JP7473092B2 - Moisture-curable polyurethane hot melt resin composition, adhesive, and laminate - Google Patents

Description

The present invention relates to a moisture-curable polyurethane hot melt resin composition, an adhesive, and a laminate.

Moisture-curable polyurethane hot melt resin compositions are used as adhesives for various building material applications. The moisture-curable polyurethane hot melt resin compositions often contain polyester as part of their composition in order to achieve ideal adhesive performance. In particular, for relatively smooth aluminum and polyvinyl chloride substrates, it is effective to include an amorphous linear aliphatic polyester polyol with a relatively low glass transition temperature in order to achieve adhesion (see, for example, Patent Document 1). However, when the proportion of polyol used is high as described above, there is a problem in that the cohesive force at the initial stage of adhesion is not expressed.

JP 2018-16703 A

The problem that the present invention aims to solve is to provide a moisture-curable polyurethane resin composition that has excellent initial adhesion and adhesion to substrates (particularly aluminum substrates and/or polyvinyl chloride substrates).

The present invention provides a moisture-curable polyurethane hot-melt resin composition that contains a urethane prepolymer (i) having an isocyanate group, which is a reaction product of a polyol (A) and a polyisocyanate (B), wherein the polyol (A) contains a long-chain crystalline polyester polyol (a1), an aliphatic polyester polyol (a2) other than the long-chain crystalline polyester polyol (a1) that is made from a glycol having a 2,2-dimethyl-1,3-propylene group, and an aromatic polyester polyol (a3), and the aliphatic polyester polyol (a2) is a combination of an aliphatic polyester polyol (a2-1) having a number average molecular weight of 1,000 to 3,000 and an aliphatic polyester polyol (a2-2) having a number average molecular weight of 5,000 to 9,000, and the mass ratio [(a2-1)/(a2-2)] between the two is 1 to 3.

The present invention also provides an adhesive comprising the moisture-curable polyurethane hot melt resin composition. The present invention also provides a laminate comprising a substrate and a coating of the adhesive.

The moisture-curable polyurethane hot melt resin composition of the present invention has excellent initial adhesion and adhesion to substrates (especially aluminum substrates and/or polyvinyl chloride substrates (hereinafter abbreviated as "PVC substrates")).

The moisture-curable polyurethane hot melt resin composition used in the present invention contains a urethane prepolymer (i) having an isocyanate group, which is a reaction product of a specific polyol (A) and a polyisocyanate (B).

The polyol (A) contains a long-chain crystalline polyester polyol (a1), an aliphatic polyester polyol (a2) other than the long-chain crystalline polyester polyol (a1) that is made from a glycol having a 2,2-dimethyl-1,3-propylene group, and an aromatic polyester polyol (a3).

The long-chain crystalline polyester polyol (a1) is an essential component for obtaining excellent adhesion due to its cohesive force, and may be, for example, a reaction product of a compound having a hydroxyl group and a polybasic acid. In the present invention, "crystalline" refers to a material in which a peak of heat of crystallization or heat of fusion can be confirmed in a DSC (differential scanning calorimeter) measurement in accordance with JIS K7121:2012, and "amorphous" refers to a material in which the peak cannot be confirmed.

Examples of the compound having a hydroxyl group include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, trimethylolpropane, trimethylolethane, and glycerin. These compounds may be used alone or in combination of two or more. Among these, it is preferable to use one or more compounds selected from the group consisting of butanediol, hexanediol, octanediol, and decanediol, in order to increase crystallinity and obtain even better adhesion.

Examples of the polybasic acid that can be used include oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, and dodecanedioic acid. These compounds may be used alone or in combination of two or more. Among these, it is preferable to use one or more selected from the group consisting of adipic acid, sebacic acid, and dodecanedioic acid, since this provides even better adhesion.

The number average molecular weight of the long-chain crystalline polyester polyol (a1) is preferably 500 to 10,000, and more preferably 1,000 to 7,000, in order to obtain even better adhesion. The number average molecular weight of the crystalline polyester polyol (a1) is a value measured by gel permeation chromatography (GPC).

