Method for producing aliphatic polycarbonate

Abstract

Provided is a method for producing an aliphatic polycarbonate by polymerizing an alkylene oxide and carbon dioxide in the presence of a metal catalyst and a chain transfer agent, wherein: the metal catalyst is at least one selected from the group consisting of a zinc-based catalyst, a cobalt-based catalyst, an aluminum-based catalyst, and a composite metal cyanide complex catalyst; and the chain transfer agent is at least one selected from the group consisting of methanol, a compound (a) having a primary hydroxyl group, and a compound (b) having a phenolic hydroxyl group.

Description

Method for producing aliphatic polycarbonate

[0001] This invention relates to a method for producing aliphatic polycarbonates.

[0002] Polycarbonate resins possess excellent mechanical strength, heat resistance, and transparency, and are used in a wide range of industrial fields, including electrical and electronic, automotive, and optical. Among polycarbonate resins, aliphatic polycarbonates have good thermal decomposition properties and are therefore used as binders for firing in semiconductor manufacturing processes to produce sintered bodies of metal particles, ceramic particles, and other materials.

[0003] Patent Document 1 discloses a sintering bonding composition containing conductive metal-containing sinterable particles, the average particle size being 70 nm or more and 2 μm or less, with a proportion of particles with a particle size of 100 nm or less being 80% by mass or more, wherein polypropylene carbonate is used as the binder resin.

[0004] Japanese Patent Publication No. 2023-41064

[0005] When using aliphatic polycarbonate as a binder resin in a sintering bonding composition, it is necessary to adjust the molecular weight of the aliphatic polycarbonate to a desired range in order to optimize the viscosity of the composition containing the binder resin, or the shape retention of the molded product. One method for adjusting the molecular weight of a polymer is to use a chain transfer agent during polymerization. However, in polymerization systems that use a chain transfer agent, unused chain transfer agent may remain after the reaction is complete. The remaining unused chain transfer agent not only increases manufacturing costs but also causes a decrease in the purity of the resulting polymer and variations in quality, so it is desirable to suppress it. Furthermore, the presence of a chain transfer agent tends to reduce the monomer conversion rate in the polymerization reaction, making it difficult to obtain a good monomer conversion rate while keeping the unused rate of the chain transfer agent low.

[0006] This invention has been made in view of the above circumstances, and aims to provide a method for producing aliphatic polycarbonate that can obtain a good monomer conversion rate while keeping the unused rate of chain transfer agents low.

[0007] The present inventors have conducted studies to solve the above problems and have found that the following embodiments can solve the problems. That is, the present invention relates to the following [1] to

[13] . [1] A method for producing an aliphatic polycarbonate, wherein an alkylene oxide and carbon dioxide are polymerized in the presence of a metal catalyst and a chain transfer agent, wherein the metal catalyst is one or more selected from the group consisting of zinc-based catalysts, cobalt-based catalysts, aluminum-based catalysts and complex metal cyanide complex catalysts, and the chain transfer agent is one or more selected from the group consisting of methanol, a compound having a primary hydroxyl group (a) and a compound having a phenolic hydroxyl group (b). [2] The method for producing an aliphatic polycarbonate according to [1], wherein the alkylene oxide is 1,2-butylene oxide. [3] The method for producing an aliphatic polycarbonate according to [1] or [2], wherein the polymerization is carried out in a solvent. [4] The method for producing an aliphatic polycarbonate according to any one of [1] to [3] above, wherein the metal catalyst is an organozinc catalyst. [5] The method for producing an aliphatic polycarbonate according to [4] above, wherein the organozinc catalyst is zinc glutarate. [6] The method for producing an aliphatic polycarbonate according to any one of [1] to [5] above, wherein the chain transfer agent is methanol or the compound (a) having a primary hydroxyl group. [7] The method for producing an aliphatic polycarbonate according to [6] above, wherein the compound (a) having a primary hydroxyl group has only one primary hydroxyl group. [8] The method for producing an aliphatic polycarbonate according to [7] above, wherein the compound (a) having a primary hydroxyl group is a compound having 2 to 12 carbon atoms. [9] The method for producing an aliphatic polycarbonate according to any one of [1] to [8] above, wherein the chain transfer agent is the compound (b) having a phenolic hydroxyl group.

[10] The method for producing an aliphatic polycarbonate according to [9] above, wherein the compound (b) having a phenolic hydroxyl group has only one phenolic hydroxyl group.

[11] The method for producing an aliphatic polycarbonate according to any one of [1] to

[10] above, wherein the amount of the chain transfer agent used is 0.01 to 5.0 parts by mass per 100 parts by mass of the alkylene oxide.

[12] A method for producing an aliphatic polycarbonate according to any one of [1] to

[11] , wherein the mass-average molecular weight (Mw) of the aliphatic polycarbonate is 30,000 to 1,000,000.

[13] A method for producing an aliphatic polycarbonate according to any one of [1] to

[12] , wherein the molecular weight dispersion (PDI) of the aliphatic polycarbonate is 3 to 70.

[0008] According to the present invention, it is possible to provide a method for producing aliphatic polycarbonate that can obtain a good monomer conversion rate while keeping the unused rate of chain transfer agents low.

[0009] In this specification, the lower and upper limits described in steps for a preferred numerical range can be combined independently. For example, from the description "preferably 10 to 90, more preferably 30 to 60," the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to arrive at "10 to 60."

