Polyurethane elastomer and polyurethane molded body

Abstract

Provided is a polyurethane elastomer which has a matrix and a plurality of domains that are dispersed in the matrix, the polyurethane elastomer being characterized in that, in a specific molded body thereof, the number of included domains is 10 to 77,000, the arithmetic mean value of the sphere equivalent diameters of the domains is 1.0 μm to 30.0 μm, the ratio of the total volume of the domains is 15 vol% to 45 vol%, the relationship between a parameter A indicating the viscoelastic term of the domains and a parameter B indicating the viscoelastic term of the matrix is A < B, the microrubber hardness and the strain at 5 seconds after unloading are each within a specific range, and if C (mass %) and D (mass %) are respective ratios of the mass of an extract E1 and the mass of an extract E2, D / C is 1.0 to 5.0.

Description

Polyurethane elastomer and polyurethane molded article

[0001] The present disclosure relates to a polyurethane elastomer and a polyurethane molded article.

[0002] Polyurethane elastomers are used in a wide range of applications, including artificial and synthetic leathers, paints, coatings, and adhesives. Generally, polyurethane elastomers are formed from the reaction product of polyisocyanate and polyol, consisting of hard segments derived from the polyisocyanate and soft segments derived from the polyol. Polyols, one of the raw materials for polyurethane elastomers, are classified into polyether polyols, polyester polyols, and polycarbonate polyols based on their molecular chain structure. The type of polyol is selected based on the required performance. Polyurethane elastomers with a polycarbonate structure, made from polycarbonate polyols, have excellent abrasion resistance. Furthermore, they are known to have superior heat resistance, weather resistance, and hydrolysis resistance compared to polyurethane elastomers with a polyether or polyester structure.

[0003] On the other hand, in polyurethane elastomers with polycarbonate structures, strong intermolecular forces act between the polycarbonate structures, causing a significant increase in hardness of the polyurethane elastomer, making it difficult to apply polyurethane elastomers with polycarbonate structures to applications requiring low hardness.

[0004] Patent Document 1 discloses a polyurethane elastomer that includes a matrix phase and a domain phase dispersed in the matrix phase, the matrix phase having repeating structural units derived from a polycarbonate diol, and the domain phase having repeating structural units derived from a polyether.

[0005] Japanese Patent Application Laid-Open No. 2022-168829

[0006] The polyurethane elastomer disclosed in Patent Document 1 can achieve both low hardness and abrasion resistance comparable to silicone elastomers, as well as low hardness and low compression set. However, the present inventors have found that when a molded article containing the polyurethane elastomer is used in, for example, a component that is expected to be in contact with another component in a compressed state for a long period of time, such as a gripper of a robot chuck, a substance that exudes from the molded article may adhere to the component.

[0007] At least one aspect of the present disclosure is directed to providing a polyurethane elastomer that provides a molded article that is flexible yet exhibits small compression set and that does not cause exudates to adhere to other members even when pressed against them. At least one aspect of the present disclosure is directed to providing a molded article that is flexible yet exhibits small compression set and that does not cause exudates to adhere to other members even when pressed against them.

[0008] According to at least one aspect of the present disclosure, there is provided a polyurethane elastomer having a matrix and a plurality of domains dispersed in the matrix, wherein a first molded body made of the polyurethane elastomer has a cubic shape with each side measuring 100 μm, the number N of the domains contained is 10 to 77,000, the arithmetic mean value Da of the equivalent sphere diameters of the domains is 1.0 to 30.0 μm, the proportion V of the total volume of the domains in the first molded body is 15 to 45 volume %, the relationship between a parameter A indicating the viscoelastic term of the domains and a parameter B indicating the viscoelastic term of the matrix, as measured in a viscoelastic image obtained by a scanning probe microscope of a cross section parallel to one face of the first molded body, is A<B, and a micro rubber hardness at a temperature of 23°C of a second molded body made of the polyurethane elastomer is 20 to 50 degrees, and In an indentation test of the second molded body using a nanoindenter at a temperature of 23°C, a Vickers indenter is pressed into the second molded body at a loading rate of 10 mN / 30 seconds, and the load of 10 mN is maintained for 60 seconds, and then the load is released. When the load is released, the strain 5 seconds after release is 1.0 μm or less. When a third molded body made of the polyurethane elastomer is subjected to Soxhlet extraction in accordance with Japanese Industrial Standards (JIS) K6229:2015 using acetone as an extraction solvent at an extraction temperature of 80°C for an extraction time of 4 hours, the ratio of the mass of the obtained extract E1 to the mass of the third molded body is defined as C (mass%). When a powder of the third molded body having a mode diameter of less than 1 μm is extracted using acetone as an extraction solvent in accordance with Japanese Industrial Standards (JIS) K6229:2015, the ratio of the mass of the obtained extract E1 to the mass of the third molded body is defined as C (mass%). In accordance with K6229:2015, Soxhlet extraction is performed using acetone as the extraction solvent at an extraction temperature of 80°C for 4 hours. When the ratio of the mass of the obtained extract E2 to the mass of the powder is defined as D (mass %), a polyurethane elastomer having a D / C ratio of 1.0 to 5.0 is provided.

[0009] Furthermore, according to at least one aspect of the present disclosure, there is provided a polyurethane molded article comprising the polyurethane elastomer of the present disclosure.

[0010] According to at least one aspect of the present disclosure, it is possible to obtain a polyurethane elastomer that provides a molded article that is flexible yet has small compression set and that does not cause exudates to adhere to other members even when pressed against them.Furthermore, at least one aspect of the present disclosure provides a molded article that is flexible yet has small compression set and that does not cause exudates to adhere to other members even when pressed against them.

[0011] 1 is a diagram illustrating deformation of a urethane elastomer according to an embodiment of the present disclosure, a schematic diagram illustrating a method for producing a urethane elastomer according to an embodiment of the present disclosure, and a schematic diagram illustrating a method for producing a urethane elastomer according to an embodiment of the present disclosure.

[0012] In this specification, expressions such as "XX or more and YY or less" or "XX to YY" representing a numerical range mean a numerical range including the lower and upper limits, which are the endpoints, unless otherwise specified. Furthermore, when a numerical range is described in stages, the upper and lower limits of each numerical range can be arbitrarily combined. Furthermore, in this disclosure, for example, a description such as "at least one selected from the group consisting of XX, YY, and ZZ" means any of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ. Note that when XX is a group, multiple XXs may be selected, and the same applies to YY and ZZ.

[0013] To evaluate the degree of exudation from molded articles of the polyurethane elastomer disclosed in Patent Document 1, the inventors conducted a solvent extraction test on a polyurethane elastomer having a matrix and multiple domains dispersed within the matrix. Specifically, a molded article of the polyurethane elastomer disclosed in Patent Document 1, measuring 25 mm in length, 10 mm in width, and 2 mm in thickness, was subjected to Soxhlet extraction in accordance with Japanese Industrial Standards (JIS) K6229:2015 using acetone as the extraction solvent at 80°C for 4 hours. The ratio of the mass of the extract to the mass of the molded article (hereinafter also referred to as solvent extraction rate) C was evaluated. It was believed that a small solvent extraction rate C would result in less exudation from the molded article and reduced adhesion to contact objects. As a result, the solvent extraction rate C from the molded article of the polyurethane elastomer disclosed in Patent Document 1 was found to be sufficiently small. However, as described above, when a molded article of the polyurethane elastomer disclosed in Patent Document 1 was maintained in contact with another object for a long period of time, exudation could cause adhesion to the other object.

[0014] Next, the inventors subjected a molded article of the polyurethane elastomer disclosed in Patent Document 1 to a powder crushed to a mode diameter of 1 μm or less to obtain a powder, and evaluated the ratio of the mass of the extractables to the mass of the powder (solvent extraction rate D) in the same manner as described above. As a result, the solvent extraction rate D of the obtained powder was approximately half of the mass of the components constituting the domains of the molded article. This indicates that the exudates observed from the molded article of the polyurethane elastomer disclosed in Patent Document 1 when the molded article is kept in a compressed state for a long period of time are primarily derived from the domains. The domains impart a low hardness function to the polyurethane disclosed in Patent Document 1 (paragraph 0018 of Patent Document 1).

[0015] Therefore, the present inventors have recognized that in order to address the issue of suppressing exudation from the domains of the polyurethane molded article according to Patent Document 1 when the article is compressed over a long period of time, it is essential to reduce the ratio of the solvent extraction rate D to the solvent extraction rate C (hereinafter, also simply referred to as "D / C") while maintaining the high flexibility and small compression set exhibited by the polyurethane elastomer molded article according to Patent Document 1.

[0016] Based on this recognition, the present inventors have conducted extensive research to reduce the D / C ratio without compromising both low hardness and abrasion resistance, and low hardness and low compression set, and have found that a polyurethane elastomer having the following composition contributes to achieving the above object.

