Aqueous polymer dispersions, paints, primer compositions, and laminates

Abstract

To provide an aqueous polymer dispersion that can form a coating film that maintains adhesion to the substrate even during high-temperature, high-pressure cleaning. [Solution] An aqueous polymer dispersion in which an olefin polymer (A) and an acrylic polymer (B) are dispersed in an aqueous medium, wherein the glass transition temperature of the acrylic polymer (B) is 105°C or higher. In some examples, the acrylic polymer (B) may contain constituent units derived from isobornyl methacrylate, the olefin polymer (A) and the acrylic polymer (B) may form composite particles, and the olefin polymer (A) may have reactive groups.

Description

[Technical Field]

[0001] The present invention relates to aqueous polymer dispersions, paints, primer compositions, and laminates. [Background technology]

[0002] In recent years, environmentally friendly polymer compositions have attracted attention. Among these, water-dispersible polymer compositions that do not contain solvents are particularly noteworthy. In the field of paints, in particular, research into solvent-free polymer compositions is progressing. On the other hand, polyolefins, such as polypropylene and copolymers of propylene with other α-olefins, are used in a wide range of fields due to their excellent mechanical properties, heat resistance, chemical resistance, and water resistance. However, when forming a coating film on polyolefins, adhesion can be difficult due to the low polarity of the polyolefins.

[0003] Methods for improving adhesion to polyolefins include chemical treatment of the polyolefin surface with chemicals, and oxidation treatment of the surface using corona discharge, plasma treatment, flame treatment, etc. However, these methods require special equipment, and there is a problem in that the effect of improving adhesion is not sufficient. On the other hand, paints that improve adhesion to polyolefins are known to contain modified olefin polymers such as so-called chlorinated polyolefins, acid-modified polyolefins, and acid-modified chlorinated polyolefins. Such paints include solvent-based paints in which modified olefin polymers are dissolved in organic solvents, and water-based paints in which they are dispersed in an aqueous medium. However, from the standpoint of safety and health and reduction of environmental pollution, water-based paints are preferred.

[0004] However, water-based paints containing modified olefin polymers do not perform sufficiently well, and further improvements are being attempted. For example, Patent Document 1 discloses an aqueous polymer dispersion using a specific propylene polymer with a low melting point and low molecular weight in combination with a specific propylene polymer with a high melting point and high molecular weight, which is modified with an unsaturated organic acid derivative. Patent Document 2 discloses the use of a composite polymer of an acrylic polymer and an olefin polymer modified with a specific radical polymerizable monomer. Patent Document 3 discloses an aqueous dispersion composition containing a modified polyolefin, a polyolefin different from the aforementioned modified polyolefin, a tackifier, and an epoxy polymer. Patent Document 4 discloses an aqueous coating composition comprising an olefin polymer and a hydroxyl group-containing polymer having a specific hydroxyl group.

[0005] Furthermore, in order to improve the performance and storage stability of aqueous polymer dispersions as paints, aqueous polymer dispersions have been proposed that are composites of modified polyolefins or graft copolymers with polymers obtained by polymerizing radically polymerizable monomers. For example, Patent Document 5 discloses an aqueous polymer dispersion containing an olefin polymer and a polymer containing constituent units derived from a radically polymerizable monomer having a reactive functional group, which has a specific particle size and solubility, and which can be easily obtained to polyolefin substrates such as polypropylene substrates and can be baked at low temperatures. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2008-031360 [Patent Document 2] International Publication No. 2017 / 213192 [Patent Document 3] International Publication No. 2019 / 181336 [Patent Document 4] Japanese Patent Publication No. 2019-210308 [Patent Document 5] International Publication No. 2019 / 112039 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, conventional products such as those disclosed in Patent Documents 1, 2, 3, 4, and 5 have room for improvement in maintaining adhesion to substrates such as olefin substrates even after high-temperature, high-pressure washing.

[0008] The object of the present invention is to provide an aqueous polymer dispersion that can form a coating film that maintains adhesion to a substrate even during high-temperature, high-pressure washing. [Means for solving the problem]

[0009] As a result of diligent research, the inventors have discovered that by using an aqueous polymer dispersion containing an olefin polymer and an acrylic polymer having a glass transition temperature greater than a specific value, it is possible to form a coating film that maintains adhesion to the substrate even after high-temperature, high-pressure washing, thus completing the present invention. Adhesion to the substrate after high-temperature, high-pressure washing is difficult to predict from the adhesion of ordinary coating films to the substrate, and the above effect discovered by the inventors can be said to be a highly advanced effect that is difficult to predict from the prior art.

[0010] In other words, the present invention has the following aspects. [1] An aqueous polymer dispersion in which an olefin polymer (A) and an acrylic polymer (B) are dispersed in an aqueous medium, The glass transition temperature of the acrylic polymer (B) is 105°C or higher. An aqueous polymer dispersion in which the mass ratio of the olefin polymer (A) to the acrylic polymer (B) is (A):(B) = 25:75 to 99:1. [2] The aqueous polymer dispersion according to [1], wherein the acrylic polymer (B) contains constituent units derived from isobornyl methacrylate. [3] The aqueous polymer dispersion according to [1] or [2], wherein the olefin polymer (A) and the acrylic polymer (B) form composite particles. [4] The aqueous polymer dispersion according to any one of [1] to [3] above, wherein the olefin-based polymer (A) contains at least one selected from the group consisting of an ethylene-propylene copolymer, an ethylene-propylene-butene copolymer, and a propylene-butene copolymer. [5] The aqueous polymer dispersion according to any one of [1] to [4] above, wherein the olefin-based polymer (A) has a reactive group. [6] The aqueous polymer dispersion according to [5], wherein the reactive group contains at least one selected from the group consisting of a carboxy group, an epoxy group, an isocyanato group, a sulfonic acid group, and a hydroxy group. [7] The aqueous polymer dispersion according to any one of [1] to [6] above, wherein the average particle diameter of the aqueous polymer dispersion is 500 nm or less. [8] A paint containing the aqueous polymer dispersion according to any one of [1] to [7] above. [9] A primer composition containing the aqueous polymer dispersion according to any one of [1] to [7] above.

[10] A laminate including a substrate and a layer formed by drying the aqueous polymer dispersion according to any one of [1] to [7] above provided on the substrate.

[11] The laminate according to

[10] , wherein the substrate is a polyolefin substrate. [Advantages of the Invention]

[0011] According to the aqueous polymer dispersion of the present invention, a coating film capable of maintaining the adhesion to the substrate even during high-temperature and high-pressure washing can be formed. [Brief Description of the Drawings]

[0012] [Figure 1] FIG. 1 shows an evaluation method for adhesion during high-temperature and high-pressure washing in an example. [Figure 2] FIG. 2 shows an example of a coating film in which peeling occurred in the evaluation of adhesion during high-temperature and high-pressure washing. [Modes for Carrying Out the Invention]

[0013] The present invention will now be described in detail. The following embodiments are merely illustrative for illustrating the present invention and are not intended to limit the present invention to these embodiments. The present invention can be implemented in various forms without departing from its spirit. In this specification and in the claims, a numerical range represented by "~" means a numerical range that includes the numbers before and after "~" as the lower and upper limits, respectively. For example, A~B is synonymous with A or greater and B or less. The numerical ranges of content, various physical properties, and characteristic values ​​disclosed herein can be modified by arbitrarily combining their lower and upper limits to create new numerical ranges.

[0014] Furthermore, in the present invention and this specification, the following terms have the following meanings. "(Meth)acrylic" is a general term for acrylic and methacrylic. "(Meth)acrylic acid" is a general term for acrylic acid and methacrylic acid. "(Meth)acrylate" is a general term for "acrylate" and "methacrylate". A "dispersion" refers to a mixture containing olefin polymers (A) and acrylic polymers (B) in a dispersed state, along with an aqueous medium. A mixture in which polymers are dispersed in an aqueous medium in this manner is called an "aqueous polymer dispersion." "Aqueous medium" refers to water, or a mixture of water and an organic solvent. "Dispersed state" means that the olefin polymer (A) and the acrylic polymer (B) exist in an aqueous medium without dissolving, either as individual particles or as composite particles. "Dispersion" is a concept that includes a state in which dispersed particles are extremely small and dispersed as single molecules, essentially a state that can be described as dissolution. The "copolymer" may be a random copolymer or a block copolymer. "Integration" refers to the process where multiple polymers with different structures are bonded together through chemical interactions (e.g., covalent bonds), physical interactions (e.g., intermolecular forces), or mechanical interactions; it is also called "compounding." "Composite particles" refer to particles formed by the integration of an olefin polymer (A) and an acrylic polymer (B). "Constituent unit" refers to the unit that makes up a polymer derived from monomers, that is, a constituent unit formed by the polymerization of monomers, or a constituent unit in which a part of the constituent unit is converted to a different structure by a modification treatment of the polymer. "Monomer components" refer to the collective term for monomer components that have polymerizable double bonds. Polymerization initiators and polymerization solvents are excluded from the definition of monomer components. "Coating film" refers to a film formed from the aqueous polymer dispersion of the present invention.

[0015] [Aqueous polymer dispersion] The aqueous polymer dispersion according to this embodiment comprises an olefin polymer (A) and an acrylic polymer (B) dispersed in an aqueous medium. That is, the aqueous polymer dispersion contains an olefin polymer (A) and an acrylic polymer (B), and an aqueous medium. In addition to the olefin polymer (A), acrylic polymer (B), and aqueous medium, the aqueous polymer dispersion may further contain, as necessary, components other than the olefin polymer (A), acrylic polymer (B), and aqueous medium (hereinafter also referred to as "optional components"), as long as they do not impair the effects of the present invention.

