Composition for polyurethane elastomer, and polyurethane elastomer

Abstract

To provide a composition which, upon curing, can form polyurethane elastomers that are flexible and excellent in terms of stretchability and restorability.SOLUTION: This composition for polyurethane elastomers comprises: one or more polyol compounds (A) including a compound which has three or more groups represented by formula (1) in each molecule and has an average molecular weight per hydroxyl group of 1,000-2,000; and a polyisocyanate compound (B). In formula (1), n indicates an integer of 2-6 and m indicates an integer of 6-20.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a composition for a polyurethane elastomer and a polyurethane elastomer obtained using the composition for a polyurethane elastomer. [Background technology]

[0002] Polyurethane elastomers are widely used in a variety of applications, including industrial rolls, sealing materials, conveyor belts, medical equipment, shoe soles, tires, shock absorbers, and sports and leisure goods.

[0003] The polyurethane elastomer is obtained by thermally curing a polyurethane elastomer composition containing a polyol compound, a polyisocyanate compound, and a curing agent. In recent years, there has been a demand for polyurethane elastomers with a softer texture, and it is known that this can be achieved by the following methods [1] and [2]. [1] Method of adding a plasticizer such as diisononyl phthalate [2] Method using a high molecular weight polyol compound

[0004] However, the above method [1] has the problem that the plasticizer in the polyurethane elastomer is prone to bleeding out in the summer.

[0005] Furthermore, Patent Document 1 describes the use of modified polytetramethylene ether glycol having a number average molecular weight of 1500 to 5000 as the method [2]. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-242725 Summary of the Invention [Problem to be solved by the invention]

[0007] However, polyurethane elastomers obtained using polyether polyols such as modified polytetramethylene ether glycol have a tensile strength of about 2 MPa, which is a drawback in that they have low mechanical strength.

[0008] Furthermore, the present inventors have found that when a high molecular weight diol such as the modified polytetramethylene ether glycol is used, the resulting polyurethane elastomer becomes soft and easy to stretch (i.e., the extensibility is improved), but the soft segment derived from the high molecular weight diol is prone to crystallization due to a decrease in crosslink density, and when stretched, it becomes difficult to return to its original shape (i.e., the recovery property is reduced).

[0009] Accordingly, an object of the present disclosure is to provide a composition that can be cured to form a polyurethane elastomer that is soft and has excellent elongation and recovery properties. Another object of the present disclosure is to provide a polyurethane elastomer that is soft and has excellent elongation and recovery properties. [Means for solving the problem]

[0010] As a result of intensive research to solve the above problems, the present inventors have found that if a polyol compound obtained by ring-opening addition polymerization of a lactone to a trivalent or higher polyol and having an average molecular weight per hydroxyl group of 1000 or more and 2000 or less is used as the polyol compound, the resulting polyurethane elastomer is soft and has high elongation and recovery properties. The present disclosure has been completed based on these findings.

[0011] That is, the present disclosure provides a composition for polyurethane elastomers, which comprises a polyol compound (A) containing a compound having three or more groups represented by the following formula (1) in one molecule and having an average molecular weight per hydroxyl group of 1,000 or more and 2,000 or less, and a polyisocyanate compound (B). [ka] (wherein n represents an integer of 2 to 6, and m represents an integer of 6 to 20)

[0012] The present disclosure also provides the composition for a polyurethane elastomer, wherein the polyol compound (A) is a compound represented by the following formula (a) or (b): [ka] (In the formula, n1 to n4 are the same or different and each represent an integer of 3 to 6. m1 to m4 are the same or different and each represent an integer of 6 to 20. R 1 ~R 3 , R 5 are the same or different and represent a single bond or a divalent hydrocarbon group. 4 represents a hydrogen atom, a hydroxyl group, or a monovalent hydrocarbon group which may have a group represented by formula (1). Ring Z represents a residue obtained by removing s hydrogen atoms from the structural formula of an alicyclic hydrocarbon ring, an aromatic hydrocarbon ring, or a heterocyclic ring, where s represents an integer of 3 or more.

[0013] The present disclosure also provides the composition for polyurethane elastomers, which contains a compound (C) having two or more groups reactive with an isocyanate group and a molecular weight of 200 or less, wherein the content of the compound (C) is 1 to 10 parts by weight per 100 parts by weight of the polyol compound (A).

[0014] The present disclosure also provides a polyurethane elastomer having a soft segment composed of an addition polymer of a polyol compound (A) having three or more groups represented by the following formula (1) in one molecule and having an average molecular weight per hydroxyl group of 1,000 or more and 2,000 or less, and a polyisocyanate compound (B): [ka] (wherein n represents an integer of 2 to 6, and m represents an integer of 6 to 20)

[0015] The present disclosure also provides the above polyurethane elastomer, further comprising a hard segment composed of an addition polymer of a polyisocyanate compound (B) and a compound (C) having two or more groups reactive with an isocyanate group and a molecular weight of 200 or less.

