Resin composition, resin cured product, method for forming resin cured product, method for re-forming resin cured product, method for recovering blocking group-containing compound, and method for peeling off resin cured product

Abstract

Provided is a resin composition comprising: a blocking group-containing compound having two or more blocking groups for isocyanate groups; and at least one isocyanate compound selected from the group consisting of an isocyanate monomer and a polyisocyanate compound. The blocking groups are preferably derived from at least one compound selected from the group consisting of an oxime-based compound, an amine-based compound, a pyrazole-based compound, and an imidazole-based compound.

Description

Resin composition, cured resin, method for forming cured resin, method for reforming cured resin, method for recovering block group-containing compound, and method for peeling cured resin

[0001] The present invention relates to a resin composition, a cured resin, a method for forming a cured resin, a method for reforming a cured resin, a method for recovering a block group-containing compound, and a method for peeling off a cured resin. This application claims priority based on Japanese Patent Application No. 2024-108460, filed on July 4, 2024, the contents of which are incorporated herein by reference.

[0002] Ordinary polyurethane resins are obtained by forming urethane bonds between hydroxyl groups of polyols and isocyanate groups of polyisocyanates, and because the presence of urethane bonds gives them excellent abrasion resistance, chemical resistance, and stain resistance, they are used in a wide range of applications, such as automobiles, building exteriors, and automobile repair paints. However, because the urethane bonds in polyurethane resins are generally strong, once the curing reaction has progressed, it is difficult for them to dissociate into hydroxyl groups and isocyanate groups.

[0003] As a technology in which an exchange reaction of the crosslinked structure proceeds upon heating after the crosslinked structure is formed, a bond-exchangeable dynamic covalent crosslinked compound using an ester exchange reaction between an ester compound and a polyol compound has been disclosed (see, for example, Patent Document 1). This crosslinked compound exhibits remoldability and repairability by heating, as an exchange reaction of the hydroxyl groups of the excess polyol compound with the ester bond proceeds.

[0004] Japanese Patent Application Laid-Open No. 2022-29617

[0005] In recent years, in order to contribute to a sustainable society, attention has been focused on the reuse of raw materials and the recycling of used substrates. Because urethane resins have strong urethane bonds, they are not easily peeled from substrates such as metals and plastics, making it difficult to recover and reuse the substrates. It is also difficult to dissociate the urethane bonds and recover the raw materials of the urethane resin. The technology described in Patent Document 1 is expected to cause a change in the viscoelasticity of the coating film, but since the bonds are not dissociated, it may be difficult to recover the raw materials used and peel them from the substrate.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a resin composition which, when formed into a cured resin, has performance equivalent to that of polyurethane resins, but which allows for easy raw material recovery and peeling by depolymerization and reformation of the crosslinked structure, and a cured resin product obtained by curing the resin composition. Also, aims to provide methods for forming the cured resin product, methods for reforming the cured resin product, methods for recovering the raw materials, and methods for peeling.

[0007] That is, the present invention includes the following aspects. [1] A resin composition comprising a blocking group-containing compound having two or more blocking groups for an isocyanate group, and one or more isocyanate compounds selected from the group consisting of an isocyanate monomer and a polyisocyanate compound. [2] The resin composition according to [1], wherein the blocking group is derived from one or more compounds selected from the group consisting of an oxime compound, an amine compound, a pyrazole compound, and an imidazole compound. [3] The resin composition according to [1] or [2], wherein the number average molecular weight of the blocking group-containing compound is 170 or more and 10,000 or less. [4] The resin composition according to any one of [1] to [3], wherein the molar ratio of the blocking group to the isocyanate group contained in the isocyanate compound, i.e., blocking group / isocyanate group, is 0.3 or more and 2.0 or less. [5] The resin composition according to any one of [1] to [4], wherein at least one of the average number of blocked groups of the blocking group-containing compound and the average number of isocyanate groups of the isocyanate compound is 2.1 or more. [6] A cured resin having a blocked isocyanate bond formed by the reaction of a blocking group with an isocyanate group. [7] A cured resin obtained by curing the resin composition according to any one of [1] to [5]. [8] The cured resin according to [7], having a crosslinked structure in which a blocking group of the blocking group-containing compound is bonded to an isocyanate group of the isocyanate compound. [9] A method for forming a cured resin, comprising applying the resin composition according to any one of [1] to [5] to a substrate and then heating to 23°C or higher to form a cured resin.

[10] A method for reforming a cured resin product, comprising: a step of curing the resin composition according to any one of [1] to [5] to obtain a cured resin product; a step of heat-treating the cured resin product at 60°C or higher and 250°C or lower; and a step of cooling the cured resin product to 23°C or lower to reform the cured resin product.

[11] The method for reforming a cured resin product according to

[10] , wherein the heat-treating step heats the cured resin product at 60°C or higher and 250°C or lower to dissociate the blocked isocyanate bond.

[12] The method for reforming a cured resin product according to

[11] , comprising a step of cooling the heat-treated cured resin product obtained in the dissociation step to 23°C or lower to reform the cured resin product.

[13] A method for recovering a block group-containing compound, comprising: heat-treating the cured resin product according to any one of [6] to [8] at 60°C or higher and 180°C or lower in the presence of an active hydrogen group-containing compound, and recovering the dissociated block group-containing compound.

[14] A method for stripping a cured resin product, comprising heat-treating the cured resin product according to any one of [6] to [8] adhered to a substrate at 60°C or higher and 180°C or lower in the presence of an active hydrogen group-containing compound, and stripping the cured resin product from the substrate.

[0008] According to the present invention, it is possible to provide a resin composition that, when formed into a cured resin, has performance equivalent to that of a polyurethane resin, but allows for depolymerization of the crosslinked structure, reformation, recovery of raw materials, and peeling, and a cured resin product using the same. It is also possible to provide methods for forming a cured resin product, reforming a cured resin product, recovering raw materials, and peeling.

[0009] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following embodiment. The present invention can be practiced with appropriate modifications within the scope of its gist.

[0010] <Resin Composition> The resin composition of the present invention contains a block group-containing compound and an isocyanate compound. The components of the resin composition of this embodiment will be described in detail below.

[0011] <Block Group-Containing Compound> The block group-containing compound in this embodiment is an organic compound having two or more blocking groups for isocyanate groups in one molecule. The blocking groups in the diblock group-containing compound in this embodiment may be the same structural unit or different structural units. When the diblock group-containing compound has blocking groups with different structures, the dissociation temperature can be easily controlled. The block group refers to a structural unit derived from a compound used as a blocking agent for known blocked polyisocyanates.

