JP7718596B2 - Moisture-curable polyurethane hot-melt resin composition, adhesive, and synthetic leather - Google Patents

Description

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

Synthetic leather generally uses polyurethane (PU), polyvinyl chloride (PVC), olefin-based thermoplastic elastomer (TPO), etc. as its surface material, and these surface materials are bonded to a base fabric such as cloth or nonwoven fabric with an adhesive (see, for example, Patent Document 1). Among these, solvent-based adhesives have been widely used until now, but as part of environmental efforts, local communities, countries, and companies are calling for a reduction in VOCs, making it necessary to replace solvent-based adhesives with water-based or solvent-free adhesives.

On the other hand, synthetic leather used in vehicle interiors and indoor furniture is required to be flame-retardant for fire prevention purposes, but the level of flexibility required at low temperatures is also increasing in anticipation of use in cold regions. However, a material that combines all of these properties has yet to be found.

Special Publication No. 2008-514403

The problem that this invention aims to solve is to provide a moisture-curable polyurethane hot melt resin composition that has excellent adhesion, low-temperature flexibility, and flame retardancy.

The present invention provides a moisture-curable polyurethane hot-melt resin composition containing a hot-melt urethane prepolymer (A) having an isocyanate group and a flame retardant (B), wherein the hot-melt prepolymer (A) is made from a polyol (a) containing 50% by mass or more of a polyether polyol (a1), and the content of the flame retardant (B) is greater than 15 parts by mass per 100 parts by mass of the hot-melt urethane prepolymer (A).

The present invention also provides an adhesive containing the moisture-curable polyurethane hot-melt resin composition. The present invention also provides synthetic leather having at least a thermoplastic resin layer and the adhesive layer.

The moisture-curable polyurethane hot-melt resin composition of the present invention has excellent adhesion, low-temperature flexibility, and flame retardancy. Therefore, the moisture-curable polyurethane hot-melt resin composition of the present invention is particularly suitable for use in the production of synthetic leather that uses a thermoplastic resin as the skin material.

The moisture-curable polyurethane hot-melt resin composition of the present invention contains a hot-melt urethane prepolymer (A) having an isocyanate group, which is made from a specific polyol (a), and a specific amount of a flame retardant (B).

In order to achieve 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). This design allows the adhesive to have a lower glass transition temperature, resulting in excellent low-temperature flexibility. The amount of polyether polyol (a1) used is preferably 50 to 90% by mass, and more preferably 55 to 70% by mass, of the polyol (a) in order to achieve even better low-temperature flexibility.

Examples of the polyether polyol (a1) that can be used include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene polyoxytetramethylene glycol, and polyoxypropylene polyoxytetramethylene glycol. These polyols may be used alone or in combination. 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 they provide even better heat resistance and moist heat resistance. Plant-derived polyether polyols may also be used. Examples of commercially available plant-derived polyether polyols include "Bio PTMG" manufactured by Mitsubishi Chemical Corporation, "Bio PTG" manufactured by Hodogaya Chemical Co., Ltd., and biomass polypropylene glycol manufactured by Vithal Castor Polyols.

As the polyol (a), other polyols can be used in combination with the polyether polyol (a). Examples of the other polyols that can be used include commercially available polyols such as polyester polyols, polycarbonate polyols, polybutadiene polyols, silicone diols, and acrylic diols. These polyols may be used alone or in combination of two or more, and may be petroleum-derived or plant-derived. As the other polyol, polyester polyols are preferred because they provide even better adhesion.

The number average molecular weight of the polyol (a) is preferably 500 to 10,000, and more preferably 1,000 to 6,000, in order to obtain even better adhesion, low-temperature flexibility, and mechanical strength. The number average molecular weight of the polyol (a) is a value measured by gel permeation chromatography (GPC).

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

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. These polyisocyanates may be used alone or in combination, and may be derived from petroleum or plants. Among these, aromatic polyisocyanates are preferred, and diphenylmethane diisocyanate is more preferred, due to their superior reactivity and adhesive properties.

The hot-melt urethane prepolymer (A) has isocyanate groups at the polymer terminals or within the 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.

The hot-melt urethane prepolymer (A) can be produced, for example, by adding the polyol (a) dropwise to a reaction vessel containing the polyisocyanate (b), heating the mixture, and reacting the polyisocyanate (b) under conditions in which the isocyanate groups in the polyisocyanate (b) are in excess relative to the hydroxyl groups in the polyol (a).

