Method for producing recycled polycarbonate resin

Abstract

The present invention provides a method for producing a recycled polycarbonate resin having good color tone and mechanical properties. The method for producing a recycled polycarbonate resin of the present invention includes: a step (S1) of dissolving a waste polycarbonate resin raw material in a good solvent to obtain a polycarbonate resin solution; a step (S2) of removing insoluble matter by contacting the polycarbonate resin solution with a coagulant and then removing the insoluble matter to obtain a solution (L) from which the insoluble matter has been removed; a step (S3) of precipitating the recycled polycarbonate resin by mixing the solution (L) with a poor solvent; and a step (S4) of recovering the precipitated recycled polycarbonate resin.

Description

Technical Field

[0001] This invention relates to a method for manufacturing recycled polycarbonate resin. Background Technology

[0002] Polycarbonate resin is a resin with excellent mechanical properties such as heat resistance and impact resistance, excellent dimensional stability, and excellent transparency. Polycarbonate resin compositions containing polycarbonate resin are used in a variety of applications.

[0003] However, waste polycarbonate resin compositions sometimes deteriorate due to use and ultraviolet radiation, leading to a decrease in color and mechanical properties. Furthermore, most polycarbonate resin compositions contain additives, inorganic substances, and other polymers in addition to polycarbonate resin, making their separation difficult. Therefore, the recycling of waste polycarbonate resin compositions is limited, and they are mostly single-use.

[0004] For sustainable development, it is important to recycle polycarbonate resin to achieve resource recycling. Methods for recycling polycarbonate resin can be broadly categorized into three types: material recycling to regenerate polycarbonate resin, chemical recycling to regenerate bisphenol A, a raw material for polycarbonate resin, and thermal recycling for energy use. Patent Document 1 discloses a method of decomposing polycarbonate resin into bisphenol A, a raw material. Patent Document 2 discloses a method of dissolving polycarbonate resin in a solvent, removing insoluble substances, and then precipitating the polycarbonate resin by adding an organic solvent. Patent Document 3, similar to Patent Document 2, discloses a technique of dissolving polycarbonate in a solvent and then precipitating it.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2022-75133

[0008] Patent Document 2: Japanese Patent Application Publication No. 11-152371

[0009] Patent Document 3: Japanese Patent Application Publication No. 2004-182746 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The method described in Patent Document 1 involves the chemical recycling of polycarbonate resin to raw material bisphenol, and the load in the decomposition and refining process is greater than that in material recycling.

[0012] The methods described in Patent Documents 2 and 3 involve material recycling, which is arguably simpler than chemical recycling. However, due to the difficulty in separating additives and deteriorating components during material recycling, the color and mechanical properties of the recycled polycarbonate resin sometimes become insufficient for practical use. As mentioned above, polycarbonate resin is also widely used in applications requiring good mechanical properties and transparency. For such applications, the recycled polycarbonate resin obtained through material recycling requires good color and mechanical properties. However, Patent Documents 2 and 3 make almost no mention of the properties of the recycled polycarbonate resin.

[0013] The present invention was made in view of the following circumstances, and its object is to provide a method for manufacturing recycled polycarbonate resins that can produce resins with good color and mechanical properties.

[0014] Methods for solving problems

[0015] In order to solve the above-mentioned problems, the inventors conducted repeated and in-depth research, and as a result, discovered that the following invention meets the above-mentioned objectives, thus completing the present invention. That is, the present invention relates to the following invention.

[0016] <1> A method for manufacturing recycled polycarbonate resin, wherein recycled polycarbonate resin is manufactured from waste polycarbonate resin raw materials, characterized in that the aforementioned manufacturing method includes the following steps (S1) to (S4).

[0017] Step (S1): The step of dissolving the aforementioned waste polycarbonate resin raw material in a soluble good solvent to obtain a polycarbonate resin solution.

[0018] Step (S2): After contacting the aforementioned polycarbonate resin solution with a coagulant, insoluble substances are removed to obtain a solution (L) with insoluble substances removed.

[0019] Step (S3): The step of precipitating the aforementioned recycled polycarbonate resin by mixing the aforementioned solution (L) with a poor solvent.

[0020] Step (S4): The step of recovering the precipitated aforementioned recycled polycarbonate resin.

[0021] <2> According to the foregoing <1> The method for manufacturing the recycled polycarbonate resin includes a step of contacting the polycarbonate resin solution with a filter aid before the removal of insoluble matter in the aforementioned step (S2).

[0022] <3> According to the foregoing <1> or <2> The method for manufacturing the recycled polycarbonate resin wherein the waste polycarbonate resin raw material contains a total of 5% by mass or more of a polycarbonate resin composition selected from the group consisting of (i) to (iii) below, and the aforementioned waste polycarbonate resin raw material contains 10% by mass or more of polycarbonate resin.

[0023] (i) Polycarbonate resin compositions for which the transmittance at 500 nm is less than 90% when the transmittance is measured using a 50 mm sample cell in a solution obtained by dissolving in dichloromethane in a manner that is 10% by mass.

[0024] (ii) A polycarbonate resin composition having a nitrogen content of 50 ppm or more by mass.

[0025] (iii) A polycarbonate resin composition having a phosphorus content of 5 ppm or more.

[0026] <4> According to the foregoing <1> to <3> In any one of the methods for manufacturing recycled polycarbonate resin, the good solvent used in the aforementioned step (S1) comprises a halogen-based solvent and / or a phenolic solvent.

[0027] <5> According to the foregoing <1> to <4> In any one of the methods for manufacturing recycled polycarbonate resin, the undesirable solvent used in the aforementioned step (S3) comprises any one selected from the group consisting of ketone solvents, saturated hydrocarbon solvents, alcohol solvents, and water.

[0028] <6> According to the foregoing <1> to <5> In any one of the methods for manufacturing recycled polycarbonate resin, the coagulant in the aforementioned step (S2) is one or more selected from the group consisting of ferric chloride (III), ferric sulfate (I), ferric sulfate (II), aluminum chloride, aluminum sulfate, titanium oxide, copper sulfate (I), copper sulfate (II), copper chloride (I), copper chloride (II), zinc sulfate, anionic polymers, cationic polymers and nonionic polymers.

[0029] <7> According to the foregoing <6> In the method for manufacturing the recycled polycarbonate resin, the coagulant in the aforementioned step (S2) is one or more selected from the group consisting of ferric chloride (III), ferric sulfate (II), ferric sulfate (III), aluminum sulfate, aluminum chloride, polyacrylamide, and polyethylene oxide.

[0030] <8> According to the foregoing <2> In the method for manufacturing the regenerated polycarbonate resin, the aforementioned filter aid is selected from one or more of the group consisting of activated carbon, montmorillonite, diatomaceous earth, silica gel, and synthetic adsorbents.

[0031] <9> According to the foregoing <1> to <8> In any one of the methods for manufacturing recycled polycarbonate resin, the total content of Na, Mg and Al in the aforementioned recycled polycarbonate resin is 0.3 ppm by mass or more and 20 ppm by mass or less (preferably 0.3 ppm by mass or more and 15 ppm by mass or less, more preferably 0.5 ppm by mass or more and 12 ppm by mass or less, and even more preferably 1.0 ppm by mass or more and 10 ppm by mass or less).

[0032] <10> According to the foregoing <1> to <9> In any one of the methods for manufacturing recycled polycarbonate resin, the L value of the aforementioned recycled polycarbonate resin based on reflectance measurement is 80 or higher.

[0033] <11> According to the foregoing <1> to <10> In any one of the methods for manufacturing recycled polycarbonate resin, the nominal tensile strain of the aforementioned recycled polycarbonate resin is 60% or more.

[0034] <x1>A method for manufacturing a molded body, comprising: through the aforementioned <1> to <11> The method for manufacturing recycled polycarbonate resin according to any one of the following steps includes the process of obtaining recycled polycarbonate resin; and the process of using the aforementioned recycled polycarbonate resin to obtain a molded article.

[0035] Invention Effects

[0036] According to the present invention, it is possible to manufacture recycled polycarbonate resin with good color and mechanical properties. Detailed Implementation

[0037] The embodiments of the present invention are described in detail below. However, the description of the constituent elements described below is only one example (representative example) of the embodiments of the present invention, and the present invention is not limited to the following content as long as its spirit is not changed. In addition, when the expression "~" is used in this specification, it is used as a description including the numerical value or physical property value before and after it.

