Polyarylene sulfide and method for producing polyarylene sulfide

Abstract

To provide a polyarylene sulfide having high molecular weight, high viscosity, and high reactivity, and having a low ash content, and an efficient production method thereof.SOLUTION: A polyarylene sulfide features: a weight-average molecular weight of 30,000 or more and 90,000 or less; a cumulative integration value of 5.0% or more and 10.0% or less at molecular weights of 3,000 or less in the molecular weight distribution curve; a melt flow rate of 50 [g / 10 min] or more and 400 [g / 10 min] or less as measured in accordance with ASTM D 1238-70 at 315.5°C and 5,000 g load; an acid value of 25 [μmol / g] or more and 50 [μmol / g] or less; and an ash content of 0.10 wt.% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention provides a polyarylene sulfide having high molecular weight, high viscosity, high reactivity, and low ash content, and a production method excellent in productivity thereof.

Background Art

[0002] Polyarylene sulfide (hereinafter sometimes abbreviated as PAS), typified by polyphenylene sulfide (hereinafter sometimes abbreviated as PPS), has properties suitable as an engineering plastic such as excellent heat resistance, gas barrier property, moldability, chemical resistance, electrical insulation property, and heat and humidity resistance, and is used in various electrical and electronic parts, mechanical parts, automotive parts, films, fibers, etc., mainly for injection molding and extrusion molding applications. Due to its excellent properties, PAS has been increasingly used in recent years. PAS used in these applications is required to be a high-viscosity and high-molecular-weight PAS due to its excellent mechanical properties. Also, PAS having a low ash content has been strongly demanded from the viewpoint of crystallization temperature.

[0003] Patent Document 1 discloses a method (quench method) of adding water as an auxiliary agent during polymerization and slowly cooling to recover a particulate PAS resin. The obtained PAS resin is disclosed to be a PAS resin with advanced high molecular weight, low ash content, high crystallization rate, and little volatile gas during molding. Patent Document 2 discloses a method of polymerizing using an alkali metal salt (SMAB) of a hydrolyzate of an aliphatic cyclic compound as an auxiliary agent and rapidly cooling to crystallize and recover the PAS resin. It is disclosed that a PAS resin having high molecular weight and excellent reactivity can be obtained by this method. Patent Document 3 discloses a method of volatilizing a solvent at a high temperature after polymerization to recover a PAS resin (flash method) and washing the recovered PAS resin with a solvent. It is disclosed that a PAS resin with few oligomer components, reduced generation gas amount and mold fouling during molding, and high reactivity can be obtained by this method.

Prior Art Documents

Patent Documents

[0004] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2020-139076 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2017-095562 [Patent Document 3] International Publication No. 2021 / 200332 [Summary of the Invention] [Problems to be Solved by the Invention]

[0005] However, in the quenching method described in Patent Document 1, due to the method of slow cooling for crystallization and filtration, relatively low molecular weight components containing many acid groups cannot be recovered, and the acid amount of the obtained PAS resin decreases, resulting in a decrease in reactivity. In addition, since the yield of the PAS resin decreases and the occupation time of the polymerization kettle is long, the productivity is low and the economy is poor. Further, the PAS resin obtained by the method described in Patent Document 2 has a large amount of ash content, a decrease in crystallinity, and an adverse effect on moldability and strength. The PAS resin obtained by the method described in Patent Document 3 has insufficient high molecular weight and a large amount of ash content, so there are problems in mechanical strength, crystallinity, etc.

[0006] As described above, in the prior art, high molecular weight of PAS, reduction of ash content, etc. are insufficient, and a method that can simultaneously solve high mechanical strength, high crystallinity, and high reactivity, and has high productivity and excellent economy has been demanded. [Means for Solving the Problems]

[0007] As a result of intensive studies to solve such problems, the present invention has found that by performing washing under specific conditions after the polymerization step of reacting a sulfidizing agent and a predetermined amount of a dihalogenated aromatic compound in a polar solvent in the presence of a polymerization aid of a predetermined amount of an alkali metal carboxylate, a PAS having a high molecular weight, a high viscosity, a high acid amount, and a low ash content rate can be obtained, and thus the present invention has been achieved. 1. A polyarylene sulfide having a weight average molecular weight of 30,000 or more and 90,000 or less, a cumulative integral value of 5.0% or more and 10.0% or less for a molecular weight of 3,000 or less in a molecular weight distribution curve, a melt flow rate measured under the conditions of 315.5 ° C and a load of 5,000 g in accordance with ASTM D 1238-70 of 50 [g / 10 min] or more and 400 [g / 10 min] or less, an acid amount of 25 [μmol / g] or more and 50 [μmol / g] or less, and an ash content rate of 0.10 wt% or less. 2. In a method for producing a polyarylene sulfide by reacting a sulfidizing agent and a dihalogenated aromatic compound in an organic polar solvent in the presence of an alkali metal hydroxide and an alkali metal carboxylate, the method for producing the polyarylene sulfide according to 1 above, characterized by performing at least the following steps 1 to 4. Step 1: A polymerization step of polyarylene sulfide in which the reaction is carried out in an organic polar solvent in the presence of an alkali metal carboxylate. Step 2: A step of distilling off the organic polar solvent from the mixture obtained at the end of the reaction to obtain a solid containing polyarylene sulfide. Step 3: A step of acid-treating after washing the solid containing polyarylene sulfide with water following Step 2. Step 4: A step of washing the polyarylene sulfide with an organic solvent following Step 3. 3. The method for producing a polyarylene sulfide according to 2 above, characterized in that 0.25 mol or more and 0.40 mol or less of an alkali metal carboxylate is present and reacted with respect to 1.00 mol of the sulfidizing agent in Step 1. 4. The method for producing a polyarylene sulfide according to 2 or 3 above, characterized in that the acid treatment is carried out at 150 ° C or higher in Step 3. 5. The method for producing a polyarylene sulfide according to any one of 2 to 4 above, characterized in that the amount of the acid is 5.0 mol% or more and 20.0 mol% or less with respect to the polyarylene sulfide in Step 3. 6. The method for producing a polyarylene sulfide according to any one of 2 to 5 above, characterized in that the polyarylene sulfide is washed at 70 ° C or higher for 15 minutes or more in Step 4. 7. In Process 4, the method for producing a polyarylene sulfide according to any one of 2 to 6 above, wherein the concentration of the organic solvent for cleaning after cleaning is 80% or more.

Advantages of the Invention

[0008] According to the present invention, a polyarylene sulfide having a high molecular weight, high viscosity, high reactivity, and low ash content can be obtained with high production efficiency, and such polyarylene sulfide exhibits high mechanical strength, high crystallinity, and high reactivity.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail.

[0010] [Characteristics of PAS] The PAS of the present invention has a weight average molecular weight of 30,000 or more and 90,000 or less, a cumulative integral value of 5.0% or more and 10.0% or less for a molecular weight of 3,000 or less in the molecular weight distribution curve, a melt flow rate measured under the conditions of 315.5 ° C and a load of 5,000 g in accordance with ASTM D 1238-70 of 50 [g / 10 min] or more and 400 [g / 10 min] or less, an acid amount of 25 [μmol / g] or more and 50 [μmol / g] or less, and an ash content of 0.10% by weight or less.

[0011] The lower limit of the weight average molecular weight of PAS is 30,000, preferably 40,000 or more, more preferably 45,000 or more. The upper limit is 90,000, preferably 80,000 or less. If the weight average molecular weight is less than 30,000, the mechanical properties will deteriorate, which is unsuitable. If the molecular weight exceeds 90,000, the melt fluidity will greatly decrease and the processability will deteriorate, which is also unsuitable. In addition, when the PAS contains branched units, the impact strength tends to decrease, which is not preferable. Regarding the method for adjusting the weight average molecular weight, details will be described later, but examples include methods of adjustment by polymerization steps such as polymerization time and amount of polymerization aid, recovery steps such as removal of fine powder by sieving, and cleaning steps such as removal of low molecular weight components by solvent cleaning.