[0016] (Olefin polymer (A)) Olefin polymer (A) is a polymer containing constituent units derived from olefins. Olefin polymer (A) may be linear or branched. The olefin polymer (A) may have reactive groups. Examples of reactive groups include carboxyl groups, epoxy groups, isocyanate groups, sulfonic acid groups, and hydroxyl groups. The olefin polymer (A) may have one type of reactive group or two or more types. Preferably, the reactive group includes at least one selected from the group consisting of carboxyl groups, epoxy groups, isocyanate groups, sulfonic acid groups, and hydroxyl groups.

[0017] Examples of olefin polymers (A) include olefin homopolymers (hereinafter referred to as "olefin homopolymer (A1)"), copolymers of monomer components (a2) containing olefins (hereinafter referred to as "olefin copolymer (A2)"), and olefin composite polymers (A3). These may be used individually or in combination of two or more.

[0018] Examples of olefins used in the olefin polymer (A) include ethylene, propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, cyclopentene, cyclohexene, and norbornene. Among the many olefins, propylene is preferred in terms of its adhesion to the olefin substrate. In other words, as the olefin polymer (A), a propylene polymer having propylene-derived structural units is preferred in terms of its adhesion to the olefin substrate.

[0019] The olefin-based homopolymer (A1) is a homopolymer of an olefin. Examples of the olefin-based homopolymer (A1) include a homopolymer of any one of the olefins exemplified for use in the olefin-based polymer (A). The olefin-based homopolymer (A1) may be used alone or in combination of two or more types.

[0020] The olefin homopolymer (A1) may also be an olefin homopolymer (A11) having reactive groups that can react with amino groups, such as carboxyl groups, epoxy groups, isocyanate groups, sulfonic acid groups (sulfo groups), and hydroxyl groups. The reactive group may also be an acid anhydride structure of a carboxyl group. Maleic anhydride and acrylic acid are preferred as the compounds to be reacted. In terms of excellent water-resistant adhesion, an olefin-based homopolymer (A11) having a reactive group is preferred as the olefin-based homopolymer (A1).

[0021] The reactive group content of the olefin homopolymer (A11) having a reactive group is preferably 0.01 to 1 mmol / g, more preferably 0.05 to 0.5 mmol / g, and even more preferably 0.1 to 0.3 mmol / g per gram of olefin polymer (A).

[0022] In an olefin homopolymer (A11) containing reactive groups, if the reactive group is an acidic group such as a carboxyl group, its anhydride, or a sulfonic acid group, the acid value of the olefin polymer (A) increases as the content of the reactive group increases. This improves mechanical stability and tends to improve the polymerizability of the radical polymerizable monomer during manufacturing. The lower the content of the acidic group, the greater the adhesion of the coating film to substrates such as olefin substrates. The acid value of the olefin polymer (A) can be adjusted by controlling the content of the acidic group.

[0023] Neutralizing acidic groups with a basic compound tends to improve the mechanical stability of the olefin polymer (A). Examples of such basic compounds include inorganic bases such as sodium hydroxide and potassium hydroxide, ammonia, triethylamine, diethylamine, ethanolamine, dimethylethanolamine, 2-methyl-2-amino-propanol, triethanolamine, morpholine, and pyridine. The neutralization rate of the acidic groups is not particularly limited as long as dispersibility in water is achieved, but it is preferably 1 to 100 mol%, and more preferably 50 mol% or more, relative to the total amount of acidic groups contained in the olefin polymer (A). The higher the neutralization rate, the more the dispersibility of the olefin polymer (A) in water tends to improve.

[0024] The olefin-based homopolymer (A1) may be a chlorinated olefin obtained by chlorinating an olefin-based polymer. In that case, the degree of chlorination of the chlorinated olefin is preferably 40% by mass or less, and more preferably 30% by mass or less, based on the total mass of the olefin-based homopolymer (A1).

[0025] The olefin copolymer (A2) is a copolymer of monomer components (a2) containing an olefin. Monomer component (a2) is a mixture containing two or more monomers, and contains at least one olefin. Monomer component (a2) may contain only two or more olefins, or it may contain one or more olefins and one or more non-olefin monomers (hereinafter referred to as "other monomers"). The olefin is the same as the olefin exemplified for use in olefin polymer (A). Other monomers are not particularly limited as long as they can copolymerize with olefins.

[0026] Examples of olefin copolymers (A2) include copolymers of ethylene and propylene; copolymers of at least one of ethylene and propylene with monomers copolymerizable with ethylene and propylene; copolymers of two or more α-olefins selected from the group consisting of α-olefins having 4 or more carbon atoms; copolymers of α-olefins having 2 or more carbon atoms with non-aromatic monomers other than α-olefins; copolymers of α-olefins having 2 or more carbon atoms with aromatic monomers or hydrogenated thereof; and conjugated diene block copolymers or hydrogenated thereof. Examples of monomers copolymerizable with ethylene and propylene include α-olefins having 4 or more carbon atoms, such as butene-1, pentene-1, hexene-1, heptene-1, octene-1, cyclopentene, cyclohexene, and norbornene. Examples of non-aromatic monomers other than α-olefins include vinyl acetate, acrylic acid esters, and methacrylic acid esters. Examples of aromatic monomers include aromatic vinyl monomers such as styrene. There may be two or more comonomers other than olefins.

[0027] Among the various olefin copolymers (A2), ethylene-propylene copolymer, ethylene-propylene-butene copolymer, and propylene-butene copolymer are more preferred. The olefin copolymer (A2) may be used individually or in combination of two or more types.

[0028] When the olefin copolymer (A2) contains propylene-derived structural units, the proportion of propylene-derived structural units is preferably 50 mol% or more, more preferably 60 mol% or more, and even more preferably 70 mol% or more, of the total olefin-derived structural units in the olefin copolymer (A2). The upper limit of the proportion of propylene-derived structural units can be 100 mol%.

[0029] The olefin copolymer (A2) may be a chlorinated olefin obtained by chlorinating an olefin polymer. In that case, the degree of chlorination of the chlorinated olefin is preferably 40% by mass or less, and more preferably 30% by mass or less, based on the total mass of the olefin copolymer (A2).

[0030] The olefin copolymer (A2) may also be an olefin copolymer (A21) having reactive groups that can react with amino groups, such as carboxyl groups, epoxy groups, isocyanate groups, sulfonic acid groups (sulfo groups), and hydroxyl groups. The reactive group may also be an acid anhydride structure of a carboxyl group. Maleic anhydride and acrylic acid are preferred as the compounds to be reacted. In terms of excellent water-resistant adhesion, an olefin copolymer (A21) having a reactive group is preferred as the olefin copolymer (A2).

[0031] The reactive group content of the olefin copolymer (A21) having reactive groups is preferably 0.01 to 1 mmol / g, more preferably 0.05 to 0.5 mmol / g or more, and even more preferably 0.1 to 0.3 mmol / g per gram of olefin polymer (A).

[0032] In an olefin copolymer (A21) containing reactive groups, if the reactive group is an acidic group such as a carboxyl group, its anhydride, or a sulfonic acid group, the acid value of the olefin polymer (A) increases as the content of the reactive group increases. Therefore, mechanical stability improves, and the polymerizability of the radical polymerizable monomer tends to improve during manufacturing. The lower the content of the acidic group, the greater the adhesion of the coating film to substrates such as olefin substrates. The acid value of the olefin polymer (A) can be adjusted by controlling the content of the acidic group.

[0033] As the olefin-based composite polymer (A3), a composite polymer (a31) is preferred, which is formed by integrating at least one polymer selected from the group consisting of olefin-based homopolymers (A1) and olefin-based copolymers (A2) with a hydrophilic polymer such as a polyether polymer. As the olefin-based composite polymer (A3), one type may be used alone, or two or more types may be used in combination. It is preferable that multiple polymers with different structures are integrated to form graft polymers, core-shell structures, microphase-separated structures, interpenetrating polymer network structures, and the like.

[0034] A hydrophilic polymer is a polymer that, when dissolved in water at 25°C at a concentration of 10% by mass, has an insoluble content of 1% by mass or less. Hydrophilic polymers may be synthetic polymers, natural polymers, or semi-synthetic polymers, as long as they are hydrophilic.

[0035] The number-average molecular weight (hereinafter referred to as "Mn") of the hydrophilic polymer is preferably 300 or higher. The larger the Mn of the hydrophilic polymer, the more likely it is that the mechanical stability of the aqueous polymer dispersion containing the olefin polymer (A) and the acrylic polymer (B) will improve. The upper limit of the Mn of the hydrophilic polymer is not particularly limited, but may be, for example, 30,000 or less, or 10,000 or less. The Mn of the hydrophilic polymer may be, for example, 300 to 30,000, or 300 to 10,000. The manganese (Mn) content of hydrophilic polymers is measured by gel permeation chromatography (GPC) and converted to a polystyrene calibration curve. GPC measurements can be performed using commercially available equipment with tetrahydrofuran (THF) or the like as a solvent, according to known methods.

[0036] Examples of hydrophilic polymers used in synthetic polymers include polyether polymers, polyvinyl alcohol polymers, and polyvinylpyrrolidone polymers. Examples of hydrophilic natural polymers that can be used include starch, gum arabic, tragacanth gum, casein, gelatin, and dextrin. Examples of hydrophilic semi-synthetic polymers that can be used include carboxylated starch, cationized starch, dextrin, ethylcellulose, carboxylated methylcellulose, hydroxyethylcellulose, and cationized cellulose.

[0037] As hydrophilic polymers, synthetic hydrophilic polymers are preferred because their degree of hydrophilicity is easy to control and their properties are stable. Hydrophilic polymers may be used individually or in combination of two or more. Among the many hydrophilic polymers, polyether polymers with high hydrophilicity are preferred. The average particle size of the aqueous polymer dispersion can be adjusted by the type and combination of hydrophilic polymers.

[0038] Polyether polymers can be produced, for example, by ring-opening polymerization of cyclic alkylene oxides or cyclic alkyleneimines. Although the polyether polymer may be integrated with the olefin polymer without being bonded to it, it is preferable that it be integrated while bonded to the olefin polymer so that it does not bleed out from the coating film.

