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

Abstract

Provided is a polyurethane aqueous dispersion excellent in adhesion to resin, heat resistance, and low tackiness. 【Solution means】The polyurethane aqueous dispersion according to the embodiment is a polyurethane aqueous dispersion used by mixing with a crosslinking agent that reacts with a carboxy group, and is formed by dispersing a carboxy group-containing polyurethane resin in an aqueous 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 to 50 mgKOH / g.

Description

Technical Field

[0001] Embodiments of the present invention relate 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.

Background Art

[0002] Polyurethane aqueous dispersions obtained by dispersing polyurethane resins in an aqueous dispersion medium are widely used in paints, inks, adhesives, and the like. 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 parts. 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.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

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

[0006] In the aqueous dispersion containing the carboxy group-containing polyurethane resin, crosslinking agents that react with the carboxy group such as carbodiimide compounds and oxazoline compounds can be added to crosslink the polyurethane resin to improve water resistance and the like, but further improvement in the above performance is required.

[0007] In view of the above points, an embodiment of the present invention aims to provide an aqueous polyurethane dispersion excellent in adhesion, heat resistance, and low tackiness to resins.

Means for Solving the Problems

[0008] The present invention includes the embodiments shown below. [1] A polyurethane aqueous dispersion in which a carboxy group-containing polyurethane resin is dispersed in an aqueous dispersion medium and used by mixing with a crosslinking agent that reacts with the carboxy group, The carboxy group-containing polyurethane resin includes a structure derived from hydrogenated polybutadiene polyol, a structure derived from carboxy group-containing polyol, a structure derived from alicyclic polyisocyanate, and a structure derived from trifunctional amine chain extender, and has an acid value of 5 to 50 mgKOH / g.

[0009] [2] A polyurethane aqueous dispersion in which a carboxy group-containing polyurethane resin is dispersed in an aqueous dispersion medium, the carboxy group-containing polyurethane resin includes a structure derived from hydrogenated polybutadiene polyol, a structure derived from carboxy group-containing polyol, a structure derived from alicyclic polyisocyanate, and a structure derived from trifunctional amine chain extender, and has an acid value of 5 to 50 mgKOH / g, and A crosslinking agent that reacts with the carboxy group, An aqueous polyurethane resin set formed by combining them.

[0010] [3] An aqueous dispersion medium, A carboxy group-containing polyurethane resin dispersed in the aqueous dispersion medium, which 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 to 50 mgKOH / g, and, A crosslinking agent that reacts with the carboxy group, An aqueous polyurethane resin composition containing the same.

[0011] [4] The polyurethane aqueous 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 contains a trifunctional aliphatic amine chain extender.

[0012] [5] The polyurethane aqueous 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 contains at least one selected from the group consisting of an oxazoline compound, a carbodiimide compound, and an epoxy compound.

[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 with respect to 100 parts by mass of the carboxy group-containing polyurethane resin.

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

Advantages of the Invention

[0015] According to an embodiment of the present invention, a polyurethane aqueous dispersion excellent in adhesion to a resin, heat resistance, heat and humidity resistance, and low tackiness can be provided.

Embodiments for Carrying Out the Invention

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

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

[0018] The hydrogenated polybutadiene polyol (A1) has a structure obtained by hydrogenating polybutadiene polyol, and part or all of the unsaturated double bonds contained in the polybutadiene polyol are hydrogenated. As the polybutadiene polyol, those having a 1,4-bond type, 1,2-bond type or a mixed structure thereof in the molecule and having a hydroxy group at the molecular end are preferred.

[0019] The degree of hydrogenation of the hydrogenated polybutadiene polyol (A1) is not particularly limited, and for example, the iodine value may be 50 g / 100 g or less, or may be 30 g / 100 g or less. In this specification, the iodine value is measured according to 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, more preferably 1000 to 1800.

[0021] In this specification, the number average molecular weight (Mn) is a value measured by the GPC method (gel permeation chromatography method) and calculated using a calibration curve with standard polystyrene. Specifically, as the GPC conditions, 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 mass%, and it can be measured.

