JP2020023664A - Polyisocyanate composition, coating composition and coating film - Google Patents

Abstract

To provide a polyisocyanate composition that is stable even when mixed with moisture and free of coloring or the like while stored and has excellent drying property and scratch resistance when formed into a coating film.SOLUTION: The polyisocyanate composition comprises a polyisocyanate, a tin-based urethanization catalyst, a dehydrator, and a solvent. The polyisocyanate is derived from an aliphatic diisocyanate including 1,6-hexamethylene diisocyanate and has an isocyanurate group and at least one functional group selected from the set consisting of a urethane group, an allophanate group and a biuret group. When molar amounts of the isocyanurate group, the urethane group, the allophanate group and the biuret group are represented by a, b, c and d, respectively, (b+c+d)/(a+b+c+d) is 0.10 or more and 0.90 or less. The dehydrator comprises an aromatic monoisocyanate.SELECTED DRAWING: None

Description

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

  A polyisocyanate composition derived from an aliphatic diisocyanate containing 1,6-hexamethylene diisocyanate (hereinafter sometimes abbreviated as “HDI”) and having an isocyanurate group has excellent weather resistance and heat resistance. Since the curing reaction proceeds even at room temperature, it has been widely used as a curing agent for various paints.

However, a polyisocyanate composition having an isocyanurate group has a high degree of reactivity, when a large amount of water in the solvent is present, or when used under high humidity conditions, the isocyanate group is deactivated, and In some cases, it was not possible to exhibit excellent coating film properties.
In order to solve the above problems, a technique of adding a dehydrating agent to a polyisocyanate composition or a coating composition has been disclosed. (For example, refer to Patent Documents 1 to 3)

Japanese Patent No. 6162912 JP-A-5-345871 JP 2015-083670 A JP-B-62-041496 JP-A-57-034107 JP-A-61-275311

However, when the dehydrating agents described in Patent Literatures 1 to 3 are added, depending on the polyisocyanate composition, coloring and precipitation may occur. Therefore, a polyisocyanate composition that is stable even when mixed with water and does not cause coloring or the like during storage is desired.
In recent years, from the viewpoint of shortening the working time, a polyisocyanate composition having excellent drying properties when formed into a coating film has been desired. On the other hand, in particular, there is a demand for a polyisocyanate composition which does not damage an automobile coating film even when a car washer or the like is used, that is, has excellent scratch resistance when formed into a coating film.

  The present invention has been made in view of the above circumstances, and is a polyisocyanate that is stable even when mixed with water, does not cause coloring or the like during storage, and has excellent drying properties and scratch resistance when formed into a coating film. Provided are a composition, and a coating composition and a coating film using the polyisocyanate composition.

That is, the present invention includes the following aspects.
The polyisocyanate composition according to the first aspect of the present invention is a polyisocyanate composition containing a polyisocyanate, a tin-based urethanization catalyst, a dehydrating agent, and a solvent, wherein the polyisocyanate is 1, The isocyanate derived from an aliphatic diisocyanate containing 6-hexamethylene diisocyanate, and having an isocyanurate group and at least one functional group selected from the group consisting of a urethane group, an allophanate group and a biuret group; (B + c + d) / (a + b + c + d) is 0.10 or more and 0.90 or less, where the molar amounts of the nurate group, the urethane group, the allophanate group, and the biuret group are a, b, c, and d, respectively. The dehydrating agent contains an aromatic monoisocyanate.
The dehydrating agent may include an orthoformate and an aromatic monoisocyanate.

  The coating composition according to the second aspect of the present invention comprises the polyisocyanate composition according to the first aspect, an acrylic polyol having a hydroxyl value of 10 mgKOH / g to 200 mgKOH / g, and a hydroxyl value of 10 mgKOH / g or more. At least one polyol selected from the group consisting of polyester polyols of 200 mgKOH / g or less.

  The coating film according to the third aspect of the present invention is obtained by curing the coating composition according to the second aspect.

  According to the polyisocyanate composition of the above embodiment, there is provided a polyisocyanate composition which is stable even when mixed with water, does not cause coloring or the like upon storage, and has excellent drying properties and scratch resistance when formed into a coating film. be able to. The coating composition of the above embodiment contains the polyisocyanate composition and has excellent drying properties and scratch resistance when formed into a coating film. The coating film of the above embodiment is obtained by curing the coating composition, and has excellent drying properties and abrasion resistance.

  Hereinafter, a mode for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. The following embodiment is an exemplification 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 invention.

  Unless otherwise specified, “(meth) acryl” includes methacryl and acryl, and “(meth) acrylate” includes methacrylate and acrylate.

In addition, in this specification, a "polyol" means the compound which has two or more hydroxy groups (-OH).
As used herein, “polyisocyanate” means a reactant in which a plurality of monomer compounds having one or more isocyanate groups (—NCO) are bonded.

≪Polyisocyanate composition≫
The polyisocyanate composition of the present embodiment contains a polyisocyanate, a tin-based urethanization catalyst, a dehydrating agent, and a solvent. The polyisocyanate is derived from an aliphatic diisocyanate containing HDI, and has an isocyanurate group and at least one functional group selected from the group consisting of a urethane group, an allophanate group and a biuret group. . In the polyisocyanate, when the molar amounts of the isocyanurate group, urethane group, allophanate group and biuret group are respectively a, b, c and d, (b + c + d) / (a + b + c + d) is 0.10 or more and 0.90 or less. is there. The dehydrating agent contains an aromatic monoisocyanate.

  The polyisocyanate composition of the present embodiment, having the above-mentioned constitution, is stable even when mixed with water, does not cause coloring or the like during storage, and is excellent in drying property and scratch resistance when formed into a coating film.

In general, the “isocyanurate group” is a functional group obtained by reacting three isocyanate groups, and is a group represented by the following formula (I).
Generally, the “urethane group” is a functional group obtained by reacting one isocyanate group with one hydroxyl group, and is a group represented by the following formula (II).
Generally, the “allophanate group” is a functional group obtained by reacting a hydroxyl group of an alcohol with an isocyanate group, and is a group represented by the following formula (III).
In general, the “biuret group” is a functional group obtained by reacting three isocyanate groups with a biuretizing agent (eg, water, tert-butanol, urea, etc.), and is a group represented by the following formula (IV). It is.

In the polyisocyanate composition of the present embodiment, when the molar amounts of isocyanurate group, urethane group, allophanate group and biuret group are respectively a, b, c and d, isocyanurate group, urethane group, allophanate group and biuret The lower limit of the ratio (b + c + d) / (a + b + c + d) of the total molar amount of the urethane group, allophanate group and biuret group to the total molar amount of the groups is 0.10, preferably 0.15, and more preferably 0.18. Preferably, 0.20 is more preferable. On the other hand, the upper limit of (b + c + d) / (a + b + c + d) is 0.90, preferably 0.75, more preferably 0.55, and even more preferably 0.40.
When (b + c + d) / (a + b + c + d) is within the above range, yellowing during storage and dryness to the touch when formed into a coating film are more excellent.
(B + c + d) / (a + b + c + d) can be measured by ¹³ C-NMR as described in Examples described later.

As a method of controlling (b + c + d) / (a + b + c + d) within the above range, a batch reaction method and a blending method are exemplified. As a batch synthesis method, for example, a method of forming a urethane group, an allophanate group, and an isocyanurate group by performing an isocyanuration reaction in a state where an alcohol is added, and forming an isocyanurate group, And a method of forming a urethane group and an allophanate group, and a method of forming a biuret group by adding a biuret agent after the isocyanuration reaction.
The blending method is a method of blending two or more polyisocyanate compositions having an isocyanurate group, a urethane group, an allophanate group, and a biuret group at an arbitrary molar ratio.
Next, each component contained in the polyisocyanate composition of the present embodiment will be described in detail below.

<Polyisocyanate>
The polyisocyanate contained in the polyisocyanate composition of the present embodiment is derived from an aliphatic diisocyanate containing HDI.
The aliphatic diisocyanate used in the production of the polyisocyanate is not limited to the following, but preferably has 4 to 30 carbon atoms. In addition to HDI, for example, 1,4-tetramethylene diisocyanate, , 5-pentamethylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisoisocyanate, lysine diisocyanate and the like. These aliphatic diisocyanates may be used alone or in combination of two or more.
Among them, the aliphatic diisocyanate used in the production of polyisocyanate preferably contains HDI from the viewpoint of industrial availability, reactivity during production of polyisocyanate, and low viscosity.

