Microcapsule and method for producing same

Abstract

Disclosed is a microcapsule which has a core-shell structure. The microcapsule includes a shell layer and a core layer that is sealed in the shell layer. The shell layer contains a urethane urea resin. The urethane urea resin contains a reaction product of a first polyisocyanate and an active hydrogen compound. The core layer contains a second polyisocyanate. The reactivity between the first polyisocyanate and the active hydrogen compound is higher than the reactivity between the second polyisocyanate and the active hydrogen compound.

Description

Microcapsules and their manufacturing method

[0001] The present invention relates to a microcapsule and a method for producing the same.

[0002] Microcapsules containing an isocyanate compound have been known. The microcapsules contain, for example, a coating made of a thermoplastic resin and an isocyanate compound encapsulated in the coating. Such microcapsules are widely used, for example, as a curing agent for a resin composition in the production of a cured resin product.

[0003] More specifically, the following isocyanate-containing microcapsules are known as microcapsules. Specifically, the coating of the microcapsules is made of a thermoplastic resin. Furthermore, an isocyanate compound is dissolved or dispersed in a hydrophobic organic compound that does not have a polar functional group. The isocyanate compound is then encapsulated in the coating. Takenate D-178N (trade name, manufactured by Mitsui Chemicals) has been proposed as such an isocyanate compound. Furthermore, a polymerized coating has been proposed, which is obtained by interfacially polymerizing an isocyanate compound (Takenate D-178N (trade name, manufactured by Mitsui Chemicals)) and diethylenetriamine at 60°C in the presence of isoparaffin and ethyl acetate (see, for example, Patent Document 1 (Example 3)).

[0004] Japanese Patent Application Laid-Open No. 2006-061802

[0005] On the other hand, from the viewpoint of obtaining a cured resin product with excellent mechanical properties, the isocyanate-containing microcapsules are required to encapsulate a sufficient amount of isocyanate groups and to have excellent storage stability.

[0006] However, the above-mentioned isocyanate-containing microcapsules may not have a sufficient amount of isocyanate groups and may not have good storage stability.

[0007] The present invention relates to microcapsules having an excellent isocyanate group content and storage stability, and a method for producing the same.

[0008] The present invention [1] relates to a microcapsule having a core-shell structure, the microcapsule comprising a shell layer and a core layer encapsulated in the shell layer, the shell layer containing a urethane-urea resin, the urethane-urea resin containing a reaction product of a first polyisocyanate and an active hydrogen compound, the core layer containing a second polyisocyanate, and the reactivity of the first polyisocyanate with the active hydrogen compound being higher than the reactivity of the second polyisocyanate with the active hydrogen compound.

[0009] The present invention [2] includes the microcapsules according to the above [1], in which the reactivity is in the order of the following formula:

[0010] Aromatic polyisocyanates, aromatic aliphatic polyisocyanates > Aliphatic polyisocyanates > Alicyclic polyisocyanates without secondary isocyanate groups > Alicyclic polyisocyanates with secondary isocyanate groups

[0011] The present invention [3] includes the microcapsules according to the above [1] or [2], in which the active hydrogen compound contains an amino group-containing compound.

[0012] The present invention [4] includes the microcapsules according to any one of [1] to [3] above, wherein the first polyisocyanate has an average number of isocyanate groups of 2.5 or more, and the second polyisocyanate has an average number of isocyanate groups of 2.5 or more.

[0013] The present invention [5] includes the microcapsules according to any one of [1] to [4] above, wherein the first polyisocyanate has an isocyanurate skeleton and the second polyisocyanate has an isocyanurate skeleton.

[0014] The present invention [6] includes the microcapsules according to any one of the above [1] to [5], wherein the first polyisocyanate has a hydrophilic group.

[0015] The present invention [7] includes the microcapsules according to the above [6], in which the hydrophilic group of the first polyisocyanate has a nonionic group.

[0016] The present invention [8] includes the microcapsules according to any one of the above [1] to [7], wherein the second polyisocyanate does not have a hydrophilic group.

[0017] The present invention [9] is a method for producing microcapsules according to any one of the above [1] to [8], and includes a method for producing microcapsules, comprising: a preparation step of preparing an isocyanate mixture containing the first polyisocyanate and the second polyisocyanate; and a reaction step of mixing the isocyanate mixture with the active hydrogen compound in the presence of a hydrophobic solvent having a ClogP value of 2.0 to 5.0, interfacially polymerizing the first polyisocyanate with the active hydrogen compound so as to encapsulate the second polyisocyanate, thereby forming the shell layer and a core layer encapsulated in the shell layer.

[0018] The present invention

[10] includes the method for producing microcapsules described in the above [9], in which, in the reaction step, a mixed liquid containing the isocyanate mixture and the hydrophobic solvent is first added to an aqueous solution containing an emulsifier to prepare an O / W emulsion, and then the active hydrogen compound is added to the O / W emulsion to interfacially polymerize the first polyisocyanate and the active hydrogen compound.

[0019] In the microcapsules of the present invention, the first polyisocyanate and the second polyisocyanate are selected based on their difference in reactivity with active hydrogen compounds. More specifically, the first polyisocyanate, which has a relatively high reactivity, forms a shell layer containing a urethane-urea resin. The second polyisocyanate, which has a relatively low reactivity, is encapsulated (enclosed) in the shell layer as a core layer. Therefore, the above-mentioned microcapsules have a superior isocyanate group content and storage stability compared to when the first polyisocyanate and the second polyisocyanate are the same type.

[0020] Furthermore, according to the method for producing microcapsules of the present invention, the above-mentioned microcapsules can be obtained efficiently.

[0021] 1. Microcapsules Microcapsules have a core-shell structure. More specifically, a microcapsule has a shell layer and a core layer enclosed in the shell layer.

[0022] (1) Shell Layer [Urethane-Urea Resin] The shell layer is a wall material that encapsulates the core layer described below. The shell layer contains a urethane-urea resin. The shell layer is preferably made of a urethane-urea resin. The urethane-urea resin is a thermoplastic resin having a urethane group and / or a urea group.

[0023] The urethane-urea resin is obtained by reacting a first polyisocyanate (shell polyisocyanate) with an active hydrogen compound, i.e., the urethane-urea resin contains a reaction product of the first polyisocyanate and the active hydrogen compound.

[0024] [First Polyisocyanate] Examples of the first polyisocyanate include a polyisocyanate compound, which is an organic compound having two or more isocyanate groups in one molecule.

[0025] Examples of the polyisocyanate compound include aromatic polyisocyanates, araliphatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates.

[0026] Examples of aromatic polyisocyanates include aromatic polyisocyanate monomers and their derivatives. Examples of aromatic polyisocyanate monomers include aromatic diisocyanates. Examples of aromatic diisocyanates include diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), toluidine diisocyanate (TODI), paraphenylene diisocyanate, and naphthalene diisocyanate (NDI). Examples of derivatives include modified aromatic polyisocyanate monomers. Examples of modified aromatic polyisocyanates include uretdione modified aromatic polyisocyanates, isocyanurate modified aromatic polyisocyanates, allophanate modified aromatic polyol modified aromatic polyisocyanates (adducts), biuret modified aromatic polyisocyanates, urea modified aromatic polyisocyanates, oxadiazinetrione modified aromatic polyisocyanates, and carbodiimide modified aromatic polyisocyanates. These may be used alone or in combination of two or more.

[0027] Examples of araliphatic polyisocyanates include araliphatic polyisocyanate monomers and derivatives thereof. Examples of araliphatic polyisocyanate monomers include araliphatic diisocyanates. Examples of araliphatic diisocyanates include xylylene diisocyanate (XDI) and tetramethylxylylene diisocyanate (TMXDI). Examples of derivatives include the various modified products described above. These can be used alone or in combination of two or more types.

[0028] Examples of aliphatic polyisocyanates include chain aliphatic polyisocyanates. Examples of chain aliphatic polyisocyanates include chain aliphatic polyisocyanate monomers and derivatives thereof. Examples of chain aliphatic polyisocyanate monomers include chain aliphatic diisocyanates. Examples of chain aliphatic diisocyanates include ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate (PDI), and hexamethylene diisocyanate (HDI). Examples of derivatives include the various modified products described above. These can be used alone or in combination of two or more types.

[0029] Examples of the alicyclic polyisocyanate include an alicyclic polyisocyanate containing at least one secondary isocyanate group (a secondary isocyanate group-containing alicyclic polyisocyanate) and an alicyclic polyisocyanate not containing a secondary isocyanate group (a secondary isocyanate group-free alicyclic polyisocyanate).

[0030] The series number of an isocyanate group is defined by the number of carbon atoms bonded to the isocyanate group relative to the carbon atom directly bonded to the isocyanate group.

[0031] More specifically, when the carbon atom (C) directly bonded to the isocyanate group (-NCO) is bonded to one carbon atom, the isocyanate group is defined as a primary isocyanate group.

