A prepolymer composition, a polyurethane elastomer, a method for producing a prepolymer composition, and a method for producing a polyurethane elastomer.

Abstract

To provide a prepolymer composition for producing a polyurethane elastomer with excellent workability and tensile properties, a polyurethane elastomer obtained using the prepolymer composition, a method for producing the prepolymer composition, and a method for producing the polyurethane elastomer. [Solution] The prepolymer composition includes an isocyanate-terminated prepolymer containing a reaction product of a polyisocyanate component and a polyol component. The polyisocyanate component contains bis(isocyanatomethyl)cyclohexane. The polyol component contains a high molecular weight polyol containing polytetramethylene ether glycol and a low molecular weight polyol containing a predetermined proportion of 1,4-butanediol. The ratio of the second viscosity to the first viscosity is 1.5 or higher.

Description

Technical Field

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

Background Art

[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 reacting the obtained isocyanate group-terminated prepolymer with 1,4-butanediol has been proposed (see, for example, Example 1 of Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, polyurethane elastomers are required to have even more excellent tensile properties (tensile strength, tensile elongation) depending on the application.

[0006] In addition, the isocyanate group-terminated prepolymer used in the production of polyurethane elastomers is required to have even more excellent workability.

[0007] Specifically, when storing isocyanate-terminated prepolymers, they are stored, for example, in containers. However, these containers may tilt during storage. When a container tilts, the isocyanate-terminated prepolymer inside may leak out. This results in a decrease in workability.

[0008] Furthermore, when using isocyanate-terminated prepolymers, the isocyanate-terminated prepolymers must be removed from the container. However, if the viscosity of the isocyanate-terminated prepolymer is high, it becomes difficult to remove the isocyanate-terminated prepolymer easily, resulting in reduced workability.

[0009] The present invention aims to provide a prepolymer composition for producing a polyurethane elastomer with excellent workability and tensile properties, a polyurethane elastomer obtained using the prepolymer composition, a method for producing the prepolymer composition, and a method for producing the polyurethane elastomer. [Means for solving the problem]

[0010] The present invention [1] is a prepolymer composition comprising an isocyanate-terminated prepolymer, wherein the isocyanate-terminated prepolymer comprises a reaction product of a polyisocyanate component and a polyol component, the polyisocyanate component comprises bis(isocyanatomethyl)cyclohexane, the polyol component comprises a high molecular weight polyol and a low molecular weight polyol, the high molecular weight polyol comprises polytetramethylene ether glycol, the low molecular weight polyol comprises 1,4-butanediol, the content of 1,4-butanediol is 2.0% by mass or more and 8.0% by mass or less relative to the polyol component, and the ratio of the second viscosity of the prepolymer composition measured under conditions of a measurement temperature of 80°C and a rotation speed of 94 rpm to the first viscosity of the prepolymer composition measured under conditions of a measurement temperature of 80°C and a rotation speed of 750 rpm (second viscosity / first viscosity) is 1.5 or more.

[0011] The present invention [2] comprises the prepolymer composition described in [1] above, wherein the ratio is 2.0 or less.

[0012] The present invention [3] comprises a polyurethane elastomer containing a reaction product of the prepolymer composition described in [1] or [2] above with a chain extender.

[0013] The present invention [4] comprises a prepolymer manufacturing step of obtaining an isocyanate-terminated prepolymer by reaction of a polyisocyanate component with a polyol component, wherein the polyisocyanate component comprises bis(isocyanatomethyl)cyclohexane, the polyol component comprises a high molecular weight polyol and a low molecular weight polyol, the high molecular weight polyol comprises polytetramethylene ether glycol, the low molecular weight polyol comprises 1,4-butanediol, and the content of 1,4-butanediol is relative to the polyol component. The prepolymer is produced in an amount of 2.0% by mass or more and 8.0% by mass or less, and the prepolymer production process comprises: a first step of reacting the polyisocyanate component and the high molecular weight polyol to obtain a reaction solution containing the reaction products and the unreacted polyisocyanate component; a second step of lowering the temperature of the reaction solution to 70°C or below after the first step; and a third step of adding the low molecular weight polyol to the reaction solution, which is at a temperature of 70°C or below after the second step, to react the reaction solution with the low molecular weight polyol.

[0014] The present invention [5] includes a method for producing a polyurethane elastomer, which involves reacting a prepolymer composition produced by the method for producing a prepolymer composition described in [4] above with a chain extender. [Effects of the Invention]

[0015] In the prepolymer composition of the present invention, the polyisocyanate component contains bis(isocyanatomethyl)cyclohexane, and the polyol component contains a high molecular weight polyol containing polytetramethylene ether glycol and a low molecular weight polyol containing 1,4-butanediol. Therefore, workability can be improved.

[0016] Furthermore, the 1,4-butanediol content is between 2.0% by mass and 8.0% by mass relative to the polyol component. This improves workability and tensile properties.

[0017] Furthermore, the ratio of the second viscosity to the first viscosity is 1.5 or higher. Therefore, workability can be improved.

[0018] The polyurethane elastomer of the present invention contains a reaction product of the prepolymer composition of the present invention and a chain extension agent. Therefore, its tensile properties can be improved.

[0019] The present invention provides a method for producing a prepolymer composition comprising a prepolymer production step of obtaining an isocyanate-terminated prepolymer by reaction of a polyisocyanate component and a polyol component. The polyisocyanate component includes bis(isocyanatomethyl)cyclohexane, and the polyol component includes a high molecular weight polyol containing polytetramethylene ether glycol and a low molecular weight polyol containing 1,4-butanediol. Therefore, a prepolymer composition with excellent workability can be produced.

[0020] Furthermore, the content of 1,4-butanediol is 2.0% by mass or more and 8.0% by mass or less relative to the polyol component. Therefore, a prepolymer composition can be produced for manufacturing polyurethane elastomers that have excellent workability and tensile properties.

