阅读说明：本技术 连续脱水方法以及聚亚芳基硫醚的制造方法 (Continuous dehydration method and method for producing polyarylene sulfide ) 是由 宫原道寿 铃木贤司 坂部宏 于 2019-07-12 设计创作，主要内容包括：本发明的用于PAS的制造的原料混合物的连续脱水方法同时并行地进行原料混合物的供给和脱水、以及脱水而含水量减少的原料混合物的抽出。通过式(1)求出的脱水效率指数为0.3以上。式(1)中,脱水时间是包含有机极性溶剂的水解所消耗的水分在内而含水量减少的原料混合物中的相对于每1摩尔硫源的水分量成为1.7摩尔以下为止的时间。脱水效率指数＝[含水量减少的原料混合物中的硫源的摩尔数(mol)]/[脱水时间(hr)×(脱水槽的总内容积(L))~(2/3)]···(1)。(The continuous dehydration method of a raw material mixture for use in the production of PAS of the present invention simultaneously performs the supply and dehydration of the raw material mixture and the extraction of the raw material mixture dehydrated to reduce the water content. The dehydration efficiency index obtained by the formula (1) is 0.3 or more. In the formula (1), the dehydration time is a time until the amount of water in the raw material mixture, which contains water consumed for hydrolysis of the organic polar solvent and has a reduced water content, becomes 1.7 moles or less per 1 mole of the sulfur source. Dehydration efficiency index [ moles of sulfur source in reduced water content feed mixture(mol)]/[ dehydration time (hr) × (total internal volume of dehydration tank (L)) 2/3 ]···(1)。)

1. A continuous dehydration method of a raw material mixture for the production of a polyarylene sulfide, which is carried out before the production of the polyarylene sulfide,

the continuous dehydration process is carried out simultaneously in parallel:

a supply step of continuously supplying a sulfur source and an organic polar solvent constituting the raw material mixture to a continuous dehydration apparatus having one or more dehydration tanks;

a dehydration step of continuously removing water from the raw material mixture; and

a drawing step of continuously drawing out the raw material mixture having a reduced water content from the continuous dehydration device,

the temperature of the dehydration tank to which the sulfur source and the organic polar solvent are supplied in the continuous dehydration device is 110 to 270 ℃,

the dehydration efficiency index obtained by the following formula (1) is 0.3 or more,

dehydration efficiency index [ the number of moles (mol) of sulfur source in the reduced water content feed mixture]/[ dehydration time (hr) × (total internal volume of dehydration tank (L))^2/3]···(1)

In the formula (1), the dehydration time is a time until the amount of water in the raw material mixture containing water consumed for hydrolysis of the organic polar solvent and having a reduced water content becomes 1.7 moles or less per 1 mole of the sulfur source.

2. The continuous dewatering process according to claim 1,

the continuous dehydration apparatus has a plurality of dehydration tanks that communicate with each other via a gas phase, the dehydration tanks are connected in sequence, and the raw material mixture moves to the dehydration tanks in sequence.

3. The continuous dewatering method according to claim 1 or 2,

in the supplying step, a polymerization assistant for the polyarylene sulfide is also supplied.

4. The continuous dewatering method according to any one of claims 1 to 3,

the raw material mixture contains a dehydration assistant.

5. The continuous dewatering method according to any one of claims 1 to 4,

the sulfur source is at least one of alkali metal sulfide, alkali metal hydrosulfide and hydrogen sulfide.

6. The continuous dewatering method according to any one of claims 1 to 5,

the water content of the raw material mixture before the dehydration step is 3mol or more per 1mol of the sulfur source, and the water content of the raw material mixture after the dehydration step, in which the water content is reduced, is in the range of 0.5 to 1.7mol per 1mol of the sulfur source.

7. The continuous dewatering method according to any one of claims 1 to 6,

the water is removed in a range of 190 to 270 ℃ for 50% or more of the time for performing the dehydration step.

8. The continuous dewatering method according to any one of claims 1 to 7,

further comprising: a resupply step of recovering the sulfur source volatilized in the dehydration step and resupplying the recovered sulfur source to the continuous dehydration apparatus.

9. The continuous dewatering method according to any one of claims 1 to 8,

the material of the dehydration tank is stainless steel.

10. A method for producing a polyarylene sulfide, which comprises polymerizing a raw material mixture having a reduced water content obtained by the continuous dehydration method according to any one of claims 1 to 9.

Technical Field

The present invention relates to a method for continuously dehydrating a raw material mixture for producing a polyarylene sulfide, and a method for producing a polyarylene sulfide using the continuous dehydration method.

Background

In the production of a polyarylene sulfide (hereinafter, abbreviated as "PAS" in some cases), a sulfur source and the like as raw materials contain water, and therefore, it is necessary to dehydrate the raw materials before the polymerization step of PAS. For example, patent documents 1 to 7 disclose batch dehydration methods for dehydrating the raw material in a polymerization reactor in a batch manner under normal pressure or under pressure.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. JP-B45-3368

Patent document 2: japanese laid-open patent publication No. Sho 51-144496

Patent document 3: japanese laid-open patent publication No. Sho 58-42623

Patent document 4: japanese laid-open patent publication No. Sho 59-105027

Patent document 5: japanese laid-open patent publication No. Sho 60-104130

Patent document 6: japanese laid-open patent publication No. 7-173290

Patent document 7: japanese laid-open patent publication No. JP-A2002-505361

Disclosure of Invention

Problems to be solved by the invention

However, in the batch dehydration method as described above, there are problems as follows: when dehydration is performed in a short time, foaming occurs, a nozzle is closed, or overflow to a dehydration tower occurs. In the batch dehydration method, if the generation of foam is to be suppressed, the dehydration step takes a long time. Alternatively, the height of the dewatering tank may be increased to prevent the nozzle from being closed by bubbling and the water from overflowing into the dewatering tower.

Accordingly, an object of the present invention is to provide a continuous dehydration method of a raw material mixture for producing PAS, which can suppress the occurrence of foaming and flooding and can perform dehydration in a short time.

