JP2023163352A - Curable composition, cured product and method for producing cured product - Google Patents

Abstract

To provide a curable composition that offers superior flexibility and also exhibits superior drying properties when heated at temperatures lower than before, a cured product and a method for producing the cured product.SOLUTION: A curable composition includes an epoxy resin (A), a latent curing agent (B), and a blocked isocyanate (C). The blocked isocyanate (C) is derived from an aliphatic and/or alicyclic isocyanate compound (C-1), a polyol compound (C-2), and an oxime-based blocking agent (C-3). The polyol compound (C-2) includes polyester polyol and/or polycarbonate polyol.SELECTED DRAWING: None

Description

The present invention relates to a curable composition, a cured product, and a method for producing the cured product.

In recent years, there has been an increasing market need for electronic devices to be lighter and more flexible. There is a tendency for lighter weight and flexibility to be desired not only in the base materials, insulating films, and conductive films that constitute electronic devices, but also in the protective films, adhesives, adhesives, sealants, and sealants that accompany them. In particular, when used in the form of a sheet or film such as an insulating sheet, a thermally conductive sheet, a laminate, or a printed wiring board, not only flexibility but also surface dryness tends to be required.
Furthermore, from the perspective of protecting the global environment, there is a need to reduce energy consumption during thermosetting, and curability at lower temperatures than before is required.

Patent Document 1 discloses a structural adhesive containing an epoxy resin, a reactive elastomer reinforcing agent containing an isocyanate group capped with a ketoxime compound, and a curing agent, which exhibits adhesive properties when heated at 180°C. It is disclosed that it has excellent tensile shear strength and peel strength as an agent.
Patent Document 2 discloses a resin composition containing an epoxy resin, an amine-based latent curing agent, a block urethane, and an active hydrogen-containing compound, which has excellent peel strength as an adhesive when heated at 180°C. This is disclosed.
Patent Document 3 also discloses a curable resin composition containing an epoxy resin, an amine-based latent curing agent, and a block urethane, which exhibits excellent adhesion to iron and aluminum as an adhesive when heated at 180°C. This is disclosed.
Patent Document 4 discloses a curing method that includes an epoxy resin, a blocked isocyanate compound obtained by masking a urethane prepolymer obtained from a polyhydroxy compound and a polyisocyanate compound with an alkylamine, and a latent curing agent as essential components. A polyurethane epoxy block urethane composition is disclosed, and it is disclosed that it has excellent tensile shear strength and peel strength as an adhesive when heated at 150°C.

International Publication No. 2011/056357 International Publication No. 2021/106962 International Publication No. 2020/095995 Japanese Patent Application Publication No. 5-155973

It is disclosed that the curable compositions described in Patent Documents 1, 2, and 3 have excellent tensile shear strength and peel strength as adhesives when heated at high temperatures as usual. It is disclosed that the curable composition described in Patent Document 4 has excellent tensile shear strength and peel strength as an adhesive even when heated at a lower temperature than conventional ones. However, the flexibility and drying properties when processed into a film are not disclosed.

The present invention has been made in view of the above circumstances, and provides a curable composition, a cured product, and a method for producing a cured product that has excellent flexibility and drying properties when heated at lower temperatures than conventional ones. do.

That is, the present invention includes the following aspects.
Embodiment (1) includes an epoxy resin (A), a latent curing agent (B), and a blocked isocyanate (C), wherein the blocked isocyanate (C) is an aliphatic and/or alicyclic isocyanate. derived from a compound (C-1), a polyol compound (C-2), and an oxime blocking agent (C-3), the polyol compound (C-2) containing a polyester polyol and/or a polycarbonate polyol, It is a curable composition.
Embodiment (2) is the curable composition according to embodiment (1), wherein the polyol compound (C-2) has a number average molecular weight of 300 or more and 5,000 or less.
In the embodiment (3), the aliphatic and/or alicyclic isocyanate compound (C-1) is a diisocyanate compound and/or a polyisocyanate compound derived from a diisocyanate monomer, (1) or (2). ) is the curable composition according to the embodiment.
In the embodiment (4), the polyol compound (C-2) further contains a polyol compound other than polyester polyol and/or polycarbonate polyol, the curable property according to any one of embodiments (1) to (3). It is a composition.
Embodiment (5) is a cured product obtained by curing the curable composition according to any one of embodiments (1) to (4).
Embodiment (6) is the production of a cured product, which includes a step of coating, impregnating, or adhering the curable composition according to any one of embodiments (1) to (4) on a substrate, and then curing the composition. It's a method.

According to the present invention, it is possible to provide a curable composition, a cured product, and a method for producing a cured product that has good flexibility and excellent drying properties when heated at a lower temperature than conventional compositions.

Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail. The present embodiment below is an illustration for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be modified in various ways without departing from the gist thereof.

≪Curable composition≫
The curable composition of this embodiment includes an epoxy resin (A), a latent curing agent (B), and a blocked isocyanate (C).
The curable composition of the present embodiment contains the above-mentioned blocked isocyanate (C), so that a cured product having excellent flexibility and drying properties when heated at a lower temperature than conventional compositions can be obtained.
Each component of the curable composition of this embodiment will be explained in detail below.

