Polyurethane water-based dispersion, water-based polyurethane resin set, water-based polyurethane resin composition, and polyurethane resin

Abstract

Provided is a polyurethane water-based dispersion having excellent adhesion to resins, heat resistance, and low tack.　A polyurethane water-based dispersion according to an embodiment is used by being mixed with a crosslinking agent that reacts with carboxy groups and is obtained by dispersing a carboxy group-containing polyurethane resin in a water-based dispersion medium. The carboxy group-containing polyurethane resin contains a structure derived from a hydrogenated polybutadiene polyol, a structure derived from a carboxy group-containing polyol, a structure derived from an alicyclic polyisocyanate, and a structure derived from a trifunctional amine chain extender, and has an acid value of 5-50 mg KOH / g.

Description

Polyurethane aqueous dispersion, aqueous polyurethane resin set, aqueous polyurethane resin composition, and polyurethane resin

[0001] An embodiment of the present invention relates to a polyurethane aqueous dispersion, an aqueous polyurethane resin set formed by combining the polyurethane aqueous dispersion and a crosslinking agent, an aqueous polyurethane resin composition containing the polyurethane aqueous dispersion and a crosslinking agent, and a crosslinked polyurethane resin obtained using the aqueous polyurethane resin composition.

[0002] A polyurethane aqueous dispersion obtained by dispersing a polyurethane resin in an aqueous dispersion medium is widely used in paints, inks, adhesives, etc. For example, Patent Document 1 discloses that an aqueous dispersion of a carboxyl group-containing polyurethane resin obtained by reacting a hydrogenated polybutadiene polyol, a carboxyl group-containing polyol, and a polyisocyanate is used in a coating agent applied to a polyester substrate.

[0003] Patent Document 2 discloses an aqueous dispersion of a carboxyl group-containing polyurethane resin obtained by reacting a hydroxyl group-containing compound, an isocyanate group-containing compound, an acidic group-containing polyol, and a chain extender, which is used as a sealing agent for electrical and electronic components. It is disclosed that a hydrogenated polybutadiene polyol is used as the hydroxyl group-containing compound and isophorone diisocyanate is used as the isocyanate group-containing compound.

[0004] Japanese Patent No. 7500810, Japanese Patent No. 6285046

[0005] In an aqueous dispersion containing a carboxyl group-containing polyurethane resin as described above, further improvement in adhesion and heat resistance to resins such as polyester resin is required. Also, it may be required that the tack (adhesiveness) of the coating film is low, that is, low tackiness is required.

[0006] In an aqueous dispersion containing a carboxyl group-containing polyurethane resin, the water resistance and the like can be improved by adding a crosslinking agent that reacts with the carboxyl group, such as a carbodiimide compound or an oxazoline compound, and crosslinking the polyurethane resin. However, further improvement in the above performance is required.

[0007] In view of the above, the embodiments of the present invention aim to provide a polyurethane aqueous dispersion that is excellent in adhesion to resin, heat resistance, and low tack.

[0008] The present invention includes the embodiments shown below. [1] A polyurethane aqueous dispersion comprising a carboxyl group-containing polyurethane resin dispersed in an aqueous dispersion medium and used in combination with a crosslinking agent that reacts with carboxyl groups, wherein the carboxyl group-containing polyurethane resin comprises a structure derived from a hydrogenated polybutadiene polyol, a structure derived from a carboxyl group-containing polyol, a structure derived from an alicyclic polyisocyanate, and a structure derived from a trifunctional amine chain extender, and has an acid value of 5 to 50 mg KOH / g.

[0009] [2] A set of aqueous polyurethane resin comprising: an aqueous polyurethane dispersion in which a carboxyl group-containing polyurethane resin is dispersed in an aqueous dispersion medium, wherein the carboxyl group-containing polyurethane resin includes a structure derived from a hydrogenated polybutadiene polyol, a structure derived from a carboxyl group-containing polyol, a structure derived from an alicyclic polyisocyanate, and a structure derived from a trifunctional amine chain extender, and has an acid value of 5 to 50 mg KOH / g; and a crosslinking agent that reacts with a carboxyl group.

[0010] [3] A water-based dispersion medium, a carboxyl group-containing polyurethane resin dispersed in the water-based dispersion medium, comprising a structure derived from a hydrogenated polybutadiene polyol, a structure derived from a carboxyl group-containing polyol, a structure derived from an alicyclic polyisocyanate, and a structure derived from a trifunctional amine chain extender, having an acid value of 5 to 50 mg KOH / g, and a crosslinking agent that reacts with carboxyl groups, comprising: an aqueous dispersion medium, a carboxyl group-containing polyurethane resin composition comprising: an aqueous dispersion medium, a carboxyl group-containing polyurethane resin comprising a structure derived from a hydrogenated polybutadiene polyol, a structure derived from a carboxyl group-containing polyol, a structure derived from an alicyclic polyisocyanate, and a structure derived from a trifunctional amine chain extender, and having an acid value of 5 to 50 mg KOH / g, and a crosslinking agent that reacts with carboxyl groups.

[0011] [4] The aqueous polyurethane dispersion according to [1], the aqueous polyurethane resin set according to [2], or the aqueous polyurethane resin composition according to [3], wherein the trifunctional amine chain extender comprises a trifunctional aliphatic amine chain extender.