The amount of the long-chain crystalline polyester polyol (a1) used is preferably 32 to 40% by mass, and more preferably 33 to 37% by mass, based on the total amount of the polyol (A) and the polyisocyanate (B), in order to obtain even better adhesion properties.

The aliphatic polyester polyol (a2) is other than the long-chain crystalline polyester polyol (a1) and is made from a glycol having a 2,2-dimethyl-1,3-propylene group.

In addition, in order to achieve both excellent initial adhesion and adhesion to substrates (particularly aluminum substrates or polyvinyl chloride substrates), it is essential that the aliphatic polyester polyol (a2) is a combination of an aliphatic polyester polyol (a2-1) having a number average molecular weight of 1,000 to 3,000 and an aliphatic polyester polyol (a2-2) having a number average molecular weight of 5,000 to 9,000, and that the mass ratio thereof [(a2-1)/(a2-2)] is 1 to 3.

The aliphatic polyester polyol (a2) is made from a glycol having a branched structure and a 2,2-dimethyl-1,3-propylene group, and is therefore an amorphous polyester polyol. However, the molecular chain has high mobility, and it follows and interacts with even the slightest irregularities in the aluminum substrate or PVC substrate, resulting in excellent adhesion. However, if the aliphatic polyester polyol (a2) is used without any ingenuity, the glass transition temperature is generally low, resulting in poor initial adhesion. In the present invention, the above-mentioned configuration increases the glass transition temperature and viscosity of the aliphatic polyester polyol as a whole, making it possible to achieve both excellent adhesion and initial adhesion.

The aliphatic polyester polyol (a2-1) and the aliphatic polyester polyol (a2-2) can both be a reaction product of a compound having a hydroxyl group, which contains as an essential component a glycol having a 2,2-dimethyl-1,3-propylene group, and a polybasic acid.

Examples of glycols having a 2,2-dimethyl-1,3-propylene group include neopentyl glycol, its dimer, and its trimer. These compounds may be used alone or in combination of two or more. Among these, neopentyl glycol is preferred because it provides even better initial adhesion.

The amount of the glycol having a 2,2-dimethyl-1,3-propylene group used is preferably 10% by mass or more, and more preferably 10 to 20% by mass, of the total amount of the compound having a hydroxyl group.

Examples of compounds having a hydroxyl group that can be used other than the glycol having a 2,2-dimethyl-1,3-propylene group include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, cyclohexanedimethanol, bisphenol A, bisphenol F, alkylene oxide adducts thereof, triethylene glycol, trimethylolpropane, trimethylolethane, glycerin, etc.

Examples of the polybasic acid that can be used include oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, and dodecanedioic acid. These compounds may be used alone or in combination of two or more.

The number average molecular weight of the aliphatic polyester polyol (a2-1) is preferably 1,500 to 2,500, since even better initial adhesion and adhesion can be obtained, and the number average molecular weight of the aliphatic polyester polyol (a2-2) is preferably 6,000 to 8,000. The number average molecular weights of the aliphatic polyester polyol (a2-1) and the aliphatic polyester polyol (a2-2) are values measured by gel permeation chromatography (GPC).

In addition, the mass ratio of the aliphatic polyester polyol (a2-1) to the aliphatic polyester polyol (a2-2) [(a2-1)/(a2-2)] is more preferably 1 to 2.5, since even better initial adhesion and adhesion can be obtained.

The total amount of the aliphatic polyester polyol (a2) used is preferably 15 to 38% by mass, and more preferably 20 to 37% by mass, based on the total amount of the polyol (A) and the polyisocyanate (B), in order to obtain even better initial adhesion and adhesion.

The aromatic polyester polyol (a3) is an essential component for obtaining excellent adhesion due to its cohesive force, and examples of the aromatic polyester polyol that can be used include a reaction product between a compound having a hydroxyl group and a polybasic acid, including an aromatic polybasic acid; a reaction product between an aromatic compound having two or more hydroxyl groups and a polybasic acid; a reaction product between an aromatic compound having two or more hydroxyl groups and a polybasic acid, including an aromatic polybasic acid; and the like.

