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

Abstract

The present invention provides a moisture-curable polyurethane hot melt resin composition which contains (A) a hot melt urethane prepolymer having an isocyanate group and (B) a flame retardant, and which is characterized in that: the hot melt prepolymer (A) uses, as a starting material, a polyol (a) that contains 50% by mass or more of a polyether polyol (a1); and the content of the flame retardant (B) is more than 15 parts by mass relative to 100 parts by mass of the hot melt urethane prepolymer (A). In addition, the present invention provides an adhesive which is characterized by containing the moisture-curable polyurethane hot melt resin composition. It is preferable that the flame retardant (B) is a phosphoric acid ester that has three or more aromatic rings.

Description

[Technical Field]

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

[0002] 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 and commonly 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.

[0003] On the other hand, synthetic leathers used in vehicle interiors and indoor furniture are 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2008-514403 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a moisture-curable polyurethane hot-melt resin composition that is excellent in adhesiveness, low-temperature flexibility, and flame retardancy. [Means for solving the problem]

[0006] 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 mass% or more of a polyether polyol (a1), and the content of the flame retardant (B) is more than 15 mass parts per 100 mass parts of the hot-melt urethane prepolymer (A).

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

[0008] The moisture-curable polyurethane hot-melt resin composition of the present invention has excellent adhesiveness, low-temperature flexibility, and flame retardancy, and is therefore particularly suitable for use in the production of synthetic leather using a thermoplastic resin as a skin material. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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).

[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 a polyether polyol (a1). By designing the adhesive in this manner, the glass transition temperature of the adhesive can be lowered, resulting in excellent low-temperature flexibility. The amount of the polyether polyol (a1) used is preferably 50 to 90% by mass, more preferably 55 to 70% by mass, of the polyol (a), in order to obtain even better low-temperature flexibility.

[0011] 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 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 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.

[0012] 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 can be used alone or in combination of two or more, and may be derived from petroleum or plants. As the other polyols, polyester polyols are preferred because they provide even better adhesiveness.

[0013] The number average molecular weight of the polyol (a) is preferably 500 to 10,000, more preferably 1,000 to 6,000, from the viewpoint of obtaining even better adhesiveness, low-temperature flexibility, and mechanical strength. The number average molecular weight of the polyol (a) is a value measured by gel permeation chromatography (GPC).

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

[0015] Examples of the polyisocyanate (b) 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 of two or more, and may be derived from petroleum or plants. Among these, aromatic polyisocyanates are preferred, and diphenylmethane diisocyanate is more preferred, because they provide superior reactivity and adhesion.

[0016] The hot-melt urethane prepolymer (A) has isocyanate groups at the polymer terminals or within the molecule, which 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] 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), followed by heating and reacting under conditions in which the isocyanate groups of the polyisocyanate (b) are in excess relative to the hydroxyl groups of the polyol (a).

[0018] When the polyol (a) and the polyisocyanate (b) are reacted, 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.

[0019] 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, adhesiveness, 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.

[0020] The flame retardant (B) is an essential component for obtaining excellent flame retardancy, and its content must be more than 15 parts by mass per 100 parts by mass of the hot-melt urethane prepolymer (A). 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) in order to maintain high levels of low-temperature flexibility and adhesiveness and obtain even better flame retardancy.

[0021] 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, in that they maintain high levels of low-temperature flexibility and adhesiveness and provide even better flame retardancy.

[0022] 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, and may contain other additives as needed.

[0023] Examples of the other additives that can be used include urethanization catalysts, neutralizing agents, crosslinking agents, silane coupling agents, thickeners, fillers, thixotropy-imparting agents, tackifiers, waxes, heat stabilizers, light resistance stabilizers, fluorescent brighteners, foaming agents, pigments, dyes, conductivity-imparting agents, antistatic agents, moisture permeability improvers, water repellents, oil repellents, hollow foams, water absorbents, moisture absorbents, deodorizers, foam stabilizers, plasticizers, antiblocking agents, hydrolysis inhibitors, etc. These additives may be used alone or in combination of two or more.

[0024] As described above, the moisture-curable polyurethane hot-melt resin composition of the present invention has excellent adhesiveness, low-temperature flexibility, and flame retardancy, and is therefore particularly suitable for use in the production of synthetic leather using a thermoplastic resin as a skin material.

[0025] Next, the synthetic leather of the present invention will be described.

[0026] The synthetic leather has at least a thermoplastic resin layer and an adhesive layer containing the moisture-curable polyurethane hot-melt resin composition, and is, for example, made by sequentially laminating a substrate, the adhesive layer, and a thermoplastic resin layer.

[0027] Examples of the substrate that can be used include nonwoven fabrics, woven fabrics, knitted fabrics, and the like made of polyester fibers, polyethylene fibers, nylon fibers, acrylic fibers, polyurethane fibers, acetate fibers, rayon fibers, polylactic acid fibers, cotton, hemp, silk, wool, glass fibers, carbon fibers, and blends thereof.