[0039] A polyether polyol is a compound having a hydroxyl group, which is a reactive group, at both ends of a polymer with a polyether skeleton. A polyetheramine is a compound having a primary amino group, which is a reactive group, at one or both ends of a polymer with a polyether skeleton. Polyetheramines are preferred as polyether polymers to be integrated with olefin polymers. Examples of polyetheramines include Huntsman's "Jeffermin" M series, D series, ED series, and "Serphonamine" L series.

[0040] The polyether polymer preferably has hydrophilic constituent units such as polyethylene oxide and polyethyleneimine, and hydrophobic constituent units such as polypropylene oxide and polypropyleneimine. It is even more preferable that the polyether polymer has constituent units derived from polyethylene oxide and constituent units derived from polypropylene oxide. The HLB (Hydrophile Lipophile Balance) of a polyether polymer can be adjusted by controlling the amounts of hydrophilic and hydrophobic constituent units. It is preferable that the polyether polymer includes highly hydrophilic polymers with an HLB in the range of 9 to 18.

[0041] As the polyether polymer, it is preferable to use in combination the highly hydrophilic polyether polymer and a less hydrophilic polyether polymer with an HLB in the range of 1 to 8. The lower the HLB of the polyether polymer, the lower the surface energy of the olefin polymer integrated with the polyether polymer. Therefore, when forming composite particles with the acrylic polymer (B) described later, the impregnation of the monomers constituting the acrylic polymer (B) into the composite polymer (a31) tends to be good. The HLB of the less hydrophilic polyether polymer is preferably 1 to 6, and more preferably 1 to 4.

[0042] It is preferable that the polyether polymer has one or more reactive groups that can react with the olefin polymer before bonding with it. Examples of such reactive groups include carboxylic acid groups, dicarboxylic acid anhydride groups, dicarboxylic acid anhydride monoester groups, hydroxyl groups, amino groups, epoxy groups, and isocyanate groups. Among the many reactive groups, polyether polymers having at least amino groups are preferred. Amino groups are highly reactive with various reactive groups such as carboxylic acid groups, carboxylic anhydride groups, glycidyl groups, and isocyanate groups, making it easy to bond olefin polymers and polyether polymers. The amino group can be primary, secondary, or tertiary, but primary amino groups are preferred.

[0043] The polyether polymer has one or more reactive groups per molecule, preferably one. If there are two or more reactive groups, there is a possibility that a three-dimensional network structure will form and gel when bonded with an olefin polymer. However, even if there are two or more reactive groups, if only one of the reactive groups is more reactive than the others, then there may be two or more reactive groups. Examples of polyether polymers having two or more reactive groups include polyether polymers having a hydroxyl group and one amino group that is more reactive. Here, "reactivity" refers to the reactivity with the reactive groups of the olefin polymer.

[0044] The weight-average molecular weight (hereinafter referred to as "Mw") of the polyether polymer is preferably 200 to 200,000, more preferably 300 to 100,000, even more preferably 500 to 10,000, and particularly preferably 500 to 3,000. The higher the Mw of the polyether polymer, the lower the surface energy of the composite polymer (a31), and the better the wettability tends to be. The lower the Mw of the polyether polymer, the lower the viscosity of the aqueous polymer dispersion of the composite polymer (a31), and therefore the easier the preparation tends to be. The Mw of the polyether polymer was measured by GPC and converted using a polystyrene calibration curve. GPC measurement can be performed using commercially available equipment with tetrahydrofuran (THF) or the like as a solvent, using known methods.

[0045] The composite polymer (a31) is preferably formed by bonding a reactive olefin polymer, such as an olefin homopolymer (A11) or an olefin copolymer (A21), with a polyether polymer in a ratio of reactive olefin polymer:polyether polymer = 100:1 to 100:100 (mass ratio). A more preferable mass ratio is 100:5 to 100:70, and even more preferable is 100:10 to 100:50. In regions where the proportion of polyether polymer is low, the particle size of the composite polymer (a31) tends to decrease as the proportion increases. Therefore, when producing composite particles of this composite polymer (a31) with the acrylic polymer (B) described later, the polymerizability of the monomers constituting the acrylic polymer (B) tends to improve. In regions where the proportion of polyether polymers is high, the lower the proportion, the higher the acid value of the composite polymer (a31), the more the polymerization properties of the monomers constituting the acrylic polymer (B) tend to improve, and the adhesion of the coating film to substrates such as olefin substrates also tends to improve.

[0046] When the olefin-based composite polymer (A3) has hydroxyl groups, the hydroxyl value of the olefin-based composite polymer (A3) is preferably 0.01 to 100 mg KOH / g, more preferably 0.05 to 80 mg KOH / g, and even more preferably 0.1 to 50 mg KOH / g. A lower hydroxyl value tends to improve adhesion to the polypropylene substrate. The hydroxyl value is calculated using the following formula (1). Hydroxyl value (mgKOH / g) = (f × M1 / Mw / M2 × [KOH] × 1,000) ... (1) (In formula (1), [KOH] is the molecular weight of KOH, f is the number of hydroxyl groups in the hydroxyl group-containing monomer, M1 is the mass (g) of the hydroxyl group-containing monomer, M2 is the solid content mass (g) of the olefin-based composite polymer (A3), and Mw is the molecular weight (weight-average molecular weight) of the hydroxyl group-containing monomer.)

[0047] The olefin-based composite polymer (A3) may be a chlorinated olefin obtained by chlorinating an olefin-based polymer. In that case, the degree of chlorination of the chlorinated olefin is preferably 40% by mass or less, and more preferably 30% by mass or less, based on the total mass of the olefin-based composite polymer (A3).

[0048] <Physical properties of olefin polymer (A)> The melting point (hereinafter referred to as "Tm") of the olefin polymer (A) is preferably 125°C or lower, more preferably 100°C or lower, and even more preferably 90°C or lower. Furthermore, the Tm of the olefin polymer (A) is preferably 60°C or higher. The higher the Tm of the olefin polymer (A), the less sticky the polymer becomes. The lower the Tm of the olefin polymer (A), the lower the drying and baking temperatures. The lower and upper limits of the Tm of the olefin polymer (A) can be any combination, for example, 60 to 125°C, 60 to 100°C, or 60 to 90°C. The Tm of an olefin polymer (A) can be measured using a differential scanning calorimeter. This measurement can be performed, for example, using the "DSCEXSTAR6000" from Hitachi High-Tech Science Corporation.

[0049] The Mw of the olefin polymer (A) in the aqueous polymer dispersion is preferably greater than 200,000. If the Mw of the olefin polymer (A) is greater than 200,000, a coating film can be formed that maintains better adhesion to the substrate even during high-temperature, high-pressure washing. The Mw of the olefin polymer (A) is more preferably between 200,000 and 2,000,000. The lower limit of the Mw of the olefin polymer (A) is more preferably 230,000, and particularly preferably 250,000. The upper limit of the Mw of the olefin polymer (A) is more preferably 1,000,000, and particularly preferably 500,000. When the Mw of the olefin polymer (A) is within the above range, the adhesion to the substrate during high-temperature, high-pressure washing is further improved. The Mw of the olefin polymer (A) in the aqueous polymer dispersion was measured by GPC and converted to a value using the polystyrene calibration curve. GPC is performed using commercially available equipment and conventionally known methods with orthodichlorobenzene or tetrahydrofuran as the solvent.

[0050] The complex viscosity of the olefin polymer (A) at 200°C and 0.1Hz is preferably 1,500 Pa·s or more, more preferably greater than 1,500 Pa·s, even more preferably 2,000 Pa·s or more, particularly preferably 3,000 Pa·s or more, and most preferably 4,500 Pa·s or more. The complex viscosity of the olefin polymer (A) at 200°C and 0.1Hz is preferably 30,000 Pa·s or less, more preferably 15,000 Pa·s or less, and even more preferably 10,000 Pa·s or less. The upper limit of the complex viscosity of the olefin polymer (A) at 200°C and 0.1Hz may be, for example, 100,000 Pa·s. The lower and upper limits of the complex viscosity of the olefin polymer (A) at 200°C and 0.1 Hz can be any combination, for example, 1,500 to 100,000 Pa·s, greater than 1,500 Pa·s and 30,000 Pa·s or less, 2,000 to 15,000 Pa·s, 3,000 to 10,000 Pa·s, or 4,500 to 10,000 Pa·s. The complex viscosity is measured using a rheometer at 200°C and 0.1 Hz after vacuum drying an aqueous polymer dispersion containing an olefin polymer (A) at 40°C for 12 hours.

[0051] The melt flow rate (hereinafter referred to as "MFR") of the olefin polymer (A) is preferably less than 20 g / 10 min, more preferably less than 10 g / 10 min, and even more preferably less than 8 g / 10 min at 230°C and a load of 2.16 kg. The lower limit of the MFR of the olefin polymer (A) is usually around 0.1 g / 10 min. The lower and upper limits of the MFR of the olefin polymer (A) can be arbitrarily combined, for example, 0.1 g / 10 min or more and less than 20 g / 10 min, 0.1 to 10 g / 10 min, or 0.1 to 8 g / 10 min. The MFR of olefin polymer (A) is measured according to the ASTM D1238 method.

[0052] <Method for producing olefin polymer (A)> Examples of methods for producing the olefin polymer (A) include radical polymerization, cationic polymerization, anionic polymerization, and coordination polymerization of olefins. Furthermore, these polymerizations may each be living polymerizations.

