TWI846379B - Urethane prepolymer composition, moisture-curing adhesive, laminate and synthetic leather - Google Patents

Abstract

The present invention provides a urethane prepolymer composition which has excellent storage stability and can form a hardened layer with excellent flexibility, heat resistance and solvent resistance. The urethane prepolymer composition comprises: a urethane prepolymer (C) which is a reaction product of a polyol (A) and a polyisocyanate (B), and a trihydroxymethylpropane adduct of toluene diisocyanate (D); and the polyol (A) contains 5-90% by weight of a polyester polyol (A-1) having a constituent unit derived from an aromatic dicarboxylic acid; the content of the trihydroxymethylpropane adduct of toluene diisocyanate (D) is 0.2-25 parts by weight relative to 100 parts by weight of the urethane prepolymer (C); and the isocyanate group content based on the total of the urethane prepolymer (C) and the trihydroxymethylpropane adduct of toluene diisocyanate (D) is 1.0-6.0% by weight.

Description

Urethane prepolymer composition, moisture-curing adhesive, laminate and synthetic leather

The present invention relates to a urethane prepolymer composition, a moisture-curing adhesive, a laminate and a synthetic leather.

Urethane prepolymers are used in adhesives, coatings, and sealing materials. Among them, moisture-curing urethane prepolymers have the advantage of being usable in one liquid because they cure due to moisture in the air. This type of urethane prepolymer is a compound that 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. Urethane prepolymers are not cured and are in liquid or solid form at room temperature. Various types have been developed according to the application.

For example, a moisture-curing hot melt composition is proposed, which contains a urethane prepolymer having a polyol structure derived from a polyester polyol, and a polyfunctional isocyanate such as polymerized MDI (Patent Document 1). In addition, a reactive adhesive is proposed, which contains a urethane prepolymer having a polyol structure derived from a polyether polyol, and a polyisocyanate such as an HDI trimer (Patent Document 2). Furthermore, a moisture-curing adhesive composition is proposed, which contains a urethane prepolymer and polymerized MDI (Patent Document 3). [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Publication No. 6836713 [Patent Document 2] Japanese Patent Publication No. 2003-515636 [Patent Document 3] Japanese Patent Publication No. 2005-75877

(Invent the problem you want to solve)

However, urethane prepolymers can also be used as adhesives when manufacturing synthetic leathers such as artificial leather or synthetic leather. Synthetic leather is used as a material for manufacturing a variety of products such as shoes, clothing, bags, furniture, and automotive interior materials (for example, dashboards, doors, consoles, seats). Synthetic leather is usually a laminate of a surface layer, an adhesive layer (hardening layer), and a base layer, and a hardening layer is formed by various urethane prepolymers. For the hardening layer constituting the synthetic leather used in the above-mentioned various products, in addition to having good softness, it is also required to have heat resistance that can withstand the heat during manufacturing and processing.

However, the hardened layer formed by hardening the known adhesives proposed in Patent Documents 1 to 3, etc., is not well-balanced and excellent in terms of softness and heat resistance. In addition, the viscosity of the known adhesives, etc., is easily changed during storage, and the storage stability is not necessarily good. The solvent resistance of the hardened layer also has room for improvement.

The present invention is completed in view of the problems of the prior art. The subject is to provide a urethane prepolymer composition which has excellent storage stability and can form a hardened layer with excellent flexibility, heat resistance and solvent resistance; and a moisture-hardening adhesive using the urethane prepolymer composition. In addition, the subject of the present invention is to provide a laminate and synthetic leather using the above-mentioned urethane prepolymer composition. (Technical means to solve the problem)

That is, according to the present invention, a urethane prepolymer composition as shown below is provided. [1] A urethane prepolymer composition comprising: a urethane prepolymer (C) which is a reaction product of a polyol (A) and a polyisocyanate (B), and a trihydroxymethylpropane adduct of toluene diisocyanate (D); wherein the polyol (A) contains 5 to 90% by weight of a polyester polyol (A-1) having constituent units derived from an aromatic dicarboxylic acid; and the content of the trihydroxymethylpropane adduct of toluene diisocyanate (D) is 0.2 to 2 parts by weight relative to 100 parts by weight of the urethane prepolymer (C). 5 parts by weight; the isocyanate group content based on the total of the urethane prepolymer (C) and the trihydroxymethylpropane adduct of toluene diisocyanate (D) is 1.0-6.0% by weight; the polyol (A) further contains at least one other polyol (A-2) selected from the group consisting of polyester polyols (except the polyester polyol (A-1)), polyether polyols, and polycarbonate polyols; the ratio of the other polyol (A-2) in the polyol (A) is 10-95% by weight. [2] The urethane prepolymer composition as described in [1] above, wherein the urethane prepolymer (C) is a resin having a carboxyl group or an amine sulfonic acid (salt) group. [3] The urethane prepolymer composition as described in [1] or [2] above, wherein the proportion of the polyester polyol (A-1) in the polyol (A) is 5 to 70% by mass; and the proportion of the other polyol (A-2) in the polyol (A) is 30 to 95% by mass. [4] The urethane prepolymer composition as described in any one of [1] to [3] above, wherein the molar ratio (NCO group/OH group) of the polyol (A) to the polyisocyanate (B) is 1.3 to 2.0. [5] The urethane prepolymer composition as described in any one of [1] to [4] above, wherein the melt viscosity of the urethane prepolymer (C) at 100°C is not more than 110 dPa·s.

