Method for reducing foul smell in polyarylene sulfide resin production process

Abstract

The invention discloses a method for reducing foul odor in a polyarylene sulfide resin production process, which comprises the following steps: S1, sieving PPS slurry to obtain a PPS filter cake and slurry mother liquor, repeatedly adding acetone into the PPS filter cake for washing, and mixing the obtained filtrate to obtain acetone mother liquor; s2, mixing the acetone mother solution with the slurry mother solution to obtain a mixed solution, cooling the mixed solution, adjusting the pH value of the mixed solution, and filtering to obtain a mixed solvent; s3, feeding the mixed solvent into an acetone rectifying tower, and extracting and recovering acetone from the tower top; and transferring a tower kettle material to a PDCB primary rectifying tower, extracting mesityl oxide / PDCB / water azeotrope from the tower top, separating to obtain a PDCB crude product, feeding the PDCB crude product into a PDCB refining tower, refining, and recovering a PDCB finished product. The method provided by the invention can reduce malodorous substances in the system recovery solvent, reduce the odor in the production process and ensure the polymerization stability.

Description

Technical Field

[0001] The present invention relates to the technical field of polyarylene sulfides, and particularly relates to a method for reducing malodorous smell in the production process of polyarylene sulfide resins. Background Art

[0002] Polyphenylene sulfide is the sixth largest engineering plastic and is widely used in the fields of environmental protection, automotive electronics, machinery, chemical industry, and aerospace. Polyarylene sulfides are high-performance polymers that can withstand high thermal stress, chemical stress, and mechanical stress and are beneficial for a variety of applications. Polyarylene sulfides are usually formed by polymerizing a dihaloaromatic monomer with an alkali metal sulfide or an alkali metal hydrosulfide in an organic amide solvent. Currently, the most commonly used synthetic route for polyphenylene sulfide is the sodium sulfide method. After polymerization, the polymer needs to be separated from the solvent, unreacted monomers, and other impurities, and then washed and purified, and finally dried to obtain polyarylene sulfide. Since acetone has good hydrophilicity, can dissolve most organic substances, has a low boiling point (56.4 °C at normal pressure), a small latent heat of vaporization, low toxicity, and high cost performance, many post-treatment processes usually preferably use an acetyl compound (i.e., acetone) for washing and purification. Acetone is used to wash away most of the oligomers generated during polymerization. However, the malodorous substances generated by side reactions of acetone remain in the recycled solvent, affecting the quality of the recycled solvent product, resulting in an obvious smell of the recycled solvent (recycled acetone, recycled PDCB). Recycling PDCB to the polymerization reaction will cause unstable product quality. The olfactory threshold of this substance is extremely low. If the solvent leaks, it will greatly affect the on-site production working environment. At the same time, the side reaction of acetone increases the consumption of acetone, which is usually not desirable.

[0003] The Chinese patent document with the application publication number CN102906160A discloses a method for manufacturing polyarylene sulfide. It is considered in the document that since the polymerization of PPS is carried out at a high temperature, the by-produced sulfur compounds from the raw material source and the decomposition products of the organic amide solvent used as the reaction solvent are the causes of the odor. To solve the above problems, after washing the recovered PPS with an organic solvent, the separated liquid of the washing discharge liquid after separating the polymer in the washing is brought into contact with a basic compound to remove the hydrogen sulfide contained in the polymer separation liquid, thereby greatly reducing the odor of the separation liquid. However, in addition to hydrogen sulfide, other odor-causing substances or impurities in the recycled solvent cannot be removed, still having a certain impact on the product quality and the production environment.

[0004] For another example, a method for forming a polyarylene sulfide is reported in a Chinese patent document with the application publication number CN114008112A. The polyarylene sulfide is subjected to a washing cycle, which includes a first washing stage and a subsequent second washing stage. The first washing stage includes contacting the polyarylene sulfide with a first washing liquid, and the second washing stage includes contacting the polyarylene sulfide with a second washing liquid. Wherein the first washing liquid contains an amount of an organic solvent of about 50 wt.% or more, the second washing liquid contains an amount of water of about 50 wt.% or more, and further wherein the second washing liquid is at a temperature of about 90 °C or higher. However, due to its use of a mixture of NMP solvent and water, the latent heat of vaporization of water is higher than that of acetone and NMP. Separating water and NMP in the later solvent recovery stage requires a large amount of energy, and this method is uneconomical. Moreover, it does not mention the removal process of the corresponding malodorous substances when using acetone as a solvent.

[0005] Again, as proposed in US Patent US20060086374 A1, a method for manufacturing PPS is to wash the polymer separated from the reaction liquid with an organic solvent such as acetone, and then add an inorganic acid such as hydrochloric acid to distill the recovered organic solvent, thereby reducing the content of basic compounds such as methylamine. However, the malodorous substances in acetone are not fundamentally removed. US Patent US20170158820A1 reports a method for reducing impurities in unreacted PDCB that may have an adverse effect on the polymerization reaction by increasing water reflux. By rectifying and increasing the bottom reflux to improve the solvent quality, but it does not mention the composition of the recovered solvent impurities and the related removal process of malodorous substances during solvent rectification.

