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 shows excellent hardness and chemical resistance as a resin film.SOLUTION: A blocked polyisocyanate composition comprises: a blocked polyisocyanate (B) that is derived from a polyisocyanate and a blocker comprising malonate, the blocked polyisocyanate comprising a constitutional unit represented by the general formula (I); and a melamine resin (M).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] Traditionally, polyurethane resin paints have exhibited excellent abrasion resistance, chemical resistance, and stain resistance. In particular, polyurethane resin paints using polyisocyanates derived from aliphatic or alicyclic diisocyanates have even better weather resistance, and demand for such paints is increasing. However, polyurethane resin paints are generally two-component, making their use extremely inconvenient. Conventional polyurethane resin paints consist of two components, a polyol and a polyisocyanate, which must be stored separately and mixed before application. Furthermore, once mixed, the paint gels within a short time, rendering it unusable. These issues with polyurethane resin paints make their use in automated painting extremely difficult in fields involving line painting, such as automotive painting or low-voltage painting. Furthermore, because isocyanates readily react with water, their use with water-based paints, such as electrocoating, is impossible. Furthermore, when using paints containing isocyanates, thorough cleaning of the sprayer and coating tank is required after each application, significantly reducing work efficiency.

[0003] To overcome the above-mentioned problems, it has been proposed to use blocked polyisocyanates in which all active isocyanate groups are blocked with a blocking agent. This blocked polyisocyanate does not react with polyols at room temperature. However, heating dissociates the blocking agent, regenerating the active isocyanate groups, which then react with polyols to initiate a crosslinking reaction, thereby overcoming the above-mentioned problems. Therefore, many blocking agents have been investigated, and representative examples include phenol and methyl ethyl ketoxime.

[0004] However, when using blocked polyisocyanates using these blocking agents, a high baking temperature of 140° C. or higher 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 be heat resistant, which limits its applications.

[0005] Meanwhile, research has been conducted on low-temperature-baking blocked polyisocyanates using active methylene compounds such as acetoacetic esters and malonic acid diesters (see, for example, Patent Document 1). Among these, technology for even lower-temperature curing is being continuously investigated. For example, Patent Documents 2 and 3 propose blocked polyisocyanate compositions that cure at low temperatures. Furthermore, it is generally known that in order to develop coating film hardness, a melamine-based compound is used as a curing agent (see, for example, Patent Document 4). [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 that use active methylene compounds tend to have low coating film hardness, which is a problem. Furthermore, in the case of melamine 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 exhibits excellent curing properties when baked at 100°C and that exhibits excellent hardness and chemical resistance when formed into a resin film, 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 (B) derived from a polyisocyanate and a blocking agent containing a malonic acid ester, the blocked polyisocyanate containing a structural unit represented by the following general formula (I): Melamine resin (M), A blocked polyisocyanate composition comprising:

[0010] [ka]

[0011] (In general formula (I), 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. 11 , the R 12 and the above R 13 The total number of carbon atoms in R is 3 or more and 20 or less. 14 , R 15 and R 16 are each independently a hydrogen atom or an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group. The wavy line represents a bond.

[0012] (2) The blocked polyisocyanate composition according to (1), wherein the blocked polyisocyanate (B) contains a structure represented by the following general formula (I-1) as the structure represented by the general formula (I):

[0013] [ka]

[0014] (In general formula (I-1), R 111 , R 112 and R 113 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. 111 , the R 112 and the above R 113 The total number of carbon atoms in R is 3 or more and 20 or less. 114 and R 115 are each independently a hydrogen atom or an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group. The wavy line represents a bond.

[0015] (3) The above R 11 , the R 12 and the above R 13 are each independently an unsubstituted alkyl group, and R 14 , the R 15 and the above R 16 and each independently represent a hydrogen atom or an unsubstituted alkyl group. (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 the average number of isocyanate groups in the polyisocyanate is 3.5 or more. (6) A resin composition comprising the blocked polyisocyanate composition according to any one of (1) to (5) and a polyvalent hydroxy compound. (7) A resin film obtained by curing the resin composition according to (6). (8) A laminate comprising one or more layers of the resin film according to (7) laminated on a substrate, The laminate has a thickness of 1 μm or more and 50 μm or less per layer of the resin film. [Effects of the Invention]

[0016] The blocked polyisocyanate composition of the above aspect can provide a blocked polyisocyanate composition that exhibits excellent curing properties when baked at 100°C and exhibits excellent hardness and chemical resistance 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 and chemical resistance when formed into a resin film. The resin film of the above aspect is formed by curing the resin composition and exhibits excellent hardness and chemical resistance. The laminate of the above aspect includes the resin film and exhibits excellent hardness and chemical resistance. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of 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 practiced with appropriate modifications within the scope of its gist.

[0018] In this specification, the term "polyol" refers to a compound having two or more hydroxy groups (-OH). As used herein, the term "polyisocyanate" refers to a reaction product in which a plurality of monomer compounds having one or more isocyanate groups (-NCO) are bonded together. In this specification, the term "structural unit" refers to a structure derived from one molecule of a monomer in the structure constituting a polyisocyanate or a blocked polyisocyanate. For example, a structural unit derived from a malonic acid ester refers to a structure derived 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 portion of the unit is converted into a different structure by treating the (co)polymer.

[0019] <Blocked polyisocyanate composition> The blocked polyisocyanate composition of the present embodiment contains a blocked polyisocyanate (B) and a melamine resin (M). The blocked polyisocyanate (B) is a blocked polyisocyanate derived from a polyisocyanate and a blocking agent containing a malonic acid ester, and contains a structural unit represented by the following general formula (I) (hereinafter, sometimes simply referred to as "structural unit (I)").

[0020] [ka]

[0021] (In general formula (I), 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. 11 , the R 12 and the above R 13 The total number of carbon atoms in R is 3 or more and 20 or less. 14 , R 15 and R 16 are each independently a hydrogen atom or an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group. The wavy line represents a bond.

[0022] The blocked polyisocyanate composition of the present embodiment has the above-described structure, and therefore exhibits excellent curability when baked at 100° C., and when formed into a resin film, exhibits excellent hardness and chemical resistance.

[0023] Next, each of the constituent components of the blocked polyisocyanate composition of the present embodiment will be described in detail below.

[0024] <Blocked polyisocyanate (B)> The blocked polyisocyanate (B) is a reaction product of a polyisocyanate and a blocking agent containing a malonic acid ester, i.e., in the blocked polyisocyanate (B), at least a portion, preferably all, of the isocyanate groups in the polyisocyanate are blocked with a blocking agent containing a malonic acid ester.

[0025] Unit The blocked polyisocyanate (B) contains a structural unit (I) in the molecule. The structural unit (I) has a structure formed by blocking the isocyanate group of a polyisocyanate with a malonic acid ester.

[0026] [ka]

[0027] (In general formula (I), 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. 11 , the R 12 and the above R 13 The total number of carbon atoms in R is 3 or more and 20 or less. 14 , R 15 and R 16 are each independently a hydrogen atom or an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group. The wavy line represents a bond.

[0028] (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 16The alkyl group in the formula (I) preferably has 1 to 20 carbon atoms, more preferably 1 to 8 carbon atoms, further preferably 1 to 6 carbon atoms, and particularly preferably 1 to 4 carbon atoms.

[0029] Specific examples of the unsubstituted alkyl group 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.

[0030] R 11 , R 12 , R 13 , R 14 , R 15 and R 16 When is an alkyl group having a substituent, the substituent is a hydroxy group or an amino group.

[0031] Examples of the alkyl group containing a hydroxy group as a substituent include a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group.

[0032] 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.

[0033] 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.

[0034] R 11 , R 12 and R 13 The total number of carbon atoms is 3 or more and 20 or less, preferably 4 or more and 20 or less, more preferably 4 or more and 12 or less, even more preferably 4 or more and 9 or less, and particularly preferably 4 or more and 6 or less. R 11 , R 12 and R 13 When the total number of carbon atoms is equal to or greater than the lower limit, the resulting resin film can exhibit hardness, whereas when the total number of carbon atoms is equal to or less than the upper limit, the resin film can exhibit curability at low temperatures of 100°C or less. In addition, from the viewpoint of chemical resistance when used as a coating, R 11 , R 12 and R 13 The total number of carbon atoms is most preferably 4.

[0035] Among them, R 11 , R 12 , R 13 , R 14 , R 15 and R 16 The alkyl group in is preferably an unsubstituted alkyl group, and more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms.

[0036] R 11 , R 12 and R 13 As for the groups, since the curing property at low temperatures of 100°C or less is further improved, they are each independently preferably an unsubstituted alkyl group, more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms, and further preferably a methyl group or an ethyl group. R 11 , R 12 and R 13 It is preferable that at least one of the groups is an ethyl group.

[0037] R 14 , R 15 and R 16are 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 even more preferably a hydrogen atom, a methyl group, or an ethyl group. R 14 , R 15 and R 16 Among 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 hardness of the resin film formed can be further improved while maintaining the curability at a low temperature of 100° C. or less.

