The present application is a National Phase entry pursuant to 35 U.S.C. § 371 or International Application No. PCT/KR2018/010862 filed on Sep. 14, 2018, and claims priority to and the benefit of Korean Patent Application No. 10-2017-0121475 filed on Sep. 20, 2017 and Korean Patent Application No. 10-2018-0108349 filed on Sep. 11, 2018, which are hereby incorporated by reference in their entireties into this application.

FIELD

The present invention relates to a method of preparing a polyarylene sulfide with a high yield, in which the polyarylene sulfide may have physical properties equivalent to or better than those of the existing method, and of which its main by-product (NaCl) may be recycled.

BACKGROUND

Polyarylene sulfide (PAS), represented by polyphenylene sulfide (PPS), is widely used in automobiles, electrical and electronic products, and machinery as a substitute for metals, and particularly for die casted metals such as aluminum or zinc, due to its excellent strength, heat resistance, flame retardancy, and processability. In particular, PPS resin is advantageous for use as a compound by kneading with a filler such as a glass fiber or a reinforcing agent, because of its good fluidity.

Generally, PAS is prepared by performing a polymerization reaction of a sulfur source and a dihalogenated aromatic compound under polymerization conditions in the presence of a polar organic compound such as N-methyl pyrrolidone (NMP), and optionally, by further using a molecular weight modifier such as alkali metal salts. A reaction product resulting from the polymerization reaction includes an aqueous phase and an organic phase, and the resulting PAS is dissolved mainly in the organic phase. Therefore, a process of separating the produced PAS is additionally performed, in which a method of precipitating PAS by cooling the reaction product is mainly used.

In this regard, a sulfur source is used for the polymerization of polyphenylene sulfide (PPS), and as the sulfur source, Na2S produced from NaHS and NaOH is used to perform PPS polymerization. In this process, after the reaction of NaHS and NaOH, Na binds to Cl of p-DCB (para-dichlorobenzene) to produce a large amount of NaCl as a by-product. However, a large amount of NaCl has caused corrosion problems in a reactor, and a method of treating excess NaCl contained in the reactor has also been problematic.

SUMMARY

To solve the above problems, an object of the present invention is to provide a method of preparing a polyarylene sulfide, wherein an aqueous alkali metal salt produced as a polymerization by-product is recycled as a reaction additive during preparation of a sulfur source to reduce production costs, and to prepare polyarylene sulfide having physical properties equivalent to or better than those of the existing method, and showing a high yield. According to one embodiment of the present invention, a method of preparing a polyarylene sulfide is provided, the method including:

a first step of preparing a sulfur source containing an alkali metal sulfide and a mixed solvent of water and an amide-based compound by dehydrating a product resulting from reaction of an alkali metal hydrosulfide, an alkali metal hydroxide, and an alkali metal salt in a mixed solvent of water and the amide-based compound in the presence of an alkali metal organic acid salt; and

a second step of polymerizing the polyarylene sulfide by adding a dihalogenated aromatic compound and an amide-based compound to a reactor containing the sulfur source,

wherein the alkali metal salt includes sodium chloride, potassium chloride, rubidium chloride, or cesium chloride.

Effect of the Invention

In the present invention, in order to reduce use of an alkali metal hydroxide such as NaOH during preparation of a sulfur source which is used in the polymerization of a polyarylene sulfide, an alkali metal salt such as NaCl which is produced as a by-product of the polyarylene sulfide polymerization is introduced during the preparation process of the sulfur source, thereby producing polyarylene sulfide having thermal properties equivalent to or greater than those of the existing method. Further, in the present invention, since the main polymerization by-product (NaCl) is not discarded but is recycled to the preparation process of the sulfur source, economic advantages as well as a high yield may be achieved, as compared to the existing processes.

