JP2011256232A - Water-based coating composition - Google Patents

Abstract

A water-based coating composition having both low-temperature crosslinkability and storage stability is provided.
A water-based coating composition comprising the following three components (A) to (C) and having a pH of 7.0 to 9.0 at the time of blending.
(A) A block obtained by reacting a polyisocyanate (a) formed from one or more selected from aliphatic and alicyclic polyisocyanates with a malonic acid diester derivative (b) Polyisocyanate composition (B) Carboxyl group-containing polyol (C) (i) Basic group is 30 mol% or more with respect to 100 mol% of carboxyl groups of the carboxyl group-containing polyol (B) (ii) Acid dissociation constant (pKa A weak basic compound (C1) of 7.0 to 8.5 and a basic compound (C2) exceeding 8.5, and the sum of the weak basic compound (C1) and the basic compound (C2) The composition ratio of the weakly basic compound (C1) to 20 mol% or more,
A basic composition that satisfies both requirements.
[Selection figure] None

Description

  The present invention relates to an aqueous coating composition having excellent low-temperature curability and storage stability.

  In recent years, water-based paints have attracted attention from the viewpoints of the global environment, safety, and hygiene. Among these, various water-based paints have been proposed for automobile paints and architectural paints. Among water-based paints, urethane-based paints that are crosslinked by isocyanate groups have very excellent wear resistance, chipping resistance, chemical resistance, and stain resistance. Among these, urethane-based paints using aliphatic polyisocyanates and alicyclic polyisocyanates as crosslinking agents have high weather resistance.

  In such a urethane-based paint, when a one-component property such as a line paint is required, a blocked isocyanate obtained by blocking a free isocyanate group of a polyisocyanate with a thermal dissociation blocking agent is usually used. Although this blocked isocyanate does not react with the polyol at room temperature, the blocking agent is dissociated by heating, and the active isocyanate group is regenerated to cause a crosslinking reaction with the polyol. As the blocking agent, those based on methyl ethyl ketoxime, caprolactam, alcohol and phenol are used. However, the oxime block isocyanate that can form a crosslinked coating film at the lowest temperature among these generally requires a high baking temperature of 140 ° C. or higher, and therefore requires a very large energy cost. Moreover, there has been a limitation that a blocked isocyanate that requires high-temperature baking cannot be used for processing into a plastic having low heat resistance.

In order to overcome such drawbacks, an active methylene-based blocked isocyanate has been proposed as a blocked isocyanate that forms a crosslinked coating film at a low temperature. (Patent Documents 1 to 4)
In Patent Document 1, malonic acid diester and acetoacetic acid ester are used as a blocking agent, and water dispersibility is improved by using a nonionic hydrophilic group compound.
In Patent Document 2, malonic acid diester and / or acetoacetic acid ester is used as a blocking agent, and further, after chain extension with an aliphatic / alicyclic diamine, formaldehyde in an incorporated form is added to improve storage stability. Yes.
In Patent Document 3, malonic acid diester and / or acetoacetate is used as a blocking agent, and the water dispersibility is improved by transesterification with an alcohol compound containing a group that can become a hydrophilic group in the ester part. .
In Patent Document 4, storage stability is improved by emulsifying malonic acid diester and / or acetoacetate as a blocking agent and further using a hydrophilic compound having a sulfonic acid group and a polyamine compound. Yes.
However, in Patent Documents 1 to 4, the decomposition reaction proceeds when water is present, and the decomposition reaction proceeds when malonic acid diester block that can cause generation of carbon dioxide gas and pH reduction, or water is present. However, since it has an acetoacetate block body in the basic structure that can lower the pH after storage, when used in an aqueous coating composition, there are problems such as generation of carbon dioxide gas and a decrease in pH after storage. It was.
Moreover, in the said patent documents 1-4, it was not described at all about the kind of neutralizing amine in the case of setting it as a water-based coating composition, and an equivalent.
Therefore, an aqueous coating composition that can form a crosslinked coating film at 100 ° C. or less and has good storage stability has been desired.

Japanese Patent No. 3947260 Special table 2003-508562 gazette JP 2006-160936 A JP 2007-45867 A

  An object of this invention is to provide the water-system coating composition which makes low temperature crosslinking property and storage stability compatible.

（式中Ｒ_１、及びＲ_２は炭素数１〜８個のアルキル基、フェニル基又はベンジル基を示し、Ｒ_１とＲ_２は同一でも、異なっていてもよい）
（Ｂ）カルボキシル基含有ポリオール
（Ｃ）以下の（ｉ）（ｉｉ）を共に満足する塩基性組成物
（ｉ）その塩基性基が前記カルボキシル基含有ポリオール（Ｂ）のカルボキシル基１００モル％に対し、３０モル％以上
（ｉｉ）該塩基性組成物を酸解離定数（ｐＫａ）７．０〜８．５の弱塩基性化合物（Ｃ１）とｐＫａが８．５を超える塩基性組成物（Ｃ２）からなり、該弱塩基性化合物（Ｃ１）と該塩基性化合物（Ｃ２）との和に対する該弱塩基性化合物（Ｃ１）の構成比が２０モル％以上
（２）前記ブロックポリイソシアネート組成物（Ａ）が、前記ポリイソシアネート（ａ）と、前記マロン酸ジエステル（ｂ）及び前記活性水素含有親水性化合物（ｃ）とを反応させることにより得られるものであることを特徴とする上記（１）記載の水系塗料組成物。
（３）前記ブロックポリイソシアネート組成物（Ａ）が前記ポリイソシアネート（ａ）のイソシアネート基１００モル％に対し、前記マロン酸ジエステル（ｂ）を主成分とするブロック剤の添加量をｘモル％、及び前記活性水素含有親水性化合物（ｃ）の添加量をｙモル％とした場合に、（ｘ＋ｙ）が７５〜１５０、ｘ／（ｘ＋ｙ）が０．５０〜０．９８、かつｙ／（ｘ＋ｙ）が０．０２〜０．５０であることを特徴とする上記（２）記載の水系塗料組成物。
（４）前記活性水素含有親水性化合物（ｃ）が、数平均分子量２００〜２０００の片末端に炭素数１〜４のモノアルコールが付加したポリエチレングリコール系化合物であることを特徴とする上記（２）、又は（３）に記載の水系塗料組成物。
（５）前記マロン酸ジエステル（ｂ）が式（Ｉ）のＲ_１、及びＲ_２が同一の構造を有し、かつ、炭素数１〜４個のアルキル基であることを特徴とする上記（１）〜（４）のいずれか１項に記載の水系塗料組成物。 As a result of diligent research, the present inventors have surprisingly found that the carboxyl group-containing polyol (B) detailed below and the block polyisocyanate composition (A) also detailed below are the main agent / curing agent. And a basic paint whose basic group is 30 mol% or more with respect to the carboxyl group of the carboxyl group-containing polyol shown in (B) with respect to the aqueous coating composition having a pH of 7.0 to 9.0 at the time of blending. A water-based coating composition is maintained while maintaining low-temperature curability by adding the composition (C) and further using 20 mol% or more of the composition as a weakly basic compound (C1) having a pKa of 7.0 to 8.5. The present inventors have found that the storage stability of can be greatly improved, and have completed the present invention.
That is, the configuration of the present invention is as follows.
(1) A water-based coating composition comprising the following three components (A) to (C) and having a pH of 7.0 to 9.0 at the time of blending.
(A) a polyisocyanate (a) formed from one or more selected from aliphatic polyisocyanates and alicyclic polyisocyanates; a malonic acid diester (b) represented by formula (I); Block polyisocyanate composition obtained by reacting