[0021] In addition, the prepolymer production step of the method for producing a prepolymer composition includes a first step of reacting a polyisocyanate component and a high molecular weight polyol to obtain a reaction solution containing the reaction product of these and the unreacted polyisocyanate component, a second step of setting the liquid temperature of the reaction solution to 70°C or lower after the first step, and a third step of blending a low molecular weight polyol with the reaction solution having a liquid temperature of 70°C or lower after the second step and reacting the reaction solution with the low molecular weight polyol. Therefore, a prepolymer composition for producing a polyurethane elastomer excellent in workability and tensile properties can be produced.

[0022] The method for producing a polyurethane elastomer of the present invention reacts the prepolymer composition produced by the method for producing a prepolymer composition of the present invention with a chain extender. Therefore, a polyurethane elastomer excellent in tensile properties can be produced.

Embodiments for Carrying Out the Invention

[0023] 1. Prepolymer Composition The prepolymer composition contains an isocyanate group-terminated prepolymer.

[0024] <Isocyanate Group-Terminated Prepolymer> The isocyanate group-terminated prepolymer contains a reaction product of a polyisocyanate component and a polyol component. The isocyanate group-terminated prepolymer preferably consists of a reaction product of a polyisocyanate component and a polyol component.

[0025] [Polyisocyanate Component] The polyisocyanate component contains bis(isocyanatomethyl)cyclohexane as an essential component.

[0026] Examples of bis(isocyanatomethyl)cyclohexane include 1,3-bis(isocyanatomethyl)cyclohexane and 1,4-bis(isocyanatomethyl)cyclohexane. Preferably, 1,4-bis(isocyanatomethyl)cyclohexane is used as the bis(isocyanatomethyl)cyclohexane.

[0027] 1,4-Bis(isocyanatomethyl)cyclohexane has two stereoisomers: cis-1,4-bis(isocyanatomethyl)cyclohexane and trans-1,4-bis(isocyanatomethyl)cyclohexane. The total amount of cis-1,4-bis(isocyanatomethyl)cyclohexane and trans-1,4-bis(isocyanatomethyl)cyclohexane is 100 mol%.

[0028] In 1,4-bis(isocyanatomethyl)cyclohexane, the content of trans-1,4-bis(isocyanatomethyl)cyclohexane is, for example, 60 mol% to 99.8 mol%, preferably 70 mol% to 99 mol%, more preferably 80 mol% to 96 mol%, and even more preferably 85 mol% to 90 mol%.

[0029] Furthermore, in 1,4-bis(isocyanatomethyl)cyclohexane, the content of cis-1,4-bis(isocyanatomethyl)cyclohexane is, for example, 0.2 mol% to 40 mol%, preferably 1 mol% to 30 mol%, more preferably 4 mol% to 20 mol%, and even more preferably 10 mol% to 15 mol%.

[0030] Bis(isocyanatomethyl)cyclohexane can be used alone or in combination with two or more other compounds.

[0031] The content of bis(isocyanatomethyl)cyclohexane 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, relative to the polyisocyanate component.

[0032] The polyisocyanate component may include other polyisocyanates as optional components.

[0033] Other polyisocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates (excluding bis(isocyanatomethyl)cyclohexane), aromatic polyisocyanates, and aromatic aliphatic polyisocyanates.

[0034] Examples of aliphatic polyisocyanates include aliphatic diisocyanates. Examples of aliphatic diisocyanates include 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.

[0035] Examples of alicyclic polyisocyanates include alicyclic diisocyanates. Examples of alicyclic diisocyanates include 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 Examples include 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.

[0036] Examples of aromatic polyisocyanates include aromatic diisocyanates. Examples of aromatic diisocyanates include 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.

[0037] Examples of aromatic aliphatic polyisocyanates include aromatic aliphatic diisocyanates. Examples of aromatic aliphatic diisocyanates include xylylene diisocyanate (1,2-, 1,3-, or 1,4-xylylene diisocyanate or mixtures thereof) (XDI), 1,3-, or 1,4-tetramethylxylylene diisocyanate or mixtures thereof (TMXDI), and ω,ω′-diisocyanate-1,4-diethylbenzene.

[0038] The content of other polyisocyanates is, for example, 20% by mass or less, preferably 10% by mass or less, more preferably 1% by mass or less, and even more preferably 0% by mass, relative to the polyisocyanate component.

[0039] Other polyisocyanates can be used alone or in combination of two or more.

[0040] The polyisocyanate component preferably consists of bis(isocyanatomethyl)cyclohexane and does not contain other polyisocyanates.

[0041] [Polyol components] The polyol component includes high molecular weight polyols and low molecular weight polyols. Preferably, the polyol component consists of high molecular weight polyols and low molecular weight polyols.

[0042] (High molecular weight polyols) High molecular weight polyols are macropolyols, which are compounds having two or more hydroxyl groups, and whose number average molecular weight is 400 or more, preferably 450 or more, and for example, 10,000 or less.

[0043] The above number-average molecular weight can be determined as polystyrene-equivalent molecular weight by known gel permeation chromatography (the same applies hereinafter).

[0044] High molecular weight polyols contain polytetramethylene ether glycol as an essential component.

[0045] {Polytetramethylene ether glycol} Specifically, examples of polytetramethylene ether glycol include ring-opening polymers obtained by cationic polymerization of tetrahydrofuran (crystalline polytetramethylene ether glycol), and amorphous (non-crystalline) polytetramethylene ether glycols obtained by copolymerizing polymerization units such as tetrahydrofuran with alkyl-substituted tetrahydrofuran and a dihydric alcohol described later. Amorphous (non-crystalline) means that it is liquid at room temperature (25°C). Preferably, crystalline polytetramethylene ether glycol is used as the polytetramethylene ether glycol.

