Method for recovering polyarylene sulfide resin, method for modifying it, and method for producing a resin composition

Abstract

To provide a method for recovering polyarylene sulfide (PAS) resin, which has excellent cleaning efficiency and generates little gas when heated, from a resin composition or molded article; a method for modifying the molecular weight of the recovered PAS resin; and a method for producing a resin composition using the obtained PAS resin. [Solution] A method for recovering PAS resin, comprising the steps of: (1) heating a mixture (A) containing at least PAS resin and an organic polar solvent as essential components to 200°C or higher to dissolve the PAS resin in the organic polar solvent; (2) separating the mixture (A) into a solid-liquid to obtain a liquid-phase component containing at least PAS resin and an organic polar solvent; (3) adding a dispersant to the liquid-phase component and then cooling it to 200°C or lower to obtain a mixture (B); and (4) separating the mixture (B) into a solid-liquid to obtain a solid-phase component, wherein the dispersant is water-soluble and insoluble in the organic polar solvent.

Description

Technical Field

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

Background Art

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

[0003] On the other hand, in order to realize a sustainable society, the demand for the recycling of various materials is increasing. Among them, since a large amount of industrial waste collected from automobiles and home appliances is discharged, efficient reuse of the waste plastic components contained therein is also required.

[0004] As for the study of reusing PAS resins, for example, Patent Document 1 discloses a method of recovering a PAS resin by heating a PAS resin composition or its molded product in an organic polar solvent. However, the resin after precipitation contains the solvent used for dissolution and those decomposed to a molecular weight of about oligomers, and washing is required to remove these. In particular, since the PPS resin after precipitation is hydrophobic, when trying to wash it with water, the dispersibility is poor and the washing efficiency is low. Due to such properties, it has been difficult to purify the PAS resin obtained by this method to a practical purity while considering the environment. In addition, since the molecular weight of the resin used for molding and products is reduced due to deterioration, in order to reuse the resin in the same product group, it has been required to extend the molecular weight again.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] Therefore, the problem that the present invention aims to solve is to provide a method for recovering PAS resin from a resin composition or molded product that has excellent cleaning efficiency and generates a small amount of gas when heated, a method for modifying the molecular weight of the recovered PAS resin, and a method for producing a resin composition using the obtained PAS resin. [Means for solving the problem]

[0007] As a result of various studies, the inventors discovered that by dissolving PAS resin from a resin composition or molded product in an organic solvent, adding a dispersant, and then cooling, the PAS resin incorporates the dispersant during crystallization, resulting in superior cleaning efficiency in subsequent cleaning processes. This led to the completion of the present invention.

[0008] In other words, the present invention encompasses the following aspects. [1] A mixture (A) containing at least a resin composition or molded article containing PAS resin and an organic polar solvent as essential components is heated to 200°C or higher to dissolve the PAS resin in the organic polar solvent (1), Step (2) to separate the mixture (A) into solid and liquid phases to obtain a liquid phase component containing at least PAS resin and an organic polar solvent. Step (3): Add a dispersant to the liquid phase component and then cool to 200°C or below to obtain a mixture (B). The process includes step (4) of separating the mixture (B) into solid and liquid components to obtain a solid phase component, A method for recovering PAS resin, wherein the dispersant is water-soluble and insoluble in the organic polar solvent. [2] The method for recovering PAS resin according to [1], wherein the dispersant is an alkali metal salt. [3] The average particle size (D) of the resin composition or the molded article 50 A method for recovering PAS resin according to [1] or [2] above, wherein the diameter is 20 mm or less. [4] The method for recovering PAS resin according to [1] to [3] above, wherein the PAS resin content in the resin composition or molded article is 20 parts by mass or more. [5] Step (5) of adding an oligoarylene sulfide to the PAS resin obtained by the recovery method described in [1] to [3] above, A method for modifying a PAS resin, comprising a step (6) of washing the obtained mixture and then performing a heat treatment. [6] Step (7) of washing the PAS resin obtained by the recovery method described in [1] to [3] above, A method for modifying a PAS resin, comprising a step (8) of adding an oligoarylene sulfide to the obtained mixture and then performing a heat treatment. [7] The method for modifying a PAS resin according to [5] or [6] above, wherein the oligoarylene sulfide is a cyclic oligoarylene sulfide. [8] A method for producing a PAS resin composition, comprising a step of blending the PAS resin obtained by the method described in [1] to [6] above as an essential component and melt-kneading at a temperature not lower than the melting point of the PAS resin. [Advantages of the Invention]

