Polyurethane elastomer and method for producing polyurethane elastomer

Abstract

This polyurethane elastomer contains a reaction product of an isocyanate group-terminated prepolymer and a curing agent. The isocyanate group-terminated prepolymer contains a reaction product of a polyisocyanate component that includes a bis(isocyanatomethyl)cyclohexane and a polyol component that includes a high molecular weight polyol and a low molecular weight polyol. The low molecular weight polyol includes 1,4-butanediol.

Description

Polyurethane elastomer and method for producing polyurethane elastomer

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

[0002] Polyurethane elastomers are widely used in various industrial equipment because they have excellent mechanical strength and abrasion resistance and are easy to process.

[0003] As such a polyurethane elastomer, for example, a polyurethane elastomer obtained by reacting 1,4-bis(isocyanatomethyl)cyclohexane with polytetramethylene ether glycol to obtain an isocyanate group-terminated prepolymer, and then reacting the obtained isocyanate group-terminated prepolymer with 1,4-butanediol has been proposed (see, for example, Example 1 of Patent Document 1).

[0004] JP 2014-231585 A

[0005] On the other hand, polyurethane elastomers are required to have even better transparency depending on their applications.

[0006] The present invention provides a polyurethane elastomer having excellent transparency and a method for producing the polyurethane elastomer.

[0007] The present invention [1] is a polyurethane elastomer comprising a reaction product of an isocyanate-terminated prepolymer and a curing agent, wherein the isocyanate-terminated prepolymer comprises a reaction product of a polyisocyanate component containing bis(isocyanatomethyl)cyclohexane and a polyol component containing a high-molecular-weight polyol and a low-molecular-weight polyol, and the low-molecular-weight polyol comprises 1,4-butanediol.

[0008] The present invention [2] includes the polyurethane elastomer according to the above [1], wherein the number average molecular weight of the high-molecular-weight polyol is 400 or more, and the number average molecular weight of the low-molecular-weight polyol is less than 400.

[0009] The present invention [3] includes the polyurethane elastomer according to the above [1] or [2], wherein the number average molecular weight of the high molecular weight polyol is 1,200 or more and 3,200 or less.

[0010] The present invention [4] includes the polyurethane elastomer according to any one of the above [1] to [3], in which the content of the low-molecular-weight polyol is 0.05 parts by mass or more and 1.50 parts by mass or less per 100 parts by mass of the high-molecular-weight polyol.

[0011] The present invention [5] includes the polyurethane elastomer according to any one of the above [1] to [4], which has a urethane group concentration of 1.3 mmol / g or more and 2.5 mmol / g or less.

[0012] The present invention [6] includes the polyurethane elastomer according to any one of the above [1] to [5], which has a haze of 80% or less.

[0013] The present invention [7] includes the polyurethane elastomer according to any one of the above [1] to [6], wherein the curing agent contains 1,4-butanediol and the content of 1,4-butanediol relative to the curing agent is 80 mass% or more.

[0014] The present invention [8] is a method for producing a polyurethane elastomer, comprising: a first step of reacting a polyisocyanate component and a polyol component to produce an isocyanate-terminated prepolymer; and a second step of reacting the isocyanate-terminated prepolymer with a curing agent to produce a polyurethane elastomer, wherein the polyisocyanate component comprises bis(isocyanatomethyl)cyclohexane, the polyol component comprises a high-molecular-weight polyol and a low-molecular-weight polyol, and the low-molecular-weight polyol comprises 1,4-butanediol.

[0015] The polyurethane elastomer of the present invention includes a reaction product of an isocyanate-terminated prepolymer and a curing agent. The polyol component of the isocyanate-terminated prepolymer includes a low-molecular-weight polyol, and the low-molecular-weight polyol includes 1,4-butanediol. This improves transparency.

[0016] The method for producing a polyurethane elastomer of the present invention includes a first step of reacting a polyisocyanate component with a polyol component to produce an isocyanate-terminated prepolymer, and a second step of reacting the isocyanate-terminated prepolymer with a curing agent to produce a polyurethane elastomer. The polyol component contains a low-molecular-weight polyol including 1,4-butanediol, which can improve transparency.

