JP7748865B2 - Method for producing polycarbonate diol and polycarbonate diol - Google Patents

Description

The present invention relates to a method for producing polycarbonate diol, polycarbonate diol, and polyurethane using the polycarbonate diol.

Traditionally, polyurethane resins and polyurea resins have been used in a wide range of applications, including synthetic leather, artificial leather, adhesives, furniture paints, and automotive paints. Polyethers and polyesters are used as polyol components to react with isocyanates (see, for example, Patent Document 1 and Non-Patent Document 1). However, in recent years, there has been an increasing demand for resin resistance, including heat resistance, weather resistance, hydrolysis resistance, mildew resistance, and oil resistance.

To meet these high performance requirements, various polycarbonate diols have been proposed as soft segments with excellent hydrolysis resistance, weather resistance, resistance to oxidative degradation, heat resistance, etc. (See, for example, Patent Documents 2 to 5).

Transesterification catalysts are typically used in the production of these polycarbonate diols. For example, metallic sodium is used as a catalyst in the production of copolymerized polycarbonate diols from diethyl carbonate with 1,6-hexanediol and 1,5-pentanediol (see, for example, Patent Document 6), and sodium ethoxide or magnesium acetate is used as a catalyst in the combination of diethyl carbonate with diols such as 1,3-propanediol, 2-methyl-1,3-propanediol, and 1,3-butanediol (see, for example, Patent Document 7).

In addition, lead acetate or tetra-n-butyl titanate is used as a catalyst in the production of copolymerized polycarbonate diols from ethylene carbonate and diols such as 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 2-methyl-1,3-propanediol, and tetra-n-butyl titanate is used as a catalyst in the production of polycarbonate diols from ethylene carbonate and various alkylene diols and oxyalkylene diols such as diethylene glycol and dibutylene glycol (see, for example, Patent Document 8).

In the past, in the combination of ethylene carbonate and 1,6-hexanediol, catalysts such as tetra-n-butyl titanate, dibutyltin dilaurate, sodium acetate, lithium hydroxide, and tin powder were used (see, for example, Patent Document 9).

Furthermore, magnesium acetate has been successfully used as a catalyst in the production of copolymerized polycarbonate diols from diphenyl carbonate, 1,6-hexanediol, and neopentyl glycol (see, for example, Patent Document 10).

In recent years, a method for improving the color tone of polycarbonate diol under milder conditions has been disclosed, which involves using a salt of acetylacetone (or a salt of an acetylacetone derivative) of at least one metal selected from the group consisting of zinc and metals in Group 2 of the long-form periodic table as a catalyst (see, for example, Patent Document 11).

Japanese Patent Application Laid-Open No. 2000-95836 Japanese Patent Application Laid-Open No. 2001-123112 Japanese Patent Application Publication No. 5-51428 Japanese Patent Application Publication No. 6-49166 WO 2002/070584 Japanese Patent Application Publication No. 2-289616 JP 2012-46659 A International Publication No. 2006/088152 Japanese Patent Application Laid-open No. 51-144492 JP 2013-010950 A Japanese Patent Application Laid-Open No. 2020-125467

"Fundamentals and Applications of Polyurethanes" pp. 96-106, edited by Katsuji Matsunaga, CMC Publishing Co., Ltd., published November 2006

Previously known techniques require high reaction temperatures or the addition of large amounts of catalyst to polycondense dihydroxy compounds with different reactivities, which can lead to discoloration and thermal degradation of the aliphatic polycarbonate. Therefore, there is room for improvement in the transesterification catalysts known in the art when it comes to producing various polycarbonate diols.

For example, if a strong base such as an alkali metal or alkaline earth metal or an alkoxide thereof is used as a catalyst, the polycarbonate diol is likely to become discolored.

Furthermore, when a titanium compound is used as a catalyst, the production of polycarbonate diol tends to take a long time due to insufficient catalytic activity. Long reaction times tend to promote the formation of undesirable ether groups and vinyl groups. When polycarbonate diol is used as a polyurethane raw material, these groups can impair the weather resistance and heat resistance of the polyurethane, making it undesirable as a polyurethane raw material.

On the other hand, lead compounds and organotin compounds have recently been found to be harmful to the human body and have adverse effects on the ecosystem. For this reason, these compounds are not desirable as components remaining in polycarbonate diol.

Furthermore, when magnesium acetate, magnesium alkoxide, or magnesium acetylacetone is used as a catalyst, the polymerization activity is higher than that of titanium compounds, and improvements in productivity are observed, but this is not sufficient, and there is room for improvement in terms of coloration of the resulting polycarbonate diol and improving productivity.

The present invention aims to provide a method for efficiently producing polycarbonate diol (specifically, for example, under milder reaction conditions and in a short time). It also aims to provide a polycarbonate diol that has excellent color tone, few ether bonds, and a high purity of terminal primary hydroxyl groups (OH), as well as a polyurethane that uses the polycarbonate diol and has excellent chemical resistance, heat resistance, and hydrolysis resistance.

As a result of extensive research aimed at solving these problems, the inventors have discovered that by using a transesterification catalyst containing a specific metal when producing polycarbonate diol by polycondensation through a transesterification reaction using a dihydroxy compound and a carbonate ester as raw material monomers, polycarbonate diol can be produced efficiently, thereby solving the above-mentioned problems. They have also discovered a polycarbonate diol that has excellent color tone, few ether bonds, and a high purity of terminal primary hydroxyl groups (OH), as well as a polyurethane that uses this polycarbonate diol and has excellent chemical resistance, heat resistance, and hydrolysis resistance.

That is, the gist of the present invention is as follows.
[1]
The method includes a step of polycondensing a dihydroxy compound and a carbonate ester as raw material monomers through an ester exchange reaction in the presence of an ester exchange catalyst to obtain a polycarbonate diol,
The transesterification catalyst contains at least one metal (M) selected from the group consisting of metals of Groups 6, 7, 8, 9, 10 and 11 of the long form periodic table.
[2]
The method for producing a polycarbonate diol according to [1], wherein the transesterification catalyst is at least one metal complex and/or a hydrate thereof represented by the following formula (1):
(In the formula, _R1 and _R3 each independently represent a monovalent hydrocarbon group having 1 to 10 carbon atoms, and the hydrocarbon groups of _R1 and _R3 may be substituted with a halogen atom or may have an oxygen atom; _R2 represents hydrogen or a monovalent hydrocarbon group having 1 to 10 carbon atoms, and the hydrocarbon group of _R2 may be substituted with a halogen atom or may have an oxygen atom; M represents at least one metal selected from the group consisting of metals of Groups 6, 7, 8, 9, 10, and 11 of the long form periodic table; and n is 1, 2, or 3. The metal complex represented by formula (1) may also be an association of multiple metals.)
[3]
The method for producing a polycarbonate diol according to [1], wherein the transesterification catalyst is a salt of at least one carboxylic acid and at least one metal (M) selected from the group consisting of metals of Groups 6, 7, 8, 9, 10, and 11 of the long form periodic table, and/or a hydrate thereof, represented by the following formula (2):
(In the formula, _R4 represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, and the hydrocarbon group of _R4 may be substituted with a halogen atom or may have an oxygen atom.)
[4]
The method for producing a polycarbonate diol according to any one of [1] to [3], wherein the metal (M) is at least one metal selected from the group consisting of molybdenum, manganese, iron, cobalt, nickel, and copper.
[5]
The method for producing a polycarbonate diol according to any one of [1] to [4], wherein the metal (M) is manganese.
[6]
The method for producing a polycarbonate diol according to any one of [1] to [5], wherein the amount of the transesterification catalyst, as the total amount of the metal (M), is 0.5 ppm or more and 20 ppm or less relative to the total amount of all dihydroxy compounds and carbonate esters.
[7]
The method for producing a polycarbonate diol according to any one of [1] to [6], wherein the dihydroxy compound comprises at least one selected from the group consisting of an aliphatic dihydroxy compound having a structure represented by the following formula (3) and an alicyclic dihydroxy compound:
(wherein _R5 represents a divalent aliphatic or alicyclic hydrocarbon having 2 to 20 carbon atoms.)
[8]
The method for producing a polycarbonate diol according to any one of [1] to [7], wherein the carbonate ester is at least one selected from the group consisting of alkylene carbonate, dialkyl carbonate, and diaryl carbonate.
[9]
It is a polycondensation product obtained by an ester exchange reaction between a dihydroxy compound and a carbonate ester,
The number average molecular weight is 250 or more and 100,000 or less,
The polycarbonate diol contains at least one metal selected from the group consisting of metals of Groups 6, 7, 8, 9, 10, and 11 of the long form periodic table in a total amount of 1 ppm to 25 ppm,
The Hazen color number measured in accordance with JIS-K0071-1 (1998) is 50 or less,
the amount of ether bonds is 5 mol% or less,
A polycarbonate diol having a terminal primary hydroxyl (OH) purity of 97% or more.
[10]
The polycarbonate diol according to [9], wherein the metal is at least one metal selected from molybdenum, manganese, iron, cobalt, nickel, and copper.
[11]
The polycarbonate diol according to [9] or [10], wherein the metal is manganese.
[12]
A polyurethane containing units derived from the polycarbonate diol according to any one of [9] to [11].

