JP5678853B2 - One-component waterborne paint composition - Google Patents

Description

  The present invention relates to an aqueous coating composition. Specifically, the present invention relates to an aqueous coating composition that can form a coating film free of white turbidity and coloring by a combination of a predetermined fluorine-containing copolymer and a predetermined block polyisocyanate.

  Isocyanate-based crosslinking agents are widely used mainly for urethane-based paint applications. When it is required to be one-component, such as a paint for lines, it is used as a blocked isocyanate in which an isocyanate group is blocked. However, coloring during storage of paints and coloring during baking and curing are problematic, and various blocked isocyanates have been proposed to solve this problem (for example, Patent Documents 1 and 2).

On the other hand, as a problem when using blocked isocyanate in the composition for water-based coatings, the coating film becomes cloudy due to poor compatibility between the polymer and blocked isocyanate, and the coating film becomes colored due to curing at a relatively high temperature. ing.
As a method for solving the problem of coloring of the obtained coating film, it has been proposed to blend at least two of hindered phenol compounds, phosphorus-containing compounds, and semicarbazide compounds in the paint (Patent Document 3). . However, such an additive may adversely affect the properties of the coating film, and the trouble of compounding is troublesome. The baking temperature is set to 100 to 300 ° C, but the baking temperature is as high as 180 ° C.

JP 2008-101220 A JP 2009-191127 A Japanese Patent Laid-Open No. 9-40905

  Therefore, an object of the present invention is to provide a one-component water-based coating composition that can form a coating film free of white turbidity and coloring without blending special additives.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors can form a coating film free of white turbidity and coloring by combining a predetermined fluorine-containing copolymer and a predetermined block polyisocyanate. The inventors have found that a liquid-type aqueous coating composition can be obtained, and have reached the present invention.

That is, the present invention is as follows.
(1) a fluorine-containing copolymer (A) having a functional group that reacts with an isocyanate group and having an acid value of 10 to 30 mgKOH / g;
A blocked polyisocyanate (B) blocked with a compound represented by the following formula (1):
And a water-based coating composition containing water.

［式（１）において、Ｒは、炭素数１〜５のアルキル基または炭素数１〜５のアルコキシ基であり、Ｒ^１は、炭素数１〜５のアルキル基である。］

[In the formula (1), R is an alkyl group or an alkoxy group having 1 to 5 carbon atoms of 1 to 5 carbon atoms, ^{R 1} is an alkyl group having 1 to 5 carbon atoms. ]

(2) The above block polyisocyanate (B) is a block isocyanate derived from at least one polyisocyanate selected from aliphatic polyisocyanate, alicyclic polyisocyanate and aromatic polyisocyanate ( The composition for water-based paints as described in 1).

(3) The aqueous coating composition according to (1) or (2), wherein R is an isopropyl group and R ¹ is any one of a methyl group, an ethyl group, and an isopropyl group.

(4) The composition for water-based paints as described in any one of said (1)-(3) whose functional group of the said fluorine-containing copolymer (A) is a hydroxyl group.

(5) The above (1) to (4), wherein the fluorine-containing copolymer (A) further has a repeating unit represented by the following formula (a1) and a repeating unit represented by the following formula (a2): The composition for water-based coating materials as described in any one of these.
^{-CFX 1 -CX 2 X 3 - (} a1)
[In Formula (a1), X ¹ and X ² are each independently a hydrogen atom, a chlorine atom or a fluorine atom, and X ³ is a chlorine atom, a fluorine atom or CY ¹ Y ² Y ³ (Y ¹ , Y ² , Y ³ is each independently a hydrogen atom, a chlorine atom or a fluorine atom. ]

［式（ａ２）において、Ｒ^ｂは水素原子またはメチル基であり、Ｒ^２は炭素数１〜１０のアルキレン基または炭素数４〜１０の２価のシクロアルキル基であり、ｍは０または１〜８の整数であり、ｎは０または１である。］

[In Formula (a2), R ^b is a hydrogen atom or a methyl group, R ² is an alkylene group having 1 to 10 carbon atoms or a divalent cycloalkyl group having 4 to 10 carbon atoms, and m is 0 or 1 It is an integer of ˜8, and n is 0 or 1. ]

(6) The aqueous unit according to (5), wherein the fluorine-containing copolymer (A) has a repeating unit (a1) of 40 to 60 mol% and a repeating unit (a2) of 5 to 40 mol%. Composition for paint.

(7) The above (1) to (6), wherein the fluorine copolymer (A) has a repeating unit that imparts an acid value, and the repeating unit is a repeating unit represented by the following formula (a3). ) The composition for water-based paints as described in any one of.

［式（ａ３）において、Ｒ^ｂ’およびＲ^２’は式（ａ２）におけるＲ^ｂおよびＲ^２の各々と同じ意味であり、Ｒ^３は炭素数２〜１０のアルキレン基または炭素数４〜１０のシクロアルキレン基であり、Ｒ^４は水素原子またはＮＨＺ^１Ｚ^２Ｚ^３（Ｚ^１、Ｚ^２、Ｚ^３はそれぞれ独立に水素原子、炭素数１〜４のアルキル基または炭素数１〜６のヒドロキシアルキル基である。）であって、少なくともＲ^４の一部は−ＮＨＺ^１Ｚ^２Ｚ^３であり、ｐは０または１〜８の整数であり、ｑは０または１である。］

[In Formula (a3), R ^b ′ and R ² ′ have the same meaning as each of R ^b and R ² in Formula (a2), and R ³ is an alkylene group having 2 to 10 carbon atoms or 4 to 10 carbon atoms. R ⁴ is a hydrogen atom or NHZ ¹ Z ² Z ³ (Z ¹ , Z ² , Z ³ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to 6 carbon atoms. And at least a part of R ⁴ is —NHZ ¹ Z ² Z ³ , p is 0 or an integer of 1 to 8, and q is 0 or 1. ]

(8) The fluorine-containing copolymer (A) is further a repeating unit represented by the following formula (a4) in an amount of 3 to 50 mol% based on all repeating units in the fluorine-containing copolymer (A). The composition for water-based paints as described in any one of said (1)-(7) containing.

［ただし、式（ａ４）において、Ｒ^ａは水素原子またはメチル基であり、Ｒ^５は炭素数１〜１２のアルキル基または炭素数４〜１０の１価のシクロアルキル基であり、ｊは０または１〜８の整数であり、ｋは０または１である。］

[In the formula (a4), R ^a is a hydrogen atom or a methyl group, R ⁵ is an alkyl group having 1 to 12 carbon atoms or a monovalent cycloalkyl group having 4 to 10 carbon atoms, and j is 0 Or it is an integer of 1-8, and k is 0 or 1. ]

(9) The molar ratio of the functional group that reacts with the isocyanate group in the fluorine-containing copolymer (A) and the blocked isocyanate group in the block polyisocyanate (B) is 1/5 to 2/1. The composition for water-based paints as described in any one of the above (1) to (8).

