JP2022168829A - Polyurethane elastomer and production method thereof - Google Patents

Abstract

To provide a urethane elastomer having satisfactory friction properties (low coefficient of friction) and having high wear resistance and a low hardness.SOLUTION: The urethane elastomer has first repeating structural units, which are represented by general formula (1), and second repeating structural units, which are represented by general formula (2), and comprises a matrix phase and a domain phase dispersed in the matrix phase, the matrix phase including the first repeating structural units and the domain phase including the second repeating structural units.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to polyurethane elastomers and methods of making same.

Polyurethane elastomers are used in a wide range of applications such as artificial leather, synthetic leather, paints, coating agents, and adhesives. Generally, a polyurethane elastomer is composed of a reaction product of a polyisocyanate and a polyol, and is composed of a hard segment derived from the polyisocyanate and a soft segment derived from the polyol. Polyols, which are one of the raw materials for polyurethane elastomers, are classified into polyether polyols, polyester polyols, polycarbonate polyols, etc., depending on the difference in molecular chain structure, and the polyol is selected according to the required performance. Among them, a polyurethane elastomer having a polycarbonate structure made from polycarbonate polyol is excellent in abrasion resistance. In addition, it is known to be superior to polyurethane elastomers having a polyether structure or polyester structure in terms of heat resistance, weather resistance, hydrolysis resistance, and the like. On the other hand, in a polyurethane elastomer having a polycarbonate structure, a strong intermolecular force acts between the polycarbonate structures, causing a remarkable increase in hardness of the polyurethane elastomer. For this reason, it has been difficult to apply polyurethane elastomers having a polycarbonate structure to applications requiring low hardness.

Moreover, a typical example of the low-hardness elastomer is a silicone elastomer. The silicone elastomer is superior in compression set but inferior in wear resistance to a polyurethane elastomer having a polycarbonate structure.
Against this background, there is a demand for elastomers that have excellent abrasion resistance similar to polyurethane elastomers having a polycarbonate structure and low compression set comparable to silicone elastomers.

Patent Document 1 discloses a structural unit derived from a polyol, a structural unit derived from a polyether carbonate diol having a specific structure, and a polycarbonate diol having two repeating units having a specific structure and/or a specific structure. Disclosed is a polyurethane elastomer comprising a structure derived from a polyalkylene ether glycol having two repeating units with . Further, Patent Document 2 discloses a developing blade for an electrophotographic apparatus, which is formed by adhering a blade member to a support. The material of the blade member is a polyurethane elastomer that is a reaction product of a polyol compound and a polyisocyanate compound, and the polyol compound is a blend of polydimethylsiloxane and polypropylene glycol having active hydrogens at least at both ends of the molecule. It is disclosed that

JP 2020-128461 A JP-A-2000-29307

According to the studies of the present inventors, the polyurethane elastomer according to Patent Document 1 is superior in flexibility to conventional polycarbonate polyurethanes, but it was difficult to achieve low hardness comparable to silicone elastomers. Moreover, in the polyurethane elastomer according to Patent Document 1, perhaps because the polyether segments are uniformly present in the polyurethane elastomer, it has been difficult to achieve good frictional properties comparable to general polycarbonate polyurethanes. Moreover, although the polyurethane elastomer according to Patent Document 2 is excellent in terms of hardness and friction properties, it has been difficult to achieve a low compression set comparable to that of silicone elastomers.
The present disclosure is directed to providing a polyurethane elastomer having good frictional properties (low coefficient of friction), high wear resistance and low hardness, and a method for producing the same.

According to one aspect of the present disclosure, the polyurethane elastomer has a first repeating structural unit represented by general formula (1) and a second repeating structural unit represented by general formula (2), A polyurethane elastomer comprising a matrix phase and a domain phase dispersed in the matrix phase, the matrix phase comprising the first repeating structural unit and the domain phase comprising the second repeating structural unit is provided.

（Ｒ_１は、炭素数３～１２のアルキレン基を示す。）

(R ₁ represents an alkylene group having 3 to 12 carbon atoms.)

（Ｒ_２は、炭素数３～６のアルキレン基を示す。）

(R ₂ represents an alkylene group having 3 to 6 carbon atoms.)

According to another aspect of the present disclosure, a method for producing the above polyurethane elastomer comprises: (i) a first polyether having at least one isocyanate group; and a first polyether having at least two hydroxyl groups; reacting with a polycarbonate polyol to obtain a urethane prepolymer having at least two hydroxyl groups;
(ii) droplets comprising at least a portion of said urethane prepolymer dispersed in a second polycarbonate polyol to obtain a dispersion; and (iii) said dispersion and at least two isocyanate groups; and then reacting the urethane prepolymer, the second polycarbonate polyol, and the polyisocyanate in the polyurethane elastomer-forming mixture to form the polyurethane elastomer. A method for producing a polyurethane elastomer is provided.

INDUSTRIAL APPLICABILITY According to the present disclosure, a polyurethane elastomer having good frictional properties (low coefficient of friction), high wear resistance and low hardness, and a suitable method for producing the same are provided.

1 is a schematic diagram showing a method for producing a urethane elastomer according to the present disclosure; FIG. 1 is a graph showing temperature-loss tangent (tan δ) curves obtained by dynamic viscoelasticity measurement (DMA) of polyurethane elastomers produced in Example 1 and Comparative Examples 1 and 2. FIG. 1 is a photograph showing a viscoelastic image of a cross-section of a polyurethane elastomer produced in Example 1 by a microviscoelastic microscope (VE-AFM).

Embodiments of the present disclosure will be described below. It should be noted that the embodiments described below are merely examples, and the present disclosure is not limited to these embodiments unless there is a specific description.
The polyurethane elastomer according to the present disclosure has, as repeating structural units, a first repeating structural unit having a polycarbonate structure represented by general formula (1) and a polyether structure represented by general formula (2). It has a second repeating structural unit.

（Ｒ_１は、炭素数３～１２のアルキレン基を示す。）

(R ₁ represents an alkylene group having 3 to 12 carbon atoms.)

（Ｒ_２は、炭素数３～６のアルキレン基を示す。）

(R ₂ represents an alkylene group having 3 to 6 carbon atoms.)

The polyurethane elastomer also includes a matrix phase and domain phases dispersed in the matrix phase. The matrix phase comprises polyurethane having the first repeating structural unit. The domain phase also includes the second repeating structural unit.

A polyurethane obtained by reacting a polyol having a polycarbonate structure (polycarbonate polyol) with a polyisocyanate has a strong intermolecular force between carbonate groups. Due to this, it exhibits mechanical properties such as good frictional properties (low coefficient of friction) and high wear resistance. However, its strong intermolecular forces cause an increase in hardness, making it unsuitable for use in soft polyurethane elastomer applications.
On the other hand, generally, a polyurethane obtained by reacting a polyol having a polyether structure (polyether polyol) with a polyisocyanate has a weak intermolecular force between ether groups. Due to this, the hardness can be kept extremely low, making it suitable for use in soft polyurethane elastomer applications. However, its weak intermolecular force causes deterioration of mechanical properties such as friction properties and wear resistance.

