Moisture-curing polyurethane hot-melt resin composition, adhesive, and synthetic leather

Abstract

To provide a moisture curable polyurethane hot melt resin composition which is excellent in adhesion to a thermoplastic resin layer, and low temperature flexibility.SOLUTION: A moisture curable polyurethane hot melt resin composition contains a hot melt urethane prepolymer (A) having an isocyanate group, and phosphate (B), wherein the hot melt prepolymer (A) uses polyol (a) containing 50 mass% or more of polyether polyol (a1) as a raw material, and a content of the phosphate (B) is more than 0.2 pts.mass with respect to 100 pts.mass of the hot melt urethane prepolymer (A).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a moisture-curable polyurethane hot-melt resin composition, an adhesive, and synthetic leather.

Background Art

[0002] For synthetic leather, polyurethane (PU), polyvinyl chloride (PVC), olefin-based thermoplastic elastomer (TPO), etc. are used as the surface material, and a material obtained by bonding these surface materials to a base fabric such as cloth or non-woven fabric with an adhesive is generally used (see, for example, Patent Document 1). Among them, solvent-based adhesives have been widely popular and generally used so far. However, as an environmental initiative, reduction of VOCs has been demanded from regions, countries, and companies, and replacement from solvent-based to water-based or solvent-free adhesives has become necessary.

[0003] As a solvent-free adhesive, much research has been conducted on moisture-curable polyurethane hot-melt adhesives (RHM). Conventional solvent-based and water-based adhesives were prepared by coating a low-viscosity formulation on the surface layer, drying to remove the solvent, and aging if necessary to obtain a strong film. Due to their low viscosity, they have good wettability to the surface material and are characterized by easy adhesion. On the other hand, RHM uses a material dissolved by heat, but its viscosity is higher than that of solvent-based and water-based adhesives, and it is difficult to obtain wettability to the surface layer. Especially for adherends such as PVC surface materials, the wettability with RHM is generally low, and it has been difficult to exhibit sufficient performance in terms of adhesion even when using conventional RHM.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The problem that this invention aims to solve is to provide a moisture-curing polyurethane hot-melt resin composition that exhibits excellent adhesion to thermoplastic resin layers and low-temperature flexibility. [Means for solving the problem]

[0006] The present invention provides a moisture-curing polyurethane hot-melt resin composition containing a hot-melt urethane prepolymer (A) having an isocyanate group and a phosphate ester (B), wherein the hot-melt prepolymer (A) is made from a polyol (a) containing 50% by mass or more of polyether polyol (a1), and the content of the phosphate ester (B) is more than 0.2 parts by mass per 100 parts by mass of the hot-melt urethane prepolymer (A).

[0007] Furthermore, the present invention provides an adhesive characterized by containing the moisture-curing polyurethane hot-melt resin composition. The present invention also provides synthetic leather characterized by having at least a thermoplastic resin layer and the adhesive layer. [Effects of the Invention]

[0008] The moisture-curing polyurethane hot-melt resin composition of the present invention exhibits excellent adhesion to thermoplastic resin layers and low-temperature flexibility. Therefore, the moisture-curing polyurethane hot-melt resin composition of the present invention is particularly suitable for use in the production of synthetic leather using thermoplastic resin as the surface material. [Modes for carrying out the invention]

[0009] The moisture-curing polyurethane hot-melt resin composition of the present invention contains a hot-melt urethane prepolymer (A) having an isocyanate group, derived from a specific polyol (a), and a specific amount of phosphate ester (B).

[0010] In order to obtain excellent low-temperature flexibility, the hot-melt urethane prepolymer (A) having isocyanate groups must be made from a polyol (a) containing 50% by mass or more of polyether polyol (a1). By designing it in this way, the glass transition temperature of the adhesive can be lowered, thereby obtaining excellent low-temperature flexibility. As for the amount of polyether polyol (a1) used, 50 to 90% by mass and more preferably 55 to 70% by mass of polyol (a) is preferred in order to obtain even better low-temperature flexibility.