≪Epoxy resin (A)≫
The epoxy resin (A) of this embodiment is not particularly limited, and known resins can be used, such as bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol AD epoxy resin, Tetrabromobisphenol A epoxy resin, biphenyl epoxy resin, tetramethylbiphenyl epoxy resin, tetrabromobiphenyl epoxy resin, diphenyl ether epoxy resin, benzophenone epoxy resin, phenylbenzoate epoxy resin, diphenyl sulfide epoxy resin, diphenyl Sulfoxide type epoxy resin, diphenylsulfone type epoxy resin, diphenyl disulfide type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, hydroquinone type epoxy resin, methylhydroquinone type epoxy resin, dibutylhydroquinone type epoxy resin, resorcin type epoxy resin, methyl Bifunctional epoxy resins such as resorcinol-type epoxy resins, catechol-type epoxy resins, N,N-diglycidylaniline-type epoxy resins; N,N-diglycidylaminobenzene-type epoxy resins, o-(N,N-diglycidyl Trifunctional epoxy resins such as amino) toluene type epoxy resins and triazine type epoxy resins; Tetrafunctional epoxy resins such as tetraglycidyldiaminodiphenylmethane type epoxy resins and diaminobenzene type epoxy resins; Phenol novolac type epoxy resins and cresol novolacs Polyfunctional epoxy resins such as type epoxy resins, triphenylmethane type epoxy resins, tetraphenylethane type epoxy resins, dicyclopentadiene type epoxy resins, naphthol aralkyl type epoxy resins, brominated phenol novolak type epoxy resins; and alicyclic resins Examples include formula epoxy resins. Furthermore, epoxy resins obtained by modifying these with isocyanates or the like can also be used in combination.

Among these epoxy resins, it is preferable to use bisphenol-type epoxy resins, biphenyl-type epoxy resins, and alicyclic epoxy resins because they provide good physical properties of the cured product and are easily available and inexpensive. It is more preferred to use type epoxy resin.
These epoxy resins may be used alone or in combination of two or more.

The content of the epoxy resin (A) of this embodiment is not particularly limited, but is 60 parts by mass or more and 95 parts by mass based on 100 parts by mass of the total mass of the epoxy resin (A) and the block isocyanate (C). It is preferably 70 parts by mass or more and 90 parts by mass or less.
It is preferable that the content of the epoxy resin (A) be within the above-mentioned range from the viewpoint of curability of the curable composition.

≪Latent curing agent (B)≫
The latent curing agent (B) of this embodiment is not particularly limited, and known ones can be used. For example, dicyandiamides, imidazoles, polyamines, imidazole adducts, and amine adducts are encapsulated. Examples include those that have been transformed into
Among these latent curing agents (B), dicyandiamides are preferred because they are easily available and inexpensive.
These latent curing agents may be used alone or in combination of two or more.

The content of the latent curing agent (B) in this embodiment is not particularly limited, but is 1 part by mass or more based on 100 parts by mass of the total mass of the epoxy resin (A) and the blocked isocyanate (C). It is preferably 20 parts by mass or less, and more preferably 2 parts by mass or more and 10 parts by mass or less.
It is preferable from the viewpoint of curability of the curable composition that the content of the latent curing agent (B) is within the above-mentioned range.

≪Blocked isocyanate (C)≫
The blocked isocyanate (C) of this embodiment is derived from an aliphatic and/or alicyclic isocyanate compound (C-1), a polyol compound (C-2), and an oxime-based blocking agent (C-3). .
Each constituent component of the blocked isocyanate (C) of this embodiment will be explained in detail below.

<Aliphatic and/or alicyclic isocyanate compound (C-1)>
The aliphatic and/or alicyclic isocyanate compound (C-1) of the present embodiment is an aliphatic diisocyanate compound, an alicyclic diisocyanate compound, or a polyisocyanate derived from an aliphatic and/or alicyclic diisocyanate monomer. Preferably, it is at least one selected from the group consisting of compounds.

[Diisocyanate]
The diisocyanate is at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates. These diisocyanates may be the above-mentioned aliphatic or alicyclic diisocyanate compounds, or may be the above-mentioned aliphatic and/or alicyclic diisocyanate monomers.

Examples of aliphatic diisocyanates include, but are not limited to, 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, ethyl (2,6-diisocyanato)hexanoate, and 1,6-diisocyanato. Natohexane (hereinafter sometimes abbreviated as "HDI"), 1,9-diisocyanatononane, 1,12-diisocyanatododecane, 2,2,4- or 2,4,4-trimethyl-1 , 6-diisocyanatohexane and the like. These aliphatic diisocyanates may be used alone or in combination of two or more.

Examples of alicyclic diisocyanates include, but are not limited to, 1,3- or 1,4-bis(isocyanatomethyl)cyclohexane (hereinafter sometimes abbreviated as "hydrogenated XDI"), 1 , 3- or 1,4-diisocyanatocyclohexane, 3,5,5-trimethyl 1-isocyanato-3-(isocyanatomethyl)cyclohexane (hereinafter sometimes abbreviated as "IPDI"), 4-4' -diisocyanato-dicyclohexylmethane (hereinafter sometimes abbreviated as "hydrogenated MDI"), 2,5- or 2,6-diisocyanatomethylnorbornane, and the like. These alicyclic diisocyanates may be used alone or in combination of two or more.

Any of these aliphatic diisocyanates and alicyclic diisocyanates may be used alone, or two or more kinds of aliphatic diisocyanates and alicyclic diisocyanates may be used in combination.
Among these, as the diisocyanate, HDI, IPDI, hydrogenated XDI, or hydrogenated MDI is preferable, HDI or IPDI is more preferable, and HDI is even more preferable.