[0038] Additionally, when only "ppm" is listed, it indicates "mass ppm".

[0039] <Manufacturing Method of Recycled Polycarbonate Resin>

[0040] The present invention relates to a method for manufacturing recycled polycarbonate resin from waste polycarbonate resin raw materials (hereinafter, sometimes referred to as "the manufacturing method of the present invention"), the aforementioned manufacturing method comprising the following steps (S1) to (S4).

[0041] Step (S1): The step of dissolving the aforementioned waste polycarbonate resin composition in a soluble good solvent to obtain a polycarbonate resin solution.

[0042] Step (S2): After contacting the aforementioned polycarbonate resin solution with a coagulant, insoluble substances are removed to obtain a solution (L) with insoluble substances removed.

[0043] Step (S3): The step of precipitating the aforementioned recycled polycarbonate resin by mixing the aforementioned solution (L) with a poor solvent.

[0044] Step (S4): The step of recovering the precipitated aforementioned recycled polycarbonate resin.

[0045] The manufacturing method of the present invention produces recycled polycarbonate resin through material recycling. That is, in the manufacturing method of the present invention, the waste polycarbonate resin raw material is not chemically decomposed, but rather degraded polycarbonate resin and other byproducts are removed and then recycled into polycarbonate resin.

[0046] One characteristic of the manufacturing method of the present invention is that, after contacting the polycarbonate resin solution with a coagulant, impurities are removed and a precipitate is formed. By employing this method, impurities can be adsorbed and removed through coagulation. Therefore, even when using waste polycarbonate resin raw materials that affect the color tone, it is possible to manufacture recycled polycarbonate resin exhibiting a color tone that is not problematic in practical applications. Furthermore, polycarbonate resin with good weather resistance and mechanical properties can be obtained. According to the manufacturing method of the present invention, even when using raw materials containing other components besides polycarbonate resin, such as other resins and additives, these other components can be efficiently removed, resulting in recycled polycarbonate resin with a color tone and other properties that are not problematic in practical applications.

[0047] The following is a description of each process.

[0048] [Process (S1)]

[0049] Process (S1) is a process of dissolving waste polycarbonate resin raw materials in a good solvent to obtain a polycarbonate resin solution.

[0050] [Waste polycarbonate resin raw material]

[0051] Waste polycarbonate resin raw material is a post-consumption material and / or pre-consumption material of polycarbonate resin composition. The waste polycarbonate resin raw material preferably contains a total of 5% by mass or more of a polycarbonate resin composition equivalent to one or more selected from the group consisting of (i) to (iii) below.

[0052] (i) Polycarbonate resin compositions for which the transmittance at 500 nm is less than 90% when the transmittance is measured using a 50 mm sample cell in a solution obtained by dissolving in dichloromethane in a manner that is 10% by mass.

[0053] (ii) A polycarbonate resin composition having a nitrogen content of 50 ppm or more by mass.

[0054] (iii) A polycarbonate resin composition having a phosphorus content of 5 ppm or more.

[0055] As a representative example of a polycarbonate resin composition that satisfies (i) above, a polycarbonate resin containing dyes, pigments, carbon black, titanium dioxide, etc. can be cited. Compounds such as dyes, pigments, and carbon black are very difficult to remove in conventional material recycling, and it is not easy to regenerate such a polycarbonate resin composition into a polycarbonate resin with good color.

[0056] As a representative example of a polycarbonate resin composition that satisfies (ii) above, a polycarbonate resin containing a nitrogen-containing compound used as an ultraviolet absorber, etc., can be cited. When such a polycarbonate resin composition is used for a long period, the nitrogen-containing compound deteriorates, becoming a cause of discoloration in the polycarbonate resin composition. In conventional material recycling, it is difficult to remove this discoloration-causing compound, which remains in the recycled polycarbonate resin, thus becoming a cause of discoloration.

[0057] As a representative example of a polycarbonate resin composition that satisfies (iii) above, a polycarbonate resin containing phosphorus-containing compounds, such as phosphorus-based flame retardants, can be cited. If such a polycarbonate resin composition is used for a long period, it is presumed that the phosphorus-containing compounds will hydrolyze and corrode the resin, thus causing a deterioration in the resin's mechanical strength. In conventional material recycling, it is difficult to remove such flame retardants, which may become a major cause of the deterioration in the mechanical strength of the recycled polycarbonate resin.

[0058] As can be seen from the above, when polycarbonate resin is recycled from a polycarbonate resin composition, additives such as pigments, dyes, ultraviolet absorbers, and flame retardants added to improve the properties of polycarbonate resin are preferably removed, considering factors such as color and mechanical strength. The manufacturing method of the present invention can remove these impurities.

[0059] In particular, when the waste polycarbonate resin raw material contains 5% or more by mass of one or more polycarbonate resin compositions satisfying (i) to (iii) above, the color tone of the obtained recycled polycarbonate resin is greatly affected, and in conventional material recycling, it is very difficult to obtain recycled polycarbonate resin with a good color tone. On the other hand, in the manufacturing method of the present invention, even when the waste polycarbonate resin raw material is used by mixing one or more polycarbonate resin compositions satisfying (i) to (iii) above in a manner that is 5% or more by mass, it is possible to regenerate polycarbonate resin with a good color tone. Therefore, it can be said that waste polycarbonate resin raw material containing 5% or more by mass of one or more polycarbonate resin compositions satisfying (i) to (iii) above is suitable as a raw material for the manufacturing method of the present invention.

[0060] Furthermore, as described below, considering ease of dissolution and operability, it is preferable to use 5% by mass or more of a pulverized polycarbonate resin composition that satisfies one or more of the above (i) to (iii) as the waste polycarbonate resin raw material.

[0061] A polycarbonate resin composition is a composition containing polycarbonate resin. Besides polycarbonate resin alone, examples include polymer alloys such as polymer mixtures of polycarbonate resin and other resins. Furthermore, a polycarbonate resin composition may contain two or more polycarbonate resins with different compositions and molecular weights. Other resins include copolymers such as ABS resin and AS resin (polymers of acrylonitrile, butadiene, and styrene), polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), and acrylic resins (PMMA).

[0062] Polycarbonate resin compositions typically contain additives appropriate to the intended purpose, and the content of polycarbonate resin in the composition is, for example, 20–100% by mass or 50–100% by mass. The polycarbonate resin can be a homopolymer of the same structural units or a copolymer containing different structural units. Examples of additives include glass fibers, carbon fibers, pigments, dyes, ultraviolet absorbers, and flame retardants.

[0063] The aforementioned waste polycarbonate resin raw material preferably contains 10% or more polycarbonate resin by mass, more preferably 20% or more by mass, and more preferably 30% or more by mass.

[0064] Polycarbonate resins typically contain repeating bisphenol units and carbonate units, i.e., structural units as shown in the following formula (A). The content of the structural units shown in the following formula (A) is typically 20 mol% or more, preferably 30 mol% or more, and more preferably 40 mol% or more.

[0065] [Chemistry 1]

[0066]

[0067] In formula (A), X is selected from any one of the following groups: single bond, alkylene group with 2 to 8 carbon atoms, cycloalkylene group with 5 to 15 carbon atoms, alkylidene group with 1 to 8 carbon atoms, cycloalkylidene group with 5 to 15 carbon atoms, fluoreneidene group, thionylidene group, thionylidene group, -O-, -S-, -CO-, -SO- and -SO2.

[0068] Alkylenes having 2 to 8 carbon atoms can be substituted or unsubstituted, and can be linear or branched. Examples of alkylenes having 2 to 8 carbon atoms include ethane-1,2-diyl, propane-1,2-diyl, propane-1,3-diyl, butane-1,2-diyl, butane-1,4-diyl, hexane-1,2-diyl, and hexane-1,6-diyl.

[0069] The cycloalkylene group having 5 to 15 carbon atoms can be either substituted or unsubstituted. Examples of cycloalkylene groups having 5 to 15 carbon atoms include cyclopropane-1,2-diyl and cyclohexane-1,2-diyl.

[0070] The alkylidene group having 1 to 8 carbon atoms can be substituted or unsubstituted, and can be linear or branched. The alkylidene group having 1 to 8 carbon atoms is preferably the group shown in the following formula (1a).

