TWI867504B - Moisture-curing urethane hot-melt resin composition, laminate and synthetic leather - Google Patents

Abstract

The present invention provides a moisture-curing urethane hot melt resin composition, which can form a cured material layer with good initial adhesion, heat resistance, hydrolysis resistance, alcohol resistance and abrasion resistance. The moisture-curing urethane hot melt resin composition of the present invention contains a reaction product of a polyol component and a polyisocyanate component, i.e., a urethane prepolymer having an isocyanate group. The polyol component includes a high molecular weight polyol component and a low molecular weight polyol component. The high molecular weight polyol component includes: a polyol (A), which is selected from: SA polyester polyol (A1); 1,4-BD/AA polyester polyol (A2) with a number average molecular weight (Mn) of 8,000 or more; and 1,6-HD/AA polyester polyol (A3) with an Mn of 6,000 or more; at least one of the group consisting; and a polyol (B), which is selected from: polyester polyol (B1) other than polyol (A); and polyether polyol (B2); at least one of the group consisting. The low molecular weight polyol component includes a trifunctional polyol (D) with a molecular weight of 300 or less and having three hydroxyl groups in one molecule. The ratio of polyol (A) to trifunctional polyol (D) satisfies: trifunctional polyol (D) (mmol)/polyol (A) (g) = 0.14 to 55 mmol/g.

Description

Moisture-curing urethane hot-melt resin composition, laminate and synthetic leather

The present invention relates to a moisture-hardening urethane hot-melt resin composition, a laminate and a synthetic leather.

The moisture-curing urethane hot melt resin composition is a composition that can be prepared without solvent at room temperature, and is a resin composition that hardens by moisture after being heated, melted and applied. Therefore, the moisture-curing urethane hot melt resin composition is widely used as various environmentally friendly adhesives because it does not use solvents. Such a moisture-curing urethane hot melt resin composition contains a urethane prepolymer, and the urethane prepolymer has functional groups such as isocyanate groups (NCO groups) in the molecule that can react with water (moisture) in the air or in the coated substrate to form a cross-linked structure.

When moisture-curing urethane hot melt resin compositions are used as various adhesives, the adhesive strength is exhibited by moisture curing, so it is difficult to exhibit excellent initial strength. Therefore, a technology for exhibiting excellent initial adhesion has been proposed. For example, Patent Document 1 discloses a reactive hot melt adhesive containing a "urethane prepolymer (1)" derived from an organic polyisocyanate compound (a) and a specific polyol (b1) and having an NCO group, and a "low molecular weight xylene resin (d1)" having no active hydrogen and having adhesiveness. [Prior art document] [Patent document]

[Patent Document 1] Japanese Patent Publication No. 5-065471

(Invent the problem you want to solve)

Urethane prepolymers used in moisture-curing urethane resin compositions can also be used as adhesives in the manufacture of synthetic leathers such as artificial leather or synthetic leather. Synthetic leather is used as a material for the manufacture of a variety of products such as shoes, clothing, bags, furniture, and vehicle interior materials (for example, dashboards, doors, consoles, seats). Previous synthetic leathers are generally laminated bodies in which a surface layer, an adhesive layer (hardening layer), and a base layer are sequentially laminated, and the hardening layer is formed by various urethane prepolymers. The hardening layer constituting the synthetic leather used in the above-mentioned various products is required to have not only good flexibility, but also heat resistance that can withstand the heat during manufacturing and processing.

The reactive hot melt adhesive disclosed in the above-mentioned patent document 1 can achieve a certain effect in terms of the initial adhesion after curing when it is cured in a specific humidity environment. However, such conventional moisture-curing urethane hot melt resin compositions have a low thermal softening point after curing and a smaller mesh structure after curing compared to two-component curing polyurethane resin compositions. Therefore, they are limited in use in applications such as the above-mentioned synthetic leather that require heat resistance or processing at high temperatures. Furthermore, when conventional moisture-curing urethane hot melt resin compositions are used for clothing, in addition to insufficient hydrolysis resistance to the extent that they can withstand washing, they also have insufficient abrasion resistance, and there is a risk of peeling off from the base material due to friction such as rubbing. In addition, due to the recent COVID-19 pandemic, resistance to alcohol disinfection is also required.

Therefore, the present invention intends to provide a moisture-curing urethane hot-melt resin composition that can form a hardened layer with good initial adhesion, heat resistance, flexibility, hydrolysis resistance, alcohol resistance and wear resistance. (Technical means to solve the problem)

The present invention provides a moisture-curing urethane hot-melt resin composition, which contains a urethane prepolymer having an isocyanate group, which is a reaction product of a polyol component and a polyisocyanate component; and the polyol component contains a high molecular weight polyol component and a low molecular weight polyol component; the high molecular weight polyol component includes: a polyol (A), which is selected from: a polyester polyol (A1) having a structural unit derived from sebacic acid; a polyester polyol (A2) having a structural unit derived from 1,4-butanediol and a structural unit derived from adipic acid and having a number average molecular weight of 8,000 or more; and a polyester polyol (A3) having a structural unit derived from 1,6-hexanediol. A polyester polyol (A3) having a number average molecular weight of 6,000 or more and a structural unit derived from adipic acid; at least one of the group consisting of; and a polyol (B) selected from: a polyester polyol (B1) other than the aforementioned polyol (A); and a polyether polyol (B2); at least one of the group consisting of; the aforementioned low molecular weight polyol component includes a trifunctional polyol (D) having a molecular weight of 300 or less and having 3 hydroxyl groups in one molecule; the ratio of the aforementioned polyol (A) to the aforementioned trifunctional polyol (D) satisfies: the aforementioned trifunctional polyol (D) (mmol)/the aforementioned polyol (A) (g) = 0.14 to 55 mmol/g. (Compared with the efficacy of the prior art)

According to the present invention, a moisture-curing urethane hot-melt resin composition can be provided, which can form a cured layer having good initial adhesion, heat resistance, flexibility, hydrolysis resistance, alcohol resistance and abrasion resistance.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

<Moisture-curing urethane hot-melt resin composition> The moisture-curing urethane hot-melt resin composition (hereinafter, sometimes referred to as "resin composition") of one embodiment of the present invention contains a urethane prepolymer which is a reaction product of a polyol component and a polyisocyanate component. The urethane prepolymer has a polyisocyanate group. The urethane prepolymer reacts with water (moisture) in the air or in a substrate coated with the resin composition through the polyisocyanate group to form a cross-linked structure, so that the resin composition having the urethane prepolymer as a main component has moisture-curing properties.

The polyol component used for the urethane prepolymer includes a high molecular weight polyol component and a low molecular weight polyol component. The high molecular weight polyol component includes the polyol (A) and the polyol (B) described below. The polyol (A) is at least one selected from the group consisting of a polyester polyol (A1) having a structural unit derived from sebacic acid; a polyester polyol (A2) having a structural unit derived from 1,4-butanediol and a structural unit derived from adipic acid and having a number average molecular weight of 8,000 or more; and a polyester polyol (A3) having a structural unit derived from 1,6-hexanediol and a structural unit derived from adipic acid and having a number average molecular weight of 6,000 or more. The polyol (B) is at least one selected from the group consisting of a polyester polyol (B1) other than the above-mentioned polyol (A); and a polyether polyol (B2). The low molecular weight polyol component includes a trifunctional polyol (D) having three hydroxyl groups in one molecule and a molecular weight of 300 or less. In addition, in the resin composition, the ratio of the polyol (A) to the trifunctional polyol (D) satisfies: trifunctional polyol (D) (mmol)/polyol (A) (g) = 0.14 to 55 mmol/g.

By means of the above-mentioned structure, the moisture-curing urethane hot-melt resin composition of the present embodiment can form a cured material layer having good initial adhesion, heat resistance, flexibility, hydrolysis resistance, alcohol resistance and abrasion resistance. In addition, the resin composition in one aspect has good stability over time in a molten state. Furthermore, the resin composition in one aspect can contribute to providing a synthetic leather having good cold-resistance bending, hydrolysis resistance, flexibility, abrasion resistance and heat resistance.

From the viewpoint of easily obtaining the above-mentioned effects, the preferred composition of the resin composition of this embodiment is described in detail below. In addition, in the description of the following compounds (each polyol component and polyisocyanate component, etc.), as long as there is no special limitation, the compounds in the description can be used in one or more than two kinds.

[Urethane prepolymer] Urethane prepolymer is a reaction product of a polyol component and a polyisocyanate component, and has an isocyanate group. The urethane prepolymer is preferably obtained by subjecting a polyol component to addition polymerization with a polyisocyanate component, and more preferably is a urethane prepolymer having an isocyanate group at the end obtained by subjecting a polyol component to addition polymerization with an excess of a polyisocyanate component.