[0032] Furthermore, when the carbon atom (C) directly bonded to the isocyanate group (-NCO) is bonded to two carbon atoms, the isocyanate group is defined as a secondary isocyanate group.

[0033] Furthermore, when the carbon atom (C) directly bonded to the isocyanate group (-NCO) is bonded to three carbon atoms, the isocyanate group is defined as a tertiary isocyanate group.

[0034] Examples of secondary isocyanate group-containing alicyclic polyisocyanates include polyisocyanates that contain only secondary isocyanate groups as isocyanate groups and do not contain primary or tertiary isocyanate groups. Examples of secondary isocyanate group-containing alicyclic polyisocyanates include polyisocyanates that contain both primary and secondary isocyanate groups and do not contain tertiary isocyanate groups.

[0035] More specifically, the secondary isocyanate group-containing alicyclic polyisocyanate may include, for example, a secondary isocyanate group-containing alicyclic polyisocyanate monomer and a derivative thereof. The secondary isocyanate group-containing alicyclic polyisocyanate monomer may include, for example, a secondary isocyanate group-containing alicyclic diisocyanate. The secondary isocyanate group-containing alicyclic diisocyanate may include, for example, cyclohexane diisocyanate, methylenebis(cyclohexyl isocyanate)(H １２ Examples of the diisocyanates include methyl methyl isocyanate (MDI), isophorone diisocyanate (IPDI), and norbornene diisocyanate (NBDI). Derivatives include the various modified products described above. These can be used alone or in combination of two or more types.

[0036] Examples of the alicyclic polyisocyanate containing no secondary isocyanate groups include polyisocyanates containing only primary isocyanate groups as isocyanate groups and containing no secondary or tertiary isocyanate groups.

[0037] More specifically, the secondary isocyanate group-free alicyclic polyisocyanate may include, for example, a secondary isocyanate group-free alicyclic polyisocyanate monomer and a derivative thereof. The secondary isocyanate group-free alicyclic polyisocyanate monomer may include, for example, a secondary isocyanate group-free alicyclic diisocyanate. The secondary isocyanate group-free alicyclic diisocyanate may include, for example, bis(isocyanatomethyl)cyclohexane (H ６ XDI). Derivatives include the various modified products described above. These can be used alone or in combination of two or more types.

[0038] The polyisocyanate compound may be used alone or in combination of two or more kinds. As the polyisocyanate compound, a derivative is preferably used.

[0039] That is, preferred examples of the polyisocyanate compound in the first polyisocyanate include aromatic polyisocyanate derivatives, araliphatic polyisocyanate derivatives, aliphatic polyisocyanate derivatives, and alicyclic polyisocyanate derivatives.

[0040] As the derivative, preferably, an isocyanurate-modified product and a polyol-modified product (adduct) are used, and more preferably, an isocyanurate-modified product is used.

[0041] In other words, the first polyisocyanate preferably has an isocyanurate skeleton and / or a urethane skeleton, and more preferably has an isocyanurate skeleton.

[0042] The type of polyisocyanate compound in the first polyisocyanate (shell polyisocyanate) is selected depending on the type of polyisocyanate compound in the second polyisocyanate (core polyisocyanate) described below, as will be described in detail later. The selection of the polyisocyanate compound will be described in detail later.

[0043] [Hydrophilic Group] The first polyisocyanate preferably has a hydrophilic group. If the first polyisocyanate has a hydrophilic group, microcapsules can be obtained more efficiently by interfacial polymerization, which will be described later. Furthermore, if the first polyisocyanate has a hydrophilic group, the dispersibility of the microcapsules in water can be improved. Examples of the hydrophilic group include a nonionic group and an ionic group, and preferably a nonionic group. That is, the first polyisocyanate preferably has a nonionic group and / or an ionic group, and more preferably has a nonionic group.

[0044] More specifically, the first polyisocyanate is preferably a hydrophilic group-containing polyisocyanate, which can be obtained, for example, by reacting the polyisocyanate compound with an active hydrogen compound containing a hydrophilic group (hereinafter referred to as a hydrophilic group-containing active hydrogen compound).

[0045] Examples of the hydrophilic group-containing active hydrogen compound include an active hydrogen compound containing a nonionic group and an active hydrogen compound containing an ionic group.

[0046] The nonionic group-containing active hydrogen compound is an organic compound having at least one nonionic group and at least one active hydrogen group.

[0047] An example of the nonionic group is a polyoxyethylene group capped at one end. That is, a nonionic group is defined as a polyoxyethylene group capped at one end with an alkoxy group (e.g., an alkoxy group having 1 to 4 carbon atoms). A polyoxyethylene group having no capped end and hydroxyl groups at both ends (i.e., polyoxyethylene glycol) is an active hydrogen compound (high molecular weight polyol) described below, and is not included in the active hydrogen group-containing compound containing a nonionic group.

[0048] Examples of the active hydrogen group include a hydroxyl group and an amino group, and a hydroxyl group is preferred.

[0049] More specifically, the active hydrogen group-containing compound containing a nonionic group includes one-end-capped (one-end alkoxy-capped) polyoxyethylene glycol and nonionic side chain-containing polyol, and preferably one-end-capped (one-end alkoxy-capped) polyoxyethylene glycol. More specifically, the one-end-capped (one-end alkoxy-capped) polyoxyethylene glycol includes, for example, polyoxyethylene methyl ether and polyoxyethylene ethyl ether. These may be used alone or in combination of two or more.

[0050] The number average molecular weight (polystyrene equivalent molecular weight measured by GPC) of the active hydrogen group-containing compound containing a nonionic group is, for example, 200 to 2,000, or preferably 400 to 1,000.

[0051] The active hydrogen compound containing an ionic group is an organic compound having at least one ionic group and at least one active hydrogen group.

[0052] Examples of the ionic group include an anionic group and a cationic group, and preferably include an anionic group. Examples of the anionic group include a carboxy group and a sulfo group, and preferably include a carboxy group. That is, examples of the active hydrogen compound containing an ionic group include an active hydrogen compound containing a carboxy group.

[0053] Examples of active hydrogen group-containing compounds that contain carboxy groups include carboxy group-containing diols. Examples of carboxy group-containing diols include dihydroxyalkanoic acids. Examples of dihydroxyalkanoic acids include 2,2-dimethylolacetic acid, 2,2-dimethylollactic acid, 2,2-dimethylolpropionic acid (also known as dimethylolpropionic acid), 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolvaleric acid. These may be used alone or in combination of two or more.

[0054] As the hydrophilic group-containing active hydrogen compound, preferably, an active hydrogen compound containing a nonionic group is used, more preferably, one-end-capped (one-end alkoxy-capped) polyoxyethylene glycol is used, and even more preferably, polyoxyethylene methyl ether is used.

[0055] The method for obtaining the hydrophilic group-containing polyisocyanate is not particularly limited. For example, the polyisocyanate compound and the hydrophilic group-containing active hydrogen compound are mixed and heated in the presence or absence of a known organic solvent.

[0056] The mixing ratio is appropriately set within a range in which the isocyanate groups of the polyisocyanate compound are in excess relative to the active hydrogen groups of the hydrophilic group-containing active hydrogen compound. For example, the lower limit of the equivalent ratio of the isocyanate groups of the polyisocyanate compound to the active hydrogen groups of the hydrophilic group-containing active hydrogen compound (isocyanate groups / active hydrogen groups) is, for example, more than 1.0, preferably 1.2 or more, more preferably 2.0 or more, and even more preferably 3.0 or more. The upper limit of the equivalent ratio of the isocyanate groups of the polyisocyanate compound (isocyanate groups / active hydrogen groups) is not particularly limited and is, for example, 50 or less, preferably 20 or less.

[0057] In terms of mass, the ratio of the hydrophilic group-containing active hydrogen compound to 100 parts by mass of the polyisocyanate compound is, for example, 1 to 30 parts by mass, preferably 5 to 20 parts by mass.

[0058] The reaction conditions are not particularly limited and are appropriately set depending on the purpose and application. For example, the reaction temperature is, for example, 20 to 200° C., preferably 40 to 100° C. The reaction time is, for example, 1 to 24 hours, preferably 3 to 12 hours.

[0059] The above reaction produces a hydrophilic group-containing polyisocyanate as a reaction product between the polyisocyanate compound and the hydrophilic group-containing active hydrogen compound. The hydrophilic group-containing polyisocyanate is preferably used as the first polyisocyanate.

[0060] [Blocked Isocyanate Group] The first polyisocyanate preferably does not have a blocked isocyanate group. The blocked isocyanate group is an isocyanate group blocked with a known blocking agent and is regenerated by elimination of the blocking agent. That is, preferably, the isocyanate group of the first polyisocyanate is not blocked with a blocking agent. As will be described in detail later, when the isocyanate group of the first polyisocyanate is not blocked with a blocking agent and the isocyanate group of the second polyisocyanate is not blocked with a blocking agent, microcapsules can be efficiently obtained by selecting the first polyisocyanate and the second polyisocyanate based on the difference in reactivity with active hydrogen compounds.

