JP6502049B2 - Polyisocyanate composition, coating composition and coating method - Google Patents

Description

  The present invention relates to a polyisocyanate composition, a coating composition and a coating method.

  Conventionally, polyurethane resin coatings are known to have excellent abrasion resistance, chemical resistance, and stain resistance, but in particular, polyurethane resin coatings using non-yellowing polyisocyanate derived from hexamethylene diisocyanate or isophorone diisocyanate. Have even better weatherability. Therefore, the use of such polyisocyanates is in the form of a two-component urethane paint of normal temperature or heat curing, and is widely used in construction, heavy duty, automobiles, industrial applications and their modifications. In each use, the curability improvement is desired for process shortening etc.

  In order to improve the curability, for example, there is a method of adding an organic tin compound etc., but this method may have different effects depending on the composition of the paint, and combustion of the processing apparatus of the organic solvent volatilized by coating etc. It has problems such as adversely affecting the catalyst.

  On the other hand, in order to solve these problems, development of high functional polyisocyanates is in progress.

  In Patent Document 1, a highly functional polyisocyanate is obtained by isocyanuration after reaction of at least one aliphatic or alicyclic diisocyanate with a polyfunctional alcohol, or isocyanuration in the presence of such alcohol. Has been proposed.

Japanese Patent Application Laid-Open No. 6-312969

  The polyisocyanate described in Patent Document 1 may have insufficient compatibility with the main agent, and has a further problem from the viewpoint of improving the appearance of the coating.

  The present invention has been made in view of the problems of the prior art described above, and the object of the present invention is to show high curability, drying property and degree of crosslinking, and further to be excellent in coating appearance such as coating surface smoothness. It is an object of the present invention to provide a polyisocyanate composition having performance, a coating composition containing the same, and a coating method.

  As a result of intensive studies, the present inventors have found that polyisocyanate compositions obtained from aliphatic diisocyanates or alicyclic diisocyanates and diols and having a predetermined functional group in a specific ratio solve the above problems. The present invention has been completed.

More specifically, the constitution of the present invention is as follows.
[1]
It is a polyisocyanate composition obtained from one or more diisocyanates selected from aliphatic diisocyanates and alicyclic diisocyanates and one or more diols,
In the polyisocyanate composition, the molar ratio of allophanate group / (isocyanurate group + allophanate group) is 0.2 to 0.9, and the molar ratio of allophanate group / (allophanate group + urethane group) is 0. Polyisocyanate compositions which are 6 to 1.0.
[2]
The polyisocyanate composition according to [1], having a number average functional group number of 3.8 to 10.0.
[3]
The polyisocyanate composition as described in [1] or [2] whose isocyanate group concentration is 14.0-21.0 mass%.
[4]
The polyisocyanate composition according to any one of [1] to [3], which has a viscosity of 8,000 to 50,000 mPa · s at 25 ° C.
[5]
The coating composition containing the polyisocyanate composition in any one of [1]-[4], and at least 1 type of polyol.
[6]
The paint composition according to [5], which is used for clear coat.
[7]
The coating composition according to [5], which is used for automobile repair paint or plastic paint.
[8]
The coating method which includes coating the coating composition in any one of [5]-[7] on the basecoat containing a pigment.

  According to the present invention, a polyisocyanate composition which exhibits high curability, drying property and crosslinking degree, and can achieve an excellent coating appearance can be obtained and a coating composition containing the same.

  Hereinafter, modes for carrying out the present invention (hereinafter, simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for describing the present invention, and is not intended to limit the present invention to the following contents. The present invention can be appropriately modified and implemented within the scope of the gist of the present invention.

  The polyisocyanate composition of the present embodiment is a polyisocyanate composition obtained from one or more diisocyanates selected from aliphatic diisocyanates and alicyclic diisocyanates and one or more diols, and the allophanate group in the polyisocyanate composition. The molar ratio of (isocyanurate group + allophanate group) is 0.2 to 0.9, and the molar ratio of allophanate group / (allophanate group + urethane group) is 0.6 to 1.0. Since it is comprised in this way, the polyisocyanate composition of this embodiment can show high curability, dryness, and a crosslinking degree, and can also achieve the outstanding coating-film appearance.

