JP6677007B2 - Method for producing aliphatic polycarbonate - Google Patents

Description

  The present invention relates to a method for producing an aliphatic polycarbonate, and more particularly, to a method for producing an aliphatic polycarbonate by ring-opening polymerization of a cyclic carbonate.

  In recent years, aliphatic polycarbonates have been attracting attention as a material capable of immobilizing carbon dioxide, which is one of greenhouse gases, on a part of a molecular skeleton due to increasing awareness of reducing the burden on the global environment.

  As a method for synthesizing this aliphatic polycarbonate, a method in which carbon dioxide is directly copolymerized with an epoxy compound as a precursor in the presence of a metal coordination compound catalyst to extend the molecular weight (Patent Document 1), a tin compound or an organic compound There are known methods for producing various aliphatic polycarbonates by ring-opening polymerization of a cyclic carbonate in the presence of a base catalyst (Patent Documents 2 to 5).

In the former synthesis method, a combustible gas such as ethylene oxide may be used as a monomer. On the other hand, the latter synthesis method is a production method that is easier to handle than the former method because polymerization is performed using a liquid monomer.
As the latter synthesis method, specifically, for example, a method for producing polyethylene carbonate or polypropylene carbonate by ring-opening polymerization of ethylene carbonate or propylene carbonate, which is a kind of ring-opening polymerizable carbonate, is being studied.
The produced aliphatic polycarbonate can be processed into, for example, fibers, sheets, films, particles, and the like, and is expected to be used for cosmetic applications, films for shopping bags, and the like.

As described above, the ring-opening polymerization method of a cyclic carbonate is a production method that is easy to handle. However, as a side reaction, decarbonation in which CO ₂ in the cyclic carbonate skeleton is eliminated during the polymerization reaction is likely to occur, and the molecular weight is desired. There is a disadvantage that it does not go up to the level. In order to suppress this side reaction, these reactions are generally performed under a high-pressure carbon dioxide atmosphere, preferably in supercritical carbon dioxide.

However, even when the reaction is carried out in supercritical carbon dioxide, in the aliphatic polycarbonate obtained, some carbonate groups are etherified by decarboxylation to form oxide units, and the generated oxide units However, there is a problem that the gas barrier property and UV stability of the polymer product are reduced.
As a method for suppressing decarboxylation and reducing the oxide unit ratio in the polymer, a method of performing ring-opening polymerization using a Lewis acid and a Lewis base in combination as a catalyst is disclosed. Rate can be reduced to 20 mol% or less (Patent Document 6).
As a method for increasing the molecular weight of a polymer obtained by ring-opening polymerization, a method of continuously adding a monomer in a state where the polymerization has progressed to some extent and the molecular weight has been increased in the polymerization of lactide or the like which is the same cyclic monomer has been studied. Thus, application to ring-opening polymerization of a cyclic carbonate has been suggested (Patent Document 7).

  The present invention relates to a method for producing an aliphatic polycarbonate by ring-opening polymerization of a cyclic carbonate, wherein a polymer having a low decarboxylation rate and a high molecular weight can be produced even in the presence of carbon dioxide under a pressure less than a critical pressure. Another object of the present invention is to provide a method for producing an aliphatic polycarbonate.

  As a result of intensive studies by the inventors to solve the above problems, in the ring-opening polymerization of cyclic carbonate, by using a specific catalyst system, surprisingly, carbon dioxide under low pressure less than the critical pressure The present inventors have found that even when the reaction is carried out in the presence, the decarboxylation rate can be kept low, and furthermore, under specific conditions, by carrying out the ring-opening polymerization in two stages, the reduction of the molecular weight can be suppressed, and the present invention Was completed.

That is, the present invention is a method for producing an aliphatic polycarbonate by ring-opening polymerization of a cyclic carbonate in the presence of carbon dioxide under low pressure below the critical pressure,
A first step of supplying a first monomer containing at least one cyclic carbonate, an acid catalyst, a base catalyst, and carbon dioxide to a reactor to polymerize the first monomer;
In a reaction mixture in which the reaction for polymerizing the first monomer is proceeding, a second monomer containing the same or different kind of the first monomer and containing at least one kind of cyclic carbonate is supplied and polymerized. And a step of
In the second step, when the total amount of the mass of the polymer formed by the polymerization reaction in the reaction mixture, the mass of the first monomer, and the mass of the second monomer is 100 mass%, the first mass The fat is characterized in that the second monomer is continuously supplied so that the total amount of the mass of the monomer and the mass of the second monomer is maintained at 3% by mass or more and less than 50% by mass. Production method of aromatic polycarbonate,
It is related to.

  According to the present invention, even in the presence of carbon dioxide under a low pressure below the critical pressure, it is possible to provide a method for producing an aliphatic polycarbonate capable of producing a polymer having a low decarboxylation rate and a high molecular weight. A high-quality aliphatic polycarbonate that can be molded for use can be produced safely at low cost.

FIG. 2 is a system diagram showing an example of a continuous polymerization step. It is a system diagram which shows an example of a semi-batch type polymerization process.

Conventional methods for synthesizing aliphatic polycarbonates have all been reactions under extremely high pressure exceeding the critical pressure of carbon dioxide. For this reason, there is a problem that high-pressure equipment corresponding to the pressure is required, and security management associated with the equipment is required, so that construction costs and maintenance costs are increased.
In addition, supercritical carbon dioxide is characterized by large changes in physical properties depending on pressure and temperature.However, it is difficult to collect sufficient physical property data required for industrialization at the lab scale. There is a problem that it is difficult to optimize the process and secure the reliability in response to the problem. Further, in such a reaction under a high pressure, there is a problem in terms of throughput, for example, a long time is required for the decompression step.
For this reason, the development of a ring-opening polymerization process at a lower pressure is desired.However, in the ring-opening polymerization at a lower pressure, the molecular weight of the aliphatic polycarbonate obtained is low, and it is necessary to be able to mold and process for various applications. It was difficult to obtain a high-molecular-weight aliphatic polycarbonate.
On the other hand, the present invention is a method for producing an aliphatic polycarbonate capable of producing a polymer having a low decarboxylation rate and a high molecular weight even in the presence of carbon dioxide under a low pressure less than the critical pressure.
Hereinafter, the present invention will be described in detail.

