JP2007284700A - Method for stabilizing color tone of polyarylenesulfide resin molding and method for producing polyarylenesulfide resin composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide color tone-stabilized polyarylenesulfide resin moldings suppressed in color uneveness, brown uneven coloring, lot by lot color tone difference and the like. <P>SOLUTION: The method for stabilizing color tone of polyarylenesulfide resin moldings comprises melt-molding of a polyarylenesulfide resin composition which comprises resin components comprising 5-95 wt.% polyarylenesulfide resin of pH ≤5.0 and 95-5 wt.% polyarylenesulfide resin of pH ≥7.1 and is in a range of pH5.5-pH8.8, when measuring each pH in an acetone/water (volume ratio=1:2) mixture solvent. The method for producing the resin composition comprises blending. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for stabilizing the color tone of a polyarylene sulfide resin molded product, and more particularly, to obtain a polyarylene sulfide resin molded product in which color unevenness, brown color spots, color variation from lot to lot, etc. are suppressed. The present invention relates to a color tone stabilization method. The present invention also relates to a method for producing a polyarylene sulfide resin composition capable of giving such a molded article having excellent color tone stability.

  Polyarylene sulfide resin (hereinafter abbreviated as PAS resin) represented by polyphenylene sulfide resin (hereinafter abbreviated as PPS resin) is excellent in heat resistance, flame retardancy, chemical resistance, dimensional stability, mechanical properties, etc. Engineering plastic, and its application is expanding as electrical / electronic equipment parts, precision machine parts, automobile parts, chemical equipment parts, etc. Since the PAS resin is a thermoplastic resin, it can be molded by a general melt processing method such as injection molding, extrusion molding, compression molding, etc. as a single or as a resin composition to which various fillers such as glass fibers are added. The product can be melt-molded.

  However, the PAS resin has a problem that the color tone of the molded product varies greatly. Conventional cross-linked PPS resins [for example, Japanese Examined Patent Publication No. 45-3368 (Patent Document 1)] are applied to a relatively low molecular weight PPS resin obtained by polymerization in the presence of oxygen. It was necessary to increase the molecular weight by heat treatment and crosslinking. However, as a result of this heat treatment, the cross-linked PPS resin is colored dark brown and cannot be adjusted to a desired color tone. On the other hand, in recent years, methods for producing linear and high molecular weight PPS resins have been developed [for example, Japanese Patent Publication No. 52-12240 (Patent Document 2), Japanese Patent Publication No. 63-33775 (Patent Document 3)]. After polymerization, it became possible to obtain a white PPS resin having a high molecular weight applicable to molding applications.

  However, when such a linear PPS resin is melt-molded at a high processing temperature of 280 to 350 ° C., the resin is partially decomposed, chemically modified, impurities are decomposed, and the like. There was a problem to do. Moreover, there is a problem that the color tone of the PPS resin molded product varies greatly even if there is a slight difference in molding conditions, and the color tone of the molded product varies from lot to lot. Moreover, the PPS resin molded product is likely to cause color unevenness and color spots due to partial coloring. Such a problem is common not only to PPS resins but also to PAS resins having a sulfur atom in the main chain. Therefore, in order to maintain the commercial value of the PAS resin molded product, various studies have been made in order to produce a PAS resin molded product excellent in color tone stability.

  Conventionally, methods for adding various stabilizers such as phosphites, phenol derivatives, amine derivatives, and thiophosphates have been proposed in order to stabilize the hue at the time of melt molding of PAS resin. No. 59-213759 (Patent Document 4), US Pat. No. 4,421,062 (Patent Document 5)], many of these stabilizers are altered or volatilized under the processing temperature conditions of PAS resin. In addition, it is easy to cause bleed out due to poor compatibility with PAS resin.

  In addition, attempts have been made to stabilize the color tone and color tone of PAS resin by adding colorants such as pigments and dyes. However, depending on the use of the colorant, the color tone of the PAS resin molded product varies. It is difficult to hide. In addition, most of the colorants cannot withstand the processing temperature conditions of the PAS resin, and have a problem that they are decomposed during melt molding to cause color unevenness or cause impurities and decomposed foreign matters.

