JP2009155409A - Blocked polyisocyanate composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blocked polyisocyanate composition capable of forming a cross-linked coated film even at ≤100°C, and having a good storage stability in the presence of water. <P>SOLUTION: This blocked polyisocyanate composition is obtained by the reaction of (a) one, or two or more polyisocyanate compositions selected from an aliphatic polyisocyanate composition, alicyclic polyisocyanate composition and aromatic polyisocyanate composition with (b) an active methylene compound expressed by formula (I) and (c) a hydrophilic compound having an active hydrogen. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a block polyisocyanate composition excellent in low-temperature curability and storage stability in the presence of water, and an aqueous coating composition using the same.

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 cross-linked by isocyanate groups have a feature that the obtained coating film has very excellent wear resistance, chemical resistance, and stain 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, since these blocked isocyanates generally require a high baking temperature of 140 ° C. or higher, a very large energy cost is required. 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, pyrazole-based blocked isocyanates have been proposed as blocked isocyanates that form a crosslinked coating film at a relatively low temperature. (Patent Documents 1 and 2)
However, pyrazole-based blocked isocyanates also require a baking temperature of about 120 ° C., and further low-temperature curing has been desired.
Furthermore, 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 3 to 6)

In Patent Document 3, water dispersibility is improved by using malonic acid diester and acetoacetate as a blocking agent and further using a nonionic hydrophilic group compound.
In Patent Literature 4, malonic acid diester and / or acetoacetate is used as a blocking agent, and further, storage stability is improved by using an aliphatic / alicyclic diamine and formaldehyde in an embedded form.
In Patent Document 5, malonic acid diester and / or acetoacetate is used as a blocking agent, and 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 6, 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 3 to 6, the decomposition reaction proceeds when water is present, and the malonic acid diester block that can generate carbon dioxide gas, or when water is present, the decomposition reaction proceeds and after storage Since it has an acetoacetate block body in the basic structure that can reduce the curability of the product, carbon dioxide is generated when used as a curing agent for one-component water-based paints, or there is a problem in storage stability, or after storage In some cases, the curability of the resin deteriorated.
Therefore, a blocked isocyanate composition that can form a crosslinked coating film at 100 ° C. or lower, has good storage stability in the presence of water, and can maintain curability after storage has been desired.

Japanese Patent No. 3970926 JP 2000-26570 A 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 block polyisocyanate composition which can form a crosslinked coating film even at 100 degrees C or less, and has the favorable storage stability in water presence.

As a result of intensive studies, the present inventors have surprisingly found that a blocked polyisocyanate composition having an active methylene-based compound having a specific structure as a blocking agent can form a crosslinked coating film at 100 ° C. or lower, and water. The present invention has been completed based on the knowledge that the storage stability in the presence is excellent.
That is, the present invention
1. (A) one or more polyisocyanate compositions selected from an aliphatic polyisocyanate composition, an alicyclic polyisocyanate composition, and an aromatic polyisocyanate composition;
(B) A block polyisocyanate composition obtained by reaction of an active methylene compound represented by formula (I) and (c) a hydrophilic compound having active hydrogen.

（式中Ｒ_１は水素または炭素数１〜８個のアルキル基、Ｒ_２は炭素数１〜８個のアルキル基、フェニル基またはベンジル基、Ｒ_３は炭素数１〜８個のアルキル基、フェニル基またはベンジル基）

(Wherein R ₁ is hydrogen or an alkyl group having 1 to 8 carbon atoms, R ₂ is an alkyl group having 1 to 8 carbon atoms, a phenyl group or a benzyl group, R ₃ is an alkyl group having 1 to 8 carbon atoms, Phenyl or benzyl)

