JP7732609B2 - Polycarbonate diol, urethane resin and coating agent - Google Patents

Description

This disclosure relates to polycarbonate diols, urethane resins, and coating agents.

Polycarbonate polyols are useful as raw materials for producing urethane resins (also called polyurethane resins) by reacting them with polyisocyanate compounds, and are also useful as raw materials for adhesives, paints, etc.
As a polycarbonate diol, which is a type of polycarbonate polyol, a polycarbonate diol using 1,6-hexanediol alone as a diol component is generally used. However, such a polycarbonate diol is crystalline and therefore solid at room temperature, which makes it difficult to handle.

To solve these problems, it has been proposed to produce polycarbonate diol using two or more types of diols. For example, Japanese Patent Laid-Open Publication No. 63-182337 (Patent Document 1) discloses a polycarbonate diol synthesized using 1,9-nonanediol and 2-methyl-1,8-octanediol as diol components.

Japanese Unexamined Patent Publication No. 182337/1983

However, when polycarbonate diols are used in production equipment involving flow, there is a problem that it is difficult to achieve both moldability and viscosity stability. Even with the polycarbonate diols described in Patent Document 1, there is still room for improvement in achieving both moldability and viscosity stability.
Therefore, an object of one aspect of the present disclosure is to provide a polycarbonate diol that has both moldability and viscosity stability at 25° C. Another object of the present disclosure is to provide a urethane resin and a coating agent obtained from the polycarbonate diol.

The present disclosure provides the following aspects:

[1] A polycarbonate diol containing a repeating unit (A) represented by the following formula (A) and having a terminal hydroxyl group:
90 to 100 mol % of the repeating units (A) are repeating units (B) represented by the following formula (B) and/or repeating units (C) represented by the following formula (C),
The polycarbonate diol contains a polycarbonate diol (D) represented by the following formula (D):
The number average molecular weight calculated from the hydroxyl value of the polycarbonate diol is 300 to 2800 g/mol,
In the LC spectrum measured for the polycarbonate diol, when the number of repeating units of the polycarbonate diol (D) corresponding to the peak of the molecular weight closest to the number average molecular weight calculated from the hydroxyl value of the polycarbonate diol is _X0 , there are 2 to 7 consecutive peaks, including the peak having the number of repeating units _X0 , whose peak area ratios are 0.90 to 1.10 relative to the area of the peak having the number of repeating units _X0 ,
A polycarbonate diol having a ratio [η ₁₀₀₀ /η ₁ ] of viscosity η ₁₀₀₀ at a shear rate of 1000 s ^-1 and a temperature of 25°C to viscosity η ₁ at a shear rate of 1 s ^-1 and a temperature of 25°C of 0.40 to 0.80.

(In formula (A), R represents a divalent aliphatic or alicyclic hydrocarbon having 2 to 15 carbon atoms.)

(In formula (D),
R ¹ represents *-(CH ₂ ) ₉ -* or *-CH ₂ CH(CH ₃ )CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ -*;
In the formula, * at both ends indicates the bonding sites with the two oxygen atoms bonded to both ends of ^R1 , respectively.
q represents an integer of 1 or more, and multiple R ^1s may be the same or different.

[2] The polycarbonate diol according to [1], wherein the amount of the repeating unit (B) is 20 to 100 mol % based on the total amount of the repeating unit (A).

[3] The polycarbonate diol according to [1] or [2], wherein the amount of the repeating unit (B) is 20 to 100 mol % based on the total amount of the repeating unit (B) and the repeating unit (C).

[4] The polycarbonate diol according to any one of [1] to [3], wherein all of the repeating units (A) are the repeating units (B) and/or the repeating units (C).

[5] The polycarbonate diol according to any one of [1] to [4], wherein 90 to 100 mol % of the polycarbonate diol is the polycarbonate diol (D).

[6] A urethane resin containing a reaction product of the polycarbonate diol described in any one of [1] to [5] and an isocyanate.

[7] A coating agent containing the urethane resin described in [6].

According to one aspect of the present disclosure, a polycarbonate diol can be provided that exhibits both moldability at 25°C and viscosity stability. Furthermore, according to another aspect of the present disclosure, a urethane resin and a coating agent obtained from the polycarbonate diol can be provided.

FIG. 1 shows the LC spectrum of the polycarbonate diol obtained in Example 1. 1 is a graph showing the relationship between shear rate and viscosity of a polymer.

Embodiments of the present disclosure are described in detail below. In this specification, numerical ranges indicated using "to" indicate ranges that include the numerical values before and after "to" as the minimum and maximum values, respectively. The minimum or maximum value of a numerical range indicated using "to" can be arbitrarily combined with the maximum or minimum value of another numerical range indicated using "to". Individually stated upper and lower limit values can also be arbitrarily combined.

<Polycarbonate diol>
A polycarbonate diol according to one embodiment of the present disclosure is a polycarbonate diol containing a repeating unit (A) represented by the following formula (A) and having a terminal hydroxyl group:
90 to 100 mol % of the repeating units (A) are repeating units (B) represented by the following formula (B) and/or repeating units (C) represented by the following formula (C),
The polycarbonate diol contains a polycarbonate diol (D) represented by the following formula (D):
The number average molecular weight calculated from the hydroxyl value of the polycarbonate diol is 300 to 2800,
In the LC spectrum measured for the polycarbonate diol, when the number of repeating units of the polycarbonate diol (D) corresponding to the peak of the molecular weight closest to the number average molecular weight calculated from the hydroxyl value of the polycarbonate diol is _X0 , there are 2 to 7 consecutive peaks, including the peak having the number of repeating units _X0 , whose peak area ratios are 0.90 to 1.10 relative to the area of the peak having the number of repeating units _X0 ,
The polycarbonate diol has a ratio [η ₁₀₀₀ /η ₁ ] of viscosity η ₁₀₀₀ at a shear rate ^of 1000 s ^-1 and a temperature of 25°C to viscosity η ₁ at a shear rate of 1 s -1 and a temperature of 25°C of 0.40 to 0.80.

(In formula (A), R represents a divalent aliphatic or alicyclic hydrocarbon having 2 to 15 carbon atoms.)

(In formula (D),
R ¹ represents *-(CH ₂ ) ₉ -* or *-CH ₂ CH(CH ₃ )CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ -*;
In the formula, * at both ends indicates the bonding sites with the two oxygen atoms bonded to both ends of ^R1 , respectively.
q represents an integer of 1 or more, and multiple R ^1s may be the same or different.

