Polyurethane resin-forming composition, polyurethane resin, and molded article

Abstract

To provide a polyurethane resin formative composition which contributes to production of a polyurethane resin that has a pot life for a long time and has excellent low temperature bendability, while reducing an organic solvent.SOLUTION: A polyurethane resin formative composition contains a main agent containing a polyol component, a curing agent containing a polyisocyanate component, and a catalyst, wherein the polyol component contains first polyol having three or more hydroxyl groups, and second polyol having two hydroxyl groups, the first polyol contains polycarbonate polyester polyol, the polyisocyanate component contains an isocyanate group-terminated urethane prepolymer having a site derived from diphenylmethane diisocyanate and a site derived from polyether polyol, the catalyst contains a metal catalyst containing at least one metal element selected from the group consisting of titanium, zinc and aluminum, and the content of the organic solvent is 0 to 10 mass%.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a polyurethane resin-forming composition, a polyurethane resin, a molded article, and a coating agent.

Background Art

[0002] Polyurethane resin-forming compositions containing a large amount of organic solvents have been widely used in coating agents, paints, adhesives, printing inks, etc. because of their high adhesion to various materials and excellent various physical properties. However, in recent years, there has been a demand for polyurethane resin-forming compositions with reduced organic solvents for reducing environmental impact.

[0003] For example, Patent Document 1 discloses a solvent-free reactive adhesive containing a trimethylolpropane adduct of tolylene diisocyanate or diphenylmethane diisocyanate, and further a polyisocyanate containing an aromatic polyisocyanate (excluding the trimethylolpropane adduct of tolylene diisocyanate or diphenylmethane diisocyanate) and a polyol, and containing a specific amount of the trimethylolpropane adduct.

[0004] Patent Document 2 discloses an isocyanate component containing an isocyanate prepolymer which is a reaction product of a reactant containing at least one polyisocyanate, at least one polyol selected from the group consisting of polyester polyols, polyether polyols, and combinations thereof, and at least one polyol having two or more OH groups and a hydrogen crosslinking group, and a polyol component containing at least one polyol selected from the group consisting of polyester polyols, polyether polyols, and combinations thereof, a two-component solvent-free adhesive.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, the polyurethane resin formed from the conventional solvent-free polyurethane resin-forming composition does not have sufficient low-temperature flexibility. Also, from the perspective of workability, a long pot life is required, but it is not always easy to extend the pot life.

[0007] Some aspects of the present disclosure are directed to providing a polyurethane resin-forming composition that has a long pot life while reducing organic solvents and contributes to the production of a polyurethane resin having excellent low-temperature flexibility, and a coating agent containing the polyurethane resin-forming composition. Also, some other aspects of the present disclosure are directed to providing a polyurethane resin formed from the above polyurethane resin-forming resin composition and a molded article comprising a cured product of the above polyurethane resin-forming resin composition. [Means for Solving the Problems]

[0008] Each aspect of the present disclosure includes the following embodiments [1] to

[12] .

[0009] [1] A polyurethane resin-forming composition comprising a main agent containing a polyol component, a curing agent containing a polyisocyanate component, and a catalyst, wherein the polyol component includes a first polyol having 3 or more hydroxyl groups and a second polyol having 2 hydroxyl groups, the first polyol includes a polycarbonate polyester polyol, the polyisocyanate component includes an isocyanate group-terminated urethane prepolymer having a site derived from diphenylmethane diisocyanate and a site derived from a polyether polyol, the catalyst includes a metal catalyst containing at least one metal element selected from the group consisting of titanium, zinc, and aluminum, and the content of the organic solvent is 0 to 10% by mass.

[0010] [2] The polyurethane resin-forming composition according to [1], wherein the first polyol includes a polycarbonate polyester polyol having a structure formed by ring-opening addition polymerization of a cyclic ester compound.

[0011] [3] The polyurethane resin-forming composition according to [1] or [2], wherein the second polyol includes a diol having a carbonate group.

[0012] [4] The polyurethane resin-forming composition according to any one of [1] to [3], wherein the second polyol includes a polycarbonate polyester diol.

[0013] [5] The polyurethane resin-forming composition according to any one of [1] to [4], wherein the main agent includes a reaction product of a polycarbonate diol, a polyester polyol having 3 or more hydroxyl groups, and a polyester diol.

[0014] [6] The polyurethane resin-forming composition according to [5], wherein the average hydroxyl number of the reaction product is 2.1 to 3.5.

[0015] [7] The content of the site derived from the polyether polyol in the isocyanate group-terminated urethane prepolymer is 20 to 80% by mass based on the total mass of the isocyanate group-terminated urethane prepolymer, and the polyurethane resin-forming composition according to any one of [1] to [6].

[0016] [8] The isocyanate group content of the polyisocyanate component is 4 to 30% by mass, and the polyurethane resin-forming composition according to any one of [1] to [7].

[0017] [9] The catalyst is liquid at 25°C, and the polyurethane resin-forming composition according to any one of [1] to [8].

[0018]

[10] A polyurethane resin formed from the polyurethane resin-forming composition according to any one of [1] to [9].

[0019]

[11] A molded article containing a cured product of the polyurethane resin-forming composition according to any one of [1] to [9].

[0020]

[12] A coating agent containing the polyurethane resin-forming composition according to any one of [1] to [9]. [Advantages of the Invention]

[0021] According to some aspects of the present disclosure, it is possible to provide a polyurethane resin-forming composition that has a long pot life and contributes to the production of a polyurethane resin having excellent low-temperature flexibility, and a coating agent containing the polyurethane resin-forming composition. Further, according to some other aspects of the present disclosure, it is possible to provide a polyurethane resin formed from the polyurethane resin-forming resin composition, and a molded article composed of a cured product of the polyurethane resin-forming resin composition. [Embodiments for Carrying Out the Invention]

[0022] Hereinafter, embodiments of the present disclosure will be described in detail. In this specification, a numerical range indicated by "~" indicates a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. The minimum value or the maximum value of a numerical range indicated by "~" can be arbitrarily combined with the maximum value or the minimum value of another numerical range indicated by "~". Also, the individually described upper limit value and lower limit value can be arbitrarily combined.

[0023] <Polyurethane resin-forming composition> One aspect of the present disclosure includes a main agent containing a polyol component, a curing agent containing a polyisocyanate component, and a catalyst. The polyol component includes a first polyol having 3 or more hydroxyl groups and a second polyol having 2 hydroxyl groups. The first polyol includes a polycarbonate polyester polyol. The polyisocyanate component includes an isocyanate group-terminated urethane prepolymer having a site derived from diphenylmethane diisocyanate and a site derived from a polyether polyol. The catalyst includes a metal catalyst containing at least one metal element selected from the group consisting of titanium, zinc, and aluminum. The content of the organic solvent is 0 to 10% by mass. It is a polyurethane resin-forming composition (hereinafter, also simply referred to as "composition").

[0024] The above composition may be a one-component type composition in which all the constituent components are contained in one liquid, or may be a multi-component type composition in which the constituent components are separated and present in a plurality of liquids. For example, the above composition may include a first liquid containing a main agent and a second liquid containing a curing agent. The above composition may include the first liquid, the second liquid, and a third liquid different from these. When the above composition is a multi-component type composition, other constituent components (such as a catalyst) may be contained in the first liquid, may be contained in the second liquid, or may be contained in the third liquid.