[0011] As the polyether polyol (a1), for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene polyoxytetramethylene glycol, polyoxypropylene polyoxytetramethylene glycol, etc., can be used. These polyols may be used alone or in combination of two or more. Among these, polypropylene glycol and / or polytetramethylene glycol are preferred because they provide even better low-temperature flexibility, and polytetramethylene glycol is even more preferred because it provides even better heat and humidity resistance.

[0012] In addition to the polyether polyol (a), other polyols can be used as the polyol (a). Examples of these other polyols include commercially available polyols such as polyester polyol, polycarbonate polyol, polybutadiene polyol, silicone diol, and acrylic diol. These polyols may be used individually or in combination of two or more.

[0013] The number-average molecular weight of the polyol (a) is preferably 500 to 10,000, and more preferably 1,000 to 5,000, respectively, from the viewpoint of obtaining even better adhesion, low-temperature flexibility, and mechanical strength. The number-average molecular weight of the polyol (a) is the value measured by gel permeation chromatography (GPC).

[0014] The hot-melt urethane prepolymer (A) having the isocyanate group can be, for example, a reaction product of the polyol (a) and polyisocyanate (b).

[0015] As the polyisocyanate (b), for example, aromatic polyisocyanates such as polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate, carbodiimide-modified diphenylmethane diisocyanate isocyanate, phenylene diisocyanate, tolylene diisocyanate, and naphthalene diisocyanate can be used; and aliphatic or alicyclic polyisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate can be used. Among these, aromatic polyisocyanates are preferred, and diphenylmethane diisocyanate is more preferred, as they provide even better reactivity and adhesion.

[0016] The hot-melt urethane prepolymer (A) has isocyanate groups at its polymer ends or within its molecule that can react with moisture present in the air or in the substrate or adherend to which the urethane prepolymer is applied to form a crosslinked structure.

[0017] As a method for producing the hot-melt urethane prepolymer (A), for example, the polyol (a) is dropped into a reaction vessel containing the polyisocyanate (b) and then heated, and the reaction is carried out under conditions such that the isocyanate groups of the polyisocyanate (b) are in excess relative to the hydroxyl groups of the polyol (a), whereby it can be produced.

[0018] When reacting the polyol (a) and the polyisocyanate (b), the molar ratio [NCO / OH] of the hydroxyl groups of the polyol (a) to the isocyanate groups contained in the polyisocyanate (b) is preferably 1.3 to 2.5, more preferably 1.5 to 2.0, from the viewpoint of obtaining more excellent hot-melting property, adhesiveness, and low-temperature flexibility.

[0019] The isocyanate group content of the hot-melt urethane prepolymer (A) (hereinafter abbreviated as "NCO%") is preferably 2.0 to 5.0% by mass, more preferably 2.5 to 3.5% by mass, from the viewpoint of obtaining more excellent hot-melting property, adhesiveness, and low-temperature flexibility. The NCO% of the hot-melt urethane prepolymer (A) indicates a value measured by the potentiometric titration method in accordance with JIS K1603-1:2007.

[0020] The phosphate ester (B) is an essential component for obtaining excellent adhesiveness to the thermoplastic resin layer. By adding the phosphate ester (B), the compatibility at the interface between the thermoplastic resin and the RHM is improved, and excellent adhesiveness is obtained.

[0021] As the phosphate ester (B), for example, a compound represented by the following formula (1) can be used, and one kind or two or more kinds can be used in combination.

[0022] [Chemical formula] (In formula (1), n represents 1 or 2, and R represents an alkyl group.)

[0023] As the phosphate ester (B), among the compounds represented by the above formula (1), those in which R has 1 to 10 carbon atoms are preferable, and those in which R has 1 to 8 carbon atoms are more preferable, from the viewpoint of obtaining better adhesion to the thermoplastic resin layer.

[0024] Also, the content of the phosphate ester (B) must exceed 0.2 parts by mass with respect to 100 parts by mass of the hot-melt urethane prepolymer (A) from the viewpoint of obtaining the above effects. The content of the phosphate ester (B) is preferably 0.2 to 1.0 parts by mass, and more preferably 0.25 to 0.60 parts by mass, with respect to 100 parts by mass of the hot-melt urethane prepolymer (A), from the viewpoint of obtaining better adhesion to the thermoplastic resin layer.