[Polyisocyanate]
The polyisocyanate may include a polyisocyanate derived from at least one selected from the group consisting of aliphatic diisocyanates and alicyclic diisocyanates.
Polyisocyanates derived from the above diisocyanates are not particularly limited, but include, for example, the polyisocyanates shown in (a) to (h) below.
(a) A polyisocyanate having a uretdione structure obtained by cyclizing and dimerizing two isocyanate groups;
(b) a polyisocyanate having an isocyanurate structure or an iminooxadiazinedione structure obtained by cyclizing and trimerizing three isocyanate groups;
(c) a polyisocyanate having a biuret structure obtained by reacting three isocyanate groups and one water molecule;
(d) a polyisocyanate having an oxadiazinetrione structure obtained by reacting two isocyanate groups with one molecule of carbon dioxide;
(e) polyisocyanate having a plurality of urethane groups obtained by reacting one isocyanate group with one hydroxyl group;
(f) a polyisocyanate having an allophanate structure obtained by reacting two isocyanate groups and one hydroxyl group;
(g) a polyisocyanate having an acylurea group obtained by reacting one isocyanate group and one carboxy group;
(h) A polyisocyanate having a urea structure obtained by reacting one isocyanate group with one primary or secondary amine.

The polyisocyanate may also include an aliphatic triisocyanate or a polyisocyanate derived from an aliphatic triisocyanate.
Examples of aliphatic triisocyanates include 1,3,6-triisocyanatohexane, 1,8-diisocyanato-4-isocyanatomethyloctane, 2-isocyanatoethyl-2,6-diisocyanato-hexanoate, and the like. .

These polyisocyanates may be used alone or in combination of two or more.

<Polyol compound (C-2)>
In the block isocyanate (C) of this embodiment, the polyol compound (C-2) contains a polyester polyol and/or a polycarbonate polyol, so that the obtained cured product exhibits the same flexibility as the conventional one, but at a lower temperature than the conventional one. Excellent drying properties when heated.

[Polyester polyol]
Polyester polyols are, for example, compounds that can be obtained by condensing a dibasic acid alone or a mixture of two or more types and a polyhydric alcohol alone or a mixture of two or more types, and lactones such as ε-caprolactone. Examples thereof include compounds obtained by ring-opening polymerization of these compounds using a polyhydric alcohol, and copolyesters thereof.

Examples of the dibasic acid include carboxylic acids such as succinic acid, adipic acid, dimer acid, maleic anhydride, phthalic anhydride, isophthalic acid, terephthalic acid, and 1,4-cyclohexanedicarboxylic acid.

Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, trimethylolpropane, glycerin, and pentaerythritol. , 2-methylolpropanediol, ethoxylated trimethylolpropane, and the like.

As a specific method for producing polyester polyol, for example, a condensation reaction can be carried out by mixing the above-mentioned components and heating the mixture at about 160° C. or higher and 220° C. or lower.
Ring-opening polymerization of ε-caprolactone is not particularly limited, but specifically, in a nitrogen gas atmosphere, the molar ratio of ε-caprolactone and the above initiator is set so as to have a desired molecular weight, and further, ε- This can be carried out by adding 0.1 mass ppm to 100 mass ppm of a catalyst to caprolactone and reacting at a temperature of 150° C. to 200° C. for 4 hours to 10 hours.
The catalyst is not particularly limited, but specific examples include organic titanium compounds such as tetrabutyl titanate, tetrapropyl titanate, and tetraethyl titanate; tin octylate, dibutyl tin oxide, dibutyl tin laurate, stannous chloride, and stannous bromide. A tin compound such as monotin is used.

The average number of hydroxyl functional groups of the polyester polyol is preferably 2.0 or more and 8.0 or less, more preferably 2.0 or more and 4.0 or less. Note that the average number of hydroxyl functional groups of the polyester polyol referred to herein is the number of hydroxyl groups present in one molecule of the polyester polyol.

The number average molecular weight of the polyester polyol is not particularly limited, but is preferably from 300 to 5,000, more preferably from 500 to 3,000.
It is preferable that the number average molecular weight of the polyester polyol is within the above range from the viewpoint of the resulting flexibility. The number average molecular weight Mn of the polyester polyol is, for example, the number average molecular weight based on polystyrene measured by gel permeation chromatography (GPC).

[Polycarbonate polyol]
Although the polycarbonate polyol is not particularly limited, specific examples thereof include those obtained by condensation polymerization of a low-molecular carbonate compound and a low-molecular polyol.
Examples of the low-molecular carbonate compound include dialkyl carbonates such as dimethyl carbonate; alkylene carbonates such as ethylene carbonate; and diaryl carbonates such as diphenyl carbonate.
Examples of the low-molecular polyol include ethylene glycol, propylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, trimethylpentanediol, cyclohexanediol, trimethylolpropane, glycerin, and pentaerythritol. , 2-methylolpropanediol, ethoxylated trimethylolpropane, and the like.

The average number of hydroxyl functional groups of the polycarbonate polyol is preferably 2.0 or more and 8.0 or less, more preferably 2.0 or more and 4.0 or less. Note that the average number of hydroxyl functional groups of the polycarbonate polyol referred to herein is the number of hydroxyl groups present in one molecule of the polycarbonate polyol.

The number average molecular weight of the polycarbonate polyol is not particularly limited, but is preferably from 300 to 5,000, more preferably from 500 to 3,000.
It is preferable that the number average molecular weight of the polycarbonate polyol is within the above range from the viewpoint of the flexibility obtained. The number average molecular weight Mn of the polycarbonate polyol is, for example, the number average molecular weight based on polystyrene measured by gel permeation chromatography (GPC).

[Other polyols]
The polyol compound (C-2) of the present embodiment may contain other polyols in addition to the polyester polyol and/or polycarbonate polyol, or may not contain other polyols.
Other polyols include alkylene diols, alkylene triols, castor oil polyols, polyolefin polyols, polyether polyols, and the like.