The polyurethane elastomer according to the present disclosure has a matrix-domain structure including a matrix phase and a domain phase. And the matrix phase comprises a polyurethane containing a first repeating structural unit. The domain also includes a second repeating structural unit. With such a configuration, the polyurethane elastomer can have good frictional properties and high wear resistance while keeping the hardness low. That is, in the polyurethane elastomer according to the present disclosure, the matrix phase has the function of good frictional properties and high wear resistance, and the domain phase has the function of lowering the hardness. Thus, by having the matrix phase and the domain phase perform different functions, the polyurethane elastomer according to the present disclosure can achieve good frictional properties, high wear resistance, and low hardness at a higher level. It is a thing.

Furthermore, the polyurethane elastomer according to the present disclosure can achieve both low hardness and low compression set due to the configuration described above. The reason for this is that the matrix phase and the domain phase are chemically linked by urethane bonds at the interface, so excellent elasticity (entropic elasticity) is exhibited without undergoing plastic deformation against external forces such as compression. It is thought that it is for That is, the entire domain phase functions as a soft cross-linking point due to the effect of entropy elasticity, so it is considered possible to achieve both low hardness and low compression set.

In addition, in the temperature-loss tangent (tan δ) curve obtained by dynamic viscoelasticity measurement (DMA) of the polyurethane elastomer according to the present disclosure, there are at least two peaks due to the glass transition observed in the temperature range of -80 to +20 ° C. It is preferable that there are at least More preferably, there are at least two peaks due to glass transition observed in the temperature range of -70 to 0°C. This indicates that the polyurethane segment containing the polycarbonate structure and the polyurethane segment containing the polyether structure are clearly phase-separated through the interface between the matrix phase and the domain phase. In addition, when the peaks overlap in the temperature-tan δ curve, it is necessary to separate each peak. Here, peak separation in the temperature-tan δ curve can be performed by a known method.

Furthermore, in the temperature-tan δ curve obtained by DMA of the polyurethane elastomer according to the present disclosure, it is preferable that at least one of the glass transition peaks is observed in the temperature range of -50°C or lower. At least one of the peaks is preferably in the temperature range of -40°C or higher. More preferably, at least one is in the temperature range of -60°C or lower, and at least one is in the temperature range of -35°C or higher. Generally, the peak due to the glass transition of polyether is observed in the temperature range of -80°C to -50°C. A peak due to the glass transition of polycarbonate is observed in the temperature range of -40°C to +20°C. Therefore, the presence of the glass transition peaks in the two temperature ranges means the following.
In the polyurethane elastomer according to the present disclosure, the segment composed of the first repeating structural unit and the segment composed of the second repeating structural unit are phase-separated. Then, the two segments exist with little compatibility with each other.
Such clear phase separation suppresses contamination of the segment composed of the second repeating structural unit into the matrix phase. Thus, in the polyurethane elastomer according to the present disclosure, the matrix achieves good frictional properties and high wear resistance.

The first repeating structural unit containing the polycarbonate structure represented by general formula (1), which is included in the matrix phase in the polyurethane elastomer according to the present disclosure, will be described. R ₁ in general formula (1) represents an alkylene group having 3 to 12 carbon atoms. Preferably, R ₁ contains an alkylene group with 3 to 9 carbon atoms, more preferably an alkylene group with 3 to 6 carbon atoms. When R ₁ is an alkylene group having 3 to 12 carbon atoms, low compatibility with the segment containing the polyether structure represented by the general formula (2) is ensured, and the matrix phase and the domain phase are distinctly separated from each other. can be separated. In addition, by containing an alkylene group having 3 to 12 carbon atoms in R ₁ , the intermolecular force between carbonate groups can be moderately suppressed, and both good friction characteristics, high wear resistance and low hardness can be achieved. From this point of view, it is more preferable. Examples of R ₁ include -(CH ₂ ) _m - (m=3 to 12), -CH ₂ C(CH ₃ ) ₂ CH ₂ -, -CH ₂ CH(CH ₃ )CH ₂ -, -(CH ₂ ) ₂ CH(CH ₃ )(CH ₂ ) ₂ — and the like. In the polyurethane elastomer, all R ₁ 's may be the same or a combination of different R ₁ 's.

The number average molecular weight (Mn) of the polycarbonate structure represented by general formula (1) is preferably 500 or more and 10000 or less as a repeating unit in the polyurethane elastomer. The number average molecular weight is based on the starting polycarbonate polyol. More preferably, it is 700 or more and 8000 or less. When the number average molecular weight is 500 or more, low compatibility with the polyurethane segment containing the polyether structure of the repeating structural unit represented by general formula (2) is ensured, and phase separation between the matrix phase and the domain phase is clear. preferred because it In addition, by setting the number average molecular weight to 10,000 or less, it is possible to suppress an increase in the viscosity of the raw polycarbonate polyol.
The number average molecular weights of polyols and the like described later, including the number average molecular weight of the polycarbonate structure, are values calculated using standard polystyrene molecular weight conversion or hydroxyl value (mgKOH/g) and valence. For example, the number average molecular weight in terms of polystyrene molecular weight can be measured using high performance liquid chromatography. For example, Tosoh Corporation, high-speed GPC device "HLC-8220GPC", column: Shodex GPCLF-804 (exclusion limit molecular weight: 2 × 106, separation range: 300 ~ 2 × 106) to measure using two series. can be done. When using a hydroxyl value and a valence, it can be calculated by the following formula. For example, the number average molecular weight of 56.1 mg KOH/g, 2-valence polyol can be calculated as 2,000.
Number average molecular weight = 56.1 x 1000 x valence / hydroxyl value

In the second repeating structural unit represented by the general formula (2) contained in the domain phase, R ₂ represents an alkylene group having 3 to 6 carbon atoms. It preferably contains an alkylene group having a branched structure with 3 to 5 carbon atoms, and more preferably contains an alkylene group having a branched structure with 3 to 4 carbon atoms. When R ₂ is an alkylene group having 3 to 6 carbon atoms, low compatibility with the polyurethane segment containing the polycarbonate structure represented by the general formula (1) is ensured, and the matrix phase and the domain phase are distinctly separated from each other. can be separated. Further, it is more preferable that R ₂ contains an alkylene group having a branched structure with 3 to 5 carbon atoms, from the viewpoint that the intermolecular force between ether groups can be kept extremely low and low hardness can be achieved. Examples of R ₂ include -(CH ₂ ) _m -(m=3 to 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 —, —(CH ₂ ) ₂ CH(CH ₃ )(CH ₂ ) ₂ — and the like. In the polyurethane elastomer, all _R2 's may be the same or a combination of different _R2 's.
The number average molecular weight (Mn) of the polyether structure represented by general formula (2) is preferably 1000 or more and 50000 or less as a repeating unit in the polyurethane elastomer. The number average molecular weight is based on the starting polyether polyol. More preferably, it is 1200 or more and 30000 or less. A number-average molecular weight of 1000 or more ensures low compatibility with the polyurethane segment containing the polycarbonate structure represented by the general formula (1), and further clarifies the phase separation between the matrix phase and the domain phase. can be done. Moreover, when the number average molecular weight is 50,000 or less, the segment containing the polyether structure can easily form a domain phase, and the phase separation structure can be further stabilized.