[0010] In this embodiment, "monomer conversion rate" refers to the conversion rate of alkylene oxide, which is a raw material monomer for aliphatic polycarbonate. Specifically, the monomer conversion rate can be measured by the method described in the examples.

[0011] In this specification, "unconsumed chain transfer agent rate" refers to the ratio of the chain transfer agent remaining in the reaction system after the polymerization reaction is completed to the amount of chain transfer agent added at the start of polymerization. Specifically, the unconsumed chain transfer agent rate can be measured by the method described in the examples.

[0012] The mechanism of action described herein is speculative and does not limit the mechanism by which the present invention achieves its effects.

[0013] [Method for producing aliphatic polycarbonate] The method for producing aliphatic polycarbonate according to this embodiment is a method for producing aliphatic polycarbonate by polymerizing alkylene oxide and carbon dioxide in the presence of a metal catalyst and a chain transfer agent, wherein the metal catalyst is one or more selected from the group consisting of zinc-based catalysts, cobalt-based catalysts, aluminum-based catalysts and complex metal cyanide catalysts, and the chain transfer agent is one or more selected from the group consisting of methanol, a compound having a primary hydroxyl group (a) and a compound having a phenolic hydroxyl group (b).

[0014] The detailed reasons why the aliphatic polycarbonate production method of this embodiment achieves a good monomer conversion rate while keeping the unused rate of the chain transfer agent low are unclear, but the following is speculated. In the aliphatic polycarbonate production method of this embodiment, one or more compounds selected from the group consisting of methanol, a compound having a primary hydroxyl group (a), and a compound having a phenolic hydroxyl group (b) are used as the chain transfer agent. These chain transfer agents have a structure that is likely to exist near the surface of the metal catalyst that exhibits reaction activity, and it is speculated that this is one of the reasons why the chain transfer reaction proceeds well.

[0015] The following describes the raw materials used in the aliphatic polycarbonate manufacturing method of this embodiment, and then explains each step in detail.

[0016] <Alkylene Oxides> Examples of alkylene oxides include ethylene oxide, propylene oxide, 1,2-butylene oxide, isobutylene oxide, 1,2-pentene oxide, 1,2-hexene oxide, 1,2-octen oxide, 1,2-decene oxide, cyclopentene oxide, cyclohexene oxide, and their derivatives. Among these, propylene oxide and 1,2-butylene oxide are preferred, and 1,2-butylene oxide is more preferred, from the viewpoint that the resulting aliphatic polycarbonate is suitable as a binder for calcination. One type of alkylene oxide may be used alone, or two or more types may be used in combination.

[0017] The content of propylene oxide or 1,2-butylene oxide in the total amount (100% by mass) of alkylene oxide used in the method for producing aliphatic polycarbonate of this embodiment is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, even more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, even more preferably 98 to 100% by mass, and particularly preferably 99 to 100% by mass.

[0018] <Metal Catalyst> The metal catalyst used in the method for producing aliphatic polycarbonate in this embodiment is one or more selected from the group consisting of zinc-based catalysts, cobalt-based catalysts, aluminum-based catalysts, and complex metal cyanide catalysts. One metal catalyst may be used alone, or two or more may be used in combination.

[0019] Examples of zinc-based catalysts include zinc halides such as zinc iodide, zinc bromide, and zinc chloride; aliphatic zinc carboxylates such as zinc acetate, zinc adipate, and zinc glutarate; complex metal cyanide catalysts containing zinc (DMC catalysts); and diethylzinc. Among these, the zinc-based catalyst is preferably an organozinc catalyst, more preferably an aliphatic zinc carboxylate, even more preferably an aliphatic zinc dicarboxylate such as zinc adipate and zinc glutarate, and even more preferably zinc glutarate. Examples of cobalt-based catalysts include cobalt halides such as cobalt iodide, cobalt bromide, and cobalt chloride; aliphatic cobalt carboxylates such as cobalt acetate; organocobalt complexes such as cobalt salen complexes and cobalt porphyrin complexes. Examples of aluminum-based catalysts include aluminum halides such as aluminum iodide, aluminum bromide, and aluminum chloride; aliphatic aluminum carboxylates such as aluminum acetate; and organoaluminum complexes such as aluminum acetylacetonate and aluminum salen complexes. As a complex metal cyanide catalyst, zinc hexacyanocobaltate (Zn ３ [Co(CN) ６ ] ２Examples include the following. Among these, zinc-based catalysts are preferred from the viewpoint of exhibiting high polymerization activity, zinc aliphatic dicarboxylates are more preferred, one or more selected from the group consisting of zinc glutarate and zinc adipate are even more preferred, and zinc glutarate is even more preferred.

[0020] The amount of metal catalyst used is preferably 1 to 40 parts by mass, more preferably 5 to 35 parts by mass, even more preferably 10 to 30 parts by mass, and particularly preferably 15 to 25 parts by mass, per 100 parts by mass of alkylene oxide used. When the amount of metal catalyst used is above the lower limit, a good monomer conversion rate is more easily obtained. Furthermore, when the amount of metal catalyst used is below the upper limit, catalyst residue is suppressed while also being more economically viable.

[0021] <Chain Transfer Agent> The chain transfer agent used in the method for producing aliphatic polycarbonate in this embodiment is one or more selected from the group consisting of methanol, compounds having a primary hydroxyl group (a), and compounds having a phenolic hydroxyl group (b). In this embodiment, compounds having both a primary hydroxyl group and a phenolic hydroxyl group are classified as compounds having a primary hydroxyl group (a). The chain transfer agent may be used alone or in combination of two or more.

