Aqueous two-component liquid-curable resin composition

Abstract

The purpose of the present invention is to provide an aqueous two-component liquid-curable resin composition from which a coating film having durability with respect to a solvent having a low solubility in water and a solvent that is soluble in water at an arbitrary ratio can be obtained. Provided is an aqueous two-component liquid-curable resin composition comprising: an aqueous acrylic emulsion (A) obtained using an emulsifier having a radically polymerizable unsaturated group and an unsaturated monomer containing a hydroxyl group; the aqueous two-component liquid-curable resin composition is characterized by satisfying the following conditions. (1) the solid hydroxyl value of the emulsion (A) is 30-160 mgKOH / g; (2) the solid acid value of the emulsion (A) is 5 mgKOH / g or less; (3) the theoretical glass transition temperature of the emulsion (A) is 30-80 DEG C; and (4) the Shore A hardness of a cured product of the aqueous two-component liquid-curable resin composition is 70 or more.

Description

Technical Field

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

[0002] In order to protect the surface or maintain the appearance of substrates such as paper substrates, wood substrates, plastic substrates, and metal substrates, various solvent-based coatings are generally used. However, there are concerns about the effects of solvents contained in solvent-based coatings on human bodies and the environment, and there is a shift towards water-based coatings.

[0003] Water-based coatings have poorer adhesion than solvent-based coatings depending on the substrate, but it is known that the adhesion to the substrate can be maintained by obtaining an aqueous emulsion using an emulsifier having a free radical polymerizable unsaturated group as in Patent Document 1. However, Patent Document 1 has problems such as insufficient strength of the coating film and insufficient solvent resistance.

[0004] As a method for improving the strength of the coating film, a two-component liquid curing type water-based coating composition is known in which a polyisocyanate is mixed with a resin having a hydroxyl group reactive with an isocyanate group, as in Patent Document 2 or Patent Document 3. However, Patent Document 2 or Patent Document 3 has the following problem: the coating composition has durability with respect to solvents having low solubility in water, but has poor durability with respect to solvents that are compatible with water in any proportion.

[0005] [Prior art literature]

[0006] [Patent Document]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 06-116528

[0008] [Patent Document 2] Japanese Patent Application Laid-Open No. 8-3437

[0009] [Patent Document 3] Japanese Patent Application Laid-Open No. 9-316392 Summary of the invention

[0010] [Problems to be solved by the invention]

[0011] An object of the present invention is to provide an aqueous two-component liquid curable resin composition which can obtain a coating film having durability with respect to a solvent having low solubility in water and a solvent compatible with water in an arbitrary ratio.

[0012] [Technical means to solve the problem]

[0013] The present inventors have found that, in an aqueous two-component liquid curable resin composition comprising an acrylic emulsion obtained using an emulsifier having a radically polymerizable unsaturated group and a self-emulsifying polyisocyanate, by regulating the solid content hydroxyl value, acid value and glass transition temperature of the acrylic emulsion and regulating the hardness of a cured product of the two-component liquid curable resin composition, a coating film having durability against a solvent miscible with water in an arbitrary ratio can be obtained.

[0014] That is, the present invention is as follows,

[0015] <1> An aqueous two-component liquid curable resin composition comprising an aqueous acrylic emulsion (A) and an aqueous self-emulsifying polyisocyanate (B), wherein the aqueous acrylic emulsion (A) is obtained using an emulsifier having a free radical polymerizable unsaturated group and an unsaturated monomer containing a hydroxyl group, wherein the aqueous two-component liquid curable resin composition is characterized in that the following conditions are satisfied:

[0016] (1) The solid content of the emulsion (A) has a hydroxyl value of 30 mgKOH / g to 160 mgKOH / g

[0017] (2) The solid acid value of the emulsion (A) is 5 mgKOH / g or less

[0018] (3) The glass transition temperature of the emulsion (A) is 30°C to 80°C

[0019] (4) The Shore A hardness of the cured product of the aqueous two-component liquid curing resin composition is 70 or more

[0020] <2> The aqueous two-component liquid curable resin composition according to <1>, further comprising 0.5% by mass to 15% by mass of a water-soluble alcohol based on the total of the emulsion (A) and the polyisocyanate (B).

