Coating composition and method for producing resin film

Abstract

To provide a coating compound having good storage stability, and a method for producing a resin film using the coating composition.SOLUTION: A coating composition comprises a blocked polyisocyanate component, a polyol, and a dispersant having amine value. The blocked polyisocyanate component contains a blocked polyisocyanate derived from a polyisocyanate and one or more blocking agents. The blocked polyisocyanate component contains structural units represented by the general formula (I).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a coating composition and a method for producing a resin film. [Background technology]

[0002] Polyurethane resin paints are known to have excellent abrasion resistance, chemical resistance, and stain resistance. Polyurethane resin paints using polyisocyanates derived from aliphatic or alicyclic diisocyanates have even better weather resistance, and demand for them is on the rise. Generally, polyurethane resin paints are two-component. Two-component polyurethane resin paints consist of two components, polyol and polyisocyanate, which must be stored separately and mixed before application.

[0003] Furthermore, once mixed, the paint gels within a short time and becomes unusable. This makes automated painting extremely difficult in fields where line painting is performed, such as automobiles or low-voltage painting. Furthermore, since isocyanates react easily with water, they cannot be used in water-based paints such as electrodeposition paints. Furthermore, the need to thoroughly clean the paint sprayer and coating tank after work reduces work efficiency.

[0004] In order to overcome the above drawbacks, 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, but when heated, the blocking agent dissociates, and the active isocyanate groups are regenerated and react with polyols to cause a crosslinking reaction, thereby overcoming the above drawbacks. Many blocking agents have been investigated, and representative examples include phenol and methyl ethyl ketoxime.

[0005] Further, a method has been known in the past in which a blocked polyisocyanate using an active methylene compound such as acetoacetic ester or malonic acid diester as a blocking agent is blended into a coating composition (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-070151 [Patent Document 2] International Publication No. 2013 / 151143 Summary of the Invention [Problem to be solved by the invention]

[0007] The coating compositions described in Patent Documents 1 and 2 have room for improvement in terms of storage stability. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coating composition having good storage stability and a method for producing a resin film using the coating composition. [Means for solving the problem]

[0008] That is, the present invention includes the following aspects.

[0009] [1] A coating composition comprising a blocked polyisocyanate component, a polyol, and a dispersant having an amine value, wherein the blocked polyisocyanate component comprises a blocked polyisocyanate derived from a polyisocyanate and one or more blocking agents, and the blocked polyisocyanate component comprises a constituent unit represented by the following general formula (I): [ka] [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, and R 11 , R 12 and R 13 The total number of carbon atoms in R is 4 or more and 20 or less. 14 , R15 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.] [2] A coating composition comprising a blocked polyisocyanate component, a polyol, and a monohydric alcohol-based compound, wherein the blocked polyisocyanate component comprises a blocked polyisocyanate derived from a polyisocyanate and one or more blocking agents, and the blocked polyisocyanate component comprises a structural unit represented by the following general formula (I): [ka] [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, and R 11 , R 12 and R 13 The total number of carbon atoms in R is 4 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.] [3] A coating composition comprising a blocked polyisocyanate component, a polyol, and at least two types of basic compounds, wherein the blocked polyisocyanate component comprises a blocked polyisocyanate derived from a polyisocyanate and one or more blocking agents, and the blocked polyisocyanate component comprises a structural unit represented by the following general formula (I): [ka] [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, and R11 , R 12 and R 13 The total number of carbon atoms in R is 4 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.] [4] The coating composition according to [1], wherein the content of the dispersant having the amine value in the total amount of the coating composition is 0.1 mass % or more and 10 mass % or less. [5] The coating composition according to [1] or [2], wherein the amine value of the dispersant having an amine value is 15 mgKOH / g or more. [6] The coating composition according to any one of [1], [2], [4] and [5], further comprising a basic compound. [7] The blocked polyisocyanate component is R in the general formula (I). 16 The coating composition according to any one of [1] to [6], which contains a structural unit (I-1) in which is a hydrogen atom. [8] The coating composition according to any one of [1] to [7], wherein the average number of isocyanate groups in the polyisocyanate is 4.0 or more and 10.0 or less. [9] A step of applying the coating composition according to any one of [1] to [8]; and a step of heating the applied coating composition at a temperature of 50°C or higher and 100°C or lower for 5 minutes or longer and 1,440 minutes or shorter, or at a temperature of 105°C or higher and 200°C or lower for 5 seconds or longer and 900 seconds or shorter, to obtain a resin film. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a coating composition having good storage stability and a method for producing a resin film using the coating composition. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Paint composition> The coating composition of the present invention comprises a blocked polyisocyanate component, a polyol, and a dispersant having an amine value. The blocked polyisocyanate component containing the structural unit represented by general formula (I) exhibits a decrease in pH in the presence of water.

[0012] One aspect of the present invention is a coating composition comprising a blocked polyisocyanate component, a polyol, and a dispersant having an amine value. This aspect is based on the technical idea of providing a coating composition whose pH is resistant to decrease. One aspect of the present invention is a coating composition containing a blocked polyisocyanate component, a polyol, and a monohydric alcohol-based compound. This aspect is based on the technical idea of providing a coating composition whose pH is resistant to decrease. One aspect of the present invention is a coating composition comprising a blocked polyisocyanate component, a polyol, and at least two basic compounds. This aspect is based on the technical idea of providing a coating composition whose pH is less likely to decrease by using at least two basic compounds that adjust the pH to make the coating composition more stable.

[0013] Hereinafter, a coating composition containing a blocked polyisocyanate component, a polyol, and a dispersant having an amine value may be referred to as a first coating composition. The coating composition containing the blocked polyisocyanate component, the polyol, and the monohydric alcohol-based compound may be referred to as the second coating composition. The coating composition containing a blocked polyisocyanate component, a polyol, and at least two basic compounds may be referred to as a third coating composition.

[0014] <Blocked polyisocyanate component> The blocked polyisocyanate component used in the present invention contains a blocked polyisocyanate derived from a polyisocyanate and one or more blocking agents, and the blocked polyisocyanate component contains a structural unit represented by general formula (I). Hereinafter, the structural unit represented by general formula (I) may be referred to as "structural unit (I)."

[0015] Unit The molecule of the blocked polyisocyanate contained in the blocked polyisocyanate component contains a structural unit (I) represented by the following general formula (I).

[0016] [ka]

[0017] In the 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, and R 11 , R 12 and R 13 The total number of carbon atoms in R is 4 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, and the wavy line represents the bonding site with the residue of the polyisocyanate excluding the isocyanate group.

[0018] R 11 , R 12 , R 13 , R 14 , R 15 and R 16 The 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.

[0019] Examples of unsubstituted alkyl groups 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.

[0020] Also, 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. Examples of the alkyl group containing a hydroxy group as a substituent include a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group. 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. 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. Among these, R is preferred because it improves the storage stability of a coating composition and the low-temperature curing properties of a resin film. 11 , R 12 and R 13 are each independently preferably an unsubstituted alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and at least one of them is preferably an ethyl group.

[0021] R 11 , R12 and R 13 The total number of carbon atoms is 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 even more preferably 4 or more and 6 or less. R 11 , R 12 and R 13 When the total number of carbon atoms in R is equal to or greater than the lower limit, storage stability can be achieved when the composition is made into a water-based coating composition. On the other hand, when the total number of carbon atoms in R is equal to or less than the upper limit, low-temperature curing properties can be achieved. In addition, from the viewpoint of improving solvent resistance when the composition is made into a coating film, R 11 , R 12 and R 13 The total number of carbon atoms is more preferably 4.