[0012] [5] The aqueous polyurethane dispersion according to [1] or [4], the aqueous polyurethane resin set according to [2] or [4], or the aqueous polyurethane resin composition according to [3] or [4], wherein the crosslinking agent comprises at least one selected from the group consisting of oxazoline compounds, carbodiimide compounds, and epoxy compounds.

[0013] [6] The polyurethane aqueous dispersion according to [1], [4] or [5], the aqueous polyurethane resin set according to [2], [4] or [5], or the aqueous polyurethane resin composition according to [3], [4] or [5], wherein the amount of the crosslinking agent is 0.1 to 10 parts by mass per 100 parts by mass of the carboxyl group-containing polyurethane resin.

[0014] [7] A crosslinked polyurethane resin obtained by drying the aqueous polyurethane resin composition described in [3], [4], [5], or [6].

[0015] According to embodiments of the present invention, it is possible to provide a polyurethane aqueous dispersion that exhibits excellent adhesion to resin, heat resistance, heat and humidity resistance, and low tack.

[0016] The polyurethane aqueous dispersion according to this embodiment (hereinafter sometimes simply referred to as "aqueous dispersion") is obtained by dispersing a carboxyl group-containing polyurethane resin (hereinafter sometimes simply referred to as "polyurethane resin") in an aqueous dispersion medium. Therefore, the aqueous dispersion contains the carboxyl group-containing polyurethane resin and the aqueous dispersion medium.

[0017] [Carboxyloid-containing polyurethane resin] In this embodiment, the carboxyloid-containing polyurethane resin includes a structure derived from a hydrogenated polybutadiene polyol, a structure derived from a carboxyloid-containing polyol, a structure derived from an alicyclic polyisocyanate, and a structure derived from a trifunctional amine chain extender. More specifically, the polyurethane resin according to this embodiment is obtained by reacting a polyol component (A) containing a hydrogenated polybutadiene polyol (A1) and a carboxyloid-containing polyol (A2) with an isocyanate component (B) containing an alicyclic polyisocyanate (B1), and extending the chain with a chain extender (C) containing a trifunctional amine chain extender (C1). Therefore, the polyurethane resin includes a structure derived from a polyol component (A), a structure derived from an isocyanate component (B), and a structure derived from a chain extender (C). The structure derived from the polyol component (A) includes a structure derived from a hydrogenated polybutadiene polyol (A1) and a structure derived from a carboxyl group-containing polyol (A2). The structure derived from the isocyanate component (B) includes a structure derived from an alicyclic polyisocyanate (B1). The structure derived from the chain extender (C) includes a structure derived from a trifunctional amine chain extender (C1).

[0018] Hydrogenated polybutadiene polyol (A1) has a structure obtained by hydrogenating polybutadiene polyol, in which some or all of the unsaturated double bonds contained in polybutadiene polyol are hydrogenated. Preferably, the polybutadiene polyol has a polybutadiene structure in which 1,4-bonds, 1,2-bonds, or a mixture thereof are present in the molecule, and has hydroxyl groups at the molecular ends.

[0019] The degree of hydrogenation of the hydrogenated polybutadiene polyol (A1) is not particularly limited; for example, the iodine value may be 50 g / 100 g or less, or 30 g / 100 g or less. In this specification, the iodine value is measured in accordance with JIS K0070:1992.

[0020] The number-average molecular weight (Mn) of the hydrogenated polybutadiene polyol (A1) is not particularly limited, but is preferably 700 to 2500, and more preferably 1000 to 1800.

[0021] In this specification, the number-average molecular weight (Mn) is measured by GPC (gel permeation chromatography) and calculated using a calibration curve with standard polystyrene. Specifically, the GPC conditions are as follows: Column: TSKgel G4000HXL + TSKgel G3000HXL + TSKgel G2000HXL + TSKgel G1000HXL + TSKgel G1000HXL manufactured by Tosoh Corporation; Mobile phase: THF (tetrahydrofuran); Mobile phase flow rate: 1.0 mL / min; Column temperature: 40°C; Sample injection volume: 50 μL; Sample concentration: 0.2% by mass.

[0022] The number of functional groups in hydrogenated polybutadiene polyol (A1) is not particularly limited, but is preferably 1.5 to 2.8, and more preferably 1.7 to 2.5. Here, the number of functional groups is the number of hydroxyl groups per molecule of hydrogenated polybutadiene polyol (A1), and is calculated by the following formula. The hydroxyl value in the formula is measured according to Method A of JIS K1557-1:2007. Number of functional groups = {(Hydroxyl value) × (Mn)} / (56.1 × 1000)

[0023] The amount of hydrogenated polybutadiene polyol (A1) in polyol component (A) is not particularly limited, but is preferably 70 to 99% by mass, more preferably 75 to 98% by mass, more preferably 80 to 96% by mass, and even more preferably 85 to 95% by mass, based on 100% by mass of polyol component (A).

[0024] In this specification, the amount of each component constituting polyol component (A) is calculated using 100% by mass of polyol component (A) as the standard, with the carboxyl group of the carboxyl group-containing polyol (A2) being in the acid form. Similarly, the amount of carboxyl group-containing polyol (A2) is also calculated with the carboxyl group being in the acid form.

[0025] In this embodiment, the polyurethane resin has carboxyl groups, and by mixing it with a crosslinking agent that reacts with carboxyl groups and heating and drying it, it can react with the crosslinking agent to form a crosslinked structure. Unless otherwise specified, the concept of carboxyl groups includes not only the acidic form (-COOH) but also the saltic form, i.e., a carboxylic acid base (-COOX, where X is a cation that forms a salt with a carboxylic acid), and acidic and saltic forms may be present together.