  The diisocyanate which can be used in the present embodiment is at least one selected from aliphatic diisocyanates and alicyclic diisocyanates. The aliphatic diisocyanate is not particularly limited, but one having 4 to 30 carbon atoms is preferable. Moreover, the alicyclic diisocyanate is not particularly limited, but one having 8 to 30 carbon atoms is preferable. Specific examples of the diisocyanates include, but are not limited to, 1,4-butane diisocyanate, 1,5-pentane diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethyl-hexamethylene-1,6. -Diisocyanate, lysine diisocyanate, isophorone diisocyanate, 1,3-bis (isocyanatomethyl) -cyclohexane, 4,4'-dicyclohexylmethane diisocyanate and the like. Among them, 1,6-hexamethylene diisocyanate (hereinafter referred to as HDI) is preferable because it has good weatherability and reactivity, and the viscosity of the resulting polyisocyanate composition tends to be low. These may be used alone or in combination.

  The polyol constituting the allophanate group and the urethane group in the polyisocyanate composition of the present embodiment contains a diol from the viewpoint of improving the compatibility with the polyol when forming the coating composition and the curability.

Examples of the diol include, but are not limited to, ethylene glycol which is a linear aliphatic diol, 1,3-propanediol, 1,2-propanediol, 1,3-butanediol, 1,4-butane, for example. Diol, 2,3-butanediol, 1,5-pentanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, neopentyl glycol, 1,6-hexanediol, 1, 7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and branched aliphatic diols 2 -Methyl 1,3-propanediol, 3-methyl-1,5 Pentanediol, 2-methyl-1,8-octanediol, and 2,2-diethyl-1,3-propanediol. These may be used alone or in combination of two or more. Among them, the lower limit of the carbon number of the diol is preferably C ₂ or more. By being C ₂ or more, the number-average functional group number tends to be high, and the curability and the drying property tend to be better. On the other hand, it is preferable that the upper limit is C _10, more preferably C _5. At C ₁₀ or less, the compatibility becomes better, and the appearance of the coating tends to be further improved.

  The concentration of the diol component constituting the polyisocyanate composition of the present embodiment is not particularly limited, but is preferably 1% by mass or more, more preferably 2% by mass or more based on the polyisocyanate composition. On the other hand, the upper limit of the concentration is preferably 20% by mass, more preferably 10% by mass. When the component concentration of the diol is 1% by mass or more and 20% by mass or less, the molar ratio of allophanate group / (isocyanurate group + allophanate group) described later tends to be in a preferable range. The diol component concentration can be determined by measuring 1 H-NMR.

  The molar ratio of allophanate group / (isocyanurate group + allophanate group) present in the polyisocyanate composition of the present embodiment is 0.2 or more, preferably 0.25 or more, more preferably 0.3 or more. is there. When the molar ratio of allophanate group / (isocyanurate group + allophanate group) is 0.2 or more, the compatibility becomes good. The molar ratio of allophanate group / (isocyanurate group + allophanate group) is 0.9 or less, preferably 0.8 or less, more preferably 0.7 or less. When the molar ratio of allophanate group / (isocyanurate group + allophanate group) is 0.9 or less, the hardness is easily increased, and as a result, the curability is improved.

  In addition, the molar ratio of an allophanate group and an isocyanurate group can be calculated | required by measuring 1 H-NMR. That is, the area (2H portion) of the signal of the hydrogen atom of the methylene group derived from HDI adjacent to the isocyanurate group around 3.85 ppm and the area of the signal of the hydrogen atom bonded to the allophanate bond around 8.50 ppm ( The molar ratio of isocyanurate group to allophanate group can be determined by measuring the ratio of 1H).

  The molar ratio of allophanate group / (allophanate group + urethane group) in the present embodiment is 0.6 or more, preferably 0.7 or more, more preferably 0.75 or more, and still more preferably 0.8. It is above. The allophanate group is formed from the isocyanate and urethane groups of the diisocyanate. On the other hand, the diisocyanate group and the hydroxyl group of the diol form a urethane group. That is, the molar ratio of allophanate group / (allophanate group + urethane group) is an index indicating the rate at which the hydroxyl group of the diol is converted to the allophanate group. Since the molar ratio when the hydroxyl group derived from diol is completely allophanized is 1.0, the upper limit of the molar ratio is 1.0. When the molar ratio of allophanate group / (allophanate group + urethane group) is 0.6 or more, the polyisocyanate composition exhibits good compatibility and curability.

