JP7625914B2 - Reaction-curable polyurethane resin-forming composition, molded body using said resin-forming composition, and coating agent - Google Patents

Description

The present invention relates to a reaction-curable polyurethane resin-forming composition having excellent wet heat durability, a molded body using the resin-forming composition, and a coating agent.

Polyurethane resin compositions have traditionally been used exclusively in organic solvents, and because they have high adhesion to a variety of materials and have a variety of excellent physical properties, they have been widely used as coating agents, paints, adhesives, printing inks, etc.

In recent years, there has been a demand from society and industry for resin compositions that do not use organic solvents, due to environmental conservation and work safety requirements.

As examples of polyurethane resin compositions that do not use organic solvents, particularly solvent-free resin compositions, urethane resin compositions that have excellent mechanical strength and wet heat stability have been proposed (Patent Document 1). However, the resulting compositions have a poor texture due to high initial stress, and are not suitable for use in materials that people come into contact with, such as synthetic leather.

JP 2015-81278 A

The present invention has been made in consideration of the above-mentioned background art, and its purpose is to provide a molded body and a coating agent that combine excellent texture, mechanical properties including breaking strength, and wet heat durability, and to provide a reactive curable polyurethane resin-forming composition that is environmentally friendly when producing the molded body and the coating agent.

As a result of intensive research conducted by the inventors to solve the above problems, they discovered that the above problems can be solved by making the base agent (A) in a reactive curable polyurethane resin-forming composition contain a multifunctional polyol with a specific structure, and by setting the ester group concentration of the resin-forming composition containing the base agent (A) and the curing agent (B) within a specific range, thereby completing the present invention.

That is, the present invention includes the following embodiments:

[1] A reactive curable polyurethane resin-forming composition comprising a base agent (A) and a curing agent (B), wherein the base agent (A) comprises a multifunctional polyol (a1) and a diol (a2), the multifunctional polyol (a1) being obtained from a polycarbonate diol (p1) and a polyester polyol (p2) having 3 or more hydroxyl functional groups, an average hydroxyl functional group number of 2.3 to 3.5, an average hydroxyl value of 70 to 285 mgKOH/g, and a mass ratio of (p1) to (p2) of (p1)/(p2) = 75/25 to 55/45;
The curing agent (B) is at least one selected from the group consisting of diphenylmethane diisocyanate and modified diphenylmethane diisocyanate (b1);
and the concentration of ester groups in the reaction-curable polyurethane resin-forming composition is 0.10 to 2.00 mmol/g.
A reaction-curable polyurethane resin-forming composition comprising:

[2] The reactive curable polyurethane resin-forming composition according to [1] above, characterized in that the diol (a2) is at least one selected from the group consisting of polycarbonate diols, polyester diols obtained by ring-opening addition polymerization of cyclic ester compounds, and copolymers thereof.

[3] The reactive curable polyurethane resin-forming composition according to [1] or [2] above, characterized in that the number average molecular weight of the multifunctional polyol (a1) is in the range of 400 to 3,000.

[4] A reaction-curable polyurethane resin-forming composition according to any one of [1] to [3] above, characterized in that the reaction-curable polyurethane resin-forming composition does not contain an organic solvent.

[5] A molded article using the reaction-curable polyurethane resin-forming composition described in any one of [1] to [4] above.

[6] A coating agent using the reaction-curable polyurethane resin-forming composition described in any one of [1] to [4] above.

The reactive curable polyurethane resin-forming composition of the present invention can provide a molded article and a coating agent that have excellent texture, mechanical properties including breaking strength, and wet heat durability. It can also provide a reactive curable polyurethane resin-forming composition that is environmentally friendly when producing the molded article and the coating agent.

The present invention is a reactive curable polyurethane resin-forming composition comprising a base agent (A) containing a specific multifunctional polyol (a1) and a diol (a2), and a curing agent (B). In the present invention, unless otherwise specified, the ester group refers to an ester group derived from a carboxylic acid.

