阅读说明：本技术 一种聚苯硫醚生产中多水硫化钠脱水的方法 (Method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production ) 是由 张定明 廖斌 于 2019-11-22 设计创作，主要内容包括：本发明涉及硫化钠脱水技术领域,具体涉及一种聚苯硫醚生产中多水硫化钠脱水的方法。具体方案为：一种聚苯硫醚生产中多水硫化钠脱水的方法,先将多水硫化钠、NMP、助剂和氢氧化钠加入到反应釜中,对反应釜内的物料进行升温脱水；脱水产生的混合蒸汽进入到分离器中,进行分离,分离出的液体返回到反应釜中,分离出的气体则进行冷凝回收、废气处理；再向反应釜中加入熔融后的对二氯苯,对反应釜内的混合溶液进行分步升温反应,最终得到聚苯硫醚产品。本发明解决现有PPS生产中脱水温度高,需蒸汽和其他能源进行两段蒸发脱水,且不稳定,脱水时多、时少,脱水时由于工艺控制不稳定,造成大量带液,导致脱出水中NMP含量较高的问题。(The invention relates to the technical field of sodium sulfide dehydration, in particular to a method for dehydrating sodium sulfide dehydrate in polyphenylene sulfide production. The specific scheme is as follows: a method for dehydrating sodium sulfide monohydrate in polyphenylene sulfide production comprises the steps of adding sodium sulfide monohydrate, NMP, an auxiliary agent and sodium hydroxide into a reaction kettle, and heating and dehydrating materials in the reaction kettle; the mixed steam generated by dehydration enters a separator for separation, the separated liquid returns to the reaction kettle, and the separated gas is condensed for recovery and is subjected to waste gas treatment; and adding the molten p-dichlorobenzene into the reaction kettle, and performing step-by-step heating reaction on the mixed solution in the reaction kettle to finally obtain the polyphenylene sulfide product. The invention solves the problems that the dehydration temperature is high, steam and other energy sources are needed for two-stage evaporation dehydration in the existing PPS production, the dehydration is unstable, more and less time is needed during dehydration, and a large amount of liquid is brought due to unstable process control during dehydration, so that the content of NMP in the dehydrated water is high.)

1. A method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production is characterized by comprising the following steps: the method comprises the following steps:

(1) adding sodium sulfide, NMP, an auxiliary agent and sodium hydroxide into a reaction kettle, stirring, pumping negative pressure to replace air in the reaction kettle in a nitrogen atmosphere, closing nitrogen after a period of time, then starting vacuum degree interlocking control, and heating and dehydrating materials in the reaction kettle under a vacuum condition; in the dehydration process, mixed steam and residual kettle liquid in the reaction kettle are generated;

(2) feeding the mixed steam generated in the step (1) into a separator for separation, returning the separated liquid into the reaction kettle, and mixing the liquid with kettle liquid to obtain kettle liquid mixed liquid; the separated gas is condensed and recycled and the waste gas is treated;

(3) and (3) adding the molten p-dichlorobenzene into the kettle liquid mixed solution obtained in the step (2), introducing nitrogen into the reaction kettle to displace air in the reaction kettle, stopping supplying nitrogen to seal the reaction kettle after displacement is finished, performing stepwise heating reaction on the mixed solution in the reaction kettle, and performing early-stage and later-stage two-step polymerization reaction under certain pressure to finally obtain the polyphenylene sulfide product.

2. The method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production as claimed in claim 1, wherein: in the step (1), the sodium sulfide polyhydrate is Na₂S·3H₂O、Na₂S·5H₂O or Na₂S·9H₂O, the molar ratio of the sodium sulfide, NMP, sodium hydroxide and the auxiliary agent is 0.5-1.5: 3-5.5: 0.01E0.5: 0.3-1; the auxiliary agent is lithium chloride or sodium acetate.

