Polyarylene sulfide resin

Abstract

The present invention provides a polyarylene sulfide resin that exhibits significant color changes before and after molding and is less prone to mold contamination, as well as a method for producing the same. [Solution] A polyarylene sulfide resin that satisfies the following (1) to (3). (1) The value of the lightness L*1 of the hot-pressed product in the L*a*b* color space is within the range of 0 to 50. (2) The value of the lightness L*2 in the L*a*b* color space of the powder obtained by dissolving and crystallizing the polyarylene sulfide resin in an organic solvent is in the range of 60 to 100. (3) The value of "L*2 / L*1" is 2.0 or greater.

Description

Technical Field

[0005] ,

[0004] , , , , , ,

[0006]

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

Background Art

[0002] Polyarylene sulfide (hereinafter sometimes abbreviated as PAS), typified by polyphenylene sulfide (hereinafter sometimes abbreviated as PPS), is an engineering plastic having excellent heat resistance, chemical resistance, flame retardancy, and electrical properties. As a resin composition containing fillers such as glass fiber and carbon fiber and additives such as elastomer, it is used mainly for automotive parts, water-related parts, and electrical and electronic parts.

[0003] Also, it is known that a black pigment such as carbon black is added to a resin composition containing a PAS resin for the purpose of coloring or the like. However, a composition containing a large amount of a black pigment has a black color tone and is difficult to distinguish from foreign matters such as metal, fiber, dust, and dirt, and may be mixed in during molding. When foreign matters are mixed in, it causes poor appearance and deterioration of mechanical properties, so a method for preventing the mixing of foreign matters is required.

[0004] Conventionally, it has been known that when crosslinked PAS is used, a dark-colored molded product can be obtained without adding carbon black. However, since the color tone of the composition is brown, it is inferior in terms of ease of distinguishing from foreign matters.

[0005] In Patent Document 1, a method for improving heat dissipation by blending carbon black to make a molded product black is described. However, since the composition was still black, it was difficult to distinguish it from foreign matters.

[0006] In Patent Document 2, a method is disclosed in which by adding iron or an iron compound to PAS, a dark-colored PAS resin molded product can be obtained even when the amount of carbon black added is reduced. However, in order to obtain a sufficiently black molded product, it is necessary to increase the blending amounts of iron or an iron compound and carbon black, and there is a problem that it becomes difficult to distinguish the composition from foreign matters. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-68971 [Patent Document 2] Japanese Patent Application Publication No. 9-194726 [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to provide a PAS resin that exhibits significant color changes before and after molding and is less prone to mold contamination, as well as a method for producing the same. [Means for solving the problem]

[0009] This invention was made to solve at least some of the above-mentioned problems and can be realized by providing the following. 1. A polyarylene sulfide resin that satisfies the following conditions (1) to (3). (1) The value of the lightness L*1 of the hot-pressed product in the L*a*b* color space is within the range of 0 to 50. (2) The value of the lightness L*2 in the L*a*b* color space of the powder obtained by dissolving and crystallizing the polyarylene sulfide resin in an organic solvent is in the range of 60 to 100. (3) The value of "L*2 / L*1" is 2.0 or greater. 2. The polyarylene sulfide resin according to claim 1, wherein the value of L*2 is in the range of 70 to 100. 3. The polyarylene sulfide resin according to claim 1 or 2, wherein the value of L*1 is in the range of 0 to 40. 4. The polyarylene sulfide resin according to 1 or 2 above, wherein the value of "L*2 / L*1" is 2.5 or greater. 5. The polyarylene sulfide resin according to 1 or 2 above, wherein the content of oligoarylene sulfide with a molecular weight of 600 to 1600 is less than 2.0% by mass. 6. The polyarylene sulfide resin according to 5, wherein the content of the oligoarylene sulfide is less than 0.5% by mass. 7. Polyarylene sulfide resin powder comprising the polyarylene sulfide resin described in 1 or 2 above, wherein the median diameter is 1 to 200 μm. 8. The polyarylene sulfide resin according to claim 1 or 2, wherein the chromaticity a* and b* values ​​of the hot-pressed molded product are each within the range of -20 to 20 in the L*a*b* color space, and the chromaticity a* and b* values ​​of the powder are each within the range of -20 to 20 in the L*a*b* color space. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a PAS resin that exhibits significant color changes before and after molding and is less likely to cause mold contamination, as well as a method for producing the same.

