METHOD FOR PRODUCING OF POLYARYLENE SULFIDES

Abstract: Disclosed is a method for producing a polyarylene sulfide comprising contacting a dihalogenated aromatic compound with an alkali metal sulfide in a polar solvent, wherein a halogenated aromatic compound containing active hydrogen is present in the reaction system.

Description: FIELD OF THE INVENTION The present invention relates to a method for producing a polyarylene sulfide comprising polymerizing a polyhalogenated aromatic primary amino compound with a dihalogenated aromatic compound and an alkali metal sulfide in a polar solvent to provide a polyarylene sulfide having a high molecular weight, which shows a low flowability when melted and contains a small amount of a contaminant salt. BACKGROUND OF THE INVENTION Polyarylene sulfides such as a polyphenylene sulfide are generally thermoplastic resins although some of them have a thermosetting property, and have excellent properties desired for engineering plastics such as high resistance to chemicals, good mechanical properties over a wide range of temperature and a high stiffness at high temperatures. It is known that polyarylene sulfides can generally be produced by polymerizing a dihalogenated aromatic compound such as p-dichlorobenzene with an alkali metal sulfide such as sodium sulfide in a polar solvent (cf. Japanese Patent Publication No. 12240/1977). However, conventional polyarylene sulfides have a low molecular weight and thus it has been necessary to cure the low molecular weight polyarylene sulfides by heat treatment in order to obtain final products having a high molecular weight so that their manufacture is complicated. Heretofore, there has been known a method for producing a polyphenylene sulfide having a high molecular weight in which a lithium halide is used as a catalyst as described in, for example, U.S. Patent 4,038,263. However, this prior art method is disadvantageous since it cannot provide a polyphenylene sulfide having such a high molecular weight that no heat treatment of the resultant polymer is needed. Further, there have been known methods for producing branched chain polyphenylene sulfides having high molecular weights in which a compound containing three or more halogen atoms are present in the reaction system as described in, for example, Japanese Patent Publication No. 87919/1979 and Japanese Patent Application (OPI) No. 197430/1984. These methods, however, are also disadvantageous in that the resultant polymers tend to gel easily so that there occur problems in productivity and quality of the products. In addition, if the resultant polymers have a high flowability it is difficult to smoothly carry out molding of the polymers into various shaped products such as films, fibers, molded articles due to the fact that the polymers partly gel. Another problem of the above-mentioned conventional methods for producing polyarylene sulfides is that the polyarylene sulfide produced contains a large amount of one or more salts such as sodium chloride which are by-produced during the polymerization reaction, and when the polyarylene sulfide is used as a material for parts of electric and electronic devices the insulation resistance to humidity of circuits is decreased, resulting in the occurrence of misoperation. DE-A-2 626 362 discloses a process for producing arylene sulfide polymers by the reaction of p-dichlorobenzene with a polyhalo-substituted aromatic compound and an alkali metal sulfide in a polar solvent in the presence of a lithium halogenide wherein carbondioxide is added to the reaction mixture during or after the formation of the polymer in order to prevent a vacuum destillation for the removal of the polar solvent. DE-A-2 623 363 as well describes a process for producing branched arylene sulfide polymers by the reaction of a halobenzene with at least one alkali metal sulfide in the presence of N-methyl-2-pyrrolidone, an alkali metal hydroxide and at least one polyhalogenated aromatic compound and lithium chloride. The reduction of nitroaromatic compounds to the corresponding anilines by sulfides is known from J. March "Advanced Organic Chemistry", McGraw-Hill, New York (1968), page 897. DE-A-2 026 655 discloses a method for producing poly(phenylenethioether) polymers having a high molecular weight by reacting the halogenated aromatic primary amino compound with a dihalogenated aromatic compound and an alkali metal sulfide in a polar solvent. The object of the present invention now is to provide a method for producing a polyarylene sulfide having a high molecular weight, a low melt flow index, an excellent stability, does not cause gellation, comprises only small amounts of a contaminant salt and can be