[0026] Examples of carboxylic acid base salts include alkali metal salts such as sodium salts and potassium salts, alkaline earth metal salts such as magnesium salts and calcium salts, ammonium salts, amine salts (primary amine salts, secondary amine salts, tertiary amine salts), and quaternary ammonium salts. Among these, salts of volatile bases such as ammonium salts and amine salts are preferred. When a volatile base is used, it vaporizes during the heating and drying of the aqueous dispersion, thereby improving the heat resistance and moisture resistance of the polyurethane resin obtained by reaction with the crosslinking agent.

[0027] Examples of carboxyl group-containing polyols (A2) used to introduce carboxyl groups include dimethylolalkanoates such as dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolvaleric acid, carboxylic acid-containing compounds such as dihydroxymaleic acid, 2,6-dihydroxybenzoic acid, and tartaric acid, and their derivatives and salts. Any one of these may be used, or two or more may be used in combination.

[0028] The amount of carboxyl group-containing polyol (A2) in polyol component (A) is not particularly limited, but is preferably 0.5 to 25% by mass, more preferably 1 to 20% by mass, more preferably 2 to 16% by mass, and even more preferably 3 to 12% by mass, based on 100% by mass of polyol component (A).

[0029] The polyol component (A) preferably further contains a low molecular weight polyol (A3) with three or more functional groups. Therefore, the carboxyl group-containing polyurethane resin preferably contains a structure derived from the low molecular weight polyol (A3). By including the low molecular weight polyol (A3), the effects of improving heat resistance and low tack can be enhanced.

[0030] Examples of low molecular weight polyols (A3) include trifunctional polyols such as glycerin, trimethylolpropane, and triethanolamine, and tetrafunctional polyols such as pentaerythritol and diglycerin. Any one of these may be used, or two or more may be used in combination. As the low molecular weight polyol (A3), a polyhydric alcohol (more preferably a trihydric alcohol) with a molecular weight of 300 or less (more preferably 200 or less) is preferably used.

[0031] The amount of low molecular weight polyol (A3) in polyol component (A) is not particularly limited, and may be 0 to 7% by mass, 0.3 to 6% by mass, 0.6 to 5% by mass, or 0.9 to 4% by mass, based on 100% by mass of polyol component (A).

[0032] The polyol component (A) may consist only of hydrogenated polybutadiene polyol (A1) and carboxyl group-containing polyol (A2), or only of hydrogenated polybutadiene polyol (A1), carboxyl group-containing polyol (A2), and low molecular weight polyol (A3). The polyol component (A) may also contain polyols other than those mentioned above, as long as the effects of this embodiment are achieved. Examples of such other polyols include polymer polyols such as polyester polyols, polyether polyols, polycarbonate polyols, and hydrogenated polybutadiene polyols, and low molecular weight diols such as ethylene glycol, propylene glycol, propanediol, butanediol, pentanediol, 3-methyl-1,5-pentanediol, hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, bisphenol A, bisphenol F, bisphenol S, and hydrogenated bisphenol A.

[0033] In this embodiment, the isocyanate component (B) includes an alicyclic polyisocyanate (B1). This improves heat resistance, heat and humidity resistance, and low tack.

[0034] Examples of alicyclic polyisocyanates (B1) include isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis(isocyanate-methyl)cyclohexane, and modified forms thereof such as isocyanurates, adducts, biuret compounds, allophenates, and carbodiimides. Any one of these may be used, or two or more may be used in combination.

[0035] The isocyanate component (B) may consist solely of an alicyclic polyisocyanate (B1), but may also include other polyisocyanates such as aromatic polyisocyanates, aromatic aliphatic polyisocyanates, and / or aliphatic polyisocyanates, as long as the effects of this embodiment are achieved. The amount of alicyclic polyisocyanate relative to 100% by mass of isocyanate component (B) is preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.

[0036] The polyurethane resin according to this embodiment is obtained by reacting a urethane prepolymer, which is obtained by reacting the polyol component (A) and the isocyanate component (B), with a chain extender (C) containing a trifunctional amine chain extender (C1). By extending the chain using the trifunctional amine chain extender (C1), heat resistance, heat and humidity resistance, and low tack properties can be improved.

[0037] The trifunctional amine chain extender (C1) is an amine compound having three primary and / or secondary amino groups in one molecule that are reactive with the isocyanate group of the urethane prepolymer. It is preferable to use an aliphatic amine compound, i.e., a trifunctional aliphatic amine chain extender (C1), such as diethylenetriamine, dipropylenetriamine, or dibutylentriamine. These may be used individually or in combination of two or more.

[0038] The chain extender (C) may consist solely of the trifunctional amine chain extender (C1), but may also include other chain extenders, such as a bifunctional amine chain extender, as long as the effects of this embodiment are achieved. Furthermore, when the urethane prepolymer is dispersed in an aqueous dispersion medium, the chain may be extended by water, in which case the water used as the dispersion medium may also act as the chain extender. However, it is preferable to add the trifunctional amine chain extender (C1) as quickly as possible during the dispersion to suppress chain extension by water. The amount of the trifunctional amine chain extender (C1) (preferably a trifunctional aliphatic amine chain extender) relative to 100% by mass of the chain extender (C) is preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass.

