WO2025229959A1 - Method for producing polycarbonate - Google Patents

Abstract

Disclosed is a method for producing a polycarbonate, the method including reacting carbon dioxide with an epoxy compound in the presence of an inorganic metal salt that contains a rare earth element (excluding a halide of scandium and a halide of cerium) so as to produce a polycarbonate.

Description

Polycarbonate manufacturing method

This disclosure relates to a method for producing polycarbonate.

Polycarbonates are used in many fields, such as ceramic binders, polyurethane raw materials, adhesives, and biocompatible materials.
Polycarbonate is produced, for example, by alternating copolymerization of carbon dioxide and an epoxy compound. Various catalysts for use in the production of polycarbonate have been investigated.

For example, Patent Document 1 describes a catalyst for producing polycarbonate from epoxide and carbon dioxide, which is characterized by comprising a mixture of one or more scandium compounds (first catalyst) selected from scandium alkoxides, halides, and triflate compounds, and one or more metal compounds (second catalyst) selected from metal alkoxides, metal halides, and metal halide alkoxides of titanium, zirconium, hafnium, and cerium.

JP 2009-242794 A

The objective of one embodiment of the present disclosure is to provide a novel method for producing polycarbonate using an easy-to-handle catalyst.

The means for solving the above problems include the following means.
<1>
A method for producing polycarbonate, comprising reacting carbon dioxide with an epoxy compound in the presence of an inorganic metal salt containing a rare earth element (excluding scandium halides and cerium halides).
<2>
The method for producing a polycarbonate according to <1>, wherein the inorganic metal salt is represented by the following formula (1):
M( _PO4 )...Formula (1)
In formula (1),
M is La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu.
<3>
<4> The method for producing a polycarbonate according to <1> or <2>, wherein the inorganic metal salt is cerium phosphate or lanthanum phosphate.
<3> The method for producing a polycarbonate according to any one of <1> to <3>, wherein the epoxy compound is an aliphatic epoxy compound.
<5>
<4> The method for producing a polycarbonate according to any one of <1> to <4>, wherein no solvent is used.

One embodiment of the present disclosure provides a novel method for producing polycarbonate using an easy-to-handle catalyst.

Hereinafter, an embodiment of the present disclosure will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention.
In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.
In the present specification, the word "to" is used to mean that the numerical values before and after it are included as the lower limit and upper limit.

Each component may contain multiple types of the corresponding substance.
When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified.

[Method for producing polycarbonate]
The method for producing a polycarbonate according to the present disclosure includes reacting carbon dioxide with an epoxy compound in the presence of an inorganic metal salt containing a rare earth element (excluding scandium halides and cerium halides), to produce a polycarbonate.

Conventionally, metal complexes have been used as catalysts in the production of polycarbonate. However, the synthesis of metal complexes is extremely complicated. Furthermore, metal complexes are generally unstable in environments where oxygen, water, etc. are present, making them difficult to handle in air.

In contrast, the polycarbonate production method disclosed herein is a novel method for producing polycarbonate using an easy-to-handle catalyst.

(inorganic metal salts)
The inorganic metal salt preferably functions as a catalyst in the production method of polycarbonate.

The inorganic metal salts may be used alone or in combination of two or more.
In the method for producing a polycarbonate according to the present disclosure, it is preferable to use only one type of inorganic metal salt.

Inorganic metal salts include rare earth elements. However, scandium halides and cerium halides are excluded from inorganic metal salts.

Examples of rare earth elements include scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

Among these, the rare earth element is preferably La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu, and more preferably La, Ce, Nd, Sm, Gd, or Dy.

Sals that make up inorganic metal salts include oxoacid salts such as phosphates, nitrates, nitrites, sulfates, sulfites, carbonates, bicarbonates, and silicates; halides such as chlorides, bromides, iodides, and fluorides; cyanides, thiocyanates, borates, chromates, manganates, and permanganates.

From the standpoint of yield, the salt that constitutes the inorganic metal salt is preferably an oxoacid salt, and more preferably a phosphate salt.

Among these, the inorganic metal salt is preferably represented by the following formula (1).
M( _PO4 )...Formula (1)

In formula (1), M is La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu.
From the viewpoint of yield, M is preferably Ce, Nd, Sm, Gd, or Dy, and more preferably Ce. From the viewpoint of practical application, M is preferably La. That is, the inorganic metal salt is more preferably cerium phosphate or lanthanum phosphate.
It should be noted that M may be Sc, Y, La, Ce, Pr, or Nd.

