JP2003155322A - Carboxy-containing water-based blocked polyisocyanate and water-based coating composition using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based blocked polyisocyanate composition having low-temperature curing properties, being a curing agent providing a coated film of a urethane coating material, having good film properties such as impact resistance and weather resistance, and obtained by covering a carboxy group into a hydrophilic group. SOLUTION: This water-based blocked polyisocyanate is obtained by using a polyisocyanate derived from a precursor derived from an aliphatic or alicyclic diisocyanate, and satisfying the following all conditions (a), and satisfies the following all conditions (b): conditions (a): 1. having 4.5-20 average number of isocyanato groups; 2. having 3,000-100,000 mPa.s viscosity at 25 deg.C; 3. having 1,000-50,000 number average molecular weight; and 4.2-23 wt.% concentration of the isocyanato group; and conditions (b): 1. containing a blocked isocyanato group and a carboxy group in one molecule; 2. having 10-100 mgKOH/g acid value per resin; 3. having 3.5-19 average number of the blocked isocyanato groups; and 4. having 1.8-20 wt.% concentration of the blocked isocyanato groups.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aqueous block polyisocyanate having excellent self-emulsifying property and an aqueous coating composition using the same.

[0002]

2. Description of the Related Art In recent years, water-based paints have been attracting attention from the viewpoints of global environment, safety and hygiene. From building exteriors to industrial products, it has come to be used for industrial paints such as food cans and coil coatings. Further, there are many proposals for a one-component paint for automobiles, which requires high quality such as weather resistance, chemical resistance, and impact resistance, and is disclosed in JP-A-56-157358.
Issue, JP-A-63-175079, JP-A-63-1
Aqueous paints are disclosed in, for example, No. 93968. Most of the curing agents used here are alkyl etherified melamine resins alone. A coating film formed by using a melamine-based resin such as an alkyl etherified melamine resin as a curing agent has excellent physical properties such as hardness and adhesiveness, but lacks flexibility such as impact resistance.

Further, a coating film obtained from urethane-based urethane-based coating composition has very excellent impact resistance, abrasion resistance, and
In addition to having chemical resistance and stain resistance, by using non-yellowing polyisocyanate made from aliphatic / alicyclic diisocyanate as a raw material as an isocyanate component, the weather resistance is further excellent and its demand is increasing. There is. Therefore, water-based urethane paints that form urethane bonds and crosslink are being actively developed. When a one-liquid type is required for line paints and the like, polyisocyanate, which is usually a curing agent, has its isocyanate group blocked with a blocking agent and is used as a blocked polyisocyanate.

As a technique for making block polyisocyanates aqueous, for example, in Japanese Patent Laid-Open No. 52-59657, a surfactant is used to make block polyisocyanates aqueous. Japanese Patent Laid-Open No. 56-151753 uses polyethylene oxide containing a higher fatty acid having 7 to 26 carbon atoms and blocks the isocyanate group of polyisocyanate with sodium bisulfite to make the blocked polyisocyanate aqueous. There is. Japanese Unexamined Patent Publication No. 61-31422 discloses a technique of reacting a polyisocyanate with a specific polyoxyethylene which is a hydrophilic group to prevent elution of a hydrophilic component and making it aqueous by using a high-speed stirring group or the like.

A technique for making a block of a polyisocyanate having a heat-resistant isocyanurate structure aqueous is disclosed in JP-A-62-151419 and JP-A-2-3465.
It is disclosed in the publication. In JP-A-62-151419, a polyoxyethylene group is added to a part of polyisocyanate, and a water-soluble polymer compound such as polyethylene glycol or a copolymer of ethylene oxide and propylene oxide is mixed. In JP-A-2-3465, hydrophilicity is imparted by hydroxycarboxylic acid.

However, these aqueous blocked polyisocyanates have a low average number of isocyanate groups in the precursor polyisocyanate, and since a part of the isocyanate groups are used for introducing hydrophilic groups, the average number of blocked isocyanate groups is higher. descend. Therefore, its cross-linking property is low, high temperature baking is required to form a cross-linked coating film, and the cross-linking density of the formed coating film is low, which limits its use in automobile line coating.

