JP7164066B2 - Emulsion composition, aqueous coating agent, and method for producing emulsion composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an emulsion composition capable of forming a coating film excellent in water resistance and oil resistance on a substrate, an aqueous coating agent containing the emulsion composition, and a method for producing the emulsion composition.

Laminated films using plastics such as polyethylene, which are typified by food packaging, are widely used because of their excellent water resistance and oil resistance. However, it is difficult to recycle these laminated wrapping papers, and in recent years there has been an increasing demand for plastic-free packaging as an environmental effort.

Until now, fluororesin coating has been proposed as a material other than laminate film that achieves both water resistance and oil resistance, but it has not been widely used due to the toxicity of fluororesin and its high price (patent Reference 1).
Also, the use of polyvinyl alcohol has been proposed as a coating agent with excellent oil resistance, but polyvinyl alcohol is conventionally inferior in water resistance, making it difficult to substitute for laminate films (Patent Document 2).

Further, an alkali-neutralized polymer of ethylene and (meth)acrylic acid has been reported as a water-based coating agent having both water resistance and oil resistance. However, since ethylene monomer is gaseous, a special reactor that satisfies high temperature and high pressure conditions is required to obtain ethylene (meth)acrylic acid polymer, and the product concentration of the water-based coating agent using this is low. Therefore, from the viewpoint of price and versatility, it has not yet been possible to replace the laminated film (Patent Document 3).

JP 2019-196564 JP 2019-073660 Special table 2016-520671

An object of the present invention is to provide an emulsion composition having both excellent water resistance and oil resistance, an aqueous coating agent containing the emulsion composition, and a method for producing the emulsion composition.

The present inventors used methyl methacrylate, butyl acrylate, and 2-ethylhexyl acrylate, which are general-purpose monomers that can be used in radical polymerization, in a specific ratio without using fluororesin or ethylene (meth)acrylic acid polymer. By designing the glass transition temperature calculated from them in the optimum range, it was found that an aqueous emulsion that exhibits both water resistance and oil resistance at extremely high levels can be obtained.

That is, the present invention
(1) An emulsion composition containing water (A) and a copolymer (B) of monomers containing at least methyl methacrylate (b1), butyl acrylate (b2), and 2-ethylhexyl acrylate (b3). Therefore, the proportion of the copolymer (B) contained in the emulsion composition is 1 to 60% by mass, and the ratio of (b1), (b2), and (b3) constituting the copolymer (B) is calculated. The glass transition temperature (Tg) is −10 to −45° C., and the ratio of (b1), (b2), and (b3) to the total polymer components contained in the emulsion composition is 70 to 100% by mass. An emulsion composition characterized by
(2) The above-described (1), further comprising a polymer emulsifier (C) in a mass ratio of copolymer (B):polymer emulsifier (C)=90:10 to 60:40. an emulsion composition of
(3) The emulsion composition according to (1) or (2) above, wherein the copolymer (B) has a weight average molecular weight of 50,000 to 3,000,000,
(4) an aqueous coating agent comprising the emulsion composition according to any one of (1) to (3);
(5) Emulsion composition containing copolymer (B) obtained by emulsion polymerization of monomers containing at least methyl methacrylate (b1), butyl acrylate (b2), and 2-ethylhexyl acrylate (b3) in water A method for producing a product, wherein the glass transition temperature (Tg) calculated from the ratio of (b1), (b2), and (b3) in the monomer subjected to emulsion polymerization is -10 to -45 ° C., A method for producing an emulsion composition, wherein the ratio of (b1), (b2), and (b3) to the total monomers subjected to emulsion polymerization is 70 to 100% by mass,
(6) Obtained by emulsion polymerization of monomers containing at least methyl methacrylate (b1), butyl acrylate (b2), and 2-ethylhexyl acrylate (b3) in water in the presence of a polymer emulsifier (C) A method for producing an emulsion composition containing a copolymer (B), wherein the glass transition temperature (Tg ) is −10 to −45° C., and (b1), (b2), and (b3) contained in the monomers subjected to the polymerization of the polymer emulsifier (C), and contained in the monomers subjected to the emulsion polymerization ( The total mass of b1), (b2), and (b3) is 70 to 100% by mass of the total mass of the monomers subjected to polymerization of the polymer emulsifier (C) and emulsion polymerization. a method for producing an emulsion composition,
is.

By using the emulsion obtained by the present invention, it is possible to obtain both high levels of water resistance and oil resistance, and it is possible to eliminate plastics by substituting laminate films.

