Method for producing anhydrous sodium sulfide physical object or anhydrous sodium polysulfide physical object

Abstract

Provided is a method for producing an anhydrous sodium sulfide physical object or an anhydrous sodium polysulfide physical object, the method being characterized in that the anhydrous sodium sulfide physical object or the anhydrous sodium polysulfide physical object is produced continuously by repeating the following steps in this order: a thin film formation step in which an aqueous sodium sulfide solution or an aqueous sodium polysulfide solution is used as a starting material, and the aqueous sodium sulfide solution or the aqueous sodium polysulfide solution is supplied to the surface of a disc to produce a thin film of the aqueous sodium sulfide solution or the aqueous sodium polysulfide solution; a drying step in which the thin film of the aqueous sodium sulfide solution or the aqueous sodium polysulfide solution is dehydrated on the surface of the disc under a reduced pressure and an inert gas atmosphere; and a separation step in which an anhydrous sodium sulfide physical object or an anhydrous sodium polysulfide physical object obtained in the drying step is removed from the surface of the disc. As a result, it is possible to provide a production method which is safe and has high production efficiency with which an anhydrous sodium sulfide physical object or an anhydrous sodium polysulfide physical object can be produced continuously.

Description

Method for producing anhydrous sodium sulfide shaped substance or anhydrous sodium polysulfide shaped substance

[0001] The present invention relates to a method for continuously producing anhydrous sodium sulfide or anhydrous sodium polysulfide shaped product containing few impurities.

[0002] Sodium sulfide (Na ２ S) is known as a raw material for organic synthesis and polyphenylene sulfide (PPS) resin. ２ Sodium sulfide (Sx) (x is a real number greater than 1 and less than or equal to 4) is known as a raw material for rubber chemicals and silane coupling agents. Commercially available tangible sodium sulfide usually contains a certain amount of water. Sodium polysulfide is also sold as an aqueous solution. This can lead to undesirable side reactions and reverse reactions. Therefore, it is necessary to remove the water before use as a raw material. Known methods for removing the water include dehydrating tangible sodium sulfide in flake, chip, or pellet form by heating under reduced pressure; dehydrating the tangible sodium sulfide in an inert gas atmosphere; or combining both methods. Anhydrous sodium polysulfide can be synthesized by the direct reaction of metallic sodium with sulfur.

[0003] For example, Patent Document 1 describes a method for dehydrating sodium sulfide tangible matter, such as sodium sulfide pentahydrate, by adding anhydrous sodium sulfide to the sodium sulfide pentahydrate and then heating and dehydrating the resulting product under reduced pressure. Patent Document 2 describes a method for producing anhydrous sodium polysulfide by directly reacting metallic sodium with sulfur.

[0004] Japanese Patent Laid-Open No. 4-310508 Japanese Patent Laid-Open No. 2001-31406

[0005] However, the dehydration method described in Patent Document 1 is a batch process, and the dehydration time is long, which can result in poor production efficiency and high costs. Another method for removing moisture from sodium sulfide involves dehydrating the sodium sulfide shaped product by passing it through an inert gas, but this method also requires a long dehydration time and is not considered to be good production efficiency. The method for producing anhydrous sodium polysulfide shaped product described in Patent Document 2 is a dangerous method that uses metallic sodium. Furthermore, the methods for producing anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product do not incorporate the technical idea of ​​using an inexpensive aqueous sodium sulfide solution or aqueous sodium polysulfide solution as a starting material.

[0006] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for producing anhydrous sodium sulfide shaped products or anhydrous sodium polysulfide shaped products safely and efficiently, which can continuously produce anhydrous sodium sulfide shaped products or anhydrous sodium polysulfide shaped products.

