JPH11169870A - Waste water treating device in production of polyarylene sulfide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple waste water treating device for decoloring a colored waste water in the production of polyarylene sulfide. SOLUTION: In the waste water treating method in the production of polyarylene sulfide, a hypochlorite compound, e.g. sodium hypochlorite, is added into the colored waster water which is discharged in a process for isolating and purifying polyarylene sulfide from a high polymer slurry containing polyarylene sulfide obtained by the reaction of an alkali metal sulfide with a polyhaloaromatic compound in an organic solvent and which is preferably adjusted to pH 7-10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment method for producing polyarylene sulfide.

[0002]

2. Description of the Related Art In a process for producing a polyarylene sulfide, a large amount of water is used to unreact sulfur-containing monomers (such as Na ₂ S) and by-product salts (such as NaCl) in a polymer.
Is generally removed by washing.

[0003]

However, the wastewater discharged from the above-mentioned process is markedly colored and cannot be disposed of as it is, but is further diluted with a large amount of water and disposed. An object of the present invention is to provide a simple wastewater treatment method for decolorizing colored wastewater during the production of polyarylene sulfide.

[0004]

Means for Solving the Problems As a result of intensive studies on the above-mentioned method for decolorizing colored wastewater, the inventors have found that when a hypochlorous acid compound is added to colored wastewater, it is easily decolorized. Was completed.

That is, the present invention provides (1) isolation of polyarylene sulfide from a polymer slurry containing polyarylene sulfide obtained by reacting an alkali metal sulfide with a polyhalo aromatic compound in an organic polar solvent. Wastewater treatment method at the time of production of polyarylene sulfide, characterized by adding a hypochlorite compound to colored wastewater discharged in the step of refining, and

(2) The present invention provides the method for treating wastewater according to the above (1), wherein the pH of the wastewater is adjusted to 7 to 10 and then a hypochlorite compound is added.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. Regarding the polymerization method of polyarylene sulfide,
Any method known to those skilled in the art may be used. Examples thereof include: (1) alkali metal sulfide, particularly sodium sulfide having water of crystallization (hereinafter abbreviated as sodium sulfide) is heated in an organic polar solvent to remove water contained in the sodium sulfide. A method of adding dichlorobenzene thereto and subjecting to heat polymerization (US Pat. No. 3,354,129),

(2) Raw materials such as an organic polar solvent, a hydrated alkali metal sulfide, and a dihaloaromatic compound are charged together,
A method in which the reaction system is dehydrated while raising the temperature, and further subjected to a polymerization reaction while continuing the dehydration (JP-A-59-105027);

(3) A mixture of a dihalo aromatic compound (which may contain a small amount of an aromatic trihalo aromatic compound or a tetrahalo aromatic compound) and an organic polar solvent is mixed with
A method in which a hydrated alkali metal sulfide is introduced at a temperature at which the water can be removed from the reaction mixture at a temperature of not less than ° C and a polymerization reaction is carried out (JP-A-60-104130).

[0010] The isolation and purification of polyarylene sulfide from the polymer slurry obtained as described above include, for example, (1) first, upon completion of polymerization, the polymer slurry as it is, or after adding an acid or a base, Or heating under normal pressure to distill off only the solvent, and then washing the solid residue with water, acetone, methyl ethyl ketone, a solvent such as alcohol, or further neutralizing and washing,

(2) After the polymerization is completed, water is added to the polymer slurry.
Solvents such as acetone, methyl ethyl ketone, alcohols, ethers, halogenated hydrocarbons, aromatic hydrocarbons, and aliphatic hydrocarbons (soluble in the polymerization solvent used and a poor solvent for at least the produced polymer. Is added as a precipitant to precipitate the polymer, which is filtered off and washed ("washing" in these cases can be carried out in the form of extraction),

(3) The polymer slurry is stirred as it is, or after adding a reaction solvent (or a solvent having a low molecular weight polymer equivalent thereto) or a reaction solvent and an acid or alkali to the polymer slurry and stirring, Separately, a method of washing with a solvent such as water, acetone, methyl ethyl ketone, and alcohols, or further neutralizing and washing, excluding the low-molecular-weight polymer, and the like can be mentioned.

In the effluent from the above-mentioned isolation and purification step,
When the composition contains an organic compound as a polymerization solvent or a washing solvent, it is separated by distillation, and the solvent and the organic compound are recovered. On the other hand, an aqueous solution containing an inorganic salt or the like is treated as wastewater. In the wastewater, unreacted monomers such as alkali metal sulfides and polysulfides in which alkali metal sulfides have changed during polymerization remain, and considerable coloring is presumed to be caused by these. It is presumed that by adding a hypochlorous acid compound to the colored wastewater, a substance presumed to cause coloring is oxidized to sodium thiosulfate and discolored. The coloring phenomenon described above is particularly severe when an acid or the like is used in the isolation and purification step, and even in such a case, the fading effect due to the addition of the hypochlorous acid compound is remarkable.

The hypochlorite compound used in the wastewater treatment method of the present invention includes sodium hypochlorite and potassium hypochlorite, each of which may be used alone or a mixture of two. You may use it. The hypochlorite compound used at this time may be in the form of a solid or an aqueous solution. It is preferable to use an aqueous solution of sodium hypochlorite from the viewpoint of availability and stability of the hypochlorous acid compound. The amount of addition may be any amount as long as the coloring degree can be discharged as colored wastewater. Generally, the addition concentration is
An aqueous solution of 12% by weight of available chlorine and sodium hypochlorite is added to the colored wastewater so as to be 1 to 30% by weight.