[0011] This PAS resin has a high brightness in powder form, making it easy to distinguish from foreign matter and prevent contamination, thus reducing the possibility of appearance defects and deterioration of mechanical properties. Furthermore, even with a reduced amount of black pigment added, sufficiently dark molded products can be obtained, leading to improvements in mold contamination and material purging efficiency. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described in detail below.

[0013] [PAS resin] In this invention, PAS refers to a homopolymer or copolymer whose main constituent unit is a repeating unit of formula -(Ar-S)-. Here, "main constituent unit" means that the repeating unit is present in an amount of 80 mol% or more of all constituent units of the PAS. Examples of Ar include any unit represented by the following formulas (A) to (K), but the unit represented by formula (A) is particularly preferred.

[0014] [ka]

[0015] (R1 and R2 are substituents selected from a hydrogen atom, an alkyl group, an alkoxy group, and a halogen group, and R1 and R2 may be the same or different).

[0016] Generally, PAS may contain branched units or crosslinked units represented by the following formulas (L) to (N), etc., and branched / crosslinked units can be introduced by copolymerization with the addition of a polyhalogenated aromatic compound having three or more halogens or by oxidative crosslinking by heating in the presence of oxygen. The introduction of branched / crosslinked units causes an increase in viscosity and an improvement in tensile strength.

[0017]

Chemical formula

[0018] Also, the PAS in the present invention may be any of a random copolymer, a block copolymer, and a mixture thereof containing the above repeating unit.

[0019] Typical examples of these include polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfide ketone, random copolymers, block copolymers, and mixtures thereof. Particularly preferred PAS includes polyphenylene sulfide resin containing 80 mol% or more, particularly 90 mol% or more of the p-phenylene sulfide unit shown below as the main constituent unit of the polymer.

[0020]

Chemical formula

[0021] The PAS resin in this invention contains 90% by mass or more of PAS. To enhance the effects of this invention, it is preferable to contain 95% by mass or more of PAS, and more preferably 98% by mass or more. Furthermore, the PAS resin obtained by this invention can be used with fillers and additives added, as long as the effects of this invention are not impaired. Specific examples of fillers and additives are described below, but the fillers and additives used in the PAS resin obtained by this invention are not limited to these.

[0022] Examples of inorganic fillers include fibrous inorganic fillers such as glass fibers, glass milled fibers, carbon fibers, potassium titanate whiskers, zinc oxide whiskers, calcium carbonate whiskers, wollastonite whiskers, aluminum borate whiskers, alumina fibers, silicon carbide fibers, ceramic fibers, gypsum fibers, metal fibers, and basalt fibers; and non-fibrous inorganic fillers such as talc, wollastonite, zeolite, sericite, mica, kaolin, clay, mica, ferrite, pyrophyllite, bentonite, aluminasilicate, silicon oxide, magnesium oxide, alumina, zirconium oxide, titanium oxide, iron oxide, magnesium oxide, calcium carbonate, magnesium carbonate, dolomite, calcium sulfate, barium sulfate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, glass beads, glass flakes, glass powder, ceramic beads, boron nitride, silicon nitride, silicon carbide, aluminum silicate, calcium silicate, silica, graphite, carbon black, and graphite.

[0023] Examples of organic fillers include fibrous organic fillers such as polyethylene fibers, polypropylene fibers, polyester fibers, polyamide fibers, polyaramid fibers, fluororesin fibers, thermosetting resin fibers, epoxy resin fibers, polyvinylidene chloride fibers, polyvinylidene fluoride fibers, and cellulose fibers; and non-fibrous organic fillers such as ebonite powder, cork powder, and wood powder.

[0024] These fillers may be pre-treated with coupling agents such as isocyanate compounds, organosilane compounds, organotitanate compounds, organoborane compounds, and epoxy compounds before use. Sizing agents may also be used.

