Aqueous two-pack curable resin composition

Abstract

To provide an aqueous two-pack curable resin composition from which a coating film having durability against a solvent having low solubility to water and a solvent compatible with water at an arbitrary ratio can be obtained.SOLUTION: An aqueous two-pack curable resin composition contains aqueous acrylic emulsion (A) obtained using an emulsifier having a radical-polymerizable unsaturated group and a hydroxyl group containing unsaturated monomer, and aqueous self-emulsifiable polyisocyanate (B). (1) A solid content hydroxyl value of emulsion (A) is 30 to 160 mgKOH / g. (2) A solid content acid value of the emulsion (A) is 5 mgKOH / g or less. (3) A theoretical glass transition temperature of the emulsion (A) is 30 to 80°C. (4) Shore A hardness of a cured product of the aqueous two-pack curable resin composition is 70 or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an aqueous two-component curable resin composition that can be used as an aqueous coating material or the like. [Background technology]

[0002] Various solvent-based paints have been commonly used to protect the surfaces and maintain the appearance of substrates such as paper, wood, plastic, and metal. However, there are concerns about the effects of the solvents contained in solvent-based paints on the human body and the environment, and there is a shift toward water-based paints.

[0003] Although water-based paints have inferior adhesion to some substrates compared to solvent-based paints, it is known that adhesion to the substrate can be maintained by obtaining an aqueous emulsion using an emulsifier having a radically polymerizable unsaturated group, as in Patent Document 1. However, Patent Document 1 had problems in that the coating film was insufficient in strength and had insufficient solvent resistance.

[0004] As a method for improving the strength of a coating film, a two-component curing type aqueous coating composition that uses a mixture of polyisocyanate and a resin having a hydroxyl group that reacts with an isocyanate group is known, as in Patent Document 2 and Patent Document 3. However, Patent Document 2 and Patent Document 3 have a problem in that although they are durable against solvents that are poorly soluble in water, they are poorly durable against solvents that are compatible with water in any ratio. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 06-116528 [Patent Document 2] Japanese Patent Application Publication No. 8-3437 [Patent Document 3] Japanese Patent Application Publication No. 9-316392 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an aqueous two-component curable resin composition which can give a coating film having durability in solvents that have low solubility in water and in solvents that are compatible with water in any ratio. [Means for solving the problem]

[0007] The present inventors have discovered that in an aqueous two-component curable resin composition comprising an acrylic emulsion obtained using an emulsifier having a radically polymerizable unsaturated group and a self-emulsifying polyisocyanate, by specifying the solids content hydroxyl value, acid value and glass transition temperature of the acrylic emulsion and by specifying the hardness of a cured product of the two-component curable resin composition, it is possible to obtain a coating film that is durable against a solvent that is miscible with water in any ratio.

[0008] That is, the present invention provides: <1> An aqueous two-component curable resin composition comprising an aqueous acrylic emulsion (A) obtained by using an emulsifier having a radical polymerizable unsaturated group and a hydroxyl group-containing unsaturated monomer, and an aqueous self-emulsifying polyisocyanate (B), the aqueous two-component curable resin composition being characterized in that it satisfies the following conditions: (1) The hydroxyl value of the solid content of the emulsion (A) is 30 to 160 mgKOH / g. (2) The acid value of the solid content of the emulsion (A) is 5 mg KOH / g or less. (3) The glass transition temperature of the emulsion (A) is 30 to 80°C. (4) The Shore A hardness of the cured product of the aqueous two-component curable resin composition is 70 or more. <2> The emulsion (A) and the polyisocyanate (B) further contain a water-soluble alcohol in an amount of 0.5 to 15% by mass based on the total amount of the emulsion (A) and the polyisocyanate (B). <1> The aqueous two-component curable resin composition according to the present invention, It is. Effect of the Invention

[0009] According to the present invention, in an aqueous two-component curable resin composition containing an acrylic emulsion obtained using an emulsifier having a radically polymerizable unsaturated group and a self-emulsifying polyisocyanate, by specifying the solids content hydroxyl value, acid value and glass transition temperature of the acrylic emulsion and specifying the hardness of the cured product of the two-component curable resin composition, it is possible to obtain a coating film that is durable against a solvent that is compatible with water in any ratio. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described in detail. Note that the following description is an example of an embodiment of the present invention, and the present invention is not limited to this description.

