JPH10130005A - Method for producing lithium sulfide and method for producing polyarylene sulfide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high purity Li2 S without using H2 S for a raw material and under a mild condition by allowing NaSH to react with LiCl and de- hydrogensulfidation after removing the deposited NaCl. SOLUTION: NaSH and LiCl are allowed to react with each other in a non- protonic organic solvent (e.g. N-methyl-2-pyrolidone) preferably at >=0 deg.C, particularly 0-130 deg.C to produce LiSH and NaCl and after the deposited NaCl is removed, de-hydrogensulfidation is performed preferably at 130-200 deg.C, particularly 170-190 deg.C. The resultant Li2 S is allowed to react with a polyhalogenated aromatic compound (e.g. paradichlorobenzene) in the aprotic organic solvent to produce a high molecular weigh polyarylene sulfide. LiCl by produced at this time is recovered and reused at it is.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing lithium sulfide. More specifically, the present invention relates to a method for producing lithium sulfide, which is particularly useful as a raw material for synthesizing polyarylene sulfide suitably used in the fields of electricity, electronics, and high rigidity materials. Furthermore, the present invention relates to a method for producing polyarylene sulfide using lithium sulfide obtained by the method.

[0002]

2. Description of the Related Art Conventionally, lithium sulfide has been formed by heating elemental lithium and sulfur to a temperature higher than the melting point and reacting them (Troost L. Ann. Chim. Phys., 1875, v. 51 (3), p. .103
) Or a method of forming lithium sulfate by reducing it with carbon, hydrogen, or ammonia while heating (Sulfide Handbook-Physical Properties and State Diagram-by Ke Ve Samsonov, Es V. Drosdova). That was being done.

[0003] However, the conditions in such a manufacturing method are very severe, and the process must be complicated and robust enough to withstand the severe conditions. On the other hand, the present inventors have disclosed in JP-A-07-3
No. 30312 proposed a method for producing lithium sulfide under mild conditions using hydrogen sulfide and lithium hydroxide. However, in this method, hydrogen sulfide is used as a raw material.Because hydrogen sulfide is a toxic substance, special equipment is required for its production and handling, and the location conditions of production plants are limited. Various problems were pointed out.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and does not use hydrogen sulfide as a raw material and is capable of producing lithium sulfide with high purity under mild conditions. The aim is to provide a method. It is another object of the present invention to provide a method for producing polyarylene sulfide having a high molecular weight, by using lithium sulfide obtained by the above method, by which lithium chloride produced as a by-product can be recovered and reused as it is.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above object can be achieved by using a specific method. The present invention has been made based on such findings. That is, the present invention provides a method for producing lithium hydrosulfide and sodium chloride by reacting sodium hydrosulfide with lithium chloride in an aprotic organic solvent, preferably at a reaction temperature of 0 ° C. or higher, and then depositing sodium chloride. After the removal of sulfide, the reaction temperature is preferably 130 to 200 ° C., and the method for producing hydrogen sulfide is provided. Another object of the present invention is to provide a method for producing a polyarylene sulfide, which comprises reacting lithium sulfide and a polyhalogen aromatic compound obtained by the production method in an aprotic organic solvent.

[0006]

Embodiments of the present invention will be described below. Hereinafter, the present invention will be described specifically. 1. Method for Producing Lithium Sulfide (1) Formation of Lithium Hydrosulfide and Sodium Chloride and Removal of Sodium Chloride In the method for producing lithium sulfide according to the present application, first, sodium hydrosulfide and lithium chloride are reacted in an aprotic organic solvent. This produces lithium hydrosulfide and sodium chloride.

Aprotic Organic Solvents The aprotic organic solvents used in the present invention generally include aprotic polar organic compounds (for example, amide compounds, lactam compounds, urea compounds, organic sulfur compounds, cyclic organic phosphorus compounds). Compound etc.) can be suitably used as a single solvent or as a mixed solvent.

