JP2007332193A - Water-based polyisocyanate composition and water-based coating composition containing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based polyisocyanate composition which is excellent in water dispersibility and develops a high cross-linking property and a high coating film hardness, and to provide a water-based coating composition using the same as a curing agent. <P>SOLUTION: This aqueous polyisocyanate composition is characterized in that the polyisocyanate is represented by the following structural formula (1): (A)<SB>m</SB>-R-(NCO)<SB>n</SB>(1), wherein A : a hydrophilic group, m: the number of the hydrophilic groups, n: the number of isocyanate group, R: the isocyanate group-removed residue of the polyisocyanate derived from at least one of an aliphatic diisocyanate and/or an alicyclic diisocyanate, and satisfies (i) the average number (n<SB>M</SB>) of the isocyanate groups is 2.3 to 3.2; the average number (n<SB>M</SB>) and hydrophilic group average number (m<SB>M</SB>) of the isocyanate groups: m<SB>M</SB>/(m<SB>M</SB>+n<SB>M</SB>)=0.02 to 0.40, (ii) the concentration of the isocyanate groups is 10 to 14 mass%, (iii) the concentration of isocyanurate trimer: 60 to 95 mass%, the concentration of uretedione dimer: 2 to 25 mass%, (iv) viscosity at 25°C is 200 to 1,000 mPa s. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an aqueous polyisocyanate composition and an aqueous coating composition using the same as a curing agent.

  A two-component urethane coating composition containing polyisocyanate as a curing agent is excellent in chemical resistance and flexibility of the coating film. In particular, when a polyisocyanate obtained from an aliphatic or alicyclic diisocyanate is used, since it is further excellent in weather resistance, its use is in the form of room temperature curable and thermosetting, and paints for automobiles, architecture, home appliances, etc. Is widely used.

  On the other hand, in recent years, water-based paints have attracted attention from the viewpoints of the global environment, safety, and hygiene. It has come to be used for industrial coatings such as for building cans and coil coatings from building exteriors. Patent Documents 1 and 2 are proposed as proposals using polyisocyanate as a curing agent. However, the polyisocyanates exemplified in Patent Documents 1 and 2 sometimes fail to balance dispersibility and crosslinkability. In Patent Documents 3 and 4, polyisocyanate having a high average number of isocyanate groups is used as a raw material isocyanate. In this case, the curability is good, but water dispersibility is given. In some cases, the coating film hardness decreased. Therefore, an aqueous polyisocyanate that is excellent in water dispersibility and that exhibits high crosslinkability and high coating film hardness has been desired.

Japanese Patent Publication No. 8-32851 JP-A-5-222150 Japanese Patent Laid-Open No. 10-060073 Japanese Patent Application Laid-Open No. 11-1000042

  An object of the present invention is to provide an aqueous polyisocyanate composition which is excellent in water dispersibility and exhibits high crosslinkability and high coating film hardness, and an aqueous coating composition using the same as a curing agent.

As a result of diligent research, the present inventors have surprisingly made this possible by using a polyisocyanate having a specific viscosity retaining a specific number of isocyanate groups as a polyisocyanate of a curing agent for aqueous two-component urethane. The present invention has been completed on the basis of the knowledge that the water-based coating composition contains water dispersibility and exhibits high crosslinkability and high coating film hardness.
That is, the present invention is an aqueous polyisocyanate composition and an aqueous coating composition containing the same as described below.

(1) An aqueous polyisocyanate composition that can be dissolved or dispersed in water, wherein the polyisocyanate is represented by the following structural formula (1) and satisfies all the following conditions 1) to 4).
(A) _m- R- (NCO) _n (1)
A: Hydrophilic group m: Number of hydrophilic groups n: Number of isocyanate groups R: Residue excluding isocyanate group of polyisocyanate derived from at least one of aliphatic diisocyanate and / or alicyclic diisocyanate Conditions:
1) The average number of isocyanate groups (n _M ) is 2.3 to 3.2, and the average number of isocyanate groups n (n _M ) and the average number of hydrophilic groups m (m _M ) have the following relationship: .
_{m M / (m M + n} M) = 0.02~0.40
2) Isocyanurate trimer and uretdione dimer constituting R satisfy the following a) and b) a) Isocyanurate trimer concentration: 60% by mass to 95% by mass
b) Uretodione dimer concentration; 2 to 25% by mass
3) The isocyanate group concentration is 10 to 24% by mass.
4) Viscosity at 25 ° C. of 200 to 1000 mPa · s
(2) The aqueous polyisocyanate composition according to the above (1), wherein the average number n of isocyanate groups is 2.4 to 3.0.
(3) The aqueous polyisocyanate composition according to the above (1) or (2), wherein the viscosity at 25 ° C. is 500 to 800 mPa · s.
(4) The aqueous polyisocyanate composition according to the above (1) to (3), wherein the aliphatic and / or alicyclic diisocyanate monomer is hexamethylene diisocyanate.
(5) (A) _m- R- (NCO) wherein R in _n is a functional group number ratio of allophanate group / isocyanurate group derived from monoalcohol; 1 to 20% above. The aqueous polyisocyanate composition according to (4).
(6) An aqueous coating composition comprising the aqueous polyisocyanate composition according to the above (1) to (5) and a polyol.

