrophilic group, wherein the content of the structure represented by the following formula (1) relative to the total mass of the polyol (a-1) is 50 mass% or more; the polyurethane contains 0.00 to 0.85 mass% of carboxyl groups and carboxylate groups relative to the total mass of the polyurethane; and the solids concentration of the polyurethane in the water-based polyurethane is 35 mass% or more. (In the formula, R may be the same or different and is a linear, branched or alicyclic divalent hydrocarbon group having 2 to 20 carbon atoms which may be optionally substituted with a heteroatom; n is an integer of 1 to 50; * represents a bond.) Here, it is preferable that the water-based polyurethane of the above <10> further has the technical feature described in any one of the above <1> to <7>.

[0020] According to the present invention, it is possible to realize an aqueous polyurethane and a method for producing the same that are excellent in storage stability and quick-drying properties and are capable of forming a urethane film that has excellent chemical resistance even when formed in a short period of time. Furthermore, according to the present invention, by having hydrophilic groups in side chains with relatively high mobility, not only is the aqueous dispersibility of the polyurethane particles improved, but also steric hindrance causes repulsion between the polyurethane particles, suppressing their aggregation. As a result of these combined effects, the dispersibility of the polyurethane particles in water is stabilized, and not only is the storage stability of the aqueous polyurethane improved, but the solids concentration of the aqueous polyurethane can be increased, and the particle size of the polyurethane particles can also be reduced.

[0021] Hereinafter, one embodiment for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. Note that the following embodiment is an example for explaining the present invention, and the present invention is not limited thereto. In other words, the present invention can be carried out by making any modifications within the scope of the gist thereof. Note that in this specification, for example, when a numerical range is expressed as "1 to 100," it is intended to include both the lower limit "1" and the upper limit "100." The same applies to other numerical ranges.

[0022] [Water-based Polyurethane] The water-based polyurethane of this embodiment is an aqueous dispersion of polyurethane containing polyurethane and water, wherein the polyurethane comprises a main chain having a urethane bond and a structure represented by the following formula (1), and a side chain branched from the main chain, the side chain having a hydrophilic group, the content of the structure represented by the following formula (1) relative to the total mass of the polyurethane being 35% by mass or more, the polyurethane containing carboxyl groups and carboxylate groups in an amount of 0.00 to 0.85% by mass relative to the total mass of the polyurethane, and the solids concentration of the polyurethane in the aqueous dispersion being 35% by mass or more. (In the formula, R may be the same or different and is a linear, branched or alicyclic divalent hydrocarbon group having 2 to 20 carbon atoms, which may be optionally substituted with a heteroatom; n is an integer of 1 to 50; and * represents a bond.)

[0023] The water-based polyurethane of this embodiment has the above-mentioned characteristics, which enable the formation of a urethane film in a short time, and can realize a water-based polyurethane that is excellent in durability even when a film is formed in a short time. Furthermore, while increasing the solids concentration of polyurethane generally tends to deteriorate storage stability, the water-based polyurethane of this embodiment has hydrophilic groups in side chains with relatively high mobility, and therefore has excellent dispersion stability of the polyurethane even though it is an aqueous polyurethane dispersion containing polyurethane and water, and can therefore realize high storage stability.

[0024] The aqueous polyurethane of this embodiment includes a branched polyurethane having a main chain having a urethane bond and a structure represented by formula (1) above, and a side chain branched from the main chain, and the side chain of the branched polyurethane has the hydrophilic group described above. The main chain of the polyurethane is not particularly limited as long as it has a urethane bond and a structure represented by formula (1) above, but in one aspect, it can be a main chain having a urethane bond, a structure represented by formula (1) above, and a skeleton Z described below. In this case, the side chain of the polyurethane can be a side chain branched from skeleton Z. Meanwhile, the side chain of the polyurethane is not particularly limited as long as it is a side chain branched from the main chain and has a hydrophilic group, but in one aspect, it can be a side chain having a hydrophilic group and a urethane bond.

[0025] The hydrophilic group refers to a functional group that has a high affinity for water. The introduction of the hydrophilic group can improve the water dispersibility of the aqueous polyurethane. The hydrophilic group is not particularly limited, but examples thereof include nonionic hydrophilic groups, anionic hydrophilic groups, cationic hydrophilic groups, and zwitterionic hydrophilic groups. Among these, from the viewpoint of versatility, nonionic hydrophilic groups and anionic hydrophilic groups are preferred, and nonionic hydrophilic groups are more preferred. Details of these will be described later, so redundant explanations will be omitted here. In this specification, the hydrophilic group does not include a hydroxy group.

[0026] The structure represented by the above formula (1) is a structure derived from carbonate. R in formula (1) is a linear or branched divalent hydrocarbon group. R may be the same or different, and the divalent hydrocarbon group may have a heteroatom. Details of the divalent hydrocarbon group will be described later, so a redundant explanation will be omitted here. The lower limit of the number of carbon atoms in R is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more. The upper limit is preferably 20 or less, more preferably 10 or less, and even more preferably 6 or less.

[0027] In addition, n in formula (1) is an integer of 1 or more, preferably 1 to 50, and more preferably 3 to 30.

[0028] The content of the structure represented by the above formula (1) is preferably 35% by mass or more relative to the total mass of the polyurethane. This tends to make it easier to obtain polyurethanes with excellent water resistance, heat resistance, chemical resistance, durability, etc. The content of the structure represented by the above formula (1) is not particularly limited, but is more preferably 40% by mass or more relative to the total mass of the polyurethane, even more preferably 45% by mass or more, still more preferably 50% by mass or more, particularly preferably 55% by mass or more, and most preferably 60% by mass or more. The upper limit is not particularly limited, but is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less relative to the total mass of the polyurethane.

[0029] The water-based polyurethane of this embodiment may contain other components as long as it is a polyurethane water dispersion containing the above-mentioned polyurethane and water. Here, the other components may be bonded to the water-based polyurethane or may be added as additives separately from the polyurethane and water.

[0030] Furthermore, the polyurethane described above may contain a predetermined amount of carboxyl groups and carboxylate groups as necessary. The carboxyl groups and carboxylate groups may be contained by being bonded to the polyurethane, or may be contained by being bonded to the polyol (A) or polyisocyanate (B) described below. Furthermore, the carboxyl groups and carboxylate groups may be contained in components other than the polyurethane, polyol (A), and polyisocyanate (B). When carboxyl groups and carboxylate groups are contained in multiple components, the total amount of carboxyl groups and carboxylate groups contained in each component is defined as the content of carboxyl groups and carboxylate groups in the aqueous polyurethane.

[0031] The aqueous polyurethane of this embodiment contains carboxyl groups and carboxylate groups in a range of 0.00% by mass or more and 0.85% by mass, based on the total mass of the polyurethane. By having the carboxyl group and carboxylate group contents within the above ranges, the resulting aqueous polyurethane has excellent storage stability and can improve the durability of the polyurethane coating film when formed. The carboxyl group and carboxylate group contents are not particularly limited, but the lower limit is preferably 0.02% by mass or more, more preferably 0.03% by mass or more, and extremely preferably 0.10% by mass or more. The upper limit is preferably 0.85% by mass or less, more preferably 0.80% by mass or less, and extremely preferably 0.75% by mass or less.

[0032] [Method for quantifying carboxyl groups and carboxylate groups in aqueous polyurethane] In this embodiment, the method for quantifying carboxyl groups and carboxylate groups in aqueous polyurethane is not particularly limited, but when the charged amount and structure are known, they can be calculated from the charged amount. In this embodiment, the carboxyl group and carboxylate group contents are calculated based on the COOH or COO content in the aqueous polyurethane mass. － In addition, when the amount and structure of the compound to be added are unknown, they are not particularly limited and can be provided by any known method or a combination thereof.

[0033] As an example, １A quantitative method using H-NMR is described below. A predetermined amount of water-based polyurethane is measured, and 0.1 N hydrochloric acid is added dropwise to the polyurethane to adjust the pH to 4-5, causing precipitation, and the supernatant is discarded. If separation is poor, a centrifuge may be used for separation, as necessary, or precipitation may be promoted by cooling. The obtained precipitate and the standard substance are dissolved in DMSO-d ６ Dissolve in １ By measuring H-NMR, the content of carboxyl groups and carboxylate groups contained in the water-based polyurethane can be quantified from the ratio of the peaks derived from the carboxyl groups to those of a standard substance.

[0034] [Qualitative and quantitative determination method of hydrophilic groups in aqueous polyurethane and structures derived from formula (1)] The qualitative and quantitative determination method of hydrophilic groups in aqueous polyurethane and structures derived from formula (1) is not particularly limited, but when the charged amount and structure are known, they can be calculated from the charged amount. When the charged amount and structure are unknown, it is desirable to first identify the hydrophilic groups and the structures of formula (1), and then quantify them using a method according to the structures of the hydrophilic groups and formula (1). For example, in the case of polyethylene glycol monomethyl ether used in the examples described below, the hydrophilic groups and the structures derived from formula (1) can be determined by hydrolyzing the aqueous polyurethane in the presence of a base, followed by gas chromatography (GC), high performance liquid chromatography (HPLC), １ It can be quantified using H-NMR. If the above method is difficult to measure, gel permeation chromatography (GPC) may be used instead. In addition, if the hydrophilic group itself is hydrolyzed or if the water-based polyurethane alone can be quantified, １ A method for quantitative determination by H-NMR may also be used.