  The molar ratio of the allophanate group to the urethane group can be determined by 1 H-NMR. That is, the area (1H) of the signal of the hydrogen atom bonded to the nitrogen of the allophanate bond around 8.50 ppm and the area (1H) of the hydrogen atom bonded to the nitrogen of the urethane bond around 4.90 ppm were measured, The molar ratio of allophanate group / (allophanate group + urethane group) can be measured by determining the ratio.

  The number average functional group number of the polyisocyanate composition of the present embodiment is preferably 3.8 or more, more preferably 4.0 or more, still more preferably 4.2 or more, and 4.5 or more. More preferred. When the number average functional group number of the polyisocyanate is 3.8 or more, the curability and the drying property of the coating composition tend to be better. The number average functional group number of the polyisocyanate composition of the present embodiment is preferably 10.0 or less, more preferably 8.0 or less, still more preferably 6.5 or less, and even more preferably 5.5 or less. is there. The coating composition tends to have a better coating appearance when the number average functional group number of the polyisocyanate is 10.0 or less. The said number average functional group number can be calculated | required based on the method as described in the Example mentioned later.

  The isocyanate group concentration of the polyisocyanate composition of the present embodiment is preferably 14.0% by mass or more, more preferably 17.5% by mass or more. When the isocyanate group concentration is 14.0% by mass or more, the polyisocyanate composition tends to develop a more easily handled viscosity. Moreover, it is preferable that the isocyanate group concentration of the polyisocyanate composition of this embodiment is 21.0 mass% or less, More preferably, it is 20.0 mass% or less. When the isocyanate group concentration is 21.0% by mass or less, the curability of the coating composition tends to be better. The said isocyanate group concentration can be measured based on the method as described in the Example mentioned later.

  The viscosity measured with an E-type viscometer of the polyisocyanate composition of the present embodiment is preferably 8,000 to 50,000 mPa · s / 25 ° C., and 8,000 to 20,000 mPa · s / 25 ° C. It is more preferable that Although the polyisocyanate composition of the present embodiment may contain volatile components such as aliphatic diisocyanate monomers, alicyclic diisocyanate monomers and solvents, the above-mentioned viscosity is a polyisocyanate composition in which the nonvolatile content is refined to 98 mass% or more. Can be measured in the same manner as described in the examples described later. When the viscosity of the polyisocyanate composition is 8,000 mPa · s / 25 ° C. or higher, the above-mentioned number average functional group number can be made higher, and the curability and the drying property of the coating composition tend to be better. is there. On the other hand, when the viscosity of the polyisocyanate composition is 50,000 mPa · s / 25 ° C. or less, the compatibility tends to be better.

  The concentration of the isocyanate cyclic trimer in the polyisocyanate composition of the present embodiment is preferably 30% by mass or less, and more preferably 25% by mass or less. If the concentration is 30% by mass or less, the curability of the coating composition tends to be better. In addition, the concentration of the isocyanurate cyclic trimer in the polyisocyanate composition is preferably 10% by mass or more, and more preferably 14% by mass or more. When the concentration is 10% by mass or more, the compatibility tends to be better. The concentration of the isocyanate cyclic trimer can be determined by GPC measurement. The isocyanate cyclic trimer is an isocyanurate consisting of three diisocyanates.

  Next, although the example of the manufacturing method of the polyisocyanate composition of this embodiment is demonstrated, it is not limited to the following.

  First, the isocyanate group of the above-mentioned diisocyanate and the hydroxyl group of the diol are urethanized. The reaction temperature at this time can be 50 to 200 ° C. The reaction temperature is preferably 50 to 150 ° C., more preferably 50 to 120 ° C., and still more preferably 50 to 100 ° C. When the temperature is 50 ° C. or higher, the urethanation reaction tends to proceed easily, and when the temperature is 200 ° C. or lower, the coloring of the obtained polyisocyanate composition tends to be reduced. The reaction time is preferably in the range of 0.5 hours to 24 hours, more preferably 0.5 hours to 10 hours, and still more preferably 0.5 hours to 5 hours.