[0022] The number of functional groups of the hydrogenated polybutadiene polyol (A1) is not particularly limited, but is preferably 1.5 to 2.8, more preferably 1.7 to 2.5. Here, the number of functional groups is the number of hydroxy groups per molecule of the 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 the hydrogenated polybutadiene polyol (A1) in the polyol component (A) is not particularly limited. For example, it is preferably 70 to 99% by mass, more preferably 75 to 98% by mass, still more preferably 80 to 96% by mass, and even more preferably 85 to 95% by mass based on 100% by mass of the polyol component (A).

[0024] In this specification, regarding the amounts of the respective components constituting the polyol component (A), the 100% by mass of the polyol component (A) as the reference is calculated with the carboxyl groups of the carboxyl group-containing polyol (A2) in the acid form. Similarly, regarding the amount of the carboxyl group-containing polyol (A2), the carboxyl groups are calculated in the acid form.

[0025] In this embodiment, the polyurethane resin has carboxyl groups, and thus, by mixing with a crosslinking agent that reacts with the carboxyl groups and heating and drying, it can react with the crosslinking agent to form a crosslinked structure. The carboxyl groups include not only the acid form (-COOH) but also the salt form, that is, carboxylate groups (-COOX, where X is a cation that forms a salt with the carboxylic acid), unless otherwise specified, and the acid form and the salt form may coexist.

[0026] Examples of the salts of the carboxylate groups 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. Being a volatile base, it can vaporize during the heating and drying of the aqueous dispersion, thereby improving the heat resistance and heat and humidity resistance of the polyurethane resin obtained by the reaction with the crosslinking agent.

[0027] Examples of the carboxyl group-containing polyol (A2) used for introducing a carboxyl group include dimethylolalkanoic acids 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, derivatives thereof, and salts thereof. Any one of these may be used, or two or more thereof may be used in combination.

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

[0029] The polyol component (A) preferably further contains a low molecular weight polyol (A3) having 3 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 tackiness can be enhanced.

[0030] Examples of the low molecular weight polyol (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 thereof may be used in combination. As the low molecular weight polyol (A3), a polyhydric alcohol (more preferably a trihydric alcohol) having a molecular weight of 300 or less (more preferably 200 or less) is preferably used.

[0031] The amount of the low molecular weight polyol (A3) in the polyol component (A) is not particularly limited, and for example, it 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 with respect to 100% by mass of the polyol component (A).

[0032] The polyol component (A) may consist only of a hydrogenated polybutadiene polyol (A1) and a carboxyl group-containing polyol (A2), or may consist only of a hydrogenated polybutadiene polyol (A1), a carboxyl group-containing polyol (A2), and a low molecular weight polyol (A3). As long as the effects according to this embodiment are achieved, the polyol component (A) may contain polyols other than the above. Examples of such other polyols include polymer polyols such as polyester polyol, polyether polyol, polycarbonate polyol, and hydrogenated polybutadiene polyol, and low molecular weight diols such as ethylene glycol, propylene glycol, propane diol, butane diol, pentane diol, 3-methyl-1,5-pentane diol, hexane diol, 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) contains an alicyclic polyisocyanate (B1). Thereby, heat resistance, heat and humidity resistance, and low tackiness can be improved.

[0034] Examples of the alicyclic polyisocyanate (B1) include isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4'-diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, and modified products such as isocyanurate, adduct, burette, allophanate, and carbodiimide of these. Any one of these may be used, or two or more thereof may be used in combination.

[0035] The isocyanate component (B) may be only an alicyclic polyisocyanate (B1), but as long as the effects according to this embodiment are achieved, it may contain other polyisocyanates such as, for example, aromatic polyisocyanates, araliphatic polyisocyanates, and / or aliphatic polyisocyanates. The amount of the alicyclic polyisocyanate with respect to 100% by mass of the isocyanate component (B) is preferably 70% by mass or more, more preferably 80% by mass or more, still 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 further reacting a urethane prepolymer obtained by reacting the above polyol component (A) and isocyanate component (B) with a chain extender (C) containing a trifunctional amine chain extender (C1). By performing chain extension using the trifunctional amine chain extender (C1), heat resistance, heat and humidity resistance, and low tackiness can be improved.

