Aqueous coating composition and method for producing the same

Abstract

To provide an aqueous coating composition that enables formation of a coating film exhibiting superior resistance to frost damage.SOLUTION: A composition according to the present disclosure is an aqueous coating composition comprising a silicone-acrylic graft copolymer resin (i) and an acrylic emulsion resin (ii) having a hydrolyzable silyl group, wherein polysiloxane units in the copolymer resin (i) include structural units derived from a silane compound having three hydrolyzable silyl groups, and the weight ratio of the copolymer resin (i) to the acrylic emulsion resin (ii) (copolymer resin (i) / acrylic emulsion resin (ii)) is from 35 / 65 to 95 / 5.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-based coating composition and a method for producing the same. [Background technology]

[0002] Coating agents have been used for the purpose of improving the appearance and protecting structures such as buildings, civil engineering structures, and vehicles. Among the compositions constituting coating agents, there is a demand for water-based coating compositions that can be stably dispersed or dissolved in an aqueous medium (to be made aqueous) from the viewpoint of environmental friendliness and the like.

[0003] Among aqueous coating compositions, aqueous coating compositions containing polysiloxane resins as described in Patent Documents 1 to 3 are becoming increasingly popular in the market due to their excellent weather resistance and minimal adverse effects on the human body and the environment, and there is a growing demand for them in a variety of applications. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 07-196975 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-97368 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-187765 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the aqueous coating compositions containing polysiloxane resins provided by conventional techniques have room for improvement in terms of the frost resistance of coating films formed using the aqueous coating compositions.

[0006] In view of the above circumstances, an object of the present invention is to provide a water-based coating composition that can provide a coating film having excellent frost resistance. [Means for solving the problem]

[0007] As a result of extensive research aimed at solving the above problems, the present inventors have discovered for the first time that an aqueous coating composition capable of providing a coating film with excellent frost resistance can be provided by mixing (i) a silicone acrylic graft copolymer resin having a specific structure and (ii) an acrylic emulsion resin having a hydrolyzable silyl group in a specific ratio, and have thus completed the present invention.

[0008] Therefore, one aspect of the present invention is an aqueous coating composition (hereinafter, sometimes referred to as "the composition") comprising a silicone acrylic graft copolymer resin (i) and an acrylic emulsion resin (ii) having a hydrolyzable silyl group, wherein the polysiloxane unit in the copolymer resin (i) comprises a constituent unit derived from a silane compound having three hydrolyzable silyl groups, and the weight ratio of the copolymer resin (i) to the acrylic emulsion resin (ii) (the copolymer resin (i) / the acrylic emulsion resin (ii)) is 35 / 65 to 95 / 5.

[0009] Another aspect of the present invention is a method for producing an aqueous coating composition comprising a silicone-acrylic graft copolymer resin (i) and an acrylic emulsion resin (ii) having a hydrolyzable silyl group, wherein the polysiloxane units in the copolymer resin (i) comprise structural units derived from a silane compound having three hydrolyzable silyl groups, and the method for producing an aqueous coating composition (hereinafter, sometimes referred to as "this production method") comprises a step of mixing the copolymer resin (i) and the acrylic emulsion resin (ii) so that the weight ratio (the copolymer resin (i) / the acrylic emulsion resin (ii)) is in the range of 35 / 65 to 95 / 5. [Effects of the Invention]

[0010] According to one aspect of the present invention, it is possible to provide a water-based coating composition that can provide a coating film having excellent frost resistance. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention will be described in detail below. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more and B or less." In addition, all documents described in this specification are incorporated herein by reference.

[0012] 1. Overview of the Invention As described above, conventionally proposed aqueous coating compositions containing polysiloxane resins (for example, the compositions described in Patent Documents 1 to 3) have room for improvement in terms of the frost resistance of coating films obtained by curing the compositions.

[0013] Therefore, the present inventors have conducted extensive research to solve the above problems, and as a result have found for the first time that it is possible to provide an aqueous coating composition capable of providing a coating film with excellent frost resistance by mixing a silicone acrylic graft copolymer resin (i) having a specific structure and an acrylic emulsion resin (ii) having a hydrolyzable silyl group in a specific ratio. More specifically, the present inventors have succeeded in obtaining the following findings: By mixing a silicone acrylic graft copolymer resin (i) containing a structural unit derived from a silane compound (a silane compound having a T-isomer skeleton) in which the polysiloxane unit in the copolymer resin (i) has three hydrolyzable silyl groups, and an acrylic emulsion resin (ii) having hydrolyzable silyl groups in a weight ratio of 35 / 65 to 95 / 5, a water-based coating composition capable of providing a coating film with excellent frost resistance can be obtained.

[0014] The inventors speculate as follows as to why the aqueous coating composition having the above-described structure can provide a coating film with excellent frost resistance, but the present invention is not limited to this speculation. By mixing the silicone acrylic graft copolymer resin with the acrylic emulsion resin in a specific ratio, the film-forming properties and water resistance of the coating film are improved. Furthermore, the presence of hydrolyzable silyl groups in the acrylic emulsion resin forms a crosslinked structure between the hydrolyzable silyl groups in the acrylic emulsion resin and the hydrolyzable silyl groups in the silicone acrylic graft copolymer resin (particularly, the hydrolyzable silyl groups derived from a silane compound having three hydrolyzable silyl groups). This crosslinked structure improves the durability of the coating film. As a result of these actions, a coating film with excellent frost resistance is formed.

[0015] Thus, it would be completely unpredictable from conventional knowledge that mixing a silicone acrylic graft copolymer resin having a specific structure with an acrylic emulsion resin (ii) having a hydrolyzable silyl group in a specific ratio improves the frost resistance of a coating film obtained by curing an aqueous coating composition, making the present invention extremely superior.

[0016] Furthermore, this composition is a water-based coating composition and does not require organic solvents for production. Therefore, this composition can reduce water and soil pollution compared to solvent-based coating compositions that use organic solvents as a medium. As a result, this composition may also contribute to achieving Goal 15 of the United Nations' Sustainable Development Goals (SDGs), "Protect and sustainably manage land."

[0017] 2. Water-based coating composition The composition comprises a silicone acrylic graft copolymer resin (i) and an acrylic emulsion resin (ii) having a hydrolyzable silyl group, wherein the polysiloxane unit in the copolymer resin (i) comprises a constituent unit derived from a silane compound having three hydrolyzable silyl groups, and the weight ratio of the copolymer resin (i) to the acrylic emulsion resin (ii) (the copolymer resin (i) / the acrylic emulsion resin (ii)) is 35 / 65 to 95 / 5.

[0018] By virtue of having the above-described constitution, the present composition has the advantage of being able to provide a coating film that is excellent in frost resistance.

[0019] In this specification, the term "water-based coating composition" refers to a coating composition that uses water as a medium. In this specification, the term "water-based coating composition" refers to a coating composition that contains 5% by weight or more of water in 100% by weight of the coating composition.

[0020] The water content in the present composition is not particularly limited as long as it is 5% by weight or more based on 100% by weight of the coating composition, but is preferably 10% by weight or more, more preferably 20% by weight or more, and particularly preferably 50% by weight or more, in order to further improve the workability of the present composition. The upper limit of the water content in the present composition is not particularly limited, and may be, for example, 90% by weight or less, or 80% by weight or less.

[0021] In addition, in this specification, the term "coating composition" means "a composition that can protect against scratches and stains, impart beauty, etc. by forming a film (coating film) on the surface of an object to be coated."

[0022] (2-1. Silicone acrylic graft copolymer resin (i)) The composition includes a silicone acrylic graft copolymer resin (i) (sometimes referred to as "copolymer resin (i)").

[0023] In this specification, the term "silicone acrylic graft copolymer resin" refers to a copolymer in which an acrylic polymer, i.e., a polymer obtained by polymerizing an acrylic monomer, is bonded (grafted) to a polyorganosiloxane, i.e., a polymer obtained by condensing a monomer having a hydrolyzable silyl group, by radical polymerization. In the silicone acrylic graft copolymer resin, the structural unit derived from the polyorganosiloxane may be referred to as a polysiloxane unit, and the structural unit derived from the acrylic polymer bonded to the polysiloxane unit by radical polymerization may be referred to as an acrylic polymer unit.

[0024] In one embodiment of the present invention, the copolymer resin (i) is a copolymer resin having polysiloxane units including a structural unit (a) derived from a silane compound (A) having a radically polymerizable unsaturated group and a hydrolyzable silyl group, and optionally a structural unit (b) derived from a silane compound (B) having a hydrolyzable silyl group but no radically polymerizable unsaturated group, and an acrylic polymer unit including a structural unit (c) derived from an acrylic monomer (C) having no hydrolyzable silyl group.

[0025] A specific embodiment of the copolymer resin (i) will be described in detail below.

[0026] (Structural unit (a)) The copolymer resin (i) according to one embodiment of the present invention contains a structural unit (a) as a structural unit of a polysiloxane unit. The structural unit (a) is derived from a silane compound (A) having a radically polymerizable unsaturated group and a hydrolyzable silyl group.

[0027] The silane compound (A) having a radical polymerizable unsaturated group and a hydrolyzable silyl group is represented by the following general formula (I): R 1 a R 2 b -Si-(OR 3 ) 4-a-b (I) (In the formula, R 1is a substituted alkyl group or alkenyl group having 1 to 10 carbon atoms and having a polymerizable unsaturated group, or an aryl group having a polymerizable unsaturated group and optionally having other substituents, and R 2 are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, or an unsubstituted or substituted aryl group, and R 3 are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, and a+b is an integer of 1 to 3. Preferably, the silane compound is a silane compound having a radical polymerizable unsaturated group and a hydrolyzable silyl group, represented by the following formula:

[0028] R in general formula (I) 1 is a substituted alkyl group having 1 to 10 carbon atoms and having a radically polymerizable unsaturated group, an alkenyl group, or an unsubstituted or substituted aryl group having a radically polymerizable unsaturated group. Examples of the radically polymerizable unsaturated group include a (meth)acryloyl group.