The area ratio of the matrix phase/the domain phase in the cross section of the polyurethane elastomer according to the present disclosure is preferably 40/60 to 90/10. More preferably, it is 45/55 to 80/20. When the area ratio of the matrix phase/the domain phase is within the above range, the phase separation state is stabilized, and the matrix phase and the domain phase tend to be stably formed, which is preferable.

The average diameter of the domain phase is preferably in the range of 0.2-30 μm. More preferably, it is in the range of 0.5 to 20 μm. An average diameter of 0.2 μm or more ensures low hardness, and an average diameter of 30 μm or less stabilizes the phase separation form, which is preferable.
The area ratio of the matrix phase/the domain phase and the average diameter of the domain phase can be determined using, for example, an optical microscope, a microviscoelasticity microscope (Visco-Elastiicty Atomic Force Microscopy, or VE-AFM), or a scanning electron microscope. It can be calculated by a known method from the cross-sectional image of the urethane elastomer obtained by the above.
In addition, the chemical structures of the components contained in the matrix phase and the domain phase can be analyzed by, for example, a spectroscopic analyzer such as an AFM infrared spectroscopic analyzer, a microscopic infrared spectroscopic analyzer, a microscopic Raman spectroscopic analyzer, or a mass spectrometer. etc. can be used for analysis.

The polyurethane elastomer according to the present disclosure can be synthesized, for example, by a method having steps (i) to (iii) below.
Step (i): A step of reacting a first polyether having at least one isocyanate group with a first polycarbonate polyol having at least two hydroxyl groups to obtain a urethane prepolymer having at least two hydroxyl groups. ,
Step (ii): obtaining a dispersion in which droplets containing at least part of the urethane prepolymer are dispersed in a second polycarbonate polyol; and Step (iii): the dispersion and at least two and then reacting the urethane prepolymer, the second polycarbonate polyol, and the polyisocyanate in the polyurethane elastomer-forming mixture to react the Forming a polyurethane elastomer.

One embodiment of the method for producing the polyurethane elastomer according to one embodiment of the present disclosure will be described with reference to FIG. Note that the method for producing a polyurethane elastomer according to the present disclosure is not limited to this form.
In step (i), a first polyether 51 having at least one isocyanate group and a first polycarbonate polyol 52 having at least two hydroxyl groups are mixed. Next, the isocyanate groups and hydroxyl groups in the resulting mixture are reacted in the presence of a curing catalyst, and the two are linked via urethane bonds to obtain a urethane prepolymer 53 having at least two hydroxyl groups. Note that FIG. 1 shows a polyether having two isocyanate groups as an example of the first polyether 51 .

In step (ii), the urethane prepolymer 53 obtained in step (i) is dispersed in the second polycarbonate polyol 55 . The segments derived from the first polyether 51 contained in the urethane prepolymer 53 are incompatible with the second polycarbonate polyol 55 and form droplets 54 . On the other hand, via the segment derived from the first polycarbonate polyol 52 contained in the urethane prepolymer 53, in the second polycarbonate polyol 55, to the first polyether constituting part of the urethane prepolymer Droplets 54 containing the derived segments are uniformly and stably dispersed. As a result, a dispersion is obtained in which droplets 54 containing segments derived from the first polyether 51 of the urethane prepolymer 53 are dispersed in the second polycarbonate polyol 55 . For the sake of explanation, the step (i) and the step (ii) are described separately, but these steps may be a continuous series of steps.
In step (ii), the second polycarbonate polyol 55 for dispersing the droplets 54 is the unreacted product of the first polycarbonate polyol used in step (i) with the first polyether. can. That is, in step (i), by using an excessive amount of the first polycarbonate polyol with respect to the first polyether, the urethane prepolymer 53 described in step (ii) is the excess first polycarbonate polyol, that is, , a dispersion in the second polycarbonate polyol 55 can be obtained. Even when the first polycarbonate polyol is used in an excessive amount, a polycarbonate polyol (second polycarbonate polyol) can be additionally added as a dispersion medium for the urethane prepolymer. In this case, the additional polycarbonate polyol may be of the same chemical composition as or different from the first polycarbonate polyol used in step (i).
On the other hand, in step (i), the first polycarbonate polyol and the first polyether are reacted in equal amounts, and when all the first polycarbonate polyol is consumed, in step (ii), a new A dispersion is prepared using a polycarbonate polyol as the second polycarbonate polyol. Also in this case, the polycarbonate polyol used as the second polycarbonate polyol may or may not have the same chemical composition as the first polycarbonate polyol.

Finally, in step (iii), a polyurethane elastomer-forming mixture is prepared comprising the dispersion prepared in step (ii) and a polyisocyanate 56 having at least two isocyanate groups. Next, the terminal hydroxyl groups of the urethane prepolymer 53, the hydroxyl groups of the second polycarbonate polyol 55, and the isocyanate groups of the polyisocyanate 56 in the mixing portion for forming the polyurethane elastomer are reacted. Thus, a network structure via urethane bonds is formed, and the polyurethane elastomer-forming mixture is cured to obtain the polyurethane elastomer according to the present disclosure. The polyurethane elastomer 33 thus obtained has a polyether structure derived from the first polyether 51, that is, the domain 32 including the second repeating structural unit is composed of the first polycarbonate polyol 52 and the second polycarbonate polyol 55. has a matrix-domain structure dispersed in a matrix 31 containing a urethane elastomer having a first repeating structural unit. Also, the domain 32 is mainly composed of a polyether structural portion (second repeating structural unit), and the interior of the domain can be substantially free of crosslinked structures. In other words, domains 32 may exist in the matrix in a substantially liquid state. This allows the domains to have a low elastic modulus in the polyurethane elastomer 33 according to the present disclosure.
Furthermore, the domains are not simply confined in the matrix in the liquid portion, but are chemically bonded to the matrix by urethane bonds at the boundary between the domains and the matrix. Therefore, the recovery from deformation of the domains when the load applied to the polyurethane elastomer 33 is removed can be linked to the recovery from deformation of the matrix. That is, the substantially liquid domain has substantially no crosslinked structure inside. Therefore, it is difficult for the domain deformed by applying a load to the polyurethane elastomer 33 to recover from the deformation autonomously. However, in the polyurethane elastomer according to the present disclosure, the domains are chemically bonded to the matrix at the interface with the matrix, so that the domains can recover from deformation together with the deformation recovery of the matrix. As a result, stable deformation (deformation amount) and stable recovery from the deformation are achieved even when the polyurethane elastomer 33 is repeatedly subjected to load loading and unloading.

The above steps (i) to (ii) are steps for stably dispersing polyether, which originally has low compatibility and is difficult to disperse stably and uniformly, in polyol. That is, a first polyether 51 is reacted with a first polycarbonate polyol 52 to form a urethane prepolymer 53 . This is a step of obtaining a dispersion in which the polyether segments derived from the first polyether 51 are stably and uniformly dispersed in the second polycarbonate polyol. As a result, it becomes possible to produce a polyurethane elastomer 33 in which domains 32 with a high degree of circularity and a relatively uniform size distribution are dispersed in the polyurethane 31 as a matrix. .
As another method of mixing materials with low compatibility, for example, there is a method of mixing and dispersing with a high shearing force. However, in this method, as a result of applying a high shearing force to the polyether, the shape of the domains becomes distorted, the degree of circularity decreases, and the sizes of the domains may become uneven. Moreover, the dispersed state is also unstable, and the aggregation of domains progresses in a relatively short period of time. In addition, incompatibility between the polyether and the polycarbonate polyol is not ensured, and phase separation between the matrix and the domains of the resulting urethane elastomer becomes unclear. Therefore, it is difficult to obtain a polyurethane elastomer that provides an elastic body that is flexible and has excellent deformation recovery properties according to the present disclosure.