[0025] The moisture-curable polyurethane hot-melt resin composition of the present invention contains the hot-melt urethane prepolymer (A) and the phosphate ester (B) as essential components, but may contain other additives as necessary.

[0026] Examples of the other additives include urethanization catalysts, neutralizing agents, crosslinking agents, silane coupling agents, thickeners, fillers, thixotropic agents, tackifiers, waxes, heat stabilizers, light stabilizers, fluorescent whitening agents, foaming agents, pigments, dyes, conductivity-imparting agents, antistatic agents, moisture permeability improvers, water repellents, oil repellents, hollow foams, flame retardants, water absorbents, moisture absorbents, deodorants, foam stabilizers, blocking preventives, hydrolysis preventives, etc. These additives may be used alone or in combination of two or more. In addition, the moisture-curable polyurethane hot-melt resin composition of the present invention has excellent adhesiveness and low-temperature flexibility even when a foaming agent is added to form a foam.

[0027] As described above, the moisture-curable polyurethane hot-melt resin composition of the present invention is excellent in adhesiveness to the thermoplastic resin layer and low-temperature flexibility. Therefore, the moisture-curable polyurethane hot-melt resin composition of the present invention can be particularly preferably used in the production of synthetic leather having a thermoplastic resin as a surface material.

[0028] Next, the synthetic leather of the present invention will be described.

[0029] The synthetic leather has at least a thermoplastic resin layer and an adhesive layer containing the moisture-curing polyurethane hot-melt resin composition, for example, a substrate, the adhesive layer, and the thermoplastic resin layer are sequentially laminated.

[0030] As the base material, for example, nonwoven fabrics, woven fabrics, knitted fabrics, etc., made from polyester fibers, polyethylene fibers, nylon fibers, acrylic fibers, polyurethane fibers, acetate fibers, rayon fibers, polylactic acid fibers, cotton, linen, silk, wool, glass fiber, carbon fiber, or blends thereof can be used.

[0031] As the thermoplastic resin layer, for example, one made from known polyvinyl chloride, polyvinyl acetate, polyvinylidene chloride, polystyrene, TPO (Thermoplastic Olefinic Elastomer), thermoplastic ester elastomer, thermoplastic polyurethane, etc., can be used. In the present invention, even when polyvinyl chloride, TPO, thermoplastic ester elastomer, or thermoplastic polyurethane is used as the thermoplastic resin, excellent adhesion and low-temperature flexibility are obtained. In particular, polyvinyl chloride, which is difficult to adhere to, has excellent adhesion and low-temperature flexibility whether it is in foamed or unfoamed form.

[0032] The adhesive layer is formed using the moisture-curing polyurethane hot-melt resin composition of the present invention. Methods for forming the adhesive layer include, for example, melting the moisture-curing polyurethane hot-melt resin composition at 100 to 140°C, then applying it to the thermoplastic resin layer or the substrate using a coater such as a roll coater, spray coater, T-die coater, knife coater, or comma coater; a precision method such as a dispenser, inkjet printing, screen printing, or offset printing; or nozzle application, and then bonding the layers together.

[0033] Furthermore, after bonding the two bundles together with the adhesive, the adhesive can be dried and cured using known methods as needed.

[0034] The synthetic leather may have a surface treatment layer provided on top of the thermoplastic resin layer. For example, the surface treatment layer may be made of a known solvent-based urethane resin, water-based urethane resin, solvent-based acrylic resin, water-based acrylic resin, etc. [Examples]

[0035] The present invention will be described in more detail below using examples.