(Wherein R ₁ and R ₂ represent an alkyl group having 1 to 8 carbon atoms, a phenyl group or a benzyl group, and R ₁ and R ₂ may be the same or different)
(B) Carboxyl group-containing polyol (C) Basic composition satisfying both of the following (i) and (ii) (i) The basic group is based on 100 mol% of the carboxyl group of the carboxyl group-containing polyol (B). (Ii) a basic composition (C2) having a weak basic compound (C1) having an acid dissociation constant (pKa) of 7.0 to 8.5 and a pKa exceeding 8.5. The composition ratio of the weakly basic compound (C1) to the sum of the weakly basic compound (C1) and the basic compound (C2) is 20 mol% or more. (2) The block polyisocyanate composition (A (1) is obtained by reacting the polyisocyanate (a) with the malonic acid diester (b) and the active hydrogen-containing hydrophilic compound (c). Water of The coating composition.
(3) The block polyisocyanate composition (A) is based on 100 mol% of the isocyanate group of the polyisocyanate (a), and the addition amount of the blocking agent containing the malonic acid diester (b) as a main component is x mol%, When the addition amount of the active hydrogen-containing hydrophilic compound (c) is y mol%, (x + y) is 75 to 150, x / (x + y) is 0.50 to 0.98, and y / (x + y ) Is 0.02 to 0.50, The water-based paint composition according to the above (2).
(4) The active hydrogen-containing hydrophilic compound (c) is a polyethylene glycol compound in which a monoalcohol having 1 to 4 carbon atoms is added to one end having a number average molecular weight of 200 to 2000 (2) ) Or the water-based coating composition according to (3).
(5) In the malonic acid diester (b), R ₁ and R _{2 in the} formula (I) have the same structure, and are alkyl groups having 1 to 4 carbon atoms. The water-based coating composition according to any one of 1) to (4).

  INDUSTRIAL APPLICABILITY The present invention can provide a water-based coating composition that can form a crosslinked coating film at a low temperature and has good storage stability.

Hereinafter, the present invention will be described in detail with a focus on preferred embodiments.
The present invention is a water-based coating composition comprising the three components (A), (B), and (C) described in detail below.
Block polyisocyanate composition (A)
First, the block polyisocyanate composition (A) will be described.
The polyisocyanate (a) which is a precursor of the block polyisocyanate composition (A) used in the present invention was formed from one or more selected from aliphatic polyisocyanates and alicyclic polyisocyanates. Polyisocyanate.
Examples of the aliphatic polyisocyanate include polyisocyanate derived from aliphatic diisocyanate, 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 polyisocyanates derived from these triisocyanates.
The aliphatic diisocyanate used in the production of the aliphatic polyisocyanate used in the present invention is preferably one having 4 to 30 carbon atoms. 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. In addition to the aliphatic diisocyanate, the aliphatic polyisocyanate of the present invention may contain a part of structural units derived from the following alicyclic diisocyanate in the skeleton.
The alicyclic polyisocyanate used in the present invention is derived from, for example, the following alicyclic diisocyanate.

  The alicyclic diisocyanate used in the production of the alicyclic polyisocyanate used in the present invention is preferably an alicyclic diisocyanate having 8 to 30 carbon atoms, such as isophorone diisocyanate (hereinafter referred to as IPDI), 1,3-bis (isocyanato). Examples thereof include methyl) -cyclohexane, 4,4′-dicyclohexylmethane diisocyanate, norbornene diisocyanate, and hydrogenated xylylene diisocyanate. 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. In addition to the alicyclic diisocyanate, the alicyclic polyisocyanate of the present invention may partially contain a structural unit derived from the aliphatic diisocyanate in the skeleton.

The average number of isocyanate groups in the polyisocyanate (a) which is the precursor of the block polyisocyanate composition (A) used in the present invention is preferably 2.0 to 20 per molecule. The lower limit is preferably 2.3, more preferably 2.5, and most preferably 3.0. The upper limit is preferably 15, and more preferably 10.
If it is 2 or more, it is easy to suppress the phenomenon that the crosslinkability is lowered and the desired film properties cannot be obtained, and if it is 20 or less, the cohesive force becomes too high, resulting in a smooth coating film. It is easy to suppress a phenomenon such as not being obtained.
The average number of isosocyanate groups is obtained by the following formula (1).

式中、具体的には、Ｒ_１及びＲ_２は、それぞれ独立に炭素数１〜８のアルキル基、フェニル基又はベンジル基である。
Ｒ_１及びＲ_２は互いに同一であっても、異なっていてもよいが、入手の容易さから、Ｒ_１とＲ_２は同一であることが好ましい。炭素数が８以下のアルキル基であると、有効ＮＣＯ質量％が高くなり、かつ、塗料とした時の主剤等との相溶性が良好になる。その中でも、炭素数１〜８のアルキル基であることが好ましく、より好ましくは炭素数１〜４のアルキル基であり、さらに好ましくはメチル基又はエチル基であり、最も好ましくは、エチル基である。
有効ＮＣＯ質量％とは、ブロックポリイソシアネート組成物の全質量に対する潜在的に存在するイソシアネート基の質量％である。 The polyisocyanate (a) used in the present invention is triisocyanate such as LTI, TTI, GTI, or derivatives thereof, except for biuret bond, urea bond, isocyanurate bond, uretdione bond, urethane bond, allophanate bond, oxadiazine trione. It is a di-isocyanate di- 20-mer oligomer produced by forming a bond or the like. The polyisocyanate may have an iminooxadiazinedione group, a carbodiimide group, an amide group, an acylurea group, an imide group, and the like. The polyisocyanate having a biuret bond is obtained by reacting a so-called biuretizing agent such as water, t-butanol and urea with a diisocyanate at a molar ratio of biuretizing agent / isocyanate group of the diisocyanate of about 1/2 to about 1/100. Unreacted diisocyanate can be removed and purified. A polyisocyanate having an isocyanurate bond is obtained by, for example, carrying out a cyclic trimerization reaction with a catalyst or the like, stopping the reaction when the conversion rate is about 5 to about 80% by mass, and removing and purifying unreacted diisocyanate. . In this case, 1 to 6 valent alcohol compounds can be used in combination.
As the catalyst for the isocyanuration reaction, those having basicity are generally preferred, for example,
(1) Tetraalkylammonium hydroxides such as tetramethylammonium, tetraethylammonium and trimethylbenzylammonium, and organic weak acid salts such as acetic acid and capric acid (2) Trimethylhydroxypropylammonium, trimethylhydroxyethylammonium and triethylhydroxypropyl Hydroxyalkylammonium hydroxides such as ammonium and triethylhydroxyethylammonium, organic weak acid salts such as acetic acid and capric acid (3) Alkyl metal salts such as tin, zinc and lead (4) Sodium and potassium (5) Aminosilyl group-containing compounds such as hexamethyldisilazane (6) Mannich bases (7) Tertiary amines and epoxy compounds Combination (8) has a phosphorus compound such as tributylphosphine, it may be used in combination of two or more thereof.
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 polyisocyanate having a urethane bond is, for example, a di-isocyanate having a bivalent to hexavalent alcohol compound such as trimethylolpropane, and the molar ratio of the hydroxyl group of the alcohol compound to the isocyanate group of the diisocyanate is about 1/2 to about 1/100. After the reaction, the unreacted diisocyanate can be removed and purified.
Derivatives of LTI, TTI, and GTI are produced in the same manner as polyisocyanates derived from diisocyanates, but in the case of these triisocyanates, removal and purification of unreacted triisocyanates is not always necessary.
The block polyisocyanate composition (A) used in the present invention is obtained by reacting the polyisocyanate (a) with a malonic acid diester (b) represented by the formula (I).

In the formula, specifically, R ₁ and R ₂ are each independently an alkyl group having 1 to 8 carbon atoms, a phenyl group, or a benzyl group.
R ₁ and R ₂ may be the same as or different from each other, but R ₁ and R ₂ are preferably the same from the standpoint of availability. When the alkyl group has 8 or less carbon atoms, the effective NCO mass% is high, and the compatibility with the main agent and the like when used as a paint is improved. Among these, it is preferable that it is a C1-C8 alkyl group, More preferably, it is a C1-C4 alkyl group, More preferably, it is a methyl group or an ethyl group, Most preferably, it is an ethyl group. .
Effective NCO weight percent is the weight percent of isocyanate groups potentially present relative to the total weight of the blocked polyisocyanate composition.

