JP2010059089A - Cationic blocked polyisocyanate and urethane composition including the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a blocked polyisocyanate which does not uses an organometallic compound and excels in low temperature curability and a urethane composition including the same. <P>SOLUTION: The blocked polyisocyanate has both an isocyanate group blocked with a pyrazole compound and a cationic group in the molecule at an equivalent weight ratio of 50:50 to 95:5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cationic block polyisocyanate and a urethane composition using the same.

  A coating film obtained from a urethane-based coating composition using polyisocyanate as a curing agent is excellent in chemical resistance and flexibility. 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.

  Thermosetting one-component urethane paint does not react at room temperature and has excellent storage stability. Unlike two-component urethane paint, there is no need to mix polyol and polyisocyanate immediately before use. Are better. However, its curing temperature is high, which not only consumes a lot of energy, but also limits the coating on materials that are not heat resistant. Therefore, it has been desired to lower the curing temperature.

  In recent years, reducing environmentally hazardous substances has also become an important technical issue.

  Block polyisocyanates that can improve the low-temperature curability of block polyisocyanates and at the same time can be used in water-based paints have been demanded, and developments for achieving these technical problems are actively being performed (Patent Documents 1 and 2).

  A blocked polyisocyanate using a pyrazole-based compound as a blocking agent that can be used in water-based paints has achieved a certain degree of low-temperature curing. It is also superior to oxime compounds, which are general-purpose blocking agents, in terms of baking yellowing of the coating film. However, further low temperature curability is required.

  Moreover, in order to improve the sclerosis | hardenability of the coating composition using block polyisocyanate, an organometallic compound may be used. Certain organometallic compounds may discuss the environmental impact.

Special table 11-512772 gazette JP 2000-26570 A

  An object of this invention is to provide the block polyisocyanate excellent in low-temperature curability which does not use an organometallic compound, and the urethane composition containing this.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have surprisingly found that a blocked polyisocyanate having both a blocked isocyanate group blocked with a pyrazole compound and a cationic group in the same molecule is curable. As a result, the present invention was completed. The number of blocked isocyanate groups that one molecule of the blocked polyisocyanate has affects the curability of the blocked polyisocyanate. When the number of blocked isocyanate groups is large, the curability is excellent. It was completely unexpected that the block polyisocyanate of the present invention was improved in its curability even though the number of blocked isocyanate groups was reduced as a result of the introduction of cationic groups.

That is, the present invention is as follows.
1. A blocked polyisocyanate characterized in that it has both an isocyanate group blocked with a pyrazole compound and a cationic group in the same molecule, and an equivalent ratio thereof is 50:50 to 95: 5.
2. 1. The diisocyanate monomer concentration contained in the polyisocyanate which is the precursor of the block polyisocyanate is 3% by mass or less. Block polyisocyanate.
3. 1. Polyisocyanates are derived from aliphatic and / or alicyclic diisocyanate monomers. Or 2. Block polyisocyanate.
4). 1. the cationic group has been neutralized; To 3. The block polyisocyanate according to any one of the above.
5). Polyol and To 4. The urethane composition containing the block polyisocyanate as described in any one of these.
6). 4. an aqueous urethane composition; An aqueous urethane composition.

  The block polyisocyanate of the present invention has excellent low-temperature curability and can be used to form an aqueous urethane composition.

  The present invention will be specifically described below.

  The aliphatic or alicyclic diisocyanate monomer that can be used in the present invention is a compound that does not contain a benzene ring in its structure. As the aliphatic diisocyanate monomer, those having 4 to 30 carbon atoms are preferable, and as the alicyclic diisocyanate monomer, those having 8 to 30 carbon atoms are preferable. For example, tetramethylene-1,4-diisocyanate, pentamethylene-1,5. -Diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene-1,6-diisocyanate, lysine diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) -cyclohexane, 4,4'-dicyclohexylmethane A diisocyanate etc. can be mentioned. Of these, hexamethylene diisocyanate (hereinafter referred to as HDI) and isophorone diisocyanate (hereinafter referred to as IPDI) are preferable, and HDI is particularly preferable because of weather resistance and industrial availability. It may be used alone or in combination.

From these diisocyanate monomers, a polyisocyanate which is a precursor of the block polyisocyanate of the present invention can be obtained.
The polyisocyanate can include, for example, a biuret bond, a urea bond, an isocyanurate bond, a uretdione bond, a urethane bond, an allophanate bond, an iminooxadiazine dione bond, and the like. For example, two or more bonds such as isocyanurate bond and allophanate bond, isocyanurate bond and uretdione bond may be included.

