Aqueous dispersion, aqueous coating material, coating film, coated article, and method for producing aqueous dispersion

Abstract

Provided is an aqueous dispersion that has resin particles containing fluorine and that is capable of providing a coating composition having excellent mechanical stability. The aqueous dispersion contains resin particles containing a unit (a) based on fluoroolefin and at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid, and a (meth)acrylic acid ester, and has a zeta potential of 52 mV or more in absolute value.

Description

Aqueous dispersion, water-based paint, coating film, coated article, and method for producing aqueous dispersion

[0001] The present disclosure relates to aqueous dispersions, water-based paints, coatings, coated articles, and methods for making aqueous dispersions.

[0002] Fluorine-containing seed polymers using acrylic monomers as monomers for seed polymerization take advantage of the weather resistance, chemical resistance, solvent resistance, heat resistance, and stain resistance of the fluoropolymer contained therein, and the processability, transparency, adhesion, and film-forming properties of the acrylic polymer, and are used as raw materials for various products or film-forming components for paints in a wide range of industrial fields, such as the automobile industry, semiconductor industry, chemical industry, paints, battery materials, and electrical materials (Patent Document 1).

[0003] Patent Publication No. 2015-199943

[0004] An object of the present disclosure is to provide an aqueous dispersion having fluorine-containing resin particles that can provide a coating composition with excellent mechanical stability.

[0005] The present disclosure relates to an aqueous dispersion comprising resin particles including units (a) based on a fluoroolefin and at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid, and a (meth)acrylic acid ester, and characterized in that the absolute value of the zeta potential is 52 mV or more.

[0006] The resin particles preferably have a structural unit (c) derived from a monomer having an oxyalkylene group copolymerized with the structural unit (b), which is preferable in that the structural unit (c) is copolymerized with the structural unit (b) to enhance water resistance and weather resistance.

[0007] The unit (b) preferably contains a functional group in which at least a portion of the —COOH groups has been neutralized with a base. The fluoroolefin preferably contains at least one fluoroolefin unit selected from the group consisting of vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene.

[0008] At least a part of the units (c) is represented by the following general formula (2): CH ２=CHCH ２ -O-R ２ (2) (wherein, R ２ is a hydrocarbon group having a nonionic hydrophilic group.

[0009] At least a part of the units (c) is represented by the following general formula (3): CH ２ =CHCH ２ -O-R ３ -X (3) (wherein, R ３ is a hydrocarbon chain which may have an oxygen atom and / or a nitrogen atom; X is SO ３ Y (Y is NH ４ or an alkali metal).

[0010] The resin particles are preferably a fluorine-containing seed polymer of fluorine-containing polymer (A) particles and a monomer containing at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid, and a (meth)acrylic acid ester. The aqueous dispersion preferably has a mechanical stability of 15 minutes or more.

[0011] The present disclosure also relates to an aqueous paint comprising the above-described aqueous dispersion.The present disclosure also relates to an aqueous paint comprising the above-described aqueous dispersion and an acrylic resin.The present disclosure also relates to a coating film obtained from the above-described aqueous dispersion.The present disclosure also relates to a coated article comprising the above-described coating film.

[0012] The present disclosure also relates to a method for producing the aqueous dispersion according to claim 1 or 2, characterized in that it comprises: step (I) of preparing particles of a fluoropolymer (A); and polymerization step (II) of polymerizing the particles of the fluoropolymer (A) in a liquid containing a monomer containing at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid, and a (meth)acrylic acid ester, and a constituent unit (c) derived from a monomer having an oxyalkylene group.

[0013] The present disclosure also provides a method for producing an aqueous dispersion, the method comprising: a step (III) of neutralizing an aqueous dispersion containing resin particles comprising units (a) based on a fluoroolefin and at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid, and a (meth)acrylic acid ester.

[0014] The present disclosure also provides a method for producing an aqueous dispersion, comprising: step (I) of preparing particles of a fluoropolymer (A); step (II) of polymerizing the particles of the fluoropolymer (A) in an aqueous medium containing a monomer comprising at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid and a (meth)acrylic acid ester, and a constituent unit (c) derived from a monomer having an oxyalkylene group; and step (III) of neutralizing the aqueous dispersion obtained in step (II).

[0015] The aqueous dispersion of the present disclosure exhibits effects such as excellent mechanical stability.

[0016] The present disclosure will be described in detail below. The aqueous dispersion of the present disclosure is an aqueous dispersion containing resin particles having a unit (a) based on a fluoroolefin and at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid, and a (meth)acrylic ester. By having these structural units in the same particle, the aqueous dispersion can exhibit high film-forming properties and weather resistance when used as a paint. Furthermore, by having a zeta potential that satisfies a predetermined value, the aqueous dispersion has good dispersibility and excellent mechanical stability.

[0017] In the aqueous dispersion of the present disclosure, the resin particles constituting the dispersion may be in a form in which the polymers based on (a) and (b) above exist as a copolymer in the particles, or may be in a form in which the polymer (A) having the unit (a) and the polymer (B) having the unit (b) exist as composite particles in which the resin particles are formed in a mixture state. When the aqueous dispersion of the present disclosure is used as a coating material, the composite particle state is particularly preferable from the viewpoint of the flexibility of the coating film.

[0018] The composite particles may have a core-shell structure in which a fluoropolymer (A) having units (a) based on a fluoroolefin forms a core and an acrylic polymer (B) having at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid, and a (meth)acrylic ester forms a shell, or the fluoropolymer (A) and the acrylic polymer (B) may be in a compatible state. When the aqueous dispersion of the present disclosure is used as a coating material, it is preferable that the fluoropolymer (A) and the acrylic polymer (B) are in a compatible state from the viewpoint of the transparency of the coating film.

[0019] The aqueous dispersion containing the fluorine-containing composite polymer particles of the present disclosure is different from an aqueous dispersion formed by simply mixing the polymer (A) and the polymer (B). However, in the aqueous dispersion of the present disclosure, the polymer (A) and the polymer (B) may or may not be chemically bonded to each other.

[0020] The average particle size of the fluoropolymer (A) particles is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 110 nm or more, from the viewpoints of film-forming ability, water resistance, and weather resistance. It is also preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less. The average particle size is a value obtained by measurement using a dynamic light scattering method.

[0021] (Zeta Potential) Zeta potential refers to the potential difference between the sliding surface in the electric double layer and a portion sufficiently distant from the interface, and represents the electrical state of the surface of the resin particles in the dispersion. The present disclosure is characterized in that the absolute value of such zeta potential is 52 mV or more. When the absolute value of the zeta potential is 52 mV or more, the electrical repulsion between the dispersion particles becomes stronger, thereby increasing the stability of the aqueous dispersion and improving mechanical stability. The improved mechanical stability suppresses gelation during coating work, making it possible to provide a coating composition with excellent coating workability.

[0022] The zeta potential of the present disclosure is measured by diluting the aqueous dispersion 100 times and using a zeta potential meter ELSZ-2000 (manufactured by Otsuka Electronics Co., Ltd.) at a set temperature of 25°C. The absolute value of the zeta potential is preferably 52 mV or more, more preferably 55 mV or more, and even more preferably 56 mV or more. There is no particular upper limit to the absolute value of the zeta potential, but it can be, for example, 100 mV or less.

[0023] (Fluoroolefin-Based Unit (a)) In the present disclosure, fluoroolefin refers to an unsaturated hydrocarbon compound having at least one fluorine atom in the molecule.

[0024] Examples of the fluoroolefin include tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoro(alkyl vinyl ether) (PAVE),

[0025]

[0026] and non-perfluoroolefins such as chlorotrifluoroethylene (CTFE), vinyl fluoride (VF), vinylidene fluoride (VdF), 1,2-difluoroethylene, trifluoroethylene, trifluoropropylene, hexafluoroisobutene, 2,3,3,3-tetrafluoropropene, 1,3,3,3-tetrafluoropropene, and 1,1,3,3,3-pentafluoropropene. Perfluoro(alkyl vinyl ethers) include perfluoro(methyl vinyl ether) (PMVE), perfluoro(ethyl vinyl ether) (PEVE), and perfluoro(propyl vinyl ether) (PPVE).

[0027] Furthermore, as the fluoroolefin, a functional group-containing fluoroolefin can also be used. Examples of the functional group-containing fluoroolefin include those represented by the formula (1): CX １ ２ =CX ２ -(Rf) ｍ -Y １ (1) (wherein, Y １ -OH, -COOM２ , -SO ２ F, -SO ３ M ２ (M ２ is a hydrogen atom, NH ４ group or alkali metal), carboxylate, carboxy ester group, epoxy group or cyano group; X １ and X ２ are the same or different and are both hydrogen atoms or fluorine atoms; Rf is a divalent fluorine-containing alkylene group or fluorine-containing oxyalkylene group having 1 to 40 carbon atoms, or a divalent fluorine-containing alkylene group or fluorine-containing oxyalkylene group having 2 to 40 carbon atoms and containing an ether bond; and m is 0 or 1.