In this disclosure, "the peak of molecular weight closest to the number average molecular weight calculated from the hydroxyl value of the polycarbonate diol" means, among the peaks of molecular weights calculated based on the number of repeating units of the polycarbonate diol (D), the peak of molecular weight with the smallest absolute difference from the number average molecular weight calculated from the hydroxyl value of the polycarbonate diol. If there are two peaks of molecular weight with the smallest absolute difference from the number average molecular weight calculated from the hydroxyl value of the polycarbonate diol, the peak with the smallest molecular weight is used.

The polycarbonate diol of one embodiment of the present disclosure is a polycarbonate diol containing the repeating unit (A) and having a terminal hydroxyl group. In the formula (A), R is a divalent aliphatic or alicyclic hydrocarbon having 2 to 15 carbon atoms. The divalent aliphatic hydrocarbon group may be linear or branched. Furthermore, multiple R groups present in the polycarbonate diol may be the same or different.

The divalent linear aliphatic hydrocarbon group represented by R has 2 to 15 carbon atoms, preferably 3 to 12, more preferably 4 to 10, and particularly preferably 6 to 9.

Specific examples of the divalent linear aliphatic hydrocarbon group having 2 to 15 carbon atoms represented by R include, but are not limited to, ethylene, propylene (trimethylene), butylene (tetramethylene), pentylene (pentamethylene), hexylene (hexamethylene), heptylene (heptamethylene), octylene (octamethylene), and nonylene (nonamethylene). Among these, from the standpoint of versatility, propylene, butylene, pentylene, hexylene, and nonylene are preferred.

The divalent branched aliphatic hydrocarbon group represented by R has 3 to 15 carbon atoms, preferably 4 to 12, more preferably 5 to 10, and particularly preferably 6 to 9.

Specific examples of the divalent branched aliphatic hydrocarbon group represented by R include, but are not limited to, an isopropylene group, an isobutylene group, a tert-butylene group, an isopentylene group, a 2,2-dimethylpropylene group, an isohexylene group, a 3-methylpentylene group, an isoheptylene group, an isooctylene group, and a 2-methyloctylene group. Among these, from the standpoint of versatility, an isopentylene group, an isohexylene group, a 3-methylpentylene group, or a 2-methyloctylene group is preferred.

The divalent alicyclic hydrocarbon group represented by R has 3 to 15 carbon atoms, preferably 4 to 12, and more preferably 6 to 9.

Specific examples of the divalent alicyclic hydrocarbon group represented by R include, but are not limited to, a cyclopropylene group, a cyclobutylene group, a cyclopentylene group, a cyclohexylene group, and a cycloheptylene group. Among these, from the viewpoint of versatility, a cyclopentylene group or a cyclohexylene group is preferred.

Among these divalent aliphatic or alicyclic hydrocarbons having 2 to 15 carbon atoms, R is preferably a divalent linear aliphatic hydrocarbon group having 3 to 9 carbon atoms or a divalent branched aliphatic hydrocarbon group having 3 to 9 carbon atoms, more preferably a divalent linear aliphatic hydrocarbon group having 6 to 9 carbon atoms or a divalent branched aliphatic hydrocarbon group having 6 to 9 carbon atoms, and even more preferably a nonylene group or a 2-methyloctylene group.

It is preferable that 90 to 100 mol % of the repeating unit (A) is the repeating unit (B) and/or the repeating unit (C) (preferably the repeating unit (B) and the repeating unit (C)), 95 to 100 mol % of the repeating unit (A) is the repeating unit (B) and/or the repeating unit (C) (more preferably the repeating unit (B) and the repeating unit (C)), and it is even more preferable that all of the repeating unit (A) is the repeating unit (B) and/or the repeating unit (C) (even more preferably the repeating unit (B) and the repeating unit (C)). When the proportion of the repeating unit (B) and/or the repeating unit (C) is within the above range, a polycarbonate diol that has good handleability and that combines moldability and viscosity stability at 25°C tends to be easily obtained.

The amount of the repeating unit (B) is preferably 20 to 100 mol%, more preferably 30 to 99 mol%, even more preferably 40 to 98 mol%, particularly preferably 50 to 95 mol%, and most preferably 65 to 90 mol%, relative to the total amount of the repeating unit (A). When the ratio is within this range, the resulting polycarbonate diol tends to be liquid at 25°C and has excellent handleability.

The amount of the repeating unit (B) is preferably 20 to 100 mol%, more preferably 30 to 99 mol%, even more preferably 40 to 98 mol%, particularly preferably 50 to 95 mol%, and most preferably 65 to 90 mol%, based on the total amount of the repeating unit (B) and the repeating unit (C). When the ratio is within this range, the resulting polycarbonate diol tends to be liquid at 25°C and have excellent handleability.

The polycarbonate diol of one embodiment of the present disclosure includes polycarbonate diol (D) represented by formula (D).

In the formula (D), R ¹ represents *-(CH ₂ ) ₉ -* or *-CH ₂ CH(CH ₃ )CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ -*, and the *s at both ends in the formula represent bonding sites with the two oxygen atoms bonded to both ends of R ¹ , respectively, and q represents an integer of 1 or more, preferably 1 to 23, more preferably 2 to 16, and even more preferably 3 to 11. Furthermore, multiple R ^1s may be the same or different.

Among such polycarbonate diols (D), the polycarbonate diols (D) containing a 1,9-nonylene group (1,9-nonanediyl group) and a 2-methyl-1,8-octylene group (2-methyloctane-1,8-diyl group) as R ¹ , i.e., containing two or more kinds of alkanediyl groups, tend to be liquid at 25°C and to easily achieve both moldability and viscosity stability at 25°C.

Furthermore, in the polycarbonate diol (D) containing two or more kinds of alkanediyl groups, from the viewpoint that it is liquid at 25°C and easily achieves both moldability and viscosity stability at 25°C, the ratio of the number of moles of 2-methyl-1,8-octylene groups to the total number of moles of alkanediyl groups contained as ^R1 in the polycarbonate diol (D) (the total number of moles of 1,9-nonylene groups and 2-methyl-1,8-octylene groups) is preferably 0.20 to 1.00, more preferably 0.30 to 0.99, even more preferably 0.40 to 0.98, still more preferably 0.50 to 0.95, particularly preferably 0.60 to 0.93, and most preferably 0.65 to 0.90.

The polycarbonate diol of one embodiment of the present disclosure is liquid at 25°C. From the viewpoint of easily achieving both moldability and viscosity stability at 25°C, it is preferable that 90 to 100 mol% of the polycarbonate diol (D) be the polycarbonate diol (D), more preferably 95 to 100 mol% of the polycarbonate diol (D), and particularly preferably that all of the polycarbonate diol (D) be the polycarbonate diol (D).

