Aliphatic polycarbonate solution and aliphatic polycarbonate film

Abstract

To provide a polymer solution having excellent stability even in a low temperature region in the vicinity of a room temperature.SOLUTION: An aliphatic polycarbonate solution contains an aliphatic polycarbonate resin including a repeating unit having a specific structure, and having a number average molecular weight of 30,000 to 200,000, and contains a chlorine-based organic solvent having a boiling point at normal pressure of 70°C or higher as a solvent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an aliphatic polycarbonate solution and an aliphatic polycarbonate membrane. [Background technology]

[0002] Plastics are used in a wide range of applications due to their light weight, electrical insulation, moldability, and durability, including as films, membranes, sealants, and partition walls.

[0003] Patent Document 1 teaches a polyester solution containing an aliphatic polyester resin having a specific structural unit in its molecular chain and using a specific solvent as a solvent, and a film obtained from the solution. Patent Document 2 teaches a resin composition containing a polymer produced from a polycarbonate diol of a specific structure as a bank-forming composition. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-152809 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-70583 Summary of the Invention [Problem to be solved by the invention]

[0005] One of the challenges in producing plastic membranes and films is the stability of the polymer solution. If the stability of a prepared polymer solution is poor, the polymer may precipitate from the solution before the membrane or film can be formed. This instability of the polymer solution not only adversely affects the properties of the resulting membrane or film, such as uniformity, and leads to poor formability, but can also cause problems such as clogged pipes at manufacturing sites. In other words, before the membrane or film can be formed, the clogging of pipes can place a heavy load on the transfer equipment, potentially leading to breakdowns in the worst case scenario.

[0006] The polyester solution of Patent Document 1 still has room for improvement in terms of polymer solution stability, particularly stability at relatively low temperatures such as room temperature. Patent Document 2 does not disclose a polymer solution in which the polymer itself is dissolved in a solvent.

[0007] The present invention has been made in view of the above circumstances, and its object is to provide a polymer solution that has excellent stability even in a low temperature range, particularly around room temperature. [Means for solving the problem]

[0008] As a result of extensive research into the above-mentioned problems, the present inventors have found that by using an aliphatic polycarbonate resin having a specific molecular weight as the polymer and a specific chlorine-based organic solvent as the solvent, it is possible to obtain a polymer solution that is highly stable, particularly at low temperatures around room temperature. That is, the present invention provides the following.

[0009] [1] An aliphatic polycarbonate solution containing an aliphatic polycarbonate resin having a number average molecular weight of 30,000 to 200,000 and including a repeating unit represented by the following formula (1), and containing a chlorine-based organic solvent as a solvent having a boiling point of 70°C or higher at normal pressure: [ka] (In the above formula (1), R represents a linear or branched alkylene group having 6 to 30 carbon atoms, and n represents a value of 1 to 40.) [2] The aliphatic polycarbonate solution according to the above item [1], wherein the chlorine-based organic solvent is at least one selected from the group consisting of tetrachloroethylene, trichloroethylene, 1,1,2-trichloroethane, and o-dichlorobenzene. [3] The aliphatic polycarbonate solution according to item [1] or [2], wherein the aliphatic polycarbonate resin is dissolved in the chlorine-based organic solvent under heating, and the amount of resin precipitated after the solution is cooled to room temperature (20°C) and allowed to stand for 2 hours is 15 mass % or less of the amount of resin dissolved in the solution before cooling. [4] An aliphatic polycarbonate film obtained by applying the aliphatic polycarbonate solution according to any one of the above items [1] to [3] and drying it. [Effects of the Invention]

[0010] According to the present invention, it is possible to obtain an aliphatic polycarbonate solution having excellent stability, particularly at low temperatures around room temperature. The aliphatic polycarbonate solution has excellent stability and excellent film-forming properties, and therefore can be used to obtain an aliphatic polycarbonate membrane. DETAILED DESCRIPTION OF THE INVENTION

[0011] An example of an embodiment of the present invention will be described in detail below. However, the present invention is not limited to the embodiment described below, and can be implemented by modifying it as desired within the scope of the gist of the present invention.

[0012] <Aliphatic polycarbonate resin> The aliphatic polycarbonate resin contained in the aliphatic polycarbonate solution of this embodiment must contain a repeating unit represented by the following formula (1). [ka] (In the above formula (1), R represents a linear or branched alkylene group having 6 to 30 carbon atoms, and n represents a value of 1 to 40.)