[0025] The PAS resin may also be an olefin copolymer resin for purposes such as improving toughness, and examples include an olefin copolymer resin having at least one functional group selected from the group consisting of epoxy groups, carboxyl groups, acid anhydride groups, amino groups, hydroxyl groups, and mercapto groups, or an olefin copolymer that does not have the above functional groups.

[0026] In PAS resin, other additives may be used to modify its properties, including resins other than olefin copolymers such as polyamide, polyethersulfone, polysulfone, polyarylsulfone, polyetherimide, polyphenylene ether, fluororesins, and polyetheretherketone; coupling agents such as epoxy compounds, amine compounds, isocyanate compounds, and anhydride compounds; antioxidants such as phenolic and phosphorus-based antioxidants; anti-coloring agents such as hypophosphate; nucleating agents such as talc, kaolin, organophosphorus compounds, and polyetheretherketone; release agents such as ethylenediamine-stearic acid-sebacic acid polycondensate and silicone compounds; and flame retardants such as phosphorus-based, bromine-based, and silicone-based agents. Colorants such as carbon black may be added, but the amount added should be as small as possible. As the amount added increases, the brightness of the PAS resin powder decreases, making it difficult to distinguish from foreign matter. Furthermore, when added in large quantities, problems such as a decrease in mechanical strength and an increase in conductivity may occur.

[0027] In this invention, the value of lightness L*1 in the L*a*b* color space of a hot-pressed molded product of PAS resin is in the range of 0 to 50, preferably in the range of 0 to 40, and more preferably in the range of 0 to 30. If the value of lightness L*1 is greater than 50, a good dark-colored molded product cannot be obtained. The hot-pressed molded product is defined as a 0.5 mm thick molded product obtained by pressing PAS resin powder at 320°C for 1 minute and then rapidly cooling it in a water bath. Furthermore, the lightness L*1 is defined as the average value of L* measured three times on the hot-pressed molded product using a spectrophotometer.

[0028] In this invention, the value of the lightness L*2 of the PAS resin powder in the L*a*b* color space is in the range of 60 to 100, preferably in the range of 70 to 100, and more preferably in the range of 80 to 100. If the value of lightness L*2 is less than 60, the brightness of the PAS resin is insufficient and it is difficult to distinguish from foreign matter. Lightness L*2 is defined as the average value of L* measured three times using a spectrophotometer on the powdered composition.

[0029] The degree of change in brightness between the PAS resin powder and the hot-pressed molded product is greater the larger the value of "L*2 / L*1", which is the ratio of brightness L*2 to brightness L*1 as described above. In this invention, this value is 2.0 or higher. It is preferably 2.5 or higher, and more preferably 3.0 or higher.

[0030] The chromaticity values ​​a* and b* of hot-pressed molded products of PAS resin in the L*a*b* color space are preferably in the range of -20 to 20, and more preferably in the range of -15 to 15. A darker molded product can be obtained when the values ​​of a* and b* are in the range of -20 to 20. Similarly, the chromaticity values ​​a* and b* of PAS resin powder in the L*a*b* color space are preferably in the range of -20 to 20, and more preferably in the range of -15 to 15. A composition that exhibits a color tone closer to white and is easily distinguishable from foreign matter can be obtained. Chromaticity a* and b* are defined as the average values ​​obtained by measuring the hot-pressed molded product or composition three times using a spectrophotometer.

[0031] PAS resins generally contain trace amounts of oligoarylene sulfide with a molecular weight of 600 to 1600. This oligoarylene sulfide volatilizes during melt molding, causing mold contamination and other problems. In the PAS resin of the present invention, the content of oligoarylene sulfide with a molecular weight of 600 to 1600 is preferably less than 2.0% by mass, more preferably less than 1.5% by mass, even more preferably less than 0.5% by mass, and most preferably less than 0.3% by mass. When the content of oligoarylene sulfide with a molecular weight of 600 to 1600 is less than 2.0 parts by mass, there is less material adhering to the mold during molding, which reduces the frequency of mold cleaning and leads to improved productivity.

