Polyurethane elastomer and method for producing the same

Abstract

To provide a method for producing a polyurethane elastomer capable of preventing an increase in reaction temperature during chain-extending reactions.SOLUTION: A method for producing a polyurethane elastomer comprises a step of reacting a first polyisocyanate component containing 1,4-bis(isocyanatomethyl)cyclohexane with a first polyol component to obtain an isocyanate-terminated prepolymer. Furthermore, the production method includes a hydroxyl-terminated prepolymer production step of reacting a second polyisocyanate component containing 1,3-bis(isocyanatomethyl)cyclohexane with a second polyol component containing 1,4-butanediol to obtain a hydroxyl-terminated prepolymer. Furthermore, the production method includes a polyurethane elastomer production step of reacting an isocyanate-terminated prepolymer with a hydroxyl-terminated prepolymer to obtain a polyurethane elastomer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyurethane elastomer and a method for producing the same. [Background technology]

[0002] Polyurethane elastomers are widely used in various molded products due to their excellent hardness.

[0003] It has been proposed to produce such polyurethane elastomers by, for example, reacting a polyisocyanate containing 1,4-bis(isocyanatomethyl)cyclohexane and 1,3-bis(isocyanatomethyl)cyclohexane with a polyester polyol to produce an isocyanate-terminated prepolymer, and then subjecting the isocyanate-terminated prepolymer to a chain extension reaction with 1,4-butanediol (see, for example, Synthesis Example 14 and Example 16 of Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 069802 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the manufacturing method described in Patent Document 1 has the drawback that a large amount of reaction heat is suddenly generated during the chain extension reaction, raising the reaction temperature, and the resulting polyurethane elastomer has a large shrinkage rate and a poor appearance.

[0006] The present invention provides a method for producing a polyurethane elastomer that can prevent the reaction temperature from increasing during the chain extension reaction, and a polyurethane elastomer that is obtained by the method and has excellent appearance and hardness. [Means for solving the problem]

[0007] The present invention [1] is a method for producing a polyurethane elastomer, comprising: an isocyanate-terminated prepolymer production step of reacting a first polyisocyanate component containing 1,4-bis(isocyanatomethyl)cyclohexane with a first polyol component to obtain an isocyanate-terminated prepolymer; a hydroxyl-terminated prepolymer production step of reacting a second polyisocyanate component containing 1,3-bis(isocyanatomethyl)cyclohexane with a second polyol component containing 1,4-butanediol to obtain a hydroxyl-terminated prepolymer; and a polyurethane elastomer production step of reacting the isocyanate-terminated prepolymer with the hydroxyl-terminated prepolymer to obtain a polyurethane elastomer.

[0008] The present invention [2] is the method for producing a polyurethane elastomer according to the above [1], wherein the first polyol component contains a high-molecular-weight polyol having a number-average molecular weight of 400 or more.

[0009] The present invention [3] is the method for producing a polyurethane elastomer according to the above [1] or [2], wherein the second polyol component further contains a high-molecular-weight polyol having a number-average molecular weight of 400 or more.

[0010] The present invention [4] is a polyurethane elastomer comprising a reaction product of an isocyanate-terminated prepolymer, which is a reaction product of a first polyisocyanate component containing 1,4-bis(isocyanatomethyl)cyclohexane and a first polyol component, and a hydroxyl-terminated prepolymer, which is a reaction product of a second polyisocyanate component containing 1,3-bis(isocyanatomethyl)cyclohexane and a second polyol component containing 1,4-butanediol, wherein the content of 1,3-bis(isocyanatomethyl)cyclohexane whose both ends have reacted with 1,4-butanediol is 70 mol % or more relative to the total amount of 1,3-bis(isocyanatomethyl)cyclohexane.

[0011] The present invention [5] is the polyurethane elastomer according to the above [4], wherein the content of 1,3-bis(isocyanatomethyl)cyclohexane relative to the total amount of the second isocyanate component is 89 mass % or more.

[0012] The present invention [6] is the polyurethane elastomer according to the above [4] or [5], wherein the first polyol component contains a high-molecular-weight polyol component having a number-average molecular weight of 400 or more.

[0013] The present invention [7] is the polyurethane elastomer according to any one of the above [4] to [6], wherein the second polyol component further contains a high-molecular-weight polyol component having a number-average molecular weight of 400 or more.

[0014] The present invention [8] is the polyurethane elastomer according to the above [7], wherein in the second polyol component, the ratio of 1,4-butanediol to the high-molecular-weight polyol is 0.5 or more in mass ratio.

[0015] The present invention [9] is the polyurethane elastomer according to any one of the above [4] to [8], which has a urethane group concentration of 3.5 mmol / g or more and 4.7 mmol / g or less. [Effects of the Invention]

[0016] According to the method for producing a polyurethane elastomer of the present invention, a polyurethane elastomer having low shrinkage and excellent appearance and hardness can be obtained. The polyurethane elastomer of the present invention has low shrinkage and excellent appearance and hardness. DETAILED DESCRIPTION OF THE INVENTION

[0017] <Method of manufacturing polyurethane elastomer> The method for producing a polyurethane elastomer includes a step of producing an isocyanate-terminated prepolymer, a step of producing a hydroxyl-terminated prepolymer, and a step of producing a polyurethane elastomer.

[0018] [Isocyanate-terminated prepolymer manufacturing process] The isocyanate-terminated prepolymer production step is a step in which a first polyisocyanate component containing 1,4-bis(isocyanatomethyl)cyclohexane is reacted with a first polyol component to obtain an isocyanate-terminated prepolymer.

