Polyarylate resin

Abstract

To provide a polyarylate resin in which the resin itself exhibits improved and sufficiently favorable color tone, can more effectively suppress coloration caused by heat deterioration in melt molding, and further allows production of a molded body that can be used in a reflow process or under high-temperature conditions.SOLUTION: A polyarylate resin contains, as monomer components, an aromatic dicarboxylic acid component and a divalent phenol component, has a formate content of 0.1 to 2.0 ppm, and has a glass transition temperature of 200 to 300°C.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyarylate resin and a method for producing the same. [Background technology]

[0002] Polyarylate resins, which are made from aromatic dicarboxylic acid components and dihydric phenol components, are amorphous, transparent, and have excellent heat resistance, making them suitable for a variety of applications. In particular, in the electrical and electronics fields, polyarylate resins are being considered for use in transparent lenses, such as substrate materials that require a reflow process, due to their excellent heat resistance. Heat resistance of 250°C or higher is required for reflow processing with lead solder, and 200°C or higher for reflow processing with low-temperature solder (lead-free).

[0003] However, due to its excellent heat resistance, polyarylate resins are often processed at higher melt-molding temperatures than general-purpose polymers, which makes them prone to thermal degradation and discoloration during melting. Furthermore, molded articles tend to yellow when used at high temperatures for long periods. Therefore, their use has been limited in applications where color tone and transparency are required and color change over time is undesirable, such as automobile lamp lenses and camera lenses for in-car or mobile phone cameras.

[0004] To solve the above problems, various methods have been investigated for adding modifiers such as dyes, pigments, and antioxidants during melt molding or melt kneading. For example, Patent Document 1 proposes a method of melt kneading a dye, pigment, and sulfur-containing carboxylic acid ester with a polycarbonate resin. Furthermore, Patent Document 2 proposes a method of melt kneading a phenolic compound, a phosphorus-based compound, and a lactone-based compound with a polyarylate resin. However, these methods rely solely on additives added during melt kneading, and therefore there is a need to improve the color tone and thermal discoloration of the polyarylate resin itself, in order to reduce the number and amount of additives used.

[0005] In order to improve the color tone and thermal discoloration of the polyarylate resin itself, it is necessary to devise an ingenuity in the stage of producing the polyarylate resin from raw materials. As polymerization methods for polyarylate resin, melt polymerization, solution polymerization, and interfacial polymerization are known. In particular, the interfacial polymerization method is suitable for polymers with high heat resistance, because the reaction proceeds to a high degree of polymerization at temperatures close to room temperature, resulting in a resin with excellent color tone, and making full use of the transparency and heat resistance that are inherent characteristics of polyarylate resin.

[0006] Furthermore, as described in Patent Document 3, although not limited to the interfacial polymerization method, adding a reducing agent such as sodium hydrosulfite during the polymerization process is effective in preventing discoloration of the dihydric phenol compound monomer and further coloration of the resulting polyarylate resin.

[0007] On the other hand, Patent Document 4 discloses a technique for producing an aromatic polycarbonate having excellent color tone and heat resistance by using sodium hydrosulfite as a reducing agent added during the polymerization step.

[0008] Furthermore, Patent Document 5 discloses a technology for producing polycarbonate with excellent hue by limiting the sodium formate content in sodium hydrosulfite used in the production of polycarbonate to 0.3 wt % or less. In particular, Patent Document 5 proposes that if the sodium formate content in the sodium hydrosulfite used in the production of polycarbonate is more than 0.3 wt %, the hue of the resin will deteriorate when heated. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 4-120164 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-265766 [Patent Document 3] Special Publication No. 1-18939 [Patent Document 4] Japanese Patent Application Publication No. 7-233253 [Patent Document 5] Japanese Patent Application Laid-Open No. 2009-096937 Summary of the Invention [Problem to be solved by the invention]

[0010] However, the conventional techniques sometimes have the following problems. It is not possible to obtain polyarylate resin with a sufficiently excellent color tone. When molding using polyarylate resin, coloration due to thermal degradation during melt molding cannot be sufficiently suppressed.

[0011] The present invention aims to provide a polyarylate resin that has a sufficiently good color tone of the resin itself, can more sufficiently suppress coloration due to thermal degradation during melt molding, and can produce molded articles that can be used even in a reflow process (or in a high-temperature environment). [Means for solving the problem]

[0012] As a result of extensive research into solving the above problems, the present inventors have found that the above object can be achieved by incorporating an appropriate amount of formate in a polyarylate resin.

[0013] The gist of the present invention is as follows. <1> Contains an aromatic dicarboxylic acid component and a dihydric phenol component as monomer components, A polyarylate resin having a formate content of 0.1 to 2.0 ppm and a glass transition temperature of 200 to 300°C. <2> The dihydric phenol component contains 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane. <1> The polyarylate resin according to claim 1. <3> The polyarylate resin has a color difference a value of -1.0 to 0.5. <1> or <2> The polyarylate resin according to claim 1. <4> The polyarylate resin has a granular shape. <1> ~ <3> The polyarylate resin according to any one of the above items. <5> the formate salt is sodium formate; <1> ~ <4> The polyarylate resin according to any one of the above items. <6> A molded plate having a thickness of 3 mm molded by injection molding the polyarylate resin has a YI value of 28 or less. <1> ~ <5> The polyarylate resin according to any one of the above items. <7> The content of the formate is 0.1 to 1.5 ppm. <1> ~ <6> The polyarylate resin according to any one of the above items. <8> A method for producing a polyarylate resin by polymerizing an aromatic dicarboxylic acid component and a dihydric phenol component, A method for producing a polyarylate resin, wherein a dithionite having a formate content of 0.4 to 1.5 mass % is added in an amount of 0.05 to 4.0 mass % based on the dihydric phenol component. <9> The dithionite is sodium dithionite produced by the sodium formate method. <8> A method for producing the polyarylate resin described in <10> <1> ~ <7> The polyarylate resin according to any one of the above is produced. <8> or <9> A method for producing the polyarylate resin described in [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a heat-resistant polyarylate resin which has a sufficiently good color tone of the resin itself, can more sufficiently suppress coloration due to thermal degradation during melt molding, and can produce molded articles which can be used even in a reflow process (or in a high-temperature environment). DETAILED DESCRIPTION OF THE INVENTION

[0015] The polyarylate resin of the present invention is an aromatic polyester resin obtained from an aromatic dicarboxylic acid component (including its derivatives) and a dihydric phenol component, and contains these components as monomer components. Therefore, the polyarylate resin of the present invention can also be described as containing residues of an aromatic dicarboxylic acid component and a dihydric phenol component. The structure of the polyarylate resin of the present invention is not particularly limited, and the present invention is applicable to polyarylate resins of any structure. The derivative refers to an organic compound in which the carboxyl group of an aromatic dicarboxylic acid is replaced with a more reactive substituent, and includes, for example, an acid halide compound having an acid halide group, as described below.

