JP4974343B2 - Water-based polyisocyanate composition and water-based coating composition containing the same - Google Patents

Description

  The present invention relates to a water-based polyisocyanate composition and a water-based 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 disclose techniques using polyisocyanate as a curing agent. However, the polyisocyanate used in these cases sometimes cannot achieve both dispersibility and crosslinkability. Patent Documents 3 and 4 disclose polyisocyanates having a high average number of isocyanate groups as the starting isocyanate. In this case, the curability is good, but when high water dispersibility is imparted, the coating film hardness may decrease.

  In order to increase the hardness of the coating film, a mixture of hexamethylene diisocyanate polyisocyanate and isophorone diisocyanate polyisocyanate, which is partially hydrophilized, is disclosed. In some cases, the crosslinkability is not sufficient due to low properties. (Patent Document 5) 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 JP 2005-535775 A

  An object of this invention is to provide the water-based polyisocyanate composition which is excellent in water dispersibility, expresses high crosslinkability, and high coating-film hardness, and the water-based coating composition which uses this as a hardening | curing agent.

As a result of diligent research, the present inventor has surprisingly found that water dispersibility can be obtained by mixing an aqueous polyisocyanate composition (A) having a hydrophilic group and a polyisocyanate composition (B) having a specific skeleton. In addition, the present invention has been completed based on the knowledge that a coating composition using this as a curing agent has high crosslinkability and that the obtained coating film exhibits 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) A water-based polyisocyanate composition which is obtained by mixing the following water-based polyisocyanate composition (A) and polyisocyanate composition (B) in a mass ratio of 90:10 to 10:90 and which can be dissolved or dispersed in water.
(A) represented by the following structural formula, the average number of isocyanate groups n (n _M) is from 2.3 to 10, the average number of isocyanate groups n (n _M) and the average number of hydrophilic groups m (m _M) Is a water-based polyisocyanate composition having a relationship of m _M / (m _M + n _M ) = 0.02 to 0.40.
(X) _m -R- (NCO) _n
X: hydrophilic group m: hydrophilic groups R: derived from residues (B) hexamethylene diisocyanate except for isocyanate group of the induced polyisocyanates from hexamethylene diisocyanate, satisfies all the following conditions while solvent-free hydrophilic A polyisocyanate composition containing no groups.
-Isocyanurate trimer concentration; 60 mass%-95 mass%.
-Uretodione dimer concentration; 2-25 mass%.
Diisocyanate monomer concentration: 1% by mass or less Viscosity at 25 ° C .: 150 to 800 mPa · s.
-Isocyanate group concentration; 22.0-25.0 mass%.
( 2 ) The polyisocyanate composition according to (1) above, wherein the polyisocyanate composition (B) has an average isocyanate group number of 2.5 or more and 3.5 or less.
(3) the polyisocyanate composition (B) further comprises an allophanate groups derived from monoalcohols, functionality ratio of allophanate groups / isocyanurate groups; above, wherein the 1 to 20% (1) or The polyisocyanate composition according to (2) .
( 4 ) A water-based coating composition comprising the water-based polyisocyanate composition as described in (1) to ( 3 ) above as a curing agent.
( 5 ) The water-based coating composition as described in ( 4 ) above, which contains a polyol.

  The water-based polyisocyanate composition of the present invention can provide a coating composition that is excellent in water dispersibility, can exhibit high crosslinkability, and high coating film hardness.

The present invention is described in detail below.
The aqueous polyisocyanate composition (A) of the present invention is obtained by a reaction between a polyisocyanate that is a precursor of an aqueous polyisocyanate and a hydrophilic group-introducing compound.
The precursor polyisocyanate of water-based polyisocyanate (hereinafter referred to as precursor AA) is derived from aliphatic and / or alicyclic diisocyanates. In the present invention using hexamethylene diisocyanate (hereinafter referred to as HDI) as the aliphatic and / or alicyclic diisocyanate.

The precursor AA can have various bonds. Specific examples include isocyanurate groups, uretdione groups, urethane groups, allophanate groups, biuret groups, iminooxadiazinedione groups, and the like, and two or more types can be included.
Among them, it preferably has an isocyanurate group represented by the following formula (1).

