JP2017014351A - Method for producing cyclic polyarylene sulfide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a cyclic polyarylene sulfide that enables controlling a ratio of raw materials with good accuracy by reducing an amount of sulfur oxide in a raw material mixture to an adequate amount in the production of a cyclic polyarylene sulfide and therefore permitting the decrease in by-products to produce the cyclic polyarylene sulfide with high purity.SOLUTION: The method for producing a cyclic polyarylene sulfide comprises heating a raw material mixture including at least a sulfidizing agent, a dihalogenated aromatic compound and an organic polar solvent under the condition that the organic polar solvent is 1.25 to 50 liters per mole of sulfur atom in the raw material mixture. The sulfur atom present as a sulfur oxide in the raw material mixture is 0.05 mol or less per mole of sulfur atom in the raw material mixture.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing cyclic polyarylene sulfide efficiently and with high purity.

  Aromatic cyclic compounds can be applied to highly functional materials and functional materials based on the properties resulting from their cyclic properties, such as properties as compounds with inclusion ability, and high molecular weight linear polymers. In recent years, it has attracted attention for its specificity derived from its structure, such as its use as an effective monomer for synthesis. Cyclic polyarylene sulfide (hereinafter, polyarylene sulfide may be abbreviated as PAS) also belongs to the category of aromatic cyclic compounds and is a notable compound as described above.

  As a method for producing a cyclic polyarylene sulfide, for example, a method of oxidative polymerization of a diaryl disulfide compound under ultra-dilution conditions has been proposed (see, for example, Patent Document 1). In this method, it is presumed that cyclic polyarylene sulfide is produced with high selectivity, and that only a small amount of linear polyarylene sulfide is produced, and it is considered that cyclic polyarylene sulfide is obtained with high production rate.

  In addition, as another method for producing cyclic polyarylene sulfide, a method of heating a copper salt of 4-bromothiophenol under ultra-dilution conditions in quinoline is also disclosed (see, for example, Patent Document 2).

  As a method for obtaining cyclic polyarylene sulfide from general-purpose raw materials such as a sulfidizing agent and a dihalogenated aromatic compound by desalting condensation, the amount of sodium sulfide relative to N-methylpyrrolidone is set to 0.1 mol / liter. A method of adding chlorobenzene and contacting at reflux temperature is disclosed (for example, see Non-Patent Document 1). In this method, it can be estimated that cyclic polyarylene sulfide can be obtained because the amount of the organic polar solvent used per 1 mol of sulfur atom of the sulfiding agent is as low as 1.25 liters or more.

  Further, as a method for producing a cyclic polyarylene sulfide other than the above, a sulfidizing agent and a dihalogenated aromatic compound are used in an organic polar solvent of 1.25 liters or more per mole of sulfur atom of the sulfidizing agent, and a mixture thereof is obtained. A method of heating beyond the reflux temperature at normal pressure is disclosed (for example, see Patent Document 3). In this method, it was confirmed that the conversion rate of the dihalogenated aromatic compound reached about 90% in a relatively short time of 0.5 to 2 hours, and the selectivity of the cyclic polyarylene sulfide was improved to about 35%. Yes.

  In addition, in the method for producing polyarylene sulfide by desalting condensation from a sulfidizing agent, a dihalogenated aromatic compound, and a polar solvent, which are the same raw materials as described above, although the target product is different, nitrogen or a rare solvent is used as the polar solvent. Polyarylene sulfide using a polar solvent that has been deoxygenated by a method of venting an inert gas such as a gas, a method of vacuum degassing while irradiating with ultrasonic waves, or a method of adding a chemical substance that reacts with oxygen A manufacturing method is disclosed (for example, see Patent Document 4). In this method, a polyarylene sulfide having a high melt viscosity and excellent thermal stability can be obtained.

  In addition, regarding a method for recovering polyarylene sulfide from a polar organic solvent slurry of polyarylene sulfide, all the atmospheres in the step where polyarylene sulfide is present at 50 ° C. or higher are set to have an acid gas concentration of 5% by volume or less. A recovery method is disclosed (for example, see Patent Document 5). In this method, it has been confirmed that a polyarylene sulfide having excellent thermal stability at the time of melting and having reduced volatile components can be obtained by suppressing generation of a component that degrades the polyarylene sulfide at the time of melting.

Japanese Patent No. 3200027 (Claims) US Pat. No. 5,869,599 (page 14) JP 2009-030012 (pages 28-33) JP 58-152021 A (Claims) JP 2003-113242 A (Claims)

Polymer (Polymer), vol.37, No.14, p.3111-3112, 1996

  However, in the method shown in Patent Document 1, it is essential to carry out the reaction under ultra-dilution conditions, and the amount of cyclic polyarylene sulfide obtained per unit volume of the reaction solution is very small. Since it is difficult to obtain sulfide, and the reaction temperature of the method is around room temperature, the reaction requires a long time of several tens of hours, resulting in inferior productivity. Since linear polyarylene sulfide is close in molecular weight to the target cyclic polyarylene sulfide, it is difficult to separate and remove, and high-purity cyclic polyarylene sulfide cannot be obtained efficiently. In this method, an expensive oxidizing agent such as dichlorodicyanobenzoquinone is required to be equivalent in amount to the starting diaryl disulfide for the progress of oxidative polymerization. , And the inability to obtain a low cost cyclic polyarylene sulfide, a problem such as.

  Even in the method disclosed in Patent Document 2, ultra-dilution conditions are essential as in the method of Patent Document 1, and a long time is required for the reaction, so that the method is extremely low in productivity. Furthermore, it is difficult to separate the by-produced copper bromide from the cyclic polyarylene sulfide, and the resulting cyclic polyarylene sulfide has a low purity.

  In the method shown in Non-Patent Document 1, since the reaction temperature is the reflux temperature, only a very small amount of cyclic polyarylene sulfide can be obtained even in a long-time reaction, and the molecular weight of the linear polyarylene sulfide produced as a by-product is small. Since it was low, separation from the cyclic polyarylene sulfide was difficult, and the resulting cyclic polyarylene sulfide had a low purity.

  In the method shown in Patent Document 3, although a cyclic polyarylene sulfide is efficiently obtained, a low-molecular-weight linear polyarylene sulfide is by-produced, and in order to improve the purity of the obtained cyclic polyarylene sulfide, There has been a desire for further reduction of the components.

  Further, in the method shown in Patent Document 4, since a polar solvent subjected to deoxygenation treatment is used, the progress of side reaction mediated by oxygen is suppressed, so that polyarylene sulfide having high melt viscosity and excellent thermal stability can be obtained. Although expected to be obtained, the target product is polyarylene sulfide, and since the amount of polar solvent used relative to the sulfiding agent is less than 1.25 liters per mole of sulfur atom of the sulfiding agent, The production rate of arylene sulfide was very low and could not be obtained efficiently.

  Further, the method shown in Patent Document 5 also recovers linear polyarylene sulfide with excellent thermal stability at the time of melting and reduced volatile components because the progress of side reactions involving oxygen is suppressed as in Patent Document 4. Although the amount of cyclic polyarylene sulfide obtained was very small.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems of the prior art and to provide a method for efficiently producing cyclic polyarylene sulfide with high purity.

