Polyurethane elastomer and method for producing polyurethane elastomer

Abstract

The polyurethane elastomer is a polyurethane elastomer comprising a reaction product of an isocyanate group terminated prepolymer and a curing agent. The isocyanate group-terminated prepolymer includes a reaction product of a polyisocyanate component including bis (isocyanatomethyl) cyclohexane and a polyol component including a high molecular weight polyol and a low molecular weight polyol. And the low molecular weight polyhydric alcohol comprises 1, 4-butanediol.

Description

Technical Field

[0001] This invention relates to polyurethane elastomers and methods for manufacturing polyurethane elastomers. Background Technology

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

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

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2014-231585 Summary of the Invention

[0005] The problem that the invention aims to solve On the other hand, for polyurethane elastomers, depending on the application, superior transparency is required.

[0006] This invention provides a polyurethane elastomer with excellent transparency and a method for manufacturing the polyurethane elastomer.

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

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

[0009] The present invention [3] includes the polyurethane elastomer described in [1] or [2] above, wherein the number average molecular weight of the aforementioned high molecular weight polyol is 1200 or more and 3200 or less.

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

[0011] The present invention [5] includes any one of the polyurethane elastomers described in [1] to [4] above, wherein the urethane group concentration is 1.3 mmol / g or more and 2.5 mmol / g or less.

[0012] The present invention [6] includes any one of the polyurethane elastomers described in [1] to [5] above, wherein the haze is 80% or less.

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

[0014] The present invention [8] is a method for manufacturing polyurethane elastomer, comprising the following steps: a first step, reacting a polyisocyanate component and a polyol component to produce an isocyanate-based end-capped prepolymer; and a second step, reacting the aforementioned isocyanate-based end-capped prepolymer and a curing agent to produce a polyurethane elastomer, wherein the aforementioned polyisocyanate component comprises bis(isocyanate-methyl)cyclohexane, the aforementioned polyol component comprises a high molecular weight polyol and a low molecular weight polyol, and the aforementioned low molecular weight polyol comprises 1,4-butanediol.

[0015] Invention Effects The polyurethane elastomer of the present invention comprises the reaction product of an isocyanate-terminated prepolymer and a curing agent. Furthermore, the polyol component of the isocyanate-terminated prepolymer comprises a low molecular weight polyol, and this low molecular weight polyol comprises 1,4-butanediol. Therefore, transparency can be improved.

[0016] The method for manufacturing the polyurethane elastomer of the present invention includes the following steps: a first step, reacting a polyisocyanate component and a polyol component to manufacture an isocyanate-terminated prepolymer; and a second step, reacting the isocyanate-terminated prepolymer and a curing agent to manufacture a polyurethane elastomer. Furthermore, the polyol component includes a low molecular weight polyol, wherein the low molecular weight polyol includes 1,4-butanediol. Therefore, transparency can be improved. Detailed Implementation

[0017] Polyurethane elastomers are cured polyurethane products containing the reaction products of isocyanate-terminated prepolymers and curing agents.

[0018] <Isocyanate-terminated prepolymer> The isocyanate-terminated prepolymer comprises the reaction product of a polyisocyanate component and a polyol component. Preferably, the isocyanate-terminated prepolymer is composed of the reaction product of a polyisocyanate component and a polyol component.

[0019] [Polyisocyanate ingredient] The polyisocyanate component contains bis(isocyanate methyl)cyclohexane as an essential component.

[0020] Examples of bis(isocyanate methyl)cyclohexane include 1,3-bis(isocyanate methyl)cyclohexane and 1,4-bis(isocyanate methyl)cyclohexane. 1,4-bis(isocyanate methyl)cyclohexane is preferred as a bis(isocyanate methyl)cyclohexane.

[0021] 1,4-Di(isocyanate-methyl)cyclohexane has cis-1,4-di(isocyanate-methyl)cyclohexane and trans-1,4-di(isocyanate-methyl)cyclohexane as stereoisomers. It should be noted that the total amount of cis-1,4-di(isocyanate-methyl)cyclohexane and trans-1,4-di(isocyanate-methyl)cyclohexane is 100 mol%.

