JP6985099B2 - Hardened polyisocyanate, coatings and encapsulants - Google Patents

Description

The present invention relates to a cured polyisocyanate, a coating film and a sealing material.

A cured product using an aliphatic diisocyanate or a polyisocyanate obtained from an alicyclic diisocyanate as a curing agent is used as a paint, ink, adhesive, etc. because it exhibits excellent performance such as weather resistance, chemical resistance, and abrasion resistance. Widely used. In this case, a polyol or polyamine is usually used as the main agent, and the hydroxyl group or amino group of the main agent reacts with the isocyanate group of the curing agent to form a compound having a urethane group or a urea group. The compound containing a urethane group or a urea group thus formed is called a polyurethane resin or a polyurea resin. Polyurethane resin and polyurea resin can be imparted with various functions such as heat resistance and elasticity by changing the structure of the main agent and the curing agent, but the heat resistance may be insufficient depending on the intended use.

For example, Patent Documents 1 to 4 disclose a technique relating to a polyisocyanate cured product which has been subjected to an isocyanurate-forming reaction using diisocyanate as a raw material as a method for increasing the heat resistance of the cured product.

Japanese Unexamined Patent Publication No. 2012-021129 Japanese Unexamined Patent Publication No. 2012-0415113 Japanese Unexamined Patent Publication No. 59-098180 International Publication No. 2015/166983

The methods described in Patent Documents 1 to 3 can form a cured product having high heat resistance, but there is a concern that the yellowness may increase. Further, since only the cyclic structure of the isocyanurate group or the uretdione group is formed, the surface property of the cured product may be deteriorated due to the curing shrinkage. In the method described in Patent Document 4, the flexibility is increased by introducing an allophanate group into the molecule, and the surface property can be expected to be improved, but there is a concern that the heat resistance may be lowered by the introduction of the allophanate group.

The present invention has been made in view of the above circumstances, and provides a cured polyisocyanate product having good heat resistance, low yellowness and surface properties.

That is, the present invention includes the following aspects.
The cured polyisocyanate according to the first aspect of the present invention has an isocyanurate group composed of at least one diisocyanate selected from the group consisting of an aliphatic diisocyanate and an alicyclic diisocyanate as a unit structure, and has a urethane group and a urea group. And, substantially free of allophanate groups, but containing diphenylamine .

The polyisocyanate cured product according to the first aspect is at least one selected from the group consisting of a hindered phenol-based antioxidant, a hindered amine-based antioxidant, a sulfur-containing antioxidant, and a phosphorus-containing antioxidant. May be contained.

The coating film according to the second aspect of the present invention contains the polyisocyanate cured product according to the first aspect.

The encapsulant according to the third aspect of the present invention contains the polyisocyanate cured product according to the first aspect.

The cured polyisocyanate of the above aspect has good heat resistance, low yellowness and surface properties.

Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments. The present invention can be appropriately modified and carried out within the scope of the gist thereof.

<Cured polyisocyanate>
The cured polyisocyanate of the present embodiment has an isocyanurate group composed of at least one diisocyanate selected from the group consisting of an aliphatic diisocyanate and an alicyclic diisocyanate as a unit structure. The isocyanurate group is a group represented by the following formula (1).

In addition, in this specification, a "polyisocyanate cured product" means a reaction product obtained by curing a polyisocyanate composition shown later.

Further, the cured polyisocyanate of the present embodiment does not substantially contain an allophanate group (a group represented by the following formula (2)). The term "substantially free of allophanate groups" as used herein means that the molar ratio of allophanate group / isocyanurate group in the allophanate group and isocyanurate group in the cured polyisocyanate is less than 1/99. .. The molar ratio of allophanate group / isocyanurate group is preferably 0/100 or more and less than 1/99, and more preferably 0/100.

The number of moles of allophanate group and isocyanurate group can be measured by ^{freeze-grinding the cured polyisocyanate and using 13 C-NMR.} The details of the measuring method can be measured by the method described in Examples described later.

Further, the cured polyisocyanate of the present embodiment substantially does not contain a urethane group (a group represented by the following formula (3)) and a urea group (a group represented by the following formula (4)). The term "substantially free of urethane groups and urea groups" as used herein means that the isocyanurate group, urethane group and urea group in the cured polyisocyanate are the molars of (urethane group + urea group) / isocyanurate group. It indicates that the ratio is 0/100 or more and 5/95 or less. The molar ratio of (urethane group + urea group) / isocyanurate group is preferably 0/100 or more and 3/97 or less, more preferably 0/100 or more and 1/99 or less, and 0/100. Is even more preferable.

In the present embodiment, the number of moles of urethane group, urea group and isocyanate group can be measured by the ATR method of FT-IR. The details of the measuring method can be measured by the method described in Examples described later.

As the cured polyisocyanate of the present embodiment, in addition to the above, it is preferable that the gel fraction is measured and the weight residue ratio is 45% or more.

The gel fraction can be measured, for example, by using the method shown below. First, about 0.1 g of a cured polyisocyanate sample is immersed in acetone at 20 ° C. for 24 hours. The sample is then removed and weighed after drying at 105 ° C. for 1 hour. Next, the gel fraction is obtained from the weight residual ratio before and after immersion. In addition to acetone, xylene, toluene, methyl ethyl ketone, benzene, water and the like can be used as the solvent. It is possible to measure at different temperatures and times depending on the purpose and application. Further, as a method for measuring the gel fraction, it is also possible to refer to the method for determining the degree of cross-linking in JIS C3005 “Rubber / Plastic Insulated Wire Test Method”.

The cured polyisocyanate of the present embodiment has good heat resistance, low yellowness, and surface properties, and is also excellent in weather resistance. Therefore, it is suitable for coating film applications in places where it is exposed to the outdoors for a long period of time or is exposed to high temperatures on a regular basis.

The cured polyisocyanate of the present embodiment preferably has a Td1 (1% weight loss temperature) of 1% or higher at 290 ° C. or higher, more preferably 295 ° C. or higher, and at 300 ° C. or higher. It is more preferable to have. The upper limit of Td1 is not particularly limited, but is, for example, 600 ° C. or lower. In this embodiment, Td1 can be measured by the method described in Examples described later.

The upper limit of the concentration of catalyst-derived cations in the cured polyisocyanate of the present embodiment is preferably 100 ppm, more preferably 80 ppm, further preferably 60 ppm, and more preferably 40 ppm. Especially preferable. When the concentration of the catalyst-derived cations in the cured polyisocyanate of the present embodiment is equal to or less than the above upper limit, the yellowness becomes better.