[0011] The aqueous two-component curable resin composition of the present invention is an aqueous two-component curable resin composition comprising an aqueous acrylic emulsion (A) obtained using an emulsifier having a radically polymerizable unsaturated group and a hydroxyl group-containing unsaturated monomer, and an aqueous self-emulsifying polyisocyanate (B), and is characterized in that it satisfies the following conditions: (1) The hydroxyl value of the solid content of the emulsion (A) is 30 to 160 mgKOH / g. (2) The acid value of the solid content of the emulsion (A) is 5 mg KOH / g or less. (3) The glass transition temperature of the emulsion (A) is 30 to 80°C. (4) The Shore A hardness of the cured product of the aqueous two-component curable resin composition is 70 or more.

[0012] <Water-based acrylic emulsion (A)> The aqueous acrylic emulsion (A) is an acrylic emulsion obtained using an emulsifier having a radically polymerizable unsaturated group (hereinafter referred to as a "reactive emulsifier") and a hydroxyl group-containing unsaturated monomer (a) as described above, and preferably further using an acid group-containing unsaturated monomer (b) and other unsaturated monomers (c).

[0013] <Reactive emulsifier> Specific examples of reactive emulsifiers include various emulsifiers having a radical polymerizable carbon-carbon unsaturated double bond and a nonionic or ionic hydrophilic group in one molecule, and in the present invention, it is preferable to use an emulsifier having an anionic or nonionic hydrophilic group. Examples of the anionic hydrophilic group include a sulfonic acid group, a phosphoric acid group, and a carboxyl group. Commercially available reactive emulsifiers having such an anionic hydrophilic group (hereinafter, sometimes simply referred to as "anionic reactive emulsifiers") include "ADEKA REASOAP SR-10", "ADEKA REASOAP SR-20", and "ADEKA REASOAP SR-3025" (all manufactured by ADEKA Corporation), "Aqualon KH-10" (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and "Spinomer NaSS" (manufactured by Tosoh Finechem Corporation). Examples of nonionic hydrophilic groups include polyoxyethylene groups. Commercially available reactive emulsifiers having such nonionic hydrophilic groups (hereinafter, sometimes simply referred to as "nonionic reactive emulsifiers") include, for example, "ADEKA REASOAP ER-10" (manufactured by ADEKA Corporation).

[0014] The amount of such reactive emulsifier used is preferably 0.1 to 5% by mass based on the total amount of unsaturated monomers to be polymerized. By using the amount within the above range, a stable aqueous acrylic emulsion can be obtained without generating aggregates after polymerization. In addition, a coating film of the aqueous two-component curable resin composition having good solvent resistance can be obtained.

[0015] <Hydroxyl-containing unsaturated monomer (a)> The hydroxyl-containing unsaturated monomer (a) can be any known ethylenically unsaturated monomer containing a hydroxyl group in the molecule, and is used to provide the aqueous acrylic emulsion with a hydroxyl group, which is a reactive site with polyisocyanate. Specific examples of (a) include (meth)acrylates containing a hydroxyl group, such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and hydroxyhexyl (meth)acrylate. Among these, it is preferable to use 2-hydroxyethyl methacrylate.

[0016] <Acid group-containing unsaturated monomer (b)> The acid group-containing unsaturated monomer (b) can be any known ethylenically unsaturated monomer containing various acid groups such as carboxyl groups and sulfonic acid groups in the molecule, and its salts, and is used to impart an acid value to the aqueous acrylic emulsion. Specific examples of the carboxyl group-containing ethylenically unsaturated monomer include unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid, and unsaturated dicarboxylic acids such as itaconic acid and maleic acid, and examples of the sulfonic acid group-containing ethylenically unsaturated monomer include sulfoethyl methacrylate, styrene sulfonic acid, and the like. Among these, it is preferable to use a carboxyl group-containing ethylenically unsaturated monomer, and it is particularly preferable to use (meth)acrylic acid.