[0007] The above-mentioned problems can be solved by providing a method for producing anhydrous sodium sulfide shaped products or anhydrous sodium polysulfide shaped products, the method comprising the steps of: a thin film forming step of using an aqueous sodium sulfide solution or an aqueous sodium polysulfide solution as a starting material and supplying the aqueous sodium sulfide solution or the aqueous sodium polysulfide solution to the surface of a disk to obtain a thin film of the aqueous sodium sulfide solution or the aqueous sodium polysulfide solution; a drying step of dehydrating the thin film of the aqueous sodium sulfide solution or the aqueous sodium polysulfide solution on the surface of the disk under reduced pressure and an inert gas atmosphere; and a separation step of removing the anhydrous sodium sulfide shaped products or the anhydrous sodium polysulfide shaped products obtained in the drying step from the surface of the disk, by repeating these steps in this order to continuously obtain the anhydrous sodium sulfide shaped products or the anhydrous sodium polysulfide shaped products.

[0008] In this case, it is preferable that the dehydration time in the drying step is 6 to 300 seconds, and the concentration of the aqueous sodium sulfide solution or aqueous sodium polysulfide solution is 3 to 60% by weight. It is also preferable that the content of the anhydrous sodium sulfide component in the anhydrous sodium sulfide shaped product is 95% by weight or more, and that the content of the anhydrous sodium polysulfide component in the anhydrous sodium polysulfide shaped product is 90% by weight or more. It is also preferable that the water content in the anhydrous sodium sulfide shaped product or the anhydrous sodium polysulfide shaped product is 3% by weight or less.

[0009] According to the present invention, there is provided a method for producing anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product safely and efficiently, which can continuously produce anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product.

[0010] FIG. 1 is a schematic diagram showing an example of a vacuum thin film dryer used in Examples 1 and 2.

[0011] The present invention will be described in detail below with reference to the drawings. Fig. 1 is a schematic diagram showing an example of a vacuum thin-film dryer used in the present invention, which includes a supply tank for supplying an aqueous sodium sulfide solution or an aqueous sodium polysulfide solution, a supply pump, a circulation tank, a circulation pump, and a supply nozzle inside the container. The vacuum thin-film dryer further includes a disk having a rotating shaft, a scraper for removing the anhydrous sodium sulfide shaped substance or the anhydrous sodium polysulfide shaped substance from the disk surface, a collection tank for collecting the anhydrous sodium sulfide shaped substance or the anhydrous sodium polysulfide shaped substance, etc. Although not shown in Fig. 1, the vacuum thin-film dryer also includes a disk heating means, an inert gas supply means, and a pressure reducing means.

[0012] The method for producing anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product of the present invention is characterized in that it uses an aqueous sodium sulfide solution or an aqueous sodium polysulfide solution as a starting material, and comprises the steps of: a thin film forming step (hereinafter sometimes abbreviated as "thin film forming step") of supplying the aqueous sodium sulfide solution or aqueous sodium polysulfide solution to the surface of a disk to form a thin film of the aqueous sodium sulfide solution or aqueous sodium polysulfide solution; a drying step (hereinafter sometimes abbreviated as "drying step") of dehydrating the thin film of the aqueous sodium sulfide solution or aqueous sodium polysulfide solution on the surface of the disk under reduced pressure and an inert gas atmosphere; and a separation step (hereinafter sometimes abbreviated as "separation step") of removing the anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product from the surface of the disk, by repeating these steps in this order to continuously obtain anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product. In the present invention, the anhydrous sodium sulfide shaped product refers to sodium sulfide (Na ２ S) in a solid state. Also, anhydrous sodium polysulfide tangible matter is sodium polysulfide (Na ２ Sx) (x is a real number greater than 1 and less than 4) in a solid state. ２ S ２ ), sodium trisulfide (Na ２ S ３ ), sodium tetrasulfide (Na ２ S ４ ) etc.