[Alkylene diol]
The skeleton of alkylene diol is a saturated hydrocarbon group, but the skeleton may contain at least one bond selected from the group consisting of an ether bond and an ester bond. Examples of such alkylene diols include 1,2-propanediol, 1,2-butanediol, 2,3-butanediol, 2-methyl-1,2-propanediol, 1,2-pentanediol, and 2-methyl-1,2-propanediol. ,3-pentanediol, 3-methyl-1,2-butanediol, 2-methyl-2,3-butanediol, 2,3-dimethyl-2,3-butanediol, 2,4-pentanediol, 1,3 -Butanediol, 2-methyl-2,4-butanediol, 2-methyl-2,4-pentanediol, 2,4-dimethyl-2,4-pentanediol, hexamethyltrimethylene glycol, neopentyl glycol, 2 ,2-dimethyl-1,3-butanediol, 2,2-dimethyl-1,3-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 3-methyl-2,5-pentanediol , 1,4-hexanediol, 2,5-hexanediol, 2,5-dimethyl-2,5-hexanediol, dipropylene glycol, 2,2-dimethyl-1,3-propanediol monohydroxypivalate, etc. Can be mentioned.

[Alkylene triol]
Although the alkylene triol is not particularly limited, specific examples thereof include trimethylolpropane, glycerin, and the like.

[Castor oil polyol]
Although the castor oil polyol is not particularly limited, specific examples thereof include castor oil, castor oil derivatives, and the like. The castor oil derivatives include castor oil fatty acids; hydrogenated castor oil obtained by hydrogenating castor oil or castor oil fatty acids; transesterified products of castor oil and other fats and oils; reaction products of castor oil and polyhydric alcohols; esterification of castor oil fatty acids and polyhydric alcohols. Reactants: Examples include addition polymerization of alkylene oxide to these.

[Polyolefin polyol]
The polyolefin polyol is not particularly limited, but specifically includes polybutadiene having two or more hydroxyl groups, hydrogenated polybutadiene, polyisoprene, hydrogenated polyisoprene, and the like.

[Polyether polyol]
The polyether polyol is not particularly limited, but specifically, a strong basic catalyst such as a hydroxide such as lithium, sodium, or potassium, an alcoholate, or an alkylamine is used in a polyhydric hydroxy compound alone or in a mixture. Then, alkylene oxide is reacted with polyether polyols obtained by adding alone or a mixture of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, and styrene oxide, and further with polyfunctional compounds such as ethylene diamines. and so-called polymer polyols obtained by polymerizing acrylamide etc. using these polyethers as a medium, as well as polyether polyols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol. .

The polyhydric hydroxy compound is not particularly limited, but specifically includes polyhydric alcohol compounds such as diglycerin, ditrimethylolpropane, pentaerythritol, and dipentaerythritol; erythritol, D-threitol, L-arabinitol, Sugar alcohol compounds such as ribitol, xylitol, sorbitol, mannitol, galactitol, rhamnitol; monosaccharides such as arabinose, ribose, xylose, glucose, mannose, galactose, fructose, sorbose, rhamnose, fucose, ribodesose; trehalose, sucrose, Examples include disaccharides such as maltose, cellobiose, gentiobiose, lactose, and melibiose; trisaccharides such as raffinose, gentianose, and meletitose; and tetrasaccharides such as stachyose.

[Number average molecular weight]
The number average molecular weight of the polyol compound (C-2) is not particularly limited, but is preferably from 300 to 5,000, more preferably from 500 to 3,000.
It is preferable that the number average molecular weight of the polyol compound (C-2) is within the above range from the viewpoint of the flexibility obtained. The number average molecular weight Mn of the polyol compound (C-2) is, for example, the number average molecular weight based on polystyrene measured by gel permeation chromatography (GPC).

When the polyol compound (C-2) of the present embodiment contains other polyols in addition to polyester polyols and/or polycarbonate polyols, the content of the other polyols is not particularly limited, but the total content of the polyester polyols and/or polycarbonate polyols is 100%. It is preferably 1 part by mass or more and 300 parts by mass or less, more preferably 10 parts by mass or more and 200 parts by mass or less.

<Urethane prepolymer>
The above-mentioned blocked isocyanate (C) is obtained by reacting the above-mentioned aliphatic and/or alicyclic isocyanate compound (C-1) and polyol compound (C-2) to obtain a urethane prepolymer, and then converted into an oxime-based block as described below. It is preferable to obtain it by reacting agent (C-3).

The urethane prepolymer of this embodiment will be described in detail below.

[Isocyanate group content (NCO content)]
The isocyanate group content (NCO content) of the urethane prepolymer is preferably 1% by mass or more and 20% by mass or less based on the total mass of the urethane prepolymer in a state substantially free of solvent, and 3 It is more preferably 4% by mass or more and 13% by mass or less, and even more preferably 4% by mass or more and 13% by mass or less.
The NCO content can be determined, for example, by reacting the isocyanate groups of the polyisocyanate composition with an excess of an amine (such as dibutylamine) and back titrating the remaining amine with an acid such as hydrochloric acid.

[Production method of urethane prepolymer]
The urethane prepolymer of this embodiment is obtained by reacting the above-mentioned isocyanate compound (C-1) with the polyol compound (C-2).

The polyol compound (C-2) can be used alone or as a mixture. When used as a mixture, they may be mixed before reacting with the isocyanate compound (C-1), or each polyol compound (C-2) may be reacted alone with the isocyanate compound (C-1) to form the urethane. It is also possible to mix after forming the prepolymer.

