Prepolymer, polyurethane composition, cured product, adhesive, sealing material, and article

Abstract

The present invention pertains to a prepolymer which has an isocyanate group at the terminal thereof and which is a reaction product obtained by reacting a polyol with a polyisocyanate in a molar ratio of the total amount of isocyanate groups of the polyisocyanate to the total amount of hydroxyl groups of the polyol of 2-10, wherein the polyol includes a polyoxyalkylene polyol having at least four functional groups and a number-average molecular weight of 300-60,000.

Description

Prepolymers, polyurethane compositions, cured products, adhesives, sealants, and articles

[0001] The present invention relates to a prepolymer, a polyurethane composition, a cured product, an adhesive, a sealant, and an article. This application claims priority to Japanese Patent Application No. 2024-068313, filed on April 19, 2024, the contents of which are incorporated herein by reference.

[0002] Urethane prepolymers with isocyanate groups at the ends are crosslinked by reacting with curing agents having hydroxyl groups, such as water, to produce cured products. These cured products are used as adhesives and sealants. When used as adhesives and sealants, the cured products must have excellent elongation and tensile strength.

[0003] Patent Document 1 discloses a linear polymer terminated with an isocyanate group, which is obtained by reacting an aromatic diisocyanate monomer with a polyether diol having an OH value in the range of 5 to 21 mgKOH / g at an NCO / OH ratio of at least 5 / 1.

[0004] Special Publication No. 2023-512156

[0005] The cured product produced from the linear polymer terminated in isocyanate groups described in Patent Document 1 has excellent elongation properties but insufficient tensile strength. An object of the present invention is to provide a prepolymer terminated in isocyanate groups that can be used to produce a cured product with excellent tensile strength, a polyurethane composition containing the prepolymer, a cured product of the polyurethane composition, an adhesive and sealant made of the cured product, and an article including the cured product.

[0006] The present invention relates to the following items [1] to

[22] . [1] A prepolymer having an isocyanate group at its terminal, which is a reaction product of reacting a polyol and a polyisocyanate in a molar ratio of the total number of isocyanate groups in the polyisocyanate to the total number of hydroxyl groups in the polyol of 2 to 10, wherein the polyol includes a polyoxyalkylene polyol having 4 or more functional groups and a number average molecular weight of 300 to 60,000. [2] The prepolymer according to item [1], in which the molar ratio is 2 to 8, 2 to 7, or 2 to 5, the polyoxyalkylene polyol has 4 to 8 or 4 to 5 functional groups, and the polyoxyalkylene polyol has a number average molecular weight of 300 to 50,000, 400 to 40,000, 500 to 30,000, or 600 to 10,000. [3] The prepolymer according to [1] or [2], wherein the content of the polyoxyalkylene polyol is 10 to 100% by mass, based on the total mass of the polyol. [4] The prepolymer according to any one of [1] to [3], wherein the content of the polyoxyalkylene polyol is 15 to 100% by mass or 20 to 100% by mass, based on the total mass of the polyol. [5] The prepolymer according to any one of [1] to [4], wherein the polyoxyalkylene polyol contains two or more types of polyoxyalkylene polyol. [6] The prepolymer according to any one of [1] to [5], wherein the polyoxyalkylene polyol contains a polyoxyalkylene polyol P1A having a number average molecular weight of 3,000 to 60,000 and a polyoxyalkylene polyol P1B having a number average molecular weight of 300 or more but less than 3,000. [7] The prepolymer according to any one of [1] to [6], wherein the polyoxyalkylene polyol P1A has a number average molecular weight of 3,000 to 40,000, 3,500 to 30,000, or 4,000 to 10,000, and the polyoxyalkylene polyol P1B has a number average molecular weight of 350 to 2,500, or 400 to 2,000. [8] The prepolymer according to any one of [1] to [7], wherein the polyol further comprises a polyoxyalkylene polyol P2 having two or three functional groups and a number average molecular weight of 500 to 15,000.[9] The prepolymer according to any one of [1] to [8], wherein the polyoxyalkylene polyol P2 has a number-average molecular weight of 600 to 12,000, 800 to 10,000, or 1,000 to 8,000.

[10] The prepolymer according to any one of [1] to [9], wherein the polyol further comprises a polyester polyol P3 having two or three functional groups and a number-average molecular weight of 500 to 15,000.

[11] The prepolymer according to any one of [1] to

[10] , wherein the polyester polyol P3 has a number-average molecular weight of 600 to 12,000, 800 to 10,000, or 1,000 to 8,000.

[12] The prepolymer according to any one of [1] to

[11] , wherein the polyisocyanate is either one or both of an alicyclic diisocyanate and an aromatic diisocyanate.

[13] The prepolymer according to any one of [1] to

[12] , wherein the polyisocyanate is either one or both of 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate and diphenylmethane 4,4'-diisocyanate.

[14] The prepolymer according to any one of [1] to

[13] , wherein the content of isocyanate groups relative to the total mass of the prepolymer is 1 to 20 mass%.

[15] The prepolymer according to any one of [1] to

[14] , wherein the content of isocyanate groups relative to the total mass of the prepolymer is 1 to 18 mass% or 1 to 15 mass%.

[16] The prepolymer according to any one of [1] to

[15] , wherein the average functionality of the polyol is 2.0 to 8.0, 2.5 to 8.0, or 3.0 to 8.0.

[17] A polyurethane composition comprising the prepolymer according to any one of [1] to

[16] , wherein the content of the prepolymer is 50 to 100 mass% relative to the total mass of the polyurethane composition.

[18] The polyurethane composition according to

[17] , wherein the content of the prepolymer is 60 to 100% by mass relative to the total mass of the polyurethane composition.

[19] A cured product of the polyurethane composition according to

[17] or

[18] .

[20] An adhesive comprising the cured product according to

[19] .

[21] A sealant comprising the cured product according to

[19] .

[22] An article comprising the cured product according to

[19] .

[0007] According to the present invention, there can be provided a prepolymer having an isocyanate group at the end that can be used to produce a cured product having excellent tensile strength, a polyurethane composition containing the prepolymer, a cured product of the polyurethane composition, an adhesive and sealant made of the cured product, and an article including the cured product.

[0008] The meanings and definitions of terms used in this specification are as follows. A numerical range expressed as "to" means a numerical range with the numbers before and after "to" as the lower and upper limits. "Polyoxyalkylene polyol" means a polymer having a polyoxyalkylene chain formed from units based on alkylene oxide monomers. "Polyester polyol" means a polymer having a polyester chain formed from units based on a monomer that is a compound having multiple carboxy groups and a monomer that is a polyol compound.