[0029] R 1is an alkyl group having a radical polymerizable unsaturated group, examples of the silane compound (A) include (meth)acryloxymethyltrimethoxysilane, (meth)acryloxymethylmethyldimethoxysilane, (meth)acryloxymethyldimethylmethoxysilane, (meth)acryloxymethyltriethoxysilane, (meth)acryloxymethylmethyldiethoxysilane, (meth)acryloxymethyldimethylethoxysilane, 2-(meth)acryloxyethyltrimethoxysilane, 2-(meth)acryloxyethylmethyldimethoxysilane, 2- (Meth)acryloxyethyl dimethyl methoxy silane, 2-(meth)acryloxyethyl triethoxy silane, 2-(meth)acryloxyethyl methyl diethoxy silane, 2-(meth)acryloxyethyl dimethyl ethoxy silane, γ-(meth)acryloxypropyl trimethoxy silane, γ-(meth)acryloxypropyl methyl dimethoxy silane, γ-(meth)acryloxypropyl dimethyl methoxy silane, γ-(meth)acryloxypropyl triethoxy silane, γ-(meth)acryloxypropyl methyl diethoxy silane, γ- (Meth)acryloxypropyldimethylethoxysilane, 4-(meth)acryloxybutyltrimethoxysilane, 4-(meth)acryloxybutylmethyldimethoxysilane, 4-(meth)acryloxybutyldimethylmethoxysilane, 4-(meth)acryloxybutyltriethoxysilane, 4-(meth)acryloxybutylmethyldiethoxysilane, 4-(meth)acryloxybutyldimethylethoxysilane, 5-(meth)acryloxypentyltrimethoxysilane, 5-(meth)acryloxypentylmethyldimethoxysilane, 5-(meth)acryloxypentylmethyldimethoxysilane p) acryloxypentyldimethylmethoxysilane, 5-(meth)acryloxypentyltriethoxysilane, 5-(meth)acryloxypentylmethyldiethoxysilane, 5-(meth)acryloxypentyldimethylethoxysilane, 6-(meth)acryloxyhexyltrimethoxysilane, 6-(meth)acryloxyhexylmethyldimethoxysilane, 6-(meth)acryloxyhexyldimethylmethoxysilane, 6-(meth)acryloxyhexyltriethoxysilane, 6-(meth)acryloxyhexylmethyldiethoxysilane,6-(meth)acryloxyhexyldimethylethoxysilane, etc.

[0030] R 1 Examples of the silane compound (A) in which is an alkenyl group include vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, and vinyldimethylethoxysilane.

[0031] R 1 is an aryl group having a polymerizable unsaturated group and optionally having other substituents, examples of the silane compound (A) include p-styryltrimethoxysilane, p-styrylmethyldimethoxysilane, p-styryldimethylmethoxysilane, p-styryltriethoxysilane, p-styrylmethyldiethoxysilane, and p-styryldimethylethoxysilane.

[0032] Among these, R 1 As the alkyl group, a (meth)acryloyl group-substituted alkyl group is preferred.

[0033] R in general formula (I) 2 are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, or an unsubstituted or substituted aryl group.

[0034] R in general formula (I) 2 Specific examples of the alkyl group in the formula (I) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, an amyl group, an isoamyl group, a hexyl group, a cyclohexyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a heptyl group, an isoheptyl group, an n-octyl group, an isooctyl group, and a 2-ethylhexyl group.

[0035] R in general formula (I) 2 Specific examples of the aryl group in include a phenyl group, a naphthyl group, and a benzyl group.

[0036] R in general formula (I) 2 When a is 1 and b is 1, it is preferably a methyl group.

[0037] R in general formula (I) 3 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, a hexyl group, an amyl group, an isoamyl group, a hexyl group, a cyclohexyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a heptyl group, an isoheptyl group, an octyl group, an n-octyl group, an isooctyl group, a 2-ethylhexyl group, a nonyl group, and a decyl group.

[0038] In the compound of general formula (I), R 3 When R is a hydrogen atom, it means that a hydroxyl group is present on the silicon atom. A group in which a hydroxyl group is bonded to a silicon atom is also called a silanol group. 3 is an alkyl group, it means that an alkoxy group is bonded to a silicon atom. A group formed by bonding an alkoxy group to a silicon atom is also called an alkoxysilyl group. In this specification, these silanol groups and alkoxysilyl groups are collectively called hydrolyzable silyl groups. Among the above hydrolyzable silyl groups, alkoxysilyl groups are preferred because the alcohol by-produced by hydrolysis can be easily removed.

[0039] From the viewpoint of facilitating condensation of the silane compound (A) with another silane compound (silane compound (B)) that does not have a radically polymerizable unsaturated group, R 2 and R 3 The alkyl group preferably has 1 to 3 carbon atoms, and most preferably 1 carbon atom.

[0040] In one embodiment of the present invention, the content of the structural unit (a) in the polysiloxane units in the copolymer resin (i) is, for example, 1% by weight or more, preferably 2% by weight or more, based on 100% by weight of the total amount of the polysiloxane units. When the content of the structural unit (a) in the polyorganosiloxane is within the above range, the polysiloxane units can be graft-polymerized directly or indirectly with the structural unit (c) sufficiently, resulting in a silicone-acrylic graft copolymer resin that can be stably dispersed or dissolved (water-based) in an aqueous medium. The upper limit of the content of the structural unit (a) is not particularly limited as long as the effects of the present invention are achieved, but it is, for example, 20% by weight or less, preferably 10% by weight or less, and more preferably 8% by weight or less. The content of the structural unit (a) in the polysiloxane unit can be calculated as the ratio of the amount of silane compound (A) charged minus the weight of the volatile components generated during polymerization to the total amount of monomers charged when polymerizing the polysiloxane unit minus the weight of the volatile components generated during polymerization.

[0041] (Structural unit (b)) The copolymer resin (i) according to one embodiment of the present invention contains a structural unit (b) as a structural unit of a polysiloxane unit. The structural unit (b) is derived from a silane compound (B) that has a hydrolyzable silyl group but does not have a radically polymerizable unsaturated group.

[0042] The silane compound (B) having a hydrolyzable silyl group and no radically polymerizable unsaturated group is represented by the following general formula (II): R 4 n -Si-(OR 5 ) 4-n (II) (In the formula, R 4 are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, or an unsubstituted or substituted aryl group, and R 4 When there are multiple R 5 are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n is an integer of 0 to 3. It is preferable that the silane compound is a silane compound represented by the following formula:

[0043] Silane compound (B) undergoes dehydration condensation with silane compound (A) and / or (B) to form a polysiloxane structure. In this specification, silane compound (B) may be referred to as monomer (B). Structural unit (b) may be composed of only one type of silane compound (B) represented by general formula (III), or may be composed of a combination of two or more types of silane compounds (B).

[0044] R in general formula (II) 4 Specific examples of the alkyl group in the formula (I) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, an amyl group, an isoamyl group, a hexyl group, a cyclohexyl group, a cyclohexylmethyl group, a cyclohexylethyl group, a heptyl group, an isoheptyl group, an n-octyl group, an isooctyl group, and a 2-ethylhexyl group.

[0045] R in general formula (II) 4 Specific examples of the aryl group in include a phenyl group, a naphthyl group, and a benzyl group.

[0046] R in general formula (II) 5 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, and a decyl group.

[0047] Specific examples of the compound represented by general formula (II) include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltriisopropoxysilane, butyltrimethoxysilane, butyltriethoxysilane, butyltriisopropoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, hexyltriisopropoxysilane, octyltrimethoxysilane, octyltriethoxysilane, octyltriisopropoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, dimethyldimethoxysilane, methylphenyldimethoxysilane, diphenyldimethoxysilane, trimethylmonomethoxysilane, and triphenylmonomethoxysilane.

[0048] As the monomer (B), a silane compound (silane compound (B1)) having a hydrolyzable silyl group but not having a radically polymerizable unsaturated group other than the compound represented by general formula (II) can also be used. Examples of such silane compounds (B1) include compounds having a hydrolyzable silyl group and a mercapto group, such as γ-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, and 3-mercaptopropylmethyldimethoxysilane.

[0049] Compounds having a hydrolyzable silyl group and a mercapto group (sometimes referred to as mercaptosilanes) have a chain transfer effect and can therefore function as grafting points during polymerization (graft polymerization) of polysiloxane units and acrylic polymer units.

[0050] In one embodiment of the present invention, the content of the structural unit (b) in the polysiloxane units in the copolymer resin (i) is, for example, preferably 80% by weight or more, more preferably 90% by weight or more, and even more preferably 92% by weight or more, based on the total amount of the polysiloxane units (100% by weight). The upper limit of the content of the structural unit (b) is not particularly limited as long as the effects of the present invention are achieved, but it may be, for example, 98% by weight or less, or 99% by weight or less. The content of the structural unit (b) can be calculated as the ratio of the amount of silane compound (B) charged minus the weight of volatile components generated during polymerization (due to hydrolysis of hydrolyzable silyl groups) to the total amount of monomers charged when polymerizing the polysiloxane units minus the weight of volatile components generated during polymerization.

[0051] (Structural unit derived from a silane compound having three hydrolyzable silyl groups) The polysiloxane units in the copolymer resin (i) according to one embodiment of the present invention contain at least one structural unit derived from a silane compound having three hydrolyzable silyl groups, which increases the degree of condensation and also improves frost resistance.

[0052] Furthermore, since copolymer resin (i) contains a structural unit derived from a silane compound having three hydrolyzable silyl groups, it becomes possible to easily make copolymer resin (i) aqueous, even when the copolymerization ratio of structural unit (c1) is smaller, compared to when copolymer resin (i) contains only a silane compound having two or less hydrolyzable silyl groups. This action makes it possible to reduce the ratio of hydrophilic components after coating film formation, thereby improving the water resistance of the coating film.

[0053] Examples of silane compounds having three hydrolyzable silyl groups include a silane compound (sometimes referred to as silane compound (A')) in which 4-ab is 3 in the above general formula (I), i.e., a is 1 and b is 0 in the general formula (I), and a silane compound (sometimes referred to as silane compound (B')) in which 4-n is 3 in the above general formula (II), i.e., n is 1 in the general formula (II). That is, the copolymer resin (i) contains a structural unit derived from at least one silane compound selected from silane compound (A') and silane compound (B').