[0053] The polymerization method may be any of the following: solution polymerization, slurry polymerization, bulk polymerization, gas-phase polymerization, etc. For solution polymerization and slurry polymerization, suitable solvents include, for example, aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, heptane, and octane, alicyclic hydrocarbons such as cyclohexane and methylcyclohexane, halogenated hydrocarbons, esters, ketones, and ethers. Among the many available solvents, aromatic hydrocarbons, aliphatic hydrocarbons, and alicyclic hydrocarbons are preferred, with toluene, xylene, heptane, and cyclohexane being more preferred. A single solvent may be used, or two or more may be used in combination.

[0054] For example, benzoyl peroxide and t-butyl peroxyisopropyl monocarbonate are preferred initiators for use in radical polymerization. A single radical polymerization initiator may be used alone, or two or more may be used in combination.

[0055] Examples of catalysts used in coordination polymerization include Ziegler-Natta catalysts and single-site catalysts. Generally, single-site catalysts can have their molecular weight distribution and stereoregularity distribution sharpened by the design of their ligands. Examples of single-site catalysts include metallocene catalysts and Brookhart-type catalysts. Examples of metallocene catalysts include C1-symmetric, C2-symmetric, C2V-symmetric, and CS-symmetric types. These can be appropriately selected depending on the stereoregularity of the desired olefin.

[0056] <<Method for producing olefin polymers containing reactive groups>> Methods for producing olefin polymers having reactive groups include, for example, graft polymerization of a radical polymerizable monomer having a reactive group onto an olefin polymer. Other methods include heating and stirring the olefin polymer and the radical polymerizable monomer having a reactive group in a solution to react them, melting and heating and stirring in a solvent-free environment to react them, or heating and kneading them in an extruder to react them. Among these methods, graft polymerization is preferred as a method for producing olefin polymers having reactive groups.

[0057] As radical polymerizable monomers having a reactive group, radical polymerizable monomers having a carboxyl group or its anhydride structure are preferred. Examples include (meth)acrylic acid, fumaric acid, maleic acid and its anhydride, itaconic acid and its anhydride, and crotonic acid. A single radical polymerizable monomer having a reactive group may be used alone, or two or more may be used in combination. Similarly, an olefin polymer used in graft polymerization may be used alone, or two or more may be used in combination.

[0058] For use in graft polymerization, a radical polymerization initiator can be appropriately selected from known radical polymerization initiators such as organic peroxides and azonitriles.

[0059] Examples of organic peroxides include peroxyketals such as di(t-butylperoxy)cyclohexane, hydroperoxides such as cumene hydroperoxide, dialkyl peroxides such as di(t-butyl)peroxide, diacyl peroxides such as benzoyl peroxide, and peroxyesters such as t-butylperoxyisopropyl monocarbonate. One organic peroxide may be used alone, or two or more may be used in combination.

[0060] Examples of azonitriles include azobisbutyronitrile and azobisisopropylnitrile. Azonitrile may be used alone or in combination of two or more types.

[0061] The ratio of radical polymerization initiator to graftable radical polymerizable monomer is preferably in the range of radical polymerization initiator:radical polymerizable monomer = 1:100 to 2:1 (molar ratio), and more preferably in the range of 1:20 to 1:1. The reaction temperature for graft polymerization is preferably 50°C or higher, more preferably 50 to 200°C, and even more preferably 80 to 200°C. The reaction time for graft polymerization is preferably 2 to 20 hours.

[0062] When manufacturing in solution, the same solvent described in the solution polymerization method for olefin polymer (A) can be used as the solvent.

[0063] <<Method for producing composite polymer (a31)>> In a composite polymer (a31) formed by integrating at least one polymer selected from the group consisting of olefin-based homopolymers (A1) and olefin-based copolymers (A2) with a hydrophilic polymer such as a polyether polymer, if the hydrophilic polymer is a polyether polymer, the polyether polymer can be integrated while bonded to the olefin-based polymer by, for example, the following method. A method for ring-opening polymerization of cyclic alkylene oxides in the presence of olefin polymers having reactive groups, such as olefin homopolymers (A11) or olefin copolymers (A21). A method for reacting reactive groups such as polyether polyols and polyetheramines obtained by ring-opening polymerization with reactive groups of olefin polymers having reactive groups.

[0064] (Acrylic polymer (B)) Acrylic polymer (B) is a polymer having constituent units derived from at least one (meth)acrylic monomer (hereinafter referred to as "monomer (b1)"). Examples of monomer (b1) include (meth)acrylic acid and (meth)acrylic acid esters. In other words, it is preferable that acrylic polymer (B) has at least one of constituent units derived from (meth)acrylic acid and constituent units derived from (meth)acrylic acid esters. The acrylic polymer (B) may, in addition to the constituent units derived from monomer (b1), optionally further contain constituent units derived from ethylenically unsaturated monomers other than monomer (b1) (hereinafter referred to as "monomer (b2)").

[0065] The acrylic polymer (B) is a homopolymer or copolymer obtained by polymerizing monomer component (b) containing monomer (b1). The acrylic polymer (B) is preferably a copolymer. Monomeric component (b) contains at least one monomer (b1). In addition to monomer (b1), monomer component (b) may further contain monomer (b2) as needed. The content and composition of constituent units derived from each monomer in the acrylic polymer (B) can be determined by NMR. Furthermore, the content of each monomer relative to the total monomer component (b) can be considered as the content of constituent units derived from that monomer in the acrylic polymer (B).

[0066] Examples of monomer (b1) include (meth)acrylic acid and (meth)acrylic acid esters. Among these, (meth)acrylic acid esters (hereinafter referred to as "monomer (b11)") are preferred. Examples of monomers (b11) include alkyl (meth)acrylates having a branched alkyl group and alkyl (meth)acrylates having a linear alkyl group. Among these, alkyl (meth)acrylates having a branched alkyl group are preferred.

[0067] Examples of alkyl (meth)acrylates having a branched alkyl group include 2-ethylhexyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isoamyl (meth)acrylate, 1-methylheptyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, isotridecyl (meth)acrylate, isomiristyl (meth)acrylate, isostearyl (meth)acrylate, and isobornyl (meth)acrylate. Alkyl (meth)acrylate esters having a branched alkyl group may be used alone or in combination of two or more. Among the many alkyl (meth)acrylate esters having a branched alkyl group, isobornyl (meth)acrylate, isobutyl methacrylate, and t-butyl methacrylate are preferred, isobornyl (meth)acrylate is more preferred, and isobornyl methacrylate is even more preferred, in that they can form a coating film that maintains better adhesion to the substrate even during high-temperature, high-pressure washing. In other words, it is preferable that the acrylic polymer (B) contains at least one constituent unit derived from isobornyl methacrylate.

[0068] The content of constituent units derived from isobornyl methacrylate is preferably 1 to 100% by mass, more preferably 10 to 95% by mass, even more preferably 20 to 90% by mass, particularly preferably 30 to 80% by mass, and most preferably 30 to 60% by mass, relative to the total mass of all constituent units contained in the acrylic polymer (B). If the content of constituent units derived from isobornyl methacrylate is above the lower limit, the adhesion of the coating film to the substrate is further improved, and the adhesion to the substrate can be maintained more well even during high-temperature, high-pressure washing. If the content of constituent units derived from isobornyl methacrylate is below the upper limit, the adhesion of the coating film to the substrate is further improved, and the adhesion can be maintained more well during high-temperature, high-pressure washing.

[0069] Examples of alkyl (meth)acrylate esters having a linear alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, lauryl (meth)acrylate, n-tridecyl (meth)acrylate, n-stearyl (meth)acrylate, and behenyl (meth)acrylate. Alkyl (meth)acrylate esters having a linear alkyl group may be used individually or in combination of two or more. Among the many alkyl (meth)acrylate esters having a linear alkyl group, methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate are preferred because they can form a coating film that maintains better adhesion to the substrate even during high-temperature, high-pressure washing.

[0070] The monomer (b11) may be a monomer having a functional group. That is, monomer component (b) may contain a functional group-containing monomer. Examples of monomers containing functional groups include hydroxyl group-containing monomers, carboxyl group-containing monomers, monomers containing a nitrogen atom-containing functional group, acetoacetyl group-containing monomers, isocyanate group-containing monomers, and glycidyl group-containing monomers. The monomers having functional groups may be used individually or in combination of two or more. Among these, monomers containing hydroxyl groups are preferred.

[0071] Examples of hydroxyl group-containing monomers include hydroxy(meth)acrylates such as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 3-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 5-hydroxypentyl(meth)acrylate, 6-hydroxyhexyl(meth)acrylate, and 8-hydroxyoctyl(meth)acrylate; Caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; Oxyalkylene-modified monomers such as diethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, and polypropylene glycol (meth)acrylate; Primary hydroxyl group-containing monomers such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid; Secondary hydroxyl group-containing monomers such as 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro-2-hydroxypropyl (meth)acrylate; Examples include tertiary hydroxyl group-containing monomers such as 2,2-dimethyl-2-hydroxyethyl (meth)acrylate. Hydroxylate-containing monomers may be used individually or in combination of two or more. Among the many hydroxylate-containing monomers, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate are preferred in terms of storage stability and adhesion, with 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate being more preferred.

[0072] In hydroxyl group-containing monomers, a lower content of di(meth)acrylate as an impurity is preferable. For example, the content of di(meth)acrylate is preferably 0.5% by mass or less, more preferably 0.2% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0% by mass, relative to the total mass of the hydroxyl group-containing monomer.

[0073] Examples of monomers containing a carboxyl group include carboxyethyl (meth)acrylate, carboxypropyl (meth)acrylate, carboxybutyl (meth)acrylate, ω-carboxypolycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxyethyl maleic acid, 2-(meth)acryloyloxypropyl maleic acid, 2-(meth)acryloyloxyethyl succinic acid, and 2-(meth)acryloyloxypropyl succinic acid. The carboxyl group-containing monomer may be used alone or in combination of two or more types.