The multifunctional polyol (a1) in the present invention is obtained from a polycarbonate diol (p1) and a polyester polyol (p2) having three or more hydroxyl functional groups.

Examples of polycarbonate diols (p1) include those obtainable by reacting carbonates such as dialkyl carbonates (e.g., dimethyl carbonate, diethyl carbonate), alkylene carbonates (e.g., ethylene carbonate, propylene carbonate), and diaryl carbonates (e.g., diphenyl carbonate, dinaphthyl carbonate, dianthryl carbonate, diphenanthryl carbonate, diindanyl carbonate, tetrahydronaphthyl carbonate), with glycols.

The glycol is selected from the group of low molecular weight polyols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, diol dimer acid, ethylene oxide or propylene oxide adduct of bisphenol A, bis(β-hydroxyethyl)benzene, and xylylene glycol. These may be used alone or in combination of two or more.

As the polyester polyol (p2) having 3 or more hydroxyl functional groups, a polyester polyol obtained from a polyol containing a polyhydric alcohol and a dicarboxylic acid component, or a polyol obtained by ring-opening addition polymerization of a cyclic ester compound such as a lactone using a polyhydric alcohol as an initiator, is preferred.

Examples of the polyhydric alcohols include trimethylolpropane, glycerin, pentaerythritol, and sorbitol. Bifunctional alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, neopentyl glycol, hexamethylene glycol, dipropylene glycol, and trimethylene glycol may be used in combination as long as the performance is not reduced. Polyester polyols obtained by condensing these alcohols with polybasic acids such as oxalic acid, malonic acid, maleic acid, adipic acid, tartaric acid, pimelic acid, sebacic acid, phthalic acid, and terephthalic acid through a known condensation method can be used.

Preferred lactones include, for example, β-propiolactone, β-butyrolactone, γ-butyrolactone, β-valerolactone, γ-valerolactone, δ-valerolactone, α-caprolactone, β-caprolactone, γ-caprolactone, δ-caprolactone, ε-caprolactone, α-methyl-ε-caprolactone, β-methyl-ε-caprolactone, 4-methylcaprolactone, γ-caprylolactone, ε-caprylolactone, and ε-palmitolactone. One or more of these may be used in combination. Among these, a ring-opening addition polymer of ε-caprolactone using trimethylolpropane as an initiator is preferred from the standpoint of stability during polymerization and economic efficiency.

In the present invention, a polyester polyol (p3) having an average number of hydroxyl functional groups of 2 or more and less than 3 may be used in combination as a component of the multifunctional polyol (a1). In particular, polyester polyols obtained from glycol and dicarboxylic acid components, and polyols obtained by ring-opening addition polymerization of cyclic ester compounds such as lactones using glycol as an initiator are preferred.

Examples of the glycols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, diol dimer acid, ethylene oxide or propylene oxide adducts of bisphenol A, bis(β-hydroxyethyl)benzene, xylylene glycol, and the like. Trimethylolpropane, glycerin, pentaerythritol, sorbitol, and the like can also be used in combination. Examples of dicarboxylic acids include polybasic acids such as oxalic acid, malonic acid, maleic acid, adipic acid, tartaric acid, pimelic acid, sebacic acid, phthalic acid, and terephthalic acid.

Preferred lactones include, for example, β-propiolactone, β-butyrolactone, γ-butyrolactone, β-valerolactone, γ-valerolactone, δ-valerolactone, α-caprolactone, β-caprolactone, γ-caprolactone, δ-caprolactone, ε-caprolactone, α-methyl-ε-caprolactone, β-methyl-ε-caprolactone, 4-methylcaprolactone, γ-caprylolactone, ε-caprylolactone, and ε-palmitolactone. One or more of these may be used in combination. Among these, a ring-opening addition polymer of ε-caprolactone using ethylene glycol as an initiator is preferred from the standpoint of stability during polymerization and economic efficiency.