[0016] The aromatic dicarboxylic acid component used to introduce the aromatic dicarboxylic acid residues that make up the polyarylate resin is an organic compound containing an aromatic ring and two carboxyl groups per molecule. The carboxyl groups may be acid halide groups. An acid halide group is a group in which the hydroxyl group of a carboxyl group is replaced with a halogen atom. Specific examples of such aromatic dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, chlorophthalic acid, nitrophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, methyl terephthalic acid, 4,4'-biphenyldicarboxylic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylmethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 4,4'-diphenylisopropylidenedicarboxylic acid, 1,2-bis(4-carboxyphenoxy)ethane, 5-sodium sulfoisophthalic acid, diphenic acid, and derivatives thereof (e.g., acid halides). These aromatic dicarboxylic acids can be used alone or in combination of two or more. Among these, it is preferred that the polyarylate resin contains at least one of terephthalic acid and isophthalic acid, and preferably both, from the viewpoint of further improving color tone, discoloration resistance, and heat resistance.

[0017] In this specification, the color tone refers to the color tone of the polyarylate resin itself, and refers to the property of having a smaller color difference a value measured by a color difference meter.

[0018] Discoloration resistance is a property that more sufficiently suppresses discoloration due to thermal degradation during melt molding of a polyarylate resin, and refers to a property that results in a smaller yellow index (YI) value of the obtained molded product measured with a color tone measuring device.

[0019] The heat resistance is the heat resistance of the polyarylate resin itself, and refers to the property of having a higher glass transition temperature as measured by a differential scanning calorimeter.

[0020] The total content of terephthalic acid and isophthalic acid in the polyarylate resin is not particularly limited, and from the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and sufficiently preferably 100 mol% based on the total amount of aromatic dicarboxylic acid components. The total content of terephthalic acid and isophthalic acid may be the total content of residues of terephthalic acid and isophthalic acid.

[0021] When the polyarylate resin contains at least one (preferably both) of terephthalic acid and isophthalic acid as the aromatic dicarboxylic acid component, their contents are not particularly limited, and from the viewpoint of further improving color tone, discoloration resistance, and heat resistance, the molar ratio of terephthalic acid / isophthalic acid is preferably 0 / 100 to 100 / 0, more preferably 10 / 90 to 90 / 10, even more preferably 20 / 80 to 80 / 20, particularly preferably 40 / 60 to 60 / 40, sufficiently preferably 45 / 55 to 55 / 45, and even more preferably 50 / 50. The contents of terephthalic acid and isophthalic acid may be the contents of residues of terephthalic acid and isophthalic acid.

[0022] The dihydric phenol component for introducing the dihydric phenol residues constituting the polyarylate resin is an organic compound containing two phenolic hydroxyl groups per molecule. The phenolic hydroxyl group is a hydroxyl group directly bonded to an aromatic ring. Specific examples of such dihydric phenol components include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2,2-bis(3-methyl-4-hydroxyphenyl)propane (bisphenol C), 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), 1,1-bis(4-hydroxyphenyl)-1-phenylethane (bisphenol AP), 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, and 2,2-bis(4-hydroxy-3,5-dibromophenyl). Examples of suitable dihydric phenols include propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxybiphenyl [4,4'-biphenol], 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC), 4,4'-(1,3-dimethylbutylidene)diphenol, and resorcinol. These compounds may be used alone or in combination of two or more. From the viewpoint of further improving heat resistance, the dihydric phenol component preferably contains an aliphatic ring-containing dihydric phenol component. The aliphatic ring-containing dihydric phenol component is an organic compound containing one or more (particularly one) aliphatic rings (e.g., cyclohexane rings) per molecule, one or more (particularly two) aromatic rings (e.g., benzene rings) per molecule, and two phenolic hydroxyl groups per molecule. Examples of the aliphatic ring-containing dihydric phenol component include bisphenol Z and bisphenol TMC.From the viewpoint of further improving color tone, discoloration resistance, and heat resistance, the polyarylate resin preferably contains one or more dihydric phenol components selected from the group consisting of bisphenol A, bisphenol C, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, and aliphatic ring-containing dihydric phenol components (e.g., bisphenol Z, bisphenol TMC), more preferably contains one or more dihydric phenol components selected from the group consisting of bisphenol A and aliphatic ring-containing dihydric phenol components (particularly bisphenol TMC), and from the viewpoint of further improving heat resistance, it is even more preferable that the polyarylate resin contains an aliphatic ring-containing dihydric phenol component (particularly 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC)).

[0023] When an aliphatic ring-containing dihydric phenol component (particularly bisphenol TMC) is used, the content of the aliphatic ring-containing dihydric phenol component (particularly bisphenol TMC) in the polyarylate resin is preferably 1 to 100 mol%, more preferably 20 to 100 mol%, even more preferably 40 to 100 mol%, particularly preferably 60 to 100 mol%, and sufficiently preferably 100 mol%, based on the total amount of dihydric phenol components, from the viewpoint of further improving heat resistance while maintaining good color tone and discoloration resistance. The content of the aliphatic ring-containing dihydric phenol component (particularly bisphenol TMC) may be the content of residues of the aliphatic ring-containing dihydric phenol component (particularly residues of bisphenol TMC).

[0024] The total content of bisphenol A and aliphatic ring-containing dihydric phenol components (particularly bisphenol TMC) in the polyarylate resin is not particularly limited, and from the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and sufficiently preferably 100 mol% based on the total amount of dihydric phenol components. The total content of bisphenol A and aliphatic ring-containing dihydric phenol components (particularly bisphenol TMC) may be the total content of residues of bisphenol A and aliphatic ring-containing dihydric phenol components (particularly bisphenol TMC).

[0025] When the polyarylate resin contains at least one of bisphenol A and an aliphatic ring-containing dihydric phenol component (particularly bisphenol TMC) as the dihydric phenol component, the content ratio is not particularly limited. From the viewpoint of further improving color tone, discoloration resistance, and heat resistance, the molar ratio of bisphenol A / aliphatic ring-containing dihydric phenol component (particularly bisphenol TMC) is preferably 0 / 100 to 100 / 0, more preferably 0 / 100 to 95 / 5, even more preferably 0 / 100 to 80 / 20, sufficiently preferably 0 / 100 to 50 / 50, even more preferably 0 / 100 to 40 / 60, particularly preferably 0 / 100 to 20 / 80, and most preferably 0 / 100. The content ratio of bisphenol A and aliphatic ring-containing dihydric phenol component (particularly bisphenol TMC) may be the content ratio of residues of bisphenol A and aliphatic ring-containing dihydric phenol component (particularly bisphenol TMC).