The diisocyanate monomer used in the production of the polyisocyanate may partially contain an alicyclic diisocyanate in addition to the aliphatic diisocyanate.
The alicyclic diisocyanate is not limited to the following, but preferably has 8 to 30 carbon atoms, for example, isophorone diisocyanate (hereinafter sometimes abbreviated as “IPDI”), 1,3- Bis (isocyanatomethyl) -cyclohexane, 4,4′-dicyclohexylmethane diisocyanate, norbornene diisocyanate, hydrogenated xylylene diisocyanate, and the like are included. These alicyclic diisocyanates may be used alone or in combination of two or more.
Above all, IPDI is preferred as the alicyclic diisocyanate from the viewpoint of weather resistance when formed into a coating film and easy industrial availability.

The polyisocyanate composition of the present embodiment preferably contains an isocyanurate trimer as a polyisocyanate. The term "isocyanurate trimer" as used herein means a polyisocyanate derived from three molecules of isocyanate monomer and having an isocyanurate group.
The content of the isocyanurate trimer is not particularly limited, but is preferably from 45% by mass to 95% by mass, more preferably from 50% by mass to 90% by mass, and more preferably from 55% by mass to 90% by mass, based on the total mass of the polyisocyanate composition. The content is more preferably from 80% by mass to 80% by mass.
The content of the isocyanurate trimer can be measured by gel permeation chromatography (hereinafter sometimes abbreviated as “GPC”).

  The polyisocyanate may have a functional group such as a uretdione group, an iminooxadiazinedione group, a urea group, a uretonimino group, a carbodiimide group, in addition to an isocyanurate group, a urethane group, an allophanate group, and a biuret group.

[Physical properties of polyisocyanate]
(viscosity)
The lower limit of the viscosity at 25 ° C. of the polyisocyanate is not particularly limited, but is preferably 100 mPa · s, more preferably 150 mPa · s, further preferably 200 mPa · s, particularly preferably 250 mPa · s, and most preferably 300 mPa · s. On the other hand, the upper limit of the viscosity is not particularly limited, but is preferably 10,000 mPa · s, more preferably 7000 mPa · s, still more preferably 4000 mPa · s, particularly preferably 2500 mPa · s, and most preferably 1500 mPa · s.
That is, the viscosity at 25 ° C. of the polyisocyanate is preferably from 100 mPa · s to 10,000 mPa · s, more preferably from 150 mPa · s to 7000 mPa · s, still more preferably from 200 mPa · s to 4000 mPa · s, and more preferably from 250 mPa · s. 2500 mPa · s or less is particularly preferable, and 300 mPa · s or more and 1500 mPa · s or less is most preferable.
When the lower limit of the viscosity is equal to or higher than the lower limit, the drying property when the coating is formed can be further improved.On the other hand, when the viscosity is equal to or lower than the upper limit, the solid content when the coating is formed. Concentration can be increased.
The viscosity at 25 ° C. of the polyisocyanate can be measured by using an E-type viscometer (manufactured by Tokimec Co.) for a polyisocyanate having a nonvolatile content of 99.5% by mass or more. It can be measured by the method described in Examples.

(Isocyanate group content (NCO content))
Although the lower limit of the isocyanate group content (NCO content) of the polyisocyanate is not particularly limited, it is preferably 19% by mass, more preferably 19.5% by mass, based on the mass of the nonvolatile component of the polyisocyanate. 0.0% by mass is more preferable, and 20.3% by mass is particularly preferable. On the other hand, the upper limit of the NCO content is not particularly limited, but is preferably 25% by mass, more preferably 24% by mass, still more preferably 23.5% by mass, and more preferably 23.5% by mass, based on the mass of the non-volatile content of the polyisocyanate. 0% by mass is particularly preferred.
That is, the NCO content of the polyisocyanate is preferably from 19% by mass to 25% by mass, more preferably from 19.5% by mass to 24% by mass, and more preferably 20.0% by mass, based on the mass of the non-volatile content of the polyisocyanate. % To 23.5% by mass, more preferably 20.3% by mass to 23.0% by mass.
When the NCO content is equal to or higher than the lower limit, the coating properties such as hardness can be improved, and when the NCO content is equal to or lower than the upper limit, the yield of polyisocyanate is kept higher. be able to.
The NCO content can be determined by back titration with 1N hydrochloric acid after neutralizing the isocyanate groups of the polyisocyanate with an excess of 2N amine.
The NCO content is a value based on the nonvolatile content of the polyisocyanate, and the nonvolatile content of the polyisocyanate can be measured according to a measuring method described in Examples described later.

(Average number of isocyanate groups (average number of NCO groups))
The lower limit of the average number of isocyanate groups (average number of NCO groups) of the polyisocyanate is not particularly limited, but is preferably 2.2, more preferably 2.4, and even more preferably 2.6. On the other hand, the upper limit of the average number of NCO groups is not particularly limited, but is preferably 4.0, more preferably 3.8, still more preferably 3.5, and particularly preferably 3.2.
That is, the average number of NCO groups in the polyisocyanate is preferably 2.2 or more, 4.0 or less, more preferably 2.4 or more and 3.8 or less, still more preferably 2.6 or more and 3.5 or less, and 2.6 or more. Particularly preferred is 3.2 or less.
When the average number of NCO groups is equal to or higher than the lower limit, the drying property when the coating film is formed is further improved. On the other hand, when the average number of NCO groups is equal to or lower than the upper limit, the polyisocyanate has a lower viscosity. can do.
The average number of isocyanate groups in the polyisocyanate can be calculated by the following equation.

  NCO group average number = (number average molecular weight of polyisocyanate × NCO content × 0.01) / 42

(Number average molecular weight)
The lower limit of the number average molecular weight of the polyisocyanate is not particularly limited, but is preferably 400, more preferably 430, still more preferably 460, and particularly preferably 480. On the other hand, the upper limit of the number average molecular weight of the polyisocyanate is not particularly limited, but is preferably 1,000, more preferably 800, more preferably 700, and particularly preferably 600.
That is, the number average molecular weight of the polyisocyanate is preferably from 400 to 1,000, more preferably from 430 to 800, still more preferably from 460 to 700, and particularly preferably from 480 to 600.
When the number average molecular weight is not less than the lower limit, the yield of the obtained polyisocyanate tends to be further improved, while the number average molecular weight is not more than the above upper limit, when a coating film The gloss tends to be further improved.
The number average molecular weight of the polyisocyanate can be determined by GPC.

[Method for producing polyisocyanate]
An example of the method for producing the polyisocyanate of the present embodiment will be described below.
As a raw material of the polyisocyanate, an aliphatic diisocyanate containing HDI is used.
Examples of the method for producing the polyisocyanate include a batch reaction method and a blending method. As a batch synthesis method, for example, a method of forming a urethane group, an allophanate group, and an isocyanurate group by performing an isocyanuration reaction in a state where an alcohol is added, and forming an isocyanurate group, And a method of forming a urethane group and an allophanate group, and a method of forming a biuret group by adding a biuret agent after the isocyanuration reaction.
The blending method is a method of blending two or more polyisocyanate compositions having an isocyanurate group, a urethane group, an allophanate group, and a biuret group at an arbitrary molar ratio.
Above all, as a method for producing a polyisocyanate, a method in which each reaction is performed sequentially by a batch reaction method, or a method in which some of them are carried out in parallel is preferable because of availability. In addition, a method is preferable in which a polymerization catalyst is added to HDI and, if necessary, other auxiliary materials, and the reaction is allowed to proceed until a predetermined degree of polymerization is reached, and then, if necessary, unreacted HDI is removed.

  The method for producing the polyisocyanate having each functional group will be described in detail below.

(Method for producing isocyanurate group-containing polyisocyanate)
Examples of a catalyst for deriving a polyisocyanate containing an isocyanurate group from a diisocyanate monomer include a generally used isocyanurate-forming reaction catalyst.

The isocyanurate-forming catalyst is not particularly limited, but is preferably generally basic. Specific examples of the isocyanurate-forming catalyst include the following.
(1) Tetraalkylammonium hydroxides such as tetramethylammonium, tetraethylammonium and tetrabutylammonium, and the above-mentioned tetraalkylammonium acetates, propionates, octylates, caprates, myristates, benzoates Organic weak salts such as salts.
(2) Hydroxides of aryltrialkylammoniums such as benzyltrimethylammonium and trimethylphenylammonium, and acetates, propionates, octylates, caprates, myristates and benzoates of the aryltrialkylammoniums And organic weak acid salts.
(3) Hydroxides of hydroxyalkylammonium such as trimethylhydroxyethylammonium, trimethylhydroxypropylammonium, triethylhydroxyethylammonium, triethylhydroxypropylammonium, and acetates, propionates, octylates, and caprins of the hydroxyalkylammonium Organic weak acid salts such as acid salts, myristic salts, and benzoates.
(4) Metal salts of alkyl carboxylic acids such as acetic acid, propionic acid, caproic acid, octylic acid, capric acid and myristic acid, such as tin, zinc and lead.
(5) Metal alcoholates such as sodium and potassium.
(6) Aminosilyl group-containing compounds such as hexamethylene disilazane.
(7) Mannich bases.
(8) A mixture of a tertiary amine and an epoxy compound.
(9) Phosphorus compounds such as tributylphosphine.