[0022] (Compound (a) having a primary hydroxyl group) In this embodiment, a primary hydroxyl group means a hydroxyl group to which the carbon atom to which the hydroxyl group (-OH) is bonded has one carbon atom bonded. The hydroxyl group in compound (a) having a primary hydroxyl group may be a primary hydroxyl group only, or it may be a combination of a primary hydroxyl group and a hydroxyl group other than a primary hydroxyl group (for example, a secondary hydroxyl group, a tertiary hydroxyl group, or a phenolic hydroxyl group). However, from the viewpoint of keeping the unused rate of the chain transfer agent low while more easily obtaining a good monomer conversion rate, it is preferable to have only a primary hydroxyl group.

[0023] The total number of hydroxyl groups in compound (a) having a primary hydroxyl group is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1, from the viewpoint of more easily obtaining a good monomer conversion rate. Among these, the number of primary hydroxyl groups is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1, from the viewpoint of more easily obtaining a good monomer conversion rate. In particular, from the viewpoint of more easily obtaining a good monomer conversion rate while keeping the unused rate of the chain transfer agent low, it is preferable that compound (a) having a primary hydroxyl group has only one primary hydroxyl group.

[0024] The number of carbon atoms in compound (a) having a primary hydroxyl group is preferably 2 to 12, more preferably 3 to 10. When the number of carbon atoms in compound (a) having a primary hydroxyl group is above the lower limit, a good monomer conversion rate is more easily obtained. Also, when the number of carbon atoms in compound (a) having a primary hydroxyl group is below the upper limit, the rate of unused chain transfer agent is more easily kept low. Particularly from the viewpoint of monomer conversion rate, the number of carbon atoms in compound (a) having a primary hydroxyl group is more preferably 2 to 11, even more preferably 3 to 10, even more preferably 4 to 9, and particularly preferably 5 to 8. Furthermore, from the viewpoint of the effect of reducing the molecular weight of the obtained aliphatic polycarbonate, the number of carbon atoms in compound (a) having a primary hydroxyl group is more preferably 2 to 10, even more preferably 2 to 7, even more preferably 2 to 5, and particularly preferably 3 or 4.

[0025] As the compound (a) having a primary hydroxyl group, an aliphatic alcohol is preferred. The aliphatic group of the aliphatic alcohol may be linear or branched, but it is preferable that it be linear, as this makes it easier to obtain a good monomer conversion rate while keeping the unused rate of the chain transfer agent low.

[0026] Examples of the compound (a) having a primary hydroxyl group include aliphatic monoalcohols such as ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, and benzyl alcohol; aliphatic dialcohols such as ethylene glycol, 1,3-propanediol, and 1,4-butanediol; and the like. Among these, aliphatic monoalcohols are preferred, and n-butanol is more preferred, from the viewpoint that good monomer conversion is more easily obtained while keeping the unconsumed ratio of the chain transfer agent low.

[0027] (Compound (b) having a phenolic hydroxyl group) The hydroxyl group contained in the compound (b) having a phenolic hydroxyl group may be only a phenolic hydroxyl group, or may be both a phenolic hydroxyl group and a hydroxyl group other than a phenolic hydroxyl group (e.g., a secondary hydroxyl group, a tertiary hydroxyl group). However, from the viewpoint that good monomer conversion is more easily obtained while keeping the unconsumed ratio of the chain transfer agent low, it is preferable that the compound has only a phenolic hydroxyl group.

[0028] From the viewpoint that good monomer conversion is more easily obtained, the total number of hydroxyl groups contained in the compound (b) having a phenolic hydroxyl group is preferably 1 to 3, more preferably 1 or 2, and still more preferably 1. Among them, from the viewpoint that good monomer conversion is more easily obtained, the number of phenolic hydroxyl groups is preferably 1 to 3, more preferably 1 or 2, and still more preferably 1. In particular, from the viewpoint that good monomer conversion is more easily obtained while keeping the unconsumed ratio of the chain transfer agent low, it is preferable that the compound (b) having a phenolic hydroxyl group has only one phenolic hydroxyl group as the hydroxyl group.

[0029] The number of carbon atoms in the compound (b) having a phenolic hydroxyl group is preferably 6 to 15, more preferably 6 to 10, and still more preferably 6 to 8. When the number of carbon atoms in the compound (b) having a phenolic hydroxyl group is not less than the above lower limit, good monomer conversion is more easily obtained. Further, when the number of carbon atoms in the compound (b) having a phenolic hydroxyl group is not more than the above upper limit, the unconsumed ratio of the chain transfer agent is easily kept lower.

[0030] Examples of the compound (b) having a phenolic hydroxyl group include monofunctional phenols such as phenol, o-cresol, m-cresol, p-cresol, 2,4-xylenol, 2,6-xylenol, p-tert-butylphenol, o-tert-butylphenol, nonylphenol, octylphenol, 2,6-di-tert-butylphenol, 2,6-di-tert-butyl-4-methylphenol, and 2,6-diisopropylphenol; and polyhydric phenols such as catechol, resorcinol, hydroquinone, bisphenol A, bisphenol F, and bisphenol S. Among these, monofunctional phenols are preferred, and phenol is more preferred, from the viewpoint that a favorable monomer conversion rate is more easily obtained while keeping the unconsumed ratio of the chain transfer agent low.