[0009] The "active hydrogen-containing group" refers to at least one group selected from the group consisting of a hydroxyl group bonded to a carbon atom, a carboxyl group, an amino group, a monovalent functional group formed by removing one hydrogen atom from a primary amine, a hydrazide group, and a sulfanyl group. The "active hydrogen" refers to a hydrogen atom derived from the active hydrogen-containing group and a hydrogen atom derived from a hydroxyl group of water.

[0010] The "hydroxyl value" of a polyol is a value measured in accordance with Method B (phthalation method) described in JIS K 1557-1: 2007. The hydroxyl value-based molecular weight is a value calculated by 56,100 × the number of functional groups of the polyol (number of hydroxyl groups) / the hydroxyl value.

[0011] The number average molecular weight (hereinafter referred to as "Mn") and the weight average molecular weight (hereinafter referred to as "Mw") are polystyrene-equivalent molecular weights obtained by GPC measurement using tetrahydrofuran as an eluent. The molecular weight distribution is a value calculated from Mw and Mn, and is the ratio of Mw to Mn (hereinafter referred to as "Mw / Mn").

[0012] The content of isocyanate groups relative to the total mass of the prepolymer is a value measured in accordance with Method A described in JIS K 1603-1:2007.

[0013] <<Prepolymer>> The prepolymer of this embodiment is a urethane prepolymer having an isocyanate group at its terminal, which is a reaction product obtained by reacting a polyol (hereinafter also referred to as "polyol P") and a polyisocyanate at a molar ratio of the total number of isocyanate groups in the polyisocyanate to the total number of hydroxyl groups in the polyol of 2 to 10. Polyol P contains a polyoxyalkylene polyol (hereinafter also referred to as "polyol P1") having four or more functional groups and a number average molecular weight of 300 to 60,000.

[0014] Preferably, Polyol P further contains a polyoxyalkylene polyol having two or three functional groups and a number average molecular weight of 500 to 15,000 (hereinafter also referred to as "Polyol P2"). Preferably, Polyol P further contains a polyester polyol having two or three functional groups and a number average molecular weight of 500 to 15,000 (hereinafter also referred to as "Polyol P3"). Polyol P may also contain a polyol other than Polyols P1 to P3 (hereinafter also referred to as "Polyol P4").

[0015] <Polyol P1> The number of functional groups (number of hydroxyl groups) of polyol P1 is 4 or more, preferably 4 to 8, and more preferably 4 to 6. When the number of functional groups is equal to or greater than the above-mentioned lower limit, the tensile strength of the resulting cured product is likely to be improved. When the number of functional groups is equal to or less than the above-mentioned upper limit, the elongation properties of the cured product are likely to be improved.

[0016] The Mn of polyol P1 is 300 to 60,000, preferably 300 to 50,000, more preferably 400 to 40,000, even more preferably 500 to 30,000, and particularly preferably 600 to 10,000. When Mn is equal to or greater than the lower limit, the elongation properties of the cured product tend to be improved. When Mn is equal to or less than the upper limit, the tensile strength of the cured product tends to be improved.

[0017] The Mn per functional group of polyol P1 is preferably 100 to 10,000, more preferably 100 to 7,000, even more preferably 100 to 5,000, and particularly preferably 120 to 2,000. When the Mn per functional group is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the Mn per functional group is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0018] The Mw of polyol P1 is preferably 600 to 70,000, more preferably 600 to 60,000, even more preferably 600 to 50,000, and particularly preferably 700 to 20,000. When the Mw is equal to or greater than the lower limit, the elongation properties of the cured product tend to be improved. When the Mw is equal to or less than the upper limit, the tensile strength of the cured product tends to be improved.

[0019] The Mw / Mn of the polyol P1 is preferably from 1.00 to 1.30, more preferably from 1.00 to 1.20, and even more preferably from 1.00 to 1.10. When the Mw / Mn is equal to or less than the upper limit, the elongation properties of the cured product tend to be improved.

[0020] The hydroxyl value-based molecular weight of polyol P1 is preferably 200 to 50,000, more preferably 200 to 35,000, even more preferably 300 to 25,000, and particularly preferably 400 to 10,000. When the hydroxyl value-based molecular weight is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the hydroxyl value-based molecular weight is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0021] The hydroxyl value-equivalent molecular weight per functional group of polyol P1 is preferably 60 to 6,000, more preferably 80 to 5,000, and even more preferably 100 to 3,500. When the hydroxyl value-equivalent molecular weight per functional group is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the hydroxyl value-equivalent molecular weight per functional group is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0022] The hydroxyl value of polyol P1 is preferably 15 to 600 mgKOH / g, more preferably 20 to 600 mgKOH / g, and even more preferably 40 to 600 mgKOH / g. In another aspect of the present invention, the hydroxyl value of polyol P1 is preferably 15 to 500 mgKOH / g, more preferably 20 to 450 mgKOH / g, and even more preferably 40 to 400 mgKOH / g. When the hydroxyl value is equal to or greater than the above lower limit, the tensile strength of the cured product is likely to be improved. When the hydroxyl value is equal to or less than the above upper limit, the elongation properties of the cured product are likely to be improved.

[0023] Polyol P1 consists of a main chain and terminal groups. The main chain of polyol P1 is a polymer chain consisting of a polyoxyalkylene chain containing residues obtained by removing active hydrogen from an initiator described below and repeating units based on alkylene oxide monomers (hereinafter, repeating units based on monomers will be simply referred to as "monomer units", for example, repeating units based on alkylene oxide monomers will be referred to as "alkylene oxide units"). The terminal groups of polyol P1 are hydroxyl groups. The polyoxyalkylene chain is preferably composed only of alkylene oxide units. When the polyoxyalkylene chain is a polyoxyalkylene chain having two or more types of alkylene oxide units, these alkylene oxide units may form a block polymer or a random polymer.

[0024] Examples of the alkylene oxide unit include an ethylene oxide unit, a propylene oxide unit, a tetramethylene oxide unit, and a butylene oxide unit, with an ethylene oxide unit and a propylene oxide unit being more preferred, and a propylene oxide unit being even more preferred. That is, the polyoxyalkylene chain is preferably a polyoxypropylene chain composed of a propylene oxide unit, a polyoxyethylene-polyoxypropylene chain composed of an ethylene oxide unit and a propylene oxide unit, or a polyoxyethylene chain composed of an ethylene oxide unit, with a polyoxypropylene chain being more preferred. Polyol P1 may be used singly or in combination of two or more types.