[0035] Hydrolysis Method: Approximately 10 g of a water-based polyurethane sample was weighed into a 100 mL recovery flask, and 50 g of ethanol and 4.0 g of potassium hydroxide were added. A magnetic stirrer was placed in the flask, and the mixture was stirred for 1 hour in an oil bath set at 105±5°C, causing alkaline decomposition of the urethane bond and carbonate bond. The mixture was then cooled to room temperature, and a few drops of phenolphthalein indicator were added to the reaction solution, followed by the addition of hydrochloric acid in small amounts until the color disappeared. Approximately 40 mL of the supernatant was collected, transferred to a sample bottle, and allowed to stand overnight in a refrigerator with an internal temperature of 5°C. After standing, the supernatant was filtered using a membrane filter with a pore size of 0.45 μm to obtain a filtrate. The obtained filtrate was analyzed by GC, GPC, and HPLC. １ In the GC analysis, GPC analysis, and HPLC analysis, the concentrations of the hydrophilic group component and formula (1) in the sample are determined from a concentration calibration curve separately prepared using the hydrophilic group component contained in the aqueous polyurethane and the monomer diol of formula (1), and the mass is calculated from the amount of solution, and the value obtained by dividing this by the mass of the solids content of the aqueous polyurethane used in the alkaline decomposition is the content of the hydrophilic group component and the structure derived from formula (1) in the aqueous polyurethane.

[0036] ・ １ Quantitative analysis by H-NMR A water-based polyurethane sample was analyzed by DMSO-d ６ Dissolve in １ H-NMR is performed. The integral value of a standard substance having a peak that does not overlap with the peak derived from the water-based polyurethane is designated as A, and the peak derived from the hydrophilic group is designated as B. The content of hydrophilic groups can be calculated from the molar concentration of A obtained from the ratio of A to B and the molecular weight of the hydrophilic group.

[0037] The aqueous polyurethane of this embodiment is not particularly limited, but the solids concentration of the polyurethane is preferably 35% by mass or more, more preferably 37% by mass or more, even more preferably 39% by mass or more, and particularly preferably 40% by mass or more. A high solids concentration of the polyurethane makes it possible to form a film in a short time, and tends to improve productivity and economic efficiency. The upper limit of the solids concentration of the polyurethane is not particularly limited, but is preferably 60% by mass or less, more preferably 57% by mass or less, even more preferably 55% by mass or less, and particularly preferably 50% by mass or less.

[0038] Although not particularly limited, the water content of the water-based polyurethane of this embodiment is preferably 40 to 65% by mass relative to the total mass of the water-based polyurethane, more preferably 43% by mass or more, even more preferably 45% by mass or more, and particularly preferably 50% by mass or more, with the upper limit being more preferably 63% by mass or less, even more preferably 61% by mass or less, and particularly preferably 60% by mass or less.

[0039] The water-based polyurethane of this embodiment may be a polyurethane aqueous dispersion containing polyurethane and water. In this case, the polyurethane is preferably dispersed in water as polyurethane particles. The average particle size of the polyurethane particles can be set appropriately depending on the desired performance and is not particularly limited, but is preferably 300 nm or less. In this specification, the average particle size of the polyurethane particles refers to the cumulative 50% particle size measured by dynamic light scattering, and can be measured, for example, using a "Nanotrack UPA" manufactured by Nikkiso Co., Ltd. The smaller the average particle size of the polyurethane particles, the less likely precipitation occurs when particles aggregate, and the better the dispersion stability tends to be. The average particle size of the polyurethane particles is more preferably 280 nm or less, even more preferably 260 nm or less, and particularly preferably 240 nm or less. The lower limit is not particularly limited, but is preferably 50 nm or more, more preferably 80 nm or more, and even more preferably 100 nm or more. On the other hand, as the average particle size decreases, the distance between particles decreases, and the interaction between particles becomes stronger, which increases the viscosity and tends to make it difficult to achieve a high solid content.

[0040] The molecular weight of the polyurethane described above can be appropriately set depending on the desired performance and is not particularly limited, but a weight average molecular weight (Mw) of 10,000 to 500,000 is preferred. A weight average molecular weight within this range tends to facilitate the production of aqueous polyurethane coatings that exhibit excellent water dispersibility and excellent appearance upon coating formation. The weight average molecular weight of the polyurethane is preferably 10,000 or more, more preferably 30,000 or more, and preferably 500,000 or less, and even more preferably 400,000 or less. The weight average molecular weight (Mw) of the polyurethane can be calculated by GPC (gel permeation chromatography) measurement (DMF) as described in the Examples below. Methods for controlling the weight average molecular weight (Mw) of the polyurethane within the above range are not particularly limited, but include, for example, adjusting the ratio of raw materials during polyurethane production so that the number average molecular weight falls within the above range, or adding and / or withdrawing a polyhydric alcohol compound during polyurethane production.

[0041] The molecular weight of the polyurethane described above can be appropriately set depending on the desired performance and is not particularly limited, but a number average molecular weight (Mn) of 5,000 to 200,000 is preferred. A number average molecular weight within this range tends to facilitate the production of aqueous polyurethane coatings that exhibit excellent water dispersibility and excellent appearance upon coating formation. The number average molecular weight of the polyurethane is preferably 5,000 or more, more preferably 10,000 or more, and preferably 200,000 or less, and even more preferably 150,000 or less. The number average molecular weight (Mn) of the polyurethane can be calculated by GPC (gel permeation chromatography) measurement (DMF) as described in the Examples below. Methods for controlling the number average molecular weight (Mn) of the polyurethane within the above range are not particularly limited, but include, for example, adjusting the ratio of raw materials during polyurethane production so that the number average molecular weight falls within the above range, or adding and / or withdrawing a polyhydric alcohol compound during polyurethane production.

[0042] The polyurethane described above is preferably an addition polymer of polyol (A) and polyisocyanate (B). For example, the polyurethane described above or an aqueous polyurethane can be easily obtained by addition polymerizing the following polyol (a-1) as the polyol (A) with polyisocyanate (B). In this case, the polyurethane described above will have a structure derived from polyol (a-1) and a structure derived from polyisocyanate (B). A preferred embodiment will be described in further detail below.

[0043] <Polyol (A)> Examples of the polyol (A) used as a raw material include, but are not limited to, polyol (a-1) having a main chain having a structure represented by the following formula (1) and a side chain branched from the main chain and having a hydrophilic group, and polyol (a-2) having a carboxyl group or a carboxylate group. Furthermore, polyol (a-1) may further contain a carboxyl group or a carboxylate group, or may contain a carboxyl group or a carboxylate group in its side chain. Polyol (A) may contain only polyol (a-1), or may contain polyol (a-1) and polyol (a-2). Furthermore, polyol (A) may contain other polyol components in addition to polyol (a-1) and polyol (a-2).

[0044] Specific examples of polyol (a-1) include those described below. This polyol (a-1) has a main chain having a structure represented by the following formula (1) and a side chain branched from the main chain and having a hydrophilic group, and the structure represented by the following formula (1) accounts for 50 mass % or more of the total mass of polyol (a-1). The structure represented by the following formula (1) is a structure derived from carbonate. (In the formula, R may be the same or different and is a linear, branched or alicyclic divalent hydrocarbon group having 2 to 20 carbon atoms, which may be optionally substituted with a heteroatom; n is an integer of 1 to 50; and * represents a bond.)

[0045] In the above formula (1), the number of carbon atoms in R is not particularly limited, but the lower limit is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more. The upper limit is preferably 20 or less, more preferably 10 or less, and even more preferably 6 or less.

[0046] In the above formula (1), specific examples of R are not particularly limited, and examples thereof include linear or branched hydrocarbon groups such as ethylene group, propylene group, butylene group, 2-methylpropyl group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, oxyethylene group, oxytetramethylene group, polyoxyethylene group, polyoxytetramethylene group, fluoroalkyl group, perfluoroalkyl group, isopropylene group, isobutylene group, tert-butylene group, isopentylene group, 2,2-dimethyltrimethylene group, 3-methylpropylene group, isohexylene group, isoheptylene group, isooctylene group, oxy1-methylethylene group, oxy2,2-dimethyltrimethylene group, and polyoxy1-methylethylene group; and alicyclic hydrocarbon groups such as cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane, and decalin. Among these, from the viewpoint of versatility and the like, a propylene group, a butylene group, a pentylene group, a hexylene group, a nonylene group, a decylene group, an oxyethylene group, an oxytetramethylene group, a polyoxyethylene group, a polyoxytetramethylene group, an isopropylene group, an isobutylene group, an isopentylene group, a 2,2-dimethyltrimethylene group or an isohexylene group, an oxy 1-methylethylene group, and a polyoxy 1-methylethylene group are preferred.

[0047] In the above formula (1), n ​​is an integer of 1 or more, preferably 1 to 50, and more preferably 3 to 30.

[0048] Here, the main chain in polyol (a-1) refers to a portion of the polymer chain whose ends are sandwiched between hydroxyl groups and has the structure represented by formula (1) above. Furthermore, the side chain in polyol (a-1) refers to a portion of the polymer chain that branches off from the main chain and extends from the branching site to a non-isocyanate-reactive functional group at the end opposite to the end bonded to the main chain. For example, in the structure below (the structure represented by formula (1) above is not shown), the solid line portion sandwiched between the hydroxyl groups is the main chain, and the dotted line portion is the side chain.

