JP2011231264A - High compatibility, aqueous block polyisocyanate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous block polyisocyanate excellent in compatibility with polyol and having low-temperature curability; and a paint composition containing the same.SOLUTION: The aqueous block polyisocyanate includes the following ingredient composition: (1) 25-75 mass% of a constitutional unit derived from polyisocyanate derived from at least one of an aliphatic diisocyanate monomer and/or an alicyclic diisocyanate monomer; (2) 2-10 mass% of a constitutional unit derived from diol; (3) 1-30 mass% of a constitutional unit derived from monool obtained by polymerizing alkylene oxide having 3 or more carbon atoms; (4) 5-40 mass% of a constitutional unit derived from polyethylene oxide having a hydroxyl group at one end; and (5) 10-40 mass% of a constitutional unit derived from a blocking agent.

Description

  The present invention relates to a blocked polyisocyanate having excellent compatibility with a polyol and having low temperature curability and a coating composition containing the same.

A coating film formed from a urethane-based coating composition using polyisocyanate as a curing agent is excellent in chemical resistance, flexibility, and the like. In particular, when a polyisocyanate obtained from an aliphatic or alicyclic diisocyanate is used, since the weather resistance is further excellent, its use is in the form of a room temperature curable two-component urethane paint, a thermosetting one-component urethane paint, It covers a wide variety of fields including architecture, heavy defense, automobiles, industrial use and repairs.
In order to reduce the burden on the global environment, water-based examination of polyisocyanate, which is a curing agent used in urethane-based coating compositions exhibiting excellent performance, has been conducted. Many proposals have also been made regarding block polyisocyanates, which are curing agents for one-component coating compositions.
One of the effective methods for making the block polyisocyanate aqueous is to add a hydrophilic group to the block polyisocyanate. The blocked polyisocyanate to which a hydrophilic group is added is lowered when the number of functional groups of the blocked isocyanate is large. In this case, there is a technique for extending the chain with a diol or the like and increasing the number of functional groups of the blocked isocyanate group.
However, this technique has been accompanied by an increase in molecular weight, which may reduce compatibility with the resin used at the same time, and its use has been limited.
Furthermore, the use of many hydrophilic groups may be limited due to poor compatibility with the polyol, which is the main component resin of the urethane coating composition.
On the other hand, improvement of the low temperature curability of block polyisocyanate is desired. There are several proposals regarding aqueous blocked polyisocyanates having a low temperature curability in which isocyanate groups are blocked with pyrazole compounds (Patent Documents 1 and 2).

Japanese National Patent Publication No. 11-512772 Japanese National Patent Publication No. 2002-511507

  An object of the present invention is to provide an aqueous block polyisocyanate having excellent compatibility with a polyol and having low temperature curability and a coating composition containing the same.

As a result of intensive studies, the present inventors have found that a block polyisocyanate derived from a polyisocyanate and a specific compound achieves the above-mentioned problem, and has completed the present invention.
1. An aqueous block polyisocyanate having the following component composition.
1) The proportion of structural units derived from a polyisocyanate derived from at least one of an aliphatic diisocyanate monomer and / or an alicyclic diisocyanate monomer is 25 to 75% by mass.
2) The ratio of the structural unit derived from diol is 2-10 mass%.
3) The proportion of structural units derived from monools in which alkylene oxides having 3 or more carbon atoms are polymerized is 1 to 30% by mass.
4) The ratio of the structural unit induced | guided | derived from the polyethylene oxide which is a single terminal hydroxyl group is 5-40 mass%.
5) The ratio of the structural unit induced | guided | derived from a blocking agent is 10-40 mass%.
2. One aqueous block polyisocyanate, wherein the blocking agent is a pyrazole compound.
3. 1 or 2 aqueous block polyisocyanate, wherein the alkylene oxide having 3 or more carbon atoms is propylene oxide.
4). 1, 2, or 3 aqueous blocked polyisocyanate, wherein the aliphatic diisocyanate monomer and / or alicyclic diisocyanate monomer is hexamethylene diisocyanate.
5. An aqueous coating composition comprising the aqueous blocked polyisocyanate according to any one of 1, 2, 3, and 4.

  The aqueous block polyisocyanate of the present invention is excellent in compatibility with polyol and has low temperature curability.