  Among them, the above (1), (2) or (3) is preferable from the viewpoint of catalyst efficiency, and the organic weak acid salt of (1) is more preferable.

  The upper limit of the amount of the above-mentioned isocyanurate-forming catalyst used is preferably 1000 ppm by mass, more preferably 500 ppm by mass, and still more preferably 100 ppm by mass, based on the mass of the charged diisocyanate monomer. On the other hand, the lower limit of the amount of the isocyanurate-forming catalyst used is not particularly limited, but may be, for example, 10 ppm by mass.

The lower limit of the isocyanuration reaction temperature is preferably 50 ° C, more preferably 54 ° C, still more preferably 57 ° C, and particularly preferably 60 ° C. On the other hand, the upper limit of the isocyanuration reaction temperature is preferably 120 ° C, more preferably 100 ° C, further preferably 90 ° C, and particularly preferably 80 ° C.
That is, the isocyanurate-forming reaction temperature is preferably from 50 ° C to 120 ° C, more preferably from 54 ° C to 100 ° C, even more preferably from 57 ° C to 90 ° C, and particularly preferably from 60 ° C to 80 ° C. When the isocyanurate-forming reaction temperature is equal to or lower than the above upper limit, there is a tendency that a change in characteristics such as coloring of the polyisocyanate can be more effectively suppressed.

(Method for producing urethane group-containing polyisocyanate)
When a polyisocyanate containing a urethane group is derived from a diisocyanate monomer, it can be produced, for example, by mixing an excess of a diisocyanate monomer and an alcohol, and adding a urethane-forming reaction catalyst as needed.
Examples of the alcohol include those similar to those exemplified in “Method for producing allophanate group-containing polyisocyanate” described below.
The ratio of the molar amount of the isocyanate group of the diisocyanate monomer to the molar amount of the hydroxyl group of the alcohol is preferably from 2/1 to 50/1. When the molar ratio is at least the lower limit, the polyisocyanate can have a lower viscosity. When the molar ratio is equal to or less than the upper limit, the yield of the urethane group-containing polyisocyanate can be further increased.

The urethanization reaction catalyst is not particularly limited, and examples thereof include a tin compound, a zinc compound, and an amine compound.
The upper limit of the amount of the urethanization reaction catalyst described above is preferably 10,000 mass ppm, more preferably 1,000 mass ppm, and even more preferably 500 mass ppm, based on the mass of the charged diisocyanate monomer. On the other hand, the lower limit of the amount of the isocyanurate-forming catalyst used is not particularly limited, but may be, for example, 10 ppm by mass.

The urethanization reaction temperature is preferably from 20 ° C to 100 ° C.
When the urethanization reaction temperature is equal to or lower than the upper limit, a change in characteristics such as coloring of the polyisocyanate tends to be more effectively suppressed.
The urethanization reaction time is preferably from 0.2 hours to 8 hours.

(Method for producing allophanate group-containing polyisocyanate)
The allophanate group-containing polyisocyanate is obtained by adding an alcohol to a diisocyanate monomer and using an allophanate-forming reaction catalyst.
The alcohol used to form the allophanate group is preferably an alcohol formed only from carbon, hydrogen and oxygen.
Specific examples of the alcohol include, but are not limited to, monoalcohols and dialcohols. These alcohols may be used alone or in combination of two or more.
Examples of the monoalcohol include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol and the like.
Examples of the dialcohol include ethylene glycol, 1,3-butanediol, neopentyl glycol, 2-ethylhexanediol, and the like.
Among them, as the alcohol, a monoalcohol is preferable, and a monoalcohol having a molecular weight of 200 or less is more preferable.

  The ratio of the molar amount of the isocyanate group of the diisocyanate monomer to the molar amount of the hydroxyl group of the alcohol is preferably from 10/1 to 1000/1, and more preferably from 100/1 to 1000/1. When the molar ratio is at least the lower limit, the average number of isocyanate groups can be more sufficiently secured.

Examples of the allophanate-forming reaction catalyst include, but are not limited to, alkyl carboxylate salts such as tin, lead, zinc, bismuth, zirconium, and zirconyl.
Examples of the tin alkylcarboxylate (organotin compound) include tin 2-ethylhexanoate, dibutyltin dilaurate, and the like.
Examples of the lead alkylcarboxylate (organic lead compound) include lead 2-ethylhexanoate.
Examples of the zinc alkylcarboxylate (organic zinc compound) include zinc 2-ethylhexanoate.
Examples of the bismuth alkyl carboxylate include bismuth 2-ethylhexanoate.
Examples of the zirconium alkylcarboxylate include zirconium 2-ethylhexanoate.
Examples of the zirconyl alkyl carboxylate include zirconyl 2-ethylhexanoate. These catalysts can be used alone or in combination of two or more.
Further, the above isocyanurate-forming reaction catalyst can also be an allophanate-forming reaction catalyst. When an allophanate-forming reaction is carried out using the above-mentioned isocyanurate-forming reaction catalyst, isocyanurate-type polyisocyanate is naturally produced.
Among them, it is preferable from the viewpoint of economic production that the allophanate-forming reaction and the isocyanurate-forming reaction be performed using the above-mentioned isocyanurate-forming reaction catalyst as the allophanate-forming reaction catalyst.

  The upper limit of the amount of the allophanate-forming catalyst used is preferably 10,000 ppm by mass, more preferably 1,000 ppm by mass, and still more preferably 500 ppm by mass, based on the mass of the charged diisocyanate monomer. On the other hand, the lower limit of the amount of the isocyanurate-forming catalyst used is not particularly limited, but may be, for example, 10 ppm by mass.

The lower limit of the allophanation reaction temperature is preferably 60 ° C, more preferably 70 ° C, further preferably 80 ° C, and particularly preferably 90 ° C. On the other hand, the upper limit of the allophanatization reaction temperature is preferably 160 ° C, more preferably 155 ° C, further preferably 150 ° C, and particularly preferably 145 ° C.
That is, the allophanate-forming reaction temperature is preferably from 60 ° C to 160 ° C, more preferably from 70 ° C to 155 ° C, even more preferably from 80 ° C to 150 ° C, and particularly preferably from 90 ° C to 145 ° C.
When the allophanatization reaction temperature is equal to or higher than the lower limit, the reaction rate can be further improved. When the allophanatization reaction temperature is equal to or lower than the above upper limit, a change in characteristics such as coloring of the polyisocyanate tends to be more effectively suppressed.

The lower limit of the allophanatization reaction time is preferably 0.2 hours, more preferably 0.4 hours, still more preferably 0.6 hours, particularly preferably 0.8 hours, and most preferably 1 hour. On the other hand, the upper limit of the allophanatization reaction time is preferably 8 hours, more preferably 6 hours, further preferably 4 hours, particularly preferably 3 hours, and most preferably 2 hours.
That is, the allophanatization reaction time is preferably from 0.2 hours to 8 hours, more preferably from 0.4 hours to 6 hours, still more preferably from 0.6 hours to 4 hours, and from 0.8 hours to 3 hours. The following is particularly preferable, and 1 hour or more and 2 hours or less are most preferable.
When the allophanation reaction time is equal to or longer than the lower limit, the polyisocyanate can have a lower viscosity.On the other hand, when the allophanation reaction time is equal to or lower than the upper limit, a property change such as coloring of the polyisocyanate can be more effectively performed. It tends to be suppressed.

(Method for producing biuret group-containing polyisocyanate)
A method for producing a polyisocyanate containing a biuret group from a diisocyanate monomer is not particularly limited, but the following method is preferably exemplified. Specifically, first, the reaction between the diisocyanate monomer and the biuretizing agent disclosed in Patent Document 4 is performed under stirring and homogeneity. Thereafter, the reaction product is further guided to a pipe reactor, and the polyisocyanate containing biuret groups is obtained by continuous production in which the reaction proceeds under an extrusion flow in the pipe reactor.

  When the polymerization reaction for forming each of the functional groups reaches a desired degree of polymerization, the polymerization reaction is stopped. Termination of the polymerization reaction is not limited to the following, for example, phosphoric acid, acid phosphate, sulfuric acid, hydrochloric acid, by adding an acidic compound such as a sulfonic acid compound to the reaction solution, to neutralize the polymerization reaction catalyst, Alternatively, it can be achieved by inactivating by thermal decomposition, chemical decomposition or the like. After the reaction is stopped, if necessary, filtration is performed. Since the reaction solution immediately after the termination of the reaction usually contains unreacted HDI monomer, it is preferable to remove this by a thin-film evaporator, extraction, or the like.