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

[0024] Bis(isocyanate methyl)cyclohexane can be used alone or in combination with two or more.

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

[0026] The polyisocyanate component includes other polyisocyanates as optional ingredients.

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

[0028] Examples of aliphatic polyisocyanates include, for example, aliphatic diisocyanates. Examples of aliphatic diisocyanates include, for example, 1,6-hexamethylene diisocyanate (1,6-HDI), 1,5-pentanediisocyanate (1,5-PDI), tetramethylene diisocyanate, trimethylene diisocyanate, 1,2-, 2,3- or 1,3-butanediisocyanate, and 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate.

[0029] Examples of alicyclic polyisocyanates include, for example, alicyclic diisocyanates. Examples of alicyclic diisocyanates include, for example, 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(isocyanate-methyl)norbornene (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, for example, aromatic diisocyanates. Examples of aromatic diisocyanates include, for example, 4,4'-, 2,4'- or 2,2'-diphenylmethane diisocyanate or mixtures thereof (MDI), 2,4- or 2,6-toluene diisocyanate or mixtures thereof (TDI), o-dimethylbiphenyl diisocyanate, 1,5-naphthalene diisocyanate (NDI), meta- or para-phenylene diisocyanate or mixtures thereof, 4,4'-diphenyl diisocyanate, and 4,4'-diphenyl ether diisocyanate.

[0031] Examples of aromatic aliphatic polyisocyanates include, for example, aromatic aliphatic diisocyanates. Examples of aromatic aliphatic diisocyanates include phenylene diisocyanate (1,2-, 1,3- or 1,4-phenylene diisocyanate or mixtures thereof) (XDI), 1,3- or 1,4-tetramethylphenylene diisocyanate or mixtures thereof (TMXDI), and ω,ω'-diisocyanate-1,4-diethylbenzene.

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

[0033] Other polyisocyanates can be used alone or in combination of two or more.

[0034] The polyisocyanate component preferably does not contain other polyisocyanates and is composed of bis(isocyanate methyl)cyclohexane.

[0035] [Polyol Components] The polyol component includes high molecular weight polyols and low molecular weight polyols.

[0036] (High molecular weight polyols) High molecular weight polyols are macromolecular polyols and are compounds with 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-terminated prepolymer and improving its workability, it is more preferably 1200 or more, further preferably 1400 or more, and especially preferably 1800 or more. In addition, it is, for example, 10000 or less, preferably 5000 or less. From the viewpoint of improving transparency, it is more preferably 3200 or less, and further preferably 2500 or less.

[0038] It should be noted that the number-average molecular weight can be calculated as the molecular weight converted to polystyrene using known gel permeation chromatography methods (the same applies below).

[0039] Examples of high molecular weight polyols include, for example, polyether polyols, polyester polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, and polymer polyols. Polyether polyols and polyester polyols are preferred examples of high molecular weight polyols.

[0040] Examples of polyether polyols include, for example, polyoxy(C2~3)alkylene polyols and polytetramethylene ether polyols.

[0041] Polyoxyalkylene polyols are, for example, addition polymers of 2-3 carbon alkylene oxides in which a low molecular weight polyol or a known polyamine compound described later is used as an initiator.

[0042] Examples of epoxides include, for example, propylene oxide and ethylene oxide. Furthermore, these epoxides can be used alone or in combination of two or more. It should be noted that polyoxyalkylene polyols include, for example, random and / or block copolymers of propylene oxide and ethylene oxide.

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

[0044] Examples of polytetramethylene ether polyols include, for instance, polytetramethylene ether glycol. Specifically, examples of polytetramethylene ether glycols include ring-opening polymers (crystalline polytetramethylene ether glycols) obtained by cationic polymerization of tetrahydrofuran, and amorphous (non-crystalline) polytetramethylene ether glycols obtained by copolymerizing alkyl-substituted tetrahydrofuran and the diols described later onto the polymerization units of tetrahydrofuran, etc. It should be noted that "amorphous (non-crystalline)" means that it is liquid at room temperature (25°C).

[0045] Polytetramethylene ether polyol is preferably an example of a polyether polyol. Polytetramethylene ether diol is more preferably an example of a polyether polyol.