Hereinafter, the present invention will be described in detail.
The aliphatic and alicyclic diisocyanates that can be used in the present invention do not contain a benzene ring in the structure. As the aliphatic diisocyanate monomer, those having 4 to 30 carbon atoms are preferable. For example, tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate, hexamethylene diisocyanate (HDI), 2,2,4- Examples thereof include trimethyl-hexamethylene-1,6-diisocyanate and lysine diisocyanate. The alicyclic diisocyanate preferably has 8 to 30 carbon atoms, and includes isophorone diisocyanate (hereinafter referred to as IPDI), 1,3-bis (isocyanatemethyl) -cyclohexane, 4,4′-dicyclohexylmethane diisocyanate and the like. Of these, HDI is preferred because of weather resistance and industrial availability. Two or more kinds can be used in combination.

The polyisocyanate used in the present invention is derived from these diisocyanate monomers. The polyisocyanate preferably contains isocyanurate groups. A coating film cured with a polyisocyanate having an isocyanurate group has good weather resistance and can achieve high coating film hardness.
This polyisocyanate can simultaneously contain, for example, a biuret group, a urea group, a uretdione group, a urethane group, an allophanate group, an oxadiazinetrione group, and the like other than the isocyanurate group.
A polyisocyanate having an isocyanurate group is obtained by, for example, carrying out an isocyanurate reaction with a catalyst or the like, stopping the reaction when a predetermined conversion rate is reached, and removing a diisocyanate monomer.

  As the isocyanuration reaction catalyst used in this case, for example, a catalyst having basicity is generally preferred. (A) Tetraalkylammonium hydroxide such as tetramethylammonium and tetraethylammonium, and organic solvents such as acetic acid and capric acid are used. Weak acid salts, (b) hydroxyalkylammonium hydroxides such as trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, triethylhydroxyethylammonium and the like, and organic weak acid salts such as acetic acid and capric acid, (c) acetic acid , Alkali metal salts such as tin, zinc and lead of alkyl carboxylic acids such as caproic acid, octylic acid and myristic acid; (E) aminosilyl group-containing compounds such as hexamethyldisilazane, (f) Mannich bases, (g) combined use of tertiary amines and epoxy compounds, (h) phosphorus compounds such as tributylphosphine Etc. The usage-amount of these catalysts is selected from the range of 10 ppm-1% with respect to the total mass of the diisocyanate and polyol which are raw materials. In order to complete the reaction, these are inactivated by, for example, addition of an acidic substance such as phosphoric acid or acidic phosphoric acid ester that neutralizes the catalyst, thermal decomposition, or chemical decomposition.

The yield of polyisocyanate is selected from the range of 10 to 70% by mass. The viscosity of the polyisocyanate obtained with a high yield is increased.
The reaction temperature of the isocyanuration reaction is 50 to 200 ° C, preferably 50 to 150 ° C. If the temperature is lower than 50 ° C, the reaction hardly proceeds. If the temperature exceeds 200 ° C, undesirable side reactions such as product coloring may occur.
After completion of the reaction, the diisocyanate monomer is removed by a thin film evaporator, extraction or the like, and is substantially free of the diisocyanate monomer. The residual unreacted diisocyanate concentration in the obtained polyisocyanate is 3% by mass or less, preferably 1% by mass or less, and more preferably 0.5% by mass or less. When the diisocyanate monomer concentration exceeds 3% by mass, the curability of the resulting block polyisocyanate may be lowered by using this.
The viscosity of the polyisocyanate that can be used in the present invention is 400 to 30,000 mPa.s at 25 ° C. s, preferably 500 to 10,000, more preferably 550 to 4000.

The number average molecular weight is preferably from 500 to 2,000, more preferably from 550 to 1,000.
The number of isocyanate groups contained in one molecule of the polyisocyanate statistical average is 3 to 15, preferably 3 to 10, and more preferably 3 to 5. When it is less than 3, the crosslinkability may be inferior, and when it exceeds 15, the solubility in a solvent may be deteriorated.

  Isocyanate group concentration is 5-25 mass%, Preferably it is 10-24, More preferably, it is 15-24 mass%.

Examples of the diol that can be used in the present invention include polyester, polyether, acrylic, polyolefin, and polycarbonate.
As the polyester diol, 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 alone or A polyester diol obtained by a condensation reaction of a mixture and a dihydric alcohol selected from the group of ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, etc., alone or in a mixture, and e.g. ε-caprolactone, are opened using the dihydric alcohol. And polycaprolactones obtained by ring polymerization.