Furthermore, the hydroxyl value of the polycarbonate diol of one embodiment of the present disclosure is preferably 30 to 350 mgKOH/g, more preferably 40 to 215 mgKOH/g, even more preferably 43 to 150 mgKOH/g, even more preferably 45 to 120 mgKOH/g, particularly preferably 50 to 105 mgKOH/g, and most preferably 55 to 100 mgKOH/g. The hydroxyl value of the polycarbonate diol may be 60 mgKOH/g or more, 65 mgKOH/g or more, 70 mgKOH/g or more, 75 mgKOH/g or more, 80 mgKOH/g or more, or 85 mgKOH/g or more, or 90 mgKOH/g or less, 85 mgKOH/g or less, 80 mgKOH/g or less, 75 mgKOH/g or less, 70 mgKOH/g or less, 65 mgKOH/g or less, or 60 mgKOH/g or less. The hydroxyl value of the polycarbonate diol refers to the number of milligrams (mg) of potassium hydroxide equivalent to the hydroxy groups in 1 g of polycarbonate diol, and can be measured in accordance with JIS K1557-1.

Furthermore, the number average molecular weight calculated from the hydroxyl value of the polycarbonate diol of one embodiment of the present disclosure is preferably 300 to 2,800 g/mol, more preferably 500 to 2,600 g/mol, even more preferably 800 to 2,500 g/mol, particularly preferably 900 to 2,300 g/mol, and most preferably 1,000 to 2,000 g/mol. The number average molecular weight calculated from the hydroxyl value of the polycarbonate diol may be 1200 g/mol or more, 1300 g/mol or more, 1450 g/mol or more, 1600 g/mol or more, 1700 g/mol or more, 1800 g/mol or more, or 1900 g/mol or more, or may be 1900 g/mol or less, 1800 g/mol or less, 1700 g/mol or less, 1600 g/mol or less, 1450 g/mol or less, or 1300 g/mol or less.

In the polycarbonate diol of one embodiment of the present disclosure, when the number of repeating units of the polycarbonate diol (D) corresponding to the peak of the molecular weight closest to the number average molecular weight ₍ absolute molecular weight) calculated from the hydroxyl value of the polycarbonate diol is _X0 in a measured LC spectrum, the polycarbonate diol has 2 to ₇ consecutive peaks, preferably 3 to 6 consecutive peaks, and particularly preferably 4 to 5 consecutive peaks, in which the peak area ratio [S(X)/S( _X0 ), S(X) is the area value of the peak where the number of repeating units of the polycarbonate diol (D) is X _{] is 0.90 to 1.10, including the peak where the number of repeating units is X0} . When the number of consecutive peaks having the peak area ratio [S(X)/S( _X0 )] of 0.90 to 1.10, including the peak where the number of repeating units is _X0, is equal to or greater than the lower limit, a polycarbonate diol with excellent moldability at 25° C. tends to be easily obtained. When the number of consecutive peaks having the peak area ratio [S(X)/S( _X0 )] of 0.90 to 1.10, including the peak where the number of repeating units is _X0 , is equal to or less than the upper limit, a polycarbonate diol with excellent viscosity stability at 25° C. tends to be easily obtained. Furthermore, when there is a peak where the number of repeating units is X= _X0 -α (α is a positive integer: 1, 2, 3, 4, ...), the peak has the peak area ratio [S(X)/S( _X0 )] of 1.10 or more, a polycarbonate diol with even better moldability at 25° C. tends to be easily obtained.

The peak area ratio [S(X)/S( _X0 )] in the LC spectrum of the polycarbonate diol can be determined by the following method. That is, in the LC spectrum of the polycarbonate diol, the peak having the smallest absolute difference from the number average molecular weight calculated from the hydroxyl value of the polycarbonate diol is determined as the peak having the molecular weight closest to the number average molecular weight calculated from the hydroxyl value of the polycarbonate diol, and the number _X0 of repeating units of the polycarbonate diol (D) corresponding to this peak is determined. Note that when there are two peaks having the smallest absolute difference from the number average molecular weight calculated from the hydroxyl value of the polycarbonate diol, the peak having the smaller molecular weight is used. Next, in the LC spectrum, the area value S(X) of each peak (X represents the number of repeating units of the polycarbonate diol (D), and X = ..., X ₀ -2, X ₀ -1, X ₀ , X ₀ +1, X ₀ +2, ...) is determined, and the area value ratio of each peak to the area value S(X ₀ ) of the peak where the number of repeating units is X ₀ , [S(X)/S(X ₀ )], is calculated. Note that X and X ₀ are the numbers of repeating units of the polycarbonate diol (D) at the peak having a molecular weight of 300 to 3400 g/mol, based on the detection limit of LC measurement, i.e., integers in the range of 1 to 17.

The correspondence between each peak obtained by LC measurement and the number X of repeating units of the polycarbonate diol (D) can be confirmed, for example, by performing MS measurement of each peak individually (apparatus: Bruker Daltonics microTOF, ion source: APCI, measurement mode: positive mode) and analyzing the main peak of the obtained spectrum.

The number of consecutive peaks having an area ratio [S(X)/S(X ₀ )] of 0.90 to 1.10 calculated in this way, including the peak having the number of repeating units X _0, is determined.

In general, the higher the molecular weight of a polymer, the more likely it is to exhibit good physical properties, but because it also has a high viscosity, it tends to be less moldable during injection molding. On the other hand, it is known that the viscosity of polymers decreases as the shear rate increases. Therefore, even if a polymer has a high viscosity at a low shear rate (close to static), if it has a low viscosity in its flow state during molding, i.e., at a high shear rate, it tends to exhibit good physical properties and is more likely to produce a polymer with excellent moldability.

For applications requiring flexibility, such as synthetic leather or artificial leather, polyols with high molecular weights are preferably used as raw materials for urethane resins in order to reduce the amount of urethane groups in the urethane resin.

In the present disclosure, the ratio [η 1000 /η _{1 ] of the viscosity η 1000 at a shear rate of 1000 s -1 and a temperature of 25° C. to the viscosity η 1 at} ^a shear rate of 1 s ^-1 and a temperature of 25° C. is used as an index of a polymer that exhibits such good physical properties and _has excellent moldability. The technical significance of this viscosity ratio [η ₁₀₀₀ /η _{1 ]} will be explained. As shown in Figure 2, the viscosity of a polymer decreases as the shear rate increases. However, if the viscosity becomes too low at high shear rates, that is, if the viscosity ratio [η ₁₀₀₀ /η ₁ ] becomes too small, although the moldability will be good, the viscosity will decrease rapidly near high shear rates, making it difficult to predict the amount of polymer discharged during molding and possibly reducing discharge stability. On the other hand, if the decrease in viscosity under high shear rate is too small, that is, if the viscosity ratio [ _η1000 / _η1 ] is around 1, the viscosity stability is good, but the viscosity does not decrease sufficiently, and molding processability may be poor. Therefore, in order to develop good physical properties of the polymer and to achieve both good molding processability and good viscosity stability (discharge stability), it is considered preferable that the viscosity ratio [ _η1000 / _η1 ] be within a specific range.

