Method for producing and evaluating cross-linked polyarylene sulfide resin

Abstract

To provide a method for producing polyarylene sulfide (PAS) resin and a method for evaluating PAS resin, which include a step for evaluating the degree of crosslinking of the PAS resin in a short time and in a simple manner. [Solution] A method for producing a crosslinked PAS resin, comprising a polymerization step to obtain a PAS resin, a purification step to purify the PAS resin, and a heat treatment step to heat-treat the PAS resin in an oxidizing atmosphere, wherein the heat treatment step includes extracting at least a portion of the PAS resin, measuring the chemiluminescence intensity of the extracted PAS resin, and estimating the degree of crosslinking progress of the PAS resin toward a target from the chemiluminescence intensity.

Description

Technical Field

[0001] The present invention relates to a method for producing and evaluating a crosslinked polyarylene sulfide resin.

Background Art

[0002] Polyarylene sulfide resins (hereinafter sometimes referred to as PAS resins) typified by polyphenylene sulfide resin (hereinafter sometimes referred to as PPS resin) are excellent in heat resistance, chemical resistance, etc., and are widely used as super engineering plastics in applications such as electric and electronic parts, automotive parts, hot water supply machine parts, fibers, and films.

[0003] PAS resins generally have linear and crosslinked structures, and crosslinked PAS resins are suitable for use in applications where high viscosity and high elastic modulus are required. Crosslinked PAS resins can be obtained by obtaining a linear PAS resin by polymerization and then heat-treating the resin in the presence of oxygen to effect crosslinking and increase the molecular weight (see Patent Document 1, etc.).

[0004] In conventional heat treatment processes, generally, in order to estimate the conditions until the PAS resin reaches the target crosslinking degree, an intermediate is sampled during the heat treatment process and the viscosity of the intermediate is measured. However, the viscosity measurement of PAS resin is carried out in a high-temperature environment exceeding 250°C, and moreover, it takes time such as maintenance of the heating furnace and parts even after the measurement, which has an adverse effect on productivity and safety.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, the problem that the present invention aims to solve is to provide a method for producing PAS resin and a method for evaluating PAS resin that includes a step for evaluating the degree of crosslinking of PAS resin in a short time and in a simple manner. [Means for solving the problem]

[0007] After various studies, the inventors discovered the application of chemiluminescence intensity measurement as a safe and simple method for evaluating the degree of crosslinking of PAS resin. This method involves placing a small amount of PAS resin in a temperature-controlled sample chamber, sealing the chamber, and then quantifying the chemiluminescence derived from the active species in the PAS resin when the PAS resin is heated. This method does not involve contact with high-temperature materials, is simple to operate, and has a short restraint time. Furthermore, because the measurement time is short, the progress of the crosslinking reaction of the PAS resin during measurement can be controlled, allowing for highly accurate measurements and contributing to quality stabilization. No other method for evaluating the degree of crosslinking of PAS resin has been found to exist.

[0008] In other words, the present invention encompasses the following aspects. [1] Polymerization process to obtain PAS resin, A purification step for purifying the PAS resin, A method for producing a crosslinked PAS resin, comprising a heat treatment step of heat-treating the PAS resin in an oxidizing atmosphere, The aforementioned heat treatment step is To extract at least some of the PAS resin, The chemiluminescence intensity of the extracted PAS resin is measured, To obtain an estimated value of the degree of crosslinking progress of the PAS resin relative to the target from the chemiluminescence intensity, A method for producing a cross-linked PAS resin containing [the specified material]. [2] A method for producing a cross-linked PAS resin according to [1], further comprising adjusting the processing conditions based on the estimated value in the heat treatment step. [3] The method for producing a crosslinked PAS resin according to [1] or [2], wherein the chemiluminescence intensity measurement is a method of measuring the cumulative value of the chemiluminescence intensity when the extracted PAS resin is heated from room temperature to 50-200°C in an inert gas atmosphere. [4] The method for producing the crosslinked PAS resin according to any one of [1] to [3] above, wherein the chemiluminescence measurement is performed by heating the extracted PAS resin from room temperature to 50 to 200 °C in an inert gas atmosphere and then switching to an oxidizing gas atmosphere and holding at 50 to 300 °C, and measuring the integrated value of the chemiluminescence intensity in the oxidizing gas atmosphere. [5] The method for producing the crosslinked PAS resin according to any one of [1] to [4] above, wherein in the chemiluminescence intensity measurement, the inert gas is nitrogen and the oxidizing gas is oxygen. [6] A method for producing a crosslinked PAS resin having a heat treatment step of heat-treating the recycled PAS resin in an oxidizing atmosphere, wherein the heat treatment step comprises: taking out at least a part of the PAS resin, measuring the chemiluminescence intensity of the taken-out PAS resin, obtaining an estimated value of the degree of crosslinking progress of the PAS resin with respect to the target from the chemiluminescence intensity, and a method for producing a crosslinked PAS resin comprising the above steps. [7] A method for measuring the chemiluminescence intensity of a PAS resin and evaluating the degree of crosslinking progress of the PAS resin.

Effect of the Invention

[0009] According to the present invention, it is possible to provide a method for producing a PAS resin and a method for evaluating a PAS resin, which have a step of evaluating the degree of crosslinking of the PAS resin in a short time and simply.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, an embodiment of the present invention will be described in detail. However, the scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention. Also, when a plurality of upper and lower limit values are described for specific parameters, any upper limit value and lower limit value can be combined to form a suitable numerical range.