[0038] That is, it is preferable that the structural unit (I) contains a structural unit represented by the following general formula (I-1) (hereinafter, sometimes referred to as "structural unit (I-1)").

[0039] [ka]

[0040] (In general formula (I-1), R 111 , R 112 and R 113 are the above R 11 , R 12 and R 13 is the same as R 114 and R 115 are the above R 15 and R 16 The wavy lines represent bonds, and represent the bonding sites with the residues of polyisocyanate excluding the isocyanate groups.)

[0041] R 111 , R 112 and R 113 The total number of carbon atoms is 3 or more and 20 or less, preferably 4 or more and 20 or less, more preferably 4 or more and 12 or less, even more preferably 4 or more and 9 or less, and particularly preferably 4 or more and 6 or less. R111 , R 112 and R 113 When the total number of carbon atoms is equal to or greater than the lower limit, the resulting resin film can exhibit hardness, whereas when the total number of carbon atoms is equal to or less than the upper limit, the resin film can exhibit curability at low temperatures of 100°C or less. In addition, from the viewpoint of solvent resistance when used as a coating film, R 111 , R 112 and R 113 The total number of carbon atoms is most preferably 4.

[0042] Among them, R 111 , R 112 and R 113 , R 114 and R 115 The alkyl group in is preferably an unsubstituted alkyl group, and more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms.

[0043] R 111 , R 112 and R 113 As the alkyl group, each independently is preferably an unsubstituted alkyl group, more preferably an unsubstituted alkyl group having 1 to 4 carbon atoms, and even more preferably a methyl group or an ethyl group, because this further improves the hardness of the resin film formed therefrom and the curability at low temperatures of 100°C or less. R 111 , R 112 and R 113 It is preferable that at least one of the groups is an ethyl group.

[0044] R 114 and R 115 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 even more preferably a hydrogen atom, a methyl group, or an ethyl group.

[0045] The content of the structural unit (I-1) relative to the total molar amount of the structural unit (I) (structural unit (I-1) / structural unit (I)) is preferably 10 mol% or more, more preferably 30 mol% or more, even more preferably 50 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more. When the content of the structural unit (I-1) is at least the above lower limit, curability at low temperatures of 100°C or less is improved. On the other hand, the upper limit of the content of the structural unit (I-1) can be, for example, 100 mol% relative to the total molar amount of the structure (I), i.e., all of the structural units (I) can be structural units (I-1), or it can be 95 mol% or 90 mol% relative to the total molar amount of the structural units (I). The content of the structural unit (I-1) relative to the total molar amount of the structural unit (I) (structural unit (I-1) / structural unit (I)) can be calculated, for example, by dividing the blocked polyisocyanate composition into 13 The molar ratio of the structural unit (I-1) to the structural unit (I) can be calculated by measuring the composition ratio of the structural unit (I-1) to the structural unit (I) by C-NMR.

[0046] [Constituent Unit (II)] It is preferable that the blocked polyisocyanate (B) further contains, in addition to the above-mentioned structural unit (I), a structural unit represented by the following general formula (II) (hereinafter, sometimes referred to as "structural unit (II)") within its molecule.

[0047] [ka] (In general formula (II), R 21 , R 22 , R 23 and R 24 are the above R 15 and R 16 The wavy lines represent bonds, and represent the bonding sites with the residues of polyisocyanate excluding the isocyanate groups.

[0048] (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 1 to 4 carbon atoms and no substituents is preferred because they have excellent hardness when made into a resin film, a hydrogen atom, a methyl group, or an ethyl group is more preferred, and a methyl group or an ethyl group is even more preferred because they have excellent curing properties at low temperatures of 100°C or less.

[0049] 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 which is a hydrogen atom and the other is a methyl group, and R 23 and R 24 When one of the above is a hydrogen atom and the other is a methyl group, the two ester moieties of the malonic acid ester of the structural unit (II) are both ethyl groups.

[0050] 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.

[0051] The molar ratio of structural unit (II) to structural unit (I) (structural unit (II) / structural unit (I)) is preferably 4 / 96 or more and 96 / 4 or less, more preferably 5 / 95 or more and 95 / 5 or less, even more preferably 7 / 93 or more and 93 / 7 or less, even more preferably 10 / 90 or more and 90 / 10 or less, even more preferably 20 / 80 or more and 85 / 15 or less, particularly preferably 30 / 70 or more and 85 / 15 or less, more particularly preferably 35 / 65 or more and 85 / 15 or less, and most preferably 50 / 50 or more and 70 / 30 or less. When the structural unit (II) / structural unit (I) ratio is above the above lower limit, the hardness of the resin film can be improved, and when it is below the above upper limit, the curing property at low temperatures of 100°C or less can be improved. The molar ratio may be, for example, the following: 1 H-NMR and 13 The molar ratio of structural unit (II) to structural unit (I) can be calculated by measuring the composition ratio of structural unit (II) to structural unit (I) by C-NMR.

[0052] [Polyisocyanate] Polyisocyanate is a reaction product obtained by reacting a plurality of monomer compounds having one or more isocyanate groups (-NCO) (hereinafter, sometimes referred to as "isocyanate monomers").

[0053] 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, an isocyanurate group is preferred because it provides excellent weather resistance.

[0054] The isocyanate monomer preferably has a carbon number of 4 or more and 30 or less. 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, diisocyanate norbornane, 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").

[0055] Among these, the isocyanate monomer is preferably one or more diisocyanates selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates, because they have excellent weather resistance. Furthermore, the isocyanate monomer is more preferably HDI or IPDI, because it is easily available industrially. Furthermore, the isocyanate monomer is even more preferably HDI, because it allows the blocked polyisocyanate component to have a low viscosity.

[0056] As the isocyanate monomer used in producing the polyisocyanate, either an aliphatic diisocyanate or an alicyclic diisocyanate may be used alone or in combination, but it is preferable to use a combination of an aliphatic diisocyanate and an alicyclic diisocyanate, 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 resulting coating film can be further improved.

[0057] In the polyisocyanate, from the viewpoint of improving the coating film hardness and strength, the mass ratio of the constituent units derived from the aliphatic diisocyanate to the constituent units derived from the alicyclic diisocyanate (constituent units derived from the aliphatic diisocyanate / constituent units derived from the alicyclic diisocyanate) is preferably 50 / 50 or more and 95 / 5 or less, more preferably 55 / 45 or more and 93 / 7 or less, even more preferably 60 / 40 or more and 91 / 9 or less, and even more preferably 65 / 35 or more and 90 / 10 or less. When the mass ratio of the structural units derived from the aliphatic diisocyanate to the structural units derived from the alicyclic diisocyanate is equal to or greater than the above lower limit, a decrease in flexibility when formed into a coating film can be more effectively prevented, while when the mass ratio is equal to or less than the above upper limit, the hardness when formed into a coating film can be further improved.

[0058] The mass ratio of the constituent units derived from aliphatic diisocyanates to the constituent units derived from alicyclic diisocyanates can be calculated, for example, using 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 concentrations and alicyclic diisocyanate concentrations in this unreacted diisocyanate obtained by gas chromatographic measurement. Next, the calculated mass of the unreacted aliphatic diisocyanate and the unreacted alicyclic diisocyanate are subtracted from the mass of the charged aliphatic diisocyanate and the mass of the alicyclic diisocyanate, respectively, and the obtained differences are taken as the masses of the constituent units derived from aliphatic diisocyanates and the masses of the constituent units derived from alicyclic diisocyanates, respectively. Next, the mass ratio of the aliphatic diisocyanate-derived structural units to the alicyclic diisocyanate-derived structural units is obtained by dividing the mass of the aliphatic diisocyanate-derived structural units by the mass of the alicyclic diisocyanate-derived structural units.

[0059] (Polyol) The polyisocyanate is preferably derived from the above-mentioned diisocyanate monomer and a polyol having an average hydroxyl functionality of 3.0 to 8.0. This allows the average number of isocyanate groups in the resulting polyisocyanate to be increased. 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.

[0060] 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.

[0061] From the viewpoint of improving the hardness and strength of the coating film, 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 measured by GPC using polystyrene as the standard.

[0062] Examples of such polyols include trimethylolpropane, glycerol, and polycaprolactone polyols derived from trihydric or higher polyhydric alcohols and ε-caprolactone.

[0063] 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).

[0064] (Production method of polyisocyanate) The method for producing polyisocyanate will be described in detail below. Polyisocyanates can be obtained, for example, by simultaneously carrying out an allophanate reaction to form allophanate groups, a uretdione reaction to form uretdione groups, an iminooxadiazinedione reaction to form iminooxadiazinedione groups, an isocyanurate reaction to form isocyanurate groups, a urethanization reaction to form urethane groups, and a biuret reaction to form biuret groups in the presence of an excess of isocyanate monomer, and then removing the unreacted isocyanate monomer after the completion of the reactions. 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 has one or more groups selected from the group consisting of allophanate groups, uretdione groups, iminooxadiazinedione groups, isocyanurate groups, urethane groups, and biuret groups. 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, but from the viewpoint of freely adjusting the molar ratio of each functional group, it is preferable to produce them separately and then mix them.