[0049] Furthermore, the hydrophilic group refers to a functional group that has a high affinity for water. By introducing a hydrophilic group into a side chain, the water dispersibility of the aqueous polyurethane can be improved. The hydrophilic group is not particularly limited, but examples thereof include nonionic hydrophilic groups, anionic hydrophilic groups, cationic hydrophilic groups, and zwitterionic hydrophilic groups. Among these, from the viewpoint of versatility, etc., nonionic hydrophilic groups and anionic hydrophilic groups are preferred, and nonionic hydrophilic groups are more preferred. In this specification, the hydrophilic group does not include a hydroxy group.

[0050] The nonionic hydrophilic group is not particularly limited, but includes an oxyalkylene group, a polyhydric ester composed of a polyhydric alcohol and a fatty acid, etc. Specific examples include, but are not particularly limited to, oxyethylene alkyl ethers (polyethylene glycol monomethyl ether, polypropylene glycol monomethyl ether, etc.) The nonionic hydrophilic group is preferably a polyalkylene glycol, more preferably polyethylene glycol monomethyl ether.

[0051] The anionic hydrophilic group is not particularly limited, but examples thereof include a carboxy group, a sulfonic acid group, a phosphate group, etc. Among these, from the viewpoint of water resistance, etc., a carboxy group and a sulfonic acid group are preferred, and a carboxylic acid group is more preferred.

[0052] The cationic hydrophilic group is not particularly limited, but examples thereof include a tetraalkylammonium group.

[0053] The zwitterionic hydrophilic group is not particularly limited, but examples thereof include groups having a betaine structure such as a carboxybetaine group, a sulfobetaine group, and a phosphorylbetaine group, which have an anionic and cationic structure in the same molecule.

[0054] The content of the hydrophilic groups is not particularly limited, but is preferably 0.1 to 30 parts by mass, more preferably 0.2 to 25 parts by mass, even more preferably 0.5 to 20 parts by mass, and particularly preferably 1.0 to 10 parts by mass, relative to 100 parts by mass of the total amount of polyurethane. When the hydrophilic group content of the aqueous polyurethane in this embodiment is within the above range, the water dispersibility and storage stability of the aqueous polyurethane are improved, and the durability of the resulting polyurethane coating film also tends to be improved at the same time.

[0055] The presence of a hydrophilic group in the side chain of the polyol (a-1) not only enhances the water dispersibility of the water-based polyurethane, but also reduces the viscosity of the water-based polyurethane due to the steric hindrance between the side chains between particles, which tends to reduce fluidity when the solid content is high. Furthermore, having the structure represented by the above formula (1) in an amount of 50 mass% or more relative to the total mass of the polyol (a-1) tends to facilitate the formation of a polyurethane coating film that is excellent in durability, such as chemical resistance, heat resistance, and water resistance. Furthermore, the excellent water dispersibility exhibited also makes it possible to reduce the amount of polyol (a-2) and other polyol components introduced, thereby suppressing the problem of a decrease in the urethane group concentration of the polyurethane coating film as the proportion of polyol (a-2) and other polyol components used increases, thereby making it possible to maintain high flexibility of the resulting polyurethane coating film. The polyol (a-1) preferably has the structure represented by the above formula (1) in an amount of 60% by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, and particularly preferably 80% by mass or more, based on the total mass of the polyol (a-1). The upper limit is not particularly limited, but is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less, based on the total mass of the polyol (a-1).

[0056] Components having functions other than hydrophilic groups may also be optionally introduced. Components other than hydrophilic groups are not particularly limited, but include hydrophobic groups that impart antifouling and water repellency, adsorptive groups that enhance adhesion to the substrate, and crosslinkable groups that harden the film. Examples of hydrophobic groups include long-chain alkyl groups having 5 or more carbon atoms, alkylsiloxane groups, and fluorinated alkyl groups. Examples of adsorptive groups include alkoxysilyl groups. Examples of crosslinkable groups include isocyanates protected with a blocking agent such as triazole.

[0057] The polyol (a-1) preferably has a skeleton Z in the main chain, which serves as a branching point between the main chain and the side chain. In this case, the side chain having a hydrophilic group preferably branches from the skeleton Z of the main chain. Specific examples of such a skeleton Z include, but are not limited to, a trivalent or higher alkyl group, an aromatic skeleton, an aliphatic skeleton, an isocyanurate skeleton, a biuret skeleton, an allophanate skeleton, and an iminooxadiazinedione skeleton. Among these, an isocyanurate skeleton, an iminooxadiazinedione skeleton, an allophanate skeleton, and a biuret skeleton are preferred, an isocyanurate skeleton and an iminooxadiazinedione skeleton are more preferred, and an isocyanurate skeleton is extremely preferred.

[0058] [Method for Producing Polyol (a-1)] Polyol (a-1) can be obtained as a hydroxy compound by, for example, a method of reacting an excess of a polyol compound with a polyisocyanate compound, or a method of reacting a polycarbonate polyol with an arbitrary polyol in the presence of a transesterification catalyst, and the method for producing it is not particularly limited. Note that, if the polyisocyanate used in the above method has some terminals that are not reactive with polyols, the resulting polyol will have the non-reactive terminals as side chains. Therefore, polyol (a-1) may be polyol (a-1) alone, or may be a mixture of polyol (a-1) and a polyol.

[0059] The method for reacting the polyol compound and the polyisocyanate compound is not particularly limited, and can be carried out, for example, by mixing the raw materials and stirring while heating. The reaction temperature is not particularly limited, and the lower limit is preferably 50°C or higher, more preferably 60°C or higher, even more preferably 70°C or higher, and even more preferably 80°C or higher. The upper limit is preferably 250°C or lower, more preferably 200°C or lower, even more preferably 180°C or lower, and even more preferably 160°C or lower. By setting the reaction temperature at or above the lower limit, the reaction can be carried out in a shorter time, which is economical. By setting the reaction temperature at or below the upper limit, thermal degradation of the resulting polyol (a-1) can be more effectively prevented.

[0060] The reaction pressure is not particularly limited, but is preferably from atmospheric pressure to 1 MPa. By setting the reaction pressure within the above range, the reaction can be carried out more easily. Furthermore, when auxiliary materials are used, the reaction can be promoted more efficiently by applying a certain amount of pressure in consideration of the vapor pressure of these materials.

[0061] The progress and completion of the reaction can be confirmed, for example, by GPC (gel permeation chromatography) measurement and FT-IR (Fourier transform infrared spectrophotometer). As the reaction progresses, the peaks derived from the raw materials measured by GPC become smaller over time, and can be confirmed by the disappearance of the peaks. In addition, the wave number of 2273 cm derived from the isocyanate group (-NCO group) is detected by FT-IR. －１ This can also be confirmed by the disappearance of an infrared absorption spectrum absorbance (Abs) peak in the vicinity of the reaction temperature. Before the reaction described above, a pretreatment step such as a dehydration treatment of the raw materials to be used may be carried out.

[0062] [Method for Qualitative and Quantitative Determination of Hydrophilic Groups in Polyol (a-1)] The method for qualitatively and quantitatively determining the hydrophilic groups in polyol (a-1) is not particularly limited. However, when the charged amount and structure are known, the amount can be calculated from the charged amount. When the charged amount and structure are unknown, it is desirable to first identify the structure of the hydrophilic group and then quantify it using a method appropriate for that hydrophilic group. As a method for quantifying the hydrophilic groups, for example, in the case of polyethylene glycol monomethyl ether used in the examples described below, polyol (a-1) is hydrolyzed in the presence of a base, and then the hydrophilic groups are analyzed by gas chromatography (GC), high performance liquid chromatography (HPLC), １ It can be quantified using H-NMR. If the above method is difficult to measure, gel permeation chromatography (GPC) may be used instead. In addition, when the hydrophilic group itself is hydrolyzed, １ A method of quantitative determination by H-NMR is preferred.

[0063] Hydrolysis method Approximately 5 g of a sample of polyol (a-1) was weighed out into a 100 mL recovery flask, and 50 g of ethanol and 4.0 g of potassium hydroxide were added. A magnetic stirrer was placed in the mixture, and the mixture was stirred for 1 hour in an oil bath set at 105±5°C, causing alkaline decomposition of the carbonate bond moiety. After that, the mixture was cooled to room temperature, and a few drops of phenolphthalein indicator were added to the reaction solution, followed by the addition of hydrochloric acid in small amounts until the color disappeared. Approximately 40 mL of the supernatant was collected, transferred to a sample bottle, and allowed to stand overnight in a refrigerator with an internal temperature of 5°C. After standing, the supernatant was filtered using a membrane filter with a pore size of 0.45 μm to obtain a filtrate. The obtained filtrate was subjected to GC analysis, GPC analysis, and １ In the GC analysis, GPC analysis, and HPLC analysis, the concentration of the hydrophilic group in the sample is determined from a concentration calibration curve separately prepared using the hydrophilic group component contained in the polyol (a-1), and the mass is calculated from the amount of the solution, and the value obtained by dividing this by the mass of the polyol (a-1) used in the alkaline decomposition is the content of the hydrophilic group in the polyol (a-1).

[0064] ・ １ Quantitative analysis by H-NMR: A sample of polyol (a-1) was dissolved in DMSO-d ６ Dissolve in １ H-NMR is performed. The integral value derived from the hydroxyl groups of the polyol is designated as A, and the peak derived from the hydrophilic groups is designated as B. The content of hydrophilic groups can be calculated from the ratio of A to B, the molar concentration of A calculated from the OHV, and the molecular weight of the functional group. Alternatively, instead of A, a standard substance having a peak that does not overlap with the peak derived from polyol (a-1) may be used for calculation.