[0017] The polyurethane elastomer is a cured polyurethane product comprising the reaction product of an isocyanate-terminated prepolymer and a curing agent.

[0018] <Isocyanate-Terminated Prepolymer> The isocyanate-terminated prepolymer includes a reaction product of a polyisocyanate component and a polyol component. The isocyanate-terminated prepolymer preferably comprises a reaction product of a polyisocyanate component and a polyol component.

[0019] [Polyisocyanate Component] The polyisocyanate component contains bis(isocyanatomethyl)cyclohexane as an essential component.

[0020] Examples of bis(isocyanatomethyl)cyclohexane include 1,3-bis(isocyanatomethyl)cyclohexane and 1,4-bis(isocyanatomethyl)cyclohexane. Preferred examples of bis(isocyanatomethyl)cyclohexane include 1,4-bis(isocyanatomethyl)cyclohexane.

[0021] 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 %.

[0022] 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.

[0023] 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.

[0024] The bis(isocyanatomethyl)cyclohexanes can be used alone or in combination of two or more kinds.

[0025] The content of bis(isocyanatomethyl)cyclohexane relative to the polyisocyanate component is, for example, 80 mass% or more, preferably 90 mass% or more, more preferably 99 mass% or more, and even more preferably 100 mass%.

[0026] The polyisocyanate component optionally contains other polyisocyanates.

[0027] Other polyisocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates (excluding bis(isocyanatomethyl)cyclohexane), aromatic polyisocyanates, and araliphatic polyisocyanates.

[0028] 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.

[0029] Examples of alicyclic polyisocyanates include alicyclic diisocyanates, such as 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), 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.

[0030] 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.

[0031] 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.

[0032] The content ratio of the other polyisocyanate relative to the polyisocyanate component is, for example, 20 mass % or less, preferably 10 mass % or less, and for example, 1 mass % or more.

[0033] The other polyisocyanates can be used alone or in combination of two or more kinds.

[0034] The polyisocyanate component preferably does not contain any other polyisocyanates and consists of bis(isocyanatomethyl)cyclohexane.

[0035] [Polyol Component] The polyol component includes a high molecular weight polyol and a low molecular weight polyol.

[0036] (High Molecular Weight Polyol) The high molecular weight polyol is a macropolyol, which is a compound having two or more hydroxyl groups.

[0037] The number average molecular weight of the high molecular weight polyol is, for example, 400 or more, preferably 500 or more. From the viewpoint of reducing the viscosity of the isocyanate group-terminated prepolymer and improving handleability, it is more preferably 1,200 or more, even more preferably 1,400 or more, and particularly preferably 1,800 or more. It is also, for example, 10,000 or less, preferably 5,000 or less. From the viewpoint of improving transparency, it is more preferably 3,200 or less, even more preferably 2,500 or less.

[0038] The number average molecular weight can be determined as a polystyrene-equivalent molecular weight by known gel permeation chromatography (the same applies hereinafter).

[0039] 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.

[0040] Examples of polyether polyols include polyoxy(C2-3) alkylene polyols and polytetramethylene ether polyols.

[0041] Polyoxy(C2-3) alkylene polyol is, for example, an addition polymer of alkylene oxide having 2 to 3 carbon atoms using a low molecular weight polyol described below or a known polyamine compound as an initiator.

[0042] Examples of alkylene oxides 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.

[0043] Specific examples of polyoxy(C2-3) alkylene polyols include polyoxyethylene polyols, polyoxypropylene polyols, and polyoxyethylene-polyoxypropylene copolymers.

[0044] Examples of polytetramethylene ether polyols include polytetramethylene ether glycol.Specific examples of polytetramethylene ether glycol include ring-opening polymers (crystalline polytetramethylene ether glycols) obtained by cationic polymerization of tetrahydrofuran, and amorphous (non-crystalline) polytetramethylene ether glycols obtained by copolymerizing polymerization units of tetrahydrofuran or the like with alkyl-substituted tetrahydrofuran and a dihydric alcohol, which will be described later.Note that the term "amorphous (non-crystalline)" refers to a liquid state at room temperature (25°C).