Examples of the compounds having a hydroxyl group 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, triethylene glycol, tetraethylene glycol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, Examples of the compounds that can be used include aliphatic compounds such as 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, and pentaerythritol; and alicyclic compounds such as cyclopentanediol, cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, and alkylene oxide adducts thereof. These compounds may be used alone or in combination of two or more.

Examples of aromatic compounds having two or more hydroxyl groups include bisphenol A, bisphenol F, and their alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adducts. These compounds may be used alone or in combination of two or more.

Examples of the aromatic polybasic acid that can be used include phthalic acid, isophthalic acid, terephthalic acid, and phthalic anhydride. Examples of other polybasic acids that can be used include oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, and 1,12-dodecanedicarboxylic acid. These polybasic acids may be used alone or in combination of two or more. The aromatic polybasic acid is preferably selected from the group consisting of phthalic acid, terephthalic acid, phthalic anhydride ...

Other polybasic acids that can be used include, for example, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedioic acid, dodecanedioic acid, eicosapentaenoic acid, citraconic acid, itaconic acid, citraconic anhydride, and itaconic anhydride.

As the aromatic polyester polyol (a3), one made from one or more phthalic acid compounds selected from the group consisting of phthalic acid, isophthalic acid, terephthalic acid, and phthalic anhydride is preferred, since this provides even better adhesion.

The number average molecular weight of the aromatic polyester polyol (a3) is preferably 500 to 10,000, and more preferably 1,000 to 5,000, in order to obtain even better adhesion. The number average molecular weight of the aromatic polyester polyol (a3) is a value measured by gel permeation chromatography (GPC).

The amount of the aromatic polyester polyol (a3) used is preferably 15 to 35% by mass, and more preferably 18 to 32% by mass, based on the total amount of the polyol (A) and the polyisocyanate (B), in order to obtain even better adhesion properties.

The polyol (A) contains the components (a1) to (a3) as essential polyol components, but may contain other polyols as necessary.

As the other polyol, for example, polyester polyols other than the components (a1) to (a3), polycarbonate polyols, polyacrylic polyols, polyether polyols, etc. can be used. These polyols may be used alone or in combination of two or more.

As the polyisocyanate (B), for example, aromatic polyisocyanates such as polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, xylylene diisocyanate, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate; aliphatic or alicyclic polyisocyanates such as hexamethylene diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and tetramethylxylylene diisocyanate can be used. These polyisocyanates may be used alone or in combination of two or more. Among these, aromatic polyisocyanates are preferred, and diphenylmethane diisocyanate is more preferred, in that they provide even better adhesion.

The urethane prepolymer (i) is obtained by reacting the polyol (A) with the polyisocyanate (B), and has isocyanate groups that can react with moisture present in the air or in the substrate to which the moisture-curable polyurethane hot melt resin composition is applied to form a crosslinked structure.

The urethane prepolymer (i) can be produced, for example, by adding the polyisocyanate (B) to a reaction vessel containing the polyol (A) and reacting them under conditions in which the isocyanate groups of the polyisocyanate (B) are in excess of the hydroxyl groups of the polyol (A).

When producing the urethane prepolymer (i), the equivalent ratio [NCO/OH] of the isocyanate groups in the polyisocyanate (B) to the hydroxyl groups in the polyol (A) is preferably 1.5 to 4, and more preferably 1.8 to 3.0, in order to obtain even better initial adhesion and adhesion.

The isocyanate group content (hereinafter abbreviated as "NCO%) of the urethane prepolymer (i) obtained by the above method is preferably 1 to 6 mass%, more preferably 2 to 4 mass%, in order to obtain even better initial adhesion and adhesion. The NCO% of the hot-melt urethane prepolymer (i) is a value measured by potentiometric titration in accordance with JIS K1603-1:2007.