[0025] The above composition cures by the reaction of the main agent and the curing agent, forming a cured product containing a polyurethane resin. According to the above composition, a polyurethane resin having excellent low-temperature flexibility can be obtained. Further, since the above composition has a long pot life, it has excellent workability. In addition, the above composition also tends to have excellent curability, and according to the above composition, it is also possible to achieve both a long pot life and a short precure time. Therefore, the above composition can also be referred to as an environmentally friendly polyurethane resin-forming composition (for example, a solvent-free reaction-curable polyurethane resin-forming composition) during production.

[0026] Moreover, the polyurethane resin formed by the above composition also tends to have excellent tensile properties. Specifically, for example, it tends to be excellent in durability under normal conditions (that is, tensile properties confirmed by breaking strength), heat resistance (heat durability), and heat and humidity resistance (heat and humidity durability).

[0027] Hereinafter, each component contained in the above composition will be described.

[0028] (Main agent) The main agent contains a polyol component. The polyol component is a component composed of a compound (polyol) having two or more hydroxyl groups, and includes a first polyol having three or more hydroxyl groups and a second polyol having two hydroxyl groups.

[0029] [First polyol] The first polyol includes a polycarbonate polyester polyol. The polycarbonate polyester polyol has two or more carbonate units, two or more ester units, and three or more hydroxyl groups.

[0030] The polycarbonate polyester polyol is obtained, for example, by an ester exchange reaction between a polycarbonate polyol and a polyester polyol. Therefore, the polycarbonate polyester polyol has, for example, a site derived from the polycarbonate polyol and a site derived from the polyester polyol.

[0031] The polycarbonate polyester polyol is preferably a compound having a site derived from a polycarbonate diol (hereinafter referred to as "polyol (p1)") and a site derived from a polyester polyol having 3 or more hydroxyl groups (hereinafter referred to as "polyol (p2)"), for example, a compound obtained by reacting polyol (p1) and polyol (p2). More preferably, it is a compound having a site derived from polyol (p1), a site derived from polyol (p2), and a site derived from a polyester diol (hereinafter referred to as "polyol (p3)"), for example, a compound obtained by reacting polyol (p1), polyol (p2), and polyol (p3). Polyols (p1) to (p3) may each be used alone or in combination of two or more.

[0032] Polyol (p1) has two or more carbonate units and two hydroxyl groups. Polyol (p1) is preferably a compound having a site derived from carbonates and a site derived from a bifunctional alcohol, for example, a compound obtained by reacting carbonates and a bifunctional alcohol.

[0033] Examples of the carbonates include dialkyl carbonates such as dimethyl carbonate and diethyl carbonate; alkylene carbonates such as ethylene carbonate and propylene carbonate; diaryl carbonates such as diphenyl carbonate, dinaphthyl carbonate, dianthryl carbonate, diphenanthryl carbonate, diindanyl carbonate, and tetrahydronaphthyl carbonate. These may be used alone or in combination of two or more.

[0034] Examples of the difunctional alcohol 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, dimer diol, ethylene oxide or propylene oxide adduct of bisphenol A, bis(β-hydroxyethyl)benzene, xylylene glycol, and the like. These may be used alone or in combination of two or more.

[0035] Considering the ease of synthesis and handling, the number average molecular weight of the polyol (p1) is preferably from 400 to 5000, more preferably from 500 to 3000. The number average molecular weight in this specification is a standard polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0036] The polyol (p2) has two or more ester units and three or more hydroxyl groups. The polyol (p2) is preferably a compound having a site derived from a polyhydric alcohol and a site derived from a dicarboxylic acid or a cyclic ester compound (for example, a compound obtained by reacting a polyol containing a polyhydric alcohol with a dicarboxylic acid, or a compound obtained by ring-opening addition polymerization of a cyclic ester compound using a polyol containing a polyhydric alcohol as an initiator). The polyol (p2) having a site derived from a cyclic ester compound can also be said to have a structure formed by ring-opening addition polymerization of the cyclic ester compound. From the viewpoint of obtaining more excellent low-temperature flexibility and good stability and economy during polymerization, the polyol (p2) more preferably has a structure formed by ring-opening addition polymerization of a cyclic ester compound.

[0037] Examples of the polyhydric alcohol include trimethylolpropane, glycerin, pentaerythritol, sorbitol, etc. These may be used alone or in combination of two or more.

[0038] Examples of the dicarboxylic acid include oxalic acid, malonic acid, maleic acid, adipic acid, tartaric acid, pimelic acid, sebacic acid, phthalic acid, terephthalic acid, etc. These may be used alone or in combination of two or more.

[0039] Examples of the cyclic ester compound include lactones. Examples of the lactones include 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, ε-palmitolactone, etc. These may be used alone or in combination of two or more.

[0040] From the viewpoints of stability during polymerization and economy, the polyol (p2) is preferably a ring-opening addition polymer of ε-caprolactone using trimethylolpropane as an initiator.

[0041] The polyol (p2) may have a site derived from a bifunctional alcohol. That is, the polyol containing the above polyhydric alcohol may contain a bifunctional alcohol. Examples of the bifunctional alcohol are the same as those of the bifunctional alcohol mentioned for the polyol (p1).

[0042] From the viewpoints of ease of synthesis and ease of handling, the number average molecular weight of the polyol (p2) is preferably 400 to 5000, more preferably 500 to 3000.

[0043] The polyol (p3) has two or more ester units and two hydroxyl groups. The polyol (p3) is preferably a compound having a site derived from a bifunctional alcohol and a site derived from a polybasic acid component or a cyclic ester compound (for example, a compound obtained by reacting a bifunctional alcohol with a polybasic acid component, or a compound obtained by ring-opening addition polymerization of a cyclic ester compound using a bifunctional alcohol as an initiator). The polyol (p3) having a site derived from a cyclic ester compound can also be said to have a structure formed by ring-opening addition polymerization of the cyclic ester compound. From the viewpoints of stability and economy during polymerization, it is more preferable for the polyol (p3) to have a structure formed by ring-opening addition polymerization of a cyclic ester compound.

[0044] Examples of the bifunctional alcohol include the same ones as those listed for the bifunctional alcohol in the polyol (p1). Examples of the polybasic acid component include the same ones as the dicarboxylic acids listed for the polyol (p2). Examples of the cyclic ester compound include lactones, and examples of the lactones include the same ones as those listed for the lactones in the polyol (p2). These may be used alone or in combination of two or more.

[0045] From the viewpoints of stability and economy during polymerization, the polyol (p3) is preferably a ring-opening addition polymer of ε-caprolactone using ethylene glycol as an initiator.

[0046] From the viewpoints of ease of synthesis and handling, the number average molecular weight of the polyol (p3) is preferably from 400 to 5000, more preferably from 500 to 3000.

[0047] In the polycarbonate polyester polyol, the ratio ((p1) / (p2)) of the content of the site derived from the polyol (p1) to the content of the site derived from the polyol (p2) is preferably from 90 / 10 to 55 / 45, more preferably from 90 / 10 to 60 / 40, by mass ratio.