2. (A) one or more polyisocyanate compositions selected from an aliphatic polyisocyanate composition, an alicyclic polyisocyanate composition, and an aromatic polyisocyanate composition;
(B) 50 to 98 mole equivalents of the active methylene compound represented by the formula (I) with respect to the molar equivalent of the isocyanate group, and (c) 2 hydrophilic compounds having active hydrogen with respect to the molar equivalent of the isocyanate group. It is obtained by a reaction of ˜50 molar equivalent%. The block polyisocyanate composition described.
3. _1. R _{1 in} formula (I) is an alkyl group having 1 to 4 carbon atoms. Or 2. The block polyisocyanate composition described in 1.
4). _1. R ₁ and R _{2 in} formula (I) are both methyl groups. ~ 3. The block polyisocyanate composition according to any one of the above.
5. 1. R _{3 in} formula (I) is a methyl group or an ethyl group. ~ 4. The block polyisocyanate composition according to any one of the above.
6. A monohydric alcohol compound is contained. ~ 5. The block polyisocyanate composition according to any one of the above.
7). 1. The hydrophilic compound having active hydrogen is a polyethylene glycol compound having at least three consecutive ethylene oxide groups and / or monohydroxycarboxylic acid, dihydroxycarboxylic acid or derivatives thereof. ~ 6. The block polyisocyanate composition according to any one of the above.
8). The above-mentioned 1 characterized in that the hydrophilic compound having active hydrogen is a polyethylene glycol compound and / or monohydroxycarboxylic acid 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. . ~ 7. The block polyisocyanate composition according to any one of the above.
9. Above 1. ~ 8. The block polyisocyanate composition according to any one of the above and an aqueous coating composition containing a polyol as a main component.

  The block polyisocyanate composition of the present invention provides a block polyisocyanate composition that can form a crosslinked coating film at 100 ° C. or lower, has good storage stability in the presence of water, and retains curability after storage. can do.

Hereinafter, the present invention will be described in detail with a focus on preferred embodiments.
The polyisocyanate composition which is a precursor of the block polyisocyanate composition of the present invention is a polyisocyanate composition selected from an aliphatic polyisocyanate composition, an alicyclic polyisocyanate composition, and an aromatic polyisocyanate composition. It is. These may be used alone or in combination of two or more.
The aliphatic polyisocyanate composition includes a polyisocyanate composition derived from an aliphatic diisocyanate, lysine triisocyanate (hereinafter referred to as LTI), 4-isocyanatomethyl-1,8-octamethylene diisocyanate (trimer triisocyanate: Examples thereof include TTI), bis (2-isocyanatoethyl) 2-isocyanatoglutarate (glutamate triisocyanate: hereinafter referred to as GTI), or polyisocyanate compositions derived from these triisocyanates.

  As the aliphatic diisocyanate used in the aliphatic polyisocyanate composition of 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 composition of the present invention is derived from the alicyclic diisocyanate shown below.
As the alicyclic diisocyanate used in the alicyclic polyisocyanate composition of 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 composition is derived from the aromatic diisocyanate shown below.
Examples of the aromatic diisocyanate used in the aromatic polyisocyanate composition of the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, and the like. Is mentioned. Aromatic diisocyanates may be used alone or in combination of two or more.
Among these polyisocyanate compositions, aliphatic polyisocyanate compositions and / or alicyclic polyisocyanate compositions are preferred because of their excellent weather resistance. Furthermore, among the aliphatic polyisocyanate compositions, aliphatic polyisocyanate compositions derived from aliphatic diisocyanates are preferred.

The average number of isocyanate groups in the polyisocyanate composition which is a precursor of the block polyisocyanate composition of the present invention is 2.0 to 20. 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 less than 2, the crosslinkability may decrease, and the desired coating film properties may not be obtained. On the other hand, if it exceeds 20, the cohesive force becomes too high, and a smooth coating film is obtained. There may not be.

The average number of isosocyanate groups is determined by the following formula (II).

  Polyisocyanate compositions other than triisocyanates such as LTI, TTI, and GTI used in the present invention or derivatives thereof include biuret bonds, urea bonds, isocyanurate bonds, uretdione bonds, urethane bonds, allophanate bonds, and oxadiazine trione bonds. It is a 2-20 mer oligomer of diisocyanate produced by forming etc. A polyisocyanate composition 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. Thereafter, unreacted diisocyanate can be removed and purified. The polyisocyanate composition having an isocyanurate bond is subjected to, for example, a cyclic trimerization reaction with a catalyst or the like, and when the conversion rate is about 5 to about 80% by mass, the reaction is stopped, and unreacted diisocyanate is removed and purified. can get. In this case, 1 to 6 valent alcohol compounds can be used in combination.

The polyisocyanate composition having a urethane bond is, for example, a divalent to hexavalent alcohol compound such as trimethylolpropane and a diisocyanate having a molar ratio of hydroxyl group of the alcohol compound / isocyanate group of the diisocyanate of about 1/2 to about 1. After the reaction at / 100, unreacted diisocyanate can be removed and purified.
Derivatives of LTI, TTI, and GTI are also produced in the same manner as polyisocyanate compositions derived from diisocyanates, but in the case of these triisocyanates, removal and purification of unreacted triisocyanates is not always necessary.
The block polyisocyanate composition of the present invention is obtained by reacting an isocyanate group of a polyisocyanate composition as a precursor with a hydrophilic compound having a blocking agent and active hydrogen.