The polycarbonate diol production method of the present invention makes it possible to efficiently produce polycarbonate diol under milder conditions than previously known techniques. Furthermore, the present invention can provide polycarbonate diols with excellent color tone, few ether bonds, and high purity of terminal primary hydroxyl groups (OH), as well as polyurethanes using such polycarbonate diols that have excellent chemical resistance, heat resistance, and hydrolysis resistance.

The following describes in detail the mode for carrying out the present invention (hereinafter abbreviated as "the present embodiment"). Note that the present invention is not limited to the following embodiment, and various modifications can be made within the scope of its gist.

[1. Method for producing polycarbonate diol]
The method for producing a polycarbonate diol of the present embodiment includes a step of using a dihydroxy compound and a carbonate ester as raw material monomers and polycondensing them by a transesterification reaction in the presence of a transesterification catalyst to obtain a polycarbonate diol,
The transesterification catalyst contains at least one metal (M) selected from the group consisting of metals of Groups 6, 7, 8, 9, 10 and 11 of the long form periodic table.

The method for producing polycarbonate diol of this embodiment uses a transesterification catalyst containing a specific metal, making it possible to produce polycarbonate diol efficiently (specifically, for example, under milder reaction conditions and in a shorter time).

<1-1. Raw material monomer>
The method for producing a polycarbonate diol of this embodiment uses a dihydroxy compound and a carbonate ester as raw material monomers.

<1-1-1. Dihydroxy compounds>
In the method for producing polycarbonate diol of the present embodiment, the dihydroxy compound serving as a raw material monomer is not particularly limited, and examples thereof include linear terminal dihydroxy compounds such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, and 1,20-eicosanediol. dihydroxy compounds having an ether group such as diethylene glycol, triethylene glycol, tetraethylene glycol, polypropylene glycol, and polytetramethylene glycol; thioether diols such as bishydroxyethyl thioether; 2-ethyl-1,6-hexanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, and 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol (hereinafter referred to as neo 2,2-dialkyl-substituted 1,3-propanediols (hereinafter sometimes referred to as 2,2-dialkyl-1,3-propanediols) such as 2,2,4,4-tetramethyl-1,5-pentanediol and 2,2,9,9-tetramethyl-1,10-decanediol; 3,9-dialkyl-substituted alkylenediols such as 2,2,4,4-tetramethyl-1,5-pentanediol and 2,2,9,9-tetramethyl-1,10-decanediol; -dihydroxy compounds containing a cyclic group such as bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane; 2,2-diphenyl-1,3-propanediol, 2,2-divinyl-1,3-propanediol, 2,2-diethynyl-1,3-propanediol, 2,2-dimethoxy-1,3-propanediol, bis(2-hydroxy-1,1-dimethylethyl)ether, bis(2-hydroxy-1,1-dimethylethyl)thioether, and 2,2,4,4-tetramethyl-3-cyano-1 dihydroxy compounds having a branched chain such as 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 4,4-dicyclohexyldimethylmethanediol, 2,2'-bis(4-hydroxycyclohexyl)propane, 1,4-dihydroxyethylcyclohexane, isosorbide, spiroglycol, 2,5-bis(hydroxymethyl)tetrahydrofuran, 4,4'-isopropylidenedicyclohexanol and 4,4'-isopropylidenebis(2,2'-hydroxymethyl)tetrahydrofuran; dihydroxy compounds having a cyclic group in the molecule, such as 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene and 9,9-bis(4-(2-hydroxyethoxy-2-methyl)phenyl)fluorene; nitrogen-containing dihydroxy compounds, such as diethanolamine and N-methyl-diethanolamine, and sulfur-containing dihydroxy compounds, such as bis(hydroxyethyl)sulfide; 2,2-bis(4-hydroxyphenyl)propane [=bisphenol A], 2,2- Bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3,5-diethylphenyl)propane, 2,2-bis(4-hydroxy-(3,5-diphenyl)phenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxyphenyl)pentane, 2,4'-dihydroxy-diphenylmethane, bis(4-hydroxyphenyl)methane, bis(4-hydroxy-5-nitrophenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 3 , 3-bis(4-hydroxyphenyl)pentane, 1,1-bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl)sulfone, 2,4'-dihydroxydiphenyl sulfone, bis(4-hydroxyphenyl)sulfide, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3,3'-dichlorodiphenyl ether, 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-2-methylphenyl)fluorene, and other aromatic bisphenols.

In particular, from the viewpoint of the weather resistance of the polyurethane obtained using the polycarbonate diol of this embodiment, the dihydroxy compound is preferably at least one compound selected from the group consisting of aliphatic dihydroxy compounds and alicyclic dihydroxy compounds represented by the following formula (3):

(wherein _R5 represents a divalent aliphatic or alicyclic hydrocarbon having 2 to 20 carbon atoms.)

Of these dihydroxy compounds, particularly preferred aliphatic dihydroxy compounds are 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and 2-methyl-1,8-octanediol, while particularly preferred alicyclic dihydroxy compounds are 1,4-cyclohexanedimethanol and tricyclodecanedimethanol.

These dihydroxy compounds may be used alone or in combination of two or more depending on the required performance of the resulting polycarbonate diol, but it is preferable to combine multiple compounds to form a copolymer polycarbonate diol. Copolymer polycarbonate diols generally have inhibited crystallization and have higher fluidity than homopolycarbonate diols, which not only makes them easier to handle when processed into polyurethane, but also imparts flexibility and texture to the polyurethane.

When using two types of dihydroxy compounds, for example, the copolymerization composition ratio is such that each dihydroxy compound accounts for 5 mol% or more, preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more of the total dihydroxy compounds.

Normally, when dihydroxy compounds with different molecular structures are copolymerized, the polymerization reaction may become uneven or may be inhibited due to differences in reactivity. However, according to this embodiment, which uses a specific transesterification catalyst described below, a copolymerized polycarbonate diol can be easily obtained.

<1-1-2. Carbonate ester>
In the method for producing a polycarbonate diol of the present embodiment, the carbonate ester that can be used as a raw material monomer is not limited as long as it does not impair the effects of the present invention, and examples thereof include dialkyl carbonate, diaryl carbonate, and alkylene carbonate.

Of the carbonate esters that can be used in the method for producing polycarbonate diol of this embodiment, specific examples of dialkyl carbonates include, but are not limited to, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate, diisobutyl carbonate, ethyl-n-butyl carbonate, and ethyl isobutyl carbonate.

Examples of diaryl carbonates include, but are not limited to, diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, and di-m-cresyl carbonate.

Examples of alkylene carbonates include ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 1,3-pentylene carbonate, 1,4-pentylene carbonate, 1,5-pentylene carbonate, 2,3-pentylene carbonate, 2,4-pentylene carbonate, and neopentyl carbonate.

These may be used alone or in combination of two or more.

