Moisture-curable polyurethane hot-melt resin composition, cured product, and laminate

Abstract

To provide a moisture-curable polyurethane hot-melt adhesive that resists foaming even after moisture-cured while ensuring its transparency, and can also exhibit adhesion to a PET substrate.SOLUTION: A moisture-curable polyurethane hot-melt resin composition contains a polyurethane resin having an isocyanate group. The polyurethane resin is a reactant between a polyol (A) and a polyisocyanate (B). The polyol (A) contains an alicyclic polyester polyol (a1), a long-chain aliphatic polyester polyol (a2) and a liquid polyester polyol (a3). A content rate of the alicyclic polyester polyol (a1), the long-chain aliphatic polyester polyol (a2), and the liquid polyester polyol (a3) is within a specific range in the polyol (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a moisture-curable polyurethane hot-melt resin composition, a cured product, and a laminate. [Background technology]

[0002] Hot melt adhesives have high initial adhesion and final strength, and are therefore used in a variety of fields, including various building material applications, decorative panels, automotive interior materials, and clothing. Known reactive hot melt adhesives include moisture-curing polyurethane hot melt adhesives, which achieve their final strength through moisture curing of the isocyanate groups in their main component, the urethane prepolymer, as well as olefin-based hot melt adhesives and polyester-based hot melt adhesives. In recent years, there has been growing demand for high-quality building materials in which highly transparent materials, such as polyethylene terephthalate (PET) film, are attached to the substrate.

[0003] Examples of such highly transparent hot melt adhesives include hot melt adhesives containing ethylene-propylene copolymers, hydrogenated rosin-based tackifying resins, other hydrogenated tackifying resins, and acid-modified olefins (see Patent Document 1); crystalline polyester resins consisting of polycarboxylic acid components and polyhydric alcohol components, which contain terephthalic acid as the polycarboxylic acid component and ethylene glycol, 1,4-butanediol, polyalkylene glycol, and diethylene glycol as the polyhydric alcohol components (see Patent Document 2); hot melt adhesives containing ethylene-propylene copolymers, hydrogenated tackifying resins, and wax with a melting point of 120 to 160°C (see Patent Document 3); and polyester resins in which polycarboxylic acid components and polyhydric alcohol components are copolymerized, and which contain, as polycarboxylic acid components, aromatic dicarboxylic acids having 8 to 14 carbon atoms and aliphatic dicarboxylic acids having 6 or more carbon atoms, and further contain a metal salt of an aliphatic carboxylic acid having 6 or more carbon atoms (see Patent Document 4). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-2283 [Patent Document 2] Japanese Patent Application Publication No. 2019-127581 [Patent Document 3] Japanese Patent Application Laid-Open No. 2018-154694 [Patent Document 4] Japanese Patent Application Laid-Open No. 2015-108113 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when reactive hot melts (RHMs) are used for such applications, high transparency of the resin itself and suppression of foaming during moisture curing are required. According to the inventors' research, using a crystalline component as a raw material is effective in suppressing foaming, but this results in the problem that the resulting cured product becomes cloudy due to crystallization of the crystalline component, resulting in reduced transparency.

[0006] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a moisture-curable polyurethane hot melt adhesive that can suppress foaming while maintaining transparency even after moisture curing, and that can also exhibit adhesion to PET substrates. [Means for solving the problem]

[0007]

[0006] Through extensive research, the present inventors came up with the idea of ​​combining an alicyclic polyester polyol, a crystalline component, and a liquid polyester. Although alicyclic polyester polyols are not usually expected to have good adhesion to PET substrates, they discovered that combining these components in a specific ratio can suppress foaming while maintaining transparency and also ensure adhesion to PET substrates, leading to the completion of the present invention.

[0008] That is, the present invention includes the following inventions. [1] A moisture-curable polyurethane hot-melt resin composition containing a polyurethane resin having an isocyanate group, wherein the polyurethane resin is a reaction product of polyol (A) and polyisocyanate (B), and the polyol (A) contains an alicyclic polyester polyol (a1), a long-chain aliphatic polyester polyol (a2), and a liquid polyester polyol (a3), wherein the content of the alicyclic polyester polyol (a1) in the polyol (A) is 20% by mass or more, the content of the long-chain aliphatic polyester polyol (a2) in the polyol (A) is 15% by mass or more, and the content of the liquid polyester polyol (a3) ​​in the polyol (A) is 15% by mass or more. [2] The moisture-curable polyurethane hot-melt resin composition according to [1], which has a haze value of less than 20 as measured by the following method. [Method for measuring haze value] The moisture-curable polyurethane hot-melt resin composition was melted at 120°C for 1 hour and applied to the release layer to a thickness of 0.1 mm. The resulting coating was maintained at 23°C and 50% humidity for 96 hours to obtain a cured product. The haze value of the cured product was measured in accordance with JIS K 7136. [3] A cured product of the moisture-curable polyurethane hot-melt resin composition according to [1] or [2]. [4] A laminate comprising the cured product according to [3]. [Effects of the Invention]