Examples of the catalyst for producing an isocyanurate type polyisocyanate containing an isocyanurate group include generally used isocyanurate-forming catalysts.
As the isocyanuration catalyst, for example, a catalyst having basicity is generally preferred,
1) For example, tetraalkylammonium hydroxide such as tetramethylammonium and tetraethylammonium, and weak organic acid salts such as acetic acid and capric acid, and 2) For example, trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, triethylhydroxyethyl Hydroxyalkylammonium hydroxides such as ammonium and organic weak acid salts such as acetic acid and capric acid 3) Alkali metal salts of alkyl carboxylic acids such as acetic acid, caproic acid, octylic acid and myristic acid 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) No. Combination with grade amines with epoxy compounds, 8) for example, a phosphorus-based compounds such as tributyl phosphine.
Of these, quaternary ammonium organic weak acid salts are preferred, and tetraalkylammonium organic weak acid salts are more preferred.

The catalyst used to stop the isocyanuration reaction is deactivated. Examples of the deactivation method include neutralization with an acidic substance such as phosphoric acid and acidic phosphoric acid ester, thermal decomposition, chemical decomposition, and the like.
The precursor AA may contain a uretdione dimer composed of two diisocyanate monomers. A uretdione group consists of two isocyanate groups and is represented by the following formula (2).

The uretdioneization reaction can be obtained using a uretdioneization 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 precursor (AA) of the present invention may have a urethane group and / or an allophanate group. The urethane group is formed from a hydroxyl group and an isocyanate group, and is represented by the following formula (3). The allophanate group is formed from a hydroxyl group and two isocyanate groups, and is represented by the following formula (4).

  Alcohol having a hydroxyl group can be used to form a urethane group or an allophanate group. Specific examples thereof include monoalcohol, diol, polyol and the like. Among them, the monoalcohol includes linear or branched alcohols and alicyclic alcohols. Specific examples thereof include, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, i-butanol, s-butanol, Examples include n-pentanol, n-hexanol, n-octanol, n-nonanol, 2-ethylbutanol, 2,2-dimethylhexanol, 2-ethylhexanol, cyclohexanol, methylcyclohexanol, and ethylcyclohexanol.

A diol is a compound having two hydroxyl groups in one molecule, such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol. 1,2-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-ethylhexane-1,3-diol, methylpentanediol, cyclohexanedimethanol, methylpentanediol, mepentylglycol, water Examples thereof include bisphenol A, diethylene glycol, and triethylene glycol.
Among the above alcohols, branched alcohols such as i-butanol, 2-ethylhexanol, and 2-ethylhexane-1,3-diol are particularly preferable.

  In order to increase the average number of isocyanate groups in the precursor AA, it is preferable to use a polyol. The polyol includes a low molecular weight polyol having a molecular weight of less than 500 and a high molecular weight polyol having a molecular weight of 500 or more. There are triols and tetraols. Examples of the low molecular polyol include triols such as glycerol and trimethylolpropane, and examples of tetraols include pentaerythritol. Of these, trimethylolpropane is particularly preferred.

Examples of the polymer polyol include acrylic polyol, polyester polyol, polyether polyol, and polyolefin 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, etc., or glycerin acrylic acid monoester or methacrylic acid. Acid monoester, trimethylolpropane acrylic acid monoester or methacrylic acid monoester alone or as a mixture thereof and methacrylic acid-2-hydroxyethyl, methacrylic acid-2-hydroxypropyl, methacrylic acid-2-hydroxy A single component or a mixture selected from the group of methacrylic acid esters having active hydrogen, such as butyl, methacrylic acid-3-hydroxypropyl, and methacrylic acid-4-hydroxybutyl, is used as an essential component. Acrylate, isopropyl acrylate, acrylic acid-n-butyl, acrylic acid ester such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacrylic acid 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 polymerized in the presence or absence of a single or mixture selected from the group of other polymerizable monomers such as glycidyl methacrylate, styrene, vinyl toluene, vinyl acetate, acrylonitrile, dibutyl fumarate and the like. Acrylic 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, 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, for example, 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.
The number of hydroxyl groups (hereinafter, the average number of hydroxyl groups) possessed by one statistical molecule of polyol is preferably 2-8, more preferably 3-5. When the average number of hydroxyl groups is less than 2, the range of n of the present invention cannot be obtained and the curability is lowered. On the other hand, if it exceeds 8, the viscosity of the obtained precursor AA becomes very high, or when the molecular weight of the polyol is increased to reduce the viscosity, the aqueous polyisocyanate composition thus obtained is used. In some cases, the resulting coating film may be reduced in curability.

