Blocked polyisocyanate composition, resin composition, resin film and laminate

Abstract

To provide a blocked polyisocyanate composition that shows excellent curability when baked at 100°C and also has excellent hardness, chemical resistance and breaking elongation as a resin film.SOLUTION: A blocked polyisocyanate composition comprises a blocked polyisocyanate derived from a polyisocyanate, a blocker comprising malonate, and a melamine compound, the blocked polyisocyanate comprising a constitutional unit represented by the general formula (X).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a blocked polyisocyanate composition, a resin composition, a resin film, and a laminate. [Background technology]

[0002] Conventionally, polyurethane resin paints have very good abrasion resistance, chemical resistance, and stain resistance. In particular, polyurethane resin paints using polyisocyanates obtained from aliphatic diisocyanates or alicyclic diisocyanates have even better weather resistance, and the demand for them is increasing. However, polyurethane resin paints are generally two-liquid, which makes their use extremely inconvenient. That is, ordinary polyurethane resin paints are composed of two components, polyol and polyisocyanate, and it is necessary to store the polyol and polyisocyanate separately and mix them when painting. In addition, once the two are mixed, the paint gels in a short time and becomes unusable. Because polyurethane resin paints have such problems, it is extremely difficult to use them for automatic painting in fields where line painting is performed, such as automobile painting or weak electric painting. In addition, isocyanates easily react with water, so they cannot be used with water-based paints such as electrodeposition paints. Furthermore, when paints containing isocyanates are used, it is necessary to thoroughly clean the painter and paint tank at the end of work, which significantly reduces work efficiency.

[0003] In order to improve the above-mentioned problems, it has been proposed to use a blocked polyisocyanate in which all active isocyanate groups are blocked with a blocking agent. This blocked polyisocyanate does not react with polyol at room temperature. However, by heating, the blocking agent dissociates, and the active isocyanate groups are regenerated and react with polyol to cause a crosslinking reaction, thereby improving the above-mentioned problems. Therefore, many blocking agents have been studied, and representative examples include phenol, methyl ethyl ketoxime, etc.

[0004] However, when using blocked polyisocyanates using these blocking agents, a high baking temperature of 140° C. or more is generally required. The need for baking at a high temperature is not only disadvantageous in terms of energy, but also requires the substrate to have heat resistance, which is a factor limiting its applications.

[0005] On the other hand, research has been conducted on blocked polyisocyanates using active methylene compounds such as acetoacetate esters and malonic acid diesters as low-temperature bake-type blocked polyisocyanates (see, for example, Patent Document 1, etc.). Among them, technology for curing at even lower temperatures is being continuously studied. For example, Patent Document 2 and Patent Document 3 propose blocked polyisocyanate compositions that cure at low temperatures. Generally, it is known that in order to develop coating hardness, a melamine-based compound is used as a curing agent (see, for example, Patent Document 4, etc.). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3547197 [Patent Document 2] International Publication No. 2019 / 065890 [Patent Document 3] Patent No. 5855091 [Patent Document 4] Japanese Patent Application Publication No. 11-228904 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in general, coating films using blocked polyisocyanates using active methylene compounds tend to have low coating hardness, which is a problem. Furthermore, in the case of melamine-based compounds, curing does not proceed at temperatures below 100°C, and coating film properties such as chemical resistance may be insufficient.

[0008] The present invention has been made in view of the above circumstances, and provides a blocked polyisocyanate composition that has excellent curing properties when baked at 100°C and that, when formed into a resin film, has excellent hardness, chemical resistance and breaking elongation, as well as a resin composition, a resin film and a laminate that use the blocked polyisocyanate composition. [Means for solving the problem]

[0009] That is, the present invention includes the following aspects. (1) A blocked polyisocyanate composition comprising a blocked polyisocyanate derived from a polyisocyanate, a blocking agent containing a malonic acid ester, and a melamine compound, the blocked polyisocyanate containing a structural unit represented by the following general formula (X):

[0010] [ka]

[0011] (In general formula (X), R 11 , R 12 , R 13 , R 14 , R 15 and R 16 R is each independently a hydrogen atom or an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxyl group and an amino group. 17 R is a group represented by the following general formula (Xa). 18 is a hydrogen atom, an alkoxymethyl group, or a hydroxymethyl group. The wavy line represents a bond.

[0012] [ka]

[0013] (In general formula (Xa), R 11a , R 12a , R 13a and R 14aare each independently a hydrogen atom, an alkoxymethyl group, or a hydroxymethyl group. The wavy lines represent bonds.

[0014] (2) In the general formula (X), 11 , R 12 and the above R 13 At least two of the above are alkyl groups which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group, and R 14 , R 15 and the above R 16 At least two of the above are alkyl groups which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group. (3) In the general formula (X), 11 , R 12 and the above R 13 each independently represents an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group, and R 11 , R 12 and the above R 13 The blocked polyisocyanate composition according to (1) or (2), wherein the total number of carbon atoms is 3 or more and 20 or less. (4) The blocked polyisocyanate composition according to any one of (1) to (3), wherein the polyisocyanate is a polyisocyanate derived from one or more diisocyanates selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates. (5) The blocked polyisocyanate composition according to any one of (1) to (4), wherein at least a portion of the isocyanate groups of the polyisocyanate is modified with a hydrophilic compound. (6) The blocked polyisocyanate composition according to any one of (1) to (5), wherein the polyisocyanate has an average number of isocyanate groups of 3.5 or more. (7) A resin composition comprising the blocked polyisocyanate composition according to any one of (1) to (6) above and a polyvalent hydroxy compound. (8) A resin film obtained by curing the resin composition according to (7). (9) A laminate comprising one or more layers of the resin film according to (8) laminated on a substrate, The thickness of each of the resin films is from 1 μm to 50 μm. Effect of the Invention

[0015] According to the blocked polyisocyanate composition of the above aspect, it is possible to provide a blocked polyisocyanate composition that exhibits excellent curing properties when baked at 100°C, and exhibits excellent hardness, chemical resistance, and breaking elongation when formed into a resin film. The resin composition of the above aspect contains the blocked polyisocyanate composition, exhibits excellent curing properties when baked at 100°C, and exhibits excellent hardness, chemical resistance, and breaking elongation when formed into a resin film. The resin film of the above aspect is formed by curing the resin composition, and exhibits excellent hardness, chemical resistance, and breaking elongation. The laminate of the above aspect includes the resin film, and exhibits excellent hardness, chemical resistance, and breaking elongation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment for carrying out the present invention (hereinafter, referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following embodiment. The present invention can be carried out with appropriate modifications within the scope of the gist of the present invention.

[0017] In this specification, the term "polyol" refers to a compound having two or more hydroxyl groups (-OH). As used herein, the term "polyisocyanate" refers to a reaction product in which multiple monomeric compounds having one or more isocyanate groups (-NCO) are bonded together. In this specification, the term "structural unit" refers to a structure resulting from one molecule of a monomer in a structure constituting a polyisocyanate or a blocked polyisocyanate. For example, a structural unit derived from a malonic acid ester refers to a structure resulting from one molecule of a malonic acid ester in a blocked polyisocyanate. The structural unit may be a unit formed directly by a (co)polymerization reaction of a monomer, or may be a unit in which a part of the unit is converted into a different structure by treating the (co)polymer.

[0018] <Blocked polyisocyanate composition> The blocked polyisocyanate composition of the present embodiment contains a blocked polyisocyanate derived from a polyisocyanate, a blocking agent containing a malonic acid ester, and a melamine compound, and contains a structural unit represented by the following general formula (X) (hereinafter, may be referred to as "structural unit (X)").

[0019] [ka]

[0020] (In general formula (X), R 11 , R 12 , R 13 , R 14 , R 15 and R 16 R is each independently a hydrogen atom or an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxyl group and an amino group. 17 R is a group represented by the following general formula (Xa) (hereinafter, sometimes referred to as "group (Xa)"). 18 is a hydrogen atom, an alkoxymethyl group, or a hydroxymethyl group. The wavy line represents a bond.

[0021] [ka]

[0022] (In general formula (Xa), R 11a, R 12a , R 13a and R 14a are each independently a hydrogen atom, an alkoxymethyl group, or a hydroxymethyl group. The wavy lines represent bonds.

[0023] The blocked polyisocyanate composition of the present embodiment has the above-described configuration, and therefore exhibits excellent curing properties when baked at 100° C., and when formed into a resin film, exhibits excellent hardness, chemical resistance, and breaking elongation.

[0024] Next, each of the constituent components of the blocked polyisocyanate composition of the present embodiment will be described in detail below.

[0025] <Blocked polyisocyanate> The blocked polyisocyanate is a reaction product of a polyisocyanate, a blocking agent containing a malonic acid ester, and a melamine compound. That is, the blocked polyisocyanate has a structure in which at least a part, and preferably all, of the isocyanate groups in the polyisocyanate are blocked with a blocking agent containing a malonic acid ester, and a melamine compound is bonded to a structural unit derived from the malonic acid ester in the blocked polyisocyanate.

[0026] As described later, examples of malonic acid esters include malonic acid esters having a primary alkyl group, malonic acid esters having a secondary alkyl group, and malonic acid esters having a tertiary alkyl group. These malonic acid esters may be used alone or in combination of two or more. For this reason, the blocked polyisocyanate has a structure in which at least a part, and preferably all, of the isocyanate groups in the polyisocyanate molecule are blocked with one or more malonic acid esters selected from the group consisting of malonic acid esters having a primary alkyl group, malonic acid esters having a secondary alkyl group, and tertiary alkyl groups, and in which a melamine compound is bonded to a structural unit derived from a malonic acid ester in the blocked polyisocyanate. The blocked polyisocyanate composition of the present embodiment may contain a single blocked polyisocyanate or may contain two or more blocked polyisocyanates in which at least a portion, and preferably all, of the isocyanate groups in the polyisocyanate molecule are blocked with one or more malonic acid esters selected from the group consisting of malonic acid esters having a primary alkyl group, malonic acid esters having a secondary alkyl group, and tertiary alkyl groups, and in which a melamine compound is bonded to a structural unit derived from a malonic acid ester in the blocked polyisocyanate.

[0027] Units The blocked polyisocyanate contains a structural unit (X) in the molecule. The structural unit (X) has a structure formed by blocking the isocyanate group of a polyisocyanate with a malonic acid ester, and has a structure in which a melamine compound is bonded to the structural unit derived from the malonic acid ester.

[0028] [ka]

[0029] (In general formula (X), R 11 , R 12 , R 13 , R 14 , R 15 and R 16 R is each independently a hydrogen atom or an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxyl group and an amino group. 17 R is a group represented by the following general formula (Xa). 18 is a hydrogen atom, an alkoxymethyl group, or a hydroxymethyl group. The wavy line represents a bond, and indicates the bonding site with the residue of the polyisocyanate excluding one isocyanate group.

[0030] [ka]

[0031] (In general formula (Xa), R 11a , R 12a , R 13a and R 14a are each independently a hydrogen atom, an alkoxymethyl group, or a hydroxymethyl group. The wavy line represents a bond, and represents the bonding site with the nitrogen atom in the above general formula (X).

[0032] (R 11 , R 12 , R 13 , R 14 , R 15 and R 16 ) R 11 , R 12 , R 13 , R 14 , R 15 and R 16 The alkyl group in the formula (I) preferably has 1 or more and 20 or less carbon atoms, more preferably has 1 or more and 8 or less carbon atoms, further preferably has 1 or more and 6 or less carbon atoms, and particularly preferably has 1 or more and 4 or less carbon atoms.

[0033] Specific examples of the alkyl group having no substituent include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, a sec-butyl group, an isobutyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, a 1-methylbutyl group, an n-hexyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 2,2-dimethylbutyl group, a 2,3-dimethylbutyl group, an n-heptyl group, a 2-methylhexyl group, a 3-methylhexyl group, a 2,2-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3,3-dimethylpentyl group, a 3-ethylpentyl group, a 2,2,3-trimethylbutyl group, an n-octyl group, an isooctyl group, a 2-ethylhexyl group, a nonyl group, and a decyl group.

[0034] R 11 , R 12 , R 13 , R 14 , R 15 and R 16When is an alkyl group having a substituent, the substituent is a hydroxy group or an amino group.

[0035] Examples of the alkyl group containing a hydroxy group as a substituent include a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group.

[0036] Examples of the alkyl group containing an amino group as a substituent include an aminomethyl group, an aminoethyl group, an aminopropyl group, and an aminobutyl group.

[0037] Examples of the alkyl group containing a hydroxy group and an amino group as a substituent include a hydroxyaminomethyl group, a hydroxyaminoethyl group, and a hydroxyaminopropyl group.

[0038] Among them, R is the most popular because it improves the hardening properties when used as a resin film. 11 , R 12 and R 13 At least two of R are alkyl groups which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group, and R 14 , R 15 and R 16 Among these, at least two are preferably alkyl groups which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group.

[0039] Also, R 11 , R 12 and R 13 are each independently an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group, and R 11 , R 12 and R 13 The total number of carbon atoms is preferably 3 or more and 20 or less.

[0040] R 11 , R 12 and R 13The total number of carbon atoms is preferably 3 or more and 20 or less, more preferably 4 or more and 20 or less, even more preferably 4 or more and 12 or less, particularly preferably 4 or more and 9 or less, and most preferably 4 or more and 6 or less. R 11 , R 12 and R 13 By making the total carbon number equal to or more than the lower limit, the hardness of the resin film formed can be exhibited, whereas by making the total carbon number equal to or less than the upper limit, the hardness at a low temperature of 100° C. or less can be exhibited. In addition, from the viewpoint of chemical resistance when applied as a coating, R 11 , R 12 and R 13 It is most preferable that the total number of carbon atoms is 4.

[0041] R 14 , R 15 and R 16 are each independently preferably a hydrogen atom or an unsubstituted alkyl group, more preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 4 carbon atoms, and further preferably a hydrogen atom, a methyl group, or an ethyl group. Also, R 14 , R 15 and R 16 Of R, it is preferable that at least one is a hydrogen atom, and it is more preferable that only one is a hydrogen atom. 14 , R 15 and R 16 When at least one of them is a hydrogen atom, the hardening property at a low temperature of 100° C. or less can be maintained, and the breaking elongation when formed into a resin film can be further improved.

[0042] (R 17 ) R 17 is the above group (Xa). In the group (Xa), R 11a , R 12a , R 13a and R 14a are each independently a hydrogen atom, an alkoxymethyl group, or a hydroxymethyl group. Among them, R 11a , R 12a , R 13a and R 14a Each of the radicals is preferably a hydrogen atom from the viewpoint of low temperature curing properties.