[0025] <Polyol P2> The number of functional groups of polyol P2 is 2 or 3, preferably 2. When the number of functional groups is equal to or greater than the above lower limit, the tensile strength of the resulting cured product is likely to be improved. When the number of functional groups is equal to or less than the above upper limit, the elongation properties of the cured product are likely to be improved.

[0026] The Mn of polyol P2 is 500 to 15,000, preferably 600 to 12,000, more preferably 800 to 10,000, and even more preferably 1,000 to 8,000. When Mn is equal to or greater than the lower limit, the elongation properties of the cured product tend to be improved. When Mn is equal to or less than the upper limit, the tensile strength of the cured product tends to be improved.

[0027] The Mn per functional group of polyol P2 is preferably 250 to 6,000, more preferably 300 to 5,000, and even more preferably 400 to 4,000. When the Mn per functional group is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the Mn per functional group is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0028] The Mw of polyol P2 is preferably 350 to 15,000, more preferably 350 to 9,000, even more preferably 500 to 7,500, and particularly preferably 800 to 6,000. When the Mw is equal to or greater than the lower limit, the elongation properties of the cured product tend to be improved. When the Mw is equal to or less than the upper limit, the tensile strength of the cured product tends to be improved.

[0029] The hydroxyl value-based molecular weight of polyol P2 is preferably 300 to 10,000, more preferably 300 to 8,000, even more preferably 500 to 7,000, and particularly preferably 800 to 6,000. When the hydroxyl value-based molecular weight is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the hydroxyl value-based molecular weight is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0030] The hydroxyl value-equivalent molecular weight per functional group of polyol P2 is preferably 300 to 5,000, more preferably 150 to 4,000, even more preferably 200 to 3,500, and particularly preferably 300 to 3,000. When the hydroxyl value-equivalent molecular weight per functional group is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the hydroxyl value-equivalent molecular weight per functional group is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0031] The hydroxyl value of polyol P2 is preferably 10 to 350 mgKOH / g, more preferably 15 to 350 mgKOH / g, even more preferably 20 to 350 mgKOH / g, and particularly preferably 20 to 200 mgKOH / g. When the hydroxyl value is equal to or greater than the lower limit, the tensile strength of the cured product is likely to be improved. When the hydroxyl value is equal to or less than the upper limit, the elongation properties of the cured product are likely to be improved.

[0032] The composition of polyol P2 may be the same as that of polyol P1 (alkylene oxide units). One type of polyol P2 may be used alone, or two or more types may be used in combination.

[0033] (Method for producing polyols P1 and P2) Polyols P1 and P2 can be produced by ring-opening polymerization of an alkylene oxide monomer with an initiator having active hydrogen in the presence of a ring-opening polymerization catalyst. The number of active hydrogens in the initiator is the same as the number of functional groups in the resulting polyols P1 and P2. The initiator preferably has a hydroxyl group as the active hydrogen-containing group. One initiator may be used alone, or two or more initiators may be used in combination.

[0034] In the case of polyol P1, an initiator having four or more active hydrogen atoms may be used. Examples of such initiators include pentaerythritol, diglycerin, meso-erythritol, methyl glucoside, sucrose, glucose, sorbitol, dipentaerythritol, trehalose, and diglycerin. Alternatively, a low-molecular-weight polymer obtained by ring-opening polymerization of an alkylene oxide monomer with such an initiator in the presence of an alkali metal hydroxide may also be used.

[0035] In the case of polyol P2, an initiator having two or three active hydrogen atoms may be used. Examples of such initiators include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, low-molecular-weight polyoxypropylene glycol, glycerin, trimethylolpropane, and trimethylolethane. Alternatively, a low-molecular-weight polymer obtained by ring-opening polymerization of an alkylene oxide monomer with such an initiator in the presence of an alkali metal hydroxide may also be used.

[0036] The alkylene oxide monomer is selected depending on the constituent units of the polyoxyalkylene chains of the polyols P1 and P2. Examples of the alkylene oxide monomer include ethylene oxide, propylene oxide, 1,2-butylene oxide, and 2,3-butylene oxide. Among these, ethylene oxide and propylene oxide are preferred, and propylene oxide is more preferred.

[0037] Examples of ring-opening polymerization catalysts include composite metal cyanide complexes and alkali metal hydroxides (potassium hydroxide, etc.). The use of composite metal cyanide complexes is preferred because they tend to narrow the molecular weight distribution of polyols P1 and P2 and tend to reduce the total degree of unsaturation of polyols P1 and P2. Conventionally known compounds can be used as the composite metal cyanide complex. For example, compounds and production methods disclosed in International Publication No. 2003 / 062301, International Publication No. 2004 / 067633, Japanese Patent Application Laid-Open No. 2004-269776, Japanese Patent Application Laid-Open No. 2005-15786, Japanese Patent Application Laid-Open No. 2013 / 065802, and Japanese Patent Application Laid-Open No. 2015-010162 can be used. The composite metal cyanide complex is preferably a composite metal cyanide complex in which glyme or t-butyl alcohol is coordinated as an organic ligand to the catalyst skeleton. The catalyst skeleton may be a Zn ３ [Co(CN) ６ ] ２(i.e., zinc hexacyanocobaltate complex) is more preferred. In particular, a double metal cyanide complex using t-butyl alcohol as an organic ligand is preferred.

[0038] When the polyoxyalkylene chains of the polyols P1 and P2 are random copolymer chains composed of propylene oxide units and ethylene oxide units, a method of obtaining the polyols P1 and P2 by reacting a mixture of propylene oxide and ethylene oxide with an initiator in the presence of a ring-opening polymerization catalyst is preferred.

[0039] When the polyoxyalkylene chain of the polyols P1 and P2 is a block copolymer chain composed of propylene oxide units and ethylene oxide units, the polyols P1 and P2 may be obtained by reacting propylene oxide with an initiator in the presence of a ring-opening polymerization catalyst to obtain a precursor, which is then reacted with ethylene oxide, or the polyols P1 and P2 may be obtained by reacting ethylene oxide with an initiator in the presence of a ring-opening polymerization catalyst to obtain a precursor, which is then reacted with propylene oxide,

[0040] <Polyol P3> The number of functional groups (number of hydroxyl groups) of polyol P3 is 2 or 3, preferably 2. When the number of functional groups is equal to or greater than the above lower limit, the tensile strength of the resulting cured product is likely to be improved. When the number of functional groups is equal to or less than the above upper limit, the elongation properties of the cured product are likely to be improved.

[0041] The Mn of polyol P3 is 500 to 15,000, preferably 600 to 12,000, more preferably 800 to 10,000, and even more preferably 1,000 to 8,000. When Mn is equal to or greater than the lower limit, the elongation properties of the cured product tend to be improved. When Mn is equal to or less than the upper limit, the tensile strength of the cured product tends to be improved.