[0011] <Method for Producing PAS Resin> The present embodiment is a method for producing a PAS resin, comprising a polymerization step to obtain a PAS resin, a purification step to purify the PAS resin, and a heat treatment step to heat-treat the PAS resin in an oxidizing atmosphere, wherein the heat treatment step includes extracting at least a portion of the PAS resin, measuring the chemiluminescence intensity of the extracted PAS resin, and estimating the degree of crosslinking of the PAS resin toward a target from the chemiluminescence intensity. Another embodiment is a method for producing a crosslinked PAS resin, comprising a heat treatment step to heat-treat recycled PAS resin in an oxidizing atmosphere, wherein the heat treatment step includes extracting at least a portion of the PAS resin, measuring the chemiluminescence intensity of the extracted PAS resin, and estimating the degree of crosslinking of the PAS resin toward a target from the chemiluminescence intensity. These will be described in detail below.

[0012] ·Polymerization process In this embodiment, the polymerization process for obtaining the PAS resin is not particularly limited, and known polymerization methods can be applied depending on the chemical structure of the PAS resin or the intended use of the PAS resin. A general polymerization method applicable to this embodiment will be described below, followed by a detailed explanation of specific polymerization conditions.

[0013] <Polymerization method> Representative examples of polymerization methods applicable to this embodiment include, for example, the following manufacturing methods 1 to 4. (Manufacturing method 1): A method of polymerization in which a dihalogeno-aromatic compound is polymerized in the presence of sulfur and sodium carbonate, with the addition of a polyhalogeno-aromatic compound or other copolymerizing component if necessary. (Manufacturing method 2): A method of polymerization in which a dihalogeno-aromatic compound is polymerized in a solvent (e.g., a polar solvent, an organic solvent, or a polar organic solvent) in the presence of a sulfidating agent, and if necessary, a polyhalogeno-aromatic compound or other copolymerization component (hereinafter referred to as dihalogeno-aromatic compounds) is added. (Manufacturing method 3): A method of self-condensing p-chlorthiophenol, with the addition of other copolymerization components if necessary. (Production Method 4): A method of melt-polymerizing a diiodoaromatic compound and elemental sulfur while reducing the pressure in the presence of a polymerization inhibitor that may have functional groups such as a carboxy group or an amino group

[0014] Among the above Production Methods 1 to 4, the method of the above (Production Method 2) is general-purpose and preferable. During the reaction, an alkali metal salt of a carboxylic acid or a sulfonic acid, or an alkali hydroxide may be added to adjust the degree of polymerization. Among the methods of the above (Production Method 2), a formulation containing dihalogenoaromatic compounds, a polar organic solvent, and a sulfidizing agent is charged into a reactor so that (polar organic solvent) / (sulfidizing agent) is in the range of 0.02 / 1 to 0.9 / 1 (molar ratio). Preferably, the temperature is started to rise in an open system under an inert gas atmosphere to dehydrate the formulation, and as the dehydration progresses, a solid substance is precipitated to obtain a low-moisture solid in which each component is uniformly dispersed. After that, it is cooled to a predetermined temperature, and if necessary, a polar organic solvent and / or dihalogenoaromatic compounds are further added to the low-moisture solid, and polymerization is carried out under an inert gas atmosphere (see Japanese Patent Publication No. 3637543), or a method in which a dihalogenoaromatic compound and, if necessary, a polyhalogenoaromatic compound or other copolymerization components are added in the presence of a solid alkali metal sulfide and an aprotic polar organic solvent, and an alkali metal hydrosulfide and an alkali metal organic acid salt are reacted while controlling the amount of the alkali metal organic acid salt in the range of 0.01 to 0.9 mol with respect to 1 mol of the sulfur source and the amount of water in the reaction system to be 0.02 mol or less with respect to 1 mol of the aprotic polar organic solvent (see WO2010 / 058713 pamphlet) is particularly preferable.

[0015] As the polymerization step of the present embodiment, a polymerization method using the above Production Method 2 will be described below by taking, as an example, a step of obtaining a reaction mixture (slurry) containing a PAS resin obtained by reacting at least one polyhalogenoaromatic compound and at least one sulfidizing agent under appropriate polymerization conditions in a polar solvent (for example, a polar organic solvent). Furthermore, this embodiment also includes a form in which the reaction mixture (slurry) is obtained by reacting a polyhalogeno-aromatic compound and / or an organic solvent in the presence of a sulfidating agent and an organic solvent, while continuously or intermittently adding them.

[0016] In this invention, the polyhalogenoaromatic compound is, for example, a halogenated aromatic compound having two or more halogen atoms directly bonded to an aromatic ring. Specifically, examples include dihaloaromatic compounds such as p-dichlorobenzene, o-dichlorobenzene, m-dichlorobenzene, trichlorobenzene, tetrachlorobenzene, dibrombenzene, diiodobenzene, tribrombenzene, dibromnaphthalene, triiodobenzene, dichlorodiphenylbenzene, dibromdiphenylbenzene, dichlorobenzophenone, dibrombenzophenone, dichlorodiphenyl ether, dibromdiphenyl ether, dichlorodiphenyl sulfide, dibromdiphenyl sulfide, dichlorobiphenyl, and dibrombiphenyl, as well as mixtures thereof. These compounds may be block copolymerized. Among these, dihalogenated benzenes are preferred, and those containing 80 mol% or more of p-dichlorobenzene are particularly preferred. Furthermore, in order to increase the viscosity of the PAS resin by creating a branched structure, polyhalo-aromatic compounds having three or more halogen substituents in one molecule may be used as branching agents as desired. Examples of such polyhalo-aromatic compounds include 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, and 1,4,6-trichloronaphthalene. Furthermore, examples include polyhalo-aromatic compounds having functional groups with active hydrogens such as amino groups, thiol groups, and hydroxyl groups. Specifically, these include dihaloanilines such as 2,6-dichloroaniline, 2,5-dichloroaniline, 2,4-dichloroaniline, and 2,3-dichloroaniline; trihaloanilines such as 2,3,4-trichloroaniline, 2,3,5-trichloroaniline, 2,4,6-trichloroaniline, and 3,4,5-trichloroaniline; dihaloaminodiphenyl ethers such as 2,2'-diamino-4,4'-dichlorodiphenyl ether and 2,4'-diamino-2',4-dichlorodiphenyl ether, and compounds in which the amino group is replaced with a thiol group or a hydroxyl group in mixtures thereof.In addition, active hydrogen-containing polyhaloaromatic compounds in which the hydrogen atoms bonded to the carbon atoms forming the aromatic rings in these active hydrogen-containing polyhaloaromatic compounds are substituted with other inert groups, such as hydrocarbon groups such as alkyl groups, can also be used.