Furthermore, according to the present invention, the following moisture-curing adhesive, laminate and synthetic leather are provided. [6] A moisture-curing adhesive, comprising the urethane prepolymer composition described in any one of the above-mentioned [1] to [5]. [7] A laminate, comprising: a substrate; and a cured layer, which is disposed on the above-mentioned substrate and is formed by a cured product of the moisture-curing adhesive described in the above-mentioned [6]. [8] A synthetic leather, which comprises: a skin layer; a cured layer, which is disposed on the above-mentioned skin layer and is formed by a cured product of the moisture-curing adhesive described in the above-mentioned [6]; and a substrate layer, which is disposed on the above-mentioned cured layer. (Compared with the effect of the prior art)

According to the present invention, a urethane prepolymer composition can be provided, which has excellent storage stability and can form a hardened layer with excellent flexibility, heat resistance and solvent resistance; and a moisture-hardening adhesive using the urethane prepolymer composition. In addition, according to the present invention, a laminate and a synthetic leather using the above urethane prepolymer composition can be provided.

<Urethane prepolymer composition> The following describes the embodiments of the present invention, but the present invention is not limited to the following embodiments. One embodiment of the urethane prepolymer composition of the present invention contains a urethane prepolymer (C) that is a reaction product of a polyol (A) and a polyisocyanate (B), and a trihydroxymethylpropane adduct of toluene diisocyanate (D). The polyol (A) contains 5 to 90% by mass of a polyester polyol (A-1) having a constituent unit derived from an aromatic dicarboxylic acid. In addition, the content of the trihydroxymethylpropane adduct of toluene diisocyanate (D) is 0.2 to 25 parts by mass relative to 100 parts by mass of the urethane prepolymer (C). Furthermore, the isocyanate group content based on the total of the urethane prepolymer (C) and the trihydroxymethylpropane adduct (D) of toluene diisocyanate is 1.0 to 6.0 mass %. The following is a description of the details of the urethane prepolymer composition of this embodiment.

(Urethane prepolymer (C)) Urethane prepolymer (C) (hereinafter, also referred to as "prepolymer (C)") is a reaction product of polyol (A) and polyisocyanate (B). The molar ratio (NCO group/OH group) of polyol (A) and polyisocyanate (B) constituting prepolymer (C) is preferably 1.1 to 2.2, more preferably 1.3 to 2.0, and particularly preferably 1.4 to 1.9. By making the molar ratio (NCO group/OH group) of isocyanate group (NCO group) of polyisocyanate (B) relative to hydroxyl group (OH group) of polyol (A) within the above range, processability can be improved and synthetic leather with better hand feel can be produced. If the NCO group/OH group (molar ratio) exceeds 2.2, the softness of the formed hardened layer is likely to decrease. In addition, the urethane prepolymer (C) is an exception to the resin having a carboxyl group or an amine sulfonic acid (salt) group. That is, the urethane prepolymer (C) does not contain a resin having a carboxyl group or a resin having an amine sulfonic acid (salt) group.

The melt viscosity of the prepolymer (C) at 100°C is preferably 120 dPa·s or less, more preferably 110 dPa·s or less, and particularly preferably 105 dPa·s or less. If the melt viscosity of the prepolymer (C) exceeds 120 dPa·s, it becomes viscous, the workability is easily reduced, and processing may become difficult. The melt viscosity of the prepolymer (C) can be controlled, for example, by the proportion of the polyester polyol (A-1) in the polyol (A). In addition, the melt viscosity of the prepolymer (C) at 100°C can be measured using a cone plate viscometer.