Among these aprotic polar organic compounds, the amide compounds include, for example, N, N-
Dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dipropylacetamide, N,
N-dimethylbenzoic acid amide and the like can be mentioned.
Examples of the lactam compound include caprolactam, N-methylcaprolactam, N-ethylcaprolactam, N-isopropylcaprolactam, N-isobutylcaprolactam, N-normalpropylcaprolactam, N-normalbutylcaprolactam, N-cyclohexylcaprolactam and the like. N-alkylcaprolactams, N-methyl-2-pyrrolidone (NMP), N
-Ethyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-isobutyl-2-pyrrolidone, N-n-propyl-2-pyrrolidone, N-n-butyl-
2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, N-methyl-3-methyl-2-pyrrolidone, N-ethyl-3-methyl-2-pyrrolidone, N-methyl-34,
5-trimethyl-2-pyrrolidone, N-methyl-2-piperidone, N-ethyl-2-piperidone, N-isopropyl-2-piperidone, N-methyl-6-methyl-2-
Piperidone, N-methyl-3-ethyl-2-piperidone and the like can be mentioned.

[0009] Examples of the urea compound include tetramethylurea, N, N'-dimethylethyleneurea, N, N'-dimethylpropyleneurea and the like. Further, as the organic sulfur compound,
For example, dimethylsulfoxide, diethylsulfoxide, diphenylsulfone, 1-methyl-1-oxosulfolane, 1-ethyl-1-oxosulfolane, 1-phenyl-1-oxosulfolane, and the like. For example, 1-methyl-1-oxophosphorane, 1-normalpropyl-1-oxophosphorane, 1-phenyl-1-oxophosphorane and the like can be mentioned.

Each of these various aprotic polar organic compounds may be used alone or in combination of two or more.
Further, it can be used as the aprotic organic solvent by mixing with another solvent component which does not disturb the object of the present invention. Among the various aprotic organic solvents,
Preferred are N-alkylcaprolactam and N-alkylpyrrolidone, particularly preferred are N-methyl-
2-pyrrolidone.

Sodium hydrosulfide (NaHS) The sodium hydrosulfide used in the present invention is not particularly limited, and a commercially available product can be used as long as it has high purity. Further, it may be obtained by a reaction between sodium hydroxide and hydrogen sulfide. An aqueous solution is used in terms of availability and transportation.

Lithium chloride (LiCl) The lithium chloride used in the present invention is not particularly limited. Lithium chloride obtained as a by-product in the production of polyarylene sulfide may be used. In this case, the by-produced lithium chloride may be purified by an operation such as crystallization, or may be a solution dissolved in an aprotic organic solvent.

Removal of Sodium Chloride Lithium hydrosulfide and sodium chloride are formed. Here, sodium chloride formed as a solid is removed. The removal method is not particularly limited. What is necessary is just to carry out by the method usually used, such as filtration and centrifugation. In this case, it is desirable from the viewpoint of separation and removal that lithium hydrosulfide is dissolved in the solvent but sodium chloride is not dissolved, but in this state, water present in the solvent is required. Desirably, the proportion is at least less than 50 mol%.

Usage ratio Usage ratio of sodium bisulfide and lithium chloride (molar ratio)
(Sodium hydroxide / lithium chloride) is usually selected in the range of 0.8 to 1.2, particularly preferably 0.95 to 1.05, since it is an equivalent reaction. Reaction method of sodium bisulfide and lithium chloride The reaction method is not particularly limited, but the aprotic organic solvent and lithium chloride are charged into a reaction vessel,
After dissolving lithium chloride in an aprotic organic solvent,
It is preferable to add sodium bisulfide from the viewpoint of allowing the reaction to proceed smoothly. Sodium bisulfide may be added at once, or may be added gradually and added gradually.