[0046] The number-average molecular weight of polytetramethylene ether glycol is, for example, 400 to 10000, preferably 450 to 5000, more preferably 500 to 3000, even more preferably 550 to 1500, particularly preferably 600 to 1000, and most preferably 630 to 800.

[0047] More specifically, the number-average molecular weight of polytetramethylene ether glycol is, for example, from the viewpoint of tensile properties, 400 or more, preferably 450 or more, more preferably 500 or more, even more preferably 550 or more, particularly preferably 600 or more, most preferably 630 or more, and also from the viewpoint of tensile properties, 10000 or less, preferably 5000 or less, more preferably 3000 or less, even more preferably 1500 or less, particularly preferably 1000 or less, most preferably 800 or less.

[0048] The hydroxyl value of polytetramethylene ether glycol is, for example, 30 mg KOH / g to 200 mg KOH / g, preferably 50 mg KOH / g to 190 mg KOH / g, more preferably 100 mg KOH / g to 180 mg KOH / g, and even more preferably 150 mg KOH / g to 175 mg KOH / g.

[0049] More specifically, the hydroxyl value of polytetramethylene ether glycol is, from the viewpoint of tensile properties, for example, 30 mg KOH / g or more, preferably 50 mg KOH / g or more, more preferably 100 mg KOH / g or more, and even more preferably 150 mg KOH / g or more. Also, from the viewpoint of tensile properties, it is, for example, 200 mg KOH / g or less, preferably 190 mg KOH / g or less, more preferably 180 mg KOH / g or less, and even more preferably 175 mg KOH / g or less.

[0050] The hydroxyl value mentioned above can be determined by acetylation or phthalation methods in accordance with Method A or Method B of JIS K1557-1 (the same applies hereinafter).

[0051] The content of polytetramethylene ether glycol 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, relative to the high molecular weight polyol.

[0052] The content of polytetramethylene ether glycol is, for example, 92.0% to 98.0% by mass, preferably 93.0% to 97.0% by mass, more preferably 94.0% to 96.5% by mass, and even more preferably 95.0% to 96.0% by mass, relative to the polyol component.

[0053] More specifically, the content of polytetramethylene ether glycol relative to the polyol component is, from the viewpoint of tensile properties, for example, 92.0% by mass or more, preferably 93.0% by mass or more, more preferably 94.0% by mass or more, and even more preferably 95.0% by mass or more. From the viewpoint of workability, it is, for example, 98.0% by mass or less, preferably 97.0% by mass or less, more preferably 96.5% by mass or less, and even more preferably 96.0% by mass or less.

[0054] {Other high molecular weight polyols} The high molecular weight polyol may optionally contain other high molecular weight polyols (excluding polytetramethylene ether glycol).

[0055] Other high molecular weight polyols are macropolyols, which are compounds having two or more hydroxyl groups, and whose number average molecular weight is 400 or more, preferably 450 or more, and for example, 10,000 or less.

[0056] Other high molecular weight polyols include, for example, polyether polyols (excluding polytetramethylene ether glycol), polyester polyols, polycarbonate polyols, polyurethane polyols, epoxy polyols, vegetable oil polyols, polyolefin polyols, acrylic polyols, and polymer polyols.

[0057] The hydroxyl values ​​of other high molecular weight polyols are, for example, 30 mg KOH / g to 200 mg KOH / g, preferably 50 mg KOH / g to 190 mg KOH / g, more preferably 100 mg KOH / g to 180 mg KOH / g, and even more preferably 150 mg KOH / g to 175 mg KOH / g.

[0058] Other high molecular weight polyols can be used alone or in combination of two or more.

[0059] The content of other high molecular weight polyols is, for example, 20% by mass or less, preferably 10% by mass or less, more preferably 1% by mass or less, and even more preferably 0% by mass, relative to the high molecular weight polyols.

[0060] The content of other high molecular weight polyols is, for example, 5% by mass or less, preferably 1% by mass or less, and more preferably 0% by mass, relative to the polyol component.

[0061] The high molecular weight polyol preferably consists of polytetramethylene ether glycol and does not contain other high molecular weight polyols.

[0062] (Low molecular weight polyols) Low molecular weight polyols are compounds having two or more hydroxyl groups, and their number-average molecular weight is less than 400, preferably 300 or less.

[0063] Low molecular weight polyols contain 1,4-butanediol as an essential component.

[0064] {1,4-butanediol} 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, relative to the low molecular weight polyol.

[0065] The content of 1,4-butanediol is 2.0% to 8.0% by mass, preferably 3.0% to 7.0% by mass, more preferably 3.5% to 6.0% by mass, and even more preferably 4.0% to 5.0% by mass, relative to the polyol component.

[0066] More specifically, the content of 1,4-butanediol is 2.0% by mass or more, preferably 3.0% by mass or more, more preferably 3.5% by mass or more, even more preferably 4.0% by mass or more, and 8.0% by mass or less, preferably 7.0% by mass or less, more preferably 6.0% by mass or less, and even more preferably 5.0% by mass or less, relative to the polyol component.

[0067] If the proportion of 1,4-butanediol relative to the polyol component is above the lower limit mentioned above, workability can be improved.

[0068] On the other hand, if the proportion of 1,4-butanediol relative to the polyol component is below the above lower limit, workability will decrease.

[0069] Furthermore, if the proportion of 1,4-butanediol relative to the polyol component is below the above upper limit, the tensile properties can be improved.

[0070] On the other hand, if the proportion of 1,4-butanediol relative to the polyol component exceeds the above upper limit, the tensile properties will decrease.

[0071] The content of 1,4-butanediol is, for example, 2.0 to 8.0 parts by mass, preferably 3.0 to 7.0 parts by mass, more preferably 3.5 to 6.0 parts by mass, and even more preferably 4.0 to 5.0 parts by mass, per 100 parts by mass of polytetramethylene ether glycol.