[0028] Specific examples of the functional group-containing fluoroolefin include:

[0029]

[0030]

[0031] etc.

[0032] Furthermore, as the fluoroolefin, iodine-containing monomers, for example, iodized products of perfluorovinyl ethers such as perfluoro(6,6-dihydro-6-iodo-3-oxa-1-hexene) and perfluoro(5-iodo-3-oxa-1-pentene) described in JP-B-5-63482 and JP-A-62-12734 can also be used.

[0033] Among these, the fluoroolefin is preferably at least one selected from the group consisting of vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene, and more preferably vinylidene fluoride and at least one selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene.

[0034] The resin particles of the present disclosure preferably contain polymerization units derived from vinylidene fluoride (VdF) in terms of providing good weather resistance and a coating film with excellent transparency. The VdF-derived polymerization units in the resin particles are preferably 40 mol% or more, more preferably 50 mol% or more, and even more preferably 70 mol% or more, based on the total amount of the fluorine-containing polymer in the resin particles. Also, the VdF-derived polymerization units are preferably 95 mol% or less.

[0035] The fluorine-containing polymer contained in the resin particles preferably contains, in addition to repeating units based on vinylidene fluoride (VdF), repeating units based on at least one fluoroolefin selected from the group consisting of tetrafluoroethylene (TFE) units, hexafluoropropylene (HFP) units, and chlorotrifluoroethylene (CTFE) units, and more preferably contains repeating units based on TFE and CTFE, repeating units based on TFE and HFP, repeating units based on TFE, or repeating units based on HFP.

[0036] The fluorine-containing polymer contained in the resin particles is preferably at least one fluorine-containing copolymer selected from the group consisting of VdF / TFE / CTFE copolymer, VdF / TFE copolymer, VdF / TFE / HFP copolymer, VdF / CTFE copolymer, VdF / HFP copolymer, and PVdF, and more preferably VdF / TFE / CTFE=40 to 99 / 1 to 50 / 0 to 30 (mol %), VdF / TFE=50 to 99 / 1 to 50 (mol %), VdF / TFE / HFP=45 to 99 / 0 to 35 / 5 to 50 (mol %), VdF / CTFE=40 to 99 / 1 to 30 (mol %), or VdF / HFP=50 to 99 / 1 to 50 (mol %).

[0037] The fluorine content of the fluorine-containing polymer (A) contained in the resin particles is preferably from 40 to 80% by mass, more preferably from 50 to 70% by mass, taking into consideration the weather resistance of the resulting coating film and the compatibility of the polymer (A) with acrylic.

[0038] (At least one unit (b) selected from the group consisting of (meth)acrylic acid, salts of (meth)acrylic acid, and (meth)acrylic acid esters) The salt of (meth)acrylic acid is not particularly limited, and may be an ammonium salt, an amine salt, an alkali metal salt, or the like.

[0039] The acrylic acid ester or methacrylic acid ester is preferably an alkyl acrylic acid ester in which the alkyl group has 1 to 10 carbon atoms, or an alkyl methacrylic acid ester in which the alkyl group has 1 to 10 carbon atoms. Examples of alkyl acrylic acid esters and alkyl methacrylic acid esters include (meth)acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, methyl methacrylate, n-propyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate. The alkyl acrylate or alkyl methacrylate may be a hydroxyl group-containing acrylic monomer having a hydroxyl group and a (meth)acryloyl group in the molecule, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, etc. These acrylic esters or methacrylic esters may be used alone or in combination of two or more, with n-butyl acrylate and methyl methacrylate being preferred.

[0040] Furthermore, the (meth)acrylic acid ester may have a reactive functional group such as a hydroxyl group. The (meth)acrylic acid ester having such a reactive functional group is not particularly limited, and examples thereof include 2-hydroxyethyl (meth)acrylate and 2-hydroxybutyl (meth)acrylate.

[0041] The unit (b) is preferably contained in a proportion of 20 to 80 mass % relative to the total amount of polymer constituting the resin particles. It is more preferably contained in a proportion of 30 to 70 mass %. By setting the content within this range, it is possible to improve the film-forming properties and weather resistance of the coating film when the aqueous dispersion of the present disclosure is used as a coating material, which is preferable.

[0042] The polymer containing the unit (b) preferably has both a salt of (meth)acrylic acid and a (meth)acrylic acid ester. In particular, since the salt of (meth)acrylic acid has a significant effect on the zeta potential of the surface, the object of the present disclosure can be more suitably achieved by introducing an appropriate amount of such a functional group.

[0043] The polymer having structural units based on the salt of (meth)acrylic acid is generally obtained by neutralizing a polymer having (meth)acrylic acid as a structural unit with a basic compound. Thus, during this neutralization, all or only a portion of the structural units derived from (meth)acrylic acid may be neutralized.

[0044] The resin in the aqueous dispersion of the present disclosure preferably has an acid value of 0.5 to 20.0. The lower limit of the acid value is more preferably 1.0, and even more preferably 2.0. The upper limit of the acid value is more preferably 15, and even more preferably 10. The acid group here may be derived from the above-mentioned (meth)acrylic acid or may be derived from another structural unit having a carboxyl group.

[0045] (Structural Unit (c) Derived from a Monomer Having an Oxyalkylene Group) In the present disclosure, the polymer containing the unit (b) may further contain a structural unit (c) derived from a monomer having an oxyalkylene group. The presence of such a structural unit (c) derived from a monomer having an oxyalkylene group makes it easier for the zeta potential to fall within a predetermined range. It is also acceptable for a polymer containing unit (a) to contain structural unit (c). The monomer having an oxyalkylene group is preferably a monomer having an ethenyl group and has a structure in which the monomer has an oxyalkylene group in its side chain. Having such a structure allows the polymer to function as a reactive emulsifier, and the introduction of hydrophilic groups into the hydrophobic resin structure can provide emulsion stability. The use of such reactive emulsifiers chemically bonds with acrylic more readily than the use of non-reactive emulsifiers, which is preferable because the resulting coating film has higher water resistance and weather resistance.

[0046] The oxyalkylene group is (In the formula, R １０ is an alkylene group having 4 or less carbon atoms). A structural unit based on a monomer having such a (poly)alkylene oxide chain and an unsaturated bond is preferred. The repeating unit n in the above general formula can be 1 to 39. Examples of the alkylene oxide include linear or branched oxyalkylene groups having 2 to 4 carbon atoms, such as ethylene oxide, propylene oxide, and butylene oxide. A copolymerized chain of these may also be used.

[0047] In the present disclosure, the above n is more preferably in the range of 1 to 30. In this way, it is thought that using an emulsifier with a small number of added moles of alkylene oxide units reduces the hydrophilicity of the particle surface and increases the amount of lipophilic functional groups (such as carboxyl groups) present on the particle surface. Therefore, the amount of charge on the particle surface increases, which is preferable in that it increases the repulsive force between particles and stabilizes the particles.

[0048] The structural unit (c) derived from a monomer having an oxyalkylene group is not particularly limited in structure, but examples thereof include those that act as anionic surfactants and those that act as nonionic surfactants. It is most preferable to use these in combination. Below, the nonionic surfactant (c-1) and the anionic surfactant (c-2) are each described.

[0049] (Nonionic Surfactant (c-1)) The nonionic surfactant (c-1) is not particularly limited, and examples thereof include those represented by the formula (2): CH ２ =CHCH ２ -O-R ２　 (2) Nonionic surfactants represented by the following formula can be mentioned.

[0050] In the formula, R ２ is a hydrocarbon group having a nonionic hydrophilic group. ２ is preferably a hydrocarbon chain containing the above-mentioned oxyalkylene group.

[0051] More specifically, the compound represented by formula (2) is a compound represented by formula (c1):

[0052]

[0053] (In the formula, R １’ is a linear or branched hydrocarbon chain which may contain an oxygen atom, a phenyl group, or a phenylene group; and n is an integer of 1 to 100. １’ The number of carbon atoms is preferably 1 to 51, more preferably 5 to 26, and still more preferably 10 to 21. n is an integer of 1 to 100, preferably an integer of 1 to 60, and more preferably an integer of 10 to 30.

[0054] The compound represented by formula (c1) includes the compound represented by the following formula (c1-1):

[0055]

[0056] (In the formula, R ３’is a hydrocarbon chain having 1 to 50 carbon atoms which may contain a phenyl group or a phenylene group; and n is an integer of 1 to 100.