[0022] R 11 , R 12 and R 13 If the total number of carbon atoms is within the above range, R 11 , R 12 and R 13 The number of carbon atoms in each of the groups is not limited.

[0023] Also, R 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, and are preferably unsubstituted alkyl groups having 1 to 4 carbon atoms.

[0024] Among them, 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 16When at least one of these is a hydrogen atom, low-temperature curing properties can be maintained while the storage stability of the aqueous resin composition can be further improved. In other words, it is more 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)).

[0025] [ka]

[0026] In the general formula (I-1), R 11 , R 12 , R 13 , R 14 and R 15 is as defined in the general formula (I) above. The wavy line represents the bonding site with the residue of the polyisocyanate excluding the isocyanate group.

[0027] The molar ratio of the structural unit (I-1) in the structural unit (I) (structural unit (I-1) / structural unit (I)) is more preferably 10 mol% or more, even more preferably 30 mol% or more, even more preferably 50 mol% or more, even more preferably 80 mol% or more, and even more preferably 90 mol% or more.

[0028] [Constituent Unit (II)] It is preferable that the blocked polyisocyanate component further contains a structural unit represented by the following general formula (II) (hereinafter, sometimes referred to as structural unit (II)) in its molecule.

[0029] [ka]

[0030] In the general formula (II), R 21 , R 22 , R 23 and R 24are 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, and the wavy line represents the bonding site with the residue of the polyisocyanate excluding the isocyanate group. R 21 , R 22 , R 23 and R 24 The alkyl group which may have one or more substituents selected from the group consisting of a hydroxy group and an amino group in the above formula "R 11 , R 12 , R 13 , R 14 , R 15 and R 16 " are examples of the same.

[0031] Among them, 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 substituent is preferred because they provide excellent storage stability when made into an aqueous resin composition, 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 provide excellent low-temperature curing properties.

[0032] 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 R 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. 21 , R 22 , R 23 and R 24are all methyl groups, that is, the two ester moieties of the malonic acid ester of the structural unit (II) are both isopropyl groups.

[0033] The molar ratio of the structural unit represented by the general formula (II) to the structural unit represented by the general formula (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, even more preferably 30 / 70 or more and 85 / 15 or less, even more preferably 35 / 65 or more and 85 / 15 or less, and even more preferably 50 / 50 or more and 70 / 30 or less. By having the molar ratio be above the lower limit, the storage stability when formed into a resin composition can be improved, and by having the molar ratio be below the upper limit, the low-temperature curing properties when formed into a resin film can be improved.

[0034] The molar ratio can be determined, for example, by mixing the coating composition with 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.

[0035] In general formula (I), R 11 , R 12 and R 13 It is preferred that all of the ester groups in the diester moiety are methyl. Blocked polyisocyanate components in which at least one ester group in the diester moiety is a tert-butyl group are known to have excellent curing properties with polyhydroxy compounds at low temperatures of around 85°C, but in aqueous coating compositions, they have high reactivity with water, and when blended into an aqueous coating composition and stored as an aqueous coating composition containing a polyhydroxy compound, a curing agent, and water, they tend to be prone to viscosity increase and gelation.

[0036] R in structural unit (I) 11 , R12 and R 13 When the total number of carbon atoms is 4 or more and 20 or less, the mixture of the polyhydroxy compound, the curing agent, and water can be effectively prevented from increasing in viscosity or gelling during storage, even when blended into an aqueous coating composition, and good storage stability can be achieved. At the same time, a resin film with excellent curing properties at a low temperature of about 85°C can be obtained.

[0037] The blocked polyisocyanate component used in the present invention may be a blocked polyisocyanate in which at least some of the isocyanate groups in the molecule are blocked with a malonic acid ester having a secondary alkyl group or a malonic acid ester having a primary alkyl group and a malonic acid ester having a tertiary alkyl group. Alternatively, the blocked polyisocyanate may be a mixture of a blocked polyisocyanate in which at least some of the isocyanate groups in the polyisocyanate are blocked with a malonic acid ester having a secondary alkyl group, or a blocked polyisocyanate in which at least some of the isocyanate groups in the polyisocyanate are blocked with a malonic acid ester having a primary alkyl group and a blocked polyisocyanate in which at least some of the isocyanate groups in the polyisocyanate are blocked with a malonic acid ester having a tertiary alkyl group.

[0038] [Other functional groups] The blocked polyisocyanate component 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.

[0039] [Polyisocyanate] (Isocyanate) The polyisocyanate used in producing the blocked polyisocyanate component is a reaction product obtained by reacting multiple monomer compounds having one or more isocyanate groups (-NCO) (hereinafter, sometimes referred to as "isocyanate monomers").

[0040] The isocyanate monomer preferably has a carbon number of 4 or more and 30 or less. Examples of the isocyanate monomer include the following: These isocyanate monomers may be used alone or in combination of two or more.

[0041] (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").

[0042] (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").

[0043] The isocyanate monomer used in producing the polyisocyanate is preferably one or more diisocyanates selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates because of their excellent weather resistance. Diisocyanate monomers other than the above-mentioned aliphatic diisocyanates and alicyclic diisocyanates may also be used. Furthermore, the isocyanate monomer is more preferably HDI or IPDI because of its ease of industrial availability. Furthermore, the isocyanate monomer is even more preferably HDI because it reduces the viscosity of the blocked polyisocyanate component.

[0044] The polyisocyanate preferably has an isocyanurate group, and may have, in addition to the isocyanurate group, 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.

[0045] (Polyol) The polyisocyanate used to produce the blocked polyisocyanate component is preferably derived from the above-mentioned diisocyanate and a polyol having an average functionality of 3.0 to 8.0. This allows the average number of isocyanate groups in the 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.

[0046] The average number of functional groups of the polyol used in producing the blocked polyisocyanate component 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 functional groups of the polyol referred to here is the number of hydroxyl groups present in one molecule of the polyol.

[0047] The number average molecular weight of the polyol used in producing the blocked polyisocyanate component 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, still 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, from the viewpoint of improving the hardness and strength of the coating film. When the number-average molecular weight of the polyol is within the above range, the blocked polyisocyanate component 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.

[0048] Examples of such polyols include trimethylolpropane, glycerol, and polycaprolactone polyols derived from trihydric or higher polyhydric alcohols and ε-caprolactone. Commercially available polycaprolactone polyols include 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).

[0049] (Production of polyisocyanates) 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.

[0050] 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 the polyisocyanate.