[0006] With the increasing strictness of clean production and environmental requirements, the environmental odor problems in the production process are increasingly being taken seriously. Summary of the Invention

[0007] In view of the above problems existing in the prior art, the present invention discloses a method for reducing the malodorous smell in the production process of polyarylene sulfide resin, which significantly reduces the residual malodorous substances in the recovered acetone and the recovered PDCB, and significantly reduces the odor intensity in the production process; the recovered PDCB is recycled into the polymerization reaction system for subsequent polymerization reactions, and the weight-average molecular weight of the prepared polymer is basically equivalent to that prepared for the first time, which can ensure the polymerization stability.

[0008] The inventors have found through a large number of studies that the main source of the odor generated during the post-treatment process of PPS with acetone is the aldol condensation reaction of acetone under alkaline conditions, generating isopropylidene acetone MO (the source of malodorous substances). Isopropylidene acetone further reacts with hydrogen sulfide and other sulfur-containing substances to generate organic compounds containing mercapto groups such as 4-mercapto-4-methyl-2-pentanone (MMP) (malodorous substances). The chemical reaction formula is as follows:

[0009]

[0010] Based on the above conclusions, the present invention provides a method for reducing the malodorous smell in the production process of polyarylene sulfide resin, and the specific technical solution is as follows:

[0011] The present invention uses the PPS slurry prepared after polymerization as the raw material, including:

[0012] S1. Sieving the PPS slurry to obtain a PPS filter cake and a slurry mother liquor, adding acetone to the PPS filter cake multiple times for washing, and mixing the obtained filtrates to obtain an acetone mother liquor;

[0013] S2. Mixing the acetone mother liquor obtained in step S1 with the slurry mother liquor to obtain a mixed solution, cooling the mixed solution to no higher than 15°C, adjusting its pH value to 6-9, and filtering to obtain a mixed solvent;

[0014] S3. Feeding the mixed solvent obtained in step S2 into an acetone rectification column, recovering acetone from the top of the column; transferring the bottom material of the column to a PDCB (p-dichlorobenzene) primary rectification column, and taking out an isopropylidene acetone / PDCB / water azeotrope from the top of the column. After separation, a crude PDCB product is obtained; feeding the crude PDCB product into a PDCB refining column, and recovering the finished PDCB product after refining.

[0015] The present invention mainly focuses on a polymerization process using a cooling crystallization process and a washing and purification process using acetone as a solvent in the post-treatment. In the later stage of polymerization, PPS is precipitated by slow cooling. After screening, the oversize material is a PPS crude filter cake containing a small amount of solvent and salt, and the undersize material is a slurry containing by-product salt, the remaining solvent, and fine powder. In this process, some low-molecular-weight PPS and small-molecule reaction by-products will be carried away by the solvent, but there are still some alkaline substances and unreacted sulfides remaining on the PPS crude filter cake; the PPS crude filter cake is further washed and purified. When washing the PPS slurry or filter cake with acetone solvent and contacting the crude filter cake, the alkaline substances remaining from the polymerization reaction entrained on the filter cake will be brought into the solvent, resulting in the final mixed solvent being alkaline with a pH of 10-12. The higher the pH, the higher the temperature, and the longer the residence time, the higher the conversion rate of acetone to form isopropylidene acetone by polycondensation reaction. By controlling the amount of isopropylidene acetone generated by the side reaction of acetone, the generation of malodorous substances is reduced while the loss of acetone is also reduced. At atmospheric pressure, the boiling point of water is 100°C, the boiling point of isopropylidene acetone is 129°C, and the boiling point of PDCB is 174°C. Among them, water and PDCB form an azeotrope, and water and isopropylidene acetone also form an azeotrope. Therefore, in the initial rectification stage of PDCB, the three will be simultaneously drawn out from the top of the rectification tower. Since isopropylidene acetone has low solubility in water and high solubility in PDCB, and water and PDCB are immiscible, in the phase separation stage of the water separator, a large amount of isopropylidene acetone will dissolve in PDCB again, resulting in excessive contents of isopropylidene acetone and MMP in the recycled PDCB. If this solvent leaks, it will cause odors in the production site. If the recycled PDCB obtained by stratification through the water separator in the initial rectification stage of PDCB is directly reused as a raw material in the polymerization reaction, it will result in a lower molecular weight of the product. Therefore, it is necessary to rectify the recycled PDCB again to remove isopropylidene acetone (the source of malodorous substances), ultimately reducing the malodorous substances in the system's recycled solvent, reducing the odor in the production process, and ensuring the polymerization stability.