[0037] The trifunctional amine chain extender (C1) is an amine compound having three primary amino groups and / or secondary amino groups having reactivity with the isocyanate groups of the urethane prepolymer in one molecule. As the trifunctional amine chain extender (C1), it is preferable to use an aliphatic amine compound, that is, a trifunctional aliphatic amine chain extender. Examples thereof include diethylenetriamine, dipropylenetriamine, dibutylenetriamine, etc. Any one of these may be used alone or two or more thereof may be used in combination.

[0038] The chain extender (C) may be only a trifunctional amine chain extender (C1), but as long as the effects according to this embodiment are achieved, for example, other chain extenders such as bifunctional amine chain extenders may be included. Also, when the urethane prepolymer is dispersed in an aqueous dispersion medium, it may be chain-extended by water, and in that case, the water as the dispersion medium may also serve as a chain extender. However, when performing the dispersion, it is preferable to add the trifunctional amine chain extender (C1) as quickly as possible 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, still 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. When the acid value is 5 mgKOH / g or more, the adhesion to the resin and low tackiness can be improved. When the acid value is 50 mgKOH / g or less, the heat resistance and heat and humidity resistance can be improved. 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 (mg) of KOH required to neutralize the carboxyl groups contained in 1 g of the polyurethane resin in accordance with JIS K0070-1992. When the polyurethane resin is a salt of a volatile base, the volatile base vaporizes when measuring the mass of the polyurethane resin. Therefore, the acid value of the polyurethane resin is a value calculated based on the mass of the acid-type polyurethane resin that is the non-volatile component. Thus, the mass of the polyurethane resin in this specification is the mass as the non-volatile component.

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

[0042] The amount of the structure derived from the 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 based on 100% by mass of the polyurethane resin. The amount of the structure derived from the hydrogenated polybutadiene polyol (A1) is not particularly limited. For example, it may be 40 to 80% by mass, or 45 to 75% by mass based on 100% by mass of the polyurethane resin. The amount of the structure derived from the carboxy group-containing polyol (A2) is not particularly limited. For example, it may be 1 to 15% by mass, or 2 to 10% by mass based on 100% by mass of the polyurethane resin. The amount of the structure derived from the 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 based on 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, and 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, and 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 preferably used as the aqueous dispersion medium, and an organic solvent may be contained but is preferably in a small amount. In one embodiment, the aqueous dispersion medium preferably 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, and examples thereof include lower monohydric alcohols such as methanol, ethanol, and propanol, polyhydric alcohols such as ethylene glycol and glycerin, and aprotic polar solvents such as N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide, acetonitrile, and butyl cellosolve.

[0047] [Polyurethane aqueous dispersion] The 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 for example, it may be 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 carboxyl 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 preventives, antioxidants, silane coupling agents, defoamers, viscosity modifiers, antistatic agents, and the like. The other components may be contained in the resin particles as the dispersed substance, or may be contained in a separately dispersed state or a 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 carboxyl group-containing polyurethane resin, or may be composed of the carboxyl group-containing polyurethane resin and other components. Further, the polyurethane aqueous dispersion may contain a surfactant for dispersing the carboxyl 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 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) to synthesize an isocyanate group-containing urethane prepolymer. Step 2: A step of neutralizing the carboxyl group 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 chain-extending 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 such that the isocyanate groups are stoichiometrically in excess of the amount of hydroxy groups contained in the polyol component (A), for example, the equivalent ratio of isocyanate groups to hydroxy groups (NCO / OH) is 1.05 to 1.70 (more preferably 1.10 to 1.60).

[0052] In Step 1, the reaction between the polyol component (A) and the isocyanate component (B) may be carried out without an organic solvent, or may be carried out in an organic solvent having no active hydrogen group such as methyl ethyl ketone or acetone.

[0053] In Step 2, examples of the base for neutralizing the carboxy 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 the aqueous dispersion medium is not particularly limited. For example, (i) a method of adding the urethane prepolymer or its solution while stirring the aqueous dispersion medium with a homogenizer or a homomixer, (ii) a method of adding the aqueous dispersion medium while stirring the urethane prepolymer or its solution with a homogenizer or a homomixer, etc. may be mentioned.