    The aqueous polyisocyanate composition of the present invention can provide a coating composition which is excellent in water dispersibility and exhibits high crosslinkability and high coating film hardness.

The present invention is described in detail below.
The average number n of isocyanate groups in the aqueous polyisocyanate composition of the present invention is 2.3 to 3.2, preferably 2.4 to 3.0, more preferably 2.5 to 2.8. When the value is less than 2.3, the curability of the aqueous polyisocyanate composition obtained using the same may be lowered. When the value exceeds 3.2, the dispersibility in water may be lowered. .
The average number of isosocyanate groups is obtained by the following formula (1).

  The isocyanate group concentration of the aqueous polyisocyanate composition of the present invention is 10 to 24% by mass, preferably 12 to 22% by mass, and more preferably 14 to 20% by mass. When the amount is less than 10% by mass, the urethane bond concentration in the formed coating film tends to decrease and the flexibility may decrease, and when it exceeds 24% by mass, the water dispersibility may decrease.

The viscosity at 25 ° C. of the aqueous polyisocyanate composition of the present invention is 200 to 1000 mPa · s, preferably 400 to 900 mPa · s, more preferably 500 to 800 mPa · s. When it is less than 200 mPa · s, the crosslinkability may be lowered, and when it exceeds 1000 mPa · s, the water dispersibility and the coating film hardness may not be balanced.
The number average molecular weight of the aqueous polyisocyanate composition of the present invention is 400 to 1000, preferably 500 to 900, and more preferably 500 to 800. If it is less than 400, the average number of isocyanate groups tends to decrease, and if it exceeds 1000, water dispersibility and coating film hardness may not be balanced.

  The aliphatic diisocyanate monomer used in the aqueous polyisocyanate composition of the present invention is preferably one having 4 to 30 carbon atoms, such as tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate, hexamethylene diisocyanate. There are 2,2,4-trimethylhexamethylene-1,6-diisocyanate, lysine diisocyanate, and the like (hereinafter referred to as HDI). Among them, HDI is preferred from the viewpoint of industrial availability.

  As the alicyclic diisocyanate monomer used in the aqueous 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. Of these, IPDI is preferred because of weather resistance and industrial availability.

  The isocyanurate trimer, which is one of the constituent components in R of the aqueous polyisocyanate composition of the present invention, is a polyisocyanate having an isocyanurate group consisting of three molecules of a diisocyanate monomer, and is represented by the following formula.

The aqueous polyisocyanate composition of the present invention can be obtained by introducing a hydrophilic group into the polyisocyanate. Hereinafter, the polyisocyanate before introducing the hydrophilic group is referred to as “precursor polyisocyanate”.
The isocyanurate trimer concentration in the precursor polyisocyanate composition is 60 to 95% by mass. When it is less than 60% by mass, the viscosity of the precursor polyisocyanate composition increases, and when it exceeds 95% by mass, the yield decreases. When the isocyanurate group-containing polyisocyanate is derived from a diisocyanate monomer, it is usually performed using an isocyanurate-forming catalyst. Specific examples of the isocyanuration catalyst are preferably those having basicity, for example. 1) Tetraalkylammonium hydroxides such as tetramethylammonium and tetraethylammonium, and organic weak acid salts such as acetic acid and capric acid; ) Hydroxyalkylammonium hydroxides such as trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, triethylhydroxyethylammonium and the like, and organic weak acid salts such as acetic acid and capric acid 3) Acetic acid, caproic acid, octylic acid Metal salts of alkyl carboxylic acids such as myristic acid such as tin, zinc, lead, sodium, potassium, etc. 4) metal alcohols such as sodium, potassium, etc. Over bets, 5) for example hexamethyl aminosilyl group-containing compound such as silazane, 6) Mannich bases, 7) there is a combination such as the tertiary amines and epoxy compounds. These catalysts can be used to obtain isocyanurate group-containing polyisocyanates.