[0074] Examples of monomers containing a functional group with a nitrogen atom include monomers containing an amino group and monomers containing an amide group. Examples of amino group-containing monomers include primary amino group-containing (meth)acrylates such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; Secondary amino group-containing (meth)acrylates such as t-butylaminoethyl (meth)acrylate and t-butylaminopropyl (meth)acrylate; Examples of tertiary amino group-containing (meth)acrylates include ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, and dimethylaminopropylacrylamide. The amino group-containing monomer may be used alone or in combination of two or more types.

[0075] Examples of monomers containing an amide group include (meth)acrylamide; N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, Nn-butyl(meth)acrylamide, diacetone(meth)acrylamide, and N,N'-methylenebis(meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-ethylmethylacrylamide, and N,N-diallyl(meth)acrylamide; Hydroxyalkyl(meth)acrylamides such as N-hydroxymethyl(meth)acrylamide and N-hydroxyethyl(meth)acrylamide; Alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide and N-(n-butoxymethyl)(meth)acrylamide; Vinylpyrrolidone is one example. The amide group-containing monomer may be used alone or in combination of two or more types.

[0076] Examples of acetoacetyl group-containing monomers include 2-(acetoacetoxy)ethyl (meth)acrylate and allyl acetoacetate. Examples of isocyanate group-containing monomers include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and alkylene oxide adducts of these monomers. Examples of glycidyl group-containing monomers include glycidyl (meth)acrylate, allyl glycidyl (meth)acrylate, and 4-hydroxybutyl glycidyl ether (meth)acrylate. Each of these monomers may be used individually or in combination of two or more.

[0077] In addition to those mentioned above, monomers (b11) include, for example, aromatic ring-containing monomers such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, phenoxypolyethylene glycol-polypropylene glycol-(meth)acrylate, orthophenylphenoxyethyl (meth)acrylate, and nonylphenol ethylene oxide adduct (meth)acrylate; alicyclic ring-containing monomers such as cyclohexyloxyalkyl (meth)acrylate; 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, and 2-butoxyethyl (meth)acrylate. Examples include ether chain-containing monomers such as ethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, octoxypolyethylene glycol-polypropylene glycol mono(meth)acrylate, lauroxypolyethylene glycol mono(meth)acrylate, and stearoxypolyethylene glycol mono(meth)acrylate; benzophenone-containing monomers such as 4-(meth)acryloyloxybenzophenone; and fluorine atom-containing monomers such as trifluoromethyl (meth)acrylate, 2-trifluoroethyl (meth)acrylate, and 2-perfluoroethyl (meth)acrylate. These monomers may be used individually or in combination of two or more.

[0078] Furthermore, monomers having two or more ethylenically unsaturated groups, such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and propylene glycol di(meth)acrylate, can also be used in combination. A monomer having two or more ethylenically unsaturated groups may be used individually or in combination of two or more.

[0079] Monomer (b2) is a monomer other than monomer (b1) and is not particularly limited as long as it is copolymerizable with monomer (b1). Examples include acrylonitrile, methacrylonitrile; aromatic compounds such as styrene and α-methylstyrene; carboxyl group-containing monomers such as crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, N-glycolic acid, and cinnamic acid; vinyl acetate, vinyl versatate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ethers, vinyltoluene, vinylpyridine, vinylpyrrolidone, dialkyl itaconic acid esters, dialkyl fumarate esters, acrylic chloride, methyl vinyl ketone, N-acrylamidomethyltrimethylammonium chloride, allyltrimethylammonium chloride, and dimethylallyl vinyl ketone. Monomer (b2) may be used alone or in combination of two or more types. Among the various monomers (b2), styrene is preferred in terms of storage stability, adhesion, and high-temperature, high-pressure cleaning properties.

[0080] <Physical properties of acrylic polymer (B)> The glass transition temperature (hereinafter referred to as "Tg") of the acrylic polymer (B) is 105°C or higher, preferably 110°C or higher, more preferably 120°C or higher, and particularly preferably 123°C or higher. Furthermore, the Tg of the acrylic polymer (B) is preferably 200°C or lower, more preferably 190°C or lower, and particularly preferably 170°C or lower, and 150°C or lower. If the Tg of the acrylic polymer (B) is above the lower limit, a coating film can be formed that maintains adhesion to the substrate even during high-temperature, high-pressure washing. If the Tg of the acrylic polymer (B) is below the upper limit, film-forming properties are improved, and when using the aqueous polymer dispersion as a paint, the amount of film-forming aid used during paint preparation can be reduced. The lower and upper limits of the acrylic polymer (B) can be arbitrarily combined, for example, they may be 105-200°C, 110-190°C, 120-170°C, or 123-150°C.

[0081] The Tg of acrylic polymer (B) is a value obtained by Fox's formula, which is shown in equation (2) below. The Tg of acrylic polymer (B) can be controlled, for example, by selecting monomers and their composition ratios. 1 / (273+Tg)=Σ(Wi / (273+Tgi)) Formula (2) (In equation (2), Wi is the mass fraction of monomer i, and Tgi is the glass transition temperature (°C) of the homopolymer of monomer i.)

[0082] Here, the glass transition temperature of each monomer homopolymer is measured by the following method. <method> Add 5 mL of the sample to a 20 mL ampoule, add 0.1% by mass of azobisisobutyronitrile as a polymerization initiator, heat and seal, then heat to 65-130°C and polymerize for 5-40 hours. Remove the obtained polymer from the ampoule, pulverize it, place 1.5 g in a 100 mL beaker, add 50 mL of methanol, stir, and let stand overnight. Then filter out the methanol, add another 50 mL of methanol, stir, and filter again, repeating this process three times. Dry at 100°C for 2 hours to obtain a sample for glass transition temperature measurement. Using a differential scanning calorimeter (DSC) (manufactured by PERKIN-ELMER), the sample obtained above for measuring the glass transition temperature is heated to 200°C at a heating rate of 10°C / min, held for 5 minutes to melt, then cooled to 0°C at 10°C / min, and the heating rate is increased again at 10°C / min, held for 5 minutes, and cooled again at 10°C / min to determine the glass transition temperature at this time.

[0083] Furthermore, the glass transition temperatures of the main monomer homopolymers are shown below. The optimal temperatures for each acrylate are: methyl methacrylate 105°C, i-butyl methacrylate 48°C, t-butyl acrylate 41°C, n-hexyl methacrylate 32.3°C, 2-ethylhexyl acrylate 55°C, benzyl methacrylate 54°C, isobornyl methacrylate 180°C, glycidyl methacrylate 46°C, 2-hydroxybutyl acrylate 39.4°C, 2-hydroxybutyl methacrylate 47°C, 4-hydroxybutyl acrylate 85.5°C, and 4-hydroxybutyl methacrylate 20.3°C.

[0084] (aqueous medium) The aqueous medium is a dispersion medium for dispersing olefin polymer (A) and acrylic polymer (B). Water is an example of an aqueous medium. Furthermore, the aqueous polymer dispersion may also contain an organic solvent in addition to water as an aqueous medium. That is, the aqueous medium may be a mixed solvent of water and an organic solvent.

[0085] The type of water is not particularly limited, but examples include tap water, deionized water, ion-exchanged water, distilled water, and purified water. Water may be used alone or in combination of two or more types.

[0086] The water content relative to the total mass of the aqueous medium is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more. The upper limit may be 100% by mass, 98% by mass, or 95% by mass. The lower and upper limits of the water content can be arbitrarily combined, for example, 50 to 100% by mass, 80 to 98% by mass, or 90 to 95% by mass.

[0087] As organic solvents, those commonly used in water-based paints can be used. For example, linear, branched, or cyclic aliphatic alcohols with 5 to 14 carbon atoms; alcohols containing aromatic groups; and alcohols with the general formula HO-(CH2CHXO). p -R 1 (R 1 (Poly)ethylene glycol or monoethers such as (poly)propylene glycol represented by the general formula R 2 COO-(CH2CHXO) q -R 3 (R 2 , R 3 Examples include (poly)ethylene glycol ether esters or (poly)propylene glycol ether esters represented by (1 to 10 carbon atoms, where X is a hydrogen atom or a methyl group, and q is an integer less than or equal to 5); aromatic organic solvents such as toluene and xylene; monoisobutyrate of 2,2,4-trimethyl-1,3-pentanediol, diisobutyrate of 2,2,4-trimethyl-1,3-pentanediol, 3-methoxybutanol, 3-methoxybutanol acetate, 3-methyl-3-methoxybutanol, and 3-methyl-3-methoxybutanol acetate. Organic solvents may be used individually or in combination of two or more. Among the many organic solvents, linear, branched, or cyclic aliphatic alcohols having 5 to 14 carbon atoms are preferred, alcohol-based solvents having 7 to 14 carbon atoms are more preferred, and at least one alcohol-based solvent selected from the group consisting of 1-octanol, 2-octanol, 2-ethyl-1-hexanol, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol mono-n-butyl ether, propylene glycol mono-n-butyl ether, dipropylene glycol mono-n-methyl ether, and dipropylene glycol mono-n-butyl ether is particularly preferred.

[0088] The content of the organic solvent relative to the total mass of the aqueous medium is preferably 50% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less. The lower limit may be 0% by mass, 2% by mass, or 5% by mass. The lower and upper limits of the organic solvent content can be any combination, for example, 0 to 50% by mass, 2 to 20% by mass, or 5 to 10% by mass.

[0089] (optional ingredient) Optional components include, for example, various pigments, polymer beads, defoamers, pigment dispersants, leveling agents, anti-sagging agents, curing catalysts, matting agents, UV absorbers, light stabilizers, antioxidants, heat resistance improvers, slip agents, preservatives, plasticizers, thickeners, wetting agents, and various other additives besides aqueous media. Additives may be used individually or in combination of two or more types.

[0090] Furthermore, the aqueous polymer dispersion may further contain, as an optional component, curing agents such as other polymer particles, water-soluble polymers, viscosity control agents, amino polymers, polyisocyanate compounds, blocked polyisocyanate compounds, melamine polymers, urea polymers, carboxyl group-containing compounds, carboxyl group-containing polymers, epoxy group-containing polymers, epoxy group-containing compounds, and carbodiimide group-containing compounds.