[0045] As the polyether polyol, preferably, polytetramethylene ether polyol is used, and more preferably, polytetramethylene ether glycol is used.

[0046] Examples of polyester polyols include condensation polyester polyols and ring-opening polyester polyols. Examples of condensation polyester polyols include adipate-based polyester polyols and phthalate-based polyester polyols. Examples of ring-opening polyester polyols include lactone-based polyester polyols, more specifically, polycaprolactone polyols.

[0047] As the polyester polyol, preferably, a ring-opening polyester polyol is used, and more preferably, a polycaprolactone polyol is used.

[0048] More preferably, the high-molecular-weight polyol is a polyether polyol. That is, the high-molecular-weight polyol is more preferably composed of a polyether polyol.

[0049] The high molecular weight polyols can be used alone or in combination of two or more kinds.

[0050] 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 100 mgKOH / g or less, and even more preferably 80 mgKOH / g or less.

[0051] The content of the high molecular weight polyol relative to the polyol component is, for example, 90.00 mass% or more, preferably 95.00 mass% or more, more preferably 98.00 mass% or more, even more preferably 99.00 mass% or more, and for example, 99.95 mass% or less, preferably 99.90 mass% or less.

[0052] (Low-Molecular-Weight Polyol) The low-molecular-weight polyol is a compound having two or more hydroxyl groups, and has a number-average molecular weight of, for example, less than 400, or preferably 300 or less.

[0053] The low molecular weight polyol contains 1,4-butanediol as an essential component.

[0054] The content of 1,4-butanediol relative to the low molecular weight polyol is, for example, 80 mass % or more, preferably 90 mass % or more, more preferably 99 mass % or more, and still more preferably 100 mass %.

[0055] The low molecular weight polyol optionally includes other low molecular weight polyols.

[0056] Other low molecular weight polyols include, for example, dihydric alcohols (excluding 1,4-butanediol), trihydric alcohols, and tetrahydric or higher alcohols.

[0057] The dihydric alcohol includes a linear dihydric alcohol and a branched dihydric alcohol.

[0058] 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, 1,5-pentanediol, and 1,6-hexanediol.

[0059] 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.

[0060] Trihydric alcohols include, for example, glycerin and trimethylolpropane.

[0061] Examples of tetrahydric or higher alcohols include pentaerythritol and diglycerin.

[0062] The content ratio of the other low molecular weight polyol relative to the low molecular weight polyol is, for example, 20 mass % or less, preferably 10 mass % or less, and for example, 1 mass % or more.

[0063] The other low molecular weight polyols can be used alone or in combination of two or more kinds.

[0064] The low molecular weight polyol preferably consists of 1,4-butanediol without other low molecular weight polyols.

[0065] The content of the low-molecular-weight polyol, relative to the polyol component, is, for example, 0.05% by mass or more, preferably 0.10% by mass or more, and for example, 10.00% by mass or less, preferably 5.00% by mass or less, more preferably 2.00% by mass or less, and even more preferably 1.00% by mass or less.

[0066] The content of the low-molecular-weight polyol is, for example, 0.05 parts by mass or more, more preferably 0.10 parts by mass or more, even more preferably 0.15 parts by mass or more, and for example, 1.50 parts by mass or less, preferably 1.00 parts by mass or less, more preferably 0.50 parts by mass or less, even more preferably 0.30 parts by mass or less, and particularly preferably 0.20 parts by mass or less, per 100 parts by mass of the high-molecular-weight polyol.

[0067] When the content of the low-molecular-weight polyol is equal to or greater than the above lower limit, transparency can be improved.

[0068] Furthermore, when the content of the low-molecular-weight polyol is equal to or less than the above upper limit, the viscosity of the isocyanate-terminated prepolymer can be reduced, and the handling properties can be improved.