<Raw materials>
First, components such as monomers used as raw materials in the method for producing an aliphatic polycarbonate of the present invention will be described.
In the present embodiment, the raw material is a material from which the polymer is manufactured, and is a material that is a constituent component of the polymer, and includes a first monomer, a second monomer, carbon dioxide, an acid catalyst, and a base catalyst. In addition, optional components such as initiators and additives appropriately selected as needed are included.

(First monomer)
The first monomer used in the production method of the present invention contains at least one kind of cyclic carbonate.
The cyclic carbonate can be used without any particular limitation as long as it has a cyclic structure and exhibits ring-opening polymerizability. Specifically, 5-membered ring alkylene carbonates such as ethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 1,2-pentylene carbonate, difluoroethylene carbonate, and tetrafluoroethylene carbonate; trimethylene carbonate , 1,3-butylene carbonate, 5-methyl-1,3-dioxan-2-one, neopentylene carbonate, 5,5-diethyl-1,3-dioxan-2-one, 5,5-diphenyl-1 And 6-membered ring alkylene carbonates such as 1,3-dioxan-2-one; 7-membered ring carbonates and 8-membered ring carbonates and larger cyclic carbonates and derivatives thereof. These ring-opening polymerizable monomers may be used alone or in combination of two or more.
Among these cyclic carbonates, in terms of reactivity and physical properties of the obtained polymer, a 5- or 6-membered alkylene carbonate is preferable, ethylene carbonate and 1,2-propylene carbonate are more preferable, and ethylene carbonate is particularly preferable. preferable.

(Second monomer)
In the method of the present invention, after the polymerization of the first monomer is started, the polymerization reaction is promoted by adding the second monomer, whereby a high molecular weight product can be obtained.
As the second monomer, those listed as the first monomer can be similarly used. The second monomer may be the same as or different from the first monomer. In terms of reactivity and physical properties of the obtained polymer, at least one of the first monomer and the second monomer is preferably ethylene carbonate, and more preferably both are ethylene carbonate.

(catalyst)
The catalyst used in the present embodiment uses a combination of an acid catalyst and a base catalyst.
By using both the acid catalyst and the base catalyst used in the present embodiment, compared with the case where the ring-opening polymerizable monomer was subjected to ring-opening polymerization using either the acid catalyst or the base catalyst in the conventional production method. It is possible to provide a method for producing a polymer having excellent decarboxylation, decarboxylation, and polymer conversion rates. As a result, a polymer having a lower decarboxylation rate and a higher molecular weight can be obtained. In the present embodiment, the acid catalyst is preferably an electrophilic Lewis acid, and the base catalyst is preferably a nucleophilic Lewis base.

(Acid catalyst)
The acid catalyst is not particularly limited, and tin compounds such as tin dibutylate and tin di (2-ethylhexanoate); aluminum compounds such as aluminum acetylacetonate and aluminum acetate; tetraisopropyl titanate; and tetrabutyl titanate Titanium compounds, zirconium compounds such as zirconium isoprooxide, antimony compounds such as antimony trioxide, cobalt compounds such as cobalt di (2-ethylhexanoate), calcium di (2-ethylhexanoate) and the like. Calcium compounds, zinc compounds such as zinc di (2-ethylhexanoate), calcium compounds such as calcium di (2-ethylhexanoate) and vanadium pentoxide, copper compounds such as copper oxide, diphenylphosphoric acid, etc. Use known catalysts such as phosphoric acid catalysts It is, be used alone or may be used in combination of two or more.

(Base catalyst)
The base catalyst is preferably a compound that acts as a basic nucleophile as described above, more preferably a basic nucleophilic nitrogen-containing compound (nitrogen compound), and more preferably a basic nucleophilic compound. Cyclic compounds having a nitrogen atom are more preferred. Note that the nucleophile (property) is a chemical species (and its properties) that reacts with the electrophile.

  The compound as described above is not particularly limited, but includes a cyclic monoamine, a cyclic diamine (particularly, a cyclic diamine compound having an amidine skeleton), a cyclic triamine compound having a guanidine skeleton, and a heterocyclic aromatic organic compound containing a nitrogen atom. , N-heterocyclic carbene and the like.

Examples of cyclic monoamines include quinuclidine.
Examples of cyclic diamines include 1,4-diazabicyclo- [2.2.2] octane (DABCO).

Examples of the cyclic diamine compound having an amidine skeleton include 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) and 1,5-diazabicyclo [4.3.0] non-5-ene. (DBN).
Examples of the cyclic triamine compound having a guanidine skeleton include 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) and diphenylguanidine (DPG).

  Examples of the nitrogen-containing heterocyclic aromatic organic compound include N, N-dimethyl-4-aminopyridine (DMAP), 4-pyrrolidinopyridine (PPY), pyrocholine, imidazole, pyrimidine, and purine. .

Examples of N-heterocyclic carbene include 1,3-di-tert-butylimidazole-2-ylidene (ITBU) and the like. Among these, DABCO, DBU, DPG, TBD, DMAP, PPY, and ITBU are preferred because they are less affected by steric hindrance and have high nucleophilicity or have a boiling point that can be removed under reduced pressure.
In addition, known compounds such as basic inorganic salt compounds such as potassium carbonate, sodium carbonate, calcium carbonate, and magnesium carbonate can be used.