used as a material for the manufacture of parts for electric and electronic devices. As a result of extensive investigations it has now been found that this problem can be solved by a method for producing a polyarylene sulfide comprising polymerizing a halogenated aromatic primary amino compound with a dihalogenated aromatic compound and an alkali metal sulfide in a polar solvent and in the presence of lithium chloride has a catalyst. The subject matter of the present invention therefore is the method according to claim 1. The subclaims 2 to 7 comprise preferred embodiments of this subject matter. DETAILED DESCRIPTION OF THE INVENTION The polar solvent which can be used in the method of the present invention includes amide compounds, lactam compounds, urea compounds, cyclic organic phosphorus compounds, etc. Specific examples of the polar solvent include N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dipropylacetamide, N,N-dimethylbenzamide, caprolactam, N-methylcaprolactam, N-ethylcaprolactam, N-isopropylcaprolactam, N-isobutylcaprolactam, N-propylcaprolactam, N-butylcaprolactam, N-cyclohexylcaprolactam, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N-isobutyl-2-pyrrolidone, N-propyl-2-pyrrolidone, N-butyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, N-methyl-3-methyl-2-pyrrolidone, N-methyl-3,4,5-trimethyl-2-pyrrolidone, N-ethyl-2-piperidone, N-ethyl-2-piperidone, N-isopropyl-2-piperidone, N-isobutyl-2-piperidone, N-methyl-6-methyl-2-piperidone, N-methyl-3-ethyl-2-piperidone, N-methyl-2-oxohexamethylenimine, N-ethyl-2-oxo-hexamethylenimine, tetramethylurea, 1,3-dimethylethyleneurea, 1,3-dimethylpropyleneurea, 1-methyl-1-oxosulfolane, 1-ethyl-1-oxosulfolane, 1-phenyl-1-oxosulfolane, 1-methyl-1-oxophosphane, 1-propyl-1-oxophosphane and 1-phenyl-1-oxophosphane. Of the above-described polar solvents, N-alkyllactams, N-alkylpyrrolidones, etc. are preferred. As the above-described dihalogenated aromatic compound, there can be enumerated dihalogenated benzenes such as m-dichlorobenzene, p-dichlorobenzene, p-dibromobenzene, m-dibromobenzene, 1-chloro-4-bromobenzene, etc., substituted dihalogenated benzenes such as 2,5-dichlorotoluene, 2,5-dichloroxylene, 1-ethyl-2,5-dichlorobenzene, 1-ethyl-2,5-dibromobenzene, 1-ethyl-2-bromo-5-chlorobenzene, 1,2,4,5-tetramethyl-3,6-dichlorobenzene, 1-cyclohexyl-2,5-dichlorobenzene, 1-phenyl-2,5-dichlorobenzene, 1-benzyl-2,5-dichlorobenzene, 1-phenyl-2,5-dibromobenzene, 1-p-toluyl-2,5-dichlorobenzene, 1-p-toluyl-2,5-di-bromobenzene and 1-hexyl-2,5-dichlorobenzene. Of these, dihalogenated benzenes are preferred, with p-dichlorobenzene being more preferred. As the alkali metal sulfide, there can be enumerated, for example, lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide, etc. and mixtures thereof. In the method of the present invention, the alkali metal sulfide can usually be used in the form of a hydrate or an aqueous mixture. Preferred example of the alkali metal sulfide include lithium sulfide and sodium sulfide. The polyhalogenated aromatic primary amino compound containing active hydrogen which can be used in the method of the present invention includes aromatic compounds having at least one aromatic ring in which at least one carbon atom of the aromatic ring is connected to a primary amino (-NH₂) radical, and at least two carbon atoms of the aromatic ring are connected to halogen atoms. Suitable examples of the above-described aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, etc. Of these, a benzene ring is preferred in the present invention. When the above-described polyhalogenated aromatic compound containing active hydrogen includes two or more aromatic rings the aromatic rings may be connected to each other either directly via a simple chemical bond or through intermediary of a divalent group. Suitable examples of the divalent group include an oxygen atom (-O-), a sulfur atom (-S-), a sulfinyl group, a sulfonyl group, a carbonyl group, and a divalent carbohydrate group such as an oxyalkylene group, a carbonylalkylene group, a polymethylene group, etc. Suitable examples of the halogen atom include fluorine, chlorine, bromine, and iodine. Of these, chlorine and bromine are preferred, with chlorine being more preferred. The two or more halogen atoms contained in two or more radicals containing active hydrogen or two or more halogenated aromatic compounds containing active hydrogen may be the same or different. Of the polyhalogenated aromatic primary amino compounds which meet the above-described conditions, dihalogenated compounds, and trihalogenated compounds are preferred, with dihalogenated aromatic primary amino compounds being more preferred. Suitable examples of the