[0032] The PAS resin powder preferably has a median diameter of 1 to 200 μm, more preferably 1 to 150 μm, and even more preferably 1 to 100 μm. The smaller the median diameter, the larger the L*2 value and the brighter the color, making it easier to distinguish from foreign matter. PAS resin powder with such a median diameter can be obtained by performing the process of the present invention, which involves dissolving and crystallizing PAS resin in an organic solvent. [Examples]

[0033] The following describes in detail the method for producing the PAS resin of the present invention, but the present invention is not limited to this method.

[0034] [Lightness L*] The value of lightness L*1 was calculated by hot-pressing a 0.5 mm thick molded product by pressing PAS resin powder (pellets were used only in Comparative Example 1) at 320°C for 1 minute, then rapidly cooling it in a water bath, and measuring the value using a spectroscopic colorimeter (Spectro Color Meter SE 2000, manufactured by Nippon Semilab Co., Ltd.).

[0035] The lightness L*2 value was calculated by filling a glass cell with PAS resin powder (pellets were used only in Comparative Example 1), covering the outside of the cell with cardboard, and measuring it using a spectroscopic colorimeter (Spectro Color Meter SE 2000, manufactured by Nippon Semilab Co., Ltd.).

[0036] [Chromaticity a*, b*] The same measurement method as described above for the brightness L* was used to calculate it.

[0037] [Oligoarylene sulfides with molecular weights of 600-1600] The content of oligoarylene sulfides with molecular weights of 600 to 1600 in PAS resin was calculated using high-performance liquid chromatography (HPLC) with the following method.

[0038] Approximately 10 mg of PAS resin was dissolved in approximately 5 g of 1-chloronaphthalene at 250°C. A precipitate formed upon cooling to room temperature. The 1-chloronaphthalene-insoluble components were filtered using a 0.45 μm pore size membrane filter to obtain the 1-chloronaphthalene-soluble components. The amount of oligoarylene sulfide with molecular weights of 600-1600 was quantified by HPLC analysis of the obtained soluble components, and the amount was calculated as mass% relative to 100 parts by mass of PAS resin. The HPLC measurement conditions are shown below. Equipment: Shimadzu Corporation LC-10Avp series Column: Mightysil RP-18 GP150-4.6 (5μm) Detector: Photodiode array detector (UV=270nm).

[0039] [MFR] MFR was measured according to ASTM D 1238-70 at a temperature of 315.5°C and a load of 5000g. A melt indexer manufactured by Toyo Seiki Co., Ltd. (orifice with length 8.00mm and hole diameter 2.095mm) was used, with a sample amount of 7g and a preheating time of 5 minutes from sample preparation to the start of measurement.

[0040] [Weight average molecular weight] The weight-average molecular weight (Mw) in polystyrene equivalent was calculated using gel permeation chromatography (GPC), a type of size exclusion chromatography (SEC). The GPC measurement conditions are described below. Device: Senshu Science SSC-7110 Column name: “Shodex” (registered trademark) UT806M x 2 Eluent: 1-Chloronaphthalene Detector: Differential refractive index detector Column temperature: 210℃ Pre-temperature bath temperature: 250℃ Pump constant temperature bath temperature: 50℃ Detector temperature: 210℃ Flow rate: 1.0mL / min Sample injection volume: 300 μL.

[0041] [Median diameter] Approximately 100 mg of polyarylene sulfide particles were mixed with approximately 5 mL of deionized water, and Triton X-100 was added dropwise until dispersible to prepare a dispersion. The dispersion was added to a Nikkiso Co., Ltd. laser diffraction particle size distribution analyzer (Microtrac MT3300EX II) until it reached a measurable concentration. Ultrasonic dispersion was performed in the analyzer at 30 W for 60 seconds, and the particle size distribution was measured after a measurement time of 10 seconds. The median diameter (μm) was calculated from the particle size distribution at which the cumulative frequency reached 50%.