[0009] According to the present invention, it is possible to provide a method for recovering a PAS resin having excellent washing efficiency and a small amount of gas generated during heating from a resin composition or a molded product, a method for modifying the molecular weight of the recovered PAS resin, and a method for producing a resin composition using the obtained PAS resin. [Embodiments for Carrying Out the Invention]

[0010] Hereinafter, an embodiment of the present invention will be described in detail. However, the scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention. Also, when a plurality of upper 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 Recovering PAS Resin> The method for recovering PAS resin according to this embodiment includes a step (1) of heating a mixture (A) containing at least a resin composition or molded product containing PAS resin and an organic polar solvent to 200°C or higher to dissolve the PAS resin in the organic polar solvent, a step (2) of subjecting the mixture (A) to solid-liquid separation to obtain a liquid-phase component containing at least the PAS resin and the organic polar solvent, a step (3) of adding a dispersant to the liquid-phase component and then cooling to 200°C or lower to obtain a mixture (B), and a step (4) of subjecting the mixture (B) to solid-liquid separation to obtain a solid-phase component, and is characterized in that the dispersant is water-soluble and insoluble in the organic polar solvent. This will be described below.

[0012] · Step (1) Step (1) is a step of heating a mixture (A) containing at least a resin composition or molded product containing PAS resin and an organic polar solvent to 200°C or higher to dissolve the PAS resin in the organic polar solvent.

[0013] The PAS resin 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)

[0014]

Chemical formula

[0015]

Chemical formula

[0016] Here, the structural part represented by the general formula (1) is, in particular, R in the formula. 1 and R 2 From the viewpoint of the mechanical strength of the PAS resin, it is preferable that the atom is a hydrogen atom, and in that case, examples include 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).

[0017] [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 and crystallinity of the PAS resin if it is bonded at the para position as represented by the general formula (3).

[0018] 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).

[0019] [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 the PAS resin. 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.

[0020] 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.

[0021] 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.

[0022] (Melting viscosity) The melt viscosity of the PAS resin used in this disclosure is not particularly limited, but in order to achieve a good balance between fluidity and mechanical strength, the melt viscosity (V6) measured at 300°C is preferably in the range of 5 Pa·s or more, more preferably in the range of 10 Pa·s or more, and preferably in the range of 45 Pa·s or less, and more preferably in the range of 40 Pa·s or less. However, the melt viscosity (V6) is measured using a Shimadzu flow tester, CFT-500D, 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.

[0023] (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 aluminum Particularly preferred is a product obtained by adding a dihalogeno-aromatic compound and, if necessary, a polyhalogeno-aromatic compound or other copolymer component in the presence of a potassium metal sulfide and an aprotic polar organic solvent, and reacting an alkali metal hydrosulfide and an alkali metal organic acid salt while controlling the amount of alkali metal organic acid salt 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.

[0024] There are no particular limitations on the post-treatment method for the reaction mixture containing the PAS resin obtained by the polymerization step. For example, (post-treatment 1) after the polymerization reaction is complete, 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. 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 complete, 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 the 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.

[0025] 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.

[0026] The amount of PAS resin blended in the resin composition and molded article used in this embodiment is not particularly limited as long as it does not impair the effects of the present invention, but is preferably in the range of 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, per 100 parts by mass of the resin composition. Within this range, the resin composition and molded article have excellent dissolution efficiency and filtration efficiency, and the PAS resin can be recovered efficiently.

[0027] The resin composition and molded articles used in this embodiment may contain, in addition to PAS resin, known and conventional additives such as fillers, coupling agents, colorants, antistatic agents, antioxidants, heat stabilizers, UV stabilizers, UV absorbers, foaming agents, flame retardants, flame retardant aids, rust inhibitors, lubricants, and mold release agents (such as metal salts or esters of fatty acids with 18 to 30 carbon atoms, including stearic acid and montanic acid, and polyolefin waxes such as polyethylene). Furthermore, depending on the application, synthetic resins such as polyester resin, polyamide resin, polyimide resin, polyetherimide resin, polycarbonate resin, polyphenylene ether resin, polysulfone resin, polyethersulfone resin, polyaryletherketone resin, polyetheretherketone resin, polyetherketone resin, polyarylate resin, polyethylene resin, polypropylene resin, polytetrafluoroethylene resin, polyvinylidene fluoride resin, polystyrene resin, ABS resin, epoxy resin, phenolic resin, urethane resin, liquid crystal polymer, thermoplastic elastomer, etc. (hereinafter simply referred to as synthetic resin) can be used as optional components. In addition, the molded product may be a composite molded product that is combined with other components such as metal components (including metal foil), ceramic components, wood, thermoplastic resin components, thermosetting resin components, etc.