[0013] As will be seen from a comparison between Example 1 and Comparative Example 1 described below, in Comparative Example 1, in which the sodium sulfide aqueous solution was sprayed in the form of a mist for dehydration, the viscosity rose sharply and the solution was sprayed out as a liquid. The color was also black, suggesting that the high-temperature, strongly alkaline sodium sulfide aqueous solution corroded the piping. This corrosion could reduce the wall thickness of the piping, potentially leading to spraying, posing a safety issue. In contrast, in Example 1, in which the thin film formation step, drying step, and separation step were repeated in this order, an anhydrous sodium sulfide shaped product with few impurities could be continuously, safely, and efficiently obtained. Similarly, in Example 2, in which the thin film formation step, drying step, and separation step were repeated in this order, an anhydrous sodium polysulfide shaped product with few impurities could be continuously, safely, and efficiently obtained. Therefore, it can be seen that the significance of the present invention, which employs such a method, is significant.

[0014] The thin-film forming process of the present invention involves supplying an aqueous sodium sulfide solution or an aqueous sodium polysulfide solution to the disk surface to obtain a thin film of the aqueous sodium sulfide solution or the aqueous sodium polysulfide solution. As shown in FIG. 1 , the aqueous sodium sulfide solution or the aqueous sodium polysulfide solution is preferably delivered from a supply tank to a circulation tank by a supply pump, and from the circulation tank to a supply nozzle by a circulation pump. The aqueous sodium sulfide solution or the aqueous sodium polysulfide solution is then preferably supplied from the supply nozzle to the rotating disk surface to obtain a thin film of the aqueous sodium sulfide solution or the aqueous sodium polysulfide solution. A preferred method is to recover excess aqueous sodium sulfide solution or the aqueous sodium polysulfide solution that has not adhered to the disk surface in the circulation tank and then return it to the supply nozzle by the circulation pump. In this process, the disk surface is preferably maintained at 50 to 170°C by a disk heating means, and more preferably at 80 to 150°C. The disk heating means is not particularly limited, and a separate heating device may be provided, or the steam removed in the drying step described below may be used as the heating means. As in the drying step described below, the thin film formation step also preferably employs a method in which the inside of the container is kept under reduced pressure and an inert atmosphere.

[0015] The concentration of the aqueous sodium sulfide solution or aqueous sodium polysulfide solution used in the present invention is not particularly limited, but is preferably 3 to 60% by weight. If the concentration of the aqueous sodium sulfide solution or aqueous sodium polysulfide solution is less than 3% by weight, production efficiency may be significantly reduced, so the concentration is more preferably 5% by weight or more, and even more preferably 8% by weight or more. On the other hand, if the concentration of the aqueous sodium sulfide solution or aqueous sodium polysulfide solution exceeds 60% by weight, the aqueous solution may solidify in the piping during delivery, so the concentration is more preferably 55% by weight or less, and even more preferably 50% by weight or less.

[0016] In the drying step of the present invention, the thin film of the aqueous sodium sulfide or sodium polysulfide solution is dehydrated on the disk surface under reduced pressure and in an inert gas atmosphere. As the disk rotates, moisture is removed from the thin film of the aqueous sodium sulfide or sodium polysulfide solution on the disk surface. As in the thin film formation step, the disk surface is preferably maintained at 50 to 170°C, more preferably 80 to 150°C, by a disk heating means. In the drying step, the method of reducing the pressure is not particularly limited, and a method of reducing the pressure inside the container using a pressure reducing means such as a vacuum pump is preferably employed, which allows moisture to evaporate uniformly and efficiently and be removed as vapor. From the viewpoint of removing vapor present in the container, it is a preferred embodiment to provide an outlet for removing vapor at any position on the container.

[0017] Furthermore, in the drying step, the method for creating an inert gas atmosphere is not particularly limited, and a method of supplying an inert gas into the container using an inert gas supply means is preferably adopted. Examples of inert gases include nitrogen, helium, and argon, and nitrogen is preferably used. It is also preferable to have a recovery means for recovering the inert gas supplied into the container. The recovery means is not particularly limited, but the inert gas may be recovered together with the steam from the exhaust port for removing the steam, and it is also a preferred embodiment to separate the recovered inert gas from the steam and then supply the inert gas again into the container using the inert gas supply means.