In order to solve the above problems, the present invention provides a method for producing a cyclic polyarylene sulfide having the following characteristics.
[1] A raw material mixture containing at least a sulfidizing agent, a dihalogenated aromatic compound and an organic polar solvent is heated under the condition that the organic polar solvent is 1.25 to 50 liters per mole of sulfur atoms in the raw material mixture. The cyclic polyarylene sulfide is a process for producing a cyclic polyarylene sulfide, wherein the sulfur atoms present as sulfur oxides in the raw material mixture are 0.05 moles or less per mole of sulfur atoms in the raw material mixture. Production method.
[2] The method for producing a cyclic polyarylene sulfide as described in [1] above, wherein an organic polar solvent subjected to deoxygenation treatment is used as the organic polar solvent.
[3] The method for producing a cyclic polyarylene sulfide according to any one of [1] or [2] above, wherein the oxygen concentration in the gas phase in contact with the raw material mixture is 5% by volume or less.
[4] The method for producing a cyclic polyarylene sulfide according to any one of [1] to [3], wherein the raw material mixture is heated beyond the reflux temperature at normal pressure.
[5] The method for producing a cyclic polyarylene sulfide according to any one of [1] to [4], wherein the sulfidizing agent is an alkali metal sulfide.
[6] The method for producing a cyclic polyarylene sulfide according to any one of [1] to [5], wherein the dihalogenated aromatic compound is dichlorobenzene.
[7] The method for producing a cyclic polyarylene sulfide as described in any one of [1] to [6] above, wherein the raw material mixture contains linear polyarylene sulfide.

  ADVANTAGE OF THE INVENTION According to this invention, the method of manufacturing cyclic polyarylene sulfide efficiently with high purity can be provided. More specifically, the ratio of raw materials can be accurately controlled by reducing the amount of sulfur oxide in the raw material mixture in the production of cyclic polyarylene sulfide to an appropriate amount. A method for efficiently producing a polyarylene sulfide of the formula with high purity can be provided.

  Embodiments of the present invention will be described below.

(1) Sulfiding agent The sulfiding agent used in the present invention may be any sulfidizing agent as long as it can introduce a sulfide bond into a dihalogenated aromatic compound. For example, alkali metal sulfide, alkali metal hydrosulfide, and hydrogen sulfide may be used. Can be mentioned.

  Specific examples of the alkali metal sulfide include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide and a mixture of two or more thereof, among which lithium sulfide and / or sodium sulfide are preferable. Sodium sulfide is more preferably used. These alkali metal sulfides can be used as hydrates or aqueous mixtures or in the form of anhydrides. The aqueous mixture refers to an aqueous solution, a mixture of an aqueous solution and a solid component, or a mixture of water and a solid component. Since generally available inexpensive alkali metal sulfides are hydrates or aqueous mixtures, it is preferred to use such forms of alkali metal sulfides.

  Specific examples of the alkali metal hydrosulfide include, for example, lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, lithium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and mixtures of two or more thereof. Lithium hydrosulfide and / or sodium hydrosulfide are preferable, and sodium hydrosulfide is more preferably used.

  In addition, an alkali metal sulfide prepared in situ in a reaction system from an alkali metal hydrosulfide and an alkali metal hydroxide can also be used. Alternatively, an alkali metal sulfide prepared by previously contacting an alkali metal hydrosulfide and an alkali metal hydroxide can be used. These alkali metal hydrosulfides and alkali metal hydroxides can be used as hydrates or aqueous mixtures, or in the form of anhydrides. From the viewpoint of availability and cost of hydrates or aqueous mixtures. preferable.

  Furthermore, alkali metal sulfides prepared in situ in the reaction system from alkali metal hydroxides such as lithium hydroxide and sodium hydroxide and hydrogen sulfide can also be used. Further, alkali metal sulfides prepared by previously contacting alkali metal hydroxides such as lithium hydroxide and sodium hydroxide with hydrogen sulfide can also be used. Hydrogen sulfide can be used in any form of gas, liquid, and aqueous solution.

  In the present invention, the amount of the sulfidizing agent is subtracted from the actual charge when the loss of the sulfidizing agent partially occurs before the start of the reaction with the dihalogenated aromatic compound due to dehydration operation or the like. It shall mean the remaining amount.

  An alkali metal hydroxide and / or an alkaline earth metal hydroxide can be used in combination with the sulfidizing agent. Specific examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, cesium hydroxide, and a mixture of two or more thereof. Specific examples of the metal hydroxide include magnesium hydroxide, calcium hydroxide, strontium hydroxide, barium hydroxide, and the like. Among them, sodium hydroxide is preferably used.

  When an alkali metal hydrosulfide is used as the sulfiding agent, it is particularly preferable to use an alkali metal hydroxide at the same time, but the lower limit of the amount used is 0.80 mol or more per mol of the alkali metal hydrosulfide. And preferably 0.95 mol or more, more preferably 1.005 mol or more. Moreover, the upper limit can illustrate 1.50 mol or less, Preferably it is 1.25 mol or less, More preferably, it is 1.20 mol or less.

  When hydrogen sulfide is used as the sulfiding agent, it is particularly preferable to use an alkali metal hydroxide at the same time. In this case, the lower limit of the amount of alkali metal hydroxide used is 1.60 mol or more per mol of hydrogen sulfide. It can be illustrated, Preferably it is 1.90 mol or more, More preferably, it is 2.01 mol or more. Moreover, the upper limit can illustrate 3.00 mol or less, Preferably it is 2.50 mol or less, More preferably, it is 2.40 mol or less. Here, cyclic PAS can be obtained at a high production rate by setting the amount of the alkali metal hydroxide used within the above range, but the produced cyclic PAS is easily decomposed even if it is more than the above range or at least. The production rate tends to decrease.

(2) Sulfur oxide The sulfur oxide in this invention refers to the thiosulfate ion, sulfite ion, and sulfate ion which originate in a sulfidation agent. These can be qualitatively and quantitatively analyzed by ion chromatography (hereinafter sometimes abbreviated as IC). More specifically, the target sample is first diluted with degassed water at a dilution ratio of 10 to 1000 times, filtered through a membrane filter to remove insoluble matters, and then subjected to IC measurement. By performing, thiosulfate ion, sulfite ion, and sulfate ion in the sample are quantified. Here, the amount of sulfur oxide is defined as the sum of the quantitative values of thiosulfate ions, sulfite ions, and sulfate ions detected by the method described above.

  In addition, since 1 mol of thiosulfate ions contains 2 mol of sulfur atoms, the sulfur atoms present as sulfur oxide are counted as 2 mol.

  The amount of sulfur oxide contained in the sulfiding agent is preferably as small as possible, but generally available sulfiding agents often contain a trace amount of sulfur oxide at the time of acquisition. Therefore, the sulfidizing agent used in the present invention is preferably a high-purity one containing little sulfur oxide, or may be subjected to a treatment for removing the sulfur oxide before use.