The first polyether is a polyether having at least one isocyanate group and a repeating structural unit represented by the general formula (2). The first polyether can be obtained, for example, by the following steps.
A polyether polyol having at least two hydroxyl groups and a repeating structural unit represented by the general formula (2) is reacted with a polyisocyanate having at least two isocyanate groups.
Examples of the polyether polyol include alkylene structure-containing polyether polyols such as polypropylene glycol, polytetramethylene glycol, copolymers of tetrahydrofuran and neopentyl glycol, and copolymers of tetrahydrofuran and 3-methyltetrahydrofuran, Examples include random or block copolymers of these polyalkylene glycols. These may be used alone or in combination of two or more.
Among the polyether polyols, amorphous polyether polyols are preferable from the viewpoint of realizing low compatibility with the second polycarbonate polyol described later and low hardness. More preferably, among polyether polyols, it contains at least one selected from polypropylene glycol, a copolymer of tetrahydrofuran and neopentyl glycol, and a copolymer of tetrahydrofuran and 3-methyltetrahydrofuran.
The polyether polyol preferably has a number average molecular weight of 1,000 or more and 50,000 or less. More preferably, it is 1200 or more and 30000 or less. A number-average molecular weight of 1000 or more is preferable because low compatibility with the polycarbonate polyol is ensured and phase separation between the matrix phase and the domain phase of the obtained urethane elastomer becomes clear. Further, when the number average molecular weight is 50,000 or less, the polyurethane segment derived from the polyether polyol tends to easily form a domain phase, which is preferable because the phase separation form is stabilized.

Examples of the polyisocyanate to be reacted with the polyether polyol include pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, or Trimer compounds (isocyanurates) or polymeric compounds of these polyisocyanates, allophanate-type polyisocyanates, burette-type polyisocyanates, water-dispersed polyisocyanates, and the like can be mentioned. These polyisocyanates may be used alone or in combination of two or more.
Among the polyisocyanates exemplified above, bifunctional isocyanates having two isocyanate groups are preferred because of their high compatibility with polyether polyols and ease of adjustment of physical properties such as viscosity. More preferably, among the above polyisocyanates, it contains at least one selected from hexamethylene diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate. be.
In the step of reacting the polyether polyol and the polyisocyanate to obtain the first polyether, the isocyanate index is preferably in the range of 0.05 to 8.0. More preferably, it ranges from 0.1 to 5.0. When the isocyanate index is within the above range, it is possible to reduce the remaining first polyether-derived components without forming a network structure, and to suppress 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 first polyether polyol and the polyisocyanate has a structure in which hydroxyl groups and isocyanate groups are linked via urethane bonds. The number average molecular weight is preferably 1,000 or more and 100,000 or less. More preferably, it is 1200 or more and 50000 or less.

The first polycarbonate polyol is a polycarbonate polyol having at least two hydroxyl groups and a repeating structural unit represented by the general formula (1). Examples of the first polycarbonate polyol include a reaction product of a polyhydric alcohol and phosgene, and a ring-opening polymer of a cyclic carbonate (such as an alkylene carbonate).
Examples of the polyhydric alcohol include propylene glycol, dipropylene glycol, trimethylene glycol, 1,4-tetramethylenediol, 1,3-tetramethylenediol, 2-methyl-1,3-trimethylenediol, 1, 5-pentamethylenediol, neopentyl glycol, 1,6-hexamethylenediol, 3-methyl-1,5-pentamethylenediol, 2,4-diethyl-1,5-pentamethylenediol, glycerin, trimethylolpropane, trimethylolethane, cyclohexanediols (1,4-cyclohexanediol, etc.), sugar alcohols (xylitol, sorbitol, etc.), and the like.
Examples of the alkylene carbonate include trimethylene carbonate, tetramethylene carbonate, hexamethylene carbonate and the like.
The number average molecular weight of the first polycarbonate polyol is preferably 500 or more and 10,000 or less. More preferably, it is 700 or more and 8000 or less. When the number average molecular weight is 500 or more, low compatibility with the polyurethane segment containing the polyether structure represented by the general formula (2) is ensured, and the phase separation between the matrix phase and the domain phase becomes clearer. It is preferable because Further, when the number average molecular weight is 10,000 or less, it is preferable because handling becomes difficult due to an increase in the viscosity of the polycarbonate polyol as a raw material.
The number average molecular weight of the first polycarbonate polyol can be calculated using the hydroxyl value (mgKOH/g) and the valence, like the number average molecular weight of the polyether polyol.

As the polyisocyanate 56 having at least two isocyanate groups used in step (iii), the same polyisocyanates as those exemplified above as the starting material for the first polyether can be used. These polyisocyanates may be used alone or in combination of two or more.
As the first polyisocyanate, among the polyisocyanates exemplified above, from the viewpoint of increasing the elastic modulus of the matrix, a polyisocyanate trimer compound (isocyanurate) or polymer compound, allophanate-type polyisocyanate, buret-type It preferably comprises a polyisocyanate having at least 3 isocyanate groups, such as a polyisocyanate. More preferably, it contains any one of a pentamethylene diisocyanate trimer compound (isocyanurate), a hexamethylene diisocyanate trimer compound (isocyanurate), and a diphenylmethane diisocyanate polymer compound. Curing catalysts for urethane elastomers are broadly classified into urethanization catalysts (reaction promoting catalysts) for promoting rubberization (resinization) and foaming, and isocyanurate catalysts (isocyanate trimerization catalysts). In the present disclosure, one of these may be used alone, or a mixture thereof may be used.

Examples of urethanization catalysts include tin-based urethanization catalysts such as dibutyltin dilaurate and stannous octoate, triethylenediamine, tetramethylguanidine, pentamethyldiethylenetriamine, diethylimidazole, tetramethylpropanediamine, N, N, N Examples include amine-based urethanization catalysts such as '-trimethylaminoethylethanolamine. One of these may be used alone, or a mixture thereof may be used.
Among these urethanization catalysts, triethylenediamine is preferable in that it particularly accelerates the urethane reaction.

Examples of isocyanurate catalysts include metal oxides such as Li ₂ O and (Bu ₃ Sn) ₂ O, hydride compounds such as NaBH ₄ , NaOCH ₃ , KO-(t-Bu), borates, and the like. alkoxide compounds, N(C ₂ H ₅ ) ₃ , N(CH ₃ ) ₂ CH ₂ C ₂ H ₅ , amine compounds such as 1,4-ethylenepiperazine (DABCO), HCOONa, Na ₂ CO ₃ , PhCOONa /DMF, CH ₃ COOK, (CH ₃ COO) ₂ Ca, alkaline soap, alkaline carboxylate salt compounds such as naphthenate, alkaline formate compounds, ((R) ₃ —NR′OH)—OCOR”, etc. and quaternary ammonium salt compounds of.In addition, the combination catalyst (cocatalyst) used as the isocyanurate catalyst includes, for example, amine/epoxide, amine/carboxylic acid, amine/alkyleneimide, etc.These isocyanurates The conversion catalyst and combination catalyst may be used alone or in combination.