  Specific examples of the malonic acid diester (b) used in the present invention include dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, and dimalonate malonate. Examples include t-butyl, methyl t-butyl malonate, di-n-hexyl malonate, di-2-ethylhexyl malonate, diphenyl malonate, and dibenzyl malonate. Among them, dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, di-t-butyl malonate, methyl t-butyl malonate, malonic acid Di n-hexyl and di-2-ethylhexyl malonate are preferred, more preferably dimethyl malonate, diethyl malonate, di-n-propyl malonate, diisopropyl malonate, di-n-butyl malonate, diisobutyl malonate, malonic acid Di-t-butyl and methyl malonate t-butyl ester, more preferably dimethyl malonate and diethyl malonate, and most preferably diethyl malonate.

In this invention, the malonic acid diester shown above can also be used independently, and 2 or more types can also be used together.
When the amount of the isocyanate group of the polyisocyanate (a) is 100 mol%, the ratio of the malonic acid diester (b) in the blocking agent is desirably 50 mol% or more, more preferably 75 mol% or more. It is.

Other blocking agents include, for example, alcohols, alkylphenols, phenols, active methylenes other than malonic diesters, mercaptans, acid amides, acid imides, imidazoles, ureas, oximes, amines, Examples include imide-based and pyrazole-based compounds. Examples of more specific blocking agents are shown below.
(1) Alcohols such as methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, etc. (2) alkylphenols Mono- and dialkylphenols having an alkyl group having 4 or more carbon atoms as a substituent, such as n-propylphenol, i-propylphenol, n-butylphenol, sec-butylphenol, t-butylphenol, n-hexylphenol; Monoalkylphenols such as 2-ethylhexylphenol, n-octylphenol, n-nonylphenol, di-n-propylphenol, diisopropylphenol, isopropylcresol, di-n-butylphenol Dialkylphenols such as diol, di-t-butylphenol, di-sec-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, di-n-nonylphenol (3) phenolic; phenol, cresol, ethylphenol, (4) Active methylene type; methyl acetoacetate, ethyl acetoacetate, acetylacetone, etc. (5) mercaptan type; butyl mercaptan, dodecyl mercaptan etc. (6) acid amide type; acetanilide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam and the like (7) acid imide series; succinimide, maleic imide and the like (8) imidazole series; imidazole, 2-methylimidazole and the like (9) urea series; urea, Ourea, ethylene urea, etc. (10) oxime type; formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, cyclohexanone oxime, etc. (11) amine type; diphenylamine, aniline, carbazole, di-n-propylamine, diisopropylamine (12) imine series such as isopropylethylamine; ethyleneimine, polyethyleneimine etc. (13) pyrazole series; pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole and the like.

  Further, the preferred active hydrogen-containing compound (c) is at least one selected from alcohol-based, oxime-based, acid amide-based, active methylene-based and pyrazole-based blocking agents, and more preferably oxime-based and active methylene-based compounds. , At least one selected from pyrazole-based blocking agents, and more preferably at least one selected from active methylene-based blocking agents. Most preferred is acetoacetate.

  The block polyisocyanate composition (A) used in the present invention is preferably partially added with a hydrophilic group in order to improve the compoundability in the water-based paint. As a method for adding a hydrophilic group, a method in which an active hydrogen site of the active hydrogen-containing hydrophilic compound (c) is reacted with a part of the isocyanate group of the polyisocyanate (a) and introduced is common. The active hydrogen-containing hydrophilic compound (c) in this case is selected from nonionic hydrophilic compounds, anionic hydrophilic compounds, and cationic hydrophilic compounds. Among these, nonionic hydrophilic compounds and anionic hydrophilic compounds are preferable from the viewpoint of ease of production, and nonionic hydrophilic compounds are more preferable. These hydrophilic compounds can also be used independently and can also use 2 or more types together.

  Nonionic hydrophilic compounds include polyethylene glycol compounds having at least three consecutive ethylene oxide groups. Furthermore, the number average molecular weight of the nonionic hydrophilic compound is preferably 200 to 2,000. The lower limit of the number average molecular weight is more preferably 300, still more preferably 400. The upper limit is more preferably 1500, still more preferably 1200, and most preferably 1000. If the number average molecular weight is 200 or more, sufficient water dispersibility is obtained, and if it is 2000 or less, the coating film properties such as water resistance after baking are good.

  The exemplified polyethylene glycol compound having three consecutive ethylene oxide groups can contain other oxyalkylene groups, specifically oxypropylene groups, oxystyrene groups, and the like in the ethylene oxide repeating unit. In this case, the molar ratio of the ethylene oxide group is preferably 60 mol% or more, more preferably 70 mol% or more, and most preferably 80 mol% or more with respect to the total amount of the polyethylene glycol compound. When the molar ratio of the ethylene oxide group is high, the compoundability in the water-based paint can be improved efficiently, which is preferable.

  Specific examples of such polyethylene glycol compounds include monoalkoxy polyethylene glycol, polyethylene glycol or triol, so-called pluronic type polypropylene glycol or triol, polyoxypropylene polyoxyethylene copolymer obtained by addition polymerization of ethylene oxide at the end of polypropylene glycol. Examples include diol or triol, polyoxypropylene polyoxyethylene block polymer diol or triol. In particular, monoalkoxy polyethylene glycol and polyethylene glycol are preferable, and monoalkoxy polyethylene glycol is more preferable. The monoalkoxy polyethylene glycol is obtained by adding an alcohol to one end of polyethylene glycol, and the monoalcohol that can be used preferably has 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, and still more preferably. It is C1-C4, Most preferably, they are methanol and ethanol.

  Specific examples of polyethylene glycol include PEG200, 300, 400, 600, 1000, 2000 manufactured by Nippon Oil & Fats Co., Ltd. Moreover, as monoalkoxy polyethylene glycol, Nippon Oil & Fats Co., Ltd. UNIOX M400, 550, 1000, 2000, the product MPG-081 of Nippon Emulsifier Co., Ltd. is mentioned.

  Specific examples of the anionic hydrophilic compound include a carboxylic acid group-containing compound and a sulfonic acid group-containing compound. Examples of the carboxylic acid group-containing compound include monohydroxycarboxylic acid, dihydroxycarboxylic acid, and derivatives thereof. Among the carboxylic acid group-containing compounds, monohydroxycarboxylic acid or dihydroxycarboxylic acid is preferable, and monohydroxycarboxylic acid is more preferable.

Specific examples of the carboxylic acid-containing compound include hydroxypiparic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and derivatives such as polycaprolactone diol and polyether polyol using these as initiators. Is mentioned.
When a carboxylic acid group-containing compound is used, it is preferable to neutralize with a neutralizing agent after the production of the block polyisocyanate composition. Examples of the neutralizing agent include tertiary amines such as alkali metals, alkaline earth metals, ammonia, trimethylamine, triethylamine, and dimethylethanolamine.

Specific examples of the sulfonic acid group-containing compound include aminoethylsulfonic acid, ethylenediamino-propyl-β-ethylsulfonic acid, 1,3-propylenediamine-β-ethylsulfonic acid, N, N-bis (2-hydroxyethyl). ) -2-aminoethanesulfonic acid.
When using a sulfonic acid group-containing compound, it is preferable to neutralize with a neutralizing agent. Examples of the neutralizing agent include tertiary amines such as alkali metals, alkaline earth metals, ammonia, trimethylamine, triethylamine, and dimethylethanolamine.
When the carboxylic acid group-containing compound is compared with the sulfonic acid group-containing compound, the carboxylic acid group-containing compound is preferable from the viewpoint of ease of production and compoundability in water-based paints.
Examples of the cationic hydrophilic compound include a hydroxyl group-containing amino compound. Specific examples include dimethylethanolamine, diethylethanolamine, and hydroxypyridine.
When using a hydroxyl-containing amino compound, it is preferable to neutralize with a neutralizing agent after manufacture of a block polyisocyanate composition (A). Examples of the neutralizing agent include organic acids such as acetic acid, propionic acid, butanoic acid, and 2-ethylhexanoic acid.