[0031] The amount of the chain transfer agent used is preferably 0.01 to 5.0 parts by mass, more preferably 0.1 to 4.5 parts by mass, still more preferably 0.3 to 4.0 parts by mass, and even more preferably 0.5 to 3.5 parts by mass, per 100 parts by mass of the alkylene oxide used. When the amount of the chain transfer agent used is not less than the above lower limit, an aliphatic polycarbonate having a sufficiently low molecular weight is easily obtained. Further, when the amount of the chain transfer agent used is not more than the above upper limit, the unconsumed ratio of the chain transfer agent is easily kept lower.

[0032] <Solvent> In the method for producing aliphatic polycarbonate in this embodiment, polymerization of alkylene oxide and carbon dioxide is preferably carried out in a solvent. Examples of solvents include aliphatic hydrocarbons such as pentane, hexane, octane, decane, and cyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; halogenated hydrocarbons such as chloromethane, dichloromethane, chloroform, carbon tetrachloride, 1,1-dichloroethane, chlorobenzene, and bromobenzene; carboxylic acid esters such as ethyl acetate, propyl acetate, butyl acetate, and isobutyl acetate; carbonate esters such as dimethyl carbonate, diethyl carbonate, propylene carbonate, and butylene carbonate; lactams such as N-methyl-2-pyrrolidone; glycol ethers or glycol ether acetates such as propylene glycol monomethyl ether acetate, diethylene glycol dimethyl ether, propylene glycol diacetate, and butyl carbitol acetate; and the like. Among these, one or more selected from the group consisting of toluene, chloroform, ethyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol dimethyl ether, propylene glycol diacetate, butyl carbitol acetate, butylene carbonate, propylene carbonate, and xylene are preferred, with toluene and ethyl acetate being more preferred. The solvent may be used alone or in combination of two or more.

[0033] The amount of solvent used is such that, when the total amount of solvent and alkylene oxide is 100% by mass, the concentration of alkylene oxide is preferably 10 to 60% by mass, more preferably 20 to 50% by mass, and even more preferably 25 to 40% by mass. When the amount of solvent used is within the above range, the viscosity of the reaction solution tends to be within an appropriate range, and the reaction proceeds more efficiently. As a result, it becomes easier to obtain a good monomer conversion rate stably while reducing the rate of unused chain transfer agent.

[0034] <Other Components> In the method for producing aliphatic polycarbonate according to this embodiment, other components besides those listed above may be used. Examples of other components include co-catalysts used together with a metal catalyst.

[0035] (Co-catalysts) Examples of co-catalysts include bis(triphenylphosphoranylidene)ammonium chloride, 4-dimethylaminopyridine, tetrabutylammonium chloride, tetrabutylammonium bromide, triphenylphosphine, 1,5,7-triazabicyclo[4.4.0]deca-5-ene, and 1,4-diazabicyclo[2.2.2]octane. Co-catalysts may be used individually or in combination of two or more.

[0036] In the method for producing aliphatic polycarbonate according to this embodiment, the method for carrying out the polymerization reaction between alkylene oxide and carbon dioxide is not particularly limited as long as the target product is obtained, and the alkylene oxide, metal catalyst, chain transfer agent, solvent used as needed, co-catalyst, etc., and carbon dioxide may be brought into contact and reacted in a reaction vessel. Specifically, for example, a method may be used in which each component is mixed and stirred in a reaction vessel equipped with a stirring device such as an autoclave, and maintained under predetermined temperature and pressure conditions. In this case, the method of supplying carbon dioxide may be to fill the reaction vessel all at once, or to continuously or intermittently supply carbon dioxide as it is consumed as the reaction progresses. The order in which carbon dioxide and alkylene oxide are supplied to the reaction vessel is not particularly limited, for example, carbon dioxide may be injected under pressure into a reaction vessel into which alkylene oxide has been charged, or alkylene oxide may be supplied into a reaction vessel into which carbon dioxide has been injected under pressure.

[0037] The pressure at which carbon dioxide is injected during the polymerization reaction is preferably 0.1 to 20 MPa, more preferably 0.1 to 10 MPa, and even more preferably 0.1 to 5 MPa. If the pressure at which carbon dioxide is injected is above the lower limit, the polymerization reaction proceeds more easily. Also, if the pressure at which carbon dioxide is injected is below the upper limit, excessive use of carbon dioxide is suppressed, improving economic efficiency.

[0038] The reaction temperature during the polymerization reaction is preferably 20 to 100°C, more preferably 25 to 90°C, and even more preferably 30 to 80°C, from the viewpoint of reaction rate and suppression of side reactions.

[0039] The reaction time for the polymerization reaction can be adjusted as appropriate depending on the reaction temperature, but is preferably 0.5 to 40 hours, more preferably 1 to 10 hours, and even more preferably 1.5 to 6 hours.

[0040] During the polymerization reaction, it is preferable to keep the amount of water in the reaction system at 3 mol% or less relative to the amount (moles) of metal catalyst used.

[0041] After the polymerization reaction is complete, the target aliphatic polycarbonate can be extracted by known methods after performing any known post-treatment procedures. The obtained aliphatic polycarbonate may also be purified if necessary.