[0016] The present disclosure also provides the polyurethane elastomer, which does not have a melting point, or if it has a melting point, has a melting enthalpy of 15 [J / g] or less during the second heating, as determined by DSC measurement under the following conditions: DSC measurement conditions: Temperature increase and decrease rate: 5°C / min Temperature increase and decrease program: decrease the temperature from room temperature to -80°C, hold at -80°C for 1 minute, then increase the temperature to 220°C, hold at 220°C for 1 minute, decrease the temperature to -80°C, hold at -80°C for 1 minute, then increase the temperature to 220°C

[0017] The present disclosure also provides the polyurethane elastomer, which has a Shore A hardness of 75 or less under the conditions of 23°C and 50% Rh.

[0018] The present disclosure also provides the polyurethane elastomer, wherein the compression set obtained by the following method is 10% or less. Compression set calculation method: A test piece made of the polyurethane elastomer and having a right cylindrical shape with a thickness of 12.5±0.5 mm and a diameter of 29.0±0.5 mm is used, and the test is carried out in an atmosphere of 70°C, in which the test piece is pressed so that the thickness is reduced by 25%, and this state is maintained for 22 hours, and the elastic modulus is calculated using the following formula. Compression set rate = [(thickness of test piece before test - thickness of test piece after test) / (thickness of test piece before test - 9.38)] x 100 [Effects of the Invention]

[0019] The polyurethane elastomer composition of the present disclosure contains a polyol compound (A) having three or more groups represented by formula (1) in one molecule and an average molecular weight per hydroxyl group of 1,000 or more and 2,000 or less. Therefore, when the composition is cured, a soft polyurethane elastomer is obtained. Furthermore, the molecular chain length of the soft segment of the polyurethane elastomer is limited by the polyol compound (A). Therefore, crystallization of the soft segment is suppressed, resulting in excellent elongation, recovery, and mechanical strength. The polyurethane elastomer composition can be used in a wide range of applications, including various industrial rolls, sealing materials, conveyor belts, medical equipment, shoe soles, tires, shock absorbers, and sports and leisure goods. DETAILED DESCRIPTION OF THE INVENTION

[0020] [Polyurethane elastomer composition] The composition for a polyurethane elastomer of the present disclosure is a composition that forms a polyurethane elastomer by heat curing, and contains a polyol compound (A) and a polyisocyanate compound (B).

[0021] (Polyol compound (A)) The polyol compound (A) is a polyol compound having three or more groups represented by the following formula (1) in one molecule and having an average molecular weight per hydroxyl group of 1,000 or more and 2,000 or less. [ka] (wherein n represents an integer of 2 to 6, and m represents an integer of 6 to 20)

[0022] The number of hydroxyl groups contained in the polyol compound (A) is 3 or more, preferably 3 to 6. The number of groups represented by formula (1) contained in the polyol compound (A) is 3 or more, preferably 3 to 6.

[0023] The polyol compound (A) is preferably a compound having a tertiary carbon atom or a quaternary carbon atom or a compound having a cyclic skeleton, since it can prevent a decrease in crosslink density and thereby prevent crystallization of the soft segment. A compound represented by the following formula (a) or a compound represented by the following formula (b) is particularly preferred.

[0024] [ka] (In the formula, n1 to n3 are the same or different and each represents an integer of 3 to 6. m1 to m3 are the same or different and each represents an integer of 6 to 20. R 1 ~R 3 are the same or different and represent a single bond or a divalent hydrocarbon group. 4 represents a hydrogen atom, a hydroxyl group, or a monovalent hydrocarbon group which may have a group represented by formula (1).

[0025] [ka] (In the formula, n4 represents an integer of 3 to 6. m4 represents an integer of 6 to 20. R 5 represents a single bond or a divalent hydrocarbon group. Ring Z represents a residue obtained by removing s hydrogen atoms from the structural formula of an alicyclic hydrocarbon ring, an aromatic hydrocarbon ring, or a heterocyclic ring, where s represents an integer of 3 or more.

[0026] Examples of the divalent hydrocarbon group include linear or branched alkylene groups having 1 to 18 carbon atoms, such as methylene, methylmethylene, dimethylmethylene, ethylene, propylene, and trimethylene; and cycloalkylene groups (including cycloalkylidene groups) having 3 to 18 carbon atoms, such as 1,2-cyclopentylene, 1,3-cyclopentylene, cyclopentylidene, 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene, and cyclohexylidene.

[0027] Of the divalent hydrocarbon groups, alkylene groups are preferred, particularly alkylene groups having 1 to 18 carbon atoms are more preferred, alkylene groups having 1 to 5 carbon atoms are most preferred, and linear alkylene groups having 1 to 5 carbon atoms are particularly preferred.