  The sulfur atom present as sulfur oxide in the sulfidizing agent is preferably as small as possible. The upper limit is 0.05 mol or less per mol of sulfur atom in the sulfidizing agent, and 0.03 mol or less. Is preferable, 0.02 mol or less is more preferable, and 0.01 mol or less is more preferable. On the other hand, there is no particular lower limit, and it is most preferable that sulfur oxides are not substantially contained in the sulfidizing agent. When sulfur atoms present as sulfur oxides in the sulfidizing agent are in the above preferred range, when the raw material mixture described below is prepared, sulfur atoms present as sulfur oxides in the raw material mixture are further reduced. It is possible to obtain cyclic PAS with higher purity by carrying out the reaction using the raw material mixture.

(3) Dihalogenated aromatic compound Examples of the dihalogenated aromatic compound used in the production of the cyclic PAS of the present invention include p-dichlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dibromobenzene, o- Dihalogenated benzene such as dibromobenzene, m-dibromobenzene, 1-bromo-4-chlorobenzene, 1-bromo-3-chlorobenzene, and 1-methoxy-2,5-dichlorobenzene, 1-methyl-2,5-di Dihalogenated aromatic compounds containing substituents other than halogen such as chlorobenzene, 1,4-dimethyl-2,5-dichlorobenzene, 1,3-dimethyl-2,5-dichlorobenzene and 3,5-dichlorobenzoic acid And so on. Especially, the dihalogenated aromatic compound which has p-dihalogenated benzene represented by p-dichlorobenzene as a main component is preferable. Particularly preferably, it contains 80 to 100 mol%, more preferably 90 to 100 mol% of p-dichlorobenzene. It is also possible to use two or more different dihalogenated aromatic compounds in combination in order to produce a cyclic PAS copolymer.

(4) Organic Polar Solvent In the production of the cyclic PAS of the present invention, an organic polar solvent is used as a reaction solvent, and an organic amide solvent is particularly preferable. Specific examples include N-alkylpyrrolidones such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone and N-cyclohexyl-2-pyrrolidone, caprolactams such as N-methyl-ε-caprolactam, An aprotic organic solvent typified by 3-dimethyl-2-imidazolidinone, N, N-dimethylacetamide, N, N-dimethylformamide, hexamethylphosphoric triamide, etc., and a mixture thereof, have a stable reaction. It is preferably used because it is expensive. Of these, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are preferably used.

  Here, in this invention, in order to reduce the sulfur atom which exists as a sulfur oxide in the below-mentioned raw material mixture, it is preferable to use the organic polar solvent which performed the deoxidation process as an organic polar solvent. By using an organic polar solvent subjected to deoxygenation treatment as the organic polar solvent, sulfur atoms present as sulfur oxides in the raw material mixture described later are 0.05 mol or less per mole of sulfur atoms in the raw material mixture. Thus, it is possible to obtain a cyclic PAS with higher purity by carrying out the reaction using a raw material mixture in which the content of sulfur oxide is further reduced.

  Although there is no restriction | limiting in particular in the method of performing a deoxygenation process about an organic polar solvent, Various well-known deoxygenation techniques can be employ | adopted (for example, refer patent document 4), For example, nitrogen, a noble gas, etc. with respect to an organic polar solvent A method of venting inert gas, a method of vacuum degassing while irradiating with ultrasonic waves, a method of adding a chemical substance that reacts with oxygen, a method of flushing an organic polar solvent in an inert gas, a method of deoxygenating an organic polar solvent Examples of a preferable method include a method of passing through a column filled with an agent.

  Here, as a parameter which prescribes | regulates the organic polar solvent which performed the deoxidation process, the amount of dissolved oxygen can be illustrated, for example, but this can be quantified using a commercially available dissolved oxygen meter (for liquid phases). The upper limit of the dissolved oxygen in the organic polar solvent is preferably 10 ppm or less, more preferably 3 ppm or less, still more preferably 1 ppm or less, and even more preferably 0.5 ppm or less. On the other hand, there is no particularly preferred lower limit, and a state where dissolved oxygen is not substantially contained is most preferred. When the dissolved oxygen in the organic polar solvent to be used is in the above preferred range, the situation is that the sulfur atoms present as sulfur oxide in the raw material mixture described later is 0.05 mol or less per mole of sulfur atoms in the raw material mixture By carrying out the reaction using a raw material mixture in which the content of sulfur oxide is further reduced, it is possible to obtain cyclic PAS with even higher purity.

(5) Cyclic polyarylene sulfide The cyclic PAS in the present invention is a cyclic compound having a repeating unit of formula:-(Ar-S)-as a main constituent unit, and preferably 80 mol% or more of the repeating unit. It is a compound such as the following general formula (A).

  Here, examples of Ar can include units represented by the following general formulas (B) to (M), among which formulas (B) to (K) are preferable, and formulas (B) and (C) are preferred. More preferred is formula (B).

(In the formula, R1 and R2 are substituents selected from hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and a halogen group, and R1 and R2 are the same or different. May be good.)

(In the formula, R1 and R2 are substituents selected from hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and a halogen group, and R1 and R2 are the same or different. May be good.)

(In the formula, R1 and R2 are substituents selected from hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and a halogen group, and R1 and R2 are the same or different. It is good.)

  In addition, in cyclic PAS, repeating units, such as said Formula (B)-Formula (M), may be included at random, may be included in a block, and any of those mixtures may be sufficient. Typical examples of these include cyclic polyphenylene sulfide, cyclic polyphenylene sulfide sulfone, cyclic polyphenylene sulfide ketone, cyclic random copolymers containing these, cyclic block copolymers, and mixtures thereof. . Particularly preferred cyclic PASs include p-phenylene sulfide units as the main structural unit.

Is a cyclic polyphenylene sulfide containing 80 mol% or more, particularly 90 mol% or more.

  Although there is no restriction | limiting in particular in the repeating number m in the said (A) formula of cyclic PAS, 2-50 are preferable, 3-40 are more preferable, and 4-30 can be illustrated as a still more preferable range. As will be described later, when converting a PAS prepolymer containing cyclic PAS to a high degree of polymerization, it is preferable to perform heating at a temperature higher than the temperature at which cyclic PAS melts. Since the melt solution temperature of PAS tends to be high, it is advantageous to set m in the above range from the viewpoint that the conversion of the PAS prepolymer to a high degree of polymerization can be performed at a lower temperature. . The cyclic PAS may be either a single compound having a single repeat number or a mixture of cyclic PASs having different repeat numbers, but a mixture of cyclic PAS having different repeat numbers is a single repeat. Use of a mixture of cyclic PASs having different repeating numbers tends to be lower than that of a single compound having a number, and is preferable because the temperature at the time of conversion to a high degree of polymerization can be further reduced.

(6) Linear polyarylene sulfide The linear PAS in the present invention is a linear compound having a repeating unit of formula:-(Ar-S)-as a main structural unit, and a compound represented by the following general formula (N) It is.

Here, as Ar, as in the case of the above-described cyclic PAS, units represented by the formula (B) to the formula (M) can be exemplified, and among them, the formula (B) to the formula (K) are preferable. B) and formula (C) are more preferred, and formula (B) is particularly preferred.