[0051] (average number of isocyanate groups in polyisocyanate) The average number of isocyanate groups in the polyisocyanate is preferably 2 or more from the viewpoint of improving the low-temperature curing property when formed into a resin film, and from the viewpoint of achieving both the low-temperature curing property when formed into a resin film and compatibility with the polyvalent hydroxy compound, it is more preferably 3 to 20, even more preferably 3.2 to 10, particularly preferably 3.5 to 8, and most preferably 4.0 to 6. The average number of isocyanate groups in a polyisocyanate can be calculated, for example, from the number average molecular weight Mn and the isocyanate group content (NCO content) of the polyisocyanate using the following formula: Average number of isocyanate groups = (Mn of polyisocyanate × NCO content × 0.01) / 42

[0052] [Blocking agent] The blocking agent used in producing the blocked polyisocyanate component preferably contains a malonic acid ester having a secondary alkyl group or a malonic acid ester having a primary alkyl group, and a malonic acid ester having a tertiary alkyl group, and more preferably contains a malonic acid ester having a secondary alkyl group and a malonic acid ester having a tertiary alkyl group. The blocking agent may contain one type of each of the malonic acid ester having a secondary alkyl group, the malonic acid ester having a primary alkyl group, and the malonic acid ester having a tertiary alkyl group, or a combination of two or more types. 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.

[0053] The malonic acid ester having a secondary alkyl group is not particularly limited, but 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.

[0054] Malonic acid esters having a tertiary alkyl group are 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, and (2-methyl-2-pentyl) isopropyl malonate are preferred, and (2-methyl-2-butyl) ethyl malonate, (2-methyl-2-butyl) isopropyl malonate, (2-methyl-2-pentyl) ethyl malonate, and (2-methyl-2-pentyl) hexyl isopropyl malonate are preferred, or di-tert-butyl malonate, (2-methyl-2-butyl) isopropyl malonate, or (2-methyl-2-pentyl) isopropyl malonate are 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).

[0055] (Other blocking agents) The blocking agent used in producing the blocked polyisocyanate component may further contain other blocking agents in addition to the malonic acid ester having a secondary alkyl group and the malonic acid ester having a tertiary alkyl group, as long as the other blocking agents do not impair the storage stability of a resin composition formed therefrom or the low-temperature curing properties of a resin film formed therefrom.

[0056] 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 having a secondary alkyl group and malonic acid esters having a tertiary alkyl group, 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:

[0057] 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. Examples of 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: dimethyl malonate, diethyl malonate, 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.

[0058] [Hydrophilic compound] The blocked polyisocyanate contained in the blocked polyisocyanate component may have a portion of its isocyanate groups modified with a hydrophilic compound, i.e., the blocked polyisocyanate may have a structural unit derived from a hydrophilic compound introduced into a portion of its isocyanate groups.

[0059] The hydrophilic compound is a compound having a hydrophilic group. In addition to the hydrophilic group, the hydrophilic compound preferably has one or more active hydrogen groups per molecule of the hydrophilic compound, which are capable of reacting with at least one isocyanate group of the polyisocyanate. Specific examples of the active hydrogen groups include hydroxyl groups, mercapto groups, carboxylic acid groups, amino groups, and thiol groups.

[0060] Examples of hydrophilic compounds include nonionic compounds, cationic compounds, and anionic compounds. These hydrophilic compounds may be used alone or in combination of two or more. Among them, nonionic compounds are preferred as hydrophilic compounds from the viewpoints of availability and being less susceptible to electrical interaction with the compound, and anionic compounds are preferred from the viewpoint of suppressing a decrease in the hardness of the resulting resin film.

[0061] (nonionic compounds) Specific examples of nonionic compounds contained in the blocked polyisocyanate component 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 compounds also have active hydrogen groups that react with isocyanate groups. Among these, polyethylene glycol monoalkyl ethers in which ethylene oxide is added to the hydroxyl group of a monoalcohol are preferred as the nonionic compound contained in the blocked polyisocyanate component, since they can improve the water dispersibility of the blocked polyisocyanate component even with a small amount used.

[0062] The number of ethylene oxide units added 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 units is equal to or more than the above-mentioned lower limit, water dispersibility tends to be more effectively imparted to the blocked polyisocyanate component, and when the number of ethylene oxide units is equal to or less than the above-mentioned upper limit, precipitation of the blocked polyisocyanate component tends to be less likely to occur during low-temperature storage.

[0063] From the viewpoint of the aqueous dispersion stability of the blocked polyisocyanate component, the lower limit of the amount of constituent units derived from a nonionic compound added to the blocked polyisocyanate (hereinafter, may be referred to as the "nonionic compound content") is preferably 0.1 mass %, more preferably 0.15 mass %, even more preferably 0.2 mass %, and particularly preferably 0.25 mass %, relative to the mass of the solid content of the blocked polyisocyanate component.

[0064] Furthermore, from the viewpoint of the water resistance of the resulting resin film, the upper limit of the content of the nonionic compound is preferably 55 mass%, more preferably 50 mass%, even more preferably 48 mass%, and particularly preferably 44 mass%, relative to the mass of the solid content of the blocked polyisocyanate component. That is, the content of the nonionic compound is preferably 0.1 mass% or more and 55 mass% or less, more preferably 0.15 mass% or more and 50 mass% or less, even more preferably 0.20 mass% or more and 48 mass% or less, and particularly preferably 0.25 mass% or more and 44 mass% or less, relative to the mass of the solid content of the blocked polyisocyanate component. When the content of the nonionic compound is within the above range, the blocked polyisocyanate component disperses better in water, and a homogeneous film tends to be obtained.

[0065] From the viewpoint of suppressing a decrease in the hardness and strength of the resulting resin film, the amount of the nonionic compound added to the blocked polyisocyanate, expressed as a molar ratio, relative to 100 mol% of the isocyanate groups in the raw material polyisocyanate, is preferably 0.05 mol% or more and 15 mol% or less, more preferably 0.10 mol% or more and 12 mol% or less, even more preferably 0.10 mol% or more and 9 mol% or less, even more preferably 0.10 mol% or more and 6 mol% or less, and most preferably 0.15 mol% or more and 4 mol% or less.

[0066] (cationic compounds) Specific examples of cationic compounds contained in the blocked polyisocyanate component include compounds having both a cationic hydrophilic group and an active hydrogen group. Alternatively, a compound having an active hydrogen group such as a glycidyl group may be combined with a compound having a cationic hydrophilic group such as a sulfide or phosphine to form 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 a sulfide or phosphine is reacted. From the viewpoint of ease of production, a compound having both a cationic hydrophilic group and an active hydrogen group is preferred.

[0067] 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.

[0068] The reaction between the cationic 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, such as ethyl acetate, propylene glycol monomethyl ether acetate, or dipropylene glycol dimethyl ether.

[0069] 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. Examples of compounds having a carboxyl group include formic acid, acetic acid, propionic acid, butyric acid, and lactic acid. Examples of compounds having a sulfonic acid group include ethanesulfonic acid. Examples of compounds having a phosphate group include phosphoric acid and acidic phosphate esters. Examples of compounds having a halogen group include hydrochloric acid. Examples of compounds having a sulfate group include sulfuric acid. Among these, compounds having an anionic group are preferably compounds having a carboxy group, and more preferably acetic acid, propionic acid or butyric acid.

[0070] (anionic compounds) Examples of the anionic hydrophilic group contained in the blocked polyisocyanate component include a carboxy group, a sulfonic acid group, a phosphoric acid group, a halogen group, and a sulfate group. Examples of anionic compounds include compounds having both an anionic group and an active hydrogen group, and more specifically, compounds having a carboxy group of a monohydroxycarboxylic acid or polyhydroxycarboxylic acid as the anionic group. Examples of monohydroxycarboxylic acids include 1-hydroxyacetic acid, 3-hydroxypropanoic acid, 12-hydroxy-9-octadecanoic acid, hydroxypivalic acid, and lactic acid. 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. Further, compounds having both a sulfonic acid group and an active hydrogen group are also included, more specifically, isethionic acid and the like. Among these, hydroxypivalic acid or dimethylolpropionic acid is preferred as a compound having both an anionic group and an active hydrogen group.