[0036] [Example 1] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser, 50 parts by mass of polytetramethylene glycol (number average molecular weight: 2,000, hereinafter abbreviated as "PEt-1"), 30 parts by mass of aromatic polyester polyol (a reaction between 1,6-hexanediol and orthophthalic acid, number average molecular weight: 2,000, hereinafter abbreviated as "PEs-1"), and 20 parts by mass of aliphatic polyester polyol (a reaction between 1,6-hexanediol and sebacic acid, number average molecular weight: 3,500, hereinafter abbreviated as "PEs-2") were added and mixed. The mixture was then heated under reduced pressure at 100°C until the moisture content in the flask was reduced to 0.05% by mass or less. Next, the flask was cooled to 90°C, and 23 parts by mass of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as "MDI"), which had been melted at 70°C, was added. The mixture was then reacted at 110°C for approximately 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, thereby obtaining a hot-melt urethane prepolymer. To 100 parts by mass of this hot-melt urethane prepolymer, 0.37 parts by mass of phosphate ester (a mixture of monobutyl phosphate and dibutyl phosphate, average molecular weight; 182, hereinafter abbreviated as "phosphate ester (1)") was added to obtain a moisture-curable polyurethane hot-melt resin composition (1).

[0037] [Example 2] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser, 55 parts by mass of PEt-1, 30 parts by mass of PEs-1, and 15 parts by mass of aliphatic polyester polyol (a reaction of ethylene glycol, 1,6-hexanediol, neopentyl glycol, and adipic acid; number average molecular weight: 5,500; hereinafter abbreviated as "PEs-3") were added and mixed. The mixture was then heated under reduced pressure at 100°C until the moisture content in the flask was reduced to 0.05% by mass or less. Next, the flask was cooled to 90°C, 20 parts by mass of MDI melted at 70°C was added, and the mixture was reacted at 110°C for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, thereby obtaining a hot-melt urethane prepolymer. To 100 parts by mass of this hot-melt urethane prepolymer, 0.48 parts by mass of phosphate ester (1) was added to obtain a moisture-curable polyurethane hot-melt resin composition (2).

[0038] [Example 3] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser, 55 parts by mass of polypropylene glycol (number average molecular weight; 2,000, hereinafter abbreviated as "PEt-2"), 20 parts by mass of PEs-1, and 25 parts by mass of PEs-2 were added and mixed. The mixture was then heated under reduced pressure at 100°C until the moisture content in the flask was reduced to 0.05% by mass or less. Next, the flask was cooled to 90°C, 21 parts by mass of MDI melted at 70°C was added, and the mixture was reacted at 110°C for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, thereby obtaining a hot-melt urethane prepolymer. To 100 parts by mass of this hot-melt urethane prepolymer, 0.30 parts by mass of phosphate ester (1) was added to obtain a moisture-curing polyurethane hot-melt resin composition (3).

[0039] [Example 4] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser, 60 parts by mass of PEt-1, 25 parts by mass of PEs-1, and 15 parts by mass of PEs-2 were added and mixed. The mixture was then heated under reduced pressure at 100°C until the moisture content in the flask was reduced to 0.05% by mass or less. Next, the flask was cooled to 90°C, 22 parts by mass of MDI melted at 70°C was added, and the mixture was reacted at 110°C for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, thereby obtaining a hot-melt urethane prepolymer. To 100 parts by mass of this hot-melt urethane prepolymer, 0.37 parts by mass of phosphate ester (1) was added to obtain a moisture-curing polyurethane hot-melt resin composition (4).

[0040] [Example 5] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser, 65 parts by mass of PEt-2, 25 parts by mass of PEs-1, and 15 parts by mass of PEs-2 were added and mixed. The mixture was then heated under reduced pressure at 100°C until the moisture content in the flask was reduced to 0.05% by mass or less. Next, the flask was cooled to 90°C, 24 parts by mass of MDI melted at 70°C was added, and the mixture was reacted at 110°C for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, thereby obtaining a hot-melt urethane prepolymer. To 100 parts by mass of this hot-melt urethane prepolymer, 0.52 parts by mass of phosphate ester (1) was added to obtain a moisture-curing polyurethane hot-melt resin composition (5).

[0041] [Example 6] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser, 65 parts by mass of PEt-1, 15 parts by mass of PEs-1, and 20 parts by mass of PEs-3 were added and mixed. The mixture was then heated under reduced pressure at 100°C until the moisture content in the flask was reduced to 0.05% by mass or less. Next, the flask was cooled to 90°C, 21 parts by mass of MDI melted at 70°C was added, and the mixture was reacted at 110°C for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, thereby obtaining a hot-melt urethane prepolymer. To 100 parts by mass of this hot-melt urethane prepolymer, 0.30 parts by mass of phosphate ester (1) was added to obtain a moisture-curing polyurethane hot-melt resin composition (6).