[0015] The reaction temperature in this case is preferably 0 ° C or higher, more preferably 0 to 130 ° C. If the temperature is lower than 0 ° C., the reaction rate becomes extremely slow, so that the time required for the synthesis becomes longer, and the process becomes uneconomical. In addition, water present in the system solidifies, or the viscosity of the generated aprotic organic solvent solution of lithium hydrosulfide increases, which hinders the separation of sodium chloride. On the other hand, when the temperature exceeds 130 ° C., there arises a problem that boiling of water present in the reaction solvent is caused. Further, the generated lithium hydrosulfide may further react with each other to generate solid lithium sulfide, which may make separation from sodium chloride difficult.

Reaction of sodium hydrosulfide with lithium chloride
The reaction itself proceeds instantaneously, but to complete the reaction,
It is preferable to hold for about one minute after the introduction of sodium chloride. (2) Lithium hydrosulfide
Generation In the present invention, lithium bisulfide is generated as described above.
After that, lithium hydrosulfide (LiSH) in the reaction solution
To hydrogen sulfide, and high-purity lithium sulfide (Li _TwoS)
Generate.

The reaction temperature at the time of performing the hydrogen sulfide is 1
30-200 degreeC is preferable and 170-190 degreeC is more preferable. If the temperature is lower than 130 ° C., the reaction rate becomes extremely slow, and the time for dehydrogenation becomes long, which is uneconomical in the process. If the temperature exceeds 200 ° C., the boiling point of the solvent may be exceeded. Economy.
Further, the reaction time is preferably 0.5 to 5 hours, more preferably 0.5 to 2 hours.

If the reaction time is less than 0.5 hour, the reaction time is insufficient, lithium hydrosulfide is mixed in the product, and the purity of the lithium sulfide is reduced. The process is uneconomical due to large size. 2. Polyarylene Sulfide Production Method The present invention is characterized in that lithium sulfide obtained by the above-mentioned production method and a polyhalogenated aromatic compound, preferably a polychlorinated aromatic compound, are polymerized in an aprotic organic solvent. And This will be specifically described below. (1) Polymerization component aprotic organic solvent The aprotic organic solvent used in the polymerization step includes:
In the method for producing lithium sulfide, the aprotic organic solvent described above for the production of lithium hydrosulfide and sodium chloride can be used.

These various aprotic organic compounds include:
Each of these may be used alone or in combination of two or more, and further mixed with other solvent components which do not disturb the object of the present invention, and used as the aprotic organic solvent. Among the various aprotic organic solvents, preferred are N-alkylcaprolactam and N-alkylpyrrolidone, and particularly preferred is N-methyl-2-
Pyrrolidone. Lithium Sulfide The lithium sulfide used in the present invention is produced by the method described above. Polyhalogenated Aromatic Compound The polyhalogenated aromatic compound used in the present invention is not particularly limited. Known compounds used for the production of arylene sulfide can be mentioned as preferred examples. Preferably, polychlorinated aromatic compounds, for example, dihalobenzenes such as m-dihalobenzene and p-dihalobenzene; 2,3-dihalotoluene, 2,5
-Dihalotoluene, 2,6-dihalotoluene, 3,4-
Dihalotoluene, 2,5-dihaloxylene, 1-ethyl-2,5-dihalobenzene, 1,2,4,5-tetramethyl-3,6-dihalobenzene, 1-normalhexyl-2,5-dihalobenzene, 1-cyclohexyl- 2,
Alkyl-substituted dihalobenzenes such as 5-dihalobenzene or cycloalkyl-substituted dihalobenzenes; 1-phenyl-2,5-dihalobenzene, 1-benzyl-2,
Aryl-substituted dihalobenzenes such as 5-dihalobenzene and 1-p-toluyl-2,5-dihalobenzene;
Dihalobiphenyls such as 4'-dihalobiphenyl: 1,
4-dihalonaphthalene, 1,6-dihalonaphthalene,
Examples thereof include dihalonaphthalenes such as 2,6-dihalonaphthalene.