  As a method for producing a blocked polyisocyanate composition of the present invention, the reaction of isocyanate groups with a blocking agent of the polyisocyanate composition, or to the reaction of the hydrophilic compound having an isocyanate group and an active hydrogen can be performed at the same time, either in advance After performing such a reaction, a second reaction can be performed. Among these, it is preferable to carry out the reaction between the isocyanate group and the hydrophilic compound having active hydrogen first, and after that, the reaction between the isocyanate group and the blocking agent is carried out.

  In the block polyisocyanate composition of the present invention, all isocyanate groups of the polyisocyanate composition may be reacted with a blocking agent or a hydrophilic compound having an active hydrogen group, and depending on the purpose, a part of the isocyanate groups may be reacted. You can leave it. When all isocyanate groups are reacted, ((number of moles of blocking agent) + (number of moles of active hydrogen of the hydrophilic compound having active hydrogen groups)) / (number of moles of isocyanate groups in the polyisocyanate composition) is 1.0 to 1.5 is preferable.

  It is preferable that the addition amount of a blocking agent is 50-98 molar equivalent% with respect to the molar equivalent of the isocyanate group in the polyisocyanate composition which is a precursor. As a lower limit, 60 molar equivalent% is more preferable, More preferably, it is 70 molar equivalent%. When the addition amount is less than 50 mole equivalent%, the crosslinking density is lowered, the desired film properties may not be obtained, or the water resistance of the obtained coating film may be lowered, and the addition rate is 98 mole equivalent%. If it exceeds 1, there is a tendency that sufficient water dispersibility cannot be obtained.

The blocking agent used in the present invention is an active methylene compound represented by Formula I. Specifically, R ₁ is hydrogen or an alkyl group having 1 to 8 carbon atoms. When the alkyl group has 9 or more carbon atoms, the latent NCO mass% is decreased, and compatibility with the main agent and the like when used as a coating material may be decreased. Among them, an alkyl group having 1 to 4 carbon atoms is preferable, a methyl group or an ethyl group is more preferable, and a methyl group is most preferable. R ₂ is an alkyl group having 1 to 8 carbon atoms, a phenyl group or a benzyl group. When the alkyl group has 9 or more carbon atoms, the latent NCO mass% is decreased, and compatibility with the main agent and the like when used as a coating material may be decreased. Among them, an alkyl group having 1 to 4 carbon atoms is preferable, a methyl group or an ethyl group is more preferable, and a methyl group is most preferable. R ₃ is an alkyl group having 1 to 8 carbon atoms, a phenyl group or a benzyl group. When the alkyl group has 9 or more carbon atoms, the latent NCO mass% is decreased, and compatibility with the main agent and the like when used as a coating material may be decreased. Among these, a C1-C8 alkyl group is preferable, More preferably, it is a C1-C4 alkyl group, More preferably, it is a methyl group or an ethyl group.
The latent NCO% by mass is the% by mass of isocyanate groups potentially present relative to the total mass of the blocked polyisocyanate composition.