[0061] [Physical Properties of First Polyisocyanate] The average number of isocyanate groups in the first polyisocyanate is, for example, 2.0 to 6.0, preferably 2.5 to 4.0, and more preferably 3.0 to 3.5, from the viewpoint of storage stability of the microcapsules.

[0062] More specifically, from the viewpoint of storage stability of the microcapsules, the lower limit of the average number of isocyanate groups of the first polyisocyanate is, for example, 2.0 or more, preferably 2.5 or more, more preferably 3.0 or more. Also, more specifically, from the viewpoint of storage stability of the microcapsules, the upper limit of the average number of isocyanate groups of the first polyisocyanate is, for example, 6.0 or less, preferably 4.0 or less, more preferably 3.5 or less.

[0063] The average number of isocyanate groups is calculated from the number average molecular weight and the isocyanate group content according to the following formula.

[0064] Average number of isocyanate groups = number average molecular weight × isocyanate group content (solid content equivalent, mass%) / 4200

[0065] The isocyanate group content (based on the solid content) of the first polyisocyanate is, for example, 5 to 30 mass %, or preferably 10 to 20 mass %. The isocyanate group content is measured using a potentiometric titrator in accordance with the n-dibutylamine method in accordance with JIS K-1556 (2006).

[0066] The number average molecular weight of the first polyisocyanate is, for example, 500 to 1500, or preferably 600 to 1200. The number average molecular weight is a molecular weight calculated as polyethylene oxide by gel permeation chromatography (GPC). The measurement conditions for the number average molecular weight are in accordance with those described in the examples below.

[0067] The first polyisocyanate may be dissolved and / or dispersed in an organic solvent. That is, a solution and / or dispersion of the first polyisocyanate may be used. Examples of the organic solvent include hydrophobic solvents described below.

[0068] The solids concentration of the solution and / or dispersion of the first polyisocyanate is, for example, 20 to 90 mass %, preferably 40 to 85 mass %, and more preferably 60 to 80 mass %.

[0069] [Active hydrogen compound] The active hydrogen compound is an organic compound having two or more active hydrogen groups in one molecule. Examples of the active hydrogen group include hydroxyl groups and amino groups. Examples of the active hydrogen compound include active hydrogen compounds other than the above-mentioned hydrophilic group-containing active hydrogen compounds (i.e., active hydrogen compounds that do not have the above-mentioned nonionic group or ionic group). More specifically, the active hydrogen compound includes hydroxyl group-containing compounds, amino group-containing compounds, and compounds that have both hydroxyl and amino groups.

[0070] The hydroxyl group-containing compound is an organic compound having two or more hydroxyl groups in one molecule and no amino group. Examples of the hydroxyl group-containing compound include polyols, more specifically low-molecular-weight polyols and high-molecular-weight polyols.

[0071] Low-molecular-weight polyols are organic compounds with relatively low molecular weights, each having two or more hydroxyl groups per molecule. The molecular weight of low-molecular-weight polyols is, for example, 40 or more and less than 400, preferably 300 or less. Examples of low-molecular-weight polyols include dihydric alcohols, trihydric alcohols, and tetrahydric or higher alcohols. Examples of dihydric alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, and dipropylene glycol. Examples of trihydric alcohols include glycerin and trimethylolpropane. Examples of tetrahydric or higher alcohols include pentaerythritol and diglycerin. Further, examples of low-molecular-weight polyols include polymers obtained by addition polymerization of alkylene (C2-3) oxide with dihydric to tetrahydric alcohols so that the number-average molecular weight is less than 400. These can be used alone or in combination of two or more kinds.

[0072] High molecular weight polyols have two or more hydroxyl groups in their molecules and are relatively high molecular weight organic compounds. The number average molecular weight of high molecular weight polyols is, for example, 400 or more, preferably 500 or more, and for example, 20,000 or less. The number average molecular weight can be calculated using a known method from the hydroxyl group equivalent and the average number of hydroxyl groups. The number average molecular weight can also be measured as a polystyrene-equivalent molecular weight by gel permeation chromatography (the same applies below). Examples of high molecular weight polyols include polyether polyols, polyester polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, and vinyl monomer-modified polyols. These can be used alone or in combination of two or more types.

[0073] An amino group-containing compound is an organic compound that has two or more amino groups in one molecule and does not have a hydroxyl group. Examples of amino group-containing compounds include polyamines, and more specifically, examples include aromatic polyamines, araliphatic polyamines, alicyclic polyamines, aliphatic polyamines, and polyoxyethylene group-containing polyamines. Examples of aromatic polyamines include 4,4'-diphenylmethanediamine and tolylenediamine. Examples of araliphatic polyamines include m-xylylenediamine (m-XDA) and p-xylylenediamine (p-XDA). Examples of alicyclic polyamines include 3-aminomethyl-3,5,5-trimethylcyclohexylamine (also known as isophoronediamine, IPDA), 4,4'-dicyclohexylmethanediamine, 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane, 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, 1,4-cyclohexanediamine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, bis-(4-aminocyclohexyl)methane, diaminocyclohexane, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, 1,3-bis(aminomethyl)cyclohexane (1,3-H ６ XDA), and 1,4-bis(aminomethyl)cyclohexane (1,4-H ６ Examples of aliphatic polyamines include ethylenediamine (EDA), propylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexamethylenediamine, hydrazine, hydrazine hydrate (HYD hydrate), diethylenetriamine (DETA), triethylenetetramine, tetraethylenepentamine, 1,2-diaminoethane, 1,2-diaminopropane, and 1,3-diaminopentane. Examples of polyoxyethylene group-containing polyamines include polyoxyalkylene ether diamines. Examples of polyoxyalkylene ether diamines include polyoxyethylene ether diamines. These can be used alone or in combination of two or more.

[0074] The hydroxyl group- and amino group-containing compound is an organic compound that contains one or more hydroxyl groups and one or more amino groups in one molecule. Examples of the hydroxyl group- and amino group-containing compound include amino alcohols. Examples of amino alcohols include 2-((2-aminoethyl)amino)ethanol (AEA) and 2-((2-aminoethyl)amino)-1-methylpropanol. Preferably, 2-((2-aminoethyl)amino)ethanol (AEA) is used. These can be used alone or in combination of two or more types.

[0075] These can be used alone or in combination of two or more kinds.As the active hydrogen compound, preferably, an amino group-containing compound can be used, more preferably, an aliphatic polyamine can be used, and even more preferably, diethylenetriamine (DETA) can be used.That is, the active hydrogen compound preferably contains an amino group-containing compound, more preferably, contains an aliphatic polyamine, even more preferably, contains diethylenetriamine, and particularly preferably, consists of diethylenetriamine.

[0076] [Method for producing urethane-urea resin] The urethane-urea resin is obtained by reacting the first polyisocyanate and the active hydrogen compound in a predetermined ratio. From the viewpoint of efficiently obtaining microcapsules, the urethane-urea resin is preferably obtained by interfacial polymerization. The method for obtaining the urethane-urea resin will be described in detail later.

[0077] (2) Core Layer The core layer is a core substance encapsulated in the shell layer. The core layer contains a second polyisocyanate (core polyisocyanate). The core layer is preferably made of the second polyisocyanate.

[0078] [Second Polyisocyanate] Examples of the second polyisocyanate include the polyisocyanate compounds described above. More specifically, the second polyisocyanate includes the aromatic polyisocyanate, the araliphatic polyisocyanate, the aliphatic polyisocyanate, and the alicyclic polyisocyanate.

[0079] The polyisocyanate compound may be used alone or in combination of two or more kinds. As the polyisocyanate compound, a derivative is preferably used.

[0080] That is, preferred examples of the polyisocyanate compound in the second polyisocyanate include aromatic polyisocyanate derivatives, araliphatic polyisocyanate derivatives, aliphatic polyisocyanate derivatives, and alicyclic polyisocyanate derivatives.

[0081] As the derivative, preferably, an isocyanurate-modified product and a polyol-modified product (adduct) are used, and more preferably, an isocyanurate-modified product is used.

[0082] In other words, the second polyisocyanate preferably has an isocyanurate skeleton and / or a urethane skeleton, and more preferably has an isocyanurate skeleton.

[0083] The type of polyisocyanate compound in the second polyisocyanate (core polyisocyanate) is selected depending on the type of polyisocyanate compound in the first polyisocyanate (shell polyisocyanate), as will be described in detail later.

[0084] [Hydrophilic Group] The second polyisocyanate preferably does not have a hydrophilic group. If the second polyisocyanate does not have a hydrophilic group, microcapsules can be obtained more efficiently by interfacial polymerization, which will be described later. More preferably, the first polyisocyanate has a hydrophilic group, and the second polyisocyanate does not have a hydrophilic group. If the first polyisocyanate has a hydrophilic group, and the second polyisocyanate does not have a hydrophilic group, microcapsules can be obtained particularly efficiently.