A plurality of halogen elements in these polyhalogenated aromatic compounds are fluorine, chlorine,
Bromine or iodine, which may be the same or different, are particularly preferably chlorine. Among them, preferred are dihalobenzenes, and particularly preferred are those containing 50 mol% or more of p-dichlorobenzene. (2) Usage Ratio The mixing ratio of the lithium sulfide and the polyhalogenated aromatic compound at the start of polymerization may be a molar ratio of polyhalogenated aromatic compound / lithium sulfide = 0.90 to 1.30. Preferably, 0.95-1.25 is more preferable,
Among them, 0.95 to 1.20 is most preferable.
By setting the molar ratio to 0.90 to 1.30, the polymerization reaction proceeds smoothly.

The mixing ratio of the lithium sulfide and the aprotic organic solvent is preferably in a molar ratio of lithium sulfide / aprotic organic solvent = 0.05 to 0.50, more preferably 0.10 to 0.50. 30 is more preferable, and among them, 0.
Most preferably, it is 10 to 0.25. By setting the molar ratio to 0.05 to 0.30, the polymerization reaction proceeds smoothly.

The amount of water contained in the aprotic organic solvent is preferably not more than 2.5 moles per mole of lithium sulfide. If it exceeds 2.5 mol, the polymerization does not proceed, and a high-molecular-weight polyarylene sulfide cannot be obtained. In the present invention, if necessary, a branching agent such as an active hydrogen-containing halogenated aromatic compound, a halogenated aromatic compound having three or more halogen atoms in a molecule, and a halogenated aromatic nitro compound may be appropriately used. Can be added to the reaction system and used.

The proportion of the branching agent used if necessary is usually 0.0 to 1 mol of the lithium sulfide.
005 to 0.05 mol, preferably 0.001 to 0.0
2 moles. (3) Polymerization Conditions The polymerization reaction between lithium sulfide and the polyhalogenated aromatic compound in the aprotic organic solvent is not particularly limited as long as polyarylene sulfide is generated. Specifically, main polymerization after pre-polymerization is preferable because higher molecular weight polyarylene sulfide can be polymerized and the reaction time can be shortened. First, as a condition of the pre-polymerization, the polymerization temperature is 180 to 24.
The temperature is preferably 5 ° C, more preferably 200 to 245 ° C. The conversion of the polyhalogenated aromatic compound is preferably 80% or more, more preferably 80 to 95.
% Is preferably carried out under the condition that the ratio becomes%. If the polymerization temperature is less than 180 ° C, the preliminary polymerization becomes insufficient,
If the temperature exceeds 245 ° C., the polymer phase may agglomerate and adhere to the stirring blade in the polymerization system. For the main polymerization, the polymerization temperature is preferably from 235 to 280 ° C, particularly preferably from 240 to 280 ° C. Further, it is preferable to carry out polymerization until the conversion of the polyhalogenated aromatic compound becomes 90 to 99%. (4) When lithium sulfide is reacted with a polychlorinated aromatic compound, polyarylene sulfide and lithium chloride as a by-product are formed in the aprotic organic solvent.
In the present invention, there is an advantage that a solution of lithium chloride in an aprotic organic solvent remaining after separating polyarylene sulfide can be reused as a starting material. That is, if sodium bisulfide is added to a solution of lithium chloride in an aprotic organic solvent remaining after separation of polyarylene sulfide, the method for producing lithium sulfide according to the present invention described above is effective, and the process is efficiently performed. It is possible to continuously produce polyarylene sulfide.