[0069] The isocyanate-terminated prepolymer is obtained by reacting a polyisocyanate component with a polyol component, as will be described in detail later.

[0070] <Curing Agent> The curing agent is a compound containing two or more active hydrogen groups (for example, a hydroxyl group and an amino group), and examples thereof include hydroxyl group-containing compounds and polyamines.

[0071] Examples of the hydroxyl group-containing compound include 1,4-butanediol and the other low molecular weight polyols mentioned above.

[0072] As the other low molecular weight polyol, preferably, a trihydric alcohol is used, and more preferably, trimethylolpropane is used.

[0073] Examples of polyamines include aliphatic diamines, alicyclic diamines, aromatic diamines, and other diamines.

[0074] Aliphatic diamines include, for example, ethylenediamine, 1,3-propanediamine, 1,3- or 1,4-butanediamine, and 1,6-hexamethylenediamine.

[0075] Examples of alicyclic diamines include 1,4-cyclohexanediamine, 3-aminomethyl-3,5,5-trimethylcyclohexylamine (isophoronediamine), 4,4′-dicyclohexylmethanediamine, 2,5(2,6)-bis(aminomethyl)bicyclo[2.2.1]heptane, and 1,3-bis(aminomethyl)cyclohexane.

[0076] Examples of aromatic diamines include o-, m-, or p-tolylenediamine (TDA, OTD), 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), 3,5-bis(methylthio)-2,6-toluenediamine, and 3,5-bis(methylthio)-2,4-toluenediamine.

[0077] Other diamines include, for example, hydrazine.

[0078] The curing agent is preferably a hydroxyl group-containing compound.

[0079] More preferably, the curing agent comprises 1,4-butanediol.

[0080] The content of 1,4-butanediol relative to the curing agent is, for example, 80 mass % or more, preferably 90 mass % or more, more preferably 95 mass % or more, and still more preferably 100 mass %.

[0081] The curing agent may contain the other low-molecular-weight polyols described above together with 1,4-butanediol. When the curing agent contains the other low-molecular-weight polyols, transparency can be improved.

[0082] The content ratio of the other low molecular weight polyol relative to the curing agent is, for example, 20 mass % or less, preferably 10 mass % or less, and for example, 1 mass % or more, preferably 5 mass % or more.

[0083] As described above, when the curing agent contains other low-molecular-weight polyols, the transparency can be improved, but when the curing agent contains other low-molecular-weight polyols, the mechanical strength tends to decrease.

[0084] Therefore, from the viewpoint of transparency, the curing agent contains 1,4-butanediol and other low-molecular-weight polyols, and from the viewpoint of mechanical strength, the curing agent does not contain other low-molecular-weight polyols and consists of 1,4-butanediol.

[0085] As described above, the polyol component of the isocyanate group-terminated prepolymer preferably contains 1,4-butanediol as the low-molecular-weight polyol, and the curing agent contains 1,4-butanediol.

[0086] That is, both the low-molecular-weight polyol as the polyol component of the isocyanate-terminated prepolymer and the curing agent contain 1,4-butanediol, which can further improve transparency.

[0087] <Method for Producing Polyurethane Elastomer> The method for producing a polyurethane elastomer is a prepolymer method, and includes a first step of reacting a polyisocyanate component with a polyol component to produce an isocyanate group-terminated prepolymer, and a second step of reacting the isocyanate group-terminated prepolymer with a curing agent to produce a polyurethane elastomer.

[0088] [First Step] In the first step, a polyisocyanate component and a polyol component are reacted in a predetermined ratio to produce an isocyanate-terminated prepolymer.

[0089] The blending ratio of the polyisocyanate component and the polyol component is adjusted so that there is an excess of isocyanate groups relative to hydroxyl groups. More specifically, the equivalent ratio of isocyanate groups in the polyisocyanate component to hydroxyl groups in the polyol component (isocyanate groups / hydroxyl groups) is, for example, 1.5 or more, preferably 1.8 or more, more preferably 2 or more, and even more preferably 2.5 or more, and for example, 10 or less.