(10) The above (1), wherein the content of the fluorine-containing copolymer (A) is 50 to 95% by mass with respect to the total mass of the fluorine-containing copolymer (A) and the block polyisocyanate (B). The composition for water-based paints as described in any one of)-(9).

(11) The composition for water-based paints as described in any one of (1) to (10) above, which contains a resin other than the fluorine-containing copolymer (A).

(12) The water-based paint according to (11) above, wherein the content of the resin other than the fluorinated copolymer (A) is 10 to 50 parts by mass with respect to 100 parts by mass of the fluorinated copolymer (A). Composition.

  According to the present invention, it is possible to provide a one-pack type composition for water-based paint that can form a coating film having a beautiful color without white turbidity and coloring without blending special additives.

The aqueous paint composition of the present invention comprises a fluorine-containing copolymer (A) having a functional group that reacts with an isocyanate group and having an acid value of 10 to 30 mgKOH / g,
A blocked polyisocyanate (B) blocked with a compound represented by the following formula (1):
And a water-based coating composition containing water.

［式（１）において、Ｒは、炭素数１〜５のアルキル基または炭素数１〜５のアルコキシ基であり、Ｒ^１は、炭素数１〜５のアルキル基である。］
以下、各成分について説明する。

[In the formula (1), R is an alkyl group or an alkoxy group having 1 to 5 carbon atoms of 1 to 5 carbon atoms, ^{R 1} is an alkyl group having 1 to 5 carbon atoms. ]
Hereinafter, each component will be described.

<Block polyisocyanate (B)>
In the present invention, the blocked polyisocyanate (B) is a blocked polyisocyanate blocked with the compound represented by the above formula (1). As such block polyisocyanate (B), the thing as described in Unexamined-Japanese-Patent No. 2009-191127 can be used.

  Examples of the alkyl group having 1 to 5 carbon atoms of R in the above formula (1) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, and an isopentyl group. Among these, an isopropyl group is preferable from the viewpoint of compatibility with the fluorine-containing copolymer.

  Examples of the alkoxy group having 1 to 5 carbon atoms of R in the formula (1) include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, an n-pentoxy group, and an isopentoxy group. Among these, a methoxy group and an ethoxy group are preferable from the viewpoint of compatibility with the fluorine-containing copolymer.

Examples of the alkyl group having 1 to 5 carbon atoms of R ^{1 in} the above formula (1) include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, and an isopentyl group. Among these, from the viewpoint of compatibility with the fluorine-containing copolymer, a methyl group, an ethyl group, and an isopropyl group are preferable.

The blocked polyisocyanate (B) is blocked by the compound represented by the above formula (1). In the above formula (1), R is isopropyl group, R ¹ is methyl group, ethyl group, isopropyl Blocked polyisocyanates blocked with compounds that are any of the groups are preferred.

The block polyisocyanate (B) may be a mixture of two or more compounds represented by the above formula (1). For example, as the first block polyisocyanate, R is an alkyl group having 1 to 5 carbon atoms, R ¹ is an alkyl group having 1 to 5 carbon atoms, and the second block polyisocyanate. As described above, it is also possible to use a mixed block polyisocyanate with a block polyisocyanate (B2) in which R is an alkoxy group having 1 to 5 carbon atoms and R ¹ is an alkyl group having 1 to 5 carbon atoms. This is preferable because it can be adjusted.

  When using 2 or more types of compounds represented by said Formula (1), it is preferable to combine alkyl isobutanoyl acetate and dialkyl malonate. Curing reactivity can be adjusted by combining 2 types.

  The block polyisocyanate (B) in the present application is preferably a block isocyanate derived from at least one polyisocyanate selected from aliphatic polyisocyanate, alicyclic polyisocyanate and aromatic polyisocyanate. .

  That is, examples of the polyisocyanate for deriving the block polyisocyanate (B) in the present application include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates. These may be used alone or in combination of two or more.

  Aliphatic polyisocyanates include polyisocyanate compositions derived from aliphatic diisocyanates, lysine triisocyanate (hereinafter referred to as “LTI”), 4-isocyanatomethyl-1,8-octamethylene diisocyanate (trimer triisocyanate). : Hereinafter referred to as “TTI”), bis (2-isocyanatoethyl) 2-isocyanatoglutarate (glutamate triisocyanate: hereinafter referred to as “GTI”), or polyisocyanate composition derived from these triisocyanates Things can be exemplified.

  As the aliphatic diisocyanate used for the aliphatic polyisocyanate in the present invention, those having 4 to 30 carbon atoms are preferable. For example, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate (hereinafter referred to as “HDI”). ), 2,2,4-trimethyl-1,6-diisocyanatohexane, lysine diisocyanate, etc. Among them, HDI is preferred because of its industrial availability. Aliphatic diisocyanates may be used alone or in combination of two or more.

  The alicyclic polyisocyanate in the present invention is derived from the alicyclic diisocyanate shown below.

  As the alicyclic diisocyanate used in the alicyclic polyisocyanate composition in the present invention, those having 8 to 30 carbon atoms are preferable, and isophorone diisocyanate (hereinafter referred to as “IPDI”), 1,3-bis ( Isocyanatomethyl) -cyclohexane, 4,4′-dicyclohexylmethane diisocyanate, norbornene diisocyanate, hydrogenated xylylene diisocyanate and the like. Of these, IPDI is preferred from the viewpoint of weather resistance and industrial availability. An alicyclic diisocyanate may be used independently and may use 2 or more types together.

The aromatic polyisocyanate is derived from the aromatic diisocyanate shown below.
Examples of the aromatic diisocyanate used in the aromatic polyisocyanate of the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, and the like. It is done. Aromatic diisocyanates may be used alone or in combination of two or more.

  Among these polyisocyanates, aliphatic polyisocyanates and / or alicyclic polyisocyanates are preferable because of excellent weather resistance. Furthermore, among the aliphatic polyisocyanates, aliphatic polyisocyanates derived from aliphatic diisocyanates are preferred.

The blocked polyisocyanate (B) is blocked by the compound represented by the above formula (1), but is further represented by the formula — (CH ₂ CH ₂ O) p— (wherein p is an integer of 3 or more). It is preferable to have a polyoxyethylene group and / or a polyhydroxyalkyl carboxylic acid residue, since dispersibility is improved in the aqueous coating composition.