3. The method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production as claimed in claim 1, wherein: in the step (1), the stirring speed of the reaction kettle is 20-130 rpm/min, and the stirring process is continued for the whole dehydration process in the step (1) of the reaction kettle; and (3) pumping negative pressure to the reaction kettle at the pressure of-0.03 to-0.08 Mpa, introducing nitrogen to replace air in the reaction kettle in the process of pumping negative pressure to the reaction kettle, and stopping introducing the nitrogen after replacing for 5-20 min.

4. The method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production as claimed in claim 1, wherein: in the step (1), the dehydration temperature is 120-170 ℃, the dehydration time is 1-4 h, the heating rate is 1-5 ℃/min, after dehydration is completed, vacuum is broken, nitrogen is continuously introduced, the reaction kettle is heated to normal pressure, and stirring is continuously kept.

5. The method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production as claimed in claim 1, wherein: in the step (2), the separation temperature in the separator is 80-170 ℃.

6. The method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production as claimed in claim 1, wherein: in the step (2), the NMP and the sodium sulfide solution separated from the mixed steam by the separator return to the reaction kettle and are mixed with the kettle liquid; and the separated water vapor containing NMP and hydrogen sulfide gas enters a dehydrating liquid cooler, the water vapor is cooled to obtain dehydrating liquid, the dehydrating liquid enters a dehydrating liquid metering tank for accurate metering and then is transferred to a storage tank for storage, and the hydrogen sulfide gas is pumped out by a vacuum pump and is sent to a hydrogen sulfide waste gas treatment device for waste gas treatment.

7. The method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production as claimed in claim 6, wherein: in the step (3), the heating temperature of the p-dichlorobenzene is 70-85 ℃, and the p-dichlorobenzene is heated until the p-dichlorobenzene is in a molten state; and (2) adding p-dichlorobenzene in the step (1), wherein the molar ratio of the water content in the kettle liquid to the p-dichlorobenzene is 0.5-2.5, and the water content in the kettle liquid is obtained by subtracting the water content in the dehydration liquid from the water content in the sodium sulfide dihydrate.

8. The method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production as claimed in claim 1, wherein: in the step (3), the pressure in the reaction kettle is between-0.03 and-0.08 MPa.

9. The method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production as claimed in claim 1, wherein: in the step (3), the step-by-step heating reaction process comprises: firstly heating to 200-240 ℃ for early-stage polymerization reaction, then continuously heating to 250-265 ℃ for later-stage polymerization reaction, and finally cooling to 110-130 ℃ to finally complete the production of the polyphenylene sulfide product.

10. The method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production as claimed in claim 9, wherein: during the temperature rise period, the time of the early polymerization reaction is 1-1.5 h, the time of the later polymerization reaction is 2-3.5 h, and the rotating speed of the reaction kettle during the early polymerization reaction and the later polymerization reaction is 30-160 rpm/min; during the cooling period, the crystallization and agglomeration time of the product is 2-3 h, and the rotating speed of the reaction kettle is 20-130 rpm/min during the cooling period.

Technical Field

The invention relates to the technical field of sodium sulfide dehydration, in particular to a method for dehydrating sodium sulfide dehydrate in polyphenylene sulfide production.

Background

Polyphenylene sulfide (hereinafter abbreviated as PPS) resin has gradually become a special engineering material with the best performance-price ratio since the industrialization thereof, the production process of PPS has a plurality of kinds, the current industrialized maturity belongs to the sodium sulfide method, the technology is firstly developed by Philips oil company in 1967, the product is formally industrialized in 1973, the product occupies the whole world in 1987, the respective process routes are successively developed on the basis of the original technology and the same production principle in Europe and Japan and the like until the patent of the company is up in 1984, Japanese eclosion chemical industry company adopts new technology in 1986, linear PPS is developed, then Philips company and Japanese Dongli industry company carry out technical cooperation, finally the PPS synthesis technology becomes mature day by day, then a dispute construction factory such as Japan ink chemical company, Dongcha company, Guanggong company and the like is built with SK in 2013 to produce PPS, in 2014, Solvay bought the PPS service of Ryton.