[0028] The resin composition and molded article used in this embodiment are not particularly limited in form, but from the viewpoint of dissolution efficiency, they are preferably pulverized, and the average particle size (D 50 The diameter is more preferably 20 mm or less, and even more preferably 10 mm or less. Within this range, dissolution efficiency and handling are excellent.

[0029] The organic polar solvents that can be used in this embodiment are not particularly limited as long as they dissolve the PAS resin at 200°C or higher, but examples include amides, ureas and lactams such as formamide, acetamide, N-methylformamide, N,N-dimethylacetamide, tetramethylurea, N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropyleneurea, and 1,3-dimethyl-2-imidazolidinonic acid. Examples include sulfolanes such as sulfolane and dimethylsulfolane; nitriles such as benzonitrile; ketones such as methylphenyl ketone and mixtures thereof. Among these, aliphatic cyclic amides such as N-methyl-2-pyrrolidone, 2-pyrrolidone, N-methyl-ε-caprolactam, ε-caprolactam, hexamethylphosphoramide, N-dimethylpropylene urea, and 1,3-dimethyl-2-imidazolidinonic acid are preferred, with N-methyl-2-pyrrolidone being even more preferred.

[0030] The amount of the organic polar solvent in the mixture (A) is preferably 100 parts by mass or more, more preferably 150 parts by mass or more, preferably 1000 parts by mass or less, and more preferably 600 parts by mass or less, per 100 parts by mass of PAS resin. By blending within this range, the PAS resin can be uniformly dissolved in the organic polar solvent, and the washing efficiency in step (2) can be improved.

[0031] The temperature at which the mixture (A) is heated is preferably 200°C or higher, more preferably 230°C or higher, and preferably 280°C or lower. Heating within this range allows the PAS resin to be sufficiently dissolved in the organic polar solvent. Stirring is optional during heating, but stirring is preferable as it shortens the time required for dissolution.

[0032] ·Process (2) Step (2) is a step of separating the mixture (A) into solid and liquid phases to obtain a liquid phase component containing at least PAS resin and an organic polar solvent. Insoluble components contained in the resin composition or the molded article can be removed as solid phase components.

[0033] The solid-liquid separation in this process is not particularly limited as long as it does not impair the effects of the present invention. For example, methods such as filtration using a filtration device, or using a washing tank with a stirrer and a centrifuge for solid-liquid separation are possible. It can also be carried out in a container with a mixing function that has stirring blades inside and a filtration filter at the bottom. Since the solid-liquid separation in this process proceeds while the PAS resin is dissolved in an organic polar solvent, it is preferable that the device used for solid-liquid separation has a heating function or a heat retention function.

[0034] ·Process (3) Step (3) is the step of adding a dispersant to the liquid phase component and then cooling it to 200°C or below to obtain mixture (B).

[0035] The dispersant used in this process may be solid or liquid, as long as it is water-soluble and insoluble in the aforementioned organic polar solvent, and improves the affinity of the PAS resin to water. Specifically, alkali metal salts are examples. Among these, sodium salts or potassium salts are preferred, and sodium chloride, potassium carbonate, sodium acetate, etc., are more preferred. The amount of dispersant added is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, and even more preferably 90 parts by mass or more, per 100 parts by mass of PAS resin. The upper limit is preferably, for example, 600 parts by mass or less, and more preferably 500 parts by mass or less. Within this range, the PAS resin becomes sufficiently wetted with water, resulting in excellent cleaning efficiency in the subsequent cleaning process. If the amount is outside this range, the cleaning process of the PAS resin will require more time and a large amount of water, or the resulting PAS resin will contain many impurities, worsening the environment during processing.

[0036] There are no particular restrictions on the cooling rate when cooling the liquid phase component, but a range of 0.1°C / min to 5°C / min is generally preferred. Furthermore, it is not necessary to cool at the same rate throughout the entire cooling process; a method of cooling at a rate of 0.1°C / min to 1°C / min until the granular PAS resin crystallizes, and then at a rate of 1°C / min or higher, is also preferred. Finally, it is preferable to cool to 70°C or higher, preferably 100°C or higher and 200°C or lower, to obtain mixture (B). Upon cooling, the PAS resin precipitates, and at that time, it forms a composite that incorporates the dispersant, which is an insoluble component in the organic polar solvent.