  The block polyisocyanate (B) having a polyoxyethylene group and / or a polyhydroxycarboxylic acid residue is, for example, a polyoxyethylene compound and / or a polyhydroxyalkylcarboxylic acid having a functional group that reacts a polyisocyanate compound with an isocyanate group. To form a polyisocyanate having a polyoxyethylene group and / or a polyhydroxyalkylcarboxylic acid residue, and then reacting with the compound represented by the above formula (1) to obtain a blocked isocyanate. . A polyisocyanate compound, a polyoxyethylene compound and / or a polyhydroxyalkyl when reacting a polyisocyanate compound with a polyoxyethylene compound and / or a polyhydroxyalkylcarboxylic acid having a functional group that reacts with an isocyanate group. 0.01-25 mass parts is preferable with respect to 100 mass parts of the polyisocyanate compound made to react, and, as for the quantitative ratio with carboxylic acid, 0.5-25 mass parts is more preferable. Examples of the polyoxyethylene compound include polyoxyethylene diamine and polyoxyethylene diol. Examples of the polyhydroxyalkyl carboxylic acid include dimethylolpropionic acid.

  Examples of the method for producing the block polyisocyanate (B) in the present invention include a method for producing the block by carrying out the reaction between the isocyanate group of the polyisocyanate composition and the compound represented by the above (1) in a reactor. When two or more compounds represented by the above (1) are used, they may be produced by carrying out the reaction in one reactor, or several block polyisocyanates synthesized separately may be mixed after synthesis. May be.

  The total addition amount of the compound represented by the above (1) is 50 to 98 mol equivalent% with respect to the molar equivalent of the isocyanate group in the polyisocyanate which is the precursor. As a lower limit, 60 molar equivalent% is preferable, More preferably, it is 70 molar equivalent%. When the total addition amount is less than 50 molar equivalent%, the crosslinking density decreases, the desired coating film physical properties may not be obtained, or the water resistance of the obtained coating film may decrease, and the total addition rate is When it exceeds 98 mol equivalent%, the compounding property to the composition for water-based paints tends to be lowered.

  The block polyisocyanate (B) in the present invention is used in combination with, for example, an active methylene-based, oxime-based, pyrazole-based blocking agent such as ethyl acetoacetate as a blocking agent other than the compound represented by (1) above. Can also be used. The existing blocking agents used in combination may be used alone or in combination of two or more.

  The reaction between the polyisocyanate and the compound represented by the above (1) (hereinafter also referred to as “block reaction”) can be carried out regardless of the presence or absence of a solvent. When using a solvent, it is preferable to use a solvent inert to the isocyanate group.

A reaction catalyst can be used in the block reaction. As a specific reaction catalyst, a catalyst having basicity is generally preferable.
(1) Tetraalkylammonium hydroxide such as tetramethylammonium and tetraethylammonium, and organic weak acid salts such as acetic acid and capric acid;
(2) Hydroxyalkylammonium hydroxides such as trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium and triethylhydroxyethylammonium, and weak organic acid salts such as acetic acid and capric acid;
(3) alkyl metal salts of alkyl carboxylic acids such as tin, zinc and lead;
(4) Metal alcoholates such as sodium and potassium;
(5) Aminosilyl group-containing compounds such as hexamethyldisilazane;
(6) Mannich bases;
(7) Combined use of tertiary amines and epoxy compounds;
(8) Phosphorus compounds such as tributylphosphine; and two or more of them may be used in combination.

When the reaction catalyst used may adversely affect the properties of the paint or coating film, it is preferable to neutralize the catalyst with an acidic compound or the like. Examples of acidic compounds in this case include inorganic acids such as hydrochloric acid, phosphorous acid, and phosphoric acid, and sulfonic acids such as methanesulfonic acid, p-toluenesulfonic acid, p-toluenesulfonic acid methyl ester, and p-toluenesulfonic acid ethyl ester. Or its derivatives, ethyl phosphate, diethyl phosphate, isopropyl phosphate, diisopropyl phosphate, butyl phosphate, dibutyl phosphate, 2-ethylhexyl phosphate, di (2-ethylhexyl) phosphate, isodecyl phosphate, diisodecyl phosphate, oleyl acid phosphate, tetracosyl acid phosphate , Ethyl glycol acid phosphate, butyl pyrophosphate, butyl phosphite, etc., and two or more of them may be used in combination.
The block reaction can be generally carried out at -20 to 150 ° C, preferably 0 to 100 ° C. If the temperature exceeds 150 ° C., side reactions may occur. On the other hand, if the temperature is too low, the reaction rate is low, which is disadvantageous.

<Fluorine-containing copolymer (A)>
The fluorine-containing copolymer (A) in the present invention is not particularly limited as long as it has a functional group that reacts with an isocyanate group and has an acid value of 10 to 30 mgKOH / g, and more preferably 15 to 25 mgKOH / g. . When the acid value is within this range, the dispersibility and dispersion stability of the fluorinated copolymer (A) in water are improved, and the compatibility with the blocked isocyanate in the present application is also improved. In order to make the fluorine-containing copolymer (A) have an acid value of 10 to 30 mgKOH / g, it has an acid group. Examples of the acid group include a carboxy group.

  Preferred examples of the functional group that reacts with an isocyanate group include a hydroxyl group, a carboxy group, and an amino group. The carboxy group becomes an acid group having an acid value of 10 to 30 mgKOH / g of the fluorine-containing copolymer (A) when dispersed in water, and becomes a functional group that reacts with an isocyanate group at the time of crosslinking. obtain. Therefore, when the fluorinated copolymer (A) has a carboxy group, the carboxy group has an acid value of 10 to 30 mgKOH / g when the fluorinated copolymer (A) is dispersed in water. It may act both as an acid group and as a functional group that reacts with an isocyanate group during the curing reaction.

  Moreover, a fluorine-containing copolymer (A) may have both a carboxy group and a functional group (a hydroxyl group, an amino group, etc.) which reacts with isocyanate groups other than a carboxy group.

  The fluorine-containing copolymer (A) has a carboxy group or a carboxy base as “an acid group having an acid value of 10 to 30 mg KOH / g” and a hydroxyl group as “a functional group that reacts with an isocyanate group”. More preferred.

Specifically, the fluorine-containing copolymer (A) in the present invention has a fluorine-containing monomer (a) (hereinafter sometimes simply referred to as “monomer (a)”) and a carboxy group. Monomer (b-1) (hereinafter sometimes simply referred to as “monomer (b-1)”) and a monomer having a hydroxyl group as the “functional group that reacts with an isocyanate group” (b— 2) (hereinafter simply referred to as “monomer (b-2)”) and / or monomer (b-3) having an amino group (hereinafter simply referred to as “monomer (b-3)”) And a copolymer thereof may be mentioned.
In addition to the method of copolymerizing the monomer (b-1), the carboxy group is introduced by reacting an acid anhydride or the like with the hydroxyl group of the fluorine-containing copolymer having a hydroxyl group as described later. You can also.

