Reactor for producing anhydrous alkali metal sulfide, method for producing anhydrous alkali metal sulfide and method for producing polyarylene sulfide using anhydrous alkali metal sulfide

Abstract

To provide an apparatus for producing anhydrous alkali metal sulfides with low crystallization water content that suppresses adhesion, solidification, sticking, or settling of a target substance inside the reaction kettle by controlling foaming, a method for producing the anhydrous alkali metal sulfides, and a method for producing polyarylene sulfide using these anhydrous alkali metal sulfides.SOLUTION: The present disclosure relates to a reactor used for producing anhydrous alkali metal sulfides, comprising: a reaction vessel 1 having a recess for accommodating a raw material solution containing an aqueous alkali metal sulfide, a cyclic aliphatic compound that can be ring-opened by hydrolysis, and a non-hydrolyzable organic solvent; a lower stirring blade 3 provided near the bottom of the reaction vessel for stirring the raw material solution; an upper stirring blade 2 provided on the opening side of the reaction vessel relative to the lower stirring blade and for stirring the raw material solution; wherein the ratio of the distance from the lowermost end of the lower stirring blade to the bottom of the reaction vessel (bottom gap: BG) to the inner diameter of the reactor (D) (BG / D) is 0.15 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an apparatus used for producing a low-hydrated alkali metal sulfide, a method for producing a low-hydrated alkali metal sulfide, and a method for producing a polyarylene sulfide using the low-hydrated alkali metal sulfide. [Background technology]

[0002] Polyarylene sulfide resins (hereinafter abbreviated as "PAS resins"), typified by polyphenylene sulfide resins (hereinafter abbreviated as "PPS resins"), have excellent heat resistance, chemical resistance, etc., and are widely used in electrical and electronic components, automobile parts, water heater parts, fibers, films, etc. In recent years, there has been a particularly high demand for high-molecular-weight PAS resins in these applications from the standpoints of strength and moldability.

[0003] One known method for producing such high-molecular-weight PAS resins is to mix a hydrous alkali metal sulfide, less than 1 mole of N-methylpyrrolidone per mole of the hydrous alkali metal sulfide, and a polyhaloaromatic compound, and then azeotropically dehydrate the mixture to obtain a slurry composition containing finely granulated low-hydrate alkali metal sulfide. This slurry composition is then heated and polymerized to produce a PAS resin (see Patent Document 1). Patent Document 1 describes a technique for producing a low-hydrate alkali metal sulfide composition with good dispersibility, and therefore describes that when this low-hydrate alkali metal sulfide composition is used to polymerize a PAS resin under polymerization conditions, it is easy to achieve a high molecular weight. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3637543 Summary of the Invention [Problem to be solved by the invention]

[0005] However, it has been confirmed that, during the production of the above-mentioned low-hydrated alkali metal sulfide, foaming occurs particularly during the dehydration stage when the aqueous solution containing the alkali metal sulfide is concentrated and solid hydrous alkali metal sulfide begins to precipitate. This foaming causes the volume of the aqueous solution to expand to about 1.3 times its volume at the start of dehydration, resulting in new problems: the precipitated solid hydrous alkali metal sulfide adheres, solidifies, adheres to, or settles on various locations within the reactor (e.g., the reactor wall, the reactor bottom, or components (stirring blades, heat transfer piping, etc.) attached to the reactor as needed); and the theoretical amount of the precipitated solid hydrous alkali metal sulfide cannot be dehydrated and remains in the system in the form of residual water of crystallization.

[0006] In view of the above problems, the present disclosure aims to provide an apparatus for producing a low-hydrated alkali metal sulfide with a low content of water of crystallization, which suppresses adhesion, solidification, adhesion or precipitation of the target substance inside a reaction vessel by suppressing foaming, a method for producing the low-hydrated alkali metal sulfide, and a method for producing a polyarylene sulfide using the low-hydrated alkali metal sulfide. [Means for solving the problem]

[0007] In order to achieve the above object, the present inventors have conducted extensive research into various factors that affect foaming, and as a result have obtained the following findings (A) and (B).

[0008] (A) When stirring a raw material solution containing a hydrated alkali metal sulfide, an aliphatic cyclic compound that can be ring-opened by hydrolysis, and a non-hydrolyzable organic solvent, if the reaction vessel has at least two stirring blades, namely a lower stirring blade installed near the bottom of the reaction vessel and an upper stirring blade installed closer to the opening of the reaction vessel than the lower stirring blade, foaming is less likely to occur, making it easier to dehydrate the theoretical amount, and any foam that does occur can be eliminated by the upper stirring blade.

[0009] (B) the ratio (dA / D) of the maximum blade diameter (dA) of the lower stirring blade to the inner diameter (D) of the reaction vessel is greater than 0.46, or the ratio (hA / D) of the maximum height (hA) of the lower stirring blade to the inner diameter (D) of the reaction vessel is greater than 0.08; a ratio (BG / D) of the distance from the lowest end of the lower stirring blade to the bottom of the reaction vessel (bottom gap: BG) to the inner diameter (D) of the reaction vessel is 0.15 or less; When the ratio (hB / D) of the maximum height (hB) of the upper stirring blade to the inner diameter (D) of the reaction vessel exceeds 0.17, the lower stirring blade easily forms an upward flow in the raw material solution, which can suppress the settling of the solid low-hydrated alkali metal sulfide, thereby reducing the amount of the sodium sulfide composition or the like adhering to the vessel or stirring blade.

[0010] The present disclosure has been completed based on the above findings, and its gist and configuration are as follows. [1] A reaction vessel having a recess for accommodating a raw material solution containing a hydrated alkali metal sulfide, an aliphatic cyclic compound capable of being ring-opened by hydrolysis, and a non-hydrolyzable organic solvent; a lower stirring blade provided near the bottom of the reaction vessel for stirring the raw material solution; an upper stirring blade that is disposed closer to the opening of the reaction vessel than the lower stirring blade and stirs the raw material solution; The ratio (dA / D) of the maximum blade diameter (dA) of the lower stirring blade to the inner diameter (D) of the reaction vessel is greater than 0.46, or the ratio (hA / D) of the maximum height (hA) of the lower stirring blade to the inner diameter (D) of the reaction vessel is greater than 0.08, a ratio (BG / D) of the distance from the lowest end of the lower stirring blade to the bottom of the reaction vessel (bottom gap: BG) to the inner diameter (D) of the reaction vessel is 0.15 or less; A reaction apparatus used for producing a low-hydrated alkali metal sulfide, wherein the ratio (hB / D) of the maximum height (hB) of the upper stirring blade to the inner diameter (D) of the reaction vessel is greater than 0.17.

[0011] [2] The reaction apparatus used for producing a low-hydrated alkali metal sulfide according to [1], wherein the ratio (dB / D) of the maximum blade diameter (dB) of the upper stirring blade to the inner diameter (D) of the reaction vessel is 0.3 or more.

[0012] [3] The reaction apparatus used for producing a low-hydrated alkali metal sulfide according to [1] or [2], wherein (hB / D), which indicates the ratio of the maximum height (hB) of the upper stirring blade to the inner diameter (D) of the reaction vessel, is 0.5 or more.

[0013] [4] A heat transfer pipe that transfers heat necessary to initiate and progress the reaction of the raw material solution, or transfers heat generated by the reaction of the raw material solution; and A baffle plate that generates turbulence when stirring the raw material solution. The reaction apparatus used for producing the low-hydrated alkali metal sulfide according to any one of [1] to [3] above further comprises one or two selected from the group consisting of:

[0014] [5] A reaction apparatus used for producing a low-hydrated alkali metal sulfide according to any one of [1] to [4], which has a stirring shaft that is arranged parallel to the inner side peripheral surface of the reaction vessel, and the lower stirring blade and the upper stirring blade are attached to the stirring shaft.

[0015] [6] The reaction apparatus used for producing a low-hydrated alkali metal sulfide according to any one of [1] to [5], wherein the ratio (dA / D) of the maximum blade diameter (dA) of the lower stirring blade to the inner diameter (D) of the reaction vessel is 0.5 or more.

[0016] [7] A reaction apparatus used for producing a low-hydrated alkali metal sulfide according to any one of [1] to [6], wherein (hA / D), which indicates the ratio of the maximum height (hA) of the lower stirring blade to the inner diameter (D) of the reaction vessel, is 0.1 or more.

[0017] [8] A method for producing a low-hydrated alkali metal sulfide using the reaction apparatus according to any one of [1] to [7].

[0018] [9] A method for producing polyarylene sulfide, comprising a step of reacting the low-hydrated alkali metal sulfide obtained in [8] with a polyhaloaromatic compound. [Effects of the Invention]

[0019] According to the present disclosure, it is possible to provide an apparatus for producing a low-hydrated alkali metal sulfide with a low content of water of crystallization, in which adhesion, solidification, adhesion or precipitation of the target substance inside a reaction vessel is suppressed by suppressing foaming, a method for producing the low-hydrated alkali metal sulfide, and a method for producing a polyarylene sulfide using the low-hydrated alkali metal sulfide. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic diagram (cross-sectional view) showing an example of a reaction apparatus 10 of the present embodiment. [Figure 2] FIG. 2 is a schematic diagram (cross-sectional view) showing another example of the reaction apparatus 10 of the present embodiment. [Figure 3] FIG. 2 is a schematic diagram showing an example of a square-shaped upper stirring blade 2 and a lower stirring blade 3 of this embodiment. [Figure 4] FIG. 2 is a schematic view showing another example of the upper agitating blade 2 and the lower agitating blade 3 of this embodiment. [Figure 5] FIG. 2 is a schematic diagram showing another example of the reaction vessel 1 of the present embodiment. [Figure 6] FIG. 6(a) shows a reactor having a conventional single-stage vertical paddle, FIG. 6(b) shows a reactor having two-stage vertical paddles according to this embodiment, and FIG. 6(c) shows a reactor having three-stage vertical paddles according to this embodiment. [Figure 7] FIG. 1 is a schematic diagram (cross-sectional view) showing an example of a reaction apparatus 10 having six vertical paddles according to the present embodiment. [Figure 8] FIG. 3 is a schematic view showing another example of the lower agitating blade 3 of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] The following describes in detail an embodiment of the present disclosure (hereinafter referred to as the "present embodiment"); however, the scope of the present disclosure is not limited to the following description, and various modifications can be made within the scope of its gist.

[0022] [Reaction apparatus] The reaction apparatus of this embodiment is a reaction apparatus used for producing a low-hydrated alkali metal sulfide, and includes a reaction vessel having a recess for accommodating a raw material solution containing a hydrous alkali metal sulfide, an aliphatic cyclic compound capable of ring-opening by hydrolysis, and a non-hydrolyzable organic solvent, a lower stirring blade provided near the bottom of the reaction vessel for stirring the raw material solution, and an upper stirring blade provided closer to the opening of the reaction vessel than the lower stirring blade and for stirring the raw material solution, wherein (dA / D), which represents the ratio of the maximum blade diameter (dA) of the lower stirring blade to the inner diameter (D) of the reaction vessel, is greater than 0.46, or (hA / D), which represents the ratio of the maximum height (hA) of the lower stirring blade to the inner diameter (D) of the reaction vessel, is greater than 0.08, a ratio (BG / D) of the distance from the lowest end of the lower stirring blade to the bottom of the reaction vessel (bottom gap: BG) to the inner diameter (D) of the reaction vessel is 0.15 or less; The ratio (hB / D) of the maximum height (hB) of the upper stirring blade to the inner diameter (D) of the reaction vessel is greater than 0.17. This makes it possible to provide an apparatus for producing low-hydrated alkali metal sulfide with a low content of water of crystallization, in which foaming is suppressed and adhesion, solidification, adhesion, or sedimentation of the target substance inside the reactor is suppressed. More specifically, in order to suppress or prevent the low-hydrated alkali metal sulfide particles obtained by the reactor of this embodiment from settling or adhering to the bottom of the reactor, a relatively large lower stirring blade is arranged at a specific distance (BG) from the bottom, and in order to prevent solid low-hydrated alkali metal sulfide produced by foaming in the middle of the dehydration process from adhering to the inner wall of the reactor or heat transfer piping (baffle section), an upper stirring blade having a specific length in the vertical direction is arranged. This makes it possible to produce low-hydrated alkali metal sulfide with little adhesion to the bottom and little residual water, even in the presence of heat transfer piping, which has a disadvantageous effect on the uniform mixing surface and the adhesion surface. In this specification, the term "low-hydrated alkali metal sulfide" refers to a hydrated alkali metal sulfide having a water content lower than that contained in the raw material hydrated alkali metal sulfide, and a low-hydrated alkali metal sulfide having a lower water content is preferred.

[0023] The reaction apparatus according to this embodiment and each component that can be included in the reaction apparatus will be described below with reference to FIGS. 1 to 8. FIG. 1 is a schematic diagram (cross-sectional view) showing an example of the reaction apparatus 10 according to this embodiment, and FIG. 2 is a schematic diagram (cross-sectional view) showing another example of the reaction apparatus 10 according to this embodiment. Meanwhile, FIGS. 3 and 4 are schematic diagrams showing examples of the upper stirring blade 2 and the lower stirring blade 3 according to this embodiment. Furthermore, FIG. 5 shows another example of the reaction vessel 1 according to this embodiment. Finally, FIGS. 6 and 7 show a reaction apparatus having vertical paddles. Furthermore, FIG. 8 is a schematic diagram showing examples of the upper stirring blade 2 and the lower stirring blade 3 according to this embodiment.