[0009] The moisture-curable polyurethane hot-melt resin composition of the present invention can maintain transparency even after moisture curing, inhibit foaming, and exhibit excellent adhesion to PET substrates. DETAILED DESCRIPTION OF THE INVENTION

[0010] The moisture-curable polyurethane hot-melt resin composition of the present invention contains a polyurethane resin having an isocyanate group.

[0011] The polyurethane resin is a reaction product of a polyol (A) and a polyisocyanate (B).

[0012] The polyol (A) includes an alicyclic polyester polyol (a1), a long-chain aliphatic polyester polyol (a2), and a liquid polyester polyol (a3).

[0013] The alicyclic polyester polyol (a1) is a polyester polyol containing an alicyclic structure in the molecule, and by including the alicyclic polyester polyol (a1), it is possible to increase transparency and suppress foaming.

[0014] The alicyclic polyester polyol (a1) is preferably, for example, a reaction product of a polybasic acid containing an alicyclic structure (hereinafter referred to as an "alicyclic structure-containing polybasic acid") and a glycol.

[0015] The alicyclic structure-containing polybasic acid may have an alicyclic structure, and examples thereof include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclopropanedicarboxylic acid, 1,2-cyclobutanedicarboxylic acid, 1,3-cyclobutanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cycloheptanedicarboxylic acid, 1,3-cycloheptanedicarboxylic acid, 1,4-cycloheptanedicarboxylic acid, 1,2-cyclooctanedicarboxylic acid, 1,3-cyclooctanedicarboxylic acid, 1,4-cyclooctanedicarboxylic acid, 1,5-cyclooctanedicarboxylic acid, 1,2-cyclononanedicarboxylic acid, 1,3-cyclononanedicarboxylic acid, and 1,4- Examples of the carboxylic acid include cyclononanedicarboxylic acid, 1,5-cyclononanedicarboxylic acid, 1,2-cyclodecanedicarboxylic acid, 1,3-cyclodecanedicarboxylic acid, 1,4-cyclodecanedicarboxylic acid, 1,5-cyclodecanedicarboxylic acid, 1,6-cyclodecanedicarboxylic acid, 1,2,3-cyclopropanetricarboxylic acid, 1,2,3-cyclobutanetricarboxylic acid, 1,2,3-cyclopentanetricarboxylic acid, 1,2,3-cycloheptanetricarboxylic acid, 1,2,3-cyclohexanetricarboxylic acid, dicyclohexyl-4,4'-dicarboxylic acid and dimer acid, 1,2-cyclohexanediacetic acid, 1,3-cyclohexanediacetic acid, 1,4-cyclohexanediacetic acid, and acid anhydrides thereof; and anhydrides such as hydrogenated phthalic acid. These may be used alone or in combination of two or more. Among these, it is preferable to use a dicarboxylic acid having a cyclohexane ring or a derivative thereof, and it is more preferable to use 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, or hydrogenated phthalic anhydride.

[0016] The glycol is not particularly limited, and examples thereof include aliphatic diols such as ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, diethylene glycol, triethylene glycol, dipropylene glycol, and tripropylene glycol; alicyclic diols such as cyclopentane-1,2-diol, cyclohexane-1,2-diol, cyclohexane-1,3-diol, cyclohexane-1,4-diol, cyclooctane-1,4-diol, and 2,5-norbornanediol; hydroxypivalic acid neopentyl glycol ester, 2-methylpropanediol, 2-methyl-1, Examples include side chain-containing glycols such as 4-butanediol, neopentyl glycol, 2,2-dimethyl-1,4-butanediol, 2,3-dimethyl-1,4-butanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,3-dimethyl-1,5-pentanediol, 3-ethyl-1,5-pentanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,6-hexanediol, 2,3,4-trimethyl-1,5-pentanediol, 3,3-dimethyl-1,6-hexanediol, 3,3-diethyl-1,5-pentanediol, and 3,3-diethyl-1,6-hexanediol; and aromatic diols such as p-xylenediol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, and 2,5-naphthalenediol, which may be used alone or in combination of two or more.