[0071] The anionic hydrophilic group added to the blocked polyisocyanate is preferably neutralized with an amine compound, which is a basic substance. Examples of the amine compounds include ammonia and water-soluble amino compounds. 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.

[0072] (Other components) The blocked polyisocyanate component may further contain additives such as a solvent in addition to the blocked polyisocyanate. The solvents 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, acetone, Examples of suitable solvents include 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 water dispersibility, the solvent preferably has a solubility in water of 5% by mass or more, and specifically, DPDM is preferred.

[0073] <<Method for producing blocked polyisocyanate component>> The method for producing the blocked polyisocyanate component is not particularly limited, but the following two methods can be mentioned. 1) A method of reacting the polyisocyanate with the malonic acid ester having a tertiary alkyl group, and the malonic acid ester having a secondary alkyl group or the malonic acid ester having a primary alkyl group. 2) A method in which the polyisocyanate is reacted with at least one blocking agent selected from the group consisting of the malonic acid ester having a tertiary alkyl group, the malonic acid ester having a secondary alkyl group, and the malonic acid ester having a primary alkyl group, and an alcohol having a chain alkyl group is added to the resulting reaction product to introduce an alkyl group derived from the alcohol by transesterification of the terminal ester moiety of the reaction product.

[0074] 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).

[0075] 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. The blocking agent may be one of a malonic acid ester having a primary alkyl group, a malonic acid ester having a secondary alkyl group, and a malonic acid ester having a tertiary alkyl group, or two or more of them may be used in combination. 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.

[0076] When a solvent is used, it is sufficient to use a solvent that is inactive to isocyanate groups. When a solvent is used, the content of nonvolatile matter derived from the polyisocyanate and the blocking agent relative to 100 parts by mass of the blocked polyisocyanate component is as described in the second embodiment.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] When the polyisocyanate is produced by the above method 2), the blocking reaction is followed by an ester exchange reaction. As the alcohol having a chain alkyl group used in the transesterification reaction in method 2), the same alcohols as those in the first embodiment can be used. The chain alkyl group of the alcohol may be the same as or different from that of the blocking agent. When the chain alkyl group is different from that of the blocking agent, it is preferable to use a monoalcohol having a chain alkyl group with a different number of alkyl substitutions than that of the blocking agent. For example, when a single malonic acid ester having a secondary alkyl group is used as the blocking agent, a monoalcohol having a tertiary alkyl group can be used.

[0081] In the case of producing by the method 2), it is preferable to remove the generated alcohol or the residual added alcohol during or after the transesterification reaction by distillation under normal pressure 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.

[0082] 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.

[0083] The molar ratio of the structural unit (II) to the structural unit (I) can be controlled by adjusting the molar ratio of the alcohol added to the blocked isocyanate group, or by adjusting the transesterification reaction temperature and transesterification reaction time, or by distilling off the generated alcohol, etc.

[0084] When a hydrophilic compound is used, the polyisocyanate, the active hydrogen compound, the blocking agent and the hydrophilic compound may be reacted with each other.

[0085] The reaction between the polyisocyanate and the active hydrogen compound, 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. It is particularly 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 an active hydrogen compound or a blocking agent simultaneously or sequentially. Either the reaction between the hydrophilic compound-modified polyisocyanate and the active hydrogen compound or the reaction between the hydrophilic compound-modified polyisocyanate and the blocking agent can be carried out first.

[0086] 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 the metal constituting the organic metal salt include tin, zinc, and lead. Examples of the alkali metal include sodium.

[0087] 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. 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 deterioration in the aqueous dispersion stability of the blocked polyisocyanate component and the low-temperature curing properties of the resulting resin film.

[0088] The reaction between the hydrophilic compound-modified polyisocyanate and the active hydrogen compound, and the reaction between the hydrophilic compound-modified polyisocyanate and the blocking agent can be carried out using the methods described above for the active hydrogen compound modification reaction and the blocking reaction.

[0089] <Polyol> The polyol contained in the coating composition refers to a compound having at least two hydroxyl groups in one molecule. Examples of polyols include aliphatic hydrocarbon polyols, polyether polyols, polyester polyols, epoxy resins, fluorine-containing polyols, and acrylic polyols, with acrylic polyols being preferred.

[0090] [Aliphatic hydrocarbon polyols] Examples of the aliphatic hydrocarbon polyols include hydroxyl-terminated polybutadiene and its hydrogenated products.

[0091] [Polyether polyols] Examples of 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.

[0092] Examples of the polyhydric alcohol in (1) above include glycerin and propylene glycol. Examples of the alkylene oxide in (2) above include ethylene oxide and propylene oxide. Examples of the polyfunctional compound in (2) above include ethylenediamine and ethanolamines.

[0093] [Polyester polyols] Examples of the polyester polyols include the following polyester polyols (1A) and (2A). (1A) Polyester polyol resins obtained by a condensation reaction between a dibasic acid alone or a mixture of two or more kinds and a polyhydric alcohol alone or a mixture of two or more kinds. (2A) Polycaprolactones obtained by ring-opening polymerization of ε-caprolactone with polyhydric alcohols. Examples of the dibasic acid include carboxylic acids such as succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, and 1,4-cyclohexanedicarboxylic acid.

[0094] Examples of the polyhydric alcohol in (1A) above include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, trimethylolpropane, glycerin, pentaerythritol, 2-methylolpropanediol, and ethoxylated trimethylolpropane.

[0095] [Epoxy resins] Examples of 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.

[0096] [Fluorine-containing polyols] Examples of fluorine-containing polyols include copolymers of fluoroolefins, cyclohexyl vinyl ethers, hydroxyalkyl vinyl ethers, and monocarboxylic acid vinyl esters, which are disclosed in Reference Document 1 (JP-A-57-34107) and Reference Document 2 (JP-A-61-275311), etc.

[0097] [Acrylic polyols] Acrylic polyols can be obtained 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 needed, another monomer copolymerizable with the polymerizable monomer.

[0098] Examples of polymerizable monomers 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 glycerin, and acrylic acid monoester or methacrylic acid monoester of trimethylolpropane.

[0099] 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.

[0100] Other examples include acrylic polyols obtained by copolymerizing polymerizable ultraviolet-stable monomers disclosed in Reference 3 (JP-A No. 1-261409) and Reference 4 (JP-A No. 3-006273).

[0101] Examples of polymerizable ultraviolet-stable monomers 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.

[0102] 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 needed to obtain an acrylic polyol.

[0103] 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.

[0104] [NCO / OH] The molar equivalent ratio (NCO / OH) of the isocyanate groups of the blocked polyisocyanate to the hydroxyl groups of the polyol contained in the coating composition of this embodiment is determined depending on the required physical properties of the resin film, but is 0.01 to 2.0, preferably 0.02 to 1.0, and more preferably 0.04 to 0.8. By keeping the ratio within the above range, a resin film with excellent storage stability and curability of the coating composition can be obtained. The isocyanate groups of the blocked polyisocyanate component refer to both the isocyanate groups that have reacted with a blocking agent and the isocyanate groups that have not reacted.