[0071] [Chemistry 2]

[0072]

[0073] R a R b Each of these can independently represent a hydrogen atom, an alkyl group with 1 to 7 carbon atoms, a cycloalkyl group with 3 to 7 carbon atoms, an alkoxy group with 1 to 7 carbon atoms, or an aryl group with 6 to 7 carbon atoms. These can be either substituted or unsubstituted. Examples include: hydrogen atom, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, n-heptyl, 2-ethylhexyl, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy, isopentoxy, n-hexoxy, n-heptoxy, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, benzyl, phenyl, tolyl, etc.

[0074] The cycloalkane group having 5 to 15 carbon atoms can be either substituted or unsubstituted. Examples of cycloalkane groups having 5 to 15 carbon atoms include: cyclopropane-1,1-diyl, cyclobutane-1,1-diyl, cyclopentane-1,1-diyl, cyclohexane-1,1-diyl, 3,3,5-trimethylcyclohexane-1,1-diyl, and cycloheptane.

[0075] Alkane-1,1-diyl, cyclooctane-1,1-diyl, cyclononane-1,1-diyl, cyclodecane-1,1-diyl, cycloundecane-1,1-diyl, cyclododecane-1,1-diyl, etc.

[0076] In formula (A), X is preferably an alkylidene group with 1 to 8 carbon atoms, a cycloalkylidene group with 5 to 15 carbon atoms, or a fluoreneidene group, more preferably an alkylidene group with 1 to 8 carbon atoms, and even more preferably propane-2,2-diyl.

[0077] In formula (A), R 1 R 2 Each R is independently selected from the group consisting of halogen atoms, alkyl groups having 1 to 12 carbon atoms, cycloalkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, and aryl groups having 6 to 12 carbon atoms. When n and m are 2 or more, multiple R 1 R 2 They can be the same group or different groups. In addition, alkyl groups with 1 to 12 carbon atoms, cycloalkyl groups with 1 to 12 carbon atoms, alkoxy groups with 1 to 12 carbon atoms, and aryl groups with 6 to 12 carbon atoms can be substituted or unsubstituted.

[0078] As R 1 R 2 Examples include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclododecyl, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, n-pentoxy, isopentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-undecyloxy, n-dodecyloxy, benzyl, phenyl, tolyl, 2,6-dimethylphenyl, etc.

[0079] R 1 R 2 Preferably, each alkyl group is independently composed of 1 to 12 carbon atoms, and more preferably, each alkyl group is independently composed of 1 to 5 carbon atoms.

[0080] In formula (A), n and m are independent integers from 0 to 3. Preferably, n and m are independent integers from 0 to 2, and more preferably, they are independent integers from 0 to 1.

[0081] Among them, formula (A) is preferably the following formula (A2).

[0082] [Chemistry 3]

[0083]

[0084] In formula (A2), X has the same meaning as in formula (A). The preferred method is also the same as in formula (A), where X in formula (A2) is preferably an alkylidene group with 1 to 8 carbon atoms, a cycloalkylidene group with 5 to 15 carbon atoms, or a fluoreneidene group, more preferably an alkylidene group with 1 to 8 carbon atoms, and even more preferably propane-2,2-diyl.

[0085] In equation (A2), R 3 It is selected from any one of the group consisting of hydrogen atoms, halogen atoms, alkyl groups having 1 to 12 carbon atoms, cycloalkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, and aryl groups having 6 to 12 carbon atoms. R 3 Preferably, it is an alkyl group having 1 to 12 hydrogen atoms, more preferably an alkyl group having 1 to 5 hydrogen atoms, and even more preferably a hydrogen atom or a methyl group.

[0086] In formula (A2), X is preferably propane-2,2-diyl, and R... 3 It can be a hydrogen atom or a methyl group.

[0087] Specifically, the bisphenol unit of the structural unit shown in formula (A) above can be exemplified by 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 3,3-bis(4-hydroxyphenyl)pentane, 3,3-bis(4-hydroxy-3-methylphenyl)pentane, etc. Substances containing bisphenols, such as alkanes, 2,2-bis(4-hydroxyphenyl)pentane, 2,2-bis(4-hydroxy-3-methylphenyl)pentane, 3,3-bis(4-hydroxyphenyl)heptane, 3,3-bis(4-hydroxy-3-methylphenyl)heptane, 2,2-bis(4-hydroxyphenyl)heptane, 2,2-bis(4-hydroxy-3-methylphenyl)heptane, 4,4-bis(4-hydroxyphenyl)heptane, and 4,4-bis(4-hydroxy-3-methylphenyl)heptane, but not limited to them in any way.

[0088] Wherein, the bisphenol unit of the structural unit shown in formula (A) above is preferably a structure selected from any one of 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane and 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane, more preferably a structure from 2,2-bis(4-hydroxyphenyl)propane or 2,2-bis(4-hydroxy-3-methylphenyl)propane, and particularly preferably a structure from 2,2-bis(4-hydroxyphenyl)propane.

[0089] Post-consumer materials used as raw materials for waste polycarbonate resins are typically used polycarbonate resin compositions that have been assembled into products as molded bodies or used as outer packaging by consumers indoors and outdoors. Examples of molded bodies using polycarbonate resin compositions include housings for electronic devices, general merchandise, lighting fixtures, automotive interior and exterior trim, handling containers, and building materials. Pre-consumer materials include purified resins produced from polymerization and compounding processes, and polycarbonate resins that have failed to meet quality standards in finished products.

[0090] From an environmental impact perspective, post-consumer materials are preferred for waste polycarbonate resin raw materials. The usage period (time of use) of post-consumer materials is preferably 3 years or more, more preferably 5 years or more, and even more preferably 7 years or more. If the usage period is too short, the polycarbonate resin will be recycled even before it has deteriorated, which is not preferable from an environmental impact perspective. Furthermore, if the usage period is too long, the polycarbonate resin will deteriorate significantly, and even if it is recycled, its physical properties may not be fully restored. Therefore, the usage period is preferably 30 years or less, more preferably 20 years or less.

[0091] Waste polycarbonate resin raw materials can be used directly as post-consumer or pre-consumer resin compositions, or they can be appropriately cut into suitable sizes through cutting, crushing, or pulverizing. There are no particular limitations on the cutting, crushing, or pulverizing methods, and the following methods can be used: cutting using cutting tools; melting cutting using gas, plasma, laser, etc.; slicing; cutting using a shredder; coarse crushing to less than 20 cm using a jaw crusher or rotary crusher; medium crushing to less than 1 cm using a rotary crusher, cone crusher, or mill; and pulverizing to less than 1 mm using a mill. These methods can be used individually or in combination.

[0092] If the waste polycarbonate resin raw material is too large, the dissolution time will be longer, which is not preferable. Therefore, it is preferable to use pulverized polycarbonate resin composition as waste polycarbonate resin raw material. The pulverized polycarbonate resin composition preferably has a shape of 53 mm or less, more preferably 22.4 mm or less, and even more preferably 11.2 mm or less. On the other hand, if the shape is too small, it may become dust when fed into the apparatus, so it is preferable to have a shape of 2.8 mm or more, and even more preferably 4.75 mm or more.

[0093] It should be noted that "below 53mm" refers to passing through a sieve with a nominal mesh size of 53mm as specified in JIS-Z-8801-1(2019), "below 22.4mm" refers to passing through a sieve with a nominal mesh size of 22.4mm, and "below 11.2mm" refers to passing through a sieve with a nominal mesh size of 11.2mm. Additionally, "above 2.8mm" refers to not passing through a sieve with a nominal mesh size of 2.8mm, and "above 4.75mm" refers to not passing through a sieve with a nominal mesh size of 4.75mm.

[0094] (Good solvent)

[0095] The solvent for dissolving waste polycarbonate resin raw materials is not particularly limited as long as it can dissolve the waste polycarbonate resin raw materials, but preferably includes halogen-based solvents and / or phenol-based solvents. Examples of halogen-based solvents include dichloromethane and dichloroethane. Examples of phenol-based solvents include phenol, cresol, xylenol, ethylphenol, propylphenol, butylphenol, methoxyphenol, ethoxyphenol, propoxyphenol, butoxyphenol, benzylphenol, phenylphenol, chlorophenol, dichlorophenol, and chloromethylphenol. The ratio of halogen-based solvents and / or phenol-based solvents can be any ratio as long as it is the ratio for dissolving waste polycarbonate resin raw materials, but their total amount relative to the good solvent is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. That is, when the good solvent includes halogen-based solvents but does not include phenolic solvents, the ratio of halogen-based solvents to the good solvent is preferably within the aforementioned range; when the good solvent includes phenolic solvents but does not include halogen-based solvents, the ratio of phenolic solvents to the good solvent is preferably within the aforementioned range; when the good solvent includes both halogen-based solvents and phenolic solvents, the ratio of the total of halogen-based solvents and phenolic solvents to the good solvent is preferably within the aforementioned range.