  After some or all of the hydroxyl groups of the diol have reacted with the isocyanate groups of the diisocyanate, the isocyanuration reaction and the allophanatization reaction are carried out. As a method for producing the polyisocyanate composition of the present embodiment, the urethanation reaction, the allophanate reaction, and the isocyanurate reaction may be changed before or after, or may be performed simultaneously. However, the reaction of isocyanate group of diisocyanate and hydroxyl group of diol It is preferable to carry out the allophanatization reaction simultaneously with the isocyanurate reaction after forming a urethane bond by These reactions can be appropriately advanced by selecting the isocyanuration reaction catalyst and the reaction conditions. When the reaction is allowed to proceed with a catalyst, the reaction temperature for isocyanuration and allophanatization is 60 to 160 ° C., preferably 70 to 100 ° C. When the reaction temperature is 60 ° C. or higher, the allophanate reaction tends to proceed, and the molar ratio of allophanate group / (allophanate group + urethane group) tends to be high. When the reaction temperature is 160 ° C. or less, the resulting polyisocyanate composition tends to be less colored. The reaction time of isocyanuration and allophanatization is preferably 1 hour to 10 hours, more preferably 1 hour to 7 hours, and still more preferably 1 hour to 5 hours. When the reaction time is 1 hour or more, the isocyanurate ratio and the allophanatization ratio tend to be high. When the reaction time is 10 hours or less, the coloring tends to be less.

  The isocyanurate and allophanatization catalysts that can be used in the above are not particularly limited but, for example, those having basicity are preferable. Although not limited to the following, for example, (i) hydroxides of tetraalkylammonium such as tetramethylammonium and tetraethylammonium, organic weak acid salts such as acetic acid and capric acid, (ii) trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, Hydroxides of hydroxyalkyl ammonium such as triethyl hydroxypropyl ammonium and triethyl hydroxyethyl ammonium, organic weak acid salts such as acetic acid and capric acid, (iii) tins of alkyl carboxylic acids such as acetic acid, caproic acid, octylic acid and myristic acid Alkali metal salts such as zinc and lead, (iv) metal alcoholates such as sodium and potassium, (v) aminosilyl group-containing compounds such as hexamethyldisilazane, (vi) Mannich bases, (vii Combination with tertiary amines and epoxy compounds include phosphorus compounds such as (viii) tributylphosphine. Among these, tetraalkylammonium hydroxides and organic weak acid salts are preferred. These catalysts may be added all at once or continuously.

  The catalyst is deactivated to complete these reactions. When the catalyst is neutralized and deactivated, an acidic substance such as phosphoric acid or acidic phosphoric acid ester is added. It can also be inactivated by thermal decomposition or chemical decomposition. Furthermore, it can be deactivated by adsorbing onto activated carbon, alumina or the like and taking it out of the system.

  The yield of the polyisocyanate composition (the mass of the obtained polyisocyanate composition / the total mass of the feed materials x 100) is preferably selected from the range of 10 to 70% by mass, more preferably 30 to 60% by mass, and high By doing this, the molar ratio of isocyanate groups to allophanate groups and urethane groups can be increased, and by lowering the molar ratio of isocyanate groups to allophanate groups and urethane groups can be reduced.

  After completion of the reaction, unreacted diisocyanate monomer is removed by a thin film evaporator, extraction or the like. The concentration of unreacted diisocyanate monomer in the obtained polyisocyanate composition is preferably 3% by mass or less, more preferably 1% by mass or less, still more preferably 0.5% by mass or less, and still more preferably Is 0.3 mass% or less. When the unreacted diisocyanate monomer concentration is 3% by mass or less, the curability tends to be better.

  Next, the coating composition containing the polyisocyanate composition of this embodiment is described. That is, the paint composition of the present embodiment contains the polyisocyanate composition of the present embodiment and at least one polyol. For example, the paint composition of the present embodiment is constituted by mixing the polyisocyanate composition obtained as described above and a compound containing two or more active hydrogens having reactivity with isocyanate groups in the molecule. Can. These components can react with one another to form a crosslinked coating.

  Examples of the compound containing two or more active hydrogens in the molecule include, but are not limited to, polyols, polyamines and polythiols, and two or more can be used in combination. Preferably it is a polyol. Examples of this polyol include, but are not limited to, acrylic polyols, polyester polyols, polyether polyols, polyolefin polyols, epoxy polyols, fluorine polyols, and among the above polyols, preferred are acrylic polyols and polyester polyols. , Polyether polyols.