[0012] Examples of compounds from which the blocking group is derived include one or more compounds selected from the group consisting of alcohol compounds, alkylphenol compounds, phenol compounds, active methylene compounds, mercaptan compounds, acid amide compounds, acid imide compounds, imidazole compounds, urea compounds, oxime compounds, amine compounds, imide compounds, bisulfites, pyrazole compounds, and triazole compounds.

[0013] Among these, the compound from which the blocking group is derived is preferably derived from one or more compounds selected from the group consisting of oxime compounds, amine compounds, pyrazole compounds, and imidazole compounds, and more preferably oxime compounds, pyrazole compounds, and imidazole compounds. The dissociation temperature can be controlled by the structure of the blocking group.

[0014] (Oxime Compound) The oxime compound is, for example, a compound represented by the following general formula (1).

[0015]

[0016] (Pyrazole Compound) The pyrazole compound is, for example, a compound represented by the following general formula (2).

[0017]

[0018] (Imidazole Compound) The imidazole compound is, for example, a compound represented by the following general formula (3).

[0019]

[0020] (Amine Compound) The amine compound is, for example, a compound represented by the following general formula (4).

[0021]

[0022] In the general formulas (1) to (4), R １ , R ２ , R ５ , R ８ , R ９ , R １０are the same or different organic groups. ３ , R ４ , R ６ , R ７ are hydrogen atoms or the same or different organic groups. In the general formulae (1) to (4), m11 to m14 are integers of 0 or 1, and n11 to n14 are integers of 2 or more.

[0023] In the general formulas (1) to (4), R １ ~R １０ When R is an organic group, it is, for example, an alkyl group, an aryl group, an alkoxy group, or an aryloxy group, each of which may have a substituent. The substituent that the alkyl group, aryl group, alkoxy group, or aryloxy group may have is one or more substituents selected from the group consisting of a carboxy group, a carbonyl group, and an amide group. ３ , R ４ , R ６ , R ７ However, in the case of an organic group, an alkyl group is preferred, an unsubstituted alkyl group is more preferred, and a methyl group or an ethyl group is most preferred.

[0024] In the general formulas (1) to (4), X １１ ~X １４ are each independently an n-valent organic group. １１ ~X １４ is an organic group derived from, for example, a polyol having a divalent or higher hydroxyl group used to derive a block group-containing compound, in which the hydrogen atom of the hydroxyl group has been removed.

[0025] Examples of polyols having divalent or higher hydroxyl groups include non-polymerizable alcohols and polymerizable alcohols. Here, "non-polymerizable alcohol" refers to an alcohol that does not have a polymerizable group. On the other hand, "polymerizable alcohol" refers to an alcohol obtained by polymerizing a monomer having a polymerizable group and a hydroxyl group.

[0026] Examples of non-polymerizable alcohols include polyhydric alcohols such as diols, triols, and tetraols.

[0027] Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,2-propanediol, 1,5-pentanediol, 2-methyl-2,3-butanediol, Examples of the hexanediol include hexanediol, 1,6-hexanediol, 1,2-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentanediol, 2,3-dimethyl-2,3-butanediol, 2-ethyl-hexanediol, 1,2-octanediol, 1,2-decanediol, 2,2,4-trimethylpentanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2-diethyl-1,3-propanediol.

[0028] Examples of triols include glycerin and trimethylolpropane, and examples of tetraols include pentaerythritol.

[0029] The polymerizable alcohol is not particularly limited, but examples thereof include polyester polyols, polyether polyols, acrylic polyols, polyolefin polyols, and the like.

[0030] The polyester polyols are not particularly limited, but examples thereof include products obtained by a condensation reaction between a dibasic acid alone or a mixture thereof and a polyhydric alcohol alone or a mixture thereof.

[0031] The dibasic acid is not particularly limited, but examples thereof include at least one dibasic acid selected from the group consisting of carboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, and terephthalic acid.

[0032] The polyhydric alcohol is not particularly limited, but examples thereof include at least one polyhydric alcohol selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, and glycerin.

[0033] Examples of polyester polyols include polycaprolactones obtained by ring-opening polymerization of ε-caprolactone with the above polyhydric alcohols.

[0034] The polyether polyols are not particularly limited, but examples thereof include polyether polyols obtained by adding alkylene oxides, either singly or in mixture, to polyhydric alcohols, either singly or in mixture, using an alkali metal hydroxide or a strongly basic catalyst; polyether polyols obtained by reacting alkylene oxides with polyamine compounds; and so-called polymer polyols obtained by polymerizing acrylamide or the like using the above polyethers as a medium.

[0035] Examples of alkali metals include lithium, sodium, potassium, etc. Examples of strongly basic catalysts include alcoholates, alkylamines, etc. Examples of polyhydric alcohols include those exemplified for the polyester polyols above.

[0036] Examples of alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, styrene oxide, etc. Examples of polyamine compounds include ethylenediamines, etc.

[0037] The acrylic polyols are not particularly limited, but examples thereof include copolymers of a single or a mixture of an ethylenically unsaturated bond-containing monomer having a hydroxyl group and a single or a mixture of other ethylenically unsaturated bond-containing monomers copolymerizable therewith.

[0038] The ethylenically unsaturated bond-containing monomer having a hydroxyl group is not particularly limited, but examples thereof include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxybutyl methacrylate.

[0039] The other ethylenically unsaturated bond-containing monomer copolymerizable with the ethylenically unsaturated bond-containing monomer having a hydroxyl group is not particularly limited, and examples thereof include acrylic acid esters, methacrylic acid esters, unsaturated carboxylic acids, unsaturated amides, vinyl-based monomers, and vinyl-based monomers having a hydrolyzable silyl group.

[0040] Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, benzyl acrylate, and phenyl acrylate.

[0041] Examples of methacrylic acid esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, benzyl methacrylate, phenyl methacrylate, etc. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc.

[0042] Examples of unsaturated amides include acrylamide, methacrylamide, N,N-methylenebisacrylamide, diacetone acrylamide, diacetone methacrylamide, maleic acid amide, and maleimide.

[0043] Examples of vinyl monomers include glycidyl methacrylate, styrene, vinyltoluene, vinyl acetate, acrylonitrile, dibutyl fumarate, etc. Examples of vinyl monomers having a hydrolyzable silyl group include vinyltrimethoxysilane, vinylmethyldimethoxysilane, γ-(meth)acryloxypropyltrimethoxysilane, etc. Examples of polyolefin polyols include hydroxyl-terminated polybutadiene and hydrogenated products thereof.