[0017] <Other unsaturated monomers (c)> The other unsaturated monomer (c) is not particularly limited as long as it does not inhibit the effects of the present invention. Specific examples of the other unsaturated monomer include esters of acrylic acid or methacrylic acid such as methyl, ethyl, propyl, butyl, hexyl, ethylhexyl, lauryl, etc., esters of vinyl alcohol and carboxylic acids such as acetic acid and propionic acid, unsaturated aromatic compounds such as styrene, α-methylstyrene, vinylnaphthalene, etc., unsaturated hydrocarbons such as butadiene and isoprene, amides such as acrylamide, methacrylamide, N,N-dimethylacrylamide, etc., polyoxyalkylene derivatives such as polyethylene glycol methyl ether acrylate or methacrylate, diacrylates and dimethacrylates of glycols such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, etc., polyacrylates and polymethacrylates of polyols such as glycerin, trimethylolpropane, pentaerythritol, etc. Among these, it is preferable to use esters of acrylic acid or methacrylic acid and unsaturated aromatic compounds, and it is particularly preferable to use methyl methacrylate, which is the methyl ester of methacrylic acid, 2-ethylhexyl methacrylate, which is the ethylhexyl ester of methacrylic acid, and styrene.

[0018] In the present invention, the mass fractions of the components (a), (b) and (c) in the aqueous acrylic emulsion (A) can be adjusted so that the hydroxyl group, acid value and glass transition temperature of (A) described below fall within the ranges specified in the present invention, and it is preferable to contain them at mass fractions such that these values ​​fall within preferred ranges.

[0019] The hydroxyl value of the aqueous acrylic emulsion (A) used in the present invention is a theoretical value of the mass of potassium hydroxide equivalent to the hydroxyl group contained in 1 g of solid content, and is calculated from the molecular weight of the hydroxyl-containing unsaturated monomer (a) by calculating the mass (mg) of potassium hydroxide (molecular weight 56.1) equivalent to the hydroxyl group per 1 g of the monomer and the composition ratio (mass%) of the hydroxyl-containing unsaturated monomer (a) in (A). The hydroxyl value of the aqueous acrylic emulsion (A) used in the present invention is 30 to 160 mgKOH / g, more preferably 50 to 100 mgKOH / g, per solid content. If the hydroxyl value is less than 30, the number of crosslinking points due to the reaction with polyisocyanate is too small, and the solvent resistance and hardness of the resulting coating film are reduced. If the hydroxyl value exceeds 160, gelation occurs when mixed with polyisocyanate, and a coating film cannot be formed. (Formula 1) ((56.1 x 1000) / (Mw(a) x number of hydroxyl groups in (a)) x ((a)% / 100) (In the formula, Mw(a) represents the molecular weight of (a), and (a)% represents the composition ratio (mass%) of (a) in (A).)

[0020] The acid value of the aqueous acrylic emulsion (A) used in the present invention is a theoretical value of the mass of potassium hydroxide required to neutralize the acid group contained in 1 g of solid content, and is calculated from the mass (mg) of potassium hydroxide (molecular weight 56.1) required to neutralize per 1 g of the acid group-containing unsaturated monomer (b) from the molecular weight of the monomer, and the composition ratio (mass%) of the acid group-containing unsaturated monomer (b) in (A) is calculated from the following formula 2. The acid value of the aqueous acrylic emulsion (A) used in the present invention is 5 mg KOH / g or less, more preferably 3 mg KOH / g or less, per solid content. If the acid value exceeds 5, the solvent resistance and hardness of the resulting coating film are reduced. (Equation 2) ((56.1 x 1000) / (Mw(b) x number of acid groups in (b)) x ((b)% / 100) (In the formula, Mw(b) represents the molecular weight of (b), and (b)% represents the composition ratio (mass%) of (b) in (A).)

[0021] The glass transition temperature (hereinafter sometimes abbreviated as Tg) of the aqueous acrylic emulsion (A) used in the present invention is calculated from the ratios of the components (a), (b), and (c) constituting the aqueous acrylic emulsion (A), and is a theoretical value determined by the following FOX formula. 1 / Tg=W1 / Tg1+W2 / Tg2+···+Wn / Tgn··· FOX formula In the formula, Tg is the glass transition temperature (K: Kelvin), W1, W2...Wn are the mass fractions of each monomer calculated from the ratio to the total amount of components (a), (b), and (c) that make up the aqueous acrylic emulsion, and Tg1, Tg2...Tgn are the glass transition temperatures of the homopolymers of each monomer. Examples of the glass transition temperatures of homopolymers of each monomer are as follows: Methyl methacrylate: 378K (105℃) 2-Ethylhexyl methacrylate: 188K (-85℃) Styrene: 373K (100℃) 2-Hydroxyethyl methacrylate: 328K (55℃) Methacrylic acid: 453K (180℃) Acrylic acid: 379K (106℃)

