JP5599696B2 - Block polyisocyanate composition - Google Patents

Description

  The present invention relates to a block polyisocyanate composition that has low temperature curability and can provide a coating film having good acid resistance, coating film elongation, and adhesion, and a coating composition containing the same.

  A coating film obtained from a urethane-based coating composition using polyisocyanate as a curing agent is excellent in terms of chemical resistance, flexibility and the like. In particular, when a polyisocyanate obtained from an aliphatic or alicyclic diisocyanate is used, a coating film having further excellent weather resistance can be obtained. Therefore, its use is various in the form of room temperature curable two-component urethane paints and thermosetting one-component urethane paints, such as architecture, heavy protection, automobiles, industrial use and repairs thereof.

  Thermosetting one-component urethane paint does not react at room temperature and has excellent storage stability. Therefore, unlike two-component urethane paint, there is no need to mix polyol and polyisocyanate immediately before workability. Are better. As such a one-component urethane coating, for example, a block polyisocyanate composition using a specific blocking agent has been proposed (Patent Document 1).

  When an object to be coated such as plastic or thin plate is deformed, the coating film needs to be stretched to follow the deformation. As a countermeasure, there is a design of a polyol, but its application is limited. Moreover, the specific polyisocyanate which can provide a coating-film elongation is disclosed (patent document 2). However, although the elongation of the coating film obtained by using this is large, the curing temperature of the block polyisocyanate composition using this is high, and the acid resistance of the coating film obtained from this is not sufficient, and its use is limited. It had been. Moreover, the further adhesiveness to a base material is an important function required for a coating film.

  Conventional coating films with high elongation have low crosslink density and poor acid resistance. Therefore, a block polyisocyanate that forms a coating film having high elongation and acid resistance has been desired.

European Publication No. 0159117 JP-A 61-28518

  An object of the present invention is to provide a block polyisocyanate composition which has a low temperature curability and can provide a coating film having good acid resistance, coating film elongation and adhesion, and a coating composition containing the same. That is.

  As a result of intensive studies, the present inventors have solved the above problem by using a specific block polyisocyanate composition containing a block polyisocyanate component having a skeleton in which a polycarbonate diol and a diisocyanate monomer trimer are reacted. As a result, the present invention has been completed.

[1]. A block polyisocyanate composition satisfying all of the following conditions obtained from an aliphatic diisocyanate monomer and / or an alicyclic diisocyanate monomer, a polycarbonate diol having a number average molecular weight of 300 to 2000, and a blocking agent.
1) Blocked diisocyanate monomer trimer component concentration: 5 to 50% by mass
2) Polycarbonate diol component concentration: 3 to 30% by mass
3) Block polyisocyanate concentration derived from 1 molecule of polycarbonate diol, 2 molecules of diisocyanate monomer trimer and 4 molecules of blocking agent: 3 to 30% by mass
[2]. The block polyisocyanate composition according to the above [1], wherein the blocking agent is an amine compound or a pyrazole compound.
[3]. The coating composition containing the block polyisocyanate composition as described in said [1] or [2].
[4]. The manufacturing method of the block polyisocyanate composition as described in said [1] or [2] including all the following processes:
(A). A step of producing a polyisocyanate by reacting an aliphatic diisocyanate monomer and / or an alicyclic diisocyanate monomer;
(B). Removing the unreacted aliphatic diisocyanate monomer and / or unreacted alicyclic diisocyanate monomer from the polyisocyanate obtained by the step (A), and (C). A step of producing a blocked polyisocyanate by reacting the polyisocyanate, a polycarbonate diol having a molecular weight of 300 to 2000, and a blocking agent.

  The block polyisocyanate composition of the present invention has low temperature curability, and the coating film obtained from the composition has good acid resistance, coating film elongation and adhesion.

Hereinafter, the present invention will be described in detail.
The aliphatic and alicyclic diisocyanate monomers that can be used to form the block polyisocyanate composition of the present invention are compounds that do not contain a benzene ring in their structure. As the aliphatic diisocyanate monomer, those having 4 to 30 carbon atoms are preferable. Specifically, tetramethylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate, hexamethylene diisocyanate (hereinafter referred to as HDI). 2,2,4-trimethyl-hexamethylene-1,6-diisocyanate, lysine diisocyanate, and the like. As the alicyclic diisocyanate, those having 8 to 30 carbon atoms are preferable. Specifically, isophorone diisocyanate (hereinafter referred to as IPDI), 1,3-bis (isocyanatemethyl) -cyclohexane, 4,4′-dicyclohexylmethane. A diisocyanate etc. can be mentioned. Of these, HDI is preferred from the viewpoint of weather resistance of the resulting coating film and industrial availability. Two or more of the above compounds can be used in combination.