[0042] [Aliphatic Polycarbonate] Next, preferred embodiments of the aliphatic polycarbonate produced by the aliphatic polycarbonate production method of this embodiment (hereinafter also referred to as "aliphatic polycarbonate of this embodiment") will be described.

[0043] The aliphatic polycarbonate of this embodiment has a polymerization chain in which structural units (hereinafter also referred to as "carbonate units") consisting of a divalent aliphatic hydrocarbon group and a carbonate group (-O-C(=O)-O-) are linked.

[0044] In this embodiment, the aliphatic polycarbonate is preferably one having substituted or unsubstituted aliphatic hydrocarbon groups having 2 to 6 carbon atoms in its side chains, which are directly or via oxygen atoms bonded to the main chain. In this embodiment, the side chain of the aliphatic polycarbonate refers to an atomic group containing carbon atoms that branch off from the carbon atom chains linearly connected to the adjacent carbonate groups, within the molecular chain formed by linking carbonate units. The main chain of the aliphatic polycarbonate refers to the molecular chain formed by linking the above carbonate units, excluding the side chains. For example, when a carbonate unit consisting of a branched divalent aliphatic hydrocarbon group and a carbonate group (-O-C(=O)-O-) is linked, the carbon atom chain linearly connected to the carbonate group constitutes the main chain, and the carbon atom chains branching off from the linearly connected carbon atom chains within the branched divalent aliphatic hydrocarbon group constitute the side chains.

[0045] In the following explanation, the "substituted or unsubstituted aliphatic hydrocarbon groups having 2 to 6 carbon atoms that are directly or via an oxygen atom attached to the main chain" that aliphatic polycarbonates have in their side chains may be referred to as "aliphatic hydrocarbon groups (Y)".

[0046] The aliphatic hydrocarbon group (Y) may be linear, branched, or cyclic, and may have both linear and cyclic structures, but it is preferable that it be linear from the viewpoint of ease of manufacture, etc.

[0047] The aliphatic hydrocarbon group (Y) has 2 to 6 carbon atoms. When the aliphatic hydrocarbon group (Y) has 2 or more carbon atoms, the coating suitability and flexibility in the film form tend to be better. When the aliphatic hydrocarbon group (Y) has 6 or fewer carbon atoms, excellent thermal decomposition properties are obtained. From the same viewpoint as above, the aliphatic hydrocarbon group (Y) is preferably 2 to 5, more preferably 2 to 4, even more preferably 2 or 3, and even more preferably 2. Note that the carbon atoms of substituents are not included in the carbon atom count of the aliphatic hydrocarbon group (Y) mentioned above.

[0048] Examples of substituents that the aliphatic hydrocarbon group (Y) may have include hydroxyl groups, thiol groups, cyano groups, amino groups, silyl groups, halogen atoms such as fluorine, chlorine, bromine, and iodine; alkoxy groups, alkenyloxy groups; aryl groups such as phenyl groups; heteroaryl groups containing oxygen, nitrogen, sulfur, selenium, and phosphorus atoms as heteroatoms; aryloxy groups such as phenoxy groups; heteroaryloxy groups containing oxygen, nitrogen, sulfur, selenium, and phosphorus atoms as heteroatoms; alkylsilyl groups; alkylsilyloxy groups; and so on. From the viewpoint of thermal decomposition, the number of carbon atoms in the substituents that the aliphatic hydrocarbon group (Y) may have is preferably 6 or less, more preferably 3 or less, even more preferably 2 or less, even more preferably 1 or less, and particularly preferably 0. From the viewpoint of thermal decomposition, it is preferable that the aliphatic hydrocarbon group (Y) does not have substituents containing hydrocarbon groups, and it is more preferable that it does not have substituents.

[0049] Examples of aliphatic hydrocarbon groups (Y) include substituted or unsubstituted C2-C6 alkyl groups; substituted or unsubstituted C2-C6 alkenyl groups; substituted or unsubstituted C2-C6 alkynyl groups; and the like. Among these, substituted or unsubstituted C2-C6 alkyl groups are preferred from the viewpoint of thermal decomposition and ease of manufacture. Examples of C2-C6 alkyl groups include chain-like alkyl groups such as ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, 3-methylbutyl group, and n-hexyl group; and cyclic alkyl groups such as cyclopropyl group, cyclopentyl group, and cyclohexyl group. Among these, from the viewpoint of thermal decomposition, substituted or unsubstituted linear alkyl groups are preferred, substituted or unsubstituted linear alkyl groups are more preferred, unsubstituted linear alkyl groups are even more preferred, and unsubstituted ethyl groups are even more preferred.

[0050] The main chain of the aliphatic polycarbonate in this embodiment may or may not have groups other than the aliphatic hydrocarbon group (Y) as side chains or substituents. From the viewpoint of thermal decomposition, it is preferable that the groups other than the aliphatic hydrocarbon group (Y) do not contain hydrocarbon groups having 2 or more carbon atoms. Examples of groups that do not contain hydrocarbon groups having 2 or more carbon atoms include substituted or unsubstituted methyl groups; substituted or unsubstituted methoxy groups; hydroxyl groups; thiol groups; cyano groups; amino groups; silyl groups; halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; and so on. However, from the viewpoint of thermal decomposition, it is preferable that the aliphatic polycarbonate in this embodiment does not have groups other than the aliphatic hydrocarbon group (Y) directly bonded to the main chain.

