CN111741992B - Moisture-curable polyurethane hot-melt resin composition - Google Patents

Abstract

The problem to be solved by the present invention is to provide a moisture-curable polyurethane hot-melt resin composition that is excellent in initial adhesive strength and can form a cured film having excellent flexibility. The present invention provides a moisture-curable polyurethane hot-melt resin composition, characterized in that the storage elastic modulus (G') of melt viscoelasticity at 20° C. before curing is 0.1 MPa or more, and the Young's modulus of the cured film is 0.1 MPa or more. The modulus is 20 MPa or less. The above-mentioned moisture-curable polyurethane hot-melt resin composition preferably contains a urethane prepolymer (i) having an isocyanate group using a polyol (A) and a polyisocyanate (B) as raw materials, and the above-mentioned polyol (A) ) and the total mass of the above-mentioned polyisocyanate (B), the crystalline polyester polyol is used in a ratio of less than 10% by mass.

Description

Moisture curable polyurethane hot melt resin composition

technical field

The present invention relates to a moisture-curable polyurethane hot-melt resin composition.

Background technique

Moisture-curing polyurethane hot-melt adhesives are solvent-free, so they have been widely used in the industry as environment-friendly adhesives. Various researches have been carried out centering on fiber bonding and building material lamination. middle.

The above-mentioned moisture-curable polyurethane adhesive exhibits final adhesive strength by moisture-curing the isocyanate group contained in the urethane prepolymer as its main ingredient, In lamination, high initial adhesive strength is required even immediately after the adhesive is applied.

In order to obtain high initial adhesive strength, it is common to use a large amount of crystalline polyester polyol (for example, refer to patent document 1). However, in such a method, the cured film becomes hard, and therefore, in fields requiring flexibility such as fiber applications, it is currently not being used due to poor texture.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2011-190309

SUMMARY OF THE INVENTION

The problem to be solved by the invention

The problem to be solved by the present invention is to provide a moisture-curable polyurethane hot-melt resin composition which is excellent in initial adhesive strength and capable of forming a cured film excellent in flexibility.

means to solve the problem

The present invention provides a moisture-curable polyurethane hot-melt resin composition, which is characterized in that the storage elastic modulus (G') of melt viscoelasticity at 20°C before curing is 0.1 MPa or more, and the Young's modulus of the cured film is The modulus is 20 MPa or less.

Invention effect

The moisture-curable polyurethane hot-melt resin composition of the present invention is excellent in initial adhesive strength and final adhesive strength, and can obtain a cured film excellent in flexibility. Therefore, the moisture-curable polyurethane hot-melt resin composition of the present invention can be used particularly suitably for fiber applications.

Detailed ways

The storage elastic modulus (G') of the melt viscoelasticity at 20°C before curing of the moisture-curable polyurethane hot-melt resin composition of the present invention is 0.1 MPa or more, and the Young's modulus of the cured film is 20 MPa or less .

In the moisture-curable polyurethane hot-melt resin composition of the present invention, in order to obtain excellent initial adhesive strength, the above-mentioned storage elastic modulus (G') of melt viscoelasticity at 20°C before curing must be 0.1 MPa or more is presumed to be in this range because the moisture-curable urethane resin composition before hardening will have a hard structure, and therefore excellent initial stage adhesive strength can be obtained. As said storage elastic modulus (G'), it is preferable that it is the range of 0.2-1,000 MPa, and it is more preferable that it is the range of 0.3-500 MPa from a viewpoint of obtaining the still more excellent initial stage adhesive strength. In addition, the measurement method of the storage elastic modulus (G') of the melt viscoelasticity at 20 degreeC before hardening the said moisture hardening type polyurethane hot-melt resin composition is described in an Example.

In addition, for the moisture-curable polyurethane hot-melt resin composition of the present invention, in order to obtain excellent flexibility, the Young's modulus of the cured film must be 20 MPa or less, preferably in the range of 0.5 to 15 MPa, more preferably 1 ~10MPa range. In addition, the measuring method of the Young's modulus of the cured coating film of the said moisture-curable polyurethane hot-melt resin composition is described in an Example.

As the above-mentioned moisture-curable polyurethane hot-melt resin composition, specifically, for example, a urethane prepolymer containing an isocyanate group obtained by reacting a polyol (A) with a polyisocyanate (B) can be used. Moisture curable polyurethane hot melt resin composition.