[0065] [Method for Quantifying the Structure Derived from Formula (1) in Polyol (a-1)] The method for quantifying the structure derived from Formula (1) in polyol (a-1) is not particularly limited, but when the charge amount and structure are known, it can be calculated from the charge amount. When the charge amount and structure are unknown, R can be identified by hydrolyzing polyol (a-1) by the above hydrolysis and then subjecting the obtained filtrate to GC analysis or HPLC analysis, and further, the content of the structure of Formula (1) in polyol (a-1) can be calculated from a concentration calibration curve prepared separately.

[0066] In addition to the above method, １ It is also possible to calculate the amount of hydroxylase from the method described above using the method described above. If necessary, the above analytical methods may be used in combination.

[0067] (Polyisocyanate) The isocyanate compound usable as a raw material when producing the polyol (a-1) is not particularly limited, but examples thereof include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate (hereinafter sometimes abbreviated as "MDI"), xylylene diisocyanate, and naphthylene diisocyanate. Examples of the isocyanate compound include aromatic diisocyanates such as benzene, isocyanate compounds having three or more isocyanate groups such as triphenylmethane-4,4'-4''-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatoene, and 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, and isocyanurate-modified products, biuret-modified products, and iminooxadiazinedione-modified products of these isocyanates. Commercially available isocyanate compounds include, but are not limited to, 24A-100, 22A-75P, TPA-100, TKA-100, P301-75E, D101, D201, 21S-75E, MFA-75B, MHG-80B, TUL-100, TLA-100, TSA-100, TSS-100, TSE-100, E402-80B, and E405-80B manufactured by Asahi Kasei Corporation. , AE700-100, A201H, 17B-60P, TPA-B80E, MF-B60B, MF-K60B, SBB-70P, SBN-70D, E402-B80B, WB40-100, WT30-100, WT31-100, WB40-80D, WT20-100, WL70-100, WE50-100, and WM44-L70G are examples of the "Duranate (trade name)" series.

[0068] In addition, polyisocyanate compounds usable as raw materials in producing aqueous polyurethanes may also be synthesized in addition to those described above. For example, polyisocyanates having an allophanate structure obtained by reacting an alcohol, a diisocyanate, and an allophanate catalyst, as described in WO 2003 / 027163, or polyisocyanates having a biuret structure obtained by reacting an amine with a diisocyanate, may also be used. In this case, if the alcohol and amine are monofunctional, polyisocyanates having side chains derived from the alcohol and amine structures can be obtained. The identification of the structure of the polyisocyanate compound is not particularly limited, but can be performed, for example, by the method described in Japanese Patent No. 6647130. １３ A method using C-NMR is exemplified.

[0069] (Polycarbonate polyol) The polycarbonate polyol usable as a raw material when producing polyol (a-1) is not particularly limited, but can be obtained, for example, by the polycarbonate polyol production method described in Synthesis Example 2-3. Commercially available products can also be used. Commercially available products include, but are not particularly limited to, the "Duranol (trade name)" series, such as T6002, T6001, T5652, T5651, T5650J, T5650E, G4672, T4672, T4671, G3452, G3450J, and AK011 manufactured by Asahi Kasei Corporation.

[0070] Furthermore, polycarbonate polyols having a diol structure introduced into the main chain can be obtained by transesterifying a polycarbonate polyol with an arbitrary diol, and these can also be used as raw materials. For example, a polycarbonate polyol can be obtained by reacting a carbonate compound with an arbitrary diol compound in the presence of a transesterification catalyst. Examples of transesterification catalysts include, but are not limited to, alkali metals and alkaline earth metals, as well as their alcoholates, hydrides, oxides, amides, hydroxides, and salts. The polycarbonate polyols synthesized by this method have a structure in which a diol is introduced into the main chain.

[0071] Specific examples of the polyol (a-2) having a carboxyl group or a carboxylate group include, but are not limited to, 2,2-dimethylolpropionic acid (DMPA), 2,2-dimethylolbutanoic acid (DMBA), and the polyols described in Example I-2 of JP 2022-183274. The use of polyol (a-2) tends to impair the flexibility and durability (against water, moist heat, and chemicals) of the resulting polyurethane coating film, but the use of polyol (a-1) makes it possible to reduce the amount of polyol (a-2) introduced, and tends to result in a polyurethane that is not only excellent in flexibility but also highly durable.

[0072] When polyol (a-1) and polyol (a-2) are used in combination, the ratio of polyol (a-1) to polyol (a-2) used can be set appropriately depending on the desired performance and is not particularly limited, but the molar ratio of polyol (a-1):polyol (a-2) is preferably 1:0.7, more preferably 1:0.6, even more preferably 1:0.4, and particularly preferably 1:0.2 or less. When these ratios are within the above-mentioned preferred numerical ranges, the flexibility of the resulting polyurethane coating film tends to be maintained at a high level.

[0073] The polyol (A) used in the synthesis of the aqueous polyurethane of this embodiment may be used in combination with a polyol other than the polyol (a-1) and the polyol (a-2) having a carboxyl group or a carboxylate group. Examples of polyols that can be used in combination include, but are not limited to, polyester polyols and polyether polyols.

[0074] (Polyester Polyol) The polyester polyol used as a raw material in producing the aqueous polyurethane of this embodiment is not particularly limited, and can be obtained, for example, by the polyester polyol production method described in JP-A-2006-328372. Commercially available products can also be used. Examples of commercially available products include, but are not limited to, the P-**10 and F-**10 series manufactured by Kuraray Co., Ltd. and the Polylite series manufactured by DIC Corporation.

[0075] (Polyether polyol) The polyether polyol used as a raw material in producing the aqueous polyurethane of this embodiment is not particularly limited, but can be obtained, for example, by the polyether polyol production method described in Japanese Patent No. 3299803. Commercially available products can also be used. Commercially available products include, but are not particularly limited to, polyethylene glycol manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0076] <Polyisocyanate (B)> The isocyanate compound usable as a raw material when producing the aqueous polyurethane of the present embodiment is not particularly limited, but examples thereof include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate (hereinafter sometimes abbreviated as "MDI"), xylylene diisocyanate, and naphthylene diisocyanate. Examples of the isocyanate include aromatic diisocyanates such as cyanate, isocyanate compounds having three or more isocyanate groups such as triphenylmethane-4,4'-4''-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatoene, and 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, and isocyanurate-modified products, biuret-modified products, and iminooxadiazinedione-modified products of these isocyanates. Commercially available isocyanate compounds include, but are not limited to, 24A-100, 22A-75P, TPA-100, TKA-100, P301-75E, D101, D201, 21S-75E, MFA-75B, MHG-80B, TUL-100, TLA-100, TSA-100, TSS-100, TSE-100, E402-80B, and E405-80B manufactured by Asahi Kasei Corporation. , AE700-100, A201H, 17B-60P, TPA-B80E, MF-B60B, MF-K60B, SBB-70P, SBN-70D, E402-B80B, WB40-100, WT30-100, WT31-100, WB40-80D, WT20-100, WL70-100, WE50-100, and WM44-L70G are examples of the "Duranate (trade name)" series.

[0077] The aqueous polyurethane of this embodiment may be, for example, an addition polymer of the polyol (A) and a polyisocyanate (an isocyanate having two or more NCO groups, preferably having two or more, i.e., 2 to 4, NCO groups). The polyisocyanate is not particularly limited, and known polyisocyanates such as diisocyanates can be used without particular limitation. Alternatively, the aqueous polyurethane of this embodiment may be an addition polymer of the polyol (A) and a polyisocyanate (B), one or more known polyols, and one or more known polyisocyanates.

[0078] The present embodiment will be described in more detail below with reference to specific examples and comparative examples. However, these examples and comparative examples are not intended to limit the scope of the present embodiment. In other words, the materials, amounts used, ratios, processing details, processing procedures, etc. shown below can be appropriately changed without departing from the spirit of the present invention. Furthermore, the values ​​of various manufacturing conditions and evaluation results described below represent preferred upper or lower limits in the embodiments of the present invention, and preferred numerical ranges may be defined by combining the above-mentioned upper or lower limits with the values ​​of the following examples or values ​​between examples. The evaluations and physical properties in the examples and comparative examples described below were evaluated and measured by the following methods. In these examples, unless otherwise specified, "parts" and "%" are based on mass.

[0079] [Measurement of Hydroxyl Value (OHV)] The hydroxyl values ​​of the polyols and polyol-containing compositions obtained in the Examples and Comparative Examples described below were measured by the following method. Using a volumetric flask, 12.5 g of acetic anhydride was added with pyridine to make 50 mL to prepare an acetylation reagent. 1.0 to 10.0 g of each of the polyols and polyol-containing compositions obtained in the Examples and Comparative Examples described below was weighed and placed in a 100 mL recovery flask. 5 mL of the acetylation reagent and 10 mL of toluene were added to the recovery flask using a volumetric pipette to obtain a solution. A cooling tube was then attached to the recovery flask, and the solution was stirred and heated at 100°C for 1 hour. 2.5 mL of distilled water was added to the recovery flask using a volumetric pipette, and the resulting solution was heated and stirred for an additional 10 minutes. After cooling the solution for 2-3 minutes, 12.5 mL of ethanol was added to the recovery flask, and 2-3 drops of phenolphthalein were added as an indicator. The solution was then titrated with 0.5 mol / L ethanolic potassium hydroxide. 5 mL of acetylation reagent, 10 mL of toluene, and 2.5 mL of distilled water were placed in a 100 mL recovery flask and heated and stirred for 10 minutes. The resulting solution was then titrated in the same manner (blank test). Based on this result, the hydroxyl values ​​of the polyol and polyol-containing composition were calculated using the following formula (III): hydroxyl value (mg-KOH / g) = {(b-a) × 28.05 × f} / e (III) (In formula (III), a represents the titration volume of the sample (mL), b represents the titration volume of the blank test (mL), e represents the sample weight (g), and f represents the titrant factor.)