[0013] In formula (1), when the number of carbon atoms and the number of repetitions n of the linear or branched alkylene group represented by R are within the above ranges, the number average molecular weight of the aliphatic polycarbonate resin can be controlled within the range described below. From the viewpoints of availability and ease of handling, R is preferably a linear alkylene group having 8 to 20 carbon atoms, more preferably 8 to 18 carbon atoms, and even more preferably 10 to 16 carbon atoms. The aliphatic polycarbonate resin may contain two or more types of alkylene oxide groups represented by (RO-), and preferably contains only one type of alkylene oxide group. The repeat number n may be an integer or a fraction, as long as it is a real number in the range of 1 to 40. From the viewpoint of controlling the number average molecular weight and ease of production, it is preferably 1 to 30, more preferably 1 to 25, and even more preferably 1 to 20.

[0014] In this embodiment, the aliphatic polycarbonate resin must have a number-average molecular weight of 30,000 to 200,000. If the number-average molecular weight is 30,000 or more, precipitation of the aliphatic polycarbonate resin from the polycarbonate solution can be suppressed, and a stable aliphatic polycarbonate solution can be obtained, especially at low temperatures around room temperature. If the number-average molecular weight is 200,000 or less, the resin can be dissolved without problems in the chlorine-based organic solvent described below. From the viewpoints of solution stability and moldability, the number average molecular weight is preferably 40,000 or more, more preferably 50,000 or more, even more preferably 60,000 or more, still more preferably 70,000 or more, and is preferably 180,000 or less, more preferably 160,000 or less, even more preferably 150,000 or less, and still more preferably 140,000 or less.

[0015] As long as the number-average molecular weight (Mn) of the aliphatic polycarbonate resin is within the above range, the range of the weight-average molecular weight (Mw) is not particularly limited. The weight-average molecular weight of the aliphatic polycarbonate resin is, for example, preferably 60,000 or more, more preferably 100,000 or more, even more preferably 140,000 or more, and preferably 400,000 or less, more preferably 350,000 or less, even more preferably 300,000 or less. When the weight-average molecular weight is within the above range, it becomes easy to obtain an aliphatic polycarbonate resin having a preferred molecular weight distribution, which will be described later.

[0016] In this specification, the number average molecular weight (Mn) and weight average molecular weight (Mw) are values ​​measured using gel permeation chromatography (GPC) and converted into polystyrene equivalent values.

[0017] In the present embodiment, the molecular weight distribution of the aliphatic polycarbonate resin is preferably 1.2 to 4.0, more preferably 1.5 to 3.0. When the molecular weight distribution is within the above range, stable solubility can be maintained.

[0018] <Chlorine-based organic solvents> In this embodiment, the solvent must be a chlorine-based organic solvent having a boiling point of 70° C. or higher at normal pressure (0.1 MPa). If the boiling point is 70° C. or higher at normal pressure, evaporation during work can be suppressed, making the polycarbonate solution easier to handle and reducing work environment problems, mainly health-related problems. The boiling point of the chlorine-based organic solvent at normal pressure is preferably 75° C. or higher, more preferably 80° C. or higher. Specifically, at least one selected from the group consisting of tetrachloroethylene, trichloroethylene, 1,1,2-trichloroethane, and o-dichlorobenzene can be preferably used. The chlorine-based organic solvents may be used alone or in combination of two or more.

[0019] The chlorine-based organic solvent preferably contains, as a main component, a chlorine-based organic solvent having a boiling point of 70°C or higher at normal pressure, specifically at least one selected from the group consisting of tetrachloroethylene, trichloroethylene, 1,1,2-trichloroethane, and o-dichlorobenzene. Here, the term "main component" refers to a component that preferably constitutes 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more of the chlorine-based organic solvent, and may be substantially 100% by mass. In the present invention, other chlorine-based organic solvents or non-chlorine-based organic solvents may be contained as long as they have a boiling point of 70° C. or higher at normal pressure, within a range that does not adversely affect the solubility of the aliphatic polycarbonate resin.