The method for producing the emulsion of the present invention will be specifically described below.

The emulsion composition of the present invention contains at least water (A) and a copolymer (B) of monomers containing at least methyl methacrylate (b1), butyl acrylate (b2), and 2-ethylhexyl acrylate (b3). include.

<Water (A)>
The water used in the present invention is preferably ion-exchanged water or soft water, and water that adversely affects radical polymerization cannot be used.

<Copolymer (B)>
The copolymer (B) of the present invention is a monomer copolymer containing at least methyl methacrylate (b1), butyl acrylate (b2), and 2-ethylhexyl acrylate (b3) as essential components. The skeleton derived from the components (b1), (b2), and (b3) constituting the copolymer (B) plays an important role in controlling the surface properties and film-forming properties from the viewpoint of water resistance and oil resistance. and the glass transition temperature (Tg) calculated from the ratio of the (b1) component, (b2) component, and (b3) component constituting the copolymer (B) must be -10 to -45 ° C. There is Here, the glass transition temperature (Tg) calculated from the ratio of the (b1) component, (b2) component, and (b3) component constituting the copolymer (B) is a theory obtained from the following FOX formula. value.
1/Tg=W1/Tg1+W2/Tg2+W3/Tg3... FOX formula (Tg in the formula is the glass transition temperature (K: Kelvin), and W1, W2, and W3 constitute the copolymer (B) ( The mass fraction of each monomer calculated from the ratio to the total amount of b1) component, (b2) component, and (b3) component, and Tg1, Tg2, and Tg3 are homogenous of each monomer represents the glass transition temperature of the polymer, which are 378K, 219K, and 188K, respectively.)

In addition to the above (b1) to (b3), other vinyl group-containing monomers may be used up to an upper limit of 30% by mass of the total monomers for the copolymer as long as the effects of the present invention are not impaired. . Other vinyl group-containing monomers include nonionic monomers and ionic monomers.

Examples of nonionic monomers include styrenes, (meth)acrylic acid alkyl esters other than (b1) to (b3), and (meth)acrylamide. Examples of ionic monomers include (meth)acrylic acid and maleic acid. In particular, it is preferable to use glycidyl methacrylate as a nonionic monomer, and acrylic acid and methacrylic acid as ionic monomers, if necessary. When the emulsifier) is not used, from the viewpoint of stably emulsifying and dispersing the copolymer (B) in water, it is preferable to use 1 to 10% by mass of (meth)acrylic acid in the copolymer (B).

The weight-average molecular weight of the copolymer (B) is preferably 50,000 to 3,000,000 from the viewpoint of water resistance, handling, and printability. Specifically, the weight-average molecular weight is preferably 50,000 or more because the water resistance deteriorates as the molecular weight of the produced polymer decreases. On the other hand, since the emulsion viscosity increases as the molecular weight increases, the weight average molecular weight is preferably 3,000,000 or less from the viewpoint of handling and print coating suitability. In the present invention, the weight average molecular weight is measured by GPC method under the following conditions.
Apparatus: HLC-8320GPC
Column: Tosoh TSK-gel SUPER MULTIPORE HZ-H and SUPER MULTIPORE HZ-M are connected and used Eluent: Tetrahydrofuran, 0.35 mL/min

The emulsion composition of the present invention may contain a copolymer other than the copolymer (B), such as the polymer emulsifier (C) described later, but it accounts for the total polymer components contained in the emulsion composition (b1 ), (b2), and (b3) must be 70 to 100% by mass because they have a large effect on the surface properties and film-forming properties of the emulsion coating film, as described for the copolymer (B). There is If the content is less than 70% by mass, both water resistance and oil resistance are greatly reduced. In addition, the glass transition temperature (Tg (total)) of all the polymer components contained in the emulsion composition makes it difficult for the problem of blocking due to the adhesiveness of the coating film to occur, and the emulsion can be sufficiently formed with only the drying heat of the coating device. A range of -45°C to 40°C is preferable because it is possible. Here, the glass transition temperature (Tg(total)) of all polymer components contained in the emulsion composition is a theoretical value obtained from the following FOX formula.
1/Tg(total)=W1/Tg1+W2/Tg2+...+Wn/Tgn... FOX formula (Tg(total) in the formula is the glass transition temperature (K: Kelvin ), W1, W2, . represents.)