The amount of the acidic catalyst and the basic catalyst varies depending on the type of the monomer, the reaction conditions, and the like, and thus cannot be specified unconditionally.For example, the total mass is based on the total mass of the first monomer and the second monomer. , 0.005 mol% or more and 5 mol% or less, more preferably 0.05 mol% or more and 1 mol% or less. When the amount is 0.005 mol% or more, the polymerization reaction rate is high, and a polymer having a target molecular weight can be obtained.
On the other hand, when the amount is 5 mol% or less, the control of the polymerization reaction becomes easy, and the quality of the obtained polymer can be stabilized. The use ratio of the acid catalyst to the base catalyst is appropriately selected depending on the properties of the catalyst. For example, the ratio is preferably in the range of 1/100 to 100/1, and more preferably in the range of 1/50 to 50/1.

(Optional component)
In the production method of the present embodiment, a ring-opening polymerization initiator (initiator) and other additives may be used as optional components in the polymerization reaction in addition to the above-mentioned monomers.

(Initiator)
Initiators are used primarily to control the molecular weight of the resulting polymer. As the initiator, known initiators can be used. If the initiator is an alcohol-based initiator, for example, any of aliphatic alcohol mono-, di-, or polyhydric alcohols may be used, and any of saturated and unsaturated alcohols may be used.

Specific examples of the initiator include monoalcohols such as methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, nonanol, decanol, lauryl alcohol, myristyl alcohol, cetyl alcohol, and stearyl alcohol; -Dialcohols such as propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, hexanediol, nonanediol, tetramethylene glycol, polyethylene glycol; glycerol, sorbitol, xylitol, ribitol, Polyhydric alcohols such as erythritol and triethanolamine; and methyl lactate and ethyl lactate.
Further, a polymer having an alcohol residue at a terminal such as polycaprolactone diol or polytetramethylene glycol can be used as the initiator. Thereby, a diblock or triblock copolymer may be synthesized.

  The amount of the initiator used may be appropriately adjusted according to the target molecular weight, and is preferably 0.05 mol% or more and 5 mol% or less based on 100 mol% of the ring-opening polymerizable monomer. In order to prevent the polymerization from being initiated unevenly, it is desirable that the initiator be well mixed with the monomer before the monomer comes into contact with the polymerization catalyst.

(Additive)
In the ring-opening polymerization, an additive may be added as necessary.
Examples of additives include surfactants, antioxidants, stabilizers, antifogging agents, ultraviolet absorbers, pigments, colorants, inorganic particles, various fillers, heat stabilizers, flame retardants, crystal nucleating agents, antistatics Agents, surface wetting improvers, incineration aids, lubricants, natural products, mold release agents, plasticizers, and the like.
If necessary, a polymerization terminator (such as benzoic acid, hydrochloric acid, phosphoric acid, metaphosphoric acid, acetic acid, or lactic acid) can be used after the polymerization reaction. The amount of the additive varies depending on the purpose of addition and the type of the additive, but is preferably from 0 to 5 parts by mass based on 100 parts by mass of the polymer composition.

As the surfactant, those which dissolve in carbon dioxide and have an affinity for both carbon dioxide and the ring-opening polymerizable monomer are suitably used. By using such a surfactant, the polymerization reaction can be promoted uniformly, and effects such as narrowing the molecular weight distribution of the product and facilitating obtaining a particulate polymer can be expected.
When a surfactant is used, the surfactant may be added to carbon dioxide or to the ring-opening polymerizable monomer. As such a surfactant, a surfactant having a parent carbon dioxide group and a parent monomer group in a molecule can be used, and specific examples thereof include a fluorine-based surfactant and a silicon-based surfactant. .

Epoxidized soybean oil, carbodiimide and the like are used as the stabilizer.
As the antioxidant, 2,6-di-t-butyl-4-methylphenol, butylhydroxyanisole and the like are used.
As the anti-fogging agent, glycerin fatty acid ester, monostearyl citrate and the like are used.
As the filler, an ultraviolet absorber, a heat stabilizer, a flame retardant, an internal mold release agent, clay, talc, silica or the like having an effect as a crystal nucleating agent is used.
Known pigments such as titanium oxide, carbon black, and ultramarine blue are used as the pigment.

(carbon dioxide)
Conventionally, carbon dioxide in a supercritical state has been used as carbon dioxide, but in the method of the present invention, carbon dioxide having a pressure lower than the critical pressure, which has not been conventionally used, can be suitably used.
When the pressure of carbon dioxide is equal to or higher than normal pressure, the reaction proceeds. However, the higher the pressure, the lower the decarboxylation rate. Therefore, the pressure is preferably 0.1 MPaG or more, more preferably 0.5 MPaG or more, and more preferably 1 MPaG or more. Is particularly preferred. On the other hand, it is clear that the method of the present invention can be applied even in a high pressure region exceeding the critical point, but from the viewpoint of equipment cost and safety, the pressure is preferably less than the critical pressure of carbon dioxide, more preferably 7 MPaG or less, and more preferably 5 MPaG or less. The following are particularly preferred.
In the present invention, the unit of pressure “MPaG” means a gauge pressure. Therefore, the actual pressure is a value obtained by adding the atmospheric pressure (0.1 MPa) thereto.
When carbon dioxide in a gaseous state is used, it can be used as a mixed gas with an inert gas such as nitrogen or argon. In this case, it is preferable that the partial pressure of carbon dioxide be in the above-mentioned pressure range.