[0024] The reactor 10 shown in FIG. 1 is the reactor 10 used in Example 1 described below. The reactor 10 includes a reactor 1, an upper agitator blade 2, and a lower agitator blade 3. More specifically, the reactor 10 includes the reactor 1, an upper agitator blade 2 and / or a lower agitator blade 3 that are rotated around a rotating shaft 5 within the reactor 1, and a baffle unit 4 that is arbitrarily disposed at a predetermined location within the reactor 1. The reactor 1 is an example of a cylindrical body with a circular cross section, and the upper agitator blade 2 is composed of two blades 2a and a connecting unit 2c that connects the two blades 2a. Similarly, the lower agitator blade 3 is also composed of two blades 3a. These two blades 2a are attached to the rotating shaft 5 via the connecting unit 2c. The two blades 3a are directly attached to the rotating shaft 5. The rotating shaft 5 is provided so as to be surrounded by the inner circumferential surface S of the reaction vessel 1, and is connected to a drive unit (not shown) provided at the upper part T outside the reaction vessel 1. Therefore, when the drive unit (not shown) is driven, the rotating shaft 5 is driven to rotate, and the upper stirring blade 2 and / or the lower stirring blade 3 can be driven to rotate within the reaction vessel 1. In FIG. 1A, two blade portions 2a and two blade portions 3a are fixed to one rotating shaft 5, but the number of rotating shafts 5 may be multiple. Furthermore, multiple rotating shafts 5 may be attached to each blade portion (e.g., blade portions 2a, 3b), and each blade portion may be driven to rotate independently. 1, the two blades 2a, the baffle 4, and the rotation shaft 5 each extend within the reactor 1 so that the longitudinal direction of the two blades 2a having rectangular surfaces, the longitudinal direction of the baffle 4 having rectangular surfaces, and the longitudinal direction of the rotation shaft 5 are (approximately) parallel to one another. The rotation shaft 5 passes through the center of gravity of the vertical cross section (for example, the center of the circle if the vertical cross section is circular), which is the shape of the vertical cross section of the reactor 1 (a cross section when cut perpendicularly to the wall of the reactor 1), and extends within the reactor 1 from near the lower part B to the upper part T.

[0025] Next, a modified version of the reaction apparatus 10 shown in FIG. 1 will be described. This modified reaction apparatus does not have the baffle 4 of the reaction apparatus 10 shown in FIG. 1, and the upper agitating blade 2 shown in FIG. 1 can be replaced with the upper agitating blade 2 shown in FIG. 3. Specifically, the modified reaction apparatus includes a reaction vessel, an upper agitating blade, and a lower agitating blade. The modified reaction apparatus is also comprised of a reaction vessel and an upper agitating blade and / or a lower agitating blade that are rotated within the reaction vessel. The upper agitating blade is comprised of two blades and a connecting portion that connects the two blades. Similarly, the lower agitating blade is also comprised of two blades. The two blades of the upper agitating blade and the two blades of the lower agitating blade are each attached to a rotating shaft. The rotating shaft is provided so as to be surrounded by the inner circumferential surface of the reaction vessel and is connected to a drive unit provided above the outside of the reaction vessel. Therefore, when the drive unit is driven, the rotating shaft is driven to rotate, and the upper stirring blade and / or the lower stirring blade can be driven to rotate in the reaction vessel. In the reaction apparatus of the modified example, the two blade units and the two blade units are fixed to one rotating shaft, but the number of rotating shafts may be multiple. For example, at least one rotating shaft may be attached to each blade unit, and each blade unit may be driven to rotate independently. 3, in the upper stirring blade of the reaction apparatus of the modified example of Fig. 1, the two blade portions 2a having (approximately) trapezoidal surfaces and the rotation shaft 5 extend into the reaction vessel 1 so that their longitudinal directions are (approximately) parallel to each other. The rotation shaft 5 passes through the center of gravity of the vertical cross section (for example, the center of the circle when the vertical cross section is circular), which is the shape of the vertical cross section of the reaction vessel 1 (a cross section when cut perpendicularly to the wall of the reaction vessel 1), and extends inside the reaction vessel 1 from the vicinity of the lower part B to the upper part T.

[0026] The reaction apparatus 10 shown in Fig. 2 is the reaction apparatus 10 used in Example 2 described later, and is a schematic diagram (cross-sectional view) showing another example of the reaction apparatus 10 of this embodiment. The configuration of the reaction apparatus 10 shown in Fig. 2 is the same as that of the reaction apparatus 10 shown in Fig. 1, except that the shape of the upper stirring blade 2 is different from that in Fig. 1. Therefore, the configuration of the reaction apparatus 10 shown in FIG. 2 other than the upper stirring blade 2 is the same as that of the reaction apparatus 10 shown in FIG. The details of the upper agitating blade 2 shown in FIG. 2 will be described later; the upper agitating blade 2 has six paddle blades. That is, if four blade portions 2a having (approximately) square surfaces are considered as one set, six sets of blade portions 2a are attached in the extension direction of the rotating shaft 5. In this case, in each set, two blade portions 2a having (approximately) square surfaces extend in approximately the same plane from the rotating shaft 5 toward the inner wall of the reaction vessel 1. Here, if two blade portions 2a extending in approximately the same plane are considered as a pair of blade portions 2a, there are two sets of pairs of blade portions 2a, and the two sets of pairs of blade portions 2a are attached to the rotating shaft 5 so that they are perpendicular to each other. In other words, the upper agitating blade 2 has six sets of agitating blades attached independently to the extension direction of the rotating shaft 5. Each pair of agitating blades is composed of four blade portions 2a that are perpendicular to each other. Each pair of blade portions 2a having six (approximately) rectangular surfaces extends in a direction (approximately) perpendicular to the extending direction of the rotation shaft 5. Furthermore, the rotation shaft 5 passes through the center of gravity of the vertical cross section (for example, the center of the circle if the vertical cross section is a circle), which is the shape of the vertical cross section of the reaction vessel 1 (a cross section when cut perpendicularly to the wall of the reaction vessel 1), and extends within the reaction vessel 1 from near the lower part B to the upper part T.

[0027] Next, a modified example of the reaction apparatus 10 shown in Figure 2 will be described. The reaction apparatus of this modified example may have a structure in which the baffle unit 4 in the reaction apparatus 10 shown in Figure 2 is absent, and an H-shaped upper stirring blade is attached instead of the upper stirring blade 2 shown in Figure 2. Therefore, the configuration of the reaction apparatus of this modified example is the same as that of the reaction apparatus 10 shown in Figure 2, except that the baffle unit 4 of Figure 2 is absent, and the shape of the upper stirring blade 2 of Figure 2 is replaced with an H-shaped upper stirring blade. Therefore, the configuration of the reaction apparatus of the modified example is based on the content of the reaction apparatus 10 shown in Figure 2. The H-shaped upper agitating impeller has a structure in which the longitudinal direction of the two blades, each having a (substantially) rectangular surface that constitute the upper agitating impeller, and the longitudinal direction of the rotation shaft are (substantially) parallel to each other, and the two blades and the rotation shaft each extend into the reactor, and an upper agitating impeller support (e.g., a rod-shaped member) that connects the two blades is fixed to the rotation shaft so that it is perpendicular to the rotation shaft and located approximately at the center of the two blades. In other words, the H-shaped upper agitating impeller can be said to have a shape in which the two outer blades 2a of the upper agitating impeller 2 shown in Figure 4 have been removed. The rotation shaft passes through the center of gravity of the vertical cross section (e.g., the center of the circle if the vertical cross section is circular), which is the shape of the vertical cross section of the reactor 1 (a cross section cut perpendicular to the wall of the reactor 1), and extends within the reactor from near the bottom to the top.

[0028] For example, the upper agitating blade 2 in Figure 1 is shown as an example of a (substantially) square-shaped (or "R"-shaped) upper agitating blade 2 having two blade portions 2a and two connecting portions that connect the two blade portions 2a. More specifically, Figure 1 shows a square-shaped upper agitating blade 2 in which a left-bracket-shaped ("["]) blade portion 2a and a right-bracket-shaped ("]") blade portion 2a are connected. On the other hand, the upper stirring blade 2 in FIG. 2 is shown as an example in which one set of four blade portions 2a is attached to a six-stage rotating shaft 5. In Figures 1 and 2, the reaction vessel 1 having an (approximately) cylindrical shape may be equipped with an impeller attachment port 5A used when attaching the upper impeller 2 and the lower impeller 3 to the reaction vessel 1, an inlet (not shown) for the raw material or raw material solution used when introducing the raw material or raw material solution into the reaction vessel 1 and provided near the upper part T of the reaction vessel 1, and / or an attachment port (not shown) for the baffle part used when attaching the baffle part (not shown) to the reaction vessel 1 and provided near the upper part T of the reaction vessel 1, as necessary.

[0029] Next, the state in which the upper agitating blade 2 and the lower agitating blade 3 are rotated will be described with reference to FIG. 6. For example, FIG. 6 shows how the upper agitating blade 2 and / or the lower agitating blade 3 are rotated in the reaction vessel by driving the rotation shaft 5 in the n direction, thereby causing convection of the solution. FIG. 6(a) shows a conventional single-stage paddle reactor in which a rectangular, flat lower agitating blade 3 is attached to the rotation shaft 5. FIG. 6(b) shows a reactor equipped with a two-stage vertical paddle of this embodiment, in which four rectangular, flat blades are attached in two stages in the axial direction (or vertical direction) of the rotation shaft 5, and the adjacent two rectangular blades are orthogonal to each other (forming a cross shape when viewed from the opening of the reaction vessel). Figure 6(c) shows a reactor with a three-tier vertical paddle of this embodiment, which has agitator blades 2 and 3 with a configuration in which four rectangular flat blades are attached in three tiers along the axial direction (or vertical direction) of the rotating shaft 5, with adjacent two rectangular blades perpendicular to each other (each agitator blade is cross-shaped when viewed from the opening of the reactor). The reactor in Figure 6(a) is configured to generate a solution flow only near the bottom of the reactor, while the reactors in Figures 6(b) and 6(c) have agitator blades attached not only to the bottom of the reactor but also in the direction of the rotating shaft 5, thereby generating convection or circulating flow throughout the reactor, from the bottom to the height near the liquid level of the solution. This further suppresses adhesion, solidification, adhesion, or sedimentation of the target substance inside the reactor.

[0030] <Mixing blade> The upper agitator blade 2 and the lower agitator blade 3 are components of a stirring means for stirring the raw solution in the reaction vessel 1. The stirring means for stirring the raw solution in the reaction vessel 1 includes a rotating shaft 5, an upper agitator blade 2, a lower agitator blade 3, and a drive unit (not shown). The rotating shaft 5 may be located anywhere in the reaction vessel 1, but is generally located near the center of the reaction vessel 1 so that rotation of the upper agitator blade 2 and the lower agitator blade 3 generates a symmetrical flow within the reaction vessel 1 around the rotating shaft 5. In other words, when the reaction vessel 1 is (approximately) cylindrical, it is preferable to locate the rotating shaft 5 so that it is concentric with the center of the circular cross section of the reaction vessel 1. The rotating shaft 5 extends from the bottom B of the reaction vessel 1 toward the top T, and rotates the upper agitator blade 2 and the lower agitator blade 3 in a (approximately) perpendicular direction (i.e., horizontal direction relative to the liquid surface) to the extension direction of the rotating shaft 5.

[0031] In this embodiment, the reactor 1 has an agitator shaft 5 that is provided parallel to the inner side peripheral surface S, and a lower agitator blade 3 and an upper agitator blade 2 are attached to the agitator shaft 5. In other words, two or more agitator blades (or two or more blade portions 2a, 3a) are attached to the agitator shaft 5, and the agitator blade attached closest to the bottom B of the reactor 1 is the lower agitator blade 3, and the other agitator blades are the upper agitator blades 2. This makes it possible to further suppress adhesion, solidification, adhesion or sedimentation of the target substance inside the reaction vessel.

[0032] In addition, in order to stably fix the upper agitating blade 2 and the lower agitating blade 3 to the rotating shaft 5, an upper agitating blade support portion 2b and a lower agitating blade 3 support portion 3b may be further provided as shown in Figures 2 and 4. The upper agitating blade support part 2b is a support means for supporting the upper agitating blade 2. The upper agitating blade 2 is fixed to the rotating shaft 5, and has the role of transmitting the rotation of the rotating shaft 5 to the upper agitating blade 2 via the upper agitating blade support part 2b.

[0033] The drive unit (not shown) is a drive means for rotating the upper agitating blade 2 and the lower agitating blade 3 via the rotating shaft 5, and various motors may be used as long as they can rotate the upper agitating blade 2 and the lower agitating blade 3 at an appropriate speed and torque.

