JP7806578B2 - Polyarylene sulfide copolymer, method for producing the same, and polyarylene sulfide copolymer composition - Google Patents

Description

The present invention relates to a polyarylene sulfide copolymer.

Polyarylene sulfides, typified by polyphenylene sulfide (hereinafter sometimes abbreviated as PPS), have properties suitable for engineering plastics, such as excellent heat resistance, barrier properties, moldability, chemical resistance, electrical insulation, and moist heat resistance, and are used in a variety of electrical and electronic parts, machine parts, automotive parts, films, fibers, and more, primarily in injection molding and extrusion molding. Due to their excellent properties, the range of applications for polyarylene sulfides has been expanding in recent years.

PPS, a typical polyarylene sulfide, is a crystalline polymer that generally has a glass transition point of 80-90°C and a melting point of 275-285°C, and is often used under high-temperature conditions due to its excellent heat resistance. Furthermore, PPS dissolves only in a very limited number of solvents at high temperatures of 200-250°C, and is widely used in applications that take advantage of its excellent chemical resistance.

The aforementioned PPS, a typical example of polyarylene sulfide, has a high melting point that allows it to withstand high-temperature use. However, it suffers from the problem that its rigidity drops sharply above its glass transition point of 80-90°C compared to temperatures below that point. Therefore, various studies are being conducted to improve the glass transition point of polyarylene sulfide.

For example, Patent Documents 1 and 2 disclose polyarylene sulfide copolymers obtained by reacting polyarylene sulfide having reactive functional groups with rigid molecules.

Patent Document 3 discloses a crystalline polyimide containing cumulative phenylene sulfide units that has an improved glass transition temperature by linking dimer to nonamer phenylene sulfide and arylene groups with imide bonds.

Patent Document 4 discloses a copolymer consisting of a polyarylene sulfide block and a polyetherimide block or a polydiorganosiloxane block.

Patent Document 5 discloses an aromatic imide sulfide polymer.

Patent Document 6 discloses a polyarylene sulfide-polyimide copolymer.

International Publication No. 2019/151288 International Publication No. 2022/045105 Japanese Patent Application Laid-Open No. 62-84124 Japanese Unexamined Patent Publication No. 64-45433 Japanese Patent Application Publication No. 5-194738 Japanese Patent Application Publication No. 4-220462

The polyarylene sulfide copolymers disclosed in Patent Documents 1 and 2 have high glass transition points, but suffer from poor crystallinity, such as a low crystallization temperature or no crystallization temperature at all. Furthermore, Patent Document 2 describes reducing the amount of gas generated during copolymer production and the associated improvement in production efficiency, but neither Patent Document 1 nor 2 describes crystallinity or how to improve crystallinity.

The crystalline polyimide disclosed in Patent Document 3 has an improved glass transition point, but has the problem of slow crystallization due to the small molecular weight of the phenylene sulfide unit.

The copolymer disclosed in Patent Document 4 also has an improved glass transition temperature, but because it has a block structure containing polyetherimide blocks and polydiorganosiloxane blocks, it has the problem of slow crystallization.

The aromatic imide sulfide polymer disclosed in Patent Document 5 has an improved glass transition temperature, but it is difficult to obtain an aromatic imide sulfide polymer with a sufficient molecular weight of arylene sulfide units, and there are problems with crystallization, such as slow crystallization.

The polyarylene sulfide-polyimide copolymer disclosed in Patent Document 6 can also improve its glass transition temperature by melt-blending it with polyimide, but has the problem of slow crystallization due to the influence of the melt-blended polyimide. Furthermore, it may also contain free polyarylene sulfide and polyimide, making it difficult to achieve high crystallinity, including stability.

Furthermore, none of Patent Documents 3 to 6 contain any description regarding crystallinity or improving crystallinity.

Therefore, the objective of the present invention is to obtain a polyarylene sulfide copolymer that has both a high glass transition point and a high crystallization temperature.

The present invention has been made to solve at least part of the above-mentioned problems, and can be realized by providing the following contents.
1. A polyarylene sulfide copolymer characterized by having, as a structural unit, an arylene sulfide unit having a number average molecular weight Mn of 1,000 or more and 10,000 or less, having a structure in which the arylene sulfide unit and a copolymerization component are linked by an imide group, having a glass transition point measured by differential scanning calorimetry of 95°C or more and 190°C or less, and having a crystallization temperature of 165°C or more.
2. The polyarylene sulfide copolymer according to 1 above, wherein the relative intensity of the absorption at 3382 cm ⁻¹ attributable to the amino group to the absorption at 1901 cm ⁻¹ attributable to the benzene ring of the arylene sulfide unit is 0.11 or more and 0.90 or less, or the relative intensity of the absorption at 1860 cm ⁻¹ attributable to the acid anhydride group is 0.20 or more and 2.2 or less.
3. The polyarylene sulfide copolymer according to 1 or 2 above, which has at least one structure selected from the following formulae (a) to (s) as a structural unit:

(R, R ¹ , and R ² are substituents selected from hydrogen, alkyl groups having 1 to 12 carbon atoms, arylene groups having 6 to 24 carbon atoms, and halogen groups, and R, R ¹ , and R ² may be the same or different.)
4. The polyarylene sulfide copolymer according to any one of 1 to 3 above, which has a melting point of 300° C. or less.
5. A method for producing a polyarylene sulfide copolymer according to any one of 1 to 4 above, which comprises heating a polyarylene sulfide (A) having a number average molecular weight Mn of 1,000 or more and 10,000 or less, and at least one compound (B) selected from the following formulae (a') to (u'), wherein the ratio of the total amount of half of the carboxyl groups and acid anhydride groups to the total amount of amino groups contained in the polyarylene sulfide (A) and compound (B) is 0.75 or more and 0.97 or less, or 1.03 or more and 1.25 or less:

(X is either two carboxyl groups bonded to two adjacent carbon atoms, or an acid anhydride group derived from the two carboxyl groups, or an amino group; R, R ¹ , and R ² are substituents selected from hydrogen, an alkyl group having 1 to 12 carbon atoms, an arylene group having 6 to 24 carbon atoms, and a halogen group; R, R ¹ , and R ² may be the same or different; the aromatic ring of each compound may be di- or tri-substituted; and the multiple substituents X substituted on one aromatic ring may be the same or different.)
6. A method for producing a polyarylene sulfide copolymer according to the above item 5, comprising mixing and heating at least a portion of the polyarylene sulfide (A) and at least a portion of at least one compound (B) selected from the following formulae (a') to (u'), and then mixing and heating the remaining polyarylene sulfide (A) and/or compound (B):

(X is either two carboxyl groups bonded to two adjacent carbon atoms, or an acid anhydride group derived from the two carboxyl groups, or an amino group; R, R ¹ , and R ² are substituents selected from hydrogen, an alkyl group having 1 to 12 carbon atoms, an arylene group having 6 to 24 carbon atoms, and a halogen group; R, R ¹ , and R ² may be the same or different; the aromatic ring of each compound may be di- or tri-substituted; and the multiple substituents X substituted on one aromatic ring may be the same or different.)
7. The method for producing a polyarylene sulfide copolymer according to the above item 5 or 6, wherein the heating is carried out substantially in the absence of a solvent.
8. A polyarylene sulfide copolymer composition comprising a polyarylene sulfide copolymer (C) having, as structural units, arylene sulfide units having a number average molecular weight Mn of 1,000 or more and 10,000 or less, in which the arylene sulfide units and copolymerization components are linked via imide groups, and a crystal nucleating agent, the polyarylene sulfide copolymer composition having a glass transition point of 95°C or more and 190°C or less and a crystallization temperature of 165°C or more as measured by differential scanning calorimetry.
9. The polyarylene sulfide copolymer composition according to 8 above, wherein the polyarylene sulfide copolymer (C) has, as a structural unit, at least one structure selected from the following formulae (a) to (s):

(R, R ¹ , and R ² are substituents selected from hydrogen, alkyl groups having 1 to 12 carbon atoms, arylene groups having 6 to 24 carbon atoms, and halogen groups, and R, R ¹ , and R ² may be the same or different.)
10. The polyarylene sulfide copolymer composition according to 8 above, wherein at least a portion of the polyarylene sulfide copolymer (C) is the polyarylene sulfide copolymer according to any one of 1 to 4 above.
11. A polyarylene sulfide copolymer composition containing the polyarylene sulfide copolymer according to any one of 1 to 4 above.
12. A molded article obtained by molding the polyarylene sulfide copolymer composition according to any one of 8 to 11 above.

The present invention provides a polyarylene sulfide copolymer that exhibits both a high glass transition point and a high crystallization temperature, and a polyarylene sulfide copolymer composition that exhibits both a high glass transition point and a high crystallization temperature. It also provides a method for producing the polyarylene sulfide copolymer from a polyarylene sulfide having a specific functional group and a reactive compound.

According to the present invention, polyarylene sulfide copolymers and polyarylene sulfide copolymer compositions (hereinafter sometimes referred to as resin compositions) having high crystallization temperatures can be obtained, improving productivity by shortening the time cycle when molding and processing these, or when producing resin compositions containing fillers and/or other additives. Furthermore, sufficient crystallization of the resulting resin compositions improves and stabilizes their mechanical properties and chemical resistance. By achieving improved productivity and stabilized properties, it becomes possible to demonstrate stable performance under high-temperature conditions in applications such as electrical and electronic components, precision machinery-related components, plumbing parts, automotive and vehicle-related components, and aerospace-related components.

The following describes in detail an embodiment of the present invention.

[Polyarylene sulfide copolymer]
The lower limit of the glass transition point of the polyarylene sulfide copolymer is 95°C or higher, preferably 100°C or higher, and more preferably 110°C or higher. If the glass transition point is below 95°C, high rigidity cannot be obtained under high temperature conditions. The upper limit of the glass transition point is 190°C or lower, preferably 180°C or lower, and more preferably 160°C or lower. If the glass transition point exceeds 190°C, the chemical resistance of the molded article will be insufficient. The glass transition point is defined as the inflection point of the baseline shift detected when the temperature is raised from 0°C to 340°C at a rate of 20°C/min using a differential scanning calorimeter.

The crystallization temperature of the polyarylene sulfide copolymer is 165°C or higher, preferably 170°C or higher, more preferably 180°C or higher, even more preferably 190°C or higher, and even more preferably 200°C or higher. A crystallization temperature below 165°C can result in reduced productivity due to insufficient crystallization when molding the copolymer or when blending the copolymer with fillers and/or other additives to produce a resin composition, as described below, and can also result in reduced mechanical properties and chemical resistance due to insufficient crystallization of the resulting resin composition. While there is no particular upper limit for the crystallization temperature, a range of 235°C or lower is typically exemplified. The crystallization temperature is defined as the peak crystallization temperature detected when a differential scanning calorimeter is used to heat a sample from 0°C to 340°C at a rate of 20°C/min, then held at 340°C for 1 minute, and then cooled to 100°C at a rate of 20°C/min.

The polyarylene sulfide copolymer preferably has a melting point of 300°C or less. A melting point of 300°C or less facilitates melt molding processing. The melting point is the melting peak temperature detected when the temperature is raised from 0°C to 340°C at a rate of 20°C/min using a differential scanning calorimeter, held at 340°C for 1 minute, cooled to 100°C at a rate of 20°C/min, held at 100°C for 1 minute, and then raised again to 340°C at a rate of 20°C/min. The melting point can be adjusted by selecting the molecular weight of the arylene sulfide units in the polyarylene sulfide copolymer.

A polyarylene sulfide copolymer is a copolymer containing 70 mol % or more, and preferably 80 mol % or more, of repeating units of the formula -(Ar-S)- as arylene sulfide units. Ar can be any of the units represented by formulas (I) to (XI) below, with the unit represented by formula (I) being particularly preferred.