[0028] The monovalent hydrocarbon group includes a monovalent aliphatic hydrocarbon group, a monovalent alicyclic hydrocarbon group, a monovalent aromatic hydrocarbon group, and a monovalent group in which two or more of these are bonded via a single bond or a linking group [for example, a carbonyl group (-CO-), an ether bond (-O-), a thioether bond (-S-), an ester bond (-COO-), etc.].

[0029] Among the monovalent hydrocarbon groups, monovalent aliphatic hydrocarbon groups are preferred. The monovalent aliphatic hydrocarbon groups include those having 1 to 20 carbon atoms (=C 1-20 ) is preferred, and examples thereof include alkyl groups having about 1 to 20 carbon atoms (preferably 1 to 10, particularly preferably 1 to 3), such as a methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, s-butyl group, t-butyl group, pentyl group, hexyl group, decyl group, and dodecyl group; and alkenyl groups having about 2 to 20 carbon atoms (preferably 2 to 10, particularly preferably 2 to 3), such as a vinyl group, allyl group, and 1-butenyl group.

[0030] The monovalent hydrocarbon group may have a group represented by formula (1) as a substituent, or may have a substituent other than the group represented by formula (1). Examples of other substituents include a hydroxyl group, an oxo group, a substituted oxy group (e.g., C 1-5 Alkoxy group, C 6-12 Aryloxy group, C 7-16 Aralkyloxy group, C 1-5 acyloxy group, etc. Furthermore, the monovalent hydrocarbon group which may have a group represented by the formula (1) may simply be a group represented by the formula (1).

[0031] The alicyclic hydrocarbon ring constituting the ring Z is preferably an alicyclic hydrocarbon ring having 3 to 20 carbon atoms, and examples thereof include cycloalkanes having 3 to 20 carbon atoms (preferably 3 to 15 carbon atoms, particularly preferably 5 to 8 carbon atoms) such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, and cyclooctane; cycloalkenes having 3 to 20 carbon atoms (preferably 3 to 15 carbon atoms, particularly preferably 5 to 8 carbon atoms) such as cyclopentene and cyclohexene; perhydronaphthalene, norbornane, norbornene, adamantane, and tricyclo[5.2.1.0] 2,6 ] Decane, Tetracyclo[4.4.0.1 2,5 .1 7,10 ] dodecane-4-ene and other bridged rings.

[0032] The aromatic hydrocarbon ring constituting the ring Z is preferably C 6-14 (Especially C 6-10 Aromatic hydrocarbon rings are preferred, such as benzene and naphthalene.

[0033] The alicyclic hydrocarbon ring and aromatic hydrocarbon ring may have various substituents [for example, an oxo group, a substituted oxy group (for example, an alkoxy group, an aryloxy group, an aralkyloxy group, an acyloxy group, etc.), a carboxyl group, etc.].

[0034] The heterocycle constituting the ring Z includes aromatic heterocycles and non-aromatic heterocycles. Examples of such heterocycles include 3- to 10-membered rings (preferably 4- to 6-membered rings) containing carbon atoms and at least one heteroatom (e.g., oxygen atom, sulfur atom, nitrogen atom, etc.) as ring-constituting atoms, and condensed rings thereof. Specific examples include heterocycles containing an oxygen atom as a heteroatom (e.g., 3-membered rings such as oxirane ring; 4-membered rings such as oxetane ring; 5-membered rings such as furan ring, tetrahydrofuran ring, oxazole ring, isoxazole ring, γ-butyrolactone ring; 6-membered rings such as 4-oxo-4H-pyran ring, tetrahydropyran ring, morpholine ring; condensed rings such as benzofuran ring, isobenzofuran ring, 4-oxo-4H-chromene ring, chroman ring, isochroman ring); 3-oxatricyclo[4.3.1.14,8 ]undecan-2-one ring, 3-oxatricyclo[4.2.1.0 4,8 ]nonan-2-one ring and other bridged rings), heterocycles containing a sulfur atom as a heteroatom (for example, five-membered rings such as a thiophene ring, a thiazole ring, an isothiazole ring, and a thiadiazole ring; six-membered rings such as a 4-oxo-4H-thiopyran ring; fused rings such as a benzothiophene ring), heterocycles containing a nitrogen atom as a heteroatom (for example, five-membered rings such as a pyrrole ring, a pyrrolidine ring, a pyrazole ring, an imidazole ring, and a triazole ring; six-membered rings such as an isocyanuric ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazine ring, a piperidine ring, and a piperazine ring; fused rings such as an indole ring, an indoline ring, a quinoline ring, an acridine ring, a naphthyridine ring, a quinazoline ring, and a purine ring). The heterocyclic group may contain, in addition to the substituents that the alicyclic hydrocarbon ring or aromatic hydrocarbon ring may have, C 1-4 Alkyl groups (e.g., methyl groups, ethyl groups, etc.), C 3-20 Cycloalkyl groups, C 6-14 It may have an aryl group (for example, a phenyl group, a naphthyl group, etc.).