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

[0047] Ring-opening polyester polyols are preferred as polyester polyols. Polycaprolactone polyols are more preferred as polyester polyols.

[0048] Polyether polyols are more preferably examples of high molecular weight polyols. That is, high molecular weight polyols are more preferably composed of polyether polyols.

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

[0050] The hydroxyl value of the high molecular weight polyol is, for example, 30 mg KOH / g or more, preferably 50 mg KOH / g or more, for example, 200 mg KOH / g or less, preferably 150 mg KOH / g or less, more preferably 100 mg KOH / g or less, and even more preferably 80 mg KOH / g or less.

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

[0052] (Low molecular weight polyols) Low molecular weight polyols are compounds having two or more hydroxyl groups, and their number average molecular weight is, for example, less than 400, preferably less than 300.

[0053] Low molecular weight polyols contain 1,4-butanediol as an essential component.

[0054] Compared to low molecular weight polyols, the content of 1,4-butanediol is, for example, 80% by mass or more, preferably 90% by mass or more, more preferably 99% by mass or more, and even more preferably 100% by mass.

[0055] Low molecular weight polyols may contain other low molecular weight polyols as optional ingredients.

[0056] Other low molecular weight polyols include, for example, diols (excluding 1,4-butanediol), triols, and alcohols with four or more nucleotides.

[0057] Examples of diols include straight-chain diols and branched-chain diols.

[0058] Examples of straight-chain diols include, for example, those with 2 to 6 carbon atoms. Examples of straight-chain diols with 2 to 6 carbon atoms include, for example, ethylene glycol, 1,3-propanediol, 1,5-pentanediol, and 1,6-hexanediol.

[0059] Examples of branched diols include, for example, diols with 3 to 6 carbon atoms. Examples of branched diols with 3 to 6 carbon atoms include 1,2-propanediol, 1,3-butanediol, 1,2-butanediol, neopentyl glycol, and 3-methyl-1,5-pentanediol.

[0060] Examples of trihydric alcohols include glycerol and trimethylolpropane.

[0061] Examples of alcohols with four or more nucleotides include pentaerythritol and diglycerides.

[0062] Compared to low molecular weight polyols, the content of other low molecular weight polyols is, for example, 20% by mass or less, preferably 10% by mass or less, and also, for example, 1% by mass or more.

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

[0064] The low molecular weight polyol is preferably composed of 1,4-butanediol and does not contain other low molecular weight polyols.

[0065] The proportion of low molecular weight polyols 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] Compared to 100 parts by mass of high molecular weight polyol, the content of 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 especially preferably 0.20 parts by mass or less.

[0067] If the proportion of low molecular weight polyols is above the lower limit mentioned above, transparency can be improved.

[0068] In addition, if the content of low molecular weight polyols is below the above-mentioned upper limit, the viscosity of isocyanate-terminated prepolymers can be reduced, thereby improving operability.

[0069] The isocyanate-terminated prepolymers will be explained in detail later, but they can be obtained by reacting the polyisocyanate component with the polyol component.

[0070] <Curing agent> Examples of curing agents include compounds containing two or more active hydrogen groups (e.g., hydroxyl and amino groups), such as hydroxyl-containing compounds and polyamines.

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

[0072] Among other low molecular weight polyols, trihydric alcohols are preferred. Among other low molecular weight polyols, trimethylolpropane is more preferred.

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

[0074] Examples of aliphatic diamines include ethylenediamine, 1,3-propanediamine, 1,3- or 1,4-butanediamine, and 1,6-hexanediamine.

[0075] Examples of alicyclic diamines include, for example, 1,4-cyclohexanediamine, 3-aminomethyl-3,5,5-trimethylcyclohexylamine (isophorone diamine), 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, for example, o-, m-, or p-toluenediamine (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] As a curing agent, compounds containing hydroxyl groups are preferred.

[0079] The curing agent more preferably contains 1,4-butanediol.

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

[0081] The curing agent may also contain other low molecular weight polyols mentioned above, along with 1,4-butanediol. The presence of other low molecular weight polyols in the curing agent can improve transparency.

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

[0083] As mentioned above, if the curing agent contains other low molecular weight polyols, it can improve transparency. However, on the other hand, if the curing agent contains other low molecular weight polyols, there is a tendency for mechanical strength to decrease.