The isocyanate group (NCO group) content of the prepolymer (C) is preferably 0.5 to 8.0% by mass, more preferably 1.0 to 6.0% by mass, and particularly preferably 1.5 to 4.0% by mass from the viewpoint of physical properties after curing, such as softness when used as synthetic leather. The "NCO group content (mass %)" in the present invention specification is a value measured by potentiometric titration in accordance with JIS K1603-1:2007.

[Polyol (A)] Polyol (A) is a polyester polyol (A-1) containing a constituent unit derived from an aromatic dicarboxylic acid. Examples of the aromatic dicarboxylic acid include isophthalic acid and terephthalic acid. Among them, isophthalic acid is preferred in consideration of melt viscosity and softness. In addition, polyol (A) is preferably a diol having two hydroxyl groups in one molecule.

Polyester polyol (A-1) is usually a reaction product of an aromatic dicarboxylic acid and a diol. Examples of the diol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,2-propylene glycol, n-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 1,9-nonanediol, and neopentyl glycol.

The proportion of the polyester polyol (A-1) in the polyol (A) is 5 to 90% by mass, preferably 10 to 80% by mass, more preferably 20 to 70% by mass, and particularly preferably 25 to 60% by mass. By making the proportion of the polyester polyol (A-1) in the polyol (A) within the above range, a prepolymer (C) having a suitable melt viscosity that is easy to handle, such as during gravure coating, can be prepared.

The number average molecular weight (Mn) of the polyester polyol (A-1) is preferably 4,000 or less, more preferably 3,000 or less, and particularly preferably 2,800 or less. If the number average molecular weight (Mn) of the polyester polyol (A-1) exceeds 4,000, the viscosity becomes too high, so there is a case where practicality is reduced. The lower limit of the number average molecular weight (Mn) of the polyester polyol (A-1) is not particularly limited, for example, it is preferably 500 or more. In addition, the "number average molecular weight (Mn)" in the present invention specification is a polystyrene conversion value measured by a gel chromatograph (GPC).

The polyol (A) usually further contains other polyols (A-2) other than the polyester polyol (A-1). The other polyols (A-2) are at least one selected from the group consisting of polyester polyols (except the polyester polyol (A-1)), polyether polyols, and polycarbonate polyols.

As polyester polyols other than polyester polyol (A-1), a reaction product of an aliphatic dicarboxylic acid and a diol can be used. As the aliphatic dicarboxylic acid, succinic acid, adipic acid, sebacic acid, glutaric acid, and azelaic acid can be mentioned. As the diols, the same diols as those that can constitute polyester polyol (A-1) can be mentioned.

Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polyethylene glycol-polytetramethylene glycol (block or random), polytetramethylene glycol, and polyhexamethylene glycol, etc. Among them, polytetramethylene glycol is preferred from the viewpoint of softness.

Examples of the polycarbonate polyol include polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyneopentyl carbonate diol, polyhexamethylene carbonate diol, poly(1,4-cyclohexanedimethylene carbonate) diol, and random/block copolymers thereof.

In the polyol (A), the ratio of the other polyol (A-2) is preferably 10 to 95% by mass, more preferably 20 to 90% by mass, particularly preferably 30 to 80% by mass, and most preferably 40 to 75% by mass. In addition, in the polyol (A), the total of the polyester polyol (A-1) and the other polyol (A-2) is preferably 100% by mass. By further containing the other polyol (A-2) in the polyol (A), a hardened layer with better flexibility can be formed.

The number average molecular weight (Mn) of the other polyol (A-2) is preferably 4,000 or less, more preferably 3,000 or less, and particularly preferably 2,800 or less. If the number average molecular weight (Mn) of the other polyol (A-2) exceeds 3,000, the viscosity becomes too high, so there is a case where practicality is reduced. In addition, the number average molecular weight (Mn) of the other polyol (A-2) is preferably 500 or more. That is, the other polyol (A-2) preferably does not contain so-called short-chain diols (low molecular weight diols) such as neopentyl glycol.

[Polyisocyanate (B)] As the polyisocyanate, it is preferred to use a bifunctional polyisocyanate such as aliphatic diisocyanate, alicyclic diisocyanate, and aromatic diisocyanate. Specific examples of the polyisocyanate include toluene diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4-butoxy-1,3-phenylene diisocyanate, 2,4-diisocyanate diphenyl ether, methylene diisocyanate, 4,4'-diphenylmethane diisocyanate, tert-butyl diisocyanate, 1,5-naphthalene diisocyanate, benzidine diisocyanate, o- -nitrobenzidine diisocyanate, 4,4-dibenzyl diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,10-decamethylene diisocyanate, 1,4-cyclohexyl diisocyanate, xylene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate and dicyclohexylmethane 4,4'-diisocyanate, etc. Among them, 4,4'-diphenylmethane diisocyanate (MDI) is preferred.