[0017] Among these various active hydrogen-containing polyhaloaromatic compounds, preferred are active hydrogen-containing dihaloaromatic compounds, and particularly preferred is dichloroaniline.

[0018] Examples of polyhaloaromatic compounds having a nitro group include mono- or dihalonitrobenzenes such as 2,4-dinitrochlorobenzene and 2,5-dichloronitrobenzene; dihalonitrodiphenyl ethers such as 2-nitro-4,4'-dichlorodiphenyl ether; dihalonitrodiphenyl sulfones such as 3,3'-dinitro-4,4'-dichlorodiphenyl sulfone; mono- or dihalonitropyridines such as 2,5-dichloro-3-nitropyridine and 2-chloro-3,5-dinitropyridine; or various dihalonitronaphthalenes and the like.

[0019] In the present invention, an alkali metal sulfide or an alkali hydrosulfide and an alkali metal hydroxide (hereinafter sometimes referred to as a sulfidizing agent) are used as raw materials.

[0020] In the present invention, examples of the alkali metal sulfide include lithium sulfide, sodium sulfide, rubidium sulfide, cesium sulfide, and mixtures thereof. Such alkali metal sulfides can be used as hydrates, aqueous mixtures, or anhydrides. In addition, the alkali metal sulfide can also be obtained by reacting an alkali metal hydrosulfide with an alkali metal hydroxide. Usually, in order to react with trace amounts of alkali metal hydrosulfide and alkali metal thiosulfate present in the alkali metal sulfide, a small amount of alkali metal hydroxide may be added without any problem.

[0021] Furthermore, the alkali metal hydrosulfides include lithium hydrogen sulfide, sodium hydrogen sulfide, rubidium hydrogen sulfide, cesium hydrogen sulfide, and mixtures thereof. Such alkali metal hydrosulfides can be used as hydrates, aqueous mixtures, or anhydrous products.

[0022] Furthermore, the alkali metal hydroxide is used together with an alkali metal hydroxide. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide, which may be used individually or in combination of two or more. Among these, lithium hydroxide, sodium hydroxide, and potassium hydroxide are preferred due to their availability, with sodium hydroxide being particularly preferred.

[0023] The present invention's method for producing PAS resin can also use a hydrated sulfidating agent as a raw material. In this case, it is preferable to dehydrate the hydrated sulfidating agent in the presence of at least an aprotic polar solvent before subjecting it to the polymerization reaction of the PAS resin. Furthermore, if the amount of aprotic polar solvent charged is small, for example, less than 1 mole per mole of sulfur atoms in the sulfidating agent, it is preferable to dehydrate the hydrated sulfidating agent and the aprotic polar solvent in the presence of a polyhalo-aromatic compound.

[0024] The dehydration step of the hydrated sulfidating agent is carried out by charging at least an aprotic polar solvent and a hydrated alkali metal sulfide or hydrated alkaline aqueous sulfide and alkali metal hydroxide as the hydrated sulfidating agent into a reaction vessel equipped with a distillation apparatus, heating to a temperature at which water is removed by azeotropy, specifically in the range of 300°C or less, preferably in the range of 80 to 220°C, more preferably in the range of 100 to 200°C, and then discharging the water from the system by distillation. In the dehydration step, it is preferable to dehydrate until the amount of water in the system carrying out the polymerization reaction is 5 moles or less, more preferably in the range of 0.01 to 2.0 moles, per mole of sulfur atoms of the sulfidating agent.

[0025] In addition, examples of organic polar solvents in the present invention include amides, ureas and lactams such as formamide, acetamide, N-methylformamide, N,N-dimethylacetamide, tetramethylurea, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropyleneurea, and 1,3-dimethyl-2-imidazolidinonic acid; sulfolanes such as sulfolane and dimethylsulfolane; nitriles such as benzonitrile; ketones such as methylphenyl ketone and mixtures thereof. Among these, amides having an aliphatic cyclic structure such as N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropyleneurea, and 1,3-dimethyl-2-imidazolidinonic acid are preferred, and N-methyl-2-pyrrolidone is even more preferred.