  The resulting isocyanurate group-containing polyisocyanate contains pentamer, heptamer and the like in addition to trimer. In order to obtain the isocyanurate trimer concentration range of the precursor polyisocyanate composition, the conversion ratio of the isocyanurate reaction (mass ratio of the polyisocyanate generated by the isocyanurate reaction to the charged liquid) is 20% or less, preferably Is 15% or less. If it exceeds 20%, it may be difficult to achieve the isocyanurate trimer concentration, which is a constituent requirement of the present invention, and it may be impossible to achieve both low viscosity and crosslinkability of the aqueous polyisocyanate composition.

  R in the aqueous polyisocyanate composition of the present invention preferably contains an allophanate group derived from a monoalcohol. The allophanate group is formed from a hydroxyl group and an isocyanate group of a monoalcohol, and is represented by the following formula.

The functional group number ratio of allophanate group / isocyanurate group is 1 to 20%, preferably 2 to 15%, more preferably 2 to 10%. If it is less than 1%, the viscosity of the resulting polyisocyanate may increase, and if it exceeds 20%, the crosslinkability may decrease.
The monoalcohol that can be used in the present invention is preferably a monoalcohol formed only of carbon, hydrogen and oxygen. More preferably, the molecular weight is 500 or less. The specific compound is, for example, a compound containing isomers such as methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, and nonanol, and two or more kinds may be used in combination.

The amount of the monoalcohol used is 1000/1 to 10/1, preferably 1000/1 to 100/1, in terms of the equivalent ratio of the isocyanate group of the polyisocyanate to the hydroxyl group of the monoalcohol. If it is less than 10/1, a compound composed of two monoalcohol molecules and one diisocyanate monomer molecule may be formed, which is not preferable because the crosslinkability is lowered. In order to generate allophanate groups, an allophanatization catalyst is usually used. Specific compounds include alkyl carboxylates such as tin, lead, zinc, bismuth, zirconium and zirconyl, organotin compounds such as tin 2-ethylhexanoate and dibutyltin dilaurate, and lead 2-ethylhexanoate. There are organic lead compounds such as, organic zinc compounds such as zinc 2-ethylhexanoate, bismuth 2-ethylhexanoate, zirconium 2-ethylhexanoate, zirconyl 2-ethylhexanoate, etc. it can.
The isocyanurate-forming catalyst can also be an allophanatization catalyst. When performing the allophanatization reaction using the above isocyanurate-forming catalyst, an isocyanurate group-containing polyisocyanate is also produced.

  The uretdione dimer, which is one of the constituent components in R of the aqueous polyisocyanate composition of the present invention, is a compound having two uretdione groups and having the uretdione group, and is represented by the following formula.

The uretdione dimer concentration in the precursor polyisocyanate composition is 2 to 25% by mass. If it is less than 2% by mass, the viscosity of the aqueous polyisocyanate composition increases, and if it exceeds 25% by mass, the crosslinkability may be lowered.
A uretdione dimer can be obtained using a uretdione-forming catalyst. Examples of this specific compound are tertiary phosphines, trialkylphosphines such as tri-n-butylphosphine and tri-n-octylphosphine, and tris (dialkylamino) such as tris- (dimethylamino) -phosphine. Examples include phosphine and cycloalkylphosphine such as cyclohexyl-di-n-hexylphosphine. These compounds can also be allophanatization catalysts. Many of these compounds also promote the isocyanuration reaction at the same time, producing isocyanurate group-containing polyisocyanates in addition to uretdione group-containing polyisocyanates.

Moreover, it can also obtain by heating, without using the above catalysts. The yield of uretdione group-containing polyisocyanate that can be obtained by heating was low, and it was not efficient as a means for obtaining only the uretdione group-containing polyisocyanate.
However, it was surprisingly found that the amount of diisocyanate monomer liberated during storage of the polyisocyanate containing uretdione groups obtained only by heating without using a catalyst was found to be remarkably low. It was thought that uretdione groups were easily decomposed by heating, so that diisocyanate monomers were liberated during storage of uretdione group-containing polyisocyanates. The uretdione group-containing polyisocyanate which is one of the components of the present invention is preferably produced by heating.