[0017] That is, a polyurethane elastomer according to one embodiment of the present disclosure has a matrix and a plurality of domains dispersed in the matrix. A first molded article made of the polyurethane elastomer and having a cubic shape with sides of 100 μm contains 10 to 77,000 domains. The arithmetic mean value Da of the equivalent sphere diameters of the domains is 1.0 to 30.0 μm, the proportion V of the total volume of the domains in the first molded article is 15 to 45 vol%, and the relationship between parameter A indicating the viscoelastic term of the domains and parameter B indicating the viscoelastic term of the matrix, as measured in a viscoelastic image obtained by a scanning probe microscope of a cut section parallel to one surface of the first molded article, is A<B. Furthermore, the second molded body made of the polyurethane elastomer has a micro rubber hardness of 20 to 50 degrees at a temperature of 23°C, and in an indentation test using a nanoindenter at a temperature of 23°C, a Vickers indenter is pressed into the second molded body at a loading rate of 10 mN / 30 seconds, and the load of 10 mN is maintained for 60 seconds. After the load is released, the strain 5 seconds after the load is released is 1.0 μm or less. Furthermore, when a third molded product made of the polyurethane elastomer is subjected to Soxhlet extraction in accordance with Japanese Industrial Standards (JIS) K6229:2015 using acetone as an extraction solvent at an extraction temperature of 80°C for an extraction time of 4 hours, the ratio of the mass of the obtained extract E1 to the mass of the third molded product is C (mass %); and when a powder of the third molded product having a mode diameter of less than 1 μm is subjected to Soxhlet extraction in accordance with Japanese Industrial Standards (JIS) K6229:2015 using acetone as an extraction solvent at an extraction temperature of 80°C for an extraction time of 4 hours, the ratio of the mass of the obtained extract E2 to the mass of the powder is D (mass %), and D / C is 1.0 to 5.0.

[0018] The polyurethane elastomer and the like of the present disclosure will be described in detail below with reference to preferred embodiments and drawings. Note that the embodiments described below are merely examples, and unless otherwise specified, the present disclosure is not limited to these embodiments.

[0019] The polyurethane elastomer satisfies the following requirements (1-1) to (1-4). Requirement (1-1): The polyurethane elastomer has a matrix and a plurality of domains dispersed in the matrix. Requirement (1-2): When a viscoelasticity image of a cross section parallel to one face of a cubic first molded article made of polyurethane elastomer and having sides of 100 μm is measured by a scanning probe microscope, the relationship between parameter A indicating the viscoelasticity term of the domain and parameter B indicating the viscoelasticity term of the matrix is ​​A<B. That is, a matrix domain structure of the polyurethane elastomer is observed in the cross section parallel to one face of the molded article. The elastic modulus of the polyurethane elastomer matrix observed in the cross section is greater than the elastic modulus of the domains.

[0020] Requirement (1-3): The second molded body made of polyurethane elastomer has a micro rubber hardness of 20 to 50 degrees at a temperature of 23° C. Requirement (1-4): In an indentation test of the second molded body using a nanoindenter at 23° C., a Vickers indenter is pressed into the second molded body at a loading rate of 10 mN / 30 seconds, and the load of 10 mN is maintained for 60 seconds. After the load is released, the strain 5 seconds after the load is released is 1.0 μm or less.

[0021] In polyurethane elastomers, the matrix is ​​responsible for the function of recovering from deformation. Furthermore, the domains are responsible for reducing the hardness of the polyurethane elastomer. Such polyurethane elastomers exhibit both softness and fast recovery from deformation. Meanwhile, common polyurethane elastomers also have a difference in modulus of elasticity between the so-called hard and soft segments. However, in common urethane elastomers, the soft segments constitute the matrix, and the hard segments constitute the domains. It is believed that no polyurethane elastomers existed that exhibited the fast recovery rate from deformation required by requirement (1-4) while retaining the flexibility required by requirement (1-3) above.

[0022] Fig. 1A is a cross-sectional view of a polyurethane molded article 3 according to one embodiment of the present disclosure. Fig. 1A schematically shows a matrix 31 of a polyurethane elastomer and a plurality of domains 32 dispersed within the matrix 31, as observed on a cross section parallel to one surface of the molded article. As described above, the polyurethane elastomer has the matrix 31 and the domains 32 dispersed within the matrix. That is, the urethane elastomer has a matrix-domain structure. The matrix exhibits higher elasticity than the domains.

[0023] 1A and 1B are explanatory diagrams of the deformation recovery of a polyurethane molded body 3 according to one embodiment of the present disclosure. As shown in FIG. 1A, a plurality of domains 32 are dispersed in a matrix 31. Because the domains 32 have lower elasticity than the matrix 31, when the polyurethane molded body 3 is compressed in the direction of arrow F as shown in FIG. 1B, the domains 32 deform preferentially. Therefore, even if the matrix 31 has high elasticity, the micro rubber hardness of the polyurethane molded body can be reduced. Furthermore, when the polyurethane molded body is released from compression, the elasticity of the matrix 31, which is the continuous phase, allows the thickness of the molded body to quickly return to the thickness before compression.

[0024] (Number of Domains N) In a first molded body made of the polyurethane elastomer and having a cubic shape with sides measuring 100 μm, the number of domains N contained in the first molded body is 10 to 77,000. The number of domains N can be 100 to 77,000, or even 700 to 77,000. By setting the number of domains N within the above range, a polyurethane elastomer that is flexible yet exhibits small compressive deformation strain can be obtained. The number of domains N can be adjusted by adjusting the mixing conditions (shear force and time) during preparation of the urethane prepolymer and the molecular weight and amount of polyol and polyisocyanate added. The number of domains N can be determined by three-dimensional measurement of the first molded body using an FIB-SEM. The first molded body may be a heat-cured polyurethane elastomer that has been directly used, or the heat-cured polyurethane elastomer may be processed into a predetermined shape using a microtome to form the first molded body.

[0025] FIB-SEM is a technique in which a sample is processed using a focused ion beam (FIB) device and the exposed cross section of the sample is observed using a scanning electron microscope (SEM). To examine the three-dimensional structure, a large number of photographs are obtained by repeatedly performing continuous processing and observation, and then the SEM images are subjected to 3D reconstruction processing using computer software. Then, by constructing the sample structure as a three-dimensional stereoscopic image, it becomes possible to examine the three-dimensional structure. A specific method for measuring the number of domains N is to use a FIB-SEM (manufactured by FEI, Inc.) to obtain three-dimensional stereoscopic images of the first compact at 60 nm intervals. Then, the number of domains N is calculated for the obtained images using 3D visualization and analysis software Avizo (registered trademark, manufactured by FEI, Inc.). A more specific measurement method will be described later.

[0026] (Arithmetic mean value Da of equivalent sphere diameters of domains) In a first molded body made of the polyurethane elastomer and having a cubic shape with sides of 100 μm, the arithmetic mean value Da of equivalent sphere diameters of the domains is 1.0 to 30.0 μm. The arithmetic mean value Da may be 2.0 to 20.0 μm, or 2.0 to 15.0 μm. By having the arithmetic mean value Da within the above range, a polyurethane elastomer is obtained that is flexible yet exhibits small compressive deformation strain. The arithmetic mean value Da can be adjusted by adjusting the mixing conditions (shear force and time) during preparation of the urethane prepolymer and the molecular weight and amount of polyol and polyisocyanate added. The arithmetic mean value Da can be determined by three-dimensional measurement of the first molded body using the above-mentioned FIB-SEM. Specific measurement methods will be described later.

[0027] (Proportion V of the Total Volume of the Domains in the First Molded Article) In a first molded article made of the polyurethane elastomer and having a cubic shape with sides of 100 μm, the proportion V of the total volume of the domains in the first molded article is 15 to 45 volume %. Furthermore, the proportion V of the total volume of the domains in the first molded article may be 20 to 45 volume %, or 25 to 42 volume %, and preferably 25 to 41 volume %. By setting the proportion V of the total volume of the domains in the first molded article within the above range, a polyurethane elastomer that is flexible yet exhibits small compressive deformation strain can be obtained. Furthermore, the proportion V of the total volume of the domains in the first molded article can be adjusted by adjusting the mixing conditions (shear force and time) during preparation of the urethane prepolymer and the molecular weight and amount of polyol / polyisocyanate added. The proportion of the total volume of the domains in the first molded article can be determined by three-dimensional measurement of the first molded article using the above-mentioned FIB-SEM. Specific measurement methods will be described later.

[0028] (Parameter Indicating Viscoelasticity) In a first molded body made of polyurethane elastomer and having a cubic shape with sides of 100 μm, the relationship between parameter A indicating the viscoelasticity of the domain and parameter B indicating the viscoelasticity of the matrix, as measured in a viscoelastic image obtained by a scanning probe microscope of a cross section parallel to one face of the first molded body, is A<B. That is, the elastic modulus of the polyurethane elastomer matrix observed in the cross section is greater than the elastic modulus of the domain. This makes it easier to achieve both hardness and recovery from deformation. The difference in the relative elastic moduli of the matrix 31 and the domain 32 can be determined by slicing the first molded body and measuring it with a scanning probe microscope (SPM / AFM). An example of a scanning probe microscope that can be used is the "S-Image" (product name) manufactured by Hitachi High-Tech Science Corporation. Examples of means for slicing include a sharp razor, a microtome, and a focused ion beam (FIB) method. In the present disclosure, a microtome is used. The slice is prepared from an arbitrary cut surface parallel to one face of the cubic first molded body having a side length of 100 μm, and the observation region for the viscoelastic image on the cut surface is an arbitrary 50 μm square region.

[0029] The measurement mode for the viscoelastic image by SPM is the microviscoelastic dynamic force mode (VE-DFM). The cantilever used is a silicon microcantilever for DMF ("SI-DF3" (product name), manufactured by Hitachi High-Tech Science Corporation, spring constant = 1.9 N / m). The scanning frequency is 0.5 Hz. VE-DFM is one of the measurement modes of SPM (scanning probe microscope). VE-DFM allows for the acquisition of a surface topography image by controlling the distance between the probe and the sample to maintain constant cantilever vibration and amplitude while the cantilever is resonating.

[0030] After acquiring the viscoelastic image, the parameters indicating the viscoelastic term in each observation region are determined for 10 points each for the matrix and domain, and their arithmetic mean values ​​are taken as parameter A indicating the viscoelastic term of the domain and parameter B indicating the viscoelastic term of the matrix. Note that the units of parameters A and B are mV, and the larger the value, the higher the elasticity.