[0080] [GPC Measurement (DMF)] The weight average molecular weight (Mw) and number average molecular weight (Mn) of polyurethane were measured by GPC using the following method. The polyurethanes and aqueous polyurethanes obtained in the application examples and application comparative examples described below were used as samples. The measurement samples were prepared with dimethylformamide (DMF) so that the concentration was 0.5% by mass, and the weight average molecular weight (Mw) and number average molecular weight (Mn) of the polyurethanes, converted into standard polystyrene, were measured using the GPC apparatus described below. GPC apparatus: Tosoh Corporation, HLC-8320 Analytical column: TSKgel Super HM-H (3 columns) Guard column: TSKgel guard column H-H Reference column: TSKgel Super H-RC Eluent: N,N-dimethylformamide (DMF) Flow rate: 0.5 mL / min Column temperature: 40°C RI detector: RI (built into the HLC-8320) Calibration curve formula: 3rd order polynomial Calibration curve: Standard polystyrene (Tosoh Corporation) ・F-40 (molecular weight: 4.27 x 105) ・F-20 (molecular weight: 1.90 x 105) ・F-10 (molecular weight: 9.64 x 104) ・F-4 (molecular weight: 3.79 x 104) ・F-2 (molecular weight: 1.81×104) ・F-1 (molecular weight: 1.02×104) ・A-5000 (molecular weight: 5.97×103) ・A-2500 (molecular weight: 2.63×103) ・A-1000 (molecular weight: 2.63×103)

[0081] [FT-IR Measurement] Using the polyol-containing compositions obtained in the Examples and Comparative Examples described below as samples, the infrared absorption spectrum absorbance of the samples was measured by FT-IR (Fourier transform infrared spectrophotometer) by the following method. The measurement sample was thinly spread on a rock salt plate (NaCl plate, 35 x 35 x 5 mm), and the infrared absorption spectrum absorbance of the sample was measured by FT-IR using the following device and conditions. FT-IR device: FT / IR-4600 type A (JASCO Corporation) Light source: Standard light source Detector: TGS Number of accumulations: 16 Resolution: 4 cm －１ Zero filling: On Apodization: Cosine Gain: Auto (2) Aperture: Auto (7.1 mm) Scan speed: Auto (2 mm / sec) Filter: Auto (30000 Hz) Data type: Equally spaced data Horizontal axis: Wave number (cm －１ ) Vertical axis: Abs Start: 400cm －１ End: 40,000 cm －１

[0082] [Structural analysis of water-based polyurethane, polyol, and polyisocyanate] The structures of water-based polyurethane, polyol, and polyisocyanate were analyzed as follows: １３ The analysis was carried out by C-NMR using a Biospin Avance 600 (trade name) manufactured by Bruker. １３ The molar ratios of isocyanurate groups, iminooxadiazinedione structures, allophanate groups, and biuret groups were determined by C-NMR measurement. The specific measurement conditions were as follows: １３C-NMR apparatus: AVANCE600 (manufactured by Bruker) Cryo Probe (manufactured by Bruker) Cryo Probe CPDUL 600S3-C / H-D-05Z Resonance frequency: 150 MHz Concentration: 60 wt / vol% Shift standard: CDCl ３ (77 ppm) Number of accumulations: 10,000 Pulse program: zgpg30 (proton complete decoupling method, waiting time 2 sec) The integral values ​​of the following signals were then divided by the number of carbons being measured, and each molar ratio was calculated from the resulting value. Molar amount of isocyanurate groups (mol%, indicated by "A"): Around 148.6 ppm: integral value ÷ 3 Molar amount of iminooxadiazinedione groups (mol%, indicated by "A"): Around any of 148.3 ppm, 144.6 ppm, or 137.3 ppm: integral value ÷ 1 Molar amount of allophanate groups (mol%, indicated by "B"): Around 154 ppm: integral value ÷ 1 Molar amount of biuret groups (mol%, indicated by "C"): Around 155.8 ppm: (integral value - allophanate group integral value) ÷ 2

[0083] [Isocyanate Group Concentration (mass %)] The isocyanate group concentration (mass %) of the polyisocyanate compound was measured as follows. 1 to 3 g of the polyisocyanate compound produced in the Production Example was weighed out (W g) into an Erlenmeyer flask, and 20 mL of toluene was added to completely dissolve the polyisocyanate (composition). Then, 10 mL of a 2 N toluene solution of di-n-butylamine was added, and after thorough mixing, the mixture was left at room temperature for 15 minutes. Furthermore, 70 mL of isopropyl alcohol was added to this solution, and the mixture was thoroughly mixed. This solution was titrated with a 1 N hydrochloric acid solution (factor F) using an indicator to obtain the titration value V ２ A similar titration operation was carried out without using polyisocyanate (composition), and the titration value V １ The obtained titration value V ２ mL and titration value V １The isocyanate group concentration (mass%) of the polyisocyanate was calculated from the mL based on the following formula: Isocyanate group concentration = (V １ -V ２ ) x F x 42 / (W x 1000) x 100

[0084] (Synthesis Example 1) [Synthesis of polyisocyanate (PI)]

[0085] (Synthesis Example 1-1) To a 300 ml separable flask were added 100 g of 24A-100 (manufactured by Asahi Kasei Corporation: NCO 24.0%) as the polyisocyanate to be modified, 171.4 g of polyethylene glycol monomethyl ether (mPEG) (manufactured by Nippon Nyukazai Co., Ltd., trade name "MPG-081") as a raw material for modification to isocyanate, and 100 ppm of dibutyltin dilaurate (manufactured by Tokyo Chemical Industry Co., Ltd.) as a catalyst relative to the other components. The mixture was reacted at 80°C for 2 hours with stirring under nitrogen. The reaction was terminated when it was confirmed that the NCO% was within ±3% of the theoretical amount. This procedure yielded polyisocyanate PI-1 having a biuret structure and a PEG side chain structure. The NCO% was 6.19%.

[0086] (Synthesis Example 1-2) 300 g of HDI and 200 g of polyethylene glycol monomethyl ether (mPEG) (manufactured by Nippon Nyukazai Co., Ltd., trade name "MPG-081") were charged into a four-neck flask equipped with a stirrer, thermometer, and condenser, and a urethanization reaction was carried out at 90°C for 1 hour with stirring. The temperature was then raised to 130°C, and 0.26 g of a 20% solids solution of zirconyl 2-ethylhexanoate in mineral spirits (manufactured by Nippon Chemical Industry Co., Ltd., trade name "Nikka Octix Zirconium 12%" diluted with mineral spirits) was added as an allophanation catalyst. After 1 hour, when the refractive index of the reaction solution increased to 0.008, 0.097 g (2.0 times the moles relative to the allophanation catalyst) of a 50% solids solution of pyrophosphoric acid (a reagent manufactured by Katayama Chemical Industry Co., Ltd.) in isobutanol was added to terminate the reaction. １３C-NMR analysis confirmed the presence of allophanate groups. Using a falling thin-film distillation apparatus, unreacted HDI was removed at 160°C (0.2 Torr) for the first time and 150°C (0.1 Torr) for the second time, yielding polyisocyanate PI-2 having a PEG side chain structure and an allophanate structure. The NCO% was 7.90%.

[0087] (Synthesis Example 1-3) Into a 300 ml separable flask were added 100 g of TLA-100 (manufactured by Asahi Kasei Corporation: NCO 23.6%) as the modified polyisocyanate, 116.5 g of polyethylene glycol monomethyl ether (mPEG) (manufactured by Nippon Nyukazai Co., Ltd., trade name "MPG-081") as a raw material for modification to isocyanate, and 300 ppm of dibutyl phosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) as a catalyst relative to the other components, and the mixture was reacted at 120°C for 4 hours with stirring under nitrogen. The ratio of the modified raw material to NCO was 30 mol%. The reaction was terminated after confirming that the NCO% was within the theoretical amount ±3%. This operation yielded polyisocyanate PI-3 having an isocyanurate structure and a PEG side chain structure. The NCO% was 7.65%.

[0088] (Synthesis Example 1-4) Into a 300 ml separable flask, 100 g of Desmodur N3900 (manufactured by Covestro: NCO 23.5%) as the modified polyisocyanate, 115.9 g of polyethylene glycol monomethyl ether (mPEG) (manufactured by Nippon Nyukazai Co., Ltd., trade name "MPG-081") as a raw material for modification to isocyanate, and 300 ppm of dibutyl phosphate (manufactured by Tokyo Chemical Industry Co., Ltd.) as a catalyst were added, relative to the other components, and the mixture was reacted at 120 ° C. for 4 hours while stirring under nitrogen. The ratio of the modified raw material to NCO was 30 mol%. The reaction was terminated after confirming that the NCO% was the theoretical amount ±3%. This operation yielded polyisocyanate PI-4 having an isocyanurate structure and a PEG side chain structure. The NCO% was 7.59%.