above-described polyhalogenated aromatic primary amino compound will be explained in greater detail with reference to general formula. That is, the polyhalogenated aromatic primary amino compounds which can be used advantageously in the present invention are represented by the following general formulae (I) to (III) In the general formula (I) above, X represents a halogen atom such as fluorine, chlorine, bromine, iodine, etc., Y represents -NH₂, k is an integer of 2 to 5, and n is an integer of 1 to 4, provided that k + n is an integer of 3 to 6. X represents preferably chlorine or bromine, and more preferably chlorine. k is preferably 2 or 3, and more preferably 2. n is 1 or 2, and more preferably 1. In the general formula (II) above, X and Y have the same meanings as defined above, Z represents a divalent group such as -O-, -S-,-SO-, -SO₂-, -CO-, (-CR¹R²-)p-, etc., or a simple chemical bond, p is 0 or an integer of 1 or more, r , t , n and m are 0 or an integer of 1 or more and simultaneously satisfy the following relationships: 2 ≦ (r + t) ≦ {10 - (n + m)} 1 ≦ (n + m) ≦ { 10 - (r + t)} (r + n) ≦ 5 (t + m) ≦ 5 R¹ and R² independently represent a hydrogen atom or a carbohydrate group such as an alkyl group. Preferably, R¹ and R² independently represent a hydrogen atom or a methyl group, and more preferably a hydrogen atom. X represents preferably chlorine or bromine, with chlorine being more preferred. Y represents -NH₂. Preferably, r and t are 0 or a positive integer and satisfy the relationship: (r + t) = 2, or (r + t) = 3, and more preferably (r + t) = 2, that is, r = 1 and t = 1, r = 2 and t = 0, or r=0 and t = 2. Preferably, n and m are such that (n + m) = 1 or (n + m) = 2, that is, n = 1 and m = 0, n = 0 and m = 1, n = 2 and m = 0, n = 1 and m = 1, or n = 0 and m = 2. In the general formula (III) above, X, Y and Z have the same meanings as defined above. o is an integer of 1 to 3, and p is an integer of 1 to 5. Suitable examples of the halogenated aromatic primary amino compounds represented by the general formula (I) include dihalogenated primary amino benzene compounds such as 2,6-dichloroaniline, 2,5-dichloroaniline, 2,4-dichloroaniline, 2,3-dichloroaniline, 2,4-dibromoaniline, (2,6-dichlorophenyl)aminobenzene, (2,5-dichlorophenyl)-aminobenzene, (2,4-dichlorophenyl)aminobenzene and 2,3-(dichlorophenyl)aminobenzene, trihalogenated benzene compounds containing such as 2,3,4-trichloroaniline, 2,3,5-trichloroaniline, 2,3,6-trichloroaniline, 2,4,5-trichloroaniline, 2,4,6-trichloroaniline, 3,4,5-trichloroaniline, 2,3,5-tribromoaniline, 2,4,5-tribromoaniline, 2,4,6-tribromoaniline, 2,5-dichloro-4-bromoaniline, 2,3,5-trichloro(phenylamino)benzene, 2,4,5-trichloro(phenylamino)benzene, 2,4,6-trichloro(phenylamino)-benzene, 2,4,5-tribromo(phenylamino)benzene and 2,4,6-tribromo(phenylamino)benzene, polyhalogenated benzene compounds such as 2,3,4,5-tetrachloroaniline and 2,3,5,6-tetrachloroaniline. Suitable examples of the polyhalogenated aromatic primary amino compounds represented by the general formula (II) include dihalogenated aromatic primary amino compounds, for example, diaminodichlorodiphenyl ethers such as 2,2'-diamino-4,4'-dichlorodiphenyl ether, 2,4'-diamino-2',4-dichlorodiphenyl ether, etc., diaminodichlorodiphenyl thioethers, such as 2,2'-diamino-4,4'-dichlorodiphenyl thioether and 2,4'-diamino-2',4-dichlorodiphenyl thioether, diaminodichlorodiphenyl sulfoxides such as 2,2'-diamino-4,4'-dichlorodiphenyl sulfoxide and 2,4'-diamino-2',4-dichlorodiphenyl sulfoxide, diaminodichlorodiphenylalkanes such as 2,2'-diamino-4,4'-dichlorodiphenylmethane and 2,4'-diamino-2'4-dichloro-4,4'-dichlorodiphenylmethane, dihalogenoaminodiphenyl ethers such as 2,5-dichloro-4'-aminodiphenyl ether, 2,5-dibromo-4'-aminodiphenyl ether and 2,5-dibromo-4'-aminodiphenyl ether, dihalogenoaminodiphenyl thioethers such as 2,5-dichloro-4'-aminodiphenyl thioether and 2,5-dibromo-4'-aminodiphenyl thioether, dihalogenoaminodiphenyl sulfoxides such as 2,5-dichloro-4'-aminodiphenyl sulfoxide and 2,5-dibromo-4'-aminodiphenyl sulfoxide, dihalogenoaminodiphenylalkanes such as 2,5-dichloro-4'-aminodiphenylmethane and 2,5-dibromo-4'-aminodiphenylmethane, trihalogenated primary amino compounds, for example, aminotrihalogenodiphenyl ethers such as 2,2'-diamino-3,4,4'-trichlorodiphenyl ether, 2,4'-diamino-2',5',4-trichlorodiphenyl ether, 2,4,5-tri-chloro-4'-aminodiphenyl ether, 2,3,4-trichloro-4'-aminodiphenyl ether, 2,4,5-tribromo-4'-aminodiphenyl ether, 2,4,6-tribromo-4'-aminodiphenyl ether, 2,5-dichloro-6-bromo-4'-aminodiphenyl ether and 2,4,5-trichloro-2'-aminodiphenyl ether, aminotrihalogenodiphenyl thioethers, such as 2,2'-diamino-3,4,4'-tri-chlorodiphenyl thioether and 