Technical scheme

The present inventors have conducted intensive studies to solve the above problems, and as a result, have completed the present invention based on the following findings: by continuously supplying a raw material mixture for use in the production of PAS, dehydrating the raw material mixture, and extracting the raw material mixture having a reduced water content by dehydration, the occurrence of rapid foaming and flooding can be suppressed, and dehydration of the raw material mixture can be performed in a short time.

That is, the present invention is a continuous dehydration method of a raw material mixture for the production of a polyarylene sulfide, which is performed before the production of the polyarylene sulfide, the continuous dehydration method simultaneously performing in parallel: a supply step of continuously supplying a sulfur source and an organic polar solvent constituting the raw material mixture to a continuous dehydration apparatus having one or more dehydration tanks; a dehydration step of continuously removing water from the raw material mixture; and a step of continuously extracting the raw material mixture having a reduced water content from the continuous dehydration device, wherein the temperature of the dehydration tank to which the sulfur source and the organic polar solvent are supplied in the continuous dehydration device is 110 to 270 ℃, and the dehydration efficiency index obtained by the following formula (1) is 0.3 or more.

Dehydration efficiency index [ the number of moles (mol) of sulfur source in the reduced water content feed mixture]/[ dehydration time (hr) × (total internal volume of dehydration tank (L))^2/3···(1)

(in the formula (1), the dehydration time is a time until the amount of water contained in the raw material mixture containing water consumed for hydrolysis of the organic polar solvent and having a reduced water content becomes 1.7 moles or less per 1 mole of the sulfur source.)

Advantageous effects

The continuous dehydration method of the present invention can suppress the occurrence of rapid foaming and flooding, and can perform dehydration of a raw material mixture for the production of a polyarylene sulfide in a short time.

Drawings

Fig. 1 is a partial sectional view showing an embodiment of a continuous dewatering device used in the continuous dewatering method according to the present embodiment.

Fig. 2 is a partial sectional view showing another embodiment of the continuous dewatering device used in the continuous dewatering method according to the present embodiment.

Detailed Description

The present invention is not limited to the following embodiments, and may be modified as desired within the scope of the technical idea.

The continuous dehydration method of the present embodiment is a continuous dehydration method of a raw material mixture for the production of a polyarylene sulfide, which is performed before the production of the polyarylene sulfide, and simultaneously performs: continuously supplying a sulfur source and an organic polar solvent constituting a raw material mixture to a continuous dehydration apparatus; a step of continuously removing water from the raw material mixture; and continuously extracting the raw material mixture having a reduced water content from the continuous dehydration device.

Before describing the details of the continuous dewatering method according to the present embodiment, an example of a continuous dewatering apparatus suitable for carrying out the continuous dewatering method according to the present embodiment will be described. The continuous dewatering method according to the present embodiment is not limited to the case of using the continuous dewatering device described below.

[ continuous dehydration device ]

In the continuous dewatering method according to the present embodiment, for example, a continuous dewatering apparatus shown in fig. 1 or fig. 2 can be used. Hereinafter, each of the continuous dewatering apparatuses will be described.

[ first embodiment of continuous dehydration apparatus ]

A first mode of the continuous dewatering apparatus will be described with reference to fig. 1. FIG. 1 is a schematic configuration of a continuous dewatering device according to a first embodiment.

As shown in fig. 1, the continuous dewatering device 100 includes: a dehydration chamber 2; a raw material supply line 3 connected to the dehydration chamber 2; a raw material mixture extraction line 4 connected to the dehydration chamber 2 for extracting the raw material mixture having a reduced water content; a first gas-liquid separation section 13 and a second gas-liquid separation section 17 connected to the dehydration chamber 2 via an exhaust line 12; and a sulfur source recovery unit 19 for recovering a sulfur source contained in the gas from the second gas-liquid separation unit 17.

< dehydration Chamber >

The dehydration chamber 2 is a cylindrical tank extending from the raw material supply side toward the raw material mixture extraction side where the water content decreases. Inside the dehydration chamber 2, the raw material mixture withdrawal side, which decreases in water content from the raw material supply side, is divided into two dehydration tanks 1a and 1 b. The dehydration tank 1a and the dehydration tank 1b are partitioned by a partition wall 5 so as to communicate with each other via a gas phase. A raw material supply line 3 to which raw material is supplied is connected to the dehydration tank 1a side of the dehydration chamber 2. Further, a raw material mixture extraction line 4 for extracting the raw material mixture having a reduced water content is connected to the dehydration tank 1b side of the dehydration chamber 2. The raw material for the dehydration is supplied from the raw material supply line 3 to the dehydration tank 1a, and the raw material mixture in the dehydration tank 1a moves to the dehydration tank 1b over the partition wall 5. Thereafter, the raw material mixture in the dehydration tank 1b is extracted to the outside of the dehydration chamber 2 through the raw material mixture extraction line 4. In the present specification, the "raw material mixture" refers to a mixture of a sulfur source and an organic polar solvent to be subjected to dehydration treatment. In the case where the sulfur source and the organic polar solvent are supplied separately, a raw material mixture is formed in the dehydration tank. The components may be supplied in a premixed state as described later. Further, details will be described later, and other polymerization aids and the like may be contained in the raw material mixture.

The dehydration tank is preferably made of a material resistant to high temperature and corrosion, and examples thereof include metal materials such as titanium, zirconium, and nickel, alloys (Hastelloy, inconel, and the like) containing these as a main component, stainless steel, and the like. The material of the dewatering tank is more preferably stainless steel from the viewpoints of resource saving, cost reduction, ease of processing, and the like. Examples of stainless steel include SUS304 and SUS 316.

The dehydration chamber 2 may be provided with a temperature control device (not shown) so that the dehydration tank 1a and the dehydration tank 1b can be independently temperature-controlled.