[0090] The polymerization method includes, for example, bulk polymerization and solution polymerization, and preferably includes bulk polymerization.

[0091] In bulk polymerization, for example, the polyisocyanate component and the polyol component are reacted under a nitrogen stream.

[0092] The reaction temperature is preferably lower than the reaction temperature in the second step described below (the reaction temperature in the reaction of the isocyanate group-terminated prepolymer and the curing agent), and is, for example, 50°C or higher, preferably 70°C or higher, and for example, 100°C or lower.

[0093] The reaction time is, for example, 0.5 hours or more, preferably 1 hour or more, and, for example, 15 hours or less.

[0094] 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 determined depending on the purpose and application.

[0095] In the above reaction, additives (for example, antioxidants, heat stabilizers, antifoaming agents) can be added in appropriate proportions, if necessary.

[0096] This results in a reaction mixture containing an isocyanate-terminated prepolymer.

[0097] The isocyanate group concentration of the reaction mixture containing the isocyanate group-terminated prepolymer is, for example, 1% by mass or more, preferably 3% by mass or more, and for example, 30% by mass or less, preferably 10% by mass or less, more preferably 5% 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.

[0098] 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.

[0099] [Second Step] In the second step, the isocyanate-terminated prepolymer (a reaction mixture containing the isocyanate-terminated prepolymer) and a curing agent are reacted to produce a polyurethane elastomer.

[0100] To react the isocyanate group-terminated prepolymer (a reaction mixture containing the isocyanate group-terminated prepolymer) with the curing agent, the isocyanate group-terminated prepolymer (a reaction mixture containing the isocyanate group-terminated prepolymer) and the curing agent are first mixed in a predetermined ratio, and then, if necessary, the mixture is degassed under vacuum to prepare a mixture of the isocyanate group-terminated prepolymer and the curing agent.

[0101] The blending ratio of the isocyanate group-terminated prepolymer and the curing agent is, for example, an equivalent ratio (isocyanate group / hydroxyl group) of the isocyanate groups in the isocyanate group-terminated prepolymer to the hydroxyl groups of the curing agent (low-molecular-weight polyol) of, for example, 0.75 or more, preferably 0.9 or more, and for example, 1.3 or less, preferably 1.2 or less.

[0102] The mixing temperature is, for example, 50°C or higher, preferably 70°C or higher, and, for example, 100°C or lower.

[0103] The mixture of the isocyanate-terminated prepolymer and the curing agent is then cured (reacted) in a preheated mold and demolded to obtain a polyurethane elastomer molded into a desired shape.

[0104] The reaction temperature is preferably higher than the reaction temperature of the reaction of the polyisocyanate component and the polyol component in the first step described above, and is, for example, more than 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.

[0105] The reaction time is, for example, 0.5 hours or more, preferably 1 hour or more, and, for example, 15 hours or less.

[0106] Thereafter, the polyurethane elastomer can be aged at an aging temperature of, for example, 10° C. or more, preferably 20° C. or more, and for example, 50° C. or less, preferably 40° C. or less. The aging time is, for example, 1 hour or more, preferably 10 hours or more, and for example, 20 days or less, preferably 10 days or less.

[0107] This produces a polyurethane elastomer containing a reaction product of the isocyanate-terminated prepolymer and the curing agent.

[0108] Furthermore, the polyurethane elastomer may contain known additives in addition to the reaction product of the isocyanate group-terminated prepolymer and the curing agent, if necessary. That is, the polyurethane elastomer may be a polyurethane elastomer composition.

[0109] 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.

[0110] The urethane group concentration of the polyurethane elastomer is, for example, 1.3 mmol / g or more, preferably 1.6 mmol / g or more, more preferably 1.8 mmol / g or more, and for example, 2.5 mmol / g or less, preferably 2.0 mmol / g or less.

[0111] When the urethane group concentration of the polyurethane elastomer is equal to or higher than the lower limit, the mechanical strength can be improved.

[0112] Furthermore, when the urethane group concentration of the polyurethane elastomer is equal to or less than the upper limit, transparency can be improved.