[0026] In the PAS polymerization process, the polymerization reaction of the PAS resin involves reacting the alkali metal sulfide and the polyhalo-aromatic compound as sulfidating agents in the presence of these organic polar solvents. Alternatively, the polymerization reaction of the PAS resin involves reacting the alkali metal hydroxide and alkali metal hydroxide as sulfidating agents with the polyhalo-aromatic compound in the presence of these organic polar solvents. The polymerization conditions are generally in the temperature range of 200 to 330°C, and the pressure should be in a range that substantially maintains the polymerization solvent and the polyhalo-aromatic compound, which is the polymerization monomer, in the liquid phase, and is generally selected from the range of 0.1 to 20 MPa, preferably from 0.1 to 2 MPa. The amount of polyhalo-aromatic compound to be charged is prepared in the range of 0.2 moles to 5.0 moles, preferably from 0.8 to 1.3 moles, and more preferably from 0.9 to 1.1 moles, per mole of sulfur atoms of the sulfidating agent. Furthermore, the amount of aprotic polar solvent charged is adjusted to be in the range of 1.0 to 6.0 moles, preferably 2.5 to 4.5 moles, per mole of sulfur atoms of the sulfidating agent. The polymerization reaction is preferably carried out in the presence of a small amount of water, and the proportion is preferably adjusted as appropriate in consideration of the polymerization method, the molecular weight of the obtained polymer, and productivity. Specifically, the dehydration operation is carried out so that the amount of water is in the range of 2.0 moles or less, preferably 1.6 moles or less, per mole of sulfur atoms of the sulfidating agent. However, if the dehydration operation is carried out in the presence of a polyhalo-aromatic compound (for example, the method in "5)" in the specific embodiment below), the amount of water should be in the range of 0.9 moles or less, preferably 0.05 to 0.3 moles, more preferably 0.01 to 0.02 moles or less.

[0027] Specific embodiments of polymerizing a sulfidating agent and a polyhalo-aromatic compound in the presence of the aforementioned aprotic polar solvent include, for example, 1) A method using polymerization aids such as alkali metal carboxylates or lithium halides. 2) A method using branching agents such as aromatic polyhalogen compounds, 3) A method in which polymerization is carried out in the presence of a small amount of water, and then water is added to further polymerize the molecule. 4) A method in which, during the reaction of an alkali metal sulfide with an aromatic dihalogen compound, the gas phase portion of the reaction vessel is cooled to condense a portion of the gas phase inside the reaction vessel and reflux it into the liquid phase. 5) A method for producing PAS resin, which has the following essential manufacturing steps: 1) Reacting an alkali metal sulfide, or a hydrated alkali metal hydroxide and alkali metal hydroxide, with an amide, urea, or lactam having an aliphatic cyclic structure in the presence of a polyhalo-aromatic compound, while dehydrating, to produce a slurry containing a solid alkali metal sulfide; 2) After producing the slurry, adding a polar organic solvent such as NMP and removing the water by distillation to dehydrate the slurry; and 3) Reacting a polyhalo-aromatic compound, an alkali metal hydroxide, and an alkali metal salt of the hydrolysis product of the amide, urea, or lactam having an aliphatic cyclic structure in the slurry obtained through the dehydration step, at a rate of 0.02 moles or less of water present in the reaction system per mole of a polar organic solvent such as NMP, to carry out polymerization.

[0028] In this way, by polymerizing a dihalo-aromatic compound with an alkali metal sulfide, or with an alkali metal hydroxide and an alkali metal hydroxide, in an organic polar solvent, PAS resin is obtained as a product, but PAS oligomers are also produced as by-products. Other substances contained after the reaction may include by-products such as alkali metal-containing inorganic salts, carboxyalkylamino group-containing compounds, terminal SH group-containing compounds, unreacted raw materials, and water.

[0029] ·Refining process The purification step in this embodiment is a step of purifying the PAS resin obtained from the polymerization step described above. In this embodiment, known purification treatments can be applied depending on the chemical structure of the PAS resin.

[0030] In this embodiment, the purification treatment of the PAS resin (reaction mixture (slurry) containing the PAS resin) obtained by the polymerization step is not particularly limited, but examples include the following purification treatments 1 to 5. Purification process 1: After the polymerization reaction is complete, the reaction mixture (slurry) is first removed under reduced pressure or atmospheric pressure, either as is or after adding an acid or base. Then, the solid matter (crude PAS resin) remaining after solvent removal is washed once or twice or more with a washing solution such as (hot) water, the reaction solvent (or an organic solvent with equivalent solubility to the low molecular weight polymer), acetone, methyl ethyl ketone, or alcohols. Further neutralization, washing with (hot) water, filtration, and drying are performed. Purification process 2: After the polymerization reaction is complete, a solvent such as (hot) water, acetone, methyl ethyl ketone, alcohols, ethers, halogenated hydrocarbons, aromatic hydrocarbons, or aliphatic hydrocarbons (solvents that are soluble in the organic solvent used for polymerization and are poor solvents for at least PAS resin) is added to the reaction mixture (slurry) as a precipitating agent to settle the solid matter (crude PAS resin) containing PAS resin and inorganic salts, etc., and then these are filtered, washed, and dried. Purification process 3: After the polymerization reaction is complete, the reaction mixture (slurry) is mixed with the reaction solvent (or an organic solvent having equivalent solubility to the low molecular weight polymer) and stirred. The solid material (crude PAS resin) obtained by filtering to remove the low molecular weight polymer is then washed once or twice or more with a washing solution such as (hot) water, acetone, methyl ethyl ketone, or alcohols, followed by neutralization, (hot) water washing, filtration, and drying. Purification process 4: After the polymerization reaction is complete, the reaction mixture (slurry) is washed with (hot) water as a washing solution, filtered, and the resulting solid (crude PAS resin) is then acid-treated by adding acid during the (hot) water washing as needed, and then dried. Purification process 5: After the polymerization reaction is complete, the reaction mixture (slurry) is filtered to obtain a solid (crude PAS resin), which may be washed once or twice or more with a reaction solvent as a washing solution, and further washed with (hot) water, filtered, and dried. In addition, in the purification processes exemplified in the above purification processes 1 to 5, the drying of the PAS resin may be carried out in a vacuum, in air, or in an inert gas atmosphere such as nitrogen.

[0031] In this embodiment, the purification step is preferably a step of adding a washing solution to the reaction mixture (slurry) containing the PAS resin obtained in the polymerization step, or to the crude PAS resin which is the solid component of the reaction mixture (slurry), and then performing a washing treatment, a filtration treatment, and a drying treatment. Furthermore, the washing treatment, filtration treatment, and drying treatment in which the washing solution is added can each be performed at least once or multiple times. In this specification, "crude PAS resin" refers to the solid content obtained by separating the reaction mixture (slurry) containing the PAS resin obtained in the polymerization process one or more times using solid-liquid separation.