[0035] The s represents an integer of 3 or more, and is preferably an integer of 3 to 6.

[0036] The average molecular weight per hydroxyl group of the polyol compound (A) is 1000 or more and 2000 or less. In order to suppress crystallization of the soft segment and obtain a polyurethane elastomer having high recovery properties, the upper limit of the average molecular weight is preferably 1900, particularly preferably 1700, and especially preferably 1600. In order to obtain a polyurethane elastomer having high elongation and mechanical strength, the lower limit is preferably 1100, more preferably 1200, particularly preferably 1300, most preferably 1400, and especially preferably 1500.

[0037] The number average molecular weight of the polyol compound (A) is, for example, 4000 to 8000. In order to suppress crystallization of the soft segment and obtain a polyurethane elastomer having high recovery properties, the upper limit of the average molecular weight is preferably 7600, particularly preferably 6800, and especially preferably 6400. In order to obtain a polyurethane elastomer having high extensibility and mechanical strength, the lower limit is preferably 4400, more preferably 4800, particularly preferably 5200, most preferably 5500, and especially preferably 6000.

[0038] The polyol compound (A) has a molecular weight dispersity (Mw / Mn) of, for example, 1.1 to 1.6.

[0039] The polyol compound (A) can be produced by using a polyol having three or more hydroxyl groups as an initiator and subjecting a 5- to 8-membered ring lactone to ring-opening polymerization with the initiator.

[0040] The polyol is, for example, a polyol having a tertiary carbon atom or a quaternary carbon atom, or a polyol having a cyclic skeleton, and has three or more, preferably three to five, hydroxyl groups.

[0041] The molecular weight of the polyol is, for example, 95 to 200, preferably 100 to 150, and particularly preferably 100 to 140.

[0042] Examples of the polyol include trimethylolpropane, pentaerythritol, tris-(2-hydroxyethyl)isocyanurate, dipentaerythritol, etc. These can be used alone or in combination of two or more.

[0043] Examples of the lactone include γ-butyrolactone, δ-valerolactone, ε-caprolactone, ζ-enantholactone, etc. These may be used alone or in combination of two or more.

[0044] By controlling the amount of lactone used, it is possible to adjust the average molecular weight per hydroxyl group of the resulting polyol compound (A). The amount of lactone used is, for example, 20 to 80 moles per mole of the initiator. From the viewpoint of suppressing crystallization of the soft segment and obtaining a polyurethane elastomer having high recovery, the upper limit of the amount of lactone used is preferably 70 moles, more preferably 65 moles, and particularly preferably 60 moles. Furthermore, from the viewpoint of obtaining a polyurethane elastomer having high elongation and mechanical strength, the lower limit of the amount of lactone used is preferably 30 moles, more preferably 35 moles, particularly preferably 45 moles, and most preferably 50 moles.

[0045] The ring-opening polymerization reaction of lactone is preferably carried out in the presence of a tin compound as a catalyst. Examples of the tin compound include stannous octoate, dibutyltin dilaurate, tin(II) chloride, tin(IV) chloride, stannous bromide, stannous iodide, dibutyldichlorotin, butyltrichlorotin, monobutyltin oxide, dibutyltin oxide, monobutyltin tris(2-ethylhexyl mercaptoacetate), monobutyltin tris(isooctyl mercaptoacetate), monobutyltin triacetate, and monobutyltin tris(2-ethylhexanoate). These compounds can be used alone or in combination of two or more.

[0046] The amount of the tin compound used (the total amount when two or more types are used in combination) is, for example, 5 to 30 ppm, preferably 10 to 25 ppm, and particularly preferably 15 to 25 ppm, based on the total amount of lactone and initiator. Using the tin compound in the above range is preferred because it allows the production of a polyol compound (A) with a narrow molecular weight distribution.

[0047] The reaction temperature in the ring-opening polymerization reaction of lactone is preferably 120° C. or higher, and particularly preferably 120 to 210° C. The reaction time is, for example, 3 to 30 hours, and the reaction pressure is, for example, 0.7 to 1.5 atmospheres. The reaction atmosphere is not particularly limited as long as it does not inhibit the reaction, but an inert gas atmosphere such as a nitrogen atmosphere or an argon atmosphere is preferred.