[0028] The thermoplastic resin layer can 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, the layer has excellent adhesion and low-temperature flexibility, and in particular, when polyvinyl chloride, which is difficult to adhere to, is used, the layer has excellent adhesion and low-temperature flexibility whether it is foamed or unfoamed.

[0029] The adhesive layer is formed from the moisture-curable polyurethane hot-melt resin composition of the present invention. Examples of a method for forming the adhesive layer include a method in which the moisture-curable polyurethane hot-melt resin composition is melted at 100 to 140°C, and then coated onto the thermoplastic resin layer or the substrate using a coater method 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 the layers are bonded together.

[0030] After the two tufts are bonded together with the adhesive, the adhesive can be dried and cured as needed using a known method.

[0031] The synthetic leather may further have a surface treatment layer formed on the thermoplastic resin layer, which may be formed from, for example, a known solvent-based urethane resin, water-based urethane resin, solvent-based acrylic resin, water-based acrylic resin, or the like. [Example]

[0032] The present invention will be described in more detail below using examples.

[0033] [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 (1,6-hexanediol and orthophthalic acid reacted, number average molecular weight: 2,000, hereinafter abbreviated as "PEs-1"), and 62 parts by mass of polyester polyol (1,6-hexanediol and sebacic acid reacted, number average molecular weight: 3,500, hereinafter abbreviated as "PEs-2"), mixed, and heated under reduced pressure at 100°C to dehydrate the flask until the water content was 0.05% by mass or less. The flask was then cooled to 90°C, and 71 parts by weight 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 weight of phosphate ester (1,3-phenylenebis(2,6-dimethylphenyl phosphate), hereinafter abbreviated as "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 (1).

[0034] [Example 2] A four-neck flask equipped with a thermometer, stirrer, inert gas inlet, and 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. The mixture was mixed and heated under reduced pressure at 100 ° C. to dehydrate the flask until the water content was 0.05% by weight or less. The flask was then cooled to 90 ° C., and 27 parts by weight of MDI 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 reached a constant value, yielding a hot-melt urethane prepolymer. 25 parts by weight of flame retardant (B1) was added to 100 parts by weight of this hot-melt urethane prepolymer to obtain a moisture-curable polyurethane hot-melt resin composition (2).

[0035] [Example 3] A four-neck flask equipped with a thermometer, stirrer, inert gas inlet, and reflux condenser was charged with 48 parts by weight of polypropylene glycol (number average molecular weight: 2,000, hereinafter abbreviated as "PEt-2"), 17 parts by weight of PEs-1, and 22 parts by weight of polyester polyol (ethylene glycol, neopentyl glycol, 16-hexanediol, and adipic acid reacted, 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 weight or less. The flask was then 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 approximately 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).

[0036] [Example 4] A four-neck flask equipped with a thermometer, stirrer, inert gas inlet, and 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. The mixture was mixed and heated under reduced pressure at 100 ° C. to dehydrate the flask until the water content was 0.05% by weight or less. The flask was then cooled to 90 ° C., and 49 parts by weight of MDI 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 reached a constant level, yielding a hot-melt urethane prepolymer. 30 parts by weight of flame retardant (B1) was added to 100 parts by weight of this hot-melt urethane prepolymer to obtain a moisture-curable polyurethane hot-melt resin composition (4).

[0037] [Example 5] A four-neck flask equipped with a thermometer, stirrer, inert gas inlet, and 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. The mixture was mixed and heated under reduced pressure at 100 ° C. to dehydrate the flask until the water content was 0.05% by weight or less. The flask was then cooled to 90 ° C., and 47 parts by weight of MDI 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 reached a constant value, yielding a hot-melt urethane prepolymer. 35 parts by weight of flame retardant (B1) was added to 100 parts by weight of this hot-melt urethane prepolymer to obtain a moisture-curable polyurethane hot-melt resin composition (5).

[0038] [Example 6] A four-neck flask equipped with a thermometer, stirrer, inert gas inlet, and 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. The mixture was mixed and heated under reduced pressure at 100 ° C. to dehydrate the flask until the water content was 0.05% by weight or less. The flask was then cooled to 90 ° C., and 26 parts by weight of MDI 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 reached a constant value, yielding a hot-melt urethane prepolymer. 40 parts by weight of flame retardant (B1) was added to 100 parts by weight of this hot-melt urethane prepolymer to obtain a moisture-curable polyurethane hot-melt resin composition (6).

[0039] [Example 7] A four-neck flask equipped with a thermometer, stirrer, inert gas inlet, and 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, mixed, and heated under reduced pressure at 100 ° C. The mixture was dehydrated until the water content in the flask was 0.05% by weight or less. The flask was then 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, yielding a hot-melt urethane prepolymer. 30 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 (7).

[0040] [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).