As an improved technique, the present inventor has previously made the average number of isocyanate groups extremely high to exhibit low-temperature curability, and thus, JP-A-10-231347 and JP-A-11-100.
No. 425 and Japanese Patent Laid-Open No. 2001-139879 are proposed. These are aqueous block polyisocyanates having nonionic hydrophilic groups. Blocked isocyanates do not disperse in water. Therefore, it must be dispersed in water in some way. If you decrease the amount of nonion,
Water dispersion is reduced and blocked isocyanate does not disperse in water. Nonionic hydrophilic group is an effective means for making water-soluble, but if the amount of nonion is increased to increase the hydrophilicity, the water resistance of the coating film formed by a coating containing this,
The adhesion may be poor.

[0008]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
To provide an aqueous block polyisocyanate composition having a carboxyl group as a hydrophilic group, which is a curing agent that has low-temperature curability and can exhibit coating properties with excellent adhesion such as impact resistance and weather resistance of urethane coating is there.

[0009]

Means for Solving the Problems As a result of intensive investigations by the present inventors, the present invention has been achieved by using the specific blocked polyisocyanate having a carboxyl group, and the present invention has been achieved. That is, the present invention is as follows.
1. A water-based blocked polyisocyanate in which a precursor is derived from an aliphatic or alicyclic diisocyanate and which satisfies all of the following conditions (a) and which satisfies all of the following conditions (b). (A) 1. Isocyanate group average number 4.5 to 20 2. Viscosity 3000 to 100000 mPa · s / 2
5 ° C 3. Number average molecular weight 1,000 to 50,000 4. Isocyanate group concentration 2 to 23 mass% (b) 1. Both a blocked isocyanate group and a carboxyl group are included in one molecule. 2. Acid value per resin 10-100 mgKOH /
g 3. Average number of blocked isocyanate groups 3.5 to 19 4. Blocked isocyanate group concentration 1.8-
20 mass%

2. Some of the isocyanate groups of the precursor polyisocyanate have reacted with monohydroxymonocarboxylic acid. Composition. 3. An aqueous coating composition comprising a polyol which is soluble, emulsified or dispersed in amine-neutralized water and 1 or 2. 4. 3. Aqueous coating composition containing 3 amino resins.

The present invention will be described in detail below. The present invention is an aqueous blocked polyisocyanate having both a blocked isocyanate group and a carboxyl group in one molecule. The diisocyanate for obtaining the precursor polyisocyanate is aliphatic or alicyclic. Although an aromatic diisocyanate can be used, an aliphatic or alicyclic diisocyanate is preferable because it has excellent yellowing resistance of the coating film and weather resistance.

The aliphatic diisocyanate preferably has 4 to 30 carbon atoms, and the alicyclic diisocyanate preferably has 8 to 30 carbon atoms. For example, tetramethylene-1,4-diisocyanate and pentamethylene-
1,5-diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene-
1,6-diisocyanate, lysine diisocyanate,
Examples thereof include isophorone diisocyanate, 1,3-bis (isocyanatomethyl) -cyclohexane, and 4,4′-dicyclohexylmethane diisocyanate. Of these, hexamethylene diisocyanate (hereinafter referred to as HDI) and isophorone diisocyanate (hereinafter referred to as IPDI) are preferable from the viewpoint of weather resistance and industrial availability, and they may be used alone or in combination.

The polyisocyanate used in the present invention can be obtained by using a polyhydric alcohol in combination with the above diisocyanate. The polyhydric alcohol includes low molecular weight polyols and high molecular weight polyols. Examples of low molecular weight polyols include diols, triols, tetraols and polyhydric polyols. Examples of the diols include ethylene glycol, diethylene glycol,
Triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,
2-propanediol, 1,3-propanediol,
1,2-butanediol, 1,3-butanediol,
1,4-butanediol, 2,3-butanediol, 2
-Methyl-1,2-propanediol, 1,5-pentanediol, 2-methyl-2,3-butanediol,
1,6-hexanediol, 1,2-hexanediol, 2,5-hexanediol, 2-methyl-2,4-
Pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethyl-hexanediol, 1,2-octanediol, 1,2-decanediol, 2,2,4
-Trimethylpentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-
1,3-propanediol, etc.

Examples of triols include glycerin and trimethylolpropane, and examples of tetraols include pentaerythritol.
Furthermore, the following is exemplified. For example, dichryserine, ditrimethylolpropane,
Dipentaerythritol etc. Erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol, rhamnitol, etc. Sugar alcohol compounds such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose. , Monosaccharides such as rhamnose, fucose and ribodeose,

For example, trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose,
Disaccharides such as melibiose, for example, trisaccharides such as raffinose, gentianose, and melezitose, tetrasaccharides such as stachyose, polyester polyols as high molecular weight polyols,
There are polyether polyols and the like.