The dehydration tank 1a and the dehydration tank 1b communicate with each other via a gas phase. As a result, the pressure of the gas phase in the dehydration chamber 2 becomes uniform. This removes water from both the dewatering tanks 1a and 1b in the same manner. Therefore, the amount of water in the dehydrated mixture can be reduced from the dehydration tank 1a toward the dehydration tank 1b, that is, from the upstream side toward the downstream side in the moving direction of the dehydrated mixture. Further, since the boiling point of the dehydrated mixture increases as the amount of water decreases, the temperature of the dehydration tank can be increased from the upstream side to the downstream side in the moving direction of the dehydrated mixture, and dehydration can be further promoted.

In the dehydration chamber 2, a stirring blade 7a for stirring the raw material mixture 6a in the dehydration tank 1a and a stirring blade 7b for stirring the raw material mixture 6b in the dehydration tank 1b are provided on the same stirring shaft 8. The stirring shaft 8 is provided to penetrate the dehydration chamber 2. A rotation driving device 9 for rotating the stirring shaft 8 is provided at the end of the stirring shaft 8 on the dewatering tank 1b side.

The shape of the dewatering chamber 2 is not particularly limited, and may be appropriately selected according to the purpose.

< raw Material supply line >

The raw material supply line 3 is a line for supplying a raw material of PAS, that is, a raw material to be subjected to dehydration treatment to the dehydration chamber 2. In the present specification, the term "raw material of PAS" means that the raw material may contain an aromatic compound or a solvent necessary for polymerization of PAS in addition to a sulfur source which is a constituent component of PAS.

The raw material supply line 3 may be a liquid phase in which a raw material of PAS is supplied to the dehydration tank 1a via a gas phase, or may be a liquid phase in which a raw material of PAS is directly supplied to the dehydration tank 1 a. The raw material is supplied through the gas phase if the supply port of the raw material supply line 3 is provided at a position higher than the height of the partition wall 5 in the dehydration chamber 2, and is directly supplied to the liquid phase if the supply port of the raw material supply line 3 is provided at a position lower than the height of the partition wall 5 in the dehydration chamber 2.

In fig. 1, only one raw material supply line 3 is shown, but lines for supplying a raw material different from each other in the sulfur source and the organic polar solvent may be provided. The raw materials to be supplied to the dehydration treatment may be supplied in a premixed state, and in this case, one raw material supply line 3 may be provided.

< raw Material mixture extraction line >

The raw material mixture extraction line 4 is a line for extracting the dehydrated raw material mixture having a reduced water content from the dehydration chamber 2. In order to prevent the dehydrated raw material mixture from flowing backward from the dehydration tank 1b to the dehydration tank 1a, the raw material mixture extraction line 4 is connected to the dehydration tank 1b at a position lower than the height of the partition 5.

< first gas-liquid separation section >

The first gas-liquid separation section 13 is a device for condensing the organic polar solvent from the gas-phase exhaust gas from the dehydration chamber 2 and resupplying the same to the dehydration chamber 2. The first gas-liquid separation section 13 is connected to the dewatering chamber 2 via a gas exhaust line 12. The first gas-liquid separation section 13 may use a known distillation column or the like. An organic polar solvent resupply line 14 for resupplying the organic polar solvent of the liquid generated by the gas-liquid separation to the dehydration chamber 2, and a first gas recovery line 15 for recovering the remaining gas are connected to the first gas-liquid separation unit 13.

< second gas-liquid separator >

The second gas-liquid separation unit 17 is a device for feeding the gas remaining in the gas phase in the first gas recovery line 15 to the sulfur source recovery unit 19, condensing the water, and discarding the condensed water through the wastewater line 16. The second gas-liquid separation unit 17 is connected to the first gas-liquid separation unit 13 via a first gas recovery line 15, and the other end is connected to a sulfur source recovery unit 19. A known condenser or the like can be used for the second gas-liquid separation section 17. A wastewater line 16 for discarding water generated by gas-liquid separation and a second gas recovery line 18 for delivering the remaining gas to the sulfur source recovery unit are connected to the second gas-liquid separation unit 17.

< Sulfur Source recovery section >

The sulfur source recovery unit 19 is connected to the other end of the second gas recovery line 18. A sulfur source absorbent supply line 21 for supplying a sulfur source absorbent such as sodium hydroxide is connected to one end (e.g., the upper portion) of the sulfur source recovery unit 19. In the sulfur source recovery unit 19, the sulfur source recovered from the second gas recovery line 18 is absorbed by the sulfur source absorbent supplied from the sulfur source absorbent supply line 21. The sulfur source absorbent having absorbed the sulfur source is supplied to the dehydration tank 1a through the sulfur source resupply line 20. Unabsorbed gas is discharged from the exhaust line 22.

With the above configuration, in the continuous dehydration apparatus 100, the raw material of PAS to be subjected to the dehydration treatment can be continuously supplied to the dehydration chamber 2, water can be continuously removed from the raw material mixture, the raw material mixture with a reduced water content can be continuously extracted from the dehydration chamber 2, and they can be simultaneously performed in parallel.

(modification of continuous dehydrator 100)

In the continuous dewatering device 100 described above, the dewatering chamber 2 is divided into two dewatering grooves, but the dewatering chamber 2 may have one or more dewatering grooves, for example, may be divided into three or more dewatering grooves, or may have only one dewatering groove instead of two or more dewatering grooves. It is preferable to have a plurality of dewatering tanks in order to suppress the occurrence of foaming and flooding and to perform dewatering in a short time. In addition, the plurality of dehydration tanks may be designed to be connected in sequence and the raw material mixture may be moved to each dehydration tank in sequence. For example, when the dehydration chamber 2 is divided into three or more dehydration tanks, the dehydration tanks may be designed such that the height of the partition wall partitioning each dehydration tank is gradually reduced from the raw material supply side toward the raw material mixture extraction side where the water content is reduced, and the liquid level of each dehydration tank is gradually reduced. In the present specification, "sequentially connected" means that all of them are preferably connected in series, but they may be partially connected in parallel.