The equivalent ratio (molar ratio; NCO group/OH group) of the isocyanate group component of the polyisocyanate group constituting the urethane prepolymer relative to the hydroxyl group (OH group) of the polyol component is preferably 1.1 to 2.2, more preferably 1.4 to 2.0, and further preferably 1.5 to 1.9. By making the NCO group/OH group within the above range, the processability at high temperature can be improved when used for clothing, and synthetic leather with better hand feel can be produced.

From the viewpoint of making the resin composition exhibit moisture curing properties, the urethane prepolymer is preferably the main component of the resin composition. The content of the urethane prepolymer can be 100% by mass, preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 90% by mass or more, based on the mass of the solid content of the resin composition.

[Polyol component] The polyol component used for urethane prepolymer includes a high molecular weight polyol component and a low molecular weight polyol component. The high molecular weight polyol component is a polyol group with a higher molecular weight than the low molecular weight polyol component, and preferably a polymer is used. The low molecular weight polyol component is a polyol group with a lower molecular weight than the high molecular weight polyol component.

(Polymer polyol component) The polymer polyol component used for the urethane prepolymer includes the polyol (A) described below and the polyol (B) other than the polyol (A). Among the polyol components, the polymer polyol component is preferably the main component of the polyol component, and is preferably used in an amount greater than the low molecular weight polyol component. The ratio of the polymer polyol component in the polyol component is preferably 60 to 99.8% by mass, more preferably 80 to 99.5% by mass, and further preferably 90 to 99% by mass, based on the total amount of the polyol component.

(Polyol (A)) The polyol (A) is at least one selected from the group consisting of the following polyester polyols (A1) to (A3). (A1): Polyester polyol (A1) having a structural unit derived from sebacic acid (A2): Polyester polyol (A2) having a structural unit derived from 1,4-butanediol and a structural unit derived from adipic acid and having a number average molecular weight of 8,000 or more (A3): Polyester polyol (A3) having a structural unit derived from 1,6-hexanediol and a structural unit derived from adipic acid and having a number average molecular weight of 6,000 or more

The polyester polyols (A1) to (A3) are crystalline polyols that are solid at 60°C. By using the polyol (A), the resin composition can form a cured layer with good initial adhesion and flexibility, and it is easy to obtain a synthetic leather with further good cold-resistant flexibility, flexibility and heat resistance. From these viewpoints, it is preferred to use at least the polyester polyol (A1) among the polyols (A).

The polyester polyol (A1) has a structural unit derived from sebacic acid (SA). Hereinafter, a polyester polyol having a structural unit derived from sebacic acid may be described as "SA-based polyester polyol". The SA-based polyester polyol (A1) is a reaction product of sebacic acid and a diol, and is a difunctional (hydroxyl group number is 2) polyol (diol). Preferably, the SA-based polyester polyol (A1) is obtained by polymerizing sebacic acid and a diol.

Diols used for SA polyester polyol (A1) include, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 1,9-nonanediol, and neopentyl glycol. Among them, 1,6-hexanediol is preferred. That is, polyester polyol (A1) is preferably a polyester polyol having a structural unit derived from sebacic acid and a structural unit derived from 1,6-hexanediol (hereinafter sometimes described as ("1,6-HD/SA polyester polyol")).

The number average molecular weight (Mn) of the SA polyester polyol (A1) is preferably 2,000 or more, more preferably 3,000 or more, further preferably 5,000 or more, and preferably 20,000 or less. In this specification, the "number average molecular weight (Mn)" is a value converted to standard polystyrene measured by gel permeation chromatography (GPC). Specifically, the measurement is performed by GPC analysis under the following conditions with dimethylformamide (DMF) as the mobile phase (the same applies to the following examples). ・Measurement device: High-speed GPC device (trade name: "HLC-8220GPC", manufactured by Tosoh Corporation) ・Column: TSK gel Super HM-N × 2, TSK guardcolumn Super H-H × 1 ・Detector: RI (differential refractometer) ・Column temperature: 40℃ ・Flow rate: 0.5 mL/min ・Injection volume: 50 μL

The polyester polyol (A2) has a structural unit derived from 1,4-butanediol and a structural unit derived from adipic acid. Hereinafter, a polyester polyol having a structural unit derived from 1,4-butanediol and a structural unit derived from adipic acid may be recorded as "1,4-BD/AA polyester polyol". The 1,4-BD/AA polyester polyol (A2) is a reaction product of 1,4-butanediol and adipic acid, and is a bifunctional (hydroxyl group 2) polyol (diol). Preferably, the polyester polyol (A2) is obtained by polymerizing 1,4-butanediol and adipic acid.

The number average molecular weight (Mn) of the 1,4-BD/AA polyester polyol (A2) is 8,000 or more. By using the 1,4-BD/AA polyester polyol (A2) having an Mn of 8,000 or more, the resin composition can form a cured layer with good initial adhesion, and it is easy to obtain a synthetic leather with further good cold-resistant flexibility and softness. The Mn of the 1,4-BD/AA polyester polyol (A2) is preferably 20,000 or less.

The polyester polyol (A3) has a structural unit derived from 1,6-hexanediol and a structural unit derived from adipic acid. Hereinafter, the polyester polyol having a structural unit derived from 1,6-hexanediol and a structural unit derived from adipic acid is sometimes described as "1,6-HD/AA polyester polyol". The 1,6-HD/AA polyester polyol (A3) is a reaction product of 1,6-hexanediol and adipic acid, and is a bifunctional (hydroxyl group number 2) polyol (diol). Preferably, the polyester polyol (A3) is obtained by polymerizing 1,6-hexanediol and adipic acid.

The number average molecular weight (Mn) of the 1,6-HD/AA polyester polyol (A3) is 6,000 or more. By using the 1,6-HD/AA polyester polyol (A3) having an Mn of 6,000 or more, the resin composition can form a cured layer with good initial adhesion, and it is easy to obtain a synthetic leather with further good cold-resistant flexibility and softness. The Mn of the 1,6-HD/AA polyester polyol (A3) is preferably 20,000 or less.

From the viewpoint that the above-mentioned effect of the polyol (A) and the effects of other polyols described below are easily expressed in a well-balanced manner, the ratio of the polyol (A) in the high molecular weight polyol component is preferably 0.5 to 30 mass %, more preferably 1 to 20 mass %, and further preferably 2 to 15 mass %, based on the total amount of the high molecular weight polyol component.

(Polyol (B)) The polyol (B) is at least one selected from the group consisting of polyester polyol (B1) other than the above-mentioned polyol (A); and polyether polyol (B2).

The polyester polyol (B1) and the polyether polyol (B2) other than the polyol (A) are polyols with lower crystallinity than the polyol (A) and can be in a liquid state at 60° C. By using at least one of the polyester polyol (B1) and the polyether polyol (B2), the resin composition can form a hardened layer with good flexibility, and it is easy to obtain a synthetic leather with good cold-resistant flexibility and flexibility.

The polyester polyol (B1) is a polyester polyol other than the above-mentioned SA polyester polyol (A1), 1,4-BD/AA polyester polyol (A2) having an Mn of 8,000 or more, and 1,6-HD/AA polyester polyol (A3) having an Mn of 6,000 or more. The polyester polyol (B1) is a reaction product of dicarboxylic acids and diols, and is a bifunctional (hydroxyl group number 2) polyol (diol). Preferably, the polyester polyol (B1) is obtained by polymerizing dicarboxylic acids and diols.

Examples of dicarboxylic acids used in the polyester polyol (B1) include aliphatic dicarboxylic acids such as succinic acid, adipic acid, glutaric acid and azelaic acid, and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid. Examples of diols used in the polyester polyol (B1) include the same diols as those described in the description of the SA polyester polyol (A1).

Specific examples of the polyester polyol (B1) include polyethylene adipate, polybutylene adipate, polyhexylene adipate, polyneopentyl adipate, polyethylene/butylene adipate, polyneopentyl/hexylene adipate, poly-3-methylpentanediol adipate, and polybutylene terephthalate.

Among the polyester polyols (B1), 1,4-BD/AA polyester polyols (B1) having structural units derived from 1,4-butanediol and structural units derived from adipic acid and having a number average molecular weight (Mn) of 1,000 to 5,000 are preferred. Among them, polybutylene adipate having an Mn of 1,200 to 4,000 is more preferred, and polybutylene adipate having an Mn of 1,500 to 3,000 is further preferred.

