Evaluation method for polyarylene sulfide resin

Abstract

This invention provides a quick and simple method for evaluating the thermal degradation susceptibility of polyarylene sulfide (PAS) resin. [Solution] A method for evaluating PAS resin, including evaluating the thermal decomposition behavior from the following rate of change. (However, the heat treatment is a process in which the PAS resin is sufficiently melted at a temperature of melting point + 10°C to melting point + 100°C, and the measurement of the integrated value of chemiluminescence intensity is a method in which the resin is heated from room temperature to 50-200°C under an inert gas atmosphere, then switched to an oxidizing gas atmosphere and held at 50-300°C, and the integrated value of chemiluminescence intensity is measured for a certain period of time immediately after switching to the oxidizing gas atmosphere.) Rate of change (%) = |(integrated value of chemiluminescence intensity after heat treatment / integrated value of chemiluminescence intensity before heat treatment - 1) × 100|

Description

[Technical Field]

[0001] This invention relates to a method for evaluating recycled polyarylene sulfide resin. [Background technology]

[0002] Polyarylene sulfide resins (hereinafter sometimes referred to as PAS resins), typified by polyphenylene sulfide resins (hereinafter sometimes referred to as PPS resins), have excellent heat resistance, chemical resistance, etc., and are widely used as super engineering plastics in electrical and electronic components, automotive parts, water heater parts, textiles, films, and other applications.

[0003] Meanwhile, in order to realize a sustainable society, the demand for the recycling of various materials is increasing. Large amounts of industrial waste are generated every day, and the waste plastics contained within it also require efficient reuse. However, generally, the resin contained in plastic products that have undergone molding and use deteriorates due to physical and chemical damage, and molecular chain breakage occurs. Therefore, when melt molding is performed again using it as raw material, it decomposes relatively easily with heat, and it is not possible to obtain a resin composition or molded product with the same physical properties as before recycling. For this reason, fiber reinforcement materials and additives are added, or non-recycled resin raw materials (virgin resin raw materials) are added to improve the physical properties. For example, Patent Document 1 discloses a resin composition that contains a specific amount of cyclic polyphenylene sulfide compound as a melt stabilizer for the purpose of minimizing the deterioration of mechanical properties even when recycled and used. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-77408 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, to date, there has been no established quantitative indicator for the extent to which PAS resin decomposes or deteriorates due to heat when recycled. Therefore, evaluation has been conducted by creating molded products and measuring their physical properties, or indirectly by measuring melt viscosity.

[0006] Therefore, the problem that this invention aims to solve is to provide a method for evaluating the thermal decomposition behavior of PAS resin quickly and easily. [Means for solving the problem]

[0007] As a result of various studies, the inventors discovered that the thermal decomposition behavior of PAS resin can be evaluated from the change in chemiluminescence intensity before and after melting, leading to the completion of the present invention. In particular, by applying this evaluation method to recycled PAS resin, it is believed that recycled PAS resin that is less susceptible to thermal degradation during recycling can be selected and reused.

[0008] In other words, the present invention encompasses the following aspects. [1] A method for evaluating PAS resin, including evaluating its thermal decomposition behavior from the following rate of change. Rate of change (%) = |(integrated value of chemiluminescence intensity after heat treatment / integrated value of chemiluminescence intensity before heat treatment - 1) × 100| [2] Prepare sample A and sample B, which are obtained by separating at least a portion from the PAS resin. To measure the integrated value of the chemiluminescence intensity of sample A, The sample B is heat-treated, and then the integrated value of the chemiluminescence intensity is measured. The degradation behavior of the PAS resin is evaluated from the rate of change of the integrated value of sample B relative to the integrated value of sample A. A method for evaluating PAS resin, including the resin itself. [3] The method for evaluating PAS resin according to [1] or [2], further comprising obtaining an estimated value of at least one indicator selected from the group consisting of melt viscosity, mechanical properties, and amount of generated gas from the cumulative value of the chemiluminescence intensity. [4] The method for evaluating the PAS resin according to [3], further comprising preparing a calibration curve representing the relationship between at least one or more indicators selected from the group consisting of melt viscosity, mechanical properties, and amount of generated gas and the integrated value of the chemiluminescence intensity. [5] The method for evaluation according to [1] to [4], wherein the measurement of the integrated value of the chemiluminescence intensity is a method of measuring the integrated value of the chemiluminescence intensity when the sample A and the sample B are heated from room temperature to 50 to 200 ° C in an inert gas atmosphere and then switched to an oxidizing gas atmosphere and held at 50 to 300 ° C. [6] The method for evaluation according to [1] to [5], wherein in the measurement of the chemiluminescence intensity, the inert gas is nitrogen and the oxidizing gas is oxygen. [7] The method for evaluation according to [1] to [6], wherein the PAS resin is a recycled PAS resin. [8] The method for evaluation according to [7], wherein the recycled PAS resin is obtained by pulverizing a resin composition or a molded product containing at least a PAS resin, or is obtained by extracting from a resin composition or a molded product containing at least a PAS resin. [Effect of the Invention]