[0031] The ratio of parameter A to parameter B (A / B) is preferably 0.65 or less, may be 0.50 or less, or may be 0.40 or less. The smaller A / B, the greater the difference in viscoelasticity between the matrix and the domain, making it easier to achieve both hardness and recovery from deformation. The lower limit of A / B is not particularly limited, but a smaller value is preferable. Specifically, for example, it is 0.10. For example, A / B is preferably 0.10 to 0.65, 0.10 to 0.50, or 0.10 to 0.40. Parameters A and B can be adjusted, for example, by changing the elastic modulus of the domain and matrix. The elastic modulus of the matrix can be adjusted by the molecular weight, bonding species, and addition amount of the polyol or polyisocyanate. The elastic modulus of the domain can be adjusted by the molecular weight, bonding species, and addition amount of the polyol or polyisocyanate, or by adding a chain extender such as a polyhydric alcohol. The value of parameter A is not particularly limited, but may be, for example, 50 to 120 mV, or 60 to 110 mV. The value of parameter B is not particularly limited, but may be, for example, 190 to 310 mV, or 210 to 290 mV.

[0032] (Micro-rubber Hardness of Molded Article) The micro-rubber hardness of the second molded article made of polyurethane elastomer at a temperature of 23°C is 20 to 50 degrees. Here, the second molded article is a cubic molded article with a side length of 2 mm. If the thickness of the sample is less than 2 mm, the second molded article is stacked in the thickness direction to form a cubic second molded article with a side length of 2 mm. A micro-rubber hardness of 50 degrees or less results in good flexibility and low hardness. A micro-rubber hardness of 20 degrees or more results in high mechanical strength and good abrasion resistance. The micro-rubber hardness is preferably 25 to 50 degrees, more preferably 30 to 50 degrees. The micro-rubber hardness can be adjusted by the elastic modulus of the matrix, the ratio of matrix to domain, etc. Specifically, for example, increasing the elastic modulus of the matrix acts to increase the micro-rubber hardness. The micro-rubber hardness is determined as follows. The measurement point is approximately the center of any one face of a cubic second molded body with sides of 2 mm. The micro-rubber hardness is measured at a temperature of 23°C using a micro-rubber hardness meter (product name: MD-1capa; manufactured by Kobunshi Keiki Co., Ltd.; push needle: Type A (cylindrical; diameter 0.16 mm; height 0.5 mm; outer diameter 4 mm; inner diameter 1.5 mm); measurement mode: peak hold mode). When the sample thickness is less than 2 mm, the measurement point is approximately the center of one face of the second molded body that can be used to measure the micro-rubber hardness from the thickness direction of the sample. In addition, the second molded body may be a heat-cured polyurethane elastomer as is, or the heat-cured polyurethane elastomer may be processed into a predetermined shape using scissors to form the second molded body.

[0033] (Recovery from Deformation) In an indentation test using a nanoindenter at a temperature of 23°C on a second molded article made of a polyurethane elastomer, a Vickers indenter is pressed into the second molded article at a loading rate of 10 mN / 30 seconds, and the load of 10 mN is maintained for 60 seconds. After the load is released, the strain after 5 seconds of unloading is 1.0 μm or less. The strain after 5 seconds of unloading is preferably 0.8 μm or less, more preferably 0.7 μm or less, and even more preferably 0.6 μm or less. The lower limit of the strain after 5 seconds of unloading is not particularly limited, but is typically 0.0 μm or 0.1 μm. For example, preferred values ​​include 0.0 to 1.0 μm, 0.0 to 0.8 μm, 0.0 to 0.7 μm, and 0.1 to 0.6 μm. By setting the strain after 5 seconds of unloading within the above range, a polyurethane elastomer exhibits a fast recovery rate from deformation. The strain after 5 seconds of unloading can be adjusted by the type of resin in the matrix, the number of domains, and the size of the domains.

[0034] The strain value 5 seconds after unloading is determined as follows. The measurement point is approximately the center of any one face of a cubic second molded body with sides of 2 mm. An indentation test is performed at a temperature of 23°C using a nanoindenter (product name: Fischerscope HM2000, manufactured by Fischer Instruments, a square pyramidal Vickers indenter with an opposing angle of 136°). The Vickers indenter is pressed into the second molded body at a loading rate of 10 mN / 30 seconds, and the 10 mN load is maintained for 60 seconds. The load is then released at a loading rate of 10 mN / 30 seconds, and the strain value 5 seconds after unloading is measured. The second molded body may be a heat-cured polyurethane elastomer as is, or the heat-cured polyurethane elastomer may be processed into a predetermined shape using scissors to obtain the second molded body.

[0035] (Solvent Extraction Rate C and Powder Solvent Extraction Rate D) When a third molded body made of the polyurethane elastomer is subjected to Soxhlet extraction in accordance with JIS K6229:2015 using acetone as the extraction solvent at an extraction temperature of 80°C for 4 hours, the ratio of the mass of the resulting extract E1 to the mass of the third molded body is defined as C (mass%). When a powder having a mode diameter of less than 1 μm from the third molded body is subjected to Soxhlet extraction in accordance with JIS K6229:2015 using acetone as the extraction solvent at an extraction temperature of 80°C for 4 hours, the ratio of the mass of the resulting extract E2 to the mass of the powder is defined as D (mass%). The D / C ratio is 1.0 to 5.0. The third molded body is a molded body having a length of 25 mm, a width of 10 mm, and a thickness of 2 mm. The D / C ratio is preferably 1.5 to 4.5, and more preferably 1.5 to 3.0. As described above, by ensuring that the D / C ratio is within the above range, it is possible to obtain a polyurethane elastomer that is flexible yet exhibits small compressive deformation strain and that provides a molded article that does not cause exudates to adhere to other members even when pressed against them. The D / C ratio can be adjusted by adjusting the value of C or the value of D as described below.

[0036] (Solvent Extraction Ratio C) The solvent extraction ratio C of a polyurethane elastomer is determined by Soxhlet extraction. First, the polyurethane elastomer is molded into a molded body using a mold for producing a 2 mm thick sheet. Then, the molded body is cut with scissors into a length of 25 mm, a width of 10 mm, and a thickness of 2 mm to obtain a third molded body. If the sample thickness is less than 2 mm, a number of samples are prepared so that when stacked, they form a thickness of 2 mm. Then, in accordance with Japanese Industrial Standards (JIS) K6229:2015, the third molded body is subjected to Soxhlet extraction using acetone as the extraction solvent, at an extraction temperature of 80°C, and for an extraction time of 4 hours. The ratio of the mass of the obtained extract E1 to the mass of the third molded body is calculated as the solvent extraction ratio C (mass%).

[0037] The value of the solvent extraction rate C is not particularly limited, but is preferably 2.2 to 4.5 mass%, more preferably 2.3 to 3.5 mass%, and even more preferably 2.3 to 3.0 mass%. By keeping it within the above range, it becomes easier to keep the D / C value within the above range. The value of the solvent extraction rate C can be adjusted by the type and amount of catalyst added and the type of matrix resin.

[0038] (Solvent Extraction Ratio D of Powder) The solvent extraction ratio D of the powder is determined by Soxhlet extraction. First, a polyurethane elastomer is molded using a mold for producing a 2 mm thick sheet. Then, the molded body is cut with scissors into a length of 25 mm, a width of 10 mm, and a thickness of 2 mm to obtain a third molded body. The third molded body is sandwiched between filter paper and pulverized to obtain a powder, and the solvent extraction ratio D of the powder is determined in the same manner as the solvent extraction ratio C described above. Examples of pulverization methods include freeze pulverization and press pulverization. However, pulverization using a filter paper press is preferred because it is easier to extract viscous materials. Specifically, the third molded body is sandwiched between two sheets of Kiriyama funnel filter paper 5B, which is then sandwiched between two degreased aluminum sheets and pressed for 1 minute at 10 MPa using a 50-ton press (product name: PEF 5041, manufactured by Kansai Roll Co., Ltd.) preheated to 130°C. After unloading, the aluminum sheet is removed, and the two sheets of Kiriyama funnel filter paper sandwiching the crushed third compact are folded and placed in a Soxhlet cylindrical filter paper, and the solvent extraction rate D of the powder is determined in the same manner as the solvent extraction rate C above.

[0039] To determine the mode diameter of a powder, a laser diffraction / scattering particle size distribution analyzer is used because it is compatible with dry methods and allows for simple measurements. Specifically, a laser diffraction / scattering particle size distribution analyzer (product name: Partica LA-960V2, manufactured by Horiba, Ltd.) equipped with a dry measurement unit is used to measure the particle size distribution and determine the particle diameter (mode diameter) showing the maximum peak. The mode diameter indicates the size of the pulverized product.

[0040] The value of the solvent extraction rate D of the powder is not particularly limited, but is preferably 3.0 to 20.0 mass%, more preferably 4.0 to 17.0 mass%, even more preferably 4.3 to 11.0 mass%, and particularly preferably 4.3 to 7.0 mass%. By keeping it within the above range, it becomes easier to keep the D / C value within the above range. The value of the solvent extraction rate D of the powder can be adjusted by the type and amount of chain extender such as polyhydric alcohol and catalyst.

[0041] The number-average molecular weight of Extract E2 obtained by Soxhlet extraction of a powder obtained in the same manner as the solvent extraction rate D of the powder is preferably 2,000 to 100,000, more preferably 2,500 to 100,000, and even more preferably 5,000 to 100,000. By falling within the above range, a polyurethane elastomer is obtained that is flexible yet exhibits small compressive deformation strain. The number-average molecular weight of Extract E2 can also be adjusted by changing the material that constitutes the domain. The method for measuring the number-average molecular weight of Extract E2 is described below. The number-average molecular weight of Extract E2 may be, for example, 2,000 to 50,000, or 25,000 to 30,000.