[0042] The Mn per functional group of polyol P3 is preferably 250 to 6,000, more preferably 400 to 5,000, and even more preferably 800 to 4,000. When the Mn per functional group is at least the above lower limit, the elongation properties of the cured product tend to be improved. When the Mn per functional group is at most the above upper limit, the tensile strength of the cured product tends to be improved.

[0043] The hydroxyl value-based molecular weight of polyol P3 is preferably 300 to 8,000, more preferably 500 to 7,000, and even more preferably 800 to 6,000. When the hydroxyl value-based molecular weight is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the hydroxyl value-based molecular weight is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0044] The hydroxyl value-equivalent molecular weight per functional group of polyol P3 is preferably 150 to 4,000, more preferably 200 to 3,500, and even more preferably 500 to 3,000. When the hydroxyl value-equivalent molecular weight per functional group is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the hydroxyl value-equivalent molecular weight per functional group is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0045] The hydroxyl value of polyol P3 is preferably 10 to 350 mgKOH / g, more preferably 15 to 350 mgKOH / g, even more preferably 20 to 350 mgKOH / g, and particularly preferably 20 to 200 mgKOH / g. When the hydroxyl value is equal to or greater than the lower limit, the tensile strength of the cured product is likely to be improved. When the hydroxyl value is equal to or less than the upper limit, the elongation properties of the cured product are likely to be improved.

[0046] Polyol P3 consists of a main chain and terminal groups. The main chain of polyol P3 is a polymer chain consisting of a polyester chain containing a compound having multiple carboxy groups (hereinafter also referred to as a "carboxylic acid compound") and a repeating unit based on a polyol compound. The terminal group of polyol P3 is a hydroxyl group at the molecular end. The polyester chain preferably consists only of a carboxylic acid compound unit and a polyol compound unit. The carboxylic acid compound and the polyol compound will be described later. The carboxylic acid compound unit of the polyester chain may be one type or two or more types. The polyol compound unit of the polyester chain may be one type or two or more types. Polyol P3 may be used alone or in combination of two or more types.

[0047] (Method for producing polyol P3) Polyol P3 can be produced by subjecting a carboxylic acid compound and a polyol compound to a dehydration condensation reaction. A catalyst may be used as necessary. The number of functional groups in polyol P3 can be adjusted by controlling the number of carboxy groups in the carboxylic acid compound, the number of hydroxyl groups in the polyol compound, and the amounts of the carboxylic acid compound and polyol compound used. The number of carboxy groups in the carboxylic acid compound is preferably 2 or 3. The number of hydroxyl groups in the polyol compound is preferably 2 or 3.

[0048] Examples of the carboxylic acid compound include dicarboxylic acids such as adipic acid, maleic acid, fumaric acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, azelaic acid, sebacic acid, and suberic acid; tricarboxylic acids such as aconitic acid, tricarballylic acid, 1,3,6-hexanetricarboxylic acid, 1,2,3-benzenetricarboxylic acid, and 1,3,5-benzenetricarboxylic acid; and acid anhydrides and dimer acids corresponding to the above dicarboxylic acids and tricarboxylic acids.

[0049] Examples of the polyol compound include saturated or unsaturated glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, octanediol, 1,9-nonanediol, 1,8-nonanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A, and hydrogenated bisphenol A; and triols such as glycerin, trimethylolpropane, and trimethylolethane.

[0050] (Polyol P4) Polyol P4 is a polyol other than polyols P1 to P3. Examples of polyol P4 include polycarbonate polyols, polybutadiene polyols, polyisoprene polyols, etc., each having 2 or 3 functional groups and an Mn of 500 to 15,000. One type of polyol P4 may be used alone, or two or more types may be used in combination.

[0051] <Polyisocyanate> Examples of polyisocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and araliphatic polyisocyanates. The number of isocyanate groups in the polyisocyanate is preferably 2 to 3, and more preferably 2.

[0052] Examples of the aliphatic polyisocyanate include linear aliphatic polyisocyanates such as tetramethylene diisocyanate, dodecamethylene diisocyanate, and hexamethylene diisocyanate, and branched aliphatic polyisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate.

[0053] Examples of alicyclic polyisocyanates include isophorone diisocyanate (3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, IPDI), hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane.

[0054] Examples of aromatic polyisocyanates include tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (diphenylmethane 4,4'-diisocyanate, MDI), 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate.

[0055] Examples of the araliphatic polyisocyanate include dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, and α,α,α,α-tetramethylxylylene diisocyanate.

[0056] The polyisocyanate is preferably an alicyclic polyisocyanate or an aromatic polyisocyanate, more preferably IPDI or MDI. One type of polyisocyanate may be used alone, or two or more types may be used in combination.

[0057] <Method for producing prepolymer> The prepolymer is a reaction product of polyol P and polyisocyanate. A urethane catalyst may be used as needed in the production of the prepolymer. A urethane bond is formed between polyol P and polyisocyanate by the urethane reaction between the hydroxyl groups of polyol P and the isocyanate groups of polyisocyanate. Of the isocyanate groups in the polyisocyanate units introduced into the prepolymer, those that remain unreacted with the hydroxyl groups of polyol P become the terminal isocyanate groups of the prepolymer.

[0058] As the polyol P, polyol P1 may be used alone, or at least one of polyols P2 to P4 may be used in combination. Polyol P1 may be used alone, or preferably contains two or more types. When two or more types of polyol P1 having different Mn are used, the elongation and strength of the resulting cured product tend to be improved.

[0059] When two or more types of polyol P1 are used in combination, it is preferable to use a polyoxyalkylene polyol having an Mn of 3,000 to 60,000 (hereinafter also referred to as "polyol P1A") in combination with a polyoxyalkylene polyol having an Mn of 300 or more but less than 3,000 (hereinafter also referred to as "polyol P1B"). Polyols P1A and P1B may each be used alone or in combination of two or more types.

[0060] The Mn of the polyol P1A is preferably 3,000 to 40,000, more preferably 3,500 to 30,000, and even more preferably 4,000 to 10,000. The hydroxyl value-based molecular weight of the polyol P1A is preferably 2,000 to 30,000, more preferably 2,500 to 20,000, and even more preferably 3,000 to 10,000.

[0061] The Mn of the polyol P1B is preferably from 350 to 2,500, more preferably from 400 to 2,000. The hydroxyl value-based molecular weight of the polyol P1B is preferably from 200 to less than 2,000, more preferably from 300 to 1,500.