[0091] Other polymer particles include, for example, dispersed particles made of other polymers such as polyester polymers, polyurethane polymers, acrylic polymers other than acrylic polymers (B), acrylic silicone polymers, silicone polymers, fluorine polymers, epoxy polymers, and alkyd polymers.

[0092] Furthermore, the aqueous polymer dispersion may further contain a surfactant as an optional component for the purpose of improving storage stability. Examples of surfactants include various anionic, cationic, or nonionic surfactants, as well as polymeric surfactants. So-called reactive surfactants, which possess ethylenically unsaturated bonds, can also be used. Surfactants may be used individually or in combination of two or more. Among the many surfactants available, it is preferable to use anionic surfactants from the viewpoint of improving the storage stability of the resulting aqueous polymer dispersion. The anionic surfactant is not particularly limited, but for example, Adekarya Soap SR, a reactive surfactant manufactured by ADEKA Corporation, and Neocall SW-C, a non-reactive surfactant, can be used.

[0093] The surfactant content is preferably 2 parts by mass or less, more preferably 1 part by mass or less, and may even be 0 parts by mass, based on 100 parts by mass of the total of the olefin polymer (A) and the acrylic polymer (B). By keeping the surfactant content below the above upper limit, stability during paint formulation can be maintained without impairing water resistance.

[0094] (Examples of aqueous polymer dispersions) In an aqueous polymer dispersion, the olefin polymer (A) and the acrylic polymer (B) may be dispersed separately in an aqueous medium, or they may be dispersed in an aqueous medium as composite particles of the olefin polymer (A) and the acrylic polymer (B). That is, the olefin polymer (A) and the acrylic polymer (B) may form composite particles. From the viewpoint of the stability of the aqueous polymer dispersion, it is preferable that the aqueous polymer dispersion contains composite particles of the olefin polymer (A) and the acrylic polymer (B). The method for manufacturing composite particles will be described later.

[0095] <Percentage> The ratio of olefin polymer (A) to acrylic polymer (B) in the aqueous polymer dispersion is such that the mass ratio ((A):(B)) of olefin polymer (A) to acrylic polymer (B) is 25:75 to 99:1, preferably 30:70 to 99:1, more preferably 40:60 to 98:2, more preferably 50:50 to 95:5, even more preferably 70:30 to 90:10, and particularly preferably 20:80 to 60:40. The higher the ratio of acrylic polymer (B) to olefin polymer (A), the more the storage stability of the aqueous polymer dispersion tends to improve. The lower the ratio of acrylic polymer (B) to olefin polymer (A), the more the adhesion of the coating film to the substrate tends to improve.

[0096] When the olefin polymer (A) has a hydroxyl group as a reactive group, the content of the acrylic polymer (B) is preferably 0.01 to 50 parts by mass, more preferably 0.05 to 40 parts by mass, and even more preferably 0.1 to 30 parts by mass, per 100 parts by mass of the olefin polymer (A). If the content of the acrylic polymer (B) is above the lower limit, the water resistance of the coating film tends to improve. If the content of the acrylic polymer (B) is below the upper limit, the adhesion of the coating film to the substrate such as the olefin substrate tends to improve.

[0097] When the olefin polymer (A) has an epoxy group as a reactive group, the content of the acrylic polymer (B) is preferably 0.01 to 50 parts by mass, more preferably 0.05 to 40 parts by mass, and even more preferably 0.1 to 30 parts by mass, per 100 parts by mass of the olefin polymer (A). If the content of the acrylic polymer (B) is above the lower limit, the water resistance of the coating film tends to improve. If the content of the acrylic polymer (B) is below the upper limit, the adhesion of the coating film to the substrate such as the olefin substrate tends to improve.

[0098] The total content of olefin polymer (A) and acrylic polymer (B) is preferably 5 to 80% by mass, more preferably 10 to 70% by mass, and even more preferably 20 to 60% by mass, relative to the total mass of the aqueous polymer dispersion. If the total content of olefin polymer (A) and acrylic polymer (B) is above the lower limit, a coating film of sufficient thickness can be easily formed in a single coating application. If the total content of olefin polymer (A) and acrylic polymer (B) is below the upper limit, the olefin polymer (A) and acrylic polymer (B) can be sufficiently dispersed in the aqueous medium.

[0099] <Average particle size> The average particle size of the aqueous polymer dispersion is preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less. If the average particle size of the aqueous polymer dispersion is below the above upper limit, the film-forming properties of the coating film tend to improve, and the adhesion to the substrate tends to improve further. The lower limit of the average particle size of the aqueous polymer dispersion is not particularly limited, but may be, for example, around 1 nm. The lower and upper limits of the average particle size of the aqueous polymer dispersion can be arbitrarily combined, and may be, for example, 1 to 500 nm, 1 to 300 nm, or 1 to 200 nm. The average particle size of an aqueous polymer dispersion is the average particle size of all components other than the aqueous medium contained in the aqueous polymer dispersion. The average particle size of an aqueous polymer dispersion is measured using a particle size distribution analyzer based on dynamic light scattering, and is the harmonic mean particle size (also called cumulant diameter) calculated based on scattered light intensity using cumulant analysis. This measurement can be performed, for example, using the concentrated particle size analyzer "FPAR-1000" from Otsuka Electronics Co., Ltd., and analyzing the data using the accompanying software.

[0100] (Method for producing aqueous polymer dispersions) The aqueous polymer dispersion is obtained by stirring and mixing an olefin polymer (A), an acrylic polymer (B), and optionally any other component in an aqueous medium. The olefin polymer (A) and the acrylic polymer (B) may each be dispersed in an aqueous medium beforehand. That is, an aqueous polymer dispersion may be produced by mixing an aqueous dispersion (α) of the olefin polymer (A) and an aqueous dispersion (β) of the acrylic polymer (B).

[0101] One method for obtaining an aqueous dispersion (α) by dispersing an olefin polymer (A) in an aqueous medium is to add an organic solvent to the olefin polymer (A), heat it appropriately to dissolve it, and then add water. This method has the advantage of easily producing an aqueous dispersion (α) with small particle sizes. The temperature for dissolving in the organic solvent and adding water is preferably 30 to 150°C, and more preferably 50 to 100°C. The organic solvent may be removed by distillation after the addition of water. Examples of water and organic solvents are those previously exemplified in the description of aqueous media.

[0102] In the method of adding an organic solvent to an olefin polymer (A), heating it appropriately to dissolve it, and then adding water, suitable equipment such as a reaction vessel with a stirrer, or a single-shaft or twin-shaft kneader can be used. The stirring speed will vary somewhat depending on the equipment selected, but is usually in the range of 10 to 1000 rpm. If the stirring speed is above the lower limit of the above numerical range, the particle size of the aqueous dispersion (α) is less likely to become excessively large.

[0103] The aqueous dispersion (β) of the acrylic polymer (B) can be obtained by the same method as the aqueous dispersion (α).

[0104] Furthermore, the following methods are examples of methods for producing an aqueous polymer dispersion containing composite particles of an olefin polymer (A) and an acrylic polymer (B). A method for polymerizing an acrylic polymer (B) by polymerizing a monomer component (b) in an aqueous dispersion (α) of an olefin homopolymer (A1), an olefin copolymer (A2), or a composite polymer (a31). A method for integrating an olefin-based homopolymer (A1), an olefin-based copolymer (A2), or a composite polymer (a31) with a monomer component (b) by dispersing them in an aqueous medium and then polymerizing the monomer component (b). From the viewpoint of the polymerizability of monomer component (b), the former method is preferred.

[0105] Polymerization of monomer component (b) may be carried out by a single polymerization, dropwise polymerization, or a combination thereof, as long as the effects of the present invention are not impaired. From the viewpoint of polymerization stability and adhesion to substrates such as polyolefin substrates, single polymerization is preferred. Here, "bulk polymerization" refers to a method of polymerization where the entire amount of monomer is added at once. "Droplet polymerization," on the other hand, refers to a method of polymerization where the monomer is added dropwise little by little.

[0106] Batch polymerization can be carried out, for example, by mixing an olefin polymer (A) and a monomer component (b), followed by radical polymerization with an initiator. Droplet polymerization can be carried out, for example, by dropping monomer component (b) into an olefin polymer (A) in the presence of an initiator.

[0107] Among the methods described above, it is preferable to polymerize monomer components (b) in an aqueous dispersion (α) to produce an aqueous polymer dispersion containing composite particles of olefin polymer (A) and acrylic polymer (B). In particular, it is more preferable to polymerize monomer components (b) in an aqueous dispersion (α) of composite polymer (a31) to produce an aqueous polymer dispersion containing composite particles of composite polymer (a31) and acrylic polymer (B).

[0108] Initiators used for polymerization of monomer component (b) are generally those used for radical polymerization. For example, persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate; oil-soluble azo compounds such as azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), and 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile; 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis{2-methyl-N-[2-(1-hydroxyethyl)]propionamide}, and 2,2'-azobis{2-methyl-N-[2-(1-hydroxybutyl)]propionamide}. Examples include water-soluble azo compounds such as 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] and its salts; 2,2'-azobis[2-(2-imidazolin-2-yl)propane] and its salts; 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} and its salts; 2,2'-azobis(2-methylpropyneamidine) and its salts; 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] and others; and organic peroxides such as benzoyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, t-butyl peroxy-2-ethylhexanoate, and t-butyl peroxyisobutyrate. The initiator may be used alone or in combination of two or more agents.

[0109] When polymerizing monomer component (b), a reducing agent may be further added to the reaction system to carry out a redox polymerization reaction. Preferred radical polymerization methods include a method using a water-soluble initiator, or a method using an organic peroxide as an initiator and a redox reaction using ferrous sulfate or isoascorbic acid as a reducing agent.