[0072] More specifically, the content of 1,4-butanediol is, from the viewpoint of workability, for example, 2.0 parts by mass or more, preferably 3.0 parts by mass or more, more preferably 3.5 parts by mass or more, and even more preferably 4.0 parts by mass or more, per 100 parts by mass of polytetramethylene ether glycol, and from the viewpoint of tensile properties, for example, 8.0 parts by mass or less, preferably 7.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 5.0 parts by mass or less.

[0073] {Other low molecular weight polyols} The low molecular weight polyol may optionally contain other low molecular weight polyols.

[0074] Other low molecular weight polyols are compounds having two or more hydroxyl groups, and their number-average molecular weight is less than 400, preferably 300 or less.

[0075] Other low molecular weight polyols include, for example, dihydric alcohols (excluding 1,4-butanediol), trihydric alcohols, and tetrahydric or higher alcohols.

[0076] Examples of dihydric alcohols include linear dihydric alcohols and branched dihydric alcohols.

[0077] Examples of linear dihydric alcohols include linear dihydric alcohols having 2 to 6 carbon atoms. Examples of linear dihydric alcohols having 2 to 6 carbon atoms include ethylene glycol, 1,3-propanediol, 1,5-pentanediol, and 1,6-hexanediol.

[0078] Examples of branched dihydric alcohols include those having 3 to 6 carbon atoms. Examples of branched dihydric alcohols having 3 to 6 carbon atoms include 1,2-propanediol, 1,3-butanediol, 1,2-butanediol, neopentyl glycol, and 3-methyl-1,5-pentanediol.

[0079] Examples of trihydric alcohols include glycerin and trimethylolpropane.

[0080] Examples of alcohols with a tetravalent or higher hydration include pentaerythritol and diglycerin.

[0081] Other low molecular weight polyols can be used alone or in combination of two or more.

[0082] The content of other low molecular weight polyols is, for example, 20% by mass or less, preferably 10% by mass or less, more preferably 1% by mass or less, and even more preferably 0% by mass, relative to the low molecular weight polyols.

[0083] The content of other low molecular weight polyols is, for example, 5% by mass or less, preferably 1% by mass or less, and more preferably 0% by mass, relative to the polyol component.

[0084] The low molecular weight polyol preferably consists of 1,4-butanediol and does not contain other low molecular weight polyols.

[0085] The isocyanate-terminated prepolymer is obtained by reacting a polyisocyanate component with a polyol component.

[0086] The isocyanate-terminated prepolymer preferably includes a reaction product consisting only of a polyisocyanate component and a high molecular weight polyol (hereinafter sometimes referred to as the first isocyanate-terminated prepolymer), a reaction product consisting only of a polyisocyanate component and a low molecular weight polyol (hereinafter sometimes referred to as the second isocyanate-terminated prepolymer), and a reaction product consisting only of a polyisocyanate component, a high molecular weight polyol, and a low molecular weight polyol (hereinafter sometimes referred to as the third isocyanate-terminated prepolymer).

[0087] <Method for producing a prepolymer composition> The method for producing a prepolymer composition comprises a prepolymer production step in which an isocyanate group-terminated prepolymer is obtained by reacting a polyisocyanate component with a polyol component.

[0088] The prepolymer manufacturing process comprises a first step of reacting a polyisocyanate component with a high molecular weight polyol to obtain a reaction solution containing these reaction products (specifically, a first isocyanate group-terminated prepolymer) and unreacted polyisocyanate components; a second step of lowering the temperature of the reaction solution to 70°C or below after the first step; and a third step of adding a low molecular weight polyol to the reaction solution, which is at a temperature of 70°C or below, after the second step, and reacting the reaction solution with the low molecular weight polyol.

[0089] [1st step] In the first step, a polyisocyanate component and a high molecular weight polyol are reacted to obtain a reaction solution containing a first isocyanate group-terminated prepolymer and unreacted polyisocyanate components.

[0090] The mixing ratio of the polyisocyanate component to the high molecular weight polyol is adjusted so that there is an excess of isocyanate groups in the polyisocyanate component compared to the hydroxyl groups in the high molecular weight polyol. Specifically, the equivalent ratio of isocyanate groups in the polyisocyanate component to hydroxyl groups in the high molecular weight polyol (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, 20 or less.

[0091] Polymerization methods include, for example, bulk polymerization and solution polymerization. Bulk polymerization is preferred as the polymerization method.

[0092] In bulk polymerization, for example, polyisocyanate components and high molecular weight polyols are reacted under atmospheric pressure and a nitrogen atmosphere.

[0093] The reaction conditions include a reaction temperature that is, for example, above 70°C, preferably 75°C or higher, and for example, below 120°C, preferably 100°C or lower. The reaction time is, for example, 0.5 hours to 24 hours, preferably 1 hour to 12 hours.

[0094] Furthermore, in the above reaction, known urethane catalysts (e.g., amines and organometallic compounds (dibutyltin dilaurate)) may be added in appropriate proportions as needed. The proportion of urethane catalyst added should be set appropriately according to the purpose and application.

[0095] Furthermore, in the above reaction, additives (e.g., antioxidants, heat stabilizers, defoamers) may be added in appropriate proportions as needed.

[0096] This yields a reaction solution containing the first isocyanate-terminated prepolymer.

[0097] On the other hand, as described above, the mixing ratio of the polyisocyanate component to the high molecular weight polyol is adjusted so that there is an excess of isocyanate groups of the polyisocyanate component compared to the hydroxyl groups of the high molecular weight polyol. Therefore, the reaction solution contains unreacted polyisocyanate components along with the first isocyanate group-terminated prepolymer.

[0098] [Second process] In the second step, after the first step, the temperature of the reaction solution is lowered to 70°C or below. This makes the reactivity of the first reaction (described later) relatively higher than that of the second reaction (described later).

[0099] Specifically, for example, the reaction solution is allowed to cool, and the temperature of the reaction solution is set to 70°C or lower, preferably 65°C or lower, and for example, 20°C or higher, preferably 40°C or higher, and more preferably 50°C or higher.