<Polymerization method>
In the method of the present invention, in a first step, a first monomer, an acid catalyst, a base catalyst, and carbon dioxide having a critical pressure or less are supplied to a reactor, and the first monomer is polymerized to polymerize the polymer. To obtain a reaction mixture.
Next, in a second step, the second monomer is continuously added to the reaction mixture obtained in the first step, and further polymerized. At this time, assuming that the total amount of the mass of the polymer formed by the polymerization reaction, the mass of the first monomer, and the mass of the second monomer is 100 mass%, the mass of the first monomer and the mass of the second monomer The second monomer is continuously supplied so that the total amount with the mass (hereinafter referred to as monomer concentration) is 3% by mass or more and less than 50% by mass.
The second monomer is added when the content of the monomer in the reaction mixture obtained in the first step falls within the range of 3% by weight or more and less than 50% by weight.
The monomer concentration in the second step is more preferably from 4% by mass to 40% by mass, and particularly preferably from 5% by mass to 30% by mass. When the monomer concentration in the second step exceeds 50% by mass, a low-molecular-weight product is easily formed, and a polymer having sufficient processability cannot be obtained. Further, when the monomer concentration in the second step is less than 3% by mass, the reaction rate becomes slow, and the ring-opening polymerization may not be carried out efficiently in some cases.
In the present embodiment, the term “continuous supply” is a concept for batch supply, and may be supplied intermittently or intermittently as long as the monomer concentration can be maintained.
The monomer concentration is detected by continuously or periodically withdrawing a sample from the reaction mixture and analyzing it, and the supply amount of the second monomer is adjusted based on the detected value.

(Polymerization temperature)
The temperature at which the first monomer and the second monomer are polymerized (polymerization temperature) is not particularly limited because it depends on the type of the monomer and the catalyst used, but is usually 40 ° C to 200 ° C, preferably 150 ° C to 180 ° C. Range. When the polymerization temperature is lower than 40 ° C., the raw materials and the polymerization product do not dissolve or melt, or the activity of the catalyst decreases. When the polymerization temperature exceeds 200 ° C., a depolymerization reaction, which is a reverse reaction of a decarboxylation reaction or a ring-opening polymerization, tends to occur in equilibrium, and the polymerization reaction hardly proceeds quantitatively. The polymerization temperature may be the same or different in the first step and the second step, but is preferably set according to the type of the monomer used.

(Polymerization pressure)
The polymerization pressure is the pressure of carbon dioxide (the total pressure when a mixed gas is used). As described above, in consideration of the effect of suppressing the decarboxylation reaction, the increase in the molecular weight, the conversion of the polymer, and the ease of handling the high-pressure gas. The pressure (partial pressure of carbon dioxide when a mixed gas is used) is 0.1 MPaG or more and less than the critical pressure, more preferably 0.5 MPa to 7 MPaG, and particularly preferably 1 MPaG to 5 PMaG.

(Polymerization time)
In the present embodiment, the polymerization time is appropriately set according to the polymerization type and the target molecular weight.

(Polymerization type)
In carrying out the present invention, the polymerization system may be any of continuous polymerization and semi-batch polymerization.
For example, in the case of continuous polymerization, it is necessary to supply the first monomer and the second monomer separately, so that it is necessary to use a production facility in which two or more reactors are connected in series. First, a first monomer, carbon dioxide, an acid catalyst, a base catalyst and an optional component are continuously supplied to a first reactor heated to a predetermined temperature and polymerized (first step). The reaction mixture continuously withdrawn from the reactor is supplied to the second reactor, and the second monomer is continuously supplied so that the monomer concentration in the second reactor is maintained within a predetermined range. To polymerize (second step).
When the present invention is carried out by continuous polymerization, for example, a polymerization reactor (100) shown in FIG. 1 can be suitably used.

  In the case of batch polymerization, a first monomer, an acid catalyst, a base catalyst and optional components are supplied to a reactor filled with carbon dioxide in advance, and carbon dioxide is further supplied and the pressure is increased to a predetermined pressure and heated. The polymerization reaction is started (first step), and then the second monomer is continuously supplied and polymerized so that the monomer concentration in the reactor is maintained within a predetermined range (second step). be able to. In this case, the first step and the second step can be performed in one reactor. Such batch polymerization can be performed, for example, using a polymerization reaction apparatus (500) shown in FIG.

  Hereinafter, an embodiment of the present invention to which continuous polymerization and batch polymerization are applied will be described in detail with reference to FIGS. 1 and 2.

<Continuous polymerization>
FIG. 1 is a system diagram showing a continuous polymerization step. In the system diagram of FIG. 1, a polymerization reactor (100) includes a supply unit (100a) for supplying a raw material such as a monomer, and a polymerization reactor main body (100b) for polymerizing the monomer supplied by the supply unit (100a). Having.

(Polymerization reactor)
First, the configuration of the device will be described in detail.
In the following, means for measuring and supplying a liquid is referred to as a "metering pump", and means for measuring and supplying a solid (powder or granular) liquid is referred to as a "metering feeder". In the following, the case where solid ones are used as the first monomer and the second monomer will be described as an example.
The supply unit (100a) has tanks (1,3,5,7,11,21,27), metering feeders (2,4), and metering pumps (6,8,12,22,28). .
In the supply unit (100a), the first monomer is stored in the tank (1), and the solid (powder or granular) of the initiator and additives is stored in the tank (3) in the tank (5). Represents the liquid initiator and additives, tank (7, 27) stores carbon dioxide, tank (11) stores the catalyst, and tank (21) stores the second monomer. Is stored.
In addition, some or all of the initiator and the additive may be previously mixed with the first monomer, and the mixture may be stored in the tank (1).
When both the initiator and the additive are solid, the supply unit (100a) may not have the tank (5) and the metering pump (6).
Similarly, when both the initiator and the additive are liquid, the supply unit (100a) may not have the tank (3) and the metering feeder (4).