A polyisocyanate having a biuret bond is obtained by reacting a so-called biuretizing agent such as water, t-butanol and urea with a diisocyanate monomer at a molar ratio of the biuretizing agent / isocyanate group of the diisocyanate monomer at about 1/2 to about 1/100. Thereafter, the diisocyanate monomer is removed. With respect to these techniques, for example, JP-A-53-106797, JP-A-55-11452, JP-A-59-95259 are disclosed.
The urea bond is formed from an isocyanate group and water or an amine group, but has a large cohesive force and a small content in ordinary polyisocyanate.

  The polyisocyanate having an isocyanurate bond is obtained by, for example, performing a cyclic trimerization reaction with a catalyst or the like, stopping the reaction when the conversion rate is about 5 to about 80% by mass, and removing the diisocyanate monomer. At this time, a 1 to 6 valent alcohol compound described later can be used in combination as a raw material. With regard to these techniques, for example, JP-A-55-38380, JP-A-57-78460, JP-A-57-47321, JP-A-61-111371, JP-A-64-33115. No. 2, JP-A-2-250872, and JP-A-6-3129969.

  The polyisocyanate having a urethane bond can be produced using a polyhydric alcohol compound which is a non-polymerized polyol and / or a polymerized polyol and a diisocyanate monomer. The polyhydric alcohol compound is a polyol that does not undergo polymerization history, and the polymerization polyol is obtained by polymerizing monomers.

  Examples of the polyhydric alcohol compound include diols, triols, and tetraols. Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3 -Butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,2-propanediol, 1,5-pentanediol, 2-methyl-2,3-butanediol, 1,6 -Hexanediol, 1,2-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethyl-hexanediol, 1 , 2-octanediol, 1,2-decanediol, 2,2,4-tri Examples include tilpentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, and examples of triols include glycerin and trimethylolpropane. Examples of tetraols include pentaerythritol.

  Examples of the polymerization polyol include polyester polyol, polyether polyol, acrylic polyol, and polyolefin polyol.

  As the polyester polyol, for example, a dibasic acid selected from the group of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, or a mixture thereof Polyester polyol obtained by a condensation reaction with a single or mixture of polyhydric alcohols selected from the group of ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, glycerin, etc., and for example, ε-caprolactone And polycaprolactones obtained by ring-opening polymerization using a monohydric alcohol compound. These polyester polyols can be modified with aromatic diisocyanates, aliphatic and alicyclic diisocyanates and polyisocyanates obtained therefrom. In this case, in particular, aliphatic and alicyclic diisocyanates and polyisocyanates obtained therefrom are preferable from the viewpoint of weather resistance, yellowing resistance and the like.

  As the polyether polyol, for example, a polyhydric alcohol compound alone or in a mixture, for example, a hydroxide such as lithium, sodium or potassium, a strongly basic catalyst such as alcoholate or alkylamine, a metal porphyrin, a hexacyanocobaltate zinc complex, etc. Polyether polyol obtained by random or block addition of an alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, styrene oxide or the like to a polyvalent hydroxy compound using a complex metal cyanide complex of In addition, polyether polyols obtained by reacting alkylene oxide with polyamine compounds such as ethylenediamines, and acrylamide etc. are polymerized using these polyethers as a medium. Obtained include so-called polymer polyols and the like.

As the polyhydric alcohol compound,
1) For example, diglycerin, ditrimethylolpropane, pentaerythritol, dipentaerythritol, etc. 2) Sugar alcohol compounds 3 such as erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol, rhamnitol ) Monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose, ribodesose,
4) Disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose, melibiose,
5) For example, trisaccharides such as raffinose, gentianose, and meletitose 6) Examples include tetrasaccharides such as stachyose.