[0037] ·Process (4) Step (4) is a step of obtaining a solid phase component by solid-liquid separation of the mixture (B). The solid phase component includes at least PAS resin and a dispersant. In this case, it is preferable that the PAS resin forms a composite with the dispersant or that the PAS resin contains the dispersant.

[0038] In this process, solid-liquid separation may be carried out using the same method as in step (2) described above, or by removing the liquid phase component by evaporating it through heating.

[0039] The solid phase component containing PAS resin obtained through the above process can then be further washed with water or an oxygen-containing solvent with 1 to 3 carbon atoms, followed by solid-liquid separation and drying to prepare a powdered or granular PAS resin. Furthermore, the obtained powdered or granular PAS resin can be heat-treated to produce a crosslinked PAS resin.

[0040] When washing with water, the amount of water added to the solid phase component is preferably in the range of 2 to 10 times the theoretical yield of the PAS resin obtained in the end, which is preferable from the viewpoint of washing efficiency, and it is preferable to divide the above amount of water into 2 to 10 times, preferably 2 to 4 times, and subject it to washing. The washing is preferably carried out under a nitrogen or air atmosphere and at a water temperature in the range of 20°C to 300°C, and from the viewpoint of good washing efficiency, it is more preferable to carry it out in the range of 50°C to 100°C, and even more preferably in the range of 70°C to 90°C. The washing can be carried out once or repeated multiple times. When washing with water repeatedly multiple times, the atmosphere and temperature conditions may be the same or different.

[0041] Since trace amounts of alkali metal halides and sulfidating agents may remain in the filtered PAS resin due to insufficient washing, it is preferable to further contact the PAS resin with water in the range of 100°C to 280°C, followed by solid-liquid separation (hereinafter sometimes referred to as "hot water washing"), and then separate and remove the PAS resin by filtration or other means, and add the resulting filtrate to the solid phase component. This is preferable from the viewpoint of reducing the COD load and suppressing the loss of sulfur atoms (reduction in raw material cost).

[0042] The temperature for hot water washing is preferably in the range of 100 to 280°C, and more preferably in the range of 120 to 275°C, as this allows for good extraction efficiency of alkali metal halides and sulfidating agents remaining in the resin. More specifically, it is preferable to perform the extraction treatment with hot water at 140 to 260°C under conditions of pressurized gas phase pressure in the reactor, more preferably 0.2 to 4.6 MPa (gauge pressure).

[0043] The PAS resin recovered by the above method may be heat-treated. When heat-treating, it is preferable to add oligoarylene sulfide (hereinafter also referred to as PAS oligomer) and then perform the heat treatment. The addition of the PAS oligomer may be carried out after the above washing treatment and drying step. When adding the PAS oligomer before or during washing, impurities and those with a significantly low molecular weight can be removed, so the labor of generating the PAS oligomer in advance can be saved. When using a purified PAS oligomer, it may be added after washing.

[0044] The structure of the PAS oligomer is not particularly limited, and chain-like or cyclic ones can be used. In particular, using a cyclic PAS oligomer is preferable from the viewpoint of the molecular weight elongation efficiency in the heat treatment. By heat-treating the mixture of the PAS resin and the PAS oligomer after the washing treatment, the cross-linking reaction can proceed efficiently, and the melt viscosity of the PAS resin can be increased.

[0045] <Method for Modifying PAS Resin> That is, as one of the other embodiments of the present disclosure, there is a method for modifying a PAS resin having a step (5) of further adding oligoarylene sulfide to the PAS resin obtained by the above-described recovery method, and a step (6) of heat-treating the obtained mixture after washing. As another embodiment, there is a method for modifying a PAS resin having a step (7) of washing the PAS resin obtained by the above-described recovery method, and a step (8) of heat-treating the obtained mixture after adding the PAS oligomer. Further, as another embodiment, there is a method for modifying a PAS resin having a step of further adding the PAS oligomer in the above steps (1) to (4), and a step (6) of heat-treating the obtained mixture after washing. Note that the modification in the present disclosure refers to extending the molecular weight of the PAS resin to increase the molecular weight.

[0046] As the heat treatment, methods such as heat-treating the mixture in an oxidizing atmosphere such as air or oxygen-enriched air, or heat-treating in an inert gas atmosphere can be mentioned. The inert gas refers to a stable gas that hardly causes a chemical reaction, typified by noble gas elements or nitrogen, etc., and for example, it is preferably at least one selected from the group consisting of nitrogen, helium, or argon. Also, the inert gas may be a mixed inert gas in which two or more kinds of inert gases are mixed.