[0021] [Effects of the Invention]

[0022] According to the present invention, in an aqueous two-component liquid curable resin composition comprising an acrylic emulsion obtained using an emulsifier having a radically polymerizable unsaturated group and a self-emulsifying polyisocyanate, the solid content hydroxyl value, acid value and glass transition temperature of the acrylic emulsion are specified, and the hardness of a cured product of the two-component liquid curable resin composition is specified, thereby obtaining a coating film having durability against a solvent that is compatible with water in an arbitrary ratio. DETAILED DESCRIPTION

[0023] Hereinafter, an embodiment of the present invention will be described in detail. In addition, the following description is an example of an embodiment of the present invention and is not limited to this description.

[0024] The aqueous two-component liquid curable resin composition of the present invention comprises an aqueous acrylic emulsion (A) and an aqueous self-emulsifiable polyisocyanate (B), wherein the aqueous acrylic emulsion (A) is obtained by using an emulsifier having a free radical polymerizable unsaturated group and an unsaturated monomer containing a hydroxyl group, and the aqueous two-component liquid curable resin composition is characterized by satisfying the following conditions.

[0025] (1) The solid content of the emulsion (A) has a hydroxyl value of 30 mgKOH / g to 160 mgKOH / g

[0026] (2) The solid acid value of the emulsion (A) is 5 mgKOH / g or less

[0027] (3) The glass transition temperature of the emulsion (A) is 30°C to 80°C

[0028] (4) The Shore A hardness of the cured product of the aqueous two-component liquid curing resin composition is 70 or more

[0029] <Water-based acrylic emulsion (A)>

[0030] The aqueous acrylic emulsion (A) is obtained by using an emulsifier having a radical 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).

[0031] <Reactive emulsifier>

[0032] As a specific example of a reactive emulsifier, for example, various emulsifiers having a free radical polymerizable carbon-carbon unsaturated double bond and a nonionic, ionic hydrophilic group in one molecule can be cited, and in the present invention, it is preferred to use an emulsifier having an anionic or nonionic hydrophilic group. Here, as an anionic hydrophilic group, a sulfonic acid group, a phosphoric acid group, a carboxyl group, etc. can be cited. As a commercially available product of such a reactive emulsifier having an anionic hydrophilic group (hereinafter sometimes simply described as "anionic reactive emulsifier"), for example, there are "ADEKAREASOAP SR-10", "ADEKAREASOAP SR-20", "ADEKAREASOAP SR-3025" (more than ADEKA Co., Ltd.), "Aqualon KH-10" (Daiichi Kogyo Seiyaku Co., Ltd.), "SPINOMAR NaSS" (Tosoh Fine Chemical Co., Ltd.), etc. In addition, as the nonionic hydrophilic group, a polyethylene oxide group can be cited. Commercially available products of such reactive emulsifiers having a nonionic hydrophilic group (hereinafter, sometimes simply referred to as "nonionic reactive emulsifiers") include, for example, "ADEKAREASOAP ER-10" (manufactured by ADEKA Co., Ltd.).

[0033] The amount of such reactive emulsifier used is preferably 0.1% to 5% by mass relative to the total amount of the polymerized unsaturated monomers. When the amount is within the above range, a stable aqueous acrylic emulsion can be obtained without generating aggregates after polymerization. In addition, a coating film of an aqueous two-component liquid curable resin composition with good solvent resistance can be obtained.

[0034] <Hydroxyl-containing unsaturated monomer (a)>

[0035] As long as the hydroxyl group-containing unsaturated monomer (a) is an ethylenically unsaturated monomer containing a hydroxyl group in the molecule, various known substances can be used, and it is used to impart a hydroxyl group as a reaction site with polyisocyanate to the aqueous acrylic emulsion. Specific examples of (a) include hydroxyl group-containing (meth)acrylates such as hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and hydroxyhexyl (meth)acrylate. Among these, 2-hydroxyethyl methacrylate is preferably used.