[0100] [3rd step] In the third step, after the second step, a low molecular weight polyol is added to the reaction solution, which has a liquid temperature of 70°C or lower, and the reaction solution and the low molecular weight polyol are reacted.

[0101] Specifically, the third step comprises a third A step in which a low molecular weight polyol is added to a reaction solution with a liquid temperature of 70°C or lower, and the reaction solution and the low molecular weight polyol are reacted at 70°C or lower, and a third B step in which the reaction solution is heated to raise its liquid temperature above 70°C, and the reaction solution and the low molecular weight polyol are reacted.

[0102] In step 3A, a low molecular weight polyol is added to a reaction solution whose liquid temperature is 70°C or lower, and the reaction solution and the low molecular weight polyol are reacted at a temperature of 70°C or lower.

[0103] As described above, the reaction solution contains unreacted polyisocyanate components and the first isocyanate-terminated prepolymer. Therefore, in step 3A, a reaction occurs in which the unreacted polyisocyanate components react with a low molecular weight polyol to produce a second isocyanate-terminated prepolymer (first reaction), and a reaction occurs in which the first isocyanate-terminated prepolymer reacts with a low molecular weight polyol to produce a third isocyanate-terminated prepolymer (second reaction).

[0104] On the other hand, in step 3A, the reaction solution temperature is below 70°C. Therefore, the low molecular weight polyol reacts more readily with the unreacted polyisocyanate component, which is relatively more reactive than the first isocyanate-terminated prepolymer. In other words, in step 3A, the first reaction is relatively more likely to occur than the second reaction. Therefore, in step 3A, the second isocyanate-terminated prepolymer is more likely to be formed than the third isocyanate-terminated prepolymer.

[0105] In step 3A, the reaction temperature is, for example, 70°C or lower, preferably 65°C or lower, and for example, 20°C or higher, preferably 40°C or higher, more preferably 50°C or higher. The reaction time is, for example, 1 minute to 120 minutes, preferably 10 minutes to 60 minutes.

[0106] In step 3B, the reaction solution is heated to a temperature exceeding 70°C, and the reaction solution is reacted with the low molecular weight polyol.

[0107] In step 3A, the reaction solution temperature exceeds 70°C. As a result, the low molecular weight polyol reacts more readily with the first isocyanate-terminated prepolymer, along with the unreacted polyisocyanate component. In other words, the second reaction is more likely to occur in step 3B than in step 3A. Therefore, the third isocyanate-terminated prepolymer is also more likely to be formed in step 3B than in step 3A.

[0108] In step 3B, the reaction temperature is, for example, above 70°C, preferably 75°C or higher, and for example, below 120°C, preferably 100°C or lower. The reaction time is, for example, 0.5 hours to 24 hours, preferably 1 hour to 12 hours.

[0109] Furthermore, the mixing ratio of the reaction solution to the low molecular weight polyol is adjusted so that there is an excess of isocyanate groups in the reaction solution relative to the hydroxyl groups in the low molecular weight polyol. Specifically, the equivalent ratio of isocyanate groups in the reaction solution to hydroxyl groups in the low molecular weight polyol (isocyanate groups / hydroxyl groups) is, for example, 1.5 or more, preferably 1.8 or more, and for example, 20 or less.

[0110] Furthermore, the known urethane catalyst and additives described above can also be incorporated into the first and second reactions described above.

[0111] As described above, the reaction solution is reacted with a low molecular weight polyol to preferably produce a second isocyanate-terminated prepolymer and a third isocyanate-terminated prepolymer. This yields a prepolymer composition containing the second isocyanate-terminated prepolymer and the third isocyanate-terminated prepolymer.

[0112] Furthermore, in the third step, some of the first isocyanate-terminated prepolymer in the reaction solution may not react with the low molecular weight polyol and may remain as is. In such cases, the prepolymer composition includes the first isocyanate-terminated prepolymer.

[0113] Furthermore, the prepolymer composition contains unreacted polyisocyanate components (isocyanate monomers).

[0114] Furthermore, the prepolymer composition may contain the known urethane catalyst and additives described above. These can be removed from the prepolymer composition by known removal methods as needed. Examples of removal methods include distillation and extraction.

[0115] As described above, this method involves, in the third step, adding a low molecular weight polyol to a reaction solution with a liquid temperature of 70°C or lower, and reacting the reaction solution with the low molecular weight polyol. This allows for a large number of hard segments (constituent units in which one polyisocyanate component and another polyisocyanate component are bonded by a low molecular weight polyol). The cohesive force of these hard segments makes it possible to increase the ratio of the second viscosity to the first viscosity of the prepolymer composition (described later) to 1.5 or higher.

[0116] The isocyanate group concentration of the prepolymer composition is, for example, 1% to 30% by mass, preferably 3% to 20% by mass, and more preferably 10% to 18% by mass.

[0117] The isocyanate group concentration (isocyanate group content) can be measured using a potentiometric titrator by the n-dibutylamine method in accordance with JIS K-1556 (2006).

[0118] Furthermore, the ratio (second viscosity / first viscosity) of the second viscosity of the prepolymer composition measured under conditions of 80°C and 94 rpm to the first viscosity of the prepolymer composition measured under conditions of 80°C and 750 rpm is 1.5 or higher, preferably 1.7 or higher, and for example, 2.0 or lower.

[0119] If the above ratio is above the above lower limit, work efficiency will improve.

[0120] On the other hand, if the value is below the lower limit mentioned above, work efficiency will decrease.

[0121] Furthermore, if the above ratio is below the above upper limit, work efficiency will improve.

[0122] The first and second viscosities are measured using the cone-plate viscometer method in accordance with JIS K 5600-2-3 (2014). The measurement methods for the first and second viscosities will be described in detail in the examples below.

[0123] 2. Polyurethane elastomer Polyurethane elastomers contain a reaction product between a prepolymer composition and a chain extender.