[0047] The heating means is not particularly limited, and publicly known and commonly used devices and methods can be used. The heat treatment may be carried out at a temperature above the melting point of the PAS resin in a state where the PAS resin is melted, but since the possibility of thermal degradation of the PAS resin increases, it is preferably carried out at a temperature of the melting point + 100°C or lower. Also, when performing the heat treatment in a solid phase (solid) state below the melting point, from the viewpoints of the time required for the heat treatment and the good thermal stability during melting of the PAS resin after the heat treatment, it is preferably in a temperature range of 180°C to 20°C lower than the melting point of the PAS resin. However, the melting point here refers to that measured in accordance with JIS K 7121 using a differential scanning calorimeter (Pyris Diamond manufactured by PerkinElmer).

[0048] The heating time of the heat treatment is not particularly limited as long as the effects of the present invention are not impaired, but adjusting it so that the consumption amount of the added PAS oligomer becomes 20% by mass or more is preferable from the viewpoint of extending the molecular weight and sufficiently modifying the resin and reducing the weight loss (amount of gas generated during heating) of the obtained resin.

[0049] As described above, the PAS resin recovered through steps (1) to (4) of the present invention or the PAS resin recovered and modified through (1) to (6) or (1) to (4) and (7) to (8) of the present invention can be used as a raw material for a resin composition or a resin molded product by blending additives such as a filler, a mold release agent, a coloring agent, a heat stabilizer, an ultraviolet stabilizer, a foaming agent, a rust preventive agent, a flame retardant, a lubricant, a pigment, a coupling agent, and other synthetic resins within a range not impairing the effects of the present invention.

[0050] <Method for producing a PAS resin composition> In other words, the method for producing the PAS resin composition of this disclosure is characterized by comprising the step of blending the PAS resin obtained by the method described above as an essential component and melt-kneading it at a temperature above the melting point of the PAS resin. More specifically, the PAS resin composition according to this embodiment is made by blending each essential component and, if necessary, other optional components. The method for producing the resin composition used in this disclosure is not particularly limited, but includes a method of blending the essential components and, if necessary, optional components and melt-kneading them, and more specifically, a method of uniformly dry-mixing them in a tumbler or Henschel mixer, etc., as necessary, and then feeding them into a twin-screw extruder and melt-kneading them.

[0051] Melt mixing can be carried out by heating to a temperature range in which the resin temperature is above the melting point of the PAS resin, preferably a temperature range of 10°C or higher above the melting point, more preferably 10°C or higher above the melting point, even more preferably 20°C or higher above the melting point, preferably 100°C or lower above the melting point, and more preferably 50°C or lower above the melting point.

[0052] As the melting and mixing machine, a twin-screw extruder is preferred from the viewpoint of dispersibility and productivity. For example, it is preferable to melt and mix while appropriately adjusting the discharge rate of the resin component in the range of 5 to 500 kg / hr and the screw rotation speed in the range of 50 to 500 rpm, and it is even more preferable to melt and mix under conditions in which the ratio of these (discharge rate / screw rotation speed) is in the range of 0.02 to 5 kg / hr / rpm. In addition, the addition and mixing of each component to the melting and mixing machine may be done simultaneously or in stages. For example, when adding graphite (B), an essential component, or other fibrous fillers as needed, it is preferable from the viewpoint of dispersibility to introduce them into the extruder from the side feeder of the twin-screw extruder. The position of such a side feeder is preferably such that the ratio of the distance from the resin input section (top feeder) to the total length of the screw of the twin-screw extruder to the side feeder is 0.1 or more, and more preferably 0.3 or more. Furthermore, such a ratio is preferably 0.9 or less, and more preferably 0.7 or less.

[0053] The PAS resin composition according to this disclosure obtained by melt-kneading in this manner is a molten mixture containing the essential components, optional components added as needed, and their derived components. Therefore, the PAS resin composition according to this disclosure has a sea-island structure morphology in which the PAS resin forms a continuous phase and island phases containing optional components are dispersed.

[0054] The PAS resin composition according to this disclosure is preferably processed after melt kneading by a known method, for example, by extruding the molten resin composition into strands, then into the form of pellets, chips, granules, powder, etc., and then pre-drying at a temperature range of 100 to 150°C as needed.