The mass ratio of polycarbonate diol (p1) to polyester polyol (p2) having 3 or more hydroxyl functional groups is in the range of (p1)/(p2) = 75/25 to 55/45, preferably in the range of (p1)/(p2) = 70/30 to 60/40. When polyester polyol (p3) having an average number of hydroxyl functional groups of 2 or more but less than 3 is used in combination, the mass ratio is preferably in the range of (p1)/(p2+p3) = 75/25 to 55/45, more preferably in the range of (p1)/(p2+p3) = 70/30 to 60/40.

By setting the mass ratio within the above range, a reaction-curable polyurethane resin composition having high strength and high elongation mechanical properties can be obtained by balancing the cohesive strength of the polycarbonate diol, the urethane group concentration, and the content of the polyester polyol having 3 or more hydroxyl functional groups.

The multifunctional polyol (a1) may be a simple mixture of polycarbonate diol (p1) and polyester polyol (p2), but a copolymer polyol obtained by an ester exchange reaction may also be used. The same applies when polyester polyol (p3) is used in combination.

The average number of hydroxyl functional groups in the multifunctional polyol (a1) is 2.3 to 3.5, preferably in the range of 2.5 to 3.0. If the average number of hydroxyl functional groups is high, the elongation at break in the tensile test tends to decrease, and if the average number of hydroxyl functional groups is low, the strength at break in the tensile test tends to decrease.

The average hydroxyl value of the multifunctional polyol (a1) is 70 to 285 mgKOH/g, preferably 90 to 180 mgKOH/g. If the average hydroxyl value is low, the urethane group concentration will be low and the strength at break in a tensile test will be low, while if the average hydroxyl value is high, the urethane group concentration will be high and the strength at break in a tensile test will be improved but the elongation at break will tend to be low.

In the present invention, the average number of functional groups is calculated as follows based on the nominal number of functional groups.
Average functionality=((number of functional groups of polycarbonate diol (p1)×mol)+(number of functional groups of polyester polyol (p2)×mol)+(number of functional groups of polyester polyol (p3)×mol))/((mol of polycarbonate diol (p1))+(mol of polyester polyol (p2))+(mol of polyester polyol (p3)).

In the present invention, the number average molecular weight of the polycarbonate diol (p1) is preferably 400 to 5,000, more preferably 500 to 2,000, taking into consideration ease of synthesis and ease of handling.

The number average molecular weight of the multifunctional polyol (a1) is preferably in the range of 400 to 3,000, and more preferably in the range of 500 to 2,000. By setting it in this range, it is possible to achieve both excellent texture and wet heat durability.

Examples of the polycarbonate diol (a2) in the present invention include those obtainable by reacting carbonates such as dialkyl carbonates, such as dimethyl carbonate and diethyl carbonate, alkylene carbonates, such as ethylene carbonate and propylene carbonate, and diaryl carbonates, such as diphenyl carbonate, dinaphthyl carbonate, dianthryl carbonate, diphenanthryl carbonate, diindanyl carbonate and tetrahydronaphthyl carbonate, with the following glycols:

The glycol is selected from the group of low molecular weight polyols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 3,3-dimethylolheptane, diethylene glycol, dipropylene glycol, neopentyl glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, diol dimer acid, ethylene oxide or propylene oxide adduct of bisphenol A, and bis(β-hydroxyethyl)benzene. These may be used alone or in combination of two or more.

The diol (a2) in the present invention is preferably at least one selected from the group consisting of polycarbonate diols, polyester diols obtained by ring-opening addition polymerization of cyclic ester compounds, and copolymers thereof. Among these, from the viewpoint of the strength and flexibility of the resulting coating, it is preferable to use a copolymer of a polycarbonate diol and a polyester diol obtained by ring-opening addition polymerization of a cyclic ester compound. As the cyclic ester compound, those listed above as lactones can be preferably used.