In the continuous dewatering device 100, the dewatering chamber 2 may be provided obliquely. When the dehydration chamber 2 is disposed obliquely, the dehydration tank 1a connected to the raw material supply line 3 may be higher than the dehydration tank 1b connected to the raw material mixture extraction line 4 with respect to the maximum liquid level of the liquid that can be contained. In the dewatering tanks other than the dewatering tank 1a at the most upstream side in the moving direction of the raw material mixture, the minimum height of the partition wall on the upstream side in the moving direction is higher than the maximum liquid level of the dewatering tank. That is, in the dewatering tank 1b, the minimum height of the partition 5 on the upstream side in the moving direction is higher than the maximum liquid level of the dewatering tank 1 b. This prevents a reverse flow from the dewatering tank 1b to the dewatering tank 1 a. The dehydration tank 1a and the dehydration tank 1b can accommodate the raw material mixture 6a and the raw material mixture 6b, respectively.

[ second embodiment of continuous dehydration apparatus ]

Next, a second embodiment of the continuous dewatering device will be described with reference to fig. 2. FIG. 2 is a schematic configuration of a continuous dehydrating apparatus according to a second embodiment. For convenience of explanation, members having the same functions as those described in the above embodiments are given the same reference numerals, and the explanation thereof will not be repeated.

As shown in fig. 2, the continuous dewatering device 200 includes: dehydration tanks 1c and 1d connected to each other via a gas phase communication section 10 and a raw material mixture communication section 11; a raw material supply line 3 connected to the dehydration tank 1 c; a raw material mixture extraction line 4 connected to the dehydration tank 1 d; a first gas-liquid separation unit 13 connected to the dehydration tank 1c through a gas discharge line 12; a second gas-liquid separation section 17; and a sulfur source recovery unit 19.

The dehydration tanks 1c and 1d are independently present, and each dehydration tank communicates with each other via a gas phase communication section 10 and a raw material mixture communication section 11.

The raw material for the dehydration process is supplied from the raw material supply line 3 to the dehydration tank 1c, and the raw material mixture communication section 11 is provided with: when the raw material mixture in the dehydration tank 1c exceeds the set height of the raw material mixture communication portion 11, the raw material mixture moves to the dehydration tank 1d through the raw material mixture communication portion 11. Thereafter, the raw material mixture in the dehydration tank 1d is extracted from the continuous dehydration apparatus 200 through the raw material mixture extraction line 4. Therefore, in the continuous dewatering device 200, the raw material mixture can be sequentially moved from the dewatering tank located above to the dewatering tank located further below by the height difference of the dewatering tanks. With this configuration, the raw material mixture moves in accordance with the difference in height and the gravity of the dehydration tank, and therefore, it is not necessary to provide another unit for moving the raw material mixture to the next dehydration tank.

The dewatering tank 1d is disposed vertically below the dewatering tank 1 c.

Stirring shafts (8a, 8b) having stirring blades (7a, 7b) are provided in the dewatering tanks 1c and 1d, respectively. Each stirring shaft is provided with a rotary drive (9a, 9 b).

A gas discharge line 12 connected to the first gas-liquid separation section 13 is connected to the dewatering tank 1 c. However, since the dehydration tank 1c and the dehydration tank 1d communicate via the gas phase communication section 10, the pressure of the gas phase in the dehydration tank 1c and the dehydration tank 1d becomes uniform.

In the continuous dehydrator 200 having the above configuration, the raw material of PAS to be subjected to the dehydration treatment can be continuously supplied to the continuous dehydrator 200, water can be continuously removed from the raw material mixture, the raw material mixture having a reduced water content can be continuously extracted from the continuous dehydrator 200, and they can be simultaneously performed in parallel.

[ continuous dehydration method ]

Next, the continuous dewatering method according to the present embodiment will be described in detail.

The continuous dehydration method of the present embodiment is performed simultaneously in parallel: a supply step of continuously supplying a sulfur source and an organic polar solvent constituting a raw material mixture to a continuous dehydration apparatus having one or more dehydration tanks; a dehydration step of continuously removing water from the raw material mixture; and a drawing step of continuously drawing out the raw material mixture with the reduced water content from the continuous dehydration device. Further, the temperature of a dehydration tank to which the sulfur source and the organic polar solvent are supplied in the continuous dehydration apparatus is 110 to 270 ℃, and the dehydration efficiency index obtained by the following formula (1) is 0.3 or more:

dehydration efficiency index [ the number of moles (mol) of sulfur source in the reduced water content feed mixture]/[ dehydration time (hr) × (total internal volume of dehydration tank (L))^2/3]···(1)

In the formula (1), the dehydration time is a time until the amount of water in the raw material mixture, which contains water consumed for hydrolysis of the organic polar solvent and has a reduced water content, becomes 1.7 moles or less per 1 mole of the sulfur source.

(supply step)

In the supply step, the sulfur source and the organic polar solvent constituting the raw material mixture are continuously supplied to a continuous dehydration apparatus having one or more dehydration tanks. In the present specification, "continuously supplying" means continuously supplying for a certain period of time, unlike a batch type in which all of the sulfur source and the organic polar solvent to be supplied for dehydration are supplied at once. It is preferable to continuously supply the sulfur source and the organic polar solvent constituting the raw material mixture at a constant flow rate from the viewpoint of sufficiently suppressing rapid foaming.

< Sulfur Source >

Examples of the sulfur source include at least one selected from the group consisting of hydrogen sulfide, an alkali metal sulfide, and an alkali metal hydride. In the case of using an alkali metal hydride and hydrogen sulfide, an alkali metal hydroxide is used together with the sulfur source. Therefore, more water may be generated. Therefore, when the alkali metal hydride and hydrogen sulfide are used as the sulfur source, the continuous dehydration method of the present embodiment having excellent dehydration efficiency is preferably used.

The sulfur source may be treated in the form of, for example, an aqueous slurry or an aqueous solution, and is preferably in the form of an aqueous solution from the viewpoint of workability such as metering properties and transportability.

Examples of the alkali metal sulfide include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide.