Hereinafter, the monomer (a), the monomer (b-1), the monomer (b-2), and the monomer (b-3) will be specifically described.
As the monomer (a), fluorine-containing unsaturated compounds such as chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), vinylidene fluoride (VdF), vinyl fluoride ( VF). Among these, as a monomer (a), since the weather resistance of a coating film is excellent, CTEF and TFE are preferable.

Examples of the monomer (b-1) include unsaturated compounds having a carboxy group.
As the monomer (b-1) having a carboxy group, 3-butenoic acid, 4-pentenoic acid, 2-hexenoic acid, 3-hexenoic acid, 5-hexenoic acid, 2-heptenoic acid, 3-heptenoic acid, 6-heptenoic acid, 3-octenoic acid, 7-octenoic acid, 2-nonenoic acid, 3-nonenoic acid, 8-nonenoic acid, 9-decenoic acid or 10-undecenoic acid, acrylic acid, methacrylic acid, vinylacetic acid, croton Unsaturated carboxylic acids such as acid and cinnamic acid; saturation of vinyloxyvaleric acid, 3-vinyloxypropionic acid, 3- (2-vinyloxybutoxycarbonyl) propionic acid, 3- (2-vinyloxyethoxycarbonyl) propionic acid, etc. Carboxylic acid vinyl ethers; allyloxyvaleric acid, 3-allyloxypropionic acid, 3- (2-allyloxybutoxycarbonyl) propionic acid, 3 Saturated carboxylic acid allyl ethers such as (2-allyloxyethoxycarbonyl) propionic acid; carboxylic acid vinyl ethers such as 3- (2-vinyloxyethoxycarbonyl) propionic acid and 3- (2-vinyloxybutoxycarbonyl) propionic acid Saturated monovalent carboxylic acid monovinyl esters such as monovinyl adipate, monovinyl succinate, vinyl phthalate, and vinyl pyromellitic acid; unsaturated such as itaconic acid, maleic acid, fumaric acid, maleic anhydride, itaconic anhydride, etc. Examples thereof include dicarboxylic acids or intramolecular acid anhydrides thereof; unsaturated carboxylic acid monoesters such as itaconic acid monoester, maleic acid monoester, and fumaric acid monoester.

  The functional group that reacts with an isocyanate group preferably has a hydroxyl group or an amino group, and more preferably a hydroxyl group. That is, the monomer (b-2) is more preferable as the monomer used for the polymerization of the fluorinated copolymer (A).

  Examples of the monomer (b-2) having a hydroxyl group include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4- Hydroxyalkyl vinyl ethers such as hydroxy-2-methylbutyl vinyl ether, 5-hydroxypentyl vinyl ether and 6-hydroxyhexyl vinyl ether; ethylene glycol monovinyl ethers such as diethylene glycol monovinyl ether, triethylene glycol monovinyl ether and tetraethylene glycol monovinyl ether; 1 -Hydroxyethyl allyl ether, 3-hydroxybutyl allyl ether, 2-hydroxyethyl allyl ether Hydroxyalkyl allyl ethers such as ether, 4-hydroxybutyl allyl ether and glycerol monoallyl ether; hydroxyalkyl vinyl esters such as 2-hydroxyethyl vinyl ester and 4-hydroxybutyl vinyl ester; 2-hydroxyethyl allyl ester, 4 -Hydroxyalkyl allyl esters such as hydroxybutyl allyl ester; and (meth) acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth) acrylate.

As the monomer (b-3) having an amino group, aminoalkyl vinyl ethers represented by CH ₂ ═C—O— (CH ₂ ) _x —NH ₂ (x = 1 to 10); CH ₂ ═CH— Aminoalkylcarboxylic acid vinyl ester represented by O—CO (CH ₂ ) _x —NH ₂ (x = 1 to 10); in addition, aminomethylstyrene, vinylamine, acrylamide, vinylacetamide, vinylformamide and the like can be mentioned.

  When the functional group that reacts with the isocyanate group is a hydroxyl group, the hydroxyl value of the fluorinated copolymer (A) is preferably from 0 to 150 mgKOH / g, more preferably from 40 to 125 mgKOH / g.

  In addition to the above monomer, the monomer (c) that does not have any of a functional group that reacts with a fluorine atom, an acid group, and an isocyanate group (hereinafter sometimes referred to simply as “monomer (c)”) .) May be used. Examples of the monomer (c) include vinyl ethers, vinyl esters, propenyl ethers, propenyl esters and acrylic acid esters, and methacrylic acid esters. Specifically, ethyl vinyl ether, cyclohexyl vinyl ether, Examples include butyl vinyl ether, vinyl pivalate, Veova 9 (neonanoic acid vinyl ester) and Veova 10 (neodecanoic acid vinyl ester) (boever 9 and Boeva 10 are both trade names manufactured by Shell Japan Co., Ltd.).

  Among these, ethyl vinyl ether and cyclohexyl vinyl ether are preferred because they have good alternating copolymerization with the monomer (a) and can easily adjust the glass transition temperature of the copolymer.

The preferable content of each repeating unit with respect to all the repeating units in the fluorine-containing copolymer (A) is as follows.
The repeating unit based on the monomer (a) is preferably 40 to 60 mol%, more preferably 45 to 55 mol%.
The total amount of the repeating unit based on the monomer (b-1) or the repeating unit in which an acid anhydride is introduced by reacting the hydroxyl group of the repeating unit having a hydroxyl group with an acid anhydride or the like is that of the fluorinated copolymer (A). The acid value is 10-30 mg KOH / g.
The total amount of the repeating unit based on the monomer (b-2) and the repeating unit based on the monomer (b-3) is preferably 5 to 40 mol%, more preferably 8 to 25 mol%. In this case, it is more preferable that the repeating unit based on the monomer (b-3) is not included and only the repeating unit based on the monomer (b-2) is used.
The repeating unit based on the monomer (c) is preferably 20 to 45 mol%.

  A copolymer in which the content ratio of the repeating unit based on the monomer (a) is in the above range does not have an excessively high glass transition temperature, and forms an amorphous and good film. Further, if the total content of the repeating unit based on the monomer (b-2) and the repeating unit based on the monomer (b-3) is too small, the crosslinking density after curing becomes low, and the monomer When there is too much content rate of (b), we are anxious about the fall of the water resistance of the coating film obtained.

More preferable fluorine-containing copolymer (A) includes a fluorine-containing copolymer described in International Publication WO 2007/125970 (hereinafter referred to as “fluorinated copolymer (a)”). The fluorine-containing copolymer (a) has a repeating unit represented by the formula (a1) described below, a repeating unit represented by the formula (a2), and a repeating unit represented by the formula (a3). It is preferable.
By using the fluorinated copolymer (a) as the fluorinated copolymer (A), the storage stability of the paint is improved, and since it does not contain an emulsifier, the water resistance of the resulting coating film is improved. The effect to do is also acquired.