[0042] The viscosity of extract E2 obtained by Soxhlet extraction of a powder obtained in the same manner as the powder solvent extraction rate D is preferably 10,000 mPa·s or less. While there is no particular lower limit, for example, a viscosity of 1,000 to 10,000 mPa·s is preferred, 1,200 to 10,000 mPa·s is more preferred, and 2,000 to 10,000 mPa·s is even more preferred. By keeping the viscosity within the above range, a polyurethane elastomer that is flexible yet exhibits small compressive deformation strain can be obtained. The viscosity of extract E2 can also be adjusted by changing the material that constitutes the domain. The method for measuring the viscosity of extract E2 is described below.

[0043] (Wear Resistance) When a ball-on-disk wear test is performed in accordance with JIS R1613:2010 on the surface of a sheet-shaped wear test piece made of polyurethane elastomer, measuring 30 mm in length, 30 mm in width, and 2 mm in thickness, under the following conditions (1) to (6), the mass loss rate of the wear test piece is preferably 10.0% by mass or less, more preferably 5.0% by mass or less, even more preferably 2.0% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably 0.5% by mass or less. By being in the above range, wear resistance is good.

[0044] (1) Ball Material: Stainless steel Diameter: 10 mm (2) Load: 100 g (3) Environment: Temperature 23°C, 50% RH (4) Time: 60 minutes (5) Sliding circle diameter: 10 mm (6) Rotation speed of the disk on which the test piece was placed: 300 rpm.

[0045] The wear test is performed as follows. First, the mass of the wear test piece is measured. Next, the wear test piece is fixed with double-sided tape to approximately the center of the sliding disk of a ball-on-disk friction and wear tester (product name: HEIDON Type: 20, manufactured by Shinto Chemical Co., Ltd.) so that the center of the wear test piece is located. At this time, the surface in the thickness direction of the wear test piece is placed in contact with the sliding disk. Next, an indenter consisting of the above-mentioned ball is pressed against the center of the wear test piece with a load of 100 g, and the wear test piece is rotated and slid for 60 minutes with a sliding circle diameter of 10 mm and a rotation speed of 300 rpm. After 60 minutes, the test is stopped, the wear powder and double-sided tape are removed, and the mass of the test piece is measured. The mass loss rate (mass %) is calculated from the mass of the test piece before and after the wear test. Here, the surface in the thickness direction of the wear test piece refers to a 30 mm square surface of the wear test piece, measuring 30 mm length x 30 mm width. The mass loss rate of the abrasion test specimen can be adjusted by the type of resin in the matrix, the number of domains, and the size of the domains.

[0046] (Polyurethane Elastomer Material) The polyurethane elastomer material will now be described. As described above, the polyurethane elastomer has a matrix 31 and a plurality of domains 32 dispersed in the matrix. That is, the urethane elastomer has a matrix-domain structure. It is preferable that the matrix 31 has a structure that can increase the deformation recovery rate, and the domains 32 have a structure that contributes to suppressing an increase in micro rubber hardness.

[0047] The matrix 31 of such polyurethane elastomer preferably has a first structure (polycarbonate structure) represented by formula (1). The matrix has at least one polycarbonate structure represented by formula (1), and preferably has a plurality of polycarbonate structures. When the matrix has a plurality of polycarbonate structures represented by formula (1), the polycarbonate structure may be a repeating structural unit. In addition, R in the first structure represented by formula (1) １ The alkylene group having 3 to 9 carbon atoms represented by the formula (I) may have a linear structure or a branched structure, but preferably has a branched structure. (In formula (1), R １ represents an alkylene group having 3 to 9 carbon atoms (preferably 6 to 9).

[0048] Polyurethane obtained by reacting a polyol having a polycarbonate structure (polycarbonate polyol) with a polyisocyanate exhibits high elasticity due to the strong intermolecular force between carbonate groups. Therefore, it is preferable as a constituent component of the matrix 31. １ By R being an alkylene group having 3 to 9 carbon atoms, incompatibility with the domain containing the second structure (polyether structure) represented by the following formula (2) described later is ensured, and clear phase separation between the matrix and the domain can be achieved. This makes it possible to more reliably exhibit the two functions of softness and fast recovery from deformation of the polyurethane elastomer. １When is an alkylene group having a branched structure and 3 to 9 carbon atoms, the intermolecular force between the carbonate groups is appropriately suppressed, and the matrix can be prevented from becoming excessively elastic.

[0049] R １ Examples of the group include -(CH ２ ) ｍ -(m=3 to 9, preferably 6 to 9), -CH ２ C(CH ３ ) ２ CH ２ -, -CH ２ CH (CH ３ ) CH ２ -, -(CH ２ ) ２ CH (CH ３ ) (CH ２ ) ２ These may be used alone or in combination of two or more.

[0050] The number average molecular weight of the polycarbonate and the polyols described below can be calculated using the hydroxyl value (mgKOH / g) and valence according to the following formula: For example, the number average molecular weight of a polyether polyol with a hydroxyl value of 56.1 mgKOH / g and a valence of 2 can be calculated to be 2000. Number average molecular weight = 56.1 x 1000 x valence / hydroxyl value

[0051] The elastic modulus of the matrix can be adjusted by, for example, increasing the crosslink density using a trimer compound or polymer compound of polyisocyanate. Normally, increasing the elastic modulus also increases the micro rubber hardness of the polyurethane elastomer, but in the present disclosure, multiple low-elasticity domains are dispersed in the matrix, so excessive hardness can be suppressed.

[0052] The domain 32 preferably includes a second structure (polyether structure) represented by formula (2). The domain has at least one polyether structure represented by formula (2), and preferably has a plurality of polyether structures represented by formula (2). When the domain has a plurality of polyether structures represented by formula (2), the polyether structure may be a repeating structural unit. In addition, R in the structural unit represented by formula (2) ２The alkylene group having 3 to 6 carbon atoms represented by the formula (I) may have a linear structure or a branched structure, but preferably has a branched structure. (In formula (2), R ２ represents an alkylene group having 3 to 6 carbon atoms (preferably 3 to 4 carbon atoms).

[0053] Polyether exhibits a low modulus of elasticity due to the weak intermolecular force between ether groups. Therefore, it is preferable as a domain component. ２ is an alkylene group having 3 to 6 carbon atoms, which is preferable because it ensures incompatibility with the matrix having the polycarbonate structure represented by formula (1) and allows clear phase separation between the matrix and the domain.

[0054] R ２ Examples of the group include -(CH ２ ) ｍ -(m=3~6), -CH ２ CH (CH ３ ) -, -CH ２ C(CH ３ ) ２ CH ２ -, -CH ２ CH (CH ３ ) CH ２ -, -(CH ２ ) ２ CH (CH ３ ) CH ２ These may be used alone or in combination of two or more.

[0055] The number-average molecular weight of the polyether structure represented by formula (2) is preferably 1,000 to 50,000, more preferably 1,200 to 30,000. A number-average molecular weight of 1,000 or more is preferred because the incompatibility between the domains and the matrix containing the polycarbonate structure represented by formula (1) is improved, resulting in clear phase separation between the matrix and the domains. A number-average molecular weight of 50,000 or less is preferred because domains are more easily formed and the phase separation morphology is stabilized.

[0056] The domain preferably has a third structure, and the third structure is formed by addition polymerization of at least one selected from the group consisting of ethylene oxide and propylene oxide to glycerin. That is, the third structure is preferably an addition polymer of glycerin and at least one selected from the group consisting of ethylene oxide and propylene oxide. When the domain has the third structure, the three-branched structure derived from glycerin forms a three-dimensional crosslinked structure, and even if the terminals are unreacted, they become entangled with the part crosslinked to the matrix due to the three-dimensional spread, thereby suppressing the exudation of components derived from the domain.

[0057] The chemical structures of the matrix and domains can be analyzed using, for example, a spectroscopic analyzer such as an AFM infrared spectroscopic analyzer, a microscopic infrared spectroscopic analyzer, or a microscopic Raman spectroscopic analyzer, or a mass spectrometer.

[0058] (Method for Producing Polyurethane Elastomer) One example of a method for producing the above-mentioned polyurethane elastomer includes a method comprising the following steps (i) to (iii): Step (i): Reacting a first polyether having at least two isocyanate groups with a first polycarbonate polyol having at least two hydroxyl groups to obtain a urethane reactive emulsifier having at least two hydroxyl groups. Step (ii): Obtaining a dispersion in which droplets containing at least a portion of the urethane reactive emulsifier are dispersed in a second polycarbonate polyol. Step (iii): Preparing a polyurethane elastomer-forming mixture containing the dispersion obtained in step (ii) and a polyisocyanate having at least two isocyanate groups, and then reacting the urethane reactive emulsifier, the second polycarbonate polyol, and the polyisocyanate in the polyurethane elastomer-forming mixture.

[0059] Each step of the above manufacturing method will be explained using Figure 2. In step (i), a first polyether 51 having at least two isocyanate groups is mixed with a first polycarbonate polyol 52 having at least two hydroxyl groups. The isocyanate groups and hydroxyl groups in the mixture are reacted in the presence of a catalyst to link them via a urethane bond, thereby obtaining a urethane reactive emulsifier 53 having at least two hydroxyl groups. The urethane reactive emulsifier is a reactive emulsifier having a urethane bond.