[0096] Good solvents can also include solvents other than halogenated and phenolic solvents. Specifically, examples include: aromatic hydrocarbon solvents such as toluene and xylene; cyclohexanone; tetrahydrofuran (THF); acetonitrile; dimethyl carbonate; hexafluoroisopropanol; and water. Good solvents can be used in appropriate combinations to dissolve waste polycarbonate resin raw materials at the dissolution temperature.

[0097] The amount of good solvent relative to the mass of the waste polycarbonate resin raw material is preferably 200% by mass or more, more preferably 250% by mass or more, and even more preferably 350% by mass or more. When the proportion of good solvent is low, the viscosity of the solution becomes extremely high, making stirring and dissolution difficult, reducing the filtration speed during filtration, or causing the filtrate to adhere to the filter material, potentially leading to a decrease in yield. Furthermore, the amount of good solvent relative to the mass of the waste polycarbonate resin raw material is preferably 5000% by mass or less, more preferably 4000% by mass or less, and even more preferably 3000% by mass or less. When the proportion of good solvent is high, the solubility of polycarbonate resin increases, and even if a poor solvent is added in step (S3), more polycarbonate resin will not precipitate when dissolved in a good solvent, potentially resulting in a deterioration in yield. Therefore, the amount of good solvent relative to the mass of the waste polycarbonate resin raw material is preferably 200 to 5000% by mass, more preferably 250 to 4000% by mass, and even more preferably 350 to 3000% by mass.

[0098] (Dissolution temperature)

[0099] When dissolving waste polycarbonate resin raw materials in a good solvent, it is preferable to control the temperature (the temperature of the solution in the dissolving tank). Without temperature control, the dissolution time becomes uneven, and undissolved components may be generated when the solution is fed to the next process. The preferred temperature is below the boiling point of the good solvent. If the boiling point of the good solvent is exceeded, a condenser is required in the dissolving tank, complicating the process. Specifically, the temperature of the good solvent (the temperature of the solution in the dissolving tank) is preferably 10°C or higher, more preferably 15°C or higher, and even more preferably 20°C or higher. At excessively low temperatures, the solubility of the polycarbonate resin decreases, and dissolution takes longer. Furthermore, when feeding the solution to the next process, the feeding time may be longer, or a heavy load may be placed on the filter during filtration. Additionally, the temperature is preferably below 140°C, more preferably below 130°C, and even more preferably below 120°C. At excessively high temperatures, the polycarbonate resin may deteriorate due to heat, potentially causing discoloration. Therefore, the preferred dissolution temperature is 10–140°C, more preferably 15–130°C, and even more preferably 20–120°C.

[0100] (Dissolution time)

[0101] The dissolution time is preferably 20 minutes or more, more preferably 40 minutes or more, and even more preferably 1 hour or more. It is also preferably 5 hours or less, more preferably 4 hours or less, and even more preferably 3 hours or less. If the dissolution time is too short, more undissolved components will appear, potentially reducing the yield or causing blockages in the process. If the dissolution time is too long, it may cause polymer decomposition and discoloration. Therefore, the dissolution time is preferably 20 minutes to 5 hours, more preferably 40 minutes to 4 hours, and even more preferably 1 hour to 3 hours.

[0102] [Process (S2)]

[0103] Step (S2) is a step in which the aforementioned polycarbonate resin solution is brought into contact with a coagulant to remove insoluble matter, thereby obtaining a solution (L) from which insoluble matter has been removed.

[0104] The purpose of step (S2) is to facilitate the removal of insoluble matter. As mentioned above, waste polycarbonate resin raw materials contain various additives in addition to the polycarbonate resin composition. Among them, carbon black, titanium dioxide, etc., used for coloring have very small particle sizes and are not captured by the filter when filtering during the removal of insoluble matter, leaving insoluble matter residues in the filtrate. Furthermore, even if insoluble matter is sedimented by centrifugation or other methods, it will not settle and is difficult to remove by centrifugation. In particular, for colored polycarbonate resin compositions, the pigments used as colorants cannot be removed, resulting in residual coloring components in the recycled polycarbonate resin and causing color deterioration. Color deterioration makes it impossible to form transparent recycled polycarbonate resin, and it is also impossible to color it to the desired color to produce recycled molded bodies, thus narrowing the scope of utilization of recycled polycarbonate resin. As can be seen from the above, the purpose of step (S2) is to promote the coagulation of fine insoluble matter by contacting the coagulant with the polycarbonate resin solution. The manufacturing method of the present invention is characterized in that, through this process, insoluble matter can be captured when filtering with a filter, or insoluble matter can be removed by centrifugation or other means to allow it to settle.

[0105] (Flocculant)

[0106] The main reason for the small particle size of insoluble substances is their dispersion due to the charge repulsion between them. Coagulants function by neutralizing the charge of the insoluble substances dispersed in the polycarbonate resin solution, thereby promoting the adsorption and aggregation of the insoluble substances and increasing their particle size. As can be seen from the above, any inorganic salt, except for alkali metal salts and alkaline earth metal salts, can be used as a coagulant, provided it can ionize and decompose polycarbonate resin in the solution. Preferred coagulants include ferric chloride (III), ferric sulfate (I), ferric sulfate (II), aluminum chloride, aluminum sulfate, titanium dioxide, copper sulfate (I), copper sulfate (II), copper chloride (I), copper chloride (II), and zinc sulfate. Alternatively, mixtures of commercially available inorganic salts can also be used as coagulants. While inorganic salts can neutralize charges, if the particle size of the aggregated particles is small, anionic, cationic, or nonionic polymers can also be added. This is because the insoluble substances dispersed in the polycarbonate resin solution adhere to the polymer chains, increasing the particle size. Furthermore, polymeric compounds can be used alone or as coagulants. Representative examples of polymeric compounds include polyacrylamide and polyethylene oxide.

[0107] Therefore, the coagulant in step (S2) is preferably one or more selected from the group consisting of ferric chloride (III), ferric sulfate (I), ferric sulfate (II), aluminum chloride, aluminum sulfate, titanium dioxide, copper sulfate (I), copper sulfate (II), copper chloride (I), copper chloride (II), zinc sulfate, anionic polymers, cationic polymers and nonionic polymers, and more preferably one or more selected from the group consisting of ferric chloride (III), ferric sulfate (II), ferric sulfate (III), aluminum sulfate, aluminum chloride, polyacrylamide and polyethylene oxide.

[0108] There are no particular limitations on the contact method between the polycarbonate resin solution and the coagulant. The coagulant can be mixed during the preparation of the polycarbonate resin solution in step (S1), or the coagulant can be contacted after the polycarbonate resin solution is prepared in step (S1).

[0109] For example, in step (S1), waste polycarbonate resin raw material, a good solvent, and a coagulant can be mixed, allowing the polycarbonate resin to dissolve in the good solvent while simultaneously contacting the coagulant. Alternatively, when contacting the polycarbonate resin solution with a coagulant after preparation in step (S1), the coagulant can be directly added to the polycarbonate resin solution, or it can be packed onto a filter material for contact with the polycarbonate resin solution. Alternatively, the coagulant can be packed into a columnar shape, allowing the polycarbonate resin solution to flow through it, thereby achieving contact.

[0110] Preferably, the coagulant is directly added to the polycarbonate resin solution for contact after step (S1).

[0111] When the polycarbonate resin solution is prepared in step (S1) and then comes into contact with the coagulant, the contact time between the polycarbonate resin solution and the coagulant is preferably 5 minutes or more, more preferably 10 minutes or more, and even more preferably 20 minutes or more. If it is too short, the coagulation effect may not be fully realized. In addition, the contact time with the coagulant is preferably within 3 hours, more preferably within 2 hours. If it is too long, the particles that have been coagulated in one step may disperse due to stirring or the like. Therefore, the contact time with the coagulant is preferably 5 minutes to 3 hours, more preferably 10 minutes to 3 hours, and even more preferably 20 minutes to 2 hours.