2,4,5-trichloro-4'-aminodiphenyl thioether, aminotrichlorodiphenyl sulfoxides such as 2,2'-diamino-4,5,4'-trichlorodiphenyl sulfoxide and 2,4,5-trichloro-4'-aminodiphenyl sulfoxide, aminotrihalogenodiphenylalkanes such as 2,2'-diamino-3,4,4'-trichlorodiphenylmethane, 2,4,5-tri-chloro-4'-aminodiphenylmethane and 2,4,4'-trichloro-2'-aminodiphenylpropane, aminotrihalogenobiphenyls such as 3,4,4'-trichloro-3'-aminobiphenyl and polyhalogenated aromatic primary amino compounds such as tetra-chloroaminodiphenyl ether and tetrachloroaminodiphenyl thioether. Suitable examples of the dihalogenated primary amino compounds represented by general formula (III) include dihalogenoaminodiphenyl ethers such as 2,5-dichloro-4'-aminodiphenyl ether and 2,5-dibromo-4'-aminodiphenyl ether, dihalogenoaminodiphenyl thioethers such as 2,5-dichloro-4'-aminodiphenyl thioether and 2,5-dibromo-4'-aminodiphenyl thioether, dihalogenoaminodiphenyl sulfoxides such as 2,5-dichloro-4'-aminodiphenyl sulfoxide and 2,5-dibromo-4'-aminodiphenyl sulfoxide, dihalogenoaminodiphenylmethanes such as 2,5-dichloro-4'-aminodiphenylmethane and 2,5-dibromo-4'-aminodiphenylmethane. In the present invention, those compounds comprising a naphthalene nucleus substituted with an amino group, can also be used in addition to the above-described halogenated aromatic primary amino compounds represented by one of general formulae (I), (II) and (III). Of the polyhalogenated aromatic primary amino compounds those represented by general formula (I) are preferred. Further, dihalogenated aromatic primary amino compounds are suitable and among them dichloroaniline is particularly preferred. In the present invention, the above-described various polyhalogenated aromatic primary amino compounds can be used singly or in combination. According to the present invention, polyarylene sulfides can be produced by reacting (A) the dihalogenated aromatic compound with (B) the alkali metal sulfide in the presence of (C) the polyhalogenated aromatic compound containing a primary amino group and lithium chloride in (D) the polar solvent. The polyhalogenated aromatic primary amino compounds containing active hydrogen represented by general formula (I), (II) or (III), can also be produced by reducing the nitro group of a halogenated aromatic nitro compound represented by general formula (IV), (V) or (VI) in the reaction system. Therefore, the method of the present invention can also be carried out by reacting the dihalogenated aromatic compound (A) with the alkali metal sulfide (B) in the presence of lithium chloride and a halogenated aromatic nitro compound (E) represented by general formula (IV), (V) or (VI), with optionally adding a reducing agent (F), instead of directly using the halogenated aromatic compound containing a primary amino group (C). That is, the polyhalogenated aromatic nitro compound (E) represented by general formula (IV), (V) or (VI) and the alkali metal sulfide (B) or the reducing agent (F) are reacted to form in the reaction system the halogenated aromatic primary amino compound containing active hydrogen (C), which makes it possible to produce polyarylene sulfide by substantially reacting the dihalogenated aromatic compound (A) with the alkali metal sulfide (B) in the presence of the halogenated aromatic primary amino compound in the polar solvent (D). The polyhalogenated aromatic compounds (E) are represented by general formula (IV), (V) or (VI) below. In general formula (IV), X and k have the same meanings as defined in general formula (I). In general formula (V), Z, m , r and t have the same meanings as defined above. In general formula (VI), X, Z, o and p have the same meanings as defined above. Specific examples of the compounds represented by general formula (IV) include 2,4-dinitrochlorobenzene, and 2,5-dinitrochlorobenzene. Specific examples of the compounds represented by general formula (V) include 2-nitro-4,4'-dichlorodiphenyl ether and 3,3'-dinitro-4,4'-dichlorodiphenylsulfone. Specific examples of the compounds represented by general formula (VI) include 2,5-dichloro-4'-nitrodiphenyl ether and 2,5-dichloro-4'-nitrodiphenyl thioether. As for the reducing agent (F), there can be mentioned of, for example, hydrazine, hydrides and alkali formates. Preferred examples thereof include hydrides such as calcium hydride (CaH₂), hydrogen sulfide, etc., borohydrides such as lithium borohydride, sodium borohydride (NaBH₄), potassium borohydride, etc. Borohydrides are particularly preferred. When the halogenated aromatic primary amino compounds (C) are used, usually the components (A), (B), (C) and (D) can be used in the polycondensation reaction in the following proportions. That is, the molar ratio of the component (A) to component (B) is from 0.75 to 2.0, preferably from 0.90 to 1.2. Since the reaction between the dihalogenated aromatic compound (A) and the alkali metal sulfide (B) is an equimolar reaction usually the above-described range is selected. The component (C) is used in an amount of from 0.005 to 2.0 mol%, preferably from 0.01 to 1.5 mol%, based on the component (A). When the amount of the component (C) is less than 0.005 mol%, it is sometimes difficult to produce polyarylene sulfides having a high molecular weight. On the other hand, when the amount of the component (C) is more than 2 mol%, gelation occurs under certain circumstances. The molar ratio of the component (D) to component (B) is from 1 to 15, preferably 2 to 10. When this value is less than 1, the reaction is sometimes non-uniform, while the productivity is decreased when the molar ratio is more than 15. The polycondensation reaction used for the production of polyarylene sulfide is carried out usually under alkaline conditions. Therefore, in order to render the reaction system alkaline, an alkali hydroxide (G) can be added to the reaction system. Suitable examples of the alkali hydroxide (G) include sodium hydroxide, lithium hydroxide, potassium hydroxide, rubidium hydroxide and cesium hydroxide. Of these, lithium hydroxide, sodium hydroxide and potassium hydroxide are preferred. The amount of the alkali hydroxide added to the reaction system is not particularly limited as far as it is sufficient for rendering the reaction system alkaline. Upon the production of polyarylene sulfides, it is lithium chloride is present as a catalyst in the reaction system since the polycondensation reaction between the dihalogenated aromatic compound and the alkali metal sulfide can proceed smoothly. The lithium chloride may be used as anhydride or hydrate or aqueous mixture. The lithium chloride present in the reaction system, in cooperation with the concomitant halogenated aromatic primary amino compound is useful in reducing the amount of contaminant salt(s) in the resultant polyarylene sulfide considerably although the underlying mechanism has not been clarified yet. Of course, use of the lithium chloride as a catalyst does not preclude use of other catalyst(s) such as the carboxylate (I) and/or sulfonate (J) simultaneously, and a combination of the alkali metal halide compound (H) and the carboxylate (I) and/or sulfonate (J) can also be used as a catalyst. The molar ratio of the carboxylate or aromatic sulfonate to be added to the component (B) is the same as the molar ratio of the component (D) to component (B). In the method of the present invention, upon condensation reaction, these components can be brought in contact all at the same time or they can be contacted separately. There is no particular limitation on the order of the addition of the components. The condensation reaction is carried out usually at a temperature in the range of from 180 to 320°C, preferably from 220 to 300°C. When the reaction temperature is above 320°C side reaction occurs during the condensation reaction, or productivity of polyarylene sulfide may sometimes be decreased. The preferred temperature is not higher than 320°C or less, and more specifically, a temperature higher than the melting point of polyarylene sulfide, preferably by 5°C higher than the melting point of polyarylene sulfide which is produced. For example, the melting point of typical polyarylene sulfide is in the vicinity of 284°C and hence the temperature of the condensation reaction is set at from 284 to 296°C, preferably at from 289 to 292°C. There is no particular limitation on the reaction pressure used in the condensation reaction but usually the pressure which can be used varies from the self inside pressure of the reactor to 4,9 MPa (50 kg/cm²) (absolute pressure), preferably from the self inside pressure of the reactor to 0,98 MPa (10 kg/cm²) (absolute pressure). The condensation reaction maybe carried out under an atmosphere of an inert gas such as nitrogen, carbon dioxide, steam etc. The reaction time is usually in the range of from 0.1 to 8 hours. After completion of the reaction, polyarylene sulfide can be separated from the reaction mixture directly or after addition of a dilute acid using a conventional method such as filtration or centrifugation. Subsequent to filtration, generally, the residue is washed with water in order to remove any inorganic components such as alkali metal sulfide and alkali hydroxide that could adhere to the resultant polymer. In addition to or after the washing step, washing using different washing solution or extraction can be carried out. The polymer obtained can be recovered by removing the solvent from