The inorganic metal salt may have a crystalline structure or may be amorphous. If it has a crystalline structure, it is preferably a hexagonal structure.
The crystal structure of the inorganic metal salt can be analyzed by X-ray diffraction.

The amount of inorganic metal salt used is preferably 0.001 to 0.1 moles per mole of epoxy compound.

(epoxy compound)
The epoxy compound used in the method for producing polycarbonate may be one kind or two or more kinds.

The epoxy compound may be an aliphatic epoxy compound or an aromatic epoxy compound.

In view of the reactivity of the epoxy compound, it is preferable that the epoxy compound be an aliphatic epoxy compound.

Examples of aliphatic epoxy compounds include ethylene oxide, propylene oxide, 1-butene oxide, 2-butene oxide, isobutylene oxide, 2,3-epoxy-2-methylbutane, 1-pentene oxide, 2-pentene oxide, 1-hexene oxide, 1-octene oxide, 1-decene oxide, 1-dodecene oxide, 3,3-dimethyl-1,2-epoxybutane, cyclopentene oxide, cyclohexene oxide, norbornene oxide, and adamantyl oxide. , 3,4-epoxytetrahydrofuran, 3,4-epoxycyclopentene, 1,4-cyclohexadiene-1,2-oxide, t-butylethylene oxide, cyclohexylethylene oxide, 2-norbornylethylene oxide, 1-adamantylethylene oxide, limonene oxide, indene oxide, 4,4-dimethyl-3,5,8-trioxabicyclo[5.1.0]octane, 1,4-dihydronaphthalene oxide, glycidol, and epichlorohydrin.
Examples of aromatic epoxy compounds include glycidyl compounds containing an aromatic ring such as a bisphenol skeleton, a fluorene skeleton, a biphenyl skeleton, a benzene ring, a naphthalene ring, an anthracene ring, etc. Examples of aromatic epoxy compounds include trans-styribene oxide, styrene oxide, 2,3-epoxypropylbenzene, and benzyl glycidyl ether.

Among these, propylene oxide is preferred as the epoxy compound.

(Polymerization initiator)
In the method for producing a polycarbonate according to the present disclosure, a polymerization initiator may be used. Use of a polymerization initiator improves the yield.
Examples of the polymerization initiator include methanol, water, and benzyl alcohol.
The amount of the polymerization initiator used is preferably 0.001 to 0.01 moles per mole of the epoxy compound.

(Reaction conditions)
In the method for producing a polycarbonate according to the present disclosure, the pressure of the carbon dioxide is preferably 1 MPa to 5 MPa.
The reaction temperature is preferably 100 to 200°C.
The reaction time is not particularly limited and is, for example, 2 to 24 hours.

In the method for producing polycarbonate according to the present disclosure, the reaction can proceed without using a solvent, which is industrially advantageous since no solvent is required.
In the present disclosure, the solvent means a solvent used in an amount of 1 mol or more per mol of the epoxy compound, and is distinguished from the above-mentioned polymerization initiator.

(Polycarbonate)
The number average molecular weight of the polycarbonate obtained by the method for producing a polycarbonate according to the present disclosure is preferably 1,000 to 30,000, and more preferably 1,000 to 10,000.

In this disclosure, number average molecular weight is measured using GPC (gel permeation chromatography).
Specifically, a high-performance liquid chromatograph (product name "HLC8420GPC", manufactured by Tosoh Corporation) equipped with a differential refractive index detector and a wavelength-tunable UV-visible detector is used, and measurements are performed at 40°C and a flow rate of 0.7 mL/min using tetrahydrofuran (THF) as an eluent and a calibration curve prepared using standard polystyrene (TSK standard polystyrene, Tosoh Corporation).

The following examples provide a more detailed explanation, but the present disclosure is not limited to these examples.

Example 1
The catalyst used was CePO ₄ (manufactured by Thermo Fisher Scientific), _which had a hexagonal crystal structure.
An autoclave equipped with a magnetic stirrer and purged with nitrogen was charged with 0.4 mmol (100 mg) of CePO ₄ , followed by 200 mmol (14 mL) of propylene oxide and 0.25 μmol (10 μL) of methanol as a polymerization initiator. Carbon dioxide was injected under pressure, and the total pressure was adjusted to 50 atmospheres (equivalent to 300 mmol of carbon dioxide). After reacting at 130°C for 24 hours, the reaction mixture was cooled to 0°C, and cold methylene chloride was added to dissolve the reaction mixture completely. A sample of this reaction mixture was analyzed by ¹ H-NMR and ¹³ C-NMR.