The number average molecular weight of diol (a2) is preferably 300 to 5,000, and more preferably 1,000 to 3,000. If the number average molecular weight is too low, the flexibility of the resulting coating may decrease, and the texture and conformability to the substrate may decrease. On the other hand, if the number average molecular weight is too high, the coating strength may be insufficient.

The curing agent (B) in the present invention is at least one selected from the group consisting of diphenylmethane diisocyanate (hereinafter also referred to as MDI) and modified diphenylmethane diisocyanate (b1). It is preferably a urethane-modified polyisocyanate obtained by urethane-modifying MDI with polycarbonate polyol (b2). Here, urethane modification refers to the formation of urethane bonds by reacting a hydroxyl group-containing compound with a polyisocyanate.

The urethane-modified polyisocyanate can be easily obtained by charging MDI and polycarbonate polyol (b2) in a reaction vessel and carrying out a urethane reaction. At this time, the content of the isomers (2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate) in the MDI used for the preparation is not particularly limited, but considering the ease of availability, it is preferably 0.5 to 60 mass%.

In the present invention, the isocyanate content of the curing agent (B) is preferably 5.0 to 33.6% by mass, and more preferably 10 to 25% by mass. If the isocyanate content is below the lower limit, the viscosity of the resulting urethane-modified polyisocyanate may be high, which may impair workability.

Furthermore, as isocyanates that can be used in the curing agent (B) of the present invention, aromatic isocyanates other than MDI, aliphatic isocyanates, alicyclic isocyanates, araliphatic isocyanates, isocyanurate group-containing polyisocyanates obtained from these isocyanates as raw materials, uretdione group-containing polyisocyanates, uretdione group- and isocyanurate group-containing polyisocyanates, urethane group-containing polyisocyanates, allophanate group-containing polyisocyanates, biuret group-containing polyisocyanates, uretoimine group-containing polyisocyanates, etc. may be used in combination within the range that does not decrease performance.

In the present invention, additives can be used in the base agent or the curing agent, or in both. Examples of additives include plasticizers, fillers, colorants, flame retardants, antioxidants, UV absorbers, leveling agents, pigments/dyes, antibacterial agents, and antifungal agents.

When a cured product is obtained from the reactive curable polyurethane resin-forming composition of the present invention, from the viewpoint of excellent reactive curing, strength and flexibility of the cured product, and suppression of unnecessary foaming, the R value [the number of moles of all isocyanate groups in the curing agent (B)/the number of moles of all hydroxyl groups in the base agent (A)] is preferably 0.8 or more, but from the viewpoint of improving the above-mentioned series of effects, it is more preferable that it is within the range of 0.9 to 5.0, and among these, from the viewpoint of extremely excellent strength and flexibility of the cured product, it is particularly preferable that it is within the range of 1.0 to 1.8.

The heating temperature during reactive curing is preferably 60 to 180°C. The heating time is preferably 2 minutes to 2 hours. If the temperature is too low or the time is too short, curing may be insufficient. On the other hand, if the temperature is too high or the time is too long, the cured product or substrate may be subjected to unnecessary thermal history, which may lead to deterioration of the resulting cured product.

When mixing the base agent (A) and the curing agent (B), a catalyst can be used to shorten the curing process and improve the reaction rate. Examples of catalysts include urethane reaction catalysts such as tertiary amine catalysts such as triethylamine, tetramethylpropylenediamine, tetramethylhexamethylenediamine, and tolylenediamine, and metal catalysts such as tin-based catalysts such as stannous octoate, stannous oleate, and dibutyltin dilaurate. These can be used alone or in combination.