[0057] In formula (c1-1), R ３’ has 1 to 50 carbon atoms, preferably 5 to 25, and more preferably 10 to 20. n is an integer of 1 to 100, preferably an integer of 1 to 60, and more preferably an integer of 10 to 30.

[0058] (Anionic Surfactant (c-2)) The anionic surfactant (c-2) is not particularly limited, and examples thereof include anionic surfactants represented by the formula (3): CH ２ =CHCH ２ -O-R ３ -X (3) is an anionic surfactant (c-2-1).

[0059] R in the above formula (3) ３ is preferably a hydrocarbon chain containing the above-mentioned oxyalkylene group. ３ Y (Y is NH ４ or an alkali metal). As the alkali metal, Na and K are preferred.

[0060] More specifically, the compound represented by formula (3) includes, for example, a compound represented by formula (c2-1):

[0061]

[0062] (In the formula, R ２’ is a linear or branched hydrocarbon chain which may contain an oxygen atom, a phenyl group, or a phenylene group; n is an integer of 1 to 100; X is SO ３ Y (Y is NH ４ or an alkali metal atom). In the compound (c-2-2), R ２’The number of carbon atoms is preferably 1 to 51, more preferably 5 to 21, and still more preferably 10 to 16. n is preferably an integer of 1 to 60, more preferably an integer of 5 or more, still more preferably an integer of 10 or more, more preferably an integer of 40 or less, and still more preferably an integer of 30 or less. As the alkali metal atom, Na and K are preferred.

[0063] The compound represented by formula (c2-1) includes the compound represented by the following formula (c2-2):

[0064]

[0065] (In the formula, R ５’ is a linear or branched hydrocarbon chain having 1 to 50 carbon atoms which may contain a phenyl group or a phenylene group; n is an integer of 1 to 100; X is SO ３ Y (Y is NH ４ or an alkali metal atom, for example, Na or K).

[0066]

[0067] (In the formula, R ４’ is an alkyl group having 1 to 50 carbon atoms; n is an integer of 1 to 100; X is SO ３ Y (Y is NH ４ or an alkali metal atom, for example, Na or K).

[0068] In formula (c2-2), R ５’ has preferably 1 to 50 carbon atoms, more preferably 5 to 20, and even more preferably 10 to 15. n is an integer of 1 to 100, and from the viewpoints of dispersion stability and water resistance, preferably an integer of 1 to 60, more preferably an integer of 5 to 35, and even more preferably an integer of 10 to 30.

[0069] In formula (c2-3), R ４’ is preferably an alkyl group having 1 to 50 carbon atoms, more preferably 5 to 20, and even more preferably 10 to 15. n is preferably an integer of 1 to 100, and from the viewpoint of dispersion stability and water resistance, more preferably an integer of 1 to 30. X is SO３ NH ４ is preferred.

[0070] The content of the structural unit (c) is preferably 0.1 to 10.0 parts by mass relative to 100 parts by mass of the solids content of the aqueous dispersion of the present disclosure. If the amount of the structural unit (c) is too small, the dispersion stability of the emulsified particles may decrease, while if the amount added is too large, the water resistance and weather resistance of the resulting coating film may decrease. The content of the structural unit (c) is more preferably 0.5 parts by mass or more, even more preferably 1.0 part by mass or more, more preferably 5.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

[0071] In the aqueous dispersion of the present disclosure, the structural unit (c) preferably uses both a nonionic surfactant (c-1) and an anionic surfactant (c-2) in combination. This is preferred from the viewpoint of improving the chemical stability, storage stability, stability during freezing, stability during transportation, paint stability, etc. of the aqueous dispersion particles. In this case, the amount of the nonionic surfactant is preferably 20 to 80 parts by mass relative to the total amount of structural unit (c), from the viewpoint of maintaining higher dispersion stability and the water resistance and weather resistance of the coating film.

[0072] The resin contained in the aqueous dispersion of the present disclosure may have a unit (hereinafter referred to as unit (d)) other than the above units (a), (b), and (c). The unit (d) may be a monomer having a radical-polymerizable ethylenically unsaturated bond that does not fall under the category of the above units (a), (b), and (c), and examples thereof include unsaturated carboxylic acids other than (meth)acrylic acid, hydrolyzable silyl group-containing monomers, hydroxyl group-containing alkyl vinyl ethers, carboxylic acid vinyl esters, and α-olefins.

[0073] Specific examples of unsaturated carboxylic acids other than (meth)acrylic acid include vinyl acetic acid, crotonic acid, cinnamic acid, 3-allyloxypropionic acid, 3-(2-allyloxyethoxycarbonyl)propionic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, maleic anhydride, fumaric acid, fumaric acid monoester, vinyl phthalate, vinyl pyromellitic acid, undecylenic acid, etc. Among these, at least one selected from the group consisting of acrylic acid, methacrylic acid, vinyl acetic acid, crotonic acid, itaconic acid, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, 3-allyloxypropionic acid, and undecylenic acid is preferred from the viewpoints of low homopolymerizability, difficulty in forming homopolymers, and ease of control over introduction of carboxyl groups.

[0074] Examples of the hydrolyzable silyl group-containing monomer include CH ２ = CHCOO(CH ２ ) ３ Si(OCH ３ ) ３ , C.H. ２ = CHCOO(CH ２ ) ３ Si(CH ３ ) (OCH ３ ) ２ , C.H. ２ = CHCOO(CH ２ ) ３ Si(OC ２ H ５ ) ３ , C.H. ２ = CHCOO(CH ２ ) ３ Si(CH ３ ) (OC ２ H ５ ) ２ , C.H. ２ =C(CH ３ ) COO(CH ２ ) ３ Si(OCH ３ ) ３ , C.H. ２ =C(CH ３ ) COO(CH ２ ) ３ Si(CH ３ ) (OCH３ ) ２ , C.H. ２ =C(CH ３ ) COO(CH ２ ) ３ Si(OC ２ H ５ ) ３ , C.H. ２ =C(CH ３ ) COO(CH ２ ) ３ Si(CH ３ ) (OC ２ H ５ ) ２ , C.H. ２ =C(CH ３ ) COO(CH ２ ) ２ O (CH ２ ) ３ Si(OCH ３ ) ３ , C.H. ２ =C(CH ３ ) COO(CH ２ ) ２ (CH ２ ) ３ Si(CH ３ ) (OCH ３ ) ２ , C.H. ２ =C(CH ３ ) COO(CH ２ ) １１ Si(OCH ３ ) ３ , C.H. ２ =C(CH ３ ) COO(CH ２ ) １１ Si(CH ３ ) (OCH ３ ) ２ These hydrolyzable silyl group-containing monomers may be used alone or in combination of two or more.

[0075] Among these, at least one selected from the group consisting of γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltriethoxysilane, and γ-methacryloxypropylmethyldiethoxysilane is preferred, and γ-methacryloxypropyltriethoxysilane is more preferred, in terms of good water resistance, warm water resistance, and storage stability.

[0076] Examples of the hydroxyl group-containing alkyl vinyl ethers include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxy-2-methylbutyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether, glycerol monoallyl ether, etc. In terms of excellent polymerization reactivity, at least one selected from the group consisting of 4-hydroxybutyl vinyl ether and 2-hydroxyethyl vinyl ether is preferred.

[0077] Examples of vinyl carboxylate esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl cyclohexylcarboxylate, vinyl benzoate, vinyl para-t-butylbenzoate, etc. Use of vinyl carboxylate esters can impart properties such as improved gloss and an increased glass transition temperature to a coating film using a fluorine-containing seed polymer obtained from the present disclosure.

[0078] Examples of α-olefins include ethylene, propylene, n-butene, isobutene, styrene, etc. By using an α-olefin, properties such as improved flexibility can be imparted to a coating film using the fluorine-containing seed polymer obtained according to the present disclosure.

[0079] (Method for Producing Aqueous Dispersion) The method for producing an aqueous dispersion of the present disclosure is a production method comprising: (I) a step of preparing fluoropolymer (A) particles; and (II) a step of seed-polymerizing units (b) to the fluoropolymer (A) particles in an aqueous dispersion of the fluoropolymer (A) particles in the presence of structural units (c) derived from a monomer having an oxyalkylene group.

[0080] Furthermore, the present disclosure also includes a method for producing an aqueous dispersion, which includes a step (III) of neutralizing an aqueous dispersion containing resin particles comprising units (a) based on a fluoroolefin, and at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid, and a (meth)acrylic acid ester, and structural units (c) derived from a monomer having an oxyalkylene group.Furthermore, the present disclosure also includes a method for producing an aqueous dispersion that includes all of these steps.Such a production method will be described in detail below.