[0020] <Other ingredients> In addition to the aliphatic polycarbonate resin, the aliphatic polycarbonate solution of this embodiment may contain other components such as various additives such as fillers, plasticizers, antistatic agents, antioxidants, light stabilizers, UV absorbers, dyes, pigments, hydrolysis inhibitors, crystal nucleating agents, antiblocking agents, weathering agents, heat stabilizers, flame retardants, release agents, antifogging agents, surface wetting improvers, incineration aids, dispersing aids, various surfactants, slip agents, freshness-preserving agents, and antibacterial agents, as long as the effects of the present invention are not significantly impaired. These components may be contained alone or in combination of two or more. When the aliphatic polycarbonate solution of the present embodiment contains other components, the amount of the other components is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and still more preferably 1 part by mass or less, relative to 100 parts by mass of the aliphatic polycarbonate resin in the solution, in order not to impair the properties of the polycarbonate solution.

[0021] [Aliphatic polycarbonate solution] The aliphatic polycarbonate solution of the present embodiment contains an aliphatic polycarbonate resin having a number average molecular weight of 30,000 to 200,000 and consisting of repeating units represented by the above-mentioned formula (1), and contains a chlorine-based organic solvent having a boiling point of 70°C or higher at normal pressure as a solvent.

[0022] The aliphatic polycarbonate solution of this embodiment is preferably obtained by dissolving the aliphatic polycarbonate resin in a chlorine-based organic solvent under heating. The heating temperature is preferably 60° C. or higher, more preferably 70° C. or higher, and even more preferably 80° C. or higher. A heating temperature of 60° C. or higher is preferred because the aliphatic polycarbonate resin can be quickly dissolved. As described above, the aliphatic polycarbonate solution of the present embodiment obtained by dissolving the aliphatic polycarbonate resin in the chlorine-based organic solvent under heating has a resin amount that precipitates after cooling the solution to room temperature (20°C) and leaving it to stand for 2 hours, which is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less of the resin amount dissolved in the solution before cooling. This means that the aliphatic polycarbonate solution has excellent stability.

[0023] The aliphatic polycarbonate solution of the present embodiment has excellent stability. In the present invention, "excellent stability" means that precipitation of the resin from the solution is significantly suppressed, and in particular, the aliphatic polycarbonate solution of the present embodiment has excellent stability even at low temperatures around room temperature. When forming membranes or films from polymer solutions, one of the important requirements is that the solution maintains a stable homogeneity without resin precipitation. Even if the polymer is dissolved in a solvent, if the polymer easily precipitates, it not only affects the homogeneity and mechanical properties of the resulting membrane or film, but also complicates the manufacturing process and increases the risk of clogging the manufacturing equipment, such as pipes, leading to breakdowns. In addition to solution stability, the polymer must also have good formability, and one of the requirements is that it can be easily produced into membranes or films.

[0024] Generally, polycarbonate diols are known to have low molecular weights because they are used as soft segments of urethane resins. The polycarbonate diol specifically disclosed in Patent Document 2 is also ultimately reacted with isocyanate to form a urethane resin, and has a low number-average molecular weight of about 2,500. A polycarbonate solution obtained by dissolving such a low number-average molecular weight polycarbonate diol in the above-mentioned chlorine-based organic solvent has poor solution stability, and resin precipitation is noticeable around room temperature.

[0025] The concentration of the aliphatic polycarbonate solution of the present embodiment is not particularly limited, but from the viewpoints of solution stability and workability during molding (film formation), it is preferably 0.1 to 40 mass%, more preferably 0.1 to 30 mass%, even more preferably 0.1 to 20 mass%, still more preferably 0.5 to 20 mass%, and particularly preferably 1 to 20 mass%. The concentration of the aliphatic polycarbonate solution here refers to the proportion of the aliphatic polycarbonate when the total of the aliphatic polycarbonate resin and the solvent is taken as 100% by mass.

[0026] The aliphatic polycarbonate solution of the present embodiment can be used as it is, or can be mixed with an emulsifier to form an emulsion, or can be dried to form a dry product. It is also preferable to emulsify the aliphatic polycarbonate solution and then dry it to form a dry product.

[0027] <Aliphatic polycarbonate membrane> In one aspect of the present embodiment, there is provided an aliphatic polycarbonate membrane obtained by coating the aliphatic polycarbonate solution described above and drying it. The thickness of the aliphatic polycarbonate membrane can be appropriately selected depending on the application, and can be controlled, for example, by the amount of the aliphatic polycarbonate solution applied. The method for producing the aliphatic polycarbonate film is not particularly limited, and the film can be obtained, for example, by applying the aliphatic polycarbonate solution of the present invention to a substrate such as a base film, and then drying the substrate to remove the solvent.