[0022] The Tg of the aqueous acrylic emulsion (A) used in the present invention is 30 to 80° C., more preferably 40 to 70° C. If the Tg is less than 30° C., the hardness of the coating film decreases, and the solvent resistance of the coating film decreases accordingly. If the Tg exceeds 80° C., the coating film cannot be formed.

[0023] As the polymerization initiator used for the polymerization of the aqueous acrylic emulsion (A) in the present invention, persulfates such as potassium persulfate and ammonium persulfate, hydrogen peroxide, etc. can be used, and in some cases, they can be used in combination with a reducing agent. Examples of the reducing agent include sodium hydrogen sulfite and ascorbic acid.

[0024] In addition, when it is necessary to adjust the degree of polymerization during polymerization, a chain transfer agent such as mercaptans, for example, dodecyl mercaptan, lauryl mercaptan, etc., can be used.

[0025] The aqueous acrylic emulsion (A) in the present invention may contain a non-reactive low molecular weight emulsifier that does not have a radically polymerizable unsaturated group, as long as the effect of the invention is not impaired. As the non-reactive low molecular weight emulsifier, a commercially available anionic or non-ionic emulsifier described below can be used. As the anionic emulsifier, sodium dodecylbenzenesulfonate, sodium polyoxyethylene styrenated phenol sulfate, a formalin condensate of sodium naphthalenesulfonate, etc. can be mentioned. As the non-ionic emulsifier, polyethylene oxide and polypropylene oxide compounds can be mentioned. These can be used in an amount of up to 5% by mass based on the total amount of the unsaturated monomers to be polymerized.

[0026] In the present invention, the aqueous acrylic emulsion (A) is not particularly limited and can be obtained by a known production method, for example, by dropping a pre-emulsified monomer emulsion into water, or dropping a monomer mixture into water in which an emulsifier is dissolved, etc.

[0027] <Water-based self-emulsifying polyisocyanate (B)> As the aqueous self-emulsifying polyisocyanate (B), various known substances can be used, but aliphatic or alicyclic polyisocyanates and their derivatives in which some of the isocyanate groups have been reacted with polyethylene oxide monoalkyl ether to impart water dispersibility are preferred.

[0028] Commercially available products of such aqueous self-emulsifying polyisocyanates include, for example, "Duranate (registered trademark) WB40-100" and "Duranate (registered trademark) WT20-100" (both manufactured by Asahi Kasei Corporation).

[0029] In the present invention, the method for mixing the aqueous acrylic emulsion (A) and the aqueous self-emulsifying polyisocyanate (B) is not particularly limited, but examples thereof include a method in which the polyisocyanate (B) previously dispersed in water is added to the acrylic emulsion (A), or a method in which the polyisocyanate (B) is directly added to the acrylic emulsion (A) and stirred to disperse.

[0030] <Water-soluble alcohol> In the present invention, the aqueous two-component curable resin composition may contain a water-soluble alcohol. The water-soluble alcohol used in the present invention refers to an alcohol having 3 or less carbon atoms, and specific examples thereof include methanol, ethanol, n-propanol, and isopropanol.

[0031] In the present invention, the aqueous two-component curable resin composition preferably contains 0.5 to 15 mass % of the water-soluble alcohol, more preferably 5 to 10 mass %, based on the total of the emulsion (A) and the polyisocyanate (B). By containing the water-soluble alcohol in the above range, the aqueous two-component curable resin composition can maintain a dispersed state. In addition, by making the content of the water-soluble alcohol 15 mass % or less, it is possible to prevent the water-soluble alcohol from reacting with the isocyanate group of the aqueous self-emulsifying polyisocyanate (B) to inhibit crosslinking with the emulsion (A), thereby preventing a decrease in the solvent resistance and hardness of the resulting coating film.