[0036] <Unsaturated monomer containing an acid group (b)>

[0037] As the unsaturated monomer (b) containing an acid group, any known ethylenic unsaturated monomer containing various acid groups such as a carboxyl group or a sulfonic acid group in the molecule and their salts can be used, and it is used to impart an acid value to the aqueous acrylic emulsion. As the ethylenic unsaturated monomer containing a carboxyl group, specifically, unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; unsaturated dicarboxylic acids such as itaconic acid and maleic acid can be listed. As the ethylenic unsaturated monomer containing a sulfonic acid group, sulfoethyl methacrylate, styrene sulfonic acid, etc. can be listed. Among these, it is preferred to use an ethylenic unsaturated monomer containing a carboxyl group, and it is particularly preferred to use (meth)acrylic acid.

[0038] <Other unsaturated monomers (c)>

[0039] The other unsaturated monomers (c) are not particularly limited as long as they do not hinder the effects of the present invention, and specifically include: esters of acrylic acid or methacrylic acid such as methyl, ethyl, propyl, butyl, hexyl, ethylhexyl, and lauryl; esters of vinyl alcohol with carboxylic acids such as acetic acid and propionic acid; unsaturated aromatic compounds such as styrene, α-methylstyrene, and vinylnaphthalene; unsaturated hydrocarbons such as butadiene and isoprene; amides such as acrylamide, methacrylamide, and N,N-dimethylacrylamide; 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, and diethylene glycol; polyacrylates and polymethacrylates of polyols such as glycerol, trimethylolpropane, and pentaerythritol. Among these, it is preferable to use esters of acrylic acid or methacrylic acid or unsaturated aromatic compounds, and it is particularly preferable to use methyl methacrylate as methyl ester of methacrylic acid, 2-ethylhexyl methacrylate as ethylhexyl ester of methacrylic acid, and styrene.

[0040] In the present invention, the mass fraction of the aqueous acrylic emulsion (A) of the components (a), (b) and (c) can be adjusted so that the hydroxyl value, acid value and glass transition temperature of (A) described later are within the ranges specified in the present invention, and it is preferred that the components are contained in a mass fraction within the preferred ranges of these values.

[0041] 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 the solid content, and is calculated by the following formula 1 by calculating the mass (mg) of potassium hydroxide equivalent to the hydroxyl group of 1 g of the unsaturated monomer (a) containing a hydroxyl group (molecular weight 56.1) and the constituent ratio (mass %) of the unsaturated monomer (a) containing a hydroxyl group in (A). The hydroxyl value of the aqueous acrylic emulsion (A) used in the present invention is 30 mgKOH / g to 160 mgKOH / g per solid content, and more preferably 50 mgKOH / g to 100 mgKOH / g. If the hydroxyl value is less than 30 mgKOH / g, there are too few crosslinking points generated by the reaction with polyisocyanate, so that the solvent resistance or hardness of the obtained coating film is reduced. If the hydroxyl value exceeds 160 mgKOH / g, it gels when mixed with polyisocyanate, and a coating film cannot be formed.

[0042] (Formula 1) ((56.1×1000) / (Mw(a)×number of hydroxyl groups in (a)))×((a)% / 100)

[0043] (Mw(a) in the formula represents the molecular weight of (a), and (a)% represents the constituent ratio (mass %) of (a) in (A))

[0044] 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 for neutralization of the acid groups contained in 1 g of the solid content, and is calculated by calculating the mass (mg) of potassium hydroxide (molecular weight 56.1) required for neutralization of each 1 g of the unsaturated monomer (b) containing an acid group, and the constituent ratio (mass %) of the unsaturated monomer (b) containing the acid group in (A) based on the molecular weight of the monomer, and by the following formula 2. The acid value of the aqueous acrylic emulsion (A) used in the present invention is 5 mgKOH / g or less per solid content, and more preferably 3 mgKOH / g or less. If the acid value exceeds 5 mgKOH / g, the solvent resistance or hardness of the obtained coating film is reduced.

[0045] (Formula 2) ((56.1×1000) / (Mw(b)×number of acid groups in (b)))×((b)% / 100)

[0046] (Mw(b) in the formula represents the molecular weight of (b), and (b)% represents the constituent ratio (mass %) of (b) in (A))

[0047] The glass transition temperature (hereinafter sometimes abbreviated as Tg) of the aqueous acrylic emulsion (A) used in the present invention is a theoretical value calculated from the ratio of the components (a), (b) and (c) constituting the aqueous acrylic emulsion (A) and obtained by the following FOX formula.