The moisture-curable polyurethane hot melt resin composition used in the present invention contains the above-mentioned urethane prepolymer (i) as an essential component, but other additives may be used as necessary.

Examples of the other additives that can be used include light resistance stabilizers, curing catalysts, plasticizers, stabilizers, fillers, dyes, pigments, carbon black, vehicles, fluorescent brighteners, silane coupling agents, waxes, thermoplastic resins, etc. These additives may be used alone or in combination of two or more.

As described above, the moisture-curable polyurethane hot-melt resin composition of the present invention has excellent initial adhesion and adhesion to substrates (especially aluminum substrates and/or PVC substrates). Therefore, the moisture-curable polyurethane hot-melt resin composition of the present invention can be suitably used as an adhesive for aluminum substrates and PVC substrates.

Next, we will explain the laminate of the present invention.

The laminate has at least a substrate and a coating of an adhesive containing the moisture-curable polyurethane hot melt resin composition.

The substrate may be, for example, a glass plate, a metal plate such as stainless steel (SUS), magnesium, or aluminum, a cycloolefin resin such as norbornene, an acrylic resin, a urethane resin, a silicon resin, an epoxy resin, a fluororesin, a polystyrene resin, a polyester resin, a polysulfone resin, a polyarylate resin, a polyvinyl chloride resin, a polyvinylidene chloride, a polyolefin resin, a polyimide resin, an alicyclic polyimide resin, a polyamide resin, a cellulose resin, a polycarbonate (PC), a polybutylene terephthalate (PBT), a polyphenylene ether (modified PPE), a polyethylene naphthalate (PEN), a polyethylene terephthalate (PET), a lactic acid polymer, an acrylonitrile-butadiene-styrene copolymer (ABS), an acrylonitrile-styrene copolymer (AS), or aluminum. The substrate may be subjected to corona treatment, plasma treatment, primer treatment, or the like, as necessary. The aluminum refers to aluminum or an aluminum alloy.

A method for applying the adhesive to the substrate can be, for example, a method in which the adhesive is heated and melted at 50 to 130°C and then applied to the substrate. A roll coater, spray coater, T-tie coater, knife coater, comma coater, etc. can be used as the application method.

After the application, a substrate can be placed on the adhesive surface and bonded together. The thickness of the adhesive layer can be set according to the intended use, but is preferably set within the range of 30 μm to 5 mm, for example.

The maturation conditions after lamination can be appropriately determined, for example, between a temperature of 20 to 80°C, a relative humidity of 50 to 90% RH, and a period of 0.5 to 5 days.

The present invention will now be described in more detail using examples.

[Example 1]
Into a four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser, 34 parts by mass of a long-chain crystalline polyester polyol (a reaction product of 1,6-hexanediol and dodecanedioic acid, number average molecular weight: 3,500, hereinafter abbreviated as "crystalline PEs (1)"), 10 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, the amount of neopentyl glycol used based on the total amount of all glycols: 14 mass%, hereinafter abbreviated as "aliphatic PEs (1)"), Aliphatic polyester polyol (diethylene glycol, neopentyl glycol, and 1,6-hexanediol, and adipic acid reaction product; number average molecular weight; 7,000, the amount of neopentyl glycol used in the total amount of all glycols; 14% by mass, hereinafter abbreviated as "aliphatic PEs (2).") 10 parts by mass, aromatic polyester polyol (neopentyl glycol and orthophthalic acid reaction product; number average molecular weight; 2,000, hereinafter abbreviated as "aromatic PEs (1)"). 30 parts by mass were charged, and the flask was heated at 100 ° C. under reduced pressure to dehydrate until the water content in the flask was 0.05% by mass. After cooling the flask to 90 ° C., 16 parts by mass of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as "MDI") melted at 70 ° C. was added, and the mixture was reacted at 110 ° C. for about 2 hours under a nitrogen atmosphere until the NCO% became constant, to obtain a moisture-curable polyurethane hot melt resin composition containing urethane prepolymer (i-1).