[0044] Examples of the pyrazole compound represented by the general formula (2) include 3-methylpyrazole and 3,5-dimethylpyrazole. Examples of the imidazole compound represented by the general formula (3) include 2-ethyl-4-methylimidazole and 4-ethylimidazole.

[0045] In the present embodiment, when the compound from which the blocking group is derived is selected from amine compounds, amine compounds represented by the following general formula (5) are excluded.

[0046]

[0047] In general formula (5), X １５ is an n-valent organic group, and R １１ and R １２ are the same or different organic groups, and n15 is an integer of 2 or more.

[0048] The number average molecular weight of the block group-containing compound is preferably 170 or more and 10,000 or less, more preferably 200 or more and 5,000 or less, even more preferably 220 or more and 2,000 or less, and most preferably 300 or more and 1,500 or less. When the number average molecular weight of the block group-containing compound is equal to or more than the above-mentioned lower limit, compatibility with the (poly)isocyanate compound when formed into a resin composition is likely to be improved, and good flexibility can be imparted to the cured resin. On the other hand, when the number average molecular weight is equal to or less than the above-mentioned upper limit, good curability can be obtained when formed into a cured resin.

[0049] The number of blocking groups in one molecule of the block group-containing compound is 2 or more, preferably 2 to 8, more preferably 2 to 6, even more preferably 2 to 4, and most preferably 2 to 3. When the number of blocking groups in one molecule of the block group-containing compound is 2 or more, coating film physical properties such as solvent resistance can be exhibited when the resulting resin is cured after crosslinking, and when the number is 8 or less, workability during coating film formation can be maintained. Furthermore, two or more different block group-containing compounds may be mixed and used.

[0050] The blocking groups in the blocking group-containing compound may be present anywhere in the compound, but it is preferable that at least one blocking group be present at a molecular terminal, and more preferably that two blocking groups be present at both molecular terminals. The presence of the blocking groups at the molecular terminals results in excellent coating film physical properties such as solvent resistance when the cured resin is formed after crosslinking.

[0051] <Isocyanate Compound> In this embodiment, the isocyanate compound is one or more compounds selected from the group consisting of an isocyanate monomer and a polyisocyanate compound. In this specification, one or more isocyanate compounds selected from the group consisting of an isocyanate monomer and a polyisocyanate compound may be referred to as a "(poly)isocyanate compound." An isocyanate monomer is a monomer compound having one or more isocyanate groups (-NCO). A polyisocyanate compound is a reaction product obtained by reacting multiple monomer compounds having one or more isocyanate groups (-NCO).

[0052] The average number of isocyanate groups per molecular weight of the (poly)isocyanate compound used in the resin composition of the present embodiment is preferably 2 or more and 10 or less, more preferably 2.1 or more and 8 or less, more preferably 2.5 or more and 6 or less, and even more preferably 3 or more and 6 or less. When the average number of isocyanate groups is 2 or more, the formed cured resin product can exhibit coating film properties such as solvent resistance, and when the average number is 10 or less, excellent workability is achieved when producing the cured resin product.

[0053] The isocyanate monomer is preferably one having 4 to 30 carbon atoms. Specific examples of the isocyanate monomer include the following (11) to (14). These isocyanate monomers may be used alone or in combination of two or more.

[0054] (11) Aromatic diisocyanates such as diphenylmethane-4,4'-diisocyanate (MDI), 1,5-naphthalene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate, and m-tetramethylxylylene diisocyanate (TMXDI).

[0055] (12) Aliphatic diisocyanates such as 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate (hereinafter sometimes referred to as "PDI"), 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").

[0056] (13) Alicyclic diisocyanates such as isophorone diisocyanate (hereinafter sometimes referred to as "IPDI"), 1,3-bis(diisocyanatemethyl)cyclohexane, 4,4'-dicyclohexylmethane diisocyanate, diisocyanatenorbornane, and di(isocyanatemethyl)norbornane.

[0057] (14) 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”).

[0058] Among these, one or more diisocyanates selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates are preferred as the isocyanate monomer because of their excellent weather resistance, and PDI, HDI, or IPDI is more preferred as the isocyanate monomer because of their ease of industrial availability.

[0059] (Method for Producing (Poly)isocyanate Compound) The method for producing a (poly)isocyanate compound will be described in detail below. The (poly)isocyanate compound can be obtained by simultaneously producing the (poly)isocyanate compound in the presence of an excess of isocyanate monomer through an allophanate conversion reaction to form an allophanate group, a uretdione conversion reaction to form a uretdione group, an iminooxadiazinedione conversion reaction to form an iminooxadiazinedione group, an isocyanurate conversion reaction to form an isocyanurate group, a urethanization reaction to form a urethane group, and a biuret conversion reaction to form a biuret group, and then removing the unreacted isocyanate monomer after completion of the reaction. 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 and which has one or more groups selected from the group consisting of an allophanate group, a uretdione group, an iminooxadiazinedione group, an isocyanurate group, a urethane group, and a biuret group.

[0060] Alternatively, the above reactions may be carried out separately and the resulting (poly)isocyanate compounds may be mixed in a specific ratio. From the viewpoint of ease of production, it is preferable to carry out the above reactions at once to obtain a (poly)isocyanate compound, and from the viewpoint of freely adjusting the molar ratio of each functional group, it is preferable to produce the compounds separately and then mix them.

[0061] [Blocking Group / Isocyanate Group] The molar equivalent ratio of the blocking group of the blocking group-containing compound to the isocyanate group of the (poly)isocyanate compound contained in the resin composition of this embodiment (blocking group / isocyanate group) is determined depending on the required physical properties of the cured resin, but is preferably 0.3 to 2.0, more preferably 0.5 to 1.5, even more preferably 0.7 to 1.3, and most preferably 0.8 to 1.2. When the blocking group / NCO molar equivalent ratio is within the above range, the cured resin can have good coating film properties such as curability and solvent resistance.

[0062] At least one of the average number of block groups in the block group-containing compound and the average number of isocyanate groups in the (poly)isocyanate compound contained in the resin composition of this embodiment is preferably 2.1 or more.

[0063] Other Additives The resin composition of the present embodiment may further contain other additives, such as curing catalysts, solvents, pigments (extender pigments, color pigments, metallic pigments, etc.), UV 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.

[0064] The curing catalyst may be a basic compound or a Lewis acid compound. Examples of the basic compound include metal hydroxides, metal alkoxides, metal carboxylates, metal acetylacetinates, hydroxides of onium salts, onium carboxylates, halides of onium salts, metal salts of active methylene compounds, onium salts of active methylene compounds, aminosilanes, amines, and phosphines. Suitable onium salts include ammonium salts, phosphonium salts, and sulfonium salts. Examples of the Lewis acid compound include organotin compounds, organozinc compounds, organotitanium compounds, and organozirconium compounds.