Hereinafter, the repeating unit represented by the formula (a1) is referred to as “repeating unit (a1)”.
The repeating unit (a1) is represented by the following formula (a1).
^{-CFX 1 -CX 2 X 3 - (} a1)

In the formula (a1), X ¹ and X ² are each independently a hydrogen atom, a chlorine atom or a fluorine atom, and X ³ is a chlorine atom, a fluorine atom or —CY ¹ Y ² Y ³ (Y ¹ , Y ² , Y ³ is each independently a hydrogen atom, a chlorine atom or a fluorine atom.

As the repeating unit (a1), among those exemplified with respect to the monomer (a), a monomer giving the repeating unit represented by the formula (a1) or a repeating unit derived from a mixture thereof is preferable. . A preferable aspect and preferable content are also the same as those of the monomer (a).
The repeating unit (a2) is represented by the following formula (a2).

式（ａ２）中のＲ^ｂは水素原子またはメチル基であり、Ｒ^２は炭素数１〜１０のアルキレン基または炭素数４〜１０の２価のシクロアルキル基であり、ｍは０または１〜８の整数、ｎは０または１である。

R ^b in the formula (a2) is a hydrogen atom or a methyl group, R ² is an alkylene group having 1 to 10 carbon atoms or a divalent cycloalkyl group having 4 to 10 carbon atoms, and m is 0 or 1 to 1. An integer of 8 and n is 0 or 1.

  As the repeating unit (a2), among those exemplified as the monomer having a hydroxyl group of the monomer (b-2), monomers that give the repeating unit represented by the formula (a2), or these monomers Repeating units derived from the mixture are preferred. Among these, as the monomer derived from the repeating unit (a2), hydroxyalkyl vinyl ethers are preferable and 4-hydroxybutyl vinyl ether is preferable in view of polymerizability and crosslinkability.

  The fluorine copolymer (A) preferably has a repeating unit (a3) that imparts an acid value in addition to the repeating unit (a1) and the repeating unit (a2) that is used if necessary. A part or all of the repeating unit (a3) imparting an acid value may be neutralized. The content ratio of the repeating unit having an acid group may be such that the acid value of the fluorine-containing copolymer (A) is 10 to 30 mgKOH / g, and the fluorine-containing copolymer (A) of the repeating unit (a3) for that purpose The content ratio with respect to all the repeating units is 1.5 to 7 mol%, more preferably 2.5 to 5.5 mol%.

R ^b ′ and R ² ′ in formula (a3) have the same meanings as R ^b and R ² in formula (a2), and R ³ represents an alkylene group having 2 to 10 carbon atoms or 4 to 4 carbon atoms. 10 is a divalent cycloalkyl group, R ⁴ is a hydrogen atom or —NHZ ¹ Z ² Z ³ (Z ¹ , Z ² , Z ³ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or And at least a part of R ⁴ is —NHZ ¹ Z ² Z ³ , p is 0 or an integer of 1 to 8, and q is 0 or 1.

Of all the repeating units (a3) of the fluorinated copolymer (A), the proportion of R ⁴ being —NHZ ¹ Z ² Z ³ is preferably 30 to 100 mol%, and preferably 50 to 100 mol%. More preferably.

  The total content ratio of the repeating unit (a2) and the repeating unit (a3) in the fluorine-containing copolymer (a) is the monomer (b-1) used for copolymerization of the fluorine-containing copolymer (A) and This is the same as the total content of the monomer (b-2).

  The content rate of the repeating unit (a3) in a fluorine-containing copolymer (A) is 2-6 mol% with respect to the whole repeating unit of a fluorine-containing copolymer. When it is 2 mol% or less, the compatibility with the block polyisocyanate (B) is poor, and when it is 6 mol% or more, there is a tendency to be inferior in long-term storage stability in water.

The repeating unit (a3) can be derived, for example, by reacting an acid anhydride of a divalent carboxylic acid with the repeating unit (a2) for esterification and neutralization.
The fluorine-containing copolymer (A) may further have a repeating unit (a4) represented by the following formula (a4).

R ^a in formula (a4) is a hydrogen atom or a methyl group, R ⁵ is an alkyl group having 1 to 12 carbon atoms or a monovalent cycloalkyl group having 4 to 10 carbon atoms, and j is 0 or 1 to 1 It is an integer of 8, and k is 0 or 1. Preferably, in formula (a2), j = 0 and k = 0 or 1.

  As the repeating unit (a4), among those exemplified with respect to the monomer (c), a monomer giving the repeating unit represented by the formula (a4) or a repeating unit derived from a mixture thereof is preferable. . A preferable aspect and preferable content are also the same as those of the monomer (c).

  The content ratio of the repeating unit (a4) in the fluorinated copolymer (A) is preferably from 3 to 50 mol%, more preferably from 20 to 45 mol, based on the entire repeating unit of the fluorinated copolymer (A). %.

  The fluorine-containing copolymer (A) is a repeating unit other than the repeating unit (a1), the repeating unit (a2), the repeating unit (a3), and the repeating unit (a4) (hereinafter sometimes referred to as “other repeating unit”). .) May be included at a content ratio of 20 mol% or less based on the entire repeating unit. Other repeating units include those other than the monomers that form the repeating units (a1), (a2), (a3), and (a4) and based on monomers having an ethylenically unsaturated bond. Can be mentioned.

  The particularly preferred constitution of the fluorinated copolymer (a) is 45 to 55 mol% of the repeating unit (a1), 14 to 46 mol% of the repeating unit (a4), 8 to 25 mol% of the repeating unit (a2), A repeating unit (a3) is 2-6 mol%, Comprising: It is the structure which does not contain another repeating unit.

  The fluorine-containing copolymer (A) can be prepared according to a conventional method as an emulsion by emulsion polymerization, or as a dispersion by converting the solvent of the copolymer solution obtained by solution polymerization into an aqueous medium.

  Since the inclusion of an emulsifier causes a decrease in water resistance of the resulting coating film, the solvent of the copolymer solution obtained by solution polymerization is changed to an aqueous medium so that the fluorinated copolymer (A) does not contain an emulsifier. Thus, it is preferable to prepare a dispersion.

<Preparation of aqueous coating composition>
The composition for water-based paints of the present invention (hereinafter sometimes referred to as “fluorine-containing copolymer composition for water-based paints”) is prepared by adding a block polymer to an emulsion or dispersion containing the fluorine-containing copolymer (A). It can be prepared by mixing the isocyanate (B) and optionally various additives described later by known means such as a mixer.

  The blending ratio of the fluorinated copolymer (A) and the block polyisocyanate (B) is blocked in the block polyisocyanate (B) with respect to the functional group that reacts with the isocyanate group of the fluorinated copolymer (A). The molar ratio of the formed isocyanate groups is preferably 1/5 to 2/1, more preferably 1/2 to 3/2.