In the polycarbonate diol of one embodiment of the present disclosure, the ratio [η ₁₀₀₀ /η ₁ ] of the viscosity η ₁₀₀₀ at a shear rate of 1000 ^{s -1} and a temperature of 25° C. to the viscosity η ₁ at a shear rate of 1 s -1 and a temperature of 25° C. is preferably 0.40 to 0.80, more preferably 0.42 to 0.75, and even more preferably 0.45 to 0.70. When the viscosity ratio [η ₁₀₀₀ /η ₁ ] is equal to or greater than the lower limit, a rapid decrease in viscosity at a shear rate of around 1000 s ^-1 can be suppressed, which tends to make it easier to estimate the discharge amount of polycarbonate diol during molding. On the other hand, when the viscosity ratio [η ₁₀₀₀ /η ₁ ] is equal to or less than the upper limit, the viscosity is sufficiently decreased at a shear rate of around 1000 s ^-1 , which tends to result in excellent molding processability.

Furthermore, the viscosity η ₁ of the polycarbonate diol of one embodiment of the present disclosure at a shear rate of 1 s ⁻¹ and a temperature of 25° C. is preferably 20,000 to 80,000 mPa·s ⁻¹ , more preferably 25,000 to 70,000 mPa·s ⁻¹ , and even more preferably 30,000 to 60,000 mPa·s ⁻¹ . The viscosity η ₁ may be 35,000 mPa·s ⁻¹ or more, 37,500 mPa·s ⁻¹ or more, 40,000 mPa·s ⁻¹ or more, 42,500 mPa·s ⁻¹ or more, 45,000 mPa·s ⁻¹ or more, 47,500 mPa·s ⁻¹ or more, 50,000 mPa·s ⁻¹ or more, 52,500 mPa·s ⁻¹ or more, or 55,000 mPa·s ⁻¹ or more, and may be 57,500 mPa·s ⁻¹ or less, 55,000 mPa·s ⁻¹ or less, 52,500 mPa·s ⁻¹ or less, 50,000 mPa·s ⁻¹ or less, 47,500 mPa·s ⁻¹ or less, 45,000 mPa·s ⁻¹ or less, 42,500 mPa·s When the viscosity η ¹ is equal to or higher than the ^lower limit, a polycarbonate diol exhibiting good physical properties tends to be easily obtained, while when _{the viscosity η 1 is} equal to or lower than the ^upper limit, a polycarbonate diol having excellent moldability tends to be easily obtained.

Furthermore, the viscosity _η1000 of the polycarbonate diol of one embodiment of the present disclosure at a shear rate of 1000 s ⁻¹ and a temperature of 25° C. is preferably 8000 to 60000 mPa·s ⁻¹ , more preferably 10000 to 40000 mPa·s ⁻¹ , and even more preferably 20000 to 30000 mPa·s ⁻¹ . The viscosity _η1000 may be 22000 mPa·s ^{or more} , 23000 mPa·s ^{or more} , 24000 mPa·s ^{or more} , 25000 mPa·s ^{or more} , or 26000 mPa·s ^{or more} , and may be 27000 mPa·s ^{or less} , 26000 mPa·s ^or less, 25000 mPa·s ^{or less} , 24000 mPa·s ^{or less} , or 23000 ^{mPa·s or} less. When the viscosity _η1000 is equal to or more than the lower limit, a polycarbonate diol having excellent viscosity stability tends to be easily obtained, while when the viscosity _η1000 is equal to or less than the upper limit, a polycarbonate diol having excellent moldability tends to be easily obtained.

<Method for producing polycarbonate diol>
The polycarbonate diol of one embodiment of the present disclosure can be obtained, for example, by reacting a carbonate compound with a diol compound in the presence of a transesterification catalyst. Specifically, the polycarbonate diol can be obtained by heating a mixture containing the carbonate compound, the diol compound, and the transesterification catalyst to perform a reflux reaction (transesterification reaction) while removing alcohol derived from the carbonate compound from the reaction system. Therefore, the polycarbonate diol of one embodiment of the present disclosure may contain a transesterification catalyst.

(carbonate compounds)
The carbonate compound used in the production of the polycarbonate diol of one embodiment of the present disclosure is not particularly limited, but examples thereof include alkylene carbonate, dialkyl carbonate, diaryl carbonate, and the like.

Alkylene carbonates are not particularly limited, but examples include ethylene carbonate, trimethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, and 1,2-pentylene carbonate.

Dialkyl carbonates are not particularly limited, but examples include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, and dibutyl carbonate.

Diaryl carbonates are not particularly limited, but examples include diphenyl carbonate.

Among these carbonate compounds, alkylene carbonates and dialkyl carbonates are preferred as carbonate compounds used in the production of polycarbonate diols, with ethylene carbonate, dimethyl carbonate, and diethyl carbonate being more preferred.

(Diol compound)
The diol compound used in the production of the polycarbonate diol of one embodiment of the present disclosure includes at least 1,9-nonanediol and/or 2-methyl-1,8-octanediol.

The diol compound used in producing the polycarbonate diol of one embodiment of the present disclosure may also contain a diol compound other than 1,9-nonanediol and/or 2-methyl-1,8-octanediol. The other diol compound is not particularly limited, but examples include linear diols other than 1,9-nonanediol, branched diols other than 2-methyl-1,8-octanediol, cyclic diols, and diols having an aromatic ring.

Straight-chain diols other than 1,9-nonanediol are not particularly limited, but examples include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,10-decanediol, 1,11-undecanediol, and 1,12-dodecanediol.

Branched diols other than 2-methyl-1,8-octanediol are not particularly limited, but examples include 3-methyl-1,5-pentanediol, neopentyl glycol, 2-ethyl-1,6-hexanediol, 2-methyl-1,3-propanediol, 2,4-dimethyl-1,5-pentanediol, and 2,4-diethyl-1,5-pentanediol.

Cyclic diols include, but are not limited to, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, and 2-bis(4-hydroxycyclohexyl)-propane.

In the diol compounds used in producing the polycarbonate diol of one embodiment of the present disclosure, the ratio of the number of moles of 1,9-nonanediol and/or 2-methyl-1,8-octanediol (preferably 1,9-nonanediol and 2-methyl-1,8-octanediol) to the total number of moles of the diol compounds is 0.90 to 1.00, preferably 0.95 to 1.00, and more preferably all of the diol compounds are 1,9-nonanediol and/or 2-methyl-1,8-octanediol (even more preferably 1,9-nonanediol and 2-methyl-1,8-octanediol). When the ratio of 1,9-nonanediol and/or 2-methyl-1,8-octanediol is within the above range, a polycarbonate diol that is liquid at 25°C and has excellent moldability and viscosity stability at 25°C tends to be easily obtained.