[0060] In step (ii), the urethane reactive emulsifier 53 obtained in step (i) is dispersed in a second polycarbonate polyol 55. The segments derived from the first polyether 51 contained in the urethane reactive emulsifier 53 are not compatible with the second polycarbonate polyol 55 and form droplets 54. Meanwhile, in the second polycarbonate polyol 55, the droplets 54 containing the segments derived from the first polyether that constitute a part of the urethane reactive emulsifier are uniformly and stably dispersed via the segments derived from the first polycarbonate polyol 52 contained in the urethane reactive emulsifier 53. As a result, a dispersion is obtained in which the droplets 54 containing the segments derived from the first polyether 51 of the urethane reactive emulsifier 53 are dispersed in the second polycarbonate polyol 55. Note that for the sake of explanation, steps (i) and (ii) are described separately, but these steps may also be a continuous series of steps.

[0061] In step (ii), the second polycarbonate polyol 55 in which the droplets 54 are dispersed can be the unreacted product of the first polycarbonate polyol used in step (i) with the first polyether. That is, by using an excess amount of the first polycarbonate polyol relative to the first polyether in step (i), it is possible to obtain the dispersion described in step (ii) in which the urethane reactive emulsifier 53 is dispersed in the excess first polycarbonate polyol, i.e., the second polycarbonate polyol 55. Even when an excess amount of the first polycarbonate polyol is used, it is also possible to add additional polycarbonate polyol (second polycarbonate polyol) as a dispersion medium for the urethane reactive emulsifier. In this case, the added polycarbonate polyol may have the same chemical composition as the first polycarbonate polyol used in step (i), or may have a different chemical composition.

[0062] On the other hand, in step (i), when the first polycarbonate polyol and the first polyether are reacted in equivalent amounts and the first polycarbonate polyol is completely consumed, a dispersion is prepared in step (ii) using a new polycarbonate polyol as the second polycarbonate polyol. In this case, the polycarbonate polyol used as the second polycarbonate polyol may have the same chemical composition as the first polycarbonate polyol or may have a different chemical composition.

[0063] Finally, in step (iii), a polyurethane elastomer-forming mixture is prepared containing the dispersion prepared in step (ii) and a polyisocyanate 56 having at least two isocyanate groups. Next, the terminal hydroxyl groups of the urethane-reactive emulsifier 53, the hydroxyl groups of the second polycarbonate polyol 55, and the isocyanate groups of the polyisocyanate 56 in the polyurethane elastomer-forming mixture are reacted. A network structure is formed via urethane bonds, and the polyurethane elastomer-forming mixture is cured to obtain a polyurethane elastomer. The polyurethane elastomer 500 thus obtained has a matrix domain structure in which domains 32 containing polyether derived from the first polyether 51 are dispersed in a matrix 31 containing a urethane elastomer having a polycarbonate derived from the first polycarbonate polyol 52 and the second polycarbonate polyol 55. Furthermore, the domains 32 are mainly composed of a polyether structure, and a component that does not substantially have a crosslinked structure, i.e., a liquid component, may exist inside the domains, which allows the domains to have a low modulus of elasticity in the polyurethane elastomer.

[0064] Furthermore, the domains are not simply liquid components trapped in the matrix, but are thought to be chemically bonded to the matrix via urethane bonds at their boundaries. Therefore, when a load applied to a polyurethane elastomer is removed, the recovery of the domains from deformation can be linked to the recovery of the matrix from deformation. As described above, the substantially liquid domains have substantially no internal crosslinking structure. Therefore, it is difficult for domains deformed by the application of a load to a polyurethane elastomer to autonomously recover from the deformation. However, in polyurethane elastomers, the domains are thought to be chemically bonded to the matrix at their boundaries. This allows the domains to recover from deformation together with the recovery of the matrix. This allows stable deformation (deformation amount) and stable recovery from the deformation to be achieved even when the polyurethane elastomer is repeatedly subjected to loading and unloading.

[0065] The above steps (i) and (ii) are steps for stably dispersing a polyether, which is inherently difficult to disperse stably and uniformly due to its low compatibility, in a polyol. That is, the first polyether 51 is reacted with the first polycarbonate polyol 52 to form a urethane-reactive emulsifier 53. This step produces a dispersion in which polyether segments derived from the first polyether 51 are stably and uniformly dispersed in the second polycarbonate polyol. This facilitates the production of a polyurethane elastomer in which domains 32 with high circularity and small sizes on the order of micrometers and a relatively uniform size distribution are dispersed in the matrix 31.

[0066] Another method for mixing materials with low compatibility is, for example, mixing and dispersing them under high shear force. However, this method applies high shear force to the polyether, resulting in distorted domain shapes, reduced circularity, and uneven domain size. Furthermore, the dispersion state is unstable, and aggregation of domains progresses over a relatively long period of time. Furthermore, the incompatibility between the polyether and polycarbonate polyol is not ensured, and the phase separation between the matrix and domains of the resulting polyurethane elastomer becomes unclear. Therefore, it is difficult to obtain a polyurethane elastomer that provides an elastic body with flexibility and excellent deformation recovery, as disclosed herein.

[0067] The first polyether has at least two isocyanate groups. The first polyether is preferably a polyether having a second structure represented by formula (2). The first polyether can be obtained, for example, by reacting a polyether polyol having at least two hydroxyl groups and a second structure represented by formula (2) (corresponding to the "first polyol" in the examples) with a polyisocyanate having at least two isocyanate groups. Examples of polyether polyols include alkylene structure-containing polyether polyols such as polypropylene glycol, polytetramethylene glycol, a copolymer of tetrahydrofuran and neopentyl glycol, and a copolymer of tetrahydrofuran and 3-methyltetrahydrofuran, as well as random or block copolymers of these polyalkylene glycols. These may be used alone or in combination of two or more. Here, the combined use of a bifunctional polyether polyol and a trifunctional polyether polyol as the polyether polyol having at least two hydroxyl groups and the second structure represented by formula (2) is preferable because it suppresses the exudation of substances derived from the domains onto the surface of the polyurethane elastomer molded article and makes it easier to adjust the D / C ratio within the range of 1.0 to 5.0. The reason for this is explained using Figure 3.

[0068] When a polyether polyol having two hydroxyl groups, a polyether polyol having three hydroxyl groups, and a polyisocyanate having at least two isocyanate groups are used in combination as the polyether polyol, the reaction with the polyisocyanate having at least two isocyanate groups results in a first polyether 51 having two isocyanate groups at its terminal, as well as a first polyether 57 having three isocyanate groups at its terminal. In step (i), these first polyethers are reacted with a first polycarbonate polyol 52 having at least two hydroxyl groups to produce a urethane reactive emulsifier 53 having at least two hydroxyl groups. The urethane reactive emulsifier 53 thus obtained has a three-dimensional network structure. Furthermore, in the polyurethane elastomer obtained through the subsequent steps (ii) and (iii) using such a urethane reactive emulsifier, the amount of polyol not bound to the matrix in the domains can be reduced. For these reasons, by using a bifunctional polyether polyol and a trifunctional polyether polyol in combination as the polyether polyol, the D value can be reduced, and therefore the D / C ratio can be more easily adjusted within the range of 1.0 to 5.0. As the trifunctional polyether polyol, triol-type polypropylene glycol, triol-type polyethylene glycol, and a copolymer of polyethylene oxide and polypropylene oxide, which is a triol-type copolymer, can be particularly preferably used. Here, for example, triol-type polypropylene glycol refers to a polypropylene glycol having three hydroxy groups in the molecule.

[0069] Among polyether polyols, amorphous polyether polyols are preferred from the viewpoints of incompatibility with the second polycarbonate polyol and the ability to achieve low hardness, and more preferably contain at least one selected from the group consisting of polypropylene glycol, a copolymer of tetrahydrofuran and neopentyl glycol, and a copolymer of tetrahydrofuran and 3-methyltetrahydrofuran.

[0070] The number-average molecular weight of the polyether polyol is preferably 1,000 to 50,000, and more preferably 1,200 to 30,000. A number-average molecular weight of 1,000 or more is preferred because it ensures incompatibility with the polycarbonate polyol and results in clear phase separation between the matrix and domains of the resulting urethane elastomer. Furthermore, a number-average molecular weight of 50,000 or less is preferred because it facilitates domain formation and stabilizes the phase separation morphology.

[0071] Examples of polyisocyanates to be reacted with polyether polyols include pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, trimer compounds (isocyanurates) or polymeric compounds of these polyisocyanates, allophanate polyisocyanates, biuret polyisocyanates, and water-dispersible polyisocyanates. These polyisocyanates can be used alone or in combination of two or more. Among polyisocyanates, bifunctional isocyanates having two isocyanate groups are preferred because of their high compatibility with the first polyether and ease of adjusting physical properties such as viscosity. More preferably, the resin contains at least one selected from hexamethylene diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate. Of these, xylylene diisocyanate is even more preferred.

[0072] In the step of reacting the polyether polyol with the polyisocyanate, the isocyanate index is preferably in the range of 1.2 to 5.0. Having an isocyanate index in this range reduces the amount of components derived from the first polyether that remain without forming a network structure, thereby suppressing the exudation of liquid substances from the polyurethane elastomer. The isocyanate index indicates the ratio ([NCO] / [OH]) of the number of moles of isocyanate groups in the isocyanate compound to the number of moles of hydroxyl groups in the polyol compound. The first polyether obtained by the reaction of the polyether polyol with the polyisocyanate has a structure in which hydroxyl groups are linked via urethane bonds formed by the reaction between the hydroxyl groups and the isocyanate groups. Its number average molecular weight is preferably 1,000 to 50,000, more preferably 1,200 to 30,000.

[0073] The first polycarbonate polyol has at least two hydroxyl groups. It is also preferable that the first polycarbonate polyol has a first structure represented by formula (1). Examples of the first polycarbonate polyol include a reaction product of a polyhydric alcohol and phosgene, and a ring-opening polymerization product of a cyclic carbonate ester (such as an alkylene carbonate).