[0048] When using polyol (p3) in combination, the ratio ((p1) / (p2 + p3)) of the content of the site derived from polyol (p1) to the total content of the site derived from polyol (p2) and the site derived from polyol (p3) is preferably 75 / 25 to 45 / 55 and more preferably 70 / 30 to 50 / 50 in terms of mass ratio.

[0049] By setting the mass ratio within the above range, the balance among the cohesive force of polyol (p1), the urethane group concentration, and the content of polyol (p2) becomes good, and it becomes easier to obtain a polyurethane resin having high strength and high elongation mechanical properties.

[0050] From the above, the polycarbonate polyester polyol in a particularly preferred embodiment has, as the site derived from polyol (p1), a site derived from carbonates and a site derived from a bifunctional alcohol, and as the site derived from polyol (p2), a site derived from a polyhydric alcohol and a site derived from a dicarboxylic acid or a cyclic ester compound. Further, when the polycarbonate polyester polyol has a site derived from polyol (p3) in addition to the above, as the site, it has a site derived from a bifunctional alcohol and a site derived from a polybasic acid component or a cyclic ester compound.

[0051] From the viewpoints of stability and economy during polymerization, the polycarbonate polyester polyol preferably has a structure formed by ring-opening addition polymerization of a cyclic ester compound.

[0052] The polycarbonate polyester polyol preferably does not contain an ether bond. Thereby, the ether bonds (ether bonds derived from the isocyanate group-terminated urethane prepolymer described later) in the polyurethane resin are uniformly arranged in a well-balanced manner, and it is possible to more highly achieve both strength and durability and excellent low-temperature flexibility.

[0053] The first polyol may contain only one type of polycarbonate polyester polyol, or may contain two or more types of polycarbonate polyester polyols. The average number of hydroxyl groups (the number of hydroxyl groups per molecule) of all the polycarbonate polyester polyols contained in the first polyol is, for example, 3 to 5.

[0054] The first polyol may consist only of polycarbonate polyester polyol. The first polyol may contain polyols other than polycarbonate polyester polyol (for example, polyol (p2) which is a raw material, etc.) as long as the effects of the present invention are not inhibited. From the viewpoint of achieving both high strength and high elongation mechanical properties to a higher degree and improving durability under heat and humid heat conditions, the content of polycarbonate polyester polyol in the first polyol may be 30 to 100% by mass, or may be 50 to 100% by mass based on the total mass of the first polyol.

[0055] The first polyol is preferably liquid at 25°C from the viewpoints of ease of handling, uniform dispersibility, improvement of physical properties of the coating film, and shortening of the curing time / reduction of curing energy of the coating film.

[0056] [Second Polyol] As the second polyol, any polyol having 2 hydroxyl groups (that is, diol) can be used without particular limitation. Examples of the second polyol include polycarbonate diol, polycarbonate polyester diol, polyester diol, polyether diol, etc. The second polyol may contain polyol (p1), polyol (p3), etc. which are raw materials of the first polyol. These diols may be used alone or in combination of two or more.

[0057] From the viewpoint of the strength and durability of the resulting polyurethane resin, the second polyol preferably contains a diol having a carbonate group, more preferably contains a polycarbonate diol or a polycarbonate polyester diol, and even more preferably contains a polycarbonate polyester diol.

[0058] The second polyol may consist only of a diol having a carbonate group. The content of the diol having a carbonate group in the second polyol may be 50 to 70% by mass or 70 to 100% by mass based on the total mass of the second polyol from the viewpoint that high strength and high elongation mechanical properties can be more highly compatible and the durability under heat and humid heat conditions is improved.

[0059] The second polyol preferably contains a polymer having a number average molecular weight of 300 to 5000. When the number average molecular weight of the polymer is 300 or more, the low-temperature flexibility of the resulting polyurethane resin is further improved. Also, when the number average molecular weight of the polymer is 5000 or less, the strength of the polyurethane resin is further improved. The polymer is preferably a diol having a carbonate group, more preferably a polycarbonate diol or a polycarbonate polyester diol, and even more preferably a polycarbonate polyester diol. The number average molecular weight of the above polymer is preferably 500 to 3000.

[0060] The second polyol may consist only of a polymer having a number average molecular weight of 300 to 5000. The content of the polymer may be 50 to 70% by mass or 70 to 100% by mass based on the total mass of the second polyol from the viewpoint that high strength and high elongation mechanical properties can be more highly compatible and the durability under heat and humid heat conditions is improved.

[0061] From the viewpoints of ease of handling, uniform dispersibility, improvement of the physical properties of the coating film, and shortening of the curing time / reduction of the curing energy of the coating film, the second polyol is preferably liquid at 25°C.

[0062] The ratio of the content of the second polyol to the content of the first polyol (second polyol / first polyol), in terms of mass ratio, may be from 40 / 60 to 95 / 5, may be from 50 / 50 to 95 / 5, may be from 60 / 40 to 90 / 10, or may be from 80 / 20 to 90 / 10 from the viewpoint of excellent mechanical properties.

[0063] In one embodiment, the main agent may contain a reaction product of polyol (p1) and polyol (p2) (hereinafter referred to as "reaction product (i)"), and may also contain a reaction product of polyol (p1), polyol (p2), and polyol (p3) (hereinafter referred to as "reaction product (ii)"). These reaction products at least contain the polycarbonate polyester polyol which is the above-mentioned first polyol. Since the details of polyols (p1) to (p3) are the same as above, they are omitted.

[0064] Reaction products (i) and (ii) can be reaction mixtures obtained by the transesterification reaction of the above polyols. Therefore, reaction products (i) and (ii) may contain by-products (for example, the above-mentioned second polyol, monofunctional alcohol, etc.) and unreacted raw materials (polyols (p1) to (p3)) generated by the above transesterification reaction.

[0065] Among the above, when the main agent contains reaction product (ii), high-strength and high-elongation mechanical properties can be more highly balanced, and the durability under heat and hydrothermal conditions tends to improve. The content of reaction product (ii) may be 10% by mass or more, 15% by mass or more, 20% by mass or more, or 30% by mass or more, and may be 95% by mass or less, 90% by mass or less, 65% by mass or less, 50% by mass or less, or 40% by mass or less based on the total mass of the main agent. The content of reaction product (ii) may be from 10 to 50% by mass, or may be from 20 to 40% by mass based on the total mass of the main agent from the viewpoint of further highly balancing high-strength and high-elongation mechanical properties and further improving the durability under heat and hydrothermal conditions.

[0066] The ratio ((p1) / (p2)) of the amount of polyol (p1) used to the amount of polyol (p2) used to obtain the reaction product (i) is preferably from 90 / 10 to 55 / 45, more preferably from 90 / 10 to 60 / 40, by mass ratio.

[0067] The ratio ((p1) / (p2 + p3)) of the amount of polyol (p1) used to the total amount of polyol (p2) and polyol (p3) used to obtain the reaction product (ii) is preferably from 75 / 25 to 45 / 55, more preferably from 70 / 30 to 50 / 50, by mass ratio.

[0068] The average number of hydroxyl groups of the reaction products (i) and (ii) is preferably from 2.1 to 3.5, more preferably from 2.2 to 3.0. When the average number of hydroxyl groups is 3.5 or less, the breaking strength and elongation at break in the tensile test are further improved, and when the average number of hydroxyl groups is 2.1 or more, the durability is further improved.