[0051] The aliphatic hydrocarbon group (Y) is bonded to the main chain either directly or via an oxygen atom, but from the viewpoint of thermal decomposition, it is preferable that the group is directly bonded to the main chain.

[0052] From the viewpoints of thermal decomposability and dispersion stability, the structural unit having an aliphatic hydrocarbon group (Y) in a side chain is preferably a structural unit represented by the following general formula (1).

[0053] (wherein, R １ and R ２ are each independently a hydrogen atom, an aliphatic hydrocarbon group (Y) or a group containing no hydrocarbon group having 2 or more carbon atoms, and all R contained in the structural unit １ and R ２ among them, at least one is an aliphatic hydrocarbon group (Y). n is an integer of 1 to 10.)

[0054] R １ and R ２ The descriptions of the "aliphatic hydrocarbon group (Y)" and "the group containing no hydrocarbon group having 2 or more carbon atoms" represented by are as described above.

[0055] Among all R contained in the structural unit represented by the above general formula (1) １ and R ２ among them, at least one is an aliphatic hydrocarbon group (Y); from the viewpoint of thermal decomposability, 1 to 3 are preferably aliphatic hydrocarbon groups (Y), more preferably 1 or 2 are aliphatic hydrocarbon groups (Y), and it is further preferable that only one is an aliphatic hydrocarbon group (Y).

[0056] Among all R contained in the structural unit represented by the above general formula (1) １ and R ２ among them, those that are not aliphatic hydrocarbon groups (Y) are all preferably hydrogen atoms.

[0057] n in the above general formula (1) is an integer of 1 to 10; from the viewpoints of thermal decomposability and dispersion stability, it is preferably 1 to 8, more preferably 2 to 6, further preferably 2 to 4, still more preferably 2 to 3, and particularly preferably 2.

[0058] When the aliphatic polycarbonate of the present embodiment has a structural unit represented by the above general formula (1), the structural unit may be a single type alone, or may be two or more types.

[0059] From the viewpoint of thermal decomposition properties and dispersion stability, the structural unit represented by the above general formula (1) is preferably the structural unit represented by the following general formula (1a).

[0060] (In the formula, R １ , R ２ , R ３ and R ４ Each of these is independently a hydrogen atom or an aliphatic hydrocarbon group (Y), and R １ , R ２ , R ３ and R ４ Of these, at least one is an aliphatic hydrocarbon group (Y).

[0061] From the viewpoint of thermal decomposition properties and dispersion stability, the structural unit represented by the above general formula (1a) is preferably the structural unit represented by the following formula (1a-1) or the structural unit represented by the following formula (1a-2).

[0062]

[0063] Aliphatic polycarbonates may or may not contain structural units other than carbonate units having an aliphatic hydrocarbon group (Y) in their side chains. From the viewpoint of thermal decomposition and dispersion stability, the content of carbonate units having an aliphatic hydrocarbon group (Y) in their side chains, structural units represented by the above general formula (1), or structural units represented by the above general formula (1a) in the aliphatic polycarbonate is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 95 mol% or more, and even more preferably 99 mol% or more, and may be 100 mol%. Note that "total structural units" of aliphatic polycarbonates means the total number of structural units based on one monomer molecule. Structures derived from carbon dioxide are not counted as a single unit; rather, a structure formed from one monomer molecule and one carbon dioxide molecule (i.e., a structure consisting of a divalent hydrocarbon group and a carbonate group (-O-C(=O)-O-) derived from one monomer molecule) is considered a single unit.

[0064] Examples of aliphatic polycarbonates in this embodiment include polyethylene carbonate, polypropylene carbonate, polybutylene carbonate, polypentylene carbonate, polyhexylene carbonate, polyheptylene carbonate, polyoctylene carbonate, and derivatives thereof. Among these, polybutylene carbonate is preferred from the viewpoint of thermal decomposition and dispersion stability.

[0065] The aliphatic polycarbonate of this embodiment preferably has at least one terminal residue of a compound (a) having a methyl group, a primary hydroxyl group, or a phenolic hydroxyl group, with the phenolic hydroxyl group removed.

[0066] Hereinafter, the "methyl group, the residue obtained by removing the primary hydroxyl group from compound (a) having a primary hydroxyl group, or the residue obtained by removing the phenolic hydroxyl group from compound (b) having a phenolic hydroxyl group" that the aliphatic polycarbonate of this embodiment has at least one terminal may be referred to as the "terminal group (X)".

[0067] The aliphatic polycarbonate of this embodiment preferably has an end group (X) at at least one end. For example, if the aliphatic polycarbonate of this embodiment is a linear polymer, it may have an end group (X) at only one end, or it may have an end group (X) at both ends. Also, if the aliphatic polycarbonate of this embodiment is a branched polymer, it may have an end group (X) at only one end, or it may have an end group (X) at only two ends, or it may have an end group (X) at three or more ends. If the aliphatic polycarbonate of this embodiment has two or more end groups (X), the two or more end groups (X) may be the same as or different from each other.

[0068] Examples of aliphatic polycarbonates having terminal groups (X) include those represented by the following general formula (2).

[0069] (In the formula, R represents a divalent aliphatic hydrocarbon group. X represents a terminal group (X). m represents an integer between 2 and 500.)

[0070] The above general formula (2) represents a linear aliphatic polycarbonate with a terminal group (X) attached to one end and an OH group at the other end. For example, if the terminal group (X) is a residue of 1-butanol excluding the hydroxyl group, then X in the above general formula (2) is an n-butyl group. Also, if the terminal group (X) is a residue of phenol excluding the phenolic hydroxyl group, then X in the above general formula (2) is a phenyl group.