Specific examples of the blocking agent used in the present invention include isobutanoyl acetate, n-propanoyl acetate, n-butanoyl acetate, n-pentanoyl acetate, n-hexanoyl acetate, 2-ethylheptanoyl acetate, and the like. It is done. Among these, isobutanoyl acetate, n-propanoyl acetate, and n-pentanoyl acetate are preferable, and isobutanoyl acetate is more preferable. More specifically, isobutanoyl acetate includes methyl isobutanoyl acetate, ethyl isobutanoyl acetate, isobutanoyl acetate n-propyl, isobutanoyl acetate isopropyl, isobutanoyl acetate n-butyl, isobutanoyl acetate isobutyl, isobutanoyl acetate t-butyl, isobutanoyl acetate n- Examples include pentyl, isobutanoyl acetate n-hexyl, isobutanoyl acetate 2-ethylhexyl, phenyl isobutanoyl acetate, and isobutanoyl acetate benzyl. Among these, methyl isobutanoyl acetate, ethyl isobutanoyl acetate, isopropyl isobutanoyl acetate, n-butyl isobutanoyl acetate, and t-butyl isobutanoyl acetate are more preferable, and methyl isobutanoyl acetate and ethyl isobutanoyl acetate are more preferable. Examples of n-propanoyl acetate include n-propanoyl acetate, n-propanoyl acetate, n-propanoyl acetate n-propyl, n-propanoyl acetate isopropyl, n-propanoyl acetate n-butyl, n-propanoyl acetate isobutyl, n-propanoyl acetate Examples include t-butyl propanoyl acetate, n-propanoyl acetate n-pentyl, n-propanoyl acetate n-hexyl, n-propanoyl acetate 2-ethylhexyl, n-propanoyl acetate phenyl, n-propanoyl acetate benzyl and the like. Among them, n-propanoyl methyl acetate, n-propanoyl ethyl acetate, n-propanoyl acetate isopropyl, n-propanoyl acetate n-butyl, n-propanoyl acetate t-butyl are more preferable, and more preferably, n-propanoyl methyl acetate, n-propanoyl ethyl acetate. Examples of n-butanoyl acetate include methyl n-butanoyl acetate, ethyl n-butanoyl acetate, n-butanoyl acetate n-propyl, n-butanoyl acetate isopropyl, n-butanoyl acetate n-butyl, n-butanoyl acetate isobutyl, n- Examples include t-butyl butanoyl acetate, n-butanoyl acetate n-pentyl, n-butanoyl acetate n-hexyl, n-butanoyl acetate 2-ethylhexyl, n-butanoyl acetate phenyl, and n-butanoyl acetate benzyl. Among these, n-butanoyl methyl acetate, n-butanoyl ethyl acetate, n-butanoyl acetate isopropyl, n-butanoyl acetate n-butyl, n-butanoyl acetate t-butyl are more preferable, and more preferably, n-butanoyl methyl acetate, n-Butanoyl ethyl acetate. Examples of n-pentanoyl acetate include n-pentanoyl acetate methyl, n-pentanoyl acetate, n-pentanoyl acetate n-propyl, n-pentanoyl acetate isopropyl, n-pentanoyl acetate n-butyl, n-pentanoyl acetate isobutyl, n- Examples include t-butyl pentanoyl acetate, n-pentanoyl acetate n-pentyl, n-pentanoyl acetate n-hexyl, n-pentanoyl acetate 2-ethylhexyl, n-pentanoyl acetate phenyl, and n-pentanoyl acetate benzyl. Among them, n-pentanoyl methyl acetate, n-pentanoyl ethyl acetate, n-pentanoyl acetate isopropyl, n-pentanoyl acetate n-butyl, n-pentanoyl acetate t-butyl are more preferable, and n-pentanoyl acetate methyl is more preferable. , N-pentanoyl ethyl acetate. Examples of n-hexanoyl acetate include n-hexanoyl acetate methyl, n-hexanoyl ethyl acetate, n-hexanoyl acetate n-propyl, n-hexanoyl acetate isopropyl, n-hexanoyl acetate n-butyl, n-hexanoyl acetate isobutyl, n- Examples include t-butyl hexanoyl acetate, n-hexanoyl acetate n-pentyl, n-hexanoyl acetate n-hexyl, n-hexanoyl acetate 2-ethylhexyl, n-hexanoyl acetate phenyl, and n-hexanoyl acetate benzyl. Among them, n-hexanoyl methyl acetate, n-hexanoyl ethyl acetate, n-hexanoyl acetate isopropyl, n-hexanoyl acetate n-butyl, n-hexanoyl acetate t-butyl are more preferable, and more preferably n-hexanoyl acetate methyl, n-Hexanoyl ethyl acetate. Examples of 2-ethylheptanoyl acetate include methyl 2-ethylheptanoyl acetate, ethyl 2-ethylheptanoyl acetate, n-propyl 2-ethylheptanoyl acetate, isopropyl 2-ethylheptanoyl acetate, and 2-ethylheptanoyl acetate. n-butyl, 2-ethylheptanoyl acetate isobutyl, 2-ethylheptanoyl acetate t-butyl, 2-ethylheptanoyl acetate n-pentyl, 2-ethylheptanoyl acetate n-hexyl, 2-ethylheptanoyl acetate 2- Examples include ethylhexyl, phenyl 2-ethylheptanoyl acetate, and benzyl 2-ethylheptanoyl acetate. Among them, 2-ethylheptanoyl methyl acetate, 2-ethylheptanoyl ethyl acetate, 2-ethylheptanoyl acetate isopropyl, 2-ethylheptanoyl acetate n-butyl, 2-ethylheptanoyl acetate t-butyl are more preferable, More preferred are methyl 2-ethylheptanoyl acetate and ethyl 2-ethylheptanoyl acetate.
In the present invention, the above blocking agents can be used alone or in combination of two or more.