[0019] (First polyisocyanate component) The first polyisocyanate component contains 1,4-bis(isocyanatomethyl)cyclohexane from the viewpoint of obtaining a polyurethane elastomer having excellent hardness. The content of 1,4-bis(isocyanatomethyl)cyclohexane relative to the total amount of the first polyisocyanate component is, for example, 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and particularly preferably 100% by mass from the viewpoint of improving the hardness of the polyurethane elastomer.

[0020] 1,4-bis(isocyanatomethyl)cyclohexane has cis-1,4-bis(isocyanatomethyl)cyclohexane and trans-1,4-bis(isocyanatomethyl)cyclohexane as stereoisomers. The total amount of cis-1,4-bis(isocyanatomethyl)cyclohexane and trans-1,4-bis(isocyanatomethyl)cyclohexane is 100 mol%.

[0021] In 1,4-bis(isocyanatomethyl)cyclohexane, the content of trans-1,4-bis(isocyanatomethyl)cyclohexane is, for example, 60 mol% or more, preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 85 mol% or more, and for example, 99.8 mol% or less, preferably 99 mol% or less, more preferably 96 mol% or less, even more preferably 90 mol% or less.

[0022] In addition, in 1,4-bis(isocyanatomethyl)cyclohexane, the content of cis-1,4-bis(isocyanatomethyl)cyclohexane is, for example, 0.2 mol% or more, preferably 1 mol% or more, more preferably 4 mol% or more, even more preferably 10 mol% or more, and for example, 40 mol% or less, preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 15 mol% or less.

[0023] The first polyisocyanate component may contain a polyisocyanate component other than 1,4-bis(isocyanatomethyl)cyclohexane, as long as the appearance and hardness of the polyurethane elastomer are not impaired.

[0024] Examples of polyisocyanate components other than 1,4-bis(isocyanatomethyl)cyclohexane include aliphatic polyisocyanates, alicyclic polyisocyanates (excluding 1,4-bis(isocyanatomethyl)cyclohexane), aromatic polyisocyanates, and aromatic aliphatic polyisocyanates.

[0025] Examples of aliphatic polyisocyanates include aliphatic diisocyanates, such as 1,6-hexamethylene diisocyanate (1,6-HDI), 1,5-pentamethylene diisocyanate (1,5-PDI), tetramethylene diisocyanate, trimethylene diisocyanate, 1,2-, 2,3-, or 1,3-butylene diisocyanate, and 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate.

[0026] Examples of alicyclic polyisocyanates (excluding 1,4-bis(isocyanatomethyl)cyclohexane) include alicyclic diisocyanates (excluding 1,4-bis(isocyanatomethyl)cyclohexane). Examples of alicyclic diisocyanates other than 1,4-bis(isocyanatomethyl)cyclohexane include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), 1,3-bis(isocyanatomethyl)cyclohexane, 4,4'-, 2,4'-, or 2,2'-methylenebis(cyclohexyl isocyanate) or mixtures thereof (H 12 MDI), bis(isocyanatomethyl)norbornane (NBDI), 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, and methyl-2,6-cyclohexane diisocyanate.

[0027] Examples of aromatic polyisocyanates include aromatic diisocyanates, such as 4,4'-, 2,4'-, or 2,2'-diphenylmethane diisocyanate or a mixture thereof (MDI), 2,4- or 2,6-tolylene diisocyanate or a mixture thereof (TDI), o-tolidine diisocyanate, 1,5-naphthalene diisocyanate (NDI), m- or p-phenylene diisocyanate or a mixture thereof, 4,4'-diphenyl diisocyanate, and 4,4'-diphenyl ether diisocyanate.

[0028] Examples of araliphatic polyisocyanates include araliphatic diisocyanates, such as xylylene diisocyanate (1,2-, 1,3-, or 1,4-xylylene diisocyanate or a mixture thereof) (XDI), 1,3- or 1,4-tetramethylxylylene diisocyanate or a mixture thereof (TMXDI), and ω,ω′-diisocyanato-1,4-diethylbenzene.

[0029] The content of polyisocyanate components other than 1,4-bis(isocyanatomethyl)cyclohexane relative to the total amount of the first polyisocyanate component is, from the viewpoint of obtaining a polyurethane elastomer with excellent hardness, for example, 20% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass (i.e., not contained).

[0030] From the viewpoint of obtaining a polyurethane elastomer excellent in appearance and hardness, the polyisocyanate component other than 1,4-bis(isocyanatomethyl)cyclohexane is preferably an alicyclic polyisocyanate, more preferably 1,3-bis(isocyanatomethyl)cyclohexane.

[0031] (First polyol component) The first polyol component is not particularly limited and includes a high molecular weight polyol and / or a low molecular weight polyol.

[0032] The high molecular weight polyol is a macropolyol having a number average molecular weight of 400 or more and is a compound having two or more hydroxyl groups. The low molecular weight polyol is a polyol having a lower number average molecular weight than the high molecular weight polyol and is a compound having two or more hydroxyl groups.

[0033] From the viewpoint of obtaining a polyurethane elastomer with low shrinkage and excellent appearance and hardness, the number average molecular weight of the high molecular weight polyol is 400 or more, preferably 600 or more, more preferably 800 or more, and even more preferably 1000 or more, and is, for example, 10000 or less, preferably 5000 or less, more preferably 3000 or less, even more preferably 2000 or less, and particularly preferably 1500 or less.

[0034] The number average molecular weight can be determined as a polystyrene-equivalent molecular weight by known gel permeation chromatography (the same applies hereinafter).

[0035] Examples of high molecular weight polyols include polyether polyols, polyester polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, and polymer polyols. Preferred high molecular weight polyols include polyether polyols and polyester polyols.