  The first monomer stored in the tank (1) is measured by the metering feeder (2) and is continuously supplied to the polymerization reactor main body (100b). The solid stored in the tank (3) is measured by a measuring feeder (4) and is continuously supplied to the polymerization reactor main body (100b). The liquid stored in the tank (5) is measured by a metering pump (6) and is continuously supplied to the polymerization reactor main body (100b). The carbon dioxide stored in the tank (7) is continuously supplied to the polymerization reactor main body (100b) at a constant pressure and flow rate by the metering pump (8). The catalyst stored in the tank (11) is measured by a metering pump (12) and supplied to the polymerization reactor main body (100b). The second monomer stored in the tank (21) is measured by a measuring feeder (22), and is continuously supplied to the polymerization reactor main body (100b). The carbon dioxide stored in the tank (27) is continuously supplied to the polymerization reactor main body (100b) at a constant pressure and flow rate by a metering pump (28).

The polymerization reactor main body (100b) includes a mixing section (9) for mixing raw materials containing the first monomer fed from the supply unit (100a), a reaction section (13) for polymerizing the first monomer, and a supply section. A mixing section (29) for mixing the raw material containing the second monomer fed from the unit (100a), and a reaction section (33) for polymerizing the reaction mixture obtained in the reaction section (13) and the second monomer. And an outlet for discharging the polymer obtained in the reaction section (33).
Each part or apparatus of the polymerization reaction device main body (100b) is connected as shown in FIG. 1 by a pressure-resistant pipe (30) for transporting raw materials or generated polymer. Further, each part or apparatus of the polymerization reaction device main body (100b) has a tubular member through which the above-mentioned raw materials and the like pass.

  The mixing section (9) has an inlet (9a) for introducing the carbon dioxide supplied from the tank (7) by the measuring pump (8), and the first port supplied from the tank (1) by the measuring feeder (2). An inlet (9b) for introducing a monomer, an inlet (9c) for introducing a solid substance supplied from a tank (3) by a measuring feeder (4), and a tank (5) by a measuring pump (6). And an introduction port (9d) for introducing the liquid supplied from. The mixing section (9) is provided with a heating means (9e) for heating the supplied raw material. The main body of the mixing section (9) is composed of a pressure-resistant tube or a stirrer, and raw materials such as a first monomer, an initiator, and additives continuously supplied from each tank (1, 3, 5). And the carbon dioxide continuously supplied from the tank (7) is continuously mixed.

As the stirrer, a tank-type stirrer, or a cylindrical stirrer may be provided, but a cylindrical stirrer capable of supplying a raw material from one end and extracting a mixture such as a molten phase or a fluid phase from the other end. The device is preferred. Such a device is preferably a single-shaft screw, a twin-shaft screw meshing with each other, a twin-shaft mixer having a number of meshing or overlapping stirring elements, a kneader having a spiral stirring element meshing with each other, a static mixer, or the like. Used. In particular, a biaxial or multiaxial stirrer that meshes with each other is preferable because reactants are less likely to adhere to the stirrer and the container and have a self-cleaning action.
When no mixing device is provided in the mixing section (9), the mixing section (9) is constituted by a part of the pressure-resistant pipe (30). Further, a liquid sending pump (10) is provided between the mixing section (9) and the reaction section (13). The liquid sending pump (10) sends the raw material containing the first monomer mixed in the mixing section (9) to the reaction section (13).

  An inlet (13a) for introducing the raw materials mixed in the mixing section (9) and a catalyst for introducing the catalyst supplied from the tank (11) by the metering pump (12) into the reaction section (13). A catalyst inlet (13b) is provided. The reaction section (13) is provided with a heating means (13c) for heating the fed raw materials. The main body of the reaction section (13) is composed of a pressure-resistant stirrer or a tube. In the reaction section (13), the raw material containing the first monomer sent by the liquid sending pump (10) comes into contact with the catalyst supplied by the metering pump (12), and as an intermediate by ring-opening polymerization. Is obtained continuously.

  When the reaction section (13) has a mixing device, the same mixing device as that exemplified for the mixing portion (9) can be used. When the reaction section (13) does not have a mixing device, the reaction section (13) is constituted by a part of a pressure-resistant pipe (30). In this case, the shape of the pipe 30 is not particularly limited, but a helical pipe is preferably used to make the apparatus compact.

The mixing section (29) has an inlet (29a) for introducing the carbon dioxide supplied from the tank (27) by the measuring pump (28), and a second port supplied from the tank (21) by the measuring pump (22). And a heating means (29c) for heating the supplied raw material, and the main body of the mixing section (29) is constituted by a pressure-resistant tube or a stirrer. The second monomer continuously supplied from each tank (22) and the carbon dioxide continuously supplied from the tank (27) are continuously mixed.
The configuration of the mixing section (29) is the same as that of the mixing section 9, and thus the detailed description is omitted.

An inlet (33a) for introducing the reaction mixture obtained in the reaction section (13) and a raw material containing the second monomer mixed in the mixing section (29) are introduced into the reaction section (33). And an introduction port (13b). The main body of the reaction section (33) is composed of a pressure-resistant mixing device or a tube. In the reaction section (33), the reaction mixture and the second monomer come into contact with each other and ring-opening-polymerize to form a desired polymer. Are continuously obtained.
The configuration of the reaction section (33) is the same as that of the reaction section (13), and thus detailed description is omitted.

At an end of the reaction section (33), a pressure adjusting valve (34) is provided. The pressure regulating valve (34) sends out the polymer product P polymerized in the reaction section (33) to the outside of the reaction section (33) by utilizing a pressure difference between the inside and outside of the reaction section (33).
FIG. 1 shows an example in which one reaction unit (13, 33) is provided in each of the first step and the second step, but two or more reaction units may be provided respectively. . When two or more reaction units are used, the first monomer or the second monomer is preferably introduced into each reaction unit. Further, the reaction (polymerization) conditions of each reaction section, that is, the temperature, the catalyst concentration, the pressure, the average residence time, the stirring speed, and the like may be the same or different.