  In addition, linear PAS may contain repeating units, such as said Formula (B)-Formula (M), at random, may be contained in a block, and may be either of those mixtures. Typical examples of these include linear polyphenylene sulfide, linear polyphenylene sulfide sulfone, linear polyphenylene sulfide ketone, cyclic random copolymers containing these, cyclic block copolymers, and mixtures thereof. .

  Here, for example, a cyclic compound having a repeating number of m is considered to be generated by generating a linear compound having a repeating number of m and cyclizing with a certain probability. Therefore, unless the probability of cyclization is not 100%, A linear body is generated with a certain probability. Therefore, in order to isolate and recover the cyclic PAS that is the object of the present invention, it is necessary to separate the cyclic PAS and the linear PAS. The separation operation will be described in detail later. As the molecular weight of linear PAS increases, cyclic PAS and linear PAS tend to be more accurately separated. The preferred molecular weight of linear PAS is 2,500 in terms of weight average molecular weight. The above can be exemplified, preferably 5,000 or more, more preferably 10,000 or more. When the weight average molecular weight of the linear PAS is within this preferred range, the solubility of the linear PAS in the organic polar solvent decreases, while the cyclic PAS has a strong tendency to dissolve in the organic polar solvent. It is possible to efficiently obtain cyclic PAS from a mixture of cyclic PAS and linear PAS by utilizing the difference in solubility in water.

(7) Method for Producing Cyclic Polyarylene Sulfide The present invention relates to a raw material mixture containing at least a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent, wherein the organic polar solvent is 1 per mole of sulfur atoms in the raw material mixture. A method for producing a cyclic PAS by heating under conditions of 25 liters or more and 50 liters or less, wherein sulfur atoms present as sulfur oxide in the raw material mixture are 0.05 per mole of sulfur atoms in the raw material mixture. The present invention relates to a process for producing a cyclic PAS that is less than or equal to mol. Below, the cyclic PAS manufacturing method in this invention is explained in full detail.

(7-1) Preparation of raw material mixture In producing cyclic PAS in the present invention, first, a raw material mixture containing at least a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent is prepared.
The raw material mixture in the present invention refers to a mixture that produces cyclic PAS by subjecting to reaction conditions described later. In addition to the above essential components, it is also possible to add linear PAS as a raw material component to the raw material mixture, as described later. In addition, a third component that does not significantly inhibit the production of cyclic PAS, and the production of cyclic PAS It is also possible to add a third component having an accelerating effect. Note that the mixture obtained by subjecting the raw material mixture to the reaction conditions described later is referred to as a reaction mixture.

  In the present invention, the amount of the organic polar solvent used for preparing the raw material mixture needs to be 1.25 to 50 liters per mole of sulfur atoms in the raw material mixture. Here, the amount of the organic polar solvent used is the amount obtained by subtracting the amount of the organic polar solvent removed from the reaction system from the amount of the organic polar solvent introduced into the reaction system, based on the volume of the solvent at normal temperature and pressure. Point to. When the amount of organic polar solvent used is less than 1.25 liters per mole of sulfur atoms, the production rate of cyclic PAS is greatly reduced, and the amount of organic polar solvent used is 50 liters per mole of sulfur atoms. When the amount is larger, the amount of cyclic PAS obtained from the reaction solution per unit volume becomes smaller, and thus cyclic PAS cannot be obtained efficiently. A preferable lower limit of the amount of the organic polar solvent used is, for example, 1.5 liters or more per mole of sulfur atoms in the raw material mixture, and more preferably 2.0 liters or more. On the other hand, as a preferable upper limit, 20 liters or less can be illustrated per mole of sulfur atoms in the raw material mixture, more preferably 15 liters or less, and even more preferably 10 liters or less. When the amount of the organic polar solvent used is in the above-mentioned preferable range, cyclic PAS can be obtained with a good production rate, and the amount of cyclic PAS that can be recovered from the reaction solution per unit volume is increased. Can be increased.

  In general, the production of a cyclic compound often requires more solvent than the above range, and the cyclic compound is often not efficiently obtained within the preferred range of the present invention. As will be described later, in the present invention, a temperature exceeding the reflux temperature of the prepared raw material mixture is adopted as a preferred reaction temperature. In this case, the amount of solvent used is smaller than that in the case of general cyclic compound production. There is a tendency that cyclic PAS is efficiently obtained even under a small condition, that is, a condition near the lower limit of the amount of solvent used. The reason for this is not clear at this time, but it is presumed that when the reaction is carried out at a high temperature that cannot be reached under atmospheric pressure conditions, the extremely high conversion rate of the raw material favorably acts on the formation of the cyclic compound. Yes.

  Here, in this invention, the sulfur atom which exists as a sulfur oxide in a raw material mixture needs to be 0.05 mol or less per mol of sulfur atoms in a raw material mixture. When there are more than 0.05 moles of sulfur atoms present as sulfur oxide in the raw material mixture per mole of sulfur atoms in the raw material mixture, the low molecular weight linear PAS produced as a by-product during the reaction increases, and the resulting cyclic There is a tendency for the purity of PAS to decrease. The reason for this is presumed that the ideal reaction is unlikely to proceed due to the ratio of the raw materials deviating from the assumption. Thus, the present inventors can reduce the low molecular weight linear PAS in the reaction mixture by reducing the amount of sulfur oxide in the raw material mixture to an appropriate amount, and the cyclic PAS has a higher purity than the prior art. As a result, the present invention has been completed.

  In addition, the sulfur atom which exists as a sulfur oxide in a raw material mixture needs to be few. That is, as an upper limit, it is 0.05 mol or less per 1 mol of sulfur atoms in the raw material mixture, 0.03 mol or less is preferable, 0.02 mol or less is more preferable, and 0.01 mol or less is more preferable. There is no particular lower limit, and it is most preferable that the lower limit is not substantially contained. When the sulfur atom present as sulfur oxide in the raw material mixture is in the above preferred range, by-product formation of low molecular weight linear PAS leading to a decrease in the purity of cyclic PAS can be further suppressed, and even higher purity can be achieved. It is possible to obtain cyclic PAS.

  As a means for reducing the sulfur atoms present as sulfur oxide in the raw material mixture to 0.05 mol or less per mole of sulfur atoms in the raw material mixture, a method using a high-purity sulfidizing agent used, organic Preferred examples of the polar solvent include a method using an organic polar solvent that has been subjected to deoxygenation treatment, and a method in which the oxygen concentration in the gas phase in contact with the raw material mixture is 5% by volume or less. It is preferable to carry out a combination of these, and it is most preferred to carry out a combination of all the methods described above.

  In the present invention, it is preferable that the oxygen concentration in the gas phase contacted when the raw material mixture is adjusted or when the raw material mixture is heated and reacted is low. That is, as an upper limit, the oxygen concentration in the gas phase in contact with the raw material mixture is preferably 5% by volume or less, more preferably 1% by volume or less, and further preferably 0.1% by volume or less. On the other hand, there is no particular lower limit, and it is most preferable that oxygen is not substantially contained in the gas phase. When the oxygen concentration in the gas phase in contact with the raw material mixture is in the above preferred range, the situation where the sulfur atoms present as sulfur oxide in the raw material mixture is 0.05 mole or less per mole of sulfur atoms in the raw material mixture It is possible to obtain cyclic PAS with higher purity.