  As a mass ratio of the fluorine-containing copolymer (A) and the block polyisocyanate (B) in the aqueous coating composition, the above-described molar ratio conditions are secured, and the fluorine-containing copolymer (A) and The total amount of the block polyisocyanate (B) is 100% by mass, and the proportion of the fluorinated copolymer (A) is preferably 50 to 95% by mass, particularly preferably 65 to 90% by mass.

  The amount of water in the aqueous coating composition is preferably 20 to 80% by mass and more preferably 30 to 70% by mass in the aqueous coating composition.

  The aqueous coating composition may appropriately contain additives such as a film-forming aid, a surface conditioner, a thickener, an ultraviolet absorber, a light stabilizer, and an antifoaming agent. Examples of the film-forming aid include diethylene glycol monoethyl ether acetate, 2,2,4-trimethyl-1,3-pentanediol mono (2-methylpropionate), diethylene glycol diethyl ether, and the like.

The film forming aid is one type of organic solvent. Therefore, when a film-forming auxiliary is contained, the total content of the film-forming auxiliary and the other organic solvent is set to 10% by mass or less in the aqueous coating composition. The content of the film-forming auxiliary is preferably 3 parts by mass or less, more preferably 1 part by mass or less with respect to 100 parts by mass of the resin solid content.
Preferred examples of the surface conditioner include polyether-modified polydimethylsiloxane and polyether-modified siloxane.
Preferred examples of the thickener include polyurethane-based associative thickeners.

  Various known ultraviolet absorbers can be used. For example, salicylic acid esters such as methyl salicylate, phenyl salicylate, cresyl salicylate, benzyl salicylate; 2-hydroxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-5- Benzophenones such as chlorobenzophenone, 2-aminobenzophenone, and high molecular weight modified products such as T-57 manufactured by Adeka Argus; 2- (2′-hydroxy-5′-t-butylphenyl) benzo Triazole, 2- (2′-hydroxy-5′-t-butylphenyl) -5-chlorobenzotriazole, 2- (2′-hydroxy-5′-methoxyphenyl) benzotriazole, 2- (2′-hydroxy- 3 ', 5'-di-neopentyl Benzyl) benzotriazole, benzotriazoles such as high molecular weight modified products such as TINUVIN 900, 1130 manufactured by Ciba-Geigy Corporation; ethyl 2-cyano-3,3-diphenylacrylate, 2-cyano-3 Substituted acrylonitriles such as 2-ethylhexyl acrylate, 3-diphenylacrylate, methyl α-cyano-β-methyl-4-methoxycinnamate; 2,2′-thiobis (4-octylphenolate) nickel complex salt, {2,2 Nickel complex salts such as' -thiobis (4-t-octylphenolate)}-n-butylamine / nickel complex salt; dimethyl p-methoxybenzylidenemalonate, resorcinol monobenzoate, hexamethylphosphate triamide, 2,5-diphenyl UV absorbers such as p-benzoquinone; and bis (2,2 6,6-tetramethyl-4-piperidine) sebacate, dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, 2- (3 5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl) and the like. It can also be used in combination as the above mixture. The ultraviolet absorber is preferably used in an amount of 0.1 to 15 parts by mass, particularly 0.1 to 5 parts by mass, based on 100 parts by mass of the copolymer solid content in the aqueous composition.

  Examples of the light stabilizer include hindered amine light stabilizers such as MARK LA 57, 62, 63, 67, 68 manufactured by Adeka Argus, and Tinuvin 622LD manufactured by Ciba-Geigy. These can also be used in combination with an ultraviolet absorber as one kind or a mixture of two or more kinds.

  Antifoaming agents include fatty acid salts, higher alcohol sulfates, liquid fatty oil sulfates, sulfates of aliphatic amines and aliphatic amides, aliphatic alcohol phosphates, sulfonates of dibasic fatty acid esters, Fatty acid amide sulfonates, alkyl allyl sulfonates, formalin condensed naphthalene sulfonates, polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxyethylene sorbitan Examples include alkyl esters, acrylic polymers, silcorn mixed acrylic polymers, vinyl polymers, polysiloxane compounds, and the like. Among these antifoaming agents, the antifoaming effect depends on the balance (HLB value) between the hydrophilic group and the hydrophobic group, and those having an HLB of 6 or less, particularly 4 or less are preferably employed.

  Furthermore, you may contain resin other than a fluorine-containing copolymer (A) of the quantity which does not inhibit the effect of this invention. Examples of other resins include fluorine-based, phenol-based, alkyd-based, melamine-based, urea-based, vinyl-based, epoxy-based, polyester-based, polyurethane-based, and acrylic resins. Among these, a fluorine resin and an acrylic resin are more preferable from the viewpoint of compatibility.

  Examples of the fluorine-based resin include a fluorine-containing copolymer having a polymer unit based on a fluoroolefin and a polymer unit based on a macromonomer having a hydrophilic portion described in Japanese Patent No. 2955336 as essential constituent components. Here, the hydrophilic part means a part having a hydrophilic group, a part having a hydrophilic bond, or a part composed of a combination thereof. The macromonomer is a low molecular weight polymer or oligomer having a radical polymerizable unsaturated group at one end. When this fluorine-containing copolymer is contained, it is preferable in that the stability of the aqueous coating composition is improved.

<Coating method>
The coating is applied by coating the aqueous coating composition of the present invention on a substrate by a known method such as air knife coating, curtain coating, roller coating, wire bar coating, or gravure coating, and heated. Can be formed. Although the heating temperature and time vary depending on the thickness of the coating film, etc., heating is performed at 80 to 150 ° C., preferably 90 to 130 ° C., for about 30 seconds to 24 hours, preferably 1 minute to 1 hour. To do.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following description.

<Synthesis Example 1: Fluorine-containing copolymer aqueous solution 1>
As the fluorinated copolymer (A), a fluorinated copolymer aqueous solution 1 was prepared as follows. Stainless steel pressure-resistant reactor with an internal volume of 2500 ml equipped with a stirrer, 590 g of xylene, 170 g of ethanol, 76 g of ethyl vinyl ether (EVE), 168 g of 4-hydroxybutyl vinyl ether (HBVE), 136 g of cyclohexyl vinyl ether (CHVE), carbonic acid 11 g of potassium and 3.5 g of perbutyl peroxypivalate (PBPV) were charged, and dissolved oxygen in the liquid was removed by degassing with nitrogen.