(First step)
Next, the procedure of continuous polymerization using the polymerization reactor (100) will be described in detail.
In the first step, first, a first monomer other than the catalyst, an initiator, and an additive in each tank (1, 3, 5, 7) are added by the metering feeders (2, 4) and the metering pumps (6, 8). The agent and carbon dioxide are continuously supplied, and are introduced into the mixing unit (9) from the respective inlets (9a, 9b, 9c, 9d). At this time, it is preferable to use a raw material having a low melting point and solid at room temperature, such as ethylene carbonate (melting point: 34 to 37 ° C.), by heating and melting.

  The feed rate of each raw material is adjusted by the metering feeders (2, 4) and the metering pumps (6, 8). The feed rate of each raw material is adjusted based on desired polymer properties, reaction time, and the like, and is not particularly limited. However, the pressure of carbon dioxide in the reaction section (13) is controlled to be in a desired range. You.

The ratio of the feed rate of the raw materials other than carbon dioxide to the feed rate of carbon dioxide (the feed rate of the raw materials other than carbon dioxide / the feed rate of carbon dioxide, referred to as the feed ratio) is preferably 1 or more, and more preferably 3 or more. More preferably, it is more preferably 5 or more, and particularly preferably 10 or more. The upper limit of the feed ratio is preferably 1,000 or less, more preferably 100 or less, and particularly preferably 50 or less.
By setting the feed ratio to 1 or more, the reaction can proceed with a high solid content in the reactor, and the polymerization can be performed efficiently and stably. On the other hand, when the feed ratio exceeds 1000, the pressure of carbon dioxide may be insufficient, and the suppression of decarbonation may be insufficient.

Each raw material is continuously introduced and mixed into the tube of the mixing section (9). When the mixing section (9) has a stirrer, each raw material may be stirred. Further, the mixing section (9) may have a heating means (9e), whereby the raw material in the pipe is heated as needed within a range where the pressure of carbon dioxide becomes a desired pressure. Is also good.
The raw materials mixed in the mixing section (9) are sent by a liquid sending pump (10) and supplied to the reaction section (13) from the inlet (13a). On the other hand, the catalyst in the tank (11) is measured by a metering pump (12) and supplied to the reaction unit (13) from the inlet (13b) in a predetermined amount. Since the catalyst can work even at room temperature, in this embodiment, the catalyst is added after mixing the raw materials other than the catalyst. However, depending on the reactivity of the monomer, the mixing unit (9) may be used similarly to the other raw materials. May also be supplied.

  Each raw material fed by the feed pump (10) and the catalyst fed by the metering pump (12) are sufficiently mixed by the mixing device of the reaction section (13) as necessary, or , And is heated to a predetermined temperature by the heating means (13c). As a result, in the reaction section (13), the ring-opening polymerizable monomer is subjected to ring-opening polymerization in the presence of a catalyst to continuously obtain a polymer as an intermediate.

(Second step)
Subsequently, in the second step, the second monomer and carbon dioxide in each tank (21, 27) are continuously supplied by the measuring feeder (22) and the measuring pump (28), and the respective inlets (29a , 29b) are continuously introduced into the tube of the mixing section (29) and mixed. The procedure and conditions for introducing the second monomer and carbon dioxide in the second step are the same as the procedures and conditions for introducing the first monomer and carbon dioxide in the first step. Omitted.
Here, the ratio between the supply amount (feed amount) of the first monomer supplied in the first step and the supply amount (feed amount) of the second monomer supplied in the second step is determined by the reaction unit The concentration of the second monomer in (33) is controlled to be within a predetermined range.

The reaction mixture containing the polymer generated in the reaction section (13) is continuously supplied from the inlet (33a) to the reaction section (33), and the second monomer mixed in the mixing section (29) is , And is continuously supplied from the inlet (33b) to the reaction section (33). As a result, the polymer formed in the reaction section (13) and the second monomer are continuously contacted in the reaction section (33), and the target polymer is obtained by ring-opening polymerization of the second monomer. Can be
The stirring means, heating means, polymerization conditions, and the like in the reaction section (33) are the same as those in the reaction section (13), and thus detailed description is omitted.
The polymerization time (average residence time of the reactants in the reactor) in each of the first step and the second step is usually preferably within 1 hour, more preferably within 45 minutes, even more preferably within 30 minutes. According to the production method of the present embodiment, the polymerization time can be set within 20 minutes.

  The polymer product P which has completed the ring-opening polymerization reaction in the reaction section (33) is sent out of the reaction section (33) from the pressure regulating valve (34). The rate at which the polymer product P is sent out from the pressure regulating valve (34) is preferably constant in order to maintain a constant pressure in the polymerization system filled with the compressive fluid and obtain a uniform polymerized product. Therefore, the liquid feed mechanism inside the reaction section (13, 33), the liquid feed mechanism inside the contact section (9, 29), and the metering feeder (2, 4, 4) so that the back pressure in the pressure adjusting valve 34 becomes constant. 22) and the feed rate of the metering pumps (6, 8, 28) are controlled. The control method may be an ON-OFF type, that is, an intermittent feed type, but a continuous or step type in which the rotation speed of a pump or the like is gradually increased or decreased is often more preferable. In any case, such control can stably obtain a uniform polymer product.

<Semi-batch polymerization>
FIG. 2 is a system diagram showing a semi-batch type polymerization step.
In the system diagram of FIG. 2, the polymerization reactor (500) has a tank (121) for storing carbon dioxide, and a pressure-resistant reactor (127) equipped with a stirring means and a valve (128). , A metering pump (122), an addition pot (125), a pressure-resistant pipe (130) with valves (123, 124, 126, 129), a metering pump (222), and an addition pot (225). , Valves (223, 224, 226, 229) are connected as shown in FIG. 2 by pressure-resistant piping (230).