the reactor and then washing the polymer in the manner described above. The polyarylene sulfide thus recovered has a sufficiently high molecular weight without needing heat treatment. Particularly, it should be noted those polyarylene sulfides which are prepared according to the method using a lithium chloride as a catalyst, and those which are obtained by performing polycondensation at a temperature higher than the melting point of the polyarylene sulfide contain salts such as sodium chloride, etc. in amounts much smaller than those contained in polyarylene sulfides prepared according to conventional methods. As a result, the polyarylene sulfide according to the present invention can be molded and processed without needing desalting beforehand, and utilized in electric and electronic fields advantageously. However, if desired, various desalting treatments can be carried out in addition to the above-described washing step or after the washing step to further decrease the content of salts such as sodium chloride in the resin prior to use. When the polyarylene sulfide obtained according to the method of the present invention is molded into various articles, it can be admixed with other polymers, pigments, fillers such as graphite, metal powders, glass powders, quartz powders or glass fiber, or additives usually used for polyarylene sulfides such as conventional stabilizers or mold lubricants. The polyarylene sulfide obtained according to the method of the present invention contains only a small amount of salts in the polymer and therefore it has a high insulational resistance to humidity and a low melt flow index which indicates that the polymer has a high molecular weight, resulting in that it can be used not only as a matrix resin for producing various molded articles and composite materials but also molded into various articles, films, fibers, etc. Therefore, it is excellent engineering plastic which can be used advantageously for producing various mechanical or electronic parts. The present invention has the following benefits or advantages; (1) High molecular weight polyarylene sulfides having a low melt flow index can be produced. (2) According to the method of the present invention, polyarylene sulfide having a high molecular weight can be produced using trichlorobenzene in an amount half that used in the conventional method by the addition of the halogenated aromatic compound containing active hydrogen. (3) In the method of the present invention, polyarylene sulfide containing less contaminant salt content can be obtained by the use of the specified catalyst. (4) In the method of the present invention, polyarylene sulfide containing less contaminant salt content can also be obtained by fixing the temperature of the condensation reaction to the specified level. The present invention will be described in greater detail with reference to examples and comparative examples. However, the present invention should not be construed as being limited to these examples. EXAMPLE 1 In a 2 ℓ autoclave were charged 81.5 g (0.56 mol) of p-dichlorobenzene, 25.0g (0.54 mol) of lithium sulfide, 0.164g (0.001 mol) of 2,5-dichloroaniline, 0.914 g (0.024 mol) of sodium borohydride, and 306 mℓ (2.93 mol) of N-methyl-2-pyrrolidone as solvent, and nitrogen gas was passed at room temperature for 10 minutes to purge the air in the autoclave. Then, while stirring the mixture the temperature of the reaction system was elevated up to 120°C, followed by sealing the autoclave, elevating the temperature up to 265°C and allowing the mixture to react for 3 hours. After completion of there action, the reaction mixture was cooled to 190°C with stirring, and then left to stand until the temperature reached room temperature. The reaction mixture was poured into 1 ℓ of water, filtered, washed with water and washed with methanol in this order. The polyphenylene sulfide obtained had a melt flow index of 0.034 mℓ/sec. The melt flow index was measured under the conditions of 300°C, a load of 4,9 MPa (50kg/cm²), and the diameter and length of nozzle used: 1 mm and 10 mm, respectively. EXAMPLE 2 The same procedures as in Example 1 were repeated except that the amount of 2,5-dichloroaniline was changed to 0.772 g (0.0048 mol). The polyphenylene sulfide had a melt flow index of 0.01 mℓ/sec. COMPARATIVE EXAMPLE 1 The same procedures as in Example 1 were repeated except that 2,5-dichloroaniline was not used. The polyphenylene sulfide obtained had a melt flow index of 0.79 mℓ/sec. COMPARATIVE EXAMPLE 2 The same procedures as in Example 1 were repeated except that 0.001 mol of trichlorobenzene was used in place of 0.001 mol of 2,5-dichloroaniline. The polyphenylene sulfide obtained had a melt