The ratio of the number of moles of 2-methyl-1,8-octanediol to the total number of moles of the diol compounds is preferably 0.20 to 1.00, more preferably 0.30 to 0.99, even more preferably 0.40 to 0.98, even more preferably 0.50 to 0.95, particularly preferably 0.60 to 0.93, and most preferably 0.65 to 0.90. By having this ratio within this range, the resulting polycarbonate diol will be liquid at 25°C and will have excellent handleability.

Furthermore, the ratio of the number of moles of 2-methyl-1,8-octanediol to the total number of moles of 1,9-nonanediol and 2-methyl-1,8-octanediol is preferably 0.20 to 1.00, more preferably 0.30 to 0.99, even more preferably 0.40 to 0.98, even more preferably 0.50 to 0.95, particularly preferably 0.60 to 0.93, and most preferably 0.65 to 0.90. When the ratio is within the above range, the resulting polycarbonate diol is liquid at 25°C and has excellent handleability.

In the polycarbonate diol of one embodiment of the present disclosure, polyol compounds having three or more hydroxy groups per molecule, such as trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol, can also be used as raw materials for the polycarbonate diol, provided that their performance is not impaired. If too much of these polyol compounds having three or more hydroxy groups per molecule are used as raw materials for the polycarbonate diol, crosslinking and gelation occur during the polycarbonate polymerization reaction. Therefore, even when using polyol compounds having three or more hydroxy groups per molecule as raw materials for the polycarbonate diol, the amount of these polyol compounds is preferably 0.1 to 20 mol%, more preferably 0.5 to 15 mol%, even more preferably 1 to 10 mol%, and particularly preferably 2 to 5 mol%, based on the total number of moles of the diol compounds used as raw materials for the polycarbonate diol.

The mixing ratio of the carbonate compound to the diol compound (carbonate compound content in the mixed solution/diol compound content in the mixed solution) is preferably 1/3 to 3/1, more preferably 1/2 to 2/1, even more preferably 1/1.3 to 1.3/1, and particularly preferably 1/1.2 to 1.2/1, by molar ratio. By keeping the mixing ratio of the carbonate compound to the diol compound within the above range, polycarbonate diol can be obtained efficiently.

Lithium acetylacetonate is preferred as the transesterification catalyst used in producing the polycarbonate diol of one embodiment of the present disclosure. By using lithium acetylacetonate as the transesterification catalyst, it is possible to obtain the polycarbonate diol having the desired molecular weight distribution.

From the viewpoint of facilitating appropriate control of the reaction temperature and suppressing an increase in the color number of the reaction product, the content of the transesterification catalyst in the mixed solution may be 0.0001 to 0.10 parts by mass, preferably 0.001 to 0.07 parts by mass, more preferably 0.002 to 0.04 parts by mass, and even more preferably 0.003 to 0.03 parts by mass, relative to 100 parts by mass of the total amount of the carbonate compound and diol compound in the mixed solution. When the content of the transesterification catalyst is at or above the lower limit, it becomes easier to appropriately control the reaction temperature. However, when the obtained polycarbonate diol is used as a raw material for producing polyurethane, a lower content of the transesterification catalyst is preferable from the viewpoint of facilitating control of the reactivity of the urethanization reaction. Furthermore, when the content of the transesterification catalyst is at or below the upper limit, it becomes possible to suppress an increase in the color number of the reaction product and the reactivity of the urethanization reaction.

The heating temperature (reaction temperature) of the mixed solution is, for example, 0 to 250°C, and may be 100 to 220°C. When the reaction temperature is equal to or higher than the lower limit, the transesterification reaction easily proceeds, making it easier to obtain the desired polycarbonate diol. When the reaction temperature is equal to or lower than the upper limit, the color number of the obtained polycarbonate diol is reduced. The transesterification reaction may be carried out by maintaining the temperature constant, or by increasing the temperature stepwise or continuously depending on the degree of reaction progress. From the viewpoint of making it easier to obtain the desired polycarbonate diol, it is preferable to carry out heating at a temperature T1 that satisfies the relationship of the following formula (α), and then heating at a temperature T2 that satisfies the relationship of the following formula (β). It is preferable that temperatures T1 and T2 satisfy the relationship of the following formula (γ). It is also preferable that the average temperature _T1m of the first heating temperature and the average temperature _T2m of the second heating temperature satisfy the relationship of the following formula (δ). Here, the degree of reaction progress can be estimated from the amount of distillate distillate.
110℃≦T1<140℃...(α)
120℃≦T2<140℃...(β)
T1<T2...(γ)
T1 _m < T2 _m ...(δ)

The mixture can be heated under normal pressure, but in the latter half of the reaction, it can also be heated under reduced pressure (for example, a pressure of 101 to 0.01 kPa). This increases the rate at which the distillate is distilled out, speeding up the progress of the reaction. In this specification, normal pressure means a pressure of 101.325 kPa ± 20.000 kPa. From the viewpoint of facilitating the production of the desired polycarbonate diol, the heating of the mixed solution preferably includes heating under a pressure of 101.325 kPa±20.000 kPa (first heating) and then heating under a reduced pressure of 0.05 kPa or less (second heating). It is more preferable that the temperature of the first heating is temperature T1 that satisfies the relationship of formula (α) above, and the temperature of the second heating is temperature T2 that satisfies the relationship of formula (β) above. It is even more preferable that the temperature of the first heating (temperature T1) and the temperature of the second heating (temperature T2) satisfy the relationship of formula (γ) above. Furthermore, from the viewpoint of facilitating the production of the desired polycarbonate diol, it is preferable to remove the alcohol derived from the carbonate compound from the reaction system by distillation at a temperature near the boiling point of the alcohol or lower (for example, 79°C or lower for ethanol derived from diethyl carbonate).

(urethane resin)
The urethane resin according to one embodiment of the present disclosure includes a reaction product of the polycarbonate diol and an isocyanate. That is, the urethane resin is a polycondensation product of the polycarbonate diol and an isocyanate or a crosslinked product thereof. Here, the crosslinked product means a product in which polycondensates are crosslinked with each other using a chain extender or the like.

(Polyisocyanate)
Examples of polyisocyanates include aromatic polyisocyanates, araliphatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Modified polyisocyanates, which are modified versions of these, can also be used. Examples of modified polyisocyanates include isocyanurate-modified polyisocyanates (isocyanate trimers), allophanate-modified polyisocyanates, uretdione-modified polyisocyanates, urethane-modified polyisocyanates, biuret-modified polyisocyanates, uretonimine-modified polyisocyanates, and acylurea-modified polyisocyanates. These can be used alone or in combination of two or more.