[0043] (R 18 ) R 18 is a hydrogen atom, an alkoxymethyl group, or a hydroxymethyl group. R 18 Examples of the alkoxymethyl group in the formula (I) include a methoxymethyl group, an ethoxymethyl group, a propoxymethyl group, a butoxymethyl group, etc. Among these, the butoxymethyl group is preferred because it is easily available. Among them, R 18 From the viewpoint of low temperature curing properties, a hydrogen atom or a hydroxymethyl group is preferred.

[0044] Unit of Construction It is preferable that the blocked polyisocyanate further contains, in addition to the above-mentioned structural unit (X), a structural unit represented by the following general formula (I) (hereinafter sometimes simply referred to as "structural unit (I)") in the molecule.

[0045] [ka]

[0046] (In general formula (I), R 11 , R 12 , R 13 , R 14 , R 15 and R 16 is R in the above general formula (X). 11 , R 12 , R 13 , R 14 , R 15 and R 16 is the same as

[0047] The molar ratio of the structural unit (X) to the total molar amount of the structural unit (X) and the structural unit (I) {structural unit (X) / (structural unit (X)+structural unit (I))} is preferably 0.01 or more and 0.99 or less, more preferably 0.03 or more and 0.95 or less, even more preferably 0.05 or more and 0.90 or less, even more preferably 0.10 or more and 0.70 or less, even more preferably 0.10 or more and 0.50 or less, and even more preferably 0.10 or more and 0.35 or less. By having the molar ratio be equal to or more than the lower limit, the hardness when made into a resin film can be made better, while by having the molar ratio be equal to or less than the upper limit, the curability when made into a resin film can be made better.

[0048] The above molar ratio can be determined, for example, by mixing the blocked polyisocyanate composition with 1 H-NMR and 13 By measuring the composition ratio of the structural unit (X) to the structural unit (I) by C-NMR, the ratio of the molar amount of the structural unit (X) to the total molar amount of the structural unit (X) and the structural unit (I) can be calculated.

[0049] [Constituent unit (II)] It is preferable that the blocked polyisocyanate further contains, in addition to the above-mentioned structural unit (X), a structural unit represented by the following general formula (II) (hereinafter, sometimes referred to as "structural unit (II)") in its molecule.

[0050] [ka]

[0051] (In general formula (II), R 21 , R 22 , R 23 and R 24 are the above R 11 , R 12 , R 13 , R 14 , R 15 and R 16The wavy lines represent bonds and represent the bonding sites with the residues of polyisocyanate excluding the isocyanate groups.)

[0052] (R 21 , R 22 , R 23 and R 24 ) R 21 , R 22 , R 23 and R 24 As the alkyl group, a hydrogen atom or an alkyl group having no substituent and having 1 to 4 carbon atoms is preferable because it has excellent hardness when made into a resin film, a hydrogen atom, a methyl group, or an ethyl group is more preferable, and a methyl group or an ethyl group is even more preferable because it has excellent curing properties at low temperatures of 100° C. or less.

[0053] R 21 , R 22 , R 23 and R 24 When all of R are methyl groups, the two ester moieties of the malonic acid ester of the structural unit (II) are both isopropyl groups. 21 and R 22 one of the groups is a hydrogen atom and the other is a methyl group, and R 23 and R 24 When one of these is a hydrogen atom and the other is a methyl group, the two ester sites of the malonic acid ester of the structural unit (II) both become ethyl groups.

[0054] Among them, R 21 , R 22 , R 23 and R 24 are all methyl groups, that is, the two ester moieties of the malonic acid ester of the structural unit (II) are both isopropyl groups.

[0055] The molar ratio of the structural unit (I) to the total molar amount of the structural unit (I) and the structural unit (II) {structural unit (I) / (structural unit (I)+structural unit (II))} is preferably 0.00 or more and 1.00 or less, more preferably 0.10 or more and 1.00 or less, even more preferably 0.20 or more and 1.00 or less, and particularly preferably 0.30 or more and 1.00 or less. By making the molar ratio equal to or more than the lower limit, the hardness of the resin film formed can be improved, and by making the molar ratio equal to or less than the upper limit, the curability at a low temperature of 100° C. or less can be improved. The molar ratio is, for example, 1 H-NMR and 13 By measuring the composition ratio of the structural unit (I) to the structural unit (II) by C-NMR, the ratio of the molar amount of the structural unit (I) to the total molar amount of the structural unit (I) and the structural unit (II) can be calculated.

[0056] [Polyisocyanate] Polyisocyanates are reaction products obtained by reacting multiple monomer compounds having one or more isocyanate groups (-NCO) (hereinafter, sometimes referred to as "isocyanate monomers").

[0057] The polyisocyanate may have one or more functional groups selected from the group consisting of an allophanate group, a uretdione group, an iminooxadiazinedione group, an isocyanurate group, a urethane group, and a biuret group. Among these, it is preferable to have an isocyanurate group because it has excellent weather resistance.

[0058] The isocyanate monomer is preferably one having a carbon number of 4 to 30. Specific examples of the isocyanate monomer include the following. These isocyanate monomers may be used alone or in combination of two or more. (1) Aromatic diisocyanates such as diphenylmethane-4,4'-diisocyanate (MDI), 1,5-naphthalene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate, and m-tetramethylxylylene diisocyanate (TMXDI). (2) Aliphatic diisocyanates such as 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (hereinafter sometimes referred to as "HDI"), 2,2,4-trimethyl-1,6-diisocyanatohexane, 2,4,4-trimethyl-1,6-hexamethylene diisocyanate, 2-methylpentane-1,5-diisocyanate (MPDI), and lysine diisocyanate (hereinafter sometimes referred to as "LDI"). (3) Alicyclic diisocyanates such as isophorone diisocyanate (hereinafter sometimes referred to as "IPDI"), 1,3-bis(diisocyanatemethyl)cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, diisocyanatenorbornane, and di(isocyanatemethyl)norbornane. (4) Triisocyanates such as 4-isocyanatomethyl-1,8-octamethylene diisocyanate (hereinafter sometimes referred to as "NTI"), 1,3,6-hexamethylene triisocyanate (hereinafter sometimes referred to as "HTI"), bis(2-isocyanatoethyl) 2-isocyanatoglutarate (hereinafter sometimes referred to as "GTI"), and lysine triisocyanate (hereinafter sometimes referred to as "LTI").

[0059] Among them, the isocyanate monomer is preferably one or more diisocyanates selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, because of their excellent weather resistance. In addition, the isocyanate monomer is more preferably HDI or IPDI, because of its industrial availability. In addition, the isocyanate monomer is even more preferably HDI, because of its low viscosity of the blocked polyisocyanate component.

[0060] As the isocyanate monomer used in the production of the polyisocyanate, either an aliphatic diisocyanate or an alicyclic diisocyanate may be used alone or in combination, but it is preferable to use an aliphatic diisocyanate and an alicyclic diisocyanate in combination, and it is particularly preferable to use HDI and IPDI. By using an aliphatic diisocyanate and an alicyclic diisocyanate, the toughness and hardness of the coating film can be further improved.

[0061] In the polyisocyanate, from the viewpoint of improving the coating hardness and strength, the mass ratio of the constituent units derived from an aliphatic diisocyanate to the constituent units derived from an alicyclic diisocyanate (constituent units derived from an aliphatic diisocyanate / constituent units derived from an alicyclic diisocyanate) is preferably from 50 / 50 to 95 / 5, more preferably from 55 / 45 to 93 / 7, even more preferably from 60 / 40 to 91 / 9, and even more preferably from 65 / 35 to 90 / 10. By setting the mass ratio of the constituent units derived from an aliphatic diisocyanate to the constituent units derived from an alicyclic diisocyanate to be equal to or greater than the above lower limit, it is possible to more effectively prevent a decrease in flexibility when the coating film is formed, whereas by setting the mass ratio to be equal to or less than the above upper limit, it is possible to more effectively improve the hardness when the coating film is formed.

[0062] The mass ratio of the constituent units derived from the aliphatic diisocyanate to the constituent units derived from the alicyclic diisocyanate can be calculated, for example, by the following method. First, the mass of the unreacted aliphatic diisocyanate and the mass of the unreacted alicyclic diisocyanate are calculated from the mass of the unreacted diisocyanate after the reaction and the aliphatic diisocyanate concentration and the alicyclic diisocyanate concentration in the unreacted diisocyanate obtained by gas chromatography measurement. Next, the mass of the unreacted aliphatic diisocyanate and the mass of the unreacted alicyclic diisocyanate calculated above are subtracted from the mass of the charged aliphatic diisocyanate and the mass of the alicyclic diisocyanate, respectively, and the obtained difference is the mass of the constituent units derived from the aliphatic diisocyanate and the mass of the constituent units derived from the alicyclic diisocyanate, respectively. Next, the mass of the constituent units derived from the aliphatic diisocyanate is divided by the mass of the constituent units derived from the alicyclic diisocyanate to obtain the mass ratio of the constituent units derived from the aliphatic diisocyanate to the constituent units derived from the alicyclic diisocyanate.

[0063] (Polyol) The polyisocyanate is preferably derived from the above-mentioned diisocyanate monomer and a polyol having an average hydroxyl functional group number of 3.0 to 8.0. This allows the average number of isocyanate groups in the resulting polyisocyanate to be larger. In the polyisocyanate, urethane groups are formed by the reaction between the hydroxyl groups of the polyol and the isocyanate groups of the diisocyanate monomer.

[0064] The average number of hydroxyl functional groups in the polyol is preferably 3.0 or more and 8.0 or less, more preferably 3 or more and 6 or less, even more preferably 3 or more and 5 or less, and particularly preferably 3 or 4. The average number of hydroxyl functional groups in the polyol referred to here is the number of hydroxyl groups present in one molecule of the polyol.

[0065] From the viewpoint of improving the coating hardness and strength, the number average molecular weight of the polyol is preferably 100 or more and 1,000 or less, preferably 100 or more and 900 or less, more preferably 100 or more and 600 or less, more preferably 100 or more and 570 or less, even more preferably 100 or more and 500 or less, even more preferably 100 or more and 400 or less, particularly preferably 100 or more and 350 or less, and most preferably 100 or more and 250 or less. When the number average molecular weight of the polyol is within the above range, the blocked polyisocyanate composition has excellent low-temperature curing properties when formed into a coating film, and is particularly excellent in hardness and strength. The number average molecular weight Mn of the polyol is, for example, the number average molecular weight based on polystyrene standard measured by GPC.

[0066] Examples of such polyols include trimethylolpropane, glycerol, and polycaprolactone polyols derived from trihydric or higher polyhydric alcohols and ε-caprolactone.

[0067] Commercially available polycaprolactone polyols include, for example, Daicel Corporation's "PLACCEL 303" (number average molecular weight 300), "PLACCEL 305" (number average molecular weight 550), "PLACCEL 308" (number average molecular weight 850), and "PLACCEL 309" (number average molecular weight 900).

[0068] (Production method of polyisocyanate) The method for producing polyisocyanate will be described in detail below. The polyisocyanate can be obtained by, for example, carrying out an allophanate reaction to form an allophanate group, a uretdione reaction to form a uretdione group, an iminooxadiazinedione reaction to form an iminooxadiazinedione group, an isocyanurate reaction to form an isocyanurate group, a urethanization reaction to form a urethane group, and a biuret reaction to form a biuret group all at once in the presence of an excess of isocyanate monomer, and removing the unreacted isocyanate monomer after the reaction is completed. That is, the polyisocyanate obtained by the above reaction is a reaction product in which a plurality of the above-mentioned isocyanate monomers are bonded together, and which has one or more groups selected from the group consisting of an allophanate group, a uretdione group, an iminooxadiazinedione group, an isocyanurate group, a urethane group, and a biuret group. Alternatively, the above reactions may be carried out separately and the resulting polyisocyanates may be mixed in a specific ratio. From the viewpoint of ease of production, it is preferable to carry out the above reaction at one time to obtain a polyisocyanate, and from the viewpoint of freely adjusting the molar ratio of each functional group, it is preferable to produce them separately and then mix them.

[0069] (1) Method for producing allophanate group-containing polyisocyanate The allophanate group-containing polyisocyanate can be obtained by adding an alcohol to an isocyanate monomer and using an allophanate 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, dialcohols, etc. These alcohols may be used alone or in combination of two or more. Examples of monoalcohols include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, and nonanol. Examples of the dialcohol include ethylene glycol, 1,3-butanediol, neopentyl glycol, and 2-ethylhexanediol. Among them, as the alcohol, a monoalcohol is preferable, and a monoalcohol having a molecular weight of 200 or less is more preferable.

[0070] Examples of the allophanate reaction catalyst include, but are not limited to, alkyl carboxylates of tin, lead, zinc, bismuth, zirconium, zirconyl, and the like. Examples of tin alkylcarboxylates (organotin compounds) include tin 2-ethylhexanoate and dibutyltin dilaurate. An example of the alkyl carboxylate of lead (organic lead compound) is lead 2-ethylhexanoate. Examples of zinc alkylcarboxylates (organic zinc compounds) include zinc 2-ethylhexanoate. An example of the alkyl carboxylate of bismuth is bismuth 2-ethylhexanoate. An example of the zirconium alkylcarboxylate is zirconium 2-ethylhexanoate. An example of the zirconyl alkylcarboxylate is zirconyl 2-ethylhexanoate, etc. These catalysts can be used alone or in combination of two or more. In addition, an isocyanurate reaction catalyst described later can also serve as an allophanate reaction catalyst. When an allophanate reaction is carried out using an isocyanurate reaction catalyst described later, an isocyanurate group-containing polyisocyanate (hereinafter, sometimes referred to as an "isocyanurate-type polyisocyanate") is naturally produced. Among these, it is preferable from the viewpoint of economical production to carry out the allophanate formation reaction and the isocyanurate formation reaction using an isocyanurate formation catalyst described below as the allophanate formation reaction catalyst.

[0071] The lower limit of the amount of the allophanate reaction catalyst used is preferably 10 ppm by mass, more preferably 20 ppm by mass, further preferably 40 ppm by mass, and particularly preferably 80 ppm by mass, relative to the mass of the charged isocyanate monomer. The upper limit of the amount of the allophanate reaction catalyst used is preferably 1000 ppm by mass, more preferably 800 ppm by mass, further preferably 600 ppm by mass, and particularly preferably 500 ppm by mass, relative to the mass of the charged isocyanate monomer. That is, the amount of the allophanate reaction catalyst used is preferably 10 ppm by mass or more and 1,000 ppm by mass or less, more preferably 20 ppm by mass or more and 800 ppm by mass or less, even more preferably 40 ppm by mass or more and 600 ppm by mass or less, and particularly preferably 80 ppm by mass or more and 500 ppm by mass or less, relative to the mass of the charged isocyanate monomer.