(Production method of urethane prepolymer (C)) The prepolymer (C) can be produced, for example, by reacting a polyol (A) and a polyisocyanate (B) by a single process or a multi-stage process, preferably at 20 to 150°C, more preferably at 60 to 110°C, until the product reaches a theoretical NCO group content (mass %). When the polyol (A) and the polyisocyanate (B) are reacted, a catalyst can also be used as needed. As catalysts, metal salts or organic metal derivatives such as dibutyltin laurate, dioctyltrin laurate, stannous octoate, lead octoate, and tetra-n-butyl titanium ester; organic amines such as triethylamine; 1,8-diazabicyclo[5.4.0]undec-7-ene catalysts, etc. can be cited.

The polyol (A) and the polyisocyanate (B) are preferably reacted in the absence of a solvent such as an organic solvent, i.e., in the absence of a solvent. By reacting the polyol (A) and the polyisocyanate (B) in the absence of a solvent such as an organic solvent, a solvent-free urethane prepolymer (C) can be obtained.

(Trihydroxymethylpropane adduct of toluene diisocyanate (D)) The urethane prepolymer composition of this embodiment contains trihydroxymethylpropane adduct of toluene diisocyanate (D) (hereinafter also referred to as "TDI adduct (D)"). By including the TDI adduct (D), an adhesive layer (cured material layer) with improved heat resistance can be formed, and a urethane prepolymer composition useful as a one-component moisture-curing adhesive can be prepared. Furthermore, by including the TDI adduct (D), a urethane prepolymer composition can be prepared that can form a cured material layer that is not only heat-resistant but also excellent in flexibility and solvent resistance.

In the urethane prepolymer composition, the content of the TDI adduct (D) is 0.2 to 25 parts by mass, preferably 0.3 to 20 parts by mass, more preferably 0.5 to 18 parts by mass, and particularly preferably 1.0 to 15 parts by mass relative to 100 parts by mass of the urethane prepolymer (C). By making the content of the TDI adduct (D) within the above range, a urethane prepolymer composition can be prepared, which can form a cured layer with excellent flexibility, heat resistance and solvent resistance. If the content of the TDI adduct (D) is less than 0.2 parts by mass relative to 100 parts by mass of the prepolymer (C), a cured layer showing sufficient heat resistance and solvent resistance cannot be formed. On the other hand, if the content of the TDI adduct (D) exceeds 25 parts by mass relative to 100 parts by mass of the prepolymer (C), the softness of the formed hardened layer decreases and the storage stability of the urethane prepolymer composition decreases.

The isocyanate group (NCO group) content (hereinafter also referred to as "total NCO group content") based on the sum of the prepolymer (C) and the TDI adduct (D) is 1.0 to 6.0% by mass, preferably 1.1 to 5.0% by mass, and more preferably 1.2 to 4.0% by mass. By making the total NCO group content within the above range, a urethane prepolymer composition can be prepared, which can form a cured layer with excellent flexibility, heat resistance and solvent resistance, and excellent storage stability. If the total NCO group content is less than 1.0% by mass, the heat resistance of the formed cured layer is reduced. On the other hand, if the total NCO group content exceeds 6.0% by mass, the flexibility of the formed cured layer is insufficient.

<Moisture-curing adhesive> An embodiment of the moisture-curing adhesive of the present invention contains the aforementioned urethane prepolymer composition. The moisture-curing adhesive of this embodiment is particularly suitable as a liquid adhesive for manufacturing various laminates in addition to synthetic leather.

In the moisture-curing adhesive of the present embodiment, various additives such as thermoplastic resin, tackifying resin, catalyst, pigment, antioxidant, ultraviolet absorber, surfactant, flame retardant, filler, and foaming agent can be appropriately blended as needed. However, the moisture-curing adhesive of the present embodiment is preferably substantially composed of the aforementioned urethane prepolymer composition. The moisture-curing adhesive of the present embodiment is preferably used as an adhesive for synthetic leather.

The adhesive of this embodiment can be applied to the surface of the adherend to facilitate adhesion of the adherends. As the adherend other than the substrate layer for the synthetic leather, for example, metal or non-metal (polycarbonate, glass, etc.) substrates can be cited.

<Laminate> One embodiment of the laminate of the present invention comprises: a film-like or sheet-like substrate; and a hardened material layer formed by the hardened material of the aforementioned moisture-curing adhesive and disposed on the substrate. That is, the laminate of the present embodiment comprises a hardened material layer (adhesive layer), which is formed by moisture curing of a coating formed by applying the aforementioned moisture-curing adhesive. As substrates, in addition to the surface layer or substrate layer for synthetic leather, optical films, optical plates, flexible printed circuit boards, glass substrates, and substrates on which ITO is evaporated, etc., can also be cited.