[0042] [Raw material PPS(1)] In an autoclave equipped with a stirrer and a bottom valve, 8.27 kg (70.0 mol) of 47.5% sodium hydroxide, 2.94 kg (70.6 mol) of 96% sodium hydroxide, 11.45 kg (115.5 mol) of N-methyl-2-pyrrolidone (NMP), 1.89 kg (23.1 mol) of sodium acetate, and 5.50 kg of deionized water were charged. The mixture was gradually heated to 245°C over approximately 3 hours under atmospheric pressure while passing nitrogen through it. After distilling off 9.77 kg of water and 0.28 kg of NMP, the reaction vessel was cooled to 200°C. The amount of residual water in the system per 1.00 mol of alkali metal sulfide charged was 1.06 mol, including the water consumed in the hydrolysis of NMP. The amount of hydrogen sulfide released was 0.02 mol per 1 mol of alkali metal sulfide charged.

[0043] 10.42 kg (70.86 mol) of p-dichlorobenzene and 9.37 kg (94.5 mol) of NMP were added, the reaction vessel was sealed under nitrogen gas, and the temperature was raised from 200°C to 270°C at a rate of 0.6°C / min while stirring at 240 rpm, and the reaction was carried out at 270°C for 140 minutes. Then, 2.40 kg (133 mol) of water was injected under pressure while cooling from 270°C to 250°C over 15 minutes. Subsequently, the temperature was gradually cooled from 250°C to 220°C over 75 minutes, and then rapidly cooled to near room temperature and the contents were removed.

[0044] The contents were diluted with approximately 35 liters of NMP to form a slurry, which was stirred at 85°C for 30 minutes. The slurry was then filtered through an 80-mesh wire mesh (mesh opening 0.175 mm) to obtain solid matter. The obtained solid matter was similarly washed and filtered with approximately 35 liters of NMP. The obtained solid matter was diluted with 70 liters of deionized water, stirred at 70°C for 30 minutes, and filtered through an 80-mesh wire mesh to recover the solid matter. This process was repeated a total of three times. The obtained solid matter and 32 g of acetic acid were diluted with 70 liters of deionized water, stirred at 70°C for 30 minutes, and filtered through an 80-mesh wire mesh. The obtained solid matter was further diluted with 70 liters of deionized water, stirred at 70°C for 30 minutes, and filtered through an 80-mesh wire mesh to recover the solid matter. The solid matter thus obtained was dried under a nitrogen stream at 120°C to obtain PPS(1). The obtained PPS(1) had an MFR of 300 g / 10 min.

[0045] [Raw material PPS(2)] PPS(2) was obtained in the same manner as the production method for PPS(1), except that 2.24 kg (27.3 mol) of sodium acetate, 10.32 kg (70.20 mol) of p-dichlorobenzene, and 2.40 kg (133 mol) of water were used. The obtained PPS(2) had an MFR of 100 g / 10 min.

[0046] [Raw material PPS(3)] In an autoclave equipped with a stirrer and a bottom valve, 8.27 kg (70.0 mol) of 47.5% sodium hydrosulfide, 2.91 kg (69.8 mol) of 96% sodium hydroxide, 11.45 kg (115.5 mol) of N-methyl-2-pyrrolidone (NMP), 1.89 kg (23.1 mol) of sodium acetate, and 10.5 kg of deionized water were charged. The mixture was gradually heated to 245°C over approximately 3 hours under atmospheric pressure while passing nitrogen through it. After distilling off 14.78 kg of water and 0.28 kg of NMP, the reaction vessel was cooled to 200°C. The amount of residual water in the system per 1.00 mol of alkali metal sulfide charged was 1.06 mol, including the water consumed in the hydrolysis of NMP. The amount of hydrogen sulfide released was 0.02 mol per 1 mol of alkali metal sulfide charged.

[0047] 10.45 kg (71.07 mol) of p-dichlorobenzene and 9.37 kg (94.5 mol) of NMP were added, the reaction vessel was sealed under nitrogen gas, and the temperature was raised from 200°C to 270°C at a rate of 0.6°C / min while stirring at 240 rpm. After reacting at 270°C for 100 minutes, the bottom valve of the autoclave was opened, and the contents were flushed into a stirrer-equipped container under pressurized nitrogen for 15 minutes, and stirred at 250°C for a while to remove most of the NMP.