[0032] The above cleaning process is not particularly limited, and can be performed once or multiple times, including acid cleaning, (hot) water cleaning, and solution cleaning with the above cleaning solution or reaction solvent. The cleaning solution that can be used in the cleaning process in this embodiment is not particularly limited, and examples include water, hot water, acid solution, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dimethyl sulfone, acetone, methyl ethyl ketone, diethyl ketone, acetophenone, dimethyl ether, dipropyl ether, tetrahydrofuran, chloroform, methylene chloride, trichloroethylene, dichloroethylene, dichloroethane, tetrachloroethane, chlorobenzene, methanol, ethanol, propanol, butanol, pentanol, ethylene glycol, propylene glycol, phenol, cresol, polyethylene glycol, benzene, toluene, xylene, and the like. The above cleaning solutions may be used individually or as a mixture of two or more.

[0033] The temperature of the above-mentioned washing solution is preferably 140 to 260°C. A preferred method of washing with a washing solution at 140 to 260°C is to wash the crude PAS resin while pressurizing the washing solution (for example, in a pressure range of 0.1 to 5 MPa). The above-mentioned drying treatment is not particularly limited, but drying at a drying temperature of 120 to 270°C is preferred. The drying atmosphere can be under reduced pressure, under a nitrogen or inert gas atmosphere, under an oxidizing atmosphere such as oxygen or air, or under a mixed gas atmosphere of air and nitrogen. The drying time is preferably 0.5 to 53 hours. The above-mentioned filtration treatment is not particularly limited as long as it can separate solid and liquid, and can be done using a filter, centrifuge, or the like.

[0034] When using recycled PAS resin as the material to be heat-treated, for example, PAS resin recovered from PAS resin compositions or PAS resin molded products can be used. Specifically, this includes sprues or runners generated during the manufacture of molded products, products recovered as off-spec molded products, and pulverized molded products that have been used as products. The recycling method is not particularly limited, and examples include PAS resin obtained by heating a PAS resin composition or PAS resin molded product in an organic polar solvent to dissolve the contained PAS, and then performing the purification process described above on the resulting solution. In addition, mechanically pulverized PAS resin compositions or PAS resin molded products can also be used as PAS resin. In this case, pulverized PAS resin compositions or PAS resin molded products containing components other than PAS resin may be used, but from the viewpoint of mechanical strength and generated gases, it is preferable that the PAS resin content be 90 parts by mass or more, more preferably 95 parts by mass or more, and even more preferably 98 parts by mass or more.

[0035] • Heat treatment process The heat treatment step in this embodiment is a step in which the PAS resin that has undergone the purification step described above is heat-treated to promote the crosslinking reaction.

[0036] The heat treatment in this process involves heating the PAS resin in an oxidizing atmosphere such as air or oxygen-enriched air. The heat treatment method is not particularly limited, and publicly known and publicly available equipment and methods can be used. For example, the PAS resin is placed in a treatment container and heated in an oxygen atmosphere or an air atmosphere. The heating conditions are preferably in a temperature range of 180°C or higher and 20°C lower than the melting point of the PAS resin, from the viewpoint of the time required for the heat treatment and good thermal stability of the PAS resin when it melts after the heat treatment. However, the melting point here refers to the melting point measured using a differential scanning calorimeter in accordance with JIS K 7121.

[0037] The oxygen concentration in the oxidizing atmosphere is preferably in the range of 5 to 30 volume%, and particularly preferably in the range of 10 to 25 volume%. Exceeding this range increases the amount of radicals generated, leading to significant thickening during heat treatment and darkening of the color, which is undesirable. Below this range, the oxidation rate slows down, requiring a long processing time, which is also undesirable.

[0038] Furthermore, in this embodiment, the heat treatment process is performed during the treatment process, To extract at least some of the PAS resin, The chemiluminescence intensity of the extracted PAS resin is measured, This includes determining an estimated value of the degree of crosslinking of the PAS resin from the chemiluminescence intensity.

[0039] In this embodiment, the method for extracting the PAS resin is not particularly limited and can be carried out by known methods.

[0040] In this embodiment, the heat treatment step includes measuring the chemiluminescence intensity of the extracted PAS resin.

[0041] In this embodiment, the specific method for measuring chemiluminescence intensity is not particularly limited, but for example, it can be measured by the following methods. Method I is preferably used when the increase rate of the melt viscosity (V6) of the PAS resin to be measured is in the range of 50 to 10000%, and Method II is preferably used when the increase rate of the melt viscosity (V6) of the PAS resin to be measured is in the range of 1 to 500%. Nitrogen is preferred as the inert gas, and oxygen is preferred as the oxidizing gas. The rate of change in melt viscosity is calculated by (melt viscosity of heat-treated PAS resin / melt viscosity of untreated PAS resin - 1) × 100. Method I: A method for measuring the cumulative value of chemiluminescence intensity (cps; Counts per Second) over a certain period of time while heating PAS resin at a constant rate from room temperature to a range of 50-200°C under an inert gas atmosphere. Method II: A method for measuring the cumulative chemiluminescence intensity for a certain period of time starting immediately after switching to an oxidizing gas atmosphere, after heating a PAS resin at a constant rate from room temperature to a range of 50-200°C under an inert gas atmosphere, and then switching to an oxidizing gas atmosphere and maintaining it isothermally at a specific temperature of 50-300°C.