  The carbon dioxide stored in the tank (121) is supplied to the reactor (127) at a constant pressure and flow rate by the metering pump (122). The first monomer, the initiator, and the additive are charged in the reactor (127) in advance, and the polymerization reaction can be started by heating the reactor (127) to a predetermined temperature.

  The catalyst may be charged into the reactor (127) together with other raw materials, or may be stored in an addition pot (125) separately from the other raw materials, and after heating the inside of the reactor (127) to a predetermined temperature, the reaction may take place. It may be put into the container (127). When the catalyst is stored in the addition pot (125), the catalyst can be added by switching the valves (123, 124, 126, 129).

  The second monomer is stored in the addition pot (225), and when the polymerization of the first monomer has progressed, is measured at a rate at which the monomer concentration in the reactor (127) is maintained within a predetermined range. It is continuously added to the reaction mixture in the reactor (127) by the pump (222). The addition of the second monomer stored in the addition pot (225) can be performed by switching valves (223, 224, 226, 229).

The polymerization time in the first step and the second step together is usually in the range of 0.5 to 24 hours, preferably in the range of 1 to 12 hours.
After the completion of the polymerization reaction, the polymer product P in the reaction vessel (127) can be discharged by opening the valve (128).

<Polymer>
According to the method of the present invention, a sufficient formability with a decarboxylation rate of 15% or less and a weight average molecular weight (Mw) of 25,000 or more measured by gel permeation chromatography (hereinafter, GPC) is obtained. The resulting polymer can be obtained.
Further, since the method of the present invention does not use an organic solvent, the obtained polymer does not substantially contain an organic solvent, and is excellent in safety and stability.

  Accordingly, the polymers obtained by the method of the present invention include various plastic molded products (extrusion / injection molded products, sheets, films, foams, etc.), architectural coatings, cosmetics, medical materials, electrophotographic developers, printing It is widely applied to various uses such as ink for printing. At that time, various additives may be used for the purpose of improving moldability, secondary workability, decomposability, tensile strength, heat resistance, storage stability, weather resistance and the like.

Hereinafter, the present embodiment will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.
In the examples, the weight average molecular weight, decarboxylation rate and deformation rate of the polymer were measured by the following methods.
In the examples, all pressures indicate gauge pressure. The actual pressure is a value obtained by adding the atmospheric pressure (0.1 MPa) thereto.

(Measurement of molecular weight)
The weight average molecular weight can be measured by gel permeation chromatography (GPC) under the following conditions.
-Equipment: GPC-8020 (manufactured by Tosoh Corporation)
・ Column: TSK G2000HXL and G4000HXL (Tosoh Corporation)
・ Temperature: 40 ° C
-Solvent: THF (tetrahydrofuran)
Flow rate: 0.5 mL / min. Inject 1 mL of a 0.5% by mass sample and use the molecular weight calibration curve prepared from the monodisperse polystyrene standard sample from the molecular weight distribution of the polymer product measured under the above conditions. The number average molecular weight (Mn) and weight average molecular weight (Mw) of the product were calculated.

(Decarbonation amount and conversion rate)
The amount of decarboxylation of the polymer product can be determined from the content of oxide units by-produced by decarboxylation during polymerization of the ring-opening polymerizable monomer. The conversion can be determined from the amount of the remaining monomer. The amounts of the oxide unit and the monomer can be determined, for example, by measuring a ¹ H nuclear magnetic resonance ( ¹ H-NMR) spectrum under the following conditions.
・ Equipment: JEOL Datum Co., Ltd. ・ Solvent: Deuterated chloroform ・ Measurement target: Proton To analyze the values (mol ratio) of the peak derived from the carbonate monomer, the peak of the oxide unit, and the peak of polycarbonate in the obtained spectrum Thus, the amount of decarbonation and the conversion can be determined.

(Deformation rate)
A polycarbonate resin was formed into a molded body having a thickness of 5 mm x 100 mm, and was allowed to stand on a horizontal table at 20 ° C and 50% Rh for 24 hours, and the deformation rate was calculated according to the following equation.
Deformation rate (%) = [(5 mm−thickness after standing) / 5 mm] × 100

[Evaluation] (Evaluation of decarbonation rate)
The numerical value of the decarboxylation rate (%) was evaluated based on the following criteria.
5 points: 0 to less than 10% 4 points: 10% to less than 12% 3 points: 12% to less than 15% 0 points: 15% or more (evaluation of deformation rate)
The numerical value of the deformation rate (%) was evaluated based on the following criteria.
5 points: 0% to less than 3% 4 points: 3% to less than 6% 3 points: 6% to less than 10% 0 points: 10% or more

(Comprehensive evaluation)
The performance of the polymer was evaluated on the basis of the following criteria based on the sum of the evaluation points of the decarboxylation rate and the evaluation points of the deformation rate.
A: 10 points B: 9 points C: 8 points D: 7 points E: 6 points or less

(Example 1)
Using a polymerization reactor (100) shown in FIG. 1, as a first step, the inside of a reaction vessel is filled with carbon dioxide of 1.0 MPaG (indicating a gauge pressure, the same applies hereinafter), and then ethylene carbonate is used as a first monomer. 100 g, tin octylate 0.05 g as an acid catalyst, and 0.05 g of 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) as a base catalyst are added together with compressible carbon dioxide. The inside of the reaction vessel was pressurized to 5.0 MPaG, and the inside of the reaction system was heated to 180 ° C. to perform ring-opening polymerization to form an intermediate polymer. Next, as a second step, 600 g of ethylene carbonate was further continuously added as a second monomer to carry out ring-opening polymerization so that the monomer concentration in the reaction system could be maintained at 5% by mass. After completion of the addition, the point at which the residual monomer concentration became less than 0.1% by mass was regarded as the reaction end point, and a target polymer was obtained. Table 1 shows the weight average molecular weight Mw, decarboxylation rate, deformation rate, and overall evaluation of the obtained polymer.