Among the urethane synthesis catalysts, N,N,N'-trimethylaminoethylethanolamine (hereinafter referred to as ETA), which acts alone as a urethanization catalyst and also acts as an isocyanurate catalyst, is preferred.

In the method for producing a polyurethane elastomer according to the present disclosure, a chain extender (polyfunctional low-molecular-weight polyol) may be used as necessary. Examples of chain extenders include glycols having a number average molecular weight of 1000 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), triethylene glycol and the like. Examples of chain extenders other than glycol include polyhydric alcohols having a valence of 3 or more. Examples of trihydric or higher polyhydric alcohols include trimethylolpropane, glycerin, pentaerythritol and sorbitol. These may be used alone or in combination.

Additives such as conductive agents, pigments, plasticizers, waterproofing agents, antioxidants, ultraviolet absorbers, and light stabilizers can also be used together as necessary.

EXAMPLES Examples according to the present invention will be described below, but the present invention is not limited to these examples.
<Materials used>
Materials used in Examples and Comparative Examples are listed below.
[Polyol]
A-1: Polyether diol (polypropylene glycol) [product name: PREMINOL S4013F, number of carbon atoms in _R2 = 3 (branched), Mn = 12,000, hydroxyl value: 9.4 mgKOH/g, manufactured by AGC]
・ A-2: Polyetherdiol (polypropylene glycol) [Product name: Uniol D-2000, number of carbon atoms in R ₂ = 3 (branched), Mn = 2,000, hydroxyl value: 55.0 mgKOH / g, NOF Corporation Made]
・A-3: Polyether diol (copolymer of tetrahydrofuran and 3-methyltetrahydrofuran) [product name: PTG-L3000, number of carbon atoms in _R2 = 5 (branched) + 4 (linear), Mn = 2,900 , hydroxyl value: 38.6 mgKOH / g, manufactured by Hodogaya Chemical Industry Co., Ltd.]
・A-4: Polyether diol (polytetramethylene glycol) [product name: PTMG2000, carbon number of _R2 = 4 (straight chain), Mn = 2.000, hydroxyl value: 57.2 mgKOH / g, Mitsubishi Chemical Co., Ltd. Made]
・A-5: Polycarbonate diol [product name: Kuraray Polyol C-2090, number of carbon atoms in _R1 = 6 (straight chain) + 6 (branched), Mn = 2,000, manufactured by Kuraray Co., Ltd.]
・A-6: Polycarbonate diol [Product name: Kuraray Polyol C-2065N, number of carbon atoms in R ₁ = 9 (straight chain) + 6 (branched), Mn = 2.000 (hydroxyl value: 56.4 mgKOH / g, Kuraray Co., Ltd. Made]
・A-7: Polycarbonate diol [product name: Duranol T6002, number of carbon atoms in R ₁ = 6 (straight chain), Mn = 1.900, hydroxyl value: 57.6 mgKOH/g, manufactured by Asahi Kasei Chemical Co., Ltd.]
・A-8 [Product name: Duranol G3452, Mn = 2.1 x 103 (hydroxyl value: 53.6 mgKOH/g), manufactured by Asahi Kasei Chemical]
A-9: Polyester diol [product name: Kuraray Polyol P-2050, Mn = 1,900, hydroxyl value: 58.1 mgKOH/g, manufactured by Kuraray Co., Ltd.]
[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]
・ B-3: isocyanurate compound [product name: Stabio D-370N, manufactured by Mitsui Chemicals]
[Curing catalyst]
· C-1: 1,4-diazabicyclo[2.2.2]octane-2-methanol (product name; RZETA) [manufactured by Tosoh Corporation]
[Chain extender]
・D-1: 1,4-butanediol

<Evaluation>
Evaluation methods in Examples and Comparative Examples are as follows.
[Evaluation 1: Appearance inspection]
Since a polyurethane elastomer having a matrix phase/domain phase tends to be less transparent due to scattering of visible light, a sample with a thickness of 2 mm was evaluated according to the following criteria.
Evaluation criteria A evaluation: opaque (an object cannot be seen through the sample.)
B rating: translucent (an object can be seen through the sample, but the transparency is not high.)
C rating: Transparent ((Objects can be clearly seen through the sample.)

[Evaluation 2: tan δ peak temperature due to glass transition]
Using a viscoelasticity measuring device (trade name: Physica MCR302, manufactured by Anton Paar), measurements were made as follows. Set a test piece with a thickness of 2 mm and a width of 5 mm molded with a punching cutter, in torsion mode (twisting) at a length of 20 mm, at a temperature increase rate of 2 ° C./min from -85 ° C. to 20 ° C. at a frequency of 1 Hz. Viscoelasticity was measured and a temperature-tan δ curve was obtained.

[Evaluation 3: micro rubber hardness]
Micro rubber hardness tester (trade 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) was used to measure the microrubber hardness of a 2 mm thick test piece at 23°C. Micro rubber hardness was evaluated according to the following criteria.
Evaluation criteria A evaluation: Micro rubber hardness is less than 40° B evaluation: Micro rubber hardness is 40° or more and less than 50° C evaluation: Micro rubber hardness is 50° or more

[Evaluation 4: Friction Properties (Evaluation 4-1: Dynamic Friction Coefficient / Evaluation 4-2: Wear Resistance)]
A ball-on-disk friction wear tester (trade name: HEIDON Type: 20, manufactured by Shinto Kagaku Co., Ltd.) was used for evaluation as follows. By pressing a SUS ball indenter (diameter: 10 mm) on a 2 mm thick test piece fixed with double-sided tape with a constant load and rotating and sliding it, a 2 mm thick test piece at a temperature of 23 ° C. under the following measurement conditions. Friction properties were evaluated.
・Load: 0.5 N (50 g)
・Rotating diameter: 1 cm
・Rotational speed: 192 rpm (10 cm/sec)
・Measurement time: 300 seconds <Evaluation 4-1>
The coefficient of dynamic friction was calculated as the average value of the measured values for 10 to 300 seconds (sampling speed: 5 ms) from the start of measurement, and evaluated according to the following criteria.
Evaluation Criteria A rating: dynamic friction coefficient of less than 1.6 B rating: dynamic friction coefficient of 1.6 or more and less than 2.4 C rating: dynamic friction coefficient of 2.4 or more <Evaluation 4-2>
Wear resistance was evaluated according to the following criteria based on the results of visual observation of wear marks after measuring the coefficient of dynamic friction measurement.
Evaluation Criteria Evaluation A: Abrasion traces cannot be confirmed.
B evaluation: Slight abrasion traces can be confirmed.
C evaluation: Abrasion traces can be clearly confirmed.