[0028] The coating method is not particularly limited, but coating methods using a roll coater, reverse roll coater, gravure coater, microgravure coater, spray coater, knife coater, bar coater, wire bar coater, die coater, or dip coater can be used. The drying method is not particularly limited, and methods such as heating, air blowing, hot air, and vacuuming can be used as appropriate.

[0029] <Method for producing aliphatic polycarbonate resin> Aliphatic polycarbonate resins having a structure represented by formula (1) can be produced by known methods. For example, they can be produced by solution polymerization or interfacial polymerization using phosgene or a carboxylic acid halide, or by melt polymerization, in which a diol compound and a carbonate compound are reacted in the presence of a transesterification catalyst without using a solvent. Among these production methods, melt polymerization is preferred because it does not use highly toxic compounds or solvents, thereby reducing the environmental impact and providing excellent productivity.

[0030] The carbonate compound is not limited as long as it does not impair the effects of the present invention, and examples thereof include dialkyl carbonate, diaryl carbonate, and alkylene carbonate. Examples of dialkyl carbonate include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate, diisobutyl carbonate, ethyl-n-butyl carbonate, and ethyl isobutyl carbonate, with dimethyl carbonate and diethyl carbonate being preferred. Examples of diaryl carbonate include diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl)carbonate, and di-m-cresyl carbonate, with diphenyl carbonate being preferred. Examples of alkylene carbonates include ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 1,3-pentylene carbonate, 1,4-pentylene carbonate, 1,5-pentylene carbonate, 2,3-pentylene carbonate, 2,4-pentylene carbonate, and neopentylene carbonate, with ethylene carbonate being preferred. These may be used alone or in combination of two or more. As the carbonate compound, diaryl carbonate is preferred because it is highly reactive and can be efficiently produced industrially, and among these, diphenyl carbonate is more preferred because it is easily and inexpensively available as an industrial raw material.

[0031] In order to obtain the aliphatic polycarbonate resin of formula (1), an aliphatic diol having 6 to 30 carbon atoms or an aliphatic polyalkylene glycol having an alkylene group in a repeating unit with 6 to 30 carbon atoms and a repeating number of 40 or less is used as the diol compound. Specific examples of aliphatic diols include 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,17-heptadecanediol, 1,18-octadecanediol, 1,20-eicosanediol, 1,21-heneicosanediol, 1,22-docosanediol, 1,23-tricosanediol, 1,24-tetracosanediol, and 1,25-pentacosanediol. aliphatic diols having no side chains, such as 1,26-hexacosanediol, 1,27-heptacosanediol, 1,28-octacosanediol, 1,29-nonacosanediol, and 1,30-triacontanediol; and aliphatic diols having side chains, such as 2-ethyl-1,6-hexanediol, 3-methyl-1,5-pentanediol, 2,4-dimethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, and 2-methyl-1,8-octanediol.

[0032] The polyalkylene glycol can be produced by, for example, the method described in Example 1 of JP 2018-165343 A. For example, similar to producing polydecamethylene glycol using a polycondensation reaction using 1,10-decanediol as a raw material, a polyalkylene glycol having an alkylene chain with an appropriate number of carbon atoms is first produced from an alkylene diol having an alkylene chain with an appropriate number of carbon atoms. This polyalkylene glycol is then hydrolyzed in an acidic or basic aqueous solution while adjusting conditions such as temperature, catalyst type, catalyst amount, polymerization temperature, and polymerization reaction time to obtain a polyalkylene glycol having an appropriate number of carbon atoms in the alkylene chain and an appropriate molecular weight. In order to obtain the aliphatic polycarbonate resin of formula (1), an aliphatic diol having 6 to 30 carbon atoms is used as the alkylene diol raw material of the polyalkylene glycol. Specifically, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,17-heptadecanediol, 1,18-octadecanediol, 1,20-eicosanediol, 1,21-heneicosanediol, 1,22-docosanediol, 1,23-tricosanediol, 1,24-tetracosanediol, and 1,25-pentacosanediol are used. aliphatic diols having no side chains, such as 1,26-hexacosanediol, 1,27-heptacosanediol, 1,28-octacosanediol, 1,29-nonacosanediol, and 1,30-triacontanediol; and aliphatic diols having side chains, such as 2-ethyl-1,6-hexanediol, 3-methyl-1,5-pentanediol, 2,4-dimethyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, and 2-methyl-1,8-octanediol.