[0048] 1 / Tg=W1 / Tg1+W2 / Tg2+…+Wn / Tgn…FOX formula

[0049] In the formula, Tg represents the glass transition temperature (K: Kelvin), W1, W2...Wn represent the mass fraction of each monomer calculated based on the ratio relative to the total amount of (a) component, (b) component and (c) component constituting the aqueous acrylic emulsion, and Tg1, Tg2...Tgn represent the glass transition temperature of the homopolymer of each monomer.

[0050] The glass transition temperatures of homopolymers of the respective monomers are exemplified as follows.

[0051] Methyl methacrylate: 378K (105°C)

[0052] 2-Ethylhexyl methacrylate: 188K (-85℃)

[0053] Styrene: 373K (100°C)

[0054] 2-Hydroxyethyl methacrylate: 328K (55°C)

[0055] Methacrylic acid: 453K (180°C)

[0056] Acrylic acid: 379K (106℃)

[0057] The Tg of the aqueous acrylic emulsion (A) used in the present invention is 30° C. to 80° C., more preferably 40° C. to 70° C. If the Tg is less than 30° C., the hardness of the coating film decreases, thereby reducing the solvent resistance of the coating film. If the Tg exceeds 80° C., the coating film cannot be formed.

[0058] As the polymerization initiator used in the polymerization of the aqueous acrylic emulsion (A) in the present invention, persulfates such as potassium persulfate and ammonium persulfate, hydrogen persulfate, 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.

[0059] When the degree of polymerization needs to be adjusted during polymerization, a chain transfer agent represented by mercaptans may be used, for example, dodecyl mercaptan, lauryl mercaptan, etc. may be mentioned.

[0060] In the aqueous acrylic emulsion (A) of the present invention, a non-reactive low molecular weight emulsifier having no free radical polymerizable unsaturated group may be included as long as the effect of the invention is not impaired. As the non-reactive low molecular weight emulsifier, a commercially available anionic or nonionic emulsifier described later may be used. Examples of anionic emulsifiers include sodium dodecylbenzenesulfonate, sodium polyoxyethylene styrenated phenol sulfate, and formaldehyde condensates of sodium naphthalenesulfonate. Examples of nonionic emulsifiers include polyethylene oxide compounds and polypropylene oxide compounds. These can be used in an amount limited to 5% by mass relative to the total amount of the polymerized unsaturated monomers.

[0061] 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 by dropping a monomer mixed solution into water in which an emulsifier is dissolved.

[0062] <Aqueous self-emulsifying polyisocyanate (B)>

[0063] As the aqueous self-emulsifying polyisocyanate (B), various known ones can be used, but preferably one obtained by reacting a part of isocyanate groups of aliphatic or alicyclic polyisocyanates and derivatives thereof with polyethylene oxide monoalkyl ether to impart water dispersibility.

[0064] Examples of commercially available products of such aqueous self-emulsifying polyisocyanates include "Duranate (registered trademark) WB40-100" and "Duranate (registered trademark) WT20-100" (both manufactured by Asahi Kasei Corporation).

[0065] In the present invention, the method for mixing the aqueous acrylic emulsion (A) and the aqueous self-emulsifiable polyisocyanate (B) is not particularly limited, and examples thereof include a method of adding the polyisocyanate (B) preliminarily dispersed in water to the acrylic emulsion (A), or a method of directly adding the polyisocyanate (B) to the acrylic emulsion (A) and stirring and dispersing the mixture.

[0066] <Water-soluble alcohol>

[0067] In the present invention, a water-soluble alcohol may be added to the aqueous two-component liquid curable resin composition. 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.