Surprisingly, the aqueous polyisocyanate composition according to the present invention has a polyisocyanate composition having the isocyanurate group, the allophanate group, and the uretdione dimer as shown in the above composition ratio as a precursor, and has a hydrophilic group. It was found that the coating film obtained by introducing it with good water dispersibility and using it as a curing agent has high crosslinkability and high coating film hardness.
Among them, the allophanate group having the above composition ratio contributes to hydrophilicity and contributes to lowering the viscosity, and the uretdione dimer having the above composition ratio is reduced in viscosity in the presence of a small amount. The aqueous polyisocyanate composition contributes to the development of low viscosity and high crosslinkability.
The precursor polyisocyanate composition does not contain biuret type polyisocyanate. The presence of biuret-type polyisocyanates leads to an increase in diisocyanate monomers after storage of the polyisocyanate composition, which is not preferred. Preferably, it is 0.5 mass% or less.

The above-described isocyanurate reaction, allophanate reaction, and uretdione reaction can be performed sequentially or in parallel. Preferably, the isocyanurate formation reaction and the allophanatization reaction are preceded, and then the uretodioneation reaction is preferably performed. The isocyanurate formation reaction and the allophanatization reaction may be performed using a common catalyst, and the uretdioneation reaction may be performed by heat. It is preferable because the manufacturing process can be simplified.
After these reactions are completed, the unreacted diisocyanate monomer is removed by a thin film evaporator, extraction or the like.
The diisocyanate monomer concentration in the precursor polyisocyanate composition is 1% by mass or less, preferably 0.5% by mass or less. If it exceeds 1% by mass, the crosslinkability is lowered, which is not preferable.

The aqueous polyisocyanate composition used in the present invention has a hydrophilic group in the molecule and has a molecular weight distribution.
The hydrophilic group of the aqueous polyisocyanate composition of the present invention is not particularly limited, and examples thereof include an anionic group and a nonionic group. Examples of the anionic group include a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group. Nonionic groups include, for example, polyethylene glycol type and polyhydric alcohol type. As the hydrophilic group, a nonionic group, a carboxylic acid group, or a sulfonic acid group is preferable.

Hereinafter, a method for introducing a hydrophilic group will be described.
In order to introduce the hydrophilic group exemplified above into polyisocyanate, a compound having both a hydrophilic group and an active hydrogen group (hereinafter referred to as a hydrophilic group-introducing compound) is used. The active hydrogen group is a functional group that reacts with an isocyanate group, and examples thereof include a hydroxyl group, a mercapto group, and a carboxylic acid group. Compounds having both anionic groups and active hydrogen groups include oxyacids having both hydroxyl and carboxylic acid groups, glycolic acid, lactic acid, tartaric acid, citric acid, oxybutyric acid, oxyvaleric acid, hydroxypivalic acid, dimethylol. Examples include acetic acid, dimethylolpropionic acid, dimethylolbutanoic acid, and polycaprolactone having a carboxylic acid group.

Examples of the compound having both a hydroxyl group and a sulfonic acid group include isethionic acid. Examples of the compound having both an active hydrogen group and a mercapto group and a carboxylic acid group include mercaptoacetic acid which is a mercaptocarboxylic acid. Examples of the compound having both a nonionic group and an active hydrogen group include polyethylene oxide. Polyethylene oxide is obtained, for example, by adding ethylene oxide to monoalcohol such as methanol, ethanol, butanol, and may contain propylene oxide.
The preferred range of the number average molecular weight of polyethylene oxide, polypyrene oxide, etc. is 200 to 1000, more preferably 300 to 800, and most preferably 400 to 600.
The active hydrogen group is preferably a hydroxyl group.
When the hydrophilic group is anionic, it is preferable to neutralize the anionic group with an organic amine or an inorganic base. This neutralization imparts water dispersibility and water solubility to the aqueous polyisocyanate composition.

  Examples of the specific organic amine compounds include, for example, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine. C 1-20 linear, branched 1, 2 or tertiary amines such as trimethylamine, triethylamine, triisopropylamine, tributylamine, ethylenediamine, cyclic amines such as morpholine, N-alkylmorpholine, pyridine, mono Isopropanolamine, methylethanolamine, methylisopropanolamine, dimethylethanolamine, diisopropanolamine, diethanolamine, triethanolamine, die Ethanolamine, a hydroxyl group-containing amines having in hydroxyl molecules such as triethanolamine and the like. Examples of the inorganic base include ammonia, potassium hydroxide, and sodium hydroxide.