[0039] In this embodiment, the acid value of the polyurethane resin is 5 to 50 mgKOH / g. An acid value of 5 mgKOH / g or higher improves adhesion to the resin and low tack. An acid value of 50 mgKOH / g or lower improves heat resistance and heat and humidity resistance. The acid value of the polyurethane resin is more preferably 10 to 40 mgKOH / g, and even more preferably 15 to 30 mgKOH / g.

[0040] In this specification, the acid value can be determined from the amount of KOH (mg) required to neutralize the carboxyl groups contained in 1 g of polyurethane resin, in accordance with JIS K0070-1992. Note that if the polyurethane resin is a salt of a volatile base, the volatile base will vaporize when the mass of the polyurethane resin is measured. Therefore, the acid value of the polyurethane resin is calculated based on the mass of the non-volatile acidic polyurethane resin. Thus, the mass of the polyurethane resin in this specification refers to the mass of the non-volatile components.

[0041] The content of each structure in the polyurethane resin may be set, for example, as follows. Here, the amount of each structure in the polyurethane resin is the amount as a component that serves as the raw material for that structure. For example, if the amount of a structure derived from hydrogenated polybutadiene polyol (A1), it is the amount as hydrogenated polybutadiene polyol (A1). In the synthesis of polyurethane resin, all of the components that serve as the raw materials for each structure are generally incorporated to constitute the polyurethane resin. Therefore, in this specification, the value (mass%) calculated from the blending amount of each component that serves as the raw material is used as the amount of each structure in the polyurethane resin.

[0042] The amount of structure derived from polyol component (A) in the polyurethane resin is not particularly limited; for example, it may be 50 to 85% by mass or 55 to 80% by mass per 100% by mass of the polyurethane resin. The amount of structure derived from hydrogenated polybutadiene polyol (A1) is not particularly limited; for example, it may be 40 to 80% by mass or 45 to 75% by mass per 100% by mass of the polyurethane resin. The amount of structure derived from carboxyl group-containing polyol (A2) is not particularly limited; for example, it may be 1 to 15% by mass or 2 to 10% by mass per 100% by mass of the polyurethane resin. The amount of structure derived from low molecular weight polyol (A3) is not particularly limited; for example, it may be 0 to 5% by mass or 1 to 3% by mass per 100% by mass of the polyurethane resin.

[0043] The amount of the structure derived from the isocyanate component (B) in the polyurethane resin is not particularly limited. For example, it may be 12 to 49% by mass, or 18 to 44% by mass, based on 100% by mass of the polyurethane resin. The amount of the structure derived from the alicyclic polyisocyanate (B1) is not particularly limited. For example, it may be 12 to 49% by mass, or 18 to 44% by mass, based on 100% by mass of the polyurethane resin.

[0044] The amount of the structure derived from the chain extender (C) in the polyurethane resin is not particularly limited. For example, it may be 0.05 to 8% by mass, or 0.1 to 5% by mass, based on 100% by mass of the polyurethane resin. The amount of the structure derived from the trifunctional amine chain extender (C1) is not particularly limited. For example, it may be 0.05 to 8% by mass, or 0.1 to 5% by mass, based on 100% by mass of the polyurethane resin.

[0045] [Aqueous dispersion medium] The aqueous dispersion medium is a dispersion medium containing water, and examples thereof include water, or a mixed medium of water and a hydrophilic organic solvent. From the viewpoint of the dispersion stability of the aqueous dispersion, water is preferable as the aqueous dispersion medium, and an organic solvent may be contained but is preferably in a small amount. In one embodiment, it is preferable that the aqueous dispersion medium contains 70% by mass or more of water, more preferably 80% by mass or more of water, still more preferably 90% by mass or more of water, and water may be 100% by mass. That is, in the aqueous dispersion medium, the mass ratio of water / hydrophilic organic solvent is preferably 70 / 30 to 100 / 0, more preferably 80 / 20 to 100 / 0, and still more preferably 90 / 10 to 100 / 0.

[0046] As the hydrophilic organic solvent, various organic solvents soluble in water are used. For example, lower monohydric alcohols such as methanol, ethanol, and propanol, polyhydric alcohols such as ethylene glycol and glycerin, aprotic polar solvents such as N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, acetonitrile, and butyl cellosolve can be mentioned.

[0047] [Polyurethane aqueous dispersion] A polyurethane aqueous dispersion is an aqueous dispersion in which a carboxy group-containing polyurethane resin is dispersed in an aqueous dispersion medium. The content of the carboxy group-containing polyurethane resin in the polyurethane aqueous dispersion is not particularly limited, and may be, for example, 1 to 60% by mass or 5 to 50% by mass based on the total mass of the aqueous dispersion.

[0048] The size of the particles of the carboxy group-containing polyurethane resin in the polyurethane aqueous dispersion is not particularly limited, and for example, the average particle diameter may be 0.001 to 0.5 μm. Here, the average particle diameter is the 50% cumulative particle diameter (d50) measured using "Microtrac UPA-UZ152" manufactured by Nikkiso Co., Ltd.

[0049] The polyurethane aqueous dispersion may contain other components as long as its effects are not impaired. Examples of other components include wetting agents, pigments, ultraviolet absorbers, light stabilizers, surface modifiers, inorganic fillers, organic fillers, dispersion aids, preservatives, rust inhibitors, antioxidants, silane coupling agents, defoamers, viscosity regulators, antistatic agents, etc. These other components may be contained in the resin particles as the dispersed substance, or may be contained in a separately dispersed or dissolved state in the aqueous dispersion medium. For example, in the polyurethane aqueous dispersion, the resin particles as the dispersed substance may be composed only of the carboxy group-containing polyurethane resin, or may be composed of the carboxy group-containing polyurethane resin together with other components. In addition, the polyurethane aqueous dispersion may contain a surfactant for dispersing the carboxy group-containing polyurethane resin in the aqueous dispersion medium.