[0065] Examples of the solvent include 1-methylpyrrolidone, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, propylene glycol monomethyl ether, 3-methoxy-3-methyl-1-butanol, ethylene glycol diethyl ether, diethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether (DPDM), propylene glycol dimethyl ether, and methyl ethyl ketone. , acetone, methyl isobutyl ketone, propylene glycol monomethyl ether acetate, ethanol, methanol, iso-propanol, 1-propanol, iso-butanol, 1-butanol, tert-butanol, 2-ethylhexanol, cyclohexanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, ethyl acetate, isopropyl acetate, butyl acetate, toluene, xylene, pentane, iso-pentane, hexane, iso-hexane, cyclohexane, solvent naphtha, mineral spirits, etc. These solvents may be used alone or in combination of two or more.

[0066] Furthermore, known pigments (extender pigments, color 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.

[0067] <Method for Producing Resin Composition> When producing the resin composition of this embodiment, for example, additives such as 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 coloration 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 block group-containing compound or a solvent dilution thereof as needed. Next, the (poly)isocyanate compound is added as a curing agent, and if necessary, a solvent is further added to adjust the viscosity. Next, the resin composition can be obtained by stirring by hand or using a stirring device such as a mixer.

[0068] The resin composition of the present embodiment is used as a curable composition such as a coating composition, a pressure-sensitive adhesive composition, an adhesive composition, or a casting composition, as well as a crosslinking agent, a modifier, or an additive for various surface treatment agent compositions such as a fiber treatment agent, various elastomer compositions, or foam compositions.

[0069] When used as a coating composition, it is preferably used as a primer, intermediate coat, or top coat on various materials by roll coating, curtain flow coating, spray coating, electrostatic coating, bell coating, etc. Furthermore, this coating composition is preferably used for pre-coated metals including rust-resistant steel plates, automobile coatings, and plastic coatings;

[0070] The coating composition is applied by roll coating, curtain flow coating, spray coating, electrostatic coating, bell coating, etc., and then baked to form a coating film. The crosslinked coating film obtained after curing of the coating composition has excellent chemical resistance, heat resistance, water resistance, etc.

[0071] When used as a pressure-sensitive adhesive composition or adhesive composition, it has excellent quick-drying and peeling properties, and when used as a surface protection film, it has good conformability to curved surfaces and unevenness, and provides good adhesion and peelability. When used as a pressure-sensitive adhesive composition or adhesive composition, its application fields include automobiles, building materials, home appliances, woodworking, and solar cell laminates. Among these, optical components for liquid crystal displays of home appliances such as televisions, personal computers, digital cameras, and mobile phones must be laminated with various adherend films and plates to exhibit various functions. Since sufficient adhesion and / or adhesiveness is required between the films and plates of various adherends, this is a preferred example of a pressure-sensitive adhesive composition or adhesive composition.

[0072] <Cured Resin> One aspect of the present invention is a cured resin obtained by curing the resin composition. In one aspect of this embodiment, the cured resin has a crosslinked structure in which a block group contained in the block group-containing compound is bonded to an isocyanate group contained in the (poly)isocyanate compound. The cured resin of this embodiment has good curability, and the block group-containing compound can be recovered from the cured resin. The shape of the cured resin is not particularly limited, but a film shape, i.e., a resin film, is preferred.

[0073] <Method for forming cured resin product> The cured resin product of this embodiment can be obtained by curing the resin composition by heating it at room temperature (e.g., 23° C.) or higher. When forming a resin film, the resin composition can be applied to a substrate by a known method such as roll coating, curtain flow coating, spray coating, bell coating, or electrostatic coating, and then heated to cure.

[0074] From the viewpoint of energy saving, the heating temperature is preferably from about 23° C. to about 120° C., more preferably from about 23° C. to about 100° C., and even more preferably from about 23° C. to about 80° C. From the viewpoint of energy saving and the heat resistance of the substrate, the heating time is preferably from about 1 minute to about 60 minutes, and more preferably from about 2 minutes to about 40 minutes.

[0075] 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.

[0076] The material of the substrate is not particularly limited, and examples thereof include metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, zinc-plated steel, and zinc alloy (Zn—Al, Zn—Ni, Zn—Fe, etc.)-plated steel; resins such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, and epoxy resin; plastic materials such as various FRPs; inorganic materials such as glass, cement, and concrete; wood; and fibrous materials such as paper and cloth. Among these, metal materials and plastic materials are preferred.

[0077] The substrate may be the surface of the above-mentioned metal material, or the surface of a metal such as a car body molded from the above-mentioned metal material, which has been subjected to a surface treatment such as phosphate treatment, chromate treatment, or composite oxide treatment, and further, may have a coating film formed thereon. The substrate with a coating film formed thereon may be one that has been subjected to a surface treatment as necessary and then a primer coating film formed thereon, for example, a car body on which a primer coating film has been formed using an electrodeposition paint. The substrate may be the surface of the above-mentioned plastic material, or the surface of a plastic such as an automobile part molded from the above-mentioned metal material, which has been subjected to a desired surface treatment. The substrate may also be a combination of a plastic material and a metal material.

[0078] <Method for Reforming Cured Resin> The cured resin of this embodiment can be depolymerized by heating and can be reformed by cooling. Heating the cured resin depolymerizes the bond between the block group-containing compound and the (poly)isocyanate compound (a bond obtained by an addition reaction between the block group of the block group-containing compound and the isocyanate group of the (poly)isocyanate compound, hereinafter referred to as a blocked isocyanate bond), regenerating the block group and the isocyanate group. Cooling the cured resin further reforms the blocked isocyanate bond.

[0079] By utilizing this bond dissociation and reformation, for example, scratches on a cured resin material on a substrate can be repaired. The heat treatment temperature is preferably 60° C. or higher and 250° C. or lower, more preferably 70° C. or higher and 200° C. or lower, and most preferably 80° C. or higher and 180° C. or lower. When the heat treatment temperature is equal to or higher than the lower limit, melting of the cured resin material proceeds efficiently, and when the heat treatment temperature is equal to or lower than the upper limit, deterioration due to decomposition of the cured resin material can be suppressed.

[0080] In one aspect of the present invention, the method for reforming a cured resin preferably includes the steps of curing the resin composition of the present invention to obtain a cured resin, heat-treating the cured resin at a temperature of 60°C or higher and 250°C or lower, and further cooling the cured resin to 23°C or lower to reform the cured resin.