Examples of the polyether diol include, for example, a divalent hydroxy compound alone or as a mixture, a hydroxide such as lithium, sodium or potassium, a strong basic catalyst such as an alcoholate or an alkylamine, a metal porphyrin, or a hexacyanocobaltate zinc complex. Polyethers obtained by random or block addition of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, styrene oxide, etc., alone or in mixtures to polyhydric hydroxy compounds using a complex metal cyanide complex of Examples include polyols, and polyether polyols obtained by reacting alkylene oxides with polyamine compounds such as ethylenediamines.
Examples of the polyolefin polyol include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene.

Polycarbonate is derived from carbonate monomers and alcohol. Examples of the carbonate monomer include dialkyl carbonate, diaryl carbonate, and alkylene carbonate.
Examples of the dialkyl carbonate include those having 1 to 12 carbon atoms in the alkyl group, specifically, dimethyl carbonate, diethyl carbonate, dibutyl carbonate and the like.
Examples of the diaryl carbonate include those having an aryl group having 6 to 20 carbon atoms, such as diphenyl carbonate and dinaphthyl carbonate.
The alkylene carbonate consists of a 5- to 7-membered ring, and specific examples include ethylene carbonate and propylene carbonate.
These carbonate monomers may be used alone or in combination of two or more.

  The alcohol used for this is, for example, a divalent and trivalent alcohol having 3 to 20 carbon atoms. Specifically, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,5 -Hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, neopentyl glycol, 2-ethyl-1,6-hexanediol, 2-methyl-1,3-propanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 2,2′-bis (4-hydroxycyclohexyl) -propane 1,4-dimethylolcyclohexanebishydroxytetrahydrofuran, di (2-hydroxy Chill) dimethylhydantoin, diethylene glycol, triethylene glycol, polypropylene glycol, polytetramethylene glycol, 6-hydroxy-ethyl hexanol, and the like 5-hydroxyethyl-pentanol.

Of these diols, polyether diols, polyester diols, and polycarbonate diols are preferred.
The number average molecular weight of these diols is 200-1500, preferably 300-1000, more preferably 300-800.

A monool obtained by polymerizing an alkylene oxide having 3 or more carbon atoms that can be used in the present invention (hereinafter referred to as monool (1)) is derived from a starting monoalcohol and an alkylene oxide having 3 or more carbon atoms. The starting monoalcohol has 1 to 10 carbon atoms, preferably 2 to 8 carbon atoms, and more preferably 4 to 8 carbon atoms. These specific monoalcohols include alcohols such as methanol, ethanol, 2-propanol, n-butanol, sec-butanol, and 2-ethyl-1-hexanol.
Examples of the alkylene oxide having 3 or more carbon atoms include propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide, and propylene oxide is preferable.
These alkylene oxides alone or in combination with the above starting monoalcohols, for example, hydroxides such as lithium, sodium and potassium, strong basic catalysts such as alcoholates and alkylamines, metal porphyrins, hexacyanocobaltate zinc complexes and the like It can be obtained by addition using a metal cyanide complex or the like.

The monool (1) used in the present invention can contain an alkylene oxide having 2 or less carbon atoms, and the mass ratio is 30 mass% or less, preferably 20 mass% or less, more preferably 20 mass% or less. Preferably it is 10 mass% or less.
The number average molecular weight of monool (1) used in the present invention is 300 to 2000, preferably 300 to 1500, and more preferably 350 to 1000. If the number average molecular weight of the monool is less than 300, the compatibility of the polyisocyanate of the block polyisocyanate obtained by using the monool may decrease, and if it exceeds 2000, the hardness of the coating film may decrease. is there.

  It was surprising that the monoblock (1) added, aqueous block polyisocyanate with a highly polar bond has excellent compatibility with polyols. The hydrophilic block and the bond formed by the isocyanate group and the blocking agent in the aqueous block polyisocyanate suppress the compatibility with the polyol.

  Monool (1) used in the present invention has a large molecular weight, and in addition, oxygen is present in the repeating unit of the molecular chain. This is considered that the monool (1) approaches the low compatibility part of the aqueous block polyisocyanate and improves the compatibility with the polyol as a whole.