[0105] [Hydroxyl value] The hydroxyl value of the polyol is preferably 30 mgKOH / g or more and 250 mgKOH / g or less, more preferably 40 mgKOH / g or more and 200 mgKOH / g or less, and even more preferably 45 mgKOH / g or more and 180 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. The hydroxyl value of the polyvalent hydroxy compound can be measured, for example, using the method described in the Examples below.

[0106] The content of the blocked polyisocyanate in the coating composition of this embodiment is preferably 5 to 200 parts by mass, more preferably 6 to 180 parts by mass, and even more preferably 10 to 150 parts by mass, relative to 100 parts by mass of polyol. When the content of the blocked polyisocyanate is within the above range, a resin film having excellent physical properties such as tensile strength can be obtained. The content of the blocked polyisocyanate can be calculated, for example, 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).

[0107] <Dispersant having an amine value> The first coating composition includes a dispersant having an amine value. A dispersant having an amine value is a dispersant having an amine value of more than 0 mgKOH / g. If the amine value is more than 0 mgKOH / g, the dispersant may have an acid value.

[0108] The dispersant having an amine value used in the present embodiment is not limited as long as it can suppress a decrease in pH, but the amine value is preferably 15 mgKOH / g or more, more preferably 40 mgKOH / g or more, and even more preferably 60 mgKOH / g or more. When the amine value of the dispersant having an amine value is equal to or greater than the above lower limit, it is preferable because it is easy to suppress a decrease in pH.

[0109] Examples of the basic functional group possessed by the dispersant having an amine value include an amino group, an imino group, an amide group, an imide group, and a nitrogen-containing heterocyclic group.

[0110] Examples of dispersants having such an amine value include the DisperBYK series manufactured by BYK Japan, trade name "DisperBYK" (amine value: 85 mg KOH / g), trade name "DisperBYK184" (amine value: 15 mg KOH / g), trade name "DisperBYK-2055" (amine value: 40 mg KOH / g), trade name "DisperBYK-2008" (amine value: 66 mg KOH / g), trade name "DisperBYK-2013" (amine value: 18 mg KOH / g), trade name "DisperBYK-145" (amine value: 71 mg KOH / g), trade name "DISPERBYK-2050" (amine value: 30.7 mg KOH / g), trade name "DISPERBYK-2200" (30.7 mg KOH / g), and trade name "DISPERBYK-2150" (amine value: 56.7 mg KOH / g).

[0111] Commercially available dispersants with an amine value include the Solsperse series manufactured by Nippon Louvre Resol Co., Ltd. (trade name "Solsperse 24000" (amine value: 41.6 mg KOH / g), trade name "Solsperse 32000" (amine value: 31.2 mg KOH / g), trade name "Solsperse 39000" (amine value: 35.7 mg KOH / g), trade name "Solsperse 71000" (amine value: 78 mg KOH / g)), and the BYKJET series manufactured by BYK Japan (trade name "BYKJET-9151" (amine value: 78 mg KOH / g). Examples include the Ajinomoto Fine-Techno Co., Ltd. Ajisper series (trade name "Ajisper PB-822" (amine value: 18.2 mg KOH / g), trade name "Ajisper PB-881" (amine value: 17.4 mg KOH / g), trade name "Ajisper PB-824" (amine value: 17 mg KOH / g), etc.), and the BASF Ajisper series (trade name "EFKAPX4731" (amine value: 25 mg KOH / g).

[0112] Dispersants with an amine value have the characteristic of dispersing the coating composition uniformly and preventing the pH of the entire composition from decreasing.

[0113] The content of the dispersant having an amine value in the total amount of the coating composition used in this embodiment is not particularly limited, but is preferably 0.1 mass % or more and 10 mass % or less, and more preferably 0.2 mass % or more and 6.0 mass % or less.

[0114] When the content of the dispersant having an amine value in the coating composition is equal to or greater than the above lower limit, a sufficient amount of dispersant having an amine value is present, making it easier to trap carbon dioxide. When the content of the dispersant having an amine value in the coating composition is not more than the above upper limit, the dispersant having an amine value is easily dispersed uniformly in the coating composition, and the pH is easily maintained uniform.

[0115] <Monohydric alcohol compounds> The second coating composition contains a monohydric alcohol-based compound. Examples of monohydric alcohol compounds include ethanol, methanol, isopropanol, 1-propanol, isobutanol, 1-butanol, 2-ethylhexanol, cyclohexanol, 3-methoxy-3-methyl-1-butanol, etc. These monohydric alcohol compounds may be used alone or in combination of two or more.

[0116] Among the above, the monohydric alcohol compound is preferably one or more selected from the group consisting of isobutanol and 2-ethylhexanol, since storage stability is more likely to be improved.

[0117] The content of the monohydric alcohol compound in the total amount of the coating composition is preferably 2.5% by mass or more and 20% by mass or less, and more preferably 2.5% by mass or more and 10% by mass or less, since this makes it easier to improve storage stability.

[0118] In one embodiment of the present invention, the coating composition comprises a dispersant having the above-described amine value and a monohydric alcohol-based compound.

[0119] In one embodiment of the present invention, the coating composition does not contain a monohydric alcohol-based compound, but contains a dispersant having the above-mentioned amine value and a basic compound.

[0120] <Basic compounds> The first coating composition and the second coating composition preferably contain a basic compound. The basic compound is a component that adjusts the pH of the coating composition to make it more stable, and is also a component that can suppress a decrease in pH during storage of the coating composition. Specific examples of basic compounds include morpholine derivatives such as morpholine, N-allylmorpholine, N-methylmorpholine, and N-ethylmorpholine; tertiary amines such as triallylamine and triethanolamine; 2-methylimidazole, phthalamide, trimethylamine, triethylamine, and dimethylethanolamine.

[0121] The basic compound is preferably a morpholine derivative, trimethylamine, triethylamine, or dimethylethanolamine. The basic compound is more preferably trimethylamine, triethylamine, or dimethylethanolamine, and even more preferably dimethylethanolamine. The basic compound may be a combination of one or more morpholine derivatives and one or more selected from the group consisting of trimethylamine, triethylamine, and dimethylethanolamine. For example, a combination of N-methylmorpholine and dimethylethanolamine is preferred.

[0122] When the first coating composition and the second coating composition contain a basic compound, from the viewpoint of further improving storage stability, the content of the basic compound in the total amount of the coating composition is preferably 0.05 mass % or more and 2.0 mass % or less, and more preferably 0.1 mass % or more and 1.0 mass % or less.

[0123] The pH of the coating composition of the present invention when blended is preferably 7.0 to 9.0 when measured at room temperature (25° C.), with the lower limit being more preferably 7.5, and even more preferably 7.8, and the upper limit being more preferably 8.6, and even more preferably 8.4, and most preferably 8.2. If the pH of the coating composition is 7.0 to 9.0, the stability of the pigments such as aluminum and additives such as rheology control agents that are blended can be maintained.

[0124] When the first coating composition contains a basic compound, the basic compound increases and stabilizes the pH of the coating composition, resulting in a coating composition whose pH is less likely to decrease. When the second coating composition contains a basic compound, the basic compound increases and stabilizes the pH of the coating composition, making the coating composition less susceptible to a decrease in pH.