[0069] The above average number of hydroxyl groups can be calculated, for example, based on the nominal functionality as follows. When polyol (p3) is not used, the number of moles of polyol (p3) is calculated as 0. Average number of hydroxyl groups = [(number of hydroxyl groups of polyol (p1) × number of moles of polyol (p1))+(number of hydroxyl groups of polyol (p2) × number of moles of polyol (p2))+(number of hydroxyl groups of polyol (p3) × number of moles of polyol (p3))] / [(number of moles of polyol (p1))+(number of moles of polyol (p2))+(number of moles of polyol (p3))]

[0070] The average hydroxyl value of the reaction products (i) and (ii) is preferably 30 to 380 mgKOH / g, more preferably 50 to 180 mgKOH / g. When the average hydroxyl value is 30 mgKOH / g or more, the urethane group concentration does not become too low, and the breaking strength in the tensile test is further improved. When the average hydroxyl value is 380 mgKOH / g or less, the urethane group concentration does not become too high, and the low-temperature flexibility is further improved. The average hydroxyl value of the reaction products (i) and (ii) may be 20 to 700 mgKOH, or may be 30 to 300 mgKOH / g. The average hydroxyl value is a value measured by a method using an acetylating reagent in accordance with JIS K 1557-1:2007.

[0071] From the viewpoints of ease of handling, uniform dispersibility, improvement of the physical properties of the coating film, and shortening of the curing time / reduction of the curing energy of the coating film, the reaction products (i) and (ii) are preferably liquid at 25°C.

[0072] From the viewpoint that the main agent can more highly achieve both high strength and high elongation mechanical properties and improve the durability under heat and humid heat conditions, in addition to the above reaction products (i) and / or (ii), it may contain a reaction product of polyol (p1) and polyol (p3) (hereinafter referred to as "reaction product (iii)"). For example, the main agent may be a mixture of the reaction product (i) and / or (ii) and the reaction product (iii).

[0073] The number average molecular weight of the reaction product (iii) is preferably 300 to 5000, more preferably 500 to 3000. When the number average molecular weight of the reaction product (iii) is 300 or more, the low-temperature flexibility of the resulting film is further improved. Also, when the number average molecular weight of the reaction product (iii) is 5000 or less, the film strength is further improved.

[0074] The average hydroxyl value of the reaction product (iii) is preferably 20 to 380 mgKOH / g, more preferably 30 to 250 mgKOH / g. When the average hydroxyl value is 20 mgKOH / g or more, the urethane group concentration does not become too low, and the breaking strength in the tensile test is further improved. When the average hydroxyl value is 380 mgKOH / g or less, the urethane group concentration does not become too high, and the low-temperature flexibility is further improved.

[0075] From the viewpoints of ease of handling, uniform dispersibility, improvement of the physical properties of the coating film, and shortening of the curing time / reduction of the curing energy of the coating film, the reaction product (iii) is preferably liquid at 25°C.

[0076] The content of the reaction product (iii) may be 5% by mass or more, 10% by mass or more, 35% by mass or more, 50% by mass or more, or 60% by mass or more, and may be 90% by mass or less, 85% by mass or less, 80% by mass or less, or 70% by mass or less, based on the total mass of the main agent. From the viewpoint of further achieving both high strength and high elongation mechanical properties and further improving the durability under heat and humid heat conditions, it may be 5 to 70% by mass, or may be 10 to 80% by mass, based on the total mass of the main agent.

[0077] The ratio of the content of the reaction product (iii) to the total content of the reaction products (i) and (ii) ((iii) / (i)+(ii)) may be 5 / 95 to 90 / 10 by mass, may be 10 / 90 to 85 / 15, or may be 60 / 40 to 80 / 20, from the viewpoint of better mechanical properties.

[0078] The content of the main agent may be adjusted within the range of the R value described later. The content of the main agent may be, for example, 20% by mass or more, 30% by mass or more, or 50% by mass or more, and may be 90% by mass or less, 85% by mass or less, or 80% by mass or less, based on the total mass of the composition. The content of the main agent may be, for example, 20 to 90% by mass, may be 30 to 85% by mass, or may be 50 to 80% by mass, based on the total mass of the composition.

[0079] (Hardener) The hardener contains a polyisocyanate component. The polyisocyanate component is a component composed of a compound having two or more isocyanates (polyisocyanate), and contains an isocyanate group-terminated urethane prepolymer having a site derived from diphenylmethane diisocyanate (hereinafter also referred to as "MDI") and a site derived from polyether polyol.

[0080] The isocyanate group-terminated urethane prepolymer is, for example, a compound obtained by reacting MDI and polyether polyol so that the isocyanate group is in excess, and has a urethane bond formed by the reaction of MDI and polyether polyol and an isocyanate group located at at least one end.

[0081] There are three isomers of MDI: 4,4'-diphenylmethane diisocyanate (hereinafter referred to as "4,4'-MDI"), 2,4'-diphenylmethane diisocyanate (hereinafter referred to as "2,4'-MDI"), and 2,2'-diphenylmethane diisocyanate (hereinafter referred to as "2,2'-MDI"). As MDI, one of these may be used alone, or two or more may be used in combination. In this specification, 4,4'-MDI may be referred to as the main component of MDI, and 2,4'-MDI and 2,2'-MDI may be referred to as isomer components.

[0082] The content of 4,4'-MDI in MDI may be, for example, 40 to 100% by mass based on the total amount of MDI. The content of 2,4'-MDI in MDI may be, for example, 0 to 60% by mass based on the total amount of MDI. The content of 2,2'-MDI in MDI may be, for example, 0 to 5% by mass based on the total amount of MDI.

[0083] As the MDI, from the viewpoint of excellent mechanical properties and ease of handling, it is preferably MDI with a high content ratio of isomer components (high isomer ratio MDI). Specifically, the total content of 2,4'-MDI and 2,2'-MDI is preferably 20 to 60% by mass based on the total amount of MDI. From the same viewpoint, the total content of 2,4'-MDI and 2,2'-MDI may be 40% by mass or more, or 50% by mass or more, and may be 70% by mass or less, or 60% by mass or less, based on the total amount of MDI.

[0084] From the viewpoint of further excellent low-temperature flexibility, tensile strength and heat resistance, the content of the site derived from MDI in the isocyanate group-terminated urethane prepolymer is preferably 20 to 80% by mass based on the total mass of the isocyanate group-terminated urethane prepolymer. From the same viewpoint, the content of the site derived from MDI in the isocyanate group-terminated urethane prepolymer may be 25% by mass or more, 35% by mass or more, 45% by mass or more, or 50% by mass or more, and may be 75% by mass or less, 70% by mass or less, 60% by mass or less, or 55% by mass or less, based on the total mass of the isocyanate group-terminated urethane prepolymer.