[0085] In other words, from the viewpoint of productivity of the microcapsules, the second polyisocyanate is preferably a hydrophilic group-free polyisocyanate. The hydrophilic group-free polyisocyanate is the polyisocyanate compound described above.

[0086] [Blocked Isocyanate Group] The second polyisocyanate preferably does not have a blocked isocyanate group. That is, preferably, the isocyanate group of the second polyisocyanate is not blocked with a blocking agent. As described above, when the isocyanate group of the first polyisocyanate is not blocked with a blocking agent and the isocyanate group of the second polyisocyanate is not blocked with a blocking agent, microcapsules can be efficiently obtained by selecting the first polyisocyanate and the second polyisocyanate based on the difference in reactivity with active hydrogen compounds. Furthermore, when the isocyanate group of the second blocked isocyanate is not blocked with a blocking agent, the microcapsules can be suitably used as a curing agent for a resin composition.

[0087] [Physical Properties of Second Polyisocyanate] The average number of isocyanate groups in the second polyisocyanate is, for example, 2.0 to 6.0, preferably 2.5 to 4.0, and more preferably 3.0 to 3.5, from the viewpoint of storage stability of the microcapsules.

[0088] More specifically, the lower limit of the average number of isocyanate groups of the second polyisocyanate is, from the viewpoint of storage stability of the microcapsules, for example, 2.0 or more, preferably 2.5 or more, more preferably 3.0 or more. Also, more specifically, the upper limit of the average number of isocyanate groups of the second polyisocyanate is, from the viewpoint of storage stability of the microcapsules, for example, 6.0 or less, preferably 4.0 or less, more preferably 3.5 or less.

[0089] The average number of isocyanate groups is calculated from the number average molecular weight and the isocyanate group content according to the following formula.

[0090] Average number of isocyanate groups = number average molecular weight × isocyanate group content (solid content equivalent, mass%) / 4200

[0091] The isocyanate group content (based on the solid content) of the second polyisocyanate is, for example, 5 to 30 mass %, or preferably 10 to 20 mass %. The isocyanate group content is measured using a potentiometric titrator in accordance with the n-dibutylamine method in accordance with JIS K-1556 (2006).

[0092] The number average molecular weight of the second polyisocyanate is, for example, 400 to 1,000, or preferably 500 to 800. The number average molecular weight is a molecular weight calculated as polyethylene oxide by gel permeation chromatography (GPC). The measurement conditions for the number average molecular weight are in accordance with those described in the examples below.

[0093] The second polyisocyanate may be dissolved and / or dispersed in an organic solvent. That is, a solution and / or dispersion of the second polyisocyanate may be used. Examples of the organic solvent include the hydrophobic solvents described below.

[0094] The solids concentration of the solution and / or dispersion of the second polyisocyanate is, for example, 20 to 90 mass %, preferably 40 to 85 mass %, and more preferably 60 to 80 mass %.

[0095] (3) Core-shell structure The microcapsules have a core-shell structure, i.e., they are core-shell particles.

[0096] The core-shell structure is formed, for example, by selecting a first polyisocyanate and a second polyisocyanate, and then subjecting the first polyisocyanate to interfacial polymerization (described later) with an active hydrogen compound so as to encapsulate the second polyisocyanate.

[0097] In order to obtain microcapsules having excellent isocyanate group content and storage stability, the first polyisocyanate (shell isocyanate) and the second polyisocyanate (core isocyanate) are each selected based on the difference in reactivity with the active hydrogen compound.

[0098] More specifically, the first polyisocyanate and the second polyisocyanate are selected so that the reactivity of the first polyisocyanate with the active hydrogen compound is higher than the reactivity of the second polyisocyanate with the active hydrogen compound.

[0099] Hereinafter, the term "reactivity" refers to the degree of ease with which the reaction between an isocyanate group and an active hydrogen group proceeds. Reactivity is classified according to the type of polyisocyanate compound.

[0100] More specifically, the reactivity of the polyisocyanate compound is in the order of the following formula.

[0101] Aromatic polyisocyanates, aromatic aliphatic polyisocyanates > Aliphatic polyisocyanates > Alicyclic polyisocyanates without secondary isocyanate groups > Alicyclic polyisocyanates with secondary isocyanate groups

[0102] That is, in polyisocyanate compounds, the type of modified product and the presence or absence of a hydrophilic group do not have a significant effect on reactivity. The presence or absence of an aromatic group, an araliphatic group, or an alicyclic group, and the number of isocyanate groups mainly determine the reactivity.

[0103] More specifically, among the polyisocyanate compounds, aromatic polyisocyanates and aromatic aliphatic polyisocyanates have higher reactivity than other polyisocyanate compounds (aliphatic polyisocyanates, alicyclic polyisocyanates containing no secondary isocyanate group, and alicyclic polyisocyanates containing a secondary isocyanate group).

[0104] In other words, the reaction rate of aromatic polyisocyanates and aromatic aliphatic polyisocyanates with active hydrogen compounds is faster than the reaction rate of other polyisocyanate compounds (aliphatic polyisocyanates, alicyclic polyisocyanates containing no secondary isocyanate groups, and alicyclic polyisocyanates containing secondary isocyanate groups) with active hydrogen compounds.

[0105] Therefore, for example, when at least one selected from the group consisting of an aliphatic polyisocyanate, an alicyclic polyisocyanate containing no secondary isocyanate group, and an alicyclic polyisocyanate containing a secondary isocyanate group is used as the second polyisocyanate (core polyisocyanate, core substance), a polyisocyanate compound having higher reactivity (i.e., an aromatic polyisocyanate and / or an araliphatic polyisocyanate) and / or a hydrophilic group-containing polyisocyanate thereof is used as the first polyisocyanate (shell polyisocyanate).

[0106] Furthermore, aliphatic polyisocyanates have higher reactivity than alicyclic polyisocyanates containing no secondary isocyanate group and alicyclic polyisocyanates containing secondary isocyanate groups.

[0107] In other words, the reaction rate of aromatic polyisocyanates, araliphatic polyisocyanates, and aliphatic polyisocyanates with active hydrogen compounds is faster than the reaction rate of other polyisocyanate compounds (alicyclic polyisocyanates not containing a secondary isocyanate group, and alicyclic polyisocyanates containing a secondary isocyanate group) with active hydrogen compounds.

[0108] Therefore, for example, when an alicyclic polyisocyanate containing no secondary isocyanate group and / or an alicyclic polyisocyanate containing a secondary isocyanate group is used as the second polyisocyanate (core polyisocyanate, core substance), a polyisocyanate compound having higher reactivity (i.e., at least one selected from the group consisting of aromatic polyisocyanates, araliphatic polyisocyanates, and aliphatic polyisocyanates) and / or a hydrophilic group-containing polyisocyanate thereof is used as the first polyisocyanate (shell polyisocyanate).

[0109] Furthermore, the alicyclic polyisocyanate containing no secondary isocyanate group has higher reactivity than the alicyclic polyisocyanate containing secondary isocyanate group.

[0110] In other words, the reaction rate of an aromatic polyisocyanate, an araliphatic polyisocyanate, an aliphatic polyisocyanate, or an alicyclic polyisocyanate containing no secondary isocyanate group with an active hydrogen compound is higher than the reaction rate of an alicyclic polyisocyanate containing a secondary isocyanate group with an active hydrogen compound.

[0111] Therefore, for example, when a secondary isocyanate group-containing alicyclic polyisocyanate is selected as the second polyisocyanate (core polyisocyanate, core substance), a polyisocyanate compound having higher reactivity (i.e., at least one selected from the group consisting of aromatic polyisocyanates, araliphatic polyisocyanates, aliphatic polyisocyanates, and secondary isocyanate group-free alicyclic polyisocyanates) and / or a hydrophilic group-containing polyisocyanate thereof is used as the first polyisocyanate (shell polyisocyanate).

[0112] As described above, a polyisocyanate compound having higher reactivity than the second polyisocyanate (core polyisocyanate) is selected as the polyisocyanate compound in the first polyisocyanate (shell polyisocyanate).

[0113] If the polyisocyanate compounds are selected in this manner, the reactivity of the first polyisocyanate (shell polyisocyanate) will be higher than the reactivity of the second polyisocyanate (core polyisocyanate).

[0114] The shell layer is formed by the first polyisocyanate having a relatively high reactivity, and the second polyisocyanate having a relatively low reactivity is encapsulated (enclosed) in the shell layer as the core layer. In other words, microcapsules having a core-shell structure can be efficiently produced. Furthermore, the resulting microcapsules have excellent storage stability.

[0115] 2. Method for Producing Microcapsules Preferably, the method for producing the microcapsules is an interfacial polymerization method. The method for producing the microcapsules is described in detail below. (1) Preparation Step In this method, for example, first, an isocyanate mixture containing a first polyisocyanate and a second polyisocyanate is prepared.

[0116] More specifically, in this method, a first polyisocyanate and a second polyisocyanate are selected based on the reactivity described above, and then the first polyisocyanate and the second polyisocyanate are mixed to obtain an isocyanate mixture.