[0062] When polyols P1A and P1B are used in combination as polyol P1, the content of polyol P1B per 100 parts by mass of polyol P1A is preferably 3 to 100 parts by mass, more preferably 5 to 100 parts by mass, and even more preferably 10 to 100 parts by mass.

[0063] The content of polyol P1 is preferably 10 to 100 mass%, more preferably 15 to 100 mass%, and even more preferably 20 to 100 mass%, relative to the total mass of polyol P. When the content of polyol P1 is at least the above lower limit, the elongation properties of the cured product tend to be improved.

[0064] When polyol P2 is used, the content of polyol P2 per 100 parts by mass of polyol P1 is preferably 30 to 700 parts by mass, more preferably 40 to 600 parts by mass, and even more preferably 50 to 500 parts by mass. When the content of polyol P2 is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the content of polyol P2 is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0065] When polyol P2 is used, the content of polyol P2 relative to the total mass of polyol P is preferably 10 to 90 mass%, more preferably 20 to 80 mass%, and even more preferably 30 to 80 mass%. When the content of polyol P2 is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the content of polyol P2 is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0066] When polyol P3 is used, the content of polyol P3 per 100 parts by mass of polyol P1 is preferably 30 to 700 parts by mass, more preferably 40 to 600 parts by mass, and even more preferably 50 to 500 parts by mass. When the content of polyol P3 is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the content of polyol P3 is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0067] When polyol P3 is used, the content of polyol P3 relative to the total mass of polyol P is preferably 10 to 90 mass%, more preferably 20 to 80 mass%, and even more preferably 30 to 80 mass%. When the content of polyol P3 is equal to or greater than the above lower limit, the elongation properties of the cured product tend to be improved. When the content of polyol P3 is equal to or less than the above upper limit, the tensile strength of the cured product tends to be improved.

[0068] The content of polyol P4 is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 10% by mass or less, based on the total mass of polyol P.

[0069] The average number of functional groups of the polyol P is preferably 2.0 to 8.0, more preferably 2.5 to 8.0, and even more preferably 3.0 to 8.0. When the average number of functional groups is equal to or greater than the above lower limit, the tensile strength of the resulting cured product is likely to be improved. When the average number of functional groups is equal to or less than the above upper limit, the elongation properties of the cured product are likely to be improved. The average number of functional groups of the polyol P is calculated using the following formula 1.

[0070] In the above formula 1, i means the number of types of polyols contained in polyol P, Fi means the number of functional groups of polyol Pi, and Ai means the content (mol %) of polyol Pi relative to the total amount of polyol P. n is an integer of 1 or more. Ai is calculated by the following formula 2.

[0071] In the above formula 2, i represents the number of types of polyols contained in the polyol P, and M ＯＨ (i) represents the hydroxyl value-based molecular weight of polyol Pi, Mi represents the content (mass %) of polyol Pi relative to the total mass of polyol, and n represents an integer of 1 or more.

[0072] For example, if i is 2 and polyol P contains 50 mass% of polyol P1 having a hydroxyl value-equivalent molecular weight of 5,000 and a functionality of 6, and 50 mass% of polyol P2 having a hydroxyl value-equivalent molecular weight of 5,000 and a functionality of 2, then according to the above formula 2, A1 is (50 / 5000) / (50 / 5000+50 / 5000)×100=50 mol%, and according to the above formula 1, the average number of functional groups is 6×(50 / 100)+2×(50 / 100)=4.0.

[0073] In the reaction of polyol P with polyisocyanate, the molar ratio of the total number of isocyanate groups in the polyisocyanate to the total number of hydroxyl groups in polyol P (hereinafter also referred to as "NCO / OH ratio") is 2 to 10, preferably 2 to 8, more preferably 2 to 7, and even more preferably 2 to 5. When the NCO / OH ratio is equal to or greater than the above lower limit, gelation is less likely to occur during the reaction. When the NCO / OH ratio is equal to or less than the above upper limit, unreacted isocyanate is reduced, resulting in good tensile strength of the cured product.

[0074] The urethanization catalyst is preferably one or more selected from tertiary amine compounds and organometallic compounds. When a highly reactive polyisocyanate is used, the urethanization catalyst may not be used.

[0075] Examples of the tertiary amine compound include triethylamine, triethylenediamine, and 1,8-diazabicyclo(5,4,0)-undecene-7.

[0076] The organometallic compound is preferably at least one selected from tin compounds and non-tin compounds, such as dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, tributyltin chloride, tributyltin trichloroacetate, and tin 2-ethylhexanoate. Examples of non-tin compounds include titanium compounds such as dibutyltitanium dichloride, tetrabutyltitanium, and butoxytitanium trichloride; lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate; iron compounds such as iron 2-ethylhexanoate and iron acetylacetonate; cobalt compounds such as cobalt benzoate and cobalt 2-ethylhexanoate; zinc compounds such as zinc naphthenate and zinc 2-ethylhexanoate; and zirconium compounds such as zirconium naphthenate.

[0077] The urethanization catalyst may be used alone or in combination of two or more. When a urethanization catalyst is used, the content of the urethanization catalyst is preferably, for example, 0.001 to 0.1 parts by mass per 100 parts by mass of the polyol P.

[0078] A solvent can be used, if necessary, in producing the prepolymer. The solvent is preferably one or more selected from ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, and aromatic hydrocarbons such as toluene and xylene. One solvent may be used alone, or two or more solvents may be used in combination. When a solvent is used, the content of the solvent is not particularly limited, but is preferably 100 to 1,000 parts by mass per 100 parts by mass of polyol P.

[0079] Examples of methods for producing the prepolymer include a method of mixing polyol P, polyisocyanate, and, if necessary, a urethanization catalyst and a solvent. Alternatively, a method may be used in which polyisocyanate is added dropwise to a mixed liquid obtained by mixing polyol, and, if necessary, a urethanization catalyst and a solvent.

[0080] The reaction temperature is preferably 50 to 100° C., more preferably 50 to 90° C. When the reaction temperature is equal to or higher than the lower limit, the urethane reaction is likely to be accelerated. When the reaction temperature is equal to or lower than the upper limit, side reactions other than the urethane reaction are likely to be suppressed.

[0081] When a urethanization catalyst is used, it is preferable to add a reaction terminator to inactivate the urethanization catalyst after the reaction is completed. Examples of the reaction terminator include acetylacetone. One type of reaction terminator may be used alone, or two or more types may be used in combination.

[0082] If unreacted polyisocyanate remains after the reaction, it is preferable to remove the polyisocyanate by distillation to purify the prepolymer.