  Conventionally, reaction by-products, impurities, oligomers, and the like are removed by performing post-treatment such as water washing, acid treatment, and extraction treatment with an organic solvent after polymerization. By such washing / extraction treatment, a PAS resin having a light color and good color tone can be obtained. However, when melt molding is performed, there is a problem in that variations in color tone and color spots tend to occur in the molded product.

Japanese Patent Publication No. 45-3368 Japanese Patent Publication No. 52-12240 Japanese Patent Publication No. 63-33775 JP 59-213759 A US Pat. No. 4,421,062

  An object of the present invention is to provide a color tone stabilization method for obtaining a color-stable polyarylene sulfide resin molded product in which color unevenness, brown color spots, variation in color tone from lot to lot, and the like are suppressed.

  Another object of the present invention is to provide a method for producing a polyarylene sulfide resin composition capable of giving such a molded article having excellent color tone stability.

  As a result of intensive studies to overcome the problems of the prior art, the present inventors have found that the pH measured in a mixed solvent of acetone / water (volume ratio = 1: 2) is in the range of 5.5 to 8.8. It was found that by using the PAS resin composition inside, a molded product having excellent color tone stability can be obtained even after melt molding at high temperature. Further, when a resin composition containing a PAS resin having a pH of 5.0 or less and a PAS resin having a pH of 7.1 or more is used as the PAS resin, the pH of the PAS resin composition is within the limited range. It becomes easy to adjust, and the stability of the color tone of the molded product can be improved, and the balance of various properties such as melt viscosity, melt crystallization temperature, and tensile strength can be improved. The present invention has been completed based on these findings.

  According to the present invention, there is provided a method for stabilizing the color tone of a polyarylene sulfide resin molded product obtained by melt-molding a polyarylene sulfide resin composition, wherein each polyarylene sulfide resin composition is acetone / water (volume ratio = 1). : 2) When the pH is measured in a mixed solvent, the polyarylene sulfide resin (a) having a pH of 5.0 or less and 5 to 95% by weight, and the polyarylene sulfide resin (b) 95 having a pH of 7.1 or more. A color tone of a polyarylene sulfide resin molded article comprising a polyarylene sulfide resin composition containing a resin component comprising ˜5 wt% and having a pH in the range of 5.5 to 8.8. A stabilization method is provided.

  According to the present invention, when the pH is measured in a mixed solvent of acetone / water (volume ratio = 1: 2), the polyarylene sulfide resin (a) having a pH of 5.0 or less is 5 to 95% by weight. And a polyarylene sulfide resin (b) having a pH of 7.1 or higher is blended in an amount of 95 to 5% by weight, containing a resin component composed of both of these resins, and having a pH of 5.5 to 8.8. There is provided a method for producing a polyarylene sulfide resin composition used for melt molding of a color-stable polyarylene sulfide resin molded product, characterized by preparing a polyarylene sulfide resin composition within the range.

  According to the color tone stabilization method of the present invention, a polyarylene sulfide resin molded product in which color unevenness, brown color spots, variation in color tone from lot to lot, and the like are suppressed is provided. Moreover, according to the manufacturing method of this invention, the polyarylene sulfide resin composition which can give the molded article excellent in color tone stability is provided.

1. Polyarylene sulfide resin (PAS resin):
The PAS resin used in the present invention is an aromatic having a repeating unit of an arylene sulfide represented by a structural formula [—Ar—S—] (wherein —Ar— is an arylene group) as a main constituent. It is a polymer. When [-Ar-S-] is defined as 1 mol (basic mol), the PAS resin used in the present invention usually has this repeating unit of 50 mol% or more, preferably 70 mol% or more, more preferably 90 mol%. It is a polymer containing above.

  As the arylene group, for example, a p-phenylene group, an m-phenylene group, a substituted phenylene group (the substituent is preferably an alkyl group having 1 to 6 carbon atoms or a phenyl group), p, p'-di Examples thereof include a phenylene sulfone group, p, p′-biphenylene group, p, p′-diphenylenecarbonyl group, and naphthylene group. As the PAS resin, polymers having the same arylene group can be preferably used. However, from the viewpoint of processability and heat resistance, a copolymer containing two or more arylene groups can also be used.