[0017] Among these, from the viewpoints of an appropriate open time at low temperatures and ease of obtaining raw materials, it is preferable to use a side chain-containing glycol, and it is more preferable to use neopentyl glycol, hydroxypivalic acid neopentyl glycol ester, or 2-methylpropanediol.

[0018] The alicyclic polyester polyol (a1) can be obtained by subjecting the alicyclic structure-containing polybasic acid and glycol to a polycondensation reaction using a conventional method. For example, the polycondensation reaction can be carried out by charging the alicyclic structure-containing polybasic acid and glycol into a reaction vessel, optionally adding a high-boiling point solvent such as xylene, an esterification catalyst, and a polymerization inhibitor, and then allowing the esterification reaction to proceed by dehydration condensation. The polycondensation reaction can be carried out at a temperature of 140 to 240°C, preferably 170 to 230°C, for a reaction time of 5 to 20 hours, preferably 7 to 17 hours.

[0019] Examples of the esterification catalyst include metal oxides such as tin oxide, antimony oxide, titanium oxide, and vanadium oxide; Bronsted acids such as paratoluenesulfonic acid, sulfuric acid, and phosphoric acid; Lewis acids such as boron trifluoride complex, titanium tetrachloride, and tin tetrachloride; and organometallic compounds such as calcium acetate, zinc acetate, manganese acetate, zinc stearate, alkyltin oxides, and titanium alkoxides. These may be used alone or in combination of two or more.

[0020] The amount of the esterification catalyst used is preferably 0.001 to 0.1% by mass, and more preferably 0.005 to 0.03% by mass, based on the total mass of the alicyclic structure-containing polybasic acid and glycol.

[0021] Examples of the polymerization inhibitor include hydroquinone, monomethyl ether hydroquinone, toluhydroquinone, di-tert-4-methylphenol, trimonomethyl Examples include ether hydroquinone, phenothiazine, tert-butylcatechol, etc., and these can be used alone or in combination of two or more.

[0022] The amount of the polymerization inhibitor used is preferably 0.001 to 0.3 mass %, more preferably 0.005 to 0.07 mass %, based on the total mass of the alicyclic structure-containing polybasic acid and glycol.

[0023] The acid value of the alicyclic polyester polyol (a1) is preferably 2.0 mgKOH / g or less, more preferably 0 to 1.0 mgKOH / g, and particularly preferably 0 to 0.80 mgKOH / g. The acid value of the alicyclic polyester polyol (a1) is a value measured in accordance with JIS K1557-5.

[0024] The alicyclic polyester polyol (a1) preferably has a hydroxyl value of 40 to 220 mgKOH / g, more preferably 50 to 150 mgKOH / g. The hydroxyl value of the alicyclic polyester polyol (a1) can be measured in accordance with JIS K0070.

[0025] From the viewpoint of synthesis and from the viewpoint of improving the balance between an appropriate open time and moisture-proof performance at low temperatures, the alicyclic polyester polyol (a1) synthesized by the above method preferably has a number-average molecular weight of 500 to 2500, more preferably 500 to 1500. The number-average molecular weight is a value determined by gel permeation chromatography (GPC) using polystyrene as a molecular weight standard.

[0026] The content of the alicyclic polyester polyol (a1) in the polyol (A) is 20% by mass or more, preferably 23% by mass or more, and preferably 70% by mass or less, more preferably 50% by mass or less, and even more preferably 48% by mass or less.

[0027] The long-chain aliphatic polyester polyol (a2) is an essential component for exerting cohesive strength as an adhesive, and represents a polyester polyol in which the total number of carbon atoms in the alkylene groups contained in the repeating units is 10 or more.

[0028] The long-chain aliphatic polyester polyol (a2) is preferably represented by the following formula (1) from the viewpoint of suppressing foaming.

[0029] [ka]

[0030] [In formula (1), R 1 and R 2 are straight-chain alkylene groups each having an even number of carbon atoms, and R 1 and R 2 The total number of carbon atoms contained in is 10 or more, and n represents an integer of 1 to 40.