  The acrylic polyol is not limited to the following, for example, acrylic acid ester having active hydrogen such as acrylic acid 2-hydroxyethyl, acrylic acid 2-hydroxypropyl, acrylic acid 2-hydroxybutyl, etc., or acrylic acid of glycerin Acid monoester or methacrylic acid monoester, acrylic acid monoester of trimethylolpropane or acrylic acid monoester selected from the group of methacrylic acid monoester or mixtures thereof with methyl acrylate, ethyl acrylate, isopropyl acrylate, acrylic acid-n- Butyl, acrylic esters such as 2-ethylhexyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate And methacrylic acid esters with active hydrogen such as 4-hydroxybutyl methacrylate, or methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, methacrylic A single or a mixture selected from the group of methacrylic acid esters such as lauryl acid; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc., acrylamides, N-methylol acrylamides, diacetone acrylamides etc. Polymerized in the presence or absence of a saturated amide and 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; And the like obtained acrylic polyol.

  Examples of the polyester polyol include, but are not limited to, dibasics 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, etc. Polyester polyols etc. obtained by condensation reaction of acid alone or mixture with ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, trimethylol propane, glycerol etc. alone or mixture of polyhydric alcohols; It can be mentioned. These polyester polyols can be modified with aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates and polyisocyanates obtained therefrom. In this case, in particular, aliphatic diisocyanates, alicyclic diisocyanates, and polyester polyols modified with polyisocyanates obtained therefrom are preferable in view of weather resistance, yellowing resistance and the like.

  The polyether polyols include, but are not limited to, for example, single or a mixture of polyols having a molecular weight of 500 or less, hydroxides such as lithium, sodium and potassium, alcoholates, strongly basic catalysts such as alkylamines, metal porphyrins Random or block addition of one or a mixture of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide and styrene oxide to the above-mentioned polyol using a complex metal cyanide compound complex such as zinc hexacyanocobaltate complex etc. Polyether polyols obtained by reacting an alkylene oxide with a polyamine compound such as ethylenediamines and the like, and these polyethers. Obtained by polymerizing acrylamide or the like as the body, it includes so-called polymer polyols.

  Examples of the polyolefin polyol include, but are not limited to, polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, hydrogenated polyisoprene, and the like.

  Examples of the epoxy polyol include, but are not limited to, novolak type, β-methylepichloro type, cyclic oxirane type, glycidyl ether type, glycol ether type, epoxy type of aliphatic unsaturated compound, epoxidized fatty acid ester type, polyvalent Examples thereof include carboxylic acid ester type, aminoglycidyl type, halogenated type, resorcinol type, and compounds obtained by modifying these with an amino compound, a polyamide compound and the like.

  The fluorine polyol is a polyol containing fluorine in the molecule, and is not limited to the following. For example, fluoroolefins, cyclohexyl vinyl ether, hydroxyalkyl vinyl ether disclosed in US Pat. No. 4,345,057, EP 180962, etc. Copolymers such as monocarboxylic acid vinyl ester and the like can be mentioned.

  In the present embodiment, the hydroxyl value of the polyol used as a component of the coating composition is preferably 30 to 200 mg KOH / g. Moreover, it is preferable that the acid value of the said polyol is 0-30 mgKOH / g. Two or more of these polyols may be used in combination. Among them, the hydroxyl value of the polyol used is preferably 70 to 165 mg KOH / g, and the acid value is preferably 2 to 20 mg KOH / g.

  When preparing a coating composition using the polyisocyanate composition of the present embodiment, the equivalent ratio of the isocyanate group of the polyisocyanate composition to the hydroxyl group of the polyol is appropriately selected from the range of 1/2 to 2/1. Is preferred.

  In addition, depending on the application of the coating composition and the purpose, various solvents, ultraviolet absorbers such as benzotriazole and benzophenone, light stabilizers such as hindered amines and hindered phenols, organic pigments such as quinacridone, pigment red and phthalocyanine blue, titanium oxide And inorganic pigments such as carbon black, metallic pigments such as aluminum powder, light interference pigments such as pearl mica powder, and curing accelerators such as tin compounds, zinc compounds and amine compounds. Examples of the solvent include, but are not limited to, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate, n-butyl acetate and cellosolve acetate, alcohols such as butanol and isopropyl alcohol, etc. According to the purpose and application, it can be used appropriately selected from the group of These solvents may be used alone or in combination of two or more.

  The coating composition prepared in this manner can be applied by methods such as roll coating, curtain flow coating, spray coating and the like, and is usually coated with a dry film thickness of about 10 to 100 μm. In particular, it is useful in the field of automobile repair paint, plastic paint and the like.