[0074] Examples of polyhydric alcohols include propylene glycol, dipropylene glycol, trimethylene glycol, 1,4-tetramethylene diol, 1,3-tetramethylene diol, 2-methyl-1,3-trimethylene diol, 1,5-pentamethylene diol, neopentyl glycol, 1,6-hexamethylene diol, 3-methyl-1,5-pentamethylene diol, 2,4-diethyl-1,5-pentamethylene diol, glycerin, trimethylolpropane, trimethylolethane, cyclohexanediols (such as 1,4-cyclohexanediol), and sugar alcohols (such as xylitol and sorbitol).

[0075] Examples of alkylene carbonates include trimethylene carbonate, tetramethylene carbonate, and hexamethylene carbonate.

[0076] The number-average molecular weight of the first polycarbonate polyol is preferably 500 to 10,000, and more preferably 700 to 8,000. When the number-average molecular weight is 500 or more, incompatibility with the domain containing the polyether of the second structural unit represented by formula (2) is ensured, and phase separation between the matrix and the domain can be made clearer. Furthermore, by setting the number-average molecular weight to 10,000 or less, an excessive increase in viscosity of the first polycarbonate polyol can be prevented.

[0077] The second polycarbonate polyol used in step (ii) may be any of the polycarbonate polyols listed above for the first polycarbonate polyol. As described above, the first polycarbonate polyol and the second polycarbonate polyol may have the same chemical composition, or may be different from each other.

[0078] The polyisocyanate 56 having at least two isocyanate groups used in step (iii) can be the same as the polyisocyanates exemplified above as raw materials for the first polyether. These polyisocyanates can be used alone or in combination of two or more. From the viewpoint of increasing the elastic modulus of the matrix, the polyisocyanate 56 preferably includes a polyisocyanate having at least three isocyanate groups, such as a polyisocyanate trimer compound (isocyanurate) or polymer compound, an allophanate-type polyisocyanate, or a biuret-type polyisocyanate, among the polyisocyanates exemplified above. More preferably, the polyisocyanate 56 includes at least one selected from the group consisting of a pentamethylene diisocyanate trimer compound (isocyanurate), a hexamethylene diisocyanate trimer compound (isocyanurate), a diphenylmethane diisocyanate polymer compound, and polymeric MDI.

[0079] Among the above, polymeric MDI is preferred. Here, polymeric MDI is a mixture of monomeric MDI and high molecular weight polyisocyanate, and is represented by the following formula (A). In formula (A), n is preferably 0 or more and 4 or less. As the polymeric MDI, commercially available products may be used, and examples thereof include Millionate MR series (manufactured by Tosoh Corporation) such as Millionate MR200 (trade name).

[0080] It is preferable to use a polyisocyanate having at least three isocyanate groups, such as polymeric MDI, in combination with a bifunctional isocyanate having two isocyanate groups as the polyisocyanate 56 having at least two isocyanate groups. This combination allows the crosslink density of the matrix to be adjusted, which is preferable from the viewpoint of achieving both low hardness and low compression set.

[0081] As the catalyst, a conventionally known urethanization catalyst or an isocyanuration catalyst (isocyanate trimerization catalyst) can be used. These catalysts can be used alone or in combination. Examples of the urethanization catalyst include tin-based urethanization catalysts such as dibutyltin dilaurate and stannous octoate, and amine-based urethanization catalysts such as triethylenediamine, tetramethylguanidine, pentamethyldiethylenetriamine, diethylimidazole, tetramethylpropanediamine, N,N,N'-trimethylaminoethylethanolamine, 1,4-diazabicyclo[2.2.2]octane-2-methanol, and N,N-dimethylaminohexanol. These catalysts can be used alone or in combination. Among these, N,N-dimethylaminohexanol is particularly preferred for obtaining the polyurethane elastomer according to the present disclosure. Specifically, 1,4-diazabicyclo[2.2.2]octane-2-methanol and N,N-dimethylaminohexanol have hydroxyl groups that can react with isocyanates to reduce amine emissions. It is believed that when the hydroxyl groups react with isocyanates, the urethanization catalytic activity of the amine segments decreases. In other words, the higher the reactivity of the hydroxyl groups with isocyanates, the lower the activity as a urethanization catalyst. Furthermore, N,N-dimethylaminohexanol has a lower reactivity of the hydroxyl groups with isocyanates than 1,4-diazabicyclo[2.2.2]octane-2-methanol, and is therefore believed to be less susceptible to a decrease in urethanization catalytic activity when used in a urethanization reaction. Therefore, in step (i), the first polyether 51 having at least two isocyanate groups can be more effectively reacted with the first polycarbonate polyol 52 having at least two hydroxyl groups. As a result, in the polyurethane elastomer obtained as a result of the step (iii), the number of urethane bonds at the boundary between the domain and the matrix can be increased compared to when 1,4-diazabicyclo[2.2.2]octane-2-methanol is used as a catalyst.Therefore, using N,N-dimethylaminohexanol as a catalyst can further suppress the exudation of domain components onto the surface of a molded polyurethane elastomer product, and is extremely effective in keeping the D / C within the range of 1.0 to 5.0.

[0082] In the present disclosure, in order to suppress the amount D of exudates onto the surface of a polyurethane elastomer molded body and adjust D / C to within the range of 1.0 to 5.0, as described above, it is effective to employ at least one selected from the group consisting of: using a polyether polyol having two hydroxyl groups and a polyether polyol having three hydroxyl groups in combination as raw materials for the first polyether; and using N,N-dimethylaminohexanol as a catalyst.

[0083] Examples of the isocyanuration catalyst include Li ２ O, (Bu ３ Sn) ２ Metal oxides such as O and NaBH ４ Hydride compounds such as NaOCH ３ , KO-(t-Bu), alkoxide compounds such as borate, N(C ２ H ５ ) ３ , N(CH ３ ) ２ CH ２ C ２ H ５ , and amine compounds such as 1,4-ethylenepiperazine (DABCO), HCOONa, Na ２ CO ３ , PhCOONa / DMF, CH ３ COOK, (CH ３ COO) ２ Ca, alkaline soaps, and alkaline carboxylate salt compounds such as naphthenates, alkaline formate compounds, and ((R) ３In this case, Bu represents a butyl group, Ph represents a phenyl group, and R, R', and R" represent any alkyl group. In addition, examples of combined catalysts (co-catalysts) used as isocyanuration catalysts include amine / epoxide, amine / carboxylic acid, and amine / alkyleneimide. These isocyanuration catalysts and combined catalysts may be used alone or in combination.

[0084] In the production method of polyurethane elastomers, a chain extender (a polyfunctional low-molecular-weight polyol) may be used as needed. Examples of chain extenders include glycols having a number-average molecular weight of 1,000 or less. Examples of glycols include ethylene glycol (EG), diethylene glycol (DEG), propylene glycol (PG), dipropylene glycol (DPG), 1,4-butanediol (1,4-BD), 1,6-hexanediol (1,6-HD), 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, xylylene glycol (terephthalyl alcohol), and triethylene glycol. Examples of chain extenders other than glycols include trihydric or higher polyhydric alcohols. Examples of trihydric or higher polyhydric alcohols include trimethylolpropane, glycerin, pentaerythritol, and sorbitol. These may be used alone or in combination. If necessary, additives such as a foaming agent, microballoons, pigments, plasticizers, waterproofing agents, antioxidants, conductive agents, ultraviolet absorbers, and light stabilizers may also be used in combination.

[0085] The polyurethane molded article includes a polyurethane elastomer. For example, a heat-cured polyurethane elastomer can be used as a polyurethane molded article. The polyurethane molded article may have a foamed structure obtained by a mechanical froth method, foaming with a chemical foaming agent, or foaming with the addition of microballoons. The polyurethane molded article can also be used in artificial muscles, artificial skin, synthetic leather, robot chucks, shoe soles, insoles, CMP polishing pads, stretchable electronics, flexible electronics, pressure sensors, elastic sensors, soft actuators, power generation elements, speakers, small pumps, and the like.

[0086] The following examples will further illustrate one embodiment of the present disclosure, but the present disclosure is not limited to the following examples.

[0087] <Materials Used> The materials used in the examples and comparative examples are listed below. [Polyol]

[0088] In the table, Kuraray Polyol C-2090 (manufactured by Kuraray Co., Ltd.) is a polycarbonate polyol having a number average molecular weight of 2000, a hydroxyl value of 56.3 mgKOH / g, and a structure corresponding to 1,6-hexanediol and a structure corresponding to 3-methyl-1,5-pentanediol. That is, with regard to the carbon numbers of polycarbonate diols and polycarbonate polyols, for example, 6 (linear) + 6 (branched) means that R １ indicates that it contains a linear structure having 6 carbon atoms and a branched structure having 6 carbon atoms. Kuraray Polyol P-2050 is a polyester polyol having a structure corresponding to adipic acid and a structure corresponding to 3-methyl-1,5-pentanediol. PREMINOL S3011, Actocol EP-950N, and PREMINOL 7012 are all triol-type polypropylene glycols.