[0026] From the viewpoint of further improving color tone, discoloration resistance, and heat resistance, the polyarylate resin of the present invention has the following monomer composition (i) or (ii) as a more preferred embodiment, and has the following monomer composition (i) as an even more preferred embodiment:

[0027] Monomer composition (i): When the polyarylate resin contains terephthalic acid and isophthalic acid in a terephthalic acid / isophthalic acid molar ratio of 40 / 60 to 60 / 40 (particularly 45 / 55 to 55 / 45), the polyarylate resin also contains bisphenol A and an aliphatic ring-containing dihydric phenol component (particularly bisphenol TMC) in a bisphenol A / aliphatic ring-containing dihydric phenol component (particularly bisphenol TMC) molar ratio of 0 / 100 to 95 / 5, preferably 0 / 100 to 80 / 20, more preferably 0 / 100 to 50 / 50, even more preferably 0 / 100 to 40 / 60, sufficiently preferably 0 / 100 to 20 / 80, and even more preferably 0 / 100 to 10 / 90;

[0028] Monomer composition (ii): When the polyarylate resin contains terephthalic acid and isophthalic acid in a molar ratio of terephthalic acid / isophthalic acid of 0 / 100 or more but less than 40 / 60, or 60 / 40 or more but less than 100 / 0, the polyarylate resin also contains bisphenol A and an aliphatic ring-containing dihydric phenol component (particularly bisphenol TMC) in a molar ratio of bisphenol A / aliphatic ring-containing dihydric phenol component (particularly bisphenol TMC) of 0 / 100 to 100 / 0, more preferably 0 / 100 to 95 / 5, even more preferably 0 / 100 to 80 / 20, sufficiently preferably 0 / 100 to 50 / 50, even more preferably 0 / 100 to 40 / 60, and particularly preferably 0 / 100 to 20 / 80. For example, a molar ratio of "0 / 100 or more but less than 40 / 60" means that the molar ratio is in the range of 0 / 100 to 40 / 60, excluding 40 / 60.

[0029] The polyarylate resin may contain at least one dihydric alcohol component selected from the group consisting of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, dodecanediol, neopentyl glycol, cyclohexanediol, 1,4-dihydroxymethylcyclohexane, etc., in place of a portion of the dihydric phenol component, as long as the properties and effects of the present invention are not impaired.

[0030] The content of the dihydric alcohol component in the polyarylate resin is not particularly limited and may be, for example, 50% by mass or less relative to the total amount of dihydric phenol components, and from the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 1% by mass or less, and sufficiently preferably 0% by mass. The content of the dihydric alcohol component may be the content of residues of the dihydric alcohol component.

[0031] The polyarylate resin may further contain a trifunctional or higher polyvalent monomer component, provided that the properties and effects of the present invention are not impaired. When the polyarylate resin contains a trifunctional or higher polyvalent monomer component, a branched structure is introduced into the polyarylate resin. Examples of trifunctional or higher polyvalent monomer components include tricarboxylic acid components such as 1,3,5-benzenecarboxylic acid and triol components such as 4,4',4''-trihydroxytriphenylmethane.

[0032] The content of the polyvalent monomer component in the polyarylate resin is not particularly limited and may be, for example, 20% by mass or less relative to the total amount of the dihydric phenol component and the aromatic dicarboxylic acid component, and from the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 2% by mass or less, particularly preferably 1% by mass or less, and sufficiently preferably 0% by mass. The content of the polyvalent monomer component may be the content of residues of the polyvalent monomer component.

[0033] The polyarylate resin may contain an end-capping agent to adjust its molecular weight. Examples of the end-capping agent include one or more compounds selected from the group consisting of monohydric phenols such as phenol, cresol, p-tert-butylphenol, 2,3,5-trimethylphenol, 2,3,6-trimethylphenol, and cumylphenol; monohydric acid chlorides such as benzoic acid chloride, methanesulfonyl chloride, and phenyl chloroformate; monohydric alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, pentanol, hexanol, dodecyl alcohol, stearyl alcohol, benzyl alcohol, and phenethyl alcohol; and monohydric carboxylic acids such as acetic acid, propionic acid, octanoic acid, cyclohexanecarboxylic acid, benzoic acid, toluic acid, phenylacetic acid, p-tert-butylbenzoic acid, and p-methoxyphenylacetic acid. The end-capping agent is preferably a monohydric phenol (particularly p-tert-butylphenol) from the viewpoint of further improving color tone, discoloration resistance, and heat resistance.

[0034] The content of the terminal blocking agent in the polyarylate resin is not particularly limited, and from the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably 0.2 to 20 parts by mass, more preferably 0.6 to 10 parts by mass, even more preferably 1.2 to 6 parts by mass, and particularly preferably 2 to 5 parts by mass, relative to 100 parts by mass of the dihydric phenol component. The content of the terminal blocking agent may be the content of residues of the terminal blocking agent.

[0035] The polyarylate resin of the present invention contains 0.1 to 2.0 ppm of formate. From the viewpoint of further improving color tone, discoloration resistance, and heat resistance, the formate content is preferably 0.1 to 1.5 ppm, more preferably 0.1 to 0.8 ppm, even more preferably 0.1 to 0.5 ppm, and particularly preferably 0.2 to 0.4 ppm. In the present invention, by containing the formate in the polyarylate resin in the appropriate amount as described above, not only is the color tone of the polyarylate resin itself sufficiently excellent, but molded articles containing the polyarylate resin also have sufficiently excellent discoloration resistance. If the formate content of the polyarylate resin exceeds 2.0 ppm, thermal degradation during melt molding is accelerated, resulting in significant yellowing of the resin molded article. On the other hand, if the formate content is less than 0.1 ppm, the color difference a value of the powder or granule will be very low, but the effect of suppressing thermal discoloration during melt molding will be insufficient, resulting in significant yellowing of the resin molded article.

[0036] The formate may be an alkali metal salt of formic acid, such as sodium formate, potassium formate, etc. From the viewpoint of further improving color tone, discoloration resistance, and heat resistance, the formate is preferably sodium formate, and the above content is preferably the content of sodium formate.

[0037] The content of formate is determined by extracting formate from 0.5 g of polyarylate resin with 50 mL of ultrapure water and quantitatively analyzing the extracted formate by ion chromatography (IC).