[0012] Regarding the PAS of the present invention, with respect to the cumulative integral value of the entire molecular weight distribution curve, the ratio of the cumulative integral value with a molecular weight of 3,000 or less has a lower limit of 5.0%, preferably 5.5% or more. The upper limit is 10.0%, preferably 9.0% or less, and more preferably 8.0% or less. Within the preferred range, the crystallinity is improved, but when it exceeds 10.0%, the strength tends to decrease during molding processing, which is unsuitable. Generally, low molecular weight substances have a high crystallization rate, and by including low molecular weight components within a preferred range, the crystallinity of the PAS resin is greatly improved. Also, if it is less than 5.0%, the crystallization rate is retarded and the melt fluidity deteriorates due to the above reasons, resulting in a decrease in moldability, which is unsuitable. Methods for adjusting the ratio of the cumulative integral value of PAS with a molecular weight of 3,000 or less include washing with an organic solvent and sieving. Also, the ratio of the cumulative integral value of PAS with a molecular weight of 3,000 or less varies depending on the manufacturing method. For example, in the method of slow cooling and crystallization and recovery by sieving (quench method), PAS with a molecular weight of 3,000 or less is removed as a fine powder component, so it tends to be low. Also, in the method of distilling off the solvent and recovering the solid (flash method), PAS with a molecular weight of 3,000 or less can also be recovered, and the ratio of the cumulative integral value of PAS with a molecular weight of 3,000 or less increases. Note that the ratio of the cumulative integral value of PAS with a molecular weight of 3,000 or less mentioned here is a value calculated in terms of polystyrene by gel permeation chromatography (GPC), which is a type of size exclusion chromatography (SEC).

[0013] The upper limit of the melt flow rate of PAS (hereinafter abbreviated as MFR) is 400 [g / 10 min], preferably 350 [g / 10 min] or less, and more preferably 300 [g / 10 min] or less. The lower limit is 50 [g / 10 min], and preferably 100 [g / 10 min] or more. When the MFR exceeds 400 [g / 10 min], the mechanical strength and toughness during molding are insufficient. Also, when it is less than 50 [g / 10 min], the melt fluidity is low, and the moldability during injection molding deteriorates, so it is unsuitable. Generally, MFR has a positive correlation with the weight average molecular weight and can be adjusted in the same manner as the weight average molecular weight. Also, when many impurities and low molecular weight components remain, the MFR increases, so generally the MFR decreases by increasing the purity of PAS by washing. In addition, it is possible to significantly reduce the MFR by using a crosslinking agent during polymerization, but gelation and deterioration of the melt fluidity are significant and not preferred in the present invention. At this time, the MFR is a value measured according to ASTM D 1238-70 at a temperature of 315.5 °C and a load of 5,000 g.

[0014] The lower limit of the acid amount of PAS is 25 [μmol / g], and preferably 30 [μmol / g] or more. The upper limit is 50 [μmol / g], and preferably 40 [μmol / g] or less. When the acid amount is within the preferred range, the adhesiveness to the filler and the reactivity with the additive increase, and the mechanical properties of the molded product when various fillers and additives are added are improved. When the acid amount is less than 25 [μmol / g], the reactivity with other materials decreases. For example, when a coupling agent is used during molding, sufficient reactivity cannot be obtained and the mechanical properties after molding deteriorate, so it is unsuitable. On the other hand, when the acid amount exceeds 50 [μmol / g], the amount of volatile components due to the decomposition of acid groups during molding tends to increase, and it is not suitable because it causes extreme viscosity changes and voids in the molded product. The acid amount of PAS generally originates from the amount of functional groups. In the case of the same molecular weight, the more the amount of functional groups and the higher the protonation rate of the functional groups, the more the acid amount. The acid amount can be increased by performing acid treatment at high concentration and high temperature. The acid amount of PAS referred to here is measured by FT-IR (IR-810 type infrared spectrophotometer manufactured by JASCO Corporation) of the amorphous film of the PAS resin, and 1,900 cm from the benzene ring -1The absorption around 1,730 cm derived from the carboxyl group for the absorption in the vicinity can be estimated by comparing the absorption around -1 . -1 It can be estimated by comparing the absorption in the vicinity.

[0015] The upper limit of the ash content rate of PAS is 0.10% by weight, preferably 0.08% by weight or less, more preferably 0.05% by weight or less. There is no particular limitation on the lower limit, but it is usually 0.01% by weight or more. If the ash content rate exceeds 0.10% by weight, it is not suitable because it causes a decrease in crystallinity due to a decrease in the cooling crystallization temperature, a decrease in electrical insulation, an extreme increase in melt viscosity, and a decrease in heat and humidity resistance. The ash of PAS is mainly a metal component, and the residue of by-products and the substitution of metal ions for functional groups cause the increase in the ash content rate. By washing with water at high temperature, acid treatment, washing with an organic solvent, etc., the removal of by-products and the proton substitution of metal ions are possible, and the ash content rate can be reduced. Also, the ash content rate can be efficiently reduced by using water washing, acid treatment, solvent washing, etc. in combination. The ash content rate here is the weight ratio of the ash remaining after sufficiently heating PAS at 538 °C and completely ashing it to the sample amount before ashing.

[0016] [Structure of PAS] The PAS in the present invention is a homopolymer or copolymer having a repeating unit of the formula -(Ar-S)- as a main constituent unit, preferably containing 80 mol% or more of the repeating unit. Examples of Ar include units represented by the following formulas (A) to (K), etc., and among them, the formula (A) is particularly preferred.

[0017] [Chemical formula]

[0018] (R1 and R2 are substituents selected from a hydrogen atom, an alkyl group, an alkoxy group, and a halogen group, and R1 and R2 may be the same or different.)

[0019] Generally, PAS may contain branched units or crosslinked units represented by the following formulas (L) to (N), etc., and branched or crosslinked units can be introduced by copolymerization with the addition of a polyhalogenated aromatic compound having three or more halogens or by oxidative crosslinking by heating in the presence of oxygen. The introduction of branched or crosslinked units causes an increase in viscosity and an improvement in tensile strength, but also causes a decrease in processability due to gelation and a decrease in impact resistance. In the present invention, PAS preferably has fewer branched or crosslinked units, and according to the present invention, high viscosity and high tensile strength can be achieved without introducing branched or crosslinked units.

[0020] [Chemical formula]

[0021] In addition, the PAS in the present invention may be any of a random copolymer, a block copolymer, and a mixture thereof containing the above repeating units.

[0022] Typical examples thereof include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, random copolymers, block copolymers, and mixtures thereof. Particularly preferred PAS includes polyphenylene sulfide resin containing 80 mol% or more, particularly 90 mol% or more of the p-phenylene sulfide unit

[0023] [Chemical formula]

[0024] shown below as the main constituent unit of the polymer.

[0025] The manufacturing method of the PAS of the present invention will be specifically described below.

[0026] First, the raw materials used for manufacturing PAS will be described.

[0027] [Sulfidizing agent] As the sulfiding agent used in the present invention, any agent capable of introducing a sulfide bond into an aromatic halide compound may be used, and examples thereof include alkali metal sulfides, alkali metal hydrosulfides, and hydrogen sulfide.

[0028] Specific examples of the alkali metal sulfides include, for example, lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide, and mixtures of two or more thereof. Among them, lithium sulfide and / or sodium sulfide are preferable, and 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, or 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 preferable to use alkali metal sulfides in such forms.

[0029] Specific examples of the alkali metal hydrosulfides include, for example, lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and mixtures of two or more thereof. Among them, lithium hydrosulfide and / or sodium hydrosulfide are preferable, and sodium hydrosulfide is more preferably used.

[0030] In addition, alkali metal sulfides prepared in the reaction system from alkali metal hydrosulfides and alkali metal hydroxides can also be used. Further, alkali metal sulfides prepared by previously contacting alkali metal hydrosulfides and alkali metal hydroxides can also be used. These alkali metal hydrosulfides and alkali metal hydroxides can be used as hydrates or aqueous mixtures, or in the form of anhydrides, and hydrates or aqueous mixtures are preferable from the viewpoints of availability and cost.

[0031] Furthermore, alkali metal sulfides prepared in the reaction system from alkali metal hydroxides such as lithium hydroxide and sodium hydroxide and hydrogen sulfide can also be used. Also, alkali metal sulfides prepared by contacting alkali metal hydroxides such as lithium hydroxide and sodium hydroxide with hydrogen sulfide in advance can be used. Hydrogen sulfide can be used in any form of gaseous state, liquid state, or aqueous solution state without any problem.