  The gas phase oxygen concentration can be measured with a commercially available oxygen concentration meter (for gas phase).

  There are no particular restrictions on the means for reducing the oxygen concentration in the gas phase in contact with the raw material mixture to 5% by volume or less, but various known gas phase oxygen reduction techniques can be employed, and the atmosphere of the process is preferably nitrogen, helium, argon, etc. A method of substituting with an inert gas or a mixture thereof can be exemplified. In the present invention, not only at the time of preparing the raw material mixture, but also the atmosphere when the raw material mixture described below is heated and reacted is preferably an inert gas atmosphere, and in particular, from the viewpoint of economy and ease of handling. Is more preferably a nitrogen atmosphere throughout the production of the cyclic PAS.

  The sulfidizing agent in the present invention can be used as it is, but when an aqueous mixture is used as the sulfiding agent, it is used for preparation of the raw material mixture after dehydration treatment, or dehydrated during preparation of the raw material mixture. It is preferable to carry out the treatment. By performing such a treatment, an increase in pressure when the raw material mixture is heated can be suppressed, and an expensive pressure-resistant manufacturing facility is not necessarily required, so that facility cost can be reduced. The water content in the raw material mixture may be 6.0 moles or less per mole of sulfur atoms in the raw material mixture, and the preferred upper limit is 4.5 moles or less per mole of sulfur atoms, more preferably 3.0 moles. Mole or less can be illustrated. On the other hand, although there is no restriction | limiting in the minimum of a moisture content, 0.05 mol or more can be illustrated per 1 mol of sulfur atoms in a raw material mixture as a practical minimum in implementing this invention. The amount of water in the raw material mixture in the present invention refers to the sulfidizing agent, dihalogenated aromatic compound and organic polar solvent charged in the reaction system, and other components including those components when charged with other components. This refers to the amount of water obtained by subtracting the amount of water removed from the system by additional operations such as dehydration from the total amount of water introduced and not included, and does not take into account the water generated during the mixing and reaction of the above components. .

  The amount of dihalogenated aromatic compound used in the preparation of the raw material mixture of the present invention is derived from an arylene unit derived from a dihalogenated aromatic compound and a sulfidizing agent when linear PAS is not included as a raw material component in the raw material mixture. As a preferred lower limit, the amount of the arylene unit per mole of sulfur atoms in the raw material mixture can be exemplified as 0.9 mole or more, preferably 0.92 mole or more, more preferably Is 0.94 mol or more. On the other hand, as a preferable upper limit, a usage amount of 1.5 mol or less per 1 mol of sulfur atom in the raw material mixture can be exemplified, preferably 1.2 mol or less, more preferably 1.15 mol or less. By making the amount of dihalogenated aromatic compound used in the above range, cyclic PAS can be obtained at a high production rate, but when it is less than the above range, the production rate of cyclic PAS tends to decrease, On the other hand, when the amount is larger than the above range, the amount of low molecular weight linear PAS produced increases, and it tends to be difficult to obtain high purity when recovering cyclic PAS. The amount of dihalogenated aromatic compound used here means the sum of the dihalogenated aromatic compounds charged in the reaction system, but the charged dihalogenated aromatic compounds are removed from the reaction system by scattering or the like. In this case, it means an amount obtained by subtracting the amount of the dihalogenated aromatic compound removed from the total.

  As will be described later, in the present invention, linear PAS may be added to the raw material mixture as a raw material component. In this case, the linear PAS is equivalent to the one obtained by reacting a dihalogenated aromatic compound with a sulfidizing agent. Therefore, the amount of all arylene units, which is the sum of the arylene units derived from dihalogenated aromatic compounds and the arylene units derived from linear PAS, is added to the sulfur atoms derived from the sulfidizing agent and the sulfur atoms contained in linear PAS. It is preferable to adjust to the total sulfur atom. There is no particular limitation on the molar balance at this time, but as a condition for obtaining cyclic PAS with a high production rate and high purity, as a preferable lower limit of all arylene units of dihalogenated aromatic compound and linear PAS, a raw material mixture The condition of 0.9 mol or more per 1 mol of all sulfur atoms therein can be exemplified, preferably 0.92 mol or more, more preferably 0.94 mol or more. On the other hand, as an upper limit, the conditions of 1.5 mol or less per 1 mol of sulfur atoms in the raw material mixture can be exemplified, preferably 1.2 mol or less, more preferably 1.15 mol or less.

  Here, the total sulfur atoms in the raw material mixture is the sum of sulfur atoms contained in the sulfidizing agent and sulfur atoms contained in the linear PAS. Here, the “number of moles” of sulfur atoms contained in the linear PAS is the “number of repeating units” of the polymer containing one sulfur atom. For example, one molecule of linear polyphenylene sulfide having a degree of polymerization of 100 is calculated as 100 mol, not 1 mol. As long as the essence of the present invention is not impaired, a compound containing a sulfur atom can be present in the raw material mixture in addition to the sulfidizing agent and linear PAS. Sulfur-containing compounds that do not act substantially need not be considered as sulfur atoms.

  The total arylene unit in the raw material mixture is the total of the arylene unit contained in the dihalogenated aromatic compound and the arylene unit contained in the linear PAS. Here, the “mole number” of the arylene unit contained in the linear PAS does not mean the number of PAS molecular chains, but means the sum of the “number of repeating units” in all linear PAS components. . For example, an arylene unit contained in one molecule of linear polyphenylene sulfide having a polymerization degree of 100 is regarded as 100 mol.

  In the present invention, linear PAS can be included in the raw material mixture. When linear PAS is included in the raw material mixture, the yield of cyclic PAS produced increases with respect to the amount of sulfiding agent and dihalogenated aromatic compound used. That is, the amount of the sulfidizing agent and dihalogenated aromatic compound used to obtain the same amount of cyclic PAS can be reduced, and an advantageous effect of being economically advantageous can be obtained. The manufacturing method of the linear PAS added here is not particularly limited, and any manufacturing method can be used, and a wide range of molded products, scraps, waste plastics and off-spec products using PAS can be used. Although it is possible, it is most preferable to use a linear PAS produced as a by-product in the production process of the cyclic PAS. In the production of a cyclic compound, since a large amount of linear PAS is produced as a byproduct, this method is economically very preferable in that it can be used without waste.

  There is no particular limitation on the molecular weight of the linear PAS contained in the raw material mixture. For example, the weight average molecular weight can range from 5,000 to 1,000,000, preferably 7,500 to 500,000. 000-100,000 are more preferable. In general, the lower the weight average molecular weight, the higher the solubility in an organic polar solvent, so there is the advantage that the time required for the reaction can be shortened. The form of the linear PAS contained in the raw material mixture is not particularly limited, and may be in a dry powder form, a granular form, a granular form or a pellet form, or used in a state containing an organic polar solvent as a reaction solvent. It is also possible to use it in a state containing a third component that essentially does not inhibit the reaction. Examples of such a third component include inorganic fillers and alkali metal halides.