The moisture-curable adhesive is applied to the substrate by a known method such as comma coating, blade coating, or roller coating to form a coating film. Next, the formed coating film is moisture-cured to form a cured layer, thereby obtaining a laminate.

<Synthetic leather> One embodiment of the synthetic leather of the present invention comprises: a skin layer; a hardened material layer disposed on the skin layer and formed by hardening of the aforementioned moisture-hardening adhesive; and a base material layer such as a base fabric disposed on the hardened material layer. Examples of the base fabric constituting the base material layer include fabrics including twill fabrics, plain fabrics, etc.; raised fabrics obtained by mechanically raising the cotton surface of the fabric, rayon fabrics, nylon fabrics, polyester fabrics, kevlar fabrics, nonwoven fabrics (polyester, nylon, various latex), various films, sheets, etc. In addition, as the epidermis layer, those formed by coating materials for forming the epidermis layer such as solvent-based polyurethane, water-based polyurethane, and TPU can be cited.

The synthetic leather can be manufactured, for example, in the following manner. First, a coating material for forming a skin layer is applied to a release paper by a known method such as comma coating, blade coating, roll coating, gravure coating, die coating, spray coating, etc. After the applied coating material is appropriately dried to form a skin layer, the aforementioned moisture-curing adhesive is applied to the formed skin layer by a known method such as comma coating, blade coating, roll coating, etc. After the applied moisture-curing adhesive is pressed against the substrate layer at 75 to 155°C, it is aged under predetermined conditions as needed. Next, the desired synthetic leather can be obtained by peeling it off from the release paper. The synthetic leather of this embodiment is preferably used as a material for shoes, clothing, bags, furniture, and automotive interior materials (e.g., dashboards, doors, consoles, seats), etc. [Example]

The present invention is specifically described below based on the embodiments, but the present invention is not limited to the embodiments. In addition, the "parts" and "%" in the embodiments and comparative examples are based on mass without special explanation.

<Production of prepolymer> (Production example 1) In a glass reaction container equipped with a stirrer, a thermometer and a gas inlet, 10 parts by mass of isophthalic acid polyester polyol (Mn: 2,000), 90 parts by mass of polytetramethylene glycol 2000 (PTMG2000) (Mn: 2,000, manufactured by Mitsubishi Chemical Corporation), and 16.3 parts of 4,4'-diphenylmethane diisocyanate (MDI) were loaded. As the isophthalic acid polyester polyol, a polyester polyol composed of isophthalic acid and 1,4-butanediol (1,4-BD) was used. In addition, the molar ratio (NCO group/OH group) of the NCO group of MDI to the OH group of the polyol (isophthalic acid polyester polyol and PTMG2000) was set to 1.3. After heating and reducing pressure for dehydration, nitrogen was sealed in. Stirring was performed at an internal temperature of 100°C for 120 minutes to allow the reaction to proceed, thereby obtaining a prepolymer (C-1). The viscosity of the obtained prepolymer (C-1) at 100°C was 95 dPa・s, and the NCO group content was 1.08%. (Production Examples 2 to 14)

In addition to using the formula shown in Tables 1-1 and 1-2, prepolymers (C-2) to (C-14) were obtained in the same manner as in the above-mentioned Production Example 1. The properties of the obtained prepolymers are shown in Tables 1-1 and 1-2. In addition, the meanings of the abbreviations in Tables 1-1 and 1-2 are shown below. In addition, the "polycarbonate polyol" in Tables 1-1 and 1-2 is a polycarbonate diol based on 1,6-hexanediol (trade name "ETERNACOLL UH-200", manufactured by Ube Industries). 1,4-BD: 1,4-butanediol IPA: isophthalic acid PTMG2000: polytetramethylene glycol 2000 AA: adipic acid 1,6-HD: 1,6-hexanediol TPA: terephthalic acid NPG: neopentyl glycol