[0042] [Example 7] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser, 30 parts by mass of PEt-1, 30 parts by mass of PEt-2, 20 parts by mass of PEs-1, and 20 parts by mass of PEs-2 were added and mixed. The mixture was then heated under reduced pressure at 100°C until the moisture content in the flask was reduced to 0.05% by mass or less. Next, the flask was cooled to 90°C, 22 parts by mass of MDI melted at 70°C was added, and the mixture was reacted at 110°C for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, thereby obtaining a hot-melt urethane prepolymer. To 100 parts by mass of this hot-melt urethane prepolymer, 0.36 parts by mass of phosphate ester (1) was added to obtain a moisture-curing polyurethane hot-melt resin composition (7).

[0043] [Comparative Example 1] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser, 55 parts by mass of PEt-1, 20 parts by mass of PEs-1, and 15 parts by mass of PEs-2 were added and mixed. The mixture was then heated under reduced pressure at 100°C until the moisture content in the flask was reduced to 0.05% by mass or less. Next, the flask was cooled to 90°C, 20 parts by mass of MDI melted at 70°C was added, and the mixture was reacted at 110°C for approximately 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, thereby obtaining a hot-melt urethane prepolymer. To 100 parts by mass of this hot-melt urethane prepolymer, 0.11 parts by mass of phosphate ester (1) was added to obtain a moisture-curing polyurethane hot-melt resin composition (R1).

[0044] [Comparative Example 2] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser, 60 parts by mass of PEt-1, 25 parts by mass of PEs-1, and 15 parts by mass of PEs-2 were added and mixed. The mixture was then heated under reduced pressure at 100°C until the moisture content in the flask was reduced to 0.05% by mass or less. Next, the flask was cooled to 90°C, 22 parts by mass of MDI melted at 70°C was added, and the mixture was reacted at 110°C for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, thereby obtaining a hot-melt urethane prepolymer. To 100 parts by mass of this hot-melt urethane prepolymer, 0.06 parts by mass of phosphate ester (1) was added to obtain a moisture-curing polyurethane hot-melt resin composition (R2).

[0045] [Comparative Example 3] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser, 35 parts by mass of PEt-1, 35 parts by mass of PEs-1, and 30 parts by mass of PEs-3 were added and mixed. The mixture was then heated under reduced pressure at 100°C until the moisture content in the flask was reduced to 0.05% by mass or less. Next, the flask was cooled to 90°C, 19 parts by mass of MDI melted at 70°C was added, and the mixture was reacted at 110°C for approximately 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, thereby obtaining a hot-melt urethane prepolymer and a moisture-curing polyurethane hot-melt resin composition (R3).

[0046] [Comparative Example 4] In a four-necked flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser, 30 parts by mass of PEt-1, 45 parts by mass of PEs-1, and 25 parts by mass of PEs-3 were added and mixed. The mixture was then heated under reduced pressure at 100°C until the moisture content in the flask was reduced to 0.05% by mass or less. Next, the flask was cooled to 90°C, 20 parts by mass of MDI melted at 70°C was added, and the mixture was reacted at 110°C for approximately 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, thereby obtaining a hot-melt urethane prepolymer. To 100 parts by mass of this hot-melt urethane prepolymer, 0.36 parts by mass of phosphate ester (1) was added to obtain a moisture-curing polyurethane hot-melt resin composition (R4).

[0047] [Methods for measuring number-average molecular weight and weight-average molecular weight] The number-average molecular weights of the polyols used in the examples and comparative examples are shown as values ​​obtained by gel permeation column chromatography (GPC) under the following conditions.

[0048] Measurement device: High-speed GPC device (HLC-8220GPC manufactured by Tosoh Corporation) Columns: 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" (7.8mmI.D. x 30cm) x 1 Detector: RI (Differential Refractometer) Column temperature: 40℃ Eluent: Tetrahydrofuran (THF) Flow rate: 1.0mL / min Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 0.4% by mass) Standard samples: Calibration curves were prepared using the following standard polystyrene samples.