(Examples 2 to 10)
Except that at least one of the second monomer species, catalyst species, polymerization pressure and monomer concentration in the second step was changed as described in Table 1, the procedure of Example 1 was repeated to obtain a cyclic carbonate. Ring opening polymerization was performed. Table 1 shows the weight average molecular weight Mw, decarboxylation rate, deformation rate, and overall evaluation of the obtained polymer.

(Comparative Example 1)
Ring-opening polymerization of a cyclic carbonate was carried out in the same procedure as in Example 1 except that argon was used instead of carbon dioxide. Table 2 shows the weight average molecule Mw, decarboxylation rate, deformation rate, and overall evaluation of the obtained polymer.

(Comparative Example 2)
Ring-opening polymerization of a cyclic carbonate was carried out in the same procedure as in Example 4, except that no acid catalyst was used and propylene carbonate was used instead of ethylene carbonate as the second monomer. Table 2 shows the weight average molecule Mw, decarboxylation rate, deformation rate, and overall evaluation of the obtained polymer.

(Comparative Example 3)
Ring-opening polymerization of cyclic carbonate was carried out in the same manner as in Example 4 except that no base catalyst was used. Table 2 shows the weight average molecule Mw, decarboxylation rate, deformation rate, and overall evaluation of the obtained polymer.

(Comparative Example 4)
Ring-opening polymerization of a cyclic carbonate was carried out in the same manner as in Example 4 except that the second monomer was not added. Table 2 shows the weight average molecule Mw, decarboxylation rate, deformation rate, and overall evaluation of the obtained polymer.

(Comparative Example 5)
Ring-opening polymerization of cyclic carbonate was carried out in the same procedure as in Example 4 except that the second monomer was added so that the monomer concentration in the reaction system could be maintained at 1% by mass. Table 2 shows the weight average molecule Mw, decarboxylation rate, deformation rate, and overall evaluation of the obtained polymer.
(Comparative Example 6)
Ring-opening polymerization of a cyclic carbonate was carried out in the same procedure as in Example 1 except that propylene glycol was used instead of ethylene carbonate as the second monomer. Table 2 shows the weight average molecule Mw, decarboxylation rate, deformation rate, and overall evaluation of the obtained polymer.

(Comparative Example 7)
Ring-opening polymerization of a cyclic carbonate was carried out in the same procedure as in Example 8 except that carbon dioxide was changed to argon. Table 2 shows the weight average molecule Mw, decarboxylation rate, deformation rate, and overall evaluation of the obtained polymer.

(Comparative Example 8)
Ring-opening polymerization of a cyclic carbonate was carried out in the same procedure as in Example 8 except that the second monomer was not added. Table 2 shows the weight average molecule Mw, decarboxylation rate, deformation rate, and overall evaluation of the obtained polymer.

1,3,5,7 Tank 2,4 Measuring feeder 6,8 Measuring pump 9 Mixing section 9a Inlet (carbon dioxide inlet)
9b Inlet (inlet of first monomer)
9c Inlet (solid inlet)
9d inlet (liquid inlet)
9e Heating means 10 Liquid feed pump 11 Tank 12 Metering pump 13 Reaction unit 13a Inlet (raw material inlet)
13b Inlet (catalyst inlet)
13c Heating means 21 Tank 22 Metering feeder 27 Tank 28 Metering pump 29 Mixing unit 29a Inlet (carbon dioxide inlet)
29b inlet (second monomer inlet)
29c Heating means 30 Pressure-resistant pipe 33 Reaction section 33a Inlet (inlet of reaction mixture)
33b inlet (inlet of second monomer)
33c heating means 34 pressure regulating valve 100 polymerization reactor 100a supply unit 100b polymerization reactor main body 121 tank 122 metering pump 125 addition pot 123, 124, 126, 129 valve 127 reactor 128 valve 130, 130a, 130b pipe 222 metering pump 223 , 224, 226, 229 Valve 225 Addition pot 230, 230a, 230b Pressure-resistant pipe 500 Polymerization reactor P Polymer product

JP-T-2012-502143 A JP 2013-057050 A JP 2013-189613 A JP 2013-224398 A JP 2014-040560 A JP 2014-214295 A JP 2013-189615 A

Claims (4)

A method for producing an aliphatic polycarbonate by ring-opening polymerization of a cyclic carbonate in the presence of carbon dioxide under low pressure below the critical pressure,
The pressure of the carbon dioxide is 0.1 MPaG or more and 7 MPaG or less,
A first step of supplying a first monomer containing at least one cyclic carbonate, an acid catalyst, a base catalyst, and carbon dioxide to a reactor to polymerize the first monomer;
In a reaction mixture in which the reaction for polymerizing the first monomer is proceeding, a second monomer containing the same or different kind of the first monomer and containing at least one kind of cyclic carbonate is supplied and polymerized. And a step of
In the second step, when the total amount of the mass of the polymer formed by the polymerization reaction in the reaction mixture, the mass of the first monomer, and the mass of the second monomer is 100 mass%, the first mass Fat, wherein the second monomer is continuously supplied so that the total amount of the mass of the monomer and the mass of the second monomer is maintained at 3% by mass or more and less than 50% by mass. For producing aromatic polycarbonate.   The method for producing an aliphatic polycarbonate according to claim 1, wherein the acid catalyst is a Lewis acid, and the base catalyst is a Lewis base. The first monomer and the second monomer is 5-membered ring or manufacturing method of the aliphatic polycarbonate according a to claim 1 or 2, monomers of the same or different selected from cyclic alkylene carbonates of 6-membered ring. The method for producing an aliphatic polycarbonate according to claim 1 or 2 , wherein one or both of the first monomer and the second monomer are ethylene carbonate.

Images