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

[0085] In addition, as mentioned above, the polyol component of the isocyanate-terminated prepolymer preferably includes 1,4-butanediol as a low molecular weight polyol, and the curing agent includes 1,4-butanediol.

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

[0087] <Manufacturing Method of Polyurethane Elastomers> The method for manufacturing polyurethane elastomers is a prepolymer method, comprising the following steps: a first step, in which a polyisocyanate component and a polyol component are reacted to produce an isocyanate-based end-capped prepolymer; and a second step, in which the isocyanate-based end-capped prepolymer is reacted with a curing agent to produce a polyurethane elastomer.

[0088] [Step 1] In the first step, the polyisocyanate component and the polyol component are reacted in a specified ratio to produce an isocyanate-based end-capped prepolymer.

[0089] The ratio of the polyisocyanate component to the polyol component is adjusted in such a way that the isocyanate group becomes excessive relative to the hydroxyl group. More specifically, the equivalent ratio (isocyanate group / hydroxyl group) of the isocyanate group in the polyisocyanate component to the hydroxyl group in the polyol component 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.

[0090] Examples of polymerization methods include bulk polymerization and solution polymerization. Bulk polymerization is preferred as a polymerization method.

[0091] In bulk polymerization, for example, polyisocyanate components and polyol components are reacted under a nitrogen flow.

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

[0093] In addition, 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 addition, known carbamate catalysts (e.g., amines and organometallic compounds (dibutyltin dilaurate)) can be added in appropriate proportions as needed in the above reactions. The proportion of carbamate catalyst added can be appropriately set according to the purpose and application.

[0095] In addition, additives (e.g., antioxidants, heat stabilizers, defoamers) can be added in appropriate proportions as needed in the above reactions.

[0096] Thus, a reaction mixture containing isocyanate-terminated prepolymers can be obtained.

[0097] The isocyanate group concentration in the reaction mixture containing the isocyanate-terminated prepolymer is, for example, 1% by mass or more, preferably 3% by mass or more, and further, for example, 30% by mass or less, preferably 10% by mass or less, and more preferably 5% by mass or less. It should be noted that the isocyanate group concentration (isocyanate group content) can be determined by known methods such as di-n-butylamine titration or FT-IR analysis.

[0098] In addition, the reaction mixture may contain unreacted polyisocyanate components (isocyanate monomers) besides the isocyanate-terminated prepolymer. The unreacted polyisocyanate components can be removed from the reaction mixture as needed by known removal methods. Examples of removal methods include distillation and extraction.

[0099] [Step 2] In the second step, isocyanate-terminated prepolymer (a reaction mixture containing isocyanate-terminated prepolymer) and curing agent are reacted to produce polyurethane elastomer.

[0100] To react the isocyanate-terminated prepolymer (the reaction mixture containing the isocyanate-terminated prepolymer) with the curing agent, the isocyanate-terminated prepolymer (the reaction mixture containing the isocyanate-terminated prepolymer) and the curing agent are first mixed in a specified ratio, and then vacuum degassing is performed as needed to prepare a mixture of isocyanate-terminated prepolymer and curing agent.

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

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

[0103] Next, the mixture of isocyanate-terminated prepolymer and curing agent is cured (reacted) in a preheated molding die, and then demolded. This yields a polyurethane elastomer molded into the desired shape.

[0104] The reaction temperature is preferably higher than the reaction temperature of the polyisocyanate component and the polyol component in the first step described above, for example, higher than 100°C, preferably 105°C or higher, and for example, 200°C or lower, preferably 150°C or lower, and more preferably 120°C or lower.

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

[0106] The polyurethane elastomer can then be aged. The aging temperature is, for example, 10°C or higher, preferably 20°C or higher, and also, 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 also, for example, 20 days or lower, preferably 10 days or lower.

[0107] Therefore, polyurethane elastomers containing the reaction product of isocyanate-terminated prepolymer and curing agent can be manufactured.

[0108] In addition, polyurethane elastomers may, as needed, contain known additives besides the reaction product of isocyanate-terminated prepolymers and curing agents. That is, polyurethane elastomers may also be polyurethane elastomer compositions.