The lower limit of the concentration of catalyst-derived cations in the cured polyisocyanate of the present embodiment is not particularly limited, but is, for example, 0.1 ppm.

That is, the concentration of catalyst-derived cations in the cured polyisocyanate of the present embodiment is preferably 0.1 ppm or more and 100 ppm or less, more preferably 0.1 ppm or more and 80 ppm or less, and 0.1 ppm or more. It is more preferably 60 ppm or less, and particularly preferably 0.1 ppm or more and 40 ppm or less.

The yellowness (Yellow Index; YI) (hereinafter, may be abbreviated as “YI”) of the cured polyisocyanate of the present embodiment can be measured by, for example, the measuring method shown below. First, for a sample of a cured polyisocyanate having a thickness of 1 mm, the transmittance of 380 nm or more and 780 nm or less is measured by a spectrophotometer. Next, X, Y and Z are obtained from JIS Z8701 from the measurement results of the spectrophotometer. YI is calculated from JIS K7373 and JIS Z8720 from the obtained X, Y and Z.

When the thickness of the cured polyisocyanate of the present embodiment is 1 mm, the upper limit of YI is preferably 10, more preferably 9, and even more preferably 8. When the thickness of the cured polyisocyanate of the present embodiment is 1 mm, the lower limit of YI is not particularly limited, but is, for example, 0.1.

That is, the cured polyisocyanate of the present embodiment preferably has a YI of 0.1 or more and 10 or less, more preferably 0.1 or more and 9 or less, and 0.1 or more when the thickness is 1 mm. It is more preferably 8 or less.

<Manufacturing method of cured polyisocyanate>
Next, a method for producing the cured polyisocyanate of the present embodiment will be described. The method described below is an example and is not limited to this method.

The cured polyisocyanate of the present embodiment is a polyisocyanate composition containing (a) a polyisocyanate obtained by isocyanurate-forming at least one kind of diisocyanate selected from the group consisting of an aliphatic diisocyanate and an alicyclic diisocyanate, and (b). It can be obtained by subjecting an isocyanurate-forming catalyst to an isocyanurate-forming reaction. The obtained cured polyisocyanate has excellent heat resistance, low yellowness and surface properties.

[(A) Polyisocyanate composition]
(A) The polyisocyanate composition contains a polyisocyanate obtained from at least one diisocyanate selected from the group consisting of an aliphatic diisocyanate and an alicyclic diisocyanate. The polyisocyanate contains an isocyanurate group. The isocyanurate group consists of three molecules of diisocyanate monomer and is a group represented by the following formula (1).

As used herein, the "aliphatic diisocyanate" is a diisocyanate having a saturated chain aliphatic hydrocarbon group in the molecule. On the other hand, the "alicyclic diisocyanate" is a diisocyanate having a cyclic aliphatic hydrocarbon group in the molecule. Hereinafter, the aliphatic diisocyanate and the alicyclic diisocyanate are collectively referred to as "diisocyanate".

It is more preferable to use an aliphatic diisocyanate because flexibility can be imparted to the obtained cured polyisocyanate. The aliphatic diisocyanate is not particularly limited, and may be, for example, 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, or 1,6-diisocyanatohexane (hereinafter, abbreviated as "HDI"). ), 1,6-Diisocyanato-2,2,4-trimethylhexane, methyl 2,6-diisocyanatohexaneate (lysine diisocyanate) and the like.

The alicyclic diisocyanate is not particularly limited, and is, for example, 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane (isophorone diisocyanate), 1,3-bis (isocyanatomethyl) cyclohexane (water). Addition xylylene diisocyanate), bis (4-isocyanatocyclohexyl) methane (hydrousated diphenylmethane diisocyanate), 1,4-diisocyanatocyclohexane and the like.

Among them, as the diisocyanate, HDI, isophorone diisocyanate, hydrogenated xylylene diisocyanate or hydrogenated diphenylmethane diisocyanate is preferable because it is easily available industrially. Further, among the diisocyanates, HDI is more preferable because the balance between the weather resistance and the flexibility of the obtained coating film is very excellent.

As a method for deriving the isocyanurate group-containing polyisocyanate from the diisocyanate monomer, a method using an isocyanurate-forming catalyst is preferable. As a specific isocyanurate-forming catalyst, a catalyst having basicity is generally preferable, and examples thereof include those shown in 1) to 7) below.

1) Hydroxide or organic weak acid salt of quaternary organic ammonium.
Examples of the quaternary organic ammonium include tetramethylammonium, tetraethylammonium, tetrabutylammonium, trimethylbenzylammonium and the like.
Examples of the organic weak acid include acetic acid and capric acid.

2) Hydroxide or organic weak acid salt of hydroxyalkylammonium.
Examples of the hydroxyalkylammonium include trimethylhydroxypropylammonium, trimethylhydroxyethylammonium, triethylhydroxypropylammonium, triethylhydroxyethylammonium and the like.
Examples of the organic weak acid include acetic acid and capric acid.

3) A metal salt of an alkylcarboxylic acid.
Examples of the alkylcarboxylic acid include acetic acid, caproic acid, octyl acid, myristic acid and the like.
Examples of the metal include tin, zinc, lead, sodium and potassium.

4) Metallic alcoholates such as sodium and potassium.
5) Aminosilyl group-containing compound such as hexamethyldisilazane.
6) Mannich bases.
7) Combined use of tertiary amines and epoxy compounds.

Among them, the isocyanurate-forming catalyst is preferably 1), 2), 3) or 4) above. Aminosilyl group-containing compounds cause side reactions such as uretdione formation depending on the conditions of use. Therefore, the isocyanurate-forming catalyst is more preferably 1) or 4) above, further preferably an organic weak acid salt of tetraalkylammonium or a sodium alkoxide, and a capricate of tetramethylammonium. It is particularly preferable to use sodium methoxide or sodium ethoxide.