[0038] The formate contained in the polyarylate resin of the present invention may be a residue of the formate contained in the reducing agent (e.g., dithionite (particularly sodium hydrosulfite)) used during the production of the polyarylate resin, or may be an additive newly added after the production of the polyarylate resin.

[0039] The formate content can be controlled by the following methods: The polyarylate resin is dissolved and washed with an organic solvent capable of dissolving the polyarylate resin. This reduces the formate content. Various organic solvents can dissolve the polyarylate resin depending on the monomer components constituting the polyarylate resin. Examples of suitable organic solvents include aliphatic chlorinated solvents such as dichloromethane, 1,2-dichloroethane, chloroform, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, dibromomethane, tribromomethane, bromoethane, 1,1-dibromoethane, and 1-bromopropane; aromatic chlorinated solvents such as chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, and p-dichlorobenzene; amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; ether solvents such as 1,4-dioxane, 1,3-dioxolane, and tetrahydrofuran; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; and mixtures thereof.

[0040] When producing a polyarylate resin, the formate content in the dithionite (particularly sodium hydrosulfite) used as a reducing agent is adjusted. For example, by reducing the formate content in the dithionite (particularly sodium hydrosulfite), the formate content in the polyarylate resin can be reduced. Furthermore, by increasing the formate content in the dithionite (particularly sodium hydrosulfite), the formate content in the polyarylate resin can be increased.

[0041] When producing a polyarylate resin, the amount of dithionite (particularly sodium hydrosulfite) used as a reducing agent is adjusted. For example, by reducing the amount of dithionite (particularly sodium hydrosulfite) used, the formate content of the polyarylate resin can be reduced. Alternatively, by increasing the amount of dithionite (particularly sodium hydrosulfite) used, the formate content of the polyarylate resin can be increased.

[0042] When producing polyarylate resin, the formate content of the polyarylate resin can be reduced by strengthening the washing process with pure water (for example, by extending the washing time).

[0043] By employing one or more of the above-mentioned methods, or by employing two or more of them in combination, the content of formate in the polyarylate resin can be controlled.

[0044] The glass transition temperature of the polyarylate resin of the present invention is 200° C. or higher, and from the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably 220° C. or higher, more preferably 250° C. or higher, even more preferably 255° C. or higher, and particularly preferably 260° C. or higher. There is no particular upper limit to the glass transition temperature, and the glass transition temperature may usually be 300° C. or lower.

[0045] The glass transition temperature of the polyarylate resin is determined by measuring the onset temperature of discontinuous change due to the glass transition temperature in the temperature rise curve obtained by heating from 30°C to 400°C at a rate of 10°C / min using a differential scanning calorimeter.

[0046] The color difference a value of the polyarylate resin of the present invention is usually -1.0 to 0.5, and from the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably -1.0 to 0.2, more preferably -1.0 to -0.1, even more preferably -1.0 to -0.4, and particularly preferably -0.8 to -0.45.

[0047] The color difference a value is obtained by filling a measurement container with polyarylate resin so that there are no gaps, and measuring in reflection mode with a colorimetric colorimeter (for example, a colorimetric colorimeter (ZE6000) manufactured by Nippon Denshoku Industries Co., Ltd.) The polyarylate resin used for measurement has a particulate shape, and the particle diameter of the particles is 0.7 to 5.0 mm (some may contain fine powder).

[0048] The YI value of a 3 mm thick plate obtained by injection molding the polyarylate resin of the present invention is usually 28 or less, and from the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably 26 or less, more preferably 24 or less, and even more preferably 20 or less. There is no particular limitation on the lower limit of the YI value, and the YI value is usually 1 or more, particularly 4 or more.

[0049] The YI value is measured by subjecting a 3 mm thick plate obtained by injection molding a polyarylate resin at a resin temperature of 400°C using a general injection molding machine (for example, a J110AD injection molding machine manufactured by JSW Corporation) to a color measurement device (for example, an SZ-Σ90 colorimeter manufactured by Nippon Denshoku Industries Co., Ltd.). The polyarylate resin used for molding has a particulate shape, and the particle diameter of the particles is 0.7 to 5.0 mm (some particles may contain fine powder).

[0050] In general, from the viewpoints of mechanical properties and workability during melt molding and melt kneading, the polyarylate resin of the present invention preferably has an inherent viscosity of 0.40 to 1.30 dl / g, more preferably 0.45 to 1.10 dl / g, even more preferably 0.50 to 0.90 dl / g, particularly preferably 0.50 to 0.80 dl / g, and sufficiently preferably 0.50 to 0.70 dl / g.

[0051] The inherent viscosity (ηinh) is an index of molecular weight, and the value measured by the following method is used. A resin solution of polyarylate resin is prepared using 1,1,2,2-tetrachloroethane as a solvent to a concentration of 1 g / dL, and the relative viscosity (ηrel) is measured at a temperature of 25°C. The inherent viscosity is calculated from the obtained relative viscosity using the following formula. ηinh(dl / g) = Ln(ηrel) / c (c: concentration)

[0052] The polymerization method for the polyarylate resin is not particularly limited as long as the resulting polyarylate resin has the above-mentioned properties, and may be any known method, for example, the following method: A solution polymerization method in which a dicarboxylic acid halide containing an aromatic dicarboxylic acid component is reacted with a diol containing a dihydric phenol component in an organic solvent; A melt polymerization method in which the dicarboxylic acid and the diol are heated in the presence of acetic anhydride or diallyl carbonate; and An interfacial polymerization method in which a dicarboxylic acid halide dissolved in an organic solvent that is not compatible with water is mixed with a diol dissolved in an alkaline aqueous solution.

[0053] The polymerization method for the polyarylate resin used in the present invention is preferably an interfacial polymerization method, since the reaction proceeds to a high degree of polymerization at a relatively low temperature, from the viewpoint of further improving color tone, discoloration resistance, and heat resistance.

[0054] When using interfacial polymerization, the organic solvent used is not particularly limited as long as it is immiscible with water and dissolves the dicarboxylic acid halide used and the resulting polyarylate resin. Suitable organic solvents include aliphatic chlorinated solvents such as dichloromethane, 1,2-dichloroethane, chloroform, 1,1,1-trichloroethane, and tetrachloroethane; aromatic chlorinated solvents such as chlorobenzene and o-dichlorobenzene; and mixtures thereof. In the isolation and drying process of the resulting polyarylate resin, it is best to avoid organic solvents with excessively high boiling points. Among these, aliphatic chlorinated solvents (especially dichloromethane) are preferred.

[0055] In the interfacial polymerization method, it is preferable to use a dithionite produced by the sodium formate method as the reducing agent, because the formate content in the polyarylate resin can be easily achieved, and as a result, the polyarylate resin of the present invention having excellent color tone and discoloration resistance can be easily produced.