[0109] Examples of additives include, for instance, antioxidants, heat stabilizers, UV absorbers, light stabilizers, anti-caking agents, release agents, pigments, dyes, lubricants, fillers, anti-hydrolysis agents, rust inhibitors, and bluing agents. The amount and timing of additive addition can be appropriately determined according to 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 also, for example, 2.5 mmol / g or less, preferably 2.0 mmol / g or less.

[0111] If the concentration of urethane groups in the polyurethane elastomer is above the lower limit mentioned above, the mechanical strength can be improved.

[0112] In addition, if the concentration of urethane groups in the polyurethane elastomer is below the above-mentioned upper limit, the transparency can be improved.

[0113] In detail, the urethane group concentration in polyurethane elastomers is an indicator of the hard segments within the elastomer. A higher urethane group concentration increases mechanical strength, but tends to decrease transparency. Conversely, a lower urethane group concentration increases transparency, but tends to increase mechanical strength. In other words, transparency and mechanical strength are mutually restrictive.

[0114] Furthermore, by setting the urethane group concentration of the polyurethane elastomer within the aforementioned range, a balance between transparency and mechanical strength can be achieved.

[0115] It should be noted that the concentration of carbamate groups can be determined according to the examples described later.

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

[0117] It should be noted that the method for measuring haze is described in detail in the examples described later.

[0118] Furthermore, the polyurethane elastomer is manufactured in the form of TPU (thermoplastic polyurethane resin) or TSU (thermosetting polyurethane resin). Preferably, the polyurethane elastomer is manufactured in the form of TSU (thermosetting polyurethane resin). The polyurethane elastomer is molded using known molding methods.

[0119] Examples of molding methods include casting, thermocompression molding, injection molding, extrusion molding, and spinning. Furthermore, examples of the resulting shape include, for example, plate-like, fibrous, wire-like, film-like, sheet-like, tubular, bottle-like, hollow, box-like, and button-like forms.

[0120] As a molding method, casting is a preferred option. Therefore, cast polyurethane elastomers are preferred. Cast polyurethane elastomers are molded articles (cast articles) obtained by casting, and are articles that individually have a prescribed shape corresponding to their purpose and use, distinguishing them from coating agents applied to a coated object.

[0121] More specifically, in the casting process, it is preferable to mix the isocyanate-terminated prepolymer and the curing agent to prepare a mixture. Then, the mixture is degassed as needed and fed into a preheated molding die. The mixture is then heated and cured within the die. This yields a polyurethane elastomer (molded article) shaped into the desired form.

[0122] As for applications in molded products, examples include transparent rigid plastics, coating materials, adhesives, bonding agents, waterproofing materials, potting compounds, inks, bonding agents, films, sheets, strips, belts, tubes, blades, speakers, sensors, outsoles, yarns, fibers, non-woven fabrics, cosmetics, footwear, thermal insulation materials, sealing materials, adhesive tape materials, sealing materials, solar power generation components, robot components, humanoid robot components, wearable components, clothing, hygiene products, cosmetics, furniture, food packaging components, sporting goods, leisure products, and medical products. Consumer goods, care products, residential components, audio components, lighting components, vibration damping components, sound insulation components, daily necessities, groceries, mats, bedding, stress-absorbing materials, stress-relieving materials, automotive interior trim materials, automotive exterior trim materials, railway components, aircraft components, optical components, OA equipment components, groceries surface protection components, semiconductor sealing materials, self-healing materials, health equipment, eyeglass lenses, toys, fillers, cable sheaths, wiring, telecommunications cables, automotive wiring, computer wiring, industrial supplies, shock-absorbing materials, and semiconductor products.

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

[0124] A method for manufacturing polyurethane elastomers includes the following steps: a first step, reacting a polyisocyanate component and a polyol component to produce an isocyanate-terminated prepolymer; and a second step, reacting the isocyanate-terminated prepolymer with a curing agent to produce a polyurethane elastomer. Furthermore, the polyol component includes a low molecular weight polyol, wherein the low molecular weight polyol includes 1,4-butanediol. Therefore, transparency can be improved.