[0032] In the present invention, in addition to the emulsion (A), the polyisocyanate (B), and the water-soluble alcohol, other additives such as a thickener, a film-forming aid, a defoamer, a leveling agent, and a preservative may be added as necessary to the aqueous two-component curable resin composition.

[0033] In addition, as an additive, organic solvents such as methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, hexyl cellosolve, ethyl carbitol, butyl carbitol, methyl cellosolve acetate, and ethyl cellosolve acetate can be used in order to improve film-forming properties and wettability.

[0034] The aqueous two-component curable resin composition of the present invention can be adjusted to an appropriate viscosity, and then applied to the surface of the substrate by a common coating method such as brush coating, spray coating, gravure coating, flexo coating, or roll coating, and then dried at room temperature or forced drying to form a coating film.

[0035] The coating material can be applied to a variety of substrates, including paper substrates, plastic substrates such as polyethylene, polypropylene, and polystyrene, various metal substrates such as iron, stainless steel, and aluminum, and glass substrates.

[0036] The Shore A hardness of the cured product of the aqueous two-component curable resin composition of the present invention is a value measured in accordance with JIS K6253-3 using two overlapping sheets of the cured product.

[0037] The Shore A hardness of the cured product of the aqueous two-component curable resin composition of the present invention must be at least 70. If the Shore A hardness is less than 70, the solvent resistance of the coating film decreases.

[0038] The aqueous two-component curable resin composition of the present invention is characterized in that it can obtain a coating film that is durable against a solvent that is compatible with water at any ratio. The solvent that is compatible with water at any ratio in the present invention is a solvent that has a solubility in water of 5 g / 100 g or more. Examples of such solvents include ethyl acetate, methyl ethyl ketone, acetone, ethylene glycol, methanol, ethanol, n-propanol, and isopropanol. Solvent resistance can be evaluated by observing the state of the coating surface when a gauze soaked in the target solvent is moved back and forth 50 times over the coating surface with a load of 1 kg using a friction tester for color fastness (manufactured by Toyo Seiki Seisakusho Co., Ltd.). EXAMPLES

[0039] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Note that, among "parts" and "%", those without a unit are all "parts by mass" and "% by mass".

[0040] <(A) Synthesis of Water-Based Acrylic Emulsion> (Production Example 1) In a separable flask equipped with a thermometer, a cooling tube, and a stirrer, 800 parts by mass of ion-exchanged water and 4 parts by mass of "ADEKA REASOAP SR-20" (manufactured by ADEKA Corporation) as an anionic reactive emulsifier were charged, and the temperature was raised to 80°C under nitrogen substitution. A monomer solution containing 260 parts by mass of methyl methacrylate as other unsaturated monomer (c), 64 parts by mass of 2-ethylhexyl methacrylate, 69.2 parts by mass of 2-hydroxyethyl methacrylate as hydroxyl group-containing unsaturated monomer (a), and 2.8 parts by mass of acrylic acid as acid group-containing unsaturated monomer (b) was added to the flask, stirred for 30 minutes, and then a dilution solution in which 1 part by mass of ammonium persulfate was dissolved in 10 parts by mass of ion-exchanged water was added to the monomer solution at 80°C. 120 minutes after the addition of ammonium persulfate, 2.8 parts by mass of 28% aqueous ammonia solution was added. Thirty minutes after the addition of the 28% aqueous ammonia solution, the mixture was cooled to give an acrylic emulsion with a resin solids content of 33.7%, a viscosity of 2000 mP·s, and a pH of 8.6.

[0041] (Production Example 2) An acrylic emulsion with a resin solid content of 33.9%, a viscosity of 1900 mPa·s, and a pH of 8.4 was obtained in the same manner as in Production Example 1, except that the anionic reactive emulsifier was changed to "ADEKA REASOAP SR-10" (manufactured by ADEKA Corporation).

[0042] (Production Example 3) An acrylic emulsion with a resin solid content of 33.8%, a viscosity of 700 mP·s, and a pH of 8.6 was obtained in the same manner as in Production Example 1, except that the reactive emulsifier was changed to a nonionic reactive emulsifier, “ADEKA REASOAP ER-10” (manufactured by ADEKA Corporation).