The principle of the sodium sulfide method for domestic industrial production of PPS is as follows: the compound is synthesized by carrying out polycondensation reaction on p-dichlorobenzene and partially dehydrated sodium sulfide crystallized from multiple water in N-methylpyrrolidone (NMP) solution under the action of lithium chloride or sodium acetate auxiliary agent and under a certain temperature and pressure.

The method has the technical advantages that the main raw material of the sodium sulfide is low in cost and easy to obtain through the crystallization of the polyhydrated sodium sulfide, the p-dichlorobenzene is easy to obtain, the reaction is controllable, the linearity of the resin product is high, but the method has the defects that the circulation amount of the solvent is large, the byproducts are more, the byproducts are enriched in the solvent and remain in the product, the production process is unstable in dehydration after being dropped integrally, particularly the dehydration process is not controlled, and the amount of the brought solvent NMP is large; the polymerization and crystallization processes are controlled to be single, so that the molecular weight of the polymer is unstable, the granularity of the polymer is unstable, and the product type is single; the problems of difficult system operation, high energy consumption, high solvent consumption, large auxiliary agent loss, difficult treatment of a large amount of environment-friendly waste residues, high product cost and the like caused by unreasonable selection of the separation process are solved.

The technological control conditions of the technology are improved in foreign countries, the impact and the toughness of PPS are improved obviously, a third substance is introduced in the reaction to reduce the crystallinity, so that the resin product is suitable for a printed circuit board, and a new method for removing a large amount of sodium chloride plasma impurities from a prepolymer, shortening the polymerization time and reducing the equipment cost and the like are researched. Foreign PPS products generally have dozens of basic variety grades, and more special grades, such as glass fiber and carbonic acid fiber reinforced grades, inorganic filling grades, blended alloy grades and the like, particularly the application of the foreign PPS products in recent years is further expanded to high heat conduction grades, laser cladding grades, high-frequency component grades, low-mold bonded carbon grades and the like, and PPS processing is expanded to coating, fibers, films, extrusion, central control blow molding, thermoforming, electronics/electricity and the like from single injection molding processing.

Therefore, the domestic situation that the PPS product has single performance, the brand types are few, the application is greatly limited, and the process has more problems, so that the running cost is high and the competitiveness is poor, so that the research on the PPS production process technology plays a great role in the development of domestic PPS.

The reaction raw material sodium sulfide is obtained by dehydrating sodium sulfide crystallized from polyhydration in a mixed solution or reacting sodium hydrosulfide with sodium hydroxide, excessive water content can cause reaction pressure rise, the molar ratio of the sodium sulfide to p-dichlorobenzene exceeds a high limit amount to cause synthesis failure, and certain water content in materials finally participating in the reaction needs to be maintained, so that water and a solvent are required to generate a synergistic effect to facilitate nucleophilic reaction, the reaction activity of chlorine on a benzene ring is increased, substitution polymerization is easy to occur, the polycondensation reaction is smoothly performed, the molar ratio of the sodium sulfide to p-dichlorobenzene exceeds a low limit amount to cause synthesis failure, and the control of the water content is particularly important.

In the existing production process, dehydration is finished under normal pressure, the dehydration temperature is controlled to be more than 200 ℃, 1.0MPa steam and other heat sources (such as electric heating or heat conducting oil) are required to finish the dehydration together, the dehydration time is 2-7 hours, the dehydration liquid enters a collecting tank, the NMP content in the dehydration liquid is usually 50% -80%, a large amount of secondary separation and a large amount of solvent NMP supplement are caused, the energy consumption and the cost are high, the dehydration amount is unstable, the quality of a synthesized product is unstable, and the stability of dehydration control is particularly important.