  In addition to the diisocyanate monomer, a divalent to hexavalent alcohol can be used as a raw material for the polyisocyanate used in the block polyisocyanate composition of the present invention. Examples of such a divalent to hexavalent alcohol (polyol) include non-polymerized polyols and polymerized polyols. A non-polymerized polyol is a polyol that does not undergo polymerization, and a polymerized polyol is a polyol obtained by polymerizing monomers.

  Non-polymerized polyols include diols, triols, tetraols and the like. 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-to Methyl pentanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2-diethyl-1,3-propanediol. Examples of the 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 polyols 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.

  Examples of polyether polyols include hydroxides such as lithium, sodium and potassium, strong basic catalysts such as alcoholates and alkylamines, and complex metal cyanide complexes such as metal porphyrins and hexacyanocobaltate zinc complexes. Polyether polyols 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 single or mixture of polyvalent hydroxy compounds, and further ethylenediamine Polyether polyols obtained by reacting alkylene oxide with polyamine compounds such as aldehydes, and obtained by polymerizing acrylamide etc. using these polyethers as a medium So-called polymer polyols and the like are included.

  The diisocyanate monomer and optionally the divalent to hexavalent alcohol (polyol) are used to derive the polyisocyanate used in the block polyisocyanate composition of the present invention. The polyisocyanate preferably contains an isocyanurate group. A coating film obtained by curing polyisocyanate having an isocyanurate group has good weather resistance and can achieve high coating film hardness.

  In addition to the isocyanurate group, this polyisocyanate can simultaneously contain, for example, a uretdione group, an allophanate group, an oxadiazinetrione group, an iminooxadiazinedione group, and the like.

  The production of a polyisocyanate having an isocyanurate group is carried out, for example, preferably by using a catalyst to carry out an isocyanurate conversion reaction (trimerization reaction) of the diisocyanate monomer, and when the predetermined conversion rate is reached, the reaction is stopped. This is done by removing

  As the isocyanuration reaction catalyst used in this case, a catalyst having basicity is generally preferred. Specifically, (1) for example, tetraalkylammonium hydroxide such as tetramethylammonium and tetraethylammonium, organic weak acid salts such as acetic acid and capric acid, (2) for example, trimethylhydroxypropylammonium and trimethylhydroxyethylammonium Hydroxyalkylammonium hydroxides such as triethylhydroxypropylammonium and triethylhydroxyethylammonium, weak organic acid salts such as acetic acid and capric acid, (3) tins of alkylcarboxylic acids such as acetic acid, caproic acid, octylic acid and myristic acid Metal salts such as zinc and lead, (4) metal alcoholates such as sodium and potassium, (5) aminosilyl group-containing compounds such as hexamethyldisilazane, and (6) Mannich bases , (7) in combination with tertiary amines with epoxy compounds, (8) For example, phosphorus compounds such as tributyl phosphine. 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 catalysts are deactivated by adding an acidic substance such as phosphoric acid or acidic phosphate ester that neutralizes the catalyst, thermal decomposition, chemical decomposition, or the like.

  The yield of polyisocyanate by such an isocyanuration reaction is usually 10 to 70% by mass. Polyisocyanates obtained with high yields tend to have higher viscosities.

  The reaction temperature of the isocyanuration reaction is usually 50 to 200 ° C, preferably 50 to 150 ° C. The reaction easily proceeds at a reaction temperature of 50 ° C. or higher. On the other hand, unfavorable side reactions such as product coloring can be suppressed by a reaction temperature of 200 ° C. or lower.

  After completion of the reaction, the diisocyanate monomer is removed by a thin film evaporator, extraction or the like. The concentration of unreacted diisocyanate remaining in the obtained polyisocyanate may be 3% by mass or less, preferably 1% by mass or less, more preferably 0.5% by mass or less. If the unreacted diisocyanate monomer concentration is 3% by mass or less, it is possible to prevent the curability of the block polyisocyanate composition obtained by using this from decreasing.