[0018] According to the studies of the present inventors, in order to perform efficient production, the dehydration time is preferably 6 to 300 seconds, more preferably 10 to 240 seconds, and even more preferably 20 to 180 seconds. The dehydration time in the present invention refers to the time required for the drying step, and refers to the time from immediately after the thin film of the aqueous sodium sulfide solution or the aqueous sodium polysulfide solution is obtained in the thin film formation step to immediately before the anhydrous sodium sulfide shaped substance or the anhydrous sodium polysulfide shaped substance is removed from the disk surface in the separation step.

[0019] The degree of reduced pressure (absolute pressure) in the container in the drying step is preferably 1 to 40 kPa, more preferably 5 to 30 kPa. By controlling the degree of reduced pressure and the temperature of the disk surface, water can be efficiently removed from the aqueous sodium sulfide solution or aqueous sodium polysulfide solution formed into a thin film on the disk surface, and an anhydrous sodium sulfide shaped product or an anhydrous sodium polysulfide shaped product can be obtained.

[0020] Next, in the separation step of the present invention, a step of removing the anhydrous sodium sulfide shaped substance or anhydrous sodium polysulfide shaped substance obtained in the drying step from the disk surface is carried out. The method of removal is not particularly limited, but as shown in Fig. 1, it is preferable that a scraper is provided in the container, and the anhydrous sodium sulfide shaped substance or anhydrous sodium polysulfide shaped substance obtained in the drying step is scraped off the disk surface with the scraper as the disk rotates, and that a collection tank is provided in which the scraped off anhydrous sodium sulfide shaped substance or anhydrous sodium polysulfide shaped substance is collected. Since the anhydrous sodium sulfide shaped substance or anhydrous sodium polysulfide shaped substance exhibits deliquescent properties, a method of maintaining the container under reduced pressure and an inert atmosphere is preferably employed in the separation step as in the drying step.

[0021] The method for producing an anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product of the present invention is characterized by repeating the above-mentioned thin film formation step, drying step, and separation step in this order, thereby enabling the safe and efficient continuous production of an anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product. In the anhydrous sodium sulfide shaped product obtained by the present invention, the content of the anhydrous sodium sulfide component is preferably 95% by weight or more, more preferably 97% by weight or more, and even more preferably 98% by weight or more. In the anhydrous sodium polysulfide shaped product, the content of the anhydrous sodium polysulfide component is preferably 90% by weight or more, more preferably 91% by weight or more, and even more preferably 92% by weight or more. The contents of the anhydrous sodium sulfide component and the anhydrous sodium polysulfide component are usually 99.5% by weight or less, and preferably 99% by weight or less.

[0022] The water content of the anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product obtained by the present invention is preferably 3% by weight or less, more preferably 2% by weight or less, even more preferably 1% by weight or less, particularly preferably 0.5% by weight or less, and most preferably substantially free of water. The water content is usually 0.01% by weight or more.

[0023] In the anhydrous sodium sulfide tangible product obtained by the present invention, sodium hydrosulfide (NaSH), sodium carbonate (Na ２ CO ３ ), sodium sulfite (Na ２ SO ３ ), sodium thiosulfate (Na ２ S ２ O ３ ), but may contain impurities such as sodium hydrosulfide (NaSH), sodium carbonate (Na ２ CO ３ ), sodium sulfite (Na ２ SO ３ ) and sodium thiosulfate (Na ２ S ２ O ３The total content of the hydroxybenzoates and hydroxybenzoates is preferably 5% by weight or less, more preferably 4% by weight or less, even more preferably 3% by weight or less, and particularly preferably 2% by weight or less. The total content is usually 0.5% by weight or more.

[0024] In particular, the anhydrous sodium sulfide tangible product obtained by the present invention preferably has a sodium hydrosulfide (NaSH) component content of 1.0 wt% or less. From the viewpoint of minimizing impurities, the sodium hydrosulfide (NaSH) component content is more preferably 0.8 wt% or less, and even more preferably 0.5 wt% or less. The sodium hydrosulfide component content is usually 0.1 wt% or more.