(A) The polyisocyanate contained in the polyisocyanate composition is substantially free of allophanate groups. As used herein, "substantially free of allophanate groups" means that the molar ratio of allophanate groups / isocyanurate groups in polyisocyanate is less than 6/94. The molar ratio of allophanate group / isocyanurate group is preferably 5/95 or less, more preferably 1/99 or less. When the molar ratio of allophanate group / (alofanate group + isocyanurate group) is less than the above upper limit value, the heat resistance of the obtained cured polyisocyanate can be maintained. The number of moles of the isocyanurate group and the number of moles of the allophanate group in the polyisocyanate can be determined by ^{1 H-NMR.}

(A) The polyisocyanate contained in the polyisocyanate composition is substantially free of uretdione groups. The term "substantially free of uretdione groups" as used herein means that the content of the polyisocyanate containing a uretdione group is 5% by mass or less in the polyisocyanate. The content of the polyisocyanate containing a uretdione group is preferably 3% by mass or less, and more preferably 1% by mass or less.

The content of uretdione groups in polyisocyanate is measured by measuring the ratio of the area of the peak with a molecular weight of about 336 in gel permeation chromatography (hereinafter, may be abbreviated as "GPC") with a differential refractometer. You can ask. If there is a peak near the peak with a molecular weight of about 336 that interferes with the measurement, use a Fourier transform infrared spectrophotometer (hereinafter, may be abbreviated as "FT-IR") to about ^{1770 cm -1.} The ratio of the peak height of the uretdione group to the peak height ^{of the carbonyl group of the isocyanurate group of about 1690 cm-1} can also be determined by a method of quantifying using an internal standard.

Hereinafter, the measurement conditions by GPC will be described in detail.

(Measurement condition)
Equipment used: HLC-8120 (manufactured by Tosoh Corporation).
Columns used: TSK GEL SuperH1000, TSK GEL SuperH2000, TSK GEL SuperH3000 (all manufactured by Tosoh Corporation).
Sample concentration: 5 wt / vol% (eg, dissolve 50 mg of sample in 1 mL of tetrahydrofuran (tetrahydrofuran; THF)).
Carrier: THF.
Detector: Differential refractometer Outflow: 0.6 mL / min.
Column temperature: 30 ° C.

In addition, the calibration curve of GPC is prepared using the following 1) to 3) as standard substances.
1) Polystyrene with a molecular weight of 2050 or more and 50,000 or less (manufactured by GL Sciences Co., Ltd., PSS-06 (Mw50000), BK13007 (Mp = 20000, Mw / Mn = 1.03), PSS-08 (Mw = 9000), PSS-09 (Mw = 4000) and 5040-35125 (Mp = 2050, Mw / Mn = 1.05)).
2) Hexamethylene diisocyanate (HDI) -based polyisocyanate (trade name: Duranate TPA-100, manufactured by Asahi Kasei Co., Ltd.) isocyanurate trimer to heptameric (isocyanurate trimer molecular weight = 504, isocyanurate pentamer) Molecular weight = 840 and isocyanurate heptamolecular weight = 1176).
3) Hexamethylene diisocyanate (HDI) (molecular weight = 168).

(A) When producing the polyisocyanate composition, the amount of the isocyanurate-forming catalyst used is preferably 0.001% by mass or more and 2% by mass or less, preferably 0.01, based on the total mass of the reaction solution. It is more preferably mass% or more and 0.5 mass% or less. When the amount of the isocyanurate-forming catalyst used is not less than the above lower limit, the effect of the catalyst can be more fully exhibited. When the amount of the isocyanurate-forming catalyst used is not more than the above upper limit, the reaction can be more easily controlled.

(A) When producing a polyisocyanate composition, the method of adding an isocyanurate-forming catalyst is not limited. As the method of addition, a method of adding a required amount of the isocyanate-forming catalyst all at once, or a method of adding the isocyanurate-forming catalyst in several portions may be used. Alternatively, a method of continuously adding at a constant addition rate can also be adopted.

(A) When producing the polyisocyanate composition, the isocyanurate-forming reaction is preferably carried out in a solvent-free environment, but an organic solvent may be used if necessary.

Examples of the organic solvent include those shown in 1) to 4) below. These organic solvents may be used alone or in combination of two or more.
1) Ester-based solvent such as ethyl acetate and butyl acetate.
2) Ketone solvent such as methyl ethyl ketone.
3) Aromatic solvents such as toluene, xylene and diethylbenzene.
4) An organic solvent that does not have reactivity with isocyanate groups such as dialkylpolyalkylene glycol ether.

(A) When producing a polyisocyanate composition, the process of the isocyanurate-forming reaction can be traced by measuring the NCO group content of the reaction solution or measuring the refractive index.

The isocyanurate-forming reaction can be stopped by cooling to room temperature or by adding a reaction terminator. Above all, when a catalyst is used, it is preferable to add a reaction terminator because side reactions can be suppressed. The amount of the reaction terminator added is preferably 0.25 times or more and 20 times or less, and more preferably 0.5 times or more and 16 times or less the molar amount of the catalyst. , 1.0 times or more and 12 times or less is more preferable. When the amount of the reaction terminator added is equal to or greater than the above lower limit with respect to the molar amount of the catalyst, the catalyst can be more completely inactivated. When the amount of the reaction terminator added is not more than the above upper limit value with respect to the amount of the catalyst, the storage stability of the obtained (a) polyisocyanate composition becomes better.

Any reaction terminator may be used as long as it deactivates the catalyst. Specific examples of the reaction terminator include compounds exhibiting phosphoric acid acidity and monoalkyl esters or dialkyl esters thereof, halogenated acetic acid, benzoyl chloride, sulfonic acid esters, sulfuric acid, sulfate esters, ion exchange resins, chelating agents and the like. These are, but are not limited to. Examples of the compound showing phosphoric acid acidity include phosphoric acid, pyrophosphoric acid, metaphosphoric acid, polyphosphoric acid and the like. Examples of the halogenated acetic acid include monochloroacetic acid and the like.

Among them, as the reaction terminator, phosphoric acid, pyrophosphoric acid, metaphosphoric acid or polyphosphoric acid is preferable from an industrial point of view. Further, a phosphoric acid monoalkyl ester or a phosphoric acid dialkyl ester is preferable because it does not easily corrode stainless steel.

Examples of the phosphoric acid monoalkyl ester include a phosphoric acid monoethyl ester, a phosphoric acid monobutyl ester, a phosphoric acid mono (2-ethylhexyl) ester, a phosphoric acid monodecyl ester, a phosphoric acid monolauryl ester, and a phosphoric acid monotridecyl ester. Examples thereof include, but are not limited to, phosphoric acid monooleyl esters.