Disclosure of Invention

The invention aims to provide a method for dehydrating sodium sulfide polyhydrate in polyphenylene sulfide production, which solves the problems that the dehydration temperature is high, two-stage evaporation dehydration needs to be carried out by steam and other energy sources, the dehydration is unstable, the dehydration time is large and short, a large amount of liquid is carried out due to unstable process control during dehydration, the content of NMP in the dehydrated water is about 50-80%, secondary separation is needed, a large amount of new NMP needs to be supplemented into a kettle, the energy consumption is high, the cost is high, and the key is that the fluctuation range of the molecular weight of a product is wide and the quality is unstable due to the instability of the mole number of water contained in the dehydrated sodium sulfide liquid and the mole number ratio of p-dichlorobenzene.

In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows:

the invention provides a method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production, which comprises the following steps:

(1) adding sodium sulfide, NMP, an auxiliary agent and sodium hydroxide into a reaction kettle, stirring, pumping negative pressure to replace air in the reaction kettle in a nitrogen atmosphere, closing nitrogen after a period of time, then starting vacuum degree interlocking control, and heating and dehydrating materials in the reaction kettle under a vacuum condition; in the dehydration process, mixed steam and residual kettle liquid in the reaction kettle are generated;

(2) feeding the mixed steam generated in the step (1) into a separator for separation, returning the separated liquid into the reaction kettle, and mixing the liquid with kettle liquid to obtain kettle liquid mixed liquid; the separated gas is condensed and recycled and the waste gas is treated;

(3) and (3) adding the molten p-dichlorobenzene into the kettle liquid mixed solution obtained in the step (2), introducing nitrogen into the reaction kettle to displace air in the reaction kettle, stopping supplying nitrogen to seal the reaction kettle after displacement is finished, performing stepwise heating reaction on the mixed solution in the reaction kettle, and performing early-stage and later-stage two-step polymerization reaction under certain pressure to finally obtain the polyphenylene sulfide product.

Preferably, in the step (1), the sodium sulfide polyhydrate is Na₂S·3H₂O、Na₂S·5H₂O or Na₂S·9H₂O, wherein the molar ratio of the sodium sulfide dihydrate to the NMP to the sodium hydroxide to the auxiliary agent is 0.5-1.5: 3-5.5: 0.01-0.5: 0.3-1; the auxiliary agent is lithium chloride or sodium acetate.

Preferably, in the step (1), the stirring speed of the reaction kettle is 20-130 rpm/min, and the stirring process is continued for the whole dehydration process in the step (1) of the reaction kettle; and (3) pumping negative pressure to the reaction kettle at the pressure of-0.03 to-0.08 Mpa, introducing nitrogen to replace air in the reaction kettle in the process of pumping negative pressure to the reaction kettle, and stopping introducing the nitrogen after replacing for 5-20 min.

Preferably, in the step (1), the dehydration temperature is 120-170 ℃, the dehydration time is 1-4 h, the heating rate is 1-5 ℃/min, after dehydration is completed, vacuum is broken, nitrogen is continuously introduced, the reaction kettle is heated to normal pressure, and stirring is continuously kept.

Preferably, in the step (2), the separation temperature in the separator is 80-170 ℃.

Preferably, in the step (2), the NMP and the sodium sulfide solution separated from the mixed steam by the separator are returned to the reaction kettle and mixed with the kettle liquid; and the separated water vapor containing NMP and hydrogen sulfide gas enters a dehydrating liquid cooler, the water vapor is cooled to obtain dehydrating liquid, the dehydrating liquid enters a dehydrating liquid metering tank for accurate metering and then is transferred to a storage tank for storage, and the hydrogen sulfide gas is pumped out by a vacuum pump and is sent to a hydrogen sulfide waste gas treatment device for waste gas treatment.