The polyether polyol (B2) is a bifunctional (hydroxyl group-2) polyol (diol). The polyether polyol (B2) is obtained, for example, by polymerizing or copolymerizing any one of alkylene oxides (ethylene oxide, propylene oxide, and butylene oxide) and heterocyclic ethers (tetrahydrofuran and 2-methyltetrahydrofuran). In addition, the polyether polyol (B2) can also be obtained by the dehydration condensation reaction of a diol such as 1,3-propylene glycol.

Examples of polyether polyols (B2) include polyethylene glycol, polypropylene glycol, polyethylene glycol-polytetramethylene glycol (block or random), polytrimethylene ether glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol, etc. Among them, polyethylene glycol, polytrimethylene ether glycol, and polytetramethylene ether glycol are preferred from the viewpoint of flexibility.

In one aspect of the moisture-curing urethane hot-melt resin composition, from the viewpoint of further preparing an environmentally friendly composition, the polyol (B) (the polyester polyol (B1) and/or the polyether polyol (B2)) preferably includes a polyol (B _b ) derived from a plant raw material. The polyol (B _b ) derived from a plant raw material may also be referred to as a biopolyol (B _b ). The polyol (B _b ) derived from a plant raw material may include, for example, polyester polyols (B _b 1) and polyether polyols (B b 2) using one or more plant-derived diols (preferably diols having 2 to 4 carbon atoms) as raw materials, and polyether polyols ( _{B b 2} ) using tetrahydrofuran or the like derived from plants. Examples of the plant-derived diols having 2 to 4 carbon atoms include plant-derived ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, and 1,4-butylene glycol.

From the viewpoint that the above-mentioned effects of the polyol (B) and the effects of other polyols are easily expressed in a well-balanced manner, the ratio of the polyol (B) in the high molecular weight polyol component is preferably 10 to 98 mass %, more preferably 50 to 95 mass %, and further preferably 60 to 90 mass %, based on the total amount of the high molecular weight polyol component.

(Polycarbonate polyol (C)) The high molecular weight polyol component preferably further includes polycarbonate polyol (C) together with the above-mentioned polyol (A) and polyol (B). By using polycarbonate polyol (C), it is easy to obtain a hardened layer and synthetic leather with further improved hydrolysis resistance and wear resistance.

Polycarbonate polyol (C) is obtained by condensing diols such as 1,4-butanediol and 1,6-hexanediol with dialkyl carbonates during a de-alcoholization reaction. Polycarbonate polyol (C) is a bifunctional (two hydroxyl groups) polyol (diol), and either crystalline or amorphous polyols can be used.

Examples of polycarbonate polyols (C) include polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyneopentyl carbonate diol, polyhexamethylene carbonate diol, poly(1,4-cyclohexane carbonate dimethylene) diol, and random/block copolymers thereof. Among these, polyhexamethylene carbonate diol (1,6-hexanediol-based polycarbonate diol), poly(tetramethylene/decamethylene) carbonate diol (1,4-butanediol and 1,10-decanediol-based polycarbonate diol), and poly(pentamethylene/hexamethylene) carbonate diol (1,5-pentanediol and 1,6-hexanediol-based carbonate diol) are preferred.

In one aspect of the moisture-curing urethane hot-melt resin composition, from the viewpoint of further preparing an environmentally friendly composition, the polycarbonate polyol (C) preferably includes a polycarbonate polyol (C _b ) derived from a plant raw material. The polycarbonate polyol (C _b ) derived from a plant raw material may also be referred to as a biomass polycarbonate polyol (C _b ). The polycarbonate polyol (C _b ) derived from a plant raw material may include, for example, one or more polycarbonate polyols (C _b ) using plant-derived diols (preferably diols having 2 to 10 carbon atoms) as raw materials. Examples of plant-derived diols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, and 1,10-decanediol, which are derived from plants.

From the viewpoint that the above-mentioned effects of the polycarbonate polyol (C) and the effects of the polyols (A) and (B) are easily expressed in a well-balanced manner, the proportion of the polycarbonate polyol (C) in the polymer polyol component is preferably 0 to 80 mass %, more preferably 4 to 40 mass %, and further preferably 8 to 30 mass %, based on the total amount of the polymer polyol component.

When the polymer polyol component includes polycarbonate polyol (C), the total amount of polyol (B) and polycarbonate polyol (C) is preferably greater than the amount of polyol (A) from the viewpoint of easily obtaining the moisture-curing urethane hot-melt resin composition targeted by the present invention. In addition, in this case, the ratio of the total amount (total mass) of polyol (A), polyol (B) and polycarbonate polyol (C) to the total amount (total mass) of the polyol components is preferably 90 mass% or more. The total amount of polyol (A), polyol (B) and polycarbonate polyol (C) may also be the total amount of the polymer polyol component. Therefore, the ratio of the high molecular weight polyol component in the polyol component is as described above, and the total ratio of the polyol (A), the polyol (B) and the polycarbonate polyol (C) relative to the total amount of the polyol component is preferably 99.8 mass % or less, more preferably 99.5 mass % or less, and further preferably 99 mass % or less.

(Low molecular weight polyol component) The low molecular weight polyol component used in the urethane prepolymer is preferably used in a smaller amount than the above-mentioned high molecular weight polyol component in the polyol component. The ratio of the low molecular weight polyol component in the polyol component is preferably 0.2 to 40% by mass, more preferably 0.5 to 20% by mass, and further preferably 1 to 10% by mass, based on the total amount of the polyol component.

(Trifunctional polyol (D)) The low molecular weight polyol component used for the urethane prepolymer includes a trifunctional polyol (D) having a molecular weight (chemical formula weight) of 300 or less and having three hydroxyl groups in one molecule. In addition to the trifunctional polyol (D), the low molecular weight polyol component may also include other low molecular weight polyols (E) as needed.

Since the trifunctional polyol (D) has three hydroxyl groups in one molecule, it can also be called a triol (D). By using this specific low molecular weight trifunctional polyol (D), the moisture-curing urethane hot melt resin composition of the present invention can be obtained.

Examples of the trifunctional polyol (D) having a molecular weight of 300 or less include glycerol, trihydroxymethylethane, trihydroxymethylpropane, butanetriol, pentanetriol, hexanetriol, heptanetriol, and octantriol. Among them, glycerol and trihydroxymethylpropane are preferred.

The relationship between the amount of trifunctional polyol (D) used and the aforementioned polyol (A) is in the following range. That is, the ratio of polyol (A) to trifunctional polyol (D) satisfies: trifunctional polyol (D) (mmol)/polyol (A) (g) = 0.14 to 55 mmol/g. By making the trifunctional polyol (D) 0.14 mmol or more and 55 mmol or less relative to the unit mass (1 g) of polyol (A), the moisture-curing urethane hot-melt resin composition of the present invention can be obtained. From the viewpoint of easily obtaining the target resin composition, trifunctional polyol (D) (mmol)/polyol (A) (g) is preferably 0.3 mmol/g or more, more preferably 0.5 mmol/g or more, and further preferably 1 mmol/g or more. Furthermore, the ratio of trifunctional polyol (D) (mmol)/polyol (A) (g) is preferably 30 mmol/g or less, more preferably 20 mmol/g or less, and even more preferably 10 mmol/g or less.

From the viewpoint that the above-mentioned effect of the trifunctional polyol (D) is easily exhibited, the ratio of the trifunctional polyol (D) in the low molecular weight polyol component is preferably 50 to 100 mass %, more preferably 70 to 100 mass %, and further preferably 90 to 100 mass %, based on the total amount of the low molecular weight polyol component.

Other low molecular weight polyols (E) include, for example, low molecular weight diols and tetrafunctional or higher low molecular weight polyols. Examples of low molecular weight diols include the same diols as those described in the description of SA polyester polyol (A1). Examples of tetrafunctional or higher low molecular weight polyols include diglycerol, pentaerythritol, and dipentaerythritol.

[Polyisocyanate component] The polyisocyanate component used for the urethane prepolymer is not particularly limited, and a compound having two or more isocyanate groups in one molecule (polyisocyanate) can be used. Examples of polyisocyanates include aromatic diisocyanates, alicyclic diisocyanates, aliphatic diisocyanates, and aliphatic diisocyanate modified products. Among them, aromatic diisocyanates, alicyclic diisocyanates, and aliphatic diisocyanate modified products are preferred, aromatic diisocyanates and aliphatic diisocyanate modified products are more preferred, and aromatic diisocyanates are further preferred.