In the production of the block polyisocyanate composition (A) used in the present invention, the addition amount of the blocking agent containing the malonic acid diester (b) as a main component with respect to 100 mol% of the isocyanate group of the polyisocyanate (a) is x. It is preferable that (x + y) is 75 to 150 when the addition amount of the mol% and the active hydrogen-containing hydrophilic compound (c) is y mol%. The lower limit is more preferably 90, still more preferably 95, and most preferably 100. As an upper limit, 130 is more preferable, More preferably, it is 120, Most preferably, it is 110. When (x + y) is 75 or more, excellent low-temperature curability is obtained, and when it is 150 or less, coating properties such as water resistance of the baked coating are improved.
The value of x / (x + y) that defines the addition amount of the blocking agent containing malonic acid diester (b) as a main component is preferably 0.50 to 0.98. As a lower limit, 0.60 is more preferable, and 0.70 is still more preferable. When x / (x + y) is 0.50 or more, the crosslink density is increased, the desired film properties are obtained, and the water resistance of the film is also increased, while 0.98 or less is sufficient. Water dispersibility is obtained.
Moreover, it is preferable that the value of y / (x + y) which prescribes | regulates the addition amount of an active hydrogen containing hydrophilic compound (c) is 0.02-0.50. As an upper limit, 0.40 is more preferable, More preferably, it is 0.35. When the value of y / (x + y) is 0.02 or more, sufficient water dispersibility is obtained, and when it is 0.50 or less, the crosslink density increases and the desired coating film properties are obtained. The water resistance of the coating film is also increased.

Next, the manufacturing method of the block polyisocyanate composition shown by (A) in this invention is demonstrated.
The block polyisocyanate composition (A) used in the present invention is obtained by reacting the isocyanate group of the polyisocyanate (a) with the malonic acid diester (b) represented by the formula (I). Moreover, when adding a hydrophilic group, an active hydrogen containing hydrophilic compound (c) is made to react with a part of isocyanate group of polyisocyanate.

  Reaction of the polyisocyanate groups with malonic acid diester of the isocyanate (a) (b), to an active hydrogen-containing hydrophilic compound reaction with the (c) can be performed simultaneously, after either of the reaction in advance, 2 A second reaction can also be carried out. Among these, it is preferable to carry out the reaction between the isocyanate group and the active hydrogen-containing hydrophilic compound (c) first, and after that, the reaction with the malonic acid diester (b).

  The block polyisocyanate composition (A) in the present invention preferably uses an active hydrogen-containing hydrophilic compound in order to improve the compoundability in water-based paints.

  The active hydrogen-containing hydrophilic compound (c) used for introducing a hydrophilic group is selected from the nonionic hydrophilic compounds, anionic hydrophilic compounds, and cationic hydrophilic compounds. Among these, nonionic hydrophilic compounds and anionic hydrophilic compounds are preferable from the viewpoint of ease of production, and nonionic hydrophilic compounds are more preferable. These hydrophilic compounds may be used alone or in combination of two or more.

  The addition amount of the active hydrogen-containing hydrophilic compound (c) and the blocking agent is preferably added at the ratio described above.

The malonic acid diester blocking agent (b) used in the present invention is a malonic acid diester represented by the formula (I), specifically, the malonic acid diester shown above.
The reaction of the isocyanate group in the polyisocyanate (a) with the active hydrogen-containing hydrophilic compound (c) and the malonic acid diester (b) can be carried out regardless of the presence or absence of a solvent. When using a solvent, it is preferable to use a solvent which is inert to the isocyanate group and hardly hydrolyzes. Preferred solvents are ether solvents such as propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, diethylene glycol dimethyl ether and diethylene glycol diethyl ether, and ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone.

  In the reaction of the isocyanate group in the polyisocyanate (a) with the malonic acid diester (b), a reaction catalyst can be used. Specific examples of the reaction catalyst include organic metal salts such as tin, zinc and lead, metal alcoholates, and tertiary amines.

  When the reaction catalyst used may adversely affect the properties of the paint or coating film, it is preferable to deactivate 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 derivatives thereof, 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 reaction can be generally carried out at -20 to 150 ° C, preferably 0 to 100 ° C, more preferably 40 to 80 ° C. If the temperature is 150 ° C. or lower, the possibility of side reaction is low, and if the temperature is not too low, the reaction rate is large and advantageous.

  In order to improve the storage stability when blended with a polyol, a monohydric alcohol may be added to the block polyisocyanate composition (A) used in the present invention. Examples of the monohydric alcohol include aliphatic, alicyclic, aromatic and the like, and aliphatic is preferable. C1-C20 is preferable, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, t-butanol, 2-ethyl-1-propanol, n-amyl alcohol, 2-pentanol, Saturated alcohols such as 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2,2-dimethyl-1-propanol And ether alcohols such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, and 3,6-dioxa-1-heptanol. The addition amount is preferably 20 to 1000 mol% when the amount of the blocked isocyanate group is 100 mol%.

Carboxyl group-containing polyol (B)
Next, the carboxyl group-containing polyol (B) constituting the water-based coating composition of the present invention will be described.
The carboxyl group-containing polyol (B) used in the present invention can be used without particular limitation as long as it has a carboxyl group in the polyol skeleton and can be used as an aqueous paint, and is finally dispersed in at least water. Any of a water-soluble polyol, a water-dispersible polyol, and an external forced emulsification type polyol using a surfactant may be used.
Examples of the polyol include polyester polyol, acrylic polyol, polyether polyol, polyolefin polyol, fluorine polyol, polycarbonate polyol, polyurethane polyol and the like.
Examples of polyester polyols include, for example, dibasic acids selected from the group of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, or the like. Polyester polyol obtained by a condensation reaction of a polyhydric alcohol selected from the group of ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, glycerin or the like alone or a mixture thereof, for example, a polyhydric alcohol was used. and polycaprolactones obtained by ring-opening polymerization of ε-caprolactone.
Acrylic polyol is a solution polymerization or emulsion polymerization of an ethylenically unsaturated bond-containing monomer having a hydroxyl group alone or a mixture thereof and another ethylenically unsaturated bond-containing monomer copolymerizable therewith. Can be obtained by copolymerization.
Examples of the ethylenically unsaturated bond-containing monomer having a hydroxyl group include, for example, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, etc. Is mentioned. Preferred are hydroxyethyl acrylate and hydroxyethyl methacrylate.

  Examples of other ethylenically unsaturated bond-containing monomers copolymerizable with the above monomers include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, acrylic acid Acrylic esters such as isobutyl, acrylic acid-n-hexyl, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, benzyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacryl Metabolites such as isopropyl acetate, n-butyl methacrylate, isobutyl methacrylate, methacrylic acid n-hexyl, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, benzyl methacrylate, and phenyl methacrylate Unsaturated carboxylic acids such as lyric acid esters, acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamide, methacrylamide, N, N-methylenebisacrylamide, diacetone acrylamide, diacetone methacrylamide, maleic acid amide, maleimide Unsaturated amides, and vinyl monomers such as glycidyl methacrylate, styrene, vinyl toluene, vinyl acetate, acrylonitrile, dibutyl fumarate, vinyltrimethoxysilane, vinylmethyldimethoxysilane, γ- (meth) acryloxypropyltri Examples thereof include vinyl monomers having a hydrolyzable silyl group such as methoxysilane.