[0031] R 1 is a straight-chain alkylene group with an even number of carbon atoms, and R 1 and R 2 The total number of carbon atoms in R can be selected appropriately within the range of 10 or more. 1 The alkylene group is preferably a straight-chain alkylene group having an even number of carbon atoms of 4 or more, and more preferably a straight-chain alkylene group having an even number of carbon atoms in the range of 4 to 10.

[0032] R 2 is the R 1 and independently are straight-chain alkylene groups having an even number of carbon atoms, and R 1 and R 2 The alkylene groups may be appropriately selected so that the total number of carbon atoms is 10 or more, and are preferably straight-chain alkylene groups having an even number of carbon atoms of 4 or more, and more preferably straight-chain alkylene groups having an even number of carbon atoms in the range of 4 to 12 (preferably 10 to 12).

[0033] R 1 and R 2 The total number of carbon atoms is preferably 10 or more, more preferably 12 or more, and for example, 30 or less, more preferably 26 or less, and even more preferably 24 or less.

[0034] R 1 and R 2However, by using a long-chain aliphatic polyester polyol, which is a straight-chain alkylene group having the number of carbon atoms within the above range, the crystallinity of the resulting urethane prepolymer is increased, making it possible to obtain a moisture-curing polyurethane hot melt adhesive that can prevent peeling of the sheet or film in areas of a substrate with a complex shape.

[0035] In formula (1), n ​​represents an integer of 1 to 40, preferably an integer of 9 to 25, and more preferably an integer of 9 to 15. By using a long-chain aliphatic polyester polyol having n within the above range, the adhesive can exhibit an appropriate cohesive strength.

[0036] The long-chain aliphatic polyester polyol (a2) can be produced, for example, by condensation of a straight-chain aliphatic diol having an even number of carbon atoms with a straight-chain aliphatic dicarboxylic acid having an even number of carbon atoms. Examples of the straight-chain aliphatic diol include ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, and 10-decanediol, and 1,6-hexanediol, 1,8-octanediol, and 1,10-decanediol are preferred.

[0037] As the straight-chain aliphatic dicarboxylic acid, for example, succinic acid, adipic acid, sebacic acid, dodecamethylenedicarboxylic acid, etc. can be used, and preferably sebacic acid, dodecamethylenedicarboxylic acid, and 1,12-dodecanedicarboxylic acid can be used.

[0038] The combination of the linear aliphatic diol and the linear aliphatic dicarboxylic acid used in producing the long-chain aliphatic polyester polyol (a2) is preferably R 1 , R 2The total number of carbon atoms contained therein can be appropriately selected from 12 or more, preferably from the range of 12 to 20. Among these, it is preferable to use a long-chain aliphatic polyester polyol obtained by reacting 1,6-hexanediol as the linear aliphatic diol with 1,12-dodecanedicarboxylic acid or sebacic acid as the linear aliphatic dicarboxylic acid. Furthermore, it is more preferable to use a long-chain aliphatic polyester polyol obtained by reacting 1,6-hexanediol as the linear aliphatic diol with 1,12-dodecanedicarboxylic acid as the linear aliphatic dicarboxylic acid, in order to produce an adhesive having a practically sufficient level of initial bond strength, even when used in a relatively high-temperature environment.

[0039] The number average molecular weight of the long-chain aliphatic polyester polyol (a2) is preferably 10,000 or less, more preferably 5,000 or less, and is preferably 500 or more, more preferably 1,000 or more, and even more preferably 3,000 or more.

[0040] In the present invention, the number average molecular weight can be measured by gel permeation chromatography (GPC) using polystyrene as a standard sample.

[0041] From the viewpoint of suppressing foaming, the content of the long-chain aliphatic polyester polyol (a2) in the polyol (A) is 15% by mass or more, preferably 20% by mass or more, more preferably 22% by mass or more, and is preferably 65% ​​by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0042] The liquid polyester polyol (a3) ​​is an essential component for ensuring adhesion to a PET substrate, and may be any polyester polyol that is liquid at room temperature (25°C), such as a reaction product of a polybasic acid including adipic acid with an aliphatic compound having two or more hydroxyl groups, provided that the long-chain aliphatic polyester polyol (a2) and the liquid polyester polyol (a3) ​​are different.