[0117] The mixing ratio of the first polyisocyanate and the second polyisocyanate is appropriately selected based on the purpose and application. For example, the first polyisocyanate (shell polyisocyanate) is, for example, 50 to 1,000 parts by mass, preferably 100 to 500 parts by mass, per 100 parts by mass of the second polyisocyanate (core polyisocyanate).

[0118] (2) Reaction Step Next, in this method, the isocyanate mixture and the active hydrogen compound are mixed in the presence of a hydrophobic solvent having a ClogP value of 2.0 to 5.0, and the first polyisocyanate and the active hydrogen compound are interfacially polymerized so as to encapsulate the second polyisocyanate, thereby forming a shell layer and a core layer encapsulated in the shell layer.

[0119] More specifically, in this method, for example, the above-described isocyanate mixture is mixed with a hydrophobic solvent having a ClogP value of 2.0 to 5.0, thereby obtaining a mixed liquid containing the isocyanate mixture and the hydrophobic solvent (hereinafter referred to as an isocyanate mixed liquid).

[0120] A hydrophobic solvent is a solvent having a ClogP value of 2.0 or greater. The ClogP value is the logarithm of the n-octanol / water partition coefficient (P), and is a parameter that indicates the degree of hydrophobicity and hydrophilicity. The ClogP value is calculated based on the chemical structure using ChemDraw (Perkin Elmer, version 22.2.0).

[0121] From the viewpoint of microcapsule productivity, the hydrophobic solvent contains a hydrophobic solvent having a ClogP value of 2.0 to 5.0. Examples of hydrophobic solvents having a ClogP value of 2.0 to 5.0 include toluene (ClogP value 2.6), xylene (ClogP value 3.1), trimethylbenzene (ClogP value 3.6), hexane (ClogP value 3.9), and methylcyclohexane (ClogP value 3.9). These may be used alone or in combination of two or more. Preferably, a hydrophobic solvent having a ClogP value of 2.5 to 4.0 is used, more preferably a hydrophobic solvent having a ClogP value of 3.0 to 4.0 is used, and even more preferably a hydrophobic solvent having a ClogP value of 3.0 to 3.5 is used.

[0122] More specifically, the lower limit of the ClogP value of the hydrophobic solvent is, for example, 5.0 or less, preferably 4.0 or less, and more preferably 3.5 or less. When the ClogP value of the hydrophobic solvent is equal to or less than the upper limit, aggregation of the oil phase can be suppressed, and an O / W emulsion (described later) can be efficiently obtained, thereby enabling microcapsules to be obtained with high productivity.

[0123] The upper limit of the ClogP value of the hydrophobic solvent is, for example, 2.0 or more, preferably 2.5 or more, and more preferably 3.0 or more. When the ClogP value of the hydrophobic solvent is equal to or more than the lower limit, the compatibility of the aqueous phase and the oil phase can be suppressed, and the O / W emulsion (described later) can be efficiently obtained, thereby enabling microcapsules to be obtained with high productivity.

[0124] The hydrophobic solvent preferably includes xylene, trimethylbenzene, hexane and methylcyclohexane, and more preferably includes xylene.

[0125] The mixing ratio of the isocyanate mixture and the hydrophobic solvent is not particularly limited and is set depending on the purpose and application. For example, the amount of the hydrophobic solvent is, for example, 50 to 500 parts by mass, preferably 100 to 200 parts by mass, per 100 parts by mass of the total solid content of the first polyisocyanate and the second polyisocyanate.

[0126] In this method, an aqueous solution containing an emulsifier (hereinafter referred to as an aqueous emulsifier solution) is prepared separately from the isocyanate mixture.

[0127] Examples of emulsifiers include known surfactants, more specifically, anionic emulsifiers, cationic emulsifiers, nonionic emulsifiers, and amphoteric emulsifiers. Anionic emulsifiers are preferred. Examples of anionic emulsifiers include metal alkylbenzenesulfonates (e.g., metal dodecylbenzenesulfonates), metal alkyldiphenylethersulfonates, metal alkylnaphthalenesulfonates, metal dialkylsulfosuccinates, ammonium polyoxyethylene styrenated phenyl ether sulfate, ammonium polyoxyethylene distyrenated phenyl ether sulfate, metal ligninsulfonates, and metal ligninsulfonates. Examples of metal salts include sodium salts, potassium salts, and magnesium salts. These may be used alone or in combination of two or more.

[0128] The method for preparing the emulsifier aqueous solution is not particularly limited. For example, an emulsifier is added to water and dissolved. The amount of emulsifier added is appropriately determined depending on the purpose and application. For example, the amount (total amount) of emulsifier added is, for example, 0.1 to 20 parts by mass, preferably 1 to 10 parts by mass, per 100 parts by mass of water.

[0129] In addition to the emulsifier, the aqueous emulsifier solution may contain additives, such as dispersing aids and antifoaming agents.

[0130] Examples of the dispersing aid include protective colloids, more specifically, polyvinyl alcohol, celluloses, gelatins, and dextrins. These may be used alone or in combination of two or more. A preferred dispersing aid is polyvinyl alcohol. The amount and timing of addition of the dispersing aid are not particularly limited and may be appropriately determined depending on the purpose and application.

[0131] Examples of the antifoaming agent include silicone-based antifoaming agents and fluorine-based antifoaming agents. These may be used alone or in combination of two or more. A preferred dispersing aid is a silicone-based antifoaming agent. The amount and timing of addition of the antifoaming agent are not particularly limited and may be appropriately determined depending on the purpose and application.

[0132] The aqueous emulsifier solution may further contain other additives (additives other than dispersing aids and antifoaming agents). Examples of other additives include pH adjusters, pH buffers, antifreeze agents, heat stabilizers, light stabilizers, and antioxidants. These may be used alone or in combination of two or more. The amount and timing of addition of the other additives are not particularly limited and may be appropriately determined depending on the purpose and application.

[0133] Next, in this method, the above-mentioned isocyanate mixture (i.e., a mixture containing an isocyanate mixture and a hydrophobic solvent) is added to the aqueous emulsifier solution to prepare an O / W emulsion.

[0134] More specifically, an isocyanate mixed solution (oil phase) is added dropwise to and mixed with an emulsifier aqueous solution (aqueous phase), and particles (oil droplets) of the isocyanate mixed solution are dispersed in water, thereby preparing an O / W emulsion (oil in water type emulsion).

[0135] The amount and rate of dropping of the isocyanate mixed solution to the aqueous emulsifier solution are not particularly limited, and may be appropriately set within the range in which an O / W emulsion is prepared.

[0136] For example, the amount of the isocyanate mixture (total amount of the first isocyanate, the second isocyanate, and the hydrophobic solvent) relative to 100 parts by mass of water in the emulsifier aqueous solution is, for example, 0.1 to 100 parts by mass, preferably 1 to 50 parts by mass, and more preferably 5 to 30 parts by mass. The dropping time is, for example, 1 to 10 hours, preferably 1 to 5 hours. The mixing time is, for example, 1 to 10 hours, preferably 3 to 8 hours.

[0137] Next, in this method, an active hydrogen compound is added to the O / W emulsion, and the first polyisocyanate and the active hydrogen compound are interfacially polymerized on the surfaces of the particles (oil droplets) of the isocyanate mixture (i.e., the water-oil interface).

[0138] More specifically, in this method, an aqueous solution containing an active hydrogen compound (hereinafter referred to as an active hydrogen compound aqueous solution) is prepared separately from the O / W emulsion.

[0139] The method for preparing the aqueous solution of active hydrogen compounds is not particularly limited. For example, an active hydrogen compound is added to water, mixed, and dissolved. The amount of the active hydrogen compound added is appropriately determined depending on the purpose and application. For example, the amount (total amount) of the active hydrogen compound added is, for example, 0.1 to 20 parts by mass, preferably 1 to 10 parts by mass, per 100 parts by mass of water.

[0140] In this method, an aqueous solution of an active hydrogen compound is then added to the O / W emulsion, and the two are mixed.

[0141] The amount of the aqueous active hydrogen compound solution added is adjusted, for example, based on the ratio of the isocyanate groups of the first polyisocyanate contained in the O / W emulsion to the active hydrogen groups of the active hydrogen compound contained in the aqueous active hydrogen compound solution.

[0142] More specifically, the lower limit of the equivalent ratio of the active hydrogen groups of the active hydrogen compound to the isocyanate groups of the first polyisocyanate (active hydrogen groups / isocyanate groups) is, for example, more than 1.0, preferably 1.2 or more, more preferably 2.0 or more, and even more preferably 3.0 or more. The upper limit of the equivalent ratio of the active hydrogen groups of the active hydrogen compound to the isocyanate groups of the first polyisocyanate (active hydrogen groups / isocyanate groups) is not particularly limited and is, for example, 50 or less, preferably 20 or less.

[0143] Then, by mixing the O / W emulsion with the aqueous active hydrogen compound solution, the isocyanate mixture in the O / W emulsion and the active hydrogen compound in the aqueous active hydrogen compound solution are mixed.