[0081] In one aspect of the present invention, the heat treatment step is preferably a step of dissociating blocked isocyanate bonds by heat treating the cured resin product at 60° C. or higher and 250° C. or lower. The step of dissociating blocked isocyanate bonds may be a step of dissociating a crosslinked structure formed by bonding a blocking group contained in the blocking group-containing compound with an isocyanate group contained in the (poly)isocyanate compound.

[0082] In one aspect of the present invention, it is preferable to include a step of cooling the heat-treated cured resin product obtained in the dissociation step to 23°C or less to reform the cured resin product.

[0083] <Method for recovering a blocked group-containing compound and a method for peeling off a cured resin product> The cured resin product of this embodiment can be subjected to a heat treatment in the presence of an active hydrogen group-containing compound to liberate and recover the blocked group-containing compound. Examples of the active hydrogen group-containing compound include compounds used as blocking agents for the above-mentioned blocked polyisocyanates. Among these, alcohol-based compounds, and more preferably, monoalcohol-based compounds from the viewpoint of recoverability of raw materials, are preferred.

[0084] Examples of monoalcohol compounds include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, n-pentanol, n-hexanol, n-octanol, n-nonanol, 2-ethylbutanol, 2,2-dimethylhexanol, 2-ethylhexanol, cyclohexanol, methylcyclohexanol, and ethylcyclohexanol. Considering volatility during heat treatment, monoalcohol compounds are preferably compounds having 4 or more carbon atoms, more preferably compounds having 5 or more carbon atoms, and most preferably compounds having 6 or more carbon atoms. From the viewpoint of workability, compounds having 12 or less carbon atoms are preferred.

[0085] The treatment method is, for example, to immerse the cured resin coated on the substrate (together with the substrate) in a treatment liquid containing an active hydrogen group-containing compound, or to spray or apply the treatment liquid containing the active hydrogen group-containing compound onto the cured resin, followed by heating. The active hydrogen group compound is preferably added in excess of the molar amount of the diblock group.

[0086] The isocyanate group regenerated by heating bonds with the active hydrogen group of the active hydrogen group-containing compound, liberating the blocked group-containing compound, which allows the blocked group-containing compound to be regenerated and recovered. Furthermore, because the blocked isocyanate bond dissociates, the cured resin product can be peeled off from the substrate and the substrate can be recovered. The heat treatment temperature is preferably 60°C or higher and 200°C or lower, more preferably 70°C or higher and 180°C or lower, and most preferably 80°C or higher and 150°C or lower. By setting the heat treatment temperature at or above the lower limit, the cured resin product can be efficiently melted, while by setting the heat treatment temperature at or below the upper limit, deterioration due to decomposition of the cured resin product can be suppressed.

[0087] Hereinafter, the present embodiment will be described in more detail based on examples and comparative examples, but the present embodiment is not limited to the following examples in any way.

[0088] <Test Items> The blocked polyisocyanate compositions obtained in the Examples and Comparative Examples were subjected to measurement of various physical properties and evaluations according to the methods described below.

[0089] [Physical Property 1] (Number Average Molecular Weight) The number average molecular weight is the number average molecular weight and weight average molecular weight based on polystyrene or polyethylene as measured by gel permeation chromatography (GPC) using the following apparatus.

[0090] (Measurement conditions) Apparatus: HLC-802A manufactured by Tosoh Corporation Column: G1000HXL x 1, G2000HXL x 1, G3000HXL x 1 manufactured by Tosoh Corporation Carrier: tetrahydrofuran Detection method: differential refractometer

[0091] [Evaluation 1] (Curability) The obtained resin composition was applied to a polypropylene (PP) plate to a dry film thickness of 40 μm, and then heated and dried at 80° C. for 15 minutes to obtain a resin film. The obtained resin film was stored at room temperature (23° C.) for 1 day, and the gel fraction was measured. The gel fraction was determined as a percentage (mass%) of the value obtained by dividing the mass of the undissolved portion of the resin film when immersed in acetone at 23° C. for 24 hours by the mass before immersion. Curability was evaluated from the obtained gel fraction according to the following evaluation criteria.

[0092] (Evaluation criteria) A: Initial gel fraction 80% or more B: Initial gel fraction 60% or more and less than 80% C: Initial gel fraction less than 60%

[0093] [Evaluation 2] (Solvent Resistance) The obtained resin composition was applied to a glass plate so that the dry film thickness was 40 μm, and then heated and dried at 80° C. for 15 minutes to obtain a resin film. The obtained resin film was stored at room temperature (23° C.) for 1 day, and then the surface of the resin film was rubbed back and forth 20 times with a cotton swab soaked in xylene. The solvent resistance was evaluated from the appearance of the resin film after the test according to the following evaluation criteria.

[0094] (Evaluation criteria) AA: No change in resin film A: Slight rubbing marks (no whitening) B: Whitening of rubbing marks C: Resin film dissolved

[0095] [Evaluation 3] (Recoverability) The obtained resin composition was applied to a polypropylene (PP) plate to a dry film thickness of 40 μm, and then heated and dried at 80°C for 15 minutes to obtain a resin film. The obtained resin film was stored at room temperature (23°C) for one week, and then 0.1 g of the resin film was cut out and immersed in approximately 10 ml of 2-ethylhexanol. After leaving it at room temperature for 30 minutes, the solution was sampled and subjected to GPC measurement under the following conditions. The film immersed in 2-ethylhexanol was heated together with the solvent at 130°C, and the state of the film was confirmed after 5 hours. In addition, the solution after heating was subjected to GPC measurement under the following conditions. Based on the state of the resin film after the test and a comparison of the GPC measurement results before and after heating, recoverability was evaluated according to the following evaluation criteria.

[0096] (Measurement conditions) Apparatus: HLC-802A manufactured by Tosoh Corporation Column: G1000HXL x 1, G2000HXL x 1, G3000HXL x 1 manufactured by Tosoh Corporation Carrier: tetrahydrofuran Detection method: differential refractometer

[0097] (Evaluation Criteria) A: The resin film dissolved, and the peak derived from the block group-containing compound increased after heating compared to before heating. B: The resin film remained, and the peak derived from the block group-containing compound increased after heating compared to before heating. C: The resin film remained, and there was no increase in the peak derived from the block group-containing compound before and after heating.