  Moreover, it is preferable to use the coating composition of this embodiment for a clear coat.

  In addition, the paint method of the present embodiment includes coating the paint composition of the present embodiment on a base coat containing a pigment. Here, as the pigment, the above-mentioned organic pigment, inorganic pigment, metallic pigment, light interference pigment and the like can be appropriately used.

  Hereinafter, the present embodiment will be described in more detail based on examples, but the present embodiments are not limited to the following examples. All parts are parts by mass.

  First, the measuring method of each physical property is described.

(Number average molecular weight)
The number average molecular weight of the polyisocyanate composition is a polystyrene-based number average molecular weight measured by gel permeation chromatograph (hereinafter referred to as GPC) using the following apparatus.
Equipment: HLC-8120 (made by Tosoh Corporation),
Column used: TSK GEL Super H1000, TSK GEL Super H2000, TSK GEL Super H 3000 (all manufactured by Tosoh Corporation),
Sample concentration: 5 wt / vol%,
Carrier: THF,
Detection method: parallax refractometer,
Effluent volume: 0.6 mL / min,
Column temperature: 30 ° C.

  The standard curve of GPC is polystyrene (molecular weight 50,000 to 5050 PSS-06 (Mw 50000), BK 13007 (Mp = 20000, Mw / Mn = 1.03), PSS-08 (Mw = 9000), PSS) -09 (Mw = 4000), and 5040-35125 (Mp = 2050, Mw / Mn = 1.05)), and an isocyanate of hexamethylene diisocyanate-based polyisocyanate composition (Duranate TPA-100, manufactured by Asahi Kasei Chemicals Corporation) The trimers to heptamers of a nurate group (isocyanurate trimer molecular weight = 504, isocyanurate pentamer molecular weight = 840, isocyanurate pentamer molecular weight = 1176) and HDI (molecular weight = 168) were prepared as standards .

(yield)
The yield was calculated from the following formula.
Yield (%) = mass of obtained polyisocyanate composition / total mass of feed materials × 100

(Number average number of functional groups)
The number average functional group number of the polyisocyanate composition was calculated from the following equation based on the number average molecular weight of the polyisocyanate composition measured as described above and the value of the isocyanate group concentration measured by the method described later.
Number average functional group number of polyisocyanate composition = number average molecular weight of polyisocyanate composition × isocyanate group concentration / 42

(Isocyanate group concentration)
N-Dibutylamine was added to the polyisocyanate composition dissolved in toluene, and the concentration of isocyanate group in the polyisocyanate composition was determined by potentiometric titration using 1N hydrochloric acid.
In addition, the non volatile matter of the polyisocyanate composition manufactured by each Example and each comparative example mentioned later is investigated by the method as described in the following, and that whose value was 98 mass% or more is provided for the measurement of the said isocyanate group concentration. did.

(Measurement of non-volatile content)
The non volatile matter was determined from the residual amount when the polyisocyanate composition was heated at 105 ° C. for 3 hours.
Nonvolatile content (% by mass) = (mass of polyisocyanate composition after heating at 105 ° C. for 3 hours) / (mass of polyisocyanate composition before heating) × 100

(Diisocyanate monomer concentration)
The peak area% corresponding to the molecular weight (for example, 168 in the case of HDI) of the diisocyanate obtained by the GPC measurement was expressed as the mass concentration of the diisocyanate monomer in the polyisocyanate composition.

(Isocyanate cyclic trimer concentration)
The concentration of the peak of the molecular weight (for example, 504 in the case of HDI) equivalent to the diisocyanate cyclic trimer obtained by the GPC measurement was represented by the area percentage.

(Measurement of viscosity)
The viscosity of the polyisocyanate composition was measured at a cone plate third temperature R12 at 25 ° C. (unit: mPa · s / 25 ° C.) using an E-type viscometer (RE-80U manufactured by Toki Sangyo Co., Ltd.).
In addition, the non volatile matter of the polyisocyanate composition manufactured by each Example mentioned later and each comparative example was investigated by the method as described above, and the thing whose value was 98 mass% or more was used for the measurement of the said viscosity.