[0124] <Chain elongators> Examples of chain elongators include compounds containing two or more active hydrogen groups (e.g., hydroxyl groups and amino groups), such as hydroxyl group-containing compounds and polyamines.

[0125] Examples of hydroxyl group-containing compounds include 1,4-butanediol and the other low molecular weight polyols mentioned above.

[0126] Examples of polyamines include aliphatic diamines, alicyclic diamines, aromatic diamines, and other diamines.

[0127] Examples of aliphatic diamines include ethylenediamine, 1,3-propanediamine, 1,3- or 1,4-butanediamine, and 1,6-hexamethylenediamine.

[0128] 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.

[0129] 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.

[0130] Other diamines include, for example, hydrazine.

[0131] Preferably, aromatic diamines are used as chain extenders. More preferably, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA) is used as a chain extender.

[0132] <Method for manufacturing polyurethane elastomer> In the method for producing polyurethane elastomers, a prepolymer composition is reacted with a chain extender. Specifically, an isocyanate-terminated prepolymer in the prepolymer composition is reacted with a chain extender.

[0133] To react the prepolymer composition with the chain extender, first, the prepolymer composition and the chain extender are mixed in a predetermined ratio, and then, if necessary, vacuum degassing is performed to prepare a mixture of the prepolymer composition and the chain extender.

[0134] Specifically, the prepolymer composition and the chain extender are blended such that, for example, the equivalent ratio of active hydrogen in the chain extender to isocyanate groups in the prepolymer composition (specifically, isocyanate groups in isocyanate-terminated prepolymers) (active hydrogen / isocyanate groups) is, for example, 0.75 to 1.30, preferably 0.90 to 1.20.

[0135] In the mixing process, the mixing temperature is, for example, 50°C to 120°C, preferably 70°C to 100°C.

[0136] Next, the mixture of the prepolymer composition and the chain extender is cured (reacted) in a preheated mold and then demolded. This yields a polyurethane elastomer molded into the desired shape.

[0137] The reaction conditions include a reaction temperature of, for example, 90°C to 150°C, preferably 100°C to 130°C. The reaction time is, for example, 0.5 hours to 6 hours.

[0138] Subsequently, the polyurethane elastomer can be aged. The aging temperature is, for example, 10°C to 50°C, or for example, 20°C to 40°C. The aging time is, for example, 1 hour to 20 days, preferably 10 hours to 10 days.

[0139] This process produces a polyurethane elastomer containing the reaction product of the prepolymer composition and the chain extender.

[0140] Furthermore, the polyurethane elastomer may, if necessary, contain known additives other than the reaction products of the prepolymer composition and the chain extender. In other words, the polyurethane elastomer may be a polyurethane elastomer composition.

[0141] Examples of additives include antioxidants, heat stabilizers, UV absorbers, light stabilizers, anti-blocking agents, mold release agents, pigments, dyes, lubricants, fillers, hydrolysis inhibitors, rust inhibitors, and bluing agents. The amount and timing of additive addition are determined as appropriate according to the purpose and application.

[0142] The polyurethane elastomer is manufactured as TPU (thermoplastic polyurethane resin) or TSU (thermosetting polyurethane resin). Preferably, the polyurethane elastomer is manufactured as TSU (thermosetting polyurethane resin). The polyurethane elastomer is molded by a known molding method.

[0143] Examples of molding methods include casting, thermal compression molding, injection molding, extrusion molding, and spinning. Examples of shapes after molding include plate-like, fibrous, strand-like, film-like, sheet-like, pipe-like, bottle-like, hollow, box-like, and button-like shapes.

[0144] Preferably, the molding method is casting. Therefore, the polyurethane elastomer is preferably a casting polyurethane elastomer. A casting polyurethane elastomer is a molded article (cast-molded article) obtained by casting, and is an article that has a predetermined shape according to its purpose and application, and is distinguished from a coating agent applied to an object to be coated.

[0145] More specifically, in casting, a prepolymer composition and a chain extender are preferably mixed to prepare a mixture. This mixture is then degassed as needed and supplied into a preheated mold. The mixture is then heated and cured within the mold. This results in a polyurethane elastomer (molded article) molded into the desired shape.

[0146] Applications for molded products include, for example, transparent rigid plastics, coating materials, adhesives, glues, waterproofing materials, potting agents, inks, binders, films, sheets, bands, belts, tubes, blades, speakers, sensors, outsoles, threads, fibers, nonwoven fabrics, cosmetics, footwear, heat insulation materials, sealants, tapes, encapsulants, solar power generation components, robot components, android components, wearable components, clothing, hygiene products, cosmetics, furniture, food packaging components, sporting goods, leisure goods, medical supplies, nursing care products, housing components, acoustic components, lighting components, vibration isolation components, soundproofing components, daily necessities, general merchandise, cushions, bedding, stress absorption materials, stress relaxation materials, automotive interior materials, automotive exterior materials, railway components, aircraft components, optical components, OA equipment components, general merchandise surface protection components, semiconductor encapsulants, self-healing materials, health equipment, eyeglass lenses, toys, gaskets, cable sheaths, wire harnesses, telecommunications cables, automotive wiring, computer wiring, industrial products, shock absorbers, and semiconductor products.

[0147] 3. Effects In the prepolymer composition, the polyisocyanate component contains bis(isocyanatomethyl)cyclohexane, and the polyol component contains a high molecular weight polyol containing polytetramethylene ether glycol and a low molecular weight polyol containing 1,4-butanediol. Therefore, workability can be improved.

[0148] Furthermore, the 1,4-butanediol content is between 2.0% by mass and 8.0% by mass relative to the polyol component. This improves workability and tensile properties.

[0149] Furthermore, the ratio of the second viscosity to the first viscosity is 1.5 or higher. Therefore, workability can be improved.