[0068] In the present invention, the aqueous two-component liquid curable resin composition preferably contains 0.5% to 15% by mass of a water-soluble alcohol relative to the total of the acrylic emulsion (A) and the polyisocyanate (B), and more preferably contains 5% to 10% by mass of a water-soluble alcohol. By containing the water-soluble alcohol within the above range, the aqueous two-component liquid curable resin composition can maintain a dispersed state. In addition, by setting the content of the water-soluble alcohol to 15% by mass or less, it is possible to prevent the water-soluble alcohol from reacting with the isocyanate group of the aqueous self-emulsifiable polyisocyanate (B) to inhibit crosslinking with the emulsion (A), thereby preventing the solvent resistance or hardness of the obtained coating film from decreasing.

[0069] In the present invention, the aqueous two-component curable resin composition may contain, in addition to the emulsion (A), polyisocyanate (B), and water-soluble alcohol, thickeners, film-forming aids, defoamers, leveling agents, preservatives, and other additives as needed.

[0070] In order to improve film forming properties or wettability, 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 may be used as additives.

[0071] The aqueous two-component liquid curable resin composition of the present invention can be applied to the surface of the object to be coated by a common coating method such as brush coating, spray coating, gravure coating, flexographic coating, roll coating, etc. after adjusting the viscosity to an appropriate level, and then dried at room temperature or forcedly dried to form a coating film.

[0072] In addition, various coating targets can be applied, including paper substrates, plastic substrates such as polyethylene, polypropylene, and polystyrene, various metal substrates such as iron, stainless steel, and aluminum, and glass substrates.

[0073] The Shore A hardness of the cured product of the aqueous two-component liquid curable resin composition in the present invention is a measured value obtained by overlapping two sheets of the cured product and measuring them in accordance with Japanese Industrial Standards (JIS) K6253-3.

[0074] The Shore A hardness of the cured product of the aqueous two-component liquid curable resin composition in the present invention is at least 70. If the Shore A hardness is less than 70, the solvent resistance of the coating film decreases.

[0075] The aqueous two-component liquid curing resin composition of the present invention is characterized in that a coating film having durability against solvents that are compatible with water in any proportion can be obtained. The solvent that is compatible with water in any proportion in the present invention is a solvent having a solubility of 5 g / 100 g or more in water. Examples thereof include: ethyl acetate, methyl ethyl ketone, ethyl ketone, ethylene glycol, methanol, ethanol, n-propanol, isopropanol, etc. Solvent resistance can be evaluated as follows: observe the state of the coating surface when a gauze with a load of 1 kg and soaked in the solvent of interest is moved back and forth 50 times on the coating surface using a friction tester for color fastness (manufactured by Toyo Seiki Seisaku-sho Co., Ltd.).

[0076] [Example]

[0077] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition, "parts" and "%" without units are all "parts by mass" and "mass %".

[0078] <Synthesis of aqueous acrylic emulsion (A)>

[0079] (Production Example 1)

[0080] In a separable flask equipped with a thermometer, a cooling tube, and a stirrer, 800 parts by mass of ion exchange water and 4 parts by mass of "ADEKAREASOAP SR-20" (manufactured by ADEKA Co., Ltd.) as an anionic reactive emulsifier were placed, and the temperature was raised to 80°C under nitrogen substitution. A monomer solution prepared by mixing 260 parts by mass of methyl methacrylate as other unsaturated monomers (c), 64 parts by mass of 2-ethylhexyl methacrylate, 69.2 parts by mass of 2-hydroxyethyl methacrylate as an unsaturated monomer containing a hydroxyl group (a), and 2.8 parts by mass of acrylic acid as an unsaturated monomer containing an acid group (b) was put into the flask, and after stirring for 30 minutes, a dilution prepared by dissolving 1 part by mass of ammonium persulfate in 10 parts by mass of ion exchange water was added to the monomer solution at 80°C. 120 minutes after the addition of ammonium persulfate, 2.8 parts by mass of a 28% ammonia solution was added. After 30 minutes from the addition of the 28% ammonia aqueous solution, the mixture was cooled to obtain an acrylic emulsion having a resin solid content of 33.7%, a viscosity of 2000 mPa·s, and a pH of 8.6.

[0081] (Production Example 2)

[0082] An acrylic emulsion having 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 "ADEKAREASOAP SR-10" (manufactured by ADEKA Co., Ltd.).