  Among these PAS resins, a PPS resin having a repeating unit of p-phenylene sulfide as a main constituent element is particularly preferable because it has excellent processability and is easily industrially available. In addition, examples of the PAS resin include polyarylene ketone sulfide and polyarylene ketone ketone sulfide. Specific examples of the copolymer include a random or block copolymer having a repeating unit of p-phenylene sulfide and a repeating unit of m-phenylene sulfide, a random or block copolymer having a repeating unit of phenylene sulfide and a repeating unit of arylene ketone sulfide, Examples thereof include a random or block copolymer having a repeating unit of phenylene sulfide and a repeating unit of arylene ketone ketone sulfide, and a random or block copolymer having a repeating unit of phenylene sulfide and a repeating unit of arylene sulfone sulfide. These PAS resins are preferably crystalline polymers. The PAS resin is preferably a linear polymer from the viewpoint of toughness and strength.

  Such a PAS resin can be obtained by a known method (for example, Japanese Patent Publication No. 63-33775) in which an alkali metal sulfide and a dihalogen-substituted aromatic compound are subjected to a polymerization reaction in a polar solvent.

  Examples of the alkali metal sulfide include lithium sulfide, sodium sulfide, potassium sulfide, rubidium sulfide, and cesium sulfide. Sodium sulfide produced by reacting NaSH and NaOH in the reaction system can also be used.

  Examples of the dihalogen-substituted aromatic compound include p-dichlorobenzene, m-dichlorobenzene, 2,5-dichlorotoluene, p-dibromobenzene, 2,6-dichloronaphthalene, 1-methoxy-2,5-dichlorobenzene. 4,4'-dichlorobiphenyl, 3,5-dichlorobenzoic acid, p, p'-dichlorodiphenyl ether, 4,4'-dichlorodiphenyl sulfone, 4,4'-dichlorodiphenyl ether, 4,4'-dichlorodiphenyl sulfone 4,4'-dichlorodiphenyl sulfoxide, 4,4'-dichlorodiphenyl ketone, and the like. These can be used alone or in combination of two or more.

  In order to introduce some branched structure or crosslinked structure into the PAS resin, a small amount of a polyhalogen-substituted aromatic compound having 3 or more halogen substituents per molecule can be used in combination. Examples of the polyhalogen-substituted aromatic compound include 1,2,3-trichlorobenzene, 1,2,3-tribromobenzene, 1,2,4-trichlorobenzene, 1,2,4-tribromobenzene, 1 , 3,5-trichlorobenzene, 1,3,5-tribromobenzene, 1,3-dichloro-5-bromobenzene, and other trihalogen-substituted aromatic compounds, and alkyl-substituted products thereof. These can be used alone or in combination of two or more. Among these, 1,2,4-trichlorobenzene, 1,3,5-trichlorobenzene, and 1,2,3-trichlorobenzene are more preferable from the viewpoints of economy, reactivity, and physical properties.

  As the polar solvent, N-alkylpyrrolidone such as N-methyl-2-pyrrolidone, 1,3-dialkyl-2-imidazolidinone, tetraalkylurea, aprotic organic amide solvent represented by hexaalkylphosphate triamide, It is preferable because the stability of the reaction system is high and a high molecular weight polymer is easily obtained.

The PAS resin used in the present invention has a melt viscosity of usually 10 to 1,000 Pa · s, preferably 20 to 800 Pa · s, more preferably 50 to 500 Pa · s, measured at a temperature of 310 ° C. and a shear rate of 1200 sec ^−1. s. If the melt viscosity of the PAS resin is too small, the mechanical properties of the molded product will be insufficient, and if it is too large, the injection moldability and extrusion moldability will decrease.