[0072] The lower limit of the allophanate reaction temperature is preferably 40°C, more preferably 60°C, further preferably 80°C, and particularly preferably 100°C. The upper limit of the allophanate reaction temperature is preferably 180°C, more preferably 160°C, and even more preferably 140°C. That is, the allophanate reaction temperature is preferably 40°C or higher and 180°C or lower, more preferably 60°C or higher and 160°C or lower, even more preferably 80°C or higher and 140°C or lower, and particularly preferably 100°C or higher and 140°C or lower. By setting the allophanate formation reaction temperature to the above lower limit or higher, it is possible to further increase the reaction rate. By setting the allophanate formation reaction temperature to the above upper limit or lower, it is possible to more effectively suppress coloration of the polyisocyanate.

[0073] (2) Method for producing uretdione group-containing polyisocyanate When a polyisocyanate having a uretdione group is derived from an isocyanate monomer, it can be produced, for example, by polymerizing the isocyanate monomer using a uretdione reaction catalyst or by heat. The uretdione reaction catalyst is not particularly limited, but examples thereof include tertiary phosphines such as trialkylphosphine, tris(dialkylamino)phosphine and cycloalkylphosphine, Lewis acids, and the like. Examples of the trialkylphosphine include tri-n-butylphosphine and tri-n-octylphosphine. Examples of tris(dialkylamino)phosphines include tris-(dimethylamino)phosphine and the like. Examples of cycloalkylphosphines include cyclohexyl-di-n-hexylphosphine. Examples of Lewis acids include boron trifluoride and zinc oxychloride.

[0074] Many of the uretdione reaction catalysts can also simultaneously promote the isocyanurate reaction. When a uretdione-forming reaction catalyst is used, it is preferable to add a deactivator for the uretdione-forming reaction catalyst such as phosphoric acid or methyl paratoluenesulfonate to terminate the uretdione-forming reaction when a desired yield is achieved. When one or more diisocyanates selected from the group consisting of the aliphatic diisocyanates and the alicyclic diisocyanates are heated to obtain a polyisocyanate having a uretdione group without using a uretdione reaction catalyst, the heating temperature is preferably 120° C. or higher, and more preferably 150° C. or higher and 170° C. or lower. The heating time is preferably 1 hour or longer and 4 hours or shorter.

[0075] (3) Method for producing iminooxadiazinedione group-containing polyisocyanate When an iminooxadiazinedione group-containing polyisocyanate is derived from an isocyanate monomer, an iminooxadiazinedione reaction catalyst is usually used. Examples of the iminooxadiazinedione catalyst include the following 1) or 2). 1) (Poly)hydrogen fluoride represented by the general formula M[Fn] or the general formula M[Fn(HF)m] (wherein m and n are integers satisfying the relationship m / n>0. M is an n-charged cation (mixture) or one or more radicals with a total valence of n.) 2) A compound comprising a compound represented by the general formula R1-CR'2-C(O)O- or R2=CR'-C(O)O- and a quaternary ammonium cation or a quaternary phosphonium cation. (In the formula, R1 and R2 are each independently a linear, branched, or cyclic, saturated or unsaturated perfluoroalkyl group having from 1 to 30 carbon atoms. Each of the multiple R's is independently a hydrogen atom, or an alkyl or aryl group having from 1 to 20 carbon atoms which may contain a heteroatom.)

[0076] Specific examples of the compound 1) ((poly)hydrogen fluoride) include tetramethylammonium fluoride hydrate, tetraethylammonium fluoride, and the like. Specific examples of the compound 2) include 3,3,3-trifluorocarboxylic acid, 4,4,4,3,3-pentafluorobutanoic acid, 5,5,5,4,4,3,3-heptafluoropentanoic acid, and 3,3-difluoroprop-2-enoic acid. Among them, as the iminooxadiazinedione reaction catalyst, 1) is preferred from the viewpoint of availability, and 2) is preferred from the viewpoint of safety.

[0077] The lower limit of the amount of the iminooxadiazinedione catalyst used is not particularly limited, but from the viewpoint of reactivity, it is preferably 5 ppm, more preferably 10 ppm, and even more preferably 20 ppm by mass relative to the raw material isocyanate monomer such as HDI. The upper limit of the amount of the iminooxadiazinedione catalyst used is preferably 5000 ppm, more preferably 2000 ppm, and even more preferably 500 ppm, in terms of mass ratio relative to the raw material isocyanate monomer such as HDI, from the viewpoints of suppressing coloration and discoloration of the product and controlling the reaction. That is, the amount of the iminooxadiazinedione catalyst used is preferably 5 ppm or more and 5000 ppm or less, more preferably 10 ppm or more and 2000 ppm or less, and even more preferably 20 ppm or more and 500 ppm or less, by mass ratio relative to the raw material isocyanate monomer such as HDI.

[0078] The lower limit of the reaction temperature for the iminooxadiazinedione formation is not particularly limited, but from the viewpoint of the reaction rate, it is preferably 40°C, more preferably 50°C, and even more preferably 60°C. The upper limit of the reaction temperature for the iminooxadiazinedione formation is preferably 150°C, more preferably 120°C, and even more preferably 110°C, from the viewpoint of suppressing coloration and discoloration of the product. That is, the reaction temperature for the iminooxadiazinedione formation is preferably 40°C or higher and 150°C or lower, more preferably 50°C or higher and 120°C or lower, and even more preferably 60°C or higher and 110°C or lower.

[0079] When the iminooxadiazine dionation reaction reaches a desired iminooxadiazine dione group content, the iminooxadiazine dionation reaction can be stopped. The iminooxadiazine dionation reaction can be stopped, for example, by adding an acidic compound to the reaction solution. Examples of the acidic compound include phosphoric acid, acidic phosphate ester, sulfuric acid, hydrochloric acid, and sulfonic acid compounds. This neutralizes the iminooxadiazine dionation reaction catalyst, or inactivates it by thermal decomposition or chemical decomposition. After the reaction is stopped, filtration is performed if necessary.

[0080] (4) Method for producing isocyanurate group-containing polyisocyanate Examples of catalysts for deriving a polyisocyanate containing an isocyanurate group from an isocyanate monomer include commonly used isocyanuration reaction catalysts.

[0081] The isocyanurate reaction catalyst is not particularly limited, but is preferably a catalyst having basicity in general. Specific examples of the isocyanurate reaction catalyst include the following. 1) Hydroxides of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium, and organic weak acid salts such as acetates, propionates, octylates, caprates, myristates, and benzoates of the above tetraalkylammonium. 2) Hydroxides of aryltrialkylammonium such as benzyltrimethylammonium and trimethylphenylammonium, and organic weak acid salts such as acetates, propionates, octylates, caprates, myristates, and benzoates of the above aryltrialkylammonium. 3) Hydroxyalkylammonium hydroxides, such as trimethylhydroxyethylammonium, trimethylhydroxypropylammonium, triethylhydroxyethylammonium, and triethylhydroxypropylammonium, and organic weak acid salts, such as acetates, propionates, octylates, caprates, myristates, and benzoates of the above hydroxyalkylammoniums. 4) Metal salts, such as tin, zinc, lead, etc., of alkyl carboxylic acids, such as acetic acid, propionic acid, caproic acid, octylic acid, capric acid, and myristic acid. 5) Metal alcoholates such as sodium and potassium. 6) Aminosilyl group-containing compounds such as hexamethylenedisilazane. 7) Mannich bases. 8) Mixtures of tertiary amines and epoxy compounds. 9) Phosphorus compounds such as tributylphosphine.

[0082] Among these, from the viewpoint of preventing the production of unnecessary by-products, the isocyanurate reaction catalyst is preferably a quaternary ammonium hydroxide or a weak organic acid salt of a quaternary ammonium, and more preferably a tetraalkylammonium hydroxide, a weak organic acid salt of a tetraalkylammonium, an aryltrialkylammonium hydroxide, or a weak organic acid salt of an aryltrialkylammonium.

[0083] The upper limit of the amount of the isocyanurate reaction catalyst used is preferably 1000 ppm by mass, more preferably 500 ppm by mass, and even more preferably 100 ppm by mass, based on the mass of the charged isocyanate monomer. On the other hand, the lower limit of the amount of the isocyanurate reaction catalyst used is not particularly limited, and may be, for example, 10 ppm by mass.

[0084] The isocyanurate reaction temperature is preferably from 50° C. to 120° C., and more preferably from 60° C. to 90° C. By keeping the isocyanurate reaction temperature at or below the upper limit, coloration of the polyisocyanate tends to be more effectively suppressed.

[0085] When a desired conversion rate (the ratio of the mass of polyisocyanate produced in the isocyanuration reaction to the mass of the charged isocyanate monomer) is reached, the isocyanuration reaction is stopped by adding an acidic compound (e.g., phosphoric acid, an acidic phosphoric acid ester, etc.). In order to obtain polyisocyanate, it is necessary to stop the reaction at an early stage. However, since the reaction rate of the isocyanurate reaction is very fast at the early stage, it is difficult to stop the reaction at an early stage, and therefore the reaction conditions, particularly the amount and method of adding the catalyst, must be carefully selected. For example, a method of adding the catalyst in portions at regular intervals is recommended as a suitable method.

[0086] Therefore, the conversion rate of the isocyanurate reaction to obtain a polyisocyanate is preferably 10% or more and 60% or less, more preferably 15% or more and 55% or less, and even more preferably 20% or more and 50% or less. By setting the conversion rate of the isocyanurate reaction to the upper limit or less, the viscosity of the blocked polyisocyanate component can be made lower. By setting the conversion rate of the isocyanurate reaction to the lower limit or more, the reaction terminating operation can be more easily carried out.

[0087] When deriving a polyisocyanate containing an isocyanurate group, a monohydric to hexahydric alcohol can be used in addition to the above isocyanate monomers. Examples of the alcohol having a valence of 1 to 6 that can be used include non-polymerizable alcohol and polymerizable alcohol. The term "non-polymerizable alcohol" used herein means an alcohol that does not have a polymerizable group. On the other hand, the term "polymerizable alcohol" means an alcohol obtained by polymerizing a monomer having a polymerizable group and a hydroxyl group. Examples of the non-polymerizable alcohol include polyhydric alcohols such as monoalcohols, diols, triols, and tetraols. Examples of monoalcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, n-pentanol, n-hexanol, n-octanol, n-nonanol, 2-ethylbutanol, 2,2-dimethylhexanol, 2-ethylhexanol, cyclohexanol, methylcyclohexanol, and ethylcyclohexanol. Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,2-propanediol, 1,5-pentanediol, 2-methyl-2,3-butanediol, and Examples of the hexanediol include hexanediol, 1,6-hexanediol, 1,2-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethyl-hexanediol, 1,2-octanediol, 1,2-decanediol, 2,2,4-trimethylpentanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2-diethyl-1,3-propanediol. Examples of triols include glycerin and trimethylolpropane. An example of the tetraols is pentaerythritol.

[0088] The polymerizable alcohol is not particularly limited, but examples thereof include polyester polyols, polyether polyols, acrylic polyols, polyolefin polyols, and the like.

[0089] The polyester polyols are not particularly limited, but examples thereof include products obtained by a condensation reaction between a dibasic acid alone or a mixture of dibasic acids and a polyhydric alcohol alone or a mixture of polyhydric alcohols. The dibasic acid is not particularly limited, but examples thereof include at least one dibasic acid selected from the group consisting of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, and terephthalic acid. The polyhydric alcohol is not particularly limited, but examples thereof include at least one polyhydric alcohol selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, and glycerin. Examples of polyester polyols include polycaprolactones obtained by ring-opening polymerization of ε-caprolactone using the above polyhydric alcohols.

[0090] The polyether polyols are not particularly limited, but examples thereof include polyether polyols obtained by adding an alkylene oxide or a mixture of an alkylene oxide to a polyhydric alcohol or a mixture of an alkylene oxide using an alkali metal hydroxide or a strong basic catalyst, polyether polyols obtained by reacting an alkylene oxide with a polyamine compound, and so-called polymer polyols obtained by polymerizing acrylamide or the like using the above-mentioned polyethers as a medium.

[0091] Examples of the alkali metal include lithium, sodium, and potassium.

[0092] Examples of the strong basic catalyst include alcoholates and alkylamines.

[0093] Examples of the polyhydric alcohol include those exemplified for the polyester polyols above.

[0094] Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide.

[0095] Examples of the polyamine compound include ethylenediamines.

[0096] The acrylic polyols are not particularly limited, but examples thereof include copolymers of a single or mixture of ethylenically unsaturated bond-containing monomers having a hydroxyl group and a single or mixture of other ethylenically unsaturated bond-containing monomers copolymerizable therewith.

[0097] The ethylenically unsaturated bond-containing monomer having a hydroxyl group is not particularly limited, but examples thereof include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate.

[0098] The other ethylenically unsaturated bond-containing monomer copolymerizable with the ethylenically unsaturated bond-containing monomer having a hydroxyl group is not particularly limited, and examples thereof include acrylic acid esters, methacrylic acid esters, unsaturated carboxylic acids, unsaturated amides, vinyl-based monomers, and vinyl-based monomers having a hydrolyzable silyl group.

[0099] Examples of acrylic esters include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, benzyl acrylate, and phenyl acrylate.

[0100] Examples of methacrylic acid esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, benzyl methacrylate, and phenyl methacrylate.

[0101] Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, and itaconic acid.

[0102] Examples of the unsaturated amide include acrylamide, methacrylamide, N,N-methylenebisacrylamide, diacetone acrylamide, diacetone methacrylamide, maleic acid amide, and maleimide.

[0103] Examples of the vinyl monomer include glycidyl methacrylate, styrene, vinyl toluene, vinyl acetate, acrylonitrile, and dibutyl fumarate.

[0104] Examples of vinyl monomers having a hydrolyzable silyl group include vinyltrimethoxysilane, vinylmethyldimethoxysilane, and γ-(meth)acryloxypropyltrimethoxysilane.

[0105] Examples of polyolefin polyols include hydroxyl-terminated polybutadiene and hydrogenated products thereof.