[0042] In the measurement of chemiluminescence intensity described above, conditions other than temperature can be set within the following range. For the specifications of the apparatus and items not listed below, the procedure should be carried out in accordance with JIS K 7351. Sample weight: 0.01~5.00g Measurement wavelength: 380~660nm Sample chamber gas flow rate: 5-100 mL / min Heating rate: 0.1~50℃ / min Measurement time: 3-100 minutes

[0043] PAS resin exhibits weak chemiluminescence, which is presumed to originate from radicals (e.g., phenyl radicals) or active groups (e.g., terminal SH groups) within the PAS molecule. Therefore, by measuring the chemiluminescence intensity of the PAS resin, the content of active groups in the PAS molecule can be estimated. For example, in Method I, when heat treatment is performed under an oxygen or air atmosphere, the PAS molecular chains are first transformed into radicals by the heat treatment, and further radicals derived from oxygen are added to the PAS molecular chains, thereby increasing the number of radicals in the PAS resin. In other words, it is thought that the chemiluminescence intensity derived from these radicals increases. On the other hand, in Method II, the PAS active groups are transformed into radicals, and these radicals are incorporated into other PAS molecules through chemical reactions to form branched structures, causing the radicals to disappear. That is, since the number of active groups in the PAS resin after the heat treatment process decreases, it is thought that the chemiluminescence intensity derived from these active groups decreases. It should be noted that the above mechanism is merely speculative, and even if the effects of the present invention are achieved for other reasons, they are still within the technical scope of the present invention.

[0044] In this embodiment, the heat treatment step includes determining an estimated value of the degree of crosslinking of the PAS resin relative to the target from the chemiluminescence intensity. The degree of crosslinking of the PAS resin can be estimated from a pre-prepared calibration curve.

[0045] First, the calibration curve will be explained. The calibration curve can be created, for example, in a heat treatment test of PAS resin, using the least squares method with the rate of change in chemiluminescence obtained from the chemiluminescence intensity of untreated PAS resin and PAS resin taken at several treatment times, and the rate of increase in melt viscosity (V6). The conditions such as the treatment temperature in the heat treatment (crosslinking reaction) for creating the calibration curve can be set to several conditions that are substantially the same as, or close to, the conditions for manufacturing crosslinked PAS resin. The melt viscosity (V6) in this disclosure can be measured by the method described in the examples. In this disclosure, the rate of change in chemiluminescence is an absolute value.

[0046] Next, the calculation of the crosslinking progress will be described. First, the melt viscosity increase rate in the heat treatment is calculated from the target melt viscosity (V6) of the PAS resin with respect to the melt viscosity (V6) of the untreated PAS resin. By applying the obtained melt viscosity (V6) increase rate to the calibration curve, the target chemiluminescence intensity change rate is obtained. Then, from the chemiluminescence intensity of the PAS resin taken out during the heat treatment, the chemiluminescence intensity change rate with respect to the untreated PAS resin is calculated, and the crosslinking progress is determined as the ratio to the target chemiluminescence intensity change rate (measured chemiluminescence intensity change rate / target chemiluminescence intensity change rate × 100).

[0047] In this embodiment, the heat treatment step may further include adjusting the treatment conditions of the PAS resin based on the estimated value of the obtained crosslinking progress. That is, based on the estimated value of the crosslinking progress of the PAS resin during the heat treatment obtained by the above method, various conditions in the heat treatment of the PAS resin until the crosslinking progress reaches the target can be controlled from the relationship between the treatment time and the crosslinking progress. Examples of the treatment conditions include the time, temperature, pressure of the treatment apparatus (flow rate of oxygen or air), stirring speed, etc. of the heat treatment.

[0048] <Method for Evaluating PAS Resin> The method for evaluating the PAS resin of the present disclosure is a method for measuring the chemiluminescence intensity of the PAS resin and evaluating the crosslinking progress of the PAS resin, and uses the method described above.

[0049] <Composition, Use, etc.>

[0050] The crosslinked PAS resin of the present disclosure produced by the above method can be processed into a molded product excellent in heat resistance, molding processability, dimensional stability, etc. by various melt processing methods such as injection molding, extrusion molding, compression molding, and blow molding.

[0051] Furthermore, the cross-linked PAS resin of the present invention can be used as a PAS resin composition in combination with various fillers to further improve performance such as strength, heat resistance, and dimensional stability. The fillers are not particularly limited, but examples include fibrous fillers and inorganic fillers. Examples of fibrous fillers include glass fibers, carbon fibers, silane glass fibers, ceramic fibers, aramid fibers, metal fibers, potassium titanate, silicon carbide, calcium sulfate, calcium silicate, and natural fibers such as wollastonite. Examples of inorganic fillers include barium sulfate, calcium sulfate, clay, pyroferrite, bentonite, sericite, zeolite, mica, talc, atalpulgite, ferrite, calcium silicate, calcium carbonate, magnesium carbonate, and glass beads. Additionally, various additives such as mold release agents, colorants, heat stabilizers, UV stabilizers, foaming agents, rust inhibitors, flame retardants, and lubricants can be included as additives during the molding process.

[0052] Furthermore, the crosslinked PAS resin obtained by the present invention may be used as a PAS resin composition that appropriately incorporates synthetic resins such as polyester, polyamide, polyimide, polyetherimide, polycarbonate, polyphenylene ether, polysulfone, polyethersulfone, polyetheretherketone, polyetherketone, polyarylate, polyethylene, polypropylene, polytetrafluoroethylene, polydifluoroethylene, polystyrene, ABS resin, epoxy resin, silicone resin, phenolic resin, urethane resin, liquid crystal polymer, or elastomers such as polyolefin rubber, fluororubber, or silicone rubber, depending on the application.