[0125] The third coating composition preferably contains at least two basic compounds, more specifically, a first basic compound and a second basic compound. The first basic compound is a component that increases and stabilizes the pH of the coating composition. The second basic compound is effective in suppressing a decrease in pH during storage of the paint.

[0126] The first basic compound is more preferably trimethylamine, triethylamine, or dimethylethanolamine, and even more preferably dimethylethanolamine.

[0127] The second basic compound is preferably at least one selected from the group consisting of morpholine, morpholine derivatives such as N-allylmorpholine, N-methylmorpholine, and N-ethylmorpholine, tertiary amines such as triallylamine and triethanolamine, 2-methylimidazole, phthalamide, trimethylamine, triethylamine, and dimethylethanolamine, and the basic compound is more preferably a morpholine derivative, trimethylamine, triethylamine, or dimethylethanolamine.

[0128] The content ratio of the first and second basic compounds in the total amount of the third coating composition is preferably 0.1 mass % or more and 2.0 mass % or less, and more preferably 0.15 mass % or more and 1.0 mass % or less. The total content of the first and second basic compounds in the total amount of the third coating composition is preferably 0.5 mass % or more and 2.0 mass % or less, and more preferably 0.6 mass % or more and 1.5 mass % or less.

[0129] <Nonionic dispersant> The coating composition of this embodiment may contain at least two or more nonionic dispersants. Here, "two or more" refers to multiple nonionic dispersants with different HLB values. The inclusion of multiple nonionic dispersants with different HLB values can improve the emulsification ability of the blocked polyisocyanate in water, thereby improving the aqueous dispersion stability. This effect is most pronounced when at least two or more nonionic dispersants are mixed, the difference between the nonionic dispersant with the highest HLB value and the nonionic dispersant with the lowest HLB value is 5 or more, and the weighted average HLB value of all nonionic dispersants contained in the coating composition is 14 to 17.

[0130] The difference between the nonionic dispersant with the maximum HLB value and the minimum HLB value is preferably 7 or more, more preferably 8 or more, and even more preferably 9 or more. The upper limit is preferably 20 or less, and more preferably 15 or less.

[0131] The HLB (Hydrophile-Lipophile Balance) value of a nonionic dispersant is commonly used to indicate the degree of affinity of the dispersant for oil and water, and can be calculated using the following formula. HLB value = 20 × total formula weight of hydrophilic parts / molecular weight

[0132] The nonionic dispersant used is not particularly limited as long as its HLB value calculated by the above method is within a specific range.Specific examples of nonionic dispersants include polyoxyethylene alkyl ether type compounds, polyoxyalkylene derivative type compounds, polyoxyethylene polycyclic phenyl ether type compounds, sorbitan fatty acid ester type compounds, glycerin fatty acid ester type compounds, polyoxyethylene fatty acid ester type compounds, polyoxyethylene castor oil type compounds, and polyoxyethylene alkylamine type compounds.Among these nonionic dispersants, polyoxyethylene alkyl ether type compounds and polyoxyethylene polycyclic phenyl ether type compounds are particularly preferred.

[0133] The content of the nonionic dispersant is preferably 1% by mass or more and 30% by mass or less, more preferably 1.5% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 15% by mass or less, and even more preferably 3% by mass or more and 10% by mass or less, relative to the total amount of the blocked polyisocyanate. When the content of the nonionic dispersant is equal to or more than the lower limit, the storage stability of the aqueous coating composition can be improved, while when the content is equal to or less than the upper limit, the hardness of the resin film can be improved.

[0134] When a nonionic dispersant satisfying the above conditions is contained in the system, an anionic dispersant may also be used.Specific examples of anionic dispersants include fatty acid salt compounds, alkyl sulfate ester compounds, polyoxyethylene alkyl ether sulfate ester salt compounds, polyoxyethylene alkyl ether sulfate salt compounds, polyoxyethylene polycyclic phenyl ether sulfate salt compounds, polyoxyalkylene alkenyl ether sulfate salt compounds, alkylbenzene sulfonate compounds, sulfosuccinate compounds, and alkyl phosphate compounds.Examples of polyoxyethylene alkyl ether sulfate salt compounds include polyoxyethylene alkyl ether ammonium sulfate and polyoxyethylene alkyl ether sodium sulfate.

[0135] Examples of polyoxyethylene polycyclic phenyl ether sulfate compounds include polyoxyethylene polycyclic phenyl ether ammonium sulfate and polyoxyethylene polycyclic phenyl ether sodium sulfate. Examples of polyoxyalkylene alkenyl ether sulfate compounds include polyoxyalkylene alkenyl ether ammonium sulfate. These anionic dispersants may be used alone or in combination of two or more.

[0136] Among these anionic dispersants, polyoxyethylene polycyclic phenyl ether ammonium sulfate, polyoxyethylene polycyclic phenyl ether sodium sulfate, polyoxyethylene alkyl ether ammonium sulfate, and polyoxyethylene alkyl ether sodium sulfate are particularly preferred.

[0137] Deionized water The coating composition of this embodiment may be an aqueous coating composition containing deionized water. The content of deionized water is preferably 20% by mass or more and 90% by mass or less, and more preferably 30% by mass or more and 80% by mass or less, based on the total amount of the aqueous coating composition.

[0138] <Other additives> The coating 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 polyol, curing catalysts, solvents, pigments (extender pigments, colored pigments, metallic pigments, etc.), ultraviolet absorbers, light stabilizers, radical stabilizers, anti-yellowing agents that suppress discoloration during the baking process, coating surface conditioners, flow conditioners, pigment dispersants, antifoaming agents, thickeners, film-forming aids, etc.

[0139] Examples of the curing agent include melamine resins, 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.

[0140] The curing catalyst may be a basic compound or a Lewis acid compound. Examples of basic compounds 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 salts are preferably ammonium salts, phosphonium salts, or sulfonium salts. Examples of Lewis acid compounds include organotin compounds, organozinc compounds, organotitanium compounds, and organozirconium compounds.

[0141] Examples of solvents 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, ethylene glycol diethyl ether, diethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, propylene glycol dimethyl ether, methyl ethyl ketone, acetone, methyl isobutyl ketone, propylene glycol monomethyl ether acetate, 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, mineral spirits, etc. 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, dipropylene glycol monomethyl ether is preferred.

[0142] 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.

[0143] <<Method for producing coating composition>> When producing a coating composition, first, additives such as a curing agent capable of reacting with the crosslinkable functional group in the polyol, a curing catalyst, a solvent, pigments (extender pigments, colored pigments, metallic pigments, etc.), an ultraviolet absorber, a light stabilizer, a radical stabilizer, an anti-yellowing agent that suppresses discoloration during the baking process, a coating surface conditioner, a flow conditioner, a pigment dispersant, an antifoaming agent, a thickener, and a film-forming aid are added to the polyol or its aqueous dispersion or solution, as needed.

[0144] Next, a blocked polyisocyanate component or a water dispersion thereof is added as a curing agent, and the viscosity is adjusted by further adding the above-mentioned two or more nonionic dispersants and deionized water.

[0145] The dispersant having an amine value, the monohydric alcohol compound, or the basic compound may be added in advance to the polyol or the blocked polyisocyanate component, or may be added after the polyol and the blocked polyisocyanate composition are mixed and dispersed. Alternatively, the dispersant having an amine value or the basic compound may be added after being dissolved in water, a solvent, or the like in advance.