Next, the decolorizing effect by the addition of the hypochlorous acid compound decreases as the pH of the colored wastewater decreases. Generally, the wastewater discharged in the above-mentioned step shows strong alkalinity (pH 10 to 14), and a hypochlorite compound may be added at that pH, but the pH is reduced to 7 with hydrochloric acid or sulfuric acid.
After adjusting to 10 to 10, it is preferable to add the amount of the hypochlorous acid compound, which is economically preferable. However, if the pH of the waste water is less than 7, chlorine gas is generated by the addition of the hypochlorite compound, which is not preferable.

[0016]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Reference Example 1 In a 4-liter autoclave, 1260 g of N-methylpyrrolidone (NMP) and 309.3 g of sodium hydrosulfide (NaSH.xH ₂ O) containing water of crystallization (4.00 mo)
1), equipped with an alkali trap, and started to raise the temperature in an open system under a nitrogen atmosphere. An aqueous solution in which 164.8 g (4.12 mol) of sodium hydroxide was previously dissolved in 178.5 g of water at 100 ° C. And the temperature was further increased. The water-NMP-H ₂ S mixture started to distill at around 145 ° C., and was distilled to 200 ° C. At this time, the distilled water was 234.1 g, NMP was 61.2 g, H ₂ S
Was 69.65 mmol. Then, the system was sealed and the temperature was raised to 220 ° C. to obtain p-dichlorobenzene.
A solution obtained by dissolving 7 g (3.93 mol) in 359.5 g of NMP was added under pressure. Then, the mixture was heated at 220 ° C. for 4 hours under a nitrogen atmosphere under pressure, and then heated to 260 ° C. and reacted for 1 hour. After the completion of the reaction, the mixture was cooled to obtain a polymer slurry.

Example 1 300 g of the polymer slurry obtained in Reference Example 1 was heated under reduced pressure, and NMP was distilled off.
After adding g, stirring and filtering, the mixture was further washed with 250 g of water. The filtrate discharged at this time had a pH of 13 and was colored yellow-brown (Gardner color value of 10). When an aqueous solution of 12% by weight of available chlorine and sodium hypochlorite was added thereto so that the concentration of the aqueous solution became 15% by weight, the filtrate turned pale yellow (Gardner color value 4). Hereinafter, the aqueous solution of sodium hypochlorite used was 12% by weight of available chlorine.

Example 2 After the pH of the filtrate obtained in Example 1 was adjusted to 9 by adding 0.1 mol / dm3 hydrochloric acid, available chlorine was 12% by weight.
When the aqueous sodium hypochlorite solution was added until the Gardner color value reached 4, the concentration of the aqueous sodium hypochlorite solution in the filtrate after addition was 5% by weight.

Example 3 300 g of the polymer slurry obtained in Reference Example 1 was put into 1 kg of water, washed with water and filtered. The filtrate discharged at this time was distilled under reduced pressure to recover NMP. When 500 g of water was added to the still residue after distillation, the pH of this aqueous solution became 1
3 was colored deep yellow (Gardner color value 8). When an aqueous solution of 12% by weight of available chlorine and sodium hypochlorite was added to the aqueous solution so that the concentration of the aqueous solution became 3% by weight, the solution turned pale yellow (Gardner color value 4).

Example 4 1.00 g of sulfuric acid was added to 300 g of a polymer slurry to obtain 1
Filtration was performed at 20 ° C. to obtain a residue and an NMP filtrate. The residue was put into 250 g of water, stirred, filtered, and then washed with 250 g of water to obtain a residue and a filtrate. When the NMP filtrate (acidic) and the filtrate (alkaline) were mixed, a precipitate (low molecular weight polymer) was found. This mixture (pH 4)
Was made alkaline with sodium hydroxide and then the filtrate was distilled to remove NMP. Water was added to the residue evaporated to dryness, and the insolubles were removed by filtration. The filtrate (pH 11) thus obtained is dark brown (Gardner color value 1).
8) I was doing. When an aqueous solution of 12% by weight of available chlorine and sodium hypochlorite was added to the filtrate so that the concentration of the aqueous solution became 15% by weight, the solution turned pale yellow (Gardner color value 4).

Example 5 The filtrate (pH 13) obtained in Example 3 was added in an amount of 0.1 mol /
After adding dm3 hydrochloric acid to adjust the pH to 9, an aqueous solution of 12% by weight of available chlorine and sodium hypochlorite was added until the Gardner color value reached 4, and the filtrate after the addition was treated with an aqueous solution of sodium hypochlorite. The concentration was 8% by weight.

[0023]

According to the wastewater treatment method of the present invention, it is easy to decolorize colored wastewater.

Claims (2)

[Claims] 1. A process for isolating and purifying polyarylene sulfide from a polymer slurry containing polyarylene sulfide obtained by reacting an alkali metal sulfide with a polyhaloaromatic compound in an organic polar solvent. A wastewater treatment method for producing polyarylene sulfide, comprising adding a hypochlorite compound to colored wastewater. 2. The wastewater treatment method according to claim 1, wherein a hypochlorite compound is added after adjusting the pH of the wastewater to 7 to 10.