[0125] Example Next, the present invention will be described based on embodiments and comparative examples, but the present invention is not limited thereto. It should be noted that unless otherwise specified, "parts" and "%" are based on mass. In addition, the specific values ​​of the proportions (including proportions), physical property values, parameters, etc. used in the following description can be replaced by the corresponding upper limit values ​​(values ​​defined in the form of "below" or "lower") or lower limit values ​​(values ​​defined in the form of "above" or "higher") of the proportions (including proportions), physical property values, parameters, etc., described in the "Specific Embodiments" above.

[0126] <Ingredient Details> 1,4-H6XDI: 1,4-bis(isocyanate-methyl)cyclohexane, trade name: FORTIMO 1,4H6XD, containing 86 mol% of trans-1,4-bis(isocyanate-methyl)cyclohexane and 14 mol% of cis-1,4-bis(isocyanate-methyl)cyclohexane. 4,4'-MDI: 4,4'-diphenylmethane diisocyanate, trade name: COSMONATE PH, manufactured by Mitsui Chemicals Co., Ltd. PTMEG#2000 (number average molecular weight 2000): Polytetramethylene ether glycol, trade name; PTMG2000, hydroxyl value = 56.1 mgKOH / 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 mgKOH / g, manufactured by Mitsubishi Chemical Corporation. PCL#2000 (number average molecular weight 2000): Polycaprolactone polyol, trade name: PLACEL220N, hydroxyl value = 56.1 mg KOH / g, manufactured by Daicel. 1,4-BD: 1,4-Butanediol, with a number average molecular weight of 90. 1,3-BG: 1,3-Butanediol, with a number average molecular weight of 90. DEG: Diethylene glycol, with a number average molecular weight of 10⁶. TMP: Trimethylolpropane, number average molecular weight 134 Antioxidant: Trade name "IRGANOX 245", manufactured by BASF Japan. Heat stabilizer: Trade name "JPP100", manufactured by Chengbei Chemical Industry Company Defoamer: Trade name "BYK-088", manufactured by BYK Japan KK <Manufacturing of Polyurethane Elastomers> Example 1 [Step 1] Following the formulation described in Table 1, the polyisocyanate and polyol components were added to a four-necked flask equipped with a reflux condenser, a nitrogen inlet tube, a thermometer, and a stirrer. Then, 0.15 parts by weight of IRGANOX 245, 0.1 parts by weight of JPP100, and 0.2 parts by weight of BYK-088 were added. Next, dibutyltin dilaurate, pre-diluted with diisononyl adipate to 2% by weight, was added at a catalytic concentration of 5 ppm. Under a nitrogen atmosphere, the polyisocyanate and polyol components were reacted at 80°C to obtain a reaction mixture containing isocyanate-terminated prepolymers.

[0127] [Step 2] A mixture containing isocyanate-terminated prepolymer and a curing agent was mixed at 80°C with an equivalence ratio (active hydrogen groups / NCO) of 0.95. The mixture was stirred and vacuum degassed to prepare a mixture of isocyanate-terminated prepolymer and curing agent. This mixture was then poured into a mold (2mm thick sheet shape, 29mm diameter × 12mm thickness button shape) preheated to 110°C and cured in an oven at 110°C for 2 hours. The cured product was then demolded. The demolded product was annealed in an oven at 110°C for 14 hours, followed by aging under constant temperature and humidity conditions (23°C, 55% relative humidity) for 7 days to obtain sheet-shaped polyurethane elastomer.

[0128] Examples 2 to 9 and Comparative Examples 1 to 4 The formulation of each component was modified according to Table 1, except that sheet-shaped polyurethane elastomers were manufactured using the same steps as in Example 1. It should be noted that the values ​​for each component in Table 1 are parts by weight.

[0129] In addition, in Comparative Example 1, dibutyltin dilaurate was not incorporated in the first step.

[0130] <Evaluation> [Isocyanate group concentration] The isocyanate concentration of the reaction mixtures containing the isocyanate-terminated prepolymers in each example and comparative example was determined. Specifically, the isocyanate concentration of the isocyanate-terminated prepolymers was determined using a potential difference titration apparatus by the di-n-butylamine method according to JIS K-1556 (2006). The results are shown in Table 1.