[0033] The above-mentioned aliphatic diols or polyalkylene glycols can be selected as the diol compound either singly or in combination of two or more. A small amount of a compound having three or more hydroxy groups per molecule, such as trimethylolethane, trimethylolpropane, hexanetriol, or pentaerythritol, can also be used. Using too much of this compound having three or more hydroxy groups per molecule is undesirable because crosslinking and gelation occur during the polymerization reaction of the polycarbonate. Therefore, the compound having three or more hydroxy groups per molecule can be used in an amount of preferably 0.01 to 5% by mass, more preferably 0.01 to 1% by mass, based on the total amount of the diol compounds.

[0034] As the diol compound, a biomass-derived aliphatic hydrocarbon can also be used. By appropriately using a biomass-derived aliphatic hydrocarbon while taking into consideration the balance of the physical properties of the final membrane and film, it is possible to further contribute to reducing the environmental load.

[0035] The transesterification catalyst can be any compound generally known to have transesterification ability. Examples of transesterification catalysts include metal compounds of Groups 1, 2, 4, 5, 9, 12, 13, and 14 of the periodic table, as well as basic compounds such as basic boron compounds, basic phosphorus compounds, basic ammonium compounds, and amine compounds. Metal compounds of Groups 1, 2, 4, 5, 9, 12, 13, and 14 of the periodic table are preferred, and metal compounds of Groups 1, 2, and 12 of the periodic table are more preferred. These metal compounds are typically used as hydroxides or salts. Examples of salts used as salts include halide salts, carboxylate salts, sulfonate salts, phosphorus-containing salts, and acetylacetonate salts. The catalytic metal can also be used as an alkoxide. For example, zinc(II) acetate can be used.

[0036] The amount of the catalyst used is not particularly limited, but is usually 0.0005% by mass or more, more preferably 0.001% by mass or more, and usually 3% by mass or less, preferably 1.5% by mass or less, based on the total mass of the monomers used. By keeping the amount of catalyst within the above range, sufficient catalytic effect can be obtained while reducing production costs, and coloration of the obtained polymer or deterioration of hydrolysis resistance can be suppressed.

[0037] The method for charging the raw materials is not particularly limited, and the method can be freely selected, for example, by charging all of the diol compound, carbonate compound, and transesterification catalyst at the same time and subjecting them to the reaction; by first charging the carbonate compound, if the carbonate compound is solid, and then adding the diol compound and transesterification catalyst while heating and melting it; or by conversely charging the diol compound first, melting it, and then adding the carbonate compound and transesterification catalyst.

[0038] The reaction rate of polycondensation and the molecular weight of the resulting resin can be controlled by strictly adjusting the molar ratio of all diol compounds to all carbonate compounds used in the reaction. For example, the molar ratio of all carbonate compounds to all diol compounds is preferably adjusted to 0.90 to 1.10, more preferably 0.96 to 1.05, and particularly preferably 0.98 to 1.03.

[0039] Known reaction conditions such as reaction temperature, polymerization time, and pressure for the transesterification reaction between a diol compound and a carbonate compound can be used. For example, the reaction temperature for the transesterification reaction between a diol compound and a carbonate compound is usually 150°C or higher, preferably 180°C or higher, and usually 280°C or lower, preferably 260°C or lower. The reaction atmosphere is preferably an inert atmosphere such as nitrogen or argon. The reaction pressure is usually 0.01 x 10 3 Pa~1×10 5 Pa (normal pressure), preferably 0.03 x 10 3 Pa or more, more preferably 0.05×10 3 Pa or more, preferably 1.0 × 10 4 Pa or less, preferably 1.4×103 Pa or less, more preferably 0.4 × 10 3 The polymerization time is usually 1 hour or longer and usually 20 hours or shorter, preferably 10 hours or shorter, more preferably 8 hours or shorter. [Example]

[0040] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. The evaluation methods used in the examples and comparative examples are as follows.