[0034] The upper stirring blade 2 of this embodiment has a maximum stirring blade length (dB) that is shorter than the inner diameter (D) of the reaction vessel 1. Moreover, the upper stirring blade 2 (or blade portion 2a) shown in Figures 1 and 2 has a maximum height (hB) of the upper stirring blade 2 that is shorter than the inner length of the reaction vessel 1 (= the length from the inner top surface of the reaction vessel 1 to the inner bottom surface of the reaction vessel 1 (= for example, the length in the direction of the rotation shaft 5). In this case, when the upper agitating blade 2 is a multi-stage paddle blade as shown in Figure 2, the maximum height (hB) of the upper agitating blade 2 does not include the gaps (d1 to d5) between a pair of adjacent blade portions 2a. In other words, the maximum height (hB) of the upper agitating blade 2 is defined as the sum of the projection lines (h1 to h6) obtained by projecting the blade portions 2a of each stage perpendicularly to the rotation axis 5.

[0035] Next, the lower agitating blade 3 (or blade portion 3a) of this embodiment (for example, the lower agitating blade 3 (or blade portion 3a) shown in Figures 1 and 2) has a maximum agitating blade length (dA) that is shorter than the inner diameter (D) of the reaction vessel 1. The lower agitating blade 3 (or blade portion 3a) has a maximum height (hA) of the lower agitating blade 3 that is shorter than the inner length of the reaction vessel 1 (the maximum length from the bottom to the top of the reaction vessel 1 in the direction of the rotation shaft 5). Furthermore, the distance from the bottom end of the lower agitating blade 3 to the bottom of the reaction vessel 1 (bottom gap: BG) can be a predetermined value.

[0036] <Upper mixing blade> The upper stirring blade 2 may be configured to have various shapes depending on the application, and may be provided, for example, at an incline with respect to the horizontal or vertical direction in order to form a vertical flow of the raw material solution inside the reaction vessel 1. By providing the upper stirring blade at an incline, a vertical flow that pushes the raw material solution up and down can be formed. The upper stirring blade 2 preferably has a shape that extends in the axial direction of the rotating shaft 5, with the rotating shaft 5 as the center. This allows the rotation of the rotating shaft 5 to be efficiently transmitted to the raw solution without loss, and also allows a flow that is symmetrical with respect to the rotating shaft 5 to be formed.

[0037] When emphasis is placed on reducing the stirring power, an impeller with a small area of ​​the blade portion 2a is selected as the upper impeller 2. Examples of the upper impeller 2 include so-called H-shaped impellers, so-called "square"-shaped impellers (see, for example, Figures 1 and 3), impellers with four rectangular blade portions 2a (see, for example, Figure 4), two-stage paddle impellers at the top of a three-stage vertical paddle impeller (see, for example, Figure 6(c)), five-stage paddle impellers at the top of a six-stage vertical paddle impeller (see, for example, Figure 7), six-stage paddle impellers at the top of a seven-stage vertical paddle impeller (see, for example, Figure 2), a "T"-shaped or lattice-shaped impeller, a flat paddle impeller, an inclined paddle impeller, a turbine impeller, or a propeller impeller. The shape of the blade portion 2a constituting the upper impeller 2 of this embodiment is not limited to these. The upper impeller 2 may also be connected to the lower impeller 3. However, as will be explained later, when the range (dB / D) indicating the ratio of the maximum impeller length (dB) of the upper impeller 2 to the inner diameter (D) of the reaction vessel 1, and / or the range (hB / D) indicating the ratio of the maximum height (hB) of the upper impeller 2 to the inner diameter (D) of the reaction vessel 1, is within a predetermined range, foaming is suppressed, thereby further suppressing adhesion, solidification, adhesion or sedimentation of the target substance inside the reaction vessel, and a low-hydrated alkali metal sulfide with a low amount of water of crystallization is obtained.

[0038] Preferred embodiments of the upper stirring blade 2 will be explained below, classified into Figs. 1, 3, 4, 2, 6(b) to 6(c), and 7. For example, the so-called square-shaped upper stirring blade 2 (or blade portion 2a) shown in Figure 1 has a maximum stirring blade length (dB) that is shorter than the inner diameter (D) of the reaction vessel 1. Also, the so-called square-shaped upper stirring blade 2 (or blade portion 2a) has a maximum height (hB) of the upper stirring blade 2 that is shorter than the inner length of the reaction vessel 1 (the length in the direction of the rotation shaft 5). The square-shaped upper agitator blade 2 has a configuration in which two (approximately) rectangular blades 2a are attached via two connecting portions 2c so that the longitudinal direction of the (approximately) rectangular blades 2a and the extension direction of the rotary shaft 5 are parallel to each other. While FIG. 1 shows an example of rectangular blades 2a, as a variant, the rectangular blades 2a may be tapered toward the upper portion T of the reaction vessel 1 (see, for example, FIG. 3). The shape of the blades 2a may be rectangular, square, elliptical, or circular. Furthermore, while FIG. 1 shows blades 2a that are line-symmetrical with respect to the rotary shaft 5 and attached to the rotary shaft 5 via connecting portions 2c, two or more blades 2a with different shapes and attachment positions may be attached to the rotary shaft 5. Furthermore, while FIG. 1 shows an upper agitator blade 2 with two blades 2a, the number of blades 2a may be one or more, and more preferably two or more. For convenience of explanation, in FIG. 1, the rotation direction of the rotary shaft 5 is shown as the direction of the arrow (clockwise), but the rotary shaft 5 may also rotate counterclockwise (the same applies to FIGS. 1 to 5). In FIG. 1, the two (approximately) rectangular blade portions 2a are attached to the rotating shaft 5 so that their main surfaces are (approximately) parallel to each other, but the two (approximately) rectangular blade portions 2a may also be attached at a predetermined angle so that their main surfaces intersect.

[0039] For example, the so-called "square-shaped" upper agitator blade 2 (or blade portion 2a) shown in Figure 3, like Figure 1, has a maximum agitator blade length (dB) that is shorter than the inner diameter (D) of the reaction vessel 1, and a maximum height (hB) of the upper agitator blade 2 that is shorter than the inner length of the reaction vessel 1 (length in the direction of the rotation axis 5). In addition, the square-shaped upper stirring blade 2 shown in Figure 3 has a configuration in which two (approximately) trapezoidal blade portions 2a are attached via two connecting portions 2c so that the longitudinal direction of the (approximately) trapezoidal blade portions 2a and the extension direction of the rotating shaft 5 are parallel to the rotating shaft 5.

[0040] Furthermore, both of the "□-shaped" upper stirring blades 2 shown in Figures 1 and 3 are examples having two ""["-shaped (bracket-shaped) blade portions 2a so that they are symmetrical about the rotation axis 5, but they may also be asymmetric. The "square"-shaped upper agitating blade 2 has a configuration in which two ""["-shaped flat blade portions 2a are attached so that the longitudinal direction of the ""["-shaped blade portions 2a and the extension direction of the rotating shaft 5 are parallel to each other with respect to the rotating shaft 5. The shape of the ""["-shaped blade portions 2a may be semicircular or semi-elliptical. Furthermore, in Figures 1 and 3, the ""["-shaped blade portions 2a are attached so as to be line-symmetrical with respect to the rotating shaft 5, but blade portions 2a with different shapes and attachment positions may be attached to the rotating shaft 5. Furthermore, Figure 3 shows an upper agitating blade 2 with two blade portions 2a, but the number of blade portions 2a may be one or more, preferably two or more. In FIG. 3, the two "["-shaped blade portions 2a are attached to the rotating shaft 5 so that their main surfaces are (approximately) parallel to each other, but the two (approximately) rectangular blade portions 2a may also be attached at a predetermined angle so that their main surfaces intersect.

[0041] For example, the so-called upper agitating blade 2 (or blade portion 2a) shown in Fig. 4, like the upper agitating blade 2 in Figs. 1 to 3, has a maximum agitating blade length (dB) that is shorter than the inner diameter (D) of the reaction vessel 1. Moreover, the upper agitating blade 2 (or blade portion 2a) shown in Fig. 4 has a maximum height (hB) of the upper agitating blade 2 that is shorter than the inner length of the reaction vessel 1 (length in the direction of the rotation shaft 5). And, as shown in Fig. 4, the upper agitating blade 2 has four (approximately) rectangular blade portions 2a. The shape of the blade portion 2a shown in FIG. 4 is the same as that shown in FIG. 2, and four (approximately) rectangular blade portions 2a are attached to the rotating shaft 5 via the stirring blade support portion 2b so that the longitudinal direction of the (approximately) rectangular blade portions 2a and the extension direction of the rotating shaft 5 are parallel to each other. Furthermore, the (approximately) rectangular blade portion 2a shown in FIG. 4 is shown to be tapered toward the upper portion T of the reaction vessel 1, but the shape of the blade portion 2a may be any of rectangular, square, elliptical, and circular. Furthermore, although four (approximately) rectangular blade portions 2a are attached so as to be line-symmetrical with respect to the rotating shaft 5 in FIG. 4, blade portions 2a with different shapes and attachment positions may be attached to the rotating shaft 5. In FIG. 4, the four (approximately) rectangular blade portions 2a are attached to the rotating shaft 5 so that their main surfaces are all (approximately) parallel, but the four (approximately) rectangular blade portions 2a may also be attached at a predetermined angle so that their main surfaces intersect with each other.

[0042] For example, the upper agitating blade 2 (or blade portion 2a) shown in Figure 2, Figures 6(b)-(c), and Figure 7 is an example of a so-called multi-stage (vertical) paddle blade. That is, Figure 2 shows a seven-stage (vertical) paddle blade. Figure 6(b) shows a two-stage (vertical) paddle blade, and Figure 6(c) shows a three-stage (vertical) paddle blade. Also, Figure 7 shows a six-stage (vertical) paddle blade. For example, if the lower agitating blade 3 is only the lowest stage, the upper agitating blade 2 (or blade portion) in Figure 2 shows a six-stage (vertical) paddle blade. And the upper agitating blade 2 (or blade portion) in Figure 6(c) becomes a two-stage paddle blade, and the upper agitating blade 2 (or blade portion) in Figure 7 becomes a five-stage paddle blade. In addition, in Figures 6(c) and 7, the lowest stirring blade is the lower stirring blade 3 and the highest stirring blade is the upper stirring blade 2, and the stirring blade between the lower stirring blade 3, which is the lowest stirring blade, and the upper stirring blade 2, which is the highest stirring blade, may belong to either the upper stirring blade 2 or the lower stirring blade 3. In Figures 2, 6(b)-(c), and 7, the upper agitating blade 2 and the lower agitating blade 3 each have four flat blades, and the flat blades are arranged so that two adjacent flat blades are perpendicular to each other. A set of four flat blades constitutes one upper agitating blade 2 or lower agitating blade 3 (also simply referred to as an agitating blade). Agitating blades each consisting of a set of four flat blades are attached to the rotating shaft in multiple stages so that they overlap each other vertically. For example, in the two-stage paddle impeller of Figure 6(b), two agitating blades (two stages) each consisting of a set of four flat blades are attached to the rotating shaft 5, and the agitating blades are positioned vertically relative to each other. Similarly, in the seven-stage paddle impeller of Figure 2, seven stirring blades (seven stages), each consisting of a set of four flat blades, are attached to the rotating shaft 5, and the relative positions of the stirring blades are vertical. In the three-stage paddle impeller of Figure 6(c), three stirring blades (three stages), each consisting of a set of four flat blades, are attached to the rotating shaft 5, and the relative positions of the stirring blades are vertical. And in the six-stage paddle impeller of Figure 7, six stirring blades (six stages), each consisting of a set of four flat blades, are attached to the rotating shaft 5, and the relative positions of the stirring blades are vertical. 2, 6(b)-(c), and 7 have a maximum impeller length (dB) that is shorter than the inner diameter (D) of the reaction vessel 1, similar to the upper impeller 2 in FIGS. 1-4. Also, the upper impeller 2 (or impeller portion 2a) shown in FIGS. 2, 6(b), (c), and 7 have a maximum height (hB) of the upper impeller 2 that is shorter than the inner length of the reaction vessel 1 (the length in the direction of the rotation shaft 5). The upper impeller 2 shown in FIG. 2 has 24 (approximately) rectangular impeller portions 2a. The upper impeller 2 shown in FIG. 6(b) has two (approximately) rectangular impeller portions 2a, and the upper impeller 2 shown in FIG. 6(c) has a maximum of eight (approximately) rectangular impeller portions 2a. The upper impeller 2 shown in FIG. 7 has a maximum of 20 (approximately) rectangular impeller portions 2a. The upper agitating blades 2 are configured such that the blade portions 2a are attached so that the main surfaces of the upper agitating blades 2 and the extension direction of the rotation shaft 5 are (approximately) parallel to the rotation shaft 5. However, if necessary, the main surfaces of the four upper agitating blades 2 may be attached at a predetermined angle so that they intersect with the extension of the rotation shaft 5.

[0043] One or more upper agitating blades 2 are provided around the rotating shaft 5 or an upper agitating blade support part 2b that is provided as needed. When each upper agitating blade 2 extending outward (for example, horizontally) from the rotating shaft 5 is counted as one blade, at least one upper agitating blade 2 is provided, and more than one upper agitating blade 2 may be provided depending on the application. In this embodiment, an example in which two upper agitating blades 2 are provided is described.