[0025] In the anhydrous sodium polysulfide shaped product obtained in the present invention, sodium thiosulfate (Na ２ S ２ O ３ ), but sodium thiosulfate (Na ２ S ２ O ３ The content of the hydroxybenzoate component is preferably 10% by weight or less, more preferably 8% by weight or less, even more preferably 6% by weight or less, and particularly preferably 5% by weight or less. The content is usually 0.1% by weight or more.

[0026] The shape of the anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product obtained by the present invention is not particularly limited, and may be any shape such as flakes, chips, pellets, etc. The anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product obtained by the present invention has a low water content and can therefore be suitably used as a raw material for organic synthesis or industrial products which are sensitive to water.

[0027] The present invention will be explained in more detail below using examples.

[0028] Example 1: 2 L of a 10 wt % aqueous solution of sodium sulfide was supplied from a supply tank of a vacuum thin-film dryer (manufactured by Nishimura Iron Works Co., Ltd.) to a circulation tank by a supply pump. The 10 wt % aqueous solution of sodium sulfide was sent from the circulation tank to a supply nozzle by the circulation pump, and the 10 wt % aqueous solution of sodium sulfide was rotated from the tip of the supply nozzle with a heat transfer area of ​​0.4 m.２ The solution was continuously supplied to the disk surface, forming a thin film of 10 wt. % sodium sulfide aqueous solution on the disk surface. The excess sodium sulfide aqueous solution that did not adhere to the disk returned to the circulation tank and was then pumped from the circulation tank to the supply nozzle again. The vacuum (absolute pressure) inside the apparatus was 20 kPa abs, the disk steam pressure (gauge pressure) was 0.3 MPaG, the nitrogen flow rate was 50 L / min (99.9% or more), and the disk surface temperature was 140°C. As the disk rotated, the water in the thin film was dehydrated within 30 seconds to form a tangible substance. The tangible substance was scraped off the disk surface with a scraper and collected in a collection tank, yielding an anhydrous sodium sulfide tangible product. The composition of the resulting anhydrous sodium sulfide tangible product was analyzed using a combination of neutralization titration and oxidation-reduction titration. The moisture content was calculated by subtracting the other components from the total. Table 1 summarizes the results.

[0029] Example 2: 2 L of a 30 wt % aqueous solution of sodium tetrasulfide was supplied from the supply tank of a vacuum thin film dryer (manufactured by Nishimura Iron Works Co., Ltd.) to a circulation tank by a supply pump. The 30 wt % aqueous solution of sodium tetrasulfide was sent from the circulation tank to a supply nozzle by the circulation pump, and the 30 wt % aqueous solution of sodium tetrasulfide was rotated from the tip of the supply nozzle with a heat transfer area of ​​0.4 m. ２ The sodium tetrasulfide solution was continuously supplied to the disk surface, forming a thin film of sodium tetrasulfide aqueous solution on the disk surface. The excess sodium tetrasulfide aqueous solution that did not adhere to the disk returned to the circulation tank and was again sent from the circulation tank to the supply nozzle. The vacuum (absolute pressure) within the apparatus was 20 kPa abs, the disk steam pressure (gauge pressure) was 0.3 MPaG, the nitrogen flow rate was 50 L / min (99.9% or more), and the disk surface temperature was 140°C. As the disk rotated, the water in the thin film was dehydrated within 30 seconds to form a tangible product. The tangible product was scraped off the disk surface with a scraper and collected in a collection tank, yielding an anhydrous sodium tetrasulfide tangible product. The components of the resulting anhydrous sodium tetrasulfide tangible product were analyzed using a combination of colorimetry and redox titration. The results are shown in Table 2.