[0043] Examples of polybasic acids other than adipic acid include aliphatic polybasic acids such as succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, dodecanedioic acid, eicosadionic acid, citraconic acid, itaconic acid, citraconic anhydride, and itaconic anhydride; and alicyclic polybasic acids such as 1,4-cyclohexanedicarboxylic acid. These polybasic acids may be used alone or in combination of two or more. The amount of adipic acid used is preferably 50% by mass or more of the polybasic acid, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0044] Examples of the aliphatic compound having two or more hydroxyl groups include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, neopentyl glycol, Straight-chain or branched-chain aliphatic compounds such as 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-methyl-1,8-octanediol, 2,4-diethyl-1,5-pentanediol, trimethylolethane, trimethylolpropane, pentaerythritol, etc. can be used. These compounds can be used alone or in combination of two or more. Among these, it is more preferable to use one or more compounds selected from the group consisting of ethylene glycol, 1,4-butanediol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butyl-1,3-propanediol, and 2,4-diethyl-1,5-pentanediol, since even better initial adhesive strength and flexibility can be obtained.

[0045] The number average molecular weight of the liquid polyester polyol (a3) ​​is preferably 300 or more, more preferably 600 or more, and even more preferably 1,000 or more, and is preferably 10,000 or less, more preferably 9,000 or less, in order to obtain even better initial adhesive strength and flexibility.

[0046] The glass transition temperature of the liquid polyester polyol (a3) ​​is preferably 20°C or lower, more preferably 10°C or lower, and even more preferably 5°C or lower, and may be, for example, -100°C or higher, or -50°C or higher.

[0047] The glass transition temperature can be measured by DSC in accordance with JIS K 7121-1987. Specifically, a measurement sample is placed in a differential scanning calorimeter, heated to (Tg+50°C) at a heating rate of 10°C / min, held for 3 minutes, and then rapidly cooled. The midpoint glass transition temperature (Tmg) read from the obtained differential thermal curve is taken as the glass transition temperature.

[0048] The content of the liquid polyester polyol (a3) ​​in the polyol (A) is 15% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and is preferably 65% ​​by mass or less, more preferably 55% by mass or less, even more preferably 50% by mass or less.

[0049] The total content of the alicyclic polyester polyol (a1), the long-chain aliphatic polyester polyol (a2), and the liquid polyester polyol (a3) ​​in the polyol (A) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and preferably 100% by mass.

[0050] As the polyol (A), in addition to the alicyclic polyester polyol (a1), the long-chain aliphatic polyester polyol (a2), and the liquid polyester polyol (a3), other polyols can be used as needed.

[0051] Examples of the other polyols that can be used include polyester polyols other than (a1), (a2), and (a3), polycarbonate polyols, polyacrylic polyols, butadiene polyols, hydrogenated polybutadiene polyols, etc. These polyols may be used alone or in combination of two or more.

[0052] Examples of the polyisocyanate (B) that can be used include aromatic polyisocyanates such as polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate isocyanate, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate; and aliphatic or alicyclic polyisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate. Among these, aromatic polyisocyanates are preferred, and diphenylmethane diisocyanate is more preferred, in view of obtaining even better reactivity and final adhesive strength.

[0053] The amount of the polyisocyanate (B) used is preferably in the range of 5 to 60% by mass, more preferably 15 to 50% by mass, of the raw materials for the polyurethane resin, in order to obtain even better adhesive strength.

[0054] The polyurethane resin is obtained by reacting the polyol (A) with the polyisocyanate (B), and has isocyanate groups at the polymer terminals or within the molecule, which are capable of forming a crosslinked structure by reacting with moisture present in the air or in a housing or an adherend to which the urethane prepolymer is applied.

[0055] The polyurethane resin can be produced, for example, by adding the polyol (A) dropwise to a reaction vessel containing the polyisocyanate (B), followed by heating, and reacting under conditions in which the isocyanate groups of the polyisocyanate (B) are in excess relative to the hydroxyl groups of the polyol (A).

[0056] The urethane bond amount of the polyurethane resin is preferably in the range of 0.5 to 3 mol / kg, more preferably in the range of 0.9 to 2.7 mol / kg, and even more preferably in the range of 1.1 to 2.4 mol / kg, in order to obtain even better initial adhesive strength, flexibility, and low viscosity.