[0131] [Carbamate group concentration] The urethane group concentration of the polyurethane elastomers in each embodiment and comparative example was determined. Specifically, assuming that all isocyanate groups in the polyisocyanate component, which is the raw material for the polyurethane elastomer, have been converted into urethane groups, the urethane group concentration was calculated using the following formula. The results are shown in Table 1.

[0132] [Number of isocyanate groups (mmol) in the polyisocyanate component used as a raw material for polyurethane elastomers] / [Weight of polyurethane elastomer (g)] [Transparency (Haze Measurement)] The haze was measured for the polyurethane elastomers of each embodiment and comparative example. Specifically, the haze of a 2 mm thick polyurethane elastomer was measured using a haze meter (Nippon Denshoku Kogyo, model: NDH 2000). The results are shown in Table 1.

[0133] [hardness] The hardness of the polyurethane elastomers in each embodiment and comparative example was measured. Specifically, according to JISK 7311 (1995), an ASKER A hardness tester was horizontally pressed onto 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.

[0134] [Viscosity of the reaction mixture containing isocyanate-terminated prepolymer] The viscosity of the reaction mixtures containing isocyanate-terminated prepolymers in each embodiment and comparative example was determined. Specifically, the viscosity was measured using a cone-plate viscometer method according to JIS K 5600-2-3 (2014) at a temperature of 80°C, a 40P plate, and a rotation speed of 188 rpm. The results are shown in Table 1.

[0135] [Table 1] It should be noted that the above-described invention is provided as an illustrative embodiment of the present invention, but it is merely illustrative and not intended to be limiting. Modifications of the present invention that will be apparent to those skilled in the art are included in the appended claims.

[0136] Industrial availability The polyurethane elastomer and its manufacturing method of the present invention can be suitably used in, for example, transparent rigid plastics, coating materials, adhesives, bonding agents, waterproofing materials, potting compounds, inks, bonding agents, films, sheets, strips, belts, tubes, blades, speakers, sensors, outsoles, yarns, fibers, nonwoven fabrics, cosmetics, footwear, thermal insulation materials, sealing materials, tape materials, sealing materials, solar power generation components, robot components, humanoid robot components, wearable components, clothing, hygiene products, cosmetics, furniture, food packaging components, sporting goods, leisure products, etc. Manufacturing of leisure goods, medical supplies, nursing supplies, residential components, audio components, lighting components, vibration damping components, sound insulation components, daily necessities, groceries, mats, bedding, stress-absorbing materials, stress-relieving materials, automotive interior trim materials, automotive exterior trim materials, railway components, aircraft components, optical components, OA equipment components, groceries surface protection components, semiconductor sealing materials, self-healing materials, health equipment, eyeglass lenses, toys, fillers, cable sheaths, wiring, telecommunications cables, automotive wiring, computer wiring, industrial supplies, shock-absorbing materials, and semiconductor products.

Claims

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

2. The polyurethane elastomer as described in claim 1, wherein, The high molecular weight polyol has a number average molecular weight of 400 or higher. The number average molecular weight of the low molecular weight polyol is less than 400.

3. The polyurethane elastomer as described in claim 1, wherein, The number average molecular weight of the high molecular weight polyol is above 1200 and below 3200.

4. The polyurethane elastomer as described in claim 1, wherein, The proportion of the low molecular weight polyol is between 0.05 and 1.50 parts by mass relative to 100 parts by mass of the high molecular weight polyol.

5. The polyurethane elastomer according to claim 1, wherein the urethane group concentration is 1.3 mmol / g or more and 2.5 mmol / g or less.

6. The polyurethane elastomer as described in claim 1, wherein the haze is below 80%.

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

8. A method for manufacturing polyurethane elastomers, comprising the following steps: The first step involves reacting the polyisocyanate and polyol components to produce an isocyanate-terminated prepolymer; and The second step involves reacting the isocyanate-terminated prepolymer with a curing agent to manufacture a polyurethane elastomer. The polyisocyanate component contains bis(isocyanate-methyl)cyclohexane. The polyol component includes high molecular weight polyols and low molecular weight polyols. The low molecular weight polyol includes 1,4-butanediol.

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