  Examples of polyether polyols include ethylene oxide, propylene, using a polybasic hydroxy compound alone or in a mixture with a strongly basic catalyst such as a hydroxide such as lithium, sodium or potassium, an alcoholate or an alkylamine. Polyether polyols obtained by adding an alkylene oxide such as oxide, butylene oxide, cyclohexene oxide, styrene oxide or a mixture thereof, and polyether polyols obtained by reacting an alkylene oxide with a polyfunctional compound such as ethylenediamine. Also included are so-called polymer polyols obtained by polymerizing acrylamide or the like using these polyethers as a medium.

Examples of the polyvalent hydroxy compound include (1) diglycerin, ditrimethylolpropane, pentaerythritol, dipentaerythritol and the like;
(2) Sugar alcohol compounds such as erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol, and rhamnitol;
(3) monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose, ribosese;
(4) Disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, melibiose;
(5) Trisaccharides such as raffinose, gentianose, meletitose;
(6) tetrasaccharides such as stachyose;
Etc.

  Examples of the polyolefin polyol include polybutene having 2 or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene. The number of hydroxyl groups (hereinafter, the average number of hydroxyl groups) possessed by one statistical molecule of polyol is preferably 2 or more. When the average number of hydroxyl groups is 2 or more, the crosslinking density of the obtained coating film increases.

  The fluorine polyol is a polyol containing fluorine in the molecule. For example, fluoroolefin, cyclovinyl ether, hydroxyalkyl vinyl ether, vinyl monocarboxylate disclosed in JP-A-57-34107 and JP-A-61-275111. There are copolymers such as esters.

Examples of polycarbonate polyols are polycondensation of low-molecular-weight carbonate compounds such as dialkyl carbonates such as dimethyl carbonate, alkylene carbonates such as ethylene carbonate, diaryl carbonates such as diphenyl carbonate, and low-molecular polyols used in the above-mentioned polyester polyols. Can be obtained.
The polyurethane polyol can be obtained by a conventional method, for example, by reacting a polyol and a polyisocyanate.

  In order to improve water dispersibility, a polyol containing a carboxyl group may be partially added to the polyurethane polyol. Examples of the polyol containing a carboxyl group include 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid.

  Examples of the polyisocyanate to be reacted with the above polyol include diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and tolylene diisocyanate, the above-described aliphatic polyisocyanate, alicyclic polyisocyanate, aromatic polyisocyanate, and the like. Can be illustrated.

  The hydroxyl value of the carboxyl group-containing polyol (B) is preferably 10 to 300 mgKOH / g per resin. If the hydroxyl value per resin is 10 mgKOH / g or more, the crosslink density is increased, and the target physical properties of the present invention can be achieved. If the hydroxyl value per resin is 300 mgKOH / g or less, the reverse is achieved. In addition, the crosslinking density does not increase excessively, and the mechanical properties of the coating film can be prevented from decreasing.

The acid value of the carboxyl group-containing polyol (B) is preferably 5 to 150 mgKOH / g, more preferably 8 to 120 mgKOH / g, and still more preferably 10 to 100 mgKOH / g per resin. When the acid value is 5 mgKOH / g or more, a decrease in water dispersibility can be prevented, and when the acid value is 150 mgKOH / g or less, a decrease in water resistance of the coating film can be prevented.
Preferred polyols are acrylic polyols and polyester polyols.

Basic composition (C)
Finally, the basic composition (C) constituting the water-based coating composition of the present invention will be described. The basic composition (C) used in the present invention is not particularly limited as long as the acid dissociation constant (pKa) is 7.0 or more. If pKa is 7.0 or more, it can function as a neutralizing agent for carboxyl groups such as polyol. The acid dissociation constant (pKa) was measured at 20 ° C. by potentiometric titration.

  The addition amount of the basic composition (C) in this invention is 30 mol% or more when the basic group makes the amount of the carboxyl group of a carboxyl group-containing polyol (B) 100 mol%. As a lower limit, Preferably, it is 50 mol%, More preferably, it is 70 mol%, More preferably, it is 100 mol% or more. Moreover, as an upper limit, Preferably, it is 500 mol%, More preferably, it is 400 mol%, More preferably, it is 300 mol%. In the present invention, it is considered that the basic composition (C) is present in excess in an amount that forms a neutralized salt of the carboxyl group of the carboxyl group-containing polyol (B). The carboxyl group of the carboxyl group-containing polyol (B) in this case is based on the charged acid component at the time of polyol production.

  In the carboxyl group-containing polyol (B) produced by emulsion polymerization, the carboxyl group distributed at the center of each particle may not function as a hydrophilic group, and the basic compound as described above is about 30 mol%. The addition can be present in excess of the amount that forms the neutralized salt.

  The basic composition (C) of the present invention comprises a weakly basic compound (C1) having an acid dissociation constant (pKa) of 7.0 to 8.5 and a basic compound (C2) having a pKa exceeding 8.5, The composition ratio of the weak basic compound (C1) to the sum of the weak basic compound (C1) and the basic compound (C2) is 20 mol% or more.

  The lower limit value of the composition ratio of the weakly basic compound (C1) in the total basic composition (C) is preferably 30 mol%, more preferably 40 mol%, still more preferably 50 mol%. In the present invention, when (C1) is added in an amount of 20 mol% or more in the total basic composition (C), it is adjusted even when it is present in excess of the neutralized salt of the carboxyl group of the polyol. This is preferable because the pH of the finished coating composition does not become too high.

As an upper limit of pKa of a weak basic compound (C1), 8.3 or less is preferable, More preferably, it is 8.0 or less.
Specific examples of the weakly basic compound (C1) having a pKa of 7.0 to 8.5 include morpholine (pKa: 8.4), N-allylmorpholine (pKa: 7.1), N-methylmorpholine ( morpholine derivatives such as pKa: 7.4) and N-ethylmorpholine (pKa: 7.7), tertiary amines such as triallylamine (pKa: 8.3), triethanolamine (pKa: 7.8), 2 -Methylimidazole (pKa: 7.8), phthalamide (pKa: 8.3), etc. are mentioned.
Among these, N-allylmorpholine, N-methylmorpholine, N-ethylmorpholine, triethanolamine, and 2-methylimidazole are more preferable, and N-methylmorpholine and N-ethylmorpholine are more preferable.
Specific examples of the basic compound (C2) having a pKa exceeding 8.5 include trimethylamine (pKa: 9.8), triethylamine (pKa: 11.0), dimethylethanolamine (pKa: 9.4) and the like. It is done.

The pH at the time of blending the water-based coating composition of the present invention is 7.0 to 9.0. The lower limit thereof is more preferably 7.5, still more preferably 8.0, and the upper limit thereof is more preferably 8.8, still more preferably 8.6.
If the pH of the water-based coating composition is 7.0 to 9.0, it is suitable because the stability of additives such as pigments such as aluminum and rheology control agents blended can be maintained.

  In general, a water-based coating composition comprising a carboxyl group-containing polyol and an existing block polyisocyanate composition as a main agent / curing agent, a technique for neutralizing the carboxyl group of the carboxyl group-containing polyol with a basic composition is a known technique. is there. However, in a water-based coating composition having a carboxyl group-containing polyol and a specific block polyisocyanate composition as a main agent / curing agent, a weak basic compound having a pKa of 7.0 to 8.5 is added to all or a specific ratio of the basic composition. The technology of adding is a new technology, and this water-based coating composition greatly improves the storage stability while maintaining low-temperature curability (both the generation amount of carbon dioxide during storage and the decrease in pH of the coating solution are greatly increased). It was surprising to suppress.

  The blending method of the block polyisocyanate composition (A) and the carboxyl group-containing polyol (B) in the water-based coating composition of the present invention is as follows. The block polyisocyanate composition (A) is directly mixed and dispersed in the carboxyl group-containing polyol (B). Alternatively, the block polyisocyanate composition (A) may be once mixed with water and then mixed with the polyol. Moreover, it is preferable that the equivalent ratio of the blocked isocyanate group and the hydroxyl group of the polyol is usually set to 10: 1 to 1:10 in terms of solid content of 100% by mass.