Examples of the phosphoric acid dialkyl ester include phosphoric acid diethyl ester, phosphoric acid dibutyl ester, phosphoric acid di (2-ethylhexyl) ester, phosphoric acid didecyl ester, phosphoric acid dilauryl ester, phosphoric acid ditridecyl ester, and phosphoric acid geo. Examples include, but are not limited to, rail esters.

These phosphoric acid monoalkyl esters or phosphoric acid dialkyl esters may be used alone or in combination of two or more.

Further, a method of stopping the reaction by using an adsorbent or a method of stopping the reaction by combining the adsorbent and the above-mentioned reaction terminator is also preferable.

Specific examples of the adsorbent include, but are not limited to, silica gel, activated carbon, and the like.

The amount of the adsorbent added is preferably 1.4 times or more and 3000 times or less, more preferably 7.0 times or more and 1500 times or less with respect to the mass of the catalyst, and 10.0 times. It is more preferable that the mass is fold or more and 700 times or less. If the amount of the adsorbent added is equal to or greater than the above lower limit with respect to the mass of the catalyst, (a) the catalyst remaining in the polyisocyanate composition, the heat-deactivated catalyst, and the reaction product of the reaction terminator and the catalyst. , The ability to adsorb unreacted reaction terminators and the like is more sufficient. On the other hand, when the amount of the adsorbent added is equal to or less than the above upper limit with respect to the mass of the catalyst, it is easier to remove the adsorbent from the (a) polyisocyanate composition.

After completion of the reaction, the obtained (a) polyisocyanate composition may contain unreacted diisocyanate or solvent, or the unreacted diisocyanate or solvent is separated from the obtained (a) polyisocyanate composition. May be. Considering safety, it is preferable to separate unreacted diisocyanate from the obtained (a) polyisocyanate composition. Examples of the method for separating the unreacted diisocyanate and the solvent include, and are not limited to, a thin film distillation method and a solvent extraction method.

(A) The lower limit of the NCO group content in the polyisocyanate contained in the polyisocyanate composition is preferably 5.0% by mass, preferably 7.0% by mass, in a state where no solvent or diisocyanate is contained. More preferably, it is more preferably 10.0% by mass.

Further, (a) the upper limit of the NCO group content in the polyisocyanate contained in the polyisocyanate composition is preferably 25.0% by mass, preferably 24.0% by mass, in a state where no solvent or diisocyanate is contained. Is more preferable, and 23.5% by mass is further preferable.

That is, (a) the NCO group content in the polyisocyanate contained in the polyisocyanate composition is preferably 5.0% by mass or more and 25.0% by mass or less in a state where no solvent or diisocyanate is contained, and 7 It is more preferably 9.0% by mass or more and 24.0% by mass or less, and further preferably 10.0% by mass or more and 23.5% by mass or less.
(A) When the NCO group content in the polyisocyanate contained in the polyisocyanate composition is within the above range, (a) the polyisocyanate composition has a lower viscosity and better compatibility with various additives. Moreover, a cured polyisocyanate having more sufficient heat resistance can be obtained.

The term "state containing no solvent or diisocyanate" as used herein means a state in which the content of the solvent and diisocyanate is less than 1% by mass.

(A) The lower limit of the viscosity of the polyisocyanate composition at 25 ° C. is preferably 100 mPa · s, more preferably 150 mPa · s, in a state where it does not contain a solvent or diisocyanate. When the viscosity is at least the above lower limit value, a cured polyisocyanate having more sufficient crosslinkability can be obtained.

(A) The upper limit of the viscosity of the polyisocyanate composition at 25 ° C. is preferably 20000 mPa · s and more preferably 10000 mPa · s in a state where it does not contain a solvent or diisocyanate. When the viscosity is not more than the above upper limit value, the compatibility of the (a) polyisocyanate composition with various additives can be improved.

That is, (a) the viscosity of the polyisocyanate composition at 25 ° C. is preferably 100 mPa · s or more and 20000 mmPa · s or less, and 150 mPa · s or more and 10,000 mPa · s or more in a state where it does not contain a solvent or diisocyanate. It is more preferable to have.

(A) The lower limit of the number average number of functional groups of NCO groups in the polyisocyanate contained in the polyisocyanate composition is preferably 2.1, more preferably 2.2, and even more preferably 2.4. (A) When the number average number of functional groups of NCO groups in the polyisocyanate contained in the polyisocyanate composition is at least the above lower limit value, the cured polyisocyanate has a higher crosslink density and becomes more tough.

(A) The upper limit of the number average number of functional groups of NCO groups in the polyisocyanate contained in the polyisocyanate composition is not particularly limited, but is, for example, 8.0.

That is, (a) the number average number of functional groups of NCO groups in the polyisocyanate contained in the polyisocyanate composition is preferably 2.1 or more and 8.0 or less, more preferably 2.2 or more and 8.0 or less, and 2.4. More than 8.0 or less is more preferable.

[(B) Isocyanurate-forming catalyst]
As the (b) isocyanurate-forming catalyst, the isocyanurate-forming catalyst exemplified in the above-mentioned (a) polyisocyanate composition can be used. Above all, the above 1), 2), 3) or 4) is preferable. Aminosilyl group-containing compounds cause side reactions such as uretdione formation depending on the conditions of use. Therefore, the isocyanurate-forming catalyst is more preferably 1) or 4) above, further preferably an organic weak acid salt of tetraalkylammonium or a sodium alkoxide, and a capricate of tetramethylammonium. It is particularly preferable to use sodium methoxide or sodium ethoxide.

The lower limit of the amount of the (b) isocyanurate-forming catalyst added is preferably 50 ppm, more preferably 100 ppm, in terms of mass ratio with respect to the solid content of the (a) polyisocyanate composition. (B) When the amount of the isocyanurate-forming catalyst added is at least the above lower limit, the reactivity is more sufficient.

The upper limit of the amount of the (b) isocyanurate-forming catalyst added is preferably 10000 ppm, more preferably 5000 ppm, and 3000 ppm in terms of mass ratio with respect to the solid content of the (a) polyisocyanate composition. It is more preferable to have. (B) When the addition amount of the isocyanurate-forming catalyst is at least the above upper limit value, the influence on the physical properties of the cured polyisocyanate can be further reduced.