[0083] <Physical Properties of Prepolymer> The content of isocyanate groups relative to the total mass of the prepolymer is preferably 1 to 20 mass%, more preferably 1 to 18 mass%, and even more preferably 1 to 15 mass%. When the content of isocyanate groups is equal to or greater than the above-mentioned lower limit, the tensile strength of the cured product is likely to be improved. When the content of isocyanate groups is equal to or less than the above-mentioned upper limit, gelation is less likely to occur during the reaction.

[0084] The viscosity of the prepolymer at a measurement temperature of 25°C is preferably 3,000 to 100,000 mPa·s, more preferably 3,000 to 75,000 mPa·s, and even more preferably 3,000 to 50,000 mPa / s. When the viscosity is equal to or less than the above upper limit, the prepolymer is easy to handle. The viscosity of the prepolymer can be measured using an E-type viscometer.

[0085] <Polyurethane Composition> The polyurethane composition of the present embodiment contains the prepolymer. The content of the prepolymer is 50 to 100% by mass, and preferably 60 to 100% by mass, based on the total mass of the polyurethane composition. The polyurethane composition may contain one type of prepolymer or two or more types of prepolymer. The polyurethane composition may further contain an optional component other than the prepolymer.

[0086] (Optional Components) Examples of optional components include catalysts, fillers, plasticizers, stabilizers, pigments, fibers, drying agents, adhesion improvers, rheology modifiers, solvents, natural resins, non-reactive polymers, and other additives. Each of the optional components may be used alone, or two or more may be used in combination. When the polyurethane composition contains optional components, the content of the optional components relative to the total mass of the polyurethane composition is preferably more than 0 mass% and 50 mass% or less.

[0087] Examples of the catalyst include the above-mentioned urethane catalysts.

[0088] Examples of fillers include metal powders such as aluminum, copper, iron, silver, and steel; powdered or hollow bead-shaped polyvinyl chloride; heavy or precipitated calcium carbonate; baryta; quartz powder; quartz sand; dolomite; wollastonite; calcined kaolin; layered silicates; mica; talc; zeolite; aluminum hydroxide; magnesium hydroxide; silica including fine silica obtained by a pyrolysis process; cement; gypsum; fly ash; carbon black; graphite; graphene; and inorganic substances such as carbon nanotubes. These fillers are preferably coated with a fatty acid. Stearic acid is preferred as the fatty acid.

[0089] Examples of the plasticizer include carboxylic acid esters, and phthalic acid esters are preferred. Examples of the plasticizer include diisononyl phthalate, diisodecyl phthalate, di(2-propylheptyl)phthalate, hydrogenated phthalate, cyclohexane-1,2-dicarboxylic acid ester, hydrogenated diisononyl phthalate, diisononyl cyclohexane-1,2-dicarboxylate, terephthalate, bis(2-ethylhexyl)terephthalate, diisononyl terephthalate, hydrogenated terephthalate, cyclohexane-1,4-dicarboxylic acid ester, hydrogenated bis(2-ethylhexyl)terephthalate, bis(2-ethylhexyl)terephthalate, and bis(2-ethylhexyl)terephthalate. Examples of the plasticizers include (butyric acid) (butyric acid diisopropyl ether), ...

[0090] As the stabilizer, any stabilizer known in the art as a stabilizer against oxidation, heat, light, and ultraviolet light can be used.

[0091] Examples of pigments include titanium oxide, chromium oxide, and iron oxide. Examples of fibers include glass fiber, carbon fiber, metal fiber, ceramic fiber, polymer fiber (e.g., polyamide fiber, polyethylene fiber), and natural fiber (e.g., wool, cellulose, hemp, sisal). Examples of desiccants include calcium oxide with a molecular sieve effect, highly reactive isocyanates such as p-tosylisocyanate, and monooxazolidines or orthoformates such as Incozol (registered trademark) 2 (Incorez). Examples of adhesion improvers include organoalkoxysilanes, epoxysilanes (e.g., 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane), (meth)acryloylsilanes, silane anhydrides, carbamatosilanes, alkylsilanes, iminosilanes, or oligomers of these silanes, titanates, and the like. Examples of the rheology modifier include bentonite, castor oil derivatives, hydrogenated castor oil, polyamide, polyamide wax, polyurethane, urea compounds, fumed silica, cellulose ether, and hydrophobically modified polyoxyethylene. Examples of solvents include acetone, methyl acetate, t-butyl acetate, 1-methoxy-2-propyl acetate, ethyl 3-ethoxypropionate, diisopropyl ether, diethylene glycol diethyl ether, ethylene glycol diethyl ether, ethylene glycol monobutyl ether, ethylene glycol mono-2-ethylhexyl ether, acetals such as propylal, butyral, 2-ethylhexylal, dioxolane, glycerol formal, 2,5,7,10-tetraoxaundecane, toluene, xylene, heptane, octane, naphtha, white spirit, petroleum ether, gasoline, propylene carbonate, dimethyl carbonate, butyrolactone, N-methylpyrrolidone, N-ethylpyrrolidone, p-chlorobenzotrifluoride, benzotrifluoride, etc. Examples of natural resins include fats or oils such as rosin, shellac, linseed oil, castor oil, and soybean oil. Examples of non-reactive polymers include homopolymers and copolymers of unsaturated monomers.Examples of unsaturated monomers include ethylene, propylene, butylene, isobutylene, isoprene, vinyl acetate, and alkyl (meth)acrylate. Examples of non-reactive polymers include polyethylene, polypropylene, polyisobutylene, and ethylene-vinyl acetate copolymer. Examples of other additives include flame retardants, wetting agents, leveling agents, antifoaming agents, degassing agents, and biocides.

[0092] <Method for Producing Cured Product> The cured product of this embodiment can be produced by reacting the polyurethane composition with a curing agent having hydroxyl groups. The isocyanate groups of the prepolymer contained in the polyurethane composition undergo a urethane reaction with the hydroxyl groups of the curing agent, causing the prepolymer to be crosslinked by urethane bonds, resulting in a cured product. The number of hydroxyl groups in the curing agent is preferably two or more, more preferably two to four, and even more preferably two to three. Water is used as a curing agent having two hydroxyl groups.

[0093] Examples of the curing agent include the above-mentioned initiator having a hydroxyl group, a low molecular weight polymer obtained by ring-opening polymerization of an alkylene oxide monomer with the above-mentioned initiator having a hydroxyl group, and water, with water being preferred. The Mn (or formula weight) of the low molecular weight polymer is preferably 300 or less.