flow index of 0.49 mℓ/sec. EXAMPLE 3 The same procedures as in Example 1 were repeated except that sodium borohydride was not used. The polyphenylene sulfide obtained had a melt flow index of 0.026 mℓ/sec. EXAMPLE 4 In a 2 ℓ autoclave were charged 130.4g (0.54 mol) of sodium sulfide nonahydrate, 35.8g (0.54 mol) of lithium acetate, 40.1g (0.54 mol) of lithium carbonate and 370 mℓ of N-methyl-2-pyrrolidone, and 88 mℓ of water was removed by azeotropic distillation. Thereafter, 81.5g (0.56 mol) of p-dichlorobenzene, 25.0g (0.54 mol) of lithium sulfide, 0.161g (0.001 mol) of 2,5-dichloroaniline and 150 mℓ of N-methyl-2-pyrrolidone were added to the reaction system, and under nitrogen gas atmosphere the reaction was carried out at a temperature of 265°C for 3 hours. The reaction mixture was poured into 0.1 N hydrochloric acid, filtered, washed with water and washed with methanol in this order. The polyphenylene sulfide obtained had a melt flow index of 0.40 mℓ/sec. EXAMPLE 5 The same procedures as in Example 4 were repeated except that the amount of 2,5-dichloroaniline was changed to 0.733 g (0.0045 mol). The polyphenylene sulfide had a melt flow index of 0.06 mℓ/sec. COMPARATIVE EXAMPLE 3 The same procedures as in Example 3 were repeated except that 0.001 mol of trichlorobenzene was used in place of 0.001 mol of 2,5-dichloroaniline. The polyphenylene sulfide obtained had a melt flow index of 0.65 mℓ/sec. EXAMPLE 6 In a 1 ℓ autoclave were charged 45.0g (0.31 mol) of p-dichlorobenzene, 13.8g (0.30 mol) of lithium sulfide, and 0.168g (0.004mol) of lithium hydroxide monohydrate, and then 0.20g (0.001 mol) of 2,5-dichloronitrobenzene, 0.5g (0.013 mol) of sodium borohydride, and 169 mℓ (1.62 mol) of N-methyl-2-pyrrolidone as solvent, and argon gas was passed at room temperature for 10 minutes to purge the air in the autoclave. Then, while stirring the mixture the temperature of the reaction system was elevated up to 110°C, followed by sealing the autoclave, elevating the temperature up to 265°C and allowing the mixture to react for 3 hours. After completion of the reaction, the reaction mixture was cooled to 215°C with stirring and then left to stand until the temperature reached room temperature. The reaction mixture was poured into 1 ℓ of water, filtered, washed with water and washed with hot methanol in this order. The polyphenylene sulfide obtained had a melt flow index shown in Table 1 below. COMPARATIVE EXAMPLE 4 The same procedures as in Example 6 were repeated except that 2,5-dichloronitrobenzene was not used. The polyphenylene sulfide obtained had a melt flow index of 0.78 mℓ/sec. This was heated at 200°C for 1 hour. The physical properties of the thus treated polymer are as shown in Table 1 below. EXAMPLE 7 The same procedures as in Example 6 were repeated except that sodium borohydride was not used. The polyphenylene sulfide obtained had a melt flow index as shown in Table 1 below. Melt Flow Index (ml/sec) Melting Point (°C) Heat Decomposition Temperature 5 wt% Reduction (°C) 10 wt% Reduction (°C) Ex. 6 0.15 273 484 502 C.Ex.4 0.78 273 486 500 Ex. 7 0.20 276 485 501 From the results shown in Table 1 above, it can be seen that in Comparative Example 4 polyphenylene sulfide having physical properties similar to those of polyphenylene sulfides of Examples 6 and 7 could not be obtained before the polyphenylene sulfide was heated at 200°C. EXAMPLE 8 The same procedures as in Example 6 were repeated except that the amount of 2,5-dichloronitrobenzene was changed to 0.48 g (0.0025 mol), and 0.004 mol of potassium hydroxide was used in place of lithium hydroxide monohydrate. The polyphenylene sulfide obtained had a melt flow index of 0.01 mℓ/sec. EXAMPLE 9 The same procedures as in Example 6 were repeated except that 0.211 g (0.001 mol) of 2,4-dinitrochlorobenzene was used in place of 2,5-dichloronitrobenzene. The polyphenylene sulfide obtained had a melt flow index of 0.48 mℓ/sec. COMPARATIVE EXAMPLE 5 The same procedures as in Example 6 were repeated except that 2,5-dichloroaniline was not used and in place of sodium borohydride were used 19.8 g (0.3 mol) of lithium acetate and 22.2 g (0.3 mol) of lithium carbonate. The polyphenylene sulfide obtained had a melt flow index of 0.58 mℓ/sec. EXAMPLE 10 The same procedures as in Example 6 were repeated except that 0.57 g (0.002 mol) of 2-nitro-4,4'-dichlorodiphenyl ether was used in place of 2,5-dichloronitrobenzene. The polyphenylene sulfide obtained had a melt flow index of 0.08 mℓ/sec. COMPARATIVE EXAMPLE 6 In a 1 ℓ autoclave were charged 13.8 g (0.30 mol) of lithium sulfide, 45.0 g (0.31 mol) of p-dichlorobenzene and 19.8 g (0.30 mol) of lithium acetate, 22.2 g (0.30 mol) of lithium carbonate and 168 