[0146] Finally, the mixture is forcibly stirred with a stirring device to obtain a water-based coating composition.

[0147] <Resin film> One aspect of the present invention is a resin film that is a cured product of the coating composition or water-based coating composition of this embodiment. The resin film can be obtained by applying the coating composition or the water-based coating composition of the present embodiment to a substrate using a known method such as roll coating, curtain flow coating, spray coating, bell coating, or electrostatic coating, and then heating to cure the composition.

[0148] <Method of manufacturing resin film> One aspect of the present invention is a method for producing a resin film, comprising the steps of applying the coating composition of the present embodiment and heating the applied coating composition at a temperature of 50°C or higher and 100°C or lower for 5 minutes to 1,440 minutes, or at a temperature of 105°C or higher and 200°C or lower for 5 seconds to 900 seconds, to obtain a resin film. By keeping the temperature conditions and curing time within the above ranges, a coating film with good hardness can be obtained.

[0149] 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.

[0150] 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; and fibrous materials such as wood, paper, and cloth. Of these, metal materials and plastic materials are preferred.

[0151] The substrate may be the surface of the above-mentioned metal material, or the metal surface of a vehicle body or the like formed 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 vehicle 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 plastic surface of an automobile part or the like formed from the above-mentioned plastic 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. [Example]

[0152] 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.

[0153] <Test items> The coating compositions obtained in the examples and comparative examples were subjected to measurement of various physical properties and evaluations according to the methods described below.

[0154] [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. Isocyanate group (NCO) content (mass%) = (V1 - V2) x F x 42 / (W x 1000) x 100

[0155] [Physical Properties 2] (number average molecular weight) The number average molecular weight is a number average molecular weight 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 measurement conditions are shown below.

[0156] (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

[0157] [Physical Properties 3] (average number of isocyanate groups) The average number of isocyanate groups (average NCO number) of the polyisocyanate was calculated by the following formula. In the formula, "Mn" is the number average molecular weight of the polyisocyanate before blocking with a blocking agent, 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. Average number of isocyanate groups = (Mn × NCO content × 0.01) / 42

[0158] [Physical Properties 4] (Solid content of blocked polyisocyanate component) The solid content of the blocked polyisocyanate component 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 component produced in the Examples and Comparative Examples was placed on the aluminum dish and precisely weighed (W1). The blocked polyisocyanate component was then adjusted to a uniform thickness. The blocked polyisocyanate component 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 component remaining on the aluminum dish was precisely weighed (W2). The solids content (mass%) of the blocked polyisocyanate component was then calculated using the following formula: Solid content of blocked polyisocyanate component (mass%) = W2 / W1 x 100

[0159] [Physical Properties 5] (Content (mol) of structural unit (I)) The content of the structural unit (I) in the blocked polyisocyanate component was calculated by 13C-NMR. 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.

[0160] [Physical Properties 6] (Molar ratio of structural unit (I-1) in structural unit (I)) The molar ratio of the structural unit (I-1) to the structural unit (I) in the blocked polyisocyanate component (structural unit (I-1) / structural unit (I)) was calculated using the method shown below. Specifically, 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 using a JEOL "JEOL-ECZ500(SC)" (trade name) manufactured by JEOL Ltd., and the molar ratio thereof was determined.

[0161] (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.

[0162] [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 evaporating the blocked polyisocyanate component at 50°C or less to remove the solvent and other components, 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.

[0163] (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.

[0164] [Rating 1] (Storage stability) Storage stability was evaluated by measuring the pH of the coating composition before and after storage under specified conditions, and by the change in pH from that immediately after blending. Specifically, the pH of the resulting coating composition was measured after 10 days of storage at 40°C in a 20 mL glass bottle, and the change (absolute value) from the pH immediately after blending was evaluated according to the following criteria: The smaller the change, the better the storage stability, and the greater the change, the worse the evaluation. A: Less than 1.2 B: 1.2 or more and less than 1.3 C: 1.3 or more and less than 1.5 D:1.5 or more

[0165] <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 5.2 parts by mass of a polyester polyol 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 88°C for 1 hour with stirring to carry out a urethane reaction. The temperature inside the reactor was then maintained at 62°C, and an isocyanuration catalyst, tetramethylammonium caprylate, was added. When the yield reached 51% 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"). The obtained polyisocyanate P-1 had an NCO content of 18.8% by mass, a number average molecular weight of 1180, and an average number of isocyanate groups of 5.3. Furthermore, the obtained polyisocyanate P-1 was subjected to 1H-NMR analysis, and the presence of isocyanurate groups was confirmed.

[0166] [Synthesis Example 2] (Synthesis of hydrophilic compound modified polyisocyanate P-2) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was mixed under a nitrogen stream with 100 parts by weight of polyisocyanate P-1, 13 parts by weight of dipropylene glycol dimethyl ether (DPDM), 15 parts by weight of methoxypolyethylene glycol (MPG-081, 15 ethylene oxide repeating units, manufactured by Nippon Nyukazai Co., Ltd.) (5 mol % relative to 100 mol % of the isocyanate groups in polyisocyanate P-2), and 0.08 parts by weight of 2-ethylhexyl acid phosphate (JP-508T, manufactured by Johoku Chemical Industry Co., Ltd.). The mixture was stirred at 120°C for 2 hours to obtain hydrophilic compound-modified polyisocyanate P-2. The resulting polyisocyanate P-2 had an NCO content of 14.0% by weight and an average number of isocyanate groups of 5.0.

[0167] [Synthesis Example 3] (Synthesis of Blocked Polyisocyanate BL-1) A four-neck flask equipped with a thermometer, stirring blade, and reflux condenser was charged with 100 parts by weight of the polyisocyanate P-2 obtained in Synthesis Example 2 and 63.9 parts by weight of 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, with stirring, 1.0 part by weight of a methanol solution containing sodium methylate (28% by weight relative to the total weight of the solution) was added dropwise, and the external bath was adjusted to a solution temperature of 55°C. The blocking reaction was carried out at 55°C for 5 hours to obtain a blocked polyisocyanate component intermediate with a solids content of 60% by weight. Subsequently, 75 parts by weight of 2-methyl-2-butanol (250 mol% relative to blocked isocyanate groups) was added, 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 % to obtain blocked polyisocyanate component BL-1.

[0168] The specific structure and composition of the blocked polyisocyanate component BL-1 produced in Synthesis Example 3 are shown in Table 1.

[0169] [Table 1]

[0170] <Production of Coating Composition> [Example 1] (Paint composition T-1) 16 g of the blocked polyisocyanate component BL-1 obtained in Synthesis Example 3 was weighed out and placed in a container. Next, a nonionic dispersant: Newcol 714 (manufactured by Nippon Nyukazai Co., Ltd., polyoxyethylene polycyclic phenyl ether, HLB value calculated by the Griffin equation: 15.0) was added to the blocked polyisocyanate component so that the total amount was 6% by mass of the resin content of the blocked polyisocyanate component.

[0171] Next, DisperBYK (manufactured by BYK Japan, nonvolatile content: 50% by mass, acid value: 85 mg KOH / g, amine value: 85 mg KOH / g) was added so that the content ratio of the total amount of the coating composition was 1.0% by mass. Next, deionized water was added so that the content ratio of the deionized water relative to the total amount of the coating composition was 40% by mass, and the mixture was stirred at 800 rpm using a propeller blade for 10 minutes.