[0056] The dithionite may be an alkali metal salt of dithionous acid, such as sodium dithionite (also known as sodium hydrosulfite), potassium dithionite, etc. From the viewpoint of further improving color tone, discoloration resistance, and heat resistance, the dithionite is preferably sodium hydrosulfite.

[0057] From the viewpoint of further improving color tone, discoloration resistance, and heat resistance, sodium hydrosulfite produced by the sodium formate method is preferred as the dithionite. Dithionite produced by a method other than the sodium formate method (e.g., an electrolytic method) does not contain formate itself.

[0058] The sodium formate method is a method for producing sodium hydrosulfite using sodium formate. Specifically, sodium formate is dissolved in aqueous alcohol (e.g., aqueous methanol), and sodium hydroxide and sulfurous anhydride are added to cause a reaction.

[0059] The content of formate contained in the dithionite (particularly the content of sodium formate contained in sodium hydrosulfite produced by the sodium formate method) is preferably 0.4 to 1.5 mass%, more preferably 0.4 to 1.0 mass%, even more preferably 0.5 to 1.0 mass%, and particularly preferably 0.5 to 0.8 mass%, from the viewpoint of further improving color tone, discoloration resistance, and heat resistance. If the content of the formate (particularly sodium formate) is too low or too high, it becomes difficult for the resulting polyarylate resin to achieve the formate content of the polyarylate resin of the present invention, and discoloration due to thermal degradation during melt molding cannot be sufficiently suppressed. The content of the formate (particularly sodium formate) is the ratio to the total amount of dithionite (particularly the total amount of sodium hydrosulfite). The total amount of dithionite refers to the total amount of dithionite and formate contained in said dithionite, and in particular, when by-products and decomposition products are contained in the dithionite, this refers to the total amount including said by-products and decomposition products. The total amount of sodium hydrosulfite refers to the total amount of sodium hydrosulfite and sodium formate contained in said sodium hydrosulfite, and in particular, when by-products and decomposition products are contained in the sodium hydrosulfite, this refers to the total amount including said by-products and decomposition products.

[0060] Methods for quantifying formate contained in dithionite (particularly methods for quantifying formate contained in sodium hydrosulfite produced by the sodium formate method) include the method specified in "Specifications and Standards for Food Additives, etc. (Ministry of Health and Welfare Notification No. 370 of 1959) Section 2: Food Additives (as of November 30, 2017)" and methods for detecting organic acids by ion chromatography. In the present invention, the method for detecting organic acids by ion chromatography is adopted.

[0061] The content of formate contained in dithionite (particularly sodium hydrosulfite) can be controlled, for example, by washing and purifying the dithionite (particularly the obtained sodium hydrosulfite) with an aqueous methanol solution. Specifically, the content of formate (particularly sodium formate) can be controlled by adjusting the number of times of washing with the aqueous methanol solution and the methanol concentration of the aqueous methanol solution. For example, the more times the washing is performed, the lower the content of formate (particularly sodium formate). On the other hand, the fewer times the washing is performed, the higher the content of formate (particularly sodium formate). Furthermore, for example, the higher the methanol concentration of the aqueous methanol solution, the lower the content of formate (particularly sodium formate). On the other hand, the lower the methanol concentration of the aqueous methanol solution, the higher the content of formate (particularly sodium formate).

[0062] From the viewpoint of further improving color tone, discoloration resistance, and heat resistance, the amount of reducing agent (e.g., dithionite (particularly sodium hydrosulfite produced by the sodium formate method)) added is preferably 0.05 to 4.0 mass% relative to the mass of the dihydric phenol component used, more preferably 0.1 to 2.0 mass%, even more preferably 0.2 to 2.0 mass%, particularly preferably 0.2 to 1.5 mass%, with 0.2 to 1.1 mass% being sufficiently preferable, and 0.3 to 0.8 mass% being even more preferable. If the amount of reducing agent added is too small or too large, it becomes difficult to achieve the desired formate content in the polyarylate resin of the present invention. For example, if the amount added is less than 0.05 mass%, the effect of preventing discoloration of the dihydric phenol component is insufficient, and discoloration due to thermal degradation during melt molding cannot be sufficiently suppressed. On the other hand, if the amount added is increased to more than 4.0 mass%, the formate content in the polyarylate resin of the present invention will be too high, and discoloration due to thermal degradation during melt molding cannot be sufficiently suppressed.

[0063] Interfacial polymerization method can use polymerization catalyst.As the polymerization catalyst of interfacial polymerization method, can be mentioned tertiary amines such as trimethylamine, triethylamine, tri-n-butylamine, tri-n-propylamine, tri-isopropylamine, trihexylamine, tridecylamine, N,N-dimethylcyclohexylamine, pyridine, quinoline, dimethylaniline; quaternary ammonium salts such as trimethylbenzylammonium halide, triethylbenzylammonium halide, tri-n-propylbenzylammonium halide, tri-n-butylbenzylammonium halide; quaternary phosphonium salts such as trimethylbenzylphosphonium halide, tetramethylbenzylphosphonium halide, triethylbenzylphosphonium halide, tri-n-butylbenzylphosphonium halide, tetra-n-butylphosphonium halide, triphenylbenzylphosphonium halide, tetraphenylphosphonium halide; crown ethers such as 18-crown-6, 18-benzocrown-6, 18-dibenzocrown-6, 15-crown-5. In particular, from the viewpoints of polymerization rate and cost, quaternary ammonium salts (particularly trimethylbenzylammonium halide and tri-n-butylbenzylammonium halide) are preferred.

[0064] The amount of the polymerization catalyst used is not particularly limited, and from the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably 0.1 to 5 mass %, more preferably 0.1 to 3 mass %, and even more preferably 0.1 to 1.5 mass % relative to the dihydric phenol component.

[0065] When the polyarylate resin of the present invention is produced by interfacial polymerization, it is preferable to employ the following method. A dihydric phenol component, end-capping agent, reducing agent, and polymerization catalyst are dissolved in an alkaline aqueous solution to obtain an aqueous layer. Separately, an aromatic dicarboxylic acid component is dissolved in an organic solvent to obtain an organic layer. The two incompatible liquids (the aqueous and organic layers described above) are mixed under strong stirring, and the polymerization reaction is carried out until a high degree of polymerization is achieved due to interlayer migration of the dihydric phenol component and end-capping agent component in the aqueous layer. After the reaction is complete, stirring is stopped and the resulting solution is separated into an organic layer containing the dissolved polyarylate resin and an aqueous layer containing by-products such as salts and unreacted monomers. The organic layer is then neutralized with an inorganic acid such as acetic acid or phosphoric acid.