<Tin based urethanization catalyst>
The polyisocyanate composition of the present embodiment contains a tin-based urethanization catalyst in order to express dryness when formed into a coating film.
Examples of the tin-based urethanization catalyst include, but are not limited to, tin octoate, tin 2-ethyl-1-hexanoate, tin ethyl caproate, tin laurate, tin palmitate, dibutyltin oxide, and dibutyltin dichloride. , Dibutyltin diacetate, dibutyltin dimaleate, dibutyltin dilaurate, dioctyltin diacetate, dioctyltin dilaurate and the like.
A non-tin-based urethanization catalyst, for example, an organic zinc compound, an organic titanium compound, an organic zirconium compound, a tertiary amine compound, or the like may be used in combination.

  The content of the tin-based urethanization catalyst is preferably from 10 ppm to 20,000 ppm, more preferably from 50 ppm to 10,000 ppm, still more preferably from 100 ppm to 5,000 ppm, particularly preferably from 300 ppm to 3,000 ppm, based on the total mass of the polyisocyanate composition. . When the content of the tin-based urethanization catalyst is equal to or more than the above lower limit, the drying property when formed into a coating film is more sufficiently expressed. It can be suppressed effectively.

<Dehydrating agent>
The polyisocyanate composition of the present embodiment contains a dehydrating agent.
Examples of the dehydrating agent include (1) organic alkoxy compounds, (2) monofunctional isocyanates, (3) powdery and porous metal oxide or carbide, (4) CaSO ₄ , CaSO _4. Examples thereof include calcium compounds having a composition such as 1 / 2H ₂ O and CaO, and (5) metal alkoxides. The polyisocyanate composition of the present embodiment contains (2) monofunctional isocyanates (preferably, aromatic monoisocyanates) as a dehydrating agent. As the dehydrating agent, (2) monofunctional isocyanates can be used alone, (2) two or more monofunctional isocyanates can be used in combination, and (2) monofunctional isocyanates and the above (1) ) And (3) to (5) can also be used in combination.

The following are listed as specific examples of the dehydrating agents (1) to (5).
(1) Organic alkoxy compounds: for example, orthoformate such as methyl orthoformate and ethyl orthoformate; dimethoxypropane and the like.
(2) Monofunctional isocyanates: for example, aliphatic monoisocyanates such as methyl isocyanate, ethyl isocyanate and propyl isocyanate; aromatic monoisocyanates such as additive TI (product name) (manufactured by Covestro, p-toluenesulfonyl isocyanate).
(3) Powdery and highly porous metal oxides or carbides: for example, synthetic silica, activated alumina, Seolite, activated carbon and the like.
(4) Calcium compounds: for example, calcined gypsum, soluble gypsum, quicklime and the like.
(5) Metal alkoxides: for example, aluminum isopropylate, aluminum sec-butylate, zirconium n-butylate, ethyl silicate, vinyltrimethoxysilane and the like.

Above all, it is preferable that the dehydrating agent contains (1) an organic alkoxy compound and (2) a monofunctional isocyanate.
Further, among them, as the organic alkoxy compounds, orthoformate esters such as methyl orthoformate and ethyl orthoformate are preferable from the viewpoint of solubility in various solvents and polyisocyanate.
Above all, as monofunctional isocyanates, aromatic monoisocyanates such as Additive TI are preferable from the viewpoint of dehydration rate.
That is, the polyisocyanate composition of the present embodiment more preferably contains two types of orthoformate and aromatic monoisocyanate as a dehydrating agent.

The content per dehydrating agent is preferably from 0.1% by mass to 3% by mass, more preferably from 0.2% by mass to 2.5% by mass, based on the total mass of the polyisocyanate composition. The content is more preferably from 0.3% by mass to 2% by mass.
Further, the total content of the dehydrating agent is preferably from 0.2% by mass to 6% by mass, more preferably from 0.4% by mass to 5% by mass, and still more preferably from 0.6% by mass to 4% by mass. .
By making the total amount of the dehydrating agent equal to or more than the lower limit, a dehydration effect is more sufficiently exhibited, while by making the amount equal to or less than the upper limit, turbidity during storage can be more effectively suppressed. .

<Solvent>
The polyisocyanate composition of the present embodiment contains a solvent. The solvent is not particularly limited, but preferably does not have a functional group that reacts with a hydroxyl group and an isocyanate group, and is preferably sufficiently compatible with polyisocyanate. Examples of such a solvent include, but are not limited to, an ester compound, an ether compound, a ketone compound, an aromatic compound, an ethylene glycol dialkyl ether compound, a polyethylene glycol dicarboxylate compound, a hydrocarbon solvent, Compounds generally used as paint solvents, such as aromatic solvents, may be mentioned.
Among them, an ester compound or an aromatic compound is preferable, and an ester compound is more preferable. Preferred ester compounds include, but are not limited to, for example, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, and the like.

The content of the solvent is usually preferably from 20 parts by mass to 300 parts by mass, more preferably from 50 parts by mass to 200 parts by mass, and even more preferably from 70 parts by mass to 170 parts by mass based on 100 parts by mass of the polyisocyanate.
By controlling the content of the solvent to be equal to or more than the lower limit, the operability of the polyisocyanate composition is more sufficiently ensured, while, by setting the content to be equal to or less than the upper limit, the dry film thickness after being applied as a paint is used. Can be maintained more sufficiently.

The water content of the solvent contained in the polyisocyanate composition of the present embodiment is preferably 2000 ppm or less, more preferably 1000 ppm or less, further preferably 500 ppm or less, and particularly preferably 300 ppm or less.
When the amount of water in the solvent is more than the above upper limit, the solvent may be any of the dehydrating agents described above, such as solid (3) powdery porous metal oxide or carbonaceous material, or (4) It is preferable to add a calcium compound having a composition such as CaSO4, CaSO4.1 / 2H2O, CaO, etc., hold the mixture at room temperature for about 1 day or more and about 3 days or less, and then use a filter obtained by filtering off a dehydrating agent.
The amount of water in the solvent is measured by a Karl Fischer moisture meter.

<Method for producing polyisocyanate composition>
The polyisocyanate composition of the present embodiment includes, for example, the above-mentioned polyisocyanate, the above-mentioned tin-based urethanization catalyst, the above-mentioned dehydrating agent, and the above-mentioned solvent at a temperature of about 10 ° C or more and 60 ° C or less for 10 minutes or more. It can be manufactured by stirring for a time not more than minutes.

≪Paint composition≫
The polyisocyanate composition of the present embodiment can be suitably used as a curing agent or the like of a coating composition.
The coating composition of the present embodiment contains the above polyisocyanate composition.

<Resin component>
The coating composition of the present embodiment further contains a resin component as a main component. The resin component is not particularly limited, but preferably contains a compound having two or more active hydrogen groups having reactivity with an isocyanate group in a molecule.
The compound having two or more active hydrogen groups in the molecule is not limited to the following, but includes, for example, polyol, polyamine, polythiol and the like. Among them, a polyol having two or more active hydrogen groups in a molecule is preferably a polyol. Examples of the polyol include, but are not limited to, polyester polyol, polyether polyol, acrylic polyol, polyolefin polyol, and fluorine polyol.

[Polyester polyol]
The polyester polyol can be obtained, for example, by subjecting a single or a mixture of two or more dibasic acids to a condensation reaction with a single or a mixture of two or more polyhydric alcohols.
Examples of the dibasic acid include carboxylic acids such as succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, and 1,4-cyclohexanedicarboxylic acid.
Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, trimethylolpropane, glycerin, and pentaerythritol , 2-methylolpropanediol, ethoxylated trimethylolpropane, and the like.

  As a specific method for producing a polyester polyol, for example, a condensation reaction can be performed by mixing the above components and heating the mixture at about 160 ° C. or more and 220 ° C. or less.

  Alternatively, for example, polycaprolactones obtained by ring-opening polymerization of a lactone such as ε-caprolactone using a polyhydric alcohol can also be used as the polyester polyol.

  The polyester polyol obtained by the above-mentioned production method can be modified with an aromatic diisocyanate, an aliphatic diisocyanate, an alicyclic diisocyanate, a compound obtained therefrom, and the like. Above all, it is preferable that the polyester polyol is modified with an aliphatic diisocyanate, an alicyclic diisocyanate, and a compound obtained therefrom, from the viewpoints of weather resistance and yellowing resistance of the obtained coating film.