2. PAS resin composition:
The PAS resin composition used in the present invention has a pH measured in a mixed solvent of acetone / water (volume ratio = 1: 2) in the range of 5.5 to 8.8. When a PAS resin composition having a pH of less than 5.5 is used, when it is melt-molded at a processing temperature of 280 to 350 ° C., the color tone of the molded product greatly changes from bluish white to milky white due to the strong influence of thermal history. And the commercial value is reduced. When a PAS resin composition having a pH of more than 8.8 is used, brown color spots are easily generated by melt molding, and it becomes difficult to obtain a molded product having a uniform color tone. Therefore, even if the pH is too small or too large, variations in the color tone of the molded product are likely to occur from lot to lot. Furthermore, the melt fluidity and mechanical properties of the PAS resin composition can be improved by adjusting the pH within the limited range.

  As a method for adjusting the pH of the PAS resin composition to a desired range, the PAS resin obtained by polymerization is subjected to (1) a washing treatment with water, warm water or hot water, (2) an acid such as hydrochloric acid or acetic acid, or Examples include acid treatments that are washed with an acid aqueous solution, (3) salt treatments that are immersed in an aqueous solution of a salt such as ammonium chloride, and (4) treatment methods such as washing with an organic solvent or a water-organic solvent mixture. Can do. These treatments may be performed in combination of two or more.

  These processes have problems as well as advantages. For example, a washing treatment with water, warm water, or hot water tends to obtain a PAS resin having a relatively low melt crystallization temperature and a high pH. When acid treatment or salt treatment is performed, a melt crystallization temperature is relatively high and a light-colored PAS resin is easily obtained, but the pH of the PAS resin tends to be low. In the washing treatment using an organic solvent, there are problems such as environmental problems caused by the organic solvent and recovery of the organic solvent, and a PAS resin having a high pH is easily obtained. Moreover, even if these treatments are applied in combination of a plurality of types in succession, it is often difficult to adjust the pH of the PAS resin within the limited range with good reproducibility.

  Therefore, in the present invention, the pH of the PAS resin composition is adjusted within a desired range by using a combination of at least two types of PAS resins having different pHs. Specifically, by using a combination of 5 to 95% by weight of PAS resin (a) having a pH of 5.0 or less and 95 to 5% by weight of PAS resin (b) having a pH of 7.1 or more, A method of adjusting the pH of the PAS resin composition within the range of 5.5 to 8.8 can be mentioned. Each of the PAS resins (a) and (b) may be two or more. By using a combination of two or more types of PAS resins having different pHs in this way, the pH of the PAS resin composition can be easily adjusted, and the balance of various properties such as melt viscosity, melt crystallization temperature, and tensile strength can be achieved. Can be made good.

  The PAS resin (a) having a pH of 5.0 or less, preferably 4.5 or less, can be prepared by acid treatment or salt treatment of the PAS resin. The PAS resin (b) having a pH of 7.1 or higher, preferably 7.2 or higher can be prepared by washing the PAS resin with water, warm water, hot water or organic solvent. The pH of the PAS resin composition is adjusted within a desired range by blending 5 to 95% by weight of the PAS resin (a) and 95 to 5% by weight of the PAS resin (b). If the blending ratio is outside this range, it will be difficult to adjust the pH of the PAS resin composition within a desired range. The difference in pH value between the PAS resin (a) and the PAS resin (b) is preferably 5.0 or less. When the difference between the pH values of the two resins is too large, the mixing tends to be uneven, and as a result, the color tone of the molded product is not stable, and the variation in color tone from lot to lot tends to increase.

  The PAS resin (a) is subjected to treatment with an acid or a salt to have a high melt crystallization temperature, and for example, the injection molding cycle can be shortened. However, since the pH of the PAS resin (a) alone is too low, when a melt molding such as injection molding is performed, the molded product tends to be blue-gray. The PAS resin (b) tends to have a high pH and a low melt crystallization temperature when washed with water or warm water. When these two resins are blended, the pH value can be adjusted to an appropriate value to obtain color tone stability, and the melt crystallization temperature can be adjusted to an appropriate range. Further, by blending PAS resins (a) and (b) having different melt viscosities, the melt viscosity of the PAS resin composition can be adjusted to a desired range. Similarly, the physical properties of a molded product such as tensile strength can be adjusted to a desired range by blending both resins.