[0036] Examples of polyether polyols include polyoxy (having 2 to 3 carbon atoms) alkylene polyols and polytetramethylene ether polyols.

[0037] Polyoxy (C2-3) alkylene polyol is, for example, an addition polymer of alkylene oxide having 2-3 carbon atoms using a low-molecular-weight polyol described below or a known polyamine compound as an initiator. Examples of alkylene oxide include propylene oxide and ethylene oxide. These alkylene oxides can be used alone or in combination of two or more. Polyoxyalkylene polyols include, for example, random and / or block copolymers of propylene oxide and ethylene oxide. Specific examples of polyoxy (C2-3) alkylene polyols include polyoxyethylene polyols, polyoxypropylene polyols, and polyoxyethylene-polyoxypropylene copolymers.

[0038] An example of the polytetramethylene ether polyol is polytetramethylene ether glycol. Specific examples of polytetramethylene ether glycol include crystalline polytetramethylene ether glycol, which is a ring-opening polymer obtained by cationic polymerization of tetrahydrofuran, and amorphous (non-crystalline) polytetramethylene ether glycol, which is obtained by copolymerizing a polymerization unit of tetrahydrofuran or the like with alkyl-substituted tetrahydrofuran and a dihydric alcohol. Here, the term "amorphous (non-crystalline)" refers to a liquid state at room temperature (25°C).

[0039] As the polyether polyol, preferably, polytetramethylene ether polyol is used, and more preferably, polytetramethylene ether glycol is used.

[0040] Examples of polyester polyols include condensation polyester polyols and ring-opening polyester polyols. Examples of condensation polyester polyols include adipate-based polyester polyols and phthalic acid-based polyester polyols. Examples of ring-opening polyester polyols include lactone-based polyester polyols, more specifically, polycaprolactone polyols, preferably polycaprolactone diols.

[0041] More preferably, the high-molecular-weight polyol is a polyester polyol. That is, the high-molecular-weight polyol is more preferably a polyester polyol, and even more preferably a polycaprolactone polyol. The high-molecular-weight polyols can be used alone or in combination of two or more kinds.

[0042] The hydroxyl value of the high molecular weight polyol is, for example, 30 mgKOH / g or more, preferably 50 mgKOH / g or more, and for example, 200 mgKOH / g or less, preferably 150 mgKOH / g or less, more preferably 120 mgKOH / g or less, even more preferably 80 mgKOH / g or less, particularly preferably 60 mgKOH / g or less. The hydroxyl value is determined in accordance with JIS K1557-1:2007 (the same applies hereinafter).

[0043] The first polyol component preferably contains a high-molecular-weight polyol, from the viewpoint of obtaining a polyurethane elastomer having low shrinkage and excellent appearance and hardness. The content of the high-molecular-weight polyol relative to the first polyol component is, for example, 90% by mass or more, preferably 95% by mass or more, more preferably 98% by mass or more, even more preferably 99% by mass or more, and particularly preferably 100% by mass, from the viewpoint of obtaining a polyurethane elastomer having low shrinkage and excellent appearance and hardness.

[0044] The low-molecular-weight polyol is a compound having two or more hydroxyl groups and a number-average molecular weight of less than 400, preferably not more than 300. Examples of the low-molecular-weight polyol include dihydric alcohols, trihydric alcohols, and tetrahydric or higher alcohols.

[0045] Examples of dihydric alcohols include linear dihydric alcohols and branched dihydric alcohols. Examples of linear dihydric alcohols include linear dihydric alcohols having from 2 to 6 carbon atoms. Examples of linear dihydric alcohols having from 2 to 6 carbon atoms include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. Examples of branched dihydric alcohols include branched dihydric alcohols having from 3 to 6 carbon atoms. Examples of branched dihydric alcohols having from 3 to 6 carbon atoms include 1,2-propanediol, 1,3-butanediol, 1,2-butanediol, neopentyl glycol, and 3-methyl-1,5-pentanediol.

[0046] Trihydric alcohols include, for example, glycerin and trimethylolpropane.

[0047] Examples of tetrahydric or higher alcohols include pentaerythritol and diglycerin.

[0048] The low molecular weight polyol is preferably a dihydric alcohol, more preferably a straight-chain dihydric alcohol. The low molecular weight polyols can be used alone or in combination of two or more kinds.

[0049] From the viewpoint of obtaining a polyurethane elastomer with a low shrinkage rate and excellent appearance and hardness, the content of the low molecular weight polyol is, for example, 10% by mass or less, preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0% by mass (i.e., not contained) relative to the first polyol component.

[0050] (Method for producing isocyanate-terminated prepolymer) In the isocyanate-terminated prepolymer production step, a first polyisocyanate component and a first polyol component are reacted in a predetermined ratio to produce an isocyanate-terminated prepolymer.

[0051] The blending ratio of the first polyisocyanate component and the first polyol component is adjusted so that there is an excess of isocyanate groups relative to the hydroxyl groups in the first polyol component. More specifically, the equivalent ratio of the isocyanate groups in the first polyisocyanate component to the hydroxyl groups in the first polyol component (isocyanate groups / hydroxyl groups) is, for example, 1.5 or more, preferably 1.8 or more, more preferably 2 or more, even more preferably 2.5 or more, and for example, 10 or less.

[0052] The polymerization method includes, for example, bulk polymerization and solution polymerization. The polymerization method is preferably bulk polymerization. In bulk polymerization, for example, a polyisocyanate component and a polyol component are reacted under a nitrogen gas flow.