[0094] The molar ratio of the total amount of isocyanate groups in the prepolymer to the total amount of hydroxyl groups in the curing agent is preferably greater than 1, more preferably greater than 1.0 and not greater than 1.2.

[0095] The polyurethane composition and curing agent may be mixed in a single-component manner, in which all components except the curing agent are premixed to form a single-component polyurethane composition, which is then sealed and stored, and cured by atmospheric moisture after application. Alternatively, a two-component method may be used, in which the polyurethane composition, which is the base composition, and a curing agent composition containing at least a curing agent are stored separately, and the curing agent composition and base composition are mixed before use. In the case of a single-component composition, atmospheric moisture (water) functions as the curing agent. In this embodiment, a single-component composition is preferred. It is preferable that the single-component composition does not contain water. It is preferable that the blending components containing water are dehydrated and dried in advance, or that the pressure is reduced during preparation of the single-component composition. In the case of a two-component composition, the curing agent composition may contain water. Although the base composition is unlikely to gel even if it contains a small amount of water, it is preferable to dehydrate and dry the blending components in advance from the perspective of storage stability. In the case of a two-component composition, the above-mentioned optional components may be included in the curing agent composition. To improve storage stability, a dehydrating agent may be added to the one-component composition or the two-component base composition. The reaction temperature is preferably 20 to 40°C. In the case of a one-component type, the relative humidity at the reaction temperature is preferably 40 to 60%.

[0096] <Uses of Cured Product> Suitable uses of the cured product of this embodiment include adhesives, sealants (for example, elastic sealants for construction, sealants for double glazing, rust-proofing and waterproofing sealants for glass edges, sealants for the rear surface of solar cells, sealants for buildings, sealants for ships, sealants for automobiles, and sealants for roads), coating materials (for paint applications), and electrical insulating materials (insulating coating materials for electric wires and cables). As an adhesive, the product is suitable as an elastic adhesive for joining plastics to each other, joining metals to each other, and joining plastics to metals. The product is also suitable as an elastic sealant or elastic coating material.

[0097] <Articles> By applying and curing the polyurethane composition, an article bonded, sealed, or coated with the polyurethane composition (cured product) can be obtained. This article is not particularly limited as long as it comprises a cured product of the polyurethane composition, and may be an architectural structure or a part thereof, in particular an architectural structure in civil engineering above or below ground, a roof, a staircase, or a facade, an industrial product or a consumer product, in particular a window, a lamp, a traffic signal, or a household appliance, or a means of transportation such as a car, bus, caravan, truck, train, ship, aircraft, or helicopter, or a part that can be attached to the architectural structure, the industrial product, the consumer product, or the means of transportation, such as a window made of organic glass, a panoramic roof, or a lamp housing.

[0098] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions. Examples 1 to 14 and 17 are working examples, and Examples 15 and 16 are comparative examples.

[0099] <Measurement Method> (Hydroxyl Value) The hydroxyl value of the polyol was measured in accordance with Method B (phthalation method) described in JIS K 1557-1:2007.

[0100] (Hydroxyl value-equivalent molecular weight) The hydroxyl value-equivalent molecular weight was calculated by 56,100×number of functional groups of polyol (number of hydroxyl groups) / hydroxyl value.

[0101] (Mn, Mw / Mn) A gel permeation chromatograph analyzer HLC-8420GPC (product name of Tosoh Corporation) was used as the measuring device. A TSKgel Supermultipore HZ-M (product name of Tosoh Corporation) column was used, and tetrahydrofuran was used as the eluent. The sample pump was set to a flow rate of 0.350 mL / min, the reference pump was set to a flow rate of 0.350 mL / min, the detector temperature was set to 40°C, and the collection time was 6 to 15 minutes. Mn, Mw, and Mw / Mn were determined by analyzing the peaks that appeared between 6 and 11 minutes of collection time. A calibration curve was created using polystyrene as a standard material.

[0102] (Isocyanate Group Content) The isocyanate group content relative to the total mass of the prepolymer was measured in accordance with the method described in JIS K 1603-1:2007.

[0103] (Measurement of Viscosity) The viscosity of the prepolymer was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name: RE80 type) under conditions of a measurement temperature of 25°C and rotor No. 4.

[0104] <Evaluation Method> (Evaluation of Tensile Properties) The prepolymers obtained in Examples 1 to 16 described below were coated onto films in a thickness of 150 μm, and aged for 7 days at 23°C and a relative humidity of 50% and then for 3 days at 50°C, to obtain dumbbell-shaped No. 5 test specimens as cured products. The mixture of the prepolymer and 1,4-butanediol obtained in Example 17 described below was coated onto films in a thickness of 150 μm, and aged for 7 days at 23°C and a relative humidity of 50% and then for 3 days at 50°C, to obtain dumbbell-shaped No. 5 test specimens as cured products. A tensile test was conducted using the above test specimen at a tensile speed of 100 mm / min in accordance with JIS K 6251:2017, a tensile test method for vulcanized rubber, and the stress at 50% elongation (shown as "M50" in Table 2, unit: MPa), maximum tensile strength (shown as "tensile strength" in Table 2, unit: MPa), and maximum point elongation (shown as "elongation" in Table 2, unit: %) were measured. The higher the M50 and tensile strength values, the higher the tensile strength. The higher the elongation value, the better the elongation properties.

[0105] [Synthesis Example 1: Polyol P1B-1] Propylene oxide was polymerized using sorbitol as an initiator and potassium hydroxide as a catalyst to obtain polyoxypropylene polyol, Polyol P1B-1. The number of functional groups, hydroxyl value, hydroxyl value-based molecular weight, Mn, and Mw / Mn of Polyol P1B-1 are shown in Table 1 (hereinafter, the same applies to other polyols).

[0106] Synthesis Example 2: Polyol P1B-2 A polyoxypropylene polyol, polyol P1B-2, was obtained in the same manner as in Synthesis Example 1, except that the amount of propylene oxide polymerized was changed.

[0107] Synthesis Example 3 Polyol P1A-1 Using the polyol P1B-1 obtained in Synthesis Example 1 as an initiator, propylene oxide was polymerized using a zinc hexacyanocobaltate complex having a t-butyl alcohol ligand as a catalyst to obtain polyol P1A-1, a polyoxypropylene polyol.

[0108] Synthesis Example 4 Polyol P1A-2 A polyoxypropylene polyol, polyol P1A-2, was obtained in the same manner as in Synthesis Example 3, except that the amount of propylene oxide polymerized was changed.

[0109] Synthesis Example 5 Polyol P2-1 Propylene oxide was polymerized using dipropylene glycol as an initiator and potassium hydroxide as a catalyst to obtain polyoxypropylene polyol, polyol P2-1.