¹ H-NMR and ¹³ C-NMR measurements were carried out at 27° C. on a Bruker DPX-400 spectrometer using CDCl ₃ as the solvent and tetramethylsilane (δ=0.00 ppm) as the internal standard.

In the ¹ H-NMR spectrum, the integral value of the signal (2.9 ppm to 3.1 ppm) of the methine hydrogen of the remaining propylene oxide indicated that the reaction conversion of propylene oxide was about 73%.
The signal of methine hydrogen of cyclic carbonate was detected at 4.8 ppm to 4.9 ppm.
Furthermore, a signal derived from the continuous polyether bond of ring-opened propylene oxide was detected at 3.5 ppm.
The molar ratios of poly(propylene carbonate), cyclic carbonate, and polyether produced were calculated from the ¹ H-NMR spectrum.
In Table 1, poly(propylene carbonate) is abbreviated as "PC," cyclic carbonate as "CC," and polyether as "PE."

The number average molecular weight was measured using a high-performance liquid chromatograph (product name "HLC8420GPC", manufactured by Tosoh Corporation) equipped with a differential refractive index detector and a tunable UV-visible detector, at 40°C and a flow rate of 0.7 mL/min, using tetrahydrofuran (THF) as the eluent and a calibration curve prepared with standard polystyrene (TSK standard polystyrene, Tosoh Corporation).

GPC spectrum showed that the number average molecular weight of the resulting poly(propylene carbonate) was 16,000 and the molecular weight distribution was 14.7.

The catalyst used was _LaPO4 (manufactured by Aldrich Co.), _which had a hexagonal crystal structure.
The reaction was carried out in the same manner as in Example 1, except that _LaPO4 was used instead of _CePO4 .

(Examples 3 to 5)
The reaction was carried out in the same manner as in Example 1, except that the epoxy compounds shown in Table 2 were used instead of propylene oxide and the reaction temperature and reaction time were changed to those shown in Table 2.

From Table 1, it was found that polycarbonate can be produced by reacting carbon dioxide with an epoxy compound in the presence of an inorganic metal salt containing a rare earth element.
From Table 2, it can be seen that the method for producing polycarbonate according to the present disclosure can be applied to various epoxy compounds.
In particular, although the epoxy compound used in Example 5 generally has low reactivity, it was found that polycarbonate can be obtained in good yield by the method for producing polycarbonate according to the present disclosure.

(Examples 11 to 22)
- Catalyst synthesis -
A solution of (NH ₄ )HPO ₄ (15 mmol) dissolved in 50 mL of water was added to a solution of a metal nitrate (6 mmol) corresponding to the target catalyst in 50 mL of water while stirring. Aqueous ammonia was added to adjust the pH to 9.5, and the mixture was left to stand overnight. The precipitate was washed with water and ethanol and centrifuged. This procedure was repeated three times. The mixture was dried overnight at 80°C to obtain the inorganic metal salts shown in Table 3. The inorganic metal salts had the crystalline structures shown in Table 3. Note that the crystalline structure could not be analyzed in Example 12. Furthermore, when no crystalline structure was present, the material was classified as "amorphous."

- Reaction of propylene oxide -
The reaction was carried out in the same manner as in Example 1, except that the inorganic metal salts shown in Table 3 were used.

Table 3 shows that polycarbonate can be produced in high yields by reacting carbon dioxide with an epoxy compound in the presence of an inorganic metal salt containing a rare earth element.

The disclosure of Japanese Patent Application No. 2024-074004, filed on April 30, 2024, is incorporated herein by reference in its entirety. Furthermore, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims (5)

A method for producing polycarbonate, comprising reacting carbon dioxide with an epoxy compound in the presence of an inorganic metal salt containing a rare earth element (excluding scandium halides and cerium halides) to produce polycarbonate. The method for producing a polycarbonate according to claim 1 , wherein the inorganic metal salt is represented by the following formula (1):
M( _PO4 )...Formula (1)
In formula (1),
M is La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. The method for producing polycarbonate according to claim 1 or 2, wherein the inorganic metal salt is cerium phosphate or lanthanum phosphate. The method for producing polycarbonate according to claim 1 or claim 2, wherein the epoxy compound is an aliphatic epoxy compound. A method for producing polycarbonate according to claim 1 or claim 2, which does not use a solvent.