Examples of the aromatic diisocyanate include 4,4'-diphenylmethane diisocyanate (MDI), 2,2'-MDI, 2,4'-MDI, 2,4-toluene diisocyanate (TDI), 2,6-TDI, meta-xylylene diisocyanate (XDI), 1,4-phenylene diisocyanate, 4-methoxy-1,3-diisobenzocyanate, 4-isopropyl-1,3-diisobenzocyanate, 4-butoxy-1,3-diisobenzocyanate, 2,4-diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate, and biphenyl diisocyanate. Among these, MDI is preferred.

Examples of the alicyclic diisocyanate include 4,4'-methylenebis(cyclohexyl isocyanate), isophorone diisocyanate (IPDI), 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated XDI), dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI), and 1-methylcyclohexane-2,4-diisocyanate (hydrogenated TDI).

Examples of the aliphatic diisocyanate include 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), and 1,10-decamethylene diisocyanate.

Examples of modified aliphatic diisocyanates include isocyanurate, allophanate, biuret, and adducts of aliphatic diisocyanates with polyols (trihydroxymethylpropane, etc.). Among these, allophanate of aliphatic diisocyanates is preferred, and allophanate of HDI is more preferred.

[Production method of urethane prepolymer] Urethane prepolymer can be produced, for example, by reacting a polyol component with a polyisocyanate component at preferably 60 to 150°C, more preferably 60 to 110°C, by a single-shot method or a multi-step method until the product reaches a theoretical NCO group content (mass %). When the polyol component and the polyisocyanate component react, a catalyst can also be used as needed. Examples of the catalyst include: metal salts or organic metal derivatives such as dibutyltin laurate, dioctytin laurate, stannous octoate, lead octoate, and tetra-n-butyl titanium; organic amines such as triethylamine; 1,8-diazabicycloundecene catalysts, etc.

The polyol component and the polyisocyanate component are preferably reacted in the absence of a solvent such as an organic solvent, that is, in the absence of a solvent. By reacting the polyol component and the polyisocyanate component in the absence of a solvent such as an organic solvent, a solvent-free urethane prepolymer can be obtained.

When producing the urethane prepolymer, it is preferred that various polyols be used in amounts within the above-mentioned range of ratios for the polyol components. For example, with respect to the high molecular weight polyol component, it is preferred that the polyol (A), the polyol (B), and the polycarbonate polyol (C) used as required be used in amounts within the above-mentioned range of ratios for the high molecular weight polyol component. In addition, it is preferred that the trifunctional polyol (D) used as the low molecular weight polyol component be used in an amount within the above-mentioned range of ratios for the low molecular weight polyol component. Preferably, the amount of the trifunctional polyol (D) used is preferably 0.5 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, and further preferably 0.5 to 10 parts by mass, relative to 100 parts by mass of the total of the polyol (A), the polyol (B) and the polycarbonate polyol (C).

In the moisture-curing urethane hot-melt resin composition, various additives such as thermoplastic resin, adhesive resin, catalyst, pigment, antioxidant, ultraviolet absorber, surfactant, flame retardant, filler and foaming agent can be appropriately blended as needed. However, the moisture-curing urethane hot-melt resin composition may be substantially composed of the aforementioned urethane prepolymer. Even when the resin composition is substantially composed of the urethane prepolymer, the composition may contain components that are inevitably present due to the production of the urethane prepolymer.

As described above, the moisture-curing urethane hot-melt resin composition has good stability over time in a molten state in one aspect, and can form a cured layer with good initial adhesion, heat resistance, alcohol resistance, flexibility, hydrolysis resistance, and abrasion resistance. Therefore, even in applications such as synthetic leather that require heat resistance or high-temperature processing, or applications such as clothing that require washing resistance or abrasion resistance, the resin composition can be appropriately used, and the expansion of processability and applications can be expected.

Furthermore, by using the moisture-curing urethane hot-melt resin composition, a laminate such as synthetic leather having good cold-resistance bending, hydrolysis resistance, softness, wear resistance, and heat resistance can be provided. For example, the resin composition can be used as a hot-melt adhesive for bonding a base layer such as a base fabric and a skin layer constituting synthetic leather. Furthermore, since the resin composition can form a cured layer having good initial adhesion and wear resistance, a cured layer having the properties of a skin layer such as wear resistance while maintaining good adhesion to a base layer such as a base fabric can be formed.

<Laminate> A laminate of one embodiment of the present invention has a substrate and a cured layer of the moisture-curing urethane hot melt resin composition described above provided on the substrate. When the resin composition described above is used as a hot melt adhesive, the substrate described above can be used as one adherend and another substrate can be used as another adherend to bond the two. As substrates (adherends), in addition to the skin layer or substrate layer for synthetic leather described below, there can also be listed: optical films, optical plates, flexible printed circuit boards, glass substrates, and substrates obtained by vapor-depositing ITO on these substrates, and other film-like or sheet-like substrates, as well as metal and non-metallic (plastic, glass, etc.) substrates.

The laminate can be manufactured by applying a moisture-hardening urethane hot melt resin composition preferably melted at 80-130°C to a substrate and hardening it by moisture to form a hardened layer. When the resin composition is used as a hot melt adhesive, the melted resin composition is applied to a substrate, and then another substrate is attached thereto and hardened by moisture.

The method for applying the moisture-curing urethane hot melt resin composition to the substrate is not particularly limited, and a coating method conventionally used in hot melt adhesives can be appropriately adopted. Examples of coating methods include comma coating, scraper coating, roller coating, screen coating, T-die coating, fiber coating, gravure transfer coating with engraving on a roller, and die coating with a gear pump.

The laminate of this embodiment can also be formed into a synthetic leather described below. In addition, the cured layer of the moisture-curing urethane hot-melt resin composition used in the laminate has good initial adhesion and wear resistance as described above, so it can form a skin layer that is directly in contact with a base material such as a base fabric constituting the synthetic leather. Therefore, a synthetic leather having a two-layer structure of a base material such as a base fabric and a skin layer composed of the cured layer provided on the base material can be provided.

A synthetic leather having a cured layer of a moisture-curing urethane hot-melt resin composition as a skin layer can be manufactured, for example, as follows. First, the moisture-curing urethane hot-melt resin composition forming the skin layer is melted by the above-mentioned coating method and coated on a release paper, a base material such as a base cloth is bonded thereto, and the resin composition is cured by moisture to form a cured layer (skin layer). Next, by peeling off the release paper, a synthetic leather having a two-layer structure of a base material and a skin layer consisting of a cured layer provided on the base material can be obtained. In addition, when bonding a base material such as a base cloth, for example, a layer press having a roller or the like can be used for pressure bonding. Furthermore, when the resin composition is hardened by moisture, it can be matured under specific temperature and humidity conditions.

<Synthetic leather> The synthetic leather of one embodiment of the present invention has a base layer, a surface layer, and an adhesive layer disposed between and connecting the base layer and the surface layer. In the synthetic leather, the adhesive layer is formed by a cured layer of the aforementioned moisture-curing urethane hot-melt resin composition.

The base fabric constituting the substrate layer may be, for example, a woven fabric formed by twill weave, plain weave, etc., a raised fabric obtained by mechanically raising the cotton fabric of the woven fabric, rayon fabric, nylon fabric, polyester fabric, Kevlar (registered trademark) fabric, non-woven fabric (polyester, nylon, various latex), various films, sheets, etc. The surface layer may be formed by a solution-type urethane resin composition, water-based urethane, and a coating for forming the surface layer such as thermoplastic urethane (TPU).

The synthetic leather can be manufactured, for example, as follows. First, a coating for forming a skin layer is applied on a release paper by a known and disclosed method such as comma coating, blade coating, roller coating, gravure coating, die coating, or spray coating. After the applied coating is dried appropriately to form a skin layer, the aforementioned moisture-curing urethane hot-melt resin composition melted on the skin layer is applied by the aforementioned coating method, and a base material layer such as a base cloth is attached thereto, and pressed and bonded by a laminating press or the like. Thereafter, the coating is aged under specific temperature and humidity conditions as needed to form a cured layer (adhesive layer). Then, by peeling off the self-release paper, the target synthetic leather can be obtained.

A surface treatment agent may be applied to the surface of the surface layer constituting the synthetic leather (including the surface layer composed of the hardened material layer described in the above description of the laminate). By surface treating the surface layer with the surface treatment agent, a synthetic leather of a quality further suitable for commercialization can be obtained. The synthetic leather of this embodiment is preferably used as a material constituting shoes, clothing, bags, furniture, and vehicle interior materials (e.g., dashboards, doors, consoles, seats), etc.