[0098] [Evaluation 4] (Depolymerization Behavior) The obtained resin composition was applied to a polypropylene (PP) plate so that the dry film thickness was 40 μm, and then heated and dried at 80° C. for 15 minutes to obtain a resin film. The obtained resin film was stored at room temperature (23° C.) for one week, and then cut into 0.5 cm square pieces. The cut resin film was placed on a Si wafer. The depolymerization behavior of the resin composition was measured using the following microscopic FT-IR device. ―１ The change in the peak of the isocyanate group near the peak was confirmed. The depolymerization behavior was evaluated according to the following criteria.

[0099] (Device) Measuring device: Hyperion (manufactured by Bruker) Measuring method: Transmission method Resolution: 4 cm ―１ Aperture size: 200 x 200 μm Measurement interval time: 5 sec Measurement time: 70 min Number of scans: 1 scan Heating device: Microscope heating / cooling stage (Linkam) Temperature program: Room temperature → (heating rate 30°C / min) → 120°C → (heating rate 5°C / min) → 250°C (held for 5 min) → (cooling rate 5°C / min) → 120°C (held for 5 min) → (cooling rate 10°C / min) → 60°C

[0100] (Evaluation criteria) A: 2260 cm ―１ A peak occurs near 2260 cm －１ Nearby peaks and 2925cm －１ The height ratio of the peaks around 2260 cm becomes 0.05 or more during heating. ―１ No change in the vicinity (2260 cm －１ Nearby peaks and 2925cm －１ The height ratio of the peaks in the vicinity becomes less than 0.05 during the temperature rise.)

[0101] [Evaluation 5] (Workability) The resulting resin composition was left to stand at 23° C., and the gel time was measured. The workability was evaluated according to the following evaluation criteria.

[0102] (Evaluation criteria) AA: Gelling time is 120 minutes or more A: Gelling time is 30 minutes or more and less than 120 minutes B: Gelling time is 5 minutes or more and less than 30 minutes C: Gelling time is less than 5 minutes

[0103] [Evaluation 6] (Dissociation Temperature) The obtained resin composition was applied to a polypropylene (PP) plate so that the dry film thickness was 40 μm, and then heated and dried at 80° C. for 15 minutes to obtain a resin film. The obtained resin film was stored at room temperature (23° C.) for one week, and then cut into 0.5 cm square pieces. The cut resin film was placed on a Si wafer. Using the following microscopic FT-IR device, the dissociation temperature of 2260 cm ―１ The change in the peak of the isocyanate group near the peak was confirmed. The depolymerization behavior was evaluated according to the following criteria.

[0104] (Device) Measuring device: Hyperion (manufactured by Bruker) Measuring method: Transmission method Resolution: 4 cm ―１ Aperture size: 200 x 200 μm Measurement interval time: 5 sec Measurement time: 70 min Number of scans: 1 scan Heating device: Microscope heating / cooling stage (Linkam Co., Ltd.) Temperature program: Room temperature → (heating rate 30°C / min) → 120°C → (heating rate 5°C / min) → 200°C (held for 5 min)

[0105] (Evaluation criteria) A: Isocyanate group peak appears below 147°C B: Isocyanate group peak appears between 147°C and 200°C C: No isocyanate group is observed up to 200°C

[0106] <Synthesis of Block Group-Containing Compound> [Synthesis Example 1] (Synthesis of Block Group-Containing Compound B-1) A four-necked flask equipped with a thermometer, a stirring blade, and a reflux condenser was charged with 350 parts by mass of PEG300, 0.667 parts by mass of p-toluenesulfonic acid monohydrate, and 298 parts by mass of replinic acid under Ar flow and stirred. The internal temperature was raised to 90 ° C. and maintained for 1 hour to carry out the reaction. Thereafter, the reactor temperature was maintained at 90 ° C., and the pressure was reduced to 60 hPa. The temperature was gradually increased and the pressure was reduced, and the internal temperature was maintained at 125 ° C. and 10 hPa, where it was maintained for 3 hours. Next, strip distillation was carried out at an external temperature of 135 ° C., and the reaction liquid was recovered, and an intermediate product was obtained.

[0107] A four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser was charged with 135 parts by mass of hydroxylamine hydrochloride, 850 ml of ion-exchanged water, and 410 parts by mass of the intermediate product obtained above. The flask was immersed in an ice bath and stirred. 137 parts by mass of potassium carbonate was dissolved in 830 ml of ion-exchanged water and added dropwise to the reaction solution using a 1 L dropping funnel. After the dropwise addition, the flask was removed from the ice bath and stirred at room temperature for 18 hours. The resulting reaction solution was added to 1.6 L of chloroform, stirred, and the organic layer was recovered. The organic layer was then diluted with MgSO 4 ４ The mixture was dried at 750°C, filtered, and concentrated to obtain a crude product of the target substance. Finally, the crude product was dissolved in 830 ml of a 9:1 chloroform / methanol solution, filtered under reduced pressure, and the filtrate was concentrated to obtain a block group-containing compound B-1 having block structural units of an oxime compound (number of block groups: 2) at both ends. The number average molecular weight (based on polyethylene) of the resulting block group-containing compound was 530.

[0108] Synthesis Example 2 Synthesis of Block Group-Containing Compound B-2 To a four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser, 614 parts by mass of PEG 1000 and 3.06 L of THF were added under Ar flow, and the flask was immersed in an ice bath and stirred. Next, 357 parts by mass of toluenesulfonic acid chloride was added, followed by dropwise addition of 249 parts by mass of triethylamine, and the mixture was stirred at an external temperature of 35°C for 20 hours. 140 parts by mass of sodium azide was added, and then 148 parts by mass of sodium bicarbonate was dispersed in 1.48 L of ion-exchanged water and added. The internal temperature was raised to 66°C, and the THF was distilled off. The external temperature was then raised to 100°C, and the mixture was stirred under reflux for 8 hours. Thereafter, 1.54 L of ethyl acetate was added and stirred, and the organic layer was recovered. The recovered organic layer was washed with saturated saline and added with MgSO ４ After drying at 400°C, the mixture was filtered and concentrated to give intermediate product 1.

[0109] In a four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser, 406 parts by mass of intermediate product 1 and 3.8 L of THF were added and stirred. After stirring, 305 parts by mass of triphenylphosphine were added, and the mixture was further stirred at room temperature for 23 hours. 1.29 L of ion-exchanged water was added dropwise, and the mixture was stirred at room temperature for 22 hours. The reaction solution was concentrated and then dispersed in 1 L of toluene, and the aqueous layer was recovered. The aqueous layer was filtered under reduced pressure, and the obtained filtrate was washed with toluene and then concentrated to obtain a crude product. The obtained crude product was dissolved in chloroform, and then MgSO ４ The mixture was added and stirred for 10 minutes. After stirring, the liquid was filtered and concentrated using an evaporator to obtain intermediate product 2. 307 parts by mass of intermediate product 2 and 3.1 L of ethanol were added to a four-neck flask equipped with a thermometer, a stirring blade, and a reflux condenser, and the mixture was stirred. After stirring, 107 parts by mass of acetone was added, the internal temperature was raised to 60°C, and the mixture was stirred for 5 hours.