[0054] The content of the structural units derived from silane compound (A') and silane compound (B') in the polysiloxane units constituting copolymer resin (i) is not particularly limited, but is preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, even more preferably 80% by weight or more, and may even be 90% by weight or more, based on 100% by weight of the total amount of the polysiloxane units. When the content of the structural units derived from silane compound (A') and silane compound (B') is within the above range, a coating film with better frost resistance and water resistance can be provided. Furthermore, the upper limit of the content of the structural units derived from silane compound (A') and silane compound (B') is not particularly limited as long as the effects of the present invention are achieved, but may be, for example, 95% by weight or less, 98% by weight or less, or even 100% by weight. Since a coating film having even more excellent frost resistance and water resistance can be provided as the content of structural units derived from silane compound (A') and silane compound (B') is higher, it is particularly preferred that the content of structural units derived from silane compound (A') and silane compound (B') is 100% by weight. In other words, it is particularly preferred that the polysiloxane units constituting copolymer resin (i) are composed only of structural units derived from silane compound (A') and silane compound (B').

[0055] (Structural unit (c)) The copolymer resin (i) according to one embodiment of the present invention contains, as a constituent unit of the acrylic polymer unit, a constituent unit (c) derived from an acrylic monomer (C) that does not have a hydrolyzable silyl group.

[0056] In this specification, the term "acrylic monomer" refers to a monomer containing an acrylic radical polymerizable group, specifically, a (meth)acryloyl group or a (meth)acrylamide group. Monomers containing a hydrolyzable silyl group in addition to the above-mentioned acrylic radical polymerizable group are classified as silane compounds (A) and are therefore not considered to be acrylic monomers (C). Furthermore, in this specification, the term "(meth)acryloyl group" refers to both an acryloyl group and a methacryloyl group, and the term "(meth)acrylamide group" refers to both an acrylamide group and a methacrylamide group.

[0057] Examples of monomers that can be used as the acrylic monomer (C) include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)methacrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, and isobornyl (meth)acrylate; and nitrile group-containing radically polymerizable monomers such as (meth)acrylonitrile. monomers having two or more polymerizable unsaturated bonds such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, ethylene glycol di(meth)acrylate, and allyl (meth)acrylate; and fluorine-containing radically polymerizable monomers such as trifluoro(meth)acrylate, pentafluoro(meth)acrylate, perfluorocyclohexyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl methacrylate, and β-(perfluorooctyl)ethyl (meth)acrylate. That is, the copolymer resin (i) may contain, as the structural unit (c), a structural unit derived from any of these monomers.

[0058] ·Constituent unit (c1) Furthermore, as the acrylic monomer (C), a monomer (sometimes referred to as monomer (C1)) that has a salt structure consisting of an acid and a base and an acrylic radically polymerizable group, does not have a hydrolyzable silyl group, is soluble in water, and does not form micelles in water may be used. In other words, the copolymer resin (i) may contain, as the structural unit (c), a structural unit (structural unit (c1)) derived from such a monomer (C1).

[0059] In this specification, the term "salt structure" refers to the structure of a neutral salt obtained by neutralizing an acid and a base. Here, the acid used for neutralization may be a strong acid or a weak acid. The base used for neutralization may be a strong base or a weak base.

[0060] In one embodiment of the present invention, the salt structure may be, for example, a neutral salt structure between a strong acid and a strong base, a neutral salt structure between a strong acid and a weak base, a neutral salt structure between a weak acid and a strong base, or a neutral salt structure between a weak acid and a weak base. More specific salt structures include, for example, sodium sulfonate, potassium sulfonate, calcium sulfonate, sodium nitrate, potassium nitrate, calcium nitrate, etc. (neutral salt structures between a strong acid and a strong base), ammonium sulfonate, ammonium nitrate, etc. (neutral salt structures between a strong acid and a weak base), sodium acetate, potassium acetate, calcium acetate, sodium phosphate, potassium phosphate, calcium phosphate, etc. (neutral salt structures between a weak acid and a strong base), ammonium acetate, ammonium phosphate, etc. (neutral salt structures between a weak acid and a weak base). In one embodiment of the present invention, the salt structure possessed by the monomer (C1) is preferably sodium sulfonate.

[0061] In this specification, "soluble in water" means that when an aqueous solution of 1 g of a target monomer in 10 g of water at 25°C is thoroughly stirred and allowed to stand at 25°C for one week, and the appearance is visually observed, the aqueous solution is transparent and no precipitate, dispersed matter, layer separation, etc. are observed.

[0062] In this specification, whether or not a monomer is "capable of forming micelles in water" is determined by the method described in the section (Monomer (C2)).

[0063] The monomer (C1) is not particularly limited as long as it is a monomer having a salt structure consisting of an acid and a base and having a radical polymerizable group, and examples thereof include sodium sulfoethyl methacrylate, sodium acrylamido-t-butylsulfonate, sodium 2-(methacryloyloxy)ethanesulfonate, sodium acrylamido-t-butylsulfonate, potassium 2-(methacryloyloxy)ethanesulfonate, potassium acrylamido-t-butylsulfonate, calcium 2-(methacryloyloxy)ethanesulfonate, calcium acrylamido-t-butylsulfonate, ammonium sulfoethyl methacrylate, ammonium acrylamido-t-butylsulfonate, ammonium 2-(methacryloyloxy)ethanesulfonate, ammonium acrylamido-t-butylsulfonate, sodium acrylate, potassium acrylate, calcium acrylate, ammonium acrylate, sodium methacrylate, potassium methacrylate, calcium methacrylate, and ammonium methacrylate.

[0064] The monomer (C1) can be obtained as a commercially available product, such as "Antox MS-2N-D" manufactured by Nippon Nyukazai Co., Ltd., "ATBS-Na" manufactured by Toagosei Co., Ltd., and "Sodium Acrylate" and "Potassium Acrylate" manufactured by Asada Chemical Industry Co., Ltd.

[0065] In one embodiment of the present invention, when the copolymer resin (i) contains the structural unit (c1), the content of the structural unit (c1) in the acrylic polymer units in the copolymer resin (i) is, for example, preferably 1% by weight or more, more preferably 2% by weight or more, and even more preferably 4% by weight or more, based on 100% by weight of the total amount of the acrylic polymer units. When the acrylic polymer units contain the structural unit (c1) in the above range, the solubility or dispersibility of the copolymer resin (i) in water is improved. The upper limit of the content of the structural unit (c1) is not particularly limited, but may be, for example, 20% by weight or less, or 10% by weight or less. The content of the structural unit (c1) in the acrylic polymer units is approximately the same as the ratio of the amount of the monomer (C1) charged to the total amount of the monomers charged when polymerizing the acrylic polymer units. Therefore, in this specification, the ratio of the amount of monomer (C1) charged to the total amount of monomers when polymerizing the acrylic polymer units is considered to be the content of structural unit (c1) in the resulting acrylic polymer units.

[0066] ·Constituent unit (c2) Furthermore, as the acrylic monomer (C), a monomer (sometimes referred to as monomer (C2)) that has an acrylic radical polymerizable group, does not have a hydrolyzable silyl group, and is capable of forming micelles in water may be used. In other words, the copolymer resin (i) may contain, as the structural unit (c), a structural unit (structural unit (c2)) derived from such a monomer (C2).

[0067] As used herein, the term "micelle" refers to an aggregate formed by amphipathic molecules associating with each other through hydrophobic interactions. Here, the term "amphipathic molecule" refers to a molecule having both a hydrophobic group and a hydrophilic group within the molecule. Therefore, the term "structure capable of forming a micelle in water" refers to a structure having both a hydrophobic group and a hydrophilic group within the molecule.

[0068] That is, in one embodiment of the present invention, the monomer (C2) may be an amphiphilic molecule having an acrylic radically polymerizable group and no hydrolyzable silyl group.

[0069] Whether a monomer is "capable of forming micelles in water" is determined by the following method: 1 g of the target monomer is added to a two-layer liquid containing 10 g of water and 2 g of butyl acetate, and after thorough stirring and leaving to stand for 12 hours, if a uniform white turbidity is observed, the target monomer is determined to be capable of forming micelles in water. If clear layers of water and butyl acetate are observed to separate after leaving to stand for 12 hours, the target monomer is determined to not form micelles in water (is unable to form micelles).

[0070] The monomer (C2) is not particularly limited as long as it has an acrylic radical polymerizable group, a structure that forms micelles in water (i.e., a structure having a hydrophobic group and a hydrophilic group in the molecule), and does not have a hydrolyzable silyl group.

[0071] The hydrophobic group in the monomer (C2) is not particularly limited, but examples thereof include alkyl groups having 3 or more carbon atoms and having an acrylic radical polymerizable group, and aryl groups.

[0072] The hydrophilic group in the monomer (C2) is not particularly limited, but examples thereof include anionic hydrophilic groups such as sulfonate, carboxylate, and sulfate ester salts; cationic hydrophilic groups such as amine salts and quaternary ammonium salts; amphoteric hydrophilic groups such as betaine; and nonionic hydrophilic groups such as polyoxyalkylene.

[0073] In one embodiment of the present invention, from the viewpoint of versatility, the monomer (C2) preferably has a polyoxyalkylene structure. Examples of the monomer (C2) having a polyoxyalkylene structure include polyoxyethylene and polyoxypropylene. The monomer (C2) preferably has a polyoxyalkylene structure having 1 to 100 oxyalkylene repeating units, more preferably 2 to 50 oxyalkylene repeating units, and even more preferably 5 to 20 oxyalkylene repeating units.