  When the coating composition of the present embodiment is used as a water-based coating, a part of carboxylic acid derived from dibasic acid or the like in the polyester polyol is left, and neutralized with a base such as amine and ammonia. The polyester polyol may be a water-soluble or water-dispersible resin.

[Polyether polyol]
The polyether polyol can be obtained, for example, by using any of the following methods (1) to (3).

(1) A method in which a polyether polyol is obtained by random or block addition of a single or mixture of alkylene oxides to a single or mixture of polyvalent hydroxy compounds using a catalyst.
Examples of the catalyst include hydroxides (such as lithium, sodium, and potassium), strong basic catalysts (such as alcoholates and alkylamines), and complex metal cyanide compound complexes (such as metalloporphyrins and zinc hexacyanocobaltate complexes). Can be
Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide.
Examples of the polyvalent hydroxy compound include the following (i) to (vi).
(I) diglycerin, ditrimethylolpropane and the like.
(Ii) Sugar alcohol compounds such as pentaerythritol, dipentaerythritol, erythritol, D-threitol, L-arabinitol, ribitol, xylitol, sorbitol, mannitol, galactitol, and rhamnitol.
(Iii) Monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose, ribodeose and the like.
(Iv) Disaccharides such as trehalose, sucrose, maltose, cellobiose, gentiobiose, lactose and melibiose.
(V) Trisaccharides such as raffinose, gentianose and meletitose.
(Vi) tetrasaccharides such as stachyose;

(2) A method of reacting an alkylene oxide with a polyamine compound to obtain polyether polyols.
Examples of the polyamine compound include ethylene diamines.
Examples of the alkylene oxide include those similar to those exemplified in (1).

  (3) A method of obtaining a so-called polymer polyol by polymerizing acrylamide or the like using the polyether polyol obtained in (1) or (2) as a medium.

[Acrylic polyol]
Acrylic polyol, for example, polymerizes only a polymerizable monomer having one or more active hydrogens in one molecule, or a polymerizable monomer having one or more active hydrogens in one molecule, and, if necessary, It can be obtained by copolymerizing the polymerizable monomer with another copolymerizable monomer.

Examples of the polymerizable monomer having one or more active hydrogens in one molecule include those shown in the following (i) to (vi). These may be used alone or in combination of two or more.
(I) Acrylic esters having active hydrogen, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate.
(Ii) Methacrylic acid having active hydrogen such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxypropyl methacrylate, and 4-hydroxybutyl methacrylate Esters.
(Iii) (meth) acrylates having polyvalent active hydrogen such as (meth) acrylate monoester of triol such as glycerin and trimethylolpropane.
(Iv) Monoethers of polyether polyols (for example, polyethylene glycol, polypropylene glycol, polybutylene glycol, etc.) with the above-mentioned (meth) acrylates having active hydrogen.
(V) An adduct of glycidyl (meth) acrylate and a monobasic acid (eg, acetic acid, propionic acid, p-tert-butylbenzoic acid, etc.).
(Vi) Adducts obtained by ring-opening polymerization of lactones (eg, ε-caprolactam, γ-valerolactone, etc.) with the active hydrogen of the (meth) acrylates having the above active hydrogen.

Examples of other monomers copolymerizable with the polymerizable monomer include those shown in the following (i) to (v). These may be used alone or in combination of two or more.
(I) Methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, methacrylic acid (Meth) acrylates such as isobutyl, n-hexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, and glycidyl methacrylate.
(Ii) unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid;
(Iii) Unsaturated amides such as acrylamide, N-methylolacrylamide, diacetoneacrylamide and the like.
(Iv) Vinyl monomers having a hydrolyzable silyl group such as vinyltrimethoxysilane, vinylmethyldimethoxysilane, and γ- (meth) acrylopropyltrimethoxysilane.
(V) Other polymerizable monomers such as styrene, vinyl toluene, vinyl acetate, acrylonitrile, and dibutyl fumarate.

  As a specific method for producing an acrylic polyol, for example, the above-described monomer is solution-polymerized in the presence of a radical polymerization initiator such as a known peroxide or an azo compound, and is diluted with an organic solvent or the like as necessary. Thereby, an acrylic polyol can be obtained.

  When the coating composition of the present embodiment is used as a water-based coating, it can be produced by a known method such as a method in which the above-mentioned monomer is solution-polymerized and converted into an aqueous layer, or an emulsion polymerization. In that case, acrylic acid, a carboxylic acid-containing monomer such as methacrylic acid or an acidic portion such as a sulfonic acid-containing monomer may be neutralized with an amine or ammonia to impart water solubility or water dispersibility to the acrylic polyol. it can.

[Polyolefin polyol]
Examples of the polyolefin polyol include polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene having two or more hydroxyl groups, polyisoprene having two or more hydroxyl groups, and hydrogenated polyisoprene having two or more hydroxyl groups.
Further, the number of hydroxyl groups of one molecule of the polyolefin polyol (hereinafter sometimes referred to as “average number of hydroxyl groups”) is preferably 2 or more.

[Fluorine polyol]
In the present specification, “fluorine polyol” means a polyol containing fluorine in a molecule. Specific examples of the fluorine polyol include copolymers such as fluoroolefins, cyclovinyl ethers, hydroxyalkyl vinyl ethers, and vinyl monocarboxylates disclosed in Patent Documents 5 and 6 and the like.

[Hydroxyl value and acid value of polyol]
The lower limit of the hydroxyl value of the polyol is preferably 10 mgKOH / g, more preferably 20 mgKOH / g, and still more preferably 30 mgKOH / g. On the other hand, the upper limit of the hydroxyl value of the polyol is preferably 200 mgKOH / g, more preferably 180 mgKOH / g, and still more preferably 160 mgKOH / g.
That is, the hydroxyl value of the polyol is preferably from 10 mgKOH / g to 200 mgKOH / g, more preferably from 20 mgKOH / g to 180 mgKOH / g, even more preferably from 30 mgKOH / g to 160 mgKOH / g.
When the hydroxyl value of the polyol is equal to or more than the lower limit, the solvent resistance of the coating film obtained from the coating composition of the present embodiment can be further improved. On the other hand, when the hydroxyl value of the polyol is equal to or less than the upper limit, the pot life after mixing with the polyisocyanate composition can be further improved.

  In general, “pot life” refers to the time during which a composition such as a paint or an adhesive is mixed with a main agent and a curing agent to prepare a composition, and that the performance as a composition before curing is secured. Means Also called pot life.

  The acid value of the polyol is preferably from 0 mgKOH / g to 30 mgKOH / g.

  The hydroxyl value and the acid value can be measured according to JIS K1557.

  Among them, an acrylic polyol is preferable as the polyol contained in the coating composition of the present embodiment from the viewpoints of weather resistance, chemical resistance, and hardness. Or, a polyester polyol is preferable from the viewpoint of mechanical strength and oil resistance.

  That is, the coating composition of the present embodiment comprises the polyisocyanate composition of the above embodiment, an acrylic polyol having a hydroxyl value of 10 mgKOH / g to 200 mgKOH / g, and a hydroxyl value of 10 mgKOH / g to 200 mgKOH / g. And at least one polyol selected from the group consisting of polyester polyols.

[NCO / OH]
The molar ratio (NCO / OH) of the isocyanate group of the polyisocyanate composition of the embodiment to the hydroxyl group of the compound having two or more active hydrogens in the molecule is preferably 0.2 or more and 5.0 or less. 4 or more and 3.0 or less are more preferable, and 0.5 or more and 2.0 or less are still more preferable.
When the NCO / OH is at least the lower limit, a tougher coating film tends to be obtained. On the other hand, when NCO / OH is less than the above upper limit, the smoothness of the coating film tends to be further improved.

<Other additives>
The coating composition of the present embodiment contains, in addition to the polyisocyanate composition and the resin component, if necessary, a melamine-based curing agent such as a complete alkyl type, a methylol type alkyl, or an imino group type alkyl. Good.

Further, the resin component and the coating composition of the present embodiment may each contain an organic solvent.
The organic solvent is not particularly limited, but preferably does not have a functional group that reacts with a hydroxyl group and an isocyanate group, and preferably has sufficient compatibility with the polyisocyanate composition. Examples of such organic solvents include, but are not limited to, ester compounds, ether compounds, ketone compounds, aromatic compounds, ethylene glycol dialkyl ether compounds, polyethylene glycol dicarboxylate compounds, and hydrocarbon solvents. And compounds generally used as coating solvents such as aromatic solvents.