[0016] Combined with the above, the present invention adopts the following two methods: First, before recovering the acetone solvent, by controlling the system temperature and pH, the generation of isopropylidene acetone is reduced; second, in the solvent recovery stage, isopropylidene acetone is concentrated and removed by rectification separation to reduce its accumulation and reuse in the system. This reduces the residual malodorous substances in the recycled solvent (acetone and PDCB) and reduces the odor intensity in the production process.

[0017] The present invention mainly focuses on PPS prepared by a cooling crystallization process in polymerization. Therefore, preferably, after the PPS slurry undergoes a sodium sulfide-based polymerization reaction, it is prepared by a cooling crystallization process.

[0018] Preferably:

[0019] In step S1, the washed PPS filter cake is further washed with water, screened, and dried to obtain dry PPS.

[0020] Preferably:

[0021] In step S2, cool the mixture to 5 - 10 °C and adjust its pH value to 7 - 8;

[0022] More preferably, cool the mixture to 5 °C.

[0023] Adjust the pH value of the mixture by adding an acidic substance, which can be specifically selected from common types in the art, such as hydrochloric acid, etc.

[0024] After cooling and adjusting the pH value, perform filtration separation to recover sodium chloride and PPS oligomers; the clear mixed solution obtained after filtration is subjected to the subsequent rectification process.

[0025] Preferably:

[0026] In step S3, for the acetone rectification column, control its top temperature at 10 - 80 °C and pressure at -90 - 100 kPaG;

[0027] More preferably, control its top temperature at 56 - 65 °C and pressure at 0 - 20 kPaG.

[0028] Preferably:

[0029] In step S3, for the PDCB primary rectification column, control the reflux ratio at (0.5 - 1.0):1, top temperature at 50 - 120 °C, and pressure at -90 - 100 kPaG;

[0030] More preferably, control its top temperature at 72 - 100 °C and pressure at -70 - 0 kPaG.

[0031] Preferably:

[0032] The isopropylidene acetone / PDCB / water azeotrope is taken out from the top of the column, and is layered in a water separator. The upper layer is waste water, and the lower layer is the crude PDCB separated.

[0033] Preferably:

[0034] In step S3, the bottom material of the PDCB primary rectification column is transferred to the NMP recovery column, and NMP is recovered by taking it out from the top of the column.

[0035] Preferably:

[0036] For the NMP recovery column, control its top temperature at 120 - 230 °C and pressure at -90 - 100 kPaG;

[0037] More preferably, control its top temperature at 159 - 202 °C and pressure at -70 - 0 kPaG.

[0038] Preferably:

[0039] In step S3, for the PDCB refining column, the reflux ratio is controlled to be (5-10):1, the temperature is 60-195°C, and the pressure is -90-100 kPaG;

[0040] More preferably, the temperature is controlled to be 120-170°C and the pressure is -70-0 kPaG.

[0041] Preferably:

[0042] In step S3, the recovered PDCB finished product is recycled to the polymerization reaction system for subsequent polymerization reaction.

[0043] By adopting the above treatment method, the content of mesityl oxide in the recovered acetone prepared by the present invention is not higher than 50 ppm, and the content of 4-mercapto-4-methyl-2-pentanone is not higher than 1 ppm;

[0044] The content of mesityl oxide in the recovered PDCB finished product is not higher than 300 ppm, the content of 4-mercapto-4-methyl-2-pentanone is not higher than 4 ppm, and the odor intensity is level 0 or 1.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] Through in-depth research on the PPS polymerization process and the post-treatment purification process, the present invention proposes a method for reducing the malodorous smell in the production process of polyarylene sulfide resin. Before recovering the acetone solvent, by controlling the system temperature and pH value, the generation of mesityl oxide is reduced; in the solvent recovery stage, mesityl oxide is concentrated and removed by distillation separation to reduce the cumulative reuse in the system; finally, the crude PDCB is refined again; the purification process is optimized from multiple perspectives, so that the residual malodorous substances in the recovered acetone and the recovered PDCB are greatly reduced, and the odor intensity in the production process is significantly reduced; the recovered PDCB is recycled to the polymerization reaction system for subsequent polymerization reaction, and the weight average molecular weight of the prepared polymer is basically the same as that of the first preparation, which can ensure the polymerization stability. Specific embodiments

[0047] In order to further understand the present invention, the present invention will be specifically described below in conjunction with embodiments. However, the present invention is not limited to these embodiments. Non-essential improvements and adjustments made by those skilled in the art under the core guiding ideology of the present invention still fall within the protection scope of the present invention.

[0048] Test method:

[0049] Volatile Content: Volatile content can be determined by subjecting the sample to an elevated temperature and then capturing any resulting "outgassing" and then analyzing it by gas chromatography using known techniques. More specifically, 3.0 grams of a dry sample can be placed in a glass tube and then heated to 320°C for 20 minutes. The resulting off-gas or volatiles are captured by a cold trap. Once captured, the off-gas is analyzed by gas chromatography in an acetonitrile solution to determine if volatile compounds (e.g., MO, MMP, BL, DAA, PhSH, MeSPh, PDCB, NMP, etc.) are present. Biphenyl is used as an internal standard for the analysis.