In addition, as a technical idea of setting the said storage elastic modulus and the said Young's modulus of the said moisture-curable polyurethane hot-melt resin composition in the said range, for example, the reduction of a crystallinity polymer is mentioned. The amount of ester polyols; use liquid polyols and other polyols; use polyols with a small number average molecular weight; adjust the reaction ratio of polyols and polyisocyanates to increase the amount of urethane bonds; reduce molecular ends, etc. Isocyanate groups, reduction of urea concentration by moisture curing, etc.

As the polyol (A), for example, crystalline polyester polyol, amorphous polyester polyol, polyether polyol, polycarbonate polyol, polyacrylic polyol, dimer alcohol (Japanese: ダイマー) can be used. Diol), polybutadiene polyol, etc. These polyols may be used alone or in combination of two or more. As the above-mentioned polyol (A), it is easy to set the Young's modulus of the above-mentioned cured film within the range specified in the present invention, and further excellent flexibility can be obtained. The crystalline polyester polyol is used in a ratio of preferably less than 10% by mass, more preferably less than 5% by mass in the total mass of the polyisocyanate (B).

In addition, as the above-mentioned polyol (A), it is preferable to contain liquid polyol (A) from the viewpoint that it is easy to set the above-mentioned storage elastic modulus and Young's modulus in the above-mentioned range, and can obtain further excellent initial adhesive strength and flexibility. The polyol (a1) and other polyols (a2). In addition, in this invention, a liquid polyol (a1) means the polyol whose viscosity at 25 degreeC is 100,000 mPa*s or less.

As the liquid polyol (a1), polyether polyol is preferably used. As said polyether polyol, the polymer of a polyol and an alkylene oxide can be used, for example.

As the above-mentioned polyhydric alcohol, for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2 ,2-Dimethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, diethylene glycol, triethylene glycol Alcohol, dipropylene glycol, tripropylene glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol and other diols; polyester polyols, etc. These compounds may be used alone or in combination of two or more.

As said alkylene oxide, ethylene oxide, propylene oxide, butylene oxide, styrene oxide, etc. can be used, for example. These compounds may be used alone or in combination of two or more.

As the polyether polyol, polypropylene glycol is preferably used because it is easy to set the storage elastic modulus and Young's modulus in the above-mentioned ranges, and further excellent initial adhesive strength and flexibility can be obtained.

As the polyol (a2) other than the above, an aromatic polyester polyol is preferably used. As said aromatic polyester polyol, the reaction product of the compound which has a hydroxyl group and the polybasic acid containing an aromatic polybasic acid, the reaction product of the aromatic compound which has 2 or more hydroxyl groups, and a polybasic acid etc. can be used, for example.

As the above-mentioned compound having a hydroxyl group, for example, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, trimethylolpropane, Trimethylolethane, glycerin, neopentyl glycol, etc. These compounds may be used alone or in combination of two or more.

As the above-mentioned aromatic compound having two or more hydroxyl groups, bisphenol A, bisphenol F, and their alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adducts, etc. can be used, for example. These compounds may be used alone or in combination of two or more. Among them, it is preferable to use an alkylene oxide adduct of bisphenol A from the viewpoint that further excellent initial adhesive strength and flexibility can be obtained, and the addition mole number of the above-mentioned alkylene oxide is preferably 1 to 10. Moore range.

As said aromatic polybasic acid, phthalic acid, isophthalic acid, terephthalic acid, phthalic anhydride, etc. can be used, for example. As other polybasic acids, oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, 1,12-dodecanedicarboxylic acid, etc. can be used, for example. These polybasic acids may be used alone or in combination of two or more. As the above-mentioned aromatic polybasic acid, it is preferable to use a compound selected from phthalic acid, isophthalic acid, terephthalic acid, and phthalic anhydride in terms of obtaining further excellent initial adhesive strength and flexibility. more than one compound.

As the number-average molecular weight of the polyol (a1) and the polyol (a2), since it is easy to set the above-mentioned storage elastic modulus and Young's modulus in the above-mentioned ranges, further excellent initial adhesive strength and flexibility can be obtained. From the viewpoint of stability, it is preferably less than 2,800, more preferably in the range of 300 to 2,500, and still more preferably in the range of 600 to 2,200. In addition, the number average molecular weight of the said polyol (a1) and polyol (a2) shows the value measured by the gel permeation chromatography (GPC) method.