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 and terephthalic acid, alone or A polyester polyol obtained by a condensation reaction of a mixture and a low molecular weight polyol alone or with a mixture,
And polycaprolactones, polycarbonates and the like obtained by ring-opening polymerization of ε-caprolactone with a low molecular weight polyol. Especially molecular weight 200 ~
2000 polycaprolactones and polycarbonates are preferable from the viewpoint of weather resistance.

These polyester polyols can be modified with aromatic diisocyanates, aliphatic or alicyclic diisocyanates or polyisocyanates obtained therefrom. In this case, it is particularly preferable to use an aliphatic or alicyclic diisocyanate or a polyisocyanate obtained from them in terms of weather resistance and yellowing resistance.

As the polyether polyols, for example, hydroxides such as lithium, sodium and potassium, alcoholates, strong basic catalysts such as alkylamines, metal porphyrins and zinc hexacyanocobaltate may be used alone or in a mixture of the above low molecular weight polyols. Using a complex metal cyanide complex such as a complex, ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, polyether polyols obtained by random or block addition of a mixture of alkylene oxides such as styrene oxide, Furthermore, polyether polyols obtained by reacting a polyamine compound such as ethylenediamine with alkylene oxide, and acrylamide etc. using these polyethers as a medium Combined obtained include so-called polymer polyols and the like. To obtain a polyisocyanate having a high average number of isocyanate groups, trivalent or higher,
A tetravalent or higher valent polyether polyol is preferred.

The reaction between an aliphatic or alicyclic diisocyanate and a polyhydric alcohol is performed by isocyanate group / hydroxyl group (equivalent ratio)
Is preferably in the range of 50/1 to 5/1. The reaction temperature is preferably 50 to 200 ° C., more preferably 60 to 200 ° C.
It is 180 ° C. If necessary, after the reaction between the aliphatic or alicyclic diisocyanate and the polyhydric alcohol, an allophanate-forming reaction or an isocyanurate-forming reaction can be carried out. Carrying out the isocyanurate-forming reaction is preferable for producing a carboxyl group-containing aqueous blocked polyisocyanate for forming a coating film having higher hardness.

The allophanate-forming reaction and the isocyanurate-forming reaction can be carried out by heating, but can also be carried out by using a reaction catalyst. As a catalyst therefor, a basic substance is generally preferable, and examples thereof include the following. 1) Quaternary ammonium such as trimethylhydroxyethylammonium, triethylhydroxyethylammonium, trimethylhydroxypropylammonium, trimethylbenzylammonium, tetramethylammonium, tetraethylammonium and their weak organic acid salts 2) of alkylcarboxylic acids such as acetic acid and caproic acid Alkali metal salts such as sodium and potassium, tin, zinc,
Metal salts such as lead and zirconium 3) Metal alcoholates such as sodium and potassium 4) Aminosilyl group-containing compounds such as hexamethyldisalazan 5) Tertiary amine such as trimethylamine and triethylamine The catalyst concentration is usually 10 pp relative to diisocyanate.
It is selected from the range of m to 5 wt%.

The reaction can also be carried out using a solvent. If a solvent is used, it should be inert to the isocyanate groups. The reaction temperature is usually 20 to 160.
C., preferably 40 to 130.degree. The end point of the reaction varies depending on the polyhydric alcohol used, but the yield is generally 2
It becomes 0 mass% or more and 75 mass% or less. When the reaction reaches the target yield, for example, for the basic compound, the catalyst is neutralized with an acidic substance such as sulfonic acid, phosphoric acid, or phosphoric acid ester, and for the aminosilyl group compound, Deactivate the catalyst with water, alcohol, etc. to stop the reaction. After completion of the reaction, the unreacted diisocyanate and the solvent can be removed by a thin film evaporator, extraction or the like to obtain the polyisocyanate used in the present invention.

The concentration of unreacted diisocyanate in the obtained polyisocyanate is 1% by mass or less, preferably 0.5% by mass or less. A low diisocyanate concentration is preferable not only in terms of environmental hygiene but also in terms of curability. The viscosity of the obtained polyisocyanate at 25 ° C. is 3000 to 100000 mPa · s,
It is preferably 5000 to 50000 mPa · s. Average number of isocyanate groups (Static 1 of polyisocyanate
The number of isocyanate groups contained in the molecule is 4.5 to 20, preferably 4.5 to 15. More preferably 5.0
~ 12. Number average molecular weight of 1,000 to 50,000,
It is preferably 2000 to 30000, and the isocyanate group concentration is 2 to 23% by mass, preferably 5 to 20% by mass.
Is.