The ester group concentration of the reactive curable polyurethane resin forming composition in the present invention can be calculated as follows. Ester group concentration of reactive curable polyurethane resin composition (mmol/g) = (ester group concentration of multifunctional polyol (a1) (mmol/g) x blended mass (g) + ester group concentration of polycarbonate diol (a2) (mmol/g) x blended mass (g) + ester group concentration of curing agent (B) (mmol/g) x blended mass (g)) / total blended mass (g). From the viewpoint of strength, flexibility and durability of the cured product obtained from the polyurethane resin forming composition, the ester group concentration of the polyurethane resin forming composition is 0.10 to 2.00 mmol/g, preferably 0.20 to 1.60 mmol/g. If the ester group concentration of the urethane resin forming composition is less than 0.10 mmol/g, the strength of the obtained cured product is reduced. If the ester group concentration is more than 2.00 mmol/g, the durability in a humid and hot environment is reduced.

Next, a molded article and a coating agent using the reaction-curable polyurethane resin-forming composition of the present invention will be described. The reaction-curable polyurethane resin-forming composition of the present invention is used as a molded article and a coating material for electronic device components such as communication tablets, clothing, furniture and home appliance components, daily necessities, and automobile components. Molded articles include components, structures, films, and sheets, and examples of such molded articles include those molded by known techniques such as casting and coating.

The coating agent is a coating film formed on a substrate by mixing the above-mentioned crosslinking agent and additives as necessary with a coating resin containing at least the polyurethane resin-forming composition of the present invention, stirring uniformly, and then applying the coating film to the substrate by known techniques such as spray coating, knife coating, wire bar coating, doctor blade coating, reverse roll coating, and calendar coating.

The substrates include stainless steel, phosphate-treated steel, galvanized steel, iron, copper, aluminum, brass, glass, acrylic resin, polycarbonate resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene phthalate resin, polystyrene resin, AS resin, ABS resin, polycarbonate-ABS resin, 6-nylon resin, 6,6-nylon resin, MXD6 nylon resin, polyvinyl chloride resin, polyvinyl alcohol resin, polyurethane resin, phenolic resin, melamine resin, polyacetal resin, chlorinated polyolefin resin, polyolefin resin, polyamide resin, polyether ether ketone Examples of such materials include substrates molded from materials such as olefin resins such as styrene resin, polyphenylene sulfide resin, NBR resin, chloroprene resin, SBR resin, SEBS resin, polyethylene, and polypropylene; organic fibers containing at least one main component selected from polyethylene terephthalate resin, polytrimethylene terephthalate resin, polybutylene terephthalate resin, polyethylene resin, polypropylene resin, polystyrene resin, 6-nylon resin, 6,6-nylon resin, acrylic resin, polyvinyl alcohol resin, cellulose, polylactic acid, cotton, and wool; inorganic fibers such as glass wool; and carbon fibers.

To improve adhesion, the surfaces of these substrates can be pretreated with corona discharge, flame treatment, ultraviolet light irradiation, ozone treatment, etc.

The following describes examples of the present invention, but the present invention is not limited to these examples. Note that percentages and parts in the examples are by weight unless otherwise specified.

[Synthesis of multifunctional polyol 1]
In a reactor equipped with a stirrer, a thermometer, a heater, and a cooler, 550 g of PCD-1, 400 g of PCL-1, and 50 g of PCL-3 were charged, and the temperature was gradually raised to 190°C under a nitrogen stream. Transesterification was carried out at 190°C for 5 hours to obtain a multifunctional polyol (Polyol-1). The average number of hydroxyl groups in Polyol-1 was 2.8, and the hydroxyl value was 145 (mgKOH/g).

[Synthesis of multifunctional polyol 2]
In the same synthesis method as in Synthesis 1 of polyfunctional polyol, 600 g of PCD-2 and 400 g of PCL-2 were charged and transesterification reaction was carried out at 190° C. for 5 hours to obtain a polyfunctional polyol (Polyol-2). The average hydroxyl functionality of Polyol-2 was 2.8 and the hydroxyl value was 250 (mgKOH/g).

[Synthesis of diol 1]
In the same synthesis method as in Synthesis 1 of polyfunctional polyol, 700 g of PCD-2 and 300 g of PCL-4 were charged and transesterification was carried out at 190° C. for 5 hours to obtain a diol (Polyol-3). The average hydroxyl functional group number of Polyol-3 was 2.0 and the hydroxyl value was 56 (mgKOH/g).