[Example 2]
A four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux condenser was charged with 34 parts by mass of crystalline PEs (1), 20 parts by mass of aliphatic PEs (1), 10 parts by mass of aliphatic PEs (2), and 20 parts by mass of aromatic PEs (1), and heated at 100 ° C. under reduced pressure to dehydrate until the water content in the flask was 0.05% by mass. After cooling the flask to 90 ° C., 16 parts by mass of MDI melted at 70 ° C. was added, and the mixture was reacted at 110 ° C. for about 2 hours under a nitrogen atmosphere until the NCO% became constant, to obtain a moisture-curable polyurethane hot melt resin composition containing urethane prepolymer (i-2).

[Example 3]
A four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux condenser was charged with 34 parts by mass of crystalline PEs (1), 20 parts by mass of aliphatic PEs (1), 15 parts by mass of aliphatic PEs (2), and 20 parts by mass of aromatic PEs (1), and heated at 100 ° C. under reduced pressure to dehydrate until the water content in the flask was 0.05% by mass. After cooling the flask to 90 ° C., 16 parts by mass of MDI melted at 70 ° C. was added, and the mixture was reacted at 110 ° C. for about 2 hours under a nitrogen atmosphere until the NCO% became constant, to obtain a moisture-curable polyurethane hot melt resin composition containing urethane prepolymer (i-3).

[Comparative Example 1]
A four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux condenser was charged with 35 parts by mass of crystalline PEs (1), 30 parts by mass of aliphatic PEs (2), and 20 parts by mass of aromatic PEs (1), and heated at 100 ° C. under reduced pressure to dehydrate until the moisture in the flask was 0.05% by mass. After cooling the flask to 90 ° C., 15 parts by mass of MDI melted at 70 ° C. was added, and the mixture was reacted at 110 ° C. for about 2 hours under a nitrogen atmosphere until the NCO% became constant, to obtain a moisture-curable polyurethane hot melt resin composition containing urethane prepolymer (iR-1).

[Comparative Example 2]
A four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux condenser was charged with 38 parts by mass of crystalline PEs (1), 10 parts by mass of aliphatic PEs (1), and 35 parts by mass of aromatic PEs (1), and heated at 100 ° C. under reduced pressure to dehydrate until the water content in the flask was 0.05% by mass. After cooling the flask to 90 ° C., 17 parts by mass of MDI melted at 70 ° C. was added, and the mixture was reacted at 110 ° C. for about 2 hours under a nitrogen atmosphere until the NCO% became constant, to obtain a moisture-curable polyurethane hot melt resin composition containing urethane prepolymer (iR-2).

[Comparative Example 3]
A four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet and a reflux condenser was charged with 35 parts by mass of crystalline PEs (1), 5 parts by mass of aliphatic PEs (1), 15 parts by mass of aliphatic PEs (2), and 30 parts by mass of aromatic PEs (1), and heated at 100 ° C. under reduced pressure to dehydrate until the water content in the flask was 0.05% by mass. After cooling the flask to 90 ° C., 15 parts by mass of MDI melted at 70 ° C. was added, and the mixture was reacted at 110 ° C. for about 2 hours under a nitrogen atmosphere until the NCO% became constant, to obtain a moisture-curable polyurethane hot melt resin composition containing urethane prepolymer (iR-3).

[Method for measuring number average molecular weight]
The number average molecular weights of the polyols used in the examples and comparative examples are values measured by gel permeation chromatography (GPC) under the following conditions.

Measurement device: High-speed GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)
Column: The following columns manufactured by Tosoh Corporation were used, connected in series.
"TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000" (7.8mm I.D. x 30cm) x 1 "TSKgel G2000" (7.8mm I.D. x 30cm) x 1 Detector: RI (differential refractometer)
Column temperature: 40°C
Eluent: tetrahydrofuran (THF)
Flow rate: 1.0 mL/min Injection volume: 100 μL (sample concentration 0.4% by mass in tetrahydrofuran solution)
Standard sample: A calibration curve was prepared using the following standard polystyrene.