[Evaluation 5: Elastic deformation work rate (ηiT)]
The elastic deformation work rate (ηiT) at a temperature of 23° C. was adopted as an evaluation index of the compression set. ηiT was measured using a nanoindenter (Fischer Scope HM2000, manufactured by Fisher Instruments Co., Ltd.) using a square pyramid Vickers indenter with a facing angle of 136° as an indenter under the following measurement conditions.
・Maximum pushing load: 10mN
・Loading speed 10 mN/30 seconds ・Maximum load holding time: 60 seconds ・Unloading time: 5 seconds ηiT was calculated from the obtained “load-displacement curve” using the following formula.
ηiT (%) = (elastic deformation work/total deformation work) x 100
The compression set was evaluated according to the following criteria based on the obtained ηiT.
Evaluation criteria A rating: ηiT is 80% or more B rating: ηiT is 60 or more and less than 80% C rating: ηiT is less than 60

[Evaluation 6: Average diameter of domain phase in cross section of polyurethane elastomer and area ratio of matrix phase/domain phase]
Using a section with a thickness of about 800 nm prepared using a cryomicrotome, the cross section of the polyurethane elastomer was observed under the following conditions with a scanning probe microscope (SPM) (trade name: S-Image, manufactured by Hitachi High-Tech Science). .
・Measurement mode: VE-DFM (Viscoelastic Dynamic Force Mode)
・Cantilever: SI-DF3 (spring constant = 1.9 N/m)
・Scanning area: 50 μm square ・Operating frequency: 0.3 to 0.5 Hz
SPM image analysis software SPIP (Scanning Probe Image Processor, manufactured by Image Metrology) was used to detect the domain phase region using the grain analysis module, and the average diameter of the domain phase and the matrix phase/domain phase were determined. The area ratio was obtained.

[Evaluation 7: Confirmation and Analysis of Matrix Phase and Domain Phase in Cross Section of Polyurethane Elastomer (Examples 1 to 12)]
Mapping measurement was performed on a section prepared using a microtome from a sheet-like polyurethane elastomer having a thickness of 2 mm using a three-dimensional microscopic laser Raman spectrometer (trade name: Nanofinder 30, manufactured by Tokyo Instruments Co., Ltd.). The measurement mode was EM, 60×60 points were measured at intervals of 500 nm, and integral images of 0 to 400 cm ⁻¹ were obtained. From the integral image obtained, it was confirmed that a matrix phase and a plurality of domain phases were dispersed in the matrix phase inside the sheet. Also, the matrix phase and the domain phase were clearly separated.
Next, the Raman spectra of the matrix phase and domain phase were measured from the integrated image. The measurement was carried out with a light source of Nd:YVO4 (wavelength of 532 nm), a laser intensity of 240 μW, an objective lens of 100×, a diffraction grating of 300 gr/mm, a pinhole diameter of 100 μm, an exposure time of 30 seconds, and an integration count of 1. rice field. From the obtained Raman spectrum, it was confirmed that the matrix phase contained a structure derived from polycarbonate urethane and the domain contained a structure derived from polyether polyol.

[Example 1]
<Preparation of urethane prepolymer UP1>
31.9 parts by mass of polyol A-1, 1.0 parts by mass of polyisocyanate B-1, and 500 ppm of curing catalyst C-1 are uniformly mixed and heated at a temperature of 100 ° C. for 24 hours to remove the terminal synthesized polyols with isocyanate groups. 59.2 parts by mass of polyol A-5 was mixed into this and heated at a temperature of 100° C. for 4 hours to produce a urethane prepolymer UP1.
<Urethane elastomer No. Synthesis of 1>
92.1 parts by mass of the urethane prepolymer UP1, 1.7 parts by mass of B-1, 2.5 parts by mass of B-2, and 3.7 parts by mass of B-3 are mixed, and a rotation-revolution type Using a vacuum stirring and defoaming mixer (product name: V-mini300, manufactured by EME), the mixture was stirred for 2 minutes at a revolution speed of 1600 rpm until homogeneous. Thus, a mixture for forming a polyurethane elastomer according to this example was obtained. Next, the polyurethane elastomer-forming mixture was preheated to a temperature of 130° C., poured into a mold for producing a 2 mm thick sheet lightly coated with a release agent, and cured by heating at a temperature of 130° C. for 2 hours. Next, the cured product was removed from the mold and post-cured at a temperature of 80° C. for 2 days to form a sheet-shaped polyurethane elastomer No. 2 having a thickness of 2 mm. got 1.

[Example 2]
<Preparation of urethane prepolymer UP2>
13.5 parts by mass of polyol A-1, 26.9 parts by mass of polyol A-2, 4.0 parts by mass of polyisocyanate B-1, and 500 ppm of curing catalyst C-1 are uniformly mixed and heated to 100 ° C. A polyol having terminal isocyanate groups was synthesized by heating for 24 hours at . 49.4 parts by mass of polyol A-5 was mixed into this and heated at a temperature of 100° C. for 4 hours to produce urethane prepolymer UP2.
<Polyurethane Elastomer No. Synthesis of 2>
93.8 parts by mass of the urethane prepolymer UP2, 2.5 parts by mass of B-2, and 3.7 parts by mass of B-3 were mixed, and a revolution speed of 1600 rpm was applied using a revolution-type vacuum stirring and defoaming mixer. A mixture for forming a polyurethane elastomer was obtained by stirring for 2 minutes until the conditions were homogeneous. Next, polyurethane elastomer No. 1 was prepared in the same manner as in Example 1, except that this polyurethane elastomer-forming mixture was used. got 2.

[Example 3]
<Preparation of urethane prepolymer UP3>
35.6 parts by mass of polyol A-2, 4.9 parts by mass of polyisocyanate B-1, and 500 ppm of curing catalyst C-1 are uniformly mixed and heated at a temperature of 100 ° C. for 24 hours to remove the terminal synthesized polyols with isocyanate groups. Into this, 53.3 parts by mass of polyol A-5 was mixed, and the mixture was heated and stirred at a temperature of 100° C. for 4 hours to produce urethane prepolymer UP3.
<Polyurethane Elastomer No. Synthesis of 3>
93.8 parts by mass of the urethane prepolymer UP3, 2.5 parts by mass of B-2, and 3.7 parts by mass of B-3 are mixed, and the revolution speed is changed using a revolution-type vacuum stirring and defoaming mixer. The mixture was stirred at 1600 rpm for 2 minutes until homogeneous to obtain a mixture for forming a polyurethane elastomer. Next, polyurethane elastomer No. 1 was prepared in the same manner as in Example 1, except that the mixture for forming polyurethane elastomer was used. got 3.

[Example 4]
<Preparation of urethane prepolymer UP4>
18.0 parts by mass of polyol A-1, 0.6 parts by mass of polyisocyanate B-1, and 500 ppm of curing catalyst C-1 are uniformly mixed and heated at a temperature of 100 ° C. for 24 hours to remove the terminal synthesized polyols with isocyanate groups. 72.1 parts by mass of polyol A-5 was mixed into this and heated at a temperature of 100° C. for 4 hours to produce urethane prepolymer UP4.
<Polyurethane Elastomer No. Synthesis of 4>
93.7 parts by mass of the urethane prepolymer, 3.1 parts by mass of B-1, and 2.5 parts by mass of B-2 and 3.7 parts by mass of B-3 were mixed and subjected to a rotation-revolution vacuum Using a stirring and defoaming mixer (product name: V-mini300, manufactured by EME), the mixture was stirred for 2 minutes at a revolution speed of 1600 rpm until it became homogeneous, to obtain a mixture for forming a polyurethane elastomer. Next, polyurethane elastomer No. 1 was prepared in the same manner as in Example 1, except that this polyurethane elastomer-forming mixture was used. Got 4.