[0074] The monomer (C2) is not particularly limited as long as it is within the above definition, and examples thereof include ADEKA REASOAP SR-05, SR-10, SR-20, SR-1025, SR-2025, SR-3025, SR-10S, NE-10, NE-20, NE-30, NE-40, SE-10, SE-20, ER-10, ER-20, ER-30, and ER-40 manufactured by ADEKA CORPORATION, and Antox-MS-60, RMA-1120, RMA-564, RMA-568, RMA-506, MA-30, and MA manufactured by Nippon Nyukazai Co., Ltd. -50, MA-100, MA-150, RMA-1120, MPG130-MA, MPG-130MA, RMA-150M, RMA-300M, RMA-450M, RA-1020, RA-1820, Aqualon KH-05, KH-10, RN-20, RN-30, RN-50, RN-2025, HS-10, HS-20, HS-1025, BC05, BC10, BC0515, BC1025 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Eleminol JS-2, JS-20, RS-30 manufactured by Sanyo Chemical Industries, Ltd., and Lathem manufactured by Kao Corporation. S-180, S-180A, PD-104, PD-420, PD-430, NOF Corporation's Blenmar PE-90, PE-200, PE-350, AE-90, AE-200, AE-350, PP-500, PP-800, PP-1000, AP-400, AP-550, AP-800, 700PEP-350B, 10PEP-550B, 55PET-400, 30PET-800, 55PET-800, 30PPT-800, 50PPT-800, 70PPT-800, PME-100, PME-200 , PME-400, PME-1000, PME-4000, AME-400, 50POEP-800B, 50AOEP-800B, AEP, AET, APT, PLE, ALE, PSE, ASE, PKE, AKE, PNE, ANE, PNP, ANP, PNEP-600, Light Ester 130MA, 041MA, MTG, Light Acrylate EC-A, MTG-A, 130A, DPM-A, P-200A, NP-4EA, NP-8EA, EHDG-A manufactured by Kyoeisha Chemical Co., Ltd., and NK-ESTER M-20G, M-40G, M-90G, M-230G, AMP-10G, AMP-20G, AMP-60G, AM-90G, and LA manufactured by Shin-Nakamura Chemical Co., Ltd.From the viewpoint of versatility and micelle stability, Adeka Reasoap SR-10 is preferred.

[0075] In one embodiment of the present invention, when the copolymer resin (i) contains the structural unit (c2), the content of the structural unit (c2) in the acrylic polymer units in the copolymer resin (i) is, for example, preferably 1% by weight or more, more preferably 3% by weight or more, and even more preferably 5% by weight or more, based on 100% by weight of the total amount of the acrylic polymer units. When the acrylic polymer units contain the structural unit (c2) in the above range, viscosity adjustment becomes easy when the copolymer resin (i) is aqueous-based in an aqueous medium. The upper limit of the content of the structural unit (c2) is not particularly limited, but may be, for example, 20% by weight or less, or 10% by weight or less. The content of the structural unit (c2) in the acrylic polymer units is approximately the same as the ratio of the amount of the monomer (C2) charged to the total amount of the monomers charged when polymerizing the acrylic polymer units. Therefore, in this specification, the ratio of the amount of monomer (C2) charged to the total amount of monomers when polymerizing the acrylic polymer units is considered to be the content of structural unit (c2) in the resulting acrylic polymer units.

[0076] (Physical properties of copolymer resin (i)) ·Structural unit ratio The ratio of structural units in the copolymer resin (i), i.e., the ratio (weight ratio) of polysiloxane units to acrylic polymer units, is not particularly limited, but since there are advantages such as improved dispersion stability when the copolymer resin (i) is aqueousized in an aqueous medium and the provision of a coating film with excellent water resistance, the weight ratio of polysiloxane units to acrylic polymer units (polysiloxane units / acrylic polymer units) is preferably 5 / 95 to 70 / 30, more preferably 20 / 80 to 60 / 40, and even more preferably 25 / 75 to 55 / 45. The ratio of polysiloxane units to acrylic polymer units in the copolymer resin (i) can be calculated based on the value obtained by subtracting the weight of volatile components generated from the amount of each structural unit charged when polymerizing the copolymer resin (i).

[0077] ·Weight average molecular weight The weight average molecular weight of the copolymer resin (i) is not particularly limited, but is preferably 30,000 to 300,000, as this makes it possible to provide a coating film with better frost resistance, and may also be 40,000 to 300,000, 50,000 to 300,000, 70,000 to 270,000, or 100,000 to 250,000.

[0078] In this specification, the weight average molecular weight of the copolymer resin (i) is a value measured and calculated under the conditions described in the Examples.

[0079] Glass transition temperature (Tg) of acrylic polymer unit The Tg of the acrylic polymer unit in copolymer resin (i) is not particularly limited, but is preferably 40°C or less, more preferably 30°C or less, and even more preferably 20°C or less, since this makes it possible to provide a coating film with superior frost resistance. The lower limit of the Tg of the acrylic polymer unit is not particularly limited, but may be, for example, -10°C or more, -7°C or more, or -5°C or less. In this specification, the Tg of the acrylic polymer unit means the value calculated by Fox's formula (T.G. Fox, Bull. Am. Phys. Soc. 1, 123 (1956)).

[0080] (Method for producing copolymer resin (i)) The method for producing the copolymer resin (i) is not particularly limited, but the copolymer resin (i) can be produced, for example, by a method including: a condensation step of condensing a silane compound (A) and a silane compound (B) in the presence of a dehydration condensation catalyst and water; and a polymerization step of radically polymerizing the condensate (polysiloxane) obtained in the condensation step with a monomer (C) in the presence of a radical polymerization initiator to form and graft-bond acrylic polymer units.

[0081] (2-2. Acrylic emulsion resin (ii) having hydrolyzable silyl groups) The present composition contains an acrylic emulsion resin (ii) having a hydrolyzable silyl group (sometimes referred to as "acrylic emulsion resin (ii)").

[0082] In this specification, "acrylic emulsion resin" means a resin having emulsion-like properties in which a polymer (resin component) whose main component is a structural unit derived from an acrylic monomer is dispersed in water, and "acrylic emulsion resin having a hydrolyzable silyl group" means an acrylic emulsion resin in which a polymer whose main component is a structural unit derived from an acrylic monomer, which is a resin component, is a copolymer that contains a structural unit derived from a monomer having a hydrolyzable silyl group in addition to the structural unit derived from the acrylic monomer.

[0083] That is, in one embodiment of the present invention, the resin component of the acrylic emulsion resin (ii) is a copolymer resin containing a structural unit (d) derived from an acrylic monomer (D), a structural unit (e) derived from a silane compound (E) having a radically polymerizable unsaturated group and a hydrolyzable silyl group, and, optionally, a structural unit (f) derived from a monomer (F) copolymerizable with the acrylic monomer (D) other than the acrylic monomer (D) and the silane compound (E), and the acrylic emulsion resin (ii) is a resin obtained by dispersing such a copolymer resin in water.

[0084] A specific embodiment of the acrylic emulsion resin (ii) will be described in detail below.

[0085] (resin component) The acrylic emulsion resin (ii) contains, as resin components, a copolymer resin (hereinafter sometimes referred to as copolymer resin (iia)) that includes a structural unit (d) derived from an acrylic monomer (D), a structural unit (e) derived from a silane compound (E) having a radically polymerizable unsaturated group and a hydrolyzable silyl group, and, optionally, a structural unit (f) derived from a monomer (F) copolymerizable with other acrylic monomers.

[0086] (Constituent unit (d)) The copolymer resin (iia) according to one embodiment of the present invention contains a structural unit (d) derived from an acrylic monomer (D). The definition of the acrylic monomer in this specification is as described above in the section (Structural Unit (c)).

[0087] The specific aspects of the monomer (D) and the functional groups contained in the compound are the same as those of the monomer (C) above, and therefore the description in the section (Structural Unit (C)) above is incorporated herein, and the description is omitted in this section.

[0088] In one embodiment of the present invention, the content of the structural unit (d) in the copolymer resin (iia) is not particularly limited, but is preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, even more preferably 90% by weight or more, and particularly preferably 95% by weight or more, relative to the total amount (100% by weight) of the copolymer resin. When the copolymer resin contains the structural unit (d) in the above range, emulsion polymerization can be stably carried out, and the copolymer resin (iia) can be stably provided. The upper limit of the content of the structural unit (d) is not particularly limited, but may be, for example, 10% by weight or less, or 5% by weight or less. The content of the structural unit (d) in the copolymer resin (iia) is approximately the same as the ratio of the amount of monomer (D) (and monomer (D1)) charged to the total amount of monomers charged when polymerizing the copolymer resin. Therefore, in this specification, the ratio of the amount (total amount) of monomer (D) (and monomer (D1)) charged to the total amount of monomers charged when polymerizing the copolymer resin is regarded as the content of structural unit (d) in the resulting copolymer resin.

[0089] ·Constituent unit (d1) Furthermore, as the acrylic monomer (D), a monomer (sometimes referred to as monomer (D1)) that has an acrylic radical polymerizable group, does not have a hydrolyzable silyl group, and is capable of forming micelles in water may be used. In other words, the copolymer resin (iia) may contain, as the structural unit (d), a structural unit (structural unit (d1)) derived from such a monomer (D1).

[0090] The monomer (D1) can be used as a reactive emulsifier in emulsion polymerization because it performs functions such as providing a site for the polymerization reaction and pre-emulsifying the monomer components. In particular, a copolymer resin (iia) polymerized in the presence of the monomer (D1) as a reactive emulsifier (i.e., containing the structural unit (d1)) can have better water resistance than a copolymer resin polymerized in the presence of a non-reactive emulsifier.

[0091] In this specification, the definition of whether a monomer is "capable of forming micelles in water" is as set forth in the section above (Structural unit (c2)).

[0092] Specific aspects of the monomer (D1) and the functional groups contained in the compound are the same as those of the monomer (C2) described above, and therefore the description in the section on structural unit (C2) above is incorporated herein, and the description is omitted here.

[0093] In one embodiment of the present invention, when the copolymer resin (iia) contains the structural unit (d1), the content of the structural unit (d1) in the copolymer resin (iia) is, for example, preferably 1% by weight or more, and more preferably 1.5% by weight or more, based on 100% by weight of the total amount of the copolymer resin (iia). When the copolymer resin (iia) contains the structural unit (d1) in the above range, it becomes possible to stably obtain a copolymer resin (iia) having excellent water resistance by emulsion polymerization. The upper limit of the content of the structural unit (d1) is not particularly limited, but may be, for example, 10% by weight or less, or 5% by weight or less. The content ratio of the structural unit (d1) in the copolymer resin (iia) is approximately the same as the ratio of the amount of the monomer (D1) charged to the total amount of the monomers charged when polymerizing the copolymer resin (iia). Therefore, in this specification, the ratio of the amount of monomer (D1) charged to the total amount of monomers charged when polymerizing the copolymer resin (iia) is considered to be the content of structural unit (d1) in the resulting copolymer resin (iia).