[0106] (5) Method for producing urethane group-containing polyisocyanate When a polyisocyanate containing a urethane group is derived from an isocyanate monomer, it can be produced, for example, by mixing an excess of the isocyanate monomer, the polyol, and, if necessary, an alcohol other than the polyol, and adding a urethane reaction catalyst as necessary.

[0107] Examples of the polyol include those exemplified in the above "polyol".

[0108] Examples of the alcohol other than the polyol include those exemplified in the above "Method for producing an isocyanurate group-containing polyisocyanate" except for those exemplified in the above "Polyol".

[0109] The urethanization reaction catalyst is not particularly limited, but examples thereof include tin-based compounds, zinc-based compounds, and amine-based compounds.

[0110] The urethanization reaction temperature is preferably 50°C or higher and 160°C or lower, and more preferably 60°C or higher and 120°C or lower.

[0111] By controlling the urethanization reaction temperature to be equal to or lower than the above upper limit, coloration of the polyisocyanate tends to be more effectively suppressed.

[0112] The urethane reaction time is preferably from 30 minutes to 4 hours, more preferably from 1 hour to 3 hours, and even more preferably from 1 hour to 2 hours.

[0113] The molar ratio of the isocyanate group of the isocyanate monomer to the molar amount of the hydroxyl group of the polyol (and, if necessary, the alcohol other than the polyol) is preferably 2 / 1 or more and 50 / 1 or less. When the molar ratio is equal to or more than the lower limit, the viscosity of the polyisocyanate can be made lower. When the molar ratio is equal to or less than the upper limit, the yield of the urethane group-containing polyisocyanate can be increased.

[0114] (6) Method for producing biuret group-containing polyisocyanate The biuretizing agent for deriving a polyisocyanate containing a biuret group from an isocyanate monomer is not particularly limited, and examples thereof include water, a monohydric tertiary alcohol, formic acid, an organic primary monoamine, and an organic primary diamine. The amount of isocyanate groups per mole of the biuretizing agent is preferably 6 moles or more, more preferably 10 moles or more, and even more preferably 10 moles or more and 80 moles or less. When the amount of molar isocyanate groups per mole of the biuretizing agent is equal to or more than the lower limit, the viscosity of the polyisocyanate becomes sufficiently low, and when it is equal to or less than the upper limit, the low-temperature curing property of the resin film is further improved.

[0115] A solvent may be used in the biuretization reaction. The solvent may be any solvent that dissolves the isocyanate monomer and the biuretization agent such as water and forms a homogeneous phase under the reaction conditions.

[0116] Specific examples of the solvent include ethylene glycol-based solvents and phosphoric acid-based solvents.

[0117] Examples of ethylene glycol solvents include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-propyl ether acetate, ethylene glycol monoisopropyl ether acetate, ethylene glycol mono-n-butyl ether acetate, ethylene glycol diacetate, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol di-n-propyl ether, ethylene glycol diisopropyl ether, ethylene glycol di-n-butyl ether, ethylene glycol methyl ethyl ether, ethylene glycol methyl isopropyl ether, ethylene glycol methyl-n-butyl ether, ethylene glycol ethyl-n-propyl ether, ethylene glycol ethyl isopropyl ether, ethylene glycol ethyl-n-butyl ether, ethylene glycol-n-propyl-n-butyl ether, ethylene glycol isopropyl-n-butyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol mono-n-propyl ether acetate, diethylene glycol monoisopropyl ether acetate, diethylene glycol mono-n-butyl ether acetate, diethylene glycol diacetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol di-n-propyl ether, diethylene glycol diisopropyl ether, diethylene glycol di-n-butyl ether, diethylene glycol methyl ethyl ether, diethylene glycol methyl isopropyl ether, diethylene glycol methyl-n-propyl ether, diethylene glycol methyl-n-butyl ether, diethylene glycol ethyl isopropyl ether, diethylene glycol ethyl-n-propyl ether, diethylene glycol ethyl-n-butyl ether, diethylene glycol-n-propyl-n-butyl ether, diethylene glycol isopropyl-n-butyl ether, and the like.

[0118] Examples of the phosphoric acid-based solvent include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and tributyl phosphate.

[0119] These solvents may be used alone or in combination of two or more. Among these, the ethylene glycol solvent is preferably ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol diacetate or diethylene glycol dimethyl ether.

[0120] As the phosphoric acid-based solvent, trimethyl phosphate or triethyl phosphate is preferred.

[0121] The biuretization reaction temperature is preferably from 70° C. to 200° C., and more preferably from 90° C. to 180° C. By keeping it below the upper limit, coloration of the polyisocyanate tends to be more effectively prevented.

[0122] The above-mentioned allophanate formation reaction, uretdione formation reaction, iminooxadiazinedione formation reaction, isocyanurate formation reaction, urethanization reaction, and biuret formation reaction may be carried out successively, or some of them may be carried out in parallel. After the reaction is completed, unreacted isocyanate monomer is removed from the reaction solution by thin-film distillation, extraction, or the like to obtain a polyisocyanate.

[0123] Furthermore, an antioxidant or an ultraviolet absorber may be added to the obtained polyisocyanate, for example, for the purpose of suppressing coloration during storage. Examples of the antioxidant include hindered phenols such as 2,6-di-tert-butyl-p-cresol. Examples of the ultraviolet absorber include benzotriazole and benzophenone. These antioxidants and ultraviolet absorbers may be used alone or in combination of two or more. The amount of these to be added is preferably 10 ppm by mass or more and 500 ppm by mass or less based on the mass of the polyisocyanate.

[0124] (Average number of isocyanate groups in polyisocyanate) The average number of isocyanate groups in the polyisocyanate is preferably 2 or more from the viewpoint of improving the curability at low temperatures of 100° C. or less, and from the viewpoint of both the curability at low temperatures of 100° C. or less and the compatibility with the polyhydric hydroxy compound, it is more preferably 3.0 to 20.0, even more preferably 3.2 to 10.0, particularly preferably 3.4 to 8.0, and most preferably 3.5 to 6.0. The average number of isocyanate functional groups of the polyisocyanate can be measured by the method described in the Examples below.

[0125] (hydrophilic compound) The polyisocyanate may be a hydrophilic compound-modified polyisocyanate in which at least a portion of the isocyanate groups of the polyisocyanate are modified with a hydrophilic compound.

[0126] Examples of the hydrophilic compound include nonionic hydrophilic compounds, anionic hydrophilic compounds, and cationic hydrophilic compounds. These hydrophilic compounds may be used alone or in combination of two or more.

[0127] Specific examples of nonionic hydrophilic compounds include monoalcohols and compounds in which ethylene oxide is added to the hydroxyl group of alcohol. Examples of monoalcohols include methanol, ethanol, butanol, etc. Examples of compounds in which ethylene oxide is added to the hydroxyl group of alcohol include ethylene glycol, diethylene glycol, polyethylene glycol, etc. These nonionic hydrophilic compounds also have active hydrogen groups that react with isocyanate groups.

[0128] Among these, as the nonionic hydrophilic compound, polyethylene glycol monoalkyl ether in which ethylene oxide is added to the hydroxyl group of a monoalcohol is preferred, since it can improve the water dispersibility of the blocked polyisocyanate composition with a small amount used.

[0129] The number of ethylene oxide additions in the ethylene oxide-added compound is preferably from 4 to 30, and more preferably from 4 to 25. When the number of ethylene oxide additions is equal to or more than the above lower limit, water dispersibility tends to be more effectively imparted to the blocked polyisocyanate composition, and when the number of ethylene oxide additions is equal to or less than the above upper limit, the blocked polyisocyanate composition tends to be less susceptible to precipitation during low-temperature storage.

[0130] As the cationic hydrophilic compound, specifically, a compound having both cationic hydrophilic group and active hydrogen group can be mentioned.In addition, a compound having active hydrogen group such as glycidyl group and a compound having cationic hydrophilic group such as sulfide, phosphine can be combined to form a hydrophilic compound.In this case, a compound having isocyanate group and a compound having active hydrogen group are reacted in advance, functional group such as glycidyl group is added, and then a compound such as sulfide, phosphine is reacted.From the viewpoint of ease of production, a compound having both cationic hydrophilic group and active hydrogen group is preferred.

[0131] Specific examples of compounds having both a cationic hydrophilic group and an active hydrogen group include dimethylethanolamine, diethylethanolamine, diethanolamine, methyldiethanolamine, etc. Furthermore, the tertiary amino groups added using these compounds can also be quaternized with, for example, dimethyl sulfate or diethyl sulfate.

[0132] The reaction between the cationic hydrophilic compound and the alicyclic polyisocyanate can be carried out in the presence of a solvent. In this case, the solvent is preferably one that does not contain an active hydrogen group, and specific examples thereof include ethyl acetate, propylene glycol monomethyl ether acetate, and dipropylene glycol dimethyl ether.

[0133] The cationic hydrophilic groups added to the blocked polyisocyanate are preferably neutralized with a compound having an anionic group, such as a carboxy group, a sulfonic acid group, a phosphoric acid group, a halogen group, or a sulfate group.

[0134] Specific examples of compounds having a carboxy group include formic acid, acetic acid, propionic acid, butyric acid, and lactic acid.

[0135] A specific example of the compound having a sulfonic acid group is ethanesulfonic acid.

[0136] Specific examples of compounds having a phosphoric acid group include phosphoric acid and acidic phosphate esters.

[0137] A specific example of the compound having a halogen group is hydrochloric acid.

[0138] Specific examples of compounds having a sulfate group include sulfuric acid.

[0139] Among them, as the compound having an anionic group, a compound having a carboxy group is preferable, and acetic acid, propionic acid or butyric acid is more preferable.

[0140] Specific examples of the anionic hydrophilic group include a carboxy group, a sulfonic acid group, a phosphoric acid group, a halogen group, and a sulfate group.

[0141] Specific examples of the anionic hydrophilic compound include compounds having both an anionic group and an active hydrogen group, and more specific examples include compounds having a carboxy group of a monohydroxycarboxylic acid or polyhydroxycarboxylic acid as the anionic group.

[0142] Examples of monohydroxycarboxylic acids include 1-hydroxyacetic acid, 3-hydroxypropanoic acid, 12-hydroxy-9-octadecanoic acid, hydroxypivalic acid, and lactic acid.

[0143] Examples of compounds having a carboxy group of a polyhydroxycarboxylic acid as an anionic group include dimethylol acetic acid, 2,2-dimethylol butyric acid, 2,2-dimethylol pentanoic acid, dihydroxysuccinic acid, and dimethylol propionic acid.

[0144] Further, compounds having both a sulfonic acid group and an active hydrogen group are also included, and more specifically, for example, isethionic acid is included.

[0145] Among these, hydroxypivalic acid or dimethylolpropionic acid is preferred as a compound having both an anionic group and an active hydrogen group.

[0146] The anionic hydrophilic group added to the blocked polyisocyanate is preferably neutralized with an amine compound, which is a basic substance.

[0147] Specific examples of the amine compound include ammonia and water-soluble amino compounds.

[0148] Specific examples of water-soluble amino compounds include monoethanolamine, ethylamine, dimethylamine, diethylamine, triethylamine, propylamine, dipropylamine, isopropylamine, diisopropylamine, triethanolamine, butylamine, dibutylamine, 2-ethylhexylamine, ethylenediamine, propylenediamine, methylethanolamine, dimethylethanolamine, diethylethanolamine, and morpholine. In addition, tertiary amines such as triethylamine and dimethylethanolamine can also be used. These amine compounds may be used alone or in combination of two or more.

[0149] [Blocking agent] The blocking agent includes a malonic acid ester. The malonic acid ester is not particularly limited, but preferably includes a malonic acid ester having a primary alkyl group, a malonic acid ester having a secondary alkyl group, or a malonic acid ester having a tertiary alkyl group, and more preferably includes a malonic acid ester having a secondary alkyl group or a malonic acid ester having a tertiary alkyl group. The blocking agent may include one type of each of a malonic acid ester having a secondary alkyl group, a malonic acid ester having a primary alkyl group, and a malonic acid ester having a tertiary alkyl group, or may include two or more types in combination.

[0150] The malonic acid ester having a primary alkyl group is not particularly limited, and examples thereof include dimethyl malonate, diethyl malonate, dipropyl malonate, dibutyl malonate, dicyclohexyl malonate, diphenyl malonate, etc. Among them, diethyl malonate is preferred as the malonic acid ester having a primary alkyl group.

[0151] The malonic acid ester having a secondary alkyl group is not particularly limited, and examples thereof include di-sec-butyl malonate, diisopropyl malonate, isopropylethyl malonate, etc. Among them, diisopropyl malonate is preferred as the malonic acid ester having a secondary alkyl group.

[0152] The malonic acid ester having a tertiary alkyl group is not particularly limited, and examples thereof include di-tert-butyl malonate, di(2-methyl-2-butyl) malonate, di(2-methyl-2-pentyl) malonate, (tert-butyl)ethyl malonate, (2-methyl-2-butyl)ethyl malonate, (2-methyl-2-butyl)isopropyl malonate, (2-methyl-2-pentyl)ethyl malonate, (2-methyl-2-pentyl)isopropyl malonate, and (2-methyl-2-pentyl)hexylisopropyl malonate. Among these, di(2-methyl-2-butyl) malonate, di(2-methyl-2-pentyl) malonate, (2-methyl-2-butyl) isopropyl malonate, (2-methyl-2-pentyl) ethyl malonate, or (2-methyl-2-pentyl) isopropyl malonate is preferred, (2-methyl-2-butyl) ethyl malonate, (2-methyl-2-butyl) isopropyl malonate, (2-methyl-2-pentyl) ethyl malonate, or (2-methyl-2-pentyl) hexyl isopropyl malonate is more preferred, and di-tert-butyl malonate, (2-methyl-2-butyl) isopropyl malonate, or (2-methyl-2-pentyl) isopropyl malonate is even more preferred. As the malonic acid ester having a tertiary alkyl group, commercially available products may be used, or products synthesized by the method described in Reference Document 1 (JP-A-11-130728) may be used.

[0153] Based on the total molar amount of all blocking agents used in the production of the blocked polyisocyanate, the content of the malonic acid ester having a secondary alkyl group and the malonic acid ester having a tertiary alkyl group is preferably 50 mol % or more, more preferably 70 mol % or more, even more preferably 90 mol % or more, particularly preferably 95 mol % or more, and most preferably 100 mol %. By having the content of the malonic acid ester having a secondary alkyl group and the content of the malonic acid ester having a tertiary alkyl group within the above range, the curability at low temperatures of 100° C. or less can be further improved.