[0172] Next, an acrylic polyol water dispersion (hydroxyl value per resin: 130 mgKOH / g, manufactured in-house) was added in such a ratio that the ratio of the molar amount of isocyanate groups to the molar amount of hydroxyl groups in the polyol (NCO / OH) was 0.4. Next, deionized water was added so that the content of deionized water in the total amount of the coating composition was 26 mass%, and the mixture was stirred at 700 rpm using a propeller blade for 10 minutes.

[0173] Finally, 50% by mass of dimethylethanolamine (50% DMEA) was added to adjust the pH of the coating composition to 8.3, and the mixture was stirred at 700 rpm for 10 minutes to obtain coating composition T-1. The coating composition T-1 was evaluated using the methods described above. The results are shown in Table 2.

[0174] [Examples 2 to 3] The coating compositions of Examples 2 and 3 (T-2 and T-3) were obtained using the same method as in Example 1, except that the addition ratios of DisperBYK and other ingredients were as shown in Table 2. Each of the prepared coating compositions was evaluated using the above-mentioned method. The results are shown in Table 2.

[0175] [Example 4] A coating composition (T-4) of Example 4 was obtained using the same method as in Example 1, except that DisperBYK was replaced with DisperBYK-184 (manufactured by BYK-Chemie Japan, non-volatile content: 52% by mass, acid value: 0 mg KOH / g, amine value: 15 mg KOH / g). The coating composition thus prepared was evaluated using the above-described method. The results are shown in Table 2.

[0176] [Example 5] A coating composition (T-5) of Example 5 was obtained using the same method as in Example 1, except that DisperBYK was replaced with isobutanol and the addition ratio of isobutanol, etc. was set as shown in Table 2. The prepared coating composition was evaluated using the above-mentioned method. The results are shown in Table 3.

[0177] [Example 6] A coating composition (T-6) of Example 6 was obtained using the same method as in Example 5, except that isobutanol was replaced with 2-ethylhexanol and the addition ratio of 2-ethylhexanol and other ingredients was set as shown in Table 2. The coating composition thus prepared was evaluated using the above-mentioned method. The results are shown in Table 3.

[0178] [Example 7] A coating composition (T-7) of Example 7 was obtained using the same method as in Example 1, except that DisperBYK was not added, and N-methylmorpholine and 50% DMEA were added as basic compounds in the proportions shown in Table 2. The coating composition thus prepared was evaluated using the above-mentioned method. The results are shown in Table 3.

[0179] [Example 8] A coating composition (T-8) of Example 8 was obtained in the same manner as in Example 7, except that the addition ratios of N-methylmorpholine and 50% DMEA were as shown in Table 2. The coating composition thus prepared was evaluated using the above-mentioned methods. The results are shown in Table 3.

[0180] [Comparative Example 1] A coating composition (t-1) of Comparative Example 1 was obtained using the same method as in Example 1, except that DisperBYK was not added and the addition ratios of each sample were as shown in Table 2. The prepared coating composition was evaluated using the above-mentioned method. The results are shown in Table 2.

[0181] Comparative Example 2 A coating composition (t-2) of Comparative Example 2 was obtained using the same method as in Example 1, except that DisperBYK was replaced with DisperBYK-193 (manufactured by BYK Japan, non-volatile content: 40% by mass, acid value: 0 mg KOH / g, amine value: 0 mg KOH / g) and the addition ratio of DisperBYK193, etc. was set as shown in Table 2. The coating composition thus prepared was evaluated using the above-mentioned method. The results are shown in Table 2. [Table 2]

[0182] As shown in Table 2 above, the coating compositions of Examples 1 to 4, which contained dispersants with an amine value of 15 mgKOH / g or more, were evaluated as A or B in storage stability, confirming that they were good. On the other hand, the coating composition of Comparative Example 1, which did not contain a dispersant with an amine value, was rated D for poor storage stability, and the coating composition of Comparative Example 2, which contained a dispersant with an amine value of 0 mgKOH / g, was also rated C for poor storage stability.

[0183] As shown in Table 2 above, the coating compositions of Examples 5 and 6, which contained a monohydric alcohol compound, were evaluated as A or B in storage stability, confirming that they were good. On the other hand, the coating composition of Comparative Example 1, which did not contain a monohydric alcohol compound, was evaluated as D for storage stability, which was poor, and the coating composition of Comparative Example 2 was also evaluated as C for storage stability, which was poor.

[0184] As shown in Table 2 above, the coating compositions of Examples 7 and 8, which contained multiple basic compounds, were evaluated as A or B in storage stability, confirming that they were good. On the other hand, the coating composition of Comparative Example 1, which contained only dimethylethanolamine as the basic compound, was evaluated as D for storage stability, which was poor, and the coating composition of Comparative Example 2 was also evaluated as C for storage stability, which was poor.

Claims

1. A coating composition comprising a blocked polyisocyanate component, a polyol, and a dispersant having an amine value, The blocked polyisocyanate component includes a blocked polyisocyanate derived from a polyisocyanate and one or more blocking agents, A coating composition, wherein the blocked polyisocyanate component contains a structural unit represented by the following general formula (I): 【Chemical 1】 [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, and R １１ , R １２ and R １３ The total number of carbon atoms in R is 4 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. A wavy line represents a bond.]

2. A coating composition comprising a blocked polyisocyanate component, a polyol, and a monohydric alcohol-based compound, The blocked polyisocyanate component includes a blocked polyisocyanate derived from a polyisocyanate and one or more blocking agents, A coating composition, wherein the blocked polyisocyanate component contains a structural unit represented by the following general formula (I): 【Chemistry 2】 [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, and R １１ , R １２ and R １３ The total number of carbon atoms in R is 4 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. A wavy line represents a bond.]

3. A coating composition comprising a blocked polyisocyanate component, a polyol, and at least two basic compounds, The blocked polyisocyanate component includes a blocked polyisocyanate derived from a polyisocyanate and one or more blocking agents, A coating composition, wherein the blocked polyisocyanate component contains a structural unit represented by the following general formula (I): 【Chemistry 3】 [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, and R １１ , R １２ and R １３ The total number of carbon atoms in R is 4 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. A wavy line represents a bond.]

4. 2. The coating composition according to claim 1, wherein the content of the dispersant having an amine value in the total amount of the coating composition is 0.1 mass % or more and 10 mass % or less.

5. 2. The coating composition according to claim 1, wherein the amine value of the dispersant having an amine value is 15 mg KOH / g or more.

6. The coating composition according to claim 1 or 2, further comprising a basic compound.

7. The blocked polyisocyanate component is a compound represented by the general formula (I) R １６ The coating composition according to any one of claims 1 to 3, comprising a structural unit (I-1) in which is a hydrogen atom.

8. The coating composition according to any one of claims 1 to 3, wherein the polyisocyanate has an average number of isocyanate groups of 4.0 or more and 10.0 or less.

9. A step of applying the coating composition according to any one of claims 1 to 3; and a step of heating the applied coating composition at a temperature of 50°C or higher and 100°C or lower for 5 minutes or longer and 1,440 minutes or shorter, or at a temperature of 105°C or higher and 200°C or lower for 5 seconds or longer and 900 seconds or shorter, to obtain a resin film.

Images