( ^R3 and ^R4 are substituents selected from hydrogen, alkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, aryl groups having 6 to 24 carbon atoms, halogen groups, and reactive functional groups, and ^R3 and ^R4 may be the same or different.)
As long as this repeating unit is the main structural unit, it may contain a small amount of branching units or crosslinking units represented by the following formulas (XII) to (XIV), etc. The copolymerization amount of these branching units or crosslinking units is preferably in the range of 0 to 1 mol % per 1 mol of -(Ar-S)- units.

(Here, Ar is a unit represented by the above formula (I) to formula (XI).)
The arylene sulfide unit may be any of a random copolymer, a block copolymer, and a mixture thereof containing the above repeating unit.

Representative examples of these include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, their random copolymers, block copolymers, and mixtures thereof. Particularly preferred polyarylene sulfides contain p-phenylene sulfide units represented by the following formula (XV) as the main structural unit of the polymer.

Examples include polyphenylene sulfides containing 80 mol % or more, particularly 90 mol % or more.

The lower limit of the number average molecular weight of the arylene sulfide units is 1,000 or more, preferably 1,500 or more, and more preferably 2,000 or more. If the number average molecular weight of the arylene sulfide units is less than 1,000, the polyarylene sulfide copolymer will not have sufficient chemical resistance. The upper limit of the number average molecular weight of the arylene sulfide units is 10,000 or less, preferably 6,000 or less, and more preferably 4,000 or less. If the number average molecular weight of the arylene sulfide units exceeds 10,000, the polyarylene sulfide copolymer will not have sufficient heat resistance. The number average molecular weight of the arylene sulfide units in the polyarylene sulfide copolymer can be determined, for example, by treating the polyarylene sulfide copolymer in a 10% aqueous sodium hydroxide solution under reflux conditions for 5 hours and then measuring the molecular weight of the residue. To ensure that the number-average molecular weight of the arylene sulfide units in the polyarylene sulfide copolymer falls within the above range, it is preferable to use a polyarylene sulfide (A) having a number-average molecular weight Mn of 1,000 or more and 10,000 or less, as described below, in the production of the polyarylene sulfide copolymer. The weight-average molecular weight and number-average molecular weight can be determined, for example, using SEC (size exclusion chromatography) equipped with a differential refractive index detector.

Examples of structures contained in the polyarylene sulfide copolymer as a copolymerization component include structures containing aromatic rings, preferably structures represented by formulas (a) to (s), more preferably structures represented by formulas (a) to (e), (i), and (j), with the structure represented by formula (i) being particularly preferred. By including these structures, the resulting polyarylene sulfide copolymer tends to have excellent crystallinity.

In the polyarylene sulfide copolymer, the arylene sulfide units consisting of repeating units of -(Ar-S)- are linked to the copolymerization components by imide groups. Linkage by imide groups results in high rigidity at high temperatures. The lower limit of the imide group content is preferably 1 mol% or more, more preferably 2 mol% or more, and even more preferably 4 mol% or more, relative to the sulfur atoms in the polyarylene sulfide copolymer. By maintaining the content within the above range, it is possible to sufficiently suppress a decrease in rigidity under high-temperature conditions. The upper limit of the imide group content is preferably 60 mol% or less, more preferably 40 mol% or less, even more preferably 30 mol% or less, and even more preferably 20 mol% or less. As the imide group content increases, the chemical resistance of the resulting polyarylene sulfide copolymer tends to decrease. However, maintaining the content within the above range tends to result in a polyarylene sulfide copolymer that exhibits sufficient chemical resistance and mechanical properties. The amount of imide groups can be determined by calculation using the amount of functional groups contained in the polyarylene sulfide (A) and the amount of functional groups contained in the compound (B) used in producing the polyarylene sulfide copolymer, or it can be determined using the FT-IR spectrum or NMR spectrum of the polyarylene sulfide copolymer.

The polyarylene sulfide copolymer preferably has a larger amount of either the amino group amount or the total amount of half the carboxyl group amount and the acid anhydride group amount. The amino group amount or the total amount of half the carboxyl group amount and the acid anhydride group amount can be evaluated using a Fourier transform infrared spectrophotometer (FT-IR) by measuring the relative intensity to the absorption intensity at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide unit. For FT-IR evaluation, it is preferable to use an amorphous film prepared by quenching from a molten state. When evaluating the relative intensity of the absorption at 3382 cm ⁻¹ derived from the amino group and the relative intensity of the absorption at 1860 cm ⁻¹ derived from the acid anhydride group, as described below, the melting temperature for preparing the amorphous film is 320°C. In a polyarylene sulfide copolymer, the lower limit of the relative intensity of the absorption at 3382 cm ⁻¹ derived from amino groups to the absorption at 1901 cm ⁻¹ derived from the benzene rings of the arylene sulfide units is preferably 0.11 or more, more preferably 0.13 or more, even more preferably 0.15 or more, even more preferably 0.20 or more, and even more preferably 0.40 or more. Furthermore, in a polyarylene sulfide copolymer, the lower limit of the relative intensity of the absorption at 1860 cm ⁻¹ derived from acid anhydride groups to the absorption at 1901 cm ⁻¹ derived from the benzene rings of the arylene sulfide units is preferably 0.20 or more, more preferably 0.30 or more, even more preferably 0.40 or more, even more preferably 0.50 or more, and even more preferably 1.0 or more. In the present invention, the total amount of carboxyl groups and acid anhydride groups is evaluated by measuring the relative intensity of the absorption at 1860 cm ⁻¹ derived from the acid anhydride groups. By having a large amount of either the amino group amount or half the carboxyl group amount and the total amount of acid anhydride groups as in the above range, the crystallization temperature of the polyarylene sulfide copolymer tends to be high and the crystallinity tends to be excellent. The reason for this is unclear, but it is thought that the presence of many similar structures in the copolymer makes it easier to align the polymer ends and polymer chains. On the other hand, from the viewpoint of the molecular weight of the polyarylene sulfide copolymer and the mechanical properties derived therefrom, the upper limit of the ratio of the absorption intensity at 3382 cm ⁻¹ derived from the amino group to the absorption intensity at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide unit is preferably 0.90 or less, more preferably 0.70 or less, and even more preferably 0.50 or less. Furthermore, from the viewpoint of the molecular weight of the polyarylene sulfide copolymer and the mechanical properties derived therefrom, the upper limit of the relative intensity of the absorption at 1860 cm ⁻¹ derived from the acid anhydride group to the absorption at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide unit is preferably 2.2 or less, more preferably 1.5 or less, even more preferably 1.0 or less, still more preferably 0.60 or less, and even more preferably 0.40 or less. Whether the amount of amino groups or half of the amount of carboxyl groups and the total amount of acid anhydride groups is greater can be selected depending on the reactivity and properties required of the polyarylene sulfide copolymer, the application and use environment of the polyarylene sulfide copolymer, and the types and structures of various fillers and other additives contained in a resin composition containing the polyarylene sulfide copolymer.

The lower limit of the molecular weight of the polyarylene sulfide copolymer is preferably a weight-average molecular weight of 10,000 or more, more preferably 20,000 or more, even more preferably 30,000 or more, and even more preferably 40,000 or more. Having a weight-average molecular weight lower limit in the above range tends to result in excellent mechanical properties of the polyarylene sulfide copolymer. There is no particular upper limit to the weight-average molecular weight, but examples include 200,000 or less, preferably 100,000 or less, and more preferably 80,000 or less. Having a weight-average molecular weight upper limit in the above range tends to result in excellent moldability and crystallinity of the polyarylene sulfide copolymer. The weight-average molecular weight can be determined, for example, using SEC (size exclusion chromatography) equipped with a differential refractive index detector.

[Method for producing polyarylene sulfide copolymer]
The polyarylene sulfide copolymer of the present invention is preferably produced by a method of heating polyarylene sulfide (A) having a number average molecular weight Mn of 1,000 to 10,000 and at least one compound (B) selected from formulae (a') to (u') (hereinafter sometimes abbreviated as compound (B)). In this case, it is preferable that the ratio of half of the amount of carboxyl groups and the total amount of acid anhydride groups to the total amount of amino groups in polyarylene sulfide (A) and compound (B) is 0.75 to 0.97, or 1.03 to 1.25. The polyarylene sulfide (A) and compound (B) will be described below.

[Polyarylene sulfide (A)]
The polyarylene sulfide (A) is a homopolymer or copolymer having a repeating unit of the formula -(Ar-S)- as a main structural unit. Here, "main structural unit" means that the repeating unit accounts for 70 mol% or more. Ar may be any of the units represented by the above formulas (I) to (XI), among which the unit represented by formula (I) is particularly preferred.

As long as this repeating unit is the main structural unit, it may contain a small amount of branching units or crosslinking units represented by formulas (XII) to (XIV), etc. The copolymerization amount of these branching units or crosslinking units is preferably in the range of 0 to 1 mol % per 1 mol of -(Ar-S)- units.

Polyarylene sulfide (A) may be a random copolymer, a block copolymer, or a mixture thereof containing the above repeating units.

Typical examples of these include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, their random copolymers, block copolymers, and mixtures thereof. Particularly preferred polyarylene sulfides include polyphenylene sulfides containing 80 mol % or more, and particularly 90 mol % or more, of p-phenylene sulfide units represented by formula (XV) above as the main structural unit of the polymer.

Polyarylene sulfide (A) contains at least one functional group selected from an amino group, two carboxyl groups bonded to adjacent carbon atoms, and an acid anhydride group derived from the two carboxyl groups. From the viewpoint of reactivity when polyarylene sulfide (A) is heated with compound (B) described below, the combination of the functional group of polyarylene sulfide (A) and the functional group of compound (B) is preferably an amino group and an acid anhydride group. Therefore, depending on the functional group of compound (B), the functional group contained in polyarylene sulfide (A) is preferably an amino group or an acid anhydride group. Furthermore, from the viewpoint of ease of polymerization reaction when producing polyarylene sulfide (A) using the production method described below, the functional group contained in polyarylene sulfide (A) is preferably an amino group, and accordingly, the functional group contained in compound (B) is preferably an acid anhydride group. The position of the functional group may be in the main chain of the polyarylene sulfide or at the terminal, but terminal introduction is preferred because it is easier to control the reaction with other polymers or compounds having the functional group, and is also preferred from the perspective of copolymerization with compound (B), as described below. In the case of terminal introduction, the position is preferably para to the sulfur bonded to Ar. Another preferred embodiment is a polyarylene sulfide having the functional group bonded to Ar. The functional group is a structure derived from compound (D), and details will be described below.

The lower limit of the amount of functional groups contained in the polyarylene sulfide (A) is preferably 400 μmol/g or more, more preferably 500 μmol/g or more, and even more preferably 700 μmol/g or more. Having the functional groups at or above the above lower limit is preferred because the glass transition temperature of the polyarylene sulfide copolymer tends to be sufficiently high. Furthermore, the upper limit of the amount of functional groups is preferably 5,000 μmol/g or less, more preferably 4,000 μmol/g or less, and even more preferably 3,000 μmol/g or less. Having the amount of functional groups at or below the above upper limit is preferred because it prevents a decrease in the chemical resistance of the polyarylene sulfide copolymer. When the functional groups are two carboxyl groups bonded to two adjacent carbon atoms, respectively, the functional groups refer to the amount of acid anhydride groups generated from the two carboxyl groups bonded to the two adjacent carbon atoms, respectively. The functional groups in the polyarylene sulfide can be quantified by subjecting the polyarylene sulfide to FT-IR analysis, for example, by comparing the absorption intensity at 3,382 cm ⁻¹ attributable to the amino group with the absorption at 1,901 m ⁻¹ attributable to the benzene ring, and the absorption intensity at 1,860 cm ⁻¹ attributable to the acid anhydride group with the absorption at 1,901 m ⁻¹ attributable to the benzene ring.