Polyethylene oxide which is a single-terminal hydroxyl group that can be used in the present invention (hereinafter referred to as monool (2)) is obtained by adding ethylene oxide to the starting monoalcohol described in monool (1). A compound. A preferred starting alcohol is methanol.
The molecular weight is 300 to 2000, preferably 300 to 1500, and more preferably 500 to 1000.

The blocking agent that can be used in the present invention is a compound having one active hydrogen in the molecule, for example, alcohol, alkylphenol, phenol, active methylene, mercaptan, acid amide, and acid imide. Imidazole, urea, oxime, amine, imide, and pyrazole compounds. Examples of more specific blocking agents are shown below.
(1) Alcohols such as methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol,
(2) alkylphenol-based mono- and dialkylphenols having an alkyl group having 4 or more carbon atoms as a substituent, such as n-propylphenol, i-propylphenol, n-butylphenol, sec-butylphenol, t-butylphenol , N-hexylphenol, 2-ethylhexylphenol, n-octylphenol, n-nonylphenol and other monoalkylphenols, di-n-propylphenol, diisopropylphenol, isopropylcresol, di-n-butylphenol, di-t-butylphenol, di- Dialkylphenols such as -sec-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, di-n-nonylphenol,
(3) phenolic; 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 series; butyl mercaptan, dodecyl mercaptan, etc.
(6) Acid amide system: acetanilide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, etc.
(7) Acid imide type; succinimide, maleic imide, etc.
(8) Imidazole series; imidazole, 2-methylimidazole, etc.
(9) Urea system; urea, thiourea, ethylene urea, etc.
(10) Oxime type: formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, cyclohexanone oxime, etc.
(11) Amine type; diphenylamine, aniline, carbazole, di-n-propylamine, diisopropylamine, isopropylethylamine, etc.
(12) Imine type; ethyleneimine, polyethyleneimine and the like; and (13) Pyrazole type; pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole and the like. Two or more of these can be used in combination. Preferred blocking agents are amine-based, preferably aliphatic amine-based or pyrazole-based compounds, and more preferable blocking agents are pyrazole-based compounds, and 3,5-dimethylpyrazole is particularly preferable.
By reacting the polyisocyanate, diol, monool (1), (2) and blocking agent described above, the aqueous blocked polyisocyanate of the present invention can be obtained. The diol, monool (1), (2) and the active hydrogen of the blocking agent all react with the isocyanate group of the polyisocyanate. The reaction order of these components may be any, but it is preferred that all of the isocyanate groups react by reacting the blocking agent with the isocyanate groups. After reacting each component other than the blocking agent with the isocyanate group, the reaction of all of the isocyanate groups may result in these components remaining in a state in which they do not finally react with the isocyanate groups due to the metering variation of the raw materials. There is not preferable. It is preferable that the blocking agent finally remains in an unreacted state.

  The reaction of the polyisocyanate, diol, monool (1), (2) and the blocking agent can be carried out with or without a solvent. When using a solvent, it is necessary to use a solvent inert to the isocyanate group. Examples of the solvent include ketone solvents such as acetone and methyl ethyl ketone, and ester solvents such as ethyl acetate and butyl acetate.

  If necessary, organic metal salts such as tin, zinc and lead, tertiary amine compounds, alkali metal alcoholates such as sodium, and the like may be used as catalysts.

  The reaction 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.

  The mass concentration of structural units derived from these components in the block polyisocyanate of the present invention will be described.

  The proportion of the structural unit derived from polyisocyanate is 25 to 75% by mass, preferably 30 to 70% by mass, and more preferably 40 to 60% by mass. If it is less than 25% by mass, the blocked isocyanate group concentration becomes low, and the curability may be lowered. If it exceeds 75% by mass, the proportion of structural units derived from the diol and monools (1) and (2) will eventually decrease, and the compatibility with polyol and water dispersibility may decrease.

  The proportion of structural units derived from diol is 2 to 10% by mass, preferably 2 to 5% by mass. If it is less than 2% by mass, the number of blocked isocyanate groups may be reduced, and if it exceeds 10% by mass, the hardness of the coating film formed thereby may be reduced.

  The proportion of structural units derived from monool (1) is 1 to 30% by mass. When the content is less than 1% by mass, the compatibility with the polyol decreases, and when it exceeds 30% by mass, the hardness of the resulting coating film may decrease.