[0144] Then, on the surface of the oil droplets of the O / W emulsion (oil / water interface), the first polyisocyanate in the isocyanate mixture reacts with the active hydrogen compound (urethane-urea reaction).

[0145] More specifically, the isocyanate mixture contains both a first polyisocyanate and a second polyisocyanate, and therefore, when the isocyanate mixture and the active hydrogen compound are mixed, both the first polyisocyanate and the second polyisocyanate are capable of reacting with the active hydrogen compound.

[0146] On the other hand, the first polyisocyanate and the second polyisocyanate are selected based on the difference in reactivity between them, i.e., the reactivity of the first polyisocyanate with the active hydrogen compound is higher than the reactivity of the second polyisocyanate with the active hydrogen compound.

[0147] Therefore, when the isocyanate mixture and the active hydrogen compound are mixed, the reaction between the first polyisocyanate and the active hydrogen compound proceeds faster than the reaction between the second polyisocyanate and the active hydrogen compound.

[0148] As a result, a urethane-urea resin, which is a reaction product of the first polyisocyanate and the active hydrogen compound, is formed on the surface of the droplets of the O / W emulsion, forming a shell layer, while the second polyisocyanate remains unreacted and is encapsulated in the shell layer.

[0149] That is, a core layer containing the second polyisocyanate is enclosed in a shell layer containing a urethane-urea resin, forming a core-shell structure.

[0150] As described above, by mixing the isocyanate mixture and the active hydrogen compound, the first polyisocyanate and the active hydrogen compound undergo interfacial polymerization to encapsulate the second polyisocyanate, forming a shell layer containing the urethane-urea resin and a core layer containing the second polyisocyanate, which is encapsulated in the shell layer.

[0151] As a result, microcapsules having a core-shell structure can be obtained with good productivity. Furthermore, due to the difference in reactivity, the shell layer containing the urethane-urea resin can more firmly encapsulate the second polyisocyanate. Therefore, the microcapsules have excellent isocyanate group content and storage stability.

[0152] 3. Effects and Effects In the microcapsules described above, the first polyisocyanate and the second polyisocyanate are selected based on the difference in their reactivities with active hydrogen compounds. More specifically, the first polyisocyanate, which has a relatively high reactivity, forms a shell layer containing a urethane-urea resin. The second polyisocyanate, which has a relatively low reactivity, is encapsulated (enclosed) in the shell layer as a core layer. Therefore, the microcapsules described above have a superior isocyanate group content and storage stability compared to, for example, when the first polyisocyanate and the second polyisocyanate are the same type.

[0153] Furthermore, according to the method for producing the microcapsules, the microcapsules can be obtained efficiently.

[0154] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited to the following examples. Note that "parts" and "%" are by mass unless otherwise specified. Furthermore, specific numerical values ​​such as blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be substituted with the corresponding upper limit values ​​(numeric values ​​defined as "equal to or less than") or lower limit values ​​(numeric values ​​defined as "equal to or more than" or "exceeding") of the blending ratios (content ratios), physical property values, parameters, etc. described in the above "Modes for Carrying Out the Invention."

[0155] 1. First Polyisocyanate Synthesis Example 1 Polyisocyanate A1 (MePEG-modified XDI isocyanurate) (1) Polyisocyanate Compound (Polyisocyanate P1) A reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a cooling tube was charged under a nitrogen atmosphere with 100 parts by mass of 1,3-xylylene diisocyanate (m-XDI, manufactured by Mitsui Chemicals, Inc.), 0.025 parts by mass of an antioxidant (2,6-di(tert-butyl)-4-methylphenol, BHT, a hindered phenol-based antioxidant), and 0.05 parts by mass of a co-catalyst (tetraphenyl dipropylene glycol diphosphite, organic phosphite ester, trade name: JPP-100, manufactured by Johoku Chemical Industry Co., Ltd.). Next, 1.96 parts by mass of 1,3-butanediol was added to the reactor. Then, 1,3-xylylene diisocyanate and 1,3-butanediol were subjected to a urethane reaction at 80°C for 2 hours to obtain a urethane reaction product liquid. The isocyanate group content of the reaction product liquid was 44.7% by mass. The isocyanate group content was measured using a potentiometric titrator in accordance with the n-dibutylamine method in accordance with JIS K-1556 (2006).

[0156] Next, a 37% by mass solution of tetrabutylammonium hydroxide (TBAOH) was added as an isocyanurate catalyst to the urethanization reaction product liquid. The solid content of the tetrabutylammonium hydroxide (TBAOH) was 0.015 parts by mass.

[0157] The urethanization reaction product containing the isocyanuration catalyst was then heated to obtain an isocyanuration reaction product containing an isocyanurate-modified xylylene diisocyanate (hereinafter referred to as XDI isocyanurate). The reaction started at 60°C and reached a maximum temperature of 70°C.

[0158] Thereafter, the isocyanurate-forming reaction product liquid was passed through a thin-film distillation apparatus (temperature: 150° C., vacuum degree: 50 Pa) to remove unreacted xylylene diisocyanate, thereby purifying XDI isocyanurate.

[0159] Next, the XDI isocyanurate was diluted with xylene to obtain a xylene solution of XDI isocyanurate (hereinafter referred to as polyisocyanate P1).

[0160] The solid content concentration of the polyisocyanate P1 was 75% by mass, and the isocyanate group content (based on the solid content) was 14.0% by mass.

[0161] (2) MePEG modified product (polyisocyanate A1) A 2L reactor equipped with a stirrer, thermometer, cooler and nitrogen gas inlet tube was charged with 1000 parts by mass of polyisocyanate P1 and 132.4 parts by mass of MePEG400 (polyoxyethylene methyl ether having a number average molecular weight of 400) at room temperature (25 ° C.). Then, 44.1 parts by mass of xylene (solvent) was added to the reactor, and the XDI isocyanurate and MePEG400 were subjected to a urethane reaction at 80 ° C. for 6 hours to obtain a MePEG modified product of XDI isocyanurate. Also, a xylene solution of the MePEG modified product of XDI isocyanurate (hereinafter, polyisocyanate A1) was obtained. The equivalent ratio (NCO / OH) of the isocyanate group of polyisocyanate P1 to the hydroxyl group of MePEG400 was 10.1.

[0162] The solid content concentration of Polyisocyanate A1 was 75% by mass, and the MePEG-modified XDI isocyanurate had an isocyanurate skeleton.

[0163] The isocyanate group content of Polyisocyanate A1 (based on a xylene solution) was 11.1% by mass, and the solid content equivalent of the isocyanate group content was 14.8% by mass.

[0164] The number average molecular weight of the MePEG-modified XDI isocyanurate was measured by gel permeation chromatography (GPC) under the following conditions, and was found to be 840.

[0165] Equipment used: HLC-8020 (manufactured by Tosoh) Columns used: G1000HXL, G2000HXL, and G3000HXL (all trade names manufactured by Tosoh) connected in series Sample concentration: 0.3 mass%, THF solution Sample injection volume: 100 μL Eluent: tetrahydrofuran Eluent flow rate: 0.8 ml / min Column temperature: 40°C Detection method: differential refractive index Standard substance: polyethylene oxide (manufactured by Tosoh, trade name: TSK Standard Polyethylene Oxide)

[0166] The average number of isocyanate groups (based on the solid content) was calculated according to the following formula: The average number of isocyanate groups (based on the solid content) of the MePEG modified XDI isocyanurate was 3.0.

[0167] Average number of isocyanate groups = number average molecular weight × isocyanate group content (solid content equivalent, mass%) / 4200

[0168] Synthesis Example 2 Polyisocyanate A2 (MePEG-modified TDI adduct) (1) Polyisocyanate compound (Polyisocyanate P2) Takenate D-103 (trade name, adduct of tolylene diisocyanate (TDI) with trimethylolpropane (TMP), solid content 75% by mass, solvent: ethyl acetate, manufactured by Mitsui Chemicals, Inc.) was subjected to reduced pressure treatment at a temperature of 50°C and a vacuum degree of 50 Pa to remove the ethyl acetate.

[0169] As a result of the above, a trimethylolpropane adduct of tolylene diisocyanate (hereinafter referred to as TDI adduct) was obtained. The TDI adduct was diluted with xylene to obtain a xylene solution of the TDI adduct (hereinafter referred to as polyisocyanate P2).

[0170] The solids concentration of the polyisocyanate P2 was 75% by mass, and the isocyanate group content (based on a xylene solution) was 13.0% by mass.

[0171] (2) MePEG-modified product (Polyisocyanate A2) A MePEG-modified TDI adduct was obtained by mixing 1,000 parts by mass of Polyisocyanate P2, 132.4 parts by mass of MePEG 400, and 44.1 parts by mass of xylene in accordance with the method described in Synthesis Example 1. A xylene solution of the MePEG-modified TDI adduct (hereinafter, Polyisocyanate A2) was also obtained.