(Qualitative or quantitative determination of allophanate group, isocyanurate group and urethane group)
Using a Bruker Corp. FT-NMR AVANCE 600, heavy chloroform CDCl ₃ solvent, the sample (polyisocyanate composition) concentration of 5 mass%, 600 MHz, with integrated 256 times, and measuring the proton nuclear magnetic resonance spectrum, allophanate groups The molar ratio of isocyanurate group and urethane group was confirmed. The isocyanurate group is the signal ratio of the hydrogen atom of the methylene group derived from HDI adjacent to the isocyanurate group in the vicinity of 3.85 ppm based on all protons in β and γ positions derived from HDI, and the allophanate group is 8.50 ppm Measure the area ratio of signals of hydrogen atoms bonded to nitrogen of nearby allophanate bond, and the ratio of signals of hydrogen atoms bonded to nitrogen of urethane bond around 4.90 ppm, and calculate the molar ratio by the following formula I asked for 1,2.
Molar ratio 1: allophanate group / (allophanate group + isocyanurate group) = (signal area around 8.50 ppm) / (signal area around 8.50 ppm + signal area around 3.85 ppm / 6)
Molar ratio 2: allophanate group / (allophanate group + urethane group) = (signal area around 8.50 ppm) / (signal area around 8.50 ppm + signal area around 4.90 ppm)

(Curable)
After the coating composition was applied to a PP plate, about 0.2 g of a coating cured at 23 ° C./50% RH for 24 hours and a coating cured for 48 hours were immersed in about 40 g of acetone at 20 ° C. for 24 hours Then, the value with respect to the mass before immersion of undissolved part mass was computed, and the obtained value was made into the parameter | index of hardenability.

(Drying test)
The coating composition was coated on a glass plate to a film thickness of 40 μm and then cured at 23 ° C./50% RH. After 5 hours and 7 hours, a cotton ball (diameter 2.5 cm, column 2.0 cm high) was placed on the coating, and a 100 g weight was placed thereon for 60 seconds. After that, the weight and the cotton were removed and the cotton mark left on the coating was observed. The case where the mark was not visible at all was represented as 1 and the case where the mark was clearly visible was represented as 5 steps of 1 to 5 as 5.

(Coating degree of crosslinking)
The period in a coating-hardening process was measured with pendulum FRB-100 and edge RBE160 using a rigid pendulum-type visco-elasticity measuring device (RPT-3000W from A & D Corporation). The coating was applied to a SUS plate so as to have a dry film thickness of 80 μm. The cycle was measured while raising the temperature to 80 ° C. at 10 ° C./min and baking at 80 ° C. for 25 minutes. The degree of coating film crosslinking was expressed by the reduction rate of the cycle. The reduction rate of the cycle is expressed as (Period before curing-Cycle after curing) / Period before curing, in%. The greater the reduction rate of the cycle, the higher the degree of crosslinking and the better the curability.

(Coating film appearance)
The paint composition was coated on an electrodeposited plate at a film thickness of 40 μm at room temperature using a general-purpose three-dimensional surface structure analyzer (NewView 600 by Canon Inc.), and then one day at 23 ° C./50% RH After curing, the coating surface was measured. The case where the amplitude of the unevenness of the coating film surface is 50 nm or less is 3; the case of 50 to 70 nm is 2; and the case of 70 nm or more is 1; The larger the value, the better the coating appearance.

(Compatibility)
Each of the polyol and the polyisocyanate composition was blended at an equivalent ratio of isocyanate group / hydroxyl group of 1.0, adjusted to 50% solid content with butyl acetate, and then evaluated on the appearance of the diluted solution. It judged on the basis of whether it was transparent, and the case where it was opaque was made into "non-uniformity." As a polyol, Lumiflon (registered trademark) LF-200 (resin concentration 60%, hydroxyl value 53.3 mg KOH / resin g) manufactured by Asahi Glass Co., Ltd., which is a fluorine-based polyol, and Acricic (registered trademark) manufactured by DIC, which is an acrylic polyol A-801-P (resin content 50%, hydroxyl value 50.0 mg KOH / resin g) was used to evaluate each.