[0032] [Aromatic dihalide compound] When producing the PAS of the present invention, an aromatic dihalide compound is used. Examples of the aromatic dihalide compound to be used include dihalogenated benzenes such as p-dichlorobenzene, o-dichlorobenzene, m-dichlorobenzene, p-dibromobenzene, o-dibromobenzene, m-dibromobenzene, 1-bromo-4-chlorobenzene, and 1-bromo-3-chlorobenzene, and aromatic dihalide compounds containing substituents other than halogen such as 1-methoxy-2,5-dichlorobenzene, 1-methyl-2,5-dichlorobenzene, 1,4-dimethyl-2,5-dichlorobenzene, 1,3-dimethyl-2,5-dichlorobenzene, 2,5-dichlorobenzoic acid, 3,5-dichlorobenzoic acid, 2,5-dichloroaniline, and 3,5-dichloroaniline. Among them, aromatic dihalide compounds mainly composed of p-dihalogenated benzenes represented by p-dichlorobenzene are preferred. From the viewpoint of preventing depolymerization of PAS during polymerization, the lower limit of the blending amount of the aromatic dihalide compound is preferably 0.99 mol or more, more preferably 1.00 mol or more, based on 1.00 mol of the sulfidizing agent. From the viewpoint of obtaining a high molecular weight PAS, the upper limit of the blending amount of the aromatic dihalide compound is preferably 1.03 mol or less, more preferably 1.02 mol or less, based on 1.00 mol of the sulfidizing agent. The aromatic dihalide compound may be used alone or as a mixture of two or more different types.

[0033] [Branching / crosslinking agent] The branching / crosslinking agent of the present invention specifically includes polyhalogenated aromatic compounds having three or more halogens such as 1,3,5-trichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, 1,2,4,5-tetrachlorobenzene, hexachlorobenzene, 1,4,6-trichloronaphthalene, and polyhalogenated aromatic compounds containing substituents other than halogens such as 2,3,6-trichlorobenzoic acid, 2,4,5-trichlorobenzoic acid, 2,4,6-trichlorobenzoic acid, 2,3,4-trichloroaniline, 2,4,6-trichloroaniline and having three or more halogens. The total amount of these branching / crosslinking agents is preferably 0.3 mol% or less, more preferably 0.1 mol% or less, and even more preferably 0.0 mol% with respect to 1.00 mol of the sulfidizing agent. Although it is preferable to use these branching / crosslinking agents in that the molecular weight, viscosity, and tensile strength are improved, it is not preferable because it causes an increase in molecular weight dispersion, a decrease in impact strength, extreme thickening, and a decrease in the crystallization temperature upon cooling.

[0034] [Organic polar solvent] In the present invention, an organic polar solvent is used as the polymerization solvent. As the organic polar solvent to be used, organic amide solvents can be preferably exemplified. Specific examples include N-alkylpyrrolidones such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, caprolactams such as N-methyl-ε-caprolactam, aprotic organic solvents represented by 1,3-dimethyl-2-imidazolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, hexamethylphosphoric triamide, and mixtures thereof, etc. are preferably used because of their high reaction stability. Among these, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are preferable, and N-methyl-2-pyrrolidone is more preferably used.

[0035] The amount of the organic polar solvent used is selected in the range of 2.00 mol to 10.00 mol, preferably 2.25 mol to 6.00 mol, and more preferably 2.50 mol to 5.50 mol per 1.00 mol of the sulfidizing agent.

[0036] [Coalescing aid] In order to obtain high molecular weight PAS in a shorter time, it is preferable to use a coalescing aid. Here, the coalescing aid means a substance having an action of increasing the viscosity of the obtained PAS. Specific examples of such a coalescing aid include, for example, organic carboxylates, water, alkali metal chlorides, organic sulfonates, alkali metal sulfates, alkaline earth metal oxides, alkali metal phosphates, and alkaline earth metal phosphates. These can be used alone or two or more of them can be used simultaneously. Among them, alkali metal carboxylates are preferable, and sodium acetate, which is inexpensive and has a high effect of increasing molecular weight, is preferable as the alkali metal carboxylate.

[0037] The above alkali metal carboxylate is represented by the general formula R(COOM) n (wherein R is an alkyl group, cycloalkyl group, aryl group, alkylaryl group or arylalkyl group having 1 to 20 carbon atoms. M is an alkali metal selected from lithium, sodium, potassium, rubidium and cesium. n is an integer of 1 to 3). The alkali metal carboxylate can also be used as a hydrate, anhydride or aqueous solution. Specific examples of the alkali metal carboxylate include, for example, lithium acetate, sodium acetate, potassium acetate, sodium propionate, lithium valerate, sodium benzoate, sodium phenylacetate, potassium p-toluylate, and mixtures thereof.

[0038] The alkali metal carboxylate may be synthesized by adding and reacting an organic acid and one or more compounds selected from the group consisting of alkali metal hydroxides, alkali metal carbonates and alkali metal bicarbonates in substantially equi-chemical equivalents. Among the above alkali metal carboxylates, the lithium salt has high solubility in the reaction system and a large auxiliary effect but is expensive. On the other hand, potassium, rubidium and cesium salts have insufficient solubility in the reaction system, so sodium acetate, which is inexpensive and has appropriate solubility in the polymerization system, is most preferably used.

[0039] The water used as the polymerization aid is preferably distilled water or ion-exchanged water in order not to impair the effect of the preferable chemical modification of PAS.

[0040] In the present invention, it is important to use an alkali metal carboxylate as the polymerization aid, and it is preferable to use sodium acetate. The alkali metal carboxylate is preferably present in an amount of 0.25 mol or more with respect to 1.00 mol of the sulfidizing agent. From the viewpoint of achieving a higher molecular weight, 0.30 mol or more is more preferable, and 0.33 mol or more is even more preferable. Further, as the upper limit of the alkali metal carboxylate, it is preferably present in an amount of 0.40 mol or less with respect to 1.00 mol of the sulfidizing agent, and 0.35 mol or less is more preferable. By adding the alkali metal carboxylate within the above preferable range, the molecular weight can be efficiently increased.

[0041] When water is used as the polymerization aid, it is preferably present in an amount of 0.50 mol or more with respect to 1.00 mol of the sulfidizing agent in the reaction vessel. In terms of obtaining a higher molecular weight, 0.60 mol or more is more preferable, and 0.70 mol or more is even more preferable. As the upper limit when water is used as the polymerization aid, from the viewpoint of safety related to the pressure in the reaction vessel and the handleability related to the particle size of the obtained polymer, it is preferably present in an amount of 1.50 mol or less with respect to 1.00 mol of the sulfidizing agent, more preferably 1.25 mol or less, and even more preferably 1.00 mol or less.

[0042] These polymerization aids can also be used in combination of two or more kinds. For example, when an alkali metal carboxylate and water are used in combination, the molecular weight can be increased even with a smaller amount of the alkali metal carboxylate.

[0043] There is no particular specification regarding the addition timing of these polymerization aids, and they may be added at any time during the pre-process, polymerization start, or polymerization reaction process described later, or they may be added in multiple portions. When using an alkali metal carboxylate as a polymerization aid, it is more preferable to add it simultaneously with other additives at the start of the pre-process or at the start of polymerization because it is easier to add. When using water as a polymerization aid, it is effective to add it during the polymerization reaction process after adding a dihalogenated aromatic compound.

[0044] [Polymerization stabilizer] In order to stabilize the polymerization reaction system and prevent side reactions, a polymerization stabilizer can also be used. The polymerization stabilizer contributes to the stabilization of the polymerization reaction system and suppresses undesirable side reactions. One indication of side reactions is the formation of thiophenol. The formation of thiophenol can be suppressed by adding a polymerization stabilizer. Specific examples of the polymerization stabilizer include compounds such as alkali metal hydroxides, alkali metal carbonates, alkaline earth metal hydroxides, and alkaline earth metal carbonates. Among them, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide are preferable. Since the above-mentioned alkali metal carboxylate also acts as a polymerization stabilizer, it falls into one of the polymerization stabilizers. Also, when using an alkali metal hydrosulfide as a sulfidizing agent, it was previously mentioned that it is particularly preferable to use an alkali metal hydroxide simultaneously, but here, an alkali metal hydroxide that is in excess with respect to the sulfidizing agent can also be a polymerization stabilizer.

[0045] These polymerization stabilizers can be used individually or in combination of two or more. The polymerization stabilizer is preferably used in a ratio of usually 0.02 mol to 0.20 mol, preferably 0.03 mol to 0.10 mol, more preferably 0.04 mol to 0.09 mol, per 1.00 mol of the charged sulfidizing agent. If this ratio is too small, the stabilizing effect is insufficient, and conversely, if it is too large, it is economically disadvantageous and the polymer yield tends to decrease.