  In the case where linear PAS is contained in the raw material mixture, the preferred molar balance of the dihalogenated aromatic compound, all the arylene units of linear PAS, and all the sulfur atoms in the raw material mixture is as described above. As a minimum of the quantity of sulfur atom derived from linear PAS to 1 mol of derived sulfur atoms, 0 mol or more can be illustrated, preferably 0.1 mol or more, more preferably 1 mol or more. On the other hand, as an upper limit, 20 mol or less can be illustrated, Preferably it is 10 mol or less, More preferably, it is 5 mol or less. In such a preferred range, the reaction between the linear PAS and the sulfidizing agent is likely to proceed, so the efficiency of producing cyclic PAS from the linear PAS can be increased.

(7-2) Synthetic Reaction of Cyclic PAS The raw material mixture prepared as described in (7-1) is subsequently heated under the following conditions to produce cyclic PAS.

  In the present invention, the heating conditions for heating and reacting the raw material mixture are not particularly limited as long as it is a temperature and a time at which cyclic PAS is generated, but it is heated beyond the reflux temperature at normal pressure of the prepared raw material mixture. It is preferable. As a method for treating the raw material mixture in such a heated state, for example, a method of heating the raw material mixture under a pressure exceeding normal pressure can be exemplified, and more specifically, a method of heating the raw material mixture in a sealed reactor is exemplified. it can.

  In the present invention, the specific reaction temperature when the raw material mixture is heated and reacted mainly depends on the type of organic polar solvent used, and further includes the type and amount of the sulfidizing agent and dihalogenated aromatic compound, and the third component. Although it cannot be uniquely determined because it varies depending on the presence or absence, the amount of water, etc., in the preferred embodiment of the present invention, the lower limit can be exemplified by 120 ° C. or more, more preferably 180 ° C. or more, and still more preferably Is 220 ° C. or higher, more preferably 225 ° C. or higher, particularly preferably 240 ° C. or higher. Moreover, 350 degrees C or less can be illustrated as a preferable upper limit, More preferably, it is 320 degrees C or less, More preferably, it is 310 degrees C or less, More preferably, it is 300 degrees C or less, Most preferably, it is 280 degrees C or less. By setting the reaction temperature to such a preferable range, a high reaction rate can be obtained, and cyclic PAS tends to be efficiently obtained. Here, the normal pressure is a pressure in the vicinity of the standard state of the atmosphere, and is an atmospheric pressure condition in which the temperature is approximately 25 ° C. and the absolute pressure is approximately 101 kPa. The reflux temperature is the temperature at which the liquid component of the raw material mixture repeats boiling and condensation.

  The temperature control method for heating the raw material mixture may be any of a method for maintaining a constant temperature, a method for gradually increasing the temperature, or a method for continuously changing the temperature.

  In the present invention, the pressure at which the raw material mixture is heated and reacted varies depending on the raw materials constituting the raw material mixture and its composition, reaction temperature, etc., but cannot be uniquely defined. It is preferable to exceed the reflux temperature at normal pressure, and examples of the method for bringing the raw material mixture into such a heated state include a method in which the raw material mixture is reacted under a pressure exceeding normal pressure. The pressure exceeds the pressure. That is, as a specific lower limit of the preferable pressure, 0.05 MPa or more can be exemplified as a gauge pressure, more preferably 0.1 MPa or more, and further preferably 0.2 MPa or more. Moreover, as an upper limit of a preferable pressure, 1.0 MPa or less can be illustrated by a gauge pressure, More preferably, it is 0.8 MPa or less, More preferably, it is 0.6 MPa or less, More preferably, it is 0.5 MPa or less. In such a preferable pressure range, the time required for producing the cyclic PAS tends to be shortened. In general, when the pressure when heating and reacting the raw material mixture exceeds 1.0 MPa, an expensive pressure-resistant manufacturing facility capable of withstanding the pressure is required. However, in the above-described preferable pressure range, it is required for manufacturing the cyclic PAS. Equipment costs can be reduced and safety is high. Here, the gauge pressure is a relative pressure based on atmospheric pressure, and is equivalent to a pressure value obtained by subtracting atmospheric pressure from absolute pressure. In addition, you may implement pressurization operation by inert gas, such as nitrogen, helium, and argon, in the range which does not exceed the upper limit of the said preferable pressure.

  On the other hand, the reaction time for heating and reacting the raw material mixture in the present invention depends on the type and amount of the raw material used or the reaction temperature, and thus cannot be specified unconditionally, but a preferable lower limit is 0.1 hour or more. More preferably, 0.5 hours or more can be exemplified. By setting the reaction time to be equal to or longer than this preferable time, unreacted raw material components can be sufficiently reduced, and thus the produced cyclic PAS tends to be easily recovered. In addition, since the reaction method of the present invention has a characteristic that an extremely high reaction rate can be obtained, the reaction proceeds sufficiently even if the upper limit is 40 hours or less, preferably 10 hours or less, more preferably 6 hours or less. Can be adopted.

  Here, the conversion rate of the dihalogenated aromatic compound in the present invention can be calculated by the following equation.

  Dihalogenated aromatic compound conversion (%) = [[Dihalogenated aromatic compound charge (mole) -Dihalogenated aromatic compound remaining amount (mole)] / [Dihalogenated aromatic compound charge (mole) ]]] × 100%.

  Moreover, when linear PAS is contained in the raw material mixture before making it react by heating, the conversion rate of a dihalogenated aromatic compound is computed by the following formula | equation.

  Conversion rate of dihalogenated aromatic compound (%) = [[total sulfur atom (mol) in raw material mixture-remaining amount of dihalogenated aromatic compound (mol)] / [total sulfur atom (mol) in raw material mixture]] ] × 100%.

  Here, the residual amount of the dihalogenated aromatic compound can be measured by gas chromatography (hereinafter sometimes abbreviated as GC).

  In the present invention, when the cyclic PAS is recovered by, for example, the method exemplified in (8) described later, the raw material is preferably converted sufficiently to obtain the cyclic PAS efficiently. Therefore, a preferable lower limit of the conversion rate of the dihalogenated aromatic compound can be 90% or more, more preferably 95% or more, and still more preferably 98% or more. In addition, there is no restriction | limiting in particular in an upper limit, and 100% which all the raw materials charged convert is most preferable.

  Here, in the evaluation method of cyclic PAS purity in the present invention, the peak detected in the high performance liquid chromatography analysis (hereinafter sometimes abbreviated as HPLC) of the reaction mixture is divided into the peak derived from cyclic PAS and the others. The ratio of the integrated value of the detected area of the peak derived from other than cyclic PAS (mainly low molecular weight linear PAS) to the integrated value of the detected area of all detected peaks (area ratio) ) Was defined as the impurity ratio, and the purity of the cyclic PAS was evaluated using this index.

  In addition, the cyclic PAS production rate in the present invention can be calculated as an actual cyclic PAS production amount relative to the cyclic PAS production amount when it is assumed that all sulfur atoms in the raw material mixture are converted to cyclic PAS. Here, the amount of cyclic PAS produced can be qualitatively and quantitatively analyzed by HPLC.

  In the present invention, the raw material mixture is heated and reacted, and at an optional stage when the raw material is converted to some extent, a sulfidizing agent and a dihalogenated aromatic compound can be added to continue the reaction. It is preferable to perform the reaction by such a method because the yield of cyclic PAS per unit volume can be increased.