[0081] (Step (I)) The above step (I) is a step of preparing fluoropolymer (A) particles. Such a step may be one in which fluoropolymer (A) particles are obtained by polymerization, or one in which commercially available fluoropolymer (A) is purchased and prepared. The fluoropolymer (A) particles are preferably in the state of an aqueous dispersion in which such particles are dispersed in water. In step (I), it is preferable to subject the above fluoroolefin-based units (a) to aqueous dispersion polymerization. Examples of aqueous dispersion polymerization include emulsion polymerization and suspension polymerization, and emulsion polymerization is particularly preferred from the viewpoint of producing a large number of polymer particles having a small particle size.

[0082] In step (I), an emulsifier may be used from the viewpoint of efficiently producing the fluoropolymer (A). Such emulsifier is not particularly limited, and examples thereof include general surfactants used in the polymerization of fluorine-containing monomers.

[0083] In the case of emulsion polymerization, the amount of the surfactant used is preferably 10 to 5000 ppm, more preferably 20 to 4000 ppm, based on the total amount of water. If the amount of the surfactant used is less than 10 ppm, the surface activity tends to be reduced, resulting in a smaller number of particles generated.

[0084] The polymerization temperature is not particularly limited, and an optimum temperature is adopted depending on the type of polymerization initiator. The polymerization temperature is preferably 40 to 120°C, more preferably 50 to 100°C, because it maintains a high monomer density in the gas phase, suppresses the branching reaction of the polymer, and makes it easy to efficiently obtain the target copolymer. The monomers may be supplied continuously or successively.

[0085] Although oil-soluble peroxides can be used as the polymerization initiator, it is preferable to use a water-soluble radical polymerization initiator in terms of high fluoropolymer production and particle stability during polymerization. Preferred examples of the water-soluble radical polymerization initiator include ammonium salts, potassium salts, and sodium salts of persulfuric acid, perborate, perchloric acid, perphosphoric acid, and percarbonate, with ammonium persulfate and potassium persulfate being particularly preferred.

[0086] The amount of the polymerization initiator to be added is not particularly limited, but may be added all at once, stepwise, or continuously at the beginning of the polymerization in an amount (for example, several ppm relative to the water concentration) that does not significantly decrease the polymerization rate. The upper limit is within the range in which the heat of the polymerization reaction can be removed from the equipment.

[0087] In step (I), a molecular weight modifier may be further added. The molecular weight modifier may be added all at once at the beginning, or may be added continuously or in portions.

[0088] Examples of the molecular weight modifier include esters such as dimethyl malonate, diethyl malonate, methyl acetate, ethyl acetate, butyl acetate, and dimethyl succinate, as well as isopentane, isopropanol, acetone, various mercaptans, carbon tetrachloride, cyclohexane, monoiodomethane, 1-iodomethane, 1-iodopropane, isopropyl iodide, diiodomethane, 1,2-diiodomethane, and 1,3-diiodopropane.

[0089] In addition, a buffering agent or the like may be added as appropriate, but it is preferable to use the amount within a range that does not impair the effects of the present disclosure.

[0090] The polymerization pressure may be appropriately selected within the range of 0.1 to 10 MPa, and more preferably 0.2 to 8 MPa. Within this range, the pressure may be low (0.1 to 1 MPa) or high (1 to 10 MPa).

[0091] As a stirring means, for example, anchor blades, turbine blades, inclined blades, etc. can be used, but stirring using large blades called Full Zone or Max Blend is preferred because they provide good monomer diffusion and polymer dispersion stability. The stirring device may be either a horizontal or vertical type.

[0092] In step (I) of the present disclosure, the concentration of the fluoropolymer in the polymerization product liquid may be increased. For example, the polymerization product liquid may be an aqueous dispersion of a fluoropolymer having a high concentration of more than about 45% by mass, for example, a concentration of 45 to 55% by mass.

[0093] The fluoropolymer (A) particles obtained in step (I) have an average particle size of 30 to 200 nm and a number average molecular weight of 1.0 × 10 ４ ~1.0 x 10 ６ The molecular weight distribution (Mw / Mn) is preferably as sharp as about 2 to 5. The number of particles in the aqueous dispersion is 1×10 １４ ~5 x 10 １６ The average particle size is a value obtained by measurement using a dynamic scattering method. The number average molecular weight and molecular weight distribution can be measured using a gel permeation chromatography (GPC) method.

[0094] The average particle size of the resin particles in the aqueous dispersion of the present disclosure is preferably 300 nm or less, in order to ensure that the resulting coating film exhibits high gloss and high sedimentation stability during storage when used as a coating composition. Therefore, the average particle size of the resin particles in the dispersion obtained by step (I) is preferably 200 nm or less, more preferably 150 nm or less, in consideration of subsequent seed polymerization. On the other hand, the average particle size of the resin particles in the dispersion obtained by step (I) is preferably 30 nm or more, more preferably 50 nm or more, in order to maintain high polymerization stability even when the amount of surfactant used, which is related to water resistance and weather resistance, is reduced.

[0095] (Step (II)) Step (II) is a step of aqueous dispersion polymerization of a monomer composition essentially containing units (b) in the presence of structural units (c) derived from a monomer having an oxyalkylene group in an aqueous dispersion of the fluoropolymer (A) particles obtained in step (I), in which a monomer composition essentially containing units (b), which is a monomer for seed polymerization, is seed polymerized using the fluoropolymer (A) particles obtained in step (I) as seed particles, to obtain an aqueous dispersion containing resin particles.

[0096] In step (II), it is preferable to use, as surfactants, a combination of the anionic surfactant (c-2) represented by formula (3) and the nonionic surfactant (c-1) represented by formula (2). When an aqueous dispersion containing fluorine-containing seed polymer particles obtained by using these in combination is used in a coating material, a coating film having excellent water resistance and weather resistance can be formed.

[0097] The seed polymerization may be carried out by a generally known method, for example, a method in which a monomer composition essentially containing the unit (b) and a polymerization initiator are added to an aqueous dispersion of fluoropolymer (A) particles in the presence of an anionic surfactant (c-2) and a nonionic surfactant (c-1), followed by emulsion polymerization.

[0098] The polymerization initiator is not particularly limited as long as it can undergo a free radical reaction in water, and in some cases, it can be used in combination with a reducing agent. Usable water-soluble polymerization initiators include, for example, persulfates and hydrogen peroxide, with persulfates being preferred. Examples of persulfates include ammonium persulfate, sodium persulfate, and potassium persulfate, with ammonium persulfate being more preferred. Usable reducing agents include sodium pyrobisulfite, sodium hydrogensulfite, sodium L-ascorbate, and Rongalit. Examples of oil-soluble polymerization initiators include diisopropyl peroxydicarbonate (IPP), benzoyl peroxide, dibutyl peroxide, and azobisisobutyronitrile (AIBN). The amount of polymerization initiator used is preferably 0.0001 to 2.0 parts by mass per 100 parts by mass of the monomer for seed polymerization.

[0099] The polymerization temperature may be from 10 to 90° C., and the polymerization time may be from 0.5 to 6 hours.

[0100] Furthermore, commonly known additives used in emulsion polymerization, such as surfactants, may also be used.

[0101] The fluorine-containing seed polymer (B) particles obtained in step (II) preferably have an average particle size of 110 to 300 nm.

[0102] The resin particles in the aqueous dispersion of the present disclosure preferably have a weight ratio (a) / (c) of the polymer of unit (a) to the polymer of unit (c) contained in the resin particles of 65 / 35 to 10 / 90, more preferably 60 / 40 to 20 / 80, and even more preferably 55 / 45 to 25 / 75.

[0103] The resin particles preferably have a fluorine content of 5 to 50% by mass, more preferably 10 to 46% by mass.

[0104] The resin particles preferably have a content of units (b) of 50 to 900% by mass relative to the unit (a). When an aqueous dispersion of the resin particles is applied to a coating composition, the upper limit of the content is more preferably 400% by mass in order to provide a coating film with better weather resistance, and the lower limit is more preferably 70% by mass in order to provide good flexibility and blocking resistance.

[0105] In the above case, the content of polymerized units based on other copolymerizable monomers having a radical-polymerizable ethylenically unsaturated bond in the resin particles is preferably 0 to 4 mass % relative to the content of units (b). More preferably, it is 0.1 to 3 mass %, and even more preferably 0.1 to 2.5 mass %. Examples of the other copolymerizable monomers having a radical-polymerizable ethylenically unsaturated bond include the above-mentioned hydroxyl group-containing alkyl vinyl ethers, carboxylic acid vinyl esters, and α-olefins.

[0106] The polymer constituting the resin particles preferably has a glass transition temperature of 10 to 50° C., more preferably 20 to 45° C. The glass transition temperature can be determined using a differential scanning calorimeter (DSC).

[0107] (Step (III)) As described above, the method for producing an aqueous dispersion according to the present disclosure may include a step (III) of neutralizing an aqueous dispersion containing resin particles comprising the unit (a) based on a fluoroolefin, at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid, and a (meth)acrylic acid ester, and the structural unit (c) derived from a monomer having an oxyalkylene group.