The number average molecular weight of polyarylene sulfide (A) is 1,000 or more, preferably 2,000 or more. If the number average molecular weight of polyarylene sulfide (A) is less than 1,000, the chemical resistance of the polyarylene sulfide copolymer will be insufficient. The upper limit of the number average molecular weight of polyarylene sulfide (A) is 10,000 or less, preferably 6,000 or less, and more preferably 4,000 or less. If the number average molecular weight of polyarylene sulfide exceeds 10,000, the heat resistance of the polyarylene sulfide copolymer and polyarylene sulfide copolymer composition will be insufficient. The number average molecular weight is a value calculated in terms of polystyrene using gel permeation chromatography (GPC), a type of size exclusion chromatography (SEC).

When polyarylene sulfide (A) is heated from 30°C to 320°C at a temperature increase rate of 10°C/min, the weight loss rate is preferably 5 wt% or less, more preferably 4 wt% or less, and even more preferably 3 wt% or less. The smaller the weight loss rate, the better, but the lower limit can be, for example, 0.01 wt% or more. When the example described below is used as a method for producing polyarylene sulfide (A), even if a large amount of functional groups are introduced into polyarylene sulfide (A), components that tend to become gaseous when heated tend not to remain.

The weight loss rate can be determined by standard thermogravimetric analysis. A non-oxidizing atmosphere at atmospheric pressure is typically used for this analysis. A non-oxidizing atmosphere refers to an atmosphere in which the oxygen concentration in the gas phase in contact with the sample is 5% by volume or less, preferably 2% by volume or less, and more preferably substantially oxygen-free. An inert gas atmosphere such as nitrogen, helium, or argon is preferred. Among these, a nitrogen atmosphere is particularly preferred from the standpoints of economy and ease of handling. Furthermore, atmospheric pressure refers to atmospheric pressure, i.e., a pressure condition of approximately 101.3 kPa absolute. Furthermore, to measure the weight loss rate, thermogravimetric analysis is performed by heating from room temperature to any temperature above 320°C at a rate of 10°C/min. This temperature range is frequently used for the practical use of polyarylene sulfides, such as polyphenylene sulfide, and for melting, molding, and reactions. The weight loss rate in this practical temperature range serves as an indicator of the amount of gas generated from polyarylene sulfide during practical use and the degree of contamination of equipment during molding, processing, and reactions. Therefore, polyarylene sulfide with a small weight loss rate within this temperature range can be said to be a high-quality, excellent polyarylene sulfide.

In addition, using the example method described below as a method for producing polyarylene sulfide (A) is preferable because the crystallinity of the polyarylene sulfide copolymer obtained using that polyarylene sulfide (A) tends to be excellent. This is also thought to be because when polyarylene sulfide (A) is produced using the production method described below, components that tend to become gaseous when heated are less likely to remain.

The following is a specific description of a method for producing polyarylene sulfide (A) of the present invention. While not limited to the following method, the present invention preferably employs a method for producing polyarylene sulfide by reacting at least a dihalogenated aromatic compound, an inorganic sulfidizing agent, and compound (D) in an organic polar solvent in the presence of an alkali metal hydroxide, wherein compound (D) is present in a reaction vessel in an amount ranging from 0.04 mol to 0.5 mol per mol of inorganic sulfidizing agent. Compound (D) has at least one aromatic ring and, on the aromatic ring, at least one functional group selected from an amino group, two carboxyl groups bonded to adjacent carbon atoms, and an acid anhydride group derived from the two carboxyl groups, and at least one functional group selected from a hydroxyl group, a salt of a hydroxyl group, a thiol group, and a salt of a thiol group. Selecting this production method results in a functional group-containing polyarylene sulfide (A) with few impurities, and the crystallization temperature of the polyarylene sulfide copolymer produced using the functional group-containing polyarylene sulfide (A) is likely to be high.

Furthermore, when two carboxyl groups bonded to two adjacent carbon atoms or acid anhydride groups derived from these two carboxyl groups are selected as the functional groups contained in polyarylene sulfide (A), employing a known method for producing polyarylene sulfide in which at least a dihalogenated aromatic compound, an inorganic sulfidizing agent, and a monohalogenated compound are reacted in an organic polar solvent in the presence of an alkali metal hydroxide is also effective from the standpoint of the reactivity of the monohalogenated compound, i.e., the ease of introducing functional groups into polyarylene sulfide (A). Examples of monohalogenated compounds used here include 3-chlorophthalic acid and 4-chlorophthalic acid.

[Inorganic sulfidizing agent]
The inorganic sulfidizing agent used in the production method of polyarylene sulfide (A) may be any agent capable of introducing a sulfide bond into a dihalogenated aromatic compound, and examples thereof include alkali metal sulfides, alkali metal hydrosulfides, and hydrogen sulfide.

Specific examples of alkali metal sulfides include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, cesium sulfide, and mixtures of two or more of these. Of these, lithium sulfide and/or sodium sulfide are preferred, with sodium sulfide being even more preferred. These alkali metal sulfides can be used as hydrates or aqueous mixtures, or in the anhydrous form. An 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. Generally available, inexpensive alkali metal sulfides are hydrates or aqueous mixtures, so it is preferable to use alkali metal sulfides in these forms.

Specific examples of alkali metal hydrosulfides include lithium hydrosulfide, sodium hydrosulfide, potassium hydrosulfide, rubidium hydrosulfide, cesium hydrosulfide, and mixtures of two or more of these. Of these, lithium hydrosulfide and/or sodium hydrosulfide are preferred, with sodium hydrosulfide being more preferred.

Alkali metal sulfides prepared in a reaction system from an alkali metal hydrosulfide and an alkali metal hydroxide can also be used. Alkali metal sulfides prepared in advance by contacting an alkali metal hydrosulfide with an alkali metal hydroxide can also be used. These alkali metal hydrosulfides and alkali metal hydroxides can be used as hydrates, aqueous mixtures, or anhydrous forms, with hydrates or aqueous mixtures being preferred from the standpoints of availability and cost.

Alkali metal sulfides prepared in situ from an alkali metal hydroxide such as lithium hydroxide or sodium hydroxide and hydrogen sulfide can also be used. Alkali metal sulfides prepared in advance by bringing an alkali metal hydroxide such as lithium hydroxide or sodium hydroxide into contact with hydrogen sulfide can also be used. Hydrogen sulfide may be used in any form, whether gaseous, liquid, or aqueous solution.

[Compound (D)]
The compound (D) used in the method for producing the polyarylene sulfide (A) is a compound having at least one aromatic ring, and on the one aromatic ring, at least one functional group selected from an amino group, two carboxyl groups bonded to two adjacent carbon atoms, and an acid anhydride group derived from the two carboxyl groups, and at least one functional group selected from a hydroxyl group, a salt of a hydroxyl group, a thiol group, and a salt of a thiol group. The compound (D) may be any aromatic compound having a functional group selected from an amino group, two carboxyl groups bonded to two adjacent carbon atoms, and an acid anhydride group derived from the two carboxyl groups, which is introduced as a functional group into the polyarylene sulfide, and a hydroxyl group, a salt of a hydroxyl group, a thiol group, or a salt of a thiol group, which reacts with a dihalogenated aromatic compound in the polymerization reaction step described below. Specific examples of preferred compounds include 2-aminophenol, 4-aminophenol, 3-aminophenol, 2-aminothiophenol, 4-aminothiophenol, 3-aminothiophenol, 3-hydroxyphthalic acid, 4-hydroxyphthalic acid, 3-mercaptophthalic acid, 4-mercaptophthalic acid, and compounds in which the hydroxyl group or thiol group of these compounds is a salt with an alkali metal or alkaline earth metal. From the viewpoint of reactivity, 4-aminophenol and 4-aminothiophenol are particularly preferred compounds. Two or more different compounds (D) can also be used in combination as long as they have the above characteristics. When a compound having a hydroxyl group or a thiol group is used as compound (D), a preferred embodiment is to simultaneously use an equal amount of an alkali metal hydroxide. Furthermore, when a compound in which the hydroxyl group or the thiol group is in the form of a salt is used as compound (D), the salt can be formed in advance and then used to produce polyarylene sulfide, or the salt can be formed by reaction in a reaction vessel.

The lower limit of the amount of compound (D) used is 0.04 mol or more, preferably 0.05 mol or more, more preferably 0.06 mol or more, even more preferably 0.08 mol or more, and even more preferably 0.1 mol or more, per mol of inorganic sulfidizing agent added. An amount of use of this value or more is preferred because it allows sufficient introduction of amino groups into the polyarylene sulfide. The upper limit of the amount of compound (D) used is 0.5 mol or less, more preferably 0.45 mol or less, and even more preferably 0.4 mol or less, per mol of inorganic sulfidizing agent added. An amount of use of this value or less is preferred because it prevents a decrease in the molecular weight of the polyarylene sulfide and a decrease in its mechanical properties.

There is no particular restriction on the timing of adding compound (D), and it may be added during the pre-processing step described below, at the start of polymerization, or during the polymerization reaction step, or it may be added in multiple batches. However, from the viewpoint of efficiently reacting with the dihalogenated aromatic compound, it is more preferable to add it at the same stage as the dihalogenated aromatic compound is added to the reaction vessel.

[Dihalogenated aromatic compound]
Examples of dihalogenated aromatic compounds used in the production method of polyarylene sulfide (A) 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, as well as dihalogenated aromatic compounds including compounds having 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, 3,5-dichloroaniline, and bis(4-chlorophenyl)sulfide. Among these, dihalogenated aromatic compounds containing p-dihalogenated benzenes, typified by p-dichlorobenzene, as the main component are preferred. Particularly preferred are those containing 80 to 100 mol % of p-dichlorobenzene, and even more preferred are those containing 90 to 100 mol %. It is also possible to use a combination of two or more different dihalogenated aromatic compounds.

Although there is no particular lower limit to the amount of dihalogenated aromatic compound used, the [monomer ratio] expressed by the following formula is preferably 0.8 or more, more preferably 0.9 or more, and even more preferably 0.95 or more. By setting the [monomer ratio] within the above range, the polymerization reaction system can be stabilized and side reactions can be prevented, which is preferable. Furthermore, there is no particular upper limit to the amount used, but the [monomer ratio] is preferably 1.2 or less, more preferably 1.1 or less, and even more preferably 1.05 or less. By setting the [monomer ratio] within the above range, the amount of halogen remaining in the polyarylene sulfide can be reduced, which is preferable. In the following formula, the [dihalogenated aromatic compound substance amount], [inorganic sulfidizing agent substance amount], and [compound (D) substance amount] indicate the amount of each compound used when producing polyarylene sulfide.
[Monomer ratio] = [amount of dihalogenated aromatic compound] / ([amount of inorganic sulfidizing agent] + [amount of compound (D)])

[Organic polar solvent]
Preferred examples of organic polar solvents used in the polyarylene sulfide production method of the present invention include organic amide solvents. 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; aprotic organic solvents such as 1,3-dimethyl-2-imidazolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, and hexamethylphosphoric triamide; and mixtures thereof, which are preferably used due to their high reaction stability. Among these, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are preferred, and N-methyl-2-pyrrolidone is more preferred.

The amount of organic polar solvent used is preferably 2.0 moles or more, more preferably 2.2 moles or more, and even more preferably 2.3 moles or more, per mole of inorganic sulfidizing agent charged. Amounts of this value or more are preferred because polyarylene sulfide can be synthesized in good yield. Furthermore, the amount of organic polar solvent used is preferably 6.0 moles or less, more preferably 5.0 moles or less, and even more preferably 4.0 moles or less, per mole of inorganic sulfidizing agent charged. Amounts of this value or less are preferred because they reduce the amount of gas generated when the resulting polyarylene sulfide is heated.

[Polymerization aid]
In order to obtain a polyarylene sulfide with a relatively high degree of polymerization in a shorter time, it is also a preferred embodiment to use a polymerization aid. Here, the polymerization aid refers to a substance that has the effect of increasing the viscosity of the resulting polyarylene sulfide. Specific examples of such polymerization aids include organic carboxylates, water, alkali metal chlorides, organic sulfonates, alkali metal sulfates, alkaline earth metal oxides, alkali metal phosphates, and alkaline earth metal phosphates. These may be used alone or in combination of two or more. Among these, organic carboxylates, water, and alkali metal chlorides are preferred, and alkali metal carboxylates are preferred as organic carboxylates, and lithium chloride is preferred as alkali metal chlorides.