[0089] [Polyisocyanate] B-1: Xylylene diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.) B-2: Polymeric MDI (product name: Millionate MR-200, manufactured by Tosoh Corporation) [Curing catalyst] C-1: N,N-dimethylaminohexanol (product name: Kao Raiser No. 25, manufactured by Kao Corporation) C-2: 1,4-diazabicyclo[2.2.2]octane-2-methanol (product name: RZETA, manufactured by Tosoh Corporation)

[0090] <Evaluation> The evaluation methods in the examples and comparative examples are described below. [Evaluation 1: Confirmation of matrix / domain and component analysis] A section was prepared from the polyurethane elastomer using a microtome to obtain a first molded article in the shape of a cube with a side length of 100 μm. Thereafter, mapping measurement was carried out using a three-dimensional microscopic laser Raman spectroscopic analyzer (product name: Nanofinder 30, manufactured by Tokyo Instruments Inc.). The measurement mode was EM (Electron Multiplying), and measurements were made at 60 × 60 points at 500 nm intervals, and the area was measured from 0 to 400 cm. －１ An integral image of the matrix was obtained. From the integral image obtained, it was confirmed that the elastic layer contained a matrix and multiple domains dispersed within the matrix. Furthermore, the matrix and domains were clearly phase-separated. Next, the Raman spectrum of the matrix and domain portions was measured from the integral image. The measurement was performed using a light source of Nd:YVO ４ (wavelength 532 nm), laser intensity 240 μW, objective lens 100x, diffraction grating 300 gr / mm, pinhole diameter 100 μm, exposure time 30 seconds, and accumulation 1. From the obtained Raman spectrum, it was confirmed that the matrix contained a structure derived from polycarbonate urethane and the domain contained a structure derived from polypropylene glycol.

[0091] [Evaluation 2: Number of Domains, Equivalent Sphere Diameter, and Total Volume Ratio] First, a cubic first molded body with a side length of 100 μm was obtained in the same manner as in Evaluation 1. Three-dimensional stereoscopic images of the first molded body were obtained at 60 nm intervals using an FIB-SEM (manufactured by FEI, Inc.). Then, using 3D visualization and analysis software Avizo (registered trademark, manufactured by FEI, Inc.), the number of domains N, the arithmetic mean value Da of the equivalent sphere diameters of the domains, and the ratio V of the total volume of the domains to the first molded body were calculated for the obtained images.

[0092] [Evaluation 3: Measurement of parameters indicating viscoelasticity] First, a cubic first molded body with a side length of 100 μm was obtained in the same manner as in Evaluation 1. A section was prepared from the first molded body using a microtome. Then, a viscoelastic image was measured using a scanning probe microscope (product name: S-Image, manufactured by SII NanoTechnology Inc.). The measurement mode for the viscoelastic image was VE-DFM. The cantilever used was an "SI-DF3" (product name, manufactured by Hitachi High-Tech Science Corporation, spring constant = 1.9 N / m). The scanning frequency was 0.5 Hz. From the obtained viscoelasticity image, parameters indicating the viscoelasticity term were calculated for 10 points each for the matrix and domain in each observation region, and parameter A (mV) indicating the viscoelasticity term of the domain and parameter B (mV) indicating the viscoelasticity term of the matrix were calculated from the arithmetic mean values.

[0093] [Evaluation 4: Measurement of Micro Rubber Hardness] First, a sheet-like polyurethane elastomer molded article having a thickness of 2 mm was cut with scissors to obtain a second molded article having a cubic shape with a side length of 2 mm. The micro rubber hardness of the second molded article was measured using a micro rubber hardness tester (product name: MD-1capa, manufactured by Kobunshi Keiki Co., Ltd.). For the measurement, the second molded article was left in an environment at a temperature of 23°C for 24 hours or more, and the measurement was performed using a measuring device placed in the same environment. In addition, a type A indenter (height 0.50 mm, diameter 0.16 mm, cylindrical, outer diameter 4 mm, inner diameter 1.5 mm) was used, and the measurement mode was peak hold mode.

[0094] [Evaluation 5: Measurement of recovery from deformation] First, a sheet-like polyurethane elastomer molded body with a thickness of 2 mm was cut with scissors to obtain a cubic second molded body with a side length of 2 mm. The measurement point was approximately the center of any one face of the second molded body, and an indentation test was performed at a temperature of 23°C using a nanoindenter (product name: Fischerscope HM2000, manufactured by Fischer Instruments, a square pyramidal Vickers indenter with an opposing angle of 136°). The Vickers indenter was pressed into the second molded body at a loading rate of 10 mN / 30 seconds, and the 10 mN load was maintained for 60 seconds. The load was then released at 10 mN / 30 seconds, and the strain value 5 seconds after release was measured to measure recovery from deformation.

[0095] [Evaluation 6: Measurement of Solvent Extraction Rate C] First, a 2 mm thick sheet-like polyurethane elastomer molded body was prepared using a mold for preparing a 2 mm thick sheet. The sheet was cut with scissors into a length of 25 mm, a width of 10 mm, and a thickness of 2 mm to obtain a third molded body. In accordance with Japanese Industrial Standards (JIS) K6229:2015, the third molded body was subjected to Soxhlet extraction using acetone as the extraction solvent, at an extraction temperature of 80°C, and for a extraction time of 4 hours. The ratio of the mass of the obtained extract E1 to the mass of the third molded body was calculated as the solvent extraction rate C (mass%).

[0096] [Evaluation 7: Measurement of the solvent extraction rate D of the powder] First, a sheet-like polyurethane elastomer molded body having a thickness of 2 mm was cut with scissors into a length of 25 mm, a width of 10 mm, and a thickness of 2 mm to obtain a third molded body. The third molded body was sandwiched between two Kiriyama funnel filter paper 5B, and then sandwiched between two degreased aluminum sheets. Using a 50-ton press (trade name: PEF 5041, manufactured by Kansai Roll Co., Ltd.) preheated to 130 ° C., the mixture was pressed and pulverized at 10 MPa for 1 minute to obtain a powder. To determine the size of the powder, a laser diffraction / scattering particle size distribution analyzer (trade name: Partica LA-960V2, manufactured by Horiba, Ltd.) equipped with a dry measurement unit was used to measure the particle size distribution, and the particle diameter (mode diameter) showing the maximum peak was determined. In addition, the two sheets of Kiriyama funnel filter paper sandwiching the crushed third molded body were folded together and placed in a Soxhlet cylindrical filter paper, and extract E2 was obtained in the same manner as the solvent extraction rate C above, and the solvent extraction rate D (mass%) of the powder was determined.

[0097] [Evaluation 8: Measurement of number average molecular weight of extract E2] Extract E2 obtained by solvent extraction of the powder was collected, dissolved in THF, and measured using the following measuring device and conditions: Measuring instrument: HLC-8320GPC (trade name, manufactured by Tosoh Corporation) Column: TSKgel SuperMultiporeHZ-N (trade name, manufactured by Tosoh Corporation) x 2 Solvent: THF Temperature: 40°C Flow rate: 0.35 mL / min

[0098] Measurements were performed using a refractive index (RI) detector. A calibration curve was also created using the following materials as standard samples: TSK standard polystyrene (trade names "A-1000", "A-2500", "A-5000", "F-1", "F-2", "F-4", "F-10", "F-20", "F-40", "F-80", and "F-128", manufactured by Tosoh Corporation). Based on this calibration curve, the number-average molecular weight of extract E2 was calculated from the retention time of the obtained measurement sample.

[0099] [Evaluation 9: Measurement of Viscosity of Extract E2] 10 μL of Extract E2 obtained in the measurement of the powder solvent extractability D was collected. Then, using an ultra-micro sample viscometer (product name: m-VROC, manufactured by Rheosens), the viscosity of the collected Extract E2 was measured at a measurement temperature of 25° C. and a shear rate of 1 (1 / s), and this was recorded as the viscosity of Extract E2.

[0100] [Evaluation 10: Measurement of Abrasion Resistance] The abrasion resistance of the surface in the thickness direction of a sheet-like abrasion test piece made of polyurethane elastomer, measuring 30 mm in length, 30 mm in width, and 2 mm in thickness, was measured using a ball-on-disk friction and abrasion tester (product name: HEIDON Type: 20, manufactured by Shinto Chemical Co., Ltd.) in accordance with JIS R1613:2010 under the following conditions (1) to (6): (1) Ball Material: Stainless Steel Diameter: 10 mm (2) Load: 100 g (3) Environment: Temperature: 23°C, 50% RH (4) Time: 60 minutes (5) Sliding circle diameter: 10 mm (6) Rotational speed of the disk on which the test piece was placed: 300 rpm

[0101] The wear test was performed as follows. First, the mass of the wear test piece was measured. Next, the wear test piece was fixed with double-sided tape to approximately the center of the sliding disk of a ball-on-disk friction and wear tester (product name: HEIDON Type: 20, manufactured by Shinto Chemical Co., Ltd.) so that the center of the wear test piece was located. At this time, the surface of the wear test piece in the thickness direction was positioned so that it was in contact with the sliding disk. Next, an indenter consisting of the above-mentioned ball was pressed against the center of the wear test piece with a load of 100 g, and the wear test piece was rotated and slid for 60 minutes with a sliding circle diameter of 10 mm and a rotation speed of 300 rpm. After 60 minutes, the test was stopped, the wear powder and double-sided tape were removed, and the mass of the test piece was measured. The mass loss rate (mass%) was calculated from the mass of the test piece before and after the wear test.

[0102] Example 1 Preparation Example of Urethane Prepolymer UP1 21.5 parts by mass of polyol A-1 as a polyether polyol (first polyol) having at least two hydroxyl groups and a second structure represented by formula (2), 0.4 parts by mass of polyisocyanate B-1 as a first polyisocyanate, and 500 ppm of curing catalyst C-1 were mixed and heated at a temperature of 100°C for 24 hours to synthesize a polyol (first polyether) having at least two isocyanate groups. 50.2 parts by mass of polyol A-4 as a third polyol (first polycarbonate polyol) was mixed therein, and the mixture was heated at a temperature of 100°C for 4 hours to produce urethane prepolymer (urethane reactive emulsifier) ​​UP1 (step (i)).