  The proportion of structural units derived from the monool (2) is 5 to 40% by mass, preferably 10 to 40% by mass. If it is less than 5% by mass, the solubility in water and dispersibility may be reduced, and if it exceeds 40% by mass, the hardness of the resulting coating film may be reduced.

  The proportion of the structural unit derived from the blocking agent is 10 to 40% by mass, preferably 10 to 30% by mass. If it is less than 10% by mass, the curability may be lowered, and if it exceeds 40% by mass, the hardness of the coating film formed thereby may be too high.

  The proportion of the structural unit derived from the diisocyanate trimer of the block polyisocyanate of the present invention thus obtained is 5 to 40% by mass, preferably 10 to 40% by mass, more preferably 10 to 10% by mass. 30% by mass. When this ratio is less than 5% by mass, the hardness and weather resistance of the resulting coating film may be reduced, and when it exceeds 40% by mass, the elongation of the obtained coating film may be reduced. The diisocyanate trimer component referred to here is a block polyisocyanate derived from 3 molecules of a isocyanate having 3 isocyanate groups and 3 molecules of a blocking agent obtained from 3 molecules of a diisocyanate monomer.

  Water can be added to the block polyisocyanate thus produced to form a block polyisocyanate aqueous solution. In this case, the block polyisocyanate is dissolved or dispersed in water. The block polyisocyanate concentration of this aqueous solution is 10 to 40% by mass.

  The number average molecular weight of the aqueous block polyisocyanate of the present invention is 1000 to 3000, preferably 1000 to 2000. If the number average molecular weight is less than 1000, the number of isocyanate groups per molecule may be reduced, and curability may be reduced. If the number average molecular weight exceeds 3000, compatibility with polyol may be reduced.

  The concentration of the isocyanate group blocked with the blocking agent of the aqueous blocked polyisocyanate of the present invention is 5 to 15% by mass. If it is less than 5% by mass, the curability is lowered, and if it exceeds 15% by mass, the coating film may become brittle.

  The aqueous block polyisocyanate of the present invention is mixed with a compound having two or more active hydrogens having reactivity with isocyanate groups in the molecule to form a coating composition of the present invention. The blocked polyisocyanate reacts with the active hydrogen of the active hydrogen-containing compound to form a crosslinked coating film. Examples of the compound having two or more active hydrogens include polyols, polyamines, and polythiols. In many cases, polyols are used. Examples of this polyol include acrylic polyol, polyester polyol, polyether polyol, fluorine polyol, and epoxy polyol. Preferred polyols are acrylic polyols, polyester polyols, and fluorine polyols. The hydroxyl value of these polyols is selected from 30 to 200 mg KOH / g and the acid value of 0 to 40 mg KOH / g.

The equivalent ratio of the isocyanate group of the aqueous block polyisocyanate / the hydroxyl group of the polyol is 0.3 to 1.5, and this ratio is appropriately selected according to the required physical properties.
If necessary, a melamine type curing agent such as a complete alkyl type, a methylol group type alkyl, an imino group type alkyl or the like can be added.

  Moreover, various solvents and additives can be used according to the application and purpose. Solvents include, for example, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate, n-butyl acetate and cellosolve, alcohols such as butanol and isopropyl alcohol, and the like for purposes and applications. It can be appropriately selected and used accordingly. These solvents may be used alone or in combination of two or more.

  Where necessary, antioxidants such as hindered phenols, ultraviolet absorbers such as benzotriazole and benzophenone, pigments such as titanium oxide, carbon black, indigo, quinacridone, pearl mica, metal powder pigments such as aluminum, etc. Rheology control agents such as hydroxyethyl cellulose, urea compounds, and microgels, and curing accelerators such as tin compounds, zinc compounds, and amine compounds may be added.

  Coating compositions prepared in this way can be used for dip coating, roll coating, curtain flow coating, spray coating, electrostatic coating, bell coating, electrodeposition coating, etc. As a primer or top coat for organic / inorganic polymers and inorganic materials, cosmetics, weather resistance, acid resistance, rust resistance, chipping resistance, etc. are added to pre-coated metal including rust-proof steel sheets and automotive coatings. Useful to do. It is also useful as a urethane raw material for adhesives, pressure-sensitive adhesives, elastomers, foams, surface treatment agents and the like.