[0112] When the polycarbonate resin solution prepared in step (S1) comes into contact with the coagulant, the contact temperature between the polycarbonate resin solution and the coagulant can be the same as the temperature at which dissolution occurs in step (S1), preferably 20°C or higher, and more preferably 140°C or lower. If the temperature is too high, the polycarbonate resin may become discolored; if the temperature is too low, coagulation may not occur. Therefore, it is further preferred that the temperature be 30°C or higher and 90°C or lower.

[0113] The amount of coagulant used relative to the mass of the dissolved waste polycarbonate resin raw material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. If the amount of coagulant used is too small, it will not be sufficient to promote the coagulation of insoluble matter, and the insoluble matter may not be removed. Furthermore, the amount of coagulant used relative to the mass of the dissolved waste polycarbonate resin raw material is preferably 20% by mass or less, more preferably 10% by mass or less. If the amount of coagulant is too large, the coagulant itself may remain in the recycled polycarbonate resin, potentially becoming a major cause of discoloration. Therefore, the amount of coagulant used relative to the mass of the dissolved waste polycarbonate resin raw material is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass.

[0114] (Filter aid)

[0115] In the manufacturing method of the present invention, the filter aid and the coagulant can be used together. Preferably, the manufacturing method includes a step of contacting the polycarbonate resin solution with the filter aid before the removal of insoluble matter in step (S2). The method of contacting the polycarbonate resin solution with the filter aid can be the same as or different from the method of contacting the polycarbonate resin solution with the coagulant. The contact between the polycarbonate resin solution and the filter aid can be performed simultaneously with or separately from the coagulant. That is, the polycarbonate resin solution can be contacted simultaneously with both the coagulant and the filter aid, or the filter aid can be contacted after the polycarbonate resin solution has been contacted with the coagulant, or the coagulant can be contacted after the polycarbonate resin solution has been contacted with the filter aid. Thus, by using the coagulant and the filter aid together, deteriorated substances, foreign resins, additives, impurities, etc., contained in the polycarbonate resin composition can be removed more efficiently.

[0116] The filter aid used in this invention is preferably selected from one or more of the group consisting of activated carbon, diatomaceous earth, montmorillonite, silica gel, and synthetic adsorbents.

[0117] Activated carbon can be in various forms, including powder, granules (crushed, granular, spherical, cylindrical, etc.), and fibers; any shape can be used. Furthermore, the raw materials for activated carbon can be any of sawdust, coconut shells, coal, charcoal, etc. Activated carbon can be activated through methods such as gas activation, steam activation, or chemical activation.

[0118] Examples of montmorillonite include bentonite and activated clay. Examples of activated clay include Galleon Earth (registered trademark) and Galleonite Celite (registered trademark) manufactured by Mizusawa Chemical Industry Co., Ltd., and Nikkanite manufactured by Toshin Kasei Corporation.

[0119] The synthetic adsorbent is a cross-linked polymer with a porous structure. Examples of synthetic adsorbents include aromatic, aromatic-modified, and methacrylic acid-based adsorbents; any of these can be used. Specifically, Sepabedas (registered trademark) manufactured by Mitsubishi Chemical Corporation is an example.

[0120] There are no particular limitations on the contact method between the polycarbonate resin solution and the filter aid. The filter aid can be mixed in during the preparation of the polycarbonate resin solution. Alternatively, after preparing the polycarbonate resin solution, the filter aid can be directly added to the polycarbonate resin solution for contact, or it can be packed onto filter material for contact with the polycarbonate resin solution, or the filter aid can be packed into a column and allowed to flow through it for contact. Furthermore, these methods can be appropriately combined to ensure that the polycarbonate resin solution and the filter aid are contacted more than once.

[0121] The amount of filter aid used can be any amount, as long as it is sufficient to adsorb the coloring components and impurities. When directly adding the filter aid, the amount used relative to the mass of the dissolved waste polycarbonate resin raw material is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. If the amount of filter aid is too small, the coloring components and impurities may not be completely removed. Furthermore, the amount of filter aid used relative to the mass of the dissolved waste polycarbonate resin raw material is preferably 30% by mass or less, more preferably 20% by mass or less. If too much filter aid is used, it may not be completely removed, potentially leading to deterioration of the color. Therefore, when directly adding the filter aid, the amount of filter aid used relative to the mass of the dissolved waste polycarbonate resin raw material is preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass.

[0122] On the other hand, when the filter aid is fully applied to the filter material and packed into a column, the amount of filter aid relative to the mass of the dissolved waste polycarbonate resin raw material is preferably 20% by mass or more, more preferably 40% by mass or more. If the amount of filter aid is too small, it may not be sufficient to remove coloring components and impurities. Furthermore, the amount of filter aid used relative to the mass of the dissolved waste polycarbonate resin raw material is preferably 5000% by mass or less, more preferably 2000% by mass or less. If the amount of filter aid is too large, impurities dissolved from the filter aid may be largely contained in the recycled polycarbonate resin. Therefore, when the filter aid is fully applied to the filter material, the amount of filter aid used relative to the mass of the dissolved waste polycarbonate resin raw material is preferably 20 to 5000% by mass, more preferably 40 to 2000% by mass.

[0123] Filter aids can be reused by regenerating them before and after use. During regeneration, the filter aids can be cleaned with steam, heat, or organic solvents. Cleaning removes impurities from the filter aids and can sometimes effectively reduce impurities in the resulting recycled polycarbonate resin.

[0124] The coagulant and filter aid are preferably a combination of one or more coagulants selected from the group consisting of ferric chloride (III), ferric sulfate (I), ferric sulfate (II), aluminum chloride, aluminum sulfate, titanium dioxide, copper sulfate (I), copper sulfate (II), copper chloride (I), copper chloride (II), zinc sulfate, anionic polymers, cationic polymers and nonionic polymers, and one or more filter aids selected from the group consisting of activated carbon, diatomaceous earth, montmorillonite, silica gel and synthetic adsorbents. More preferably, it is a combination of one or more coagulants selected from the group consisting of ferric chloride (III), ferric sulfate (II), ferric sulfate (III), aluminum sulfate, aluminum chloride, polyacrylamide and polyethylene oxide, and one or more filter aids selected from the group consisting of activated carbon, diatomaceous earth, montmorillonite, silica gel and synthetic adsorbents.

[0125] (Removal of insoluble matter)

[0126] Methods for removing insoluble matter from polycarbonate resin solutions include filtration, centrifugation, cyclone filtration, and other methods using filters; and solid-liquid separation of the insoluble matter by means of settling, centrifugation, flotation, etc., to remove the liquid side. When using filters to remove insoluble matter, any of the following can be used: filter paper, glass filter, bag filter, candle filter, etc. Furthermore, multiple stages and methods can be employed with the filter. The minimum mesh size of the filter material is preferably 5 μm or less, more preferably 2 μm or less, and even more preferably 1 μm or less. If the mesh size is too large, the removal of foreign matter becomes insufficient; if it is too small, the filterability tends to deteriorate. In addition, to improve filterability, an aromatic hydrocarbon solvent can be added during the removal of insoluble matter. For example, the insoluble matter can be removed by passing the polycarbonate resin solution through the filter material after supplying the aromatic hydrocarbon solvent to the solution, or the polycarbonate resin solution and the aromatic hydrocarbon solvent can be passed through the filter material in parallel to remove the insoluble matter.

[0127] [Process (S3)]

[0128] Step (S3) is a process of precipitating the aforementioned recycled polycarbonate resin by mixing the aforementioned solution (L) with a poor solvent.

[0129] (Poor solvent)

[0130] There are no particular limitations on unsuitable solvents that can precipitate recycled polycarbonate resin, as long as they can cause the recycled polycarbonate resin to precipitate. Examples of unsuitable solvents include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone (MIBK), and cyclohexanone; saturated hydrocarbon solvents such as hexane, heptane, and cyclohexane; alcohol solvents such as methanol, ethanol, and isopropanol; water; toluene and xylene; THF; acetonitrile; dimethyl carbonate; and hexafluoroisopropanol.