[0046] The timing of adding the polymerization stabilizer is not particularly specified, and it may be added at any time during the pre-step, at the start of polymerization, or during the polymerization reaction step described below, or may be added in multiple portions. However, it is more preferable to add it simultaneously at the start of the pre-step or at the start of polymerization, as this is easier.

[0047] Next, a preferred method for producing the PAS of the present invention will be specifically described in order, including a pre-process, a polymerization reaction process, a recovery process, and a post-treatment process.

[0048] [Pre-process] When producing the PAS of the present invention, the sulfidizing agent is used in the form of a hydrate, and it is preferable to heat the mixture containing the organic polar solvent and the sulfidizing agent and remove excess water from the system before adding the dihalogenated aromatic compound.

[0049] As described above, the sulfidizing agent may be prepared in situ in the reaction system from an alkali metal hydrosulfide and an alkali metal hydroxide, or in a tank separate from the polymerization tank. There is no particular restriction on this method, but a preferable method is to add an alkali metal hydrosulfide and an alkali metal hydroxide to an organic polar solvent in an inert gas atmosphere at room temperature to 150°C, preferably from room temperature to 100°C, and then heat the mixture to at least 150°C or higher, preferably 180°C to 260°C, under normal pressure or reduced pressure, to distill off water. A polymerization aid may be added at this stage. The order of charging these raw materials may be random, or they may be charged simultaneously. Toluene or the like may be added to promote the distillation of water, and the reaction may be carried out.

[0050] At the end of the previous step, i.e., before the polymerization reaction step, the amount of water in the system is preferably 0.01 mol to 1.00 mol per 1.00 mol of the charged sulfidizing agent. Here, the amount of water in the system is the amount of water charged into the polymerization system minus the amount of water removed from the polymerization system. The charged water may be in any form, such as water, an aqueous solution, or water of crystallization.

[0051] [Coincidence Process (Process 1)] When manufacturing the PAS of the present invention, it is preferable to perform a polymerization process in which the reactant prepared in the previous process and the dihalogenated aromatic compound are brought into contact with each other in an organic polar solvent to cause a polymerization reaction.

[0052] In the polymerization process, it is preferable that 0.25 mol or more and 0.40 mol or less of an alkali metal carboxylate is present with respect to 1.00 mol of the sulfidizing agent, and 0.99 mol or more and 1.03 mol or less of the dihalogenated aromatic compound is present with respect to 1.00 mol of the sulfidizing agent.

[0053] Here, the alkali metal carboxylate serves as a polymerization aid as described above. When 0.25 mol or more of the alkali metal carboxylate is present, the molecular weight of the obtained PAS becomes high, which is preferable. More preferably, it is 0.30 mol or more, and still more preferably, it is 0.33 mol or more. Also, it is preferable that the alkali metal carboxylate is present in an amount of 0.40 mol or less, and more preferably 0.35 mol or less. By using within the above preferable range, the molecular weight of PAS is efficiently increased. If used beyond the preferable range, the efficiency of increasing the molecular weight decreases and it becomes economically disadvantageous. Also, as described above, the alkali metal carboxylate may be added in the previous process.

[0054] When starting the polymerization process, desirably in an inert gas atmosphere, the organic polar solvent, the sulfidizing agent, and the dihalogenated aromatic compound are mixed in a temperature range of 25°C to 260°C, preferably 100°C to 250°C. The polymerization aid may be added at this stage. The charging order of these raw materials may be in any order or simultaneously without any problem.

[0055] This mixture is usually heated to a temperature in the range of 200°C or higher and 280°C or lower. There is no particular limitation on the heating rate, but a rate of usually 0.01°C / min to 5°C / min is selected, and a range of 0.1°C / min to 3°C / min is more preferable. As long as it is within the above-mentioned heating rate range, it is not necessarily required to be at a constant rate. There may be a constant temperature section, or heating can be carried out in multiple stages without any problem, and there may even be a section with a temporarily negative heating rate as long as the essence of the present invention is not impaired.

[0056] Generally, finally, the temperature is raised to a temperature of 250°C to 280°C or lower, and the reaction is carried out at that temperature for usually 0.25 hours to 50 hours, preferably 0.5 hours to 20 hours.

[0057] Before reaching the final temperature, for example, a method of reacting at a constant temperature for a certain period of time at 200°C to 250°C and then raising the temperature to 250°C to 280°C or lower is effective for obtaining a higher molecular weight. At this time, the reaction time at 200°C to 250°C is usually selected in the range of 0.25 hours to 20 hours, preferably in the range of 0.25 hours to 10 hours. Also, when raising the temperature to the range of 250°C to 280°C or lower after reacting at a constant temperature for a certain period of time at 200°C to 250°C, it is desirable to carry out the operation so that the conversion rate of the halogenated aromatic compound in the system at that time is 60% or more, preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more. The conversion rate of the halogenated aromatic compound (abbreviated as HA here) is the value calculated by the following formula. The remaining amount of HA can usually be determined by gas chromatography. (A) When the halogenated aromatic compound is added in excess in a molar ratio to the alkali metal sulfide Conversion rate = [Charged amount of HA (mol) - Remaining amount of HA (mol)] / [Charged amount of HA (mol) - Excess amount of HA (mol)] (B) In cases other than the above (A) Conversion rate = [Charged amount of HA (mol) - Remaining amount of HA (mol)] / [Charged amount of HA (mol)]

[0058] In the present invention, from the viewpoint of increasing the molecular weight of PAS, the polymerization time in the polymerization step is preferably 60 minutes or more, more preferably 120 minutes or more. On the other hand, from the viewpoint of productivity, the upper limit of the polymerization time is preferably 240 minutes or less, more preferably 210 minutes or less, and even more preferably 190 minutes or less. The polymerization time referred to here is the time including the temperature rise and fall time within the temperature range of 200°C or higher and 280°C or lower from the time when the sulfidizing agent and the halogenated aromatic compound are charged until the polymerization reaction product is discharged from the reaction vessel.

[0059] In the polymerization step, it is preferable that water is present in the reaction vessel in an amount of 0.50 mol or more per 1.00 mol of the sulfidizing agent. In terms of obtaining a higher molecular weight, 0.60 mol or more is more preferable, and 0.70 mol or more is even more preferable. As the upper limit when water is used as a polymerization aid, from the viewpoint of safety related to the pressure in the reaction vessel and handleability related to the particle size of the resulting polymer, it is preferable that water is present in an amount of 1.50 mol or less per 1.00 mol of the sulfidizing agent, more preferably 1.25 mol or less, and even more preferably 1.00 mol or less. The amount of water in the polymerization step represents the amount of water within the temperature range of 250°C or higher and 280°C or lower in the polymerization step, and is the amount obtained by subtracting the amount of water removed from the polymerization system from the amount of water charged into the polymerization system and the amount of water generated by the polymerization reaction.

[0060] As a method of allowing water to be present in the reaction vessel in an amount of 0.50 mol or more and 1.50 mol or less per 1.00 mol of the sulfidizing agent, water may be added to the reaction vessel, or the reaction vessel may be partially opened to remove water. It is also possible to combine these. From the viewpoints of safety and simplicity, it is preferable to add water.

[0061] [Recovery Step (Step 2)] In the method for producing a polyarylene sulfide of the present invention, after the polymerization is completed, a solid is recovered from the polymerization reaction product containing a polymer, a solvent, and the like. In the present invention, how to perform the recovery is an important requirement. That is, in the present invention, it is preferable to recover the polyarylene sulfide by distilling off the organic polar solvent, and one of the recovery methods is the flash method. The flash method is a method in which the polymerization reaction product is flashed from a state of high temperature and high pressure (usually 250 ° C or higher, 8 kg / cm 2 or higher) into an atmosphere of normal pressure or reduced pressure, and at the same time as recovering the solvent, the polymer is recovered in a powder form. Here, the flash means ejecting the polymerization reaction product from a nozzle. Specifically, the atmosphere for flashing includes, for example, nitrogen or steam in normal pressure, and the temperature thereof is usually selected in the range of 150 ° C to 250 ° C. The flash method is an economically excellent recovery method because it can recover the solid at the same time as recovering the solvent and can also shorten the recovery time. On the other hand, since ionic impurities typified by Na and organic impurities are incorporated into the polymer during the solidification process, there is a demerit that it is more difficult to remove or ion-exchange them than in the slow cooling method described later.