[0113] Specifically, the urethane group concentration of a polyurethane elastomer is an index of the hard segment in the polyurethane elastomer, and as the urethane group concentration of the polyurethane elastomer increases, the mechanical strength tends to improve but the transparency tends to decrease. On the other hand, as the urethane group concentration of the polyurethane elastomer decreases, the transparency tends to improve but the mechanical strength tends to improve. In other words, there is a trade-off between transparency and mechanical strength.

[0114] If the urethane group concentration of the polyurethane elastomer is within the above range, it is possible to achieve both transparency and mechanical strength.

[0115] The urethane group concentration can be measured in accordance with the examples described later.

[0116] In view of transparency, the haze of the polyurethane elastomer is, for example, 80% or less, preferably 60% or less, or more preferably 40% or less.

[0117] The method for measuring the haze will be described in detail in the examples below.

[0118] The polyurethane elastomer is manufactured as a TPU (thermoplastic polyurethane resin) or a TSU (thermosetting polyurethane resin). Preferably, the polyurethane elastomer is manufactured as a TSU (thermosetting polyurethane resin). The polyurethane elastomer is molded by a known molding method.

[0119] 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.

[0120] 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.

[0121] More specifically, in cast molding, an isocyanate-terminated prepolymer and a curing agent are preferably mixed to prepare a mixture. The mixture is then degassed, if necessary, and fed into a preheated mold. The mixture is heated and cured in the mold, resulting in a polyurethane elastomer (molded product) molded into a desired shape.

[0122] Applications of molded articles include, for example, transparent hard plastics, coating materials, pressure-sensitive adhesives, adhesives, waterproofing materials, potting agents, inks, binders, films, sheets, bands, belts, tubes, blades, speakers, sensors, outsoles, threads, fibers, nonwoven fabrics, cosmetics, shoe supplies, heat insulation materials, sealing materials, tape materials, encapsulants, solar power generation components, robot components, android components, wearable components, clothing supplies, sanitary products, cosmetics, furniture supplies, food packaging components, sporting goods, leisure goods, medical supplies, nursing care products, housing components, acoustic components, lighting components, vibration-damping components, soundproofing components, daily necessities, miscellaneous goods, cushions, bedding, stress absorbing materials, stress relaxation materials, automotive interior materials, automotive exterior materials, railway components, aircraft components, optical components, office automation equipment components, miscellaneous surface protection materials, semiconductor encapsulants, self-repairing materials, health appliances, eyeglass lenses, toys, packing, cable sheaths, wire harnesses, telecommunications cables, automotive wiring, computer wiring, industrial products, shock absorbing materials, and semiconductor components.

[0123] <Effects> The polyurethane elastomer contains a reaction product of an isocyanate-terminated prepolymer and a curing agent. The polyol component of the isocyanate-terminated prepolymer contains a low-molecular-weight polyol, and the low-molecular-weight polyol contains 1,4-butanediol. This improves transparency.

[0124] The method for producing a polyurethane elastomer includes a first step of reacting a polyisocyanate component with a polyol component to produce an isocyanate-terminated prepolymer, and a second step of reacting the isocyanate-terminated prepolymer with a curing agent to produce a polyurethane elastomer. The polyol component contains a low-molecular-weight polyol containing 1,4-butanediol, which improves transparency.

[0125] 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."