(Standard polystyrene)
"TSKgel Standard Polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-550" manufactured by Tosoh Corporation

[Method for evaluating initial adhesion]
The moisture-curable polyurethane hot melt resin compositions obtained in the examples and comparative examples were each melted at 120°C for 1 hour, and then coated on a polyethylene terephthalate sheet with an applicator to a thickness of 0.1 mm. An aluminum substrate, a PVC substrate, or a medium density fiberboard was placed on the coated surface, and laminated using a press roll. A 25 mm wide cut was made, and a creep test was carried out at a temperature of 35°C and a load of 150 g 3 minutes after lamination. The peel distance was measured 15 minutes after the load was applied, and evaluated as follows.
"Good": The peel distance was 5 mm or less for each substrate.
"X": Other than the above.

[Method for evaluating adhesion]
The moisture-curable polyurethane hot melt resin compositions obtained in the examples and comparative examples were each melted at 120°C for 1 hour, and then coated on a polyethylene terephthalate sheet with an applicator to a thickness of 0.1 mm. An aluminum substrate, a PVC substrate, or a medium density fiberboard was placed on the coated surface, and laminated using a press roll. A 25 mm wide cut was made, and the sheet was left for 48 hours in an environment of 23°C and 50% humidity. A creep test was then carried out at a temperature of 60°C and a load of 500 g. The peel distance was measured 60 minutes after the load was applied, and the evaluation was as follows:
"Good": The peel distance was 5 mm or less for each substrate.
"X": Other than the above.

The numbers in Tables 1 and 2 indicate parts by mass.

It has been found that the moisture-curable polyurethane hot melt resin composition of the present invention has excellent initial adhesion and adhesion.

On the other hand, Comparative Example 1 is an embodiment in which aliphatic polyester polyol (a2-1) is not used, and the initial adhesion was poor.

Comparative example 2 is an embodiment in which aliphatic polyester polyol (a2-2) is not used, but the adhesion was poor.

Comparative example 3 is an embodiment in which the mass ratio of aliphatic polyester polyols (a2-1) and (a2-2) is less than 1, but the adhesion was poor.

Claims (6)

A moisture-curable polyurethane hot-melt resin composition comprising a urethane prepolymer (i) having an isocyanate group, the urethane prepolymer (i) being a reaction product of a polyol (A) and a polyisocyanate (B),
The polyol (A) is
Long-chain crystalline polyester polyol (a1),
an aliphatic polyester polyol (a2) other than the long-chain crystalline polyester polyol (a1) that is produced from a glycol having a 2,2-dimethyl-1,3-propylene group;
and an aromatic polyester polyol (a3),
the aliphatic polyester polyol (a2) is a combination of an aliphatic polyester polyol (a2-1) having a number average molecular weight of 1,000 to 3,000 and an aliphatic polyester polyol (a2-2) having a number average molecular weight of 5,000 to 9,000;
The moisture-curable polyurethane hot melt resin composition is characterized in that the mass ratio [(a2-1)/(a2-2)] is 1 to 3. The moisture-curable polyurethane hot melt resin composition according to claim 1, wherein the glycol having a 2,2-dimethyl-1,3-propylene group is neopentyl glycol. Relative to the total amount of the polyol (A) and the polyisocyanate (B),
the amount of the long-chain crystalline polyester polyol (a1) used is 32 to 40 % by mass,
the total amount of the aliphatic polyester polyol (a2) used is 15 to 38 % by mass,
The moisture-curable polyurethane hot melt resin composition according to claim 1, wherein the amount of the aromatic polyester polyol (a3) used is 15 to 35 mass % . An adhesive comprising the moisture-curable polyurethane hot melt resin composition according to claim 1. A laminate comprising a substrate and a coating of the adhesive described in claim 4. The laminate according to claim 5, wherein the substrate is an aluminum substrate or a polyvinyl chloride substrate.