[0065] (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 the monoalcohol 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 these, the alcohol is preferably a monoalcohol, and more preferably a monoalcohol having a molecular weight of 200 or less.

[0066] The allophanatization reaction catalyst includes, but is 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. Examples of lead alkylcarboxylates (organic lead compounds) include lead 2-ethylhexanoate. Examples of zinc alkylcarboxylates (organic zinc compounds) include zinc 2-ethylhexanoate. Examples of bismuth alkylcarboxylates include bismuth 2-ethylhexanoate. Examples of zirconium alkylcarboxylates include zirconium 2-ethylhexanoate. Examples of zirconyl alkylcarboxylates include zirconyl 2-ethylhexanoate, etc. These catalysts can be used alone or in combination of two or more. Furthermore, an isocyanurate reaction catalyst described below can also serve as an allophanate reaction catalyst. When an allophanate reaction is carried out using an isocyanurate reaction catalyst described below, an isocyanurate group-containing polyisocyanate (hereinafter, sometimes referred to as an "isocyanurate-type polyisocyanate") is naturally also 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.

[0067] The lower limit of the amount of the allophanate reaction catalyst used is preferably 10 ppm by mass, more preferably 20 ppm by mass, even more 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, even more 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 1000 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.

[0068] The lower limit of the allophanatization 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 reaction temperature to the above lower limit or higher, the reaction rate can be further improved. By setting the allophanate reaction temperature to the above upper limit or lower, coloration of the polyisocyanate tends to be more effectively suppressed.

[0069] (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-forming 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 trialkylphosphines include tri-n-butylphosphine and tri-n-octylphosphine. Examples of tris(dialkylamino)phosphines include tris-(dimethylamino)phosphine. Examples of cycloalkylphosphines include cyclohexyl-di-n-hexylphosphine. Examples of Lewis acids include boron trifluoride and zinc oxychloride.

[0070] Many of the catalysts for the uretdione formation reaction can also promote the isocyanurate formation reaction at the same time. 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 the desired yield is achieved. When one or more diisocyanates selected from the group consisting of the aliphatic diisocyanates and the alicyclic diisocyanates are heated without using a uretdione reaction catalyst to obtain a polyisocyanate having uretdione groups, the heating temperature is preferably 120° C. or higher, more preferably 150° C. or higher and 170° C. or lower, and the heating time is preferably 1 hour or longer and 4 hours or shorter.

[0071] (3) Method for producing iminooxadiazinedione group-containing polyisocyanate When an iminooxadiazinedione group-containing polyisocyanate is derived from an isocyanate monomer, an iminooxadiazinedione-forming reaction catalyst is usually used. Examples of the iminooxadiazinedione catalyst include those shown in 1) or 2) below. 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 the general formula R2=CR'-C(O)O- and a quaternary ammonium cation or a quaternary phosphonium cation. (In the formula, R1 and R2 each independently represent a linear, branched, or cyclic, saturated or unsaturated perfluoroalkyl group having from 1 to 30 carbon atoms. Each of the multiple R's each independently represents a hydrogen atom, or an alkyl or aryl group having from 1 to 20 carbon atoms which may contain a heteroatom.)

[0072] 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-forming reaction catalyst, 1) is preferred from the viewpoint of availability, and 2) is preferred from the viewpoint of safety.

[0073] 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 by mass relative to the raw material isocyanate monomer such as HDI, from the viewpoint 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.

[0074] 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.

[0075] The iminooxadiazinedione formation reaction can be terminated when the desired iminooxadiazinedione group content is reached. The iminooxadiazinedione formation reaction can be terminated, for example, by adding an acidic compound to the reaction solution. Examples of acidic compounds include phosphoric acid, acidic phosphate esters, sulfuric acid, hydrochloric acid, and sulfonic acid compounds. This neutralizes the iminooxadiazinedione formation reaction catalyst or inactivates it by thermal decomposition or chemical decomposition. After the reaction is terminated, filtration is performed, if necessary.

[0076] (4) Method for producing isocyanurate group-containing polyisocyanate Examples of catalysts for deriving polyisocyanates containing isocyanurate groups from isocyanate monomers include commonly used isocyanuration reaction catalysts.

[0077] The isocyanuration reaction catalyst is not particularly limited, but is preferably a basic catalyst in general. Specific examples of the isocyanuration reaction catalyst include the following: 1) Hydroxides of tetraalkylammonium such as tetramethylammonium, tetraethylammonium, and tetrabutylammonium, and organic weak acid salts of the above tetraalkylammonium such as acetate, propionate, octylate, caprate, myristate, and benzoate. 2) Hydroxides of aryltrialkylammonium such as benzyltrimethylammonium and trimethylphenylammonium, and organic weak acid salts of the above aryltrialkylammonium such as acetate, propionate, octylate, caprate, myristate, and benzoate. 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 of tin, zinc, lead, etc. of alkylcarboxylic 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.

[0078] Among these, from the viewpoint of preventing the generation of unnecessary by-products, the isocyanuration 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.

[0079] 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, relative to 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, but may be, for example, 10 ppm by mass.

[0080] The isocyanurate reaction temperature is preferably 50° C. or higher and 120° C. or lower, and more preferably 60° C. or higher and 90° C. or lower. When the isocyanurate reaction temperature is equal to or lower than the upper limit, coloration of the polyisocyanate tends to be more effectively suppressed.

[0081] When a desired conversion rate (the ratio by 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, acidic phosphate ester, etc.). In order to obtain polyisocyanate, it is necessary to stop the reaction in an early stage. However, since the reaction rate of the isocyanuration reaction is very fast in the early stage, it is difficult to stop the reaction in 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.

[0082] Therefore, the conversion rate of the isocyanurate reaction to obtain 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 keeping the conversion rate of the isocyanurate reaction at or below the upper limit, the viscosity of the blocked polyisocyanate component can be further reduced. Furthermore, by keeping the conversion rate of the isocyanurate reaction at or above the lower limit, the reaction termination operation can be more easily carried out.

[0083] When deriving a polyisocyanate containing an isocyanurate group, a monohydric to hexahydric alcohol can be used in addition to the above isocyanate monomer. Examples of alcohols that can be used include non-polymerizable alcohols and polymerizable alcohols. The term "non-polymerizable alcohol" used herein refers to an alcohol that does not have a polymerizable group. Meanwhile, the term "polymerizable alcohol" refers to an alcohol obtained by polymerizing a monomer that has a polymerizable group and a hydroxyl group. Examples of non-polymerizable alcohols 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, and 2-methyl-2,3-butanediol. 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.

[0084] The polymerizable alcohol is not particularly limited, but examples thereof include polyester polyols, polyether polyols, acrylic polyols, polyolefin polyols, and the like.

[0085] 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 thereof and a polyhydric alcohol alone or a mixture thereof. 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.

[0086] The polyether polyols are not particularly limited, but examples thereof include polyether polyols obtained by adding alkylene oxides, either singly or in mixture, to polyhydric alcohols, either singly or in mixture, using an alkali metal hydroxide or a strongly basic catalyst; polyether polyols obtained by reacting alkylene oxides with polyamine compounds; and so-called polymer polyols obtained by polymerizing acrylamide or the like using the above polyethers as a medium.

[0087] Examples of alkali metals include lithium, sodium, and potassium.

[0088] Examples of the strong basic catalyst include alcoholates and alkylamines.

[0089] Examples of the polyhydric alcohol include the same ones as those exemplified above for the polyester polyols.

[0090] Examples of alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide.

[0091] Examples of polyamine compounds include ethylenediamines.

[0092] The acrylic polyols are not particularly limited, but examples thereof include copolymers of a single or a mixture of an ethylenically unsaturated bond-containing monomer having a hydroxyl group and a single or a mixture of other ethylenically unsaturated bond-containing monomers copolymerizable therewith.

[0093] 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.

[0094] 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.

[0095] Examples of acrylic acid 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.

[0096] 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.

[0097] Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, and itaconic acid.

[0098] Examples of unsaturated amides include acrylamide, methacrylamide, N,N-methylenebisacrylamide, diacetone acrylamide, diacetone methacrylamide, maleic acid amide, and maleimide.

[0099] Examples of vinyl monomers include glycidyl methacrylate, styrene, vinyltoluene, vinyl acetate, acrylonitrile, and dibutyl fumarate.

[0100] Examples of vinyl monomers having a hydrolyzable silyl group include vinyltrimethoxysilane, vinylmethyldimethoxysilane, and γ-(meth)acryloxypropyltrimethoxysilane.

[0101] Examples of polyolefin polyols include hydroxyl-terminated polybutadiene and hydrogenated products thereof.

[0102] (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 by, for example, mixing an excess of the isocyanate monomer, the polyol, and, if necessary, an alcohol other than the polyol, and, if necessary, adding a urethanization reaction catalyst.