In the blocked polyisocyanate obtained from such a polyisocyanate, even if the reactivity of the blocked isocyanate groups is the same, the range of the average number of the isocyanate groups can realize a high degree of crosslinking (curability). Even if the reaction rates are the same, the crosslinkability with a high average number of isocyanate groups is excellent. A part of the isocyanate groups of the polyisocyanate is blocked with a blocking agent, and at least a part of the remaining isocyanate groups reacts with monohydroxymonocarboxylic acid. In this case, the reaction between the isocyanate group and the hydroxyl group has priority over the reaction between the isocyanate group and the carboxyl group, and this reaction imparts the carboxyl group to the polyisocyanate.

Either the reaction of blocking the isocyanate group with a blocking agent or the reaction of the isocyanate group with the monohydroxymonocarboxylic acid may take precedence. It is also possible to divide the blocking reaction and perform it before and after the carboxyl group introduction reaction. When the isocyanate group reacts with the carboxyl group, it is preferable to give priority to the blocking reaction with the blocking agent. Examples of the blocking agent include alcohol-based, alkylphenol-based, phenol-based, active methylene, mercaptan-based, acid amide-based, acid imide-based, imidazole-based, urea-based, oxime-based, amine-based, imide-based, and pyrazole-based compounds. is there.

Examples of more specific blocking agents are shown below. (1) Alcohol type: methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2
-Alcohols such as ethyl-1-hexanol, 2-methoxyethanol, 2-etokashiethanol, and 2-butoxyethanol (2) Alkylphenols: mono- and dialkylphenols having an alkyl group having 4 or more carbon atoms as a substituent. And, for example, n-propylphenol, i
-Propylphenol, n-butylphenol, sec
-Butylphenol, t-butylphenol, n-hexylphenol, 2-ethylhexylphenol, n-
Monoalkylphenols such as octylphenol and n-nonylphenol, di-n-propylphenol, diisopropylphenol, isopropylcresol, di-n-butylphenol, di-t-butylphenol,
Di-sec-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, di-n-
Dialkylphenols such as nonylphenol

(3) Phenol type: phenol, cresol, ethylphenol, styrenated phenol, hydroxybenzoic acid ester, etc. (4) Active methylene type: dimethyl malonate, diethyl malonate, 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, etc. (7) Acid imide type: succinimide, maleic imide, etc.

(8) Imidazole type: imidazole, 2
-Methylimidazole, etc. (9) Urea type: Urea, thiourea, ethyleneurea, etc. (10) Oxime type: formaldoxime, acetoaldoxime, acetoxime, methylethylketoxime, cyclohexanone oxime, etc. (11) Amine type: diphenylamine, aniline Carbazole, di-n-propylamine, diisopropylamine, isopropylethylamine and the like (12) imine type: ethyleneimine, polyethyleneimine and the like (13) pyrazole type: pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole and the like.

The blocking agent used in the present invention is preferably at least one selected from alcohols, oximes and active methylenes. The monohydroxymonocarboxylic acid that can be used in the present invention is a compound having one hydroxyl group and one carboxyl group, for example, glycolic acid, lactic acid, 2-hydroxycarboxylic acid, 2-hydroxy-2-methylpropanoic acid, There are 3-hydroxypropionic acid, hydroxypivalic acid and the like, and hydroxypivalic acid having different reactivity between a hydroxyl group and a carboxyl group is preferable. When watering a block polyisocyanate having a polyisocyanate skeleton with a high average number of isocyanate groups, when using only polyhydroxycarboxylic acid such as dimethylolpropionic acid that is widely used to introduce anionic groups However, it was difficult to make water-soluble, such as insufficient water-forming ability and gelation during the reaction of polyhydroxycarboxylic acid and isocyanate groups.

Further, compounds other than the above-mentioned compounds having active hydrogen capable of reacting with an isocyanate group and an anion group may be used in combination. The active hydrogen is, for example, a mercapto group or the like in addition to the hydroxyl group, and the anion group is, for example, a sulfonic acid group or a phosphoric acid group in addition to the carboxyl group. Examples of the compound include hydroxycarboxylic acids such as glyceric acid, tartronic acid, malic acid,
Tartaric acid, dimethylolpropionic acid, dimethylolbutanoic acid, etc. are mercaptocarboxylic acids, such as mercaptoacetic acid, mercaptosuccinic acid, etc., aminocarboxylic acids, such as glycine, alanine, etc., aminosulfonic acids, such as taurine, etc. .