Moreover, the block polyisocyanate composition of the present invention is an existing blocking agent, for example,
Active methylene-based, oxime-based, pyrazole-based blocking agents and the like can also be used in combination during the blocking reaction. The existing blocking agents used in combination may be used alone or in combination of two or more.
Examples of the active methylene-based blocking agent include dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone. Among these, dimethyl malonate and diethyl malonate are preferable because they are excellent in low-temperature curability.
Examples of the oxime blocking agent include formal oxime, acetoald oxime, acetone oxime, methyl ethyl ketoxime, and cyclohexanone oxime.
Examples of the pyrazole-based blocking agent include pyrazole, 3-methylpyrazole, and 3,5-dimethylpyrazole.

In addition, the block polyisocyanate composition of the present invention may be used alone or in combination with a block polyisocyanate composition derived from two or more types of block agents selected from active methylene-based, oxime-based and pyrazole-based blocking agents. it can.
The reaction between the polyisocyanate composition and the blocking agent can be performed 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.

In the block reaction, a reaction catalyst can be used. 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) Trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, triethylhydroxy Hydroxyalkylammonium hydroxides such as ethylammonium, etc. Organic weak acid salts such as acetic acid and capric acid (3) Alkyl metal salts such as 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) Tributylphosphine There are phosphorus compounds and the like, 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 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.

The block polyisocyanate composition in the present invention is obtained by reacting an isocyanate group of a polyisocyanate composition as a precursor with a hydrophilic compound having active hydrogen in order to improve the compoundability in a water-based paint.
The addition amount of the hydrophilic compound having active hydrogen is preferably 2 to 50 mol equivalent% with respect to the molar equivalent of the isocyanate group in the polyisocyanate composition as a precursor, based on the number of moles of active hydrogen. As an upper limit, 40 molar equivalent% is more preferable, More preferably, it is 35 molar equivalent%. When the addition amount is less than 2 mol equivalent%, sufficient water dispersibility tends to be not obtained, and when the addition amount exceeds 50 mol equivalent%, the crosslinking density decreases, and the desired coating film properties are obtained. In some cases, the water resistance of the obtained coating film may not be obtained or may be deteriorated.

The hydrophilic compound having active hydrogen used in the block polyisocyanate composition of the present invention is selected from nonionic hydrophilic compounds, anionic hydrophilic compounds, and cationic hydrophilic compounds. These hydrophilic compounds may be used alone or in combination of two or more.
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. When the lower limit of the number average molecular weight is less than 200, sufficient water dispersibility may not be obtained, and when the upper limit exceeds 2000, physical properties of the coating such as water resistance after baking may be deteriorated.

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

  As such polyethylene glycol compounds, monoalkoxy polyethylene glycol, polyethylene glycol or triol, so-called pluronic type polypropylene glycol or triol obtained by addition polymerization of ethylene oxide at the end of polypropylene glycol, polyoxypropylene polyoxyethylene copolymer 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 & Fat Co., Ltd. UNIOX M400, 550, 1000, 2000 is mentioned.
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 using a carboxylic 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.

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. Examples of the neutralizing agent include organic acids such as acetic acid, propionic acid, butanoic acid, and 2-ethylhexanoic acid.

In the present invention, the block polyisocyanate composition using the active methylene compound represented by the formula (I) as a blocking agent is excellent in low-temperature curability as compared with acetoacetate, and compared with malonic acid diester. The result of excellent storage stability in the presence of water (the amount of carbon dioxide generated during storage was small) was a surprising result.
Further, depending on the purpose of improving the compoundability in the water-based paint, a surfactant, a solvent showing a miscibility tendency with respect to water, or the like may be used. Specific examples of the surfactant include anions such as aliphatic soap, rosin acid soap, alkyl sulfonate, dialkyl aryl sulfonate, alkyl sulfosuccinate, polyoxyethylene alkyl sulfate, polyoxyethylene alkyl aryl sulfate, etc. 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, isobutanol, butyl glycol, N-methylpyrrolidone, butyl diglycol, and butyl diglycol acetate.