[0055] The PAS resin composition according to this embodiment can be used for various molding processes such as injection molding, compression molding, composite molding, extrusion molding of sheets and pipes, pultrusion molding, blow molding, and transfer molding, but is particularly suitable for injection molding due to its excellent release properties. When molding by injection molding, the molding conditions are not particularly limited and can be molded using a general method. For example, the PAS resin composition can be melted in an injection molding machine at a temperature range above the melting point of the PAS resin (A), preferably at a temperature range of 10°C or higher than the melting point, more preferably at a temperature range of 10°C to 100°C, and even more preferably at a temperature range of 20°C to 50°C, after which it can be injected into a mold from the resin outlet for molding. In this case, the mold temperature can also be set to a known temperature range, for example, room temperature (23°C) to 300°C, preferably 130 to 190°C.

[0056] The method for manufacturing a molded article according to this embodiment may include a step of annealing the molded article. The optimal conditions for annealing are selected depending on the application or shape of the molded article, but the annealing temperature is in a temperature range above the glass transition temperature of the PAS resin (A), preferably in a temperature range of the glass transition temperature + 10°C or higher, and more preferably in a temperature range of the glass transition temperature + 30°C or higher. On the other hand, it is preferably in a range of 260°C or lower, and more preferably in a range of 240°C or lower. The annealing time is not particularly limited, but is preferably in a range of 0.5 hours or more, and more preferably in a range of 1 hour or more. On the other hand, it is preferably in a range of 10 hours or less, and more preferably in a range of 8 hours or less. Within this range, the strain of the resulting molded article is reduced, the crystallinity of the resin is improved, and the dimensional stability, mechanical properties and chemical resistance are further improved, which is preferable. The annealing treatment may be carried out in air, but it is preferable to carry it out in an inert gas such as nitrogen gas. [Examples]

[0057] 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.

[0058] <Manufacturing Example 1: Manufacturing of PAS Oligomers> 12.942 kg of flake sodium sulfide (60.3 wt% Na2S) and 30.000 kg of N-methyl-2-pyrrolidone (NMP) were charged into a 100 L autoclave equipped with a stirring blade and connected to a pressure gauge, thermometer, and condenser. The mixture was heated to 209°C while stirring under a nitrogen stream, and 3.096 kg of water was distilled off (the remaining water content was 1.13 moles per mole of sodium sulfide). The autoclave was then sealed and cooled to 180°C, and 14.790 kg of p-dichlorobenzene (hereinafter abbreviated as DCB) and 12.000 kg of NMP were charged. At a liquid temperature of 150°C, the mixture was pressurized to 0.1 MPa using nitrogen gas, and the heating was started. The reaction proceeded at a liquid temperature of 260°C for 3 hours with stirring. The maximum pressure during the reaction was 0.85 MPa. After the reaction, the reaction slurry was cooled, and the entire resulting slurry was filtered at 120°C. 32.000 kg of NMP was added, and the mixture was washed and filtered. The amount of NMP filtrate obtained was 53.600 kg. The entire obtained NMP filtrate was charged into a 150 L vacuum stirring dryer, and NMP was removed by distillation under reduced pressure at 150°C to obtain 1.835 kg of a composition containing cyclic PPS oligomers. 3.0 kg of ion-exchanged water at 70°C was added to the obtained composition containing cyclic PPS oligomers and mixed. After three washes (stirring and filtering), the mixture was dried in a hot air dryer at 120°C for 4 hours to obtain 0.5 kg of PPS oligomers.

[0059] <Example 1> Process (1): A 1L autoclave equipped with a stirring blade, connected to a content transfer nozzle, pressure gauge, thermometer, and condenser, was charged with 116.8g of PPS resin composition (40wt% glass fiber, additive content of 1wt% or less) and 680.0g of N-methyl-2-pyrrolidone (NMP). The mixture was heated to 250°C under a nitrogen stream while stirring, and stirred for 1 hour. After that, the autoclave was pressurized to 0.5MPa with nitrogen, and the valve of the transfer nozzle was opened. Process (2): Before transferring the mixture to the destination container, the liquid phase component containing PPS was recovered by solid-liquid separation using a 5 μm diameter wire mesh filter. Process (3): 70.0 g of sodium chloride (NaCl) was added to the liquid phase component, and the mixture was cooled to below 200°C to obtain a solid phase component containing PPS. Process (4): The solid phase component containing PPS precipitated in step (3) was recovered by solid-liquid separation using a filter. The obtained solid phase component was treated in a 2L vacuum stirring dryer with stirring blades under vacuum at 150°C for 4 hours to remove NMP, and then cooled to room temperature. A crude PPS mixture with a solid content of 99.4% was obtained. 100g of the obtained crude PPS mixture was added to 400g of ion-exchanged water at 70°C and stirred for 30 minutes, then filtered. After filtering, 1L of ion-exchanged water at 70°C was added to the cake to wash it. Furthermore, the obtained water-containing cake and 400g of ion-exchanged water were placed in a 1L autoclave with stirring blades, and the temperature was raised to 230°C over 2 hours while stirring, followed by 30 minutes of stirring for extraction, and then cooled to room temperature. The entire obtained mixture was filtered, and after filtering, 1L of ion-exchanged water at 70°C was added to the cake to wash it. Then it was dried at 120°C for 4 hours to obtain PPS resin. The evaluation results of the obtained PPS resin are shown in Table 1.