  These organic amine compounds and inorganic bases are used in the range of 0.5 to 1.5 equivalents relative to the carboxyl group. If it is less than 0.5, the water dispersibility and water solubility of the aqueous polyisocyanate composition may decrease, and if it exceeds 1.5, the pH of the aqueous polyisocyanate solution will be high, and the paint using this The stability of the may decrease.

The value of _/ ratio _m M hydrophilic group average number _{m M} to the total number of isocyanate groups average number _{n M} and a hydrophilic group average number _{m M (m M + n M} ) of the aqueous polyisocyanate composition, 0.02 It is -0.40, Preferably it is 0.02-0.30, More preferably, it is 0.04-0.20, Most preferably, it is 0.05-0.10. If it is less than 0.02, water dispersibility may be insufficient, and if it exceeds 0.40, crosslinkability may be reduced.

The addition reaction between the precursor polyisocyanate and the hydrophilic group-introducing compound described above can generally be carried out at -20 to 150 ° C, preferably 30 to 100 ° C. If the temperature exceeds 150 ° C., a side reaction may occur, and if it is less than −20 ° C., the reaction rate decreases, which is disadvantageous.
In this reaction, organometallic salts such as tin, zinc and lead, tertiary amine compounds, alkali metal alcoholates such as sodium, and the like may be used as catalysts.

  Further, nonionic, anionic, cationic and amphoteric surfactants can be added depending on the purpose such as improvement of water dispersibility. Specific examples of the surfactant include nonionic compounds such as polyethylene glycol and polyhydric alcohol fatty acid esters, fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, sulfosuccinates, alkyl phosphates, and the like, alkyls There are surfactants such as amine salts, cationic systems such as alkylbetaines, carboxylic acid amine salts, sulfonic acid amine salts, and sulfate ester salts.

The aqueous polyisocyanate composition of the present invention can be obtained by adding the hydrophilic group-introducing compound exemplified above at any stage before, during or after the production of the polyisocyanate composition as a precursor. It is preferable to add a hydrophilic group-introducing compound after the production of the precursor polyisocyanate composition.
A polyisocyanate to which no hydrophilic group is added can also be mixed with the obtained aqueous polyisocyanate composition.
Surprisingly, when the precursor polyisocyanate composition having the specific constituents shown above is used, water dispersion is good even if the ratio of hydrophilic groups to be introduced is small, and high crosslinkability and high coating film. Hardness was developed.

The aqueous polyisocyanate composition of the present invention can contain a solvent.
Examples of the above specific organic solvent include, for example, 1-methylpyrrolidone, methyl ethyl ketone, acetone, methyl isobutyl ketone, propylene glycol monomethyl ether acetate, ethyl acetate, isopropyl acetate, butyl acetate, toluene, xylene, pentane, iso- Pentane, hexane, iso-hexane, cyclohexane, solvent naphtha, mineral spirit, etc. can be mentioned, and two or more kinds can be used in combination. As the organic solvent, those having a solubility in water of 5% by mass or more are preferable. If an organic solvent having a solubility in water of less than 5% by mass is used, the water dispersibility of the aqueous polyisocyanate composition may decrease. Moreover, the thing whose boiling point is 100 degreeC or more is preferable, and when the organic solvent whose boiling point is less than 100 degreeC is used, volatilization of the organic solvent will become quick at the time of coating-film formation, and it may affect the coating-film surface appearance. The usage-amount of a solvent is 0-20 mass% of an aqueous polyisocyanate composition. If it exceeds 20% by mass, the solvent that volatilizes increases when used as a coating material, which is not environmentally preferable.

The aqueous polyisocyanate composition of the present invention constitutes the main component of the aqueous coating composition of the present invention together with a polyol. The isocyanate group in the aqueous polyisocyanate composition can react with the hydroxyl group of this polyol to form a crosslinked coating film.
As the polyol used in the aqueous coating composition of the present invention, it can be used without particular limitation as long as it is usually used for an aqueous coating. Specific examples include acrylic polyol, polyester polyol, polyether polyol, polyolefin polyol, epoxy polyol, and fluorine polyol.