[0050] The method for producing the polyurethane aqueous dispersion is not particularly limited. For example, it may be produced by the following steps 1 to 4. Step 1: A step of synthesizing an isocyanate group-containing urethane prepolymer by reacting a polyol component (A) containing a hydrogenated polybutadiene polyol (A1) and a carboxyl group-containing polyol (A2) with an isocyanate component (B) containing an alicyclic polyisocyanate (B1). Step 2: A step of neutralizing the carboxyl groups of the isocyanate group-containing urethane prepolymer. Step 3: A step of dispersing the isocyanate group-containing urethane prepolymer in an aqueous dispersion medium. Step 4: A step of extending the chains of the isocyanate group-containing urethane prepolymer with a chain extender (C) containing a trifunctional amine chain extender (C1).

[0051] In step 1, the isocyanate component (B) may be used in such a stoichiometric excess that the amount of isocyanate groups is greater than the amount of hydroxyl groups contained in the polyol component (A), for example, that the equivalent ratio of hydroxyl groups to isocyanate groups (NCO / OH) is 1.05 to 1.70 (more preferably 1.10 to 1.60).

[0052] Furthermore, in step 1, the reaction between the polyol component (A) and the isocyanate component (B) may be carried out without an organic solvent, or in an organic solvent that does not have active hydrogen groups, such as methyl ethyl ketone or acetone.

[0053] In step 2, examples of bases used to neutralize the carboxyl group include non-volatile bases such as sodium hydroxide and potassium hydroxide, tertiary amines such as trimethylamine, triethylamine, dimethylethanolamine, methyldiethanolamine, and triethanolamine, and volatile bases such as ammonia.

[0054] In step 3, the method for dispersing the urethane prepolymer in an aqueous dispersion medium is not particularly limited. Examples include (i) adding the urethane prepolymer or a solution thereof while stirring the aqueous dispersion medium with a homogenizer or homomixer, and (ii) adding the aqueous dispersion medium while stirring the urethane prepolymer or a solution thereof with a homogenizer or homomixer.

[0055] In step 4, the amount of chain extender (C) (preferably trifunctional amine chain extender (C1)) added is not particularly limited, but is preferably 0.05 to 8 parts by mass, and more preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the total of polyol component (A) and isocyanate component (B).

[0056] The neutralization in step 2 and the dispersion in step 3 may be carried out in this order, but two or more steps may be carried out simultaneously. For example, if an aqueous solution of a base is used to neutralize the carboxyl group, the dispersion in the aqueous dispersion medium may be carried out at the same time as the neutralization. Furthermore, it is preferable to carry out the chain extension in step 4 by adding the chain extension agent as quickly as possible after adding the aqueous dispersion medium to the urethane prepolymer in step 3. If the reaction between the polyol and polyisocyanate in step 1 is carried out in an organic solvent, the organic solvent may be removed after dispersion in the aqueous dispersion medium in step 4.

[0057] The pH of the polyurethane aqueous dispersion is not particularly limited; for example, at 25°C, the pH may be 6.0 to 9.0 or 6.5 to 8.5.

[0058] The polyurethane aqueous dispersion according to this embodiment is used in combination with a crosslinking agent that reacts with carboxyl groups. By mixing with the crosslinking agent and heating and drying, the polyurethane resin is crosslinked, thereby obtaining a polyurethane resin with excellent adhesion to resins such as polyester resins, heat resistance, heat- and moisture resistance, and low tack. The polyurethane aqueous dispersion may be a component of an aqueous polyurethane resin set or a component of an aqueous polyurethane resin composition. That is, an aqueous polyurethane resin set according to one embodiment is a combination of the above-mentioned polyurethane aqueous dispersion and a crosslinking agent that reacts with carboxyl groups. Furthermore, an aqueous polyurethane resin composition according to one embodiment includes an aqueous dispersion medium, a carboxyl group-containing polyurethane resin dispersed in the aqueous dispersion medium, and a crosslinking agent that reacts with carboxyl groups.

[0059] [Crosslinking agent] The crosslinking agent is not particularly limited as long as it is a compound that can crosslink polyurethane resin by reacting with a carboxyl group, but it is preferable to use at least one selected from the group consisting of oxazoline compounds, carbodiimide compounds, and epoxy compounds.

[0060] Oxazoline compounds used as crosslinking agents are compounds containing multiple oxazoline groups within their molecule, and they form a crosslinked structure (amide ester bond) by reacting with the carboxyl groups of polyurethane resins. The oxazoline group is a five-membered heterocyclic group containing an oxygen atom and a nitrogen atom, represented by the following formula, and may have substituents as long as they can react with the carboxyl group to form an amide ester bond.

[0061] As the oxazoline compound, an oxazoline group-containing water-soluble polymer is preferred, and more preferably, an oxazoline group-containing water-soluble acrylic polymer in which the polymer main chain is an acrylic polymer. Here, an acrylic polymer refers to a polymer that contains acrylic monomers such as (meth)acrylic acid, (meth)acrylic acid esters, and acrylonitrile as the main raw materials.

