阅读说明：本技术 聚苯硫醚副产盐的回收方法 (Method for recovering polyphenylene sulfide byproduct salt ) 是由 李勇 梁平 于 2020-06-16 设计创作，主要内容包括：本发明涉及聚苯硫醚副产盐的回收方法,具体涉及聚苯硫醚树脂的工业化生产中的副产盐氯化钠的回收处理,属于三废治理技术领域。本发明解决的技术问题是提供一种工艺简单的聚苯硫醚副产盐的回收方法,该方法将聚苯硫醚副产盐置于真空中,300～500℃停留1.5～3h,然后加水溶解,采用微孔过滤器过滤,得到氯化钠溶液。本方法采用真空干馏的方法,不仅产生的尾气少而且产生的尾气收集容易,方便采用高级氧化除臭,减少对环境的不友好排放,所生产的氯化钠溶液具有低SS、NH<Sub>3</Sub>-N及COD,且为无色溶液,同时将此氯化钠溶液蒸发结晶,可以得到纯净的盐,该方法流程短,操作简单,对设备要求不高,且同时具有成本低,温度低的特点。(The invention relates to a method for recovering a polyphenylene sulfide byproduct salt, in particular to a method for recovering a byproduct salt sodium chloride in the industrial production of polyphenylene sulfide resin, belonging to the technical field of three-waste treatment. The invention solves the technical problem of providing a simple-process method for recovering polyphenylene sulfide byproduct salt, which comprises the steps of placing the polyphenylene sulfide byproduct salt in vacuum, staying for 1.5-3 h at 300-500 ℃, adding water for dissolving, and filtering by using a microporous filter to obtain a sodium chloride solution. The method adopts a vacuum dry distillation method, not only produces less tail gas, but also easily collects the produced tail gas, conveniently adopts advanced oxidation deodorization, reduces the unfriendly emission to the environment, and produces the sodium chloride solution with low SS and NH 3 The method has the advantages of short flow, simple operation, low requirement on equipment, low cost and low temperature.)

1. The method for recovering the polyphenylene sulfide byproduct salt is characterized by comprising the following steps of:

1) dry distillation: placing the polyphenylene sulfide byproduct salt in vacuum, and staying for 1.5-3 h at 300-500 ℃ to obtain dry distilled salt;

2) dissolving: dissolving the dry distilled salt in water to obtain salt solution;

3) and (3) filtering: and filtering the salt solution by using a microporous filter to obtain a sodium chloride solution.

2. The method according to claim 1, wherein the polyphenylene sulfide byproduct salt is recovered by: further comprises a step 4), wherein the step 4) is to obtain sodium chloride solid by evaporation crystallization from a sodium chloride solution.

3. The method according to claim 1, wherein the polyphenylene sulfide byproduct salt is recovered by: in the step 1), the pressure of the vacuum is 0.003-0.005 MPa.

4. The method according to claim 1, wherein the polyphenylene sulfide byproduct salt is recovered by: in the step 2), the water is deionized water or sodium chloride solution.

5. The method for recovering a polyphenylene sulfide byproduct salt according to claim 2, wherein: in the step 2), the water is condensed water evaporated and crystallized in the step 4).

6. The method according to claim 1, wherein the polyphenylene sulfide byproduct salt is recovered by: in the step 3), the filtering precision of the microporous filter is 0.2-100 μm; preferably, the filtration precision of the microporous filter is 60 to 100 μm.

7. The method according to claim 1, wherein the polyphenylene sulfide byproduct salt is recovered by: the polyphenylene sulfide byproduct salt is prepared by the following method: dehydrating sodium sulfide polyhydrate, reacting with p-dichlorobenzene to produce polyphenylene sulfide, adding water after the reaction is finished, filtering and washing to obtain polyphenylene sulfide, evaporating and rectifying washing liquor, filtering to separate out a filter cake, and drying to obtain the byproduct salt of the polyphenylene sulfide.

Technical Field

The invention relates to a method for recovering a polyphenylene sulfide byproduct salt, in particular to a method for recovering a byproduct salt sodium chloride in the industrial production of polyphenylene sulfide resin, belonging to the technical field of three-waste treatment.

Background

Polyphenylene sulfide (hereinafter abbreviated as PPS) is an engineering plastic having excellent heat resistance, chemical resistance, flame retardancy, mechanical strength, electrical characteristics, dimensional stability, and the like. PPS can be processed into various molded articles, films, plates, fibers and other molded articles, and is widely used in the fields of electric and electronic equipment, automobile equipment and the like, because it can be processed by a general melt processing method such as extrusion molding, injection molding, compression molding and the like.

A typical production method for PPS is a method of reacting a sulfur source with a dihalo-aromatic compound in an organic amide solvent such as NMP, and is a well-known method. Polyphenylene sulfide produced by using sodium sulfide, hydrogen sulfide and alkali, sodium hydrosulfide and the like as sulfur sources is produced by this process, and a large amount of sodium chloride by-product is produced. Sodium chloride, which is a by-product of polyphenylene sulfide, is produced in an amount equivalent to that of polyphenylene sulfide resin, and therefore its recovery is particularly important in the production process as well as NMP.