Examples of the alkali metal hydrosulfide include lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, and cesium hydrosulfide.

< organic polar solvent >

Examples of the organic polar solvent include: n, N-dialkylformamide compounds or N, N-dialkylacetamide compounds such as N, N-dimethylformamide and N, N-dimethylacetamide; caprolactam compounds such as epsilon-caprolactam and N-methyl-epsilon-caprolactam or N-alkyl caprolactam compounds; pyrrolidone compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone, and N-cyclohexyl-2-pyrrolidone, N-alkyl pyrrolidone compounds, and N-cycloalkyl pyrrolidone compounds; n, N-dialkyl imidazolidinone compounds such as 1, 3-dialkyl-2-imidazolidinone; tetraalkylurea compounds such as tetramethylurea; hexaalkylphosphoric triamide compounds such as hexamethylphosphoric triamide. The organic polar solvent is preferably an amide compound, a caprolactam compound, a pyrrolidone compound, or an imidazolidinone compound, more preferably an N-alkylpyrrolidone compound or an N-cycloalkylpyrrolidone compound, and still more preferably N-methyl-2-pyrrolidone (NMP), from the viewpoint of promoting the polymerization reaction.

In the supply step, the total amount of the sulfur source to be supplied is preferably 0.05 to 1mol, more preferably 0.1 to 0.7 mol, and still more preferably 0.2 to 0.6 mol, in terms of sulfur atom, per 100g of the solvent.

The temperature of the dehydration tank (for example, dehydration tank 1a in fig. 1) to which the sulfur source and the organic polar solvent are supplied may be 110 to 270 ℃, preferably 140 to 250 ℃, and more preferably 150 to 235 ℃. When a plurality of dehydration tanks are provided, the temperature of the dehydration tanks other than the dehydration tank to which the sulfur source and the organic polar solvent are supplied may be 140 to 270 ℃, preferably 150 to 260 ℃, and more preferably 180 to 240 ℃.

< polymerization auxiliary >

In the supply step, a polymerization assistant for the polyarylene sulfide may be further supplied. From the viewpoint of handling property and easiness of obtaining in polymerization of PAS, an aqueous polymerization aid or a water-containing polymerization aid is preferable. On the other hand, since the presence of water inhibits the polymerization of PAS, it is preferable to dehydrate the water carried by the polymerization assistant together with the raw material mixture.

Specific examples of such a polymerization assistant include organic carboxylates, organic sulfonates, alkali metal sulfates, alkaline earth metal oxides, alkali metal phosphates, and alkaline earth metal phosphates. Among them, sodium salt, potassium salt or lithium salt of organic carboxylic acid having C2-C12 is preferably used. More specifically, sodium salts, potassium salts, or lithium salts of short-chain fatty acids or aromatic carboxylic acids are exemplified. Among them, preferred are sodium salts, potassium salts, and lithium salts of acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid, valeric acid, caproic acid, lactic acid, succinic acid, and benzoic acid, phenylacetic acid, p-methylbenzoic acid, and the like. The organic carboxylic acid salt may be used singly or in combination of two or more. From the viewpoint of promoting the polymerization reaction, etc., sodium or lithium salts of acetic acid, caproic acid, valeric acid, isovaleric acid, 2-ethylbutyric acid, benzoic acid are preferably used.

These materials may be used alone, or two or more of them may be used in combination as long as they can produce PAS.

The amount of the polymerization assistant to be supplied varies depending on the kind of the compound, and is usually supplied in the range of 0.01 to 10 mol, preferably 0.1 to 2mol, more preferably 0.2 to 1.8mol, and particularly preferably 0.3 to 1.7mol, based on 1mol of the sulfur source to be supplied.

(dehydration step)

In the dehydration step, water is continuously removed from the raw material mixture. The dehydration step may be carried out at a temperature in the range of 190 to 270 ℃, preferably 193 to 250 ℃, more preferably 195 to 235 ℃ for 50% or more, preferably 70% or more, more preferably 90% or more of the time for the dehydration step. If the temperature in the dehydration step exceeds 270 ℃, the sulfur source is easily decomposed.

In the present specification, the term "time for performing the dehydration step" means a time until the raw material mixture having a reduced water content is extracted from the dehydration apparatus after the sulfur source and the organic polar solvent constituting the raw material mixture are supplied. This time is calculated taking into account the material balance.

By setting the dehydration tank to the above temperature range, water in the raw material mixture is vaporized and removed from the raw material mixture, thereby dehydrating the raw material mixture.

In the present specification, "continuously removing water from the raw material mixture" means continuously removing water from the raw material mixture for a certain time.

< dehydration auxiliary >

In the continuous dehydration method of the present embodiment, a dehydration assistant may be contained in the raw material mixture. The dehydration assistant may be supplied to the dehydration tank together with the raw material, or may be supplied to the dehydration tank in advance. By including a dehydration assistant in the raw material mixture, dehydration can be promoted by azeotropy.

In the present specification, the "dehydration auxiliary" refers to an azeotropic agent that promotes dehydration of a raw material mixture by azeotropy. The dehydration assistant may be any one known to those skilled in the art, and examples of the dehydration assistant include, but are not limited to, benzene, toluene, xylene, chlorobenzene, and chlorobenzene.

The amount of dehydration aid in the raw material mixture may be used in an appropriate amount depending on the amount of water to be removed and the embodiment of the process.

< Water content of raw Material mixture >

From the viewpoint of availability, handling properties, and the like, the water content of the raw material mixture before the dehydration step is preferably 3mol or more, more preferably 3.5mol or more, and still more preferably 4mol or more per 1mol of the sulfur source. The water content is not limited to the amount of water such as a sulfur source or the amount of water generated therefrom, but is the total amount of water added to other components such as a polymerization assistant which may contain water.