3. Other ingredients:
In the present invention, as necessary, fillers, other synthetic resins, pigments, dyes, antioxidants, ultraviolet absorbers, lubricants, nucleating agents, flame retardants, resin modifiers, coupling agents, antistatic agents, release agents. A mold agent, a plasticizer, etc. can be added suitably. The PAS resin composition containing these other components needs to have a pH in the range of 5.5 to 8.8 from the viewpoint of color stability.

  Other synthetic resins are preferably thermoplastic resins that are stable at high temperatures. Specific examples thereof include aromatic polyesters such as polyethylene terephthalate and polybutylene terephthalate; polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymers , Tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride / hexafluoropropylene copolymer, propylene / tetrafluoroethylene copolymer, vinylidene fluoride / chlorotrifluoro Fluororesin such as ethylene copolymer, ethylene / hexafluoropropylene copolymer; polyacetal, polystyrene, polyamide, polycarbonate, polyphenylene ether, It can be mentioned trialkyl acrylate, ABS resins, polyvinyl chloride and the like. These thermoplastic resins can be used alone or in combination of two or more.

  Examples of the filler include inorganic fibers such as glass fiber, carbon fiber, asbestos fiber, silica fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate whisker; stainless steel, aluminum And fibrous fillers such as metal fibrous materials such as titanium, steel and brass; high melting point organic fibrous materials such as polyamide, fluororesin, polyester resin and acrylic resin; Examples of the filler include mica, silica, talc, alumina, kaolin, calcium sulfate, calcium carbonate, titanium oxide, ferrite, glass powder, zinc oxide, nickel carbonate, iron oxide, quartz powder, magnesium carbonate, and barium sulfate. And a granular or plate-like filler such as clay. These fillers can be used alone or in combination of two or more.

  These fillers may be treated with a sizing agent or a surface treatment agent as necessary. Examples of the sizing agent or surface treatment agent include functional compounds such as epoxy compounds, isocyanate compounds, silane compounds, and titanate compounds. These compounds may be used after having been subjected to surface treatment or focusing treatment on the filler in advance, or may be added simultaneously when the composition is adjusted.

  In the present invention, it is particularly preferable to use a PAS resin composition containing a filler such as glass fiber. The filler is usually blended in the range of 0 to 800 parts by weight, preferably 0 to 500 parts by weight, and more preferably 0 to 300 parts by weight with respect to 100 parts by weight of the PAS resin component. In particular, when an inorganic fibrous filler such as glass fiber is blended as a filler, a resin composition and a molded article excellent in mechanical properties such as tensile strength can be obtained.

4). Method for producing PAS resin composition:
The PAS resin composition can be prepared by facilities and methods generally used for preparing a synthetic resin composition. For example, each raw material component is premixed with a Henschel mixer, tumbler, etc., and if necessary, a filler such as glass fiber is added and further mixed, then kneaded using a single or twin screw extruder and extruded. To form a pellet for molding. A method of mixing a part of the necessary ingredients with the remaining ingredients and mixing with the remaining ingredients. In addition, in order to improve the dispersibility of each ingredient, a part of the raw materials to be used is pulverized, mixed to be mixed and melt extruded. It is also possible.

5). Molding method:
The PAS resin molded product of the present invention is molded into various shapes by a general melt molding process such as injection molding or extrusion molding using a PAS resin composition having a pH in the range of 5.5 to 8.8. It can be molded into molded products such as products, sheets, films, and tubes.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited only to these examples. The measuring method of physical properties is as follows.

(1) Melt viscosity Melt viscosity was measured for each sample using Capillograph 1C (manufactured by Toyo Seiki Co., Ltd.) at a temperature of 310 ° C. and a shear rate of 1200 sec ⁻¹ .

(2) Melt crystallization temperature The melt crystallization temperature (Tc ₂ ) is 340 ° C. at a rate of 10 ° C./min in a nitrogen atmosphere using a differential scanning calorimeter (DSC7) manufactured by PerkinElmer. After the temperature increase, the temperature was subsequently decreased to 50 ° C. at a rate of 10 ° C./min, and the crystallization exothermic peak temperature that appeared at the time of temperature decrease was read from the chart.

(3) Tensile strength The tensile strength of each sample was measured according to ASTM D638 at a measurement temperature of 23 ° C., a distance between gauge points of 50 mm, and a crosshead speed of 5 mm / min.