In the present invention, it is preferable to include a monohydric alcohol compound in order to improve storage stability when blended with a polyol. 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.

The block polyisocyanate composition thus adjusted is blended with a polyol described later to form a main constituent of the aqueous coating composition.
The polyol used in the present invention can be used without particular limitation as long as it is used as a water-based paint, and may be finally dispersed in water at least, and is a water-soluble polyol having a hydrophilic group in the polyol skeleton. It may be a water-dispersible polyol, a partly water-soluble, a partly water-dispersible polyol, or an externally forced emulsification type using a surfactant. Good.

Examples of the polyol include polyester polyol, acrylic polyol, polyether polyol, polyolefin polyol, fluorine polyol, and polycarbonate polyol.
As the polyester polyol, for example, a dibasic acid 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 a mixture thereof, Polyester polyol obtained by a condensation reaction with a single or mixture of polyhydric alcohols selected from the group such as ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, glycerin and the like, and ε- using polyhydric alcohol, for example And polycaprolactones obtained by ring-opening polymerization of caprolactone.

Acrylic polyol is a co-solution polymerization or emulsification 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. It is obtained by copolymerizing by polymerization.
Examples of the ethylenically unsaturated bond-containing monomer having a hydroxyl group include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate. It is done. Preferred are hydroxyethyl acrylate and hydroxyethyl methacrylate.

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

Polyether polyols include, for example, ethylene oxide, propylene oxide, a single or mixture of polyvalent hydroxy compounds, using, for example, hydroxides such as lithium, sodium and potassium, strong basic catalysts such as alcoholates and alkylamines. Polyether polyols obtained by adding a single or mixture of alkylene oxides such as butylene oxide, cyclohexene oxide and styrene oxide, polyether polyols obtained by reacting alkylene oxide with a polyfunctional compound such as ethylenediamine, and So-called polymer polyols obtained by polymerizing acrylamide or the like using these polyethers as a medium are included.

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

Examples of the polyolefin polyol include polybutadiene having two 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 less than 2, the resulting coating film may have a reduced crosslinking density.
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.

Polycarbonate polyols include polyalkylenes such as dialkyl carbonates such as dimethyl carbonate, alkylene carbonates such as ethylene carbonate, low molecular carbonate compounds such as diaryl carbonates such as diphenyl carbonate, and low molecular polyols used in the aforementioned polyester polyols. What is obtained is mentioned.
The hydroxyl value of the polyol is preferably 10 to 300 mg KOH / resin g. When the hydroxyl value is less than 10 mgKOH / resin g, the crosslinking density decreases, and the physical properties intended by the present invention cannot always be achieved sufficiently. When the hydroxyl value exceeds 300 mgKOH / resin g, In some cases, the crosslink density increases and the mechanical properties of the coating film decrease.
Preferred polyols are acrylic polyols and polyester polyols.

The blending method of the block polyisocyanate composition and the polyol may be such that the block polyisocyanate composition is mixed and dispersed as it is in the polyol, or once the block polyisocyanate composition is blended with water and then mixed with the polyol. Good. Moreover, the equivalent ratio of the blocked isocyanate group to the hydroxyl group of the polyol is usually set to 10: 1 to 1:10 in terms of solid content of 100% by mass.
Where necessary, antioxidants such as hindered phenols, ultraviolet absorbers such as benzotriazole and benzophenone, pigments such as titanium oxide, carbon black, indigo, quinacridone, pearl mica, metal powder pigments such as aluminum, etc. Rheology control agents such as hydroxyethyl cellulose, urea compounds, and microgels, and curing accelerators such as tin compounds, zinc compounds, and amine compounds may be added.
Usually, a polyol, a hardening | curing agent, an additive, etc. are mixed, the medium which has water as a main component is added, and it becomes an aqueous coating composition by adjusting to the coating-material viscosity according to a coating method.

  The water-based paint prepared in this way is used as a primer for materials such as steel, surface-treated steel and other metals and plastics, and inorganic materials by methods such as roll coating, curtain flow coating, spray coating, electrostatic coating, and bell coating. It is also useful as an intermediate coating or top coating, and is also useful for imparting cosmetic properties, weather resistance, acid resistance, rust resistance, chipping resistance, etc. to pre-coated metals including rust-proof steel sheets, automobile coating, and plastic coating. is there. 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.
(Measurement of number average molecular weight)
The number average molecular weight of the polyisocyanate composition 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 measured by GPC measurement described below.
Equipment: Tosoh Corporation HLC-8120GPC (trade name)
Column: Tosoh Corporation TSKgel SuperHM-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.