The alkali metal carboxylate is a compound 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; and n is an integer of 1 to 3). The alkali metal carboxylate can also be used as a hydrate, anhydrous form, or aqueous solution. Specific examples of the alkali metal carboxylate include lithium acetate, sodium acetate, potassium acetate, sodium propionate, lithium valerate, sodium benzoate, and mixtures thereof.

Alkali metal carboxylates may be synthesized by adding and reacting an organic acid with one or more compounds selected from the group consisting of alkali metal hydroxides, alkali metal carbonates, and alkali metal bicarbonates in approximately equal chemical equivalents. Among the alkali metal carboxylates listed above, lithium salts are highly soluble in the reaction system and have a significant auxiliary effect, but are expensive. On the other hand, potassium, rubidium, and cesium salts are thought to have insufficient solubility in the reaction system, so sodium acetate, which is inexpensive and has adequate solubility in the polymerization system, is most preferably used.

When these alkali metal carboxylates are used as polymerization aids, the amount used is typically in the range of 0.01 to 2 moles per mole of inorganic sulfidizing agent charged. To achieve a higher degree of polymerization, the amount is preferably in the range of 0.1 to 0.6 moles, and more preferably in the range of 0.2 to 0.5 moles.

When water is used as a polymerization aid, the amount added is usually in the range of 0.3 to 15 moles per mole of inorganic sulfidizing agent charged. To achieve a higher degree of polymerization, a range of 0.6 to 10 moles is preferred, and a range of 1 to 5 moles is even more preferred.

It is of course possible to use two or more of these polymerization aids in combination. For example, using an alkali metal carboxylate in combination with water makes it possible to achieve a high molecular weight with smaller amounts of alkali metal carboxylate and water.

There is no particular restriction on the timing of addition of these polymerization aids; they may be added during the pre-processing step, at the start of polymerization, or during the polymerization reaction step, as described below, or they may be added in multiple batches. When an alkali metal carboxylate salt is used as the polymerization aid, it is preferable to add it simultaneously with other additives at the start of the pre-processing step or at the start of polymerization, as this makes addition easier. When water is used as the polymerization aid, it is effective to add it during the polymerization reaction step after the dihalogenated aromatic compound has been charged.

[Polymerization stabilizer]
Polymerization stabilizers can be used to stabilize the polymerization reaction system and prevent side reactions. Polymerization stabilizers contribute to stabilizing the polymerization reaction system and suppress undesirable side reactions. One indicator of side reactions is the formation of thiophenol. The addition of a polymerization stabilizer can suppress the formation of thiophenol. Specific examples of polymerization stabilizers include compounds such as alkali metal hydroxides, alkali metal carbonates, alkaline earth metal hydroxides, and alkaline earth metal carbonates. Among these, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide are preferred. The aforementioned alkali metal carboxylates also function as polymerization stabilizers and are therefore classified as polymerization stabilizers. Furthermore, when using alkali metal hydrosulfides as inorganic sulfidizing agents, it is particularly preferable to use alkali metal hydroxides simultaneously. However, alkali metal hydroxides in excess of the sulfidizing agent can also function as polymerization stabilizers.

These polymerization stabilizers can be used alone or in combination of two or more. The polymerization stabilizer is typically used in a ratio of 0.02 to 0.2 moles, preferably 0.03 to 0.1 moles, and more preferably 0.04 to 0.09 moles, per mole of inorganic sulfidizing agent charged. If this ratio is too low, the stabilizing effect will be insufficient; conversely, if it is too high, it is economically disadvantageous and polymer yields will tend to decrease.

There is no particular requirement for the timing of adding the polymerization stabilizer; it may be added during the pre-processing step, at the start of polymerization, or during the polymerization reaction step, as described below. It may also be added in multiple batches, but it is more preferable to add it simultaneously at the start of the pre-processing step or at the start of polymerization, as this is easier.

Next, a preferred method for producing the polyarylene sulfide of the present invention will be specifically described in order, including the pre-process, polymerization reaction process, recovery process, and post-treatment process, but of course, the method is not limited to this.

[Pre-process]
In the method for producing polyarylene sulfide (A), the inorganic sulfidizing agent is usually used in the form of a hydrate. However, it is preferable to heat the mixture containing the organic polar solvent and the inorganic sulfidizing agent and remove excess water from the system before adding the dihalogenated aromatic compound.

As mentioned above, inorganic sulfidizing agents can also be used that are prepared in situ in the reaction system from alkali metal hydrosulfide and alkali metal hydroxide, or in a vessel separate from the polymerization vessel. While there are no particular limitations on this method, a preferred method involves adding alkali metal hydrosulfide and alkali metal hydroxide to an organic polar solvent in an inert gas atmosphere at a temperature ranging from room temperature to 150°C, preferably from room temperature to 100°C, and then heating the mixture to at least 150°C or higher, preferably 180°C to 260°C, under atmospheric or reduced pressure, to distill off water. At this stage, a polymerization aid or compound (D) may be added. Toluene or the like may also be added to facilitate the distillation of water during the reaction.

At the end of the previous step, i.e., before the polymerization reaction step, the amount of water in the system is preferably 0.3 to 10.0 moles per mole of charged sulfidizing agent. Here, the amount of water in the system is the amount of water charged to 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.

[Polymerization reaction step]
Polyarylene sulfide (A) is produced by reacting at least an inorganic sulfidizing agent, a dihalogenated aromatic compound, and compound (D) in an organic polar solvent within a temperature range of 200°C or higher but lower than 290°C.

To initiate the polymerization reaction process, the organic polar solvent, sulfidizing agent, and dihalogenated aromatic compound are mixed, preferably in an inert gas atmosphere, at a temperature ranging from room temperature to 240°C, and preferably from 100°C to 230°C. Compound (D) and a polymerization aid may also be added at this stage. These raw materials may be added in any order, or simultaneously.

The mixture is typically heated to a temperature in the range of 200°C to less than 290°C. There are no particular restrictions on the heating rate, but a rate of 0.01°C/min to 5°C/min is usually selected, with a range of 0.1°C/min to 3°C/min being more preferred.

Generally, the temperature is finally raised to between 250°C and 290°C, and the reaction is carried out at that temperature for typically 0.25 hours to 50 hours, preferably 0.5 hours to 20 hours.

A method that effectively achieves a higher degree of polymerization involves reacting for a certain period of time at, for example, 200°C to 260°C, and then raising the temperature to 270°C to less than 290°C before reaching the final temperature. In this case, the reaction time at 200°C to 260°C is usually selected to be in the range of 0.25 to 20 hours, preferably 0.25 to 10 hours.

In order to adjust the molecular weight of the polymer, compound (D) can be added during the polymerization. However, from the viewpoint of efficient reaction of compound (D), it is more preferable to add at least a portion of compound (D) at the same stage as the dihalogenated aromatic compound.

[Recovery process]
In the method for producing the polyarylene sulfide (A), after the polymerization is completed, a solid is recovered from the polymerization reaction product containing the polymer, the solvent, etc. Any known method may be used for the recovery method.

For example, after the polymerization reaction is complete, the mixture may be slowly cooled to recover the particulate polymer. There are no particular restrictions on the cooling rate, but it is typically about 0.1°C/min to 3°C/min. It is not necessary to cool at the same rate throughout the entire cooling process; instead, it is possible to cool at a rate of 0.1°C/min to 1°C/min until the polymer particles crystallize and precipitate, and then at a rate of 1°C/min or faster.

Another preferred method is to carry out the above recovery under rapid cooling conditions. Among these recovery methods, a preferred one is the flash method. The flash method is a method in which the polymerization reaction product is flashed from a high-temperature, high-pressure state (usually 250°C or higher, 8 kg/ ^cm2 or higher) into an atmosphere of normal pressure or reduced pressure, and the polymer is recovered in powder form while the solvent is recovered. The term "flash" as used herein means that the polymerization reaction product is ejected from a nozzle. Specific examples of the flashing atmosphere include nitrogen or water vapor at normal pressure, and the temperature is usually selected from the range of 150°C to 250°C.

[Post-processing process]
After the polyarylene sulfide is produced through the above-mentioned polymerization reaction step and recovery step, it can be subjected to a post-treatment step of acid treatment, hot water treatment, or washing with an organic solvent. From the viewpoint of removing impurities, the post-treatment step is preferably any one of acid treatment, hot water treatment, and washing with an organic solvent, and more preferably two or more of these treatments are used in combination.

Acid treatment is performed as follows. The acid used in the acid treatment is not particularly limited as long as it does not decompose the polyarylene sulfide (A), and examples include acetic acid, hydrochloric acid, sulfuric acid, phosphoric acid, silicic acid, carbonic acid, and propylic acid. Among these, acetic acid and hydrochloric acid are more preferably used. On the other hand, acids that decompose or deteriorate the polyarylene sulfide (A), such as nitric acid, are not preferred. The acid treatment method includes, for example, immersing the polyarylene sulfide (A) in an acid or an aqueous solution of an acid, with stirring or heating as necessary. When an acid solution is used, the solution may be either an organic solvent or an aqueous solution. However, an aqueous solution is preferred in view of the tendency for acid miscibility and the relatively high solubility of salts and basic components contained in the polyarylene sulfide. The water used is preferably distilled water or deionized water in order not to impair the desired chemical modification effect of the polyarylene sulfide. For example, when using acetic acid, a sufficient effect can be obtained by immersing the polyarylene sulfide (A) powder in an aqueous acetic acid solution of pH 4 heated to 80°C to 200°C and stirring for 30 minutes. The pH after treatment may be 4 or higher, for example, about pH 4 to 8. To remove any acid or salt remaining in the acid-treated polyarylene sulfide (A), it is preferable to further wash the polyarylene sulfide (A) several times with water or warm water. The water used for washing is preferably distilled water or deionized water so as not to impair the desired chemical modification effect of the polyarylene sulfide (A). Acid treatment is preferred because it tends to produce a polyarylene sulfide copolymer with a higher molecular weight when using the polyarylene sulfide (A) to obtain a polyarylene sulfide copolymer.

When hot water treatment is performed, the procedure is as follows. When hot water treatment of polyarylene sulfide (A), it is preferable to set the temperature of the hot water to 100°C or higher, more preferably 120°C or higher, even more preferably 150°C or higher, and particularly preferably 170°C or higher. Temperatures below 100°C are not preferred because the desired chemical modification effect of polyarylene sulfide is small. In order to achieve the desired chemical modification effect of polyarylene sulfide (A) by hot water treatment, it is preferable that the water used is distilled water or deionized water. There are no particular restrictions on the hot water treatment procedure. It can be performed by adding a predetermined amount of polyarylene sulfide (A) to a predetermined amount of water and heating and stirring in a pressure vessel, or by continuously performing hot water treatment. The ratio of polyarylene sulfide (A) to water is preferably higher, but a bath ratio (weight of washing solution relative to weight of dry polyarylene sulfide (A)) of 200 g or less per liter of water is usually selected. Furthermore, to avoid undesirable decomposition of reactive terminal functional groups, it is desirable to perform the treatment in an inert atmosphere. Furthermore, to remove any remaining components, it is preferable to wash the polyarylene sulfide (A) several times with warm water after this hot water treatment.