[0085] The polyether polyol has two or more ether units and two or more hydroxyl groups. When the isocyanate group-terminated urethane prepolymer has a site derived from the polyether polyol, not only the durability and low-temperature flexibility of the resin (for example, the coating) are improved, but also the storage stability is improved, and the crystallization at room temperature (for example, 25 ° C) is suppressed. Effects such as improvement of handleability due to reduction of viscosity can also be obtained. Examples of the polyether polyol include polypropylene glycol, polyethylene glycol, and polytetramethylene ether glycol. Among these, polypropylene glycol is preferable from the viewpoint of more highly achieving both the durability and low-temperature flexibility of the resin (for example, the coating). These may be used alone or in combination of two or more.

[0086] The average number of hydroxyl groups in the polyether polyol is 2 or more, for example, it is 2 to 3. The number average molecular weight of the polyether polyol is preferably 500 to 5000, and more preferably 2000 to 4000.

[0087] From the viewpoint of further excellent low-temperature flexibility, tensile strength and heat resistance, the content of the site derived from the polyether polyol in the isocyanate group-terminated urethane prepolymer is preferably 20 to 80% by mass based on the total mass of the isocyanate group-terminated urethane prepolymer. From the same viewpoint, the content of the site derived from the polyether polyol in the isocyanate group-terminated urethane prepolymer may be 25% by mass or more, 30% by mass or more, 40% by mass or more, or 45% by mass or more, or 75% by mass or less, 65% by mass or less, 55% by mass or less, or 50% by mass or less based on the total mass of the isocyanate group-terminated urethane prepolymer.

[0088] The isocyanate group-terminated urethane prepolymer may have a site derived from an isocyanate other than diphenylmethane diisocyanate (other isocyanate). That is, the isocyanate group-terminated urethane prepolymer may be a compound obtained by the reaction of diphenylmethane diisocyanate, another isocyanate, and a polyether polyol.

[0089] Examples of other isocyanates include 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, and the like.

[0090] The content of the site derived from other isocyanates in the isocyanate group-terminated urethane prepolymer may be 30% by mass or less, or may be 0% by mass, based on the total mass of the isocyanate group-terminated urethane prepolymer.

[0091] From the viewpoints of ease of handling, uniform dispersibility, improvement of the physical properties of the coating film, and shortening of the curing time / reduction of the curing energy of the coating film, the isocyanate group-terminated urethane prepolymer is preferably liquid at 25°C.

[0092] The polyisocyanate component may contain one kind of isocyanate group-terminated urethane prepolymer alone, or may contain two or more kinds of isocyanate group-terminated urethane prepolymers.

[0093] The polyisocyanate component may consist only of the isocyanate group-terminated urethane prepolymer. The polyisocyanate component may contain a polyisocyanate other than the isocyanate group-terminated urethane prepolymer (for example, MDI as a raw material) as long as the effects of the present invention are not inhibited. The content of the isocyanate group-terminated urethane prepolymer in the polyisocyanate component may be, for example, 30 to 100% by mass based on the total mass of the polyisocyanate component.

[0094] From the viewpoints of good handling properties due to low viscosity and excellent heat resistance, the isocyanate group content (NCO content) of the polyisocyanate component is preferably 4 to 30% by mass, may be 5% by mass or more, 7% by mass or more, or 10% by mass or more, and may be 26% by mass or less or 20% by mass or less. The isocyanate group content in all the isocyanate group-terminated urethane prepolymers contained in the polyisocyanate component may also be in the same range as described above.

[0095] In one embodiment, the curing agent may contain a reaction product of MDI and a polyether polyol (hereinafter referred to as "reaction product (iv)"), and may also contain a reaction product of MDI, another isocyanate, and a polyether polyol (hereinafter referred to as "reaction product (v)"). These reaction products at least contain the isocyanate group-terminated urethane prepolymer described above. Since the details of MDI, other isocyanates, and polyether polyols are the same as those above, they are omitted.

[0096] Reaction products (iv) and (v) can be reaction mixtures obtained by the urethanization reaction of the above polyisocyanate and polyether polyol. Therefore, reaction products (iv) and (v) may contain by-products and unreacted raw materials generated by the above urethanization reaction.

[0097] The amount of MDI used to obtain the above reaction products (iv) and (v) is preferably 20 to 80% by mass based on the total mass of the reaction product from the viewpoint of further excellent low-temperature flexibility, tensile strength, and heat resistance. From the same viewpoint, the amount of MDI used to obtain the above reaction products (iv) and (v) may be 25% by mass or more, 35% by mass or more, 45% by mass or more, or 50% by mass or more based on the total mass of the reaction product, and may be 75% by mass or less, 70% by mass or less, 60% by mass or less, or 55% by mass or less.

[0098] The amount of polyether polyol used to obtain the above reaction products (iv) and (v) is preferably 15 to 80% by mass based on the total mass of the reaction product from the viewpoint of further excellent low-temperature flexibility, tensile strength, and heat resistance. From the same viewpoint, the amount of polyether polyol used to obtain the above reaction products (iv) and (v) may be 20% by mass or more, 25% by mass or more, 30% by mass or more, 40% by mass or more, or 45% by mass or more based on the total mass of the reaction product, and may be 75% by mass or less, 65% by mass or less, 55% by mass or less, or 50% by mass or less.

[0099] The content of the curing agent may be adjusted within the range of the R value described later. The content of the curing agent may be, for example, 5% by mass or more, 10% by mass or more, 15% by mass or more, or 20% by mass or more based on the total mass of the composition, and may be 60% by mass or less, 55% by mass or less, 50% by mass or less, or 45% by mass or less. The content of the curing agent may be, for example, 5 to 60% by mass based on the total mass of the composition, and may also be 10 to 60% by mass, 15 to 55% by mass, 20 to 50% by mass, or 20 to 45% by mass.

[0100] (Catalyst) The catalyst is a urethanization catalyst that catalyzes the reaction between the main agent and the curing agent, and includes a metal catalyst containing at least one metal element selected from the group consisting of titanium, zinc, and aluminum. These may be used alone or in combination of two or more.

[0101] The metal catalyst may be a catalyst composed of a simple metal, or may be a metal complex (organometallic catalyst) in which metal atoms are bonded to one or more organic ligands.

[0102] Examples of the metal catalyst containing titanium (titanium catalyst) include titanium 2-ethylhexanoate, tetrakis(2,4-pentanedionato)titanium(IV), etc.

[0103] Examples of the metal catalyst containing zinc (zinc catalyst) include zinc bis(2-ethylhexanoate), zinc bis(2,4-pentanedionato)(II), etc.

[0104] Examples of the metal catalyst containing aluminum (aluminum catalyst) include aluminum monoacetylacetonate bis(ethylacetoacetate), tris(2,4-pentanedionato)aluminum(III), aluminum 2-ethylhexanoate, etc.

[0105] The catalyst may include a metal catalyst containing a metal element other than titanium, zinc, and aluminum, and may also include a non-metal catalyst such as an amine catalyst, as long as it does not impair the pot life or curability.

[0106] From the viewpoints of ease of handling, uniform dispersibility, improvement of physical properties of the coating film, and shortening of the curing time / reduction of curing energy of the coating film, the catalyst is preferably liquid at 25°C.