[0172] The solids concentration of Polyisocyanate A2 was 75% by mass, and the MePEG-modified TDI adduct had a urethane skeleton.

[0173] The isocyanate group content of Polyisocyanate A2 (based on a xylene solution) was 10.3% by mass, and the isocyanate group content calculated as solids was 13.7% by mass.

[0174] The number-average molecular weight of the MePEG-modified TDI adduct was measured by gel permeation chromatography (GPC) under the above conditions and was found to be 937.

[0175] The average number of isocyanate groups (based on the solid content) was calculated according to the above formula. The average number of isocyanate groups (based on the solid content) of the MePEG-modified TDI adduct was 3.1.

[0176] Synthesis Example 3 Polyisocyanate A3 (MePEG-modified XDI adduct) (1) Polyisocyanate compound (Polyisocyanate P3) Takenate D-110N (trade name, adduct of xylylene diisocyanate with trimethylolpropane (TMP), solid content 75% by mass, solvent: ethyl acetate, manufactured by Mitsui Chemicals, Inc.) was subjected to reduced pressure treatment at a temperature of 50°C and a vacuum degree of 50 Pa to remove the ethyl acetate.

[0177] As a result of the above, a trimethylolpropane adduct of xylylene diisocyanate (hereinafter referred to as XDI adduct) was obtained. The XDI adduct was diluted with xylene to obtain a xylene solution of the XDI adduct (hereinafter referred to as polyisocyanate P3).

[0178] The solids concentration of the polyisocyanate P3 was 75% by mass, and the isocyanate group content (based on a xylene solution) was 11.5% by mass.

[0179] (2) MePEG-modified product (Polyisocyanate A3) A MePEG-modified product of an XDI adduct was obtained by mixing 1,000 parts by mass of Polyisocyanate P3, 132.4 parts by mass of MePEG 400, and 44.1 parts by mass of xylene in accordance with the method described in Synthesis Example 1. A xylene solution of the MePEG-modified product of the XDI adduct (hereinafter, Polyisocyanate A3) was also obtained.

[0180] The solid content concentration of Polyisocyanate A3 was 75% by mass, and the MePEG-modified XDI adduct had a urethane skeleton.

[0181] The isocyanate group content of Polyisocyanate A3 (based on a xylene solution) was 8.9% by mass, and the isocyanate group content calculated as solids was 11.9% by mass.

[0182] The number average molecular weight of the MePEG-modified XDI adduct was measured by gel permeation chromatography (GPC) under the above conditions and was found to be 1,083.

[0183] The average number of isocyanate groups (based on the solid content) was calculated according to the above formula. The average number of isocyanate groups (based on the solid content) of the MePEG-modified XDI adduct was 3.1.

[0184] Synthesis Example 4 Polyisocyanate A4 (MePEG-modified HDI isocyanurate) (1) Polyisocyanate Compound (Polyisocyanate P4) Takenate D-170N (trade name, isocyanurate of hexamethylene diisocyanate, solid content 100% by mass, manufactured by Mitsui Chemicals, Inc.) (hereinafter referred to as HDI isocyanurate) was diluted with xylene to obtain a xylene solution of HDI isocyanurate (hereinafter referred to as polyisocyanate P4).

[0185] The solids concentration of polyisocyanate P4 was 75% by mass, and the isocyanate group content (based on a xylene solution) was 15.5% by mass.

[0186] (2) MePEG-modified product (Polyisocyanate A4) A MePEG-modified product of HDI isocyanurate was obtained by mixing 1,000 parts by mass of Polyisocyanate P4, 132.4 parts by mass of MePEG 400, and 44.1 parts by mass of xylene in accordance with the method described in Synthesis Example 1. A xylene solution of the MePEG-modified product of HDI isocyanurate (hereinafter, Polyisocyanate A4) was also obtained.

[0187] The solid content concentration of Polyisocyanate A4 was 75% by mass, and the MePEG-modified HDI isocyanurate had an isocyanurate skeleton.

[0188] The isocyanate group content of Polyisocyanate A4 (based on a xylene solution) was 12.5% ​​by mass, and the solid content equivalent of the isocyanate group content was 16.7% by mass.

[0189] The number average molecular weight of the MePEG-modified HDI isocyanurate was measured by gel permeation chromatography (GPC) under the above conditions and was found to be 884.

[0190] The average number of isocyanate groups (based on the solid content) was calculated according to the above formula. The average number of isocyanate groups (based on the solid content) of the MePEG modified HDI isocyanurate was 3.5.

[0191] Synthesis Example 5 Polyisocyanate A5 (MePEG-modified HDI allophanate) (1) Polyisocyanate Compound (Polyisocyanate P5) Takenate D-178NL (allophanate of hexamethylene diisocyanate, solids content 100% by mass, manufactured by Mitsui Chemicals, Inc.) (hereinafter referred to as HDI allophanate) was diluted with xylene to prepare a xylene solution of HDI allophanate (hereinafter referred to as polyisocyanate P5).

[0192] The solids concentration of the polyisocyanate P5 was 75% by mass, and the isocyanate group content (based on a xylene solution) was 14.4% by mass.

[0193] (2) MePEG-modified product (Polyisocyanate A5) A MePEG-modified product of HDI allophanate was obtained by mixing 1,000 parts by mass of Polyisocyanate P5, 132.4 parts by mass of MePEG 400, and 44.1 parts by mass of xylene in accordance with the method described in Synthesis Example 1. A xylene solution of the MePEG-modified product of HDI allophanate (hereinafter, Polyisocyanate A5) was also obtained.

[0194] The solids concentration of Polyisocyanate A5 was 75% by mass, and the MePEG-modified HDI allophanate had an allophanate skeleton.

[0195] The isocyanate group content of Polyisocyanate A5 (based on a xylene solution) was 11.5% by mass, and the isocyanate group content calculated as solid content was 15.3% by mass.

[0196] The number average molecular weight of the MePEG-modified HDI allophanate was measured by gel permeation chromatography (GPC) under the above conditions and was found to be 555.

[0197] The average number of isocyanate groups (based on the solid content) was calculated according to the above formula. The average number of isocyanate groups (based on the solid content) of the MePEG-modified HDI allophanate was 2.0.

[0198] Synthesis Example 8 Polyisocyanate A8 (TDI Adduct) Takenate D-103 (trade name, adduct of tolylene diisocyanate (TDI) with trimethylolpropane (TMP), solid content 75% by mass, solvent: ethyl acetate, manufactured by Mitsui Chemicals, Inc.) was used as polyisocyanate A8.

[0199] The number average molecular weight of the TDI adduct was measured by gel permeation chromatography (GPC) under the above conditions and was found to be 877.

[0200] The average number of isocyanate groups (based on the solid content) was calculated according to the above formula. The average number of isocyanate groups (based on the solid content) of the TDI adduct was 3.6.

[0201] 2. Second Polyisocyanate Synthesis Example 6 Polyisocyanate Compound (Polyisocyanate A6) 2,000 parts by mass of hexamethylene diisocyanate (HDI, manufactured by Tosoh Corporation) and 3.2 parts by mass of isobutanol were charged into a four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube, and these were subjected to a urethane reaction at 80° C. for 2 hours to obtain a urethane reaction product liquid. The equivalent ratio (NCO / OH) of the isocyanate groups of hexamethylene diisocyanate to the hydroxyl groups of isobutanol was 600.

[0202] Next, DABCO-TMR (N-(2-hydroxypropyl)-N,N,N-trimethylammonium-2-ethylhexanoate, manufactured by Air Products Co.) was added as an isocyanurate catalyst to the urethanization reaction product liquid in an amount of 0.52 parts by mass.

[0203] The urethane-forming reaction product containing the isocyanurate catalyst was then heated to obtain an isocyanurate-formed reaction product containing an isocyanurate-modified hexamethylene diisocyanate (hereinafter referred to as HDI isocyanurate). The reaction temperature was 80 to 86°C, and the reaction time was 2 hours.

[0204] Furthermore, the isocyanate group content of the isocyanurate reaction product solution was measured to confirm that 10% of the isocyanate group content of the urethanization reaction product solution (residual isocyanate groups after urethanization) had been added. Next, the reaction was stopped by adding 0.60 parts by mass of orthotoluenesulfonic acid.

[0205] Thereafter, the isocyanurate-forming reaction product liquid was passed through a thin-film distillation apparatus (temperature: 140° C., vacuum degree: 50 Pa) to remove unreacted hexamethylene diisocyanate.

[0206] The resulting reaction liquid was distilled using a thin film distillation apparatus (temperature: 140°C, vacuum degree: 50 Pa) to remove unreacted hexamethylene diisocyanate, thereby purifying HDI isocyanurate.

[0207] Next, the HDI isocyanurate was diluted with xylene to obtain a xylene solution of HDI isocyanurate (hereinafter referred to as Polyisocyanate A6).

[0208] The solids concentration of Polyisocyanate A6 was 75% by mass, and the isocyanate group content (based on a xylene solution) was 17.0% by mass, and the solids-equivalent value of the isocyanate group content was 22.7% by mass.