  The block polyisocyanate composition of the present invention can be obtained by reacting the polyisocyanate thus obtained, a polycarbonate diol having a specific number average molecular weight, and a blocking agent. The reaction of polyisocyanate, polycarbonate diol and blocking agent can be carried out by three-component reaction at the same time, or after the reaction of polyisocyanate and polycarbonate diol, further reaction with blocking agent, reaction of polyisocyanate and blocking agent. Any method of further reacting with polycarbonate diol is possible.

  The number average molecular weight of the polycarbonate diol used in the block polyisocyanate composition of the present invention is usually 300 to 2000, preferably 300 to 1500. By setting the number average molecular weight of the polycarbonate diol to 300 or more, the elongation at break of the coating film obtained from the block polyisocyanate composition obtained using the polycarbonate diol is improved. Moreover, the fall of the hardness of the coating film can be prevented by making this number average molecular weight 2000 or less.

  The polycarbonate diol used in the present invention can be represented by the following formula (1), wherein R is a divalent linear, branched or cyclic alkylene group, and among these, the carbon number is 2 to 12 An alkylene group is preferred. R in the more preferable formula is a group represented by the following formula (2), (3), (4) or (5), or a cyclohexenyl group. Two or more of these may be included. More preferable R is a group in which m is 5 or 6 in the following formula (2).

  Although it does not specifically limit as a blocking agent which can be used for the block polyisocyanate composition of this invention, An amine compound or a pyrazole type compound is mentioned. Specific examples of the amine compound include diphenylamine, aniline, carbazole, di-n-propylamine, diisopropylamine, and isopropylethylamine. Specific pyrazole compounds include pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole and the like. Preferred blocking agents include 3,5-dimethylpyrazole.

Depending on the situation, in addition to the above blocking agent, 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, Monoalkylphenols such as 2-ethylhexylphenol, n-octylphenol, n-nonylphenol, di-n-propylphenol, diisopropylphenol, isopropylcresol, di-n-butylphenol Dialkylphenols such as enol, di-t-butylphenol, di-sec-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, di-n-nonylphenol (3) Phenol: phenol, cresol, ethylphenol, Styrenated phenol, hydroxybenzoate, etc. (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 type: acetanilide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, etc. (7) Acid imide type: succinimide, maleic imide, etc. (8) Imidazole type: imidazole, 2- Chill imidazole (9) urea: urea, thiourea, ethylene urea, etc. (10) oxime: formaldoxime, aceto aldoxime, acetoxime, methyl ethyl ketoxime, cyclohexanone oxime, etc.

  The reaction of polyisocyanate, polycarbonate diol and 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 a catalyst.

  The reaction of polyisocyanate, polycarbonate diol and blocking agent can be generally carried out at -20 to 150 ° C, preferably 30 to 100 ° C. If the reaction temperature is 150 ° C. or lower, the possibility of causing a side reaction is reduced. On the other hand, if the reaction temperature is −20 ° C. or higher, the reaction rate does not become too low.

  The blocked diisocyanate monomer trimer component concentration in the block polyisocyanate composition of the present invention thus obtained is usually 5 to 50% by mass, preferably 10 to 45% by mass, and more preferably Is 10-30 mass%. When this concentration is 5% by mass or more, the resulting coating film has excellent hardness and weather resistance, and when it is 50% by mass or less, the resulting coating film has good elongation. Here, the blocked diisocyanate monomer trimer component is a block polyisocyanate derived from 3 diisocyanate monomer molecules obtained from 3 diisocyanate monomer molecules and 3 blocking agent molecules per molecule. is there.

  The polycarbonate diol component density | concentration in the block polyisocyanate composition of this invention is a density | concentration of the polycarbonate diol which reacts and exists in a block polyisocyanate composition. Since polycarbonate diol has high reactivity, all of the polycarbonate diol used as a raw material is considered to be involved in the reaction. This concentration is usually 3 to 30% by mass, preferably 5 to 30% by mass, and more preferably 10 to 30% by mass. When the concentration is 3% by mass or more, a decrease in the elongation of the obtained coating film is prevented, adhesion and acid resistance are improved, and when the concentration is 30% by mass or less, a decrease in the hardness of the obtained coating film is prevented. The

  The block polyisocyanate concentration derived from 1 molecule of polycarbonate diol, 2 molecules of diisocyanate monomer trimer and 4 molecules of blocking agent in the block polyisocyanate composition of the present invention is usually 3 to 30% by mass, preferably 5 to 5%. It is 30 mass%, More preferably, it is 5-25 mass%. If this concentration is 3% by mass or more, the elongation of the obtained coating film is good, and if it is 30% by mass or less, excellent coating film hardness is obtained. The diisocyanate monomer trimer has 3 isocyanate groups. The diisocyanate monomer trimer preferably contains an isocyanurate group.