[0066] The organic layer after neutralization contains unreacted monomers, low-molecular-weight polyarylate resins, by-product salts, and other impurities. To remove these impurities, the organic layer is thoroughly washed with pure water using a method such as static separation or centrifugation. Both static separation and centrifugation involve extracting various impurities contained in the organic layer into pure water, and either method may be used as appropriate. Washing with pure water can reduce the formate content in the polyarylate resin. Furthermore, increasing the number of times and duration of washing with pure water can further reduce the formate content.

[0067] The process of granulating polyarylate resin from the organic layer in which the thoroughly washed polyarylate resin is dissolved includes the hot water granulation method in which the organic solvent is distilled off in hot water, the kneader method in which the organic solvent is evaporated by heating using a kneader or the like and the residual polymer is pulverized, the spray dry method in which the organic solvent is sprayed with a spray to instantly evaporate the organic solvent, and the reprecipitation method in which the organic solvent solution is introduced into a poor solvent for the polyarylate resin to precipitate and precipitate the polymer component, etc. Any method may be used as appropriate, but in the present invention, the hot water granulation method is preferred in view of the properties of the particles obtained and the simplicity of the equipment.

[0068] When dichloromethane is used as the organic solvent, hot water granulation involves placing 50°C hot water in a hot water jacket tank equipped with an agitator, stirring it, and then circulating the hot water by withdrawing it from the bottom of the tank and introducing it into a wet pulverizer and returning it to the same tank, while supplying an organic solvent solution in which polyarylate resin has been dissolved.While maintaining the liquid temperature in the tank at 50°C, the organic solvent is distilled off to granulate the polyarylate resin, and a polyarylate / hot water slurry is obtained in the wet pulverizer on the circulation line, taking care not to generate large particles.This slurry is then withdrawn through a filter to obtain only the polyarylate resin powder.

[0069] The granulated polyarylate resin powder is dried using an appropriate dryer and method depending on the production volume, etc. At this time, if the drying temperature exceeds 140°C, the vaporized dichloromethane will undergo thermal decomposition, generating hydrogen chloride, which will severely corrode the inner walls of the dryer; therefore, operation at 140°C or below (particularly 120 to 135°C) is desirable. By setting the drying temperature to 120 to 135°C, it is possible to sufficiently remove moisture and dichloromethane while keeping the formate content of the polyarylate resin within the above-mentioned range.

[0070] When the polyarylate resin of the present invention has a powdery or granular shape (or a powdery or granular form), the particle diameter of the particles is 0.7 to 5.0 mm (some particles may be fine powders). Furthermore, the polyarylate resin of the present invention may contain some particles in which two or more particles are pressed together.

[0071] The particle size of the polyarylate resin is a value obtained by measuring 50 random particles of the polyarylate resin using a microscope (VHX-6000) manufactured by Keyence Corporation.

[0072] The polyarylate resin of the present invention can be melt-kneaded with various thermoplastic resins and various additives to produce a polyarylate resin composition with distinctive properties. Kneading methods include those using common extruders, such as single-screw extruders, twin-screw extruders, roll mixers, and Brabender mixers. Among these, the twin-screw extruder method is preferred because it ensures a good kneading state of multiple raw materials. It is also preferable to use a static mixer or dynamic mixer in combination. The raw materials may be added from a hopper or a side feeder. The resin composition obtained by melt-kneading is preferably in the form of pellets. The polyarylate resin composition contains the polyarylate resin of the present invention and may further contain at least one selected from thermoplastic resins and additives. For example, the polyarylate resin composition may contain only a polyarylate resin, a thermoplastic resin, and an additive. In this case, the polyarylate resin composition may or may not contain the thermoplastic resin and the additive independently.

[0073] Examples of thermoplastic resins include nylon resin, polycarbonate resin, polyester resin, polyphenylene ether resin, polystyrene resin, acrylonitrile-butadiene-styrene resin, liquid crystal polymer, etc. The polyester resin refers to a polyester resin other than the polyarylate resin of the present invention.

[0074] The content of the thermoplastic resin in the polyarylate resin composition is not particularly limited, and may be, for example, 100% by mass or less, particularly 50% by mass or less, relative to the polyarylate resin, and from the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less. The lower limit of the content of the thermoplastic resin is not particularly limited, and the content of the thermoplastic resin may be 0% by mass.

[0075] As the additives, additives that may be conventionally added to polyarylate resins can be used, such as antioxidants, lubricants, dyes and pigments, flow improvers, flame retardants, and fillers. Examples of the antioxidant include various antioxidants such as hindered phenol-based, hindered amine-based, thioether-based, and phosphorus-based antioxidants. Examples of lubricants include fatty acid salts such as stearates. Examples of dyes and pigments include metal complex dyes, anthraquinone dyes, perinone dyes, inorganic pigments such as carbon black and inorganic metals, and organic pigments containing organic compounds such as azo pigments and polycyclic pigments. Examples of flow improvers include inorganic compounds such as fatty acid salts, and organic compounds including fluorine-based and amide-based compounds. Examples of the flame retardant include various halogen-based, phosphorus-based, nitrogen-based and hydrated metal-based flame retardants. Examples of the filler include inorganic fillers such as glass fiber, glass beads, mica, talc, and silica.

[0076] The content of additives in the polyarylate resin composition is not particularly limited, and may be, for example, 50% by mass or less, particularly 30% by mass or less, relative to the polyarylate resin. From the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, particularly preferably 0.8% by mass or less, sufficiently preferably 0.4% by mass or less, and even sufficiently preferably 0% by mass. When two or more additives are contained, the total content thereof may be within the above range. The lower limit of the content of additives is not particularly limited, and the content of additives may be 0% by mass.

[0077] In particular, the content of antioxidant in the polyarylate resin composition is not particularly limited, but the polyarylate resin composition of the present invention is sufficiently excellent in color tone and discoloration resistance even without containing an antioxidant. Therefore, the content of antioxidant in the polyarylate resin composition may be 20% by mass or less, particularly 10% by mass or less, relative to the polyarylate resin. From the viewpoint of further improving color tone, discoloration resistance, and heat resistance, it is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.4% by mass or less, particularly preferably 0.2% by mass or less, and sufficiently preferably 0% by mass. When two or more antioxidants are contained, the total content thereof may be within the above range. [Example]

[0078] The present invention will be described in detail with reference to examples, but the present invention is not limited to these examples and various modifications and applications are possible within the scope of the present invention.