That is, (b) the amount of the isocyanurate-forming catalyst added is preferably 50 ppm or more and 10,000 ppm or less, and 100 ppm or more and 5000 ppm or less in terms of mass ratio with respect to the solid content of the (a) polyisocyanate composition. It is more preferably 100 ppm or more and 3000 ppm or less.

The reaction temperature at the time of producing the cured polyisocyanate of the present embodiment is not particularly limited, but is preferably 60 ° C. or higher and 200 ° C. or lower, more preferably 80 ° C. or higher and 180 ° C. or lower, and 100. It is more preferably ℃ or more and 170 ℃ or less, and particularly preferably 120 ℃ or more and 160 ℃ or less. When the reaction temperature is at least the above lower limit value, the curability of the cured polyisocyanate product is more excellent, and when the reaction temperature is at least the above upper limit value, the color tone of the cured polyisocyanate product, particularly the yellowness, becomes smaller.

(B) The isocyanurate-forming catalyst can be used together with a diluent if necessary. As the diluent, (a) one that reacts with the NCO group in the polyisocyanate contained in the polyisocyanate composition and is incorporated into the system can be used. The diluent is not particularly limited, and examples thereof include compounds having an active hydrogen group such as an alcohol solvent. In addition, these diluents may be used individually by 1 type, and may be used by mixing 2 or more types. Among them, as the diluent, an alcohol solvent is preferable because the viscosity becomes low and the dispersibility of the catalyst is improved.

In the method for producing a cured polyisocyanate of the present embodiment, it is preferable that the step of performing the isocyanurate-forming reaction is carried out under conditions that do not substantially contain a solvent. The term "conditions containing substantially no solvent" as used herein means a condition in which (a) the solvent is 5% by mass or less with respect to the mass of the polyisocyanate composition. Further, (a) the solvent is preferably 3% by mass or less, more preferably 1% by mass or less, based on the mass of the polyisocyanate composition. (A) When the solvent is not more than the above upper limit with respect to the mass of the polyisocyanate composition, the influence on the weight reduction of the cured polyisocyanate can be further reduced.

[(C) Diphenylamine]
The cured polyisocyanate of the present embodiment may further contain (c) diphenylamine in addition to the above (a) polyisocyanate composition and (b) isocyanurate-forming catalyst. The inclusion of diphenylamine surprisingly significantly improves the surface properties.

The lower limit of the amount of (c) diphenylamine added is preferably 100 ppm, more preferably 200 ppm, and more preferably 500 ppm in terms of mass ratio with respect to the solid content of the (a) polyisocyanate composition. More preferred. (C) When the amount of diphenylamine added is at least the above lower limit, the surface property becomes better.

The upper limit of the amount of (c) diphenylamine added is preferably 20,000 ppm, more preferably 10,000 ppm, and 5,000 ppm in terms of mass ratio with respect to the solid content of the (a) polyisocyanate composition. More preferred. (C) When the amount of diphenylamine added is not more than the above upper limit value, the occurrence of bleeding or the like can be further suppressed in the cured product.

That is, the amount of (c) diphenylamine added is preferably 100 ppm or more and 20000 ppm or less, more preferably 200 ppm or more and 10000 ppm or less, in terms of mass ratio with respect to the solid content of the (a) polyisocyanate composition. It is more preferably 500 ppm or more and 5000 ppm or less.

[(D) Antioxidant]
The cured polyisocyanate of the present embodiment contains (a) a polyisocyanate composition, (b) an isocyanurate-forming catalyst, and (c) diphenylamine, and (d) an antioxidant. May be. The (d) antioxidant may be added at the stage of producing the cured polyisocyanate product, or may be added in advance to the (a) polyisocyanate composition. Further, (d) the antioxidant may be used alone or in combination of two or more.

(D) The antioxidant is not particularly limited, and examples thereof include substances having an antioxidant action used as a light-resistant stabilizer, a heat-resistant stabilizer, and the like.

The antioxidant used as a light-resistant stabilizer is not particularly limited, and for example, a hindered amine-based antioxidant, a benzophenone-based antioxidant, a benzotriazole-based antioxidant, a triazine-based antioxidant, and a cyanoacrylate-based oxidation. Examples include inhibitors.

The hindered amine antioxidant is not particularly limited, but is, for example, Adeka Stub LA-52 (trade name), Adeka Stub LA-68 (trade name), Adeka Stub LA-77Y (trade name) (manufactured by Adeka Corporation), and Chinubin. (Tinuvin) 622 (trade name), Tinubin 765 (trade name), Tinubin 770 (trade name), Tinubin 791 (trade name) (each manufactured by BASF) and the like can be mentioned.

The benzophenone-based antioxidant is not particularly limited, and examples thereof include Chimassorb 81 (trade name) (manufactured by BASF).

The benzotriazole-based antioxidant is not particularly limited, and examples thereof include chinubin P (trade name) and chinubin 234 (trade name) (each manufactured by BASF).

The triazine-based antioxidant is not particularly limited, and examples thereof include tinubin 1577ED (trade name) (manufactured by BASF).

The cyanoacrylate-based antioxidant is not particularly limited, and examples thereof include Uvinul 3035 (trade name) (manufactured by BASF).

The antioxidant used as a heat-resistant stabilizer is not particularly limited, and for example, a hindered phenol-based antioxidant, a phosphorus-containing antioxidant, a sulfur-containing antioxidant, a vitamin E-based antioxidant, and the like. Examples thereof include hydroxyamine-based antioxidants.

The hindered phenolic antioxidant is not particularly limited, but for example, dibutylhydroxytoluene (hereinafter, may be abbreviated as “BHT”), Irganox 1010 (trade name), Irganox 1135 (trade name), and the like. Irganox 1330 (trade name), Irganox 3114 (trade name), Irganox 565 (trade name), Irganox 1520L (trade name) (manufactured by BASF), Adecastab AO-20 (trade name), Adecastab AO- 30 (trade name), Adecastab AO-50 (trade name), Adecastab AO-60 (trade name), Adecastab AO-80 (trade name) (each manufactured by Adeca Co., Ltd.) and the like can be mentioned.

The phosphorus-containing antioxidant is not particularly limited, but is, for example, Adekastab PEP-8 (trade name), Adekastab HP-10 (trade name), Adekastab 1178 (trade name), Adekastab C (trade name) (each stock). (Manufactured by Adeka Corporation), Irgafoss 168, Irgafoss 38 (trade name) (manufactured by BASF), Sumilyzer GP (trade name) (manufactured by Sumitomo Chemical Co., Ltd.) and the like.