[0062] In addition, as another method for recovering polyarylene sulfide, there is a slow cooling method in which the polymerization reaction product is gradually cooled while being crystallized, and then the solid is filtered and recovered. In this method, since it is gradually cooled, it takes more time for recovery than the flash method, and due to the nature of filtration, the fine powder component of the polymer cannot be recovered, resulting in poor yield and productivity. In addition, a step of separating the undersize from NMP is required separately. However, probably because it is excluded from the particles during the crystallization process, the removal and ion exchange of residual ionic impurities and organic impurities from the recovered oversize are relatively easier than the flash method.

[0063] In the present invention, it has been found that even when the solid and the solvent are separated and recovered by the flash method, a high-purity PAS having high viscosity and low ash content can be obtained by following the procedure of the post-treatment step described later.

[0064] [Post-treatment step] After being produced through the above polymerization and recovery steps, PAS is preferably washed with water, treated with an acid, and washed with an organic solvent.

[0065] [Washing with water - Acid treatment (Step 3)] In the present invention, after Step 2, it is preferable to perform Step 3 of washing the PAS resin with water and then treating it with an acid.

[0066] The solid obtained in Step 2 contains not only PAS but also water-soluble substances such as by-produced salts and unreacted sulfiding agents, so it is preferable to wash it with water. When washing with water, it is as follows. When washing PAS, the temperature of the water is preferably 100°C or higher, more preferably 120°C or higher, still more preferably 150°C or higher, and particularly preferably 170°C or higher. Washing at 100°C or higher is preferable because the effect of favorable chemical modification of PAS can be obtained. In order to exhibit the effect of favorable chemical modification of PAS by washing with water, the water used is preferably distilled water or ion-exchanged water. There is no particular limitation on the operation of washing with water. Examples include a method of charging a predetermined amount of PAS into a predetermined amount of water and heating and stirring in a pressure vessel, and a method of continuously performing washing with water. The ratio of PAS to water is preferably higher in water, and usually, a bath ratio (weight of the cleaning liquid relative to the weight of dry PAS) of 200 g or less of PAS per 1 liter of water is selected.

[0067] Next, from the viewpoint of obtaining PAS with a high acid amount and a low ash content rate in the present invention, it is preferable to treat PAS with an acid. When performing acid treatment, it can be exemplified as follows. The acid used for acid treatment of PAS is not particularly limited as long as it does not have an action of decomposing PAS, and examples include acetic acid, hydrochloric acid, sulfuric acid, phosphoric acid, silicic acid, carbonic acid, and propionic acid. Among them, acetic acid and hydrochloric acid are more preferably used. On the other hand, those that decompose and deteriorate PAS, such as nitric acid, are not preferable.

[0068] In addition, in order to avoid undesirable decomposition of the reactive functional groups, it is desirable that the treatment atmosphere be an inert atmosphere. Further, in order to remove the remaining components, it is preferable that the PAS after this acid treatment operation be washed several times with water.

[0069] The method of acid treatment includes, for example, immersing PAS in an acid or an aqueous solution of an acid, and heating is preferably performed. Stirring can also be carried out if necessary. The amount of the acid is preferably 5.0 mol% or more, more preferably 7.0 mol% or more, based on the amount of substance of PAS when dried. Also, it is preferably 20.0 mol% or less, more preferably 15.0 mol% or less, and even more preferably 10.0 mol% or less. At this time, the amount of the acid uses the value obtained by multiplying the amount of substance of the used acid by the valence of the acid, and the amount of substance of PAS refers to the value obtained by dividing the weight of PAS by the unit molecular weight of PAS. If the acid concentration is low, the cleaning effect decreases, the ash content increases, and the crystallinity decreases, which is not preferable. If it is too high, it is not preferable from the viewpoints of corrosion of equipment and economy. Also, the temperature of the acid treatment is preferably 150°C or higher, more preferably 170°C or higher, and even more preferably 190°C or higher. Also, the maximum temperature is preferably 220°C or lower, more preferably 210°C or lower, and even more preferably 200°C or lower. If the temperature is low, the cleaning effect decreases, the ash content increases, and the crystallinity decreases, which is not preferable. If it is too high, the danger increases from the viewpoint of safety related to the pressure in the reaction vessel, which is not preferable. There is no particular limitation on the bath ratio during the acid treatment, and it can generally be arbitrarily selected between 1 and 50. At this time, the bath ratio refers to the total amount (g) of the cleaning liquid with respect to the weight (g) of the dried PAS. The method of acid treatment at a high temperature is not particularly limited, but generally, treatment at high temperature and high pressure using a pressure-resistant container or the like is performed. For example, when using acetic acid, an aqueous solution containing 5.0 mol% of acetic acid with respect to PAS is heated to 170°C to 200°C in a pressure-resistant reaction vessel, and PAS powder is immersed therein, and sufficient effect can be obtained by stirring for 30 minutes. In order to remove the remaining acid or salt etc. from the acid-treated PAS, it is preferable to wash it several times with water. The water used for washing is preferably distilled water or ion-exchanged water so as not to impair the preferable chemical modification effect of PAS by the acid treatment, and a higher temperature is preferable as the washing efficiency is higher. The acid-treated PAS is preferable because it has excellent reactivity during molding processing, has a low ash content rate, and has a high temperature-lowering crystallization temperature.

[0070] Generally, the properties of PAS obtained by the manufacturing method are different. In particular, after the polymerization step, the recovery step of recovering PAS from the polymerization reaction product affects the properties of PAS. Since the flash method incorporates impurities into PAS, the conventional acid treatment method could not achieve a low ash content rate. In the present invention, by performing the acid treatment at a high concentration and high temperature, we successfully reduced the ash content rate significantly. In the acid treatment in the present invention, concentration and temperature are important. If outside the preferred range, the washing efficiency drops sharply and the ash content rate increases. In the present invention, by using a pressure-resistant reaction vessel or the like and heating at a temperature above the boiling points of the acid and water, it is possible to penetrate the acid into PAS, and as a result of efficiently causing chemical modification by the acid treatment, we succeeded in obtaining PAS with a low ash content rate and a crystallization temperature upon cooling higher than before.

[0071] Also, when performing acid washing at a high concentration and high temperature, impurities that are hardly soluble in water are generated. Leaving these impurities not only causes the dried PAS powder to become sticky and the operability to deteriorate, but also leads to an increase in volatile components during molding. Although it is difficult to remove these impurities by water washing after the acid treatment, they can be removed by performing washing with an organic solvent in the subsequent step 4.

[0072] [Solvent Washing (Step 4)] In the present invention, in order to make the ash content rate and viscosity of the obtained PAS fall within a preferable range, it is preferable to wash the PAS with an organic solvent. It is more preferable to carry out the washing after acid washing because the removal efficiency of the oligomer component is improved. The case of washing with an organic solvent is as follows. The organic solvent used for washing the PAS is not particularly limited as long as it has no action of decomposing the PAS or the like. For example, nitrogen-containing polar solvents such as N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, 1,3-dimethylimidazolidinone, hexamethylphosphoramide, and piperazinones; sulfoxide-sulfone solvents such as dimethyl sulfoxide, dimethyl sulfone, and sulfolane; ketone solvents such as acetone, methyl ethyl ketone, diethyl ketone, and acetophenone; ether solvents such as dimethyl ether, dipropyl ether, dioxane, and tetrahydrofuran; halogen solvents such as chloroform, methylene chloride, trichloroethylene, dichloroethylene, perchloroethylene, monochloroethane, dichloroethane, tetrachloroethane, perchloroethane, and chlorobenzene; alcohol-phenol solvents such as methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, propylene glycol, phenol, cresol, polyethylene glycol, and polypropylene glycol; and aromatic hydrocarbon solvents such as benzene, toluene, and xylene can be mentioned as the organic solvent used for washing the PAS. Among these organic solvents, the use of N-methyl-2-pyrrolidone, acetone, dimethylformamide, chloroform, etc. is particularly preferable. Further, these organic solvents are used singly or in a mixture of two or more kinds.