  Examples of the acrylic polyol include acrylic acid esters having active hydrogen such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate, or monoester or methacrylic acid glycerol. Acid monoester, trimethylolpropane acrylic acid monoester or methacrylic acid monoester alone or in mixture thereof and 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxymethacrylate A single component or a mixture selected from the group of methacrylic acid esters having active hydrogen such as butyl, methacrylic acid-3-hydroxypropyl, methacrylic acid-4-hydroxybutyl and the like, and methyl acrylate, acrylic acid Acrylic esters such as chill, isopropyl acrylate, acrylate-n-butyl, acrylate-2-ethylhexyl, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, methacrylate-n-butyl, isobutyl methacrylate, methacryl Methacrylic acid esters such as acid-n-hexyl and lauryl methacrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid; unsaturated amides such as acrylamide, N-methylolacrylamide, and diacetoneacrylamide; And glycidyl methacrylate, styrene, vinyl toluene, vinyl acetate, acrylonitrile, dibutyl fumarate, vinyltrimethoxysilane, vinylmethyldimethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane Examples thereof include acrylic polyols obtained by polymerization in the presence or absence of a single or a mixture selected from the group of other polymerizable monomers such as vinyl monomers having hydrolyzable silyl groups such as run.

  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 e.g., ε-caprolactone to polyhydric alcohol. And polycaprolactones obtained by ring-opening polymerization.

  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) e.g. erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol Sugar alcohol compounds such as rhamnitol (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) For example, trisaccharides such as raffinose, gentianose, and meletitose (6) There are tetrasaccharides such as stachyose.

Examples of the polyolefin polyol include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene.
Examples of the epoxy polyol include bisphenol-type epoxy resins modified with amine or amino alcohol.
Examples of the fluorine polyol include a resin composed of a monomer copolymerizable with fluorinated ethylene.
Preferred polyols are acrylic polyols and polyester polyols.

The polyol must be emulsified, dispersed or dissolved in water. Therefore, the carboxyl group, sulfone group, etc. contained in the polyol can be neutralized.
Examples of the compound for neutralizing a carboxyl group, a sulfone group, and the like include organic amines and inorganic bases. Examples of the organic amine include water-soluble amino compounds such as monoethanolamine, ethylamine, dimethylamine, diethylamine, triethylamine, propylamine, dipropylamine, isopropylamine, diisopropylamine, triethanolamine, butylamine, dibutylamine, 2 -One or more types selected from ethylhexylamine, ethylenediamine, propylenediamine, methylethanolamine, dimethylethanolamine, diethylethanolamine, morpholine and the like can be used. As the inorganic base, ammonia, potassium hydroxide, or sodium hydroxide can be used. Preferably, tertiary amines such as triethylamine and dimethylethanolamine are preferable.

The hydroxyl value per resin component of the polyol is preferably 20 to 300 mgKOH / g, and the acid value is preferably 20 to 100 mgKOH / g.
When the hydroxyl value of the polyol is less than 20 mgKOH / g, the crosslinkability due to reaction with the isocyanate group may be inferior. When the hydroxyl value exceeds 300 mgKOH / g, the crosslinking density increases, and the elongation of the coating film, etc. Physical properties may deteriorate. Moreover, when an acid value is less than 20 mgKOH / g, water dispersibility may fall, and when it exceeds 100 mgKOH / g, physical properties, such as water resistance of the obtained coating film, may fall.

The blending ratio of the aqueous polyisocyanate composition of the present invention and the above polyol is selected as necessary so that the equivalent ratio of the isocyanate group of the aqueous polyisocyanate composition to the hydroxyl group of the polyol is in the range of 0.3 to 1.5. .
If necessary, a resin such as urethane dispersion can be used in combination with the aqueous coating composition of the present invention.

The present invention can contain an acidic compound and a basic compound as a curing accelerator.
Specific examples of the acidic compound include carboxylic acids such as acetic acid and succinic acid, sulfonic acids such as paratoluenesulfonic acid, and acidic phosphate esters such as dioctyl phosphate.
These acidic compounds can be reacted with amine compounds to improve storage stability. Examples of the amine compound include alkylamines such as ethylamine, diethylamine and triethylamine, and alkanolamines such as ethanolamine, diethanolamine and triethanolamine.
Specific examples of the basic compound include amine compounds such as triethylamine and 1,4-diazabicyclooctane, dibutyltin dilaurate, and zinc naphthenate metal carboxylate.
The addition amount of a hardening accelerator is 0.1-10 mass% with respect to the coating resin component mix | blended, Preferably it is 0.1-5 mass%.

If necessary, an antioxidant, an ultraviolet absorber, a pigment, for example, a metal powder pigment such as aluminum, an inorganic pigment such as titanium oxide or carbon black, a rheology control agent, a leveling agent, a solvent, etc. may be added. .
Usually, an aqueous coating composition is obtained by mixing an aqueous polyisocyanate composition, a polyol, an additive, and the like, adding a medium containing water as a main component, and adjusting the coating viscosity according to the coating method.
Examples of the material to be coated of the aqueous coating composition thus prepared include metals, plastics, and inorganic materials.