<Polymer emulsifier (C)>
The emulsion composition of the present invention may optionally contain a polymer emulsifier (C) for the purpose of stably emulsifying and dispersing the copolymer (B) in the emulsion composition. As a polymer emulsifier, an anionic styrene acrylic resin or acrylic resin having a weight average molecular weight of 5,000 to 30,000 is neutralized with a basic compound such as ammonia, an organic amine, or sodium hydroxide. and water-soluble resins such as polyacrylamide and starch. Preferably, an anionic styrene-acrylic resin having a weight-average molecular weight of 5,000 to 30,000, which is generally used for emulsifying an acrylic emulsion, or an ammonia-neutralized acrylic resin.

When the polymer emulsifier (C) is used, the ratio between the copolymer (B) and the polymer emulsifier (C) is such that the water resistance is not lowered due to the hydrophilicity of the polymer emulsifier, and the emulsification Copolymer (B):polymer emulsifier (C)=95:5 to 50:50 is preferred, particularly 90:10 to 60, because side reactions such as extramicellar polymerization and aggregation of the emulsion are less likely to occur during polymerization. :40. In the present invention, when determining the mass ratio of the copolymer (B) and the polymer emulsifier (C), both the copolymer (B) and the polymer emulsifier (C) are the initiator used at the time of each polymerization. The total ratio of only the monomer components constituting each is used without including the agent, chain transfer agent, or basic compound used for neutralization.

<Others>
The emulsion composition of the present invention may contain a low-molecular-weight emulsifier as long as it does not impair the effects of the invention. As the low-molecular-weight emulsifier, a commercially available nonionic emulsifier or anionic emulsifier, which will be described later, can be used. Nonionic emulsifiers include polyethylene oxide and polypropylene oxide compounds. Examples of anionic emulsifiers include sodium dodecylbenzenesulfonate, sodium polyoxyethylenestyrenated phenol sulfate, formalin condensates of sodium naphthalenesulfonate, and the like. These can be used up to a limit of 0.1 to 10% by weight based on the polymer contained in the emulsion composition.

<Method for producing emulsion composition>
In the production of the emulsion composition of the present invention, the copolymer (B) contains at least methyl methacrylate (b1), butyl acrylate (b2), and 2-ethylhexyl acrylate (b3) in water (A). It is obtained by emulsion polymerization of a monomer. The proportions of components (b1), (b2), and (b3) in the monomers used for emulsion polymerization must be 70 to 100% by mass because they greatly affect the surface properties and film-forming properties of the emulsion coating film. There is

Further, in the production of the emulsion composition of the present invention, the copolymer (B) is mixed with methyl methacrylate (b1), butyl acrylate (b2) and acrylic in the presence of the polymer emulsifier (C) in water. It may be obtained by emulsion polymerization of a monomer containing at least 2-ethylhexyl acid (b3). (b1), (b2), and (b3) contained in the monomers subjected to polymerization of the polymer emulsifier (C), and (b1) and (b1) contained in the monomers subjected to emulsion polymerization of the copolymer (B), Since the total mass of b2) and (b3) has a large effect on the surface properties and film-forming properties of the emulsion coating film, It should be 70-100% by weight.

As a method for producing the emulsion composition of the present invention, a conventionally known emulsion polymerization method can be applied. For example, a reaction vessel equipped with a stirrer and a nitrogen gas inlet tube is charged with water (A) and, if necessary, a polymer emulsifier (C) and a low molecular weight emulsifier, and polymerization initiators such as ammonium persulfate, potassium persulfate, and persulfate. Any redox initiator consisting of a peroxide such as hydrogen oxide or a combination of these peroxides and a reducing agent such as ferrous sulfate, sodium bisulfite, ascorbic acid, or sodium ascorbate is used, and the reaction temperature is adjusted to At 60 to 90° C., a mixture of monomers containing components (b1) to (b3) and optionally a known chain transfer agent such as alkyl mercaptan was added dropwise over 60 to 180 minutes, and after completion of dropping, An emulsion composition can be obtained by reacting for ~480 minutes.

The emulsion composition of the present invention is useful as a component of an aqueous coating agent, and if necessary, general-purpose organic solvents such as isopropyl alcohol (IPA) and butyl cellosolve, fillers, waxes, film-forming aids, and leveling agents. , defoamers and preservatives can be added.

The coating base material when using the aqueous coating agent containing the emulsion composition of the present invention is paper or paperboard, and specific examples include base paper for cups, food packaging paper, kraft paper, liner paper, woodfree paper, and the like.