When washing with an organic solvent, the procedure is as follows: There are no particular restrictions on the organic solvent used to wash polyarylene sulfide (A), so long as it does not have the effect of decomposing polyarylene sulfide. Examples of organic solvents that can be used to wash polyarylene sulfide (A) include nitrogen-containing polar solvents such as N-methyl-2-pyrrolidone, dimethylformamide, and dimethylacetamide; 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; halogenated solvents such as chloroform, methylene chloride, trichloroethylene, ethylene dichloride, and perchloroethylene; alcohol solvents such as methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, and propylene glycol; and aromatic hydrocarbon solvents such as benzene, toluene, and xylene. Among these organic solvents, N-methyl-2-pyrrolidone, acetone, dimethylformamide, chloroform, and the like are preferred. Furthermore, from the viewpoint of removing impurities having an arylene sulfide structure, N-methyl-2-pyrrolidone, dimethylformamide, and chloroform, which are nitrogen-containing polar solvents that tend to provide relatively high solubility, are particularly preferred. These organic solvents may be used alone or in combination with two or more, or may be mixed with water. Examples of methods for washing with an organic solvent include immersing the polyarylene sulfide (A) in the organic solvent, with appropriate stirring or heating, if necessary. The washing temperature when washing the polyarylene sulfide (A) with an organic solvent is not particularly limited, and any temperature from room temperature to approximately 300°C can be selected. While higher washing temperatures tend to increase the washing efficiency, a washing temperature of room temperature to 150°C is usually sufficient to achieve the desired effect. Washing can also be performed under pressure in a pressure vessel at a temperature above the boiling point of the organic solvent. The washing time is also not particularly limited. Although it depends on the washing conditions, in the case of batch washing, washing for 5 minutes or more usually produces sufficient results. Continuous washing is also possible. The use of an organic solvent reduces the amount of gas generated when polyarylene sulfide (A) is heated, and is preferred because it tends to facilitate the production of high molecular weight polyarylene sulfide copolymers, as described below, when using polyarylene sulfide (A).

[Thermal oxidation crosslinking treatment]
The polyarylene sulfide (A) can be used after being polymerized by a thermal oxidation crosslinking treatment, such as heating in an oxygen atmosphere or heating with a crosslinking agent such as a peroxide added thereto, to increase the molecular weight, provided that the number average molecular weight of the polyarylene sulfide (A) is 10,000 or less.

[Compound (B)]
The compound (B) is at least one selected from the formulae (a') to (u').

X is any one selected from two carboxyl groups bonded to two adjacent carbon atoms, or an acid anhydride group derived from the two carboxyl groups, and an amino group. From the viewpoint of reactivity when the above-mentioned polyarylene sulfide (A) and compound (B) are heated, the combination of the functional group of polyarylene sulfide (A) and the functional group of compound (B) is preferably an amino group and an acid anhydride group. Therefore, depending on the functional group of polyarylene sulfide (A), the functional group contained in compound (B) is preferably an amino group or an acid anhydride group. Furthermore, from the viewpoint of ease of polymerization reaction when producing polyarylene sulfide (A) by the above-mentioned production method, the functional group of polyarylene sulfide (A) is preferably an amino group, and accordingly, the functional group of compound (B) is preferably an acid anhydride group. R, R ¹ , and R ² are substituents selected from hydrogen, an alkyl group having 1 to 12 carbon atoms, an arylene group having 6 to 24 carbon atoms, and a halogen group, and R, R ¹ , and R ² may be the same or different. Hydrogen, a methyl group, an ethyl group, or a propyl group is preferred from the viewpoint of ease of availability. Furthermore, the aromatic ring of each compound may be di- or tri-substituted, and the multiple substituents X substituted on one aromatic ring may be the same or different.

Specific examples of compound (B) include pyromellitic acid, 3,3',4,4'-thiodiphthalic acid, 3,3',4,4'-sulfonyldiphthalic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 3,3',4,4'-sulfinyldiphthalic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 3,3',4,4'-tetracarboxyldiphenylmethane, 9,9-bis(3,4-dicarboxyphenyl)fluorene, naphthalene-1,4,5,8-tetracarboxylic acid, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid, 3,4,9,10-perylenetetracarboxylic acid, and pyromellitic anhydride. dianhydride, 3,3',4,4'-thiodiphthalic anhydride, 3,3',4,4'-sulfonyldiphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-sulfinyldiphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-tetracarboxylicdiphenylmethane dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, glycerin bisanhydrotrimellitate monoacetate, ethylene glycol bisanhydrotrimellitate, bicyclo[2.2. 2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 4,4'-thiodibenzoic acid, 4,4'-dicarboxylbenzophenone, 4,4'-sulfinyldibenzoic acid, 4,4'-dicarboxylbiphenyl, p-phenylenediamine, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 2,7-diaminofluorene, o-toluidine, 1,5-diaminonaphthalene, and from the viewpoint of reactivity, 3 , 3',4,4'-thiodiphthalic anhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-sulfinyldiphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 4,4'-thiodibenzoic acid, 4,4'-dicarboxylbenzophenone, 4,4'-sulfinyldibenzoic acid, 4,4'-dicarboxylbiphenylpyromellitic acid, pyromellitic anhydride, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzophenone, and 2,7-diaminofluorene are preferably used.

[Heating conditions for polyarylene sulfide (A) and compound (B)]
The polyarylene sulfide copolymer of the present invention can be produced by heating polyarylene sulfide (A) having a number average molecular weight Mn of 1,000 or more and 10,000 or less and compound (B) under the condition that the ratio of the total amount of amino groups to half of the total amount of carboxyl groups and acid anhydride groups contained in the compound (B) is 0.75 or more and 0.97 or less, or 1.03 or more and 1.25 or less.

As mentioned above, it is preferable that the polyarylene sulfide copolymer have a large amount of either the amino group amount or the total amount of two carboxyl groups and acid anhydride groups bonded to two adjacent carbon atoms. Therefore, it is preferable that the ratio of half of the carboxyl group amount and the total amount of acid anhydride groups contained in polyarylene sulfide (A) and compound (B) to the total amount of amino groups be within the above range.

When a high amino group content is desired, the lower limit of the ratio of the total amount of amino groups to half the total amount of carboxyl groups and acid anhydride groups in polyarylene sulfide (A) and compound (B) is 0.75 or more. This range allows the resulting polyarylene sulfide copolymer to have a sufficient amount of imide groups, thereby sufficiently suppressing a decrease in rigidity under high-temperature conditions. When a high amino group content is desired, the upper limit of the ratio of the total amount of amino groups to half the total amount of carboxyl groups and acid anhydride groups in polyarylene sulfide (A) and compound (B) is 0.97 or less, preferably 0.95 or less, more preferably 0.93 or less, even more preferably 0.90 or less, and even more preferably 0.85 or less. Setting the upper limit within this range tends to result in the resulting polyarylene sulfide copolymer having excellent crystallinity, a high crystallization temperature, and excellent mechanical properties and chemical resistance.

When a high content of acid anhydride groups and two carboxyl groups bonded to two adjacent carbon atoms is desired, the upper limit of the ratio of half the number of carboxyl groups and the total number of acid anhydride groups in polyarylene sulfide (A) and compound (B) to the total number of amino groups is 1.25 or less. This range ensures that the resulting polyarylene sulfide copolymer has a sufficient number of imide groups, thereby sufficiently suppressing a decrease in rigidity under high-temperature conditions. Furthermore, when a high content of acid anhydride groups and two carboxyl groups bonded to two adjacent carbon atoms is desired, the lower limit of the ratio of half the number of carboxyl groups and the total number of acid anhydride groups in polyarylene sulfide (A) and compound (B) to the total number of amino groups is 1.03 or more, preferably 1.06 or more, more preferably 1.10 or more, and even more preferably 1.15 or more. By setting the lower limit within the above range, the resulting polyarylene sulfide copolymer tends to have excellent crystallinity, a high crystallization temperature, and excellent mechanical properties and chemical resistance.

The polyarylene sulfide (A) and compound (B) may be heated by mixing the entire amount from the beginning, or by mixing and heating at least a portion of the polyarylene sulfide (A) and at least a portion of the compound (B) and then mixing and heating the remaining polyarylene sulfide (A) and/or compound (B). In the latter case, at least a portion of the polyarylene sulfide (A) and at least a portion of the compound (B) may be mixed and heated, and then the remaining polyarylene sulfide (A) and/or compound (B) may be mixed and heated, or at least a portion of the polyarylene sulfide (A) and at least a portion of the compound (B) may be mixed and heated, and then the product may be removed, and then the remaining polyarylene sulfide (A) and/or compound (B) may be mixed and heated.

From the viewpoint of efficiently obtaining a polyarylene sulfide copolymer, it is preferable to mix and heat the entire amount of polyarylene sulfide (A) and compound (B) from the beginning. On the other hand, from the viewpoint of easily controlling and adjusting the thermal properties of the polyarylene sulfide copolymer, such as the glass transition temperature, crystallization temperature, and melting point, as well as the molecular weight, terminal type and amount depending on the application, it is preferable to mix and heat at least a portion of polyarylene sulfide (A) and at least a portion of compound (B), and then mix and heat the remaining polyarylene sulfide (A) and/or compound (B).

The lower limit of the heating temperature can be 200°C or higher, preferably 230°C or higher, and more preferably 250°C or higher. Setting the lower limit of the heating temperature within this range can easily promote the reaction between polyarylene sulfide (A) and compound (B), and setting the temperature above the temperature at which polyarylene sulfide (A) melts tends to complete the reaction in a shorter time. The temperature at which polyarylene sulfide (A) melts cannot be uniquely determined because it varies depending on the composition and molecular weight of polyarylene sulfide (A) and the heating environment. However, it can be determined, for example, by analyzing polyarylene sulfide (A) with a differential scanning calorimeter. The upper limit of the heating temperature can be 400°C or lower, preferably 380°C or lower, and more preferably 360°C or lower. Setting the upper limit of the heating temperature within this range tends to suppress undesirable side reactions, such as crosslinking reactions and decomposition reactions between polyarylene sulfides (A), and to suppress deterioration in the properties of the resulting polyarylene sulfide copolymer.

The heating time cannot be specified uniquely because it varies depending on the composition and molecular weight of the polyarylene sulfide (A) and the heating environment. However, it is preferable to set it so as to minimize the occurrence of the undesirable side reactions described above. The lower limit of the heating time can be, for example, 0.1 minutes or more, with 1 minute or more being preferred, 2 minutes or more being more preferred, and 3 minutes or more being even more preferred. Setting the lower limit of the heating time within this range allows the reaction between the polyarylene sulfide (A) and the compound (B) to proceed more sufficiently. The upper limit of the heating time can be, for example, 100 hours or less, with 20 hours or less being preferred, 10 hours or less being more preferred, and 1 hour or less being even more preferred. Setting the upper limit of the heating time within this range is economical and tends to avoid the undesirable side reactions described above.

In the method for producing a polyarylene sulfide copolymer of the present invention, an imide group is formed by reaction between an amino group possessed by polyarylene sulfide (A) and compound (B) and two carboxyl groups or acid anhydride groups bonded to two adjacent carbon atoms. The combination that forms the imide group may be either an amino group and two carboxyl groups bonded to two adjacent carbon atoms, or an amino group and an acid anhydride group. However, from the viewpoint of reactivity when polyarylene sulfide (A) and compound (B) are heated, a preferred combination of functional groups is an amino group and an acid anhydride group. Furthermore, from the viewpoint of ease of polymerization reaction when producing polyarylene sulfide (A) by the above-described production method, the functional group possessed by polyarylene sulfide (A) is preferably an amino group, and accordingly, the functional group possessed by compound (B) is preferably an acid anhydride group.

Heating can be carried out in the absence or presence of a solvent. When heating is carried out in the presence of a solvent, there are no particular restrictions on the solvent, as long as it does not substantially cause undesirable side reactions such as decomposition or crosslinking of the resulting polyarylene sulfide copolymer. One type of solvent or a mixture of two or more types can be used. From the perspective of efficiently obtaining the polyarylene sulfide copolymer, however, heating under substantially solvent-free conditions is preferred. Furthermore, from the perspective of preventing contamination of molded products by evolved gases during molding of the resulting polyarylene sulfide copolymer, heating under substantially solvent-free conditions is also preferred. Here, substantially solvent-free conditions refer to a system in which the polyarylene sulfide (A) and compound (B) are heated, with the solvent content being 10% by weight or less, preferably 3% by weight or less.