The present invention will be specifically described with reference to the following examples.
-Number average molecular weight measurement:
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-802A
Column: Tosoh Corporation G1000HXL x 1
G2000HXL x 1
G3000HXL × 1 carrier: Tetrahydrofuran Detection method: differential refractometer / hexane dilution (compatibility index with polyol):
The block polyisocyanate is diluted to 75% by weight with toluene. At 23 ° C., n-hexane is added dropwise to 10 g of the diluted solution. Record the mass of n-hexane when turbidity occurs. The greater the mass of n-hexane, the better the compatibility with the polyol.
・ Water dispersibility:
Pure water is mixed and stirred so that the aqueous block polyisocyanate is 30% by mass. After stirring, the presence or absence of a precipitate was visually observed, and the case where there was no precipitate was shown as ◯ and the case where there was no precipitate was shown as x.
(Production Example 1: Production of polyisocyanate)

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 by mass of HDI was charged, and the reactor internal temperature was maintained at 70 ° C. with stirring. Isocyanuration catalyst tetramethylammonium capriate was added, and when the yield reached 40%, phosphoric acid was added to stop the reaction. After the reaction solution was filtered, unreacted HDI was removed using a thin film evaporator. The resulting polyisocyanate had a viscosity at 25 ° C. of 2700 mPa · s, an isocyanate content of 21.7% by mass, a number average molecular weight of 660, and an average number of isocyanate groups of 3.4.
Example 1

100 parts by mass of the polyisocyanate obtained in Production Example 1 in a reactor similar to Production Example 1, a monool obtained by polymerizing propylene oxide (trade name of Asahi Glass Co., Ltd., “Preminol SX1050”, resin hydroxyl value of 94 mgKOH / g, molecular weight 600) 15 parts by mass, diol (trade name “EXCENOL 420” from Asahi Glass Co., Ltd., resin partial hydroxyl value 280 mg KOH / g, molecular weight 400), 6 parts by mass, polyethylene oxide having one terminal hydroxyl group (trade name “MPG081” from Nippon Emulsifiers, Resin content hydroxyl value 81 mgKOH / g, number average molecular weight 690) 53 parts by mass were charged, and kept under nitrogen atmosphere at 120 ° C. for 2 hours. Then, after making the inside of a reactor into 70 degreeC, 38 mass parts (1.05 times equivalent with respect to the isocyanate group blocked) of 3, 5- dimethyl pyrazole was added. Thereafter, it was confirmed by the infrared spectrum that the characteristic absorption of the isocyanate group disappeared. The average molecular weight of the resin was 1450, and the concentration of isocyanate groups blocked with a blocking agent was 7.4% by mass.
This aqueous block polyisocyanate had a water dispersibility of ◯ and a hexane dilution of 13.
(Example 2, Comparative Example 1)

  The procedure was the same as in Example 1 except for the conditions described in Table 1. The results are shown in Table 1. The hexane dilution of the comparative example was lower than that of the example.

The aqueous block polyisocyanate of the present invention and a coating composition containing the same can be suitably used in the field of coatings and the like.

Claims (5)

An aqueous block polyisocyanate having the following component composition.
1) The proportion of structural units derived from a polyisocyanate derived from at least one of an aliphatic diisocyanate monomer and / or an alicyclic diisocyanate monomer is 25 to 75% by mass.
2) The ratio of the structural unit derived from diol is 2-10 mass%.
3) The proportion of structural units derived from monools in which alkylene oxides having 3 or more carbon atoms are polymerized is 1 to 30% by mass.
4) The ratio of the structural unit induced | guided | derived from the polyethylene oxide which is a single terminal hydroxyl group is 5-40 mass%.
5) The proportion of structural units derived from the blocking agent is 10 to 40% by mass   The aqueous blocked polyisocyanate according to claim 1, wherein the blocking agent is a pyrazole compound.   The aqueous block polyisocyanate according to claim 1 or 2, wherein the alkylene oxide having 3 or more carbon atoms is propylene oxide.   The aqueous blocked polyisocyanate according to claim 1, 2 or 3, wherein the aliphatic diisocyanate monomer and / or alicyclic diisocyanate monomer is hexamethylene diisocyanate.   An aqueous coating composition containing the aqueous blocked polyisocyanate according to any one of claims 1, 2, 3 and 4.