When reacting the polyol (a) and the polyisocyanate (b), the molar ratio [NCO/OH] of the hydroxyl groups in the polyol (a) to the isocyanate groups in the polyisocyanate (b) is preferably 1.3 to 2.5, more preferably 1.5 to 2.0, in order to obtain even better hot melt properties, adhesive properties, and low-temperature flexibility.

The isocyanate group content (hereinafter abbreviated as "NCO %) of the hot-melt urethane prepolymer (A) is preferably 1.2 to 5.0 mass%, more preferably 1.7 to 3.5 mass%, in order to obtain even better hot-melt properties, adhesion, and low-temperature flexibility. The NCO % of the hot-melt urethane prepolymer (A) is a value measured by potentiometric titration in accordance with JIS K1603-1:2007.

The flame retardant (B) is an essential component for achieving excellent flame retardancy, and its content must exceed 15 parts by mass per 100 parts by mass of the hot-melt urethane prepolymer (A). To maintain high levels of low-temperature flexibility and adhesiveness and achieve even better flame retardancy, the content of the flame retardant (B) is preferably 17.5 to 55 parts by mass per 100 parts by mass of the hot-melt urethane prepolymer (A).

Examples of the flame retardant (B) that can be used include phosphate esters, phosphate-containing flame retardants, red phosphorus, bromine-containing flame retardants, boron-containing flame retardants, antimony-containing flame retardants, metal hydroxides, graphite, phosphorus-boron compounds, and vinyl polymers. These flame retardants may be used alone or in combination of two or more. Among these, phosphate esters having three or more aromatic rings are preferred, and phosphate esters having four or more aromatic rings are more preferred, as they maintain high levels of low-temperature flexibility and adhesiveness and provide even better flame retardancy.

The moisture-curable polyurethane hot-melt resin composition of the present invention contains the hot-melt urethane prepolymer (A) and the flame retardant (B) as essential components, but may also contain other additives as needed.

Examples of the other additives that can be used include urethane catalysts, neutralizing agents, crosslinking agents, silane coupling agents, thickeners, fillers, thixotropic agents, tackifiers, waxes, heat stabilizers, light resistance stabilizers, fluorescent brighteners, foaming agents, pigments, dyes, conductivity imparting agents, antistatic agents, moisture permeability enhancers, water repellents, oil repellents, hollow foams, water absorbents, moisture absorbents, deodorizers, foam stabilizers, plasticizers, antiblocking agents, and hydrolysis inhibitors. 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 adhesion, low-temperature flexibility, and flame retardancy. Therefore, the moisture-curable polyurethane hot-melt resin composition of the present invention is particularly suitable for use in the production of synthetic leather that uses a thermoplastic resin as the skin material.

Next, we will explain the synthetic leather of the present invention.

The synthetic leather has at least a thermoplastic resin layer and an adhesive layer containing the moisture-curable polyurethane hot melt resin composition, and can be, for example, a product obtained by sequentially laminating a substrate, the adhesive layer, and a thermoplastic resin layer.

The substrate may be, for example, a nonwoven fabric, woven fabric, knitted fabric, or the like made from polyester fiber, polyethylene fiber, nylon fiber, acrylic fiber, polyurethane fiber, acetate fiber, rayon fiber, polylactic acid fiber, cotton, hemp, silk, wool, glass fiber, carbon fiber, or blends thereof.

The thermoplastic resin layer may be formed from, for example, known polyvinyl chloride, polyvinyl acetate, polyvinylidene chloride, polystyrene, TPO (thermoplastic olefinic elastomer), thermoplastic ester elastomer, thermoplastic polyurethane, etc. 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 achieved. In particular, polyvinyl chloride, which is difficult to adhere to, exhibits excellent adhesion and low-temperature flexibility in both foamed and unfoamed forms.

The adhesive layer is formed from the moisture-curable polyurethane hot melt resin composition of the present invention. Examples of methods for forming the adhesive layer include melting the moisture-curable polyurethane hot melt resin composition at 100 to 140°C, 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 a nozzle coater, and then laminating the layers together.

After bonding the two tufts together with the adhesive, the adhesive can be dried and cured as needed using known methods.

The synthetic leather may further have a surface treatment layer formed on top of the thermoplastic resin layer. The surface treatment layer may be formed, for example, from a known solvent-based urethane resin, water-based urethane resin, solvent-based acrylic resin, water-based acrylic resin, or the like.