[0094] (Structural unit (e)) The copolymer resin (iia) according to one embodiment of the present invention contains a structural unit (e) derived from a silane compound (E) having a radically polymerizable unsaturated group and a hydrolyzable silyl group.

[0095] The silane compound (E) having a radical polymerizable unsaturated group and a hydrolyzable silyl group is represented by the following general formula (III): R 6 x R 7 y -Si-(OR 8 ) 4-x-y (III) (In the formula, R 6 is a substituted alkyl group or alkenyl group having 1 to 10 carbon atoms and having a polymerizable unsaturated group, or an aryl group having a polymerizable unsaturated group and optionally having other substituents, and R 7 are each independently an unsubstituted or substituted alkyl group having 1 to 10 carbon atoms, or an unsubstituted or substituted aryl group, and R 8are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, x is an integer of 1 to 3, y is an integer of 0 to 2, and x+y is an integer of 1 to 3. The compound is a silane compound having a radical polymerizable unsaturated group and a hydrolyzable silyl group, represented by the formula:

[0096] The specific aspects of the silane compound (E) and the functional groups contained in the compound are the same as those of the silane compound (A) described above, and therefore the description in the section (Structural unit (a)) above is incorporated herein, and the description is omitted here.

[0097] In one embodiment of the present invention, the content of the structural unit (e) in the copolymer resin (iia) is not particularly limited, but is preferably 0.5 to 20 wt %, more preferably 1 to 15 wt %, even more preferably 1.5 to 10 wt %, and even more preferably 2 to 8 wt %, relative to the total amount (100 wt %) of the copolymer resin (iia). By including the structural unit (e) in the copolymer resin (iia) in the above range, it is possible to achieve both water resistance and flexibility, and it is advantageous in providing an aqueous coating composition with better frost resistance. The content of the structural unit (e) in the copolymer resin (iia) is approximately equal to the ratio of the amount of the monomer (E) charged to the total amount of the monomers charged when polymerizing the copolymer resin (iia). Therefore, in this specification, the ratio of the amount (total amount) of the monomer (E) charged to the total amount of the monomers charged when polymerizing the copolymer resin (iia) is regarded as the content ratio of the structural unit (e) in the resulting copolymer resin (iia).

[0098] (structural unit (f)) The copolymer resin (iia) according to one embodiment of the present invention may contain a structural unit (f) derived from a monomer other than the silane compound (E) that is copolymerizable with the silane compound (E), i.e., a silane compound (F) that has a hydrolyzable silyl group but does not have a radically polymerizable unsaturated group.

[0099] The specific aspects of the silane compound (F) and the functional groups contained in the compound are the same as those of the silane compound (B) described above. Therefore, except for the matters described below, the description in the above section (Structural unit (b)) is incorporated by reference, and the description is omitted in this section.

[0100] Among silane compounds having a hydrolyzable silyl group but no radically polymerizable unsaturated group, compounds having a hydrolyzable silyl group and a mercapto group (mercaptosilane), such as γ-mercaptopropyltrimethoxysilane, are preferred as the silane compound (F). Mercaptosilane exhibits a chain transfer effect in radical polymerization (including emulsion polymerization) and is introduced into the molecular terminal of the resulting copolymer resin (iia). When a coating film is formed, a crosslinked structure is formed between the hydrolyzable silyl group derived from the mercaptosilane introduced into the molecular terminal of this copolymer resin (iia) and the hydrolyzable silyl group of the copolymer resin (i), thereby further improving the frost resistance of the coating film.

[0101] In one embodiment of the present invention, the content of the structural unit (f) in the copolymer resin (iia) is not particularly limited, but is preferably 0.1 to 5 wt %, more preferably 0.1 to 3 wt %, and even more preferably 0.2 to 1 wt %, relative to 100 wt % of the total amount of the copolymer resin (iia). In particular, when the structural unit (f) is derived from mercaptosilane, the frost resistance of the coating film can be further improved by including the structural unit (f) in the copolymer resin (iia) in the above range. The content of the structural unit (f) in the copolymer resin (iia) is approximately the same as the ratio of the amount of monomer (F) charged to the total amount of monomers charged when polymerizing the copolymer resin (iia). Therefore, in this specification, the ratio of the amount (total amount) of the monomer (F) charged to the total amount of the monomers charged when polymerizing the copolymer resin (iia) is regarded as the content ratio of the structural unit (f) in the resulting copolymer resin (iia).

[0102] The hydrolyzable silyl groups possessed by the structural units (e) and (f) become the hydrolyzable silyl groups possessed by the resulting copolymer resin (iia), and ultimately the acrylic emulsion resin (ii). From the viewpoint of the storage stability of the acrylic emulsion resin (ii), the hydrolyzable silyl groups possessed by the acrylic emulsion resin (ii) are preferably alkoxysilyl groups. In other words, the structural units (e) and (f) preferably have alkoxysilyl groups as the hydrolyzable silyl groups, and are preferably structural units derived from the monomers (E) and (F) having alkoxysilyl groups.

[0103] (constituent unit (g)) The copolymer resin (iia) according to one embodiment of the present invention may contain a structural unit (g) derived from a monomer (G) copolymerizable with the acrylic monomer (D), other than the acrylic monomer (D) and the silane compound (E).

[0104] Monomers that can be used as monomer (G) are not particularly limited as long as they are monomers other than the acrylic monomer (D) and the silane compound (E) that are copolymerizable with the acrylic monomer (D), and examples include aromatic hydrocarbon vinyl monomers such as styrene, α-methylstyrene, chlorostyrene, 4-hydroxystyrene, and vinyltoluene; vinyl esters or allyl compounds such as vinyl acetate, vinyl propionate, vinyl versatate, and diallyl phthalate; nitrile group-containing vinyl monomers such as (meth)acrylonitrile; vinyl methyl ether; propylene; butadiene; etc. Among these, styrene is preferred as monomer (G) because it can provide a coating film that is high in gloss and has excellent appearance.

[0105] In one embodiment of the present invention, the content of the structural unit (g) in the copolymer resin (iia) is not particularly limited, but is preferably 0.5 to 20 wt%, more preferably 1 to 15 wt%, even more preferably 1.5 to 10 wt%, and even more preferably 2 to 8 wt%, relative to the total amount (100 wt%) of the copolymer resin (iia). By including the structural unit (g) in the copolymer resin (iia) within the above range, the effect of incorporating the structural unit (g) (in the case of styrene, improved appearance) can be favorably exhibited. The content of the structural unit (g) in the copolymer resin (iia) is approximately equal to the ratio of the amount of the monomer (G) charged to the total amount of the monomers charged when polymerizing the copolymer resin (iia). Therefore, in this specification, the ratio of the amount (total amount) of the monomer (G) charged to the total amount of the monomers charged when polymerizing the copolymer resin (iia) is regarded as the content ratio of the structural unit (g) in the resulting copolymer resin.

[0106] (Method for producing acrylic emulsion resin (ii)) The method for producing the acrylic emulsion resin (ii) is not particularly limited, but may be, for example, a method for producing a core / shell emulsion, more specifically, a method including the steps of emulsion polymerizing a portion of the monomer (D), a portion of the monomer (E), and optionally a portion of the monomer (F) in the presence of an emulsifier, preferably a reactive emulsifier (e.g., monomer (D1)), to obtain a core component, and emulsion polymerizing the obtained core component, the remainder of the monomer (D), the remainder of the monomer (E), and optionally the remainder of the monomer (F) in the presence of an additional emulsifier, preferably a reactive emulsifier, to obtain a shell component. Furthermore, in the above method, a step of polymerizing a portion of the monomer (D) and a portion of the monomer (E) to obtain a seed component may be carried out prior to the step of obtaining the core component. By carrying out such a step, the seed component functions as a nucleus for the polymerization of the core component, thereby enabling the polymerization of the core component, and in turn the polymerization of the entire acrylic emulsion resin, to be carried out more effectively.

[0107] The Tg and crosslinking points (hydrolyzable silyl groups) of the core component and shell component can be adjusted, and as a result, the coating film can exhibit both weather resistance and flexibility. Therefore, the acrylic emulsion resin (ii) according to one embodiment of the present invention is preferably a core / shell acrylic emulsion resin obtained by the above-mentioned method for producing a core / shell emulsion.

[0108] (Ratio of copolymer resin (i) and acrylic emulsion resin (ii)) In this composition, the weight ratio of copolymer resin (i) to acrylic emulsion resin (ii) (copolymer resin (i) / acrylic emulsion resin (ii)) is 35 / 65 or more, preferably 40 / 60 or more, more preferably 45 / 65 or more, more preferably 50 / 50 or more, even more preferably 55 / 45 or more, even more preferably 60 / 40 or more, even more preferably 65 / 35 or more, even more preferably 70 / 30 or more, and may be 75 / 25 or more, 80 / 20 or more, 85 / 15 or more, or 90 / 10 or more. The weight ratio of copolymer resin (i) to acrylic emulsion resin (ii) may be 95 / 5 or less, 90 / 10 or less, 85 / 15 or less, 80 / 20 or less, or 75 / 25 or less. For example, the weight ratio of copolymer resin (i) to acrylic emulsion resin (ii) in the composition (copolymer resin (i) / acrylic emulsion resin (ii)) is 35 / 65 to 95 / 5, or may be 45 / 55 to 90 / 10, 55 / 45 to 85 / 15, 60 / 40 to 80 / 20, or 65 / 35 to 75 / 25. By setting the weight ratio of copolymer resin (i) to acrylic emulsion resin (ii) within the above range, it is possible to provide an aqueous coating composition that can provide a coating film with excellent frost resistance.

[0109] (2-3. Other ingredients) (curing catalyst) The present composition may contain a curing catalyst. By containing a curing catalyst in the present composition, it is possible to provide a coating film that is excellent in stain resistance as well as frost resistance.

[0110] In this specification, the term "curing catalyst" refers to a substance that catalyzes the reaction in which hydrolyzable silyl groups condense with each other to form siloxane bonds.