[0041] (1) Molecular weight measurement Approximately 3 mg of the aliphatic polycarbonate resin of each Example and Comparative Example 1, or the aliphatic polyester resin of Comparative Example 2, was placed in a glass vial, and approximately 3 ml of reagent-grade tetrahydrofuran was added. The mixture was heated and stirred at 50°C for 1 hour, and then allowed to stand overnight to prepare a sample solution with a concentration of approximately 0.1% by mass. The prepared sample solution was filtered through a 0.45 μm pretreatment filter (Merck, centrifugal filter Durapore PVDF) and subjected to GPC measurement. The GPC measurements were carried out using columns such as Shodex KF-604L, Shodex KF-603, and Shodex KF-602.5 manufactured by Showa Denko K.K., and a Waters e2695GPC equipped with an RI detector. The measurement conditions were as follows: Sample injection volume: 10 μL Column temperature: 40℃ Elution solvent: Reagent-grade tetrahydrofuran Flow rate: 0.6 mL / min The converted average molecular weight was calculated as follows. Commercially available monodisperse polystyrenes (Tosoh Corporation, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000, A-2500, A-1000, A-500) were used as standard samples to create a calibration curve relating retention time and molecular weight of the polystyrene standard samples. Based on the calibration curve, the polystyrene-equivalent mass average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn) of the polyester resin were calculated.

[0042] (2) Solvent solubility 10% by mass solvent solubility test The aliphatic polycarbonate resin of each Example and Comparative Example 1, or the aliphatic polyester resin of Comparative Example 2 (600 mg) was introduced into a flask, and then 3.3 mL of tetrachloroethylene (boiling point: 121°C) was added to the flask. After stirring the contents of the flask at 100°C for 60 minutes, the solution was visually observed, and the resin was evaluated as "dissolved" when it was completely dissolved, and as "insoluble" when some resin residue remained.

[0043] (3) Decipherability at room temperature The solutions that were evaluated as "soluble" in the solvent solubility test in (2) above were left to stand for 2 hours at room temperature (20°C), and then filtered using analytical quantitative filter paper No. 704 manufactured by Nippon Rikagaku Kikai Co., Ltd. The filter paper was washed five times with 5 mL of the same solvent used in the solvent solubility test (5 mL per wash), and the solvent in the filtrate and washings was then distilled off under reduced pressure. The mass of the remaining resin was measured, and the proportion of the resin that precipitated at room temperature was calculated.

[0044] (4) Film formability A resin solution was prepared under the same conditions as for the solvent solubility in (2) above, and the solution was placed on a glass plate and applied with a #20 bar coater. The glass plate was heated to 80°C to volatilize the solvent, and then it was confirmed whether the resin film could be isolated from the glass plate. If it could be isolated, it was evaluated as having film-forming ability, and if it could not be isolated from the glass plate, it was evaluated as not having film-forming ability.

[0045] Example 1 A reactor equipped with a stirrer, nitrogen inlet, heater, thermometer, and pressure reduction port was charged with 87.02 g of 1,10-decanediol, 106.97 g of diphenyl carbonate, and 183.3 mg of zinc(II) acetate as raw materials. The reactor was then conditioned under a nitrogen atmosphere and dissolved at 210°C. Subsequently, while stirring at 100 rpm, the pressure was reduced to 130 Pa over 90 minutes to distill off phenol, allowing the transesterification and polycondensation reactions to proceed. The reaction was completed 3 hours after the start of pressure reduction, and aliphatic polycarbonate resin was extracted from the bottom of the reactor in the form of strands. The resin was cooled in a cooling water bath and then pelletized to obtain aliphatic polycarbonate 1 in the form of pellets approximately 2-3 mm square. The molecular weight of aliphatic polycarbonate 1 was measured using the molecular weight measurement method described above in (1). The resulting aliphatic polycarbonate 1 was dissolved in a solvent listed in Table 1 to obtain the target aliphatic polycarbonate 1 solution. The solvent solubility of the aliphatic polycarbonate 1 was confirmed using the measurement method described in (2) above. The room temperature precipitability of the aliphatic polycarbonate 1 solution was measured using the method described in (3) above, and the film-forming ability was evaluated using the method described in (4) above. The results are shown in Table 1. For Example 1, the solvent solubility (2) and room temperature precipitability (3) were evaluated using trichloroethylene (boiling point: 87°C) and o-dichlorobenzene (boiling point: 180°C) as solvents.

[0046] Example 2 The reaction was carried out under reduced pressure under the same conditions as in Example 1, except that the 1,10-decanediol used in Example 1 was replaced with 1,12-dodecanediol, and 88.62 g of 1,12-dodecanediol, 93.82 g of diphenyl carbonate, and 160.7 mg of zinc(II) acetate were used. The reaction was completed 2 hours after the start of pressure reduction, and pellets of aliphatic polycarbonate 2 were obtained in the same manner as in Example 1. The molecular weight of the resulting aliphatic polycarbonate 2 was measured in the same manner as in Example 1, and its solvent solubility when dissolved in the solvents listed in Table 1 was confirmed. The resulting polycarbonate resin 2 solution was tested for room temperature deposition and film-forming properties. The results are shown in Table 1.