[0154] (Other blocking agents) The blocking agent used in the production of the blocked polyisocyanate (B) may further contain other blocking agents in addition to the malonic acid ester, within a range that does not impair the effects achieved by the blocked polyisocyanate composition of the present embodiment.

[0155] Examples of other blocking agents include 1) alcohol compounds, 2) alkylphenol compounds, 3) phenol compounds, 4) active methylene compounds other than malonic acid esters, 5) mercaptan compounds, 6) acid amide compounds, 7) acid imide compounds, 8) imidazole compounds, 9) urea compounds, 10) oxime compounds, 11) amine compounds, 12) imide compounds, 13) bisulfites, 14) pyrazole compounds, 15) triazole compounds, etc. More specifically, examples of blocking agents include the following:

[0156] 1) Alcohol compounds: Alcohols such as methanol, ethanol, 2-propanol, n-butanol, sec-butanol, 2-ethyl-1-hexanol, 2-methoxyethanol, 2-ethoxyethanol, and 2-butoxyethanol. 2) Alkylphenol compounds: mono- and di-alkylphenols having an alkyl group having 4 or more carbon atoms as a substituent. Specific examples of the alkylphenol compounds include monoalkylphenols such as n-propylphenol, iso-propylphenol, n-butylphenol, sec-butylphenol, tert-butylphenol, n-hexylphenol, 2-ethylhexylphenol, n-octylphenol, and n-nonylphenol; and dialkylphenols such as di-n-propylphenol, diisopropylphenol, isopropyl cresol, di-n-butylphenol, di-tert-butylphenol, di-sec-butylphenol, di-n-octylphenol, di-2-ethylhexylphenol, and di-n-nonylphenol. 3) Phenolic compounds: phenol, cresol, ethylphenol, styrenated phenol, hydroxybenzoic acid esters, etc. 4) Active methylene compounds: methyl acetoacetate, ethyl acetoacetate, methyl isobutanoylacetate, ethyl isobutanoylacetate, acetylacetone, etc. 5) Mercaptan compounds: butyl mercaptan, dodecyl mercaptan, etc. 6) Acid amide compounds: acetanilide, acetic acid amide, ε-caprolactam, δ-valerolactam, γ-butyrolactam, etc. 7) Acid imide compounds: succinimide, maleimide, etc. 8) Imidazole compounds: imidazole, 2-methylimidazole, etc. 9) Urea compounds: urea, thiourea, ethyleneurea, etc. 10) Oxime compounds: formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, cyclohexanone oxime, etc. 11) Amine compounds: diphenylamine, aniline, carbazole, di-n-propylamine, diisopropylamine, isopropylethylamine, etc. 12) Imine compounds: ethyleneimine, polyethyleneimine, etc. 13) Bisulfite compounds: sodium bisulfite, etc. 14) Pyrazole compounds: pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, etc. 15) Triazole compounds: 3,5-dimethyl-1,2,4-triazole, etc.

[0157] [Melamine compounds] Melamine compounds generally refer to thermosetting resins synthesized from melamine and aldehyde, and contain three reactive functional groups -NX in one triazine nucleus molecule. 1 X 2 has.

[0158] Examples of melamine compounds include four types: a fully alkyl type containing -N-(CH2OR)2 (R is an alkyl group, same below) as a reactive functional group; a methylol group type containing -N-(CH2OR)(CH2OH) as a reactive functional group; an imino group type containing -N-(CH2OR)(H) as a reactive functional group; and a methylol / imino group type containing -N-(CH2OR)(CH2OH) and -N-(CH2OR)(H) or containing -N-(CH2OH)(H) as a reactive functional group.

[0159] As the melamine compound, a partially methylolated melamine resin or a fully methylolated melamine resin obtained by reacting a melamine component with an aldehyde component can be used. As the aldehyde component, formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, etc. can be mentioned.

[0160] In addition, the methylol melamine compounds may be used in which the methylol groups are partially or completely etherified with a suitable alcohol, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, iso-propyl alcohol, n-butyl alcohol, iso-butyl alcohol, 2-ethyl-1-butanol, 2-ethyl-1-hexanol, etc.

[0161] The melamine compound is preferably a methyl etherified melamine resin in which the methylol groups of a partially or fully methylolated melamine resin are partially or completely etherified with methyl alcohol, a butyl etherified melamine resin in which the methylol groups of a partially or fully methylolated melamine resin are partially or completely etherified with butyl alcohol, or a methyl-butyl mixed etherified melamine resin in which the methylol groups of a partially or fully methylolated melamine resin are partially or completely etherified with methyl alcohol and butyl alcohol, and a methyl-butyl mixed etherified melamine resin is more preferred.

[0162] The weight average molecular weight of the melamine compound is preferably 400 or more and 6,000 or less, more preferably 500 or more and 4,000 or less, and even more preferably 600 or more and 3,000 or less. The weight average molecular weight of the melamine resin is a weight average molecular weight based on polystyrene standards as measured by gel permeation chromatography (GPC).

[0163] The melamine compound may be a commercially available product. Examples of the trade names of commercially available products include "Cymel 202", "Cymel 203", "Cymel 204", "Cymel 211", "Cymel 212", "Cymel 238", "Cymel 251", "Cymel 253", "Cymel 254", "Cymel 303", "Cymel 323", "Cymel 324", "Cymel 325", "Cymel 327", "Cymel 350", "Cymel 370", "Cymel 380", "Cymel 385", "Cymel 1156", "Cymel 1158", "Cymel 1116", and "Cymel 1158". Examples of such compounds include "Resimin 1130" (all manufactured by Allnex Japan Co., Ltd.); "Resimin 735", "Resimin 740", "Resimin 741", "Resimin 745", "Resimin 746", and "Resimin 747" (all manufactured by Monsanto); "U-ban 120", "U-ban 20HS", "U-ban 20SE", "U-ban 2021", "U-ban 2028", and "U-ban 28-60" (all manufactured by Mitsui Chemicals, Inc.); "Sumimal M55", "Sumimal M30W", and "Sumimal M50W" (all manufactured by Sumitomo Chemical Co., Ltd.).

[0164] The ratio of the mass of the solid content of the melamine compound to the mass of the solid content of the blocked polyisocyanate composition is not particularly limited, but is preferably 0.001 or more and 0.50 or less, more preferably 0.005 or more and 0.30 or less, even more preferably 0.01 or more and 0.10 or less, and particularly preferably 0.02 or more and 0.06 or less. When the mass ratio is equal to or more than the lower limit, the hardness of the obtained resin film tends to be higher, whereas when the mass ratio is equal to or less than the upper limit, the viscosity of the blocked polyisocyanate composition tends to be kept lower.

[0165] <Other components> The blocked polyisocyanate composition of the present embodiment may further contain additives such as a solvent, in addition to the blocked polyisocyanate.

[0166] Examples of the solvent include 1-methylpyrrolidone, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol, ethylene glycol diethyl ether, diethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether (DPDM), propylene glycol dimethyl ether, methyl ethyl ketone, and acetonitrile. Examples of the solvent include ethanol, methyl isobutyl ketone, propylene glycol monomethyl ether acetate, ethanol, methanol, iso-propanol, 1-propanol, iso-butanol, 1-butanol, tert-butanol, 2-ethylhexanol, cyclohexanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, ethyl acetate, isopropyl acetate, butyl acetate, toluene, xylene, pentane, iso-pentane, hexane, iso-hexane, cyclohexane, solvent naphtha, and mineral spirits. These solvents may be used alone or in combination of two or more. From the viewpoint of dispersibility in water, the solvent is preferably one having a solubility in water of 5% by mass or more, and specifically, DPDM is preferred.

[0167] <Method for producing blocked polyisocyanate composition> The blocked polyisocyanate composition may be produced by any method. In view of the simplicity of the production method, the method is not particularly limited. For example, a step of reacting the polyisocyanate (or the hydrophilic group compound-modified polyisocyanate) with the blocking agent (hereinafter, sometimes referred to as the "first reaction step"); The reaction intermediate composition obtained in the first reaction step is reacted with a melamine compound (hereinafter, sometimes referred to as the "second reaction step"). Preferably, the method comprises:

[0168] Hereinafter, each step of the method for producing the blocked polyisocyanate composition of the present embodiment will be described in detail.

[0169] [First reaction step] When a hydrophilic compound-modified polyisocyanate is used as the polyisocyanate, the reaction between the polyisocyanate and the hydrophilic compound and the reaction between the polyisocyanate and the blocking agent can be carried out simultaneously, or one of the reactions can be carried out in advance before the second or subsequent reaction is carried out. Among these, it is preferable to carry out the reaction between the polyisocyanate and the hydrophilic compound first, obtain a hydrophilic compound-modified polyisocyanate modified with the hydrophilic compound, and then react the obtained hydrophilic compound-modified polyisocyanate with the blocking agent.

[0170] The reaction between the polyisocyanate and the hydrophilic compound may be carried out using an organic metal salt, a tertiary amine compound, or an alcoholate of an alkali metal as a catalyst. Examples of the metal constituting the organic metal salt include tin, zinc, and lead. Examples of the alkali metal include sodium.

[0171] The reaction temperature between the polyisocyanate and the hydrophilic compound is preferably from -20°C to 150°C, more preferably from 30°C to 130°C. The reaction temperature being equal to or higher than the lower limit tends to increase the reactivity. The reaction temperature being equal to or lower than the upper limit tends to suppress side reactions more effectively.

[0172] It is preferable to completely react the hydrophilic compound with the polyisocyanate so that no unreacted hydrophilic compound remains. By not leaving any unreacted hydrophilic compound, the aqueous dispersion stability of the blocked polyisocyanate composition and the deterioration of curability at low temperatures of 100° C. or less tend to be more effectively suppressed.

[0173] The blocking reaction between the polyisocyanate (or the hydrophilic group compound-modified polyisocyanate) and the blocking agent is not particularly limited, but examples thereof include the following two methods. 1) A method in which the above polyisocyanate is reacted with a blocking agent containing a malonic acid ester. 2) A method in which the above polyisocyanate is reacted with a blocking agent containing a malonic acid ester, and an alcohol having a chain alkyl group is added to the obtained reaction product to introduce an alkyl group derived from the alcohol by transesterification of the terminal ester moiety of the reaction product.

[0174] Of the above two methods, method 2) is preferred, taking into consideration the ease of the process and the ease of control of the molar ratio of structural unit (I) / structural unit (I) and structural unit (II).

[0175] The blocking reaction between the polyisocyanate and the blocking agent can be carried out regardless of the presence or absence of a solvent, to give a blocked polyisocyanate.

[0176] As the blocking agent, each of the malonic acid esters may be used alone or in combination of two or more.

[0177] The amount of the blocking agent added may usually be 80 mol % or more and 200 mol % or less, and preferably 90 mol % or more and 150 mol % or less, based on the total molar amount of isocyanate groups.

[0178] In addition, when a malonic acid ester having a secondary alkyl group and a malonic acid ester having a tertiary alkyl group are used in the blocking agent to be added, the molar ratio of the malonic acid ester having a secondary alkyl group to the malonic acid ester having a tertiary alkyl group (malonic acid ester having a secondary alkyl group / malonic acid ester having a tertiary alkyl group) is preferably more than 5 / 95 and less than 95 / 5, more preferably 7 / 93 or more and 93 / 7 or less, even more preferably 10 / 90 or more and 93 / 7 or less, even more preferably 20 / 80 or more and 93 / 7 or less, and particularly preferably 30 / 70 or more and 93 / 7 or less. By having the molar ratio be equal to or more than the lower limit, the hardness of the resin film can be made good, and by having the molar ratio be equal to or less than the upper limit, the curability at a low temperature of 100°C or less can be made good.

[0179] When a solvent is used during the blocking reaction, it is sufficient to use a solvent that is inactive to the isocyanate group. When a solvent is used, the content of the non-volatile matter per 100 parts by mass of the blocked polyisocyanate composition may usually be 10 parts by mass or more and 95 parts by mass or less, preferably 20 parts by mass or more and 80 parts by mass or less, and more preferably 30 parts by mass or more and 75 parts by mass or less.

[0180] In the blocking reaction, an organic metal salt of tin, zinc, lead or the like, a tertiary amine compound, an alcoholate of an alkali metal such as sodium, or the like may be used as a catalyst. The amount of catalyst added varies depending on the temperature of the blocking reaction, etc., but may usually be from 0.05 to 1.5 parts by mass, and preferably from 0.1 to 1.0 part by mass, per 100 parts by mass of polyisocyanate.

[0181] The blocking reaction can generally be carried out at a temperature of from −20° C. to 150° C., preferably from 0° C. to 100° C., and more preferably from 10° C. to 80° C. When the temperature of the blocking reaction is equal to or higher than the lower limit, the reaction rate can be increased, and when the temperature is equal to or lower than the upper limit, side reactions can be suppressed.

[0182] After the blocking reaction, a neutralization treatment may be carried out by adding an acidic compound or the like. The acidic compound may be an inorganic acid or an organic acid. Examples of the inorganic acid include hydrochloric acid, phosphorous acid, and phosphoric acid. Examples of the organic acid include methanesulfonic acid, p-toluenesulfonic acid, dioctyl phthalate, and dibutyl phthalate.

[0183] In the case of producing the polyvinyl alcohol by the above method 2), the above blocking reaction is followed by an ester exchange reaction. The alcohol having a chain alkyl group used in the transesterification reaction of the method 2) is preferably a monoalcohol, and examples thereof include primary monoalcohols such as methanol, ethanol, propanol, butanol, hexanol, and 2-ethylhexanol; secondary monoalcohols such as isopropanol, 2-butanol, 2-pentanol, and 2-hexanol; and tertiary monoalcohols such as tert-butanol, 2-methyl-2-butanol, 2-methyl-2-pentanol, 2-methyl-2-hexanol, 2-methyl-2-heptanol, 2-methyl-2-octanol, 3-methyl-3-pentanol, 3-ethyl-3-hexanol, and 3-ethyl-3-octanol.

[0184] In addition, the chain alkyl group of the alcohol may be the same as that of the malonic acid ester, or may be a different chain alkyl group. In the case of an alcohol having a chain alkyl group different from that of the malonic acid ester, it is preferable to use a monoalcohol having a chain alkyl group with a different number of alkyl substitutions from that of the malonic acid ester. Specifically, for example, when a malonic acid ester having a secondary alkyl group is used alone as a blocking agent, a monoalcohol having a tertiary alkyl group can be used.