Among these carbonate esters, dimethyl carbonate, diethyl carbonate, ethylene carbonate, and diphenyl carbonate are particularly preferred because they are inexpensive industrial raw materials, highly reactive, and produce small amounts of alcohol as by-products.

<1-1-3. Usage ratio of raw material monomers>
In the method for producing a polycarbonate diol of this embodiment, the amount of carbonate ester used needs to be appropriately changed depending on the target molecular weight of the polycarbonate diol, and is not particularly limited, but usually the lower limit in terms of molar ratio to 1 mole of the total of dihydroxy compounds is preferably 0.5, more preferably 0.7, and even more preferably 0.8, and the upper limit is usually 1.5, preferably 1.3, and more preferably 1.2. When the amount of carbonate diester used is equal to or less than the above upper limit, the proportion of the polycarbonate diol obtained having terminal groups other than hydroxyl groups can be suppressed, or there is a tendency that the polycarbonate diol of this embodiment having a molecular weight within a predetermined range can be produced, and when it is equal to or more than the above lower limit, there is a tendency that polymerization proceeds up to the predetermined molecular weight.

<1-2. Transesterification catalyst>
The method for producing a polycarbonate diol of the present embodiment uses a transesterification catalyst containing at least one metal (M) selected from the group consisting of metals of Groups 6, 7, 8, 9, 10, and 11 of the long form periodic table.

One preferred form of a transesterification catalyst containing at least one metal (M) selected from the group consisting of metals in Groups 6, 7, 8, 9, 10, and 11 of the long periodic table is at least one metal complex and/or a hydrate thereof represented by the following formula (1):

(In the formula, _R1 and _R3 each independently represent a monovalent hydrocarbon group having 1 to 10 carbon atoms, and the hydrocarbon groups of _R1 and _R3 may be substituted with a halogen atom or may have an oxygen atom; _R2 represents hydrogen or a monovalent hydrocarbon group having 1 to 10 carbon atoms, and the hydrocarbon group of _R2 may be substituted with a halogen atom or may have an oxygen atom; M represents at least one metal selected from the group consisting of metals of Groups 6, 7, 8, 9, 10, and 11 of the long form periodic table; and n is 1, 2, or 3. The metal complex represented by formula (1) may also be an association of multiple metals.)

The ligand to the metal in the metal complex represented by formula (1) is an acetylacetone analog, and can be expressed in a form in which the anion is delocalized, as shown in formula (6) below. Similarly, it can also be expressed as an equilibrium state of three organic anions, as shown in formula (7) below.

(In formula (6) and formula (7), _R1 and _R3 each independently represent a monovalent hydrocarbon group having 1 to 10 carbon atoms, and the hydrocarbon groups of _R1 and _R3 may be substituted with a halogen atom or may have an oxygen atom; _R2 represents hydrogen or a monovalent hydrocarbon group having 1 to 10 carbon atoms, and the hydrocarbon group of _R2 may be substituted with a halogen atom or may have an oxygen atom.)

Methods for preparing the transesterification catalyst represented by formula (1) include, but are not limited to, a method for preparing the transesterification catalyst represented by formula (1) by reacting a metal halide salt with an acetylacetone analogue in the presence of a base, as shown in formula (8) below, or a method for preparing the transesterification catalyst represented by formula (1) by exchanging a metal alkoxide with an acetylacetone analogue, as shown in formula (9) below.

(In the above formulas (8) and (9), R ₁ , R ₂ , R ₃ , M, and n are defined as in the above formula (1), X is any halogen atom, and R ₇ is any hydrocarbon group.)

In addition, together with these transesterification catalysts represented by formula (1), it is also possible to use auxiliary basic compounds such as transition metal compounds, basic boron compounds, basic phosphorus compounds, basic ammonium compounds, and amine compounds.

R ₁ and R ₃ in formula (1) are not particularly limited, and examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, phenyl, benzyl, monofluoromethyl, difluoromethyl, trifluoromethyl, monochloromethyl, dichloromethyl, and trichloromethyl groups, with methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, phenyl, benzyl, trifluoromethyl, and trichloromethyl being particularly preferred. R ₁ and R ₃ may be the same or different.

Furthermore, _R2 is not particularly limited, and examples thereof include hydrogen, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a neopentyl group, a hexyl group, a cyclohexyl group, a phenyl group, a benzyl group, a monofluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a monochloromethyl group, a dichloromethyl group, a trichloromethyl group, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Of these, hydrogen, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group are preferred, and hydrogen is particularly preferred.

The metal (M) selected from the group consisting of Groups 6, 7, 8, 9, 10, and 11 of the long periodic table is not particularly limited, but from the standpoint of catalytic activity, molybdenum, manganese, iron, cobalt, nickel, and copper are preferred, and of these, manganese is particularly preferred.

In addition, in this embodiment, the organometallic complexes with these acetylacetone analogues used as transesterification catalysts can also be used as hydrates.

Another form of transesterification catalyst containing at least one metal (M) selected from the group consisting of metals in Groups 6, 7, 8, 9, 10, and 11 of the long periodic table is preferably a salt and/or hydrate thereof of at least one carboxylic acid and at least one metal (M) selected from the group consisting of metals in Groups 6, 7, 8, 9, 10, and 11 of the long periodic table, as represented by the following formula (2):

(In the formula, _R4 represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, and the hydrocarbon group of _R4 may be substituted with a halogen atom or may have an oxygen atom.)

Carboxylic acids are not particularly limited, but examples include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, palmitic acid, margaric acid, and stearic acid. Of these, acetic acid, propionic acid, and butyric acid are preferred, with acetic acid being particularly preferred.

The metal (M) selected from the group consisting of Groups 6, 7, 8, 9, 10, and 11 of the long periodic table is not particularly limited, but from the standpoint of catalytic activity, molybdenum, manganese, iron, cobalt, nickel, and copper are preferred, and of these, manganese is particularly preferred.

The salts of these carboxylic acids used as transesterification catalysts in this embodiment can also be used as hydrates.

The amount of transesterification catalyst used in this embodiment, as the total amount of the metal (M), is preferably 0.5 ppm to 20 ppm, more preferably 1 ppm to 15 ppm, and even more preferably 3 ppm to 10 ppm, relative to the total amount of all dihydroxy compounds and carbonate esters. When the amount of transesterification catalyst, as the total amount of metal (M), is 0.5 ppm or more, the transesterification reaction rate tends to be faster. Furthermore, when the amount of transesterification catalyst, as the total amount of metal (M), is 20 ppm or less, coloration of the resulting polycarbonate diol can be suppressed, and when used as a urethane raw material, the urethane reaction tends to be stable.

<1-3. Method for producing polycarbonate diol>
In this embodiment, one or more of the dihydroxy compounds described above and one or more of the carbonate esters described above are transesterified in the presence of the transesterification catalyst described above to produce a polycarbonate diol.

<1-3-1. Reaction conditions, etc.>
The method for charging the reaction raw materials is not particularly limited, and the method can be freely selected, for example, by charging all of one or more dihydroxy compounds, the carbonate ester, and the catalyst at the same time and subjecting them to the reaction; by first charging the carbonate ester when the carbonate ester is solid, heating it to melt it, and then adding the dihydroxy compound and the catalyst; or, conversely, by charging the dihydroxy compound when the dihydroxy compound is solid, melting it, and then adding the carbonate ester and the catalyst.

Any reaction temperature can be used during the transesterification reaction, provided that it results in a practical reaction rate. There are no particular limitations on the temperature, but the lower limit is preferably 80°C, more preferably 110°C, and even more preferably 130°C. The upper limit of the reaction temperature is preferably 220°C, more preferably 200°C, even more preferably 180°C, and particularly preferably 170°C. When the reaction temperature is above the lower limit, the transesterification reaction tends to proceed at a practical rate. When the reaction temperature is below the upper limit, coloration of the resulting polycarbonate diol can be suppressed, and the formation of ether bonds can be suppressed, leading to improved quality, such as improved turbidity.