In addition, it is useful as an overcoat, undercoat, paint for exterior parts, paint for plastic parts such as bumpers, paint for repairing automobiles, paint for organic coating such as precoat metal, etc.
Examples of the coating method include bell coating, spray coating, roll coating, shower coating, and immersion coating.
The aqueous polyisocyanate composition of the present invention is useful as an ink, an adhesive, an inorganic material such as fiber, film, and ceramic, a modifier for paper, wood, resin, etc., or a surface treatment agent in addition to a paint.

Below, based on an Example, this invention is demonstrated still in detail.
First, the measurement method will be described.
(Measurement of number average molecular weight)
The number average molecular weight 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
Column: Tosoh Corporation TSKgel superH1000 x 1
TSKgel superH2000 x 1
TSKgel superH3000 × 1 carrier: Tetrahydrofuran Detection method: Differential refractometer

(Unreacted diisocyanate monomer concentration)
The peak area% of the molecular weight corresponding to the unreacted diisocyanate monomer obtained by the GPC measurement (for example, 168 for HDI) was expressed as its mass concentration.
(Measurement of isocyanurate trimer concentration)
The peak area% corresponding to the molecular weight three times that of the diisocyanate monomer obtained by the GPC measurement is shown as the isocyanurate trimer concentration.
(Ratio of monoalcohol-derived allophanate groups / isocyanurate groups)
From the measurement of proton nuclear magnetic resonance spectrum using JNM-LA400 manufactured by JEOL Ltd., the number ratio of allophanate groups and isocyanurate groups was determined.
(Measurement of uretdione dimer concentration)
The peak area% corresponding to the molecular weight twice that of the diisocyanate obtained by the GPC measurement was shown as the uretdione dimer concentration.
(Measurement of isocyanurate conversion rate)
The reaction liquid refractive index was determined by measurement.

(Measurement of viscosity)
It measured at 25 degreeC using the E-type viscosity meter (Toki Sangyo Co., Ltd. RE-80R).
(Water dispersibility of aqueous polyisocyanate composition)
The aqueous polyisocyanate composition and pure water were mixed at a mass ratio of 2:10, and the subsequent solution state was observed with the naked eye. A state where the mixed liquid was uniform and no precipitate was indicated as ◯, and a case where there was a precipitate was indicated as x. The results are shown in Table 2.
(Gel fraction)
After immersing the cured coating film in acetone at 20 ° C. for 24 hours, the ratio of the undissolved part mass to the mass before immersion was calculated, and the case of less than 60% by mass was represented by x, and the case of 60% by mass or more was represented by ◯. . The results are shown in Table 3.
(Coating hardness)
Using a Koenig hardness meter (Pendulum hardness tester (trade name) manufactured by BYK Garder), the measurement was performed at a temperature of 20 ° C. and a coating film thickness of 40 μm. When the coating film hardness was 10 or more, ◯ and less than 10 were evaluated as x. The results are shown in Table 3.

<Production Example 1> (Production of precursor polyisocyanate composition)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was placed in a nitrogen atmosphere, and 600 parts of HDI and 0.6 part of isobutanol were charged. The temperature was maintained at 2 ° C. for 2 hours. Thereafter, the isocyanurate-forming catalyst tetramethylammonium capryate was added to carry out an isocyanurate-forming reaction. When the conversion rate reached 13%, phosphoric acid was added to stop the reaction. The reaction solution was further maintained at 160 ° C. for 1 hour. This heating produced uretdione group-containing polyisocyanate. The reaction solution was cooled, filtered, and unreacted HDI was removed using a thin film evaporator. The properties of the obtained precursor polyisocyanate composition are shown in Table 1.

<Production Example 2> (Production of precursor polyisocyanate composition)
The same procedure as in Production Example 1 was conducted except that the conversion rate of the isocyanurate reaction was 17%. Table 1 shows the physical properties of the obtained precursor polyisocyanate composition.

<Comparative Production Example 1> (Production of precursor polyisocyanate composition)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was placed in a nitrogen atmosphere, 600 parts of HDI was charged, and maintained at 60 ° C. for 2 hours. Thereafter, tetramethylammonium capriate was added as an isocyanurate-forming catalyst, and an isocyanurate-forming reaction was performed. After 4 hours, when the conversion reached 40%, phosphoric acid was added to stop the reaction.
Then, after filtering a reaction liquid, the unreacted HDI monomer was removed with the thin film distillation apparatus.
Table 1 shows the physical properties of the obtained precursor polyisocyanate composition.