[0053] The reaction temperature is preferably lower than the reaction temperature in the production process of the polyurethane elastomer described below (the reaction temperature in the reaction between the isocyanate group-terminated prepolymer and the hydroxyl group-terminated prepolymer), and is, for example, 50°C or higher, preferably 70°C or higher, and, for example, 100°C or lower.

[0054] The reaction time is, for example, 0.5 hours or more, preferably 1 hour or more, and, for example, 15 hours or less.

[0055] In the above reaction, if necessary, a known urethanization catalyst (e.g., amines and organometallic compounds (dibutyltin dilaurate)) can be added in an appropriate ratio. The ratio of the urethanization catalyst added is appropriately set depending on the purpose and application.

[0056] In the above reaction, additives (for example, antioxidants, heat stabilizers, antifoaming agents) can be added in appropriate proportions, if necessary.

[0057] This results in a reaction mixture containing an isocyanate-terminated prepolymer.

[0058] The isocyanate group concentration of the reaction mixture containing the isocyanate group-terminated prepolymer is, for example, 10% by mass or more, preferably 15% by mass or more, and for example, 20% by mass or less, preferably 18% by mass or less. The isocyanate group concentration (isocyanate group content) can be determined by known methods such as titration with di-n-butylamine or FT-IR analysis.

[0059] The reaction mixture may contain unreacted polyisocyanate components (isocyanate monomers) in addition to the isocyanate-terminated prepolymer. If necessary, the unreacted polyisocyanate components are removed from the reaction mixture by a known removal method. Examples of the removal method include distillation and extraction.

[0060] [Hydroxyl-terminated prepolymer manufacturing process] The hydroxyl-terminated prepolymer production process is a process in which a second polyisocyanate component containing 1,3-bis(isocyanatomethyl)cyclohexane (1,3-BIC) is reacted with a second polyol component containing 1,4-butanediol (1,4-BD) to obtain a hydroxyl-terminated prepolymer.

[0061] (Second polyisocyanate component) The second polyisocyanate component contains 1,3-bis(isocyanatomethyl)cyclohexane from the viewpoint of obtaining a polyurethane elastomer having low shrinkage and excellent appearance and hardness. The content of 1,3-bis(isocyanatomethyl)cyclohexane relative to the total amount of the first polyisocyanate component is, for example, 60% by mass or more, preferably 69% by mass or more, more preferably 79% by mass or more, even more preferably 89% by mass or more, and particularly preferably 100% by mass from the viewpoint of reducing the shrinkage of the polyurethane elastomer and improving its appearance.

[0062] The second polyisocyanate component may contain a polyisocyanate component other than 1,3-bis(isocyanatomethyl)cyclohexane, as long as the appearance and hardness of the polyurethane elastomer are not impaired.

[0063] Examples of polyisocyanate components other than 1,3-bis(isocyanatomethyl)cyclohexane include aliphatic polyisocyanates, alicyclic polyisocyanates (excluding 1,3-bis(isocyanatomethyl)cyclohexane), aromatic polyisocyanates, and aromatic aliphatic polyisocyanates.

[0064] The content of polyisocyanate components other than 1,3-bis(isocyanatomethyl)cyclohexane relative to the total amount of the second polyisocyanate component is, for example, 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and particularly preferably 0% by mass (i.e., not contained), from the viewpoint of obtaining a polyurethane elastomer with a low shrinkage rate and excellent appearance and hardness.

[0065] The aliphatic polyisocyanates, aromatic polyisocyanates, and araliphatic polyisocyanates include the same polyisocyanates as the first polyisocyanate.

[0066] Examples of alicyclic polyisocyanates (excluding 1,3-bis(isocyanatomethyl)cyclohexane) include alicyclic diisocyanates (excluding 1,3-bis(isocyanatomethyl)cyclohexane). Examples of alicyclic diisocyanates other than isocyanatomethylcyclohexane include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), 1,4-bis(isocyanatomethyl)cyclohexane (1,4-BIC), 4,4'-, 2,4'-, or 2,2'-methylenebis(cyclohexyl isocyanate) or mixtures thereof (H 12 MDI), bis(isocyanatomethyl)norbornane (NBDI), 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, and methyl-2,6-cyclohexane diisocyanate.

[0067] The polyisocyanate component other than 1,3-bis(isocyanatomethyl)cyclohexane is preferably an alicyclic polyisocyanate, more preferably 1,4-bis(isocyanatomethyl)cyclohexane, from the viewpoint of obtaining a polyurethane elastomer with low shrinkage and excellent appearance. The content of 1,4-bis(isocyanatomethyl)cyclohexane relative to the total amount of the first polyisocyanate component is, for example, 40% by mass or less, preferably 31% by mass or less, more preferably 21% by mass or less, even more preferably 11% by mass or less, and particularly preferably 0% by mass (i.e., not contained), from the viewpoint of reducing the shrinkage of the polyurethane elastomer and improving the appearance.

[0068] (Second polyol component) The second polyol component contains 1,4-butanediol (1,4-BD) from the viewpoint of obtaining a polyurethane elastomer with low shrinkage and excellent appearance and hardness. The content of 1,4-butanediol is, for example, 30% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, relative to the second polyol component, from the viewpoint of increasing the hardness of the polyurethane elastomer. Furthermore, the content of 1,4-butanediol is, for example, 100% by mass or less, preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, relative to the second polyol component, from the viewpoint of reducing the shrinkage of the polyurethane elastomer and improving its appearance.