(Gel fraction)
After the cured coating film was immersed in acetone at 23 ° C. for 24 hours, the value of the undissolved part mass relative to the mass before immersion was calculated. 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%.
(Gel fraction retention after storage)
The gel fraction after storage is ◯ when the gel fraction after storage / initial gel fraction = 0.9 or more, Δ when 0.8 or less and less than 0.9, and × when less than 0.8. did.

(Appearance of coating liquid)
The condition after blending the coating solution was observed with the naked eye. When there is no abnormality such as separation or sedimentation in the emulsified, dispersed or dissolved state, it is described as good, and when there is an abnormality, the state is described.
(Gas generation during storage test)
When the amount of gas (carbon dioxide) generated during storage at 40 ° C. for 10 days is less than 10 cc,
The case of 10 cc or more and less than 20 cc is indicated by Δ, and the case of 20 cc or more is indicated by ×.

(Production Example 1) (Production of isocyanurate type polyisocyanate composition)
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 g of HDI, and stirred at 60 ° C., tetramethylammonium caprate as a catalyst: 0.1 g Was added. After 4 hours, when the refractive index of the reaction solution reached 1.4680 (conversion rate was 38%), 0.2 g 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 urethane bond, allophanate bond-containing isocyanurate type polyisocyanate composition)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen blowing tube was placed in a nitrogen atmosphere, 1000 parts of HDI, polycaprolactone polyester polyol “Placcel 303” (trade name of Daicel Chemical) 50 parts of a molecular weight of 300) was charged, and the temperature in the reactor was kept at 90 ° C. for 1 hour with stirring to perform urethanization. The refractive index at this time was 1.4530. Thereafter, the reaction liquid temperature was kept at 60 ° C., an isocyanurate-forming catalyst tetramethylammonium capriate was added, and phosphoric acid was added when the refractive index reached 1.4735 (conversion rate was 54%) to stop the reaction. Then, after filtering a reaction liquid, unreacted HDI was removed with the thin film distillation apparatus.
The resulting polyisocyanate had a viscosity at 25 ° C. of 9500 mPa · s, an isocyanate group content of 19.2% by mass, a number average molecular weight of 1100, and an isocyanate group average number of 5.1. Thereafter, the presence of urethane bond, allophanate bond and isocyanurate bond was confirmed by NMR measurement.

(Example 1) (Production of block polyisocyanate composition)
A 4-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel is placed in a nitrogen atmosphere, and 100 parts of the polyisocyanate composition obtained in Production Example 1, methoxypolyethylene having a number average molecular weight of 400 42.3 parts of glycol (trade name “Uniox M400” of Japanese fats and oils) (corresponding to 20 molar equivalents of the isocyanate group in the polyisocyanate composition) and 27.6 parts of propylene glycol monomethyl ether acetate were charged at 7O 0 C at 7O 0 C Held for hours. Thereafter, the temperature of the reaction solution was kept at 60 ° C., and 64.0 parts of methyl isobutanoyl acetate (corresponding to 84 mole equivalent% of isocyanate groups in the polyisocyanate composition) and 0.67 part of 28% methanol solution of sodium methylate were added. Held for 4 hours. 55.2 parts of n-butanol was added, the reaction solution temperature was maintained at 80 ° C. for 2 hours, and then 0.66 part of 2-ethylhexyl acid phosphate was added. As a result of measuring the infrared spectrum of the reaction solution, the isocyanate group disappeared and a block polyisocyanate composition having a solid content of 70% by mass was obtained. The physical properties of the resulting block polyisocyanate composition are shown in Table 1.

(Example 2-11, Comparative example 1-5)
The procedure was the same as in Example 1 except that it was shown in Table 1. The physical properties of the resulting block polyisocyanate composition are shown in Table 1.