[0048] The ring-opening polymerization of lactones can be carried out by any of the following polymerization methods: bulk polymerization, solution polymerization, and suspension polymerization. As the solvent used in the solution polymerization, aromatic hydrocarbons such as toluene and xylene are preferred because they have a relatively high boiling point and are inert to the reaction. The solvent is preferably substantially anhydrous.

[0049] The polymerization reaction can be carried out by any method such as a batch method, a semi-batch method, a continuous method, etc. After completion of the reaction, the reaction product can be separated and purified by a separation and purification means such as filtration, concentration, distillation, extraction, crystallization, recrystallization, adsorption, column chromatography, etc., or a combination of these means.

[0050] (Polyisocyanate compound (B)) Examples of the polyisocyanate compound (B) include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, xylylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, xylylene diisocyanate, 1,5-naphthalene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 2,4-tolylene ... diisocyanate compounds such as 2,4-trimethylhexamethylene diisocyanate and 2,4,4-trimethylhexamethylene diisocyanate; diisocyanate compounds obtained by hydrogenating aromatic isocyanate compounds among the above diisocyanate compounds (for example, diisocyanate compounds such as hydrogenated xylylene diisocyanate and hydrogenated diphenylmethane diisocyanate); tri- or higher valent isocyanate compounds such as triphenylmethane triisocyanate and dimethylene triphenyl triisocyanate; and polymerized polyisocyanates obtained by polymerizing these. These can be used alone or in combination of two or more.

[0051] As the polyisocyanate compound (B), a diisocyanate compound is preferred, and an aromatic diisocyanate compound is particularly preferred.

[0052] Regarding the content of the polyisocyanate compound (B), the molar ratio [NCO groups / (OH groups+groups reactive with isocyanate groups)] of the isocyanate groups contained in the polyisocyanate compound (B) to the hydroxyl groups contained in the polyol compound (A) (in the case where a curing agent described later is contained, the total of the groups reactive with the hydroxyl groups contained in the polyol compound (A) and the isocyanate groups contained in the curing agent) is, for example, preferably in the range of 1 / 3 to 3 / 3, and more preferably in the range of 1 / 2 to 2 / 1.

[0053] (others) The composition may contain one or more other components in addition to the polyol compound (A) and the polyisocyanate compound (B), such as a chain extender, a crosslinking agent, a curing agent, a flame retardant, a plasticizer, an antioxidant, an ultraviolet absorber, a colorant, and a filler.

[0054] Examples of the chain extender include compound (C), which is a compound having two or more groups reactive with an isocyanate group and has a low molecular weight (the molecular weight is, for example, 200 or less, preferably 150 or less, particularly preferably 120 or less, and particularly preferably 100 or less; the lower limit of the molecular weight is, for example, 50).

[0055] When the composition contains the compound (C), the resulting polyurethane elastomer has soft segments composed of an addition polymer of the polyol compound (A) and the polyisocyanate compound (B), as well as hard segments composed of an addition polymer of the polyisocyanate compound (B) and the compound (C). The elongation, recovery, and mechanical strength can be controlled by adjusting the content ratio of the soft segments and the hard segments.

[0056] The compound (C) has two or more groups reactive with an isocyanate group, and preferably two to three groups.

[0057] In the compound (C), examples of the group reactive with an isocyanate group include a hydroxyl group and an amino group.

[0058] Examples of the compound (C) include polyols, polyamines, and amino alcohols.

[0059] Examples of the polyol include aliphatic polyols having 2 to 10 carbon atoms, such as ethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexamethylenediol, glycerin, and trimethylolpropane.

[0060] Examples of the polyamine include aliphatic polyamines such as ethylenediamine, propylenediamine, 1,3-diaminopentane, and 2-methyl-1,5-pentanediamine; and alicyclic polyamines such as 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and 4,4'-dicyclohexylmethanediamine.

[0061] Examples of the amino alcohol include N-methylethanolamine, diethanolamine, and diisopropanolamine.

[0062] The compound (C) is preferably a polyol, particularly preferably a diol, and particularly preferably an aliphatic diol having 2 to 10 carbon atoms (particularly, 2 to 6 carbon atoms).

[0063] The content of the compound (C) is, for example, 1 to 10 parts by weight, preferably 2 to 8 parts by weight, and particularly preferably 3 to 7 parts by weight, relative to 100 parts by weight of the polyol compound (A).

[0064] The composition may contain other polyols in addition to the polyol compound (A) and the polyol compound (C), but the content of other polyols is, for example, 30% by weight or less, preferably 20% by weight or less, particularly preferably 10% by weight or less, most preferably 5% by weight or less, and particularly preferably 1% by weight or less of the total amount of polyols contained in the composition. Note that a polyol is a compound having two or more hydroxyl groups in one molecule.