Examples of preferred polyols are the above-mentioned low molecular weight polyols and polycaprolactone polyols obtained by ring-opening polymerization of ε-caprolactone to the low molecular weight polyols.
Low molecular polyols, particularly triols, are preferred for obtaining high coating hardness. The alcohol for forming the urethane group and allophanate group can be added simultaneously with the isocyanurate-forming catalyst, or can be added prior to the addition of the catalyst.
After completion of the reaction, unreacted diisocyanate monomer is removed by a thin film evaporator, extraction or the like.
The concentration of the diisocyanate monomer in the precursor AA is 1% by mass or less, preferably 0.7% by mass or less, and more preferably 0.5% by mass or less.

  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 the precursor AA, a compound having both a hydrophilic group and an active hydrogen group 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.
The anionic group is preferably neutralized 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 compound include, for example, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, and 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 water-based polyisocyanate composition may decrease, and if it exceeds 1.5, the pH of the water-based polyisocyanate solution will be high, and the paint using this The stability of the may decrease.
The ratio _{m M / (m M + n} M) of the hydrophilic group average number _{m M} to the total number of the average number _{m M} of the average number _{n M} and a hydrophilic base m of the isocyanate groups n of the precursor AA 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 AA and the hydrophilic group-introducing compound can be generally 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 (A) 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 precursor AA. It is preferable to add a hydrophilic group after the production of AA.

The water-based polyisocyanate composition (A) of the present invention can contain a solvent for the purpose of reducing the viscosity of the paint.
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. When 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 be lowered. 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, Preferably, it is 0-10 mass%, More preferably, it is 0-5 mass%. 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 (A) used in the present invention has a molecular weight distribution.

The polyisocyanate composition (B) of the present invention is derived from an aliphatic and / or alicyclic diisocyanate, and the usable aliphatic and / or alicyclic diisocyanate is an aqueous polyisocyanate composition (A ) Are used.
The concentration of the diisocyanate trimer having an isocyanurate structure in the polyisocyanate composition (B) of the present invention (hereinafter referred to as isocyanurate trimer) is 60 to 95% by mass. When it is less than 60% by mass, the viscosity of the polyisocyanate composition (B) increases, and when it exceeds 95% by mass, the yield of the polyisocyanate composition (B) decreases. When the isocyanurate group-containing polyisocyanate is derived from a diisocyanate monomer, the same compounds as those described for the precursor AA can be used.

  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 present invention, the conversion rate of the isocyanurate reaction (mass ratio of the polyisocyanate produced by the isocyanurate reaction is 20% or less, preferably 15% or less) It is. 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 polyisocyanate.

At the same time, a polyisocyanate other than an isocyanurate group-containing polyisocyanate such as a uretdione group-containing polyisocyanate may be formed at the same time. Formation of a uretdione dimer by an isocyanuration reaction when obtaining the polyisocyanate of the present invention is not preferred. The uretdione dimer concentration produced by the isocyanuration reaction is 2% by mass or less, preferably 1% by mass or less, based on the polyisocyanate produced by the isocyanuration reaction. If it exceeds 2% by mass, the amount of diisocyanate monomer generated when the polyisocyanate composition (B) is stored increases, which is not preferable. As described above, it was surprising that the suppression of the uretdione dimer generated by the isocyanuration reaction suppresses the generation of the diisocyanate monomer during storage of the polyisocyanate composition (B).
As the catalyst used for the isocyanurate-forming reaction, the above-mentioned 1), 2) and 3) having a high selectivity for the isocyanurate group-containing polyisocyanate are preferable. 5) also produces a biuret group-containing polyisocyanate, and surprisingly, the diisocyanate monomer is liberated during storage of the polyisocyanate, which is not preferable.