[0073] As a method of washing with an organic solvent, for example, there is a method of immersing PAS in an organic solvent, and it is preferable to heat. Also, it is possible to appropriately stir if necessary. There is no particular limitation on the washing temperature when washing PAS with an organic solvent, but it is preferably washed at a temperature of 70 °C or higher, more preferably 80 °C or higher, and even more preferably 90 °C or higher. There is no particular limitation on the upper limit, and the washing efficiency tends to increase as the washing temperature increases, but it is at most 300 °C, and a sufficient effect can be obtained at about 150 °C. It is also possible to wash under pressure at a temperature above the boiling point of the organic solvent in a pressure vessel. Also, there is no particular limitation on the washing time. Depending on the washing conditions, in the case of batch washing, usually a sufficient effect can be obtained by washing for 15 minutes or more. Also, it is preferably at most 24 hours, more preferably within 12 hours, and even more preferably within 7 hours. When the temperature is low or the time is short, a sufficient washing effect cannot be obtained and the viscosity and ash content do not fall within the preferable range. Even when washing for a long time, the washing effect does not change and it becomes economically disadvantageous as the time extends. It is also possible to wash continuously. The post-treatment process can greatly reduce impurities by using water washing, acid treatment, drying, and washing with an organic solvent in combination, which is preferable from the viewpoints of viscosity and ash content.

[0074] When washing with an organic solvent, the concentration of the organic solvent for washing after washing for a predetermined time is preferably 80% or more. In washing with an organic solvent, mainly soluble components such as low molecular weight substances and impurities in PAS are eluted, but if a large amount of soluble components or moisture from the previous process remains, the concentration of the organic solvent for washing decreases and a sufficient washing effect cannot be obtained. The organic solvent for washing here refers to the liquid component when coexisting with the PAS resin in the washing tank, and basically includes the organic solvent added as the washing liquid and low molecular weight components, impurities, moisture, etc. remaining in the PAS resin. The concentration of the organic solvent for washing here is [(amount of organic solvent added)+(amount of organic solvent contained in PAS)] / [(amount of organic solvent added)+(amount of organic solvent remaining in PAS)+(soluble components such as low molecular weight components, impurities, and moisture in PAS into the washing liquid)]×100(%) can be represented by.

[0075] When using an organic solvent mixed as a cleaning liquid, the total amount of the mixed organic solvents is considered as the (amount of the added organic solvent) in the above formula. When using a water-soluble organic solvent as the cleaning liquid, if a large amount of water remains in the PAS resin, the concentration of the cleaning organic solvent will be greatly reduced during cleaning. Therefore, it can be said that it is a more preferable method to reduce the water content before Step 4. Examples of methods for reducing the water content include a method of substituting with a water-soluble organic solvent and a method of sandwiching a drying process. When performing cleaning with a water-insoluble organic solvent, since the organic solvent and water are immiscible and the concentration of the cleaning organic solvent does not substantially decrease in the concentration measurement using the gas chromatograph described later, the step of reducing the water content is not necessarily required. Also, from the viewpoint of maintaining the concentration of the cleaning organic solvent, the bath ratio of the organic solvent added to the weight of the dried PPS is preferably 1 or more, more preferably 3 or more, and even more preferably 5 or more. Although there is no limitation on the preferable range for the upper limit, it is generally carried out with a bath ratio of 10 or less due to economic efficiency and constraints due to the scale of the equipment. The concentration of the cleaning organic solvent can be measured in accordance with JIS K 0114 using a gas chromatograph and a calibration curve. Regarding the method of analysis, the cleaning liquid may be sampled and analyzed after cleaning for a predetermined time, or the filtrate after cleaning may be analyzed.

[0076] In the present invention, as a post-treatment step, it is preferable to perform in the order of a step of washing a solid containing polyarylene sulfide with water and then performing an acid treatment (Step 3), and a step of washing with an organic solvent following Step 3 (Step 4). Thereby, low molecular weight components can be efficiently removed.

[0077] The yield of PAS obtained after completion of all steps can be considered based on the amount of sulfur substance in the system, and the more the better, but from the viewpoint of productivity, it is preferably 90% or more.

[0078] [Uses of PAS] The high molecular weight, high viscosity, highly reactive, and low ash content PAS of the present invention is excellent in heat resistance, chemical resistance, flame retardancy, electrical properties, and mechanical properties, and can be formed into extrusion-molded products such as sheets, films, fibers, and pipes not only by injection molding, injection compression molding, and blow molding, but also by extrusion molding.

[0079] Generally, PAS may be heat-treated for the purpose of improving strength and removing volatile components. However, the PAS obtained by the present invention exhibits sufficient strength without heat treatment and has the characteristics of low volatile components.

[0080] Since the PAS of the present invention is excellent in fluidity and moldability, its applications include electrical and electronic related parts, precision machinery related parts, water-related parts, office equipment, automobile and vehicle related parts, building materials, packaging materials, furniture, daily necessities, especially electrical and electronic related parts, water-related parts, and automobile and vehicle related parts.

[0081] The PAS obtained by the present invention can also be used by blending fillers and additives within a range that does not impair the effects of the present invention. As specific examples of such fillers, either organic fillers or inorganic fillers may be used, and either fibrous fillers or non-fibrous fillers may be used. The shape of the fibrous filler is not particularly limited, and it can be appropriately selected from among chopped strands, fiber bundles such as rovings, woven fabrics such as plain weave and twill weave, knitted fabrics, non-woven fabrics, fiber papers, fibrous filler sheets such as UD materials (uni-directional materials), etc., as needed. The type of fibrous filler is not particularly limited, and examples include carbon fibers, metal fibers, organic fibers, and inorganic fibers. Two or more of these may be used. As specific examples of such additives, coupling agents, release agents, antioxidants, elastomers, etc. can be appropriately selected as needed. One or two or more of these may be used.

[0082] As a method for manufacturing a PAS film using the PAS of the present invention, a known melt film-forming method can be employed. For example, after melting the PAS in a single-screw or twin-screw extruder, it is extruded from a film die and cooled on a cooling drum to form a film. Alternatively, it can be manufactured by a biaxial stretching method in which the film thus formed is stretched longitudinally and transversely using a roller-type longitudinal stretching device and a transverse stretching device called a tenter, but it is not particularly limited thereto.

[0083] The PAS film thus obtained has excellent mechanical properties, electrical properties, and heat resistance, and can be suitably used for various applications such as dielectric film applications for film capacitors and chip capacitors, and release film applications.

[0084] As a method for manufacturing PAS fibers using the PAS of the present invention, a known melt spinning method can be applied. For example, while kneading by supplying a PAS chip as a raw material to a single-screw or twin-screw extruder, it is then extruded from a spinneret through a polymer streamline exchanger, a filtration layer, etc. installed at the tip of the extruder, and methods such as cooling, stretching, and heat setting can be employed, but it is not particularly limited thereto.

[0085] The PAS monofilaments or staple fibers thus obtained can be suitably used for various applications such as paper drying dryer canvases, net conveyors, and bag filters.

Examples

[0086] Hereinafter, the method of the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited only to these examples.

[0087] [Yield] Based on the molar amount of sulfur present in the system during polymerization, the theoretical yield (g) of the PAS resin was calculated, and the yield was calculated from the weight (g) of the finally obtained dried PPS. Specifically, it is calculated by the following formula. (Weight of the obtained dry PPS) / (Theoretical yield of PPS calculated based on the amount of sulfur substance in the system) × 100 (%)

[0088] [Weight average molecular weight, cumulative integral value ratio of molecular weight distribution] The weight average molecular weight Mw and the cumulative integral value of the molecular weight distribution were calculated in terms of polystyrene by gel permeation chromatography (GPC), which is a type of size exclusion chromatography (SEC). The measurement conditions of GPC are shown below. Apparatus: Senshu Science SSC-7110 Column name: Shodex UT806M×2 Eluent: 1-chloronaphthalene Detector: Differential refractive index detector Column temperature: 210 °C Pre-thermostat temperature: 250 °C Pump thermostat temperature: 50 °C Detector temperature: 210 °C Flow rate: 1.0 mL / min Sample injection volume: 300 μL.

[0089] [Melt flow rate (MFR)] Measured according to ASTM D 1238-70 at a temperature of 315.5 °C and a load of 5,000 g. Using a melt indexer manufactured by Toyo Seiki Co., Ltd. (orifice with a length of 8.00 mm and a hole diameter of 2.095 mm), the measurement was carried out under the conditions of a sample amount of 7 g and a preheating time of 5 minutes from the sample charging to the start of measurement.

[0090] [Amount of acid] The amount of acid in PAS can be quantified by measuring the amount of carboxyl groups contained in PAS. The amorphous film of the above PAS was measured by FT-IR (IR-810 type infrared spectrophotometer manufactured by JASCO Corporation), and the absorption near 1,730 cm -1 derived from the carboxyl group was estimated by comparing with the absorption near 1,900 cm -1 derived from the benzene ring.