[0083] (Production Example 3)

[0084] An acrylic emulsion having a resin solid content of 33.8%, a viscosity of 700 mPa·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 "ADEKAREASOAP ER-10" (manufactured by ADEKA Co., Ltd.) which is a nonionic reactive emulsifier.

[0085] (Production Example 4)

[0086] An acrylic emulsion having 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 Dai-ichi Kogyo Seiyaku Co., Ltd.).

[0087] (Manufacturing Examples 5 to 11, Manufacturing Examples 14 to 16)

[0088] Except changing the monomer preparation and the addition amount of ADEKAREASOAP SR-20 as an anionic reactive emulsifier to the parts by mass described in Table 1, an acrylic emulsion having the resin solid content, viscosity and pH values ​​described in Table 2 was obtained in the same manner as in Production Example 1.

[0089] (Production Example 12)

[0090] Except for adding styrene to the monomer, the same procedure as in Production Example 1 was carried out to obtain an acrylic emulsion having the resin solid content, viscosity, and pH values ​​shown in Table 2.

[0091] (Production Example 13)

[0092] Except having changed the acrylic acid in the monomer into methacrylic acid, it carried out similarly to Production Example 1, and obtained the acrylic emulsion which has the resin solid content, viscosity, and pH value shown in Table 2.

[0093] The theoretical values ​​of hydroxyl value, acid value and Tg and the measured values ​​of solid 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.

[0094] [Table 1]

[0095]

[0096] Abbreviation in the table

[0097] SR-10: ADEKAREASOAP SR-10 (manufactured by ADEKA Co., Ltd.)

[0098] SR-20: ADEKAREASOAP SR-20 (manufactured by ADEKA Co., Ltd.)

[0099] ER-10: ADEKAREASOAP ER-10 (manufactured by ADEKA Co., Ltd.)

[0100] KH-10: Aqualon KH-10 (First Industrial Pharmaceutical Co., Ltd.)

[0101] MMA: Methyl methacrylate (Tg of homopolymer: 105°C)

[0102] 2EHA: 2-ethylhexyl methacrylate (homopolymer Tg: -85°C)

[0103] St: Styrene (Tg of homopolymer: 100°C)

[0104] HEMA: 2-Hydroxyethyl methacrylate (Tg of homopolymer: 55°C)

[0105] MAA: Methacrylic acid (Tg of homopolymer: 180°C)

[0106] AA: Acrylic acid (homopolymer Tg: 106°C)

[0107] [Table 2]

[0108]

[0109] <Preparation of aqueous two-component liquid curing resin composition>

[0110] (Example 1)

[0111] "Duranate WT20-100" (manufactured by Asahi Kasei Corporation) as an aqueous self-emulsifying polyisocyanate (B) was dispersed in ion exchange water to prepare a 50% aqueous solution, and then added to 30 parts by mass of the acrylic emulsion described in Preparation Example 1 so that the ratio of the hydroxyl group of the acrylic emulsion described in Preparation Example 1 to the isocyanate group of the polyisocyanate was 1 to prepare a mixed solution. Next, ethanol as a water-soluble alcohol was dissolved in ion exchange water to prepare a 50% aqueous solution, and this was added so as to be 5% by mass relative to the total of the emulsion and the polyisocyanate in the mixed solution, thereby obtaining an aqueous two-component liquid curable resin composition.

[0112] (Example 2 to Example 13)

[0113] Aqueous two-component liquid curable resin compositions were obtained in the same manner as in Example 1 except that the acrylic emulsions were changed to those in Production Examples 2 to 13, respectively.

[0114] (Example 14)

[0115] An aqueous two-component liquid curable resin composition was obtained in the same manner as in Example 1 except that the acrylic emulsion was changed to that of Production Example 5 and the 50% ethanol aqueous solution was not added.

[0116] (Example 15)

[0117] 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 of Production Example 5 and a 50% ethanol aqueous solution was added in an amount of 0.5% by mass based on the total amount of the emulsion and the polyisocyanate.

[0118] (Example 16)

[0119] 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 of Production Example 5 and a 50% ethanol aqueous solution was added in an amount of 15% by mass relative to the total of the emulsion and the polyisocyanate.