  It was surprising that the coating film cured with the block polyisocyanate composition thus obtained had high elongation and improved acid resistance. A coating film cured with a block polyisocyanate composition obtained from a polyisocyanate and a diol has been considered to have an improved coating film elongation but a reduced crosslinking density, resulting in a decrease in acid resistance of the coating film. Further surprisingly, the block polyisocyanate of the present invention is excellent in adhesion to a substrate.

  The block polyisocyanate composition of the present invention is preferably mixed with a compound having two or more active hydrogens having reactivity with isocyanate groups in the molecule to form a coating composition. The block polyisocyanate can react 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 in the molecule include polyols, polyamines, polythiols and the like, and polyols are usually 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. These polyols are usually selected from polyols having a hydroxyl value of 30 to 200 mgKOH / g and an acid value of 0 to 30 mgKOH / g.

  The equivalent ratio of isocyanate group / polyol hydroxyl group in the coating composition is 0.3 to 1.5, and this ratio is appropriately selected according to the required physical properties of the coating film.

  A melamine curing agent such as a complete alkyl type, a methylol group type alkyl, or an imino group type alkyl can be added to the coating composition as necessary.

  Various solvents and additives can be used depending on the purpose and purpose. Examples of the solvent include ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, esters such as ethyl acetate, n-butyl acetate, and cellosolve acetate, and alcohols such as butanol and isopropyl alcohol. These solvents may be used alone or in combination of two or more.

  If necessary, an antioxidant such as hindered phenol; an ultraviolet absorber such as benzotriazole and benzophenone; a pigment such as titanium oxide, carbon black, indigo, quinacridone, and pearl mica; metal powder A pigment such as aluminum or the like; a rheology control agent such as hydroxyethyl cellulose, a urea compound or a microgel; a curing accelerator such as a tin compound, zinc compound or amine compound may be added.

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

Next, the present invention will be specifically described with reference to examples. The measuring method of various physical properties is as follows.
Blocked diisocyanate monomer trimer component concentration:
The area% of the equivalent molecular weight peak obtained by gel permeation chromatograph (hereinafter referred to as GPC) measurement using the following apparatus was expressed as the concentration.
Equipment: Tosoh Corporation HLC-802A
Column: Tosoh Corporation G1000HXL x 1
G2000HXL x 1
G3000HXL x 1 Carrier: Tetrahydrofuran Detection method: Differential refractometer

Block polyisocyanate concentration derived from 1 molecule of diol, 2 molecules of diisocyanate monomer trimer and 4 molecules of blocking agent:
The area% of the equivalent molecular weight peak obtained by GPC measurement using the above apparatus was expressed as the concentration.

・ Diol component concentration:
The value obtained by dividing the mass of the diol used in the production of the block polyisocyanate composition by the mass of the block polyisocyanate composition was defined as the diol component concentration.

・ Adhesion test:
The cured coating film produced on the mild steel plate is tested according to JIS K5600-5-6 (Coating film adhesion: cross-cut method). The coating film was cured at 140 ° C. for 30 minutes. At this time, the number of remaining cells was evaluated as 100 for ◯, 50 to 99 for Δ, and 49 or less for ×.

・ Acid resistance test:
To the cured coating film prepared on the glass plate, 0.3 g of 80% sulfuric acid aqueous solution is dropped, heated at 80 ° C. for 30 minutes, washed away with sulfuric acid, and dried at room temperature. Thereafter, the surface state was observed at 50 times using the following apparatus. The coating film was cured at 140 ° C. for 30 minutes. On the 0.6 mm square field of the test surface, less than 20 coating film damaged portions having a diameter of 100 μm or more were evaluated as ○, and 20 or more portions were evaluated as ×.
Device: DIGITAL MICROSCOPE KH-7700 from HIROX
Lens: MXRO-5040RZ from HIROX

・ Paint breaking elongation:
Using a trade name TENSILON (TESILON) RTE-1210 manufactured by A & D (A & D), the elongation at break of the coating film was measured under the following conditions. The coating film was cured at 140 ° C. for 30 minutes. At this time, the breaking elongation of the coating film was evaluated as 50% or more as ◯, 10% or more and less than 50% as Δ, and less than 10% as x.
Tensile speed: 20mm / min
Sample size: 20 mm long x 10 mm wide x 30-50 μm thick
Temperature 23 ° C / Humidity 50%

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. Tetramethylammonium capryate as an isocyanuration catalyst 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%, a number average molecular weight of 660, and an isocyanate average number of 3.4.