In particular, the method for producing polycarbonate diol of this embodiment uses a transesterification catalyst containing a specific metal (M) that is more active than conventional methods, making it possible to efficiently produce polycarbonate diol in a short time under mild reaction conditions, for example, at a low temperature of 160°C or less (preferably 150°C or less).

Although the reaction can be carried out at normal pressure, since the transesterification reaction is an equilibrium reaction, the reaction can be biased toward the product system by distilling off the produced monohydroxy compound or dihydroxy compound outside the system. Therefore, it is usually preferable to use reduced pressure conditions in the latter half of the reaction and carry out the reaction while distilling off the monohydroxy compound or dihydroxy compound. Alternatively, it is possible to gradually reduce the pressure during the reaction and carry out the reaction while distilling off the produced monohydroxy compound or dihydroxy compound. By gradually reducing the pressure during the reaction, it is possible to suppress the volatilization of low-boiling point unreacted monomers, improving the yield and tending to produce polycarbonate diol with a specified molecular weight, or, in the case of copolymerization, polycarbonate diol with a specified copolymer composition ratio.

The pressure during the reaction is selected appropriately depending on the type of alcohol derived from the carbonate ester to be distilled. For example, if the alcohol to be distilled has a relatively low boiling point, such as methanol, the preferred pressure in the reactor is 5 kPa to atmospheric pressure, more preferably 7 kPa to 15 kPa. Furthermore, if the alcohol to be distilled has a relatively high boiling point, such as ethylene glycol, the preferred pressure in the reactor is 1 to 10 kPa, more preferably 3 kPa to 7 kPa.

Furthermore, in order to prevent the distillation of raw materials in the early stages of the reaction, the reactor can be equipped with a fractionation column with a theoretical number of 10 or more stages, preferably 15 or more stages, and even more preferably 20 or more stages, which allows the monohydroxy compound or dihydroxy compound produced by the reaction from the carbonate ester to be efficiently separated and distilled off while azeotropically separating the monohydroxy compound or dihydroxy compound produced by the reaction from the carbonate ester. This is preferable because the raw material monomers charged are not lost and the quantitative ratio of the reagents can be accurately adjusted.

Furthermore, towards the end of the reaction, it is usually preferable to switch to simple distillation and increase the degree of vacuum to efficiently remove by-products such as monohydroxy or dihydroxy compounds such as alcohols, diols, and phenols, residual monomers such as carbonate esters, and even cyclic carbonates (cyclic oligomers) that may cause turbidity.

The reaction pressure at the end of the reaction is not particularly limited, but the upper limit is usually preferably 5 kPa, more preferably 2 kPa, and even more preferably 1 kPa or less. To effectively distill off these low-boiling components, the reaction can also be carried out while passing a small amount of an inert gas such as nitrogen, argon, or helium through the reaction system.

When using a carbonate ester or dihydroxy compound with a low boiling point during the transesterification reaction, it is possible to carry out the reaction at a temperature close to the boiling point of the carbonate diester or dihydroxy compound in the early stages of the reaction, and then gradually raise the temperature as the reaction progresses to further promote the reaction. This is preferable because it prevents unreacted carbonate diester or dihydroxy compound from distilling off in the early stages of the reaction.

<1-3-2. Polymerization reactor>
The polymerization reaction (polycondensation reaction) can be carried out either batchwise or continuously, but continuous reaction is preferable in terms of the stability of the quality of the product, such as the molecular weight. The apparatus used may be any of tank, tubular, and tower types, and known polymerization vessels equipped with various stirring blades can be used. There are no particular restrictions on the atmosphere during the temperature increase of the apparatus, but from the viewpoint of product quality, it is preferable to carry out the reaction in an inert gas such as nitrogen gas at normal pressure or reduced pressure.

<1-3-3. Reaction time>
In the method for producing the polycarbonate diol of the present embodiment, the time required for the transesterification reaction (polymerization reaction or polycondensation reaction) cannot be generally specified because it varies greatly depending on the types and amounts of the dihydroxy compound, carbonic acid diester, and transesterification catalyst used, but the reaction time required to reach a predetermined molecular weight is usually preferably 30 hours or less, more preferably 20 hours or less, and even more preferably 10 hours or less.

<1-3-4. Catalyst deactivation>
As mentioned above, when a transesterification catalyst is used in the transesterification reaction, the resulting polycarbonate diol usually contains the transesterification catalyst or its residue, which can make it difficult to control the polyurethane-forming reaction. To suppress the effects of this residual catalyst, a catalyst deactivator, such as an acidic compound or a phosphorus- or sulfur-based compound that decomposes to an acidic compound, may be added in an amount approximately equimolar to the transesterification catalyst used. Furthermore, by carrying out a heat treatment after the addition, as described below, the transesterification catalyst can be efficiently deactivated. Furthermore, by deactivating the catalyst, color development due to the transesterification catalyst can be reduced, and a polycarbonate diol can be obtained having a Hazen color scale of preferably 50 or less, more preferably 30 or less, measured in accordance with JIS-K0071-1 (1998).

Furthermore, the addition of a catalyst deactivator can suppress coloration and changes in physical properties that occur when the obtained polycarbonate diol composition is stored or handled at high temperatures for long periods of time, due to changes in the terminal structure and skeleton of the polycarbonate diol and residual catalyst.

The compound used to inactivate the transesterification catalyst (hereinafter sometimes referred to as a catalyst deactivator) is not particularly limited, but examples include inorganic phosphoric acids such as phosphoric acid and phosphorous acid, organic phosphoric acid esters such as monobutyl phosphate, dibutyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, and triphenyl phosphite, sulfonic acid, sulfonate esters, etc. These may be used alone or in combination of two or more.

The amount of catalyst deactivator used is not particularly limited, but as mentioned above, it should be approximately equimolar with the transesterification catalyst used. Specifically, the upper limit is preferably 5 mols, more preferably 2 mols, and the lower limit is preferably 0.8 mols, more preferably 1.0 mol, per 1 mol of transesterification catalyst used. When an amount of catalyst deactivator equal to or greater than the lower limit is used, the transesterification catalyst in the reaction product is sufficiently deactivated. When the resulting polycarbonate diol is used as, for example, a raw material for producing polyurethane, the reactivity of the polycarbonate diol with isocyanate groups tends to be sufficiently reduced. Furthermore, when an amount of catalyst deactivator equal to or less than the upper limit is used, coloration of the resulting polycarbonate diol can be suppressed, and urethane polymerization tends to proceed smoothly when used as a urethane raw material.

While deactivation of the transesterification catalyst by adding a catalyst deactivator can be carried out at room temperature, heating is more efficient. The temperature for this heat treatment is not particularly limited, but the upper limit is preferably 140°C, more preferably 130°C, and even more preferably 120°C, and the lower limit is preferably 80°C, more preferably 100°C, and even more preferably 110°C. At temperatures above the lower limit, the time required for deactivation of the transesterification catalyst is shortened, making it more efficient and ensuring a sufficient degree of deactivation. On the other hand, at temperatures below 140°C, when a phosphorus-based compound is used as the deactivator, decomposition of the phosphorus-based compound can be suppressed, and deactivation tends to be more stable. Therefore, discoloration of the resulting polycarbonate diol can be suppressed, and when used as a urethane raw material, the urethane-forming reaction tends to be more stable.

The reaction time with the catalyst deactivator is not particularly limited, but is, for example, 1 to 5 hours.

<1-4. Physical properties of polycarbonate diol>
Preferred physical properties of the polycarbonate diol of this embodiment produced by the method for producing a polycarbonate diol of this embodiment will be described below.

<1-4-1. Molecular weight/molecular weight distribution＞
The lower limit of the number average molecular weight (Mn) of the polycarbonate diol of this embodiment is 250, preferably 500, more preferably 750, and even more preferably 1,000. On the other hand, the upper limit of the number average molecular weight (Mn) of the polycarbonate diol of this embodiment is 100,000, preferably 50,000, more preferably 10,000, and particularly preferably 3,000. When the number average molecular weight of the polycarbonate diol is equal to or greater than the above lower limit, the flexibility and the like tend to be improved when the polycarbonate diol is made into a polyurethane. On the other hand, when the number average molecular weight of the polycarbonate diol is equal to or less than the above upper limit, the viscosity of the polycarbonate diol decreases, and handling during polyurethane formation tends to be easier.