[0185] In the case of producing by the method 2), it is preferable to remove the generated alcohol or the residual added alcohol during or after the transesterification reaction by distillation under normal or reduced pressure. Among them, in order to efficiently proceed with the transesterification reaction, it is preferable to remove the generated alcohol during the transesterification reaction by performing an operation such as distillation. In this case, in order to efficiently remove the alcohol component generated by the transesterification reaction, it is more preferable that the alcohol component to be added has a boiling point higher than that of the generated alcohol component.

[0186] The transesterification reaction can generally be carried out at 0° C. or higher and 150° C. or lower, preferably 30° C. or higher and 120° C. or lower, and more preferably 50° C. or higher and 100° C. or lower. When the temperature of the transesterification reaction is equal to or higher than the lower limit, the reaction rate can be increased, and when the temperature is equal to or lower than the upper limit, side reactions can be suppressed.

[0187] The content of the alcohol in the reaction intermediate composition in the first reaction step is preferably 0.05 parts by mass or more and 41 parts by mass or less, more preferably 0.1 parts by mass or more and 30 parts by mass or less, and even more preferably 0.5 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the solid content of the reaction intermediate composition. When the content of the alcohol is equal to or more than the lower limit, the storage stability of the paint is improved, and when the content is equal to or less than the upper limit, thickening of the paint during blending can be suppressed.

[0188] [Second reaction step] The second reaction step is a step of reacting the reaction intermediate composition obtained in the first reaction step with a melamine compound.

[0189] The mixing ratio of the reaction intermediate composition obtained in the first reaction step and the melamine compound is not particularly limited, but the ratio of the mass of the solid content of the melamine compound to the total mass of the solid content of the reaction intermediate composition and the melamine compound is not particularly limited, but is preferably 0.001 or more and 0.50 or less, more preferably 0.005 or more and 0.30 or less, even more preferably 0.01 or more and 0.10 or less, and particularly preferably 0.02 or more and 0.06 or less. When the mass ratio is equal to or more than the lower limit, the hardness of the obtained resin film tends to be higher, whereas when the mass ratio is equal to or less than the upper limit, the viscosity of the blocked polyisocyanate composition tends to be kept lower.

[0190] Alternatively, in the case of considering the ratio of functional groups between the reaction intermediate composition obtained in the first reaction step and the melamine compound, where the moles of methine groups of the malonic acid diester derivative in the reaction intermediate composition are r and the moles of amino groups of the melamine compound are m, the molar ratio r / m is preferably 100 / 200 or more and 100 / 1 or less, more preferably 100 / 100 or more and 100 / 5 or less, even more preferably 100 / 60 or more and 100 / 10 or less, particularly preferably 100 / 50 or more and 100 / 15 or less, and most preferably 100 / 40 or more and 100 / 20 or less. When the molar ratio r / m is equal to or more than the above lower limit, the hardness of the formed resin film tends to be higher, whereas when the molar ratio r / m is equal to or less than the above upper limit, the viscosity of the blocked polyisocyanate composition can be maintained at a level at which workability does not pose any problems.

[0191] When a solvent is used, the content of the non-volatile matter per 100 parts by mass of the blocked polyisocyanate composition can usually be 10 parts by mass or more and 95 parts by mass or less, preferably 20 parts by mass or more and 80 parts by mass or less, and more preferably 30 parts by mass or more and 75 parts by mass or less.

[0192] The reaction temperature in the second reaction step can generally be from 0° C. to 150° C., preferably from 20° C. to 120° C., more preferably from 40° C. to 110° C., and even more preferably from 60° C. to 100° C. By setting the reaction temperature to be equal to or higher than the lower limit, the reaction rate can be increased, and by setting the reaction temperature to be equal to or lower than the upper limit, side reactions can be suppressed.

[0193] ≪Resin composition≫ The resin composition of the present embodiment includes the above-mentioned blocked polyisocyanate composition and a polyvalent hydroxy compound. The resin composition of the present embodiment can also be called a one-liquid type resin composition including a curing agent component and a base component.

[0194] The resin composition of the present embodiment contains the above-mentioned blocked polyisocyanate composition, and thus has excellent curing properties when baked at a low temperature of 100°C or less, and when formed into a resin film, has excellent hardness, chemical resistance, and breaking elongation.

[0195] The components of the resin composition of the present embodiment will be described in detail below.

[0196] <Polyhydroxy compounds> In this specification, the term "polyhydric hydroxy compound" refers to a compound having at least two hydroxy groups (hydroxyl groups) in one molecule, and is also called a "polyol."

[0197] Specific examples of the polyhydric hydroxy compound include aliphatic hydrocarbon polyols, polyether polyols, polyester polyols, epoxy resins, fluorine-containing polyols, and acrylic polyols. Among these, the polyhydric hydroxy compound is preferably a polyester polyol, a fluorine-containing polyol or an acrylic polyol.

[0198] [Aliphatic hydrocarbon polyols] Examples of the aliphatic hydrocarbon polyols include hydroxyl-terminated polybutadiene and hydrogenated products thereof.

[0199] [Polyether polyols] Examples of the polyether polyols include those obtained by any one of the following methods (1) to (3). (1) Polyether polyols or polytetramethylene glycols obtained by adding an alkylene oxide, either alone or in a mixture, to a polyhydric alcohol, either alone or in a mixture. (2) Polyether polyols obtained by reacting alkylene oxide with a polyfunctional compound. (3) Polymer polyols obtained by polymerizing acrylamide or the like using the polyether polyols obtained in (1) or (2) as a medium. Examples of the polyhydric alcohol include glycerol and propylene glycol. Examples of the alkylene oxide include ethylene oxide and propylene oxide. Examples of the polyfunctional compound include ethylenediamine and ethanolamines.

[0200] [Polyester polyols] Examples of the polyester polyols include the following polyester polyols (1) and (2). (1) Polyester polyol resins obtained by a condensation reaction between a dibasic acid, either alone or in a mixture of two or more kinds, and a polyhydric alcohol, either alone or in a mixture of two or more kinds. (2) Polycaprolactones obtained by ring-opening polymerization of ε-caprolactone with 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, glycerol, pentaerythritol, 2-methylolpropanediol, and ethoxylated trimethylolpropane.

[0201] [Epoxy resins] Examples of the epoxy resins include novolac type epoxy resins, β-methylepicrotype epoxy resins, cyclic oxirane type epoxy resins, glycidyl ether type epoxy resins, glycol ether type epoxy resins, epoxy type aliphatic unsaturated compounds, epoxidized fatty acid esters, ester type polycarboxylic acids, aminoglycidyl type epoxy resins, halogenated type epoxy resins, and resorcinol type epoxy resins, as well as resins obtained by modifying these epoxy resins with amino compounds, polyamide compounds, or the like.

[0202] [Fluorine-containing polyols] Examples of the fluorine-containing polyols include copolymers of fluoroolefins, cyclohexyl vinyl ethers, hydroxyalkyl vinyl ethers, and monocarboxylic acid vinyl esters, as disclosed in Reference Documents 2 (JP-A-57-34107) and 3 (JP-A-61-275311).

[0203] [Acrylic polyols] The acrylic polyols can be obtained, for example, by polymerizing a polymerizable monomer having one or more active hydrogens in one molecule, or by copolymerizing a polymerizable monomer having one or more active hydrogens in one molecule with another monomer copolymerizable with the polymerizable monomer, as necessary.

[0204] Examples of the polymerizable monomer having one or more active hydrogens in one molecule include the following (i) to (iii). 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 esters having active hydrogen, such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 2-hydroxybutyl methacrylate. (iii) (meth)acrylic acid esters having polyvalent active hydrogen, such as acrylic acid monoester or methacrylic acid monoester of glycerol, and acrylic acid monoester or methacrylic acid monoester of trimethylolpropane.

[0205] Examples of other monomers copolymerizable with the polymerizable monomer include the following (i) to (v). These may be used alone or in combination of two or more. (i) Acrylic esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate. (ii) Methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, and glycidyl methacrylate. (iii) Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid. (iv) Unsaturated amides such as acrylamide, N-methylol acrylamide, and diacetone acrylamide. (v) Styrene, vinyl toluene, vinyl acetate, acrylonitrile, etc.

[0206] Further examples include acrylic polyols obtained by copolymerizing polymerizable ultraviolet-stable monomers disclosed in Reference Document 4 (JP-A-1-261409) and Reference Document 5 (JP-A-3-006273), etc.

[0207] Specific examples of the polymerizable ultraviolet-stable monomer include 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, and 2-hydroxy-4-(3-methacryloxy-2-hydroxypropoxy)benzophenone.

[0208] For example, the above-mentioned monomer components are solution-polymerized in the presence of a known radical polymerization initiator such as a peroxide or an azo compound, and the resulting solution is diluted with an organic solvent, etc., as necessary, to obtain an acrylic polyol.

[0209] When obtaining a water-based acrylic polyol, it can be produced by a known method such as a method of solution polymerization of an olefinic unsaturated compound and converting it into an aqueous phase, or emulsion polymerization, etc. In this case, water solubility or water dispersibility can be imparted by neutralizing the acidic moiety of a carboxylic acid-containing monomer such as acrylic acid or methacrylic acid, or a sulfonic acid-containing monomer, etc., with an amine or ammonia.

[0210] [Hydroxyl value and acid value of polyhydric hydroxy compounds] The hydroxyl value of the polyvalent hydroxy compound contained in the resin composition of this embodiment is preferably 5 mgKOH / g or more and 300 mgKOH / g or less, more preferably 10 mgKOH / g or more and 280 mgKOH / g or less, and even more preferably 30 mgKOH / g or more and 250 mgKOH / g or less. When the hydroxyl value of the polyvalent hydroxy compound is within the above range, a resin film having various excellent physical properties such as tensile strength can be obtained. Specifically, when the hydroxyl group of the polyvalent hydroxy compound is equal to or more than the above lower limit, the crosslink density of the urethane due to the reaction with the polyisocyanate is further increased, and the function of the urethane bond is more easily exhibited. On the other hand, when the hydroxyl group of the polyvalent hydroxy compound is equal to or less than the above upper limit, the crosslink density does not increase too much, and the mechanical properties of the resin film are better. The hydroxyl value of the polyvalent hydroxy compound is measured, for example, by potentiometric titration and calculated as a value relative to the solid content in the polyvalent hydroxy compound.

[0211] [Glass transition temperature Tg of polyhydroxy compounds] The glass transition temperature Tg of the polyhydric hydroxy compound contained in the resin composition of this embodiment is preferably 0°C or more and 100°C or less, more preferably 0°C or more and 90°C or less, even more preferably 0°C or more and 80°C or less, and particularly preferably 5°C or more and 70°C or less. When the glass transition temperature of the polyhydric hydroxy compound is within the above range, a resin film having superior tensile strength can be obtained. The glass transition temperature of the polyhydric hydroxy compound can be measured, for example, using a differential scanning calorimeter (DSC) measuring device.

[0212] [Weight average molecular weight Mw of polyhydroxy compound] The weight average molecular weight Mw of the polyhydric hydroxy compound is 5.0×10 3 Above 2.0×10 5 It is preferable that the value is less than 5.0×10 3 More than 1.5 x 10 5 More preferably, it is 5.0×10 or less. 3 Above 1.0×10 5It is more preferable that the weight average molecular weight Mw of the polyhydric hydroxy compound is within the above range, so that a resin film having excellent physical properties such as tensile strength can be obtained. The weight average molecular weight Mw of the polyhydric hydroxy compound is a weight average molecular weight based on polystyrene standard measured by gel permeation chromatography (GPC).

[0213] [NCO / OH] The molar equivalent ratio (NCO / OH) of the isocyanate groups of the blocked polyisocyanate composition to the hydroxyl groups of the polyvalent hydroxy compound contained in the resin composition of the present embodiment is determined depending on the physical properties of the resin film required, and is usually 0.01 or more and 10.00 or less, preferably 0.10 or more and 5.00 or less, more preferably 0.20 or more and 3.00 or less, and even more preferably 0.25 or more and 2.00 or less.

[0214] [Blocked polyisocyanate composition content] In the resin composition of the present embodiment, the content of the blocked polyisocyanate may be an amount such that the molar equivalent ratio of the isocyanate group of the blocked polyisocyanate to the hydroxyl group of the polyvalent hydroxy compound is within the above range, and for example, it is preferably 1 part by mass or more and 200 parts by mass or less, more preferably 5 parts by mass or more and 180 parts by mass or less, and even more preferably 10 parts by mass or more and 150 parts by mass or less, relative to 100 parts by mass of the polyvalent hydroxy compound. When the content of the blocked polyisocyanate is within the above range, a resin film having excellent various physical properties such as tensile strength can be obtained. The content of the blocked polyisocyanate can be calculated, for example, from the blending amount, or can be calculated by identifying and quantifying using a nuclear magnetic resonance (NMR) method and a gas chromatography / mass spectrometry (GC / MS method).

[0215] <Other additives> The resin composition of the present embodiment may further contain other additives. Other additives include, for example, curing agents capable of reacting with crosslinkable functional groups in the polyhydric hydroxy compound, curing catalysts, solvents, pigments (extender pigments, colored pigments, metallic pigments, etc.), ultraviolet absorbers, light stabilizers, radical stabilizers, yellowing inhibitors that suppress coloring during the baking process, coating surface conditioners, flow conditioners, pigment dispersants, defoamers, thickeners, film-forming assistants, and the like.

[0216] Examples of the curing agent include urea resins, epoxy group-containing compounds or resins, carboxyl group-containing compounds or resins, acid anhydrides, alkoxysilane group-containing compounds or resins, and hydrazide compounds.

[0217] The curing catalyst may be a basic compound or a Lewis acid compound.

[0218] Examples of the basic compound include metal hydroxides, metal alkoxides, metal carboxylates, metal acetylacetinates, hydroxides of onium salts, onium carboxylates, halides of onium salts, metal salts of active methylene compounds, onium salts of active methylene compounds, aminosilanes, amines, phosphines, etc. As the onium salts, ammonium salts, phosphonium salts, or sulfonium salts are preferable.

[0219] Examples of the Lewis acid compound include an organotin compound, an organozinc compound, an organotitanium compound, and an organozirconium compound.

[0220] Examples of the solvent include the same solvents as those exemplified in the blocked polyisocyanate composition.

[0221] In addition, known pigments (extender pigments, colored pigments, metallic pigments, etc.), ultraviolet absorbers, light stabilizers, radical stabilizers, yellowing inhibitors that suppress coloring during the baking process, coating surface conditioners, flow conditioners, pigment dispersants, defoamers, thickeners, and film-forming aids can be appropriately selected and used.