The reaction between the isocyanate group and the compound having both active hydrogen and anion group can be carried out by neutralizing the anion group before the reaction or can be carried out without neutralization. The basic compound used for neutralizing the anion group before the reaction is a basic compound having no active hydrogen reactive with the isocyanate group. Examples of the basic compound include alkali metals, alkaline earth metals,
There are tertiary amines such as trimethylamine and triethylamine, and the basic compound used for neutralizing after the reaction is, for example, ammonia, methylamine, ethylamine, dimethylamine, diethylamine, in addition to the above, regardless of the presence or absence of active hydrogen. , Methyldiethanolamine, dimethylethanolamine, diethanolamine, triethanolamine, propylamine, monoisopropanolamine, diisopropanolamine, 2-amino-2-
Methyl-1-propanol and the like.

The addition of amine is carried out as necessary, and it may be equal to or more than the equivalent amount of the anion group. Further, as a supplementary method of adding a hydrophilic group, addition of a nonionic group such as one-terminal ether polyethylene glycol having active hydrogen to polyisocyanate and a surfactant can be used in combination. The above reaction can be carried out in the presence of a solvent.
The solvent used here is preferably a solvent having no active hydrogen described above, which is an ester solvent, for example, methyl acetate,
There are ketone solvents such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, etc., such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc., and also N-methylpyrrolidone, etc.

The reaction temperature is 50 to 150 ° C. A basic reaction catalyst can be used in the reaction. The obtained carboxyl group-containing aqueous block polyisocyanate has an acid value of 10 to 100 mgKOH / g per resin,
It is preferably 20 to 60 mgKOH / g. 10 mg
If it is less than KOH / g, the dispersibility in water will be reduced to 100
If it exceeds mgKOH / g, the average number of blocked isocyanate groups (the number of blocked isocyanate groups that one statistical molecule of blocked polyisocyanate has) may decrease, resulting in poor curability.

The average number of isocyanate groups blocked by the blocking agent is at least 3.5 to 19, preferably 4.
It is 0 to 14, more preferably 5.0 to 12. The concentration of the isocyanate group blocked by the blocking agent (hereinafter referred to as latent isocyanate group) is 1.8 to 20 wt%. The carboxyl group-containing aqueous blocked polyisocyanate thus obtained functions as a curing agent. An aqueous polyol is used as a main agent as a reaction partner. The aqueous polyol is a polyol that dissolves, emulsifies, and disperses in water, and has an acid value of 10 mgKOH / g to 100 per resin.
Is preferable, and the hydroxyl value is 10 to 500 mgKOH / g, preferably 30 to 150 mgKOH / g. The acid value is neutralized with a basic compound. The basic compounds used here include the amine compounds described above, and dimethylethanolamine is preferable for coatings for lines such as automobile outer panels.

An amino resin can be used in combination as a curing agent. The amino resin used in the present invention is preferably an alkyl etherified melamine resin, and the production method thereof is, for example, urea, melamine, benzoguanamine, glycoluril or the like is added with formaldehyde in an alcohol under alkaline conditions to perform methylolation, and then at least a methylol group is added. One part is alkyletherified. Examples of the alkyl group include methyl, ethyl, propyl, butyl, ethyl cellosolve, and butyl cellosolve, and two or more kinds may be used. Preferably methyl, ethyl, propyl,
Butyl is more preferable, and methyl and butyl are more preferable.
It may have an imino group.

The mass ratio of the carboxyl group-containing blocked polyisocyanate and the amino resin is 9/1 to 1/9, preferably 8/2 to 2/8. The amino resin can be added to increase the hardness of the coating film, and the compounding ratio is determined as necessary. When the curing agent is a carboxyl group-containing aqueous block polyisocyanate alone, the mixing ratio of the polyol and the curing agent is such that the equivalent ratio of isocyanate group / hydroxyl group is 0.5 / 1 to 2/1, preferably 0.7 /
It is 1 to 1.5 / 1. When an amino resin is used in combination with the curing agent, the mass ratio of polyol / curing agent is 5/5 to 9/1.
And preferably 6/4 to 8/2, and the mass ratio of the carboxyl group-containing aqueous block polyisocyanate to the melamine resin is 95/5 to 5/95, preferably 80 /
20 to 20/80.