[0060] <Example 2> The procedure was carried out in the same manner as in Example 1, except that 70.0 g of sodium acetate (CH3COONa) was added in step (3). The evaluation results of the obtained PPS resin are shown in Table 1.

[0061] <Example 3> The procedure was carried out in the same manner as in Example 1, except that 35.0 g of NaCl was added in step (3). The evaluation results of the obtained PPS resin are shown in Table 1.

[0062] <Example 4> The procedure was carried out in the same manner as in Example 1, except that in step (1), a 5L autoclave with a stirring blade connected to a contents transfer nozzle, pressure gauge, thermometer, and condenser was used, and in step (3), 3,500g of NaCl was added. The evaluation results of the obtained PPS resin are shown in Table 1.

[0063] <Reference example 1> Process (1): 116.8 g of PPS composition (40 wt% glass fiber, additive content 1 wt% or less) and 680.0 g of NMP were charged into a 1 L autoclave equipped with a stirring blade, connected to a content transfer nozzle, pressure gauge, thermometer, and condenser. The temperature was raised to 250°C while stirring under a nitrogen stream and stirred for 1 hour. After that, the autoclave was pressurized to 0.5 MPa with nitrogen, and the valve of the transfer nozzle was opened. Process (2): Before transferring the mixture to the destination container, the liquid phase component containing PPS was recovered by solid-liquid separation using a 5 μm diameter wire mesh filter. Process (3): The liquid phase component obtained in step (2) was cooled to 150°C to obtain a solid phase component containing PPS. Process (4): The solid phase component containing PPS precipitated in step (3) was recovered by solid-liquid separation using a filter. The obtained solid phase component was treated in a 2L vacuum stirring dryer with stirring blades under vacuum at 150°C for 4 hours to remove NMP, and then cooled to room temperature. A crude PPS mixture with a solid content of 99.4% was obtained. 100g of the obtained crude PPS mixture was added to 400g of ion-exchanged water at 70°C and stirred for 30 minutes, then filtered. After filtering, 1L of ion-exchanged water at 70°C was added to the cake to wash it. Furthermore, the obtained water-containing cake and 400g of ion-exchanged water were placed in a 1L autoclave with stirring blades, and the temperature was raised to 230°C over 2 hours while stirring, followed by extraction by stirring for 30 minutes, and then cooled to room temperature. The entire obtained mixture was filtered, and after filtering, 1L of ion-exchanged water at 70°C was added to the cake to wash it. Then it was dried at 120°C for 4 hours to obtain PPS resin. The evaluation results of the obtained PPS resin are shown in Table 1.

[0064] <Comparative Example 1> The procedure was carried out in the same manner as in Example 1, except that 70.0 g of lithium chloride (LiCl) was added instead of NaCl in step (3). The evaluation results of the obtained PPS resin are shown in Table 1.

[0065] <Comparative Example 2> The procedure was carried out in the same manner as in Reference Example 1, except that 70.0 g of NaCl was added after solid-liquid separation by filtration in step (4). The evaluation results of the obtained PPS resin are shown in Table 1.

[0066] [Table 1]

[0067] <Example 5> PPS resin was obtained in the same manner as in Example 1, except that 3 g of PPS oligomer was added during the washing of the crude PPS mixture in step (4) so ​​that the PPS oligomer amounted to 5% by mass relative to the PPS resin. 10 g of the obtained PPS was heat-treated in an inert gas oven at 240°C for 35 hours under an inert gas atmosphere. The properties of the PPS resin obtained after treatment are shown in Table 2.