  The method for blending the basic composition (C) in the aqueous coating composition of the present invention may be previously added to the carboxyl group-containing polyol (B) or the block polyisocyanate composition (A), or the carboxyl group. You may add, after mixing and disperse | distributing a containing polyol and block polyisocyanate composition. Further, the basic composition (C) may be added in advance dissolved in water, a solvent or the like.

  In order to improve the storage stability when the block polyisocyanate composition (A) and the carboxyl group-containing polyol (B) are blended, a monohydric alcohol compound may be added. Examples of the monohydric alcohol compound include aliphatic, alicyclic, and aromatic, with aliphatic being preferred. C1-C20 is preferable, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, t-butanol, 2-ethyl-1-propanol, n-amyl alcohol, 2-pentanol, Saturated alcohols such as 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 2,2-dimethyl-1-propanol , 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, ether alcohols such as 3,6-dioxa-1-heptanol, and the like. The addition amount is preferably 0.2 to 10 times the molar amount relative to the blocked polyisocyanate group.

  An existing melamine resin, epoxy resin, polyurethane resin, oxazoline group-containing compound, carbodiimide group-containing compound, and the like can be blended with the water-based coating composition of the present invention, and the carboxyl group-containing polyol (B) is a carbonyl group. Can be blended with a hydrazide group-containing compound, a semicarbazide group-containing compound, or the like. These compounds can be blended not only alone but also two or more compounds.

  Examples of the melamine resin include a partial or completely methylolated melamine resin obtained by a reaction between melamine and an aldehyde, and examples of the aldehyde include formaldehyde and paraformaldehyde. In addition, it is also possible to use a methylol group of the methylolated melamine resin partially or completely etherified with alcohol. Examples of alcohols used for etherification include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, 2-ethylbutanol, 2-ethylhexanol and the like.

Specific examples of the melamine resin include, for example, Cymel 303, Cymel 323, Cymel 327, Cymel 327, Cymel 350, Cymel 370, Cymel 380, Cymel 385, Cymel 212, Cymel 251 and Cymel 254 manufactured by Nippon Cytec Industries, Ltd. Examples include My Coat 776 (all are trade names).
When melamine resin is used, sulfonic acids such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and salts of these acids and amines are used as catalysts for baking and curing. be able to.

  The epoxy resin is not particularly limited as long as it is a resin having two or more epoxy groups in one molecule, and a known one can be used, for example, obtained by adding epoxychlorohydrin to bisphenol. Examples thereof include bisphenol-type epoxy resins, novolak-type epoxy resins obtained by adding epichlorohydrin to phenol novolac resins, and polyethylene glycol diglycidyl ether. The epoxy resin can be used after being dispersed in water as necessary.

  The polyurethane resin is not limited as long as it is generally used in paints, but a polyurethane resin that is chain-extended by reacting an isocyanate group with a polyol is preferable.

  The polyurethane resin includes those having a carboxyl group and those having a terminal hydroxyl group. A polyurethane resin having a carboxyl group can be obtained by using a polyol containing a carboxyl group as part of the polyol. The polyurethane resin having a carboxyl group is preferably neutralized with a basic substance. Examples of commercially available products include Superflex series 110, 150, 460S (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Neoletz R9649, R966 (trade name, manufactured by Avicia).

  Examples of the oxazoline group-containing compound include a polymer compound having at least two oxazoline groups in the side chain, and a monomeric compound having at least two oxazoline groups in the molecule.

  The carbodiimide group-containing compound can be obtained, for example, by reacting the isocyanate groups of a polyisocyanate compound with each other, and commercially available products include, for example, carbodilite V-02, caribodilite V-02-L2, carbodilite V. -04, Carbodilite E-01, Carbodilite E-02 (all Nisshinbo Co., Ltd., trade name) and the like.

Examples of the hydrazide group-containing compound include compounds having at least 2, preferably 2 to 10, hydrazide groups represented by —CO—NH—NH ₂ in one molecule, such as oxalic acid dihydrazide, malonic acid dihydrazide, Saturated dicarboxylic acid dihydrazides having 2 to 18 carbon atoms such as glutaric acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide; monoolefinic unsaturated dicarboxylic acids such as maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide Examples include acid dihydrazide; polyhydrazide obtained by reacting a low polymer having a carboxylic acid lower alkyl ester group with hydrazine or hydrazine hydrate.

Examples of the semicarbazide group-containing compound include compounds having at least 2, preferably 2 to 10, semicarbazide groups represented by —NH—CO—NH—NH ₂ in one molecule, such as bissemicarbazide; hexamethylene diisocyanate. And polyisocyanate compounds obtained by reacting N, N-substituted hydrazines such as N, N-dimethylhydrazine and the hydrazines exemplified above with a diisocyanate such as benzene or isophorone diisocyanate or a polyisocyanate compound derived therefrom.

  Furthermore, for the purpose of improving the compoundability in the water-based paint, a surfactant, a solvent showing a tendency to be miscible with water, and the like may be used in the water-based paint composition of the present invention as necessary. Specific examples of surfactants include anions such as aliphatic soaps, rosin acid soaps, alkyl sulfonates, dialkylaryl sulfonates, alkylsulfosuccinates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl aryl sulfates, and the like. Nonionic surfactants such as a reactive surfactant, polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, and polyoxyethylene oxypropylene block copolymer. Examples of the solvent that tends to be miscible with water include propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, isobutanol, butyl glycol, N-methylpyrrolidone, butyl diglycol, and butyl diglycol acetate.

  Further, antioxidants such as hindered phenols, ultraviolet absorbers such as benzotriazole and benzophenone, pigments such as titanium oxide, carbon black, indigo, quinacridone and pearl mica, metal powder pigments such as aluminum, and rheology control agents such as hydroxy A curing accelerator such as ethyl cellulose, urea compound, or microgel, for example, a tin compound, a zinc compound, an amine compound, or the like may be added.

  The water-based coating composition of the present invention is a mixture of a block polyisocyanate composition (A), a carboxyl group-containing polyol (B), a basic composition (C), and, if necessary, the additives described above, A water-based coating composition is prepared by adding a medium containing water as a main component and adjusting the coating viscosity according to the coating method.

Water-based paint compositions prepared in this way are made of materials such as steel, surface-treated steel plates and other metals, plastics, and inorganic materials by methods such as roll coating, curtain flow coating, spray coating, electrostatic coating, and bell coating. It is useful when used as a primer, intermediate coating or top coating, and also for pre-coating metal including anti-rust steel plate, automotive coating, plastic coating, etc., cosmetics, weather resistance, acid resistance, rust resistance, chipping resistance, This is useful for imparting adhesion and the like.
It is also useful as a urethane raw material for adhesives, pressure-sensitive adhesives, elastomers, foams, surface treatment agents and the like.