[0069] The second polyol component may contain a low-molecular-weight polyol and / or a high-molecular-weight polyol other than 1,4-butanediol, as long as the low shrinkage, excellent hardness, and appearance of the polyurethane elastomer are not impaired. The low-molecular-weight polyol and the high-molecular-weight polyol may be the same polyols as those used in the first polyol component. The second polyol component preferably contains a high-molecular-weight polyol. Preferred high-molecular-weight polyols include polycaprolactone polyol and polytetramethylene ether glycol, and more preferably polycaprolactone polyol.

[0070] The second polyol component preferably contains a high-molecular-weight polyol from the viewpoint of obtaining a polyurethane elastomer with low shrinkage and excellent hardness and appearance. The content of the high-molecular-weight polyol is, for example, 10% by mass or more, preferably 20% by mass or more, and more preferably 30% by mass or more, relative to the second polyol component, from the viewpoint of reducing the shrinkage of the polyurethane elastomer and improving its appearance. Furthermore, the content of the high-molecular-weight polyol is, for example, 70% by mass or less, preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less, relative to the second polyol component, from the viewpoint of increasing the hardness of the polyurethane elastomer.

[0071] In the second polyol component, the ratio of 1,4-butanediol to the polymer polyol is, in terms of mass ratio, for example, 0.5 or more, preferably 0.6, more preferably 0.7 or more, even more preferably 1.0 or more, and particularly preferably 1.5 or more, from the viewpoint of increasing the hardness of the polyurethane elastomer. Also, in terms of mass ratio, for example, 5.0 or less, preferably 3.0 or less, more preferably 2.5 or less, even more preferably 2.0 or less, and particularly preferably 1.8 or less, from the viewpoint of reducing the shrinkage rate of the polyurethane elastomer and improving the appearance.

[0072] (Method of producing hydroxyl-terminated prepolymer) In the hydroxyl-terminated prepolymer production step, the second polyisocyanate component and the second polyol component are reacted in a predetermined ratio to produce a hydroxyl-terminated prepolymer.

[0073] The blending ratio of the second polyisocyanate component and the second polyol component is adjusted so that there is an excess of hydroxyl groups relative to the isocyanate groups, i.e., so that there is a deficiency of isocyanate groups relative to the hydroxyl groups. More specifically, the equivalent ratio of the isocyanate groups in the second polyisocyanate component to the hydroxyl groups in the second polyol component (isocyanate groups / hydroxyl groups) is, for example, 0.1 or more and, for example, 0.67 or less, preferably 0.55 or less, and more preferably 0.4 or less.

[0074] The polymerization method includes, for example, bulk polymerization and solution polymerization. The polymerization method is preferably bulk polymerization. In bulk polymerization, for example, a polyisocyanate component and a polyol component are reacted under a nitrogen gas flow.

[0075] The reaction temperature is preferably lower than the reaction temperature in the production process of the polyurethane elastomer described below (the reaction temperature in the reaction between the isocyanate group-terminated prepolymer and the hydroxyl group-terminated prepolymer), and is, for example, 50°C or higher, preferably 70°C or higher, and, for example, 100°C or lower.

[0076] The reaction time is, for example, 0.5 hours or more, preferably 1 hour or more, and, for example, 15 hours or less.

[0077] In the above reaction, if necessary, a known urethanization catalyst (e.g., amines and organometallic compounds (dibutyltin dilaurate)) can be added in an appropriate ratio. The ratio of the urethanization catalyst added is appropriately set depending on the purpose and application.

[0078] In the above reaction, additives (for example, antioxidants, heat stabilizers, antifoaming agents) can be added in appropriate proportions, if necessary.

[0079] This results in a reaction mixture containing a hydroxyl-terminated prepolymer.

[0080] The hydroxyl value of the reaction mixture containing the hydroxyl-terminated prepolymer is, for example, 200 mgKOH / g or more, preferably 300 mgKOH / g or more, more preferably 400 mgKOH / g or more, and for example, 1000 mgKOH / g or less, preferably 800 mgKOH / g or less, more preferably 600 mgKOH / g or less.

[0081] In addition to the hydroxyl-terminated prepolymer, the reaction mixture may contain unreacted polyol components (polyol monomers). If necessary, the unreacted polyol components are removed from the reaction mixture by a known removal method. Examples of the removal method include distillation and extraction.

[0082] Here, the isocyanate-terminated prepolymer production step and the hydroxyl-terminated prepolymer production step may be carried out in either order, or may be carried out in parallel at the same time.

[0083] [Polyurethane elastomer manufacturing process] The polyurethane elastomer production process includes a polyurethane elastomer production step in which an isocyanate-terminated prepolymer and a hydroxyl-terminated prepolymer are reacted to obtain a polyurethane elastomer.

[0084] (Method of manufacturing polyurethane elastomer) In the polyurethane elastomer production process, an isocyanate-terminated prepolymer (a reaction mixture containing an isocyanate-terminated prepolymer) and a hydroxyl-terminated prepolymer (a reaction mixture containing a hydroxyl-terminated prepolymer) are reacted to produce a polyurethane elastomer.

[0085] To react an isocyanate-terminated prepolymer (a reaction mixture containing an isocyanate-terminated prepolymer) with a hydroxyl-terminated prepolymer (a reaction mixture containing a hydroxyl-terminated prepolymer), the isocyanate-terminated prepolymer (a reaction mixture containing an isocyanate-terminated prepolymer) and the hydroxyl-terminated prepolymer (a reaction mixture containing a hydroxyl-terminated prepolymer) are first mixed in a predetermined ratio, and then, if necessary, the mixture is degassed under vacuum to prepare a mixture of the isocyanate-terminated prepolymer and the hydroxyl-terminated prepolymer (a polyurethane elastomer composition).