[0030] Comparative Example 1: A 15 wt. % sodium sulfide aqueous solution was continuously supplied to the heat exchange piping of a vacuum spray dryer at a rate of 7.2 L / h. The entire apparatus was depressurized to 10 Torr. The heat exchange piping was heated to 150°C, and the sprayed 15 wt. % sodium sulfide aqueous solution became a highly viscous liquid and adhered to the inside of the collector. The collector jacket was heated to 120°C to prevent moisture absorption and condensation. After cooling, the sodium sulfide solids adhered to the collector were recovered. The composition of the resulting sodium sulfide solids was analyzed using the method described in Example 1. The results are shown in Table 1. The sodium sulfide liquid was a highly viscous black liquid at the time of spraying, and it is believed to have condensed while corroding the heat exchange piping inside. The collector piping also turned black. It is assumed that the highly alkaline sodium sulfide aqueous solution became hot due to piping corrosion and sprayed out from the piping. This indicates problems with quality, durability, and safety.

[0031] Comparative Example 2: 200 g of flake sodium sulfide was placed in a 500-milliliter rotary evaporator, and nitrogen gas heated to 95°C was introduced into the bottom of the rotary evaporator at a rate of 10 normal liters per minute. After 9 minutes, whitening began, and after 60 minutes, the entire contents had almost completely turned white, so the introduction of nitrogen gas was stopped. The internal temperature at this time was 76°C. The rotary evaporator was then connected to a vacuum pump, and dehydration was carried out under reduced pressure and heating at a pressure of 40 Torr. 20 minutes after the start of reduced pressure and heating, some of the tangible matter began to melt.

[0032]

[0033]

[0034] REFERENCE SIGNS LIST 1 Vacuum thin film dryer 2 Container 3 Sodium sulfide aqueous solution or sodium polysulfide aqueous solution 4 Supply tank 5 Supply pump 6 Circulation tank 7 Circulation pump 8 Supply nozzle 9 Rotating shaft 10 Disk 11 Scraper 12 Anhydrous sodium sulfide shaped material or anhydrous sodium polysulfide shaped material 13 Collection tank

Claims

1. A method for producing anhydrous sodium sulfide shaped matter or anhydrous sodium polysulfide shaped matter, comprising the steps of: (1) using an aqueous sodium sulfide solution or an aqueous sodium polysulfide solution as a starting material, and supplying said aqueous sodium sulfide solution or an aqueous sodium polysulfide solution to a disk surface to obtain a thin film of said aqueous sodium sulfide solution or an aqueous sodium polysulfide solution; (2) drying said thin film of said aqueous sodium sulfide solution or an aqueous sodium polysulfide solution on the disk surface under reduced pressure and in an inert gas atmosphere; and (3) removing from the disk surface the anhydrous sodium sulfide shaped matter or anhydrous sodium polysulfide shaped matter obtained in the drying step, by repeating the steps in this order to continuously obtain anhydrous sodium sulfide shaped matter or anhydrous sodium polysulfide shaped matter.

2. The method for producing anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product according to claim 1, wherein the dehydration time in the drying step is 6 to 300 seconds.

3. The method for producing anhydrous sodium sulfide shaped products or anhydrous sodium polysulfide shaped products according to claim 1 or 2, wherein the concentration of the aqueous sodium sulfide solution or the aqueous sodium polysulfide solution is 3 to 60% by weight.

4. The method for producing an anhydrous sodium sulfide shaped product according to any one of claims 1 to 3, wherein the content of anhydrous sodium sulfide component in said anhydrous sodium sulfide shaped product is 95% by weight or more.

5. A method for producing an anhydrous sodium polysulfide shaped product according to any one of claims 1 to 3, wherein the content of anhydrous sodium polysulfide component in said anhydrous sodium polysulfide shaped product is 90% by weight or more.

6. A method for producing an anhydrous sodium sulfide shaped product or anhydrous sodium polysulfide shaped product according to any one of claims 1 to 3, wherein the water content in the anhydrous sodium sulfide shaped product or the anhydrous sodium polysulfide shaped product is 3% by weight or less.

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