The water content of the raw material mixture having a reduced water content after the dehydration step (hereinafter, sometimes simply referred to as "dehydrated raw material mixture") is usually 1.8 to 2mol or less per 1mol of the sulfur source. The minimum water content suitable for the polymerization reaction of PAS is preferably in the range of 0.5 to 1.7mol, more preferably in the range of 0.6 to 1.5mol, and still more preferably in the range of 0.7 to 1.4 mol. If the water content in the dehydrated raw material mixture exceeds 1.8mol, polymerization of PAS is inhibited.

The dehydration tank to which the raw material is supplied has a higher water content in the raw material mixture than the other dehydration tanks. Therefore, the amount of water vaporized from the raw material mixture in the dehydration tank (dehydration tank 1a in fig. 1) increases, and the temperature of the dehydration tank becomes lower than the temperature of the raw material mixture in the dehydration tank (dehydration tank 1b in fig. 1) downstream thereof. This can efficiently reduce or prevent the occurrence of rapid foaming and flooding in the dewatering tank to which the raw material is supplied.

(extraction step)

In the extraction step, the raw material mixture having a reduced water content is continuously extracted from the continuous dehydration device.

In the present specification, "continuously withdrawing the raw material mixture with a reduced water content" means not withdrawing all of the raw material mixture with a reduced water content at once, but continuously withdrawing for a certain period of time.

In the continuous dewatering method according to the present embodiment, the supply step, the dewatering step, and the extraction step are performed simultaneously and in parallel. That is, while the dehydration step is being performed, the supply of the raw material for dehydration is continued, and the extraction of the raw material mixture whose water content is reduced by dehydration is also performed.

< index of dewatering efficiency >

In the continuous dehydration method of the present embodiment, the dehydration efficiency index obtained by the following formula (1) is 0.3 or more, preferably 0.6 or more, more preferably 1.0 or more, and further preferably 1.7 or more. The higher the dehydration efficiency index, the more efficient the dehydration is.

Dehydration efficiency index [ moles (mol) of sulfur source in raw material mixture with reduced water content)]/[ dehydration time (hr) × (total internal volume of dehydration tank (L))^2/3]···(1)

The dehydration time in the formula (1) is a time (hr) in which the water content in the raw material mixture before the dehydration step is a minimum water content that can be used for the polymerization reaction of PAS. That is, the dehydration time is a time until the amount of water in the raw material mixture containing water consumed for hydrolysis of the organic polar solvent and having a reduced water content is 1.7mol or less, preferably 1.5mol or less, and particularly preferably 1.05 mol or less, per 1mol of the sulfur source.

For example, as shown in fig. 1, when the continuous dehydration apparatus has a dehydration chamber including one or more dehydration tanks, the total internal volume of the dehydration tanks in the formula (1) is the total amount of internal volumes including the gas phase portion of each dehydration tank, that is, the internal volume of the dehydration chamber. In addition, as shown in fig. 2, when the dewatering tanks are independent of each other, the total internal volume of the dewatering tanks in the formula (1) is the total amount of the internal volumes of the dewatering tanks.

The dehydration efficiency index is represented by the above range: the raw material mixture can be dehydrated to the minimum water content for the polymerization reaction of PAS in a short time without increasing the volume of the dehydration tank. In addition, the dehydration tank having the same volume means that more raw material mixture can be dehydrated in the same dehydration time.

(other steps)

The continuous dehydration method of the present embodiment may further include other steps as necessary. As an example of the other step, there is a resupply step of recovering the sulfur source volatilized in the dehydration step and resupplying the recovered sulfur source to the continuous dehydration tank. By resupplying the sulfur source volatilized out in the dehydration step to the dehydration tank, it is possible to prevent the decrease of the sulfur source to be supplied and to prevent the discharge of harmful sulfur sources such as hydrogen sulfide to the environment.

In the conventional batch dehydration method, it is necessary to feed the sulfur source volatilized in the dehydration step into a polymerization reaction tank in order to recover and utilize the sulfur source. Therefore, the stoichiometric balance between the dihalo aromatic compound and the sulfur source is lost, and the polymerization degree of PAS is often varied. On the other hand, in the present embodiment, since the dehydration step and the supply step are performed simultaneously and in parallel, the sulfur source volatilized in the dehydration step can be resupplied to the dehydration tank. This makes the polymerization degree of PAS less likely to vary.

In the conventional batch dehydration method, if the raw material is supplied in the above-described temperature range, bumping or rapid foaming is likely to occur. Further, if foaming occurs, there is a possibility that the foam overflows the dehydration column. Therefore, in the conventional batch dehydration method, it is necessary to set the temperature at the time of supplying the raw material to a low temperature and gradually increase the temperature to perform dehydration. On the other hand, in the continuous dewatering method of the present embodiment, the following effects are exhibited: it is not necessary to carry out dehydration by gradually raising the temperature, and overflow due to bumping and rapid foaming is less likely to occur even if dehydration is carried out in a high temperature state from the time of supplying the raw material to the continuous dehydration apparatus.

[ Process for producing polyarylene sulfide ]

The method for producing a polyarylene sulfide according to the present embodiment performs polymerization using the raw material mixture having a reduced water content obtained by the above-described continuous dehydration method. The polymerization is not particularly limited as long as it is a conventionally known method, and it can be carried out by a known method such as a continuous method or a batch method.

In general, PAS can be produced by mixing a dehydrated raw material mixture and a dihalo aromatic compound in a reaction tank and carrying out a polymerization reaction of a sulfur source and the dihalo aromatic compound in an organic polar solvent.

Examples of the dihalo aromatic compound include o-dihalobenzene, m-dihalobenzene, p-dihalobenzene, dihalotoluene, dihalonaphthalene, methoxy-dihalobenzene, dihalobiphenyl, dihalobenzoic acid, dihalodiphenyl ether, dihalodiphenyl sulfone, dihalodiphenyl sulfoxide, dihalodiphenyl ketone and the like, the halogen atom means each atom of fluorine, chlorine, bromine and iodine, and two halogen atoms in the dihalo aromatic compound may be the same or different. Particular preference is given to using p-dichlorobenzene.