That is, as a method for producing a urethane prepolymer, for example, an isocyanate compound (C-1), a first type of polyol compound (C-2), and a second type of polyol compound (C-2) are simultaneously reacted. Method for obtaining urethane prepolymer; one obtained by reacting an isocyanate compound (C-1) with a first type of polyol compound (C-2), and one obtained by reacting an isocyanate compound (C-1) with a second type of polyol compound (C-2). -2) to obtain a urethane prepolymer; after reacting the isocyanate compound (C-1) with the first type of polyol compound (C-2), Examples include a method of further reacting the polyol compound (C-2) to obtain a urethane prepolymer.

The reaction between the isocyanate compound (C-1) and the polyol compound (C-2) is carried out as follows. The reaction temperature is usually from room temperature (approximately 23°C) to 200°C, preferably from 80°C to 120°C. If the reaction temperature is above the above lower limit, the reaction time will be shorter, while if it is below the above upper limit, an increase in the viscosity of the urethane prepolymer due to undesirable side reactions can be avoided.
The reaction may be carried out without a solvent, or may be carried out using any solvent that is inert to the isocyanate group. Further, if necessary, a known catalyst may be used to promote the reaction between the isocyanate group and the hydroxyl group.

When the isocyanate compound (C-1) is a diisocyanate compound, during the reaction, the molar ratio of the isocyanate group of the isocyanate compound (C-1) to the hydroxyl group of the polyol compound (C-2) (molar ratio of isocyanate group/hydroxyl group) ) is preferably 2 or more and 50 or less, more preferably 3 or more and 20 or less. When the molar ratio of isocyanate groups/hydroxyl groups is equal to or higher than the above lower limit, an increase in the viscosity of the urethane prepolymer due to the sequential addition reaction between the isocyanate and the polyol can be further avoided. On the other hand, if it is below the above upper limit, productivity becomes better.
At the end of the reaction, unreacted diisocyanate compounds in the reaction mixture may be recovered by a known method such as a thin film distillation apparatus or solvent extraction.

When the isocyanate compound (C-1) is a polyisocyanate compound, during the reaction, the molar ratio of the isocyanate group of the isocyanate compound (C-1) to the hydroxyl group of the polyol compound (C-2) (mole of isocyanate group/hydroxyl group) The ratio) is preferably 3 or more and 100 or less, more preferably 4 or more and 50 or less. When the molar ratio of isocyanate groups/hydroxyl groups is at least the above lower limit, an increase in the viscosity of the urethane prepolymer can be avoided.

The polyol compound (C-2) is not limited to the above-mentioned polyester polyol and/or polycarbonate polyol. Even when the polyol compound (C-2) further contains other polyols, the other polyols can be reacted with the isocyanate compound (C-1) in the same manner as the above-mentioned polyester polyols and/or polycarbonate polyols.

<Oxime-based blocking agent (C-3)>
The oxime-based blocking agent (C-3) of the present embodiment is not particularly limited, and examples thereof include oxime-based compounds such as formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, and cyclohexanone oxime. Any of these oxime compounds may be used alone or in combination of two or more.

<Production method of blocked isocyanate (C)>
The blocked isocyanate (C) of the present embodiment is obtained by a reaction between the above-mentioned urethane prepolymer and an oxime-based blocking agent (C-3) (hereinafter sometimes referred to as "blocking reaction").

In the blocking reaction, the amount of the oxime blocking agent (C-3) added may be 80 mol% or more and 120 mol% or less, and 90 mol% or more and 110 mol% or less based on the total molar amount of isocyanate groups in the urethane prepolymer. It is preferably mol% or less, and more preferably 95 mol% or more and 100 mol% or less.
It is preferable that the molar ratio of the oxime blocking agent (C-3) is within the above range from the viewpoint of storage stability of the resulting curable composition.

The blocking reaction can generally be carried out at -20°C or higher and 150°C or lower, preferably at 0°C or higher and 100°C or lower, and more preferably at 10°C or higher and 90°C or lower. When the reaction temperature is equal to or higher than the above lower limit, the reaction rate can be further increased, and when the reaction temperature is equal to or lower than the above upper limit, side reactions can be further suppressed.

The blocking reaction may be carried out without a solvent, or may be carried out using any solvent that is inert to the isocyanate group. Furthermore, if necessary, a known catalyst may be used to promote the reaction between the isocyanate group and the oxime compound.

<<Method for producing curable composition>>
The curable composition of this embodiment is obtained by mixing the above-mentioned epoxy resin (A), latent curing agent (B), and blocked isocyanate (C).

When mixing, the ratio of the epoxy resin (A), the latent curing agent (B), and the block isocyanate (C) is as follows: The epoxy resin (A) is preferably 60 parts by mass or more and 95 parts by mass or less, more preferably 70 parts by mass or more and 90 parts by mass or less, and the latent curing agent (B) is 1 part by mass or more and 20 parts by mass. It is preferably the following, more preferably 2 parts by mass or more and 10 parts by mass or less, and preferably the blocked isocyanate (C) is 5 parts by mass or more and 40 parts by mass or less, 10 parts by mass or more and 30 parts by mass or less. It is more preferable that

The curable composition of this embodiment contains, in addition to the above-mentioned epoxy resin (A), latent curing agent (B), and blocked isocyanate (C), a liquid rubber, a powdered rubber, and at least one epoxy group. Reactive diluent, organic solvent, plasticizer, curing accelerator for epoxy resin, ultraviolet absorber, antioxidant, light stabilizer, flame retardant, anti-yellowing agent, coating conditioner, flow conditioner, pigment dispersant , antifoaming agents, thickeners, inorganic fillers, fillers, pigments, etc. Each of these components may be added in any amount depending on desired performance.