[0089] The raw materials used in Synthesis Example 1 are as follows: Modified polyisocyanates: 24A-100: aliphatic polyisocyanate having a biuret structure, manufactured by Asahi Kasei Corporation, NCO 24.0%; TLA-100: aliphatic polyisocyanate having an isocyanurate structure, manufactured by Asahi Kasei Corporation, NCO 23.6%; Desmodur N3900: polyisocyanate having an iminooxadiazinedione structure, manufactured by Covestro, NCO 23.5%.

[0090] Modified raw materials: mPEG: polyethylene glycol monomethyl ether (used to introduce hydrophilic groups into the side chain, manufactured by Nippon Nyukazai Co., Ltd., trade name "MPG-081", monofunctional)

[0091] (Synthesis Example 2) [Synthesis of polycarbonate polyol (PCD)]

[0092] (Synthesis Example 2-1) Polycarbonate polyol PCD-1 having carboxyl groups in side chains was obtained in the same manner as in [Example I-2] of JP 2022-183274 A. The hydroxyl value was 50.0 mg KOH / g and the acid value was 13.1 mg KOH / g. The proportion of hydrophilic groups in PCD-1 was 0.83% by mass.

[0093] (Synthesis Example 2-2) Polycarbonate polyol PCD-2 having polyethylene glycol groups in its side chains was obtained in the same manner as in Example 1 of JP 2019-131689 A. The hydroxyl value was 58.4 mg KOH / g. The proportion of hydrophilic groups in PCD-2 was 24.1% by mass.

[0094] Synthesis Example 2-3 A 2-L glass flask (hereinafter also referred to as the "reactor") equipped with a rectification column packed with structured packing and a stirrer was charged with 396 g of 1,4-butanediol, 500 g of 1,6-hexanediol, and 760 g of ethylene carbonate, and then 0.086 g of titanium tetra-n-butoxide was added as a catalyst. While withdrawing a portion of the distillate, the reaction was carried out at a reaction temperature of 160 to 175°C for 12 hours. The reactor was then directly connected to a condenser, and the reaction temperature was raised to 175 to 190°C. The pressure was then gradually reduced, and the diol component in the reactor was distilled off while appropriately sampling and measuring the hydroxyl value of the produced polycarbonate polyol, thereby obtaining 700 g of polycarbonate polyol with a hydroxyl value of 56.1 mgKOH / g. 500 g of the obtained polycarbonate polyol and 67.9 g of PI-1 (NCO: 6.19%) were added to a 1 L separable flask, and after purging with nitrogen, the mixture was reacted at 100°C for 3 hours to obtain PCD-3 having a PEG side chain structure. The disappearance of the peak derived from NCO was confirmed by FT-IR and was taken as the end point. The NCO / OH (molar ratio) was set to 0.20. The hydroxyl value of PCD-3 was 40.1 mg KOH / g. The proportion of hydrophilic groups in PCD-3 was 7.55% by mass.

[0095] Synthesis Example 2-4 A 2-L glass flask (hereinafter also referred to as the "reactor") equipped with a rectification column packed with structured packing and a stirrer was charged with 396 g of 1,4-butanediol, 441 g of 1,5-pentanediol, and 760 g of ethylene carbonate, and then 0.086 g of titanium tetra-n-butoxide was added as a catalyst. While withdrawing a portion of the distillate, the reaction was carried out at a reaction temperature of 160 to 175°C for 12 hours. The reactor was then directly connected to a condenser, and the reaction temperature was raised to 175 to 190°C. The pressure was then gradually reduced, and the diol component in the reactor was distilled off while appropriately sampling and measuring the hydroxyl value of the polycarbonate polyol produced, to obtain 680 g of polycarbonate polyol with a hydroxyl value of 56.3 mgKOH / g. 500 g of the obtained polycarbonate polyol and 13.3 g of PI-2 (NCO: 7.90%) were added to a 1 L separable flask, and after purging with nitrogen, the mixture was reacted at 100°C for 3 hours to obtain PCD-4 having a PEG side chain structure. The NCO / OH (molar ratio) was set to 0.05. The disappearance of the peak derived from NCO was confirmed by FT-IR and was taken as the end point. The hydroxyl value of PCD-4 was 52.4 mg KOH / g. The proportion of hydrophilic groups in PCD-4 was 1.74 mass%.

[0096] Synthesis Example 2-5 A 2-L glass flask (hereinafter also referred to as the "reactor") equipped with a rectification column packed with structured packing and a stirrer was charged with 458 g of 1,5-pentanediol, 500 g of 1,6-hexanediol, and 760 g of ethylene carbonate, and then 0.086 g of titanium tetra-n-butoxide was added as a catalyst. While withdrawing a portion of the distillate, the reaction was carried out at a reaction temperature of 160 to 175°C for 12 hours. The reactor was then directly connected to a condenser, and the reaction temperature was raised to 175 to 190°C. The pressure was then gradually reduced, and the diol component in the reactor was distilled off while appropriately sampling and measuring the hydroxyl value of the polycarbonate polyol produced, thereby obtaining 790 g of polycarbonate polyol with a hydroxyl value of 112.5 mgKOH / g. 500 g of the obtained polycarbonate polyol and 99.1 g of PI-3 (NCO: 7.65%) were added to a 1 L separable flask, and after purging with nitrogen, the mixture was reacted at 100°C for 3 hours to obtain PCD-5 having a PEG side chain structure. The NCO / OH (molar ratio) was set to 0.18. The disappearance of the peak derived from NCO was confirmed by FT-IR and was taken as the end point. The hydroxyl value of PCD-5 was 75.6 mg KOH / g. The proportion of hydrophilic groups in PCD-5 was 8.90% by mass.

[0097] Synthesis Example 2-6 A 2-L glass flask (hereinafter also referred to as the "reactor") equipped with a rectification column packed with structured packing and a stirrer was charged with 458 g of 1,5-pentanediol, 500 g of 1,6-hexanediol, and 760 g of ethylene carbonate, and then 0.086 g of titanium tetra-n-butoxide was added as a catalyst. While withdrawing a portion of the distillate, the reaction was carried out at a reaction temperature of 160 to 175°C for 12 hours. The reactor was then directly connected to a condenser, and the reaction temperature was raised to 175 to 190°C. The pressure was then gradually reduced, and the diol component in the reactor was distilled off while appropriately sampling and measuring the hydroxyl value of the polycarbonate polyol produced, to obtain 690 g of polycarbonate polyol with a hydroxyl value of 55.8 mgKOH / g. 500 g of the obtained polycarbonate polyol and 49.2 g of PI-3 (NCO: 7.65%) were added to a 1 L separable flask, and after purging with nitrogen, the mixture was reacted at 100°C for 3 hours to obtain PCD-6 having a PEG side chain structure. The NCO / OH (molar ratio) was set to 0.18. The disappearance of the peak derived from NCO was confirmed by FT-IR and was taken as the end point. The hydroxyl value of PCD-6 was 45.6 mg KOH / g. The proportion of hydrophilic groups in PCD-6 was 4.82 mass%.

[0098] Synthesis Example 2-7 A 2-L glass flask (hereinafter also referred to as the "reactor") equipped with a rectification column packed with structured packing and a stirrer was charged with 396 g of 1,4-butanediol, 737 g of 1,10-decanediol, and 760 g of ethylene carbonate, and then 0.086 g of titanium tetra-n-butoxide was added as a catalyst. While withdrawing a portion of the distillate, the reaction was carried out at a reaction temperature of 160 to 175°C for 12 hours. The reactor was then directly connected to a condenser, and the reaction temperature was raised to 175 to 190°C. The pressure was then gradually reduced, and the diol component in the reactor was distilled off while appropriately sampling and measuring the hydroxyl value of the polycarbonate polyol produced, to obtain 720 g of polycarbonate polyol having a hydroxyl value of 56.5 mgKOH / g. 500 g of the obtained polycarbonate polyol and 27.7 g of PI-3 (NCO: 7.65%) were added to a 1 L separable flask, and after purging with nitrogen, the mixture was reacted at 100°C for 3 hours to obtain PCD-7 having a PEG side chain structure. The NCO / OH (molar ratio) was set to 0.10. The disappearance of the peak derived from NCO was confirmed by FT-IR and was taken as the end point. The hydroxyl value of PCD-7 was 48.6 mg KOH / g. The proportion of hydrophilic groups in PCD-7 was 2.82 mass%.

[0099] Synthesis Example 2-8 A 2-L glass flask (hereinafter also referred to as the "reactor") equipped with a rectification column packed with structured packing and a stirrer was charged with 635 g of 1,3-butanediol, 39.6 g of 2-methyl-propanediol, and 760 g of ethylene carbonate, and then 0.086 g of titanium tetra-n-butoxide was added as a catalyst. While withdrawing a portion of the distillate, the reaction was carried out at a reaction temperature of 160 to 175°C for 12 hours. The reactor was then directly connected to a condenser, and the reaction temperature was raised to 175 to 190°C. The pressure was then gradually reduced, and the diol component in the reactor was distilled off while appropriately sampling and measuring the hydroxyl value of the polycarbonate polyol produced, to obtain 680 g of polycarbonate polyol with a hydroxyl value of 54.2 mgKOH / g. 500 g of the obtained polycarbonate polyol and 53.5 g of PI-4 (NCO: 7.59%) were added to a 1 L separable flask, and after purging with nitrogen, the mixture was reacted at 100°C for 3 hours to obtain PCD-8 having a PEG side chain structure. The NCO / OH (molar ratio) was set to 0.20. The disappearance of the peak derived from NCO was confirmed by FT-IR and was taken as the end point. The hydroxyl value of PCD-8 was 40.1 mg KOH / g. The proportion of hydrophilic groups in PCD-8 was 5.19% by mass.