[0057] When producing the polyurethane resin, the equivalent ratio ([isocyanate group / hydroxyl group]) of the isocyanate groups in the polyisocyanate (B) to the hydroxyl groups in the polyol (A) is preferably in the range of 1.1 to 1.5, more preferably in the range of 1.15 to 1.45, in order to obtain even better initial adhesive strength, flexibility, and low viscosity.

[0058] The isocyanate group content (hereinafter abbreviated as "NCO%") of the polyurethane resin is preferably in the range of 1 to 4 mass%, more preferably 1.2 to 3.5 mass%, in order to obtain even better initial adhesive strength, flexibility, and low viscosity. The NCO% of the polyurethane resin is a value measured by potentiometric titration in accordance with JIS K1603-1:2007.

[0059] The content of the polyurethane resin in the moisture-curable polyurethane hot-melt resin composition is preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more, with the upper limit being 100% by mass.

[0060] The moisture-curable polyurethane hot-melt resin composition of the present invention may contain other additives in addition to the polyurethane resin, as required.

[0061] Examples of the other additives that can be used include antioxidants, tackifiers, plasticizers, stabilizers, fillers, dyes, pigments, fluorescent brighteners, silane coupling agents, waxes, etc. These additives may be used alone or in combination of two or more.

[0062] A method for obtaining a cured coating of the moisture-curable polyurethane hot-melt resin composition includes, for example, melting the moisture-curable polyurethane hot-melt resin composition at 50 to 130°C, applying it to a substrate, and then moisture-curing it.

[0063] Examples of the substrate that can be used include wood substrates such as plywood, MDF (medium density fiberboard), and particle board; metal substrates such as aluminum and iron; sheet substrates made from resins such as polyester, polyamide, polystyrene, polycarbonate, vinyl chloride, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyethylene, and polypropylene; calcium silicate board; paper; metal foil; veneer; fiber substrates such as nonwoven fabric and woven fabric; synthetic leather; paper; rubber substrates; and glass substrates. The thickness of the substrate is determined depending on the intended use, but is, for example, in the range of 1 to 500 mm.

[0064] Examples of methods for applying the moisture-curable urethane hot-melt resin composition to the substrate include methods in which the moisture-curable urethane hot-melt resin composition melted at 70 to 140°C is applied to the substrate using a coater method such as a roll coater, spray coater, T-tie coater, knife coater, or comma coater; or a precision method such as a dispenser, spray, inkjet printing, screen printing, or offset printing.

[0065] The thickness of the cured layer of the moisture-curable urethane hot-melt composition is determined appropriately depending on the intended use, but is, for example, in the range of 0.001 to 3 cm.

[0066] After the coating, the adhesive is aged for 0.5 to 3 days at a temperature of 20 to 80° C. and a relative humidity of 50 to 90%, for example, to obtain the final adhesive strength.

[0067] The moisture-curable polyurethane hot-melt resin composition of the present invention maintains transparency even after moisture curing, suppresses foaming, and exhibits adhesion to PET substrates. Therefore, the moisture-curable polyurethane hot-melt resin composition of the present invention can be suitably used for building panels, decorative panels, automotive interior materials, etc. [Example]

[0068] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is possible to carry out the invention by making appropriate modifications within the scope of the above and below-described aims, and all such modifications are included in the technical scope of the present invention.

[0069] [Example 1] A four-neck flask equipped with a stirrer and a thermometer was charged with 24 parts by mass of an aliphatic polyester polyol (a reaction product of diethylene glycol, neopentyl glycol, 1,6-hexanediol, and adipic acid; number average molecular weight: 2,000 or less; hereinafter abbreviated as "DEG / NPG / HG / AA2000"), 38 parts by mass of an alicyclic polyester polyol (a reaction product of neopentyl glycol and hexahydrophthalic anhydride; number average molecular weight: 2,000; hereinafter abbreviated as "NPG / HHPA2000"), and 20 parts by mass of a crystalline polyester polyol (a reaction product of 1,6-hexanediol and dodecanedioic acid; number average molecular weight: 3,500; hereinafter abbreviated as "HG / DDA3500"), and the mixture was heated under reduced pressure at 100°C to dehydrate the flask until the water content was 0.05% by mass. After cooling the flask to 90°C, 18 parts by mass of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as "MDI") melted at 70°C was added, and the mixture was allowed to react at 110°C for approximately 1 hour under a nitrogen atmosphere until the NCO% became constant, thereby obtaining a moisture-curable polyurethane hot-melt resin composition.