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

[Example 1]
A four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 171 parts by mass of polytetramethylene glycol (number average molecular weight: 2,000, hereinafter abbreviated as "PEt-1"), 78 parts by mass of polyester polyol (resulting from a reaction of 1,6-hexanediol and orthophthalic acid, number average molecular weight: 2,000, hereinafter abbreviated as "PEs-1"), and 62 parts by mass of polyester polyol (resulting from a reaction of 1,6-hexanediol and sebacic acid, number average molecular weight: 3,500, hereinafter abbreviated as "PEs-2"), and the mixture was mixed and heated at 100°C under reduced pressure to dehydrate the flask until the water content was 0.05% by mass or less. Next, the flask was cooled to 90°C, and 71 parts by mass of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as "MDI") melted at 70°C was added. The mixture was allowed to react at 110°C for approximately 3 hours under a nitrogen atmosphere until the isocyanate group content reached a constant level, yielding a hot-melt urethane prepolymer. 35 parts by mass of phosphate ester (1,3-phenylenebis(2,6-dimethylphenyl phosphate), hereinafter abbreviated as "flame retardant (B1)") was blended with 100 parts by mass of this hot-melt urethane prepolymer to obtain a moisture-curable polyurethane hot-melt resin composition (1).

[Example 2]
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 74 parts by weight of PEt-1, 31 parts by weight of PEs-1, and 18 parts by weight of PEs-2, mixed, and heated under reduced pressure at 100 ° C. to dehydrate the water content in the flask to 0.05% by weight or less. Next, the flask was cooled to 90 ° C., and 27 parts by weight of MDI melted at 70 ° C. was added. The mixture was reacted at 110 ° C. for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, resulting in a hot-melt urethane prepolymer. 100 parts by weight of this hot-melt urethane prepolymer was blended with 25 parts by weight of flame retardant (B1), to obtain a moisture-curable polyurethane hot-melt resin composition (2).

[Example 3]
A four-neck flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 48 parts by mass of polypropylene glycol (number average molecular weight: 2,000, hereinafter abbreviated as "PEt-2"), 17 parts by mass of PEs-1, and 22 parts by mass of polyester polyol (ethylene glycol, neopentyl glycol, 16-hexanediol, and adipic acid reacted therewith, number average molecular weight: 5,500, hereinafter abbreviated as "PEs-3"), mixed, and heated under reduced pressure at 100 ° C. to dehydrate the flask until the water content in the flask was 0.05% by mass or less. Next, the flask was cooled to 90 ° C., and 18 parts by mass of MDI melted at 70 ° C. was added. The mixture was reacted at 110 ° C. for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, yielding a hot-melt urethane prepolymer. 35 parts by mass of a flame retardant (B1) was blended with 100 parts by mass of this hot-melt urethane prepolymer to obtain a moisture-curable polyurethane hot-melt resin composition (3).

[Example 4]
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 133 parts by weight of PEt-1, 56 parts by weight of PEs-1, and 33 parts by weight of PEs-2, mixed, and heated under reduced pressure at 100 ° C. to dehydrate the water content in the flask to 0.05% by weight or less. Next, the flask was cooled to 90 ° C., and 49 parts by weight of MDI melted at 70 ° C. was added. The mixture was allowed to react for about 3 hours at 110 ° C. under a nitrogen atmosphere until the isocyanate group content became constant, resulting in a hot-melt urethane prepolymer. 100 parts by weight of this hot-melt urethane prepolymer was blended with 30 parts by weight of flame retardant (B1), to obtain a moisture-curable polyurethane hot-melt resin composition (4).

[Example 5]
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 139 parts by weight of PEt-2, 32 parts by weight of PEs-1, and 43 parts by weight of PEs-3, mixed, and heated under reduced pressure at 100 ° C. to dehydrate the water content in the flask to 0.05% by weight or less. Next, the flask was cooled to 90 ° C., and 47 parts by weight of MDI melted at 70 ° C. was added. The mixture was allowed to react for about 3 hours at 110 ° C. under a nitrogen atmosphere until the isocyanate group content became constant, resulting in a hot-melt urethane prepolymer. 35 parts by weight of flame retardant (B1) was blended with 100 parts by weight of this hot-melt urethane prepolymer to obtain a moisture-curable polyurethane hot-melt resin composition (5).