In order to form a branched polymer or a crosslinked polymer, a polyhalogen compound (may not necessarily be an aromatic compound) to which three or more halogen atoms are bonded, a halogenated aromatic compound containing active hydrogen, a halogenated aromatic nitro compound, or the like may be used in combination. Preferred examples of polyhalogenated compounds as branching/crosslinking agents are trihalobenzenes.

< polyarylene sulfide >

The PAS obtained by the production method of the present embodiment is a linear or branched PAS, and is Preferably Polyphenylene Sulfide (PPS).

The weight average molecular weight (Mw) of PAS is not particularly limited, and is in a wide range. The PAS generally has a lower limit value of 2000 or more, preferably 10000 or more, and more preferably 15000 or more in terms of a weight average molecular weight in terms of standard polystyrene obtained by Gel Permeation Chromatography (GPC). The upper limit of the weight average molecular weight is 300000 or less, preferably 100000 or less.

[ conclusion ]

The continuous dehydration method of the raw material mixture for the production of polyarylene sulfide of the present embodiment is performed before the production of polyarylene sulfide, and the continuous dehydration method simultaneously performs in parallel: a supply step of continuously supplying a sulfur source and an organic polar solvent constituting the raw material mixture to a continuous dehydration apparatus having one or more dehydration tanks; a dehydration step of continuously removing water from the raw material mixture; and a step of continuously extracting the raw material mixture having a reduced water content from the dehydration tank, wherein the temperature of the dehydration tank to which the sulfur source and the organic polar solvent are supplied in the dehydration tank is 110 to 270 ℃, and the dehydration efficiency index obtained by the following formula (1) is 0.3 or more.

Dehydration efficiency index [ the number of moles (mol) of sulfur source in the reduced water content feed mixture]/[ dehydration time (hr) × (total internal volume of dehydration tank (L))^2/3]···(1)

In the formula (1), the dehydration time is a time until the amount of water in the raw material mixture containing water consumed for hydrolysis of the organic polar solvent and having a reduced water content becomes 1.7 moles or less per 1 mole of the sulfur source.

In the continuous dehydration method according to the present embodiment, it is preferable that the dehydration tank has a plurality of dehydration tanks that communicate with each other via a gas phase, the dehydration tanks are connected in sequence, and the raw material mixture moves to the dehydration tanks in sequence.

In addition, it is preferable that a polymerization aid for the polyarylene sulfide is further supplied in the supplying step.

In the continuous dehydration method according to the present embodiment, it is preferable that a dehydration assistant is contained in the raw material mixture.

In the continuous dehydration method according to the present embodiment, the sulfur source is preferably at least one of an alkali metal sulfide, an alkali metal hydrosulfide and hydrogen sulfide.

In the continuous dehydration method according to the present embodiment, the water content of the raw material mixture before the dehydration step is preferably 3mol or more per 1mol of the sulfur source, and the water content of the raw material mixture after the dehydration step, in which the water content is reduced, is preferably in the range of 0.5 to 1.7mol per 1mol of the sulfur source.

It is also preferable that the water is removed in a range of 190 to 270 ℃ for 50% or more of the time for performing the dehydration step.

In the continuous dehydration method of the present embodiment, it is preferable that the method further comprises: a resupply step of recovering the sulfur source volatilized in the dehydration step and resupplying the recovered sulfur source to the dehydration tank.

In the continuous dewatering method according to the present embodiment, the material of the dewatering tank is preferably stainless steel.

The method for producing a polyarylene sulfide according to the present embodiment performs polymerization using the raw material mixture having a reduced water content obtained by the above-described continuous dehydration method.

The following examples are provided to further explain embodiments of the present invention in detail. Needless to say, the present invention is not limited to the following embodiments of the present invention, and various modifications can be made to the details. The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and embodiments obtained by appropriately combining the respective disclosed technical means are also included in the technical scope of the present invention. In addition, the documents described in the present specification are all cited as reference.

Examples

EXAMPLE 1 continuous dehydration of raw Material mixture in titanium Cylinder dehydration apparatus

A continuous dewatering apparatus shown in fig. 1 was used in which the dewatering chamber 2 had two dewatering tanks formed by a partition wall (height of about 10 cm). The dehydration tank was a titanium (Ti) cylindrical dehydration apparatus having a diameter of about 28cm and a length of about 32cm (total internal volume of about 20L). After NMP7.0kg was charged into the dehydration tank 1a, the temperature of the dehydration tank 1a was maintained at 220 ℃ and the temperature of the dehydration tank 1b was maintained at 240 ℃. From each supply line, a raw material was continuously supplied using a fixed displacement pump at a flow rate of 4.07kg/hr of NMP and a flow rate of 2.39kg/hr of a 47.4 wt% sodium hydrosulfide (NaSH) aqueous solution (the water content in the supplied raw material mixture was 6.2mol per 1mol of the sulfur source). While the pressure was controlled to a gage pressure of 0.32MPa by the pressure regulating valve, water and NMP were continuously removed from the dehydration chamber 2.

At the same time, NMP is separated by a first gas-liquid separation section 13 connected to the dehydration chamber 2 and supplied to the dehydration tank 1a through an organic polar solvent supply line 13.

The gas recovered from the first gas-liquid separation unit 13 is sent to the second gas-liquid separation unit 17 through the first gas recovery line 15, and separated into water and gas. Water is discarded through waste line 16.

Further, the gas recovered from the second gas-liquid separation section 17 is sent to a sulfur source recovery section 19 through a second gas recovery line 18.

The gas was absorbed by NMP2.00kg/hr and 47.94 wt% NaOH1.69kg/hr supplied from the sulfur source absorbent supply line 21 to the sulfur source recovery unit 19. At this time, the total amount of the NMP and the NaOH aqueous solution having absorbed the gas is resupplied to the dehydration tank 1a through the sulfur source resupply line 20. When the amounts of the NMP and the NaOH aqueous solution absorbed in the gas were taken into consideration, the water content in the raw material supplied to the dehydration tank 1a was 6.8mol per 1mol of the sulfur source.