[0131] The undesirable solvent preferably includes one or more solvents selected from the group consisting of ketone solvents, saturated hydrocarbon solvents, alcohol solvents, and water; more preferably, it includes one or more solvents selected from the group consisting of acetone, ethanol, water, methanol, isopropanol, hexane, cyclohexane, heptane, and MIBK. Acetone is preferred because its low boiling point facilitates solvent recovery.

[0132] The solvent selected from the group consisting of ketone solvents, saturated hydrocarbon solvents, alcohol solvents and water can be any ratio that causes the polycarbonate resin to precipitate. The total of these solvents relative to the undesirable solvents is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more.

[0133] The undesirable solvent relative to the mass of the waste polycarbonate resin raw material is preferably 200% by mass or more, more preferably 250% by mass or more, and even more preferably 350% by mass or more. When the proportion of undesirable solvent is low, precipitation may not occur sufficiently, or the fluidity may decrease in subsequent processes (S4). Furthermore, the undesirable solvent relative to the mass of the waste polycarbonate resin raw material is preferably 5000% by mass or less, more preferably 4000% by mass or less, and even more preferably 3000% by mass or less. When the proportion of undesirable solvent is high, the polycarbonate resin may also dissolve in the undesirable solvent, potentially leading to a deterioration in yield. Therefore, the amount of undesirable solvent relative to the mass of the waste polycarbonate resin raw material is preferably 200 to 5000% by mass, more preferably 250 to 4000% by mass, and even more preferably 350 to 3000% by mass.

[0134] When adding a poor solvent to precipitate regenerated polycarbonate resin, it is preferable to control the temperature (solution temperature within the apparatus). Without temperature control, precipitation time becomes uneven, and when feeding the solution to the next process, precipitation may be insufficient, leading to a deterioration in yield. The temperature for the precipitation operation is preferably below the boiling points of both the good and poor solvents. If the boiling points of the good and poor solvents are exceeded, the solubility of the polycarbonate resin increases, making it difficult to fully recover the polycarbonate resin. The specific solution temperature (solution temperature within the apparatus) for the precipitation operation is preferably 10°C or higher, more preferably 15°C or higher, and even more preferably 20°C or higher. If the temperature is too low, feeding the solution to the next process may take longer, or a heavy load may be placed on the filtration process. Furthermore, it is preferable to be below 140°C, more preferably below 130°C, and even more preferably below 120°C. At excessively high temperatures, the polycarbonate resin may deteriorate due to heat, potentially causing discoloration. Therefore, the temperature at which the recycled polycarbonate resin precipitates is preferably 10 to 140°C, more preferably 15 to 130°C, and even more preferably 20 to 120°C.

[0135] The good solvent and the bad solvent are preferably a combination of a good solvent comprising halogen-based solvents and / or phenol-based solvents and a bad solvent comprising any one of the groups selected from ketone-based solvents, saturated hydrocarbon-based solvents, alcohol-based solvents and water, more preferably the aforementioned combination, and the good solvent and the bad solvent are respectively 200% by mass or more and 5000% by mass or less relative to the waste polycarbonate resin raw material.

[0136] The ratio of poor solvent to good solvent is preferably 0.4 times or more, more preferably 1 times or more, and preferably 2 times or less. If the ratio of poor solvent to good solvent is too low, the amount of recycled polycarbonate resin precipitated will be less; if it is too high, there is a possibility that the process becomes redundant and the solvent recovery load increases. Therefore, the ratio of poor solvent to good solvent is preferably 0.4 to 2 times, more preferably 1 to 2 times.

[0137] [Process (S4)]

[0138] Step (S4) is the process of recovering the precipitated aforementioned recycled polycarbonate resin.

[0139] (Collection of recycled polycarbonate resin)

[0140] In step (S3), a suspension of the precipitated recycled polycarbonate resin is obtained in a solvent (good solvent and poor solvent). The recycled polycarbonate resin in this suspension can be collected by methods such as centrifugation and filtration. The temperature of the suspension is preferably above 10°C and below 120°C. If the temperature is too low, the viscosity will increase; if the temperature is too high, the resin may deteriorate.

[0141] Since the collected recycled polycarbonate resin contains solvents (good solvents and bad solvents), it is preferable to dry it under reduced pressure or normal pressure. The preferred drying temperature is 30–120°C. If the drying temperature is too low, the drying process will take longer; if it is too high, it may cause deterioration of the polycarbonate resin.

[0142] (The solvent used)

[0143] Solvents used in each stage are preferably separated by distillation and membrane separation, and then reused as good and bad solvents, respectively. Additionally, 2-30% by mass can be discarded during reuse. With small amounts of waste, impurities from the process may remain, potentially increasing impurities in the recycled polycarbonate resin. Conversely, with excessive waste, more solvent is used, resulting in a greater environmental impact.

[0144] It should be noted that steps (S1) to (S4) can be repeated multiple times. That is, the recycled polycarbonate resin recovered in step (S4) can be dissolved again in a good solvent, treated with a coagulant, and then a poor solvent can be added to precipitate it. The same solvent or different solvents can be used in each step. When steps (S1) to (S4) are repeated, the number of repetitions can be appropriately determined based on the intended use, for example, by using indicators such as the L value, Na, Mg, and Al content of the recycled polycarbonate resin (described later). By repeatedly performing steps (S1) to (S4), the impurities contained in the recycled polycarbonate decrease. On the other hand, excessive repetition may reduce the amount recovered. Therefore, when repetitions of steps (S1) to (S4) are performed, the number of repetitions is preferably 2 to 3 times.

[0145] [Recycled polycarbonate resin]

[0146] The recycled polycarbonate resin obtained by the method for manufacturing recycled polycarbonate resin of the present invention comprises the structural unit shown in formula (A) above, and preferably has the following characteristics.

[0147] (L value)

[0148] The L-value of the recycled polycarbonate resin, based on reflectance measurement, is preferably 80 or higher, more preferably 85 or higher, and even more preferably 90 or higher. When the L-value is low, the recycled polycarbonate resin, when molded into a molded article, results in poor color tone or low transparency.

[0149] It should be noted that the L value of recycled polycarbonate resin based on reflectance measurement can be measured using a spectrophotometer (such as the Spectrophotometer SE6000 manufactured by Nippon Denshoku Kogyo Co., Ltd.) via reflectance mode.

[0150] (N quantity)

[0151] The nitrogen content in the recycled polycarbonate resin is preferably less than 6 ppm by mass, more preferably less than 5 ppm by mass, and even more preferably less than 3 ppm by mass. This nitrogen content can be determined using a trace total nitrogen analyzer.

[0152] (P quantity)

[0153] The phosphorus content in the recycled polycarbonate resin is preferably less than 10 ppm by mass, more preferably less than 5 ppm by mass, and even more preferably less than 2 ppm by mass. This phosphorus content can be determined by inductively coupled plasma mass spectrometry (ICP-MS).

[0154] (Na, Mg, Al amounts)

[0155] The total content of Na, Mg, and Al in the recycled polycarbonate resin is, for example, 20 ppm by mass or less, preferably 15 ppm by mass or less, more preferably 12 ppm by mass or less, and even more preferably 10 ppm by mass or less. If the polycarbonate resin contains a large amount of Na, Mg, and Al, there is a tendency for the color tone to deteriorate during molding. Furthermore, the total content of Na, Mg, and Al in the recycled polycarbonate resin is preferably 0.3 ppm by mass or more, more preferably 0.5 ppm by mass or more, and even more preferably 1.0 ppm by mass or more. If this content is too low, although the color tone may be good, multiple washing processes are required to achieve this color tone, resulting in poor efficiency and a high probability of reduced yield.

[0156] It should be noted that the total content of Na, Mg, and Al in the recycled polycarbonate resin can be measured by inductively coupled plasma mass spectrometry (ICP-MS). Therefore, the total content of Na, Mg, and Al in the recycled polycarbonate resin is preferably 0.3 ppm by mass or more and 15 ppm by mass or less, more preferably 0.5 ppm by mass or more and 12 ppm by mass or less, and even more preferably 1.0 ppm by mass or more and 10 ppm by mass or less.

[0157] (3mmYI)

[0158] The YI (yellowness index) of the 3mm thick sheet molded body of recycled polycarbonate resin is preferably 3.0 or less, more preferably 2.9 or less, and even more preferably 2.7 or less. When the YI is too high, it becomes a yellowish substance, which limits its applicable uses.