[0050] (1) Odor sensory test

[0051] The odor of the PPS polymer and the separated liquid was judged by three inspectors according to the "6-level odor intensity representation method", and all the inspectors came to the conclusion of "Level 0 (MMP content of 0-1ppm): no odor", "Level 1 (MMP content of 1-10ppm): barely perceptible odor", "Level 2 (MMP content of 10-25ppm): weak odor with a slight odor", "Level 3 (MMP content of 25-100ppm): easy to smell obvious odor", "Level 4 (MMP content of 100-500ppm): strong odor" or "Level 5 (MMP content of 500ppm or more): very strong odor". If the inspectors' evaluation results differ by more than two levels, at least five people will re-test and evaluate.

[0052] (2) Odor components

[0053] The quantitative determination of the odor components was performed by gas chromatography (hereinafter abbreviated as GC) using recovered acetone, crude PDCB and finished PDCB after distillation separation of a mixture of polymerization slurry mother liquor and washing acetone mother liquor, and the residual amounts of mesityl oxide (MO) and 4-mercapto-4-methyl-2-pentanone (MMP), which are substances with strong odors, in the recovered solvent.

[0054] (3) Analysis of impurities in recovered acetone and PDCB: GC analysis

[0055] GC device:

[0056] Detector: FID (hydrogen flame ionization detector) 230℃;

[0057] Vaporization chamber temperature: 200°C;

[0058] Column: ZB-WAX;

[0059] Column temperature: increase from 50°C to 250°C at a rate of 5°C / min and maintain for 10 minutes;

[0060] Carrier gas: Helium, 5 ml / min (10 kPa);

[0061] Sample volume: 1 μl;

[0062] Values were determined using the standard curves of commercially available mesityl oxide (MO) and 4-mercapto-4-methyl-2-pentanone (MMP).

[0063] Among them, the contents of MO and MMP in the recovered acetone, the crude PDCB, and the finished PDCB in Table 1 were all tested by this method.

[0064] (4) Mw analysis of PPS product:

[0065] The weight-average molecular weight (Mw) was calculated in terms of polystyrene by gel permeation chromatography (GPC), which is one of the size exclusion chromatographies.

[0066] Apparatus: PL GPC220;

[0067] Column name: Plgel Mixed-B;

[0068] Eluent: 1-chloronaphthalene;

[0069] Detector: Differential refractive index detector;

[0070] Column temperature: 210 °C;

[0071] Pre-heating bath temperature: 240 °C;

[0072] Detector temperature: 210 °C;

[0073] Flow rate: 1.0 mL / min;

[0074] Sample injection volume: 100 μL.

[0075] Example 1

[0076] In a 100 L reactor, 19.8 kg (200.0 mol) of N-methylpyrrolidone and 10.0 kg (100.0 mol) of 40% aqueous sodium hydroxide solution were added. Under a stirring speed of 300 rpm and nitrogen protection, the temperature was raised to 120 °C at a rate of 2.0 °C / min and held for 1 hour. After the holding period, the temperature was raised to 200 °C at a rate of 2.0 °C / min to remove 5.8 kg of aqueous solution (water content 98.0%), and then the temperature was lowered to 130 °C. 14.02 kg (100.0 mol) of 40% aqueous sodium hydrosulfide solution, 4.95 kg (50 mol) of NMP, and 3.72 kg of sodium C5 fatty acid salt were added. At the same stirring speed, the temperature was raised to 200 °C at a rate of 1.5 °C / min to remove 6.74 kg of aqueous solution (water content 98.0%). After dehydration, the temperature was lowered to 160 °C. At this time, the amount of sulfur in the system was 98.0 mol, and the water content was 117.6 mol.

[0077] 15.14 kg (103.0 mol) of p-dichlorobenzene and 4.95 kg (104.8 mol) of NMP were added to the above reactor. The temperature was raised to 220 °C at a rate of 1.0 °C / min, held for 3 hours, then raised to 270 °C at a rate of 1.0 °C / min, held for 4 hours, and then lowered to 160 °C at a rate of 1.0 °C / min to obtain a slurry containing PPS.

[0078] The slurry was sieved to obtain a PPS filter cake and a slurry mother liquor. 40 kg of acetone was added to the PPS filter cake and washed 3 times, then sieved. The filtrates obtained after the three washes were mixed to obtain an acetone mother liquor. Then, 40 kg of pure water was added to the PPS filter cake and washed 6 times, then sieved to obtain a wet PPS filter cake, which was dried at 120 °C to obtain 9.28 kg of dry PPS with an Mw of 42000 g / mol.