[0048] The obtained solid material and 76 liters of deionized water were placed in an autoclave with a stirrer, washed at 70°C for 30 minutes, and then filtered by suction using a glass filter. Next, 76 liters of deionized water heated to 70°C were poured into the glass filter and filtered by suction to obtain the cake.

[0049] The resulting cake and 90 liters of deionized water were placed in an autoclave equipped with a stirrer, and acetic acid was added to bring the pH to 7. After purging the inside of the autoclave with nitrogen, the temperature was raised to 192°C and held for 30 minutes. The autoclave was then cooled and the contents were removed.

[0050] The contents were filtered by suction using a glass filter, and then 76 liters of ion-exchanged water at 70°C were poured in and filtered by suction to obtain the cake. The obtained cake was dried under a nitrogen stream at 120°C to obtain dried PPS(3). The obtained PPS(3) had an MFR of 700 g / 10 min.

[0051] [Raw material PPS(4)] The aforementioned PPS(3) was placed in a heating device with a stirrer and heat-treated at 220°C for 12 hours at an oxygen concentration of 2% to obtain PPS(4). For the heat treatment at an oxygen concentration of 2%, 0.18 liters / min of air and 1.78 liters / min of nitrogen were introduced into the heating device, and the oxygen concentration was measured by placing an oxygen concentration meter inside the heating device. The obtained PPS(4) had an MFR of 450 g / 10 min.

[0052] [Raw material PPS(5)] PPS(3) was heat-treated at 200°C under an oxygen stream until the MFR reached 140 g / 10 min to obtain PPS(5).

[0053] [Bag filter PCR material] Fibers composed of PPS were recovered from bag filters used in a thermal power plant, washed with water, and pulverized to obtain bag filter PCR material. The bag filter PCR material consisted of approximately 97% by mass of PPS, approximately 2% by mass of PTFE, and approximately 1% by mass of ash. Analysis of the ash revealed the presence of iron compounds and glass particles. The MFR of the bag filter PCR material was 10 g / 10 min, and the weight-average molecular weight of PPS in the bag filter PCR material was 54,000.

[0054] [Process] The following describes the steps for obtaining the PAS resin of the present invention, but the PAS resin of the present invention is not limited to that obtained by these steps.

[0055] A 1L autoclave equipped with a bottom valve and a high-temperature filter capable of nitrogen pressurization directly connected below the bottom valve were prepared. 50g of PPS or bag filter PCR material and 500g of NMP were placed in the autoclave as raw materials, and stirring was started at 240 rpm. After purging with nitrogen, the temperature was raised to 270°C over 30 minutes, and then held for 20 minutes to dissolve the PAS resin in the NMP. Subsequently, the bottom valve of the autoclave was opened, and the mixture was transferred to the high-temperature filter at 240°C. The high-temperature filter was pressurized with nitrogen to 0.3 MPa, and the PAS resin solution was filtered through a metal filter with a mesh size of 200 μm to separate the PAS resin solution from the insoluble components. The obtained PAS resin solution was cooled to room temperature to obtain a PAS resin slurry. The PAS resin slurry was then added to 0.3L of NMP, stirred at 80°C for 30 minutes, and filtered by suction using filter paper with a mesh size of 1 μm. The obtained slurry was added to 0.5 L of water, stirred at 80°C for 15 minutes, and filtered by suction using filter paper with a mesh size of 1 μm. After repeating the washing and suction filtration process two more times, the mixture was dried at 120°C to obtain the PAS resin of the present invention.

[0056] [Example 1] PAS resin (1) was obtained by using the bag filter PCR material as the raw material for the above process. The brightness, chromaticity, oligoarylene sulfide content, and median diameter of PAS resin (1) were calculated using the above method.

[0057] [Comparative Example 1] The raw materials PPS(1) and carbon black were dry-blended according to the composition shown in Table 1. Then, using a TEX30α twin-screw extruder (L / D=45) manufactured by Japan Steel Works Ltd. equipped with a vacuum vent, the mixture was melt-kneaded at two kneading sections, with the kneading section ratio to the total screw length being 15%, at a cylinder temperature of 300°C and a rotation speed of 200 rpm. After that, the mixture was pelletized using a strand cutter and dried at 120°C for 3 hours. The lightness, chromaticity, and oligoarylene sulfide content of the pellets were calculated using the same method.