The curable composition of this embodiment can be manufactured by a conventionally known method.
For example, general machines such as rotation and revolution stirrers, pot mills, ball mills, bead mills, roll mills, homogenizers, super mills, homodispers, all-purpose mixers, Banbury mixers, single screw extruders, twin screw extruders, co-kneaders, multi-screw extruders, etc. It can be manufactured by uniformly mixing using a standard mixer.

Applications of the curable composition of this embodiment are not particularly limited, and include paints, coating agents, pressure-sensitive adhesives, adhesives, sealants, sealants, molding materials, insulating materials, conductive materials, heat dissipating materials, protective films, It can be used as a fiber treatment agent, fiber binding agent, etc.

The cured product of this embodiment is obtained by curing a curable composition by heating. There are no particular restrictions on heating conditions such as heating time and heating temperature, and known conditions can be employed. Specifically, the heating temperature is preferably 160 to 200°C, more preferably 170 to 190°C, and the heating time is preferably 20 to 40 minutes, more preferably 30 to 40 minutes.

The cured product of this embodiment may be obtained by a manufacturing method in which the curable composition is poured into a mold and cured by heating as it is, or a step of applying, impregnating, or adhering the curable composition to a base material and then curing it. It may be obtained by a manufacturing method including.

Examples of the base material include, but are not particularly limited to, a base material constituting an electronic device, an insulating base material, a conductive base material, a metal base material, a plastic base material, a glass base material, a fiber base material, and the like.

Hereinafter, this embodiment will be described in more detail based on Examples and Comparative Examples, but this embodiment is not limited to the following Examples.

Regarding the polyisocyanate compositions produced in Examples and Comparative Examples, physical properties were measured and evaluated according to the methods shown below.

[Physical properties 1]
(Isocyanate group (NCO) content)
First, 2 g or more and 3 g or less of a measurement sample was accurately weighed in a flask (Wg). Next, 20 mL of toluene was added to dissolve the measurement sample. Next, 20 mL of a 2N toluene solution of di-n-butylamine was added, and after mixing, the mixture was left at room temperature for 15 minutes. Then, 70 mL of isopropyl alcohol was added and mixed. Next, this solution was titrated with a 1N hydrochloric acid solution (Factor F) as an indicator. The obtained titration value was defined as V2mL. The titration value obtained was then taken as V1 ml without the polyisocyanate sample. Next, the isocyanate group (NCO) content (NCO%) (mass%) of the polyisocyanate was calculated from the following formula.

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

[Physical properties 2]
(Number average molecular weight of polyol compound)
The number average molecular weight of the polyol compound is the number average molecular weight based on polystyrene as measured by gel permeation chromatography (GPC) using the following apparatus.

(Measurement condition)
Equipment: manufactured by Tosoh Corporation, HLC-802A
Column: Tosoh Corporation, G1000HXL x 1
G2000HXL x 1
G3000HXL x 1 Carrier: Tetrahydrofuran Detection method: Differential refractometer

<Synthesis of blocked isocyanate (C)>
[Synthesis example 1]
In a flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen blowing tube, 1,000 g of HDI and polycaprolactone (PCL) triol (product name: Plaxel (registered trademark) 305, manufactured by Daicel Corporation, trifunctional, number average) were added. 150 g of molecular weight 550) was charged, and the reaction was carried out by stirring at 95° C. for 1 hour under a nitrogen atmosphere. A urethane prepolymer was obtained by removing unreacted HDI from the obtained reaction solution using a falling film distillation apparatus under conditions of 160 ° C. (27 Pa) for the first time and 150 ° C. (13 Pa) for the second time. . The isocyanate group content of this urethane prepolymer was 11.5% by mass.

Next, 100 g of the obtained urethane prepolymer was charged into a flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen blowing tube, and 1.0 g of methyl ethyl ketoxime (MEKO) was added to the molar amount of NCO contained in the polyisocyanate. A 0-fold molar amount was gradually added. After everything was added, the mixture was heated to 60°C and stirred for 2 hours. After confirming that the NCO absorption had disappeared in the IR absorption spectrum, the reaction was terminated, and a blocked isocyanate composition (C1) was obtained.

[Synthesis example 2]
In a flask equipped with a stirrer, thermometer, cooling tube, and nitrogen blowing tube, 1,000 g of HDI and polycaprolactone (PCL) triol (product name: Polylite (registered trademark) OD-X-2586, manufactured by DIC Corporation, 3 237 g (functional, number average molecular weight: 850) was charged, and the reaction was carried out by stirring at 95° C. for 1 hour under a nitrogen atmosphere. A urethane prepolymer was obtained by removing unreacted HDI from the obtained reaction solution using a falling film distillation apparatus under conditions of 160 ° C. (27 Pa) for the first time and 150 ° C. (13 Pa) for the second time. . The isocyanate group content of this urethane prepolymer was 9.1% by mass.

Next, 100 g of the obtained urethane prepolymer was charged into a flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen blowing tube, and 1.0 g of methyl ethyl ketoxime (MEKO) was added to the molar amount of NCO contained in the polyisocyanate. 05 times the molar amount was gradually added. After everything was added, the mixture was heated to 60°C and stirred for 2 hours. After confirming that the NCO absorption had disappeared in the IR absorption spectrum, the reaction was terminated and a blocked isocyanate composition (C2) was obtained.

[Synthesis example 3]
In a flask equipped with a stirrer, thermometer, cooling tube, and nitrogen blowing tube, 1,000 g of HDI and polycaprolactone (PCL) triol (product name: Polylite (registered trademark) OD-X-2588, manufactured by DIC Corporation, 3 496 g (functional, number average molecular weight: 1250) was charged, and the reaction was carried out by stirring at 95° C. for 1 hour under a nitrogen atmosphere. A urethane prepolymer was obtained by removing unreacted HDI from the obtained reaction solution using a falling film distillation apparatus under conditions of 160 ° C. (27 Pa) for the first time and 150 ° C. (13 Pa) for the second time. . The isocyanate group content of this urethane prepolymer was 7.0% by mass.