[Table 1-1] (Unit in the middle section: copy) Manufacturing example 1 2 3 4 5 6 7 Prepolymer (C-1) (C-2) (C-3) (C-4) (C-5) (C-6) (C-7) Isophthalic acid polyester polyol (1,4-BD/IPA, Mn: 2,000) 10 50 70 80 50 50 Isophthalic acid polyester polyol (1,4-BD/IPA, Mn: 1,000) 50 Polyether polyol (PTMG2000, Mn: 2,000) 90 50 30 20 50 Adipic acid polyester polyol (1,4-BD/AA, Mn: 2,000) 50 Polycarbonate polyol (Mn: 2,000) 50 Adipic acid polyester polyol (1,6-HD/AA, Mn: 2,000) Terephthalic acid polyester polyol (1,4-BD/TPA, Mn: 2,000) NPG (molecular weight: 104) MDI 16.3 18.3 22.5 25.0 22.5 22.5 28.1 NCO group/OH group (molar ratio) 1.3 1.5 1.8 2.0 1.8 1.8 1.5 Viscosity (dPa・s/100℃) 95 90 100 100 100 100 80 NCO group content (%) 1.08 1.77 2.74 3.36 2.74 2.74 2.46

[Table 1-2] (Unit in the middle section: copy) Manufacturing example 8 9 10 11 12 13 14 Prepolymer (C-8) (C-9) (C-10) (C-11) (C-12) (C-13) (C-14) Isophthalic acid polyester polyol (1,4-BD/IPA, Mn: 2,000) 100 90 50 50 Isophthalic acid polyester polyol (1,4-BD/IPA, Mn: 1,000) 80 Polyether polyol (PTMG2000, Mn: 2,000) 50 20 25 Adipic acid polyester polyol (1,4-BD/AA, Mn: 2,000) 50 25 25 Polycarbonate polyol (Mn: 2,000) Adipic acid polyester polyol (1,6-HD/AA, Mn: 2,000) 50 25 Terephthalic acid polyester polyol (1,4-BD/TPA, Mn: 2,000) 50 NPG (molecular weight: 104) 10 MDI 18.3 22.5 45 25.0 53.2 22.5 22.5 NCO group/OH group (molar ratio) 1.5 1.8 2.0 2.0 1.5 1.8 1.8 Viscosity (dPa・s/100℃) 85 110 80 150 40 80 100 NCO group content (%) 1.77 2.74 5.21 3.36 3.89 2.74 2.74

<Preparation of prepolymer composition> (Example 1) To 100 parts of the prepolymer (C-1) obtained in Preparation Example 1 (including non-volatile components), 0.67 parts of TDI adduct (trade name "Takenate D-103H", manufactured by Mitsui Chemicals, NCO group content: 13.0%, solid content: 75%) were added. The amount of TDI adduct (non-volatile components) was 0.3 parts to 100 parts of the non-volatile components of the prepolymer (C-1). Heat and reduce pressure, stir while desolvating, and obtain a prepolymer composition. The total NCO group content of the obtained prepolymer composition was 1.13%.

(Examples 2 to 15, Comparative Examples 1 to 12) Except for using the formula shown in Tables 2-1 to 2-3, the prepolymer composition is obtained in the same manner as in the above-mentioned Production Example 1. The total NCO group content of the obtained prepolymer composition is shown in Tables 2-1 to 2-3. In addition, the details of each component in Tables 2-1 to 2-3 are shown below. ž  Polymeric MDI: Trade name "Lupranate M20S", manufactured by BASF INOAC POLYURETHANES ž  HDI isocyanurate: Trade name "Duranate TPA-100", manufactured by Asahi Kasei Corporation ž  HDI adduct: Trade name "Duranate AE700-100", manufactured by Asahi Kasei Corporation ž  HDI biuret: Trade name "Duranate 24A-100", manufactured by Asahi Kasei Corporation

<Production of synthetic leather> After applying a solution-type urethane resin (trade name "RESAMIN NE-8875-30M", manufactured by Dainichi Seika Co., Ltd.) on release paper, it was dried at 120°C for 5 minutes to form a surface layer with a film thickness of 40 µm. On the other hand, each of the produced prepolymer compositions (moisture-curing adhesive) was applied to other release papers and aged at 25°C and 60% RH for 48 hours to form an adhesive layer with a film thickness of 100 µm. The adhesive layer peeled off from the release paper was sandwiched between the surface layer and the base fabric (test polyester mesh material). Using a sealing machine, place a heat source on the side of the release paper in contact with the surface layer, and press for 30 seconds at 170°C and 0.15 MPa. Then, peel off the release paper in contact with the surface layer to obtain the synthetic leather.