In the method for producing the polyarylene sulfide copolymer of the present invention, heating can be carried out using a conventional polymerization reaction apparatus, or it can be carried out in a mold for producing a molded product, or it can be carried out using an extruder or melt kneader, or any other apparatus equipped with a heating mechanism, without particular limitations. Well-known methods such as batch and continuous methods can be used.

The heating atmosphere is preferably a non-oxidizing atmosphere, and it is also preferable to carry out the reaction under reduced pressure. Furthermore, when carrying out the reaction under reduced pressure, it is preferable to first change the atmosphere in the reaction system to a non-oxidizing atmosphere and then to a reduced pressure. This tends to suppress undesirable side reactions, such as crosslinking reactions and decomposition reactions between polyarylene sulfides (A) or between the resulting polyarylene sulfide copolymers. A non-oxidizing atmosphere refers to an atmosphere in which the oxygen concentration in the gas phase is 5% by volume or less, preferably 2% by volume or less, and more preferably an atmosphere that is substantially oxygen-free, i.e., an inert gas atmosphere such as nitrogen, helium, or argon. Among these, a nitrogen atmosphere is particularly preferred from the standpoints of economy and ease of handling. Furthermore, reduced pressure refers to a pressure lower than atmospheric pressure within the reaction system. The upper limit of the pressure is preferably 50 kPa or less, more preferably 20 kPa or less, and even more preferably 10 kPa or less. Setting the upper limit of the pressure within this range tends to suppress undesirable side reactions, such as crosslinking reactions. An example of a lower limit of the pressure is 0.1 kPa or more. By setting the lower pressure limit to 0.1 kPa or higher, it is possible to avoid putting strain on the reactor due to reducing the pressure more than necessary.

[Polyarylene sulfide copolymer composition]
The polyarylene sulfide copolymer of the present invention can also be used as a polyarylene sulfide copolymer composition containing the polyarylene sulfide copolymer of the present invention. As long as the polyarylene sulfide copolymer composition contains the polyarylene sulfide copolymer of the present invention, other optional components such as a crystal nucleating agent, various fillers, and other additives can also be blended therein.

The present invention also makes it possible to obtain a polyarylene sulfide copolymer composition containing a polyarylene sulfide copolymer (C) having, as structural units, arylene sulfide units with a number-average molecular weight Mn of 1,000 or more and 10,000 or less, in which the arylene sulfide units and copolymerization components are linked via imide groups, and a crystal nucleating agent.

The lower limit of the glass transition point of the polyarylene sulfide copolymer composition is 95°C or higher, preferably 100°C or higher, and more preferably 110°C or higher. If the glass transition point is below 95°C, high rigidity cannot be achieved under high-temperature conditions. The upper limit of the glass transition point is 190°C or lower, preferably 180°C or lower, and more preferably 160°C or lower. If the glass transition point exceeds 190°C, the chemical resistance of the molded product will be insufficient. The glass transition point is defined as the inflection point of the baseline shift detected when the temperature is raised from 0°C to 340°C at a rate of 20°C/min using a differential scanning calorimeter.

The crystallization temperature of the polyarylene sulfide copolymer composition is 165°C or higher, preferably 170°C or higher, more preferably 180°C or higher, even more preferably 190°C or higher, and even more preferably 200°C or higher. A crystallization temperature below 165°C can result in reduced productivity due to insufficient crystallization when molding the copolymer composition or when further blending the copolymer composition with fillers and/or other additives to produce a resin composition, as described below, and can also result in reduced mechanical properties and chemical resistance due to insufficient crystallization of the resulting resin composition. While there is no particular upper limit for the crystallization temperature, a range of 235°C or lower is typically exemplified. The crystallization temperature is defined as the peak crystallization temperature detected when a differential scanning calorimeter is used to heat a sample from 0°C to 340°C at a rate of 20°C/min, then held at 340°C for 1 minute, and then cooled to 100°C at a rate of 20°C/min.

The polyarylene sulfide copolymer composition preferably has a melting point of 300°C or less. A melting point of 300°C or less facilitates melt molding processing. The melting point is the melting peak temperature detected when the composition is heated using a differential scanning calorimeter from 0°C to 340°C at a rate of 20°C/min, held at 340°C for 1 minute, cooled to 100°C at a rate of 20°C/min, held at 100°C for 1 minute, and then heated again to 340°C at a rate of 20°C/min. The melting point can be adjusted by selecting the molecular weight of the arylene sulfide units in the polyarylene sulfide copolymer composition.

[Polyarylene sulfide copolymer (C)]
The polyarylene sulfide copolymer (C) contained in the polyarylene sulfide copolymer composition has the same characteristics as the polyarylene sulfide copolymer in terms of the repeating unit of the arylene sulfide unit, the number average molecular weight of the arylene sulfide unit, the structure contained as a copolymerization component, the linking group between the arylene sulfide unit and the copolymerization component, the glass transition point of the polyarylene sulfide copolymer (C), the melting point of the polyarylene sulfide copolymer (C), and the molecular weight of the polyarylene sulfide copolymer (C). The crystallization temperature of the polyarylene sulfide copolymer (C) is not particularly limited, but is preferably 150°C or higher, more preferably 160°C or higher, and even more preferably 165°C or higher. When the crystallization temperature of the polyarylene sulfide copolymer (C) is within the above range, the crystallization temperature of the resulting polyarylene sulfide copolymer composition tends to be higher.

[Nucleating agent]
The nucleating agent contains at least one selected from talc, kaolin, an organic phosphorus compound, and polyether ether ketone. Among these, in terms of the effect of improving the crystallization temperature, talc and polyether ether ketone are preferred, and polyether ether ketone is more preferred. Talc and polyether ether ketone have excellent dispersibility and compatibility in the polyarylene sulfide copolymer (C), and are therefore thought to be effective in improving the crystallization temperature. The inclusion of a nucleating agent tends to further improve the crystallization temperature of the polyarylene sulfide copolymer composition, and a sufficient crystallization rate can be obtained when molding the polyarylene sulfide copolymer composition or when further blending a filler and/or other additives to produce a resin composition. This improves productivity during the production of molded articles, and the resulting molded articles tend to exhibit excellent mechanical properties and chemical resistance due to crystallization. The lower limit of the amount of the nucleating agent can be 0.01 parts by weight or more, preferably 0.02 parts by weight or more, more preferably 0.05 parts by weight or more, more preferably 0.1 parts by weight or more, even more preferably 0.2 parts by weight or more, and even more preferably 0.5 parts by weight or more, relative to 100 parts by weight of the polyarylene sulfide copolymer (C).By setting the lower limit of the amount of the nucleating agent to this range, a higher crystallization temperature improvement effect tends to be obtained.The upper limit of the amount of the nucleating agent can be 5 parts by weight or less, preferably 3 parts by weight or less, more preferably 2 parts by weight or less, and even more preferably 1 part by weight or less.By setting the upper limit of the amount of the nucleating agent to this range, the mechanical properties of the polyarylene sulfide copolymer composition tend to be sufficiently maintained.

The polyarylene sulfide copolymer of the present invention can also be used as a resin composition blended with various fillers and other additives in addition to the crystal nucleating agent. The blending method for producing the resin composition is not particularly limited, but a typical example is a method in which the copolymer is fed into a known melt-kneading machine such as a single-screw or twin-screw extruder, Banbury mixer, kneader, or mixing roll, and kneaded at a processing temperature of 5 to 100°C above the melting peak temperature of the polyarylene sulfide copolymer.

Examples of fillers include inorganic fillers and organic fillers. The type of filler is not limited, but considering the reinforcing effect of the filler in the resin composition, fibrous inorganic fillers such as glass fiber and carbon fiber are preferred. Carbon fiber not only improves mechanical properties but also reduces the weight of molded products. Furthermore, carbon fiber is more preferred as the filler has a greater effect of improving the mechanical properties and chemical resistance of the resin composition.

Polyarylene sulfide copolymer compositions have excellent heat resistance, chemical resistance, flame retardancy, electrical properties, and mechanical properties, and can be molded not only by injection molding, injection compression molding, and blow molding, but also by extrusion molding into extruded products such as sheets, films, fibers, and pipes.

Further examples of uses for polyarylene sulfide copolymer compositions include electrical and electronic components, audio equipment components, household and office electrical appliance components, machine-related components, optical equipment, precision machinery-related components, plumbing components, automobile and vehicle-related components, aerospace-related components, and a variety of other uses.

The method of the present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to these examples.

[Analysis of Functional Group Content]
The amount of amino groups contained in the polyarylene sulfide, polyarylene sulfide copolymer, polyarylene sulfide copolymer composition, and polyarylene sulfide copolymer (C), as well as the total amount of two carboxyl groups and acid anhydride groups bonded to two adjacent carbon atoms, were estimated by measuring an amorphous film prepared by quenching from a molten state obtained by heating at 320°C using FT-IR (using an IR-810 infrared spectrophotometer manufactured by JASCO Corporation) and comparing the absorption intensity at 3382 cm ⁻¹ derived from the amino groups or the absorption intensity at 1860 cm ⁻¹ derived from the acid anhydride groups with the absorption intensity at 1901 cm ⁻¹ derived from the benzene rings of the arylene sulfide units.

[Molecular weight measurement]
The number average molecular weight Mn and the weight average molecular weight Mw were calculated in terms of polystyrene by gel permeation chromatography (GPC), which is a type of size exclusion chromatography (SEC). The measurement conditions for GPC are shown below.
Equipment: Senshu Scientific SSC-7110
Column name: Shodex UT806M x 2
Eluent: 1-chloronaphthalene Detector: differential refractive index detector Column temperature: 210°C
Pre-thermostat temperature: 250°C
Pump thermostatic bath temperature: 50°C
Detector temperature: 210°C
Flow rate: 1.0mL/min
Sample injection volume: 300 μL.

[Measurement of weight loss rate upon heating]
The weight loss rate of the polyarylene sulfide upon heating was measured using a thermogravimetric analyzer under the following conditions.
Apparatus: PerkinElmer TGA7
Measurement atmosphere: Nitrogen flow Sample weight: Approximately 5 mg
Measurement conditions: (a) Program temperature was held at 30°C for 1 minute; (b) Program temperature was increased from 30°C to 340°C at a rate of 10°C/min.
The weight loss rate was calculated from the weight measured under the above conditions at 320°C and the weight measured at 30°C using the following formula.
Weight loss rate (%) = ((weight (mg) at 30°C - weight (mg) at 320°C) / weight (mg) at 30°C) x 100.

[Measurement of glass transition temperature, melting point and crystallization temperature]
The glass transition point (Tg), melting point (Tm), and crystallization temperature (Tmc) were measured by differential scanning calorimetry (DSC) using approximately 10 mg of amorphous film prepared by quenching from a molten state. The glass transition point was the inflection point of the baseline shift detected when the temperature was increased from 0 ° C. to 340 ° C. at a rate of 20 ° C./min. The crystallization temperature was the crystallization peak temperature detected when the temperature was increased from 0 ° C. to 340 ° C. at a rate of 20 ° C./min, held at 340 ° C. for 1 minute, and cooled to 100 ° C. at a rate of 20 ° C./min. The melting point was the melting peak temperature detected when the temperature was increased from 0 ° C. to 340 ° C. at a rate of 20 ° C./min, held at 340 ° C. for 1 minute, cooled to 100 ° C. at a rate of 20 ° C./min, held at 100 ° C. for 1 minute, and then heated again to 340 ° C. at a rate of 20 ° C./min.
Device: TA Instruments TA-Q200
Carrier gas: nitrogen Sample purge flow rate: 50 mL/min.

[Reference example 1]
An autoclave equipped with a stirrer and a bottom plug valve was charged with 7.14 kg (61.6 mol) of 48.4% sodium hydrosulfide, 2.87 kg (69.3 mol) of 97% sodium hydroxide, 14.57 kg (147 mol) of N-methyl-2-pyrrolidone (NMP), and 4.19 kg of ion-exchanged water, and gradually heated to 225°C over approximately 3 hours under atmospheric pressure while passing nitrogen through. Heating was terminated and cooling was initiated when 7.88 kg of water and 0.039 kg of NMP had been distilled. At this point, the amount of hydrogen sulfide released was 1.4 mol, and therefore the amount of inorganic sulfidizing agent in the system after this step was 60.2 mol.