[0041] [Comparative Example 1] A four-neck flask equipped with a thermometer, stirrer, inert gas inlet, and 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. The mixture was dehydrated until the water content in the flask was 0.05% by weight or less. The flask was then 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, yielding 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).

[0042] Comparative Example 2 A four-neck 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, mixed, and heated under reduced pressure at 100 ° C. to dehydrate the flask until the water content was 0.05% by mass or less. Next, the flask was cooled to 90 ° C., and 40 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, resulting in a hot-melt urethane prepolymer and a moisture-curable polyurethane hot-melt resin composition (R2).

[0043] Comparative Example 3 A four-neck flask equipped with a thermometer, stirrer, inert gas inlet, and 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. The mixture was mixed and heated under reduced pressure at 100 ° C. to dehydrate the flask until the water content was 0.05% by weight or less. The flask was then cooled to 90 ° C., and 50 parts by weight of MDI 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 reached a constant value, yielding a hot-melt urethane prepolymer. 65 parts by weight of flame retardant (B1) was added to 100 parts by weight of this hot-melt urethane prepolymer to obtain a moisture-curable polyurethane hot-melt resin composition (R3).

[0044] Comparative Example 4 A four-neck flask equipped with a thermometer, stirrer, inert gas inlet, and 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. The mixture was mixed and heated under reduced pressure at 100 ° C. to dehydrate the flask until the water content was 0.05% by weight or less. The flask was then cooled to 90 ° C., and 18 parts by weight of MDI 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 reached a constant value, yielding a hot-melt urethane prepolymer. 40 parts by weight of flame retardant (B1) was added to 100 parts by weight of this hot-melt urethane prepolymer to obtain a moisture-curable polyurethane hot-melt resin composition (R4).

[0045] [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.

[0046] Measurement equipment: High-speed GPC equipment (Tosoh Corporation "HLC-8220GPC") 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" (7.8mmI.D. x 30cm) x 1 Detector: RI (differential refractometer) Column temperature: 40℃ Eluent: tetrahydrofuran (THF) Flow rate: 1.0mL / min Injection volume: 100 μL (sample concentration 0.4% by mass in tetrahydrofuran solution) Standard sample: A calibration curve was prepared using the following standard polystyrene.

[0047] (standard polystyrene) Tosoh Corporation's "TSKgel Standard Polystyrene A-500" Tosoh Corporation's "TSKgel Standard Polystyrene A-1000" Tosoh Corporation's "TSKgel Standard Polystyrene A-2500" Tosoh Corporation's "TSKgel Standard Polystyrene A-5000" "TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation Tosoh Corporation's "TSKgel Standard Polystyrene F-2" Tosoh Corporation's "TSKgel Standard Polystyrene F-4" Tosoh Corporation's "TSKgel Standard Polystyrene F-10" Tosoh Corporation's "TSKgel Standard Polystyrene F-20" Tosoh Corporation's "TSKgel Standard Polystyrene F-40" Tosoh Corporation's "TSKgel Standard Polystyrene F-80" Tosoh Corporation's "TSKgel Standard Polystyrene F-128" Tosoh Corporation's "TSKgel Standard Polystyrene F-288" Tosoh Corporation's "TSKgel Standard Polystyrene F-550"

[0048] [How to make synthetic leather] In a constant temperature and humidity chamber adjusted to a temperature of 23°C and a humidity of 50±5%, the moisture-curable polyurethane hot melt resin compositions obtained in the examples and comparative examples were applied to a polyvinyl chloride sheet using a gravure coater at a rate of 40±5 g / m 2 The mixture was applied intermittently so that the thickness was as follows: 100 μm, ...

[0049] [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 value of 6 N / cm or more was evaluated as "Good", and a value of less than 6 N / cm was evaluated as "Poor".

[0050] [Evaluation method for low-temperature flexibility] Each of the synthetic leathers obtained was subjected to a bending test using a flexometer (-10°C, 100 times per minute) 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".

[0051] [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 at least 72 hours 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 subjected to a flammability test (FMVSS302). Test specimens that did not ignite or self-extinguished just before the A-mark, within a burning distance of 51 mm (and within 60 seconds), or had a burning rate of 102 mm / min or less were rated "○," while all other specimens were rated "×."

[0052] [Table 1]

[0053] [Table 2]

[0054] [Table 3]

[0055] It was found that Examples 1 to 8, which are moisture-curable polyurethane hot-melt resin compositions of the present invention, were excellent in adhesiveness, low-temperature flexibility, and flame retardancy.

[0056] On the other hand, Comparative Example 1, in which the content of the flame retardant (B) was below the range specified in the present invention, had poor flame retardancy.

[0057] Comparative Example 2 is an embodiment in which the flame retardant (B) was not used, but the flame retardancy was poor.

[0058] 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 and the like were poor.

Claims

1. 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. 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.

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); The synthetic leather is characterized in that the flame retardant (B) is 1,3-phenylenebis(2,6-dimethylphenyl phosphate).

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