The sulfur-containing antioxidant is not particularly limited, and examples thereof include Irganox PS800FL (trade name) (manufactured by BASF).

The vitamin E-based antioxidant is not particularly limited, and examples thereof include Irganox E201 (trade name) (manufactured by BASF).

The hydroxyamine-based antioxidant is not particularly limited, and examples thereof include Irgastab FS042 (trade name) (manufactured by BASF).

Among them, (d) the antioxidant is at least one selected from the group consisting of a hindered phenol-based antioxidant, a hindered amine-based antioxidant, a sulfur-containing antioxidant, and a phosphorus-containing antioxidant. It is preferable to have. Further, as the (d) antioxidant, at least selected from the group consisting of chinubin 765 (trade name), BHT, Irganox 565 (trade name), Adecastab C (trade name), and Smilizer GP (trade name). It is more preferably one kind. Further, as the (d) antioxidant, it is more preferable that the antioxidant is at least one selected from the group consisting of BHT and Smilizer GP (trade name) because it is effective when added in a small amount.

[(E) Other additives]
In addition to the above-mentioned (a) polyisocyanate composition, the above-mentioned (b) isocyanurate-forming catalyst, (c) diphenylamine, and (d) antioxidant, the polyisocyanate cured product of the present embodiment can be used according to the purpose and application. Further, other additives may be contained as long as the effects of the present invention are not impaired. Examples of other additives include a curing accelerator as a co-catalyst, a silane coupling agent for improving adhesion, a coating film surface hydrophilic agent, a leveling agent, a plasticizer, a surfactant, a coloring pigment, a dye and the like. Various additives of.
These additives may be added at the stage of producing the cured polyisocyanate product, or may be added in advance to the (a) polyisocyanate composition. In addition, these additives may be used alone or in combination of two or more.

Specific examples of the curing accelerator as a co-catalyst include, but are not limited to, dialkyltin dicarboxylate, tin oxide compounds, metal carboxylates, tertiary amines and the like.

Examples of the dialkyl tin dicarboxylate include dibutyl tin dilaurate, dioctyl tin dilaurate, and dibutyl tin diacetate.

Examples of the tin oxide compound include dibutyl tin oxide and the like.

Examples of the metal carboxylate include tin 2-ethylhexanoate, zinc 2-ethylhexanoate, and cobalt salts.

Examples of tertiary amines include triethylamine, pyridine, methylpyridine, benzyldimethylamine, N, N-dimethylcyclohexylamine, N-methylpiperidine, pentamethyldiethylenetriamine, N, N'-endethylenepiperazine, N, N'. -Includes dimethylpiperazine and the like.

The silane coupling agent for improving adhesion is not particularly limited, but for example, 3aminopropyltriethoxysilane, 3aminopropyltrimethoxysilane, N2 (aminoethyl) 3aminopropyltrimethoxysilane, and ureido. Propyltriethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, 3methacryloxypropyltrimethoxysilane, 3methacryloxypropyltriethoxysilane, 2 (3,4 epoxycyclohexyl) ethyltrimethoxysilane, 3glycidoxypropyltri Examples thereof include methoxysilane, 3 mercaptopropyltrimethoxysilane, 3 isocyanatepropyltriethoxysilane, methyltriethoxysilane, and methyltrimethoxysilane.

Specific examples of the coating film surface hydrophilizing agent include, but are not limited to, silicate compounds and the like.

Specific examples of the leveling agent include, but are not limited to, silicone oil and the like.

Specific examples of the plasticizer include, but are not limited to, phthalates, phosphoric acid compounds, polyester compounds and the like.

Specific examples of the surfactant include, but are not limited to, known anionic surfactants, cationic surfactants, amphoteric surfactants and the like.

The coloring pigment and the dye are not particularly limited, and may be an inorganic pigment or an organic pigment. Examples of the inorganic pigment include carbon black and titanium oxide having good weather resistance. Examples of the organic pigment include phthalocyanine blue, phthalocyanine green, quinacridone red, indanthrone orange, isoindolinone yellow and the like.

≪Use of cured polyisocyanate product≫
The cured polyisocyanate of the present embodiment has good heat resistance, low yellowness, and surface properties. Therefore, the cured polyisocyanate of the present embodiment can be used as a raw material for coating films, encapsulants, foams, and plastic materials. Above all, the cured polyisocyanate of the present embodiment is particularly suitable for coating films and encapsulants.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded. In addition, Example 1 is a reference example.

Each measurement method in this example is as follows.

<Physical characteristics 1: NCO group content (NCO%)>
The isocyanate group (NCO group) content (NCO%) in the polyisocyanate is the reaction solution obtained after reacting the isocyanate group in the polyisocyanate with an excess of 2N amine (di-n-butylamine toluene solution). It was determined by back-titling with 1N hydrochloric acid.

<Physical characteristics 2: Viscosity>
The viscosity was measured at 25 ° C. using an E-type viscometer (Tokimec Co., Ltd.).

In the measurement, a standard rotor (1 ° 34'× R24) was used, and the rotation speed of the standard rotor was as follows.
100 rpm (when the viscosity is less than 128 mPa · s)
50 rpm (when the viscosity is 128 mPa · s or more and less than 256 mPa · s)
20 rpm (when the viscosity is 256 mPa · s or more and less than 640 mPa · s)
10 rpm (when the viscosity is 640 mPa · s or more and less than 1280 mPa · s)
5 rpm (when the viscosity is 1280 mPa · s or more and less than 256 mPa · s)

<Physical characteristics 3: Number average number of functional groups>
The number average number of functional groups of isocyanate groups (NCO groups) in polyisocyanate was determined by the following formula (A).

Number average number of functional groups = {(NCO group content) x (number average molecular weight from GPC)} / 42 ... (A)

<Physical characteristics 4: Molar ratio of allophanate group / isocyanurate group in polyisocyanate composition>
The molar ratio of allophanate group / isocyanurate group in the polyisocyanate composition was determined as follows. First, polyisocyanate was dissolved in deuterated chloroform at a concentration of 10% by mass (0.03% by mass of tetramethylsilane was added to polyisocyanate). ^{Next, 1} H-NMR (BioSpin Avance 500, manufactured by Bruker Biospin Co., Ltd.) was measured for the obtained solution. The chemical shift criterion was 0 ppm for the hydrogen signal of tetramethylsilane. ^{1 From} the spectrum obtained by H-NMR measurement, a signal of a hydrogen atom bonded to nitrogen of an allophanate group near 8.5 ppm (1 mol hydrogen atom for 1 mol of allophanate group) and an isocyanurate near 3.85 ppm. The area of the hydrogen atom of the methylene group adjacent to the group (6 mol of hydrogen atom for 1 mol of isocyanurate group) was measured.