[0079] Mix the acetone mother liquor obtained above with the slurry mother liquor to obtain 122 kg of a mixed solution, with a temperature of 50 °C and a pH value of 10.5; lower the temperature of the mixed solution to 5 °C, adjust the pH to 7.1 by adding hydrochloric acid, then filter and separate to recover sodium chloride and fine powder (i.e., PPS oligomers). The filtered clear mixed solvent (temperature 55 °C, pH 7.5) enters the acetone rectification column at a rate of 5 kg / h. The top temperature of the acetone rectification column is 58 °C, and the pressure is 0.5 kPaG. Recovered acetone is taken from the top of the column. After testing, the MMP content in the recovered acetone is 0.11 ppm; the material at the bottom of the acetone rectification column is transferred to the PDCB primary rectification column, with a reflux ratio of 0.5:1, a top temperature of 82 °C, and a pressure of -60 kPaG. An isopropylidene acetone / PDCB / water azeotrope is taken from the top of the column. After stratification in a water separator, the upper layer is wastewater, and the lower layer is crude PDCB. After testing, the MO content in the recovered crude PDCB is 980 ppm, and the MMP content is 9 ppm. The material at the bottom of the PDCB primary rectification column is transferred to the NMP recovery column, with a top temperature of 169 °C and a pressure of -60 kPaG. NMP is taken from the top of the column. The odor evaluation of the crude PDCB is relatively good, and a faint odor can barely be detected.

[0080] Feed the crude PDCB into the PDCB refining column, and carry out PDCB refining again. The pressure is -60 kPaG, the reflux ratio is 5:1, and the finished product is taken out at 140 °C. Finally, 0.35 kg of recovered PDCB finished product is obtained; after testing, the MO content in the PDCB finished product is 100 ppm, and the MMP content is 1 ppm. The odor evaluation of the PDCB finished product is relatively good, and no odor is detected.

[0081] Reuse the recovered PDCB finished product in the polymerization reaction system at a ratio of 2.5% for subsequent polymerization reactions. After testing, the Mw of the PPS product prepared after reuse is 42,000 g / mol.

[0082] Example 2

[0083] The preparation process is basically the same as that in Example 1, except that the temperature of the mixed solution obtained by mixing the acetone mother liquor with the slurry mother liquor is lowered to 10 °C.

[0084] In this example, the MMP content in the recovered acetone taken from the top of the acetone rectification column is 0.5 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator is 4300 ppm, and the MMP content is 45 ppm. The crude PDCB passes through the PDCB refining column to recover the PDCB finished product, with an MO content of 300 ppm and an MMP content of 4 ppm. Among them, the odor of the crude PDCB is relatively easy to detect, and the odor evaluation of the PDCB finished product recovered by rectification is relatively good, and a faint odor can barely be detected.

[0085] The recycled PDCB product was reused in the polymerization reaction system at a ratio of 2.5%, and the Mw of the prepared PPS product after reuse was 41,500 g / mol.

[0086] Example 3

[0087] The preparation process was basically the same as that of Example 1, except that the pH of the mixed solution obtained by mixing the acetone mother liquor and the slurry mother liquor was adjusted to 7.0 by adding hydrochloric acid.

[0088] In this example, the MMP content in the recycled acetone taken from the top of the acetone rectification column was 0.1 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator was 910 ppm, and the MMP content was 7 ppm. The crude PDCB was recovered through the PDCB refining column to obtain the PDCB product, with an MO content of 92 ppm and an MMP content of 0.8 ppm. Among them, the crude PDCB could barely be smelled, and the odor evaluation of the PDCB product recovered by distillation was good, without any odor.

[0089] The recycled PDCB product was reused in the polymerization reaction system at a ratio of 2.5%, and the Mw of the prepared PPS product after reuse was 41,800 g / mol.

[0090] Example 4

[0091] The preparation process was basically the same as that of Example 1, except that the pH of the mixed solution obtained by mixing the acetone mother liquor and the slurry mother liquor was adjusted to 8.0 by adding hydrochloric acid.

[0092] In this example, the MMP content in the recycled acetone taken from the top of the acetone rectification column was 0.55 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator was 970 ppm, and the MMP content was 11 ppm. The crude PDCB was recovered through the PDCB refining column to obtain the PDCB product, with an MO content of 99 ppm and an MMP content of 1.1 ppm. Among them, the crude PDCB could be smelled, and the odor evaluation of the PDCB product recovered by distillation was good, and it could barely be smelled.

[0093] The recycled PDCB product was reused in the polymerization reaction system at a ratio of 2.5%, and the Mw of the prepared PPS product after reuse was 41,650 g / mol.

[0094] Example 5

[0095] The preparation process was basically the same as that of Example 1, except that when the crude PDCB was refined, the temperature and pressure of the PDCB refining column were adjusted. The pressure was replaced with -50 kPaG, and the temperature was replaced with 152 °C to produce the finished product.

[0096] In this embodiment, the MMP content in the recovered acetone taken from the top of the acetone rectification column is 0.11 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator is 950 ppm, and the MMP content is 9 ppm. The crude PDCB is recovered through the PDCB refining column to obtain the PDCB finished product, with an MO content of 105 ppm and an MMP content of 1.1 ppm. Among them, the crude PDCB can barely be smelled, and the odor of the PDCB finished product recovered by distillation is reduced and hardly smells.