When an amino resin is used in combination, it is preferable to use an acidic compound in combination because the curability is improved. Specific examples of the acid compound that can be used in the present invention include carboxylic acids such as acetic acid, lactic acid, succinic acid, oxalic acid, maleic acid, and decanedicarboxylic acid.Sulfonic acids include, for example, paratoluenesulfonic acid, There are dodecylbenzene sulfonic acid, dinonyl naphthalene disulfonic acid and the like, and examples of the phosphoric acid esters include dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dioctyl phosphate, dilauryl phosphate, monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monophosphate. Acidic phosphates such as octyl phosphate such as diethyl phosphite, dibutyl phosphite, dioctyl phosphite, dilauryl phosphite, monoethyl phosphite, mono Chill phosphite, mono octyl phosphite, there is such as thing lauryl phosphite. Preferred are sulfonic acids and phosphoric acid esters.

These acidic compounds can be used by reacting with an amine compound. As the amine compound,
For example, alkylamines such as ethylamine, diethylamine, triethylamine, n-butylamine, di-n-butylamine, ethanolamine, diethanolamine,
Examples include alkanolamines such as triethanolamine. The acidic compound is contained in an amount of 0.01 to 10% by mass, preferably 0.1% by mass based on the resin content of the polyol and the curing agent.
It is 01 to 5 mass%.

When the carboxyl group-containing aqueous block polyisocyanate and the amino resin are used in combination, the blocking agent of the carboxyl group-containing aqueous block polyisocyanate is preferably an alcohol which improves the yellowing resistance of the coating film upon baking. In addition to the ion-exchanged water depending on the application and purpose,
Various solvents and additives can be used. Examples of the solvent include ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate, -n-butyl acetate and cellosolve acetate, 2-ethoxyethanol, 2-butoxyethanol, 2-hexyloxyethanol and the like. Ethers. Alcohols such as butanol and isopropyl alcohol, N-methyl-2-
It can be appropriately selected and used from the group of lactams such as pyrrolidone according to the purpose and application. These solvents may be used alone or in combination of two or more.

If necessary, antioxidants such as hindered phenols, ultraviolet absorbers such as benzotriazole and benzophenone, pigments such as titanium oxide, carbon black, indigo, quinacridone, pearl mica and the like, metal powder pigments such as A rheology control agent such as aluminum, for example, hydroxyethyl cellulose, a urea compound or the like may be added. The coating composition thus prepared is subjected to roll coating, curtain flow coating, spray coating, electrostatic coating, etc., for steel and metal such as surface-treated steel and plastics, as a primer or top intermediate coating on materials such as inorganic materials, It is useful for imparting cosmetic properties, weather resistance, acid resistance, rust resistance, chipping resistance, etc. to pre-coated metal containing rust-proof steel plates, water-based top clear coats for automobile coating, water-based base coats, water-based intermediate coats 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.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to the following examples. All parts are parts by mass. (Measurement of number average molecular weight) The number average molecular weight is determined by gel permeation chromatograph (hereinafter referred to as GPC) using the following device.
It is the number average molecular weight based on polystyrene measured. Carrier: Tetrahydrofuran Detection method: Differential refractometer

(Unreacted Monomer Concentration) The concentration of the peak of the molecular weight corresponding to the unreacted diisocyanate (for example, 168 in the case of HDI) obtained by the GPC measurement was expressed by its area%. (Measurement of viscosity) E-type viscometer (VISCO manufactured by Tokimec Co., Ltd.
NIC ED type) at 25 ° C. (Gel fraction) After the cured coating film was immersed in acetone at 20 ° C. for 24 hours, the value of the undissolved part mass with respect to the mass before immersion was calculated, and when it was less than 80%, x, and 80% or more and less than 90% In the case of 90% or more, it is represented by ⊚.

(Evaluation of Impact Resistance) The coating temperature was evaluated at 25 ° C. by using a DuPont type impact resistance tester with a strike point of 6.35 mm and a load of 500 g. When the height at which no abnormality was found in the coating film was 10 cm or less, it was represented by x, when it was 20 cm or less, it was represented by o, and 40 cm or more was represented by ⊚. The height is 10
Evaluation was made in cm increments.