  Next, 432 g of chlorotrifluoroethylene (CTFE) was introduced, the temperature was gradually raised, and the reaction was continued while maintaining the temperature at 65 ° C. After 10 hours, the reaction was stopped by cooling the reactor with water. After the reaction solution was cooled to room temperature, the reactor was opened to purge unreacted monomers, and then xylene and ethanol were distilled off under reduced pressure to obtain a solid fluoropolymer. The obtained fluoropolymer had a CTFE / EVE / CHVE / HBVE molar ratio of 50/15/15/20.

The obtained fluoropolymer was dissolved in methyl ethyl ketone (MEK) to obtain a varnish having a solid content of 60% by mass. To 300 g of this varnish, 4.8 g of succinic anhydride and 0.072 g of triethylamine as a catalyst were added and reacted at 70 ° C. for 6 hours for esterification. When the infrared absorption spectrum of the reaction solution was measured, the characteristic absorption (1850 cm ⁻¹ , 1780 cm ⁻¹ ) of the acid anhydride observed before the reaction disappeared after the reaction, and the carboxyl group (1710 cm ⁻¹ ) and ester Absorption of the group (1735 cm ⁻¹ ) was observed. The hydroxyl value of the fluorinated copolymer after esterification was 85 mg / KOH, and the acid value was 15 mgKOH / g.

The acid value was determined by dissolving the fluorine-containing copolymer in tetrahydrofuran and titrating with a 0.1N potassium hydroxide-ethyl alcohol solution.
The hydroxyl value was measured as follows. First, the fluorine-containing copolymer was dissolved in tetrahydrofuran, the hydroxyl group was acetylated using acetic anhydride, then water was added to make excess acetic anhydride acetic acid, and the acid value was measured. By quantifying the amount of acetic anhydride that was in excess, the amount of acetic anhydride consumed for the acetylation of the hydroxyl group was determined, and the hydroxyl group was calculated. If the original fluorine-containing copolymer had an acid value, it was subtracted.

  Next, 4.9 g of triethylamine was added to the fluorinated copolymer after esterification, and the mixture was stirred at room temperature for 20 minutes to neutralize the carboxyl group in the fluorinated copolymer, and then 160 g of ion-exchanged water was gradually added. Added to.

  Finally, acetone and methyl ethyl ketone were distilled off under reduced pressure. Furthermore, 20 g part of ion-exchanged water was added to obtain a fluorine-containing copolymer aqueous solution 1 having a solid content concentration of 50% by mass.

<Synthesis Example 2: Fluorine-containing copolymer aqueous solution 2>
As the fluorinated copolymer (A), a fluorinated copolymer aqueous solution 2 was prepared as follows. In a stainless steel pressure resistant reactor with a stirrer having an internal volume of 2500 ml, 1280 g of water, 185 g of ethyl vinyl ether (EVE), 244 g of cyclohexyl vinyl ether (CHVE), 47 g of hydrophilic macromonomer (CM-EOVE), a hydroxyl group-containing single unit 194 g of monomer (CHMVE), 1280 g of ion-exchanged water, 2.0 g of potassium carbonate (K ₂ CO ₃ ), 1.3 g of ammonium persulfate (APS), nonionic emulsifier (Newcol-2320: manufactured by Nippon Emulsifier Co., Ltd.) And 1.4 g of anionic emulsifier (sodium lauryl sulfate) were charged, cooled with ice, and pressurized with nitrogen gas to 3.5 kg / cm ² and degassed. After repeating this pressure degassing twice and degassing to 10 mmHg to remove dissolved air, 664 g of chlorotrifluoroethylene (CTFE) was charged and reacted at 50 ° C. for 24 hours. The reaction was stopped by cooling with water. After the reaction solution was cooled to room temperature, unreacted monomers were purged to obtain a fluoropolymer copolymer aqueous solution 2. The hydroxyl value of the fluorine-containing copolymer was 55 mgKOH / g, and the solid content concentration of the fluorine-containing copolymer aqueous solution was 50%.
The acid value of the obtained fluorine-containing copolymer was 0 mgKOH / g.

The structures of the hydrophilic macromonomer (CM-EOVE) and the hydroxyl group-containing monomer (CHMVE) are as follows.
_{CM-EOVE: CH 2 = CHOCH} 2 -cycloC 6 H 10 -CH 2 O (CH 2 CH 2 O) n H ( average molecular weight 830)
_{CHMVE: CH 2 = CHOCH 2 -cycloC} 6 H 10 -CH 2 OH

<Synthesis Example 3: Adjustment of blocked isocyanate 1>
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen blowing tube was purged with nitrogen, charged with 1000 g of hexamethylene diisocyanate (HDI), and stirred at 60 ° C., tetramethylammonium · 0.1 g of capriate was added. Four hours later, when the refractive index of the reaction solution reached 1.4680 (conversion rate: 38%), 0.2 g of phosphoric acid was added to stop the reaction, and polyisocyanate 1 was obtained.
Thereafter, the reaction solution was filtered, and unreacted HDI monomer was removed by thin film distillation.
The obtained polyisocyanate 1 had a viscosity at 25 ° C. of 2700 mPa · s, an isocyanate group content of 22.2% by mass, a number average molecular weight of 650, and an average number of isocyanate groups of 3.4. Thereafter, the presence of an isocyanurate bond was confirmed by NMR measurement.

Next, the inside of the four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was put into a nitrogen atmosphere, and 100 parts by mass of polyisocyanate 1 and methoxypolyethylene glycol having a number average molecular weight of 400 (Nippon Yushi) 42.3 parts by mass of trade name “Uniox M400” manufactured by Co., Ltd.) and 29.5 parts by mass of propylene glycol monomethyl ether acetate were charged and held at 80 ° C. for 7 hours. Thereafter, the reaction solution temperature was maintained at 60 ° C., 35.8 parts by mass of methyl isobutanoyl acetate, 32.2 parts by mass of dimethyl malonate, and 0.88 parts by mass of a 28% methanol solution of sodium methylate were added and maintained for 4 hours. .
58.9 parts by mass of n-butanol was added and held at a reaction solution temperature of 80 ° C. for 2 hours, and then 0.86 parts by mass of 2-ethylhexyl acid phosphate was added. As a result of measuring the infrared spectrum of the reaction solution, the isocyanate group had disappeared. A block polyisocyanate composition 1 having a solid content of 70% by mass was obtained.

<Synthesis Example 4 Synthesis of Blocked Isocyanate 2>
A 4-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was placed in a nitrogen atmosphere, and 100 parts by mass of polyisocyanate 1 obtained in Synthesis Example 3 and methoxy having a number average molecular weight of 400 42.3 parts by mass of polyethylene glycol (trade name “Uniox M400” manufactured by NOF Corporation) and 29.5 parts by mass of propylene glycol monomethyl ether acetate were charged and held at 80 ° C. for 7 hours. Thereafter, the reaction solution temperature was maintained at 60 ° C., 58 parts by mass of methyl isobutanoyl acetate and 0.88 parts by mass of a 28% methanol solution of sodium methylate were added and maintained for 4 hours.
58.9 parts by mass of n-butanol was added and held at a reaction solution temperature of 80 ° C. for 2 hours, and then 0.86 parts by mass of 2-ethylhexyl acid phosphate was added. As a result of measuring the infrared spectrum of the reaction solution, the isocyanate group had disappeared. A block polyisocyanate composition 2 having a solid content of 70% by mass was obtained.