[0009] According to the present invention, it is possible to provide a method for easily evaluating the thermal degradation susceptibility of a PAS resin in a short time. [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. Further, when a plurality of upper limit values 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 Evaluating PAS Resin] The evaluation method of the PAS resin of the present disclosure is an evaluation method of the PAS resin including evaluating the thermal decomposition behavior from the change rate of the integrated value of the chemiluminescence intensity. Another evaluation method of the PAS resin of the present disclosure includes preparing sample A and sample B obtained by separating at least a part from the PAS resin, measuring the integrated value of the chemiluminescence intensity of the sample A, heat-treating the sample B and then measuring the integrated value of the chemiluminescence intensity, and evaluating the thermal decomposition behavior of the PAS resin from the change rate of the integrated value of the sample B with respect to the integrated value of the sample A. Details will be described below.

[0012] <PAS resin> The PAS resin used in the present embodiment has a resin structure having a structure in which an aromatic ring and a sulfur atom are bonded as a repeating unit. Specifically, the following general formula (1)

[0013]

Chemical formula

[0014]

Chemical formula

[0015] Here, the structural site represented by the general formula (1) is such that R 1 and R 2 in the formula are preferably hydrogen atoms from the viewpoint of the mechanical strength of the PAS resin. In that case, those bonded at the para position represented by the following formula (3) and those bonded at the meta position represented by the following formula (4) are exemplified.

[0016] [ka] Among these, the bond of the sulfur atom to the aromatic ring in the repeating unit is particularly preferable in terms of the heat resistance of the PAS resin if it is bonded at the para position as represented by the general formula (3).

[0017] Furthermore, the PAS resin includes not only the structural parts represented by the general formulas (1) and (2), but also the following structural formulas (5) to (8).

[0018] [ka] The structural components represented by the above general formulas (1) and (2) may be included in an amount of 30 mol% or less of the total of the structural components represented by the above general formulas (1) and (2). In particular, in this disclosure, it is preferable that the structural components represented by the above general formulas (5) to (8) be 10 mol% or less, from the viewpoint of the heat resistance and mechanical strength of PAS. When the above general formulas (5) to (8) are included in the PAS resin, the bonding mode may be either a random copolymer or a block copolymer.

[0019] Furthermore, the PAS resin may have naphthyl sulfide bonds or the like in its molecular structure, but it is preferable that the amount of these bonds is 3 mol% or less, and particularly preferable that it is 1 mol% or less, relative to the total number of moles of other structural parts.

[0020] Furthermore, the physical properties of the PAS resin are not particularly limited as long as they do not impair the effects of the present invention, but are as follows.

[0021] (Melting viscosity) The melt viscosity of the PAS resin used in this embodiment is not particularly limited, but a good balance between processability and toughness is achieved, so a melt viscosity (V6) measured at 300°C is preferably 1 to 800 Pa·s, more preferably 5 to 400 Pa·s, and even more preferably 10 to 300 Pa·s. However, the melt viscosity (V6) is measured using a Shimadzu CFT-500D flow tester on the PAS resin at 300°C with a load of 1.96 × 10⁻⁶. 6 The measured melt viscosity was obtained after holding the mixture at Pa and L / D = 10(mm) / 1(mm) for 6 minutes.