The Chinese patent application No. 201610748072.3 discloses a method for recovering a byproduct sodium chloride in the production Process of Polyphenylene Sulfide (PPS), which comprises the following steps of filtering mixed slurry obtained after polymerization reaction is finished to obtain a filter cake and byproduct slurry, washing the filter cake with deionized water to obtain a washing liquid and a PPS wet material, mixing washing water and the byproduct slurry, and then filtering, acidifying, aerating, filtering, neutralizing, dehydrating and filtering to obtain a byproduct sodium chloride product. The process flow is complex and long. The purity of the recovered by-product sodium chloride is more than or equal to 99.55 wt%, and the by-product sodium chloride still contains low molecular polymer less than or equal to 0.3 wt%.

The Chinese patent with application number 201210167664.8 discloses a solid-liquid separation method of salt-containing mixed liquid in polyphenylene sulfide production. And squeezing and filtering the salt-containing mixed solution by using a belt type squeezing filter to remove sodium chloride, p-dichlorobenzene and undissolved polyphenylene sulfide oligomers in the mixed solution, mixing water and the filtrate according to a ratio of 3-10, and filtering by using a plate-and-frame filter to remove the polyphenylene sulfide oligomers separated out from the filtrate. The method utilizes multiple times of filtration and washing, and has complicated recovery process and high energy consumption.

The Chinese patent with application number 201210189622.4 discloses a method for recovering a byproduct sodium chloride in polyphenylene sulfide production, which comprises the following steps: the method comprises the steps of performing adsorption impurity removal, namely putting an aqueous solution containing sodium chloride into a collection tank, stirring and mixing, controlling the temperature to be 55-65 ℃, adding activated carbon, mixing and stirring uniformly, and performing adsorption for 25-35 minutes; secondly, solid-liquid separation, namely filtering the mixed liquid in the step to separate out activated carbon and a sodium chloride water solution; and thirdly, concentrating and crystallizing, injecting the sodium chloride aqueous solution separated in the second step into a multi-effect distillation system for concentration, and performing solid-liquid separation after sodium chloride is separated out to obtain sodium chloride crystals. This method is a method for recovering sodium chloride from a sodium chloride-containing aqueous solution produced in PPS production by adsorption purification and evaporative crystallization, but by-product sodium chloride cannot be completely recovered by treating only the sodium chloride aqueous solution in PPS production.

Chinese patent application No. 201410494193.0 discloses a method for removing salts in polyphenylene sulfide recovery solvent, which comprises filtering mixed slurry obtained by polymerization reaction, washing a filter cake with low-boiling alcohol washing liquid, replacing NMP solvent in the filter cake, mixing and rectifying the alcohol washing liquid and filtrate to remove the alcohol washing liquid, and then recovering the NMP solvent by reduced pressure rectification; washing the filter cake washed by alcohol with deionized water, removing impurities in the filter cake to obtain a PPS wet material, and drying the PPS wet material to obtain a finished product. The washing liquid is rectified to remove alcohol liquid with low boiling point, and the residual salt water is evaporated and crystallized to obtain solid salt. Although the process does not have a rectification dehydration process, the problem of tower blockage is avoided, the process does not remove byproducts generated in the process, such as low molecular polymers and unreacted sodium sulfide, and the obtained solid salt contains a lot of impurities and cannot be directly used as industrial salt.

Chinese patent application No. 02807699.0 discloses a method for treating a by-product salt produced in the production of a polyarylene sulfide, comprising drying a solid substance containing an aprotic organic solvent and the by-product salt, and then burning the resultant dried substance at 500 to 1000 ℃. The method can improve the solubility of a byproduct salt containing sodium chloride as a main component in water when producing the polyarylene sulfide, and can reduce SS and COD of wastewater when the byproduct salt is dissolved in water and discharged out of a system as wastewater. However, the method has high calcination temperature and high equipment requirement, and more tail gas and decomposition products are generated by means of high-temperature calcination.

In conclusion, the existing method for recovering the sodium chloride as the byproduct of polyphenylene sulfide is complex in process and high in equipment requirement, and the purity of the obtained sodium chloride is to be further improved.

Disclosure of Invention

In order to overcome the defects, the invention provides a method for recovering polyphenylene sulfide byproduct salt with simple process, and sodium chloride with high purity can be obtained by the method.

The invention relates to a method for recovering polyphenylene sulfide byproduct salt, which comprises the following steps:

1) dry distillation: placing the polyphenylene sulfide byproduct salt in vacuum, and staying for 1.5-3 h at 300-500 ℃ to obtain dry distilled salt;

2) dissolving: dissolving the dry distilled salt in water to obtain salt solution;

3) and (3) filtering: and filtering the salt solution by using a microporous filter to obtain a sodium chloride solution.

Further, the method of the present invention preferably further comprises a step 4), wherein the step 4) is to obtain sodium chloride solid by evaporation crystallization from a sodium chloride solution.

Preferably, in the step 1), the pressure of the vacuum is 0.003-0.005 MPa. Preferably, in step 2), the water is deionized water or a sodium chloride solution.