[0103] Examples of the polyol include the same polyols as those exemplified above in the "polyol" section.

[0104] Examples of the alcohol other than the polyol include those exemplified in the above "Method for producing isocyanurate group-containing polyisocyanate" except for those exemplified in the above "Polyol".

[0105] The urethanization reaction catalyst is not particularly limited, but examples thereof include tin-based compounds, zinc-based compounds, and amine-based compounds.

[0106] The urethane 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.

[0107] When the urethanization reaction temperature is equal to or lower than the upper limit, coloration of the polyisocyanate tends to be more effectively suppressed.

[0108] The urethane reaction time is preferably 30 minutes to 4 hours, more preferably 1 hour to 3 hours, and even more preferably 1 hour to 2 hours.

[0109] The molar ratio of the isocyanate groups of the isocyanate monomer to the molar amount of hydroxyl groups of the polyol (and, if necessary, alcohol other than the polyol) is preferably 2 / 1 or more and 50 / 1 or less. When this molar ratio is equal to or more than the above-mentioned lower limit, the viscosity of the polyisocyanate can be made lower. When this molar ratio is equal to or less than the above-mentioned upper limit, the yield of the urethane group-containing polyisocyanate can be made higher.

[0110] (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, but examples thereof include water, monohydric tertiary alcohols, formic acid, organic primary monoamines, and organic primary diamines. The amount of isocyanate groups per mole of biuretizing agent is preferably 6 moles or more, more preferably 10 moles or more, and even more preferably 10 moles or more but 80 moles or less. When the molar amount of isocyanate groups per mole of biuretizing agent is equal to or greater than the above-mentioned lower limit, the viscosity of the polyisocyanate becomes sufficiently low, and when it is equal to or less than the above-mentioned upper limit, the low-temperature curing property of the resin film formed is further improved.

[0111] A solvent may be used in the biuretization reaction, as long as it dissolves the isocyanate monomer and the biuretization agent such as water and forms a homogeneous phase under the reaction conditions.

[0112] Specific examples of the solvent include ethylene glycol-based solvents and phosphoric acid-based solvents.

[0113] 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, and diethylene glycol isopropyl-n-butyl ether.

[0114] Examples of the phosphoric acid solvent include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, and tributyl phosphate.

[0115] 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.

[0116] As the phosphoric acid-based solvent, trimethyl phosphate or triethyl phosphate is preferred.

[0117] The biuretization reaction temperature is preferably 70° C. or higher and 200° C. or lower, and more preferably 90° C. or higher and 180° C. or lower. By keeping the temperature at or below the upper limit, coloration of the polyisocyanate tends to be more effectively prevented.

[0118] 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 sequentially, or some of them may be carried out in parallel. After the reaction is completed, unreacted isocyanate monomer can be removed from the reaction mixture by thin film distillation, extraction, or the like to obtain a polyisocyanate.

[0119] 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 antioxidants include hindered phenols such as 2,6-di-tert-butyl-p-cresol. Examples of ultraviolet absorbers include benzotriazole and benzophenone. These antioxidants and ultraviolet absorbers may be used alone or in combination of two or more. The amount of these added is preferably 10 ppm by mass or more and 500 ppm by mass or less relative to the mass of polyisocyanate.

[0120] (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 curability at low temperatures of 100°C or less, and from the viewpoint of achieving both curability at low temperatures of 100°C or less and compatibility with the polyvalent 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.

[0121] (hydrophilic compound) The polyisocyanate may be a hydrophilic compound-modified polyisocyanate obtained by modifying a portion of the polyisocyanate with a hydrophilic compound.

[0122] 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.

[0123] Specific examples of nonionic hydrophilic compounds include monoalcohols and compounds in which ethylene oxide is added to the hydroxyl group of an alcohol. Examples of monoalcohols include methanol, ethanol, and butanol. Examples of compounds in which ethylene oxide is added to the hydroxyl group of an alcohol include ethylene glycol, diethylene glycol, and polyethylene glycol. These nonionic hydrophilic compounds also have active hydrogen groups that react with isocyanate groups.

[0124] Among these, polyethylene glycol monoalkyl ethers in which ethylene oxide is added to the hydroxyl group of a monoalcohol are preferred as the nonionic hydrophilic compound, since they can improve the water dispersibility of the blocked polyisocyanate composition even with a small amount used.

[0125] The number of ethylene oxide addition units in the ethylene oxide-added compound is preferably 4 or more and 30 or less, and more preferably 4 or more and 25 or less. When the number of ethylene oxide addition units is equal to or more than the above-mentioned lower limit, water dispersibility tends to be more effectively imparted to the blocked polyisocyanate composition, and when the number of ethylene oxide addition units is equal to or less than the above-mentioned upper limit, the blocked polyisocyanate composition tends to be less likely to precipitate during low-temperature storage.

[0126] Specific examples of cationic hydrophilic compounds include compounds having both cationic hydrophilic groups and active hydrogen groups.Also, a compound having an active hydrogen group such as a glycidyl group and a compound having a cationic hydrophilic group such as sulfide or phosphine may be used as a hydrophilic compound.In this case, a compound having an isocyanate group and a compound having an active hydrogen group are reacted in advance to add a functional group such as a glycidyl group, and then a compound such as sulfide or phosphine is reacted.From the viewpoint of ease of production, a compound having both cationic hydrophilic groups and active hydrogen groups is preferred.

[0127] Specific examples of compounds having both a cationic hydrophilic group and an active hydrogen group include dimethylethanolamine, diethylethanolamine, diethanolamine, methyldiethanolamine, etc. Tertiary amino groups added using these compounds can also be quaternized with, for example, dimethyl sulfate or diethyl sulfate.

[0128] 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.

[0129] 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 phosphate group, a halogen group, or a sulfate group.

[0130] Specific examples of compounds having a carboxy group include formic acid, acetic acid, propionic acid, butyric acid, and lactic acid.

[0131] Specific examples of compounds having a sulfonic acid group include ethanesulfonic acid.

[0132] Specific examples of compounds having a phosphate group include phosphoric acid and acidic phosphate esters.

[0133] Specific examples of compounds having a halogen group include hydrochloric acid.

[0134] Specific examples of compounds having a sulfate group include sulfuric acid.

[0135] Among these, compounds having an anionic group are preferably compounds having a carboxy group, and more preferably acetic acid, propionic acid or butyric acid.

[0136] Specific examples of the anionic hydrophilic group include a carboxy group, a sulfonic acid group, a phosphate group, a halogen group, and a sulfate group.

[0137] Specific examples of anionic hydrophilic compounds 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.

[0138] Examples of monohydroxycarboxylic acids include 1-hydroxyacetic acid, 3-hydroxypropanoic acid, 12-hydroxy-9-octadecanoic acid, hydroxypivalic acid, and lactic acid.

[0139] Examples of compounds having a carboxy group of a polyhydroxycarboxylic acid as an anionic group include dimethylolacetic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolpentanoic acid, dihydroxysuccinic acid, and dimethylolpropionic acid.

[0140] 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.

[0141] Among these, hydroxypivalic acid or dimethylolpropionic acid is preferred as a compound having both an anionic group and an active hydrogen group.

[0142] The anionic hydrophilic group added to the blocked polyisocyanate is preferably neutralized with an amine compound, which is a basic substance.

[0143] Specific examples of the amine compound include ammonia and water-soluble amino compounds.

[0144] 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. 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.

[0145] [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 a combination of two or more types.

[0146] 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 these, diethyl malonate is preferred as the malonic acid ester having a primary alkyl group.

[0147] 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 these, diisopropyl malonate is preferred as the malonic acid ester having a secondary alkyl group.

[0148] 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. The malonic acid ester having a tertiary alkyl group may be a commercially available product, or may be synthesized by the method described in Reference Document 1 (JP-A-11-130728).

[0149] Based on the total molar amount of all blocking agents used in producing the blocked polyisocyanate (B), 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 ensuring that the contents of the malonic acid ester having a secondary alkyl group and the malonic acid ester having a tertiary alkyl group are within the above ranges, it is possible to further improve the curability at low temperatures of 100°C or less.

[0150] (Other blocking agents) The blocking agent used in producing the blocked polyisocyanate (B) may further contain other blocking agents in addition to the malonic acid ester, as long as the effects achieved by the blocked polyisocyanate composition of the present embodiment are not impaired.

[0151] Examples of other blocking agents include 1) alcohol-based compounds, 2) alkylphenol-based compounds, 3) phenol-based compounds, 4) active methylene-based compounds other than malonic acid esters, 5) mercaptan-based compounds, 6) acid amide-based compounds, 7) acid imide-based compounds, 8) imidazole-based compounds, 9) urea-based compounds, 10) oxime-based compounds, 11) amine-based compounds, 12) imide-based compounds, 13) bisulfites, 14) pyrazole-based compounds, 15) triazole-based compounds, etc. More specific examples of blocking agents include the following:

[0152] 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 mono-alkylphenols such as n-propylphenol, iso-propylphenol, n-butylphenol, sec-butylphenol, tert-butylphenol, n-hexylphenol, 2-ethylhexylphenol, n-octylphenol, and n-nonylphenol; and 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.