Here, the number average molecular weight of the polycarbonate diol can be determined from the hydroxyl value (average hydroxyl value) of the polycarbonate diol, as shown in the examples below.

The method for controlling the number average molecular weight (Mn) of the polycarbonate diol within the above range is not particularly limited, but examples include a method for controlling the number average molecular weight (Mn) of the polycarbonate diol within the above range by adjusting the polycondensation reaction time of the polycarbonate diol and adjusting the amount of the dihydroxy compound, which is the raw material monomer, that is withdrawn.

<1-4-2. APHA value>
The color of the polycarbonate diol of this embodiment is preferably 50 or less, more preferably 40 or less, even more preferably 30 or less, and particularly preferably 20 or less, in terms of the Hazen color number (based on JIS K0071-1:1998) (hereinafter referred to as "APHA value"). The lower limit of the APHA value is not particularly limited, but is, for example, 0 or more. When the APHA value is 50 or less, the color tone of the polyurethane obtained using the polycarbonate diol as a raw material tends to be good, which improves the commercial value and improves the thermal stability.

The method for controlling the APHA value of the polycarbonate diol within the above range is not particularly limited, but examples include a method in which the reaction temperature during the ester exchange reaction is within the above-mentioned preferred temperature range, and a method in which the time required for the ester exchange reaction (polymerization reaction or polycondensation reaction) is within the above-mentioned preferred range.

In this embodiment, the APHA value of the polycarbonate diol can be measured by the method described in the Examples below.

<1-4-3. Metals contained in polycarbonate diol>
The polycarbonate diol of the present embodiment preferably contains, as a metal, at least one metal selected from the group consisting of metals in Groups 6, 7, 8, 9, 10, and 11 of the long form periodic table.

The total metal content in the polycarbonate diol is preferably 1 ppm to 25 ppm, more preferably 2 ppm to 15 ppm, and particularly preferably 5 ppm to 10 ppm.

When the amount of transesterification catalyst is 1 ppm or more in total as metal, the APHA value of the polycarbonate diol becomes low, which is preferable. Furthermore, when the amount of transesterification catalyst is 25 ppm or less in total as metal, discoloration of the polycarbonate diol due to heating can be suppressed, and when used as a urethane raw material, the urethane reaction tends to be stable, which is preferable.

The polycarbonate diol of this embodiment preferably contains at least one metal selected from molybdenum, manganese, iron, cobalt, nickel, and copper. Of these, manganese is particularly preferred.

The metals contained in these polycarbonate diols may be present as residues of the polymerization catalyst, but may also be intentionally added in a specified amount after production.

In this embodiment, the content of at least one metal selected from the group consisting of metals in Groups 6, 7, 8, 9, 10, and 11 of the long periodic table in the polycarbonate diol can be measured by the method described in the Examples below.

<1-4-4. Ether bond>
The polycarbonate diol of this embodiment has a basic structure in which a dihydroxy compound is polymerized via a carbonate group. However, depending on the production method, ether bonds may be formed as a result of side reactions such as the dehydration of a dihydroxy compound or the decarboxylation of a carbonate ester. If the amount of ether bonds present increases, weather resistance and heat resistance may decrease. Therefore, it is preferable to produce the polycarbonate diol so that the proportion of ether bonds is not excessively high. In order to reduce the ether bonds in the polycarbonate diol and ensure properties such as weather resistance and heat resistance, the amount of ether bonds contained in the molecular chain of the polycarbonate diol of this embodiment is usually 5 mol% or less, preferably 3 mol% or less, and more preferably 1 mol% or less, in terms of mole percent. These values can be determined by alkaline hydrolysis followed by gas chromatography. Specifically, they can be measured by the method described in the Examples below.

The method for controlling the amount of ether bonds contained in the polycarbonate diol within the above range is not particularly limited, but examples include a method using the transesterification catalyst of the present application to produce the polycarbonate diol under milder reaction conditions in a short period of time.

In this embodiment, the amount of ether bonds contained in the polycarbonate diol can be measured by the method described in the Examples below.

<1-4-5. Terminal primary hydroxyl group (OH) ratio>
The terminal primary hydroxyl (OH) purity of the polycarbonate diol of this embodiment is preferably 97% or more, more preferably 98% or more, and even more preferably 99% or more. When the terminal primary OH ratio is 97% or more, the reaction rate tends to be high when polyurethane (particularly thermoplastic polyurethane) is produced (synthesized) using the polycarbonate diol of this embodiment as a raw material compound, and the strength of the resulting polyurethane tends to be high.

The method for controlling the terminal primary hydroxyl (OH) purity of polycarbonate diol within the above range is not particularly limited, but examples include a method using the transesterification catalyst of the present application to produce the polycarbonate diol under milder reaction conditions in a short time.

In this embodiment, the terminal primary hydroxyl (OH) purity of the polycarbonate diol can be measured by the method described in the Examples below.

<1-5. Uses of Polycarbonate Diol>
The polycarbonate diol of this embodiment has excellent mechanical properties and durability and can be used in a variety of applications. For example, it can be widely used in foams, elastomers, paints, fibers, adhesives, flooring materials, sealants, medical materials, artificial leather, coating agents, water-based polyurethane paints, etc. In particular, when the polycarbonate diol of this embodiment is used as a raw material for applications such as artificial leather, synthetic leather, water-based polyurethane, adhesives, medical materials, flooring materials, and coating agents, it has excellent weather resistance, heat resistance, moist heat resistance, and abrasion resistance, and can impart good surface properties such as little coloring, resistance to scratches, and little deterioration due to friction, making it suitable for use as a raw material for various coatings.

The polyurethane of this embodiment contains units derived from the above-described polycarbonate diol. By containing units derived from the above-described polycarbonate diol, the polyurethane of this embodiment has excellent chemical resistance, heat resistance, and hydrolysis resistance.

The present embodiment will be explained in more detail below using examples, but the present embodiment is not limited to these examples. Note that the number of parts in the examples is by weight unless otherwise specified.

In the following examples and comparative examples, the physical properties of the polycarbonate diol and polyurethane film were tested according to the following test methods.

<Test Method>
[Evaluation of transesterification catalyst performance]
In the production of polycarbonate diol (PCD) from a dihydroxy compound and a carbonate ester, for example, as shown in the following formula (10), the monomer raw materials, carbonate ester (e.g., ethylene carbonate (EC)) and dihydroxy compound (raw material diol), decrease in the esterification step, polycarbonate diol (PCD) is produced, and a hydroxy compound derived from the carbonate ester (a monohydroxy compound when the raw material carbonate ester is a dialkyl carbonate, or a dihydroxy compound when the raw material carbonate ester is an alkylene carbonate, e.g., ethylene glycol (EG)) is produced as a by-product.

(Here, an example is shown in which ethylene carbonate (EC) is used as the carbonate ester. In this case, ethylene glycol (EG) is produced as a by-product of the reaction.)

To evaluate catalytic performance, in the reaction to produce polycarbonate diol (PCD) from a dihydroxy compound and a carbonate ester, the amount of hydroxy compound (monohydroxy compound when the raw material carbonate ester is a dialkyl carbonate; dihydroxy compound when the raw material carbonate ester is an alkylene carbonate, for example, ethylene glycol (EG)) distilled out 2 hours and 5 hours after the start of the reaction was determined by gas chromatography, and the carbonate conversion was calculated using the following formula (11), (12), or (13).

(Method of calculating carbonate conversion rate when alkylene carbonate is used)
Carbonate conversion rate (%) = (number of moles of dihydroxy compound distilled) / (number of moles of charged carbonate ester) × 100 (11)

(Method of calculating carbonate conversion rate when dialkyl carbonate is used)
Carbonate conversion rate (%) = (number of moles of distilled hydroxy compound/2)/(number of moles of charged carbonate ester) × 100 (12)

(Method of calculating carbonate conversion rate when diphenyl carbonate is used)
Carbonate conversion rate (%) = (number of moles of distilled phenol/2)/(number of moles of charged carbonate ester) × 100 (13)

The conditions for gas chromatographic analysis were as follows:
A gas chromatograph GC-14B (Shimadzu Corporation) equipped with a DB-WAX (J&W) column was used, 1,3-propanediol was used as the internal standard, and an FID detector was used. The column temperature profile was maintained at 100°C for 5 minutes, and then increased to 200°C at a rate of 5°C/min.