[Example 6]
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 83 parts by weight of PEt-1, 19 parts by weight of PEs-1, and 26 parts by weight of PEs-3, mixed, and heated under reduced pressure at 100 ° C. to dehydrate the water content in the flask to 0.05% by weight or less. Next, the flask was cooled to 90 ° C., and 26 parts by weight of MDI melted at 70 ° C. was added. The mixture was reacted at 110 ° C. for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, resulting in a hot-melt urethane prepolymer. 100 parts by weight of this hot-melt urethane prepolymer was blended with 40 parts by weight of flame retardant (B1), to obtain a moisture-curable polyurethane hot-melt resin composition (6).

[Example 7]
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 121 parts by weight of PEt-1, 121 parts by weight of PEt-2, 81 parts by weight of PEs-1, and 81 parts by weight of PEs-2, and mixed. By heating under reduced pressure at 100 ° C., the water content in the flask was dehydrated to 0.05% by weight or less. Next, the flask was cooled to 90 ° C., and 87 parts by weight of MDI melted at 70 ° C. was added. The mixture was reacted at 110 ° C. for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, resulting in a hot-melt urethane prepolymer. 100 parts by weight of this hot-melt urethane prepolymer was blended with 30 parts by weight of flame retardant (B1), and a moisture-curable polyurethane hot-melt resin composition (7) was obtained.

[Example 8]
A moisture-curable polyurethane hot-melt resin composition (8) was obtained in the same manner as in Example 1, except that PEt-1 was replaced with biomass polytetramethylene glycol ("Bio PTMG" manufactured by Mitsubishi Chemical Corporation, number average molecular weight: 2,000).

[Comparative Example 1]
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 92 parts by weight of PEt-1, 33 parts by weight of PEs-1, and 25 parts by weight of PEs-2, mixed, and heated under reduced pressure at 100 ° C. to dehydrate the water content in the flask to 0.05% by weight or less. Next, the flask was cooled to 90 ° C., and 33 parts by weight of MDI melted at 70 ° C. was added. The mixture was reacted at 110 ° C. for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, resulting in a hot-melt urethane prepolymer. 100 parts by weight of this hot-melt urethane prepolymer was blended with 10 parts by weight of flame retardant (B1), to obtain a moisture-curable polyurethane hot-melt resin composition (R1).

[Comparative Example 2]
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 109 parts by mass of PEt-2, 45 parts by mass of PEs-1, and 27 parts by mass of PEs-2, and mixed. The water content in the flask was dehydrated to 0.05% by mass or less by heating under reduced pressure at 100 ° C. The flask was then cooled to 90 ° C., and 40 parts by mass of MDI melted at 70 ° C. was added. The mixture was allowed to react for about 3 hours at 110 ° C. under a nitrogen atmosphere until the isocyanate group content became constant. A hot-melt urethane prepolymer was obtained, and a moisture-curable polyurethane hot-melt resin composition (R2) was obtained.

[Comparative Example 3]
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 111 parts by weight of PEt-1, 77 parts by weight of PEs-1, and 66 parts by weight of PEs-3, mixed, and heated under reduced pressure at 100 ° C. to dehydrate the water content in the flask to 0.05% by weight or less. Next, the flask was cooled to 90 ° C., and 50 parts by weight of MDI melted at 70 ° C. was added. The mixture was reacted at 110 ° C. for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, resulting in a hot-melt urethane prepolymer. 100 parts by weight of this hot-melt urethane prepolymer was blended with 65 parts by weight of flame retardant (B1), to obtain a moisture-curable polyurethane hot-melt resin composition (R3).

[Comparative Example 4]
A four-necked flask equipped with a thermometer, a stirrer, an inert gas inlet, and a reflux condenser was charged with 27 parts by weight of PEt-1, 41 parts by weight of PEs-1, and 23 parts by weight of PEs-3, mixed, and heated under reduced pressure at 100 ° C. to dehydrate the water content in the flask to 0.05% by weight or less. Next, the flask was cooled to 90 ° C., and 18 parts by weight of MDI melted at 70 ° C. was added. The mixture was reacted at 110 ° C. for about 3 hours under a nitrogen atmosphere until the isocyanate group content became constant, resulting in a hot-melt urethane prepolymer. 100 parts by weight of this hot-melt urethane prepolymer was blended with 40 parts by weight of flame retardant (B1), to obtain a moisture-curable polyurethane hot-melt resin composition (R4).