[0065] [Polyurethane elastomer] The polyurethane elastomer of the present disclosure comprises a soft segment consisting of an addition polymer of a polyol compound (A) having three or more groups represented by the formula (1) in one molecule and having an average molecular weight per hydroxyl group of 1000 or more and 2000 or less, and a polyisocyanate compound (B).

[0066] The polyurethane elastomer can be obtained, for example, by curing the polyurethane elastomer composition. The polyurethane elastomer composition is cured, for example, by heating at a temperature of 80 to 150° C. The heating time is, for example, 5 to 24 hours.

[0067] When the polyurethane elastomer composition contains the compound (C), the polyurethane elastomer has, in addition to the soft segments, hard segments composed of an addition polymer of the polyisocyanate compound (B) and the compound (C). The polyurethane elastomer may have the soft segments and the hard segments randomly or regularly. That is, the polyurethane elastomer may be a random copolymer or a block copolymer of the soft segments and the hard segments.

[0068] The soft segment of the polyurethane elastomer is composed of an addition polymer of a polyol compound (A) and a polyisocyanate compound (B). Therefore, the soft segment does not have a melting point, or even if it does have a melting point, the melting point is 30°C or less (for example, in the range of 20 to 30°C), thereby suppressing crystallization and preventing a decrease in recovery due to crystallization.

[0069] The melting point is the melting peak temperature detected using a DSC (differential scanning calorimeter) when the temperature is lowered from room temperature (25°C) to -80°C at a rate of 5°C / min, held at -80°C for 1 minute, heated to 220°C at a rate of 5°C / min, held at 220°C for 1 minute, cooled to -80°C at a rate of 5°C / min, held at -80°C for 1 minute, and heated again to 220°C at a rate of 5°C / min. In the present disclosure, "having no melting point" means that no clear melting peak of the polyol compound (A) is observed when DSC measurement is performed under the above conditions.

[0070] When the polyurethane elastomer has a melting point, the melting enthalpy during the second heating when DSC measurement is performed under the above conditions is, for example, 15 [J / g] or less, preferably 10 [J / g] or less, and particularly preferably 5 [J / g] or less.

[0071] The polyurethane elastomer has a suitable hardness, and the Shore A hardness is, for example, 75 or less, and preferably 70 or less. The lower limit of the Shore A hardness is, for example, 60. The Shore A hardness is a value measured under conditions of 23°C and 50% RH.

[0072] The polyurethane elastomer has a suitable hardness and a modulus of elasticity of, for example, 3 to 10 MPa, preferably 3 to 6 MPa, and particularly preferably 3 to 5 MPa. The modulus of elasticity can be determined by the method described in the Examples.

[0073] The polyurethane elastomer has excellent recovery properties, and the compression set determined by the method described below is, for example, 10% or less, preferably 5 or less, particularly preferably less than 3, and most preferably 2 or less. Compression set calculation method: A test specimen made of the polyurethane elastomer and having a right cylindrical shape with a thickness of 12.5±0.5 mm and a diameter of 29.0±0.5 mm is used, and the test is carried out in an atmosphere of 70°C, in which the test specimen is compressed so that the thickness is reduced by 25%, and this state is maintained for 22 hours, and the thickness is calculated using the following formula: The test specimen thickness after the test is completed and the compression is released. Compression set rate = [(thickness of test piece before test - thickness of test piece after test) / (thickness of test piece before test - 9.38)] x 100

[0074] The polyurethane elastomer has excellent recovery properties, and the elastic recovery is, for example, 35% or more, preferably 45% or more, more preferably 50% or more, particularly preferably 70% or more, and most preferably 80% or more. The elastic recovery is determined by the method described in the Examples.

[0075] The polyurethane elastomer has excellent mechanical strength, and the tensile strength is, for example, 3 MPa or more, preferably 5 MPa or more, and particularly preferably 10 MPa or more. The tensile strength is measured by the method described in the Examples.

[0076] The polyurethane elastomer has excellent extensibility, and the tensile elongation is, for example, 100% or more, preferably 130% or more, particularly preferably 150% or more, and most preferably 180% or more. The tensile elongation is, for example, 500% or less. The tensile elongation is measured by the method described in the Examples.

[0077] The above-described configurations and combinations thereof of the present disclosure are merely examples, and additions, omissions, substitutions, and modifications of the configurations are possible as appropriate within the scope of the present disclosure. Furthermore, the present disclosure is not limited to the embodiments, but is limited only by the claims. [Example]

[0078] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to these examples. It should be noted that Examples 1 and 5 should be read as Reference Examples 1 and 2.