Examples of coating conditions for the water-based coating agent include methods using printing machines such as flexographic printing and gravure printing, and methods using coating machines such as roll coaters, size presses, blade coaters and curtain coaters. The coating amount may be about 0.5 to 30 g/m ² of the solid content of the water-based coating agent on one side of the substrate, depending on the level of water resistance and oil resistance required. Moreover, the drying method after coating is not particularly limited, and drying by non-contact infrared drying, hot air drying, and contact-type cylinder drying may be mentioned.

The application of the water-based coating agent is not particularly limited, but it is suitable for any application that requires water resistance and/or oil resistance. It is suitable as a substitute for polyethylene laminate in

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples. In addition, % is mass % unless otherwise specified.

<Measurement of molecular weight>
The weight average molecular weight was measured by the GPC method under the following conditions.
Apparatus: HLC-8320GPC
Column: Tosoh TSK-gel SUPER MULTIPORE HZ-H and SUPER MULTIPORE HZ-M are connected and used Eluent: Tetrahydrofuran, 0.35 mL/min

<Synthesis of polymer emulsifier (C)>
(Synthesis example 1)
Propylene glycol monomethyl ether (500 g) was charged into a separable flask equipped with a thermometer, a condenser and a stirrer, and the temperature was raised to 145°C under nitrogen substitution. Then, a mixture of styrene (175 g), α-methylstyrene (200 g), acrylic acid (125 g) and ditertiarybutyl peroxide (7.5 g) was added dropwise over 120 minutes. After 60 minutes from the end of dropping, atmospheric distillation and vacuum distillation were carried out to remove propylene glycol monomethyl ether and obtain polymer emulsifier (1) having an acid value of 195 mgKOH/g.

(Synthesis example 2)
Propylene glycol monomethyl ether (500 g) was charged into a separable flask equipped with a thermometer, a condenser and a stirrer, and the temperature was raised to 145°C under nitrogen substitution. Then, a mixture of styrene (125 g), α-methylstyrene (150 g), acrylic acid (125 g), methyl methacrylate (100 g) and ditertiarybutyl peroxide (7.5 g) was added dropwise over 120 minutes. After 60 minutes from the completion of the dropwise addition, atmospheric distillation was carried out, followed by vacuum distillation to remove propylene glycol monomethyl ether and obtain a polymer emulsifier (2) having an acid value of 195 mgKOH/g.

(Synthesis Example 3)
Propylene glycol monomethyl ether (500 g) was charged into a separable flask equipped with a thermometer, a condenser and a stirrer, and the temperature was raised to 145°C under nitrogen substitution. Then, a mixture of styrene (100 g), α-methylstyrene (150 g), acrylic acid (125 g), methyl methacrylate (125 g) and ditertiarybutyl peroxide (7.5 g) was added dropwise over 120 minutes. After 60 minutes from the completion of the dropwise addition, atmospheric distillation was carried out, followed by vacuum distillation to remove propylene glycol monomethyl ether and obtain a polymer emulsifier (3) having an acid value of 195 mgKOH/g.

(Synthesis Example 4)
Propylene glycol monomethyl ether (500 g) was charged into a separable flask equipped with a thermometer, a condenser and a stirrer, and the temperature was raised to 145°C under nitrogen substitution. Then, a mixture of styrene (25 g), α-methylstyrene (100 g), acrylic acid (125 g), methyl methacrylate (250 g) and ditertiarybutyl peroxide (7.5 g) was added dropwise over 120 minutes. After 60 minutes from the completion of the dropwise addition, atmospheric distillation was carried out, followed by vacuum distillation to remove propylene glycol monomethyl ether and obtain a polymer emulsifier (4) having an acid value of 195 mgKOH/g.

<Preparation of emulsion composition>
(Example 1)
Ion-exchanged water (563 g) was charged into a separable flask equipped with a thermometer, a condenser, and a stirrer, and the temperature was raised to 80° C. under nitrogen substitution. Next, a diluted solution of ammonium persulfate (3.5 g) dissolved in ion-exchanged water (35 g) was added, and after 5 minutes, methyl methacrylate (154 g), butyl acrylate (133 g), and 2-ethylhexyl acrylate (49 g) were added. , acrylic acid (14 g) was added dropwise over 120 minutes. After 60 minutes from the completion of dropping, a 28% aqueous ammonia solution (10.6 g) was added. After 120 minutes from the completion of dropping, the mixture was cooled and diluted with deionized water to a concentration of 35% to obtain an emulsion composition (1) having a viscosity of 350 mPa·s and a pH of 7.9.