[0107] The content of the catalyst may be 0.05% by mass or more, 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more based on the total mass of the composition, from the viewpoints of excellent pot life, curability, and mechanical properties. The content of the catalyst may be 3.0% by mass or less, 2.5% by mass or less, 2.0% by mass or less, 1.5% by mass or less, or 1.0% by mass or less based on the total mass of the composition, from the viewpoints of excellent pot life, curability, and mechanical properties. From these viewpoints, the content of the catalyst may be, for example, 0.05 to 3.0% by mass, 0.05 to 2.5% by mass, 0.1 to 2.0% by mass, 0.2 to 1.5% by mass, or 0.3 to 1.0% by mass based on the total mass of the composition.

[0108] When only a titanium catalyst is used as the catalyst, the content of the titanium catalyst is preferably 0.3 to 3.0% by mass based on the total mass of the composition. When the content of the titanium catalyst is 0.3% by mass or more, there is a tendency to cure in a short time under heating conditions, and when the content of the titanium catalyst is 3.0% by mass or less, there is a tendency to obtain higher mechanical properties. From the same viewpoints, the content of the titanium catalyst may be 0.4% by mass or more, 2.5% by mass or less, 2.0% by mass or less, or 1.0% by mass or less.

[0109] When only an aluminum catalyst is used as the catalyst, the content of the aluminum catalyst is preferably 0.15 to 3.0% by mass based on the total mass of the composition. When the content of the aluminum catalyst is 0.15% by mass or more, there is a tendency to cure in a short time under heating conditions, and when the content of the aluminum catalyst is 3.0% by mass or less, there is a tendency to obtain higher mechanical properties. From the same viewpoints, the content of the aluminum catalyst may be 0.5% by mass or more or 1.0% by mass or more, 2.5% by mass or less, or 2.0% by mass or less.

[0110] When only a zinc catalyst is used as the catalyst, the content of the zinc catalyst is preferably 0.1 to 0.5% by mass based on the total mass of the composition. When the content of the zinc catalyst is 0.1% by mass or more, it tends to cure in a short time under heating conditions, and when the content of the aluminum catalyst is 0.5% by mass or less, the pot life becomes longer and higher mechanical properties tend to be obtained. From the same viewpoint, the content of the zinc catalyst may be 0.2% by mass or more and may be 0.45% by mass or less.

[0111] (Additive) The composition may contain, as additives, a leveling agent, a plasticizer, a filler, a colorant, a flame retardant, an antioxidant, an ultraviolet absorber, a pigment / dye, an antibacterial agent, an antifungal agent, etc. When the composition is a multi-component type, these additives may be contained in any of the liquids.

[0112] (Organic solvent) The composition may contain an organic solvent, and its content is 0 to 10% by mass based on the total mass of the composition. The content of the organic solvent may be 9% by mass or less, 8% by mass or less, 7% by mass or less, 5% by mass or less, 3% by mass or less, 1% by mass or less. In the present specification, the organic solvent is an organic compound generally used for dissolving polyol and / or polyisocyanate in the technical field, and examples thereof include methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), tetrahydrofuran (THF), ethyl acetate, etc.

[0113] (R value) The R value (the number of moles of all isocyanate groups in the curing agent / the number of moles of all hydroxyl groups in the main agent) is preferably from 0.8 to 5.0 from the viewpoints of excellent reaction curability, strength and flexibility of the cured product, and suppression of unnecessary foaming. From the viewpoint of improving the above-described series of effects, the R value is more preferably from 0.9 to 3.0, and particularly preferably from 1.0 to 2.0. When the R value is 0.8 or more, the strength and flexibility of the polyurethane resin are further improved. When the R value is 5.0 or less, the reaction curability is further improved and the generation of unnecessary foaming can be further reduced.

[0114] The polyurethane resin-forming composition described above is used for forming adhesives, molded articles, coating materials, etc., in addition to adhesives. Examples of the molded article include members, structures, films, and sheets, and those molded by known techniques such as casting and coating can be mentioned. Specifically, for example, members of electronic devices such as communication tablets, clothing, furniture and home appliance members, daily necessities, automobile members, etc. can be mentioned.

[0115] <Coating agent> Another aspect of the present disclosure is a coating agent containing the polyurethane resin-forming composition of the above-described embodiment. The coating agent may be any one that is applied to the surface of a substrate, and adhesives are also included in the concept of coating agents.

[0116] The coating agent may contain a crosslinking agent and an additive as the above-described additives. After stirring the coating agent containing these to be uniform, it is applied onto a substrate by known techniques such as spray coating, knife coating, wire bar coating, doctor blade coating, reverse roll coating, calendar coating, etc. to form a coating film as a coating film, and further cured to obtain a coating film (for example, a coating material).

[0117] The heating temperature during film curing is preferably 80 to 180 °C, the heating time is preferably 30 seconds to 2 hours, and more preferably 1 minute to 30 minutes. When the heating temperature and heating time are within these ranges, the occurrence of poor curing can be further reduced, and unnecessary heat history can be suppressed from being applied to the cured product and the substrate, so that the occurrence of deterioration can be further reduced.

[0118] Examples of the substrate include substrates molded from materials such as stainless steel, phosphated steel, zinc 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, phenol resin, melamine resin, polyacetal resin, chlorinated polyolefin resin, polyolefin resin, polyamide resin, polyetheretherketone resin, polyphenylene sulfide resin, NBR resin, chloroprene resin, SBR resin, SEBS resin, polyethylene, polypropylene and other olefin resins; organic fibers mainly composed of at least one 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; carbon fibers.

[0119] In order to improve the adhesiveness, these substrates can also be subjected to treatments such as corona discharge treatment, flame treatment, ultraviolet irradiation treatment, and ozone treatment on the substrate surface in advance.

[0120] <Formed body> Another aspect of the present disclosure is a molded article including a cured product of the polyurethane resin-forming composition of the above-described embodiment. The cured product contains a polyurethane resin. Examples of the molded article include members of electronic devices such as communication tablets described above, clothing, furniture and home appliance members, daily necessities, automotive members, and the like. These can be molded by known techniques such as casting and coating.

Examples

[0121] Hereinafter, examples of the present invention will be described, but the present invention is not limited to these examples. In the examples, the % and part notations are based on mass unless otherwise specified.

[0122] Details of the raw materials used in this example are as follows. (1) PCD-1: 1,6-Hexanediol-based polycarbonate diol, number average molecular weight 2000 (2) PCD-2: 1,6-Hexanediol-based polycarbonate diol, number average molecular weight 3000 (3) PCL-1: Polycaprolactone diol, number average molecular weight 1000 (trade name: Placcel 210, manufactured by Daicel Corporation) (4) PCL-2: Polycaprolactone diol, number average molecular weight 2000 (trade name: Placcel 220, manufactured by Daicel Corporation) (5) PCL-3: Polycaprolactone triol, number average molecular weight 550 (trade name: Placcel 305, manufactured by Daicel Corporation) (6) Low isomer ratio MDI: 2,2'-MDI + 2,4'-MDI = 1.5%, 4,4'-MDI = 98.5%, NCO content = 33.6% (7) High isomer ratio MDI: 2,2'-MDI + 2,4'-MDI = 55.0%, 4,4'-MDI = 45.0%, NCO content = 33.6% (8) PPG-1: Polypropylene glycol, number average molecular weight 2000 (trade name: Sunnex PP-2000, manufactured by Sanyo Chemical Industries, Ltd.) (9) PPG-2: Polypropylene glycol, number average molecular weight 3000 (trade name: Sunnex PP-3000, manufactured by Sanyo Chemical Industries, Ltd.) (10) Aluminum complex: K-KAT 5218 (manufactured by Kusumoto Chemical Co., Ltd.) (11) Zinc complex: K-KAT XK-635 (manufactured by Kusumoto Chemical Co., Ltd.) (12) Titanium complex: Titanium 2-ethylhexanoate (manufactured by Fujifilm Wako Pure Chemical Corporation) (13) Bismuth complex: Neo-Stan U-600 (manufactured by Nitto Kasei Co., Ltd.) (14) BYK-331: Polyether-modified polydimethylsiloxane (manufactured by BYK-Chemie GmbH)