[Example 1] (Production of aqueous 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 precursor polyisocyanate composition obtained in Production Example 1 and methoxy having a molecular weight of 550 were obtained. 30 parts of polyethylene glycol (trade name “Uniox M550” of NOF Corporation) (reacted with 10% of all isocyanate groups of the precursor polyisocyanate composition) was charged and held at 80 ° C. for 6 hours. The physical properties and water dispersibility evaluation results of the obtained aqueous polyisocyanate composition are shown in Table 2.

[Examples 2 to 4] (Production of aqueous polyisocyanate composition)
The procedure was the same as in Example 1 except that it was shown in Table 2. Table 2 shows the physical properties of the aqueous polyisocyanate composition obtained.

[Comparative Examples 1 to 3] (Production of aqueous polyisocyanate composition)
The same procedure as in Example 1 was performed except that the precursor polyisocyanate composition obtained in Comparative Production Example 1 was used and shown in Table 2. The results are shown in Table 2.

[Examples 5 to 8] (Adjustment of aqueous coating composition)
Water-dispersible acrylic polyol neutralized with dimethylethanolamine at a carboxylic acid / amine molar ratio of 1.0 (trade name “SETALUX6512” of Akzo Nobel, resin concentration 42% by mass, hydroxyl value 69 mg KOH / resin g, acid 16 mg KOH / resin g) and the aqueous polyisocyanate composition obtained in Examples 1 to 5 were mixed at an isocyanate group / hydroxyl group equivalent ratio of 1.0. Furthermore, water was added and the viscosity of the paint was changed. 4 was adjusted to 30 seconds. This paint was applied with an applicator and cured at 80 ° C. for 60 minutes. The coating film evaluation results are shown in Table 3.

[Comparative Examples 4 to 5] (Adjustment of aqueous coating composition)
The same operation as in Example 5 was performed except that the aqueous polyisocyanate composition obtained in Comparative Examples 1 and 2 was used. The results are shown in Table 3.

  The aqueous polyisocyanate composition of the present invention is suitable as a curing agent for aqueous coating compositions since it exhibits excellent water dispersibility, high crosslinkability, and high coating film hardness. In addition, inks, adhesives, fibers and films -It is also useful as a modifier or surface treatment agent for inorganic materials such as ceramics, paper, wood and resin.

Claims (6)

An aqueous polyisocyanate composition that can be dissolved or dispersed in water, wherein the polyisocyanate is represented by the following structural formula (1) and satisfies all the following conditions 1) to 4).
(A) _m- R- (NCO) _n (1)
A: Hydrophilic group m: Number of hydrophilic groups n: Number of isocyanate groups R: Residue excluding isocyanate group of polyisocyanate derived from at least one of aliphatic diisocyanate and / or alicyclic diisocyanate Conditions:
1) The average number of isocyanate groups (n _M ) is 2.3 to 3.2, and the average number of isocyanate groups n (n _M ) and the average number of hydrophilic groups m (m _M ) have the following relationship: .
_{m M / (m M + n} M) = 0.02~0.40
2) Isocyanurate trimer and uretdione dimer constituting R satisfy the following a) and b) a) Isocyanurate trimer concentration: 60% by mass to 95% by mass
b) Uretodione dimer concentration; 2 to 25% by mass
3) The isocyanate group concentration is 10 to 24% by mass.
4) Viscosity at 25 ° C. of 200 to 1000 mPa · s   The aqueous polyisocyanate composition according to claim 1, wherein the average number n of isocyanate groups is 2.4 to 3.0.   3. The aqueous polyisocyanate composition according to claim 1, wherein the viscosity at 25 ° C. is 500 to 800 mPa · s.   The aqueous polyisocyanate composition according to any one of claims 1 to 3, wherein the aliphatic and / or alicyclic diisocyanate monomer is hexamethylene diisocyanate. (A) _m- R- (NCO) R in _n is a functional group number ratio of allophanate group / isocyanurate group derived from monoalcohol; 1 to 20%, wherein any one of claims 1 to 4 The aqueous polyisocyanate composition described in 1.   An aqueous coating composition comprising the aqueous polyisocyanate composition according to any one of claims 1 to 5 and a polyol.