[0044] As in the multistage agitator blades 2 shown in Figures 2, 6, and 7, the upper agitator blades 2 may be provided in multiple stages in the axial direction of the rotating shaft 5. Figure 1 shows an example in which the upper agitator blade 2 is provided in one unit (one square-shaped agitator blade per unit). As the length of the reactor 1 (= the longitudinal length of the reactor 1, i.e., the axial length of the rotating shaft 5) increases, it may become difficult to create a sufficient flow of the raw material solution with just one unit. Therefore, when the reactor 1 is vertically long, as shown in the multistage examples of Figures 2, 6, and 7, the upper agitator blades 2 and the upper agitator blade support parts 2b attached as needed may be provided in one or more units each at the upper and middle stages of the rotating shaft 5. Alternatively, instead of providing one unit each on the rotating shaft 5, the shape or length of the upper agitator blade 2 may be changed. Specifically, it is preferable to set the longitudinal length of the H-shaped upper agitator blade 2 or the upper agitator blade 2 shown in Figure 4, in other words, the blade part 2a, to a predetermined length.

[0045] In the case of multistage impellers 2, 3 as shown in Figures 2, 6, and 7, the impeller closest to the bottom of the reaction vessel 1 is referred to as the lower impeller 3 (or blade portion 3a) for convenience, and the other impellers are referred to as the impeller 2. In addition, in the case of multistage impellers 2, 3 as shown in Figures 6 and 7, the maximum impeller length (dB) of the upper impeller 2 is the maximum impeller length of the upper impeller 2 (blade portion 2a), which is the longest among the multiple impellers 2. In addition, in the case of multistage impellers 2, 3 as shown in Figures 2, 6, and 7, the maximum height (hB) of the upper impeller 2 is the sum of the lengths (hi) (e.g., h1 to h6) of the projection lines generated when each blade portion 2a of the upper impeller 2 is projected perpendicularly to the rotation axis 5 (Σhi (i represents an integer between 1 and n, and corresponds to the number of stages n), e.g., h1 + h2 + h3 + h4 + h5 + h6). In other words, it is the value obtained by subtracting the total value (e.g., d1+d2+d3+d4+d5) of the shortest distances (e.g., d1 to d5) of the gaps between adjacent blades 2a from the length (h) from the top of the uppermost projection line to the bottom of the lowermost projection line among the projection lines generated when each blade 2a of the upper agitating impeller 2 is projected perpendicularly to the rotation shaft 5. Therefore, the gaps between adjacent blades 2a are not included in the maximum height (hB).

[0046] The upper stirring blade 2 may be a stirring blade 2b provided to form and straighten a downward flow inside the reaction vessel 1. It is preferable that the upper stirring blade 2 is configured to form a downward flow among the vertical flows of the raw material solution inside the reaction vessel 1. This allows a good circulation flow to be formed throughout the entire inside of the reaction vessel 1, which is thought to suppress foaming. In this embodiment, both the upper stirring blade 2 and the lower stirring blade 3 are provided, and the lower stirring blade 3 plays a role in forming an upward flow of the raw material solution. Therefore, in order to form a good circulation flow within the reaction vessel 1, the upper stirring blade 2 functions to form a downward flow of the raw material solution within the reaction vessel 1.

[0047] The maximum impeller length (dB) of the upper impeller 2 in this embodiment is set appropriately depending on the inner diameter of the reaction vessel 1 and the size of components to be installed as needed inside the reaction vessel 1. Therefore, when the reaction vessel 1 shown in FIG. 5 is used as the reaction vessel 1, the maximum impeller length (dB) may be restricted by the size of the components to be installed inside the reaction vessel 1, such as the baffle section 4 (or coiled heat transfer pipe). The maximum impeller length (dB) is preferably set so that the ratio of the maximum impeller length (dB) to the inner diameter (D) of the reaction vessel 1 falls within a predetermined range. In this specification, "the maximum impeller length (dB) of the upper impeller 2" refers to the maximum length of the projection formed when the upper impeller 2 is projected perpendicularly onto an imaginary plane perpendicular to the extension direction of the rotation shaft 5, when the imaginary plane is provided on the bottom surface B of the reaction vessel 1 (see, for example, Figures 1 and 2). Furthermore, when the upper impeller 2 is composed of multiple blade portions 2a, the maximum length refers to the maximum length from the outermost end of the outermost projection (toward the inner wall of the reaction vessel 1) to the innermost end of the innermost projection (toward the rotation shaft 5), when an imaginary plane perpendicular to the extension direction of the rotation shaft 5 is provided on the bottom surface B of the reaction vessel 1.

[0048] The maximum height (hB) of the upper stirring blade 2 in this embodiment is set appropriately depending on the inner length of the reaction vessel 1 (the length in the direction of the rotation shaft 5). Therefore, the maximum height (hB) is set so that the ratio between the maximum height (hB) of the upper stirring blade 2 and the inner diameter (D) of the reaction vessel 1 falls within a predetermined range. Foaming occurs in the middle of the dehydration reaction when the raw material solution is concentrated and solid hydrous alkali metal sulfide begins to precipitate. However, by using the upper agitator blade 2 with a predetermined length in the vertical direction, the foam is made to flow and disappear, and the liquid level of the raw material solution drops as the dehydration reaction progresses, which has the effect of suppressing adhesion of hydrous alkali metal sulfide to the wall surface S of the reaction vessel 1. In this specification, the "maximum height (hB) of the upper agitating blade 2" refers to the length of the projection line generated when the upper agitating blade 2 is projected perpendicularly to the rotation shaft 5 (see Figures 1 and 2). Furthermore, when the upper agitating blade 2 is composed of multiple blade portions 2a, the "maximum height (hB)" refers to the value obtained by subtracting the total length (e.g., d1 to d5) of the gaps between adjacent blade portions 2a (Σdi (i represents an integer between 1 and n-1, and corresponds to the number of stages n in an n-stage system) for example, d1 + d2 + d3 + d4 + d5) from the length (h) from the top of the uppermost projection line to the bottom of the lowermost projection line generated when each blade portion 2a of the upper agitating blade 2 is projected perpendicularly to the rotation shaft 5. Therefore, the length of the gap between adjacent blade portions 2a (the shortest distance between adjacent blade portions 2a) is not included in the maximum height (hB). In other words, it refers to the total value of the lengths (hi) of the projection lines that are generated when each blade portion 2 a of the upper agitating blade 2 is projected perpendicularly to the rotation axis 5 .

[0049] In the upper agitating blade 2 of this embodiment, the upper limit of (dB / D), which indicates the ratio of the maximum agitating blade length (dB) of the upper agitating blade 2 to the inner diameter (D) of the reaction vessel 1, can be preferably 0.7 or less, more preferably 0.6 or less, and even more preferably 0.5 or less. On the other hand, the lower limit of (dB / D), which indicates the ratio of the maximum agitating blade length (dB) of the upper agitating blade 2 to the inner diameter (D) of the reaction vessel 1, can be preferably 0.3 or more, more preferably 0.4 or more, and even more preferably 0.5 or more. The upper and lower limits can be combined as appropriate. In particular, the ratio (dB / D) of the maximum impeller length (dB) of the upper impeller 2 to the inner diameter (D) of the reaction vessel 1 is preferably in the range of 0.3 to 0.7, more preferably 0.4 to 0.6. As a result, during dehydration, the liquid level rises to the top of the upper agitator blade due to foaming of the contents, but the foam does not stagnate and remains in a fluid state, which has the effect of preventing the adhesion of solid alkali metal sulfide composition to the walls of the reaction vessel when the liquid level drops as dehydration progresses.

[0050] In the upper agitating blade 2 of this embodiment, the upper limit of (hB / D), which indicates the ratio of the maximum height (hB) of the upper agitating blade 2 to the inner diameter (D) of the reaction vessel 1, can be preferably 0.9 or less, more preferably 0.8 or less, and even more preferably 0.7 or less. On the other hand, the lower limit of (hB / D), which indicates the ratio of the maximum height (hB) of the upper agitating blade 2 to the inner diameter (D) of the reaction vessel 1, can be preferably more than 0.17, more preferably 0.2 or more, even more preferably 0.5 or more, even more preferably 0.6 or more, and even more preferably 0.7 or more. The upper limit and the lower limit can be combined as appropriate. In particular, the ratio (hB / D) of the maximum height (hB) of the upper stirring blade 2 to the inner diameter (D) of the reaction vessel 1 is preferably in the range of 0.5 to 0.9, more preferably in the range of 0.6 to 0.8. As a result, during dehydration, the liquid level rises to the top of the upper agitator blade due to foaming of the contents, but the foam does not stagnate and remains in a fluid state, which has the effect of preventing the adhesion of solid alkali metal sulfide composition to the walls of the reaction vessel when the liquid level drops as dehydration progresses.

[0051] <Lower mixing blade> The lower stirring blade 3 can be a stirring blade 3a provided to form and rectify an upward flow inside the reaction vessel 1. The upper stirring blade 2 forms a downward flow inside the reaction vessel 1, and the lower stirring blade 3 forms an upward flow, which is thought to form a good circulation flow throughout the entire reaction vessel 1, thereby suppressing foaming. The lower agitator blade support part 3b is a member for supporting the lower agitator blade 3, and is fixed to the rotary shaft 5 and supports the lower agitator blade 3 that extends radially outward from the rotary shaft 5 in the radial direction of the reaction vessel 1. The lower agitator blade support part 3b can be composed of a rod-shaped member such as a cylinder or a square pillar that does not have a paddle-like shape.

[0052] The shape of the lower agitator 3 in this embodiment is not particularly limited as long as the ratio (BG / D) of the bottle gap (BG), which is the distance from the bottom of the lower agitator 3 to the bottom of the reactor 1, to the inner diameter (D) of the reactor 1 is 0.15 or greater. However, a shape that mimics the shape of the bottom B of the reactor 1 is preferred. For example, in FIGS. 1 to 4 and 8(a) and 8(b), the bottom B of the reactor 1 is (nearly) hemispherical, so the lower agitator 3 is composed of two blades 3a with a C-shaped bend. On the other hand, in FIGS. 6(b) and 6(c) and 7, the lower agitator 3 has the same structure as the upper agitator 2, with a set of four rectangular blades attached to the rotating shaft 5 as one stage, and two adjacent rectangular blades intersect at right angles (a cross shape when viewed from above the reactor). Also, in FIG. 8(b), the lower agitator 3 is composed of a propeller-shaped blade. In addition, when the shape of the bottom B of the reaction vessel 1 is a flat dish shape, it may be composed of two (approximately) polygonal (or trapezoidal) blades 3a. Other shapes of the lower stirring blade 3 include a half-moon paddle blade, a swept-back blade (Pfaudler blade), a flat blade, a horseshoe blade, and an anchor blade. More specifically, the lower agitating blade 3 (or two blade portions 3a) shown in Figures 1 to 4 has a maximum blade length (dA) that is shorter than the inner diameter (D) of the reaction vessel 1. Also, the lower agitating blade 3 (or blade portion 3a) shown in Figures 1 to 4 has a maximum height (hA) of the lower agitating blade 3 that is shorter than the inner length of the reaction vessel 1 (the length in the direction of the rotation shaft 5). And, as shown in Figures 1 to 4, the lower agitating blade 3 has two flat blade portions 3a that have C-shaped bends. The lower agitating blade 3 has a configuration in which two blades 3a having a C-shaped bend are attached so that the main surface of the blade 3a having a C-shaped bend is parallel to the extension direction of the rotating shaft 5. In Figures 1 to 4, an example is shown in which the blade 3a has a bend that follows the shape of the bottom B of the reaction vessel 1, but the shape of the blade 3a may be any of rectangular, square, elliptical, and circular. Furthermore, in Figures 1 to 4, the blades 3a are attached line-symmetrically with respect to the rotating shaft 5, but blades 3a having different shapes and attachment positions may be attached to the rotating shaft 5. Furthermore, in Figures 1 to 4, the lower agitating blade 2 has two blades 3a, but the number of blades 3a may be one or more, preferably two or more.

[0053] In Figures 1 to 4, the flat blade portions 3a having two C-shaped bends are attached to the rotating shaft 5 so that their main surfaces are (approximately) parallel to each other, but the flat blade portions 3a having two C-shaped bends may also be attached at a predetermined angle so that their main surfaces intersect. The lower stirring blade 3 may be configured to have various shapes depending on the application, and may be provided, for example, at an incline with respect to the horizontal or vertical direction in order to form a vertical flow of the raw material solution in the reaction vessel 1. By providing the lower stirring blade at an incline, a vertical flow that pushes the raw material solution up and down can be formed. The lower agitator blade 3 preferably has a shape that extends in the axial direction of the rotating shaft 5, with the rotating shaft 5 as the center. This allows the rotation of the rotating shaft 5 to be efficiently transmitted to the raw solution without loss, and also allows a flow that is symmetrical with respect to the rotating shaft 5 to be formed.

[0054] Preferred forms of the lower agitator blade 3 in this embodiment include, for example, a Pfaudler impeller, an anchor impeller, and a propeller impeller. The Pfaudler impeller may be, for example, a three-blade swept-back impeller as shown in FIG. 8(a). The three-blade swept-back impeller is an agitator blade equipped with three curved, flat blades, and has a small gap between the bottom B of the reactor 1 and the lower agitator blade 3. This makes it easy to set the ratio of the distance from the bottom end of the lower agitator blade 3 to the bottom of the reactor 1 (bottom gap: BG) to the inner diameter (D) of the reactor 1 to 0.15 or less. Furthermore, due to the configuration of the Pfaudler impeller, it is easy to form an up-and-down circulating flow (arrows in the figure), and the relatively strong swirling flow can effectively suppress the settling of low-hydrate alkali metal sulfide particles and their adhesion to the reactor bottom. The anchor impeller has, for example, an anchor-type impeller as shown in Fig. 8(b). The anchor-type impeller can be easily manufactured to fit the shape of the reaction vessel 1, making it easy to set the (BG / D) ratio and the (dA / D) ratio within the desired range. Furthermore, due to the configuration of the anchor impeller, a swirling flow is dominant, so a defoaming effect can be exhibited. The propeller blade has, for example, 2 to 5 blades as shown in Fig. 8(c). The propeller blade discharges the solution in the reaction vessel 1 directly below the propeller blade, which tends to form a circulating flow (arrow in the figure), and therefore can effectively suppress the settling of low-hydrated alkali metal sulfide particles and their adhesion to the vessel bottom.