[0209] The number average molecular weight of the HDI isocyanurate was measured by gel permeation chromatography (GPC) under the above conditions and was found to be 682.

[0210] The average number of isocyanate groups (based on the solid content) was calculated according to the above formula. The average number of isocyanate groups (based on the solid content) of the HDI isocyanurate was 3.7.

[0211] Synthesis Example 7 Polyisocyanate Compound (Polyisocyanate A7) An isocyanuration reaction product liquid containing an isocyanurate-modified product of pentamethylene diisocyanate (hereinafter referred to as PDI isocyanurate) was obtained in the same manner as in Synthesis Example 6, except that pentamethylene diisocyanate (PDI, manufactured by Mitsui Chemicals) was used instead of hexamethylene diisocyanate.

[0212] Furthermore, PDI isocyanurate was purified in the same manner as in Synthesis Example 6 and then diluted with xylene to obtain a xylene solution of PDI isocyanurate (hereinafter, referred to as Polyisocyanate A7).

[0213] The solids concentration of Polyisocyanate A7 was 75% by mass, and the isocyanate group content (based on a xylene solution) was 18.8% by mass, and the isocyanate group content calculated as a solids content was 25.1% by mass.

[0214] The number average molecular weight of the PDI isocyanurate was measured by gel permeation chromatography (GPC) under the above conditions and was found to be 681.

[0215] The average number of isocyanate groups (based on solid content) was calculated according to the above formula. The average number of isocyanate groups (based on solid content) of HDI isocyanurate was 4.1.

[0216] 3. Microcapsules Examples 1 to 9 and Comparative Examples 1 to 4 A first polyisocyanate, a second polyisocyanate, and a solvent were charged into a flask equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet tube according to the formulations shown in Tables 1 to 3. The contents of the flask were then stirred at 25°C for 30 minutes to obtain an isocyanate mixture.

[0217] Separately, according to the formulations shown in Tables 1 to 3, sodium dodecylbenzenesulfonate (emulsifier, DDBSNa), polyvinyl alcohol (protective colloid, PVA), and an antifoaming agent (trade name BYK-028, silicone-based antifoaming agent, manufactured by BYK) were dissolved in distilled water to obtain aqueous emulsifier solutions.

[0218] The aqueous emulsifier solution was then cooled to 10°C and stirred at 4000 rpm using a homomixer. The isocyanate mixture was gradually added to the stirred aqueous emulsifier solution to obtain an O / W emulsion. The O / W emulsion was stirred for 5 minutes.

[0219] Thereafter, according to the formulations shown in Tables 1 to 3, an aqueous solution of diethylenetriamine (active hydrogen compound) was added dropwise to the O / W emulsion over a period of 1 hour, and the mixture was then stirred for 4 hours. The first polyisocyanate and the active hydrogen compound were then subjected to interfacial polymerization at the oil / water interface. As a result, a dispersion of microcapsules was obtained. The microcapsules had a core-shell structure containing a shell layer made of a reaction product (urethane-urea resin) of the first polyisocyanate and the active hydrogen compound, and a core layer made of the second polyisocyanate.

[0220] The microcapsules were then separated from the dispersion by suction filtration and dried at 40°C for 24 hours.

[0221] In Examples 1 to 9 and Comparative Examples 2 to 4, the first polyisocyanate and the active hydrogen compound were reacted at 10°C.

[0222] On the other hand, in Comparative Example 1, the first polyisocyanate and the active hydrogen compound were reacted at 60°C.

[0223] 4. Evaluation (1) Initial Isocyanate Group Content Microcapsules and dimethylformamide (solvent) were mixed for 30 minutes, and the second polyisocyanate in the microcapsules was dissolved into the solvent to obtain a sample. Using the sample, the content of isocyanate groups encapsulated in the microcapsules (initial isocyanate group content) was measured. The isocyanate group content was measured using a potentiometric titrator in accordance with the n-dibutylamine method in accordance with JIS K-1556 (2006).

[0224] (2) Dispersibility and storage stability Microcapsules were dispersed in distilled water using a magnetic stirrer (1000 rpm) to obtain a microcapsule dispersion. The solid content of the microcapsules in the dispersion was 10% by mass.

[0225] Next, 30 minutes after the preparation of the dispersion, the dispersion was dried to obtain a non-volatile component. Next, the non-volatile component was subjected to FT-IR measurement (transmission method), and an absorption peak (2260 cm) due to the stretching vibration of the isocyanate group was detected. －１ ) was calculated.

[0226] Dispersibility was evaluated based on the appearance of the microcapsule dispersion, using the following criteria:

[0227] In addition, 7 days after the preparation of the dispersion, the dispersion was dried to obtain a non-volatile component. Then, the non-volatile component was subjected to FT-IR measurement, and an absorption peak (2260 cm) due to the stretching vibration of the isocyanate group was detected. －１ ) was calculated.

[0228] The rate of change in isocyanate group content was calculated using the following formula: Rate of change in isocyanate group content (%) = Absorption peak height after 7 days / Absorption peak height after 30 minutes

[0229] The storage stability was evaluated based on the rate of change in the isocyanate group content, according to the following criteria.

[0230] [Dispersibility] ◯: No precipitation and / or adhesion of solid matter was observed. ×: Precipitation and / or adhesion of solid matter was observed.

[0231] [Storage stability] ◯: The isocyanate group content was 70% or more. Δ: The isocyanate group content was 50% or more and less than 70%. ×: The isocyanate group content was less than 50%.

[0232] 5. Discussion In each example, microcapsules having relatively excellent isocyanate group contents and storage stability were obtained.

[0233] On the other hand, a sufficient isocyanate group content was not obtained in Comparative Example 1. Furthermore, sufficient storage stability was not obtained in Comparative Example 2. Furthermore, a sufficient isocyanate group content was not obtained in Comparative Example 3. Furthermore, in Comparative Example 4, the isocyanate mixture separated, the dispersibility of the O / W emulsion was insufficient, and microcapsules were not obtained.

[0234]

[0235]

[0236]

[0237] Details of the abbreviations in the table are as follows: PVA: polyvinyl alcohol DDBSNa: sodium decylbenzenesulfonate BYK-028: silicone-based defoaming agent, trade name BYK-028, manufactured by BYK

[0238] The above invention is provided as an exemplary embodiment of the present invention, but it is merely an example and should not be interpreted as being limiting. Modifications of the present invention that are obvious to those skilled in the art are intended to be included in the scope of the following claims.

[0239] The microcapsules and the method for producing the same of the present invention are suitable for use as a curing agent for a resin composition.

Claims

1. A microcapsule having a core-shell structure, the microcapsule comprising a shell layer and a core layer encapsulated in the shell layer, the shell layer containing a urethane-urea resin, the urethane-urea resin containing a reaction product of a first polyisocyanate and an active hydrogen compound, the core layer containing a second polyisocyanate, and the reactivity of the first polyisocyanate with the active hydrogen compound being higher than the reactivity of the second polyisocyanate with the active hydrogen compound.

2. The microcapsule according to claim 1, wherein the reactivity is in the following order: aromatic polyisocyanate, araliphatic polyisocyanate > aliphatic polyisocyanate > secondary isocyanate group-free alicyclic polyisocyanate > secondary isocyanate group-containing alicyclic polyisocyanate.

3. The microcapsule according to claim 1, wherein the active hydrogen compound comprises an amino group-containing compound.

4. The microcapsule according to claim 1, wherein the first polyisocyanate has an average number of isocyanate groups of 2.5 or more, and the second polyisocyanate has an average number of isocyanate groups of 2.5 or more.

5. The microcapsule according to claim 1, wherein the first polyisocyanate has an isocyanurate skeleton, and the second polyisocyanate has an isocyanurate skeleton.

6. The microcapsule of claim 1, wherein the first polyisocyanate has a hydrophilic group.

7. The microcapsule according to claim 6, wherein the hydrophilic group of the first polyisocyanate has a nonionic group.

8. The microcapsule according to claim 1, wherein the second polyisocyanate has no hydrophilic groups.

9. A method for producing a microcapsule according to any one of claims 1 to 8, comprising: a preparation step of preparing an isocyanate mixture containing the first polyisocyanate and the second polyisocyanate; and a reaction step of mixing the isocyanate mixture with the active hydrogen compound in the presence of a hydrophobic solvent having a ClogP value of 2.0 to 5.0, interfacially polymerizing the first polyisocyanate with the active hydrogen compound so as to encapsulate the second polyisocyanate, thereby forming the shell layer and a core layer to be encapsulated in the shell layer.

10. A method for producing microcapsules as described in claim 9, wherein in the reaction process, first, a mixed liquid containing the isocyanate mixture and the hydrophobic solvent is added to an aqueous solution containing an emulsifier to prepare an O / W emulsion, and then, the active hydrogen compound is added to the O / W emulsion to interfacially polymerize the first polyisocyanate and the active hydrogen compound.