[Synthesis of diol 2]
Using the same synthesis method as in Synthesis 1 of polyfunctional polyol, 800 g of PCD-2 and 200 g of MPD were charged and transesterification was carried out at 190° C. for 5 hours to obtain a diol (Polyol-4). The average hydroxyl functionality of Polyol-4 was 2.0 and the hydroxyl value was 234 (mgKOH/g).

The raw materials used are as follows:
(1) PCD-1: 1,6-hexanediol-based polycarbonate diol, number average molecular weight 3,000
(2) PCD-2: 1,6-hexanediol-based polycarbonate diol, number average molecular weight 2,000
(3) PCL-1: Polycaprolactone triol (manufactured by Daicel Corporation, product name: Plaxel 305, number average molecular weight 550)
(4) PCL-2: Polycaprolactone triol (manufactured by Daicel Corporation, product name: Plaxel 303, number average molecular weight 300)
(5) PCL-3: Polycaprolactone diol (manufactured by Daicel Corporation, product name: Plaxel 210, number average molecular weight 1,000)
(6) PCL-4: Polycaprolactone diol (manufactured by Daicel Corporation, product name: Plaxel 220, number average molecular weight 2,000)
(7) MPD: 3-methyl-1,5-pentanediol (manufactured by Tokyo Chemical Industry Co., Ltd.).

[Synthesis of isocyanate prepolymer 1]
In a reactor equipped with a stirrer, a thermometer, a heater, and a cooler, 508 g of high isomer ratio MDI and 492 g of Polyol-3 were charged, and a urethane reaction was carried out for 3 hours at 75°C under a nitrogen atmosphere to obtain an isocyanate prepolymer (Isocyanate-1). The NCO content of Isocyanate-1 was 15.0%.

[Synthesis of isocyanate prepolymer 2]
In the same synthesis method as in Synthesis 1 of Isocyanate Prepolymer, 575 g of high isomer ratio MDI and 425 g of PCD-2 were charged and subjected to a urethane reaction at 75° C. for 3 hours under a nitrogen atmosphere to obtain an isocyanate prepolymer (Isocyanate-2). The NCO content of Isocyanate-2 was 17.5%.

[Synthesis of isocyanate prepolymer 3]
In the same synthesis method as in Synthesis 1 of Isocyanate Prepolymer, 200 g of low isomer ratio MDI, 176 g of high isomer ratio MDI, and 624 g of PCD-2 were charged, and a urethane reaction was carried out at 75°C for 3 hours under a nitrogen atmosphere to obtain an isocyanate prepolymer (Isocyanate-3). The NCO content of Isocyanate-3 was 10.0%.

[Synthesis of Polyisocyanate 1]
A reactor having a capacity of 1 L equipped with a stirrer, a thermometer, a cooler and a nitrogen gas inlet tube was charged with 950 g of HDI, 50 g of MPD, and 0.1 g of zirconium octylate (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.), and reacted at 110 ° C. for 4 hours. Next, 0.04 g of JP-508 (manufactured by Johoku Kagaku Co., Ltd., trade name) was charged into this reactor, and a termination reaction was carried out at 80 ° C. for 1 hour. The isocyanate content of the reaction product after the termination reaction was 40.3%. This reaction product was subjected to thin-film distillation at 130 ° C. and 0.04 kPa to obtain polyisocyanate (Isocyanate-4). The isocyanate content of Isocyanate-4 was 19.2%, the viscosity at 25 ° C. was 1800 mPa · s, and the free diisocyanate content was 0.1%. Furthermore, FT-IR and ¹³ C-NMR analyses confirmed almost no urethane groups or isocyanurate groups.