As the mass ratio [(a1)/(a2)] of the above-mentioned polyol (a1) to the above-mentioned polyol (a2), since it is easy to set the above-mentioned storage elastic modulus and Young's modulus in the above-mentioned ranges, more In terms of further excellent low viscosity, initial adhesive strength and flexibility, it is preferably in the range of 20/80 to 90/10, more preferably in the range of 30/70 to 85/15, still more preferably in the range of 40/60 to 80/20 range.

As the polyisocyanate (B), for example, polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate isocyanate, phenylene diisocyanate, toluene diisocyanate can be used, for example. , naphthalene diisocyanate and other aromatic polyisocyanates; hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate , tetramethylxylylene diisocyanate and other aliphatic or alicyclic polyisocyanates, etc. Among them, aromatic polyisocyanate is preferably used, and diphenylmethane diisocyanate is more preferably used since further excellent reactivity and final adhesive strength can be obtained.

In addition, as the usage-amount of the said polyisocyanate (B), it is preferable that it is the range of 5-60 mass % in the raw material of a urethane prepolymer (i) from the point which can obtain a still more excellent adhesive strength, More preferably, it is the range of 15-50 mass %.

The above-mentioned urethane prepolymer (i) is obtained by reacting the above-mentioned polyol (A) with the above-mentioned polyisocyanate (B), and has a polymer terminal and a molecule capable of interacting with air and coating with urethane. The frame of the prepolymer and the moisture present in the adherend react to form isocyanate groups of a crosslinked structure.

As a method for producing the above-mentioned urethane prepolymer (i), it can be produced, for example, by adding the above-mentioned polyol (A) dropwise into a reaction vessel containing the above-mentioned polyisocyanate (B) and then heating it, and then The isocyanate group which the said polyisocyanate (B) has is reacted under conditions which become excess with respect to the hydroxyl group which the said polyol (A) has.

As the urethane bond amount of the above-mentioned urethane prepolymer (i), it is easy to set the above-mentioned storage elastic modulus and Young's modulus in the above-mentioned ranges, and further excellent low viscosity can be obtained, From the viewpoint of initial adhesive strength and flexibility, it 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 still more preferably in the range of 1.1 to 2.4 mol/kg.

The aforementioned urethane prepolymer is produced from the viewpoint that it is easy to set the aforementioned storage elastic modulus and Young's modulus within the aforementioned range, and further excellent low viscosity, initial adhesive strength, and flexibility can be obtained. In the case of (i), the equivalent ratio ([isocyanate group/hydroxyl group]) of the isocyanate group of the polyisocyanate (B) to the hydroxyl group of the polyol (A) is preferably in the range of 1.1 to 1.5, more preferably 1.15 to 1.45 range.

As the isocyanate group content rate (hereinafter abbreviated as "NCO%") of the above-mentioned urethane prepolymer (i), it is easy to set the above-mentioned storage elastic modulus and Young's modulus in the above-mentioned ranges, and obtain From the viewpoint of further excellent low viscosity, initial adhesive strength, and flexibility, it is preferably in the range of 1 to 4% by mass, and more preferably in the range of 1.2 to 3.5% by mass. In addition, NCO% of the said urethane prepolymer (i) shows the value measured by the potentiometric titration method based on JISK1603-1:2007.

The moisture-curable polyurethane hot-melt resin composition of the present invention may contain other additives as necessary in addition to the above-mentioned urethane prepolymer (i).

As a method of obtaining the cured film of the above-mentioned moisture-curable polyurethane hot-melt resin composition, for example, melting the above-mentioned moisture-curable polyurethane hot-melt resin composition at 50 to 130° C., applying it to a substrate, and performing Method of moisture curing.

As the base material, for example, acrylic resins, urethane resins, silicone resins, epoxy resins, fluorine resins, polystyrene resins, polyester resins, polysulfone resins, polyester resins, Aryl ester resin, polyvinyl chloride resin, polyvinylidene chloride, cycloolefin resin, polyolefin resin, polyimide resin, alicyclic polyimide resin, cellulose resin, PC (poly Carbonate), PBT (polybutylene terephthalate), modified PPE (polyphenylene ether), PEN (polyethylene naphthalate), PET (polyethylene terephthalate ester), lactic acid polymer, ABS resin, AS resin, etc.; wood substrates such as MDF, plywood, and particle board; fiber substrates such as non-woven fabrics, woven fabrics, and braids, etc. The aforementioned substrate may be subjected to corona treatment, plasma treatment, primer treatment, or the like as necessary.

Examples of methods for applying the above moisture-curable polyurethane hot-melt resin composition include roll coaters, spray coaters, T-die coaters, knife coaters, and comma coaters. machine method.