As an acrylic polyol, for example,
Acrylic acid ester with active hydrogen such as acrylic acid-2-hydroxyethyl, acrylic acid-2-hydroxypropyl, acrylic acid-2-hydroxybutyl, etc., acrylic acid monoester or methacrylic acid monoester, trimethylolpropane Acrylic acid monoester or methacrylic acid monoester, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate As an essential component, a single or mixture selected from the group of methacrylic acid esters having active hydrogen and the like,
Acrylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic acid-n-butyl, acrylic acid-2-ethylhexyl, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, methacrylate-n-butyl, Methacrylic acid esters such as isobutyl methacrylate, methacrylic acid-n-hexyl, lauryl methacrylate, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, acrylamide, N-methylol acrylamide, diacetone acrylamide, etc. Unsaturated amide and glycidyl methacrylate, styrene, vinyl toluene, vinyl acetate, acrylonitrile, dibutyl fumarate, vinyltrimethoxysilane, vinylmethyldimethoxysilane, γ-methacryloxypro The presence of other polymerizable alone or mixtures selected from the group of monomers such as vinyl monomers having a hydrolyzable silyl group such as Le silane, or by polymerizing in the absence and acrylic polyols obtained.

  Examples of the polyolefin polyol include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, and hydrogenated polyisoprene. Furthermore, isobutanol, n-butanol, 2-ethylhexanol and the like, which are monoalcohol compounds having 50 or less carbon atoms, can be used in combination.

  These polyol and / or polyhydric alcohol compound and diisocyanate monomer are reacted at a molar ratio of hydroxyl group of the polyol and / or polyhydric alcohol compound / isocyanate group of the diisocyanate monomer at about 1/2 to about 1/100, and then the diisocyanate monomer. Is obtained by removing

The polyisocyanate having an allophanate bond can be produced from the above polyol and / or alcohol compound and a diisocyanate monomer. The allophanate bond is a bond in which an isocyanate group is added to a urethane bond, and this bond is formed by using a catalyst, heat, or the like.
The polyisocyanate having an iminooxadiazinedione bond can be obtained by reacting, for example, using a catalyst. For example, Japanese Patent Application Laid-Open No. 2004-534870 discloses a technique related to this.

  The diisocyanate monomer concentration in the obtained polyisocyanate is 3% by mass or less, preferably 1% by mass or less. If it exceeds 3% by mass, curability may be lowered. Two or more of these polyisocyanates can be mixed and used.

  Moreover, the viscosity at 25 degreeC of the polyisocyanate used for this invention is 50-20000000 mPa * s. If it is less than 50 mPa · s, the statistical average number of isocyanate groups of one molecule of polyisocyanate (hereinafter referred to as the average number of isocyanate groups) may decrease as a result. The viscosity of the block polyisocyanate to be produced may increase, and the appearance of the coating film using the block polyisocyanate may deteriorate.

  The average number of isocyanate groups in the polyisocyanate is preferably 2.5 or more, more preferably 3.0 or more and 20 or less, and still more preferably 3.5 or more and 10 or less. If it is less than 2.5, the curability of the finally obtained aqueous block polyisocyanate may be lowered, and if it is more than 20, the reactivity after partial curing of the obtained block polyisocyanate may be lowered.

  At least a part of the isocyanate groups of the polyisocyanate thus obtained reacts with the pyrazole compound, and the isocyanate groups are blocked. The isocyanate group thus blocked is referred to as a blocked isocyanate group, and the compound that blocks the isocyanate group is referred to as a blocking agent. The pyrazole compound that can be used in the present invention is a compound represented by the following formula (1).

Ｒ_１とＲ_２は異なっていても、同一でもよく、水素又は炭素数１〜６のアルキル基である。アルキル基としては、メチル、エチル、ｎ−プロピル、イソプロピルなどがある。具体的な化合物としては、ピラゾール、３，５−ジメチルピラゾール、３−メチルピラゾールなどがあり、３，５−ジメチルピラゾールが好ましい。

R ₁ and R ₂ may be different or the same, and are hydrogen or an alkyl group having 1 to 6 carbon atoms. Alkyl groups include methyl, ethyl, n-propyl, isopropyl and the like. Specific compounds include pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole and the like, and 3,5-dimethylpyrazole is preferable.