[0091] [Ash content rate] Using an electric furnace FP310 manufactured by Yamato Kagaku Co., Ltd., the crucible was baked at 538°C for 1 hour or more, and the weight was measured. 5 g of the PAS sample was precisely weighed and heated under the following conditions until it was completely ashed. The temperature was raised from room temperature to 440°C in 1 hour Maintained at 440°C for 5 hours The temperature was raised from 440°C to 490°C in 2 hours Maintained at 490°C for 1 hour The temperature was raised from 490°C to 538°C in 1 hour Maintained at 538°C for 6 hours (if the ashing is insufficient, an additional 2 hours is added)

[0092] The residue (ash) remaining in the crucible was precisely weighed, and the ash content was measured as the ratio to the weight of the charged PAS sample.

[0093] [Injection molding] Using a HAAKE MiniJet from Thermo Fisher Scientific, a JIS K6251 dumbbell-shaped No. 6 test piece was obtained at a melting temperature (cylinder temperature) of 320°C and a mold temperature of 130°C.

[0094] [Cooling crystallization temperature, crystallinity] Using the amorphous film and the injection-molded test piece, with a differential scanning calorimeter DSCQ200 manufactured by TA Instruments, under a nitrogen stream, the temperature was raised from 50°C to 340°C at a heating rate of 20°C / min, held for 1 minute, and then cooled from 340°C to 100°C at a cooling rate of 20°C / min to measure the cooling crystallization temperature (Tmc) of PAS.

[0095] The crystallinity was calculated by the following formula using the cold crystallization heat, the melting heat obtained by DSC measurement, and the melting heat of the completely crystalline PPS of 80.1 J / g (literature value). [(Melting heat) - (Cold crystallization heat)] / (Melting heat of completely crystalline body) × 100 (%).

[0096] [Preparation of amorphous film] A PAS and a spacer (aluminum plate of about 0.3 mm) were sandwiched between polyimide films. The polyimide film together with the PAS was sandwiched between press molds heated to 340 °C and pressurized for 1 minute. After pressurizing for 1 minute to retain the PAS, the polyimide film together with the PAS was taken out and immersed in the prepared water and rapidly cooled to obtain an amorphous film.

[0097] [Elastic modulus and tensile strength] Using an AG-20kNx universal testing machine, the dumbbell-shaped No. 6 test pieces obtained by injection molding were measured for elastic modulus and tensile strength in accordance with ISO527-1 under the conditions of a tensile speed of 10 mm / min, an ambient temperature of 23 °C, and a relative humidity of 50%, and the average value of 5 measurements was obtained.

[0098] [Example 1] Into an autoclave equipped with a stirrer and a bottom plug valve, 118.03 g (1.00 mol) of 47.5% sodium hydrosulfide, 41.04 g (1.00 mol) of 96% sodium hydroxide, 208.17 g (2.10 mol) of N-methyl-2-pyrrolidone (NMP), 27.07 g (0.33 mol) of sodium acetate, and 78.57 g of ion-exchanged water were charged, and while passing nitrogen at normal pressure, it was gradually heated to 225 °C over about 3 hours. Heating was terminated and cooling was started when 140.57 g of water and 4.00 g of NMP were distilled off. Since the amount of hydrogen sulfide scattered at this point was 0.02 mol, the sulfidizing agent in the system after this step was 0.98 mol.

[0099] (Step 1) Then, it was cooled to 200 °C, 147.24 g (1.00 mol) of p-dichlorobenzene (p-DCB) and 79.30 g (0.80 mol) of NMP were added, and then the reaction vessel was sealed under nitrogen gas and heated from 200 °C to 240 °C at a rate of 0.6 °C / min while stirring, and then heated from 240 °C to 276 °C at a rate of 0.8 °C / min and reacted for 93 minutes.

[0100] (Step 2) Next, the bottom plug valve of the autoclave was opened, and while pressurizing with nitrogen, the contents were flushed into a container equipped with a stirrer over 15 minutes and stirred at 250 °C for a while to remove most of the NMP.

[0101] (Process 3) The obtained recovered product and 1.10 liters of ion-exchanged water were placed in an autoclave equipped with a stirrer, washed at 70 °C for 30 minutes, and then suction filtered through a glass filter. Next, 1.10 liters of ion-exchanged water heated to 70 °C was poured into the glass filter and suction filtered to obtain a cake.

[0102] The obtained cake and 1.30 liters of ion-exchanged water were charged into an autoclave equipped with a stirrer, and acetic acid was added so as to be 11 wt% with respect to PPS (19.8 mol% with respect to PAS). After replacing the inside of the autoclave with nitrogen, the temperature was raised to 195 °C and held for 30 minutes. Then the autoclave was cooled and the contents were taken out. The contents were suction filtered through a glass filter, and then 1.10 liters of ion-exchanged water at 70 °C was poured into this and suction filtered to obtain a cake. The obtained cake was dried at 120 °C under a nitrogen stream to obtain dry PAS.

[0103] (Process 4) The obtained dry PAS was placed in an autoclave equipped with a stirrer, NMP was added so that the bath ratio became 5, and it was stirred at 95 °C for 30 minutes, and then suction filtered through a glass filter to obtain a cake. The cake was washed with NMP having a bath ratio of 2 and replaced with ion-exchanged water, and then the obtained wet cake was vacuum dried at 130 °C for 4 hours to obtain dry PAS. The properties of the obtained PPS were as shown in Table 1.

[0104] [Example 2] Dry PPS was obtained in the same manner as in Example 1 except that the amount of acetic acid in Process 3 was changed to 3 wt% (7.2 mol% with respect to PAS) and the washing temperature in Process 4 was changed to 70 °C. The properties of the obtained PPS were as shown in Table 1.

[0105] [Comparative Example 1] Into an autoclave, 9.44 kg (80 mol) of 47.0% sodium hydrosulfide, 3.43 kg (82.4 mol) of 96% sodium hydroxide, 13.0 kg (131 mol) of N-methyl-2-pyrrolidone (NMP), 1.86 kg (22.6 mol) of sodium acetate, and 12 kg of ion-exchanged water were charged. While passing nitrogen at normal pressure, it was gradually heated to 235°C over about 3 hours. Heating was terminated and cooling was started when 17.0 kg of water and 0.3 kg (3.23 mol) of NMP were distilled off. At this point, the amount of hydrogen sulfide scattered was 2 mol.

[0106] Next, 11.9 kg (80.7 mol) of p-dichlorobenzene (p-DCB) and 10.5 kg (106 mol) of NMP were additionally charged, and the reaction vessel was sealed under nitrogen gas. While stirring, the temperature was raised from 200°C to 270°C at a rate of 0.6°C / min, and the reaction was continued at 270°C for 140 minutes. Then, while cooling to 240°C over 20 minutes, 2.67 kg (148 mol) of water was injected into the system, and then it was cooled from 240°C to 210°C at a rate of 0.4°C / min. Then it was rapidly cooled to near room temperature.

[0107] The content was taken out, diluted with 32 liters of NMP, and then the solvent and solid were filtered off with a sieve (80 mesh). The obtained particles were diluted again with 38 liters of NMP and filtered off. Then it was washed with 67 liters of water at 70°C and filtered off.

[0108] The obtained cake and 67 liters of ion-exchanged water were charged into an autoclave equipped with a stirrer, and acetic acid was added so that it was 0.5 wt% with respect to PPS (0.9 mol% with respect to PAS). After replacing the inside of the autoclave with nitrogen, the temperature was raised to 75°C and held for 30 minutes. Then the autoclave was cooled and the content was taken out. The content was suction filtered through a glass filter, and then 67 liters of ion-exchanged water at 70°C was poured into it and suction filtered to obtain a cake. The obtained cake was dried at 120°C under a nitrogen stream to obtain dry PAS. The properties of the obtained PPS were as shown in Table 1.

[0109] [Comparative Example 2] In Example 1, dry PPS was obtained in the same manner except that the amount of sodium acetate was 18.87 g (0.23 mol), the polymerization time was 190 minutes, and the amount of acetic acid during washing was reduced to 0.5 wt% (0.9 mol% based on PAS). The properties of the obtained PPS were as shown in Table 1.

[0110] [Comparative Example 3] In Example 2, dry PPS was obtained in the same manner except that Step 4 was not carried out. The properties of the obtained PPS were as shown in Table 1.