[0022] (Non-Newtonian exponents) The non-Newtonian index of the PAS resin used in this embodiment is not particularly limited, but is preferably in the range of 0.90 or higher and 2.00 or lower. When a linear PAS resin is used, the non-Newtonian index is preferably in the range of 0.90 or higher, more preferably in the range of 0.95 or higher, more preferably in the range of 1.50 or lower, and more preferably in the range of 1.20 or lower. Such a PAS resin has excellent mechanical strength and fluidity. However, in this disclosure, the non-Newtonian index (N value) is a value calculated using the following formula by measuring the shear rate (SR) and shear stress (SS) using a capillograph under the conditions of melting point +20°C and the ratio of orifice length (L) to orifice diameter (D), L / D = 40. The closer the non-Newtonian index (N value) is to 1, the closer the structure is to linear, and the higher the non-Newtonian index (N value), the more branched the structure is.

[0023]

number

[0024] (Manufacturing method) The method for producing the PAS resin is not particularly limited, but examples include: (Method 1) polymerizing a dihalogeno-aromatic compound in the presence of sulfur and sodium carbonate, with the addition of a polyhalogeno-aromatic compound or other copolymerizing component if necessary; (Method 2) polymerizing a dihalogeno-aromatic compound in a polar solvent in the presence of a sulfidating agent, with the addition of a polyhalogeno-aromatic compound or other copolymerizing component if necessary; (Method 3) self-condensing p-chlorthiophenol, with the addition of other copolymerizing components if necessary; (Method 4) melt-polymerizing a diiodo-aromatic compound and elemental sulfur under reduced pressure in the presence of a polymerization inhibitor which may have functional groups such as carboxyl groups or amino groups. Among these methods, Method 2 is the most versatile and preferred. During the reaction, alkali metal salts of carboxylic acids or sulfonic acids, or alkali hydroxides may be added to adjust the degree of polymerization. Among the above (manufacturing method 2) methods, there is a method for producing PAS resin by introducing a hydrated sulfidating agent into a mixture containing a heated organic polar solvent and a dihalogeno-aromatic compound at a rate at which water can be removed from the reaction mixture, and reacting the dihalogeno-aromatic compound and the sulfidating agent in the organic polar solvent with a polyhalogeno-aromatic compound as needed, and controlling the amount of water in the reaction system to be in the range of 0.02 to 0.5 moles per mole of the organic polar solvent (see Japanese Patent Publication No. 07-228699), and solid A Particularly preferred is a product obtained by adding a dihalogeno-aromatic compound and, if necessary, a polyhalogeno-aromatic compound or other copolymerizing component in the presence of a rucali metal sulfide and an aprotic polar organic solvent, and reacting the alkali metal hydrosulfide and the alkali metal salt of an organic acid while controlling the amount of alkali metal salt of the organic acid in the range of 0.01 to 0.9 moles per mole of sulfur source and the amount of water in the reaction system to be 0.02 moles or less per mole of aprotic polar organic solvent (see WO2010 / 058713 pamphlet).Specific examples of dihalogenoaromatic compounds include p-dihalobenzene, m-dihalobenzene, o-dihalobenzene, 2,5-dihalotoluene, 1,4-dihalonaphthalene, 1-methoxy-2,5-dihalobenzene, 4,4'-dihalobiphenyl, 3,5-dihalobenzoic acid, 2,4-dihalobenzoic acid, 2,5-dihalonitrobenzene, 2,4-dihalonitrobenzene, 2,4-dihaloanisole, p,p'-dihalodiphenyl ether, 4,4'-dihalobenzophenone, 4,4'-di Examples include halodiphenylsulfones, 4,4'-dihalodiphenyl sulfoxides, 4,4'-dihalodiphenyl sulfides, and compounds having an alkyl group with 1 to 18 carbon atoms in the aromatic ring of each of the above compounds. Examples of polyhalogenoaromatic compounds include 1,2,3-trihalobenzene, 1,2,4-trihalobenzene, 1,3,5-trihalobenzene, 1,2,3,5-tetrahalobenzene, 1,2,4,5-tetrahalobenzene, and 1,4,6-trihalonaphthalene. Furthermore, it is desirable that the halogen atoms contained in each of the above compounds be chlorine atoms and bromine atoms.