Based on the measured value, the molar ratio of allophanate group / isocyanurate group was determined by the following formula (B).

Molar ratio of allophanate group / isocyanurate group = (signal area around 8.5 ppm) / {(signal area around 3.85 ppm) / 6} ... (B)

<Physical characteristics 5: Molar ratio of (urethane group + urea group) / isocyanurate group in the cured polyisocyanate>
The IR spectrum of the cured polyisocyanate was measured by the ATR method of FT-IR (FT / IR-4200 manufactured by Nippon Spectroscopy Co., Ltd.). Obtain the molar ratio of (urethane group + urea group) / isocyanurate group from the peak of the carbonyl group of the isocyanurate group ( ^{around 1690 cm -1} ) and the NH peak of the urethane group and the urea group ( ^{around 3400 cm -1).} rice field.

<Physical characteristics 6: Molar ratio of allophanate group / isocyanurate group in cured polyisocyanate>
The molar ratio of allophanate group / isocyanurate group in the cured polyisocyanate was determined as follows. First, the cured polyisocyanate was freeze ^{-grinded, and 13} C-NMR DD / MAS (Dipolar Decoupling / Magic Angle Spinning) (BioSpin Avance 500, manufactured by Bruker Biospin Co., Ltd.) was measured for the obtained pulverized product. From the spectrum obtained by the measurement, the carbonyl group signal area of the isocyanate group (around 149 ppm) and the carbonyl group signal area of the allophanate group (152 to 160 ppm region) were determined. Based on the results, the molar ratio of allophanate group / isocyanurate group was determined by the following formula (C).

Molar ratio of allophanate group / isocyanurate group = (signal area in the region of 152 ppm or more and 160 ppm or less / 2) / {(signal area near 149 ppm) / 3} ... (C)

<Evaluation 1: Heat resistance>
The heat resistance test was conducted as follows. First, the obtained 1 mm-thick cured polyisocyanate was cut into sections of about 1 mm. Next, using TG-DTA (TG / DTA6200 manufactured by Seiko Instruments Inc.), the sections were tested under the conditions of a nitrogen flow rate of 100 mL / min and a heating rate of 10 ° C./min. In addition, Td1 indicates the 1% weight loss temperature of the measurement sample. When Td1 was 300 ° C. or higher, it was evaluated as ◯, and when it was lower than 300 ° C., it was evaluated as ×.

<Evaluation 2: Yellowness>
The degree of yellowness was evaluated as follows. First, the obtained 1 mm-thick cured polyisocyanate was cut into sections of about 1 mm. Next, the transmittance of the section was measured at 380 nm or more and 780 nm or less with a spectrophotometer (V-650 manufactured by JASCO Corporation). From the measurement results of the spectrophotometer, X, Y and Z were obtained from JIS Z8701. From the obtained X, Y and Z, YI (yellowness; Yellow Index) was calculated from JIS K7373 and JIS Z8720. The obtained YI was evaluated as ◯ if it was less than 10, Δ if it was 10 or more and less than 20, and × if it was 20 or more.

<Evaluation 3: Surface (cured product)>
The surface property (cured product) was evaluated as follows. First, the transmittance of a 1 mm thick polyisocyanate cured product sample at 450 nm was measured with a spectrophotometer (V-650 manufactured by JASCO Corporation). When the obtained transmittance was 80% or more, it was evaluated as ◯, when it was 60% or more and less than 80%, it was evaluated as Δ, and when it was less than 60%, it was evaluated as ×.

<Evaluation 4: Surface (reflector)>
The surface properties (reflectors) were evaluated as follows. First, the raw material of the cured polyisocyanate was potted on a reflector for LED (505010-8R manufactured by TTOP) and cured at 150 ° C. for 5 hours. As a result, a reflector sample for LED sealed with a cured polyisocyanate was prepared. The surface was visually observed and evaluated as ◯ if it was smooth, Δ if it was uneven, and × if it was uneven and cloudy.

[Synthesis Example 1] Synthesis of polyisocyanate composition N-1 The inside of a four-necked flask (reactor) equipped with a stirrer, a thermometer and a cooling tube was replaced with nitrogen, and 500 g of HDI was charged into the reactor. .. Then, under stirring, when the temperature inside the reactor reached 70 ° C., 0.05 g of N, N, N-trimethyl-N-benzylammonium hydroxide was added to the reactor as an isocyanurate-forming catalyst. Then, when the change in the refractive index of the reaction solution became 0.011, 0.04 g of an 85% phosphoric acid aqueous solution was added to stop the reaction. Then, the reaction solution was kept at 90 ° C. for 1 hour to completely inactivate the catalyst. Then, the reaction solution was filtered. Then, the unreacted HDI was removed from the filtrate using a flow-down thin film distillation apparatus to obtain a polyisocyanate composition N-1.

The obtained polyisocyanate composition N-1 was a transparent liquid having a yield of 130 g, a viscosity of 1600 mPa · s, an NCO group content of 23.4% by mass, and a number average number of functional groups of 3.4. The yield was 26%. When the obtained polyisocyanate composition N-1 was measured by NMR, the allophanate group / isocyanurate group was 0/100.

[Synthesis Example 2] Synthesis of Polyisocyanate Composition N-2 Using the same reactor as in Synthesis Example 1, 500 g of HDI was charged, and the temperature inside the reactor was set to 90 ° C. under stirring. Next, 0.05 g of tetramethylammonium capriate was added to the reactor as an isocyanurate-forming catalyst to carry out an isocyanurate-forming reaction. Then, when the change in the refractive index of the reaction solution became 0.026, 0.04 g of an 85% phosphoric acid aqueous solution was added to stop the reaction. Then, the reaction solution was held at 100 ° C. for 1 hour to completely inactivate the catalyst. Then, the reaction solution was filtered. Then, the unreacted HDI was removed using a flow-down thin film distillation apparatus to obtain a polyisocyanate composition N-2.