[0097] The recovered PDCB finished product is recycled into the polymerization reaction system at a ratio of 2.5%, and the Mw of the PPS product prepared after recycling is 41,800 g / mol.

[0098] Example 6

[0099] The preparation process is basically the same as that of Example 1, except that when the isopropylidene acetone / PDCB / water azeotrope is taken out from the PDCB primary rectification column, the reflux ratio of the PDCB primary rectification column is increased to 1:1, and the temperature and pressure remain unchanged.

[0100] In this embodiment, the MMP content in the recovered acetone taken from the top of the acetone rectification column is 0.13 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator is 520 ppm, and the MMP content is 6 ppm. The crude PDCB is recovered through the PDCB refining column to obtain the PDCB finished product, with an MO content of 55 ppm and an MMP content of 0.8 ppm. Among them, the crude PDCB can barely be smelled, and the odor evaluation of the PDCB finished product recovered by distillation is good and there is no odor.

[0101] The recovered PDCB finished product is recycled into the polymerization reaction system at a ratio of 2.5%, and the Mw of the PPS product prepared after recycling is 42,000 g / mol.

[0102] Example 7

[0103] The preparation process is basically the same as that of Example 1, except that when the crude PDCB is refined, the reflux ratio of the PDCB refining column is increased to 10:1, and the temperature and pressure remain unchanged.

[0104] In this embodiment, the content of MMP in the recovered acetone taken from the top of the acetone rectification column is 0.12 ppm; the content of MO in the crude PDCB recovered from the lower layer of the water separator is 970 ppm, and the content of MMP is 9 ppm. The crude PDCB is recovered through the PDCB refining column to obtain the PDCB finished product, the content of MO is 45 ppm, and the content of MMP is 0.7 ppm. Among them, the crude PDCB can barely be smelled, and the PDCB finished product obtained by its rectification recovery has a good odor evaluation and no bad smell.

[0105] The recovered PDCB finished product is recycled into the polymerization reaction system at a ratio of 2.5%, and the Mw of the PPS product prepared after recycling is 42100 g / mol.

[0106] Comparative Example 1

[0107] The preparation process is basically the same as that of Example 1, except that the pH value of the mixed solution is not adjusted, and the pH value of the mixed solution is still 10.5.

[0108] In this comparative example, the content of MMP in the recovered acetone taken from the top of the acetone rectification column is 11 ppm; the content of MO in the crude PDCB recovered from the lower layer of the water separator is 75000 ppm, and the content of MMP is 720 ppm. The crude PDCB is recovered through the PDCB refining column to obtain the PDCB finished product, the content of MO is 5000 ppm, and the content of MMP is 60 ppm. Among them, the crude PDCB has a strong bad smell, and the PDCB finished product obtained by its rectification recovery is relatively easy to smell the bad smell, but the bad smell is reduced.

[0109] The recovered PDCB finished product is recycled into the polymerization reaction system at a ratio of 2.5%, and the Mw of the PPS product prepared after recycling is 31800 g / mol.

[0110] Comparative Example 2

[0111] The preparation process is basically the same as that of Example 1, except that the untreated mixed solution (temperature 50 °C, pH value 10.5) is directly fed into the acetone rectification column at a rate of 5 kg / h.

[0112] In this comparative example, the content of MMP in the recovered acetone taken from the top of the acetone rectification column is 35 ppm; the content of MO in the crude PDCB recovered from the lower layer of the water separator is 190000 ppm, and the content of MMP is 2169 ppm. The crude PDCB is recovered through the PDCB refining column to obtain the PDCB finished product, the content of MO is 15000 ppm, and the content of MMP is 150 ppm. Among them, the crude PDCB has a very strong bad smell and a very poor odor evaluation. The bad smell of the PDCB finished product obtained by its rectification recovery is alleviated, but there is still a strong odor.

[0113] The recycled PDCB product was recycled into the polymerization reaction system at a ratio of 2.5%, and the Mw of the prepared PPS product after recycling was 25,000 g / mol.

[0114] Comparative Example 3

[0115] The preparation process was basically the same as that of Example 1, except that the mixed solution was not cooled, and the temperature of the mixed solution remained at 50 °C.

[0116] In this comparative example, the MMP content in the recycled acetone collected from the top of the acetone distillation column was 8 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator was 45,000 ppm, and the MMP content was 477 ppm. The crude PDCB was recycled through the PDCB refining column to obtain the PDCB product, with an MO content of 4,300 ppm and an MMP content of 50 ppm. Among them, the crude PDCB had a strong odor, and the PDCB product recovered by distillation was relatively easy to smell the odor, but the odor was reduced.

[0117] The recycled PDCB product was recycled into the polymerization reaction system at a ratio of 2.5%, and the Mw of the prepared PPS product after recycling was 32,300 g / mol.