Next, 100 g of the obtained urethane prepolymer was placed in a flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen blowing tube, and 0.0 g of methyl ethyl ketoxime (MEKO) was added to the molar amount of NCO contained in the polyisocyanate. A 98-fold molar amount was gradually added. After everything was added, the mixture was heated to 60°C and stirred for 2 hours. After confirming that the NCO absorption had disappeared in the IR absorption spectrum, the reaction was terminated and a blocked isocyanate composition (C3) was obtained.

[Synthesis example 4]
In a flask equipped with a stirrer, thermometer, cooling tube, and nitrogen blowing tube, 1,000 g of HDI and polycaprolactone (PCL) triol (product name: Polylite (registered trademark) OD-X-2735, manufactured by DIC Corporation, 3 A mixture of 65 g (functional, number average molecular weight 500) and 130 g of polyoxytetramethylene diol (product name: PTG1000, manufactured by Hodogaya Chemical Industry, bifunctional, number average molecular weight 1,000) was charged, and the mixture was heated at 95°C under a nitrogen atmosphere. The reaction was carried out by stirring for 1 hour. A urethane prepolymer was obtained by removing unreacted HDI from the obtained reaction solution using a falling film distillation apparatus under conditions of 160 ° C. (27 Pa) for the first time and 150 ° C. (13 Pa) for the second time. . The isocyanate group content of this urethane prepolymer was 8.8% by mass.

Next, 100 g of the obtained urethane prepolymer was charged into a flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen blowing tube, and 1.0 g of methyl ethyl ketoxime (MEKO) was added to the molar amount of NCO contained in the polyisocyanate. 05 times the molar amount was gradually added. After everything was added, the mixture was heated to 60°C and stirred for 2 hours. The reaction was terminated after confirming that the NCO absorption had disappeared in the IR absorption spectrum, and a blocked isocyanate composition (C4) was obtained.

[Synthesis example 5]
In a separable flask equipped with a stirrer, thermometer, cooling tube, and nitrogen blowing tube, 200 g of polyester polyol (product name: Plaxel (registered trademark) 220, manufactured by Daicel Corporation, bifunctional, number average molecular weight 2000) and isophorone diisocyanate. 44.4 g of (IPDI) and 0.1 g of a tin catalyst were added, and the mixture was reacted at 80° C. under nitrogen for 3 hours to obtain a urethane prepolymer. The isocyanate group content of this urethane prepolymer was 3.5% by mass.

Next, methyl ethyl ketoxime (MEKO) was gradually added to the urethane prepolymer in an amount 1.0 times the molar amount of NCO contained in the polyisocyanate. After everything was added, it was stirred at 80°C for 3 hours. After confirming that the NCO absorption had disappeared in the IR absorption spectrum, the reaction was terminated and a blocked isocyanate composition (C5) was obtained.

[Synthesis example 6]
In a separable flask equipped with a stirrer, thermometer, cooling tube, and nitrogen blowing tube, 200 g of polycarbonate polyol (product name: Duranol (registered trademark) T5652, manufactured by Asahi Kasei, bifunctional, number average molecular weight 2000) and isophorone diisocyanate (IPDI) were placed. ), and 0.1 g of a tin catalyst were added, and the mixture was reacted at 80°C under nitrogen for 3 hours to obtain a urethane prepolymer. The isocyanate group content of this urethane prepolymer was 3.5% by mass.

Next, methyl ethyl ketoxime (MEKO) was gradually added to the urethane prepolymer in an amount 1.0 times the molar amount of NCO contained in the polyisocyanate. After everything was added, it was stirred at 80°C for 3 hours. After confirming that the NCO absorption had disappeared in the IR absorption spectrum, the reaction was terminated, and a blocked isocyanate composition (C6) was obtained.

[Synthesis example 7]
In a flask equipped with a stirrer, a thermometer, a cooling tube, and a nitrogen blowing tube, 100 g of HDI polyisocyanate (product name: A201H, manufactured by Asahi Kasei, NCO content = 17.2%), polycarbonate polyol (product name: Duranol ( 40 g of (registered trademark) T5651, manufactured by Asahi Kasei, bifunctional, number average molecular weight 1000) was charged and reacted at 100° C. for 3 hours under nitrogen to obtain a urethane prepolymer. The isocyanate group content of this urethane prepolymer was 10.0% by mass.

Next, methyl ethyl ketoxime (MEKO) was gradually added to the urethane prepolymer in an amount 1.0 times the molar amount of NCO contained in the polyisocyanate. After everything was added, it was stirred at 80°C for 3 hours. 20 g of butyl acetate was added, and the mixture was further stirred for 30 minutes. After confirming that the NCO absorption had disappeared in the IR absorption spectrum, the reaction was terminated, and a blocked isocyanate composition (C7) was obtained.

[Comparative synthesis example 1]
In a separable flask equipped with a stirrer, thermometer, cooling tube, and nitrogen blowing tube, PTMG-2000: 80.1 parts of polytetramethylene glycol (number average molecular weight 2000, manufactured by Mitsubishi Chemical Corporation), trimethylolpropane ( TMP) and 0.1 part of tin catalyst were mixed under nitrogen and heated at 85° C. until a homogeneous mixture was obtained. Next, 13.4 parts of 1,6-hexamethylene diisocyanate (HDI) was added, and the mixture was reacted at 85° C. under nitrogen for 1 hour to obtain a urethane prepolymer. The isocyanate group content of this urethane prepolymer was 3.0% by mass.