The dehydrated raw material mixture is continuously withdrawn from the raw material mixture withdrawal line 4. The water content in the dehydrated raw material mixture with the reduced water content was 1.01mol per 1mol of the sulfur source.

After the operation of the continuous dehydration apparatus was stabilized, a dehydrated mixture containing 14.4mol of the number of moles of the sulfur source in the raw material mixture having a reduced water content was recovered over a period of 1 hour. The dehydration has no bubbling and overflowing, and the dehydration efficiency index is 2.0.

The degree of corrosion of the dehydration tank after dehydration was evaluated by the following criteria, and the result was AA.

< evaluation criteria for Corrosion >

AA: the degree of corrosion in the dewatering trough is relatively minimal and the dewatering trough is very corrosion resistant.

A: the degree of corrosion in the dewatering tank is relatively low and the dewatering tank is corrosion resistant.

C: the degree of corrosion in the dewatering tank is relatively high and the dewatering tank is hardly resistant to corrosion.

EXAMPLE 2 production of PAS

The dehydrated raw material mixture obtained in example 1 was charged into a Ti reactor (total internal volume: about 3L) under a nitrogen atmosphere, in which the number of moles of the sulfur source was 3.0 mol and p-dichlorobenzene was 3.09 mol.

After the reaction at 230 ℃ for 3 hours, 10.5 mol of water was added under pressure, and the reaction was further carried out at 260 ℃ for 3 hours. The obtained reaction mixture was sieved with a 100-mesh sieve to recover granular PPS.

Further, granular PPS was washed and sieved 3 times using the same weight of acetone as the obtained reaction mixture. Further, washing with water and sieving were carried out 3 times, and the obtained granular PPS was dried under vacuum at 80 ℃ for 8 hours to obtain PPS particles. The weight average molecular weight Mw of the PPS particles was 32000 in terms of standard polystyrene obtained by GPC.

Comparative example 1 batch-wise dehydration in titanium Autoclave

A20-liter titanium autoclave was charged with NMP6001g, 2000g of NaSH aqueous solution (purity: 61.8% by mass), and 1171g of NaOH aqueous solution (purity: 73.7% by mass). As the dehydration step, the inside of the autoclave was replaced with nitrogen, and then the temperature was gradually raised from room temperature to 200 ℃ over about 3 hours, thereby obtaining 1014g of distillate water, NMP763g, and hydrogen sulfide (H)₂S)5.5 g. No overflow was observed during the dewatering pass. The amount of water remaining per 1mol of the sulfur source, including water consumed for hydrolysis of NMP, which is an organic polar solvent, was 1.14 mol. In the case of the batch system, a loss time (about 1 hour for charging, 2 hours for cooling, 1 hour for disassembling, and 1 hour for cleaning the autoclave) due to the multiple polymerization occurs. When these values are added to the dehydration time, the dehydration efficiency index obtained by the above formula (1) is calculated to be 0.4.

Comparative example 2 batch-type rapid dehydration in titanium autoclave

The dehydration was carried out in the same manner as in comparative example 1 except that the temperature was rapidly increased so that the residual moisture content per 1 mole of the sulfur source, including the moisture consumed in the hydrolysis of the organic polar solvent NMP, became 1.7 moles or less in the dehydration time of 1 hour, and as a result, the dehydrated raw material mixture overflowed from the dehydration apparatus, and the dehydration operation could not be normally continued.

Example 3 continuous dehydration of raw Material mixture in SUS316 cylindrical dehydration apparatus

Continuous dehydration of the raw material mixture was performed in the same manner as in example 1, except that the material of the dehydration tank of the cylindrical dehydration apparatus was SUS 316. All steps were performed in the same manner as in example 1. For example, no foaming and overflow occurred during dehydration, and the dehydration efficiency index was 2.0.

The degree of corrosion of the dehydration tank after dehydration was evaluated by the standard of example 1, and the result was AA.

EXAMPLE 4 production of PAS

Using the dehydrated raw material mixture obtained in example 3, PAS was produced in the same manner as in example 2. Then, granular PPS equivalent to that of example 2 was obtained.

Comparative example 3 batch-wise dehydration in an Autoclave made of SUS316

Batch dehydration of the raw material mixture was performed in the same manner as in comparative example 2, except that the material of the autoclave was SUS 316. The degree of corrosion of the dehydration tank after dehydration was evaluated by the standard of example 1, and the result was C.

< summary of the examples >

The following facts can be understood from the above-described examples and comparative examples.

The present invention can reduce or prevent rapid foaming and overflow of liquid, thereby improving the efficiency of dewatering the raw material mixture used for producing PAS. Thus, the raw material mixture can be dehydrated to the minimum water content for the polymerization reaction of PAS in a short time without increasing the volume of the dehydration tank.

Further, a PAS having a high molecular weight can be easily produced from a raw material mixture having a reduced water content.

Further, by setting the temperature of the dehydration tank to which the aqueous raw material mixture is supplied to a high temperature, the degree of corrosion of the dehydration tank using SUS316, which is stainless steel, can be suppressed to the same degree as the case of the dehydration tank using titanium. Titanium is a material generally used in the production of PAS, and is difficult and expensive to process as compared with stainless steel. According to the present invention, corrosion of the dewatering tank can be suppressed equally, and the material of the dewatering tank can be changed from titanium to stainless steel, so that resource saving and cost reduction can be achieved.

Description of the symbols

1 a-1 d dehydration tank

2 dehydration chamber

3 raw material supply line

4 raw material mixture withdrawal line

5 partition wall

6a, 6b raw material mixture

7a, 7b stirring blade

8 stirring shaft

9 Rotary drive device

10 gas phase communication part

11 communicating part of raw material mixture

12 exhaust line

13 first gas-liquid separation part

14 organic polar solvent resupply line

15 first gas recovery line

16 waste water line

17 second gas-liquid separation section

18 second gas recovery line

19 Sulfur Source recovery section

20 sulfur source resupply line

21 Sulfur source absorbent supply line

22 waste gas line

100. 200 continuous dewatering device