[0108] The neutralization described above is preferably carried out in an equivalent amount according to the amount of base added to the -COOH groups present in the resin. However, the -COOH groups in the resin are present in the resin chain and are not exposed to the outside, which may make it difficult for the neutralization reaction to proceed. In such cases, it is preferable to carry out the neutralization reaction at a relatively high temperature, as this activates molecular motion and makes the neutralization reaction more likely to occur.

[0109] Although the aqueous dispersion to be treated in the above-mentioned step (III) is not particularly limited, it is particularly preferred to carry out step (III) on the aqueous dispersion obtained by the above steps (I) and (II). Neutralizing agents used for neutralization include ammonia; organic amines such as diethylamine, ethylethanolamine, diethanolamine, monoethanolamine, monopropanolamine, isopropanolamine, ethylaminoethylamine, hydroxyethylamine, diethylenetriamine, and triethylamine; inorganic neutralizing agents such as sodium bicarbonate, ammonium hydroxide, alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, or alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide, and zinc oxide. Among these, ammonia and sodium bicarbonate are particularly advantageous in terms of availability, emulsion stability, and ease of handling.

[0110] (Method for adjusting zeta potential) In the aqueous dispersion of the present disclosure, it is important that the absolute value of the zeta potential is 52 mV or more. Methods for obtaining an aqueous dispersion having such a specific absolute value of the zeta potential include the selection of an emulsifier to be used and the preparation of a polymer resin composition.

[0111] Furthermore, after polymerization, the acid groups present in the polymer are often neutralized to increase the polymer's affinity for water. The content of such acid groups and the conditions for neutralization are also important.

[0112] When neutralizing acid groups after polymerization, it is preferable that the neutralization proceeds more smoothly and a high proportion of acid groups are neutralized. In particular, acid groups in the resin may be surrounded by resin chains, making it difficult for the neutralization reaction to proceed. In such cases, by proceeding with neutralization at a higher proportion, the zeta potential can be further increased and stability can be improved.

[0113] For this reason, the neutralization temperature for the neutralization reaction is preferably 20 to 80° C., more preferably 50 to 70° C. When the neutralization reaction is carried out at such a temperature, the neutralization reaction tends to proceed smoothly. This makes it possible to easily obtain an aqueous dispersion having the desired zeta potential according to the present disclosure.

[0114] (Mechanical Stability Test) The aqueous dispersion of the present disclosure preferably has a mechanical stability test result of 15 minutes or more. The above "mechanical stability test result of 15 minutes or more" means that, when the mechanical stability test described below is conducted, the time from the start of stirring until the rotation speed increases by 50% or more is 15 minutes or more. A mechanical stability test result of 15 minutes or more is an indicator of good storage stability and is therefore preferred.

[0115] (Uses) The aqueous dispersion obtained in the present disclosure can be used in various applications as it is or after appropriate modification. Typical applications include, for example, various paints, particularly aqueous paint compositions, and molding materials for films and sheets.

[0116] (Aqueous Paint) The aqueous dispersion of the present disclosure can be used as an aqueous paint as is, or by adding components necessary for a paint. In addition to using the aqueous dispersion of the present disclosure as a film-forming material, conventionally known additives and blending ratios can be used. For example, the aqueous paint preferably contains the above-mentioned aqueous dispersion in such a way that the resin particles therein account for 10 to 60 mass %.

[0117] The aqueous dispersion of the present disclosure may also be mixed with other resins to form aqueous coating materials. The other resins are most preferably acrylic resins in terms of compatibility with the aqueous dispersion. Aqueous coating materials containing the aqueous dispersion of the present disclosure are also preferred aspects of the present disclosure. Coating films formed using the aqueous coating materials have excellent water resistance and weather resistance.

[0118] When applied to a pigmented aqueous paint, for example, a predetermined amount of a pigment dispersion prepared by previously dispersing water, a pigment such as titanium oxide, an antifoaming agent, a pigment dispersant, a pH adjuster, etc. in a pigment disperser such as a sand mill, and a predetermined amount of a film-forming aid may be mixed and stirred into the aqueous dispersion of the present disclosure, and then a predetermined amount of a thickener may be added and mixed, and other necessary additives may be added as appropriate.When preparing an aqueous paint without added pigment, water, a film-forming aid, an antifoaming agent, a thickener, a pH adjuster, and other necessary additives may be added to the aqueous dispersion of the present disclosure as needed, and the mixture may be stirred and mixed by a known method.

[0119] Additives for coating applications may include, as needed, film-forming aids, antifreeze agents, pigments, fillers, pigment dispersants, antifoaming agents, leveling agents, rheology adjusters, preservatives, ultraviolet absorbers, antioxidants, matting agents, lubricants, crosslinking agents, and the like.

[0120] As the film-forming aid, various commercially available film-forming aids can be used, and specific examples thereof include polyhydric alcohol alkyl ethers and organic acid esters such as dipropylene glycol-n-butyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol diethyl ether, ethylene glycol mono-2-ethylhexyl ether, diethyl adipate, and 2,2,4-trimethylpentane-1,3-diol monoisobutyrate, but are not limited thereto.

[0121] The water-based paint can be applied by known methods and conditions. For example, a coating film is formed by applying the paint to a substrate by a coating method such as spray coating, roll coating, flow coating, roller coating, or brush coating, and then the coating film is dried at 5 to 200°C. This method makes it possible to form a coating film that has excellent weather resistance, gloss, and transparency, little foaming, is highly resistant to warm water, and does not easily deteriorate even when subjected to repeated freezing and thawing.

[0122] A coating film formed by applying the above-mentioned aqueous coating material and a coated article having the coating film are also preferred embodiments of the present disclosure. The coated article obtained by applying the above-mentioned aqueous coating composition can be used in a wide range of applications. For example, the interior and exterior of electrical appliances (microwave ovens, toasters, refrigerators, washing machines, hair dryers, televisions, videos, amplifiers, radios, electric kettles, rice cookers, radio cassette players, cassette decks, compact disc players, video cameras, etc.), the interior and exterior of air conditioners such as indoor and outdoor units, air outlets and ducts of air conditioners, air purifiers, and heaters, lighting fixtures such as fluorescent lamps, chandeliers, and reflectors, furniture, machine parts, ornaments, combs, eyeglass frames, natural fibers, synthetic fibers (threads and woven fabrics obtained therefrom), and the interior and exterior of office equipment (telephones, facsimiles, copiers (including rolls), cameras, overhead projectors, real-image projectors, clocks, slide projectors, desks, bookshelves, lockers, filing cabinets, chairs, bookends, electronic whiteboards, etc.). The water-based paint has a wide range of applications, including painting automobiles (wheels, door mirrors, moldings, door knobs, license plates, steering wheels, instrument panels, etc.) and kitchen appliances (range hoods, sinks, countertops, knives, cutting boards, faucets, gas ranges, extractor fans, etc.), interior applications such as room partitions, bathroom units, shutters, blinds, curtain rails, accordion curtains, walls, ceilings, and floors, exterior applications such as exterior walls, handrails, gates, shutters, and other general residential and building exteriors, architectural exterior materials such as ceramic sizing materials, foam concrete panels, concrete panels, aluminum curtain walls, steel sheets, galvanized steel sheets, stainless steel sheets, PVC sheets, PET films, polycarbonate films, and acrylic films, sizing materials, window glass, and others. In particular, the water-based paint of the present disclosure has excellent weather resistance and water resistance, and is therefore preferably used to paint architectural exterior materials, and is preferably used as a heat-shielding paint for roofs and exterior walls, or as a waterproof paint for concrete exterior walls.

[0123] Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details may be made without departing from the spirit and scope of the claims.

[0124] The present disclosure will be specifically described below with reference to examples, but the present disclosure is not limited to these examples. In the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass," respectively.

[0125] Example 1 Into a separable flask equipped with a thermometer, a dropping funnel, a reflux condenser and a stirrer, 936 g of an aqueous dispersion (solid content concentration 45.5% by mass) of particles of a fluoropolymer (A) (VdF / TFE / CTFE copolymer (=72.1 / 14.9 / 13 (mol %)) (VTC), ammonium={α-[1-(allyloxy)methyl]alkyl (a mixture of C=11 and 13, and which includes both linear and branched types)}-ω-(sulfonatooxy)poly(n=1 to 30 (oxyethylene) as the main component, {2-alkyl (a mixture of C=10 and 12, and which includes both linear and branched types)}oxysilane, oxysilane and An aqueous solution of 17.4 g of AQUALON KH1025 (c-2), which is a reaction product of {a reaction product of an alkanol (C=10-14, branched) and 1-(allyloxy)-2,3-epoxypropane} and sulfamic acid, and 22 g of ADEKA REASOAP ER-20 (c-1), which is an oxirane polymerization adduct of {a reaction product of an alkanol (C=10-14, branched) and 1-(allyloxy)-2,3-epoxypropane} having an EO value of 20 and mainly composed of {α-[2-(allyloxy)1-({[alkyl(C=10-14)]oxy}methyl)ethyl]-ω-hydroxypoly(n=1-100)(oxyethylene), and 33 g of pure water, was added, and stirred for 15 minutes. After stirring, the solution was heated to raise the internal temperature to 80°C.