[Method 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 values measured by gel permeation column 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 connected in series and used.
"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
Tosoh Corporation's "TSKgel Standard Polystyrene A-5000"
"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
Tosoh Corporation's "TSKgel Standard Polystyrene F-550"

[Method for producing synthetic leather]
In a constant temperature and humidity chamber adjusted to a temperature of 23°C and a humidity of 50±5%, a polyvinyl chloride sheet was intermittently coated with the moisture-curable polyurethane hot-melt resin compositions obtained in the Examples and Comparative Examples using a gravure coater so as to give a coating of 40±5 g/ ^m2. The sheet was then laminated with a polyester fabric and aged for 24 hours at a temperature of 23°C and a humidity of 50±5%, to obtain synthetic leather.

[Method for evaluating adhesiveness]
The peel strength of each of the obtained synthetic leathers was measured using a Tensilon (Tensilon universal testing machine "RTC-1210A" manufactured by Orientec Co., Ltd.) at a crosshead speed of 200 mm/min, and a peel strength of 6 N/cm or more was evaluated as "Good", and a peel strength of less than 6 N/cm was evaluated as "Poor".

[Method for evaluating low-temperature flexibility]
Each of the obtained synthetic leathers was subjected to a bending test (-10°C, 100 times/min) using a flexometer to measure the number of times it took for cracks to appear on the surface of the synthetic leather. 20,000 times or more was evaluated as "Good", and less than 20,000 times was evaluated as "Poor".

[Flame retardancy evaluation method]
The moisture-curable polyurethane hot-melt resin compositions obtained in the examples and comparative examples were applied to a thickness of 300 microns using a roll coater, and then aged for 72 hours or more at a temperature of 23°C and a humidity of 50±5% to produce films. The resulting films were then cut into rectangles measuring 102 mm wide and 356 mm long, and a flammability test (FMVSS302) was performed. Test pieces that did not ignite or self-extinguished just before the A-marked line, those that self-extinguished within a burning distance of 51 mm (and within 60 seconds), and those with a burning rate of 102 mm/min or less were rated "○", while others were rated "×".

Examples 1 to 8, which are moisture-curable polyurethane hot melt resin compositions of the present invention, were found to have excellent adhesion, low-temperature flexibility, and flame retardancy.

On the other hand, in Comparative Example 1, the content of flame retardant (B) was below the range specified in the present invention, but the flame retardancy was poor.

Comparative example 2 is an embodiment in which flame retardant (B) is not used, but the flame retardancy was poor.

In Comparative Examples 3 and 4, the amount of polyether polyol (a1) used was below the range specified in the present invention, and the low-temperature flexibility, etc. were poor.

Claims (3)

A synthetic leather characterized by having at least a thermoplastic resin layer and an adhesive layer made of an adhesive containing a moisture-curable polyurethane hot-melt resin composition,
the thermoplastic resin is polyvinyl chloride,
The moisture-curable polyurethane hot-melt resin composition contains a hot-melt urethane prepolymer (A) having an isocyanate group and a flame retardant (B),
the hot-melt prepolymer (A) is made from a polyol (a) containing a polyether polyol (a1) and a polyester polyol, and the amount of the polyether polyol (a1) used is in the range of 50 to 90 mass% of the polyol (a);
the content of the flame retardant (B) is 17.5 to 55 parts by mass per 100 parts by mass of the hot-melt urethane prepolymer (A);
1. A synthetic leather characterized in that the flame retardant (B) is a phosphate ester having three or more aromatic rings and a phosphorus content of 9.0 mass% or more. 2. The synthetic leather according to claim 1, wherein the flame retardant (B) is a phosphate ester having five aromatic rings and a phosphorus content of 9.0 mass% or more . A synthetic leather characterized by having at least a thermoplastic resin layer and an adhesive layer made of an adhesive containing a moisture-curable polyurethane hot-melt resin composition,
the thermoplastic resin is polyvinyl chloride,
The moisture-curable polyurethane hot-melt resin composition contains a hot-melt urethane prepolymer (A) having an isocyanate group and a flame retardant (B),
the hot-melt prepolymer (A) is made from a polyol (a) containing a polyether polyol (a1) and a polyester polyol, and the amount of the polyether polyol (a1) used is in the range of 50 to 90 mass% of the polyol (a);
the content of the flame retardant (B) is 17.5 to 55 parts by mass per 100 parts by mass of the hot-melt urethane prepolymer (A);
The synthetic leather is characterized in that the flame retardant (B) is 1,3-phenylenebis(2,6-dimethylphenyl phosphate).