[0126] <Details of ingredients> 1,4-H ６ XDI: 1,4-bis(isocyanatomethyl)cyclohexane, trade name: Fortimo 1,4H ６XD, content of trans-1,4-bis(isocyanatomethyl)cyclohexane: 86 mol%, content of cis-1,4-bis(isocyanatomethyl)cyclohexane: 14 mol% 4,4'-MDI: 4,4'-diphenylmethane diisocyanate, trade name; Cosmonate PH, manufactured by Mitsui Chemicals, Inc. PTMEG #2000 (number average molecular weight 2000): polytetramethylene ether glycol, trade name; PTMG2000, hydroxyl value = 56.1 mg KOH / g, manufactured by Mitsubishi Chemical Corporation PTMEG #1400 (number average molecular weight 1400): polytetramethylene ether glycol, trade name; PTG1400SN, hydroxyl value = 80.1 mg KOH / g, manufactured by Hodogaya Chemical Co., Ltd. PTMEG #3000 (number average molecular weight 3000): polytetramethylene ether glycol, trade name; PTMG3000, hydroxyl value = 37.4 mg KOH / g, manufactured by Mitsubishi Chemical Corporation. PCL #2000 (number average molecular weight 2000): polycaprolactone polyol, trade name; PLACCEL220N, hydroxyl value = 56.1 mg KOH / g, manufactured by Daicel Corporation. 1,4-BD: 1,4-butanediol, number average molecular weight 90. 1,3-BG: 1,3-butylene glycol, number average molecular weight 90. DEG: diethylene glycol, number average molecular weight 106. TMP: trimethylolpropane, number average molecular weight 134. Antioxidant: trade name "Irganox 245", manufactured by BASF Japan. Heat resistance stabilizer: trade name "JPP100", manufactured by Johoku Chemical Industry Co., Ltd. Antifoaming agent: product name "BYK-088", manufactured by BYK Japan

[0127] <Production of Polyurethane Elastomer> Example 1 [Step 1] According to the formulations listed in Table 1, the polyisocyanate component and polyol component were charged into a four-neck flask equipped with a reflux condenser, a nitrogen inlet tube, a thermometer, and a stirrer. 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 so that the catalytic amount was 5 ppm. The polyisocyanate component and polyol component were reacted at 80°C under a nitrogen atmosphere to obtain a reaction mixture containing an isocyanate-terminated prepolymer.

[0128] [Step 2] A reaction mixture containing an isocyanate-terminated prepolymer and a curing agent were mixed at 80°C in an equivalent ratio (active hydrogen group / NCO) of 0.95, followed by stirring and vacuum degassing to prepare a mixture of isocyanate-terminated prepolymer and curing agent. This mixture was then poured into a mold (2 mm thick sheet, 29 mm diameter x 12 mm thick button shape) preheated to 110°C and cured in an oven at 110°C for 2 hours. The cured product was then demolded from the mold. The demolded product was annealed in an oven at 110°C for 14 hours and then aged for 7 days under constant temperature and humidity conditions of room temperature 23°C and relative humidity 55%, yielding a sheet-shaped polyurethane elastomer.

[0129] Examples 2 to 9 and Comparative Examples 1 to 4 Sheet-shaped polyurethane elastomers were produced in the same manner as in Example 1, except that the compounding formulation of each component was changed according to Table 1. In Table 1, the numerical values ​​for each component are in parts by mass.

[0130] In Comparative Example 1, dibutyltin dilaurate was not added in the first step.

[0131] <Evaluation> [Isocyanate Group Concentration] The isocyanate group concentration of the reaction mixture containing the isocyanate group-terminated prepolymer of each Example and Comparative Example was measured. Specifically, the isocyanate group concentration of the isocyanate group-terminated prepolymer was measured using a potentiometric titrator by the n-dibutylamine method in accordance with JIS K-1556 (2006). The results are shown in Table 1.

[0132] [Urethane group concentration] The urethane group concentration of the polyurethane elastomers of each example and each comparative example was measured. Specifically, assuming that all isocyanate groups in the polyisocyanate component, which is the raw material for the polyurethane elastomer, were converted to urethane groups, the urethane group concentration was calculated using the following formula. The results are shown in Table 1. [Number of isocyanate groups (mmol) in the polyisocyanate component, which is the raw material for the polyurethane elastomer] / [Weight of polyurethane elastomer (g)]

[0133] [Transparency (Haze Measurement)] The haze of each polyurethane elastomer in each Example and Comparative Example was measured. Specifically, the haze of a 2 mm thick polyurethane elastomer was measured using a Haze Meter (manufactured by Nippon Denshoku Industries Co., Ltd., Model: NDH 2000). The results are shown in Table 1.