[0071] During the manufacturing process of aliphatic polycarbonates, structural units constituting ether bonds may be formed within the molecule through the reaction of alkylene oxides. In such cases, the aliphatic polycarbonate of this embodiment may also have a structure of the following general formula (3) or (4).

[0072] (In the formula, R represents a divalent aliphatic hydrocarbon group. X represents a terminal group (X). m represents an integer from 2 to 500. s represents an integer from 1 to 50.)

[0073] (In the formula, R represents a divalent aliphatic hydrocarbon group. X represents a terminal group (X). m represents an integer from 2 to 500. p represents an integer from 1 to 10. t represents an integer from 1 to 10.)

[0074] (Mass-average molecular weight (Mw)) The mass-average molecular weight (Mw) of the aliphatic polycarbonate in this embodiment is preferably 30,000 to 1,000,000, more preferably 70,000 to 800,000, even more preferably 100,000 to 600,000, even more preferably 130,000 to 530,000, even more preferably 160,000 to 480,000, even more preferably 190,000 to 430,000, and particularly preferably 220,000 to 380,000. When the mass-average molecular weight (Mw) of the aliphatic polycarbonate is within the above range, the viscosity of the composition containing the binder resin, or the shape retention of the molded article, tends to be good when the aliphatic polycarbonate is used as a binder resin. The mass-average molecular weight (Mw) of the aliphatic polycarbonate can be measured by the method described in the example.

[0075] (Number-average molecular weight (Mn)) The number-average molecular weight (Mn) of the aliphatic polycarbonate in this embodiment is preferably 3,000 to 50,000, more preferably 4,000 to 45,000, even more preferably 5,000 to 40,000, even more preferably 6,000 to 35,000, even more preferably 7,000 to 30,000, even more preferably 7,500 to 25,000, and particularly preferably 8,000 to 20,000. When the number-average molecular weight (Mn) of the aliphatic polycarbonate is within the above range, the viscosity of the composition containing the binder resin, or the shape retention of the molded article, tends to be good when the aliphatic polycarbonate is used as a binder resin. The number-average molecular weight (Mn) of the aliphatic polycarbonate can be measured by the method described in the example.

[0076] (Molecular weight dispersibility (PDI)) The molecular weight dispersibility (PDI) of the aliphatic polycarbonate in this embodiment is preferably 3 to 70, more preferably 6 to 50, even more preferably 10 to 40, even more preferably 12 to 35, and even more preferably 15 to 30. When the molecular weight dispersibility (PDI) of the aliphatic polycarbonate is within the above range, the coating suitability and flexibility in the film form tend to be good when the aliphatic polycarbonate is used as a binder resin. The molecular weight dispersibility (PDI) of the aliphatic polycarbonate can be measured by the method described in the examples.

[0077] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0078] [Measurement of Mass-Average Molecular Weight (Mw) and Number-Average Molecular Weight (Mn)] The mass-average molecular weight (Mw) and number-average molecular weight (Mn) of the polybutylene carbonate obtained in each example and comparative example were measured using a gel permeation chromatograph (Tosoh Corporation, product name "HLC-8320") under the following conditions, and the measurements were converted to standard polystyrene equivalents. In addition, the molecular weight dispersion (PDI = Mw / Mn) was calculated from the obtained mass-average molecular weight (Mw) and number-average molecular weight (Mn). <GPC Measurement Conditions> • Column: A sequence of "TSK guard column SuperH-H", "TSK gel SuperHM-H", "TSK gel SuperHM-H", and "TSK gel SuperH2000" (all manufactured by Tosoh Corporation) linked together. • Column temperature: 40°C • Developing solvent: Tetrahydrofuran • Injection volume: 20 μL • Flow rate: 0.6 mL / min • Detector: Differential refractometer • Standard sample: Polystyrene

[0079] [Measurement of monomer conversion rate and unused rate of chain transfer agent] Nuclear magnetic resonance spectroscopy is used to measure the reaction solution obtained by polymerization. １ ¹H-NMR (Biospin Avance 500, Bruker) was used as the solvent, with CDClone. ３Measurements were performed using (containing 0.03 volume% tetramethylsilane). From the measurement results, the monomer conversion rate was calculated based on the ratio of residual monomer to generated polymer. The unused rate of the chain transfer agent was calculated by the following method. First, the amount of residual monomer was calculated based on the conversion rate (%) calculated above. Specifically, the number of moles of residual monomer was calculated as M. Ｒ [mol], the number of moles of monomer added M ０ When the number of moles of residual monomer is [mol] and the monomer conversion rate is C [%], then the number of moles of residual monomer is M. Ｒ [mol] was calculated using the following formula (i). M Ｒ [m] = M ０ [mol] × (100 - C) / 100 ... (i) The number of moles of residual monomer M obtained by the above formula (i) Ｒ [mol] and, １ Based on the proportional relationship with the integral value of residual monomers in the H-NMR spectrum, １ From the integral value of the residual chain transfer agent in the H-NMR spectrum, the number of residual moles of the chain transfer agent CTA can be determined. ＲＥＳ [mol] was calculated. Furthermore, the number of moles of chain transfer agent added (CTA) was calculated. ０ [mol] and the number of residual moles of the chain transfer agent CTA ＲＥＳ From [mol], the percentage of unconsumed chain transfer agent was calculated using the following formula (ii): Percentage of unconsumed chain transfer agent (%) = CTA ＲＥＳ [mol] / CTA ０ [mol]×100...(ii)

[0080] Production Example 1 (Production of Zinc Glutarate) 2.00 g of zinc oxide and 3.12 g of glutaric acid were placed in a 50 mL glass container. The reaction vessel was rotated at room temperature for 24 hours using a mix rotor (set rotation speed 100 rpm) to agitate the raw materials. After agitation, a white powder was obtained. The mixture was then dried in a vacuum dryer at 120°C for 5 hours to obtain zinc glutarate as a zinc-based catalyst.