[0086] The blending ratio of the isocyanate group-terminated prepolymer and the hydroxyl group-terminated prepolymer is, for example, an equivalent ratio (isocyanate group / hydroxyl group) of the isocyanate groups in the isocyanate group-terminated prepolymer to the hydroxyl groups in the hydroxyl group-terminated prepolymer of, for example, 0.75 or more, preferably 0.9 or more, and for example, 1.3 or less, preferably 1.2 or less.

[0087] The mixing temperature is, for example, 50°C or higher, preferably 70°C or higher, and, for example, 100°C or lower.

[0088] The mixture of isocyanate-terminated prepolymer and hydroxyl-terminated prepolymer is then cured (reacted) in a preheated mold and demolded to obtain a polyurethane elastomer molded into the desired shape.

[0089] The reaction temperature is preferably higher than the reaction temperatures of the reaction between the first polyisocyanate component and the first polyol component in the isocyanate-terminated prepolymer production step and the reaction between the polyisocyanate component and the polyol component in the hydroxyl-terminated prepolymer production step, and is, for example, above 100°C, preferably 105°C or higher, and is, for example, 200°C or lower, preferably 150°C or lower, more preferably 120°C or lower.

[0090] The reaction time is, for example, 0.5 hours or more, preferably 1 hour or more, and, for example, 5 hours or less.

[0091] Thereafter, the polyurethane elastomer can be annealed at an annealing temperature of, for example, 100° C. or higher, preferably 105° C. or higher, and for example, 200° C. or lower, preferably 150° C. or lower. The annealing time is, for example, 5 hours or higher, preferably 10 hours or higher, and for example, 20 hours or lower, preferably 18 hours or lower.

[0092] Thereafter, the polyurethane elastomer can be further aged at an aging temperature of, for example, 10° C. or higher, preferably 20° C. or higher, and at, for example, 50° C. or lower, preferably 40° C. or lower. The aging time is, for example, 1 hour or higher, preferably 10 hours or higher, and at, for example, 20 days or lower, preferably 10 days or lower.

[0093] This produces a polyurethane elastomer containing a reaction product of an isocyanate-terminated prepolymer and a hydroxyl-terminated prepolymer.

[0094] Furthermore, the polyurethane elastomer may contain known additives in addition to the reaction product of the isocyanate-terminated prepolymer and the hydroxyl-terminated prepolymer, if necessary. That is, the polyurethane elastomer may be a polyurethane elastomer composition.

[0095] Examples of additives include antioxidants, heat stabilizers, ultraviolet absorbers, light stabilizers, antiblocking agents, release agents, pigments, dyes, lubricants, fillers, hydrolysis inhibitors, rust inhibitors, and bluing agents. The amount and timing of addition of the additives are appropriately determined depending on the purpose and application.

[0096] The polyurethane elastomer is produced as a TPU (thermoplastic polyurethane resin) or a TSU (thermosetting polyurethane resin). Preferably, the polyurethane elastomer is produced as a TSU (thermosetting polyurethane resin). The polyurethane elastomer is molded by a known molding method.

[0097] Examples of molding methods include cast molding, thermocompression molding, injection molding, extrusion molding, and spinning. Examples of shapes after molding include plate, fiber, strand, film, sheet, pipe, bottle, hollow, box, and button shapes.

[0098] A preferred molding method is cast molding. Therefore, the polyurethane elastomer is preferably a cast polyurethane elastomer. A cast polyurethane elastomer is a molded product (cast molded product) obtained by cast molding, and is an article that independently has a predetermined shape depending on the purpose and use, and is distinguished from a coating agent that is applied to a substrate.

[0099] More specifically, in cast molding, an isocyanate-terminated prepolymer and a hydroxyl-terminated prepolymer are preferably mixed to prepare a mixture. The mixture is then degassed as necessary and fed into a preheated mold. The mixture is heated and cured (reacted) in the mold. This results in a polyurethane elastomer (molded product) molded into a desired shape.

[0100] <Polyurethane elastomer> (Content of 1,3-bis(isocyanatomethyl)cyclohexane, both ends of which have reacted with 1,4-butanediol) The content of 1,3-bis(isocyanatomethyl)cyclohexane whose both ends have reacted with 1,4-butanediol is expressed as mol % (mole percentage) relative to the total amount of 1,3-bis(isocyanatomethyl)cyclohexane.

[0101] The content of 1,3-bis(isocyanatomethyl)cyclohexane whose both ends have reacted with 1,4-butanediol is 70 mol% or more and 100 mol% or less because the polyurethane elastomer contains a reaction product of the isocyanate-terminated prepolymer and the hydroxyl-terminated prepolymer. From the viewpoint of increasing the hardness of the polyurethane elastomer, the content of 1,3-bis(isocyanatomethyl)cyclohexane whose both ends have reacted with 1,4-butanediol is preferably 80 mol% or more, more preferably 90 mol% or more. From the viewpoint of reducing the shrinkage rate of the polyurethane elastomer and improving its appearance, the content of 1,3-bis(isocyanatomethyl)cyclohexane whose both ends have reacted with 1,4-butanediol is, for example, 100 mol% or less, preferably 95 mol% or less.

[0102] The content of 1,3-bis(isocyanatomethyl)cyclohexane, both ends of which have reacted with 1,4-butanediol, can be calculated by the methods shown in Examples 1 to 9 and Comparative Examples 1 to 4 described later.