[0110] Synthesis Example 6 Polyol P2-2 Propylene oxide was polymerized using glycerin as an initiator and potassium hydroxide as a catalyst to obtain polyol P2-2, which is a polyoxypropylene polyol.

[0111] Synthesis Example 7 Polyol P2-3 Polyol P2-3, a polyoxypropylene polyol, was obtained in the same manner as in Synthesis Example 5, except that the amount of propylene oxide polymerized was changed.

[0112] Synthesis Example 8 Polyol P2-4 Using dipropylene glycol as an initiator and a zinc hexacyanocobaltate complex having t-butyl alcohol as a ligand as a catalyst, propylene oxide was polymerized to obtain polyoxypropylene polyol, polyol P2-4.

[0113] The following compounds were used as polyol P3. Polyol P3-1: A polyester polyol having two functional groups obtained by a dehydration condensation reaction of adipic acid, neopentyl glycol, and 1,6-hexanediol (manufactured by Toyokuni Oil Mills, product name "HS 2F-231AS") Polyol P3-2: A polyester polyol having two functional groups obtained by a dehydration condensation reaction of adipic acid, ethylene glycol, neopentyl glycol, and 1,6-hexanediol (manufactured by EVONIK, product name "DYNACOLL 7210").

[0114]

[0115] The following compounds were used as polyisocyanates: 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.; hereinafter, including in Table 2, this will be referred to as "IPDI"), and diphenylmethane 4,4'-diisocyanate (manufactured by Tosoh Corporation, product name "Millionate MT"; hereinafter, including in Table 2, this will be referred to as "MDI").

[0116] The following compounds were used as catalysts: Dibutyltin dilaurate (manufactured by Tokyo Chemical Industry Co., Ltd.).

[0117] Example 1 46.1 parts by mass of IPDI as polyisocyanate, 100 parts by mass of polyol P1A-1 as polyol P, and 50 ppm by mass of dibutyltin dilaurate as a catalyst relative to the total mass of polyol P1A-1 were added, and the mixture was allowed to react with stirring at 80°C for 2 hours under a nitrogen atmosphere at an NCO / OH ratio of 5.0 to obtain the prepolymer of Example 1. The obtained prepolymer was used to evaluate its tensile properties after moisture curing. Table 2 shows the viscosity of the prepolymer, the average number of functional groups, the content of isocyanate groups relative to the total mass of the prepolymer, and the evaluation results of its tensile properties (the same applies to Examples 2 to 17 below).

[0118] [Examples 2 to 16] Prepolymers of Examples 2 to 16 were obtained in the same manner as in Example 1, except that the type and amount of polyisocyanate, polyol P, and urethanization catalyst, as well as the NCO / OH ratio, were changed as shown in Table 2. The units of the values ​​for polyol P and polyisocyanate in Table 2 are parts by mass, and "-" indicates that the corresponding compound was not used. The content of the urethanization catalyst is the content relative to the total mass of polyol P (unit: ppm by mass).

[0119] [Example 17] 27.2 parts by mass of IPDI as polyisocyanate, 35.2 parts by mass of Polyol P1A-1, 4.8 parts by mass of Polyol P1B-1, and 60.0 parts by mass of Polyol P2-1 as polyol P, and 500 ppm by mass of dibutyltin dilaurate as a catalyst relative to the total mass of Polyol P were added, and the mixture was reacted with stirring at 80°C for 2 hours under a nitrogen atmosphere at an NCO / OH ratio of 2.0 to obtain the prepolymer of Example 17. 0.45 parts by mass of 1,4-butanediol as a curing agent was mixed with 100 parts by mass of this prepolymer, and the tensile properties were evaluated. The molar ratio of the total amount of isocyanate groups in the prepolymer to the total amount of hydroxyl groups in the 1,4-butanediol curing agent was 1.1.

[0120]

[0121] It was found that the cured products obtained from the prepolymers of Examples 1 to 14 and 17 had significantly superior tensile strength compared to the cured products obtained from the prepolymers of Examples 15 and 16. Furthermore, the elongation properties of the cured products obtained from the prepolymers of Examples 1 to 14 and 17 were at a practical level considering their applications as adhesives, coating materials, and sealants. The elongation properties of the cured products are affected by the number of functional groups in the polyol used to produce the prepolymer. Comparing Examples 2 to 5, 9 to 12, and 16 to 17, which have an average functionality of approximately 3.0, Examples 2 to 5, 9 to 12, and 17 had superior elongation properties to Example 16. Furthermore, Example 1, which had an average functionality of 6.0, exhibited significantly better tensile strength and elongation properties than Example 16, which had an average functionality of 3.0.

Claims

1. A prepolymer having an isocyanate group at the end, which is the reaction product of reacting a polyol and a polyisocyanate in a molar ratio of the total number of isocyanate groups of the polyisocyanate to the total number of hydroxyl groups of the polyol of 2 to 10, wherein the polyol comprises a polyoxyalkylene polyol having 4 or more functional groups and a number average molecular weight of 300 to 60,000.

2. The prepolymer according to claim 1, wherein the content of said polyoxyalkylene polyol is 10 to 100% by mass based on the total mass of said polyol.

3. The prepolymer according to claim 1, comprising two or more types of said polyoxyalkylene polyols.

4. The prepolymer according to claim 1, wherein the polyoxyalkylene polyol comprises a polyoxyalkylene polyol having a number average molecular weight of 3,000 to 60,000 and a polyoxyalkylene polyol having a number average molecular weight of 300 or more but less than 3,000.

5. The prepolymer of claim 1, wherein the polyol further comprises a polyoxyalkylene polyol having a functionality of 2 or 3 and a number average molecular weight of 500 to 15,000.

6. The prepolymer of claim 1, wherein the polyol further comprises a polyester polyol having a functionality of 2 or 3 and a number average molecular weight of 500 to 15,000.

7. The prepolymer of claim 1, wherein the polyisocyanate is one or both of 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate and diphenylmethane 4,4'-diisocyanate.

8. The prepolymer according to claim 1, wherein the content of isocyanate groups is 1 to 20% by mass relative to the total mass of the prepolymer.

9. A polyurethane composition comprising the prepolymer according to any one of claims 1 to 8, wherein the content of said prepolymer is 50 to 100% by weight based on the total weight of the polyurethane composition.

10. A cured product of the polyurethane composition according to claim 9.

11. An adhesive comprising the cured product according to claim 10.

12. A sealant comprising the cured product according to claim 10.

13. An article comprising the cured product of claim 10.

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