The uretdione dimer concentration in the polyisocyanate composition (B) of the present invention is 2 to 20% by mass. If it is less than 2% by mass, the viscosity of the polyisocyanate composition increases, and if it exceeds 20% by mass, the crosslinkability may be lowered.
The uretdione dimer can be obtained using the same uretdione catalyst as described above for the precursor AA.

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.

  The polyisocyanate composition (B) in the present invention preferably further contains an allophanate group derived from a monoalcohol. In this case, the functional group number ratio of the allophanate group / isocyanurate group derived from the monoalcohol in the polyisocyanate composition (B) 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 polyisocyanate composition (B) of 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 monoalcohol added in the polyisocyanate composition (B) of the present invention 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. is there. If it is less than 10/1, a compound composed of two monoalcohol molecules and one diisocyanate monomer may be produced, which is not preferable for obtaining a polyisocyanate having a low viscosity.

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 polyisocyanate composition (B) of the present invention preferably contains no 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 uretdioneation reaction is preferably performed. The isocyanurate formation reaction and the allophanatization reaction are performed using a common catalyst, and the uretdioneation reaction can 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 polyisocyanate composition (B) of the present invention 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 viscosity at 25 ° C. of the polyisocyanate composition (B) of the present invention is 150 to 800 mPa · s, preferably 150 to 700 mPa · s. If it is less than 150 mPa · s, the crosslinkability is lowered, and if it exceeds 800 mPa · s, the solid content concentration of the paint is lowered, which is not preferable.

  The average number of isocyanate groups in the polyisocyanate composition (B) of the present invention is 2.5 or more. Preferably they are 2.8 or more and 3.5 or less. If it is less than 2.5, the crosslinkability may decrease. The average number of isosocyanate groups is determined by the following formula (I).

  The isocyanate group concentration of the polyisocyanate composition (B) of the present invention is 22.0 to 25.0 mass%, preferably 22.5 to 24.0 mass%, more preferably 23.0 to 24.0. % By mass. When the content is less than 22.0% by mass, the concentration of the urethane group in the formed coating film tends to decrease, and the water dispersibility may decrease. When the content exceeds 25.0% by mass, the crosslinkability may be inferior. .

The polyisocyanate composition (B) used in the present invention has a molecular weight distribution.
The aqueous polyisocyanate composition of the present invention is obtained by mixing the aqueous polyisocyanate composition (A) and the polyisocyanate composition (B) in a ratio of 90:10 to 10:90 (mass ratio), preferably 70: 30 to 10:90, more preferably 50:50 to 10:90. If it exceeds 90:10, the water dispersibility is satisfactory, but the crosslinkability and the coating film hardness may be inferior. If it is less than 10:90, the water dispersibility may decrease.

The aqueous polyisocyanate composition used in the present invention has a molecular weight distribution.
The water-based polyisocyanate composition of the present invention constitutes the main component of the water-based 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 water-based coating composition of the present invention, any polyol can be used without particular limitation as long as it is usually used for water-based coatings. Specific examples include epoxy polyols and fluorine polyols in addition to the polyols exemplified above.
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 mixing ratio of the water-based 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 water-based 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 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, a water-based coating composition is obtained by mixing a water-based 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 water-based 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 water-based polyisocyanate composition of the present invention is useful as an ink, an adhesive, an inorganic material such as a fiber, a film, and a ceramic, a modifier for paper, wood, a resin, 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 obtained by the GPC measurement was 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 water-based 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 solution 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 pre-immersion mass was calculated. . The results are shown in Table 3.
(Coating hardness)
Using a König hardness meter (trade name Pendulum hardness tester of BYK Garder), the measurement was performed at a measurement temperature of 20 ° C. and a coating film thickness of 40 μm. The coating film hardness was 20 or more, and less than 20 was x. The results are shown in Table 3.

<Production Example 1> (Production of Precursor AA)
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 AA.

<Production Example 2> (Production of Precursor AA)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen blowing tube, and dropping funnel was placed in a nitrogen atmosphere, 1000 parts of HDI, polycaprolactone polyol-based polyester polyol “PLAXEL 303” (Daicel) Chemical product name: Molecular weight 300) 50 parts were charged, and the temperature in the reactor was kept at 90 ° C. for 1 hour with stirring to conduct a urethanization reaction. Thereafter, the temperature in the reactor was kept at 60 ° C., the isothiocyanuration catalyst tetramethylammonium capriate was added, the refractive index of the reaction solution was measured, and the yield was 54 when the mass of HDI and polyol was taken as 100. At a time corresponding to mass%, phosphoric acid was added to stop the reaction. After the reaction solution was filtered, unreacted HDI was removed using a thin film distillation can. Table 1 shows the physical properties of the obtained precursor AA.