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

[0056] The neutralization in Step 2 and the dispersion in Step 3 may be carried out in this order, or two or more steps may be carried out simultaneously. For example, when an aqueous solution of a base is used for neutralizing the carboxy group, the dispersion into the aqueous dispersion medium may be carried out simultaneously with the neutralization. Further, for the chain extension in Step 4, after adding the aqueous dispersion medium to the urethane prepolymer in Step 3, it is preferable to add the chain extender as soon as possible. In addition, when the reaction between the polyol and the polyisocyanate is carried out in an organic solvent in Step 1, the organic solvent may be removed after dispersing in the aqueous dispersion medium in Step 4.

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

[0058] The aqueous polyurethane dispersion according to this embodiment is used by mixing with a crosslinking agent that reacts with the carboxy group. By mixing with the crosslinking agent and heating and drying, the polyurethane resin is crosslinked, whereby a polyurethane resin excellent in adhesion, heat resistance, heat and humidity resistance, and low tackiness to resins such as polyester resin can be obtained. The aqueous polyurethane 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 aqueous polyurethane dispersion and a crosslinking agent that reacts with the carboxy group. Further, an aqueous polyurethane resin composition according to one embodiment contains an aqueous dispersion medium, a carboxy group-containing polyurethane resin dispersed in the aqueous dispersion medium, and a crosslinking agent that reacts with the carboxy group.

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

[0060] An oxazoline compound as a crosslinking agent is a compound containing a plurality of oxazoline groups in the molecule, and forms a crosslinked structure (amide ester bond) by reacting with the carboxy group of the polyurethane resin. 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 a substituent as long as it can react with the carboxy group to form an amide ester bond. [Chemical formula]

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

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

[0063] The number average molecular weight (Mn) of the oxazoline compound is not particularly limited, and may be, for example, 5000 to 100000, may be 10000 to 80000, or may be 15000 to 50000.

[0064] As the oxazoline compound, for example, "Epocros WS-300", "Epocros WS-500", "Epocros WS-700" manufactured by Nippon Shokubai Co., Ltd. can be easily obtained commercially, and these can be used.

[0065] A carbodiimide compound as a crosslinking agent is a compound containing a plurality of carbodiimide groups (-N=C=N-) in the molecule, and forms a crosslinked structure by reacting with the carboxy group of the polyurethane resin (A).

[0066] As the carbodiimide compound, an aqueous polycarbodiimide in which a hydrophilic segment is introduced into a polycarbodiimide having a plurality of carbodiimide groups in the molecule is preferable. Examples of such an aqueous polycarbodiimide include "Carbodilite V-02", "Carbodilite V-02-L2", "Carbodilite SV-02", "Carbodilite V-04", "Carbodilite V-10" as the water-soluble type, and "Carbodilite E-02", "Carbodilite E-05" (all of the above are manufactured by Nisshinbo Chemical Inc.) as the emulsion / dispersion type.

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

[0068] The epoxy compound as the crosslinking agent is a compound containing a plurality of epoxy groups in the molecule, and forms a crosslinked structure by reacting with the carboxyl group of the polyurethane resin (A).

[0069] As the epoxy compound, a water-soluble epoxy compound obtained by glycidyl etherifying the hydroxyl groups of polyols such as sorbitol, glycerin, diglycerin, and polyglycerin is preferable. Specific examples of the epoxy compound 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 thereof 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 may be 130 to 200. Here, the epoxy equivalent represents the chemical formula amount per mole of the epoxy group.

[0071] The amount of the crosslinking agent (preferably at least one selected from the group consisting of oxazoline compounds, carbodiimide compounds, and epoxy compounds) 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 with respect to 100 parts by mass of the carboxy group-containing polyurethane resin from the viewpoint of enhancing its effect. The crosslinking agent is preferably used such that the amount of the functional group (for example, oxazoline group, carbodiimide group, epoxy group) that reacts with the carboxy group is equimolar or more with respect to the carboxy group contained in the polyurethane resin. For example, the amount of the above functional group is preferably 50 to 300 moles, more preferably 100 to 250 moles, per 100 moles of the carboxy group of the polyurethane resin.

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

[0073] The aqueous polyurethane resin composition according to one embodiment can be prepared by mixing a polyurethane aqueous dispersion and a crosslinking agent. In the aqueous polyurethane resin composition, the content of the carboxy 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 with respect to 100 parts by mass of the carboxy group-containing polyurethane resin as described above.