[0043]

[Production Example 1] (Production of polyisocyanate) A 4-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen blowing tube was filled with a nitrogen atmosphere, and 600 parts of HDI, a hexavalent polyether polyol (a product of Asahi Denka Co., Ltd. Name "ADEKA polyether polyol SP-600" number average molecular weight 61
0) 49 parts (isocyanate group / hydroxyl group equivalent ratio 15 /
1) was charged, and the temperature inside the reactor was maintained at 160 ° C. for 9 hours with stirring. Unreacted diisocyanate was removed with a thin film distiller. The number average molecular weight of the obtained polyisocyanate is 1
940, the isocyanate group concentration was 16.9 mass%, the viscosity was 6200 mPa · s / 25 ° C., and the unreacted monomer concentration was 0.3 mass%. The average number of isocyanate groups is 7.
It was 8.

[0044]

Production Example 2 (Production of Aliphatic Polyisocyanate Used in Examples of the Present Invention) A 4-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen blowing tube was filled with a nitrogen atmosphere to obtain 600 parts of HDI and trivalent. 60 parts of polyester polyol (trade name “Placcel 303” of Daicel Chemical Industries, Ltd., number average molecular weight 300) of alcohol was charged, and the temperature inside the reactor was maintained at 90 ° C. for 1 hour while stirring. Thereafter, the temperature of the reaction liquid in the reactor was maintained at 60 ° C., and 0.03 part of a cyclic trimerization catalyst tetramethylammonium capryate was added. When the yield reached 63 wt%, phosphoric acid was added to stop the reaction. After filtering the reaction solution, the unreacted diisocyanate was removed with a thin film distiller. The viscosity of the obtained polyisocyanate at 25 ° C. is 31,000 mPa · s,
The isocyanate group concentration was 17.5% by mass, and the unreacted monomer concentration was 0.3% by mass. Number average molecular weight is 182
It was 0, and the average number of isocyanate groups was 7.6.

[0045]

Example 1 (Production of carboxyl group-containing aqueous block polyisocyanate) The same apparatus as in Production Example 1 was charged with 400 parts of the polyisocyanate obtained in Production Example 1 and 236 parts of N-methylpyrrolidone, and a nitrogen atmosphere was sufficient. After stirring, 112 g of methyl ethyl ketoxime was added dropwise over 30 minutes so that the temperature of the reaction solution did not exceed 50 ° C.
Thirty minutes after the completion of dropping, 38 parts of hydroxypivalic acid was added, and after dissolution, 0.28 part of dibutyltin dilaurate was added. It was kept at 80 ° C. for 3 hours, and disappearance of isocyanate group was confirmed by infrared spectrum. Resin solid content 70% by mass, physical properties per resin, latent isocyanate group concentration 9.9% by mass, number average molecular weight 2700, average number of blocked isocyanate groups 6.4, acid value 33 mgKOH / g carboxyl group-containing aqueous block poly Isocyanate B
-1 was obtained.

[0046]

Example 2 (Production of Carboxyl Group-Containing Aqueous Block Polyisocyanate) The same apparatus as in Production Example 1 was charged with 400 parts of the polyisocyanate obtained in Production Example 2 and 238 parts of N-methylpyrrolidone, and a nitrogen atmosphere was sufficient. After stirring, 116 parts of methyl ethyl ketoxime is added dropwise over 30 minutes so that the temperature of the reaction solution does not exceed 50 ° C.
Thirty minutes after the completion of dropping, 39 parts of hydroxypivalic acid was added, and after dissolution, 0.28 part of dibutyltin dilaurate was added. It was kept at 80 ° C. for 3 hours, and disappearance of isocyanate group was confirmed by infrared spectrum. Resin solid content 70 mass%, physical properties per resin, latent isocyanate group concentration 1
0.1 mass%, number average molecular weight 2550, average number of blocked isocyanate groups 6.1, acid value 34 mgKOH / g carboxyl group-containing aqueous blocked polyisocyanate B
-2 was obtained.

[0047]

Example 3 (Production of Carboxyl Group-Containing Aqueous Block Polyisocyanate) 400 parts of the polyisocyanate obtained in Production Example 1, 231 parts of N-methylpyrrolidone and 0.04 of dibutyltin dilaurate were placed in the same apparatus as in Production Example 1.
After charging 0 part and sufficiently stirring in a nitrogen atmosphere, the reaction solution temperature is maintained at 70 ° C., and 99 parts of n-butanol is added dropwise over 30 minutes. After the completion of dropping, the mixture is maintained for 30 minutes, 39 parts of hydroxypivalic acid is added, and after dissolution, 0.080 part of dibutyltin dilaurate is added. Hold at 80 ℃ for 3 hours,
The disappearance of the isocyanate group was confirmed by the infrared spectrum. Resin solid content 70% by mass, physical properties per resin, latent isocyanate group concentration 10.5% by mass, number average molecular weight 2
600, the average number of blocked isocyanate groups was 6.5, and the acid value was 34 mgKOH / g, and carboxyl group-containing aqueous blocked polyisocyanate B-3 was obtained.