[0055] In this embodiment, the bottle gap (BG), which is the distance from the lowest end of the lower stirring blade 3 to the bottom of the reaction vessel 1, is set appropriately depending on the size of the reaction vessel 1 or the shape of the bottom B of the reaction vessel 1. Therefore, the bottle gap (BG) is set so that the ratio of the bottle gap (BG) to the inner diameter (D) of the reaction vessel 1 falls within a predetermined range. By shortening the distance (BG) from the lowest end of the lower agitator blade 3 to the bottom of the reaction vessel 1, a strong upward discharge flow from the vessel bottom is generated, which has the effect of exhibiting high uniform mixing performance and suppressing the settling of the generated low-hydrated alkali metal sulfide particles and their adhesion to the vessel bottom. In this specification, the "bottle gap (BG) which is the distance from the lowest end of the lower agitator blade 3 to the bottom of the reaction vessel 1" refers to the length from the end of the projection line on the bottom B side of the projection line that is generated when the lower agitator blade 3 is projected perpendicularly to the rotation axis 5 to the bottom of the reaction vessel 1 (see Figures 1 and 2).

[0056] The maximum impeller length (dA) of the lower impeller 3 in this embodiment is set appropriately depending on the inner diameter of the reaction vessel 1. Therefore, the maximum impeller length (dA) is set so that the ratio of the maximum impeller length (dA) of the lower impeller 3 to the inner diameter (D) of the reaction vessel 1 falls within a predetermined range. In this specification, the "maximum impeller length (dA) of the lower impeller 3" refers to the length of the projection line that is generated when the lower impeller 3 is projected perpendicularly onto an imaginary plane that is perpendicular to the extension direction of the rotation shaft 5 and is provided on the bottom surface B of the reaction vessel 1 (see Figures 1 and 2).

[0057] The maximum height (hA) of the lower stirring blade 3 in this embodiment is set appropriately depending on the inner length (length in the direction of the rotation shaft 5) of the reaction vessel 1. Therefore, the maximum height (hA) is set so that the ratio of the maximum height (hA) of the lower stirring blade 3 to the inner diameter (D) of the reaction vessel 1 falls within a predetermined range. In this specification, the "maximum height (hA) of the lower agitating blade 3" refers to the length of the projection line generated when the lower agitating blade 3 is projected perpendicularly onto the rotation axis 5 (see FIGS. 1 and 2).

[0058] In the lower agitating blade 3 of this embodiment, the upper limit of (BG / D), which indicates the ratio of the bottle gap (BG), which is the distance from the lowest end of the lower agitating blade 3 to the bottom of the reaction vessel 1, to the inner diameter (D) of the reaction vessel 1, is preferably 0.15 or less, more preferably 0.10 or less, and even more preferably 0.05 or less. On the other hand, the lower limit of (BG / D), which indicates the ratio of the bottle gap (BG), which is the distance from the lowest end of the lower agitating blade 3 to the bottom of the reaction vessel 1, to the inner diameter (D) of the reaction vessel 1, is 0.05 or more, more preferably 0.03 or more, and even more preferably 0.01 or more. The upper and lower limits can be combined as appropriate. In particular, the (BG / D) is preferably in the range of 0.03 to 0.10, and more preferably in the range of 0.05 to 0.15. This has the effect of preventing the solid alkali metal sulfide composition from settling and adhering to the bottom of the vessel.

[0059] In the lower agitating blade 3 of this embodiment, the upper limit of (dA / D), which indicates the ratio of the maximum agitating blade length (dA) of the lower agitating blade 3 to the inner diameter (D) of the reaction vessel 1, may be preferably 0.9 or less, more preferably 0.8 or less, and even more preferably 0.7 or less. On the other hand, the lower limit of (dA / D), which indicates the ratio of the maximum agitating blade length (dA) of the lower agitating blade 3 to the inner diameter (D) of the reaction vessel 1, may be preferably more than 0.46, more preferably 0.5 or more, even more preferably 0.6 or more, and even more preferably 0.7 or more. The upper and lower limits may be combined as appropriate. In particular, (dA / D), which indicates the ratio of the maximum impeller length (dA) of the lower impeller 3 to the inner diameter (D) of the reaction vessel 1, is preferably in the range of 0.5 to 0.9, more preferably in the range of 0.5 to 0.9, and even more preferably in the range of 0.6 to 0.8. The upper limit and the lower limit can be combined in any desired manner. This has the effect of preventing the solid alkali metal sulfide composition from settling and adhering to the bottom of the vessel without requiring a large stirring power.

[0060] In the lower agitating blade 3 of this embodiment, the upper limit of (hA / D), which indicates the ratio of the maximum height (hA) of the lower agitating blade 3 to the inner diameter (D) of the reaction vessel 1, may be preferably 0.5 or less, more preferably 0.4 or less, and even more preferably 0.3 or less. On the other hand, the lower limit of (hA / D), which indicates the ratio of the maximum height (hA) of the lower agitating blade 3 to the inner diameter (D) of the reaction vessel 1, may be preferably more than 0.08, more preferably 0.1 or more, even more preferably 0.2 or more, and even more preferably 0.3 or more. The upper limit and the lower limit can be combined arbitrarily. In particular, the ratio (hA / D) of the maximum height (hA) of the lower stirring blade 3 to the inner diameter (D) of the reaction vessel 1 is preferably in the range of 0.1 to 0.5, more preferably in the range of 0.2 to 0.4. This has the effect of preventing the solid alkali metal sulfide composition from settling and adhering to the bottom of the vessel without requiring a large stirring power. Furthermore, in this embodiment, the combination of the upper agitating blade 2 and the lower agitating blade 3 described above exhibits high uniform mixing performance, and as a result, the heat transfer efficiency is improved, which also has the effect of shortening the dewatering time.

[0061] <Reaction vessel> The reactor 1 includes a space (recess) for accommodating raw materials and has a (substantially) cylindrical side wall S and bottom B. The reactor 1 also serves as a means for retaining raw materials or raw material solutions (not shown) within the reactor (recess of the reactor 1) and for stirring the raw materials or raw material solutions (not shown) retained within the reactor using an upper stirring blade 2 and a lower stirring blade 3 to promote a reaction. The reactor 1 may also be provided with heat transfer piping for transferring heat required to initiate and promote the reaction of the raw material solution or for transferring heat generated by the reaction of the raw material solution, and / or a baffle unit for generating turbulence when stirring the raw material solution, or a baffle unit equipped with the heat transfer piping, as needed.

[0062] 5 is a schematic diagram showing an example of the reaction vessel 1. Hereinafter, the reaction vessel 1 will be described with reference to FIGS. In FIG. 5, the reactor 1 has a (nearly) cylindrical shape and is provided with a baffle unit 4 and a rotating shaft 5. The reactor 1 has an impeller mounting port 5A at its top, which is used to mount the upper impeller 2 and lower impeller 3 inside the reactor 1; an inlet (not shown) near the top of the reactor 1, which is used to feed the raw material or raw material solution into the reactor 1; and a baffle mounting port (not shown), which is used to mount the baffle unit 4 inside the reactor 1. The rotating shaft 5 passes through the impeller mounting port 5A and is connected to a drive unit (shown) located above it. The reactor 1 may also have a bottom outlet, which is used to remove the product from the reactor. To control the temperature of the raw material or raw material solution in the reactor 1, the sidewall of the reactor 1 may be wrapped with a jacket, such as an external heat exchanger. Furthermore, the side wall S of the reaction vessel 1 may be formed into a double-wall structure (not shown) if necessary. By using a double-wall structure, a fluid for heat exchange can be circulated inside the double-wall structure. The raw material or raw material solution (not shown) is in a liquid state or a slurry state consisting of liquid and fine particles when the raw material is introduced. In particular, during the dehydration process, solid particles are generated as the raw material is stirred. Therefore, the reaction vessel 1 usually holds a raw material solution in which liquid and solid particles are mixed inside the vessel.

[0063] The reaction vessel 1 is preferably configured to be (approximately) cylindrical. This shape facilitates the formation of a vertical circulation flow. The shape of the bottom B of the reaction vessel 1 can be a dish-like shape, a truncated cone-like shape, a semi-conical shape, a truncated pyramidal shape, a truncated semi-pyramidal shape, a hemispherical shape, a semi-elliptical shape, a quarter sphere-like shape, a parallelepiped shape, or a prismatic shape. Among these, a dish-like shape or a hemispherical shape is more preferred. When the bottom B of the reaction vessel 1 is dish-like, the presence of the lower stirring blade 3 tends to generate an upward discharge flow in the raw material solution in the reaction vessel 1. In particular, a 10% dish-like shape is effective in suppressing the stagnation of the discharge flow at the bottom B.

[0064] The inner diameter (D) of the reaction vessel 1 of this embodiment is set appropriately depending on the purpose of use. In this specification, the "inner diameter (D) of the reaction vessel 1" refers to the maximum length measured between the inner walls of the reaction vessel 1 so as to pass through the center of the rotation shaft 5 (see FIGS. 1 and 2).

[0065] A preferred embodiment of the present invention is a reactor having a recess for accommodating a raw material solution containing a hydrated alkali metal sulfide, an aliphatic cyclic compound capable of being ring-opened by hydrolysis, and a non-hydrolyzable organic solvent; a lower stirring blade provided near the bottom of the reactor for stirring the raw material solution; and an upper stirring blade provided closer to the opening of the reactor than the lower stirring blade and for stirring the raw material solution. the ratio (dA / D) of the maximum blade diameter (dA) of the lower stirring blade to the inner diameter (D) of the reaction vessel is 0.5 or more, and the ratio (hA / D) of the maximum height (hA) of the lower stirring blade to the inner diameter (D) of the reaction vessel is 0.1 or more; a ratio (BG / D) of the distance from the lowest end of the lower stirring blade to the bottom of the reaction vessel (bottom gap: BG) to the inner diameter (D) of the reaction vessel is 0.15 or less; The ratio (dB / D) of the maximum impeller length (dB) of the upper impeller to the inner diameter (D) of the reaction vessel 1 is 0.3 or more, The ratio (hB / D) of the maximum height (hB) of the upper stirring blade to the inner diameter (D) of the reaction vessel is 0.5 or more. This is a reactor used to produce low-hydrated alkali metal sulfides. This makes it possible to further suppress adhesion, solidification, adhesion or sedimentation of the target substance inside the reaction vessel by suppressing foaming.

[0066] <Raw material or raw material solution> Various raw materials or raw material solutions are selected depending on the purpose and application of the synthesis or polymerization. As will be described in detail in the section on the method for producing a low-hydrated alkali metal sulfide below, the raw material or raw material solution of this embodiment essentially contains a hydrated alkali metal sulfide, an aliphatic cyclic compound that can be ring-opened by hydrolysis, and a non-hydrolyzable organic solvent (e.g., a polyhaloaromatic compound).

[0067] <Baffle section and heat transfer piping> FIG. 5 shows an example of a reaction vessel 1 provided with a baffle section 4 equipped with heat transfer piping. The reaction apparatus 10 according to this embodiment preferably further comprises one or two components selected from the group consisting of a heat transfer pipe (not shown) that transfers heat required to initiate and progress the reaction of the raw solution or transfers heat generated by the reaction of the raw solution, and a baffle section 4 that generates turbulence when stirring the raw solution.

[0068] -Baffle section- The baffle section 4 is also a straightening plate for converting the flow of the raw solution in the direction of the liquid surface or in a direction oblique to the liquid surface into a vertical or axial flow, and is provided so as to extend vertically along the inner circumferential side surface of the reaction vessel 1 and protrude toward the center of the reaction vessel 1, i.e., the rotation axis 5. Specifically, the baffle section 4 serves to form a vertical flow of the raw solution between the inner circumferential side surfaces of the reaction vessel 1. A unidirectional flow, vertically, is formed inside the reaction vessel 1. This allows the raw solution to form a circulating flow that circulates vertically inside the reaction vessel 1, thereby promoting the reaction. Furthermore, the baffle sections 4 are preferably provided in pairs, sandwiching the rotating shaft 5 from the side. For example, only one pair of baffle sections 4 may be provided, sandwiching the rotating shaft 5 from the left and right, or two pairs may be provided, sandwiching the rotating shaft 5 from all four sides. Alternatively, more than one pair may be provided as needed. In this way, the number of baffle sections 4 may be set appropriately depending on the application.