[0053] The cross-linked PAS resin of the present invention possesses the inherent properties of PAS resin, such as heat resistance and dimensional stability, and is therefore widely useful as a material for various molding processes, such as injection molding or compression molding of electrical and electronic components such as connectors, printed circuit boards and encapsulated molded products, automotive parts such as lamp reflectors and various electrical components, plumbing parts such as pipes and valves for transporting liquids, interior materials for various buildings, aircraft and automobiles, or precision parts such as OA equipment parts, camera parts and watch parts, or as a material for various molding processes such as extrusion molding or pultrusion of composites, sheets and pipes, or as a material for fibers or films. In particular, the cross-linked PAS resin of the present invention is useful when used as a material for injection molding because it has high toughness and excellent processability. [Examples]

[0054] The present invention will be specifically described below with reference to examples. These examples are illustrative and not limiting. Unless otherwise specified, "%" and "parts" refer to mass.

[0055] <Example 1> (Polymerization process) A 150-liter autoclave equipped with stirring blades and connected to a pressure gauge, thermometer, condenser, decanter, and rectification column was charged with 33.472 kg (228 mol) of p-dichlorobenzene (hereinafter abbreviated as p-DCB), 4.560 kg (46 mol) of NMP, 27.300 kg (230 mol) of 47.23% by mass NaSH aqueous solution, and 18.533 g (228 mol) of 49.21% by mass NaOH aqueous solution. The mixture was heated to 173°C over 5 hours under a nitrogen atmosphere while stirring, and 26.794 kg of water was distilled off, after which the autoclave was sealed. The DCB distilled off by azeotrope during dehydration was separated in the decanter and returned to the autoclave as it was removed. After dehydration, the autoclave contained particulate anhydrous sodium sulfide composition dispersed in the DCB. After the above dehydration process was completed, the internal temperature was cooled to 160°C, 45.203 kg (456 mol) of NMP was charged, and the temperature was raised to 185°C. When the pressure reached 0.00 MPa, the valve connected to the rectification column was opened, and the internal temperature was raised to 200°C over 1 hour. During this time, the temperature at the outlet of the rectification column was controlled by cooling and valve opening to keep it below 110°C. The distilled DCB and water mixture was condensed in a condenser, separated in a decanter, and the DCB was returned to the boiler. The amount of water distilled was 273 g. The internal temperature was raised from 200°C to 230°C over 3 hours, stirred at 230°C for 1 hour, then raised to 250°C and stirred for 1 hour. The final pressure was 0.50 MPa.

[0056] (purification process) NMP contained in 260 g of slurry obtained after cooling was removed by vacuum distillation at 150°C for 2 hours. 360 g of ion-exchanged water at 70°C was added to this mixture and stirred for 10 minutes, then filtered. 480 g of ion-exchanged water at 70°C was added to the filtered cake for cake washing. The resulting hydrated cake and 180 g of ion-exchanged water were placed in a 0.5 liter autoclave and stirred at 220°C for 30 minutes. After cooling to room temperature, the mixture was filtered, and 480 g of ion-exchanged water at 70°C was added to the filtered cake for cake washing. The mixture was then dried at 120°C for 4 hours to obtain PPS resin (1a). The melt viscosity (V6) of the obtained PPS resin (1a) was 39 Pa·s.

[0057] (Heat treatment process) The target melt viscosity (V6) for the heat-treated product was set to 400 Pa·s, and the corresponding rate of change in chemiluminescence intensity of 9000% was set as the target value (value for 100% crosslinking) from a calibration curve prepared in advance by Method I. The PPS resin (1a) obtained after drying was heat-treated in a hot air dryer at a set temperature of 240°C. PPS resins (1p), (1q), and (1r) were sampled at 4.0 hours, 8.0 hours, and 12.0 hours after the start of heat treatment. The rate of change in chemiluminescence intensity for each sample was measured to be 4000%, 6200%, and 7900%, respectively, and the rates of crosslinking were 44%, 69%, and 88%. The time required for measurement per sample (from sample setup to completion of measurement) was 15 minutes, of which the operator's time commitment was 3 minutes. In addition, it took 30 minutes for the detector to stabilize during the startup of the chemiluminescence intensity measuring device. Based on these results, the process time required to reach the target viscosity was adjusted to 17.5 hours. PPS resin (1b) was obtained 17.5 hours after the start of heat treatment. The rate of change (increase rate) of the chemiluminescence intensity of the obtained PPS resin (1b) was 9000%, and the degree of crosslinking progressed to 100%, achieving the target. The melt viscosity (V6) was 400 Pa·s.

[0058] <Example 2> In Example 1, the target melt viscosity (V6) of the heat-treated product was set to 100 Pa·s, and the target value (value for 100% crosslinking progress) was set to a corresponding rate of change in chemiluminescence intensity of 83% from a calibration curve prepared in advance by Method II. The PPS resin (1a) obtained after drying was heat-treated in a hot air dryer at a set temperature of 240°C. PPS resins (1s), (1t), and (1u) were sampled at 0.5 hours, 1.0 hours, and 2.0 hours after the start of the heat treatment. The rate of change in chemiluminescence intensity for each sample was measured to be 26%, 45%, and 70%, and the crosslinking progress was 31%, 54%, and 84%, respectively. The time required for measurement per sample was 15 minutes, of which the holding time was 3 minutes. In addition, it took 30 minutes for the detector to stabilize when starting up the chemiluminescence intensity measuring device. Based on these results, the process time to reach the target viscosity was adjusted to 3.0 hours. PPS resin (1c) was obtained 3.0 hours after the start of heat treatment. The rate of change (decrease rate) of the chemiluminescence intensity of the obtained PPS resin (1c) was 83%, and the degree of crosslinking progressed to 100%, achieving the target. The melt viscosity (V6) was 100 Pa·s.