[0222] <Method of producing resin composition> The resin composition of the present embodiment can be used as either a solvent-based or water-based composition.

[0223] When producing a water-based resin composition (water-based resin composition), first, additives such as a curing agent capable of reacting with a crosslinkable functional group in the polyhydroxy compound, a curing catalyst, a solvent, pigments (body pigments, coloring pigments, metallic pigments, etc.), an ultraviolet absorber, a light stabilizer, a radical stabilizer, an anti-yellowing agent for suppressing coloring during the baking process, a coating surface conditioner, a flow conditioner, a pigment dispersant, an antifoaming agent, a thickener, and a film-forming assistant are added to the polyhydroxy compound or its water dispersion or water solution as necessary. Next, the above-mentioned blocked polyisocyanate composition or its water dispersion is added as a curing agent, and water or a solvent is further added as necessary to adjust the viscosity. Next, the mixture is forcibly stirred with a stirring device to obtain a water-based resin composition (water-based resin composition).

[0224] When producing a solvent-based resin composition, first, additives such as a curing agent capable of reacting with a crosslinkable functional group in the polyhydroxy compound, a curing catalyst, a solvent, pigments (body pigments, coloring pigments, metallic pigments, etc.), ultraviolet absorbers, light stabilizers, radical stabilizers, yellowing inhibitors for suppressing coloring during the baking process, coating surface conditioners, flow conditioners, pigment dispersants, defoamers, thickeners, and film-forming assistants are added to the polyhydroxy compound or its solvent dilution as necessary. Then, the above-mentioned blocked polyisocyanate composition is added as a curing agent, and a solvent is further added as necessary to adjust the viscosity. Then, the solvent-based resin composition can be obtained by stirring by hand or using a stirring device such as a mixer.

[0225] <Resin film> The resin film of the present embodiment is formed by curing the above-mentioned resin composition, and is excellent in hardness, chemical resistance, and breaking elongation.

[0226] The resin film of the present embodiment is obtained by applying the above-mentioned resin composition to a substrate using a known method such as roll coating, curtain flow coating, spray coating, bell coating, electrostatic coating, etc., and then curing the composition by heating.

[0227] From the viewpoints of energy saving and heat resistance of the base material, the heating temperature is preferably 70°C or higher and 120°C or lower, more preferably 70°C or higher and 110°C or lower, and even more preferably 75°C or higher and 100°C or lower.

[0228] From the viewpoints of energy saving and heat resistance of the base material, the heating time is preferably from 1 minute to 60 minutes, and more preferably from 2 minutes to 40 minutes.

[0229] The substrate is not particularly limited, and examples thereof include outer panels of automobile bodies such as passenger cars, trucks, motorcycles, and buses; automobile parts such as bumpers; outer panels of household electrical appliances such as mobile phones and audio equipment; and various films. Among these, outer panels of automobile bodies or automobile parts are preferred.

[0230] The material of the substrate is not particularly limited, and examples thereof include metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, zinc-plated steel, and zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.)-plated steel; resins such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, and epoxy resin, and plastic materials such as various FRPs; inorganic materials such as glass, cement, and concrete; wood; and fibrous materials such as paper and cloth. Among these, metal materials and plastic materials are preferred.

[0231] The substrate may be a surface treatment such as phosphate treatment, chromate treatment, complex oxide treatment, etc., performed on the surface of the above-mentioned metal material, or a metal surface such as a car body formed from the above-mentioned metal material, and further, a coating film may be formed thereon. The substrate on which a coating film is formed may be a substrate that has been subjected to a surface treatment as necessary and has a primer coating film formed thereon, for example, a car body on which a primer coating film is formed by electrochemical paint. The substrate may be a surface treatment performed as desired on the surface of the above-mentioned plastic material, or a plastic surface such as an automobile part formed from the above-mentioned metal material. The substrate may also be a combination of a plastic material and a metal material.

[0232] Since the resin film of this embodiment has excellent curing properties at low temperatures of 100° C. or less, it is suitable for use as a coating film for products in various fields where energy saving is required or for materials with low heat resistance.

[0233] <Laminate> The laminate of the present embodiment is formed by laminating one or more layers of the above-mentioned resin film on a substrate. The thickness of each resin film layer is 1 μm or more and 50 μm or less.

[0234] The laminate of the present embodiment contains the resin film, and thus is excellent in hardness, chemical resistance, and breaking elongation.

[0235] The laminate of the present embodiment may include two or more layers of the above resin films having the same composition, or may include two or more layers of the above resin films having different compositions.

[0236] Examples of the substrate include the same ones exemplified in the above "resin film".

[0237] The laminate of the present embodiment can be obtained by coating the above-mentioned resin composition on a substrate using a known method such as roll coating, curtain flow coating, spray coating, bell coating, electrostatic coating, etc., and then heating and curing the composition, or by coating all layers and then heating and curing the entire layer at once.

[0238] The laminate of the present embodiment may include, in addition to the substrate and the resin film, layers made of other known components, such as a primer layer, an adhesive layer, and a decorative layer. EXAMPLES

[0239] Hereinafter, the present embodiment will be described in more detail based on examples and comparative examples, but the present embodiment is not limited to the following examples in any way.

[0240] <Test items> The polyisocyanates and blocked polyisocyanates (B) obtained in the Synthesis Examples, and the blocked polyisocyanate compositions obtained in the Examples and Comparative Examples were subjected to measurement of various physical properties and evaluations according to the methods described below.

[0241] [Physical Properties 1] (Isocyanate group (NCO) content) In order to measure the NCO content of the polyisocyanate, the polyisocyanate before being blocked with a blocking agent was used as a measurement sample. First, 2 g to 3 g of the measurement sample was weighed out (Wg) in a flask. Then, 20 mL of toluene was added to dissolve the measurement sample. Then, 20 mL of a 2N toluene solution of di-n-butylamine was added, mixed, and left at room temperature for 15 minutes. Then, 70 mL of isopropyl alcohol was added and mixed. Then, this liquid was titrated with a 1N hydrochloric acid solution (factor F) as an indicator. The titration value obtained was V2 mL. Then, the titration value obtained without the polyisocyanate sample was V1 ml. Then, the isocyanate group (NCO) content (mass%) of the polyisocyanate was calculated from the following formula.

[0242] Isocyanate group (NCO) content (mass%) = (V1-V2) x F x 42 / (W x 1000) x 100

[0243] The effective NCO content of the reaction intermediate composition and the blocked polyisocyanate composition was calculated by the following formula.

[0244] "Available NCO content of reaction intermediate composition [mass%]" = {100 × (mass of isocyanate groups in the solid content of the polyisocyanate)} / (mass of the reaction intermediate composition)

[0245] "Available NCO content of blocked polyisocyanate composition [mass%]" = {100 × (mass of isocyanate groups in the solid content of polyisocyanate)} / (mass of reaction intermediate composition + mass of melamine compound)

[0246] [Physical Properties 2] (Number average molecular weight and weight average molecular weight) The number average molecular weight and weight average molecular weight are those measured by gel permeation chromatography (GPC) using the following apparatus, using polystyrene as a standard. In order to measure the number average molecular weight of the polyisocyanate, the polyisocyanate before being blocked with a blocking agent was used as a measurement sample. The weight average molecular weight was measured using the blocked polyisocyanate (B) as it was under the following measurement conditions.

[0247] (Measurement conditions) Equipment: Tosoh Corporation, HLC-802A Column: Tosoh Corporation, G1000HXL x 1 G2000HXL x 1 G3000HXL x 1 Carrier: Tetrahydrofuran Detection method: Differential refractometer

[0248] [Physical Properties 3] (average number of isocyanate groups) The average number of isocyanate groups (average number of NCO groups) of the polyisocyanate was calculated by the following formula. In the formula, "Mn" is the number average molecular weight of the polyisocyanate, and the value measured in the above "Physical Properties 2" was used. "NCO content" is the isocyanate group content of the polyisocyanate measured before blocking with a blocking agent, and the value calculated in the above "Physical Properties 1" was used.

[0249] Average number of isocyanate groups = (Mn x NCO content x 0.01) / 42

[0250] [Physical Properties 4] (Solid content of reaction intermediate composition) The solid content of the reaction intermediate composition was determined as follows. First, an aluminum dish with a bottom diameter of 38 mm was precisely weighed. Then, about 1 g of the reaction intermediate composition was precisely weighed on the aluminum dish (W1). Then, the reaction intermediate composition was adjusted to a uniform thickness. Then, the reaction intermediate composition placed on the aluminum dish was kept in an oven at 105°C for 1 hour. Then, after the aluminum dish reached room temperature, the reaction intermediate composition remaining on the aluminum dish was precisely weighed (W2). Then, the solid content (mass%) of the reaction intermediate composition was calculated from the following formula.

[0251] Solid content of reaction intermediate composition (mass%)=W2 / W1×100

[0252] [Physical Properties 5] (molar ratio of structural unit (I) / structural unit (I) + structural unit (II)) The molar amounts of structural units (I) and (II) are as follows: 13 The molar ratio of structural unit (I) / structural unit (I)+structural unit (II) was calculated using the respective molar amounts by C-NMR.

[0253] (Measurement conditions) Device: JEOL “JEOL-ECZ500(SC)” (product name) Solvent: deuterated chloroform Accumulation count: 5120 times Sample concentration: 50w / v% Chemical shift standard: deuterated chloroform was set at 77.0 ppm. Integral value of methine carbon of structural unit (I): Sum of integral values ​​of absorption from 59.3 ppm to 60.5 ppm chemical shift Integral value of methine carbon of structural unit (II): Sum of integral values ​​of absorption from 58.5 ppm to 59.2 ppm chemical shift

[0254] [Physical Properties 6] (molar amount r of malonic acid diester addition group in the reaction intermediate composition) The molar amount r of the malonic acid diester addition group in the reaction intermediate composition is measured under the following measurement conditions. 13 Calculated by C-NMR.

[0255] (Measurement conditions) Device: JEOL “JEOL-ECZ500(SC)” (product name) Solvent: deuterated chloroform Accumulation count: 5120 times Sample concentration: 50w / v% Chemical shift standard: deuterated chloroform was set at 77.0 ppm. Isocyanurate groups: integral value (n) of 148 ppm Methine carbon: Chemical shift, integral value of absorption from 58.5 ppm to 60.5 ppm (mc)

[0256] The molar amount r was calculated using the following formula.

[0257] r=3mc / n

[0258] [Physical Properties 7] (Molar amount y of structural unit (I)) The molar amount y of the structural unit (I) in the blocked polyisocyanate composition was analyzed under the same measurement conditions as those for the above Physical Property 5, and calculated according to the following reaction formula. Isocyanurate groups: integral value (n) of 148 ppm Methine carbon: Chemical shift, integral value of absorption from 58.5 ppm to 60.5 ppm (mc)

[0259] y=3mc / n

[0260] [Physical Properties 8] (structural unit (X) / (structural unit (X) + structural unit (I)) The molar ratio of structural unit (X) / (structural unit (X)+structural unit (I)) was calculated according to the following formula using the values ​​calculated in the above Physical Properties 6 and Physical Properties 7.

[0261] Structural unit (X) / (Structural unit (X) + Structural unit (I))=(ry) / r

[0262] [Preparation of resin composition] An acrylic polyol (manufactured by Allnex, "Setalux (registered trademark) 1767" (product name), hydroxyl value 150 mg KOH / g resin, solid content 65 mass%) and each blocked polyisocyanate composition were blended so that the mass ratio per solid content was 60:40. Furthermore, butyl acetate was blended to adjust the solid content to 40 mass%, and a resin composition was obtained.

[0263] [Rating 1] (Low temperature curing) The resin composition obtained in the above "Preparation of resin composition" was applied to a polypropylene (PP) plate so that the dry film thickness was 40 μm, and then the plate was dried by heating at 100° C. for 30 minutes to obtain a resin film. The gel fraction was calculated by dividing the mass of the undissolved portion of the resin film obtained by immersing the resin film in acetone at 23° C. for 24 hours by the mass before immersion (mass %). The calculated gel fraction was used to evaluate the low-temperature curing property according to the following evaluation criteria.

[0264] (Evaluation Criteria) A: Gel fraction was 85% by mass or more B: Gel fraction was 70% or more and less than 85% by mass C: Gel fraction was less than 70% by mass

[0265] [Rating 2] (Coating film hardness (König hardness)) The resin composition obtained in the above "Preparation of resin composition" was applied to a glass plate so that the dry film thickness was 40 μm, and then heated and dried at 100 ° C for 30 minutes to obtain a resin film. The obtained resin film was measured for Konig hardness (times) in a 23 ° C environment using a Konig hardness tester (Pendulum hardness tester of BYK Gardner). The measured Konig hardness (times) was evaluated according to the following evaluation criteria.

[0266] (Evaluation Criteria) A: More than 60 times B: 30 to less than 60 times C: Less than 30 times

[0267] [Rating 3] (Chemical resistance (acid resistance)) Five minutes after preparation, the resin composition was applied to a glass plate with an applicator so that the dry film thickness was 40 μm, and then baked at 100 ° C for 30 minutes to obtain a resin film. 0.5 mL of 0.1 mmol / L sulfuric acid aqueous solution was dripped onto the obtained resin film, and heated at a temperature of 40 ° C for 30 minutes. After that, the glass plate was cooled, lightly washed with water, and the state of the coating film after wiping with a flannel cloth was confirmed, and the chemical resistance (acid resistance) was evaluated according to the following evaluation criteria.

[0268] (Evaluation Criteria) A: No change in the appearance of the coating B: Linear marks around the dripped part of the coating C: There is a loss of gloss in part of the dripped part of the coating film. D: Gloss loss over the entire surface of the dripped portion of the coating film

[0269] [Rating 4] (Elongation at break) The resin composition was applied to a PP plate 5 minutes after preparation so that the dry film thickness was 40 μm, and then the applied resin film was dried at 100° C. for 30 minutes to obtain a resin film. The Young's modulus (MPa) of the obtained resin film was measured under the following measurement conditions. (Measurement conditions) Test piece dimensions: width 10 x length 20 mm Tensile speed: 20mm / min Measurement temperature: 23℃

[0270] For the measured Young's modulus (MPa), the breaking elongation was evaluated according to the following evaluation criteria.