(Application Example 1) (Evaluation of Block Polyisocyanate Composition)
100 parts of acrylic emulsion (hydroxyl value 40 mg KOH / resin g, Tg 20 ° C., number average molecular weight 170,000, solid content 42% by mass) and 15 parts of the block polyisocyanate composition obtained in Example 1 (main ingredient and block poly) The weight per solid content of the isocyanate composition was blended at 100: 25), and 16 parts of water were blended. (Adjusted so that the solid content of the paint was 40% by mass) The prepared coating solution was dried and then applied with an applicator to a film thickness of 40 μm, baked at 90 ° C. for 30 minutes, and the initial gel fraction was measured. The results are shown in Table 2.
After blending this paint, it was stored at 40 ° C. for 10 days, and after storage, it was coated in the same manner as described above, and the gel fraction was measured. The results are shown in Table 2.

(Application Example 2-11, Application Comparative Example 1-5) (Evaluation of Block Polyisocyanate Composition)
The procedure was the same as in Application Example 1 except that it was shown in Table 2. Table 2 shows the evaluation results of the obtained block polyisocyanate composition.

(Application Example 12) (Aqueous solution stability of block polyisocyanate composition)
20.7 g of the block polyisocyanate composition obtained in Example 1 (corresponding to 30 mmol as a latent NCO group) and 179.3 g of water were blended to obtain an aqueous solution of the block polyisocyanate composition. 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 3.

(Application Examples 13-22, Application Comparative Example 6) (Aqueous solution stability of block polyisocyanate composition)
The procedure was the same as in Application Example 12 except that it was shown in Table 3. The amount of gas generated during storage of the aqueous solution of the obtained block polyisocyanate composition was measured. The results are shown in Table 3.
The block polyisocyanate composition of the present invention can form a crosslinked coating film even at 100 ° C. or less, and has good storage stability in the presence of water, according to Examples, Comparative Examples, Application Examples, and Application Comparative Examples. It was confirmed that it was suitable as a curing agent for liquid water-based paints.

  The block polyisocyanate composition obtained by the reaction of the polyisocyanate composition, the specific active methylene compound, and the hydrophilic compound having active hydrogen can form a cross-linked coating at 100 ° C. or lower, and is stored in the presence of water. The stability is good and the curability after storage can be maintained, so that it can be suitably used for an aqueous coating composition.

Claims (9)

(A) one or more polyisocyanate compositions selected from an aliphatic polyisocyanate composition, an alicyclic polyisocyanate composition, and an aromatic polyisocyanate composition;
(B) A block polyisocyanate composition obtained by reaction of an active methylene compound represented by formula (I) and (c) a hydrophilic compound having active hydrogen.

(Wherein R ₁ is hydrogen or an alkyl group having 1 to 8 carbon atoms, R ₂ is an alkyl group having 1 to 8 carbon atoms, a phenyl group or a benzyl group, R ₃ is an alkyl group having 1 to 8 carbon atoms, Phenyl or benzyl) (A) one or more polyisocyanate compositions selected from an aliphatic polyisocyanate composition, an alicyclic polyisocyanate composition, and an aromatic polyisocyanate composition;
(B) 50 to 98 mole equivalents of the active methylene compound represented by the formula (I) with respect to the molar equivalent of the isocyanate group, and (c) 2 hydrophilic compounds having active hydrogen with respect to the molar equivalent of the isocyanate group. The block polyisocyanate composition according to claim 1, which is obtained by a reaction of ˜50 mole equivalent%. The block polyisocyanate composition according to claim 1 or 2, wherein R _{1 in the} formula (I) is an alkyl group having 1 to 4 carbon atoms. The block polyisocyanate composition according to any one of claims 1 to 3, wherein R ₁ and R _{2 in} the formula (I) are both methyl groups. The block polyisocyanate composition according to any one of claims 1 to 4, wherein R _{3 in the} formula (I) is a methyl group or an ethyl group.   The block polyisocyanate composition according to any one of claims 1 to 5, comprising a monohydric alcohol compound.   The hydrophilic compound having active hydrogen is a polyethylene glycol compound having at least three consecutive ethylene oxide groups and / or a monohydroxycarboxylic acid, a dihydroxycarboxylic acid, or a derivative thereof. The block polyisocyanate composition according to any one of the above. The hydrophilic compound having active hydrogen is a polyethylene glycol compound and / or monohydroxycarboxylic acid in which a monoalcohol having 1 to 4 carbon atoms is added to one end of a number average molecular weight of 200 to 2000. The block polyisocyanate composition in any one of 1-7.   The water-based coating composition which has as a main component the block polyisocyanate composition and polyol in any one of Claims 1-8.