  The resin component, the polyisocyanate composition of the above-described embodiment, and the coating composition of the present embodiment all promote curing according to the purpose and application within a range that does not impair the desired effects of the present embodiment. Various additives used in the art, such as a catalyst for use, a pigment, a leveling agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a plasticizer, and a surfactant, may be used in combination.

Examples of the catalyst for promoting curing include, but are not limited to, metal salts and tertiary amines.
Examples of the metal salt include dibutyltin dilaurate, tin 2-ethylhexanoate, zinc 2-ethylhexanoate, and cobalt salt.
Examples of the tertiary amines include triethylamine, pyridine, methylpyridine, benzyldimethylamine, N, N-dimethylcyclohexylamine, N-methylpiperidine, pentamethyldiethylenetriamine, N, N′-endoethylenepiperazine, and N, N ′. -Dimethylpiperazine and the like.

  Examples of the pigment include titanium oxide, carbon black, indigo, quinacridone, and pearl mica.

  Examples of the leveling agent include, but are not particularly limited to, silicone, aerosil, wax, stearate, and polysiloxane.

Examples of antioxidants, ultraviolet absorbers, and light stabilizers include, for example, aliphatic, aromatic or alkyl-substituted aromatic esters of phosphoric acid or phosphorous acid, hypophosphorous acid derivatives, phosphorus compounds, phenolic derivatives (Particularly, hindered phenol compounds), compounds containing sulfur, and tin compounds. These may be contained alone or in combination of two or more.
Examples of the phosphorus compound include phenylphosphonic acid, phenylphosphinic acid, diphenylphosphonic acid, polyphosphonate, dialkylpentaerythritol diphosphite, dialkylbisphenol A diphosphite, and the like.
Examples of the compound containing sulfur include a thioether compound, a dithioate compound, a mercaptobenzimidazole compound, a thiocarbanilide compound, and a thiodipropionate.
Examples of the tin-based compound include tin malate and dibutyltin monoxide.

Although it does not specifically limit as a plasticizer, For example, a phthalate ester, a phosphate ester, a fatty acid ester, a pyromellitic ester, an epoxy plasticizer, a polyether plasticizer, a liquid rubber, a non-aromatic paraffin Oil and the like.
Examples of the phthalic esters include dioctyl phthalate, dibutyl phthalate, diethyl phthalate, butyl benzyl phthalate, di-2-ethylhexyl phthalate, diisodecyl phthalate, diundecyl phthalate, diisononyl phthalate and the like.
Examples of the phosphate esters include tricresyl phosphate, triethyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, trimethylhexyl phosphate, tris-chloroethyl phosphate, and tris-dichloropropyl phosphate.
Examples of the fatty acid esters include octyl trimellitate, isodecyl trimellitate, trimellitate, dipentaerythritol esters, dioctyl adipate, dimethyl adipate, di-2-ethylhexyl azelate, and dioctyl azelate. , Dioctyl sebacate, di-2-ethylhexyl sebacate, methyl acetyl lisinocate and the like.
Examples of the pyromellitic acid ester include octyl pyromellitic acid ester.
Examples of the epoxy plasticizer include epoxidized soybean oil, epoxidized linseed oil, and epoxidized fatty acid alkyl esters.
Examples of the polyether plasticizer include adipic acid ether ester and polyether.
Examples of the liquid rubber include liquid NBR, liquid acrylic rubber, liquid polybutadiene, and the like.

  Examples of the surfactant include known anionic surfactants, cationic surfactants, amphoteric surfactants, and the like.

<Production method of coating composition>
The polyisocyanate composition of the present embodiment can be suitably used for a solvent-based coating composition.
As a production method when a solvent-based coating composition is used, for example, first, a resin containing a compound having two or more active hydrogens in the molecule, or a solvent dilution thereof, if necessary, other resin A catalyst, a pigment, a leveling agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a plasticizer, a surfactant, and other additives are prepared. Next, the polyisocyanate composition of the present embodiment is added as a curing agent, and if necessary, a solvent is further added to adjust the viscosity. Next, a solvent-based coating composition can be obtained by stirring manually or using a stirring device such as Magellar.

<Uses of paint composition>
Although not limited to the following, the coating composition of the present embodiment can be used as a coating material such as roll coating, curtain flow coating, spray coating, bell coating, and electrostatic coating. For example, it is useful as a primer or top coat for materials such as metals (steel plates, surface-treated steel plates, etc.), plastics, woods, films, and inorganic materials. It is also useful as a paint for imparting aesthetics, weather resistance, acid resistance, rust resistance, chipping resistance, etc. to pre-coated metal including rust-proof steel plates, automotive coatings and the like. Further, it is useful as a urethane raw material such as an adhesive, a pressure-sensitive adhesive, an elastomer, a foam, and a surface treatment agent.

≪Coating film≫
The coating film of the present embodiment is obtained by curing the coating composition of the above embodiment. The coating film of the present embodiment is obtained by coating and curing the coating composition of the above embodiment on a substrate, for example, by roll coating, curtain flow coating, spray coating, bell coating, electrostatic coating, or the like. Can be Therefore, the coating film of the present embodiment always exhibits stable quality, and is excellent in drying property and scratch resistance.

  Hereinafter, the present embodiment will be described in more detail based on examples and comparative examples, but the present embodiment is not limited by the following examples.

<Test items>
With respect to the polyisocyanate obtained in the synthesis example, and the polyisocyanate compositions manufactured in the examples and the comparative examples, measurement and evaluation of respective physical properties were performed in accordance with the following methods.

[Physical Properties 1] Viscosity The viscosity was measured at 25 ° C. using an E-type viscometer (manufactured by Tokimec). In the measurement, a standard rotor (1 ° 34 ′ × R24) was used. The rotation speed was as follows.

(Rotation speed)
100 rpm (less than 128 mPa · s)
50 rpm (in the case of 128 mPa · s or more and less than 256 mPa · s)
20 rpm (when it is 256 mPa · s or more and less than 640 mPa · s)
10 rpm (in the case of 640 mPa · s or more and less than 1280 mPa · s)
5 rpm (when it is 1280 mPa · s or more and less than 2560 mPa · s)

  The non-volatile content of the polyisocyanate obtained in a synthesis example described later was examined by the method described below, and those having a value of 98% by mass or more were directly subjected to measurement.

[Physical Properties 2] Non-volatile content The non-volatile content was determined from the residual mass obtained by heating the polyisocyanate obtained in Synthesis Example at 105 ° C for 3 hours and the mass before heating by the following formula.

Non-volatile content (% by mass)
= (Mass of polyisocyanate composition after heating) / (mass of polyisocyanate composition before heating) x 100

[Physical property 3] NCO content The NCO content (% by mass) was determined by back titration with 1N hydrochloric acid after neutralizing an isocyanate group in the polyisocyanate obtained in the synthesis example with an excess of 2N amine.
In addition, the non-volatile content of the polyisocyanate obtained in the synthesis example was examined by the above-described method, and those having a value of 98% by mass or more were subjected to measurement as they were.

[Physical property 4] (b + c + d) / (a + b + c + d)
Using the polyisocyanate obtained in the synthesis example as a sample, the molar amount a of the isocyanurate group, the molar amount b of the urethane group, the molar amount c of the allophanate group, and the biuret were determined by ¹³ C-NMR measurement under the following measurement conditions. The molar amount d of the group was determined.
Specific measurement conditions were as follows.

(Measurement condition)
¹³ C-NMR apparatus: AVANCE600 (manufactured by Bruker Biospin)
Cryoprobe: CP DUL 600S3 C / HD-05Z (manufactured by Bruker Biospin)
Resonant frequency: 150MHz
Concentration: 60 wt / vol%
Shift standard: CDCl ₃ (77 ppm)
Number of integration: 10000 times Pulse program: zgpg30 (proton complete decoupling method, waiting time 2 sec)

  In the above measurement, the integral value of the following signal was divided by the number of measured carbons, and each molar amount was determined from the value. (B + c + d) / (a + b + c + d) was calculated from the obtained molar amount of each functional group.

Isocyanurate group: around 148.6 ppm: integrated value ÷ 3
Urethane group: around 156.9 ppm: integral value ÷ 1
Allophanate group: around 154 ppm: integral value ÷ 1
Biuret group: around 156.2 ppm: integral value ÷ 2

[Evaluation 1] Yellowing after storage The initial chromaticity of each of the polyisocyanate compositions obtained in Examples and Comparative Examples was measured using a colorimeter PFXi-195 manufactured by Lovbond. Thereafter, 30 g of the polyisocyanate composition was added to the dried 50 mL glass screw bottle, nitrogen-sealed, sealed, and kept at 50 ° C. × 1 week. Next, the sample after storage was cooled to 25 ° C., and the chromaticity of the reaction solution was measured again using the same apparatus. The difference between the chromaticity before storage and the chromaticity after storage was calculated, and the yellowing after storage was evaluated according to the following evaluation criteria.