Depending on the situation, other blocking agents can be used in combination. The blocking agents that can be used in combination are listed below.
(1) Alcohols such as methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, etc. (2) alkylphenols : Mono- and dialkylphenols having an alkyl group having 4 or more carbon atoms as a substituent, such as n-propylphenol, isopropylphenol, n-butylphenol, sec-butylphenol, t-butylphenol, n-hexylphenol, 2 -Monoalkylphenols such as ethylhexylphenol, n-octylphenol, n-nonylphenol, di-n-propylphenol, diisopropylphenol, isopropylcresol, di-n-butylphenol Dialkylphenols such as diol, di-t-butylphenol, di-sec-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, di-n-nonylphenol, etc. (3) Phenols: phenol, cresol, ethylphenol (4) Active methylene series: dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, etc. (5) Mercaptan series: butyl mercaptan, dodecyl mercaptan, etc. (6) Acid amide series: acetanilide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam etc. (7) Acid imide series: succinimide, maleic imide etc. (8) Imidazole series: imidazole, 2-methyl (9) Urea series: urea, thiourea, ethylene urea, etc. (10) Oxime series: formaldoxime, acetaldoxime, acetoxime, methylethylketoxime, cyclohexanone oxime, etc. (11) Amine series: diphenylamine, aniline, carbazole , Di-n-propylamine, diisopropylamine, isopropylethylamine, etc. The block polyisocyanate of the present invention has a cationic group.

  For the introduction of the cationic group, a method using a compound having both a cationic group and an active hydrogen that reacts with an isocyanate group, a functional group such as a glycidyl group is introduced into the polyisocyanate in advance, and then, for example, a sulfide or a phosphine. And the like, but the former method is easy.

  Examples of the active hydrogen that reacts with an isocyanate group include a hydroxyl group and a thiol group.

  Examples of the compound having both a cationic group and an active hydrogen that reacts with an isocyanate group include dimethylethanolamine, diethylethanolamine, diethanolamine, and methyldiethanolamine. The introduced tertiary amino group can be quaternized with dimethyl sulfate, diethyl sulfate or the like.

  The cationic group can be introduced either before or after the isocyanate group is blocked with a pyrazole compound. Cationic group introduction and isocyanate group blocking reaction can be carried out in the presence of a solvent. In this case, the solvent preferably contains no active hydrogen.

  The equivalent ratio of the blocked isocyanate group, which is an isocyanate group blocked with a pyrazole compound, and a cationic group is 50:50 to 95: 5, and preferably 60:40 to 90:10. When the number of blocked polyisocyanate groups is less than this range, the curability is lowered, and when the number of blocked isocyanate groups is more than this range, the resulting cationic groups are lowered and water dispersibility is lowered.

  When the block polyisocyanate of the present invention is used as a raw material for the aqueous urethane composition, the introduced cationic group is preferably neutralized with a compound having an anionic group.

  Examples of the anionic group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group. Examples of the compound having a carboxyl group include formic acid, acetic acid, propionic acid, butyric acid, and lactic acid. Examples of the compound having a sulfone group include ethanesulfonic acid and the like. Examples include acids and acidic phosphates. A compound having a carboxyl group is preferred, and acetic acid, propionic acid, and butyric acid are more preferred. If necessary, the cationic group can be quaternized.

  In the case of neutralization, the equivalent ratio of cationic group: anionic group introduced into the blocked polyisocyanate is from 1: 0.5 to 1: 3, preferably from 1: 1 to 1: 1.5.

  The 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 (hereinafter also referred to as a polyvalent active hydrogen compound) to form the urethane composition of the present invention.

  The block polyisocyanate reacts with the active hydrogen of the polyvalent active hydrogen compound to form a crosslinked urethane resin.

  Examples of the compound having two or more active hydrogens in the molecule include polyol, polyamine, polythiol and the like, and in many cases, polyol is used. These polyols preferably have a cationic group in the molecule. When it has an anionic group, it may be difficult to disperse and dissolve in water together with the cationic block polyisocyanate. Examples of this polyol include epoxy polyol, acrylic polyol, polyester polyol, polyether polyol, and fluorine polyol. If the medium is aqueous, they can take the form of water solubility, dispersion, emulsion, and the like. The epoxy polyol can be obtained by introducing a hydroxyl group and a cationic group into the epoxy resin by reacting an epoxy group of the epoxy resin with an amine group of a compound having both a hydroxy group and an amine group, for example. Preferred polyols are epoxy polyols, acrylic polyols, and polyester polyols. The hydroxyl value of these polyols is selected from 30 to 400 mgKOH / g and the amine value of 0 to 400 mgKOH / g. In particular, the amine value for use in an aqueous urethane composition is selected from 30 to 400 mg KOH / g as required.

  The equivalent ratio of (isocyanate group of block polyisocyanate) / (hydroxyl group of polyol) is 0.5 to 1.5, and this ratio is appropriately selected according to the required physical properties.