[0025] The post-treatment method for the reaction mixture containing the PAS resin obtained by the polymerization step is not particularly limited, but for example, (post-treatment 1) after the polymerization reaction is completed, first the reaction mixture is treated as is, or an acid or base is added, and the solvent is removed under reduced pressure or atmospheric pressure, and then the solid after solvent removal is washed once or twice or more with a solvent such as water, the reaction solvent (or an organic solvent having equivalent solubility to the low molecular weight polymer), acetone, methyl ethyl ketone, or alcohols, and then neutralized, washed with water, filtered and dried, or (post-treatment 2) after the polymerization reaction is completed, the reaction mixture is treated with a solvent such as water, acetone, methyl ethyl ketone, alcohols, ethers, halogenated hydrocarbons, aromatic hydrocarbons, or aliphatic hydrocarbons (solubilable in the polymerization solvent used and poorly soluble in at least PAS). Methods include adding a solvent (as a medium) as a precipitating agent to precipitate solid products such as PAS and inorganic salts, then filtering, washing, and drying them; (post-treatment 3) after the polymerization reaction is complete, adding a reaction solvent (or an organic solvent having equivalent solubility to the low molecular weight polymer) to the reaction mixture and stirring, then filtering to remove the low molecular weight polymer, washing once or twice or more with a solvent such as water, acetone, methyl ethyl ketone, or alcohols, then neutralizing, washing with water, filtering, and drying; (post-treatment 4) after the polymerization reaction is complete, adding water to the reaction mixture and washing with water, filtering, adding acid during water washing as needed for acid treatment, and then drying; (post-treatment 5) after the polymerization reaction is complete, filtering the reaction mixture, washing once or twice or more with the reaction solvent as needed, and then further washing with water, filtering, and drying. Among these methods, method (post-treatment 4) is preferred because it yields a PAS resin having carboxyl groups at the molecular ends of the PAS resin.

[0026] Furthermore, in the post-treatment methods exemplified above (Post-treatment 1) to (Post-treatment 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.

[0027] Furthermore, the PAS resin used in this embodiment may be newly polymerized PAS resin using the method described above, or recycled PAS resin may be used. The raw materials (history) of the recycled PAS resin are not particularly limited and may be post-consumer recycled materials (so-called PCR materials) or post-industry recycled materials (so-called PIR materials). Specifically, PIR materials include dust and chips generated when manufacturing PAS resin or compositions containing at least PAS resin, or sprues or runners or off-spec molded products recovered when manufacturing molded products containing at least PAS resin. PCR materials include molded products containing at least PAS resin that have been used as products once. As a method for obtaining recycled PAS resin from these, for example, one method is to crush or crush the above-mentioned PIR materials or PCR materials. Alternatively, PAS resin can be extracted from the above-mentioned PIR materials or PCR materials and used. Specifically, this includes PAS resin obtained by heating the above-mentioned PIR materials or PCR materials in an organic polar solvent to dissolve the contained PAS resin, and then performing the above-mentioned post-treatment on the resulting solution.

[0028] When using recycled PAS resin, it may be PAS resin recycled from PAS resin compositions or PAS resin molded products that contain components other than PAS resin. However, from the viewpoint of measurement accuracy, it is preferable that the PAS resin is 70 parts by mass or more, more preferably 80 parts by mass or more, and even more preferably 90 parts by mass or more, per 100 parts by mass of resin components contained in the pulverized product. Optional components to be included in the recycled PAS resin include fillers, colorants, antistatic agents, antioxidants, heat stabilizers, UV stabilizers, UV absorbers, foaming agents, flame retardants, flame retardant aids, rust inhibitors, and known and commonly used additives such as mold release agents, antibacterial agents, antiviral agents, and coupling agents, as well as synthetic resins other than PAS resin.

[0029] In this embodiment, first, samples A and B are prepared by separating at least a portion from the PAS resin. Samples A and B are separated from the same batch of PAS resin in order to evaluate the change in measured values ​​due to heat treatment in a later step. There are no particular limitations on the amount, and it can be adjusted as appropriate according to the measurement conditions, but it is preferable that the amounts of sample A and sample B are the same.

[0030] In this embodiment, sample B is heat-treated before measuring its chemiluminescence intensity. The conditions for the heat treatment, such as the melting temperature and melting time, are not particularly limited. For example, the temperature can be appropriately selected according to the melt molding conditions of the PAS resin, and it is preferable to select a temperature between the melting point + 10°C and the melting point + 100°C. The melting time can be appropriately selected according to the molding conditions of the resin, with the time required for the PAS resin to be sufficiently molten being the lower limit. By performing heat treatment under these conditions, the thermal degradation behavior of the PAS resin before and after melt molding can be appropriately evaluated.