[0074] The aqueous polyurethane resin composition may contain an aqueous dispersion medium, a carboxy group-containing polyurethane resin, and components other than the crosslinking agent. Such other components include, for example, wetting agents, pigments, ultraviolet absorbers, light stabilizers, surface modifiers, inorganic fillers, organic fillers, dispersion aids, preservatives, rust preventives, antioxidants, silane coupling agents, defoamers, viscosity modifiers, antistatic agents, and the like.

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

Examples

[0076] Hereinafter, it will be described in more detail based on examples and comparative examples, but the present invention is not limited thereby.

[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, functionality 2 · Trimethylolpropane: functionality 3 · Polybutadiene polyol 1: non-hydrogenated, manufactured by Nippon Soda Co., Ltd. "NISSO-PB G-1000", number average molecular weight 1400, functionality 1.8 · Polybutadiene polyol 2: non-hydrogenated, manufactured by CRAY VALLEY "Krasol LBH-P2000", number average molecular weight 2000, functionality 1.9

[0079] [Isocyanate component (B)] · Hydrogenated MDI: dicyclohexylmethane 4,4'-diisocyanate (functionality 2) · IPDI: isophorone diisocyanate (functionality 2) · TDI: tolylene diisocyanate (functionality 2)

[0080] [Chain extender (C)] · DETA: diethylenetriamine · DPTA: dipropylenetriamine · EDA: ethylenediamine

[0081] [Neutralizing agent] · Triethylamine · NaOH

[0082] [Crosslinking agent] · Oxazoline compound: water-soluble acrylic polymer containing oxazoline groups, manufactured by Nippon Shokubai Co., Ltd. "Epocros WS-700", solid content 25% by mass (solvent: water), oxazoline equivalent 220, number average molecular weight 20000 · Carbodiimide compound: water-soluble polycarbodiimide, manufactured by Nisshinbo Chemicals Inc. "Carbodilite V-02-L2", solid content 40% by mass (solvent: water), NCN equivalent 385 · Epoxy compound: sorbitol polyglycidyl ether, manufactured by Nagase ChemteX Corporation "Denacol EX-614B", epoxy equivalent 173, active ingredient 100% by mass

[0083] The evaluation method of the aqueous polyurethane resin composition is as follows.

[0084] [Preparation of Test Specimens] One side of a polyethylene terephthalate (PET) film ("Lumirror T-60" manufactured by Toray Industries, Inc.) was treated with corona discharge and used as a substrate. Using the aqueous polyurethane resin compositions of the examples and comparative examples as paints, they were applied to the corona-discharged surface of the substrate with a bar coater so that the dry film thickness became 10 μm, and dried at 120 °C for 10 minutes to obtain test specimens on which a cured polyurethane resin coating film was formed.

[0085] [Adhesion to Resin] Regarding the above test specimens, a 1 mm crosshatch peel test was carried out in accordance with JIS K5400-8.5:1990 to evaluate the adhesion to the resin. The value obtained by subtracting the number of peeled squares out of 100 squares was determined, and when the value was 70 or more and 100 or less, it was evaluated as "A (excellent)", when it was 30 or more and less than 70, it was evaluated as "B (good)", and when it was less than 30, it was evaluated as "C (not acceptable)".

[0086] [Heat Resistance] The above test specimens were treated at 180 °C for 24 hours, and after the treatment, the Haze value (cloudiness) was measured to evaluate the heat resistance. The Haze value was measured with a "Haze Meter NDH4000" manufactured by Nippon Electric Industry Co., Ltd. (the same applies to the evaluation of heat and humidity resistance). When the Haze value was less than 1.5%, it was evaluated as "A (excellent)", when the Haze value was 1.5% or more and less than 2%, it was evaluated as "B (good)", and when the Haze value was 2% or more, it was evaluated as "C (not acceptable)".

[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 the heat and humidity resistance. When the Haze value was less than 2%, it was evaluated as "A (excellent)", when the Haze value was 2% or more and less than 3%, it was evaluated as "B (good)", and when the Haze value was 3% or more, it was evaluated as "C (not acceptable)".

[0088] [Low Tackiness (Blocking Test)] Using two of the above test pieces, with the painted surfaces facing inward, they were overlapped and a load of 10 kg / 5 cm 2 was applied, and they were left standing at 50 °C for 24 hours. After 24 hours, they were cooled to room temperature, and the two test pieces were peeled off by hand for evaluation. Those with no adhesion between the painted surfaces were rated as "A (excellent)", those with adhesion but could be peeled off were rated as "B (good)", and those with adhesion and could not be peeled off were rated as "C (unacceptable)".