Examples of aromatic isocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate/2,6-tolylene diisocyanate mixtures, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate/4,4'-diphenylmethane diisocyanate mixtures, m-xylylene diisocyanate, p-xylylene diisocyanate, and 4,4'-diphenyl ether. Examples of suitable diisocyanates include 1,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, and 3,3'-dimethoxydiphenyl-4,4'-diisocyanate. Among these, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and a 2,4'-diphenylmethane diisocyanate/4,4'-diphenylmethane diisocyanate mixture are preferred from the standpoint of versatility.

Examples of aralkyl isocyanates include 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, and mixtures thereof; 1,3-bis(1-isocyanato-1-methylethyl)benzene, 1,4-bis(1-isocyanato-1-methylethyl)benzene, and mixtures thereof; ω,ω'-diisocyanato-1,4-diethylbenzene, etc.

Examples of aliphatic isocyanates include hexamethylene diisocyanate, pentamethylene diisocyanate, tetramethylene diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, lysine diisocyanate, trioxyethylene diisocyanate, ethylene diisocyanate, trimethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, 2,2'-dimethylpentane diisocyanate, 2,2,4-trimethylhexane diisocyanate, decamethylene diisocyanate, butene diisocyanate, 1,3-butadiene-1,4-diisocyanate, 2,4, Examples of the isocyanate include 4-trimethylhexamethylene diisocyanate, 1,6,11-undecane triisocyanate, 1,3,6-hexamethylene triisocyanate, 1,8-diisocyanato-4-(isocyanatomethyl)octane, 2,5,7-trimethyl-1,8-diisocyanato-5-(isocyanatomethyl)octane, bis(isocyanatoethyl)carbonate, bis(isocyanatoethyl)ether, 1,4-butylene glycol dipropyl ether-α,α'-diisocyanate, lysine diisocyanatomethyl ester, 2-isocyanatoethyl-2,6-diisocyanatohexanoate, and 2-isocyanatopropyl-2,6-diisocyanatohexanoate. Among these, hexamethylene diisocyanate, pentamethylene diisocyanate, and tetramethylene diisocyanate are preferred from the perspective of versatility.

Examples of alicyclic isocyanates include isophorone diisocyanate, cyclohexyl diisocyanate, bis(isocyanatomethyl)cyclohexane, dicyclohexylmethane diisocyanate, methylcyclohexyl diisocyanate, dicyclohexyldimethylmethane diisocyanate, 2,2'-dimethyldicyclohexylmethane diisocyanate, bis(4-isocyanato-n-butylidene)pentaerythritol, and hydrogenated dimer acid diisocyanate. ester, 2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-(isocyanatomethyl)bicyclo[2.2.1]heptane, 2-(isocyanatomethyl)3-(3-isocyanatopropyl)-6-(isocyanatomethyl)-bicyclo[2.2.1]heptane, 2-(isocyanatomethyl)-2-(3-isocyanatopropyl)-5-(isocyanatomethyl)bicyclo[2.2.1]heptane, 2-(isocyanatomethyl)-2-(3-isocyanatopropyl)-5-(isocyanatomethyl)bicyclo[2.2.1]heptane, 2-(isocyanatomethyl)-3-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)bicyclo[2.2.1]heptane, 2-(isocyanatomethyl)-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)bicyclo[2.2.1]heptane, 2-(isocyanatomethyl)-2-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)bicyclo[2.2.1]heptane, Examples include cyclo[2.2.1]heptane, 2-(isocyanatomethyl)-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)bicyclo[2.2.1]heptane, 2,5-bis(isocyanatomethyl)bicyclo[2.2.1]heptane, hydrogenated diphenylmethane diisocyanate, norbornane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, and hydrogenated tetramethylxylene diisocyanate. Of these, isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate are preferred from the standpoint of versatility.

(Chain extender)
The chain extender can be appropriately selected depending on the purpose, application, etc. Examples of the chain extender include water, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, xylylene glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, and bis[4-(2-hydroxyethoxy)phenyl]sulfonyl. Examples of suitable chain extenders include low molecular weight polyols such as cyclohexane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, and 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane; high molecular weight polyols such as polyester polyols, polyesteramide polyols, polyether polyols, polyetherester polyols, polycarbonate polyols, and polyolefin polyols; and polyamines such as ethylenediamine, isophoronediamine, 2-methyl-1,5-pentanediamine, aminoethylethanolamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. The amount of chain extender (the proportion of the chain extender-derived structure contained in the urethane resin) may be 0.1 to 50 parts by mass per 100 parts by mass of the total amount of polycarbonate diol and isocyanate. When the chain extender is a polyol, the content of the polyol is calculated assuming that the polyol is included in both the chain extender and the polyol component.

(Coating agent)
The coating agent according to one embodiment of the present disclosure includes the urethane resin. Specific embodiments of the urethane resin may be as described above.

The following describes examples of the present invention, but the present invention is not limited to these examples. The resulting polycarbonate diol was analyzed and evaluated using the following methods.

[Evaluation of properties]
The obtained polycarbonate diol was heated at 80° C. for 1 hour and then left to stand at 25° C. for 3 days. The state of the sample after standing was visually confirmed, and if it had even a slight fluidity at room temperature (25° C.), it was rated as "liquid," and if it had no fluidity, it was rated as "solid."

[Measurement of number average molecular weight by GPC]
The obtained polycarbonate diol was subjected to GPC analysis under the following conditions to measure the number average molecular weight of the polycarbonate diol.
-conditions-
(1) Measuring instrument: HLC-8420 (manufactured by Tosoh Corporation)
(2) Column: TSKgel (manufactured by Tosoh Corporation)
・G3000H-XL
・G3000H-XL
・G2000H-XL
・G2000H-XL
(3) Mobile phase: THF (tetrahydrofuran)
(4) Detector: RI (refractive index) detector (accessory for HLC-8420)
(5) Temperature: 40℃
(6) Flow rate: 1.000ml/min
(7) Calibration curve: A calibration curve was obtained using the following commercial products (all bifunctional polyoxypropylene polyols manufactured by Sanyo Chemical Industries, Ltd.).
- "Sanix PP-200" (number average molecular weight = 200, average number of functional groups: 2)
- "Sanix PP-400" (number average molecular weight = 400, average number of functional groups: 2)
- "Sanix PP-1000" (number average molecular weight = 1000, average number of functional groups: 2)
- "Sanix PP-2000" (number average molecular weight = 2000, average number of functional groups: 2)
- "Sanix PP-3000" (number average molecular weight = 3200, average number of functional groups: 2)
- "Sannix PP-4000" (number average molecular weight = 4160, average number of functional groups: 2)
(8) Approximation formula of calibration curve: cubic equation (9) Concentration of sample solution: 0.5 mass% THF solution

[Measurement of hydroxyl value]
The hydroxyl value of the obtained polycarbonate diol was measured by a method using an acetylating reagent in accordance with JIS K1557-1.