[0031] In this embodiment, the method for measuring the chemiluminescence intensity of sample A and sample B is not particularly limited, but for example, it can be measured under the following conditions. Sample A and sample B should be measured under the same conditions. A smooth film is produced from PAS resin. For example, a smooth film is produced by melting the resin at 250-350°C, immediately pressing it, and then rapidly cooling it. The PAS resin film is heated at a constant rate from room temperature to a specific temperature of 50-200°C under an inert gas atmosphere, then switched to an oxidizing gas atmosphere and held isothermally at a specific temperature of 50-300°C. The cumulative value of the chemiluminescence intensity (cps; Counts per Second) for a certain period of time immediately after switching to the oxidizing gas atmosphere is measured.

[0032] In the measurement of chemiluminescence intensity described above, conditions other than temperature can be set within the following ranges. 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

[0033] PAS resin exhibits weak chemiluminescence, which is presumed to originate from radicals (e.g., phenyl radicals) or active groups (e.g., terminal SH groups) in the PAS chain. Therefore, it is presumed that the content of active groups generated by the decomposition of PAS resin can be estimated by measuring the chemiluminescence intensity of the PAS resin. However, the above mechanism is merely a hypothesis, 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.

[0034] In this embodiment, the degradation behavior of the polyarylene sulfide resin is evaluated from the rate of change of the integrated chemiluminescence intensity of sample B relative to the integrated chemiluminescence intensity of sample A. That is, in this disclosure, the rate of change of chemiluminescence intensity is expressed as rate of change (%) = |(integrated chemiluminescence intensity after heat treatment / integrated chemiluminescence intensity before heat treatment - 1) × 100|, and is an absolute value. The smaller this rate of change, the less degradation of the resin due to melting is evaluated, and the larger the rate of change, the greater the degradation of the resin due to melting is evaluated.

[0035] In this embodiment, it is possible to obtain estimated values ​​of at least one indicator selected from the group consisting of melt viscosity, mechanical properties, and generated gas amount from the integrated value of the chemiluminescence intensity of sample B. In this case, the estimated values ​​can be obtained by preparing a calibration curve that shows the relationship between chemiluminescence intensity and at least one indicator selected from the group consisting of melt viscosity, mechanical properties, and generated gas amount, using the method described later. Examples of melt viscosity include melt viscosity measured using a flow tester, melt flow rate, melt volume rate, capillary rheometer, etc. Examples of mechanical properties include tensile properties, bending properties, impact resistance properties, fatigue properties, creep properties, thermal shock resistance properties, viscoelasticity, and wear resistance properties. Examples of generated gas amount include weight loss during heating and the amount of specific gas components generated. Alternatively, estimated values ​​of the rate of change of the indicators described above can be obtained from the rate of change of the integrated value of chemiluminescence intensity.

[0036] In this embodiment, estimated values ​​of the above-mentioned indicators for PAS resin can also be estimated from a pre-prepared calibration curve. That is, estimated values ​​of at least one indicator selected from the group consisting of melt viscosity, mechanical properties, and generated gas amount can be estimated from the integrated value of the chemiluminescence intensity of sample B from a pre-prepared calibration curve. The calibration curve can be created, for example, by the least squares method using the chemiluminescence intensity change rate obtained from the chemiluminescence intensity of untreated PAS resin and PAS resin heat-treated under several treatment conditions, and the measured indicator (e.g., melt viscosity).

[0037] By using the evaluation method described above, the state of the resin can be determined based on the rate of change of the cumulative chemiluminescence intensity before and after melting. Alternatively, an estimated index value can be set in advance, and the cumulative chemiluminescence intensity after melting can be calculated using a calibration curve based on that value, and the resin can be sorted based on that value. As a criterion for judgment, for example, a value of 50% or more, 70% or more, or 90% or more of the index value of the PAS resin before recycling may be used. It can be appropriately selected according to the design philosophy. Furthermore, PAS resin excluded in the sorting process can be recovered in a lower molecular weight grade, used as a depolymerization raw material, or used as an organic filler in resins with a lower melting point than PAS resin.