[0159] It should be noted that Yi can be measured according to ASTM D1925.

[0160] (Nominal tensile strain)

[0161] The nominal tensile strain of the recycled polycarbonate resin is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. If the nominal tensile strain is too low, the molded product may become brittle due to cracking during the molding process or in use.

[0162] Regarding the nominal tensile strain of recycled polycarbonate resin, a dumbbell-shaped resin plate with a total length of 75 mm, a parallel section length of 30 mm, a parallel section width of 5 mm, a thickness of 2 mm, and a clamping section width of 10 mm can be formed to obtain a test piece, which is then measured according to ISO 527.

[0163] [Instructions for using recycled polycarbonate resin]

[0164] Recycled polycarbonate resin, as a material with low environmental impact, can be used for the same purposes as unused polycarbonate resin. For example, recycled polycarbonate resin can be widely used in applications such as mobile phone casings, graphics, automotive interiors / exteriors, displays, medical devices, and building materials.

[0165] Recycled polycarbonate resin can be used alone to form molded articles at 100% total volume, or it can be mixed with waste polycarbonate resin or unused (new) polycarbonate resin. Additionally, it can be combined with additives or formulated into polymer alloys with resins other than polycarbonate resin. Regarding additives and alloys, commonly used additives and alloys can be used appropriately.

[0166] Recycled polycarbonate resin can be used, for example, in a method for manufacturing molded articles that includes a step of obtaining recycled polycarbonate resin using the method of the present invention, and a step of obtaining a molded article using the obtained recycled polycarbonate resin, thereby enabling the production of molded articles containing recycled polycarbonate resin. Examples of molded articles include granules; housings; automotive interior / exterior components; display components; medical device components; building materials, and other components or articles. The method for obtaining the molded article can be the same as in conventional cases using unused polycarbonate resin, with the appropriate addition of other resins and additives. Components or articles can be manufactured using recycled polycarbonate resin; alternatively, granules formed from recycled polycarbonate resin can also be used.

[0167] Example

[0168] The present invention will be described in more detail below through embodiments, but the present invention is not limited to the following embodiments as long as its spirit is not changed.

[0169] [Waste polycarbonate resin raw material]

[0170] •PC(1): Crushed polycarbonate housing of smart meters for outdoor use (500nm transmittance: 0%, nitrogen content: 2 ppm by mass, phosphorus content: 1.1% by mass)

[0171] •PC(2): Crushed polycarbonate carports (500nm transmittance: 52%, nitrogen content: 86 ppm by mass, phosphorus content: 38 ppm by mass)

[0172] • PC(3): Crushed product of used projector (PC / ABS) (500nm transmittance: 0%, nitrogen content: ND (not detected), phosphorus content: 0.82% by mass)

[0173] Each raw material is pre-crushed using a pulverizer to a size of approximately 10mm square before use.

[0174] [evaluate]

[0175] (500nm transmittance)

[0176] Regarding the 500nm transmittance, a solution was prepared by dissolving waste polycarbonate resin raw material in dichloromethane at a concentration of 10% by mass. Using a 50mm sample cell, the transmittance was measured using a Shimadzu UV1800 microscope to determine the transmittance at 500nm.

[0177] (Nitrogen content)

[0178] The nitrogen content of waste polycarbonate resin raw materials or recycled polycarbonate resin was determined using a TN-10 trace total nitrogen analyzer (manufactured by Dia Instruments).

[0179] (Phosphorus content)

[0180] Phosphorus content was determined by wet decomposition of waste polycarbonate resin raw materials or recycled polycarbonate resin with sulfuric acid, nitric acid, and hydrogen peroxide water, followed by recovery with pure water and volume adjustment. The phosphorus content was then measured using an ICP-OES apparatus (Agilent Technologies Corporation "5800ICP-OES").

[0181] (L value)

[0182] After placing the obtained recycled polycarbonate resin into a circular sample cell, cover it with a ZERO BOX, and measure the L value using a spectrophotometer SE6000 manufactured by Nippon Denshoku Kogyo Co., Ltd. in reflection mode.

[0183] (Quantitative analysis of Na, Mg, and Al)

[0184] 200 mg of the obtained recycled polycarbonate resin was weighed and subjected to pressurized and sealed decomposition using nitric acid in a microwave pretreatment device (Anton Paar Multiwave 7000). After adjusting the volume, it was appropriately diluted and quantitatively determined by ICP-MS using a Thermo Fisher Scientific ELEMENT2.

[0185] (3mmYI)

[0186] Using the obtained recycled polycarbonate resin as raw material, a small injection molding machine (SELLBICC Mobile, Shinshin Co., Ltd.) was used to mold a plate with a thickness of 3 mm, a length of 25 mm, and a width of 25 mm. This plate was used as a test piece, and the yellow index (YI) was determined according to ASTM D1925 using a spectrophotometer (CM-3700d, Konica Minolta Co., Ltd.).

[0187] (Nominal tensile strain)

[0188] Using the obtained recycled polycarbonate resin as raw material, a dumbbell-shaped resin plate with a total length of 75 mm, a parallel section length of 30 mm, a parallel section width of 5 mm, a thickness of 2 mm, and a clamping section width of 10 mm was formed using a small injection molding machine (SELLBIC C, Mobile, Shine Manufacturing Co., Ltd.) at a barrel temperature of 280°C and a mold temperature of 60°C. This dumbbell-shaped resin plate was used as a test piece, and the nominal tensile strain was measured using a universal testing machine AGS-5kNX (manufactured by Shimadzu Corporation).

[0189] [Example 1]

[0190] In a 10L flask, 500g of pulverized PC(1) and 4.5kg of dichloromethane were supplied under a nitrogen atmosphere at 20°C and stirred for 30 minutes (step (1)). Next, 5g of ferric chloride(III) as a coagulant was added to the solution, and stirring was continued for 60 minutes. The solution was then filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0191] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 1.

[0192] [Example 2]

[0193] In a 10L flask, 500g of pulverized PC(1) and 4.5kg of phenol were supplied under a nitrogen atmosphere at 60°C and stirred for 30 minutes (step (1)). Next, 15g of ferric sulfate(II) as a coagulant was added to the solution, and stirring was continued for 60 minutes. The solution was then filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0194] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 1.

[0195] [Example 3]

[0196] In a 10L flask, 500g of pulverized PC(1) and 4.5kg of dichloromethane were supplied under a nitrogen atmosphere at 20°C and stirred for 30 minutes (step (1)). Next, 15g of ferric sulfate(III) as a coagulant was added to the solution, and stirring was continued for 60 minutes. The solution was then filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0197] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 1.

[0198] [Example 4]

[0199] In a 10L flask, 500g of pulverized PC (1) and 4.5kg of phenol were supplied under a nitrogen atmosphere at 80°C and stirred for 30 minutes (step (1)). Next, 25g of aluminum sulfate as a coagulant was added to the solution at 60°C, and stirring was continued for 60 minutes. The solution was then filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0200] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 1.

[0201] [Example 5]

[0202] In a 10L flask, 500g of pulverized PC (1) and 4.5kg of dichloromethane were supplied under a nitrogen atmosphere at 20°C and stirred for 30 minutes (step (1)). Next, 25g of aluminum chloride as a coagulant was added to the solution, and stirring was continued for 60 minutes. The solution was then filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0203] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 1.

[0204] [Example 6]

[0205] In a 10L flask, 500g of pulverized PC (1) and 4.5kg of phenol were supplied under a nitrogen atmosphere at 60°C and stirred for 30 minutes (step (1)). Next, 25g of polyethylene oxide as a coagulant was added to the solution, and stirring was continued for 60 minutes. The solution was then filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0206] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 1.

[0207] [Example 7]

[0208] In a 10L flask, under a nitrogen atmosphere and at 80°C, 500g of pulverized PC(1) and 4.5kg of a solvent consisting of a 1:1 mass ratio of phenol and toluene were supplied and stirred for 30 minutes (step (1)). Next, at 60°C, 5g of ferric sulfate(II) as a coagulant was added to the solution, and after stirring for 10 minutes, 5g of polyacrylamide was added. After stirring for another 60 minutes, the solution was filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a 40°C dryer for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0209] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 1.