[0134] [Hardness] The hardness of the polyurethane elastomers of each Example and Comparative Example was measured. Specifically, in accordance with JIS K7311 (1995), an ASKER A hardness tester was pressed horizontally against a 12 mm thick polyurethane elastomer, and the stable value of the needle was read after 15 seconds. The results are shown in Table 1.

[0135] [Viscosity of reaction mixture containing isocyanate-terminated prepolymer] The viscosity of the reaction mixture containing the isocyanate-terminated prepolymer of each example and each comparative example was measured. Specifically, the viscosity was measured at a temperature of 80°C, a 40P plate, and a rotation speed of 188 rpm by the cone-plate viscometer method in accordance with JIS K 5600-2-3 (2014). The results are shown in Table 1.

[0136]

[0137] The above invention is provided as an exemplary embodiment of the present invention, but this is merely an example and should not be interpreted as limiting. Modifications of the present invention that are obvious to those skilled in the art are intended to be included in the scope of the following claims.

[0138] The polyurethane elastomer and the method for producing the polyurethane elastomer of the present invention can be suitably used for the production of, for example, transparent hard plastics, coating materials, pressure-sensitive adhesives, adhesives, waterproofing materials, potting agents, inks, binders, films, sheets, bands, belts, tubes, blades, speakers, sensors, outsoles, threads, fibers, nonwoven fabrics, cosmetics, shoe supplies, heat insulating materials, sealing materials, tapes, encapsulants, solar power generation components, robot components, android components, wearable components, clothing, sanitary products, cosmetics, furniture components, food packaging components, sporting goods, leisure goods, medical supplies, nursing care products, housing components, acoustic components, lighting components, vibration-damping components, soundproofing components, daily necessities, miscellaneous goods, cushions, bedding, stress absorbing materials, stress relaxation materials, automotive interior materials, automotive exterior materials, railway components, aircraft components, optical components, office automation equipment components, miscellaneous surface protective materials, semiconductor encapsulants, self-repairing materials, health appliances, eyeglass lenses, toys, packing, cable sheaths, wire harnesses, telecommunications cables, automotive wiring, computer wiring, industrial products, shock absorbing materials, and semiconductor components.

Claims

1. A polyurethane elastomer comprising the reaction product of an isocyanate-terminated prepolymer and a curing agent, wherein the isocyanate-terminated prepolymer comprises the reaction product of a polyisocyanate component comprising bis(isocyanatomethyl)cyclohexane and a polyol component comprising a high molecular weight polyol and a low molecular weight polyol, and the low molecular weight polyol comprises 1,4-butanediol.

2. The polyurethane elastomer according to claim 1, wherein the number average molecular weight of said high molecular weight polyol is 400 or more, and the number average molecular weight of said low molecular weight polyol is less than 400.

3. The polyurethane elastomer according to claim 1, wherein the number average molecular weight of the high molecular weight polyol is 1,200 or more and 3,200 or less.

4. The polyurethane elastomer according to claim 1, wherein the content of the low molecular weight polyol is from 0.05 parts by mass to 1.50 parts by mass per 100 parts by mass of the high molecular weight polyol.

5. The polyurethane elastomer according to claim 1, having a urethane group concentration of 1.3 mmol / g or more and 2.5 mmol / g or less.

6. The polyurethane elastomer according to claim 1, having a haze of 80% or less.

7. The polyurethane elastomer according to any one of claims 1 to 6, wherein the curing agent contains 1,4-butanediol, and the content of 1,4-butanediol relative to the curing agent is 80 mass% or more.

8. A method for producing a polyurethane elastomer, comprising: a first step of reacting a polyisocyanate component and a polyol component to produce an isocyanate-terminated prepolymer; and a second step of reacting the isocyanate-terminated prepolymer and a curing agent to produce a polyurethane elastomer, wherein the polyisocyanate component contains bis(isocyanatomethyl)cyclohexane, the polyol component contains a high molecular weight polyol and a low molecular weight polyol, and the low molecular weight polyol contains 1,4-butanediol.

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