Then, the mixture was cooled to 200°C, and 9.45 kg (64.3 mol) of p-dichlorobenzene (p-DCB), 1.02 kg (8.23 mol) of 4-aminothiophenol (4-ATP), and 2.78 kg (28.0 mol) of NMP were added. The reaction vessel was then sealed under nitrogen gas, and the temperature was raised to 260°C at a rate of 0.6°C/min while stirring. The reaction was carried out at 260°C for 120 minutes.

After the reaction was complete, the autoclave's bottom plug valve was immediately opened, and the contents were flushed into a stirrer. The contents were then dried and solidified for 1.5 hours at 230°C in the stirrer, and a solid containing PPS and salts was recovered.

The recovered material and ion-exchanged water were placed in an autoclave equipped with a stirrer, washed at 75°C for 15 minutes, and then filtered three times to obtain a cake. The resulting cake and 30 liters of ion-exchanged water were placed in an autoclave equipped with a stirrer, and the inside of the autoclave was replaced with nitrogen, after which the temperature was raised to 195°C. The autoclave was then cooled, and the contents were filtered to obtain a cake. The resulting cake was dried at 120°C under a nitrogen stream.

3 kg of the resulting PPS and 30 kg of N-methyl-2-pyrrolidone (NMP) were placed in a container equipped with a stirrer and stirred for 30 minutes, then filtered to obtain a cake. The resulting cake was washed with 30 liters of ion-exchanged water for 15 minutes and filtered three times, and then dried at 120°C for 4 hours under a nitrogen stream to obtain dried PPS. The amino group content was 730 μmol/g, the number average molecular weight was 1,800, and the weight loss upon heating was 1 wt%.

[Example 1]
The PPS and pyromellitic anhydride obtained in Reference Example 1 were placed in a reactor equipped with a stirring blade and capable of being evacuated and purged with nitrogen so that the ratio of the amount of acid anhydride groups in the pyromellitic anhydride to the amount of amino groups in the PPS was 0.81, and the reactor was then repeatedly evacuated and purged with nitrogen three times. The reactor was filled with a nitrogen atmosphere and heated to 300°C with stirring for 3 minutes, after which it was cooled to room temperature to obtain a polyarylene sulfide copolymer.

From the FT-IR spectrum, it was confirmed that the obtained polyarylene sulfide copolymer contained phenylene sulfide units as structural units and that imide groups had been introduced. Furthermore, from the FT-IR spectrum, the ratio of the absorption intensity at 3382 cm ⁻¹ derived from amino groups to the absorption intensity at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide units was 0.64. Absorption at 1860 cm ⁻¹ derived from acid anhydride groups was not observed. From the DSC measurement, the glass transition temperature was 97°C, the crystallization temperature was 196°C, and the melting point was 266°C. The results are summarized in Table 1.

[Example 2]
The PPS and pyromellitic anhydride obtained in Reference Example 1 were placed in a reactor equipped with a stirring blade and capable of being reduced in pressure and substituted with nitrogen so that the ratio of the amount of acid anhydride groups in the pyromellitic anhydride / the amount of amino groups in the PPS was 1.20, and then the pressure in the reactor was reduced and substituted with nitrogen three times. The reactor was filled with a nitrogen atmosphere and heated to 300 ° C. for 3 minutes while stirring, and then cooled to room temperature to obtain a polyarylene sulfide copolymer. Thereafter, the PPS obtained in Reference Example 1 was further added to the obtained polyarylene sulfide copolymer so that the ratio of the amount of acid anhydride groups in the pyromellitic anhydride / the amount of amino groups in the PPS of the total amount used in the reaction of Example 2 was 0.95, and then placed in a reactor equipped with a stirring blade and capable of being reduced in pressure and substituted with nitrogen, and then the pressure in the reactor was reduced and substituted with nitrogen three times. The reactor was filled with a nitrogen atmosphere and heated to 300 ° C. for 3 minutes while stirring, and then cooled to room temperature to obtain a polyarylene sulfide copolymer.

From the FT-IR spectrum, it was confirmed that the obtained polyarylene sulfide copolymer contained phenylene sulfide units as structural units and that imide groups had been introduced. Furthermore, from the FT-IR spectrum, the ratio of the absorption intensity at 3382 cm ⁻¹ derived from amino groups to the absorption intensity at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide units was 0.13. Absorption at 1860 cm ⁻¹ derived from acid anhydride groups was not observed. From the DSC measurement, the glass transition temperature was 112°C, the crystallization temperature was 172°C, and the melting point was 256°C. The results are summarized in Table 1.

[Comparative Example 1]
The same conditions as in Example 1 were used to obtain a polyarylene sulfide copolymer, except that the PPS obtained in Reference Example 1 and pyromellitic anhydride were placed in a reaction vessel equipped with a stirring blade that could be reduced in pressure and substituted with nitrogen, so that the ratio of the amount of acid anhydride groups in pyromellitic anhydride to the amount of amino groups in PPS was 0.98.

From the FT-IR spectrum, it was confirmed that the obtained polyarylene sulfide copolymer contained phenylene sulfide units as structural units and that imide groups had been introduced. Furthermore, from the FT-IR spectrum, the ratio of the absorption intensity at 3382 cm ⁻¹ derived from amino groups to the absorption intensity at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide units was 0.10. Absorption at 1860 cm ⁻¹ derived from acid anhydride groups was not observed. From the DSC measurement, the glass transition temperature was 112°C, the crystallization temperature was 163°C, and the melting point was 256°C. The results are summarized in Table 1.

[Example 3]
The same conditions as in Example 1 were carried out, except that the PPS obtained in Reference Example 1 and pyromellitic anhydride were charged into a reaction vessel equipped with a stirring blade that could be reduced in pressure and substituted with nitrogen, so that the ratio of the amount of acid anhydride groups in pyromellitic anhydride to the amount of amino groups in PPS was 1.20, and a polyarylene sulfide copolymer was obtained.

From the FT-IR spectrum, it was confirmed that the obtained polyarylene sulfide copolymer contained phenylene sulfide units as structural units and that imide groups had been introduced. Furthermore, from the FT-IR spectrum, the ratio of the absorption intensity at 1860 cm ⁻¹ derived from the acid anhydride group to the absorption intensity at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide unit was 1.79. No absorption at 3382 cm ⁻¹ derived from the amino group was observed. From the DSC measurement, the glass transition temperature was 113°C, the crystallization temperature was 206°C, and the melting point was 259°C. The results are summarized in Table 1.

[Example 4]
The same conditions as in Example 1 were used to obtain a polyarylene sulfide copolymer, except that the PPS obtained in Reference Example 1 and pyromellitic anhydride were placed in a reaction vessel equipped with a stirring blade that could be reduced in pressure and substituted with nitrogen, so that the ratio of the amount of acid anhydride groups in pyromellitic anhydride to the amount of amino groups in PPS was 1.03.

From the FT-IR spectrum, it was confirmed that the obtained polyarylene sulfide copolymer contained phenylene sulfide units as structural units and that imide groups had been introduced. Furthermore, from the FT-IR spectrum, the ratio of the absorption intensity at 1860 cm ⁻¹ derived from the acid anhydride group to the absorption intensity at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide unit was 0.50. No absorption at 3382 cm ⁻¹ derived from the amino group was observed. From the DSC measurement, the glass transition temperature was 113°C, the crystallization temperature was 198°C, and the melting point was 256°C. The results are summarized in Table 1.

[Example 5]
The same conditions as in Example 1 were used to obtain a polyarylene sulfide copolymer, except that the PPS obtained in Reference Example 1 and pyromellitic anhydride were placed in a reaction vessel equipped with a stirring blade that could be reduced in pressure and substituted with nitrogen, so that the ratio of the amount of acid anhydride groups in pyromellitic anhydride to the amount of amino groups in PPS was 1.02.

From the FT-IR spectrum, it was confirmed that the obtained polyarylene sulfide copolymer contained phenylene sulfide units as structural units and that imide groups had been introduced. Furthermore, from the FT-IR spectrum, the ratio of the absorption intensity at 1860 cm ⁻¹ derived from the acid anhydride group to the absorption intensity at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide unit was 0.38. Absorption at 3382 cm ⁻¹ derived from the amino group was not observed. From the DSC measurement, the glass transition temperature was 114°C, the crystallization temperature was 197°C, and the melting point was 256°C. The results are summarized in Table 1.

[Example 6]
The PPS and pyromellitic anhydride obtained in Reference Example 1 were placed in a reactor equipped with a stirring blade and capable of being reduced in pressure and substituted with nitrogen so that the ratio of the amount of acid anhydride groups in the pyromellitic anhydride / the amount of amino groups in the PPS was 1.20, and then the pressure in the reactor was reduced and nitrogen replacement was repeated three times. The reactor was filled with a nitrogen atmosphere and heated to 300 ° C. for 3 minutes while stirring, and then cooled to room temperature to obtain a polyarylene sulfide copolymer. Thereafter, the PPS obtained in Reference Example 1 was further added to the obtained polyarylene sulfide copolymer so that the ratio of the amount of acid anhydride groups in the pyromellitic anhydride / the amount of amino groups in the PPS of the total amount used in the reaction of Example 6 was 1.01, and then placed in a reactor equipped with a stirring blade and capable of being reduced in pressure and substituted with nitrogen, and then the pressure in the reactor was reduced and nitrogen replacement was repeated three times. The reactor was filled with a nitrogen atmosphere and heated to 300 ° C. for 3 minutes while stirring, and then cooled to room temperature to obtain a polyarylene sulfide copolymer.

From the FT-IR spectrum, it was confirmed that the obtained polyarylene sulfide copolymer contained phenylene sulfide units as structural units and that imide groups had been introduced. Furthermore, from the FT-IR spectrum, the ratio of the absorption intensity at 1860 cm ⁻¹ derived from the acid anhydride group to the absorption intensity at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide unit was 0.26. Absorption at 3382 cm ⁻¹ derived from the amino group was not observed. From the DSC measurement, the glass transition temperature was 114°C, the crystallization temperature was 171°C, and the melting point was 254°C. The results are summarized in Table 1.

[Comparative Example 2]
The same conditions as in Example 1 were used to obtain a polyarylene sulfide copolymer, except that the PPS obtained in Reference Example 1 and pyromellitic anhydride were placed in a reaction vessel equipped with a stirring blade that could be reduced in pressure and substituted with nitrogen, so that the ratio of the amount of acid anhydride groups in pyromellitic anhydride to the amount of amino groups in PPS was 1.002.

From the FT-IR spectrum, it was confirmed that the obtained polyarylene sulfide copolymer contained phenylene sulfide units as structural units and that imide groups had been introduced. Furthermore, from the FT-IR spectrum, the ratio of the absorption intensity at 1860 cm ⁻¹ derived from the acid anhydride group to the absorption intensity at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide unit was 0.18. Absorption at 3382 cm ⁻¹ derived from the amino group was not observed. From the DSC measurement, the glass transition temperature was 115°C, the crystallization temperature was 161°C, and the melting point was 252°C. The results are summarized in Table 1.

[Reference example 2]
In Reference Example 2, an amino group-containing polyarylene sulfide was obtained by the method disclosed in WO 2019/151288.

An autoclave equipped with a stirrer was charged with 8.27 kg (70.00 mol) of 47.5% sodium hydrosulfide, 2.96 kg (70.97 mol) of 96% sodium hydroxide, 11.4 kg (115.50 mol) of N-methyl-2-pyrrolidone (NMP), 2.58 kg (31.50 mol) of sodium acetate, and 10.5 kg of ion-exchanged water. The mixture was gradually heated to 245°C over approximately 3 hours under atmospheric pressure while nitrogen was passed through. 14.8 kg of water and 280 g of NMP were distilled off, and the reactor was then cooled to 160°C. The amount of water remaining in the system per mole of charged alkali metal sulfide, including the water consumed in the hydrolysis of NMP, was 1.06 mol. The amount of hydrogen sulfide released was 0.02 mol per mole of charged alkali metal sulfide.