[0210] [Example 8]

[0211] In a 10L flask, under a nitrogen atmosphere and at 80°C, 500g of pulverized PC(2) and 4.5kg of a solvent consisting of phenol and toluene mixed in a 3:7 mass ratio were supplied and stirred for 30 minutes (step (1)). Next, at 60°C, 5g of ferric chloride(III) as a coagulant was added to the solution, and stirring was continued for 60 minutes. The solution was then filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0212] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 1.

[0213] [Example 9]

[0214] In a 10L flask, 500g of pulverized PC(3) and 4.5kg of a solvent consisting of phenol and toluene mixed in a 1:1 mass ratio were supplied under a nitrogen atmosphere at 80°C and stirred for 30 minutes (step (1)). Next, 5g of ferric sulfate(II) as a coagulant was added to the solution at 60°C, and stirring was continued for 60 minutes. The solution was then filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0215] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 1.

[0216] [Table 1]

[0217]

[0218] [Example 10]

[0219] In a 10L flask, 500g of pulverized PC(1) and 4.5kg of dichloromethane were supplied under a nitrogen atmosphere at 80°C and stirred for 30 minutes (step (1)). Next, 5g of activated carbon was added to the solution at 60°C and stirred for 30 minutes. Then, 5g of ferric chloride(III) as a coagulant was added to the solution and stirred for another 60 minutes. The solution was then filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain powdered recycled polycarbonate resin (step (4)).

[0220] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 2.

[0221] [Example 11]

[0222] In a 10L flask, 500g of pulverized PC(1) and 4.5kg of phenol were supplied under a nitrogen atmosphere at 80°C and stirred for 30 minutes (step (1)). Next, 5g of activated carbon and 5g of ferric sulfate(II) as a coagulant were added to the solution at 60°C, and stirring was continued for 90 minutes. The solution was then filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0223] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 2.

[0224] [Example 12]

[0225] In a 10L flask, under a nitrogen atmosphere and at 80°C, 500g of pulverized PC(1) and 4.5kg of a solvent consisting of phenol and toluene mixed in a 3:7 mass ratio were supplied and stirred for 30 minutes (step (1)). Next, at 60°C, 5g of activated carbon and 5g of ferric sulfate(II) as a coagulant were added to the solution, and stirring was continued for 90 minutes. The solution was then filtered through a 0.5μm glass filter to obtain a filtrate (step (2)). 4.5kg of acetone was added to the filtrate, resulting in a white precipitate (step (3)). The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0226] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 2.

[0227] [Table 2]

[0228]

[0229] [Comparative Example 1]

[0230] In a 10L flask, 500g of pulverized PC(1) and 4.5kg of dichloromethane were supplied under a nitrogen atmosphere at 20°C and stirred for 30 minutes. The solution was filtered through a glass filter, which turned black, but a black filtrate was obtained. 4.5kg of acetone was added to the filtrate, resulting in a precipitate. The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain powdered recycled polycarbonate resin (step (4)).

[0231] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 3.

[0232] [Comparative Example 2]

[0233] In a 10L flask, 500g of pulverized PC(2) and 4.5kg of dichloromethane were supplied under a nitrogen atmosphere at 20°C and stirred for 30 minutes. The solution was filtered through a glass filter to obtain a filtrate. 4.5kg of acetone was added to the filtrate, resulting in a precipitate. The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain powdered recycled polycarbonate resin (step (4)).

[0234] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 3.

[0235] [Comparative Example 3]

[0236] In a 10L flask, 500g of pulverized PC(3) and 4.5kg of phenol were supplied under a nitrogen atmosphere at 80°C and stirred for 30 minutes. The solution was filtered through a glass filter, which turned black, but a black filtrate was obtained. 4.5kg of acetone was added to the filtrate, resulting in a precipitate. The polycarbonate precipitate (recycled polycarbonate resin) was filtered off using filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0237] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 3.

[0238] [Comparative Example 4]

[0239] In a 10L flask, 500g of pulverized PC(1) and 4.5kg of dichloromethane were supplied under a nitrogen atmosphere at 20°C and stirred for 30 minutes. Then, 5g of activated carbon was added to the solution at 60°C and stirred for 60 minutes. The solution was then filtered through a glass filter, which turned black, resulting in a filtrate. 4.5kg of acetone was added to the filtrate, resulting in a precipitate. The polycarbonate precipitate (recycled polycarbonate resin) was filtered through filter paper and dried in a dryer at 40°C for 10 hours to obtain recycled polycarbonate resin powder (step (4)).

[0240] The obtained recycled polycarbonate resin was evaluated according to the steps described above. The results are shown in Table 3.

[0241] [Table 3]

[0242]

Claims

1. A method for manufacturing recycled polycarbonate resin, comprising manufacturing recycled polycarbonate resin from waste polycarbonate resin raw materials, characterized in that, The manufacturing method includes the following steps (S1) to (S4), Step (S1): The step of dissolving the waste polycarbonate resin raw material in a soluble good solvent to obtain a polycarbonate resin solution. Step (S2): This step involves contacting the polycarbonate resin solution with a coagulant and a filter aid, and then removing insoluble matter from the resulting polycarbonate resin solution through solid-liquid separation to obtain a solution (L) from which the insoluble matter has been removed. Step (S3): A step of precipitating the recycled polycarbonate resin by mixing the solution (L) with a poor solvent. Step (S4): The step of recovering the precipitated recycled polycarbonate resin. The soluble good solvent does not contain water.

2. The method for manufacturing recycled polycarbonate resin according to claim 1, wherein the waste polycarbonate resin raw material comprises a total of 5% by mass or more of a polycarbonate resin composition equivalent to one or more polycarbonate resin compositions selected from the group consisting of (i) to (iii) below, and the waste polycarbonate resin raw material comprises 10% by mass or more of polycarbonate resin. (i) For polycarbonate resin compositions that have a transmittance of less than 90% at 500 nm when the transmittance is measured using a 50 mm sample cell when the solution is dissolved in dichloromethane in a manner that is 10% by mass, the transmittance is measured. (ii) A polycarbonate resin composition having a nitrogen atom content of 50 ppm or more by mass. (iii) A polycarbonate resin composition having a phosphorus atom content of 5 ppm or more by mass.

3. The method for manufacturing recycled polycarbonate resin according to claim 1, wherein the good solvent used in step (S1) comprises halogen-based solvents and / or phenol-based solvents.

4. The method for manufacturing recycled polycarbonate resin according to claim 1, wherein the soluble good solvent comprises more than 30% by mass of halogen-based solvent and / or phenol-based solvent.

5. The method for manufacturing recycled polycarbonate resin according to claim 4, wherein the soluble good solvent is composed of halogen-based solvents and / or phenol-based solvents.

6. The method for manufacturing recycled polycarbonate resin according to claim 1, wherein the undesirable solvent used in step (S3) comprises any one selected from the group consisting of ketone solvents, saturated hydrocarbon solvents, alcohol solvents and water.

7. The method for manufacturing recycled polycarbonate resin according to claim 1, wherein the coagulant in step (S2) is one or more selected from the group consisting of ferric chloride (III), ferric sulfate (I), ferric sulfate (II), aluminum chloride, aluminum sulfate, titanium oxide, copper sulfate (I), copper sulfate (II), copper chloride (I), copper chloride (II), zinc sulfate, anionic polymers, cationic polymers, and nonionic polymers.

8. The method for manufacturing recycled polycarbonate resin according to claim 7, wherein the coagulant in step (S2) is one or more selected from the group consisting of ferric chloride (III), ferric sulfate (II), ferric sulfate (III), aluminum sulfate, aluminum chloride, polyacrylamide and polyethylene oxide.

9. The method for manufacturing recycled polycarbonate resin according to claim 1, wherein the filter aid is selected from one or more of the group consisting of activated carbon, montmorillonite, diatomaceous earth, silica gel and synthetic adsorbents.

10. The method for manufacturing recycled polycarbonate resin according to claim 1, wherein the total content of Na, Mg and Al in the recycled polycarbonate resin is 0.3 ppm by mass or more and 20 ppm by mass or less.

11. The method for manufacturing recycled polycarbonate resin according to claim 1, wherein the L value of the recycled polycarbonate resin based on reflectance measurement is 80 or higher.

12. The method for manufacturing recycled polycarbonate resin according to claim 1, wherein the nominal tensile strain of the recycled polycarbonate resin is 60% or more.

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