[0271] (Evaluation Criteria) A:1,100MPa or more B: 900MPa or more and less than 1,100MPa C: Less than 900MPa

[0272] <Synthesis of polyisocyanate> [Synthesis Example 1] (Synthesis of Polyisocyanate P-1) In a four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser, 100 parts by mass of HDI and 5.3 parts by mass of polyester polyol (polycaprolactone triol) derived from a trihydric alcohol and ε-caprolactone (manufactured by Daicel Chemical Industries, Ltd., "Placcel 303" (trade name), average number of functional groups: 3, number average molecular weight: 300) were charged under a nitrogen gas flow, and the temperature inside the reactor was kept at 89°C for 1 hour under stirring to carry out a urethane reaction. Thereafter, the temperature inside the reactor was kept at 63°C, and an isocyanurate catalyst tetramethylammonium caprylate was added, and when the yield reached 52% by mass, phosphoric acid was added to stop the reaction. After filtering the reaction liquid, unreacted HDI was removed using a thin-film evaporator to obtain an isocyanurate-type polyisocyanate (hereinafter, sometimes referred to as "polyisocyanate P-1").

[0273] The NCO content of the obtained polyisocyanate P-1 was 18.6% by mass, the number average molecular weight was 1220, and the average number of isocyanate groups was 5.4. 1 H-NMR analysis confirmed the presence of isocyanurate groups.

[0274] <Production of Blocked Polyisocyanate Composition> [Example 1] (Production of Blocked Polyisocyanate Composition BP-a1) 1. Preparation of Reaction Intermediate Composition B-1 In a four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser, 100 parts by mass of the polyisocyanate P-1 obtained in Synthesis Example 1 was charged under a nitrogen gas flow, and 102 mol% was charged relative to 100 mol% of di-tert-butyl malonate. Dipropylene glycol dimethyl ether (DPDM) was further added to adjust the solid content to 60% by mass. Next, 0.8 parts by mass of a methanol solution containing sodium methylate (28% by mass relative to the total mass of the solution) was dropped while stirring, and the external bath was adjusted so that the solution temperature was 55°C. Blocking reaction was carried out at 55°C for 5 hours to obtain a reaction intermediate composition B-1 with a solid content of 60% by mass.

[0275] 2. Preparation of blocked polyisocyanate composition BP-a1 A four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser was charged with 125 parts by mass of the reaction intermediate composition B-1 obtained in the above step "1." and 27.8 parts by mass of a melamine resin (product name "Cymel (registered trademark) 327", manufactured by Allnex, solid content 90% by mass) under a nitrogen stream, and mixed at 30°C for 1 hour to obtain a blocked polyisocyanate composition BP-a1.

[0276] [Example 2] (Production of Blocked Polyisocyanate Composition BP-a2) 1. Preparation of Reaction Intermediate Composition B-2 In a four-neck flask equipped with a thermometer, a stirring blade and a reflux condenser, 100 parts by mass of polyisocyanate P-1 obtained in Synthesis Example 1, 70 mol% of diisopropyl malonate relative to 100 mol% of NCO groups, and 30 mol% of (2-methyl-2-butyl)isopropyl malonate relative to 100 mol% of NCO groups were charged under nitrogen gas flow, and dipropylene glycol dimethyl ether (DPDM) was added to adjust the solid content to 60% by mass. Next, 0.8 parts by mass of a methanol solution containing sodium methylate (28% by mass relative to the total mass of the solution) was dropped while stirring, and the external bath was adjusted so that the solution temperature was 55°C, and the blocking reaction was carried out at 55°C for 5 hours to obtain a reaction intermediate composition B-2 with a solid content of 60% by mass.

[0277] 2. Preparation of blocked polyisocyanate composition BP-a2 A blocked polyisocyanate composition BP-a2 was obtained in the same manner as in “2.” of Example 1, except that the reaction intermediate composition B-2 was used instead of the reaction intermediate composition B-1.

[0278] [Example 3] (Production of Blocked Polyisocyanate Composition BP-a3) 1. Preparation of Reaction Intermediate Composition B-3 In a four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser, 100 parts by mass of polyisocyanate P-1 obtained in Synthesis Example 1 and diisopropyl malonate were charged under nitrogen gas flow so that the amount was 102 mol% relative to 100 mol% of NCO groups, and dipropylene glycol dimethyl ether (DPDM) was further added to adjust the solid content to 60 mol%. Next, while stirring, 0.8 parts by mass of a methanol solution containing sodium methylate (28 mol% relative to the total mass of the solution) was dropped, and the external bath was adjusted so that the solution temperature was 55°C, and a blocking reaction was carried out at 55°C for 5 hours to obtain a blocked polyisocyanate intermediate with a solid content of 60 mol%. Then, 2-methyl-2-butanol was added so that the amount was 100 mol% relative to the blocked isocyanate groups, and the reaction was carried out at 80°C for 3 hours while removing the generated isopropyl alcohol by distillation under normal pressure. Thereafter, isopropanol and 2-methyl-2-butanol were further distilled off at 60° C. under reduced pressure (50 kPa), and finally, dipropylene glycol dimethyl ether (DPDM) was added to adjust the solid content to 60 mass %, thereby obtaining a reaction intermediate composition B-3.

[0279] 2. Preparation of blocked polyisocyanate composition BP-a3 A blocked polyisocyanate composition BP-a3 was obtained in the same manner as in “2.” of Example 1, except that the reaction intermediate composition B-3 was used instead of the reaction intermediate composition B-1.

[0280] [Examples 4, and 6 to 7] Each blocked polyisocyanate composition was produced in the same manner as in Example 1, except that the type of reaction intermediate composition and the amount of melanin compound added were as shown in the table below.

[0281] [Example 5] (Production of Blocked Polyisocyanate Composition BP-a5) In a four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser, 125 parts by mass of the reaction intermediate composition B-1 obtained in “1.” of Example 1 and 3.9 parts by mass of Cymel 325 (trade name, manufactured by Allnex, melamine resin, solid content 80% by mass) were charged under a nitrogen stream and mixed at 100° C. for 1 hour to obtain a blocked polyisocyanate composition BP-a5.

[0282] [Example 8] (Production of Blocked Polyisocyanate Composition BP-a8) 1. Preparation of Reaction Intermediate Composition B-4 In a four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser, 100 parts by mass of polyisocyanate p-1 obtained in Synthesis Example 1 and diisopropyl malonate were charged under nitrogen gas flow so that the content was 102 mol% relative to 100 mol% of NCO groups, and dipropylene glycol dimethyl ether (DPDM) was further added to adjust the solid content to 60 mass%. Next, while stirring, 0.8 parts by mass of a methanol solution containing sodium methylate (28 mass% relative to the total mass of the solution) was dropped, and the external bath was adjusted so that the solution temperature was 55°C, and a blocking reaction was carried out at 55°C for 5 hours to obtain a reaction intermediate composition B-4 with a solid content of 60 mass%.

[0283] 2. Preparation of blocked polyisocyanate composition BP-a8 A blocked polyisocyanate composition BP-a8 was obtained in the same manner as in “2.” of Example 1, except that the reaction intermediate composition B-4 was used instead of the reaction intermediate composition B-1.

[0284] [Example 9] (Production of Blocked Polyisocyanate Composition BP-a9) 1. Preparation of Reaction Intermediate Composition B-5 In a four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser, 100 parts by mass of polyisocyanate p-1 obtained in Synthesis Example 1 and diethyl malonate were charged under nitrogen gas flow so that the content was 102 mol% relative to 100 mol% of NCO groups, and dipropylene glycol dimethyl ether (DPDM) was further added to adjust the solid content to 60 mol%. Next, while stirring, 0.8 parts by mass of a methanol solution containing sodium methylate (28 mol% relative to the total mass of the solution) was dropped, and the external bath was adjusted so that the solution temperature was 55°C, and a blocking reaction was carried out at 55°C for 5 hours to obtain a reaction intermediate composition B-5 with a solid content of 60 mol%.

[0285] 2. Preparation of blocked polyisocyanate composition BP-a9 A blocked polyisocyanate composition BP-a9 was obtained in the same manner as in “2.” of Example 1, except that the reaction intermediate composition B-5 was used instead of the reaction intermediate composition B-1.

[0286] [Comparative Example 1] (Production of Blocked Polyisocyanate Composition BP-b1) In a four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser, 125 parts by mass of the reaction intermediate composition B-4 obtained in “1.” of Example 8 and 3.4 parts by mass of Cymel 327 (trade name, manufactured by Allnex, melamine resin, solid content 90% by mass) were charged under a nitrogen stream and mixed at 20° C. for 1 hour to obtain a blocked polyisocyanate composition BP-b1.

[0287] [Comparative Example 2] (Production of Blocked Polyisocyanate Composition BP-b2) In a four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser, 125 parts by mass of the reaction intermediate composition B-3 obtained in “1.” of Example 3 and 3.5 parts by mass of Cymel 327 (trade name, manufactured by Allnex, melamine resin, solid content 90% by mass) were charged under a nitrogen stream and mixed at 20° C. for 1 hour to obtain a blocked polyisocyanate composition BP-b2.

[0288] [Comparative Example 3] (Production of blocked polyisocyanate composition BP-b3) The reaction intermediate composition B-3 obtained in “1.” of Example 3 was used as it was as a blocked polyisocyanate composition BP-b3.

[0289] [Comparative Example 4] (Preparation of Curing Agent Composition M-1) A melamine resin (product name "Cymel 327", manufactured by Allnex, solid content 90 mass %) was used as it was as hardener composition M-1.

[0290] The physical properties and evaluation results of each blocked polyisocyanate composition are shown in the following table, where "H" represents a hydrogen atom.

[0291] [Table 1]

[0292] [Table 2]

[0293] As shown in the above table, the blocked polyisocyanate compositions BP-a1 to BP-a9 (Examples 1 to 9), which contained a blocked polyisocyanate having the structural unit (X), exhibited good low-temperature curing properties when formed into a resin composition, and good hardness, chemical resistance, and breaking elongation when formed into a resin film. Furthermore, in comparing the blocked polyisocyanate compositions BP-a2 and BP-a3 (Examples 2 and 3) having different molar ratios of the structural unit (I) / (structural unit (I) + structural unit (II)), there was a tendency that the chemical resistance of the resin film when formed increased with an increase in the molar ratio of the structural unit (I) / (structural unit (I) + structural unit (II)). Furthermore, in a comparison of blocked polyisocyanate compositions BP-a3 and BP-a4 (Examples 3 and 4) having different molar ratios of the structural unit (X) / (structural unit (X) + structural unit (I)), and in a comparison of blocked polyisocyanate compositions BP-a2, BP-a6, and BP-a7 (Examples 2, 6, and 7), it was found that when the molar ratio of the structural unit (X) / (structural unit (X) + structural unit (I)) was 0.05 or more and 0.15 or less, the low temperature curing properties tended to be particularly excellent, when the molar ratio of the structural unit (X) / (structural unit (X) + structural unit (I)) was 0.15 or more and 0.35 or less, the hardness when formed into a resin film tended to be particularly excellent, and when the molar ratio of the structural unit (X) / (structural unit (X) + structural unit (I)) was 0.05 or more and 0.25 or less, the breaking elongation when formed into a resin film tended to be particularly excellent. In comparing the blocked polyisocyanate compositions BP-a3 and BP-a5 (Examples 3 and 5) which contain different types of melamine compounds, the composition using Cymel 327 tended to have particularly superior low-temperature curing properties.

[0294] On the other hand, in the blocked polyisocyanate compositions BP-b1 to BP-b3 (Comparative Examples 1 to 3) containing a blocked polyisocyanate not having the structural unit (X), and the curing agent composition M-1 (Comparative Example 4) not containing a blocked polyisocyanate (B) having the structural unit (X) and containing a melamine compound, the low-temperature curing properties when made into a resin composition, and the hardness and chemical resistance when made into a resin film were all not good. [Industrial Applicability]

[0295] According to the blocked polyisocyanate composition of the present embodiment, it is possible to provide a blocked polyisocyanate composition that exhibits excellent curing properties when baked at 100°C, and exhibits excellent hardness, chemical resistance, and breaking elongation when formed into a resin film. The resin composition of the present embodiment contains the blocked polyisocyanate composition, exhibits excellent curing properties when baked at 100°C, and exhibits excellent hardness, chemical resistance, and breaking elongation when formed into a resin film. The resin film of the present embodiment is formed by curing the resin composition, and exhibits excellent hardness, chemical resistance, and breaking elongation. The laminate of the present embodiment includes the resin film, and exhibits excellent hardness, chemical resistance, and breaking elongation.

Claims

1. A blocked polyisocyanate composition comprising a blocked polyisocyanate derived from a polyisocyanate, a blocking agent containing a malonic acid ester, and a melamine compound, the blocked polyisocyanate containing a structural unit represented by the following general formula (X): 【Chemistry 1】 (In general formula (X), R １１ , R １２ , R １３ , R １４ , R １５ and R １６ R is each independently a hydrogen atom or an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxyl group and an amino group. １７ R is a group represented by the following general formula (Xa). １８ is a hydrogen atom, an alkoxymethyl group, or a hydroxymethyl group. The wavy line represents a bond. 【Chemistry 2】 (In general formula (Xa), R １１ａ , R １２ａ , R １３ａ and R １４ａ are each independently a hydrogen atom, an alkoxymethyl group, or a hydroxymethyl group. The wavy line represents a bond.

2. In the general formula (X), １１ , the R １２ and the R １３ At least two of the above are alkyl groups which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group, and The R １４ , the R １５ and the R １６ 2. The blocked polyisocyanate composition according to claim 1, wherein at least two of the above are alkyl groups which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group.

3. In the general formula (X), １１ , the R １２ and the R １３ each independently represents an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group, and The R １１ , the R １２ and the R １３ The blocked polyisocyanate composition according to claim 1 or 2, wherein the total number of carbon atoms is 3 or more and 20 or less.

4. The blocked polyisocyanate composition according to any one of claims 1 to 3, wherein the polyisocyanate is a polyisocyanate derived from one or more diisocyanates selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.

5. The blocked polyisocyanate composition according to any one of claims 1 to 4, wherein at least a portion of the isocyanate groups of the polyisocyanate is modified with a hydrophilic compound.

6. The blocked polyisocyanate composition according to any one of claims 1 to 5, wherein the polyisocyanate has an average number of isocyanate groups of 3.5 or more.

7. A resin composition comprising the blocked polyisocyanate composition according to any one of claims 1 to 6 and a polyvalent hydroxy compound.

8. A resin film obtained by curing the resin composition according to claim 7.

9. A laminate comprising one or more layers of the resin film according to claim 8 laminated on a substrate, The thickness of each of the resin films is 1 μm or more and 50 μm or less.

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