[0123] <Synthesis Example 1> 700 g of PCD-1 and 300 g of PCL-2 were charged into a reaction apparatus equipped with a stirrer, a thermometer, a heating device, and a cooler, and the temperature was gradually raised to 190°C under a nitrogen stream. The transesterification reaction was carried out at 190°C for 5 hours to obtain a reaction product (Polyol-1) containing polycarbonate polyester diol. The average number of hydroxyl groups of the obtained Polyol-1 was 2.0, the hydroxyl value was 56.1 (mgKOH / g), and the number average molecular weight (Mn) was 2000.

[0124] <Synthesis Example 2> 664 g of PCD-1, 20 g of PCL-1, and 316 g of PCL-3 were charged into a reaction apparatus equipped with a stirrer, a thermometer, a heating device, and a cooler, and the temperature was gradually raised to 190°C under a nitrogen stream. The transesterification reaction was carried out at 190°C for 5 hours to obtain a reaction product (Polyol-2) containing polycarbonate polyester polyol having 3 or more hydroxyl groups. The average number of hydroxyl groups of the obtained Polyol-2 was 2.6, the hydroxyl value was 136.2 (mg-KOH / g), and the number average molecular weight (Mn) was 1080.

[0125] <Synthesis Example 3> Into a reaction apparatus equipped with a stirrer, a thermometer, a heating device, and a cooler, 678 g of PCD-2, 236 g of PCL-2, and 86 g of PCL-3 were charged, and the temperature was gradually raised to 190 °C under a nitrogen stream. The transesterification reaction was carried out at 190 °C for 5 hours to obtain a reaction product (Polyol-3) containing a polycarbonate polyester polyol having 3 or more hydroxyl groups. The average number of hydroxyl groups of the obtained Polyol-3 was 2.3, the hydroxyl value was 64.8 (mg-KOH / g), and the number average molecular weight (Mn) was 2000.

[0126]

Table 1

[0127] <Synthesis Example 4> Into a reaction apparatus equipped with a stirrer, a thermometer, a heating device, and a cooler, 790 g of high-isomer ratio MDI and 210 g of PPG-1 were charged, and a urethanization reaction was carried out at 75 °C for 3 hours under a nitrogen atmosphere to obtain a reaction product (Isocyanate-1) containing an isocyanate group-terminated urethane prepolymer. The NCO content was 25.5%. The viscosity at 25 °C was 500 mPa·s.

[0128] <Synthesis Example 5> Into a reaction apparatus equipped with a stirrer, a thermometer, a heating device, and a cooler, 240 g of high-isomer ratio MDI and 760 g of PPG-1 were charged, and a urethanization reaction was carried out at 75 °C for 3 hours under a nitrogen atmosphere to obtain a reaction product (Isocyanate-2) containing an isocyanate group-terminated urethane prepolymer. The isocyanate group content (NCO content) was 4.7%. The viscosity at 25 °C was 8500 mPa·s.

[0129] <Synthesis Example 6> Into a reaction apparatus equipped with a stirrer, a thermometer, a heating device, and a cooler, 470 g of high-isomer ratio MDI and 530 g of PPG-1 were charged, and a urethanization reaction was carried out at 75 °C for 3 hours under a nitrogen atmosphere to obtain a reaction product (Isocyanate-3) containing an isocyanate group-terminated urethane prepolymer. The NCO content was 13.6%. The viscosity at 25 °C was 1300 mPa·s.

[0130] <Synthesis Example 7> Into a reaction apparatus equipped with a stirrer, a thermometer, a heating device, and a cooler, 360 g of high-isomer ratio MDI and 640 g of PPG-1 were charged, and a urethanization reaction was carried out at 75 °C for 3 hours under a nitrogen atmosphere to obtain a reaction product (Isocyanate-4) containing an isocyanate group-terminated urethane prepolymer. The NCO content was 9.1%. The viscosity at 25 °C was 3700 mPa·s.

[0131] <Synthesis Example 8> Into a reaction apparatus equipped with a stirrer, a thermometer, a heating device, and a cooler, 300 g of high-isomer ratio MDI and 700 g of PPG-1 were charged, and a urethanization reaction was carried out at 75 °C for 3 hours under a nitrogen atmosphere to obtain a reaction product (Isocyanate-5) containing an isocyanate group-terminated urethane prepolymer. The NCO content was 7.1%. The viscosity at 25 °C was 6400 mPa·s.

[0132] <Synthesis Example 9> Into a reaction apparatus equipped with a stirrer, a thermometer, a heating device, and a cooler, 450 g of low-isomer ratio MDI and 550 g of PPG-2 were charged, and a urethanization reaction was carried out at 75 °C for 3 hours under a nitrogen atmosphere to obtain a reaction product (Isocyanate-6) containing an isocyanate group-terminated urethane prepolymer. The NCO content was 13.6%. The viscosity at 25 °C was 3000 mPa·s.

[0133] <Synthesis Example 10> Into a reactor equipped with a stirrer, a thermometer, a heating device, and a cooler, 510 g of high isomer ratio MDI and 490 g of Polyol-1 were charged, and a urethanization reaction was carried out at 75 °C for 3 hours under a nitrogen atmosphere to obtain a reaction product (Isocyanate-7) containing an isocyanate group-terminated urethane prepolymer. The NCO content was 15.0%. The viscosity at 25 °C was 8100 mPa·s.

[0134]

Table 2

[0135] <Examples 1 to 18 and Comparative Examples 1 to 2> Polyol-1 to 3 obtained in Synthesis Examples 1 to 3 were mixed at the compounding ratios shown in Tables 3 to 5 to prepare a main agent. Also, any one of Isocyanate-1 to 7 obtained in Synthesis Examples 4 to 10 was prepared as a curing agent. Further, the materials shown in Tables 3 to 5 were prepared as a catalyst and a leveling agent.

[0136] The main agent, the curing agent, the catalyst, and the leveling agent were mixed as described in the formulations shown in Tables 3 to 5. At this time, the compounding amounts of the main agent and the curing agent were adjusted so that the R value (mole number of all isocyanate groups in the curing agent / mole number of all hydroxyl groups in the main agent) was 1.1. As a result, polyurethane resin-forming compositions of Examples 1 to 18 and Comparative Examples 1 to 2 were obtained respectively.