In addition, when the amount of water in the raw material mixture changes due to the addition of the sulfidizing agent and the dihalogenated aromatic compound, it is also possible to perform an additional operation so as to obtain the above-mentioned preferable amount of water. It is also desirable to remove an arbitrary amount of water from the raw material mixture after addition. In addition, when components other than water are removed from the raw material mixture during the removal of water, a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent can be further added and removed as necessary. The operation of returning the components to the raw material mixture may be performed again.
In the production of the cyclic PAS of the present invention, various known polymerization methods and reaction methods such as a batch method and a continuous method can be employed.

  Furthermore, the reactor for preparing the raw material mixture and the reactor for heating and reacting the raw material mixture may use the same reactor or separate reactors. By separating the reactors in this way, it is possible to incorporate a continuous process into the reaction, and it is possible to produce cyclic PAS more efficiently. These reactors are preferably equipped with a stirrer.

(8) Method for recovering cyclic polyarylene sulfide In the production of cyclic PAS of the present invention, it is also possible to separate and recover cyclic PAS from the reaction mixture obtained by the reaction described above. The reaction mixture obtained by the reaction contains cyclic PAS, linear PAS and an organic polar solvent, and other components include unreacted sulfating agent, dihalogenated aromatic compound, water, by-product salt, and the like. May be included.

  Although there is no restriction | limiting in particular in the method of collect | recovering cyclic | annular PAS from this reaction mixture, For example, the collection | recovery method shown by patent document 3 can be illustrated. By using such a method, cyclic PAS can be easily recovered with high purity. In addition, due to the effects of the present invention, the unreacted sulfidizing agent and dihalogenated aromatic compound contained in the reaction mixture are reduced as compared with the prior art, so that an even higher purity cyclic PAS can be obtained. Is possible.

(9) Characteristics of the cyclic polyarylene sulfide of the present invention The cyclic PAS thus obtained usually has a purity containing 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more of cyclic PAS. It is expensive and has high utility value even industrially having characteristics different from the generally obtained linear PAS. In addition, the cyclic PAS obtained by the production method of the present invention is characterized in that m in the formula (A) is not single, and the formula (A) having m different from m = 2 to 50 is easily obtained. . Here, the preferable range of m is 3 to 40, more preferably 4 to 30. When m is in this range, as will be described later, when cyclic PAS is used as a raw material for obtaining PAS, the polymerization reaction tends to proceed, and a high molecular weight product tends to be obtained. The reason for this is not clear at present, but it is assumed that cyclic PAS in this range has a large bond distortion due to the cyclic nature of the molecule, and is likely to have a high molecular weight during polymerization.

  In addition, since cyclic PAS having a single m is obtained as a single crystal, it has a very high melting temperature. However, in the present invention, cyclic PAS is easy to obtain a mixture having different m, and thus melting of cyclic PAS There is a feature that the temperature is low, which expresses an excellent feature that, for example, the heating temperature when the cyclic PAS is melted and used can be lowered.

(10) Resin composition blended with cyclic polyarylene sulfide of the present invention The cyclic PAS obtained in the present invention can be blended with various resins, and a resin blended with such a cyclic PAS. The composition has a strong tendency to exhibit excellent fluidity during melt processing, and tends to have excellent residence stability. In addition, there is no restriction | limiting in particular in the method of manufacturing the resin composition which mix | blended cyclic PAS obtained by this invention, For example, the manufacturing method of the resin composition shown by patent document 3 can be illustrated.

(11) Conversion of cyclic polyarylene sulfide to a high degree of polymerization The cyclic PAS produced according to the present invention has excellent characteristics as described in (9) and is therefore suitable as a prepolymer for obtaining a polymer. It is possible to use. Here, as the prepolymer, the cyclic PAS obtained by the cyclic PAS production method of the present invention may be used alone or may contain a predetermined amount of other components, but if it contains components other than the cyclic PAS, A PAS component such as a linear PAS or a PAS having a branched structure is particularly preferable. Although there is no restriction | limiting in particular in the method to convert such a PAS prepolymer into a polymer, For example, the conversion method from the PAS prepolymer to a polymer shown by patent document 3 can be illustrated.

  The present invention will be specifically described below with reference to examples. These examples are illustrative and not limiting.

<Measurement of formation rate and impurity rate of cyclic polyphenylene sulfide>
The production rate and impurity rate of the cyclic polyphenylene sulfide compound in the reaction mixture were measured under the following conditions using high performance liquid chromatography.
Apparatus: LC-10Avp series manufactured by Shimadzu Corporation Column: Mightysil RP-18 GP150-4.6 (5 μm) manufactured by Kanto Chemical Co., Inc.
Detector: Photodiode array detector (wavelength 270 nm)

  The structure of each component separated by HPLC is determined by liquid chromatography / mass spectrometry (LC-MS) and by matrix-assisted laser desorption / ionization of the fraction in preparative liquid chromatography (preparative LC). The analysis was performed by mass spectrometry (MALDI-MS), analysis by nuclear magnetic resonance spectroscopy (NMR), and infrared spectroscopy (IR measurement). Thereby, it was confirmed that cyclic polyphenylene sulfide having 4 to 15 repeating units can be qualitatively and quantitatively analyzed by HPLC measurement under these conditions.

  In addition, the peaks detected in the above HPLC analysis are classified into peaks derived from cyclic polyphenylene sulfide and peaks derived from others, and other than cyclic polyphenylene sulfide with respect to the integrated value of the detection areas of all detected peaks. The ratio (area ratio) of the integrated value of the detection areas of the peaks derived from (primarily low molecular weight linear PAS) was defined as the impurity ratio (ppm), and the purity of the cyclic PAS was evaluated using this index.

<Analysis of sulfidizing agent and sulfur oxide>
Quantification of the sulfidizing agent and sulfur oxide in the raw material mixture and reaction mixture was carried out under the following conditions using ion chromatography.
Apparatus: HIC-20 Asper made by Shimadzu Corporation
Column: Shimadzu Shim-pack IC-SA2 (250 mm × 4.6 mm ID)
Detector: Electrical conductivity detector (suppressor)
Eluent: 4.0 mM sodium bicarbonate / 1.0 mM aqueous sodium carbonate flow rate: 1.0 ml / min Injection volume: 50 microliters Column temperature: 30 ° C.

Regarding the quantification of the sulfidizing agent, first, hydrogen peroxide solution was added to the sample to oxidize sulfide ions contained in the sample, then IC was performed to determine sulfate ions, and then the hydrogen peroxide solution was added. The amount of sulfide ions in the sample was calculated by the method of subtracting the quantitative value of sulfur oxide when IC analysis was performed on an untreated sample not added, and this was used as the amount of sulfiding agent.
For the determination of sulfur oxides, the sample was diluted 100 times with degassed water, filtered through a membrane filter to remove insoluble matters, and then IC was performed to detect thiosulfate ions and substreams. From the sum of the quantitative values of acid ions and sulfate ions, sulfur atoms present as sulfur oxide were quantified and used for evaluation.