[0110] Furthermore, when polymerizing monomer component (b), molecular weight modifiers can be used. Examples of molecular weight modifiers include known chain transfer agents such as n-dodecyl mercaptan, t-dodecyl mercaptan, and α-methylstyrene dimer.

[0111] From the viewpoint of polymerization rate, the polymerization temperature of monomer component (b) is preferably 50°C or higher. In this case, it is preferable to use sodium bisulfite, ferrous sulfate and isoascorbate, or a reducing agent such as rongalit in combination with a water-soluble radical polymerization catalyst as an initiator. The upper limit of the polymerization temperature of monomer component (b) is not particularly limited, but may be, for example, 95°C or lower.

[0112] The polymerization time for monomer component (b) is preferably 30 minutes or more. If it is less than 30 minutes, monomer component (b) does not polymerize sufficiently, and the polymerization rate tends to be poor. Furthermore, the polymerization time is preferably 3 hours or less. If it exceeds 3 hours, a large amount of cullet is generated during polymerization, and the manufacturing stability tends to be poor.

[0113] After the polymerization reaction is complete, when cooling and extracting the aqueous polymer dispersion, it is preferable to perform a filtration operation to prevent contamination with foreign matter or cullet. Known filtration methods can be used, such as nylon mesh, bag filters, filter paper, or metal mesh.

[0114] (Effects and Benefits) As described above, the aqueous polymer dispersion of this embodiment contains the olefin polymer (A) and the acrylic polymer (B) having a glass transition temperature greater than a specific value, so it can form a coating film that maintains adhesion to the substrate even after high-temperature, high-pressure washing.

[0115] As the substrate, polymer substrates are preferred, and examples include olefin substrates, acrylonitrile-butadiene-styrene copolymer (ABS polymer) substrates, polycarbonate substrates, polymethacrylate substrates (acrylic polymers), polystyrene substrates, and polyamide substrates (nylon substrates). Among these, the coating film formed from the aqueous polymer dispersion of this embodiment exhibits excellent adhesion to olefin substrates and ABS polymer substrates, and is particularly excellent to olefin substrates. Examples of olefin substrates include ethylene substrates and propylene substrates. Among olefin substrates, propylene substrates are preferred because they improve the adhesion of the coating film to the substrate after high-temperature, high-pressure cleaning, and polypropylene substrates containing elastomer components such as rubber are even more preferred.

[0116] The coating film can be obtained, for example, by coating a water-based polymer dispersion onto a substrate and drying it to remove the aqueous medium. The coating method is not particularly limited, and general methods can be used, but examples include spin coating, slit coating, spray coating, gravure coating, bar coating, and roll coating. The drying temperature is not particularly limited as long as it is a temperature that can remove the aqueous medium, but for example, 60 to 140°C is preferred, and 70 to 120°C is more preferred. The thickness of the coating film is not particularly limited and can be determined appropriately depending on the application, but for example, 0.1 to 100 μm is preferred, and 1 to 50 μm is more preferred.

[0117] (Application) The aqueous polymer dispersion can be usefully used as a binder component in paints such as primers and topcoats, adhesives, inks, and the like. Applications of the aqueous polymer dispersion include, for example, automotive paints for car interiors and exteriors, paints for home appliances such as mobile phones and personal computers, paints for building materials, and heat sealants. Among these, its use as a paint is preferred, and its use as a primer composition (primer paint) for olefin substrates is particularly preferred.

[0118] Paints, adhesives, and inks containing an aqueous polymer dispersion may each contain, in addition to the aqueous polymer dispersion, components other than the aqueous polymer dispersion (hereinafter also referred to as "other components") as needed. Examples of other components include the optional components exemplified earlier in the description of the aqueous polymer dispersion. Furthermore, other components may include polymers other than the aqueous polymer dispersion (other binder components). Other binder components include, for example, polyolefin polymers, polyurethane polymers, and polyester polymers. For example, a polyolefin polymer may be mixed as another component into an aqueous polymer dispersion containing composite particles of an olefin polymer (A) and an acrylic polymer (B) to produce paints, adhesives, and inks. In this case, the polyolefin polymer as the other component exists independently of the composite particles of the olefin polymer (A) and the acrylic polymer (B), and does not form an integral part with the acrylic polymer.

[0119] For example, by coating the aqueous polymer dispersion of this embodiment onto a substrate and drying it, a laminate can be obtained that includes a substrate and a layer (coating film) formed by drying the aqueous polymer dispersion of this embodiment provided on the substrate. The above-mentioned materials are examples of substrates, and the present invention is useful for olefin substrates, and particularly useful for propylene substrates. The laminate may have another coating film on top of a layer (coating film) formed by drying the aqueous polymer dispersion of this embodiment. For example, a primer layer may be provided on the surface of the substrate as a layer formed by drying the aqueous polymer dispersion of this embodiment, and a color layer or clear layer may be provided on the primer layer using a color coating or a clear coating. [Examples]

[0120] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples as long as it does not exceed the gist thereof, and various modifications are possible without departing from the gist of the present invention.

[0121] [Measurement and Evaluation] The detailed methods of measurement and evaluation in the examples are as follows.

[0122] (Average Particle Diameter of Aqueous Polymer Dispersion) As the average particle diameter of the aqueous polymer dispersion, the cumulant diameter of the aqueous polymer dispersion was determined using a concentrated particle size analyzer "FPAR-1000" (product of Otsuka Electronics Co., Ltd.).

[0123] (Composition Ratio of Each Olefin Component) After vacuum drying the aqueous dispersion (α) at 40 °C for 12 hours, dichlorobenzene was added to a concentration of 2% by mass and dissolved at 100 °C to prepare a NMR sample. Using NMR (manufactured by JEOL Ltd., product name "JNM-ECS400 type"), at a frequency of 400 MHz, measurement nuclide 13 C, pulse width 3.47 [μs], pulse repetition time 3.04 [s], measurement temperature 100 °C, and number of scans 4096 times, the NMR spectrum was measured. Regarding the measurement results, the spectral assignment was carried out according to the methods described in the Polymer Analysis Handbook (4th Edition, edited by the Polymer Analysis Research Discussion Group of the Japanese Society for Analytical Chemistry), Study of Propylene-1-butene-ethylene Terpolymer and Reactor Blend by TREF and 13 C-NMR (authors: Adilson Arli Silva Filho, Griselda Barrera Galland, journal name: Journal of Applied Polymer Science). Then, the composition ratio of each olefin component was calculated from the area ratio of the peaks of each olefin component.

[0124] (Adhesiveness during High Temperature and High Pressure Cleaning) A water-based polymer dispersion was coated onto an olefin substrate (propylene substrate, manufactured by Nippon Polypropylene Co., Ltd., trade name "TSOP-6"). The mixture was then dried at 80°C for 5 minutes to obtain a 15 μm thick coating (primer layer). Next, a mixture of 100 g of Dianal LR-7677 (manufactured by Mitsubishi Chemical Corporation), 3.8 g of aluminum paste MH-8801 (manufactured by Asahi Kasei Corporation), 20 g of cellulose ester CAB381-0.5 (manufactured by Eastman Chemical Japan Co., Ltd.) butyl acetate 25% solution, and 160 g of solvent mixture (xylene / ethyl acetate / toluene / PGMAc / MIBK (mass ratio) = 10 / 60 / 30 / 30 / 30) was applied. The mixture was then left at room temperature for 5 minutes or more to obtain a 15 μm thick coating (1) on the primer layer. Subsequently, a mixture of 100g of Dianal JR-C211 (manufactured by Mitsubishi Chemical Corporation), 0.8g of surface modifier (manufactured by Bic Chemie Japan Co., Ltd., product name "BYK-333"), 0.04g of curing catalyst (manufactured by Tokyo Chemical Industry Co., Ltd., product name "BDBTDL"), 45.7g of mixed solvent (S100 / PGMAc / butyl acetate / ethyl acetate (mass ratio) = 18.3 / 13.7 / 9.1 / 4.6), and 24.3g of isocyanate polymer (manufactured by Asahi Kasei Corporation, product name "Duranate TPA-100") was applied. After that, it was left at room temperature for 15 minutes and dried at 80°C for 30 minutes to form a coating film with a thickness of 40 μm on coating film (1). After the formation of the three-layer coating film consisting of the primer layer, coating film (1), and coating film (2), cross-shaped cuts were made in the coating film with a cutter. Using a test device (Kärcher HDS4 / 7C), high-pressure hot water was sprayed onto a coating with cross-shaped cuts at a water pressure of 6 MPa, a water flow rate of 7 L / min, and a water temperature of 65°C, at a spray angle of 90 degrees and a spray time of 1 minute. More specifically, as shown in Figure 1, high-pressure hot water was sprayed onto the coating 11 with cross-shaped cuts from the tip of the nozzle 10 of the test device. After spraying, the coating was observed to check for peeling. If there was no peeling, the spray distance d shown in Figure 1 was shortened and the same test was performed. This process of shortening the spray distance d and performing the test was repeated until peeling of the coating occurred. For example, as shown in Figure 2, the spray distance d when peeling f occurred on the coating 11 with cross-shaped cuts 12 was recorded. A smaller spray distance d indicates better adhesion during high-temperature, high-pressure cleaning. "PGMAc" is propylene glycol monomethyl ether acetate, "MIBK" is methyl isobutyl ketone, and "S100" is a high-boiling point aromatic hydrocarbon solvent (manufactured by Ando Parachemy Co., Ltd.).