Preferably, in step 2), the water is condensed water crystallized by evaporation in step 4).

Preferably, in the step 3), the filtration precision of the microporous filter is 0.2-100 μm. Preferably, the filtration precision of the microporous filter is 60-100 μm.

Preferably, the polyphenylene sulfide byproduct salt is prepared by the following method: dehydrating sodium sulfide polyhydrate, reacting with p-dichlorobenzene to produce polyphenylene sulfide, adding water after the reaction is finished, filtering and washing to obtain polyphenylene sulfide, evaporating and rectifying washing liquor, filtering to separate out a filter cake, and drying to obtain the byproduct salt of the polyphenylene sulfide.

Compared with the prior art, the invention has the following beneficial effects:

the method adopts vacuum dry distillation, not only produces less tail gas, but also easily collects the produced tail gas, and is convenient to adopt high gradeOxidizing for deodorization, reducing environment-friendly discharge, and producing sodium chloride solution with low suspended solid particles (SS), ammonia Nitrogen (NH)₃-N) and low Chemical Oxygen Demand (COD) and is a colorless solution, and the sodium chloride solution is evaporated and crystallized to obtain pure salt.

Drawings

FIG. 1 is a flow chart of a specific process of the method of the present invention.

FIG. 2 is a TGA analysis of by-product salts in examples of the present invention.

Detailed Description

After the polyphenylene sulfide byproduct sodium chloride is simply dried to recover the solvent, the polyphenylene sulfide byproduct sodium chloride also contains residual solvent, oligomers, PPS low-distribution material and the like, has dark color, cannot be directly used as industrial salt, and cannot be randomly discharged, disposed or discarded, so that the recovery of the sodium chloride seriously influences the production of polyphenylene sulfide resin, and the recovery, purification and disposal of the sodium chloride byproduct salt are completely necessary to obtain pure sodium chloride solution or pure sodium chloride.

The invention relates to a method for recovering polyphenylene sulfide byproduct salt, which comprises the following steps:

1) dry distillation: placing the polyphenylene sulfide byproduct salt in vacuum, and staying for 1.5-3 h at 300-500 ℃ to obtain dry distilled salt;

2) dissolving: dissolving the dry distilled salt in water to obtain salt solution;

3) and (3) filtering: and filtering the salt solution by using a microporous filter to obtain a sodium chloride solution.

The method can obtain pure colorless transparent sodium chloride solution with low SS and COD, can be used for producing industrial sodium chloride solution,

preferably, the invention also comprises a step 4), wherein the step 4) is to obtain sodium chloride solid by evaporation crystallization from the sodium chloride solution.

The step 1) is a dry distillation step and can be carried out in a dry distillation furnace. During dry distillation, only a small amount of generated tail gas is generated, the generated tail gas is easy to collect, advanced oxidation deodorization is convenient to adopt, and the unfriendly emission to the environment is reduced.

Preferably, in the step 1), the pressure of the vacuum is 0.03-0.05 MPa.

And step 2) is a dissolving step, and the salt after dry distillation is dissolved by adding water. Preferably, in step 2), the water is deionized water or a sodium chloride solution.

In order to save cost and achieve recycling of resources at the same time, it is preferable that in step 2), the water is condensed water evaporated and crystallized in step 4).

Step 3) is a filtering step, and low SS and NH can be obtained by filtering through a microporous filter₃N and COD and colorless solution.

Preferably, in the step 3), the filtration precision of the microporous filter is 0.2-100 μm. Preferably, the filtration precision of the microporous filter is 60-100 μm.

The byproduct salt sodium chloride in the production process of polyphenylene sulfide is suitable for the method. Preferably, the polyphenylene sulfide byproduct salt is prepared by the following method: dehydrating sodium sulfide polyhydrate, reacting with p-dichlorobenzene to produce polyphenylene sulfide, adding water after the reaction is finished, filtering and washing to obtain polyphenylene sulfide, evaporating and rectifying washing liquor, filtering to separate out a filter cake, and drying to obtain the byproduct salt of the polyphenylene sulfide.

As a specific embodiment, as shown in fig. 1, the method of the present invention comprises the steps of:

1) the polyphenylene sulfide byproduct salt is kept in a vacuum rotary dry distillation furnace for 1.5 to 3 hours at the pressure of 0.03 to 0.05MPa and the temperature of 350 to 500 ℃.

2) Adding the by-product salt after dry distillation into pure deionized water or sodium chloride solution or condensed water evaporated from brine to prepare solution.

3) Filtering the solution obtained in the step 2) by a microporous filter, wherein the filtrate has very low SS and NH₃-N, COD content.

4) Concentrating and evaporating the filtrate obtained in the step 4), wherein a crystallized product is industrial salt, and the mother liquor or the evaporated liquor is recycled for dissolving the salt obtained after the dry distillation in the step 2). The obtained industrial byproduct salt has the characteristics of high purity and no color. A

The following examples are provided to further illustrate the embodiments of the present invention and are not intended to limit the scope of the present invention.