[0062] The oxazoline equivalent of an oxazoline compound is not particularly limited and may be, for example, 100 to 300 or 150 to 250. Here, oxazoline equivalent refers to the chemical formula weight per mole of oxazoline groups.

[0063] The number-average molecular weight (Mn) of the oxazoline compound is not particularly limited and may be, for example, 5,000 to 100,000, 10,000 to 80,000, or 15,000 to 50,000.

[0064] Oxazoline compounds, such as "Epocross WS-300," "Epocross WS-500," and "Epocross WS-700" manufactured by Nippon Shokubai Co., Ltd., are readily available commercially and can be used.

[0065] Carbodiimide compounds used as crosslinking agents are compounds containing multiple carbodiimide groups (-N=C=N-) within their molecule, and they form a crosslinked structure by reacting with the carboxyl groups of polyurethane resin (A).

[0066] As carbodiimide compounds, aqueous polycarbodiimides are preferred, which are obtained by introducing a hydrophilic segment into a polycarbodiimide having multiple carbodiimide groups in the molecule. Examples of such aqueous polycarbodiimides include the water-soluble types "Carbodilite V-02," "Carbodilite V-02-L2," "Carbodilite SV-02," "Carbodilite V-04," and "Carbodilite V-10," and the emulsion / dispersion types "Carbodilite E-02" and "Carbodilite E-05" (all manufactured by Nisshinbo Chemical Co., Ltd.).

[0067] The NCN equivalent of the carbodiimide compound is not particularly limited and may be, for example, 300 to 600 or 350 to 500. Here, the NCN equivalent represents the chemical formula weight per mole of carbodiimide groups.

[0068] Epoxy compounds used as crosslinking agents are compounds containing multiple epoxy groups within their molecules, and they form a crosslinked structure by reacting with the carboxyl groups of polyurethane resin (A).

[0069] Preferred epoxy compounds are water-soluble epoxy compounds in which the hydroxyl groups of polyols such as sorbitol, glycerin, diglycerin, and polyglycerin have been converted into glycidyl ethers. Specific examples of epoxy compounds include sorbitol polyglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, and polyglycerol polyglycidyl ether. Any one of these may be used, or two or more may be used in combination.

[0070] The epoxy equivalent of the epoxy compound is not particularly limited and may be, for example, 100 to 250 or 130 to 200. Here, epoxy equivalent refers to the chemical formula weight per mole of epoxy groups.

[0071] The amount of crosslinking agent (preferably at least one selected from the group consisting of oxazoline compounds, carbodiimide compounds, and epoxy compounds) used is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 8 parts by mass, and even more preferably 1 to 5 parts by mass, per 100 parts by mass of carboxyl group-containing polyurethane resin, from the viewpoint of enhancing its effect. It is preferable that the crosslinking agent is used such that the amount of functional group that reacts with the carboxyl group (e.g., oxazoline group, carbodiimide group, epoxy group) is equal to or greater than the amount of carboxyl groups contained in the polyurethane resin. For example, the amount of the above functional group per 100 moles of carboxyl groups in the polyurethane resin is preferably 50 to 300 moles, and more preferably 100 to 250 moles.

[0072] In one embodiment of the aqueous polyurethane resin set, the form of the crosslinking agent is not particularly limited and may be in liquid form such as an aqueous solution or an aqueous dispersion (emulsion / dispersion), or in solid form such as a powder. Preferably, the crosslinking agent is in liquid form, and therefore the aqueous polyurethane resin set may be a two-component kit resin raw material in which a polyurethane aqueous dispersion as the first liquid and a liquid crosslinking agent as the second liquid are each filled in separate containers.

[0073] An aqueous polyurethane resin composition according to one embodiment can be prepared by mixing an aqueous polyurethane dispersion with a crosslinking agent. In the aqueous polyurethane resin composition, the content of carboxyl group-containing polyurethane resin is not particularly limited and may be, for example, 0.9 to 59.9% by mass or 9 to 45% by mass. The content of the aqueous dispersion medium is not particularly limited and may be, for example, 40 to 99% by mass or 50 to 90% by mass. The content of the crosslinking agent is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 8 parts by mass, and even more preferably 1 to 5 parts by mass, per 100 parts by mass of carboxyl group-containing polyurethane resin.

[0074] The aqueous polyurethane resin composition may contain components other than the aqueous dispersion medium, the carboxyl group-containing polyurethane resin, and the crosslinking agent. Examples of such other components include wetting agents, pigments, ultraviolet absorbers, light stabilizers, surface modifiers, inorganic fillers, organic fillers, dispersion aids, preservatives, rust inhibitors, antioxidants, silane coupling agents, defoamers, viscosity modifiers, and antistatic agents.

[0075] The applications of the polyurethane aqueous dispersion, aqueous polyurethane resin set, and aqueous polyurethane resin composition according to this embodiment are not particularly limited and can be widely used, for example, in paints, inks, adhesives, sealants, etc. Among these, they are particularly suitable for use as aqueous coatings applied to resin substrates such as polyester resin substrates due to their excellent adhesion to resins such as polyester resins. Here, the substrate may be a film or a plate-shaped substrate, and its shape, such as thickness, is not particularly limited. Examples of polyester resin substrates include PET (polyethylene terephthalate) film, PBT (polybutylene terephthalate) film, and PEN (polyethylene naphthalate) film.

[0076] The present invention will be described in more detail below based on examples and comparative examples, but it is not limited thereto.