[0137] <Evaluation> (Low-temperature Flexibility Evaluation) The polyurethane resin-forming composition immediately after mixing was poured onto a release paper and cast into a film shape with a thickness of 100 μm using a bar coater. Next, the cast polyurethane resin-forming composition was placed in a drying device (precision thermostat DF612S, manufactured by Yamato Scientific Co., Ltd.) and heated at 150 °C for 1 to 2 minutes to form a film. The obtained film (semi-cured film) was pressure-bonded to a woven fabric (commercially available polyester product), and further cured by heating at 150 °C for 5 minutes. The pressure bonding at this time was performed by applying one reciprocating pressure with a 5 kg metal roller. Then, it was cured at 60 °C for 18 hours to obtain a laminate composed of a cured film and a woven fabric. Using the obtained laminate, a flexo test was conducted under the following devices and conditions, and the number of bending times until cracks occurred in the film was measured. If the number of times until cracks occurred in the film was 10,000 times or more, it was evaluated that the low-temperature bendability was good. The results are shown in Tables 3 to 5. [Devices, Conditions] · Test device: Flexiometer FOM-100C (manufactured by Daiei Kagaku Seiki Co., Ltd.) · Bending reciprocating speed: 150 times / min · Rotation angle: 22.5 degrees · Temperature: -30 °C

[0138] (Curing property evaluation) The polyurethane resin-forming composition immediately after mixing was poured onto a release paper and cast into a film shape with a thickness of 100 μm using a bar coater. Next, the cast polyurethane resin-forming composition was placed in a drying device (precision thermostat DF612S, manufactured by Yamato Scientific Co., Ltd.) and heated at 150 °C, and the time until the composition became semi-cured by fingertip touch was measured. When the tack became weak, it was judged that the composition was semi-cured, and if the pre-cure time (the time required to reach semi-cure) was within 2 minutes, it was evaluated that the curing property was good. The results are shown in Tables 3 to 5. Note that "when the tack became weak" refers to the state when the composition did not adhere to the finger but clear fingerprints remained on the composition.

[0139] (Stability evaluation) When preparing the polyurethane resin-forming composition, the main agent, catalyst, and leveling agent were mixed to prepare a mixed solution. After adjusting the liquid temperature of this mixed solution to 25°C, it was mixed with a curing agent whose liquid temperature was adjusted to 25°C. The immediately obtained liquid (polyurethane resin-forming composition) was stirred at 300 rpm for 30 seconds using a stirrer, and then the time until the viscosity reached 90,000 mPa·s was measured. If this time was 10 minutes or more, it was evaluated that the pot life was sufficiently long and the stability was good. The results are shown in Tables 3 to 5. The viscosity measurement was carried out under the following apparatus and conditions. [Apparatus, Conditions] ·Test apparatus: Brookfield B-type viscometer ·Spindle: SC4-27 ·Spindle rotation speed: 0.2 RPM

[0140] (Tensile Property Evaluation) The polyurethane resin-forming composition immediately after mixing was poured onto a release paper and cast with a bar coater to form a film with a thickness of 100 μm. Next, the cast polyurethane resin-forming composition was cured by heating at 150°C for 10 minutes, and then cured at 60°C for 18 hours to obtain a cured film (film) made of polyurethane resin.

[0141] [Normal Durability Evaluation] The breaking strength of the film obtained above was measured under the following apparatus and conditions in accordance with JIS K6251. If the breaking strength was 15 MPa or more, it was evaluated that the durability under normal conditions was good. The results are shown in Tables 3 to 5. In the table, "-" indicates unmeasured (the same applies hereinafter). [Apparatus, Conditions] ·Test apparatus: AutoCom type universal testing machine AC-10KN-CM-PL (manufactured by T.S.E. Co., Ltd.) ·Measurement conditions: 25°C × 50% RH ·Head speed: 200 mm / min ·Dumbbell No. 4

[0142] [Heat Resistance Evaluation] A heat resistance test was conducted on the film (a cured film made of a polyurethane resin) obtained above, and the breaking strength retention rate after the test was measured. Specifically, first, the film was placed in a forced-air constant temperature and humidity chamber DNE850 (manufactured by Yamato Scientific Co., Ltd.) and left standing at 120 °C for 400 hours. Next, in the same manner as in the case of the above normal durability evaluation, the breaking strength of the film after the test was measured. Using the breaking strength (T0) of the film obtained in the normal durability evaluation and the breaking strength (T1) of the film after the above test, the breaking strength retention rate was calculated from the following formula. If the breaking strength retention rate was 60% or more, it was evaluated that the heat resistance was good. The results are shown in Tables 3 to 5. Breaking strength retention rate (%) = T1 / T0 × 100

[0143] 〔Evaluation of damp heat resistance〕 A damp heat resistance test was conducted on the film (a cured film made of a polyurethane resin) obtained above, and the breaking strength retention rate after the test was measured. Specifically, first, the film was placed in a low-temperature constant temperature and humidity chamber GLMP-62 (manufactured by FUTABA SCIENCE CO., LTD.) and left standing at 80 °C and a humidity of 95% RH for 400 hours. Next, in the same manner as in the case of the above normal durability evaluation, the breaking strength of the film after the test was measured. Using the breaking strength (T0) of the film obtained in the normal durability evaluation and the breaking strength (T2) of the film after the above test, the breaking strength retention rate was calculated from the following formula. If the breaking strength retention rate was 60% or more, it was evaluated that the damp heat resistance was good. The results are shown in Tables 3 to 5. Breaking strength retention rate (%) = T2 / T0 × 100

[0144]

Table 3

[0145]

Table 4

[0146]

Table 5

Claims

1. A main agent containing a polyol component, a curing agent containing a polyisocyanate component, and a catalyst, wherein the polyol component includes a first polyol having 3 or more hydroxyl groups and a second polyol having 2 hydroxyl groups, the first polyol includes a polycarbonate polyester polyol, the second polyol includes a polycarbonate polyester diol, the polyisocyanate component includes an isocyanate group-terminated urethane prepolymer having a site derived from diphenylmethane diisocyanate and a site derived from a polyether polyol, the catalyst includes a metal catalyst containing at least one metal element selected from the group consisting of titanium, zinc, and aluminum, A polyurethane resin-forming composition having an organic solvent content of 0 to 10% by mass.

2. The polyurethane resin-forming composition according to claim 1, wherein the first polyol includes a polycarbonate polyester polyol having a structure formed by ring-opening addition polymerization of a cyclic ester compound.

3. The polyurethane resin-forming composition according to claim 1 or 2, wherein the main agent includes a reaction product of a polycarbonate diol, a polyester polyol having 3 or more hydroxyl groups, and a polyester diol.

4. The polyurethane resin-forming composition according to claim 3, wherein the average hydroxyl group number of the reaction product is 2.1 to 3.

5.

5. The polyurethane resin-forming composition according to claim 1 or 2, wherein the content of the site derived from the polyether polyol in the isocyanate group-terminated urethane prepolymer is 20 to 80% by mass based on the total mass of the isocyanate group-terminated urethane prepolymer.

6. The polyurethane resin-forming composition according to claim 1 or 2, wherein the isocyanate group content of the polyisocyanate component is 4 to 30% by mass.

7. The polyurethane resin-forming composition according to claim 1 or 2, wherein the catalyst is liquid at 25°C.

8. A polyurethane resin formed from the polyurethane resin-forming composition according to claim 1 or 2.

9. A molded article including a cured product of the polyurethane resin-forming composition according to claim 1 or 2.

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