[0079] A. Evaluation Method (1) Quantitative determination of sodium formate in sodium hydrosulfite Approximately 0.1 g of sodium hydrosulfite was weighed into a PP container, 20 mL of ultrapure water was added, and the mixture was left to dissolve at room temperature overnight. The solution was then diluted 100 times with ultrapure water, and the diluted solution was filtered through a 0.2 μm membrane filter and quantitatively analyzed by ion chromatography (IC). A calibration curve method (multi-point calibration curve) was used for quantification.

[0080] (2) Quantitative determination of residual sodium formate in polyarylate resin powder Approximately 0.5 g of freeze-pulverized polyarylate resin powder was weighed into a polypropylene (PP) container. The freeze-pulverized polyarylate resin consisted of particles with diameters of 0.3 to 1.5 mm, including fine particles of 0.3 mm or less. The particle diameter was determined by measuring 50 randomly selected particles using a Keyence microscope (VHX-6000). Next, 50 mL of ultrapure water was added, and extraction was performed by heating in a dryer set at 120°C for 1 hour. The mixture was then filtered through a 0.2 μm membrane filter and quantitatively analyzed by ion chromatography (IC). For quantification, the calibration curve method (single-point calibration curve) was used to calculate the amount of formate ions using the following formula (1), which was then converted to the amount of sodium formate using the following formula (2).

[0081] Amount of formate ions = A × (BC) × D ÷ E ÷ F (Equation (1)) A = Concentration of calibration standard (formic acid) B = IC peak area of the analyte C = Blank IC peak area D = dilution ratio E = IC peak area of calibration standard F = sample weight to be analyzed

[0082] Sodium formate equivalent = G × H ÷ I (Equation (2)) G = amount of formate ions H = sodium formate formula weight (68.01) I = formula weight of formate ion (45.02)

[0083] (3) Glass transition temperature of polyarylate resin powder The obtained polyarylate resin powder was heated from 30°C to 400°C at a heating rate of 10°C / min using a differential scanning calorimeter (Diamond DSC manufactured by PerkinElmer), and the temperature at which a discontinuous change originating from the glass transition temperature in the obtained temperature rise curve began was taken as the glass transition temperature. Evaluation was made according to the following criteria. ◎◎: 255℃ or above (excellent); ◎: 250℃ or higher, less than 255℃ (excellent); ○: 220℃ or higher, less than 250℃ (good); △: 200℃ or higher, less than 220℃ (pass: no practical problems); ×: Less than 200°C (failed: problematic in practical use).

[0084] (4) Color difference a value of polyarylate resin powder A colorimeter (ZE6000) manufactured by Nippon Denshoku Industries Co., Ltd. was used. The polyarylate resin powder was packed into a measurement container without gaps, set on a sample holder, and measurement was performed in reflection mode. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Evaluation was performed according to the following criteria. ◎◎: -0.45 or less (excellent); ◎: More than -0.45, less than -0.4 (excellent); ○: More than -0.4, less than 0.2 (good); △: Over 0.2, 0.5 or less (pass: no practical problems); ×: More than 0.5 (fail: problematic in practical use).

[0085] (5) Inherent viscosity of polyarylate resin powder A resin solution was prepared using 1,1,2,2-tetrachloroethane as a solvent to a concentration of 1 g / dl, and the relative viscosity (ηrel) was measured at a temperature of 25° C. The inherent viscosity was calculated from the obtained relative viscosity using the following formula (3). ηinh(dl / g) = Ln(ηrel) / c (c: concentration) (Equation (3))

[0086] (6) Yellow Index (YI) Value of Injection Molded Polyarylate Resin Powder The obtained polyarylate resin powder was molded into a 3 mm thick sample plate at a resin temperature of 360°C using a general injection molding machine (for example, JSW J110AD injection molding machine), and the color was measured using a colorimeter (Nippon Denshoku Industries SZ-Σ90 colorimeter). Evaluation was based on the following criteria. ◎◎: 20 or less (excellent); ◎: More than 20, less than 24 (excellent); ○: More than 24, less than 26 (good); △: Over 26, 28 or less (Pass: No practical problems); ×: Over 28 (Failed: Problems in practical use).

[0087] B. Raw materials <Sodium hydrosulfite> Sodium hydrosulfite was prepared by the following method.

[0088] Sodium hydrosulfite A (manufacturing method: sodium formate method) (sodium formate content 0.7% by mass) and sodium hydrosulfite B (manufacturing method: sodium formate method) (sodium formate content 0.9% by mass). Sodium hydrosulfite was produced by the sodium formate method. The amount of sodium formate contained in the produced sodium hydrosulfite was quantitatively analyzed by ion chromatography (IC). The sodium formate content varied slightly depending on the production lot, and those with a sodium formate content of 0.7% by mass were designated sodium hydrosulfite A, and those with a sodium formate content of 0.9% by mass were designated sodium hydrosulfite B.

[0089] Sodium hydrosulfite C (manufacturing method: sodium formate method): sodium formate content 3.0 mass% (used in Comparative Examples 1 and 2). Sodium hydrosulfite C was produced by blending commercially available sodium formate with sodium hydrosulfite A (sodium formate content: 0.7% by mass) so that the sodium formate content was 3.0% by mass.

[0090] Sodium hydrosulfite D (manufacturing method: electrolytic method): sodium formate content 0% by mass (used in Comparative Example 5). Sodium hydrosulfite D was produced by electrolysis.

[0091] Example 1 (Method for synthesizing polyarylate resin powder) A reaction vessel equipped with a stirrer was charged with 100 parts by weight of 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1.2 parts by weight of p-tert-butylphenol, 47 parts by weight of sodium hydroxide, 2.3 parts by weight of trimethylbenzylammonium chloride, and sodium hydrosulfite A (0.5% by weight relative to the weight of the dihydric phenol component). This was dissolved in 2304 parts by weight of water to form an aqueous layer. Separately, 66 parts by weight of a 1 / 1 mixture of terephthaloyl chloride and isophthaloyl chloride (by weight) was dissolved in 1424 parts by weight of dichloromethane to form an organic layer. This organic layer was added to the previously prepared aqueous layer with vigorous stirring, and the polymerization reaction was carried out at 15°C for 2 hours. After this, the aqueous and organic layers were separated, and 10 parts by weight of acetic acid was added to the organic layer to terminate the reaction. The solution was then repeatedly washed with water until neutral, yielding a 17% by weight dichloromethane solution of polyarylate. The dichloromethane solution of polyarylate was granulated by a hot water granulation method, and the water and dichloromethane were thoroughly dried using a paddle-type hot air dryer at 120 to 135°C to obtain the polyarylate resin powder granules of Example 1. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Other characteristic values of the obtained polyarylate resin powder granules are as shown in Table 1.