[0068] <Example 6> The procedure was the same as in Example 1, except that 3g of PPS oligomer was added during the drying process so that it corresponded to 5% by mass of PPS. The properties of the obtained PPS resin are shown in Table 2.

[0069] <Comparative Example 3> Without adding PPS oligomers, 10 g of the obtained PPS was heat-treated in an inert gas oven at 240°C for 35 hours under an inert gas atmosphere. The properties of the PPS resin obtained after treatment are shown in Table 2.

[0070] [Table 2]

[0071] <Rating>

[0072] (1) Measurement of the amount of gas generated (weight loss) The powder samples of PPS resin obtained in Examples 1-4, Reference Example 1, and Comparative Examples 1-2 were weighed into 4.0000 g aluminum petri dishes using a precision balance. The samples were left to stand in a drying oven set to 150°C for 1 hour, then the petri dishes were removed, allowed to cool to room temperature, and then weighed. Next, the same petri dishes were left to stand in a drying oven set to 370°C for 1 hour, then the petri dishes were removed, allowed to cool to room temperature, and then weighed. The amount of gas generated (wt%) for each sample was calculated using the following formula. Amount of generated gas (wt%) = {(Weighing value after heating at 150°C) - (Weighing value after heating at 370°C)} ÷ (Weighing value after heating at 150°C) × 100

[0073] Furthermore, the ratio of the amount of gas generated to that in Reference Example 1 was calculated as the reduction rate (%). Reduction rate (%) = Amount of gas generated in each example / Amount of gas generated in reference example 1 The results are shown in Table 1.

[0074] (2) Measurement of Mtop The peak molecular weight (Mtop) of the PPS resins obtained in Examples 5-9 and Comparative Example 3 was measured using gel permeation chromatography under the following measurement conditions, and the Mtop was calculated. The results are shown in Table 2. Six types of monodisperse polystyrene were used for calibration. Equipment: Ultra-high temperature polymer molecular weight distribution analyzer (SSC-7000, manufactured by Senshu Science Co., Ltd.) Column: UT-805L (manufactured by Showa Denko Corporation) Column temperature: 210℃ Solvent: 1-Chloronaphthalene Measurement method: UV detector (360nm)

[0075] Table 1 shows that the resin in the example produced less gas compared to the resin in the comparative example. Table 2 shows that when an oligomer was added to the resin with reduced gas production and heat-treated, it exhibited superior molecular chain extension.

Claims

1. A mixture (A) containing at least a polyarylene sulfide resin and an organic polar solvent as essential components is heated to 200°C or higher to dissolve the polyarylene sulfide resin in the organic polar solvent (1). Step (2) is to separate the mixture (A) into solid and liquid phases to obtain a liquid phase component containing at least a polyarylene sulfide resin and an organic polar solvent. Step (3) to obtain a mixture (B) by adding a dispersant to the liquid phase component and then cooling it to 200°C or below. The process includes step (4) of separating the mixture (B) into solid and liquid components to obtain a solid phase component, A method for recovering polyarylene sulfide resin, wherein the dispersant is water-soluble and insoluble in the organic polar solvent.

2. The method for recovering polyarylene sulfide resin according to claim 1, wherein the dispersant is an alkali metal salt.

3. The average particle size (D) of the resin composition or the molded article. ５０ A method for recovering polyarylene sulfide resin according to claim 1 or 2, wherein the diameter is 20 mm or less.

4. The method for recovering polyarylene sulfide resin according to claim 1 or 2, wherein the content of polyarylene sulfide resin in the resin composition or molded article is 20 parts by mass or more.

5. A further step (5) to add oligoarylene sulfide to the polyarylene sulfide resin obtained by the recovery method described in claim 1, A method for modifying polyarylene sulfide resin, comprising the step (6) of washing the obtained mixture and then heat-treating it.

6. A step (7) of washing the polyarylene sulfide resin obtained by the recovery method described in claim 1, A method for modifying a polyarylene sulfide resin, comprising the step (8) of adding oligoarylene sulfide to the obtained mixture and then heat-treating it.

7. The method for modifying a polyarylene sulfide resin according to claim 5 or 6, wherein the oligoarylene sulfide is a cyclic oligoarylene sulfide.

8. A method for producing a polyarylene sulfide resin composition, comprising the step of blending a polyarylene sulfide resin obtained by the method described in claims 1 to 6 as an essential component and melt-kneading it at a temperature above the melting point of the polyarylene sulfide resin.

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