<Synthesis Example 5 Synthesis of Blocked Isocyanate 3>
In a four-necked flask equipped with a thermometer, a drying tube, a condenser, and a stirrer, 100 parts by mass of polyisocyanate 1 obtained in Synthesis Example 3 and 50 parts by mass of methoxypolyethylene glycol having a number average molecular weight of 400 (Japan) The oil and fat Co., Ltd. brand name "Uniox M400") and 30 mass parts of propylene glycol monomethyl ether acetate were filled, and it hold | maintained at 80 degreeC for 7 hours. Next, 49 parts by mass of methyl ethyl ketoxime and 58.9 parts by mass of n-butanol were added and maintained at 80 ° C. for 2 hours. As a result of measuring the infrared spectrum of the reaction solution, the isocyanate group had disappeared. A block polyisocyanate composition 3 having a solid content of 70% by mass was obtained.

<Examples 1-4 and Comparative Examples 1-4>
With the formulation (mass%) shown in Table 1, the fluorine-containing copolymer solution and the block polyisocyanate solution were mixed using a disperser to prepare an aqueous coating composition. The prepared paint was applied to a chromate-treated aluminum plate and a glass plate using an applicator so that the dry film thickness was about 30 microns, and each was dried under the drying conditions shown in Table 1. The appearance and solvent resistance of the obtained coating films were compared.

The appearance of the coating film and the solvent resistance of the coating film were evaluated as follows.
[Appearance of coating film]
The film | membrane coated on the glass plate was peeled off from the glass plate, and the film-form coating film was obtained. This was measured with a haze meter manufactured by Nippon Denshoku Industries Co., Ltd., and a haze value of 10 or less was transparent and the others were clouded.

[Solvent resistance]
Using a rubbing tester manufactured by Taihei Rika Kogyo Co., Ltd., rubbing the coated film on a chromate-treated aluminum plate with a load of 500 g with felt containing xylene, the coating film dissolved, and the base aluminum plate was exposed The number of rubbing was recorded.

  As Table 1 shows, the composition for water-based paints of the present application uses a block polyisocyanate blocked with a compound represented by the above formula (1), so that crosslinkability is good even at low temperatures, and compatibility is achieved. Since it is excellent, it turns out that the external appearance of the obtained coating film has neither cloudiness nor coloring and is excellent in solvent resistance.

  The aqueous coating composition of the present invention is very useful because it can form a beautiful coating film at a low temperature.

Claims (9)

A fluorine-containing copolymer (A) having a functional group that reacts with an isocyanate group and having an acid value of 10 to 30 mgKOH / g;
A blocked polyisocyanate (B) blocked with a compound represented by the following formula (1):
A one-component aqueous coating composition containing water ,

[In the formula (1), R is an alkyl group or an alkoxy group having 1 to 5 carbon atoms of 1 to 5 carbon atoms, ^{R 1} is an alkyl group having 1 to 5 carbon atoms. ]
The blocked polyisocyanate (B) includes a blocked isocyanate derived from an aliphatic polyisocyanate,
The fluorine-containing copolymer (A) includes a repeating unit represented by the following formula (a1), a repeating unit represented by the following formula (a2), a repeating unit represented by the following formula (a3), and the following formula: A composition for a one-component water-based paint having a repeating unit represented by (a4) .
^{-CFX 1 -CX 2 X 3 - (} a1)
[In Formula (a1), X ¹ and X ² are each independently a hydrogen atom, a chlorine atom or a fluorine atom, and X ³ is a chlorine atom, a fluorine atom or CY ¹ Y ² Y ³ (Y ¹ , Y ² , Y ³ is each independently a hydrogen atom, a chlorine atom or a fluorine atom. ]

[In Formula (a2), R ^b is a hydrogen atom or a methyl group, R ² is an alkylene group having 1 to 10 carbon atoms or a divalent cycloalkyl group having 4 to 10 carbon atoms, and m is 0 or 1 It is an integer of ˜8, and n is 0 or 1. ]

[In Formula (a3), R ^b ′ and R ² ′ have the same meaning as each of R ^b and R ² in Formula (a2) , and R ³ is an alkylene group having 2 to 10 carbon atoms or 4 to 10 carbon atoms. R ⁴ is a hydrogen atom or NHZ ¹ Z ² Z ³ (Z ¹ , Z ² , Z ³ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to 6 carbon atoms. And at least a part of R ⁴ is —NHZ ¹ Z ² Z ³ , p is 0 or an integer of 1 to 8, and q is 0 or 1. ]

[In Formula (a4), R ^a is a hydrogen atom or a methyl group, R ⁵ is an alkyl group having 1 to 12 carbon atoms or a monovalent cycloalkyl group having 4 to 10 carbon atoms, and j is 0 or 1 It is an integer of ˜8, and k is 0 or 1. ] In the formula (1), wherein R is an isopropyl group, wherein R ¹ is either a methyl group, an ethyl group, an isopropyl group, one-pack aqueous coating composition according to claim 1. The one-component water-based coating composition according to claim 1 or 2 , wherein the functional group of the fluorine-containing copolymer (A) is a hydroxyl group. The repeating unit (a1) which the said fluorine-containing copolymer (A) has is 40-60 mol%, and a repeating unit (a2) is 5-40 mol%, Any one of Claims 1-3. A one-component water-based coating composition as described in 1. above. The one-component water-based coating composition according to any one of Claims 1 to 4 , wherein the fluorine-containing copolymer (A) has 3 to 50 mol% of the repeating unit (a4) . The molar ratio of the functional group that reacts with the isocyanate group in the fluorine-containing copolymer (A) and the blocked isocyanate group in the block polyisocyanate (B) is 1/5 to 2/1. Item 6. The one-component aqueous coating composition according to any one of Items 1 to 5 . The fluorine-containing copolymer content of (A) is the 50 to 95% by weight relative to the total weight of the fluorocopolymer (A) and the blocked polyisocyanate (B), according to claim 1 to 6 The one-component water-based coating composition according to any one of the above. The one-component water-based coating composition according to any one of claims 1 to 7 , comprising a resin other than the fluorine-containing copolymer (A). The one-component water-based paint according to claim 8 , wherein the content of the resin other than the fluorinated copolymer (A) is 10 to 50 parts by mass with respect to 100 parts by mass of the fluorinated copolymer (A). Composition.