After the above coating, for example, aging can be carried out at a temperature of 20-80° C. and a relative humidity of 50-90% RH for 0.5-3 days to obtain the final adhesive strength.

As described above, the moisture-curable polyurethane hot-melt resin composition of the present invention has excellent initial adhesive strength and final adhesive strength, and can obtain a cured film excellent in flexibility. Therefore, the moisture-curable polyurethane hot-melt resin composition of the present invention can be used particularly suitably for fiber applications.

Example

Hereinafter, the present invention will be described in more detail using examples.

[Example 1]

Add polypropylene glycol (number average molecular weight: 1000, hereinafter abbreviated as "PPG1000 ".) 51 parts by mass, aromatic polyester polyol ( A product obtained by reacting neopentyl glycol with phthalic anhydride, number average molecular weight: 1,000, hereinafter abbreviated as "NPG/oPA1000.") 24 parts by mass, heated at 90°C under reduced pressure, thereby dehydrating until the moisture content The ratio is 0.05% by mass or less.

Next, after cooling the temperature inside the container to 60°C, add 25 parts by mass of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as "MDI-1"), raise the temperature to 110°C, and react for about 3 hours until the isocyanate The group content rate becomes constant, the urethane prepolymer (i-1) which has an isocyanate group is obtained, and the moisture hardening type polyurethane hot-melt resin composition is obtained. The NCO% of the urethane prepolymer (i-1) was 1.8% by mass, the amount of urethane bonds was 1.50 mol/kg, and [NCO/OH] at the time of synthesis was 1.33.

[Measurement method of number average molecular weight]

In the above-mentioned examples, the number-average molecular weight of the polyhydric alcohol represents the value measured under the following conditions by the gel permeation chromatography (GPC) method.

Measuring device: high-efficiency GPC device ("HLC-8220GPC" manufactured by Tosoh Corporation)

Column: The following columns manufactured by Tosoh Corporation were connected in series and used.

"TSKgel G5000" (7.8mmI.D.×30cm)×1

"TSKgel G4000" (7.8mmI.D.×30cm)×1

"TSKgel G3000" (7.8mmI.D.×30cm)×1

"TSKgel G2000" (7.8mmI.D.×30cm)×1

Detector: RI (differential refractometer)

Column temperature: 40°C

Eluent: Tetrahydrofuran (THF)

Flow rate: 1.0mL/min

Injection volume: 100 μl (tetrahydrofuran solution with a sample concentration of 0.4% by mass)

Standard sample: A standard 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

[Example 2]

Put 43 parts by mass of PPG1000 and 32 parts by mass of NPG/oPA1000 into a four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser, and heat at 90°C under reduced pressure to dehydrate until the moisture content becomes 0.05. Mass% or less.

Next, after cooling the temperature in the container to 60°C, add 25 parts by mass of MDI-1, raise the temperature to 110°C, and react for about 3 hours until the isocyanate group content becomes constant to obtain a urethane prepolymer having an isocyanate group ( i-2) to obtain a moisture-curable polyurethane hot-melt resin composition. The NCO% of the said urethane prepolymer (i-2) was 1.8 mass %, the urethane bond amount was 1.50 mol/kg, and [NCO/OH] at the time of synthesis was 1.33.

[Example 3]

In a four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser, 50 parts by mass of polypropylene glycol (number average molecular weight: 700, hereinafter abbreviated as "PPG700"), 21 parts by mass of NPG/oPA1000, By heating under reduced pressure at 90° C., dehydration was carried out until the moisture content became 0.05% by mass or less.

Next, after cooling the temperature in the container to 60°C, add 29 parts by mass of MDI-1, raise the temperature to 110°C, and react for about 3 hours until the isocyanate group content becomes constant, thereby obtaining a urethane prepolymer having an isocyanate group ( i-3) to obtain a moisture-curable polyurethane hot-melt resin composition. The NCO% of the above-mentioned urethane prepolymer (i-3) was 1.7% by mass, the amount of urethane bonds was 1.85 mol/kg, and [NCO/OH] at the time of synthesis was 1.26.

[Example 4]

22 parts by mass of PPG1000, polypropylene glycol (number average molecular weight: 2,000, hereinafter abbreviated as "PPG2000") 22 parts by mass, NPG/ 33 parts by mass of oPA1000 was dehydrated by heating under reduced pressure at 90°C until the water content became 0.05% by mass or less.