[0069] -Heat transfer piping- The reaction apparatus 10 of this embodiment may be provided with heat transfer tubes (not shown). The heat transfer tubes may be arranged around the upper stirring blade and the lower stirring blade, preferably in a plate-like or circumferential shape, inside the reaction vessel 1. Therefore, if the number of heat transfer tubes is increased to increase the heat transfer area, the flow of the raw material solution between the inner side of the heat transfer tube and the outer side of the heat transfer tube inside the reaction vessel 1 may be restricted, resulting in a decrease in mixing ability. The number of heat transfer tubes is not particularly limited, but it is preferable to provide one or more, preferably multiple. The multiple heat transfer tubes heat the raw material solution contained inside the reaction vessel 1 to initiate and progress the dehydration reaction or polymerization reaction. On the other hand, they absorb the reaction heat or polymerization heat generated by the dehydration reaction or polymerization reaction from the raw material solution. A heat transfer medium (heating medium or cooling medium) can be passed through the heat transfer tubes. The heat transfer tubes may have a double-tube structure. For example, a tube plate (not shown) to which the inner tube of the heat transfer tube is fixed and a tube plate (not shown) to which the outer tube of the heat transfer tube is fixed are provided inside the reactor 1. For example, when the reactor 1 is cooled using the heat transfer tubes, water (boiler feed water) is supplied into the heat transfer tubes as a heat transfer medium. Then, while the water passes through the inner and outer tubes of the heat transfer tubes, the water is heated, and hot water or steam is discharged from the outer tube.

[0070] <Preferred baffle part> The baffle unit 4 may also have a heat transfer pipe such as a baffle coil in which a pipe through which a heat transfer medium or refrigerant flows is folded back multiple times, a helical coil in which the pipe is wound, a rocket baffle, a hairpin coil, or a serpentine coil. The baffle unit 4 not only functions as a so-called flow plate that controls the flow of the raw material solution, but also as a heat transfer pipe, thereby increasing the heat transfer area. In other words, it is preferable that the baffle unit 4 is a heat transfer pipe. When the baffle section 4 has a heat transfer piping, the cylindrical baffle section 4 may be provided with a heat transfer piping such as a baffle coil or a helical coil inside, or the baffle section 4 itself may be the heat transfer piping. When scaling up to a production machine, the heat transfer area per unit volume decreases, and the wall jacket of the reactor 1 alone is inefficient in heating, so it is common to place heat transfer piping inside the reactor 1. This heat transfer piping reduces the fluidity inside the reactor, and as the liquid level drops as dehydration progresses, there is an increased risk of low-hydrated alkali metal sulfide adhering to the heat transfer piping surface; however, this risk can be reduced by combining the upper agitator blade 2 and lower agitator blade 3 described above. The baffle section 4 in this embodiment is preferably a heat transfer pipe that also functions as a flow straightening section for converting the raw solution that is rotating and flowing in the circumferential direction into an up-and-down circulating flow.

[0071] [Method for producing low-hydrated alkali metal sulfide] The present disclosure relates to a method for producing a low-hydrated alkali metal sulfide using the above-described reaction apparatus 10. The method for producing a low-hydrated alkali metal sulfide uses a hydrated alkali metal sulfide as a starting material, fills the reaction vessel 1 of the above-described reaction apparatus 10 with the hydrated alkali metal sulfide, and produces a low-hydrated alkali metal sulfide by dehydrating the hydrated alkali metal sulfide. The method for producing a polyarylene sulfide, which will be described later, is a method for obtaining the target product, polyarylene sulfide, by polymerizing the produced low-hydrated alkali metal sulfide. Specifically, the method for producing a low-hydrated alkali metal sulfide of this embodiment includes a step (1) of preparing a raw material solution by charging a hydrous alkali metal sulfide, an aliphatic cyclic compound that can be ring-opened by hydrolysis, and a non-hydrolyzable organic solvent into a reaction vessel 1 of a reaction apparatus 10, and a step (2) of heating and dehydrating the raw material solution in the presence of the non-hydrolyzable organic solvent to a temperature that is equal to or higher than the boiling point of the hydrous alkali metal sulfide and at which water is removed by azeotropy, for example, 80 to 220°C, in the reaction apparatus 10. This suppresses foaming, thereby suppressing adhesion, solidification, adhesion or precipitation of the target substance inside the reaction vessel, and thereby provides a low-hydrated alkali metal sulfide with a low amount of water of crystallization.

[0072] <Process (1)> Step (1) is a step of mixing raw material components in the reaction vessel 1 of the reaction device 10 to obtain a raw material solution. In the above step (1), it is preferable to prepare a raw material solution containing a low-hydrated alkali metal sulfide, an aliphatic cyclic compound capable of being ring-opened by hydrolysis, and a non-hydrolyzable organic solvent, such as a polyhaloaromatic compound, by charging a non-hydrolyzable organic solvent into a reaction vessel 1. This makes it easier to obtain a low-hydrated alkali metal sulfide with a lower water content. Hereinafter, each of the raw materials used in step (1) will be described.

[0073] -Hydrated alkali metal sulfide- In this embodiment, examples of the hydrated alkali metal sulfide used in step (1) include hydrates of lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide, and the like. These may be used alone or in combination of two or more. Among these, hydrates of lithium sulfide or sodium sulfide are preferred, and sodium sulfide hydrate (e.g., sodium sulfide hexahydrate) is more preferred. Since trace amounts of alkali metal hydrosulfides are typically present in hydrated alkali metal sulfides, they are often used as aqueous mixtures containing alkali metal hydroxides to react with these. Instead of such hydrated alkali metal sulfides, aqueous mixtures capable of producing hydrated alkali metal sulfides by reaction can be used. Examples of such aqueous mixtures include a combination of an alkali metal hydrosulfide and an alkali metal hydroxide, and a combination of hydrogen sulfide and an alkali metal hydroxide. Examples of alkali metal hydrosulfides include solid hydrates and anhydrous compounds such as lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, and cesium hydrosulfide. These may be used alone or in combination of two or more. Among these, hydrates such as lithium hydrosulfide and sodium hydrosulfide are preferred, and sodium hydrosulfide hydrate is particularly preferred. The solid content concentration is preferably 10 to 80 mass%. Among these, lithium hydrosulfide hydrate and sodium hydrosulfide hydrate are preferred, and sodium hydrosulfide hydrate is particularly preferred. When an alkali metal hydrosulfide or hydrogen sulfide is used, it is used in combination with an alkali metal hydroxide. The amount of alkali metal hydroxide used in this case is preferably in the range of 0.85 to 1.20 in molar ratio relative to the alkali metal hydrosulfide. When hydrogen sulfide is used, the molar ratio relative to the hydrogen sulfide is preferably in the range of 1.70 to 2.40. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide, and these may be used alone or in combination of two or more. Among the alkali metal hydroxides, lithium hydroxide, sodium hydroxide, and potassium hydroxide are preferred, with sodium hydroxide being particularly preferred.

[0074] - Aliphatic cyclic compounds that can be ring-opened by hydrolysis - In this embodiment, the aliphatic cyclic compound capable of being ring-opened by hydrolysis used in step (1) is preferably a lactam compound, a cyclic organophosphorus compound, or an amide having an aliphatic cyclic structure. Specific examples of the lactam compound include caprolactam, N-methylcaprolactam, N-ethylcaprolactam, N-isopropylcaprolactam, N-cyclohexylcaprolactam, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, and N-cyclohexyl-2-pyrrolidone.

[0075] Specific examples of the cyclic organic phosphorus compounds include 1-methyl-1-oxosulfolane, 1-ethyl-1-oxosulfolane, 1-phenyl-1-oxosulfolane, and 1-methyl-1-oxophosphorane. Examples of the amide having an aliphatic cyclic structure include N-dimethylpropylene urea and 1,3-dimethyl-2-imidazolidinic acid. The above-mentioned aliphatic cyclic compounds capable of ring-opening by hydrolysis may be used alone or in combination of two or more. Among the above-mentioned various compounds, N-alkylpyrrolidone is preferred, more preferably N-alkylpyrrolidone having an alkyl group with 1 to 5 carbon atoms, and particularly preferably N-methylpyrrolidone.

[0076] -Non-hydrolytic organic solvents- In this embodiment, the non-hydrolyzable organic solvent used in step (1) and / or (2) may be any organic solvent inert to water, such as general-purpose aliphatic hydrocarbons and / or aromatic hydrocarbons. However, it is preferable to use the polyhaloaromatic compound used in the subsequent step as the non-hydrolyzable organic solvent, as this dramatically improves production efficiency. Examples of the general-purpose aliphatic hydrocarbons and / or aromatic hydrocarbons include organic solvents that form azeotropes with water, such as toluene, xylene, ethylbenzene, hexane, heptane, octane, and cyclohexane.

[0077] --Polyhaloaromatic compounds-- The polyhaloaromatic compound used as necessary in step (1) of the present embodiment is a halogenated aromatic compound having two or more halogen atoms directly bonded to an aromatic ring, and may be one or more compounds selected from the group consisting of (i) polyhalobenzenes, (ii) polyhalonaphthalenes, and (iii) polyhalides of biphenyl, diphenyl ether, diphenyl sulfide, diphenyl sulfone, and diphenyl ketones. Examples of the polyhaloaromatic compound include dihalobenzenes such as o-dihalobenzene, m-dihalobenzene, and p-dihalobenzene; dihalogenobiphenyls such as 2,3-dihalotoluene, 2,5-dihalotoluene, 2,6-dihalotoluene, 3,4-dihalotoluene, 2,5-dihaloxylene, 1-ethyl-2,5-dihalobenzene, and 4,4'-dihalobiphenyl; 1,4-dihalonaphthalene, 1,6-dihalonaphthalene, 2,6 4,4'-dihalodiphenyl ether, 4,4'-dihalobenzophenone, 4,4'-dihalodiphenyl sulfone, 4,4'-dihalodiphenyl sulfide, and compounds in which the aromatic ring of each of the above compounds has an alkyl group having 1 to 18 carbon atoms as a nuclear substituent.

[0078] The plurality of halogen elements in the polyhalo aromatic compound are each fluorine, chlorine, bromine or iodine, and the plurality of halogen elements in the polyhalo aromatic compound may be the same or different from each other.

[0079] Of the above polyhalo aromatic compounds, p-dichlorobenzene, o-dichlorobenzene, m-dichlorobenzene, trichlorobenzene, tetrachlorobenzene, dibromobenzene, diiodobenzene, tribromobenzene, dibromonaphthalene, triiodobenzene, dichlorodiphenylbenzene, dibromodiphenylbenzene, dichlorobenzophenone, dibromobenzophenone, dichlorodiphenyl ether, dibromodiphenyl ether, dichlorodiphenyl sulfide, dibromodiphenyl sulfide, dichlorobiphenyl, dibromobiphenyl, 4,4'-dichlorobenzophenone and 4,4'-dichlorodiphenyl sulfone are preferably used. Among the above polyhaloaromatic compounds, polyhalobenzenes are preferred, dihalobenzenes are more preferred, and p-dichlorobenzene is particularly preferred.

[0080] The polyhaloaromatic compounds may be used alone or in combination of two or more. For example, p-dichlorobenzene may be combined with 4,4'-dichlorobenzophenone or 4,4'-dichlorodiphenyl sulfone. Particularly preferred are those containing 80 mol% or more of p-dichlorobenzene. Furthermore, in step (1) and step (2) described below, if a reaction raw material containing a polyhaloaromatic compound is used, a low-hydrated alkali metal sulfide having a lower water content is more likely to be obtained. Among the above-mentioned polyhaloaromatic compounds, when emphasis is placed on the efficient production of a linear high-molecular-weight PAS resin, bifunctional dihaloaromatic compounds are preferred, and when emphasis is placed on the mechanical strength and moldability of the final PAS resin, p-dichlorobenzene, m-dichlorobenzene, 4,4'-dichlorobenzophenone, and 4,4'-dichlorodiphenyl sulfone are preferred, with p-dichlorobenzene being particularly preferred.Furthermore, when it is desired to impart a branched structure to part of the polymer structure of the linear PAS resin, it is preferred to use a portion of 1,2,3-trihalobenzene, 1,2,4-trihalobenzene, or 1,3,5-trihalobenzene in combination with the above-mentioned dihaloaromatic compounds.

[0081] <Process (2)> The step (2) is a dehydration step in which the raw material solution obtained in the step (1) is dehydrated by heating it in the reaction apparatus 10 to a temperature that is equal to or higher than the boiling point of the hydrated alkali metal sulfide and at which water is removed by azeotropy. In step (2), the dehydration is preferably carried out by heating to 100 to 200°C. Alternatively, the azeotropically distilled solvent may be returned to the system using a decanter, or an additional amount equivalent to the amount of the azeotropically distilled solvent may be added. At the beginning of dehydration, two layers of the nonhydrolyzable organic solvent and the dissolved hydrated alkali metal sulfide are present. As dehydration progresses, the alkali metal sulfide precipitates as fine particles and becomes uniformly dispersed in the nonhydrolyzable organic solvent. Dehydration may be continued until the sum of the moles of the nonhydrolyzable organic solvent and the amount of water remaining in the system falls within the range of 0.02 to 0.9 moles relative to the hydrated alkali metal sulfide. Step (2) may be terminated.

[0082] When a polyhaloaromatic compound is used as the non-hydrolyzable organic solvent in steps (1) and (2), the compound can be used in an amount of 0.2 to 5.0 moles per mole of the hydrated alkali metal sulfide added. However, if the amount is insufficient for the polyarylene sulfide production process (polymerization process) described below, additional use may be made. The amount of the polyhaloaromatic compound used in step (2) is preferably 0.2 to 1.3 moles per mole of the hydrated alkali metal sulfide added. A range of 0.3 to 1.2 moles is particularly preferred.