[0038] <Composition / Applications, etc.>

[0039] The recycled PAS resin obtained by the above method can be mixed with fillers, other resins, or virgin PAS resin, and then melt-kneaded to produce molded products with excellent heat resistance, moldability, and dimensional stability, either directly or after being first formed into pellets, by various melt processing methods such as injection molding, extrusion molding, compression molding, and blow molding, similar to conventional PAS resin. To further improve performance such as strength, heat resistance, and dimensional stability, it is also possible to use it in combination with various fillers, within the limits that do not impair the objectives of the present invention. Examples of fillers include fibrous fillers and inorganic fillers. Furthermore, small amounts of release agents, colorants, heat stabilizers, UV stabilizers, foaming agents, rust inhibitors, flame retardants, lubricants, and coupling agents can be included as additives during the molding process, within the limits that do not deviate from the objectives of the present invention. In addition, synthetic resins and elastomers as described below can be mixed and used in the same manner.

[0040] The 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 components 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]

[0041] 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.

[0042] <Examples 1-9 and Reference Examples 1-9> The following evaluations were performed using the PPS resins listed in Table 1. For the heat treatment, the PPS resins were heated to the temperatures and times shown in Table 1 until they were completely melted.

[0043] (1) Evaluation of the rate of change in melt viscosity 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 was measured after holding the mixture for 6 minutes at a ratio of L / D = 10(mm) / 1(mm). The rate of change in melt viscosity was calculated using the following formula. The results are shown in Table 2. [Calculation formula] • Vis0; Measurement of the melt viscosity of PPS resin before pretreatment. • Vis1; Measurement of melt viscosity of PPS resin before and after pretreatment. • (Melting viscosity change rate, %) = |(Vis1 / Vis0-1) × 100|

[0044] (2) Measurement of chemiluminescence intensity and calculation of rate of change The measurement was performed using a "Chemiluminescence Analyzer CLA-FS5" manufactured by Tohoku Denshi Sangyo Co., Ltd. After melting and pressing PPS resin at 350 °C, a smooth film was prepared by rapid cooling. The prepared film (0.10 g) was placed in the sample chamber of the apparatus, and the temperature inside the chamber was raised from 40 °C to 150 °C under a nitrogen atmosphere, maintained at 150 °C for 5 minutes, and then cooled to 75 °C. The measurement atmosphere was switched from nitrogen to oxygen, maintained at 75 °C for 5 minutes, and then the temperature was raised to 270 °C and maintained at 270 °C for 20 minutes as it was. The value obtained by dividing the integrated value of the chemiluminescence intensity [count / second] shown by the sample during the 20-minute maintenance at 270 °C by the sample weight was taken as the measured value. The change rate of chemiluminescence intensity was calculated using the following formula. The results are shown in Table 1. [Calculation formula] ·CL0: Measured value of chemiluminescence intensity of PPS resin before melting ·CL1: Measured value of chemiluminescence intensity of PPS resin after melting ·(Change rate of chemiluminescence intensity, %) = |(CL1 / CL0 - 1) × 100|

[0045] (3) Calculation of correlation coefficient between change rate of melt viscosity and change rate of chemiluminescence intensity (evaluation of calibration curve) Using the numerical values of each example and reference example, the correlation coefficient R between the change rate of melt viscosity and the change rate of chemiluminescence intensity was calculated by the least squares method 2 The correlation coefficient R 2 was about 0.94.

[0046]

Table 1

[0047]

Table 2

[0048] The resins in Tables 1 and 2 are as follows. PPS -1: PPS resin obtained by the following Production Example 1. PPS -2: Recycled PPS resin obtained by the following Production Example 2. PPS-3: Recycled PPS resin obtained by manufacturing example 3 below.

[0049] <Manufacturing Example 1> 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.

[0050] NMP contained in the slurry obtained after cooling was removed by vacuum distillation at 150°C for 2 hours. 142 kg of ion-exchanged water at 70°C was added to this mixture and stirred for 10 minutes, then filtered. 190 kg of ion-exchanged water at 70°C was added to the filtered cake for cake washing. 71 kg of the resulting hydrated cake and ion-exchanged water were placed in an autoclave and stirred at 220°C for 30 minutes. After cooling to room temperature, the mixture was filtered, and 190 kg 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-1.

[0051] <Manufacturing Example 2> A molded product containing 95 parts by mass of PPS resin (post-consumer recycled product) was crushed using a benchtop crusher, and the crushed material was classified using a 500 μm mesh sieve. The components that passed through the sieve were collected as recycled PPS resin (PPS-2).