[0079] The molecular weight of the obtained compound was measured under the following measurement conditions, and the number average molecular weight (Mn) was determined by comparison with a polystyrene standard. <Measurement conditions> Measurement equipment: High-speed GPC equipment "HLC-8220GPC", manufactured by Tosoh Corporation Mobile phase: tetrahydrofuran

[0080] Preparation Example 1 Into a five-neck flask equipped with a reflux condenser, a thermometer, an air-mixing gas inlet pipe, and a stirrer, 3.5 parts by weight of pentaerythritol as an initiator, 100 parts by weight of ε-caprolactone (an amount equivalent to 33.9 moles per mole of the initiator), and 0.002 part by weight of stannous octoate were charged under a nitrogen gas atmosphere, and the internal temperature was then raised to 170°C. After confirming by gas chromatography that the concentration of ε-caprolactone was less than 1.0%, the reaction was terminated by cooling. This yielded polyol compound (A1). The number average molecular weight (Mn) of the resulting polyol compound (A1) was 4,000.

[0081] Preparation Example 2 A polyol compound (A2) was obtained in the same manner as in Preparation Example 1, except that the amount of pentaerythritol used was changed to 2.7 parts by weight (corresponding to 43.5 moles per mole of the initiator). The number average molecular weight (Mn) of the obtained polyol compound (A2) was 5,100.

[0082] Preparation Example 3 A polyol compound (A3) was obtained in the same manner as in Preparation Example 1, except that the amount of pentaerythritol used was changed to 2.2 parts by weight (equivalent to 54.9 moles per mole of the initiator). The number average molecular weight (Mn) of the obtained polyol compound (A3) was 6,400.

[0083] Preparation Example 4 Polyol compound (A4) was obtained in the same manner as in Preparation Example 1, except that the amount of pentaerythritol used was changed to 1.9 parts by weight (corresponding to 61.9 moles per mole of the initiator). The number average molecular weight (Mn) of the obtained polyol compound (A4) was 7,200.

[0084] Preparation Example 5 A polyol compound (A5) was obtained in the same manner as in Preparation Example 1, except that the amount of pentaerythritol used was changed to 1.7 parts by weight (corresponding to 68.9 moles per mole of the initiator). The number average molecular weight (Mn) of the obtained polyol compound (A5) was 8,000.

[0085] Examples 1 to 5, Comparative Examples 1 and 2 A polyol, a polyisocyanate, and a chain extender were charged into a cup container as shown in the table below, and the mixture was mixed and degassed using a vacuum foam mixer to obtain a composition. The NCO / OH (molar ratio) in the composition was 1.00, and the diol content was 3.71% by weight.

[0086] The resulting composition was poured into a mold measuring 2 mm thick x 13 mm long x 20 mm wide, and cured in an oven at 80°C for 2 hours, then at 120°C for 16 hours. It was then cured for 48 hours in a constant temperature and humidity environment of 23°C and 50% Rh. This yielded a polyurethane elastomer.

[0087] The polyurethane elastomer obtained was evaluated as follows.

[0088] (color tone, feel) The appearance of the polyurethane elastomer was visually observed under an environment of 23°C and 50% RH to judge the color tone, and the feel with the fingers was also checked.

[0089] (Shore A hardness) The hardness of the polyurethane elastomer was measured using a Hardness Tester Type A (Shimadzu Corporation) under an environment of 23°C and 50% Rh.

[0090] (Suppression of crystallization of soft segments) Using a DSC (AUTO Q2000 MDSC, manufactured by TA Instruments), the temperature of the polyurethane elastomer was changed according to the following program, and the melting point and melting enthalpy of the soft segment were measured to determine whether or not the polyurethane elastomer had a melting point. If the polyurethane elastomer had a melting point, the melting enthalpy was measured during the second temperature increase. Temperature rising / cooling rate: 5℃ / min Temperature increase / decrease cycle: Temperature is decreased from room temperature to -80°C, held at -80°C for 1 minute, then heated to 220°C, held at 220°C for 1 minute, then cooled to -80°C, held at -80°C for 1 minute, then heated to 220°C

[0091] (tensile properties) The tensile strength, tensile elongation, and modulus of elasticity were measured using a Tensilon universal testing machine (RTC-1350A, manufactured by A&D Co., Ltd.) under the following conditions. <Measurement conditions> Test piece: The polyurethane elastomer was cut into a No. 3 dumbbell size (length 100 mm x width 25 mm x thickness 2 mm). Measurement environment: 23°C, 50% RH Distance between gauge lines: 20mm Tensile test speed: 500 mm / min

[0092] (Elastic recovery rate) Using a Tensilon universal testing machine (RTC-1350A, manufactured by A&D Co., Ltd.), an expansion / contraction test was carried out for three cycles under the following conditions, and the elastic recovery rate was calculated using the following formula. Elastic recovery rate = (300 - elongation at the third cycle) / 300 x 100 <Test conditions> Test piece: The polyurethane elastomer was cut into a No. 3 dumbbell size (length 100 mm x width 25 mm x thickness 2 mm). Test environment: 23°C, 50% RH Chuck distance: 20mm Stretching test speed: 50 mm / min Maximum elongation: 300% The elongation was kept constant at 0% and 300% for 10 minutes.