[0126] To this mixture, 144 g of acrylic monomers, 121 g of n-butyl acrylate (n-BA), 2.7 g of acrylic acid (AA), 0.3 g of N-dodecyl mercaptan, 80 g of pure water, 17.4 g of (c-2), and 4.6 g of (c-1) were added to 6.9 g of pure water to form an aqueous solution, which was then mixed and pre-emulsified. This emulsion was mixed with an aqueous solution of 0.9 g of ammonium persulfate dissolved in 22 g of pure water, placed in a dropping funnel, and added dropwise to the separable flask over 3 hours to allow polymerization to proceed. After aging at 80 °C, the reaction solution was cooled to room temperature (20-30 °C) to terminate the reaction. After neutralization with 19 g of saturated sodium bicarbonate water, the pH was adjusted to 7-8 using a 28% aqueous ammonia solution to obtain an aqueous dispersion of resin particles (solids concentration: 50% by mass). The average particle size of the resin particles in the resulting aqueous dispersion was 159 nm.

[0127] Example 2 To a separable flask equipped with a thermometer, a dropping funnel, a reflux condenser and a stirrer were placed 936 g of an aqueous dispersion of a fluoropolymer (A) adjusted to a solids concentration of 43.5% by mass, 17.4 g of (c-2), 14 g of (c-1) and 19 g of pure water, and the mixture was stirred for 15 minutes and then heated to raise the internal temperature to 80°C.

[0128] Here, as acrylic monomers, 144 g of methyl methacrylate (MMA), 121 g of n-butyl acrylate (n-BA), 2.7 g of acrylic acid (AA), 0.3 g of N-dodecyl mercaptan, 80 g of pure water, 17.4 g of (c-2), and 4.6 g of (c-1) were dissolved in 6.9 g of pure water, and the resulting solution was mixed and pre-emulsified. This emulsion was mixed with an aqueous solution in which 0.9 g of ammonium persulfate was dissolved in 22 g of pure water, and the mixture was placed in a dropping funnel. The mixture was then added dropwise to the separable flask over 3 hours to allow polymerization to proceed. Thereafter, the reaction solution was aged at 80 ° C. and then cooled to room temperature to terminate the reaction. After neutralization with 19 g of saturated sodium bicarbonate water, the pH was adjusted to 7-8 using a 28% aqueous ammonia solution, and an aqueous dispersion of fluorine-containing seed polymer (B) particles was obtained (solid content concentration 50% by mass). The average particle size of the obtained fluorine-containing seed polymer (B) particles was 149 nm.

[0129] Example 3 To a separable flask equipped with a thermometer, a dropping funnel, a reflux condenser and a stirrer were placed 1,170 g of an aqueous dispersion of a fluoropolymer (A) adjusted to a solids concentration of 43.5% by mass, 21.8 g of (c-2), 28 g of (c-1) and 40.8 g of pure water, and the mixture was stirred for 15 minutes and then heated to raise the internal temperature to 80°C.

[0130] Here, as acrylic monomers, 180 g of methyl methacrylate (MMA), 151 g of n-butyl acrylate (n-BA), 3.4 g of acrylic acid (AA), 0.4 g of N-dodecyl mercaptan, 89 g of pure water, 21.8 g of (c-2), and 5.8 g of (c-1) were dissolved in 8.6 g of pure water, and mixed to form a pre-emulsified solution. This emulsion was mixed with an aqueous solution in which 0.9 g of ammonium sulfate was dissolved in 22 g of pure water, and the mixture was placed in a dropping funnel and added dropwise to the separable flask over 3 hours to allow polymerization to proceed. Thereafter, the mixture was aged at 80 ° C. for 1 hour. The reaction solution was cooled to 70 ° C., neutralized with 19 g of saturated sodium bicarbonate water, and then the pH was adjusted to 7-8 using a 28% aqueous ammonia solution. The mixture was then cooled to room temperature to obtain an aqueous dispersion of fluorine-containing seed polymer (B) particles (solids concentration 50% by mass). The average particle size of the resulting fluorine-containing seed polymer (B) particles was 166 nm.

[0131] Example 4 To a separable flask equipped with a thermometer, a dropping funnel, a reflux condenser and a stirrer were placed 1,170 g of an aqueous dispersion of fluoropolymer (A) adjusted to a solids concentration of 43.5% by mass, 21.8 g of (c-2), 5.8 g of (c-1) and 8.6 g of pure water, and the mixture was stirred for 15 minutes and then heated to raise the internal temperature to 80°C.

[0132] Here, as acrylic monomers, 180 g of methyl methacrylate (MMA), 151 g of n-butyl acrylate (n-BA), 3.4 g of acrylic acid (AA), 0.4 g of N-dodecyl mercaptan, 89 g of pure water, 21.8 g of (c-2), and 5.8 g of (c-1) were dissolved in 8.6 g of pure water, and mixed to form a pre-emulsified solution. This emulsion was mixed with an aqueous solution in which 0.9 g of ammonium persulfate was dissolved in 22 g of pure water, and the mixture was placed in a dropping funnel and added dropwise to the separable flask over 3 hours to allow polymerization to proceed. Thereafter, the mixture was aged at 80 ° C. for 1 hour. The reaction solution was cooled to 70 ° C., neutralized with 19 g of saturated sodium bicarbonate water, and then the pH was adjusted to 7-8 using a 28% aqueous ammonia solution. The mixture was then cooled to room temperature to obtain an aqueous dispersion of fluorine-containing seed polymer (B) particles (solids concentration 50% by mass). The average particle size of the resulting fluorine-containing seed polymer (B) particles was 156 nm.

[0133] Example 5 To a separable flask equipped with a thermometer, a dropping funnel, a reflux condenser and a stirrer, were placed 1,170 g of an aqueous dispersion of fluoropolymer (A) adjusted to a solids concentration of 43.5% by mass, 21.8 g of (c-2), 16.5 g of (c-1) and 25 g of pure water, and the mixture was stirred for 15 minutes and then heated to raise the internal temperature to 80°C.

[0134] Here, as acrylic monomers, 180 g of methyl methacrylate (MMA), 151 g of n-butyl acrylate (n-BA), 3.4 g of acrylic acid (AA), 0.4 g of N-dodecyl mercaptan, 89 g of pure water, 21.8 g of (c-2), and 5.8 g of (c-1) were dissolved in 8.6 g of pure water, and mixed to form a pre-emulsified solution. This emulsion was mixed with an aqueous solution in which 0.9 g of ammonium persulfate was dissolved in 22 g of pure water, and the mixture was placed in a dropping funnel and added dropwise to the separable flask over 3 hours to allow polymerization to proceed. Thereafter, the mixture was aged at 80 ° C. for 1 hour. The reaction solution was cooled to 70 ° C., neutralized with 19 g of saturated sodium bicarbonate water, and then the pH was adjusted to 7-8 using a 28% aqueous ammonia solution. The mixture was then cooled to room temperature to obtain an aqueous dispersion of fluorine-containing seed polymer (B) particles (solids concentration 50% by mass). The average particle size of the resulting fluorine-containing seed polymer (B) particles was 151 nm.

[0135] Example 6 To a separable flask equipped with a thermometer, a dropping funnel, a reflux condenser and a stirrer were placed 1,170 g of an aqueous dispersion of a fluoropolymer (A) adjusted to a solids concentration of 43.5% by mass, 21.8 g of (c-2), 28 g of (c-1) and 40.8 g of pure water, and the mixture was stirred for 15 minutes and then heated to raise the internal temperature to 80°C.

[0136] Here, as acrylic monomers, 180 g of methyl methacrylate (MMA), 151 g of n-butyl acrylate (n-BA), 3.4 g of acrylic acid (AA), 1.9 g of N-dodecyl mercaptan, 89 g of pure water, 21.8 g of (c-2), and 5.8 g of (c-1) were dissolved in 8.6 g of pure water, and mixed to form a pre-emulsified solution. This emulsion was mixed with an aqueous solution in which 0.9 g of ammonium persulfate was dissolved in 22 g of pure water, and the mixture was placed in a dropping funnel and added dropwise to the separable flask over 3 hours to allow polymerization to proceed. Thereafter, the mixture was aged at 80 ° C. for 1 hour. The reaction solution was cooled to 70 ° C., neutralized with 19 g of saturated sodium bicarbonate water, and then the pH was adjusted to 7-8 using a 28% aqueous ammonia solution. The mixture was then cooled to room temperature to obtain an aqueous dispersion of fluorine-containing seed polymer (B) particles (solids concentration 50% by mass). The average particle size of the resulting fluorine-containing seed polymer (B) particles was 160 nm.