[0048]

[Comparative Example 1] An HDI-based isocyanurate type polyisocyanate (trade name "Duranate TPA-100" manufactured by Asahi Kasei Co., Ltd., viscosity 1350 mPa · s) was used in the same apparatus as in Production Example 1.
/ 25 ° C., isocyanate group concentration 23.2 wt%, number average molecular weight 580, isocyanate group average number 3.2) 40
After charging 0 part and 260 parts of N-methylpyrrolidone and thoroughly stirring in a nitrogen atmosphere, 154 parts of methylethylketoxime are added dropwise over 30 minutes so that the temperature of the reaction solution does not exceed 50 ° C. After completion of dropping, hydroxypivalic acid 5
After adding and dissolving 2 parts, dibutyltin dilaurate 0.30
Parts are added. It was kept at 80 ° C. for 3 hours, and disappearance of isocyanate group was confirmed by infrared spectrum. Resin solid content 70% by mass, physical properties per resin, latent isocyanate group concentration 12.3% by mass, number average molecular weight 880, blocked isocyanate group average number 2.6, acid value 41 mgKOH
A carboxyl group-containing aqueous blocked polyisocyanate B-4 was obtained.

[0049]

[Example-4] (Aqueous coating composition) 100 parts of polyester polyol (trade name: Cetal 63 manufactured by Akzo Nobel)
06SS-60, resin hydroxyl group concentration 2.7 mass%, resin acid value 25 mgKOH / g, solid content 60 mass%) and Example 1.
58 parts of the carboxyl group-containing aqueous block polyisocyanate composition obtained in (1) was mixed, 4.5 parts of dimethylethanolamine was added, and 89 parts of ion-exchanged water was further added to obtain a resin solid content of 40% and a pH of 8.5. An aqueous coating composition was obtained. Applicator coating is applied to the PP plate and the temperature is 30
After the minute setting, it was kept in an oven at 150 ° C. for 30 minutes. The coating film was evaluated and the gel fraction was good and the impact resistance was good.

[0050]

Examples 5 to 6 and Comparative Examples 2 and 3 (Aqueous coating composition) The same procedure as in Example 3 was carried out except that the formulation was shown in Table 1. The results are also shown in Table 1.

[0051]

[Table 1]

[0052]

EFFECTS OF THE INVENTION The aqueous blocked polyisocyanate having a carboxyl group as a hydrophilic group of the present invention can form a coating film excellent in low temperature curability, impact resistance, weather resistance and coating film adhesion.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4J034 CA03 CA04 CA05 CC03 CC08                       DA01 DF02 DF12 DF20 DF22                       DG03 DG04 DG05 DG14 EA07                       HA01 HA07 HC03 HC09 HC17                       HC22 HC46 HC52 HC64 HC67                       HC71 HC73 HD03 HD05 HD06                       HD07 HD08 HD12 RA07                 4J038 DA112 DG051 DG291 DG301                       MA08 MA10

Claims (4)

[Claims] 1. An aqueous block characterized in that the precursor is a polyisocyanate derived from an aliphatic or alicyclic diisocyanate that satisfies all of the following conditions (a), and that satisfies all of the following conditions (b): Polyisocyanate. (A) 1. Isocyanate group average number 4.5 to 20 2. Viscosity 3000 to 100000 mPa · s / 2
5 ° C 3. Number average molecular weight 1,000 to 50,000 4. Isocyanate group concentration 2 to 23 mass% (b) 1. Both a blocked isocyanate group and a carboxyl group are included in one molecule. 2. Acid value per resin 10-100 mgKOH /
g 3. Average number of blocked isocyanate groups 3.5 to 19 4. Blocked isocyanate group concentration 1.8-
20 mass% 2. A composition according to claim 1, in which some of the isocyanate groups of the precursor polyisocyanate have reacted with monohydroxymonocarboxylic acid. 3. An aqueous coating composition comprising a polyol which is soluble, emulsified or dispersed in amine-neutralized water and the composition according to claim 1 or 2. 4. The aqueous coating composition according to claim 3, which contains an amino resin.