[0081] [Production of Aliphatic Polycarbonates] Examples 1-9, Comparative Examples 1-4 1,2-butylene oxide as a raw material monomer, a chain transfer agent of the type shown in Table 1, and a metal catalyst were dissolved in toluene as a solvent to obtain a mixture. The amount of 1,2-butylene oxide used was 3.0 g, and the chain transfer agent and metal catalyst were added in the proportions shown in Table 1 per 100 parts by mass of 1,2-butylene oxide. The amount of solvent was set so that the concentration of the raw material monomer was 30% by mass when the total amount of solvent and monomer was 100% by mass. Next, the system of a 50 mL autoclave equipped with a stirrer, gas inlet tube, and thermometer was pre-filled with a nitrogen atmosphere, and the above mixture was charged in. Subsequently, while stirring the mixture in the autoclave, carbon dioxide gas was added to the reaction system until the pressure reached 2.5 MPa, and then the temperature was raised to the temperature shown in Table 1. After that, carbon dioxide gas was added to the reaction system until the pressure reached 4 MPa, and the polymerization reaction was carried out for the time shown in Table 1. After the reaction was complete, the autoclave was cooled and depressurized, the contents were diluted with toluene, and the metal catalyst was removed by reprecipitation purification. The resulting solution was then dried to obtain polybutylene carbonate.

[0082] [Evaluation Method] The reaction solution and polybutylene carbonate obtained above were analyzed and evaluated using the method described above. The results are shown in Table 1.

[0083]

[0084] The meanings of each symbol in Table 1 are as follows: ZnGA: Zinc glutarate produced in Production Example 1; DMC: Zinc(II) hexacyanocobalt(III)ate; Mw: Mass-average molecular weight; Mn: Number-average molecular weight; PDI: Molecular weight dispersion (Mw / Mn)

[0085] In Table 1, "-" indicates that the corresponding component was not used, or that the reaction did not proceed and the corresponding physical properties could not be measured or evaluated. In Table 1, "*1" indicates that measurement was not possible because the sample was outside the measurement range of the gel permeation chromatograph.

[0086] Table 1 shows that the method for producing aliphatic polycarbonate according to this embodiment provides a method for producing aliphatic polycarbonate that can obtain a good monomer conversion rate while keeping the unused rate of the chain transfer agent low.

Claims

1. A method for producing an aliphatic polycarbonate, comprising polymerizing an alkylene oxide and carbon dioxide in the presence of a metal catalyst and a chain transfer agent, wherein the metal catalyst is one or more selected from the group consisting of zinc-based catalysts, cobalt-based catalysts, aluminum-based catalysts and complex metal cyanide catalysts, and the chain transfer agent is one or more selected from the group consisting of methanol, a compound having a primary hydroxyl group (a) and a compound having a phenolic hydroxyl group (b).

2. The method for producing an aliphatic polycarbonate according to claim 1, wherein the alkylene oxide is 1,2-butylene oxide.

3. A method for producing an aliphatic polycarbonate according to claim 1 or 2, wherein the polymerization is carried out in a solvent.

4. The method for producing an aliphatic polycarbonate according to claim 1 or 2, wherein the metal catalyst is an organozinc catalyst.

5. The method for producing an aliphatic polycarbonate according to claim 4, wherein the organozinc catalyst is zinc glutarate.

6. The method for producing an aliphatic polycarbonate according to claim 1 or 2, wherein the chain transfer agent is methanol or the compound (a) having a primary hydroxyl group.

7. The method for producing an aliphatic polycarbonate according to claim 6, wherein the compound (a) having a primary hydroxyl group has only one primary hydroxyl group.

8. The method for producing an aliphatic polycarbonate according to claim 7, wherein the compound (a) having a primary hydroxyl group is a compound having 2 to 12 carbon atoms.

9. The method for producing an aliphatic polycarbonate according to claim 1 or 2, wherein the chain transfer agent is the compound (b) having a phenolic hydroxyl group.

10. The method for producing an aliphatic polycarbonate according to claim 9, wherein the compound (b) having a phenolic hydroxyl group has only one phenolic hydroxyl group.

11. The method for producing an aliphatic polycarbonate according to claim 1 or 2, wherein the amount of the chain transfer agent used is 0.01 to 5.0 parts by mass per 100 parts by mass of the alkylene oxide.

12. The method for producing an aliphatic polycarbonate according to claim 1 or 2, wherein the mass-average molecular weight (Mw) of the aliphatic polycarbonate is 30,000 to 1,000,000.

13. The method for producing an aliphatic polycarbonate according to claim 1 or 2, wherein the molecular weight dispersion (PDI) of the aliphatic polycarbonate is 3 to 70.

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