[0110] After heating, the mixture was allowed to cool to room temperature, and the reaction vessel was immersed in an ice-water bath. ４ 34.9 parts by mass of toluene was added, and after the heat of reaction subsided, the mixture was stirred at room temperature for 15 hours. The mixture was again placed in an ice-water bath, and 132 L of ion-exchanged water was added and stirred. The solvent was then distilled off to obtain a crude product. The crude product was suspended in 3.8 L of chloroform and filtered through a funnel packed with amino silica gel and cellulose. The solvent was distilled off from the filtrate to obtain a block group-containing compound B-2 having block structural units of a diisopropylamine compound (number of block groups: 2) at both ends. The obtained block group-containing compound was not dissolved in THF solvent, and the number average molecular weight was not measured. (The number average molecular weight from the estimated structure is 1080)

[0111] Synthesis Example 3 Synthesis of Block Group-Containing Compound B-3 A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel was conditioned with a nitrogen atmosphere, and 60 parts of HDI and 9.5 parts of PEG 400 were charged and maintained at 90°C for 4 hours. The mixture was then cooled, and unreacted HDI monomer was removed using a thin-film distillation apparatus. The viscosity of the resulting polyisocyanate P-3 at 25°C was 600 mPa·s, the isocyanate group concentration was 11.2% by mass, the number average molecular weight was 850, and the average number of isocyanate groups was 2.0. 10 parts of the above polyisocyanate P-3 and 3.5 parts of butyl acetate were added, and the mixture was maintained at 30°C. 4.2 parts of 3-amino-5-phenylpyrazole (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added, and the mixture was maintained for 1 hour, yielding an 80% butyl acetate solution of diblock group-containing compound B-3. The number average molecular weight (based on polyethylene) of the resulting block group-containing compound was 1,200.

[0112] [Synthesis Example 4] (Synthesis of Polyisocyanate Compound P-1) A four-necked flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel was conditioned with a nitrogen atmosphere, and 600 parts of HDI was charged and maintained at 60°C for 2 hours. Thereafter, tetramethylammonium caprylate was added as an isocyanuration catalyst to carry out an isocyanuration reaction. When the isocyanate group concentration of the reaction solution reached 44.6% by mass, phosphoric acid was added to terminate the reaction. Thereafter, the reaction solution was filtered, and unreacted HDI monomer was removed using a thin-film distillation apparatus. The viscosity of the resulting polyisocyanate P-1 at 25°C was 1300 mPa s, the isocyanate group concentration was 23.0% by mass, the number average molecular weight (based on polystyrene) was 590, and the average number of isocyanate groups was 3.2.

[0113] Synthesis Example 5 (Synthesis of Polyisocyanate Compound P-2) A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel was conditioned with a nitrogen atmosphere, and 560 parts by mass of HDI, 240 parts by mass of IPDI, and 20 parts by mass of trimethylolpropane (molecular weight 134) were charged. The temperature inside the reactor was maintained at 90°C for 1 hour with stirring to carry out a urethanization reaction. Thereafter, the temperature inside the reactor was maintained at 80°C, and 0.096 parts by mass of an isocyanuration catalyst, tetramethylammonium capriate, was added. When the isocyanate group concentration of the reaction solution reached 34.1% by mass, phosphoric acid was added to terminate the reaction. The reaction solution was filtered, and unreacted HDI and IPDI were removed using a thin-film evaporator. The resulting polyisocyanate P-2 had a viscosity of 165,000 mPa·s at 25° C., an isocyanate group concentration of 19.2 mass %, a number average molecular weight (based on polystyrene) of 1050, and an average number of isocyanate groups of 4.8.

[0114] Synthesis Example 6 (Synthesis of Polyisocyanate Compound P-3) A four-neck flask equipped with a stirrer, thermometer, reflux condenser, nitrogen inlet tube, and dropping funnel was conditioned with a nitrogen atmosphere, and 1000 g of PDI and 4.0 g of isobutanol were charged. The temperature inside the reactor was maintained at 70°C with stirring. Tetramethylammonium caprylate was added thereto, and when the NCO content of the reaction solution reached 42.5% by mass, phosphoric acid was added to terminate the reaction. The reaction solution was then filtered, and unreacted HDI was removed using a thin-film evaporator to obtain Polyisocyanate P-3. The viscosity of the obtained Polyisocyanate P-3 at 25°C was 2000 mPa s, the isocyanate group content was 25.0% by mass, the number average molecular weight (based on polystyrene) was 530, and the average number of isocyanate groups was 3.2.

[0115] <Production of Resin Compositions> [Example 1] (Production of Resin Composition C-1) Polyisocyanate P-1 obtained in Synthesis Example 4 and block group-containing compound B-1 obtained in Synthesis Example 1 were blended in a ratio such that the ratio of the molar amount of block groups to the molar amount of isocyanate groups (block group / isocyanate group) was 1.0, and butyl acetate was further blended to prepare a resin composition C-1 in a ratio such that the solid content was 50 mass%.

[0116] Example 2 (Production of Resin Composition C-2) Polyisocyanate P-1 obtained in Synthesis Example 4 and block group-containing compound B-1 obtained in Synthesis Example 1 were blended in a ratio such that the ratio of the molar amount of block groups to the molar amount of isocyanate groups (block group / isocyanate group) was 1.25, and butyl acetate was further blended therein to prepare a resin composition C-2 in a ratio such that the solid content was 50% by mass.

[0117] Example 3 Production of Resin Composition C-3 Polyisocyanate P-1 obtained in Synthesis Example 4 and block group-containing compound B-1 obtained in Synthesis Example 1 were blended in a ratio such that the ratio of the molar amount of block groups to the molar amount of isocyanate groups (block group / isocyanate group) was 1.5, and butyl acetate was further blended therein to prepare a resin composition C-3 in a ratio such that the solid content was 50% by mass.

[0118] Example 4 (Production of Resin Composition C-4) Polyisocyanate P-2 obtained in Synthesis Example 5 and block group-containing compound B-1 obtained in Synthesis Example 1 were blended in a ratio such that the ratio of the molar amount of block groups to the molar amount of isocyanate groups (block group / isocyanate group) was 1.0, and butyl acetate was further blended therein to prepare a resin composition C-4 in a ratio such that the solid content was 50% by mass.