[0089] [Example 1] Into a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 62.0 parts by mass of hydrogenated polybutadiene polyol 1, 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 stirred and dissolved thoroughly. Then, 31.5 parts by mass of hydrogenated MDI was added, and the reaction was carried out 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 an isocyanate group-containing urethane prepolymer. This prepolymer solution was cooled to 45 °C, and while stirring using a homogenizer, a solution obtained by mixing 3.4 parts by mass of triethylamine and 170 parts by mass of water was gradually added to carry out neutralization and emulsion dispersion. 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, under heating and reduced pressure, methyl ethyl ketone was distilled off, and water for solid content adjustment was added to obtain an aqueous dispersion of a polyurethane resin having a solid content of 30% by mass. In the obtained aqueous dispersion, the acid value of the polyurethane resin was 19 mgKOH / g. 8.9 parts by mass (2.225 parts by mass as solid content) of an oxazoline compound was added to the aqueous dispersion and stirred to obtain the aqueous polyurethane resin composition of Example 1.

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

[0091] For the aqueous polyurethane resin compositions of Examples 1 to 17 and Comparative Examples 1 to 6, the adhesion to the resin, heat resistance, heat and humidity resistance, and low tackiness were evaluated. The results are shown in Tables 1 to 4.

[0092] In Tables 1 to 4, the amounts of the oxazoline compound and the carbodiimide compound are the amounts including the solvent, and the numerical values in parentheses are the amounts of the active ingredients. The "free NCO content" is the content of free isocyanate groups with respect to the solid content in the urethane prepolymer solution before emulsification. The "acid value of the polyurethane resin" is the acid value of the polyurethane resin before adding the crosslinking agent.

[0093] [Table 1]

[0094] [Table 2]

[0095] [Table 3]

[0096] [Table 4]

[0097] The results were as shown in Tables 1 to 4. In Examples 1 to 17, the adhesion to the resin was excellent, and the heat resistance, heat and humidity resistance, and low tackiness were also excellent. On the other hand, in Comparative Examples 1 and 2, non-hydrogenated polybutadiene polyol was used instead of hydrogenated polybutadiene polyol, and the heat resistance and heat and humidity resistance were inferior.

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

[0099] In addition, the various numerical ranges described in the specification can arbitrarily combine their upper limit values and lower limit values, and all of these combinations are described in the specification as preferred numerical ranges. Also, the description of the numerical range of "X to Y" means X or more and Y or less.

[0100] As described above, some embodiments of the present invention have been described. However, 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, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their omissions, replacements, changes, etc. are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope.

Claims

1. A polyurethane aqueous dispersion in which a carboxy group-containing polyurethane resin is dispersed in an aqueous dispersion medium and used by mixing with a crosslinking agent that reacts with a carboxy group, 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 to 50 mgKOH / g; Polyurethane water-based dispersion.

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

3. A polyurethane aqueous dispersion in which a carboxy group-containing polyurethane resin is dispersed in an aqueous dispersion medium, the carboxy group-containing polyurethane resin containing 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 having an acid value of 5 to 50 mgKOH / g; and A crosslinker that reacts with carboxy groups, A water-based polyurethane resin set consisting of a combination of the above.

4. The aqueous polyurethane resin set described in claim 3, wherein the crosslinking agent comprises at least one selected from the group consisting of oxazoline compounds, carbodiimide compounds, and epoxy compounds.

5. The aqueous polyurethane resin set according to claim 3, wherein the amount of the crosslinking agent is 0.1 to 10 parts by mass per 100 parts by mass of the carboxy group-containing polyurethane resin.

6. aqueous dispersion medium, a carboxy group-containing polyurethane resin dispersed in the aqueous dispersion medium, the carboxy group-containing polyurethane resin including 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 having an acid value of 5 to 50 mgKOH / g; and A crosslinker that reacts with carboxy groups, 1. A water-based polyurethane resin composition comprising:

7. A crosslinked polyurethane resin obtained by drying the aqueous polyurethane resin composition according to claim 6.

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