<Evaluation> (Softness) 100 parts of polyurethane resin adhesive (trade name "RESAMIN UD-8351NT", manufactured by Dainichi Seika Co., Ltd.) and 10 parts of isocyanate crosslinking agent (trade name "C-50 crosslinking agent", manufactured by Dainichi Seika Co., Ltd.) were mixed to prepare an adhesive. The prepared adhesive was applied to the surface layer of the release paper formed in the aforementioned "Manufacturing of Synthetic Leather" to form an adhesive layer with a film thickness of 100 µm. After the formed adhesive layer was pre-dried at 80°C for 2 minutes, it was press-bonded to the base material (fabric) at a laminating roller temperature of 40°C. After that, it was aged at 50°C for 48 hours to obtain standard synthetic leather for softness evaluation.

The softness of the synthetic leather was evaluated by comparing the touch of the manufactured synthetic leather and the standard synthetic leather according to the evaluation criteria shown below. The results are shown in Tables 2-1 to 2-3. In addition, "◎", "○" and "△" are qualified. ◎: Softer than the standard synthetic leather. ○: Softer to the same extent as the standard synthetic leather. △: Slightly harder than the standard synthetic leather. ×: Much harder than the standard synthetic leather.

(Heat resistance) The prepolymer composition heated to 100°C was applied to release paper. After aging at 25°C and 60% RH for more than 48 hours, it was peeled off from the release paper to obtain a translucent film with a thickness of 50 µm, a width of 8 cm, and a length of 15 cm. The obtained film was subjected to a heat resistance test by keeping it at 120°C for 400 hours. Using a tensile tester (model "Autograph AGS-100A", manufactured by Shimadzu Corporation), the breaking strength of the film before and after the heat resistance test was measured at 25°C and a tensile speed of 200 mm/min, and the heat resistance was evaluated according to the evaluation criteria shown below. The results are shown in Tables 2-1 to 2-3. In addition, "◎" and "○" are qualified. ◎: The breaking strength retention rate is 50% or more. ○: The breaking strength retention rate is 25% or more and less than 50%. ×: The breaking strength retention rate is less than 25%, or the film is dissolved.

(Usable life (storage stability)) The manufactured prepolymer composition was placed in a container and stored at 100°C for 8 hours with the container open. The viscosity of the prepolymer composition before and after storage was measured, and the usable life was evaluated according to the evaluation criteria shown below. The results are shown in Tables 2-1 to 2-3. In addition, "◎" and "○" are qualified. ◎: Viscosity change rate is less than 150%. ○: Viscosity change rate is more than 150% and less than 250%. ×: Viscosity change rate is more than 250%.

(Solvent resistance) The prepolymer composition heated to 100°C was applied to release paper. After aging at 25°C and 60% RH for more than 48 hours, it was peeled off from the release paper to obtain a translucent film with a thickness of 50 µm, a width of 5 cm, and a length of 5 cm. The obtained film was immersed in acetone for 10 minutes and then taken out. The linear expansion rate of the film taken out (={(width of the film after immersion)/(width of the film before immersion)}×100(%)) was calculated, and the solvent resistance was evaluated according to the criteria shown below. The results are shown in Tables 2-1 to 2-3. In addition, "◎" and "○" are qualified. ◎: The linear expansion rate of one side of the film is less than 120%. ○: The linear expansion rate of one side of the film is 120% or more and less than 150%. △: The linear expansion rate of one side of the film is 150% or more. ×: The film is dissolved.

[table 2-1] Embodiment 1 2 3 4 5 6 7 8 9 Prepolymer Type (C-1) (C-1) (C-1) (C-2) (C-2) (C-2) (C-3) (C-3) (C-4) Quantity (portion) 100 100 100 100 100 100 100 100 100 TDI adduct (NCO group: 13.0%) Quantity (portion) 0.3 5 10 0.5 10 20 0.5 10 20 Polymeric MDI (NCO group: 31.3%) Quantity (portion) HDI isocyanurate (NCOg: 23.1%) Quantity (portion) HDI adduct (NCO group: 11.9%) Quantity (portion) HDI biuret (NCO group: 23.5%) Quantity (portion) Total NCO group content (%) 1.13 1.86 2.56 1.85 3.18 4.36 2.82 4.07 5.69 Softness ◎ ◎ ○ ◎ ◎ ○ ◎ ◎ ○ Heat resistance ○ ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ Available time ○ ○ ○ ○ ○ ○ ○ ○ ○ Solvent resistance ○ ○ ◎ ○ ◎ ◎ ○ ◎ ◎