Example 1
A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen blow-in pipe is made into a nitrogen atmosphere, and 600 parts of HDI and 10.8 parts of 1,3-butanediol which is a dihydric alcohol are charged. The temperature in the reactor was maintained at 90 ° C. for 1 hour to carry out the urethanization reaction. Thereafter, the temperature in the reactor is maintained at 80 ° C., 0.03 part of tetramethylammonium capriate is added as an isocyanurate conversion catalyst, and the refractive index of the reaction solution is measured. The reaction was stopped by adding. After filtering the reaction solution, unreacted HDI was removed using a thin film evaporator. The nonvolatile content of the 343 g polyisocyanate composition obtained is 99.8% by mass, the viscosity at 25 ° C. is 20,400 mPa · s, the isocyanate group concentration is 19.3% by mass, the diisocyanate monomer concentration is 0.15% by mass, The number average molecular weight was 970, and the number average functionality was 4.4. The molar ratio of (allophanate group / (allophanate group + urethane group)) was 0.99. The composition of the starting materials, the reaction conditions and the physical properties of the prepared polyisocyanate composition are shown in Table 1.

(Example 2)
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen blow-in tube is made into a nitrogen atmosphere, and 600 parts of HDI and 24 parts of 1,3-butanediol which is a dihydric alcohol are charged. The internal temperature was maintained at 90 ° C. for 1 hour to carry out the urethanization reaction. Thereafter, the temperature in the reactor is maintained at 80 ° C., 0.03 part of tetramethylammonium capriate is added as an isocyanurate conversion catalyst, and the refractive index of the reaction solution is measured. The reaction was stopped by adding. After filtering the reaction solution, unreacted HDI was removed using a thin film evaporator. The nonvolatile content of the obtained 343 g polyisocyanate composition is 99.8% by mass, the viscosity at 25 ° C. is 14,000 mPa · s, the isocyanate group concentration is 19.1% by mass, the diisocyanate monomer concentration is 0.09% by mass, The number average molecular weight was 1040 and the number average functionality was 4.7. The molar ratio of (allophanate group / (allophanate group + urethane group)) was 0.98. The composition of the starting materials, the reaction conditions and the physical properties of the prepared polyisocyanate composition are shown in Table 1.

(Examples 3 to 7)
The synthesis was performed in the same manner as in Example 1 except that the composition of the starting materials and the reaction conditions were changed as shown in Table 1. Table 1 shows the composition and reaction conditions of the charged materials, and the physical properties of the polyisocyanate composition.

  The evaluation results of the compatibility of the polyisocyanate compositions obtained in Examples 1 to 7 are shown in Table 2.

(Examples 8 to 14)
Each of the acrylic polyol (trade name “SETALUX 1753” manufactured by Nuplex, resin concentration 70%, hydroxyl value 138.6 mg KOH / g) and the polyisocyanate composition obtained in Examples 1 to 7 is an isocyanate group / hydroxy group After blending with an equivalent ratio of 1.0 and adjusting the coating viscosity appropriately with an organic solvent, the coating film was evaluated. Physical properties of the used curing agent and the coating are shown in Table 2.

(Comparative Examples 1 to 5)
The synthesis was performed in the same manner as in Example 1 except that the composition of the starting materials and the reaction conditions were changed as shown in Table 1. Table 1 shows the composition and reaction conditions of the charged materials, and the physical properties of the polyisocyanate composition.

(Comparative Examples 6 to 10)
Evaluation was performed in the same manner as in Example 8 except that the curing agent shown in Table 2 was used. Physical properties of the used curing agent and the coating are shown in Table 2.

  The coating composition of the present invention is useful in a wide range of fields such as automobile repair paints and plastic paints. In particular, low temperature drying and curing are useful. In addition, it is also useful as a paint excellent in acid rain resistance and weather resistance as a clear paint containing no pigment.

Claims (7)

It is a polyisocyanate composition obtained from one or more diisocyanates selected from aliphatic diisocyanates and alicyclic diisocyanates and one or more diols,
In the polyisocyanate composition, the molar ratio of allophanate group / (isocyanurate group + allophanate group) is 0.2 to 0.7 , and the molar ratio of allophanate group / (allophanate group + urethane group) is 0. 6 to 1.0 der is,
Viscosity at 25 ° C. is Ru 8,000~50,000mPa · s der polyisocyanate composition.   The polyisocyanate composition according to claim 1, wherein the number average functional group number is 3.8 to 10.0.   The polyisocyanate composition according to claim 1 or 2, wherein the isocyanate group concentration is 14.0 to 21.0% by mass. A paint composition comprising the polyisocyanate composition according to any one of claims 1 to 3 and at least one polyol. The coating composition according to claim 4 , which is used for a clear coat. The paint composition according to claim 4 , which is used for automobile repair paint or plastic paint. A coating method comprising coating the paint composition according to any one of claims 4 to 6 on a base coat containing a pigment.