Preferably, in the step (3), the heating temperature of the p-dichlorobenzene is 70-85 ℃, and the p-dichlorobenzene is heated until the p-dichlorobenzene is in a molten state; and (2) adding p-dichlorobenzene in the step (1), wherein the molar ratio of the water content in the kettle liquid to the p-dichlorobenzene is 0.5-2.5, and the water content in the kettle liquid is obtained by subtracting the water content in the dehydration liquid from the water content in the sodium sulfide dihydrate.

Preferably, in the step (3), the pressure in the reaction kettle is between-0.03 and-0.08 MPa.

Preferably, in the step (3), the step-by-step temperature-raising reaction process is as follows: firstly heating to 200-240 ℃ for early-stage polymerization reaction, then continuously heating to 250-265 ℃ for later-stage polymerization reaction, and finally cooling to 110-130 ℃ to finally complete the production of the polyphenylene sulfide product.

Preferably, during the temperature rise, the time of the early polymerization reaction is 1-1.5 h, the time of the later polymerization reaction is 2-3.5 h, and the rotating speed of the reaction kettle during the early polymerization reaction and the later polymerization reaction is 30-160 rpm/min; during the cooling period, the crystallization and agglomeration time of the product is 2-3 h, and the rotating speed of the reaction kettle is 20-130 rpm/min during the cooling period.

The invention has the following beneficial effects:

1. the invention adopts vacuum degree interlocking control to stabilize the pressure in the reaction kettle at a set value, reduce the dehydration temperature and stably control the dehydration rate, and because of the adoption of the vacuum degree interlocking control, the dehydration amount of the sodium sulfide is completely controlled, and because the boiling point of the solution is reduced, two energy sources are not needed for supplying heat. Moreover, the NMP and sodium sulfide liquid drops in the mixed steam are separated from water by a separator, the separated NMP and sodium sulfide liquid drops are returned to the reaction kettle, the NMP content in the obtained dehydration liquid is not more than 10% after the mixed steam is separated by the separator, a large amount of NMP does not need to be supplemented in the process of producing polyphenylene sulfide, the separated gas is cooled by a dehydration liquid cooler, the cooled dehydration liquid is recycled, and the NMP content in the dehydration liquid is not more than 10% after detection; the gas is treated by a hydrogen sulfide waste gas treatment device.

2. By adopting the dehydration method, the NMP content in the dehydration liquid obtained after separation by the separator is greatly reduced, the secondary separation cost is reduced, and the addition amount of NMP is reduced, and the key point is to stabilize the water content in the kettle liquid mixed liquid, so that the product quality is stable, a large amount of energy is saved, and certain economic benefit and social benefit are generated.

Drawings

FIG. 1 is a process flow diagram of the present invention;

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Unless otherwise indicated, the technical means used in the examples are conventional means well known to those skilled in the art.

The invention provides a method for dehydrating sodium sulfide dihydrate in polyphenylene sulfide production, which comprises the following steps: adding sodium sulfide monohydrate, NMP (N-methyl pyrrolidone), an auxiliary agent (lithium chloride or sodium acetate) and sodium hydroxide into a reaction kettleDehydrating at 120-170 ℃ in a nitrogen atmosphere by using steam as a heat source, wherein the dehydration pressure is-0.03 to-0.08 Mpa (G). The molar ratio of the sodium sulfide, NMP, sodium hydroxide and the auxiliary agent is 0.5-1.5: 3-5.5: 0.01-0.5: 0.3-1, preferably 1:4.5:0.04:0.55, and the sodium sulfide is Na₂S·3H₂O、Na₂S·5H₂O or Na₂S·9H₂O。

Referring to fig. 1, the specific dehydration process is:

(1) early preparation: starting an alkali liquor absorption hydrogen sulfide absorption tower device, starting a dehydration exhaust valve of a reaction kettle, starting an NMP and water separator inlet valve, starting a dehydration liquid condenser cooling water valve, and starting a vacuum pump bypass valve; and closing a discharge valve at the bottom of the reaction kettle.