[0137] Example 7 To a separable flask equipped with a thermometer, a dropping funnel, a reflux condenser and a stirrer were added 936 g of an aqueous dispersion of a fluoropolymer (A) adjusted to a solids concentration of 43.5% by mass, and an aqueous solution prepared by dissolving 15.8 g of Eleminol JS-20 (c-4) which is sodium alkylarylsulfosuccinate, 20 g of RMA-450M (c-6) which is a methacrylic acid ester of polyethylene glycol monomethyl ether, and 1.8 g of Eleminol RS-3000 (c-5) which is sodium methacryloyloxypropylene sulfate in 20 g of pure water, and the mixture was stirred for 15 minutes.

[0138] To this mixture, 144 g of acrylic monomers, methyl methacrylate (MMA), 121 g of n-butyl acrylate (n-BA), 2.7 g of acrylic acid (AA), 0.3 g of N-dodecyl mercaptan, 80 g of pure water, and 2.3 g of (c-4) were added and mixed to form a pre-emulsified emulsion. The emulsion was mixed and poured into a dropping funnel, and then introduced into the separable flask and stirred at room temperature for 1 hour. The temperature was then raised to 75°C, and an aqueous solution of 0.3 g of ammonium persulfate dissolved in 22 g of pure water was poured into the dropping funnel and added dropwise from the dropping funnel over 3 hours to polymerize, followed by aging at 80°C for 1 hour. The reaction solution was cooled to 70°C, neutralized with 19 g of saturated sodium bicarbonate water, and then the pH was adjusted to 7-8 using a 28% aqueous ammonia solution. The mixture was then cooled to room temperature to obtain an aqueous dispersion of fluorine-containing seed polymer (B) particles (solids concentration 50% by mass). The average particle size of the resulting fluorine-containing seed polymer (B) particles was 157 nm.

[0139] Example 8 50.00 g of pure water, 2.60 g of (c-2), and 2.00 g of (c-1) were placed in a 200-milliliter stainless steel autoclave equipped with a stirrer, and 14.25 g of cyclohexyl vinyl ether (CHVE), 0.2 g of acrylic acid, 8.45 g of ethyl vinyl ether (EVE), and potassium carbonate (K ２ CO ３ ) 0.35 g, sodium hydrogen sulfite (NaHSO ３ ) and 0.08 g of ammonium persulfate (initiator), and cooled with ice and nitrogen gas was supplied at 3.5 kg / cm ２ The mixture was pressurized and degassed to a pressure of 10 mmHg. This pressurized degassing was repeated twice, and then degassed to 10 mmHg to remove dissolved oxygen. 27.10 g of chlorotrifluoroethylene (CTFE) was then added, and the reaction was carried out at 70°C for 8 hours to obtain a fluoropolymer aqueous dispersion. The mixture was then aged at 80°C, and the concentration was adjusted, and the reaction solution was cooled to room temperature to terminate the reaction. The pH was adjusted to 7 to 8 using a 28% aqueous ammonia solution to obtain an aqueous dispersion of resin particles (solid content concentration: 50% by mass). The average particle size of the resin particles in the obtained aqueous dispersion was 121 nm.

[0140] Comparative Example 1 To a separable flask equipped with a thermometer, a dropping funnel, a reflux condenser and a stirrer were placed 1,170 g of an aqueous dispersion of fluoropolymer (A) adjusted to a solids concentration of 43.5% by mass, 21.8 g of (c-2), 5.8 g of (c-1) and 8.6 g of pure water, and the mixture was stirred for 15 minutes and then heated to raise the internal temperature to 80°C.

[0141] Here, as acrylic monomers, 180 g of methyl methacrylate (MMA), 151 g of n-butyl acrylate (n-BA), 3.4 g of acrylic acid (AA), 0.4 g of N-dodecyl mercaptan, 89 g of pure water, 21.8 g of (c-2), and 5.8 g of (c-1) were dissolved in 8.6 g of pure water, and the resulting solution was mixed and pre-emulsified. This emulsion was mixed with an aqueous solution in which 0.9 g of ammonium persulfate was dissolved in 22 g of pure water, and the mixture was placed in a dropping funnel. The mixture was then added dropwise to the separable flask over 3 hours to allow polymerization to proceed. Thereafter, the reaction solution was aged at 80 ° C. and then cooled to room temperature to terminate the reaction. After neutralization with 19 g of saturated sodium bicarbonate water, the pH was adjusted to 7-8 using a 28% aqueous ammonia solution, and an aqueous dispersion of fluorine-containing seed polymer (B) particles was obtained (solids concentration 50% by mass). The average particle size of the obtained fluorine-containing seed polymer (B) particles was 158 nm.

[0142] Comparative Example 2 To a separable flask equipped with a thermometer, a dropping funnel, a reflux condenser and a stirrer were added 936 g of an aqueous dispersion of a fluoropolymer (A) adjusted to a solids concentration of 43.5% by mass and an aqueous solution prepared by dissolving 15.8 g of (c-4), 20 g of (c-6) and 1.8 g of (c-5) in 20 g of pure water, and the mixture was stirred for 15 minutes.

[0143] To this mixture, 144 g of acrylic monomers, methyl methacrylate (MMA), 121 g of n-butyl acrylate (n-BA), 2.7 g of acrylic acid (AA), 0.3 g of N-dodecyl mercaptan, 80 g of pure water, and 2.3 g of (c-4) were added and mixed to form a pre-emulsified solution. The mixture was mixed with this emulsion and poured into a dropping funnel, then introduced into the separable flask and stirred at room temperature for 1 hour. The mixture was then heated to 75°C, and an aqueous solution of 0.3 g of ammonium persulfate dissolved in 22 g of pure water was poured into the dropping funnel and added dropwise from the dropping funnel over 3 hours to polymerize. The mixture was then aged at 80°C for 1 hour, and the reaction solution was then cooled to room temperature to terminate the reaction. After neutralization with 19 g of saturated sodium bicarbonate water, the pH was adjusted to 7-8 using a 28% aqueous ammonia solution to obtain an aqueous dispersion of fluorine-containing seed polymer (B) particles (solids concentration 50% by mass). The average particle size of the resulting fluorine-containing seed polymer (B) particles was 161 nm.

[0144] Comparative Example 3 To a separable flask equipped with a thermometer, a dropping funnel, a reflux condenser and a stirrer were added 936 g of an aqueous dispersion of a fluoropolymer (A) adjusted to a solids concentration of 43.5% by mass, 17.4 g of (c-2), and an aqueous solution prepared by adding 22 g of pure water to 33 g of Adeka Reasoap ER-40 (c-3) which is an oxirane polymerization adduct of {a reaction product of an alkanol (C=10-14, branched) and 1-(allyloxy)-2,3-epoxypropane} comprising α-[2-(allyloxy)1-({[alkyl(C=10-14)]oxy}methyl)ethyl]-ω-hydroxypoly(n=1-100)(oxyethylene) as the main component, and which has an EO value of 40. The mixture was stirred for 15 minutes, and then heated to raise the internal temperature to 80°C.

[0145] Here, as acrylic monomers, 144 g of methyl methacrylate (MMA), 121 g of n-butyl acrylate (n-BA), 2.7 g of acrylic acid (AA), 0.3 g of N-dodecyl mercaptan, 80 g of pure water, 17.4 g of (c-2), and 5.8 g of (c-3) were dissolved in 5.7 g of pure water, and the resulting solution was mixed and pre-emulsified. This emulsion was mixed with an aqueous solution in which 0.9 g of ammonium persulfate was dissolved in 22 g of pure water, and the mixture was placed in a dropping funnel. The mixture was then added dropwise to the separable flask over 3 hours to allow polymerization to proceed. Thereafter, the reaction solution was aged at 80 ° C. and then cooled to room temperature to terminate the reaction. After neutralization with 19 g of saturated sodium bicarbonate water, the pH was adjusted to 7-8 using a 28% aqueous ammonia solution, and an aqueous dispersion of fluorine-containing seed polymer (B) particles was obtained (solid content concentration 50% by mass). The average particle diameter of the obtained fluorine-containing seed polymer (B) particles was 159 nm.

[0146] (Evaluation Method) (Zeta Potential) The aqueous dispersion was diluted 100 times with pure water, and the zeta potential was measured using a zeta potential meter ELSZ-2000 (manufactured by Otsuka Electronics Co., Ltd.).