[0043] (Production Example 4) An acrylic emulsion with a resin solid content of 33.9%, a viscosity of 1300 mPa·s, and a pH of 8.4 was obtained in the same manner as in Production Example 1, except that the anionic reactive emulsifier was changed to “Aqualon KH-10” (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

[0044] (Examples 5 to 11, Examples 14 to 16) Except for changing the monomer composition and the amount of Adeka Reasoap SR-20 added as an anionic reactive emulsifier to the parts by mass shown in Table 1, the same procedure as in Production Example 1 was repeated to obtain an acrylic emulsion having the resin solid content, viscosity, and pH values ​​shown in Table 2.

[0045] (Production Example 12) An acrylic emulsion having the resin solid content, viscosity and pH values ​​shown in Table 2 was obtained in the same manner as in Production Example 1, except that styrene was added to the monomers.

[0046] (Production Example 13) An acrylic emulsion having the resin solid content, viscosity and pH values ​​shown in Table 2 was obtained in the same manner as in Production Example 1, except that the acrylic acid in the monomer was changed to methacrylic acid.

[0047] The theoretical values ​​of hydroxyl value, acid value, and Tg, and the measured values ​​of solids content (%), viscosity (mPa s), and pH of the aqueous acrylic emulsions of Production Examples 1 to 16 are shown in Table 2. The hydroxyl value, acid value, and Tg were calculated by the calculation method specified in the present invention.

[0048] [Table 1]

[0049] Abbreviations in the table SR-10: Adeka Rear Soap ER-10 (manufactured by ADEKA Corporation) SR-20: Adeka Rear Soap SR-20 (manufactured by ADEKA Corporation) ER-10: Adeka Rear Soap ER-10 (manufactured by ADEKA Corporation) KH-10: Aqualon KH-10 (Dai-ichi Kogyo Seiyaku Co., Ltd.) MMA: Methyl methacrylate (Tg of homopolymer: 105°C) 2EHA: 2-ethylhexyl methacrylate (Tg of homopolymer: -85°C) St: styrene (Tg of homopolymer: 100°C) HEMA: 2-hydroxyethyl methacrylate (Tg of homopolymer: 55°C) MAA: Methacrylic acid (Tg of homopolymer: 180°C) AA: acrylic acid (Tg of homopolymer: 106℃)

[0050] [Table 2]

[0051] <Preparation of Water-Based Two-Component Curable Resin Composition> Example 1 As the aqueous self-emulsifying polyisocyanate (B), "Duranate WT20-100" (manufactured by Asahi Kasei Corporation) was dispersed in ion-exchanged water to prepare a 50% aqueous solution, which was then added to 30 parts by mass of the acrylic emulsion described in Production Example 1 so that the ratio of the hydroxyl groups of the acrylic emulsion described in Production Example 1 to the isocyanate groups of the polyisocyanate was 1 to prepare a mixed solution. Next, ethanol was dissolved in ion-exchanged water as a water-soluble alcohol to prepare a 50% aqueous solution, which was then added to the mixed solution in an amount of 5% by mass relative to the total amount of the emulsion and polyisocyanate in the mixed solution to obtain an aqueous two-component curable resin composition.

[0052] (Examples 2 to 13) Water-based two-component curable resin compositions were obtained in the same manner as in Example 1, except that the acrylic emulsions were changed to those of Production Examples 2 to 13, respectively.

[0053] Example 14 An aqueous two-component curable resin composition was obtained in the same manner as in Example 1, except that the acrylic emulsion was changed to that in Production Example 5 and the 50% aqueous ethanol solution was not added.

[0054] Example 15 An aqueous two-component curable resin composition was obtained in the same manner as in Example 1, except that the acrylic emulsion was changed to that in Production Example 5 and a 50% aqueous ethanol solution was added so that the amount was 0.5 mass % based on the total amount of the emulsion and polyisocyanate.

[0055] Example 16 An aqueous two-component curable resin composition was obtained in the same manner as in Example 1, except that the acrylic emulsion was changed to that in Production Example 5, and a 50% aqueous ethanol solution was added so that the amount was 15 mass % based on the total amount of the emulsion and polyisocyanate.

[0056] (Comparative Examples 1 to 3) Water-based two-component curable resin compositions were obtained in the same manner as in Example 1, except that the acrylic emulsions were changed to those of Production Examples 14 to 16, respectively.