(2) Pumping weighed sodium sulfide (based on the content of sodium sulfide), NMP, an auxiliary agent lithium chloride and sodium hydroxide into a reaction kettle by using a pump, stirring at the rotating speed of 20-130 rpm/min, and continuously carrying out the whole dehydration process in the stirring process; simultaneously introducing nitrogen into the reaction kettle to drive oxygen in the reaction kettle and prevent external oxygen from entering the kettle, and introducing nitrogen for 20 min; and (3) closing a bypass valve of the vacuum pump, starting the vacuum pump, pumping negative pressure to-0.03 to-0.08 Mpa (G) to the reaction kettle, introducing nitrogen to replace air in the reaction kettle in the process of pumping negative pressure to the reaction kettle, and closing a nitrogen valve after replacing for 5 to 20min to ensure that the oxygen content in the reaction kettle is as low as possible. Then, the vacuum degree interlocking control is started to ensure that the vacuum degree is stabilized at a set value (-0.03 to-0.08 MPa) during the dehydration period; and opening a coil heating steam inlet valve in the reaction kettle, and heating and dehydrating the sodium sulfide polyhydrate mixed solution, wherein the dehydration temperature is 120-170 ℃, the dehydration time is 1-4 h, and the temperature rise rate is 1-5 ℃/min. When the dehydration amount reaches the required amount, closing a steam valve, namely completing dehydration to obtain mixed steam and residual kettle liquid in the reaction kettle, breaking vacuum, continuously introducing nitrogen to prevent air from entering the reaction kettle, adjusting vacuum degree interlocking control to enable the interior of the reaction kettle to be close to normal pressure, and continuously keeping stirring.

The required amount here means: after dehydration is finished, the water content in the residual kettle liquid in the reaction kettle is obtained by subtracting the water content in the dehydration liquid from the water content in the sodium sulfide polyhydrate; the time for the dehydration amount to reach the required amount is different with the content of sodium sulfide in the raw material and the change of the temperature rising rate. The rate of temperature rise is limited to avoid sodium sulfide scabbing at a rate that is too fast and to a dehydration rate that results in sodium sulfide dehydration carryover. The vacuum degree interlocking control process comprises the following steps: a set value is given, and if the measured vacuum value is higher than the set value, a signal is given to the frequency converter, the rotating speed of the vacuum pump is reduced, the suction force is reduced, and the vacuum degree is reduced to the set value, and vice versa.

(3) Feeding the mixed steam generated in the step (2) into a separator, monitoring the gas temperature of gas-liquid separation, wherein the separation temperature is 80-170 ℃, the separation temperature is set according to the difference of the boiling points of water and NMP, separating NMP liquid and sodium sulfide liquid drops in the mixed steam from the water steam, returning the separated NMP and a small amount of sodium sulfide liquid drops into a reaction kettle, and mixing the NMP liquid and a small amount of sodium sulfide liquid drops with kettle liquid in the reaction kettle to obtain kettle liquid mixed liquid; and the separated gas enters a dehydrating liquid metering tank for accurate metering and component analysis after passing through a dehydrating liquid cooler, and then is transferred to a storage tank for storage.

It should be understood that: mixed steam discharged from a reaction kettle contains water vapor, an NMP solution, hydrogen sulfide gas partially hydrolyzed by sodium sulfide and sodium sulfide liquid drops, separated liquid (NMP and sodium sulfide liquid drops) returns to the reaction kettle after the mixed steam passes through a separator, water vapor containing a small amount of NMP and hydrogen sulfide gas enters a dehydrating liquid cooler, water vapor containing a small amount of NMP is cooled to obtain dehydrating liquid, the dehydrating liquid enters a dehydrating liquid metering tank for accurate metering, and the content of NMP in water is analyzed on line; the hydrogen sulfide gas is pumped by a vacuum pump and is sent into a hydrogen sulfide waste gas treatment device for waste gas treatment. The hydrogen sulfide waste gas treatment device is an existing device.