[0147] (Mechanical Stability) The aqueous dispersion was diluted with water to 50%. 100 g of the emulsion was placed in a metal container and stirred at 2000 rpm using a homodisper while heating the emulsion to 50°C using a water bath. The time from the start of stirring until the rotation speed increased by 50% or more was measured. Evaluation was performed based on the following criteria: ◎: 25 minutes or more; ◯: 15 minutes or more but less than 25 minutes; ×: Less than 15 minutes

[0148] (Amount of Aggregates) The aqueous dispersion after polymerization was filtered through a 400 mesh, and it was visually determined whether aggregates remained on the mesh. The presence of aggregates was marked with "x", and the absence of aggregates was marked with "o".

[0149] (Storage Stability) The aqueous dispersion was stored at 50°C for 10 weeks. The solids concentration, viscosity, pH, and MFT (minimum film formation temperature) of the aqueous dispersion were measured, and a rating of ◯ was given if all of the following conditions were met: solids content 50-52%, pH 6-8, viscosity 10-45 mPa·s, and MFT 10-18°C; and an X was given if any of these conditions were not met. The MFT was measured using a thermal gradient tester (manufactured by Nichiri Shoji Co., Ltd.), where the aqueous dispersion was applied to a wet film thickness of 90 μm, and the film was dried under the following conditions, and the maximum temperature at which no cracks were observed in the coating was visually read. Set temperature gradient 5°C to 25°C

[0150] (Water resistance) A few grams of the aqueous dispersion was dropped onto a glass plate and applied with a 6-mil applicator. After drying at 60°C for 15 minutes, the plate was immersed in water at room temperature for 24 hours. When the plate was removed, the state of whitening was visually judged, with "x" indicating whitening and "o" indicating no whitening.

[0151] (Weather Resistance QUV) 5 g of diethyl adipate was added to 100 g of an aqueous dispersion adjusted with water to a solids concentration of 50% while stirring, and the mixture was stirred for 30 minutes. 0.1 g of BYK028 (manufactured by BYK-Chemie) and 0.3 g of ADEKA NOL UH420 were then added and stirred for 30 minutes. A few grams of the resulting paint were dropped onto an aluminum plate and painted with a #30 bar coater. The 60° gloss, L*, a*, and b* values ​​of the resulting test pieces were measured using a gloss meter and a color difference meter. The test pieces were tested for 1000 hours using an accelerated weather resistance tester QUV (manufactured by Q-Lab). The test conditions were as follows. The 60° gloss, L*, a*, and b* values ​​of the test pieces after the test were measured. The gloss retention and ΔE ([(ΔL*) ２ +(Δa*) ２ +(Δb*) ２ 〕 １／２ The weather resistance was evaluated from the values ​​of the gloss retention of 80% or more, ΔE of 1.0 or less, and no abnormality in appearance. If any of the criteria were not met, the rating was ◯. Test conditions: 1 cycle = 8-hour cycle (i) Irradiation (black panel temperature: 60°C, illuminance: 0.63 W / m ２ (ii) Darkness / condensation (temperature inside the tank: 50°C): 4 hours

[0152] (Average Particle Diameter) The average particle diameter of the aqueous dispersion was measured using a particle diameter measuring device Nanotrac Wave (manufactured by Otsuka Electronics Co., Ltd.).

[0153]

[0154]

[0155]

[0156]

[0157] It is clear from the results in Tables 1 to 4 that the aqueous dispersions of the present disclosure have excellent performance. From the examples, it was confirmed that aqueous dispersions having units (b) having an acidic functional group and a basic functional group and having an absolute value of zeta potential of 52 mV or more have high mechanical stability, low amounts of aggregates, and high storage stability, water resistance, and weather resistance.

[0158] The aqueous dispersion of the present disclosure exhibits effects such as excellent mechanical stability and can be suitably used in the field of paints.

Claims

1. An aqueous dispersion comprising resin particles containing units (a) based on a fluoroolefin and at least one unit (b) selected from the group consisting of (meth)acrylic acid, salts of (meth)acrylic acid, and (meth)acrylic acid esters, and characterized in that the absolute value of the zeta potential is 52 mV or more.

2. The aqueous dispersion according to claim 1, wherein the resin particles are copolymerized with a structural unit (c) derived from a monomer having an oxyalkylene group (b).

3. The aqueous dispersion according to claim 1 or 2, wherein the unit (b) contains a functional group in which at least a portion of the --COOH groups have been neutralized with a base.

4. The aqueous dispersion according to any one of claims 1 to 3, wherein the fluoroolefin comprises at least one fluoroolefin unit selected from the group consisting of vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene.

5. At least a part of the units (c) is represented by the following general formula (2): CH ２ =CHCH ２ -O-R ２ (2) (wherein, R ２ The aqueous dispersion according to any one of claims 2 to 4, wherein the nonionic surfactant (c-1) is a nonionic surfactant represented by the formula:

6. At least a part of the units (c) is represented by the following general formula (3): CH ２ =CHCH ２ -O-R ３ -X (3) (wherein, R ３ is a hydrocarbon chain which may have an oxygen atom and / or a nitrogen atom; X is SO ３ Y (Y is NH ４ 5. The aqueous dispersion according to claim 2, wherein the anionic surfactant (c-2) is an anionic surfactant represented by the formula:

7. The unit (c) is partly represented by the following general formula (2): CH ２ =CHCH ２ -O-R ２ (2) (wherein, R ２ is a hydrocarbon group having a nonionic hydrophilic group.) and a part of which is represented by the following general formula (3): CH ２ =CHCH ２ -O-R ３ -X (3) (wherein, R ３ is a hydrocarbon chain which may have an oxygen atom and / or a nitrogen atom; X is SO ３ Y (Y is NH ４ 5. The aqueous dispersion according to claim 2, wherein the anionic surfactant (c-2) is an anionic surfactant represented by the formula:

8. The aqueous dispersion according to any one of claims 1 to 7, wherein the resin particles are a fluorine-containing seed polymer of fluorine-containing polymer (A) particles and a monomer containing at least one unit (b) selected from the group consisting of (meth)acrylic acid, salts of (meth)acrylic acid, and (meth)acrylic acid esters.

9. The aqueous dispersion according to any one of claims 1 to 8, wherein the result of a mechanical stability test is 15 minutes or more.

10. The resin particles are copolymerized with (b) structural units (c) derived from a monomer having an oxyalkylene group, and the units (b) contain functional groups in which at least some of the -COOH groups have been neutralized with a base, and some of the units (c) are represented by the following general formula (2): CH ２ =CHCH ２ -O-R ２ (2) (wherein, R ２ is a hydrocarbon group having a nonionic hydrophilic group.) and a part of which is represented by the following general formula (3): CH ２ =CHCH ２ -O-R ３ -X (3) (wherein, R ３ is a hydrocarbon chain which may have an oxygen atom and / or a nitrogen atom; X is SO ３ Y (Y is NH ４ or an alkali metal). The aqueous dispersion according to any one of claims 1 to 9, wherein the anionic surfactant (c-2) is represented by the formula (I), the fluoroolefin contains at least one fluoroolefin unit selected from the group consisting of vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene, and the absolute value of the zeta potential is 56 mV or more.

11. An aqueous paint comprising the aqueous dispersion according to any one of claims 1 to 10.

12. A water-based paint comprising the aqueous dispersion according to any one of claims 1 to 10 and an acrylic resin.

13. A coating film obtained from the aqueous dispersion according to any one of claims 1 to 10.

14. A coated article comprising the coating film of claim 13.

15. A method for producing an aqueous dispersion according to any one of claims 1 to 10, characterized in that it comprises: a step (I) of preparing particles of a fluoropolymer (A); and a polymerization step (II) of polymerizing the particles of the fluoropolymer (A) in a liquid containing a monomer containing at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid, and a (meth)acrylic acid ester, and a constituent unit (c) derived from a monomer having an oxyalkylene group.

16. A method for producing an aqueous dispersion according to any one of claims 1 to 10, characterized in that it comprises a step (III) of neutralizing an aqueous dispersion containing resin particles comprising units (a) based on a fluoroolefin, and at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid, and a (meth)acrylic acid ester, and structural units (c) derived from a monomer having an oxyalkylene group.

17. A method for producing an aqueous dispersion according to any one of claims 1 to 10, comprising: a step (I) of preparing particles of a fluoropolymer (A); a polymerization step (II) of polymerizing the particles of the fluoropolymer (A) in an aqueous medium containing a monomer comprising at least one unit (b) selected from the group consisting of (meth)acrylic acid, a salt of (meth)acrylic acid and a (meth)acrylic acid ester, and a constituent unit (c) derived from a monomer having an oxyalkylene group; and a step (III) of neutralizing the aqueous dispersion obtained by the step (II).

Images