In addition, as described above, in one embodiment of the present invention, the following structure can be adopted. [1] A moisture-curing urethane hot-melt resin composition, which contains a urethane prepolymer having an isocyanate group, which is a reaction product of a polyol component and a polyisocyanate component; and the polyol component includes a high molecular weight polyol component and a low molecular weight polyol component; the high molecular weight polyol component includes: A polyol (A) selected from the group consisting of: a polyester polyol (A1) having a structural unit derived from sebacic acid; a polyester polyol (A2) having a structural unit derived from 1,4-butanediol and a structural unit derived from adipic acid and having a number average molecular weight of 8,000 or more; and a polyester polyol (A3) having a structural unit derived from 1,6-hexanediol and a structural unit derived from adipic acid and having a number average molecular weight of 6,000 or more; and a polyol (B) selected from the group consisting of: a polyester polyol (B1) other than the aforementioned polyol (A); and a polyether polyol (B2); the aforementioned low molecular weight polyol component comprises a trifunctional polyol (D) having a molecular weight of 300 or less and having three hydroxyl groups in one molecule; The ratio of the polyol (A) to the trifunctional polyol (D) satisfies: the trifunctional polyol (D) (mmol)/the polyol (A) (g) = 0.14 to 55 mmol/g. [2] The moisture-curing urethane hot-melt resin composition as described in [1] above, wherein the polyol (B) comprises a polyol (B _b ) derived from a plant raw material. [3] The moisture-curing urethane hot-melt resin composition as described in [1] or [2] above, wherein the polymer polyol component further comprises a polycarbonate polyol (C). [4] The moisture-curing urethane hot-melt resin composition as described in [3] above, wherein the polycarbonate polyol (C) comprises a polycarbonate polyol (C _b ) derived from a plant raw material. [5] A moisture-curing urethane hot-melt resin composition as described in [3] or [4] above, wherein the total amount of the polyol (B) and the polycarbonate polyol (C) is greater than the amount of the polyol (A); and the total ratio of the polyol (A), the polyol (B) and the polycarbonate polyol (C) to the total amount of the polyol components is 90% by mass or more. [6] A laminate comprising a substrate and a cured layer of the moisture-curing urethane hot-melt resin composition as described in any one of [1] to [5] above disposed on the substrate. [7] A synthetic leather comprising a base layer, a surface layer, and an adhesive layer disposed between and connected to the base layer; wherein the adhesive layer is a cured layer of a moisture-curing urethane hot-melt resin composition as described in any one of [1] to [5]. [Example]

Hereinafter, the present invention will be specifically described based on embodiments, but the present invention is not limited to these embodiments.

<Materials used> The high molecular weight polyol materials used are shown in Table 1 below.

[Table 1] Raw materials and material systems Product Name/Manufacturer Name Mn Remarks Polyol (A) Polyester polyol (A1) 1,6-HD/SA polyester polyol Ac1050SA (Taiwan Fine Chemicals Corporation) 5000 Polyester polyol (A2) 1,4-BD/AA polyester polyol AC1580 (Taiwan Fine Chemicals Corporation) 8000 Polyester polyol (A3) 1,6-HD/AA polyester polyol AC2660 (Taiwan Fine Chemicals Corporation) 6000 Polyol (B) Polyester polyol (B1-1) 1,4-BD/AA polyester polyol TPEP 85 (Taiwan Fine Chemicals Corporation) 2000 Polyester polyol (B1-2) 1,4-BD/AA polyester polyol AC1570 (Taiwan Fine Chemicals Corporation) 7000 Polyester polyol (B1-3) 1,6-HD/AA polyester polyol AC2650 (Taiwan Fine Chemicals Corporation) 5000 Polyether polyol (B2-1) Polytetramethylene ether glycol PTMG2000 (Mitsubishi Chemical Corporation) 2000 Polyether polyol (B2-2) Polytetramethylene ether glycol Bio PTMG2000 (Mitsubishi Chemical Corporation) 2000 Plant-derived Polyether polyol (B2-3) 1,3-Propanediol Polyether Polyol VELVETOL H-2000 (Made by Alexa) 2000 Plant-derived Polyether polyol (B2-4) Polyethylene glycol PEG 2000 (manufactured by Sanyo Chemical Industries, Ltd.) 2000 Polycarbonate polyol (C) Polycarbonate polyol (C1) Polyhexamethylene carbonate glycol UH200NT (made by UBE) 2000 Crystallinity Polycarbonate polyol (C2) Poly(tetramethylene/decamethylene) carbonate diol BENEBioL NL2030DB (Made by Mitsubishi Chemical Corporation) 2000 Crystalline; Plant-derived Polycarbonate polyol (C3) Poly(pentamethylene/hexamethylene) carbonate diol T5652 (Made by Asahi Kasei Corporation) 2000 Amorphous

<Manufacturing of moisture-curing urethane hot melt resin composition> (Example 1) In a glass reaction vessel equipped with a stirrer, a thermometer and a gas inlet, a polyol component and a polyisocyanate component are placed and mixed, and the reaction vessel is heated and depressurized to perform a dehydration treatment, and then nitrogen is sealed in, and the reaction is carried out while stirring for 120 minutes at an internal temperature of 100°C. The above-mentioned polyol component uses a high molecular weight polyol component (total 100 parts by mass) composed of 10 parts by mass of polyester polyol (A1), 45 parts by mass of polyester polyol (B1-1) and 45 parts by mass of polyether polyol (B2-1), and 0.5 parts by mass of trihydroxymethylpropane, which is a trifunctional polyol (D) component with a molecular weight of less than 300. The ratio of polyol (A) to trifunctional polyol (D) was set to trifunctional polyol (D) (mmol)/polyol (A) (g) = 0.37 mmol/g. As the above-mentioned polyisocyanate component, 22.35 parts by weight of 4,4'-diphenylmethane diisocyanate (MDI) was used, and the molar ratio of the NCO group of MDI to the OH group of the polyol component (NCO group/OH group) was set to 1.7. In this way, the urethane prepolymer of Example 1 was obtained.

(Examples 2 to 17 and Comparative Examples 1 to 10) Except that the type and amount of the polyol component and the amount of the polyisocyanate component (MDI) used were changed to those shown in the upper part of Table 2 (Tables 2-1 to 2-6) below, urethane prepolymers of each example were obtained in the same manner as in Example 1. The values of "trifunctional polyol (D)/polyol (A) [mmol/g]" and "NCO group/OH group (molar ratio)" are shown simultaneously in the middle part of Table 2 along with the changes in the amounts of the polyol component and the polyisocyanate component used. In addition, Comparative Example 10, where trifunctional polyol (D) (mmol)/polyol (A) (g) = 56.0 mmol/g, gelled during the stirring reaction and could not be evaluated as described below.

<Evaluation> The urethane prepolymer obtained in each example was regarded as the moisture-curing urethane hot-melt resin composition of each example (hereinafter sometimes referred to as "hot-melt resin composition"), and the following items were evaluated. In the evaluation standard of each item, AA, A and B are acceptable good levels, and C is unacceptable level. The evaluation results are shown in Table 2.

(Time stability in molten state) The hot melt resin composition of each example was heated to 100°C and melted, and the change in viscosity over time and the visual confirmation of sediment were carried out under the conditions of 100°C and 24 hours. The viscosity of the hot melt resin composition was measured using a BM type viscometer (Tokyo Metering Co., Ltd.) at rotor No. 4, 30 rpm and 100°C. Based on the above-mentioned time change in viscosity (viscosity change rate) and the presence or absence of sediment, the time stability of the hot melt resin composition in the molten state was evaluated according to the following evaluation criteria. The viscosity change rate is calculated by the following formula: Viscosity change rate (%) = {(viscosity after 24 hours at 100°C - initial viscosity at 100°C) / initial viscosity at 100°C} × 100. AA: No sediment, and the viscosity change rate is less than 20%. A: No sediment, and the viscosity change rate is 20% or more and less than 50%. B: Sediment, and the viscosity change rate is less than 100%. C: Sediment, and the viscosity change rate is 100% or more.

(Production of evaluation film) The hot-melt resin composition of each example was melted at 100°C and coated on release paper to a film thickness of 50 to 70 μm. After that, it was aged for 72 hours at a temperature of 25°C and a relative humidity of 60% (60% RH), and then stored at room temperature (20°C) for 1 day to obtain an evaluation film with release paper.