[0111] [Comparative Example 4] An autoclave equipped with a stirrer and a bottom plug valve was charged with 8.26 kg (70.00 mol) of 47.5% sodium hydrosulfide, 2.63 kg (68.53 mol) of 96% sodium hydroxide, 14.57 kg (147.00 mol) of N-methyl-2-pyrrolidone (NMP), 1.89 kg (23.1 mol) of sodium acetate, and 5.78 kg of ion-exchanged water. While passing nitrogen at normal pressure, it was gradually heated to 245 °C over about 3 hours. Heating was terminated and cooling was started when 9.70 kg of water and 0.28 kg of NMP were distilled off. Since the amount of hydrogen sulfide scattered at this point was 1.4 mol, the sulfidizing agent in the system after this step was 68.6 mol.

[0112] (Step 1) Then, it was cooled to 200 °C. After adding 10.36 kg (70.45 mol) of p-dichlorobenzene (p-DCB) and 5.55 kg (56.00 mol) of NMP, the reaction vessel was sealed under nitrogen gas and heated from 200 °C to 240 °C at a rate of 0.6 °C / min while stirring, then heated from 240 °C to 276 °C at a rate of 0.8 °C / min, and further reacted at 276 °C for 75 minutes.

[0113] (Step 2) Next, the bottom plug valve of the autoclave was opened, and while pressurizing with nitrogen, the contents were flushed into a container equipped with a stirrer over 15 minutes and stirred at 250 °C for a while to remove most of the NMP.

[0114] (Step 3) The obtained solid and 76 liters of ion-exchanged water were placed in an autoclave equipped with a stirrer, washed at 70°C for 30 minutes, and then suction-filtered through a glass filter. Subsequently, 76 liters of ion-exchanged water heated to 70°C was poured into the glass filter and suction-filtered to obtain a cake.

[0115] The obtained cake and 90 liters of ion-exchanged water were charged into an autoclave equipped with a stirrer, and acetic acid was added so that it was 2.8 wt% with respect to PPS (5.0 mol% with respect to PAS). After replacing the inside of the autoclave with nitrogen, the temperature was raised to 170°C and held for 30 minutes. Then the autoclave was cooled and the contents were taken out.

[0116] The contents were suction-filtered through a glass filter, then 76 liters of ion-exchanged water at 70°C was poured into this and suction-filtered to obtain a cake. The obtained cake was dried at 120°C under a nitrogen stream to obtain dried PPS. The properties of the obtained PPS were as shown in Table 1.

[0117] [Comparative Example 5] Dried PPS was obtained in the same manner as in Comparative Example 4, except that acetic acid was added so that it was 1.7 wt% with respect to PPS (3.0 mol% with respect to PAS). The properties of the obtained PPS were as shown in Table 1.

[0118] [Comparative Example 6] Dried PPS was obtained in the same manner as in Comparative Example 4, except that the temperature during washing using acetic acid was set to 130°C. The properties of the obtained PPS were as shown in Table 1.

[0119]

Table 1

[0120] The results of the above Examples and Comparative Examples will be compared and explained.

[0121] In Example 1, the weight-average molecular weight was 30,000 or more and 90,000 or less, the cumulative integral value of a molecular weight of 3,000 or less was 5.0% or more and 10.0% or less, the MFR was 50 [g / 10 min] or more and 400 [g / 10 min] or less, the acid amount was 25 [μmol / g] or more and 50 [μmol / g] or less, and the ash content was also 0.10% by weight or less. Therefore, a PAS resin having high mechanical properties and good crystallinity and reactivity was obtained.

[0122] Also in Example 2, the weight-average molecular weight was 30,000 or more and 90,000 or less, the cumulative integral value of a molecular weight of 3,000 or less was 5% or more and 10% or less, the MFR was 50 [g / 10 min] or more and 400 [g / 10 min] or less, the acid amount was 25 [μmol / g] or more and 50 [μmol / g] or less, and the ash content was also 0.10% by weight or less. Therefore, a PAS resin having high mechanical properties and good crystallinity and reactivity was obtained. When compared with Example 1, as a result of reducing the amount of the acid in the acid treatment, the acid amount decreased and the ash content rate slightly increased. However, a high-viscosity PAS was obtained, and when injection molding was performed with this resin, the degree of crystallinity was 52%, the elastic modulus was 2.8 GPa, and the tensile strength was 71 MPa.

[0123] In Comparative Example 1, the weight-average molecular weight, viscosity, acid amount, and ash content rate were within the range, but the cumulative integral value of a molecular weight of 3,000 or less was as small as 4%, the crystallization temperature was lower than that of the examples, and the crystallinity was deteriorated. Also, when compared with Example 2, the viscosity was decreased and the strength was inferior to that of Example 2. Further, since the polymerization time was long and the yield was low, the productivity was poor.

[0124] In Comparative Example 2, the weight-average molecular weight, the cumulative integral value of a molecular weight of 3,000 or less, and the acid amount were within the range described in the claims. However, since polymerization was carried out under conditions with less sodium acetate as compared with Example 1, the viscosity was lowered, and since the amount of acetic acid during acid washing was reduced, the ash content rate increased. Since the viscosity decreased, the tensile strength became 57 MPa and decreased. Since the ash content rate increased, the cooling crystallization temperature also slightly decreased.

[0125] In Comparative Example 3, the weight-average molecular weight, acid amount, and ash content are within the ranges described in the claims. However, compared with Example 2, since solvent washing was not performed, in addition to the low viscosity, the cumulative integral value of the molecular weight of 3,000 or less is high, so the tensile strength when molded is 62 MPa, which is lower than that of Example 2.

[0126] In Comparative Examples 4 to 6, the conditions of acid washing were changed.

[0127] In Comparative Example 4, as a result of performing acid washing with an acid amount of 5.0 mol% and a washing temperature of 170°C during acid washing, the ash content could be sufficiently reduced. However, the weight-average molecular weight and viscosity are insufficient, and the cumulative integral value of the molecular weight of 3,000 or less is also high, so the strength is insufficient.

[0128] In Comparative Example 5, the acid amount during acid washing was reduced to 3.0 mol% compared with Comparative Example 4, but the result was a high ash content.

[0129] In Comparative Example 6, as a result of lowering the washing temperature during acid washing to 130°C compared with Comparative Example 4, the ash content increased.

Claims

1. A polyarylene sulfide having a weight average molecular weight of 30,000 or more and 90,000 or less, a cumulative integral value of 5.0% or more and 10.0% or less for a molecular weight of 3,000 or less in a molecular weight distribution curve, conforming to ASTM D 1238-70, and having a melt flow rate measured under the conditions of 315.5 °C and a load of 5,000 g of 50 [g / 10 min] or more and 400 [g / 10 min] or less, an acid amount of 25 [μmol / g] or more and 50 [μmol / g] or less, and an ash content of 0.10 wt% or less.

2. In a method for producing a polyarylene sulfide by reacting a sulfidizing agent and a dihalogenated aromatic compound in an organic polar solvent in the presence of an alkali metal hydroxide and an alkali metal carboxylate, the method for producing a polyarylene sulfide according to claim 1, characterized by performing at least the following steps 1 to 4. Step 1: A polymerization step of polyarylene sulfide in which a reaction is carried out in an organic polar solvent in the presence of an alkali metal carboxylate. Step 2: A step of distilling off the organic polar solvent from the mixture obtained at the end of the polymerization reaction to obtain a solid containing polyarylene sulfide. Step 3: A step of acid-treating after washing the solid containing polyarylene sulfide with water following step 2. Step 4: A step of washing the polyarylene sulfide with an organic solvent following step 3.

3. The method for producing a polyarylene sulfide according to claim 2, characterized in that in step 1, an alkali metal carboxylate is present in an amount of 0.25 mol or more and 0.40 mol or less per 1.00 mol of the sulfidizing agent and allowed to react.

4. The method for producing a polyarylene sulfide according to claim 2, characterized in that in step 3, the acid treatment is carried out at 150 °C or higher.

5. In step 3, the method for producing a polyarylene sulfide according to claim 2, characterized in that the amount of acid is 5.0 mol% or more and 20.0 mol% or less based on the polyarylene sulfide.

6. In step 4, the method for producing a polyarylene sulfide according to claim 2, characterized in that the polyarylene sulfide is washed at 70 °C or higher for 15 minutes or longer.

7. In step 4, the method for producing a polyarylene sulfide according to claim 2, characterized in that the concentration of the organic solvent for washing after washing is 80% or higher.

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