[0125] [Production of olefin polymer (A)] (Manufacturing Example 1: Manufacturing and Analysis of Composite Polymer (a31)) 200 kg of propylene-butene copolymer polymerized with a metallocene catalyst (manufactured by Mitsui Chemicals, Inc., trade name "Tafmer XM-7070", melting point 75°C, propylene content 70 mol%, weight-average molecular weight [Mw] 250,000 (polypropylene equivalent), molecular weight distribution [Mw / Mn] 2.2) and 5 kg of maleic anhydride were dry-blended in a super mixer. Subsequently, using a twin-screw extruder (manufactured by Japan Steel Works Ltd., product name "TEX54αII"), t-butyl peroxyisopropyl monocarbonate (manufactured by NOF Corporation, product name "Perbutyl I") was added via a liquid pump at a ratio of 1 part by mass per 100 parts by mass of propylene-butene copolymer. The mixture was kneaded under the conditions of a cylinder temperature of 200°C, a screw rotation speed of 125 rpm, and a discharge rate of 80 kg / hour to obtain a pellet-shaped maleic anhydride-modified propylene-butene copolymer (corresponding to olefin copolymer (A21)). The maleic anhydride-modified propylene-butene copolymer obtained in this manner had a maleic anhydride group content (graft rate) of 1.0% by mass (0.1 mmol / g as maleic anhydride groups and 0.2 mmol / g as carboxylic acid groups). The weight-average molecular weight (polystyrene equivalent) [Mw] was 156,000, and the number-average molecular weight [Mn] was 84,000.

[0126] Next, 72 g of the previously obtained maleic anhydride-modified propylene-butene copolymer, 48 g of propylene-butene copolymer (manufactured by Mitsui Chemicals, Inc., trade name "Tafmer XM-7070"), and 79.9 g of toluene were placed in a glass flask equipped with a reflux condenser, thermometer, and stirrer. The container was then purged with nitrogen gas and the temperature was raised to 110°C. After raising the temperature, 1.8 g of maleic anhydride was added, followed by 0.9 g of t-butyl peroxyisopropyl monocarbonate (manufactured by NOF Corporation, trade name "Perbutyl I"), and the reaction was carried out by continuing to stir at 110°C for 7 hours. The maleic anhydride-modified propylene-butene copolymer (polyolefin (A-1)) obtained had a maleic anhydride group content (graft rate) of 2.0% by mass (0.2 mmol / g as maleic anhydride groups and 0.4 mmol / g as carboxylic acid groups).

[0127] After the reaction was complete, the reaction system was cooled to near room temperature, 85.7 g of toluene was added, followed by 24 g of polyetheramine (Huntsman, trade name "Jeffermin M-2005") dissolved in 156 g of 2-propanol (equivalent to 20 parts by mass of polyether polymer per 100 parts by mass of polyolefin (A-1)), and the mixture was reacted at 70°C for 1 hour. Subsequently, 12 g of polyetheramine (Huntsman, trade name "Jeffermin M-1000") dissolved in 84 g of 2-propanol (equivalent to 10 parts by mass of polyether polymer per 100 parts by mass of polyolefin (A-1)), and the mixture was reacted at 70°C for 1 hour. Subsequently, 1.8 g of dimethylethanolamine, 62 g of water, and 45 g of 2-propanol were added to neutralize the reaction system. The resulting reaction solution was heated and stirred while maintaining its temperature at 50°C, and 434.4 g of water was added dropwise while the degree of vacuum in the reaction system was reduced. Toluene and 2-propanol were removed by distillation under reduced pressure until the polymer concentration reached 30% by mass, yielding an aqueous dispersion (α) of the milky white composite polymer (a31).

[0128] [Example 1] In a flask equipped with a stirrer, reflux condenser, and temperature control device, 222.2 parts by mass (66.6 parts by mass in terms of solid content) of the aqueous dispersion (α) of the previously obtained composite polymer (a31) and 178.95 parts by mass of deionized water were charged, and the temperature was raised to 30°C. Separately, a pre-emulsion was prepared by mixing 45.8 parts by mass of isobornyl methacrylate (IBXMA) and 9.4 parts by mass of 2-hydroxyethyl methylene (HEMA) as monomers (b11), 44.8 parts by mass of styrene as monomer (b2), 7 parts by mass of a reactive surfactant (manufactured by ADEKA Corporation, product name "ADEKA ARENA SOAP SR1025"), and 45 parts by mass of deionized water, and emulsifying with TK Homodisper. 152.0 g of the obtained preemulsion was placed in a flask containing an aqueous dispersion (α), etc., and heated to 55°C while stirring, and held for 1.5 hours. Then, while maintaining the temperature at 55°C, 0.05 parts by mass of initiator (manufactured by NOF Corporation, trade name "Perbutyl® H69", solids content 69% by mass), 0.0002 parts by mass of ferrous sulfate as a reducing agent, 0.00027 parts by mass of ethylenediaminetetraacetic acid (EDTA), 0.08 parts by mass of sodium isoascorbate monohydrate, and 2 parts by mass of deionized water were added to start polymerization. After detecting the exothermic peak of polymerization, an additional 0.06 parts by mass of initiator (manufactured by NOF Corporation, trade name "Perbutyl® H69") and 12 parts by mass of deionized water were added. Subsequently, the mixture was aged at 60°C for 30 minutes to obtain an aqueous polymer dispersion in which composite particles of the composite polymer (a31) and acrylic polymer (B) were dispersed in an aqueous medium, with an average particle size of 84 nm and a solid content of 30% by mass. The obtained aqueous polymer dispersion (111.1 parts by mass, equivalent to 33.33 parts by mass in terms of solid content) was mixed with PO polymer, PUD, pigment, solvent, wetting agent, and defoamer in the composition shown in Table 1, and its adhesion during high-temperature, high-pressure washing was evaluated. The results are shown in Table 1. In addition, the composition ratio of each olefin component in the aqueous dispersion (α) was measured, and the Tg of the acrylic polymer (B) was calculated using Fox's formula represented by equation (2) above. The calculation results are shown in Table 1.

[0129] [Examples 2-4, Comparative Examples 1,2] Except for changing the content of the polyolefin polymer (A) and the monomer content used in the acrylic polymer (B) as shown in Table 1, aqueous polymer dispersions were obtained and evaluated in the same manner as in Example 1.

[0130] The Tg values ​​of the monomer homopolymers used in the examples and comparative examples are shown below. IBXMA: Isobornyl methacrylate (Tg: 180℃) IBMA: Isobutyl methacrylate (Tg: 48℃) 2EHA: 2-Ethylhexyl acrylate (Tg: -55℃) St: Styrene (Tg: 100℃) HEMA: 2-hydroxyethyl methylate (Tg: 55℃) 4HBA: 4-Hydroxybutyl acrylate (Tg: -85.5℃)

[0131] [Table 1]

[0132] In Table 1, "parts" refers to "parts by mass." "PO polymer" is polyolefin polymer (product name "APTOLOK(registered trademark) BW-5710" manufactured by Mitsubishi Chemical Corporation). "PUD" is product name "Baihidol UH-2648 / 1" manufactured by Covestro. "Pigment" is product name "WT-9004" manufactured by Nippon Pigment Co., Ltd. "Solvent" is product name "BDG" manufactured by Nippon Emulsifier Co., Ltd. "Wetting agent" is product name "TEGO WetKL245" manufactured by EVONIK. "Defoaming agent" is product name "BYK-028" manufactured by Bic Chemie Japan Co., Ltd. The content of PO polymer, PUD, pigment, solvent, wetting agent, and defoaming agent is the actual component amount, i.e., the amount in its actual form (parts by mass). If any of the PO polymer, PUD, pigment, wetting agent, or defoaming agent contains a solvent, etc., the value includes that solvent. A blank space in the table indicates that the ingredient is not included (0 parts by mass).

[0133] In Examples 1-4, the spray distance d at which the coating peeled off during the high-temperature, high-pressure cleaning test was shorter than in Comparative Examples 1-2. In other words, the adhesion during high-temperature, high-pressure cleaning was better in Examples 1-4 than in Comparative Examples 1-2. [Industrial applicability]

[0134] According to the present invention, a coating film can be formed that maintains adhesion to substrates such as olefin substrates even during high-temperature, high-pressure cleaning. [Explanation of Symbols]

[0135] 10 Nozzles of testing equipment for high-temperature, high-pressure cleaning 11. Coating film 12 Cross-shaped cuts d. Spray distance of high-pressure hot water f. Peeling of the coating

Claims

1. An aqueous polymer dispersion in which an olefin polymer (A) and an acrylic polymer (B) are dispersed in an aqueous medium, The glass transition temperature of the acrylic polymer (B) is 105°C or higher. An aqueous polymer dispersion in which the mass ratio of the olefin polymer (A) to the acrylic polymer (B) is (A):(B) = 25:75 to 99:

1.

2. The aqueous polymer dispersion according to claim 1, wherein the acrylic polymer (B) contains a constituent unit derived from isobornyl methacrylate.

3. The aqueous polymer dispersion according to claim 1, wherein the olefin polymer (A) and the acrylic polymer (B) form composite particles.

4. The aqueous polymer dispersion according to claim 1, wherein the olefin polymer (A) comprises at least one selected from the group consisting of ethylene-propylene copolymer, ethylene-propylene-butene copolymer, and propylene-butene copolymer.

5. The aqueous polymer dispersion according to claim 1, wherein the olefin polymer (A) has a reactive group.

6. The aqueous polymer dispersion according to claim 5, wherein the reactive group comprises at least one selected from the group consisting of a carboxyl group, an epoxy group, an isocyanate group, a sulfonic acid group, and a hydroxyl group.

7. The aqueous polymer dispersion according to claim 1, wherein the average particle size of the aqueous polymer dispersion is 500 nm or less.

8. A paint containing the aqueous polymer dispersion described in any one of claims 1 to 7.

9. A primer composition containing an aqueous polymer dispersion according to any one of claims 1 to 7.

10. A laminate comprising a base material and a layer provided on the base material, the layer being formed by drying an aqueous polymer dispersion according to any one of claims 1 to 7.

11. The laminate according to claim 10, wherein the base material is a polyolefin base material.

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