(Thermal Softening Point) The thermal softening point was measured using an evaluation film (width 1.5 cm, length 6 cm) obtained by peeling off the release paper from the evaluation film with release paper. Specifically, first, as shown in FIG1, a clamp 12 was installed above and below the evaluation film 10, and the clamp 12 was further fixed with Cellotape (registered trademark). A weight 14 with a load of 450 g/ ^cm2 was installed and hung on the clamp 12, thereby preparing a sample 16. In addition, the central part of the evaluation film 10 was not covered with Cellotape (registered trademark) for 2 cm in the longitudinal direction. Next, as shown in FIG2 , the fixture 12 without the sample 16 and the weight 14 is mounted on the rotating disk 22 of the gear oven 20. Thereafter, the temperature inside the gear oven 20 is raised from room temperature at a rate of 3°C/min while the rotating disk 22 is rotated at 5 rpm. The temperature (°C) when the evaluation film 10 is cut or stretched to 2 times is taken as the thermal softening point. Based on the value of the thermal softening point (°C), the heat resistance of the thermal softening point is evaluated according to the following evaluation criteria. The higher the thermal softening point, the higher the heat resistance as a film. A: The thermal softening point is above 185°C. B: The thermal softening point is above 170°C and less than 185°C. C: The thermal softening point is less than 170°C.

(Alcohol resistance) Cut the evaluation film obtained by peeling off the release paper from the evaluation film with release paper into a 50 mm × 50 mm piece and immerse it in 25°C ethanol placed in a culture dish for 10 minutes. After 10 minutes, take out the evaluation film from the ethanol, visually check the state of the evaluation film, and evaluate the alcohol resistance according to the following evaluation criteria. The following linear expansion rate is calculated by the following formula: Linear expansion rate (%) = (length of one side of the evaluation film after immersion (mm) / length of one side of the evaluation film before immersion (50 mm)) × 100. AA: The linear expansion rate of one side of the evaluation film is less than 120%. A: The linear expansion rate of one side of the evaluation film is 120% or more and less than 150%. B: The linear expansion rate of one side of the evaluation film is 150% or more. C: The evaluation film is dissolved.

(Initial Adhesion) The hot melt resin composition of each example was heated to 100°C and melted, and uniformly coated on a PET film (width 3 cm) with a coating thickness of 100 μm/wet to form a coating layer of the hot melt resin composition. After coating, the base fabric (woven fabric) was immediately pressed and bonded by a layer press with a roll temperature of 30°C and a layer gap set to 70% relative to the total thickness of the base fabric, coating layer and PET film. After 10 minutes of bonding, the bonding strength was measured with a digital dynamometer (manufactured by Nidec SHIMPO Co., Ltd.), and the initial adhesion was evaluated according to the following evaluation criteria. In addition, when the bonding strength after 10 minutes is less than 0.2 kg/3 cm, the bonding strength after 10 minutes is considered acceptable if it is 0.2 kg/3 cm or more, based on the understanding that the risk of defects may increase due to the re-peeling or wrinkling of the resin layer caused by the base fabric and the hot-melt resin composition during the subsequent processing. A: Bonding strength is 0.4 kg/3 cm or more. B: Bonding strength is 0.2 kg/3 cm or more and less than 0.4 kg/3 cm. C: Bonding strength is less than 0.2 kg/3 cm.

<Preparation of synthetic leather for evaluation> (1) Preparation of the surface layer The surface layer of the synthetic leather was prepared as follows. First, 100 parts by mass of a solution-type urethane resin (trade name "RESAMIN NE-8875-30M", manufactured by Dainichi Seika Co., Ltd.), 10 parts by mass of a colorant (trade name "SeicaSeven BS-780(S) Black", manufactured by Dainichi Seika Co., Ltd.), 25 parts by mass of methyl ethyl ketone (MEK) and 25 parts by mass of dimethylformamide (DMF) were mixed as a diluent to prepare a urethane resin composition for the surface layer. Next, the prepared urethane resin composition was evenly applied on the release paper with a rod coater at a coating amount of 250 μm/wet. Afterwards, it was dried at 120°C for 5 minutes to obtain a surface layer with a film thickness of 30 to 50 μm formed on the release paper.

(2) Preparation of standard synthetic leather for softness evaluation Using the surface layer and adhesive obtained in the above "(1) Preparation of surface layer", standard synthetic leather for softness evaluation was prepared as follows. First, 100 parts by weight of a solution-type urethane resin (trade name "RESAMINNE UD-8373BL", manufactured by Dainichi Seika Co., Ltd.), 12 parts by weight of an isocyanate crosslinking agent (trade name "RESAMINNE NE", manufactured by Dainichi Seika Co., Ltd.), and 30 parts by weight of methyl ethyl ketone (MEK) and 30 parts by weight of dimethylformamide (DMF) as a diluent were mixed to prepare an adhesive. Next, the prepared adhesive is applied to the skin layer on the release paper obtained in the above "(1) Preparation of skin layer" to a dry film thickness of about 100 μm to form an adhesive coating layer. After removing the solvent in the adhesive coating layer by heating, the base fabric (woven fabric) is immediately pressed and bonded by a laminating press with a roll temperature of 40°C and a laminating gap set to 70% of the total thickness of the base fabric, coating layer (adhesive layer), skin layer and release paper. After that, the coating layer is cured at 50°C for 48 hours to form an adhesive layer, and then the release paper in contact with the surface layer is peeled off to obtain standard synthetic leather.

(3) Preparation of synthetic leather in each example The skin layer obtained in the above "(1) Preparation of skin layer" and the hot-melt resin composition in each example were used to prepare the synthetic leather in each example as follows. First, the hot-melt resin composition was heated to 100°C to melt, and the melted hot-melt resin composition was applied to the skin layer on the release paper obtained in the above "(1) Preparation of skin layer" in a manner to have a dry film thickness of about 100 μm, thereby forming a coating layer of the hot-melt resin composition. After coating, the base fabric (woven fabric) is immediately pressed and bonded by a laminating press with a roll temperature of 30°C and a laminating gap set to 70% of the total thickness of the base fabric, coating layer (hot-melt resin composition layer), skin layer and release paper. After aging for 48 hours at 25°C and 60% RH to form a cured layer of the hot-melt resin composition, the release paper in contact with the skin layer is peeled off. In this way, a synthetic leather is obtained in which the base fabric (woven fabric) as the base material layer and the skin layer are bonded via the cured layer of the hot-melt resin composition as the adhesive layer.

(Bending property under cold weather) For each synthetic leather, a test piece with a width of 50 mm and a length of 150 mm (evaluation range of 100 mm) was prepared. Using the prepared test piece, a bending test was performed at a low temperature of -10°C with a DE MATTIA flexion tester (model "No.119-L DEMATTIA FLEXING TESTER", manufactured by Yasuda Seiki Seisakusho Co., Ltd.) in an environment of -10°C, with a tensile bending range of 72 to 108%, and a bending test at a low temperature of -10°C. Afterwards, the bending property under cold weather was evaluated according to the following evaluation criteria. AA: No cracks after 60,000 times. A: No cracks after 30,000 times, and cracks were found before 60,000 times. B: No cracks after 10,000 times, and cracks were found before 30,000 times. C: Cracks appear after 10,000 times.

(Hydrolysis resistance) For each synthetic leather, the hydrolysis resistance was evaluated by measuring the bonding strength before and after the hydrolysis resistance test and comparing the bonding strengths. Specifically, a hot melt tape was pressed on the upper surface of the surface layer of the synthetic leather with a 140°C iron for 1 minute. After cooling at room temperature (20°C) for 1 hour, the base fabric in the synthetic leather and the surface layer adhered to the hot melt tape were peeled off in a 180° direction at a speed of 200 mm/min. The strength was measured using a tensile tester (model "Autograph AGS-100A", manufactured by Shimadzu Corporation) and used as the bonding strength. On the other hand, after placing the synthetic leather of each example in a constant temperature chamber at 70°C and 95% RH for a predetermined period of time, the adhesive strength after the hydrolysis resistance test was measured in the same manner as above. The adhesive strength before the test was compared with the adhesive strength after the test, and the hydrolysis resistance was evaluated according to the following evaluation criteria. In addition, the so-called adhesive strength retention rate means the ratio of the adhesive strength after being stored in the chamber for a predetermined period of time to the adhesive strength before being placed in the chamber. AA: The adhesive strength retention rate after 8 weeks of storage is 70% or more. A: The adhesive strength retention rate after 5 weeks of storage is 70% or more. B: The adhesive strength retention rate after 5 weeks of storage is 50% or more and less than 70%. C: The adhesive strength retention rate after 5 weeks of storage is less than 50%.

(Softness) The softness of each synthetic leather was evaluated by touching it with the hand and the standard synthetic leather obtained in the above "(2) Preparation of standard synthetic leather for softness evaluation" according to the following evaluation criteria based on the standard synthetic leather. AA: Much softer than the standard synthetic leather. A: Softer than the standard synthetic leather. B: Equally soft as the standard synthetic leather. C: Much harder than the standard synthetic leather.