(Example 2)
An emulsion composition (2) having a viscosity of 950 mPa·s and a pH of 7.8 was obtained in the same manner as in Example 1, except that methacrylic acid (14 g) was used instead of acrylic acid (14 g).

(Example 3)
In the same manner as in Example 1, except that ion-exchanged water (546 g) was used instead of ion-exchanged water (563 g), and Neogen S20 (17.5 g, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used as a low-molecular-weight emulsifier. An emulsion composition (3) having a viscosity of 330 mPa·s and a pH of 7.9 was obtained.

(Example 4)
In the same manner as in Example 1, except that ion-exchanged water (560 g) was used instead of ion-exchanged water (563 g), and Newcol N2360 (3.5 g, manufactured by Nippon Nyukazai Co., Ltd.) was used as a low-molecular emulsifier. An emulsion composition (4) of 340 mPa·s and pH 7.9 was obtained.

(Example 5)
Methyl methacrylate (154 g), butyl acrylate (133 g), acrylic acid (14 g), 28% aqueous ammonia solution (10.6 g) replaced with methyl methacrylate (133 g), butyl acrylate (150.5 g), acrylic An emulsion composition (5) having a viscosity of 260 mPa·s and a pH of 7.9 was obtained in the same manner as in Example 1 except that an acid (17.5 g) and a 28% aqueous ammonia solution (13.3 g) were used.

(Example 6)
Methyl methacrylate (133 g), butyl acrylate (150.5 g), 2-ethylhexyl acrylate (49 g) replaced with methyl methacrylate (66.5 g), butyl acrylate (182 g), 2-ethylhexyl acrylate (84 g) An emulsion composition (6) having a viscosity of 220 mPa·s and a pH of 7.9 was obtained in the same manner as in Example 5 except that

(Example 7)
An emulsion composition (7) having a viscosity of 210 mPa·s and a pH of 7.9 was obtained in the same manner as in Example 5, except that tertiary dedodecyl mercaptan (3.5 g) was added as a chain transfer agent to the monomer mixture. .

(Example 8)
An emulsion composition (8) having a viscosity of 1650 mPa·s and a pH of 8.1 was prepared in the same manner as in Example 5, except that glycidyl methacrylate (3.5 g) was added as another vinyl group-containing monomer to the monomer mixture. Obtained.

(Example 9)
An emulsion composition (9) having a viscosity of 90 mPa·s and a pH of 7.9 was obtained in the same manner as in Example 5, except that tertiary dedodecyl mercaptan (7.0 g) was added as a chain transfer agent to the monomer mixture. .

(Example 10)
Ion-exchanged water (410 g), polymer emulsifier (1) (135 g), and 28% ammonia aqueous solution (25.6 g) were charged into a separable flask equipped with a thermometer, condenser, and stirrer, and the temperature was adjusted to 90 under nitrogen substitution. °C. After holding at 90°C for 180 minutes, it was cooled to 80°C. Next, a diluted solution of ammonium persulfate (2.5 g) dissolved in ion-exchanged water (25 g) was added. After 5 minutes, methyl methacrylate (157.5 g), butyl acrylate (75.6 g), acrylic acid A mixture of ethylhexyl (81.9 g) was added dropwise over 120 minutes. After 60 minutes from the completion of dropping, a diluted solution of ammonium persulfate (0.3 g) dissolved in ion-exchanged water (3 g) was added. After 180 minutes from the completion of dropping, the mixture was cooled and diluted with deionized water to a concentration of 45% to obtain an emulsion composition (10) having a viscosity of 380 mPa·s and a pH of 8.2.

(Example 11)
Methyl methacrylate (157.5 g), butyl acrylate (75.6 g), 2-ethylhexyl acrylate (81.9 g) replaced with methyl methacrylate (63 g), butyl acrylate (163.8 g), acrylic acid 2 An emulsion composition (11) having a viscosity of 360 mPa·s and a pH of 8.2 was obtained in the same manner as in Example 10, except that ethylhexyl (88.2 g) was used.