mℓ of N-methyl-2-pyrrolidone and the reaction was continued under nitrogen gas atmosphere at a temperature of 262 to 265 °C for 3 hours. The reaction mixture was poured into 1 ℓ of ion-exchanged water, filtered, washed with water and washed with methanol in this order. The Li⁺ content in the polymer obtained was 930 ppm according to the atomic absorption spectroscopy. The polymer had a melt flow index of 0.76 mℓ and inherent viscosity of 0.14. EXAMPLE 11 In a 2 ℓ autoclave were charged 130.4 g (0.54 mol) of sodium sulfide nonahydrate, 23.0 g (0.54 mol) of lithium chloride and 356 mℓ of N-methyl-2-pyrrolidone, and 88 mℓ of water was removed by azeotropic distillation. Thereafter, 81.5 g (0.56 mol) of p-dichlorobenzene, 0.80 g (0.005 mol) of 2,5-dichloroaniline and 150 ml of N-methyl-2-pyrrolidone were added to the reaction system, and under nitrogen gas atmosphere the reaction was carried out at a temperature of 287°C for 3 hours. Ion-exchanged water (1 ℓ) was poured to the reaction mixture, filtered, washed with ion-exchanged water and washed with methanol in this order. The polyphenylene sulfide obtained had a melt flow index of 0.0031 mℓ/sec. The solution thereof had an inherent viscosity η inh (in 1-chloronaphthalene, 206°C) of 0.30. The content of residual ion in the polymer was 60 ppm for Na⁺ and 120 ppm for Li⁺. EXAMPLE 12 The same procedures as in Example 11 were repeated except that 15.3 g (0.36 mol) of lithium chloride was used and the reaction temperature was 265°C. The polyphenylene sulfide obtained had a melt flow index of 0.007 mℓ/sec. The solution thereof had an inherent viscosity η inh (in 1-chloronaphthalene, 206°C) of 0.35. The content of residual ion in the polymer was 40 ppm for Na⁺ and 70 ppm for Li⁺. EXAMPLE 13 The same procedures as in Example 12 were repeated using the same reaction system as in Example 11 except that 0.30 g (0.008 mol) of sodium hydride was added, 0.80 g (0.005 mol) of 2,5-dichloroaniline was used and the reaction temperature was 285°C. The polyphenylene sulfide obtained had a melt flow index of 0.028 mℓ/sec. The solution thereof had an inherent viscosity η inh (in 1-chloronaphthalene, 206°C) of 0.31. The content of residual ion in the polymer was 60 ppm for Na⁺ and 270 ppm for Li⁺. COMPARATIVE EXAMPLE 7 The same procedures as in Example 11 were repeated except that 0.89 g (0.005 mol) of trichlorobenzene was used in place of 2,5-dichloroaniline. The polymer formed gelled and became insoluble in the autoclave. The content of residual ion in the polymer was 2200 ppm for Na⁺ and 1000 ppm for Li⁺. COMPARATIVE EXAMPLE 8 The same procedures as in Example 11 were repeated except that lithium chloride was not used. The polyphenylene sulfide obtained had a melt flow index of 0.78 mℓ/sec. The solution thereof had an inherent viscosity η inh (in 1-chloronaphthalene, 206°C) of 0.13. The content of residual ion in the polymer was 640 ppm for Na⁺. COMPARATIVE EXAMPLE 9 The same procedures as in Example 11 were repeated except that 2,5-dichloroaniline was not used. The polyphenylene sulfide obtained had a melt flow index of 0.15 mℓ/sec. The solution thereof had an inherent viscosity η inh (in 1-chloronaphthalene, 206°C) of 0.23. The content of residual ion in the polymer was 70 ppm for Na⁺ and 200 ppm for Li⁺.

Claims: A method for producing a polyarylene sulfide comprising polymerizing halogenated aromatic primary amino compound with a dihalogenated aromatic compound and an alkali metal sulfide in a polar solvent, characterized in that lithium chloride is present in the reaction system as a catalyst. The method as claimed in claim 1, characterized by reducing a halogenated aromatic nitro compound to the corresponding halogenated aromatic amino primary amino compound and carrying out the reduction step and the polymerization step as a one-pot reaction. The method as claimed in claim 1, characterized in that the dihalogenated aromatic compound is p-dichlorobenzene. The method as claimed in claim 1, characterized in that the halogenated aromatic primary amino compound is a dihalogenated aromatic primary amino compound. The method as claimed in claim 4, characterized in that the dihalogenated aromatic primary amino compound is dichloroaniline. The method as claimed in claim 1, wherein the reaction for the production of the polyarylene sulfide is carried out at a temperature not lower than the melting point of the polyarylene sulfide. The method as claimed in claim 6, wherein the temperature is by 5°C higher than the melting point of the polyarylene sulfide.

Inventors: OGATA, NORIO, SENGA, MINORU, YAMATO, HIROYASU
Applicants: IDEMITSU PETROCHEMICAL CO. LTD.
Application year: 1986
Main classification: C08G75
IPC codes: C08G75