(Evaluation criteria)
：: Difference in chromaticity before and after storage is less than 10 〇: Difference in chromaticity before and after storage is 10 or more and less than 20 Δ: Difference in chromaticity before and after storage is 20 or more and less than 30 ×: Difference in chromaticity before and after storage 30 or more

[Evaluation 2] Storage stability when sealed at room temperature The initial viscosity of each of the polyisocyanate compositions obtained in Examples and Comparative Examples was measured with an E-type viscometer. After adding 30 g of the polyisocyanate composition to the dried 50 mL glass screw bottle, the container was sealed with nitrogen, sealed, and stored at 23 ° C. for 7 days. Then, the viscosity after storage was measured again. The ratio of the viscosity after storage to the viscosity before storage was calculated as a viscosity change rate, and the storage stability when sealed at room temperature was evaluated according to the following evaluation criteria.

(Evaluation criteria)
Δ: Viscosity change rate is less than 120% Δ: Viscosity change rate is 120% or more and less than 150% ×: Viscosity change rate is 150% or more

[Evaluation 3] Storage stability at opening The initial viscosities of the polyisocyanate compositions obtained in Examples and Comparative Examples were measured with an E-type viscometer. After adding 30 g of the polyisocyanate composition to the dried 50 mL glass screw bottle, the container was kept at 23 ° C. for 24 hours in a glass desiccator with water placed at the bottom with the lid opened. Then, the viscosity after storage was measured again. The ratio of the viscosity after storage to the viscosity before storage was calculated as a viscosity change rate, and the storage stability at opening was evaluated according to the following evaluation criteria.

(Evaluation criteria)
Δ: Viscosity change rate is less than 120% Δ: Viscosity change rate is 120% or more and less than 250% ×: Viscosity change rate is 250% or more

[Evaluation 4] Dryness to the touch To each polyisocyanate composition obtained in Examples and Comparative Examples, Setalux 1903 (manufactured by Allnex, acrylic polyol) was used so that the molar ratio of NCO groups / OH groups was 1/1. Mixed. Further, butyl acetate was added to the mixture so that the coating solid content became 50% by mass to prepare a coating composition. The prepared coating composition was applied to a glass plate and left at 35 ° C. and 50% humidity. Every hour, the time when tackiness disappeared was confirmed by finger touch. For the time when the tack disappeared, the dryness to the touch was evaluated according to the evaluation criteria shown below.

(Evaluation criteria)
◎: Within 1 hour 〇: Within 2 hours △: Within 4 hours ×: Over 4 hours

[Evaluation 5] Scratch resistance A coating composition was prepared in the same manner as in the above "Evaluation 4". The obtained coating composition was applied to a glass plate and dried at 100 ° C. for 30 minutes. After cooling, the gloss value of the initial coating film was measured. Thereafter, under the condition of a load of 1 kg, the steel wool was reciprocated 50 times with $ 0000 steel wool, left at 23 ° C. for 3 hours, and the gloss value was measured. The ratio of the gloss value of the coating film after the test to the gloss value of the initial coating film was calculated as a gloss retention, and the scratch resistance was evaluated according to the following evaluation criteria.

(Evaluation criteria)
◎: Gloss retention rate of 99% or more Δ: Gloss retention rate of 98% or more and less than 99% Δ: Gloss retention rate of 96% or more and less than 98% ×: Gloss retention rate of less than 96%

<Synthesis of polyisocyanate>
[Synthesis Example 1] Synthesis of polyisocyanate P-1 A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube and a dropping funnel was set to a nitrogen atmosphere, HDI: 1000 g, and 2-ethyl Hexanol: 30 g was charged, and the temperature in the reactor was kept at 90 ° C. for 1 hour with stirring. Thereafter, 0.6 g of an isobutanol solution containing tetramethylammonium capryate (solid content: 5%) was added to the reaction solution. When the NCO content of the reaction solution reached 43.5%, an aqueous 85% phosphoric acid solution (a reagent manufactured by Wako Pure Chemical Industries, Ltd.): 0.06 g (42-fold mol with respect to the catalyst) was added to stop the reaction. . After filtering the reaction solution, unreacted HDI was removed using a thin film evaporator to obtain polyisocyanate P-1. The viscosity at 25 ° C. of the obtained polyisocyanate P-1 was 340 mPa · s, the NCO content was 20.3%, and (b + c + d) / (a + b + c + d) was 0.50.

[Synthesis Example 2] Synthesis of polyisocyanate P-2 A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube, and a dropping funnel was set to a nitrogen atmosphere, HDI: 1000 g, and isobutanol: 32 g was charged and the temperature inside the reactor was kept at 130 ° C. for 1 hour under stirring. Thereafter, a mineral spirit solution containing zirconyl 2-ethylhexanoate (solid content 20%) in the reaction solution (a product of Nippon Kagaku Sangyo Co., Ltd., trade name "Nikka Octix Zirconium 12%" diluted with mineral spirit) : 0.55 g was added. When the NCO content of the reaction solution reached 43.9%, 0.32 g of phosphoric acid 2-ethylhexyl ester (4.1 times mol with respect to the catalyst) was added to stop the reaction. After filtering the reaction solution, unreacted HDI was removed using a thin film evaporator to obtain polyisocyanate P-2. The viscosity at 25 ° C. of the obtained polyisocyanate P-2 was 110 mPa · s, the NCO content was 19.4%, and (b + c + d) / (a + b + c + d) was 0.97.

[Synthesis Example 3] Synthesis of polyisocyanate P-3 A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube and a dropping funnel was set to a nitrogen atmosphere, HDI: 1000 g was charged, and the mixture was stirred. The temperature inside the reactor was raised to 60 ° C. Thereafter, 2.0 g of an isobutanol solution containing tetramethylammonium capryate (solid content: 5%) was added to the reaction solution. When the NCO content of the reaction solution reached 44.1%, an 85% aqueous solution of phosphoric acid (a reagent manufactured by Wako Pure Chemical Industries, Ltd.): 0.06 g (42 times the amount of the catalyst) was added to stop the reaction. After filtering the reaction solution, unreacted HDI was removed using a thin-film evaporator to obtain polyisocyanate P-3. The viscosity at 25 ° C. of the obtained polyisocyanate P-3 was 1,400 mPa · s, the NCO content was 23.2%, and (b + c + d) / (a + b + c + d) was 0.05.

[Synthesis Example 4] Synthesis of polyisocyanate P-4 A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube, and a dropping funnel was set to a nitrogen atmosphere, and polyisocyanate P-1 was 85 parts by mass. And 15 parts by mass of polyisocyanate P-3 were added, and the mixture was kept at 50 ° C. for 1 hour with stirring to obtain polyisocyanate P-4. The viscosity at 25 ° C. of the obtained polyisocyanate P-4 was 1150 mPa · s, the NCO content was 22.8%, and (b + c + d) / (a + b + c + d) was 0.12.

[Synthesis Example 5] Synthesis of polyisocyanate P-5 A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube and a dropping funnel was set to a nitrogen atmosphere, and polyisocyanate P-1 was 45 parts by mass. And 55 parts by mass of polyisocyanate P-3 were added, and the mixture was maintained at 50 ° C. for 1 hour with stirring to obtain polyisocyanate P-5. The viscosity at 25 ° C. of the obtained polyisocyanate P-5 was 700 mPa · s, the NCO content was 21.9%, and (b + c + d) / (a + b + c + d) was 0.30.

[Synthesis Example 6] Synthesis of polyisocyanate P-6 A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube and a dropping funnel was set to a nitrogen atmosphere, and polyisocyanate P-1 was 90 parts by mass. , And 10 parts by mass of polyisocyanate P-3 were added, and the mixture was maintained at 50 ° C. for 1 hour with stirring to obtain polyisocyanate P-6. The viscosity at 25 ° C. of the obtained polyisocyanate P-6 was 420 mPa · s, the NCO content was 20.6%, and (b + c + d) / (a + b + c + d) was 0.45.

[Synthesis Example 7] Synthesis of polyisocyanate P-7 A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube, and a dropping funnel was set to a nitrogen atmosphere, and polyisocyanate P-3: 75 parts by mass. , And 24-100 (manufactured by Asahi Kasei, biuret-type polyisocyanate composition, viscosity at 25 ° C: 1800 mPa · s, NCO content: 23.5%): 25 parts by mass, and kept at 50 ° C for 1 hour with stirring Thus, polyisocyanate P-7 was obtained. The viscosity at 25 ° C. of the obtained polyisocyanate P-7 was 1500 mPa · s, the NCO content was 23.3%, and (b + c + d) / (a + b + c + d) was 0.28.