(Example 12)
Ion-exchanged water (405 g), polymer emulsifier (1) (112.5 g), and 28% aqueous ammonia solution (21.4 g) were charged into a separable flask equipped with a thermometer, condenser, and stirrer, and the mixture was replaced with nitrogen. , and the temperature was raised to 90°C. After holding at 90°C for 180 minutes, it was cooled to 80°C. Next, a diluted solution of ammonium persulfate (2.7 g) dissolved in ion-exchanged water (27 g) was added, and after 5 minutes, methyl methacrylate (114.8 g), butyl acrylate (111.4 g), A mixture of ethylhexyl (111.4 g) was added dropwise over 120 minutes. After 60 minutes from the completion of dropping, a diluted solution of ammonium persulfate (0.3 g) dissolved in ion-exchanged water (3 g) was added. After 180 minutes from the completion of dropping, the mixture was cooled and diluted with deionized water to a concentration of 45% to obtain an emulsion composition (12) having a viscosity of 310 mPa·s and a pH of 8.0.

(Example 13)
An emulsion composition (13) having a viscosity of 610 mPa·s and a pH of 8.0 was obtained in the same manner as in Example 12, except that the polymer emulsifier (2) was used instead of the polymer emulsifier (1).

(Example 14)
Ion-exchanged water (330 g), polymer emulsifier (3) (180 g), and 28% aqueous ammonia solution (34.2 g) were charged into a separable flask equipped with a thermometer, condenser, and stirrer, and the temperature was adjusted to 90 under nitrogen substitution. °C. After holding at 90°C for 180 minutes, it was cooled to 80°C. Next, a diluted solution of ammonium persulfate (2.2 g) dissolved in ion-exchanged water (22 g) was added, and after 5 minutes, methyl methacrylate (91.8 g), butyl acrylate (89.1 g), acrylic acid A mixture of ethylhexyl (89.1 g) was added dropwise over 120 minutes. After 60 minutes from the completion of dropping, a diluted solution of ammonium persulfate (0.3 g) dissolved in ion-exchanged water (3 g) was added. After 180 minutes from the completion of dropping, the mixture was cooled and diluted with deionized water to a concentration of 45% to obtain an emulsion composition (14) having a viscosity of 1420 mPa·s and a pH of 7.9.

(Example 15)
Ion-exchanged water (410 g), polymer emulsifier (1) (45 g), and 28% ammonia aqueous solution (8.6 g) were charged into a separable flask equipped with a thermometer, condenser, and stirrer, and the temperature was adjusted to 90 under nitrogen substitution. °C. After holding at 90°C for 180 minutes, it was cooled to 80°C. Next, a diluted solution of ammonium persulfate (3.2 g) dissolved in ion-exchanged water (32 g) was added, and after 5 minutes, methyl methacrylate (137.7 g), butyl acrylate (133.7 g), A mixture of ethylhexyl (133.7 g) was added dropwise over 120 minutes. After 60 minutes from the completion of dropping, a diluted solution of ammonium persulfate (0.4 g) dissolved in deionized water (4 g) was added. After 180 minutes from the completion of dropping, the mixture was cooled and diluted with deionized water to a concentration of 45% to obtain an emulsion composition (15) having a viscosity of 210 mPa·s and a pH of 8.3.

(Example 16)
A separable flask equipped with a thermometer, condenser, and stirrer was charged with ion-exchanged water (412 g), polymer emulsifier (1) (22.5 g), and Neogen S20 (21.5 g, Daiichi Kogyo Seiyaku Co., Ltd.) as a low-molecular emulsifier. company) and 28% aqueous ammonia solution (4.3 g) were charged, and the temperature was raised to 90°C under nitrogen substitution. After holding at 90°C for 180 minutes, it was cooled to 80°C. Next, a diluted solution of ammonium persulfate (3.4 g) dissolved in ion-exchanged water (34 g) was added, and after 5 minutes, methyl methacrylate (145.4 g), butyl acrylate (141.1 g), A mixture of ethylhexyl (141.1 g) was added dropwise over 120 minutes. After 60 minutes from the completion of dropping, a diluted solution of ammonium persulfate (0.4 g) dissolved in deionized water (4 g) was added. After 180 minutes from the completion of dropping, the mixture was cooled and diluted with deionized water to a concentration of 45% to obtain an emulsion composition (16) having a viscosity of 95 mPa·s and a pH of 8.3.