<Measurement of gas phase oxygen concentration>
The gas phase oxygen concentration in the present invention was measured by an oxygen concentration meter “OX-95G” (manufactured by Riken Keiki Co., Ltd.).

[Example 1]
Here, a preferred embodiment of the present invention, that is, an example of cyclic PAS production when the sulfur atoms present as sulfur oxides in the raw material mixture are 0.05 moles or less per mole of sulfur atoms in the raw material mixture. Show.
In a dry box with a gas phase oxygen concentration of 0.01% by flow by nitrogen flow, 3.26 g (0.0280 mol as sodium hydrosulfide) of 48% by weight aqueous solution of sodium hydrosulfide was placed in an autoclave vessel made of SUS316, 48 2.45 g (0.0294 mol as sodium hydroxide) of a weight% sodium hydroxide aqueous solution, 4.20 g (0.0286 mol) of p-dichlorobenzene, 71.8 g of N-methyl-2-pyrrolidone (NMP) (0.0700 liters) was charged and sealed with a flange equipped with a stirrer, taking care not to come in contact with air. NMP was deoxygenated in advance through nitrogen and a dissolved oxygen concentration of 0.1 ppm was used. The amount of the organic polar solvent per mole of sulfur atoms in this raw material mixture was 2.50 liters.

  Next, the above-mentioned sealed autoclave was heated from room temperature to 200 ° C. over 25 minutes while stirring at 800 rpm, and then heated from 200 ° C. to 250 ° C. over 35 minutes. Then, the raw material mixture was heated and reacted by being kept at 250 ° C. for 2 hours. When heating started, the internal pressure gradually increased, and the gauge pressure was 0.65 MPa at the end of the reaction. After completion of the reaction, the autoclave was cooled to near room temperature, and the reaction mixture was recovered.

<Evaluation of the amount of sulfur oxide in the raw material mixture>
Prepare a raw material mixture separately in the same manner as in Example 1, dilute the raw material mixture 100 times with degassed water, perform filtration with a membrane filter, and perform IC after removing insoluble materials. From the quantitative values of thiosulfate ion, sulfite ion, and sulfate ion detected in Step 1, the sulfur atom present as sulfur oxide was quantified and found to be 0.02 mol per mol of sulfur atom in the raw material mixture. Therefore, it was confirmed that Example 1 satisfies the requirements of the present invention.

<Reaction mixture evaluation>
A part of the obtained reaction mixture was dispersed in a large excess of water to recover water-insoluble components, and then dried to obtain a solid content. As a result of structural analysis by infrared spectroscopic analysis, it was confirmed that the solid content was a compound composed of phenylene sulfide units.

  Further, as a result of analyzing the obtained reaction mixture by HPLC and GC, the conversion rate of p-dichlorobenzene was 93%, and the cyclic polyphenylene was assumed when all the sulfidizing agents in the raw material mixture were converted to cyclic polyphenylene sulfide. The production rate of sulfide was 14%. Moreover, the ratio of the peak area derived from other than cyclic PAS to the total peak area detected by HPLC of the reaction solution, that is, the impurity ratio was 2600 ppm.

  As described above, when the cyclic PAS was produced in a preferred embodiment of the present invention, the cyclic PAS could be obtained with high purity efficiently.

[Comparative Example 1]
Here, an example of cyclic PAS production in the case where the sulfur atom present as sulfur oxide in the raw material mixture is more than 0.05 mole per mole of sulfur atom in the raw material mixture is shown.

  A raw material mixture was prepared in exactly the same manner as in Example 1 except that the NMP was not subjected to deoxygenation treatment in an autoclave with a stirrer made of SUS316 and the raw materials were charged in the atmosphere. The dissolved oxygen concentration of the used NMP was measured and found to be 20 ppm. The amount of the organic polar solvent per mole of sulfur atoms in this raw material mixture was 2.50 liters.

  Next, the inside of the autoclave was purged with nitrogen three times and sealed, and the temperature was raised from room temperature to 200 ° C. over 25 minutes while stirring at 800 rpm, and then from 200 ° C. to 250 ° C. over 35 minutes. Then, the raw material mixture was heated and reacted by being kept at 250 ° C. for 2 hours. When heating started, the internal pressure gradually increased, and the gauge pressure was 0.65 MPa at the end of the reaction. After completion of the reaction, the autoclave was cooled to near room temperature, and the reaction mixture was recovered.

<Evaluation of the amount of sulfur oxide in the raw material mixture>
Prepare a raw material mixture separately in the same manner as in Comparative Example 1, dilute the raw material mixture 100 times with degassed water, perform filtration with a membrane filter, and perform IC after removing insoluble materials. From the quantitative values of thiosulfate ion, sulfite ion, and sulfate ion detected in Step 1, the sulfur atoms present as the sulfur oxide were quantified and found to be 0.15 mol per mol of sulfur atom in the raw material mixture. Therefore, Example 1 does not satisfy the requirements of the present invention.

<Reaction mixture evaluation>
As a result of structural analysis of the reaction mixture in the same manner as in Example 1, it was confirmed that a compound composed of phenylene sulfide units was formed.

  Further, as a result of analyzing the obtained reaction mixture by HPLC and GC, the conversion rate of p-dichlorobenzene was 93%, and the cyclic polyphenylene was assumed when all the sulfidizing agents in the raw material mixture were converted to cyclic polyphenylene sulfide. The production rate of sulfide was 14%. Moreover, the ratio of the peak area derived from other than cyclic PAS to the total peak area detected by HPLC of the reaction solution, that is, the impurity ratio was 4000 ppm.

  As described above, when the essential requirements of the present invention are not satisfied, that is, when the sulfur atoms present as sulfur oxide in the raw material mixture are more than 0.05 mol per mol of sulfur atoms in the raw material mixture, In the PAS production, it was found that the impurity ratio was higher than that in Example 1.

Claims (7)

A raw material mixture containing at least a sulfidizing agent, a dihalogenated aromatic compound, and an organic polar solvent is heated under the condition that the organic polar solvent is 1.25 to 50 liters per mole of sulfur atoms in the raw material mixture. A method for producing a polyarylene sulfide, wherein the sulfur atoms present as sulfur oxides in the raw material mixture are 0.05 moles or less per mole of sulfur atoms in the raw material mixture. The method for producing a cyclic polyarylene sulfide according to claim 1, wherein an organic polar solvent subjected to deoxygenation treatment is used as the organic polar solvent. The method for producing a cyclic polyarylene sulfide according to claim 1, wherein the oxygen concentration in the gas phase in contact with the raw material mixture is 5% by volume or less. The method for producing a cyclic polyarylene sulfide according to any one of claims 1 to 3, wherein the raw material mixture is heated beyond the reflux temperature at normal pressure. The method for producing a cyclic polyarylene sulfide according to any one of claims 1 to 4, wherein the sulfiding agent is an alkali metal sulfide. The method for producing a cyclic polyarylene sulfide according to any one of claims 1 to 5, wherein the dihalogenated aromatic compound is dichlorobenzene. The method for producing cyclic polyarylene sulfide according to any one of claims 1 to 6, wherein the raw material mixture contains linear polyarylene sulfide.