[0111] The curing catalyst that may be contained in the composition is preferably an organotin curing catalyst, and more specifically, dialkyltin carboxylates (dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diethylhexanolate, dibutyltin dioctate, dibutyltin dimethyl maleate, dibutyltin diethyl maleate, dibutyltin dibutyl maleate, dibutyltin diisooctyl maleate, dibutyltin ditridecyl maleate, dibutyltin dibenzyl maleate, dibutyltin maleate, dioctyltin diacetate, dioctyltin distearate, dioctyltin dilaurate, dioctyltin diethyl maleate, dioctyltin diisooctyl maleate, etc.), dialkyltin oxides (dibutyltin oxide, dioctyltin oxide, a mixture of dibutyltin oxide and a phthalate ester, etc.), tetravalent tin compounds (dialkyltin oxide, dialkyltin diacetate, etc.) and acetones. Examples of the reactants include reaction products with alkoxysilyl group-containing low molecular weight silicon compounds (tetraethoxysilane, methyltriethoxysilane, diphenyldimethoxysilane, phenyltrimethoxysilane, etc.), divalent tin compounds (tin octoate, tin naphthenate, tin stearate, etc.), monoalkyltins (monobutyltin compounds (monobutyltin trisoctoate, monobutyltin triisopropoxide, etc.), monooctyltin compounds, reaction products or mixtures of amine compounds and organic tin compounds (reaction products or mixtures of laurylamine and tin octoate, etc.), chelate compounds (dibutyltin bisacetylacetonate, dioctyltin bisacetylcetonate, dibutyltin bisethylacetonate, dioctyltin bisethylacetonate, etc.), tin alcoholates (dibutyltin dimethylate, dibutyltin diethylate, dioctyltin dimethylate, dioctyltin diethylate, etc.).

[0112] (silicate) When the present composition contains a curing catalyst, it is preferable that the present composition further contains a silicate from the viewpoint of further improving stain resistance. In this specification, silicate is a silicon compound having four hydrolyzable silyl groups in the molecule.

[0113] Examples of silicates that may be included in the present composition include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane, tetra-n-butoxysilane, tetra-i-butoxysilane, tetra-t-butoxysilane, and partial hydrolysates or condensates thereof.

[0114] (water) The composition may contain water. The amount of water in the composition is not particularly limited, but is, for example, 5 to 50% by weight, preferably 7 to 30% by weight, and more preferably 10 to 15% by weight, relative to 100% by weight of the total amount of the composition.

[0115] (Other additives) In addition to the above components, the present composition may contain additives (other additives) commonly used in the relevant technical field (particularly the field of paints) within the scope of the effects of the present invention. Examples of such other additives include pigments, fillers, plasticizers, film-forming aids, wetting agents, dispersants, thickeners, antifoaming agents, preservatives, antioxidants, antisettling agents, leveling agents, UV absorbers, antistatic agents, antifreeze agents, antibacterial agents, antifungal and antialgal agents, tackifiers, rust inhibitors, and hydrophilizing agents. Only one type of other additive may be contained, or two or more types may be contained. Furthermore, the amount of these other additives can be appropriately determined by one skilled in the art depending on the intended use.

[0116] 3. Method for producing water-based coating composition In one embodiment of the present invention, there is provided a method for producing an aqueous coating composition comprising a silicone-acrylic graft copolymer resin (i) and an acrylic emulsion resin (ii) having a hydrolyzable silyl group, wherein the polysiloxane units in the copolymer resin (i) comprise structural units derived from a silane compound having three hydrolyzable silyl groups, and the method comprises a step of mixing the copolymer resin (i) and the acrylic emulsion resin (ii) so that the weight ratio (the copolymer resin (i) / the acrylic emulsion resin (ii)) is in the range of 35 / 65 to 95 / 5.

[0117] The present production method, having the above-mentioned features, can provide a water-based coating composition that can provide a coating film that has excellent frost resistance.

[0118] Regarding this production method, specific embodiments of the silicone acrylic graft copolymer resin (i) and the acrylic emulsion resin having a hydrolyzable silyl group (ii), including preferred embodiments, are as described above in the section [2. Water-based coating composition]. Therefore, the description in the section [2. Water-based coating composition] above is incorporated by reference and will not be repeated here.

[0119] (Mixing process) This production method includes a step (mixing step) of mixing copolymer resin (i) and acrylic emulsion resin (ii) so that the weight ratio (copolymer resin (i) / acrylic emulsion resin (ii)) is in the range of 35 / 65 to 95 / 5. The amount of each component mixed (mixing ratio) in the mixing step determines the content (content ratio) of each component in the resulting aqueous coating composition. Therefore, by mixing copolymer resin (i) and acrylic emulsion resin (ii) in the mixing step so that the ratio is as described above, it is possible to provide an aqueous coating composition (i.e., this composition) with the desired mixing ratio.

[0120] In the mixing step, the mixing ratio of the copolymer resin (i) to the acrylic emulsion resin (ii) (copolymer resin (i) / acrylic emulsion resin (ii)) is not particularly limited as long as it is in the range of 35 / 65 to 95 / 5, but is preferably 45 / 55 to 90 / 10, more preferably 55 / 45 to 85 / 15, and even more preferably 65 / 35 to 75 / 25.

[0121] In the mixing step, other components may be further mixed in addition to the copolymer resin (i) and the acrylic emulsion resin (ii). Specific aspects of such other components, including preferred aspects, are as described above in the section (2-3. Other Components). Therefore, the description in the section (2-3. Other Components) above is incorporated by reference, and will not be repeated here.

[0122] 4. Use of Water-Based Coating Composition The present composition can be applied to any substrate and cured to provide a coating film with excellent frost resistance. That is, in one embodiment of the present invention, there are provided a coating film obtained by curing the present composition, and a laminate comprising a substrate and a coating film obtained by curing the present composition.

[0123] In one embodiment of the present invention, the substrate to which the composition is applied is not particularly limited, and may be either an organic substrate or an inorganic substrate, and may be coated on the substrate.Specifically, the substrate may be metal (e.g., aluminum, stainless steel), glass, porcelain, tile, stone, wood, resin molding, mortar, slate, ABS, acrylic, PVC steel plate, polycarbonate, Galvanized steel plate (registered trademark), electrocoated plate, cold-rolled steel plate, calcium silicate plate, etc.In addition, the coating applied to the substrate may be acrylic paint, acrylic urethane paint, acrylic silicone paint, fluorine paint, etc.

[0124] The method for applying the present composition to a substrate is not particularly limited, and for example, application may be performed using a brush, roller, air spray, airless spray, or the like, which are commonly used for painting. Application can also be performed using a reverse coating method, gravure coating method, bar coating method, die coating method, spray coating method, kiss coating method, wire bar coating method, curtain coating method, or the like.

[0125] Any known method can be used to cure the composition applied to the substrate.

[0126] [5. Other] One aspect of the present invention may include the following configuration.

[0127] [1] A water-based coating composition comprising a silicone-acrylic graft copolymer resin (i) and an acrylic emulsion resin (ii) having a hydrolyzable silyl group, wherein the polysiloxane unit in the copolymer resin (i) contains a constituent unit derived from a silane compound having three hydrolyzable silyl groups, and the weight ratio of the copolymer resin (i) to the acrylic emulsion resin (ii) (the copolymer resin (i) / the acrylic emulsion resin (ii)) is 35 / 65 to 95 / 5.

[0128] [2] The aqueous coating composition according to [1], wherein the copolymer resin (i) has a weight average molecular weight of 30,000 to 300,000.

[0129] [3] The aqueous coating composition according to [1] or [2], wherein the acrylic emulsion resin (ii) contains 0.5 to 20 wt % of a constituent unit derived from a monomer having a hydrolyzable silyl group, relative to 100 wt % of the total amount of the acrylic emulsion resin (ii).

[0130] [4] A method for producing an aqueous coating composition comprising a silicone-acrylic graft copolymer resin (i) and an acrylic emulsion resin (ii) having a hydrolyzable silyl group, wherein the polysiloxane unit in the copolymer resin (i) comprises a constituent unit derived from a silane compound having three hydrolyzable silyl groups, and the method for producing an aqueous coating composition comprises a step of mixing the copolymer resin (i) and the acrylic emulsion resin (ii) so that the weight ratio (the copolymer resin (i) / the acrylic emulsion resin (ii)) is in the range of 35 / 65 to 95 / 5.

[0131] [5] The method for producing the aqueous coating composition according to [4], wherein the copolymer resin (i) has a weight average molecular weight of 30,000 to 300,000.

[0132] [6] The method for producing an aqueous coating composition according to [4] or [5], wherein the acrylic emulsion resin (ii) contains 0.5 to 20 wt % of a constituent unit derived from a monomer having a hydrolyzable silyl group, relative to 100 wt % of the total amount of the acrylic emulsion resin (ii). [Example]

[0133] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0134] 〔material〕 <Copolymer resin (i)> (polysiloxane unit) Monomer (A) Vinyltrimethoxysilane (abbreviated as "Vi-TMS"): "A-171" manufactured by Momentive Performance Materials Japan, LLC Monomer (B) Methyltrimethoxysilane (abbreviated as "M-TMS"): "OFS-6070" manufactured by Dow Toray Industries, Inc. Phenyltrimethoxysilane (abbreviated as "Ph-TMS"): "Z-6124" manufactured by Dow Toray Industries, Inc. Condensed water pure water Condensation catalyst Dibutyl phosphate (abbreviated as "DBP"): "DBP" manufactured by Johoku Chemical Industry Co., Ltd. (acrylic polymer unit) Monomer (C) Methyl methacrylate (abbreviated as "MMA"): manufactured by Mitsubishi Gas Chemical Company, Inc. Butyl acrylate (abbreviated as "BA"): manufactured by Nippon Shokubai Co., Ltd. 2-Hydroxyethyl methacrylate (abbreviated as "HEMA"): Nippon Shokubai Co., Ltd. Monomer (C1) Sodium acrylamido-t-butyl sulfonate (abbreviated as "ATBS-Na"): "ATBS-Na" manufactured by Toagosei Co., Ltd. Monomer (C2) Ether sulfate type ammonium salt (abbreviated as "SR-10"): "ADEKA REASOAP SR-10" manufactured by ADEKA Corporation, commercially available as a "reactive anionic emulsifier", a compound represented by the following formula (A):