[Table 2-2] Embodiment Comparison Example 10 11 12 13 14 15 1 2 3 4 Prepolymer Type (C-5) (C-6) (C-7) (C-9) (C-13) (C-14) (C-2) (C-4) (C-2) (C-2) Quantity (portion) 100 100 100 100 100 100 100 100 100 100 TDI adduct (NCO group: 13.0%) Quantity (portion) 10 10 10 10 10 10 30 Polymeric MDI (NCO group: 31.3%) Quantity (portion) 5 HDI isocyanurate (NCO group: 23.1%) Quantity (portion) HDI adduct (NCO group: 11.9%) Quantity (portion) HDI biuret (NCO group: 23.5%) Quantity (portion) Total NCO group content (%) 4.07 4.07 3.81 4.07 4.07 4.07 1.77 3.36 5.36 3.17 Softness ◎ ○ ○ △ ◎ ○ ◎ × × × Heat resistance ◎ ◎ ◎ ○ ◎ ◎ × × ◎ ○ Available time ○ ○ ○ ○ ○ ○ ○ ○ × × Solvent resistance ◎ ◎ ◎ ○ ◎ ◎ × × ○ ○

[Table 2-3] Comparison Example 5 6 7 8 9 10 11 12 Prepolymer Type (C-2) (C-8) (C-2) (C-2) (C-2) (C-10) (C-11) (C-12) Quantity (portion) 100 100 100 100 100 100 100 100 TDI adduct (NCO group: 13.0%) Quantity (portion) 10 10 20 10 Polymeric MDI (NCO group: 31.3%) Quantity (portion) 10 HDI isocyanurate (NCO group: 23.1%) Quantity (portion) 10 HDI adduct (NCO group: 11.9%) Quantity (portion) 10 HDI biuret (NCO group: 23.5%) Quantity (portion) 10 Total NCO group content (%) 4.45 3.18 3.71 2.69 3.74 6.32 5.69 5.11 Softness × × △ ○ ○ × × × Heat resistance ○ ○ ◎ ◎ ◎ ○ ◎ ◎ Available time × ○ ◎ ◎ ◎ ◎ ○ × Solvent resistance ○ ○ △ △ △ ○ ◎ ◎

It is known that by using TDI adducts, mechanical strengths such as solvent resistance required for synthetic leather applications are improved compared to the case of using aliphatic polyisocyanates such as HDI. In addition, it is known that by using TDI adducts, softness and usable time that cannot be obtained when using polymeric MDI are improved. In addition, it is known that even when using TDI adducts, if a polyol (A) containing a specific amount of polyester polyol (A-1) having constituent units derived from aromatic dicarboxylic acids is not used, the softness of the resulting synthetic leather is poor (Comparison Example 6). (Industrial Applicability)

The urethane prepolymer composition of the present invention is useful as an adhesive for making synthetic leather and various laminates.

Claims (7)

A urethane prepolymer composition, comprising: a urethane prepolymer (C) which is a reaction product of a polyol (A) and a polyisocyanate (B), and a trihydroxymethylpropane adduct (D) of toluene diisocyanate; wherein the urethane prepolymer (C) is a resin having a carboxyl group or an amine sulfonic acid (salt) group; the polyol (A) is a polyester polyol (A-1) containing 5 to 90% by weight of a constituent unit derived from an aromatic dicarboxylic acid; and the trihydroxymethylpropane adduct (D) of toluene diisocyanate is 0.1 to 0.1 parts by weight of the urethane prepolymer (C). The content of the product (D) is 0.2-25 parts by mass; the isocyanate group content based on the total of the urethane prepolymer (C) and the trihydroxymethylpropane adduct (D) of toluene diisocyanate is 1.0-6.0% by mass; the polyol (A) further contains at least one other polyol (A-2) selected from the group consisting of polyester polyol (wherein the polyester polyol (A-1) is excluded), polyether polyol, and polycarbonate polyol; the ratio of the other polyol (A-2) in the polyol (A) is 10-95% by mass. The urethane prepolymer composition of claim 1, wherein the proportion of the polyester polyol (A-1) in the polyol (A) is 5-70% by mass; and the proportion of the other polyol (A-2) in the polyol (A) is 30-95% by mass. The urethane prepolymer composition of claim 1 or 2, wherein the molar ratio (NCO group/OH group) of the aforementioned polyol (A) to the aforementioned polyisocyanate (B) is 1.3 to 2.0. The urethane prepolymer composition of claim 1 or 2, wherein the melt viscosity of the urethane prepolymer (C) at 100°C is less than 110 dPa‧s. A moisture-curing adhesive containing the urethane prepolymer composition of any one of claims 1 to 4. A laminated body comprising: a substrate; and a cured layer disposed on the substrate and formed by the cured product of the moisture-curing adhesive of claim 5. A synthetic leather comprising: a skin layer; a hardened material layer disposed on the skin layer and formed by a hardened material of the moisture-curing adhesive of claim 5; and a base material layer disposed on the hardened material layer.