[0059] <Reference example 1> The process up to sampling the PPS resins (1p), (1q), and (1r) in the heat treatment process was carried out in the same manner as in Example 1. The melt viscosity (V6) of each intermediate was measured. The results were 121 Pa·s, 203 Pa·s, and 285 Pa·s. The time required for measurement per sample was 25 minutes, of which 20 minutes was the holding time. In addition, it took 2 hours for the instrument to heat up to the measurement temperature and for the temperature to stabilize. Based on these results, the process time required to reach the target viscosity was set to 17.5 hours. PPS resin (C1b) was obtained 17.5 hours after the start of heat treatment. The melt viscosity (V6) of the obtained PPS resin (C1b) was 400 Pa·s.

[0060] <Reference example 2> The process up to sampling the PPS resins (1s), (1t), and (1u) during the heat treatment process was carried out in the same manner as in Example 2. The melt viscosity (V6) of each intermediate was measured. The results were 49 Pa·s, 60 Pa·s, and 80 Pa·s. The time required for measurement per sample was 25 minutes, of which 20 minutes was the holding time. In addition, it took 2 hours for the equipment to heat up to the measurement temperature and for the temperature to stabilize. Based on these results, the process time required to reach the target viscosity was set to 3.0 hours. PPS resin (C1c) was obtained 3.0 hours after the start of heat treatment. The melt viscosity (V6) of the obtained PPS resin (C1c) was 100 Pa·s.

[0061] <Rating> (1) Measurement of melt viscosity (V6) Using a Shimadzu CFT-500D flow tester, the temperature was set to 300°C and the load to 20 kgf / cm². 2 The melt viscosity (Pa·s) was measured after holding the mixture for 6 minutes at a ratio of L / D = 10(mm) / 1(mm). (2) Measurement of chemiluminescence intensity and calculation of rate of change In the heat treatment process of the examples and comparative examples, the chemiluminescence intensity of the PPS resin was measured before and after heat treatment. The measurement was performed using a "Chemiluminescence Analyzer CLA-FS5" manufactured by Tohoku Electronics Industry Co., Ltd. Specifically, PPS resin (0.10 g sample) was placed in the sample chamber of the instrument, and the measurement was performed using either Method I or Method II below. The rate of change in the measured value due to heat treatment was calculated using the following formula. [Method I] Under a nitrogen atmosphere, the room temperature was increased from 40°C to 150°C and maintained at 150°C for 5 minutes. The measured value was the cumulative value of the chemiluminescence intensity [counts / second] exhibited by the sample during the 5 minutes at 150°C, divided by the sample weight. [Method II] Under a nitrogen atmosphere, the room temperature was raised from 40°C to 150°C and maintained at 150°C for 5 minutes, then cooled to 75°C. The measurement atmosphere was switched from nitrogen to oxygen, maintained at 75°C for 5 minutes, then raised again to 150°C and maintained at 150°C for 5 minutes. The measured value was obtained by dividing the cumulative value of the chemiluminescence intensity [counts / second] exhibited by the sample during the 5 minutes of maintenance at 150°C by the sample weight. [Calculation formula] • CL0; Measurement of chemiluminescence intensity of PPS resin before heat treatment process • CL1; Measurement of chemiluminescence intensity of PPS resin after heat treatment process. • (Percentage change in chemiluminescence intensity, %) = (CL0 - CL1) ÷ CL0 × 100

Claims

1. Polymerization process to obtain polyarylene sulfide resin, A purification step for purifying the polyarylene sulfide resin, A method for producing a crosslinked polyarylene sulfide resin, comprising a heat treatment step of heating the polyarylene sulfide resin in an oxidizing atmosphere, The aforementioned heat treatment step, To extract at least a portion of the polyarylene sulfide resin, The chemiluminescence intensity of the extracted polyarylene sulfide resin is measured, To estimate the degree of crosslinking of the polyarylene sulfide resin relative to the target from the chemiluminescence intensity, A method for producing a cross-linked polyarylene sulfide resin containing [the specified compound].

2. A method for producing a crosslinked polyarylene sulfide resin according to claim 1, further comprising adjusting the processing conditions based on the estimated value in the heat treatment step.

3. A method for producing a crosslinked polyarylene sulfide resin according to claim 1 or 2, wherein the chemiluminescence intensity measurement is a method for measuring the integrated value of the chemiluminescence intensity when the extracted polyarylene sulfide resin is heated from room temperature to 50 to 200°C in an inert gas atmosphere.

4. A method for producing a crosslinked polyarylene sulfide resin according to claim 1 or 2, wherein the chemiluminescence intensity measurement is a method of measuring the cumulative value of the chemiluminescence intensity under an oxidizing gas atmosphere when the extracted polyarylene sulfide resin is heated from room temperature to 50 to 200°C under an inert gas atmosphere, and then switched to an oxidizing gas atmosphere and held at 50 to 300°C.

5. A method for producing a crosslinked polyarylene sulfide resin according to claim 3 or 4, wherein the inert gas used for the chemiluminescence intensity measurement is nitrogen and the oxidizing gas is oxygen.

6. A method for producing a cross-linked polyarylene sulfide resin, comprising a heat treatment step of heat-treating a recycled polyarylene sulfide resin in an oxidizing atmosphere, The aforementioned heat treatment step, To extract at least a portion of the polyarylene sulfide resin, The chemiluminescence intensity of the extracted polyarylene sulfide resin is measured, To estimate the degree of crosslinking of the polyarylene sulfide resin relative to the target from the chemiluminescence intensity, A method for producing a cross-linked polyarylene sulfide resin containing [the specified compound].

7. A method for measuring the chemiluminescence intensity of polyarylene sulfide resin and evaluating the degree of crosslinking of the polyarylene sulfide resin.