Next, after the temperature in the container was cooled to 60°C, 23 parts by mass of MDI-1 was added, the temperature was raised to 110°C, and the reaction was carried out for about 3 hours until the isocyanate group content became constant to obtain a urethane prepolymer having an isocyanate group ( i-4) to obtain a moisture-curable polyurethane hot-melt resin composition. The NCO% of the said urethane prepolymer (i-4) was 1.9 mass %, the urethane bond amount was 1.32 mol/kg, and [NCO/OH] at the time of synthesis was 1.39.

[Example 5]

40 parts by mass of PPG1000, aromatic polyester polyol (6 moles of propylene oxide adduct of bisphenol A and sebacic acid The reaction product, number average molecular weight: 1,000, hereinafter abbreviated as "SEBA/BisA6PO".) 35 parts by mass, heated at 90°C under reduced pressure, thereby dehydrating until the moisture content becomes 0.05 mass% or less.

Next, after cooling the temperature in the container to 60° C., an equal mixture of 2,4′-diphenylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate (hereinafter abbreviated as “MDI-2”) was added. ) 25 parts by mass, heated up to 110°C, reacted for about 3 hours until the isocyanate group content became fixed, and obtained a urethane prepolymer (i-5) with isocyanate groups, and obtained a moisture-curable polyurethane hot-melt resin combination things. The NCO% of the above-mentioned urethane prepolymer (i-5) was 1.8% by mass, the amount of urethane bonds was 1.50 mol/kg, and [NCO/OH] at the time of synthesis was 1.33.

[Comparative example 1]

40 parts by mass of PPG1000, 20 parts by mass of NPG/oPA1000, crystalline polyester polyol (1,6-hexanediol and Adipic acid reaction product, number average molecular weight: 2,000, hereinafter abbreviated as "crystalline PEs") 18 parts by mass, heated at 90°C under reduced pressure, thereby dehydrating until the water content becomes 0.05 mass% or less.

Next, after cooling the temperature in the container to 60°C, add 25 parts by mass of MDI-1, raise the temperature to 110°C, and react for about 3 hours until the isocyanate group content becomes constant to obtain a urethane prepolymer having an isocyanate group ( i'-1) to obtain a moisture-curable polyurethane hot-melt resin composition. The NCO% of the above-mentioned urethane prepolymer (i'-1) was 1.7% by mass, the amount of urethane bonds was 1.37 mol/kg, and [NCO/OH] at the time of synthesis was 1.34.

[Comparative example 2]

Put 28 parts by mass of NPG/oPA1000, amorphous polyester polyol (ethylene glycol, 1,6-hexanediol, A substance obtained by reacting neopentyl glycol and adipic acid at a molar ratio of 25/18/8/49, number average molecular weight: 5,500, hereinafter abbreviated as "amorphous PEs".) 56 parts by mass, heated at 90°C under reduced pressure , thereby dehydrating until the moisture content becomes 0.05% by mass or less.

Next, after the temperature in the container was cooled to 60°C, 16 parts by mass of MDI-1 was added, the temperature was raised to 110°C, and the reaction was carried out for about 3 hours until the isocyanate group content became constant to obtain a urethane prepolymer having an isocyanate group ( i'-2) to obtain a moisture-curable polyurethane hot-melt resin composition. The above-mentioned urethane prepolymer (i'-2) was obtained to obtain a moisture-curable polyurethane hot-melt resin composition. The NCO% of the above-mentioned urethane prepolymer (i'-2) was 1.9% by mass, the amount of urethane bonds was 0.76 mol/kg, and [NCO/OH] at the time of synthesis was 1.68.

[Measuring method of storage elastic modulus]

After the moisture-curable polyurethane hot-melt resin compositions obtained in Examples and Comparative Examples were melted at 110° C. for 1 hour, 10 ml of a sample was taken and placed in parallel with a melt viscoelasticity measuring device (“MCR-302” manufactured by Anton Paar Co., Ltd.). Melt viscoelasticity was measured on the plate from 110°C to 10°C at a cooling rate of 1°C/min and a frequency of 1 Hz, and the storage elastic modulus (G') at 20°C was measured.

[Measurement method of Young's modulus]

The moisture-curable polyurethane hot-melt resin compositions obtained in Examples and Comparative Examples were melted at 110° C. for 1 hour, and then coated with a knife coater so that the film thickness after curing became 100 μm. The polyethylene terephthalate substrate was left for 3 days to obtain a cured film. The cured film was peeled off from the release PET, and the piece obtained by punching out with a No. 2 dumbbell was used as a test piece. The test piece was subjected to a tensile test using a TENSILON tensile tester ("RTM-100" manufactured by Orientec Co., Ltd.) at a crosshead speed of 200 mm/min in an atmosphere of 25° C., based on the origin of the graph when the tensile test was performed. Young's modulus was determined from the stress at 2.5% elongation.