[0120] (Comparative Example 1 to Comparative Example 3)

[0121] Aqueous two-component liquid curable resin compositions were obtained in the same manner as in Example 1 except that the acrylic emulsions were changed to those in Production Examples 14 to 16, respectively.

[0122] <Evaluation of aqueous two-component liquid curing resin composition>

[0123] ·Applicable period

[0124] The state of the aqueous two-component liquid curable resin composition obtained was visually checked over time, and the time from gelation to loss of fluidity was measured and the results are shown in Table 3. The aqueous two-component liquid curable resin composition of Comparative Example 1 gelled immediately after preparation, so the pot life could not be evaluated.

[0125] <Measurement of Shore A Hardness of Cured Product of Aqueous Two-Component Liquid Curable Resin Composition>

[0126] The aqueous two-component liquid curable resin composition of Examples 1 to 16 and Comparative Example 2 was injected into a silicone cup so that the coating thickness became 3 mm, and after drying at 140°C for 30 minutes, it was left to stand at 50°C for two days to obtain a cured product. According to JIS K6253-3, two sheets of the cured product were overlapped and measured using a constant pressure load device CL-150 (manufactured by ASKER) and a rubber hardness meter type A (manufactured by ASKER). Comparative Example 1 gelled immediately after adjustment, and Comparative Example 3 could not obtain a cured product by the method described above, so the Shore A hardness of the cured product could not be measured. The results are shown in Table 3.

[0127] <Film formation>

[0128] The aqueous two-component curable resin compositions of Examples 1 to 16 and Comparative Example 2 were applied to coated paper printed with black ink using a bar coater No. 8, dried for 10 seconds at 140°C, and left to stand for two days at 50°C to obtain a coating film. Comparative Example 1 gelled immediately after preparation, and Comparative Example 3 could not obtain a coating film by the method described above, so the coating film could not be evaluated. The results of the evaluation of the obtained coating films by the following method are shown in Table 3.

[0129] <Evaluation of coating film>

[0130] Ethanol resistance

[0131] The state of the coating surface was visually evaluated by using a color fastness friction tester (manufactured by Toyo Seiki Seisaku-sho Co., Ltd.) according to the following criteria when gauze soaked in ethanol with a load of 1 kg was moved back and forth 50 times on the coating surface.

[0132] A: No change

[0133] B: Ink layer exposed

[0134] C: Peeling observed in the ink layer

[0135] Resistance to methyl ethyl ketone

[0136] The state of the coating surface was visually evaluated by using a color fastness friction tester (manufactured by Toyo Seiki Seisaku-sho Co., Ltd.) with a load of 1 kg and gauze soaked in methyl ethyl ketone reciprocating 50 times on the coating surface according to the following criteria.

[0137] A: No change

[0138] B: Ink layer exposed

[0139] C: Peeling observed in the ink layer

[0140] Regarding ethanol resistance and methyl ethyl ketone resistance, evaluation A was a practical level.

[0141] [Table 3]

[0142]

[0143] WT20-100: Duranate WT20-100 (manufactured by Asahi Kasei Co., Ltd.)

[0144] MEK: Methyl Ethyl Ketone

[0145] As can be seen from Table 3, Examples 1 to 13 in which the aqueous acrylic emulsion (A) satisfies all the conditions specified in the present invention have excellent Shore A hardness of the cured product, and a coating film having excellent durability against a solvent compatible with water in any proportion can be obtained, compared with Comparative Examples in which none of the conditions of the emulsion (A) are satisfied, such as Comparative Example 1 in which the hydroxyl value of the emulsion (A) is outside the range, Comparative Example 2 in which the acid value of the emulsion (A) is outside the range, and Comparative Example 3 in which the Tg of the emulsion (A) is outside the range.

[0146] Compared with Example 14 in which the water-based two-component liquid curable resin composition does not contain a water-soluble alcohol, Examples 5, 15, and 16 showed that the pot life was prolonged and the dispersion stability was excellent.

Claims

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

2. The aqueous two-component liquid curable resin composition according to claim 1, characterized in that: The water-soluble alcohol is contained in an amount of 0.5% by mass to 15% by mass based on the total amount of the emulsion (A) and the polyisocyanate (B).

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