[0093] (Compression set rate) A compression set test was carried out using a compression set tester (Kobunshi Keiki Co., Ltd.) under the following conditions, and the compression set rate was calculated using the following formula. Compression set rate = [(thickness of test piece before test - thickness of test piece after test) / (thickness of test piece before test - 9.38)] x 100 <Test conditions> Test piece: The polyurethane elastomer was cut into a right cylindrical shape with a thickness of 12.5±0.5 mm and a diameter of 29.0±0.5 mm. Compression ratio: 25% Compression time: 22 hours Test environment temperature: 70℃

[0094] [Table 1]

[0095] <Polyol> A1 to A5: Compounds (A1) to (A5) obtained in the preparation examples are used. A6: PLACCEL 240CP (manufactured by Daicel Corporation, neopentyl glycol caprolactone adduct, number average molecular weight 4000) A7: PLACCEL 220N (manufactured by Daicel Corporation, ethylene glycol caprolactone adduct, number average molecular weight 2000) <Polyisocyanate> B: Millionate MT (manufactured by Tosoh Corporation, polyisocyanate, NCO content 33.6%) <Chain extender> C: 1,4-butanediol (Mitsubishi Chemical Corporation)

Claims

1. The composition includes a polyol compound (A) containing a compound having three or more groups represented by the following formula (1) in one molecule and having an average molecular weight per hydroxyl group of 1,275 or more and 1,800 or less, a polyisocyanate compound (B), and a compound (C) having two or more groups reactive with an isocyanate group and having a molecular weight of 200 or less, The composition for polyurethane elastomers, wherein the polyol compound (A) is a compound represented by the following formula (a): 【Chemistry 1】 (wherein n represents an integer of 2 to 6, and m represents an integer of 6 to 20) 【Chemistry 2】 (In the formula, n1 to n4 are the same or different and represent integers of 3 to 6. m1 to m4 are the same or different and represent an integer of 6 to 20. R 1 to R 3 are the same or different and represent a single bond or a divalent hydrocarbon group. R 4 represents a hydrogen atom or a monovalent hydrocarbon group which may have a group represented by formula (1).

2. A composition for polyurethane elastomers as described in claim 1, wherein the content of compound (C) is 1 to 10 parts by weight per 100 parts by weight of polyol compound (A).

3. The present invention provides a soft segment comprising an addition polymer of a polyol compound (A) having three or more groups represented by the following formula (1) in one molecule and having an average molecular weight per hydroxyl group of 1,275 or more and 1,800 or less, and a polyisocyanate compound (B), The composition further comprises a hard segment composed of an addition polymer of a polyisocyanate compound (B) and a compound (C) having two or more groups reactive with an isocyanate group and having a molecular weight of 200 or less, The polyurethane elastomer, wherein the polyol compound (A) is a compound represented by the following formula (a): 【Transformation 3】 (wherein n represents an integer of 2 to 6, and m represents an integer of 6 to 20) 【Chemistry 4】 (In the formula, n1 to n4 are the same or different and represent integers of 3 to 6. m1 to m4 are the same or different and represent an integer of 6 to 20. R 1 to R 3 are the same or different and represent a single bond or a divalent hydrocarbon group. R 4 represents a hydrogen atom or a monovalent hydrocarbon group which may have a group represented by formula (1).

4. The polyurethane elastomer according to claim 3, which does not have a melting point, or if it has a melting point, has a melting enthalpy of 15 [J / g] or less during the second heating, as determined by DSC measurement under the following conditions: DSC measurement conditions: Temperature increase and decrease rate: 5°C / min Temperature increase and decrease program: decrease the temperature from room temperature to -80°C, hold at -80°C for 1 minute, then increase the temperature to 220°C, hold at 220°C for 1 minute, decrease the temperature to -80°C, hold at -80°C for 1 minute, and then increase the temperature to 220°C.

5. 5. The polyurethane elastomer according to claim 3, which has a Shore A hardness of 75 or less under conditions of 23°C and 50% Rh.

6. The polyurethane elastomer according to any one of claims 3 to 5, which has a compression set of 10% or less as determined by the following method: Compression set calculation method: A test piece made of the polyurethane elastomer and having a right cylindrical shape with a thickness of 12.5±0.5 mm and a diameter of 29.0±0.5 mm is used, and a test is performed in which the test piece is pressed in an atmosphere of 70°C so that the thickness is reduced by 25%, and this state is maintained for 22 hours, and the elastic modulus is calculated using the following formula. Compression set rate = [(thickness of test piece before test - thickness of test piece after test) / (thickness of test piece before test - 9.38)] x 100

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