[0153] [Method for producing blocked polyisocyanate (B)] The blocked polyisocyanate (B) can be obtained by reacting the above polyisocyanate (or the hydrophilic group compound-modified polyisocyanate) with the above blocking agent.

[0154] 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 preferred to carry out the reaction between the polyisocyanate and the hydrophilic compound first to obtain a hydrophilic compound-modified polyisocyanate modified with the hydrophilic compound, and then to react the obtained hydrophilic compound-modified polyisocyanate with the blocking agent.

[0155] The reaction between polyisocyanate and 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 metals constituting the organic metal salt include tin, zinc, and lead. Examples of the alkali metal include sodium.

[0156] The reaction temperature between the polyisocyanate and the hydrophilic compound is preferably −20° C. or higher and 150° C. or lower, and more preferably 30° C. or higher and 130° C. or lower. When the reaction temperature is equal to or higher than the lower limit, reactivity tends to be increased. Furthermore, when the reaction temperature is equal to or lower than the upper limit, side reactions tend to be more effectively suppressed.

[0157] It is preferable to completely react the hydrophilic compound with the polyisocyanate so that no unreacted hydrophilic compound remains, which tends to more effectively prevent the aqueous dispersion stability of the blocked polyisocyanate composition and the deterioration of curability at low temperatures of 100°C or less.

[0158] 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, an alcohol having a chain alkyl group is added to the obtained reaction product, and an alkyl group derived from the alcohol is introduced by transesterification of the terminal ester moiety of the reaction product.

[0159] Of the two methods above, method 2) is preferred, taking into consideration the ease of the process and the ease of controlling the molar ratio of structural unit (II) / structural unit (I).

[0160] The blocking reaction between the polyisocyanate and the blocking agent can be carried out regardless of the presence or absence of a solvent, and a blocked polyisocyanate is obtained.

[0161] As the blocking agent, one type of malonic acid ester may be used, or two or more types may be used in combination.

[0162] 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.

[0163] Furthermore, 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 (secondary alkyl malonic acid ester / tertiary alkyl malonic acid ester) 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. When the molar ratio is equal to or greater than the lower limit, the hardness of the resin film formed can be improved, and when the molar ratio is equal to or less than the upper limit, the curability at low temperatures of 100°C or less can be improved.

[0164] 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 nonvolatile components 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.

[0165] In the blocking reaction, organic metal salts of tin, zinc, lead, etc., tertiary amine compounds, alcoholates of alkali metals such as sodium, etc., may be used as catalysts. The amount of catalyst added varies depending on the temperature of the blocking reaction, etc., but is usually from 0.05 to 1.5 parts by mass, preferably from 0.1 to 1.0 part by mass, per 100 parts by mass of polyisocyanate.

[0166] The blocking reaction can generally be carried out at a temperature of −20° C. or higher and 150° C. or lower, preferably at a temperature of 0° C. or higher and 100° C. or lower, and more preferably at a temperature of 10° C. or higher and 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.

[0167] 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 inorganic acids include hydrochloric acid, phosphorous acid, and phosphoric acid. Examples of organic acids include methanesulfonic acid, p-toluenesulfonic acid, dioctyl phthalate, and dibutyl phthalate.

[0168] When the polyisocyanate is produced by the above method 2), the blocking reaction is followed by an ester exchange reaction. The alcohol having a chain alkyl group used in the transesterification reaction of 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.

[0169] The chain alkyl group of the alcohol may be the same as or different from that of the malonic acid ester. When the alcohol has 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.

[0170] When producing by 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 these, in order to efficiently proceed with the transesterification reaction, it is preferable to remove the generated alcohol by performing an operation such as distillation during the transesterification reaction. 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.

[0171] The transesterification reaction can generally be carried out at a temperature of 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. When the temperature of the transesterification reaction is equal to or higher than the lower limit, the reaction rate can be further increased, and when the temperature is equal to or lower than the upper limit, side reactions can be further suppressed.

[0172] The content of alcohol in the blocked polyisocyanate composition is preferably 0.05 to 41 parts by mass, more preferably 0.1 to 30 parts by mass, and even more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the solids content of the blocked polyisocyanate composition. When the alcohol content is equal to or greater than the lower limit, the storage stability of the coating material is improved, and when the alcohol content is equal to or less than the upper limit, thickening during formulation of the coating material can be suppressed. Note that the "content of alcohol in the blocked polyisocyanate composition" herein refers to the amount of alcohol remaining in the blocked polyisocyanate composition as a simple compound.

[0173] <Melamine resin (M)> Melamine resin (M) generally refers to a thermosetting resin synthesized from melamine and aldehyde, and contains three reactive functional groups -NX in one triazine nucleus molecule. 1 X 2 It has.

[0174] Examples of melamine resins (M) include four types: a fully alkyl type containing -N-(CH2OR)2 (R is an alkyl group, the same applies 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 -N-(CH2OH)(H) as reactive functional groups.

[0175] The melamine resin (M) may be a partially methylolated melamine resin or a fully methylolated melamine resin obtained by reacting a melamine component with an aldehyde component, such as formaldehyde, paraformaldehyde, acetaldehyde, or benzaldehyde.

[0176] Alternatively, the methylolated melamine resin may be partially or completely etherified with an appropriate alcohol, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethyl-1-butanol, or 2-ethyl-1-hexanol.

[0177] The melamine resin (M) is preferably a methyl-etherified melamine resin in which the methylol groups of a partially or fully methylolated melamine resin have been 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 have been 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 have been partially or completely etherified with methyl alcohol and butyl alcohol, and more preferably a methyl-butyl mixed etherified melamine resin.

[0178] The weight average molecular weight of the melamine resin 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 measured by gel permeation chromatography (GPC) using polystyrene as a standard.

[0179] Commercially available melamine resins can be used. Examples of 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); "Uvan 120", "Uvan 20HS", "Uvan 20SE", "Uvan 2021", "Uvan 2028", and "Uvan 28-60" (all manufactured by Mitsui Chemicals, Inc.); and "Sumimar M55", "Sumimar M30W", and "Sumimar M50W" (all manufactured by Sumitomo Chemical Co., Ltd.).

[0180] The content of the solid content of the melamine resin (M) relative to 100% by mass of the solid content of the blocked polyisocyanate composition is not particularly limited, but is preferably from 1% by mass to 50% by mass, more preferably from 5% by mass to 40% by mass, and even more preferably from 10% by mass to 30% by mass. When the solid content of the melamine resin (M) is equal to or greater than the above lower limit, the hardness of the obtained resin film tends to be higher, while when the solid content is equal to or less than the above upper limit, the chemical resistance of the obtained resin film tends to be improved.

[0181] <Other components> The blocked polyisocyanate composition of the present embodiment may further contain additives such as a solvent in addition to the blocked polyisocyanate (B) and the melamine resin (M).

[0182] 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 suitable solvents include ethanol, methyl isobutyl ketone, propylene glycol monomethyl ether acetate, ethanol, methanol, isopropanol, 1-propanol, isobutanol, 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, isopentane, hexane, isohexane, 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 preferably has a solubility in water of 5% by mass or more, and specifically, DPDM is preferred.

[0183] <Method for producing blocked polyisocyanate composition> The blocked polyisocyanate composition is not particularly limited, but can be obtained, for example, by mixing the blocked isocyanate (B) and the melamine resin (M). The melamine resin (M) may be added during or after the blocking reaction. The temperature at which the blocked isocyanate (B) and the melamine resin (M) are mixed is not particularly limited, but is preferably 20°C or higher and 100°C or lower. When the reaction temperature is equal to or higher than the lower limit, the hardness tends to be higher. When the reaction temperature is equal to or lower than the upper limit, side reactions tend to be more effectively suppressed.

[0184] ≪Resin composition≫ The resin composition of the present embodiment includes the above-described blocked polyisocyanate composition and a polyvalent hydroxy compound. The resin composition of the present embodiment can also be referred to as a one-component resin composition including a curing agent component and a main component.

[0185] The resin composition of the present embodiment contains the above-described blocked polyisocyanate composition, and therefore 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 and chemical resistance.

[0186] The components of the resin composition of this embodiment will be described in detail below.

[0187] <Polyhydroxy compounds> In this specification, the term "polyhydroxy compound" refers to a compound having at least two hydroxy groups (hydroxyl groups) in one molecule, and is also called a "polyol."

[0188] 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.

[0189] [Aliphatic hydrocarbon polyols] Examples of the aliphatic hydrocarbon polyols include hydroxyl-terminated polybutadiene and hydrogenated products thereof.

[0190] [Polyether polyols] Examples of the polyether polyols include those obtained by any of the following methods (1) to (3). (1) Polyether polyols or polytetramethylene glycols obtained by adding alkylene oxides, either singly or in mixture, to polyhydric alcohols, either singly or in 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.