Next, 5.9 parts of methyl ethyl ketoxime (MEKO) was added to the obtained urethane prepolymer, and the mixture was further stirred at 85° C. for 60 minutes to react. After confirming that the NCO absorption had disappeared in the IR absorption spectrum, the reaction was terminated, and a blocked isocyanate composition (C11) was obtained.

[Comparative synthesis example 2]
A blocked isocyanate composition (C12) was obtained in the same manner as in Synthesis Example 2 except that methyl ethyl ketoxime (MEKO) was changed to PTBP (p-tert-butylphenol).

[Comparative synthesis example 3]
In a separable flask equipped with a stirrer, thermometer, cooling tube, and nitrogen blowing tube, 300.0 g of PTMG-2000: polytetramethylene glycol (number average molecular weight 2000, manufactured by Mitsubishi Chemical Corporation) and trimethylolpropane ( 3.96 g of TMP) and 68.2 g of IPDI were added and reacted under nitrogen at 100 to 110° C. for 3 hours to obtain a urethane prepolymer. The isocyanate group content of this urethane prepolymer was 2.50% by mass.

Next, methyl ethyl ketoxime (MEKO) was gradually added to the obtained urethane prepolymer in an amount 1.05 times the molar amount of NCO contained in the polyisocyanate. After all the mixture was added, the reaction was further carried out at 90 to 100°C for 3 hours. After confirming that the NCO absorption had disappeared in the IR absorption spectrum, the reaction was terminated, and a blocked isocyanate composition (C13) was obtained.

A summary of each synthesis example and comparative synthesis example is shown in Table 1 below.

[Example 1]
60 g of bisphenol A type epoxy resin (product name: jER (registered trademark) 828, manufactured by Mitsubishi Chemical Corporation), 40 g of blocked isocyanate composition (C1), latent curing agent dicyandiamide (product name: jER Cure (registered trademark) DICY7) , manufactured by Mitsubishi Chemical Corporation) into a 300 mL cup, stirred with a spatula at 25° C. for 3 minutes, and further stirred using a rotation/revolution mixer to obtain a curable composition.

[Examples 2 to 11, Comparative Examples 1 to 3]
A curable composition was obtained in the same manner as in Example 1 using the formulations shown in Table 2.

<Surface dryness>
3.0 g of the curable composition was weighed out onto an aluminum plate with a diameter of 54 mm, and heated at 80° C. for 30 minutes. After confirming that there were no bubbles on the surface, the mixture was further heated at 160° C. for 30 minutes. Thereafter, it was cooled at 23° C. for 1 hour to obtain a cured product with a thickness of about 1 mm.
The obtained cured product was weighed together with the aluminum plate, and the weight before the test was measured. Next, a cotton ball (cylindrical shape with a diameter of 2.5 cm and a height of 2.0 cm) was placed on the cured product, and a 100 g weight was placed on it for 60 seconds. Thereafter, the weight and cotton were removed, the weight of the aluminum plate after the test was measured, and the amount of cotton remaining on the cured product was determined.
Amount of cotton attached (mg) = (Weight of aluminum plate after test) - (Weight of aluminum plate before test)

(Evaluation criteria for dryness)
◎: Amount of cotton adhesion is less than 0.5 mg ○: Amount of cotton adhesion is 0.5 mg or more and less than 1.0 mg △: Amount of cotton adhesion is 1.0 mg or more and less than 2.0 mg ×: Amount of cotton adhesion is 2.0mg or more

<Flexibility of cured product>
The curable composition was applied to a tin plate with a thickness of 0.1 mm, and then heated at 160° C. for 60 minutes to produce a film with a thickness of about 30 μm.
A test was conducted in accordance with JIS K5600-5-1 (Bending resistance (cylindrical mandrel)), and the results are shown using a mandrel diameter of 2 mm.

(Flexibility evaluation criteria)
○: No abnormality in the coating film ×: Cracks and peeling were observed in the coating film.

The evaluation results obtained in Examples and Comparative Examples are shown in Table 2 below.
Note that the curable composition of Comparative Example 2 was not cured even when heated at 160° C. for 60 minutes, so the flexibility could not be evaluated. The drying properties of Comparative Example 2 were tested in the same manner as the cured product even if the curable composition was not cured.

According to the curable composition of the present embodiment, it is possible to provide a curable composition, a cured product, and a method for producing a cured product that has good flexibility and has excellent drying properties when heated at a lower temperature than conventional ones. can.

Claims (6)

Epoxy resin (A),
a latent curing agent (B);
Blocked isocyanate (C),
The blocked isocyanate (C) is derived from an aliphatic and/or alicyclic isocyanate compound (C-1), a polyol compound (C-2), and an oxime blocking agent (C-3),
The polyol compound (C-2) contains a polyester polyol and/or a polycarbonate polyol,
Curable composition. The curable composition according to claim 1, wherein the polyol compound (C-2) has a number average molecular weight of 300 or more and 5000 or less. The curable composition according to claim 1 or 2, wherein the aliphatic and/or alicyclic isocyanate compound (C-1) is a diisocyanate compound and/or a polyisocyanate compound derived from a diisocyanate monomer. The curable composition according to claim 1 or 2, wherein the polyol compound (C-2) further contains a polyol compound other than polyester polyol and/or polycarbonate polyol. A cured product obtained by curing the curable composition according to claim 1 or 2. A method for producing a cured product, comprising the steps of applying, impregnating, or adhering the curable composition according to claim 1 or 2 to a base material, and then curing the composition.