(4) pH
Add 20 ml of acetone to 20 g of PAS resin, mix well, add 100 ml of ion-exchanged water, shake for 30 minutes with a shaker, take 60 ml of supernatant, measure its pH, and measure PAS The pH of the resin was taken. About PAS resin composition, the pH was measured in the same procedure as the above using 20 g of each component premixed with a Henschel mixer.

(5) Color tone A molded product obtained by injection molding the PAS resin or PAS resin composition was visually observed to evaluate the color tone stability of the surface.

[Synthesis Example 1]
373 kg of hydrous sodium sulfide (purity: 46.03 wt%) and 880 kg of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) were charged into a titanium-clad polymerization can and gradually heated to about 203 ° C. in a nitrogen gas atmosphere. The NMP solution containing 135 kg of water was distilled off. Next, 297 kg of p-dichlorobenzene (hereinafter abbreviated as p-DCB) was charged, and polymerization was performed at 220 ° C. for 4.5 hours. Further, after 47.5 kg of water was injected, the temperature was raised to 255 ° C. and polymerization was carried out for 4 hours. After completion of the reaction, the reaction mixture was cooled, and the reaction solution was sieved with a screen having an opening of 0.1 mm to separate the granular polymer. The granular polymer was washed with methanol 3 times (solid-liquid ratio 1/5) and water-washed (solid-liquid ratio 1/5) 5 times to obtain a polymer slurry. Next, it is immersed in a 2% ammonium chloride aqueous solution, treated at 40 ° C. for 30 minutes (solid-liquid ratio 1/5), washed with water (solid-liquid ratio 1/5) three times, dried and polymer ( PPS-1) was obtained. The obtained PPS-1 had a melt viscosity of 55 Pa · s, a pH of 4.5, and a melt crystallization temperature of 255 ° C.

[Synthesis Example 2]
370 kg of hydrous sodium sulfide (purity 46.4 wt%) and 1100 kg of NMP were charged into a titanium-clad polymerization can, and the NMP solution containing water was distilled off while gradually raising the temperature to about 203 ° C. in a nitrogen gas atmosphere. Next, 311 kg of p-DCB was charged and polymerization was performed at 220 ° C. for 5 hours. Furthermore, after 4.4 kg of water was injected, the temperature was raised to 255 ° C. and polymerization was carried out for 5 hours. After completion of the reaction, the reaction solution was cooled, and the reaction solution was sieved with a screen having an opening of 0.1 mm to separate the granular polymer. The granular polymer was washed with methanol 3 times (solid-liquid ratio 1/5) and water-washed (solid-liquid ratio 1/5) 5 times to obtain a polymer slurry. Next, it is immersed in a 1% hydrochloric acid aqueous solution, treated at 40 ° C. for 60 minutes (solid-liquid ratio 1/5), then washed with water (solid-liquid ratio 1/5) three times, dried and polymer (PPS -2) was obtained. The obtained PPS-2 had a melt viscosity of 200 Pa · s, a pH of 4.7, and a melt crystallization temperature of 240 ° C.

[Synthesis Example 3]
370 kg of hydrous sodium sulfide (purity 46.2 wt%) and 880 kg of NMP were charged into a titanium-clad polymerization can and gradually heated to about 200 ° C. in a nitrogen gas atmosphere to distill an NMP solution containing 127 kg of water. Next, 283 kg of p-DCB was added and polymerized at 210 ° C. for 9 hours. Next, 50 kg of water was added to the polymerization system, and then the temperature was raised in a nitrogen atmosphere and polymerization was carried out at 260 ° C. for 5 hours. After completion of the reaction, the mixture was cooled, the contents were filtered, washed with deionized water (solid-liquid ratio 1/5) five times, and then dried at 100 ° C. for 3 hours to obtain a polymer (PPS-3). . The obtained PPS-3 had a melt viscosity of 145 Pa · s, a pH of 7.2, and a melt crystallization temperature of 206 ° C.