[0070] [Example 2, Comparative Examples 1 to 3] A moisture-curable polyurethane hot-melt resin composition was obtained in the same manner as in Example 1, except that the amounts of polyol and polyisocyanate used were changed as shown in Table 1.

[0071] The resulting moisture-curable polyurethane hot-melt resin composition was evaluated as follows.

[0072] [Transparency evaluation method] The moisture-curing polyurethane hot melt adhesives obtained in the examples and comparative examples were melted at 120°C for 1 hour, and then a 0.10 mm thick film was produced on the inside of a release liner using a roll coater. The film was then aged for at least 4 days at 23°C and 50% humidity to allow the moisture-curing reaction to proceed completely. The haze value of the cured RHM film was measured using a haze meter and evaluated as follows: "Good": Haze value is less than 20. "X": Haze value is 20 or more.

[0073] [Method for evaluating foam appearance] The moisture-curing polyurethane hot melt adhesives obtained in the examples and comparative examples were melted at 120°C for 1 hour, and then a 0.10 mm thick film was produced on the inside of a release liner using a roll coater. The film was then aged for at least 12 hours in an environment of 40°C and 50% humidity to allow the moisture-curing reaction to proceed rapidly. The cured RHM film was visually inspected and evaluated as follows: "Good": No bubbles can be visually observed. "X": Air bubbles can be visually confirmed.

[0074] [PET adhesiveness evaluation method] The moisture-curable polyurethane hot melt adhesives obtained in the examples and comparative examples were melted at 120°C for 1 hour and then applied to a PET sheet at a thickness of 0.05 mm using an applicator. The adhesive was then laminated to a melamine decorative panel using a press roll. After leaving the adhesive in an environment of 23°C and 50% humidity for 4 days, a 180° peeling test was performed at a width of 2.5 cm. The peel strength was measured and evaluated as follows: "Good": Peel strength is 40 N / inch or more. "X": Peel strength is less than 40 N / inch.

[0075] The evaluation results are shown in Table 1.

[0076] [Table 1]

[0077] Examples 1 and 2 are examples of the present invention, and even after moisture curing, the transparency was maintained while foaming was suppressed, and the adhesion to the PET substrate was also good.

[0078] Comparative Example 1 is an example in which the content of long-chain aliphatic polyester polyol was low, and foaming during moisture curing was not sufficiently suppressed.

[0079] Comparative Example 2 is an example in which the content of liquid polyester polyol was low, and the adhesion to the PET substrate was insufficient.

[0080] Comparative Example 3 is an example in which the content of alicyclic polyester polyol was low, and the transparency was insufficient. [Industrial Applicability]

[0081] The moisture-curable polyurethane hot-melt resin composition of the present invention maintains transparency even after moisture curing, suppresses foaming, and exhibits adhesion to PET substrates. Therefore, the moisture-curable polyurethane hot-melt resin composition of the present invention can be suitably used for building panels, decorative panels, automotive interior materials, etc.

Claims

1. A moisture-curable polyurethane hot-melt resin composition containing a polyurethane resin having an isocyanate group, the polyurethane resin is a reaction product of a polyol (A) and a polyisocyanate (B), the polyol (A) comprises an alicyclic polyester polyol (a1), a long-chain aliphatic polyester polyol (a2), and a liquid polyester polyol (a3); the content of the alicyclic polyester polyol (a1) in the polyol (A) is 20 mass% or more, the content of the long-chain aliphatic polyester polyol (a2) in the polyol (A) is 15 mass% or more, the content of the liquid polyester polyol (a3) ​​in the polyol (A) is 15 mass% or more, A moisture-curable polyurethane hot-melt resin composition, wherein the liquid polyester polyol (a3) ​​is a reaction product of a polybasic acid including adipic acid and an aliphatic compound having two or more hydroxyl groups.

2. 2. The moisture-curable polyurethane hot-melt resin composition according to claim 1, wherein the haze value measured by the following method is less than 20. [Method for measuring haze value] The moisture-curable polyurethane hot-melt resin composition is melted at 120°C for 1 hour and applied to the release layer to a thickness of 0.1 mm. The resulting coating is maintained at 23°C and 50% humidity for 96 hours to obtain a cured product. The haze value of the cured product is measured in accordance with JIS K 7136.

3. A cured product of the moisture-curable polyurethane hot-melt resin composition according to claim 1 or 2.

4. A laminate comprising the cured product according to claim 3.

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