[0057] <Evaluation of Water-Based Two-Component Curable Resin Composition> Pot life The state of the aqueous two-component curable resin composition obtained above was visually observed over time, and the time until it gelled and lost fluidity was measured, and the results are shown in Table 3. The aqueous two-component curable resin composition of Comparative Example 1 gelled immediately after preparation, so that the pot life could not be evaluated.

[0058] <Measurement of Shore A hardness of cured product of aqueous two-component curable resin composition> The aqueous two-component curable resin compositions of Examples 1 to 16 and Comparative Example 2 were poured into a silicone cup so that the coating thickness was 3 mm, and the mixture was dried in a 140°C atmosphere for 30 minutes, and then allowed to stand in a 50°C atmosphere for 2 days to obtain a cured product. In accordance with JIS K6253-3, two of the cured products were stacked and measured using a constant pressure loader CL-150 (manufactured by ASKER) and a rubber hardness tester A type (manufactured by ASKER). Comparative Example 1 gelled immediately after preparation, and Comparative Example 3 was unable to obtain a cured product by the above-mentioned method, so the Shore A hardness of the cured product could not be measured. The results are shown in Table 3.

[0059] <Formation of coating film> The aqueous two-component curable resin compositions of Examples 1 to 16 and Comparative Example 2 were applied to coated paper on which black ink had been offset printed using a bar coater No. 8, dried for 10 seconds in a 140°C atmosphere, and then allowed to stand for 2 days in a 50°C atmosphere to obtain a coating film. Comparative Example 1 gelled immediately after preparation, and Comparative Example 3 was unable to obtain a coating film by the above-mentioned method, so the coating film could not be evaluated. The obtained coating films were evaluated by the following method, and the results are shown in Table 3.

[0060] <Evaluation of coating film> ·Ethanol resistance Using a dye fastness abrasion tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), a gauze soaked in ethanol was rubbed back and forth over the coating surface 50 times under a load of 1 kg, and the condition of the coating surface was visually evaluated according to the following criteria. A: No change B: Ink layer exposed C: Ink layer peeling is observed. ·Methyl ethyl ketone resistance Using a dye fastness abrasion tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.), a gauze soaked in methyl ethyl ketone was rubbed back and forth over the coating surface 50 times under a load of 1 kg, and the condition of the coating surface was visually evaluated according to the following criteria. A: No change B: Ink layer exposed C: Ink layer peeling is observed. For ethanol resistance and methyl ethyl ketone resistance, a rating of A is the practical level.

[0061] [Table 3]

[0062] WT20-100: Duranate WT20-100 (manufactured by Asahi Kasei Corporation) MEK: Methyl ethyl ketone

[0063] From Table 3, it can be seen that Examples 1 to 13, in which the aqueous acrylic emulsion (A) satisfies all of the conditions stipulated in the present invention, have superior Shore A hardness of the cured product compared to comparative examples in which even one of the conditions for emulsion (A) is not satisfied, such as Comparative Example 1 in which the hydroxyl value of emulsion (A) is outside the range, Comparative Example 2 in which the acid value is outside the range, and Comparative Example 3 in which the Tg is outside the range, and a coating film having excellent durability against solvents that are compatible with water in any ratio can be obtained.

[0064] Examples 5, 15 and 16 showed longer pot life and better dispersion stability than Example 14, which did not contain a water-soluble alcohol in the aqueous two-component curable resin composition.

Claims

1. The aqueous two-component curable resin composition comprises an aqueous acrylic emulsion (A) obtained by using an emulsifier having a radically polymerizable unsaturated group and a hydroxyl group-containing unsaturated monomer, and an aqueous self-emulsifying polyisocyanate (B), and is characterized in that the aqueous two-component curable resin composition satisfies the following conditions: (1) The hydroxyl value of the solid content of the emulsion (A) is 30 to 160 mgKOH / g. (2) The acid value of the solid content of the emulsion (A) is 5 mgKOH / g or less. (3) The glass transition temperature of the emulsion (A) is 30 to 80° C. (4) The Shore A hardness of the cured product of the aqueous two-component curable resin composition is 70 or more.

2. 2. The aqueous two-component curable resin composition according to claim 1, further comprising 0.5 to 15 mass % of a water-soluble alcohol based on the total amount of the emulsion (A) and the polyisocyanate (B).

Images