[Example 5]
Urethane prepolymer UP5 was prepared in the same manner as in Example 1, except that polyol A-6 was used instead of polyol A-5. Polyurethane elastomer No. 1 was prepared in the same manner as in Example 1 except that urethane prepolymer UP5 was used. Got 5.

[Example 6]
Urethane prepolymer UP6 was prepared in the same manner as in Example 1, except that polyol A-7 was used instead of polyol A-5. Polyurethane elastomer No. 1 was prepared in the same manner as in Example 1, except that urethane prepolymer UP6 was used. got 6.

[Example 7]
Urethane prepolymer UP7 was prepared in the same manner as in Example 1, except that polyol A-8 was used instead of polyol A-5. Polyurethane elastomer No. 1 was prepared in the same manner as in Example 1 except that urethane prepolymer UP7 was used. got 7.

[Example 8]
<Preparation of urethane prepolymer UP8>
32.5 parts by mass of polyol A-1, 1.0 parts by mass of polyisocyanate B-1, and 500 ppm of curing catalyst C-1 are uniformly mixed and heated at a temperature of 100 ° C. for 24 hours to remove the terminal synthesized polyols with isocyanate groups. 56.8 parts by mass of polyol A-5 was mixed into this and heated at a temperature of 100° C. for 4 hours to produce urethane prepolymer UP8.
<Polyurethane Elastomer No. Synthesis of 8>
90.2 parts by mass of the urethane prepolymer UP8 and 0.8 parts by mass of D-1 were mixed. Next, 2.8 parts by mass of B-1, 2.5 parts by mass of B-2, and 3.7 parts by mass of B-3 are mixed, and a rotation-revolution vacuum stirring and defoaming mixer (product name: V -mini300, manufactured by EME), the mixture was stirred for 2 minutes at a revolution speed of 1600 rpm until homogeneous, to obtain a mixture for forming a polyurethane elastomer. Next, polyurethane elastomer No. 8 was obtained in the same manner as in Example 1 except that this polyurethane elastomer-forming mixture was used.

[Example 9]
<Preparation of urethane prepolymer UP9>
35.9 parts by mass of polyol A-3, 4.1 parts by mass of polyisocyanate B-1, and 500 ppm of curing catalyst C-1 are uniformly mixed and heated at a temperature of 100 ° C. for 4 hours to remove the terminal synthesized polyols with isocyanate groups. Into this, 53.8 parts by mass of polyol A-5 was mixed and heated with stirring at a temperature of 100° C. for 4 hours to prepare urethane prepolymer UP9.
<Polyurethane Elastomer No. Synthesis of 9>
93.8 parts by mass of the urethane prepolymer UP9, 2.5 parts by mass of B-2, and 3.7 parts by mass of B-3 are mixed, and the revolution speed is adjusted using a revolution-type vacuum stirring and defoaming mixer. The mixture was stirred at 1600 rpm for 2 minutes until homogeneous to obtain a mixture for forming a polyurethane elastomer. Next, polyurethane elastomer No. 1 was prepared in the same manner as in Example 1, except that this polyurethane elastomer-forming mixture was used. got 9.

[Example 10]
<Preparation of urethane prepolymer UP10>
35.6 parts by mass of polyol A-4, 4.9 parts by mass of polyisocyanate B-1, and 500 ppm of curing catalyst C-1 are uniformly mixed and heated at a temperature of 100 ° C. for 4 hours to remove the terminal synthesized polyols with isocyanate groups. 53.3 parts by mass of polyol A-5 was mixed with this, and the mixture was heated and stirred at a temperature of 100° C. for 4 hours to produce urethane prepolymer UP10.
<Polyurethane Elastomer No. Synthesis of 10>
93.8 parts by mass of the urethane prepolymer UP10, 2.5 parts by mass of B-2, and 3.7 parts by mass of B-3 are mixed, and the revolution speed is adjusted using a revolution-type vacuum stirring and defoaming mixer. The mixture was stirred at 1600 rpm for 2 minutes until homogeneous to obtain a mixture for forming a polyurethane elastomer. Next, polyurethane elastomer No. 1 was prepared in the same manner as in Example 1, except that this polyurethane elastomer-forming mixture was used. Got 10.

[Example 11]
<Preparation of urethane prepolymer UP11>
31.9 parts by mass of polyol A-1, 0.3 parts by mass of polyisocyanate B-1, and 500 ppm of curing catalyst C-1 are uniformly mixed and heated at a temperature of 100 ° C. for 24 hours to remove the terminal synthesized polyols with isocyanate groups. 59.2 parts by mass of polyol A-5 was mixed into this and heated at a temperature of 100° C. for 4 hours to produce urethane prepolymer UP11.
<Polyurethane Elastomer No. Synthesis of 11>
92.1 parts by mass of the urethane prepolymer UP11, 2.4 parts by mass of B-1, 2.5 parts by mass of B-2, and 3.7 parts by mass of B-3 are mixed, and a rotation-revolution type Using a vacuum stirring and defoaming mixer (product name: V-mini300, manufactured by EME), the mixture was stirred for 2 minutes at a revolution speed of 1600 rpm until it became homogeneous, to obtain a mixture for forming a polyurethane elastomer. Next, polyurethane elastomer No. 1 was prepared in the same manner as in Example 1, except that this polyurethane elastomer-forming mixture was used. 11 was obtained.

[Example 12]
<Preparation of urethane prepolymer UP12>
31.9 parts by mass of polyol A-1, 1.5 parts by mass of polyisocyanate B-1, and 500 ppm of curing catalyst C-1 are uniformly mixed and heated at a temperature of 100 ° C. for 24 hours to remove the terminal synthesized polyols with isocyanate groups. 59.2 parts by mass of polyol A-5 was mixed into this and heated at a temperature of 100° C. for 4 hours to produce urethane prepolymer UP12.
<Polyurethane Elastomer No. Synthesis of 12>
92.1 parts by mass of the urethane prepolymer UP12, 1.2 parts by mass of B-1, 2.5 parts by mass of B-2, and 3.7 parts by mass of B-3 are mixed, and a rotation-revolution type Using a vacuum stirring and defoaming mixer (product name: V-mini300, manufactured by EME), the mixture was stirred for 2 minutes at a revolution speed of 1600 rpm until it became homogeneous, to obtain a mixture for forming a polyurethane elastomer. Next, polyurethane elastomer No. 1 was prepared in the same manner as in Example 1, except that this polyurethane elastomer-forming mixture was used. 12 was obtained.

[Comparative Example 1]
87.7 parts by weight of polyol A-5, 4.5 parts by weight of B-1, 3.1 parts by weight of B-2, 4.7 parts by weight of B-3, and 500 ppm of curing catalyst C-1 and stirred for 2 minutes at a revolution speed of 1600 rpm until homogeneous using a rotation-revolution type vacuum agitating and defoaming mixer to obtain a mixture for forming a polyurethane elastomer. Next, polyurethane elastomer No. 1 was prepared in the same manner as in Example 1, except that this polyurethane elastomer-forming mixture was used. C1 was obtained.