[0103] (urethane group concentration) The urethane group concentration of the polyurethane elastomer is, for example, 3.5 mmol / g or more, preferably 3.7 mmol / g or more, and for example, 4.7 mmol / g or less, preferably 4.5 mmol / g or less. If the urethane group concentration is equal to or higher than the lower limit, the hardness of the polyurethane elastomer can be increased. On the other hand, if the urethane group concentration is equal to or lower than the upper limit, the appearance of the polyurethane elastomer can be improved. The urethane group concentration can be measured according to the examples described later. [Example]

[0104] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited thereto. Note that "parts" and "%" are by mass unless otherwise specified. Furthermore, specific numerical values ​​such as blending ratios (content ratios), physical property values, and parameters used in the following description can be substituted with the corresponding upper limit values ​​(numeric values ​​defined as "equal to or less than") or lower limit values ​​(numeric values ​​defined as "equal to or more than" or "exceeding") of the blending ratios (content ratios), physical property values, parameters, etc. described in the above "Modes for Carrying Out the Invention."

[0105] <Raw materials> [Polyisocyanate component] 1) 1,4-BIC: 1,4-bis(isocyanatomethyl)cyclohexane, trade name: FORTIMO 1,4H6XDI, manufactured by Mitsui Chemicals, Inc., containing 86 mol% trans-1,4-bis(isocyanatomethyl)cyclohexane and 14 mol% cis-bis(isocyanatomethyl)cyclohexane. 2) 1,3-BIC: 1,3-bis(isocyanatomethyl)cyclohexane, trade name: Takenate 600, manufactured by Mitsui Chemicals, Inc.

[0106] [High molecular weight polyol component] 1) PCL#1000 (number average molecular weight 1000): polycaprolactone polyol, trade name: PLACCEL 210N, hydroxyl value = 112.2 mg KOH / g, manufactured by Daicel Corporation 2) PCL#2000 (number average molecular weight 2000): polycaprolactone polyol, trade name: PLACCEL220N, hydroxyl value = 56.1 mgKOH / g, manufactured by Daicel Corporation 3) PTMEG #1000 (number average molecular weight 1000): polytetramethylene ether glycol, trade name: PTMG1000, hydroxyl value = 112.2 mg KOH / g, manufactured by Mitsubishi Chemical Corporation

[0107] [Low molecular weight polyol component] 1) 1,3-BD: 1,3-butanediol 2) 1,4-BD: 1,4-butanediol

[0108] [Additives] 1) Antioxidant: Trade name: Irganox 245, manufactured by BASF Japan Ltd. 2) Heat stabilizer: Trade name: JPP100, manufactured by Johoku Chemical Industry Co., Ltd. 3) Defoaming agent: Product name: BYK-088, manufactured by BYK Japan

[0109] <Production of polyurethane elastomer> [Isocyanate-terminated prepolymer manufacturing process] According to the formulation shown in Table 1, the first polyisocyanate component and the first polyol component were charged into a flask. Then, 0.15 parts by mass of Irganox 245, 0.1 parts by mass of JPP100, and 0.2 parts by mass of BYK-088 were added. Then, dibutyltin dilaurate, previously diluted to 2% by mass with diisononyl adipate, was added to a catalytic amount of 5 ppm. The mixture was reacted at 80°C under a nitrogen atmosphere to obtain an isocyanate-terminated prepolymer.

[0110] [Hydroxyl-terminated prepolymer manufacturing process] According to the formulations shown in Table 1, the second polyisocyanate component and the second polyol component were charged into a flask. Then, dibutyltin dilaurate, which had been diluted to 2% by mass with diisononyl adipate, was added to a catalytic amount of 5 ppm. The mixture was reacted at 80°C under a nitrogen atmosphere to obtain a hydroxyl-terminated prepolymer.

[0111] [Polyurethane elastomer manufacturing process] An isocyanate-terminated prepolymer and a hydroxyl-terminated prepolymer were mixed at an equivalent ratio (isocyanate group / hydroxyl group) of 1.05 at 80°C. Dibutyltin dilaurate, previously diluted to 2% by mass with diisononyl adipate, was then added to the mixture in a catalytic amount of 200 ppm. The mixture was stirred and degassed under vacuum to obtain a polyurethane elastomer composition. The polyurethane elastomer composition was then poured into a mold (2 mm thick, 320 mm wide) preheated to 110°C and cured in a 110°C oven for 1 hour. The cured product was then demolded from the mold. The demolded product was annealed in a 110°C oven for 15 hours and then aged for 7 days at room temperature (23°C) and a constant humidity of 55%, yielding a polyurethane elastomer sheet. The results are summarized in Table 1.

[0112] <Physical property evaluation> [Maximum reaction temperature] The isocyanate-terminated prepolymer and the hydroxyl-terminated prepolymer were mixed at an equivalent ratio (isocyanate group / hydroxyl group) of 1.05 at 80°C. Subsequently, dibutyltin dilaurate, previously diluted to 2% by mass with diisononyl adipate, was added to the mixture in a catalytic amount of 200 ppm and stirred. The temperature of the mixture (liquid temperature) was then monitored, and the maximum liquid temperature was recorded and used as the maximum reaction temperature. The results are summarized in Table 1.

[0113] [Shore D hardness] The Shore D hardness of the polyurethane elastomer sheet was measured according to JIS K7312 (1996). The results are shown in Table 1.

[0114] Shrinkage Rate The width W of the polyurethane elastomer sheet is measured, and the width W of the mold is measured. M The shrinkage rate was calculated using the following formula (1). (Shrinkage rate) = 100 × (W M -W) / W M ···(1) The results are summarized in Table 1.