[0077] Details of each component used in the examples are as follows.

[0078] [Polyol component (A)] ・Hydrogenated polybutadiene polyol 1: "NISSO-PB GI-1000" manufactured by Nippon Soda Co., Ltd., number average molecular weight 1500, number of functional groups 1.8 ・Hydrogenated polybutadiene polyol 2: "Krasol HLBH-P2000" manufactured by Cray Valley, number average molecular weight 2000, number of functional groups 1.9 ・Dimethylolpropionic acid: 2,2-bis(hydroxymethyl)propionic acid, number of functional groups 2 ・Dimethylolbutanoic acid: 2,2-bis(hydroxymethyl)butyric acid, number of functional groups 2 ・Trimethylolpropane: number of functional groups 3 ・Polybutadiene polyol 1: Non-hydrogenated, "NISSO-PB G-1000" manufactured by Nippon Soda Co., Ltd., number average molecular weight 1400, number of functional groups 1.8 • Polybutadiene polyol 2: non-hydrogenated, Krasol LBH-P2000 manufactured by Cray Valley, number average molecular weight 2000, number of functional groups 1.9

[0079] [Isocyanate component (B)] ・Hydrogenated MDI: Dicyclohexylmethane 4,4'-diisocyanate (2 functional groups) ・IPDI: Isophorone diisocyanate (2 functional groups) ・TDI: Tolylene diisocyanate (2 functional groups)

[0080] [Chain extenders (C)] DETA: Diethylenetriamine DPTA: Dipropylenetriamine EDA: Ethylenediamine

[0081] [Neutralizing agent] Triethylamine NaOH

[0082] [Crossing Agents] ・Oxazoline compound: Oxazoline group-containing water-soluble acrylic polymer, "Epocross WS-700" manufactured by Nippon Shokubai Co., Ltd., solids content 25% by mass (solvent: water), oxazoline equivalent 220, number average molecular weight 20000 ・Carbodiimide compound: Water-soluble polycarbodiimide, "Carbodilite V-02-L2" manufactured by Nisshinbo Chemical Co., Ltd., solids content 40% by mass (solvent: water), NCN equivalent 385 ・Epoxy compound: Sorbitol polyglycidyl ether, "Denacol EX-614B" manufactured by Nagase ChemteX Corporation, epoxy equivalent 173, active ingredient 100% by mass

[0083] The evaluation method for water-based polyurethane resin compositions is as follows.

[0084] [Preparation of Test Specimens] One side of a polyethylene terephthalate (PET) film (Toray Industries, Inc.'s "Lumirror T-60") was subjected to corona discharge treatment and used as a substrate. The aqueous polyurethane resin compositions of the examples and comparative examples were used as coatings and applied to the corona-discharged surface of the substrate using a barcoder to a dry film thickness of 10 μm. The film was dried at 120°C for 10 minutes to obtain test specimens with a crosslinked polyurethane resin coating.

[0085] [Adhesion to Resin] The above test specimens were subjected to a 1 mm grid peel test in accordance with JIS K5400-8.5:1990 to evaluate their adhesion to the resin. The value obtained by subtracting the number of peeled squares out of 100 squares was calculated, and a value of 70 or more and 100 or less was evaluated as "A (Excellent)", a value of 30 or more and less than 70 as "B (Good)", and a value of less than 30 as "C (Poor)".

[0086] [Heat Resistance] The above test specimens were treated at 180°C for 24 hours, and the heat resistance was evaluated by measuring the haze value (degree of cloudiness) after treatment. The haze value was measured using the "Haze Meter NDH4000" manufactured by NEC Corporation (the same method was used for evaluating heat resistance to moisture). Specimens with a haze value of less than 1.5% were evaluated as "A (Excellent)", those with a haze value of 1.5% or more and less than 2% were evaluated as "B (Good)", and those with a haze value of 2% or more were evaluated as "C (Unacceptable)".

[0087] [Heat and humidity resistance] The above test specimens were placed in an atmosphere of 85°C and 85% humidity for 120 hours, and then the haze value was measured to evaluate their heat and humidity resistance. Specimens with a haze value of less than 2% were evaluated as "A (Excellent)", those with a haze value of 2% or more and less than 3% were evaluated as "B (Good)", and those with a haze value of 3% or more were evaluated as "C (Poor)".

[0088] [Low Tackiness (Blocking Test)] Using two of the above test pieces, with the painted surfaces facing inward, stack them and apply 10 kg / 5 cm ２The samples were subjected to a load and left to stand at 50°C for 24 hours. After 24 hours, they were cooled to room temperature and evaluated by manually separating the two test pieces. Samples with no adhesion between the painted surfaces were rated "A (Excellent)", those that were adhered but could be separated were rated "B (Good)", and those that were adhered and could not be separated were rated "C (Unacceptable)".