[0100] Comparative Synthesis Example 2-1 In accordance with Example 2 of Japanese Patent No. 6,276,848, 458 g of 1,5-pentanediol, 500 g of 1,6-hexanediol, and 760 g of ethylene carbonate were charged into a 2-L glass flask (hereinafter also referred to as the "reactor") equipped with a rectification column packed with structured packing and a stirrer, and then 0.086 g of titanium tetra-n-butoxide was added as a catalyst. While withdrawing a portion of the distillate, the reaction was carried out at a reaction temperature of 160 to 175°C for 12 hours. The reactor was then directly connected to a condenser, and the reaction temperature was raised to 175 to 190°C. After gradually reducing the pressure, the diol component in the reactor was distilled off while appropriately sampling and measuring the hydroxyl value of the polycarbonate polyol produced, to obtain a polycarbonate polyol (860 g) with a hydroxyl value of 109.8 mgKOH / g. To the obtained polycarbonate polyol (600 g) was added 369 g of PEG-1000 (manufactured by Wako Pure Chemical Industries, Ltd., "Polyethylene Glycol 1000" (trade name)) as a raw material for forming nonionic hydrophilic groups, and after stirring at 150°C for 6 hours, the reaction temperature was lowered to 115°C, 0.056 g of 85% phosphoric acid was added, and the mixture was stirred at 115°C for 3 hours to obtain rPCD-1 having a PEG structure in the main chain and a hydroxyl value of 112.2 mg KOH / g.

[0101] Comparative Synthesis Example 2-2: To a 1 L separable flask were added 115 g of PTMG-2000 (manufactured by Mitsubishi Chemical Corporation), 232 g of ETERNACOLL UH-200 (manufactured by Ube Industries, Ltd.), a polycarbonate diol having a molecular weight of 2000 made from 1,5-pentanediol and 1,6-hexanediol, 122 g of 1,4-butanediol, and 126 g of PI-3 (NCO: 7.65%). After purging under nitrogen, the mixture was reacted at 100°C for 3 hours to obtain rPCD-2 having a PEG side chain structure. The NCO / OH (molar ratio) was 0.075. The disappearance of the peak derived from NCO was confirmed by FT-IR and was used as the end point. The hydroxyl value of rPCD-2 was 267.6 mg KOH / g. The proportion of hydrophilic groups in rPCD-2 was 13.4% by mass.

[0102] (Synthesis Example 3) [Method for producing water-based polyurethane coating film (polyurethane dispersion (PUD))] The raw materials used in the synthesis of PUD are as follows. <Polyol> - Polyols described in Synthesis Examples (PCD-1 to PCD-9, rPCD-1, rPCD-2) - DMPA: 2,2-dimethylolpropionic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) - PTMG-2000: Polytetramethylene glycol (molecular weight 2000, manufactured by Mitsubishi Chemical Corporation) - rPCD-3: Polycarbonate diol having a molecular weight of 1000 made from 1,5-pentanediol and 1,6-hexanediol (manufactured by Asahi Chemical Industry Co., Ltd., T5651) <Polyisocyanate> - H １２ - MDI: 4,4' methylenebis (cyclohexyl isocyanate) (manufactured by Tokyo Chemical Industry Co., Ltd.) - IPDI: isophorone diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) <Base> - TEA: triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) <Solvent> - MEK: methyl ethyl ketone (manufactured by Tokyo Chemical Industry Co., Ltd.) <Chain extender> - EDA: ethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) - 2-methyl-1,5-diaminopentane (manufactured by Tokyo Chemical Industry Co., Ltd.) <Catalyst> - DBTDL: dibutyltin dilaurate (manufactured by Tokyo Chemical Industry Co., Ltd.) <Others> - purified water

[0103] (Synthesis Example 3-1) 160.0 g of PCD-1 as polyol (A), 106.3 g of MEK, and 100 ppm of DBTDL as a catalyst relative to the above two components were added to a 1000 mL separable flask, and the mixture was refluxed at 90°C for 15 minutes under nitrogen. １２37.5 g of methyl-MDI was added and stirred under reflux at 90°C until the NCO% reached 3.5±0.3% by mass, yielding an MEK solution of a urethane prepolymer containing terminal isocyanate groups. The NCO% is the mass ratio of the isocyanate groups possessed by the polyisocyanate relative to the total mass of the raw materials used in the prepolymerization process, and was determined by the method described in [Isocyanate Group Concentration (mass%)]. The resulting urethane prepolymer solution was cooled to 35°C, and 3.8 g of TEA was added while stirring at 500 rpm. Next, while maintaining the solution at 35°C and continuing stirring at 500 rpm, 296.2 g of pure water was added dropwise at a rate of 10 mL / min to obtain an emulsion (emulsified liquid). While maintaining the resulting emulsion at 35°C and continuing stirring at 500 rpm, 2.1 g of EDA was added, and a chain extension reaction was carried out. Finally, the solution after the chain extension reaction was heated under reduced pressure to distill off methyl ethyl ketone, yielding aqueous polyurethane PUD-1 of Synthesis Example 3. The aqueous polyurethane had a polyurethane solids concentration of 40%.

[0104] (Synthesis Examples 3-2 to 3-10, Comparative Synthesis Examples 1 to 6) Water-based polyurethanes PUD-2 to PUD-10 of Synthesis Examples 3-2 to 3-10 and rPUD-1 to rPUD-6 of Comparative Synthesis Examples 1 to 6 were obtained in the same manner as in Synthesis Example 3-1 using the raw materials and charged amounts shown in Table 1. The solids concentrations of polyurethane in the obtained water-based polyurethanes were as shown in Table 1.

[0105] (Synthesis Examples 3-11 to 3-12) Water-based polyurethanes PUD-11 and PUD-12 of Synthesis Examples 3-11 and 3-12 were obtained in the same manner as in Synthesis Example 3-1, using the raw materials and charged amounts shown in Table 2. The solids concentrations of polyurethane in the obtained water-based polyurethanes were as shown in Table 2.

[0106]

[0107]

[0108] The structure derived from formula (1) and carboxylate content in PUD-3 obtained in Synthesis Example 3-3 were quantified by the methods described in [Method for Quantifying Carboxyl Groups and Carboxylate Groups in Water-Based Polyurethane] and [Method for Qualitative and Quantitative Analysis of Hydrophilic Groups and Structures Derived from Formula (1) in Water-Based Polyurethane]. The carboxylate group content was 0.07 mass% and the structure derived from formula (1) was 88% relative to the urethane resin. It was also identified that the structure contained polyethylene glycol monomethyl ether.

[0109] (PUD coating film preparation process) (Examples 1 to 10, Comparative Examples 1 to 6) The obtained aqueous polyurethane was coated onto a polypropylene plate (JIS K6921) fitted with a formwork so that the dry film thickness was 300 μm, and the obtained aqueous polyurethane coating film was evaluated for various physical properties using the methods described below. The evaluation results are shown in Table 3.

[0110]

[0111] (PUD Coating Film Preparation Process) (Examples 11 and 12) The obtained water-based polyurethanes PUD-11 and 12 were each applied to a polypropylene plate (JIS K6921) fitted with a formwork so that the dry film thickness was 300 μm, and the various physical properties of the obtained water-based polyurethane coating films were evaluated by the methods described below. The evaluation results are shown in Table 4.

[0112] Comparative Example 7: 154.5 g of rPCD-3, 3.0 g of DMPA, and 133.4 g of MEK were added to a 1000 mL separable flask, and 100 ppm of DBTDL was added as a catalyst relative to the three components. The mixture was refluxed at 90°C for 15 minutes under nitrogen. Next, 59.8 g of IPDI and 30.5 g of PI-3 were added, and the mixture was stirred under reflux at 90°C until the NCO% reached 3.5±0.3% by mass, yielding an MEK solution of a urethane prepolymer containing terminal isocyanate groups. The NCO% is the ratio of the mass of isocyanate groups possessed by the polyisocyanate to the total mass of the raw materials used in the prepolymerization step, and was determined by the method described in [Isocyanate Group Concentration (mass%)]. The resulting urethane prepolymer solution was cooled to 35°C, and 2.3 g of TEA was added while stirring at 500 rpm. Next, while maintaining the solution at 35°C and continuing stirring at 500 rpm, 247.8 g of pure water was added dropwise at a rate of 10 mL / min to obtain an emulsion (emulsified liquid). While maintaining the resulting emulsion at 35°C and continuing stirring at 500 rpm, 4.5 g of EDA was added to carry out a chain extension reaction. Finally, the solution after the chain extension reaction was heated under reduced pressure to distill off methyl ethyl ketone, yielding aqueous polyurethane rPUD-7 of Synthesis Example 3-1. The solids concentration of polyurethane in the aqueous polyurethane was 50%. rPUD-7 has the same constituent components and their ratios as PUD-5, but differs in its manufacturing method in that PI-3 was used as a polyisocyanate during PUD synthesis. The evaluation results are shown in Table 5.