[Measurement of hydroxyl group (OH) value]
An acetylation reagent was prepared by diluting 12.5 g of acetic anhydride with 50 mL of pyridine. 2.5 to 5.0 g of sample was precisely weighed into a 100 mL recovery flask. 5 mL of acetylation reagent and 10 mL of toluene were added to the recovery flask using a volumetric pipette. A condenser was attached, and the solution in the recovery flask was stirred and heated at 100°C for 1 hour. 2.5 mL of distilled water was added to the recovery flask using a volumetric pipette, and the solution in the recovery flask was heated and stirred for an additional 10 minutes. After cooling the solution in the recovery flask for 2 to 3 minutes, 12.5 mL of ethanol was added. After adding 2 to 3 drops of phenolphthalein as an indicator to the recovery flask, the solution in the recovery flask was titrated with 0.5 mol/L ethanolic potassium hydroxide.

As a blank test, 5 mL of acetylation reagent, 10 mL of toluene, and 2.5 mL of distilled water were placed in a 100 mL recovery flask, heated and stirred for 10 minutes, and then titrated in the same manner as above. Based on this result, the hydroxyl (OH) value was calculated using the following formula (2).

OH number (mg-KOH/g) = {(b-a) × 28.05 × f}/e (2)
a: titer of sample (mL)
b: Titration volume of blank test (mL)
e: sample mass (g)
f: factor of titrant

[Number average molecular weight (Mn)]
The number average molecular weight was calculated by the following formula (3).
Number average molecular weight = 2 / (OH number × ¹⁰ / 56.11) (3)

[Measurement of APHA value]
The Hazen color number (APHA value) was measured by comparing with a standard solution placed in a colorimetric tube in accordance with JIS K0071-1. For polycarbonate diols that are solid at room temperature, the polycarbonate diols were heated to 70°C, dissolved, and the APHA value was measured.

[Method for analyzing the amount of ether bonds in polycarbonate diol]
1 g of polycarbonate diol was placed in a 100 mL recovery flask, and 30 g of methanol and 8 g of 28% sodium methoxide methanol solution were added and reacted at 100°C for 1 hour. After cooling the reaction solution to room temperature, 2-3 drops of phenolphthalein were added as an indicator and neutralized with hydrochloric acid. The neutralized reaction solution was cooled in a refrigerator for 1 hour and then filtered. The resulting filtrate was then analyzed using gas chromatography (GC). GC analysis was performed using a gas chromatograph GC-14B (Shimadzu Corporation, Japan) equipped with a DB-WAX column (J&W, USA). 1,3-propanediol was used as the internal standard and a flame ionization detector (FID) was used as the detector, and quantitative analysis of each component was performed. The column temperature profile was maintained at 110°C for 5 minutes, followed by a temperature increase of 5°C/min to 200°C.

Ether bonds are thought to be formed by the dehydration of hydroxyl groups or the decomposition (decarboxylation) of carbonate esters. For example, when polycarbonate diol is produced using ethylene carbonate and hexanediol as raw materials, diethylene glycol and 6-(2-hydroxyethoxy)hexan-1-ol are detected as compounds having ether bonds. The amount of ether bonds (%) shown in the examples and comparative examples of this application refers to the ratio (mol %) of the total amount of diethylene glycol and 6-(2-hydroxyethoxy)hexan-1-ol to the total amount of the raw material diol, diethylene glycol, and 6-(2-hydroxyethoxy)hexan-1-ol, as quantified by gas chromatography after alkaline decomposition.

[Method for Analyzing Terminal Primary Hydroxyl Group (OH) Ratio of Polycarbonate Diol]
70g to 100g of polycarbonate diol was weighed into a 300ml recovery flask, and using a rotary evaporator connected to a trap bulb for fraction collection, the mixture was heated in a heating bath at about 180°C under a pressure of 0.1kPa or less and stirred to obtain a fraction equivalent to about 1 to 2% by mass of the polycarbonate diol, i.e., about 1g (0.7 to 2g) of fraction, in the trap bulb. This fraction was recovered using about 100g (95 to 105g) of ethanol as a solvent. The recovered solution was analyzed by gas chromatography (hereinafter referred to as GC analysis), and the terminal primary hydroxyl (OH) ratio (%) of the polycarbonate diol was calculated from the peak area of the obtained chromatograph using the following formula (4): The GC analysis was performed using a Gas Chromatography 6890 (Hewlett-Packard, USA) equipped with a 30 m DB-WAX (J&W, USA) column with a film thickness of 0.25 μm, and a flame ionization detector (FID). The column temperature profile was as follows: the temperature was raised from 60°C to 250°C at a rate of 10°C/min, and then the temperature was maintained for 15 minutes.

Identification of each peak in the GC analysis was performed using the following GC-MS device. The GC device used was a 6890 (Hewlett-Packard, USA) equipped with a DB-WAX (J&W, USA) column. The GC device was heated from an initial temperature of 40°C to 220°C at a rate of 10°C/min. The MS device used was an Auto-mass SUN (JEOL, Japan). The MS device was set to an ionization voltage of 70 eV, a scan range of m/z = 10-500, and a photomultiplier gain of 450V.

Terminal primary OH ratio (%) = B÷A×100 (4)
A: Sum of peak areas of alcohols (excluding ethanol) containing diols B: Sum of peak areas of diols having primary OH groups at both ends

[Residual catalyst amount in polycarbonate diol]
Approximately 0.1 g of polycarbonate diol was weighed out and dissolved in 4 mL of acetonitrile to obtain a solution. Then, 20 mL of pure water was added to the obtained solution to precipitate polycarbonate diol. The precipitated polycarbonate diol was removed by filtration. The filtered solution was then diluted with pure water to a predetermined concentration. The metal ion concentration in the diluted solution was analyzed by ion chromatography. The metal ion concentration of the acetonitrile used as the solvent was measured as a blank value, and the metal ion concentration of this solvent was subtracted from the metal ion concentration in the diluted solution to obtain the metal ion concentration in the polycarbonate diol product. The measurement conditions were as shown below. The concentrations of manganese and titanium remaining in the polycarbonate diol were determined using previously prepared calibration curves for manganese and titanium.

High-performance liquid chromatograph (HPLC) measurement conditions: Apparatus: Waters 2690
Column: IonPac CS12A
Flow rate: 1.0ml/min
Injection volume: 1.5ml
Pressure: 950-980 psi
Column temperature: 35°C
Detector sensitivity: RANGE 200 μS
Suppressor: CSRS 60mA
Eluent: 20 mmol/L methanesulfonic acid aqueous solution

[Measurement of molecular weight of polyurethane]
A portion of the polyurethane film was cut out, and an N,N-dimethylacetamide (DMF) solution was prepared so that the polyurethane concentration was 0.1% by mass. Using the prepared DMF solution, the molecular weights of the polyurethane were measured as follows. For the measurement, a GPC device (manufactured by Tosoh Corporation, product name "HLC-8320" (column: Tskgel Super HM-H, 4 columns) was used. Furthermore, a solution of 2.6 g of lithium bromide dissolved in 1 L of dimethylacetamide was used as the eluent. From the measurement results obtained, the number average molecular weight (Mn) and weight average molecular weight (Mw) of the polyurethane, converted into standard polystyrene, were calculated.

[Room temperature tensile test of polyurethane film]
In accordance with JIS K6301 (2010), rectangular test pieces measuring 10 mm in width, 100 mm in length, and approximately 0.5 mm in thickness were prepared from the polyurethane film. A tensile test was performed on the prepared test pieces using a tensile tester (manufactured by Orientec Co., Ltd., product name "Tensilon, Model RTE-1210") at a chuck distance of 20 mm, a tensile speed of 100 mm/min, and a temperature of 23°C (relative humidity of 55%). In the tensile test, the stress at the time when the test piece was elongated by 100% (100% modulus), as well as the strength at break and elongation at break were measured.