(4) And (3) adding heated p-dichlorobenzene into the kettle liquid mixed solution obtained in the step (3) by using a pump, adjusting the rotating speed of the reaction kettle to be 30-160 rpm/min, heating the p-dichlorobenzene to be 70-85 ℃, melting the p-dichlorobenzene solid, opening a nitrogen valve, filling nitrogen into the reaction kettle to replace air, closing the nitrogen valve, and finally closing the reaction kettle. During the process of filling nitrogen, the negative pressure is pumped in the reaction kettle, and the pressure is-0.03 to-0.08 MPa (G), and the preferable pressure is-0.05 MPa. The method comprises the following steps of carrying out step-by-step heating reaction on a mixed solution in a reaction kettle by using electric heating or heat conducting oil, and specifically comprises the following steps: firstly heating to 200-240 ℃ for early-stage polymerization reaction, preferably 225 ℃, continuing heating after reacting for 1-1.5 h, heating to 250-265 ℃ for later-stage polymerization reaction, preferably 260 ℃, cooling to 110-130 ℃ after reacting for 2-3.5 h, preferably 130 ℃, wherein the product crystallization and agglomeration time is 2-3 h during cooling, the rotating speed of the reaction kettle is controlled to be 20-130 rpm/min during cooling, the polymer is agglomerated and crystallized, and finally the production of the polyphenylene sulfide product is finished.

It should be understood that: and (3) mixing the kettle liquid after the dehydration in the step (2) and the NMP and sodium sulfide solution separated by the separator in the step (3). And (3) the kettle liquid obtained after the dehydration in the step (2) contains sodium sulfide, water, NMP, sodium hydroxide and lithium chloride.

The addition amount of p-dichlorobenzene is as follows: in the step (2), after the dehydration is finished, the molar ratio of the water content in the residual kettle liquid to the p-dichlorobenzene is 0.5-2.5. And the water content of the residual kettle liquid is obtained by subtracting the water content of the dehydrating liquid from the water content of the sodium sulfide.

The method is adopted to dehydrate the polyhydrated sodium sulfide in the production of the polyphenylene sulfide, and the specific reaction conditions are shown in the following table 1.

TABLE 1 reaction conditions of the examples

Group of	Sodium sulfide	Heat source	Pressure of reaction kettle	Whether or not to be processed by a separator
					Example 1	Sodium sulfide pentahydrate	1.0MPa steam	-0.03MPa	Whether or not
Example 2	Sodium sulfide pentahydrate	1.0MPa steam	-0.03MPa	Is that
					Example 3	Sodium sulfide pentahydrate	1.0MPa steam	-0.04MPa	Whether or not
Example 4	Sodium sulfide pentahydrate	1.0MPa steam	-0.04MPa	Is that
					Example 5	Sodium sulfide pentahydrate	1.0MPa steam	-0.05MPa	Whether or not
Example 6	Sodium sulfide pentahydrate	1.0MPa steam	-0.05MPa	Is that
					Example 7	Sodium sulfide pentahydrate	1.0MPa steam	-0.08MPa	Whether or not
Example 8	Sodium sulfide pentahydrate	1.0MPa steam	-0.08MPa	Is that

After dehydrating the sodium sulfide dihydrate by using the data in table 1, the content of NMP in the obtained dehydrated liquid is analyzed at different dehydration time and dehydration temperature, which is specifically shown in table 2 below.

Table 2 shows the dewatering effect of each example

Group of	The dehydrated liquid contains NMP	Time of dehydration	Temperature of dehydration
				Example 1	40％	3.5h	170℃
Example 2	10％	3.0h	170℃
				Example 3	50％	2.7h	160℃
Example 4	10％	2.5h	160℃
				Example 5	50％	2.0h	155℃
Example 6	10％	1.8h	155℃
				Example 7	60％	1.5h	120℃
Example 8	10％	1.4h	120℃

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.