Next, 10.24 kg (69.63 mol) of p-dichlorobenzene and 9.01 kg (91.00 mol) of NMP were added, and the reaction vessel was sealed under nitrogen gas. The temperature was raised to 238°C at a rate of 0.6°C/min while stirring. After 95 minutes of reaction at 238°C, the temperature was raised to 270°C at a rate of 0.8°C/min. After 100 minutes of reaction at 270°C, the mixture was cooled to 250°C at a rate of 1.3°C/min while 1.26 kg (70 mol) of water was injected over 15 minutes. The mixture was then cooled to 200°C at a rate of 1.0°C/min, and then rapidly cooled to near room temperature.

The contents were removed and diluted with 26.3 kg of NMP. The solvent and solids were filtered through an 80-mesh sieve, and the resulting particles were washed with 31.9 kg of NMP and filtered. These were then washed several times with 56 kg of ion-exchanged water and filtered. After washing with 70 kg of ion-exchanged water and filtering, the resulting hydrated PPS particles were dried with hot air at 80°C and then dried under reduced pressure at 120°C to obtain PPS.

80 g of the resulting PPS and 12 g of 4,4'-thiodianiline (TDA) were placed in a glass test tube equipped with a stirring blade and capable of reducing pressure and replacing the atmosphere with nitrogen. The test tube was then repeatedly reduced pressure and replaced with nitrogen three times. The test tube was filled with a nitrogen atmosphere and heated to 340°C for 180 minutes while stirring to obtain PPS. The amino group content was 1,100 μmol/g, the number average molecular weight was 2,300, and the weight loss upon heating was 7 wt%.

[Comparative Example 3]
The PPS and pyromellitic anhydride obtained in Reference Example 2 were placed in a reactor equipped with a stirring blade and capable of reducing pressure and replacing with nitrogen so that the ratio of the amount of acid anhydride groups in the pyromellitic anhydride to the amount of amino groups in the PPS was 1.02, and the reactor was then repeatedly reduced in pressure and replaced with nitrogen three times. The reactor was filled with a nitrogen atmosphere and heated to 320°C with stirring for 20 minutes, after which it was cooled to room temperature to obtain a polyarylene sulfide copolymer.

From the FT-IR spectrum, it was confirmed that the obtained polyarylene sulfide copolymer contained phenylene sulfide units as structural units and that imide groups had been introduced. Furthermore, from the FT-IR spectrum, the ratio of the absorption intensity at 1860 cm ⁻¹ derived from the acid anhydride group to the absorption intensity at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide unit was 0.53. No absorption at 3382 cm ⁻¹ derived from the amino group was observed. From the DSC measurement, the glass transition temperature was 122°C, no crystallization peak was observed, and the melting point was 250°C. The results are summarized in Table 1.

Note that PDA in the table refers to pyromellitic anhydride.

As shown in Examples 1 to 6, the present invention makes it possible to obtain a polyarylene sulfide copolymer with high crystallinity, having a crystallization temperature of 165°C or higher.

A comparison of the IR measurement results and the ratio of acid anhydride group amount to amino group amount in Examples 1, 2, and Comparative Example 1 shows that higher crystallinity can be obtained by having a polyarylene sulfide copolymer with a large number of amino groups, and therefore by reducing the ratio of acid anhydride group amount to amino group amount. Furthermore, the results of Examples 1 and 2 show that the polyarylene sulfide and compound (B) can be heated by mixing the entire amount from the beginning and heating, or by mixing and heating at least a portion of the polyarylene sulfide and at least a portion of compound (B) and then mixing and heating the remainder.

A comparison of the IR measurement results and the ratio of acid anhydride group amount to amino group amount in Examples 3 to 6 and Comparative Example 2 shows that higher crystallinity can be obtained by having a polyarylene sulfide copolymer with a large number of acid anhydride groups, and therefore by increasing the ratio of acid anhydride group amount to amino group amount. Furthermore, the results of Examples 3 to 5 and Example 6 show that the entire amounts of polyarylene sulfide and compound (B) can be mixed and heated from the beginning, or at least a portion of the polyarylene sulfide and at least a portion of compound (B) can be mixed and heated, and the remainder can then be mixed and heated.

Furthermore, as shown in Comparative Example 3, when a conventional method for producing polyarylene sulfide is used, even if the polyarylene sulfide copolymer contains many acid anhydride groups and therefore the ratio of acid anhydride groups to amino groups is increased, no crystallization temperature is observed, indicating that the crystallinity is not excellent. The polyarylene sulfide of Reference Example 2 contains residual components that tend to become gaseous when heated, and it is believed that these components, or some of them, affected the crystallinity.

[Example 7]
The polyarylene sulfide copolymer obtained in Example 2 and 0.1 part by weight of polyether ether ketone (PEEK 450PF, manufactured by Victrex) were charged into a reaction vessel equipped with a stirring blade and capable of reducing pressure and replacing with nitrogen, and the reaction vessel was then repeatedly reduced in pressure and replaced with nitrogen three times. With the reaction vessel filled with a nitrogen atmosphere, the temperature was adjusted to 300°C and the mixture was heated with stirring for 3 minutes, and then cooled to room temperature to obtain a polyarylene sulfide copolymer composition.

DSC measurement results showed a glass transition temperature of 112°C, a crystallization temperature of 174°C, and a melting point of 256°C. The results are summarized in Table 2.

[Example 8]
An operation was carried out under the same conditions as in Example 7, except that the polyarylene sulfide copolymer obtained in Example 2 and 0.5 parts by weight of polyether ether ketone (PEEK 450PF, manufactured by Victrex) were charged into a reaction vessel equipped with a stirring blade and capable of being reduced in pressure and substituted with nitrogen, to obtain a polyarylene sulfide copolymer composition.

DSC measurement results showed a glass transition temperature of 112°C, a crystallization temperature of 177°C, and a melting point of 255°C. The results are summarized in Table 2.

[Example 9]
The same conditions as in Example 8 were used except that the temperature inside the reaction vessel was changed to 340° C., to obtain a polyarylene sulfide copolymer composition.

DSC measurement results showed a glass transition temperature of 112°C, a crystallization temperature of 174°C, and a melting point of 255°C. The results are summarized in Table 2.

[Example 10]
An operation was carried out under the same conditions as in Example 8, except that talc ("Hitron" (average particle size 4.0 μm) manufactured by Takehara Chemical Industry Co., Ltd.) was used as the nucleating agent, to obtain a polyarylene sulfide copolymer composition.

DSC measurement results showed a glass transition temperature of 113°C, a crystallization temperature of 180°C, and a melting point of 255°C. The results are summarized in Table 2.

[Example 11]
An operation was carried out under the same conditions as in Example 9, except that the polyarylene sulfide copolymer obtained in Comparative Example 2 was used as the polyarylene sulfide copolymer, to obtain a polyarylene sulfide copolymer composition.

DSC measurement results showed a glass transition temperature of 116°C, a crystallization temperature of 178°C, and a melting point of 253°C. The results are summarized in Table 2.

[Example 12]
An operation was carried out under the same conditions as in Example 10, except that the polyarylene sulfide copolymer obtained in Comparative Example 2 was used as the polyarylene sulfide copolymer, to obtain a polyarylene sulfide copolymer composition.

DSC measurement results showed a glass transition temperature of 114°C, a crystallization temperature of 166°C, and a melting point of 252°C. The results are summarized in Table 2.

Note that PEEK in the table refers to polyether ether ketone.

As shown in Examples 7 to 12, the present invention makes it possible to obtain a polyarylene sulfide copolymer composition with high crystallinity, having a crystallization temperature of 165°C or higher.

A comparison of Example 2 with Examples 7 to 10 shows that a polyarylene sulfide copolymer exhibiting high crystallinity can achieve even higher crystallinity by further incorporating a crystal nucleating agent. A comparison of Examples 7 and 8 shows that higher crystallinity can be achieved by increasing the amount of crystal nucleating agent added.

A comparison of Comparative Example 2 with Examples 11 and 12 shows that a nucleating agent is effective even for polyarylene sulfide copolymers with insufficient crystallinity, and that the inclusion of a nucleating agent results in high crystallinity.

Claims (10)

A polyarylene sulfide copolymer characterized by having a number average molecular weight Mn of 1,000 or more and 10,000 or less, having, as structural units, arylene sulfide units containing 80 moles or more of p-phenylene sulfide units represented by the following formula (XV) , and having a structure in which the arylene sulfide units and a structure represented by the following formula (i) are linked via imide groups, and having a glass transition point of 95°C or more and 190°C or less as measured by differential scanning calorimetry, and having a crystallization temperature of 165°C or more.
(R1 ^and R2 ^are substituents selected from hydrogen, alkyl groups having 1 to 12 carbon atoms, arylene groups having 6 to 24 carbon atoms, and halogen groups, and R1 ^and R2 ^may be the same or different.) The polyarylene sulfide copolymer according to claim 1, characterized in that the relative intensity of the absorption at 3382 cm ⁻¹ derived from the amino group to the absorption at 1901 cm ⁻¹ derived from the benzene ring of the arylene sulfide unit is 0.11 or more and 0.90 or less, or the relative intensity of the absorption at 1860 cm ⁻¹ derived from the acid anhydride group is 0.20 or more and 2.2 or less. 3. The polyarylene sulfide copolymer according to claim 1, which has a melting point of 300° C. or less. 4. The method for producing a polyarylene sulfide copolymer according to claim 1, comprising heating an arylene sulfide (A) having a number average molecular weight Mn of 1,000 or more and 10,000 or less, the arylene sulfide (A) having amino groups and containing 80 moles or more of p-phenylene sulfide units represented by formula (XV), and a compound (B) represented by formula (i'):
(X is either selected from two carboxyl groups bonded to two adjacent carbon atoms, or an acid anhydride group derived from the two carboxyl groups; R ¹ and R ² are substituents selected from hydrogen, an alkyl group having 1 to 12 carbon atoms, an arylene group having 6 to 24 carbon atoms, and a halogen group; R ¹ and R ² may be the same or different; the aromatic ring of each compound may be di- or tri-substituted, and the multiple substituents X substituted on one aromatic ring may be the same or different.) The method for producing a polyarylene sulfide copolymer according to claim 4, wherein at least a part of the polyarylene sulfide (A) and at least a part of the compound (B) are mixed and heated, and then the remaining polyarylene sulfide (A) and/or the compound ( B ) are mixed and heated. The method for producing a polyarylene sulfide copolymer according to claim 4 or 5 , wherein the heating is carried out substantially in the absence of a solvent. A polyarylene sulfide copolymer composition comprising: a polyarylene sulfide copolymer (C) having a number average molecular weight Mn of 1,000 or more and 10,000 or less, which has, as structural units, arylene sulfide units containing 80 moles or more of p-phenylene sulfide units represented by the following formula (XV), and which has a structure in which the arylene sulfide units and a structure represented by the following formula (i) are linked via an imide group; and a crystal nucleating agent; and the polyarylene sulfide copolymer composition has a glass transition point of 95°C or more and 190°C or less, as measured by differential scanning calorimetry, and a crystallization temperature of 165°C or more.
(R1 ^and R2 ^are substituents selected from hydrogen, alkyl groups having 1 to 12 carbon atoms, arylene groups having 6 to 24 carbon atoms, and halogen groups, and R1 ^and R2 ^may be the same or different.) The polyarylene sulfide copolymer composition according to claim 7 , wherein at least a part of the polyarylene sulfide copolymer (C) is the polyarylene sulfide copolymer according to any one of claims 1 to 3 . A polyarylene sulfide copolymer composition comprising the polyarylene sulfide copolymer according to any one of claims 1 to 3 . A molded article obtained by molding the polyarylene sulfide copolymer composition according to any one of claims 7 to 9 .