[0150] Polyurethane elastomers contain reaction products between a prepolymer composition and a chain extension agent. Therefore, their tensile properties can be improved.

[0151] The prepolymer manufacturing step of the method for producing a prepolymer composition comprises: a first step of reacting a polyisocyanate component with a high molecular weight polyol to obtain a reaction solution containing these reaction products and unreacted polyisocyanate components; a second step of lowering the temperature of the reaction solution to 70°C or below after the first step; and a third step of adding a low molecular weight polyol to the reaction solution, which is at a temperature of 70°C or below, and reacting the reaction solution with the low molecular weight polyol after the second step. As a result, a prepolymer composition for producing polyurethane elastomers with excellent workability and tensile properties can be manufactured.

[0152] The method for producing polyurethane elastomers involves reacting a prepolymer composition, produced by a prepolymer composition production method, with a chain extension agent. This allows for the production of polyurethane elastomers with excellent tensile properties.

[0153] 4. Variations In the modified examples, components and processes similar to those in the first embodiment are given the same reference numerals, and their detailed descriptions are omitted. Furthermore, the modified examples can achieve the same effects and advantages as the first embodiment, unless otherwise specified. Moreover, the first embodiment and its modified examples can be combined as appropriate.

[0154] In the above description, the prepolymer composition is produced by the method for producing the prepolymer composition described above. However, the method for producing the prepolymer composition is not particularly limited, as long as the ratio of the second viscosity to the first viscosity described above is 1.5 or higher. In other words, although the temperature of the reaction solution in the third step of the method for producing the prepolymer composition described above is 70°C or lower, the temperature of the reaction solution is not limited to this. By changing the reaction conditions (reaction time, reaction time), the type of urethane catalyst, and the amount of urethane catalyst added, it is possible to produce a prepolymer composition in which the ratio of the second viscosity to the first viscosity described above is 1.5 or higher, even if the temperature of the reaction solution is set to more than 70°C.

[0155] Furthermore, in the above-mentioned method for producing the prepolymer composition, the polyisocyanate component and the high molecular weight polyol are reacted first, and then the low molecular weight polyol is added. However, the method is not limited to this, and for example, even when the high molecular weight polyol and the low molecular weight polyol are added to the polyisocyanate component, a prepolymer composition having a ratio of the second viscosity to the first viscosity of 1.5 or higher can be produced by changing the reaction conditions (reaction time, reaction time), the type of urethane catalyst, and the amount of urethane catalyst added.

[0156] Furthermore, the prepolymer composition does not need to contain all of the first isocyanate-terminated prepolymer, the second isocyanate-terminated prepolymer, and the third isocyanate-terminated prepolymer, as long as the ratio of the second viscosity to the first viscosity described above is 1.5 or more. In other words, the prepolymer composition has a ratio of the second viscosity to the first viscosity described above that is 1.5 or more, and contains at least one of the first isocyanate-terminated prepolymer, the second isocyanate-terminated prepolymer, and the third isocyanate-terminated prepolymer. [Examples]

[0157] Next, the present invention will be described based on examples and comparative examples, but the present invention is not limited thereto. Unless otherwise specified, "parts" and "%" refer to mass. Furthermore, specific numerical values ​​such as blending ratios (content), physical properties, and parameters used in the following description may be replaced with the corresponding upper limits (numerical values ​​defined as "less than or equal to" or "less than") or lower limits (numerical values ​​defined as "greater than or equal to" or "greater than or equal to" or "greater than or equal to") of the blending ratios (content), physical properties, and parameters described in the "Modes for Carrying Out the Invention" above.

[0158] <Details of ingredients> 1,4-H6XDI: 1,4-bis(isocyanatomethyl)cyclohexane, trade name "Fortimo 1,4H6XD", trans-1,4-bis(isocyanatomethyl)cyclohexane content 86 mol%, cis-1,4-bis(isocyanatomethyl)cyclohexane content 14 mol% 2,4-TDI: 2,4-Tolylene diisocyanate, trade name "Cosmonate T-100", manufactured by Mitsui Chemicals, Inc. PTMEG#650: Polytetramethylene ether glycol, trade name "PTMG650", hydroxyl value = 172.6 mgKOH / g, number average molecular weight 650, manufactured by Mitsubishi Chemical Corporation. PTMEG#2000: Polytetramethylene ether glycol, trade name "PTMG2000", hydroxyl value = 56.1 mgKOH / g, number average molecular weight 2000, manufactured by Mitsubishi Chemical Corporation. PCL#650: Polycaprolactone polyol, trade name "Capa2065", hydroxyl value = 172.6 mgKOH / g, number average molecular weight 650, manufactured by Ingevity. 1,4-BD:1,4-butanediol 1,3-BG:1,3-Butylene glycol Irganox 245: Antioxidant, product name "Irganox 245", manufactured by BASF Japan. BYK-088: Antifoaming agent, product name "BYK-088", manufactured by Big Chemie Japan Co., Ltd. MOCA: 3,3'-Dichloro-4,4'-diaminodiphenylmethane (4,4'-methylenebis(2-chloroaniline)

[0159] <Production of prepolymer compositions and polyurethane elastomers> Example 1 [Prepolymer Manufacturing Process] (1st step) According to the formulation described in Table 1, the polyisocyanate component and the high molecular weight polyol were charged into a flask. Next, 0.15 parts by mass of Irganox 245 and 0.1 parts by mass of BYK-088 were added. Then, a urethane catalyst (dibutyltin dilaurate diluted to 2% by mass with diisononyl adipate) was added in a catalytic amount of 5 ppm. Next, the polyisocyanate component and the high molecular weight polyol were reacted under a nitrogen atmosphere at 80°C to obtain a reaction solution containing these reaction products and unreacted polyisocyanate components.

[0160] (2nd process) The reaction solution was allowed to cool, and its temperature was adjusted to the temperatures listed in Table 1.