[0092] Example 2 Polyarylate resin powder particles were synthesized in the same manner as in the "method for synthesizing polyarylate resin powder particles" carried out in Example 1, except that sodium hydrosulfite A was added in an amount of 1.0 mass % relative to the mass of the dihydric phenol component, and p-tert-butylphenol was 2.0 mass parts. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Other characteristic values of the obtained polyarylate resin powder particles were as shown in Table 1.

[0093] Example 3 Polyarylate resin powder particles were synthesized in the same manner as in the "method for synthesizing polyarylate resin powder particles" carried out in Example 1, except that sodium hydrosulfite B was added in an amount of 1.2 mass % relative to the mass of the dihydric phenol component, and p-tert-butylphenol was 0.5 mass parts. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Other characteristic values of the obtained polyarylate resin powder particles were as shown in Table 1.

[0094] Example 4 Polyarylate resin powder particles were synthesized in the same manner as in the "method for synthesizing polyarylate resin powder particles" carried out in Example 1, except that sodium hydrosulfite B was added in an amount of 3.0 mass % relative to the mass of the dihydric phenol component, and p-tert-butylphenol was 0.8 mass parts. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Other characteristic values of the obtained polyarylate resin powder particles were as shown in Table 1.

[0095] (Examples 5 to 9) Polyarylate resin was synthesized in the same manner as in Example 1, except that the charged composition was changed as shown in Table 1. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Other characteristic values of the obtained polyarylate resin powder were as shown in Table 1.

[0096] (Comparative Example 1) Polyarylate resin powder particles were synthesized in the same manner as in the "method for synthesizing polyarylate resin powder particles" carried out in Example 1, except that sodium hydrosulfite C was added in an amount of 3.0 mass % relative to the mass of the dihydric phenol component. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Other characteristic values of the obtained polyarylate resin powder particles were as shown in Table 1.

[0097] (Comparative Example 2) Polyarylate resin powder particles were synthesized in the same manner as in the "method for synthesizing polyarylate resin powder particles" carried out in Example 1, except that sodium hydrosulfite C was added in an amount of 0.5% by mass relative to the mass of the dihydric phenol component. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Other characteristic values of the obtained polyarylate resin powder particles were as shown in Table 1.

[0098] (Comparative Example 3) Polyarylate resin powder particles were synthesized in the same manner as in the "method for synthesizing polyarylate resin powder particles" carried out in Example 1, except that sodium hydrosulfite B was added in an amount of 7.0 mass % relative to the mass of the dihydric phenol component. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Other characteristic values of the obtained polyarylate resin powder particles were as shown in Table 1.

[0099] Comparative Example 4 Polyarylate resin powder particles were synthesized in the same manner as in the "method for synthesizing polyarylate resin powder particles" carried out in Example 1, except that sodium hydrosulfite A was added in an amount of 0.1 mass % relative to the mass of the dihydric phenol component. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Other characteristic values of the obtained polyarylate resin powder particles were as shown in Table 1.

[0100] (Comparative Example 5) Polyarylate resin powder particles were synthesized in the same manner as in the "method for synthesizing polyarylate resin powder particles" carried out in Example 1, except that sodium hydrosulfite D was added in an amount of 0.5% by mass relative to the mass of the dihydric phenol component. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Other characteristic values of the obtained polyarylate resin powder particles were as shown in Table 1.

[0101] (Comparative Example 6) Polyarylate resin powder particles were synthesized in the same manner as in Example 1, except that the charged composition was changed as shown in Table 1. The particle diameter of the particles was 0.7 to 5.0 mm (some fine powder may be included). Other characteristic values of the obtained polyarylate resin powder particles were as shown in Table 1.

[0102] [Table 1]

[0103] The abbreviations in Table 1 represent the following: TPC: Terephthalic acid dichloride IPC: Isophthalic acid dichloride TPA: Terephthalic acid IPA: Isophthalic acid BisA: 2,2-bis(4-hydroxyphenyl)propane BisTMC: 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane

[0104] The following points became clear from the above examples and comparative examples: By adjusting the amount of sodium formate contained in the polyarylate resin to an appropriate level, the color tone of the polyarylate resin itself becomes good, yellowing of molded products caused by thermal degradation due to heat melting can be more sufficiently reduced, and the resin can have heat resistance that allows it to be used in reflow processes, etc.; and The polyarylate resin of the present invention can be produced by using a specific amount of sodium hydrosulfite having a specific sodium formate content.

[0105] From Comparative Example 5, it is clear that even if the color tone of the polyarylate resin itself is good, coloration due to thermal degradation during melt molding is not necessarily suppressed. From Comparative Example 6, it is clear that even if the color tone of the polyarylate resin itself is good and coloring due to thermal degradation during melt molding can be suppressed, the obtained molded body may not be able to withstand use in the reflow process or in a high-temperature environment due to its low heat resistance. [Industrial Applicability]

[0106] The polyarylate resin of the present invention is useful in various applications requiring prevention of yellowing and / or improved heat resistance of molded articles, such as lamp covers and camera lenses for automobiles, camera lenses for mobile phones and smartphones, modules constituting electronic substrates, and replacement of plastic materials for parts that are primarily made of glass.

Claims

1. Contains an aromatic dicarboxylic acid component and a dihydric phenol component as monomer components, A polyarylate resin having a formate content of 0.1 to 2.0 ppm and a glass transition temperature of 200 to 300°C.

2. The polyarylate resin according to claim 1, which contains 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane as the dihydric phenol component.

3. The polyarylate resin according to claim 1, wherein the polyarylate resin has a color difference a value of -1.0 to 0.

5.

4. The polyarylate resin according to claim 1 , wherein the polyarylate resin has a granular shape.

5. The polyarylate resin of claim 1 , wherein the formate salt is sodium formate.

6. 2. The polyarylate resin according to claim 1, wherein a molded plate having a thickness of 3 mm obtained by injection molding the polyarylate resin has a YI value of 28 or less.

7. The polyarylate resin according to claim 1, wherein the content of the formate is 0.1 to 1.5 ppm.

8. A method for producing a polyarylate resin by polymerizing an aromatic dicarboxylic acid component and a dihydric phenol component, A method for producing a polyarylate resin, wherein a dithionite having a formate content of 0.4 to 1.5 mass % is added in an amount of 0.05 to 4.0 mass % based on the dihydric phenol component.

9. 9. The method for producing a polyarylate resin according to claim 8, wherein the dithionite is sodium dithionite produced by a sodium formate method.

10. A method for producing the polyarylate resin according to claim 8, which produces the polyarylate resin according to any one of claims 1 to 7.

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