[Evaluation of oleic acid resistance of polyurethane]
A 3 cm x 3 cm test piece was cut out from the polyurethane film. The weight of the test piece was measured using a precision balance. The test piece was then placed in a 250 mL glass bottle containing 50 mL of oleic acid as a test solvent, and left to stand in a constant temperature bath under a nitrogen atmosphere at 80°C for 16 hours to perform a chemical resistance test. After the test, the test piece was removed and the front and back were lightly wiped with a paper wiper. The weight of the test piece was then measured using a precision balance. The weight change rate (increase rate) from before the test was calculated using the following formula. A weight change rate closer to 0% indicates better oleic acid resistance (chemical resistance).
Weight change rate (%)=(weight of test piece after test−weight of test piece before test)/weight of test piece before test×100

[Evaluation of heat resistance of polyurethane]
A rectangular test piece measuring 10 mm in width, 100 mm in length, and approximately 50 μm in thickness was prepared from the polyurethane film. The test piece was heated in a gear oven at 120°C for 1000 hours. After heating, the test piece was measured for breaking strength in the same manner as in the room temperature tensile test described above. The breaking strength retention (%) was calculated using the following formula:

Breaking strength retention (%) = Breaking strength of test piece after heating / Breaking strength of test piece before testing x 100

[Evaluation of Hydrolysis Resistance of Polyurethane]
A rectangular test piece measuring 10 mm in width, 100 mm in length, and approximately 50 μm in thickness was prepared from the polyurethane film. The test piece was heated in a thermo-hygrostat at a temperature of 85°C and a relative humidity of 85% for 200 hours. After heating, the test piece was measured for breaking strength in the same manner as in the above-mentioned [Room Temperature Tensile Test]. The breaking strength retention (%) was calculated using the following formula:

Breaking strength retention (%) = Breaking strength of test piece after heating / Breaking strength of test piece before testing x 100

[Compound abbreviation]
The abbreviations for compounds in the following examples and comparative examples are as follows:
Mn(acac) ₂ ·2H ₂ O: Manganese(II) acetylacetonate dihydrate Mn(acac) ₃ : Manganese(III) acetylacetonate Mn(OAc) ₂ ·4H ₂ O: Manganese(II) acetate tetrahydrate Mn(tBuCOCH2COtBu) ₂ ·2H ₂ O: 2,2,6,6-tetramethyl-3,5-heptanedionato manganese(II) dihydrate Mn(CF ₃ COCH ₂ COCF ₃ ) ₂ ·2H 2 O: Hexafluoroacetylacetonato manganese dihydrate [Mo(acac)] ₂ : Molybdenum(II) acetylacetonate dimer Mg(acac) ₂ : Magnesium(II) acetylacetonate Fe(acac) ₃ : Iron(III) acetylacetonate Co(acac) _{2.2H 2} O: Cobalt(II) acetylacetonate dihydrate Ni(acac) _{2.2H 2} O: Nickel(II) acetylacetonate dihydrate Cu(acac) ₂ : Copper(II) acetylacetonate Ti(OBu) ₄ : Tetra-n-butyl titanate Ti(acac) ₂ (OiPr) ₂ : Titanium(IV) bis(acetylacetonate)diisopropoxide Mg(acac) ₂ : Magnesium (II) acetylacetonate EC: Ethylene carbonate EG: Ethylene glycol DMC: Dimethyl carbonate DEC: Diethyl carbonate DPC: Diphenyl carbonate 13PDO: 1,3-propanediol 14BDO: 1,4-butanediol 15PDO: 1,5-pentanediol 16HDO: 1,6-hexanediol 110DDO: 1,10-decanediol 3M15PDO: 3-methyl-1,5-pentanediol

[Example 1]
A 1-L separable flask equipped with a stirrer, thermometer, and vacuum-jacketed Oldershaw flask (15 theoretical plates) with a reflux head on top was charged with 355 g (3.00 mol) of 1,6-hexanediol as raw material monomers and 264 g (3.00 mol) of ethylene carbonate, and 16.3 mg of manganese(II) acetylacetonate dihydrate as a catalyst was added (5 ppm in terms of metal amount relative to the total amount of all dihydroxy compounds and carbonate esters). The raw materials in the flask were heated in an oil bath set to 170°C, and the raw material monomers were polycondensed by transesterification at an internal temperature of 150°C and a vacuum of 4 kPa for 5 hours while removing a portion of the distillate from the reflux head, to obtain a polycarbonate diol. The carbonate conversion was analyzed by gas chromatography 2 and 5 hours after the start of the reaction. The results are shown in Table 1.

[Examples 2 to 10, Comparative Examples 1 to 3]
A polycarbonate diol was obtained by polycondensing raw material monomers through transesterification in the same manner as in Example 1, except that the type and amount of catalyst added were the type and amount shown in Table 2. The carbonate conversion was analyzed by gas chromatography 2 hours and 5 hours after the start of the reaction, in the same manner as in Example 1. The results are shown in Table 2.

[Examples 19 to 22, Comparative Examples 8 to 10]
A polycarbonate diol was obtained by polycondensing raw material monomers through transesterification in the same manner as in Example 1, except that the type and amount of catalyst added, the type and amount of carbonate ester used, and the reaction temperature were changed as shown in Table 3. The carbonate conversion rates were analyzed by gas chromatography 2 hours and 5 hours after the start of the reaction, as in Example 1. The results are shown in Table 3.

[Examples 23 to 30, Comparative Examples 11 to 15]
A polycarbonate diol was obtained by polycondensing raw material monomers through transesterification in the same manner as in Example 1, except that the type and amount of catalyst added and the type and amount of dihydroxy compound used were changed to those shown in Table 4. The carbonate conversion was analyzed by gas chromatography 2 hours and 5 hours after the start of the reaction, as in Example 1. The results are shown in Table 4.

[Example 31]
A 1 L separable flask equipped with a stirrer, a thermometer, and a vacuum jacketed Oldershaw reactor (15 theoretical plates) with a reflux head on top was charged with 355 g (3.00 mol) of 1,6-hexanediol as raw material monomers and 264 g (3.00 mol) of ethylene carbonate, and 13.8 mg of manganese (II) acetate tetrahydrate was added as a catalyst (5 ppm as metal amount relative to the total amount of all dihydroxy compounds and carbonate esters). The raw materials in the flask were heated in an oil bath set to 170°C, and the raw material monomers were polycondensed by transesterification at an internal temperature of 150°C and a vacuum degree of 4 kPa for 5 hours while removing a portion of the distillate from the reflux head, to obtain a polycarbonate diol.
Thereafter, the distillation was switched to simple distillation, and while gradually reducing the pressure to 0.5 kPa, the oil bath temperature was set to 175°C, and the reaction was carried out for 2 hours at an internal flask temperature of 160°C, and the monomer was distilled to obtain a polycarbonate diol. Nitrogen gas was introduced into the flask to return to normal pressure, and then the oil bath temperature was set to 125°C, and the internal flask temperature was set to 110-120°C. Monobutyl phosphate was added as a catalyst deactivator in an amount equimolar to the amount of catalyst charged, and the mixture was stirred for 3 hours at a temperature of 110-120°C. The analysis results of the obtained polycarbonate diol are shown in Table 5. This polycarbonate polyol is referred to as PC1.

[Examples 32 to 34]
Polycarbonate diols were synthesized in the same manner as in Example 31, except that the dihydroxy compounds used were of the types and amounts shown in Table 5. The carbonate conversion after 5 hours and the properties of the resulting polycarbonate diols are shown in Table 5. The resulting polycarbonates are designated PC2, PC3, and PC4, respectively.

[Example 35]
Polycarbonate diol was synthesized in the same manner as in Example 31, except that the type and amount of dihydroxy compound used were as shown in Table 5 and the reaction time after switching to simple distillation was 1 hour. The carbonate conversion after 5 hours and the properties of the obtained polycarbonate diol are shown in Table 5. The obtained polycarbonate is referred to as PC5.