[0118] Comparative Example 4

[0119] The preparation process was basically the same as that of Example 1, except that the temperature of the mixed solution was reduced to 20 °C, and the pH was adjusted to 7.5 by adding hydrochloric acid.

[0120] In this comparative example, the MMP content in the recycled acetone collected from the top of the acetone distillation column was 2.6 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator was 15,400 ppm, and the MMP content was 187 ppm. The crude PDCB was recycled through the PDCB refining column to obtain the PDCB product, with an MO content of 1,340 ppm and an MMP content of 14 ppm. Among them, the crude PDCB had a strong odor, and the PDCB product recovered by distillation could feel the odor, but the odor was reduced.

[0121] The recycled PDCB product was recycled into the polymerization reaction system at a ratio of 2.5%, and the Mw of the prepared PPS product after recycling was 36,000 g / mol.

[0122] Comparative Example 5

[0123] The preparation process was basically the same as that of Example 1, except that the pH of the mixed solution was adjusted to 4.0 by adding hydrochloric acid.

[0124] In this comparative example, the MMP content in the recovered acetone taken from the top of the acetone rectification column was 5 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator was 30,000 ppm, and the MMP content was 274 ppm. The crude PDCB was recovered through the PDCB refining column to obtain the PDCB finished product, with an MO content of 2,700 ppm and an MMP content of 28 ppm. Among them, the crude PDCB had a strong odor, and the PDCB finished product obtained through rectification recovery was relatively easy to smell the odor, but the odor was reduced.

[0125] The recovered PDCB finished product was recycled into the polymerization reaction system at a ratio of 2.5%. The Mw of the PPS product prepared after recycling was 35,000 g / mol.

[0126] Comparative Example 6

[0127] The preparation process was basically the same as that of Example 1, except that the crude PDCB was not refined but directly recycled into the polymerization reaction system.

[0128] In this comparative example, the MMP content in the recovered acetone taken from the top of the acetone rectification column was 0.11 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator was 980 ppm, and the MMP content was 9 ppm. There was a barely perceptible odor, and the odor evaluation was good.

[0129] The directly recovered crude PDCB was recycled into the polymerization reaction system at a ratio of 2.5%. The Mw of the PPS product prepared after recycling was 37,000 g / mol.

[0130] Comparative Example 7

[0131] The preparation process was basically the same as that of Comparative Example 1, except that the crude PDCB was not refined but directly recycled into the polymerization reaction system.

[0132] In this comparative example, the MMP content in the recovered acetone taken from the top of the acetone rectification column was 11 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator was 75,000 ppm, and the MMP content was 720 ppm. There was a very strong odor, and the odor evaluation was very poor.

[0133] The directly recovered crude PDCB was recycled into the polymerization reaction system at a ratio of 2.5%. The Mw of the PPS product prepared after recycling was 20,500 g / mol.

[0134] Comparative Example 8

[0135] The preparation process was basically the same as that of Comparative Example 3, except that the crude PDCB was not refined but directly recycled into the polymerization reaction system.

[0136] In this comparative example, the MMP content in the recovered acetone taken from the top of the acetone rectification column was 8 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator was 45,000 ppm, and the MMP content was 477 ppm, which was the same as that in Comparative Example 3. The crude PDCB had a strong odor and a poor odor evaluation.

[0137] The directly recovered crude PDCB was recycled into the polymerization reaction system at a ratio of 2.5%. The Mw of the PPS product prepared after recycling was 22,800 g / mol.

[0138] Comparative Example 9

[0139] The preparation process was basically the same as that in Comparative Example 2, except that the crude PDCB was not refined but directly recycled into the polymerization reaction system.

[0140] In this comparative example, the MMP content in the recovered acetone taken from the top of the acetone rectification column was 35 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator was 190,000 ppm, and the MMP content was 2,169 ppm, which was the same as that in Comparative Example 2. The crude PDCB had a very strong odor and a very poor odor evaluation.

[0141] The directly recovered crude PDCB was recycled into the polymerization reaction system at a ratio of 2.5%. Polymerization occurred abnormally and Mw was not measured.

[0142] Comparative Example 10

[0143] The preparation process was basically the same as that in Comparative Example 9, except that when the isopropylidene acetone / PDCB / water azeotrope was taken out from the PDCB primary rectification column, the reflux ratio of the PDCB primary rectification column was increased to 1:1, and the temperature and pressure remained unchanged.

[0144] In this comparative example, the MMP content in the recovered acetone taken from the top of the acetone rectification column was 35 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator was 130,000 ppm, and the MMP content was 1,560 ppm. It had a very strong odor and a very poor odor evaluation.

[0145] The directly recovered crude PDCB was recycled into the polymerization reaction system at a ratio of 2.5%. Polymerization occurred abnormally and Mw was not measured.