(Abrasion resistance) The hot melt resin composition of each example was heated to 100°C and melted, and the melted hot melt resin composition was applied to the release paper in a manner to a dry film thickness of about 100 μm, thereby forming a coating layer of the hot melt resin composition. After coating, the base fabric (woven fabric) was immediately pressed and bonded by a laminating press with a roll temperature of 30°C and a laminating gap set to 70% of the total thickness of the base fabric, coating layer (hot melt resin composition layer) and release paper. After that, after aging at 25°C and 60% RH for 48 hours to form a cured layer of the hot-melt resin composition, the release paper in contact with the cured layer was peeled off. In this way, a laminated body having a two-layer structure of a synthetic leather having a base fabric (woven fabric) and a surface layer composed of a cured layer of the hot-melt resin composition provided on the base fabric was produced. It was used as a synthetic leather for the wear resistance test described below.

For each synthetic leather used for the wear resistance test, a circular test piece with a diameter of 11.5 cm was prepared. The wear resistance test was conducted using the test piece and a TABER abrasion tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) under the conditions of a load of 500 g, a rotation speed of 60±2 rpm, and a wear wheel CS-10. Afterwards, the wear resistance was evaluated according to the following evaluation criteria. AA: No appearance changes such as scratches at 1500 times. A: No appearance changes such as scratches at 1000 times, and appearance changes such as scratches before 1500 times. B: No appearance changes such as scratches at 500 times, and appearance changes such as scratches before 1000 times. C: Appearance changes such as scratches are present when the number of times is less than 500.

<Heat resistance (heat creep test)> As a creep test, a certain load is applied to the test piece for a long time at high temperature, and the deformation and time until fracture are measured. The specific steps are as follows 1) to 8). 1) The hot melt resin composition and coating rod of each example, which are the test objects, are placed in an oven at 100°C for preheating. 2) The hot melt resin composition is applied to the polyurethane (PU) resin layer of the wet film-forming cloth (A) with a gap of 200 μgap (thickness of 200 μm), and then bonded to the PU resin layer of the wet film-forming cloth (B). In addition, the wet film-forming cloth (A) and the wet film-forming cloth (B) use the following synthetic leather: by applying a urethane resin solution with DMF as a medium on a non-woven fabric used as a substrate (the trade name "REZAMIN CU-4340NS" (resin solid content 30% by mass, manufactured by Dainichi Seika Co., Ltd.) is diluted with DMF to a solution with a solid content of 15% by mass), solidifying and removing DMF in a water tank, and then drying to form a PU resin layer, and forming a porous layer with a thickness of 800 to 1000 μm on the substrate after drying. 3) After the above-mentioned laminated product is cured at 25°C/60% RH for 24 hours, the heat resistance is measured according to the following procedure. 4) The oven is set to 170°C. In addition, the laminated product is cut into pieces with a width of 3 cm and a length of more than 12 cm as test pieces. 5) The end of the test piece is peeled off with the laminated surface, and a fixing clamp is installed on the wet film-forming cloth (A) side and the wet film-forming cloth (B) side, respectively, and a 3 kg weight is hung on one side. 6) After placing in a 170°C oven and hanging the test sample, the oven door is quickly closed. 7) After closing the door, leave it for 5 minutes. 8) After 5 minutes, take out the test piece immediately, observe the length and peeling state after leaving it at 170°C/5 minutes, and evaluate the heat resistance according to the following evaluation criteria. A: The peeling length is less than 2 cm, and the peeling state is the base material damage. B: The peeling length is more than 2 cm and less than 5 cm, and the peeling state is the base material damage. C: The peeling length is more than 5 cm, or the peeling state is the peeling of the PU resin surface.

[Table 2-1] Reaction ingredients Functional base Embodiment 1 2 3 4 5 Polyol ingredients (weight) Polyol ingredients (A) Polyester polyol (A1) 2.0 10 10 10 10 10 Polyester polyol (A2) 2.0 Polyester polyol (A3) 2.0 (B) Polyester polyol (B1-1) 2.0 45 45 45 45 45 Polyester polyol (B1-2) 2.0 Polyester polyol (B1-3) 2.0 Polyether polyol (B2-1) 2.0 45 45 Polyether polyol (B2-2) 2.0 45 Polyether polyol (B2-3) 2.0 45 Polyether polyol (B2-4) 2.0 45 (C) Polycarbonate polyol (C1) 2.0 Polycarbonate polyol (C2) 2.0 Polycarbonate polyol (C3) 2.0 Low molecular weight polyol ingredients (D) Trihydroxymethylpropane 3.0 0.5 3 3 3 3 glycerin 3.0 (E) 1,4-Butanediol 2.0 1,3-Butanediol 2.0 Neopentyl glycol 2.0 Polyisocyanate component (weight) MDI 2.0 22.35 34.25 34.25 34.25 34.25 Trifunctional polyol (D)/polyol (A) [mmol/g] 0.37 2.24 2.24 2.24 2.24 NCO group/OH group (molar ratio) 1.7 1.7 1.7 1.7 1.7 Stability over time in the molten state A A A A B Membrane Evaluation Heat resistance (thermal softening point) A A A A A Alcohol resistance B A A A A Initial adhesion B B B B B Synthetic leather reviews Cold resistance and flexibility AA AA AA AA AA Hydrolysis resistance B B B B B Softness AA AA AA AA AA Wear resistance B A A A A Heat resistance (thermal creep resistance) B A A A B

[Table 2-2] Reaction ingredients Functional base Embodiment 6 7 8 9 10 Polyol ingredients (wt.%) Polyol ingredients (A) Polyester polyol (A1) 2.0 10 10 10 10 Polyester polyol (A2) 2.0 10 Polyester polyol (A3) 2.0 (B) Polyester polyol (B1-1) 2.0 45 45 45 25 25 Polyester polyol (B1-2) 2.0 Polyester polyol (B1-3) 2.0 Polyether polyol (B2-1) 2.0 45 45 45 45 45 Polyether polyol (B2-2) 2.0 Polyether polyol (B2-3) 2.0 Polyether polyol (B2-4) 2.0 (C) Polycarbonate polyol (C1) 2.0 20 20 Polycarbonate polyol (C2) 2.0 Polycarbonate polyol (C3) 2.0 Low molecular weight polyol ingredients (D) Trihydroxymethylpropane 3.0 5 3 3 glycerin 3.0 2.1 4.1 (E) 1,4-Butanediol 2.0 1,3-Butanediol 2.0 Neopentyl glycol 2.0 Polyisocyanate component (weight) MDI 2.0 43.76 34.25 48.52 34.25 33.90 Trifunctional polyol (D)/polyol (A) [mmol/g] 3.70 2.24 4.50 2.24 2.24 NCO group/OH group (molar ratio) 1.7 1.7 1.7 1.7 1.7 Stability over time in the molten state B A B A A Membrane Evaluation Heat resistance (thermal softening point) A A A A A Alcohol resistance AA A AA A A Initial adhesion A B A B B Synthetic leather reviews Cold resistance and flexibility A AA A A A Hydrolysis resistance A B A AA A Softness A AA A A A Wear resistance A A A AA AA Heat resistance (thermal creep resistance) A A A A A

[Table 2-3] Reaction ingredients Functional base Embodiment 11 12 13 14 15 Polyol ingredients (weight) Polyol ingredients (A) Polyester polyol (A1) 2.0 10 10 10 10 Polyester polyol (A2) 2.0 Polyester polyol (A3) 2.0 10 (B) Polyester polyol (B1-1) 2.0 25 25 25 Polyester polyol (B1-2) 2.0 Polyester polyol (B1-3) 2.0 Polyether polyol (B2-1) 2.0 45 45 10 45 10 Polyether polyol (B2-2) 2.0 Polyether polyol (B2-3) 2.0 Polyether polyol (B2-4) 2.0 (C) Polycarbonate polyol (C1) 2.0 20 80 Polycarbonate polyol (C2) 2.0 20 Polycarbonate polyol (C3) 2.0 20 80 Low molecular weight polyol ingredients (D) Trihydroxymethylpropane 3.0 3 3 3 3 3 glycerin 3.0 (E) 1,4-Butanediol 2.0 1,3-Butanediol 2.0 Neopentyl glycol 2.0 Polyisocyanate component (weight) MDI 2.0 34.11 34.25 34.25 34.25 34.25 Trifunctional polyol (D)/polyol (A) [mmol/g] 2.24 2.24 2.24 2.24 2.24 NCO group/OH group (molar ratio) 1.7 1.7 1.7 1.7 1.7 Stability over time in the molten state A A A A A Membrane Evaluation Heat resistance (thermal softening point) A A A A A Alcohol resistance A A AA A AA Initial adhesion B B B A A Synthetic leather reviews Cold resistance and flexibility A A B A B Hydrolysis resistance AA AA AA AA AA Softness A A B A A Wear resistance AA AA A AA A Heat resistance (thermal creep resistance) A A A A A