[0119] Example 5 (Production of Resin Composition C-5) Polyisocyanate P-1 obtained in Synthesis Example 4 and block group-containing compound B-2 obtained in Synthesis Example 2 were blended in a ratio such that the ratio of the molar amount of block groups to the molar amount of isocyanate groups (block group / isocyanate group) was 1.0, and butyl acetate was further blended therein to prepare a resin composition C-5 in a ratio such that the solid content was 50% by mass.

[0120] Example 6 (Production of Resin Composition C-6) Polyisocyanate P-1 obtained in Synthesis Example 4 and blocking group-containing compound B-3 obtained in Synthesis Example 3 were blended in a ratio such that the ratio of the molar amount of blocking groups to the molar amount of isocyanate groups (blocking groups / isocyanate groups) was 1.0, and butyl acetate was further blended therein to prepare a resin composition C-5 in a ratio such that the solid content was 50% by mass.

[0121] Example 7 Production of Resin Composition C-7 Block group-containing compound B-1 obtained in Synthesis Example 1 and block group-containing compound B-3 obtained in Synthesis Example 3 were mixed in a weight ratio of 70 / 30. Polyisocyanate P-1 obtained in Synthesis Example 4 and the mixed diblock group-containing compound were blended in a ratio such that the ratio of the molar amount of blocking groups to the molar amount of isocyanate groups (block group / isocyanate group) was 1.0, and butyl acetate was further blended to prepare a resin composition C-7 in a ratio such that the solids content was 50% by mass.

[0122] Example 8 Production of Resin Composition C-7 Block group-containing compound B-1 obtained in Synthesis Example 1 and PEG300 were mixed in a weight ratio of 70 / 30. Polyisocyanate P-1 obtained in Synthesis Example 4 and the mixed diblock group-containing compound were blended in a ratio such that the ratio of the molar amount of blocking groups to the molar amount of isocyanate groups (block group / isocyanate group) was 1.0, and butyl acetate was further blended to prepare a resin composition C-8 in a ratio such that the solids content was 50% by mass.

[0123] Example 9 (Production of Resin Composition C-9) Polyisocyanate P-3 obtained in Synthesis Example 4 and block group-containing compound B-1 obtained in Synthesis Example 1 were blended in a ratio such that the ratio of the molar amount of block groups to the molar amount of isocyanate groups (block group / isocyanate group) was 1.0, and butyl acetate was further blended therein to prepare a resin composition C-9 in a ratio such that the solid content was 50% by mass.

[0124] Comparative Example 1 (Production of Resin Composition D-1) Polyisocyanate P-1 obtained in Synthesis Example 3 and PEG300 were blended in such a ratio that the ratio of the molar amount of hydroxyl groups to the molar amount of isocyanate groups (hydroxyl groups / isocyanate groups) was 1.0, and butyl acetate was further blended therein to prepare a resin composition B-1 in such a ratio that the solid content was 50 mass%.

[0125] Comparative Example 2 (Production of Resin Composition D-2) Polyisocyanate P-1 obtained in Synthesis Example 3 and an acrylic polyol (Setalux 1767, trade name of Allnex Corporation, hydroxyl group concentration 4.5% by mass (based on resin), resin solid content 65% by mass) were blended in a ratio such that the ratio of the molar amount of hydroxyl groups to the molar amount of isocyanate groups (hydroxyl groups / isocyanate groups) was 1.0, and butyl acetate was further blended to prepare a ratio such that the solid content was 50% by mass, thereby obtaining Resin Composition D-2.

[0126]

[0127]

[0128] The resin film, which is a cured product obtained by curing the resin composition of this embodiment, can be heated to recover coating materials such as block group-containing compounds, and the resin film can be applied to a substrate and crosslinked, allowing the coating materials and the substrate to be reused by peeling it off. Furthermore, by cooling after heating, the crosslinked structure of the resin film can be depolymerized and reformed, making it suitable for repairing coated objects, etc.

Claims

1. A resin composition comprising a blocking group-containing compound having two or more blocking groups for an isocyanate group, and one or more isocyanate compounds selected from the group consisting of isocyanate monomers and polyisocyanate compounds.

2. The resin composition according to claim 1, wherein the blocking group is derived from one or more compounds selected from the group consisting of oxime compounds, amine compounds, pyrazole compounds, and imidazole compounds.

3. The resin composition according to claim 1 or 2, wherein the number average molecular weight of the block group-containing compound is 170 or more and 10,000 or less.

4. A resin composition according to claim 1 or 2, wherein the molar ratio of the blocking group to the isocyanate group contained in the isocyanate compound, i.e., blocking group / isocyanate group, is 0.3 or more and 2.0 or less.

5. A resin composition according to claim 1 or 2, wherein at least one of the average number of blocking groups of the blocking group-containing compound and the average number of isocyanate groups of the isocyanate compound is 2.1 or more.

6. A cured resin having a blocked isocyanate bond formed by the reaction of a blocking group with an isocyanate group.

7. A cured resin obtained by curing the resin composition according to claim 1 or 2.

8. The cured resin material according to claim 7, which has a crosslinked structure in which the blocking group of the blocking group-containing compound and the isocyanate group of the isocyanate compound are bonded together.

9. A method for forming a cured resin product, comprising applying the resin composition according to claim 1 or 2 to a substrate, and then heating the composition to 23°C or higher to form a cured resin product.

10. A method for reforming a cured resin, comprising the steps of: curing the resin composition according to claim 1 or 2 to obtain a cured resin; heat-treating the cured resin at a temperature of 60°C or higher and 250°C or lower; and cooling the cured resin to 23°C or lower to reform the cured resin.

11. A method for reforming a cured resin material according to claim 10, wherein the heat treatment step is a step of heat treating the cured resin material at a temperature of 60°C or higher and 250°C or lower to dissociate blocked isocyanate bonds.

12. A method for reforming a cured resin material according to claim 11, further comprising a step of cooling the heat-treated cured resin material obtained in the dissociation step to 23°C or less to reform the cured resin material.

13. A method for recovering a block group-containing compound, comprising heating the cured resin product according to claim 6 at a temperature of 60°C to 180°C in the presence of an active hydrogen group-containing compound, and recovering the dissociated block group-containing compound.

14. A method for peeling off a cured resin, comprising heating the cured resin according to claim 6 adhered to a substrate at a temperature of 60°C or higher and 180°C or lower in the presence of an active hydrogen group-containing compound, and peeling off the cured resin from the substrate.

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