(Example 17)
Ion-exchanged water (398 g), polymer emulsifier (4) (225 g), and 28% aqueous ammonia solution (42.7 g) were charged into a separable flask equipped with a thermometer, condenser, and stirrer, and the temperature was adjusted to 90 under nitrogen substitution. °C. After holding at 90°C for 180 minutes, it was cooled to 80°C. Next, a diluted solution of ammonium persulfate (1.8 g) dissolved in ion-exchanged water (18 g) was added, and after 5 minutes, methyl methacrylate (103.5 g), butyl acrylate (78.8 g), A mixture of ethylhexyl (42.8 g) was added dropwise over 120 minutes. After 60 minutes from the completion of dropping, a diluted solution of ammonium persulfate (0.2 g) dissolved in deionized water (2 g) was added. After 180 minutes from the completion of dropping, the mixture was cooled and diluted with deionized water to a concentration of 40% to obtain an emulsion composition (17) having a viscosity of 1130 mPa·s and a pH of 8.0.

(Comparative example 1)
Methyl methacrylate (133 g), butyl acrylate (150.5 g), 2-ethylhexyl acrylate (49 g) replaced with methyl methacrylate (98 g), butyl acrylate (17.5 g), 2-ethylhexyl acrylate (217 g) An emulsion composition (18) having a viscosity of 140 mPa·s and a pH of 7.9 was obtained in the same manner as in Example 5 except that

(Comparative example 2)
A viscosity of 380 mPa was obtained in the same manner as in Example 5, except that methyl methacrylate (133 g) and butyl acrylate (150.5 g) were replaced with methyl methacrylate (168 g) and butyl acrylate (115.5 g). * An emulsion composition (19) having a pH of 7.9 was obtained.

(Comparative Example 3)
In the same manner as in Example 10, except that butyl acrylate (75.6 g) and 2-ethylhexyl acrylate (81.9 g) were replaced with butyl acrylate (94 g) and 2-ethylhexyl acrylate (93 g). An emulsion composition (20) having a viscosity of 260 mPa·s and a pH of 8.2 was obtained.

(Comparative Example 4)
Ion-exchanged water (402 g), polymer emulsifier (1) (157.5 g), and 28% aqueous ammonia solution (29.9 g) were charged into a separable flask equipped with a thermometer, condenser, and stirrer, and the mixture was replaced with nitrogen. , and the temperature was raised to 90°C. After holding at 90°C for 180 minutes, it was cooled to 80°C. Next, a diluted solution of ammonium persulfate (2.3 g) dissolved in ion-exchanged water (23 g) was added, and after 5 minutes, methyl methacrylate (58.5 g), butyl acrylate (152.1 g), A mixture of ethylhexyl (81.9 g) was added dropwise over 120 minutes. After 60 minutes from the completion of dropping, a diluted solution of ammonium persulfate (0.3 g) dissolved in ion-exchanged water (3 g) was added. After 180 minutes from the completion of dropping, the mixture was cooled and diluted with deionized water to a concentration of 45% to obtain an emulsion composition (21) having a viscosity of 860 mPa·s and a pH of 8.0.

(Comparative Example 5)
Methyl methacrylate (157.5 g), butyl acrylate (75.6 g), 2-ethylhexyl acrylate (81.9 g) replaced with methyl methacrylate (56.7 g), butyl acrylate (69.3 g), acrylic An emulsion composition (22) having a viscosity of 230 mPa·s and a pH of 8.2 was obtained in the same manner as in Example 10, except that 2-tylhexyl acid (189 g) was used.

(Comparative Example 6)
Instead of a mixture of methyl methacrylate (114.8 g), butyl acrylate (111.4 g), and 2-ethylhexyl acrylate (111.4 g), methyl methacrylate (54 g), butyl acrylate (64.1 g), An emulsion composition (23) having a viscosity of 290 mPa·s and a pH of 8.0 was obtained in the same manner as in Example 12, except that a mixed solution of 2-tylhexyl acrylate (175.5 g) and styrene (43.9 g) was used. rice field.

(Comparative Example 7)
Instead of a mixture of methyl methacrylate (157.5 g), butyl acrylate (75.6 g), and 2-ethylhexyl acrylate (81.9 g), methyl methacrylate (126 g), butyl acrylate (94.5 g), An emulsion composition (24) having a viscosity of 610 mPa·s and a pH of 8.0 was prepared in the same manner as in Example 10, except that a mixed solution of 2-tylhexyl acrylate (66.2 g) and ethyl acrylate (28.4 g) was used. got

Table 1 shows the compositions and physical properties of the emulsion compositions (1) to (24) obtained in Examples 1 to 17 and Comparative Examples 1 to 7.