[0089] [Example 1] In a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen blowing tube, 62.0 parts by mass of hydrogenated polybutadiene polyol, 4.5 parts by mass of dimethylolpropionic acid, 2.0 parts by mass of trimethylolpropane, and 100 parts by mass of methyl ethyl ketone were added and thoroughly stirred until dissolved. Then, 31.5 parts by mass of hydrogenated MDI was added, and the mixture was reacted at 75°C until the content of free isocyanate groups relative to the solid content reached 2.1% by mass to obtain a methyl ethyl ketone solution of isocyanate group-containing urethane prepolymer. This prepolymer solution was cooled to 45°C, and neutralization and emulsification dispersion were carried out by gradually adding a mixture of 3.4 parts by mass of triethylamine and 170 parts by mass of water while stirring with a homogenizer. Immediately thereafter, 1.5 parts by mass of diethylenetriamine was added, and the chain extension reaction was completed by stirring at 20°C for 60 minutes. Next, methyl ethyl ketone was removed by distillation under reduced heating pressure, and water for adjusting the solid content was added to obtain an aqueous dispersion of polyurethane resin with a solid content of 30% by mass. In the obtained aqueous dispersion, the acid value of the polyurethane resin was 19 mg KOH / g. 8.9 parts by mass of an oxazoline compound (2.225 parts by mass as solid content) was added to the aqueous dispersion and stirred to obtain the aqueous polyurethane resin composition of Example 1.

[0090] [Examples 2-17 and Comparative Examples 1-6] The types and amounts (parts by mass) of the polyol component (A), isocyanate component (B), chain extender (C), neutralizing agent, and crosslinking agent were changed as shown in Tables 1-4 below, and the rest of the procedure was the same as in Example 1 to obtain the aqueous polyurethane resin compositions of Examples 2-17 and Comparative Examples 1-6.

[0091] The water-based polyurethane resin compositions of Examples 1 to 17 and Comparative Examples 1 to 6 were evaluated for their adhesion to resin, heat resistance, heat and humidity resistance, and low tack. The results are shown in Tables 1 to 4.

[0092] Note that in Tables 1-4, the amounts of oxazoline compounds and carbodiimide compounds include the amount of solvent, and the numbers in parentheses represent the amount of active ingredient. "Free NCO content" refers to the amount of free isocyanate groups relative to the solid content in the urethane prepolymer solution before emulsification. "Acid value of polyurethane resin" refers to the acid value of the polyurethane resin before the addition of the crosslinking agent.

[0093]

[0094]

[0095]

[0096]

[0097] The results are shown in Tables 1 to 4. Examples 1 to 17 exhibited excellent adhesion to the resin, as well as superior heat resistance, heat and humidity resistance, and low tack. In contrast, Comparative Examples 1 and 2 used unhydrogenated polybutadiene polyol instead of hydrogenated polybutadiene polyol, resulting in inferior heat resistance and heat and humidity resistance.

[0098] In Comparative Example 3, the polyurethane resin had a low acid value, resulting in poor adhesion to the resin and low tack. In Comparative Example 4, an aromatic polyisocyanate was used instead of an alicyclic polyisocyanate, resulting in poor heat resistance, heat and humidity resistance, and low tack. In Comparative Example 5, a bifunctional amine chain extender was used instead of a trifunctional amine chain extender, resulting in poor heat resistance, heat and humidity resistance, and low tack. In Comparative Example 6, no crosslinking agent was included, resulting in poor adhesion to the resin, heat resistance, heat and humidity resistance, and low tack.

[0099] Furthermore, the various numerical ranges described in this specification can be any combination of their upper and lower limits, and all such combinations are described herein as preferred numerical ranges. Also, the description of a numerical range as "X to Y" means X or greater and Y or less.

[0100] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their omissions, substitutions, and modifications are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

Claims

1. A polyurethane aqueous dispersion comprising a carboxyl group-containing polyurethane resin dispersed in an aqueous dispersion medium and used in combination with a crosslinking agent that reacts with carboxyl groups, wherein the carboxyl group-containing polyurethane resin includes a structure derived from a hydrogenated polybutadiene polyol, a structure derived from a carboxyl group-containing polyol, a structure derived from an alicyclic polyisocyanate, and a structure derived from a trifunctional amine chain extender, and has an acid value of 5 to 50 mg KOH / g.

2. The polyurethane aqueous dispersion according to claim 1, wherein the trifunctional amine chain extender comprises a trifunctional aliphatic amine chain extender.

3. The polyurethane aqueous dispersion according to claim 1 or 2, wherein the crosslinking agent comprises at least one selected from the group consisting of oxazoline compounds, carbodiimide compounds, and epoxy compounds.

4. The polyurethane aqueous dispersion according to claim 1 or 2, wherein the amount of the crosslinking agent is 0.1 to 10 parts by mass per 100 parts by mass of the carboxyl group-containing polyurethane resin.

5. A set of aqueous polyurethane resin comprising: an aqueous polyurethane dispersion in which a carboxyl group-containing polyurethane resin is dispersed in an aqueous dispersion medium, wherein the carboxyl group-containing polyurethane resin includes a structure derived from a hydrogenated polybutadiene polyol, a structure derived from a carboxyl group-containing polyol, a structure derived from an alicyclic polyisocyanate, and a structure derived from a trifunctional amine chain extender, and has an acid value of 5 to 50 mg KOH / g; and a crosslinking agent that reacts with carboxyl groups.

6. An aqueous dispersion medium, a carboxyl group-containing polyurethane resin dispersed in the aqueous dispersion medium, comprising a structure derived from a hydrogenated polybutadiene polyol, a structure derived from a carboxyl group-containing polyol, a structure derived from an alicyclic polyisocyanate, and a structure derived from a trifunctional amine chain extender, having an acid value of 5 to 50 mg KOH / g, and a crosslinking agent that reacts with carboxyl groups, comprising the carboxyl group-containing polyurethane resin and an aqueous polyurethane resin composition.

7. A crosslinked polyurethane resin obtained by drying the aqueous polyurethane resin composition described in claim 6.

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