[0083] On the other hand, when a non-hydrolyzable organic solvent is used in steps (1) and (2), the amount of the non-hydrolyzable organic solvent is preferably 0.1 to 10 parts by weight, more preferably 0.3 to 5 parts by weight, per part by weight of the hydrated alkali metal sulfide to be added. The amount of the non-hydrolyzable organic solvent to be used in step (2) is preferably 0.02 to 0.9 mol, more preferably 0.03 to 0.6 mol, and particularly preferably 0.04 to 0.4 mol, per mole of the hydrated alkali metal sulfide to be added. An amount less than 0.02 mol results in poor dispersibility of the resulting low-hydrated alkali metal sulfide. An amount exceeding 0.9 mol is undesirable from the viewpoints of increasing the molecular weight of the polyarylene sulfide to be obtained in the subsequent step and increasing the reactant concentration per polymerization vessel volume.

[0084] In step (2), a polyhalo aromatic compound may be used in combination with a non-hydrolyzable organic solvent other than the polyhalo aromatic compound. If a non-hydrolyzable organic solvent other than the polyhalo aromatic compound is used during dehydration, it is removed at an early stage of the subsequent step (the polymerization step described below), and if it is a polyhalo aromatic compound, it can be used in the polyarylene sulfide production step described below.

[0085] In a typical dehydration process for hydrous alkali metal sulfide, it is observed that, in the initial stage of the dehydration process, jelly-like hydrates begin to precipitate when half of the total water content in the hydrous alkali metal sulfide has been dehydrated. At the same time, foam similar to that seen in beer is generated. However, when the dehydration process is carried out using the reaction apparatus 10 of this embodiment, while the raw solution is heated and stirred with both the upper agitating blade 2 and the lower agitating blade 3, jelly-like hydrates begin to precipitate when half of the total water content in the hydrous alkali metal sulfide has been dehydrated. However, it has been confirmed that the amount of foam adhering to the wall surface is significantly reduced because foam retention near the wall surface can be suppressed. In particular, it was confirmed that the amount of bubbles adhering to the wall surface can be drastically reduced by setting the ratio (hB / D) of the maximum height (hB) of the upper agitating blade 2 to the inner diameter (D) of the reaction vessel 1 to 0.5 or more, or by setting the ratio (dB / D) of the maximum agitating blade length (dB) of the upper agitating blade 2 to the inner diameter (D) of the reaction vessel 1 to 0.3 or more. Similarly, it was confirmed that the amount of bubbles adhering to the wall surface can be drastically reduced by using various blade portions 2a of the upper agitating blade 2 shown in Figures 1 to 4. Since the blade portions 2a of these four types of upper agitating blades 2 all have surfaces that extend in the axial direction of the rotating shaft 5, it is believed that they can generate convection up to the vicinity of the water surface of the raw solution, and as a result, the amount of bubbles adhering to the wall surface can be continuously reduced (in other words, the wall surface of the reaction vessel 1 can be kept exposed at all times). Furthermore, these blade portions 2a that have surfaces that extend in the axial direction of the rotating shaft 5, or blade portions 2a that have a predetermined maximum height (hB) or a predetermined maximum agitating blade length (dB), can continuously respond to the liquid level that fluctuates as the dehydration process progresses, and therefore it is believed that the amount of bubbles adhering to the wall surface can be drastically reduced. Furthermore, due to foaming, the liquid volume expands to approximately 1.3 times its volume at the start of the dehydration process, but the upper stirring blades 3, which are positioned above the liquid surface of the raw material solution at the start of the dehydration process, also eliminate the expanded foam due to foaming, thereby preventing the hydrated alkali metal sulfide from adhering to the wall of the reaction vessel 1.

[0086] Next, in the intermediate stage of a general dehydration process of a hydrous alkali metal sulfide, the foamed bubbles dry as the liquid level of the raw material solution drops and begin to adhere to the wall surface of the reaction vessel. However, by using the reaction apparatus 10 of this embodiment, the retention of bubbles near the wall surface can be suppressed, and therefore the adhesion of the dried product or raw material to the wall surface is drastically reduced. In the final stage of a typical dehydration process, precipitated crystal particles (e.g., hydrated alkali metal sulfide or low-hydrated alkali metal sulfide) settle and begin to accumulate at the bottom of a reaction vessel or the like. However, it has been confirmed that the use of the reaction apparatus 10 of this embodiment can suppress the accumulation of precipitated crystal particles. In the reaction apparatus 10 of this embodiment, an upward flow is likely to occur near the bottom B of the reaction vessel 1, which is thought to improve the mixing ability of the raw material solution. Furthermore, (dA / D), which indicates the ratio of the maximum blade diameter (dA) of the lower agitating blade 3 to the inner diameter (D) of the reaction vessel 1, is greater than 0.46 (preferably 0.5 or greater), or (hA / D), which indicates the ratio of the maximum height (hA) of the lower agitating blade 3 to the inner diameter (D) of the reaction vessel 1, is greater than 0.08 (preferably 0.1 or greater), and (BG / D), which indicates the ratio of the distance from the lowest end of the lower agitating blade 3 to the bottom of the reaction vessel 1 (bottom gap: BG) to the inner diameter (D) of the reaction vessel 1, is 0.15 or less. Furthermore, (hB / D), which indicates the ratio of the maximum height (hB) of the upper agitating blade to the inner diameter (D) of the reaction vessel 1, is greater than 0.17 (preferably 0.2 or greater). Therefore, convection or upward flow can be generated in every corner of the bottom B of the reaction vessel 1. As a result, the precipitated crystal particles can be circulated by the generated convection or upward flow before they settle and adhere to the bottom B of the reaction vessel 1, which is thought to suppress the deposition of the precipitated crystal particles.

[0087] <Preferable method for producing low-hydrated alkali metal sulfide> A preferred method for producing a low-hydrated alkali metal sulfide of this embodiment includes a step (1A) of preparing a raw material solution by charging a hydrated alkali metal sulfide, an aliphatic cyclic compound capable of being ring-opened by hydrolysis, and a polyhaloaromatic compound into the reaction vessel 1 of the reaction apparatus 10 of this embodiment; and (2) a step of heating the raw material solution in the reaction device 10 to a temperature equal to or higher than the boiling point of the hydrated alkali metal sulfide and at which water is removed by azeotropy to dehydrate the raw material solution. As described above, the reaction apparatus 10 of this embodiment is provided with both the upper stirring blade 2 and the lower stirring blade 3, and has a predetermined BG / D, so that a good circulation flow can be formed in the reaction vessel 1. As a result, foaming of the raw material solution is suppressed in the dehydration step, which is thought to suppress adhesion, solidification, adhesion or sedimentation of the target substance inside the reaction vessel. It was also confirmed that adhesion, solidification, or adhesion of the product can be significantly suppressed when the ratio (hB / D) of the maximum height of the upper agitating blade 2 to the inner diameter of the reaction vessel exceeds 0.17, since the amount of foam generated is small or the foam is easily defoamed by the upper agitating blade 2. Furthermore, it was confirmed that when the ratio (hA / D) of the maximum height of the upper agitating blade 2 to the inner diameter of the reaction vessel exceeds 0.08, or when the ratio (dA / D) of the maximum length of the upper agitating blade 2 to the inner diameter of the reaction vessel exceeds 0.46, a good circulation flow can be formed within the reaction vessel 1, thereby significantly suppressing settling of the product at the bottom B of the reaction vessel 1.

[0088] [Method for producing polyarylene sulfide] The method for producing polyarylene sulfide according to the present disclosure includes a step (3) of polymerizing the low-hydrated alkali metal sulfide obtained by the above-described method for producing a low-hydrated alkali metal sulfide with a polyhaloaromatic compound. This makes it possible to obtain a polyarylene sulfide resin that is highly productive on an industrial scale and that allows the resulting PAS resin to have a significantly high molecular weight.

[0089] Step (3) of polymerizing the low-hydrated alkali metal sulfide and the polyhalogenated aromatic compound is not particularly limited, and any known method can be used. In step (3), after step (2) above, it is preferable to add an aliphatic cyclic compound and / or a polyhalogenated aromatic compound that can be ring-opened by hydrolysis to reaction vessel 1 of reaction device 10, and polymerize the low-hydrated alkali metal sulfide and the polyhalogenated aromatic compound. The total amount of polyhaloaromatic compound, including the amount used in step (2) (dehydration step) for producing a low-hydrated alkali metal sulfide, is preferably in the range of 0.8 to 1.3 mol, particularly preferably 0.9 to 1.20 mol, per mol of alkali metal sulfide. If the amount is less than 0.8 mol or more than 1.3 mol, it is difficult to obtain a polyarylene sulfide with a desired molecular weight. If necessary, additional polyhaloaromatic compound may be charged in step (3).

[0090] In step (3), it is preferable to add a necessary amount of the aliphatic cyclic compound capable of ring-opening by hydrolysis. The total amount of the aliphatic cyclic compound capable of ring-opening by hydrolysis present in the process system is 0.6 to 10 mol, and if the purpose is to increase the molecular weight, it is preferably in the range of 3.0 to 6.0 mol per mol of alkali metal sulfide, and if the purpose is to increase the reactant concentration per volume of the polymerization vessel, it is preferably in the range of 1.0 to 3.5 mol. Furthermore, the amount of water in the system in step (3) is preferably 0.02 to 0.9 moles per mole of alkali metal sulfide. Therefore, if necessary, water may be added in such a range that the sum of the aliphatic cyclic compound capable of ring-opening by hydrolysis added in step (2) (dehydration step) and the water in the system is 0.02 to 0.9 moles.

[0091] When a polyhalogenated aromatic compound is added to reactor 1 in step (1), the low-hydrated alkali metal sulfide obtained using the polyhalogenated aromatic compound is in a state in which fine granular alkali metal sulfide is dispersed in a mixture of an aliphatic cyclic compound capable of being ring-opened by hydrolysis and a polyhalogenated aromatic compound. Alternatively, the aliphatic cyclic compound capable of being ring-opened by hydrolysis required for polymerization may be added in step (3), and then polymerization may be carried out. Polymerization using a low-hydrated alkali metal sulfide proceeds by heating to a polymerization temperature of preferably 180 to 300° C., more preferably 200 to 280° C. The polymerization reaction can be carried out at a constant temperature, or can be carried out while increasing the temperature stepwise or continuously. Furthermore, when a non-hydrolyzable organic solvent is added to the reaction vessel 1 in step (1), and when a low-hydrated alkali metal sulfide obtained using the non-hydrolyzable organic solvent is used, it is preferable to add an aliphatic cyclic compound that can be ring-opened by hydrolysis, which is necessary for polymerization, in step (3), remove the non-hydrolyzable organic solvent, and then add a polyhaloaromatic compound, which is necessary for polymerization, and then carry out polymerization.

[0092] The polymerization pressure in step (3) is generally 0 to 20 kg / cm 2 is preferable, and more preferably 1 to 10 kg / cm 2 The polymerization time in step (3) is preferably in the range of 1 to 50 hours, more preferably 2 to 30 hours. The polymerization method in step (3) can be any of the usual polymerization methods such as a batch method, a batch method, or a continuous method. The atmosphere during polymerization in step (3) is preferably a non-oxidizing atmosphere, and it is preferable to replace the atmosphere in the system with an inert gas such as nitrogen or argon at the start of polymerization.

[0093] In addition, within the scope of the present disclosure, if necessary, polymerization additives such as active hydrogen-containing haloaromatic compounds, haloaromatic nitro compounds, organometallic salts, reducing agents, inert organic solvents, etc. may be appropriately selected and added to the reaction system to carry out the reaction, etc. Examples of the active hydrogen-containing haloaromatic compounds include haloaromatic compounds having a functional group with active hydrogen, such as an amino group, a thiol group, a hydroxyl group, or a carboxyl group.

[0094] (Polymer recovery) After the step (3), it is preferable to have a step (4) of recovering the polymer (polyarylene sulfide). The polymer can be recovered by first heating the reaction mixture under reduced pressure or under normal pressure at the end of the reaction to distill off only the solvent, then washing the remaining solid matter once or twice or more times with a solvent such as water, acetone, methyl ethyl ketone, or an alcohol, neutralizing it, washing with water, filtering it, and drying it. Alternatively, the polymer can be recovered by adding water, acetone, methyl ethyl ketone, an alcohol, or an ether (which is soluble in the polymerization solvent used and is a poor solvent for at least the produced polymer) as a precipitant to the reaction mixture after the reaction has ended, thereby precipitating the solid products such as the polymer and inorganic salts, which can then be filtered, washed, and dried.

[0095] The polymer obtained by the method for producing polyarylene sulfide of the present disclosure can be made to have a high melt viscosity by subjecting the polymer itself to a slight oxidation treatment as needed. It can be processed into various molded articles by injection molding, extrusion molding, rotational molding, etc.