[0113] Comparative Example 8: 21.5 g of UH-200, 1.5 g of DMPA, 65.3 g of MEK, 11.3 g of 1,4-butanediol, and 10.6 g of PTMG-2000 were added to a 1000 mL separable flask, and 100 ppm of DBTDL was added as a catalyst relative to the total of the above components. The mixture was refluxed at 90°C for 15 minutes under nitrogen. Next, 62.8 g of IPDI and 11.7 g of PI-3 were added, and the mixture was refluxed at 90°C and stirred until the NCO% reached 3.5±0.3% by mass, yielding an MEK solution of a urethane prepolymer containing terminal isocyanate groups. The NCO% is the ratio of the mass of isocyanate groups possessed by the polyisocyanate to the total mass of the raw materials used in the prepolymerization step, and was determined by the method described in [Isocyanate Group Concentration (mass%)]. The resulting urethane prepolymer solution was cooled to 35°C, and 1.1 g of TEA was added while stirring at 500 rpm. Next, while maintaining the solution at 35°C and continuing stirring at 500 rpm, 181.8 g of pure water was added dropwise at a rate of 10 mL / min to obtain an emulsion (emulsion). While maintaining the resulting emulsion at 35°C and continuing stirring at 500 rpm, 4.1 g of EDA was added to carry out a chain extension reaction. Finally, the solution after the chain extension reaction was heated under reduced pressure to remove methyl ethyl ketone, yielding aqueous polyurethane rPUD-8 of Synthesis Example 3-1. The solids concentration of polyurethane in the aqueous polyurethane was 40%. rPUD-8 has the same constituent components and their ratios as rPUD-4, but differs in its manufacturing method in that PI-3 was used as the polyisocyanate during PUD synthesis. The evaluation results are shown in Table 5.

[0114]

[0115]

[0116] [Measurement of solid content of PUD] Mass of aluminum dish w ０ Next, the PUD obtained in each of the Examples and Comparative Examples is weighed into a weighed aluminum dish, and the mass is recorded. The mass at that time is referred to as w １ The aluminum dish on which the PUD is placed is baked in an oven at 105°C for 3 hours, and then the mass of the aluminum dish is weighed again. The mass at this time is w ２The solid content of the PUD is calculated using the following formula: (Solid content) = (w ２ -w ０ ) / (w １ -w ０ )

[0117] [Evaluation of PUD storage stability] The PUD solution was sealed in a glass container and the particle size of the dispersed particles was measured before and after a 4-week heating test in an incubator at 50°C. Note that a "Nanotrac UPA" manufactured by Nikkiso Co., Ltd. was used to measure the volume average particle size of the water-based polyurethane. The evaluation criteria are as shown below, and it was determined that the smaller the change in particle size, the better the storage stability (aqueous dispersion stability). (Evaluation criteria) A: The rate of change in particle size is less than 2% B: The rate of change in particle size is 2% or more but less than 5% C: The rate of change in particle size is 5% or more

[0118] [Evaluation of quick-drying property] A water-based polyurethane coating film was obtained by leaving it at room temperature for 6 hours and then baking it at 80° C. for 1 hour, and a water-based polyurethane coating film was obtained by leaving it at room temperature for 24 hours and then baking it at 80° C. for 3 hours. The breaking strength of the water-based polyurethane coating film baked at room temperature for 6 hours and at 80° C. for 1 hour in the following tensile test was measured. １ The breaking strength of the water-based polyurethane coating film after baking at room temperature for 24 hours and at 80°C for 3 hours was measured in N. ２ Then, the quick-drying factor F = N １ / N ２ The higher the quick-drying factor F, the higher the quality of the coating film that can be formed in a short time, and the better the quick-drying property.

[0119] [Tensile Test] A 1 cm x 10 cm strip sample was prepared from the aqueous polyurethane coating film, and a tensile test was carried out using a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon, Model RTE-1210") at a chuck distance of 20 mm, a tensile speed of 100 mm / min, and a temperature of 23°C (relative humidity of 55%) to measure the 100% modulus and breaking strength. In evaluating flexibility, a low 100% modulus is preferable from the viewpoint of texture, etc.

[0120] [Chemical Resistance Test] The water-based polyurethane coating film was left to stand at room temperature for 6 hours, and then baked at 80°C for 1 hour, and then cut out to prepare a strip sample of 1 cm x 10 cm, and the mass was measured. １ The cut sample was immersed in oleic acid at 23°C for seven days. After that, the sample was taken out of the oleic acid, the oleic acid was wiped off with a Kimtowel, and the mass was measured again. The mass at this time was defined as w ２ Swelling ratio S = (w ２ -w １ ) / w １ The swelling ratio was calculated from the above. The lower the swelling ratio, the better the chemical resistance of the urethane film.

[0121] (Flexibility Evaluation) The flexibility of the aqueous urethane coatings PUD-5, rPUD-4, 7, and 8 obtained above was evaluated using the tensile test described below. The evaluation results are shown in Table 6. PUD-5 and rPUD-4, and rPUD-7 and rPUD-8 have the same constituent components and their ratios, but the timing of adding polyisocyanate PI-3 differs. PUD-5 and rPUD-7 are used during PCD synthesis, while rPUD-4 and rPUD-8 are used during PUD synthesis. As shown in Table 6, the use of PI-3 during PCD synthesis resulted in a flexible coating.

[0122]

[0123] One possible mechanism by which differences in manufacturing methods affect flexibility is the effect of the sequence of the constituent components in the PUD. Specifically, adding a polyisocyanate with a hydrophilic group during PCD synthesis ensures that the polyisocyanate reacts with the polymer PCD. However, if added during PUD synthesis, the polyisocyanate may react not only with the PCD but also with low-molecular-weight monomers such as DMPA. Both polyisocyanate structures with high cohesive strength and low-molecular-weight monomers that increase the concentration of urethane groups in the urethane impair the flexibility of the urethane. In the latter case, it is thought that a non-flexible component is generated by the reaction of the polyisocyanate structure with DMPA, impairing flexibility.

[0124] The present invention can provide an aqueous polyurethane and a method for producing the same that are capable of forming a urethane film that has excellent storage stability and quick-drying properties and that has excellent chemical resistance even when formed in a short period of time. Therefore, the present invention can be widely and effectively used in the field of polyurethane or aqueous polyurethane materials.

Claims

1. A water-based polyurethane comprising polyurethane and water, the polyurethane having a main chain having a urethane bond and a structure represented by the following formula (1), and a side chain branched from the main chain, the side chain having a hydrophilic group; the content of the structure represented by the following formula (1) relative to the total mass of the polyurethane is 35% by mass or more; the polyurethane contains 0.00 to 0.85% by mass of carboxyl groups and carboxylate groups relative to the total mass of the polyurethane; and the solids concentration of the polyurethane in the water dispersion is 35% by mass or more. (In the formula, R may be the same or different and is a linear, branched or alicyclic divalent hydrocarbon group having 2 to 20 carbon atoms which may be optionally substituted with a heteroatom; n is an integer of 1 to 50; and * is a bond.) 2. The aqueous polyurethane according to claim 1, wherein the polyurethane is an addition polymerization product of polyol (A) and polyisocyanate (B), the polyol (A) includes polyol (a-1) having a main chain having a structure represented by the following formula (1) and a side chain branched from the main chain, the side chain having a hydrophilic group, and the content of the structure represented by the following formula (1) relative to the total mass of the polyol (a-1) is 50 mass% or more. (In the formula, R may be the same or different and is a linear, branched or alicyclic divalent hydrocarbon group having 2 to 20 carbon atoms which may be optionally substituted with a heteroatom; n is an integer of 1 to 50; and * is a bond.) 3. The aqueous polyurethane according to claim 2, wherein the hydrophilic group possessed by the polyol (a-1) is a nonionic hydrophilic group, and the polyol (A) further comprises a polyol (a-2) having a carboxyl group or a carboxylate group.

4. The aqueous polyurethane according to claim 3, wherein the hydrophilic group possessed by the polyol (a-1) is a polyalkylene glycol.

5. The aqueous polyurethane according to claim 2, wherein the polyol (a-1) has at least one skeleton Z selected from the group consisting of an isocyanurate skeleton, an iminooxadiazinedione skeleton, an allophanate skeleton, and a biuret skeleton in the main chain, and the side chain having the hydrophilic group is branched from the skeleton Z.

6. The water-based polyurethane according to claim 5, wherein said skeleton Z comprises at least one isocyanurate skeleton.

7. The water-based polyurethane according to claim 1, wherein the polyurethane has an average particle size of 300 nm or less.

8. A method for producing an aqueous polyurethane, comprising the step of reacting a polyol (A) with a polyisocyanate (B) to synthesize an aqueous polyurethane dispersion containing polyurethane and water, wherein the polyol (A) comprises polyol (a-1) having a main chain having a structure represented by the following formula (1) and a side chain branched from the main chain, the side chain having a hydrophilic group, the content of the structure represented by the following formula (1) relative to the total mass of the polyol (a-1) being 50 mass% or more, and the solids concentration of the polyurethane in the aqueous dispersion being 35 mass% or more. (In the formula, R may be the same or different and is a linear, branched or alicyclic divalent hydrocarbon group having 2 to 20 carbon atoms which may be optionally substituted with a heteroatom; n is an integer of 1 to 50; and * is a bond.)

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