[Synthesis Example 4]
373 kg of hydrous sodium sulfide (purity 46.03 wt%) and 800 kg of NMP were charged into a titanium-capped polymerization can, and the NMP solution containing 142 kg of water was distilled off while gradually raising the temperature to about 203 ° C. in a nitrogen gas atmosphere. Next, a mixed solution of p-DCB 325 kg, 1,2,4-trichlorobenzene 0.372 kg and NMP 255 kg was supplied, and polymerization was carried out at 220 ° C. for 5 hours. Next, after 97 kg of water was injected, the temperature was raised to 255 ° C. and polymerized for 5 hours, and then the temperature was lowered to 245 ° C. and polymerization was continued for 5.5 hours. After completion of the reaction, the mixture was cooled, the contents were filtered, washed with deionized water (solid-liquid ratio 1/5) three times, and then dried to obtain a polymer (PPS-4). The obtained PPS-4 had a melt viscosity of 450 Pa · s, a pH of 9.1, and a melt crystallization temperature of 179 ° C.

  Table 1 shows the physical properties of the PPS resins obtained in Synthesis Examples 1 to 4.

[Reference Example 1, Examples 1 to 7, and Comparative Examples 1 to 3]
Using each PPS resin and glass fiber (commercially available glass fiber; diameter 13 μm, length 3 mm) obtained in Synthesis Examples 1 to 4, a PAS resin or a PAS resin composition was prepared according to the formulation shown in Table 2. A predetermined amount of each component of the PAS resin composition was premixed for 5 minutes with a Henschel mixer. In addition, when mix | blending glass fiber, after adding glass fiber, it mixed for 2 minutes. The PAS resin and PAS resin premix were fed to an extruder with a cylinder temperature of 310 ° C. to produce pellets. Each pellet was supplied to an injection molding machine and injection molded at a cylinder temperature of 320 ° C. and a mold temperature of 150 ° C. to obtain a test piece. Table 2 shows the measurement results of each physical property.

  As is apparent from the results in Table 2, the molded articles (Examples 1 to 7) obtained using the PAS resin composition having a pH in the range of 5.5 to 8.8 are all light yellow and colored. There are no spots and color stability is excellent. On the other hand, when a PAS resin having a pH too low was used (Comparative Example 1), the color of the injection molded product was changed to blue-gray, and color spots due to melt flow were also observed. When a PAS resin or a PAS resin composition having an excessively high pH was used (Comparative Examples 2 to 3), the injection-molded product was changed to dark brown, and color spots were observed.

  The polyarylene sulfide resin molded product of the present invention can be used for various applications as molded products, sheets, films, tubes, and the like having various shapes by utilizing the characteristics excellent in color tone stability. The PAS resin composition obtained by the production method of the present invention can be molded into a molded product having excellent color stability by a general melt molding method such as injection molding or extrusion molding.

Claims (3)

  A method for stabilizing the color tone of a polyarylene sulfide resin molded product obtained by melt-molding a polyarylene sulfide resin composition, wherein the polyarylene sulfide resin composition is an acetone / water (volume ratio = 1: 2) mixed solvent, respectively. When the pH was measured at 5 to 95% by weight of the polyarylene sulfide resin (a) having a pH of 5.0 or less and 95 to 5% by weight of the polyarylene sulfide resin (b) having a pH of 7.1 or more. A method for stabilizing the color tone of a polyarylene sulfide resin molded article, comprising using a polyarylene sulfide resin composition containing a resin component and having a pH within a range of 5.5 to 8.8.   When the pH was measured in a mixed solvent of acetone / water (volume ratio = 1: 2), the polyarylene sulfide resin (a) having a pH of 5.0 or less and a pH of 7.1 or more were obtained. The polyarylene sulfide resin (b) is blended with 95 to 5% by weight, contains a resin component composed of both resins, and has a pH in the range of 5.5 to 8.8. A method for producing a polyarylene sulfide resin composition for use in melt molding of a color-stable polyarylene sulfide resin molded article, characterized by preparing a composition.   When the polyarylene sulfide resin (a) and the polyarylene sulfide resin (b) are blended, a filler is further blended to contain a resin component and a filler composed of both resins, and the pH is 5 The manufacturing method of Claim 2 which prepares the polyarylene sulfide resin composition which exists in the range of 0.5-8.8.