<Production Example 3> (Production of aqueous polyisocyanate composition (A))
A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube, and a dropping funnel was placed in a nitrogen atmosphere, and 100 parts of the aqueous polyisocyanate precursor (AA) obtained in Production Example 1 was molecular weight 550. Of methoxypolyethylene glycol (trade name “Uniox M550” of NOF Corporation) (reacts with 30% of all isocyanate groups of the precursor AA) was charged and held at 80 ° C. for 6 hours. Table 2 shows the physical properties and water dispersibility evaluation results of the water-based polyisocyanate composition (A) obtained.

<Production Examples 4 and 5> (Production of aqueous polyisocyanate composition (A))
The procedure was the same as in Production Example 3 except for those shown in Table 2. Table 2 shows the physical properties of the obtained water-based polyisocyanate composition (A).

<Production Example 6> (Production of polyisocyanate composition (B))
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. Held 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 increase in uretdione dimer mass concentration was 1% or less. 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 resulting polyisocyanate composition (B) are shown in Table 3.

<Production Example 7> (Production of polyisocyanate composition (B))
The same procedure as in Production Example 6 was performed except that the conversion after the isocyanurate reaction was 17%. Table 3 shows the physical properties of the resulting polyisocyanate composition (B).

[Examples 1 to 5] (Production of aqueous polyisocyanate composition)
The water-based polyisocyanate composition (A) shown in Production Examples 3 to 5 and the polyisocyanate composition (B) shown in Production Examples 6 to 7 were mixed at a mass ratio shown in Table 4. Table 4 shows the water dispersibility at that time.

[Comparative Examples 1 to 4] (Production of aqueous polyisocyanate composition)
The procedure was the same as in Example 1 except that it was shown in Table 4. Table 4 shows the water dispersibility at that time.

[Examples 6 to 10] (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” from 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 Example 1-5 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 30 minutes. The coating film evaluation results are shown in Table 5.

[Comparative Examples 5 to 7] (Adjustment of water-based coating composition)
It carried out similarly to Example 6 except having used the water-system polyisocyanate composition obtained by Comparative Examples 1-3. The results are shown in Table 5.

  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 (5)

A water-based polyisocyanate composition that can be dissolved or dispersed in water by mixing the following water-based polyisocyanate composition (A) and polyisocyanate composition (B) in a mass ratio of 90:10 to 10:90.
(A) represented by the following structural formula, the average number of isocyanate groups n (n _M) is from 2.3 to 10, the average number of isocyanate groups n (n _M) and the average number of hydrophilic groups m (m _M) Is a water-based polyisocyanate composition having a relationship of m _M / (m _M + n _M ) = 0.02 to 0.40.
(X) _m -R- (NCO) _n
X: hydrophilic group m: hydrophilic groups R: derived from residues (B) hexamethylene diisocyanate except for isocyanate group of the induced polyisocyanates from hexamethylene diisocyanate, satisfies all the following conditions while solvent-free hydrophilic A polyisocyanate composition containing no groups.
-Isocyanurate trimer concentration; 60 mass%-95 mass%.
-Uretodione dimer concentration; 2-25 mass%.
Diisocyanate monomer concentration: 1% by mass or less Viscosity at 25 ° C .: 150 to 800 mPa · s.
-Isocyanate group concentration; 22.0-25.0 mass%. The polyisocyanate composition according to claim 1 , wherein the average number of isocyanate groups in the polyisocyanate composition (B) is 2.5 or more and 3.5 or less. The polyisocyanate composition (B) further contains an allophanate group derived from a monoalcohol, and has a functional group number ratio of allophanate group / isocyanurate group; 1 to 20% according to claim 1 or 2 , Polyisocyanate composition. A water-based coating composition comprising the water-based polyisocyanate composition according to claim 1 as a curing agent. The water-based coating composition according to claim 4 , comprising a polyol.