[Comparative Example 2]
35.1 parts by weight of polyol A-2, 52.6 parts by weight of polyol A-9, 4.6 parts by weight of B-1, 3.1 parts by weight of B-2, 4.7 parts by weight of B- 3 and 500 ppm of curing catalyst C-1 were mixed, and stirred for 2 minutes using a rotation-revolution vacuum stirring and defoaming mixer at a revolution speed of 1600 rpm until homogeneous, to obtain a mixture for forming a polyurethane elastomer. . Next, polyurethane elastomer No. 1 was prepared in the same manner as in Example 1, except that this polyurethane elastomer-forming mixture was used. C2 was obtained.
The evaluation results of the polyurethane elastomers according to Examples 1-12 and Comparative Examples 1-2 are shown in Tables 1-1 and 1-2.

<Structure of Polyurethane Elastomer>
FIG. 2 shows representative temperature-tan δ curves (Example 1, Comparative Examples 1 and 2) obtained by viscoelasticity measurement in the results shown in Tables 1-1 and 1-2. As shown in FIG. 2, in Example 1, two tan δ peak temperatures (glass transition temperatures) were confirmed in the range of -80 to 10 ° C., whereas in Comparative Examples 1 and 2, Only one peak temperature was identified. Also, regarding the appearance of the polyurethane elastomer, the polyurethane elastomer Nos. 1-12 were opaque. On the other hand, polyurethane elastomer Nos. according to Comparative Examples 1 and 2. C1 and C2 had high transparency.
Polyurethane elastomer No. 1 according to Example 1; The tan δ peak temperatures observed in No. 1 are −65° C. and −22° C., and the polyether polyurethane derived from raw material A-1 (polypropylene glycol) and the polycarbonate polyurethane derived from raw material A-3 (polycarbonate polyol) (comparative (see Example 1)). That is, polyurethane elastomer No. 1 obtained in Example 1; Regarding No. 1, it was found that the polycarbonate-containing polyurethane and the polyether-containing polyurethane were hardly compatible with each other, and were clearly phase-separated. Moreover, the polyurethane elastomer No. shown in FIG. From the viscoelastic image of the cross section of No. 1 by a microviscoelastic microscope (VE-AFM), a clear phase separation structure of the domain phase and the matrix phase was observed. In addition, the domain phase with high black density in the viscoelastic image is derived from the ether structure (general formula (2)) in the polyurethane elastomer with low hardness, and the matrix phase with low black density is It was shown that the carbonate structure in the high-hardness polyurethane elastomer (derived from the general formula (1).
Polyurethane elastomer Nos. according to Examples 2-12. Polyurethane elastomer Nos. 2 to 12 are also used. As in No. 1, two peaks due to glass transition were observed in the temperature range of -80 to +20°C in the temperature-loss tangent (tan δ) curve obtained by dynamic viscoelasticity measurement (DMA). Also, polyurethane elastomer No. A distinct phase separation structure between the domain phase and the matrix phase was observed from the viscoelastic images of each of the sections 2 to 12 by a microviscoelastic microscope (VE-AFM). In addition, the domain phase with high black density in the viscoelastic image is derived from the ether structure (general formula (2)) in the polyurethane elastomer with low hardness, and the matrix phase with low black density is It was shown that the carbonate structure in the high-hardness polyurethane elastomer (derived from the general formula (1).
On the other hand, the polyurethane elastomer No. 2 obtained in Comparative Example 2; For C2, highly transparent appearance and cross-sectional observation results were obtained. Furthermore, in addition to these, only one tan δ peak was observed at −53° C., which indicates that the polyether polyurethane and the polyester polyurethane are almost completely compatible and do not have a phase separation structure. confirmed.

<Physical properties of polyurethane elastomer>
Polyurethane elastomer No. 1 according to Example 1; 1 is the single polycarbonate polyurethane No. 1 obtained in Comparative Example 1; Compared to C1, the hardness was significantly reduced, and a reduction in the dynamic friction coefficient was also observed. In addition, the polyurethane elastomer obtained in Example 1 had good abrasion resistance and exhibited a high elastic deformation work rate (low compression set) comparable to silicone elastomers.
On the other hand, the polyurethane elastomer No. 2 obtained in Comparative Example 2; Although C2 has low hardness, it has low wear resistance, and when evaluating friction characteristics, the stainless steel (SUS304) ball indenter floats and bounces due to surface roughness due to wear, and the dynamic friction coefficient is measured. was difficult. In addition, compared with Examples 1 and 2, the elastic deformation work rate was low, and the compression set tended to deteriorate.
From the above results, it has been clarified that the polyurethane elastomer according to the present disclosure exhibits an excellent effect of realizing low hardness, good frictional properties, and low compression set. These effects are believed to be due to the phase-separated structure in which the polycarbonate polyurethane is arranged in the matrix phase and the polyether polyurethane is arranged in the domain phase.

Claims (9)

A polyurethane elastomer,
Having a first repeating structural unit represented by general formula (1) and a second repeating structural unit represented by general formula (2),
comprising a matrix phase and a domain phase dispersed in the matrix phase;

the matrix phase comprises the first repeating structural unit;
A polyurethane elastomer characterized in that said domain phase comprises said second repeating structural unit:

(R ₁ represents an alkylene group having 3 to 12 carbon atoms.)

(R ₂ represents an alkylene group having 3 to 6 carbon atoms). A temperature-loss tangent (tan δ) curve obtained by dynamic viscoelasticity measurement (DMA) of the polyurethane elastomer has at least two peaks due to glass transition observed in a temperature range of -80 to +20°C. Polyurethane elastomer according to. 3. The polyurethane elastomer according to claim 1, wherein at least one of the glass transition peaks is observed in a temperature range of -50° C. or lower and at least one is observed in a temperature range of -40° C. or higher. The glass transition according to any one of claims 1 to 3, wherein at least one of the glass transition peaks is observed in a temperature range of -60°C or lower, and at least one is observed in a temperature range of -35°C or higher. polyurethane elastomer. The polyurethane elastomer according to any one of claims 1 to 4, wherein the area ratio of said matrix phase/ said domain phase is 40/60 to 90/10. The polyurethane elastomer according to any one of claims 1 to 5, wherein the domain phase has an average diameter in the range of 0.2 to 30 µm. The polyurethane elastomer according to any one of claims 1 to 6, wherein R ₁ in the first repeating structural unit is an alkylene group having 3 to 9 carbon atoms. The polyurethane elastomer according to any one of claims 1 to 7, wherein R ₂ in the second repeating structural unit is an alkylene group containing a branched structure having 3 to 5 carbon atoms. A method for producing the polyurethane elastomer according to any one of claims 1 to 8,
(i) reacting a first polyether having at least one isocyanate group with a first polycarbonate polyol having at least two hydroxyl groups to obtain a urethane prepolymer having at least two hydroxyl groups;
(ii) droplets comprising at least a portion of said urethane prepolymer dispersed in a second polycarbonate polyol to obtain a dispersion; and (iii) said dispersion and at least two isocyanate groups; and then reacting the urethane prepolymer, the second polycarbonate polyol, and the polyisocyanate in the polyurethane elastomer-forming mixture to form the polyurethane elastomer. A method for producing a polyurethane elastomer, comprising the step of:

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