[0146] Comparative Example 11

[0147] The preparation process was basically the same as that in Comparative Example 2, except that in the PDCB primary rectification column, the reflux ratio was increased to 1:1, and the temperature and pressure remained unchanged. When the crude PDCB was refined, the reflux ratio of the PDCB refining column was increased to 10:1, and the temperature and pressure remained unchanged.

[0148] In this comparative example, the MMP content in the recovered acetone taken from the top of the acetone rectification column was 35 ppm; the MO content in the crude PDCB recovered from the lower layer of the water separator was 130,000 ppm, and the MMP content was 1,560 ppm. Subsequently, the crude PDCB was recovered through the PDCB refining column to obtain the PDCB finished product, with an MO content of 1,800 ppm and an MMP content of 26 ppm. Among them, the crude PDCB had a very strong odor and a poor odor evaluation. The odor of the PDCB finished product recovered by distillation was alleviated, but the odor was still relatively easy to smell.

[0149] The recovered PDCB finished product was recycled into the polymerization reaction system at a ratio of 2.5%. The Mw of the PPS product prepared after recycling was 36,500 g / mol.

[0150] The test data during the production processes of each example and comparative example are all listed in Table 1 below.

[0151] Table 1

[0152]

[0153] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The above uses specific examples to elaborate on the present invention, which is only used to help understand the present invention and is not used to limit the present invention. Those skilled in the technical field to which the present invention pertains can also make several simple deductions, deformations, substitutions, or combinations based on the concept of the present invention. These deduction, deformation, substitution, or combination schemes also fall within the scope of the claims of the present invention.

Claims

1. A method for reducing the malodorous smell in the production process of polyarylene sulfide resin, using the PPS slurry prepared after polymerization as the raw material, characterized in that Including: S1. Sieve the PPS slurry to obtain a PPS filter cake and a slurry mother liquor. Add acetone to the PPS filter cake multiple times for washing, and mix the obtained filtrates to obtain an acetone mother liquor; S2. Mix the acetone mother liquor obtained in step S1 with the slurry mother liquor to obtain a mixed solution. Cool the mixed solution to no higher than 15°C, and adjust its pH value to 6 - 9. After filtration, a mixed solvent is obtained; S3. Feed the mixed solvent obtained in step S2 into an acetone rectification column, and recover acetone from the top of the column; Transfer the bottom material of the column to a PDCB primary rectification column, and take out an isopropylidene acetone / PDCB / water azeotrope from the top of the column. After separation, a crude PDCB product is obtained; Feed the crude PDCB product into a PDCB refining column, and recover the finished PDCB product after refining.

2. The method for reducing the malodorous smell in the production process of polyarylene sulfide resin according to claim 1, wherein The PPS slurry is prepared by a sodium sulfide method polymerization reaction followed by a cooling crystallization process.

3. The method for reducing the malodorous smell in the production process of polyarylene sulfide resin according to claim 1, wherein In step S1, the washed PPS filter cake is further washed with water, sieved, and dried to obtain a PPS dry product.

4. The method for reducing malodorous smell in the production process of polyarylene sulfide resin according to claim 1, characterized in that, In step S2, cool the mixed solution to 5 - 10°C, and adjust its pH value to 7 - 8.

5. The method for reducing the malodorous smell in the production process of polyarylene sulfide resin according to claim 1, characterized in that, In step S3, for the acetone rectification column, control the top temperature at 10 - 80°C and the pressure at -90 - 100 kPaG.

6. The method for reducing the malodorous smell in the production process of polyarylene sulfide resin according to claim 1, characterized in that, In step S3, for the PDCB primary rectification column, control the reflux ratio at (0.5 - 1.0):1, the top temperature at 50 - 120°C, and the pressure at -90 - 100 kPaG.

7. The method for reducing the malodorous smell in the production process of polyarylene sulfide resin according to claim 1, characterized in that, In step S3, transfer the bottom material of the PDCB primary rectification column to an NMP recovery column, and recover NMP from the top of the column.

8. The method for reducing the malodorous smell in the production process of polyarylene sulfide resin according to claim 1, wherein In step S3, for the PDCB refining column, control the reflux ratio at (5 - 10):1, the temperature at 60 - 195°C, and the pressure at -90 - 100 kPaG.

9. The method for reducing the malodorous smell in the production process of polyarylene sulfide resin according to claim 1, wherein In step S3, the recovered finished PDCB product is recycled to the polymerization reaction system for subsequent polymerization reactions.

10. The method for reducing the malodorous smell in the production process of polyarylene sulfide resin according to any one of claims 1 - 9, characterized in that: The content of isopropylidene acetone in the recovered acetone is not higher than 50 ppm, and the content of 4-mercapto-4-methyl-2-pentanone is not higher than 1 ppm; The content of isopropylidene acetone in the recovered finished PDCB product is not higher than 300 ppm, the content of 4-mercapto-4-methyl-2-pentanone is not higher than 4 ppm, and the odor intensity is grade 0 or grade 1.

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