[0135] [ka]

[0136] Radical polymerization initiator 2,2'-Azobis(2,4-dimethylvaleronitrile) (abbreviated as "V65"): "V-65" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. <Acrylic emulsion resin (ii)> (resin component) Monomer (D) Methyl methacrylate (abbreviated as "MMA"): manufactured by Mitsubishi Chemical Corporation 2-Ethylhexyl acrylate (EHA): Nippon Shokubai Co., Ltd. Butyl methacrylate (abbreviated as "BMA"): manufactured by Mitsubishi Chemical Corporation Isobutyl methacrylate (abbreviated as "IBMA"): manufactured by Mitsubishi Chemical Corporation Glycidyl methacrylate (abbreviated as "GMA"): Fujifilm Wako Pure Chemical Industries, Ltd. 2-Hydroxyethyl methacrylate (abbreviated as "HEMA"): Nippon Shokubai Co., Ltd. Monomer (D1) (reactive emulsifier) ER-20 (75%): "ADEKA REASOAP ER-20" manufactured by ADEKA Corporation, a diluted solution containing 75% by weight of the monomer component Ether sulfate type ammonium salt (abbreviated as "SR-1025 (25%)"): "ADEKA Reasoap SR-1025" manufactured by ADEKA Corporation, a diluted solution containing 25% by weight of ether sulfate type ammonium salt (monomer component) Monomer (E) γ-Methacryloxypropylmethyldimethoxysilane (abbreviated as "Z6033"): "Z-6033" manufactured by Dow-Toray γ-Methacryloxypropyltriethoxysilane (abbreviated as "Y9936"): "Y-9936" manufactured by Momentive Performance Materials Japan, LLC Monomer (F) γ-Mercaptopropyltrimethoxysilane (A1891): A-1891 manufactured by Momentive Performance Materials Japan, LLC Monomer (G) Styrene (abbreviated as "St"): manufactured by Kishida Chemical Co., Ltd. <Other ingredients> (water) pure water (antifreeze) Propylene glycol: Fujifilm Wako Pure Chemical Industries, Ltd. (wetting agent) "Dispex Ultra FA 4437" manufactured by BASF Japan (dispersant) Cray Valley's "SMA1440H Solution" "Disperbyk-2090" manufactured by BYK Japan (pigment) Ishihara Sangyo Co., Ltd.'s "PFC105" (preservatives) "Slout 99N" manufactured by Japan EnviroChemicals (Antifoaming agent) Acrylic defoamer: "Agitan 295" manufactured by MUNZING CHEMIE (Film-forming aid) 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate: "CS-12" manufactured by JNC Corporation (thickener) San Nopco's "SN Thickener 612NC" (Anti-mold and anti-algae agent) "Monicide AZ" manufactured by Japan EnviroChemicals [Measurement and evaluation methods] Measurements and evaluations in the examples and comparative examples were carried out by the following methods.

[0137] (molecular weight measurement) The weight-average molecular weight (Mw) of the silicone acrylic graft copolymer resin (i) was measured using a high-speed GPC system HLC-8320GPC manufactured by Tosoh Corporation, using TSKgel superH5000, TSKgel superH4000, TSKgel superH3000, or TSKgel guard column SuperH-L as the column, THF (tetrahydrofuran) as the mobile phase, a measurement temperature of 40°C, and a flow rate of 0.6 ml / min, and calculated in terms of polystyrene.

[0138] (Tg of acrylic polymer unit) The Tg of the acrylic polymer unit was calculated using the Fox equation.

[0139] (Frost resistance test) An aqueous cationic sealer (manufactured by Nippon Paint Co., Ltd.) was applied as a primer coat to a slate board substrate, followed by an intermediate coat of DAN Filler Epo (manufactured by Nippon Paint Co., Ltd.) using a sand roller. Finally, the aqueous coating composition was sprayed on and then cured for one week in a thermostatic chamber at 23°C and 50% relative humidity. The resulting laminate consisting of the substrate and coating film was left standing in an atmosphere set at -20°C for two hours and then immersed in water set at 10°C for two hours. This total of four hours of standing in a low-temperature atmosphere and immersion in water constituted one cycle, and this cycle was repeated five to 30 times for the same substrate (cycle test). The appearance of the coating film after the cycle test was visually observed, and the frost resistance of the coating film was evaluated based on the following criteria: A: There is no peeling or falling off of the coating, nor any abnormalities such as cracks. B: There is no peeling or falling off of the coating film, and although there are a few cracks, they are all less than 1 mm. C: No peeling or falling off of the coating, but slight cracks exceeding 1 mm. Dc: There is no peeling or falling off of the coating, but there are many cracks exceeding 1 mm. Dp: The coating film is peeled or fallen off.

[0140] In this specification, an aqueous coating composition capable of providing a coating film that is rated B or higher in the above evaluation is evaluated as being capable of providing a coating film with excellent frost resistance, and an aqueous coating composition capable of providing a coating film that is rated A in the above evaluation is evaluated as being capable of providing a coating film with even better frost resistance. Furthermore, an aqueous coating composition that shows better test results (preferably a rating of A) under test conditions with a greater number of cycles is evaluated as being capable of providing a coating film that is particularly excellent in frost resistance.

[0141] (Weather resistance test) Weather resistance was evaluated with reference to International Publication No. 2016 / 052636 and Japanese Patent No. 5555449.

[0142] Briefly, the aqueous coating composition was first applied to an aluminum plate (50 mm x 150 mm) using an air spray to a thickness of approximately 40 μm after drying (dry film thickness). The resulting coating was then dried for 4 hours at 23°C and 50% RH. A second aqueous coating composition was then applied to the resulting coating using an air spray to a dry film thickness of approximately 40 μm (i.e., a total of approximately 80 μm), and the resulting coating was then dried for 1 week at 23°C and 50% RH to prepare a test specimen. Accelerated weathering tests were then conducted using the resulting test specimens and a metal halide lamp tester (Model KU-R5CI-A, manufactured by Daipla Wintes Co., Ltd.). The 60° gloss values ​​of the coating layers were measured before and after 400 hours of accelerated weathering testing, and the gloss retention was calculated. A higher gloss retention indicates better weather resistance of the coating. The test conditions for the accelerated weather resistance test were as follows: Illuminance: 85mW / cm 2 Irradiation: 63℃ 50% 6 hours Condensation: 30°C, 98% humidity, 2 hours Shower: 30 seconds before and after condensation.

[0143] <Evaluation criteria> The weather resistance was evaluated based on the 60° gloss retention of the coating surface before and after the accelerated weather resistance test, according to the following criteria: A: 60° gloss retention is 80% or more. B: 60° gloss retention is 70% or more. C: 60° gloss retention is 60% or more.

[0144] [Synthesis Example 1] <Preparation of Silicone Acrylic Graft Copolymer Resin (i)> (Synthesis of polysiloxane units) A reactor equipped with a stirrer, thermometer, and reflux condenser was charged with the types of monomer (A), monomer (B), pure water, and condensation catalyst listed in Table 1, and the mixture was reacted at a reaction temperature of 68°C for 3 hours with stirring to obtain polyorganosiloxane, which is a polysiloxane unit. In Table 1, the unit of the amount of each component is "parts by weight." The amounts of monomer (A) and monomer (B) in Table 1 are the amounts of each monomer charged in the synthesis of the polysiloxane unit, and the amount of polysiloxane unit was calculated based on the value obtained by subtracting the weight of the volatile components generated by the hydrolysis reaction from the amount of each monomer charged.

[0145] (Polymerization of acrylic polymer units) A mixed solution of the type and amount of monomer (C) (including monomer (C1) and monomer (C2)) and radical polymerization initiator listed in Table 1 was added dropwise from the dropping funnel at a constant rate over 3 hours to the reactor containing the polysiloxane units. Next, a mixed solution of 0.14 parts by weight of radical polymerization initiator and 10 parts by weight of methanol was added dropwise at a constant rate over 0.5 hours. After the addition, the mixture was stirred at 75°C for 2 hours and then diluted with water. The mixture was then subjected to devolatilization using a rotary evaporator to adjust the nonvolatile content to 50% or less, and then cooled to room temperature to obtain a composition containing silicone acrylic graft copolymer resin (i) and water. The structural unit ratio in the resulting silicone acrylic graft copolymer resin (i) and the molecular weight of the copolymer resin (i) are shown in Table 1.

[0146] [Synthesis Examples 2 and 3] A composition containing silicone acrylic graft copolymer resin (i) and water was obtained in the same manner as in Synthesis Example 1, except that the type and amount of each monomer was changed to the amounts shown in Table 1. The structural unit ratio in the obtained silicone acrylic graft copolymer resin (i) and the molecular weight of the copolymer resin (i) are shown in Table 1.

[0147] [Table 1]

[0148] [Synthesis Example 4] <Synthesis of acrylic emulsion resin (ii)> (Synthesis of core components) A reaction vessel equipped with a stirrer, reflux condenser, nitrogen gas inlet, and dropping funnel was charged with 39 parts by weight of deionized water, 0.16 parts by weight of Adeka Reasoap SR-1025, and 0.25 parts by weight of a 5% aqueous solution of sodium bicarbonate. The temperature was raised to 50°C while introducing nitrogen gas. After the temperature was raised, 0.5 parts by weight of a 7% aqueous solution of t-butyl hydroperoxide, 0.35 parts by weight of a 10% aqueous solution of Brggolite FF-6, and 0.7 parts by weight of a mixed aqueous solution of ferrous sulfate heptahydrate (0.10%) and disodium ethylenediaminetetraacetate (0.40%) were added. Next, a monomer emulsion prepared by adding 9 parts by weight of monomer (D1) (reactive emulsifier) ​​and the type and amount specified in Table 2 as the core formulation to a mixture of monomers (D) and (E) in the types and amounts specified in Table 2 as the core formulation, and the type and amount specified in Table 2 as the core formulation, was added to the reaction system at a constant rate over 120 minutes. During the addition of the monomer emulsion, 0.25 parts by weight of a 7% aqueous solution of t-butyl hydroperoxide and 0.4 parts by weight of a 2.5% aqueous solution of Bruggolite FF-6 were added in two separate additions. After the addition of the monomer emulsion was completed, the polymerization reaction was carried out for one hour. During the polymerization reaction, 0.1 parts by weight of a 7% aqueous solution of t-butyl hydroperoxide and 0.15 parts by weight of a 2.5% aqueous solution of Bruggolite FF-6 were added to the reaction system. This procedure yielded the core component of acrylic emulsion resin (ii). In Table 2, the amount of each component is expressed in parts by weight.