[0052] <Manufacturing Example 3> An autoclave with a bottom valve and a high-temperature filter connected below the bottom valve were installed. 20 g of a molded product made from a PPS resin composition (post-industry recycled product) containing 55 parts by mass of PPS resin and 40 parts by mass of glass fiber, and 300 g of NMP were placed in the autoclave and stirred at 250°C for 30 minutes. The bottom valve was opened, and the contents were transferred to a filter with a 250°C, nitrogen atmosphere. The filter was pressurized to 0.2 MPa with nitrogen, and the mixture was filtered to separate the PPS solution from the NMP insoluble matter. The PPS solution was cooled to room temperature to precipitate the PPS resin. The obtained slurry was filtered, and 480 g of ion-exchanged water at 70°C was added to the filtered cake to wash the cake. 180 g of ion-exchanged water at 70°C was added to the obtained water-containing cake and stirred for 10 minutes. The obtained slurry was filtered, and 480 g of ion-exchanged water at 70°C was added to the filtered cake to wash the cake. Subsequently, it was dried at 120°C for 4 hours to obtain recycled PPS resin (PPS-3).

[0053] Comparing the examples and reference examples in Tables 1 and 2, it can be seen that the evaluation method in the examples allows for measurements to be performed in a shorter time. Furthermore, the correlation coefficient between the rate of change in chemiluminescence intensity and the rate of change in melt viscosity was 0.94, indicating that the evaluation method in the examples can evaluate the degradation behavior of the resin in the same way as conventional melt viscosity evaluations. It was also suggested that the rate of change in melt viscosity (the value of melt viscosity when melted and thermally degraded) can be estimated using the rate of change in chemiluminescence intensity.

Claims

1. A method for evaluating polyarylene sulfide resins, including evaluating the thermal decomposition behavior from the following rate of change. Rate of change (%) = |(integrated value of chemiluminescence intensity after heat treatment / integrated value of chemiluminescence intensity before heat treatment - 1) × 100| (However, the heat treatment involves thoroughly melting the polyarylene sulfide resin at a temperature of 10°C to 100°C above its melting point, and the measurement of the integrated chemiluminescence intensity is performed by heating the material from room temperature to 50-200°C under an inert gas atmosphere, then switching to an oxidizing gas atmosphere and holding it at 50-300°C, and measuring the integrated chemiluminescence intensity for a certain period of time immediately after switching to the oxidizing gas atmosphere.)

2. Prepare sample A and sample B, which are obtained by separating at least a portion from polyarylene sulfide resin. To measure the integrated value of the chemiluminescence intensity of sample A, The sample B is heat-treated, and then the integrated value of the chemiluminescence intensity is measured. The thermal decomposition behavior of the polyarylene sulfide resin is evaluated from the rate of change of the integrated value of sample B relative to the integrated value of sample A. A method for evaluating polyarylene sulfide resins, including [specific components]. (However, the heat treatment is a process in which sample B is sufficiently melted at a temperature of the melting point of polyarylene sulfide resin + 10°C to the melting point + 100°C, and the integrated value of chemiluminescence intensity is measured by heating from room temperature to 50 to 200°C under an inert gas atmosphere, then switching to an oxidizing gas atmosphere and holding at 50 to 300°C, and measuring the integrated value of chemiluminescence intensity for a certain period of time immediately after switching to the oxidizing gas atmosphere.)

3. Furthermore, estimates of at least one indicator selected from the group consisting of melt viscosity, mechanical properties, and generated gas amount are obtained from the integrated value of the chemiluminescence intensity. A method for evaluating a polyarylene sulfide resin according to claim 1 or 2, comprising:

4. The evaluation method involves preparing a calibration curve that shows the relationship between at least one index selected from the group consisting of melt viscosity, mechanical properties, and generated gas volume, and the integrated value of the chemiluminescence intensity. A method for evaluating a polyarylene sulfide resin according to claim 3, further comprising:

5. The evaluation method according to claim 1 or 2, wherein the inert gas is nitrogen and the oxidizing gas is oxygen in the measurement of the chemiluminescence intensity.

6. The evaluation method according to claim 1 or 2, wherein the polyarylene sulfide resin is a recycled polyarylene sulfide resin.

7. The evaluation method according to claim 6, wherein the recycled polyarylene sulfide resin is obtained by pulverizing a resin composition or molded article containing at least a polyarylene sulfide resin, or by extracting it from a resin composition or molded article containing at least a polyarylene sulfide resin.

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