[0115] [exterior] From the above sheet-shaped polyurethane elastomer, 100cm 2 A square piece (10 cm x 10 cm) was cut out and its appearance was evaluated on the following 5-point scale. Rating 5: 0.1 mm 2 There are less than three of the above white spots. Rating 4: 0.1 mm 2 There are three or more of the above white spots. Rating 3: 0.1 mm 2 There are 10 or more of the above white spots. Rating 2: 0.1 mm 2 There are 20 or more of the above white spots. Rating 1: 0.1 mm 2 There are 50 or more of the above white spots. The results are summarized in Table 1.

[0116] [Calculation method for the content of 1,3-bis(isocyanatomethyl)cyclohexane whose both ends have reacted with 1,4-butanediol] The content ratio of 1,3-BIC whose both ends had reacted with 1,4-BD to the total amount of 1,3-BIC was calculated as follows.

[0117] Examples 1 to 9 In Example 1, in the hydroxyl-terminated prepolymer production process, the molar ratio of 1,4-BD to PCL#1000 was 95:5, meaning that it was present in excess relative to 1,3-BIC. Therefore, the proportion of 1,4-BD reacting with both ends of 1,3-BIC was calculated to be 90 mol% from 0.95 × 0.95 = 0.90. It was assumed that 1,4-BD and PCL#1000 have the same reactivity toward 1,3-BIC and that there are no side reactions other than urethanization.

[0118] (Comparative Examples 1 and 3) In Comparative Examples 1 and 3, since 1,3-BIC was not present, the proportion of 1,4-BD reacting with both ends of 1,3-BIC was not calculated.

[0119] (Comparative Example 2) In Comparative Example 2, 1,3-BIC was present but 1,4-BD was not present, and therefore the proportion of 1,4-BD reacting with both ends of 1,3-BIC was calculated to be 0 mol %.

[0120] Comparative Example 4 In Comparative Example 4, the amounts charged in the isocyanate-terminated prepolymer production process were 1 mol (193 g) of 1,3-BIC, 4 mol (773 g) of 1,4-BIC, and 1 mol (1000 g) of PCL#1000. The amount of 1,3-BIC remaining after the reaction was determined to be X mol (193X g), and the amount of 1,4-BIC remaining after the reaction was calculated to be 4X mol (773X g), resulting in a mass of isocyanate-terminated prepolymer of 1966-966X g. Separately, the total amount of monomeric BIC in the isocyanate-terminated prepolymer after the reaction (the sum of the monomeric 1,3-BIC and 1,4-BIC) was determined to be 33% by mass by high-performance liquid chromatography (HPLC). Therefore, X = 0.67 was calculated from (193X + 773X) / 1966 = 0.33. That is, in the isocyanate-terminated prepolymer, 67% of the total amount of 1,3-BIC was considered to be 1,3-BIC with both ends free. It was considered that this 1,3-BIC with both ends free reacted with 1,4-BD in a chain extension reaction to produce 1,3-BIC with both ends reacted with 1,4-BD. Therefore, the content of 1,3-BIC with both ends reacted with 1,4-BD was calculated to be 67 mol%. It was assumed that 1,3-BIC and 1,4-BIC have the same reactivity toward 1,4-BD, and that 1,4-BD and PCL#1000 have the same reactivity toward 1,3-BIC, and that there were no side reactions other than urethanization.

[0121] [Table 1]

Claims

1. an isocyanate-terminated prepolymer production step of reacting a first polyisocyanate component containing 1,4-bis(isocyanatomethyl)cyclohexane with a first polyol component to obtain an isocyanate-terminated prepolymer; a hydroxyl-terminated prepolymer production step of reacting a second polyisocyanate component including 1,3-bis(isocyanatomethyl)cyclohexane with a second polyol component including 1,4-butanediol to obtain a hydroxyl-terminated prepolymer; a polyurethane elastomer production step of reacting the isocyanate group-terminated prepolymer with the hydroxyl group-terminated prepolymer to obtain a polyurethane elastomer.

2. The method for producing a polyurethane elastomer according to claim 1 , wherein the first polyol component comprises a high-molecular-weight polyol having a number-average molecular weight of 400 or more.

3. The method for producing a polyurethane elastomer according to claim 1 or 2, wherein the second polyol component further comprises a high-molecular-weight polyol having a number-average molecular weight of 400 or more.

4. an isocyanate group-terminated prepolymer that is a reaction product of a first polyisocyanate component containing 1,4-bis(isocyanatomethyl)cyclohexane and a first polyol component; a hydroxyl-terminated prepolymer that is the reaction product of a second polyisocyanate component comprising 1,3-bis(isocyanatomethyl)cyclohexane and a second polyol component comprising 1,4-butanediol; and A polyurethane elastomer, in which the content of 1,3-bis(isocyanatomethyl)cyclohexane, both ends of which have reacted with 1,4-butanediol, is 70 mol % or more relative to the total amount of 1,3-bis(isocyanatomethyl)cyclohexane.

5. 5. The polyurethane elastomer according to claim 4, wherein the content of 1,3-bis(isocyanatomethyl)cyclohexane relative to the total amount of the second isocyanate component is 89 mass% or more.

6. The polyurethane elastomer according to claim 4 or 5, wherein the first polyol component comprises a high-molecular-weight polyol component having a number-average molecular weight of 400 or more.

7. The polyurethane elastomer according to claim 4 or 5, wherein the second polyol component further comprises a high-molecular-weight polyol component having a number-average molecular weight of 400 or more.

8. 8. The polyurethane elastomer according to claim 7, wherein the ratio of 1,4-butanediol to the high-molecular-weight polyol in the second polyol component is 0.5 or more in terms of mass ratio.

9. 6. The polyurethane elastomer according to claim 4, wherein the urethane group concentration is 3.5 mmol / g or more and 4.7 mmol / g or less.

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