[Calculation of number average molecular weight from hydroxyl value]
The number average molecular weight of the obtained polycarbonate diol was calculated from the hydroxyl value using the following formula: The number average molecular weight calculated from the hydroxyl value corresponds to the absolute molecular weight (true molecular weight) of the polymer.
Number average molecular weight calculated from hydroxyl value [g/mol]
= 2 × 56.11 [KOH g/mol] × 1000 / hydroxyl value [KOH mg/g]

[LC Measurement]
The obtained polycarbonate diol was subjected to liquid chromatography (LC) measurement under the following conditions to obtain an LC spectrum of the polycarbonate diol.
-conditions-
(1) Measuring instrument: Agilent 1290 Infinity II series (manufactured by Agilent Technologies)
(2) Column: TSKgel (manufactured by Tosoh Corporation)
・TSKgel ODS-100V (4.6mm I.D. x 15cm)
(3) Mobile phase:
Solution A: water/methanol = 5/5 (vol/vol%)
Solution B: tetrahydrofuran (THF)
Water: Purified water THF: HPLC grade THF manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. Methanol: HPLC grade THF manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. (4) Pretreatment The obtained polycarbonate diol was weighed, and a predetermined mobile phase (liquid B) was added and left to stand overnight at room temperature to dissolve. The obtained sample solution was gently shaken and filtered through a 0.45 μm PTFE cartridge filter.
(5) Solvent Gradient Conditions The solvent gradient conditions were as shown in Table 1.

(6) Detector: Evaporative Light Scattering Detector (ELSD) G4260B (manufactured by Agilemt Technologies)
(7) Temperature: 40℃
(8) Flow rate: 0.40ml/min
(9) Injection volume: 10μL
(10) Sample solution concentration (THF): 2.0 mg/L
The molecular structure of each peak in the obtained LC spectrum was identified by MS measurement of each peak alone (apparatus: Bruker Daltonics microTOF, ion source: APCI, measurement mode: positive mode).

[Calculation of peak area ratio]
In the obtained LC spectrum, the peak of the molecular weight closest to the number average molecular weight (absolute molecular weight) calculated from the hydroxyl value was determined, and the number of repeating units of the polycarbonate diol (D) _{, X0} , corresponding to this peak was determined. The "peak of the molecular weight closest to the number average molecular weight calculated from the hydroxyl value" was defined as the peak of the molecular weight having the smallest absolute value of difference from the number average molecular weight calculated from the hydroxyl value. In addition, when there are two peaks of molecular weights having the smallest absolute value of difference from the number average molecular weight calculated from the hydroxyl value of the polycarbonate diol, the peak of the smallest molecular weight is used. Next, the area value S(X) of each peak in the LC spectrum (X represents the number of repeating units of the polycarbonate diol (D), and X = ..., _X0 -2, X0 _-1 , _X0 , _X0 +1, _X0 +2, ...) was calculated. The area ratio [S(X)/S( _X )] of each peak to the area value S(X) of the peak whose repeating unit is X ₀ was calculated. Furthermore, the number of consecutive peaks whose area ratio [S(X)/S(X ₀ )] was in _the range of 0.90 to 1.10, including the peak whose repeating unit is X _0, was calculated.

[Viscosity measurement]
The viscosity of the obtained polycarbonate diol was measured under the following conditions in accordance with JIS Z 8803:2011-10 "Viscosity measurement method using a cone-plate rotational viscometer." Specifically, using a cone-plate viscometer (HAAKE MARS Modular Advanced Rheometer System: manufactured by Thermo Scientific), 0.20 ^cm3 of polycarbonate diol was placed between a flat plate and a cone, the cone was rotated at a constant shear rate, and after 5 minutes, the torque acting on the flat plate or cone when a steady state was reached was measured, and the viscosity of the polycarbonate diol was calculated.
-conditions-
(1) Rotor: Thermo Scientific rotor (type (product number): C25 1°/Ti, diameter: 25.00 mm, angle between flat plate and cone (cone angle: α): 1°)
(2) Shear rate: 1 s ⁻¹ or 1000 s ⁻¹
(3) Measurement temperature: 25℃

Example 1
76.9 g of 1,9-nonanediol, 435.9 g of 2-methyl-1,8-octanediol, 367.8 g of diethyl carbonate, and 0.048 g of lithium acetylacetonate were mixed in a 1 L two-neck glass reactor (reactor A) equipped with a stirrer, thermometer, heater, and cooler. The resulting mixture was heated at 110 to 138°C (initial temperature 110°C, final temperature 138°C) under atmospheric pressure and reacted for 8 hours while removing low-boiling components (such as alcohol derived from carbonate esters). The distillate temperature was 77°C or higher but less than 79°C. Furthermore, the pressure in the flask was gradually reduced to 0.04 kPa at a reaction temperature of 138°C, and the reaction was continued for another 8 hours to obtain polycarbonate diol (PCD-1), which is liquid at room temperature.

(Comparative Example 1)
A polycarbonate diol (PCD-2) that is liquid at room temperature was obtained in the same manner as in Example 1, except that a mixed liquid obtained by mixing 76.9 g of 1,9-nonanediol, 436.0 g of 2-methyl-1,8-octanediol, 389.8 g of diethyl carbonate, and 0.047 g of lithium acetylacetonate was used in reactor A.

(Comparative Example 2)
Into reactor A, 88.9 g of 1,9-nonanediol, 504.0 g of 2-methyl-1,8-octanediol, 393.5 g of diethyl carbonate, and 0.033 g of tetrabutyl titanate were mixed. The resulting mixture was heated at 120 to 190°C (initial temperature 120°C, final temperature 190°C) under atmospheric pressure, and reacted for 8 hours while removing low-boiling components (such as alcohol derived from carbonate esters). The distillate temperature was 77°C or higher but less than 79°C. Furthermore, the pressure inside the flask was gradually reduced to 0.5 kPa at a reaction temperature of 190°C, and the reaction was continued for another 8 hours to obtain polycarbonate diol (PCD-3), which is liquid at room temperature.

(Comparative Example 3)
A polycarbonate diol (PCD-4) that is liquid at room temperature was obtained in the same manner as in Example 1, except that a mixed liquid obtained by mixing 88.9 g of 1,9-nonanediol, 504.0 g of 2-methyl-1,8-octanediol, 310.6 g of diethyl carbonate, and 0.048 g of lithium acetylacetonate was used in reactor A.