[0191] [Polyester polyols] Examples of the polyester polyols include the following polyester polyols (1) and (2). (1) Polyester polyol resins obtained by the condensation reaction of a dibasic acid, either alone or in a mixture of two or more kinds, with 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 succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and other carboxylic acids. 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.

[0192] [Epoxy resins] Examples of the epoxy resins include novolac-type epoxy resins, β-methylepicro-type 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 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.

[0193] [Fluorine-containing polyols] Examples of the fluorine-containing polyols include copolymers of fluoroolefins, cyclohexyl vinyl ethers, hydroxyalkyl vinyl ethers, and monocarboxylic acid vinyl esters, which are disclosed in Reference Document 2 (JP-A-57-34107) and Reference Document 3 (JP-A-61-275311).

[0194] [Acrylic polyols] The acrylic polyols can be obtained, for example, by polymerizing a polymerizable monomer having one or more active hydrogen atoms in one molecule, or by copolymerizing a polymerizable monomer having one or more active hydrogen atoms in one molecule with, as necessary, another monomer copolymerizable with the polymerizable monomer.

[0195] Examples of the polymerizable monomer having one or more active hydrogen atoms in one molecule include the following (i) to (iii), which may be used singly or in combination of two or more. (i) Acrylic acid esters having active hydrogen, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxybutyl acrylate. (ii) Methacrylates 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.

[0196] Examples of other monomers copolymerizable with the polymerizable monomer include the following (i) to (v), which may be used singly or in combination of two or more. (i) Acrylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate. (ii) Methacrylates 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-methylolacrylamide, and diacetoneacrylamide. (v) Styrene, vinyl toluene, vinyl acetate, acrylonitrile, etc.

[0197] Other examples include acrylic polyols obtained by copolymerizing polymerizable ultraviolet-stable monomers disclosed in Reference 4 (JP-A No. 1-261409) and Reference 5 (JP-A No. 3-006273).

[0198] 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.

[0199] 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 or the like as necessary to obtain an acrylic polyol.

[0200] Aqueous-based acrylic polyols can be produced by known methods such as solution polymerization of an olefinically unsaturated compound followed by conversion into an aqueous phase, 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, with an amine or ammonia.

[0201] [Hydroxyl value and acid value of polyhydroxy 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 excellent physical properties such as tensile strength can be obtained. Specifically, when the hydroxyl group content of the polyvalent hydroxy compound is equal to or greater than the above lower limit, the crosslink density of the urethane formed by the reaction with the polyisocyanate is increased, making it easier for the urethane bond to function. On the other hand, when the hydroxyl group content of the polyvalent hydroxy compound is equal to or less than the above upper limit, the crosslink density is not increased too much, resulting in better mechanical properties of the resin film. 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 of the polyvalent hydroxy compound.

[0202] [Glass transition temperature Tg of polyhydroxy compounds] The glass transition temperature Tg of the polyhydroxy compound contained in the resin composition of this embodiment is preferably 0°C or higher and 100°C or lower, more preferably 0°C or higher and 90°C or lower, even more preferably 0°C or higher and 80°C or lower, and particularly preferably 5°C or higher and 70°C or lower. When the glass transition temperature of the polyhydroxy compound is within the above range, a resin film with superior tensile strength can be obtained. The glass transition temperature of the polyhydroxy compound can be measured, for example, using a differential scanning calorimetry (DSC) measurement device.

[0203] [Weight-average molecular weight Mw of polyhydroxy compound] The weight average molecular weight Mw of the polyhydroxy compound is 5.0 × 10 3 Over 2.0 x 10 5 Preferably, it is 5.0 x 10 or less. 3 Over 1.5 x 10 5 More preferably, it is 5.0×10 or less. 3 Over 1.0 x 10 5It is more preferable that the weight-average molecular weight Mw of the polyhydroxy compound is within the above range, thereby obtaining a resin film having excellent physical properties such as tensile strength. The weight-average molecular weight Mw of the polyhydroxy compound is the weight-average molecular weight based on polystyrene as measured by gel permeation chromatography (GPC).

[0204] [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 required physical properties of the resin film, but 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.

[0205] [Blocked polyisocyanate composition content] In the resin composition of this embodiment, the content of the blocked polyisocyanate (B) may be any amount such that the molar equivalent ratio of the isocyanate groups of the blocked polyisocyanate (B) to the hydroxyl groups of the polyhydroxy compound falls within the above-mentioned range. For example, the content is preferably 1 part by mass to 200 parts by mass, more preferably 5 parts by mass to 180 parts by mass, and even more preferably 10 parts by mass to 150 parts by mass, per 100 parts by mass of the polyhydroxy compound. By ensuring that the content of the blocked polyisocyanate (B) falls within the above-mentioned range, a resin film having superior physical properties such as tensile strength can be obtained. The content of the blocked polyisocyanate (B) can be calculated from the blend amount, or can be calculated by identifying and quantifying the blocked polyisocyanate using nuclear magnetic resonance (NMR) and gas chromatography / mass spectrometry (GC / MS).

[0206] <Other additives> The resin composition of the present embodiment may further contain other additives. Examples of other additives include 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, anti-yellowing agents that suppress coloring during the baking process, coating surface conditioners, flow conditioners, pigment dispersants, antifoaming agents, thickeners, film-forming aids, etc.

[0207] 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.

[0208] The curing catalyst may be a basic compound or a Lewis acid compound.

[0209] 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. The onium salt is preferably an ammonium salt, a phosphonium salt, or a sulfonium salt.

[0210] Examples of the Lewis acid compound include organotin compounds, organozinc compounds, organotitanium compounds, and organozirconium compounds.

[0211] Examples of the solvent include the same solvents as those exemplified for the blocked polyisocyanate composition.

[0212] In addition, known pigments (extender pigments, colored pigments, metallic pigments, etc.), ultraviolet absorbers, light stabilizers, radical stabilizers, anti-yellowing agents that suppress coloring during the baking process, coating surface conditioners, flow conditioners, pigment dispersants, antifoaming agents, thickeners, and film-forming aids can be appropriately selected and used.

[0213] <Method of manufacturing resin composition> The resin composition of this embodiment can be used as either a solvent-based or water-based composition.

[0214] When producing an aqueous resin composition (waterborne resin composition), first, additives such as a curing agent capable of reacting with the crosslinkable functional group in the polyhydroxy compound, a curing catalyst, a solvent, pigments (extender pigments, colored pigments, metallic pigments, etc.), UV absorbers, light stabilizers, radical stabilizers, anti-yellowing agents that suppress discoloration during the baking process, coating surface conditioners, flow control agents, pigment dispersants, antifoaming agents, thickeners, and film-forming aids are added to the polyhydroxy compound or its aqueous dispersion or solution, as needed. Next, the blocked polyisocyanate composition or its aqueous dispersion is added as a curing agent, and if necessary, water or a solvent is further added to adjust the viscosity. Next, the mixture is forcedly stirred with a stirring device to obtain an aqueous resin composition (waterborne resin composition).

[0215] When producing a solvent-based resin composition, first, additives such as a curing agent capable of reacting with the crosslinkable functional group in the polyhydroxy compound, a curing catalyst, a solvent, pigments (extender pigments, colored pigments, metallic pigments, etc.), UV absorbers, light stabilizers, radical stabilizers, anti-yellowing agents that suppress discoloration during the baking process, coating surface conditioners, flow conditioners, pigment dispersants, defoamers, thickeners, and film-forming aids are added to the polyhydroxy compound or its solvent dilution, as needed. Next, the above-mentioned blocked polyisocyanate composition is added as a curing agent, and if necessary, a solvent is further added to adjust the viscosity. Next, the mixture is stirred by hand or using a stirring device such as a mixer to obtain a solvent-based resin composition.

[0216] <Resin film> The resin film of this embodiment is formed by curing the resin composition, and has excellent hardness and chemical resistance.

[0217] The resin film of this 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, or electrostatic coating, and then curing it by heating.

[0218] From the viewpoint of energy saving and heat resistance of the substrate, 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.

[0219] The heating time is preferably from 1 minute to 60 minutes, more preferably from 2 minutes to 40 minutes, from the viewpoint of energy saving and heat resistance of the substrate.

[0220] 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 which outer panels of automobile bodies or automobile parts are preferred.

[0221] 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; plastic materials such as various FRPs; inorganic materials such as glass, cement, and concrete; wood; and fibrous materials such as paper and cloth. Of these, metal materials and plastic materials are preferred.

[0222] The substrate may be the surface of the above-mentioned metal material, or the surface of a metal such as a car body molded from the above-mentioned metal material, which has been subjected to a surface treatment such as phosphate treatment, chromate treatment, or composite oxide treatment, and further, may have a coating film formed thereon. The substrate with a coating film formed thereon may be one that has been subjected to a surface treatment as necessary and then a primer coating film formed thereon, for example, a car body on which a primer coating film has been formed using an electrodeposition paint. The substrate may be the surface of the above-mentioned plastic material, or the surface of a plastic such as an automobile part molded from the above-mentioned metal material, which has been subjected to a desired surface treatment. The substrate may also be a combination of a plastic material and a metal material.