The obtained polyisocyanate composition N-2 was a transparent liquid having a yield of 260 g, a viscosity of 3000 mPa · s, an NCO group content of 21.0% by mass, and a number average number of functional groups of 3.3. When the obtained polyisocyanate composition N-2 was measured by NMR, the allophanate group / isocyanurate group was 0/100.

[Synthesis Example 3] Synthesis of Polyisocyanate Composition N-3 Using the same reactor as in Synthesis Example 1, 500 g of HDI and 0.2 g of 2-ethyl-1-hexanol were charged, and the temperature inside the reactor was stirred under stirring. Was held at 80 ° C. for 10 minutes. Next, 0.03 g of tetramethylammonium capriate was added to the reactor to carry out urethanization, allophanate formation and isocyanurate formation reactions. Then, when the change in the refractive index of the reaction solution became 0.012, 0.02 g of an 85% phosphoric acid aqueous solution was added to stop the reaction. Then, the reaction solution was held at 80 ° C. for 1 hour to completely inactivate the catalyst. Then, the reaction solution was filtered. Then, the unreacted HDI was removed from the filtrate using a flow-down thin film distillation apparatus to obtain a polyisocyanate composition N-3.

The obtained polyisocyanate composition N-3 was a transparent liquid having a yield of 120 g, a viscosity of 1100 mPa · s, an NCO group content of 22.2% by mass, and a number average number of functional groups of 3.2. When the obtained polyisocyanate composition N-3 was measured by NMR, the allophanate group / isocyanurate group was 5/95.

[Synthesis Example 4] Synthesis of Polyisocyanate Composition N-4 Using the same reactor as in Synthesis Example 1, 500 g of HDI and 5 g of 2-ethyl-1-hexanol were charged, and the temperature inside the reactor was set to 80 under stirring. It was held at ° C. for 10 minutes. Next, 0.01 g of tetramethylammonium capriate was added to the reactor to carry out urethanization, allophanate formation and isocyanurate formation reactions. Then, when the change in the refractive index of the reaction solution became 0.010, 0.01 g of an 85% phosphoric acid aqueous solution was added to stop the reaction. Then, the reaction solution was held at 80 ° C. for 1 hour to completely inactivate the catalyst. Then, the reaction solution was filtered. Then, the unreacted HDI was removed from the filtrate using a flow-down thin film distillation apparatus to obtain a polyisocyanate composition N-4.

The obtained polyisocyanate composition N-4 was a transparent liquid having a yield of 135 g, a viscosity of 900 mPa · s, an NCO group content of 22.4% by mass, and a number average number of functional groups of 3.2. When the obtained polyisocyanate composition N-4 was measured by NMR, the allophanate group / isocyanurate group was 10/90.

[Example 1]
(A) 10 g of N-1 as a polyisocyanate composition, (d) 3000 ppm of BHT as an antioxidant, 2000 ppm of a simulator GP (trade name) (manufactured by Sumitomo Chemical Co., Ltd.), and (b) N as an isocyanurate-forming catalyst. , N, N-trimethyl-N-benzylammonium hydroxide was blended at 2000 ppm. The blending amounts of (d) the antioxidant and (b) the isocyanurate-forming catalyst are the mass ratios of (a) the polyisocyanate composition to the solid content, respectively. Then, using a vacuum stirring and defoaming mixer (EME Co., Ltd., V-mini300), the mixture was left in a vacuum state for 1 minute, and then stirred at 1500 rpm for 3 minutes while maintaining the vacuum to obtain a reaction solution. .. The obtained reaction solution was poured into a petri dish and left at 150 ° C. for 1 hour to obtain a 1 mm thick polyisocyanate cured product K-1. In K-1, the molar ratio of allophanate group / isocyanurate group + allophanate group was 0/100, and the molar ratio of (urethane group + urea group) / isocyanurate group was 0/100. Table 1 shows various measurement results for K-1.

[Examples 2 to 5 and Comparative Examples 1 to 2]
Polyisocyanate cured products K-2 to K-5 and L-1 to L-2 were obtained by the same method as in Example 1 except that the raw materials and reaction conditions were as shown in Table 1. The blending amounts of (d) antioxidant, (c) diphenylamine and (b) isocyanurate-forming catalyst are each based on the mass ratio of (a) the solid content of the polyisocyanate composition. Table 1 shows various measurement results for the obtained cured polyisocyanate products K-2 to K-5 and L-1 to L-2.

In Table 1, "2EHOH" means 2-ethylhexanol. "IPA" means 2-propanol. Further, "antioxidant A" means dibutylhydroxytoluene (BHT). "Antioxidant B" means a simulator GP (trade name) (manufactured by Sumitomo Chemical Co., Ltd.). "Antioxidant C" means Tinuvin765 (trade name) (manufactured by BASF Japan Ltd.). "Catalyst A" means N, N, N-trimethyl-N-benzylammonium hydroxide. "Catalyst B" means tetramethylammonium capriate. "Catalyst C" means sodium methoxide. "Catalyst D" means N, N'-dimethylaminopropyl hexahydrotriazine.

Examples 1 to 5, which are polyisocyanate cured products containing an isocyanurate group and substantially free of allophanate group, urethane group and urea group, are the allophanate group or the polyisocyanate cured product containing a urethane group and a urea group. Unlike Comparative Examples 1 and 2, both heat resistance and yellowness were excellent while maintaining surface properties. Further, it was very surprising that the surface properties were improved in Examples 2 to 5 which are the cured polyisocyanate products containing diphenylamine.

From the above, it was confirmed that the cured polyisocyanate of the present embodiment has good heat resistance, low yellowness and surface properties.

The cured polyisocyanate of the present embodiment has good heat resistance, low yellowness, and surface properties. Therefore, the cured polyisocyanate of the present embodiment can be suitably used as a raw material for coating films, adhesives, casting materials, encapsulants, foams and plastic materials.

Claims (4)

It has an isocyanurate group consisting of at least one diisocyanate selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates as a unit structure.
A cured polyisocyanate product containing diphenylamine and substantially free of urethane group, urea group and allophanate group. The polyisocyanate curing according to claim 1, further comprising at least one selected from the group consisting of a hindered phenolic antioxidant, a hindered amine-based antioxidant, a sulfur-containing antioxidant and a phosphorus-containing antioxidant. thing. A coating film containing the cured polyisocyanate according to claim 1 or 2. A sealing material containing the cured polyisocyanate according to claim 1 or 2.