[0049] (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.

[0050] [Method for manufacturing synthetic leather] In a constant temperature and humidity chamber adjusted to 23°C and 50±5% humidity, a gravure coater was used to coat a polyvinyl chloride sheet with the moisture-curing polyurethane hot-melt resin compositions obtained in the examples and comparative examples at a rate of 40±5 g / m². 2 Synthetic leather was obtained by intermittently applying the coating in this manner, bonding it with a polyester-based fabric, and then aging it for 24 hours under conditions of 23°C and 50±5% humidity.

[0051] [Method for evaluating adhesiveness] For each of the obtained synthetic leather samples, peel strength was measured and adhesive strength was measured using a Tensilon universal testing machine (RTC-1210A, manufactured by Orientec Co., Ltd.) at a crosshead measurement of 200 mm / min. Samples with a value of 6 N / cm or higher were evaluated as "○" and samples with a value of less than 6 N / cm were evaluated as "×".

[0052] [Method for evaluating low-temperature flexibility] Each of the obtained synthetic leather samples was subjected to a flexural test using a flexometer (-10°C, 100 rotations / minute). The number of rotations until cracks appeared on the surface of the synthetic leather was measured, and samples with 20,000 rotations or more were evaluated as "○" and samples with less than 20,000 rotations as "×".

[0053] [Table 1]

[0054] [Table 2]

[0055] [Table 3]

[0056] The numbers in Tables 1-3 represent parts by mass. The amount of phosphate ester (B) is expressed in parts by mass relative to 100 parts by mass of hot-melt urethane prepolymer (A).

[0057] Examples 1 to 7, which are moisture-curing polyurethane hot-melt resin compositions of the present invention, were found to have excellent adhesion to polyvinyl chloride and low-temperature flexibility.

[0058] On the other hand, Comparative Examples 1 and 2, although their content of phosphate ester (B) was below the range specified in the present invention, exhibited poor adhesion.

[0059] Comparative Example 3 uses a polyether polyol (a1) in an amount below the range specified in the present invention and does not use phosphate ester (B), but it exhibited poor adhesion and low-temperature flexibility.

[0060] Comparative Example 4 is an embodiment in which the amount of polyether polyol (a1) used is below the range specified in the present invention, but it had poor low-temperature flexibility.

Claims

1. A moisture-curing polyurethane hot-melt resin composition containing a hot-melt urethane prepolymer (A) having an isocyanate group and a phosphate ester (B), The hot melt urethane prepolymer (A) is made from a polyol (a) containing 50% by mass or more of polyether polyol (a1), A moisture-curing polyurethane hot-melt resin composition characterized in that the content of the phosphate ester (B) is greater than 0.2 parts by mass and less than or equal to 0.60 parts by mass per 100 parts by mass of the hot-melt urethane prepolymer (A).

2. A moisture-curing polyurethane hot-melt resin composition according to claim 1, used for bonding to a thermoplastic resin selected from polyvinyl chloride, TPO (Thermoplastic Olefinic Elastomer), thermoplastic ester elastomer, and thermoplastic polyurethane.

3. An adhesive characterized by containing the moisture-curing polyurethane hot-melt resin composition described in claim 1.

4. The adhesive according to claim 3, used for bonding to a thermoplastic resin layer.

5. The adhesive according to claim 4, wherein the thermoplastic resin forming the thermoplastic resin layer is selected from polyvinyl chloride, TPO (Thermoplastic Olefinic Elastomer), thermoplastic ester elastomer, and thermoplastic polyurethane.

6. A synthetic leather characterized by having at least a thermoplastic resin layer and an adhesive layer containing the moisture-curing polyurethane hot-melt resin composition described in claim 1.

7. The synthetic leather according to claim 6, wherein the thermoplastic resin layer is formed of a thermoplastic resin selected from polyvinyl chloride, TPO (Thermoplastic Olefinic Elastomer), thermoplastic ester elastomer, and thermoplastic polyurethane.

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