[Example 36]
Polycarbonate diol was synthesized in the same manner as in Example 31, except that the type and amount of dihydroxy compound used were as shown in Table 5 and the reaction time after switching to simple distillation was 3 hours. The carbonate conversion after 5 hours and the properties of the obtained polycarbonate diol are shown in Table 5. The obtained polycarbonate is called PC6.

[Comparative Example 16]
A 1 L separable flask equipped with a stirrer, a thermometer, and a vacuum jacketed Oldershaw reactor (15 theoretical plates) with a reflux head on top was charged with 355 g (3.00 mol) of 1,6-hexanediol as raw material monomers and 264 g (3.00 mol) of ethylene carbonate, and 22.0 mg of tetra-n-butyl titanate as a catalyst (5 ppm as metal amount relative to the total amount of all dihydroxy compounds and carbonate esters). The raw materials in the flask were heated in an oil bath set to 170°C, and the raw material monomers were polycondensed by transesterification at an internal temperature of 150°C and a vacuum degree of 4 kPa for 20 hours while removing a portion of the distillate from the reflux head, to obtain a polycarbonate diol.
Thereafter, the distillation was switched to simple distillation, and while gradually reducing the pressure to 0.5 kPa, the oil bath temperature was set to 180°C, and the reaction was carried out for 6 hours at an internal flask temperature of 160-170°C, and the monomer was distilled to obtain a polycarbonate diol. Nitrogen gas was introduced into the flask to return to normal pressure, and then the oil bath temperature was set to 125°C, and the internal flask temperature was set to 110-120°C. Monobutyl phosphate was added as a catalyst deactivator in an amount equimolar to the amount of catalyst charged, and the mixture was stirred for 3 hours at a temperature of 110-120°C. The analysis results of the obtained polycarbonate diol are shown in Table 5. This polycarbonate polyol is called PC7.

[Comparative Example 17]
Polycarbonate diols were synthesized in the same manner as in Comparative Example 16, except that the dihydroxy compounds used were of the types and amounts shown in Table 5. The carbonate conversion after 5 hours and the properties of the resulting polycarbonate diols are shown in Table 5. The resulting polycarbonates are referred to as PC8.

[Example 37]
A 200 mL separable flask equipped with a stirring blade was heated in a 60°C oil bath and sealed with nitrogen. It was charged with 15.7 g of diphenylmethane-4,4'-diisocyanate (hereinafter also referred to as "MDI"), 180 g of N,N-dimethylformamide (hereinafter also referred to as "DMF") as a solvent, and 0.003 g of dibutyltin dilaurate as a catalyst. A solution of 42 g of polycarbonate diol PC1 and 60 g of DMF, which had been preheated to 60°C, was added dropwise using a dropping funnel over approximately 1 hour to obtain a solution. The resulting solution was stirred for 1 hour, after which 3.2 g of 1,4-butanediol (hereinafter also referred to as "14BDO") was added. The solution was further stirred at 60°C for 3 hours, after which 1 g of ethyl alcohol was added to quench the reaction. The resulting polyurethane solution was applied to a polypropylene resin sheet (100 mm wide, 1200 mm long, 1 mm thick) using an applicator to a width of 80 mm, length of 100 mm, and thickness of 0.6 mm to obtain a coating film. The resulting coating film was dried on a hot plate at a surface temperature of 60°C for 2 hours, and then dried in an oven at 100°C for 12 hours. The film was then left to stand at a constant temperature and humidity of 23°C and 55% RH for at least 48 hours to obtain a polyurethane film. The resulting polyurethane film was subjected to evaluation of various physical properties. The evaluation results are shown in Table 6.

[Examples 38 to 42, Comparative Examples 18 and 19]
Polyurethane films were obtained in the same manner as in Example 37, except that PC2 to PC8 were used as polycarbonate diols and the amounts of MDI and 14BDO were changed to those shown in Table 6. The obtained polyurethane films were subjected to evaluation of various physical properties. The evaluation results are shown in Table 6.

Claims (11)

The method includes a step of polycondensing a dihydroxy compound and a carbonate ester as raw material monomers through an ester exchange reaction in the presence of an ester exchange catalyst to obtain a polycarbonate diol,
the transesterification catalyst contains at least one metal (M) selected from the group consisting of metals of Groups 6, 7, 8, 9, 10, and 11 of the long form periodic table ,
The method for producing a polycarbonate diol , wherein the transesterification catalyst is at least one metal complex and/or a hydrate thereof represented by the following formula (1) :
(In the formula, R1 _and R3 _each independently represent a monovalent hydrocarbon group having 1 to 10 carbon atoms, and the hydrocarbon groups of R1 _and R3 _may be substituted with a halogen atom or may have an oxygen atom; R2 _represents hydrogen or a monovalent hydrocarbon group having 1 to 10 carbon atoms, and the hydrocarbon group of R2 _may be substituted with a halogen atom or may have an oxygen atom; M represents at least one metal selected from the group consisting of metals of Groups 6, 7, 8, 9, 10, and 11 of the long form periodic table; and n is 1, 2, or 3. The metal complex represented by formula (1) may also be an association of multiple metals.) The method includes a step of polycondensing a dihydroxy compound and a carbonate ester as raw material monomers through an ester exchange reaction in the presence of an ester exchange catalyst to obtain a polycarbonate diol,
the transesterification catalyst contains at least one metal (M) selected from the group consisting of metals of Groups 6, 7, 8, 9, 10, and 11 of the long form periodic table,
The transesterification catalyst is a salt of at least one carboxylic acid and at least one metal (M) selected from the group consisting of metals of Groups 6, 7, 8, 9, 10, and 11 of the long form periodic table, and/or a hydrate thereof, represented by the following formula (2):
(In the formula, R ₄ represents a monovalent hydrocarbon group having 1 to 20 carbon atoms, R ₄ The hydrocarbon group may be substituted with a halogen atom or may have an oxygen atom. 3. The method for producing a polycarbonate diol according to claim 1 or 2 , wherein the metal (M) is at least one metal selected from the group consisting of molybdenum, manganese, iron, cobalt, nickel, and copper. The method for producing a polycarbonate diol according to any one of claims 1 to 3 , wherein the metal (M) is manganese. The method for producing a polycarbonate diol according to any one of claims 1 to 4 , wherein the amount of the transesterification catalyst, as the total amount of the metal (M), is 0.5 ppm or more and 20 ppm or less with respect to the total amount of all dihydroxy compounds and carbonate esters. The method for producing a polycarbonate diol according to any one of claims 1 to 5 , wherein the dihydroxy compound comprises at least one selected from the group consisting of aliphatic dihydroxy compounds and alicyclic dihydroxy compounds having a structure represented by the following formula (3):
(wherein _R5 represents a divalent aliphatic or alicyclic hydrocarbon having 2 to 20 carbon atoms.) The method for producing a polycarbonate diol according to any one of claims 1 to 6 , wherein the carbonate ester is at least one selected from the group consisting of alkylene carbonate, dialkyl carbonate, and diaryl carbonate. It is a polycondensation product obtained by an ester exchange reaction between a dihydroxy compound and a carbonate ester,
The number average molecular weight is 250 or more and 100,000 or less,
The polycarbonate diol contains at least one metal selected from the group consisting of metals of Groups 6, 7, 8, 9, 10, and 11 of the long form periodic table in a total amount of 1 ppm to 25 ppm,
The Hazen color number measured in accordance with JIS-K0071-1 (1998) is 50 or less,
the amount of ether bonds is 5 mol% or less,
A polycarbonate diol having a terminal primary hydroxyl (OH) purity of 97% or more. The polycarbonate diol according to claim 8 , wherein the metal is at least one metal selected from molybdenum, manganese, iron, cobalt, nickel, and copper. The polycarbonate diol according to claim 8 or 9 , wherein the metal is manganese. A polyurethane comprising units derived from the polycarbonate diol according to any one of claims 8 to 10 .