  The cationic block polyisocyanate thus obtained and the urethane composition containing the same are, for example, materials such as metals, plastics, fibers (plants, animals, carbon fibers, etc.), inorganic and organic materials, etc. In addition, it is useful as a primer or an intermediate coating material, and as an adhesive, pressure-sensitive adhesive, elastomer, foam, surface treatment agent, and the like.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples. All parts are parts by weight.
(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-802A
Column: Tosoh Corporation G1000HXL x 1
G2000HXL x 1
G3000HXL × 1 carrier: tetrahydrofuran detection method: differential refractometer (unreacted diisocyanate monomer concentration)
The concentration of the peak of the molecular weight corresponding to the unreacted diisocyanate obtained by the GPC measurement (for example, 168 for HDI) was expressed in area%.
(Measurement of viscosity)
It measured at 25 degreeC using the E-type viscosity meter (VISICONIC ED type | mold by Tokimec).
(Water dispersibility)
Water having the same mass as the block polyisocyanate solution was mixed, and the appearance was visually observed after 24 hours. There was no change in the solution state immediately after mixing and after 24 hours, and the state without sediment was indicated as ◯ (good), and the state where there was a change such as the presence of sediment was indicated as x (bad).
(Gel fraction)
The cured coating film is immersed in acetone when acrylic polyol is used, and when immersed in methanol at 20 ° C. for 24 hours when epoxy polyol is used, the undissolved part weight is divided by the weight before immersion, and is expressed in%. When it was less than 80%, it was represented by x (defect), when it was 80% or more and less than 90%, it was indicated by ○ (good), and when it was 90% or more, it was indicated by ◎ (excellent).
(Production Example 1)
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 was charged, and the reactor internal temperature was maintained at 70 ° C. with stirring. The isocyanurate-forming catalyst tetramethylammonium capryate was added, and when the yield reached 40% (3 hours from the addition of the catalyst), 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 2800 mPa · s, an isocyanate group content of 21.7% by mass, a diisocyanate monomer concentration of 0.2% by mass, a number average molecular weight of 660, and an isocyanate functional average number of 3.4. Met. Absorption of isocyanurate groups was observed by infrared spectrum measurement.
(Production Example 2)
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, polycaprolactone polyester polyol “Placcel 303” (Daicel Chemical) The product was charged with 30 parts of a molecular weight of 300), and the urethanization reaction was carried out while maintaining the temperature in the reactor at 90 ° C. for 1 hour with stirring. Thereafter, the temperature in the reactor was maintained at 60 ° C., the isocyanurate-forming catalyst tetramethylammonium capriate was added, and when the yield reached 54%, 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 9500 mPa · s, an isocyanate content of 19.2%, an HDI concentration of 0.2% by weight, a number average molecular weight of 1100, and an isocyanate functional average number of 5.1. .
(Production Example 3)
Using the same apparatus as in Production Example 1, 600 parts of HDI and 134 parts of polyether polyol (ADEKA product name “HP-1030”), which is a pentahydric alcohol, are charged in a nitrogen atmosphere and stirred in the reactor. The temperature was held at 160 ° C. for 5 hours. 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 31000 mPa · s, an isocyanate content of 12.0%, an HDI concentration of 0.2% by weight, a number average molecular weight of 2520, and an isocyanate functional average number of 7.2. .
Example 1
Using the same apparatus as in Production Example 1, 500 parts of polyisocyanate obtained in Production Example 1 and 319 parts of propylene glycol monomethyl ether acetate were charged and mixed in a nitrogen atmosphere. After holding the mixture at 60 ° C. An additional 46 parts of dimethylethanolamine having one cationic group was added. After 30 minutes, the isocyanate group concentration of the polyisocyanate, excluding propylene glycol monomethyl ether, was 15.8%, and it was confirmed that the polyisocyanate and diethylethanolamine had reacted. Thereafter, 208 parts of 3,5-dimethylpyrazole was added. The infrared absorption spectrum of the reaction solution was measured, and it was confirmed that the isocyanate group absorption disappeared. A block polyisocyanate solution having a resin concentration of 70% by mass was obtained. The equivalent ratio of blocked isocyanate groups blocked with 3,5-dimethylpyrazole and diethylethanolamine was 80:20.
(Examples 2 to 5)
The reaction was carried out in the same manner as in Example 1 except that the conditions described in Table 1 were used. The results are shown in Table 1.