[0223] The resin film of this embodiment has excellent curing properties at low temperatures of 100° C. or less, and is therefore suitable for use as a coating film for products in various fields where energy conservation is required, or for materials with low heat resistance.

[0224] <Laminate> The laminate of this embodiment is formed by laminating one or more of the above-described resin films on a substrate. The thickness of each resin film layer is 1 μm or more and 50 μm or less.

[0225] The laminate of the present embodiment includes the resin film, and therefore has excellent hardness and chemical resistance.

[0226] The laminate of this 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.

[0227] Examples of the substrate include the same materials as those exemplified above for the "resin film."

[0228] The laminate of the present embodiment can be obtained by coating the resin composition on a substrate using a known method such as roll coating, curtain flow coating, spray coating, bell coating, or electrostatic coating, and then heating and curing the composition, or by coating all layers and then heating and curing the layers together.

[0229] The laminate of the present embodiment may include, in addition to the substrate and the resin film, other layers made of known components, such as a primer layer, an adhesive layer, and a decorative layer. [Example]

[0230] The present embodiment will be described in more detail below based on examples and comparative examples, but the present embodiment is not limited to the following examples in any way. In the following, Example 1 will be referred to as Reference Example 1.

[0231] <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.

[0232] [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 into a flask (Wg). Next, 20 mL of toluene was added to dissolve the measurement sample. Next, 20 mL of a 2 N toluene solution of di-n-butylamine was added, mixed, and left at room temperature for 15 minutes. Next, 70 mL of isopropyl alcohol was added and mixed. Next, this liquid was titrated with a 1 N hydrochloric acid solution (factor F) as an indicator. The obtained titration value was V2 mL. Next, the titration value obtained without the polyisocyanate sample was V1 mL. Next, the isocyanate group (NCO) content (mass%) of the polyisocyanate was calculated using the following formula.

[0233] Isocyanate group (NCO) content (mass%) = (V1 - V2) x F x 42 / (W x 1000) x 100

[0234] The effective NCO content of the blocked isocyanate (B) was calculated by the following formula.

[0235] Effective NCO content [mass%] = {100 × (mass of isocyanate groups in the solid content of the polyisocyanate used in the blocking reaction)} / (mass of blocked polyisocyanate (B) after the blocking reaction)

[0236] [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 equipment, using polystyrene standards. 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.

[0237] (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

[0238] [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 "Property 2" above was used. "NCO content" is the isocyanate group content of the polyisocyanate measured before blocking with a blocking agent, and the value calculated in "Property 1" above was used.

[0239] Average number of isocyanate groups = (Mn × NCO content × 0.01) / 42

[0240] [Physical Properties 4] (Solid content of blocked polyisocyanate (B)) The solid content of the blocked polyisocyanate (B) was determined as follows. First, an aluminum dish with a bottom diameter of 38 mm was precisely weighed. Then, approximately 1 g of the blocked polyisocyanate (B) produced in the Examples and Comparative Examples was placed on the aluminum dish and precisely weighed (W1). The blocked polyisocyanate (B) was then adjusted to a uniform thickness. The blocked polyisocyanate (B) placed on the aluminum dish was then kept in an oven at 105°C for 1 hour. After the aluminum dish returned to room temperature, the blocked polyisocyanate (B) remaining on the aluminum dish was precisely weighed (W2). The solids content (% by mass) of the blocked polyisocyanate (B) was then calculated using the following formula:

[0241] Solid content of blocked polyisocyanate (B) (mass%) = W2 / W1 × 100

[0242] [Physical Properties 5] (Content (mol) of structural unit (I)) The content of the structural unit (I) in the blocked polyisocyanate (B) is determined under the following conditions: 13 Calculated by C-NMR.

[0243] (Measurement conditions) Device: JEOL “JEOL-ECZ500(SC)” (product name) Solvent: deuterated chloroform Accumulation count: 5120 times Sample concentration: 50 wt / vol% Chemical shift standard: deuterated chloroform was used as 77.0 ppm.

[0244] [Physical Properties 6] (Content of structural unit (I-1) relative to total molar amount of structural unit (I)) The content (mol %) of the structural unit (I-1) relative to the total molar amount of the structural unit (I) in the blocked polyisocyanate (B) was calculated using the method shown below.

[0245] Specifically, we used the JEOL-ECZ500 (SC) (product name) manufactured by JEOL. 13 The total molar amount of the structural unit (I) (including the structural unit (I-1)) and the molar amount of the structural unit (I-1) were calculated by C-NMR measurement, and the molar ratio was determined.

[0246] (Measurement conditions) Device: JEOL “JEOL-ECZ500(SC)” (product name) Solvent: deuterated chloroform Accumulation count: 5120 times Sample concentration: 50 wt / vol% Chemical shift standard: deuterated chloroform was used as 77.0 ppm.

[0247] [Physical Properties 7] (molar ratio of structural unit (II) / structural unit (I)) The molar ratio of the structural unit (II) to the structural unit (I) (structural unit (II) / structural unit (I)) is determined by removing the solvent and other components from the blocked polyisocyanate (B) using an evaporator at 50°C or less, drying under reduced pressure, and then 13 The molar ratio of the structural unit (II) to the structural unit (I) was calculated by measuring the composition ratio of the structural unit (II) to the structural unit (I) by C-NMR.

[0248] (Measurement conditions) Device: JEOL “JEOL-ECZ500(SC)” (product name) Solvent: deuterated chloroform Accumulation count: 5120 times Sample concentration: 50 wt / vol% Chemical shift standard: deuterated chloroform was used as 77.0 ppm.

[0249] [Preparation of resin composition] Acrylic polyol (manufactured by Allnex, "Setalux (registered trademark) 1767" (trade name), hydroxyl value 150 mg KOH / g resin, solid content 65% by 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% by mass, thereby obtaining a resin composition.

[0250] [Rating 1] (Low temperature curing) The resin composition obtained in the above "Preparation of Resin Composition" was applied to a polypropylene (PP) plate to a dry film thickness of 40 μm, and then heated and dried at 100°C for 30 minutes to obtain a resin film. The obtained resin film was immersed in acetone at 23°C for 24 hours, and the gel fraction was calculated as the percentage (mass%) of the undissolved portion mass divided by the mass before immersion. The calculated gel fraction was used to evaluate low-temperature curability according to the following evaluation criteria.

[0251] (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

[0252] [Rating 2] (Coating film hardness (Konig 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 König hardness (cycles) in an environment of 23°C using a König hardness tester (Pendulum hardness tester from BYK Gardner). The measured König hardness (cycles) was evaluated according to the following evaluation criteria.

[0253] (Evaluation criteria) A: More than 60 times B: 30 to less than 60 times C: Less than 30 times

[0254] [Rating 3] (Chemical resistance (acid resistance)) Five minutes after preparation, the resin composition was applied to a glass plate with an applicator to a dry film thickness of 40 μm, and then baked at 100°C for 30 minutes to obtain a resin film. 0.5 mL of 0.1 mmol / L aqueous sulfuric acid solution was added to the resulting resin film, which was then heated at 40°C for 30 minutes. After cooling, the glass plate was lightly rinsed with water and wiped with a flannel cloth. The condition of the coating film was confirmed, and the chemical resistance (acid resistance) was evaluated according to the following evaluation criteria.

[0255] (Evaluation criteria) A: No change in the appearance of the coating B: Linear marks around the dripped area of ​​the coating film 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 coating film

[0256] <Synthesis of Polyisocyanate> [Synthesis Example 1] (Synthesis of Polyisocyanate P-1) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was charged with 100 parts by mass of HDI and 5.3 parts by mass of a polyester polyol (polycaprolactone triol) derived from a trihydric alcohol and ε-caprolactone (Daicel Chemical Industries, Ltd., "PLACCEL 303" (trade name), average functionality: 3, number-average molecular weight: 300) under a nitrogen stream. The temperature inside the reactor was maintained at 89°C for 1 hour while stirring, allowing for a urethane reaction. The temperature inside the reactor was then maintained at 63°C, and an isocyanuration catalyst, tetramethylammonium caprylate, was added. When the yield reached 52% by mass, phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI was removed using a thin-film evaporator to obtain an isocyanurate-type polyisocyanate (hereinafter sometimes referred to as "polyisocyanate P-1").

[0257] 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.

[0258] <Production of Blocked Polyisocyanate (B)> [Synthesis Example 2-1] (Production of Blocked Polyisocyanate B-1) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was charged with 100 parts by mass of the polyisocyanate P-1 obtained in Synthesis Example 1 (102 mol % relative to 100 mol % di-tert-butyl malonate) under a nitrogen stream, and dipropylene glycol dimethyl ether (DPDM) was added to adjust the solids 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 added dropwise with stirring, and the external bath was adjusted so that the solution temperature was 55°C. A blocking reaction was carried out at 55°C for 5 hours to obtain a blocked polyisocyanate B-1-containing solution with a solids content of 60% by mass.