[Measurement method of initial bond strength]

The moisture-curable polyurethane hot-melt compositions obtained in Examples and Comparative Examples were each melted at a temperature of 120° C. for 1 hour. This adhesive was applied on a polyethylene terephthalate sheet using an applicator so as to have a thickness of 100 μm. A polyethylene terephthalate sheet was bonded to the coating layer and pressure-bonded with a pressure-bonding roller. Five minutes after the crimping, the adhesive strength (N/25 mm) was measured using a precision universal testing machine "AG-10NX" manufactured by Shimadzu Corporation, and the initial strength was evaluated as follows.

"T": The adhesive strength is 15 (N/25mm) or more.

"F": The bonding strength is less than 15 (N/25mm).

[Evaluation method of softness]

The moisture-curable polyurethane hot-melt resin compositions obtained in Examples and Comparative Examples were melted at 110° C. for 1 hour, and then coated on a polyester nonwoven fabric using a knife coater so that the cured film thickness became 100 μm. and left for 3 days to obtain a cured film. From the feeling of touch thereof, softness was evaluated as follows.

"T": rich in flexibility.

"F": Get a hard impression.

[Evaluation of low viscosity]

After melting the moisture-curable polyurethane hot-melt resin compositions obtained in Examples and Comparative Examples at 120° C. for 1 hour, sample 1 ml, measure the melt viscosity with a cone-plate viscometer (40P cone, rotor speed: 50 rpm), and evaluate as follows Low viscosity.

"T": less than 30,000mPa·s

"F": 30,000mPa·s or more

[Table 1]

Examples 1 to 5, which are the moisture-curable polyurethane hot-melt resin compositions of the present invention, were excellent in initial adhesive strength and flexibility.

On the other hand, in Comparative Example 1, the Young's modulus of the cured film exceeded the range specified in the present invention, and the flexibility was poor.

In Comparative Example 2, the storage elastic modulus before curing was lower than the range specified in the present invention, and the initial bonding strength was poor.

Claims (6)

1. A moisture-curable polyurethane hot-melt resin composition characterized in that the storage elastic modulus G 'of the melt viscoelasticity at 20 ℃ before curing is 0.1MPa or more, the Young's modulus of the cured coating film is 0.5MPa or more and 20MPa or less,

the moisture-curable polyurethane hot-melt resin composition contains a urethane prepolymer i having an isocyanate group, which is prepared from a polyol A and a polyisocyanate B,

the urethane prepolymer i has a urethane bond amount in the range of 1.1 to 2.4mol/kg,

a crystalline polyester polyol is used in a proportion of less than 10% by mass of the total mass of the polyol A and the polyisocyanate B,

the polyol A contains only a liquid polyol a1 and the other polyols a2,

the polyol a1 is polyether polyol which is polypropylene glycol,

the polyol a2 is an aromatic polyester polyol which is at least one selected from the group consisting of a reaction product of a compound having a hydroxyl group and a polybasic acid comprising an aromatic polybasic acid, and a reaction product of an aromatic compound having 2 or more hydroxyl groups and a polybasic acid,

the compound having a hydroxyl group is at least one selected from the group consisting of ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, heptylene glycol, octylene glycol, nonylene glycol, decylene glycol, trimethylolpropane, trimethylolethane, and glycerin.

2. The moisture-curable polyurethane hot melt resin composition according to claim 1, wherein the pentanediol is neopentyl glycol.

3. The moisture-curable polyurethane hot-melt resin composition according to claim 1, wherein the number average molecular weight of the polyol a1 and the polyol a2 is less than 2,800.

4. The moisture-curable polyurethane hot-melt resin composition according to claim 1 or 3, wherein the molar ratio of the polyol A to the polyisocyanate B, i.e., NCO/OH, is in the range of 1.1 to 1.5.

5. The moisture-curable polyurethane hot-melt resin composition according to claim 1 or 3, wherein the urethane prepolymer i has an isocyanate group content in the range of 1% to 4%.

6. The moisture-curable polyurethane hot-melt resin composition according to claim 4, wherein the urethane prepolymer i has an isocyanate group content in the range of 1 to 4%.