[0058] [Comparative Example 2] The brightness, chromaticity, oligoarylene sulfide content, and median diameter of the bag filter PCR material were calculated using the method described above.

[0059] [Comparative Example 3] The lightness, chromaticity, and oligoarylene sulfide content of the raw material PPS(2) were calculated using the method described above.

[0060] [Comparative Example 4] The lightness, chromaticity, oligoarylene sulfide content, and median diameter of the raw material PPS(3) were calculated using the method described above.

[0061] [Comparative Example 5] The lightness, chromaticity, oligoarylene sulfide content, and median diameter of the raw material PPS(4) were calculated using the method described above.

[0062] [Example 2] The lightness, chromaticity, oligoarylene sulfide content, and median diameter of the raw material PPS(5) were calculated using the method described above.

[0063] [Example 3] PAS resin (2) was obtained by using the raw material PPS (5) as the raw material for the above process. The brightness, chromaticity, oligoarylene sulfide content, and median diameter of the PAS resin (2) were calculated using the above method.

[0064] [Table 1]

[0065] As shown in the examples, the present invention can provide a polyarylene sulfide resin that satisfies the following (1) to (3). (1) The value of the lightness L*1 of the hot-pressed product in the L*a*b* color space is within the range of 0 to 50. (2) The value of the lightness L*2 of the powder in the L*a*b* color space is in the range of 60 to 100. (3) The value of "L*2 / L*1" is 2.0 or greater.

[0066] Comparative Examples 1 and 2 had L*2 values ​​less than 60, making it difficult to distinguish between powder and foreign matter.

[0067] Comparative Examples 3-5 had an L*1 value greater than 50, and dark-colored molded products could not be obtained.

[0068] Comparative Example 1 contained 0.3 parts by mass of carbon black, resulting in mold contamination. Comparative Examples 4 and 5 had an oligoarylene sulfide content of 2.0% by mass or more with a molecular weight of 600 to 1600, and produced a large amount of decomposition gas at the PPS molding temperature, resulting in mold contamination. [Industrial applicability]

[0069] The PAS resin of this invention is superior in that, due to the high brightness of the powder, it is easy to distinguish from foreign matter and prevent contamination, thereby reducing the possibility of appearance defects and deterioration of mechanical properties. Furthermore, even with a reduced amount of black pigment added, sufficiently dark molded products can be obtained, which also leads to improvements in mold contamination and material purging efficiency.

Claims

1. A polyarylene sulfide resin that satisfies the following conditions (1) to (3). (1) The value of the lightness L*1 of the hot-pressed molded product in the L*a*b* color space is within the range of 0 to 50. (2) The value of the lightness L*2 in the L*a*b* color space of the powder obtained by dissolving and crystallizing the polyarylene sulfide resin in an organic solvent is in the range of 60 to 100. (3) The value of "L*2 / L*1" is 2.0 or greater.

2. The polyarylene sulfide resin according to claim 1, wherein the value of L*2 is in the range of 70 to 100.

3. The polyarylene sulfide resin according to claim 1 or 2, wherein the value of L*1 is in the range of 0 to 40.

4. The polyarylene sulfide resin according to claim 1 or 2, wherein the value of "L*2 / L*1" is 2.5 or more.

5. The polyarylene sulfide resin according to claim 1 or 2, wherein the content of oligoarylene sulfide having a molecular weight of 600 to 1600 is less than 2.0% by mass.

6. The polyarylene sulfide resin according to claim 5, wherein the content of the oligoarylene sulfide is less than 0.5% by mass.

7. A polyarylene sulfide resin powder comprising the polyarylene sulfide resin according to claim 1 or 2, wherein the median diameter is 1 to 200 μm.

8. The polyarylene sulfide resin according to claim 1 or 2, wherein the chromaticity values ​​a* and b* of the hot-pressed molded product in the L*a*b* color space are each in the range of -20 to 20, and the chromaticity values ​​a* and b* of the powder in the L*a*b* color space are each in the range of -20 to 20.

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