[0096] The polymers produced by the polyarylene sulfide production method of the present disclosure fall into the category of thermoplastic polymers, and therefore can be modified in various ways as is possible with thermoplastic polymers. For example, these polymers can be filled with powder fillers such as carbon black, calcium carbonate powder, silica powder, and titanium oxide powder, or fibrous fillers such as carbon fiber, glass fiber, asbestos, and polyaramid fiber. These polymers can also be mixed with one or more synthetic resins, such as polycarbonate, polyphenylene oxide, polyamide, polyacetal, polysulfone, polyethersulfone, polybutylene terephthalate, polyethylene terephthalate, liquid crystal polyester, polyimide, polystyrene, ABS, and various elastomers. [Example]

[0097] The present invention will now be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The resins and molded articles in the examples and comparative examples were analyzed and evaluated as follows. 1. Evaluation Method (1) Measurement of residual water volume (residual H2O / S) It was calculated by (total amount of water in the raw materials (mol) - amount of dehydration (mol)) ÷ charged NaSH (mol). (2) Measurement of the amount of adhesion to the pot (g) After dehydration, 900 g of NMP (N-methylpyrrolidone) was added to the reactor and cooled to room temperature. Then, a slurry of the sodium sulfide composition dispersed in the DCB / NMP solution was removed from the reactor. 500 g of water was added to the reactor to dissolve the sodium sulfide composition adhering to the reactor wall and stirring blades. The aqueous solution was removed from the reactor, and the amount of adhesion was calculated from the weight increase. (3) Measurement of dehydration time (minutes) The dehydration time was defined as the time from the liquid temperature of 125°C when dehydration started to 174°C when dehydration finished. (4) Evaluation of the presence or absence of foaming Using a glass autoclave kettle, the state in which the contents foamed and the liquid level rose during dehydration, the state in which the foam flowed / stagnated, and the state in which the solid sodium sulfide composition adhered to the kettle wall as the liquid level dropped with the progress of dehydration were visually observed and evaluated. (5) Measurement of melt viscosity The melt viscosity of the obtained PPS resin was measured using a flow tester "CFT500D" manufactured by Shimadzu Corporation after holding the resin at 300°C, 1.96 MPa, and L / D=10 for 6 minutes.

[0098] 2. Example of production of low-hydrated alkali metal sulfide Example 1 A 2-liter cylindrical glass autoclave with a hemispherical bottom, an inner diameter of 120 mm, a liquid depth of L = 230 mm when filled with liquid, and a pressure gauge, thermometer, condenser, and decanter were prepared as a reaction apparatus. Four plate-shaped titanium baffles, each 15 mm wide and 170 mm high, were installed inside the autoclave. A plate-shaped lower stirring blade (A) with a crescent shape at the bottom and a square-shaped upper stirring blade (B) with a hole cut out in the center of a 55 mm wide x 100 mm high plate over a range of 26 mm wide x 80 mm high were installed above the lower stirring blade (A). The ratio of the distance (BG) from the bottom of the lower stirring blade (A) to the inner diameter (D) of the reaction vessel was BG / D = 0.08, and the stirring blade (A The ratio of the maximum impeller diameter (dA) of the impeller (A) to the inner diameter (D) of the reaction vessel was dA / D = 0.66, the ratio of the maximum height (hA) of the impeller (A) to the inner diameter (D) of the reaction vessel was hA / D = 0.17, the ratio of the maximum impeller diameter (dB) of the upper mouth-shaped impeller (B) to the inner diameter (D) of the reaction vessel was dB / D = 0.46, and the ratio of the maximum height (hB) of the impeller (B) to the inner diameter (D) of the reaction vessel was hB / D = 0.83. The shapes of the upper impeller (B) and lower impeller (A) used in Example 1 are as shown in Figure 1. This reactor was charged with 612.99 g (4.17 mol) of p-dichlorobenzene (DCB), 42.13 g (0.425 mol) of NMP, 496.28 g (4.25 mol) of 48% by weight NaSH aqueous solution, and 347.50 g (4.17 mol) of 48% by weight NaOH aqueous solution. The temperature was raised from 125°C (at which point dehydration begins) to 174°C under a nitrogen atmosphere while stirring. 504.64 g of water was distilled off, and the reactor was then sealed. The DCB distilled off by azeotropy was separated in a decanter and returned to the reactor as needed. During dehydration, foaming of the contents caused the liquid level to rise to the top of the upper stirring blade (B). However, the foam did not stagnate and the mixture remained fluid. As the liquid level dropped with the progress of dehydration, no adhesion of the sodium sulfide composition to the reactor wall was observed. After dehydration, no sodium sulfide composition was found adhering to the bottom of the reactor, and the sodium sulfide composition in the form of fine particles was dispersed in DCB inside the reactor. After dehydration, the molar ratio of water to sodium sulfide composition present in the reactor, HO / S, was 0.12, the dehydration time was 242 minutes, and the amount of adhered sodium sulfide composition was 5 g.

[0099] Example 2 Instead of the square-shaped upper impeller (B), six flat paddle impellers (B2), each consisting of four impellers, were arranged in rows. More specifically, six flat paddle impellers, each 55 mm wide and approximately 10 mm high, were arranged at approximately 10 mm intervals. The same procedure as in Example 1 was performed, except that the ratio of the paddle impeller (B2) blade diameter (dB2) to the inner diameter (D) of the reactor was set to dB2 / D = 0.53, and the ratio of the total maximum height (hB2) of the impellers (B2) to the inner diameter (D) of the reactor was set to hB2 / D = 0.50. During dehydration, foaming of the contents caused the liquid level to rise to the top of the upper impeller (B2). However, the foam did not stagnate and remained fluid, and no adhesion of the sodium sulfide composition to the reactor wall was observed as the liquid level dropped with the progress of dehydration. No adhesion of the sodium sulfide composition to the reactor bottom was observed after dehydration. The amount of water distilled by dehydration was 504.49 g, the molar ratio of water to sodium sulfide composition remaining in the reaction vessel after dehydration was HO / S = 0.12, the dehydration time was 245 minutes, and the amount of adhesion was 7 g. Note that the shape of the upper stirring blade (B) used in Example 2 above is shown in Figure 2. The shape of the lower stirring blade (A) used in Example 2 above is the same as that in Example 1.

[0100] (Comparative Example 1) The same operation as in Example 1 was performed, except that the ratio of the distance (BG) from the lowest end of the lower stirring blade (A) to the bottom of the reactor to the inner diameter (D) of the reactor was set to BG / D = 0.17. During dehydration, foaming of the contents caused the liquid level to rise to the top of the upper stirring blade (B), but the foam did not stagnate and remained in a fluid state, and no adhesion of the sodium sulfide composition to the reactor wall was observed as the liquid level dropped with the progress of dehydration. However, adhesion of the sodium sulfide composition was observed mainly around the bottom of the reactor after dehydration. The amount of water distilled during dehydration was 499.29 g, the molar ratio of water to sodium sulfide composition remaining in the reactor after dehydration was HO / S = 0.19, the dehydration time was 260 minutes, and the amount of adhesion was 33 g.

[0101] (Comparative Example 2) The same procedure as in Example 1 was performed, except that the ratio of the maximum blade diameter (dA2) of the impeller (A2) to the inner diameter (D) of the reactor was dA2 / D = 0.46, and the ratio of the maximum height (hA2) of the impeller (A2) to the inner diameter (D) of the reactor was hA2 / D = 0.08. During dehydration, foaming of the contents caused the liquid level to rise to the top of the upper impeller (B). However, the foam did not stagnate and remained fluid, and no adhesion of the sodium sulfide composition to the reactor wall was observed as the liquid level dropped with the progress of dehydration. However, adhesion of the sodium sulfide composition was observed mainly around the bottom of the reactor after dehydration. The amount of water distilled during dehydration was 497.76 g. The molar ratio of water to sodium sulfide composition present in the reactor after dehydration was HO / S = 0.21. The dehydration time was 265 minutes, and the amount of adhesion was 42 g.

[0102] (Comparative Example 3) Instead of the square-shaped upper agitator blade (B), a set of four flat paddle blades (B2) was arranged in two rows (see, for example, Figure 6). The same operation as in Example 1 was performed, except that the ratio of the blade diameter (dB2) of the paddle blade (B2) to the inner diameter (D) of the reaction vessel was dB2 / D = 0.53, and the ratio of the total maximum height (hB2) of the agitator blades (B2) to the inner diameter (D) of the reaction vessel was hB2 / D = 0.17. During dehydration, foaming of the contents caused the liquid level to rise to the top of the upper agitator blade (B2). However, as the liquid level dropped with the progress of dehydration, adhesion of the sodium sulfide composition to the reactor wall was observed. On the other hand, no adhesion of the sodium sulfide composition to the reactor bottom was observed after dehydration. The amount of water distilled by dehydration was 496.99 g, and the molar ratio of water to sodium sulfide composition present in the reaction vessel after dehydration was H2O / S = 0.22, the dehydration time was 268 minutes, and the amount of adhesion was 45 g.

[0103] [Table 1]

[0104] 3. Production example of polyarylene sulfide resin Example 3 After carrying out the same dehydration procedure as in Example 1, the reactor was cooled to 160°C and 877.57 g (8.85 mol) of NMP was added. The internal temperature was raised to 220°C and stirred for 2 hours, then raised to 250°C and stirred for 1 hour. After cooling, 650 g of the resulting slurry was poured into 3 L of water and stirred at 80°C for 1 hour, followed by filtration. The cake was again stirred in 3 L of warm water for 1 hour, washed, and then filtered. This procedure was repeated four times. After filtration, the mixture was dried overnight at 120°C in a hot air dryer, yielding 150 g of white powdered PPS resin. The melt viscosity of this polymer was 54 Pa·s.

[0105] Comparative Example 4 After carrying out the same dehydration procedure as in Comparative Example 3, the reactor was cooled to 160°C and 877.57 g (8.85 mol) of NMP was added. The internal temperature was raised to 220°C and stirred for 2 hours, then raised to 250°C and stirred for 1 hour. After cooling, 650 g of the resulting slurry was poured into 3 L of water and stirred at 80°C for 1 hour, then filtered. The cake was stirred again with 3 L of warm water for 1 hour, washed, and then filtered. This procedure was repeated four times. After filtration, the mixture was dried overnight at 120°C in a hot air dryer, yielding 141 g of white powdered PPS resin. The melt viscosity of this polymer was 6 Pa·s. From the above, it was confirmed that when a compound obtained using the low-hydrated alkali metal sulfide production apparatus of the present disclosure is used, the melt viscosity of the polyarylene sulfide resin finally obtained is high.

Claims

1. a reaction vessel having a recess for accommodating a raw material solution containing a hydrated alkali metal sulfide, an aliphatic cyclic compound capable of being ring-opened by hydrolysis, and a non-hydrolyzable organic solvent; a lower stirring blade provided near the bottom of the reaction vessel for stirring the raw material solution; an upper stirring blade that is disposed closer to the opening of the reaction vessel than the lower stirring blade and stirs the raw material solution; the ratio (dA / D) of the maximum blade diameter (dA) of the lower stirring blade to the inner diameter (D) of the reaction vessel is greater than 0.46, or the ratio (hA / D) of the maximum height (hA) of the lower stirring blade to the inner diameter (D) of the reaction vessel is greater than 0.08; a ratio (BG / D) of a distance from the lowest end of the lower stirring blade to the lowest bottom of the reaction kettle (bottom gap: BG) to an inner diameter (D) of the reaction kettle is 0.15 or less; The ratio (hB / D) of the maximum height (hB) of the upper stirring blade to the inner diameter (D) of the reaction vessel is greater than 0.17; A reactor used to produce low-hydrated alkali metal sulfides.

2. 2. The reaction apparatus used for producing a low-hydrated alkali metal sulfide according to claim 1, wherein the ratio (dB / D) of the maximum blade diameter (dB) of the upper stirring blade to the inner diameter (D) of the reaction vessel is 0.3 or more.

3. 3. The reaction apparatus used for producing a low-hydrated alkali metal sulfide according to claim 1 or 2, wherein (hB / D), which indicates a ratio of a maximum height (hB) of the upper stirring blade to an inner diameter (D) of the reaction vessel, is 0.5 or more.

4. a heat transfer pipe for transferring heat required to initiate and progress the reaction of the raw material solution, or for transferring heat generated by the reaction of the raw material solution; and A baffle section that generates turbulence when stirring the raw material solution The reaction apparatus used for producing the low-hydrated alkali metal sulfide according to claim 1, further comprising one or two selected from the group consisting of:

5. 3. The reaction apparatus used for producing a low-hydrated alkali metal sulfide according to claim 1 or 2, further comprising an agitation shaft provided parallel to the inner circumferential surface of the reaction vessel, and the lower agitation blade and the upper agitation blade are attached to the agitation shaft.

6. 3. The reaction apparatus used for producing a low-hydrated alkali metal sulfide according to claim 1 or 2, wherein (dA / D), which indicates the ratio of the maximum blade diameter (dA) of the lower stirring blade to the inner diameter (D) of the reaction vessel, is 0.5 or more.

7. 3. The reaction apparatus used for producing a low-hydrated alkali metal sulfide according to claim 1 or 2, wherein (hA / D), which indicates the ratio of the maximum height (hA) of the lower stirring blade to the inner diameter (D) of the reaction vessel, is 0.1 or more.

8. A method for producing a low-hydrated alkali metal sulfide using the reaction apparatus according to claim 1 or 2.

9. A method for producing polyarylene sulfide, comprising a step of reacting the low-hydrated alkali metal sulfide obtained according to claim 6 with a polyhaloaromatic compound.

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