[0259] [Synthesis Example 2-2] (Production of Blocked Polyisocyanate B-2) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was charged with 100 parts by weight of the polyisocyanate P-1 obtained in Synthesis Example 1, diisopropyl malonate (70 mol % relative to 100 mol % of NCO groups), and (2-methyl-2-butyl)isopropyl malonate (30 mol % relative to 100 mol % of NCO groups) under a nitrogen stream. Dipropylene glycol dimethyl ether (DPDM) was then added dropwise to the mixture to obtain a solids content of 60% by weight. Next, 0.8 parts by weight of a methanol solution containing sodium methylate (28% by weight relative to the total weight of the solution) was added dropwise with stirring. The external bath was then adjusted to a solution temperature of 55°C, and the blocking reaction was carried out at 55°C for 5 hours to obtain a blocked polyisocyanate B-2-containing solution with a solids content of 60% by weight.

[0260] [Synthesis Example 2-3] (Production of Blocked Polyisocyanate B-3) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was charged with 100 parts by weight of the polyisocyanate P-1 obtained in Synthesis Example 1 and diisopropyl malonate (102 mol % relative to 100 mol % NCO groups) under a nitrogen stream. Dipropylene glycol dimethyl ether (DPDM) was then added to adjust the solids content to 60% by weight. Next, 0.8 parts by weight of a methanol solution containing sodium methylate (28% by weight relative to the total weight of the solution) was added dropwise with stirring. The external bath was then adjusted to a solution temperature of 55°C. The blocking reaction was carried out at 55°C for 5 hours, yielding a blocked polyisocyanate intermediate with a solids content of 60% by weight. 2-Methyl-2-butanol was then added to a concentration of 100 mol % relative to the blocked isocyanate groups, and the reaction was carried out at 80°C for 3 hours, while the generated isopropyl alcohol was removed by distillation under atmospheric 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 blocked polyisocyanate B-3-containing liquid.

[0261] [Synthesis Example 2-4] (Production of Blocked Polyisocyanate B-4) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was charged with 100 parts by mass of the polyisocyanate P-1 obtained in Synthesis Example 1 and diisopropyl malonate (102 mol % relative to 100 mol % NCO groups) under a nitrogen stream, and dipropylene glycol dimethyl ether (DPDM) was added to adjust the solids 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 added dropwise with stirring, and the external bath was adjusted so that the solution temperature was 55°C. A blocking reaction was carried out at 55°C for 5 hours to obtain a blocked polyisocyanate B-4-containing solution with a solids content of 60% by mass.

[0262] <Production of Blocked Polyisocyanate Composition> [Example 1] (Production 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 blocked polyisocyanate B-1-containing liquid obtained in Synthesis Example 2-1 and 27.8 parts by mass of melamine resin (trade name "Cymel (registered trademark) 327", manufactured by Allnex, solids content 90% by mass) under a nitrogen gas flow, and mixed at 30°C for 1 hour to obtain a blocked polyisocyanate composition BP-a1.

[0263] [Example 5] (Production of Blocked Polyisocyanate Composition BP-a5) A four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser was charged with 125 parts by mass of the blocked polyisocyanate B-3-containing liquid obtained in Synthesis Example 2-1 and 31.3 parts by mass of a melamine resin (trade name "Cymel (registered trademark) 350", manufactured by Allnex, solids content 80% by mass) under a nitrogen gas flow, and mixed at 30°C for 1 hour to obtain a blocked polyisocyanate composition BP-a5.

[0264] [Examples 2 to 4, 6 to 7 and Comparative Example 1] (Production of Blocked Polyisocyanate Compositions BP-a2 to BP-a4, BP-a6 to BP-a7, and BP-b1) Each blocked polyisocyanate composition was produced using the same method as in Example 1, except that the combinations and mixing ratios of the blocked polyisocyanate (B) and melamine resin (M) to be blended were as shown in the table below.

[0265] Comparative Example 2 (Production of Blocked Polyisocyanate Composition BP-b2) The blocked polyisocyanate B-3-containing liquid was used as it was as blocked polyisocyanate composition BP-b2.

[0266] Comparative Example 3 (Production of Composition X-1) A melamine resin (product name "Cymel 327", manufactured by Allnex, solid content 90% by mass) was used as it was as composition X-1.

[0267] The physical properties and evaluation results of each blocked polyisocyanate composition are shown in the following table, where "H" represents a hydrogen atom.

[0268] [Table 1]

[0269] [Table 2]

[0270] As shown in the above table, the blocked polyisocyanate compositions BP-a1 to BP-a7 (Examples 1 to 7), which contained a blocked polyisocyanate (B) having the structural unit (I) and a melamine resin (M), exhibited good low-temperature curing properties when formed into a resin composition, and good hardness and chemical resistance when formed into a resin film. Furthermore, in a comparison of blocked polyisocyanate compositions BP-a3 and BP-a4 (Examples 3 and 4) with different contents of melamine resin (M), 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 content of melamine resin (M) was 5% by mass or more and 25% by mass or less, the low-temperature curing property tended to be particularly excellent, when the content of melamine resin (M) was 25% by mass or more and 40% by mass or less, the hardness when formed into a resin film tended to be particularly excellent, and when the content of melamine resin (M) was 25% by mass, the chemical resistance when formed into a resin film tended to be particularly excellent. In a comparison of blocked polyisocyanate compositions BP-a3 and BP-a5 (Examples 3 and 5) containing different types of melamine resin (M), the composition using Cymel 327 tended to have particularly superior low-temperature curing properties.

[0271] On the other hand, with regard to the blocked polyisocyanate composition BP-b1 (Comparative Example 1) containing a blocked polyisocyanate that does not have the structural unit (I) and a melamine resin (M), the blocked polyisocyanate composition BP-b2 (Comparative Example 2) containing a blocked polyisocyanate (B) that has the structural unit (I) but does not contain a melamine resin (M), and the composition X-1 (Comparative Example 3) that does not contain a blocked polyisocyanate (B) that has the structural unit (I) but does contain a melamine resin (M), neither the low-temperature curing properties when made into a resin composition nor the hardness and chemical resistance when made into a resin film were good. [Industrial Applicability]

[0272] The blocked polyisocyanate composition of this embodiment can provide a blocked polyisocyanate composition that exhibits excellent curing properties when baked at 100°C and exhibits excellent hardness and chemical resistance when formed into a resin film. The resin composition of this embodiment contains the blocked polyisocyanate composition, exhibits excellent curing properties when baked at 100°C, and exhibits excellent hardness and chemical resistance when formed into a resin film. The resin film of this embodiment is formed by curing the resin composition and exhibits excellent hardness and chemical resistance. The laminate of this embodiment includes the resin film and exhibits excellent hardness and chemical resistance.

Claims

1. a blocked polyisocyanate (B) derived from a polyisocyanate and a blocking agent containing a malonic acid ester, the blocked polyisocyanate containing a structural unit represented by the following general formula (I-1-1) and a structural unit represented by the following general formula (I-1); a melamine resin (M); A blocked polyisocyanate composition comprising: 【Chemical 1】 In general formula (I-1-1), R 11 , R 12 , R 13 , R 14 , R 15 and R 16 each independently represent an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group. １１ , the R １２ and the R １３ The total number of carbon atoms is 3 or more and 20 or less. Wavy lines represent bonds.) 【Chemistry 2】 (In general formula (I-1), R 111 , R 112 and R 113 each independently represent an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group. The total number of carbon atoms in R 111 , R 112 and R 113 is 3 or more and 20 or less. R 114 and R 115 each independently represent a hydrogen atom or an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group. The wavy lines represent bonds.)

2. A blocked polyisocyanate (B) derived from a polyisocyanate and a blocking agent containing a malonic acid ester, the blocked polyisocyanate comprising a constituent unit represented by the following general formula (I) and a constituent unit represented by the following general formula (II); a melamine resin (M); A blocked polyisocyanate composition comprising: 【Chemistry 3】 In general formula (I), R 11 , R 12 and R 13 each independently represent an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group. The total number of carbon atoms of R 11 , R 12 and R 13 is 3 to 20. R 14 , R 15 and R 16 each independently represent a hydrogen atom or an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group. Wavy lines represent bonds. 【Chemistry 4】 (In general formula (II), R 21 , R 22 , R 23 and R 24 each independently represent a hydrogen atom or an alkyl group which may contain one or more substituents selected from the group consisting of a hydroxy group and an amino group. The wavy lines represent bonds, and represent bonding sites with residues of polyisocyanate excluding the isocyanate groups.) 3. The blocked polyisocyanate composition according to claim 1, wherein R 11 , R 12 , R 13 , R 14 , R 15 and R 16 are each independently an unsubstituted alkyl group.

4. The R 11 , R 12 and R 13 each independently represent an unsubstituted alkyl group, and The blocked polyisocyanate composition according to claim 2, wherein R 14 , R 15 and R 16 each independently represent a hydrogen atom or an unsubstituted alkyl group.

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

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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