[0047] Example 3 The reaction was carried out under reduced pressure under the same conditions as in Example 1, except that the 1,10-decanediol in Example 1 was replaced with polydecamethylene glycol (hydroxyl value 147 mgKOH / g) and 19.35 g of polydecamethylene glycol, 5.42 g of diphenyl carbonate, and 9.3 mg of zinc(II) acetate were used. The reaction was terminated 5 hours after the start of pressure reduction, and pellets of aliphatic polycarbonate 3 were obtained in the same manner as in Example 1. The molecular weight of the resulting aliphatic polycarbonate 3 was measured in the same manner as in Example 1, and its solvent solubility when dissolved in the solvents listed in Table 1 was confirmed. The resulting polycarbonate resin 3 solution was tested for its room temperature deposition and film-forming properties. The results are shown in Table 1.

[0048] Comparative Example 1 The reaction was carried out under reduced pressure under the same conditions as in Example 3, except that 21.05 g of polydecamethylene glycol and 5.44 g of diphenyl carbonate were used. The reaction was terminated 5 hours after the start of pressure reduction, and pellets of aliphatic polycarbonate 4 were obtained in the same manner as in Example 1. The molecular weight of the obtained aliphatic polycarbonate 4 was measured in the same manner as in Example 1, and the solvent solubility when dissolved in the solvents listed in Table 1 was confirmed. The room temperature deposition property and film-forming property of the obtained polycarbonate resin 4 solution were tested. The results are shown in Table 1.

[0049] Comparative Example 2 Based on the method described in Reference 1 (JP 2023-152809 A), a pellet-shaped aliphatic polyester was obtained using decanedioic acid and 1,10-decanediol as raw materials. The molecular weight of the obtained aliphatic polyester was measured in the same manner as in Example 1, and the solvent solubility when dissolved in the solvents listed in Table 1 was confirmed. The obtained polyester solution was tested for its room temperature deposition property and film-forming property. The results are shown in Table 1.

[0050] [Table 1]

[0051] From Examples 1 to 3, it was confirmed that the aliphatic polycarbonate solution of the present embodiment has excellent solvent solubility, extremely low resin precipitation even at room temperature, and excellent stability even at low temperatures around room temperature.Furthermore, it also has excellent film-forming properties. On the other hand, in Comparative Example 1, which used an aliphatic polycarbonate resin with a number average molecular weight outside the range of the present invention, the solvent solubility was good, but the resin precipitated from the aliphatic polycarbonate solution at room temperature, resulting in poor stability at low temperatures around room temperature. Furthermore, a membrane could not be isolated, resulting in poor membrane-forming properties. In the aliphatic polyester solution of Comparative Example 2, which used an aliphatic polyester resin as the resin, the resin precipitated significantly at room temperature, resulting in poor stability at low temperatures around room temperature.

Claims

1. An aliphatic polycarbonate solution containing an aliphatic polycarbonate resin having a number average molecular weight of 30,000 to 200,000 and including a repeating unit represented by the following formula (1), and containing a chlorine-based organic solvent as a solvent having a boiling point of 70°C or higher at normal pressure: 【Chemistry 1】 (In the above formula (1), R represents a linear or branched alkylene group having 6 to 30 carbon atoms, and n represents a value of 1 to 40.)

2. 2. The aliphatic polycarbonate solution according to claim 1, wherein the chlorine-based organic solvent is at least one selected from the group consisting of tetrachloroethylene, trichloroethylene, 1,1,2-trichloroethane, and o-dichlorobenzene.

3. 3. The aliphatic polycarbonate solution according to claim 1 or 2, wherein the aliphatic polycarbonate solution is prepared by dissolving the aliphatic polycarbonate resin in the chlorine-based organic solvent under heating, and the amount of resin precipitated after the solution is cooled to room temperature (20°C) and allowed to stand for 2 hours is 15 mass % or less of the amount of resin dissolved in the solution before cooling.

4. An aliphatic polycarbonate film obtained by applying the aliphatic polycarbonate solution according to claim 1 or 2 and drying it.

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