Hereinafter, the present invention will be described more specifically with reference to examples. Example 1 Production Method of Lithium Sulfide (Li ₂ S) Production of Lithium Hydrosulfide (LiSH) In a 500 ml flask equipped with a stirring blade, 12.72 g (0.3 mol) of lithium chloride and N-methyl-2 were added. -300 ml of pyrrolidone (NMP) were added and the lithium chloride was dissolved with stirring. After dissolution, sodium bisulfide having a concentration of 49% by weight (manufactured by Sankyo Chemical Co., Ltd.)
g (0.3 mol) was added and reacted for about 10 minutes. The resulting precipitate was separated by filtration, washed repeatedly with acetone, and dried under reduced pressure for 24 hours. As a result, 16.0
7 g of a white powder was obtained. Elemental analysis of the obtained white powder showed that Na / Cl = 1/1 (molar ratio),
And the X-ray diffraction results were also consistent with those of NaCl.

On the other hand, a part of the solution obtained by the filtration was sampled and quantitatively analyzed for Li and S. Li / S = 1/1 (molar ratio), which was LiSH. It was confirmed that. Production of lithium sulfide (Li ₂ S) 300 g of the LiSH solution obtained above was put into a 500 ml flask equipped with a stirring blade, and the temperature was raised under a nitrogen stream. As the temperature rises, a gas thought to be hydrogen sulfide is generated,
The by-product water started to evaporate, but this water was condensed by the condenser and extracted out of the system. When the temperature reached 180 ° C., the heating was stopped and the reaction was carried out for 3 hours.

After the completion of the reaction, a solid was deposited in the solvent. After cooling, the content was opened in a glass filter and filtered under reduced pressure. The solid was washed three times with NMP and twice with acetone. When the yield after drying was measured, the initial L
The yield was 92% assuming that all of the Li in the iSH was converted to Li ₂ S. Further, when the X-ray diffraction of the obtained white powder was measured, the diffraction peak coincided with that of the reagent Li ₂ S. Example 2 Method for Producing Polyarylene Sulfide Resin The lithium sulfide (Li ₂ S) 0.7 obtained in Example 1 was placed in a 1-liter stainless steel autoclave equipped with stirring blades.
Mol (32.16 g), 0.7 mol (102.91 g) of paradichlorobenzene, 0.35 mol (6.3 g) of water and 303 ml of N-methyl-2-pyrrolidone (NMP) were charged and the temperature was raised to 220 ° C. Then, prepolymerization was performed for 2 hours.
After the completion of the prepolymerization, the temperature was further raised to 260 ° C., and polymerization was performed for 3 hours. The stirring rotation speed during this period was 300 rpm.

After completion of the polymerization, the reaction solution was cooled, and the obtained polymer was washed with water and acetone sequentially and dried to obtain polyarylene sulfide. 0.4 g / d of this polyarylene sulfide was added to α-chloronaphthalene.
and dissolved at a temperature of 206 ° C. using an Ubbelohde viscometer. As a result, the intrinsic viscosity of this polyarylene sulfide is η _inh = 0.24
dl / g.

[0028]

As described above, according to the present invention, high-purity lithium sulfide can be obtained by simple means without using hydrogen sulfide as a raw material and under mild conditions. Further, by using lithium sulfide obtained by the method, lithium chloride as a by-product can be recovered and reused as it is, and a polyarylene sulfide having a high molecular weight can be produced.

Claims (4)

[Claims] 1. A method comprising reacting sodium bisulfide and lithium chloride in an aprotic organic solvent to produce lithium bisulfide and sodium chloride, removing the precipitated sodium chloride, and then removing hydrogen sulfide. Of producing lithium sulfide. 2. The reaction temperature during the formation of lithium hydrogen sulfide is 0 ° C. or higher, and the reaction temperature during the dehydrosulfide reaction is 130 ° C. to 200 ° C. For producing lithium sulfide. 3. A process for producing polyarylene sulfide, comprising reacting lithium sulfide and a polyhalogenated aromatic compound obtained by the process according to claim 1 or 2 in an aprotic organic solvent. 4. The method for producing polyarylene sulfide according to claim 3, wherein the polyhalogenated aromatic compound is a polychlorinated aromatic compound.