[0149] (Shell component synthesis) To the reaction system containing the core components, 0.25 parts by weight of a 7% aqueous solution of t-butyl hydroperoxide and 0.5 parts by weight of a 2.5% aqueous solution of Bruggolite FF-6 were added. Next, a monomer emulsion was prepared by adding 24.05 parts by weight of monomer (D1) (reactive emulsifier) ​​and 24.05 parts by weight of deionized water to a mixture of monomers (D), (E), and (F) in the amounts and types specified in Table 2 as the shell formulation. This emulsion was then added to the reaction system at a constant rate over 300 minutes. During the addition of the monomer emulsion, 1.0 parts by weight of a 7% aqueous solution of t-butyl hydroperoxide and 1.4 parts by weight of a 2.5% aqueous solution of Bruggolite FF-6 were added in six separate additions. After the addition of the monomer emulsion was completed, the polymerization reaction was allowed to proceed for 1.5 hours. During the polymerization reaction, 0.10 parts by weight of a 7% aqueous solution of t-butyl hydroperoxide and 0.15 parts by weight of a 2.5% aqueous solution of Bruggolite FF-6 were added to the reaction system. This procedure yielded the shell component of acrylic emulsion resin (ii). 3.5 parts by weight of a 5% aqueous solution of sodium bicarbonate was added to the resulting emulsion containing synthetic resins consisting of the core and shell components, and the solids content was then adjusted to 50% with deionized water to yield acrylic emulsion resin (ii). The content of structural units derived from monomers having hydrolyzable silyl groups in the resulting acrylic emulsion resin (ii) is shown in Table 2.

[0150] <Synthesis Example 5> <Synthesis of acrylic emulsion resin (ii)> (Synthesis of seed components) A reactor equipped with a stirrer, reflux condenser, nitrogen gas inlet, and dropping funnel was charged with 85.80 parts by weight of deionized water, 0.25 parts by weight of a 5% aqueous solution of sodium bicarbonate, and 2.30 parts by weight of ADEKA REASOAP SR-1025 (25%). The temperature was raised to 50°C while introducing nitrogen gas. After the temperature was raised, a mixture of monomers (D) and (E) in the types and amounts listed as the seed formulation in Table 2 was added and emulsified. Next, 0.5 parts by weight of a 7% aqueous solution of t-butyl hydroperoxide, 0.35 parts by weight of a 10% aqueous solution of Brggolite FF-6, and 0.7 parts by weight of a mixed aqueous solution of ferrous sulfate heptahydrate (0.10%) and disodium ethylenediaminetetraacetate (0.40%) were added. This procedure yielded the seed component for acrylic emulsion resin (ii).

[0151] (Synthesis of core components) To the reaction vessel containing the seed component, 0.25 parts by weight of a 7% aqueous solution of t-butyl hydroperoxide and 0.7 parts by weight of a 20% aqueous solution of Bruggolite FF-6 were added. Next, a monomer emulsion was prepared by adding a mixture of monomers (D) and (E) of the types and amounts specified in Table 2 as the core formulation to 25.1 parts by weight of monomer (D1) (reactive emulsifier) ​​of the type and amount specified in Table 2 as the core formulation, and deionized water. This monomer emulsion was added to the reaction system at a constant rate over 200 minutes. During the addition of the monomer emulsion, 0.5 parts by weight of a 7% aqueous solution of t-butyl hydroperoxide and 0.89 parts by weight of a 2.5% aqueous solution of Bruggolite FF-6 were added in three separate additions. After the addition of the monomer emulsion was completed, the polymerization reaction was allowed to proceed for one hour. This procedure yielded the core component of acrylic emulsion resin (ii).

[0152] (Shell component synthesis) To the reaction system containing the core component, 0.20 parts by weight of a 7% aqueous solution of t-butyl hydroperoxide and 0.40 parts by weight of a 2.5% aqueous solution of Bruggolite FF-6 were added. Next, a monomer emulsion was prepared by adding 10.50 parts by weight of monomer (D1) (reactive emulsifier) ​​and 10.50 parts by weight of deionized water to a mixture of monomers (D), (E), and (F) in the amounts and types specified in Table 2 as the shell formulation. This monomer emulsion was added to the reaction system at a constant rate over 120 minutes. During the addition of the monomer emulsion, 0.3 parts by weight of a 7% aqueous solution of t-butyl hydroperoxide and 0.45 parts by weight of a 2.5% aqueous solution of Bruggolite FF-6 were added in two separate additions. After the addition of the monomer emulsion was completed, the polymerization reaction was allowed to proceed for 1.5 hours. This procedure yielded the shell component of acrylic emulsion resin (ii). To the resulting emulsion containing synthetic resins consisting of seed, core, and shell components, 7.06 parts by weight of a 5% aqueous solution of sodium bicarbonate was added, and the solid content was then adjusted to 40% with deionized water to obtain acrylic emulsion resin (ii). The content of structural units derived from monomers having hydrolyzable silyl groups in the resulting acrylic emulsion resin (ii) is shown in Table 2.

[0153] [Table 2]

[0154] Example 1 The types and amounts of each component shown in the "Millbase" column of Table 3 were blended to obtain a millbase, and the resulting millbase was then mixed with the types and amounts of silicone acrylic graft copolymer resin (i), acrylic emulsion resin (ii), and other components shown in the "Cutback" column of Table 3 to prepare an aqueous coating composition. The frost resistance of the resulting aqueous coating composition was evaluated. The results are shown in Table 3. In Table 3, the unit of each component amount is "parts by weight." The blend amount of acrylic emulsion resin (ii) is expressed in terms of solids content.

[0155] [Examples 2 to 3, Comparative Examples 1 to 3] A water-based coating composition was prepared in the same manner as in Example 1, except that the type and amount of each component was changed to the amounts shown in Table 3. The frost resistance of the obtained water-based coating composition was evaluated after 5 cycles. The results are shown in Table 3. The frost resistance of the water-based coating composition of Example 2 was also evaluated after 30 cycles. The results are shown in Table 4. In Table 3, the ratio of each structural unit is the ratio to the total amount of copolymer resin (i) and acrylic emulsion resin (ii) in the composition.

[0156] [Table 3]

[0157] Examples 4 and 5 A water-based coating composition was prepared in the same manner as in Example 1, except that the type and amount of each component was changed to the amounts shown in Table 4. The freeze resistance of the obtained water-based coating composition was evaluated after 30 cycles. The results are shown in Table 4. In Table 4, the unit of each component amount is "parts by weight." The blend amount of acrylic emulsion resin (ii) is expressed as a solids content value. In Table 4, the ratio of each structural unit is the ratio to the total amount of copolymer resin (i) and acrylic emulsion resin (ii) in the composition.

[0158] [Table 4]

[0159] Tables 3 and 4 show that the aqueous coating compositions (Examples 1 to 5) obtained by mixing silicone acrylic graft copolymer resin (i) and acrylic emulsion resin (ii) in a specific ratio can provide coating films with excellent frost resistance.

[0160] Furthermore, a comparison of Examples 2 and 4 with Example 5 suggests that by controlling the weight average molecular weight of the copolymer resin (i) within a predetermined range, it is possible to provide a coating film that is particularly excellent in frost resistance. [Industrial Applicability]

[0161] The present composition is suitably used, for example, as an aqueous coating composition for the interior and exterior decoration of buildings; for automobiles as a metallic base or a clear coat on a metallic base; for direct coating on metals such as aluminum, stainless steel and silver; for direct coating on ceramic materials such as slate, concrete, roofing tiles, mortar, gypsum board, asbestos slate, asbestos board, precast concrete, lightweight aerated concrete, calcium silicate board, tile and brick; for glass; and for stone materials such as natural marble and granite.

Claims

1. A water-based coating composition comprising (i) a silicone acrylic graft copolymer resin and (ii) an acrylic emulsion resin having a hydrolyzable silyl group, the polysiloxane unit in the copolymer resin (i) contains a constituent unit derived from a silane compound having three hydrolyzable silyl groups, a weight ratio of the copolymer resin (i) to the acrylic emulsion resin (ii) (the copolymer resin (i) / the acrylic emulsion resin (ii)) of 35 / 65 to 95 / 5;

2. 2. The aqueous coating composition according to claim 1, wherein the copolymer resin (i) has a weight average molecular weight of 30,000 to 300,000.

3. 3. The aqueous coating composition according to claim 1, wherein the acrylic emulsion resin (ii) contains 0.5 to 20 wt % of a constituent unit derived from a monomer having a hydrolyzable silyl group, relative to 100 wt % of the total amount of the acrylic emulsion resin (ii).

4. A method for producing a water-based coating composition comprising a silicone acrylic graft copolymer resin (i) and an acrylic emulsion resin (ii) having a hydrolyzable silyl group, comprising: the polysiloxane unit in the copolymer resin (i) contains a constituent unit derived from a silane compound having three hydrolyzable silyl groups, a step of mixing the copolymer resin (i) and the acrylic emulsion resin (ii) so that the weight ratio (copolymer resin (i) / acrylic emulsion resin (ii)) is in the range of 35 / 65 to 95 / 5.

5. The method for producing a water-based coating composition according to claim 4, wherein the copolymer resin (i) has a weight average molecular weight of 30,000 to 300,000.

6. 6. The method for producing an aqueous coating composition according to claim 4 or 5, wherein the acrylic emulsion resin (ii) contains 0.5 to 20 wt % of a constituent unit derived from a monomer having a hydrolyzable silyl group, relative to 100 wt % of the total amount of the acrylic emulsion resin (ii).

Images