[0161] (3rd step) {3rd A process} While maintaining the liquid temperature in the second step, the low molecular weight polyol was added to the reaction solution and left to stand for 30 minutes. This allowed the reaction solution and the low molecular weight polyol to react.

[0162] {3rd B process} The reaction mixture was heated to a temperature of 80°C and reacted with the low molecular weight polyol until the isocyanate group concentration reached 12.5% ​​by mass. The isocyanate group concentration was determined using a potentiometric titrator by the n-dibutylamine method in accordance with JIS K-1556 (2006).

[0163] Based on the above, a prepolymer composition was prepared.

[0164] [Manufacturing of polyurethane elastomers] The prepolymer composition and chain extender were mixed at 80°C to an equivalent ratio (active hydrogen groups / NCO) of 0.95. Next, a urethane catalyst (dibutyltin dilaurate diluted to 2% by mass with diisononyl adipate) was added in a catalytic amount of 200 ppm, and the mixture was stirred and degassed under vacuum to obtain a polyurethane elastomer composition. Subsequently, the polyurethane elastomer composition was poured into a mold (2 mm thick sheet shape, 320 mm wide) that had been preheated to 110°C, and cured in a 110°C oven for 1 hour. The cured product was then demolded from the mold, and the resulting demolded product was annealed in a 110°C oven for 15 hours, followed by aging for 7 days under constant temperature and humidity conditions of 23°C and 55% relative humidity. This yielded a sheet-shaped polyurethane elastomer.

[0165] Examples 2 to 4, and Comparative Examples 1 to 8 A prepolymer composition and a polyurethane elastomer were prepared using the same procedure as in Example 1. However, in Comparative Example 7, the urethane catalyst was not incorporated in the production of the polyurethane elastomer.

[0166] <Rating> [First viscosity and second viscosity] The first viscosity of the prepolymer compositions of each example and comparative example was measured using the cone-plate viscometer method with a CV-2 cone-plate viscometer (manufactured by Toa Kogyo Co., Ltd.) in accordance with JIS K 5600-2-3 (2014), under the conditions of a measurement temperature of 80°C, a rotation speed of 750 rpm, and a 10P plate.

[0167] Furthermore, the second viscosity of the prepolymer compositions of each example and comparative example was measured using a cone-plate viscometer CV-2 (manufactured by Toa Kogyo Co., Ltd.) in accordance with JIS K 5600-2-3 (2014) under the cone-plate viscometer method, with a measurement temperature of 80°C, a rotation speed of 94 rpm, and a 10P plate.

[0168] The ratio of the second viscosity to the first viscosity was calculated from the obtained first and second viscosities. The results are shown in Table 1.

[0169] [Workability] 50 g of each prepolymer composition from each example and comparative example was placed in a 100 mL glass bottle, sealed, and left to stand in an 80°C constant temperature bath for 1 hour. Afterward, the glass bottle was tilted 90 degrees. Workability was evaluated based on the following criteria. {standard} Even after exceeding 5 minutes and 10 seconds, the liquid level did not become horizontal. 4: The liquid level became horizontal within 7 seconds to 10 seconds. 3: The liquid level became horizontal between 5 seconds and 7 seconds. The liquid level became horizontal within 2.3 seconds to 5 seconds. The liquid level became horizontal in less than 1:3 seconds.

[0170] <Tensile properties> For each example and comparative example, the polyurethane elastomer was tested for tensile strength and elongation at break using a Tensilon universal material tester RTG-1310 in accordance with JIS K 7312 (1996), with a No. 3 dumbbell test specimen and a tensile speed of 500 mm / min. The results are shown in Table 1.

[0171] [Table 1]

Claims

1. A prepolymer composition comprising an isocyanate-terminated prepolymer, The isocyanate-terminated prepolymer comprises a reaction product of a polyisocyanate component and a polyol component. The aforementioned polyisocyanate component includes bis(isocyanatomethyl)cyclohexane, The polyol component includes high molecular weight polyols and low molecular weight polyols. The aforementioned high molecular weight polyol contains polytetramethylene ether glycol, The low molecular weight polyol comprises 1,4-butanediol, The content of 1,4-butanediol is 2.0% by mass or more and 8.0% by mass or less relative to the polyol component. A prepolymer composition in which the ratio (second viscosity / first viscosity) of the second viscosity of the prepolymer composition measured under the conditions of a measurement temperature of 80°C and a rotation speed of 94 rpm to the first viscosity of the prepolymer composition measured under the conditions of a measurement temperature of 80°C and a rotation speed of 750 rpm is 1.5 or more.

2. The prepolymer composition according to claim 1, wherein the ratio is 2.0 or less.

3. A polyurethane elastomer comprising a reaction product of a prepolymer composition according to claim 1 or 2 and a chain extender.

4. The process includes a prepolymer manufacturing step that obtains an isocyanate-terminated prepolymer by reacting a polyisocyanate component with a polyol component. The aforementioned polyisocyanate component includes bis(isocyanatomethyl)cyclohexane, The polyol component includes high molecular weight polyols and low molecular weight polyols. The aforementioned high molecular weight polyol contains polytetramethylene ether glycol, The low molecular weight polyol comprises 1,4-butanediol, The content of 1,4-butanediol is 2.0% by mass or more and 8.0% by mass or less relative to the polyol component. The aforementioned prepolymer manufacturing process is: The first step involves reacting the polyisocyanate component with the high molecular weight polyol to obtain a reaction solution containing the reaction products and the unreacted polyisocyanate component. After the first step, a second step is taken to reduce the temperature of the reaction solution to 70°C or lower. A method for producing a prepolymer composition, comprising the third step of adding the low molecular weight polyol to the reaction solution, which has a liquid temperature of 70°C or lower, after the second step, and reacting the reaction solution with the low molecular weight polyol.

5. A method for producing a polyurethane elastomer, comprising reacting a prepolymer composition produced by the method for producing a prepolymer composition described in claim 4 with a chain extender.

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