[Table 2-4] Reaction ingredients Functional base Embodiment 16 17 Polyol ingredients (wt.%) Polyol ingredients (A) Polyester polyol (A1) 2.0 2 2 Polyester polyol (A2) 2.0 Polyester polyol (A3) 2.0 (B) Polyester polyol (B1-1) 2.0 49 49 Polyester polyol (B1-2) 2.0 Polyester polyol (B1-3) 2.0 Polyether polyol (B2-1) 2.0 49 49 Polyether polyol (B2-2) 2.0 Polyether polyol (B2-3) 2.0 Polyether polyol (B2-4) 2.0 (C) Polycarbonate polyol (C1) 2.0 Polycarbonate polyol (C2) 2.0 Polycarbonate polyol (C3) 2.0 Low molecular weight polyol ingredients (D) Trihydroxymethylpropane 3.0 8 glycerin 3.0 8 (E) 1,4-Butanediol 2.0 1,3-Butanediol 2.0 Neopentyl glycol 2.0 Polyisocyanate component (weight) MDI 2.0 60.59 77.24 Trifunctional polyol (D)/polyol (A) [mmol/g] 29.90 43.50 NCO group/OH group (molar ratio) 1.7 1.7 Stability over time in the molten state B B Membrane Evaluation Heat resistance (thermal softening point) A A Alcohol resistance A A Initial adhesion B B Synthetic leather reviews Cold resistance and flexibility B B Hydrolysis resistance B B Softness A A Wear resistance A A Heat resistance (thermal creep resistance) A A

[Table 2-5] Reaction ingredients Functional base Comparison Example 1 2 3 4 5 Polyol ingredients (weight) Polyol ingredients (A) Polyester polyol (A1) 2.0 30 10 Polyester polyol (A2) 2.0 Polyester polyol (A3) 2.0 (B) Polyester polyol (B1-1) 2.0 45 55 30 45 Polyester polyol (B1-2) 2.0 Polyester polyol (B1-3) 2.0 Polyether polyol (B2-1) 2.0 45 45 30 45 Polyether polyol (B2-2) 2.0 Polyether polyol (B2-3) 2.0 Polyether polyol (B2-4) 2.0 (C) Polycarbonate polyol (C1) 2.0 10 10 100 Polycarbonate polyol (C2) 2.0 Polycarbonate polyol (C3) 2.0 Low molecular weight polyol ingredients (D) Trihydroxymethylpropane 3.0 3 0.5 3 glycerin 3.0 (E) 1,4-Butanediol 2.0 3.5 1,3-Butanediol 2.0 Neopentyl glycol 2.0 Polyisocyanate component (weight) MDI 2.0 21.30 35.50 19.80 35.52 29.68 Trifunctional polyol (D)/polyol (A) [mmol/g] ‒ ‒ 0.12 ‒ 0 NCO group/OH group (molar ratio) 1.7 1.7 1.7 1.7 1.7 Stability over time in the molten state AA A A B A Membrane Evaluation Heat resistance (thermal softening point) B A B A C Alcohol resistance C A A A B Initial adhesion C C C B C Synthetic leather reviews Cold resistance and flexibility AA A C C A Hydrolysis resistance C B A AA B Softness C C C C A Wear resistance C A B C B Heat resistance (thermal creep resistance) C B B A C

[Table 2-6] Reaction ingredients Functional base Comparison Example 6 7 8 9 10 Polyol ingredients (weight) Polyol ingredients (A) Polyester polyol (A1) 2.0 10 10 2 Polyester polyol (A2) 2.0 Polyester polyol (A3) 2.0 (B) Polyester polyol (B1-1) 2.0 45 45 45 45 49 Polyester polyol (B1-2) 2.0 10 Polyester polyol (B1-3) 2.0 10 Polyether polyol (B2-1) 2.0 45 45 45 45 49 Polyether polyol (B2-2) 2.0 Polyether polyol (B2-3) 2.0 Polyether polyol (B2-4) 2.0 (C) Polycarbonate polyol (C1) 2.0 Polycarbonate polyol (C2) 2.0 Polycarbonate polyol (C3) 2.0 Low molecular weight polyol ingredients (D) Trihydroxymethylpropane 3.0 3 3 15 glycerin 3.0 (E) 1,4-Butanediol 2.0 1,3-Butanediol 2.0 3.5 Neopentyl glycol 2.0 3.5 Polyisocyanate component (weight) MDI 2.0 29.68 34.26 34.00 34.24 92.36 Trifunctional polyol (D)/polyol (A) [mmol/g] 0 0 ‒ ‒ 56.0 NCO group/OH group (molar ratio) 1.7 1.7 1.7 1.7 ‒ Stability over time in the molten state A A A A ‒ Membrane Evaluation Heat resistance (thermal softening point) C C A A ‒ Alcohol resistance C C A A ‒ Initial adhesion C C C C ‒ Synthetic leather reviews Cold resistance and flexibility C C A A ‒ Hydrolysis resistance B B B B ‒ Softness A C A A ‒ Wear resistance B C A A ‒ Heat resistance (thermal creep resistance) C C A A ‒

10: Evaluation film 12: Clamp 14: Weight 16: Sample 20: Gear oven 22: Rotating plate

FIG. 1 is a schematic diagram illustrating the shape of the sample used in the evaluation of the embodiment. FIG. 2 is a schematic diagram illustrating the shape of the gear oven used in the evaluation of the embodiment.

Claims (7)

A moisture-curing urethane hot-melt resin composition, comprising a urethane prepolymer having an isocyanate group, which is a reaction product of a polyol component and a polyisocyanate component; wherein the polyol component comprises a high molecular weight polyol component and a low molecular weight polyol component; wherein the high molecular weight polyol component comprises: a polyol (A), which is selected from: a polyester polyol (A1) having a structural unit derived from sebacic acid; a polyester polyol (A2) having a structural unit derived from 1,4-butanediol and a structural unit derived from adipic acid and having a number average molecular weight of 8,000 or more; and a polyester polyol (A3) having a structural unit derived from 1,6-hexanediol and a structural unit derived from adipic acid and having a number average molecular weight of 1,6-hexanediol and a structural unit derived from adipic acid. The invention relates to a polyester polyol (A3) having a molecular weight of 6,000 or more; at least one of the group consisting of; and a polyol (B) selected from: a polyester polyol (B1) other than the aforementioned polyol (A); and a polyether polyol (B2); at least one of the group consisting of; the aforementioned polyol (B) contains at least the aforementioned polyether polyol (B2); the aforementioned low molecular weight polyol component comprises a trifunctional polyol (D) having a molecular weight of 300 or less and having three hydroxyl groups in one molecule; the ratio of the aforementioned polyol (A) to the aforementioned trifunctional polyol (D) satisfies: the aforementioned trifunctional polyol (D) (mmol)/the aforementioned polyol (A) (g) = 0.14~55mmol/g. The moisture-curing urethane hot-melt resin composition of claim 1, wherein the polyol (B) comprises a polyol (B _b ) derived from a plant raw material. As in claim 1, the moisture-curing urethane hot-melt resin composition, wherein the aforementioned polymer polyol component further comprises a polycarbonate polyol (C). The moisture-curing urethane hot-melt resin composition of claim 3, wherein the polycarbonate polyol (C) comprises a polycarbonate polyol (C _b ) derived from a plant raw material. The moisture-curing urethane hot-melt resin composition of claim 3, wherein the total amount of the aforementioned polyol (B) and the aforementioned polycarbonate polyol (C) is greater than the amount of the aforementioned polyol (A); and the total ratio of the aforementioned polyol (A), the aforementioned polyol (B) and the aforementioned polycarbonate polyol (C) relative to the total amount of the aforementioned polyol components is 90% by mass or more. A laminate having a substrate and a cured layer of a moisture-curing urethane hot-melt resin composition according to any one of claims 1 to 5 disposed on the substrate. A synthetic leather having a base layer, a surface layer, and an adhesive layer disposed between and connected to the base layer; and the adhesive layer is a cured layer of a moisture-curing urethane hot-melt resin composition of any one of claims 1 to 5.