(Production Example 1)
A polycarbonate diol (PCD-5) that is liquid at room temperature was obtained in the same manner as in Comparative Example 2, except that a mixed liquid obtained by mixing 247.7 g of 1,9-nonanediol, 1403.4 g of 2-methyl-1,8-octanediol, 1262.9 g of diethyl carbonate, and 0.095 g of tetrabutyl titanate was used in reactor A.

(Production Example 2)
A polycarbonate diol (PCD-6) that is liquid at room temperature was obtained in the same manner as in Example 1, except that a mixed liquid obtained by mixing 81.7 g of 1,9-nonanediol, 463.2 g of 2-methyl-1,8-octanediol, 361.2 g of diethyl carbonate, and 0.049 g of lithium acetylacetonate was used in reactor A.

(Production Example 3)
A polycarbonate diol (PCD-7) that is liquid at room temperature was obtained in the same manner as in Example 1, except that a mixed liquid obtained by mixing 96.2 g of 1,9-nonanediol, 544.9 g of 2-methyl-1,8-octanediol, 168.9 g of diethyl carbonate, and 0.042 g of lithium acetylacetonate was used in reactor A.

(Examples 2 to 7, Comparative Examples 4 to 11)
PCD-1 obtained in Example 1, PCD-2 and PCD-4 obtained in Comparative Examples 1 and 3, and PCD-5 to PCD-7 obtained in Production Examples 1 to 3 were mixed at 40°C according to the blending amounts shown in Table 1, to obtain polycarbonate diols (PCD-8 to PCD-21).

The properties at room temperature (25°C) measured for the polycarbonate diols obtained in Examples 1 to 7 and Comparative Examples 1 to 11 according to the above-mentioned methods are shown in Tables 2 and 3. These properties include the number average molecular weight measured by GPC, the hydroxyl value, the number average molecular weight calculated from the hydroxyl value, the number _X0 of repeating units of the polycarbonate diol (D) corresponding to the peak having the molecular weight _closest to the number average molecular weight calculated from the hydroxyl value, the area ratio [S(X)/S( _X0 )] of each peak to the area S( _X0 ) of the peak having the number of repeating units _X0 , and the number of consecutive peaks having the area ratio [S(X)/S( _X0 )] within a predetermined range, including the peak having the number of repeating units X0. For reference, the LC spectrum of the polycarbonate diol (PCD-1) obtained in Example 1 is shown in Figure 1.

The viscosities (25°C) [η ₁ and η ₁₀₀₀ ] at a shear rate of 1 s ^-1 or 1000 s ^-1 , measured for the polycarbonate diols obtained in Examples 1 to 7 and Comparative Examples 1 to 11 according to the above-mentioned method, and the ratios [η 1000 /η ₁ ] of the viscosity (25°C) η ₁ at a shear rate of 1 s ^-1 to the viscosity (25°C) η ₁₀₀₀ at a shear rate of 1000 s ^-1 , measured according to the _{above-mentioned} method, are shown in Tables 4 and 5.

As explained above, according to the present disclosure, it is possible to obtain a polycarbonate diol that combines moldability at 25°C with viscosity stability. Furthermore, the polycarbonate diol of one embodiment of the present disclosure has excellent abrasion resistance and can form a surface treatment layer or coating film that has good resistance to moist heat and sweat.

Therefore, the polycarbonate diol of one embodiment of the present disclosure is useful as a surface treatment agent capable of stably forming a surface treatment layer having the above-mentioned properties on synthetic leather or artificial leather, and as a constituent material of a coating agent capable of stably forming a coating film having the above-mentioned properties on a film.

Claims (7)

A polycarbonate diol containing a repeating unit (A) represented by the following formula (A) and having a terminal hydroxyl group:
90 to 100 mol % of the repeating units (A) are repeating units (B) represented by the following formula (B) and repeating units (C) represented by the following formula (C),
The polycarbonate diol contains a polycarbonate diol (D) represented by the following formula (D):
the amount of the repeating unit (B) is 20 to 99 mol % based on the total amount of the repeating unit (B) and the repeating unit (C);
The number average molecular weight calculated from the hydroxyl value of the polycarbonate diol is 300 to 2800 g/mol,
The viscosity η ₁ at a shear rate of 1 s ⁻¹ and a temperature of 25° C. is 20,000 to 80,000 mPa·s ⁻¹ ;
The viscosity η ₁₀₀₀ at a shear rate of 1000 s ⁻¹ and a temperature of 25° C. is 8000 to 60000 mPa·s ⁻¹ ;
the ratio [η ₁₀₀₀ /η ₁ ] of viscosity η ₁₀₀₀ at a shear rate of 1000 s ^-1 and a temperature of 25°C to viscosity η ₁ at a shear rate of 1 s ^-1 and a temperature of 25°C is 0.40 to 0.80;
90 to 100 mol % of the polycarbonate diol is the polycarbonate diol (D),
A polycarbonate diol, wherein the ratio of the number of moles of 2-methyl-1,8 ^- octylene groups to the total number of moles of alkanediyl groups (total number of moles of 1,9-nonylene groups and 2-methyl-1,8-octylene groups) contained as R1 in the polycarbonate diol (D) is 0.20 to 1.00 .
(In formula (A), R represents a divalent aliphatic or alicyclic hydrocarbon having 2 to 15 carbon atoms.)
(In formula (D),
R ¹ represents *-(CH ₂ ) ₉ -* or *-CH ₂ CH(CH ₃ )CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ -*;
In the formula, * at both ends indicates the bonding sites with the two oxygen atoms bonded to both ends of ^R1 , respectively.
q represents an integer of 1 or more, and multiple R ^1s may be the same or different. Shear rate 1 s ^-1 , viscosity η at 25°C ₁ However, 25,000 to 70,000 mPa·s ^-1 The polycarbonate diol according to claim 1, wherein Shear rate 1 s ^-1 , viscosity η at 25°C ₁ 30,000 to 60,000 mPa·s ^-1 The polycarbonate diol according to claim 1, wherein Shear rate 1000 s ^-1 , viscosity η at 25°C ₁₀₀₀ However, 10,000 to 40,000 mPa·s ^-1 The polycarbonate diol according to claim 1, wherein Shear rate 1000 s ^-1 , viscosity η at 25°C ₁₀₀₀ However, 20,000 to 30,000 mPa·s ^-1 The polycarbonate diol according to claim 1, wherein A urethane resin comprising a reaction product of the polycarbonate diol according to any one of claims 1 to 5 and an isocyanate. A coating agent comprising the urethane resin according to claim 6.