[Synthesis Example 8] Synthesis of polyisocyanate P-8 In a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube, and a dropping funnel, a nitrogen atmosphere was introduced, and polyisocyanate P-2: 23 parts by mass And 77 parts by mass of polyisocyanate P-3 were added, and the mixture was maintained at 50 ° C. for 1 hour with stirring to obtain polyisocyanate P-8. The viscosity at 25 ° C. of the obtained polyisocyanate P-8 was 950 mPa · s, the NCO content was 22.3%, and (b + c + d) / (a + b + c + d) was 0.26.

[Synthesis Example 9] Synthesis of polyisocyanate P-9 A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube and a dropping funnel was set to a nitrogen atmosphere, and polyisocyanate P-1 was 78 parts by mass. , And 22 parts by mass of polyisocyanate P-3 were added, and the mixture was kept at 50 ° C. for 1 hour with stirring to obtain polyisocyanate P-9. The viscosity at 25 ° C. of the obtained polyisocyanate P-9 was 270 mPa · s, the NCO content was 20.1%, and (b + c + d) / (a + b + c + d) was 0.60.

[Synthesis Example 10] Synthesis of polyisocyanate P-10 A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube, and a dropping funnel was set to a nitrogen atmosphere, and HDI: 1000 g, and 1.3. -Butanediol: 60 g was charged, and the temperature in the reactor was kept at 90 ° C. for 1 hour under stirring. Thereafter, 0.6 g of an isobutanol solution containing tetramethylammonium capryate (solid content: 5%) was added to the reaction solution. When the NCO content of the reaction solution became 33%, an aqueous 85% phosphoric acid solution (a reagent manufactured by Wako Pure Chemical Industries, Ltd.): 0.06 g (42-fold mol with respect to the catalyst) was added to stop the reaction. After filtering the reaction solution, unreacted HDI was removed using a thin film evaporator to obtain polyisocyanate P-10. The viscosity at 25 ° C. of the obtained polyisocyanate P-10 was 2700 mPa · s, the NCO content was 20.0%, and (b + c + d) / (a + b + c + d) was 0.92.

[Synthesis Example 11] Synthesis of polyisocyanate P-11 A four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blowing tube and a dropping funnel was set to a nitrogen atmosphere, and polyisocyanate P-10: 90 parts by mass. And 10 parts by mass of polyisocyanate P-3 were added, and the mixture was kept at 50 ° C. for 1 hour with stirring to obtain polyisocyanate P-11. The viscosity at 25 ° C. of the obtained polyisocyanate P-11 was 2,600 mPa · s, the NCO content was 20.3%, and (b + c + d) / (a + b + c + d) was 0.83.

<Production of polyisocyanate composition>
[Example 1] Production of polyisocyanate composition A-1 Acetic acid adjusted to 200 ppm in water in a four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, a nitrogen blower, and a dropping funnel. Butyl: 59.4 parts by mass, dibutyltin dilaurate: 0.4 parts by mass as an organotin compound, methyl orthoformate: 0.2 parts by mass as a dehydrating agent, and additive Ti (p-toluenesulfonyl, manufactured by Covestro) Isocyanate): 0.4 parts by mass was added and stirred at 40 ° C. for 30 minutes. Thereafter, polyisocyanate P-4 was added, and the mixture was further stirred at 40 ° C. for 30 minutes to obtain a polyisocyanate composition A-1. Various evaluations were performed on the obtained polyisocyanate composition A-1 using the methods described above. The results are shown in Table 1 below.

[Examples 2 to 8 and Comparative Examples 1 to 4] Production of polyisocyanate compositions A-2 to A-8 and B-1 to B-4 The components used and the amounts added are shown in Tables 1 and 2 below. Polyisocyanate compositions A-2 to A-8 and B-1 to B-4 were produced in the same manner as in Example 1, except that Various evaluations were performed on each of the obtained polyisocyanate compositions by using the method described above. The results are shown in Tables 1 and 2 below.

In Tables 1 and 2, the compounds indicated by the abbreviations are as follows.
MOF: Methyl orthoformate EOF: Ethyl orthoformate Ti: Product name, Additive TI manufactured by Covestro
DBTL: Nitto Kasei, product name, Neostan U-100
DOTL: Nitto Kasei, product name, Neostan U-810

From Tables 1 and 2, poly (isocyanate) in which (b + c + d) / (a + b + c + d) is 0.12 to 0.83, a tin-based urethanization catalyst, a dehydrating agent containing an aromatic monoisocyanate, and a solvent-containing polyisocyanate The isocyanate compositions A-1 to A-8 (Examples 1 to 8) were yellowed after storage, storage stability when sealed at room temperature and storage stability when opened, and touch when formed into a coating film. Drying and scratch resistance were all good.
Polyisocyanate compositions A-1 to A-6 and A-8 (Examples 1 to 6 and 8) containing both orthoformate and aromatic monoisocyanate as dehydrating agents contain only aromatic monoisocyanate. The storage stability at the time of opening was particularly good as compared with the polyisocyanate composition A-7 (Example 7).
The polyisocyanate composition A-1 (Example 1) containing a polyisocyanate having (b + c + d) / (a + b + c + d) of 0.12 is different from other polyisocyanate compositions A-2 to A-8 (Examples 2 to 2). The dryness to the touch when formed into a coating film was particularly good as compared with 8).
The polyisocyanate composition A-2 containing ethyl orthoformate as a dehydrating agent (Example 2) and the polyisocyanate composition A-5 containing polyisocyanate P-8 (Example 5) are other polyisocyanate compositions. Abrasion resistance as a coating film was particularly good as compared with A-1, A-3, A-4, and A-6 to A-8 (Examples 1, 3, 4, and 6 to 8). Was.

  On the other hand, polyisocyanate compositions B-1 (Comparative Example 1) and B-4 (Comparative Example 4) in which (b + c + d) / (a + b + c + d) is less than 0.1 or more than 0.90, and a tin-based urethanization catalyst are included. Both polyisocyanate composition B-2 (Comparative Example 2) and polyisocyanate composition B-3 (Comparative Example 3) containing no aromatic monoisocyanate as a dehydrating agent were yellowed after storage and sealed at room temperature. Good storage stability at the time of opening, storage stability at the time of opening, and good dryness to the touch and abrasion resistance as a coating film could not be obtained.

  The polyisocyanate composition of the present embodiment is stable even when mixed with water, does not cause coloring or the like during storage, and is excellent in dryness and scratch resistance when formed into a coating film. The coating composition of the present embodiment contains the polyisocyanate composition as a curing agent and can be used as a coating such as roll coating, curtain flow coating, spray coating, bell coating, and electrostatic coating. The coating composition of the present embodiment can be used as a primer or top coat for metals such as steel sheets and surface-treated steel sheets, plastics, wood, films, inorganic materials and the like. The coating composition of the present embodiment is also useful as a coating that imparts heat resistance, cosmetic properties (surface smoothness, sharpness) and the like to a precoated metal including a rust-proof steel plate, an automobile coating, and the like. The coating composition of the present embodiment is also useful as a urethane raw material such as an adhesive, a pressure-sensitive adhesive, an elastomer, a foam, and a surface treatment agent. When the coating composition of the present embodiment is a water-based coating, the VOC component can be reduced, so that it can be used in a wide range of fields such as solvent-free coatings, water-based plastic coatings, and raw materials for water-based automotive coatings.

Claims (4)

A polyisocyanate, a tin-based urethanization catalyst, a dehydrating agent, and a solvent, comprising a polyisocyanate composition,
The polyisocyanate is derived from an aliphatic diisocyanate including 1,6-hexamethylene diisocyanate, and an isocyanurate group and at least one functional group selected from the group consisting of a urethane group, an allophanate group, and a biuret group. , And
When the molar amounts of the isocyanurate group, the urethane group, the allophanate group, and the biuret group are a, b, c, and d, respectively, (b + c + d) / (a + b + c + d) is 0.10 or more and 0.90 or less. Yes,
A polyisocyanate composition, wherein the dehydrating agent contains an aromatic monoisocyanate.   The polyisocyanate composition according to claim 1, wherein the dehydrating agent comprises an orthoformate and an aromatic monoisocyanate. A polyisocyanate composition according to claim 1 or 2,
An acrylic polyol having a hydroxyl value of 10 mgKOH / g to 200 mgKOH / g, and at least one polyol selected from the group consisting of a polyester polyol having a hydroxyl value of 10 mgKOH / g to 200 mgKOH / g;
A coating composition comprising:   A coating film obtained by curing the coating composition according to claim 3.