Below, based on an Example, this invention is demonstrated still in detail. The scope of the present invention is not limited by these examples in any sense.
Below, the measuring method of each characteristic in a manufacture example, an Example, and a comparative example is demonstrated. Hereinafter, “parts” and “%” represent “parts by mass” and “mass%”, respectively, unless otherwise specified.
(Measurement of number average molecular weight)
The number average molecular weight of the polyisocyanate is a polystyrene-based number average molecular weight measured by gel permeation chromatography (hereinafter referred to as GPC) using the following apparatus.
Equipment: Tosoh Corporation HLC-8120GPC (trade name)
Column: Tosoh Corporation TSKgel SuperH1000 (trade name) x 1
TSKgel SuperH2000 (trade name) x 1
TSKgel SuperH3000 (trade name) x 1 Carrier: Tetrahydrofuran Detection method: Differential refractometer The number average molecular weight of the polyol is a polystyrene-based number average molecular weight by GPC measurement described below.
Equipment: Tosoh Corporation HLC-8120GPC (trade name)
Column: Tosoh Corporation TSKgel Super HM-H (trade name) x 2 Carrier: N, N-dimethylformamide Detection method: differential refractometer (measurement of viscosity)
Using an E type viscometer (VISCONIC ED type (trade name) manufactured by Tokimec Co., Ltd.), the measurement was performed at 25 ° C.
(Confirmation of urethane bond, allophanate bond, isocyanurate bond)
The presence of urethane bonds, allophanate bonds and isocyanurate bonds was confirmed by NMR measurement using the following apparatus.
Apparatus: JNM-LA400 (trade name) manufactured by JEOL Ltd.
(PH at the time of coating liquid formulation)
The case where the pH at the time of coating liquid mixing was 7.0-9.0 was set as (circle) and the case where pH was less than 7.0 or exceeded 9.0 was set as x.
(Gel fraction measurement)
After the cured coating film was immersed in acetone at 20 ° C. for 24 hours, the value of the undissolved part mass relative to the mass before immersion was calculated to obtain the gel fraction. The case where the gel fraction was 80% or more was evaluated as ◯, the case where it was 70% or more and less than 80%, and the case where it was less than 70%.

(Gas generation during storage test)
The blended water-based paint composition (the effective NCO group of the block polyisocyanate composition present in the water-based paint composition is 10 mmol) is taken, and then water is added to prepare a 200 g aqueous solution. The adjusted solution is stored at 40 ° C. for 10 days, the amount of gas (carbon dioxide) generated during that period is less than 2 cc, ◎ if 2 cc or more but less than 6 cc, ◯ if 6 cc or more and less than 10 cc, The case of 10 cc or more was rated as x.
(Coating solution pH change before and after storage)
The pH at the initial blending of the water-based coating composition was adjusted to 7.0 to 9.0. When the change in pH of the coating solution after storage at 40 ° C. for 10 days is within ± 0.5, ○, over ± 0.5, Δ within 1.0, × over ± 1.0 It was.

(Production Example 1) (Production of isocyanurate type polyisocyanate)
The inside of a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen blowing tube was purged with nitrogen, charged with 1000 parts of HDI, stirred at 60 ° C., and trimethylbenzylammonium hydroxide as a catalyst: 0 .1 part was added. After 4 hours, when the conversion rate reached 38%, 0.2 part of phosphoric acid was added to stop the reaction.
Thereafter, the reaction solution was filtered, and unreacted HDI monomer was removed by thin film distillation.
The resulting polyisocyanate 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.

(Production Example 2) (Production of HDI urethane bond, allophanate bond-containing isocyanurate type polyisocyanate)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen blowing tube is placed in a nitrogen atmosphere, and 1000 parts of HDI and 22 parts of trimethylolpropane (molecular weight 134), a trihydric alcohol, are added and reacted with stirring. The inside temperature was kept at 90 ° C. for 1 hour to perform urethanization. Thereafter, the temperature of the reaction solution was kept at 60 ° C., an isocyanuration catalyst trimethylbenzylammonium hydroxide was added, and phosphoric acid was added when the conversion rate reached 48% to stop the reaction. Then, after filtering a reaction liquid, unreacted HDI was removed with the thin film distillation apparatus.

  The obtained polyisocyanate had a viscosity at 25 ° C. of 25,000 mPa · s, an isocyanate group content of 19.9% by mass, a number average molecular weight of 1080, and an average number of isocyanate groups of 5.1. Thereafter, the presence of urethane bond, allophanate bond and isocyanurate bond was confirmed by NMR measurement.

(Production Example 3) (Production of HDI, IPDI-based urethane bond, allophanate bond-containing isocyanurate type polyisocyanate)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen blowing tube is placed in a nitrogen atmosphere, 700 parts of HDI, 300 parts of IPDI, polycaprolactone polyester polyol “Placcel 303” (Daicel) Chemical product name: Molecular weight 300) 30 parts were charged, and the temperature in the reactor was maintained at 90 ° C. for 1 hour with stirring to perform urethanization. Thereafter, the reaction liquid temperature was kept at 60 ° C., an isocyanuration catalyst trimethylbenzylammonium hydroxide was added, and phosphoric acid was added when the conversion rate was 42% to stop the reaction. Then, after filtering a reaction liquid, unreacted HDI and IPDI were removed with the thin film distillation apparatus.

  The obtained polyisocyanate had a viscosity at 25 ° C. of 60,000 mPa · s, an isocyanate group content of 18.9% by mass, a number average molecular weight of 900, and an isocyanate group average number of 4.1. Thereafter, the presence of urethane bond, allophanate bond and isocyanurate bond was confirmed by NMR measurement.

(Production Example 4) (Production of Block Polyisocyanate Composition)
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 of the polyisocyanate obtained in Production Example 1, methoxypolyethylene glycol having a number average molecular weight of 400 ( 42.3 parts (corresponding to 20 mol% of isocyanate group in polyisocyanate) and 102.1 parts of diethylene glycol diethyl ether were charged and maintained at 80 ° C. for 6 hours. Thereafter, the temperature of the reaction solution was cooled to 60 ° C., 72.0 parts of diethyl malonate (corresponding to 85 mol% of the isocyanate group in polyisocyanate) and 0.88 part of 28% methanol solution of sodium methylate were added, and maintained for 4 hours. After that, 33.3 parts of n-butanol was added and further maintained for 2 hours. Thereafter, 0.86 part of 2-ethylhexyl acid phosphate was added to obtain a block polyisocyanate composition having a solid concentration of 60% by mass. The physical properties of the resulting block polyisocyanate composition are shown in Table 1.

＊１ （各化合物のモル数）／（ポリイソシアネートのイソシアネート基のモル数）のモル％
＊２ ２−エチルヘキシルアシッドホスフェート（城北化学工業の商品名）
＊３ 表１記載の配合物としての有効ＮＣＯ基質量％
＊４ ＤＥＤＧ：ジエチレングリコールジエチルエーテル
＊５ ユニオックスＭ４００（数平均分子量４００のメトキシポリエチレングリコール：日本油脂株式会社商品名）
＊６ ＤＥＭ：マロン酸ジエチル（Ｒ１：エチル基、Ｒ２：エチル基）
＊７ ＤＭＤＰ：ジプロピレングリコールジメチルエーテル
＊８ ユニオックスＭ５５０（数平均分子量５５０のメトキシポリエチレングリコール：日本油脂株式会社の商品名）
＊９ ＤＭＰ：プロピレングリコールジメチルエーテル
＊１０ ユニオックスＭ１０００（数平均分子量１０００のメトキシポリエチレングリコール：日本油脂株式会社の商品名）
＊１１ ＤＩＰＭ：マロン酸ジイソプロピル（Ｒ１：イソプロピル基、Ｒ２：イソプロピル基）
＊１２ ＶＥＳＴＡＮＡＴ Ｔ１８９０−１００（イソホロンジイソシアネートのイソシアヌレート型ポリイソシアネート：エボニックデグサ社の商品名）
＊１３ ＤＭＤＧ：ジエチレングリコールジメチルエーテル
＊１４ ＭＰＧ−０８１（数平均分子量６８０のメトキシポリエチレングリコール：日本乳化剤株式会社の商品名）
＊１５ ＤＭＭ：マロン酸ジメチル（Ｒ１：メチル基、Ｒ２：メチル基） (Production Example 5-8, Comparative Production Example 1-3) (Production of Block Polyisocyanate Composition)
Manufacture was performed under the same conditions as in Example 1 except that the conditions were changed as shown in Table 1. The physical properties of the resulting block polyisocyanate composition are shown in Table 1.