<Coating evaluation>
Emulsion compositions (1) to (24) were coated on one side of liner paper (basis weight: 160 g/m ² ) using wire bar #5. The coating amount of the coating liquid was 6 g/m ² . After coating, water repellency was measured as an index of water resistance, and Kit value was measured as an index of oil resistance. Table 2 shows the results.

Water repellency: Evaluated according to JAPAN TAPPI No68.
The evaluation of water repellency (R0 to R10) indicates the cases where the following states are obtained.
R0: Continuous mark showing a uniform width R2: Continuous mark showing a width slightly narrower than the water droplet R4: Continuous mark but broken in places, clearly more than a water droplet R6: Half of the trace is wet R7: 1/4 of the trace is wet with elongated water droplets R8: More than 1/4 of the trace is scattered spherical droplets R9: Spherical droplets scattered here and there R10: Completely rolling down In the present invention, the practical level of water repellency is from R6 to R10.

Kit value: Evaluated according to JAPAN TAPPI No41.
Incidentally, in the present invention, the range of the Kit value is 6 to 12 at a practical level.

From the examples and comparative examples, the examples that satisfy the conditions of the present invention are superior to the comparative examples that do not satisfy the conditions of the present invention because they have the desired performance in terms of both water resistance and oil resistance.

Claims (3)

water (A);
An aqueous coating agent comprising an emulsion composition comprising a copolymer (B) of monomers comprising at least methyl methacrylate (b1), butyl acrylate (b2), and 2-ethylhexyl acrylate (b3),
The ratio of the copolymer (B) contained in the emulsion composition is 1 to 60% by mass, and is calculated from the ratio of (b1), (b2), and (b3) constituting the copolymer (B). The glass transition temperature (Tg) is -10 to -45°C, and the ratio of (b1), (b2), and (b3) to the total polymer components contained in the emulsion composition is 70 to 100% by mass,
The glass transition temperature (Tg) calculated from the ratio of the (b1) component, (b2) component, and (b3) component constituting the copolymer (B) is a theoretical value obtained from the following FOX formula. can be,
An aqueous coating agent further comprising a polymer emulsifier (C) in a mass ratio of copolymer (B):polymer emulsifier (C)=90:10 to 60:40.
1/Tg=W1/Tg1+W2/Tg2+W3/Tg3... FOX formula
(Tg in the formula is the glass transition temperature (K: Kelvin), and W1, W2, and W3 are the total amount of the components (b1), (b2), and (b3) constituting the copolymer (B). and Tg1, Tg2, and Tg3 represent the glass transition temperatures of the homopolymers of the monomers (b1) to (b3), which are 378K, 219K, and 188K, respectively. .) 2. The water-based coating agent according to claim 1, wherein the copolymer (B) has a weight average molecular weight of 50,000 to 3,000,000. A copolymer obtained by emulsion polymerization of monomers containing at least methyl methacrylate (b1), butyl acrylate (b2), and 2-ethylhexyl acrylate (b3) in water in the presence of a polymer emulsifier (C). A method for producing an aqueous coating agent containing an emulsion composition containing (B), wherein the glass transition temperature calculated from the ratio of (b1), (b2), and (b3) in the monomer subjected to emulsion polymerization (Tg) is -10 to -45 ° C., contained in the monomers (b1), (b2), and (b3) subjected to polymerization of the polymer emulsifier (C), and contained in the monomers subjected to emulsion polymerization. The total mass of (b1), (b2), and (b3) is 70 to 100% by mass of the total mass of the monomers subjected to polymerization of the polymer emulsifier (C) and the monomers subjected to emulsion polymerization,
The glass transition temperature (Tg) calculated from the ratio of the (b1) component, (b2) component, and (b3) component constituting the copolymer (B) is a theoretical value obtained from the following FOX formula. can be,
A method for producing an aqueous coating agent, further comprising polymer emulsifier (C) in a mass ratio of copolymer (B):polymer emulsifier (C)=90:10 to 60:40.
1/Tg=W1/Tg1+W2/Tg2+W3/Tg3... FOX formula
(Tg in the formula is the glass transition temperature (K: Kelvin), and W1, W2, and W3 are the total amount of the components (b1), (b2), and (b3) constituting the copolymer (B). and Tg1, Tg2, and Tg3 represent the glass transition temperatures of the homopolymers of the monomers (b1) to (b3), which are 378K, 219K, and 188K, respectively. .)