[0103] <Preparation Example of Urethane Elastomer Molded Product No. 1> 72.1 parts by mass of urethane prepolymer UP1, 2.2 parts by mass of B-1 as a second polyisocyanate, and 3.8 parts by mass of B-2 as a third polyisocyanate were mixed and stirred for 2 minutes at a revolution speed of 1600 rpm using a planetary-type vacuum stirring / degassing mixer (product name: V-mini300, manufactured by EME) until the mixture became homogeneous (steps (ii) and (iii)). This produced a polyurethane elastomer-forming mixture according to this example. The polyurethane elastomer-forming mixture was then preheated to 130°C, poured into a 2 mm-thick sheet mold thinly coated with a release agent, and cured by heating at 130°C for 2 hours (step (iii)). The cured product was then demolded and post-cured at 80°C for 2 days to produce a 2 mm-thick sheet-like polyurethane elastomer molded product No. 1.

[0104] Example 2 Preparation Example of Urethane Prepolymer UP2 15.0 parts by mass of Polyol A-1 as the first polyol, 6.4 parts by mass of Polyol A-7 as the second polyol, 0.5 parts by mass of Polyisocyanate B-1 as the first polyisocyanate, and 500 ppm of curing catalyst C-1 were uniformly mixed and heated at a temperature of 100°C for 24 hours to synthesize a polyol (first polyether) having an isocyanate group at its terminal. 50.2 parts by mass of Polyol A-4 as the third polyol (first polycarbonate polyol) was mixed therein, and the mixture was heated at a temperature of 100°C for 4 hours to produce Urethane Prepolymer (urethane reactive emulsifier) ​​UP2 (step (i)).

[0105] <Preparation Example of Urethane Elastomer Molded Product No. 2> A polyurethane elastomer molded product No. 2 was obtained in the same manner as in Example 1, except that 72.1 parts by mass of the urethane prepolymer UP2, 2.1 parts by mass of B-1 as the second polyisocyanate, and 3.8 parts by mass of B-2 as the third polyisocyanate were used.

[0106] [Examples 3 and 4] Polyurethane elastomer molded body No. 3 and polyurethane elastomer molded body No. 4 were produced in the same manner as in Example 2, except that the materials shown in Table 2 were used in the amounts shown in Table 2.

[0107] [Examples 5 to 9, Comparative Examples 1 and 2] Polyurethane elastomer molded bodies Nos. 5 to 9 and polyurethane elastomer molded bodies Nos. C1 and C2 were produced in the same manner as in Example 1, except that the materials shown in Table 2 were used in the amounts shown in Table 2.

[0108] Comparative Example 3 Production Example of Urethane Elastomer Molded Product No. C3 87.8 parts by mass of Polyol A-5 as the first polyol, 4.9 parts by mass of B-1 as the first polyisocyanate, 7.3 parts by mass of B-2 as the second polyisocyanate, and 500 ppm of curing catalyst C-1 were mixed and stirred for 2 minutes at a revolution speed of 1600 rpm using a planetary vacuum stirring / degassing mixer until the mixture became homogeneous, thereby obtaining a polyurethane elastomer-forming mixture. Next, a polyurethane elastomer molded product No. C3 was obtained in the same manner as in Example 1, except that this polyurethane elastomer-forming mixture was used.

[0109] Comparative Example 4 Production Example of Urethane Elastomer Molded Product No. C4 23.5 parts by mass of Polyol A-2 as the first polyol, 43.6 parts by mass of Polyol A-6 as the second polyol, 3.8 parts by mass of B-1 as the first polyisocyanate, 5.7 parts by mass of B-2 as the second polyisocyanate, and 500 ppm of curing catalyst C-1 were mixed and stirred for 2 minutes at a revolution speed of 1600 rpm using a planetary vacuum stirring / degassing mixer until homogeneous, thereby obtaining a polyurethane elastomer-forming mixture. Next, polyurethane elastomer molded product No. C4 was obtained in the same manner as in Example 1, except that this polyurethane elastomer-forming mixture was used.

[0110] The evaluation results of the polyurethane elastomers according to Examples 1 to 9 and Comparative Examples 1 to 4 are shown in Table 4. In the table, PPG indicates a structure derived from polypropylene glycol, PTMG indicates a structure derived from polytetramethylene glycol, PC indicates a structure derived from polycarbonate urethane, PE indicates a structure derived from polyester urethane, and F3 indicates an addition polymer of glycerin and at least one selected from the group consisting of ethylene oxide and propylene oxide.

[0111] The polyurethane elastomer molding No. 1 according to Example 1 had a significantly reduced solvent extraction rate D of the pulverized material compared to the polyurethane elastomer molding No. C1 obtained in Comparative Example 1, which differed only in the catalyst used. Furthermore, the polyurethane elastomer molding No. C2 obtained in Comparative Example 2, in which the amount of catalyst was increased compared to Comparative Example 1, showed an improvement in the solvent extraction rate D of the pulverized material, but the micro rubber hardness increased. The polyurethane elastomer moldings No. C3 and C4 obtained in Comparative Examples 3 and 4, which did not have a domain structure, had a D / C ratio close to 1, but exhibited significantly reduced abrasion resistance compared to Example 1 and the like.

[0112] Furthermore, polyurethane elastomer molded body No. 2 according to Example 2 and polyurethane elastomer molded body No. 3 according to Example 3 further contain in their domains a structure that is an addition polymer of glycerin and at least one selected from the group consisting of ethylene oxide and propylene oxide. Therefore, the three-branched structure derived from glycerin increases the number of urethane bonds at the boundary between the matrix and the domains, thereby further suppressing the exudation of domain-derived components to the surface of the polyurethane elastomer molded body. Polyurethane elastomer molded body No. 4 according to Example 4 used the same curing catalyst as Comparative Example 1, but further contains in its domains a structure that is an addition polymer of glycerin and at least one selected from the group consisting of ethylene oxide and propylene oxide. This enabled the solvent extraction rate D of the powder to be equivalent to that of Example 1.

[0113] The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to clarify the scope of the present disclosure. This application claims priority based on Japanese Patent Application No. 2023-138464 filed on August 28, 2023, and Japanese Patent Application No. 2024-134221 filed on August 9, 2024, the entire contents of which are incorporated herein by reference.

[0114] 3: Polyurethane molded body, 31: Matrix, 32: Domain

Claims

1. A polyurethane elastomer having a matrix and a plurality of domains dispersed in the matrix, wherein a first molded body made of the polyurethane elastomer has a cubic shape with each side measuring 100 μm, the number N of the domains contained is 10 to 77,000, the arithmetic mean value Da of the equivalent sphere diameters of the domains is 1.0 to 30.0 μm, the proportion V of the total volume of the domains in the first molded body is 15 to 45 volume %, the relationship between parameter A indicating the viscoelasticity term of the domains and parameter B indicating the viscoelasticity term of the matrix, which are measured in a viscoelastic image obtained by a scanning probe microscope of a cut surface parallel to one face of the first molded body, is A<B, and the micro rubber hardness at a temperature of 23°C of a second molded body made of the polyurethane elastomer is 20 to 50 degrees, and In an indentation test of the second molded body using a nanoindenter at a temperature of 23°C, a Vickers indenter is pressed into the second molded body at a loading rate of 10 mN / 30 seconds, and the load of 10 mN is maintained for 60 seconds and then released, and the strain 5 seconds after release is 1.0 µm or less; when a third molded body made of the polyurethane elastomer is subjected to Soxhlet extraction in accordance with Japanese Industrial Standards (JIS) K6229:2015 using acetone as an extraction solvent at an extraction temperature of 80°C for an extraction time of 4 hours, the ratio of the mass of the obtained extract E1 to the mass of the third molded body is C (mass%); and when a powder of the third molded body having a mode diameter of less than 1 µm is extracted using acetone as an extraction solvent at a extraction temperature of 80°C for an extraction time of 4 hours, the ratio of the mass of the obtained extract E1 to the mass of the third molded body is C (mass%); A polyurethane elastomer characterized in that, when Soxhlet extraction is performed in accordance with K6229:2015 using acetone as an extraction solvent at an extraction temperature of 80°C for an extraction time of 4 hours, the ratio of the mass of the obtained extract E2 to the mass of the powder is defined as D (mass%), and D / C is 1.0 to 5.

0.

2. The polyurethane elastomer according to claim 1, wherein the number average molecular weight of said extract E2 is 2,000 to 100,000.

3. The polyurethane elastomer according to claim 1 or 2, wherein the viscosity of the extract E2 is 10,000 mPa·s or less.

4. The polyurethane elastomer according to any one of claims 1 to 3, wherein the polyurethane elastomer has a first structure represented by the following formula (1) and a second structure represented by the following formula (2), the matrix contains the first structure, and the domain contains the second structure: (In formula (1), R １ represents an alkylene group having 3 to 12 carbon atoms. (In formula (2), R ２ represents an alkylene group having 3 to 6 carbon atoms.

5. The polyurethane elastomer according to claim 4, wherein the domain has a third structure, the third structure being an addition polymer of glycerin and at least one selected from the group consisting of ethylene oxide and propylene oxide.

6. The polyurethane elastomer according to any one of claims 1 to 5, wherein a mass loss rate of a sheet-like wear test piece made of the polyurethane elastomer and having a length of 30 mm, a width of 30 mm and a thickness of 2 mm on a surface in the thickness direction of the sheet-like wear test piece is 10.0 mass % or less when a ball-on-disk wear test is performed in accordance with JIS R1613:2010 under the following conditions (1) to (6): (1) Ball Material: Stainless steel Diameter: 10 mm (2) Load: 100 g (3) Environment: Temperature 23°C, 50% RH (4) Time: 60 minutes (5) Sliding circle diameter: 10 mm (6) Rotational speed of the disk on which the wear test piece is placed: 300 rpm.

7. A polyurethane molding comprising the polyurethane elastomer according to any one of claims 1 to 6.

8. The polyurethane molding according to claim 7, which has a foamed structure.

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