* 1 mol% of (number of moles of each compound) / (number of moles of isocyanate group of polyisocyanate)
* 2 2-Ethylhexyl acid phosphate (trade name of Johoku Chemical Industry)
* 3 Effective NCO group mass% as a formulation shown in Table 1
* 4 DEDG: Diethylene glycol diethyl ether * 5 UNIOX M400 (methoxypolyethylene glycol having a number average molecular weight of 400: trade name of NOF Corporation)
* 6 DEM: diethyl malonate (R1: ethyl group, R2: ethyl group)
* 7 DMDP: Dipropylene glycol dimethyl ether * 8 UNIOX M550 (methoxypolyethylene glycol with a number average molecular weight of 550: trade name of NOF Corporation)
* 9 DMP: Propylene glycol dimethyl ether * 10 UNIOX M1000 (Methoxypolyethylene glycol with a number average molecular weight of 1000: trade name of NOF Corporation)
* 11 DIPM: Diisopropyl malonate (R1: isopropyl group, R2: isopropyl group)
* 12 VESTANAT T1890-100 (Isocyanurate-type polyisocyanate of isophorone diisocyanate: trade name of Evonik Degussa)
* 13 DMDG: Diethylene glycol dimethyl ether * 14 MPG-081 (methoxypolyethylene glycol having a number average molecular weight of 680: trade name of Nippon Emulsifier Co., Ltd.)
* 15 DMM: dimethyl malonate (R1: methyl group, R2: methyl group)

(Example 1) (Adjustment and evaluation of water-based coating composition)
As a carboxyl group-containing polyol, acrylic emulsion (hydroxyl value per resin 40 mgKOH / g, acid value 13 mgKOH / g per resin, Tg 20 ° C., number average molecular weight 100,000, resin solid content 42% by mass) 100 parts, dimethylethanolamine 0 .22 parts (corresponding to 25 mol% with respect to the carboxyl group of the polyol) and 7.4 parts of the block polyisocyanate composition obtained in Production Example 4 (the molar equivalent A of the blocked isocyanate group of the block polyisocyanate composition and the main agent) In the order of A / B = 0.3) and 24.0 parts of water (adjusted so that the solid content of the paint is 35% by mass) were blended in this order. Furthermore, 1.1 parts of N-ethylmorpholine (corresponding to 100 mol% with respect to the carboxyl group of the polyol) was added, and the pH was measured to be 8.5. The prepared coating solution was allowed to stand at room temperature for 2 hours, and the appearance of the coating solution was observed. After drying, an applicator was applied to a film thickness of 40 μm, baked at 90 ° C. for 30 minutes, and the gel fraction was measured. The results are shown in Table 2.
Further, the pH of the coating solution after storage at 40 ° C. for 10 days was measured.
Further, 147.7 g of the water-based coating composition obtained in Example 1 (corresponding to 10 mmol as a blocked isocyanate group of the blocked polyisocyanate composition) and 52.3 g of water (added so that the total mass becomes 200.0 g) were added. It mix | blended and the aqueous solution of the block polyisocyanate composition was obtained. The amount of gas (carbon dioxide) generated during storage of this aqueous solution at 40 ° C. for 10 days was measured. The results are shown in Table 2.

＊１６ 全塩基性化合物の添加量：ポリオールのカルボキシル基に対する全塩基性化合物の添加量（モル％）
＊１７ アクリルエマルジョン（樹脂固形分４２質量％、媒体：水、樹脂あたりの水酸基価４０ｍｇＫＯＨ／ｇ、樹脂あたりの酸価１３ｍｇＫＯＨ／ｇ Ｔｇ２０℃、数平均分子量１００，０００）
＊１８ ＮＥＭＯ：Ｎ−エチルモルホリン
＊１９ ＤＭＥＡ：ジメチルエタノールアミン
＊２０ ２ＭＩＭ：２−メチルイミダゾール
＊２１ ＴＥＡ：トリエタノールアミン
＊２２ アクリルポリオール（樹脂固形分６０質量％、溶剤：ＤＭＤＧ、樹脂あたりの水酸基価８０ｍｇＫＯＨ／ｇ、樹脂あたりの酸価４７ｍｇＫＯＨ／ｇ、Ｔｇ３０℃、数平均分子量７，４００）
＊２３ ＮＭＭＯ：Ｎ−メチルモルホリン
＊２４ 塗液配合時のｐＨが高くなりすぎたため、貯蔵後塗液ｐＨ変化、ガス発生試験は実施しなかった。 (Example 2-5, Comparative Example 1-3) (Evaluation of water-based coating composition)
The same procedure as in Example 6 was performed except for the conditions shown in Table 2. Table 2 shows the evaluation results of the obtained block polyisocyanate composition.

* 16 Addition amount of all basic compounds: Addition amount of all basic compounds to the carboxyl group of the polyol (mol%)
* 17 Acrylic emulsion (solid content of resin: 42% by mass, medium: water, hydroxyl value per resin: 40 mgKOH / g, acid value per resin: 13 mgKOH / g Tg, 20 ° C., number average molecular weight 100,000)
* 18 NEMO: N-ethylmorpholine * 19 DMEA: dimethylethanolamine * 20 2MIM: 2-methylimidazole * 21 TEA: triethanolamine * 22 Acrylic polyol (resin solid content 60 mass%, solvent: DMDG, hydroxyl group per resin 80 mg KOH / g, acid value per resin 47 mg KOH / g, Tg 30 ° C., number average molecular weight 7,400)
* 23 NMMO: N-methylmorpholine * 24 Since the pH at the time of blending the coating solution became too high, the coating solution pH change after storage and the gas generation test were not performed.

  The water-based coating composition of the present invention can be suitably crosslinked as a water-based coating composition because it can be crosslinked usually at a baking temperature of 100 ° C. or lower and is excellent in storage stability.

Claims (5)

A water-based coating composition comprising the following three components (A) to (C) and having a pH of 7.0 to 9.0 at the time of blending.
(A) a polyisocyanate (a) formed from one or more selected from aliphatic polyisocyanates and alicyclic polyisocyanates; a malonic acid diester (b) represented by formula (I); Block polyisocyanate composition obtained by reacting

(Wherein R ₁ and R ₂ represent an alkyl group having 1 to 8 carbon atoms, a phenyl group or a benzyl group, and R ₁ and R ₂ may be the same or different)
(B) Carboxyl group-containing polyol (C) Basic composition satisfying both of the following (i) and (ii) (i) The basic group is 100 mol% of the carboxyl group of the carboxyl group-containing polyol (B). On the other hand, 30 mol% or more (ii) The basic composition is a weakly basic compound (C1) having an acid dissociation constant (pKa) of 7.0 to 8.5 and a basic compound (C2) having a pKa of more than 8.5 The composition ratio of the weakly basic compound (C1) to the sum of the weakly basic compound (C1) and the basic compound (C2) is 20 mol% or more.   The block polyisocyanate composition (A) is obtained by reacting the polyisocyanate (a) with the malonic acid diester (b) and the active hydrogen-containing hydrophilic compound (c). The water-based paint composition according to claim 1, wherein   The block polyisocyanate composition (A) is based on 100 mol% of the isocyanate group of the polyisocyanate (a), the addition amount of the block agent containing the malonic acid diester (b) as a main component is x mol%, and the activity When the addition amount of the hydrogen-containing hydrophilic compound (c) is y mol%, x + y is 75 to 150, x / (x + y) is 0.50 to 0.98, and y / (x + y) is 0.02. The water-based paint composition according to claim 2, which is ˜0.50.   The active hydrogen-containing hydrophilic compound (c) is a polyethylene glycol compound in which a monoalcohol having 1 to 4 carbon atoms is added to one terminal having a number average molecular weight of 200 to 2000. 4 or 3 The water-based paint composition described in 1. The malonic acid diester (b) is characterized in that R ₁ and R _{2 in the} formula (I) have the same structure and are alkyl groups having 1 to 4 carbon atoms. The water-based coating composition according to any one of the above.