Example 1
In a reactor similar to Production Example 1, 100 parts by mass of the polyisocyanate obtained in Production Example 1, polycarbonate diol (trade name “Duranol T5651” of Asahi Kasei Chemicals Corporation, number average molecular weight 1000, formula 6 below) 13 mass Part, butyl acetate as a solvent was charged so that the final block polyisocyanate component concentration was 80% by mass, and kept at 100 ° C. for 3 hours in a nitrogen atmosphere. Thereafter, 47 parts by mass of 3,5-dimethylpyrazole was added as a blocking agent, and it was confirmed that there was no characteristic absorption of isocyanate groups in the infrared spectrum. The characteristic values of the obtained block polyisocyanate composition were as follows: solid content 80% by mass, effective isocyanate group concentration (NCO group concentration) 13.0% by mass, blocked diisocyanate monomer trimer component concentration 39% by mass, polycarbonate diol The concentration of the blocked polyisocyanate derived from the component concentration of 8.1% by mass, 1 molecule of the polycarbonate diol component, 2 molecules of the diisocyanate monomer trimer and 4 molecules of the blocking agent was 26% by mass.

Examples 2-5, Comparative Examples 1-6
The same procedure as in Example 1 was performed except that the raw materials used in the block polyisocyanate composition were changed as described in Table 1. The result of the characteristic value of each block polyisocyanate composition is shown in Table 1.

Example 6 (paint preparation and coating film performance)
100 parts by mass of acrylic polyol (trade name Setalux 1767 of NUPLEX, hydroxyl group concentration 4.5 mass% (resin standard), resin solid content 65 mass%) and 69.5 mass of the block polyisocyanate composition obtained in Example 1 Parts (isocyanate group / hydroxyl group = 1.0 (equivalent ratio)), 0.6 parts by weight of dibutyltin dilaurate (based on resin concentration of 0.5% by weight) and 71 parts by weight of butyl acetate were mixed, and the solid content was 50% by weight. A coating composition was prepared. This coating composition was applied to an mild steel plate and a glass plate by an applicator so as to have a resin film thickness of 40 μm. After setting for 10 minutes at room temperature, the coating film was cured at a predetermined temperature, and various physical properties were evaluated. The evaluation results are shown in Table 2.

Examples 7-10, Comparative Examples 7-12
The same operation as in Example 6 was performed except that the block polyisocyanate composition used was changed as described in Table 2. Table 2 shows the evaluation results of various physical properties.

  The block polyisocyanate composition of the present invention and a coating composition containing the block polyisocyanate composition have low-temperature curability and can provide a coating film excellent in acid resistance, coating film elongation and adhesion. Can be suitably used.

Claims (3)

A block polyisocyanate composition satisfying all of the following conditions, which is obtained from hexamethylene diisocyanate , a polycarbonate diol having a number average molecular weight of 300 to 2000, and 3,5-dimethylpyrazole .
1) Concentration of hexamethylene diisocyanate trimer component blocked with 3,5-dimethylpyrazole : 5 to 50% by mass
2) Polycarbonate diol component concentration: 3 to 30% by mass
3) Block polyisocyanate concentration derived from 1 molecule of polycarbonate diol, 2 molecules of hexamethylene diisocyanate trimer and 4 molecules of 3,5-dimethylpyrazole : 3 to 30% by mass A coating composition comprising the blocked polyisocyanate composition according to claim 1 . The manufacturing method of the block polyisocyanate composition of Claim 1 including all the following processes:
(A). Reacting hexamethylene diisocyanate to produce polyisocyanate,
(B). A step of removing unreacted hexamethylene diisocyanate from the polyisocyanate obtained by the step (A), and (C). A step of reacting the polyisocyanate, a polycarbonate diol having a molecular weight of 300 to 2000, and 3,5-dimethylpyrazole to produce a block polyisocyanate.