(Comparative Examples 1 and 2)
The reaction was carried out in the same manner as in Example 1 except that the conditions described in Table 1 were used. The results are shown in Table 1. For Comparative Example 1, water dispersibility was evaluated, and the results are shown in Table 3.
(Comparative Example 3)
The same procedure as in Example 1 was performed except that 284 parts (equal molar amount of the cationic compound) of methoxypolyethylene glycol (Nippon Yushi Co., Ltd., trade name “Uniox M550”, molecular weight 550) was used instead of the cationic compound. . Water dispersibility was evaluated and the results are shown in Table 3.
(Example 6) (Non-aqueous urethane composition)
The block polyisocyanate of Example 1 and an acrylic polyol (Nuplex's trade name Setalux 1767, resin hydroxyl value 150 mg KOH / g) were mixed so that the isocyanate group / hydroxyl equivalent ratio = 1/1, and further the butyl acetate part was mixed. Then, a paint having a solid content of 50% was prepared. This paint was applied to an PP applicator so that the resin film thickness was 40 μm. After setting for 10 minutes at room temperature, it was kept in an oven at 120 ° C. for 30 minutes. The cured coating film physical properties were evaluated. The evaluation results are shown in Table 2.
(Examples 7 to 10, Comparative Examples 4 to 6)
The reaction was carried out in the same manner as in Example 5 except that the blocked polyisocyanate shown in Table 2 was used. The results are shown in Table 2.
(Example 11) Production of aqueous blocked polyisocyanate To 100 parts of the blocked polyisocyanate solution of Example 1, 2.9 parts of acetic acid (equivalent neutralization) was added to evaluate water dispersibility. The results are shown in Table 3.
(Examples 12 to 15, Comparative Example 7)
The reaction was carried out by carrying out equivalent neutralization in the same manner as in Example 11 except that the blocked polyisocyanate shown in Table 3 was used. The results are shown in Table 3. The water dispersibility of Comparative Examples 1 and 3 was also evaluated.
(Production Example 4) Production of epoxy polyol Using the same apparatus as in Example 1, 300 parts of bisphenol A type epoxy resin (trade name AER260, epoxy equivalent 190 of Asahi Kasei Chemicals Corporation) and 777 parts of ethylene glycol monobutyl ether were charged. 166 parts of diethanolamine was added dropwise over 30 minutes while maintaining the temperature of the charged liquid at 90 ° C. After completion of dropping, the reaction solution temperature was raised to 120 ° C. and held for 1 hour. An epoxy polyol solution having a resin solid content of 60% and a resin content hydroxyl value of 400 mgKOH / g was obtained.
(Example 16)
100 parts of the blocked polyisocyanate solution of Example 1, 233 parts of the epoxy polyol solution of Production Example 4, and 37 parts of acetic acid (equivalent neutralization) were added and mixed. Further, 236 parts of pure water was added to obtain an aqueous urethane composition having a solid content of 40%. The weight ratio of block polyisocyanate resin to epoxy polyol resin is 1: 2. The aqueous urethane composition was applied to a polypropylene plate by an applicator so as to have a resin film thickness of 40 μm and cured at 160 ° C. for 30 minutes. The gel fraction was measured. The results are shown in Table 4.
(Examples 17 to 20, Comparative Example 8)
The reaction was carried out in the same manner as in Example 16 except that the blocked polyisocyanate shown in Table 4 was used. The results are shown in Table 4.
(Comparative Example 9)
The same procedure as in Example 16 was performed except that the block polyisocyanate of Comparative Example 3 was used and acid neutralization was not performed (Comparative Example 3 was a nonionic block polyisocyanate). The results are shown in Table 4.

The block polyisocyanate of the present invention and the urethane composition containing the block polyisocyanate have low-temperature curability in the field of coatings including various surface treatments, and can be suitably used.

Claims (6)

  A blocked polyisocyanate characterized in that it has both an isocyanate group blocked with a pyrazole compound and a cationic group in the same molecule, and an equivalent ratio thereof is 50:50 to 95: 5.   The block polyisocyanate according to claim 1, wherein the concentration of diisocyanate monomer contained in the polyisocyanate which is a precursor of the block polyisocyanate is 3% by mass or less.   The blocked polyisocyanate according to claim 1 or 2, wherein the polyisocyanate is derived from an aliphatic and / or alicyclic diisocyanate monomer.   The block polyisocyanate according to any one of claims 1 to 3, wherein the cationic group is neutralized.   A urethane composition comprising a polyol and the blocked polyisocyanate according to any one of claims 1 to 4. The urethane composition according to claim 5, which is an aqueous urethane composition.