The raw materials used are as follows:
(8) Low isomer ratio MDI: 2,2'-MDI + 2,4'-MDI = 1.5%, 4,4'-MDI = 98.5%, NCO group content = 33,6%
(9) High isomer ratio MDI: 2,2'-MDI + 2,4'-MDI = 55.0%, 4,4'-MDI = 45.0%, NCO group content = 33,6%
(10) HDI: hexamethylene diisocyanate (manufactured by Tosoh Corporation).

[Preparation of Cured Polyurethane Coating]
The base material (A), the curing agent (B), and the curing catalyst were mixed (unit: grams) as shown in Table 3, and the liquid immediately after mixing was poured onto release paper and cast with a bar coater to give a film with a thickness of 100 μm, which was cured at 150° C. for 5 minutes and then aged at 50° C. for 24 hours to obtain a polyurethane coating (film). This film was used as a sample and the following evaluations were carried out.

[Tensile properties]
The tensile properties of the obtained film were measured in accordance with JIS K6251. The results are shown in Table 3.
Test equipment: Tensilon UTA-500 (manufactured by A&D Co., Ltd.)
Measurement conditions: 25°C x 50% RH
・Head speed: 200 mm/min・Dumbbell No. 4.

[Moisture and heat resistance test]
The obtained film was left to stand in a thermostatic chamber controlled at a temperature of 80° C. and a relative humidity of 95%. After 400 hours, the film was taken out and the tensile properties were measured in accordance with JIS K6251. The property retention was calculated from the measured values of the strength at break before and after leaving the film under the moist heat conditions.

[Evaluation criteria for cured polyurethane films]
The properties of the cured film are considered to be good if the 100% modulus before the durability test is 0.5-5.0 MPa, the strength at break is 30 MPa or greater, and the retention of strength at break after the moist heat resistance test is 60% or greater.

The raw materials used are as follows:
(11) Polyol-5: A copolymer polycarbonate diol of 3-methyl-1,5-pentanediol/1,6-hexanediol=5/5 (molar ratio), number average molecular weight 2,000
(12) PCL-5: Polycaprolactone triol (manufactured by Daicel Corporation, product name: Plaxel 320, number average molecular weight 2,000)
(13) DOTDL: dioctyltin dilaurate (Kishida Chemical Co., Ltd.)
(14) BYK-331: Polyether-modified polydimethylsiloxane (manufactured by BYK Chemie Co., Ltd.)

Claims (6)

A reactive curable polyurethane resin-forming composition comprising a base agent (A) and a curing agent (B), wherein the base agent (A) comprises a multifunctional polyol (a1) and a diol (a2), the multifunctional polyol (a1) being obtained from a polycarbonate diol (p1) and a polyester polyol (p2) having 3 or more hydroxyl functional groups, an average hydroxyl functional group number of 2.3 to 3.5, an average hydroxyl value of 70 to 285 mgKOH/g, and a mass ratio of (p1) to (p2) of (p1)/(p2)=75/25 to 55/45;
The curing agent (B) is at least one selected from the group consisting of diphenylmethane diisocyanate and modified diphenylmethane diisocyanate (b1);
and the concentration of ester groups in the reaction-curable polyurethane resin-forming composition is 0.10 to 2.00 mmol/g.
A reaction-curable polyurethane resin-forming composition comprising: The reactive curable polyurethane resin-forming composition according to claim 1, characterized in that the diol (a2) is at least one selected from the group consisting of polycarbonate diols, polyester diols obtained by ring-opening addition polymerization of cyclic ester compounds, and copolymers thereof. The reactive curable polyurethane resin-forming composition according to claim 1 or 2, characterized in that the number average molecular weight of the multifunctional polyol (a1) is in the range of 400 to 3,000. The reaction-curable polyurethane resin-forming composition according to any one of claims 1 to 3 is characterized in that it does not contain an organic solvent. A molded article made using the reaction-curable polyurethane resin-forming composition according to any one of claims 1 to 4. A coating agent using the reaction-curable polyurethane resin-forming composition according to any one of claims 1 to 4.